JP2019214311A - Rear wheel steering device and vehicle - Google Patents

Abstract

To provide a compact rear wheel steering device.SOLUTION: A motor output shaft 28 is supported by a first bearing 23L having a rolling element 43 rolling along an inside raceway surface 41a and an outside raceway surface 42a, and a retainer 44 for retaining the rolling element 43. A planetary reduction gear is constituted of the first bearing by performing traction drive between the inside raceway surface 41a of the first bearing 23L and the rolling element 43, and between the outside raceway surface 42a and the rolling element 43. The reduction gear 23L is interposed on a torque transmission path between the motor output shaft 28 and a motion conversion mechanism 24L.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a rear wheel steering device used for a vehicle such as an automobile.

  A car equipped with a mechanism to steer the rear wheels in addition to a mechanism to steer the front wheels in order to enhance the running stability when the car is traveling straight or turning, or the toe angle of the rear wheels according to the running condition of the vehicle A vehicle equipped with a mechanism for changing the pressure is being put to practical use.

  For example, Patent Literature 1 discloses a rear wheel steering device that steers a rear wheel according to a steering angle of a front wheel when a driver steers a steering wheel. In this rear wheel steering device, a linear motion actuator is provided for each of the left and right rear wheels, and the linear motion actuator enables the left and right rear wheels to be independently steered. Therefore, this rear wheel steering device, by the command signal of the higher-level control device, to steer the rear wheels in phase or opposite phase with respect to the steering angle of the front wheels in order to increase the running stability when the vehicle turns, Alternatively, the toe angle can be adjusted by changing the left and right rearward steering angles in order to enhance running stability when the vehicle goes straight.

JP 2015-202826 A

  In vehicles in recent years, the number of devices to be mounted is increasing, and thus there is a tendency that it is difficult to secure an installation space for various devices when designing the vehicle. Further, due to environmental issues, it is necessary to improve fuel efficiency, and it is important to reduce the size and weight of the mounting device. Further, in order to increase added value such as ride comfort and comfort, it is necessary to suppress vibration and noise of the device. On the other hand, it is desirable to be inexpensive.

  In the rear wheel steering device, a feed screw mechanism is used as a motion conversion mechanism, and a trapezoidal screw (a screw having a trapezoidal cross section of a screw thread) is often used for the feed screw mechanism. In order to reduce and transmit the output of the electric motor to the feed screw mechanism, a planetary gear reducer or a belt drive having a different pulley ratio is often used. Also in the rear wheel steering device of Patent Literature 1, a trapezoidal screw is exemplified as a motion conversion mechanism, and a planetary gear reducer is exemplified as a mechanism for transmitting the power of an electric motor in a reduced manner.

  Since the planetary gear reducer uses gears for power transmission, there is a backlash and vibration is likely to occur. And the gear meshing noise causes noise. Further, the planetary gear reducer has a large number of components such as a sun gear, a planetary gear, an internal gear, a carrier, a shaft for a planetary gear, and a bearing for supporting and smoothly rotating these components, and cannot be said to be an inexpensive configuration.

  Similarly, when the deceleration transmission is a belt drive, loosening of the belt due to aging causes vibration. Further, the two pulleys used for driving the belt have cylindrical surfaces parallel to each other, and one is attached to a motor output shaft and the other is attached to a nut member such as a feed screw mechanism, so that it is difficult to realize a compact structure.

  Therefore, an object of the present invention is to provide a compact rear wheel steering device.

  In order to solve the above problems, according to the present invention, an electric motor having a motor output shaft, a motion converting mechanism for converting a rotational motion output from the electric motor into a linear motion, and a linear motor driven by the motion converting mechanism. A rear wheel steering device having a rod that changes the direction of the rear wheel of the vehicle in accordance with the linear motion, wherein the motor output shaft includes a rolling element that rolls on an inner raceway surface and an outer raceway surface. Supported by a first bearing having a retainer for holding the rolling element, and performing traction drive between the inner raceway surface and the rolling element and between the outer raceway surface and the rolling element of the first bearing. Thus, a speed reducer is constituted by the first bearing, and the speed reducer is interposed in a torque transmission path between the motor output shaft and the motion conversion mechanism.

