JPH0122777Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device in which fluid pressure acting on a fluid pressure cylinder is controlled by relative displacement of a pair of valve members constituting a servo valve device.

In general, in a power steering system equipped with a servo valve device consisting of a flapper valve mechanism, the flow of pressure fluid changes suddenly when the steering wheel is suddenly operated.
As a result, fluid pressure acts unevenly on the valve member, and as a result, self-excited vibration occurs in the servo valve device, and this vibration is transmitted to the driver, which may cause discomfort.

In order to prevent such self-excited vibrations of the servo valve device, conventionally a damping plunger is housed in a valve hole formed in the diametrical direction of the flapper valve, and a damping plunger is housed in the valve hole to control the fluid pressure acting on the fluid pressure cylinder. The damping plunger is pressed against the main valve member housing the flapper valve with a pressing force corresponding to the fluid pressure, thereby preventing self-excited vibration of each valve member.

In such conventional devices, the vibration damping plunger functions effectively when the fluid pressure in the valve hole is high, but when the handle is quickly returned to the neutral state, for example, the fluid pressure acting on the fluid pressure cylinder decreases. However, as a result, the pressure acting on the plunger also decreases, and even if a vibration damping plunger is provided, an effective vibration damping action cannot be obtained, and self-excited vibration cannot be sufficiently suppressed.

The present invention was made to solve these conventional problems, and its purpose is to reduce the pressure in the valve hole with a time delay in response to the pressure drop of the fluid pressure acting on the fluid pressure cylinder. In this way, the damping action of the damping plunger can be sustained for a long time, and self-excited vibration can be more reliably prevented.

Embodiments of the present invention will be described below based on the drawings. What is shown in FIG. 1 is a power steering device,
A fluid pressure cylinder 1 into which a piston 2 is fitted on one side
A valve housing 10 housing a servo valve device 3 for controlling the pressure fluid supplied to the hydraulic cylinder 1 is provided on the other side. A rack 4 is carved on a part of the circumference of the piston 2, and this rack 4 meshes with a sector gear 6 of an output shaft 5 connected to a steering wheel via a link mechanism. A screw shaft 9 is screwed onto the piston 2 with a ball 8 interposed therebetween, and a sleeve valve member 11 is fitted and fixed on the outer periphery of one end of the screw shaft 9, and is fitted into the valve housing 10. The main valve member 12 is fixed. A valve chamber having opposing side walls is formed penetrating through the main valve member 12 in the axial direction, and this valve chamber is connected to the main valve member 12 as shown in FIG.
Two valve chambers 14 and 15 at both ends are sealed and separated by a sealing member 13 fixed to the central portion of the valve chamber.
The valve chambers 14, 15 communicate with a supply port 16 and a discharge port 17, respectively, and distribution ports 18, 19 and jet injection ports are provided on both side walls of each valve chamber 14, 15, facing each other, as shown in FIGS. 2 and 3. Outlets 20 and 21 are open, respectively. Further, one valve chamber 14 has a protrusion in the diametrical direction, and valve seats 2 are provided on both sides of the protrusion.
A first flapper valve 24 having valves 2 and 23 is housed therein, and a second flapper valve 27 having a diametrically protruding portion in the other valve chamber 15 and having valve seats 25 and 26 on both sides of the protruding portion. is stored. The first and second flapper valves 24 and 27 are configured such that the radius of rotation of the first flapper valve 24 is smaller than that of the second flapper valve 27 in order to obtain an appropriate steering reaction force during operation. Further, the first and second flapper valves 24 and 27 are integrally molded, and a steering shaft 28 is integrally provided and protrudes to the outside of the valve housing 100. The screw shaft 9, the first and second flapper valves 24,
A single torsion bar 29 is inserted through the centers of 27 and the steering shaft 28, and is connected to the screw shaft 9 and the steering shaft 28 by pins 30 and 31, respectively. Note that the end of the steering shaft 28 is connected to a steering handle via a not-illustrated joint and a handle shaft, so that it can be rotated by the driver.

42 is a bearing that rotatably supports the main valve member 12 on the valve housing 10. Its outer ring 42a is fitted into the support member 41 fixed to the open end of the valve housing 10, and the inner ring 42b is integrally attached to the main valve member 12. It is fitted properly. Therefore, this inner ring 42
b rotates integrally with the main valve member 12. Further, the steering shaft 28 is rotatably supported by an inner ring 42b via rollers 43, and this inner ring 42b constitutes a bearing member that supports the steering shaft 28. 44 is the steering shaft 28
This is a roller interposed between the screw shaft 9 and the screw shaft 9. A damping plunger 45 and a synthetic resin piece 46 are interposed between the inner surface of the main valve member 12 and the second flapper valve 27. The vibration damping plunger 45
are the two flapper valves 2 that protrude in the diametrical direction.
Valve holes 4 bored in the diametrical direction at 7 and 27, respectively.
7 in a slidable manner. A spring 50 is further inserted into the valve hole 47, and the repulsive force of the spring 50 causes the damping plunger 45 to
At the same time, the synthetic resin piece 46 is pressed toward the inner surface of the main valve member 12.

