JP2000168597A - Electric power steering device - Google Patents

Abstract

(57) [Problem] To provide a compact electric power steering device in the axial direction using a short steering shaft in the axial direction. A steering shaft (30) is supported on a housing (10) so as to be axially movable and non-rotatable.
A rotary shaft 51 of an electric motor 50 coaxially disposed on the outer periphery of the motor is supported so as to be axially immovable and rotatable with respect to the housing 10, and converts a rotation of the rotary shaft 51 into an axial movement of the steering shaft 30. 40 is a steering shaft 30 and a rotating shaft 51
In the electric power steering device interposed between the housing 10 and the portion of the steering shaft 30 projecting in the axial direction from the rotation shaft 51, the steering shaft 30 can be moved in the axial direction with respect to the housing 10. The bearing (end bush 71) supported on the housing 10 is movable in the axial direction within a predetermined range with respect to the housing 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus used in a vehicle such as an automobile.

[0002]

2. Description of the Related Art As one type of electric power steering apparatus, a steering shaft is axially movable and non-rotatably supported with respect to a housing, and a rotating shaft of an electric motor arranged coaxially around the steering shaft is provided. A ball screw mechanism that is axially immovable and rotatable with respect to the housing and that converts the rotation of the rotation shaft into the axial movement of the steering shaft is interposed between the steering shaft and the rotation shaft. For example, it is disclosed in JP-A-7-309245.

[0003]

In the electric power steering apparatus disclosed in the above-mentioned publication, a bearing for supporting the steering shaft so as to be movable in the axial direction with respect to the housing is assembled in the housing so as not to be movable in the axial direction. An attached bush is used, and the flat portion (the portion where no screw is formed) of the steering shaft is supported by the bush so as to be movable in the axial direction. For this reason, both the screw portion and the flat portion having the necessary axial length from the right turning end to the left turning end of the steering are required for the steering shaft, and the steering shaft becomes long. Therefore, it is difficult to construct a compact electric power steering device in the axial direction with a short steering shaft. If the bushing is configured to support the screw portion of the steering shaft so that it can move in the axial direction (the bush is arranged closer to the ball screw mechanism in the axial direction), the axial length of the steering shaft can be reduced. However, with such a configuration, the threaded portion of the steering shaft wears the bush early due to the axial movement of the steering shaft, so that the durability of the bush cannot be ensured.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problem, and a steering shaft is axially movable and non-rotatably supported with respect to a housing. The rotating shaft of the electric motor arranged coaxially is supported so as to be axially immovable and rotatable with respect to the housing, and a ball screw mechanism that converts the rotation of the rotating shaft into the axial movement of the steering shaft is provided with the steering shaft. An electric power steering device interposed between the rotating shafts,
A bearing interposed between a portion of the steering shaft protruding from the rotation shaft in the axial direction and the housing and supporting the steering shaft so as to be movable in the axial direction with respect to the housing; There is a feature (the invention according to claim 1) in that it can be moved in the direction.

Further, a steering shaft is axially movable and non-rotatably supported with respect to the housing, and a rotating shaft of an electric motor coaxially arranged around the outer periphery of the steering shaft is axially immovable and non-rotatable with respect to the housing. An electric power steering apparatus, which is freely supported and has a ball screw mechanism that converts rotation of the rotation shaft into axial movement of the steering shaft and is interposed between the steering shaft and the rotation shaft. As a bearing interposed between a portion protruding in the axial direction from the rotation shaft and the housing to support the steering shaft so as to be movable in the axial direction with respect to the housing, the ball screw mechanism is formed on the steering shaft. A conversion mechanism that engages with a thread part that forms a part and converts the axial displacement of the steering shaft into a rotational displacement around the axis; and a rotatable support for the conversion mechanism with respect to the housing. That characterized by employing a bearing having a support mechanism (according to the second aspect of the present invention) is.

Further, a steering shaft is axially movable and non-rotatably supported with respect to the housing, and a rotating shaft of a motor coaxially arranged on the outer periphery of the steering shaft is axially non-movable and rotatable with respect to the housing. An electric power steering device, which is freely supported and has a ball screw mechanism that converts rotation of the rotating shaft into axial movement of the steering shaft and is interposed between the steering shaft and the rotating shaft. An end stopper is provided at one end of the steering shaft so as to restrict the axial movement of the steering shaft by engagement with the one end of the steering shaft (the invention according to claim 3).

