JP2008219977A - Motor and electric power steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small and lightweight motor, and an electric power steering system equipped therewith. <P>SOLUTION: The outer ring of a bearing 6 is fitted in a tubular rotor 4 on one end side 4a, the inner ring of the bearing 6 is fitted over a supporting protrusion 2b protruding from the bottom wall 2a of a tubular bottomed case 2, and a motor shaft 5 having one end 5a fitted in the rotor 4 on the other side 4b thereof is supported only by a bearing 7 on the opening side of the case 2. Axial length of the motor 1 is shortened by arranging the bearing 6 on the bottom wall 2a side of the case 2 in the case 2 and thereby the motor 1 is made compact. Since the motor shaft 5 does not penetrate the rotor 4, the motor shaft 5 is shortened and the weight of the motor 1 is reduced. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a motor for assisting steering, for example, and an electric power steering apparatus including the motor.

  The electric power steering device drives a steering assist motor in accordance with the rotation operation of the steering wheel, and assists the steering by adding the rotational force of the motor to the steering mechanism. It is classified into pinion assist type, rack assist type, column assist type, etc. depending on the mounting position of the eggplant motor.

  The pinion assist type and the rack assist type are equipped with a steering assist mechanism in the engine room and a motor that is a part of the steering assist mechanism, and are arranged in a limited space in the engine room. There is a desire to make the motor as small as possible. In addition, the column assist type is equipped with a steering assist mechanism and a motor that forms part of the steering assist mechanism on the outside of the column case that supports the steering shaft, ensuring sufficient space for the driver's feet in the passenger compartment. Therefore, there is a demand for miniaturizing the motor as much as possible. In any case, it is particularly important to shorten the axial length of the motor, and the motor is also required to be lightweight.

FIG. 5 is a longitudinal sectional view schematically showing the configuration of the conventional motor 11. Hereinafter, the axial center refers to the axial center of the motor 11.
The motor 11 includes a bottomed cylindrical case 12, a stator 13, and a cylindrical rotor 14 that is rotatably supported inside the case 12. Further, the lid member 18 closes the opening of the case 12.

  A motor shaft 15 that passes through the rotor 14 is fixed to the axial center position of the rotor 14. Both ends of the motor shaft 15 are rotatably supported by bearings 16 and 17, and the bearings 16 and 17 are attached to the case 12 with the inner ring on the motor shaft 15 side. More specifically, the bearing 17 is indirectly attached to the case 12 by being attached to the outer surface of the lid member 18, and the bearing 16 is attached to a recess provided in the bottom wall in the case 12. . Since this recess is formed, a part of the bottom wall of the case 12 protrudes outward by the size of the bearing 16.

As described above, the motor shaft 15 is supported at both ends by the bearings 16 and 17 fixed to the bottom wall side and the opening side of the case 12.
By the way, in a motor having another conventional configuration, a bearing is fitted in a hole formed in the bottom wall of the case with the outer ring on the case side and the inner ring on the motor shaft side (see Patent Document 1). .
JP 2003-309957 A

The conventional motor 11 has a long shaft length because a part of the bottom wall of the case 12 protrudes outward.
Even if the bearing 16 is fitted into the case 12 so that the axial length of the motor is shorter than the axial length of the motor 11, the weight is almost the same as the weight of the motor 11.

  The present invention has been made in view of such circumstances, and a main object thereof is to provide a small and lightweight motor and an electric power steering apparatus including the motor.

  A motor according to a first aspect of the present invention includes a cylindrical case with a bottom and a casing, and both the cylindrical stator and the rotor, and both ends of the rotor are supported by the case by bearings. In order to support the rotor, a support protrusion provided on an inner surface of the bottom wall of the case, and is fitted to the support protrusion and is fitted to one end of the rotor. A first bearing, a motor shaft in which one end is spaced from the support protrusion and is fitted into the other end of the rotor, and the other end projects from the opening of the case; And a second bearing for supporting the end portion.

  A motor according to a second aspect of the present invention includes a bottomed cylindrical case, a cylindrical stator housed in the case, and a bottomed cylindrical rotor, and both ends of the rotor are supported by the case by bearings. In order to support the rotor, a support projection provided on the inner surface of the bottom wall of the case and an outer fit to the support projection, and an inner fit to the opening side of the rotor A first bearing that is provided, a motor shaft that is integrally provided on the bottom side of the rotor and has a tip protruding from the opening of the case, and a second bearing that supports the tip. It is characterized by.

  The motor according to a third aspect of the invention is characterized in that the support protrusion is integrally formed at the axial center position of the inner surface of the bottom wall of the case.

