JPH0249110Y2 - - Google Patents

Description

[Detailed description of the invention] The invention relates to a power steering valve.
In particular, it relates to a power steering valve with improved operating performance.

A power steering mechanism for a vehicle is configured to expand and contract a power cylinder in response to a steering operation from the vehicle body, thereby changing or maintaining the direction of the wheels. This power steering mechanism is equipped with a power steering valve, which is a valve formed to supply oil to the power cylinder or drain oil from the power cylinder during steering operation. The valve is also configured to unload oil when the steering is stopped. Therefore, this power steering valve must be configured to allow oil to pass therethrough during steering operation, and to quickly unload oil when steering is stopped.

To meet this need, for example, a power steering valve as shown in FIG. 1 has been proposed.

In other words, this power steering valve is
It has a subur 2 slidably disposed within the housing 1 as appropriate. And this spool 2
is held between holders 4 and 4 interposed on a spool bolt 3 that is linked to a steering shaft (not shown), and the spool bolt 3
The movement of the housing 1 simultaneously causes the housing 1 to slide. And this spool 2
Inside, there is a spring 6 whose both ends abut against plungers 5, 5 which are slidably interposed on the spool bolt 3. The plungers 5, 5 are in contact with stoppers 7, 7, which are inserted through the through holes 4', 4' of the holders 4, 4, from the back side.
The stoppers 7, 7 are provided in a protruding manner on caps 8, 8 fitted into the housing 1.

Therefore, when the steering is operated, the spool bolt 3 that is interlocked with the steering shaft moves, for example, to the right in the figure, and the oil from the pump P flows through the annular groove 1a of the housing 1, the annular groove 2a of the spool 2, and one oil. Oil is supplied to one chamber of the power cylinder (not shown) through passage C ₁ and oil from the other chamber of the power cylinder is supplied to the other oil passage C ₂ , the annular groove 2b of the spool 2, and the annular groove of the housing 1. The fuel is discharged into the tank T through the groove 1b, and the power cylinder expands or contracts, making it possible to turn the wheels (not shown) in a desired direction. On the other hand, when the turning of the wheels reaches the desired state and the steering operation is stopped, the spool 2 is returned to the neutral position within the housing 1 by the repulsive force of the spring 6, and the oil from the pump P is removed. By unloading the tank T, the desired turning state of the wheels is maintained.

However, in the power steering valve described above, the pressure oil from the pump P acts on both outer surfaces of the spool 2 and the outer surfaces of each plunger 5 through the gap between the housing 1 and the spool 2, but the spool bolt 3 The proximal end of the spool bolt 3 is inserted into the housing 1, and the distal end surface of the spool bolt 3 protrudes outside the plunger 5, so there is a pressure receiving surface difference corresponding to the cross-sectional area of the spool bolt 3. The spool 2 and the spool bolt 3 are always urged in the direction of arrow A by hydraulic back pressure. For this reason, when the spool 2 is switched to the left or right through the spool bolt 3 by steering operation, there is a difference between the left and right steering forces, resulting in a problem in operability.

Therefore, the purpose of this invention is to cancel the difference in the back pressure thrust of the spool on the left and right sides due to the difference in cross-sectional area of the spool bolt, and to reduce the difference in steering operation force between the left and right sides. It is an object of the present invention to provide a power steering valve that eliminates the above problem and improves operability.

In order to achieve the above purpose, the configuration of the present invention is as follows:
A cap is provided in the housing, a hollow spool is slidably inserted into the housing, plungers are interposed on both sides of the spool, and the base end of a spool bolt that is interlocked with the steering shaft is slidably inserted into the cap. The tip of the spool bolt is movably inserted into the plunger, and the holders provided on both sides of the tip of the spool bolt are brought into contact with both end surfaces of the spool and the outer end surface of each plunger. During movement, the spool is switched while moving one of the plungers, and the spool bolt is attached to the proximal side in a power steering valve in which the spool bolt is always biased in the proximal direction by hydraulic pressure acting on the end face of the distal end. This is characterized in that a spring with a small repulsive force that urges the spool bolt and a spring with a large repulsive force that urges the spool bolt toward the distal end are interposed in the spool.

An embodiment of the present invention will be described below based on FIG. 2.

The basic structure of the power steering valve according to the present invention is the same as the conventional example shown in Fig. 1, and in the present invention, instead of the spring 6 shown in Fig. 1, two coil springs 6a and 6b with different repulsive forces are provided. That's true.

That is, there are caps 8, 8 on both sides inside the housing 1.
A hollow spool 2 is slidably inserted into the housing 1, two plungers 5, 5 are slidably inserted on both sides of the spool 2, and a spool bolt 3 interlocked with the steering shaft is inserted into one side. The cap 8 is movably inserted into the two plungers 5, 5, and the holders 4, 4 provided on both sides of the tip of the spool bolt 3 are brought into contact with both end surfaces of the spool 2 and the outer ends of the plungers 5, 5. When the spool bolt 3 is moved, the plungers 5, 5
The spool 2 is switched while moving one of the spool bolts, and the spool bolt 3 is always urged toward the proximal end in the direction of arrow A by the hydraulic pressure acting on its tip due to the difference in cross-sectional area of the spool bolt 3. .

The housing 1 is configured integrally with a power cylinder (not shown), and includes an oil passage C ₁ communicating with one chamber (not shown) of the power cylinder and the other chamber (not shown) of the power cylinder. It has an oil passage C ₂ that communicates with the pump P, an oil passage C ₃ that communicates with an external pump P, and an oil passage C ₄ that communicates with an external pump P. The inner peripheral surface of the housing 1 includes an annular groove 1a in which the oil passage _C3 opens, an annular groove 1b in which the oil passage _C4 opens,
1c.

The spool 2 has annular grooves 2a and 2b on its outer periphery so as to form a land 2' in the center. The land 2' of the spool 2 is
It faces the annular groove 1a of the housing 1, and when the spool 2 is in the neutral position, oil from the pump P flows through the oil path 3 ₃ , the annular groove 1a of the housing 1, the annular groove 2a of the spool 2, and the annular groove 2a of the spool 2. 2c, it is unloaded into the tank T via the annular parts 1b and 1c of the housing 1 and the oil passage 4.

On the other hand, the spool 2 is held by a spool bolt 3 that interlocks with a steering shaft (not shown) of a vehicle. That is, holders 4, 4 are interposed on the spool bolt 3, and the spool 2 is held between the holders 4, 4 under pressure. In addition, in this embodiment, the holder 4,
The clamping pressure of the spool 2 between the spool bolts 3 and 4 is maintained by a nut 3a screwed onto the tip of the spool bolt 3.

Inside the spool 2 held between the holders 4 and 4, plungers 5 and 5 are slidably inserted into the spool bolt 3. Two coil springs 6a and 6b having different repulsive forces are provided between the plungers 5 and 5.

That is, one coil spring 6a having a large repulsive force has one end in contact with one of the plungers 5 and the other end in contact with a flange 20 protruding from the inner peripheral surface of the spool 2, and the other coil spring 6a having a small repulsive force The coil spring 6b has one end attached to the flange 2.
0 and the other end is connected to the other plunger 5.
Two coil springs 6a, 6 are connected in series in contact with
b is arranged.

On the other hand, stoppers 7, 7 are abutted on the back sides of the plungers 5, 5. The stoppers 7, 7 are brought into contact with the plungers 5, 5 through the through holes 4', 4' of the holders 4, 4, and in this embodiment, the stoppers 7, 7 are It is formed by protruding from caps 8, 8 fitted into the housing 1.

Next, the operation of the power steering valve according to the present invention configured as above will be explained.

First, when the steering wheel is not operated, that is, when the steering wheel is at rest, the oil supplied into the housing 1 from the pump P via the oil passage _C3 is maintained at the neutral position, so that the oil is supplied into the housing 1 through the oil passage C3. Annular groove 1a, spool 2
annular grooves 2a, 2b, annular groove 1 of housing 1;
b, 1c and is unloaded into tank T via oil passage _C4 .

Next, during steering operation, the spool bolt 3 interlocked with the steering shaft moves, for example.
The spool 2 moves to the right in the figure, and the spool 2 also moves to the right. As a result, communication between the annular groove 1a of the housing 1 and the annular groove 2a of the spool 2 and communication between the annular groove 1b of the housing 1 and the annular groove 2b of the spool are ensured.
and the annular groove 2b of the spool 2, and the annular groove 1c of the housing 1 and the annular groove 2a of the spool 2.
Each of them will be cut off from communication with the
Oil from pump P via oil passage _C3 is supplied to one chamber of the power cylinder via oil passage _C1 , and oil from the other chamber of the power cylinder via oil passage _C2 is supplied to one chamber of the power cylinder via oil passage C1. It will be discharged into tank T via channel _C4 . This causes the power cylinder to extend, for example, and cause the wheel to pivot in one direction.

In addition, contrary to the above, spool bolt 3
If spool 2 moves to the left in the diagram,
Due to the movement of the land 2', the oil from the pump P is supplied via the oil passage _C3 to the other chamber of the power cylinder via the oil passage _C2 , and the oil is supplied to the other chamber of the power cylinder via the oil passage _C1 . The oil from one chamber of the power cylinder is in the oil path.
It will be discharged to tank T via C ₄ ,
The power cylinder is retracted, thereby causing the wheel to turn in the other direction.

When the above-mentioned steering operation is stopped, that is, when the steering wheel is turned in a predetermined direction so that the vehicle can make a desired turn, the spool bolt 3 is moved by the coil spring 6a.
Alternatively, the spool 2 is returned to the neutral position by the repulsive force of the spool 6b.

That is, the spool bolt 3 has the spool 2
Pressure oil from the pump P is supplied to the outer surfaces of the plungers 5 and 5 through the gap between the housing 1 and the spool 22, but the base end of the spool bolt 3 is inserted into one cap 8. , since the tip protrudes to the outside of the plunger 5, a difference occurs in the pressure receiving surface due to the difference in cross section of the spool bolt 3, and due to the pressure difference, a back pressure is always applied to the spool 2 in the direction shown by arrow A in the figure. However, when the spool bolt 3 is moved to the right in the figure to overcome this back pressure, the repulsive force in the return direction of the spool 2 is due to the back pressure A acting on the spool bolt 3. Therefore, a small repulsive force is sufficient. On the other hand, when the spool bolt 3 is moved to the left in the figure, the repulsive force in the return direction of the spool 2 must be large enough to overcome the back pressure A and still move the spool 2 to the right.

In order to satisfy the above requirements, the present invention uses two coil springs 6a and 6b with different repulsive forces.
is housed in the spool 2, and this is also a feature of the present invention.

Note that the setting of the repulsive force between these two coil springs 6a and 6b is conditioned on the following equation being established.

That is, if the installed length of the coil spring 6a is l ₁ , the installed length of the coil spring 6b is l ₂ , and the diameter of the large diameter part of the spool bolt 3 is d, then the initial load of the coil spring 6a [K ₁ ×Δl ₁ ]+[π/ 4dt ² × back pressure〕=
Initial load of coil spring 6b [K ₂ ×Δl ₂ ] −
When [π/4d ² ×back pressure] is established, the neutral position of the spool 2 is obtained.

When the spool bolt 3 moves to the right, the plunger 5 on the left in the figure moves to the right together with the spool bolt 3, but the plunger 5 on the right in the figure is prevented from moving by the stopper 7. Therefore, only the coil spring 6b disposed between the plunger 5 and the flange 20 is contracted and has a repulsive force. Further, when the spool bolt 3 moves to the left, the plunger 5 on the right side in the figure moves to the left together with the spool bolt 3, but the plunger 5 on the left side in the figure is prevented from moving by the stopper 7. Therefore, only the coil spring 6a disposed between the plunger 5 and the housing 20 contracts, and its repulsive force is maintained.

FIG. 3 shows a power steering valve according to another embodiment of the present invention, which is suitable when the direction of back pressure is reversed. coil spring 6a,
This embodiment differs from the embodiment shown in FIG. 2 in that the spool 6b is disposed within the spool 2.

One coil spring 6a is attached to the spool 2.
The coil spring 6b is disposed between plungers 5 and 5 which are slidably interposed in the spool bolt 3, and the other coil spring 6b has one end in contact with one of the plungers 5. However, the other end is in contact with a spring 30 protruding from the outer periphery of the spool bolt 3.

Therefore, when the steering is stopped, the oil from the pump P is unloaded into the tank T, and
This embodiment is similar to the embodiment shown in FIG. 2 in that the spool 2 can be moved to the right or left during steering operation to supply oil to the power cylinder or to drain oil from the power cylinder.

When the spool 2 moves to the right in the housing 1, the plunger 5 on the right side in the figure is prevented from moving by the stopper 7, but the plunger 5 on the left side in the figure moves, so one coil spring 6a contracts. conversely, when the spool 2 moves to the left, the movement of the plunger 5 on the left in the figure is prevented by the stopper 7, but the spring seat 30 Since it moves together with the bolt 3, the other coil spring 6b
Only the repulsive force is contracted and the large repulsive force is retained.

According to the present invention, since two springs with different repulsive forces are interposed in the spool 2, the spool causes a difference in back pressure thrust on the left and right sides of the spool due to the pressure difference caused by the difference in pressure receiving area on both sides of the spool bolt. However, the spring cancels out this difference. This has the effect of eliminating left and right differences in steering operation force and significantly improving operability.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a conventional power steering valve, Fig. 2 is a sectional view showing a power steering valve according to the present invention in the same way as Fig. 1, and Fig. 3 is a partial sectional view showing another embodiment. be. 1... Housing, 2... Spool, 3... Spool bolt, 4... Holder, 5... Plunger, 6... Spring, 6a, 6b... Coil spring, 7... Stopper, 8... Cap, 20... …
Flange, 30...spring seat, A...back pressure, _C1 , _C2 , _C3 , _C4 ...oil path, P...pump,
T...Tank.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A cap is provided in the housing, a hollow spool is slidably inserted into the housing, plungers are interposed on both sides of the spool, and the spool bolt is interlocked with the steering shaft. The base end is slidably inserted into the cap, and the tip of the spool bolt is movably inserted into the plunger, and holders provided on both sides of the tip of the spool bolt are inserted between both end surfaces of the spool and each plunger. The spool bolt is brought into contact with the outer end surface of the spool bolt, and when the spool bolt is moved, the spool is switched while moving one of the plungers, and the spool bolt is always urged in the proximal direction by hydraulic pressure acting on the end surface of the distal end. A power steering valve characterized in that a spring with a small repulsive force that biases the spool bolt toward the proximal end and a spring with a large repulsive force that biases the spool bolt toward the distal end are interposed in the spool. (2) The power steering valve according to claim 1, wherein a flange is provided protruding from the inner peripheral surface of the spool, and coil springs having different repulsive forces are interposed between the flange and each plunger. (3) Practical use of a spring seat protruding from the outer circumferential surface of the spool bolt, a coil spring with a small repulsive force interposed between two plungers, and the other coil spring with a large repulsive force interposed between one plunger and the spring seat. A power steering valve according to claim 1 of patent registration.