JP2000125488A - Rotor of motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the motor efficiency of a motor whose rotor is driven by a magnet torque. SOLUTION: The magnetization of each of magnets 10 is oriented extending in the radial direction from the center of a circular arc outside the outer circumferential circle of a rotor core 9. The magnet 10 has end surfaces 10a, 10c and 10d which face the outer circumferential circle of the rotor core 9. The center of the circular arc is provided at a position opposite to the center of the rotor core 9, with respect to tangents at the end parts in the circumferential directions of the end surfaces 10a, 10c and 10d.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor for an electric motor, and is suitable, for example, as a rotor for a motor for driving a fuel pump.

[0002]

2. Description of the Related Art Hitherto, as described in Japanese Patent Application Laid-Open No. 10-126886, there is known a structure for effectively utilizing reluctance torque in addition to magnet torque for the purpose of improving motor efficiency. In the above-described conventional technology, the magnetic flux is concentrated on a point outside the rotor core by forming the magnet provided on the rotor core into an arcuate shape that is curved in a direction opposite to the outer circumferential circle of the rotor core. Then, the reluctance torque due to the saliency of the magnetic resistance of the magnet rotor is obtained to try to improve the motor efficiency.

[0003]

However, the inventor has experimentally studied that this reluctance torque is very small as compared with the magnet torque obtained by the excited magnetic poles and the magnet. For example, when the motor is operated at a duty of about 10%, an effect of improving the efficiency can be obtained.
%), It was noticed that it had little effect.

Further, in the magnet arrangement as in the prior art described above, if the magnet is magnetized in a radially anisotropic orientation that is magnetized perpendicularly to the arc of the magnet, the magnetic flux density on the surface of the magnet rotor is partially improved. Since the orientations at both ends of the arc-shaped magnet are substantially parallel to the outer periphery of the magnet rotor, no magnetic flux flows from this portion toward the stator, and the amount of magnetic flux cannot be increased as a whole. For this reason, the inventors have also noticed that there is a problem that the magnet torque that occupies most of the drive torque of the magnet rotor cannot be increased, and as a result, the motor efficiency cannot be improved.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to improve the motor efficiency of a rotor of a motor that does not use both magnet torque and reluctance torque. More specifically, an object of the present invention is to make the magnetic flux of the magnet concentrate toward the outer peripheral side of the magnet rotor and to flow the magnetic flux from the entire outside of the magnet toward the stator in order to improve the magnet torque.

[0006]

In order to achieve the above object, according to the first aspect of the invention, the magnet (10) is magnetized radially from a point (B) outside the outer circumference of the rotor core (9). The magnet (10) has an end face (10a, 10c, 10d, 10e) facing the outer circumference of the rotor core (9), and a magnetic flux is applied to the end face (10a, 10c, 10d, 10e). It is characterized by a shape that passes through the whole.

According to the second aspect of the present invention, the magnet (10)
Is oriented to extend radially from a point (B) outside the outer circumference of the rotor core (9), and the magnet (10) has end faces (10a, 10c, 10d) facing the outer circumference of the rotor core (9). 10e), and the one point (B) is located on a side opposite to the center of the rotor core (9) with respect to a tangent at a circumferential end of the end face (10a, 10c, 10d, 10e). It is characterized by.

According to this, since the magnetizing orientation of the magnet (10) is radially extending from one point (B) outside the outer circumferential circle of the rotor core (9), the magnetic flux is transferred to the outer circumferential side of the magnet rotor (8). Can be concentrated on one point (B). The point (B) where the magnetic flux is concentrated, that is, the orientation center (B) is located at the end faces (10a, 10c, 10d,
e) rotor core (9) with respect to the tangent at any point
It is located on the opposite side of the center. Therefore, the magnetic flux heading for the orientation center (B) passes through the entire end faces (10a, 10c, 10d, 10e) facing the outer circumferential circle of the rotor core (9).

Therefore, the magnetic flux of the magnet (10) is concentrated toward a point outside the magnet rotor (7), and the end faces (10a, 10c, 10c) of the magnet (10) are concentrated.
d, 10e) Since the magnetic flux flows from the whole toward the stator, the magnet torque can be improved. As a result, since the magnet torque and the reluctance torque are used together and the magnet torque can be improved, the motor efficiency can be improved as a whole.

