JP2018162011A - Steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering device which steers a steering wheel by moving a rack shaft housed in a housing in a vehicle width direction and enables tilting operation of a nut member, which threadedly engages with a rach shaft through balls, relative to the housing with a simple structure.SOLUTION: A steering assist device 4 applies steering assist force for assisting steering operation of a steering wheel 10 to a rack shaft 2 and includes: a nut member 5 forming a ball screw part 40 with the rack shaft 2; a rolling bearing 6 which supports the nut member 5 so that the nut member 5 can rotate relative to a housing 3; and an electric motor 42 which rotates the nut member 5 relative to the rack shaft 2. The rolling bearing 6 has an outer ring 61 and an inner ring 62 and multiple rolling elements 43. A shape of an outer peripheral surface 61a of the outer ring 61 or an inner peripheral surface 62a of the inner ring 62 enables tilting operation in which the nut member 5 tilts with the rack shaft 2 relative to the housing 3.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a vehicle steering apparatus including a steering assist device that assists a steering operation.

  2. Description of the Related Art Conventionally, a vehicle steering apparatus in which a rack shaft moves in the vehicle width direction in response to a steering operation of a steering wheel has been widely used that includes an electric steering assist device that assists the steering operation. In such a steering assist device, there is one in which a cylindrical nut member is screwed into a spiral thread groove formed on a rack shaft via a plurality of balls, and this nut member is driven by an electric motor. (For example, refer to Patent Document 1).

  In the steering device described in Patent Document 1, the nut member is driven by an electric motor via a cylindrical collar member. The collar member has a large-diameter portion and a small-diameter portion that are aligned in the axial direction, and a belt that meshes with a pinion attached to the rotary shaft of the electric motor is wound around the outer periphery of the large-diameter portion. A nut member is disposed on the inner peripheral side of the small diameter portion, and the nut member receives the driving force of the electric motor transmitted by the belt from the small diameter portion and rotates. A rolling bearing is disposed between the outer periphery of the small diameter portion and the housing.

  The inner peripheral surface of the small-diameter portion of the collar member has a crown shape that swells toward the inner diameter side like a drum. Then, the nut member can be tilted with respect to the collar member by the shape of the collar member, and the binding force of the ball in the ball screw portion is relaxed.

International Publication No. 2013/083538

  In the steering device described in Patent Document 1, the inner peripheral surface of the small-diameter portion of the collar member interposed between the rolling bearing and the nut member has a crown shape, so that the ball binding force in the ball screw portion is reduced. However, the number of parts increases by using the color member having such a shape as a part. Moreover, since the shape of the collar member is complicated, the number of processing steps increases. Furthermore, the structure for transmitting the rotational force from the collar member to the nut member while permitting the tilting of the nut member with respect to the collar member becomes complicated, and there is a possibility that a transmission loss of the rotational force may occur.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a steering device capable of tilting the nut member with a simple configuration.

  In order to achieve the above object, the present invention provides a steered shaft coupled to a steered wheel via a link mechanism, a steering assist device that applies a steering assist force to the steered shaft, and one of the steered shafts. And a steering housing device that steers the steered wheels by moving the steered shaft in the vehicle width direction. A cylindrical nut member that is screwed into a spiral thread groove formed on the outer peripheral surface via a plurality of balls, a rolling bearing that rotatably supports the nut member with respect to the housing, and the nut member An electric motor that rotates with respect to the steered shaft, and the rolling bearing opposes an outer ring having an outer peripheral surface facing the inner surface of the housing and an outer peripheral surface of the nut member. An inner ring having a peripheral surface, and a plurality of rolling elements disposed between the outer ring and the inner ring, and the shape of the outer peripheral surface of the outer ring or the inner peripheral surface of the inner ring, Provided is a steering apparatus in which a nut member can be tilted together with the steering shaft.

  According to the steering device according to the present invention, the nut member can be tilted with a simple configuration.

