JP2509326B2 - Active suspension - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides a fluid pressure cylinder between a vehicle body and a wheel, and controls this fluid pressure cylinder by a control valve such as a pressure control valve. , Improvement of active suspension that suppresses posture changes such as vehicle height, roll and pitch.

[Conventional technology]

A conventional active suspension is disclosed in
Some are described in Japanese Patent Laid-Open No. 63-219408.

In this conventional example, in the active suspension, the fluid pressure check means is provided in the line pressure pipe between the pressure control valve and the hydraulic pressure supply device, and the return pipe is provided only when the output of the hydraulic pressure supply device falls below a predetermined pressure. A fluid closing means for preventing passage of a fluid and a pressure adjusting means for keeping the pressure on the upstream side of the fluid closing means at a predetermined value are arranged in parallel to prevent a sudden change in vehicle height. Is something that can be done.

[Problems to be Solved by the Invention]

However, in the above-mentioned conventional active suspension, when the hydraulic pressure supply device is stopped and the pressure of the output side pipeline thereof drops below a predetermined value, the fluid closing means prevents the passage of fluid. , Pressure control valve 1
By closing the secondary side, it is possible to prevent a sudden pressure drop in the fluid pressure cylinder.However, when the vehicle has a heavy load, the pressure in the fluid pressure cylinder must be maintained in order to maintain an appropriate vehicle height at that time. , Predetermined pressure of fluid closing means
The pressure is controlled to be higher than P _N, and when the hydraulic pressure supply device is stopped in this state, the pressure drops to the prescribed pressure P _N of the fluid closing means, which reduces the vehicle height and stops at the curb. However, there is an unsolved problem that the open door and the curb may interfere with each other.

In order to solve this unsolved problem, a shut-off valve may be inserted between the control valve and the hydraulic cylinder to shut off the control valve and the hydraulic cylinder when the hydraulic supply device is stopped. In this case, it is possible to prevent the vehicle height from decreasing, but there is a new problem that the vehicle height changes suddenly when the shutoff valve is opened after the hydraulic pressure supply device is started.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above conventional example, and prevents the vehicle height from decreasing when the fluid pressure supply device is in the inoperative state, and It is an object of the present invention to provide an active suspension that can prevent a sudden change in vehicle height when it is in an operating state.

[Means for solving problems]

In order to achieve the above object, the active suspension according to claim (1) comprises a fluid pressure cylinder interposed between each wheel and a vehicle body, and a fluid pressure supply device supplied to the fluid pressure cylinder. A control valve for controlling the working fluid pressure in accordance with the command value, and a posture change suppression control means for outputting the command value based on the detection value of the posture change detecting means for detecting the posture change of the vehicle body. In the provided active suspension, an operating state detecting means for detecting whether or not the fluid pressure supply device is in an operating state, an open position inserted between the fluid pressure supply device and the control valve, and supply of the control valve. A solenoid switching valve having a closed position for connecting the pressure port and the return port through a throttle and shutting off the fluid pressure supply device side; and the fluid pressure supply device being in the inoperative state by the operating state detecting means. When detected When the electromagnetic switching valve is switched to the closed position and the operating state is detected, the command value of the posture change suppression control means is corrected according to the enclosed pressure of the fluid pressure cylinder at that time, and the electromagnetic switching valve is operated. And a valve control means for switching to an open state.

The active suspension according to claim (2) is
In the invention of claim (1), the control valves are individually connected in parallel on the front wheel side and the rear wheel side, and a front wheel side electromagnetic switching valve is interposed between the front wheel side control valve and the fluid pressure supply device, A rear wheel side electromagnetic switching valve is inserted between the wheel side control valve and the fluid pressure supply device, and when the valve control means detects the operating state of the fluid pressure supply device by the operating state detecting means, the front wheel and Calculate the equilibrium control pressures on the front and rear wheels according to the enclosed pressure in the rear fluid pressure cylinder, and correct the front and rear wheel command values of the posture change suppression control means based on these. It is characterized by being configured in.