  In this case, by using the retainer of the first bearing as an output member of the speed reducer, the first bearing can be used as a compact planetary speed reducer.

  In addition, it is preferable to provide a housing for accommodating the first bearing, and to provide a second bearing for supporting the output member of the speed reducer with respect to the housing.

  In this case, by providing a thrust bearing as the second bearing and disposing the thrust bearing on the inner diameter side of the first bearing, the axial dimension of the rear wheel steering device can be reduced. Specifically, the output member of the speed reducer is hollow, an annular concave portion is provided on the inner diameter surface at the end of the output member, and a thrust bearing is disposed in the annular concave portion.

  By making the motor output shaft hollow, arranging the output member of the speed reducer on the inner diameter side of the motor output shaft, and arranging the third bearing between the motor output shaft and the output member of the speed reducer, the rigidity against the moment load is improved. Can be enhanced.

  By making the output member of the speed reducer hollow and disposing the rod on the inner diameter side of the output member, the axial size of the rear wheel steering device can be reduced.

  As the first bearing, a radial deep groove ball bearing or a radial cylindrical roller bearing can be used.

  Since the rear-wheel steering device described above is compact, a vehicle having this rear-wheel steering device can secure an empty space around the rear wheels, and can increase the degree of freedom in designing the vehicle.

  According to the present invention, since the output of the electric motor can be reduced and transmitted to the motion conversion mechanism without using a planetary gear reducer or a belt drive, the rear wheel steering device can be made compact. In comparison with the planetary gear reducer, it is possible to reduce the size in the radial direction, and when the reducer has the same outer diameter, an empty space can be secured on the inner diameter side of the first bearing. By making effective use of this empty space, it is possible to achieve further compactness and higher performance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view schematically showing a vehicle equipped with a rear wheel steering device according to an embodiment of the present invention. FIG. 1 is a sectional view of a rear wheel steering device according to a first embodiment of the present invention. FIG. 3 is an enlarged cross-sectional view near the L-side drive unit of the rear wheel steering device shown in FIG. FIG. 3 is an enlarged cross-sectional view of the vicinity of an L-side speed reducer and an R-side speed reducer of the rear wheel steering device shown in FIG. 2. FIG. 4 is a comparison diagram of sizes of a rolling bearing also serving as a speed reducer and a planetary gear speed reducer. It is a sectional view of a rear wheel steering device concerning a 2nd embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows a vehicle 1 equipped with a rear wheel steering device according to the present invention. The vehicle 1 is an automobile and has a pair of left and right front wheels 2L and 2R and a pair of left and right rear wheels 3L and 3R.

  The front wheels 2L, 2R are steered by the movement of the steering rod 6 of the front wheel steering mechanism 5 according to the steering angle of the steering wheel 4. When the driver steers the steering wheel 4, the rotation of the steering wheel 4 is transmitted to the front wheel steering mechanism 5 via the steering column 7, and the steering rod 6 of the front wheel steering mechanism 5 moves in the axial direction. When this linear movement is transmitted via the tie rod 90, the directions of the front wheels 2L and 2R change integrally. A steering angle sensor 8 is provided on a steering column 7 that rotates integrally with the steering wheel 4. Outputs of the steering angle sensor 8, the vehicle speed sensor 9, and the yaw rate sensor 10 are input to an electronic control unit (ECU) 11. An ECU (engine control unit) is a microcontroller (microcomputer) that comprehensively controls the operation of an automobile when the operation is controlled using an electric auxiliary device.

  The rear wheels 3L, 3R are steered by the rear wheel steering device 12 according to the present invention. This rear wheel steering device 12 is attached to a vehicle body 13. The steering angles of the rear wheels 3L and 3R are determined by receiving a command from the electronic control unit 11 based on the traveling information of the vehicle 1 and the steering angle information of the front wheels, such as the steering angle sensor 8, the vehicle speed sensor 9, and the yaw rate sensor 10. It is controlled by the wheel steering control device 14. The steering angles of the rear wheels 3L, 3R are independently controlled on the left and right.

