JPH11146624A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor which makes torque on the rotor roughly constant within the rotating range of the rotor. SOLUTION: The rotor 30 is contained in a stator 40 so as to rotate freely, and consists of a rotor core 32, permanent magnets 33, 34 fixed at the outer surface of the rotor core 32, and a cylindrical member 35 consisting of a magnetic body covering the outer periphery of the permanent magnets 33, 34. The respective permanent magnets 33, 34 are constituted of a plurality of flat permanent magnets 33a, 34a. The outer periphery of the flat permanent magnets 33a, 34a is covered with the cylindrical member 35 consisting of a magnetic body. Therefore, the magnetic flux direction and the magnetic flux density of the outer periphery of the rotor 30 are roughly uniform to the inner periphery surface of the stator 40, and an air gap between the cylindrical member 35 and the stator 40 is equal in a circumferential direction. It is thus possible to make torque on the rotor 30 roughly constant within the range of rotating angle of the rotor 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor, and more particularly, to a motor rotor structure.

[0002]

2. Description of the Related Art As shown in FIG. 9, a plurality of permanent magnets 102, 10
3 is fixed with an adhesive or the like to form a magnetic pole of the rotor 100. However, in the rotor 100 as shown in FIG. 9, the centrifugal force and the magnetic force acting on the permanent magnets 102 and 103 cause the permanent magnets 102 and 103 to move away from the rotor core 101.
103 may fall off.

In order to prevent such a permanent magnet from falling off, Japanese Unexamined Patent Publication No. 9-84283 and Japanese Unexamined Patent Publication No.
No. 4 and Japanese Patent Application Laid-Open No. 9-93844, a permanent magnet mounted on a rotor core is covered with a non-magnetic resin or metal material formed in a cylindrical shape and a permanent magnet is mounted on the rotor core. There are known ones that prevent falling off.

[0004]

However, when a plurality of permanent magnets are arranged on the outer periphery of the rotor core, if the permanent magnets are magnetized not parallel to the center of rotation of the rotor core but in parallel in one direction, the rotor is The permanent magnet is magnetized in a different direction with respect to the inner peripheral surface of the stator facing the above. Even when the permanent magnets are arranged in contact with each other, a gap is formed between the permanent magnets on the stator side, so that the magnetic flux density on the outer periphery of the rotor fluctuates in the circumferential direction. Further, when the permanent magnet is formed in a flat plate shape, the air gap between the permanent magnet and the stator fluctuates periodically.

[0005] For the above and reasons,
When power is turned on and power is turned off to the coil unit mounted on the stator, the torque acting on the rotor periodically swells due to the rotation angle (opening) of the rotor as shown in FIG.
That is, fluctuation occurs. Such a fluctuation in torque cannot be reduced even if the permanent magnet is covered with a cylindrical member made of a non-magnetic material as in the rotor described in the above-mentioned publication. For example, when an electric motor is used as an actuator of a throttle device of an internal combustion engine, the throttle opening cannot be set to a predetermined value if the torque acting on the rotor that rotates together with the throttle valve varies with the throttle opening. Therefore, there arises a problem that the intake flow rate cannot be controlled with high accuracy. Further, in the case of a motor rotating in a fixed direction, particularly in the case of a motor rotating at a low speed, there is a problem that the rotor does not rotate at a constant speed.

An object of the present invention is to provide an electric motor that makes the torque acting on the rotor substantially constant within the rotation range of the rotor.

[0007]

According to the first aspect of the present invention, the plurality of permanent magnets disposed on the outer periphery of the rotor core are covered with the magnetic member. On the other hand, it is magnetized almost radially.
Even if there is a gap between the permanent magnets, the magnetic member located at a position corresponding to the gap is also magnetized. When the rotor is provided with two poles of N and S, the magnetic flux flows between the magnetic poles through the magnetic member, so that the magnetic flux does not concentrate on the circumferential end of each magnetic pole. Therefore, the magnetic flux density on the outer periphery of the rotor and the magnetic flux direction on the outer periphery of the rotor with respect to the inner peripheral surface of the stator become substantially equal.
Furthermore, since the shape of the outer peripheral surface of the magnetic member approaches a curved surface corresponding to the inner peripheral surface of the stator, the difference in the air gap between the rotor and the stator in the circumferential direction is reduced.

As described above, since the torque acting on the rotor becomes substantially constant within the rotation range of the rotor, the rotation angle and the rotation speed of the rotor can be controlled with high accuracy. Further, since the magnetic member covers the permanent magnet, it is possible to prevent the permanent magnet from dropping from the rotor core. According to the electric motor according to the second aspect of the present invention, even if the magnetic pole of the rotor is formed by a flat permanent magnet having a low manufacturing cost, the magnetic member covers the flat permanent magnet so that the rotor can be rotated within the rotation range of the rotor. The torque that acts on becomes almost constant. Therefore, the rotation angle and the rotation speed of the rotor can be controlled with high accuracy while reducing the manufacturing cost.

According to the electric motor according to claim 3 of the present invention,
By forming the magnetic member in a cylindrical shape, the air gap formed between the rotor and the stator becomes substantially equal in the circumferential direction. Therefore, the rotation angle and the rotation speed of the rotor can be controlled with higher accuracy. According to the electric motor described in claim 4 of the present invention, the permanent magnet groups form a gap extending on the outer periphery of the rotor core in the axial direction of the rotor core. Since the cylindrical member has the non-magnetic portion at a position corresponding to the gap, it is possible to prevent magnetic flux from leaking from the end of one permanent magnet group to the end of the other permanent magnet group through the cylindrical member. When a magnetic flux leaks from one end of one permanent magnet group to the end of the other permanent magnet group, a cylindrical member and a stator located near a gap including a gap formed by extending in the axial direction between the permanent magnet groups. The suction force and the repulsion force acting between them are reduced. On the other hand, by providing a non-magnetic portion on the magnetic member and suppressing leakage of magnetic flux between the permanent magnet groups, the rotor and the stator are attracted and repelled at circumferential ends of the magnetic member sandwiching the non-magnetic portion. Therefore, if the rotor has the same diameter as the rotor using the magnetic member without the nonmagnetic portion, the torque generation range can be expanded without increasing the circumferential length of the permanent magnet group, that is, the amount of magnets. If the same torque generation range as that of a rotor using a magnetic member without a non-magnetic portion is realized, the apparatus can be downsized and the manufacturing cost can be reduced by reducing the magnet amount and the rotor diameter.

According to the electric motor according to claim 5 of the present invention,
The magnetic flux density in the circumferential direction of the magnetic member becomes substantially equal by making the gap between the facing surfaces of the plurality of radially opposed permanent magnets and the magnetic member substantially uniform in the circumferential direction. The torque acting on the rotor becomes almost constant.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIGS. 1, 2 and 3 show examples in which a torque motor is constituted by an electric motor according to a first embodiment of the present invention.
The torque motor 10 shown in FIG. 1 is used, for example, as an actuator of a throttle device of an internal combustion engine.

As shown in FIG. 2, the throttle body 11 of the throttle device 1 rotatably supports a throttle shaft 31 via bearings 15 and 16. The throttle valve 13 is formed in a disk shape, and the throttle shaft 3
1 is fixed with screws 14. When the throttle valve 13 rotates together with the throttle shaft 31, the flow passage area of the intake passage 11a formed by the inner wall of the throttle body 11 is adjusted, and the flow rate of intake air passing through the intake passage 11a is controlled.

The throttle lever 17 is press-fitted and fixed to one end of the throttle shaft 31, and the throttle lever 17 rotates together with the throttle shaft 31. The stopper screw 18 defines the fully closed position of the throttle valve 13 by making contact with the throttle lever 17. By changing the screwing amount of the stopper screw 18, the fully closed position of the throttle valve 13 can be adjusted. Within a range having a flat torque characteristic around 0 ° shown in FIG.
The opening of the throttle valve 13 is controlled from a fully closed position on the negative side to a fully open position on the positive side. The control opening range varies depending on the required characteristics of the throttle device.

The rotation angle sensor 20 includes a throttle lever 1
It is further provided on the end side of the throttle shaft 31 than 7 and includes a contact portion 21, a substrate 22 coated with a resistor, and a housing 23. Contact part 2
1 is press-fitted into the throttle shaft 31 and rotates together with the throttle shaft 31. The substrate 22 is fixed to the housing 23, and the contact portion 21 slides on the resistor applied to the substrate 22. A constant voltage of 5 V is applied to the resistor applied to the substrate 22, and when the sliding position between the resistor and the contact portion 21 changes according to the opening of the throttle valve 13, the output voltage value changes. An electronic control unit (ECU) (not shown) receives the output voltage value from the rotation angle sensor 20 and detects the opening of the throttle valve 13.

A torque motor 10 is formed at the other end of the throttle shaft 31 by a rotor 30, a stator 40, and a pair of solenoids 50 and 55 as a coil. As shown in FIG. 1 and FIG.
Are a rotor core 32 press-fitted and fixed to a throttle shaft 31 of the throttle device 1, permanent magnet groups 33 and 34 fixed to the outer peripheral surface of the rotor core 32 with an adhesive, and a permanent magnet group 3
An iron cylindrical member 35 as a magnetic member that covers the outer circumferences of the permanent magnets 3 and 34 and is in close contact with the permanent magnet groups 33 and 34 is provided. A gap 36 extending in the axial direction on the outer periphery of the rotor core 32 is formed between the permanent magnet group 33 and the permanent magnet group 34, and each of the permanent magnet groups 33 and 34 has a plurality of flat permanent magnets 33a and 34a, respectively. It is composed of Although the permanent magnets 33a and 34a are in contact with each other on the rotor core 32 side, a gap is formed between the permanent magnets toward the cylindrical member 35 side. The permanent magnets 33a and 34a are magnetized in parallel in one direction, and are bonded to the rotor core 32 in the permanent magnet group 33 and the permanent magnet group 34 with the magnetization directions opposite to each other. Thereby, two poles of N and S are formed on the rotor 30. Permanent magnet group 33, 34
Is positioned in the circumferential direction by convex portions 32 a having a circular cross section provided on the opposite side in the radial direction of the rotor core 32. The permanent magnets 33a and 34a are so-called rare earth magnets that generate a high magnetic force, such as a neodymium-based magnet and a samarium-cobalt-based magnet.

In these permanent magnets, a plurality of permanent magnets (eight in the figure) are assembled to form one of an N pole and an S pole. Each of the permanent magnets has a plate-like or strip-like shape whose width is sufficiently smaller than the width of the arc-shaped magnetic pole formed on the rotor 30, and may be formed into a rod-like shape by making its width sufficiently small. In the rotor 30, the cylindrical member 35 is fitted into the rotor core 32, and the permanent magnets 33a, 34
a into the rotor core 3
2. The permanent magnets 33a and 34a and the cylindrical member 35 are fixed to each other.

The stator 40 shown in FIG. 1 is formed by laminating thin plates made of a magnetic material in the axial direction of the throttle shaft 31, and rotatably accommodates the rotor 30 in an accommodation hole 40a. The stator 40 has a continuous slotless structure around the rotor 30. The solenoids 50 and 55 are formed by winding coils 52 and 57 around iron cores 51 and 56, respectively, and are press-fitted and fixed to the stator 40. The coil 6 has a connector 6
Control currents are supplied from terminals 61 and 62 buried at 0, respectively.

In the torque motor 10 having the rotor 30 configured as described above, the outer circumferences of the plate-shaped permanent magnets 33a and 34a are covered with the cylindrical member 35 made of a magnetic material.
The cylindrical member 35 is radially magnetized with respect to the rotation center of the rotor 30 by the permanent magnets 33a and 34a. The cylindrical members at positions corresponding to the gaps formed between the permanent magnets 33a and between the permanent magnets 34a are also magnetized. Since the magnetic flux reaches the opposite magnetic pole from the circumferential ends of the permanent magnet groups 33 and 34 through the cylindrical member 35, the magnetic flux does not concentrate on the circumferential ends of the permanent magnet groups 33 and 34. Therefore, the magnetic flux directions on the outer periphery of the rotor 30 at positions corresponding to the permanent magnet groups 33 and 34 are substantially equal to the inner peripheral surface of the stator 40, and the permanent magnet groups 33 and 3
The magnetic flux density on the outer periphery of the rotor 30 at the position corresponding to No. 4 becomes substantially equal. Further, the air gap formed between the cylindrical member 35 and the stator 40 is equal in the circumferential direction. As described above, as shown in FIG. 4, when the power to the solenoid units 50 and 55 is turned on, the torque acting on the rotor 30 does not change regardless of the rotation angle (opening degree) of the rotor 30 and is flat. Torque characteristics. Also,
When the power to the solenoid units 50 and 55 is turned off, the detent torque acting on the rotor 30 becomes substantially zero.

In contrast to the first embodiment, as shown in FIG. 9, a conventional rotor 100 which does not cover the outer circumferences of the permanent magnets 102 and 103.
In the configuration described above, the magnetic flux direction and the magnetic flux density on the outer periphery of the rotor 100 fluctuate in the circumferential direction, and the permanent magnets 102 and 103
Since the air gap formed between the rotor and the stator fluctuates in the circumferential direction, the torque acting on the rotor 100 fluctuates depending on the rotation angle of the rotor 100.

In the first embodiment described above, the permanent magnet 3
Although the outer circumferences of 3a and 34a are covered with the cylindrical member 35, the outer circumference of the permanent magnets 33a and 34a may be equally covered with a wire made of a magnetic material to constitute a magnetic member. In addition, each permanent magnet 3
The gap between 3a and 34a may be filled in advance with a non-magnetic resin material, and the outer periphery of the permanent magnets 33a and 34a may be molded with a resin material mixed with a fine or granular magnetic material to form a magnetic member. .

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention.
And FIG. Components that are substantially the same as those in the first embodiment are denoted by the same reference numerals. Cylindrical member 37 which is an iron magnetic member
Covers the permanent magnet group 33 and the permanent magnet group 34,
A slit 37a as a nonmagnetic portion using air as a magnetic resistance is formed in the cylindrical member 37 at a position corresponding to the gap 36 so as to extend in the axial direction. Slit 3 of cylindrical member 37
Portions other than 7a cover the permanent magnet groups 33 and 34,
The connecting portion 37 is provided so that the cross-sectional shape of the cylindrical
b.

A slit 37a is provided at a position corresponding to the gap 36.
Is formed, so that leakage of magnetic flux in the circumferential direction through the cylindrical member 37 between the circumferential end of the permanent magnet group 33 and the circumferential end of the permanent magnet group 34 is suppressed. Therefore, in the second embodiment, when the rotor has the same diameter and the same amount of magnets, as shown in FIG. 7, as compared with the rotor 30 using the cylindrical member 35 having no slit as in the first embodiment, In addition, since the rise of the initial torque at the time of starting rotation from the fully closed position on the negative opening side becomes earlier, the range of generation of the flat torque is expanded. In the second embodiment, only the negative opening range is expanded as shown in FIG. 7, but by adjusting the slit width, the shape of the stator, and the like, the flat torque characteristic range can be adjusted, The opening range can be expanded evenly. For example, by increasing the slit width, the value at the time of the rise of the initial torque can be increased. As a result, the throttle valve 13 quickly rotates in the valve opening direction from the fully closed position receiving a large air resistance, and the responsiveness of the throttle valve 13 is improved.

On the other hand, the permanent magnet groups 33 and 34
7, the torque acting on the rotor 70 has a flat characteristic. Further, since the portion of the cylindrical member 37 that covers the permanent magnet group 33 and the permanent magnet group 34 is connected by the connecting portion 37b, the permanent magnets 33a and 34a fall off due to the centrifugal force of the rotor 70, the impact applied to the throttle device, and the like. Can be prevented.

In the second embodiment, in the rotor 70 having the same diameter and the same amount of magnets as the first embodiment, a slit 37a is formed in the cylindrical member 37 to generate a torque as compared with the first embodiment. Although the range is expanded, if a torque generation range similar to that of the first embodiment is realized, the rotor diameter can be reduced and the amount of magnets can be reduced. This reduces the size of the device and the manufacturing cost.

In the second embodiment, the magnetic member forming the cylindrical member 37 is omitted, and the slit 37a for making the magnetic resistance air is provided as the non-magnetic portion. If the magnetic flux can be prevented from leaking to the magnet group and the deformation of the cylindrical member can be prevented, for example, a plurality of circular missing portions may be provided in the axial direction. Further, a non-magnetic metal material may be used as the non-magnetic portion.

(Third Embodiment) FIG. 8 shows a third embodiment of the present invention.
Shown in Components that are substantially the same as those in the first embodiment are denoted by the same reference numerals. The cylindrical member 38 is formed by ironing or cold forging, and the inner peripheral surface 38a of the cylindrical member 38 has a polygonal cross section in accordance with the outer peripheral surfaces of the bar-shaped permanent magnets 33a and 34a having a trapezoidal cross section. ing. Compared with the configuration in which the outer circumferences of the permanent magnets 33a and 34a are covered with the cylindrical member 35 having a circular cross section on both the outer circumference and the inner circumference as in the first embodiment, the outer circumferences of the permanent magnets 33a and 34a and the inner circumference of the cylindrical member 38 are different. Face 3
8a, that is, the permanent magnets 33a radially opposed to each other,
Since the gap 72 formed between the facing surfaces of the cylindrical member 38 and the cylindrical member 38 is substantially uniform in the circumferential direction, the magnetic flux density of the cylindrical member 38 is substantially uniform in the circumferential direction. Therefore, since the torque acting on the rotor 71 becomes substantially constant within the rotation angle range of the rotor 71, the occurrence of fluctuations in the torque acting on the rotor 71 can be suppressed as compared with the first embodiment.

In the above-described embodiment showing the embodiment of the present invention described above, since the outer circumferences of the permanent magnets 33a and 34a are covered with a cylindrical member made of a magnetic material, the torque acting on the rotor falls within the rotation angle range of the rotor. Can be made substantially constant. As a result, the throttle opening can be controlled with high precision, and the intake flow rate can be controlled with high precision. If the electric motor of the present invention is used as an actuator of the fluid flow control device other than the throttle device, the fluid flow can be controlled with high accuracy. Further, when the electric motor of the present invention is applied to an electric motor that rotates in one direction, it is possible to configure an electric motor having a uniform rotational speed and a uniform rotational speed.

Further, since the magnetic material covers the outer periphery of the permanent magnets 33a, 34a, the permanent magnets 33a, 34a can be prevented from dropping from the rotor core 32.

[Brief description of the drawings]

FIG. 1 is a front view showing a torque motor constituted by an electric motor according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a throttle device using the electric motor according to the first embodiment.

FIG. 3 is a plan view showing the rotor of the first embodiment.

FIG. 4 is a characteristic diagram illustrating a relationship between an opening degree of the torque motor and a generated torque according to the first embodiment.

FIG. 5 is a plan view showing a rotor according to a second embodiment of the present invention.

FIG. 6 is a view taken in the direction of arrow VI in FIG. 5;

FIG. 7 is a characteristic diagram showing the relationship between the opening degree of the torque motor and the generated torque when there is no slit and when there is a slit.

FIG. 8 is a plan view showing a rotor according to a third embodiment of the present invention.

FIG. 9 is a plan view showing a rotor of a conventional electric motor.

FIG. 10 is a characteristic diagram showing a relationship between an opening degree of a torque motor and a generated torque according to a conventional example.

[Explanation of symbols]

 Reference Signs List 1 throttle device 10 torque motor (motor) 30 rotor 32 rotor core 33, 34 permanent magnet group 33a, 34a permanent magnet 35, 37, 38 cylindrical member (magnetic member) 36 gap 37a slit (non-magnetic portion) 38 cylindrical member (magnetic member) ) 38a Inner peripheral surface (opposing surface) 50, 55 Solenoid part (coil part) 70, 71 Rotor

Claims (5)

[Claims] 1. A rotor having a rotor core, a plurality of permanent magnets disposed on the outer periphery of the rotor core, a stator located on the outer periphery of the rotor, and a magnetic force generated during energization, mounted on the stator. An electric motor, comprising: a coil unit that rotates the rotor; and a magnetic member that covers the plurality of permanent magnets. 2. The electric motor according to claim 1, wherein the permanent magnet has a plate shape or a rod shape. 3. The electric motor according to claim 1, wherein the magnetic member is formed in a cylindrical shape. 4. The plurality of permanent magnets constitute two permanent magnet groups, and a gap extending in the axial direction of the rotor core on the outer periphery of the rotor core is formed between one permanent magnet group and the other permanent magnet group. 4. The electric motor according to claim 1, wherein the magnetic member has a non-magnetic portion at a position corresponding to the gap. 5. 5. The magnetic head according to claim 1, wherein a gap between the plurality of radially opposed permanent magnets and the facing surface of the magnetic member is substantially uniform in a circumferential direction. Electric motor.