  An electric power steering apparatus according to a fourth aspect of the present invention drives a motor based on a torque sensor that detects a steering torque value applied to a steering member, a motor for assisting steering, and a steering torque value detected by the torque sensor. An electric power steering apparatus comprising a drive control unit for controlling, wherein the motor is any one of the first to third inventions.

  In the case of the motor of the first invention or the motor of the second invention, the bearing on the case bottom wall side is arranged inside the case with the outer ring on the rotor side and the inner ring on the case support projection side. Thus, the motor can be reduced in size. Further, since the motor shaft that is cantilevered by the bearing on the case opening side does not penetrate the rotor, the motor shaft can be shortened, and as a result, the motor can be reduced in weight.

  In the case of the motor according to the third aspect of the invention, since the support protrusion is formed integrally with the case, the number of parts, processing and assembly steps can be reduced, and the coaxial accuracy between the rotor and the stator can be improved.

  In the case of the electric power steering apparatus according to the fourth aspect of the invention, since the motor is reduced in size and weight, the apparatus can be made compact.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.

FIG. 1 is a longitudinal sectional view schematically showing the configuration of a motor 1 according to the present invention. Hereinafter, the axis means the axis of the motor 1.
The motor 1 includes a cylindrical case 2 with a bottom, and the case 2 accommodates a cylindrical stator 3 and a rotor 4. The stator 3 is fitted and fixed to the inner peripheral surface of the case 2 so that the center position in the radial direction of the stator 3 coincides with the axial center position of the motor 1. Both end positions are aligned in the longitudinal direction, and are opposed to each other with a slight air gap in the radial direction.

  The motor 1 further includes a motor shaft 5 inserted into the opening of the case 2 along the axial center position, bearings 6 and 7 for rotatably supporting the rotor 4 inside the case 2, and the axial position. A disc-shaped lid member 8 that is loosely penetrated by the motor shaft 5 and closes the opening of the case 2 is provided.

A cylindrical support protrusion 2b is integrally formed at the axial center position of the inner surface of the bottom wall 2a of the case 2, and a bearing 6 is fitted on the support protrusion 2b. That is, the inner ring of the bearing 6 is disposed on the outer peripheral surface side of the support protrusion 2 b of the case 2.
The inner diameter of the one end side 4a of the rotor 4 is larger than the inner diameter of the other end side 4b. That is, the one end side 4a is formed thinner than the other end side 4b, and the one end side 4a formed so as to be thin is directed to the case 2 bottom wall 2a side and is externally fitted to the bearing 6. Thus, the rotor 4 is rotatably supported by the bearing 6. That is, the outer ring of the bearing 6 faces the inner peripheral surface of the rotor 4.

  As described above, one end side 4 a of the rotor 4 is supported by the case 2 by the bearing 6. Further, since the support protrusion 2b is integrally formed at the axial center position of the inner surface of the bottom wall 2a, the rotor 4 that is externally fitted to the support protrusion 2b via the bearing 6 and the case 2 are internally fitted. The coaxial accuracy with the stator 3 is improved.

One end portion 5 a of the motor shaft 5 (specifically, the end portion on the inside of the case 2) is internally fitted to the other thickness side 4 b of the rotor 4. The motor shaft 5 does not penetrate the rotor 4, and the one end portion 5a and the support protrusion 2b are spaced apart.
Further, the central portion of the motor shaft 5 is loosely penetrated with respect to the lid member 8 that closes the opening of the case 2.

The other end 5b of the motor shaft 5 (specifically, the end on the outside of the case 2) protrudes to the outside of the case 2 and is further fitted into the bearing 7 so that it can rotate freely on the bearing 7. It is supported. That is, the motor shaft 5 is cantilevered by the bearing 7.
Here, the bearing 7 is fixed to the outer surface of the lid member 8.

  As described above, the other end 4 b of the rotor 4 is supported by the case 2 via the motor shaft 5, the bearing 7 and the lid member 8, and the rotor 4 rotates integrally with the motor shaft 5.

In such a motor 1, a part of the bottom wall 2a of the case 2 does not protrude outward. Moreover, the bearing 6 is disposed inside the rotor 4, and a space for arranging the bearing 6 is not separately provided between the case 2 and the rotor 4. For this reason, the axial length dimension of the motor 1 is shortened, and the motor 1 is small.
Further, the motor shaft 5 is shortened so as not to penetrate the rotor 4, and thus the motor 1 is lightweight. In addition, since it is not necessary to shorten the axial length dimension of the rotor 4 (that is, the rotor length), the motor torque is not sacrificed. Further, since the motor shaft 5 is shortened, the inertia is reduced, and the response of the motor 1 is improved.

Furthermore, the case 2 having such a shape is easily formed by die casting using aluminum, deep drawing, resin insert molding, or the like. At this time, the support protrusion 2b is integrally formed. Assembly time is reduced.
The rotor 4 is easily formed by sintering, cold forging, or the like.

  The rotor 4 and the motor shaft 5 are not limited to separate structures, and may be integrated (see FIG. 2 described later). Further, the support protrusion 2b is not limited to the structure formed integrally with the case 2, and may be a separate body (see FIG. 3 described later).

FIG. 2 is a longitudinal sectional view schematically showing another configuration of the motor 1 according to the present invention.
This motor 1 has a cylindrical rotor 4 and a motor shaft 92 provided integrally with the rotor 91 instead of the rotor 4 and the motor shaft 5 separate from the rotor 4. Is provided. For this reason, the bearing 6 that is externally fitted to the support protrusion 2b is internally fitted to the opening side 91a of the rotor.
The motor shaft 92 is integrally provided on the bottom side 91 b of the rotor 91, and the tip end portion 92 b projects from the opening of the case 2. Furthermore, the tip 92 b is rotatably supported by the bearing 7 by being fitted into the bearing 7.

Even in such a configuration, the motor 1 has a part of the bottom wall 2a of the case 2 that does not protrude outward. Moreover, the bearing 6 is disposed inside the rotor 91, and a space for arranging the bearing 6 is not separately provided between the case 2 and the rotor 91. For this reason, the axial length dimension of the motor 1 is shortened, and the motor 1 is small. Further, the motor shaft 92 is shortened so as not to penetrate the rotor 91, and thus the motor 1 is lightweight. Moreover, since it is not necessary to shorten the rotor length of the rotor 91, the motor torque is not sacrificed. Further, since the motor shaft 92 is shortened, the inertia is reduced and the response of the motor 1 is improved.
Furthermore, the rotor 91 and the motor shaft 92 are easily formed integrally by, for example, cold forging.

FIG. 3 is an enlarged longitudinal sectional view schematically showing still another configuration of the motor 1 according to the present invention.
A recess 2d is formed at the axial center position of the inner surface of the bottom wall 2a of the case 2 provided in the motor 1 instead of the support protrusion 2b. Further, the motor 1 includes a columnar support protrusion 2c that has a convex portion that fits in the concave portion 2d on the base end surface, and the bearing 6 is fitted on the distal end portion.
The recess 2d is formed for positioning the support protrusion 2c, and the support protrusion 2c is fixed to the inner surface of the bottom wall 2a of the case 2 by, for example, adhesion.
The support protrusion 2 c has the same function as the support protrusion 2 b integrated with the case 2 except that it is separate from the case 2.

In the case of the motor 1 shown in FIG. 3, since the shape of the case 2 is simple, the case 2 is manufactured at low cost.
The case 2 and the support protrusion 2c can be formed of different materials. For example, in the case of using iron to improve the strength of the case 2, the iron case 2 to which the non-ferrous support protrusions 2c are attached is far more than the case 2 integrally having the support protrusions 2b. Light weight.
Furthermore, the degree of freedom in designing the motor 1 increases. For example, an axial center adjustment mechanism, a worm reducer backlash adjustment mechanism, or the like can be incorporated between the case 2 and the support protrusion 2c to suppress generation of noise, vibration, and the like.

  The motor 1 configured as described above is used, for example, as a steering assist motor of an electric power steering apparatus. FIG. 4 is a schematic diagram illustrating an example of an electric power steering apparatus including the motor 1 according to the present invention.

  The electric power steering apparatus includes a rack shaft 20 that is supported so as to be movable in the axial direction in a rack case 21 that extends in the left-right direction of a vehicle body (not shown), and a pinion housing 31 that crosses the rack case 21 in the middle. And a known rack and pinion type steering mechanism including a pinion shaft 30 rotatably supported therein. Both ends of the rack shaft 20 projecting outward from both sides of the rack case 21 are connected to the left and right front wheels 23, 23 via separate tie rods 22, 22, and a pinion projecting outward from one side of the pinion housing 31 The upper end of the shaft 30 is connected to a steering wheel (steering member) 41 via a steering shaft 40.

In addition, a pinion is formed in the lower part of the pinion shaft 30 extending into the pinion housing 31, and the pinion is formed on the outer surface of the rack shaft 20 at an appropriate length at the intersection with the rack case 21. It is meshed with the rack teeth.
With the above configuration, when the steering wheel 41 is rotated for steering, this rotation is transmitted to the pinion shaft 30 via the steering shaft 40, and the rotation of the pinion shaft 30 moves in the axial direction of the rack shaft 20. By this movement, the left and right front wheels 23 and 23 are pushed and pulled through the respective tie rods 22 and 22 to steer.

