JP6379412B2 - Power steering device - Google Patents

Description

  The present invention relates to a power steering apparatus.

  As this type of technique, a technique described in Patent Document 1 below is disclosed. Patent Document 1 discloses that the driving force of an electric motor is transmitted to a ball nut via a driving pulley, a belt, and a driven pulley, and used as the axial driving force of the rack shaft. In order to prevent foreign matter from entering between the driving pulley and the belt or between the driven pulley and the belt, a guide plate is provided inside the belt and between the driving pulley and the driven pulley.

JP 2013-159294 A

In the technique described in Patent Document 1, since a guide plate is provided between the drive pulley and the driven pulley, it is not possible to prevent the foreign matter that has been detached on the driven pulley side from falling on the rack shaft. If foreign matter adheres to the rack shaft, the foreign matter may be caught between the ball nut and the rack shaft, and the resistance of the ball screw may increase.
The present invention has been focused on the above problems, and an object of the present invention is to provide a power steering device capable of suppressing foreign matter from adhering to the steered shaft (rack shaft).

In order to achieve the above object, in the power steering device according to an embodiment of the present invention, the axis of the steered shaft on the side surface of the housing facing the output pulley in the axial direction is radially inward from the outer edge of the output pulley. while being arranged in succession in at least a portion of the vertical way improved side from not disposed vertically lower than the axis of the steering shaft, a projecting portion formed to the nut overlap in the axial direction Provided.

Therefore, it is possible to suppress foreign matter from adhering to the steered shaft and to reduce the weight of the device by suppressing the increase in mass .

2 is a front view of a power steering device of Reference Example 1. FIG. 3 is a cross-sectional view of a power steering device of Reference Example 1. FIG. 5 is an enlarged cross-sectional view of the vicinity of an assist mechanism of a power steering device of Reference Example 1. FIG. 6 is a schematic diagram showing an installation range of a protruding portion of Reference Example 1. FIG. 6 is a schematic diagram showing an installation range of a protruding portion of Reference Example 2. FIG. 10 is a schematic diagram showing an installation range of a protruding portion of Reference Example 3. FIG. FIG. 6 is a schematic diagram showing an installation range of protrusions in Reference Example 4 . 10 is an enlarged cross-sectional view of the vicinity of an assist mechanism of a power steering device of Reference Example 5. FIG. 10 is an enlarged cross-sectional view of the vicinity of an assist mechanism of a power steering device of Reference Example 6. FIG.

[ Reference Example 1 ]
A power steering device 1 of Reference Example 1 will be described. The power steering device 1 of Reference Example 1 applies assist force to the driver's steering force by transmitting the driving force of the electric motor 40 to the steered shaft 10 via the ball screw mechanism 26.
[Configuration of power steering system]
FIG. 1 is a front view of the power steering apparatus 1. FIG. FIG. 2 is a cross-sectional view of the power steering device 1 cut along the axis of the steered shaft 10.
The power steering apparatus 1 includes a steering mechanism 2 that transmits rotation of a steering wheel steered by a driver to a steered shaft 10 that steers steered wheels, and an assist mechanism 3 that applies assist force to the steered shaft 10. Have.
Each component of the power steering device 1 is accommodated in a housing 30 including a first housing 31, a second housing 32, and a motor housing 33.
The steering mechanism 2 includes a steering input shaft 80 connected to the steering wheel, and a pinion 81 that rotates integrally with the steering input shaft 80. The pinion 81 meshes with a rack formed on the outer periphery of the steered shaft 10.

