JP6379414B2 - 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 screw mechanism via a driving pulley, a belt, and a driven pulley, and used as an axial driving force of the rack shaft. The driven pulley is fastened to the ball screw mechanism by bolts.

JP 2006-027577

In the technique described in Patent Document 1, when the driven pulley is fastened to the ball screw mechanism with a bolt, the driven pulley may rotate with respect to the ball screw mechanism, and workability may be reduced.
The present invention pays attention to the above problem, and the object is to rotate the output pulley relative to the nut when the output pulley (driven pulley) is fastened to the nut (ball screw mechanism) with a screw (bolt). It is providing the power steering device which can suppress this.

  In order to achieve the above object, the power steering device of the present invention is provided with a rotation restricting portion that is provided on the output pulley and restricts the rotation of the output pulley around the rotation axis of the nut by contacting the jig.

  Therefore, when the output pulley is fastened to the nut, the rotation of the output pulley can be restricted.

1 is a front view of a power steering device according to Embodiment 1. FIG. 1 is a cross-sectional view of a power steering device of Embodiment 1. FIG. FIG. 3 is an enlarged cross-sectional view of the vicinity of the assist mechanism of the power steering device of Embodiment 1. 1 is a perspective view of an output pulley of Example 1. FIG. FIG. 3 is a view showing a state where the nut and the output pulley of Example 1 are assembled. FIG. 3 is a cross-sectional view of a state where the nut and output pulley of Example 1 are assembled. FIG. 3 is a cross-sectional view of a state where the nut and output pulley of Example 1 are assembled. 3 is a perspective view of a fixing jig of Example 1. FIG. 3 is a perspective view of a fixing jig of Example 1. FIG. FIG. 3 is a view of the fixing jig of Example 1 as viewed from the axial direction. 2 is a cross-sectional view of a fixing jig of Example 1. FIG. It is a perspective view of the power steering device of a comparative example. It is a perspective view of the output pulley of a comparative example. It is a figure of the state which assembled | attached the nut and output pulley of the comparative example. It is sectional drawing of the state which assembled | attached the nut and output pulley of the comparative example. It is sectional drawing of the state which assembled | attached the nut and output pulley of the comparative example.

[Example 1]
A power steering device 1 according to a first embodiment will be described. The power steering device 1 according to the first embodiment applies an 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 the left side in the axial direction of the nut 20 (the steering mechanism 2 side).
The right side in the figure in the axial direction of the inner race 24b of the nut 20 constitutes the main body 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.
A female threaded portion 20c is formed on the right end surface of the nut 20 in the drawing. The female screw portion 20c is formed at a position corresponding to a screw through hole 27f of the output pulley 27 described later. The screw 41 penetrating the screw through hole 27f is screwed with the female screw portion 20c, and the nut 20 and the output pulley 27 are fastened. An inclined portion 20b is formed in the opening on the right side of the nut 20 in the axial direction of the drawing. The inclined portion 20b is formed so that the inner diameter gradually increases.

[Configuration of output pulley]
FIG. 4 is a perspective view of the output pulley 27. FIG. The output pulley 27 is formed in a bottomed cup shape. The bottom of the output pulley 27 constitutes a bottom portion 27a. A cylindrical portion 27b formed in a cylindrical shape is formed so as to extend from the outer peripheral surface of the bottom portion 27a in the direction of the first reference axis L1.
The bottom 27a has a through hole 27c that penetrates in the direction of the first reference axis L1. In the through hole 27c, a large diameter portion 27d having a large distance from the first reference axis L1 to the inner periphery of the through hole 27c and a small diameter portion 27e having a small distance are alternately provided in the circumferential direction. A pair of jig contact portions 27g facing each other is formed between the large diameter portion 27d and the small diameter portion 27e. The turning shaft 10 is inserted into the through hole 27c.
A screw through hole 27f through which the screw 41 that fastens the nut 20 and the output pulley 27 passes is formed on the radially outer side of the small diameter portion 27e.

[Assembly of nut and output pulley]
FIG. 5 is a view showing a state in which the nut 20 and the output pulley 27 are assembled. 6 is a cross-sectional view taken along the line AA in FIG. FIG. 7 is a cross-sectional view taken along the line BB in FIG.
A part on the right side in FIGS. 6 and 7 in the axial direction of the nut 20 is accommodated in the inner periphery of the output pulley 27. The end face of the nut 20 on the right side in FIGS. 6 and 7 faces the bottom 27a of the output pulley 27. When the nut 20 and the output pulley 27 are viewed from the axial direction as shown in FIG. 5, a part of the end surface on the right side of the nut 20 in FIGS. 6 and 7 is exposed through the large diameter portion 27d of the through hole 27c. .

[Configuration of fixing jig]
FIG. 8 is a perspective view of the fixing jig 29. FIG. 9 is a perspective view of the fixing jig 29. FIG. 10 is a view of the fixing jig 29 viewed from the axial direction. FIG. 11 is a cross-sectional view taken along CC in FIG.
In the fixing jig 29, an insertion portion 29b is formed at the tip of a hexagonal columnar holding portion 29a so as to be fitted in the through hole 27c of the output pulley 27. The insertion portion 29b has a large diameter portion 29d whose outer diameter is slightly smaller than the inner diameter of the large diameter portion 27d of the through hole 27c, and a small diameter portion whose outer diameter is slightly smaller than the inner diameter of the small diameter portion 27e. 29e are alternately provided in the circumferential direction. Between the large diameter portion 29d and the small diameter portion 29e, a pair of output pulley contact portions 29f are formed on both end sides of the large diameter portion 29d. Further, the side surface of the large-diameter portion 29d (the side surface opposite to the holding portion 29a) constitutes a nut contact portion 29g.
Adjacent to the insertion portion 29b, an axial center adjustment portion 29c formed so as to be fitted to the inclined portion 20b of the nut 20 is formed. The shaft center adjusting portion 29c is formed such that the outer diameter gradually decreases toward the tip. The fixing jig 29 is formed hollow.
When the nut 20 and the output pulley 27 are fastened by the screw 41, the insertion portion 29b of the fixing jig 29 is inserted into the through hole 27c while the nut 20 is inserted into the output pulley 27. Thereby, the insertion part 29b and the through-hole 27c are fitted. Further, the shaft center adjusting portion 29c and the inclined portion 20b are fitted. Further, the nut contact portion 29g contacts the exposed portion of the end surface of the nut 20 in the axial direction through the large diameter portion 27d. And the holding | maintenance part 29a is held non-rotatably with another jig.
When the output pulley 27 tries to rotate with respect to the nut 20 at the time of fastening, the output pulley abutting portion 29f of the insertion portion 29b abuts one of the pair of jig abutting portions 27g of the through hole 27c to restrict the rotation. To do. The jig contact portion 27g that contacts the output pulley contact portion 29f constitutes a rotation restricting portion 27h.
When the shaft center adjusting portion 29c is fitted to the inclined portion 20b of the nut 20, the shaft center of the nut 20 and the shaft center of the output pulley 27 are brought closer to each other. In addition, the rotation of the nut 20 is restricted when the nut contact portion 29g contacts the end surface of the nut 20.

[Comparative example]
As a comparative example, a conventional mechanism for restricting relative rotation of the output pulley 27 with respect to the nut 20 will be described.
FIG. 12 is a perspective view of the power steering apparatus 1, and shows a state in which the second housing 32 and the motor housing 33 are removed. FIG. 13 is a perspective view of the output pulley 27. FIG. FIG. 14 is a view showing a state in which the nut 20 and the output pulley 27 are assembled. FIG. 15 is a sectional view taken along the line DD in FIG. 16 is a cross-sectional view taken along the line EE in FIG.
In the first embodiment, the through hole 27c is constituted by the large diameter portion 27d and the small diameter portion 27e. In the comparative example, the through hole 27c is formed in a circular shape having the same diameter as the small diameter portion 27e. In the comparative example, a rotation stop hole 27i is formed in the bottom 27a. The rotation stop hole 27i is a through hole that penetrates the bottom 27a. The rotation stop holes 27i are provided in two places.
When the nut 20 and the output pulley 27 are screwed together by the screw 41, a jig is inserted into the rotation stop hole 27i so that the output pulley 27 does not rotate with respect to the nut 20.
In the comparative example, only the work of screwing the nut 20 and the output pulley 27 with the screw 41 had to be drilled in the bottom 27a.

[Action]
If the output pulley 27 rotates with respect to the nut 20 during the operation of screwing the nut 20 and the output pulley 27 with the screw 41, the workability may be reduced. Further, the shaft center of the nut 20 and the shaft center of the output pulley 27 may be shifted during the work.
Therefore, in the first embodiment, the rotation of the output pulley 27 relative to the nut 20 is restricted by contacting the fixing jig 29 and the rotation restricting portion 27h of the output pulley 27. Thereby, since the rotation of the output pulley 27 with respect to the nut 20 is restricted, workability can be improved. In addition, it is possible to suppress the deviation between the axis of the nut 20 and the axis of the output pulley 27 during operation.
The length of the output pulley 27 in the axial direction needs to be secured at a minimum so that the belt 28 can be wound. In the first embodiment, the rotation restricting portion 27h is provided on the bottom portion 27a of the output pulley 27. Since the rotation restricting portion 27h is not provided on the cylindrical portion 27b of the output pulley 27, the axial length of the output pulley 27 only needs to be secured to the extent that the belt 28 can be wound, and the axial length of the output pulley 27 is shortened. Can be

In order to restrict the rotation of the output pulley 27 relative to the nut 20, it is also necessary to restrict the rotation of the nut 20.
Therefore, in the first embodiment, the fixing jig 29 abuts on the rotation restricting portion 27h of the output pulley 27, and abuts on a portion of the axial end surface of the nut 20 exposed through the large-diameter portion 27d. The rotation of 27 and nut 20 was regulated.
Thereby, the fixing jig 29 can also regulate the rotation of the nut 20 together with the output pulley 27. Accordingly, the relative positional deviation between the nut 20 and the output pulley 27 is suppressed, and the coaxiality between the nut 20 and the output pulley 27 can be improved.
The diameter of the output pulley 27 increases as the screw through hole 27f of the output pulley 27 is provided on the outer peripheral side of the bottom 27a. Therefore, in the first embodiment, the screw through hole 27f is provided on the radially outer side of the small diameter portion 27e of the through hole 27c.
Thereby, the diameter of the output pulley 27 can be reduced as compared with the case where the screw through hole 27f is provided on the radially outer side of the large diameter portion 27d.

When screwing the nut 20 and the output pulley 27 with the screw 41, the coaxiality between the nut 20 and the output pulley 27 may be impaired.
Therefore, in Example 1, the output pulley contact portion 29f of the fixing jig 29 contacts the rotation restricting portion 27h of the output pulley 27, and the shaft center adjustment portion 29c of the fixing jig 29 contacts the inclined portion 20b of the nut 20. I made contact.
Thereby, since the fastening operation by the screw 41 can be performed in a state where the shaft center of the nut 20 and the shaft center of the output pulley 27 are close to each other, the coaxiality between the nut 20 and the output pulley 27 can be improved.

〔effect〕
(1) A steered shaft 10 that steers the steered wheels by moving in the axial direction along with the rotation of the steering wheel, and a steered shaft-side ball that is provided on the outer peripheral side of the steered shaft 10 and has a spiral groove shape A screw groove 11, a nut 20 provided in an annular shape so as to surround the steered shaft 10, a spiral groove shape provided on the inner peripheral side of the nut 20, and the steered shaft side ball screw groove 11 And a ball screw groove 21 on the nut side constituting the ball circulation groove 12, a plurality of balls 22 provided in the ball circulation groove, and a ball for circulating the plurality of balls 22 from one end side to the other end side of the ball circulation groove 12 A tube 23 (circulation mechanism), and a plurality of balls 22 move in the ball circulation groove 12 as the nut 20 rotates with respect to the steered shaft 10, and the steered shaft 10 is turned with respect to the nut 20. A ball screw mechanism 26 that moves in the longitudinal direction of 10 and a cylindrical shape to surround the steered shaft 10 The formed output pulley 27, the screw through hole 27f formed in the output pulley 27, the female screw portion 20c provided in the nut 20 at a position corresponding to the screw through hole 27f, and the screw through hole 27f The nut 41 and the output pulley 27 are screwed into the female screw portion 20c so that the nut 41 and the output pulley 27 are screwed together. The rotation restricting portion 27h for restricting the rotation of the output pulley 27 around the shaft and the rotation axis of the nut 20 is the first reference axis L1, and the radial direction of the first reference axis L1 is the first rotation axis. The second reference axis L2 is arranged so as to be offset in the radial direction with respect to the first reference axis 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, and the input pulley Transmit 35 rotations to output pulley 27 A belt 28 (transfer member), the electric motor 40 for rotating the input pulley 35, and the provided.
Therefore, since the rotation of the output pulley 27 with respect to the nut 20 is restricted, workability can be improved. In addition, it is possible to suppress the deviation between the axis of the nut 20 and the axis of the output pulley 27 during operation.

(2) The output pulley 27 is formed in a cylindrical shape so as to extend in the first reference axis L1 direction from the bottom 27a and the bottom 27a provided to face the end surface of the nut 20 on the one end side in the first reference axis L1 direction. The rotation restricting portion 27h is provided on the bottom portion 27a.
Therefore, the axial length of the output pulley 27 can be shortened.
(3) The output pulley 27 has a through hole 27c (jig through hole) provided in the bottom portion 27a and formed so as to penetrate in the direction of the first reference axis L1, and the direction around the first reference axis L1 Is the circumferential direction, the through-holes 27c are alternately provided with a large-diameter portion 27d having a large distance from the first reference axis L1 to the inner peripheral surface of the through-hole 27c and a small-diameter portion 27e having a small distance in the circumferential direction. When the nut 20 side of the first reference axis is the one side in the axial direction and the opposite side is the other side in the axial direction with respect to the bottom 27a, the large-diameter portion 27d overlaps with the nut 20 in the radial direction. 20 is formed so as to be exposed from the other side in the axial direction through the large-diameter portion 27d, and includes a pair of jig contact portions 27g (inner wall surfaces) facing each other in the circumferential direction. Provided on at least one side of the pair of jig contact portions 27g, and the fixing jig 29 contacts the rotation restricting portion 27h. At the same time, the rotation of the output pulley 27 and the nut 20 is restricted by coming into contact with the exposed nut 20 through the large diameter portion 27d.
Therefore, the relative displacement between the nut 20 and the output pulley 27 is suppressed, and the coaxiality between the nut 20 and the output pulley 27 can be improved.

(4) The screw through hole 27f is provided at the bottom portion 27a of the output pulley 27 and on the radially outer side of the small diameter portion 27e.
Therefore, the diameter of the output pulley 27 can be reduced.
(5) The nut 20 includes an inclined portion 20b that opens toward the other side in the axial direction and is provided so that the inner diameter gradually increases around the first reference axis L1, and the through hole 27c is formed in the radial direction. , A rotation restricting portion 27h (contact portion) that comes into contact with the fixing jig 29, and the fixing jig 29 comes into contact with the inclined portion 20b and the rotation restricting portion 27h so that the rotation axes of the nut 20 and the output pulley 27 are brought closer to each other. To be formed.
Therefore, the coaxiality between the nut 20 and the output pulley 27 can be improved.

[Other embodiments]
As described above, the present invention has been described based on the first embodiment. However, the specific configuration of each invention is not limited to the first embodiment, and even if there is a design change or the like without departing from the gist of the present invention. Are included in the present invention.

10 Steering shaft
11 Steering shaft side ball screw groove
12 Ball circulation groove
20 nuts
20b ramp
20c Female thread
21 Nut side ball screw groove
22 balls
23 Ball tube (circulation mechanism)
26 Ball screw mechanism
27 Output pulley
27a bottom
27b Tube
27c Through hole (Jig through hole)
27d Large diameter part
27e Small diameter part
27g Jig contact part (inner wall surface)
27f Screw through hole
27h Rotation restriction part
28 Belt (Transmission member)
29 Fixing jig
35 Input pulley
40 Electric motor
41 screw

Claims (3)

A steered shaft that steers the steered wheels by moving in the axial direction as the steering wheel rotates, and
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;
A circulation mechanism that circulates the plurality of balls from one end side to the other end side of the ball circulation groove, and the plurality of balls move in the ball circulation groove as the nut rotates relative to the steered shaft. A ball screw mechanism for moving the steered shaft in the longitudinal direction of the steered shaft with respect to the nut;
An output pulley formed in a cylindrical shape so as to surround the steered shaft;
A screw through hole formed in the output pulley;
An internal thread portion provided in the nut and formed at a position corresponding to the screw through hole;
A screw that passes through the screw through hole and is screwed into the female screw portion to screw the nut and the output pulley;
A rotation restricting portion that is provided on the output pulley and restricts the rotation of the output pulley around the rotation axis of the nut, by contacting a jig;
When the rotation axis of the nut is the first reference axis and the radial direction of the first reference axis is the radial direction, the second reference axis serving as the rotation axis is offset in the radial direction with respect to the first reference axis. And an input pulley formed in a cylindrical shape,
A transmission member 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;
I have a,
The output pulley has a bottom portion provided to face an end surface of the nut on one end side in the first reference axis direction, and a cylindrical shape formed in a cylindrical shape so as to extend from the bottom portion in the first reference axis direction. A jig through-hole formed to penetrate in the direction of the first reference axis, provided at the bottom,
When the direction around the first reference axis is the circumferential direction, the jig through hole has a large diameter portion from which the distance from the first reference axis to the inner peripheral surface of the jig through hole is small and the distance is small. Small diameter portions are provided alternately in the circumferential direction,
When the nut side of the first reference axis is the one side in the axial direction and the opposite side is the other side in the axial direction with respect to the bottom, the large diameter portion overlaps the nut in the radial direction. The nut is formed so as to be exposed from the other axial side through the large diameter portion, and includes a pair of inner wall surfaces facing each other in the circumferential direction,
The rotation restricting portion is provided on at least one side of the pair of inner wall surfaces,
The jig controls the rotation of the output pulley and the nut by contacting the rotation restricting portion and contacting the nut exposed through the large diameter portion. . The power steering apparatus according to claim 1, wherein
The screw through-hole is provided at the bottom of the output pulley and on the radially outer side of the small-diameter portion. The power steering apparatus according to claim 1, wherein
The nut includes an inclined portion that opens toward the other side in the axial direction and is provided so that an inner diameter gradually increases around the first reference axis,
The jig through hole includes a contact portion that contacts the jig in the radial direction, and the jig contacts the inclined portion and the contact portion, thereby rotating the rotation shaft of the nut and the output pulley. A power steering device formed so as to be close to each other.

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