JP2017206193A - Steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering device that can suppress torque fluctuation of a ball screw mechanism.SOLUTION: In an elastic support mechanism, plates 50 and disc springs 60 are provided between a housing 16 and a bearing 34. Flat parts 50b of the plates 50 are provided with annular grooves 50c whose cross sections cut off by flat surfaces including shaft lines thereof are formed in a V-shape. A corner part V2 of the disc spring 60 contacts a valley part V1 of the groove 50c. By elastic force of the disc spring 60, an outer ring 34b and the plate 50 are pressed toward a direction in which the ring and the plate separate in a shaft direction. The bearing 34 is supported by the disc spring 60 to be movable along the shaft direction. A side at the bearing 34 side of the plate 50 is magnetized to an N-pole, and an outer peripheral surface 60a of the disc spring 60 and an inner peripheral surface 60b of a small-diameter side end part of the disc spring 60, including the corner part V2 of the disc spring 60, are magnetized to an S pole.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a steering device.

  Conventionally, as described in Patent Document 1, there is an EPS (electric power steering device) provided with a bearing that rotatably supports a ball screw nut with respect to a housing. By providing a metal spring and a plate formed in an annular shape with an L-shaped cross section on both sides in the axial direction of the bearing, the bearing is supported by the housing so as to be movable in the axial direction. A gap in the radial direction of the rack shaft exists between the metal spring and the holding portion as the short side of the L-shaped plate and the housing. This gap is provided to assist the elastic deformation of the metal spring.

JP 2014-227047 A

  However, in the EPS configured as described above, when the metal spring and the plate are assembled, there is a radial gap between the metal spring and the plate, so that the metal spring is mounted eccentrically with respect to the plate in the radial direction. There is a risk. For this reason, the positions at which the metal springs press against the side surfaces of the bearings are radially displaced from each other on both side surfaces of the bearings, and the bearings and thus the ball screw nuts are inclined. As a result, torque fluctuation may occur when the ball screw nut rotates.

  The objective of this invention is providing the steering apparatus which can suppress the inclination of the bearing which supports a ball screw nut.

  A steering device that can achieve the above object has a screw groove on the outer periphery, and is screwed into the screw groove of the steered shaft through a plurality of balls and a steered shaft that moves in the axial direction in accordance with a steering operation. A ball screw nut; a housing that houses the steered shaft and the ball screw nut; a bearing that rotatably supports the ball screw nut with respect to the housing; and a portion of the housing within the housing; It is assumed that a plate and an annular elastic member are provided between both side surfaces in the axial direction of the bearing. The plate is provided so as to extend in parallel to the axial direction on an annular flat portion sandwiching the elastic member between an end surface of the bearing or a housing in the axial direction and an axial side surface of the flat portion. And an annular groove in which an end of the elastic member in the axial direction is fitted on the side surface in the axial direction of the flat portion. It is the gist.

  According to the above configuration, the end of the elastic member in the axial direction is fitted in the annular groove provided in the flat portion of the plate, so that the elastic member is eccentric with respect to the radial direction of the steered shaft during assembly. Can be suppressed. That is, since the elastic member abuts against both side surfaces in the axial direction of the bearing and the position where the bearing is pressed is suppressed from shifting in the radial direction, the bearing is inclined with respect to the axis of the steered shaft. Inclination of the ball screw nut with respect to the axis of the steered shaft is suppressed.

It is preferable that at least one of the elastic member and the plate is magnetized so that an attractive force acts between the elastic member and the plate.
A suction force acts between the elastic member and the plate, so that the elastic member is maintained in a state where the elastic member is fitted in the annular groove of the flat portion. For this reason, it can suppress more that an elastic member decenters to radial direction.

  In the steering device, the elastic member has a truncated cone shape, and an outer corner portion at an end portion on the small diameter side is fitted into the annular groove, and an end portion on the large diameter side in the axial direction, Preferably, a gap is formed between at least the outer peripheral surface of the elastic member and the inner surface of the annular groove, which contacts the outer ring or housing of the bearing.