The assist mechanism 3 includes an electric motor 40 and a ball screw mechanism 26 that transmits the output of the electric motor 40 to the steered shaft 10. The output of the electric motor 40 is controlled by a motor controller in accordance with the steering torque and the steering amount input to the steering wheel by the driver.
The ball screw mechanism 26 includes a nut 20 and an output pulley 27. The appearance of the output pulley 27 is a cylindrical member, and is fixed to the nut 20 so as to be integrally rotatable. A cylindrical input pulley 35 is fixed to the drive shaft 40a of the electric motor 40 so as to rotate integrally. The rotation axis of the nut 20 is a first reference axis L1, and the rotation axis of the input pulley 35 is a second reference axis L2. The second reference axis L2 is arranged so as to be offset in the radial direction with respect to the first reference axis L1. Note that the output pulley 27 fixed integrally with the nut 20 also has the first reference axis L1 as the rotation axis.

A belt 28 is wound between the input pulley 35 and the output pulley 27. The belt 28 is made of resin. The driving force of the electric motor 40 is transmitted to the nut 20 via the input pulley 35, the belt 28, and the output pulley 27. The outer diameter of the input pulley 35 is smaller than the outer diameter of the output pulley 27. The input pulley 35, the output pulley 27, and the belt 28 constitute a speed reducer.
The nut 20 is formed in a cylindrical shape so as to surround the steered shaft 10, and is provided to be rotatable with respect to the steered shaft 10. A groove is spirally formed on the inner periphery of the nut 20, and this groove forms a nut-side ball screw groove 21. A spiral groove is formed on the outer periphery of the turning shaft 10 at a position away from the portion where the rack is formed in the axial direction, and this groove constitutes the turning shaft side ball screw groove 11. .
In a state where the nut 20 is inserted into the steered shaft 10, a ball circulation groove 12 is formed by the nut-side ball screw groove 21 and the steered shaft-side ball screw groove 11. The ball circulation groove 12 is filled with a plurality of balls 22 made of metal. When the nut 20 rotates, the ball 22 moves in the ball circulation groove 12 so that the steered shaft 10 moves in the longitudinal direction with respect to the nut 20.

[Configuration of nut]
FIG. 3 is an enlarged cross-sectional view of the vicinity of the assist mechanism 3 of the power steering device 1.
The nut 20 is rotatably supported on the first housing 31 by a bearing 24. The bearing 24 has an outer race 24a and an inner race 24b. A ball 24c is provided between the outer race 24a and the inner race 24b. The inner race 24b is formed integrally with the nut 20 on one axial end side (steering mechanism 2 side) of the nut 20.
The other end side in the axial direction of the nut 20 from the inner race 24b constitutes a main body portion 20a. A connection hole communicating with the end of the ball circulation groove 12 is provided on the outer periphery of the main body portion 20a, and the ball tube 23 is inserted into the connection hole. The ball tube 23 connects both ends of the ball circulation groove 12, and the ball 22 can be circulated through the ball circulation groove 12 and the ball tube 23.

[Configuration of output pulley]
The output pulley 27 is formed in a bottomed cup shape. A through hole 27 a is formed at the bottom of the output pulley 27. The steered shaft 10 passes through the through hole 27a. The output pulley 27 is attached to the nut 20 with the opening facing the bearing 24 side. A part of the nut 20 is inserted on the inner peripheral side of the output pulley 27.
A recess 27 b is formed on the side surface of the bottom of the output pulley 27 opposite to the bearing 24. The recess 27b is provided on the outer peripheral side of the through hole 27a. The recess 27b is formed in a concave shape with respect to the outer peripheral side surface (outer peripheral surface 27c). The output pulley 27 is fixed to the axial end surface of the nut 20 by a screw 41 in the recess 27b.

