JP2002284020A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of stably reducing a shock force in a torque transmission path of an electric motor by a simple configuration. SOLUTION: In this electric power steering device 10, a rotary shaft 32 and an assist shaft 33 of the electric motor 30 are connected by faucet in a connection part of both, and a torque limiter 81 slipping at a predetermined torque is provided between both of them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an electric power steering apparatus.

[0002]

2. Description of the Related Art An electric power steering apparatus is disclosed in
As described in 11-342856, the electric motor is fixed to the housing, the housing supports the assist shaft of the steering device,
An assist shaft is connected to a rotating shaft of the electric motor, and torque of the electric motor is transmitted to a steering device to assist steering.

[0003]

In a conventional electric power steering apparatus, when a stroke of a torque transmission gear connected to an assist shaft is suddenly stopped, for example, when a tire rides on a curb during steering, the electric motor becomes inoperable. Even if the power supply is stopped, an inertia torque is generated to keep rotating due to inertia, and this inertia torque may damage the torque transmission gear and deteriorate the steering feeling.

[0004] It is an object of the present invention to stably reduce an impact force in a torque transmission path of an electric motor with a simple configuration in an electric power steering device.

[0005]

According to a first aspect of the present invention, there is provided an electric motor in which an electric motor is fixed to a housing, an assist shaft of a steering device is supported on the housing, and an assist shaft is connected to a rotating shaft of the electric motor. In a power steering apparatus, a connecting part between a rotary shaft and an assist shaft of an electric motor is spigot-coupled to each other, and a torque limiter that slips at a predetermined torque is interposed between the two.

According to a second aspect of the present invention, when the rotating shaft and the assist shaft of the electric motor are connected via a connecting member, the rotating shaft is inserted into the connecting member. A torque limiter is interposed between the inner periphery of the shaft and the outer periphery of the rotating shaft.

According to a third aspect of the present invention, when the assist shaft is supported by the housing, the assist shaft is elastically supported bidirectionally in the axial direction.

[0008]

According to the first aspect of the present invention, the following effects are obtained. When the stroke of the torque transmission gear is suddenly stopped, for example, when the tire rides on a curb, inertia torque is generated due to the fact that the electric motor keeps rotating even if the power supply to the electric motor is stopped. The torque can be absorbed by the slip of the torque limiter. That is, the presence of the torque limiter between the rotating shaft and the assist shaft interrupts the inertia torque equal to or greater than the limit torque transmitted from the rotating shaft of the electric motor to the assist shaft, thereby preventing the torque transmission gear from being damaged, and reducing the steering torque. The deterioration of the ring can be avoided.

[0009] The rotary shaft and the assist shaft are spigot-coupled so that the rotational centers of the two can easily and stably coincide with each other, so that an eccentric load caused by the deviation of the rotational centers of both does not act on the torque limiter. Therefore, the torque limiter acts only on the rotational torque, and with a simple configuration that is not affected by the processing and assembling accuracy of the parts, the stability of the limit torque can be maintained, and the stable shock absorbing characteristics can be secured. Further, the durability of the torque limiter can be improved.

Since the impact force transmitted from the electric motor to the torque transmission gear can be reduced, the durability of the housing supporting the torque transmission gear can be improved, and the weight of the device can be reduced by reducing the thickness of the housing.

According to the second aspect of the present invention, the following operations are provided. By disposing the torque limiter inside the connection body that connects the rotating shaft and the assist shaft, it is possible to prevent the torque limiter from falling off.