  When an axial compressive force acts on the elastic member, the elastic member tends to be elastically deformed so that the end on the large diameter side spreads radially outward with the outer corner at the end on the small diameter side of the elastic member as a base point. That is, the elastic member is elastically deformed so that the outer peripheral surface of the elastic member approaches flat along the radial direction. According to the above configuration, when the elastic member is elastically deformed, the elastic member is elastically deformed so that the outer peripheral surface of the elastic member is close to the inner surface of the annular groove. Therefore, by providing a gap between the outer peripheral surface of the elastic member and the inner surface of the annular groove, the elastic member is easily elastically deformed.

In the above steering apparatus, it is preferable that the gap is formed so as to increase in an axial direction of the elastic member as it goes toward an outer periphery of the elastic member.
According to the said structure, it elastically deforms so that the outer peripheral surface of an elastic member may adjoin to the inner surface of an annular | circular shaped groove | channel. The gap is formed so as to increase in the axial direction of the elastic member as it goes toward the outer periphery of the elastic member, so that the elastic member is more easily elastically deformed.

The cross-sectional shape of the annular groove when the plate is cut along a plane including the axis of the plate is preferably V-shaped.
According to the said structure, if the cross-sectional shape which cut | disconnected the groove | channel in the radial direction is V shape, the outer corner | angular part in the edge part by the side of the small diameter of an elastic member will fit in the V-shaped groove | channel of a flat part. Therefore, the eccentricity of the elastic member in the radial direction can be further suppressed. Moreover, it becomes easier to provide a gap between the outer peripheral surface of the elastic member and the inner surface of the groove.

  In the above steering apparatus, it is preferable that the positions of the central axes of the groove of the plate provided on both sides in the axial direction of the bearing coincide with each other in the radial direction of the steered shaft.

  When the annular groove is provided on the side surface in the axial direction of the flat portion of the plate, the center axis of the outer diameter of the plate and the center axis of the groove rarely coincide with each other. In that case, when the plate and the elastic member are assembled, the elastic member may be eccentrically attached to the radial direction of the steered shaft.

  In that respect, according to the above configuration, the eccentricity of the elastic member with respect to the radial direction during assembly can be further suppressed by assembling so that the center axes of the annular grooves on both sides in the axial direction of the bearing coincide with each other. That is, since the elastic member abuts against both side surfaces in the axial direction of the bearing and the pressing position is prevented from being displaced in the radial direction, the bearing is inclined with respect to the axis of the steered shaft, and hence the ball screw. Inclination of the nut with respect to the axis of the steered shaft is suppressed.

  In the steering apparatus, the elastic member is preferably a disc spring that presses the entire circumference of the side surface of the outer ring portion of the bearing and the entire circumference of the flat portion where the annular groove is provided.

In the steering device, there are concerns about the following.
In the axial direction of the steered shaft, when a disc spring is provided so as to press between the flat portion provided with the annular groove and the housing, one end portion in the axial direction of the disc spring is on the housing. Abut. At this time, since the housing is made of a soft metal such as aluminum, the surface of the housing on which the disc spring comes into contact is gradually dented. When the dent is generated, the elastic force of the disc spring that has pressed the flat portion provided with the annular groove and the housing apart from each other is weakened. As the elastic force becomes weaker, the disc spring becomes more difficult to maintain the elastic support of the bearing, which may cause the bearing to tilt.

  In that respect, according to the above configuration, the disc spring is provided so as to press between the side surface of the outer ring portion of the bearing and the flat portion where the annular groove is provided. That is, the disc spring does not come into contact with the housing. Therefore, the disc spring can maintain the elastic support of the bearing.

The bearing is preferably a double row angular contact ball bearing.
The following may be a concern for the bearings in the steering device described above.
For example, when the steering device is used for a vehicle, a force that rotates the steered shaft in a direction orthogonal to the axial direction may occur due to the force transmitted from the road surface. The rotating force is transmitted from the steered shaft to the bearing via the ball screw nut, and the bearing may be inclined with respect to the axis of the steered shaft.