According to the third aspect of the present invention, the end face (10
a, 10c, 10d, and 10e) are characterized by having an arcuate curved surface (10a) centered on the one point (B). Further, in the invention according to claim 5, the magnet (10) has the end faces (10a, 10c, 10d, 10e).
It is characterized in that it has an arc-shaped curved surface (10b) centered on the one point (B) on the center side of the rotor core (9).

The magnet (10) is usually formed from a magnetized cylindrical ferrite or the like in a radially anisotropic orientation. Therefore, the magnet (10) having the above-described shape can be formed by using the outer peripheral arc portion and the inner peripheral arc portion of the cylinder. Therefore, processing of the magnet (10) becomes easy. The invention according to claim 4 is characterized in that the end faces (10a, 10c, 10d, 10e) are arc-shaped curved surfaces (10e) concentric with and the same diameter as the rotor core (9).

According to this, since the end faces (10a, 10c, 10d, 10e) of the magnet (10) and the outer circumferential circle of the rotor core (9) coincide, the magnet (1)
Since the rotor core (9) does not exist outside of (0), the core loss generated in the rotor core (9) outside of the magnet (10) can be reduced, and the motor efficiency can be further improved.

The reference numerals in parentheses indicate the correspondence with specific means described in the embodiments described later.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. (First Embodiment) FIG. 1 is a cross-sectional view of a pump device to which a rotor of an electric motor of the present invention is attached, FIG. 2 is a cross-sectional view of a magnet rotor and a stator taken along the line AA in FIG. 1, and FIG. FIG. 2 is an enlarged view of a main part in FIG. This pump device is disposed in a fuel tank of a vehicle, for example, and supplies fuel from the fuel tank to a fuel injection device of an internal combustion engine.

The pump device 1 comprises an electric motor unit 2, a pump unit 3, and a discharge unit 4. The motor unit 2 includes a stator 6, a magnet rotor 7, and a cylindrical casing 5.
The driving circuit 8 is provided. The magnet rotor 7 includes a cylindrical rotor core 9 formed by laminating electromagnetic steel sheets, and eight magnets 10 made of ferrite or the like, which are buried in the rotor core 9 and arranged in the circumferential direction. Note that the magnet 10 is N
It is magnetized so that the pole and the S pole are reversed. The rotor core 9 is provided with a through hole in the axial direction, and the shaft 11 is press-fitted and fixed in the through hole.

As shown in the sectional views of FIGS. 2 and 3,
The cross section of the magnet 10 has a substantially arcuate shape. The outer peripheral side arc portion 10a and the inner peripheral side arc portion 10b are
Are curved substantially in parallel in the opposite direction with respect to the outer circumference. Further, the arc centers of the arc portions 10 c and 10 d which are circumferentially adjacent to the outer peripheral side arc portion 10 a coincide with the center of the rotor core 9. Further, the arc centers B of the outer circular arc portion 10a and the inner circular arc portion 10b are located on the outer diameter side with respect to the intersection C of the tangents at both circumferential ends of the circular arc portions 10c and 10d.

The magnet 10 is formed in a generally arcuate shape by using a magnetized cylindrical ferrite in a radially anisotropic orientation by a known method. Accordingly, the outer circumferential side arc portion 10a and the inner circumferential side arc portion 10b of the magnet 10 are magnetized in a direction perpendicular to both the arc portions 10a and 10b. The magnet 10 thus magnetized
In, the magnetic flux is concentrated toward the arc center B of the outer and inner arc portions 10a and 10b of the magnet.

In the magnet 10 configured as described above, the magnetic flux passes not only through the outer circular arc portion 10a but also through the circular arc portions 10c and 10d. Therefore, the magnetic flux passes substantially all around the surface of the magnet rotor 7 on the side facing the stator 6. The stators 6 are arranged at predetermined intervals in the radial direction on the outer periphery of the magnet rotor 7. Stator 6
Is a stator core 1 formed by laminating silicon steel plates.
3 and a three-phase field winding 14 provided in a slot of the stator core 13. After the field winding 14 is installed in the slot of the stator core 13, the entire field winding 14, that is, the inside of the slot and the coil end portion 20 are molded with an insulating resin. The stator 6 thus formed is inserted and fixed inside the casing 5.