According to the third aspect of the invention, the following effects are obtained. The assist shaft is elastically supported on the housing in both axial directions. Therefore, when an excessive thrust acts on the assist shaft at the time of reversing drive of the electric power steering device or at the time of riding on a curb of the tire, the assist shaft can move in the axial direction under the elastic support state, and as a result, the assist shaft is connected to the assist shaft. The impact force generated on the tooth surface of the torque transmission gear is reduced to reduce the tapping noise between the tooth surfaces, or the torque transmission path is prevented from being damaged by the inertial thrust of the assist shaft.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a front view showing an electric power steering apparatus partially cut away, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. 3 is a sectional view taken along the line III-III of FIG. 4 is a sectional view taken along line IV-IV in FIG. 3, FIG. 5 shows a magnet holder, (A) is a side view, (B) is a front view, and (C)
6 is a cross-sectional view taken along the line CC, FIG. 6 is a cross-sectional view showing a connection portion between the rotation shaft and the assist shaft in FIG. 3, FIG. 7 is a cross-sectional view showing an elastic deformation tool, and FIG. It is sectional drawing which follows the VIII line.

As shown in FIGS. 1 and 2, the electric power steering device 10 is a gear housing 1 made of an aluminum alloy and fixed to a vehicle body frame or the like by a bracket (not shown).
1 (first to third gear housings 11A to 11C). A pinion shaft 14 is connected to a steering shaft 12 to which a steering wheel is coupled via a torsion bar 13. It is supported by the first gear housing 11A so as to be movable left and right. Steering shaft 12 and pinion shaft 14
Between them, a steering torque detecting device 17 is provided. still,
The steering shaft 12 and the pinion shaft 14 have bearings 12A, 1
It is supported by the gear housing 11 via 4A and 14B.

As shown in FIG. 2, the steering torque detector 17 includes two detection coils 17A surrounding a cylindrical core 17C engaged with the steering shaft 12 and the pinion shaft 14,
17B is provided in the third gear housing 11C. The core 17C is provided with a vertical groove 17E that engages with the guide pin 17D of the pinion shaft 14 so as to be movable only in the axial direction, and has a spiral groove 17G that engages with the slider pin 17F of the steering shaft 12. As a result, the steering torque applied to the steering wheel is applied to the steering shaft 12, and when a relative displacement in the rotational direction occurs between the steering shaft 12 and the pinion shaft 14 due to the elastic torsional deformation of the torsion bar 13, the steering shaft 12 The displacement of the pinion shaft 14 in the rotation direction causes the core 17C to be displaced in the axial direction, and the displacement of the core 17C changes the inductance of the detection coils 17A and 17B due to magnetic changes around the detection coils 17A and 17B. . That is, when the core 17C moves toward the steering shaft 12, the inductance of the detection coil 17A closer to the core 17C increases, and the inductance of the detection coil 17B closer to the core 17C decreases. Can be detected.

The rack shaft 1 in the first gear housing 11A
As shown in FIG. 2, a rack guide 19 is built in a cylinder portion 18 provided at a portion opposed to the pinion 15 with one end of the bush 6 interposed therebetween.
9A) is repelled toward the rack shaft 16 by a spring 21 supported on the back surface by a cap 20 attached to the cylinder portion 18 to press the rack 16A of the rack shaft 16 against the pinion 15 and to connect one end of the rack shaft 16 to the pinion 15. It is slidably supported. The other end of the rack shaft 16 is supported by a bearing 22. In the middle part of the rack shaft 16, left and right tie rods 23A, 23 are connected by connecting bolts 22A, 22B.
B is connected.

As shown in FIG. 3, a motor case 31 of the electric motor 30 is fixed to the second gear housing 11B, and an assist shaft 33 is connected to a rotating shaft 32 of the electric motor 30 via a connector 80. The assist shaft 33 is supported at both ends of the second gear housing 11B by bearings 91 and 92 such as ball bearings. And assist axis 3
A worm gear 37 is integrally provided at an intermediate portion of the pinion shaft 3, and a worm wheel 38 meshing with the worm gear 37 is fixed to an intermediate portion of the pinion shaft 14. The torque generated by the electric motor 30 is applied to the rack shaft 16 as a steering assist force via the engagement between the worm gear 37 and the worm wheel 38 and the engagement between the pinion 15 and the rack 16A. To assist the steering force.

