JP2017141011A - Steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering device which can reduce an impact load added to an assist mechanism.SOLUTION: A brake device 20 is provided between a drive pulley 51 and a wall surface 17c. The brake device 20 comprises braking rotary members 21 and 22, a ball 23, friction plates 24 and 25, and a spring 26. The braking rotary member 21 is attached to an end face of the drive pulley 51 in an axial direction. An inclined plane 21b is provided on one end face of the braking rotary member 21. The braking rotary member 22 is provided between the braking rotary member 21 and the wall surface 17c. The ball 23 is sandwiched between the braking rotary member 21 and the braking rotary member 22. The friction plate 24 is attached to an end face on the wall surface 17c side in an axial direction of the braking rotary member 22. The friction plate 25 is provided on a face which is opposite, in an axial direction, to the friction plate 24 on an internal surface of the wall surface 17c. The spring 26 is provided between the friction plate 24 and an inner ring 35a of a bearing 35.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a steering device.

  2. Description of the Related Art Conventionally, there is known an electric power steering device (EPS) that assists a driver's steering operation by applying axial thrust to a rack shaft provided as a steered shaft by a ball screw mechanism. For example, in the EPS of Patent Document 1, a motor is mounted in parallel with a rack shaft, and a ball screw mechanism assists a driver's steering operation by converting the rotational torque of the motor into a force that linearly moves the rack shaft. To do.

JP 2012-144202 A

  By the way, in recent years, with the increase in axial thrust, the moment of inertia of the assist mechanism that converts the torque of the motor provided in the EPS into the assist force of the rack shaft has increased. Therefore, when a reverse input acts on the rack shaft and the rack shaft reaches the end of the movable range and stops, the impact load acting on the assist mechanism of the EPS becomes large, and measures such as increasing the strength of the assist mechanism are taken. It was necessary.

  These measures include increasing the size of the end damper, reducing the moment of inertia of the assist mechanism, and reducing the reduction ratio of the EPS, but these measures require time and effort because it is necessary to redesign each part of the EPS. . For this reason, there has been a demand for a method for reducing the impact load without changing the inertia or the reduction ratio of the assist mechanism.

  The objective of this invention is providing the steering device which can reduce the impact load added to an assist mechanism.

  The steering device that can achieve the above object includes a motor, a turning shaft that reciprocates in the axial direction, a drive rotating member that rotates by the rotational force of the motor, and an axial direction on the turning shaft based on its own rotation. A driven rotating member for applying a force; a speed reducer for transmitting the rotational force of the drive rotating member to the driven rotating member; the steering shaft; the drive rotating member; the driven rotating member; and the speed reducer. A housing, and a braking device provided between at least one of the drive rotating member and the driven rotating member and an inner wall surface of the housing. The braking device includes a first braking rotating member attached to an end surface in at least one axial direction of the driving rotating member and the driven rotating member, the first braking rotating member, and an inner wall surface of the housing or the housing. A second braking rotary member, a first braking rotary member, and a second braking rotary member provided so as to be movable in an axial direction between a fixed member and a wall surface exposed to the inside of the housing; A ball sandwiched between the first braking rotary member, a biasing member that constantly biases the second braking rotary member toward the first braking rotary member, and the first braking rotary member in the second braking rotary member. A first braking member provided on an end surface opposite to the rotating member; and the first braking member on the inner wall surface of the housing or the wall surface of the member fixed to the housing. A second braking member provided at a portion facing the rolling member, and the mutually opposing surfaces of the first braking rotating member and the second braking rotating member are the drive rotating member or the driven It is provided so that it may approach as it leaves | separates from the rotation center of a rotation member, and when the 1st braking member moves in the direction approaching the 2nd braking member, between the 1st braking member and the 2nd braking member In the meantime, the braking force against the rotation of the first braking member is exhibited.

  According to this configuration, when the driving rotating member and the driven rotating member rotate, a centrifugal force corresponding to the rotational speeds of the driving rotating member and the driven rotating member acts on the balls of the braking device. Then, the ball moves in a direction away from the rotation axis of the portion provided with the braking device according to the centrifugal force acting on the ball, and the first braking rotation member and the second braking rotation according to the movement amount. The member is separated. Then, the first braking member provided on the second braking rotating member approaches the second braking member provided on the inner wall surface of the housing, whereby the rotation of the first braking member is braked. For this reason, the rotational speed of the member provided with the braking device can be reduced among the drive rotating member and the driven rotating member. For this reason, the impact load which acts on each part of a steering device accompanying reverse input, for example can be reduced.

  In the steering apparatus, the first braking member and the second braking member are preferably friction plates that brake the first braking member by friction when they are in contact with each other.

  According to this configuration, the first braking member is braked against the second braking member by friction when the first braking member and the second braking member come into contact. The rotational speed of the member provided with the braking device can be reduced.

