JPH0577746A - Rack and pinion type hydraulic power steering device - Google Patents

Abstract

PURPOSE:To prevent hammering noise and impulse from producing at the end of rack movement by moving an opening/closing member in the direction that a bypass flow path is opened to flow high-pressure oil fed to a hydraulic cylinder to low pressure side, when a rack nears its movement end. CONSTITUTION:In a rack and pinion type hydraulic power steering device, a travelling wheel W is connected to both ends of a rack 5 with which a pinion 4 interlocked with an input shaft connected to a steering wheel of a vehicle through a torsion bar is engaged. Also a hydraulic cylinder 10 in which a piston 12 provided on the outer side of the rack 5 is fitted closely is provided in a cylinder tube comprising a rack housing 11 to give an assist steering force to the rack 5. In this case, a pair of right and left cam surfaces 63 and 64 are formed on the back surface of the rack 5. When the rack 5 is moved to the end restricted by stoppers 40 and 41, a ball 61 is engaged with the cam surfaces 63 and 64 and a opening/closing member 51 opens a bypass flow path to reduce a steering assist force to be given by the hydraulic cylinder 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a rack movement restricting structure in a rack and pinion type hydraulic power steering device.

[0002]

2. Description of the Related Art A rack that steers steering wheels by moving in the vehicle width direction, and a stopper that restricts movement of the rack in the vehicle width direction within a certain range by contacting a contacted portion that moves along with the rack. A rack and pinion type hydraulic power steering device including a hydraulic cylinder that applies a steering assist force is used.

In such a hydraulic power steering device, if high-pressure oil is supplied to the hydraulic cylinder until the abutted portion abuts on the stopper, a large impact noise or impact is generated at the time of abutting, and it is unnecessary. This will give a steering operation assisting force.

Therefore, it is necessary to cancel the assisting force for the steering operation just before the rack reaches the moving end.
No. 277 is disclosed. This is because by forming a recess on the inner peripheral surface of the cylinder tube of the hydraulic cylinder that gives the assisting force for the steering operation, and allowing the piston of the hydraulic cylinder to enter the recess just before the rack reaches the moving end, The left and right oil chambers of the hydraulic cylinder are communicated with each other to release the assisting force for the steering operation.

[0005]

A seal ring, which is in contact with the inner circumference of the cylinder tube, is attached to the outer circumference of the piston of the hydraulic cylinder that applies a steering force assisting force.
Therefore, if a concave portion is formed on the inner peripheral surface of the cylinder tube as in the conventional power steering device, the seal ring is caught and damaged at the edge of the concave portion when the piston that has entered the concave portion moves, and is put to practical use. I can't.

An object of the present invention is to provide a rack and pinion type hydraulic power steering system which can solve the above-mentioned problems of the prior art.

[0007]

A feature of the present invention is that a rack that steers steering wheels by movement in the vehicle width direction, and regulation means that regulates movement of the rack in the vehicle width direction to a certain range. In a rack and pinion type hydraulic power steering device including a hydraulic cylinder for applying a steering operation assisting force, a bypass flow path connecting a high pressure oil flow path supplied to the hydraulic cylinder to a low pressure side, and the bypass flow path An opening / closing member for opening and closing the opening / closing member is provided, and the opening / closing member and the rack move in a direction in which the opening / closing member opens the bypass flow path when the rack approaches the moving end, and when the rack separates from the moving end, At the point of engagement via the cam so as to move in the direction of closing the bypass flow path.

[0008]

According to the structure of the present invention, when the rack approaches the moving end, the opening / closing member moves in the direction of opening the bypass passage.
As a result, the high-pressure oil supplied to the hydraulic cylinder flows to the low-pressure side, so that the assisting force for the steering operation can be reduced or eliminated.

When the rack separates from the moving end, the opening / closing member moves in the direction of closing the bypass flow passage. As a result, high-pressure oil is supplied to the hydraulic cylinder, and a steering operation assisting force is applied.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

The rack and pinion type hydraulic power steering apparatus 1 shown in FIGS. 1 and 2 is connected to an input shaft 2 connected to a steering wheel (not shown) of an automobile and a torsion bar 3 connected to the input shaft 2. The pinion 4 and the rack 5 that meshes with the pinion 4 are provided. Steering wheels W are connected to both ends of the rack 5 via ball joints 6 and 7. Thus, the rotation of the input shaft 2 is transmitted to the pinion 4 via the torsion bar 3 by the operation of the handle, and the rotation of the pinion 4 moves the rack 5 in the vehicle width direction to steer the steering wheels W. It

Stoppers 40 and 41 are formed at both ends of the rack housing 11 in order to restrict the movement of the rack 5 in the vehicle width direction within a certain range. As a result, when the rack 5 reaches the moving end, the ball joints 6 and 7 attached to both ends of the rack 5 come into contact with the stoppers 40 and 41, and the movement of the rack in the vehicle width direction is restricted. The stoppers 40 and 41 are constituted by, for example, a step portion integrally formed on the inner circumference of the rack 5 or a rack supporting bush fitted on the inner circumference of the rack 5.

A hydraulic cylinder 10 is provided to provide an assisting force for the steering operation. This hydraulic cylinder 10 is
A cylinder tube is formed by the rack housing 11, and a piston 12 is provided on the outer periphery of the rack 5. Oil chamber 13 partitioned by the piston 12,
A rotary valve 20 is formed on the outer periphery of the input shaft 2 in order to supply high pressure oil to the rack 14 in accordance with the steering direction and the reaction force acting on the rack 5 from the road surface. The rotary valve 20 includes a valve housing 21 that is integrated with the rack housing 11, and a tubular valve member 22 that surrounds the input shaft 2 inside the valve housing 21. The valve member 22 is connected to the pinion 4 so as to rotate together. Further, the valve housing 21 has an inlet port 24 connected to the pump 23 and the tank 2
5 and the outlet port 26 connected to the hydraulic cylinder 1
No. 1 first cylinder port 2 connected to one oil chamber 13
7 and a second cylinder port 28 connected to the other oil chamber 14. Each port 24, 26, 27, 28
Communicate with each other via a flow path that is opened and closed by relative rotation of the input shaft 2 and the valve member 22. That is, when the steering is not performed, the inlet port 24 and the outlet port 26 communicate with each other, the high-pressure oil supplied from the pump 23 flows back to the tank 25, and the steering assist force does not act. Also,
When the steering operation is performed by rotating the handle, the torsion bar 3 is twisted in response to the reaction force acting on the rack 5 from the road surface via the steering wheel W, and the valve member 22 integrated with the pinion 4 is provided.
Rotates relative to the input shaft 2. Then, the entrance port 2
4 and the outlet port 26 are closed, high-pressure oil is supplied from the inlet port 24 to one of the oil chambers 13, 14 of the hydraulic cylinder 10 in accordance with the steering direction, and the oil chamber 13,
Oil from the other 14 passes through outlet port 26 to tank 25
Reflux to. As a result, the hydraulic cylinder 10 applies a steering assisting force corresponding to the steering direction and the reaction force acting on the rack 5 from the road surface via the steering wheels W.

In order to adjust the meshing state of the pinion 4 and the rack 5, a cylindrical support yoke 30 and a spring 31 are inserted into an insertion hole 11a formed in the rack housing 11, and the insertion hole 11a is adjusted by the adjusting member 32. It is closed by being screwed. The support yoke 30 is movable in the horizontal direction in FIG. 1, and the rack 5 is pressed against the pinion 4 by the elastic force of the spring 31, and the pressing force is changed by changing the screwing amount of the adjusting member 32 into the rack housing 11. Adjustable.

A bypass passage 50 is formed to connect the passage of the high pressure oil supplied to the hydraulic cylinder 10 to the low pressure side. In this embodiment, the bypass flow passage 50 includes the inlet port 24 of the rotary valve 20 and the tank 25.
And a first flow path 50a formed in the valve housing 21, and a second flow path 5 formed in the rack housing 11 so as to communicate with the first flow path 50a.
0b, a third flow path 50c formed in the support yoke 30 so as to communicate with the second flow path 50b, and the insertion hole 1
1a and the fourth flow path 50d inside the pipe connected to the adjusting member 32. The first flow path 50
a is connected to the inlet port 24, and the fourth flow path 50d is connected to the tank 25. First channel 50a and second channel 50
A seal ring 55 is interposed between the valve housing 21 and the rack housing 11 for a seal between the valve housing 21 and the rack housing 11.
Because of the seal between the second flow path 50 and the third flow path 50c,
Seal rings 56 and 57 are provided between the outer circumference of the support yoke 30 and the inner circumference of the insertion hole 11a, and between the outer circumference of the adjustment member 32 and the inner circumference of the insertion hole 11a, respectively.

A cylindrical opening / closing member 51 for opening / closing the bypass flow passage 50 is movably inserted into the inner peripheral hole 30a of the support yoke 30. The moving direction of the opening / closing member 51 is the same as the moving direction of the support yoke 30.
A peripheral groove 52 communicating with the third flow path 50c is formed in the inner peripheral hole 30a of the support yoke 30. A peripheral groove 53 is formed on the outer periphery of the opening / closing member 51, and a communication hole 54 that connects the peripheral groove 53 and the insertion hole 11 a is formed in the opening / closing member 50. When the opening / closing member 51 is at the position shown in FIG. 1, the circumferential groove 52 and the circumferential groove 53 do not overlap each other, whereby the third flow passage 50c is closed by the outer peripheral surface of the opening / closing member 51 and the bypass flow passage 50 is closed. Be done. When the opening / closing member 51 moves to the rack 5 side from the position shown in FIG.
And the peripheral groove 53 overlap each other, the third flow path 50c and the fourth flow path 50d communicate with each other through the peripheral grooves 52 and 53 and the communication hole 54, and the bypass flow path 50 is opened.

The opening / closing member 51 and the rack 5 move in a direction in which the opening / closing member 51 opens the bypass passage when the rack 5 approaches the moving end, and when the rack 5 separates from the moving end, the opening / closing member 51 bypasses. Engage via a cam to move in the direction of closing the flow path 50. That is, the opening / closing member 51 abuts on the back surface of the rack 5 on the side opposite to the tooth forming side via the ball (cam follower) 61, and the spring 62 for pushing the opening / closing member 51 in the abutting direction is inserted into the insertion hole 11a. .. A pair of left and right cam surfaces 63, 64 are formed on the back surface of the rack 5, the rack 5 moves in the vehicle width direction, and the ball joints 6, 7 stop the stoppers 40, 41.
Immediately before contact with the ball, the ball 61 moves the cam surface 63, 6
Engage with 4. Due to the engagement between the ball 61 and the cam surfaces 63 and 64, the opening / closing member 51 is pushed by the spring 62 and gradually moves toward the rack 5. As a result, the bypass flow passage 50 is gradually opened, and the high-pressure oil supplied to the hydraulic cylinder 10 flows back to the tank 25 through the bypass flow passage 50.
The assisting force of the steering operation provided by the hydraulic cylinder 10 is gradually reduced. Then, as shown in FIG. 3, with the opening / closing member 51 moved to the most rack 5 side, the amount of oil that flows back to the tank 25 through the bypass flow passage 50 becomes maximum.
In this state, the assisting force for the steering operation may be completely eliminated or only reduced.

When the rack 5 moves in the vehicle width direction and the ball joints 6 and 7 separate from the stoppers 40 and 41, the engagement between the cam surface 63 and the ball 61 is released,
The opening / closing member 51 is pushed by the back surface of the rack 5 and moves in a direction away from the rack 5. As a result, the bypass passage 50 is closed, high-pressure oil is supplied to the hydraulic cylinder 10, and a steering operation assisting force is applied.

A seal ring 59 is interposed between the outer circumference of the opening / closing member 51 and the inner circumference of the support yoke 30.
The hydraulic pressure is prevented from acting on the back surface of the rack 5.

According to the power steering device 1 having the above-mentioned structure, the hydraulic cylinder 10 is provided near the moving end of the rack 5.
Since the assisting force of the steering operation given by is reduced or eliminated, the ball joints 6, 7 and the stopper 40 do not come into contact with each other violently, and a large impact sound and impact are prevented from occurring. The assisting force for steering operation is not unnecessarily applied. Further, since the opening / closing member 51 and the rack 5 are engaged with each other via the cam 60 outside the hydraulic cylinder 10, there is no problem that the seal ring on the outer circumference of the piston of the hydraulic cylinder is damaged as in the conventional case. Not practical.

In the above embodiment, the support yoke 30 is used.
Since the opening / closing member 51 is inserted in and the part 50c of the bypass flow passage 50 formed in the support yoke is opened / closed, the structure is simplified as compared with the case where the opening / closing member or the bypass flow passage is provided at another position. Further, since the rotary valve 20 and the support yoke 30 are close to each other, the bypass passage 50
Can be directly formed in the valve housing 21 and the rack housing 11 without using piping, and the structure is simplified.

The cam surfaces 63 and 64 of the above embodiment are
Since the opening / closing member 51 has a tapered surface that gradually moves toward the rack side as the rack 5 approaches the moving end, the resistance when moving the rack 5 in the direction of separating from the moving end is reduced. There is.

The present invention is not limited to the above embodiment.

For example, the opening / closing member 51 and the cam surfaces 63 and 64
In place of the ball 61, a needle roller bearing may be interposed between and, or the opening / closing member 51 may be brought into direct contact with the cam surface. Further, the cam surfaces may be formed into concave portions 63 'and 64' as shown by phantom lines in FIG.

[0025]

According to the rack and pinion type hydraulic power steering apparatus of the present invention, the assisting force of the steering operation provided by the hydraulic cylinder can be reduced or eliminated in the vicinity of the moving end of the rack, and the rack can be moved. It is possible to prevent a large impact sound and impact from being generated due to the regulation, and it is possible to eliminate unnecessary application of the assisting force for the steering operation. Moreover, there is no problem that the seal ring of the piston of the hydraulic cylinder is damaged, which is practical.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a power steering device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the power steering device according to the embodiment of the present invention.

FIG. 3 is a transverse cross-sectional view of a main part of the power steering device according to the embodiment of the present invention.

[Explanation of symbols]

 4 pinion 5 rack 10 hydraulic cylinder 50 bypass flow path 51 opening / closing member 63, 64 cam surface

Claims (1)

[Claims] 1. A rack for steering steering wheels by movement in the vehicle width direction, a regulation means for regulating movement of the rack in the vehicle width direction within a certain range, and a hydraulic cylinder for applying assisting force for steering operation. In a rack and pinion type hydraulic power steering apparatus provided with, a bypass flow passage connecting a flow passage of high pressure oil supplied to the hydraulic cylinder to a low pressure side, and an opening / closing member capable of opening and closing the bypass flow passage are provided,
The opening / closing member and the rack move in a direction in which the opening / closing member opens the bypass passage when the rack approaches the moving end, and move in a direction in which the opening / closing member closes the bypass passage when the rack separates from the moving end. A rack and pinion type hydraulic power steering device characterized by being engaged with a cam via a cam.