The shaft holder 21 is press-fitted and fixed inside the upper end of the stator 6, and a bearing 22 is press-fitted and fixed from below in a hole provided at the center of the shaft holder 21. The pump casing 23 is press-fitted and fixed inside the lower end of the stator 6 and inside the lower part of the casing 5, and a bearing 24 is press-fitted and fixed in a hole provided in the center of the pump casing 23. And bearing 22,
By 24, the shaft 11 fixed to the magnet rotor 7 is rotatably supported. The pump casing 23 also forms an accommodating portion for an impeller 28 described later.

A circuit holder 25 having a built-in motor drive circuit 8 is press-fitted and fixed in the upper hollow portion of the shaft holder 21. An intermediate terminal 26 for connecting the motor drive circuit 8 and the field winding 14 is insert-molded in the circuit holder 25. The pump unit 3 includes the motor unit 2
, And includes a pump casing 23, a pump cover 27, and an impeller 28. The lower part of the pump casing 23 has a concave portion 23 for accommodating the impeller 28.
a and a flow path 23b are formed. The depth of the concave portion 23 a in the axial direction is configured to be several μm to several tens μm deeper than the thickness of the impeller 28.

The pump cover 27 is inserted into a lower portion of the casing 5 and is fixed by caulking or the like. Also,
Support hole 2 provided in the upper center of pump cover 27
The shaft 11 is supported by 7a. In addition, the pump cover 27 is provided with the flow path 23 of the pump casing 23.
A suction port 27b is bored so as to communicate with b.

The flow path 23b is formed so as to surround the blades of the impeller 28 described later. The starting end of the flow path 23b communicates with a suction port 27b in which the pump cover 27 is formed, and the flow path 23b extends in the circumferential direction over an angle range of about 300 degrees, for example. The disk-shaped impeller 28 is provided at the lower portion 23 of the pump casing 23.
a. The shaft 11 is fitted in the center hole of the impeller 28, and is driven to rotate in conjunction with the operation of the magnet rotor 7. The outer peripheral side of the impeller 28 extends to the flow path 23b. In addition, a large number of blades are vertically arranged over the entire circumference at the upper and lower outer peripheral portions.

A bottomed cylindrical end cover 29 forming the discharge section 4 is press-fitted and fixed inside the upper end of the casing 5 so as to cover the motor drive circuit 8. A discharge pipe 29 projecting upward is provided at the bottom of the end cover 29.
a is formed. The discharge pipe 29a communicates with the flow path 23b. Then, the fuel sucked from the suction port 27b is supplied to the fuel injection device of the internal combustion engine from the discharge pipe 29a via the flow path 23b.

Next, the operation of the pump device 1 of the present invention will be described. A voltage is applied from a battery (not shown) to the drive circuit 8 via a power supply terminal (not shown). Drive circuit 8
Thereafter, power is supplied to two phases of the three-phase field windings 14 wound in the slots 18 in accordance with the rotational position of the magnet rotor 7. That is, the motor unit is of a three-phase full-wave type. The rotational position of the magnet rotor 7 is calculated based on an induced voltage generated in the field winding 14.

When a current flows from the drive circuit 8 to the field winding 14, the teeth 16 are excited to form magnetic poles. Then, a magnet torque is generated by an attraction force or a repulsion force of the magnet rotor 7 disposed inside the stator core 13 with the magnet 10, and the magnet rotor 7 starts rotating. The drive circuit 8 changes the combination of the two phases to be energized and the energization direction in accordance with the rotation of the magnet rotor 7, and sequentially changes the magnetism of the teeth 16 to be energized. Thereby, the magnet rotor 7 rotates continuously.