[0007]

In the electric power steering apparatus according to the present invention (the invention according to claim 1), the bearing can be moved in the same direction as the steering shaft moves in the axial direction. When the bearing is mounted so that it cannot move in the axial direction with respect to the housing after securing the support stiffness with the bearing (necessary between the right-hand end of steering and the left-hand end of steering between the bearing end of the steering shaft and the bearing). When the axial length is required and the axial length from the bearing end of the rotating shaft to the bearing position is required, the steering shaft moves from the rotating shaft to the bearing side in the axial direction. The length of the projecting portion in the axial direction can be reduced, and a compact electric power steering device can be configured in the axial direction by using a short steering shaft in the axial direction.

Further, in the electric power steering apparatus according to the present invention (the invention according to claim 2), the steering shaft is supported on the housing by effectively using the screw portion of the ball screw mechanism formed on the steering shaft. It is possible to secure the durability of the bearing (a configuration in which the bearing is not worn out early by the screw part of the steering shaft due to the axial movement of the steering shaft). It is possible to arrange the power steering devices closer to each other, so that the steering shaft can be shortened in the axial direction, and a compact electric power steering device can be configured in the axial direction by using the shorter steering shaft in the axial direction. Can be.

Further, in the electric power steering device according to the present invention (the invention according to claim 3), one end of the steering shaft projects from one end of the rotary shaft as compared with the case where the end stopper is provided in the housing. The axial length can be shortened, the steering shaft can be shortened in the axial direction, and a compact electric power steering device can be configured in the axial direction using the short steering shaft in the axial direction. can do.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 show a first embodiment of an electric power steering device according to the present invention. In this power steering device, the power steering device extends in the left-right direction of the vehicle and is mounted on a vehicle body (not shown). The input shaft 20 and the steering shaft 3 are attached to the housing 10 to be assembled.
0, a ball screw mechanism 40, an electric motor 50, and the like.

The input shaft 20 is mounted on the housing 10 so as to be rotatable and immovable in the axial direction, and has a universal joint, an intermediate shaft,
Rotational force (torque) applied to steering wheel (all not shown) via universal joint, steering main shaft, etc.
It comprises a sensor shaft 21 communicatively connected and a pinion shaft 22 connected to the sensor shaft 21 via a torsion bar (not shown). The pinion shaft 22 has a pinion 22a, and engages with a rack tooth 31 formed on one outer periphery of the steering shaft 30 by the pinion 22a so as to transmit a steering force. The vehicle is moved in the left-right direction (axial direction of the steering shaft) of the vehicle. In addition,
A torque sensor S1 that converts the torsion angle of the torsion bar into a voltage is provided on the outer periphery of the intermediate portion of the input shaft 20.

The steering shaft 30 is also called a rack bar, and has a portion (rack teeth 3) corresponding to the pinion 22a.
1 is formed by a well-known rack guide (not shown and attached to the housing 10) provided opposite to the pinion 22a so as to be movable in the radial direction of the steering shaft 30. The housing 10 is supported and has a left end that functions as an end bush 71 (an end stopper that functions as a bearing and regulates rightward movement by contact with a left rack end ball joint 32). Is mounted so as to be movable in the left-right direction of the vehicle (axial direction of the steering shaft) and non-rotatable, and penetrates the housing 10. , Tie rods 6 at both ends
0 and a steering wheel (not shown) via a knuckle arm (not shown) so as to be capable of transmitting a steering force. The screw shaft 41 of the ball screw mechanism 40 is formed integrally with the steering shaft 30. The leftward movement of the steering shaft 30 is restricted by the right rack end ball joint 33 abutting the step (end stopper) 11 of the housing 10.

The ball screw mechanism 40 includes a rotating shaft 51 of the electric motor 50 between an elastic supporting portion (a portion supported by a rack guide) of the steering shaft 30 and a fixed supporting portion (a portion supported by an end bush 71). Is a rotational displacement converting means for converting the rotation of the steering shaft 30 into an axial displacement of the steering shaft 30 and transmitting the converted rotation. The screw shaft 41 is provided coaxially with the steering shaft 30 and is formed integrally with the steering shaft 30. A nut 42 integrally formed on the outer periphery of the screw shaft 41 at the left end of the rotating shaft 51 of the electric motor 50, and a number of balls (steel balls) 43 interposed between the nut 42 and the screw shaft 41. It is configured.

The electric motor 50 applies an axial steering assisting force to the steering shaft 30 via the ball screw mechanism 40, and is mounted coaxially with the steering shaft 30. It has a cylindrical rotary shaft (rotor) 51 that is rotatably mounted via bearings 72 and 73 and cannot move in the axial direction, and a stator 52 that also forms a part of the housing 10. It is controlled by a control device (not shown) based on signals from a torque sensor S1 and a sensor S2 for detecting rotation of the rotating shaft 51.