  In the middle of the column housing 42 that supports the steering shaft 40, a torque sensor 50 that detects a steering torque value applied to the steering shaft 40 by a rotation operation of the steering wheel 41 is provided, and the motor 1 is positioned below the torque sensor 50. Is installed.

  The motor 1 is attached to the outside of the column housing 42 with its axis substantially orthogonal, and for example, a worm fixed to an output end extending inside the column housing 42 is attached to a worm wheel that is externally fixed to the steering shaft 40. The transmission is configured so that the rotation of the motor 1 is decelerated by the worm and the worm wheel and transmitted to the steering shaft 40. According to this configuration, the rotation of the motor 1 is transmitted to the steering shaft 40 at a reduced speed, and a rotational force is applied to the pinion shaft 30 connected to the lower end of the steering shaft 40. The steering performed as described above is assisted.

  The motor 1 is driven in accordance with a control command given from an assist control unit (drive control unit) 60 via a motor drive circuit (not shown). The detected value of the steering torque by the torque sensor 50 is given to the assist control unit 60. The assist control unit 60 issues a control command to the motor 1 based on this, and performs an assist control operation for increasing / decreasing the drive current of the motor 1. Do. Further, the motor 1 for steering assistance is provided with a motor current sensor 70, and the detected value of the drive current of the motor 1 by the motor current sensor 70 is given to the assist control unit 60, and the assist control unit 60 The deviation between the value and the drive current value is calculated, and feedback control is performed to correct the drive current supplied to the steering assist motor 1 based on this deviation.

  The motor 1 used in the electric power steering apparatus configured as described above is reduced in size by reducing the length in the axial direction. Therefore, in the column assist type electric power steering apparatus in which the motor 1 is attached to the outside of the column housing 42 as shown in the figure and is configured to transmit to the steering shaft 40, the protrusion length of the motor 1 to the outside of the column housing 42 is shown. In addition to being able to secure a sufficient space for the driver's feet in the passenger compartment, the electric power steering device can be installed in a narrow space without sacrificing the assist force. The indoor space can be expanded.

On the other hand, in the pinion assist type and rack assist type electric power steering apparatus in which the motor 1 is mounted on the rack case 21 and is transmitted to the rack shaft 20, the motor 1 is reduced in size, so that the space in the engine room is reduced. For example, it is easy to secure a crushable zone for absorbing impact energy at the time of a car collision, and to secure an installation space when the motor 1 has a large output for a medium-sized vehicle.
The motor 1 may be provided in a device other than the electric power steering device.

1 is a longitudinal sectional view schematically showing the configuration of a motor according to the present invention. FIG. 6 is a longitudinal sectional view schematically showing another configuration of the motor according to the present invention. FIG. 6 is an enlarged longitudinal sectional view schematically showing still another configuration of the motor according to the present invention. It is a mimetic diagram showing an example of an electric power steering device provided with a motor concerning the present invention. It is a longitudinal cross-sectional view which briefly shows the structure of the conventional motor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Motor, 2 Case, 2a Bottom wall, 2b, 2c Support protrusion, 3 Stator, 4,91 Rotor, 5,92 Motor shaft, 6,7 Bearing, 41 Steering wheel (steering member), 50 Torque sensor, 60 Assist control Part (drive control part)

Claims (4)

A bottomed cylindrical case,
The case is housed, and both have a cylindrical stator and a rotor,
In the motor where both ends of the rotor are supported by the case by bearings,
A support protrusion provided on the inner surface of the bottom wall of the case to support the rotor;
A first bearing that is externally fitted to the support protrusion and is internally fitted to one end of the rotor;
One end portion is spaced from the support protrusion and is internally fitted to the other end side of the rotor, and the other end portion protrudes from the opening of the case;
A motor comprising: a second bearing that supports the other end portion. A bottomed cylindrical case,
A cylindrical stator housed in the case and a bottomed cylindrical rotor,
In the motor where both ends of the rotor are supported by the case by bearings,
A support protrusion provided on the inner surface of the bottom wall of the case to support the rotor;
A first bearing that is externally fitted to the support protrusion and is internally fitted to the opening side of the rotor;
A motor shaft provided integrally on the bottom side of the rotor and having a tip protruding from the opening of the case;
A motor comprising: a second bearing that supports the tip portion.   The motor according to claim 1, wherein the support protrusion is integrally formed at an axial center position of an inner surface of the bottom wall of the case. A torque sensor for detecting a steering torque value applied to the steering member;
A steering assist motor;
An electric power steering apparatus comprising: a drive control unit that drives and controls the motor based on a steering torque value detected by the torque sensor;
4. The electric power steering apparatus according to claim 1, wherein the motor is a motor according to claim 1.
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