JPH10250611A - Rack-and-pinion type steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress occurrence of cogging sounds and establish easy adjustability for the set load. SOLUTION: A rack guide 18 is urged by a coil spring 20, and thereby a set load is applied between a rack gear 40 and a pinion gear 38. A cushion member 50 is fastened by a nut 46, and its resilient restoring force acts in the direction of decreasing the set load. The cushion member 50 has a high rigidity, and accordingly the rack guide 18 is retained with a high rigidity in the direction of arrows B1 and B2. On the other hand, the spring constant of the coil spring 20 is small, and it is possible to adjust easily the set load with the amount of a cap 44 being screwed in.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rack-and-pinion type steering device, and more particularly to a rack-and-pinion type steering device suitable for easily adjusting a set load between a rack gear and a pinion gear.

[0002]

2. Description of the Related Art Conventionally, a rack and pinion type steering device disclosed in Japanese Utility Model Laid-Open No. 64-41477 has been known as a vehicle steering device. The conventional steering device includes a rack shaft that meshes with a pinion shaft, a rack guide that holds the rack shaft, a spring that urges the rack guide so that the rack shaft is pressed toward the pinion shaft, and compression of the spring. An adjusting screw for changing the amount of deformation. The amount of contraction deformation of the spring is changed by the adjustment screw,
The pressing force between the rack shaft and the pinion shaft (hereinafter, referred to as a set load) is adjusted.

[0003]

When the set load becomes excessive, a large torque is required to rotate the pinion, so that the operation of the steering wheel becomes heavy and the operability of the steering wheel is reduced.
In order to avoid such inconvenience, it is necessary to set the set load low. On the other hand, in order to maintain the meshing state between the rack shaft and the pinion shaft, it is necessary to set the set load to a certain value or more. Therefore, the set load must be accurately adjusted so that these two contradictory conditions are compatible.

[0004] Further, when an impact force acts on the steered wheels due to the vehicle traveling on an irregular road or the like, the impact force is transmitted to the rack shaft via a tie rod connected to the steered wheels.
This force is converted into a force for separating the rack guide from the pinion shaft by meshing the rack shaft and the pinion shaft. Therefore, when the spring constant of the spring is set to be small, the rack shaft is easily detached from the pinion shaft when the above-described impact force is applied. Then, when the rack shaft meshes with the pinion shaft again, an abnormal noise (hereinafter referred to as a rattling noise) is generated due to the collision of the two teeth with each other. In order to suppress the occurrence of such rattling noise, it is necessary to increase the spring constant of the spring.

[0005] However, as described above, in the above-mentioned conventional steering device, the adjustment of the set load is performed by changing the contraction deformation amount of the spring using the adjustment screw. For this reason, if a spring with a large spring constant is used in order to suppress the generation of rattle noise, the set load will change greatly by only slightly changing the amount of contraction deformation of the spring, and the set load will be adjusted with high accuracy It will be difficult to do.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide a rack-and-pinion type steering apparatus capable of suppressing generation of rattling noise and easily adjusting a set load. Aim.

[0007]

The above object is achieved by the present invention.
As described in the above, a pinion shaft, a rack shaft that meshes with the pinion shaft, a rack guide that supports the rack shaft, and biases the rack guide so that the rack shaft is pressed toward the pinion shaft. In a rack-and-pinion type steering device including an elastic body that performs, and an adjustment member that adjusts an urging force generated by the elastic body by changing the amount of expansion and contraction of the elastic body, a spring constant different from that of the elastic member is set. An auxiliary elastic body that urges the rack guide in a direction opposite to the elastic member; and an auxiliary adjustment that changes an urging force generated by the auxiliary elastic body by changing an amount of expansion and contraction of the auxiliary elastic body. This is achieved by a rack and pinion type steering device including a member.

In the present invention, the auxiliary elastic body urges the rack guide in a direction opposite to that of the elastic member. Therefore, the pressing force between the rack shaft and the pinion shaft (hereinafter, referred to as a set load) is a value obtained by subtracting the urging force generated by the auxiliary elastic body from the urging force generated by the elastic body. Therefore, the set load can be adjusted by both the adjusting member and the auxiliary adjusting member. The adjusting member and the auxiliary adjusting member change the biasing force by changing the amount of expansion and contraction of the elastic body and the auxiliary elastic body, respectively. The smaller the spring constant of the elastic body and the auxiliary elastic body, the smaller the rate of change of the biasing force with respect to the amount of expansion and contraction. Therefore, the adjustment of the biasing force can be performed more easily as the spring constant is smaller. That is, the set load can be easily adjusted by adjusting the urging force generated by the smaller spring constant of the elastic member or the auxiliary elastic member by the corresponding adjusting member or the auxiliary adjusting member.

When the rack guide is displaced by Δx away from the pinion shaft, the elastic body contracts by Δx, while the auxiliary elastic body expands by Δx. Accordingly, when the spring constants of the elastic body and the auxiliary elastic body are respectively k1 and k2, the urging force generated by the elastic body increases by k1 · Δx, while the urging force generated by the auxiliary elastic body decreases by k2 · Δx. I do. As a result, the set load is (k1 + k2)
Increase by Δx. Similarly, when the rack guide is displaced by Δx in a direction approaching the pinion shaft, the set load decreases by (k1 + k2) · Δx. Therefore, in the present invention, the rack guide has a spring constant (k1 +
This is equivalent to being urged by the elastic body having k2). That is, the rack guide is at least k1,
It is urged by an elastic body having a larger spring constant than the larger one of k2. Thereby, displacement generated in the rack guide when an external force acts on the rack guide is suppressed.

[0010]

FIG. 1 is a configuration diagram of a rack and pinion type steering device 10 (hereinafter, simply referred to as a steering device 10) according to an embodiment of the present invention. FIG. 2 is a sectional view taken along the line II-II shown in FIG. As shown in FIGS. 1 and 2, the steering device 10 according to the present embodiment includes a gear box 12. The pinion shaft 14 is disposed so as to protrude upward from inside the gear box 12. As shown in FIG.
Inside the gear box 12, a rack shaft 16, a rack guide 18, a coil spring 20, and the like are provided. The upper end of the pinion shaft 14 is connected to a steering wheel (not shown). The rotation of the steering wheel is transmitted to the pinion shaft, and is converted by the gear box 12 into a linear motion of the rack shaft 16 in the A1 and A2 directions shown in FIG. The configuration of the gear box 12 will be described later.

The steering apparatus 10 of this embodiment employs power steering, and a power cylinder 22 constituting a booster is provided on the left side of the gear box 12 in FIG. As shown in FIG. 2, a control valve 24 is provided inside the gear box 12. The control valve 24 selectively supplies high-pressure oil supplied from an oil pump to a cylinder right chamber 22a or a cylinder left chamber 22b formed in the power cylinder 22 according to a turning operation direction of the steering wheel. Assists the steering wheel turning operation.

As shown in FIG. 1, tie rods 30 and 32 are connected to both ends of the rack shaft 16 via ball joints 26 and 28, respectively. Tie rod 30,
32 can linearly move in the same direction as the rack shaft 16 moves in the directions of arrows A1 and A2 in FIG. Steering wheels (not shown) (not shown) are connected to the tie rods 30 and 32. The tie rods 30, 32 are indicated by arrows A1, A in the figure.
By moving linearly in two directions, the direction of the steered wheels is changed, and the vehicle is steered.

Next, referring to FIG.
Will be described in detail. FIG. 3 is an enlarged sectional view of a main part of the gear box 12. As shown in FIG. 3, the gearbox 12 includes a housing 34. The housing 34 is fixed to a vehicle frame. The pinion shaft 14 is rotatably supported with respect to the housing 34 by a bearing 36. A pinion gear 38 is formed integrally with the pinion shaft 14.

The rack shaft 16 moves relative to the housing 34.
The direction perpendicular to the plane of FIG. 3 (that is, A
1, A2 direction).
A rack gear 40 that meshes with the pinion gear 38 is formed on the rack shaft 16. Therefore, the rotational torque applied to the pinion shaft 14 causes the rack shaft 16 to move linearly in a direction perpendicular to the plane of the paper of FIG. 1 (A1, A2 directions shown in FIG. 1) due to the engagement between the pinion gear 38 and the rack gear 40. Converted to force. Then, as described above, the direction of the steered wheels is changed by the linear movement of the rack shaft 16.

The housing 34 has a cylindrical portion 34a extending rightward in FIG. On the inner peripheral surface of the cylindrical portion 34a,
A screw portion 34b is formed in a substantially right half portion in FIG. The rack guide 18 is provided inside the cylindrical portion 34a as shown in FIG.
It is slidably arranged in the middle and left and right. Rack guide 18
Is formed with a curved concave portion 18a on the left end surface thereof. The rack guide sheet 4 is provided in the concave portion 18a of the rack guide 18.
2 are arranged so as to follow the shape of the concave portion 18a. The rack shaft 16 is slidably engaged with the rack guide sheet 42. By such engagement, the displacement of the rack shaft 16 in the directions B1 and B2 in FIG. 3, that is, the axial direction of the pinion shaft 14 is restricted. The rack guide 18 is shown in FIG.
It has a cylindrical portion 18b extending to the middle right. Column part 18
A threaded portion 18c is formed on the outer peripheral surface of b.

The thread portion 3 of the cylindrical portion 34a of the housing 34
A cap 44 is screwed to 4b. Cap 44
Is a cylindrical member whose one end (the left end in FIG. 3) is closed. The open end (the right end in FIG. 3) of the cap 44 projects rightward in FIG. 3 from the cylindrical portion 34a of the housing 34. An opening 44a is provided on the left end face of the cap 44 in FIG. 3, that is, on the closed end face. The column portion 18b of the rack guide 18 extends through the opening 44a into the cap 44.

A coil spring 20 is disposed between the left end surface of the cap 44 in FIG. 3 and the back surface of the concave portion 18a of the rack guide 18 so as to surround the cylindrical portion 18b. The urging force F1 generated by the coil spring 20 acts as a force for pressing the rack gear 40 toward the pinion gear 38 via the rack guide 18 and the rack guide sheet 42. Nuts 46 and 48 are screwed into the screw portion 18c of the cylindrical portion 18b of the rack guide 18.
A cushion member 50 is provided between the nut 46 provided on the left side in FIG. 3 and the inner bottom surface of the cap 44. The cushion member 50 is a member made of an elastic material having high rigidity, such as rubber, resin, urethane, or the like. The cushion member 50 is held in a state of being elastically contracted and deformed by being tightened by the nut 46.

The elastic restoring force F generated by the cushion member 50
Numeral 2 acts as a biasing force via the nut 46 so that the rack guide 18 faces right in FIG. 3, that is, a direction in which the rack guide 18 is separated from the rack shaft 16. Therefore,
The pressing force F (hereinafter, referred to as set load F) acting between the rack gear 40 and the pinion gear 38 is a value obtained by subtracting the elastic restoring force F2 generated by the cushion member 50 from the urging force F1 generated by the spring 18. That is, F = F1-F2 (1) holds.

A lock nut 52 is screwed on the outer periphery of a portion of the cap 44 projecting from the cylindrical portion 34a of the housing 34. The lock nut 52 allows the cap 4
4 is locked in a predetermined position. Also, cap 4
4, a cover cap 54 is press-fitted and fixed to the inner periphery at the right end in FIG. As described above, the set load F expressed by the equation (1) is applied between the rack gear 40 and the pinion gear 38.
Works. Due to the set load F, the rack gear 4
The meshing state between 0 and the pinion gear 38 is favorably maintained. However, when the set load F increases, the torque required to rotate the pinion gear 38 increases, so that the steering wheel operation becomes heavy and the operability is reduced. Therefore, the set load F must be accurately adjusted so that the meshing state between the rack gear 40 and the pinion gear 38 is maintained well, and the operability of the steering wheel is not reduced.

On the other hand, when a reverse input acts from the steered wheels due to, for example, a curb collision, the reverse input is applied to the rack shaft 16 via the tie rods 28 and 30 in the axial direction (FIG. 1).
(In the directions indicated by arrows A1 and A2). This force is converted into an external force P in a direction in which the rack guide 18 and the rack gear 40 are separated from the pinion gear 38 by the engagement between the rack gear 40 and the pinion gear 38. When the external force P exceeds the set load F, the rack gear 40 is displaced together with the rack guide 18 in the direction of arrow B1 shown in FIG. 3, and a gap is generated between the rack gear 40 and the pinion gear 38. When the rack gear 40 returns to the original position, the teeth of the rack gear 40 and the pinion gear 38
Abnormal noise (hereinafter referred to as rattling noise) is generated by the collision of the tooth with the tooth. In this case, if the set load F is larger than the external force P, the rack gear 40 does not separate from the pinion gear 38, so that rattling noise does not occur. However, as described above, increasing the set load F is not preferable in that the operability of the steering wheel is maintained.