  In the above steering apparatus, at least one of the first braking member and the second braking member is a magnet, and the first braking member may be braked by a magnetic action when approaching each other.

  According to this configuration, when the first braking member and the second braking member are close to each other, the magnetic action between the first braking member and the second braking member is increased. The brake is applied to the member. For this reason, the rotational speed of the member provided with the braking device can be reduced among the drive rotating member and the driven rotating member. Even in the process in which the first braking member and the second braking member are close to each other, the rotational speed of the member provided with the braking device can be reduced to some extent.

  In the steering apparatus, it is preferable that the first braking rotation member is attached between the drive rotation member and the housing in the axial direction of the steered shaft.

  According to this configuration, by providing the braking device between the drive rotation member and the housing, the rotation speed of the drive rotation member that tends to be higher than the driven rotation member due to the reduction ratio can be reduced.

  In the above steering apparatus, of the axial end surfaces of at least one of the first braking rotation member and the second braking rotation member, an end surface that is in contact with the ball is guided to the ball. It is preferable that the groove extends in the radial direction from the axial center.

  According to this configuration, since the groove for guiding the ball is provided in at least one of the first braking rotating member and the second braking rotating member in the radial direction from the center of the shaft, The rotating member rotates at the same angular velocity as the first braking rotating member or the second braking rotating member, and the centrifugal force acts on the ball.

  In the steering apparatus, a rotation shaft of the motor is inserted into a through hole provided in a wall surface of the housing, and the rotation shaft of the motor and the through hole are spaced from the through hole with respect to the through hole. A bearing that rotatably supports the rotating shaft is provided, and the second braking member is provided over a range from a portion of the inner wall surface of the housing facing the first braking rotating member to an inner periphery of the outer ring of the bearing. It is preferable that

  According to this configuration, by providing the second braking member also on the outer ring of the bearing, it is possible to secure an area for arranging the second braking member. For example, when friction plates are employed for the first braking member and the second braking member, the frictional force increases as the contact area between the two increases, so that the rotational speed of the member provided with the braking device can be further reduced.

  In the above steering device, a rotation shaft of the motor is inserted into a through hole provided in a wall surface of the housing, and a fitting hole is provided in a portion of the end portion of the motor facing the through hole. A motor bearing that rotatably supports the rotary shaft with respect to the fitting hole is provided between the rotary shaft of the motor and the fitting hole, and the second braking member is provided in the through hole. It is preferable that the end portion of the motor exposed inside is provided over a range from a portion facing the outer periphery of the first braking rotation member to the inner periphery of the fitting hole.

  According to this configuration, since the motor bearing is provided between the rotating shaft and the fitting hole, the motor bearing can be attached to the housing together with the motor, and the motor and the motor bearing can be easily assembled to the housing.

  In the above steering apparatus, the steered shaft includes a cylindrical nut screwed into a thread groove provided on an outer periphery via a plurality of balls, and is axially directed to the steered shaft based on rotation of the nut. A ball screw mechanism for applying a force, and a reduction pulley fixed to the nut so as to be integrally rotatable, a driven pulley having a plurality of pulley teeth provided on an outer peripheral surface thereof, and a rotation shaft of the motor A driving pulley having a plurality of pulley teeth provided on its outer peripheral surface and a belt tooth wound around the driven pulley and the driving pulley and meshing with the pulley teeth. Preferably, the drive rotation member includes a rotation shaft of the motor and the drive pulley, and the driven rotation member includes the nut and the driven pulley.

  According to the steering device of the present invention, the impact load applied to the assist mechanism can be reduced.

The block diagram which shows schematic structure of the steering device of one Embodiment. Sectional drawing which shows schematic structure of an assist mechanism about the steering device of one Embodiment. (A) is sectional drawing which shows schematic structure of a braking mechanism about the steering apparatus of one Embodiment, (b) is schematic sectional drawing along the 3b-3b line | wire of Fig.3 (a). Sectional drawing which shows schematic structure of the braking mechanism when the rotational speed of a drive rotation member becomes large about the steering device of one Embodiment. Sectional drawing which shows schematic structure of a braking mechanism about the steering device of other embodiment. (A) is a schematic sectional drawing along the 6a-6a line of FIG. 5, (b) is a schematic sectional drawing along the 6b-6b line of FIG. Sectional drawing which shows schematic structure of a braking mechanism about the steering device of other embodiment. Sectional drawing which shows schematic structure of an assist mechanism about the steering device of other embodiment. Sectional drawing which shows schematic structure of a braking mechanism about the steering device of other embodiment.

Hereinafter, an EPS according to an embodiment of the steering apparatus will be described.
As shown in FIG. 1, the EPS 1 includes a steering mechanism 2 that steers the steered wheels 16 based on the driver's operation of the steering wheel 10 and an assist mechanism 3 that assists the driver's steering operation.

  The steering mechanism 2 includes a steering wheel 10 and a steering shaft 11 that rotates integrally with the steering wheel 10. The steering shaft 11 includes a column shaft 11a connected to the steering wheel 10, an intermediate shaft 11b connected to the lower end portion of the column shaft 11a, and a pinion shaft 11c connected to the lower end portion of the intermediate shaft 11b. doing. A lower end portion of the pinion shaft 11 c is connected to a rack shaft 12 that is a steered shaft via a rack and pinion mechanism 13. The lower end portion (pinion teeth) of the pinion shaft 11c is meshed with the rack shaft 12 (rack teeth). Therefore, the rotational movement of the steering shaft 11 is caused by the axial direction X () of the rack shaft 12 via the rack and pinion mechanism 13 including pinion teeth provided at the tip of the pinion shaft 11c and rack teeth provided on the rack shaft 12. It is converted into a reciprocating linear motion in the left-right direction in FIG. The reciprocating linear motion is transmitted to the tie rod 15 via rack ends 14 respectively connected to both ends of the rack shaft 12. The movement of these tie rods 15 is transmitted to the left and right steered wheels 16, whereby the steered angle of the steered wheels 16 is changed. The rack shaft 12 is accommodated in the rack housing 17. Between the both ends of the rack housing 17 and the tie rod 15, a bellows cylindrical rack boot 18 is disposed.

  The assist mechanism 3 is provided around the rack shaft 12. The assist mechanism 3 transmits to the ball screw mechanism 40 the rotational force of the rotating shaft 31 of the motor 30 that is a source of the assist force, the ball screw mechanism 40 that is integrally attached around the rack shaft 12, and the motor 30. It consists of the reduction gear 50 which carries out. The assist mechanism 3 assists the driver's steering operation by converting the rotational force of the rotating shaft 31 of the motor 30 into a force in the axial direction X of the rack shaft 12 via the speed reducer 50 and the ball screw mechanism 40. .

  The ball screw mechanism 40, the speed reducer 50, the pinion shaft 11c, and the rack shaft 12 are covered with a rack housing 17. The rack housing 17 is provided with an insertion portion 17a through which the rack shaft 12 is inserted in the axial direction X. The rack housing 17 has a reduction gear housing 17b that is a portion protruding in a direction intersecting with the direction in which the rack shaft 12 extends (downward in FIG. 1). A part of the speed reducer 50 is accommodated in the speed reducer housing 17b. A through hole 33 is provided in the wall surface 17c of the reduction gear housing 17b (the right side wall of the reduction gear housing 17b in FIG. 2). The rotation shaft 31 of the motor 30 extends into the reduction gear housing 17b through a through hole 33 provided in the reduction gear housing 17b. The motor 30 is fixed to the speed reducer housing 17b by bolts 32 so that the rotating shaft 31 is parallel to the rack shaft 12 and the motor 30 is parallel to the rack shaft 12. A slight gap is provided between the insertion portion 17a and the rack shaft 12 in the radial direction.

Next, the assist mechanism 3 will be described in detail.
As shown in FIG. 2, the ball screw mechanism 40 includes a cylindrical nut 41 that is screwed onto the rack shaft 12 via a plurality of balls 42. The nut 41 is rotatably supported with respect to the inner peripheral surface of the rack housing 17 via a bearing 44. A spiral thread groove 12 a is provided on the outer peripheral surface of the rack shaft 12. A spiral screw groove 43 corresponding to the screw groove 12 a of the rack shaft 12 is provided on the inner peripheral surface of the nut 41. A spiral space surrounded by the thread groove 43 of the nut 41 and the thread groove 12a of the rack shaft 12 functions as a rolling path R on which the ball 42 rolls. Moreover, although not shown in figure, the nut 41 is provided with the circulation path which opens to two places of the rolling path R, and short-circuits the opening of the two places. Therefore, the ball 42 can circulate infinitely in the rolling path R through the circulation path in the nut 41.

  The speed reducer 50 includes a drive pulley 51 that is integrally attached to the rotating shaft 31 of the motor 30, a driven pulley 52 that is integrally attached to the outer periphery of the nut 41, and a driven pulley that is integrally attached to the outer periphery of the nut 41. 52, and a belt 53 wound between the driving pulley 51 and the driven pulley 52. A rotation shaft 31 of the motor 30, a drive pulley 51 attached to the rotation shaft 31, and a part of the belt 53 are arranged in the internal space of the reduction gear housing 17b. The belt 53 is a rubber toothed belt including a core wire, for example.