[Action]

In the active suspension according to claim (1), the solenoid control valve is switched to the open state by the valve control means when the fluid pressure supply device is in the operating state,
The working fluid from the fluid pressure supply device is supplied to the control valve, the control valve is controlled based on the command value from the posture change suppression control means, and its output is supplied to the fluid pressure cylinder, whereby the posture of the vehicle body is changed. Control for suppressing the change is performed.
After that, when the fluid pressure supply device is deactivated, the electromagnetic switching valve is controlled to be closed to shut off the fluid pressure supply device side, and the supply pressure port and the return port of the control valve are connected via the throttle. As a result, the working fluid of the control valve and the fluid pressure cylinder is sealed, and the decrease in vehicle height is prevented. After that, when the fluid pressure supply device is activated again,
The valve control means corrects the command value of the attitude change suppression control means to a command value according to the sealed pressure of the fluid pressure cylinder, and the electromagnetic switching valve is controlled to the open state to smoothly change the vehicle height.

Further, in the active suspension according to claim (2), when the fluid pressure supply device is in the inoperative state, the front side and the rear wheel side are individually shut off by the electromagnetic switching valve on the side of the fluid pressure supply device. Therefore, the primary sides of the left and right control valves on the front wheel side and the rear wheel side are brought into communication with each other, so that the pressures of the left and right fluid pressure cylinders are substantially equalized. Then, when the fluid pressure supply device is activated, the equilibrium control pressure is calculated based on the enclosed pressure of the left and right fluid pressure cylinders on the front and rear wheels, and based on this, the equilibrium control pressure is calculated on the front and rear wheels. The command values are individually corrected, and the front-wheel-side and rear-wheel-side electromagnetic switching valves are controlled to the open state to smoothly change the vehicle height.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a hydraulic circuit diagram showing a first embodiment of the present invention.

In the figure, FS is a fluid pressure supply device, which is rotationally driven by being connected to an output shaft 2a of the engine 2 as a rotational drive source,
A hydraulic pump 1 connected to an oil tank 3 on the suction side,
A line pressure pipe 5 connected to the discharge side via a check valve 4 and a drain pipe 7 connected to the oil tank 3 via an oil cooler 6 are provided, and the line pressure pipe 5 is for absorbing pulsation. The accumulator 8 is connected and a filter 9 is inserted on the downstream side of the accumulator 8. A bypass flow passage is formed in the filter 9 in parallel with the filter 7 when the filter 7 is clogged, and a check valve 10 is inserted in the bypass flow passage.

The line pressure pipe 5 is connected to the supply pressure ports 21i of the pressure control valves 13FL to 13RR corresponding to each wheel via the check valve 11, and the other end of the drain pipe 7 is directly connected to the pressure control valve 13FL.
Connected to return port 21o of ~ 13RR. Further, a relief valve 12 for setting the line pressure P _L (kg / cm ² ) in a normal state is inserted between the line pressure pipe 5 and the drain pipe 7.

As shown in FIG. 2, each of the pressure control valves 13FL to 13RR has a cylindrical valve housing 21 and a proportional solenoid 22 integrally provided on the valve housing 21. An upper insertion hole 21U in FIG. 2 and a lower insertion hole 21L in FIG. 2 which are defined by a partition wall 21A having a valve seat 21c having a predetermined diameter are coaxially formed in the central portion of the valve housing 21. ing. A fixed diaphragm 23 is provided above the insertion hole 21L and below the partition wall 21A by a predetermined distance.
A pilot chamber C is formed between the partition wall and the partition wall 21A.
Further, a main spool 24 is disposed below the fixed throttle 23 in the insertion hole 21L so as to be slidable in the axial direction, and a feedback chamber is provided above and below the main spool 24.
F _U and F _L are formed respectively, and the upper and lower ends of the main spool 24 are regulated by offset springs 25A and 25B arranged in the feedback chambers F _U and F _L , respectively. And
A supply pressure port 21i, a control port 21n, and a return port 21o are formed to communicate with the insertion hole 21L in this order.

The main spool 24 includes a land 24a facing the input port 21i, a land 24b facing the drain port 21o, a pressure chamber 24c formed by an annular groove formed between the ports 24a and 24b, and the pressure chamber 24c and Lower feedback room _FL
And a pilot passage 24d that communicates with the.

