Steering device

Abstract

This steering device (1) comprises a housing (10), a motor (6), a steering shaft (42), a nut (80), a bearing (20), a first elastic support member (31), and a second elastic support member (32). The bearing has an inner ring (21), an outer ring (22), a plurality of balls (23), and a holder (25) and has a lubricating agent sealed in the interior thereof. A shield member (24) is mounted on a first side of the plurality of balls in the axial direction. The holder has a base part (25A), a plurality of claw parts (25B), and a plurality of pockets (25C). The base part is a cylindrical body having a circular cross-sectional shape and is disposed on a second side of the plurality of balls in the axial direction. The claw parts protrude from the base part toward the first side in the axial direction. Each pocket is provided between two claw parts adjacent to each other, among the plurality of claw parts, and holds a ball. A minute annular gap (δ2) is formed between the outer peripheral surface of the base part and the inner peripheral surface of the outer ring. The second elastic support member is disposed so as to cover the minute annular gap.

Description

Steering apparatus

[0001] The present disclosure relates to a steering apparatus.

[0002] For example, the steering apparatus disclosed in Patent Document 1 includes a ball screw mechanism and a belt transmission mechanism. The ball screw mechanism has a screw shaft integrally formed with a steering shaft, and a nut screwed onto the screw shaft via a plurality of balls. The nut is rotatably supported via a bearing relative to a housing that accommodates the steering shaft. The belt transmission mechanism has a drive pulley fixed to an output shaft of a motor, a driven pulley fitted onto an outer circumferential surface of the nut, and a belt wound around outer circumferential surfaces of the drive pulley and the driven pulley. Torque of the motor is transmitted to the nut via the belt transmission mechanism.

[0003] The bearing is a sealed bearing and includes a shield member. The shield member is provided at both axial ends of the bearing so as to close a gap between an inner ring and an outer ring.

[0004] Japanese Unexamined Patent Publication No. 2018-070008

[0005] A bearing including a shield member has the following concerns. For example, when shield members are provided at both axial ends of the bearing, there is a risk that the axial length of the bearing will increase.

[0006] A steering device according to one aspect of the present disclosure comprises a housing, a motor, a steering shaft, a nut, a bearing, a first elastic support member, and a second elastic support member. The steering shaft is configured to steer the steering wheels of a vehicle by moving linearly inside the housing. The nut is screwed onto the steering shaft and is configured to rotate in conjunction with the rotation of the motor. The bearing has a lubricant sealed inside. The bearing is provided between the outer circumferential surface of the nut and the inner circumferential surface of the housing and is configured to rotatably support the nut relative to the housing. The first elastic support member is provided in a compressed state between a first portion of the housing and the first axial end face of the bearing. The second elastic support member is provided in a compressed state between a second portion of the housing and the second axial end face of the bearing. The bearing has an inner ring mounted on the outer circumferential surface of the nut, an outer ring radially facing the inner ring, a plurality of balls interposed between the inner ring and the outer ring, and a cage configured to hold the plurality of balls. A shielding member configured to suppress leakage of the lubricant is attached to the first axial side of the plurality of balls. The retainer has a base, a plurality of claws, and a pocket. The base is a cylindrical body having a circular cross-sectional shape and is positioned on the second axial side of the plurality of balls. The claws protrude from the base toward the first axial side and are arranged at equal intervals in the circumferential direction of the base. The pocket is provided between two adjacent claws among the plurality of claws and is configured to hold the ball. An annular minute gap is formed between the outer circumferential surface of the base and the inner circumferential surface of the outer ring, and the second elastic support member is positioned to cover the gap.

[0007] Figure 1 is a cross-sectional view showing a schematic configuration of one embodiment of a steering device. Figure 2 is a cross-sectional view of the assist mechanism of Figure 1. Figure 3 is a cross-sectional view of the bearing and its surroundings in Figure 2, cut along the axial direction. Figure 4 is a perspective view of the cage constituting the bearing of Figure 2.

[0008] A steering device according to one embodiment will be described. As shown in Figure 1, the steering device 1 is, for example, an electric power steering device. The steering device 1 has a steering mechanism 4 and an assist mechanism 5. The steering mechanism 4 steers the steering wheels 3 in response to the driver's operation of the steering wheel 2. The assist mechanism 5 assists the driver's steering operation by providing an assist force to the steering mechanism 4.

[0009] The steering mechanism 4 includes a steering shaft 40 and a steering shaft 42. The steering wheel 2 is connected to the upper end of the steering shaft 40. The lower end of the steering shaft 40 is connected to the steering shaft 42 via a rack and pinion mechanism 41. The rack and pinion mechanism 41 converts the rotational motion of the steering shaft 40, which occurs when the steering wheel 2 is operated, into axial reciprocating linear motion of the steering shaft 42. The axial reciprocating linear motion of the steering shaft 42 is transmitted to tie rods 43 connected to both ends of the steering shaft 42. This changes the steering angle of the steering wheel 3.

[0010] The assist mechanism 5 includes a motor 6 and a power transmission mechanism 7. The power transmission mechanism 7 is housed inside the housing 10 together with the steering shaft 42. The housing 10 has a first housing member 11 and a second housing member 12, which are divided in the axial direction of the steering shaft 42 near the power transmission mechanism 7. The first housing member 11 and the second housing member 12 are connected to each other in the axial direction of the steering shaft 42.

[0011] The motor 6 is attached to the outer wall of the housing 10, specifically the outer wall of the second housing member 12, by bolts 13. The motor 6 has an output shaft 60. The output shaft 60 is parallel to the axis of the steering shaft 42. The output shaft 60 extends into the interior of the housing 10 through a through hole 14 provided in the outer wall of the housing 10. The power transmission mechanism 7 has a ball screw mechanism 8 and a belt drive mechanism 9. The ball screw mechanism 8 is attached to the outer circumference of the steering shaft 42. The belt drive mechanism 9 reduces the rotation of the output shaft 60 of the motor 6 and transmits the reduced rotation of the output shaft 60 to the ball screw mechanism 8.

[0012] As shown in Figure 2, the ball screw mechanism 8 has a nut 80. The nut 80 is a cylindrical body with a circular cross-sectional shape. The nut 80 is screwed onto the outer circumferential surface of the steering shaft 42 via a plurality of balls 82. The outer circumferential surface of the steering shaft 42 is provided with a helical screw groove 44. The inner circumferential surface of the nut 80 is provided with a helical screw groove 81 that is opposite to the screw groove 44 of the steering shaft 42. The helical space enclosed by the screw groove 44 of the steering shaft 42 and the screw groove 81 of the nut 80 functions as a rolling path R on which the balls 82 roll. The nut 80 has a ring channel (not shown) that short-circuits two points in the rolling path R. The balls 82 can circulate indefinitely within the rolling path R via the ring channel of the nut 80.

[0013] The nut 80 is rotatably supported relative to the housing 10 via a bearing 20 provided between the outer circumferential surface of the nut 80 and the inner circumferential surface of the housing 10. The bearing 20 is, for example, a single-row ball bearing. The bearing 20 has an inner ring 21, an outer ring 22, and a plurality of balls 23.

[0014] The inner circumferential surface of the inner ring 21 is fitted onto the outer circumferential surface of the nut 80. The inner ring 21 abuts against the flange portion 83 in the axial direction of the nut 80. The flange portion 83 is a plate-like body with a circular cross-sectional shape and is provided at the first end of the nut 80. The outer ring 22 faces the inner ring 21 radially. The outer circumferential surface of the outer ring 22 abuts against the inner circumferential surface of the housing 10. The outer circumferential surface of the outer ring 22 is slidable against the inner circumferential surface of the housing 10 in the axial direction of the steering shaft 42. The ball 23 is interposed between the inner ring 21 and the outer ring 22. A lubricant is sealed inside the bearing 20. The lubricant is, for example, grease or oil.

[0015] A driven pulley 91 is attached to the outer circumferential surface of the nut 80. The driven pulley 91 is positioned on the opposite side of the flange portion 83 of the bearing 20. The bearing 20 and the driven pulley 91 are adjacent to each other in the axial direction of the nut 80. The driven pulley 91 is fixed to the nut 80 by being screwed into the male threaded portion 84 of the nut 80. The male threaded portion 84 is provided on the outer circumferential surface of the second end of the nut 80. The second end is the end of the nut 80 opposite to the first end. The inner ring 21 is fixed to the nut 80 while sandwiched between the driven pulley 91 and the flange portion 83.

[0016] A first wave washer 31 is interposed between the first end face of the outer ring 22 and the support portion 11a of the first housing member 11. The first wave washer 31 is a washer made by bending a thin, annular metal plate into a corrugated shape. The first end face is the end face of the outer ring 22 opposite to the driven pulley 91 in the axial direction of the steering shaft 42. The support portion 11a is a stepped portion provided by changing the inner diameter of the first housing member 11 and has a circular cross-sectional shape. The first wave washer 31 is slightly compressed in the axial direction of the steering shaft 42. The nut 80 passes through the first wave washer 31 in the axial direction without contacting the first wave washer 31.

[0017] The first end face of the outer ring 22 is also the first axial end face of the bearing 29. The first axial side refers to the side of the steering shaft 42 opposite to the driven pulley 91 relative to the bearing 20, which is the left side in Figure 2. The support portion 11a corresponds to the first part of the housing 10. The first wave washer 31 corresponds to the first elastic support member.

[0018] A second wave washer 32 is interposed between the second end face of the outer ring 22 and the open end 12a of the second housing member 12. The second wave washer 32 is a washer made by bending a thin, annular metal plate into a corrugated shape. The second end face is the end face of the outer ring 22 opposite to the first end face. The open end is the portion of the second housing member 12 that is fitted axially into the opening of the first housing 11 and extends toward the second end face of the outer ring 22. The second wave washer 32 is slightly compressed in the axial direction of the steering shaft 42. The nut 80 passes through the second wave washer 32 axially without contacting it.

[0019] The second end face of the outer ring 22 is also the second axial end face of the bearing 29. The second axial side refers to the side of the steering shaft 42 in the axial direction that is the same side as the driven pulley 91 relative to the bearing 20, which is the right side in Figure 2. The open end 12a of the second housing member 12 corresponds to the second part of the housing 10. The second wave washer 32 corresponds to the second elastic support member.

[0020] When an axial load from the steering shaft 42 is applied to the first wave washer 31 and the second wave washer 32, the first wave washer 31 and the second wave washer 32 deflect in a direction that reduces their height, exhibiting a spring action. The first wave washer 31 and the second wave washer 32 act elastically on the first and second end faces of the outer ring 22 in opposite directions. In other words, the first wave washer 31 and the second wave washer 32 elastically support the outer ring 22 in the axial direction of the steering shaft 42. Furthermore, the first wave washer 31 and the second wave washer 32 indirectly elastically support the nut 80 in the axial direction of the steering shaft 42 via the bearing 20.

[0021] The belt drive mechanism 9 includes a drive pulley 90, a driven pulley 91, and a belt 92. The drive pulley 90 is integrally attached to the output shaft 60 of the motor 6. The belt 92 is endless and is wrapped between the drive pulley 90 and the driven pulley 91. The drive pulley 90 and the driven pulley 91 may be toothed pulleys having teeth on their outer surfaces. Alternatively, the belt 92 may be a toothed belt having teeth on its inner surface. The teeth of the belt 92 mesh with the teeth of the drive pulley 90 and the driven pulley 91.

[0022] Therefore, when the motor 6 is driven, the drive pulley 90 rotates together with the output shaft 60. The rotation of the drive pulley 90 is transmitted to the driven pulley 91 via the belt 92. As a result, the driven pulley 91 and the nut 80 rotate together. When the nut 80 rotates relative to the steering shaft 42, the ball 82 receives friction as a load from the nut 80 and the steering shaft 42 and circulates indefinitely within the rolling path R. The indefinite circulation of the ball 82 exerts an axial force on the steering shaft 42, causing the steering shaft 42 to move axially relative to the nut 80. The axial force acting on the steering shaft 42 is an assist force that helps the driver's steering operation.

[0023] <Configuration of Bearing 20> Next, the configuration of the bearing 20 will be described in detail. As shown in Figure 3, the inner ring 21 is a cylindrical body having a circular cross-sectional shape. The inner ring 21 has a groove 21A, an outer shoulder 21B, and an inner shoulder 21C. The groove 21A extends around the entire circumference of the outer circumferential surface of the inner ring 21. The groove 21A is recessed radially inward of the inner ring 21 and constitutes a track for the rolling of the balls 23. In the axial direction of the inner ring 21, the groove 21A is located between the outer shoulder 21B and the inner shoulder 21C. The outer shoulder 21B is the portion of the inner ring 21 that includes the area on the outer circumferential surface of the inner ring 21 that is axially outward from the groove 21A. Outer means the side of the inner ring 21 opposite to the driven pulley 91 relative to the groove 21A in the axial direction of the inner ring 21. The axially outward side is also the axial first side. The inner shoulder portion 21C is the part of the inner ring 21 that includes the region on the outer circumferential surface of the inner ring 21 that is axially inward of the groove portion 21A. Inward means the side of the inner ring 21 that is the same as the driven pulley 91 relative to the groove portion 21A in the axial direction. The axially inward side is also the axial second side. The outer shoulder portion 21B and the inner shoulder portion 21C are smooth cylindrical surfaces without irregularities.

[0024] The outer ring 22 is a cylindrical body with a circular cross-sectional shape. Like the inner ring 21, the outer ring 22 has a groove 22A, an outer shoulder 22B, and an inner shoulder 22C. The groove 22A extends around the entire circumference of the inner surface of the outer ring 22. The groove 22A is recessed radially outward of the outer ring 22 and forms a track on which the ball 23 rolls. The groove 22A of the outer ring 22 faces radially with the groove 21A of the inner ring 21. In the axial direction of the outer ring 22, the groove 22A is located between the outer shoulder 22B and the inner shoulder 22C. The outer shoulder 22B is the portion of the outer ring 22 that includes the area axially outward of the groove 22A on the inner surface of the outer ring 22. The axially outward side is also the axial first side. The outer shoulder portion 22B of the outer ring 22 faces radially with the outer shoulder portion 21B of the inner ring 21. The inner shoulder portion 22C is the portion of the outer ring 22 that includes the region on the inner circumferential surface of the outer ring 2 that is axially inward from the groove portion 22A. The axially inward side is also the axial second side. The inner shoulder portion 22C of the outer ring 22 faces radially with the inner shoulder portion 21C of the inner ring 21. The outer shoulder portion 22B and the inner shoulder portion 22C are smooth cylindrical surfaces without irregularities. The outer shoulder portion 22B corresponds to the first shoulder portion, and the inner shoulder portion 22C corresponds to the second shoulder portion.

[0025] The bearing 20 includes an inner ring 21, an outer ring 22, and a plurality of balls 23, as well as a shielding member 24 and a cage 25. The shielding member 24 is a member that prevents leakage of lubricant sealed inside the bearing 20 and prevents foreign matter from entering the bearing 20. Foreign matter includes, for example, dust, metal powder, and resin powder. The cage 25 is a member that holds the plurality of balls 23 at intervals in the circumferential direction of the bearing 20. The cage 25 also functions as a shielding member that prevents leakage of lubricant sealed inside the bearing 20 and prevents foreign matter from entering the bearing 20.

[0026] The shield member 24 and the cage 25 are both positioned between the inner ring 21 and the outer ring 22. However, in the axial direction of the bearing 20, the shield member 24 and the cage 25 are positioned on opposite sides of each other. The shield member 24 is positioned, for example, between the outer shoulder portion 21B of the inner ring 21 and the outer shoulder portion 22B of the outer ring 22. That is, the shield member 24 is mounted on the first axial side of the plurality of balls 23. A portion of the cage 25 is positioned, for example, between the inner shoulder portion 21C of the inner ring 21 and the inner shoulder portion 22C of the outer ring 22. That is, the cage 25 has a portion that is positioned on the second axial side of the plurality of balls 23.

[0027] As shown in Figure 3, the shield member 24 is fixed to the outer shoulder portion 22B of the outer ring. The shield member 24 is manufactured, for example, by plastically deforming a thin metal plate. The shield member 24 has a shielding wall 24A, a first opposing wall 24B, and a second opposing wall 24C.

[0028] The shielding wall 24A is provided around the entire circumference of the gap between the outer shoulder portion 21B of the inner ring 21 and the outer shoulder portion 22B of the outer ring 22. The shielding wall 24A is a cylindrical body with a circular cross-sectional shape and extends radially around the bearing 20.

[0029] The first opposing wall 24B is provided at the first end of the shielding wall 24A. The first end is the end of the shielding wall 24A on the inner ring 21 side. The first opposing wall 24B is an annular plate-like body and is provided around the entire circumference of the first end of the shielding wall 24A. The first opposing wall 24B is perpendicular to the shielding wall 24A and extends from the first end of the shielding wall 24A toward the ball 23. A minute gap is formed between the first opposing wall 24B and the outer shoulder portion 21B of the inner ring 21. That is, the shielding member 24 is not in contact with the inner ring 21.

[0030] The second opposing wall 24C is provided at the second end of the shielding wall 24A. The second end is the end of the shielding wall 24A opposite to the first end, that is, the end of the shielding wall 24A on the outer ring 22 side. The second opposing wall 24C is an annular plate-like body and is provided around the entire circumference of the second end of the shielding wall 24A. The second opposing wall 24C is perpendicular to the shielding wall 24A and extends from the second end of the shielding wall 24A toward the ball 23. The second opposing wall 24C faces the first opposing wall 24B in the radial direction of the bearing 20. In the axial direction of the bearing 20, the length of the second opposing wall 24C is longer than the length of the first opposing wall 24B. The second opposing wall 24C is fixed to the outer shoulder 22B of the outer ring 22.

[0031] As shown in Figure 4, the retainer 25 is a so-called crown-shaped retainer and has a circular cross-sectional shape. The retainer 25 is made of resin and has a base portion 25A and a plurality of claw portions 25B. The base portion 25A is a cylindrical body with a circular cross-sectional shape. The plurality of claw portions 25B all have the same shape and protrude axially from the base portion 25A. The plurality of claw portions 25B all protrude in the same direction. The plurality of claw portions 25B are arranged at equal intervals in the circumferential direction of the base portion 25A. In the radial direction of the retainer 25, the thickness of the claw portions 25B is the same as the thickness of the base portion 25A.

[0032] In the retainer 25, a pocket 25C is provided between two adjacent claw portions 25B in the circumferential direction. That is, the multiple pockets 24 are arranged at equal intervals in the circumferential direction of the base portion 25A. The pocket 25C is the part of the retainer 25 that holds the ball 23. The inner surface of the pocket 25C is a concave spherical surface. The diameter of the inner surface of the pocket 25C, i.e., the spherical diameter, is slightly larger than the diameter of the ball 23. As a result, the pocket 25C can hold the ball 23 in a state where it can roll.

[0033] As shown in Figure 3, the axial end face of the cage 25 is a flat surface extending radially from the bearing 20. The axial end face is the end face of the cage 25 opposite to the claw portion 25B. The axial end face of the cage 25 is also the axial end face of the base portion 25A. The base portion 25A is part of the cage 25 and is located on the axial second side of the plurality of balls 23. The claw portion 25B protrudes from the base portion 25 toward the axial first side.

[0034] The axial end face of the retainer 25 is substantially flush with the second end faces of the inner ring 21 and the outer ring 22. Flushness means that there is no step between the second end faces of the inner ring 21 and the outer ring 22 and the axial end face of the retainer 25, and they are flat. For example, the axial end face of the retainer 25 is slightly offset toward the ball 23 with respect to a virtual plane that includes the second end faces of the inner ring 21 and the outer ring 22. That is, on the second axial side, the axial end face of the base 25A is located on the first axial side with respect to the axial end faces of the inner ring 21 and the outer ring 22.

[0035] The radial thickness of the retainer 25 is slightly thinner than the distance between the inner shoulder portion 21C of the inner ring 21 and the inner shoulder portion 22C of the outer ring 22. A first gap δ1 is formed between the inner shoulder portion 21C of the inner ring 21 and the inner circumferential surface of the base portion 25A of the retainer 25. The inner shoulder portion 21C of the inner ring 21 is part of the outer circumferential surface of the inner ring 21. A second gap δ2 is formed between the inner shoulder portion 22C of the outer ring 22 and the outer circumferential surface of the base portion 25A of the retainer 25. The inner shoulder portion 22C of the outer ring 22 is part of the inner circumferential surface of the outer ring 2. The first gap δ1 and the second gap δ2 are annular minute gaps. The term "annular" refers to a loop, i.e., an endless continuous shape.

[0036] The second wave washer 32 is positioned to cover the second gap δ2. The inner diameter of the second wave washer 32 is, for example, larger than the outer diameter of the inner ring 21 and smaller than the inner diameter of the outer ring 22. The outer diameter of the second wave washer 32 is larger than the inner diameter of the outer ring 22. The outer diameter of the second wave washer 32 may also be, for example, the same as the outer diameter of the outer ring 22. As a result, when the steering device 1 is assembled, the portion of the second wave washer 32 between its inner and outer surfaces faces the second gap δ2 in the axial direction. That is, the portion of the second wave washer 32 between its inner and outer surfaces is positioned to cover the second gap δ2.

[0037] <Operation of the Embodiment> Next, the operation of this embodiment will be described. The second wave washer 32 is curved in a gentle wave shape. Therefore, depending on the position of the curved portion of the second wave washer 32, a part of the second wave washer 32 comes into contact with the second end face of the outer ring 22. In this case, the path on the outer ring 22 side that connects the inside and outside of the bearing 20 is blocked by a part of the second wave washer 32. Therefore, when the inner ring 21 rotates together with the nut 80 due to the drive of the motor 6, leakage of the lubricant sealed inside the bearing 20 to the outside of the bearing 20 through the second gap δ2 is suppressed. In addition, the intrusion of foreign matter into the inside of the bearing 20 is suppressed.

[0038] Depending on the position of the curved portion of the second wave washer 32, a third gap δ3 may be formed between the second end face of the outer ring 22 and the second wave washer 32. The third gap δ3 is a very small gap with an axial width of, for example, about 80 μm to 100 μm. In this case, the second gap δ2 and the third gap δ3 are in communication, and there is a risk that a path connecting the inside and outside of the bearing 20 will be formed on the outer ring 22 side. However, both the second gap δ2 and the third gap δ3 are narrow and perpendicular to each other. That is, the second gap δ2 and the third gap δ3 function as a so-called labyrinth structure. For this reason, when the inner ring 21 rotates together with the nut 80 due to the drive of the motor 6, the lubricant sealed inside the bearing 20 has difficulty passing through the second gap δ2 and the third gap δ3. Therefore, leakage of the lubricant sealed inside the bearing 20 to the outside of the bearing 20 through the second gap δ and the third gap δ2 is suppressed. In addition, the intrusion of foreign matter into the inside of the bearing 20 is suppressed.

[0039] When the motor 6 is driven, the inner ring 21 rotates together with the nut 80, causing the balls 23 to roll. The centrifugal force generated by the rotation of the inner ring 21 causes the lubricant sealed inside the bearing 20 to flow from the inner ring 21 toward the outer ring 22. The shield member 24 is positioned between the outer shoulder portion 21B of the inner ring 21 and the outer shoulder portion 22B of the outer ring 22. Therefore, it is sufficient to cover only the second gap δ2 with the second wave washer 32.

[0040] <Effects of the Embodiment> This embodiment provides the following effects: (1) A shield member 24 is attached to the first axial side of the plurality of balls 23 to suppress leakage of lubricant sealed inside the bearing 20. The base 25A of the cage 25 is positioned on the second axial side of the plurality of balls 23, and the plurality of claws 25B protrude from the base 25A toward the first axial side. An annular second gap δ2 is formed between the outer circumferential surface of the base 25A and the inner circumferential surface of the outer ring 22. The second gap δ2 is an annular minute gap. The second wave washer 32 is positioned to cover the second gap δ2.

[0041] According to this configuration, the axial length of the bearing 20 can be shortened compared to the case where shield members 24 are provided on both the first axial side and the second axial side of the plurality of balls 23. When the shield member 24 is provided not only on the first axial side of the plurality of balls 23 but also on the second axial side of the plurality of balls 23, the shield member 24 needs to be arranged on the second axial side of the base portion 25A so as not to interfere with the base portion 25A. For this reason, the axial length of the bearing 20 becomes longer.

[0042] According to the present embodiment, the cage 25 also functions as a shield member that suppresses leakage of the lubricant sealed inside the bearing 20. Since it is not necessary to arrange the shield member 24 on the second axial side of the plurality of balls 23, the axial length of the bearing 20 can be shortened. Further, the product cost can be reduced by the amount that the shield member 24 is not arranged on the second axial side of the plurality of balls 23.