On the other hand, an oil passage 48 is formed between the steering shaft 28 and the torsion bar 29, one end of which communicates with the valve chamber 14 through a gap between the rollers 44, and the other end of the oil passage 48. It communicates with the valve hole 47 via a throttle hole 49 . These oil passages 48 and throttle holes 49 function as introduction passages for introducing the pressure generated in the valve chamber 14, that is, the fluid pressure acting on the fluid pressure cylinder 1, into the valve hole 47, and the fluid corresponding to the generated pressure is The pressure is applied to the damping plunger 45. Further, the throttle hole 49 functions as a restriction part that restricts the outflow of fluid from the valve hole 47, and when the pressure in the valve chamber 14 decreases, the pressure in the valve hole 47 is lowered with a delay. It's becoming like that.

Servo valve device 3 and fluid pressure cylinder 1 configured as above
The fluid passage connecting them is as follows. As shown in FIG.
A pair of arcuate grooves 32 and 33 each communicating with 1.
are separately carved, and these circular grooves 32 and 33 are connected to flow passages 34 and 35 carved on the outer periphery of the main valve member 12.
are in communication with the distribution ports 18 and 19, respectively. Further, an annular groove 36 is formed on the outer periphery of the sleeve valve member 11, and this annular groove 36 communicates with the one arcuate groove 32 and the distribution port 18 via flow passages 37 and 38. The annular groove 36 is connected to the valve housing 10 and the hydraulic cylinder 1.
The left chamber 1a of the cylinder is connected through a passage 39 carved in the cylinder.
is communicated with. The other distribution port 19 communicates with a passage 40 bored at one end of the screw shaft 9, and this passage 40 communicates with the cylinder right chamber 1b. The supply port 16 is connected to an unillustrated pressure fluid supply source to supply pressure fluid to one valve chamber 14, and the discharge port 17 communicating with the other valve chamber 15 is used to eject pressure fluid from the jet ports 20 and 21. Fluid is adapted to be withdrawn to the source.

Next, the operation of the power steering device with the above configuration will be explained. In the neutral state of the steering wheel, the first
The second flapper valves 24 and 27 both have valve chambers 14 and 1.
Therefore, the pressure fluid supplied into the valve chamber 14 from the supply port 16 flows through the distribution ports 18 and 1.
9 and flows out through the jet ports 20 and 21 into the valve chamber 15 and the discharge port 17. In such a neutral state, the fluid pressures acting on the left and right cylinder chambers 1a and 1b are balanced, so the piston 2 does not operate and the steering wheel maintains the neutral state.

Now, when the steering wheel is rotated to the right, road resistance is acting on the screw shaft 9, so the torsion bar 29 is twisted and the steering shaft 28 is rotated to the main valve member 1.
rotated relative to 2. As a result, the first and second flapper valves 24 and 27 tilt to the right and act to close one distribution port 18 and spout 21, and the other distribution port 19 and spout 2.
It acts to open 0. As a result, the pressure fluid supplied into the valve chamber 14 is forced to be sent to the spout 21 through the other distribution port 19, but the amount of pressure fluid flowing out from the spout 21 is limited by the valve seat 26. Therefore, the distributed pressure fluid is introduced into the cylinder right chamber 1b through the aforementioned fluid passage 40, presses the piston 2 to the left, and deflects the steering wheel to the right. In this way, the small steering torque applied to the steering wheel by the steering person is assisted by the movement of the piston 2, making it possible to easily deflect the steering wheels. In addition, pressure fluid acts on the valve seat 26 to generate a steering reaction force that attempts to return the steering shaft 28 in the opposite direction to the steering direction, thereby causing the first and second flapper valves 24 and 27 to move. The driver can sense a steering reaction force corresponding to the difference in rotation moment, that is, a steering sensation corresponding to the deflection angle of the steered wheels.

By the way, when the first and second flapper valves 24, 27 are rotated with the rotation of the handle, the fluid pressure changes rapidly, causing self-excited vibration in the first and second flapper valves 24, 27. trying to occur. However, when a predetermined fluid pressure is generated in the valve chamber 14 as the handle rotates, this fluid pressure acts on the other end of the damping plunger 45 through the valve chamber 14, roller 44, oil passage 48, and throttle hole 49. In order to extend this in the diametrical direction and press the synthetic resin piece 46 against the inner surface of the main valve member 12, one end of the second flapper valve 27 and the main valve member 12 are connected to each other. The second flapper valve 27 which is in the state
Self-excited vibration of the flapper valves 24 and 27 is prevented.

Then, by returning the handle, the first and second
When the flapper valves 24, 27 are quickly returned to the neutral position, a sudden change occurs in the flow of the pressure fluid as described above, and self-excited vibration occurs in the first and second flapper valves 24, 27. In this case, the fluid pressure acting on the fluid pressure cylinder 1, that is, the pressure inside the valve chamber 14, has already become a low pressure, and the damping plunger 45
It is not possible to apply sufficient pressure to the vibration, and an effective vibration damping effect cannot be expected.

However, in the present invention, the valve hole 4 is
By restricting the outflow of pressure fluid from 7,
With a time delay due to the pressure drop in the valve chamber 14, the valve hole 4
Because it is designed to reduce the pressure inside 7,
Even if the fluid pressure in the valve chamber 14 decreases, the damping action of the damping plunger 45 is maintained for a long time, and during this period, the self-excited vibrations of the first and second flapper valves 24 and 27 are effectively absorbed.

Next, when the steering wheel is turned to the left, the first and second flapper valves 24 and 2
7 is rotated to the left, and the other distribution port 19 and jet port 20 are closed by the valve seats 23 and 25. Therefore, the pressure fluid that is about to flow out from the spout 20 is bleed-off controlled by the valve seat 25, and flows from one distribution port 18 to the arcuate groove 32, the flow path 34,
37, 38, is introduced into the cylinder left chamber 1a through the annular groove 36 and the passage 39, presses the piston 2 to the right, and deflects the steering wheel to the left. In this case, as in the case where the handle is tightened to the right, when fluid pressure is generated as the handle rotates, this fluid pressure acts on the other end of the vibration damping plunger 45 and the first and second flapper valves 24 , 27 are prevented. Even if self-excited vibrations are to occur when the handle is subsequently returned to its original position, the damping action of the damping plunger 45 is maintained for a long time by the action of the restricting portion formed by the throttle hole 49 as described above. 1. Self-excited vibration of the second flapper valves 24 and 27 is reliably prevented.

In the above embodiment, the restricting hole 49 is used as a restricting part, but the restriction is not limited to this. For example, as shown in FIG. 5, a restricting plate 60 may be inserted into the valve hole 47 to restrict It may also constitute a section. In this case, the restriction plate 60 allows pressurized fluid to flow into the valve hole 47 from the oil passage 48, and in the opposite direction only allows an outflow of so-called leakage, which is more restrictive than in the previous embodiment. The vibration damping effect of the swing plunger 45 can be maintained for a long time.

As described above, the power steering device of the present invention includes a restriction portion in the introduction path for introducing fluid pressure acting on the fluid pressure cylinder, and this restriction portion restricts the outflow of pressure fluid from the valve hole. As a result, the pressure in the valve hole can be lowered with a time lag than the pressure drop in the valve chamber, thereby making it possible to maintain the limiting action of the damping plunger for a long time. , self-excited vibration can be more reliably prevented.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a vertical sectional view of the power steering device of the present invention, and FIG.
Figure 3 is a - line cross-sectional view of the figure, - of Figure 1.
FIG. 4 is a cross-sectional view taken along the line - in FIG. 1, and FIG. 5 is a first sectional view showing another embodiment of the present invention.
It is a cross-sectional view taken along the line - in the figure. 1...Fluid pressure cylinder, 12...Main valve member, 24...
First flapper valve, 27...Second flapper valve, 2
8... Steering shaft, 45... Vibration damping plunger, 47... Valve hole, 48... Oil passage, 49... Throttle hole, 50... Spring, 60... Limiting plate.

Claims (1)

[Scope of utility model registration request] A fluid pressure cylinder is connected to the steering wheel via a required connection means, and a valve chamber having axially opposing side walls with a fluid port opened is formed and rotates in conjunction with the operation of the fluid pressure cylinder. a main valve member;
a flapper valve that is rotatably housed in the valve chamber and has a protrusion in the diametrical direction that opens and closes the fluid port and controls fluid supplied to the fluid pressure cylinder; and a steering shaft that is integrally connected to the flapper valve. In the power steering device, a valve hole is formed in the protruding part of the flapper valve in the diametrical direction, a damping plunger is slidably fitted into the valve hole, and the damping plunger is connected to the main valve. A spring that presses toward the inner circumferential surface of the member is housed, and the valve hole is communicated with an introduction passage that introduces fluid pressure acting on the fluid pressure cylinder so as to act in the same direction as the pressing force by the spring. A power steering device characterized in that a restriction portion is provided in the introduction passage for restricting outflow of pressure fluid from the valve hole.