In the upper insertion hole 21U, a poppet 26 is axially slidably arranged with its valve portion facing the valve seat 21c. The poppet 26 allows the insertion hole 21U to move in two axial directions.
The chambers 29u and 29l are defined, and the flow rate of the hydraulic oil flowing through the valve seat 21c, that is, the pressure in the pilot chamber C can be adjusted.

Further, the input port 21i is communicated with the pilot chamber C via a pilot passage 21s having a flow rate adjusting orifice _21s0 formed therein, and the drain port 21o is a drain passage having orifices _21t0 and _21t1 formed on the way. The poppet pressure chambers 29u and 29l defined by the poppet 26 of the insertion hole 21U are communicated with each other via 21t. Here, the orifice 21 _t0 is for adjusting the moving speed of the poppet 26, and the orifice 21 _t1 is for adjusting the back pressure for reducing the influence of the pressure fluctuation of the drain port 21o on the pilot pressure.

On the other hand, the proportional solenoid 22 includes an axially slidable plunger 27, an actuator 27A fixed to the poppet 26 side of the plunger 27, and an exciting coil 28 for driving the plunger 27 in the axial direction. Has and this excitation coil
28 is appropriately excited by the command values I _{FL to} I _RR which are DC currents from the control device 17. As a result, the movement of the plunger 27 controls the position of the poppet 26 via the actuator 27A, and controls the flow rate passing through the communication hole 21A. And
When the pressures of the feedback chambers F _L and F _U are in balance while the pressing force of the proportional solenoid 22 is applied to the poppet 26, the spool 24 is in the neutral position and the control port 21n and the input port 21i and The connection with the drain port 21o is cut off.

Here, as shown in FIG. 3, the relationship between the command values I _{FL to} I _RR and the control oil pressure P _C output from the control port 21n is P when the command values I _{FL to} I _RR are near zero. _{When MIN} is output and the command values I _{FL to} I _RR increase in the positive direction from this state, the control output P _C increases with a predetermined proportional gain K _{1 to} the line setting pressure P _L of the pressure holding unit 11. Saturate.

And, the control port 21n of the pressure control valves 13FL to 13RR is
It is connected to the pressure chamber 31a of hydraulic cylinders 31FL to 31RR as fluid pressure cylinders interposed between the wheels and the vehicle body.

On the other hand, between the fluid pressure supply device FS and the pressure control valves 13FL to 13RR, a spring offset type 4-port 2-position electromagnetic switching valve 60FL to 60 is used.
RR is inserted.

In these electromagnetic switching valves 60FL to 60RR, the P port is connected to the check valve 11, the T port is connected to the oil cooler 6, and the A port is the supply pressure port 21 of the pressure control valves 13FL to 13RR.
i, the B port is connected to the return port 21o of the pressure control valves 13FL to 13RR, and the P port and the T port are in the normal position.
The port is blocked and the A port and the B port are in communication with each other through the aperture 61, and the P port and the A port are in communication with each other at the offset position, and the T port and the B port are in communication with each other.

Also, the cylinder tube for each hydraulic cylinder 31FL to 31RR
Vehicle height sensors 35FL to 35RR configured by, for example, potentiometers for detecting the vehicle height are disposed between the 31b and the piston rod 31c.

Note that 45F is an accumulator for accumulating pressure connected to the hydraulic piping between the check valve 11 and the input ports 21i of the pressure control valves 13FL and 13FR, and 45R is between the check valve 11 and the input ports 21i of the pressure control valves 13RL and 13RR. Accumulator connected to the hydraulic piping of the above, 46FL to 46RR and 47FL to 47RR are hydraulic cylinders 31FL
A damping valve and an accumulator for absorbing pressure fluctuations in the high frequency range of vehicle unsprung vibrations from the road surface, which are input to ~ 31RR.

Then, the vehicle height detection values H _{FL to} H _{RR of} the vehicle height sensors 35 _{FL to} 35 _RR
Are the pressure control valves 13FL to 13RR and the electromagnetic switching valves 60FL to 60RR.
Is input to the control device 36 for controlling.