  In that respect, according to the above configuration, when the bearing is a double-row angular ball bearing, the rigidity against the rotating force transmitted from the steered shaft is further improved as compared with the deep groove ball bearing (single row). Therefore, the inclination of the bearing that supports the ball screw nut can be further suppressed.

  According to the steering device of the present invention, the inclination of the bearing that supports the ball screw nut can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows the schematic structure about the electric power steering apparatus of embodiment. Sectional drawing which shows the cross-section of the assist mechanism about the electric power steering apparatus of embodiment. Sectional drawing which shows the cross-section of the ball screw mechanism about the electric power steering apparatus of embodiment. The perspective view of the disc spring and plate in embodiment. Sectional drawing which showed the assembly | attachment condition of the disc spring and plate in embodiment. Sectional drawing which showed the magnetization condition of the disc spring and plate in embodiment.

  Hereinafter, embodiments of the steering device will be described. The steering device according to the present embodiment assists the user's steering operation by transmitting the rotational motion of the motor to the ball screw mechanism via the belt-type reduction mechanism and converting the rotational motion of the motor into the linear motion of the rack shaft. The electric power steering device (hereinafter referred to as “EPS”).

  As shown in FIG. 1, the EPS 1 includes a steering mechanism 2 that steers the steered wheels 15 based on a user's operation of the steering wheel 10 and an assist mechanism 3 that assists the user'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 as a steered shaft via a rack and pinion mechanism 13. Therefore, the rotational motion of the steering shaft 11 is converted into a reciprocating linear motion in the axial direction of the rack shaft 12 (the left-right direction in FIG. 1) via the rack and pinion mechanism 13 including the pinion shaft 11c and the rack shaft 12. The reciprocating linear motion is transmitted to the left and right steered wheels 15 via the tie rods 14 respectively connected to both ends of the rack shaft 12, whereby the steered angle of the steered wheels 15 changes.

In the following description, “axial direction” means the axial length direction of the rack shaft 12, and “radial direction” means a direction orthogonal to the “axial direction”.
The assist mechanism 3 is provided around the rack shaft 12. The assist mechanism 3 transmits to the ball screw mechanism 30 the rotational force of the rotating shaft 21 of the motor 20, the ball screw mechanism 30 that is integrally attached around the rack shaft 12, and the motor 20 that is the source of assist force. Belt-type reduction mechanism (hereinafter referred to as “deceleration mechanism”) 40. The assist mechanism 3 converts the rotational force of the rotating shaft 21 of the motor 20 into a force that causes the rack shaft 12 to reciprocate linearly in the axial direction via the speed reduction mechanism 40 and the ball screw mechanism 30. The axial force applied to the rack shaft 12 becomes an assist force, which assists the user's steering operation.

  The ball screw mechanism 30, the speed reduction mechanism 40, the pinion shaft 11 c, and the rack shaft 12 are covered with a housing 16 that extends along the axial direction of the rack shaft 12. The housing 16 is configured by connecting a first housing 16 a and a second housing 16 b which are divided in the axial direction in the vicinity of the speed reduction mechanism 40. The first housing 16a and the second housing 16b protrude in a direction (downward in the drawing) that intersects the direction in which the rack shaft 12 extends. A through hole 22 is provided in the outer wall (right side wall in the figure) of the second housing 16b. The housing 16 is made of a soft metal such as aluminum.

  The rotating shaft 21 of the motor 20 extends into the second housing 16 b through the through hole 22. The motor 20 is fixed to the second housing 16b by connecting the flange portion 17 provided in the second housing 16b and the flange portion 24 provided in the motor 20 with a bolt 23. The rotating shaft 21 is parallel to the rack shaft 12.

  Inner ball joints (hereinafter referred to as “IBJ”) 18 as end members for rotatably connecting the tie rods 14 are provided at both ends of the rack shaft 12. The IBJ 18 is provided so as to be able to go in and out of the enlarged diameter portions 16 c provided at both ends of the housing 16 in the axial direction. The inner diameter of the enlarged diameter portion 16c is set larger than the inner diameter of the rack accommodating portion 16d in which the housing 16 accommodates the rack shaft 12. A stepped portion 16e having a wall surface on the IBJ 18 side is provided at a portion where the enlarged diameter portion 16c and the rack accommodating portion 16d are connected. On the other hand, the outer diameter of the IBJ 18 is set smaller than the inner diameter of the enlarged diameter portion 16c of the housing 16 and larger than the inner diameter of the rack accommodating portion 16d. The movement of the rack shaft 12 in the axial direction is limited by the end contact generated by hitting the stepped portion 16e of the IBJ 18. That is, the stroke end (movement limit) of the movement of the rack shaft 12 in the axial direction is defined by the IBJ 18.

Next, the assist mechanism 3 will be described in detail.
As shown in FIG. 2, the ball screw mechanism 30 includes a ball screw nut 31 as a cylindrical rotating body that is screwed onto the rack shaft 12 via a plurality of balls 32. The ball screw nut 31 is rotatably supported with respect to the inner peripheral surface of the housing 16 via a cylindrical bearing 34. A spiral thread groove 12 a is provided on the outer peripheral surface of the rack shaft 12. A helical thread groove 33 corresponding to the thread groove 12 a of the rack shaft 12 is provided on the inner peripheral surface of the ball screw nut 31. A spiral space surrounded by the thread groove 33 of the ball screw nut 31 and the thread groove 12a of the rack shaft 12 functions as a rolling path R on which the ball 32 rolls. Although not shown, the ball screw nut 31 is provided with a circulation path that opens at two places on the rolling path R and short-circuits the two openings. Therefore, the ball 32 can circulate infinitely in the rolling path R through the circulation path in the ball screw nut 31. Note that, for example, a lubricant such as grease is applied to the rolling path R to reduce frictional resistance or the like when the ball 32 rolls.

  The speed reduction mechanism 40 includes a drive pulley 41 integrally attached to the rotating shaft 21 of the motor 20, a driven pulley 42 as a rotating body integrally attached to the outer periphery of the ball screw nut 31, and the drive pulley 41 and the driven pulley. A belt 43 wound around the belt 42 is provided. In the internal space of the first housing 16a, a rotating shaft 21 of the motor 20, a driving pulley 41 attached to the rotating shaft 21, and a belt 43 are arranged. The belt 43 is a rubber toothed belt including a core wire. The driving pulley 41 and the driven pulley 42 are toothed pulleys.

  An annular flange portion 35 is provided at one end portion of the ball screw nut 31 in the axial direction. An inner ring 34a of a bearing 34 is fitted to the outer peripheral surface of the ball screw nut 31 so as to engage with the flange portion 35 in the axial direction, and a driven pulley 42 is fitted adjacent to the inner ring 34a. Yes. For example, the bearing 34 is a deep groove ball bearing (single row) or a double row angular ball bearing (a general and versatile bearing), but in the present embodiment, a double row angular ball bearing is adopted. The driven pulley 42 is fixed to the ball screw nut 31. Further, the inner ring 34 a of the bearing 34 is sandwiched in the axial direction by the driven pulley 42 and the flange portion 35, so that the inner ring 34 a is fixed to the ball screw nut 31. The outer peripheral surface of the outer ring 34b of the bearing 34 is in contact with the first housing 16a so as to be movable in the axial direction.

  A locking portion 25 is provided at the tip of the second housing 16b on the outer ring 34b side. In the axial direction, a locking portion 26 is provided at a portion of the first housing 16a that faces the outer ring 34b. A plate 50 and a disc spring 60 as an elastic member are disposed in the gap between the outer ring 34b in the axial direction and the locking portions 25, 26 as a configuration for elastically supporting the outer ring 34b in the axial direction. ing.

As shown in FIG. 4, the plate 50 and the disc spring 60 are each formed in an annular shape from a magnetic metal.
The plate 50 has an annular flat portion 50b and a cylindrical holding portion 50a. In the flat portion 50b, an annular groove 50c is provided on the side surface on the side where the holding portion 50a is provided. When the plate 50 is cut along a plane including the axis, the cross-sectional shape of the groove 50c is V-shaped.

The disc spring 60 has a truncated cone shape. A corner provided on the outer peripheral side of the end portion on the small diameter side of the disc spring 60 is inserted into the flat portion 50 b of the plate 50.
As shown in FIG. 3, in the state where the plate 50 and the disc spring 60 are disposed between the bearing 34 and the housing 16, the flat portions 50 b and 50 b on the opposite side of the end surface provided with the annular groove 50 c are provided. The end surfaces are in contact with the locking portions 25 and 26 in the axial direction by the elastic force of the disc spring 60. The outer peripheral surfaces of the flat portions 50b and 50b are in contact with the inner peripheral surface of the first housing 16a. Further, the end portion on the large diameter side of the disc spring 60 is in contact with the side surface in the axial direction of the outer ring 34b. The small diameter end of the disc spring 60 is in contact with the annular groove 50c of the flat portion 50b.

  As shown in FIG. 6, the plate 50 and the disc spring 60 are magnetized. The side surface where the groove 50c of the flat portion 50b of the plate 50 is provided is magnetized to N pole, and the side surface opposite to the side surface where the groove 50c of the flat portion 50b is provided is magnetized to S pole. The outer peripheral surface 60a of the disc spring 60 and the inner peripheral surface 60b of the small-diameter side end of the disc spring 60 are attached to the S pole, and the outer peripheral surface of the disc spring 60 and the outer peripheral surface of the large-diameter end of the disc spring 60 are attached to the N pole. It is magnetized.

  As shown in FIG. 5, the groove 50c has two inclined surfaces 51 and 52 that incline away from each other in the radial direction as the holding portion 50a extends from the thickness center of the flat portion 50b. The two inclined surfaces 51 and 52 are provided so that the angle θ formed by these becomes larger than 90 degrees. A portion where the two slopes 51 and 52 intersect is defined as a valley V1. The central axis Ax1 of the groove 50c and the central axis Ax2 of the plate 50 coincide with each other.

The disc spring 60 has a rectangular cross section cut along a plane including its axis. A portion where the outer peripheral surface 60a of the disc spring 60 and the inner peripheral surface 60b of the end portion on the small diameter side of the disc spring 60 intersect is defined as a corner portion V2.
As shown in FIG. 5, when the plate 50 and the disc spring 60 are provided between the housing 16 and the bearing 34, the disc spring 60 is inserted into the groove 50 c until the corner portion V <b> 2 contacts the valley portion V <b> 1 of the plate 50. Is done. In a state in which the corner portion V2 is in contact with the valley portion V1, a first gap CL1 is formed between the inclined surface 51 and the outer peripheral surface 60a of the disc spring 60. A second gap CL2 is formed between the peripheral surface 60b. The first gap CL1 becomes wider in the axial direction of the disc spring 60 as it goes to the outer periphery of the disc spring 60 and the second gap CL2 goes to the inner circumference of the disc spring 60. The angle formed between the inclined surface 51 and the outer peripheral surface 60a is θ1, and the angle formed between the inclined surface 52 and the inner peripheral surface 60b is θ2.

  As shown in FIG. 3, in a state where the plate 50 and the disc spring 60 are provided between the housing 16 and the bearing 34, the corner portion V <b> 2 is in contact with the valley portion V <b> 1. Further, the corner portion on the inner peripheral side at the end portion on the large diameter side of the disc spring 60 is in contact with the side surface of the outer ring 34b. In addition, a gap is provided between the outer peripheral corner of the large diameter end of the disc spring 60 and the inner peripheral surface of the first housing 16a. A gap is also provided between the corner portion on the inner peripheral side at the end portion on the small diameter side of the disc spring 60 and the outer peripheral surface of the holding portion 50a.

The position of the bearing 34 is held in the axial direction by the elastic force from the two disc springs 60.
As described above in detail, according to the present embodiment, the following effects can be obtained.
(1) When the plate 50 and the disc spring 60 are assembled, the corner portion V2 of the disc spring 60 contacts the valley portion V1 of the plate 50, whereby the disc spring 60 is positioned in the radial direction with respect to the plate 50. . At this time, since the respective disc springs 60 abut against both side surfaces of the bearing 34 in the axial direction and the positions for pressing the bearing 34 are suppressed from being shifted in the radial direction, the plates on both sides of the bearing 34 are suppressed. The spring 60 and the plate 50 are stably positioned on the same axis. Therefore, the bearing 34 that supports the ball screw nut 31 can be prevented from tilting.

  (2) Also, the outer peripheral surface 60a of the disc spring 60 and the inner peripheral surface 60b of the small-diameter side end surface of the disc spring 60 including the N pole on the bearing 34 side surface of the flat portion 50b and the corner portion V2 of the disc spring 60 are S. The pole is magnetized. That is, when the plate 50 and the disc spring 60 are assembled, a magnetic force acts so that the flat portion 50b and the disc spring 60 are close to each other, so that the corner portion V2 of the disc spring 60 and the valley portion V1 of the plate 50 are in contact with each other. The state can be maintained. That is, it is possible to further suppress the disc spring 60 from being eccentric in the radial direction with respect to the plate 50 during assembly.

  (3) Further, in the disc spring 60, when a compressive force acts in the axial direction, the disc spring 60 has the large-diameter side end portion radially outward so that the small-diameter side end portion narrows radially inward. Try to elastically deform so that it spreads. That is, the outer peripheral surface 60a of the disc spring 60 is elastically deformed in a direction approaching the plate 50 side, and the corner portion V2 is elastically deformed in a direction toward the central axis Ax2.

  In this regard, a first gap CL1 is formed between the inclined surface 51 and the outer peripheral surface 60a of the disc spring 60, and a second gap is formed between the inclined surface 52 and the inner peripheral surface 60b of the end portion on the small diameter side of the disc spring 60. A gap CL2 is formed. This gap is a space where the disc spring 60 allows elastic deformation. For this reason, the disc spring 60 can be elastically deformed smoothly.

  (4) The first gap CL1 becomes wider in the axial direction of the disc spring 60 as it goes toward the outer periphery of the disc spring 60 and the second gap CL2 goes toward the inner periphery of the disc spring 60. Yes. For this reason, the disc spring 60 can be elastically deformed more smoothly.

  (5) Further, if the cross-sectional shape is V-shaped, in this embodiment, the cross-section cut along the plane including the axis of the disc spring is rectangular, so that the corner of the disc spring 60 is located at the valley V1 of the plate 50. By fitting the portion V <b> 2, it is possible to further suppress the disc spring 60 from being eccentric with respect to the plate 50. Furthermore, since the cross-sectional shape is V-shaped, it is easier to form the first gap CL1 and the second gap CL2 than when the cross-sectional shape cut in the radial direction is not V-shaped. Therefore, smoother elastic deformation of the disc spring 60 can be assisted.

  (6) The annular groove 50c is provided in the flat portion 50b of the plate 50 so that the center axis Ax1 of the annular groove 50c and the center axis Ax2 of the plate 50 coincide with each other. With this configuration, when the disc springs 60 are fitted in the grooves 50c of the plate 50 on both sides in the axial direction of the bearing 34, the disc springs 60 press the both side surfaces in the axial direction of the bearing 34. Acts on a coaxial position. Therefore, the inclination of the bearing 34 caused by the radial eccentricity of the disc spring 60 with respect to the plate 50 can be suppressed.

  (7) When the plate 50 and the disc spring 60 are disposed between the bearing 34 and the housing 16 in their axial directions, the following may be a concern. For example, in the axial direction of the rack shaft 12, when the disc spring 60 is provided so as to press between the flat portion 50b provided with the annular groove 50c and the housing 16, the disc spring 60 in the axial direction. One end abuts the housing. Since the housing 16 is made of a soft metal such as aluminum, for example, the surface of the housing 16 on which the disc spring 60 abuts is gradually dented. Due to the dent, the elastic force of the disc spring 60 that presses the flat portion 50b provided with the annular groove 50c and the housing 16 away from each other is weakened. As the elastic force becomes weaker, the disc spring becomes more difficult to maintain the elastic support of the bearing, which may cause the bearing to tilt.

  In that respect, the small diameter end portion (more precisely, the corner portion V2) of the disc spring 60 is in contact with the annular groove 50c (more precisely, the valley portion V1) of the flat portion 50b. With this configuration, the disc spring 60 does not contact the housing 16. Therefore, the disc spring 60 can maintain the elastic support of the bearing 34.

(8) When the bearing 34 is used in the steering device, there are concerns about the following.
For example, when the steering device is used for a vehicle, a force that rotates the rack shaft 12 in a direction orthogonal to the axial direction may occur due to the force transmitted from the road surface. The rotating force is transmitted from the rack shaft 12 to the bearing 34 via the ball screw nut 31, and the bearing 34 may be inclined with respect to the axis of the rack shaft 12.

  In that respect, according to the above configuration, the bearing is a double-row angular contact ball bearing. Compared with the case where a deep groove ball bearing (single row) is adopted as the bearing 34, the rigidity against the rotating force transmitted from the rack shaft 12 is further improved. Therefore, the inclination of the bearing 34 that supports the ball screw nut 31 can be further suppressed.

<Other embodiments>
Note that the present embodiment may be modified as follows within a technically consistent range.
In the present embodiment, the angle θ formed by the slope 51 and the slope 52 is greater than 90 degrees, but the present invention is not limited to this. For example, when the angle θ is set to 90 degrees or less, the angle V2 of the disc spring 60 is smaller than the angle θ formed by the inclined surface 51 and the inclined surface 52, and the corner V2 is set to the valley V1. What is necessary is just to change the shape of the corner | angular part V2 so that 1st clearance CL1 and 2nd clearance CL2 may be formed when it is made to contact | abut.

  -In this Embodiment, although the cross-sectional shape of the groove | channel 50c which cut | disconnected the plate 50 with the plane containing the axis line was V shape, it is not restricted to this. For example, the cross-sectional shape may be U-shaped. However, in this case, when the shape of the portion corresponding to the corner portion V2 of the disc spring 60 is appropriately changed, and the portion corresponding to the corner portion V2 of the disc spring 60 is brought into contact with the groove 50c, the first gap CL1. The second gap CL2 may be formed. Note that the first gap CL1 may be formed and the second gap CL2 may not be formed.

  -In this Embodiment, although the side surface of the flat part 50b on the opposite side to the side provided with the annular groove 50c is flat, it is not restricted to this. You may provide the annular protrusion of the shape where the unevenness | corrugation was reversed with respect to the annular groove 50c on the side surface on the opposite side to the side which provided the annular groove 50c. By providing the groove and the protrusion at symmetrical positions on both side surfaces of the flat portion 50b, the thickness of the plate 50 in the groove portion becomes uniform, and the annular groove 50c can be formed with high accuracy by pressing. When the plate 50 having the above-described configuration is applied to a steering device, grooves for fitting the annular protrusions may be provided on both side surfaces in the axial direction of the locking portions 25 and 26 of the housing 16 or the bearing 34. . The shape of the groove into which the annular protrusion is fitted may be appropriately changed depending on the use of the product, but at least the surface other than the protrusion on the surface of the flat portion 50b where the annular protrusion is provided is the locking portion 25 of the housing 16. , 26 or the bearing 34 may be in contact with the side surface in the axial direction.

  -In this Embodiment, although the flat part 50b was provided so that it might contact | abut to the latching | locking parts 25 and 26 in an axial direction, it is not restricted to this. For example, the plate 50 and the disc spring 60 may be provided in opposite directions in the axial direction. In this case, the flat portions 50b and 50b are in contact with both side surfaces of the bearing 34 in the axial direction.

