JPH07110568B2 - Vehicle suspension - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a suspension device for a vehicle, and more particularly to a suspension device for a vehicle that is most suitable for mounting on a special vehicle such as a rough terrain vehicle or a crane vehicle.

[Conventional technology]

Suspending equipment such as rough terrain vehicles and crane vehicles that suspend heavy objects at work sites and perform work such as rearrangement of them is the most compressed state of the hydraulic cylinder when lifting heavy objects. It is formed so as to exert the function of holding the suspension spring in the inactive state, that is, the compression holding function, and is capable of traveling on a high speed road surface like a normal vehicle, and has stability and riding stability. It is preferably formed so as to improve comfort.

That is, during normal traveling of the vehicle in a state in which the compression holding function for deactivating the suspension spring is released and the suspension spring is in operation, the suspension spring absorbs road surface vibrations and the wheelbase of a rough terrain vehicle or the like. For short vehicles,
It is preferable that the suspension device be formed so that an anti-nose dive function that prevents a nose dive phenomenon when the vehicle is braked is exerted.

However, although the conventional suspension device has a compression holding function for making the suspension spring inoperative, it does not have a cushioning function for attenuating road surface vibration absorbed by the suspension spring. There was a problem that stability was poor and the maximum speed was limited to low speed driving of about 40 km / h.

Also, when the anti-nose dive function is exerted when the brake is operated while the vehicle is running and the hydraulic cylinder is in a completely locked state, road surface vibration is directly transmitted to the vehicle body frame, which considerably deteriorates the riding comfort and makes it possible to ride over bumps. If there is a thrust from under the unsprung, the impact will be directly transmitted to the body frame, and there is a danger that the steering stability of the vehicle will be deteriorated.

Therefore, the applicant of the present application, in a suspension system for a vehicle formed so as to exhibit a compression holding function, exhibits a cushioning function of attenuating road surface vibrations absorbed by suspension springs when the vehicle normally runs on a road surface, and We first proposed a vehicle suspension system that can exert an anti-nose dive function without deteriorating the riding comfort and steering stability of the vehicle (Japanese Patent Application No.
59-102629).

The proposal by the applicant of the present application as the above-mentioned conventional proposal is formed, for example, as shown in FIG.

That is, the hydraulic cylinder 1 is a checker which prevents passage of oil from the rod side chamber A to the piston side chamber B in the piston portion 1c which divides the cylinder 1a into the rod side chamber A which is the expansion side chamber and the piston side chamber B which is the pressure side chamber. A damping valve 10 having a valve 1d and a rod cover portion 1e through which a piston rod 1b is inserted is provided in a central portion of an axis of the damping valve 10 which also functions as a shutoff valve.
The damping valve 10 opens the passage 6 that allows the rod side chamber A and the reservoir tank 5 side to communicate with each other when the back pressure can be released by opening the operating check valve 10 ′ on the back side. As a result, the desired damping force is generated when the oil passes through the opening, and the escape of back pressure is prevented by closing the operate check valve 10 '. The oil in the rod-side chamber A is prevented from flowing out, so that the so-called extension-side oil lock in the hydraulic cylinder 1 is enabled.

The compression holding function of the hydraulic cylinder 1 is based on the main solenoid valve 3
By the operation, the oil from the main pump 2 is circulated into the rod cover portion 1e through the passage 4, and the check valve 7 is opened to flow into the rod side chamber A. From the piston side chamber B, the oil once guided into the rod cover portion 1e flows out into the passage 6 through the operate check valve 7'released by the hydraulic pressure from the passage 4, and , Is returned to the reservoir tank 5. Then, after the hydraulic cylinder 1 is compressed to a desired state by the supply of oil into the rod side chamber A, the check valve 7 and the operate check valve 7'are closed by operating the main solenoid valve 3. Moreover, in the rod side chamber A, the oil outflow by the damping valve 10 is blocked, and in the piston side chamber B, the oil outflow through the passage b is blocked by the check valve 9.
The hydraulic cylinder 1 is maintained in the oil lock state. Further, 8 in FIG. 2 is a pressure regulating valve,
Reference numeral 12 is a pilot solenoid valve, and 13 is a pilot pump.