As shown in FIG. 4, the control device 36 includes at least an interface circuit 37a, an arithmetic processing device 37b, and a storage device.
Comprised of a microcomputer 37 having a 37c, the vehicle height detection value H _FL ~ H _RR from the vehicle height sensor 35FL ~ 35RR is input to the input side of the interface circuit 37a via the A / D converter 38FL ~ 38RR, and output Command value I _{FL to} I _RR output from the
It is supplied to the solenoid drive circuits 40FL to 40RR composed of a floating constant current circuit using an operational amplifier via the A converters 39FL to 39RR.
40FL to 40RR supply an exciting current according to the command values I _{FL to} I _RR to the proportional solenoid 22 of each pressure control valve 13 _FL to 13 _RR , and the control signal CS similarly output from the output side is supplied to the solenoid drive circuit 62. The solenoids of the solenoid operated directional control valves 60FL to 60RR are energized and controlled by the solenoid drive circuit 62.

The arithmetic processing unit 37b executes the process shown in FIG. 5 when the ignition switch is turned on, and when a predetermined time elapses, the command values I _{FL to} I _RR are based on the stored values in the nonvolatile memory 37d described later. In addition to outputting the control signal CS having a logical value "1" to enter the control start state, the vehicle height detection values H _{FL to} H _RR from the vehicle height sensors 35FL to 35RR are read, and these and the target vehicle height value H Based on _S and _S , the command values I _{FL to} I _RR are selected so that they match, and the vehicle height adjustment process is performed. Further, when the ignition switch is turned from the on state to the off state, the control signal CS is changed to the logical value “ The value is set to 0 ", and the command values I _{FL to} I _RR at that time are written in the nonvolatile memory 37d.

The storage device 37c stores a program necessary for the arithmetic processing of the arithmetic processing device 37b, stores a storage table corresponding to FIG. 3, and sequentially stores data of the arithmetic process of the arithmetic processing device 37b. In addition, an electrically writable / erasable nonvolatile memory (EEPROM) 37d is incorporated.

Further, the controller 36 is supplied with power from a DC power supply 41 such as a battery via a power supply holding unit 42 having an off-delay timer, and the ignition switch is turned off in the power supply holding unit 42 to stop the engine 2. After that, the power-on state is maintained until a predetermined time elapses, and the control device
36 remains active.

Next, the operation of the first embodiment will be described. Now, assuming that the vehicle is in a stopped state and the key switch is in an off state, in this state, the solenoid opening / closing valves 60FL to 60RR are switched to the normal position, and the working fluid from the fluid pressure supply device FS is shut off. Further, since the supply pressure port 21i and the return port 21o of the pressure control valves 13FL to 13RR are communicated with each other through the throttle 61, the pressure control valves 13FL to 13RR and the hydraulic cylinder 31 are connected.
Pressure is filled in FL to 31RR at the time of the previous operation stop.
On the other hand, the non-volatile memory 37d of the control device 36 stores the command values I _{FL to} I _RR at the time of the previous enclosure.

In this state, by turning on the ignition switch, the control device 36 is powered on. Therefore, the microcomputer 37 of the control device 36 executes the posture change suppression control process shown in FIG.

That is, it is determined in step whether or not a predetermined time sufficient for the discharge pressure of the hydraulic pump 1 of the fluid pressure supply device FS to reach the line pressure P _L set by the relief valve 12 has elapsed, and the predetermined time has elapsed. If not, the process waits until this elapses, and when a predetermined time elapses, the process proceeds to step and the command value I _FL stored in the non-volatile memory 37d
I _RR is stored as an initial value in the command value storage area, and
The command values I _{FL to} I _RR stored in the non-volatile memory 37d are erased, and then the step proceeds to the command values I _{FL to} I _RR stored in the command value storage area to the D / A converters 39FL to 39RR. Output.

Next, shift to the step, and the solenoid opening / closing valves 50FL-50
A control signal CS having a logical value "1" for controlling the open state of RR is output to the solenoid drive circuit 51.

