JP2003040118A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering device having less noises and long life. SOLUTION: The power steering device comprises a holding cylinder 6 to be rotated around a steering shaft 1 having a spiral thread groove 10 formed in the peripheral face and a plurality of feed bearings R1 -R4 having outer rings 32 held by the holding cylinder 6 so that one peripheral portion of each inner ring 34 engages the thread groove 10. A motion changer for assisting the movement of the steering shaft 1 in the axial direction with force applied from one peripheral portion to the thread groove 10 when rotating the feed bearings R1 -R4 is composed of the bearings R1 -R4 each having the outer ring 32 split into two half rings.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering apparatus using a motor as a source of steering assist force.

[0002]

2. Description of the Related Art Japanese Patent Application No. 10-532733 discloses a power steering system equipped with a motion converting device using a feed bearing for converting the rotary motion of a rotary drive source such as a motor into a linear motion.
And Japanese Patent Application No. 2000-233601.

For example, like the motion conversion device shown in FIG.
When the holding cylinder 2 rotates, the feed bearings R _{1 to} R ₄ held by the holding cylinder 2 roll while maintaining the engagement between the respective inner races 34 and the thread grooves 10, and the steering shaft 1 moves each feed. Bearing R
It is pushed by the axial component force of the acting force applied along the inclination of the screw groove 10 from the engaging portion of _{1 to} R ₄ and moved in the axial direction, so that the rotational movement of the holding cylinder 2 is changed. Converted to a linear motion of 1.

[0004]

When the steering shaft 1 is moved in the axial direction, the feed bearings R _{1 to} R ₄ receive the force of the component in the moving direction of the steering shaft 1. For example, as shown in FIG. 6, when the steering shaft 1 moves in the direction of arrow M, a force is applied to the feed bearing in the direction of arrow F including the force Fm of the component in the direction opposite to the moving direction of the steering shaft 1. . A large force applied in the axial direction of the steering shaft 1 may cause the ball 30 of the feed bearing to ride on the shoulder portion 36a of the outer ring 36, as shown in FIG. When the ball 30 rides on the shoulder portion 36a, stress concentration occurs, which causes damage or vibration.

As a method for preventing stress concentration due to riding on the shoulder portion 36a, the shoulder portion 36a is raised.
(L in FIG. 7 may be lengthened), that is, the depth of the recess on the raceway surface that contacts the ball 30 may be increased. However, when the shoulder portion 36a is raised, the gap H on the side surface between the outer ring 36 and the inner ring 34 of the feed bearing shown in FIG. 8A becomes smaller. For manufacturing the feed bearing, for example, as shown in FIG. 8B, the outer ring 36 and the inner ring 34 are brought into contact with each other at one circumferential portion, and the ball 30 is moved from a large gap between the outer ring 36 and the inner ring 34 formed on the opposite side of the contacted circumferential portion. Since it is manufactured by pressing
8B, the gap for pushing the ball 30 shown in FIG. 8B becomes smaller, the number of balls 30 that can be mounted between the outer ring 36 and the inner ring 34 decreases, and the load of one ball increases and the feed bearing Shortens the life of.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a power steering apparatus which has a low noise and a long life.

[0007]

According to a first aspect of the present invention, there is provided a power steering apparatus, wherein a spiral groove is formed on a peripheral surface of the power steering apparatus, and the steering shaft is axially moved by rotation of steering wheels. A holding cylinder that rotates around a center, a plurality of feed bearings in which an outer ring is held by the holding cylinder and an inner ring is engaged with the groove, and a motor for steering assist that rotates the holding cylinder. In the power steering device that rotates the holding cylinder by means of the force applied to the groove from the feed bearing to assist the axial movement of the steering shaft, the outer ring of the feed bearing is composed of two annular outer ring halves. It is characterized by being configured.

In such a power steering apparatus, the outer ring of the feed bearing of the motion converting device is divided into two ring-shaped outer ring halves, and the ball (rolling element) between the outer ring and the inner ring is divided into two ring-shaped outer ring halves. Since the feed bearing can be manufactured by being sandwiched between the bodies, it is not necessary to reduce the number of balls even if the shoulder height is increased.

A power steering apparatus according to a second aspect is the first aspect.
In the above, the feed bearing includes a rolling element between the outer ring and the inner ring, and the holding cylinder is configured such that the rolling element makes contact with the raceways of the outer ring and the inner ring supporting the rolling element at four points. Holding means for holding the outer ring by applying a preload between the two annular outer ring halves.

In such a power steering system, the balls (rolling elements) are supported by the outer ring and the inner ring by preloading and holding the two ring-shaped outer ring halves obtained by dividing the outer ring of the feed bearing of the motion conversion device. Since it contacts the curved surface at four points, it is possible to prevent vibration and reduce noise.

A power steering apparatus according to a third aspect is the first aspect.
The feed bearing includes a rolling element between the outer ring and the inner ring, and the rolling element makes contact with the raceways of the outer ring and the inner ring supporting the rolling element at a contact angle of about 45 degrees. And

In such a power steering apparatus, the position where the balls (rolling elements) come into contact with the raceways of the outer ring and the inner ring can be set at a position which forms an angle of about 45 degrees with respect to the steering shaft. The holding force of the force applied in the axial direction of the steering shaft can be increased and the shoulder can be prevented from riding up.

A power steering apparatus according to a fourth aspect is the first aspect.
In any one of 3 to 3, the holding cylinder is provided with an adjusting unit that matches an axis of the steering shaft with a rotation center axis of the holding cylinder.

In such a power steering apparatus, the rotation center axis of the holding cylinder of the motion converting apparatus is made to coincide with the steering axis, whereby vibration due to axis misalignment rotation can be prevented.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to the drawings showing the embodiments thereof. FIG. 1 shows an example of a power steering apparatus according to the present invention, and FIG. 2 shows an example of a motion conversion apparatus included in the power steering apparatus. The power steering device transmits the rotation of the steering assisting motor 5 to the rack shaft (steering shaft) 1 via the motion conversion device and moves the rack shaft 1 in the axial direction to assist steering. Has become.

The rack shaft 1 is movably supported in the axial direction in a tubular rack housing 40, and extends in the left-right direction of a vehicle body (not shown). Both ends of the rack shaft 1 projecting on both sides of the rack housing 40 are connected to steering wheels (generally left and right front wheels) not shown through respective tie rods.

A pinion housing 41 is continuously provided in the middle of the rack housing 40 so as to intersect the shaft center, and a pinion shaft 42 is rotatably supported inside the pinion housing 41. In FIG. 1, the pinion shaft 42
Shows only the projecting end of the pinion housing 41 to the upper part, and is connected to a steering wheel (steering wheel) not shown through this projecting end so as to rotate around the axis according to the operation of the steering wheel for steering. It is designed to rotate.

A pinion (not shown) is integrally formed on the lower portion of the pinion shaft 42 extending inside the pinion housing 41. Further, rack teeth 43 are formed on the rack shaft 1 supported in the rack housing 40 over an appropriate length including a position intersecting with the pinion housing 41, and are meshed with the pinion below the pinion shaft 42. . Then, the rotation of the pinion shaft 42 due to the operation of the steering wheel is converted into movement in the axial direction of the rack shaft 1 by the meshing of the pinion shaft 42 and the rack teeth 43, and further, the rack shaft 1 in the rack housing 40 is moved. A rack and pinion steering mechanism is configured in which movement is transmitted to the left and right steering wheels via the tie rods, and these wheels are steered in accordance with the operation of the steered wheels.

The steering assisting motor 5 for assisting the steering operation as described above has a cylindrical motor housing 50 integrally formed by expanding the middle portion of the rack housing 40 over an appropriate length. It is configured as a three-phase brushless motor including a stator 51 fixedly provided on the inner peripheral surface of the motor housing 50 and a rotor 52 coaxially arranged inside the stator 51.

The rotor 52 is constructed by holding the magnetic poles 53 facing each other with a slight gap on the inner surface of the stator 51 on the outer circumference of a cylinder having an inner diameter larger than the outer diameter of the rack shaft 1. , A pair of left and right ball bearings 54, 55
It is rotatably supported around the axis of the motor housing 50, and rotates in both forward and reverse directions according to the energization of the stator 51. The rotation of the motor 5 is converted into movement in the axial direction of the rack shaft 1 and transmitted by the operation of the motion conversion device arranged on one side of the rotor 52.

Similar to the conventional motion converting device shown in FIG. 5, the motion converting device has a spiral groove (hereinafter referred to as a screw groove) on its peripheral surface.
A holding cylinder 6 that rotates around a rack shaft (steering shaft) 1 on which the 10 is formed, and a plurality of outer rings 32 that are held by the holding cylinder 6 so that one circumferential portion of the inner ring 34 is engaged with the thread groove 10. and a feed bearing R ₁ to R ₄ of the feed bearing R ₁ to R ₄
When the rack rotates, the rack shaft 1 is moved in the axial direction by the force applied to the thread groove 10 from the one circumferential portion.

The feed bearings R _{1 to} R ₄ are ball bearings provided with a large number of balls (rolling elements) 30 between the outer ring 32 and the inner ring 34, and are larger than the outer diameter of the rack shaft 1 inserted inside. Has a large inner diameter. The holding cylinder 6 is the motor housing 5
0 is extended to the same side, and is supported by a ball bearing 20 inside a cylindrical housing 3 and one side of the rotor 52 (ball bearing 5
5, which is coaxially connected to the end of the rack 5 via a connecting bracket 56, and is configured as a rotary cylinder that rotates around the rack shaft 1 in accordance with the rotation of the motor 5.

The feed bearings R _{1 to} R ₄ are held eccentrically in different directions in a plane orthogonal to the axis of the holding cylinder 6. This eccentricity is caused by the two feed bearings R located at both axial ends of the rotation center axis of the holding cylinder 6.
₁ and R ₄ are in the same direction, and are also located in the center 2
The feed bearings R ₂ and R ₃ are eccentric by substantially equal amounts so that they are in substantially the same direction. The feed bearings R _{1 to} R ₄ are engaged with the thread groove 10 of the rack shaft 1 via the protrusions provided on the inner ring 34 at the circumferential positions closest to each other due to their eccentricity.

In FIG. 2, the feed bearings R ₁ , R
It is illustrated that the engagement positions of ₄ coincide with each other in the circumferential direction of the rack shaft 1 and the engagement positions of the feed bearings R ₂ and R _{3 also} coincide with each other. The rack shaft 1 is in a state of being supported from four different directions. Further, the holding cylinder 6 is rotatably supported inside the cylindrical housing 3 by a ball bearing 20, and is configured to be rotated by the transmission from the motor 5 with the rack shaft 1 as the rotation center axis. There is.

The outer ring 32 of the feed bearings R _{1 to} R ₄ is
As shown in FIG. 3, it is divided into two ring-shaped outer ring halves (hereinafter referred to as half wheels) 32p and 32q. 2 outer ring 32
The ball 3 is divided into two half wheels 32p and 32q.
It is possible to manufacture a feed bearing by sandwiching 0 between the half wheels 32p and 32q. Therefore, it is not necessary to reduce the number of balls even when the shoulder portion 32a is raised, and the outer ring 3
It is also possible to insert the ball 30 with almost no gap between the inner ring 34 and the inner ring 34.

The holding tube 6, is holding unit 2a~2d fitting the feed bearing R ₁ to R ₄ are provided. Figure 4
FIG. 3 is an external perspective view schematically showing one half of a holding cylinder 6, showing a holding structure for _two feed bearings R ₁ and R ₂ . Holding part 2b for holding the feed bearing R ₂
As shown in FIG. 4, a holding cylinder in which a groove hole having a semicircular cross section corresponding to the outer shape of the feed bearing R ₂ of interest is formed inside the holding cylinder 6, and the open side of the groove hole is extended tangentially. A fitting inlet 2 s is provided on the outer circumference of 6. Such holding of the feed bearing R ₂ on the holding portion 2b is carried out via the fitting inlet 2s on the outer periphery of the holding cylinder 6 as shown by the arrow in FIG.
The feed bearing R ₂ pushed in is abutted against a semicircular slot forming the bottom of the holding portion 2b, and the inner surface of the feed bearing R ₂ corresponding to approximately the center of the abutting half is shown in FIG. As described above, it is realized by engaging with the thread groove 10 on the outer periphery of the rack shaft 1. The remaining feed bearing R ₃ is also held in the holding portion 2c having the same configuration as the holding portion 2b in the same manner.

At the end of the holding tube 6, as shown in FIG.
A holding portion 2a for holding the feed bearing R ₁ is formed. This holding portion 2a is provided with a feed bearing R ₁
Is a circular hole having an inner diameter substantially equal to the outer diameter, and is formed continuously at the end surface on the same side at a position eccentric to the axial center of the holding cylinder 6 by a predetermined length. The feed bearing R ₁ is press-fitted into the holding portion 2a from the end of the holding cylinder 6 as indicated by the arrow in FIG. 4, and one side is projected to the bottom surface of the holding portion 2a as shown in FIG. It is held so as to be immovable in the axial direction by a stop ring 2t. The retaining ring 2t has a ring shape, and a thread and a thread groove are formed on the peripheral portion of the retaining ring 2t and the inner surface of the holding portion 2a. The retaining ring 2t is screwed to the retaining portion 2a, and the feed bearing R ₁ is attached. Hold. The remaining feed bearing R ₄ has a holding portion 2d having the same shape as the holding portion 2a.
Similarly retained within.

Holding portions 2b and 2c, holding portions 2a and 2d and
And retaining ring 2t are feed bearings R ₂ , R₃ Outer ring 32
And the ball 30 between the inner ring 34 and the outer ring 36 and the inner ring 34.
Half wheels 32p and 32q so that they contact the raceway surface of
Hold the outer ring 32 with a predetermined gap that gives a preload to
Acts as a means to As shown in FIG.
Two points, contact with half wheels 32p and 32q of outer ring 32 at one point each
To do. Further, not limited to the present embodiment, a biasing member is provided to preload
May be given.

The ball 30 of the feed bearing is replaced by the outer ring 36.
And the inner ring orbit at a contact angle of about 45 degrees.

In the motion converting apparatus, in order to make the rack shaft 1 coincide with the rotation center axis of the holding cylinder 6, the feed bearings R ₂ ,
A means for adjusting the holding position of R ₃ is provided. As shown in FIG. 2, screw holes penetrating the peripheral wall of the holding cylinder 6 in the radial direction are formed substantially at the centers of the semicircular slots of the holding portions 2b and 2c, and the screw holes are screwed into these screw holes. screw 2f, it is brought into contact with the tip of 2f to the outer surface of the corresponding feed bearing R _2, R _3. When the adjusting screws 2f and 2f are respectively advanced in the screw holes, the feed bearings R ₂ and R ₃ that come into contact with the tips of these screws are attached.
The position of the rack shaft 1 is adjusted, and the axial direction of the rack shaft 1 with respect to the axial direction of the rotation center shaft of the holding cylinder 6 can be adjusted. For example, both shaft centers can be aligned. Although the adjusting screws are provided only on the feed bearings R ₂ and R ₃ in the drawing, they may be provided on the feed bearings R ₁ and R ₄ if necessary.

The distance between the half wheels 32p and 32q constituting the outer ring 32 is adjusted so that the feed bearings R _{1 to} R ₄ provided in the motion converting device are in four-point contact. By making four-point contact, the bearing is in the best condition and the life can be extended.

The shoulders 32a of the feed provided to the motion converter bearing R ₁ to R ₄ of the outer ring 32 is high, the rack shaft 1
So that the load applied to the outer ring 32 when moving in the axial direction is applied in a direction of 45 degrees with respect to the axial direction.
Since the spacing between the half wheels 32p and 32q that form part 2 is adjusted, it is possible to prevent a load from being applied to the shoulder portion 32a and to apply a load to the feed bearings R _{1 to} R ₄ in parallel or perpendicularly to the rack shaft 1. Can be dispersed in any direction. Since the shoulder portion 32a does not ride on the shoulder portion 32a, noise can be prevented.

Further, the half wheels 32p and 3 constituting the outer ring 32 are
To adjust the distance from 2q, the feed bearings R ₁ and R ₄ are held by the snap ring 2t, or the feed bearings R ₂ and R _{3 are held.}
It suffices to fit the holding parts 2b and 2c into the holding parts 2b and 2c, which can be easily performed. When the feed bearings R _{1 to} R ₄ are held by the holding cylinder 6, the adjustment of the distance between the half wheels 32p and 32q is completed.

Further, in the above-mentioned embodiments, the configuration provided with _four feed bearings R _{1 to} R ₄ has been described, but the motion conversion device according to the present invention has three or more feed bearings. It is also possible to adopt a configuration provided with.
Further, the direction F of the force applied from the ball 30 to the outer ring 32 (ring 32p in the figure) shown in FIG. 3 is a direction forming 45 degrees with respect to the moving direction of the rack shaft, but this angle is 45 degrees. The angle is not limited and can be set to an arbitrary angle. 45
When the angle is smaller than the degree, the force applied in the axial direction of the rack shaft becomes large, and the possibility that a load is applied to the shoulder portion becomes large. When the angle is larger than 45 degrees, the load applied to the rack shaft becomes large.

[0035]

According to the power steering apparatus of the present invention, since the outer ring of the feed bearing is divided into two ring-shaped outer ring halves, the ball (rolling element) between the outer ring and the inner ring is divided into two ring-shaped outer ring halves. Since the feed bearing can be manufactured by being sandwiched between the bodies, it is not necessary to reduce the number of balls even when the shoulder is raised. By increasing the height of the shoulder portion, it is difficult to apply a load to the shoulder portion, so that it is possible to prevent noise from being generated.

Further, according to the power steering apparatus of the present invention, the balls (rolling elements) are retained between the outer ring and the inner ring by maintaining the distance between the two ring-shaped outer ring halves constituting the outer ring of the feed bearing at a predetermined angle. It can contact the raceway surface at four points. By making four-point contact, the bearing is in the best condition and the life can be extended.

Further, according to the power steering apparatus of the present invention, the force applied in the axial direction of the steering shaft is set by setting the angle at which the balls (rolling elements) contact the raceways of the outer ring and the inner ring to around 45 degrees. It is possible to increase the holding force of the force applied in the direction perpendicular to the steering axis and prevent the shoulder from riding up.

Further, according to the power steering apparatus of the present invention, the axial direction of the steering shaft can be adjusted so that the axial center of the steering shaft coincides with the rotation center axis of the holding cylinder.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing an example of a power steering apparatus according to the present invention.

FIG. 2 is a vertical cross-sectional view showing an example of a motion conversion device included in the power steering device according to the present invention.

FIG. 3 is an enlarged view of a main part of the feed bearing shown in FIG.

FIG. 4 is an explanatory view of a procedure for mounting a feed bearing.

FIG. 5 is a vertical cross-sectional view showing an example of a motion conversion device included in a conventional power steering device.

6 is an enlarged view of a main part of the motion conversion device shown in FIG.

7 is an enlarged view of a main part of the feed bearing shown in FIG.

FIG. 8 is a diagram showing an example of manufacturing a feed bearing.

[Explanation of symbols]

1 rack shaft (steering shaft) 6 holding cylinders 2a, 2b, 2c, 2d holding portion (holding means) 2f adjusting screw 2s fitting inlet 2t snap ring 10 thread groove 30 ball (rolling element) 32 outer ring 32p, 32q ring-shaped outer ring half body 32a shoulder 34 the inner ring R ₁ to R ₄ feed bearings

Claims (4)

[Claims] 1. A steering shaft having a spiral groove formed on a peripheral surface thereof, the steering shaft moving axially by rotation of the steering wheel, a holding cylinder rotating about the steering shaft, and an outer ring serving as the holding cylinder. A plurality of feed bearings that are held and whose inner ring is engaged with the groove and a steering assist motor that rotates the holding cylinder are provided, and the holding cylinder is rotated by the motor and is added to the groove from the feed bearing. A power steering apparatus for assisting axial movement of the steering shaft by a force, wherein the outer ring of the feed bearing is composed of two ring-shaped outer ring halves. 2. The feed bearing includes a rolling element between the outer ring and the inner ring, and the holding cylinder has the rolling element in contact with raceway surfaces of the outer ring and the inner ring supporting the rolling element at four points. Like the above 2
2. The power steering apparatus according to claim 1, further comprising holding means for holding the outer ring by applying a preload between the two half halves of the outer ring. 3. The feed bearing includes a rolling element between the outer ring and the inner ring, and the rolling element makes contact with raceway surfaces of the outer ring and the inner ring supporting the rolling element at a contact angle of about 45 degrees. The power steering apparatus according to claim 1, wherein: 4. The holding cylinder according to claim 1, further comprising adjusting means for aligning an axis of the steering shaft with a rotation center axis of the holding cylinder. Power steering device.