Therefore, according to the above conventional proposal, the hydraulic cylinder 1 is
Is provided on the left and right sides of the front wheels of the four-wheel vehicle, a compression holding function for making the suspension spring inoperative is possible, and at least a damping function for using the hydraulic cylinder 1 as a so-called shock absorber. It will be demonstrated.

[Problems to be solved by the invention]

However, in the above conventional proposal, the piston part
Since the check valve 1d is arranged on the 1c, there is not only an inconvenience that the number of processing strokes is increased in forming the piston part 1c, but also a small check space due to the limited space of the piston part 1c. In addition to the inconvenience of being the valve 1d, there is the inconvenience of having a structure that is stable against internal leakage.

Further, in the above-mentioned conventional proposal, since the damping valve 10 also functions as a shutoff valve at the time of oil lock of the rod side chamber A, in forming the damping valve 10 itself, selection of material and processing accuracy are required. In view of the above, there is an inconvenience that it is required to be sophisticated so that it can withstand harsh conditions.

Further, when the damping valve 10 that functions as a shutoff valve is opened to allow the oil in the rod side chamber A to flow out, the passage opening is increased to ensure the function of the damping valve 10. On the other hand, if the damping valve 10 is opened in order to release the oil lock in the rod side chamber A, there is a disadvantage that a sudden extension is caused and a large shock is brought to the vehicle body.

Therefore, in view of the above-mentioned circumstances, the present invention not only exhibits predetermined functions, but can further improve the running stability and riding comfort of the vehicle, and further improve the durability of the hydraulic cylinder to improve the economy. It is another object of the present invention to newly provide a suspension system for a vehicle that is also advantageous in terms of physical properties.

[Means for solving problems]

In order to achieve the above object, the structure of the present invention is such that a suspension spring and a hydraulic cylinder are interposed between a vehicle body frame and a wheel, and the hydraulic cylinder includes a cylinder, a rod cover integral with the cylinder, and a piston in the cylinder. A piston rod movably inserted through the rod cover and penetrating the rod cover, a rod-side oil chamber and a piston-side oil chamber defined by the piston portion, and the hydraulic cylinder is compressed to maintain its compressed state. However, in a suspension system for a vehicle in which the suspension spring is maintained in an inoperative state, a first passage for selectively communicating the rod-side oil chamber with the main pump or the reservoir tank in the rod cover and a rod-side oil chamber are provided. A second passage connected to the reservoir tank, a first bypass provided between the second passage and the rod-side oil chamber, and a piston-side oil chamber connected to the second passage. A third passage to be continued, a second bypass provided between the third passage and the second passage, and a pilot passage selectively communicating with the pilot pump or the reservoir tank are provided, and the first passage is provided. A first check valve that selectively opens with pressure oil from the main pump or pilot pressure from the pilot passage is provided in the passage, and a shut-off valve that is controlled to open and close with the pilot pressure from the pilot passage in the second passage. And a damping valve that is controlled to open and close in conjunction with the opening and closing operation of the shutoff valve and that opens only when the hydraulic cylinder extends. Opening and closing control is performed in the first bypass in conjunction with the opening and closing operation of the shutoff valve. And a second check valve that is opened only when the hydraulic cylinder is compressed, and a third check valve that is controlled to open and close by pilot pressure in a pilot passage is provided in the third passage. The inside of the bypass pilot pressure or the pilot passage is characterized in the provision of the pressure regulating valve that opens selectively in internal pressure in the piston side oil chamber.

〔Example〕

 Hereinafter, the present invention will be described based on the illustrated embodiments.

As shown in FIG. 1, a suspension system for a vehicle according to an embodiment of the present invention has a suspension spring and a hydraulic cylinder 1 interposed between a body frame and wheels, and the hydraulic cylinder 1 is a cylinder 1a.
, Rod cover 1e that is integral with cylinder 1a, and cylinder 1a
A piston rod 1b that is movably inserted into the piston cover 1c and penetrates the rod cover 1e;
It is provided with a rod-side oil chamber A and a piston-side oil chamber B partitioned by 1c so that the hydraulic cylinder 1 is compressed to maintain its compressed state while maintaining the suspension spring in an inoperative state.

The rod side oil chamber A is installed in the rod cover 1e with the main pump 2
Or, between the first passage 4 that selectively communicates with the reservoir tank 5, the second passage 6 that connects the rod-side oil chamber A to the reservoir tank 5, and the second passage 6 and the rod-side oil chamber A. The first bypass c provided in the
Third passage b connected to the passage 6 of the second passage, a second bypass d provided between the third passage b and the second passage 6, and selectively communicates with the pilot pump 13 or the reservoir tank 5. A pilot passage 11a is provided.

The first passage 4 is provided with a first check valve 7 which is selectively opened by pressure oil from the main pump 2 or pilot pressure from the pilot passage 11a.

In the second passage 6, a shutoff valve 11 which is controlled to be opened / closed by pilot pressure from a pilot passage 11a, is controlled to be opened / closed in conjunction with the opening / closing operation of the shutoff valve 11, and is opened only when the hydraulic cylinder 1 is extended. A damping valve 10 is provided.

In the first bypass c, a second check valve 14 is provided which is controlled to open and close in conjunction with the opening and closing operation of the shutoff valve 11 and which opens only when the hydraulic cylinder is compressed.

In the third passage b, a third check valve 9 which is controlled to open / close by the pilot pressure in the pilot passage 11a is provided.

In the second bypass d, a pressure adjusting valve 8 that is selectively opened by the pilot pressure of the pilot passage 11a or the internal pressure of the piston side oil chamber B is provided. Pressure oil from the main pump 2 is supplied to the hydraulic cylinder 1 via the main solenoid valve 3 and the passage 4, and oil is discharged from the hydraulic cylinder 1 to the reservoir tank 5 via the passage 6. Has been done.

The hydraulic cylinder 1 has suspension springs (not shown) and is arranged on the left and right sides of the front wheel of the vehicle. The upper end of the hydraulic cylinder 1 is connected to the vehicle body frame side of the vehicle and the lower end of the vehicle is connected to the vehicle body frame. It is connected to the wheel side. The hydraulic cylinder 1 has a piston portion 1c arranged at the tip of a piston rod 1b inserted into the cylinder 1a and partitioning the inside of the cylinder 1a into a rod side chamber A which is an expansion side chamber and a piston side chamber B which is a pressure side chamber. is doing.

The main solenoid valve 3 has a supply position 3a for supplying the pressure oil from the main pump 2 into the passage 4, and a discharge position for discharging the supply oil into the passage 4 to the reservoir tank 5. Has 3b. still,
In this discharge position 3b, pressure oil can be supplied to the power steering mechanism PS (not shown) of the vehicle. A relief valve 2a is attached to the main pump 2.

The passage 4 is connected to a check valve 7 provided in the rod cover portion 1e of the hydraulic cylinder 1, and the pressure oil flowing through the check valve 7 in the rod side chamber A is opened through the passage 7a. It is about to flow into. In the present embodiment, the check valve 7 is a poppet 70,
The poppet 70, which has a spring 71 for urging the poppet 70 in the forward direction, retreats when pressure oil is supplied from the main pump 2 slides by the supply of external supply pressure, that is, pilot pressure. It is formed in a so-called operated check valve shape in which the plunger 72 is provided adjacently and is opened even when the plunger 72 slides.

The passage 6 has a suction valve 6a at its reservoir tank 5 side end.
And the back pressure valve 6b are arranged in parallel, and are formed so that the return oil from the power steering mechanism PS of the vehicle flows in. The action of this return oil and the back pressure valve 6b improves the suction of oil into the hydraulic cylinder 1.