Next, it is determined whether or not the ignition switch is switched from the ON state to the OFF state by shifting to the step, and when the ignition switch is in the ON state, the procedure is shifted to step and the vehicle height corresponding to the posture change suppression control means is controlled. The adjustment process is executed every predetermined time (for example, 50 msec) and then the process returns to the step. When the ignition switch is switched from the on state to the off state, the process proceeds to step and the control signal CS for the electromagnetic switching valves 50FL to 50RR is transmitted. The logical value is set to "0", the solenoid on-off valves 50FL to 50RR are closed, the pressure of the hydraulic cylinders 31FL to 31RR is sealed, and then the process proceeds to step. The command values I _{FL to} I _RR at that time are stored in the nonvolatile memory 37d. After writing to, the processing ends.

Here, in the vehicle height adjustment process of step, as shown in FIG. 6, in step a, the vehicle height detection values H _{FL to} H _RR of the vehicle height sensors 35FL to 35RR are read, and then the process proceeds to step b to read. Then, a difference value (H _s −H _i ) between each vehicle height detection value H _i (i = FL to RR) and a preset target vehicle height value H _s is calculated, and then the process proceeds to step c to calculate the difference value. It is determined whether or not the absolute value | H _s −H _i | exceeds a predetermined set value ΔH which is a preset dead zone for hunting prevention. This determination is to determine whether or not to adjust the vehicle height. When | H _s −H _i | ≦ ΔH, it is determined that the vehicle height is normal, and the timer interrupt process is terminated. , | H _s −H _i |> ΔH,
When it is determined that the vehicle height is out of the proper value, the process proceeds to step d.

In step d, it is determined whether or not the difference value (H _s −H _i ) calculated in step b is positive. This determination is to determine whether or not the vehicle height is lower than the target vehicle height. When H _s −H _i > 0, it is determined that the vehicle height is low and the process proceeds to step e. , The value obtained by adding the predetermined value ΔI to the previous command value I _i-1 is updated and stored in the command value storage area formed in the storage device 37c as the current command value I _i , and then the process proceeds to step g, where H _s − When H _i <0, it is determined that the vehicle height is high, the process proceeds to step f, and the value obtained by subtracting the predetermined value ΔI from the previous command value I _i-1 is the current command value.
After updating and storing in the command value storage area as I _i , the process proceeds to step g.

In step g, the command values I _{FL to} I _RR stored in the command value storage area are output to the D / A converters 39 _FL to 39 _RR , the timer interrupt processing is terminated, and the main program is restored.

Here, the predetermined value ΔI in the processing of step e or step f is selected to be a relatively small value so as to prevent a sudden vehicle height change and perform a gentle vehicle height adjustment.

In the processing shown in FIG. 5 above, the steps 1 to 3 and the processing of steps and steps correspond to the valve control means.

According to the first embodiment, the hydraulic cylinder 3 is stored in the nonvolatile memory 37d when the ignition switch is turned off last time.
Since the command values I _{FL to} I _RR corresponding to the enclosed pressure of 1FL to 31RR are stored, when the ignition switch is in the off state when the vehicle is stopped, the occupant gets on and turns the ignition switch on. When a predetermined time sufficient for the discharge pressure of the hydraulic pump 1 of the fluid pressure supply device FS to reach the line pressure P _L has elapsed, command values for the pressure control valves 13FL to 13RR
I _FL 〜 I _RR becomes a value corresponding to the filled pressure of the hydraulic cylinders 31FL 〜 31RR, and the solenoid opening / closing valves 60FL 〜 60RR can be switched to the open state in this state, so when switching these solenoid opening / closing valves 60FL 〜 60RR It is possible to prevent a sudden change in vehicle height due to pressure fluctuations of up to 31 RR. After that, the process proceeds to step and the vehicle height detection values H of the vehicle height sensors 35FL to 35RR are detected.
Vehicle height adjustment processing is performed based on _{FL to} H _RR , and the vehicle height is changed in steps so that the vehicle height matches the target vehicle height.

After that, when the vehicle is brought into a traveling state, the control device 36 continues the vehicle height adjustment processing for maintaining the vehicle height at the target vehicle height, and the command values I _{FL to} I _RR corresponding thereto are set to the pressure control valves 13 _{FL to} 13 _FL.
By outputting to RR, the pressures of the hydraulic cylinders 31FL to 31RR are controlled, and changes in vehicle height of the vehicle body are suppressed.

Also, when a relatively low-frequency vibration input corresponding to the sprung resonance frequency range is transmitted from the wheel side to the hydraulic cylinders 31FL to 31RR when traveling on a swell or rough road, the hydraulic cylinders 31FL to 31RR are responsive to this vibration input. The internal pressure of V fluctuates, and the pressure of the control port 21n of the pressure control valves 13FL to 13RR fluctuates. When this happens, the pressure control valve
When the pressure in the feedback chamber F _L of 13 FL to 13 _RR fluctuates and becomes lower than the pressure in the feedback chamber F _U based on the command value I _{FL to} I _RR from the control device 36, the spool
24 the line pressure P _L to the input port 21i is lowered and the control port 21n is the communicating state is supplied to the hydraulic cylinder 31FL～31RR. Thus, it increased internal pressure of the hydraulic cylinder 31FL～31RR, which spool 24 is raised to increase the pressure in the feedback chamber F _L according to, equal to the pressure in the pressure feedback chamber F _U feedback chamber F _L Then, the line 24a closes the input port 21i. On the other hand, when the pressure in the feedback chamber F _L becomes higher than the pressure in the feedback chamber F _U , the spool 24 rises and the drain port 21o and the control port 21n are in communication with each other, and the hydraulic cylinders 31FL to 31RR.
The hydraulic oil therein is returned to the oil tank 3 via the drain pipe 7. Therefore, the internal pressure of the hydraulic cylinders 31FL~31RR is reduced, the spool 24 is lowered by lowering the pressure in the feedback chamber F _L In response, equal to the pressure in the pressure feedback chamber F _U feedback chamber F _L Then, the land 24a closes the input port 21i. Eventually, vibration input of a relatively low frequency in the sprung resonance frequency range from the road surface transmitted to the hydraulic cylinders 31FL to 31RR is prevented from being absorbed and transmitted to the vehicle body.

After that, when the vehicle is stopped and the ignition switch is turned off, the microcomputer 37 outputs the control signal CS having the logical value "0", which switches the solenoid operated directional control valves 60FL to 60RR to the normal position, and the fluid pressure is changed. Since the supply device FS side is shut off and the supply pressure port 21i and the return port 21o of the pressure control valves 13FL to 13RR are communicated via the throttle 61, the high pressure fluid on the supply pressure port 21i side is gradually transferred to the return port 21o side. The pressure of the working fluid in the pressure control valves 13FL to 13RR and the hydraulic cylinders 31FL to 31RR is equalized and sealed. And the pressure control valve 13FL at this time
Command value I _{FL to} I of microcomputer 37 for ~ 13RR
_{The RR} is stored in the nonvolatile memory 37d.

Thus, according to the first embodiment, the fluid pressure supply device by turning off the ignition switch.
The pressure of the hydraulic cylinders 31FL to 31RR can be sealed without being affected by the sudden drop in the discharge pressure of the FS, and the drop in vehicle height can be prevented, and the ignition switch is turned on to supply fluid pressure. Even when the device FS is started, it is possible to reliably prevent sudden pressure fluctuations in the hydraulic cylinders 31FL to 31RR.

Next, a second embodiment of the present invention will be described with reference to FIG.

In the second embodiment, the solenoid switching valve common to the first embodiment supplies and shuts off the working fluid from the fluid pressure supply device to the two pressure control valves on the front wheel side and the rear wheel side. It was done like this.

That is, as shown in FIG. 7, the solenoid switching valves 60FL and 60RR are omitted in the configuration of FIG.
Pressure control valves 13FL and 13RR on A port and B port of 60FL
Supply pressure ports 21i and 21o are connected in parallel, and supply pressure ports 21i and 21o of the pressure control valves 13RL and 13RR are connected in parallel to the A port and B port of the electromagnetic switching valve 60RL.

On the other hand, the processing unit 37b of the microcomputer 37 in the control unit 36 executes the process of FIG. 8 corresponding to FIG.

That is, when the ignition switch reverses from the on state to the off state, the process moves from step to step, the control signal CS is set to the logical value "0", and the electromagnetic switching valve 60 is turned on.
Switch FL to 60RR to the offset position. Then, the process shifts to step, and the command value I _i ( _i) is referred to by referring to the storage table corresponding to FIG. 3 based on the command values I _{FL to} I _RR stored in the command value storage area of the storage device 37c. The control pressure _Ci corresponding to i = FL to RR) is calculated.

Then, the process proceeds to step to calculate the equilibrium control pressures P _AVF and P _AVR on the front wheel side and the rear wheel side. This balance control pressure P
To calculate the _AVF , the gas charging pressure and volume of the accumulators 43FL, 43FR connected to each hydraulic cylinder 31FL, 31RR in the initial state are P ₀ and V _0, and the desired gas charging pressure of the accumulators 43FL, 43FR and If the volumes are P _FL , P _FR and V _FL , V _FR , then there is a relationship of P ₀ V ₀ = P _FL V _FL = P _FR V _FR (1).

In this state, the solenoid control valve 60FL controls the pressure control valve 13FL.
And the gas volume when equalizing 13FR is V _AVF , it is expressed by P _AVF V _AVF = 2P ₀ V ₀ (2), and the gas volume V _AVF is both accumulators 42FL and 42FL.
Since it is the sum of the gas volumes V _FL and V _FR of RR (V _AVF = V _FL + V _FR ), the equilibrium pressure P _AVF is Can be represented by

Similarly, the equilibrium pressure P _AVR on the rear wheel side is Can be represented by

Then, the process shifts to the step, the command values I _{FL to} I _RR are calculated by referring to the storage table corresponding to FIG. 3 based on the equilibrium pressures P _AVF and P _AVR calculated in the above step, and then the step After storing the command values I _{FL to} I _RR calculated by shifting to the non-volatile memory 37d, the process is terminated.

In the process of FIG. 8 described above, the process from step to step and the processing from step to step correspond to the valve control means.

According to the second embodiment, when the ignition switch is turned from the ON state to the OFF state, the pressure of the hydraulic cylinders 31FL to 31RR at that time is sealed, so that the vehicle height changes due to the pressure fluctuation of the hydraulic cylinders 31FL to 31RR. it is possible to reliably prevent, when the starting state a fluid pressure supply device FS an ignition switch is turned on to the control pressure P _C of the pressure control valve 13FL~13RR is corresponding to filling pressure at that time Since it becomes a value and then gradually changes according to the vehicle height detection value, it is possible to reliably prevent a sudden vehicle height change.

In addition, in the said 1st and 2nd Example, although the case where the operating state of the fluid pressure supply apparatus FS was determined by whether the ignition switch is an ON state was demonstrated, it is not limited to this. The rotation speed of the rotating shaft of the engine 2 may be directly detected, or the discharge pressure of the hydraulic pump 1 may be detected.

Further, in the first and second embodiments, the control device
Although the case where the 36 is configured to include the microcomputer 37 has been described, the configuration is not limited to this, and may be configured by combining electronic circuits such as a comparison circuit, a timer, and a logic circuit.

Further, in the above-mentioned first and second embodiments, the case where the rotational driving force of the hydraulic pump 1 is obtained from the engine 2 has been described, but the present invention is not limited to this, and a rotational driving source such as an electric motor is provided. Needless to say, can be applied.

Further, the control valve of the hydraulic suspension is not limited to the pressure control valves 13FL to 13RR, and other flow control servo valves and the like can be applied.

Further, in the above-described embodiment, the case where the working oil is applied as the working fluid has been described. However, the present invention is not limited to this, and any working fluid may be applied as long as the fluid has a low compression ratio.