[Outline of rear wheel steering system]
The configuration of the rear wheel steering device 12 according to the first embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 2, the rear wheel steering device 12 includes an L-side steering unit 15L that steers the left rear wheel 3L and an R-side steering unit 15R that steers the right rear wheel 3R. The L-side steering unit 15L and the R-side steering unit 15R are substantially symmetrical with respect to the center of the rear wheel steering device 12. For this reason, the structure of the L-side steering unit 15L will be described, and detailed description of the structure of the R-side steering unit 15R will be omitted unless it is particularly necessary. In addition, L is attached to the reference numeral of each component of the L-side steering unit 15L, and R is appended to the reference numeral of each component of the R-side steering unit 15R. Further, when it is not necessary to distinguish them, symbols of R and L are omitted.

  The L-side steering unit 15L includes a rod 16L supported movably in the axial direction, and a driving unit 17L that moves the rod 16L in the axial direction. Similarly, the R-side steering unit 15R includes a rod 16R supported movably in the axial direction, and a drive unit 17R that moves the rod 16R in the axial direction. The rod 16L and the driving unit 17L constitute a direct-acting electric actuator, and the rod 16R and the driving unit 17R constitute a direct-acting electric actuator.

  The rods 16L, 16R and the driving units 17L, 17R are housed in a housing 18. The housing 18 of the present embodiment has a form in which a left housing part 18L, a central housing part 18C, and a right housing part 18R are combined. The housing 18 is fixed to the vehicle body 13 (see FIG. 1) by fixing means such as a bolt (not shown).

  As shown in FIG. 1, the rod 16L of the L-side steering portion 15L is connected to the rear wheel 3L such that the direction of the rear wheel 3L changes according to the axial movement. Specifically, one end of a tie rod 62 is connected to an end of the rod 16L via a ball joint 88, and the other end of the tie rod 62 is connected to the knuckle arm 20 via a ball joint 19. Therefore, when the rod 16L moves in the axial direction, the knuckle arm 20 swings about the fulcrum 21 in conjunction with the movement, and the direction of the rear wheel 3L changes. Similarly, the rod 16R of the R-side steering portion 15R is connected to the rear wheel 3R such that the direction of the rear wheel 3R changes according to the axial movement.

  As shown in FIG. 2, the drive unit 17L of the L-side steering unit 15L includes an electric motor 22L, a motion conversion mechanism 24L that converts a rotational motion output from the electric motor 22L into a linear motion, and a motion conversion And a speed reducer 23L interposed in a torque transmission path between the transmission and the mechanism 24L. Hereinafter, a specific configuration of each element will be sequentially described.

[Electric motor]
As shown in FIG. 3, the electric motor 22L has a hollow rotor 25 disposed on the outer diameter side of the rod 16L, and a stator 26 disposed on the outer diameter side of the rotor 25. The rotor 25 has a hollow motor output shaft 28 and a rotor core 29 fixed to the outer periphery of the motor output shaft 28. The rotor core 29 is, for example, a permanent magnet provided such that N poles and S poles appear alternately along the circumferential direction. The stator 26 includes a stator core 30 fixed to the inner periphery of the housing 18 (left housing portion 18L), and an electromagnetic coil 31 wound around the stator core 30. Therefore, when the electromagnetic coil 31 is energized, a rotating force is generated in the rotor core 29 by an electromagnetic force acting between the stator core 30 and the rotor core 29, and the motor output shaft 28 rotates integrally with the rotor core 29.

[Decelerator]
The reduction gear 23L is configured by a traction drive type planetary reduction gear. In the present embodiment, a rolling bearing (first bearing) is used as the speed reducer 23L. The rolling bearing 23L includes an inner ring 41 press-fitted and fixed to the outer periphery of the motor output shaft 28, an outer ring 42 press-fitted and fixed to the inner periphery of the housing 18 (left housing portion 18L), a plurality of rolling elements 43, and rolling elements 43. And a seal member 45 for sealing an opening between the inner ring 41 and the outer ring 42. Each rolling element 43 is disposed between an inner raceway surface 41 a provided on the inner race 41 and an outer raceway surface 42 a provided on the outer race 42, and is held at equal intervals in a circumferential direction by a retainer 44. Each rolling element 43 rolls on the inner raceway surface 41a and the outer raceway surface 42a.

