JP2699648B2 - Active suspension for vehicles - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active suspension for a vehicle, and more particularly to an active suspension mainly for saving energy of a fluid pressure source.

[Conventional technology]

As a conventional active suspension, there is known a suspension disclosed in Japanese Patent Application Laid-Open No. 62-295714, which has been proposed by the present applicant.

One embodiment of the conventional device includes a fluid pressure cylinder interposed between a vehicle body and each wheel, a pressure control valve for controlling a working fluid pressure of the fluid pressure cylinder according to a command value, and a lateral direction of the vehicle body. And a control means for calculating a command value according to the detected value or the estimated value of the means and outputting the calculated value to the pressure control valve. Specifically, the control means includes a process of multiplying the detected value or the estimated value of the lateral acceleration by a control gain, thereby calculating a control output in the anti-roll direction, that is, a command value.

[Problems to be solved by the invention]

In such a conventional active suspension,
In order to generate a force against the inertial force in the hydraulic cylinder,
The supply port of the pressure control valve, which is an electromagnetic proportional pressure reducing valve, must always be supplied with high-pressure fluid energy. Therefore, the supply flow rate of a fluid pressure source composed of a hydraulic pump, a tank, and the like that supplies energy to those loads must be set high, and the energy consumption inevitably increases.
Fuel economy is inevitably worse than a vehicle without an active suspension. Therefore, there has been a demand for an active suspension capable of reducing the supply energy while enabling the same control.

The present invention has been made in view of such a situation,
It is an object of the present invention to reduce the supply energy of the fluid pressure source itself without lowering the load control performance.

[Means for solving the problem]

In order to achieve the above object, the invention according to claims (1) to (5) is characterized in that a supply port and a return port to which a supply line and a return line to a fluid pressure source are connected, and an output line to an actuator. A three-way spool valve having an output port for supplying a pilot pressure to one spool end of the spool valve and feeding back a control pressure output from the output port to the other spool end, and In a vehicle active suspension provided with a pressure control valve adapted to adjust the control pressure according to the pressure, a bypass flow path that communicates the supply port and the output port while bypassing the spool valve, A flow path opening / closing mechanism (for example, a check valve as in the invention according to claim (2)) for opening / closing the bypass flow path; The open state of the flow path opening and closing mechanism when the pressure forces the port exceeds the pressure in the supply port,
The working fluid pressure is returned from the output port to the supply port to increase the supply pressure.

In particular, in the invention according to claim (3), a throttle is inserted in the bypass flow passage in series with the flow passage opening / closing mechanism. In the invention described in claim (4), the bypass flow path and the flow path opening / closing mechanism are individually provided in a pressure control valve of each wheel or a line connected to the pressure control valve.

Further, in the invention according to claim (5), the configuration according to claim (1) is provided with a check valve inserted into the supply line and a relief valve connected between the supply line and the return line, The valve is located upstream of the supply line connection point of the relief valve.

[Action]

The active suspension for a vehicle according to any one of claims (1) to (5) attempts to obtain an anti-roll moment by increasing the operating pressure of the outer wheel side actuator and decreasing the inner wheel side operating pressure, for example, during turning. . At the time of this roll control, the supply pressure from the fluid pressure source is lower than the value at the time of non-control due to an increase in the consumption flow rate of the outer ring side pressure control valve.
Therefore, especially when such a supply pressure drops,
For example, if vibration due to a road surface protrusion is input to the inner ring side, and the working pressure on the inner ring side due to the vibration input (that is, the pressure at the output port of the pressure control valve = control pressure) becomes larger than the supply pressure, the flow path opening / closing mechanism Is opened, and the working fluid pressure is returned from the output port side to the supply port side through the bypass flow path. This increases the supply pressure and improves the roll control effect. That is, the vibration energy due to the road surface protrusion is effectively taken into the active suspension as the fluid energy, so that the supply flow rate of the fluid pressure source can be reduced by the regenerative energy, thereby achieving energy saving.

In particular, in the invention described in claim (2), since the check valve is used, the configuration is simple. According to the invention described in claim (3), when there is a steep vibration input during high-speed running or the like, the working fluid regenerated through the bypass passage can be throttled by the throttle. For this reason, it is possible to prevent a sudden change in pressure on the supply side due to energy regeneration.

According to the invention described in claim (4), since the vibration energy input to each wheel can be regenerated, after the front wheel passes through the same projection, the rear wheel further passes, thereby improving the regenerative efficiency.

Furthermore, in the invention according to claim (5), even if there is a very large vibration input and the supply pressure exceeds the set relief pressure even if the supply pressure rises abnormally, the working fluid is moved to the tank side by the relief valve. Will be returned. Therefore, the supply pressure does not exceed the normal line pressure when the suspension is not controlled, and damage to components and instability of control can be avoided.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 5 of the accompanying drawings.

In FIG. 1, reference numeral 10 denotes an active suspension for a vehicle. As shown, the active suspension 10 includes a hydraulic pump 12 and a reservoir tank 14 which constitute a fluid pressure source.
A multi-valve assembly 16 disposed on the load side of the fluid pressure source, and a front control valve assembly 18F disposed on the load side of the assembly 16 and corresponding to the front and rear wheels. A control valve assembly 18R, hydraulic cylinders 20FL to 20RR as actuators individually arranged at respective wheel positions, and a control unit 22 for instructing suppression of posture change.
And at least.

More specifically, the hydraulic pump 12 is constituted by, for example, a plunger type pump using the vehicle engine as a rotational drive source, and its suction side is connected to a reservoir tank via a pipe 23.
Connected to 14. A supply pipe (supply line) 24 is connected to the discharge side of the hydraulic pump 12.
Branch through an oil filter 26 and a check valve 28 in the multi-valve assembly 16 to reach the front and rear control valve assemblies 18F and 18R, respectively. In the figure, reference numeral 29 denotes a pump accumulator. Meanwhile, the control valve assembly 18
A return pipe (return line) 30 extends from F and 18R,
This return pipe 30 leads to an operation check valve 32 and a throttle 34 in the multi-valve assembly 16. This assembly 16
The return pipe 30 that has exited from the reservoir is further connected to the reservoir tank 14 via an oil cooler 36.

Operate check valve 32 is a pilot operated check valve for the supply pressure of the check valve 28 downstream the pilot pressure P _P, the open state when exceeding the pilot pressure P _P is the predetermined pressure (e.g. hydraulic neutral pressure) maintaining, in the closed state when the pilot pressure P _P falls below a predetermined pressure. Therefore, when the operation check valve 32 is closed when the engine or the like stops, the hydraulic circuit on the load side is sealed at a predetermined pressure.

Also, in the multi-valve assembly 16, the supply piping
A relief valve 38 having a predetermined relief pressure is connected between a downstream side of the check valve 28 in 24 and a load side of the operation check valve 32 in the return pipe 30.

In the front control valve assembly 18F, the supply pipe 24 is branched into front left and front right pressure control valves 40FL, 40FR.
The return pipe 30 connected to a supply port described later and connected to return ports of the pressure control valves 40FL and 40FR.
Join to the multi-valve assembly 16. Similarly, the rear control valve assembly 18R includes rear left and rear right pressure control valves 40RL and 40RR.

Here, as shown in FIG. 2, each of the pressure control valves 40FL to 40RR has a cylindrical valve housing 43 with a built-in valve body.
And a proportional solenoid 44 provided integrally therewith.

Spool insertion hole drilled in the center of valve housing 43
A main spool 45 is slidably inserted into 43A, and a poppet valve 46 serving as a pilot valve is inserted into a pilot valve insertion hole 43B formed coaxially with the insertion hole 43A at one axial end of the insertion hole 43A. Is slidably inserted. A feedback chamber FR and a pilot chamber PR are formed at both ends of the main spool 45, respectively, and springs 47A and 47B for centering the spool 45 are provided in both chambers FR and PR. In addition, 43Aa
Is a fixed aperture for communicating the pilot chamber PR with the insertion hole 43B.

The valve housing 43 is provided with lands 45a, 45 of the main spool 45.
A supply port 43s, a return port 43r, and an output 43o communicating with the insertion hole 43A are provided at positions opposing the pressure chamber b and the pressure chamber 45c. In addition, the poppet valve 4
6, a valve seat 43Ba having a predetermined diameter is provided facing the distal end side.

The supply port 43s communicates with the pilot valve insertion hole 43B via the supply-side passage 48, the return port 43r communicates with the insertion hole 43B via the drain-side passage 49, and a part of the hydraulic oil of the supply port 43s passes through the passage 48. Thus, circulation can be made to the return port 43r via the valve seat 43Ba and the passage 49. At this time, the drain side passage
49 communicates with the insertion hole 43B at both axial ends of the poppet valve 46, and also communicates with the inside of the proportional solenoid 44.

Further, the output port 43o communicates with the feedback chamber FR via the feedback passage 50. A bypass passage 52 is formed between the feedback chamber FR and the pilot valve insertion hole 43B on the poppet valve 46 side to bypass the spool insertion hole 43A, and a check valve 54 is inserted into the bypass passage 52. The direction of the check valve 54 is a direction that allows the flow from the insertion hole 43B to the feedback chamber FR.

The proportional solenoid 44 has a plunger 58 that can move in the axial direction, and an exciting coil 59 that drives the plunger 58. When excited by the command value i, the exciting coil 59 moves the plunger 58 to move the poppet valve 46.
Therefore, the flow rate of the hydraulic oil flowing through the valve seat 43Ba can be adjusted by the degree of the urging, and the pressure of the pilot chamber PR can be adjusted. In the drawings, a to e are apertures.

Therefore, when the pressure of the feedback chamber FR and the pressure of the pilot chamber PR are balanced in a state where the pressing force of the proportional solenoid 44 is applied to the poppet valve 46, the spool 45 moves to the output port 43o, the supply port 43s, and the return port 43r. To take an overlap position (position shown).
Therefore, the pressure in the pilot chamber PR is adjusted according to the magnitude of the command value i, and the spool 45 is slightly moved to perform the pressure adjusting operation until the pilot pressure and the pressure in the feedback chamber FR are balanced, and the output pressure from the output port 43o is output. (control pressure) P _C the third
As shown in the figure, control can be performed in proportion to the command value i. In the figure, the maximum line pressure P ₂ is supplied. Further, when a vibration is input from the road surface in a low frequency sprung resonance region (for example, about 1 Hz), the hydraulic oil moves between the fluid pressure source side and the load side due to the slight movement of the spool 45, and a predetermined limit is reached. The pressure fluctuation up to is absorbed.

Output pipes (output lines) 62 are connected to the output ports 43o of the pressure control valves 40FL to 40RR, respectively, and the output ports 43o and the hydraulic cylinders 20FL (to 20R) are connected by the pipes 62.
R) is in communication with the cylinder chamber.

Further, in the front and rear control valve assemblies 18F and 18R in this embodiment, four pressure control valves 40FL to 40R are provided.
A bypass pipe (bypass flow path) 64 connecting the output pipe 62 and the supply pipe 24 bypassing the control valve 40FL (（40RR) is provided integrally with each of the R valves. However, the connection position of this bypass pipe 64 to the output pipe 62 is determined by the output port
The position is closer to the cylinder than the throttle c of 43o.

A check valve 66 as a flow path opening / closing mechanism is inserted into each of the bypass pipes 64, and the insertion direction of the check valve 66 is set so that hydraulic oil can flow from the output pipe 26 to the supply pipe 24. Has become.

In the drawing, reference numeral 68 denotes an accumulator connected to the supply pipe 24 on the front side and the rear side.

The hydraulic cylinders 20FL to 20RR as actuators are
These are single-acting cylinders interposed between the vehicle body and the wheels, respectively, and have a cylinder chamber L into which hydraulic oil controlled by a pressure control valve 40FL (（40RR) flows. This cylinder chamber L is
It is connected to a throttle 70 and an accumulator 72 for absorbing pressure fluctuations in the unsprung resonance region. A coil spring (not shown) for supporting a static load of the vehicle body is provided between the vehicle body and the wheels.

Further, the control unit 22 of the present embodiment is, for example, a lateral acceleration sensor.
74, a vehicle height sensor 75 and a controller 76. The controller 76 is equipped with a microcomputer.
Then, the controller 76 multiplies the anti-roll control gain to the detection signal Y _G of the lateral acceleration sensor 74 inputs to calculate the instruction current i for each wheel, the command current i, ..., i the pressure control valve
While output to each of 40FL to 40RR, the command current calculated so that the detection value h of the vehicle height sensor 75 falls within the target vehicle height range is superimposed on the command current i, ..., i. I have.

 Next, the operation of this embodiment will be described.

First, it is assumed that the vehicle is traveling straight ahead at a constant speed in a standard loaded state. In this running state, since the detection value Y _G which depends on the lateral acceleration sensor 74 is zero, the controller 76 vehicle height sensor
Command current i 75 of the detection value h enters the target vehicle height range, ..., i (= the example, the value i _N corresponding to the neutral pressure P _N in FIG. 3) calculates for each wheel, which pressure control Output to valves 40FL-40RR.
Therefore, the control of the cylinder pressure = P _N of the hydraulic cylinder 20FL～20RR, cylinder stroke is set to a value corresponding to the operating pressure P _N, thereby the body takes a flat posture holding the target vehicle height.

If performed during this straight example left-handed, because the lateral acceleration detection signal Y _G takes a value corresponding to the left turn, the controller 76
, Depending on the value of the lateral acceleration Y _G, the pressure control valve 40FR of the right wheel side serving as the outer side, to increase the command current i of 40RR, the pressure control valve 40FL for the left wheel side of the inner ring on the opposite, the 40RL Command current i
Lower. As a result, the outer cylinder hydraulic cylinder 18F
R, rises from the neutral pressure P _N of the far working pressure of 18RR, for example, the inner side of the hydraulic cylinder 18FL Conversely, because operating pressure of 18RL for example falls below the neutral pressure P _N, the outer ring side cylinder 18F
In the R and 18RR, a force against the sinking of the vehicle body due to the inertial force is generated, and in the inner ring side cylinders 18FL and 18RL, the force decreases, and the lifting of the vehicle body is not promoted. Therefore, an anti-roll moment is generated for the entire vehicle, the roll angle of the vehicle body is suppressed, and a substantially flat vehicle body posture is maintained.

Further, it is assumed that the vehicle travels straight on a good road at a constant speed with a large load weight. Such time increased load, by the vehicle height adjustment based on the detection value h of the vehicle height sensor 75, as shown in the control pressure P _C (e.g. 4 and 5 shown without the non-attitude control 80 kgf / cm ^2:
P _N ′) is the control pressure at the time of standard loading (for example, 50 kgf / cm
² : P _N ), the margin with the supply pressure P _S (for example, 100 kgf / cm ^{2 as} shown in FIGS. 4 and 5) becomes smaller, and the pressure control allowance on the roll outer ring side may become narrower.

Here, in order to easily understand the point of view of the present invention, the bypass path 64 and the check valve 66 for the pressure control valves 40FL to 40RR are used.
With reference to FIG. 4, a description will be given of an example of a pressure change in a state where a large load is applied in a structure in which is not provided (that is, a structure corresponding to a conventional example).

Now, it is assumed that the loaded weight is large and the vehicle is in the above-described straight traveling state. During the straight high control pressure ^{_{P C (= 80kgf / cm 2}} )
Is set to the neutral value P _N ′, but the flat attitude of the target vehicle height value is maintained by the command from the controller 76 described above. If a left turn is performed temporarily during this straight traveling, the pressure control valves 40FR, 40R on the outer ring side will be
We tried to increase the control pressure of the R P _C (i.e. cylinder operating pressure) as shown in FIG. 4, the pressure control valve of the inner ring side opposite 40F
L, thereby forming attempt to reduce the control pressure P _C of 40RL.

However, since the supply pressure P _S twist to the hydraulic supply to the outer ring begins to decrease, right in the wheel side at the time t ₁ to the supply pressure P _S coincides with the control pressure P _C, the control as commanded as shown pressure (indicated by a broken line in the figure) can not be obtained, then the control pressure P _C changes as shown by following the decrease in the supply pressure P _S. In contrast, in the left wheel side, reduction instruction of the control pressure P _C is because it is issued as shown by the broken line, even when the supply pressure P _S is decreased, attempts to hold the instruction control pressure P _C.

At the time of this roll control, for example, at time t ₁ , a relatively large excitation force accompanying the road surface protrusion is generated near the inner ring (left wheel).
Suppose that you input only to the side. When such a vibration input is present, the internal pressure of the cylinder oil increases due to the compression of the hydraulic oil in the cylinder chamber L, and the internal pressure rises as shown in the figure while deviating from the command control pressure. Therefore, projections or large, if the vibration input or a high speed is large, as shown by the shaded area in FIG. 4, at time t ₂ ~t ₃ is the control pressure P _C of the left wheel side supply pressure situation is brought to be higher than P _S.

The phenomenon of pressure reversal caused by the situation where the control pressure P _C > the supply pressure P _S is a result of the conversion of the vibration energy from the road surface into the hydraulic energy. It is believed that this can reduce the hydraulic energy that must be generated by the vehicle itself.

Therefore, a case where running under the same conditions as described above (large load, turning left, overstepping on the left wheel side projection) is applied to the suspension of this embodiment will be described with reference to FIG. The excitation force due to the left wheel (inner) side projections during turning, and increases the control pressure P _C of the left wheel side, P _C at time t ₂ as shown in Figure 5
> Becomes a P _S, opens the check valve 66 which bypasses the example the front wheel of the pressure control valve 40FL for the left wheel side. Therefore, through the interior of the hydraulic fluid check valve 66 which communicates with the cylinder chamber L and the chamber L is output, is returned to its supply port 43s side, the supply pressure P _S starts to rise. When the supply pressure P _S rises in this way, at the same time, this supply pressure P _S is consumed on the right wheel side. As a result, the supply pressure P _S eventually becomes the control pressure P _S in FIG. 4 as shown in FIG. Draw a rising trajectory through the excess of the _C curve.

In other words, the work energy of the hatched area A of the left wheel side turning to the right wheel side, since raising the energy amount corresponding control pressure P _C of the hatched area C (= hatched area A), than one-dot chain line shows a conventional value drop allowance of the control pressure P _C from the target value is small, the roll control effect is enhanced. At the same time, the hatched region C the projection of the control pressure P _C due to the projections when energy regeneration is not the left wheel side
Can only be suppressed.

As described above, while merely adding a simple structure using the bypass pipe 64 and the check valve 66, the hydraulic energy corresponding to the shaded area "A + B" in FIG. 5 utilizing the road surface input is regenerated. It can be the actual control pressure P _C in both the left and right wheels is closer to curve the goals of the controller 76, good roll control characteristics can be obtained.

From a different point of view, even if the supply flow rate (rated flow rate) of the hydraulic pump 12 is slightly reduced, control performance equivalent to that of the conventional active suspension can be secured. Therefore, the supply hydraulic energy of the hydraulic system itself is reduced by an amount corresponding to the reduced supply flow rate, and the engine load is reduced, thereby improving fuel efficiency. Also, the manufacturing cost is low, and it can be easily applied to existing systems.

The control pressure P _C of the left wheel side, characterized by a rebound after the projections pass as shown in 4 and 5 Figure is vibrating.

Here, in the configuration of the present embodiment, the vibration is abnormally large energy, is by its energy regeneration, the supply pressure P _S exceeds the set pressure of the relief valve 38, the mounting position of the relief valve 38 is a load close Therefore, the excess hydraulic oil is returned to the tank 14 through the relief valve 38. This will suppress the maximum value of the supply pressure P _S by the regenerative energy, it can be prevented damage to the hydraulic components such as a pressure control valve 40FL～40RR.

Note that, in this embodiment, the case where only the inner wheel side rides over the protrusion during the roll control is representatively described.However, even when the outer wheel side gets over the protrusion at the same time as the inner wheel side, the reduced supply pressure is similarly pushed up, Energy regeneration becomes possible, and effective use of vibration energy can be achieved.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, as shown in the figure, an orifice 78 as a throttle is inserted in the middle of a bypass pipe 64 in series with a check valve 66, and the other configuration is the same as that of FIG. The description is omitted using the reference numerals). According to this embodiment, the same operation and effect as described above can be obtained, and when an excessive vibration input is generated from the road surface, a sudden change in supply pressure due to energy regeneration
Thus, the pressure control valve can be operated more stably.

In the above-described embodiment, the case where the bypass pipe 64 and the check valve 66 are separately provided from the pressure control valves 40FL to 40RR is described. However, the bypass pipe 64 and the check valve 66 may be integrally provided inside each of the pressure control valves 40FL to 40RR.

Further, the passage opening / closing mechanism in the present invention is not necessarily limited to a check valve. For example, a supply pressure detected by a sensor and a cylinder are compared, and according to the comparison result, an electromagnetic switching mechanism inserted into a bypass passage is used. It is good also as a structure which carries out switching control of a valve.

Further, the working fluid of the active suspension according to the present invention is not limited to the working oil, but may be a gas.

〔The invention's effect〕

As described above, according to the present invention, a bypass flow path that connects a supply port and an output port while bypassing a spool valve of a pressure control valve is provided, and the pressure of the output port (control When the pressure exceeds the pressure (supply pressure) at the supply port, the working fluid pressure is returned from the output port to the supply port to increase the supply pressure. Because
For example, when the supply pressure is greatly reduced and a large vibration input is made from the road surface, for example, during roll control in a turning state, the control pressure exceeds the supply pressure and the working fluid is sent to the supply line through the bypass flow path. Is done. As a result, the supply pressure increases and the roll control effect is enhanced, so that the vibration energy from the road surface is effectively regenerated as fluid energy. As a result, even if the supply flow rate of the fluid pressure source is made smaller than that of the conventional device, the same control performance can be exhibited, so that the supply energy of the fluid pressure source itself can be smaller than before, and
Energy consumption of the whole system can be reduced,
Thereby, the fuel efficiency of the vehicle can be improved.

In particular, the invention according to claim (2) merely adds a bypass flow path and a check valve (flow path opening / closing mechanism), so that the configuration is simple and the existing active suspension can be easily manufactured at low cost. Applicable to Further, according to the invention described in claim (3), even when an excessive vibration input is made from the road surface at the time of high-speed running or the like, it is possible to prevent a sudden pressure fluctuation due to energy regeneration, and to more stably operate the pressure control valve. Can be done. According to the invention described in claim (4), the vibration energy can be regenerated for each wheel, and the regenerative efficiency is improved. Further, in the invention described in claim (5),
Even if there is a very large vibration input and the supply pressure rises abnormally, the working fluid can be reliably relieved to the tank side through the relief valve, and damage to the hydraulic components can be prevented beforehand.

[Brief description of the drawings]

1 to 5 are views showing an embodiment of the present invention. FIG. 1 is a block diagram showing an entire configuration, FIG. 2 is a schematic sectional view of a pressure control valve, and FIG. FIG. 4 is a timing chart illustrating the pressure control state of the conventional device in correspondence with the present embodiment, and FIG. 5 is a timing chart illustrating the pressure control state based on the configuration of the present embodiment. . FIG. 6 is an overall configuration diagram according to another embodiment of the present invention. The main symbols in the figure are: 10 ... active suspension, 12 ... hydraulic pump, 14 ... reservoir tank, 20FL-20RR ... hydraulic cylinder, 24 ... supply pipe, 28 ... check valve, 30 ... return pipe, 38 ... relief valve, 40FL-40RR… Pressure control valve, 43s…
Supply port, 43r… Return port, 43o… Output port, 62…
Output pipe, 64: bypass pipe, 66: check valve, 78: orifice.

Claims (5)

(57) [Claims] 1. A three-way spool valve having a supply port and a return port to which a supply line and a return line to a fluid pressure source are connected, and an output port to which an output line to an actuator is connected. A pressure control valve that supplies pilot pressure to one spool end and feeds back control pressure output from the output port to the other spool end to adjust the control pressure in accordance with the pilot pressure. In the active suspension for a vehicle provided with, a bypass flow path that communicates the supply port and the output port while bypassing the spool valve, and a flow path opening and closing mechanism that opens and closes the bypass flow path, When the pressure at the output port exceeds the pressure at the supply port, the flow path opening / closing mechanism is opened, and the supply from the output port is performed. An active suspension for a vehicle, wherein the working fluid pressure is returned to a supply port to increase the supply pressure. 2. The active suspension according to claim 1, wherein said passage opening / closing mechanism is a check valve. 3. The device according to claim 1, wherein a throttle is inserted in the bypass passage in series with the passage opening / closing mechanism.
The active suspension for a vehicle according to the above. 4. The apparatus according to claim 1, wherein the bypass flow path and the flow path opening / closing mechanism are individually provided in a pressure control valve of each wheel or a line connected to the pressure control valve. Active suspension for vehicles. 5. A check valve interposed in the supply line, and a relief valve connected between the supply line and the return line, wherein the check valve is upstream of a connection point of the relief valve on the supply line side. The active suspension for a vehicle according to claim 1, wherein