In order to satisfy the two requirements of ensuring the operability of the steering wheel and preventing the generation of rattling noise, the set load F is suppressed to a small value and the rack gear 40 is pressed toward the pinion gear 38. It is effective to increase the rigidity of the spring system (hereinafter, set rigidity). This is because, even if the set load F is small, if the set rigidity is large, the amount of displacement of the rack gear 40 when a constant external force P is applied is reduced, thereby suppressing the generation of rattling noise.

Suppose that the set load F is applied to the cushion rubber 5
When the elastic restoring force of 0 is not used and the spring is generated only by the urging force of the coil spring 20, in order to obtain a large set rigidity, the spring constant k1 of the coil spring 20 must be set large. In this case, the adjustment of the set load F is performed by changing the amount of screwing of the cap 44 to change the amount of contraction deformation of the coil spring 20. However, when the spring constant of the coil spring 20 is increased, the set load F changes greatly only by slightly changing the amount of contraction deformation of the coil spring 20, and it becomes difficult to adjust the set load F with high accuracy.

On the other hand, the steering apparatus 10 of the present embodiment is characterized in that the provision of the cushion member 50 makes it possible to easily adjust the set load F. Hereinafter, such a characteristic portion of the present embodiment will be described. In the steering device 10 of the present embodiment, the spring constant of the coil spring 20 is k1, the spring constant of the cushion member 50 for elastic deformation in the directions of arrows B1 and B2 in FIG. 3 is k2, and no external force P acts on the rack guide 18. The amount of contraction deformation of the coil spring 20 in the (normal state) is x1, and the arrow B of the cushion member 50 in the normal state
Assuming that the amount of expansion and contraction in the directions B1 and B2 is x2, the urging force F1 generated by the coil spring 20 and the cushion member 5
The elastic restoring forces F2 generated by 0 are k1 · x1 and k2 · x2, respectively. Therefore, from equation (1), F = k1 · x1−k2 · x2 (2) holds.

The reverse input acts on the steered wheels, and the rack guide 1
Assuming that the rack guide 18 is displaced by Δx in the direction B1 shown in FIG.
Is further contracted by Δx, and the cushion member 50 is extended by Δx, that is, elastically deformed. Therefore, in this case, F1 + ΔF = k1 · (x1 + Δx) −k2 · (x2-Δx) (3) From equations (2) and (3), ΔF = (k1 + k2) · Δx (4) is obtained. From equation (4), it can be seen that the set rigidity is the sum of k1 and k2. As described above, the cushion member 5
0 is a member made of a highly rigid material, and its spring constant k
2 is a value large enough to suppress the occurrence of the rattle. Accordingly, since the set stiffness is obtained as the sum of k1 and 2, even if the spring constant k1 of the coil spring 20 is set small, a sufficiently large set stiffness can be realized. Can be suppressed.

On the other hand, from the equation (2), it can be seen that the set load F can be adjusted by any of the contraction deformation amounts x1 and x2 of the coil spring 20 and the cushion member 50, respectively. Therefore, if the spring constant k1 of the coil spring 20 is set to be small and the set load F is adjusted by the amount of expansion / contraction x1, the rate of change of the set load F with respect to the change in the amount of expansion / contraction x1 becomes small, and the set load F Is easy to adjust.

Therefore, in the present embodiment, the spring constant k1 of the coil spring 20 is set to a small value such that the set load F can be easily adjusted. The contraction deformation x2 of the coil spring 20 is changed after adjusting the amount of contraction deformation x2 of the elastic restoring force F2 generated by the coil spring 50 so as to substantially match the desired set load F. Adjustments will be made.

Hereinafter, the set load F based on the above principle will be described.
A specific adjustment procedure will be described. As described above, as the set load F increases, the torque required to rotate the pinion shaft 14 increases. Therefore, in the following adjustment procedure, the magnitude of the set load F can be estimated by measuring the torque.

Before the adjustment of the set load F, the nuts 46, 48 and the lock nut 52 are loosened, and the cover cap 54 is not press-fitted. Therefore, no elastic deformation occurs in the cushion member 50, and the cap 44 and the nuts 46, 48 can be freely rotated. In adjusting the set load F, first, the cap 44 is rotated in a predetermined direction and screwed toward the inside of the cylindrical portion 34a of the housing 34, so that the set load F becomes sufficiently larger than a desired value F0. Up to coil spring 20
Is shrunk and deformed. In this case, the set load F matches the urging force F1 generated by the coil spring 20 = k1 · x1.

Next, the cushion member 50 is contracted and deformed by tightening the nut 46 to the cushion member 50. In this case, the cushion member 50 has an elastic restoring force F2 = k2 ·
x2 occurs, and the set load F decreases as the amount of tightening by the nut 46 increases. Then, when the set load F becomes approximately near the desired value F0, the nut 4
6 is stopped, and the nut 46 is locked by tightening the nut 48.

Then, the final adjustment of the set load F is performed by changing the screwing amount of the cap 44 again. That is, when the set load F is smaller than the desired value F0, the cap 44 is further screwed to increase the amount of elastic deformation of the coil spring 20, thereby increasing the set load F toward the desired value F0. Let it.
When the set load F is larger than the desired value F0, the screw 44 is loosened to reduce the amount of elastic deformation of the coil spring 20 so that the set load F is adjusted to the desired value F0. Decrease. In this case, as described above, since the spring constant k1 of the coil spring 20 is set small, the rate of change of the set load F when the screwing amount of the cap 44 is changed is small. Therefore, it is possible to easily finely adjust the set load F toward a desired value F0.

When the set load F is set to a desired value F0, the cap 48 is locked by tightening the lock nut 52 and the cover cap 54 is pressed into the cap 48, thereby completing the adjustment operation. As described above, according to the steering device 10 of the present embodiment,
Since the cushion member 50 that generates an elastic force in the direction opposite to the direction of the set load F is provided, large set rigidity can be obtained, and thereby, generation of rattling noise can be suppressed. Further, the final adjustment of the set load F is performed by the coil spring 2 having a small spring constant k1.
The setting load F can be easily and accurately adjusted by changing the amount of contraction deformation of 0.

In the above embodiment, the coil spring 20 is used for the above-mentioned elastic member, the cap 44 is used for the above-mentioned adjusting member, the cushion member 50 is used for the above-mentioned auxiliary elastic member, and the nut 46 is used for the above-mentioned auxiliary adjusting member. , Respectively. It should be noted that the configuration may be such that the elastic body has greater rigidity than the auxiliary elastic body by replacing the coil spring 20 and the cushion member 50 in the above embodiment. In this case, the adjustment work can be easily performed by adjusting the set load F with the nut 46. Further, a high-rigidity spring may be provided instead of the cushion member 50.

[0033]

As described above, according to the present invention, generation of rattling noise can be suppressed, and adjustment of the set load can be easily performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a rack and pinion type steering device according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along a line II-II shown in FIG.

FIG. 3 is an enlarged sectional view of a main part of a gear box provided in the steering device of the embodiment.

[Explanation of symbols]

 Reference Signs List 10 rack and pinion type steering device 14 pinion shaft 16 rack shaft 18 rack guide 20 spring 38 pinion gear 40 rack gear 44 cap 46 nut 50 cushion member

Claims (1)

[Claims] 1. A pinion shaft, a rack shaft meshing with the pinion shaft, a rack guide supporting the rack shaft, and urging the rack guide so that the rack shaft is pressed toward the pinion shaft. A rack and pinion type steering device comprising: an elastic member that adjusts a biasing force generated by the elastic member by changing an amount of expansion and contraction of the elastic member. An auxiliary elastic body that urges the rack guide in a direction opposite to the elastic member; and an auxiliary adjustment that changes an urging force generated by the auxiliary elastic body by changing an amount of expansion and contraction of the auxiliary elastic body. A rack and pinion type steering device, comprising: