JP2010023796A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering device which suppresses engaging defects of a rack tooth with a pinion tooth. <P>SOLUTION: The power steering device includes a first bearing provided to the opposite side of a steering input shaft, in relation to the pinion tooth to journal a pinion shaft on a housing; a second bearing provided on the steering input shaft side in relation to the pinion tooth to journal the pinion shaft on the housing and constituted of a roller bearing or a sliding bearing; and a third bearing provided on the steering input shaft side, in relation to the second bearing to journal the pinion shaft on the housing. A radial direction gap which is formed between the housing or the pinion shaft and the second bearing and on a side, in which the opposed members with each other relatively rotate and is in a smallest part in the circumferential direction is made smaller than any part in the peripheral direction of the radial direction gap which is formed between the housing or the pinion shaft and the third bearing and on the side in which the opposed members relatively rotate with each other. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power steering apparatus that applies a steering assist force to a driver's steering.

  As this type of technology, the technology described in Patent Document 1 is disclosed.

In this publication, there is disclosed a bank-like convex portion formed on a part of the inner surface of a cylindrical portion that houses a pinion shaft over the entire circumference of the cylindrical portion.
JP 2005-112037 A

  In the above prior art, the outer peripheral surface of the intermediate portion of the pinion shaft and the inner peripheral surface of the convex portion are opposed to each other through a minute gap in a state where power is not transmitted between the pinion and the rack. . For this reason, the pinion shaft is supported by ball bearings provided on the upper side and the lower side until the pinion shaft and the convex portion come into contact with each other, and the distance between the support positions becomes longer. There was a risk of poor meshing with the pinion teeth.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a power steering device that suppresses a meshing failure between rack teeth and pinion teeth.

  In order to achieve the above object, according to the first aspect of the present invention, a first bearing provided on the opposite side of the steering input shaft with respect to the pinion teeth and supporting the pinion shaft with respect to the housing, and the pinion teeth A second bearing that is provided on the steering input shaft side, supports the pinion shaft with respect to the housing, and is constituted by a roller bearing or a sliding bearing, and is provided on the steering input shaft side with respect to the second bearing. A third bearing that pivotally supports the pinion shaft, and is a radial clearance on the side where the opposing members formed between the housing or the pinion shaft and the second bearing rotate relative to each other. The radial clearance at the smallest portion in the circumferential direction is any portion in the circumferential direction of the radial clearance on the side formed between the housing or pinion shaft and the third bearing and on which the opposing members relatively rotate. It was also small.

  In the second aspect of the invention, the first bearing provided on the opposite side to the steering input shaft with respect to the pinion teeth and supporting the pinion shaft with respect to the housing, and the steering input shaft side with respect to the pinion teeth. The pinion teeth are formed so that at least a part of the pinion teeth is overlapped, and a second bearing that supports the pinion shaft with respect to the housing is provided.

  In the third invention, the pinion shaft is rotatably provided in the housing and meshes with the rack teeth in a state shifted from a position orthogonal to the rack shaft, and has pinion teeth formed by forging or rolling; A first bearing that is provided on the opposite side of the steering input shaft with respect to the pinion teeth and that supports the pinion shaft with respect to the housing; and a steering input shaft side with respect to the pinion teeth, and the pinion shaft with respect to the housing A second bearing that pivotally supports the second bearing and a third bearing that pivotally supports the pinion shaft with respect to the housing. The housing or the pinion shaft and the second bearing Is a radial gap on the side where the opposing members are relatively rotated, and the radial gap in the smallest portion in the circumferential direction is the housing or pinion shaft and the third shaft Member each other and facing the formation is less than any part of the circumferential direction of the radial clearance on the side relative rotation between.

  Therefore, the first bearing and the second bearing close to the pinion teeth receive a load, the bending rigidity of the pinion shaft can be increased, and the meshed state of the pinion teeth and the rack teeth can be kept good.

  Hereinafter, the best mode for realizing the power steering device of the first invention, the second invention, and the third invention will be described in the first to eighth embodiments.

A configuration of the power steering apparatus 1 according to the first embodiment will be described.
[Outline of power steering system]
FIG. 1 is a system configuration diagram of a pinion assist type power steering apparatus 1.
The power steering apparatus 1 includes a steering wheel 30 that is steered by a driver, a steering shaft 31 to which a steering force is input from the steering wheel 30, an intermediate shaft 33 that is connected to the steering shaft 31 via a universal joint 32, The steering input shaft 7 connected to the shaft 33 via the universal joint 34, the rack and pinion portion 27 for converting the steering force in the rotational direction transmitted by the steering input shaft 7 into the force in the vehicle width direction, and the motor 21 And a gear box 29 including a power assist unit 28 that applies an assist force to the steering force.

  In the rack and pinion portion 27, the pinion teeth 9 formed on the lower side of the pinion shaft 8 and the rack teeth 10 a formed on the rack shaft 10 are twisted in the axial direction of the pinion shaft 8 with respect to the axial direction of the rack shaft 10. Meshing direction.

  The power assist unit 28 includes a torque sensor 4 that detects torque acting on the steering input shaft 7, a worm wheel 19 that rotates integrally with the pinion shaft 8, and a worm shaft that is fixed to the output shaft of the motor 21 and meshes with the worm wheel 19. And 20. Torque detected by the torque sensor 4 is input to an electronic control unit (hereinafter referred to as ECU) 22, and the ECU 22 controls the output torque of the motor 21 based on the input torque information.

  The steering force input to the steering wheel 30 by the driver is transmitted in the order of the steering shaft 31, the universal joint 32, the intermediate shaft 33, the universal joint 34, the steering input shaft 7, and the pinion shaft 8. The assist torque generated in the motor 21 is transmitted to the pinion shaft 8 in the order of the worm shaft 20 and the worm wheel 19. The steering force of the driver transmitted to the pinion shaft 8 and the assist torque of the motor 21 are steered wheels via the pinion shaft 8, the rack shaft 10, the rack end 35, the universal joint 36, the tie rod 37, the tie rod end 38, and the knuckle arm 39. 40.

[Gearbox configuration]
FIG. 2 is a partial cross-sectional view of the gear box 29. The gear box 29 includes a first housing 6 that houses the pinion shaft 8, the rack shaft 10, and the like, and a second housing 5 that houses the worm wheel 19, the worm shaft 20, the steering input shaft 7, the torque sensor 4, and the like.

  In the following description, in FIG. 2, the axial direction of the steering input shaft 7 and the pinion shaft 8 is the lower side on the pinion shaft 8 side and the upper side on the steering input shaft 7 side.

(Configuration of steering input shaft)
A spline groove 7a is formed on the upper side of the steering input shaft 7, and is connected to the universal joint 34 by a spline.

A fourth bearing fitting portion 7b having a larger diameter than the outer diameter of the spline groove 7a is formed below the spline groove 7a of the steering input shaft 7.
A middle cylinder engaging portion 7c having a diameter larger than the outer diameter of the fourth bearing fitting portion 7b is formed below the fourth bearing fitting portion 7b of the steering input shaft 7.

A pinion shaft insertion portion 7 e with a part cut away is formed below the middle cylinder engaging portion 7 c of the steering input shaft 7.
A hollow torsion bar accommodating portion 7d is formed on the steering input shaft 7, and a torsion bar fitting portion 7f having a smaller diameter than the torsion bar accommodating portion 7d is formed on the upper side of the torsion bar accommodating portion 7d.

(Configuration of pinion shaft)
Pinion teeth 9 are formed on the lower side of the pinion shaft 8. The pinion teeth 9 are formed by cutting, and a rounded-up portion 9a is formed on the root side.
A first bearing insertion portion 8 a having a smaller diameter than the outer diameter of the pinion teeth 9 is formed at the lower end of the pinion shaft 8.

A second bearing insertion portion 8 b having a diameter larger than the outer diameter of the pinion teeth 9 is formed above the pinion teeth 9 of the pinion shaft 8.
A third bearing insertion portion 8c having a larger diameter than the second bearing insertion portion 8b is formed above the second bearing insertion portion 8b of the pinion shaft 8.

  A flange portion 8d having a diameter larger than that of the third bearing insertion portion 8c is formed on the pinion shaft 8 above the third bearing insertion portion 8c. The flange portion 8d is formed to have substantially the same diameter as the outer periphery of an inner race 16c of the third bearing 16 described later. Further, on the outer peripheral side surface of the third bearing insertion portion 8c, the diameter of the third bearing insertion portion 8c is smaller than that of the third bearing insertion portion 8c in the vicinity of a position separated from the lower side surface of the flange portion 8d in the axial direction thickness of the third bearing 16 described later. A concave groove-shaped ring locking portion 8i is formed.

On the upper side of the flange portion 8d of the pinion shaft 8, a worm wheel fitting portion 8e having a diameter smaller than that of the flange portion 8d and larger than that of the third bearing insertion portion 8c is formed.
An outer cylinder engaging portion 8 f is formed at the upper end of the pinion shaft 8.

A hollow portion is formed at the upper end of the pinion shaft 8 in the shape of a bottomed cup that opens above the pinion shaft 8, and the steering formed in the hollow portion along the shape of the pinion shaft insertion portion 7 e of the steering input shaft 7. An input shaft insertion portion 8h is formed.
A torsion bar fitting portion 8g is formed at the bottom of the opening of the pinion shaft.

(Configuration of first housing)
The first housing 6 has a bottomed cup-shaped hollow pinion shaft accommodating portion 41 having an opening on the upper side and a bottom on the lower side, and a first bearing holding portion 6a is formed on the bottom.

A pinion tooth accommodating portion 6b having a diameter larger than that of the first bearing holding portion 6a is formed above the first bearing holding portion 6a of the first housing 6. The pinion tooth accommodating portion 6 b is formed larger than the outer diameter of the pinion teeth 9.
A second bearing holding portion 6c having a larger diameter than the pinion tooth accommodating portion 6b is formed above the pinion tooth accommodating portion 6b of the first housing 6.

  On the upper side of the second housing holding portion 6c of the first housing 6, a step portion 6m perpendicular to the axial direction is formed after the diameter is increased in a curved shape. The inner diameter of the step portion 6m is formed to be substantially the same as the inner diameter of an outer race 16a of the third bearing 16 described later, and the outer diameter is formed to be substantially the same as the outer diameter of the outer race 16a.

A third bearing holding portion 6d having the same diameter as the outer diameter of the step portion 6m is formed continuously with the step portion 6m.
A locking ring fitting portion 6e having a diameter larger than that of the third bearing holding portion 6d is formed above the third bearing holding portion 6d of the first housing 6.

On the upper end of the first housing 6, a second housing engaging portion 6g that is convex upward is formed. A concave seal member insertion portion 6h is formed on the outer peripheral side surface of the second housing engaging portion 6g. A seal member 94 is inserted into the seal member insertion portion 6h.
The first housing 6 is provided with a rack shaft housing portion 6 i formed to extend in the twisting direction with respect to the axial direction of the pinion shaft 8. At a position where the rack shaft housing portion 6i and the pinion tooth housing portion 6b intersect, the rack shaft housing portion 6i and the pinion tooth housing portion 6b communicate with each other.

In the first housing 6, a pressing portion accommodating portion 6 j is formed in a direction perpendicular to the axial direction of the pinion shaft 8 at a position where the rack shaft accommodating portion 6 i and the pinion tooth accommodating portion 6 b communicate with each other.
The first housing 6 has a bolt insertion portion 6f formed at a position away from the pinion tooth accommodating portion 6b and the like in the radial direction.

(Configuration of second housing)
The second housing 5 has a through hole in the axial direction, and the lower opening of the second housing 5 has an inner peripheral surface having substantially the same diameter as the outer periphery of the second housing engaging portion 6g of the first housing 6. A first housing engaging portion 5h is formed.

  On the upper side of the first housing engaging portion 5h of the second housing 5, a worm wheel accommodating portion 5a having a smaller diameter than the first housing engaging portion 5h is formed. The worm wheel housing portion 5 a is formed with a larger diameter than the worm wheel 19.

  The second housing 5 is formed with a worm shaft housing portion 5b in a direction perpendicular to the axial direction of the worm wheel housing portion 5a. The worm shaft housing portion 5 b is formed with a larger diameter than the worm shaft 20.

On the upper side of the worm wheel housing portion 5a of the second housing 5, a locking plate housing portion 5c having a smaller diameter than the worm wheel housing portion 5a is formed.
A torque sensor accommodating portion 5d having a smaller diameter than the engaging plate accommodating portion 5c is formed above the engaging plate accommodating portion 5c of the second housing 5.

On the upper side of the torque sensor housing portion 5d of the second housing 5, a locking portion 5e having a diameter smaller than that of the torque sensor housing portion 5d and larger than that of an outer cylinder 4d of the torque sensor 4 described later is formed. Yes. The locking portion 5e is formed to have a smaller diameter than an inner diameter of an outer race 17a of the fourth bearing 17 described later.
A fourth bearing housing portion 5f having a diameter larger than that of the locking portion 5e is formed above the locking portion 5e of the second housing 5.
In the second housing 5, a bolt insertion portion 5 g is formed at a position where the first housing 6 and the second housing 5 are combined to communicate with the bolt insertion portion 6 f of the first housing 6.

(Configuration of torque sensor)
The torque sensor 4 includes a first coil 4a, a second coil 4b, a middle cylinder 4c, and an outer cylinder 4d.
The first coil 4a and the second coil 4b are arranged side by side in the axial direction. The middle cylinder 4c rotates integrally with the steering input shaft 7, and the outer cylinder 4d rotates integrally with the pinion shaft 8. In addition, on the peripheral side surfaces of the middle cylinder 4c and the outer cylinder 4d, an opening window is provided at a position facing the first coil 4a and the second coil 4b.

  When the steering input shaft 7 and the pinion shaft 8 rotate relative to each other, the overlapping amount of the opening windows of the middle cylinder 4c and the outer cylinder 4d changes, and the change in magnetic force corresponding to this change changes the first coil 4a and the second coil 4b. To detect. The magnetic force detected by the first coil 4a and the second coil 4b is transmitted to the ECU 22 via the communication lines 4e and 4f.

(Gearbox assembly)
A third bearing 16, which is a radial ball bearing, is inserted from below the pinion shaft 8 and is fitted to the third bearing insertion portion 8 c. At this time, the upper side surface of the third bearing 16 contacts the lower side surface of the flange portion 8d. Further, the ring 96 is inserted from the lower side of the pinion shaft 8 and engaged with the ring locking portion 8i. The upper side of the ring 96 is formed to have a larger diameter than the inner diameter of the inner race 16 c of the third bearing 16, and the movement of the third bearing 16 in the axial direction is restricted by the ring 96.

The second bearing 15 which is a radial roller bearing is inserted from the lower side of the pinion shaft 8 and is fitted to the second bearing insertion portion 8b.
A first bearing 14 that is a radial roller bearing is inserted from the lower side of the pinion shaft 8 and fitted into the first bearing insertion portion 8a.

  The pinion shaft 8 with the first bearing 14, the second bearing 15, and the third bearing 16 attached thereto is inserted from the upper opening of the first housing 6. When the pinion shaft 8 is inserted into the first housing 6, the first bearing 14 is held in the first bearing holding portion 6a, the second bearing 15 is held in the second bearing holding portion 6c, and the third bearing 16 is held in the third bearing holding portion 6d. Is done. At this time, the lower surface of the third bearing 16 is in contact with the step portion 6m.

  After the pinion shaft 8 is inserted into the first housing 6, the locking ring 88 is inserted into the locking ring fitting portion 6e and fitted. At this time, the lower surface of the locking ring 88 contacts the upper surface of the outer race 16 a of the third bearing 16. Therefore, the outer race 16a is clamped by the step 6m and the locking ring 88, and the third bearing 16 is restricted from moving in the axial direction.

  Thereafter, the worm wheel 19 is inserted from the upper side of the pinion shaft 8 and is fitted to the worm wheel fitting portion 8e. The lower surface of the worm wheel 19 is in contact with the upper surface of the flange portion 8d.

Next, the vicinity of the rack shaft 10 will be described.
The rack shaft 10 is inserted into the rack shaft housing portion 6 i of the first housing 6.
After the rack shaft 10 is inserted into the rack shaft housing portion 6i, the pressing member 11 is inserted into the pressing portion housing portion 6j. A contact surface 11 a is formed on the surface of the pressing member 11 on the rack shaft 10 side along the curved surface of the back surface of the rack tooth 10 a of the rack shaft 10, and the contact surface 11 a is contacted with the rack shaft 10. A hollow spring insertion portion 11b is formed on the opposite side of the contact surface 11a of the pressing member 11, and the spring 13 is inserted into the spring insertion portion 11b.

  Next, the stopper 12 is inserted into the pressing portion accommodating portion 6j. A hollow spring insertion portion 12a is formed on the pressing member 11 side of the stopper 12, and the spring 13 is inserted into the spring insertion portion 12a. The stopper 12 is locked to the first housing 6 by a locking member 93.

The steering input shaft 7 and the pinion shaft 8 are connected via a torsion bar 26. Both ends of the torsion bar 26 have a large diameter, a steering input shaft fitting portion 26a is formed at the upper end, and a pinion shaft fitting portion 26b is formed at the lower end.
The torsion bar 26 is inserted into the torsion bar accommodating portion 7d of the steering input shaft 7, and the steering input shaft fitting portion 26a is fitted to the torsion bar fitting portion 7f.

  The pinion shaft insertion portion 7e of the steering input shaft 7 is inserted into the steering input shaft insertion portion 8h of the pinion shaft 8, and the pinion shaft fitting portion 26b of the torsion bar 26 is fitted to the torsion bar fitting portion 8g. A seal member 97 is provided in part between the outer periphery of the pinion shaft insertion portion 7 e of the steering input shaft 7 and the inner periphery of the steering input shaft insertion portion 8 h of the pinion shaft 8.

  The middle cylinder engaging portion 7 c of the steering input shaft 7 is engaged with the middle cylinder 4 c of the torque sensor 4, and the outer cylinder engaging portion 8 f of the pinion shaft 8 is engaged with the outer cylinder 4 d. A seal member 95 is provided between the outer cylinder engaging portion 8f and the outer cylinder 4d.

  The first coil 4 a and the second coil 4 b of the torque sensor 4 are inserted into the torque sensor housing portion 5 d of the second housing 5. A locking plate 91 having a through-hole that is smaller than the outer diameter of the first coil 4 a and the second coil 4 b and larger than the outer diameter of the outer cylinder 4 d is provided in the locking plate housing portion 5 c of the second housing 5. The locking plate 91 is inserted and fixed to the second housing 5 by screws 90. The locking plate 91 restricts the axial movement of the first coil 4 a and the second coil 4 b of the torque sensor 4.

  The second housing 5 to which the first coil 4 a and the second coil 4 b of the torque sensor 4 are attached is inserted from the upper side of the steering input shaft 7, and the second housing engaging portion 6 g of the first housing 6 and the first housing engagement are inserted. The joint portion 5h is engaged.

  A fourth bearing 17 that is a ball bearing is inserted from the upper side of the steering input shaft 7 and is fitted to the fourth bearing fitting portion 7b. The 4th bearing 17 is hold | maintained by the 4th bearing accommodating part 5f of the 2nd housing 5, and is positioned to the axial direction by the latching | locking part 5e. Further, a seal member 18 is inserted from the upper side of the steering input shaft 7, and the seal member 18 allows a space between the fourth bearing fitting portion 7 b of the steering input shaft 7 and the fourth bearing housing portion 5 f of the second housing 5. It is sealed.

The worm shaft 20 is inserted into the worm shaft housing portion 5b, and the worm shaft 20 and the worm wheel 19 are engaged with each other.
After the first housing 6 and the second housing 5 are combined, the bolt 92 is inserted into the bolt insertion portion 6f and the bolt insertion portion 5g to fix the first housing 6 and the second housing 5 together.

[Bearing configuration]
FIG. 3 is an axial sectional view and a circumferential sectional view of the first bearing 14, the second bearing 15, and the third bearing 16.

  The 3rd bearing 16 is comprised from the outer race 16a, the ball | bowl 16b, and the inner race 16c, as shown to Fig.3 (a). The third bearing insertion portion 8c of the pinion shaft 8 is fitted to the inner periphery of the inner race 16c. The outer periphery of the outer race 16 a is held by the third bearing holding portion 6 d of the first housing 6. Therefore, the outer race 16 a does not rotate relative to the first housing 6, and the inner race 16 c does not rotate relative to the pinion shaft 8. The balls 16b are arranged at substantially equal intervals in the circumferential direction by a gauge, and rotate relative to the outer race 16a and the inner race 16c with the gauge as the rotation of the ball 16b in the revolution direction. The third bearing 16 is a radial ball bearing, but can receive a thrust load.

  As shown in FIG. 3B, the second bearing 15 includes an outer race 15a and a roller 15b. Rollers 15b are arranged at substantially equal intervals in the circumferential direction on the inner peripheral side of the outer race 15a and are rotatably supported. The second bearing insertion portion 8b of the pinion shaft 8 is inserted inside the rollers 15b arranged on the circumference. The outer periphery of the outer race 15 a is held by the second bearing holding portion 6 c of the first housing 6. Therefore, the outer race 15 a does not rotate relative to the first housing 6. Since the roller 15b is supported by the outer race 15a, the rotation of the roller 15b in the revolution direction is prevented from rotating relative to the first housing 6.

  As shown in FIG. 3C, the first bearing 14 includes an outer race 14a and a roller 14b. Rollers 14b are arranged at substantially equal intervals in the circumferential direction on the inner peripheral side of the outer race 14a, and are rotatably supported. The first bearing insertion portion 8a of the pinion shaft 8 is inserted inside the outer race 14a arranged on the circumference. The outer diameter of the first bearing 14 is smaller than the outer diameter of the second bearing 15. The outer circumference of the outer race 14 a is held by the first bearing holding portion 6 a of the first housing 6. Therefore, the outer race 14 a is not rotated relative to the first housing 6. Since the roller 14b is supported by the outer race 14a, the rotation of the roller 14b in the revolving direction is prevented from rotating relative to the first housing 6.

  Here, in order to support the pinion shaft 8 by the first bearing 14 and the second bearing 15 that are close to the pinion tooth 9 among the first bearing 14, the second bearing 15, and the third bearing 16, the diameter of the third bearing 16 is used. The radial gap between the first bearing 14 and the second bearing 15 needs to be smaller than the directional gap. For that purpose, it is necessary to design in the range which set the radial direction clearance of the 1st bearing 14, the 2nd bearing 15, and the 3rd bearing 16. FIG. The radial clearances of the first bearing 14, the second bearing 15, and the third bearing 16 are a member that rotates relative to the first housing 6 or the pinion shaft 8 (hereinafter referred to as a relative rotating member), and a member that faces the relative rotating member. (Hereinafter, a radial gap with an opposing member) is shown.

  In the third bearing 16, the relative rotation members for the first housing 6 are the balls 16b and the inner races 16c, and the relative rotation members for the pinion shaft 8 are the balls 16b and the outer races 16a. In the third bearing 16, opposing members for the ball 16b are the outer race 16a and the inner race 16c, and opposing members for the outer race 16a and the inner race 16c are the balls 16b.

  That is, the radial clearance of the third bearing 16 indicates the radial clearance between the outer race 16a and the ball 16b and the radial clearance between the inner race 16c and the ball 16b. Here, of the radial gap between the outer race 16a and the ball 16b and the radial gap between the inner race 16c and the ball 16b, the size of the smallest radial gap in the circumferential direction is A.

  In the second bearing 15, the relative rotation member with respect to the first housing 6 is the pinion shaft 8, and the relative rotation member with respect to the pinion shaft 8 is a roller 15b. In the second bearing 15, the facing member for the pinion shaft 8 is the roller 15 b, and the facing member for the roller 15 b is the pinion shaft 8.

  That is, the radial clearance of the second bearing 15 indicates the radial clearance between the roller 15 b and the pinion shaft 8. Here, B is the size of the radial gap between the roller 15b and the pinion shaft 8 and the smallest radial gap in the circumferential direction.

  In the first bearing 14, the relative rotation member with respect to the first housing 6 is the pinion shaft 8, and the relative rotation member with respect to the pinion shaft 8 is a roller 14b. In the first bearing 14, the facing member for the pinion shaft 8 is the roller 14 b, and the facing member for the roller 14 b is the pinion shaft 8.

  That is, the radial clearance of the first bearing 14 indicates the radial clearance between the roller 14 b and the pinion shaft 8. Here, C is the size of the radial gap between the roller 14b and the pinion shaft 8 and the smallest radial gap in the circumferential direction.

  At this time, the first bearing 14, the second bearing 15, and the third bearing 16 are formed so that the size of each radial clearance is “A ≧ B” and “A ≧ C”. That is, the radial load of the pinion shaft 8 is always received by the first bearing 14 and the second bearing 15.

[Action]
When the pinion shaft 8 is shortened, the bending rigidity of the pinion shaft 8 is higher and the meshing state between the pinion teeth 9 and the rack teeth 10a is improved. However, the pinion shaft 8 needs to be lengthened for convenience of layout.

  For example, in the power steering apparatus 1 according to the first embodiment, the axial direction of the pinion shaft 8 and the axial direction of the rack shaft 10 are in a twisted position. Further, the pinion assist type power steering device 1 needs to be provided with a motor 21 in the vicinity of the pinion shaft 8. However, since the motor 21 is relatively bulky, the pinion shaft 8 is lengthened to separate the motor 21 from the meshing position of the pinion teeth 9 and the rack teeth 10a so that the motor 21 and the housing that houses the rack shaft 10 do not interfere with each other. There is a need.

  Therefore, in the power steering apparatus 1 according to the first embodiment, the first pinion shaft 8 is supported by the first housing 6 on the opposite side of the pinion teeth 9 from the steering input shaft 7, that is, below the pinion teeth 9. One bearing 14 was provided. A second bearing 15, which is a radial roller bearing that supports the pinion shaft 8 with respect to the first housing 6, is provided on the steering input shaft 7 side with respect to the pinion teeth 9, that is, on the upper side of the pinion teeth 9. A third bearing 16 that supports the pinion shaft 8 with respect to the first housing 6 is provided on the steering input shaft 7 side with respect to the second bearing 15, that is, on the upper side of the second bearing 15.

  Further, B is the radial clearance between the roller 15b of the second bearing 15 and the pinion shaft 8, and the size of the radial clearance at the smallest portion in the circumferential direction is B is the radial clearance between the outer race 16a and the ball 16b. The size of the radial gap at the smallest portion in the circumferential direction of the radial gap between the inner race 16c and the ball 16b is made smaller than A.

  Therefore, the first bearing 14 and the second bearing 15 close to the pinion teeth 9 receive a load with respect to input of force from the rack shaft 10 side and input of force from the motor 21 side. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

  Further, since the second bearing 15 is a radial roller bearing having a small radial dimension, the second bearing 15 can be brought close to the pinion teeth 9. Therefore, the distance between the first bearing 14 and the second bearing 15 can be shortened, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good. Can do.

  Further, in the power steering apparatus 1 of the first embodiment, the first bearing holding portion 6 a, the second bearing holding portion 6 c, and the third bearing holding the first bearing 14, the second bearing 15, and the third bearing 16 in the first housing 6. A bearing holding portion 6d was provided.

  Therefore, it is possible to hold all the bearings that support the pinion shaft 8 in the first housing 6, and the assembly accuracy of the first bearing 14, the second bearing 15, and the third bearing 16 can be improved.

  In the power steering apparatus 1 of the first embodiment, the first housing 6 has an opening on the steering input shaft 7 side, that is, on the upper side, and the inner diameter of the second bearing holding portion 6c is larger than the inner diameter of the first bearing holding portion 6a. The inner diameter of the third bearing holding portion 6d is larger than the inner diameter of the second bearing holding portion 6c.

  Accordingly, the first bearing holding portion 6a, the second bearing holding portion 6c, and the third bearing holding portion 6d can be all processed from the upper side, and the first bearing holding portion 6a, the second bearing holding portion 6c, and the third bearing holding can be processed. The workability of the part 6d can be improved. Moreover, the 1st bearing 14, the 2nd bearing 15, and the 3rd bearing 16 can be assembled | attached from the upper side, and the assembly workability | operativity of the 1st bearing 14, the 2nd bearing 15, and the 3rd bearing 16 can be improved.

In the power steering device 1 of the first embodiment, the first bearing 14 is configured by a roller bearing.
Since the roller bearing has a large load resistance against the size of the outer diameter, it is possible to sufficiently secure the load resistance of the first bearing 14 while reducing the outer diameter of the first bearing 14 and the outer diameter of the second bearing 15. .

In the power steering device 1 of the first embodiment, a radial ball bearing is used as the third bearing 16 so that a load in the thrust direction can be received.
Therefore, the first bearing 14 and the second bearing 15 can be bearings that receive only a radial load, and the degree of freedom in selecting the first bearing 14 and the second bearing 15 close to the pinion teeth 9 is increased. A bearing having a small outer diameter can be selected. Therefore, the first bearing 14 and the second bearing 15 can be brought closer to the pinion teeth 9, and the distance between the first bearing 14 and the second bearing 15 can be reduced to increase the bending rigidity of the pinion shaft 8. The meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

In the power steering device 1 of the first embodiment, the first bearing 14, the second bearing 15, and the third bearing 16 are inserted into the pinion shaft 8 from the first bearing 14, that is, from the lower side.
Therefore, all the bearings that support the pinion shaft 8 can be inserted from the same direction, and the assembly workability of the first bearing 14, the second bearing 15, and the third bearing 16 can be improved.

Further, the power steering apparatus 1 of the first embodiment includes a worm wheel 19 provided on the pinion shaft 8 and a worm shaft 20 that transmits a steering assist force from the motor 21 to the worm wheel 19. It was inserted into the pinion shaft from the 7th side, that is, the upper side.
Since the worm wheel 19 is inserted from the upper side of the pinion shaft 8 and the third bearing 16 is inserted from the lower side of the pinion shaft 8 as described above, by providing one flange portion 8d on the pinion shaft 8, The flange portion 8 d can also serve as both abutting portions for the worm wheel 19 and the third bearing 16.

In the power steering apparatus 1 of the first embodiment, the first bearing 14 and the second bearing 15 are always subjected to a radial load when the vehicle goes straight and when the vehicle is steered.
Therefore, since the first bearing 14 and the second bearing 15 close to the pinion teeth 9 always receive a radial load, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be improved. Can keep good.

  Further, in the power steering apparatus 1 of the first embodiment, the radial gap on the side where the opposing members formed between the first housing 6 or the pinion shaft 8 and the second bearing 15 rotate relative to each other in the circumferential direction. The smallest part is assembled so that the pinion shaft 8 and the members facing the pinion shaft 8 are always in contact with each other. In other words, the pinion shaft 8 and the roller 15b are always in contact with each other in the radial gap formed between the pinion shaft 8 and the roller 15b of the second bearing 15 and the smallest portion in the circumferential direction.

  Therefore, since the first bearing 14 and the second bearing 15 close to the pinion teeth 9 always receive a radial load, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be improved. Can keep good.

[effect]
Below, the effect of the power steering apparatus 1 of Example 1 is listed.

  (1) The first housing 6 having the pinion shaft accommodating portion 41, the rack shaft 10 having the rack teeth 10a connected to the steered wheels 40 of the vehicle, the rack shaft 10 provided rotatably in the first housing 6 , A pinion shaft 8 having pinion teeth 9 meshing with the rack teeth 10a in a state shifted from a position orthogonal to the steering wheel 7, a steering input shaft 7 connected to the pinion shaft 8, a steering input shaft 7, a pinion shaft 8, and a rack shaft A motor 21 for applying a steering assist force to a steering mechanism composed of 10 and a pinion tooth 9 on the opposite side of the steering input shaft 7, and the pinion shaft 8 is pivoted with respect to the first housing 6. A first bearing 14 to be supported and a second bearing 15 provided on the side of the steering input shaft 7 with respect to the pinion teeth 9, supporting the pinion shaft 8 with respect to the first housing 6, and constituted by a roller bearing. A third bearing 16 provided on the steering input shaft 7 side with respect to the second bearing 15 and supporting the pinion shaft 8 with respect to the first housing 6, and the first housing 6 or the pinion shaft 8. The radial gap at the smallest portion in the circumferential direction, which is a radial gap on the side where the opposing members rotate relative to each other and formed between the second bearing 15 and the first housing 6 or the pinion shaft 8, The members formed between the three bearings 16 and facing each other are made smaller than any part in the circumferential direction of the radial gap on the side where the relative rotation is performed.

  The smallest portion (size B) of the radial clearance between the second bearing 15 and the pinion shaft 8 is the smallest portion (size A) of the radial clearance between the ball 16b and the inner race 16c of the third bearing 16. ) Is set smaller. Therefore, the first bearing 14 and the second bearing 15 close to the pinion teeth 9 receive a load with respect to input of force from the rack shaft 10 side and input of force from the motor 21 side. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

  Further, since the second bearing 15 is a radial roller bearing having a small radial dimension, the second bearing 15 can be brought close to the pinion teeth 9. Therefore, the distance between the first bearing 14 and the second bearing 15 can be shortened, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good. Can do.

  (2) In addition to the configuration described in (1) above, the first housing 6 includes a first bearing 14, a second bearing 15, and a third bearing 16 that are held in the first housing 6 that is a single block. It has 1 bearing holding part 6a, 2nd bearing holding part 6c, and 3rd bearing holding part 6d.

  Therefore, it is possible to hold all the bearings that support the pinion shaft 8 in the first housing 6 that is a single block, and to improve the assembly accuracy of the first bearing 14, the second bearing 15, and the third bearing 16. Can do.

  (3) In addition to the configuration described in (2) above, the first housing 6 has an opening on the steering input shaft 7 side, and the inner diameter of the second bearing holding portion 6c is the inner diameter of the first bearing holding portion 6a. The inner diameter of the third bearing holding part 6d is larger than the inner diameter of the second bearing holding part 6c.

  Accordingly, the first bearing holding portion 6a, the second bearing holding portion 6c, and the third bearing holding portion 6d can be all processed from the upper side, and the first bearing holding portion 6a, the second bearing holding portion 6c, and the third bearing holding can be processed. The workability of the part 6d can be improved. Moreover, the 1st bearing 14, the 2nd bearing 15, and the 3rd bearing 16 can be assembled | attached from the upper side, and the assembly workability | operativity of the 1st bearing 14, the 2nd bearing 15, and the 3rd bearing 16 can be improved.

(4) In addition to the configuration described in (3) above, the first bearing 14 is configured by a roller bearing.
Since the roller bearing has a large load resistance against the size of the outer diameter, it is possible to sufficiently secure the load resistance of the first bearing 14 while making the outer diameter of the first bearing 14 smaller than the outer diameter of the second bearing 15. .

(5) In addition to the configuration described in (1) above, the third bearing 16 is a ball bearing capable of receiving a load in the thrust direction.
Therefore, the first bearing 14 and the second bearing 15 can be bearings that receive only a radial load, and the degree of freedom in selecting the first bearing 14 and the second bearing 15 close to the pinion teeth 9 is increased. A bearing having a small outer diameter can be selected. Therefore, the distance between the first bearing 14 and the second bearing 15 can be reduced to increase the bending rigidity of the pinion shaft 8, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

(6) In addition to the configuration described in (1) above, the first bearing 14, the second bearing 15, and the third bearing 16 are inserted into the pinion shaft 8 from the first bearing 14 side.
Therefore, all the bearings that support the pinion shaft 8 can be inserted from the same direction, and the assembly workability of the first bearing 14, the second bearing 15, and the third bearing 16 can be improved.

(7) In addition to the configuration described in (6) above, the worm wheel 19 further includes a worm wheel 19 provided on the pinion shaft 8 and a worm shaft 20 that transmits a steering assist force from the motor 21 to the worm wheel 19. 19 is inserted into the pinion shaft 8 from the steering input shaft 7 side.
Since the worm wheel 19 is inserted from the upper side of the pinion shaft 8 and the third bearing 16 is inserted from the lower side of the pinion shaft 8 as described above, by providing one flange portion 8d on the pinion shaft 8, The flange portion 8 d can also serve as both abutting portions for the worm wheel 19 and the third bearing 16.

(8) In addition to the configuration described in (1) above, the first bearing 14 is a roller bearing.
Since the roller bearing has a large load resistance against the size of the outer diameter, it is possible to sufficiently secure the load resistance of the first bearing 14 while reducing the outer diameter of the first bearing 14 and the outer diameter of the second bearing 15. .

(9) In addition to the configuration described in (1) above, the first bearing 14 and the second bearing 15 are always subjected to a radial load.
Therefore, since the first bearing 14 and the second bearing 15 close to the pinion teeth 9 always receive a radial load, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be improved. Can keep good.

  (10) In addition to the configuration described in (1) above, there is a radial clearance on the side where the opposing members formed between the first housing 6 or the pinion shaft 8 and the second bearing 15 rotate relative to each other. The smallest part in the circumferential direction was assembled so that the pinion shaft 8 and the members facing the pinion shaft 8 were always in contact with each other.

  Therefore, since the first bearing 14 and the second bearing 15 close to the pinion teeth 9 always receive a radial load, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be improved. Can keep good.

A configuration of the power steering apparatus 1 according to the second embodiment will be described. The same components as those of the power steering device 1 of the first embodiment are denoted by the same reference numerals and description thereof is omitted.
In the power steering apparatus 1 of the first embodiment, the second bearing 15 is provided above the pinion teeth 9. However, in the power steering apparatus 1 of the second embodiment, the second bearing 15 is provided so as to overlap the pinion teeth 9.

[Gearbox configuration]
FIG. 4 is a partial cross-sectional view of the gear box 29. The gear box 29 has a first housing 6 that accommodates the pinion shaft 8, the rack shaft 10, and the like, and a second housing 5 that accommodates the worm wheel 19, the worm shaft 20, the steering input shaft 7, the torque sensor 4, and the like.

  In the following description, in FIG. 4, the axial directions of the steering input shaft 7 and the pinion shaft 8 are the lower side on the pinion shaft 8 side and the upper side on the steering input shaft 7 side.

(Configuration of pinion shaft)
Pinion teeth 9 are formed on the lower side of the pinion shaft 8. The pinion teeth 9 are formed by cutting, and a rounded-up portion 9a is formed on the root side.
A first bearing insertion portion 8 a having a smaller diameter than the outer diameter of the pinion teeth 9 is formed below the pinion teeth 9 of the pinion shaft 8.
A stopper insertion portion 8j having a smaller diameter than the first bearing insertion portion 8a is formed below the first bearing insertion portion 8a of the pinion shaft 8.

A second bearing insertion portion 8 b having a diameter larger than the outer diameter of the pinion teeth 9 is formed above the pinion teeth 9 of the pinion shaft 8.
A flange portion 8d having a diameter larger than that of the second bearing insertion portion 8b is formed on the pinion shaft 8 above the second bearing insertion portion 8b.

On the upper side of the flange portion 8d of the pinion shaft 8, a worm wheel fitting portion 8e having a diameter smaller than that of the flange portion 8d and larger than that of the second bearing insertion portion 8b is formed.
An outer cylinder engaging portion 8 f is formed at the upper end of the pinion shaft 8.

A hollow portion is formed at the upper end of the pinion shaft 8 in the shape of a bottomed cup that opens above the pinion shaft 8, and the steering formed in the hollow portion along the shape of the pinion shaft insertion portion 7 e of the steering input shaft 7. An input shaft insertion portion 8h is formed.
A torsion bar fitting portion 8g is formed at the bottom of the opening of the pinion shaft.

(Configuration of first housing)
The first housing 6 has a pinion shaft accommodating portion 41 having openings on the upper side and the lower side, and a first bearing holding portion 6a is formed in the lower opening.

A pinion tooth accommodating portion 6b having a smaller diameter than the first bearing holding portion 6a is formed above the first bearing holding portion 6a of the first housing 6. The pinion tooth accommodating portion 6 b is formed larger than the outer diameter of the pinion teeth 9.
A second bearing holding portion 6c having a larger diameter than the pinion tooth accommodating portion 6b is formed above the pinion tooth accommodating portion 6b of the first housing 6.

On the upper end of the first housing 6, a second housing engaging portion 6g that is convex upward is formed. A concave seal member insertion portion 6h is formed on the outer peripheral side surface of the second housing engaging portion 6g. A seal member 94 is inserted into the seal member insertion portion 6h.
The first housing 6 is provided with a rack shaft housing portion 6 i formed to extend in the twisting direction with respect to the axial direction of the pinion shaft 8. At a position where the rack shaft housing portion 6i and the pinion tooth housing portion 6b intersect, the rack shaft housing portion 6i and the pinion tooth housing portion 6b communicate with each other.

In the first housing 6, a pressing portion accommodating portion 6 j is formed in a direction perpendicular to the axial direction of the pinion shaft 8 at a position where the rack shaft accommodating portion 6 i and the pinion tooth accommodating portion 6 b communicate with each other.
The first housing 6 has a bolt insertion portion 6f formed at a position away from the pinion tooth accommodating portion 6b and the like in the radial direction.

(Gearbox assembly)
Since the assembly of the steering input shaft 7 and the torque sensor 4 to the second housing is the same as in the first embodiment, only the assembly of the pinion shaft 8 to the first housing 6 will be described below.

  The cylindrical member 24 is press-fitted from the lower side of the pinion shaft 8 and is fitted into the second bearing insertion portion 8b. In the state where the cylindrical member 24 is fitted to the second bearing insertion portion 8 b, the lower portion overlaps the portion where the pinion teeth 9 are formed. The cylindrical member 24 is cured, and the axial length of the cylindrical member 24 is longer than the axial length of the second bearing 15 described later.

After the cylindrical member 24 is press-fitted, the second bearing 15, which is a radial roller bearing, is inserted from the lower side of the pinion shaft 8 and is fitted to the outer periphery of the cylindrical member 24. The second bearing 15 is overlapped with a part of the portion where the pinion teeth 9 are formed in a state where the second bearing 15 is fitted to the cylindrical member 24.
Further, the worm wheel 19 is inserted from the upper side of the pinion shaft 8 and fitted to the worm wheel fitting portion 8e. The lower surface of the worm wheel 19 is in contact with the upper surface of the flange portion 8d.

  The pinion shaft 8 with the second bearing 15 and the worm wheel 19 attached thereto is inserted from the upper opening of the first housing 6. When the pinion shaft 8 is inserted into the first housing 6, the second bearing 15 is held by the second bearing holding portion 6c.

  After the pinion shaft 8 is inserted into the first housing 6, the first bearing 23, which is a radial ball bearing, is inserted from the lower opening of the first housing 6 and fitted into the first bearing insertion portion 8a. At this time, the first bearing 23 is held by the first bearing holding portion 6 a of the first housing 6. Further, the upper surface of the outer race 23a of the first bearing 23 abuts the stepped portion 6k between the first bearing holding portion 6a and the pinion tooth accommodating portion 6b, and the upper surface of the inner race 23c abuts the lower end surface 9c of the pinion tooth 9.

  After the first bearing 23 is inserted into the pinion shaft 8, the stopper 89 is inserted into the tip end of the pinion shaft 8 from the lower opening of the first housing 6 and fitted into the stopper insertion portion 8 j of the pinion shaft 8. The outer diameter of the stopper 89 is substantially the same as the outer diameter of the inner race 23 c of the first bearing 23, and the first bearing 23 is sandwiched between the lower end surface 9 c of the pinion teeth 9.

  After the stopper 89 is inserted into the pinion shaft 8, the sealing member 98 is inserted into the lower opening of the first housing 6. The sealing member 98 is locked to the first housing 6 by a locking member 99. The upper surface of the sealing member 98 abuts on the outer race 23 a of the first bearing 23 and sandwiches the first bearing 23 with the step 6 k of the first housing 6.

Next, the vicinity of the rack shaft 10 will be described.
The rack shaft 10 is inserted into the rack shaft housing portion 6 i of the first housing 6.
After the rack shaft 10 is inserted into the rack shaft housing portion 6i, the pressing member 11 is inserted into the pressing portion housing portion 6j. A contact surface 11 a is formed on the surface of the pressing member 11 on the rack shaft 10 side along the curved surface of the back surface of the rack tooth 10 a of the rack shaft 10, and the contact surface 11 a contacts the rack shaft 10. A hollow spring insertion portion 11b is formed on the opposite side of the contact surface 11a of the pressing member 11, and the spring 13 is inserted into the spring insertion portion 11b.

  Next, the stopper 12 is inserted into the pressing portion accommodating portion 6j. A hollow spring insertion portion 12a is formed on the pressing member 11 side of the stopper 12, and the spring 13 is inserted into the spring insertion portion 12a. The stopper 12 is locked to the first housing 6 by a locking member 93.

[Action]
When the pinion shaft 8 is shortened, the bending rigidity of the pinion shaft 8 is higher and the meshing state between the pinion teeth 9 and the rack teeth 10a is improved. However, the pinion shaft 8 needs to be lengthened for convenience of layout.

  For example, as in the power steering device 1 of the second embodiment, the axial direction of the pinion shaft 8 and the axial direction of the rack shaft 10 are in a twisted position. Further, the pinion assist type power steering device 1 needs to be provided with a motor 21 in the vicinity of the pinion shaft 8. However, since the motor 21 is relatively bulky, the pinion shaft 8 is lengthened to separate the motor 21 from the meshing position of the pinion teeth 9 and the rack teeth 10a so that the motor 21 and the housing that houses the rack shaft 10 do not interfere with each other. There is a need.

  Therefore, in the power steering device 1 according to the second embodiment, the first pinion shaft 8 is supported by the first housing 6 on the opposite side of the steering input shaft 7 from the pinion teeth 9, that is, on the lower side of the pinion teeth 9. One bearing 23 was provided. In addition, the pinion shaft 8 is located with respect to the first housing 6 at a position on the steering input shaft 7 side with respect to the pinion teeth 9, that is, on the upper side of the pinion teeth 9 and overlapping with the raised portion 9 a of the pinion teeth 9. A supporting second bearing 15 was provided.

  Therefore, the second bearing 15 can be brought closer to the pinion teeth, and the distance between the first bearing 23 and the second bearing 15 can be shortened. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

Further, in the power steering device 1 of the second embodiment, the cylindrical member 24 is provided on the outer peripheral side of the pinion shaft 8 so as to overlap with the raised portion 9a of the pinion tooth 9, and the second bearing 15 is provided as the cylindrical member. 24 on the outer peripheral side and provided in the axial range.
Therefore, since the second bearing 15 is held by the cylindrical member 24 in the entire axial direction, the holding performance of the second bearing 15 can be improved.

  Further, in the power steering device 1 of the second embodiment, a part of the cylindrical member 24 overlaps with a part where the pinion teeth 9 are formed, and the other part is a part where the pinion teeth 9 are not formed, that is, the pinion shaft above the pinion teeth 9. 8 so as to overlap.

  Therefore, the cylindrical member 24 can be fitted to the pinion shaft 8, and the retainability of the cylindrical member 24 can be improved.

In the power steering device 1 of the second embodiment, the cylindrical member 24 is press-fitted into the pinion shaft 8.
Therefore, the cylindrical member 24 can be assembled with a simple structure, and the assembling work can be improved.

Moreover, in the power steering apparatus 1 of Example 2, the cylindrical member 24 was cured.
Therefore, it is possible to ensure the load resistance of the second bearing 15 on which a high load acts on the radial load.

In the power steering device 1 of the second embodiment, a radial ball bearing that can receive a load in the thrust direction is used for the first bearing 23.
Therefore, the second bearing 15 can be a bearing that receives only a load in the radial direction, and the degree of freedom in selecting the second bearing 15 is increased, so that a bearing having a small outer diameter can be selected. Therefore, the second bearing 15 can be provided on the pinion tooth 9 side to reduce the distance between the first bearing 23 and the second bearing 15. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

In the power steering device 1 of the second embodiment, the first bearing 23 is inserted into the first housing 6 from the first bearing 23 side, that is, from the lower side.
Therefore, it is possible to select a bearing having an outer diameter of the first bearing 23 larger than the outer diameter of the second bearing 15, and a sufficient load resistance of the first bearing can be ensured.

In the power steering device 1 of the second embodiment, the second bearing 15 is constituted by a roller bearing.
Therefore, since the radial dimension of the second bearing 14 can be reduced, the distance between the first bearing 23 and the second bearing 15 can be shortened by bringing the second bearing 14 closer to the pinion teeth 9. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

[effect]
The effects of the power steering apparatus 1 according to the second embodiment are listed below.

  (11) The first housing 6 having the pinion shaft accommodating portion 41, the rack shaft 10 having the rack teeth 10a connected to the steered wheels 40, and the first housing 6 are rotatably provided. From the pinion shaft 8 having pinion teeth 9 meshing with the rack teeth 10 a in a state shifted from the orthogonal position, the steering input shaft 7 connected to the pinion shaft 8, the steering input shaft 7, the pinion shaft 8 and the rack shaft 10. A motor 21 that applies a steering assist force to the configured steering mechanism, and a pinion tooth 9 that is provided on the opposite side of the steering input shaft 7, and supports the pinion shaft 8 with respect to the first housing 6. The first bearing 23 is provided on the side of the steering input shaft 7 with respect to the pinion teeth 9 and is provided so that at least a part of the formation portion of the pinion teeth 9 overlaps the first housing. And to have a second bearing 15 for supporting the pinion shaft 8, the relative.

  Therefore, the second bearing 15 can be brought closer to the pinion teeth, and the distance between the first bearing 23 and the second bearing 15 can be shortened. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

(12) In addition to the configuration described in the above (11), a tubular member 24 provided on the outer peripheral side of the pinion shaft 8 so as to at least partially overlap with the formation portion of the pinion teeth 9 is further provided. The second bearing 15 is provided on the outer peripheral side of the cylindrical member 24 and within the axial range.
Therefore, since the second bearing 15 is held by the cylindrical member 24 in the entire axial direction, the holding performance of the second bearing 15 can be improved.

(13) In addition to the configuration described in (12) above, the cylindrical member 24 includes a part of the cylindrical member 24 that overlaps with a part where the pinion teeth 9 are formed, and the remaining part is a part where the pinion teeth 9 are not formed. And provided to overlap.
Therefore, the cylindrical member 24 can be fitted to the pinion shaft 8, and the retainability of the cylindrical member 24 can be improved.

(14) In addition to the configuration described in (12) above, the cylindrical member 24 is press-fitted into the pinion shaft 8.
Therefore, the cylindrical member 24 can be assembled with a simple structure, and the assembling work can be improved.

(15) In addition to the configuration described in (12) above, the cylindrical member 24 is subjected to a curing treatment.
Therefore, it is possible to ensure the load resistance of the second bearing 15 on which a high load acts on the radial load.

(16) In addition to the configuration described in (11) above, the first bearing 23 is a thrust bearing.
Therefore, the second bearing 15 can be a bearing that receives only a load in the radial direction, and the degree of freedom in selecting the second bearing 15 is increased, so that a bearing having a small outer diameter can be selected. Therefore, the second bearing 15 can be provided on the pinion tooth 9 side, and the distance between the first bearing 23 and the second bearing 15 can be reduced. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

(17) In addition to the configuration described in (16) above, the first bearing 23 is inserted into the first housing 6 from the first bearing 23 side with respect to the pinion teeth 9.
Therefore, it is possible to select a bearing having an outer diameter of the first bearing 23 larger than the outer diameter of the second bearing 15, and a sufficient load resistance of the first bearing can be ensured.

(18) In addition to the configuration described in (11) above, the second bearing 15 is configured by a roller bearing.
Therefore, since the radial dimension of the second bearing 14 can be reduced, the distance between the first bearing 23 and the second bearing 15 can be shortened by bringing the second bearing 14 closer to the pinion teeth 9. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

A configuration of the power steering apparatus 1 according to the third embodiment will be described. The same components as those of the power steering device 1 of the first embodiment are denoted by the same reference numerals and description thereof is omitted.
In the power steering device 1 of the first embodiment, the pinion teeth 9 are formed by cutting, but in the power steering device 1 of the third embodiment, the pinion teeth 9 are formed by forging or rolling. In the power steering device 1 of the first embodiment, a radial roller bearing is used as the first bearing 14, but in the power steering device 1 of the third embodiment, a radial ball bearing is used as the first bearing 23.

[Gearbox configuration]
FIG. 5 is a partial cross-sectional view of the gear box 29. The gear box 29 has a first housing 6 that accommodates the pinion shaft 8, the rack shaft 10, and the like, and a second housing 5 that accommodates the worm wheel 19, the worm shaft 20, the steering input shaft 7, the torque sensor 4, and the like.

  In the following description, in FIG. 5, the axial directions of the steering input shaft 7 and the pinion shaft 8 are the lower side on the pinion shaft 8 side and the upper side on the steering input shaft 7 side.

(Configuration of pinion shaft)
An even number of pinion teeth 9 are formed below the pinion shaft 8. The pinion teeth 9 are formed by forging or rolling, and the cut-up portion 9b is formed smaller than the case where the pinion teeth 9 are formed by cutting.
A first bearing insertion portion 8 a having a smaller diameter than the outer diameter of the pinion teeth 9 is formed at the lower end of the pinion shaft 8.

A second bearing insertion portion 8 b having a diameter larger than the outer diameter of the pinion teeth 9 is formed above the pinion teeth 9 of the pinion shaft 8.
A third bearing insertion portion 8c having a larger diameter than the second bearing insertion portion 8b is formed above the second bearing insertion portion 8b of the pinion shaft 8.

  A flange portion 8d having a diameter larger than that of the third bearing insertion portion 8c is formed on the pinion shaft 8 above the third bearing insertion portion 8c. The flange portion 8d is formed to have substantially the same diameter as an outer diameter of an inner race 16c of the third bearing 16 described later. Further, on the outer peripheral side surface of the third bearing insertion portion 8c, the diameter of the third bearing insertion portion 8c is smaller than that of the third bearing insertion portion 8c in the vicinity of a position separated from the lower side surface of the flange portion 8d in the axial direction thickness of the third bearing 16 described later. A concave groove-shaped ring locking portion 8i is formed.

On the upper side of the flange portion 8d of the pinion shaft 8, a worm wheel fitting portion 8e having a diameter smaller than that of the flange portion 8d and larger than that of the third bearing insertion portion 8c is formed.
An outer cylinder engaging portion 8 f is formed at the upper end of the pinion shaft 8.

A hollow portion is formed in the shape of a bottomed cup that opens above the pinion shaft 8, and a steering input shaft insertion portion 8h that is formed along the shape of the pinion shaft insertion portion 7e of the steering input shaft 7 is formed in the opening. Yes.
A torsion bar fitting portion 8g is formed at the bottom of the opening of the pinion shaft.

(Configuration of first housing)
The first housing 6 has a pinion shaft accommodating portion 41 having openings on the upper side and the lower side, and a first bearing holding portion 6a is formed in the lower opening.

A pinion tooth accommodating portion 6b having a smaller diameter than the first bearing holding portion 6a is formed above the first bearing holding portion 6a of the first housing 6. The pinion tooth accommodating portion 6 b is formed larger than the outer diameter of the pinion teeth 9.
A second bearing holding portion 6c having a larger diameter than the pinion tooth accommodating portion 6b is formed above the pinion tooth accommodating portion 6b of the first housing 6.

  On the upper side of the second housing holding portion 6c of the first housing 6, a step portion 6m perpendicular to the axial direction is formed after the diameter is increased in a curved shape. The inner diameter of the step portion 6m is formed to be substantially the same as the inner diameter of an outer race 16a of the third bearing 16 described later, and the outer diameter is formed to be substantially the same as the outer diameter of the outer race 16a.

A third bearing holding portion 6d having the same diameter as the outer diameter of the step portion 6m is formed continuously with the step portion 6m.
A locking ring fitting portion 6e having a diameter larger than that of the third bearing holding portion 6d is formed above the third bearing holding portion 6d of the first housing 6.

On the upper end of the first housing 6, a second housing engaging portion 6g that is convex upward is formed. A concave seal member insertion portion 6h is formed on the outer peripheral side surface of the second housing engaging portion 6g. A seal member 94 is inserted into the seal member insertion portion 6h.
The first housing 6 is provided with a rack shaft housing portion 6 i formed to extend in the twisting direction with respect to the axial direction of the pinion shaft 8. At a position where the rack shaft housing portion 6i and the pinion tooth housing portion 6b intersect, the rack shaft housing portion 6i and the pinion tooth housing portion 6b communicate with each other.

In the first housing 6, a pressing portion accommodating portion 6 j is formed in a direction perpendicular to the axial direction of the pinion shaft 8 at a position where the rack shaft accommodating portion 6 i and the pinion tooth accommodating portion 6 b communicate with each other.
The first housing 6 has a bolt insertion portion 6f formed at a position away from the pinion tooth accommodating portion 6b and the like in the radial direction.

(Gearbox assembly)
Since the assembly of the steering input shaft 7 and the torque sensor 4 to the second housing 5 is the same as in the first embodiment, only the assembly of the pinion shaft 8 to the first housing 6 will be described below.

  A third bearing 16, which is a radial ball bearing, is inserted from below the pinion shaft 8 and is fitted to the third bearing insertion portion 8 c. At this time, the upper side surface of the third bearing 16 contacts the lower side surface of the flange portion 8d. Further, the ring 96 is inserted from the lower side of the pinion shaft 8 and engaged with the ring locking portion 8i. The upper side of the ring 96 is formed to have a larger diameter than the inner diameter of the inner race 16 c of the third bearing 16, and the movement of the third bearing 16 in the axial direction is restricted by the ring 96.

The second bearing 15 which is a radial roller bearing is inserted from the lower side of the pinion shaft 8 and is fitted to the second bearing insertion portion 8b.
With the second bearing 15 and the third bearing 16 attached to the pinion shaft 8, the pinion shaft 8 is inserted from the upper opening of the first housing 6. When the pinion shaft 8 is inserted into the first housing 6, the second bearing 15 is held by the second bearing holding portion 6c, and the third bearing 16 is held by the third bearing holding portion 6d. At this time, the lower surface of the third bearing 16 is in contact with the step portion 6m.

  After the pinion shaft 8 is inserted into the first housing 6, the first bearing 23, which is a radial ball bearing, is inserted from the lower opening of the first housing 6 and fitted into the first bearing insertion portion 8 a. At this time, the first bearing 23 is held by the first bearing holding portion 6a of the first housing 6, and the upper surface of the outer race 23a of the first bearing 23 is between the first bearing holding portion 6a and the pinion tooth accommodating portion 6b. It contacts the step 6k.

  The sealing member 98 is inserted into the lower opening of the first housing 6. The sealing member 98 is locked to the first housing 6 by a locking member 99. The upper surface of the sealing member 98 abuts on the outer race 23 a of the first bearing 23 and sandwiches the first bearing 23 with the step 6 k of the first housing 6.

  Next, the locking ring 88 is inserted and fitted into the locking ring fitting portion 6e. At this time, the lower surface of the locking ring 88 contacts the upper surface of the outer race 16 a of the third bearing 16. Therefore, the outer race 16a is sandwiched between the step portion 6m and the locking ring 88 to restrict the axial movement of the third bearing 16.

  Thereafter, the worm wheel 19 is inserted from the upper side of the pinion shaft 8 and fitted to the worm wheel fitting portion 8e. The lower surface of the worm wheel 19 is in contact with the upper surface of the flange portion 8d.

Next, the vicinity of the rack shaft 10 will be described.
The rack shaft 10 is inserted into the rack shaft housing portion 6 i of the first housing 6.
After the rack shaft 10 is inserted into the rack shaft housing portion 6i, the pressing member 11 is inserted into the pressing portion housing portion 6j. A contact surface 11 a is formed on the surface of the pressing member 11 on the rack shaft 10 side along the curved surface of the back surface of the rack tooth 10 a of the rack shaft 10, and the contact surface 11 a is contacted with the rack shaft 10. A hollow spring insertion portion 11b is formed on the opposite side of the contact surface 11a of the pressing member 11, and the spring 13 is inserted into the spring insertion portion 11b.

  Next, the stopper 12 is inserted into the pressing portion accommodating portion 6j. A hollow spring insertion portion 12a is formed on the pressing member 11 side of the stopper 12, and the spring 13 is inserted into the spring insertion portion 12a. The stopper 12 is locked to the first housing 6 by a locking member 93.

[Bearing configuration]
FIG. 6 is an axial sectional view and a circumferential sectional view of the first bearing 23, the second bearing 15, and the third bearing 16.

  The 3rd bearing 16 is comprised from the outer race 16a, the ball | bowl 16b, and the inner race 16c, as shown to Fig.3 (a). The third bearing insertion portion 8c of the pinion shaft 8 is fitted to the inner periphery of the inner race 16c. The outer periphery of the outer race 16 a is supported by the third bearing holding portion 6 d of the first housing 6. Therefore, the outer race 16 a does not rotate relative to the first housing 6, and the inner race 16 c does not rotate relative to the pinion shaft 8. The balls 16b are arranged at substantially equal intervals in the circumferential direction by a gauge, and rotate relative to the outer race 16a and the inner race 16c with the gauge as the rotation of the ball 16b in the revolution direction. The third bearing 16 is a radial ball bearing, but can receive a thrust load.

  As shown in FIG. 3B, the second bearing 15 includes an outer race 15a and a roller 15b. Rollers 15b are arranged at substantially equal intervals in the circumferential direction on the inner peripheral side of the outer race 15a and are rotatably supported. The second bearing insertion portion 8b of the pinion shaft 8 is inserted inside the rollers 15b arranged on the circumference. The outer periphery of the outer race 15 a is held by the second bearing holding portion 6 c of the first housing 6. Therefore, the outer race 15 a does not rotate relative to the first housing 6. Since the roller 15b is supported by the outer race 15a, the rotation of the roller 15b in the revolution direction is prevented from rotating relative to the first housing 6.

  As shown in FIG. 6C, the first bearing 23 includes an outer race 23a, balls 23b, and an inner race 23c. The first bearing insertion portion 8a of the pinion shaft 8 is fitted to the inner periphery of the inner race 23c. The outer periphery of the outer race 23 a is held by the first bearing holding portion 6 a of the first housing 6. Therefore, the outer race 23 a does not rotate relative to the first housing 6, and the inner race 23 c does not rotate relative to the pinion shaft 8. The balls 23b are arranged at substantially equal intervals in the circumferential direction by a gauge, and the balls 23b rotate relative to the outer race 23a and the inner race 23c together with the gauge in the revolution direction of the balls 23b. The first bearing 23 is a radial ball bearing, but can also receive a thrust load.

  Here, in order to support the pinion shaft 8 by the first bearing 23 and the second bearing 15 which are close to the pinion tooth 9 among the first bearing 23, the second bearing 15 and the third bearing 16, the diameter of the third bearing 16 is used. The radial clearance between the first bearing 23 and the second bearing 15 needs to be smaller than the directional clearance. For that purpose, it is necessary to design in the range which set the radial direction clearance of the 1st bearing 23, the 2nd bearing 15, and the 3rd bearing 16. FIG. The radial clearances of the first bearing 23, the second bearing 15, and the third bearing 16 are a member that rotates relative to the first housing 6 or the pinion shaft 8 (hereinafter referred to as a relative rotating member) and a member that faces the relative rotating member. (Hereinafter, a radial gap with an opposing member) is shown.

  In the third bearing 16, the relative rotation members for the first housing 6 are the balls 16b and the inner races 16c, and the relative rotation members for the pinion shaft 8 are the balls 16b and the outer races 16a. In the third bearing 16, opposing members for the ball 16b are the outer race 16a and the inner race 16c, and opposing members for the outer race 16a and the inner race 16c are the balls 16b.

  That is, the radial clearance of the third bearing 16 indicates the radial clearance between the outer race 16a and the ball 16b and the radial clearance between the inner race 16c and the ball 16b. Here, of the radial gap between the outer race 16a and the ball 16b and the radial gap between the inner race 16c and the ball 16b, the size of the radial gap at the smallest portion in the circumferential direction is defined as D.

  In the second bearing 15, the relative rotation member with respect to the first housing 6 is the pinion shaft 8, and the relative rotation member with respect to the pinion shaft 8 is a roller 15b. In the second bearing 15, the facing member for the pinion shaft 8 is the roller 15 b, and the facing member for the roller 15 b is the pinion shaft 8.

  That is, the radial clearance of the second bearing 15 indicates the radial clearance between the roller 15 b and the pinion shaft 8. Here, E is the size of the radial gap between the roller 15b and the pinion shaft 8 and the smallest radial gap in the circumferential direction.

  In the first bearing 23, the relative rotation members for the first housing 6 are balls 23b and inner races 23c, and the relative rotation members for the pinion shaft 8 are balls 23b and outer races 23a. In the first bearing 23, the opposing members for the ball 23b are the outer race 23a and the inner race 23c, and the opposing members for the outer race 23a and the inner race 23c are the balls 23b.

  That is, the radial clearance of the first bearing 23 indicates the radial clearance between the outer race 23a and the ball 23b and the radial clearance between the inner race 23c and the ball 23b. Here, the radial gap between the outer race 23a and the ball 23b and the radial gap between the inner race 23c and the ball 23b, and the size of the radial gap at the smallest portion in the circumferential direction is defined as F.

  At this time, the first bearing 23, the second bearing 15, and the third bearing 16 are formed such that the sizes of the respective radial clearances are “D ≧ E” and “D ≧ F”. That is, the radial load of the pinion shaft 8 is always received by the first bearing 14 and the second bearing 15.

[Action]
When the pinion shaft 8 is shortened, the bending rigidity of the pinion shaft 8 is higher and the meshing state between the pinion teeth 9 and the rack teeth 10a is improved. However, the pinion shaft 8 needs to be lengthened for convenience of layout.

  For example, in the power steering device 1 according to the third embodiment, the axial direction of the pinion shaft 8 and the axial direction of the rack shaft 10 are in a twisted position. Further, the pinion assist type power steering device 1 needs to be provided with a motor 21 in the vicinity of the pinion shaft 8. However, since the motor 21 is relatively bulky, the pinion shaft 8 is lengthened to separate the motor 21 from the meshing position of the pinion teeth 9 and the rack teeth 10a so that the motor 21 and the housing that houses the rack shaft 10 do not interfere with each other. There is a need.

Therefore, in the power steering device 1 of the third embodiment, the pinion teeth 9 are formed by forging or rolling.
Therefore, the cut-up portion 9b of the pinion tooth 9 can be made smaller than when the pinion tooth 9 is formed by cutting. Therefore, the second bearing 15 can be brought close to the pinion teeth, and the distance between the first bearing 23 and the second bearing 15 can be shortened. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

In the power steering device 1 of the third embodiment, a radial ball bearing is used as the first bearing 23 so that it can receive a load in the thrust direction.
Therefore, the second bearing 15 can be a bearing that receives only a radial load, and a radial roller bearing having a small outer diameter can be selected. Therefore, the distance between the first bearing 23 and the second bearing 15 can be reduced by bringing the second bearing 15 closer to the pinion teeth 9. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

In the power steering device 1 of Example 3, an even number of pinion teeth 9 is provided in the circumferential direction.
Therefore, the pinion teeth 9 can be formed by rolling.

[effect]
Below, the effect of the power steering apparatus 1 of Example 3 is listed.

  (19) The first housing 6 having the pinion shaft accommodating portion 41, the rack shaft 10 connected to the steered wheels 40 and having the rack teeth 10a, and the first housing 6 are rotatably provided. And the pinion shaft 8 having the pinion teeth 9 formed by forging or rolling while being engaged with the rack teeth 10a in a state of being deviated from the orthogonal position, the steering input shaft 7 connected to the pinion shaft 8, and the steering input shaft 7 A motor 21 for applying a steering assist force to the steering mechanism constituted by the pinion shaft 8 and the rack shaft 10, and a pinion tooth 9 on the opposite side of the steering input shaft 7. A first bearing 23 that supports the pinion shaft 8 and a second shaft that is on the steering input shaft 7 side with respect to the pinion teeth 9 and supports the pinion shaft 8 with respect to the first housing 6. 16 and a third bearing 16 provided on the steering input shaft 7 side with respect to the second bearing 16 and supporting the pinion shaft 8 with respect to the first housing 6, and the first housing 6 or the pinion shaft 8. Between the first housing 6 and the pinion shaft 8, and the radial gap at the smallest portion in the circumferential direction. The members formed between the third bearings 23 and facing each other are made smaller than any portion in the circumferential direction of the radial gap on the side where the relative rotation is performed.

  Therefore, the cut-up portion 9b of the pinion tooth 9 can be made smaller than when the pinion tooth 9 is formed by cutting. Therefore, the second bearing 15 can be brought close to the pinion teeth, and the distance between the first bearing 23 and the second bearing 15 can be shortened. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

(20) In addition to the configuration described in (19) above, the first bearing 23 is a ball bearing capable of receiving a load in the thrust direction.
Therefore, the second bearing 15 can be a bearing that receives only a radial load, and a radial roller bearing having a small outer diameter can be selected. Therefore, the distance between the first bearing 23 and the second bearing 15 can be reduced by bringing the second bearing 15 closer to the pinion teeth 9. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

(21) In addition to the configuration described in (19) above, an even number of pinion teeth 9 is provided in the circumferential direction.
Therefore, the pinion teeth 9 can be formed by rolling.

A configuration of the power steering apparatus 1 according to the fourth embodiment will be described. The same components as those of the power steering device 1 of the first to third embodiments are denoted by the same reference numerals and description thereof is omitted.
In the power steering device 1 of the first embodiment, the second bearing 15 is provided above the pinion teeth 9. However, in the power steering device 1 of the fourth embodiment, the second bearing 15 is provided so as to overlap the pinion teeth 9.

[Gearbox configuration]
FIG. 7 is a partial cross-sectional view of the gear box 29. The gear box 29 has a first housing 6 that accommodates the pinion shaft 8, the rack shaft 10, and the like, and a second housing 5 that accommodates the worm wheel 19, the worm shaft 20, the steering input shaft 7, the torque sensor 4, and the like.

  In the following description, in FIG. 7, the axial directions of the steering input shaft 7 and the pinion shaft 8 are the lower side on the pinion shaft 8 side and the upper side on the steering input shaft 7 side.

(Configuration of pinion shaft)
Pinion teeth 9 are formed on the lower side of the pinion shaft 8. The pinion teeth 9 are formed by cutting, and a rounded-up portion 9a is formed on the root side.
A first bearing insertion portion 8 a having a smaller diameter than the outer diameter of the pinion teeth 9 is formed at the lower end of the pinion shaft 8.

  A flange portion 8d having a diameter larger than that of the third bearing insertion portion 8c is formed on the pinion shaft 8 above the third bearing insertion portion 8c. The flange portion 8d is formed to have substantially the same diameter as an outer diameter of an inner race 16c of the third bearing 16 described later. Further, on the outer peripheral side surface of the third bearing insertion portion 8c, the diameter of the third bearing insertion portion 8c is smaller than that of the third bearing insertion portion 8c in the vicinity of a position separated from the lower side surface of the flange portion 8d in the axial direction thickness of the third bearing 16 described later. A concave groove-shaped ring locking portion 8i is formed.

A second bearing insertion portion 8 b having a diameter larger than the outer diameter of the pinion teeth 9 is formed above the pinion teeth 9 of the pinion shaft 8.
A third bearing insertion portion 8c having a larger diameter than the second bearing insertion portion 8b is formed above the second bearing insertion portion 8b of the pinion shaft 8.

  A flange portion 8d having a diameter larger than that of the third bearing insertion portion 8c is formed on the pinion shaft 8 above the third bearing insertion portion 8c. The flange portion 8d is formed to have substantially the same diameter as an outer diameter of an inner race 16c of the third bearing 16 described later. Further, on the outer peripheral side surface of the third bearing insertion portion 8c, the diameter of the third bearing insertion portion 8c is smaller than that of the third bearing insertion portion 8c in the vicinity of a position separated from the lower side surface of the flange portion 8d in the axial direction thickness of the third bearing 16 described later. A concave groove-shaped ring locking portion 8i is formed.

On the upper side of the flange portion 8d of the pinion shaft 8, a worm wheel fitting portion 8e having a diameter smaller than that of the flange portion 8d and larger than that of the third bearing insertion portion 8c is formed.
An outer cylinder engaging portion 8 f is formed at the upper end of the pinion shaft 8.

A hollow portion is formed in a bottomed cup shape opened on the upper side of the pinion shaft 8, and a steering input shaft insertion portion 8h formed along the shape of the pinion shaft insertion portion 7e of the steering input shaft 7 is formed in the hollow portion. ing.
A torsion bar fitting portion 8g is formed at the bottom of the opening of the pinion shaft.

(Configuration of first housing)
The first housing 6 has a pinion shaft accommodating portion 41 having openings on the upper side and the lower side, and a first bearing holding portion 6a is formed in the lower opening.

A pinion tooth accommodating portion 6b having a smaller diameter than the first bearing holding portion 6a is formed above the first bearing holding portion 6a of the first housing 6. The pinion tooth accommodating portion 6 b is formed larger than the outer diameter of the pinion teeth 9.
A second bearing holding portion 6c having a larger diameter than the pinion tooth accommodating portion 6b is formed above the pinion tooth accommodating portion 6b of the first housing 6.

  On the upper side of the second housing holding portion 6c of the first housing 6, a step portion 6m perpendicular to the axial direction is formed after the diameter is increased in a curved shape. The inner diameter of the step portion 6m is formed to be substantially the same as the inner diameter of an outer race 16a of the third bearing 16 described later, and the outer diameter is formed to be substantially the same as the outer diameter of the outer race 16a.

A third bearing holding portion 6d having the same diameter as the outer diameter of the step portion 6m is formed continuously with the step portion 6m.
A locking ring fitting portion 6e having a diameter larger than that of the third bearing holding portion 6d is formed above the third bearing holding portion 6d of the first housing 6.
On the upper end of the first housing 6, a second housing engaging portion 6g that is convex upward is formed. A concave seal member insertion portion 6h is formed on the outer peripheral side surface of the second housing engaging portion 6g. A seal member 94 is inserted into the seal member insertion portion 6h.

  The first housing 6 is provided with a rack shaft housing portion 6 i formed to extend in the twisting direction with respect to the axial direction of the pinion shaft 8. At a position where the rack shaft housing portion 6i and the pinion tooth housing portion 6b intersect, the rack shaft housing portion 6i and the pinion tooth housing portion 6b communicate with each other.

In the first housing 6, a pressing portion accommodating portion 6 j is formed in a direction perpendicular to the axial direction of the pinion shaft 8 at a position where the rack shaft accommodating portion 6 i and the pinion tooth accommodating portion 6 b communicate with each other.
The first housing 6 has a bolt insertion portion 6f formed at a position away from the pinion tooth accommodating portion 6b and the like in the radial direction.

(Gearbox assembly)
Since the assembly of the steering input shaft 7 and the torque sensor 4 to the second housing is the same as in the first embodiment, only the assembly of the pinion shaft 8 to the first housing 6 will be described below.

  A third bearing 16, which is a radial ball bearing, is inserted from below the pinion shaft 8 and is fitted to the third bearing insertion portion 8 c. At this time, the upper side surface of the third bearing 16 contacts the lower side surface of the flange portion 8d. Further, the ring 96 is inserted from the lower side of the pinion shaft 8 and engaged with the ring locking portion 8i. The upper side of the ring 96 is formed to have a larger diameter than the inner diameter of the inner race 16 c of the third bearing 16, and the movement of the third bearing 16 in the axial direction is restricted by the ring 96.

  The cylindrical member 24 is press-fitted from the lower side of the pinion shaft 8 and is fitted into the second bearing insertion portion 8b. In the state where the cylindrical member 24 is fitted to the second bearing insertion portion 8 b, the lower portion overlaps the portion where the pinion teeth 9 are formed. The cylindrical member 24 is cured, and the axial length of the cylindrical member 24 is longer than the axial length of the second bearing 15 described later.

  After the cylindrical member 24 is inserted, the second bearing 15, which is a radial roller bearing, is inserted from the lower side of the pinion shaft 8 and is fitted to the outer periphery of the cylindrical member 24. The second bearing 15 is overlapped with a part of the portion where the pinion teeth 9 are formed in a state where the second bearing 15 is fitted to the cylindrical member 24.

  The pinion shaft 8 with the second bearing 15 and the third bearing 16 attached thereto is inserted from the upper opening of the first housing 6. When the pinion shaft 8 is inserted into the first housing 6, the second bearing 15 is held by the second bearing holding portion 6c, and the third bearing 16 is held by the third bearing holding portion 6d. At this time, the lower surface of the third bearing 16 is in contact with the step portion 6m.

  After the pinion shaft 8 is inserted into the first housing 6, the locking ring 88 is inserted into the locking ring fitting portion 6e and fitted. The lower surface of the locking ring 88 contacts the upper surface of the outer race 16 a of the third bearing 16. Therefore, the outer race 16a is sandwiched between the step 6m and the locking ring 88 to restrict the axial movement of the third bearing 16.

  Thereafter, the worm wheel 19 is inserted from the upper side of the pinion shaft 8 and is fitted to the worm wheel fitting portion 8e. The lower surface of the worm wheel 19 is in contact with the upper surface of the flange portion 8d.

Next, the vicinity of the rack shaft 10 will be described.
The rack shaft 10 is inserted into the rack shaft housing portion 6 i of the first housing 6.
After the rack shaft 10 is inserted into the rack shaft housing portion 6i, the pressing member 11 is inserted into the pressing portion housing portion 6j. A contact surface 11 a is formed on the surface of the pressing member 11 on the rack shaft 10 side along the curved surface of the back surface of the rack tooth 10 a of the rack shaft 10, and the contact surface 11 a contacts the rack shaft 10. A hollow spring insertion portion 11b is formed on the opposite side of the contact surface 11a of the pressing member 11, and the spring 13 is inserted into the spring insertion portion 11b.

  Next, the stopper 12 is inserted into the pressing portion accommodating portion 6j. A hollow spring insertion portion 12a is formed on the pressing member 11 side of the stopper 12, and the spring 13 is inserted into the spring insertion portion 12a. The stopper 12 is locked to the first housing 6 by a locking member 93.

[Action]
When the pinion shaft 8 is shortened, the bending rigidity of the pinion shaft 8 is higher and the meshing state between the pinion teeth 9 and the rack teeth 10a is improved. However, the pinion shaft 8 needs to be lengthened for convenience of layout.

  For example, in the power steering device 1 according to the fourth embodiment, the axial direction of the pinion shaft 8 and the axial direction of the rack shaft 10 are in a twisted position. Further, the pinion assist type power steering device 1 needs to be provided with a motor 21 in the vicinity of the pinion shaft 8. However, since the motor 21 is relatively bulky, the pinion shaft 8 is lengthened to separate the motor 21 from the meshing position of the pinion teeth 9 and the rack teeth 10a so that the motor 21 and the housing that houses the rack shaft 10 do not interfere with each other. There is a need.

  Therefore, in the power steering device 1 according to the fourth embodiment, the first pinion shaft 8 is supported by the first housing 6 on the opposite side of the steering input shaft 7 from the pinion teeth 9, that is, below the pinion teeth 9. One bearing 23 was provided. In addition, the pinion shaft 8 is located with respect to the first housing 6 at a position on the steering input shaft 7 side with respect to the pinion teeth 9, that is, on the upper side of the pinion teeth 9 and overlapping with the raised portion 9 a of the pinion teeth 9. A supporting second bearing 15 was provided.

  Therefore, the second bearing 15 can be brought closer to the pinion teeth, and the distance between the first bearing 23 and the second bearing 15 can be shortened. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

[effect]
Below, the effect of the power steering apparatus 1 of Example 4 is described.

  (22) The first housing 6 having the pinion shaft accommodating portion 41, the rack shaft 10 having the rack teeth 10a connected to the steered wheels 40, and the first housing 6 are rotatably provided. From the pinion shaft 8 having the pinion teeth 9 meshing with the rack teeth 10 a in a state shifted from the orthogonal position, the steering input shaft 7 connected to the pinion shaft 8, the steering input shaft 7, the pinion shaft 8 and the rack shaft 10. A motor 21 that applies a steering assist force to the configured steering mechanism, and a pinion tooth 9 that is provided on the opposite side of the steering input shaft 7, and supports the pinion shaft 8 with respect to the first housing 6. The first bearing 23 is provided on the side of the steering input shaft 7 with respect to the pinion teeth 9 and is provided so that at least a part of the formation portion of the pinion teeth 9 overlaps the first housing. And to have a second bearing 15 for supporting the pinion shaft 8, the relative.

  Therefore, the second bearing 15 can be brought closer to the pinion teeth, and the distance between the first bearing 23 and the second bearing 15 can be shortened. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

The configuration of the power steering apparatus 1 according to the fifth embodiment will be described. The same components as those of the power steering device 1 of the first to fourth embodiments are denoted by the same reference numerals and description thereof is omitted.
In the power steering device 1 of the first embodiment, the second bearing 15 is provided above the pinion teeth 9. However, in the power steering device 1 of the fifth embodiment, the second bearing 15 is provided so as to overlap the pinion teeth 9.

[Gearbox configuration]
FIG. 8 is a partial cross-sectional view of the gear box 29. The gear box 29 includes a first housing 6 that accommodates the pinion shaft 8, the rack shaft 10, and the like, and a second housing 5 that accommodates the worm wheel 19, the worm shaft 20, the steering input shaft 7, the torque sensor 4, and the like.

  In the following description, in FIG. 8, the axial direction of the steering input shaft 7 and the pinion shaft 8 is the lower side on the pinion shaft 8 side and the upper side on the steering input shaft 7 side.

(Configuration of pinion shaft)
Pinion teeth 9 are formed on the lower side of the pinion shaft 8. The pinion teeth 9 are formed by cutting, and a rounded-up portion 9a is formed on the root side.
A first bearing insertion portion 8 a having a smaller diameter than the outer diameter of the pinion teeth 9 is formed at the lower end of the pinion shaft 8.

A second bearing insertion portion 8 b having a diameter larger than the outer diameter of the pinion teeth 9 is formed above the pinion teeth 9 of the pinion shaft 8.
A third bearing insertion portion 8c having a larger diameter than the second bearing insertion portion 8b is formed above the second bearing insertion portion 8b of the pinion shaft 8.

  A flange portion 8d having a diameter larger than that of the third bearing insertion portion 8c is formed on the pinion shaft 8 above the third bearing insertion portion 8c. The flange portion 8d is formed to have substantially the same diameter as an outer diameter of an inner race 16c of the third bearing 16 described later. Further, on the outer peripheral side surface of the third bearing insertion portion 8c, the diameter of the third bearing insertion portion 8c is smaller than that of the third bearing insertion portion 8c in the vicinity of a position separated from the lower side surface of the flange portion 8d in the axial direction thickness of the third bearing 16 described later. A concave groove-shaped ring locking portion 8i is formed.

On the upper side of the flange portion 8d of the pinion shaft 8, a worm wheel fitting portion 8e having a diameter smaller than that of the flange portion 8d and larger than that of the third bearing insertion portion 8c is formed.
An outer cylinder engaging portion 8 f is formed at the upper end of the pinion shaft 8.

A hollow portion is formed in a bottomed cup shape opened on the upper side of the pinion shaft 8, and a steering input shaft insertion portion 8h formed along the shape of the pinion shaft insertion portion 7e of the steering input shaft 7 is formed in the hollow portion. ing.
A torsion bar fitting portion 8g is formed at the bottom of the opening of the pinion shaft.

(Configuration of first housing)
The first housing 6 has a bottomed cup-shaped hollow pinion shaft accommodating portion 41 having an opening on the upper side and a bottom on the lower side, and a first bearing holding portion 6a is formed on the bottom.

A pinion tooth accommodating portion 6b having a diameter larger than that of the first bearing holding portion 6a is formed above the first bearing holding portion 6a of the first housing 6. The pinion tooth accommodating portion 6 b is formed larger than the outer diameter of the pinion teeth 9.
A second bearing holding portion 6c having a larger diameter than the pinion tooth accommodating portion 6b is formed above the pinion tooth accommodating portion 6b of the first housing 6.

  On the upper side of the second housing holding portion 6c of the first housing 6, a step portion 6m perpendicular to the axial direction is formed after the diameter is increased in a curved shape. The inner diameter of the step portion 6m is formed to be substantially the same as the inner diameter of an outer race 16a of the third bearing 16 described later, and the outer diameter is formed to be substantially the same as the outer diameter of the outer race 16a.

A third bearing holding portion 6d having the same diameter as the outer diameter of the step portion 6m is formed continuously with the step portion 6m.
A locking ring fitting portion 6e having a diameter larger than that of the third bearing holding portion 6d is formed above the third bearing holding portion 6d of the first housing 6.

On the upper end of the first housing 6, a second housing engaging portion 6g that is convex upward is formed. A concave seal member insertion portion 6h is formed on the outer peripheral side surface of the second housing engaging portion 6g. The seal member 94 is inserted into the seal member insertion portion 6h.
The first housing 6 is provided with a rack shaft housing portion 6 i formed to extend in the twisting direction with respect to the axial direction of the pinion shaft 8. At a position where the rack shaft housing portion 6i and the pinion tooth housing portion 6b intersect, the rack shaft housing portion 6i and the pinion tooth housing portion 6b communicate with each other.

In the first housing 6, a pressing portion accommodating portion 6 j is formed in a direction perpendicular to the axial direction of the pinion shaft 8 at a position where the rack shaft accommodating portion 6 i and the pinion tooth accommodating portion 6 b communicate with each other.
The first housing 6 has a bolt insertion portion 6f formed at a position away from the pinion tooth accommodating portion 6b and the like in the radial direction.

(Gearbox assembly)
Since the assembly of the steering input shaft 7 and the torque sensor 4 to the second housing is the same as in the first embodiment, only the assembly of the pinion shaft 8 to the first housing 6 will be described below.

  A third bearing 16, which is a radial ball bearing, is inserted from below the pinion shaft 8 and is fitted to the third bearing insertion portion 8 c. At this time, the upper side surface of the third bearing 16 contacts the lower side surface of the flange portion 8d. Further, the ring 96 is inserted from the lower side of the pinion shaft 8 and engaged with the ring locking portion 8i. The upper side of the ring 96 is formed to have a larger diameter than the inner diameter of the inner race 16 c of the third bearing 16, and the movement of the third bearing 16 in the axial direction is restricted by the ring 96.

  The cylindrical member 24 is press-fitted from the lower side of the pinion shaft 8 and is fitted into the second bearing insertion portion 8b. In the state where the cylindrical member 24 is fitted to the second bearing insertion portion 8 b, the lower portion overlaps the portion where the pinion teeth 9 are formed. The cylindrical member 24 is cured, and the axial length of the cylindrical member 24 is longer than the axial length of the second bearing 15 described later.

After the cylindrical member 24 is inserted, the second bearing 15, which is a radial roller bearing, is inserted from the lower side of the pinion shaft 8 and is fitted to the outer periphery of the cylindrical member 24. The second bearing 15 is overlapped with a part of the portion where the pinion teeth 9 are formed in a state where the second bearing 15 is fitted to the cylindrical member 24.
A first bearing 14 that is a radial roller bearing is inserted from the lower side of the pinion shaft 8 and fitted into the first bearing insertion portion 8a.

  The pinion shaft 8 with the first bearing 14, the second bearing 15, and the third bearing 16 attached thereto is inserted from the upper opening of the first housing 6. When the pinion shaft 8 is inserted into the first housing 6, the first bearing 14 is held in the first bearing holding portion 6a, the second bearing 15 is held in the second bearing holding portion 6c, and the third bearing 16 is held in the third bearing holding portion 6d. Is done. At this time, the lower surface of the third bearing 16 is in contact with the step portion 6m.

  After the pinion shaft 8 is inserted into the first housing 6, the locking ring 88 is inserted into the locking ring fitting portion 6e and fitted. At this time, the lower surface of the locking ring 88 contacts the upper surface of the outer race 16 a of the third bearing 16. Therefore, the outer race 16a is clamped by the step 6m and the locking ring 88, and the third bearing 16 is restricted from moving in the axial direction.

  Thereafter, the worm wheel 19 is inserted from the upper side of the pinion shaft 8 and is fitted to the worm wheel fitting portion 8e. The lower surface of the worm wheel 19 is in contact with the upper surface of the flange portion 8d.

Next, the vicinity of the rack shaft 10 will be described.
The rack shaft 10 is inserted into the rack shaft housing portion 6 i of the first housing 6.
After the rack shaft 10 is inserted into the rack shaft housing portion 6i, the pressing member 11 is inserted into the pressing portion housing portion 6j. A contact surface 11 a is formed on the surface of the pressing member 11 on the rack shaft 10 side along the curved surface of the back surface of the rack tooth 10 a of the rack shaft 10, and the contact surface 11 a is contacted with the rack shaft 10. A hollow spring insertion portion 11b is formed on the opposite side of the contact surface 11a of the pressing member 11, and the spring 13 is inserted into the spring insertion portion 11b.

  Next, the stopper 12 is inserted into the pressing portion accommodating portion 6j. A hollow spring insertion portion 12a is formed on the pressing member 11 side of the stopper 12, and the spring 13 is inserted into the spring insertion portion 12a. The stopper 12 is locked to the first housing 6 by a locking member 93.

[Action]
When the pinion shaft 8 is shortened, the bending rigidity of the pinion shaft 8 is higher and the meshing state between the pinion teeth 9 and the rack teeth 10a is improved. However, the pinion shaft 8 needs to be lengthened for convenience of layout.

  For example, in the power steering device 1 according to the fifth embodiment, the axial direction of the pinion shaft 8 and the axial direction of the rack shaft 10 are in a twisted position. Further, the pinion assist type power steering device 1 needs to be provided with a motor 21 in the vicinity of the pinion shaft 8. However, since the motor 21 is relatively bulky, the pinion shaft 8 is lengthened to separate the motor 21 from the meshing position of the pinion teeth 9 and the rack teeth 10a so that the motor 21 and the housing that houses the rack shaft 10 do not interfere with each other. There is a need.

  Therefore, in the power steering device 1 according to the fifth embodiment, the first pinion shaft 8 is supported by the first housing 6 on the opposite side of the pinion teeth 9 from the steering input shaft 7, that is, below the pinion teeth 9. One bearing 23 was provided. In addition, the pinion shaft 8 is located with respect to the first housing 6 at a position on the steering input shaft 7 side with respect to the pinion teeth 9, that is, on the upper side of the pinion teeth 9 and overlapping with the raised portion 9 a of the pinion teeth 9. A supporting second bearing 15 was provided.

  Therefore, the second bearing 15 can be brought closer to the pinion teeth, and the distance between the first bearing 23 and the second bearing 15 can be shortened. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

[effect]
Below, the effect of the power steering apparatus 1 of Example 5 is described.

  (23) The first housing 6 having the pinion shaft accommodating portion 41, the rack shaft 10 having the rack teeth 10a connected to the steered wheels 40, and the first housing 6 are rotatably provided. From the pinion shaft 8 having the pinion teeth 9 meshing with the rack teeth 10 a in a state shifted from the orthogonal position, the steering input shaft 7 connected to the pinion shaft 8, the steering input shaft 7, the pinion shaft 8 and the rack shaft 10. A motor 21 that applies a steering assist force to the configured steering mechanism, and a pinion tooth 9 that is provided on the opposite side of the steering input shaft 7, and supports the pinion shaft 8 with respect to the first housing 6. The first bearing 23 is provided on the side of the steering input shaft 7 with respect to the pinion teeth 9 and is provided so that at least a part of the formation portion of the pinion teeth 9 overlaps the first housing. And to have a second bearing 15 for supporting the pinion shaft 8, the relative.

  Therefore, the second bearing 15 can be brought closer to the pinion teeth, and the distance between the first bearing 23 and the second bearing 15 can be shortened. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

A configuration of the power steering apparatus 1 according to the sixth embodiment will be described. The same components as those of the power steering device 1 of the first to fifth embodiments are denoted by the same reference numerals and description thereof is omitted.
In the power steering device 1 of the first embodiment, the second bearing 15 is provided above the pinion teeth 9. However, in the power steering device 1 of the fifth embodiment, the second bearing 15 is provided so as to overlap the pinion teeth 9.
In the power steering device 1 of the first embodiment, the pinion teeth 9 are formed by cutting, but in the power steering device 1 of the sixth embodiment, the pinion teeth 9 are formed by forging or rolling.

[Gearbox configuration]
FIG. 9 is a partial cross-sectional view of the gear box 29. The gear box 29 includes a first housing 6 that accommodates the pinion shaft 8, the rack shaft 10, and the like, and a second housing 5 that accommodates the worm wheel 19, the worm shaft 20, the steering input shaft 7, the torque sensor 4, and the like.

  In the following description, in FIG. 9, the axial direction of the steering input shaft 7 and the pinion shaft 8 is the lower side on the pinion shaft 8 side and the upper side on the steering input shaft 7 side.

(Configuration of pinion shaft)
An even number of pinion teeth 9 are formed below the pinion shaft 8. The pinion teeth 9 are formed by forging or rolling, and the cut-up portion 9b is formed smaller than the case where the pinion teeth 9 are formed by cutting.
A first bearing insertion portion 8 a having a smaller diameter than the outer diameter of the pinion teeth 9 is formed at the lower end of the pinion shaft 8.

A second bearing insertion portion 8 b having a diameter larger than the outer diameter of the pinion teeth 9 is formed above the pinion teeth 9 of the pinion shaft 8.
A third bearing insertion portion 8c having a larger diameter than the second bearing insertion portion 8b is formed above the second bearing insertion portion 8b of the pinion shaft 8.

  A flange portion 8d having a diameter larger than that of the third bearing insertion portion 8c is formed on the pinion shaft 8 above the third bearing insertion portion 8c. The flange portion 8d is formed to have substantially the same diameter as an outer diameter of an inner race 16c of the third bearing 16 described later. Further, on the outer peripheral side surface of the third bearing insertion portion 8c, the diameter of the third bearing insertion portion 8c is smaller than that of the third bearing insertion portion 8c in the vicinity of a position separated from the lower side surface of the flange portion 8d in the axial direction thickness of the third bearing 16 described later. A concave groove-shaped ring locking portion 8i is formed.

On the upper side of the flange portion 8d of the pinion shaft 8, a worm wheel fitting portion 8e having a diameter smaller than that of the flange portion 8d and larger than that of the third bearing insertion portion 8c is formed.
An outer cylinder engaging portion 8 f is formed at the upper end of the pinion shaft 8.

A hollow portion is formed in the shape of a bottomed cup that opens above the pinion shaft 8, and a steering input shaft insertion portion 8h that is formed along the shape of the pinion shaft insertion portion 7e of the steering input shaft 7 is formed in the opening. Yes.
A torsion bar fitting portion 8g is formed at the bottom of the opening of the pinion shaft.

(Configuration of first housing)
The first housing 6 has a bottomed cup-shaped hollow pinion shaft accommodating portion 41 having an opening on the upper side and a bottom on the lower side, and a first bearing holding portion 6a is formed on the bottom.

A pinion tooth accommodating portion 6b having a diameter larger than that of the first bearing holding portion 6a is formed above the first bearing holding portion 6a of the first housing 6. The pinion tooth accommodating portion 6 b is formed larger than the outer diameter of the pinion teeth 9.
A second bearing holding portion 6c having a larger diameter than the pinion tooth accommodating portion 6b is formed above the pinion tooth accommodating portion 6b of the first housing 6.

  On the upper side of the second housing holding portion 6c of the first housing 6, a step portion 6m perpendicular to the axial direction is formed after the diameter is increased in a curved shape. The inner diameter of the step portion 6m is formed to be substantially the same as the inner diameter of an outer race 16a of the third bearing 16 described later, and the outer diameter is formed to be substantially the same as the outer diameter of the outer race 16a.

A third bearing holding portion 6d having the same diameter as the outer diameter of the step portion 6m is formed continuously with the step portion 6m.
A locking ring fitting portion 6e having a diameter larger than that of the third bearing holding portion 6d is formed above the third bearing holding portion 6d of the first housing 6.

On the upper end of the first housing 6, a second housing engaging portion 6g that is convex upward is formed. A concave seal member insertion portion 6h is formed on the outer peripheral side surface of the second housing engaging portion 6g. The seal member 94 is inserted into the seal member insertion portion 6h.
The first housing 6 is provided with a rack shaft housing portion 6 i formed to extend in the twisting direction with respect to the axial direction of the pinion shaft 8. At a position where the rack shaft housing portion 6i and the pinion tooth housing portion 6b intersect, the rack shaft housing portion 6i and the pinion tooth housing portion 6b communicate with each other.

In the first housing 6, a pressing portion accommodating portion 6 j is formed in a direction perpendicular to the axial direction of the pinion shaft 8 at a position where the rack shaft accommodating portion 6 i and the pinion tooth accommodating portion 6 b communicate with each other.
The first housing 6 has a bolt insertion portion 6f formed at a position away from the pinion tooth accommodating portion 6b and the like in the radial direction.

(Gearbox assembly)
Since the assembly of the steering input shaft 7 and the torque sensor 4 to the second housing is the same as in the first embodiment, only the assembly of the pinion shaft 8 to the first housing 6 will be described below.
A third bearing 16, which is a radial ball bearing, is inserted from below the pinion shaft 8 and is fitted to the third bearing insertion portion 8 c. At this time, the upper side surface of the third bearing 16 contacts the lower side surface of the flange portion 8d. Further, the ring 96 is inserted from the lower side of the pinion shaft 8 and engaged with the ring locking portion 8i. The upper side of the ring 96 is formed to have a larger diameter than the inner diameter of the inner race 16 c of the third bearing 16, and the movement of the third bearing 16 in the axial direction is restricted by the ring 96.

The second bearing 15 which is a radial roller bearing is inserted from the lower side of the pinion shaft 8 and is fitted to the second bearing insertion portion 8b.
A first bearing 14 that is a radial roller bearing is inserted from the lower side of the pinion shaft 8 and fitted into the first bearing insertion portion 8a.

  The pinion shaft 8 with the first bearing 14, the second bearing 15, and the third bearing 16 attached thereto is inserted from the upper opening of the first housing 6. When the pinion shaft 8 is inserted into the first housing 6, the first bearing 14 is held in the first bearing holding portion 6a, the second bearing 15 is held in the second bearing holding portion 6c, and the third bearing 16 is held in the third bearing holding portion 6d. Is done. At this time, the lower surface of the third bearing 16 is in contact with the step portion 6m.

  After the pinion shaft 8 is inserted into the first housing 6, the locking ring 88 is inserted into the locking ring fitting portion 6e and fitted. At this time, the lower surface of the locking ring 88 contacts the upper surface of the outer race 16 a of the third bearing 16. Therefore, the outer race 16a is clamped by the step 6m and the locking ring 88, and the third bearing 16 is restricted from moving in the axial direction.

  Thereafter, the worm wheel 19 is inserted from the upper side of the pinion shaft 8 and is fitted into the worm wheel fitting portion 8e. The lower surface of the worm wheel 19 is in contact with the upper surface of the flange portion 8d.

Next, the vicinity of the rack shaft 10 will be described.
The rack shaft 10 is inserted into the rack shaft housing portion 6 i of the first housing 6.
After the rack shaft 10 is inserted into the rack shaft housing portion 6i, the pressing member 11 is inserted into the pressing portion housing portion 6j. A contact surface 11 a is formed on the surface of the pressing member 11 on the rack shaft 10 side along the curved surface of the back surface of the rack tooth 10 a of the rack shaft 10, and the contact surface 11 a is contacted with the rack shaft 10. A hollow spring insertion portion 11b is formed on the opposite side of the contact surface 11a of the pressing member 11, and the spring 13 is inserted into the spring insertion portion 11b.

  Next, the stopper 12 is inserted into the pressing portion accommodating portion 6j. A hollow spring insertion portion 12a is formed on the pressing member 11 side of the stopper 12, and the spring 13 is inserted into the spring insertion portion 12a. The stopper 12 is locked to the first housing 6 by a locking member 93.

[Action]
When the pinion shaft 8 is shortened, the bending rigidity of the pinion shaft 8 is higher and the meshing state between the pinion teeth 9 and the rack teeth 10a is improved. However, the pinion shaft 8 needs to be lengthened for convenience of layout.

  For example, in the power steering apparatus 1 according to the sixth embodiment, the axial direction of the pinion shaft 8 and the axial direction of the rack shaft 10 are in a twisted position. Further, the pinion assist type power steering device 1 needs to be provided with a motor 21 in the vicinity of the pinion shaft 8. However, since the motor 21 is relatively bulky, the pinion shaft 8 is lengthened to separate the motor 21 from the meshing position of the pinion teeth 9 and the rack teeth 10a so that the motor 21 and the housing that houses the rack shaft 10 do not interfere with each other. There is a need.

Therefore, in the power steering device 1 of Example 6, the pinion teeth 9 are formed by forging or rolling.
Therefore, the cut-up portion 9b of the pinion tooth 9 can be made smaller than when the pinion tooth 9 is formed by cutting. Therefore, the second bearing 15 can be brought close to the pinion teeth, and the distance between the first bearing 23 and the second bearing 15 can be shortened. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

[effect]
Below, the effect of the power steering apparatus 1 of Example 6 is described.

  (24) The first housing 6 having the pinion shaft accommodating portion 41, the rack shaft 10 connected to the steered wheels 40 and having the rack teeth 10a, and the first housing 6 are rotatably provided. And the pinion shaft 8 having the pinion teeth 9 formed by forging or rolling while being engaged with the rack teeth 10a in a state of being deviated from the orthogonal position, the steering input shaft 7 connected to the pinion shaft 8, and the steering input shaft 7 A motor 21 for applying a steering assist force to the steering mechanism constituted by the pinion shaft 8 and the rack shaft 10, and a pinion tooth 9 on the opposite side of the steering input shaft 7. A first bearing 23 that supports the pinion shaft 8 and a second shaft that is on the steering input shaft 7 side with respect to the pinion teeth 9 and supports the pinion shaft 8 with respect to the first housing 6. 16 and a third bearing 16 provided on the steering input shaft 7 side with respect to the second bearing 16 and supporting the pinion shaft 8 with respect to the first housing 6, and the first housing 6 or the pinion shaft 8. Between the first housing 6 and the pinion shaft 8, and the radial gap at the smallest portion in the circumferential direction. The members formed between the third bearings 23 and facing each other are made smaller than any portion in the circumferential direction of the radial gap on the side where the relative rotation is performed.

  Therefore, the cut-up portion 9b of the pinion tooth 9 can be made smaller than when the pinion tooth 9 is formed by cutting. Therefore, the second bearing 15 can be brought close to the pinion teeth, and the distance between the first bearing 23 and the second bearing 15 can be shortened. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

A configuration of the power steering apparatus 1 according to the seventh embodiment will be described. The same components as those of the power steering device 1 of the first to sixth embodiments are denoted by the same reference numerals and description thereof is omitted.
In the power steering device 1 of the first embodiment, the pinion teeth 9 are formed by cutting, but in the power steering device 1 of the third embodiment, the pinion teeth 9 are formed by forging or rolling.

[Gearbox configuration]
FIG. 10 is a partial cross-sectional view of the gear box 29. The gear box 29 has a first housing 6 that accommodates the pinion shaft 8, the rack shaft 10, and the like, and a second housing 5 that accommodates the worm wheel 19, the worm shaft 20, the steering input shaft 7, the torque sensor 4, and the like.

  In the following description, in FIG. 4, the axial directions of the steering input shaft 7 and the pinion shaft 8 are the lower side on the pinion shaft 8 side and the upper side on the steering input shaft 7 side.

(Configuration of pinion shaft)
An even number of pinion teeth 9 are formed below the pinion shaft 8. The pinion teeth 9 are formed by forging or rolling, and the cut-up portion 9b is formed smaller than the case where the pinion teeth 9 are formed by cutting.
A first bearing insertion portion 8 a having a smaller diameter than the outer diameter of the pinion teeth 9 is formed below the pinion teeth 9 of the pinion shaft 8.
A stopper insertion portion 8j having a smaller diameter than the first bearing insertion portion 8a is formed below the first bearing insertion portion 8a of the pinion shaft 8.

A second bearing insertion portion 8 b having a diameter larger than the outer diameter of the pinion teeth 9 is formed above the pinion teeth 9 of the pinion shaft 8.
A flange portion 8d having a diameter larger than that of the second bearing insertion portion 8b is formed on the pinion shaft 8 above the second bearing insertion portion 8b.

On the upper side of the flange portion 8d of the pinion shaft 8, a worm wheel fitting portion 8e having a diameter smaller than that of the flange portion 8d and larger than that of the second bearing insertion portion 8b is formed.
An outer cylinder engaging portion 8 f is formed at the upper end of the pinion shaft 8.

A hollow portion is formed at the upper end of the pinion shaft 8 in the shape of a bottomed cup that opens above the pinion shaft 8, and the steering formed in the hollow portion along the shape of the pinion shaft insertion portion 7 e of the steering input shaft 7. An input shaft insertion portion 8h is formed.
A torsion bar fitting portion 8g is formed at the bottom of the opening of the pinion shaft.

(Configuration of first housing)
The first housing 6 has a pinion shaft accommodating portion 41 having openings on the upper side and the lower side, and a first bearing holding portion 6a is formed in the lower opening.

A pinion tooth accommodating portion 6b having a smaller diameter than the first bearing holding portion 6a is formed above the first bearing holding portion 6a of the first housing 6. The pinion tooth accommodating portion 6 b is formed larger than the outer diameter of the pinion teeth 9.
A second bearing holding portion 6c having a larger diameter than the pinion tooth accommodating portion 6b is formed above the pinion tooth accommodating portion 6b of the first housing 6.

On the upper end of the first housing 6, a second housing engaging portion 6g that is convex upward is formed. A concave seal member insertion portion 6h is formed on the outer peripheral side surface of the second housing engaging portion 6g. The seal member 94 is inserted into the seal member insertion portion 6h.
The first housing 6 is provided with a rack shaft housing portion 6 i formed to extend in the twisting direction with respect to the axial direction of the pinion shaft 8. At a position where the rack shaft housing portion 6i and the pinion tooth housing portion 6b intersect, the rack shaft housing portion 6i and the pinion tooth housing portion 6b communicate with each other.

In the first housing 6, a pressing portion accommodating portion 6 j is formed in a direction perpendicular to the axial direction of the pinion shaft 8 at a position where the rack shaft accommodating portion 6 i and the pinion tooth accommodating portion 6 b communicate with each other.
The first housing 6 has a bolt insertion portion 6f formed at a position away from the pinion tooth accommodating portion 6b and the like in the radial direction.

(Gearbox assembly)
Since the assembly of the steering input shaft 7 and the torque sensor 4 to the second housing is the same as in the first embodiment, only the assembly of the pinion shaft 8 to the first housing 6 will be described below.

The second bearing 15 which is a radial roller bearing is inserted from the lower side of the pinion shaft 8 and is fitted to the second bearing insertion portion 8b.
Further, the worm wheel 19 is inserted from the upper side of the pinion shaft 8 and fitted to the worm wheel fitting portion 8e. The lower surface of the worm wheel 19 is in contact with the upper surface of the flange portion 8d.

  The pinion shaft 8 with the second bearing 15 and the worm wheel 19 attached thereto is inserted from the upper opening of the first housing 6. When the pinion shaft 8 is inserted into the first housing 6, the second bearing 15 is held by the second bearing holding portion 6c.

  After the pinion shaft 8 is inserted into the first housing 6, the first bearing 23, which is a radial ball bearing, is inserted from the lower opening of the first housing 6 and fitted into the first bearing insertion portion 8a. At this time, the first bearing 23 is held by the first bearing holding portion 6 a of the first housing 6. Further, the upper surface of the outer race 23a of the first bearing 23 abuts the stepped portion 6k between the first bearing holding portion 6a and the pinion tooth accommodating portion 6b, and the upper surface of the inner race 23c abuts the lower end surface 9c of the pinion tooth 9.

  After the first bearing 23 is inserted into the pinion shaft 8, the stopper 89 is inserted into the tip end of the pinion shaft 8 from the lower opening of the first housing 6 and fitted into the stopper insertion portion 8 j of the pinion shaft 8. The outer diameter of the stopper 89 is substantially the same as the outer diameter of the inner race 23 c of the first bearing 23, and the first bearing 23 is sandwiched between the lower end surface 9 c of the pinion teeth 9.

  After the stopper 89 is inserted into the pinion shaft 8, the sealing member 98 is inserted into the lower opening of the first housing 6. The sealing member 98 is locked to the first housing 6 by a locking member 99. The upper surface of the sealing member 98 abuts on the outer race 23 a of the first bearing 23 and sandwiches the first bearing 23 with the step 6 k of the first housing 6.

Next, the vicinity of the rack shaft 10 will be described.
The rack shaft 10 is inserted into the rack shaft housing portion 6 i of the first housing 6.
After the rack shaft 10 is inserted into the rack shaft housing portion 6i, the pressing member 11 is inserted into the pressing portion housing portion 6j. A contact surface 11 a is formed on the surface of the pressing member 11 on the rack shaft 10 side along the curved surface of the back surface of the rack tooth 10 a of the rack shaft 10, and the contact surface 11 a contacts the rack shaft 10. A hollow spring insertion portion 11b is formed on the opposite side of the contact surface 11a of the pressing member 11, and the spring 13 is inserted into the spring insertion portion 11b.

  Next, the stopper 12 is inserted into the pressing portion accommodating portion 6j. A hollow spring insertion portion 12a is formed on the pressing member 11 side of the stopper 12, and the spring 13 is inserted into the spring insertion portion 12a. The stopper 12 is locked to the first housing 6 by a locking member 93.

[Action]
When the pinion shaft 8 is shortened, the bending rigidity of the pinion shaft 8 is higher and the meshing state between the pinion teeth 9 and the rack teeth 10a is improved. However, the pinion shaft 8 needs to be lengthened for convenience of layout.

  For example, in the power steering device 1 according to the seventh embodiment, the axial direction of the pinion shaft 8 and the axial direction of the rack shaft 10 are in a twisted position. Further, the pinion assist type power steering device 1 needs to be provided with a motor 21 in the vicinity of the pinion shaft 8. However, since the motor 21 is relatively bulky, the pinion shaft 8 is lengthened to separate the motor 21 from the meshing position of the pinion teeth 9 and the rack teeth 10a so that the motor 21 and the housing that houses the rack shaft 10 do not interfere with each other. There is a need.

Therefore, in the power steering device 1 of the seventh embodiment, the pinion teeth 9 are formed by forging or rolling.
Therefore, the cut-up portion 9b of the pinion tooth 9 can be made smaller than when the pinion tooth 9 is formed by cutting. Therefore, the second bearing 15 can be brought close to the pinion teeth, and the distance between the first bearing 23 and the second bearing 15 can be shortened. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

[effect]
Below, the effect of the power steering apparatus 1 of Example 7 is described.

  (25) The first housing 6 having the pinion shaft accommodating portion 41, the rack shaft 10 connected to the steered wheels 40 and having the rack teeth 10a, and the first housing 6 are rotatably provided. And the pinion shaft 8 having the pinion teeth 9 formed by forging or rolling while being engaged with the rack teeth 10a in a state of being deviated from the orthogonal position, the steering input shaft 7 connected to the pinion shaft 8, and the steering input shaft 7 A motor 21 for applying a steering assist force to the steering mechanism constituted by the pinion shaft 8 and the rack shaft 10, and a pinion tooth 9 on the opposite side of the steering input shaft 7. A first bearing 23 that supports the pinion shaft 8 and a second shaft that is on the steering input shaft 7 side with respect to the pinion teeth 9 and supports the pinion shaft 8 with respect to the first housing 6. 16 and a third bearing 16 provided on the steering input shaft 7 side with respect to the second bearing 16 and supporting the pinion shaft 8 with respect to the first housing 6, and the first housing 6 or the pinion shaft 8. Between the first housing 6 and the pinion shaft 8, and the radial gap at the smallest portion in the circumferential direction. The members formed between the third bearings 23 and facing each other are made smaller than any portion in the circumferential direction of the radial gap on the side where the relative rotation is performed.

  Therefore, the cut-up portion 9b of the pinion tooth 9 can be made smaller than when the pinion tooth 9 is formed by cutting. Therefore, the second bearing 15 can be brought close to the pinion teeth, and the distance between the first bearing 23 and the second bearing 15 can be shortened. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

A configuration of the power steering apparatus 1 according to the eighth embodiment will be described.
[Outline of power steering system]
FIG. 11 is a system configuration diagram of the steer-by-wire power steering apparatus 1.
The power steering device 1 includes a steering wheel 30 that is steered by a driver, a steering shaft 31 to which a steering force is input from the steering wheel 30, a torque sensor 3 that detects a steering torque of the driver, and a force in the rotational direction. A rack and pinion unit 27 that converts the force into a directional force, and a gear box 29 that includes a power assist unit 28 that outputs a steering torque according to the steering torque of the driver.

  In the rack and pinion portion 27, the pinion teeth 9 formed on the lower side of the pinion shaft 8 and the rack teeth 10 a formed on the rack shaft 10 are twisted in the axial direction of the pinion shaft 8 with respect to the axial direction of the rack shaft 10. Meshing direction.

  The power assist unit 28 includes a resolver 2 that detects the rotational position of the pinion shaft 8, a worm wheel 19 that rotates integrally with the pinion shaft 8, and a worm shaft 20 that is fixed to the output shaft of the motor 21 and meshes with the worm wheel 19. Have. The torque detected by the torque sensor 3 and the rotational position of the pinion shaft 8 detected by the resolver 2 are input to the ECU 22, and the ECU 22 controls the output torque of the motor 21 based on the input torque information and rotational position information.

  Steering torque is generated by the motor 21 in accordance with the steering torque input to the steering wheel 30 by the driver. The generated steering torque is transmitted to the pinion shaft 8 in the order of the worm shaft 20 and the worm wheel 19. The steering force of the driver transmitted to the pinion shaft 8 and the assist torque of the motor 21 are steered wheels via the pinion shaft 8, the rack shaft 10, the rack end 35, the universal joint 36, the tie rod 37, the tie rod end 38, and the knuckle arm 39. 40.

[Gearbox configuration]
FIG. 12 is a partial cross-sectional view of the gear box 29. The gear box 29 includes a first housing 6 that houses the pinion shaft 8, the rack shaft 10, and the like, and a second housing 5 that houses the worm wheel 19 and the worm shaft 20.

  In the following description, it is the axial direction of the pinion shaft 8 in FIG. 12, and the first housing 6 side is the lower side and the second housing 5 side is the upper side.

(Configuration of pinion shaft)
Pinion teeth 9 are formed on the lower side of the pinion shaft 8. The pinion teeth 9 are formed by cutting, and a rounded-up portion 9a is formed on the root side.
A first bearing insertion portion 8 a having a smaller diameter than the outer diameter of the pinion teeth 9 is formed at the lower end of the pinion shaft 8.

A second bearing insertion portion 8 b having a diameter larger than the outer diameter of the pinion teeth 9 is formed above the pinion teeth 9 of the pinion shaft 8.
A third bearing insertion portion 8c having a larger diameter than the second bearing insertion portion 8b is formed above the second bearing insertion portion 8b of the pinion shaft 8.

  A flange portion 8d having a diameter larger than that of the third bearing insertion portion 8c is formed on the pinion shaft 8 above the third bearing insertion portion 8c. The flange portion 8d is formed to have substantially the same diameter as an outer diameter of an inner race 16c of the third bearing 16 described later. Further, on the outer peripheral side surface of the third bearing insertion portion 8c, the diameter of the third bearing insertion portion 8c is smaller than that of the third bearing insertion portion 8c in the vicinity of a position separated from the lower side surface of the flange portion 8d in the axial direction thickness of the third bearing 16 described later. A concave groove-shaped ring locking portion 8i is formed.

On the upper side of the flange portion 8d of the pinion shaft 8, a worm wheel fitting portion 8e having a diameter smaller than that of the flange portion 8d and larger than that of the third bearing insertion portion 8c is formed.
An outer cylinder engaging portion 8 f is formed at the upper end of the pinion shaft 8.

(Configuration of first housing)
The first housing 6 has a bottomed cup-shaped hollow pinion shaft accommodating portion 41 having an opening on the upper side and a bottom on the lower side, and a first bearing holding portion 6a is formed on the bottom.

A pinion tooth accommodating portion 6b having a diameter larger than that of the first bearing holding portion 6a is formed above the first bearing holding portion 6a of the first housing 6. The pinion tooth accommodating portion 6 b is formed larger than the outer diameter of the pinion teeth 9.
A second bearing holding portion 6c having a larger diameter than the pinion tooth accommodating portion 6b is formed above the pinion tooth accommodating portion 6b of the first housing 6.

  On the upper side of the first housing 6 above the second bearing holding portion 6c, a step portion 6m perpendicular to the axial direction is formed after smoothly expanding the diameter. The inner diameter of the step portion 6m is formed to be substantially the same as the inner diameter of an outer race 16a of the third bearing 16 described later, and the outer diameter is formed to be substantially the same as the outer diameter of the outer race 16a.

A third bearing holding portion 6d having the same diameter as the outer diameter of the step portion 6m is formed continuously with the step portion 6m.
A locking ring fitting portion 6e having a diameter larger than that of the third bearing holding portion 6d is formed above the third bearing holding portion 6d of the first housing 6.

On the upper end of the first housing 6, a second housing engaging portion 6g that is convex upward is formed.
The first housing 6 is provided with a rack shaft housing portion 6 i formed to extend in the twisting direction with respect to the axial direction of the pinion shaft 8. At a position where the rack shaft housing portion 6i and the pinion tooth housing portion 6b intersect, the rack shaft housing portion 6i and the pinion tooth housing portion 6b communicate with each other.

In the first housing 6, a pressing portion accommodating portion 6 j is formed in a direction perpendicular to the axial direction of the pinion shaft 8 at a position where the rack shaft accommodating portion 6 i and the pinion tooth accommodating portion 6 b communicate with each other.
The first housing 6 has a bolt insertion portion 6f formed at a position away from the pinion tooth accommodating portion 6b and the like in the radial direction.

(Configuration of second housing)
The second housing 5 is formed in a bottomed cup shape having an open bottom, and the lower opening of the second housing 5 has a diameter substantially the same as the outer periphery of the second housing engaging portion 6g of the first housing 6. A first housing engaging portion 5h having an inner peripheral surface is formed.

  On the upper side of the first housing engaging portion 5h of the second housing 5, a worm wheel accommodating portion 5a having a smaller diameter than the first housing engaging portion 5h is formed. The worm wheel housing portion 5 a is formed with a larger diameter than the worm wheel 19.

  The second housing 5 is formed with a worm shaft housing portion 5b in a direction perpendicular to the axial direction of the worm wheel housing portion 5a. The worm shaft housing portion 5 b is formed with a larger diameter than the worm shaft 20.

A resolver fixing portion 5i and a bolt insertion portion 5j are formed on the bottom portion on the upper side of the second housing.
In the second housing 5, a bolt insertion portion 5 g is formed at a position where the first housing 6 and the second housing 5 are combined to communicate with the bolt insertion portion 6 f of the first housing 6.

(Resolver configuration)
The resolver 2 includes a stator 2a, a rotor 2b, a stator coil 2c, and a rotor coil 2d. The stator 2 a is installed on the resolver fixing portion 5 i of the second housing 5 and is fixed to the second housing by a bolt 87. The stator coil 2 c is attached to the stator 2 a so as not to rotate relative to the second housing 5. The rotor 2b is fixed to the pinion shaft 8 via an engagement member 2e attached to the pinion shaft 8. The rotor coil 2d is fixed to the rotor 2b so as not to rotate relative to the pinion shaft 8.

  A current is applied to the stator coil 2c, whereby a magnetic flux is generated. Due to the generated magnetic flux, a voltage is excited in the rotor coil 2d constituting the magnetic circuit to generate a current. When the pinion shaft 8 rotates, the voltage of the rotor coil 2d changes for each rotation position. This voltage information is transmitted to the ECU 22.

(Gearbox assembly)
A third bearing 16, which is a radial ball bearing, is inserted from below the pinion shaft 8 and is fitted to the third bearing insertion portion 8 c. At this time, the upper side surface of the third bearing 16 contacts the lower side surface of the flange portion 8d. Further, the ring 96 is inserted from the lower side of the pinion shaft 8 and engaged with the ring locking portion 8i. The upper side of the ring 96 is formed to have a larger diameter than the inner diameter of the inner race 16 c of the third bearing 16, and the movement of the third bearing 16 in the axial direction is restricted by the ring 96.

The second bearing 15 which is a radial roller bearing is inserted from the lower side of the pinion shaft 8 and is fitted to the second bearing insertion portion 8b.
A first bearing 14 that is a radial roller bearing is inserted from the lower side of the pinion shaft 8 and fitted into the first bearing insertion portion 8a.

  The pinion shaft 8 with the first bearing 14, the second bearing 15, and the third bearing 16 attached thereto is inserted from the upper opening of the first housing 6. When the pinion shaft 8 is inserted into the first housing 6, the first bearing 14 is held in the first bearing holding portion 6a, the second bearing 15 is held in the second bearing holding portion 6c, and the third bearing 16 is held in the third bearing holding portion 6d. Is done. At this time, the lower surface of the third bearing 16 is in contact with the step portion 6m.

  After the pinion shaft 8 is inserted into the first housing 6, the locking ring 88 is inserted into the locking ring fitting portion 6e and fitted. At this time, the lower surface of the locking ring 88 contacts the upper surface of the outer race 16 a of the third bearing 16. Therefore, the outer race 16a is clamped by the step 6m and the locking ring 88, and the third bearing 16 is restricted from moving in the axial direction.

  Thereafter, the worm wheel 19 is inserted from the upper side of the pinion shaft 8 and is fitted into the worm wheel fitting portion 8e. The lower surface of the worm wheel 19 is in contact with the upper surface of the flange portion 8d.

Next, the vicinity of the rack shaft 10 will be described.
The rack shaft 10 is inserted into the rack shaft housing portion 6 i of the first housing 6.
After the rack shaft 10 is inserted into the rack shaft housing portion 6i, the first pressing member 42 is inserted into the pressing portion housing portion 6j. On the outer peripheral surface of the first pressing member 42, two rows of groove-shaped seal member insertion portions 42a are formed, and the seal member 86 is inserted into the seal member insertion portion 42a.

  A contact surface 42 b is formed on the surface of the first pressing member 42 on the rack shaft 10 side along the curved surface of the back surface of the rack teeth 10 a of the rack shaft 10. Further, a hollow portion 42c is formed on the opposite side of the contact surface 11a of the first pressing member 42, and a through hole 42d penetrating the contact surface 42b and the hollow portion 42c is formed.

The second pressing member 43 is inserted into the hollow portion 42c. The second pressing member 43 includes a shaft member 43a and a fifth bearing 43b that is a radial ball bearing. The second pressing member 43 is inserted into the hollow portion 42c with the fifth bearing 43b inserted into the second pressing member 43 shaft member 43a, the shaft member 43a is locked at the bottom of the hollow portion 42c, and the fifth bearing 43b is It is inserted into the through hole 42d.
The shaft member 43 a is urged toward the rack shaft 10 by the spring 13 via the urging member 44.

  Next, the stopper 12 is inserted into the pressing portion accommodating portion 6j. A hollow spring insertion portion 12a is formed on the pressing member 11 side of the stopper 12, and the spring 13 is inserted into the spring insertion portion 12a. The stopper 12 is locked to the first housing 6 by a locking member 93.

  Thereby, a small force acting on the rack shaft 10 is received by the fifth bearing 43 b of the second pressing member 43, and a large force is received by the contact surface 42 b of the first pressing member 42.

The worm shaft 20 is inserted into the worm shaft housing portion 5b, and the worm shaft 20 and the worm wheel 19 are engaged with each other.
After the first housing 6 and the second housing 5 are combined, the bolt 92 is inserted into the bolt insertion portion 6f and the bolt insertion portion 5g, and the first housing 6 and the second housing 5 are fixed.

[Bearing configuration]
FIG. 3 is an axial sectional view and a circumferential sectional view of the first bearing 14, the second bearing 15, and the third bearing 16.

  The 3rd bearing 16 is comprised from the outer race 16a, the ball | bowl 16b, and the inner race 16c, as shown to Fig.3 (a). The third bearing insertion portion 8c of the pinion shaft 8 is fitted to the inner periphery of the inner race 16c. The outer periphery of the outer race 16 a is held by the third bearing holding portion 6 d of the first housing 6. Therefore, the outer race 16 a does not rotate relative to the first housing 6, and the inner race 16 c does not rotate relative to the pinion shaft 8. The balls 16b are arranged at substantially equal intervals in the circumferential direction by a gauge, and rotate relative to the outer race 16a and the inner race 16c with the gauge as the rotation of the ball 16b in the revolution direction. The third bearing 16 is a radial ball bearing, but can receive a thrust load.

  As shown in FIG. 3B, the second bearing 15 includes an outer race 15a and a roller 15b. Rollers 15b are arranged at substantially equal intervals in the circumferential direction on the inner peripheral side of the outer race 15a and are rotatably supported. The second bearing insertion portion 8b of the pinion shaft 8 is inserted inside the rollers 15b arranged on the circumference. The outer periphery of the outer race 15 a is held by the second bearing holding portion 6 c of the first housing 6. Therefore, the outer race 15 a does not rotate relative to the first housing 6. Since the roller 15b is supported by the outer race 15a, the rotation of the roller 15b in the revolution direction is prevented from rotating relative to the first housing 6.

  As shown in FIG. 3C, the first bearing 14 includes an outer race 14a and a roller 14b. Rollers 14b are arranged at substantially equal intervals in the circumferential direction on the inner peripheral side of the outer race 14a, and are rotatably supported. The first bearing insertion portion 8a of the pinion shaft 8 is inserted inside the outer race 14a arranged on the circumference. The outer diameter of the first bearing 14 is smaller than the outer diameter of the second bearing 15. The outer circumference of the outer race 14 a is held by the first bearing holding portion 6 a of the first housing 6. Therefore, the outer race 14 a is not rotated relative to the first housing 6. Since the roller 14b is supported by the outer race 14a, the rotation of the roller 14b in the revolving direction is prevented from rotating relative to the first housing 6.

  Here, in order to support the pinion shaft 8 by the first bearing 14 and the second bearing 15 that are close to the pinion tooth 9 among the first bearing 14, the second bearing 15, and the third bearing 16, the diameter of the third bearing 16 is used. The radial gap between the first bearing 14 and the second bearing 15 needs to be smaller than the directional gap. For that purpose, it is necessary to design in the range which set the radial direction clearance of the 1st bearing 14, the 2nd bearing 15, and the 3rd bearing 16. FIG. The radial clearances of the first bearing 14, the second bearing 15, and the third bearing 16 are a member that rotates relative to the first housing 6 or the pinion shaft 8 (hereinafter referred to as a relative rotating member), and a member that faces the relative rotating member. (Hereinafter, a radial gap with an opposing member) is shown.

  In the third bearing 16, the relative rotation members for the first housing 6 are the balls 16b and the inner races 16c, and the relative rotation members for the pinion shaft 8 are the balls 16b and the outer races 16a. In the third bearing 16, opposing members for the ball 16b are the outer race 16a and the inner race 16c, and opposing members for the outer race 16a and the inner race 16c are the balls 16b.

  That is, the radial clearance of the third bearing 16 indicates the radial clearance between the outer race 16a and the ball 16b and the radial clearance between the inner race 16c and the ball 16b. Here, of the radial gap between the outer race 16a and the ball 16b and the radial gap between the inner race 16c and the ball 16b, the size of the smallest radial gap in the circumferential direction is A.

  In the second bearing 15, the relative rotation member with respect to the first housing 6 is the pinion shaft 8, and the relative rotation member with respect to the pinion shaft 8 is a roller 15b. In the second bearing 15, the facing member for the pinion shaft 8 is the roller 15 b, and the facing member for the roller 15 b is the pinion shaft 8.

  That is, the radial clearance of the second bearing 15 indicates the radial clearance between the roller 15 b and the pinion shaft 8. Here, B is the size of the radial gap between the roller 15b and the pinion shaft 8 and the smallest radial gap in the circumferential direction.

  In the first bearing 14, the relative rotation member with respect to the first housing 6 is the pinion shaft 8, and the relative rotation member with respect to the pinion shaft 8 is a roller 14b. In the first bearing 14, the facing member for the pinion shaft 8 is the roller 14 b, and the facing member for the roller 14 b is the pinion shaft 8.

  That is, the radial clearance of the first bearing 14 indicates the radial clearance between the roller 14 b and the pinion shaft 8. Here, C is the size of the radial gap between the roller 14b and the pinion shaft 8 and the smallest radial gap in the circumferential direction.

  At this time, the first bearing 14, the second bearing 15, and the third bearing 16 are formed so that the size of each radial clearance is “A ≧ B” and “A ≧ C”. That is, the radial load of the pinion shaft 8 is always received by the first bearing 14 and the second bearing 15.

[Action]
When the pinion shaft 8 is shortened, the bending rigidity of the pinion shaft 8 is higher and the meshing state between the pinion teeth 9 and the rack teeth 10a is improved. However, the pinion shaft 8 needs to be lengthened for convenience of layout.

  For example, in the power steering apparatus 1 according to the eighth embodiment, the axial direction of the pinion shaft 8 and the axial direction of the rack shaft 10 are in a twisted position. Further, the pinion assist type power steering device 1 needs to be provided with a motor 21 in the vicinity of the pinion shaft 8. However, since the motor 21 is relatively bulky, the pinion shaft 8 is lengthened to separate the motor 21 from the meshing position of the pinion teeth 9 and the rack teeth 10a so that the motor 21 and the housing that houses the rack shaft 10 do not interfere with each other. There is a need.

  Therefore, in the power steering apparatus 1 of the eighth embodiment, the first pinion shaft 8 is supported by the first housing 6 on the opposite side of the pinion teeth 9 from the steering input shaft 7, that is, below the pinion teeth 9. One bearing 14 was provided. A second bearing 15, which is a radial roller bearing that supports the pinion shaft 8 with respect to the first housing 6, is provided on the steering input shaft 7 side with respect to the pinion teeth 9, that is, on the upper side of the pinion teeth 9. A third bearing 16 that supports the pinion shaft 8 with respect to the first housing 6 is provided on the steering input shaft 7 side with respect to the second bearing 15, that is, on the upper side of the second bearing 15.

  Further, B is the radial clearance between the roller 15b of the second bearing 15 and the pinion shaft 8, and the size of the radial clearance at the smallest portion in the circumferential direction is B is the radial clearance between the outer race 16a and the ball 16b. The size of the radial gap at the smallest portion in the circumferential direction of the radial gap between the inner race 16c and the ball 16b is made smaller than A.

  Therefore, the first bearing 14 and the second bearing 15 close to the pinion teeth 9 receive a load with respect to input of force from the rack shaft 10 side and input of force from the motor 21 side. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

[effect]
Below, the effect of the power steering apparatus 1 of Example 8 is described.

  (26) The first housing 6 having the pinion shaft accommodating portion 41, the rack shaft 10 having the rack teeth 10a connected to the steered wheels 40 of the vehicle, and the rack shaft 10 provided rotatably in the first housing 6. , A pinion shaft 8 having pinion teeth 9 meshing with the rack teeth 10a in a state of being deviated from a position perpendicular to the motor, and a motor 21 for applying a steering assist force to a steering mechanism composed of the pinion shaft 8 and the rack shaft 10. A first bearing 14 provided below the pinion teeth 9 and supporting the pinion shaft 8 with respect to the first housing 6, and provided above the pinion teeth 9, with respect to the first housing 6. A pinion shaft 8 is supported on the second bearing 15 constituted by a roller bearing, and is provided on the steering input shaft 7 side with respect to the second bearing 15. A third bearing 16 that supports the shaft, and is a radial gap on the side where the opposing members formed between the first housing 6 or the pinion shaft 8 and the second bearing 15 rotate relative to each other. The radial gap in the smallest portion in the circumferential direction is any of the circumferential gaps of the radial gap formed between the first housing 6 or the pinion shaft 8 and the third bearing 16 and the members facing each other relatively rotate. It was made smaller than that part.

  The smallest portion (size B) of the radial clearance between the second bearing 15 and the pinion shaft 8 is the smallest portion (size A) of the radial clearance between the ball 16b and the inner race 16c of the third bearing 16. ) Is set smaller. Therefore, the first bearing 14 and the second bearing 15 close to the pinion teeth 9 receive a load with respect to input of force from the rack shaft 10 side and input of force from the motor 21 side. Therefore, the bending rigidity of the pinion shaft 8 can be increased, and the meshing state of the pinion teeth 9 and the rack teeth 10a can be kept good.

(Other examples)
In the power steering device 1 according to the first to seventh embodiments, the pinion assist type power steering device has been described. However, as shown in FIG. 13, the power steering device 1 may be used for a column assist type power steering device.

  In the power steering device 1 according to the first to eighth embodiments, the radial roller bearing is used as the second bearing 15, but a sliding bearing may be used.

1 is a system configuration diagram of a power steering apparatus according to Embodiment 1. FIG. It is a fragmentary sectional view of the gear box of Example 1. It is an axial sectional view and a circumferential sectional view of the bearing of Example 1. It is a fragmentary sectional view of the gear box of Example 2. It is a fragmentary sectional view of the gear box of Example 3. FIG. 6 is an axial sectional view and a circumferential sectional view of a bearing of Example 3. It is a fragmentary sectional view of the gear box of Example 4. It is a fragmentary sectional view of the gear box of Example 5. It is a fragmentary sectional view of the gear box of Example 6. FIG. 10 is a partial cross-sectional view of a gear box according to a seventh embodiment. FIG. 10 is a system configuration diagram of a power steering apparatus according to an eighth embodiment. FIG. 10 is a partial cross-sectional view of a gear box according to an eighth embodiment. It is a system block diagram of the power steering apparatus of another Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power steering apparatus 6 1st housing 7 Steering input shaft 8 Pinion shaft 9 Pinion tooth 10 Rack shaft 10a Rack tooth 14 and 23 First bearing 15 Second bearing 16 Third bearing 21 Motor (actuator)
40 steered wheel 41 pinion shaft housing

Claims (21)

A housing having a pinion shaft accommodating portion;
A rack shaft having rack teeth connected to the steered wheels of the vehicle;
A pinion shaft that is rotatably provided in the housing and has pinion teeth that mesh with the rack teeth in a state shifted from a position perpendicular to the rack shaft;
A steering input shaft connected to the pinion shaft;
An actuator for applying a steering assist force to a steering mechanism including the steering input shaft, the pinion shaft, and the rack shaft;
A first bearing provided on a side opposite to the steering input shaft with respect to the pinion teeth, and supporting the pinion shaft with respect to the housing;
A second bearing provided on the side of the steering input shaft with respect to the pinion teeth, supporting the pinion shaft with respect to the housing, and configured by a roller bearing or a sliding bearing;
A third bearing provided on the side of the steering input shaft with respect to the second bearing and supporting the pinion shaft with respect to the housing;
Have
The radial gap at the smallest part in the circumferential direction is a radial gap on the side where the opposing members formed between the housing or the pinion shaft and the second bearing rotate relative to each other. A power steering device characterized in that a member formed between the pinion shaft and the third bearing and facing each other is smaller than any portion in the circumferential direction of a radial gap on the side where relative rotation is performed. The power steering apparatus according to claim 1, wherein
The power steering apparatus, wherein the housing has first, second, and third bearing holding portions that hold the first, second, and third bearings in a single block. The power steering apparatus according to claim 2,
The housing has an opening on the steering input shaft side,
The inner diameter of the second bearing holding part is formed larger than the inner diameter of the first bearing holding part,
An inner diameter of the third bearing holding part is formed larger than an inner diameter of the second bearing holding part. In the power steering device according to claim 3,
The power steering device according to claim 1, wherein the first bearing is constituted by a roller bearing or a sliding bearing. The power steering apparatus according to claim 1, wherein
The power steering device according to claim 3, wherein the third bearing is a thrust bearing. The power steering apparatus according to claim 1, wherein
The power steering device, wherein the first, second and third bearings are inserted into the pinion shaft from the first bearing side. The power steering apparatus according to claim 6, wherein
A worm wheel provided on the pinion shaft;
A worm shaft for transmitting a steering assist force from the actuator to the worm wheel;
Further comprising
The power steering device, wherein the worm wheel is inserted into the pinion shaft from the steering input shaft side. The power steering apparatus according to claim 1, wherein
The power steering device according to claim 1, wherein the first bearing is constituted by a roller bearing or a sliding bearing. The power steering apparatus according to claim 1, wherein
The power steering apparatus, wherein the first and second bearings always receive a radial load. The power steering apparatus according to claim 1, wherein
The radial gap on the side where the opposing members formed between the housing or the pinion shaft and the second bearing rotate relative to each other, and the smallest portion in the circumferential direction is the pinion shaft and the pinion shaft. The power steering device is assembled so that members facing each other are always in contact with each other. A housing having a pinion shaft accommodating portion;
A rack shaft having rack teeth connected to the steered wheels;
A pinion shaft that is rotatably provided in the housing and has pinion teeth that mesh with the rack teeth in a state shifted from a position orthogonal to the rack shaft;
A steering input shaft connected to the pinion shaft;
An actuator for applying a steering assist force to a steering mechanism including the steering input shaft, the pinion shaft, and a rack shaft;
A first bearing provided on a side opposite to the steering input shaft with respect to the pinion teeth, and supporting the pinion shaft with respect to the housing;
A second bearing that is provided on the side of the steering input shaft with respect to the pinion teeth so as to at least partially overlap with a portion where the pinion teeth are formed, and that supports the pinion shaft with respect to the housing; ,
A power steering apparatus comprising: The power steering apparatus according to claim 11, wherein
A cylindrical member provided on the outer peripheral side of the pinion shaft and provided so that at least a part of the pinion tooth formation portion overlaps;
The power steering device according to claim 1, wherein the second bearing is provided on an outer peripheral side of the cylindrical member and within an axial range. The power steering apparatus according to claim 12,
The cylindrical member is provided such that a part of the cylindrical member overlaps with a portion where the pinion teeth are formed and a remaining portion overlaps with a portion where the pinion teeth are not formed. . The power steering apparatus according to claim 12,
The power steering device, wherein the cylindrical member is press-fitted into the pinion shaft. The power steering apparatus according to claim 12,
The power steering device according to claim 1, wherein the cylindrical member is cured. The power steering apparatus according to claim 11, wherein
The power steering device according to claim 1, wherein the first bearing is a thrust bearing. The power steering apparatus according to claim 16, wherein
The power steering device according to claim 1, wherein the first bearing is inserted into the housing from the first bearing side with respect to the pinion teeth. The power steering apparatus according to claim 11, wherein
The power steering device, wherein the second bearing is constituted by a roller bearing or a sliding bearing. A housing having a pinion shaft accommodating portion;
A rack shaft connected to the steered wheels and having rack teeth;
A pinion shaft that is rotatably provided in the housing and has pinion teeth that are formed by forging or rolling while meshing with the rack teeth in a state shifted from a position orthogonal to the rack shaft;
A steering input shaft connected to the pinion shaft;
An actuator for applying a steering assist force to a steering mechanism including the steering input shaft, the pinion shaft, and the rack shaft;
A first bearing provided on a side opposite to the steering input shaft with respect to the pinion teeth, and supporting the pinion shaft with respect to the housing;
A second bearing on the side of the steering input shaft with respect to the pinion teeth and supporting the pinion shaft with respect to the housing;
A third bearing provided on the side of the steering input shaft with respect to the second bearing and supporting the pinion shaft with respect to the housing;
Have
The radial gap at the smallest part in the circumferential direction is a radial gap on the side where the opposing members formed between the housing or the pinion shaft and the second bearing rotate relative to each other. A power steering device characterized in that a member formed between the pinion shaft and the third bearing and facing each other is smaller than any portion in the circumferential direction of a radial gap on the side where relative rotation is performed. The power steering device according to claim 19,
The power steering device according to claim 1, wherein the first bearing is a thrust bearing. The power steering device according to claim 19,
An even number of the pinion teeth is provided in the circumferential direction.

Images