JPS5822759A - Power steering device - Google Patents

Abstract

PURPOSE:To perform smooth and sudden steer by disposing two bypass valves in series with each other in a control valve, and operating one valve in response to the differential pressure of a power cylinder chamber and the other valve in response to the differential pressure higher than the prescribed value between the supply passage and the drain passage. CONSTITUTION:A bypass valve unit 14 provided in the bypass passage 10 of a control valve 2 has first and second bypass valves 18, 19 which communicate or interrupt the bypass passage 10 slidably engaged with spools 16, 17 in a pair of spool guide holes 15a, 15b formed in a valve body 15. Chambers 24-27 are formed at both sides of the spools 16, 17 in the body 15. The chambers 24, 25 are connected to th chambers 7a, 7b of the power cylinder 7 through communicating passages (12, 13), (8, 9). On the other hand, the chamber 26 is connected through a connecting circuit 39 to a drain passage 5, and the chamber 27 is connected through a connecting circuit 40 to the supply passage 4. Further, an orifice 42 or 41 is formed at one of the connecting circuits 39, 40.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device used in a vehicle steering device for the purpose of reducing the steering force of the vehicle.

As shown in FIG. 1, the power steering device usually includes a control pulp 2 that responds to steering operations on the steering wheel l.
The working fluid from the lump J is constantly passed through the control pulp through the supply path, and then the working fluid is returned to the reservoir tank 4, which is normally built in the pump 3, through the drain path J. - During steering operation, the control pulp 2 narrows the working fluid passage from the pump 3 to generate pressure on its upstream side, that is, in the supply path, and this pressure is transferred to one of the power cylinder chambers 7a or 7b of the power cylinder 7.
The IP is led through the connection WAl or 9, and the other power cylinder chamber 7b or 7a is connected to the drain path through the connection path 9 or 11 and the control valve! Connect the power cylinder chambers 7a and 7b to create a no-pressure state. ! A pressure is generated, and this differential pressure assists the steering operation by the steering wheel l via the power piston 7C, and power steering is possible.

However, in such a power steering device, back pressure is generated in the supply path due to the flow resistance of the control valve during non-steering operation outside the power steering tool, and the female control valve. This places an extra load on the pump J at all times, and a large amount of energy is consumed in driving the pump 3.

Therefore, as similarly shown in FIG. 1, it is conceivable to install a bypass path IO to short-circuit the supply path 1 and the drain path S, and to insert a bypass valve /l into this bypass path. This bypass valve has a spool inside the valve body//&
) are slidably fitted, and chambers I10.
//d is set, and the spool //b is elastically restrained in the illustrated position by balance springs //e and //f acting on both end surfaces thereof. A through hole //g that passes through the annular chamber set by the small diameter part in the middle at the position where the spool //b is applied is bored in the valve body //&, and an orifice //h is provided in this through hole. The hole //g is inserted and connected to the bypass path /θ. Further, the chambers I10 and //d are connected to the power cylinder chamber yeb by means of communication paths /2 and /J, respectively.
, 7b.

Thus, the bypass valve // is connected to both power cylinder chambers 7a17b.
However, during non-rudder increase operations, both power cylinder chambers are in an unpressurized state and no pressure difference occurs.
The spool //b is held in the position shown and the through hole //g is opened. Therefore, a part of the working fluid from the pump 3 heading to the control valve control valve via the supply path passes through the orifice.
Only the flow rate determined by h bypasses the control valve and is returned to the reservoir tank ≦, and the corresponding amount is generated in the supply path d. It is possible to prevent a large amount of time from being wasted.

On the other hand, when the steering wheel is operated, a pressure difference is generated between the power cylinder chambers 7a and 7b, which causes the spool/IeL to be displaced leftward or rightward from the position shown in the figure, closing the through hole/Ig and preventing the above-mentioned flow of working fluid. The bypass can be stopped and all of the working fluid from the dump truck 3 can be directed to the control nozzle 2, making it possible to perform the predetermined power steering described above.