(Structure of protrusion)
A projecting portion 32a is formed on a side surface of the housing 30 (second housing 32) on the portion of the output pulley 27 that faces the concave portion 27b. The protruding portion 32a protrudes toward the recessed portion 27b of the output pulley 27. The protruding portion 32a is formed such that the protruding portion 32a and the outer peripheral surface 27c of the output pulley 27 overlap in the first reference axis L1 direction. The protrusion 32a is formed so that a gap is formed between the protrusion 32a and the screw 41 in the first reference axis L1 direction. This gap is formed so as to be shorter than the length of the male screw portion of the screw 41.
FIG. 4 is a schematic diagram showing the installation range of the protrusion 32a. FIG. 4 shows the arrangement of each member when the power steering device 1 is mounted on a vehicle. As shown in FIG. 4, the protrusion 32a is provided on the upper side of the steered shaft 10 in the vertical direction. The protruding portion 32a is provided on the radially inner side of the outer edge of the output pulley 27. More specifically, the protruding portion 32a is provided on the radially inner side with respect to the outer peripheral surface 27c of the output pulley 27. Both ends of the projecting portion 32a are positioned above the upper end in the vertical direction of the steered shaft 10.

[Action]
Since the belt 28 is made of resin, the belt 28 is worn on the contact surfaces of the input pulley 35 and the output pulley 27, and wear powder is generated. If the wear powder scatters on the steered shaft side ball screw groove 11, the wear powder may enter between the ball circulation groove 12 and the ball 22 of the ball screw mechanism 26, and the resistance of the ball screw mechanism 26 may increase. is there. In the worst case, there is a possibility that the ball screw mechanism 26 is locked and the steering becomes impossible.
The wear powder falls from the input pulley 35 disposed on the upper side in the vertical direction with respect to the steered shaft 10 to the steered shaft 10 side. Although the upper side in the vertical direction of the output pulley 27 is not in contact with the belt 28, the abrasion powder generated at the contact portion between the output pulley 27 and the belt 28 moves to the upper side in the vertical direction of the steered shaft 10 as the output pulley 27 rotates. However, it may fall from the upper side in the vertical direction to the steered shaft 10 side.
Therefore, in Reference Example 1 , the protrusion 32a is provided on the housing 30 (second housing 32) facing the opposite end of the bearing 24 of the output pulley 27 in the first reference axis L1 direction. The protruding portion 32a is provided on the radially inner side of the outer edge of the output pulley 27.
Thereby, the clearance in the first reference axis L1 direction between the output pulley 27 and the second housing 32 can be covered by the protruding portion 32a. Therefore, not only the wear powder generated on the contact surface between the input pulley 35 and the belt 28 but also the wear powder generated on the contact surface between the output pulley 27 and the belt 28 is directly scattered on the steered shaft side ball screw groove 11. Can be suppressed.
In Reference Example 1 , the protruding portion 32a is formed so as to overlap the outer peripheral surface 27c of the output pulley 27 in the direction of the first reference axis L1.
As a result, a labyrinth structure can be formed between the output pulley 27 and the second housing 32, and wear powder can be prevented from entering the steered shaft side ball screw groove 11.

〔effect〕
(1) and the turning shaft 10 to steer the steered wheels in accordance with the rotation of the steering wheel, provided on the rolling outer periphery of the steering shaft 10, a steering shaft side ball screw groove 11 having a spiral groove shape, rolling A nut 20 that is annularly provided so as to surround the rudder shaft 10 and a spiral groove shape that is provided on the inner peripheral side of the nut 20 and that has a ball circulation groove 12 together with the ball screw groove 11 on the steered shaft side. The nut-side ball screw groove 21 to be configured and a plurality of balls 22 provided in the ball circulation groove 12, and a plurality of balls 22 pass through the ball circulation groove 12 as the nut 20 rotates with respect to the steered shaft 10. The ball screw mechanism 26 moves the steered shaft 10 in the longitudinal direction of the steered shaft 10 with respect to the nut 20, and is formed in a cylindrical shape so as to surround the steered shaft 10, and is integrated with the nut 20 Output pulley 27 and the rotation axis of the nut 20 as the first reference axis L1, the second base that becomes the rotation axis The quasi-axis line L2 is arranged so as to be offset in the radial direction with respect to the first reference axis line L1, and is provided so as to straddle the input pulley 35 formed in a cylindrical shape, the output pulley 27, and the input pulley 35. A belt 28 that transmits the rotation of the output pulley 27, an electric motor 40 that rotationally drives the input pulley 35, a housing 30 that houses the output pulley 27, the input pulley 35, and the belt 28, and between the housing 30 and the nut 20 The bearing 24 is offset from the output pulley 27 in the first reference axis L1 direction , and rotatably supports the nut 20 with respect to the housing 30, and the radial direction of the first reference axis L1 is the radial direction. Then, in the portion of the housing 30 that houses the output pulley 27, on one side of a pair of inner wall surfaces that face each other in the first reference axis L1 direction, both ends of the output pulley 27 in the first reference axis L1 direction Bearing 24 is provided on the opposite side to the opposite end of the output pulley 27, is radially inward of the outer edge of the output pulley 27, and is vertically above the first reference axis L1, and the output pulley in the first reference axis L1 direction. 27 or a protrusion 32a formed so as to overlap with the nut 20.
Therefore, not only the wear powder generated on the contact surface between the input pulley 35 and the belt 28 but also the wear powder generated on the contact surface between the output pulley 27 and the belt 28 is directly scattered on the steered shaft side ball screw groove 11. Can be suppressed. Further, a labyrinth structure can be formed between the output pulley 27 and the second housing 32, and intrusion of wear powder into the steered shaft side ball screw groove 11 can be suppressed.

[ Reference Example 2 ]
The reference example 2 is different from the reference example 1 in the installation range of the protrusion 32a. About the same structure as the reference example 1 , the same code | symbol is attached | subjected and description is abbreviate | omitted.
(Structure of protrusion)
FIG. 5 is a schematic diagram showing the installation range of the protrusion 32a. FIG. 5 shows the arrangement of each member when the power steering device 1 is mounted on a vehicle.
As shown in FIG. 5, the projecting portion 32a is provided vertically above the steered shaft 10. The protruding portion 32a is provided on the radially inner side of the outer edge of the output pulley 27. More specifically, the protruding portion 32a is provided on the radially inner side with respect to the outer peripheral surface 27c of the output pulley 27. Both end portions of the projecting portion 32a extend to the lower side in the vertical direction than the upper end in the vertical direction of the steered shaft 10, but are positioned above the first reference axis L1 in the vertical direction.
[Action]
Compared to the protruding portion 32a of the reference example 1, the protruding portion 32a of the reference example 2 can cover a wider range of the steered shaft 10. Therefore, it is possible to suppress the abrasion powder from directly scattering onto the steered shaft side ball screw groove 11.
〔effect〕
(2) The protruding portion 32a is formed so as to extend to the lower side in the vertical direction than the upper end portion in the vertical direction of the steered shaft 10.
Therefore, it is possible to suppress the abrasion powder from directly scattering onto the steered shaft side ball screw groove 11.

[ Reference Example 3 ]
In the reference example 3 , the installation range of the protruding portion 32a is different from that of the reference example 1 . About the same structure as the reference example 1 , the same code | symbol is attached | subjected and description is abbreviate | omitted.
(Structure of protrusion)
FIG. 6 is a schematic diagram showing an installation range of the protrusion 32a. FIG. 6 shows the arrangement of each member when the power steering device 1 is mounted on a vehicle.
As shown in FIG. 6, the protrusion 32a is provided vertically above the steered shaft 10. The protruding portion 32a is provided on the radially inner side of the outer edge of the output pulley 27. More specifically, the protruding portion 32a is provided on the radially inner side with respect to the outer peripheral surface 27c of the output pulley 27. Both ends of the projecting portion 32a are positioned below the first reference axis L1 in the vertical direction, but are formed so that the both ends are not connected to each other.
[Action]
Compared with the protrusion 32a of the reference example 1, the protrusion 32a of the reference example 3 can cover a wider range of the steered shaft 10. Therefore, it is possible to suppress the abrasion powder from directly scattering onto the steered shaft side ball screw groove 11.
〔effect〕
(3) The protruding portion 32a is formed so as to extend to the lower side in the vertical direction than the first reference axis L1.
Therefore, it is possible to suppress the abrasion powder from directly scattering onto the steered shaft side ball screw groove 11.