Further, the passage 6 is formed so as to communicate with the passage b via a pressure adjusting valve 8 arranged in the rod cover 1e. That is, when a high oil pressure in the piston side chamber B acts on the pressure adjusting valve 8 via the passage b, the oil pressure is released when it exceeds the set oil pressure of the pressure adjusting valve 8, and the oil is released on the passage 6 side. It is designed to flow out to. Further, in the present embodiment, the pressure adjusting valve 8 is a poppet 80 for closing the opening on the side of the passage b.
And a spring that biases the poppet 80 from the passage 6 side.
And a plunger 82 that slides by the supply of an external supply pressure, that is, a pilot pressure, is adjacently provided, and the sliding of the plunger 82 allows the poppet 80 to optionally Is formed so that the pressure control valve 8 can be released by retracting the pressure control valve 8. The pressure adjusting valve 8 functions as a check valve for the oil flow from the passage 6 side to the passage b side, and blocks the oil flow.

The passage 6 is also connected to the passage b via a check valve 9, and the check valve 9 allows passage of oil from the passage b side to the passage 6 side, but conversely from the passage 6 side. The passage of oil to the passage b side is prohibited. The check valve 9 is the spring 90 in the present embodiment.
The valve body 91 is urged by the valve body 91, and the tip of the valve body 91 closes the opening communicating with the passage b. However, the check valve 9 forcibly bends the spring 90 when the external supply pressure, that is, the pilot pressure is supplied, so that the valve body 91 can be retracted to allow passage of the passage 6 and the passage b.
It is formed so that it can be distributed without giving direction to and.

The rod cover portion 1e of the hydraulic cylinder 1 has a damping valve 10
Is provided. The damping valve 10 has a poppet 101 biased by a spring 100 from the rear side, and is formed so that the poppet 101 can be retracted by the hydraulic pressure from the rod side chamber A. The poppet 101 is formed so as to obtain a desired damping force when the oil in the rod side chamber A flows out to the passage 6 side which is the outside through the gap with the seat portion formed by retracting. ing.

A shut-off valve 11 for enabling the operation of the damping valve 10 is provided in the rod cover portion 1e, and the damping valve 10 and the passage 10a are provided.
Is formed so as to communicate with each other. Further, the shut-off valve 11 is connected to a pilot passage 11a, which is opened when the pilot pressure is supplied through the pilot passage 11a and released when the pilot pressure is released. It is formed to function as a check valve.

In the present embodiment, the shut-off valve 11 is arranged on the back pressure side of the damping valve 10, and includes a valve body 110 that slides and retracts when a pilot pressure is supplied, and the valve body 110. When the valve element 110 slides to open the passage 10a, the damping valve is formed of a spring 111 for urging 110 in the forward direction.
The pressure is released in the oil chamber, which is the spring chamber behind the poppet 101, and the poppet 101 is retracted so that the oil in the rod-side chamber A can flow out toward the passage 6 side. There is.

Therefore, when the shutoff valve 11 is supplied with the pilot pressure from the outside, the poppet 101 in the damping valve 10 can be retracted, that is, the damping valve 10 is operated and the pilot pressure is increased. When released, the valve element 110 of the shutoff valve 11 is advanced by the urging force of the spring 111 to shut off the communication between the passage 10a and the passage 6, and the damping valve 10 does not operate.

The pilot passage 11a, which enables the supply of the pilot pressure to the shutoff valve 11, is connected to the pilot solenoid valve 12.
A pilot pump 13 is connected to the pilot solenoid valve 12. Further, the pilot solenoid valve 12 stops the supply of the pilot pressure from the pilot pump to the shutoff valve 11 via the pilot passage 11a and the supply of the pilot pressure to the pilot passage 11a. Together with the pilot passage
It has a discharge position 12b for discharging the oil in 11a into the reservoir tank 5. The above pilot pump 13
Is equipped with a relief valve 13a.

In the present embodiment, the pilot pressure supplied from the pilot pump 13 is adjacent to the plunger 72 adjacent to the tip of the poppet 70 of the check 7 and the tip of the poppet 80 of the pressure regulating valve 8 in the present embodiment. Plunger 82
It is also used as an external supply pressure for sliding the valve body 91 of the check valve 9 capable of blocking the communication between the passage b and the passage 6.

A check valve 14 is also arranged in the rod cover portion 1e. The check valve 14 includes the damping valve 10 and the shutoff valve.
11 has a poppet 140 that closes an opening that communicates with the passage 10a that allows communication with 11, and a spring 141 that biases the poppet 140 in the forward direction, and the piston portion 1c It is formed for so-called flow passage setting so that the oil from inside the rod side chamber A always passes through the damping valve 10 during the expansion side stroke of moving inside the cylinder 1a. The check valve 14 has its poppet 140 retracted so as to allow the oil from the passage 10a to flow into the rod side chamber A during the pressure side stroke opposite to the extension side stroke. Will be done.

Here, the operation of the vehicle suspension system according to the present invention will be briefly described.

First, in order to make the suspension spring inoperative for the vehicle to perform crane work etc. at the work site, the pilot solenoid valve 12
The shutoff valve 11 is deactivated as a discharge position 12b to prevent the damping valve 10 from operating, and the rod side chamber A
The oil inside is prevented from flowing out to the reservoir tank 5 side through the damping valve 10.

From this state, the main solenoid valve 3 is switched to the supply position 3a. As a result, the pressure oil from the main pump 2 flows into the rod-side chamber A through the passage 4 and the check valve 7. On the other hand, the oil in the piston side chamber B flows out into the passage 6 via the pressure adjusting valve 8 opened by the hydraulic pressure from the passage b and the piston side chamber B, and the reservoir tank 5
It will be discharged to the side and the hydraulic cylinder 1 will be compressed. Then, when the hydraulic cylinder 1 is brought into a desired compressed state, that is, when the spring effect in the suspension device is diminished, the main solenoid valve 3 is discharged from the discharge position.
Switch to 3b. As a result, the supply of pressure oil into the rod-side chamber A is stopped, and the oil is contained in the rod-side chamber A, so-called an oil lock state is established, and the extension by the suspension spring of the hydraulic cylinder 1 is prevented, and the compression is performed. Hold function is demonstrated.

Next, when releasing the above-mentioned compression holding function, that is, when releasing the oil lock state in the rod side chamber A, the pilot solenoid valve 12 is switched to the supply position 12a. As a result, the pilot pressure is supplied to the inside of the rod cover 1e, and the plungers 72, 82 of the check valve 7 and the pressure regulating valve 8 first retract the poppets 70, 80 of the valves 7, 8 and, The valve 7 and the pressure adjusting valve 8 are opened to allow the oil in the rod side chamber A to flow out and to allow the oil to flow into the piston side chamber B. Due to the supply of the pilot pressure, the valve body 110 of the shutoff valve 11
Slides so as to move backward so that the passage 10a and the passage 6 can communicate with each other, and the damping valve 10 can be operated. That is,
It is possible to allow the oil to flow from the inside of the rod side chamber A to the outside.

Therefore, in the operation for canceling the compression holding function, the oil in the rod side chamber A once flows out to the outside via the check valve 7 which is a small oil passage, and then the damping valve 10 which is a large oil passage and It will flow out to the outside through the shut-off valve 11, the hydraulic cylinder 1 will not be suddenly extended, and the shock for that will not occur.

When releasing the oil lock, the piston side chamber B
In the inside, the insufficient oil corresponding to the withdrawal of the piston rod 1b is supplied from the return of the reservoir tank 5 and the PS circuit into the piston side chamber B through the passage 6, the opened pressure adjusting valve 8 and the passage b. The hydraulic cylinder 1 will be extended.

Further, the pilot solenoid valve 12 is maintained at the supply position 12a when the vehicle is traveling on the road surface. When the hydraulic cylinder 1 is compressed in this state, the oil in the piston side chamber B is forced to open the check valve 9, the shutoff valve 11 and the check valve 14 to flow into the rod side chamber A. Then, the oil corresponding to the entering volume of the piston rod 1b flows out to the reservoir tank 5 via the check valve 14, the passage 4 and the main solenoid valve 3 which are in the open state.

Then, when the hydraulic cylinder 1 is extended, the oil in the rod side chamber A flows into the piston side chamber B through the damping valve 10, the shutoff valve 11, the check valve 9 and the passage b, which are in the operating state, and the piston rod 1b. The oil equivalent to the exit of
The return oil from the power steering mechanism PS is sucked in, and if the return oil is insufficient, the suction valve 6a is sucked from the reservoir tank 5.
Is sucked through and is replenished in the piston side chamber B through the opened check valve 9 and the passage b.

During the expansion side stroke, part of the oil from the rod side chamber A is returned to the reservoir tank 5 via the opened check valve 7 and the passage 4 and the main solenoid valve 3.

Therefore, the hydraulic cylinder 1 can be expanded / contracted in accordance with the vibration of the vehicle, and at the time of the expansion / contraction operation, the oil from the rod side chamber A passes through the damping valve 10, so that the road surface can be prevented. The cushioning function for damping the vibration is exhibited.

In order to exert the anti-nose dive function that prevents the nose dive phenomenon of the vehicle during the brake operation from the above state, the pilot solenoid valve 12 is switched to the discharge position 12b in conjunction with the brake operation, and the check valve 9 and the shutoff valve 1 are connected.
Deactivate 1 and, in particular, deactivate damping valve 10.

As a result, the oil in the rod side chamber A is prevented from flowing out to the passage 6 side, and the oil in the piston side chamber B is prevented from flowing out by the check valve 9, so that the nose dive at the time of brake operation is prevented. The phenomenon is prevented.

In this state, if the piston side chamber B is pushed up from the road surface due to riding over the protrusion or is subjected to strong vibration.
Oil pressure rises, the pressure control valve 8 operates, and the piston side chamber B
The oil inside is discharged to the reservoir tank 5, and it is possible to absorb the shock and strong vibration due to the thrusting up, and the riding comfort and steering stability of the vehicle are not deteriorated.

In the above description, the embodiment in which the hydraulic cylinder 1 according to the present invention is disposed on the left and right sides of the front wheel of the vehicle has been described. However, instead of this, the hydraulic cylinder 1 is also disposed on the left and right sides of the rear wheel of the vehicle. In particular, in order to prevent compression for the anti-nose dive function in the front wheel hydraulic cylinder 1, the rear wheel hydraulic cylinder 1 is prevented from floating on the rear wheel side. As a result, the ground resistance of the rear wheels can be secured.

Further, the set hydraulic pressure of the pressure regulating valve 8 in the above-described embodiment can be made variable, for example, in proportion to the brake hydraulic pressure, and the resistance for preventing the nose dive becomes larger as the brake pressing force becomes stronger. Is. And
By arranging a throttle in parallel with the pressure adjusting valve 8 to allow some nose dive when the anti-nose dive function is exerted, to prevent deterioration of riding comfort and steering stability of the vehicle. May be

〔The invention's effect〕

 As described above, the present invention has the following effects.

Since the rod-side oil chamber can be locked by the first check valve and the shutoff valve during compression, the suspension device of the vehicle can exert a compression holding function.

Since the damping valve, which is controlled to be opened and closed by the shutoff valve, is provided in the second passage, it is possible to exert a cushioning function of damping road surface vibration while the vehicle is traveling, and the riding comfort in normal road surface traveling is improved. In particular, even in a vehicle with a short wheelbase such as a rough terrain vehicle and traveling is unstable, high speed driving is possible.

Since the third check valve is provided in the third passage and the pressure adjusting valve is provided in the second bypass, the anti-nose dive function for preventing the nose dive phenomenon while the vehicle is traveling is exhibited, and the anti-nose dive function is also provided. When the dive function is exerted, even if the push-up action causes the push-up action, the push-up action is absorbed by the pressure regulating valve. Therefore, even in a special vehicle such as a rough terrain vehicle that has a short wheel base and is likely to cause a nose dive phenomenon, the nose dive phenomenon is prevented, the riding comfort and running stability of the vehicle are improved, and high speed running is performed. It has an advantage that the ride comfort and the steering stability are not deteriorated even when the vehicle is thrust up from the road surface.

Since the second check valve for securing the outflow of oil in the rod side chamber to the damping valve section is supposed to be arranged in the lot cover, there is a risk of internal leakage when forming the second check valve. There is an advantage that a check valve having no structure can be provided and the size of the check valve can be freely selected.

Since the first check valve can be opened by the pilot pressure from the pilot passage, when the hydraulic cylinder is extended to release the compression holding state, the first check valve that is initially opened. It is possible to discharge to the outside from the small oil passage part formed by, and further to the outside from the large oil passage part that is formed by the shutoff valve opened subsequently. Therefore, there is an advantage that sudden extension of the hydraulic cylinder is prevented in advance, and there is no fear of a shock during extension.

Since the damping valve and the shutoff valve are provided in the second passage and they function separately, it is possible to form each valve separately. In particular, when forming the damping valve itself, There is an advantage that no special limitation is required for selection and setting of shape.

[Brief description of drawings]

FIG. 1 is a view showing an embodiment of a vehicle suspension device according to the present invention, and FIG. 2 is a view showing a conventional example similar to FIG. 1 ... hydraulic cylinder, 1a ... cylinder, 1b ... piston rod, 1c ... piston part, 1e ... rod cover, 2 ...
... Main pump, 3 ... Main solenoid valve, 4 ... First passage, 5 ... Reservoir tank, 6 ... Second passage, 7 ...
1st check valve, 8 ... pressure regulating valve, 9 ... third check valve, 10 ... damping valve, 11 ... shutoff valve, 11a ... pilot passage, 12 ... pilot solenoid valve, 13 ... Pilot pump, 14 ... Second check valve, A ... Rod side chamber, B ... Piston side chamber, b ... Third passage, c ... First bypass, d ... Second bypass.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Bibliography Syo 59-89708 (JP, U) Sumi 41-6090 (JP, Y2)

Claims (1)

[Claims] 1. A suspension spring and a hydraulic cylinder are interposed between a body frame and a wheel, and the hydraulic cylinder is a cylinder.
A rod cover that is integral with the cylinder; a piston rod that is movably inserted into the cylinder through the piston portion and that penetrates the rod cover; and a rod-side oil chamber and a piston-side oil chamber that are partitioned by the piston portion. In a vehicle suspension system in which a hydraulic cylinder is compressed to maintain the compressed state while maintaining the suspension spring inactive, the rod side oil chamber is selectively connected to the main pump or reservoir tank in the rod cover. A first passage for connecting the rod-side oil chamber to the reservoir tank, a first bypass provided between the second passage and the rod-side oil chamber, and a piston-side oil chamber for the first passage. A third passage connected to the second passage, a second bypass provided between the third passage and the second passage, and a passage selectively communicating with the pilot pump or the reservoir tank. An ilot passage is provided, a first check valve that is selectively opened by pressure oil from a main pump or pilot pressure from a pilot passage is provided in the first passage, and a pilot passage is provided in the second passage. And a damping valve that is controlled to open and close by the pilot pressure of 1. and a damping valve that is controlled to open and close in conjunction with the opening and closing operation of the shutoff valve and that opens only when the hydraulic cylinder extends, and the shutoff valve is provided in the first bypass. A second check valve that is controlled to open and close in conjunction with the opening and closing operation of the valve and that opens only when the hydraulic cylinder is compressed is provided. In the third passage, the third check is opened and closed by the pilot pressure in the pilot passage. A suspension system for a vehicle, characterized in that a valve is provided, and a pressure adjusting valve that is selectively opened by the pilot pressure in the pilot passage or the internal pressure in the oil chamber on the piston side is provided in the second bypass. .