  In the present embodiment, the outer peripheral surface 60a of the disc spring 60 and the inner peripheral surface 60b of the small-diameter side end of the disc spring 60 are the S pole, the inner peripheral surface of the disc spring 60, and the large-diameter side end of the disc spring 60. Although the outer peripheral surface is magnetized to the N pole, it is not limited to this. That is, the magnetization directions of the plate 50 and the disc spring 60 shown in FIG. 6 may be reversed. Even in this case, when the plate 50 and the disc spring 60 are assembled, the adsorbing force acts so that the flat portion 50b and the disc spring 60 are close to each other, and therefore, the corner portion V2 of the disc spring 60 and the valley portion of the plate 50 are used. The state where V1 is in contact can be maintained. That is, it is possible to further suppress the disc spring 60 from being eccentric in the radial direction with respect to the plate 50 during assembly. Further, the plate 50 and the disc spring need not be magnetized. Even in such a case, the eccentricity of the disc spring 60 with respect to the plate 50 can be suppressed by fitting the corner portion V2 of the disc spring 60 into the valley portion V1 of the annular groove 50c in the flat portion 50b. For example, the plate 50 is made of steel and only the disc spring 60 is magnetized, whereby an attractive force can be generated between the plate 50 and the disc spring 60. Further, the same effect can be obtained even when the disc spring 60 is made of steel and only the plate 50 is magnetized.

  In the present example, an EPS (electric power steering device) is taken as an example of the steering device, but it can also be applied to steer-by-wire.

DESCRIPTION OF SYMBOLS 12 ... Rack shaft, 12a ... Screw groove (of rack shaft), 15 ... Steering, 16 ... Housing, 16a ... 1st housing, 16b ... 2nd housing, 31 ... Ball screw nut, 33 ... Screw (of ball screw nut) Groove, 34 ... bearing, 34b ... outer ring, 50 ... plate, 50a ... holding part, 50b ... flat part, 50c ... (annular) groove, 51 ... slope, 52 ... slope, 60 ... disk spring, 60a ... disk spring 60b: inner peripheral surface at the small-diameter end of the disc spring, CL1: first gap, CL2: second gap, Ax1 ... central axis (of annular groove), Ax2 ... (plate outer diameter) Center axis.

Claims (8)

A steered shaft that includes a screw groove on the outer periphery and moves in the axial direction in accordance with a steering operation,
A ball screw nut threadably engaged with the thread groove of the steered shaft via a plurality of balls;
A housing that houses the steered shaft and the ball screw nut;
A bearing that rotatably supports the ball screw nut with respect to the housing;
A plate and an annular elastic member respectively disposed between a part of the housing and both side surfaces in the axial direction of the bearing inside the housing;
The plate is provided so as to extend in parallel to the axial direction on an annular flat portion sandwiching the elastic member between an end surface of the bearing or a housing in the axial direction and an axial side surface of the flat portion. And an annular groove in which an end of the elastic member in the axial direction is fitted on the side surface in the axial direction of the flat portion. Steering device.   The steering apparatus according to claim 1, wherein at least one of the elastic member and the plate is magnetized so that an attractive force acts between the elastic member and the plate.   The elastic member has a truncated cone shape, and an outer corner portion at an end portion on the small diameter side is fitted into the annular groove, and an end portion on the large diameter side in the axial direction is an outer ring of the bearing or The steering device according to claim 1 or 2, wherein the steering device is in contact with a housing, and a gap is formed at least between an outer peripheral surface of the elastic member and an inner surface of the annular groove.   The steering apparatus according to claim 3, wherein the gap becomes wider in an axial direction of the elastic member as it goes toward an outer periphery of the elastic member.   The steering device according to any one of claims 1 to 4, wherein a cross-sectional shape of the annular groove when the plate is cut along a plane including an axis of the plate is V-shaped.   The steering device according to any one of claims 1 to 5, wherein positions of central axes of grooves of the plate provided on both sides in the axial direction of the bearing coincide with each other in a radial direction of the steered shaft. .   The elastic member is a disc spring that presses the entire circumference of the side surface of the outer ring portion of the bearing and the entire circumference of the flat portion provided with the annular groove in a direction away from each other. The steering device according to item.   The steering device according to any one of claims 1 to 7, wherein the bearing is a double-row angular ball bearing.

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