JPS6149147B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power steering system for a vehicle equipped with a rotary servo control valve.

[Conventional technology]

Conventionally, as this type of power steering device,
-There is something disclosed in Publication No. 20097. As shown in FIG. 1, a pin hole 66 is provided on the outer periphery of the collar portion 10a of the ball screw shaft 10, and an outer sleeve 6 having a partial notch 62 is fitted to the outer periphery of the pin hole 66. and the notch 62, and the pin 63 is press-fitted in the radial direction to connect them. During steering, hydraulic pressure is generated simultaneously with the axial movement of the piston 12, and an axial load is also applied to the ball screw shaft 10 and the outer sleeve 6. In order to prevent movement of the outer sleeve 6 and the ball screw shaft 10 due to this load, one end of the ball screw shaft 10 is applied to the end wall 32 of the cylinder 13 via a bearing 43, and the other is of the valve housing 17. A plug 64 is screwed into the screw hole, and the outer sleeve 6 is pressed against it through the bearing 15. By tightening the plug 64, a preload is applied to the abutting surface between the collar portion 10a and the outer sleeve 6. There are drawbacks such as.

(a) Due to the collar portion 10a of the ball screw shaft 10 and the axial bearing 15 of the valve portion (outer sleeve), the valve housing portion becomes large in both outer diameter and length, which poses a problem in weight reduction.

(b) When steering, a load is applied in the axial direction, and unnecessary force other than valve operation is applied, resulting in unsmooth operation.
Steering sensation deteriorates.

(c) The axial movement of the ball screw shaft 10 is supported by the bearing 43 at the distal end and the bearing 15 through the outer sleeve 6 at the base end, but the external force from the wheel moves through the piston 12 to the ball screw shaft. 10, this external force acts on the outer sleeve 6,
This results in an unsmooth movement, which adversely affects the steering feel.

Furthermore, in the power steering device disclosed in Japanese Patent Publication No. 51-2178, the ball screw shaft is supported on the end wall of the cylinder with one four-point support bearing. Since the valve element is formed in the area adjacent to the four-point support bearing, the external force from the wheel passes from the piston to the valve element on the ball screw shaft, and is received by the end wall of the cylinder at the four-point support bearing. Since the valve element is disposed in the transmission path of the external force, the external force causes an uneven movement of the valve element, which adversely affects the steering feel.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a small-sized power rudder with a simple configuration, which prevents external force from the wheels from being transmitted to the valve element of the ball screw shaft, and maintains smooth operation of the valve element at all times. The objective is to provide a device for removing

[Means to solve the problem]

In order to achieve the above object, the present invention includes a piston having a rack partially provided on the outer periphery that meshes with the output gear shaft, and a piston partitioned by the piston.
a cylinder having a pair of liquid chambers, a steering shaft and a ball screw shaft screwed onto the piston are connected through a flexible shaft, and a cylindrical first valve element is coupled to the ball screw shaft. and a second valve element integrally formed with the steering shaft and fitted into the first valve element, by twisting the flexible shaft, one of the pair of liquid chambers is used as a hydraulic pressure source and the other is used as a hydraulic pressure source. In a power steering device that forms a hydraulic circuit that communicates with each liquid tank, a flange forming an inner ring is integrally formed at the tip of the ball screw shaft, and a four-point support bearing including the inner ring allows the ball screw shaft to is supported immovably in the axial and radial directions on the end wall of the cylinder, and the outer dimensions of the ball screw shaft and the steering shaft are approximately the same, and the ball screw shaft is provided with a base end of the ball screw shaft. 1
The valve element is fitted onto the outside and rotationally connected with a radial pin.

[Effect]

The tip of the ball screw shaft 10 is a four-point support bearing 43
while being supported on the end wall 32 of the cylinder with
Since the outer sleeve 6, which is a valve element, is supported at the base end of the ball screw shaft 10, when external force from the wheel is transmitted to the ball screw shaft 10 via the piston 12, it is received by the four-point support bearing 43. Since the outer sleeve 6 is outside the external force transmission path, very smooth operation of the control valve can be achieved.