By the way, in the first embodiment,
An end bush 71 serving as a bearing for supporting the steering shaft 30 so as to be movable in the axial direction with respect to the housing 10 is mounted on the housing 10 so as to be movable in the axial direction. The end bush 71 has its axial movement range set to a predetermined range by a clip 81 and a stopper ring 82 attached to the housing 10, and the steering shaft 30 is moved from the straight traveling state of FIG. When it moves, it is pushed leftward by the clip 34 attached to the steering shaft 30, and when it moves rightward from the right-hand end state to the left-hand end state (not shown) in FIG. The rack end ball joint 32 is pushed rightward by the assembled rack end ball joint 32. Also, the end bush 7
A rubber ring 83 that can abut against the stopper ring 82 is attached to the right end surface of the cylinder 1 so as to buffer the abutment between the end bush 71 and the stopper ring 82 when the steering shaft 30 moves to the left end position. It has become.

In the electric power steering apparatus of the first embodiment configured as described above, the steering force is directly transmitted from the pinion 22a of the input shaft 20 to the portion where the rack teeth 31 of the steering shaft 30 are formed, and the steering shaft 30 is moved. While moving in the axial direction, the output of the electric motor 50 is transmitted to the portion of the steering shaft 30 where the screw shaft 41 is formed via the ball screw mechanism 40 under the control of a control device (not shown). The steering torque is accurately assisted by the assisting force.

By the way, in the electric power steering apparatus of the first embodiment configured as described above, the end bush 71 is attached to the housing 10 so as to be movable in the axial direction, and the steering shaft 30 is not shown. When moving leftward from the straight traveling state of FIG. 1 to the right-turning end state of FIG. 2, the end bush 71 can be pushed leftward by the clip 34 attached to the steering shaft 30, and the steering shaft 30 of FIG. When moving rightward from the right-end end state to the left-end end state (not shown), the end bush 71 can be pushed rightward by the rack end ball joint 32 attached to the left end of the steering shaft 30 to perform steering. The end bush 71 can be moved in the same direction as the shaft 30 moves in the axial direction.

For this reason, after the support rigidity of the steering shaft 30 is secured by the end bush 71, the end bush 7
1 is mounted to the housing 10 so that it cannot be moved in the axial direction (an axial length required between the right-hand end and the left-hand end of the steering is required between the end bush of the steering shaft and the end bush). And the axial length from the end portion of the rotary shaft on the end bush side to the end bushing position is required), and the steering shaft 30 projects from the rotary shaft 51 toward the end bush in the axial direction. Part (substantially left rack end ball joint 32
The axial length of the flat portion from to the clip 34) can be reduced, and a compact electric power steering device can be configured in the axial direction using the steering shaft 30 that is short in the axial direction.

FIG. 3 shows a second embodiment of the electric power steering apparatus according to the present invention. In this power steering apparatus, the end bush 71 is formed as a stepped cylindrical end bush 71 in a right-cut end state. A configuration in which a portion projects outside the housing 10 is employed. Other configurations are the same as those of the first embodiment shown in FIGS.
Since it is the same as the device of the embodiment, the same reference numeral is given and the description is omitted. The operation and effect of the second embodiment are substantially the same as the operation and effect of the first embodiment.
Description is omitted.

FIG. 4 shows a third embodiment of an electric power steering apparatus according to the present invention. In this power steering apparatus, a screw shaft 4 is used as a steering shaft 30.
1 is formed by rolling to the left end, and a structure in which a sleeve 35 is screwed to the left end of the screw shaft 41 is adopted. The sleeve 35 is supported by the end bush 71 so as to be movable in the axial direction. I have. Other configurations are shown in FIG.
Are substantially the same as those of the above-described second embodiment, the same reference numerals are given, and the description is omitted. The operation and effect of the third embodiment are substantially the same as the operation and effect of the first embodiment, and a description thereof will be omitted.

FIGS. 5 and 6 show a fourth embodiment of the electric power steering apparatus according to the present invention. In this power steering apparatus, a steering shaft 130 is supported so as to be axially movable with respect to a housing 110. Three ball bearings (also applicable to other bearings such as needle bearings) 171 as a bearing are mounted on the left rack end ball joint 132 and are movable in the axial direction with respect to the housing 110. Have been.

Each of the ball bearings 171 is disposed at equal intervals in the circumferential direction, is mounted on the left rack end ball joint 132 via a pin 171a, and has a stopper ring mounted on the housing 110. 182
5, the abutment between the right rack end ball joint 133 in the state shown in FIG. 5 and the step portion 111 of the housing 110 makes the axial movement range a predetermined range. Further, each ball bearing 171 is provided on the steering shaft 130.
The axial groove 110a provided in the housing 110 when the rack end ball joint 132 on the left side moves from the right-end end state shown in FIG. 5 to a left-end end state (not shown) in which the left rack end ball joint 132 contacts the stopper ring 182. Along with the left rack end ball joint 132.

The electric power steering apparatus according to the fourth embodiment employs a steering shaft 130 formed by rolling a screw shaft 141 to the left end.
Rack end ball joint 1 on the left end of screw shaft 141
32 are provided. The other configuration is substantially the same as the device of the first embodiment shown in FIGS. 1 and 2, and thus the same reference numerals in the hundreds are used and the description is omitted.

In the electric power steering apparatus of the fourth embodiment configured as described above, the ball bearing 171 can be moved in the same direction as the steering shaft 130 moves in the axial direction. When the bearing for supporting the steering shaft 130 so as to be able to move in the axial direction is assembled to the housing so as not to be able to move in the axial direction after securing the support rigidity by the ball bearing 171 (between the bearing side end of the steering shaft and the bearing). The required axial length from the right-hand end to the left-hand end of the steering, and the axial length from the bearing end of the rotating shaft to the bearing position is required. , Rotating shaft 15 of steering shaft 130
It is possible to shorten the axial length of the portion that protrudes leftward from 1 and to configure a compact electric power steering device in the axial direction using the short steering shaft 130 in the axial direction. it can.

FIG. 7 shows a fifth embodiment of the electric power steering apparatus according to the present invention. In this power steering apparatus, a sleeve 35 is attached to the screw shaft 41 of the third embodiment shown in FIG. Instead, a nut 274 is attached to the end bush 271, and a plurality of balls (steel balls) 275 are interposed between the nut 274 and the screw shaft 241. Other configurations are substantially the same as those of the device of the third embodiment shown in FIG. 4, and therefore, the same reference numerals in the 200s are used and the description is omitted.

The nut 274 is engaged with a screw shaft 241 forming a part of the ball screw mechanism 240 via a ball 275, and converts the axial displacement of the steering shaft 230 into a rotational displacement around the axis. And is rotatably mounted on the end bush 271 via a needle bearing 276 so as not to move in the axial direction. The needle bearing 276 constitutes a support mechanism that rotatably supports the nut 274 with respect to the housing 210 with the end bush 271.
The 71, the nut 274, the ball 275, and the like constitute a bearing that supports the steering shaft 230 so as to be movable in the axial direction with respect to the housing 210.

In the electric power steering apparatus according to the fifth embodiment configured as described above, the screw shaft 241 of the ball screw mechanism 240 formed on the steering shaft 230 is effectively used to move the steering shaft 230 to the housing 210. End bush 271, nut 27
4. The bearing is composed of the ball 275, the needle bearing 276, etc., in which the durability of the bearing is secured (the bearing is not worn out early by the threaded portion of the steering shaft 230 due to the axial movement of the steering shaft 230). The ball screw mechanism 240 can be disposed closer to the axial direction, so that the steering shaft 230 can be configured to be shorter in the axial direction. A compact electric power steering device can be configured.

FIG. 8 shows a sixth embodiment of the electric power steering apparatus according to the present invention. In this power steering apparatus, a nut 274 is connected to the housing 2.
A ball bearing 277 is employed as a support mechanism rotatably supporting the bearing 10. The ball bearing 277 is assembled to the housing 210 via a holder 278 that also functions as an end stopper that regulates the rightward movement of the steering shaft 230 in the axial direction.
9 prevents it from falling off. The other configuration is substantially the same as the device of the fifth embodiment shown in FIG. 7, and thus the same reference numerals are given and the description is omitted. In addition, this sixth
The operation and effect of the fifth embodiment are substantially the same as those of the fifth embodiment, and a description thereof will be omitted.

FIGS. 9 and 10 show a seventh embodiment of the electric power steering apparatus according to the present invention. In this power steering apparatus, an end stopper 380 is integrated with the left end of the rotating shaft 351 of the electric motor 350. It is attached to. The end stopper 380 restricts the axial movement of the steering shaft 330 to the right by engaging with the left end of the steering shaft 330, that is, the rack end ball joint 332, and has a rubber cushion for the left end surface. A ring 383 is attached. The other configuration is substantially the same as the device of the sixth embodiment shown in FIG. 8 (however, members corresponding to the nut 274, the ball 275, the ball bearing 277, the holder 278, and the clip 279 are not provided). Therefore, similar reference numerals in the 300's are attached and description thereof is omitted.

In the electric power steering apparatus of the seventh embodiment configured as described above, the left end of the steering shaft 330 is different from the case where the end stopper (holder 278) is provided on the housing 310 as shown in FIG. Is the rotating shaft 35
1, the axial length protruding from the left end can be shortened, and the steering shaft 330 can be shortened in the axial direction. A compact electric power steering device can be configured. The left end of the steering shaft 330 is the rotating shaft 3
The inertial energy of the rotating shaft 351 can be absorbed by the frictional engagement force generated by engaging the end stopper 380 provided at the left end of the shaft 51 via the rubber ring 383, and the load applied to the ball screw mechanism 340 can be reduced. Can be reduced.

[Brief description of the drawings]

FIG. 1 is an overall view showing a first embodiment of an electric power steering apparatus according to the present invention.

FIG. 2 is an overall view of the electric power steering apparatus shown in FIG. 1, in which a steering shaft has moved to a right-turn end position.

FIG. 3 is an overall view showing a second embodiment of the electric power steering apparatus according to the present invention.

FIG. 4 is an overall view showing a third embodiment of the electric power steering apparatus according to the present invention.

FIG. 5 is an overall view showing a fourth embodiment of the electric power steering apparatus according to the present invention.

FIG. 6 is a sectional view taken along line 6-6 in FIG. 5;

FIG. 7 is an overall view showing a fifth embodiment of the electric power steering apparatus according to the present invention.

FIG. 8 is an overall view showing a sixth embodiment of the electric power steering apparatus according to the present invention.

FIG. 9 is an overall view showing a seventh embodiment of the electric power steering apparatus according to the present invention.

10 is an overall view of the electric power steering apparatus shown in FIG. 9 in a state where a steering shaft has moved to a right-turn end position.

[Explanation of symbols]

10 housing, 11 step, 20 input shaft, 30
Steering shaft, 40: ball screw mechanism, 41: screw shaft, 42 ...
Nut, 43 ... ball, 50 ... electric motor, 51 ... rotating shaft,
52: stator, 71: end bush (bearing), 7
2,73 ... Ball bearing.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hajime Uemae 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Kenichi Fukumura 1-1-1, Asahimachi, Kariya City, Aichi Prefecture Toyoda Machine Works Co., Ltd. In-house F-term (reference) 3D032 CC48 DA04 DA15 EA01 EB11 EC22 GG01 3D033 CA02 CA04 JB02 JB15

Claims (3)

[Claims] 1. A steering shaft is axially movable and non-rotatably supported with respect to a housing, and a rotating shaft of an electric motor coaxially arranged on the outer periphery of the steering shaft is axially immovable and non-rotatable with respect to the housing. An electric power steering apparatus, which is freely supported and has a ball screw mechanism that converts rotation of the rotation shaft into axial movement of the steering shaft and is interposed between the steering shaft and the rotation shaft. A bearing interposed between a portion protruding in the axial direction from the rotary shaft and the housing and supporting the steering shaft so as to be movable in the axial direction with respect to the housing is movable in a predetermined range with respect to the housing in the axial direction. An electric power steering device, characterized in that: 2. A steering shaft is axially movable and non-rotatably supported with respect to a housing, and a rotating shaft of an electric motor coaxially arranged on an outer periphery of the steering shaft is axially immovable and non-rotatable with respect to the housing. An electric power steering apparatus, which is freely supported and has a ball screw mechanism that converts rotation of the rotation shaft into axial movement of the steering shaft and is interposed between the steering shaft and the rotation shaft. As a bearing interposed between a portion protruding in the axial direction from the rotation shaft and the housing to support the steering shaft so as to be movable in the axial direction with respect to the housing, the ball screw mechanism is formed on the steering shaft. A conversion mechanism that engages a threaded part of the steering shaft to convert the axial displacement of the steering shaft into a rotational displacement about the axis; and a support that rotatably supports the conversion mechanism with respect to the housing. An electric power steering device comprising a bearing having a holding mechanism. 3. A steering shaft is axially movable and non-rotatably supported with respect to the housing, and a rotating shaft of an electric motor coaxially arranged around the outer periphery of the steering shaft is axially immovable and non-rotatable with respect to the housing. An electric power steering device, which is freely supported and has a ball screw mechanism that converts rotation of the rotating shaft into axial movement of the steering shaft and is interposed between the steering shaft and the rotating shaft. An electric power steering device, wherein an end stopper is provided at one end to restrict axial movement of the steering shaft by engagement with one end of the steering shaft.