  In the assist mechanism 3 having such a configuration, when the rotation shaft 31 of the motor 30 rotates, the drive pulley 51 rotates together with the rotation shaft 31. The rotation of the driving pulley 51 is transmitted to the driven pulley 52 via the belt 53, and thereby the driven pulley 52 rotates. For this reason, the nut 41 attached integrally with the driven pulley 52 also rotates integrally. Since the nut 41 rotates relative to the rack shaft 12, the plurality of balls 42 interposed between the nut 41 and the rack shaft 12 receive a load from both and circulate infinitely in the rolling path R. When the ball 42 rolls in the rolling path R, the rotational torque applied to the nut 41 is converted into a force applied in the axial direction X of the rack shaft 12. For this reason, the rack shaft 12 moves in the axial direction X with respect to the nut 41. The force in the axial direction X applied to the rack shaft 12 becomes an assist force, and assists the driver's steering operation.

  A member rotating on the motor 30 side (driving side) is a driving rotating member, and a member rotating on the rack shaft 12 side (driving side) is a driven rotating member. That is, the drive rotation member includes the rotation shaft 31, the drive pulley 51, and the inner ring 35 a of the bearing 35. The driven rotating member includes a nut 41, a driven pulley 52, and an inner ring of the bearing 44.

Next, the braking device 20 provided between the drive pulley 51 and the wall surface 17c of the reduction gear housing 17b will be described in detail.
As shown in FIG. 3A, between the outer peripheral surface of the rotary shaft 31 and the inner peripheral surface of the through hole 33, the rotary shaft 31 is rotatably supported with respect to the speed reducer housing 17b (through hole 33). A bearing 35 is provided. An inner ring 35 a of the bearing 35 is fitted to the outer circumferential surface of the rotary shaft 31, and an outer ring 35 b of the bearing 35 is fitted to the inner circumferential surface of the through hole 33.

  When the rotational speed of the drive pulley 51 increases, the braking device 20 brakes the drive pulley 51 against the reduction gear housing 17b so as to suppress the rotational speed. The braking device 20 includes two braking rotating members 21 and 22, a plurality of balls 23, two friction plates 24 and 25 as braking members, and a spring 26 as an urging member.

  The brake rotating member 21 has a disk shape with a hole in the center, and a rotating shaft 31 is inserted into the hollow portion. The braking rotating member 21 is attached to the end surface (the right end surface in FIG. 3) in the axial direction of the drive pulley 51. A flat surface portion 21 a orthogonal to the axial direction of the rotation shaft 31 is provided on the end surface of the braking rotation member 21 on the drive pulley 51 side. That is, the flat surface portion 21a is provided in parallel with the end surface of the drive pulley 51 and the inner wall surface of the wall surface 17c. Further, an inclined surface 21b that is not parallel to the planar portion 21a is provided on the end surface of the braking rotating member 21 opposite to the planar portion 21a (the end surface on the wall surface 17c side of the braking rotating member 21). The inclined surface 21b is, for example, a conical surface.

  The braking rotary member 22 has a disk shape with a hole at the center thereof, and a rotary shaft 31 is inserted into the hollow portion. The braking rotation member 22 is provided between the braking rotation member 21 and the inner wall surface of the wall surface 17c. Both end surfaces in the axial direction of the braking rotating member 22 are planes parallel to each other. Further, both end surfaces of the braking rotating member 22 in the axial direction are parallel to the flat portion 21a. Therefore, the distance between the inclined surface 21b and the end surface of the braking rotating member 22 facing the inclined surface 21b becomes narrower as the distance from the central axis of the rotating shaft 31 increases (toward the radial direction). The braking rotary member 22 is provided so as to be slidable in the axial direction with respect to the rotary shaft 31. The braking rotary member 22 is provided so as to be rotatable integrally with the rotary shaft 31.

  The ball 23 is sandwiched between the braking rotary member 21 and the braking rotary member 22. The force with which the braking rotary member 21 and the braking rotary member 22 sandwich the ball 23 acts as a force that brings the ball 23 closer to the rotation shaft 31 as a component force corresponding to the angle of the inclined surface 21b. For this reason, when the rotating shaft 31 is not rotating, the ball 23 is in contact with the rotating shaft 31.

  The friction plate 24 is attached to the end surface (the right end surface in the drawing) on the wall surface 17c side in the axial direction of the braking rotary member 22. As an example, the outer diameter of the friction plate 24 is set larger than the outer diameter of the braking rotary member 22 in order to ensure frictional resistance when contacting the friction plate 25. Note that the outer diameter of the friction plate 24 may be set in any way as long as sufficient frictional resistance can be ensured. The frictional resistance between the friction plate 24 and the friction plate 25 depends on how much the rotation speed of the drive pulley 51 is to be suppressed and how much time the rotation speed of the drive pulley 51 is to be reduced. Set to an appropriate frictional resistance. The friction plate 24 is provided so as to be slidable in the axial direction with respect to the rotary shaft 31 in the same manner as the braking rotary member 22. The friction plate 24 is provided so as to be rotatable integrally with the rotary shaft 31.

  The friction plate 25 is provided over a range from a portion of the inner wall surface of the wall surface 17c facing the friction plate 24 in the axial direction to the inner peripheral surface of the outer ring 35b of the bearing 35. When the friction plate 24 is moved in the axial direction, the friction plate 25 and the friction plate 24 come into contact with each other. A surface of the inner ring 35 a of the bearing 35 facing the friction plate 24 does not contact the friction plate 24. Further, when the friction plate 24 comes into contact with the friction plate 25, a gap corresponding to the thickness of the friction plate 25 is formed between the friction plate 24 and the inner ring 35a. Note that the portion of the friction plate 24 facing the inner ring 35a may not be provided. That is, the friction plate 24 may be provided only in a portion facing the friction plate 25.

  The spring 26 is interposed between the friction plate 24 and the inner ring 35a of the bearing 35 in a compressed state. For example, a compression coil spring is used as the spring 26 and is inserted through the rotary shaft 31. The braking rotary member 22 and the friction plate 24 are constantly urged toward the direction close to the braking rotary member 21 (left direction in the drawing) by the elastic force of the spring 26. The movement of the braking rotating member 22 and the friction plate 24 in the direction approaching the braking rotating member 21 is restricted by the braking rotating member 22 coming into contact with the braking rotating member 21 via the ball 23. As a result, the ball 23 is sandwiched between the braking rotary member 21 and the braking rotary member 22. The ball 23 is pressed against the rotating shaft 31 by being sandwiched between the braking rotating member 22 and the braking rotating member 21.

  As the ball 23 moves in the radial direction, the braking rotary member 22 and the friction plate 24 move in a direction closer to the friction plate 25 against the elastic force of the spring 26. The distance between the friction plate 24 and the friction plate 25 is set such that the friction plate 24 comes into contact with the friction plate 25 when the ball 23 moves a certain distance in the radial direction.

  As shown in FIG. 3B, the inclined surface 21b of the braking rotary member 21 is provided with a radial groove 21c that functions as a guide when the ball 23 moves in the radial direction. Here, as an example, the balls 23 are respectively fitted in four grooves 21 c provided at equal intervals in the circumferential direction of the rotating shaft 31.

Next, the operation and effect of this embodiment will be described. First, the centrifugal force F generated on the ball 23 as the rotating shaft 31 rotates will be described.
As the rotary shaft 31 rotates, the braking rotary member 21 attached to the drive pulley 51 also rotates. For this reason, the rotational force of the rotary shaft 31 is also transmitted to the ball 23 through the groove 21 c provided in the braking rotary member 21. The ball 23 rotates about the rotation shaft 31. At this time, the centrifugal force F acting on the ball 23 can be expressed by the following equation (1) using the mass m, the rotation speed (angular velocity) ω, and the rotation radius r of the ball 23.

F = mrω ^ 2 (1)
For this reason, the centrifugal force F acting on the ball 23 increases as the rotational speed of the ball 23 increases. Then, when the centrifugal force F acts on the ball 23, the ball 23 tries to move in a direction away from the rotation shaft 31 (outside in the radial direction of the rotation shaft 31).

  Of the centrifugal force F of the ball 23, when the axial component force corresponding to the inclination of the inclined surface 21 b is larger than the elastic force of the spring 26, the braking rotary member 22 and the friction plate 24 have the elastic force of the spring 26. Against the friction plate 25. The ball 23 moves in a direction away from the rotation shaft 31 as the distance between the braking rotating member 21 and the braking rotating member 22 increases.

  As shown in FIG. 4, when the rotating shaft 31 rotates at a higher speed and the centrifugal force F of the ball 23 becomes sufficiently large, the ball 23 further moves in a direction away from the rotating shaft 31. Accordingly, the braking rotating member 22 and the friction plate 24 further move toward the friction plate 25, and the friction plate 24 eventually contacts the friction plate 25. Due to the friction between the friction plate 24 and the friction plate 25, the rotational speed of the rotary shaft 31 and the drive pulley 51 is reduced.

  Further, when the rotational speeds of the rotary shaft 31 and the drive pulley 51 are reduced, the centrifugal force F of the ball 23 is also reduced, so that the ball 23 moves in a direction approaching the rotary shaft 31 as the centrifugal force F decreases. The braking rotating member 22 moves toward the braking rotating member 21 according to the position of the ball 23 by the elastic force of the spring 26. As a result, the friction plate 24 and the friction plate 25 are separated from each other, and the braking action of the rotating shaft 31 and the drive pulley 51 by the friction plate 24 and the friction plate 25 is released.

  By the way, a large reverse input (load) accompanying the curb climbing or the like acts on the rack shaft 12, and when the rack shaft 12 moves in the axial direction, the rack shaft 12 contacts the end of the rack housing 17. A guess may occur. The rack shaft 12 can no longer move in the same direction. Along with this, the nut 41 of the driven rotating member also comes into contact with the rack shaft 12 via the ball 42, so that the nut 41 is restricted from rotating. When the rotation of the nut 41 is stopped, the rotation of other driven rotating members including the driven pulley 52 is also stopped. On the other hand, since the motor 30 and the drive pulley 51 continue to rotate due to their own inertial force, there is a possibility that tooth skipping or wear may occur on the teeth of the belt 53.

  In particular, as the rotational speed of the drive rotating member increases, the rotational energy of the drive rotating member also increases. Therefore, when the rotation of the drive rotating member is about to stop, a larger load is applied to the teeth of the belt 53. 53 teeth are more likely to have tooth skipping and wear.

  In this regard, in the present embodiment, when the rotational speed of the drive rotating member increases, the rotational speed of the drive rotating member is suppressed by the friction plate 24 coming into contact with the friction plate 25. As the rotational speed of the drive rotating member decreases, the rotational energy when the drive rotating member rotates also decreases, so that tooth skipping of the belt 53 is suppressed. This is because the impact load acting on each part of the EPS 1 is reduced.

  The braking device 20 also has an action of suppressing uneven wear of the rack teeth of the rack shaft 12 and the pinion teeth of the pinion shaft 11c. For example, when the rack shaft 12 is stopped by the end contact where the rack shaft 12 abuts against the end of the rack housing 17, the nut 41 that continues to rotate due to inertia rotates the rack shaft 12 about the axis via the ball 42. Try to let them. As a result, when the rack shaft 12 rotates and rotates, the end portion of the rack teeth of the rack shaft 12 in the streak direction is strongly pressed against the pinion teeth of the pinion shaft 11c, and uneven wear of the rack teeth and the pinion teeth is promoted. There is a fear. In this respect, in the present embodiment, since the rotational speed of the drive rotating member is suppressed, the torque for rotating the rack shaft 12 is reduced, so that the rack teeth of the rack shaft 12 and the pinion teeth of the pinion shaft 11c are reduced. Uneven wear is suppressed. Similarly, even when reverse input acts on the rack shaft 12, the impact load acting on each part of the EPS 1 is reduced by the decrease in the rotational speed of the drive rotating member, and the durability of the EPS 1 against reverse input is enhanced. It is done. Note that the effect of reducing the rotation speed of the drive rotation member is great because the rotation speed of the drive rotation member is likely to be higher than that of the driven rotation member due to the reduction ratio.

  Further, the counter electromotive force may be generated in the motor 30 due to the reverse input, but the voltage value of the counter electromotive force is also reduced by the decrease in the rotational speed of the drive rotating member. For this reason, it is suppressed that the control apparatus which controls the motor 30 by back electromotive force is influenced.

  In order to further reduce the influence exerted on each part of the EPS 1 when reverse input is applied, the end damper is increased in size to reduce the acceleration (impact load) of the rack shaft 12 at the time of end application, and the drive rotating member and driven rotation are driven. Although the reduction of the moment of inertia of the member and the reduction of the reduction ratio can be raised, these measures require a redesign of each part of the EPS 1, which takes time. In this regard, in the present embodiment, the rotational speed of the drive rotating member can be reduced by providing the braking device 20 without redesigning each part of the EPS 1.

In addition, you may change this embodiment as follows. The following other embodiments can be combined with each other within a technically consistent range.
In the present embodiment, a plurality of grooves 21c and a plurality of balls 23 are used in the braking rotary member 21, but this is not restrictive. That is, if the rotational stability of the braking rotating member 21 can be maintained, only one groove 21c is provided, and only one ball 23 is sandwiched between the braking rotating member 21 and the braking rotating member 22. Also good.

  -In this embodiment, although the inclined surface 21b was provided in the rotating member 21 for braking, it is not restricted to this. For example, an inclined surface may be provided on the surface of the braking rotation member 22 that faces the braking rotation member 21. In addition, both the braking rotary member 21 and the braking rotary member 22 may be provided with inclined surfaces on the mutually opposing surfaces.

  -In this embodiment, although the friction plate 25 was attached to the area | region containing the inner surface of the wall surface 17c and the outer ring | wheel 35b of the bearing 35, it is not restricted to this. For example, the friction plate 25 may be attached only to the inner surface of the wall surface 17 c or may be attached only to the outer ring 35 b of the bearing 35.

  -In this embodiment, although the spring 26 as an urging | biasing member was employ | adopted, it is not restricted to this. For example, an elastic member such as rubber may be employed as the biasing member. That is, the urging member may be any member as long as it urges the braking rotating member 21 and the braking rotating member 22 in a direction in which they are separated.

  In the present embodiment, the friction plate 24 and the friction plate 25 are brought into contact with each other in order to suppress the rotation speed of the drive rotation member, but the present invention is not limited to this. That is, as shown in FIG. 5, the magnet 27 may be attached to the braking rotating member 22 instead of the friction plate 24, and the magnet 28 may be attached to the wall surface 17 c instead of the friction plate 25. The distance between the braking rotary member 22 and the wall surface 17c and the spring force of the spring 26 are set so that the magnet 27 and the magnet 28 do not contact each other. The braking rotary member 22 is braked by a magnetic action (for example, attractive force) when the magnet 27 and the magnet 28 are close to each other. As an example, as shown in FIGS. 6A and 6B, the magnet 27 and the magnet 28 are alternately arranged with two N poles and two S poles around the axis of the rotation shaft 31 (circumferential direction). Has been. The number of poles of the magnet 27 and the magnet 28 may be any number. When the magnet 27 and the magnet 28 are close to each other, the N pole (or S pole) of the magnet 27 is attracted to the S pole (or N pole) of the magnet 28, thereby suppressing the rotation speed of the rotating shaft 31. The The closer the magnet 27 and the magnet 28 are, the larger the magnetic action is (the magnetic force has a relationship inversely proportional to the square of the distance), so that the braking action of the braking rotary member 22 is further enhanced. In addition, when using the magnet 27 and the magnet 28, the effect which suppresses the rotational speed of a drive rotation member to some extent is acquired also in the process in which the magnet 27 and the magnet 28 adjoin. Further, instead of the friction plate 25, a conductor such as a copper plate may be used. In this case, a braking force for braking the braking rotating member 22 is generated by an eddy current generated in the conductor.

  -In this embodiment, although rotation of the drive rotation member was suppressed by the braking device 20, it is not restricted to this. For example, as shown in FIG. 7, the rotation of the driven rotation member may be suppressed. In this case, for example, the brake rotating member 21 is attached to an end portion (right end portion in the drawing) of the nut 41 which is one of the driven rotating members, and the brake rotating member 22 is provided between the nut 41 and the wall surface 17c. It is done. A ball 23 is provided between the braking rotary member 21 and the braking rotary member 22, and a friction plate 24 is attached to the end surface of the braking rotary member 22 on the wall surface 17 c side, so as to face the friction plate 24 on the wall surface 17 c. The friction plate 25 is attached to the part to be performed. The spring 26 is a tension spring provided between the driven rotating member (driven pulley 52) and the braking rotating member 22.

  In the present embodiment, the inner ring 35a of the bearing 35 is fitted to the outer circumferential surface of the rotary shaft 31, and the outer ring 35b of the bearing 35 is fitted to the inner circumferential surface of the through hole 33 of the reduction gear housing 17b. Not limited to.

  For example, as shown in FIG. 8, a fitting hole 36 is provided at the end of the motor 30 facing the through hole 33 at the end on the wall surface 17 c side. A motor bearing 37 that rotatably supports the rotating shaft 31 of the motor 30 may be provided.

  In this case, as shown in FIG. 9, the inner ring 37 a of the motor bearing 37 is fitted to the outer circumferential surface of the rotating shaft 31, and the outer ring 37 b of the motor bearing 37 is fitted to the inner circumferential surface of the fitting hole 36 of the motor 30. . The friction plate 25 is provided on the end face of the motor 30 exposed inside the through hole 33. The friction plate 25 is provided over a range from the portion facing the outer periphery of the friction plate 24 to the inner periphery of the fitting hole 36. A part of the friction plate 24 and the braking rotating member 22 may be accommodated in the through hole 33.

  In the present embodiment, the motor 30 having the rotation shaft 31 arranged in parallel to the rack shaft 12 is specifically illustrated as EPS 1 that applies assist force to the rack shaft 12, but is not limited thereto. In other words, any steering device including the ball screw mechanism 40 and the speed reducer 50 may be used. A steering device that transmits the torque of the motor 30 to the pinion shaft 11c via a worm reduction gear may be used. In addition, although the electric power steering device that assists the linear motion of the rack shaft 12 interlocked with the steering operation by using the rotational force of the motor 30 has been described as an example, it may be applied to a steer-by-wire (SBW). It should be noted that, when embodied in SBW, not only as a front wheel steering device, but also as a rear wheel steering device or a four wheel steering device (4WS).

  DESCRIPTION OF SYMBOLS 1 ... EPS, 2 ... Steering mechanism, 3 ... Assist mechanism, 10 ... Steering wheel, 11 ... Steering shaft, 11a ... Column shaft, 11b ... Intermediate shaft, 11c ... Pinion shaft, 12 ... Rack shaft (steering shaft), 12a ... thread groove, 13 ... rack and pinion mechanism, 14 ... rack end, 15 ... tie rod, 16 ... steered wheel, 17 ... rack housing (housing), 17a ... insertion part, 17b ... speed reducer housing, 18 ... rack boot, DESCRIPTION OF SYMBOLS 19 ... Bearing, 20 ... Brake device, 21 ... Brake rotary member (first brake rotary member), 21a ... Planar portion, 21b ... Inclined surface, 21c ... Groove, 22 ... Brake rotary member (second brake rotation) Members), 23 ... balls, 24 ... friction plates (first braking members), 25 ... friction plates (second braking members), 26 ... (Biasing member), 27, 28 ... magnet, 30 ... motor, 31 ... rotating shaft, 32 ... bolt, 33 ... through hole, 40 ... ball screw mechanism, 41 ... nut, 42 ... ball, 43 ... screw groove, 44 ... bearing, R ... rolling path, 50 ... speed reducer, 51 ... driving pulley, 52 ... driven pulley, 53 ... belt.

Claims (8)

A motor,
A steering shaft that reciprocates in the axial direction;
A drive rotating member that rotates by the rotational force of the motor;
A driven rotating member that applies an axial force to the steered shaft based on its rotation;
A speed reducer that transmits the rotational force of the drive rotating member to the driven rotating member;
A housing that houses the steered shaft, the drive rotation member, the driven rotation member, and the speed reducer;
A braking device provided between at least one of the drive rotating member and the driven rotating member and an inner wall surface of the housing;
The braking device includes a first braking rotating member attached to an end surface in at least one axial direction of the driving rotating member and the driven rotating member, the first braking rotating member, and an inner wall surface of the housing or the housing. A second braking rotary member, a first braking rotary member, and a second braking rotary member provided so as to be movable in an axial direction between a fixed member and a wall surface exposed to the inside of the housing; A ball sandwiched between the first braking rotary member, a biasing member that constantly biases the second braking rotary member toward the first braking rotary member, and the first braking rotary member in the second braking rotary member. A first braking member provided on an end surface opposite to the rotating member; and the first braking member on the inner wall surface of the housing or the wall surface of the member fixed to the housing. And a second braking member provided on the rolling member and the opposed portion, a
The mutually opposing surfaces of the first braking rotation member and the second braking rotation member are provided so as to approach each other as they move away from the rotation center of the drive rotation member or the driven rotation member, A steering device in which a braking force against rotation of the first braking member is exerted between the first braking member and the second braking member by moving one braking member in a direction approaching the second braking member. The steering apparatus according to claim 1, wherein
The steering device, wherein the first braking member and the second braking member are friction plates that brake the first braking member by friction when they are in contact with each other. The steering apparatus according to claim 1, wherein
A steering device, wherein at least one of the first braking member and the second braking member is a magnet, and brakes the first braking member by a magnetic action when approaching each other. In the steering device according to any one of claims 1 to 3,
The first braking rotation member is a steering device attached between the drive rotation member and the housing in the axial direction of the steered shaft. In the steering device according to any one of claims 1 to 4,
Of the end faces in the axial direction of at least one of the first braking rotation member and the second braking rotation member, a groove for guiding the ball has a diameter from the axial center on the end face in contact with the ball. Steering device extending in the direction. In the steering device according to any one of claims 1 to 5,
The rotating shaft of the motor is inserted into the through hole provided in the wall surface of the housing,
Between the rotating shaft of the motor and the through hole, a bearing that rotatably supports the rotating shaft with respect to the through hole is provided,
The second braking member is a steering device provided over a range from a portion of the inner wall surface of the housing facing the first braking rotating member to an inner periphery of the outer ring of the bearing. In the steering device according to any one of claims 1 to 5,
The rotating shaft of the motor is inserted into the through hole provided in the wall surface of the housing,
A fitting hole is provided in a portion facing the through hole in the end of the motor,
Between the rotation shaft of the motor and the fitting hole, a motor bearing that rotatably supports the rotation shaft with respect to the fitting hole is provided,
The second braking member is provided over a range from a portion facing the outer periphery of the first braking rotating member to an inner periphery of the fitting hole at an end portion of the motor exposed inside the through hole. Steering device. In the steering device according to any one of claims 1 to 7,
A ball having a cylindrical nut screwed into a screw groove provided on the outer periphery of the steered shaft via a plurality of balls, and applying an axial force to the steered shaft based on rotation of the nut A screw mechanism;
The speed reducer is fixed to the nut so as to be integrally rotatable, a driven pulley having a plurality of pulley teeth provided on an outer peripheral surface thereof, and a plurality of pulleys fixed to the outer peripheral surface of the motor so as to be integrally rotatable with a rotation shaft of the motor. A driving pulley provided with a pulley tooth, and a belt provided with a belt tooth that is wound between the driven pulley and the driving pulley and meshes with the pulley tooth,
The drive rotation member includes a rotation shaft of the motor and the drive pulley,
The driven rotation member includes a steering device including the nut and the driven pulley.

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