However, in such an energy-saving power steering system, when the steering wheel is steered in one direction and then quickly steered in the opposite direction, the pressure in the supply path temporarily increases. Although it is necessary to be maintained continuously with almost no drop and to enable smooth turning power steering, the high pressure sides of the power cylinder chambers 7a and yb are reversed by the above turning of the steering wheel l. The spool llb, which responds to these differential pressures, moves from the left or right position to the position shown in the figure, and then moves to the right or left in the opposite direction, once opening the through hole //g on the way, and at this time the supply The pressure in the passageway is temporarily removed, and the steering force suddenly becomes heavy, which is dangerous. A bypass valve is installed,
If these bypass valves are connected in series with each other and inserted into the bypass path, the pressure in the supply path can be maintained without a temporary drop during the rapid reversal maneuver and can be used for the reversal power steering. Therefore, even if the first bypass valve is kept in the closed position by continuously receiving the differential pressure above a certain level between the supply path and the drain path, and the first bypass valve is temporarily opened as described above,
From the viewpoint of being able to solve the above-mentioned problem in which the pressure in the supply path is not released through the bypass path and the turning power steering becomes temporarily heavy, we aim to provide a power steering device that embodies this idea. It is something.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 2 shows an embodiment of the present invention, in which the same parts as in FIG. 1 are designated by the same reference numerals.

In the present invention, a set of two bypass valves to be inserted into the bypass passage 10 is constructed as a single unit as a bypass valve device. This objective bypass valve device /f has a pair of spool guide holes /3&, /Sb formed in its valve body /j, and the spool /j is formed in these holes.
, /7 are slidably fitted to constitute a first bypass valve II and a second bypass valve /9.

The openings at both ends of the spool guide holes /jeL, /jb are closed with plugs x, 2/, n, and H, respectively, to form chambers 2# to 1 between the corresponding spool end faces, and chambers 2F, 2
Balance springs 21 and 29 housed in chamber 5 act between the end faces of the corresponding plugs 〃, 2/ and spool /l to elastically restrain the spool /j in the axially balanced position shown in the figure. The spring X housed in is applied between the corresponding plug n and the end face of the spool 17 to urge the spool 17 to the right in the figure.〇In addition, each plug n is connected to the end face of the corresponding spool/4゜17. Stoppers za, 2/a, and 22a are oriented toward the direction.

27&, these stoppers restrict the axial movement of spools /6°/7, but the axial movement amount of spools /A and /7 from the position shown in the figure is all the same.

The valve body 75 is further formed with a through hole 33 passing through the annular chambers 3/ and Jj defined by the intermediate small diameter portion l≦a and /7a at the position shown in the figure at /7 in the spool /, An orifice 3 is provided in this through hole, and the through hole 33 is
is inserted into the bypass path lo and connected. The valve body /j also has chambers 2g, 35 and 34 which open into chamber B,
Boats 33 and 33 are connected to access routes /2 and /J, respectively, and boats n and 3g are provided that open to room 27.

31 is the connection circuit, gong and drain path! and connect to the supply line.

In this configuration, the bypass valve n is exactly the same as the bypass valve // in FIG.
In response to the pressure difference between the springs 21 and 7b, both of these power cylinder chambers are kept in an unpressurized state during non-steering operations, and since no pressure difference occurs between them, the spool/6 is moved by the spring 21. E is maintained in the illustrated balanced position, and the through hole 33 is opened. On the other hand, even during such non-steering operations, back pressure is generated in the supply path due to the flow resistance of the control valve, etc., as described above, and this back pressure is transferred to the chamber through the connection circuit V and bow) 31. 1
The bypass valve 1 connects its spool /7 to the stopper 27a, since the chamber is connected to the drain path J by the connection circuit and is maintained in an almost unpressurized state.
The back pressure inside the chamber 1 pushes the spring 3θ back against the spring 3θ to the position shown in the figure, thereby opening the through hole 33.

In this way, a part of the working fluid from the pump 3 heading to the control valve via the supply path Hiroshi bypasses the Funtrol valve by the flow rate determined by the oriice 3 and flows into the reservoir tank t via the bypass path 10 and the through hole 33. This makes it possible to reduce the back pressure generated in the supply path and reduce the load on the pump 3, thereby preventing unnecessary consumption of pump drive energy during non-steering operation.

The back pressure reduced in this way balances the spring force of the spring 30 in the chamber 1, keeps the spool 17 in the position shown and keeps the through hole 33 open, and the back pressure inside the supply path is reduced during non-steering operation. During this time, the pump drive energy is kept at a constant low value determined by the spring force of the spring 30, and during this period, it is possible to continuously prevent the pump drive energy from being wasted.

However, during steering operation, the power cylinder chamber 7a.

A differential pressure is generated between 7b and the bypass valve 27b causes the spool 4 to move leftward or rightward (depending on the steering direction) from the balance position shown in the figure, and to strike the stopper 27a or 2/a. Since the contact point is at the limit position, the through hole 3
Close 3. At the same time, a pressure corresponding to the pressure in the power cylinder chamber 7a or 7b, which is made high as described above during the steering operation, is generated in the supply path, and this high pressure moves the spool 17 in the chamber r from the position shown in the figure. The bypass valve 9 also closes the through hole 33 in order to move further to the left in the figure against the angle 3θ and reach the limit position where it collides with the stopper 22a. Therefore, the above-mentioned bypass of the working fluid is reliably stopped at the time of the relevant steering operation, and the working fluid from the pump 3 can be directed to the Roll Valve Co. It is possible to cause the direction to occur in a predetermined manner.

On the other hand, when performing a rapid turn-over maneuver in which the steering wheel l is steered in one direction and then immediately steered in the opposite direction, the high pressure sides of the power cylinder chambers 7L and 7b are reversed, so that The bypass valve /1, which responds to the differential pressure of . However, even when the steering wheel is turned, the pressure change in the supply path is rapid compared to the moving speed of the spool/7, and the spool/7 hardly moves from the leftward position described above, so the pressure in the supply path does not change. As mentioned above, the pressure remains high with almost no pressure drop, even temporarily. Therefore, the bypass valve /9 operated as described above by this pressure continues to close the through hole 33 because the spool 17 is maintained at the limit position where it abuts against the stopper 22a. Thus, even if the bypass valve /I temporarily opens the through hole 33 as described above during the rapid reversal maneuver, this through hole will continue to be closed by the bypass valve /9.
As a result, the pressure inside the supply path increases to the bypass path 10 and the through hole 3.
3, and smooth rapid turning power steering can be performed while keeping the pressure high.

In addition, in the above-mentioned structure, when performing a relatively slow turn-around maneuver in which the pressure in the supply passageway once decreases, the spool 17 is pushed back by the spring 30 due to this pressure decrease, and the bypass valve/return is pushed back by the spring 30. Temporary through hole 33
However, the timing may coincide with the timing at which the bypass valve/I opens the through hole 33 as described above due to the movement of the spool 16 accompanying the reverse steering. in this case,
The working fluid in the supply path d temporarily passes through the bypass path lθ and the through hole 33.
As a result, the rise of the assist pressure during such steering is delayed, and the responsiveness of power steering becomes worse. From this point of view, it is preferable to keep the through hole 33 closed and to stop bypassing the working fluid even during such a relatively slow turning maneuver, as in the case of the rapid turning steering described above.

In the example of Fig. 4, for this purpose, a +27tr-drain passage is provided in the bypass valve/9 chamber! and the connection circuit J? connected to the supply line D? . In this case, the bypass valve 19 operates with a time delay from the bypass valve /I by the resistance of the orifice U or Hiro λ, and it is possible to prevent both bypass valves from opening the through hole 33 at the same time during the turning maneuver. It is possible to prevent a delay in the response of power steering during relatively slow turnaround steering.

Alternatively, as shown in Fig. 3, the stopper 22a may be shortened to reduce the gap α between it and the spool/7 in the open position.
, the spool 16 and stoppers 20a, 2 in the open position
) If the gap between a and a is larger than β, then spool 1
The time required for the spool 7 to move from the closed position where it collides with the stopper 22a to the illustrated open position is the same as the time required for the spool /, < to move from the closed position where it collides with the stopper 27a or 2/a to the illustrated open position. This can be made longer by the distance difference α-1 minute than the time required for
I can operate with a time delay and achieve the same purpose as described above.

Furthermore, the pump 3 is normally driven by the vehicle engine, and when the pump rotation speed increases above the value of the vehicle when the vehicle is running at high speed, its discharge volume decreases as shown in Figure 2. 70-down) to increase the steering force when driving at high speeds.
Flow control that improves steering stability during high-speed running (Rotation speed sensitive pumps with built-in loops are often used. However, in this case, as mentioned above, when operating the gun without rudder,
(A) If the valves /g and /? both open the through hole 33, the amount of discharge from the pump 3 will be the minimum (Get j1/'min in the example shown in Figure 3). During high-speed driving, the amount of working fluid to the control valve 2 decreases further and becomes extremely small.Therefore, when the steering wheel t is operated in this state, all of the above-mentioned small amount of working fluid is used to steer the control valve 2. It is used to fill the increased volume of the nozzle chamber 7a or 7b of the workpiece 1 due to the handling operation, and it becomes impossible to generate assist pressure and the power steering force τ is disabled, and the bypass valve/ I cannot close the valve I, and for the same reason, there is not enough pressure in the supply path L to close the bypass valve 9 as described above, so the power steering is maintained indefinitely. .

By the way, in the example of FIGS. 2 and 3, the spool/7 in the open position and the stopper 2? Since we have set a gap between the pump 3 and the spool 7 that allows the spool 7 to be in the closed position,
When the back pressure generated in the supply path during non-steering operation due to the 70-down of 70-down becomes less than the above-mentioned constant value determined by the spring force of the spring 3θ, the spool 17 is moved by the spring 3θ to the stopper 2? It is pushed to a position where it collides with a. Therefore, the bypass valve lwo closes the through hole 33 when the pump 3 is down 70, and the working fluid is transferred from the supply path Hiro to the bypass path lθ and the through hole 3.
3 to the reservoir tank 6, and the pump 3 reduced by 70-down (
7) Does it work? Ifl can be directed to the full control valve control, eliminating the above-mentioned disadvantage that power steering becomes impossible during high-speed driving. The operation of the bypass valves /I and /9 during this dynamic blade steering is the same as described above, and does not interfere with the power steering in any way.

Thus, as described above, the power steering system of the present invention includes two bypass valves (n,
/ ) is inserted in series in the bypass path / θ,
One bypass valve/l is connected to the power cylinder chamber 7a, 7
Since the structure is configured so that the other bypass valve /q responds to the pressure difference between the supply path l and the drain path j above a certain level, the bypass valve IO responds to the pressure difference between the supply path l and the drain path j.
9 is always closed, and the pressure that continues to be generated in the supply path during this steering is not released through the bypass path 10, and smooth turning power steering can be performed. This can prevent the danger of the force suddenly becoming too heavy.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a conventional power steering device, Fig. 2 is a system diagram of a power steering device of the present invention, and Fig. 3 is a front view of a bypass valve device showing another example of the present invention. The figure shows 7 of the pump.
It is a 0-down characteristic diagram. l... Steering wheel, λ... Funtrol pulp, 3... Pump, Hiro... Supply path,! ...Drain path, t...Reservoir tank, 7...Power cylinder, 7a. 7b...Power cylinder chamber, la...I pass l
, /41... Bypass valve device, 15... Valve body, /4, /7.
...Spool, /l...First bypass valve, /9...
・Second bypass valve, ~n... plug, la-λ3
a... Stopper, 2 keys to 1, chamber, X, Zt...
Balance spring, 30... Spring, 33... Through hole, 34L... Orifice, 33~3K,... Port, B, ψ... Connection circuit. Patent applicant Nissan Motor Co., Ltd.

Claims (1)

[Claims] L: The working fluid supplied from the pump through the supply path is passed through the control pulp that responds to the steering operation, and then returned to the pump through the drain path. A power rudder that enables power steering by narrowing the passage to generate pressure on the upstream side of the passage, and transmitting this pressure to one power cylinder chamber while keeping the other power cylinder chamber in a pressure-free state. a first bypass valve that closes in response to a differential pressure between the two power cylinder chambers in a bypass path that short-circuits the supply path and the drain path;
A power steering device characterized in that a second bypass valve that closes in response to a pressure difference of a certain level or more between the supply path and the drain path is inserted in series. 2. The power steering device according to claim 1, wherein the second bypass valve has an orifice inserted in a connection circuit with the supply path or the drain path. The power steering system according to claim 1, wherein the second bypass valve has a closing valve stroke larger than that of the first bypass valve. The power steering device according to claim 1, wherein the second bypass valve is closed also by a pressure difference below a certain level between the supply path and the drain path.