US20050084397A1

US20050084397A1 - Gas compressor

Info

Publication number: US20050084397A1
Application number: US10/961,099
Authority: US
Inventors: Hiroshi Okada
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2003-10-17
Filing date: 2004-10-12
Publication date: 2005-04-21
Also published as: DE102004050412A1; JP4321206B2; JP2005120947A

Abstract

Compression chambers adjacent to each other in the axial direction of the rotors are communicated with each other. Therefore, a volume of air flowing and leaking from the chamber on the high pressure side into the chamber on the low pressure side is increased as compared with a case of no groove. Otherwise, a volume of air leaking from the chamber on the low pressure side into the chamber on the further lower pressure side than this chamber on the low pressure side is equal to that of the case of no groove. Therefore, the pressure in the chamber on the low pressure side becomes higher than that of the case of no groove. Accordingly, as the inner compression pressure can be enhanced, a difference between the discharge pressure and the inner compression pressure can be reduced. Therefore, a pulsation noise caused by the discharge pulsation can be reduced.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a compressor for compressing gas. The present invention is effective when it is applied to a screw pump.
2. Description of the Related Art
A pressure loss generated when a fluid is flowing is increased according to an increase in the flow rate, that is, the flow velocity. Therefore, in general, the pressure (the discharge pressure) of gas discharged from a gas compressor is increased according to an increase in the flow rate.
In the case of a displacement compressor in which gas is compressed when the volume of a compression chamber is reduced, the pressure of gas discharged from the compression chamber is determined by a compression ratio, that is, the pressure of the gas discharged from the compression chamber is determined by the ratio of the maximum volume of the compression chamber to the minimum volume of the compression chamber and is also determined by any leakage of gas from the compression chamber, the suction pressure and so forth.
At this time, in the case of a screw type or a scroll type displacement compressor, while the compression chamber is being moved to the discharge port side when the rotor is rotated, the volume of the compression chamber is gradually reduced so as to compress gas. However, when the rotating speed of the rotor is increased and the flow rate is increased, the discharge pressure is raised as described above. Therefore, the discharge pressure becomes higher than the pressure of gas discharged from the compression chamber. This pressure of gas discharged from the compression chamber is referred to as an inner compression pressure in this specification, hereinafter.
When the discharge pressure becomes higher than the inner compression pressure, gas flows from the discharge port side to the compression chamber side at the time when the compression chamber is communicated with the discharge port. As a result, the discharge pressure periodically fluctuates, and a pulsation is generated in the pressure. Accordingly, pulsation noise is generated.
In order to solve the above problems, it is conventional to take the following countermeasures. A bypass passage to communicate the compression chamber in the middle of compression, that is, a bypass passage to communicate the compression chamber, before the communication with the discharge port, with the discharge port is provided. When a pulsation flow, the phase of which is shifted from the phase of a pulsation flow generated on the discharge port side, is introduced into the discharge port, the two pulsation flows, the phases of which are shifted from each other, are made to collide with each other so as to reduce the pulsation of pressure.
However, according to the above invention, the pulsation of pressure can be reduced in a portion where the two pulsation flows, the phases of which are shifted from each other, collide with each other, that is, the pulsation of pressure can be reduced in the neighborhood of a portion of the discharge port where the bypass passage is open. However, in other portions, it is impossible to sufficiently reduce the pulsation of pressure. Therefore, noise generated by the pulsation of pressure can not be sufficiently decreased.
In this connection, in order to reduce the noise caused by the pulsation of pressure, it is necessary to enhance the rigidity of a portion in the neighborhood of the discharge port of a gas compressor so as to prevent the gas compressor from vibrating together with the pulsation of pressure. However, this means is disadvantageous in that the manufacturing cost of the gas compressor is raised.

SUMMARY OF THE INVENTION

In view of the above points, it is a first object of the present invention to provide a novel gas compressor, the structure of which is different from the structure of the conventional gas compressor. It is a second object of the present invention to reduce a pulsation of pressure by reducing a difference between the inner compression pressure and the discharge pressure.
In order to accomplish the above object, according to a first aspect of the present invention, there is provided a gas compressor having a compressing mechanism (1, 2) for compressing gas by operating movable members (1, 2) in a housing (7), comprising: a communicating passage (41) for communicating between a plurality of compression chambers (10 a, 10 b) formed by the housing (7) and the movable members (1, 2).
Due to the foregoing, a volume of gas leaking from the high pressure side compression chamber (10 b) into the low pressure side compression chamber (10 a) is increased as compared with a case in which the communication passage (41) is not provided.
On the other hand, a volume of gas leaking from the low pressure side compression chamber (10 a) to the lower pressure side compression chamber (10 c), the pressure of which is much lower than the pressure of the low pressure side compression chamber (10 a), is the same as a volume of gas in the case where the communicating passage (41) is not provided. Therefore, the pressure in the low pressure side compression chamber (10 a) becomes higher than that of the case where the communicating passage (41) is not provided.
Accordingly, as the inner compression pressure can be increased, a difference between the discharge pressure and the inner compression pressure can be reduced as compared with the conventional case. Accordingly, the pulsation noise caused by the pulsation of discharge pressure can be reduced.
Accordingly, as the necessity of enhancing the rigidity of a portion in the neighborhood of the discharge port of a gas compressor so as to prevent the gas compressor from vibrating together with the pulsation of pressure is low, it is possible to suppress a rise in the manufacturing cost of the gas compressor.
According to a second aspect of the present invention, the compressor mechanism is a screw type compressing mechanism including a pair of screw-shaped rotors (1, 2), which are meshed with each other, provided as the movable members.
According to a third aspect of the present invention, the communicating passage is composed when a groove portion (41) is formed on an inner circumferential face, which is formed in the housing (7), facing the movable members (1, 2).
Due to the foregoing, in the screw type compressor mechanism, an inner circumferential face of the housing (7) facing the movable member (1, 2) can be easily machined. Therefore, the communicating passage (41) can be easily formed.
According to a fourth aspect of the present invention, the groove portion (41) is provided on a circumferential curved face (7 a) on the inner circumferential face of the housing (7).
Due to the foregoing, the load of machining the groove portion (41) composing the communicating passage can be minimized. Accordingly, a deterioration of the rigidity of the housing (7) can be minimized.
Accordingly, factors of generating the noise caused by the deterioration of the rigidity of the housing (7) can be suppressed, that is, an increase in the vibration and an increase in the sound emitted from the inside can be suppressed.
According to a fifth aspect of the present invention, a cross sectional shape of the communicating passage (41) is substantially triangular.
Due to the foregoing, the communicating passage (41) can be easily formed by means of cutting such as milling or by means of casting such as die-casting.
According to a sixth aspect of the present invention, the groove portion (41) composing the communicating passage extends substantially in parallel with the axial direction of the movable members (1, 2).
Due to the foregoing, the groove portion (41), the cross sectional area of which is constant, can be easily formed by means of cutting such as milling. Accordingly, it is possible to obtain the groove (41) capable of exhibiting the same effect as that of the groove obtained by numerical simulation. Therefore, the time necessary for designing and developing the gas compressor can be reduced.
According to a seventh aspect of the present invention, the groove portion (41) composing the communicating passage is formed at a position on an inner wall opposing to a suction port (35) provided on the inner wall of the housing (7).
Due to the foregoing, cutting such as milling for forming the groove portion (41) can be easily conducted from the suction port (35).
According to an eighth aspect of the present invention, a length in the axial direction of the groove portion (41) composing the communicating passage is not more than a pitch size of the rotors (1, 2) composing the movable member.
Due to the foregoing, the compression chambers (10 a, 10 b) adjacent to each other can be communicated with each other. Therefore, the inner compression pressure can be easily increased, and the pulsation noise caused by the discharge pulsation can be reduced.
According to a ninth aspect of the present invention, the communicating passage (41) communicates between the adjoining compression chambers (10 a, 10 b).
Due to the foregoing, the inner compression pressure can be easily increased, and the pulsation noise caused by the discharge pulsation can be reduced.
Incidentally, the reference numerals in parentheses, to denote the above means, are intended to show the relationship of the specific means which will be described later in an embodiment of the invention.
The present invention may be more fully understood from the description of preferred embodiments of the invention set forth below, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawing:
FIG. 1 is a sectional view taken in the axial direction of the gas compressor of the first embodiment of the present invention;
FIG. 2 is a perspective view showing a pair of rotors of the gas compressor of the first embodiment of the present invention;
FIG. 3 is a sectional view taken on line A-A of the housing 7 shown in FIG. 1;
FIG. 4 is a sectional view taken in the axial direction of the gas compressor of the second embodiment of the present invention; and
FIG. 5 is a sectional view taken on line A-A in FIG. 4.

DESCRIPTION OF PREFERRED EMBODIMENTS

First, the first embodiment of the present invention will be explained below. In this embodiment, the gas compressor of the present invention is applied to a supercharger in which the combustion air supplied to an internal combustion engine is pressurized.
In this connection, FIGS. 1 to 3 are views showing the gas compressor of the present invention. FIG. 1 is a sectional view of the gas compressor, FIG. 2 is a perspective view of a pair of rotors, and FIG. 3 is a sectional view taken on line A-A of the housing 7 shown in FIG. 1.
As shown in FIG. 1, the gas compressor of the present embodiment is a screw type pump including: a screw-shaped male rotor 1 and a screw-shaped female rotor 2 (shown in FIG. 2) which are meshed with each other; a rotation transmission mechanism 3 for driving the pair of rotors 1, 2; and a casing 4 for accommodating the pair of rotors 1, 2 and the rotation transmission mechanism 3 under the condition that the pair of rotors 1, 2 and the rotation transmission mechanism 3 are isolated form each other.
In this connection, as shown in FIG. 2, the male rotor 1 and the female rotor 2 respectively have a male-screw-shape in which a spiral protrusion is formed. As shown in FIG. 1, the rotation transmission mechanism 3 is driven by a drive source such as an electric motor 50 so as to drive the pair of rotors 1, 2.
The casing 4 is comprised of three parts, which are a lubrication box 6, a rotor housing 7 and a cover 8 arranged in this order. The lubrication box 6, the rotor housing 7 and the cover 8 are strongly joined to each other by a joining means such as bolts (not shown).
In the lubricating oil space 9 formed in the lubrication box 6, the rotation transmission mechanism 3 and the lubricant (for example, oil having the same viscosity as that of engine oil) supplied to the rotation transmission mechanism 3 are accommodated. Gears composing the rotation transmission mechanism 3 are lubricated when the lubricant accommodated in the lubricant space 9 splashes.
A pair of rotors 1, 2 are accommodated in the rotor chamber 10 formed in the rotor housing 7. When the pair of rotors 1, 2 are rotated in the rotor chamber 10, the compression chamber 10 a formed by the rotor chamber 10 and the pair of rotors 1, 2 is successively reduced, so that the sucked combustion air (suction air) can be pressurized and compressed.
The lubrication box 6 supports the input shaft 5, which is driven by the motor 50, through the first bearing 11 arranged on the motor 50 side and the second bearing 12 arranged on the lubricant space 9 side. Inside the insertion hole, which is formed in the lubrication box 6, into which the input shaft 5 is inserted, the first oil seal 13 is provided in order to prevent the lubricant, which is supplied to the first bearing 11 and the second bearing 12, from leaking outside the casing 4.
One end side of the male rotor rotary shaft 14 is pivotally supported by the rotor housing 7 through the third bearing 15, and the other end side of the male rotor rotary shaft 14 is pivotally supported by the cover 8 through the fourth bearing 16.
To the bulkhead for partitioning the rotor housing 7 into the lubricant space 9 and the rotor chamber 10, the second oil seal 18 is attached in order to prevent the lubricant, which is supplied to the third bearing 15, from leaking out from the insertion hole, into which the male rotor rotary shaft 14 is inserted into the rotor chamber 10.
Into the insertion hole, which is formed on the cover 8, into which the male rotor rotary shaft 14 is inserted, the third oil seal 19 is attached in order to prevent the grease, which is enclosed in the fourth bearing 16, from leaking out into the rotor chamber 10.
In the same manner as that of the above male rotor rotary shaft 14, one end side of the female rotor rotary shaft 20 is pivotally supported by the rotor housing 7 through the fifth bearing 21, and the other end side of the female rotor rotary shaft 20 is pivotally supported by the cover 8 through the sixth bearing 22.
To the bulkhead for partitioning the rotor housing 7 into the lubricant space 9 and the rotor chamber 10, the fourth oil seal 23 is attached in order to prevent the lubricant, which is supplied to the fifth bearing 21, from leaking out from the insertion hole, into which the female rotor rotary shaft 20 is inserted, into the rotor chamber 10.
Into the insertion hole, which is formed on the cover 8, into which the female rotor rotary shaft 20 is inserted, the fifth oil seal 24 is attached in order to prevent the grease, which is enclosed in the sixth bearing 22, from leaking out into the rotor chamber 10.
In this connection, the rotation transmission mechanism 3 transmits a rotation of the input shaft 5 to the male rotor rotary shaft 14 and the female rotor rotary shaft 20 so that the pair of rotors 1, 2 can be synchronously rotated. The rotation transmission mechanism 3 includes: a first gear 31 and a second gear 32 for transmitting a rotation of the input shaft 5, which is driven by the motor 50, to the male rotor rotary shaft 14; and a third gear 33 and a fourth gear 34 for transmitting a rotation, which has been transmitted from the second gear 32 to the male rotor rotary shaft 14, to the female rotor rotary shaft 20.
In this connection, the third gear 33 and the fourth gear 34 are timing gears for synchronously rotating a pair of rotors 1, 2.
On the inner circumferential face of the rotor housing 7, on the arcuate circumferential curved face 7 a facing spiral protruding portions of the pair of rotors 1, 2, as shown in FIG. 3, the groove 41 extending in the direction parallel with the axial direction of the pair of rotors 1, 2 is provided. In this embodiment, a communication passage for communicating between the compression chambers 10 a is composed of this groove 41.
In this embodiment, the size L of a portion of the groove 41 parallel with the axial direction of the rotor 1, 2 is determined to be a predetermined size not more than screw pitch p (shown in FIG. 2) of the rotor 1, 2. Therefore, the groove 41 of this embodiment, that is, the communication passage of this embodiment can communicate between the compression chambers 10 a, 10 b which are adjacent to each other.
In this embodiment, the groove 41 is formed by means of cutting on a face of the circumferential curved face of the rotor housing 7 opposed to the suction port 35. The cross sectional shape of the groove 41 is substantially triangular.
Next, an outline of the operation of the compression mechanism of the present embodiment comprised of a pair of rotors 1, 2 will be described below.
As described before, shapes of the pair of rotors 1, 2 are like male screws in which spiral protruding portions are formed. When the pair of rotors 1, 2 are synchronously rotated via the rotation transmission mechanism 3, combustion air is sucked into the compression chamber 10 a from the suction port 35 provided in the end portion of the rotor housing 7 in the axial direction on the cover side 8.
A volume of the compression chamber 10 a is reduced while the compression chamber 10 a is moving from the cover 8 side to the lubricant space side 9 together with the rotation of the pair of rotors 1, 2. Therefore, combustion air sucked into the compression chamber 10 a is moved onto the lubricant space 9 side while the combustion air is being gradually compressed.
When a rotary angle of the pair of rotors 1, 2 reaches a predetermined value, the compression chamber 10 a reaches the discharge port 36 provided on the lubricant space 9 side, and the compression chamber 10 a, which has been tightly closed up until now, is open to the discharge port 36. Accordingly, the compressed combustion air can be discharged from the discharge port 36.
In this connection, in the present embodiment, the tightly closed property of the compression chamber 10 a, which is formed on the opposite side to the suction port 35 with respect to the pair of rotors 1, 2, is made to be higher than the tightly closed property of the compression chamber 10 a formed on the suction port 35 side, so that the combustion air can be mainly compressed in the compression chamber 10 a formed on the opposite side to the suction port 35 with respect to the pair of rotors 1, 2. Therefore, the discharge port 36 is provided at a diagonal position to the suction port 35 of the rotor housing 7. However, of course, the present invention is not limited to the above specific embodiment.
Next, the operational effects of the gas compressor of the present embodiment will be described below.
As described above, the compression chamber 10 a is moved from the suction port 35 side to the discharge port 36 side while the volume of the compression chamber 10 a is being reduced. Therefore, when the compression chambers 10 a, 10 b, which are adjacent to each other in the axial direction of the rotor 1, 2, are communicated with each other, the high pressure side compression chamber 10 b is communicated with the low pressure side compression chamber 10 a.
Accordingly, in the present embodiment, a volume of the combustion air flowing from the high pressure side compression chamber 10 b into the low pressure side compression chamber 10 a by leakage is increased as compared with a case in which the groove 41 not provided. On the other hand, a volume of the combustion air leaking out from the low pressure side compression chamber 10 a into the further lower pressure side compression chamber 10 c is the same as that of the case in which the groove 41 is not provided. Therefore, pressure in the low pressure side compression chamber 10 a becomes higher than that of the case in which the groove 41 not provided.
Accordingly, as the inner compression pressure can be increased, it is possible to reduce a difference in pressure between the discharge pressure and the inner compression pressure. Therefore, a pulsation noise caused by the discharge pulsation can be reduced.
Since noise caused by the pulsation can be reduced, the necessity for preventing the gas compressor from vibrating together with the pulsation by enhancing the rigidity of the neighborhood of the discharge port 36 of the gas compressor is low. Therefore, it is possible to suppress an increase in the manufacturing cost of the gas compressor.
As the cross section of the groove 41 is substantially triangular, the groove 41 can be easily formed by means of cutting such as milling.
As the groove 41 is provided on a face of the circumferential curved face of the rotor housing 7 opposed to the suction port 35, cutting such as milling can be easily conducted from the suction port 35.
In this connection, in the present embodiment, the groove 41 is formed by means of cutting such as milling. However, the means for forming the groove 41 is not limited to the above specific embodiment. When the rotor housing 7 is manufactured by means of casting or die-casting, the groove 41 may be simultaneously formed.
Even in this case in which the rotor housing 7 is manufactured by means of casting or die-casting, when the cross section of the groove 41 is substantially triangular, a draft taper can be easily ensured in the process of casting. Accordingly, the time necessary for manufacturing the rotor housing 7 can be reduced in the same manner as that of the means of cutting such as milling.
Next, the second embodiment will be explained below. FIGS. 4 and 5 are views showing the second embodiment of the present invention. FIG. 4 is a sectional view of the gas compressor, and FIG. 5 is a sectional view taken on line A-A in FIG. 4. Referring to FIGS. 4 and 5, the second embodiment will be explained while the points of difference from the first embodiment are emphasized.
In this embodiment, the groove, which composes a communication passage, is formed into a conical hollow portion 41. In this connection, the maximum diameter of the hollow portion 41 is not more than the size of screw pitch p of the rotor 1, 2.
Due to the foregoing, the time necessary for machining the hollow portion 41, which composes a communication passage, can be reduced.
In this connection, in FIGS. 4 and 5, like reference characters are used to indicate like parts in the first and the second embodiment. Therefore, the explanations are omitted in this embodiment.
Finally, another embodiment will be explained below. In the above embodiment, the adjoining compression chambers 10 a, 10 b are communicated with each other, however, it should be noted that the present invention is not limited to the above specific embodiment.
In the above embodiment, the communicating passage is comprised of the groove 41 or the hollow portion 41 formed on the inner circumference of the rotor housing 7. However, it should be noted that the present invention is not limited to the above specific embodiment.
In the above embodiment, the present invention is applied to a gas compressor for compressing the combustion air. However, it should be noted that the present invention is not limited to the above specific embodiment. For example, the present invention may be applied to a gas compressor for compressing other gas such as hydrogen gas.
A position at which the groove 41 or the hollow portion 41 composing a communication passage is formed and a size of the groove 41 or the hollow portion 41 are not limited to the above specific embodiment. The position at which the groove 41 or the hollow portion 41 composing a communication passage is formed and the size of the groove 41 or the hollow portion 41 are appropriately selected according to a volume of the leakage between the adjoining compression chambers 10 a, 10 b, that is, according to a gap between the rotor 1, 2 and the inner wall of the rotor housing 7, a compression ratio, a rotating speed (leakage length), a pressure loss of the discharge section and a machining accuracy of each part.
In the above embodiment, the present invention is applied to a screw type gas compressor. However, it should be noted that the present invention is not limited to the above specific embodiment. For example, the present invention can be also applied to a Roots type or a scroll type displacement compressor. As long as it agrees with the points described in claims of the present invention, any embodiment is included in the present invention. It should be noted that the present invention is not limited to the above specific embodiment.
While the invention has been described by reference to specific embodiments for purposes of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention.

Claims

1. A gas compressor having a compressing mechanism (1, 2) for compressing gas by operating movable members (1, 2) in a housing (7), comprising:

a communicating passage (41) for communicating between a plurality of compression chambers (10 a, 10 b) formed by the housing (7) and the movable members (1, 2).

2. A gas compressor according to claim 1, wherein the compressor mechanism is a screw type compressing mechanism including a pair of screw-shaped rotors (1, 2), which are meshed with each other, provided as the movable members.

3. A gas compressor according to claim 2, wherein the communicating passage is composed when a groove portion (41) is formed on an inner circumferential face, which is formed in the housing (7), facing the movable members (1, 2).

4. A gas compressor according to claim 3, wherein the groove portion (41) is provided on a circumferential curved face (7 a) on the inner circumferential face of the housing (7).

5. A gas compressor according to claim 3, wherein a cross sectional shape of the communicating passage (41) is substantially triangular.

6. A gas compressor according to claim 3, wherein the groove portion (41) composing the communicating passage extends substantially in parallel with the axial direction of the movable members (1, 2).

7. A gas compressor according to claim 3, wherein the groove portion (41) composing the communicating passage is formed at a position on an inner wall opposing to a suction port (35) provided on the inner wall of the housing (7).

8. A gas compressor according to claim 3, wherein a length in the axial direction of the groove portion (41) composing the communicating passage is not more than a pitch size of the rotors (1, 2) composing the movable member.

9. A gas compressor according to claim 3, wherein the communicating passage (41) communicates between the adjoining compression chambers (10 a, 10 b).