[Embodiments of the invention]

The present invention will be described below with reference to embodiments shown in the drawings. As shown in FIG. 2, the power steering device is constructed by first fitting a piston 12 with a rack 18 on a part of its outer periphery into a cylinder 13 that is closed by an end wall 32 and a valve housing 17. A gear shaft 19 that transmits deflection power to the steering wheel is engaged with the gear shaft 19, and a hollow ball screw shaft 10 is screwed into the axial center of the piston 12 via a ball 11, and the base end of the ball screw shaft 10 is hollow. The tip of the steering shaft 1 is supported through a bearing 38 in a relatively rotatable manner, and the flexible shaft 8 is inserted into the hollow part of the ball screw shaft 10, and the tip is connected to the ball screw shaft 1 with a pin 44.
0, the base end is rotatably coupled to the steering shaft 1 with a pin 3, and the distal end of the ball screw shaft 10 is supported on the end wall 32 by a four-point support bearing 43,
The steering shaft 1 is supported in the shaft hole of the valve housing 17 with a bearing 35, and when the steering shaft 1 is rotated, the twisting of the flexible shaft 8 caused by the drag force of the steering wheel which the ball screw shaft 10 receives is prevented. A rotational differential is generated between the two valve elements of the servo control valve, and the liquid chambers A and B of the cylinder are divided into two by the piston 12.
The piston 12 is pushed in a direction that facilitates rotation of the ball screw shaft 10 by applying hydraulic pressure to one side of the ball screw shaft 10.

As shown in FIG. 3, a flange 10b is integrally formed at the tip of the ball screw shaft 10, and an inner ring having an annular groove with a gossic arch cross section for engaging the ball on its outer periphery and an inner ring that clamps the ball from both sides. A split type bearing, that is, a four-point support bearing 43 is constituted of a split type outer ring 16, and the outer ring 16 is supported by the end wall 32 and a restraining plate 36 screwed into this screw hole.

As shown in FIG. 4, the servo control valve has a pair of outer sleeves 6 and inner sleeves 2 that are rotatably supported concentrically within a valve housing 17 that is integrally formed with a cylinder 13. It has a valve element. The outer sleeve 6 has this left end,
A seal ring 3 is attached to the outer periphery of the base end of the ball screw shaft 10.
The small diameter portion of the tip of the pin 34, which is fitted through the pin 7 and screwed into the outer sleeve 6, is inserted into the pin hole of the ball screw shaft 10 and rotationally coupled, and a lockite 39 is tightened on the outer end of the pin 34. It will be done. An annular groove 22 is formed on the inner peripheral surface of the valve chamber 61 into which the outer sleeve 6 is fitted, and this groove communicates with the liquid supply port 20 . A pair of annular grooves are cut on both sides of the annular groove 22, and seal rings 50 and 51 are attached to these. The inner sleeve 2 is constructed integrally with the steering shaft 1,
An outer sleeve 6 is fitted onto this outer peripheral side via a damper seal 41 to prevent mutual vibration of the valve elements.

The steering shaft 1 is thinner on the left end side than the inner sleeve 2, and a relative rotation limiting member 65 similar to a spline with a sufficient gap between teeth is configured between the steering shaft 1 and the ball screw shaft 10, and a relative rotation limiting member 65 is formed between the steering shaft 1 and the ball screw shaft 10. When steering power cannot be obtained due to failure of the steering wheel, the rotational force of the steering shaft 1 can be manually transmitted to the ball screw shaft 10. The right end side of the inner sleeve 2 of the steering shaft 1 is supported in the shaft hole of the valve housing 17 with a bearing 35, and this bearing portion is supported by a retaining ring 45.
It is sealed from the outside by a sealing member 55 supported by. A gap 61 a is formed in the valve chamber 61 between the right end portion of the outer sleeve 6 and the bearing 35 , and this gap 61 a is connected to the liquid return port 21 . As mentioned above, the tip side of the steering shaft 1 is hollow, and the flexible shaft 8 is fitted with the seal ring 4 inside.
7 and are rotationally connected to each other by radial pins 3.

The outer sleeve 6 and the inner sleeve 2 have valve grooves on their sliding surfaces, and one of the valve grooves of the outer sleeve 6
One is the cylinder liquid chamber B via the inclined liquid hole 24a.
and one of the valve grooves of the inner sleeve 2 is connected to the hollow part of the steering shaft 1 through the radial liquid hole 33,
Furthermore, as shown in FIG. 2, the liquid passes through a liquid passage 29 formed by the hollow part of the ball screw shaft 10, and enters the cylinder liquid chamber A through a radial liquid hole 28 provided at the tip of the ball screw shaft 10. Continuing. The other valve groove of the inner sleeve 2 is connected to the closed end of the shaft hole 30 of the steering shaft 1 through the radial liquid hole 26a, and further connected to the closed end of the shaft hole 30 of the steering shaft 1 through the radial liquid passage 42 provided in the steering shaft 1 to the above-mentioned valve. room 61
The gap 61a continues to the reflux port 21.

To explain in detail the structure of the outer sleeve 6 and the inner sleeve 2, which are valve elements, as shown in FIGS. 4 and 5, the outer sleeve 6 has radial liquid holes 22a and 24a formed at different positions in the circumferential direction. be done. The outer peripheral end of the liquid hole 22a is connected to the above-mentioned annular groove 22 connected to the liquid supply port 20.
The inner end of the liquid hole 24a is directly connected to the communication groove 24, and the outer end is directly connected to the liquid chamber B.

The inner sleeve 2 has control grooves 25 and 26 cut in the outer circumference at different positions in the circumferential direction and extending in the axial direction.In particular, the control groove 26 is provided with a radial liquid hole 26a to provide flexibility to the steering shaft 1. Shaft hole 30 for fitting the shaft 8
communicates with the closed end of.

Furthermore, a radial liquid hole 33 is provided in the inner sleeve 2 with respect to the control groove 23 .

Then, both the inner and outer sleeves 2 and 6 are in the neutral position.
In other words, when the flexible shaft 8 is not twisted,
The control groove 25 allows the liquid hole 22a to communicate with the communication grooves 23 and 24, and the control groove 26 allows the communication groove 23 and 24 to communicate with the liquid hole 26a.

In order to obtain liquid tightness between the liquid chambers A and B partitioned by the piston 12, a seal ring 48 is provided on the outer periphery of the piston in sliding contact with the cylinder 13, and a seal ring 5 is provided on the sliding portion between the ball screw shaft 10 and the piston 12.
6 is installed, and the annular groove 2 connected to the liquid supply port 20
A seal ring 50 for obtaining liquid tightness between the valve chamber B and the liquid chamber B, and a seal ring 51 for obtaining liquid tightness between the annular groove 22 and the gap 61a connected to the liquid return port 21 are installed inside the valve chamber 61, respectively. Attached to the surrounding wall. In addition, a closed end of the shaft hole 30 connected to the liquid return port 21,
In order to obtain liquid tightness between the flexible shaft 8 and the liquid path 29 connected to the chamber A, a seal ring 47 is attached to the outer periphery of the end of the flexible shaft 8.

Next, the operation of the hydraulic power steering device having the above configuration will be explained. Figure 5 shows the power steering system in its neutral state (vehicle is running straight); at this time, the pressurized fluid enters the control groove 25 from the fluid supply port 20 via the annular groove 22 and fluid hole 22a, and is connected from here. Groove 24, liquid hole 24
It enters the liquid chamber B through a, while the communication groove 23 and the liquid hole 3
3. It enters the liquid chamber A through the liquid passages 29 and 28 and exerts pressure on both end surfaces of the piston 12, but each communication groove 2
4 and 23 also enter the shaft hole 30 of the steering shaft 1, the liquid path 42, and the gap 61a through the liquid hole 26a, lubricate the bearing 35, and return to the liquid return port 21, so that they act on the piston 12. The hydraulic pressure caused by the piston 12 is extremely low due to the fluid path resistance, and the pressure is the same on both sides, so no thrust is generated in the piston 12.

If you turn the handle to the right now, the ball screw shaft 10
is receiving drag from the steering wheel, so the steering axis 1
The inner sleeve 2 is rotated with the twist of the flexible shaft 8, and the inner sleeve 2 is rotated in the hour hand direction (the fifth
(Figure) produces a rotational differential. Therefore, the grooves 25, 24
Since the gap between the grooves 23 and 26 closes, and the gap between the grooves 25 and 23 and the grooves 24 and 26 widen, the pressure liquid from the liquid supply port 20 flows through the annular groove 22, the liquid hole 22a, the liquid groove 25, the liquid groove 23, The liquid in the cylinder liquid chamber A enters the cylinder liquid chamber A through the liquid hole 33 and the liquid passages 29 and 28 and exerts liquid pressure on the left end of the piston 12, while the liquid in the cylinder liquid chamber B flows through the liquid hole 24a, the communication groove 24, the control groove 26, and the liquid hole. 26a, the shaft hole 30 of the steering shaft 1, the liquid passage 42, and the bearing 3 through the gap 61a.
5 and return to the liquid return port 21. Since the ball screw shaft 10 is a right-handed screw shaft, the rightward movement of the piston 12 is facilitated by applying a slight rotational force that causes twisting to the flexible shaft 8, and the piston 12 is easily rotated clockwise. The gear shaft 19 is rotated clockwise by the hydraulic power received by the gear shaft 12, and the steering wheels are deflected to the right via a pitman arm and a link mechanism (not shown).

Such a hydraulic circuit only occurs during the period of twisting of the flexible shaft 8, during which the deflection angle of the wheels increases. When the required deflection angle is reached, if the application of rotational force to the steering shaft 1 is stopped, the movement of the piston 12 follows until the position where the twist of the flexible shaft 8 is released, and then the outer sleeve 6 and the inner sleeve The relationship with the sleeve 2 is in the neutral state shown in FIG. 5, and the gear shaft 19 is stopped, thus making a servo movement to the steering shaft 1.

Next, when the steering shaft 1 is rotated to the left together with the steering wheel, a hydraulic pressure circuit is formed in the opposite direction to the case where the steering shaft 1 is rotated to the right as described above, but the operation is exactly the same, so the explanation will be omitted. do.

〔Effect of the invention〕

Since the present invention is configured as described above, the following effects can be obtained.

(a) Bearing 4 supports the tip of the ball screw shaft 10 at four points.
3 is supported on the end wall 32 of the cylinder, and the outer sleeve 6, which is the valve element of the control valve, is supported on the base end of the ball screw shaft 10, so that the pressure is transmitted to the ball screw shaft 10 through the piston. The external force from the wheels is received by the end wall 32 by the four-point support bearing 43, and the transmission of the external force to the base end of the ball screw shaft 10 that supports the outer sleeve 6 is suppressed. That is, since no valve element is disposed between the four-point support bearing 43 that supports the ball screw shaft 10, which is the external force transmission path, and the portion of the ball screw shaft 10 that is screwed into the piston 12, the valve element is not directly subjected to external force,
Smooth operation as a control valve can be obtained.

(b) The outer diameters of the ball screw shaft 10 and the steering shaft 1 are approximately the same, and the inner sleeve 2 formed integrally with the steering shaft 1 is fitted into the outer sleeve 6 supported on the ball screw shaft 10. As a result, the outer diameter of the control valve as a whole becomes smaller, which affects the placement of the brake pedal and accelerator pedal even when the underfloor and front part of the driver's cab is narrow, such as in cab-over type trucks. It can be installed without causing any damage.

(c) While the inner sleeve 2 is formed integrally with the steering shaft 1, the outer sleeve 6 is formed integrally with the ball screw shaft 1.
Since the control valve is floatingly supported at the base end of the control valve, smoother operation of the control valve can be achieved.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional power steering device;
The figure is a longitudinal sectional view of the power steering device according to the present invention,
The figure is a longitudinal cross-sectional view of the rotation support part at the tip of the ball screw shaft in the device, Figure 4 is a vertical cross-sectional view of the servo control valve part of the device, and Figure 5 is a cross-sectional view explaining the operation of the servo control valve It is a front view. A, B: Liquid chamber, 1: Steering shaft, 2: Inner sleeve,
6: Outer sleeve, 8: Flexible shaft, 10: Ball screw shaft, 10b: Flange, 12: Piston, 13:
Cylinder, 16: Outer ring, 17: Valve housing, 1
9: Output gear shaft, 20: Liquid supply port, 21: Liquid return port,
28, 29: Liquid path, 34: Pin, 35: Bearing, 3
6: Holding plate, 38: Bearing, 43: Bearing, 61: Valve chamber.

Claims (1)

[Scope of Claims] 1. A piston with a rack provided on a part of its outer periphery meshing with an output gear shaft, and a cylinder having a pair of liquid chambers partitioned by the piston, and the steering shaft and the piston are connected to each other. A cylindrical first valve element coupled to the ball screw shaft is integrally formed with the steering shaft and is fitted into the first valve element. In the power steering device, the combined second valve element forms a hydraulic circuit that communicates one of the pair of liquid chambers with a liquid pressure source and the other with a liquid tank by twisting the flexible shaft. ,
A flange forming an inner ring is integrally formed at the tip of the ball screw shaft, and the ball screw shaft is immovably supported in the axial and radial directions on the end wall of the cylinder by a four-point support bearing including the inner ring. , the outer diameters of the ball screw shaft and the steering shaft are approximately the same, the first valve element is externally fitted onto the base end of the ball screw shaft, and the first valve element is rotatably coupled to the ball screw shaft by a radial pin. Features a power steering device.