  One end of the motor output shaft 28 is rotatably supported by the housing 18 (left housing portion 18L) by the rolling bearing 23L also serving as the planetary reduction gear. The other end of the motor output shaft 28 is rotatably supported by a rolling bearing 27 arranged between the housing 18 (left housing portion 18L).

  By applying a radial preload to the rolling bearing 23L, a normal force is applied between the inner raceway surface 41a and the rolling element 43, and between the outer raceway surface 42a and the rolling element 43, respectively. Traction drive is performed. While the electric motor 22L is being driven, the inner raceway surface 41a rotates at the same speed as the motor output shaft 28, while the outer raceway surface 42a is stationary. In addition, the rolling element 43 revolves on the inner raceway surface 41a with the rotation of the inner raceway surface 41a, and the retainer 44 that has received this orbital motion rotates. At this time, the rotation speed of the retainer 44 is lower than that of the inner ring 41. Therefore, by using the cage 44 as an output member of the speed reducer, the rolling bearing 23L can be used as a traction drive type speed reducer. The speed reducer 23L has a configuration equivalent to a planetary gear device. The inner ring 41 corresponds to a sun gear, the outer ring 42 corresponds to an internal gear, the rolling elements 43 correspond to planetary gears, and the retainer 44 corresponds to a carrier.

  The preload is applied to the rolling bearing 23L by, for example, reducing the diameter of the outer ring 42 to the inner diameter side by giving a margin to a fitting portion between the outer peripheral surface of the outer ring 42 and the inner peripheral surface of the housing 18 (the left housing portion 18L). The inner ring 41 is expanded to the outer diameter side by a method of giving a normal force to the inner ring 41 by giving a margin to a fitting portion between the inner peripheral surface of the inner ring 41 and the outer peripheral surface of the motor output shaft 28. This can be done by employing a method of giving power.

  In addition, when the bearing assembly including the inner ring 41, the outer ring 42, the rolling elements 43, and the cage 44 is completed, the contact portion between the inner ring raceway surface 41a and the rolling elements 43 and the contact between the outer ring raceway surface 42a and the rolling elements 43 are formed. By matching the actual dimensions of the outer ring 42, the inner ring 41, and the rolling element 43 so that a predetermined interference is given to each part, a preload is applied in a state of the rolling bearing 23L alone before being incorporated into the housing 18. You can also.

  The rolling bearing 23L has a simple structure, is highly available, does not require other components to apply a preload, and is provided with a radial deep groove ball bearing or a radial cylinder which is preloaded by the preloading methods listed above. Roller bearings are suitable. In the present embodiment, a case where a radial deep groove ball bearing is used as the rolling bearing 23L is illustrated.

[Motion conversion mechanism]
As shown in FIG. 3, the motion conversion mechanism 24L includes a hollow shaft 37L inserted into the inner periphery of the motor output shaft 28, a detent mechanism 38 that allows the rod 16L to move in the axial direction and stops the rod 16L from rotating. , A feed screw mechanism 39 for converting the rotational movement of the shaft 37L into a linear movement of the rod 16L.

  The shaft 37L constitutes an output member of the speed reducer 23L together with the retainer 44 of the rolling bearing 23L described above. The shaft 37L and the retainer 44 need only be rotatable integrally, and may be formed integrally with each other as shown in FIG. 3, or may be formed of separate members.

  A sliding bearing 32 is fixed to the inner peripheral surface of the shaft 37L on the opening end side of the housing 18 (the left housing portion 18L). The rod 16L is inserted into the inner periphery of the slide bearing 32. The sliding bearing 32 allows relative rotation and relative axial movement of the rod 16L and the shaft 37L. The rod 16L is supported movably in the axial direction by a slide bearing 48 attached to the inner periphery of the open end of the housing 18 (left housing portion 18L).