[ Reference Example 4 ]
The reference example 4 is different from the reference example 1 in the installation range of the protrusion 32a. About the same structure as the reference example 1 , the same code | symbol is attached | subjected and description is abbreviate | omitted.
(Structure of protrusion)
FIG. 7 is a schematic diagram showing the installation range of the protrusion 32a. FIG. 7 shows the arrangement of each member when the power steering device 1 is mounted on a vehicle.
As shown in FIG. 7, the protrusion 32a is provided on the radially inner side of the outer edge of the output pulley 27. More specifically, the protruding portion 32a is provided on the radially inner side with respect to the outer peripheral surface 27c of the output pulley 27. The protrusion 32a is formed so as to surround the entire circumference of the steered shaft 10.
[Action]
Compared with the protrusion 32a of the reference example 1, the protrusion 32a of the reference example 4 can cover a wider range of the steered shaft 10. Therefore, it is possible to suppress the abrasion powder from directly scattering onto the steered shaft side ball screw groove 11.
The protrusion 32a also covers the lower side of the steered shaft 10 in the vertical direction. Therefore, even when the wear powder accumulated in the lower portion of the housing 30 is wound up, it is possible to suppress the wear powder from directly scattering onto the steered shaft side ball screw groove 11.
Further, the protruding portion 32a is a side surface of the housing 30 (second housing 32), and a protruding portion 32a is formed at a portion facing the recessed portion 27b of the output pulley 27. Furthermore, a screw 41 is provided in the recess 27b. The protrusion 32a is formed such that the gap between the protrusion 32a and the screw 41 is shorter than the length of the male screw portion of the screw 41. Therefore, even when the screw 41 is loosened, the screw 41 and the protruding portion 32a come into contact with each other, so that loosening of the screw 41 is suppressed after contact. Therefore, it is possible to suppress the output pulley 27 from dropping from the nut 20.
〔effect〕
(4) The protrusion 32a is formed so as to surround the entire circumference of the steered shaft 10.
Therefore, it is possible to suppress the abrasion powder from directly scattering onto the steered shaft side ball screw groove 11. Further, even when the wear powder accumulated in the lower part of the housing 30 is wound up, it is possible to suppress the wear powder from directly scattering onto the steered shaft side ball screw groove 11.
(5) The output pulley 27 is fixed by the screw 41 at the end of the nut 20 in the first reference axis L1 direction opposite to the protruding portion 32a, and the protruding portion 32a is connected to the screw 41 and the first reference axis. Opposite in the L1 direction and provided so that the gap in the first reference axis L1 direction with the screw 41 is shorter than the length of the male screw portion of the screw 41.
Therefore, it is possible to prevent the output pulley 27 from dropping from the nut 20.

[ Reference Example 5 ]
In Reference Example 1 , the protruding portion 32a is provided in the housing 30 (second housing 32), but in Reference Example 5 , the protruding portion 27d is provided in the output pulley 27. About the same structure as the reference example 1 , the same code | symbol is attached | subjected and description is abbreviate | omitted.
[Structure of housing]
A recess 32b is formed in a side surface of the second housing 32 that faces the output pulley 27 in the first reference axis L1 direction. The inner diameter of the recess 32b is formed larger than the outer diameter of the protruding portion 27d of the output pulley 27.
(Structure of protrusion)
Projections 27d are formed at opposite ends of the bearing 24 in both ends of the output pulley 27 in the first reference axis L1 direction. The protrusion 27d protrudes toward the recess 32b of the second housing 32. The protrusion 27d is provided on the outer peripheral side of the through hole 27a. The protruding portion 27d is formed in a convex shape with respect to the outer peripheral side surface (outer peripheral surface 27c).
The protrusion 27d is formed so that the protrusion 27d and the recess 32b of the second housing 32 overlap in the first reference axis L1 direction. The protrusion 27d is formed so as to surround the entire circumference of the steered shaft 10. A screw insertion hole 27d1 is formed in the protruding portion 27d at a position where the screw 41 is provided.

[Action]
In Reference Example 5 , in the direction of the first reference axis L1, protrusions 27d are provided at the ends opposite to the bearings 24 of the both ends of the output pulley 27. The protrusion 27d is disposed on the inner peripheral side of the outer edge of the output pulley 27.
Thereby, the gap in the first reference axis L1 direction between the output pulley 27 and the second housing 32 can be covered by the protruding portion 27d. Therefore, not only the wear powder generated on the contact surface between the input pulley 35 and the belt 28 but also the wear powder generated on the contact surface between the output pulley 27 and the belt 28 is directly scattered on the steered shaft side ball screw groove 11. Can be suppressed.
In Reference Example 5 , the recess 32b is formed on the surface of the second housing 32 that faces the output pulley 27. The protrusion 27d enters the recess 32b, and the protrusion 27d and the recess 32b are formed to overlap in the first reference axis L1 direction.
As a result, a labyrinth structure can be formed between the output pulley 27 and the second housing 32, and wear powder can be prevented from entering the steered shaft side ball screw groove 11.

〔effect〕
(6) A steered shaft 10 that steers the steered wheels as the steering wheel rotates, a steered shaft-side ball screw groove 11 that is provided on the outer peripheral side of the steered shaft 10 and has a spiral groove shape, A nut 20 that is annularly provided so as to surround the rudder shaft 10 and a spiral groove shape that is provided on the inner peripheral side of the nut 20 and that has a ball circulation groove 12 together with the ball screw groove 11 on the steered shaft side. The nut-side ball screw groove 21 to be configured and a plurality of balls 22 provided in the ball circulation groove 12, and a plurality of balls 22 pass through the ball circulation groove 12 as the nut 20 rotates with respect to the steered shaft 10. The ball screw mechanism 26 moves the steered shaft 10 in the longitudinal direction of the steered shaft 10 with respect to the nut 20, and is formed in a cylindrical shape so as to surround the steered shaft 10, and is integrated with the nut 20 Output pulley 27 and the rotation axis of the nut 20 as the first reference axis L1, the second base that becomes the rotation axis The quasi-axis line L2 is arranged so as to be offset in the radial direction with respect to the first reference axis line L1, and is provided so as to straddle the input pulley 35 formed in a cylindrical shape, the output pulley 27, and the input pulley 35. A belt 28 that transmits the rotation of the output pulley 27, an electric motor 40 that rotationally drives the input pulley 35, a housing 30 that houses the output pulley 27, the input pulley 35, and the belt 28, and between the housing 30 and the nut 20 The first reference axis L1 is offset from the output pulley 27, the bearing 24 rotatably supports the nut 20 with respect to the housing 30, and the radial direction of the first reference axis L1 is the radial direction. When the output pulley 27 is provided at the opposite end of the bearing 24 in both ends of the first reference axis L1 direction, and is disposed radially inward from the outer edge of the output pulley 27 and surrounds the entire circumference of the steered shaft 10 And in the direction of the first reference axis L1 Provided, a protrusion 27d formed so as to protrude from the output pulley 27.
Therefore, not only the wear powder generated on the contact surface between the input pulley 35 and the belt 28 but also the wear powder generated on the contact surface between the output pulley 27 and the belt 28 is directly scattered on the steered shaft side ball screw groove 11. Can be suppressed.
(7) A recess 32b is formed in the housing 30 on the side facing the protruding portion 27d and formed so that the protruding portion 27d enters in the first reference axis L1 direction.
Therefore, a labyrinth structure can be formed between the output pulley 27 and the second housing 32, and intrusion of wear powder into the steered shaft side ball screw groove 11 can be suppressed.

[ Reference Example 6 ]
In Reference Example 1 , the protruding portion 32a is provided in the housing 30 (second housing 32). In Reference Example 6 , the nut 20 is provided with the protruding portion 20b. About the same structure as the reference example 1 , the same code | symbol is attached | subjected and description is abbreviate | omitted.
[Structure of housing]
A recess 32b is formed in a side surface of the second housing 32 that faces the output pulley 27 in the first reference axis L1 direction. The inner diameter of the recess 32b is formed larger than the outer diameter of the protrusion 20b of the nut 20.
(Structure of protrusion)
Projections 20b are formed at opposite ends of the bearing 24 at both ends of the nut 20 in the first reference axis L1 direction. The protruding portion 20b passes through the through hole 27a of the output pulley 27 and protrudes toward the concave portion 32b of the second housing 32.
The protrusion 20b is formed so that the protrusion 20b and the recess 32b of the second housing 32 overlap in the first reference axis L1 direction. The protruding portion 20b is formed so as to surround the entire circumference of the steered shaft 10.

[Action]
In Reference Example 6 , the protruding portion 20b is provided at the end of the nut 20 opposite to the bearing 24 in the direction of the first reference axis L1. The protruding portion 20b passes through the through hole 27a of the output pulley 27 and protrudes toward the concave portion 32b of the second housing 32. That is, the protruding portion 20b is disposed on the inner peripheral side with respect to the outer edge of the output pulley 27.
Thereby, the gap in the first reference axis L1 direction between the output pulley 27 and the second housing 32 can be covered by the protruding portion 27d. Therefore, not only the wear powder generated on the contact surface between the input pulley 35 and the belt 28 but also the wear powder generated on the contact surface between the output pulley 27 and the belt 28 is directly scattered on the steered shaft side ball screw groove 11. Can be suppressed.
In Reference Example 6 , the recess 32b is formed on the surface of the second housing 32 that faces the output pulley 27. The protrusion 20b enters the recess 32b, and the protrusion 20b and the recess 32b are formed so as to overlap in the first reference axis L1 direction.
As a result, a labyrinth structure can be formed between the output pulley 27 and the second housing 32, and wear powder can be prevented from entering the steered shaft side ball screw groove 11.

〔effect〕
(8) A steered shaft 10 that steers the steered wheels as the steering wheel rotates, a steered shaft-side ball screw groove 11 that is provided on the outer peripheral side of the steered shaft 10 and has a spiral groove shape, A nut 20 that is annularly provided so as to surround the rudder shaft 10 and a spiral groove shape that is provided on the inner peripheral side of the nut 20 and that has a ball circulation groove 12 together with the ball screw groove 11 on the steered shaft side. The nut-side ball screw groove 21 to be configured and a plurality of balls 22 provided in the ball circulation groove 12, and a plurality of balls 22 pass through the ball circulation groove 12 as the nut 20 rotates with respect to the steered shaft 10. The ball screw mechanism 26 moves the steered shaft 10 in the longitudinal direction of the steered shaft 10 with respect to the nut 20, and is formed in a cylindrical shape so as to surround the steered shaft 10, and is integrated with the nut 20 Output pulley 27 and the rotation axis of the nut 20 as the first reference axis L1, the second base that becomes the rotation axis The quasi-axis line L2 is arranged so as to be offset in the radial direction with respect to the first reference axis line L1, and is provided so as to straddle the input pulley 35 formed in a cylindrical shape, the output pulley 27, and the input pulley 35. A belt 28 that transmits the rotation of the output pulley 27, an electric motor 40 that rotationally drives the input pulley 35, a housing 30 that houses the output pulley 27, the input pulley 35, and the belt 28, and between the housing 30 and the nut 20 A bearing 24 that is offset from the output pulley 27 in the first reference axis L1 and rotatably supports the nut 20 relative to the housing 30;
When the radial direction of the first reference axis L1 is the radial direction, the nut 20 is provided at the end on the output pulley 27 side with respect to the bearing 24 in the first reference axis L1 direction out of both ends of the first reference axis L1 direction, A projecting portion 20b that is disposed radially inward from the outer edge of the output pulley 27, surrounds the entire circumference of the steered shaft 10, and is formed to project from the output pulley 27 in the first reference axis L1 direction; Was provided.
Therefore, not only the wear powder generated on the contact surface between the input pulley 35 and the belt 28 but also the wear powder generated on the contact surface between the output pulley 27 and the belt 28 is directly scattered on the steered shaft side ball screw groove 11. Can be suppressed.
(9) A recess 32b is formed in the housing 30 on the side facing the protruding portion 27d and formed so that the protruding portion 20b enters in the direction of the first reference axis L1.
Therefore, a labyrinth structure can be formed between the output pulley 27 and the second housing 32, and intrusion of wear powder into the steered shaft side ball screw groove 11 can be suppressed.

[ Example ]
As described above , in Reference Example 1 to Reference Example 6 , the gap in the first reference axis L1 direction between the second housing 32 and the output pulley 27 has a labyrinth structure, but each protruding portion covers the outer periphery of the steered shaft 10. The labyrinth structure does not have to be provided.
In Reference Examples 1 to 4 , the protrusion 32a provided on the second housing 32 is provided so as to overlap the output pulley 27 in the axial direction. The protruding portion 32a may be provided so as to overlap the nut 20 in the axial direction.

10 Steering shaft
11 Steering shaft side ball screw groove
12 Ball circulation groove
20 nuts
20b Protrusion
21 Nut side ball screw groove
22 balls
23 Ball tube (sealing material)
24 Bearing
26 Ball screw mechanism
27 Output pulley
27d Protrusion
28 belts
30 Housing
32a Protrusion
32b recess
35 Input pulley
40 Electric motor
41 screw

Claims (1)

A steered shaft that steers steered wheels as the steering wheel rotates,
A steered shaft side ball screw groove provided on the outer peripheral side of the steered shaft and having a spiral groove shape;
A nut provided in an annular shape so as to surround the steered shaft;
A nut-side ball screw groove that is provided on the inner peripheral side of the nut, has a spiral groove shape, and forms a ball circulation groove together with the steered shaft-side ball screw groove;
A plurality of balls provided in the ball circulation groove;
The ball is configured to move in the ball circulation groove with the rotation of the nut relative to the steered shaft, and move the steered shaft in the longitudinal direction of the steered shaft with respect to the nut. A screw mechanism;
An output pulley that is formed in a cylindrical shape so as to surround the steered shaft, and rotates integrally with the nut;
When the rotation axis of the nut is the first reference axis, the second reference axis serving as the rotation axis is arranged so as to be offset in the radial direction with respect to the first reference axis, and an input pulley formed in a cylindrical shape,
A belt provided to straddle the output pulley and the input pulley, and transmitting the rotation of the input pulley to the output pulley;
An electric motor for rotationally driving the input pulley;
A housing that houses the output pulley, the input pulley, and the belt;
A bearing which is provided between the housing and the nut and is offset from the output pulley in the first reference axis direction, and rotatably supports the nut with respect to the housing;
When the radial direction of the first reference axis is the radial direction, one side of the pair of inner wall surfaces facing each other in the first reference axis direction in the portion of the housing that houses the output pulley,
Of the both ends of the first pulley in the first reference axial direction of the output pulley, provided on the side facing the opposite end of the bearing, the inner side in the radial direction from the outer edge of the output pulley, more than the first reference axis While arranged continuously at least partly on the upper side in the vertical direction , it is not arranged on the lower side in the vertical direction than the first reference axis, and is formed so as to overlap the nut in the first reference axis direction. A protrusion,
Have
There is a gap between the protruding portion and the nut in the radial direction, and the output pulley, the contact portion of the belt, and the steered shaft side ball screw groove communicate with each other through the gap. Power steering device.

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