The rotation of the magnet rotor 7 is
1 to the impeller 28. When the impeller 28 is rotationally driven, the fuel in the fuel tank is sucked from the suction port 27b into the flow path 23b. Then, it is discharged from the discharge pipe 29a while being pressure-fed in the flow path 23b. In the present embodiment, the magnet 10 is formed into an arcuate shape that is curved in a direction opposite to the outer circumferential circle of the rotor core 9, so that the magnetic flux is transferred to the arc center B outside the rotor core 9.
Focus on

Further, in the present embodiment, as described above, since the magnetic flux passes substantially all around the surface of the magnet rotor 7 on the side facing the stator 6, the magnetic flux flows from the magnet 10 toward the stator 6. The amount of effective magnetic flux flowing is increased.
As a result, the magnet torque can be increased, so that the motor efficiency can be further improved as a whole. (Second Embodiment) FIG. 4 is a sectional view of a magnet rotor showing a second embodiment of the present invention. In the second embodiment, the arc on the outer peripheral side of the magnet 10 is concentric with the rotor core 9 and has the same diameter. As in the first embodiment, the arc center of the arc portion on the inner circumference side of the magnet 10 is located on the outer diameter side from the intersection of the tangents at both ends in the circumferential direction of the arc on the outer circumference side. The magnet 10 is magnetized in a direction perpendicular to the inner circumferential arc, and the magnetic flux is concentrated toward the center of the inner circumferential arc.

Also in the second embodiment having such a configuration, the magnetic flux passes through the entire arc on the outer peripheral side of the magnet 10, so that the effective magnetic flux amount can be increased and the motor efficiency can be improved. Further, in the second embodiment, since the rotor core 9 is not provided on the outer peripheral portion of the magnet 10, the iron loss generated here can be reduced, and the motor efficiency can be further improved. (Other Embodiments) In the above embodiment, the rotor core 9 is formed by laminating electromagnetic steel sheets. However, the rotor core 9 may be formed by other methods such as sintered metal and forging. When the rotor core 9 is formed by a sintered metal, forging, or the like, 1
Since the rotor core 9 can be formed from components, manufacturing costs can be reduced.

Further, in a motor which does not control the rotation speed by the PWM control or the like, since the iron loss is small, even if the rotor core 9 is formed of such an integral metal, the motor efficiency does not decrease so much.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a pump device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a stator and a rotor showing one embodiment of the present invention.

FIG. 3 is an enlarged view of a main part in FIG. 2;

FIG. 4 is a sectional view of a stator and a rotor showing another embodiment of the present invention.

[Explanation of symbols]

6 ... stator, 7 ... magnet rotor, 9 ... rotor core,
DESCRIPTION OF SYMBOLS 10 ... Magnet, 10a ... Outer side arc part, 10b ... Inner side arc part, 10c, 10d ... Arc part 11 ... Shaft, 13 ... Stator core, 14 ... Field winding.

Claims (5)

[Claims] 1. A magnet (10) on a rotor core (9).
Wherein the magnet (10) is magnetized such that the magnetization of the magnet (10) extends radially from a point (B) outside the outer circumference of the rotor core (9). End faces (10a, 10c, 10d, 10d) facing the outer circumference of the rotor core (9).
e), and the magnetic flux is applied to the end faces (10a, 10c, 10c).
A rotor for an electric motor, wherein the rotor passes through the entirety of d, 10e). 2. A magnet (10) on a rotor core (9).
Wherein the magnet (10) is magnetized such that the magnetization of the magnet (10) extends radially from a point (B) outside the outer circumference of the rotor core (9). End faces (10a, 10c, 10d, 10d) facing the outer circumference of the rotor core (9).
e), wherein the one point (B) includes the end faces (10a, 10c, 10).
A rotor for an electric motor, which is located on a side opposite to a center of the rotor core (9) with respect to a tangent line at a circumferential end of (d, 10e). 3. The end face (10a, 10c, 10d, 1
3. The rotor of the electric motor according to claim 2, wherein 0 e) has an arcuate curved surface (10 a) centered on the one point (B). 4. 4. The end face (10a, 10c, 10d, 1
The rotor of the electric motor according to claim 2, wherein 0e) is an arc-shaped curved surface (10e) concentric with and the same diameter as the rotor core (9). 5. The magnet (10) has an arcuate curved surface (10b) centered on the point (B) on the center side of the rotor core (9) from the end faces (10a, 10c, 10d, 10e). The rotor of the electric motor according to any one of claims 2 to 4, wherein the rotor has: