JP2018177100A - Steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering device configured so that a cylindrical nut member, which is screwed to a turning shaft through a plurality of balls, is driven by an electric motor and an outer wheel of a rolling bearing rotatably supporting the nut member is arranged to be movable in a shaft direction with respect to a housing, which can suppress hammering sound generated by butting of the outer wheel to an inner surface of the housing.SOLUTION: The steering device comprises a positioning mechanism part 8 that elastically positions an outer wheel 71 at a center position in a prescribed range, where the outer wheel 71 can move in a shaft direction in the prescribed range. The positioning mechanism part 8 has a spherical body 81 that contacts an inner surface of a recessed part 710 formed on an outer peripheral surface of the outer wheel 71, and a coil spring 84 that presses the spherical body 81 against the recessed part 710. In the recessed part 710, a depth of the inner surface in a radial direction of the outer wheel 71 becomes shallower gradually as separating away in a shaft direction from the deepest part 711 which the spherical body 81 contacts at the deepest side.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a steering apparatus for a vehicle provided with a moving force applying mechanism that applies an axial moving force to a steered shaft that turns steered wheels.

  Conventionally, in a vehicle having an electric motor as a driving source for traveling, such as a so-called hybrid vehicle or an electric vehicle, an axial moving force is applied to a rack shaft which is a steered shaft to assist the driver's steering operation. It is widely used that is equipped with a motorized steering assist device. Such a steering assist device includes a cylindrical nut member that constitutes a ball screw mechanism together with a rack shaft, and this nut member is driven by an electric motor (see, for example, Patent Document 1).

  The steering assist device described in Patent Document 1 supports a nut member screwed to a spiral thread groove formed on the outer peripheral surface of a rack shaft via a plurality of balls, and a nut member rotatably relative to a housing And an electric motor for rotating the nut member relative to the rack shaft. The rolling bearing has an inner ring fixed to the nut member, an outer ring fitted in a gap on the inner surface of the housing, and a plurality of rolling elements disposed between the raceways of the inner ring and the outer ring. A pair of disc springs are in contact with the axially opposite end faces of the outer ring, and the disc springs are disposed between the pair of plates held by the housing.

  According to such a configuration, when the rack shaft is moved in the axial direction by the driver's steering operation, the nut member and the rolling bearing are integrated with the rack shaft as an initial operation while resisting the elastic force of the disc spring. After axial movement, the nut member rotates relative to the rack shaft. Thereby, a good steering feeling can be obtained.

JP, 2015-186949, A

  In the steering assist device described in Patent Document 1, a slight gap is formed between the outer peripheral surface of the outer ring and the inner surface of the housing in order to allow the rolling bearing to move in the axial direction together with the nut member. When the outer ring abuts against the inner surface of the housing due to the movement of the nut member at the time of initial operation, a hitting sound is generated, which may cause discomfort to the occupants of the driver and the like. In particular, in a vehicle having an electric motor as a drive source for traveling, the hitting sound is easily heard by a passenger since the quietness in the vehicle interior is high.

  Therefore, according to the present invention, the cylindrical nut member screwed to the steered shaft via the plurality of balls is driven by the electric motor, and the outer ring of the rolling bearing rotatably supporting the nut member is the shaft relative to the housing. It is an object of the present invention to provide a steering device capable of suppressing a striking sound due to the outer ring striking an inner surface of a housing in a steering device of a configuration movably disposed in a direction.

  In order to achieve the above object, the present invention provides a steered shaft that moves forward and backward in an axial direction, a moving force applying mechanism that is driven by an electric motor and applies a moving force in the axial direction to the steered shaft; A steering apparatus comprising: a housing for housing a part of a steered shaft together with the moving force applying mechanism, the steered wheels being steered by the steered shaft moving in the axial direction, wherein the moving force applying mechanism A cylindrical nut member is screwed to the helical thread groove formed on the outer peripheral surface of the turning shaft via a plurality of balls, and the inner ring among the inner ring and the outer ring is fixed to the nut member A rolling bearing in which the outer ring is axially movable within a predetermined range with respect to the housing, and a positioning mechanism for elastically positioning the outer ring at a central position of the predetermined range; The outer ring is A recess is formed in the surface, and the positioning mechanism unit has a contact member that contacts the inner surface of the recess, and a spring member that presses the contact member toward the recess, the recess being the contact A steering device is provided, in which the depth of the inner surface in the radial direction of the outer ring gradually becomes smaller as the member is separated in the axial direction from the deepest portion where the members are in contact at the deepest side.

  According to the present invention, in the steering apparatus in which the rolling bearing supporting the nut member is arranged to be movable in the axial direction with respect to the housing, it is possible to suppress striking sound due to the outer ring of the rolling bearing hitting the inner surface of the housing It becomes.

FIG. 1 is an external view showing a steering device according to a first embodiment of the present invention. It is a schematic diagram which shows the structure in the housing of a steering device typically. It is a sectional view showing the composition of the important section of a steering auxiliary device. It is the elements on larger scale of FIG. 3 which expands and shows a positioning mechanism part and its peripheral part. (A) shows the state in which the outer ring has moved most to one side in the axial direction, and (b) shows the state in which the outer ring has moved to the other side in the axial direction. (A)-(c) show the modification of the shape of the recessed part of an outer ring | wheel.

Embodiment
Embodiments of the present invention will be described with reference to FIGS. 1 to 5. Note that the embodiments described below are shown as preferable specific examples for carrying out the present invention, and there are portions that specifically exemplify various technical matters that are technically preferable. The technical scope of the present invention is not limited to this specific embodiment.

(Whole 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 view schematically showing the structure in the housing of the steering device. FIG. 3 is a cross-sectional view showing the configuration of the 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, in accordance with a driver's steering operation. FIG. 1 shows the steering apparatus as 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. In addition, character "R" in the code | symbol in FIG.1 and FIG.2 shows the right side of a vehicle, and character "L" has shown the left side of a vehicle. In the following description, “upper”, “lower”, “left”, and “right” mean directions in the vertical direction of the vehicle and in the lateral direction of the vehicle.

  The steering apparatus 1 includes a steering shaft 11 to which a steering wheel 10 steered by a driver is connected, and a rack shaft 2 as a steering shaft axially moved in the vehicle width direction by steering operation of the steering wheel 10 , A housing 3 for housing the rack shaft 2, an electric motor 40 fixed to the housing 3, and a movement force application mechanism 5 driven by the electric motor 40 to apply an axial movement force to the rack shaft 2 ing.

  The housing 3 accommodates the moving force application mechanism 5 and a part of the rack shaft 2. The electric motor 40 and the moving force application mechanism 5 constitute a steering assist device 4 that assists the steering operation of the steering wheel 10 by the driver. The steering device 1 steers the left and right front wheels 19L and 19R, which are steered wheels, by the rack shaft 2 moving in the axial direction. In FIG. 1, the front wheels 19 </ b> L and 19 </ b> R are shown by imaginary lines (two-dot chain lines).

  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. And a pinion shaft 14 connected via 152. The universal joints 151 and 152 are, for example, cardan joints.

  Pinion teeth 140 (see FIG. 2) are formed at the tip of the pinion shaft 14. The rack shaft 2 is formed with rack teeth 20 that mesh with the pinion teeth 140, and a spiral thread 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 the torsion angle of the torsion bar 141 is detected by the torque sensor 41. . The torque sensor 41 detects the steering torque based on the magnitude of the twist angle of the torsion bar 141.

  The rack shaft 2 is connected to the left and right front wheels 19L, 19R via link mechanisms including left and right tie rods 17L, 17R and knuckle arms not shown. Between the both ends of the housing 3 and the tie rods 17L, 17R, bellows 18L, 18R having an expandable bellows structure are respectively provided. As shown in FIG. 2, one end portions of left and right tie rods 17L and 17R are connected to both end portions of the rack shaft 2 via ball joints 16L and 16R. When the rack shaft 2 moves forward and backward in the vehicle width direction (left and right direction), the left and right front wheels 19L and 19R are turned by the left and right tie rods 17L and 17R. The tie rods 17L and 17R are inclined with respect to the rack shaft 2, and the inclination angle changes in accordance with the steering angle. Therefore, the rack shaft 2 is slightly inclined with respect to the housing 3 at the time of steering operation.

  The moving force application mechanism 5 includes a cylindrical nut member 6 screwed with a screw groove 21 formed on the outer peripheral surface of the rack shaft 2 via a plurality of balls 42 and a rolling bearing rotatably supporting the nut member 6. And a positioning mechanism 8 for positioning the rolling bearing 7 with respect to the housing 3. As shown in FIG. 2, the electric motor 40 has a drive unit 401 having a stator and a rotor, and a control unit 402 that supplies motor current to the stator of the drive unit 401. The control unit 402 supplies the driving unit 401 with a motor current according to the steering torque detected by the torque sensor 41 and the vehicle speed. The drive unit 401 generates torque by the motor current supplied from the control unit 402, and rotates the nut member 6 with respect to the housing 3 via the belt 43 made of synthetic rubber.

  The housing 3 has a cylindrical rack shaft receiving portion 31 for receiving the rack shaft 2, a pinion shaft receiving portion 32 for receiving the pinion shaft 14, and a nut member receiving portion 33 for receiving the nut member 6. . The rack shaft housing portion 31 has mounting portions 311 and 312 (see FIG. 1) at both end portions in the axial direction, and the mounting portions 311 and 312 are bolted to a steering member (not shown) to which the vehicle body is mounted. It is fixed.

  The housing 3 has a first member 301 and a second member 302. The nut member housing portion 33 is constituted by the combination of the first member 301 and the second member 302, and the rack shaft housing portion 31 on the vehicle right side (left side in the drawing) of the nut member housing portion 33 is constituted by the first member 301. ing. The rack shaft accommodation portion 31 on the vehicle left side (right side in the drawing) of the nut member accommodation portion 33 is configured by the second member 302. The first member 301 and the second member 302 are fastened by a plurality of bolts 303. The electric motor 40 is fixed to the second member 302 by a plurality of bolts 304. In FIG. 3, one bolt 303, 304 is shown among the plurality of bolts 303, 304, respectively.

  The nut member 6 constitutes a ball screw portion 60 with the rack shaft 2. On the inner circumferential surface of the nut member 6, a spiral thread groove 61 is formed to face the thread groove 21 of the rack shaft 2. The plurality of balls 42 roll on a rolling path 600 formed by the screw groove 21 of the rack shaft 2 and the screw groove 61 of the nut member 6. Further, in the nut member 6, an annular flow passage 62 opened at two places of the rolling passage 600 is formed. The plurality of balls 42 circulate in the rolling path 600 and the annular flow path 62 by the rotation of the nut member 6.

  Further, in the nut member 6, a driven pulley portion 63 in which a belt 43 is wound is formed. The belt 43 is wound around a driving pulley 404 coupled to a shaft 403 of the electric motor 40 and a driven pulley portion 63, and transmits the rotational force of the electric motor 40 to the nut member 6. The driven pulley portion 63 is larger in diameter than the drive pulley 404, and the rotational force of the electric motor 40 is decelerated by the belt 43 and transmitted to the driven pulley portion 63. The belt 43 is stretched between the driven pulley portion 63 and the drive pulley 404 in a state where the belt 43 is elastically stretched more than the natural length and tension is generated.

  The rolling bearing 7 is a double row ball bearing having a plurality of rolling elements 70 arranged in double rows, and has an outer ring 71 and an inner ring 72, and first and second cages 73 and 74. The outer ring 71 has a first outer ring raceway surface 71a on which a plurality of rolling elements 70 in one row roll, and a second outer ring raceway surface 71b on which a plurality of rolling elements 70 in the other row roll. . The rolling elements 70 are spherical, and the rolling elements 70 in one row are held at equal intervals by the first cage 73, and the rolling elements 70 in the other row are equally spaced by the second cage 74. It is done. An outer peripheral surface 71 c of the outer ring 71 faces the inner peripheral surface 33 a of the nut member housing portion 33 in the housing 3.

  The inner ring 72 has a first inner ring raceway surface 72a on which a plurality of rolling elements 70 in one row roll and a second inner ring raceway surface 72b on which a plurality of rolling elements 70 in the other row roll, It is fixed to the member 6. The plurality of rolling elements 70 in one row are disposed between the first outer ring raceway surface 71a and the first inner ring raceway surface 72a. The plurality of rolling elements 70 in the other row are disposed between the second outer ring raceway surface 71 b and the second inner ring raceway surface 72 b. In the present embodiment, the inner ring 72 is composed of a first inner ring member 721 and a second inner ring member 722. A first inner raceway surface 72 a is formed on the first inner race member 721, and a second inner raceway surface 72 b is formed on the second inner race member 722.

  The nut member 6 integrally has a large diameter portion 601 and a small diameter portion 602 having different outer diameters, and a driven pulley portion 63 is formed at one end portion of the large diameter portion 601. A stepped surface 6 a is formed between the large diameter portion 601 and the small diameter portion 602. A male screw portion 64 is formed on the outer peripheral surface at one end of the small diameter portion 602, and a ring nut 65 is screwed to the male screw portion 64. The ring nut 65 is secured, for example, by caulking so as to axially clamp and fix the inner ring 72 between the ring nut 65 and the step surface 6a.

  The outer ring 71 is not fixed to the housing 3 and is disposed so as to be axially movable within a predetermined range with respect to the housing 3. Thereby, when an axial movement force is applied to the rack shaft 2 by the rotation of the pinion shaft 14 at the initial stage of steering where the steering wheel 10 is steered leftward or rightward from the position of the steering angle zero, the nut member 6 and the rolling bearing 7 move axially with the rack shaft 2. Therefore, even if the rotational force of the electric motor 40 does not rise sufficiently in the initial stage of steering, axial movement of the rack shaft 2 is not hindered by the ball screw portion 60, and a good steering feeling can be obtained. Further, for example, as in the case of traveling on a gentle curve of an expressway, even when the electric motor 40 does not operate because the steering torque is small, the rack shaft 2 can move in the axial direction.

  The positioning mechanism 8 elastically positions the outer ring 71 at the central position of the predetermined range. Here, to position elastically is to position the outer ring 71 at the center position of the predetermined range by an elastic force when no external force acts on the rolling bearing 7, and when an external force in the axial direction acts, the external force To allow the movement of the rolling bearing 7 in the above direction within the above predetermined range. Next, the configuration and operation of the positioning mechanism 8 will be described in detail with reference to FIGS. 4 and 5.

  FIG. 4 is a partially enlarged view of FIG. 3 showing the positioning mechanism 8 and its periphery in an enlarged manner. FIG. 5 (a) shows the state where the outer ring 71 is at the first movement end position where it has moved most to one side in the axial direction, and FIG. 5 (b) shows that the outer ring 71 has moved most to the other side in the axial direction The state of being at the second movement end position is shown. The outer ring 71, together with the inner ring 72 and the plurality of rolling elements 70, can axially move between the first moving end position shown in FIG. 5A and the second moving end position shown in FIG. 5B. It is. FIG. 4 shows a state where the outer ring 71 is at the center position of this predetermined range (an intermediate position between the first moving end position and the second moving end position).

  As shown in FIG. 4, the outer ring 71 is formed with a recess 710 which is recessed in the radial direction on the outer peripheral surface 71 c. The recess 710 is annularly formed over the entire circumference of the outer peripheral surface 71 c by, for example, grinding or cutting. The shape of the recess 710 in the axial cross section of the outer ring 71 is substantially arc-shaped without a step, and the depth in the radial direction is the deepest at the axial center position. A slight gap is formed between the outer peripheral surface 71 c of the outer ring 71 and the inner peripheral surface 33 a of the nut member housing 33 in the vicinity of the positioning mechanism 8. The dimension of the gap is, for example, 0.1 mm, but in FIGS. 4 and 5 the gap is shown exaggerated for clarity of the description.

  The positioning mechanism 8 includes a ball 81 as a contact member to be in contact with the inner surface of the recess 710, a retainer 82 for holding the ball 81, a receiving member 83 fixed to the nut member accommodating portion 33 of the housing 3, and a retainer 82. And a receiving member 83, and a coil spring 84 as a spring member. The coil spring 84 presses the ball 81 toward the recess 710 of the outer ring 71 via the retainer 82.

  The retainer 82 is formed with a bowl-shaped first accommodation recess 821 for accommodating a portion of the sphere 81 and a cylindrical second accommodation recess 822 for accommodating the coil spring 84, and has a substantially cylindrical shape as a whole. is there. The radius of curvature of the inner surface of the first accommodation recess 821 is equal to or greater than the radius of the sphere 81, and the sphere 81 can roll in the first accommodation recess 821. The second accommodation recess 822 is provided inside the cylindrical portion 823 formed in a cylindrical shape, and one end of the coil spring 84 resiliently contacts the bottom surface 822 a of the second accommodation portion 822. The tip end surface 823 a of the cylindrical portion 823 faces the receiving member 83.

  In the present embodiment, a male screw 831 is formed on the outer peripheral surface of the receiving member 83, and the male screw 831 is screwed into a screw hole 331 provided in the nut member accommodation portion 33 of the housing 3. The screw hole 331 communicates with the inner cylindrical holding hole 332 that accommodates the retainer 82 together with the coil spring 84. The holding hole 332 extends along the radial direction of the outer ring 71 and opens in the inner circumferential surface 33 a of the nut member accommodation portion 33, and holds the retainer 82 movably in the same direction. The inner diameter of the holding hole 332 is formed slightly larger than the outer diameter of the retainer 82. At least a portion of the ball 81 protrudes from the holding hole 332 toward the outer ring 71.

  The other end of the coil spring 84 is in elastic contact with the axial end surface 83 a of the receiving member 83. The coil spring 84 is disposed in a compressed state between the bottom surface 822 a of the second accommodation portion 822 of the retainer 82 and the axial end surface 83 a of the receiving member 83. The receiving member 83 is, for example, tightened by a hexagonal wrench fitted in a hexagonal hole 832 provided on the side opposite to the axial end face 83a, and secured by caulking.

  In the recess 710 of the outer ring 71, the ball 81 abuts on one point in the circumferential direction. In other words, the moving force application mechanism 5 has a single positioning mechanism 8. The outer diameter of the outer ring 71 is smaller than the inner diameter of the nut member housing 33, and the outer peripheral surface 71 c of the outer ring 71 and the inner peripheral surface 33 a of the nut member housing 33 contact the opposite side of the positioning mechanism 8. It abuts at the contact position 33b (see FIG. 3).

  When the nut member accommodation portion 33 is viewed in the axial direction, the positioning mechanism portion 8 is disposed at a position where the nut member 6 is sandwiched between the positioning mechanism portion 8 and the drive pulley 404. In other words, the nut member 6 is disposed between the positioning mechanism 8 and the drive pulley 404. With this configuration, the pressing direction of the ball 81 by the coil spring 84 is the same as the direction in which the nut member 6 is pressed in the radial direction by the tension of the belt 43. As a result, the nut member 6 is prevented from being inclined with respect to the rack shaft 2, and the ball 42 smoothly rotates the rolling path 600.

  The depth d of the inner surface in the radial direction of the outer ring 71 is gradually reduced as the concave portion 710 is separated in the axial direction of the outer ring 71 from the deepest portion 711 where the spherical body 81 comes in contact at the deepest side. The deepest portion 711 is at a central position in the width direction of the recess 710 (the axial direction of the outer ring 71), and FIG. 4 shows a state where the sphere 81 is in contact with the deepest portion 711 of the recess 710. Hereinafter, the position of the outer ring 71 is referred to as a neutral position. The deepest portion 711 refers to the deepest portion in the radial direction d of the inner surface of the recess 710 in the range in which the ball 81 which receives the spring force (restoring force) of the coil spring 84 can contact. When the spherical body 81 comes in contact with a position deviated from the deepest portion 711 in the width direction of the concave portion 710, the outer ring 71 takes a component force according to the inclination angle formed by the tangential direction at the contact point and the axial direction of the outer ring 71. It is biased towards the neutral position.

  The shape of the recess 710 in the axial cross section of the outer ring 71 is a shape in which the curvature of the portion where the spherical body 81 abuts when the outer ring 71 is at the end of the predetermined range is larger than the curvature of the deepest portion 711. In the present embodiment, the inner surface of the recess 710 is formed by first to third arc portions 710a, 710b, and 710c having different curvatures. The first arc portion 710a has the largest curvature among the first to third arc portions 710a, 710b, and 710c, and is provided near the center in the width direction of the recess 710 including the deepest portion 711. The second arc portion 710 b is formed on both sides sandwiching the first arc portion 710 a in the width direction of the recess 710. The third arc portion 710 c is provided at both ends in the width direction of the recess 710.

  The radius of curvature of the third arc portion 710 c is, for example, equal to the radius of the sphere 81. The curvature of the second arc portion 710b is smaller than the curvature of the first arc portion 710a and larger than the curvature of the third arc portion 710c. In FIG. 4, a boundary point 710 d between the first arc portion 710 a and the second arc portion 710 b and a boundary point 710 e between the second arc portion 710 b and the third arc portion 710 c are indicated by black circles.

  In the present embodiment, the shape and size of the first accommodation recess 821 of the retainer 82 in the cross section along the axial direction of the outer ring 71 are the same as the recess 710 of the outer ring 71. However, the shape and size of the first accommodation recess 821 may be different from the recess 710 of the outer ring 71 without being limited thereto. However, when the shape and size of the first accommodation recess 821 of the retainer 82 and the recess 710 of the outer ring 71 are common as in the present embodiment, the outer ring 71 moves in the axial direction with respect to the housing 3 It is preferable because the balls 81 roll smoothly.

  When the outer ring 71 is in the neutral position, as shown in FIG. 4, a gap is formed between the tip end surface 823 a of the cylindrical portion 823 of the retainer 82 and the axial end surface 83 a of the receiving member 83. Then, when the outer ring 71 moves in the axial direction from the neutral position, the ball 81 abuts on a portion where the depth of the recess 710 is shallower than the deepest portion 711, so the retainer 82 moves inside the holding hole 332 toward the receiving member 83 .

  Further, in the present embodiment, as described above, the shape and the size of the first accommodation recess 821 of the retainer 82 are the same as the recess 710 of the outer ring 71, and the ball 81 rolls in the first accommodation recess 821. Therefore, the retainer 82 also moves to the receiving member 83 side by the ball 81 rolling in the first accommodation recess 821 along with the axial movement of the outer ring 71. Then, when the end surface 823a of the cylindrical portion 823 abuts on the axial end surface 83a of the receiving member 83, the further movement of the retainer 82 and the outer ring 71 becomes impossible. At this time, the spherical body 81 contacts the third arc portion 710 c of the recess 710.

  As described above, in the present embodiment, axial movement of the outer ring 71 is restricted by the retainer 82 coming into contact with the receiving member 83, whereby the outer peripheral surface 71c of the portion where the recess 710 is not formed is spherical 81 It is deterred that it runs. That is, the depth d of the recess 710 in the deepest portion 711 is deeper than the dimension of the gap between the tip end surface 823a of the cylindrical portion 823 of the retainer 82 and the axial end face 83a of the receiving member 83 when the outer ring 71 is in the neutral position. .

(Operation and effect of the embodiment)
According to the embodiment described above, the ball bearing 81 of the positioning mechanism 8 is pressed against the recess 710 of the outer ring 71, so that the rolling bearing 7 is elastically positioned with respect to the housing 3. As a result, the rattling noise due to the outer peripheral surface 71 c of the outer ring 71 hitting the inner peripheral surface 33 a of the nut member housing 33 can be suppressed.

  In addition, as the ball 81 rolls in the recess 710 along with the axial movement of the outer ring 71, the coil spring 84 is gradually compressed and the pressing force applied to the ball 81 increases, thereby increasing the steering angle. Along with this, the steering reaction force gradually increases, and a good steering feeling without a feeling of abutment at the initial stage of steering can be obtained. That is, for example, in a configuration in which a pair of disc springs abuts on both axial end surfaces of the outer ring as in the conventional steering apparatus described above, the steering reaction force increases rapidly when the disc spring is completely deformed depending on the steering speed. Although there is a possibility of reduction, it is possible in the present embodiment to suppress a rapid change in the steering reaction force. Furthermore, by selecting the curvatures of the first to third arc portions 710a to 710c, it is possible to freely set the characteristics of the restoring force with respect to the axial displacement of the outer ring 71.

  In addition, the concave portion 710 of the outer ring 71 has the curvature of the third arc portion 710c with which the ball 81 abuts at the end in the width direction larger than the curvature of the first arc portion 710a. The reaction force of the moving force applied to the shaft 2 can be sufficiently received by the sphere 81.

  In addition, since the recess 710 is formed over the entire circumference of the outer peripheral surface 71 c of the outer ring 71, machining of the recess 710 is easy and positioning of the outer ring 71 in the circumferential direction in the nut member housing 33 is not necessary. . Furthermore, since the spherical body 81 of the positioning mechanism 8 abuts on the recess 710 at one point in the circumferential direction and the outer ring 71 is elastically positioned, there is no need to provide a plurality of positioning mechanisms 8, and a moving force application mechanism The miniaturization and cost reduction of 5 can be achieved.

  Further, in the positioning mechanism portion 8, the retainer 82 and the coil spring 84 are accommodated in the holding hole 332 formed in the nut member accommodation portion 33 of the housing 3, and a part of the sphere 81 protrudes inward from the holding hole 332 Therefore, the positioning mechanism 8 can be disposed using the thickness of the nut member housing 33, and the enlargement of the housing 3 can be suppressed.

  In addition, when the outer ring 71 moves to the end of the predetermined movable range in the axial direction, the axial movement of the outer ring 71 is restricted by the contact of the retainer 82 with the receiving member 83, so that the recess 710 is formed. The spherical body 81 does not ride on the outer peripheral surface 71c of the portion where it is not located.

(Modification)
6A to 6C show modifications of the shape of the recess 710 of the outer ring 71. FIG. The recessed portion 710 may have any shape as long as the depth in the radial direction is gradually reduced as it is separated from the deepest portion 711 in the axial direction of the outer ring 71, and can be variously modified to practice the present invention. 6A to 6C, the deepest portion 711 is indicated by a black circle, and the sphere 81 in contact with the deepest portion 711 is indicated by an imaginary line (two-dot chain line).

  FIG. 6A shows an example in which the inner surface of the recess 710 is formed by an arc 710 f of uniform curvature. In the modification shown in FIG. 6 (b), the inner surface of the recess 710 consists of a pair of arcs 710g and 710h connected at the center in the width direction, and the sphere 81 is in the deepest portion 711 of each of the pair of arcs Two point contact. Further, in the modification shown in FIG. 6C, the inner surface of the recess 710 is formed of a pair of tapered inclined surfaces 710i and 710j connected at the central portion in the width direction, and the spherical body 81 is a pair of inclined surfaces 710i and 710j. Contact the respective deepest portions 711 of Also in such a modification, the outer ring 71 is backlash-packed with respect to the nut member accommodating portion 33 of the housing 3, and the hitting sound due to the outer peripheral surface 71c of the outer ring 71 striking the inner peripheral surface 33a of the nut member accommodating portion 33 is It becomes possible to suppress.

(Supplementary note)
As mentioned above, although this invention was demonstrated based on embodiment, these embodiments do not limit the invention which concerns on a claim. In addition, it should be noted that not all 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 scope of the invention. For example, although the above-mentioned embodiment explained the case where sphere 81 as a contact member was separate from retainer 82 as a holding member, these may be integral. In the above embodiment, the moving force application mechanism 5 has the single positioning mechanism portion 8 and the spherical body 81 of the positioning mechanism portion 8 abuts on one of the concave portions 710 of the outer ring 71. Not limited to this, the moving force application mechanism 5 may have a plurality of positioning mechanism parts 8. In this case, it is desirable that the spherical bodies 81 of the respective positioning mechanism parts 8 abut on the recessed part 710 at equal intervals in the circumferential direction.

  Furthermore, in the above embodiment, although the case where the present invention is applied to the steering device 1 in which the front wheels 19L and 19R are turned by the rotation of the steering shaft 11 connected to the steering wheel 10 has been described, the present invention is not limited thereto. The present invention may be applied to a steering actuator for a steer-by-wire device without an intermediate shaft or a pinion shaft, or a rear wheel steering actuator for a four-wheel steering device.

1 ... steering device 2 ... rack shaft (steering shaft)
3 ... housing 332 ... holding hole (hole)
DESCRIPTION OF SYMBOLS 40 Electric motor 5 Movement force application mechanism 6 Nut member 60 Ball screw part 7 Rolling bearing 71 Outer ring 710 Recess 711 Deepest part 71c Outer peripheral surface 72 Inner ring 8 Positioning mechanism part 81 Sphere Contact member)
82: Retainer (holding member) 83: Receiving member 84: Coil spring (spring member)

Claims (5)

A steered shaft that moves axially back and forth, a moving force applying mechanism that is driven by an electric motor and applies the axial moving force to the steered shaft, and a part of the steered shaft is the movable force applying mechanism And a housing for housing the steering wheel, and the steering shaft steers the steered wheels by moving the steering shaft in the axial direction,
The moving force application mechanism includes a cylindrical nut member screwed to a spiral thread groove formed on the outer peripheral surface of the steered shaft via a plurality of balls, and the inner ring of the inner ring and the outer ring is the nut A rolling bearing fixed to a member and arranged such that the outer ring is axially movable within a predetermined range with respect to the housing, and a positioning mechanism for elastically positioning the outer ring at a central position of the predetermined range Have and
The outer ring has a recess formed on the outer peripheral surface thereof,
The positioning mechanism portion includes an abutting member abutting on an inner surface of the recess, and a spring member pressing the abutting member toward the recess.
In the recess, the depth of the inner surface in the radial direction of the outer ring gradually becomes smaller as it is separated in the axial direction from the deepest portion where the contact member comes in contact at the deepest side.
Steering device. The shape of the recess in the axial cross section of the outer ring is a shape in which the curvature of the portion where the contact member abuts when the outer ring is at the end of the predetermined range is larger than the curvature of the deepest portion.
The steering apparatus according to claim 1. The concave portion is formed over the entire circumference of the outer peripheral surface of the outer ring, and the contact member abuts on one place in the circumferential direction.
The steering device according to claim 1. In the positioning mechanism portion, the spring member is accommodated in a hole formed in the housing, and at least a part of the contact member protrudes from the hole toward the outer ring.
The steering apparatus according to any one of claims 1 to 3. The positioning mechanism portion has a holding member for holding the contact member, and a receiving member fixed to the housing, and the spring member is compressed between the holding member and the receiving member. Placed
When the outer ring moves to the end of the predetermined range, the axial movement of the outer ring is restricted by the holding member coming into contact with the receiving member.
The steering apparatus according to any one of claims 1 to 4.

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