〔The invention's effect〕

As described above, according to the active suspension of the first aspect, it is possible to electrically detect that the fluid pressure supply device has changed from the operating state to the non-operating state, and based on this, the fluid pressure supply device. By switching the electromagnetic switching valve inserted between the control valve and the control valve to a switching position where the supply pressure port and the return port of the control valve communicate with each other through a throttle, and by sealing the working fluid in the control valve and the fluid pressure cylinder, It is possible to reliably prevent changes in vehicle height, and to control sudden changes in vehicle height by controlling the control valve to the command value corresponding to the working fluid pressure enclosed in the fluid pressure cylinder when the fluid pressure supply device is started. The effect that can be prevented is obtained.

According to the active suspension of claim (2), when the fluid pressure supply device is in the inoperative state, the fluid pressure supply device side is individually shut off by the electromagnetic switching valve on the front wheel side and the rear wheel side, and the front wheel side is shut off. Since the primary side of the left and right control valves on the left and right wheels are in communication, the pressures of the left and right fluid pressure cylinders become almost equal enclosure pressures, and the left and right fluids on the front and rear wheels are activated when the fluid pressure supply device is started. Equilibrium control pressure is calculated based on the enclosed pressure of the pressure cylinder, and based on this, the command values for the front and rear wheels are individually corrected, and the front and rear electromagnetic switching valves are controlled to open. Therefore, it is possible to obtain an effect that the posture of the vehicle body is stable when the vehicle is stopped and that the electromagnetic opening / closing valves are only required to be provided on the front wheel side and the rear wheel side.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system diagram showing a first embodiment of the present invention, FIG. 2 is a longitudinal sectional view showing an example of a pressure control valve applicable to the present invention, and FIG. 3 is a pressure control. A characteristic diagram showing the relationship of the control pressure to the command value of the valve, FIG. 4 is a block diagram showing an example of the control device, FIG. 5 is a flow chart showing an example of processing in the control device, and FIG. 6 is in FIG. FIG. 7 is a flow chart showing an example of vehicle height adjustment processing, FIG. 7 is a system diagram showing a second embodiment of the present invention, and FIG. 8 is a flow chart showing an example of processing of the control device in the second embodiment. In the figure, FS is a fluid pressure supply device, 1 is a hydraulic pump, 2 is an engine, 5 is line pressure piping, 7 is drain piping, and 13FL to 13RR.
Is a pressure control valve, 21i is an input port, 21o is a drain port,
21c is a control port, a proportional solenoid 22, 24 are spool, F _U, F _L feedback chamber, 35FL～35RR the vehicle height sensors, 36 controller, 60FL～60RR the electromagnetic switching valve 62 is a solenoid drive circuit is there.

Claims (2)

(57) [Claims] 1. A fluid pressure cylinder interposed between each wheel and a vehicle body, and a control valve for controlling a working fluid pressure from a fluid pressure supply device supplied to the fluid pressure cylinder in accordance with a command value. In the active suspension, the control valve is provided with an attitude change suppression control means that outputs the command value based on a detection value of an attitude change detection means that detects an attitude change of the vehicle body, and the fluid pressure supply device is in an operating state. Is connected to the open position inserted between the fluid pressure supply device and the control valve, the supply pressure port and the return port of the control valve through a throttle, and An electromagnetic switching valve having a closed position for shutting off the pressure supply device side, and switching the electromagnetic switching valve to the closed position when it is detected by the operating state detection means that the fluid pressure supply device is in an inactive state, Check operating status In this case, there is provided valve control means for correcting the command value of the posture change suppression control means according to the enclosed pressure of the fluid pressure cylinder at that time and switching the electromagnetic switching valve to the open state. Active suspension. 2. The control valves are individually connected in parallel on the front wheel side and the rear wheel side, and a front wheel side electromagnetic switching valve is interposed between the front wheel side control valve and the fluid pressure supply device, and a rear wheel side control valve. The rear wheel side electromagnetic switching valve is inserted between the fluid pressure supply device and the valve control means, and when the operation state detection means detects the operating state of the fluid pressure supply device, the front wheel side and the rear wheel side at that time are detected. The equilibrium control pressures on the front wheel side and the rear wheel side are calculated according to the enclosed pressure of the fluid pressure cylinder, and based on these, the front wheel side command value and the rear wheel side command value of the posture change suppression control means are configured to be corrected. The active suspension according to claim 1, characterized in that: