JPH0547407B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vehicle suspension system, and particularly to a vehicle suspension system that is most suitable for equipping special vehicles such as rough terrain vehicles and crane trucks.

[Conventional technology]

Vehicle suspension systems for rough terrain vehicles, crane trucks, etc. that lift heavy objects and perform work such as rearranging them at work sites, etc., have their hydraulic cylinders in the maximum compression state when lifting heavy objects. The suspension spring is held in place so that it can be held in place to deactivate the suspension spring, that is, it is designed to perform a compression holding function. It is preferable that it is formed so as to provide improved comfort.

In other words, when the vehicle is running normally with the compression holding function that keeps the suspension springs inactive and the suspension springs are activated, the suspension springs absorb road vibrations and reduce the wheelbase of rough terrain vehicles. In the case of a short vehicle, it is preferable that the suspension system is configured so as to exhibit an anti-nose dive function that prevents a nose dive phenomenon when the brakes are applied to the vehicle.

[Problem that the invention seeks to solve]

However, conventional suspension systems do not have a buffering function to attenuate road vibrations absorbed by the suspension springs, resulting in poor ride comfort and running stability, and the maximum speed is limited to a low speed of about 40 km/h. A problem arose.

In addition, when the anti-nose dive function is activated when the brakes are operated while the vehicle is running, and the hydraulic cylinder is completely locked, road vibrations are transmitted directly to the vehicle frame, resulting in extremely poor ride comfort and the risk of driving over a bump. When there is an upward thrust from below the spring, the impact is directly transmitted to the vehicle body frame, and there is a risk that the handling stability of the vehicle may also be deteriorated.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a suspension system for a vehicle that is formed to exhibit a compression holding function, which exhibits a buffering function to attenuate road vibrations absorbed by suspension springs when the vehicle is normally running on a road surface, and also provides The purpose of the present invention is to provide a suspension system for a vehicle that can exhibit an anti-nose dive function without deteriorating comfort or handling stability.

[Means for solving problems]

In order to solve the above-mentioned problems, the configuration of the present invention is to provide a suspension spring and a hydraulic cylinder between the vehicle body frame and the wheels, compress the hydraulic cylinder, and maintain the compressed state while compressing the suspension spring. In a vehicle suspension system that maintains an inoperative state, a hydraulic cylinder includes a cylinder, a piston rod movably inserted into the cylinder via a piston part, a rod-side oil chamber partitioned by the piston part, and a piston. The rod side oil chamber is equipped with a first oil chamber that selectively communicates with the main pump or a reservoir tank, and a check valve that is provided in the piston part and allows flow only from the piston side oil chamber to the rod side oil chamber. passage and a second passage connected only to the reservoir tank.
A damping valve is provided in the second passage to be freely opened and closed, and the damping valve is controlled to open and close by a pilot switching valve. A check valve is provided so that it can be opened and closed freely, and the piston side oil chamber is connected to the second oil chamber.
A third passage is connected to the passage between the reservoir and the damping valve, and an operable check valve is provided in the third passage so as to be openable and closable. This is characterized in that a pressure regulating valve is connected to release the abnormally increased oil pressure in the piston side oil chamber.

〔Example〕

The present invention will be explained below based on the illustrated embodiments.

As shown in the embodiments of FIGS. 1 and 2, the vehicle suspension system of the present invention has the following configuration. That is, the suspension spring and the hydraulic cylinder 1 are interposed between the vehicle body frame and the wheels, and the hydraulic cylinder 1
The hydraulic cylinder 1 is inserted into the cylinder 1a and is movably inserted into the cylinder 1a via the piston part 1c. a piston rod 1b, a rod-side oil chamber A and a piston-side oil chamber B partitioned into the piston portion, and a check valve provided in the piston portion 1c to allow flow only from the piston-side oil chamber B to the rod-side oil chamber. 1d. The rod-side oil chamber A is connected to a first passage 4 that selectively communicates with the main pump 2 or the reservoir tank 5, and a second passage 6 that connects only to the reservoir tank 5. A damping valve 10 is provided in the second passage 6 so as to be openable and closable, and the damping valve 10 is normally biased in the closing direction by a spring 100 and is controlled to open and close by a pilot switching valve 11 or 11'.
A check valve 7 that allows flow only from the main pump 2 to the rod side oil chamber A is provided in the passage 4 so as to be openable and closable. The piston side oil chamber B is the second oil chamber B.
The third passage b is connected to the passage 6 between the reservoir 5 and the damping valve 10 . Furthermore, an operating check valve 8 is provided in the third passage b so as to be openable and closable, and a pressure regulating valve 9' is connected to the third passage b for releasing abnormally increased oil pressure in the piston side oil chamber B. ing.
In the embodiment shown in FIG. 2, a relief valve 13a is used as the pressure regulating valve. This will be explained in more detail below.

