EP3904696A1

EP3904696A1 - Centrifugal blower, blower device, air conditioner, and refrigeration cycle device

Info

Publication number: EP3904696A1
Application number: EP18944300.5A
Authority: EP
Inventors: Takuya Teramoto; Hiroyasu Hayashi; Kazuya MICHIKAMI; Ryo Horie; Takahiro Yamatani; Hiroshi Tsutsumi
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2018-12-27
Filing date: 2018-12-27
Publication date: 2021-11-03
Anticipated expiration: 2038-12-27
Also published as: JPWO2020136788A1; CN113195903A; WO2020136788A1; ES2945787T3; EP3904696A4; JP7130061B2; EP3904696B1; CN113195903B

Abstract

A centrifugal air-sending device includes an impeller having a main plate having a disk shape and blades and a fan casing having a bell mouth. The bell mouth has an inlet port and an air-suction portion having an opening having a diameter gradually decreasing from an upstream end toward a downstream end of the air-suction portion in a direction of a flow of gas to be suctioned into the fan casing. In a vertical section of the bell mouth, in a case in which the upstream end is defined as one of a vertex of a major axis and a vertex of a minor axis of a virtual ellipse, the downstream end is defined as the other one of the vertex of the major axis and the vertex of the minor axis of the virtual ellipse, an intersection of the major axis and the minor axis is defined to be further away from a rotation shaft of the impeller than is the downstream end, and a part of an outline of the virtual ellipse having a shortest distance connecting the upstream end and the downstream end along the outline of the virtual ellipse is defined as a first outline, and in a range defined by a virtual first tangent of the virtual ellipse touching the upstream end, a virtual second tangent of the virtual ellipse touching the downstream end, and the first outline, the air-suction portion has a wall extending between the upstream end and the downstream end, and the wall of the air-suction portion extends away from the intersection in a direction from the intersection across the first outline.

Description

Technical Field

The present disclosure relates to a centrifugal air-sending device including a casing having a bell mouth, an air-sending apparatus including the centrifugal air-sending device, an air-conditioning apparatus including the centrifugal air-sending device, and a refrigeration cycle apparatus including the centrifugal air-sending device.

Background Art

There has been proposed a centrifugal air-sending device having a bell mouth having a first curved surface defined by a wall shrinking from an outer periphery toward an inner periphery of the bell mouth and a second curved surface defined by a wall located downstream of the first curved surface in a direction in which air is suctioned along the first curved surface and expanding from the inner periphery toward the outer periphery (see, for example, Patent Literature 1). A case is described in which, in the centrifugal air-sending device, a radius of curvature of the first curved surface in a direction of shrinkage from the outer periphery toward the inner periphery is defined as a radius of curvature Y, and a radius of curvature of the second curved surface in a direction of expansion from the inner periphery toward the outer periphery is defined as a radius of curvature Z. In this case, the centrifugal air-sending device of Patent Literature 1 brings about an effect of reducing noise through a smooth flow of gas at an inlet port, as the bell mouth has a shape in which a relationship is satisfied in which the radius of curvature Y is greater than the radius of curvature Z.

Citation List

Patent Literature

Patent Literature 1: U.S. Patent Application Publication No. 2006/0034686

Summary of Invention

Technical Problem

However, with a bell mouth shaped to extend in a radial direction or in an axial direction of a rotation shaft for further characteristic improvement, radii of curvature of curved surfaces of the bell mouth decrease, so that a flow of gas is easily separated from the bell mouth. Such flow separation may increase noise.
The present disclosure is to solve such a problem, and is to provide a centrifugal air-sending device configured to reduce noise even with a bell mouth shaped to extend in a radial direction or in an axial direction of a rotation shaft, an air-sending apparatus including the centrifugal air-sending device, an air-conditioning apparatus including the centrifugal air-sending device, and a refrigeration cycle apparatus including the centrifugal air-sending device.

Solution to Problem

A centrifugal air-sending device according to an embodiment of the present disclosure includes an impeller having a main plate having a disk shape and a plurality of blades arranged on a peripheral edge of the main plate, and a fan casing accommodating the impeller and having a bell mouth formed to rectify a flow of gas to be suctioned into the impeller. The bell mouth has an inlet port through which the gas flows into the fan casing, and an air-suction portion having an opening having a diameter gradually decreasing from an upstream end toward a downstream end of the air-suction portion in a direction of the flow of the gas to be suctioned into the fan casing. In a vertical section of the bell mouth, in a case in which the upstream end is defined as one of a vertex of a major axis and a vertex of a minor axis of a virtual ellipse, the downstream end is defined as the other one of the vertex of the major axis and the vertex of the minor axis of the virtual ellipse, an intersection of the major axis and the minor axis is defined to be further away from a rotation shaft of the impeller than is the downstream end, and a part of an outline of the virtual ellipse having a shortest distance connecting the upstream end and the downstream end along the outline of the virtual ellipse is defined as a first outline, and in a range defined by a virtual first tangent of the virtual ellipse touching the upstream end, a virtual second tangent of the virtual ellipse touching the downstream end, and the first outline, the air-suction portion has a wall extending between the upstream end and the downstream end, and the wall of the air-suction portion extends away from the intersection in a direction from the intersection across the first outline. Advantageous Effects of Invention
In the centrifugal air-sending device according to an embodiment of the present disclosure, in the range defined by the virtual first tangent of the virtual ellipse touching the upstream end, the virtual second tangent of the virtual ellipse touching the downstream end, and the first outline, the air-suction portion has the wall extending between the upstream end and the downstream end, and the wall of the air-suction portion extends away from the intersection in the direction from the intersection across the first outline. As the centrifugal air-sending device includes such a configuration, the curvature of a portion of the bell mouth close to the downstream end, which corresponds to the innermost diameter of the bell mouth, is set such that a direction in which the bell mouth extends to the downstream end approximates an axial direction of the rotation shaft. The centrifugal air-sending device therefore causes a fast flow of gas flowing into the bell mouth to move along the bell mouth from an outer periphery toward an inner periphery of the bell mouth and causes the flow of the gas to naturally turn into the axial direction in the air-suction portion. As a result, the centrifugal air-sending device reduces flow separation of the gas in the vicinity of the downstream end, which corresponds to the innermost diameter of the bell mouth, reduces inflow of a disturbed flow of gas into the impeller, and thereby reduces noise.

Brief Description of Drawings

[Fig. 1] Fig. 1 is a perspective view of a centrifugal air-sending device according to Embodiment 1 of the present disclosure.
[Fig. 2] Fig. 2 is a side view of the centrifugal air-sending device shown in Fig. 1 as the centrifugal air-sending device is seen from the outside of an inlet port.
[Fig. 3] Fig. 3 is a partial cross-sectional view of the centrifugal air-sending device shown in Fig. 2 taken along line A-A.
[Fig. 4] Fig. 4 is an enlarged view of a part B of a bell mouth shown in Fig. 3.
[Fig. 5] Fig. 5 is a partially-enlarged view of a bell mouth of a centrifugal air-sending device according to Embodiment 2 of the present disclosure.
[Fig. 6] Fig. 6 is a partially-enlarged view of a bell mouth of a centrifugal air-sending device according to Embodiment 3 of the present disclosure.
[Fig. 7] Fig. 7 is a partially-enlarged view of a bell mouth of a centrifugal air-sending device according to Embodiment 4 of the present disclosure.
[Fig. 8] Fig. 8 is a partially-enlarged view of a bell mouth of a centrifugal air-sending device according to Embodiment 5 of the present disclosure.
[Fig. 9] Fig. 9 is a partially-enlarged view of a bell mouth of a centrifugal air-sending device according to Embodiment 6 of the present disclosure.
[Fig. 10] Fig. 10 is a partially-enlarged view of a bell mouth of a centrifugal air-sending device according to Embodiment 7 of the present disclosure.
[Fig. 11] Fig. 11 is a partially-enlarged view of a bell mouth of a centrifugal air-sending device according to Embodiment 8 of the present disclosure.
[Fig. 12] Fig. 12 is a side view of a centrifugal air-sending device according to Embodiment 9 of the present disclosure.
[Fig. 13] Fig. 13 is a cross-sectional view of the centrifugal air-sending device shown in Fig. 12 taken along line B-B.
[Fig. 14] Fig. 14 is a cross-sectional view of the centrifugal air-sending device shown in Fig. 12 taken along line C-C.
[Fig. 15] Fig. 15 is a diagram showing a configuration of an air-sending apparatus according to Embodiment 10 of the present disclosure.
[Fig. 16] Fig. 16 is a perspective view of an air-conditioning apparatus according to Embodiment 11 of the present disclosure.
[Fig. 17] Fig. 17 is a diagram showing an internal configuration of the air-conditioning apparatus according to Embodiment 11 of the present disclosure.
[Fig. 18] Fig. 18 is a cross-sectional view of the air-conditioning apparatus according to Embodiment 11 of the present disclosure.
[Fig. 19] Fig. 19 is another cross-sectional view of the air-conditioning apparatus according to Embodiment 11 of the present disclosure.
[Fig. 20] Fig. 20 is a diagram showing a configuration of a refrigeration cycle apparatus according to Embodiment 12 of the present disclosure.

Description of Embodiments

In the following, centrifugal air-sending devices 1 to 1H according to embodiments of the present disclosure, an air-sending apparatus 30 according to an embodiment of the present disclosure, an air-conditioning apparatus 40 according to an embodiment of the present disclosure, and a refrigeration cycle apparatus 50 according to an embodiment of the present disclosure are described, for example, with reference to the drawings. In the following drawings including Fig. 1, relative relationships in dimension between components, the shapes of the components, or other features of the components may be different from actual ones. Further, components given identical reference signs in the following drawings are identical or equivalent to each other, and these reference signs are common throughout the full text of the specification. Further, the directional terms, such as "upper", "lower", "right", "left", "front", and "back", used as appropriate for ease of comprehension are merely so written for convenience of explanation, and the placement or orientation of a device or a component is not limited by the directional terms.

Embodiment 1

[Centrifugal Air-sending Device 1]

Fig. 1 is a perspective view of a centrifugal air-sending device 1 according to Embodiment 1 of the present disclosure. Fig. 2 is a side view of the centrifugal air-sending device 1 shown in Fig. 1 as the centrifugal air-sending device 1 is seen from the outside of an inlet port 5. Fig. 3 is a partial cross-sectional view of the centrifugal air-sending device 1 shown in Fig. 2 taken along line A-A. Fig. 3 shows arrows representing flows of air flowing through the inside of the centrifugal air-sending device 1. A basic structure of the centrifugal air-sending device 1 is described with reference to Figs. 1 to 3. The centrifugal air-sending device 1 is a multi-blade centrifugal air-sending device 1 such as a sirocco fan and a turbo fan, and includes an impeller 2 configured to generate a flow of gas and a fan casing 4 accommodating the impeller 2.