Here, the electric motor 30 is configured as follows. That is, the electric motor 30 is, as shown in FIG.
A cylindrical yoke 52 formed of a magnetic material such as iron;
A magnet holder 53 composed of a cylindrical body 53A formed of an insulating resin material forming a magnet housing section 53B at a plurality of circumferential positions on the inner circumference of the yoke 52, and a magnet holder 53 of the magnet holder 53 positioned and housed in the magnet housing section 53B. The stator 51 includes a magnet 54 to be held and a magnet cover 55 (not shown) formed of an extremely thin plate of a non-magnetic material which is press-fitted inside the magnet 54 positioned and held by the magnet holder 53.

The electric motor 30 has a rotor 56 inserted inside the stator 51 and fixed to the rotating shaft 32. The rotor 56 includes an amateur core 57 and a commutator 58 provided on the outer periphery of the rotating shaft 32.

As shown in FIG. 4, the electric motor 30 is made of a brush 61 which is brought into contact with a commutator 58 of a rotor 56, and an insulating resin material which forms a brush holding portion 62B for positioning and holding the brush 61. And a brush holder 62 made of a short cylindrical body 62A. In addition, the electric motor 30 is connected to the brush 61 positioned and held by the brush holder 62 via the pigtail through the connection terminal 63.
A, and a power supply connector 63 integrally formed with the brush holder 62 with an insulating resin material containing the connection terminal 63A.

When electric power is supplied from the brush 61 to the armature core 57 via the commutator 58 of the rotor 56, the magnetic lines of force of the armature core 57 are applied to the stator 51.
By cutting off the magnetic field generated by the magnet 54, the rotor 56 rotates.

[0022] However, the electric motor 30 is provided with a characteristic structure of the following as. (1) In the electric motor 30, the yoke 52 is a cylindrical body with one end opened and the other end closed, and the yoke 52 is used as the motor case 31. The yoke 52 has one end flange portion 52A fixed to the housing 11B and the other end closing portion 52B.

(2) As shown in FIG. 5, the magnet holder 53 has a cylindrical body 53A having a magnet accommodating section 53B.
The outer periphery of the tubular body 53A is spigot-coupled to the yoke 52, and the engaging portion 53C that engages with the engaging portion 62C of the brush holder 62 is connected to the outer periphery of the tubular body 53A so that the circumferential specific position And the outer periphery of the engaging portion 53C can be spigot-coupled to the housing 11B.

(3) As shown in FIG. 4, the brush holder 62 forms a short cylindrical body 62A having a brush holding portion 62B, and the brush holding portions 62B are formed at a plurality of circumferential positions on the inner periphery of the short cylindrical body 62A. The spring 6 is attached to the brush holding portion 62B.
4. The brush 61 is inserted, and the brush 61 is pressed against the commutator 58 of the rotor 56 by the spring force of the spring 64. In the brush holder 62, one end of the outer periphery of the short cylinder 62A is spigot-coupled to the yoke 52 constituting the motor case 31, and the other end of the outer periphery of the short cylinder 62A is spigot-coupled to the housing 11B.

The brush holder 62 has a concave engaging portion 62C at a specific position on one end in the circumferential direction. By engaging the engaging portion 53C of the magnet holder 53 with the engaging portion 62C of the brush holder 62, the magnet holder 5
3 eliminates a phase shift of the brush 61 held by the brush holder 62 with respect to the magnet 54 of the stator 51 positioned by the stator 3, and prevents the rotation performance of the electric motor 30 from being different in the normal rotation direction and the reverse rotation direction. Avoid drop.

(4) The grommet 66 is provided in the brush holder 62.
There is assembled is deposited. The grommet 66 is a connection portion between the housing 11B and the motor case 31 (yoke 52), and is a connector seal portion 6 which is mounted on a connector insertion portion 68 formed by cutting out a flange portion 67 of the housing 11B.
6A and an O-ring 66B that is loaded into a ring groove 69 formed in the flange 67 of the housing 11B. The brush holder 62 includes a connector seal portion 66A of the grommet 66 on the power supply connector 63 and an O-ring 6 of the grommet 66 on the short cylindrical body 62A of the brush holder 62.
6B, the housing 11B and the motor case 3
1 (yoke 52) is assembled in a liquid-tight manner at the connection portion.