FIG. 1 shows a suspension system for a vehicle according to an embodiment of the present invention, in which pressure oil from a main pump 2 is supplied to a hydraulic cylinder 1 via a main solenoid valve 3 and a passage 4. At the same time, oil is discharged from the hydraulic cylinder 1 to a reservoir tank 5 via a passage 6.

The hydraulic cylinders 1 are disposed on the left and right sides of the front wheels of a vehicle, and their upper ends are connected to the body frame of the vehicle, and their lower ends are connected to the wheels of the vehicle. The hydraulic cylinder 1 is disposed at the tip of a piston rod 1b inserted into the cylinder 1a.
It has a piston portion 1c that partitions the inside into a rod-side oil chamber A and a piston-side oil chamber B.

The piston portion 1c is provided with a check valve 1d that prevents oil from flowing from the rod side oil chamber A into the piston side oil chamber B.

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

The passage 4 is connected to a check valve 7 disposed on the rod cover portion 1e of the hydraulic cylinder 1, and when the check valve 7 is opened, pressure oil is inserted into the rod side oil chamber through the passage 7a. It is designed to flow into A. In addition, the above check valve 7
In this embodiment, the steel ball 70 is composed of a steel ball 70 and a spring 71 that biases the steel ball 70.

The passage 6 has a suction valve 6a and a back pressure valve 6b in parallel at its end on the side of the reservoir tank 5, and is formed so that return oil from the power steering mechanism PS of the vehicle flows into the passage 6. The ability of oil to be sucked into the hydraulic cylinder 1 is improved by this return oil and the action of the back pressure valve 6b.

Further, the passage 6 is connected to a passage b connected to the piston side oil chamber B via an operating check valve 8 disposed on the rod cover portion 1e. That is, the passage b is connected to the passage 8a, the passage 8a is communicated with the passage 8b via the operating check valve 8 which is in an open state, and the passage 8b is connected to the passage 6. It is something. In this embodiment, the operating check valve 8 is equipped with a plunger 80 that slides with pressure oil, a steel ball 81 that is opened by sliding of the plunger 80, and the steel ball 81. It consists of a spring 82 that applies pressure. When the supply of pressure oil to the plunger 80 is released, it becomes a check valve and the passages 8a and 8
Block communication with b.

The passage 6 is also connected to the passage b via a check valve 9, allowing passage from the passage 6 side to the passage b side, but conversely from the passage b side to the passage 6.
Oil shall not be allowed to pass to the side. The check valve 9 has a valve body 91 energized by a spring 90.
1 closes the opening of the passage 9a communicating with the passage 6. Further, the valve body 91 is provided with a through hole 92 that communicates the back pressure side of the valve body 91 with the passage b side. As a result, when the inside of the piston-side oil chamber B becomes almost negative pressure, that is, during the extension stroke of the hydraulic cylinder 1, the valve body 91 is moved by the spring 9.
0 and retreats, allowing oil to be sucked into the piston-side oil chamber B from the passage 6 side.

Note that the operated check valve 8 has the same function as the check valve 9, so if the operated check valve 8 is made larger to increase the flow of oil, as shown in FIG. The settings can be omitted. Furthermore, the operated check valve 8 shown in FIG. 2 includes a plunger 80 and a spring 8 that urges the plunger 80 from behind.
2, and is formed so that this pilot pressure can be supplied from the rear side and front side of the plunger 80 through pilot passages 8c and 8d, respectively. When pilot pressure is supplied through the pilot passage 8c, the plunger 80 moves forward and its tip blocks communication between the passages 8a and 8b. Furthermore, when pilot pressure is supplied via the pilot passage 8d, the passage 8a
and 8b are allowed to communicate with each other, and oil can freely pass therethrough.

In the embodiment shown in FIG. 1, the check valve 9 is connected to a pressure regulating valve 9'. This pressure regulating valve 9' is used when oil from the piston side oil chamber B via the passage b is prevented from flowing out to the passage 6 side by the check valve 9. It is formed so as to restrict the flow of oil from chamber B to the passage 6 side. In this embodiment, it consists of a poppet 90' that faces the communication hole 9b with the check valve 9, and a spring 91' that biases the poppet 90'.

A damping valve 10 is disposed in the rod cover portion 1e of the hydraulic cylinder 1 shown in FIG. This damping valve 10 has a poppet 10 which is biased from behind by a spring 100 and has an orifice 101 in the center.
2, and is formed so that the poppet 102 can be retracted by oil from the rod side oil chamber A. The valve is formed so that a desired damping force can be obtained when the oil in the rod-side oil chamber A flows out into the passage 6 through the gap in the seat formed when the poppet 102 retreats.

An operable check valve 11 that enables the operation of the damping valve 10 is connected to the rod cover portion 1.
e and is connected to the damping valve 10.
A pilot passage 11a is connected to this operating check valve 11, and it is opened when pilot pressure is supplied through the pilot passage 11a, and the pilot pressure is released. Sometimes formed to function as a check valve.

In the embodiment shown in FIG. 1, the operating check valve 11 is disposed behind the poppet 102 of the damping valve 10, and is a plunger that slides when pilot pressure is supplied. 110, a steel ball 111 that opens when the plunger 110 slides, and a spring 112 that biases the steel ball 111, and when the plunger 110 slides and the steel ball 111 opens the through hole. , the orifice 1 of the poppet 102 constituting the damping valve 10
01 and flows into the back pressure side of the poppet 102, the oil flows into the passage 6 through the passage 113 and the through hole opened by the steel ball 111. Therefore, since the valve opening is controlled by the pilot flow, the operable check valve 11 connected thereto can be small.

Therefore, when the pilot pressure is supplied to the operating check valve 11, the poppet 102 in the damping valve 10 can be moved back, that is, the damping valve 10 is activated and the pilot pressure is released. If there is, Poppet 102
The oil that has passed through the orifice is trapped and is moved to the poppet 1 by the oil pressure and the force of the spring 100.
02 is maintained in a closed state, and the damping valve 10 is not operated. Furthermore, since the back pressure chamber behind the poppet 102 that houses the spring 100 is formed with a large diameter, the operating check valve 11
It is easy to press and hold the poppet 102 in the closed position when the valve is closed.

Since the operation check valve 11 selectively enables the damping valve 10 to be activated or deactivated, a second embodiment may be used instead of the embodiment shown in FIG.
As shown in the figure, a pilot switching valve 11' may be used to enable the damping valve 10 to operate when pilot pressure is supplied from the pilot passage 11a, and to disable the damping valve 10 when the pilot pressure is released. good.

Then, this pilot switching valve 11'
In the embodiment shown in the figure, the poppet 111' is biased from behind by a spring 110', and the tip pressure receiving surface 11 of the poppet 111'
When pilot pressure is supplied to 2', the passage 113' which moves backward and communicates with the rod side oil chamber A and the damping valve 1
It is formed to allow communication with a passage 114' that communicates with 0.

Therefore, when pilot pressure is supplied to the pilot switching valve 11', it moves to a communication position that allows the oil in the rod side oil chamber A to flow out to the passage 6 side, and the pilot pressure is released. When this happens, the poppet 111' is pushed back by the spring 110' and moves to a blocking position that prevents the oil in the rod side oil chamber A from flowing out to the passage 6 side.

A pilot passage 11a connected to the operating check valve 11 shown in FIG. 1 is connected to a pilot solenoid valve 12. A pilot pump 13 is connected to the pilot solenoid valve 12. The pilot solenoid valve 12 also has a supply position 12a in which pilot pressure from the pilot pump is supplied to the operating check valve 11 via the pilot passage 11a, and a supply position 12a in which the pilot pressure is stopped being supplied to the pilot passage 11a. It also has a discharge position 12b for discharging the oil in the pilot passage 11a into the reservoir tank 5. Incidentally, the pilot pump 13 is provided with a relief valve 13a.

In the embodiment shown in FIG. 2, the pilot solenoid valve 12 is located at a supply position 1 in which pilot pressure from a pilot pump 13 is supplied to a pilot switching valve 11' via a pilot passage 11a.
2a and the pilot pressure from the pilot pump 13 to the operating check valve 8.
Another supply position 12c for supplying via c
and a discharge position 12b that allows the oil supplied to the pilot passages 8c and 11a to flow out into the reservoir tank 5.

Here, the operation of the vehicle suspension system according to the present invention will be explained based on the embodiment shown in FIG.

First, in order to deactivate the suspension spring so that the vehicle can perform crane work etc. at a work site, the pilot solenoid valve 12 is set to the discharge position 12b,
The operation of the damping valve 10 is prevented by an operating check valve 11 which is connected to the pilot passage 11a. That is, the oil in the rod side oil chamber A is prevented from flowing out to the reservoir tank 5 side via the damping valve 10.

From this state, the main solenoid valve 3 is switched to the supply position 3a. As a result, pressure oil from the main pump 2 flows into the rod-side oil chamber A through the passage 4 and the check valve 7. On the other hand, the oil in the piston-side oil chamber B flows out into the passage 6 via the passage b, passage 8a, and the operating check valve 8, which is released by the supply of pressure oil from the passage 4, and the passage 8b, and then enters the reservoir. This will flow out to the tank 5 side, causing the hydraulic cylinder 1 to be compressed. As a result, when the hydraulic cylinder 1 reaches the desired compression state, that is, when the spring effect in the suspension system is reduced, the main electromagnetic valve 3 is switched to the discharge position 3b. As a result, the supply of pressure oil to the rod-side oil chamber A is stopped, and the oil is sealed in the rod-side oil chamber A, resulting in a so-called oil lock state where the extension of the hydraulic cylinder 1 by the suspension spring is prevented. The compression retention function is achieved.

Furthermore, when the main solenoid valve 3 is switched and the pressure oil is no longer supplied through the passage 4, the operating check valve 8 will also prevent the oil from flowing out from the piston side oil chamber B side. , the inside of the piston side oil chamber B also exhibits a so-called oil lock state. Furthermore, when releasing the oil lock state in the rod side oil chamber A, the pilot solenoid valve 12 is switched to the supply position 12a. Since the return force of the suspension spring is acting on cylinder 1,
The oil in the rod side oil chamber A is in the operating state of the damping valve 1.
0, passage 6, operating check valve 8, check valve 9, and passage b into the piston side oil chamber B, and the insufficient oil corresponding to the withdrawal of piston rod 1b is returned to the hydraulic cylinder and PS circuit. from the piston side oil chamber B via the passage 6, the operating check valve 8 and the check valve 9, and the passage b.
The hydraulic cylinder 1 is extended.

Next, when driving on the road surface, the pilot solenoid valve 1
2 is maintained in the supply position 12a. When the hydraulic cylinder 1 is compressed in this state, the oil in the piston side oil chamber B is prevented from flowing from the passage b to the passage 6 by the check valve 9 and the operated check valve 8, so the check valve 1d into the rod-side oil chamber A, and the oil corresponding to the volume of the piston rod 1b flows through the damping valve 10 in the operating state, the passage 6,
It flows out into the reservoir tank 5 through the back pressure valve 6b.

Further, when the hydraulic cylinder 1 is extended, the damping valve 10, in which the oil in the rod side oil chamber is in an operating state,
Piston side oil chamber B through passage 6 and check valve 9
At the same time, the oil corresponding to the volume of the piston rod 1b sucks return oil from the power steering mechanism PS, and if this return oil is insufficient, it is sucked from the reservoir tank 5 through the suction valve 6a.

Therefore, the hydraulic cylinder 1 is able to expand and contract in response to the vibrations of the vehicle, and during the expansion and contraction, oil from the rod side oil chamber A passes through the damping valve 10. This results in a buffering function that dampens road vibrations.

In order to activate the anti-nose dipping function that prevents the nose type phenomenon of the vehicle during brake operation in the above-mentioned state, the pilot solenoid valve 12 is switched to the discharge position 12b in conjunction with the brake operation, etc., and the damping valve 10 is placed in the inactive state. Make it.

As a result, the oil in the rod side oil chamber A is removed from the passage 6.
The piston side oil chamber B is prevented from flowing to the side.
The check valve 9 prevents the oil inside from flowing out to the outside, thereby preventing a nose type phenomenon during brake operation.

In this state, if the vehicle is pushed up from the road surface due to riding on a bump or receives strong vibrations,
The oil pressure in the piston side oil chamber B increases and the pressure regulating valve 9'
is activated, the oil in the piston-side oil chamber B is discharged to the reservoir tank 5, and the impact and strong vibration caused by upthrust can be absorbed, and the riding comfort and steering stability of the vehicle will not be deteriorated.

In addition, in the suspension system according to the embodiment shown in FIG. 2, when the compression holding function is to be performed, the pilot solenoid valve 12 is switched to the discharge position 12b, and the main solenoid valve 3 is switched to the supply position 3.
At the same time, the main solenoid valve 3 is switched to the supply position 3a, and the pressure oil from the main pump 2 is supplied into the rod side oil chamber A.
Compress the hydraulic cylinder 1. At this time, the oil in the piston-side oil chamber B flows out into the reservoir tank 5 through the passage b, the passage 8a, the operating check valve 8, the passage 8b, and the passage 6.

When the hydraulic cylinder 1 reaches the desired maximum compression state by supplying oil in the rod side oil chamber A,
The main solenoid valve 3 will be switched to the discharge position 3b.

Further, when this device is to exhibit a buffering function, the pilot solenoid valve 12 is switched to the supply position 12a. As a result, when the hydraulic cylinder 1 is compressed, the oil in the piston side oil chamber B flows into the rod side oil chamber A via the check valve 1d, and the oil corresponding to the intrusion volume of the piston rod 1b is It flows out into the reservoir tank 5 through the passage b, the passage 8a, the opened operating check valve 8, the passage 8b, and the passage 6. Further, when the hydraulic cylinder 1 is extended, the oil in the rod side oil chamber A reaches the damping valve 10 via the pilot switching valve 11' in the communication position, and passes through the damping valve 10 as well as the passage 8a and the passage b. The insufficient oil corresponding to the withdrawal of the piston rod 1b flows into the piston-side oil chamber B through the piston rod 1b and returns from the power steering mechanism PS and from the reservoir tank 5 through passage 6, passage 8b, and operating check valve 8. , passage 8a, and passage b into the piston-side oil chamber B.

Therefore, since oil passes through the damping valve 10 during the extension stroke of the hydraulic cylinder 1, the desired damping function is achieved.

When the buffer function is in a state where the buffer function can be exerted, the pilot solenoid valve 12 is switched to another supply position 12c when the anti-nose dive function for preventing the nose dive phenomenon of the vehicle is to be exerted. .

As a result, the oil in the piston side oil chamber B is prevented from flowing out to the outside because the operating check valve 8 connected to the passage b is in the closed state, and the compression of the hydraulic cylinder 1 is prevented. It will be done. In this state, when the piston is pushed up from the road surface due to a bump or the like, the oil pressure in the piston-side oil chamber B increases, and the relief valve 13a of the pilot pump 13, which is balanced with the operating check valve 8, releases pressure. It functions as a regulating valve, that is, the oil in the piston side oil chamber B is discharged to the reservoir tank 5 side by opening the operating check valve 8.

Here, other changes to each of the above embodiments will be briefly explained.

The operating check valve 8 and the check valve 9 in the embodiment shown in FIG. 1 may be omitted when the hydraulic cylinders 1 are respectively disposed on the left and right sides of the rear wheels of the vehicle. Further, the operating check valve 11 shown in FIG. 1 may be replaced with the pilot switching valve 11' shown in FIG. 2, and the operating check valve 11 and the pilot switching valve 11' are electromagnetic switching valves. Good too. In particular, when the operating check valve 11 shown in FIG. 1 is a solenoid switching valve, there is an advantage that the pilot passage 11a, the pilot solenoid valve 12, and the pilot pump 13 are omitted.