[0043] (2) On the second axial side of the bearing 20, the axial end surface of the base portion 25A is located on the first axial side with respect to the axial end surfaces of the inner ring 21 and the outer ring 22. Therefore, interference between the base portion 25A and the second wave washer 32 is suppressed.

[0044] (3) The first wave washer 31 and the second wave washer 32 elastically support the outer ring 22 in the axial direction. The configuration of the steering device 10 can be simplified compared to a case where both axial ends of the outer ring 22 are elastically supported by two sets of support mechanisms including a plurality of components.

[0045] (4) The outer shoulder portion 22B and the inner shoulder portion 22C of the outer ring 22 are smooth cylindrical surfaces without irregularities. Since it is not necessary to perform processing such as forming irregularities on the outer shoulder portion 22B and the inner shoulder portion 22C, the processing cost of the outer ring 22 can be reduced. Incidentally, some sealed bearings include a groove for mounting a shield member on at least one of the outer shoulder portion 22B and the inner shoulder portion 22C of the outer ring. In this case, the cost for processing the groove on the inner peripheral surface of the outer ring is required.

[0046] In this specification, "at least one of A and B" means "only A, only B, or both A and B". <Other Embodiments> The present embodiment may be modified and implemented as follows.

[0047] - The motor 6 does not necessarily need to be provided outside the housing 10, and may be provided inside the housing 40. - The bearing 20 may be a double-row ball bearing.

[0048] - On the second axial side, the axial end surface of the base portion 25A may be aligned with the axial end surfaces of the inner ring 21 and the outer ring 25. It is sufficient that the axial end surface of the cage 25 is not located on the opposite side of the balls 23 with respect to an imaginary plane including the second end surfaces of the inner ring 21 and the outer ring 22.

[0049] - The first wave washer 31 and the second wave washer 32 may be replaced with, for example, disc springs. - The arrangement of the shield member 24 and the cage 25 may be reversed.

[0050] - The steering apparatus 1 may be a steer-by-wire steering apparatus. In a steer-by-wire steering apparatus, power transmission between a steering wheel 2 and steered wheels 3 is disconnected. In this case, the motor 6 functions as a steering motor that generates a steering force, which is a force for steering the steered wheels 3.

Claims

1. A steering device comprising: a housing; a motor; a steering shaft configured to steer the steering wheels of a vehicle by linear motion inside the housing; a nut screwed onto the steering shaft and configured to rotate in conjunction with the rotation of the motor; a bearing having a lubricant sealed inside, provided between the outer circumferential surface of the nut and the inner circumferential surface of the housing, and configured to rotatably support the nut relative to the housing; a first elastic support member provided in a compressed state between a first portion of the housing and the first axial end face of the bearing; and a second elastic support member provided in a compressed state between a second portion of the housing and the second axial end face of the bearing, wherein the bearing has an inner ring mounted on the outer circumferential surface of the nut, an outer ring facing radially with respect to the inner ring, a plurality of balls interposed between the inner ring and the outer ring, and a retainer configured to hold the plurality of balls, wherein a shielding member configured to suppress leakage of the lubricant is mounted on the first axial side of the plurality of balls, and the retainer is A steering device comprising a cylindrical body having a circular cross-sectional shape, a base portion positioned on the second axial side of a plurality of balls, a plurality of claw portions projecting from the base portion toward the first axial side and arranged at equal intervals in the circumferential direction of the base portion, and a pocket provided between two adjacent claw portions and configured to hold the balls, wherein an annular minute gap is formed between the outer circumferential surface of the base portion and the inner circumferential surface of the outer ring, and the second elastic support member is positioned to cover the gap.

2. The steering device according to claim 1, wherein, on the second axial side of the bearing, the axial end face of the base is located on the first axial side with respect to the axial end faces of the inner ring and the outer ring.

3. The steering device according to claim 1 or claim 2, wherein the first elastic support member and the second elastic support member are wave washers.

4. The steering device according to claim 1 or 2, wherein the outer ring has a groove extending over the entire circumference of the inner surface of the outer ring and forming a track on which the ball rolls; a first shoulder portion including a region of the inner surface of the outer ring that is on the first axial side of the groove portion; and a second shoulder portion including a region of the inner surface of the outer ring that is on the second axial side of the groove portion, and the first shoulder portion and the second shoulder portion are smooth cylindrical surfaces without irregularities.

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