(5) According to the above (2) to (4), the electric motor 30
Is fixed to the housing 11B as follows.

The grommet 66 is attached to the brush holder 62. The cylindrical body 53A of the magnet holder 53 is spigot-coupled to the motor case 31 (yoke 52) of the electric motor 30. Subsequently, the motor case 31 (yoke 52)
One end side of the short cylindrical body 62A of the brush holder 62 is spigot-coupled. At this time, the engaging portion 62 of the brush holder 62
C is engaged with the engaging portion 53C of the magnet holder 53.

The engaging portion 53C of the magnet holder 53 is spigot-coupled to the spigot coupling portion 65 of the housing 11B. At the same time, the other end side of the short cylindrical body 62A of the brush holder 62 is spigot-coupled to the spigot coupling portion 65 of the housing 11B.

At the same time as described above, the connector seal 66A of the grommet 66 is connected to the flange 6 of the housing 11B.
The O-ring 66 </ b> B of the grommet 66 is sealed to the connector
B is loaded into the ring groove 69 provided in the flange 67 and is sealed between the flange 67 and the flange 52 </ b> A of the yoke 52.

The motor case 31 (yoke 52) of the electric motor 30 includes the motor case 31 (yoke 52) using the magnet holder 53 described above and the housing 1
The flange portion 52 of the yoke 52 is centered on the housing 11B by the spigot connection with the housing 11B by the spigot connection with the housing 11B and the spigot connection between the motor case 31 (yoke 52) and the housing 11B using the brush holder 62.
A is fastened and fixed to the flange 67 of the housing 11B.

Next, a structure for supporting the rotating shaft 32 of the electric motor 30 and the assist shaft 33 on the motor case 31 and the housing 11B will be described.

(A) Supporting Structure of Assist Shaft 33 (FIG. 6) As shown in FIG.
It is elastically supported in both directions in the axial direction with respect to the housing 11B.
Excessive thrust acting on the assist shaft 33 can be absorbed when the tire runs on a curb.

Specifically, as shown in FIG. 6, both ends of the assist shaft 33 are supported by the housing 11B by bearings 91 and 92 mounted on both sides of the worm gear 37. The bearing 91 is constituted by an angular ball bearing or the like including an inner ring 91A, an outer ring 91B, and a rolling element 91C. The inner ring 91A is clearance-fitted to the assist shaft 33 so as to be relatively movable in the axial direction, and the outer ring 91B is connected to the housing 11B. A step 93 of
It is fixed to the housing 11B while being sandwiched between stopper rings 94 engaged with the housing 11B. The bearing 92 is constituted by an angular ball bearing or the like including an inner ring 92A, an outer ring 92B and a rolling element 92C.
3, the outer ring 92B is press-fitted into the stepped portion 95 of the housing 11B and fixed to the stepped portion 95 so as to be relatively movable in the axial direction.

The assist shaft 33 has an elastic deformation member 97 interposed between an inner ring engaging portion 96 provided on the side of the worm gear 37 with respect to the bearing 91 and the inner ring 91A of the bearing 91, and the worm gear 37 with respect to the bearing 92. An elastic deformation tool 99 is interposed between the inner ring engaging portion 98 provided on the side of the inner ring and the inner ring 92A of the bearing 92. As shown in FIG. 7, the elastic deforming member 97 and the elastic deforming member 99 are elastic plates 97A and 99A made of rubber having an annular shape with a rectangular cross section, and a flat plate disk bonded to both side surfaces of the elastic members 97A and 99A by burning. Washer 97B, 9
7C, 99B, and 99C. The elastic bodies 97A and 99A are provided with a fixed pre-compression amount (a fixed shock absorbing performance) under the above-described loading state on the assist shaft 33, and are assembled.
As a result, the assist shaft 33 is elastically supported in both directions in the axial direction.

(B) Structure for supporting the rotating shaft 32 (FIGS. 3, 6 to 6)
As shown in FIGS. 3 and 6, one end of the rotating shaft 32 of the electric motor 30 is supported by a bearing 71 provided at the center of the other end closing portion 52B of the motor case 31 (yoke 52). The end has an unsupported structure.

More specifically, one end of the rotating shaft 32 is connected to the motor case 3 by a bearing 71 constituted by an angular ball bearing or the like comprising an inner ring 71A, an outer ring 71B and a rolling element 71C.
Supported by 1. Then, the other end of the rotating shaft 32 and one end of the assist shaft 33 are coaxially connected inside the connector 80, and a fitting shaft (or fitting hole) provided at the other end of the rotating shaft 32. 32A is spigot-coupled to a fitting hole (or fitting shaft) 33A provided at one end of the assist shaft 33.

Further, the fitting shaft portion 32B adjacent to the fitting shaft portion 32A of the rotary shaft 32 is inserted into the connection body 80, and the large inner diameter portion 80A of the connection body 80 and the outer periphery of the fitting shaft portion 32B are inserted. A torque limiter 81 that slips at a predetermined torque is interposed therebetween, and a fitting shaft 33B adjacent to the fitting hole 33A of the assist shaft 33 is splined (or serrated) to a small inner diameter portion 80B of the connecting body 80. did. As shown in FIG. 8, the torque limiter 81 is formed by an elastic ring of a spring resin or the like which is press-fitted between the large inner diameter portion 80A of the connecting body 80 and the outer periphery of the fitting shaft portion 32B and is elastically supported in the radial direction. With the normally used torque of the electric power steering device 10 (torque smaller than the limit torque), the connecting body 80 and the fitting shaft portion 32B continue to be connected without slipping by the elastic force of the elastic ring, while the tire is steered. If the inertia torque of the electric motor 30 exceeds the elastic force of the elastic ring when the stroke of the rack shaft 16 is suddenly stopped due to, for example, riding on a curb, etc. (torque exceeding the limit torque). , The rotating shaft 32 is slipped with respect to the connecting body 80,
It functions so as not to transmit the torque of the electric motor 30 to the connector 80 side.

Accordingly, the rotating shaft 32 and the assist shaft 33 of the electric motor 30 are spliced to each other so that they are coaxially coupled to each other. As a result, the end of the rotating shaft 32 connected to the assist shaft 33 is the motor case 31. The two ends of the assist shaft 33 are supported at two points on the housing 11B via the bearings 91 and 92, and only one end of the rotating shaft 32 is supported by the bearing 71 described above. 31 is supported at one point.

In the electric motor 30, the step 80C at the boundary between the large-diameter portion 80A and the small-diameter portion 80B of the connector 80 is connected to the step 32C at the boundary between the fitting shaft 32A and the fitting shaft 32B of the rotary shaft 32. In an abutting state in the axial direction, an O-ring (or disc spring) elastic body 85 is provided between the end face of the connecting body 80 and the end face of the inner ring 91A of the bearing 91 (or the flange-shaped step portion of the assist shaft 33). Is interposed. The elastic body 85 includes the rotating shaft 32.
To the anti-assist shaft 33 side in the axial direction,
The play in the axial direction of the rotating shaft 32 can be eliminated, and the occurrence of a tapping sound can be prevented.

Therefore, according to the present embodiment, the following operations are provided. When the stroke of the rack shaft 16 is suddenly stopped, for example, at the time of riding on a curb of a tire, an inertia torque is generated by the electric motor 30 continuing to rotate even when the power supply to the electric motor 30 is stopped. This inertia torque can be absorbed by the slip of the torque limiter 81. That is, the inertia torque equal to or greater than the limit torque transmitted from the rotating shaft 32 of the electric motor 30 to the assist shaft 33 is cut off by the presence of the torque limiter 81 between the rotating shaft 32 and the assist shaft 33. As a result, the worm gear 37 and the worm wheel 38 can be prevented, and the steering feeling can be prevented from deteriorating.

The rotating shaft 32 and the assist shaft 33 are spigot-coupled, so that the rotational centers of the two can easily and stably coincide with each other. do not do. Therefore, the torque limiter 81 acts only on the rotational torque, and with a simple configuration that is not affected by the precision of processing and assembling the parts, the stability of the limit torque can be maintained and the stable impact relaxation characteristics can be secured. Further, the durability of the torque limiter 81 can be improved.

From the electric motor 30 to the worm gear 37,
Since the impact force transmitted to the worm wheel 38 and the like can be reduced, the durability of the housing 11B supporting the worm gear 37 and the worm wheel 38 can be improved, and the weight of the device can be reduced by making the housing 11B thinner.

The torque limiter 81 can be prevented from falling off by interposing the torque limiter 81 inside the connecting body 80 connecting the rotary shaft 32 and the assist shaft 33.

The assist shaft 33 is elastically supported on the housing in both axial directions. Therefore, when an excessive thrust acts on the assist shaft 33 at the time of the inversion drive of the electric power steering device or at the time of riding on a curb of the tire, the assist shaft 33 can move in the axial direction under the elastically supported state, and as a result, the assist shaft The impact force generated on the tooth surface of the torque transmission gear connected to the gear 33 is reduced to reduce the tapping noise between the tooth surfaces, or the torque transmission path is prevented from being damaged by the inertial thrust of the assist shaft 33.

The embodiment of the present invention has been described with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and changes in design and the like can be made without departing from the scope of the present invention. The present invention is also included in the present invention. For example, when the rotating shaft and the assist shaft of the electric motor are spigot-coupled, the two are not limited to those directly spigot-coupled, but may be those in which spurs are indirectly spliced via a connector 80 or the like.

[0047]

As described above, according to the present invention, in the electric power steering apparatus, the impact force in the torque transmission path of the electric motor can be stably reduced with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a front view showing an electric power steering apparatus partially cut away.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a sectional view taken along the line III-III of FIG. 2;

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3;

5A and 5B show a magnet holder, wherein FIG. 5A is a side view, FIG. 5B is a front view, and FIG. 5C is a cross-sectional view along the line CC.

FIG. 6 is a cross-sectional view showing a connection portion between the rotation shaft and the assist shaft in FIG. 3;

FIG. 7 is a sectional view showing an elastic deformation tool.

FIG. 8 is a sectional view taken along line VIII-VIII in FIG.

[Explanation of symbols]

 Reference Signs List 10 electric power steering device 11B housing 30 electric motor 32 rotating shaft 33 assist shaft 80 connector 81 torque limiter

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hiroshi Fujita 112-1 Hagadai, Haga-cho, Haga-gun, Tochigi Prefecture F-term in Showa Automobile Development Center Co., Ltd. 3D033 CA05

Claims (3)

[Claims] 1. An electric power steering apparatus comprising an electric motor fixed to a housing, an assist shaft of a steering device supported on the housing, and an assist shaft connected to a rotating shaft of the electric motor. An electric power steering device, comprising: a connecting portion of an assist shaft, which is spigot-coupled to each other, and a torque limiter that slips at a predetermined torque is interposed between the two. 2. When connecting the rotating shaft and the assist shaft of the electric motor via a connecting member, a rotating shaft is inserted into the connecting member, and a torque limiter is provided between an inner periphery of the connecting member and an outer periphery of the rotating shaft. The electric power steering device according to claim 1, further comprising: 3. The electric power steering apparatus according to claim 1, wherein the assist shaft is elastically supported in both directions in the axial direction when the assist shaft is supported by the housing.