  The detent mechanism 38 has an axially extending groove 35 formed on the outer periphery of the first rod 16L, and a stopper pin 45 inserted into the groove 35.

  The stopper pin 45 is inserted into a pin insertion hole 46 formed at an end of the housing 18 (left housing 18L). The pin insertion hole 46 is formed in a stepped hole shape having a large diameter at the outer diameter end. A bearing 47 is incorporated in the large-diameter hole portion of the pin insertion hole 46, and the stopper 47 rotatably supports the stopper pin 45. The engagement of the stopper pin 45 with the circumferential wall surface of the groove 35 restricts the rotation of the rod 16L.

  The axial movement of the rod 16L is restricted by the contact of the stopper pins 45 with the axially opposite end surfaces of the groove 35. Therefore, the stopper pin 45 and the groove 35 also function as a mechanical limit that determines the stroke end of the first rod 16L.

  The feed screw mechanism 39 includes a screw shaft portion 39a provided on the rod 16L and a nut portion 39b provided on the inner diameter of the shaft 37L. The screw shaft portion 39a and the nut portion 39b are in a screwed state. Instead of the feed screw mechanism 39, a ball screw mechanism can be adopted.

[Support of shaft 37L]
As shown in FIG. 4, the shaft 37L is rotatably supported by the housing 18 (central housing portion 18c) by a radial bearing 33L as a second bearing and a pair of thrust bearings 34L.

  The radial bearing 33L is a radial rolling bearing (illustrated as a needle roller bearing with an outer ring in the figure) disposed between the cylindrical outer peripheral surface of the carrier 44 and the inner peripheral surface of the housing 18 (central housing portion 18C). It is. The thrust bearing 34L has a structure in which rollers with holding are sandwiched between a pair of races, and supports the rotation of the shaft 37L and also supports an axial load acting on the shaft 37L via the rod 16L.

  An annular concave portion 36 is formed at an end of the shaft 37L on the center side of the housing 18 so as to open to an end surface of the shaft 37L. A connection shaft 55L integrally having a flange 54L is arranged in the annular concave portion 36. The pair of thrust bearings 33L are arranged so as to sandwich the flange 54L from both sides.

  An annular spacer 56 is accommodated in the annular concave portion 36 in a state where a part thereof protrudes in the axial direction from the end surface of the shaft 37L. An annular pressing plate 57 </ b> L that faces the spacer 56 in the axial direction is disposed closer to the center of the housing 18 than the spacer 56. The screw portion of the bolt 58 inserted into the through hole 59 of the shaft 37L is screwed into the holding plate 57L. By tightening the bolt 58, the spacer 56 is pressed toward the thrust bearing 34L, and a preload is applied to the thrust bearing 34L via the spacer 56.

  The central housing section 18C has a partition wall 61 between the L-side drive section 17L and the R-side drive section 17R. An L-side connection shaft 55L and an R-side connection shaft 55R are fixed to the partition wall 61. Here, a screw hole 62 formed in the L-side connection shaft 55L and a screw shaft 63 formed in the R-side connection shaft 55R are screwed together through a through hole formed in the partition wall 61 of the central housing portion 18C. By tightening the partition wall 61 with the L-side connection shaft 55L and the R-side connection shaft 55R, the L-side connection shaft 55L and the R-side connection shaft 55R are fixed to the central housing portion 18C.

  The motor output shaft 28, the speed reducer 23L, the shaft 37L, and the rod 16L described above are all coaxially arranged (see FIG. 3).

[Control system]
As shown in FIG. 3, a rotation detector 49 that detects the rotation angle of the rotor 25 of the electric motor 22L is disposed inside the housing 18. As the rotation detector 49, for example, a resolver having a resolver rotor 49a fixed to one end of the motor output shaft 28 and a resolver stator 49b fixed to the left housing portion 18L to face the resolver rotor 49a may be employed. it can.

  A position detector 51 for detecting the axial position of the first rod 16L is disposed inside the housing 18. The steering angle of the rear wheel 3L can be detected based on the axial position (absolute position) of the first rod 16L detected by the position detector 51. The output signal of the position detector 51 is input to the rear wheel steering control device 14 (see FIG. 1).