(Impeller 2)

The impeller 2 is driven, for example, by a motor, which is not illustrated, into rotation. The rotation generates a centrifugal force with which the impeller 2 forcibly sends out air outward in radial directions. As shown in Fig. 1, the impeller 2 has a main plate 2a having a disk shape and a plurality of blades 2d arranged on a peripheral edge 2a1 of the main plate 2a. The impeller 2 has a shaft portion 2b provided in a central part of the main plate 2a. The impeller 2 rotates with a driving force of a fan motor, which is not illustrated, connected to a center of the shaft portion 2b.
Further, as shown in Fig. 3, the impeller 2 has a ring-shaped side plate 2c facing the main plate 2a at ends of the plurality of blades 2d opposite to the main plate 2a in an axial direction of a rotation shaft RS of the shaft portion 2b. The side plate 2c connects the plurality of blades 2d with one another, thereby maintains a positional relationship between the tips of the blades 2d and thereby reinforces the plurality of blades 2d. Alternatively, the impeller 2 may be structured not to include the side plate 2c. In a case in which the impeller 2 has the side plate 2c, one end of each of the plurality of blades 2d is connected to the main plate 2a, and the other end of each of the plurality of blades 2d is connected to the side plate 2c. The plurality of blades 2d are thus disposed between the main plate 2a and the side plate 2c. The impeller 2 is formed by the main plate 2a and the plurality of blades 2d into a cylindrical shape, and the impeller 2 has an inlet port 2e formed close to the side plate 2c opposite to the main plate 2a in the axial direction of the rotation shaft RS of the shaft portion 2b.
The plurality of blades 2d are arranged in a circular pattern centered at the shaft portion 2b, and have their base ends fixed on a surface of the main plate 2a. The plurality of blades 2d are provided on both surfaces of the main plate 2a in the axial direction of the rotation shaft RS of the shaft portion 2b. Each blade 2d is placed at a regular spacing from another blade 2d on the peripheral edge 2a1 of the main plate 2a. Each blade 2d is formed, for example, in the shape of a curved rectangular plate, and is placed along the radial direction or inclined toward the radial direction at a predetermined angle.
The impeller 2 thus configured, by being rotated, allows air suctioned into a space surrounded by the main plate 2a and the plurality of blades 2d to be sent out outward in the radial directions as shown in Fig. 3 through a space between a blade 2d and an adjacent blade 2d. Although, in Embodiment 1, each blade 2d is provided to stand substantially perpendicularly to the main plate 2a, the present disclosure is not limited to this configuration. Alternatively, each blade 2d may be inclined toward the perpendicular to the main plate 2a.

(Fan Casing 4)

The fan casing 4 surrounds the impeller 2 and rectifies air blown out from the impeller 2. The fan casing 4 has a scroll portion 41 and a discharge portion 42.

(Scroll Portion 41)

The scroll portion 41 forms an air passage through which a dynamic pressure of a flow of gas generated by the impeller 2 is converted into a static pressure. The scroll portion 41 has side walls 4a each covering the impeller 2 in the axial direction of the rotation shaft RS of the shaft portion 2b of the impeller 2 and each having an inlet port 5 formed in the side wall 4a and through which air is suctioned and a peripheral wall 4c surrounding the impeller 2 in radial directions of the rotation shaft RS of the shaft portion 2b. Further, the scroll portion 41 has a tongue 43, located between the discharge portion 42 and a scroll start portion 41a of the peripheral wall 4c, that has a curved surface and guides a flow of gas generated by the impeller 2 toward the discharge port 42a through the scroll portion 41. The radial directions of the shaft portion 2b are each a direction perpendicular to the shaft portion 2b. The scroll portion 41 has an internal space, defined by the peripheral wall 4c and the side walls 4a, in which air blown out from the impeller 2 flows along the peripheral wall 4c.

(Side Wall 4a)

The side walls 4a are each placed perpendicular to the axial direction of the rotation shaft RS of the impeller 2 and cover the impeller 2. The side walls 4a of the fan casing 4 each have the inlet port 5 formed in the side wall 4a so that air can flow between the impeller 2 and an area around the fan casing 4. The inlet port 5 is formed in a circular shape, and is disposed such that the center of the inlet port 5 and the center of the shaft portion 2b of the impeller 2 substantially coincide with each other. Such a configuration of the side wall 4a allows air close to the inlet port 5 to smoothly flow and efficiently flow from the inlet port 5 into the impeller 2. As shown in Figs. 1 to 3, the centrifugal air-sending device 1 includes the double suction fan casing 4 having the side walls 4a across the main plate 2a in the axial direction of the rotation shaft RS of the shaft portion 2b with the inlet port 5 each formed in the side walls 4a. That is, the fan casing 4 of the centrifugal air-sending device 1 has two side walls 4a, and the side walls 4a are disposed to face each other.

(Peripheral Wall 4c)

The peripheral wall 4c has an inner peripheral surface surrounding the impeller 2 in the radial directions of the shaft portion 2b and facing the plurality of blades 2d. The peripheral wall 4c is placed parallel to the axial direction of the rotation shaft RS of the impeller 2 and covers the impeller 2. As shown in Fig. 2, the peripheral wall 4c is provided over an area from the scroll start portion 41a located at a boundary between the tongue 43 and the scroll portion 41 to a scroll end portion 41b located at a boundary between the discharge portion 42 and an end of the scroll portion 41 that is away from the tongue 43 along a direction of rotation R of the impeller 2. The scroll start portion 41a is an end of the peripheral wall 4c, which has a curved surface, located upstream of a flow of gas generated by rotation of the impeller 2, and the scroll end portion 41b is an end of the peripheral wall 4c located downstream of a flow of gas generated by rotation of the impeller 2.
The peripheral wall 4c has a width in the axial direction of the rotation shaft RS of the impeller 2. As shown in Fig. 2, the peripheral wall 4c is formed in a volute shape defined by a predetermined rate of expansion such that a distance from the rotation shaft RS of the shaft portion 2b gradually increases in the direction of rotation R of the impeller 2. That is, the peripheral wall 4c defines a gap between the peripheral wall 4c and an outer periphery of the impeller 2 that expands at a predetermined rate from the tongue 43 toward the discharge portion 42, and forms an air flow passage whose area gradually increases from the tongue 43 toward the discharge portion 42. An example of the volute shape defined by the predetermined rate of expansion is a volute shape formed by a logarithmic spiral, a spiral of Archimedes, or an involute curve. An inner peripheral surface of the peripheral wall 4c has a curved surface smoothly curved along a circumferential direction of the impeller 2 from the scroll start portion 41a, at which the volute shape starts rolling, to the scroll end portion 41b, at which the volute shape finishes rolling. Such a configuration allows air sent out from the impeller 2 to smoothly flow through the gap between the impeller 2 and the peripheral wall 4c in a direction toward the discharge portion 42. A static pressure of air from the tongue 43 toward the discharge portion 42 in the fan casing 4 thus efficiently increases.

(Discharge Portion 42)

The discharge portion 42 forms a discharge port 42a through which a flow of gas generated by the impeller 2 and having passed through the scroll portion 41 is discharged. The discharge portion 42 is formed by a hollow pipe having a rectangular cross-section orthogonal to a direction of a flow of air flowing along the peripheral wall 4c. As shown in Figs. 1 and 2, the discharge portion 42 forms a flow passage through which air sent out from the impeller 2 and flowing through the gap between the peripheral wall 4c and the impeller 2 is guided to be discharged out from the fan casing 4.
As shown in Fig. 1, the discharge portion 42 is defined by an extension plate 42b, a diffuser plate 42c, a first side plate 42d, a second side plate 42e, or other components. The extension plate 42b is formed integrally with the peripheral wall 4c to smoothly continue into the scroll end portion 41b downstream of the peripheral wall 4c. The diffuser plate 42c is formed integrally with the tongue 43 of the fan casing 4 and faces the extension plate 42b. The diffuser plate 42c is formed at a predetermined angle to the extension plate 42b such that the cross-sectional area of the flow passage gradually increases along a direction of a flow of air in the discharge portion 42. The first side plate 42d is formed integrally with the side wall 4a of the fan casing 4, and the second side plate 42e is formed integrally with the opposite side wall 4a of the fan casing 4. The first side plate 42d and the second side plate 42e, which face each other, are formed between the extension plate 42b and the diffuser plate 42c. Thus, the discharge portion 42 has a rectangular cross-section flow passage formed by the extension plate 42b, the diffuser plate 42c, the first side plate 42d, and the second side plate 42e.

(Tongue 43)

In the fan casing 4, the tongue 43 is formed between the diffuser plate 42c of the discharge portion 42 and the scroll start portion 41a of the peripheral wall 4c. The tongue 43 is provided at a boundary division between the scroll portion 41 and the discharge portion 42 and is a raised portion that extends toward the inside of the fan casing 4. The tongue 43 extends in a direction parallel to the axial direction of the rotation shaft RS of the shaft portion 2b in the fan casing 4. The tongue 43 guides a flow of air generated by the impeller 2 toward the discharge port 42a through the scroll portion 41.
The tongue 43 is formed with a predetermined radius of curvature, and the peripheral wall 4c is smoothly connected to the diffuser plate 42c via the tongue 43. When air sent out through the impeller 2 from the inlet port 5 is gathered by the fan casing 4 and flows into the discharge portion 42, the tongue 43 is used as a branch point of a flow passage of air. That is, at an inlet of the discharge portion 42, a flow of gas flowing toward the discharge port 42a and a flow of gas flowing in again upstream from the tongue 43 are formed. Further, a flow of air flowing into the discharge portion 42 rises in static pressure during passage through the fan casing 4 to be higher in pressure than that in the fan casing 4. The tongue 43 is thus formed to separate different pressures and, with a curved surface, is formed to guide, toward each flow passage, air flowing into the discharge portion 42.

(Bell mouth 3)

The inlet port 5 provided in each of the side walls 4a is formed by a corresponding one of bell mouths 3. The bell mouth 3 rectifies a flow of gas to be suctioned into the impeller 2 and causes the flow of the gas to flow into the inlet port 2e of the impeller 2. The bell mouth 3 has an opening having a diameter gradually decreasing from the outside toward the inside of the fan casing 4. The bell mouth 3 is provided upstream of the impeller 2 in a direction of the flow of the gas to be suctioned into the fan casing 4. The bell mouth 3 is formed in a place facing the inlet port 2e of the impeller 2. The bell mouth 3 has an air-suction portion 3c formed to guide, into the fan casing 4, the flow of the gas to be suctioned into the fan casing 4.
The air-suction portion 3c is formed in a tubular shape, and an inner peripheral surface of the air-suction portion 3c forms the inlet port 5. Gas flowing from the outside to the inside of the fan casing 4 passes through this inlet port 5. The air-suction portion 3c has an opening having a diameter gradually decreasing from an upstream end 3a toward a downstream end 3b of the air-suction portion 3c in a direction of the flow of the gas to be suctioned into the fan casing 4 through the inlet port 5. That is, the air-suction portion 3c is provided to extend in the axial direction of the rotation shaft RS, and has an air passage decreasing in width from the upper stream toward the lower stream of the flow of the gas to be suctioned into the fan casing 4 through the inlet port 5.
The bell mouth 3 is formed in a ring shape in a plan view of the bell mouth 3 as the bell mouth 3 is seen in the axial direction of the rotation shaft RS. The upstream end 3a forms an outer edge of the bell mouth 3, and the downstream end 3b forms an inner edge of the bell mouth 3. The upstream end 3a is thus a part of the bell mouth 3 at which the bell mouth 3 reaches its outermost diameter, and is the most expanded portion of the bell mouth 3 formed in a tubular shape. Further, the downstream end 3b is thus a part of the bell mouth 3 at which the bell mouth 3 reaches its innermost diameter, and is the most shrunk portion of the bell mouth 3 formed in a tubular shape.
The air-suction portion 3c has a circular arc cross-section on a plane of rotation centered at the axial direction of the rotation shaft RS, and the surface of the inlet port 5 is formed by a curved surface. That is, as shown in Fig. 3, in a vertical section of the bell mouth 3, the air-suction portion 3c has a wall 3c1 that is formed in a circular arc shape and forms the inlet port 5.
Fig. 4 is an enlarged view of a part B of the bell mouth shown in Fig. 3. Next, as shown in Fig. 4, a detailed configuration of the bell mouth 3 is described with reference to the cross-sectional view of the bell mouth 3. It should be noted that the rotation shaft RS is described for the purpose of describing a positional relationship among the rotation shaft RS, the downstream end 3b, and an intersection EC. In Fig. 4, an ellipse EL is a virtual ellipse having a minor axis MI whose first end E1 is located at the upstream end 3a of the bell mouth 3 and having a major axis MA whose second end E2 is located at the downstream end 3b of the bell mouth 3. In the vertical section of the bell mouth 3, the minor axis MI of the virtual ellipse EL extends from the upstream end 3a toward the inside of the fan casing 4, and the major axis MA of the virtual ellipse EL extends from the downstream end 3b in a direction parallel to the radial direction of the impeller 2. The intersection EC is an intersection of the minor axis MI and the major axis MA and a center point of the virtual ellipse EL.
The upstream end 3a is a part of the bell mouth 3 at which the bell mouth 3 reaches its outermost diameter in the radial direction, and the downstream end 3b is a part of the bell mouth 3 at which the bell mouth 3 reaches its innermost diameter in the radial direction. In the vertical section of the bell mouth 3, the upstream end 3a is one of a vertex of the major axis MA and a vertex of the minor axis MI of the virtual ellipse EL, the downstream end 3b is the other one of the vertex of the major axis MA and the vertex of the minor axis MI of the virtual ellipse EL, and the intersection EC of the major axis MA and the minor axis MI is further away from the rotation shaft RS of the impeller 2 than is the downstream end 3b.
As shown in Fig. 4, a first outline L1 is a part of an outline of the virtual ellipse EL having a shortest distance connecting the upstream end 3a and the downstream end 3b along the outline of the virtual ellipse EL.
A first tangent HT is a virtual tangent of the virtual ellipse EL touching the first end E1, and a second tangent VT is a virtual tangent of the virtual ellipse EL touching the second end E2. That is, the first tangent HT is a virtual tangent of the virtual ellipse EL touching the upstream end 3a, and the second tangent VT is a virtual tangent of the virtual ellipse EL touching the downstream end 3b.
A curved surface ES is a virtual surface created by a locus of the first outline L1 when the virtual ellipse EL is rotated about the rotation shaft RS. An arrow F1 is an arrow representing a direction in which gas flows in a case in which the air-suction portion 3c of the bell mouth 3 is in the shape of the curved surface ES. An arrow F2 is an arrow representing a direction in which gas flows along the air-suction portion 3c of the bell mouth 3 in the centrifugal air-sending device 1 of Embodiment 1.
The air-suction portion 3c of the bell mouth 3 has the wall 3c1 extending between the upstream end 3a and the downstream end 3b, and the wall 3c1 of the air-suction portion 3c extends toward an inner periphery of the bell mouth 3 from the first outline L1 of the virtual ellipse EL having the minor axis MI whose first end E1 is located at the upstream end 3a and having the major axis MA whose second end E2 is located at the downstream end 3b. In other words, the air-suction portion 3c has the wall 3c1 extending between the upstream end 3a and the downstream end 3b, and the wall 3c1 of the air-suction portion 3c extends away from the intersection EC in a direction from the intersection EC across the first outline L1. As shown in Fig. 4, the air-suction portion 3c is thus formed in a curved line drawing an arc in the vertical section of the bell mouth 3.
The air-suction portion 3c extends in a range defined by the virtual first tangent HT of the virtual ellipse EL touching the first end E1, the virtual second tangent VT of the virtual ellipse EL touching the second end E2, and the first outline L1.
That is, in a range defined by the virtual first tangent HT of the virtual ellipse EL touching the upstream end 3a, the virtual second tangent VT of the virtual ellipse EL touching the downstream end 3b, and the first outline L1, the air-suction portion 3c has the wall 3c1 extending between the upstream end 3a and the downstream end 3b, and the wall 3c1 of the air-suction portion 3c extends away from the intersection EC in a direction from the intersection EC across the first outline L1. It should be noted that the bell mouth 3 of the centrifugal air-sending device 1 is one obtained by expanding a common bell mouth in a radial direction and an axial direction. As the centrifugal air-sending device 1 has such a shape that the wall 3c1 extending between the upstream end 3a and the downstream end 3b extends away from the intersection EC in a direction from the intersection EC across the first outline L1, the curvature of a portion of the bell mouth 3 close to the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3, is set such that a direction in which the bell mouth 3 extends to the downstream end 3b approximates the axial direction.

[Operation of Centrifugal Air-sending Device 1]

Rotation of the impeller 2 causes air outside the fan casing 4 to be suctioned into the fan casing 4 through the inlet port 5. The air to be suctioned into the fan casing 4 flows along the air-suction portion 3c of the bell mouth 3, and is suctioned into the impeller 2. In the process in which the air passes through spaces between the plurality of blades 2d, the air suctioned into the impeller 2 turns into a flow of gas to which a dynamic pressure and a static pressure are applied, and the flow of the gas is blown out outward in the radial directions of the impeller 2. The flow of the gas blown out from the impeller 2 has its dynamic pressure converted into a static pressure while the flow of the gas is being guided through the gap between the inside of the peripheral wall 4c and the blades 2d in the scroll portion 41. Then, the flow of the gas blown out from the impeller 2 passes through the scroll portion 41, and then is blown out from the fan casing 4 through the discharge port 42a formed in the discharge portion 42.

[Advantageous Effects of Centrifugal Air-sending Device 1]

In a range defined by a virtual first tangent HT of the virtual ellipse EL touching the upstream end 3a, a virtual second tangent VT of the virtual ellipse EL touching the downstream end 3b, and the first outline L1, the air-suction portion 3c has a wall 3c1 extending between the upstream end 3a and the downstream end 3b, and the wall 3c1 of the air-suction portion 3c extends away from the intersection EC in a direction from the intersection EC across the first outline L1. As the centrifugal air-sending device 1 includes such a configuration, the curvature of a portion of the bell mouth 3 close to the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3, is set such that a direction in which the bell mouth 3 extends to the downstream end 3b approximates the axial direction of the rotation shaft RS. The centrifugal air-sending device 1 therefore causes a fast flow of gas flowing into the bell mouth 3 to move along the bell mouth 3 from an outer periphery toward an inner periphery of the bell mouth 3 and causes the flow of the gas to naturally turn into the axial direction in the air-suction portion 3c. As a result, the centrifugal air-sending device 1 reduces flow separation of the gas in the vicinity of the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3, reduces inflow of a disturbed flow of gas into the impeller 2, and thereby reduces noise. Further, as the bell mouth 3 reduces flow separation of the gas in the vicinity of the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3, and reduces inflow of a disturbed flow of gas into the impeller 2, the centrifugal air-sending device 1 efficiently suctions air. If the centrifugal air-sending device 1 according to Embodiment 1 is not applied, that is, if a common bell mouth is shaped along the virtual ellipse EL in a case in which the bell mouth is expanded in a radial direction and in an axial direction of a rotation shaft, a flow of gas may be separated from the bell mouth at an inner periphery of the bell mouth. The bell mouth 3 of the centrifugal air-sending device 1 according to Embodiment 1, which is formed as described above, makes it possible to reduce flow separation of the gas in the vicinity of the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3.

Embodiment 2

Fig. 5 is a partially-enlarged view of a bell mouth 3A of a centrifugal air-sending device 1A according to Embodiment 2 of the present disclosure. It should be noted that components that are identical in configuration to those of the centrifugal air-sending device 1 shown in Figs. 1 to 4 are given identical reference signs and a description of such components is omitted. The centrifugal air-sending device 1A according to Embodiment 2 is one obtained by further specifying the configuration of the bell mouth 3 of the centrifugal air-sending device 1 according to Embodiment 1, and configurations of components other than a configuration of the bell mouth 3A are identical to those in the centrifugal air-sending device 1 according to Embodiment 1. The following thus gives a description with reference to Fig. 5 with a focus on the configuration of the bell mouth 3A of the centrifugal air-sending device 1A according to Embodiment 2.
In the axial direction of the rotation shaft RS, a distance between the upstream end 3a and the downstream end 3b of the bell mouth 3A is defined as a first axial direction distance D1. In other words, in a case in which the upstream end 3a and the downstream end 3b of the bell mouth 3A are projected onto the rotation shaft RS in a direction perpendicular to the rotation shaft RS, the first axial direction distance D1 is a distance between the upstream end 3a and the downstream end 3b in a place in which the upstream end 3a and the downstream end 3b are projected onto the rotation shaft RS. It should be noted that the first axial direction distance D1 also corresponds to the radius of the minor axis MI of the virtual ellipse EL. That is, the first axial direction distance D1 is also a distance between the upstream end 3a and the intersection EC in the virtual ellipse EL. Further, in the radial direction from the rotation shaft RS, a distance between the upstream end 3a and the downstream end 3b of the bell mouth 3A is defined as a first radial direction distance D2. In other words, in a plan view of the bell mouth 3A as the bell mouth 3A is seen in the axial direction of the rotation shaft RS, the first radial direction distance D2 is a distance between the upstream end 3a and the downstream end 3b of the bell mouth 3A located on the same virtual plane. It should be noted that the first radial direction distance D2 also corresponds to the radius of the major axis of the virtual ellipse EL. That is, the first radial direction distance D2 is also a distance between the downstream end 3b and the intersection EC in the virtual ellipse EL.
The bell mouth 3A is formed such that a relationship is satisfied in which the first radial direction distance D2 is greater than the first axial direction distance D1. It should be noted that a part of the bell mouth 3A formed such that the relationship is satisfied in which the first radial direction distance D2 is greater than the first axial direction distance D1 may be formed on the whole circumference of the bell mouth 3 or may be partially formed in a circumferential direction. The bell mouth 3A of the centrifugal air-sending device 1A is one obtained by expanding a common bell mouth in a radial direction. As the centrifugal air-sending device 1A has such a shape that the wall 3c1 extending between the upstream end 3a and the downstream end 3b extends away from the intersection EC in a direction from the intersection EC across the first outline L1, the curvature of a portion of the bell mouth 3A close to the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3A, is set such that a direction in which the bell mouth 3A extends to the downstream end 3b approximates the axial direction.

[Advantageous Effects of Centrifugal Air-sending Device 1A]

As described above, the bell mouth 3A is formed such that a relationship is satisfied in which the first radial direction distance D2 is greater than the first axial direction distance D1. Moreover, the centrifugal air-sending device 1A has such a shape that the wall 3c1 extending between the upstream end 3a and the downstream end 3b extends away from the intersection EC in a direction from the intersection EC across the first outline L1. The curvature of a portion of the bell mouth 3A of the centrifugal air-sending device 1A close to the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3A, therefore is set such that a direction in which the bell mouth 3A extends to the downstream end 3b approximates the axial direction of the rotation shaft RS. Moreover, the centrifugal air-sending device 1A causes a fast flow of gas flowing into the bell mouth 3A to move along the bell mouth 3A from an outer periphery toward an inner periphery of the bell mouth 3A and causes the flow of the gas to naturally turn into the axial direction in the air-suction portion 3c. As a result, the centrifugal air-sending device 1A reduces flow separation of the gas in the vicinity of the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3A, reduces inflow of a disturbed flow of gas into the impeller 2, and thereby reduces noise. Further, as the bell mouth 3A reduces flow separation of the gas in the vicinity of the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3A, and reduces inflow of a disturbed flow of gas into the impeller 2, the centrifugal air-sending device 1A efficiently suctions air. If the centrifugal air-sending device 1A according to Embodiment 2 is not applied, that is, if a common bell mouth is shaped along the virtual ellipse EL in a case in which the bell mouth is expanded in a radial direction, a flow of gas may be separated from the bell mouth at an inner periphery of the bell mouth. The bell mouth 3A of the centrifugal air-sending device 1A, which is formed as described above, makes it possible to reduce flow separation of the gas in the vicinity of the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3A.

Embodiment 3

Fig. 6 is a partially-enlarged view of a bell mouth 3B of a centrifugal air-sending device 1B according to Embodiment 3 of the present disclosure. It should be noted that components that are identical in configuration to those of the centrifugal air-sending device 1 or other devices shown in Figs. 1 to 5 are given identical reference signs and a description of such components is omitted. The centrifugal air-sending device 1B according to Embodiment 3 is one obtained by further specifying the configuration of the bell mouth 3 of the centrifugal air-sending device 1 according to Embodiment 1, and configurations of components other than a configuration of the bell mouth 3B are identical to those in the centrifugal air-sending device 1 according to Embodiment 1. The following thus gives a description with reference to Fig. 6 with a focus on the configuration of the bell mouth 3B of the centrifugal air-sending device 1B according to Embodiment 3.
In Fig. 6, an ellipse FL is a virtual ellipse having a major axis MA2 whose first end G1 is located at the upstream end 3a of the bell mouth 3B and having a minor axis MI2 whose second end G2 is located at the downstream end 3b of the bell mouth 3B. More specifically, in a vertical section of the bell mouth 3B, the major axis MA2 of the virtual ellipse FL extends from the upstream end 3a toward the inside of the fan casing 4, and the minor axis MI2 of the virtual ellipse FL extends from the downstream end 3b in a direction parallel to the radial direction of the impeller 2.
The intersection EC is an intersection of the minor axis MI2 and the major axis MA2 and a center point of the virtual ellipse FL.
In the vertical section of the bell mouth 3B, the upstream end 3a is one of a vertex of the major axis MA2 and a vertex of the minor axis MI2 of the virtual ellipse FL, the downstream end 3b is the other one of the vertex of the major axis MA2 and the vertex of the minor axis MI2 of the virtual ellipse FL, and the intersection EC of the major axis MA2 and the minor axis MI2 is further away from the rotation shaft RS of the impeller 2 than is the downstream end 3b.
As shown in Fig. 6, a first outline L1 is a part of an outline of the virtual ellipse FL having a shortest distance connecting the upstream end 3a and the downstream end 3b along the outline of the virtual ellipse FL.
A first tangent HT2 is a virtual tangent of the virtual ellipse FL touching the first end G1, and a second tangent VT2 is a virtual tangent of the virtual ellipse FL touching the second end G2. That is, the first tangent HT2 is a virtual tangent of the virtual ellipse FL touching the upstream end 3a, and the second tangent VT2 is a virtual tangent of the virtual ellipse FL touching the downstream end 3b.
The air-suction portion 3c of the bell mouth 3B has the wall 3c1 extending between the upstream end 3a and the downstream end 3b, and the wall 3c1 of the air-suction portion 3c extends toward an inner periphery of the bell mouth 3B from the first outline L1 of the virtual ellipse FL having the major axis MA2 whose first end G1 is located at the upstream end 3a and having the minor axis MI2 whose second end G2 is located at the downstream end 3b. In other words, the air-suction portion 3c has the wall 3c1 extending between the upstream end 3a and the downstream end 3b, and the wall 3c1 of the air-suction portion 3c extends away from the intersection EC in a direction from the intersection EC across the first outline L1. As shown in Fig. 6, the air-suction portion 3c is thus formed in a curved line drawing an arc in the vertical section of the bell mouth 3B.
The air-suction portion 3c extends in a range defined by the virtual first tangent HT2 of the virtual ellipse FL touching the first end G1, the virtual second tangent VT2 of the virtual ellipse FL touching the second end G2, and the first outline L1.
That is, in a range defined by the virtual first tangent HT2 of the virtual ellipse FL touching the upstream end 3a, the virtual second tangent VT2 of the virtual ellipse FL touching the downstream end 3b, and the first outline L1, the air-suction portion 3c has the wall 3c1 extending between the upstream end 3a and the downstream end 3b, and the wall 3c1 of the air-suction portion 3c extends away from the intersection EC in a direction from the intersection EC across the first outline L1. It should be noted that the bell mouth 3B of the centrifugal air-sending device 1B is one obtained by expanding a common bell mouth in an axial direction. As the centrifugal air-sending device 1B has such a shape that the wall 3c1 extending between the upstream end 3a and the downstream end 3b extends away from the intersection EC in a direction from the intersection EC across the first outline L1, the curvature of a portion of the bell mouth 3 close to the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3, is set such that a direction in which the bell mouth 3 extends to the downstream end 3b approximates the axial direction.
As shown in Fig. 6, a distance between the upstream end 3a and the downstream end 3b of the bell mouth 3B in the axial direction of the rotation shaft RS is defined as a second axial direction distance D3. In other words, in a case in which the upstream end 3a and the downstream end 3b of the bell mouth 3B are projected onto the rotation shaft RS in a direction perpendicular to the rotation shaft RS, the second axial direction distance D3 is a distance between the upstream end 3a and the downstream end 3b in a place in which the upstream end 3a and the downstream end 3b are projected onto the rotation shaft RS. It should be noted that the second axial direction distance D3 also corresponds to the radius of the major axis of the virtual ellipse FL. That is, the second axial direction distance D3 is also a distance between the upstream end 3a and the intersection EC in the virtual ellipse FL. Further, in the radial direction from the rotation shaft RS, a distance between the upstream end 3a and the downstream end 3b of the bell mouth 3B is defined as a second radial direction distance D4. In other words, in a plan view of the bell mouth 3B as the bell mouth 3B is seen in the axial direction of the rotation shaft RS, the second radial direction distance D4 is a distance between the upstream end 3a and the downstream end 3b of the bell mouth 3B located on the same virtual plane. It should be noted that the second radial direction distance D4 also corresponds to the radius of the minor axis of the virtual ellipse FL. That is, the second radial direction distance D4 is also a distance between the downstream end 3b and the intersection EC in the virtual ellipse FL.
The bell mouth 3B is formed such that a relationship is satisfied in which the second radial direction distance D4 is less than the second axial direction distance D3. It should be noted that a part of the bell mouth 3B formed such that the relationship is satisfied in which the second radial direction distance D4 is less than the second axial direction distance D3 may be formed on the whole circumference of the bell mouth 3B or may be partially formed in a circumferential direction. The bell mouth 3B of the centrifugal air-sending device 1B is one obtained by expanding a common bell mouth in the axial direction of the rotation shaft RS. As the centrifugal air-sending device 1B has such a shape that the wall 3c1 extending between the upstream end 3a and the downstream end 3b extends away from the intersection EC in a direction from the intersection EC across the first outline L1, the curvature of a portion of the bell mouth 3B close to the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3B, is set such that a direction in which the bell mouth 3B extends to the downstream end 3b approximates the axial direction.

[Advantageous Effects of Centrifugal Air-sending Device 1B]

As described above, the bell mouth 3B is formed such that a relationship is satisfied in which the second radial direction distance D4 is less than the second axial direction distance D3. Moreover, in a vertical section of the bell mouth 3B, the centrifugal air-sending device 1B has such a shape that the wall 3c1 extending between the upstream end 3a and the downstream end 3b extends away from the intersection EC in a direction from the intersection EC across the first outline L1.
The curvature of a portion of the bell mouth 3B of the centrifugal air-sending device 1B close to the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3B, therefore is set such that a direction in which the bell mouth 3B extends to the downstream end 3b approximates the axial direction of the rotation shaft RS. Moreover, the centrifugal air-sending device 1B causes a fast flow of gas flowing into the bell mouth 3B to move along the bell mouth 3B from an outer periphery toward an inner periphery of the bell mouth 3B and causes the flow of the gas to naturally turn into the axial direction in the air-suction portion 3c. As a result, the centrifugal air-sending device 1B reduces flow separation of the gas in the vicinity of the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3B, reduces inflow of a disturbed flow of gas into the impeller 2, and thereby reduces noise. Further, as the bell mouth 3B reduces flow separation of the gas in the vicinity of the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3B, and reduces inflow of a disturbed flow of gas into the impeller 2, the centrifugal air-sending device 1B efficiently suctions air. If the centrifugal air-sending device 1B according to Embodiment 3 is not applied, that is, if a common bell mouth is shaped along the virtual ellipse FL in a case in which the bell mouth is expanded in an axial direction of a rotation shaft, a flow of gas may be separated from the bell mouth at an inner periphery of the bell mouth. The bell mouth 3B of the centrifugal air-sending device 1B according to Embodiment 3, which is formed as described above, makes it possible to reduce flow separation of the gas in the vicinity of the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3B.

Embodiment 4

Fig. 7 is a partially-enlarged view of a bell mouth 3C of a centrifugal air-sending device 1C according to Embodiment 4 of the present disclosure. It should be noted that components that are identical in configuration to those of the centrifugal air-sending device 1 or other devices shown in Figs. 1 to 6 are given identical reference signs and a description of such components is omitted. The centrifugal air-sending device 1C according to Embodiment 4 is one obtained by further specifying the configuration of the bell mouth 3 of the centrifugal air-sending device 1 according to Embodiment 1, and configurations of components other than a configuration of the bell mouth 3C are identical to those in the centrifugal air-sending device 1 according to Embodiment 1. The following thus gives a description with reference to Fig. 7 with a focus on the configuration of the bell mouth 3C of the centrifugal air-sending device 1C according to Embodiment 4. It should be noted that the bell mouth 3C represents an example of a case in which a common bell mouth is expanded in a radial direction.
The bell mouth 3C of the centrifugal air-sending device 1C has walls extending between the upstream end 3a and the downstream end 3b and having curved surfaces differing in radius of curvature from one another. As shown in Fig. 7, the bell mouth 3C has a first wall S1, a second wall S2, and a third wall S3 integrally formed in succession to extend from the downstream end 3b to the upstream end 3a, that is, from an inner periphery to an outer periphery of the bell mouth 3C. The first wall S1, the second wall S2, and the third wall S3 form a curved surface that projects toward the inside of the bell mouth 3C. In a vertical section of the bell mouth 3C, the first wall S1, the second wall S2, and the third wall S3 are formed in circular arc shapes and have curved surfaces differing in radius of curvature from one another. Note here that in the vertical section of the bell mouth 3C, the radius of curvature of the first wall S1 is defined as a first radius of curvature a, the radius of curvature of the second wall S2 is defined as a second radius of curvature b, and the radius of curvature of the third wall S3 is defined as a third radius of curvature c. The first wall S1, the second wall S2, and the third wall S3 of the bell mouth 3C are formed such that a relationship is satisfied in which the third radius of curvature c is greater than the first radius of curvature a and the first radius of curvature a is greater than the second radius of curvature b.

[Advantageous Effects of Centrifugal Air-sending Device 1C]

The bell mouth 3C is one obtained by expanding a common bell mouth in a radial direction. In a vertical section of the bell mouth 3C, the centrifugal air-sending device 1C has such a shape that the wall 3c1 extending between the upstream end 3a and the downstream end 3b extends away from the intersection EC in a direction from the intersection EC across the first outline L1. Further, the bell mouth 3C has a first wall S1, a second wall S2, and a third wall S3 integrally formed in succession to extend from an inner periphery to an outer periphery of the bell mouth 3C.
Moreover, the first wall S1, the second wall S2, and the third wall S3 of the bell mouth 3C are formed such that a relationship is satisfied in which the third radius of curvature c is greater than the first radius of curvature a and the first radius of curvature a is greater than the second radius of curvature b. The bell mouth 3C therefore causes a fast flow of gas flowing into the bell mouth 3C to move along the third wall S3 located at the outer periphery and having the third radius of curvature c, which is large, and then, with the second wall S2 having the second radius of curvature b, which is the smallest, causes the flow of the gas, without direction changed, to move along the bell mouth 3C. Furthermore, with the first wall S1 having the first radius of curvature a, which is the second largest, the bell mouth 3C causes the flow to naturally turn into the axial direction of the rotation shaft RS.
Such a configuration and workings of the bell mouth 3C make it possible to reduce flow separation of the gas in an area extending from an outer edge to an inner edge of the bell mouth 3C, reduce inflow of a disturbed flow of gas into the impeller 2, and thereby reduce noise. Further, as the bell mouth 3C reduces flow separation of the gas in the vicinity of the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3C, and reduces inflow of a disturbed flow of gas into the impeller 2, the centrifugal air-sending device 1C efficiently suctions air.

Embodiment 5

Fig. 8 is a partially-enlarged view of a bell mouth 3D of a centrifugal air-sending device 1D according to Embodiment 5 of the present disclosure. It should be noted that components that are identical in configuration to those of the centrifugal air-sending device 1 or other devices shown in Figs. 1 to 7 are given identical reference signs and a description of such components is omitted. The centrifugal air-sending device 1D according to Embodiment 5 is one obtained by further specifying the configuration of the bell mouth 3 of the centrifugal air-sending device 1 according to Embodiment 1, and configurations of components other than a configuration of the bell mouth 3D are identical to those in the centrifugal air-sending device 1 according to Embodiment 1. The following thus gives a description with reference to Fig. 8 with a focus on the configuration of the bell mouth 3D of the centrifugal air-sending device 1D according to Embodiment 5. It should be noted that the bell mouth 3D represents an example of a case in which a common bell mouth is expanded in a radial direction.
The bell mouth 3D of the centrifugal air-sending device 1D has walls extending between the upstream end 3a and the downstream end 3b and having curved surfaces differing in radius of curvature from each other. As shown in Fig. 8, the bell mouth 3D has a first wall S11 and a second wall S12 integrally formed in succession to extend from the downstream end 3b to the upstream end 3a, that is, from an inner periphery to an outer periphery of the bell mouth 3D. The first wall S11 and the second wall S12 form a curved surface that projects toward the inside of the bell mouth 3D. In a vertical section of the bell mouth 3D, the first wall S11 and the second wall S12 are formed in circular arc shapes and have curved surfaces differing in radius of curvature from each other. Note here that in the vertical section of the bell mouth 3D, the radius of curvature of the first wall S11 is defined as a first radius of curvature a1 and the radius of curvature of the second wall S12 is defined as a second radius of curvature c1. The first wall S11 and the second wall S12 of the bell mouth 3D are formed such that a relationship is satisfied in which the second radius of curvature c1 is greater than the first radius of curvature a1.

[Advantageous Effects of Centrifugal Air-sending Device 1D]

The bell mouth 3D is one obtained by expanding a common bell mouth in a radial direction. In a vertical section of the bell mouth 3D, the centrifugal air-sending device 1D has such a shape that the wall 3c1 extending between the upstream end 3a and the downstream end 3b extends away from the intersection EC in a direction from the intersection EC across the first outline L1. Further, the bell mouth 3D has a first wall S11 and a second wall S12 integrally formed in succession to extend from an inner periphery to an outer periphery of the bell mouth 3D, and the first wall S11 and the second wall S12 of the bell mouth 3D are formed such that a relationship is satisfied in which the second radius of curvature c1 is greater than the first radius of curvature a1. The bell mouth 3D therefore causes a fast flow of gas flowing into the bell mouth 3D to move along the second wall S12 located at the outer periphery and having the second radius of curvature c1, which is large, and then, with the first wall S11 having the first radius of curvature a1, which is the second largest, causes the flow to naturally turn into the axial direction of the rotation shaft RS. Such a configuration and workings of the bell mouth 3D make it possible to reduce flow separation of the gas in an area extending from an outer edge to an inner edge of the bell mouth 3D, reduce inflow of a disturbed flow of gas into the impeller 2, and thereby reduce noise. Further, as the bell mouth 3D reduces flow separation of the gas in the vicinity of the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3D, and reduces inflow of a disturbed flow of gas into the impeller 2, the centrifugal air-sending device 1D efficiently suctions air.

Embodiment 6

Fig. 9 is a partially-enlarged view of a bell mouth 3E of a centrifugal air-sending device 1E according to Embodiment 6 of the present disclosure. It should be noted that components that are identical in configuration to those of the centrifugal air-sending device 1E or other devices shown in Figs. 1 to 8 are given identical reference signs and a description of such components is omitted. The centrifugal air-sending device 1E according to Embodiment 6 is one obtained by further specifying the configuration of the bell mouth 3 of the centrifugal air-sending device 1 according to Embodiment 1, and configurations of components other than a configuration of the bell mouth 3E are identical to those in the centrifugal air-sending device 1 according to Embodiment 1. The following thus gives a description with reference to Fig. 9 with a focus on the configuration of the bell mouth 3E of the centrifugal air-sending device 1E according to Embodiment 6. It should be noted that the bell mouth 3E represents an example of a case in which a common bell mouth is expanded in an axial direction of a rotation shaft.
The bell mouth 3E of the centrifugal air-sending device 1E has walls extending between the upstream end 3a and the downstream end 3b and having curved surfaces differing in radius of curvature from one another. As shown in Fig. 9, the bell mouth 3E has a first wall S21, a second wall S22, and a third wall S23 integrally formed in succession to extend from the downstream end 3b to the upstream end 3a, that is, from an inner periphery to an outer periphery of the bell mouth 3E. The first wall S21, the second wall S22, and the third wall S23 form a curved surface that projects toward the inside of the bell mouth 3E. In a vertical section of the bell mouth 3E, the first wall S21, the second wall S22, and the third wall S23 are formed in circular arc shapes and have curved surfaces differing in radius of curvature from one another. Note here that in the vertical section of the bell mouth 3E, the radius of curvature of the first wall S21 is defined as a first radius of curvature a2, the radius of curvature of the second wall S22 is defined as a second radius of curvature b2, and the radius of curvature of the third wall S23 is defined as a third radius of curvature c2. The first wall S21, the second wall S22, and the third wall S23 of the bell mouth 3E are formed such that a relationship is satisfied in which the first radius of curvature a2 is greater than the third radius of curvature c2 and the third radius of curvature c2 is greater than the second radius of curvature b2.

[Advantageous Effects of Centrifugal Air-sending Device 1E]

The bell mouth 3E is one obtained by expanding a common bell mouth in an axial direction of a rotation shaft. In a vertical section of the bell mouth 3E, the centrifugal air-sending device 1E has such a shape that the wall 3c1 extending between the upstream end 3a and the downstream end 3b extends away from the intersection EC in a direction from the intersection EC across the first outline L1. Further, the bell mouth 3E has a first wall S21, a second wall S22, and a third wall S23 integrally formed in succession to extend from an inner periphery to an outer periphery of the bell mouth 3E. Moreover, the first wall S21, the second wall S22, and the third wall S23 of the bell mouth 3E are formed such that a relationship is satisfied in which the first radius of curvature a2 is greater than the third radius of curvature c2 and the third radius of curvature c2 is greater than the second radius of curvature b2. The bell mouth 3E therefore causes a fast flow of gas flowing into the bell mouth 3E to move along the third wall S23 located at the outer periphery and having the third radius of curvature c2, which is large, and then, with the second wall S22 having the second radius of curvature b2, which is the smallest, causes the flow of the gas, without direction changed, to move along the bell mouth 3E. Furthermore, with the first wall S21 having the first radius of curvature a2, which is the largest, the bell mouth 3E causes the flow to naturally turn into the axial direction of the rotation shaft RS. Such a configuration and workings of the bell mouth 3E make it possible to reduce flow separation of the gas in an area extending from an outer edge to an inner edge of the bell mouth 3E, reduce inflow of a disturbed flow of gas into the impeller 2, and thereby reduce noise. Further, as the bell mouth 3E reduces flow separation of the gas in the vicinity of the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3E, and reduces inflow of a disturbed flow of gas into the impeller 2, the centrifugal air-sending device 1E efficiently suctions air.

Embodiment 7

Fig. 10 is a partially-enlarged view of a bell mouth 3F of a centrifugal air-sending device 1F according to Embodiment 7 of the present disclosure. It should be noted that components that are identical in configuration to those of the centrifugal air-sending device 1 or other devices shown in Figs. 1 to 9 are given identical reference signs and a description of such components is omitted. The centrifugal air-sending device 1F according to Embodiment 7 is one obtained by further specifying the configuration of the bell mouth 3 of the centrifugal air-sending device 1 according to Embodiment 1, and configurations of components other than a configuration of the bell mouth 3F are identical to those in the centrifugal air-sending device 1 according to Embodiment 1. The following thus gives a description with reference to Fig. 10 with a focus on the configuration of the bell mouth 3F of the centrifugal air-sending device 1F according to Embodiment 7. It should be noted that the bell mouth 3F represents an example of a case in which a common bell mouth is expanded in an axial direction of a rotation shaft.
The bell mouth 3F of the centrifugal air-sending device 1F has walls extending between the upstream end 3a and the downstream end 3b and having curved surfaces differing in radius of curvature from each other. As shown in Fig. 10, the bell mouth 3F has a first wall S31 and a second wall S32 integrally formed in succession to extend from the downstream end 3b to the upstream end 3a, that is, from an inner periphery to an outer periphery of the bell mouth 3F. The first wall S31 and the second wall S32 form a curved surface that projects toward the inside of the bell mouth 3F. In a vertical section of the bell mouth 3F, the first wall S31 and the second wall S32 are formed in circular arc shapes and have curved surfaces differing in radius of curvature from each other. Note here that in the vertical section of the bell mouth 3F, the radius of curvature of the first wall S31 is defined as a first radius of curvature a3 and the radius of curvature of the second wall S32 is defined as a second radius of curvature c3. The first wall S31 and the second wall S32 of the bell mouth 3F are formed such that a relationship is satisfied in which the first radius of curvature a3 is greater than the second radius of curvature c3.

[Advantageous Effects of Centrifugal Air-sending Device 1F]

The bell mouth 3F is one obtained by expanding a common bell mouth in an axial direction of a rotation shaft. In a vertical section of the bell mouth 3F, the centrifugal air-sending device 1F has such a shape that the wall 3c1 extending between the upstream end 3a and the downstream end 3b extends away from the intersection EC in a direction from the intersection EC across the first outline L1. Further, the bell mouth 3F has a first wall S31 and a second wall S32 integrally formed in succession to extend from an inner periphery to an outer periphery of the bell mouth 3F, and the first wall S31 and the second wall S32 of the bell mouth 3F are formed such that a relationship is satisfied in which the first radius of curvature a3 is greater than the second radius of curvature c3. The bell mouth 3F therefore causes a fast flow of gas flowing into the bell mouth 3F to move along the second wall S32 located at the outer periphery and having the second radius of curvature c3, which is large, and then, with the first wall S31 having the first radius of curvature a1, which is the largest, causes the flow to naturally turn into the axial direction of the rotation shaft RS. Such a configuration and workings of the bell mouth 3F make it possible to reduce flow separation of the gas in an area extending from an outer edge to an inner edge of the bell mouth 3F, reduce inflow of a disturbed flow of gas into the impeller 2, and thereby reduce noise. Further, as the bell mouth 3F reduces flow separation of the gas in the vicinity of the downstream end 3b, which corresponds to the innermost diameter of the bell mouth 3F, and reduces inflow of a disturbed flow of gas into the impeller 2, the centrifugal air-sending device 1E efficiently suctions air.

Embodiment 8

Fig. 11 is a partially-enlarged view of a bell mouth 3G of a centrifugal air-sending device 1G according to Embodiment 8 of the present disclosure. It should be noted that components that are identical in configuration to those of the centrifugal air-sending device 1 or other devices shown in Figs. 1 to 10 are given identical reference signs and a description of such components is omitted. The centrifugal air-sending device 1G according to Embodiment 8 is one obtained by further specifying the configuration of the bell mouth 3 of the centrifugal air-sending device 1 according to Embodiment 1, and configurations of components other than a configuration of the bell mouth 3G are identical to those in the centrifugal air-sending device 1 according to Embodiment 1. The following thus gives a description with reference to Fig. 11 with a focus on the configuration of the bell mouth 3G of the centrifugal air-sending device 1G according to Embodiment 8.
The bell mouth 3G has its downstream end 3b disposed on a virtual first plane P1 perpendicular to the rotation shaft RS. In other words, the downstream end 3b of the bell mouth 3G is formed in a ring shape in the bell mouth 3G, and the virtual first plane P1 including the downstream end 3b formed in the ring shape is a plane perpendicular to the rotation shaft RS. Further, the bell mouth 3G has its upstream end 3a disposed on a virtual second plane P2 perpendicular to the rotation shaft RS. In other words, the upstream end 3a of the bell mouth 3G is formed in a ring shape in the bell mouth 3G, and the virtual second plane P2 including the upstream end 3a formed in the ring shape is a plane perpendicular to the rotation shaft RS. Moreover, the virtual first plane P1 and the virtual second plane P2 are parallel to each other.

[Advantageous Effects of Centrifugal Air-sending Device 1G]

As described above, the bell mouth 3G has its downstream end 3b disposed on a virtual first plane P1 perpendicular to the rotation shaft RS. Further, the bell mouth 3G has its upstream end 3a disposed on a virtual second plane P2 perpendicular to the rotation shaft RS. Such a configuration of the bell mouth 3G makes it hard for pressure fluctuations to occur because of air being suctioned into the centrifugal air-sending device 1G. The centrifugal air-sending device 1G therefore minimizes the effect of a loss of pressure in a unit such as an outdoor unit when the centrifugal air-sending device 1G is mounted in the unit.

Embodiment 9

Fig. 12 is a side view of a centrifugal air-sending device 1H according to Embodiment 9 of the present disclosure. Fig. 13 is a cross-sectional view of the centrifugal air-sending device 1H shown in Fig. 12 taken along line B-B. Fig. 14 is a cross-sectional view of the centrifugal air-sending device 1H shown in Fig. 12 taken along line C-C. It should be noted that components that are identical in configuration to those of the centrifugal air-sending devices 1 to 1G or other devices shown in Figs. 1 to 11 are given identical reference signs and a description of such components is omitted.
As shown Fig. 12, in a range of a single rotation in a circumferential direction along the direction of rotation R of the impeller 2 from the tongue 43, the bell mouth 3 of the centrifugal air-sending device 1H has a part of the wall 3c1 of the air-suction portion 3c that is larger in width in a radial direction than is a part of the wall 3c1 located at the tongue 43. For example, as shown in Figs. 13 and 14, in a direction in which the bell mouth 3 extends from the tongue 43 toward the scroll end portion 41b and returns to the tongue 43 along the direction of rotation R of the impeller 2, a width of the bell mouth 3 in a radial direction gradually increases in the order of W1, W2, and then W3 and gradually decreases in the order of W3, W4, and then W1.
That is, the bell mouth 3 is formed such that during a single rotation along the direction of rotation R of the impeller 2 from the tongue 43, the width of the wall 3c1 of the air-suction portion 3c gradually increases in a radial direction and the width of the wall 3c1 gradually returns to its original size while the wall 3c1 is returning to the tongue 43 from a place where the width of the wall 3c1 is at its maximum. A configuration of the bell mouth 3 shown in Figs. 12, 13, and 14 is an example. In a circumferential direction of the bell mouth 3, the place where the width of the wall 3c1 of the air-suction portion 3c is at its maximum in a radial direction is determined, for example, by a relationship with an apparatus in which the centrifugal air-sending device 1H is installed. In Figs. 13 and 14, the bell mouth 3 is formed in the same configuration at each of the inlet ports 5 of the double suction centrifugal air-sending device 1. Alternatively, the width of the wall 3c1 of the bell mouth 3 may increase differently for each inlet port 5.
Further, the bell mouth 3 is formed such that in a range of a single rotation in a circumferential direction along the direction of rotation R of the impeller 2 from the tongue 43, the width of the wall 3c1 of the air-suction portion 3c increases in a radial direction and the radius of curvature of an inner periphery of the wall 3c1 gradually increases. Moreover, in a range of a single rotation in a circumferential direction along the direction of rotation R of the impeller 2 from the tongue 43, the wall 3c1 of the air-suction portion 3c has a part where the radius of curvature of the inner periphery of the wall 3c1 is at its maximum. The term "inner periphery" here refers to a part of the wall 3c1 of the air-suction portion 3c that is closer to the downstream end 3b than the upstream end 3a.
Further, the air-suction portion 3c of the bell mouth 3 is formed such that in a circumferential direction in which the wall 3c1 returns to the tongue 43 from the part where the radius of curvature of the inner periphery of the wall 3c1 is at its maximum, the width of the wall 3c1 in a radial direction decreases and the radius of curvature of the inner periphery of the wall 3c1 gradually decreases. Moreover, the air-suction portion 3c of the bell mouth 3 is formed such that in the circumferential direction in which the wall 3c1 returns to the tongue 43 from the part where the radius of curvature of the inner periphery of the wall 3c1 is at its maximum, the radius of curvature of the inner periphery gradually returns to the original radius of curvature at the tongue 43.
That is, the bell mouth 3 is formed such that in a circumferential direction, the width of the wall 3c1 of the air-suction portion 3c increases in a radial direction and the radius of curvature of the inner periphery of the wall 3c1 increases and such that in the circumferential direction, the width of the wall 3c1 in a radial direction decreases and the radius of curvature of the inner periphery of the wall 3c1 decreases. As mentioned above, the configuration of the bell mouth 3 shown in Figs. 12, 13, and 14 is an example. In the circumferential direction of the bell mouth 3, the place where the radius of curvature of the inner periphery of the wall 3c1 of the air-suction portion 3c is at its maximum is determined, for example, by a relationship with an apparatus in which the centrifugal air-sending device 1H is installed. In Figs. 13 and 14, the bell mouth 3 is formed in the same configuration at each of the inlet ports 5 of the double suction centrifugal air-sending device 1. Alternatively, the radius of curvature of the wall 3c1 of the bell mouth 3 may be different for each inlet port 5.
The bell mouth 3 is formed such that the position in which the upstream end 3a of the bell mouth 3 is formed against the main plate 2a of the impeller 2, which is used as the reference position, changes along with the increase in the radius of curvature of the inner periphery of the wall 3c1 of the air-suction portion 3c. More specifically, in the circumferential direction of the bell mouth 3, the distance of the upstream end 3a of the bell mouth 3 from the main plate 2a of the impeller 2 increases along with the increase in the radius of curvature of the inner periphery of the wall 3c1. That is, the position of the upstream end 3a of the bell mouth 3 against the main plate 2a of the impeller 2 changes along the direction of rotation R of the impeller 2.

[Advantageous Effects of Centrifugal Air-sending Device 1H]

At a place other than the tongue 43 in a circumferential direction, the bell mouth 3 of the centrifugal air-sending device 1H is formed to be large in size of the wall of the air-suction portion 3c in a radial direction and large in radius of curvature at the inner periphery of the bell mouth 3. Such a configuration of the centrifugal air-sending device 1H reduces separation from the bell mouth 3 of a fast flow of gas flowing through the bell mouth 3. The centrifugal air-sending device 1H therefore increases air-sending efficiency and reduces noise.

Embodiment 10

[Air-sending Apparatus 30]

Fig. 15 is a diagram showing a configuration of an air-sending apparatus 30 according to Embodiment 10 of the present disclosure. Components that are identical in configuration to those of the centrifugal air-sending device 1 or other devices shown in Figs. 1 to 14 are given identical reference signs, and a description of such components is omitted. The air-sending apparatus 30 according to Embodiment 10 is, for example, a ventilation fan or a desk-top fan. The air-sending apparatus 30 includes any one of the centrifugal air-sending devices 1 to 1H according to Embodiments 1 to 9 and a case 7 accommodating the centrifugal air-sending device 1 or other devices. In the following description, the term "centrifugal air-sending device 1" refers to any one of the centrifugal air-sending devices 1 to 1H according to Embodiments 1 to 9. The case 7 has two openings, namely an inlet port 71 and a discharge port 72, formed in the case 7. As shown in Fig. 15, the air-sending apparatus 30 is formed in a place in which the inlet port 71 and the discharge port 72 face each other. It should be noted that the air-sending apparatus 30 does not necessarily need to be formed in a place in which the inlet port 71 and the discharge port 72 face each other. For example, either one of the inlet port 71 and the discharge port 72 may be formed above or below the centrifugal air-sending device 1. The interior of the case 7 is divided by a divider 73 into a space SP1 including a part of the case 7 in which the inlet port 71 is formed and a space SP2 including a part of the case 7 in which the discharge port 72 is formed. The centrifugal air-sending device 1 has its inlet ports 5 located in the space SP1, in which the inlet port 71 is formed, and has its discharge port 42a located in the space SP2, in which the discharge port 72 is formed.
The air-sending apparatus 30 is configured such that rotation of the impeller 2 by driving of a motor 6 causes air to be suctioned into the case 7 through the inlet port 71. The air suctioned into the case 7 is guided to the bell mouth 3 and suctioned into the impeller 2. The air suctioned into the impeller 2 is blown out outward in the radial directions of the impeller 2. The air blown out from the impeller 2 passes through the inside of the fan casing 4 first, is blown out from the fan casing 4 through the discharge port 42a, and then is blown out from the case 7 through the discharge port 72.
The air-sending apparatus 30 according to Embodiment 10, which includes any one of the centrifugal air-sending devices 1 to 1H according to Embodiments 1 to 9, achieves a reduction of noise and efficiently suctions air.

Embodiment 11

[Air-conditioning Apparatus 40]

Fig. 16 is a perspective view of an air-conditioning apparatus 40 according to Embodiment 11 of the present disclosure. Fig. 17 is a diagram showing an internal configuration of the air-conditioning apparatus 40 according to Embodiment 11 of the present disclosure. Fig. 18 is a cross-sectional view of the air-conditioning apparatus 40 according to Embodiment 11 of the present disclosure. Fig. 19 is another cross-sectional view of the air-conditioning apparatus 40 according to Embodiment 11 of the present disclosure. It should be noted that components that are identical in configuration to those of the centrifugal air-sending devices 1 shown in Figs. 1 to 15 are given identical reference signs and a description of such components is omitted. Further, an upper surface 16a is omitted from Fig. 17 to show an internal configuration of the air-conditioning apparatus 40. The air-conditioning apparatus 40 according to Embodiment 11 includes any one or more of the centrifugal air-sending devices 1 to 1H according to Embodiments 1 to 9 and a heat exchanger 10 disposed in a place facing the discharge port 42a of the centrifugal air-sending device 1 or other devices. Further, the air-conditioning apparatus 40 according to Embodiment 11 includes a case 16 placed above a ceiling of a room to be air-conditioned. In the following description, the term "centrifugal air-sending device 1" refers to any one of the centrifugal air-sending devices 1 to 1H according to Embodiments 1 to 9. Further, the term "bell mouth 3" refers to any one of the aforementioned bell mouths 3 to 3G.

(Case 16)

As shown in Fig. 16, the case 16 is formed in a cuboidal shape including the upper surface 16a, a lower surface 16b, and side surfaces 16c. The shape of the case 16 is not limited to the cuboidal shape but may be another shape such as a columnar shape, a prismatic shape, a conical shape, a shape having a plurality of corners, and a shape having a plurality of curved surfaces. One of the side surfaces 16c of the case 16 is a side surface 16c in which a case discharge port 17 is formed. As shown in Fig. 16, the case discharge port 17 is formed in a rectangular shape. The shape of the case discharge port 17 is not limited to the rectangular shape but may be another shape such as a circular shape and an oval shape. One of the side surfaces 16c of the case 16 located behind the surface in which the case discharge port 17 is formed is a side surface 16c in which a case inlet port 18 is formed. As shown in Fig. 17, the case inlet port 18 is formed in a rectangular shape. The shape of the case inlet port 18 is not limited to the rectangular shape but may be another shape such as a circular shape and an oval shape. A filter formed to remove dust from air may be disposed in the case inlet port 18.
The case 16 has two centrifugal air-sending devices 1, a fan motor 9, and a heat exchanger 10, which are accommodated in the case 16. Each of the centrifugal air-sending devices 1 includes an impeller 2 and a fan casing 4 having a bell mouth 3 formed in the fan casing 4. The fan motor 9 is supported by a motor support 9a fixed to the upper surface 16a of the case 16. The fan motor 9 has an output shaft 6a. The output shaft 6a is disposed to extend parallel to the side surface 16c in which the case inlet port 18 is formed and parallel to the side surface 16c in which the case discharge port 17 is formed. As shown in Fig. 17, the air-conditioning apparatus 40 has two impellers 2 attached to the output shaft 6a. The impellers 2 form a flow of air that is suctioned into the case 16 through the case inlet port 18 and blown out through the case discharge port 17 into an air-conditioned space. The number of centrifugal air-sending devices 1 that are disposed in the case 16 is not limited to two but may be one or three or more. While the aforementioned configuration in which the curvature of a portion of the bell mouth 3 changes can be applied to the whole circumference of the bell mouth 3 of a centrifugal air-sending device 1 used in the air-conditioning apparatus 40, the aforementioned effects are more remarkably achieved in a case in which the aforementioned configuration is applied to a part of the whole circumference of the bell mouth 3 facing the case inlet port 18. That is, the application of the aforementioned configuration in which the curvature of a portion of the bell mouth 3 changes to a part of the whole circumference of the bell mouth 3 in which a large amount of flow of gas flows into the bell mouth 3 is effective.
As shown in Fig. 17, the centrifugal air-sending devices 1 are attached to a divider 19, and a space in the case 16 is divided by the divider 19 into a space SP11 from which air is suctioned into the fan casings 4 and a space SP12 from which air is blown out from the fan casings 4.
As shown in Fig. 18, the heat exchanger 10 is disposed in a place facing the discharge port 42a of each of the centrifugal air-sending devices 1, and is disposed in the case 16 to be on an air passage on which air is discharged by the centrifugal air-sending devices 1. The heat exchanger 10 adjusts the temperature of air that is suctioned into the case 16 through the case inlet port 18 and blown out through the case discharge port 17 into the air-conditioned space. As the heat exchanger 10, a heat exchanger having a publicly-known structure may be applied. Further, the case inlet port 18 needs only be formed in a place perpendicular to the axial direction of the rotation shaft RS of each of the centrifugal air-sending devices 1. For example, as shown in Fig. 19, a case inlet port 18a may be formed in the lower surface 16b. In this case, while the aforementioned configuration in which the curvature of a portion of the bell mouth 3 changes can be applied to the whole circumference of the bell mouth 3 of a centrifugal air-sending device 1 used in the air-conditioning apparatus 40, the aforementioned effects are more remarkably achieved in a case in which the aforementioned configuration is applied to a part of the whole circumference of the bell mouth 3 facing the case inlet port 18a. That is, the application of the aforementioned configuration in which the curvature of a portion of the bell mouth 3 changes to a part of the whole circumference of the bell mouth 3 in which a large amount of flow of gas flows into the bell mouth 3 is effective.
Rotation of the impellers 2 by driving of the motor 6 causes air in the air-conditioned space to be suctioned into the case 16 through the case inlet port 18 or the case inlet port 18a. The air suctioned into the case 16 is guided to the bell mouths 3 and suctioned into the impellers 2. The air suctioned into the impellers 2 is blown out outward in the radial directions of the impellers 2. The air blown out from the impellers 2 passes through the inside of the fan casings 4 first, is blown out from the fan casings 4 through the discharge ports 42a, and then is supplied to the heat exchanger 10. The air supplied to the heat exchanger 10 has its temperature and humidity adjusted by exchanging heat when the air is passing through the heat exchanger 10. The air having passed through the heat exchanger 10 is blown out through the case discharge port 17 into the air-conditioned space.
The air-conditioning apparatus 40 according to Embodiment 11, which includes any one of the centrifugal air-sending devices 1 to 1H according to Embodiments 1 to 9, achieves a reduction of noise and efficiently suctions air.

Embodiment 12

[Refrigeration Cycle Apparatus 50]

Fig. 20 is a diagram showing a configuration of a refrigeration cycle apparatus 50 according to Embodiment 12 of the present disclosure. As an indoor unit 200 of the refrigeration cycle apparatus 50 according to Embodiment 12, any one of the centrifugal air-sending devices 1 to 1H according to Embodiments 1 to 9 is used. Further, although the following describes a case in which the refrigeration cycle apparatus 50 is used for an air-conditioning purpose, the refrigeration cycle apparatus 50 is not limited to being used for an air-conditioning purpose. The refrigeration cycle apparatus 50 is used for a refrigerating purpose or an air-conditioning purpose, for example, in a refrigerator, a freezer, an automatic vending machine, an air-conditioning apparatus, a refrigeration apparatus, or a water heater.
The refrigeration cycle apparatus 50 according to Embodiment 12 performs air conditioning by heating or cooling the air in a room by transferring heat between outside air and the air in the room via refrigerant. The refrigeration cycle apparatus 50 according to Embodiment 12 includes an outdoor unit 100 and the indoor unit 200. The refrigeration cycle apparatus 50 is formed such that the outdoor unit 100 and the indoor unit 200 are connected by a refrigerant pipe 300 and a refrigerant pipe 400 to form a refrigerant circuit through which refrigerant circulates. The refrigerant pipe 300 is a gas pipe through which gas-phase refrigerant flows, and the refrigerant pipe 400 is a liquid pipe through which liquid-phase refrigerant flows. Two-phase gas-liquid refrigerant may flow through the refrigerant pipe 400. Moreover, in the refrigerant circuit of the refrigeration cycle apparatus 50, a compressor 101, a flow switching device 102, an outdoor heat exchanger 103, an expansion valve 105, and an indoor heat exchanger 201 are connected in sequence via the refrigerant pipes.

(Outdoor Unit 100)

The outdoor unit 100 includes the compressor 101, the flow switching device 102, the outdoor heat exchanger 103, and the expansion valve 105. The compressor 101 compresses and discharges suctioned refrigerant. The compressor 101 may include an inverter device, and may be configured such that a capacity of the compressor 101 can be changed by a variation in operating frequency by the inverter device. The capacity of the compressor 101 is the amount of refrigerant that the compressor 101 sends out per unit time. The flow switching device 102 is, for example, a four-way valve, and is a device configured to switch directions of refrigerant flow passages. The refrigeration cycle apparatus 50 is configured to operate heating operation or cooling operation by switching the flows of refrigerant through the use of the flow switching device 102 in accordance with an instruction from a controller 110.
The outdoor heat exchanger 103 allows heat exchange between refrigerant and outdoor air. The outdoor heat exchanger 103 is used as an evaporator during heating operation to allow heat exchange between low-pressure refrigerant having flowed in from the refrigerant pipe 400 and outdoor air to evaporate and gasify the refrigerant. The outdoor heat exchanger 103 is used as a condenser during cooling operation to allow heat exchange between refrigerant having flowed in from the flow switching device 102 and compressed by the compressor 101 and outdoor air to condense and liquefy the refrigerant. The outdoor heat exchanger 103 is provided with an outdoor air-sending device 104 to enhance the efficiency of heat exchange between refrigerant and outdoor air. An inverter device may be attached to the outdoor air-sending device 104 to change the rotational speed of a fan by varying the operating frequency of a fan motor. The expansion valve 105 is an expansion device (flow rate control unit), is used as an expansion valve by adjusting the flow rate of refrigerant flowing through the expansion valve 105, and adjusts the pressure of refrigerant by varying an opening degree of the expansion valve 105. For example, in a case in which the expansion valve 105 is an electronic expansion valve or other valves, the opening degree is adjusted in accordance with an instruction from the controller 110.

(Indoor Unit 200)

The indoor unit 200 includes an indoor heat exchanger 201 allowing heat exchange between refrigerant and indoor air and an indoor air-sending device 202 configured to adjust a flow of air that is subjected to heat exchange by the indoor heat exchanger 201. The indoor heat exchanger 201 is used as a condenser during heating operation to allow heat exchange between refrigerant having flowed in from the refrigerant pipe 300 and indoor air to condense and liquefy the refrigerant and cause the refrigerant to flow out toward the refrigerant pipe 400. The indoor heat exchanger 201 is used as an evaporator during cooling operation to allow heat exchange between refrigerant brought into a low-pressure state by the expansion valve 105 and indoor air to evaporate and gasify the refrigerant by causing the refrigerant to remove heat from the air and cause the refrigerant to flow out toward the refrigerant pipe 300. The indoor air-sending device 202 is provided to face the indoor heat exchanger 201. As the indoor air-sending device 202, any one or more of the centrifugal air-sending devices 1 to 1H according to Embodiments 1 to 8 are applied. The operating speed of the indoor air-sending device 202 is determined by a user's setting. An inverter device may be attached to the indoor air-sending device 202 to change the rotational speed of the impeller 2 by varying the operating frequency of a fan motor, which is not illustrated.

[Example Actions of Refrigeration Cycle Apparatus 50]

Next, actions of cooling operation are described as example actions of the refrigeration cycle apparatus 50. High-temperature and high-pressure gas refrigerant compressed and discharged by the compressor 101 flows into the outdoor heat exchanger 103 via the flow switching device 102. The gas refrigerant having flowed into the outdoor heat exchanger 103 is condensed into low-temperature refrigerant by exchanging heat with outside air sent by the outdoor air-sending device 104 and flows out from the outdoor heat exchanger 103. The refrigerant having flowed out from the outdoor heat exchanger 103 is expanded and decompressed by the expansion valve 105 and turns into low-temperature and low-pressure two-phase gas-liquid refrigerant. This two-phase gas-liquid refrigerant flows into the indoor heat exchanger 201 of the indoor unit 200, evaporates by exchanging heat with indoor air sent by the indoor air-sending device 202, and turns into low-temperature and low-pressure gas refrigerant that flows out from the indoor heat exchanger 201. At this point in time, indoor air cooled by having its heat removed by the refrigerant turns into air-conditioning air that is blown out through a discharge port of the indoor unit 200 into an air-conditioned space. The gas refrigerant having flowed out from the indoor heat exchanger 201 is suctioned into the compressor 101 via the flow switching device 102 and compressed again. These actions are repeated.
Next, actions of heating operation are described as example actions of the refrigeration cycle apparatus 50. High-temperature and high-pressure gas refrigerant compressed and discharged by the compressor 101 flows into the indoor heat exchanger 201 of the indoor unit 200 via the flow switching device 102. The gas refrigerant having flowed into the indoor heat exchanger 201 condenses by exchanging heat with indoor air sent by the indoor air-sending device 202 and turns into low-temperature refrigerant that flows out from the indoor heat exchanger 201. At this point in time, indoor air heated by receiving heat from the gas refrigerant turns into air-conditioning air that is blown out through the discharge port of the indoor unit 200 into the air-conditioned space. The refrigerant having flowed out from the indoor heat exchanger 201 is expanded and decompressed by the expansion valve 105 and turns into low-temperature and low-pressure two-phase gas-liquid refrigerant. This two-phase gas-liquid refrigerant flows into the outdoor heat exchanger 103 of the outdoor unit 100, evaporates by exchanging heat with outside air sent by the outdoor air-sending device 104, and turns into low-temperature and low-pressure gas refrigerant that flows out from the outdoor heat exchanger 103. The gas refrigerant having flowed out from the outdoor heat exchanger 103 is suctioned into the compressor 101 via the flow switching device 102 and compressed again. These actions are repeated.
The refrigeration cycle apparatus 50 according to Embodiment 12, which includes any one of the centrifugal air-sending devices 1 to 1H according to Embodiments 1 to 9, achieves a reduction of noise and efficiently suctions air.
The configurations shown in the foregoing embodiments show examples of contents of the present disclosure and may be combined with another publicly-known technology, and parts of the configurations may be omitted or changed, as long as the configurations whose parts thus omitted or changed do not depart from the scope of the present disclosure. For example, in Embodiment 4, the bell mouth 3C has a first wall S1, a second wall S2, and a third wall S3 integrally formed in succession to extend from the downstream end 3b to the upstream end 3a, that is, from an inner periphery to an outer periphery of the bell mouth 3C. Instead of having three walls differing in radius of curvature from one another, the bell mouth 3C may have four or more walls differing in radius of curvature from one another. Similarly, in Embodiment 6, the bell mouth 3E has a first wall S21, a second wall S22, and a third wall S23 integrally formed in succession to extend from the downstream end 3b to the upstream end 3a, that is, from an inner periphery to an outer periphery of the bell mouth 3E. Instead of having three walls differing in radius of curvature from one another, the bell mouth 3E may have four or more walls differing in radius of curvature from one another.

Reference Signs List

1 centrifugal air-sending device 1A centrifugal air-sending device 1B centrifugal air-sending device 1C centrifugal air-sending device 1D centrifugal air-sending device 1E centrifugal air-sending device 1F centrifugal air-sending device 1G centrifugal air-sending device 1H centrifugal air-sending device 2 impeller 2a main plate 2a1 peripheral edge 2b shaft portion 2c side plate 2d blade 2e inlet port 3 bell mouth 3A bell mouth 3B bell mouth 3C bell mouth 3D bell mouth 3E bell mouth 3F bell mouth 3G bell mouth 3a upstream end 3b downstream end 3c air-suction portion 3c1 wall 4 fan casing 4a side wall 4c peripheral wall 5 inlet port 6 motor 6a output shaft 7 case 9 fan motor 9a motor support 10 heat exchanger 16 case 16a upper surface 16b lower surface 16c side surface 17 case discharge port 18 case inlet port 18a case inlet port 19 divider 30 air-sending apparatus 40 air-conditioning apparatus 41 scroll portion 41a scroll start portion 41b scroll end portion 42 discharge portion 42a discharge port 42b extension plate 42c diffuser plate 42d first side plate 42e second side plate 43 tongue 50 refrigeration cycle apparatus 71 inlet port 72 discharge port 73 divider 100 outdoor unit 101 compressor 102 flow switching device 103 outdoor heat exchanger 104 outdoor air-sending device 105 expansion valve 110 controller 200 indoor unit 201 indoor heat exchanger 202 indoor air-sending device 300 refrigerant pipe 400 refrigerant pipe

Claims

A centrifugal air-sending device, comprising:
an impeller having a main plate having a disk shape and a plurality of blades arranged on a peripheral edge of the main plate; and

a fan casing accommodating the impeller and having a bell mouth formed to rectify a flow of gas to be suctioned into the impeller,

the bell mouth having

an inlet port through which the gas flows into the fan casing, and

an air-suction portion having an opening having a diameter gradually decreasing from an upstream end toward a downstream end of the air-suction portion in a direction of the flow of the gas to be suctioned into the fan casing,

in a vertical section of the bell mouth, in a case in which the upstream end is defined as one of a vertex of a major axis and a vertex of a minor axis of a virtual ellipse, the downstream end is defined as an other one of the vertex of the major axis and the vertex of the minor axis of the virtual ellipse, an intersection of the major axis and the minor axis is defined to be further away from a rotation shaft of the impeller than is the downstream end, and a part of an outline of the virtual ellipse having a shortest distance connecting the upstream end and the downstream end along the outline of the virtual ellipse is defined as a first outline, and

in a range defined by a virtual first tangent of the virtual ellipse touching the upstream end, a virtual second tangent of the virtual ellipse touching the downstream end, and the first outline,

the air-suction portion having a wall extending between the upstream end and the downstream end, the wall of the air-suction portion extending away from the intersection in a direction from the intersection across the first outline.
The centrifugal air-sending device of claim 1, wherein, in the vertical section of the bell mouth, the minor axis of the virtual ellipse extends from the upstream end into the fan casing, and the major axis of the virtual ellipse extends from the downstream end in a direction parallel to a radial direction of the impeller.
The centrifugal air-sending device of claim 1, wherein, in the vertical section of the bell mouth, the major axis of the virtual ellipse extends from the upstream end into the fan casing, and the minor axis of the virtual ellipse extends from the downstream end in a direction parallel to a radial direction of the impeller.
The centrifugal air-sending device of claim 1 or 2, wherein, in a case in which in the vertical section of the bell mouth, a distance between the upstream end and the intersection of the virtual ellipse is defined as a first axial direction distance and a distance between the downstream end and the intersection of the virtual ellipse is defined as a first radial direction distance, the bell mouth is formed such that a relationship is satisfied in which the first radial direction distance is greater than the first axial direction distance.
The centrifugal air-sending device of claim 1 or 3, wherein, in a case in which in the vertical section of the bell mouth, a distance between the upstream end and the intersection of the virtual ellipse is defined as a second axial direction distance and a distance between the downstream end and the intersection of the virtual ellipse is defined as a second radial direction distance, the bell mouth is formed such that a relationship is satisfied in which the second radial direction distance is less than the second axial direction distance.
The centrifugal air-sending device of claim 1 or 2, wherein
the bell mouth has a first wall, a second wall, and a third wall integrally formed in succession to extend from the downstream end to the upstream end,

in the vertical section of the bell mouth, the first wall, the second wall, and the third wall are formed in circular arc shapes and have curved surfaces differing in radius of curvature from one another, and

in a case in which a radius of curvature of the first wall is defined as a first radius of curvature, a radius of curvature of the second wall is defined as a second radius of curvature, and a radius of curvature of the third wall is defined as a third radius of curvature, the bell mouth is formed such that a relationship is satisfied in which the third radius of curvature is greater than the first radius of curvature and the first radius of curvature is greater than the second radius of curvature.
The centrifugal air-sending device of claim 1 or 2, wherein
the bell mouth has a first wall and a second wall integrally formed in succession to extend from the downstream end to the upstream end,

in the vertical section of the bell mouth, the first wall and the second wall are formed in circular arc shapes and have curved surfaces differing in radius of curvature from each other, and

in a case in which a radius of curvature of the first wall is defined as a first radius of curvature and a radius of curvature of the second wall is defined as a second radius of curvature, the bell mouth is formed such that a relationship is satisfied in which the second radius of curvature is greater than the first radius of curvature.
The centrifugal air-sending device of claim 1 or 3, wherein
the bell mouth has a first wall, a second wall, and a third wall integrally formed in succession to extend from the downstream end to the upstream end,

in the vertical section of the bell mouth, the first wall, the second wall, and the third wall are formed in circular arc shapes and have curved surfaces differing in radius of curvature from one another, and

in a case in which a radius of curvature of the first wall is defined as a first radius of curvature, a radius of curvature of the second wall is defined as a second radius of curvature, and a radius of curvature of the third wall is defined as a third radius of curvature, the bell mouth is formed such that a relationship is satisfied in which the first radius of curvature is greater than the third radius of curvature and the third radius of curvature is greater than the second radius of curvature.
The centrifugal air-sending device of claim 1 or 3, wherein
the bell mouth has a first wall and a second wall integrally formed in succession to extend from the downstream end to the upstream end,

in the vertical section of the bell mouth, the first wall and the second wall are formed in circular arc shapes and have curved surfaces differing in radius of curvature from each other, and

in a case in which a radius of curvature of the first wall is defined as a first radius of curvature and a radius of curvature of the second wall is defined as a second radius of curvature, the bell mouth is formed such that a relationship is satisfied in which the first radius of curvature is greater than the second radius of curvature.
The centrifugal air-sending device of any one of claims 1 to 9, wherein
the downstream end of the bell mouth is disposed on a virtual first plane perpendicular to the rotation shaft of the impeller, and

the upstream end of the bell mouth is disposed on a second plane parallel to the virtual first plane.
The centrifugal air-sending device of any one of claims 1 to 10, wherein, during a single rotation in a circumferential direction along a direction of rotation of the impeller from a tongue, the air-suction portion has a part formed to be larger in a radial direction than is a part of the air-suction portion located at the tongue and be large in radius of curvature at an inner periphery.
An air-sending apparatus, comprising:
the centrifugal air-sending device of any one of claims 1 to 11; and

a case accommodating the centrifugal air-sending device.
An air-conditioning apparatus, comprising:
the centrifugal air-sending device of any one of claims 1 to 11; and

a heat exchanger disposed in a place facing a discharge port of the centrifugal air-sending device.
A refrigeration cycle apparatus, comprising the centrifugal air-sending device of any one of claims 1 to 11.