1 is an external view showing a steering apparatus according to a first embodiment of the present invention. It is a schematic diagram which shows typically the structure in the housing of a steering device. It is sectional drawing which shows the structure of the principal part of a steering assistance apparatus. It is sectional drawing which shows the periphery part of a rolling bearing, (a) shows the state when a steering wheel exists in a neutral position, (b), (c) shows the state when a steering wheel is steered, respectively. . It is sectional drawing which shows the principal part of the steering assistance apparatus which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the peripheral part of the rolling bearing of the steering auxiliary device which concerns on 2nd Embodiment, (a) is a state when a steering wheel exists in a neutral position, (b), (c) is steering Each state when the wheel is steered is shown.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. In addition, although embodiment described below is shown as a suitable specific example in implementing this invention, although there are some parts which have illustrated various technical matters that are technically preferable. The technical scope of the present invention is not limited to this specific embodiment.

(Overall structure of steering device)
FIG. 1 is an external view showing a steering apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic diagram schematically showing the structure inside the housing of the steering device. FIG. 3 is a cross-sectional view illustrating a configuration of a main part of the steering assist device.

  The steering device 1 is mounted on a vehicle and steers left and right front wheels, which are steered wheels, according to a driver's steering operation. FIG. 1 shows a state in which the steering device is viewed obliquely from the front of the vehicle. The left side of the drawing corresponds to the right side of the vehicle, and the right side of the drawing corresponds to the left side of the vehicle. Note that the letter “R” in the reference numerals in FIGS. 1 and 2 indicates the right side of the vehicle, and the letter “L” indicates the left side of the vehicle. In the following description, “upper”, “lower”, “left”, and “right” refer to the vehicle up-down direction and the vehicle left-right direction.

  The steering device 1 includes a steering shaft 11 to which a steering wheel 10 that is steered by a driver is coupled, a rack shaft 2 that moves in the vehicle width direction by a steering operation of the steering wheel 10, and a metal that houses the rack shaft 2. A housing 3 and a steering assist device 4 that applies a steering assist force to assist the steering operation of the steering wheel 10 to the rack shaft 2 are provided. The housing 3 accommodates a part of the steering assist device 4 and the rack shaft 2. The steering device 1 steers the left and right front wheels, which are steered wheels, as the rack shaft 2 moves in the vehicle width direction. The rack shaft 2 is an aspect of the steered shaft of the present invention.

  The steering shaft 11 includes a column shaft 12 to which the steering wheel 10 is fixed at one end, an intermediate shaft (intermediate shaft) 13 connected to the column shaft 12 via a universal joint 151, and a universal joint to the intermediate shaft 13. The pinion shaft 14 is connected via the pin 152. The universal joints 151 and 152 are, for example, cardan joints.

  The pinion shaft 14 has pinion teeth 140 (see FIG. 2) formed at the tip thereof. The rack shaft 2 is formed with rack teeth 20 that mesh with the pinion teeth 140 and a helical thread groove 21 (see FIG. 3). The pinion shaft 14 is configured as a torsion bar 141 having a flexibility that is partially twisted by a steering torque applied to the steering wheel 10, and a twist angle of the torsion bar 141 is detected by the torque sensor 41. . The torque sensor 41 detects the steering torque based on the torsion angle of the torsion bar 141.

The rack shaft 2 is connected to the left and right front wheels via a link mechanism including left and right tie rods 17L and 17R. As shown in FIG. 2, one end of each of the left and right tie rods 17L, 17R is connected to both ends of the rack shaft 2 at an angle with respect to the rack shaft 2 via ball joints 16L, 16R. The inclination angles θ ₁ and θ ₂ of the tie rods 17L and 17R with respect to the rack shaft 2 change according to the steering angle. Bellows 18L and 18R having an expandable bellows structure are provided between both ends of the housing 4 and the tie rods 17L and 17R, respectively. The other ends of the left and right tie rods 17L and 17R are connected to the left and right front wheels, respectively. When the rack shaft 2 moves back and forth in the vehicle width direction (left and right direction), the left and right front wheels are turned by the left and right tie rods 17L and 17R, respectively.

  The steering assist device 4 includes a torque sensor 41, an electric motor 42, a cylindrical nut member 5 that is screwed into a thread groove 21 formed on the outer peripheral surface of the rack shaft 2 via a plurality of balls 43, and a nut member. 5 which rotatably supports 5 with respect to the housing 3, a pair of left and right elastic support mechanisms 7 which elastically support the rolling bearing 6 in the axial direction, and a composition which transmits the rotational force of the electric motor 42 to the nut member 5. And a belt 44 made of rubber. As shown in FIG. 2, the electric motor 42 includes a drive unit 421 having a stator and a rotor, and a control unit 422 that supplies a motor current to the stator of the drive unit 421. The control unit 422 supplies a motor current corresponding to the steering torque and vehicle speed detected by the torque sensor 41 to the drive unit 421. The drive unit 421 generates torque by the motor current supplied from the control unit 422, and rotates the nut member 5 with respect to the housing 3 via the belt 44.

  The housing 3 includes a cylindrical rack shaft accommodating portion 31 that accommodates the rack shaft 2, a pinion shaft accommodating portion 32 that accommodates the pinion shaft 14, and a nut member accommodating portion 33 that accommodates the nut member 5. . The rack shaft accommodating portion 31 has attachment portions 311 and 312 at both ends in the axial direction, and the attachment portions 311 and 312 are fixed to a steering member (not shown) to which the vehicle body is attached by bolts. Note that neither end of the rack shaft housing 31 is provided with an elastic body such as a rack bush for supporting the rack shaft 2.

  The housing 3 has a first member 301 and a second member 302. The nut member accommodating portion 33 is configured by coupling the first member 301 and the second member 302, and the rack shaft accommodating portion 31 on the vehicle right side (left side in the drawing) of the nut member accommodating portion 33 is configured by the first member 301. ing. The rack shaft housing part 31 on the vehicle left side (right side in the drawing) with respect to the nut member housing part 33 is constituted by a second member 302. The electric motor 42 is fixed to the second member 302 with a bolt 303.

  The nut member 5 includes a main body 50 and a ring nut 500 as a separate part coupled to the main body 50 by screwing. The nut member 5 forms a ball screw portion 40 between the nut member 5 and the rack shaft 2. A spiral thread groove 51 facing the thread groove 21 of the rack shaft 2 is formed on the inner peripheral surface of the main body 50 of the nut member 5. The plurality of balls 43 roll on a rolling path 400 formed by the thread groove 21 of the rack shaft 2 and the thread groove 51 of the nut member 5. In addition, the main body 50 of the nut member 5 is formed with an annular flow path 52 that opens at two locations of the rolling path 400. The plurality of balls 43 circulate through the rolling path 400 and the annular flow path 52 by the rotation of the nut member 5. Hereinafter, the longitudinal direction of the rack shaft housing portion 31 along the central axis of the rack shaft 2 is referred to as an axial direction.

  Further, the nut member 5 is formed with a driven pulley portion 53 in which a belt 44 is wound around the outer peripheral surface of the main body portion 50. The belt 44 is wound between a driving pulley 421 and a driven pulley portion 53 that rotate integrally with the shaft 420 of the electric motor 42, and transmits the rotational force of the electric motor 42 to the nut member 5. The driven pulley portion 53 has a larger diameter than the drive pulley 421, and the rotational force of the electric motor 42 is decelerated by the belt 44 and transmitted to the driven pulley portion 53.

  The rolling bearing 6 is a double row ball bearing having a plurality of rolling elements 60 arranged in a double row, and has an outer ring 61, an inner ring 62, and first and second cages 63 and 64. . The outer ring 61 includes an outer peripheral surface 61a facing the inner surface of the nut member accommodating portion 33 in the housing 3, a first outer ring raceway surface 61b on which the plurality of rolling elements 60 in one row roll, and a plurality of rolling elements in the other row. 60 has the 2nd outer ring raceway surface 61c which rolls. The rolling elements 60 are spherical, and the plurality of rolling elements 60 in one row are held at equal intervals by the first holder 63, and the plurality of rolling elements 60 in the other row are held at equal intervals by the second holder 64. Has been.

  The inner ring 62 includes an inner circumferential surface 62a facing the outer circumferential surface 5a of the nut member 5, a first inner ring raceway surface 62b on which a plurality of rolling elements 60 in one row rolls, and a plurality of rolling elements 60 in the other row. And a second inner ring raceway surface 62c that rolls. The inner peripheral surface 62a of the inner ring 62 and the outer peripheral surface 5a of the nut member 5 facing the inner peripheral surface 62a of the inner ring 62 are parallel to the axial direction. The plurality of rolling elements 60 in one row are disposed between the first outer ring raceway surface 61b and the first inner ring raceway surface 62b. The plurality of rolling elements 60 in the other row are disposed between the second outer ring raceway surface 61c and the second inner ring raceway surface 62c.

  In the present embodiment, the inner ring 62 includes a first inner ring member 621 and a second inner ring member 622. The first inner ring member 621 is formed with a first inner ring raceway surface 62b, and the second inner ring member 622 is formed with a second inner ring raceway surface 62c.

  The main body portion 50 of the nut member 5 integrally includes a large diameter portion 501 and a small diameter portion 502 having different outer diameters, and a driven pulley portion 53 is formed at one end portion of the large diameter portion 501. A step surface 50 a is formed between the large diameter portion 501 and the small diameter portion 502. A male screw portion 54 is formed on the outer peripheral surface at one end of the small diameter portion 502. The ring nut 500 is screwed into the male screw portion 54 and is prevented from loosening by a retaining ring 55. The ring nut 500 fastens the inner ring 62 in the axial direction between the step surface 50a. In the inner ring 62, the first inner ring member 621 contacts the end surface 500 a of the ring nut 500, and the second inner ring member 622 contacts the step surface 50 a of the nut member 5.

  The nut member accommodating portion 33 of the housing 3 has an annular recess 330 formed on the inner surface thereof. The annular recess 330 has a bottom surface 330 a formed by the inner peripheral surface of the first member 301, and both axial side surfaces 330 b and 330 c formed by stepped surfaces formed on the first member 301 and the axial end surface of the second member 302. Is formed. At least a part of the outer ring 61 is accommodated in the annular recess 330.

  The outer ring 61 is a convex curved surface in which the axial cross-sectional shape of the outer peripheral surface 61 a in contact with the bottom surface 330 a of the annular recess 330 in the housing 3 protrudes radially outward. In the present embodiment, the entire outer peripheral surface 61a of the outer ring 61 is a convex curved surface. However, the present invention is not limited to this, and the portion that does not contact the bottom surface 330a of the annular recess 330 may be, for example, linear. In the present embodiment, the outer peripheral surface 61a has the largest outer diameter at the central portion of the outer ring 61 in the axial direction width, and the outer diameter decreases monotonously as the outer circumferential surface 61a is separated from the maximum outer diameter portion in the axial direction. However, the maximum outer diameter portion of the outer peripheral surface 61a does not necessarily have to be in the center portion of the axial width of the outer ring 61.

  The bottom surface 330a of the annular recess 330 is a surface parallel to the axial direction. The outer diameter at the maximum outer diameter portion of the outer ring 61 is slightly smaller than the inner diameter of the bottom surface 330 a of the annular recess 330. With this configuration, the rolling bearing 6 can move in the axial direction with respect to the housing 3 when the outer peripheral surface 61 a of the outer ring 61 slides on the bottom surface 330 a of the annular recess 330.

  FIG. 4 is a cross-sectional view showing the peripheral portion of the rolling bearing 6, where (a) shows the state when the steering wheel 10 is in the neutral position, and (b) and (c) show that the steering wheel 10 has been steered. Each state is shown.

  As shown in FIG. 4A, the outer ring 61 is elastically displaceable in the axial direction by the elastic support mechanisms 7 disposed between the axial end surfaces 61d and 61e and the both side surfaces 330b and 330c of the annular recess 330, respectively. It is supported. The elastic support mechanism 7 includes a first elastic body 71 and a second elastic body 72 having different elastic moduli, and holds the first and second elastic bodies 71 and 72 and the first elastic body 71. 1 holding member 73 and a second holding member 74 that holds the second elastic body 72.

  In the present embodiment, the first and second elastic bodies 71 and 72 are disc springs, and the elastic modulus of the first elastic body 71 is larger than the elastic modulus of the second elastic body 72. In other words, the first elastic body 71 is harder to deform than the second elastic body 72, and the spring constant of the first elastic body 71 is larger than the spring constant of the second elastic body 72. The second elastic body 72 is mainly deformed at the initial stage of steering when the steering wheel 10 is steered leftward or rightward from the neutral position. That is, in the initial stage of steering, when the axial movement force is applied to the rack shaft 2 by the rotation of the pinion shaft 14 of the steering shaft 11, the second elastic force is generated before the steering assist device 4 generates the steering assist force. The rack shaft 2 moves in the axial direction by elastic deformation of the body 72. Thereby, the axial movement of the rack shaft 2 in the initial stage of steering is not hindered by the ball screw portion 40, and a good steering feeling can be obtained.

  In the elastic support mechanism 7 disposed between the axial end surface 61 d of the outer ring 61 and one side surface 330 b of the annular recess 330, the inner diameter side end portion of the first elastic body 71 is held by the first holding member 73. In addition, the outer diameter side end of the first elastic body 71 is in contact with the second holding member 74. The second elastic body 72 has an inner diameter side end held by the second holding member 74, and an outer diameter side end contacting the axial end surface 61 d of the outer ring 61. The first holding member 73 is in contact with one side surface 330 b of the annular recess 330. The 1st holding member 73 and the 2nd holding member 74 are the ring shape arrange | positioned at the outer periphery of the nut member 5, The axial direction cross section is formed in the L-shape.

  Similarly, in the elastic support mechanism 7 disposed between the axial end surface 61e of the outer ring 61 and the other side surface 330c of the annular recess 330, the inner diameter side end of the first elastic body 71 is the first holding member. 73, the outer diameter side end of the first elastic body 71 is in contact with the second holding member 74. The second elastic body 72 has an end on the inner diameter side held by the second holding member 74, and an end on the outer diameter side is in contact with the axial end surface 61 e of the outer ring 61. The first holding member 73 is in contact with the other side surface 330 b of the annular recess 330.

By the way, during the steering operation of the steering wheel 10, the inclination angles θ ₁ and θ _{2 of} the tie rods 17L and 17R with respect to the rack shaft 2 change as the rack shaft 2 moves in the axial direction. For example, when the steering wheel 10 is steered in the right direction, the inclination angle θ ₁ formed by the tie rod 17L and the rack shaft 2 decreases, and the inclination angle θ ₂ formed by the tie rod 17R and the rack shaft 2 increases. At this time, the rack shaft 2 is inclined with respect to the housing 3 by the reaction force that the rack shaft 2 receives from the tie rods 17L and 17R.

  In this case, if the nut member 5 cannot be tilted with respect to the housing 3, the ball 43 is strongly sandwiched between the thread groove 21 of the rack shaft 2 and the thread groove 51 of the nut member 5, and the rolling resistance increases. Resulting in. An increase in the rolling resistance of the ball 43 appears as a change in the steering reaction force when the driver steers the steering wheel 10, so that a good steering feeling may not be obtained.

  Therefore, the steering assist device 4 according to the present embodiment can be tilted with respect to the housing 3 along with the rack shaft 2 by the shape of the outer peripheral surface 61 a of the outer ring 61. That is, the outer peripheral surface 61 a of the outer ring 61 is a convex curved surface protruding outward in the radial direction, so that the nut member 5 can be inclined with respect to the housing 3 together with the rolling bearing 6. The tilting operation relaxes the binding force that the balls 43 receive from the rack shaft 2 and the nut member 5 even when the rack shaft 2 is tilted with respect to the housing 3 at the time of turning, and a good steering feeling is maintained. It is.

  As shown in FIG. 4B, when the rack shaft 2 moves to the right side (left side in the drawing) in the vehicle width direction, the first and second elastic support mechanisms 7 disposed on the axial end surface 61e side of the outer ring 61 are arranged. The second elastic bodies 71 and 72 are compressed in the axial direction, and the first and second elastic bodies 71 and 72 of the elastic support mechanism 7 disposed on the axial end face 61d side of the outer ring 61 extend in the axial direction. On the other hand, when the rack shaft 2 moves to the left side in the vehicle width direction (right side in the drawing) as shown in FIG.

  As described above, the elastic support mechanism 7 on the side compressed by the outer ring 61 of the pair of left and right elastic support mechanisms 7 is mainly in the initial stage of steering when the steering wheel 10 is steered leftward or rightward from the neutral position. When the second elastic body 72 is compressed in the axial direction and the steering wheel 10 is further steered from this state, the first elastic body 71 is mainly compressed. The elastic modulus (spring constant) of the first elastic body 71 is set to a value that is not compressed in the axial direction and is not completely cut by a normal steering operation. The first elastic body 71 can be deformed to allow the axial end surfaces 61 d and 61 e of the outer ring 61 to tilt with respect to the housing 3 even after the second elastic body 72 is completely compressed in the axial direction. is there. Thus, the outer ring 61 is supported by the elastic support mechanism 7 so as to be axially displaceable and tiltable.

When the steering wheel 10 is largely steered and the rack shaft 2 is tilted with respect to the housing 3, the nut member 5 and the rolling bearing 6 are tilted with respect to the housing 3 together with the rack shaft 2. When the rack shaft 2 is moved to the right in the vehicle width direction is moved, the slope of the arrow A ₁ direction rack shaft 2 relative to the housing 3 is shown in FIG. 4 (b), the rack shaft 2 on the left side in the vehicle width direction when the rack shaft 2 is inclined in the arrow a ₂ direction shown in FIG. 4 (c) with respect to the housing 3. 4B and 4C, for the sake of clarity, the inclination of the nut member 5 and the rolling bearing 6 with respect to the housing 3 is exaggerated. 1 to 0.2 °.

(Operation and effect of the first embodiment)
As described above, according to the first embodiment of the present invention described above, the outer peripheral surface 61a of the outer ring 61 is a convex curved surface, and the nut member 5 is attached to the rack shaft 2 with respect to the housing 3 by the shape of the outer peripheral surface 61a. A tilting motion that tilts together is possible. Then, when the nut member 5 is tilted together with the rack shaft 2 with respect to the housing 3, the binding force that the ball 43 receives from the rack shaft 2 and the nut member 5 is relaxed, and the increase in rolling resistance of the ball 43 is suppressed.

  Further, according to the present embodiment, for example, the nut member 5 can be smoothly tilted together with the rack shaft 2 with respect to the housing 3 without using parts such as the collar member of the steering device described in Patent Document 1. It becomes possible, and the increase in the number of parts and the number of processing steps is suppressed. In addition, the process which makes the outer peripheral surface 61a of the outer ring | wheel 61 the convex curved surface can be easily performed by the centerless grinding using a pair of grindstone in which the grinding surface was formed in concave shape, for example.

  Furthermore, since the outer ring 61 is elastically supported by the elastic support mechanism 7 having the first and second elastic bodies 71 and 72 having different elastic moduli, a good steering feeling can be obtained during the steering operation of the steering wheel 10. As a result, the rolling bearing 6 can be smoothly tilted with respect to the housing 3 together with the nut member 5.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.

  FIG. 5 is a cross-sectional view showing a configuration of a main part of the steering assist device 4 according to the second embodiment of the present invention. FIG. 6 is a cross-sectional view showing a peripheral portion of the rolling bearing 6 of the steering assist device 4 according to the second embodiment. FIG. 6A shows a state when the steering wheel 10 is in the neutral position. , (C) respectively show states when the steering wheel 10 is steered. 5 and 6, members and the like having the same functions as those described in the first embodiment are denoted by the same reference numerals as those in FIGS. 3 and 4, and redundant descriptions are omitted. .

  In the first embodiment, the case where the nut member 5 tilts with the rack shaft 2 with respect to the housing 3 by the shape of the outer peripheral surface 61a of the outer ring 61 has been described, but in the present embodiment, This tilting operation is made possible by the shape of the inner peripheral surface 62a of the inner ring 62. In the first embodiment, the case where the inner ring 62 is configured by the first inner ring member 621 and the second inner ring member 622 has been described. However, in the present embodiment, the outer ring 61 is the first outer ring member. 611 and the 2nd outer ring member 612, and the inner ring | wheel 62 is comprised by the integral member.

  The outer ring 61 is sandwiched between a step surface 301 a formed on the first member 301 and an axial end surface 302 a of the second member 302. In the present embodiment, the outer peripheral surface 61a of the outer ring 61 and the inner peripheral surface 301b of the first member 301 facing the outer peripheral surface 61a are parallel to the axial direction. That is, in the rolling bearing 6, the outer ring 61 is fixed to the inner periphery of the nut member accommodating portion 33 of the housing 3 and does not tilt with the nut member 5 with respect to the housing 3.

  Further, in the present embodiment, the pair of elastic support mechanisms 7 is provided between one axial end face 62d of the inner ring 62 and the end face 500a of the ring nut 500, and the other axial end face 62e of the inner ring 62 and the nut member. 5 between the five step surfaces 50a. Each elastic support mechanism 7 includes a first elastic body 71 and a second elastic body 72 having different elastic moduli, and an annular plate disposed between the first elastic body 71 and the second elastic body 72. And a washer 75. The 1st elastic body 71 and the 2nd elastic body 72 consist of disc springs, and each elastic modulus is the same as that of 1st Embodiment.

  In one elastic support mechanism 7 on the ring nut 500 side of the pair of elastic support mechanisms 7, the first elastic body 71 has an inner diameter side end abutting against an end surface 500 a of the ring nut 500 and an outer diameter side. The end is in contact with the washer 75. The second elastic body 72 has an inner diameter side end in contact with the washer 75 and an outer diameter side end in contact with one axial end face 62 d of the inner ring 62.

  Further, in the other elastic support mechanism 7 of the pair of elastic support mechanisms 7, the first elastic body 71 has an end on the inner diameter side abutting on the step surface 50 a of the nut member 5, and an end on the outer diameter side. Is in contact with the washer 75. The second elastic body 72 has an inner diameter side end in contact with the washer 75 and an outer diameter side end in contact with the other axial end faces 62 e of the inner ring 62.

  A space between the end surface 500a of the ring nut 500 and the stepped surface 50a of the nut member 5 is an annular recess 56 in which at least a part of the inner ring 62 is accommodated. The bottom surface of the annular recess 56 is formed by the outer peripheral surface 5 a of the main body 50 that is parallel to the rotation axis of the nut member 5. Both side surfaces of the annular recess 56 are formed by the end surface 500 a of the ring nut 500 and the step surface 50 a of the nut member 5. The inner ring 62 is elastically supported in the annular recess 56 so as to be axially displaceable and tiltable by the pair of elastic support mechanisms 7.

  The inner ring 62 is a convex curved surface in which the axial cross-sectional shape of the inner peripheral surface 62a that is in contact with the outer peripheral surface 5a of the nut member 5 protrudes radially inward. In the present embodiment, the entire inner peripheral surface 62a of the inner ring 62 is a convex curved surface. However, the present invention is not limited to this, and a portion that does not contact the outer peripheral surface 5a of the nut member 5 may be, for example, linear. Further, in the present embodiment, the inner peripheral surface 62a has the smallest inner diameter at the central portion of the axial width of the inner ring 62, and the inner diameter monotonously increases as the distance from the smallest inner diameter portion in the axial direction increases. The minimum inner diameter portion of the inner peripheral surface 62a does not necessarily have to be at the center of the axial width of the inner ring 62.

  The inner diameter at the minimum inner diameter portion of the inner ring 62 is slightly larger than the outer diameter of the outer peripheral surface 5 a of the nut member 5. With this configuration, the rolling bearing 6 is movable in the axial direction with respect to the nut member 5 when the inner peripheral surface 62 a of the inner ring 62 slides on the outer peripheral surface 5 a of the nut member 5.

  As shown in FIG. 6B, when the rack shaft 2 moves to the right side in the vehicle width direction (left side in the drawing), the first and second elastic support mechanisms 7 disposed on the axial end surface 62d side of the inner ring 62 are provided. The second elastic bodies 71 and 72 are compressed in the axial direction, and the first and second elastic bodies 71 and 72 of the elastic support mechanism 7 disposed on the axial end face 62e side of the inner ring 62 extend in the axial direction. On the other hand, when the rack shaft 2 moves to the left side in the vehicle width direction (right side in the drawing) as shown in FIG.

When the steering wheel 10 is steered greatly and the rack shaft 2 is tilted with respect to the housing 3, the nut member 5 is tilted with respect to the housing 3 and the rolling bearing 6 together with the rack shaft 2. When the rack shaft 2 is moved to the right in the vehicle width direction is moved, the slope of the arrow A ₃ direction rack shaft 2 is shown in FIG. 6 (b) with respect to the housing 3, the rack shaft 2 on the left side in the vehicle width direction when the rack shaft 2 is inclined in the arrow a ₄ direction shown in FIG. 6 (c) with respect to the housing 3.

(Operation and effect of the second embodiment)
Also in the present embodiment, as in the first embodiment, the nut member 5 is tilted together with the rack shaft 2 with respect to the housing 3, so that the binding force that the ball 43 receives from the rack shaft 2 and the nut member 5 is reduced. Thus, an increase in rolling resistance of the ball 43 is suppressed. Further, the shape of the inner peripheral surface 62a of the inner ring 62 allows the nut member 5 to be tilted with the rack shaft 2 with respect to the housing 3, so that an increase in the number of parts and processing man-hours is suppressed.

  Furthermore, since the inner ring 62 is elastically supported by the nut member 5 by the elastic support mechanism 7 having the first and second elastic bodies 71 and 72 having different elastic moduli, the inner ring 62 is good during the steering operation of the steering wheel 10. Thus, the nut member 5 can be smoothly tilted with respect to the housing 3 and the rolling bearing 6.

(Appendix)
As mentioned above, although this invention was demonstrated based on 1st and 2nd embodiment, these embodiment does not limit the invention which concerns on a claim. In addition, it should be noted that not all the combinations of features described in the embodiments are essential to the means for solving the problems of the invention.

  Further, the present invention can be appropriately modified and implemented without departing from the spirit of the present invention. For example, in the above-described embodiment, the case where the first elastic body 71 and the second elastic body 72 are made of disc springs has been described. May be made of synthetic rubber. In this case, the first and second holding members 73 and 74 may be omitted. Moreover, although the said embodiment demonstrated the case where the rolling bearing 6 consisted of a double-row ball bearing, it is possible to use not only this but various types of bearings as the rolling bearing 6.

  Further, the present invention may be applied to a steering actuator for a steer-by-wire device without an intermediate shaft and a pinion shaft and a rear wheel steering actuator for a four-wheel steering device.

DESCRIPTION OF SYMBOLS 1 ... Steering device 10 ... Steering wheel 11 ... Steering shaft 2 ... Rack shaft 20 ... Rack tooth 21 ... Screw groove 3 ... Housing 330 ... Annular recessed part 330a ... Bottom surface 330b, 330c ... Side surface 4 ... Steering auxiliary device 42 ... Electric motor 43 ... Ball 5 ... Nut member 51 ... Screw groove 56 ... Annular recess 5a ... Outer peripheral surface 6 ... Rolling bearing 60 ... Rolling body 61 ... Outer ring 61a ... Outer peripheral surface 61d, 61e ... Axial end surface 62 ... Inner ring 62a ... Inner peripheral surface 62d, 62e ... Axial end face 7 ... Elastic support mechanisms 71, 72 ... Elastic body

Claims (5)

A steered shaft connected to the steered wheels via a link mechanism, a steering assist device that applies a steering assist force to the steered shaft, and a housing that houses a part of the steered shaft together with the steering assist device. A steering device for turning steered wheels by moving the steered shaft in the vehicle width direction,
The steering assist device includes a cylindrical nut member that is screwed into a spiral thread groove formed on an outer peripheral surface of the steered shaft via a plurality of balls, and the nut member is rotatable with respect to the housing. A rolling bearing to be supported on, and an electric motor for rotating the nut member relative to the steering shaft,
The rolling bearing includes an outer ring having an outer peripheral surface facing the inner surface of the housing, an inner ring having an inner peripheral surface facing the outer peripheral surface of the nut member, and a plurality of rollers disposed between the outer ring and the inner ring. Rolling elements,
According to the shape of the outer peripheral surface of the outer ring or the inner peripheral surface of the inner ring, the nut member can be tilted with the steered shaft with respect to the housing.
Steering device. In the rolling bearing, the inner ring is fixed to the nut member, and an outer peripheral surface of the outer ring that is in contact with the housing is a convex curved surface.
The steering apparatus according to claim 1. The housing is formed with an annular recess for accommodating at least a part of the outer ring,
The outer ring is supported so that the outer peripheral surface is in contact with the bottom surface of the annular recess and is axially displaceable and tiltable by elastic support mechanisms respectively disposed between both axial end surfaces and both side surfaces of the annular recess. And
The elastic support mechanism includes a plurality of elastic bodies having different elastic moduli,
The steering apparatus according to claim 2. In the rolling bearing, an inner peripheral surface of the inner ring that is fixed to the housing and is in contact with the nut member is a convex curved surface.
The steering apparatus according to claim 1. The nut member is formed with an annular recess that accommodates at least a part of the inner ring,
The inner ring is supported in such a manner that the inner peripheral surface is in contact with the bottom surface of the annular recess and is axially displaceable and tiltable by elastic support mechanisms respectively disposed between both axial end surfaces and both side surfaces of the annular recess. Has been
The elastic support mechanism includes a plurality of elastic bodies having different elastic moduli,
The steering apparatus according to claim 4.

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