  The position detector 51 includes, for example, a permanent magnet 52 fixed to the first rod 16L and an analog output Hall IC 53 fixed to the left housing portion 18L so as to face the permanent magnet 52. can do.

  The position detector 51 detects the axial position (absolute position) of the rod 16L by converting the magnetic flux density detected by the Hall IC 53 into position information. If a programmable Hall IC 53 is used, the absolute position accuracy can be improved by programming the relationship between the position of the rod 16L and the magnetic flux density in advance. Further, if the output of the Hall IC 53 having two systems is selected, even if one of the systems fails, the remaining system can detect the position, and the reliability is improved.

[motion]
In the rear-wheel steering device 12 described above, when the L-side electric motor 22L is driven in the forward and reverse directions, the rotation of the motor output shaft 28 is reduced by the rolling bearing 23L also serving as a speed reducer, and the rotation of the motor output shaft 28 is changed to the motion conversion mechanism 24L. The rod 16L is transmitted in the axial direction according to the rotation amount of the shaft 37L. By the axial movement of the rod 16L, the knuckle arm 20 moves via the ball joint 88, the tie rod 62, and the ball joint 19 shown in FIG. 1, so that the steering of the rear wheel 3L and the adjustment of the toe angle can be performed. . Similar operations are performed on the rear wheel 3R independently of the L side.

[Explanation of characteristic matters]
As in the present embodiment, by using the rolling bearings 23L, 23R also serving as a speed reducer as the first bearings 23L, 23R supporting the motor output shaft 28, the planetary gear speed reducer and the belt drive mechanism are not used. The rotational speeds of the electric motors 22L, 22R can be reduced and transmitted to the motion conversion mechanisms 24L, 24R. For this reason, the rear wheel steering device 12 can be made more compact than when a planetary gear reducer or a belt drive mechanism is used. Also, the number of parts can be reduced as compared with a planetary gear reducer or a belt drive, and an inexpensive device with a simple structure can be realized.

  As shown in FIG. 5A, the rolling bearings 23L and 23R also serving as reduction gears can be made more radially compact than the planetary gear reduction gears 66L and 66R shown in FIG. 5B. For example, when a radial deep groove ball bearing No. 6008 or equivalent is used as the rolling bearings 23L and 23R, the bearing outer diameter is 68 mm, the bearing inner diameter is 40 mm, and the difference between the inner and outer diameters is 14 mm on one side. The difference between the inner and outer diameters is substantially the same as the diameter of the planetary gear having 14 teeth of the module 1. If the outer diameter of the speed reducer is the same as 72 mm, the rolling bearing 23L also serving as the speed reducer corresponds to the input member of the speed reducer (the inner ring 41) of the motor shaft 28 by the thickness of the internal gear and the sun gear. (Or a sun gear). Therefore, an empty space α can be secured on the inner diameter side of the rolling bearing 23L.

  This empty space α can be used as an arrangement space for the thrust bearings 34L, 34R that support the shafts 37L, 37R. Specifically, on the L side, at least one (preferably both) of the pair of thrust bearings 34L can be disposed on the inner diameter side of the rolling bearing 23L. On the other hand, when the planetary gear reducer 66L is used, such a free space does not exist, so that both of the pair of thrust bearings 34L must be disposed outside the axial region of the planetary gear. Therefore, with the configuration of the present embodiment, the axial dimension of the rear wheel steering device 12 can be reduced.

The rolling bearing 23L also serving as a speed reducer has a reduction ratio of about 1 / 2.6 due to dimensional restrictions of commercially available rolling bearings. In order to realize a rear wheel steering device with a maximum moving speed of the rod 16L of 30 mm / s and a propulsion force of 3000 N at a reduction ratio of 1 / 2.6, the output is approximately 350 W and the rotation speed is approximately An electric motor 22L of 3000 r / min- ¹ and a trapezoidal screw with a lead of 2 mm may be used. Therefore, it is possible to obtain a reduction ratio having no problem in design.

  In addition, since the reduction gear is of a traction drive type, it is possible to achieve high accuracy and reduce backlash. Therefore, vibration and noise of the rear wheel steering device can be reduced, and high added value can be achieved.

  FIG. 6 shows the configuration of the rear wheel steering device 12 according to the second embodiment of the present invention.

  In the second embodiment, two radial bearings 65 are interposed as third bearings between the outer peripheral surface of the shaft 37L and the inner peripheral surface of the motor output shaft 28. Thus, since the shaft 37L can be supported at two points, the rigidity against a moment load can be increased as compared with the first embodiment, and vibration and noise can be reduced and durability can be improved. As described above, the use of the rolling bearing 23L also serving as a speed reducer creates an empty space on the inner diameter side of the motor output shaft 28. Therefore, there is a particular obstacle to inserting the two radial bearings 65 into the above positions. However, the rear wheel steering device 12 can be assembled efficiently.

  In the first embodiment, since the shaft 37L is supported by one radial bearing 33L, it is necessary to use the radial bearing 33L having a large axial width as much as possible in order to prevent the shaft 37L from being tilted. The axial length of the rear wheel steering device 12 becomes longer. Therefore, from the viewpoint of compactness, the second embodiment is superior.

  As described above, in the present invention, the motor output shaft 28 is hollow, and the motion conversion mechanism 24 and the like are included in the hollow portion, thereby further reducing the size. However, the initial function can be realized by a structure in which the motion conversion mechanism 24L is arranged in parallel with the electric motor 22L and the rolling bearing 23L also serving as a reduction gear.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 Vehicle 12 Rear wheel steering device 16L, 16R Rod 18 Housing 22L, 22R Electric motor 23L, 23R Planetary reducer (first bearing)
24L, 24R Motion conversion mechanism 28 Motor output shaft 33L, 33R Radial bearing (second bearing)
34L, 34R thrust bearing (second bearing)
36 annular recess 37L, 37R shaft (output member of reduction gear)
41 inner ring 41a inner raceway surface 42 outer race 42a outer raceway surface 43 rolling element 44 retainer (output member of reduction gear)
65 Radial rolling bearing (third bearing)

Claims (10)

An electric motor having a motor output shaft, a motion conversion mechanism for converting the rotary motion output from the electric motor into a linear motion, and a linear motion driven by the motion conversion mechanism; A rear wheel steering device including a rod that changes the direction of the rear wheel;
The motor output shaft is supported by a first bearing having a rolling element rolling on an inner raceway surface and an outer raceway surface, and a retainer holding the rolling element, and the inner raceway surface of the first bearing and the rolling element And a traction drive between the outer raceway surface and the rolling element to form a speed reducer with the first bearing, and a torque transmission path between the motor output shaft and the motion conversion mechanism. A rear wheel steering device having a speed reducer interposed.   The rear wheel steering device according to claim 1, wherein a retainer of the first bearing is used as an output member of the speed reducer.   The rear wheel steering device according to claim 2, further comprising a housing that houses the first bearing, and a second bearing that supports an output member of the speed reducer with respect to the housing.   The rear wheel steering device according to claim 3, wherein a thrust bearing is provided as the second bearing, and the thrust bearing is arranged on an inner diameter side of the first bearing.   The rear wheel steering device according to claim 4, wherein the output member of the speed reducer is hollow, an annular concave portion is provided on an inner diameter surface of an end portion of the output member, and the thrust bearing is disposed in the annular concave portion.   The motor output shaft is hollow, an output member of the speed reducer is arranged on the inner diameter side of the motor output shaft, and a third bearing is arranged between the motor output shaft and the output member of the speed reducer. The rear wheel steering device according to any one of claims 2 to 5.   The rear wheel steering device according to any one of claims 2 to 6, wherein an output member of the speed reducer is hollow, and the rod is disposed on an inner diameter side of the output member.   The rear wheel steering device according to claim 1, wherein a radial deep groove ball bearing is used as the first bearing.   The rear wheel steering device according to any one of claims 1 to 7, wherein a radial cylindrical roller bearing is used as the first bearing.   A vehicle comprising the rear wheel steering device according to claim 1.

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