Furthermore, in any of the embodiments described above, when the vehicle is in a state where the buffer function can be exerted, that is, when the vehicle is running on the road, the pilot solenoid valve 12 moves to the discharge position 12b in conjunction with the brake operation.
Alternatively, by forming the supply position 12c so that it can be switched to another supply position, the hydraulic cylinder 1 on the front wheel side can be locked to prevent the nose dive phenomenon when the brake is operated, and the hydraulic cylinder 1 on the rear wheel side can be switched to the rear position. It is possible to prevent the wheel side from lifting up, and the steering stability of the vehicle can be improved.

Furthermore, the oil pressure setting of the pressure regulating valve 9' in FIG. 1 can be made variable in proportion to the brake oil pressure, for example, so that the stronger the brake depression force, the greater the resistance to prevent nose dive. It is. By arranging a throttle in parallel with the pressure regulating valve 9', a slight nose type is allowed when the anti-nose type function is exerted, thereby preventing deterioration of vehicle riding comfort and handling stability. It is also possible to aim for this.

〔Effect of the invention〕

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

Since the damping valve is controlled to open and close by the pilot switching valve, it has a compression holding function and an anti-nose type function when the second passage is closed, and has a buffering function when it is opened. For this reason, the suspension system of the vehicle can exhibit a compression holding function and a buffering function that dampens road vibrations while the vehicle is running, which improves ride comfort during normal road running, and in particular, Even if the vehicle has a short wheelbase and is unstable to run, such as a rough terrain vehicle, it can run at high speed.

Further, it is possible to exhibit an anti-nose dive function that prevents the nose dive phenomenon while the vehicle is running. Furthermore, since it is equipped with a pressure adjustment valve, even if the oil pressure in the piston side oil chamber B abnormally increases due to upheaval caused by a protrusion or the like when the anti-nose dive function is activated, the upthrust action will adjust the pressure. Since the water is absorbed by the valve, the nose dive phenomenon is prevented and the riding comfort of the vehicle is improved, even in special vehicles such as rough terrain vehicles that have short wheel bases and are prone to nose dive phenomena. Driving stability is improved, high-speed driving is possible, and riding comfort and handling stability are not deteriorated even when the vehicle is pushed up from the road surface.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of a vehicle suspension system according to the present invention, and FIG. 2 is a diagram showing another embodiment. DESCRIPTION OF SYMBOLS 1... Hydraulic cylinder, 2... Main pump, 3... Main solenoid valve, 4, 6... Passage, 5... Reservoir tank, 7, 9... Check valve, 9'... Pressure adjustment valve, 8,
11... Operate check valve, 8c, 11a... Pilot passage, 10... Damping valve, 11'... Pilot switching valve, 12... Pilot solenoid valve, 13... Pilot pump, A... Rod side oil chamber, B... Piston side oil chamber, b...Aisle.

Claims (1)

[Claims] 1. In a vehicle suspension system in which a suspension spring and a hydraulic cylinder are interposed between a vehicle body frame and a wheel, and the suspension spring is maintained in an inoperative state while compressing the hydraulic cylinder and maintaining the compressed state. The hydraulic cylinder includes a cylinder, a piston rod movably inserted into the cylinder via a piston part, a rod-side oil chamber and a piston-side oil chamber divided into the piston part, and a piston-side oil chamber provided in the piston part. The rod side oil chamber is equipped with a first check valve that allows flow only from the rod side oil chamber to the main pump or reservoir tank.
and a second passage connected only to the reservoir tank, a damping valve is provided in the second passage for opening and closing controlled by a pilot switching valve, and a damping valve is provided in the first passage. A check valve that allows flow only from the main pump to the rod side oil chamber is provided so as to be openable and closable, and the piston side oil chamber is connected to the second passage between the reservoir and the damping valve. Further, an operating check valve is provided in the third passage so as to be openable and closable, and a pressure regulating valve is connected to the third passage to release abnormally increased oil pressure in the oil chamber on the piston side. A vehicle suspension system characterized by: