JPH0636973Y2 - Active suspension device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention has a hydraulic cylinder interposed between a vehicle body and each wheel, and the pressure of a working fluid supplied to the hydraulic cylinder is supplied via a pressure control valve. The present invention relates to an active suspension device which suppresses a change in posture of a vehicle body by controlling according to a command value based on a running state, and particularly relates to improvement of a hydraulic circuit thereof.

[Conventional technology]

As a hydraulic suspension of an automobile, for example, JP-A-51
There is known a hydropneumatic suspension device as disclosed in Japanese Patent Publication No. 42215/1992. In this system, a hydraulic pump driven by an engine is used as a power source, and the hydraulic pressure produced by the power source is sent to a hydraulic cylinder via a poppet valve type switching valve to adjust the vehicle height.

For example, when the vehicle stops, the hydraulic pump also stops, but at that time, the poppet valve type switching valve is manually operated to force the poppet valve between the circuit from the hydraulic pump to the hydraulic cylinder inlet and the circuit from the hydraulic cylinder to the oil tank. Cut off. By configuring the switching valve in the poppet valve type in this manner, internal leakage of oil from the gap between the valve spool and the valve guide does not occur unlike in the spool valve type. Therefore, it is possible to completely confine the hydraulic pressure in the hydraulic cylinder and maintain a predetermined vehicle height.

However, such a poppet valve type switching valve is on / off control, and pressure feedback control is structurally impossible. Therefore, the hydraulic pressure of the hydraulic cylinder is automatically controlled by the servo valve according to the relative displacement between the vehicle body and the wheels, and the suspension characteristics are actively changed.
In a so-called active suspension device, it is inappropriate to adopt a poppet valve type switching valve as a servo valve, and a spool valve type is inevitable.

As the above active suspension device, for example, Japanese Patent Laid-Open No.
There is one disclosed in Japanese Patent Publication No. 61-213910. This is a switching valve including a spool valve that controls the pressure of a hydraulic cylinder that is interposed between the sprung and unsprung portions of a vehicle, and a control device that controls the switching valve according to the relative displacement between the sprung and unsprung portions. When either one of the upper and lower pressure chambers of the hydraulic cylinder is boosted due to vibration input, that pressure is supplied to the switching valve as pilot pressure, and this switching valve is set to the pressure chamber on the boosting side. By switching to the direction of pressure reduction, that is, the direction of canceling, the vibration input is absorbed by the hydraulic cylinder to suppress the vibration and swing of the vehicle body.

Even in such an active suspension device, since the switching valve is a spool valve and in-valve leakage of hydraulic oil is unavoidable, if the hydraulic pump driven by the engine stops when the vehicle is stopped, it is added until then. There is an unsolved problem that the pressure of the hydraulic cylinder leaks from the switching valve in a pressure state and decreases, resulting in a sudden decrease in vehicle height. Therefore, the applicant of the present application, according to Japanese Patent Application No. 62-7482, intervenes between each wheel and the vehicle body so that a predetermined line pressure can be secured if necessary even when the hydraulic pump is stopped. A hydraulic cylinder, a hydraulic pressure supply device that supplies an operating pressure to the hydraulic cylinder, and a pressure control valve that controls the operating pressure according to a command value from a posture change control device, and the primary side of the pressure control valve Is provided with a fluid check means for passing the fluid only in the output direction of the hydraulic pressure supply device, and the fluid return side of the pressure control valve allows passage of the fluid when the output of the hydraulic pressure supply device drops below a predetermined pressure. It proposes an active suspension device provided with a fluid blocking means for blocking the above.

[Problems to be solved by the invention]

However, in the active suspension device as described above, in the unlikely event that some abnormality occurs in the pressure control valve, the pressure control valve causes an operation different from the command value, which causes the pressure in the hydraulic cylinder to change. There is a problem in that it may happen that the steering stability and the traveling stability are impaired without being properly controlled.

[Means for solving problems]

The present invention has been made in view of such conventional problems, and operates by using a hydraulic cylinder interposed between each wheel and a vehicle body and a vehicle engine as a drive source, and A hydraulic pressure supply device that supplies a working fluid, an attitude change suppression control device that outputs a command value that suppresses an attitude change of the vehicle body based on the running state of the vehicle, and a supply side flow path and a return side flow path to the hydraulic pressure supply device. Connected to each of the hydraulic cylinders via a supply / discharge passage, and the working fluid supplied to the hydraulic cylinders can be individually controlled according to a command value from the posture change suppressing device. A pressure check valve is provided, and a fluid check valve that allows a working fluid to pass only in the output direction of the hydraulic pressure supply device is provided in the supply side flow path, and the output of the hydraulic pressure supply device is provided in the return side flow path. Drop below a certain pressure In an active suspension device provided with a fluid closing means for preventing the passage of working fluid, when an abnormal operation of the pressure control valve is detected, the hydraulic pressure is supplied based on an output signal from the abnormal detection means. Pressure adjusting means for reducing the output of the device to the predetermined pressure or less is provided.

[Action]

In this invention, when the engine is in operation and the hydraulic pump of the hydraulic pressure supply device is being driven, the output of the hydraulic pressure supply device is equal to or higher than a predetermined pressure, so that the fluid closing means is in the open state, and The return-side flow passage between the control valve and the hydraulic tank is open. In this state, the pressure control valve operates according to the command value from the posture change suppression control device, and controls the pressure in the hydraulic cylinder,
It suppresses changes in the body posture. Then, when the engine stops and the hydraulic pump of the hydraulic supply device stops, the discharge pressure of the hydraulic pump immediately drops. At this time, in the flow path on the supply side of the pressure control valve, the check function of the fluid check means provided therein works to prevent the reverse flow of the fluid to the hydraulic pump side. On the other hand, in the return side flow path of the pressure control valve, the closing mechanism of the fluid closing means provided therein works to prevent the fluid from returning to the oil tank in the hydraulic pressure supply device. As a result, the pressure in the hydraulic cylinder is maintained even when the vehicle stops,
It is possible to suppress sudden changes in body posture.

When the hydraulic pressure supply device is operating and the discharge pressure is equal to or higher than the predetermined pressure, if an abnormal operation occurs in the pressure control valve for any reason, the abnormal pressure detection means detects that The output of the hydraulic pressure supply device is reduced below a predetermined pressure by the adjusting means. As a result, as in the case where the engine is stopped, the fluid check means prevents the backflow of the supply-side flow passage, and the fluid closing means closes the return-side passage, so that the pressure control valve and the hydraulic cylinder side are closed. The pressure is maintained at a predetermined pressure, and pressure control by the pressure control valve is stopped.

〔Example〕

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

1 to 3 are views showing an embodiment of the present invention.

FIG. 1 shows a hydraulic circuit including a hydraulic pressure supply device 1. The hydraulic pressure supply device 1 is connected to a rotary shaft 3 of an engine 2 and is driven to rotate, and is connected to a discharge side of the hydraulic pump 4. Supply side flow path 5, a tank 6 for supplying hydraulic oil to the hydraulic pump 4, and a pressure control valve for the tank 6 which will be described later
A return-side flow passage 17 for returning the return oil from 11, an electromagnetic relief valve 8 inserted in a communication pipe 7 for communicating between the supply-side flow passage 5 and the return-side flow passage 17, and a return-side flow passage 17 It consists of an oil cooler 20 installed in the.

Here, the electromagnetic relief valve 8 also has a function as a pressure adjusting means, and a pressure control valve abnormality detecting device 27 as an abnormality detecting means provided in a control unit 28, which will be described later, is supplied to the electromagnetic solenoid 8a. When the exciting current W is zero and in a non-energized state, the line pressure in the supply-side flow path 5 is maintained at the rated pressure. It is configured to reduce to the following.

A check valve 9 (for example, a simple in-line type) as a fluid check means that allows the pressure oil discharged from the hydraulic pump 4 of the hydraulic supply device 1 to pass only in the output direction is provided further downstream of the supply-side flow path 5. Spring-loaded check valve), accumulator 10 for stabilizing line pressure, pressure control valve 11
Are connected in sequence. Further, a hydraulic cylinder 14 constituting an active suspension inserted between the vehicle body 12 and the wheel 13 is connected to the end of the pressure control valve 11 via a supply / discharge passage 5A. Reference numeral 15 is an accumulator attached to the supply / discharge channel 5A via a diaphragm 16.

The return port 17 is connected to the return port of the pressure control valve 11 so that the return oil from the hydraulic cylinder 14 is returned to the tank 7. Then, this return side flow path 17
As a fluid closing means for preventing passage of return oil when the output of the hydraulic pressure supply device 1 drops below a predetermined pressure during
A pilot operated check valve 18 is mounted, and its pilot channel 19 is connected to the supply side channel 5 upstream of the check valve 9.

The pilot operated check valve 18 has, for example, a well-known configuration in which a pilot piston is incorporated in a normal spring-loaded check valve, and a poppet, which is a valve element, is pressed against a valve seat to allow fluid flow in only one direction. To allow the passage of the air flow and prevent the flow in the opposite direction. However, when pilot pressure is applied, the tip of the poppet is pressed by a spring-return type pilot piston to push the poppet up from the valve seat, allowing the fluid to flow backward.

Further, in the return side flow passage 17, the pilot operated check valve
A bypass passage 17a is provided from the upstream side to the downstream side of 18, and the relief valve VR is provided in the bypass passage 17a. The illustrated relief valve VR is a so-called direct-acting relief valve, but other types may be used, in short, the maximum pressure on the primary side of the relief valve VR is limited to prevent the pressure from exceeding a preset pressure. If The set pressure in this case is below the rated pressure Ps of the line pressure shown in FIG. 3, which will be described later, and below the offset pressure P _o (for example, 30 kgf / cm ² ).
I will keep it.

Here, as shown in FIG. 2, the pressure control valve 11 includes a cylindrical valve housing 21, a spool 22 and a rod 23 slidably disposed in an insertion hole 21a provided in the valve housing 21.
And a spring 24 interposed between the spool 22 and the rod 23, and the pressing force of the spring 24 is controlled via the rod 23 to control the movement of the spool 22 between the offset position and the operating positions on both ends thereof. And a proportional solenoid 25. Here, in the valve housing 21, one end communicates with the insertion hole 21a and the other end connects with the input port 21b connected to the supply side flow path 5 of the hydraulic pressure supply device 1, and the hydraulic pressure supply device 1
Of the pressure chamber 1 of the hydraulic cylinder 14 via the return port 21c connected to the tank 6 of FIG.
An input / output port 21d communicating with 4a is provided. The return port 21c is connected to drain passages 21e and 21f that communicate with the return port 21c and the upper end and the lower end of the spool 22.

Further, the spool 22 is formed with a land 22a facing the input port 21b and a land 22b facing the return port 21c, and the land 2 having a smaller diameter than both the lands 22a, 22b.
2c is formed at the lower end, and a pressure control chamber C is formed between the land 22a and the land 22c. This pressure control chamber C is
It is connected to the input / output port 21d via the pilot passage 21g.

Further, the proportional solenoid 25 is composed of an actuator 25a which is slidable in the axial direction and an exciting coil 25b for driving the same. The proportional solenoid 25 is provided in the control unit 28, and the exciting coil 25b is provided with a lateral acceleration, a vertical acceleration of the vehicle, A command value V is supplied from a posture change suppression control device 26 that outputs a command value for suppressing a posture change of the vehicle body based on a detection signal such as longitudinal acceleration. Here, the relationship between the command value V and the hydraulic pressure P output from the input / output port 21d is as shown in FIG.
That is, when the command value V is zero, a predetermined offset pressure P _o is output, and when the command value V increases in the positive direction from this state, the output pressure P increases with a predetermined proportional gain K ₁ . When the line pressure of the hydraulic pressure supply device 1 reaches the rated pressure Ps, it is saturated, and when the command value V increases in the negative direction, the output pressure P decreases in proportion to this.

The pressing force of the proportional solenoid 25 on the pressure control valve 11 is applied to the spool 22 via the spring 24.
Moreover, the pressing force of the spring 24 and the pressure of the pressure control chamber C are balanced. In this state, when the vibration input of the relatively low frequency corresponding to the upward sprung resonance frequency range of the vehicle due to the passage of the convex portion of the road surface (or the downward vibration input due to the passage of the concave portion) is transmitted to the wheel 13, As a result, the piston rod 14b of the hydraulic cylinder 14 tries to move upward (or downward), and the pressure in the pressure chamber 14a rises (or decreases). In this way, the pressure in the pressure chamber 14a rises (or decreases)
Then, in response thereto, the pressure of the pressure control chamber C communicated with the pressure chamber 14a through the supply / discharge passage 5A, the input / output port 21d and the pilot passage 21g rises (or falls), and the spring 24
The balance with the pressing force of is lost. Then, the spool 22 moves upward (or downward), and the input port 21b and the input / output port 21d are
Since the space between and changes to the direction of being closed (or the direction of opening), a part of the pressure of the pressure chamber 14a is discharged from the input / output port 21d to the tank 6 via the return port 21c and the return side flow path 17 ( Alternatively, the hydraulic pressure is supplied from the hydraulic pressure supply device 1 to the pressure chamber 14a via the input port 21b, the input / output port 21d, and the supply / discharge channel 5A). As a result, the pressure of the pressure chamber 14a of the hydraulic cylinder 14 is reduced (or increased), and the pressure increase of the pressure chamber 14a due to the upward vibration input (or the pressure decrease of the pressure chamber 14a due to the downward vibration input) is suppressed. Therefore, the vibration input transmitted to the vehicle body 12 can be reduced.

A pressure sensor (not shown) is attached to the input / output port 21d of the pressure control valve 11, and an output signal U from this pressure sensor is input to the pressure control valve abnormality detection device 27 in the control unit 28. . Based on this input signal U,
The hydraulic cylinder 14 whose target is the pressure control valve abnormality detection device 27
Calculate the deviation from the pressure of the pressure control valve based on that value.
Judge 11 abnormalities.

Next, the operation of the above embodiment will be described.

Now, it is assumed that the vehicle is traveling straight at a constant speed on a flat and smooth road without any unevenness, and the vehicle height value is also within a proper range.

While the engine is operating, the hydraulic pump 4 is driven, and the hydraulic pressure in the supply side flow path 5 becomes a value determined by the set value of the relief valve 8. Then, the pressure is input to the pilot port of the pilot operated check valve 18 via the pilot flow path 19. As a result, the function of the pilot operated check valve 18 as a check valve is released, so that the return side flow path 17 is opened and the return fluid can freely flow to the tank 6.

When the vehicle runs on a good road at a constant speed, swinging such as pitch, roll and bounce of the vehicle body does not occur, so the detection signal from the vertical acceleration detector (not shown) provided for each wheel is zero. Therefore, the command value V from the posture change suppression control device 26 is also zero. At this time, a predetermined offset current is supplied to the exciting coil 25b of the proportional solenoid 25 of the pressure control valve 11 in the excited state, the spool 22 is set to a predetermined neutral position, and the pressure in the pressure chamber 14a of the hydraulic cylinder 14 is set. Is also maintained at offset pressure P _o . Then, a hydraulic cylinder that fluctuates in response to vibration input due to fine unevenness from the road surface
The spool 22 is slightly moved in response to small pressure fluctuations in the fourteen pressure chambers 14a, and transmission of vibration input to the vehicle body is suppressed.

When the wheel 13 passes, for example, a relatively large convex portion on the road surface and the vibration input is transmitted, the piston rod 14b of the hydraulic cylinder 14 tries to move upward, and the pressure in the pressure chamber 14a rises. As a result, as described above, the spool 22 moves upward from the neutral position, the return port 21c is opened, and a part of the pressure oil in the pressure chamber 14a is discharged to the return side flow passage 17 to open the pilot. It is discharged to the tank 6 via the operation type check portion 18. As a result, the vibration input transmitted to the vehicle body 13 can be reduced.

Further, for example, when a steering wheel (not shown) is steered clockwise to turn right, lateral acceleration occurs in the vehicle body in accordance with the vehicle speed and steering angle at that time, which causes the vehicle body to roll to the left and tilt downward. . When the vehicle rolls in this way, the vehicle body 12
The right side position is displaced upward and the left side position is displaced downward. Then, a positive vertical acceleration detection signal is output from the vertical acceleration detector (not shown) provided at the right position, and a negative vertical acceleration detection signal is output from the vertical acceleration detector (not shown) provided at the left position. Vertical acceleration detection signals are output, and these signals are supplied to the posture change suppression control device 26.

The posture change suppression control device 26 calculates based on these signals and outputs a negative command value V to the hydraulic cylinder 14R corresponding to the right wheel 13R, while the hydraulic pressure corresponding to the left wheel 13L is output. A positive command value V is output to the cylinder 14L.

Therefore, in the right hydraulic cylinder 14R, the exciting current of the proportional solenoid 25 decreases, so that the actuator 25a rises and the spool 22 accordingly rises to return the input / output port 21d to the tank 6. Connect to port 21c. On the other hand, the left hydraulic cylinder 14L has its proportional solenoid 25
Since the exciting current of increases, the actuator 25a moves down,
In response to this, the spool 22 descends and the I / O port 21d
To the input port 21b. Therefore, the right hydraulic cylinder 14R is in the contracting direction, and the left hydraulic cylinder 14L
Since it is in the stretching direction, the anti-roll effect can be exhibited.

Not only when the vehicle rolls, but also when the vehicle pitches in the front-rear direction and when the vehicle bounces in the up-down direction, the posture change of the vehicle body can be similarly suppressed.

When the vehicle stops from the running state and the engine 2 stops, the hydraulic pump 4 of the hydraulic pressure supply device 1 stops at the same time,
The discharge pressure immediately becomes zero. As a result, the pressure on the upstream side of the check valve 9 in the supply-side flow path 5 becomes zero, but the pressure drop on the downstream side is blocked by the check valve 9. Therefore, after the check valve 9, the hydraulic pressure on the primary side (high pressure side) of the pressure control valve 11 is maintained at the same pressure as the internal pressure of the accumulator 10.

Further, the pressure in the pilot passage 19 branched from the upstream side of the check valve 9 in the supply-side passage 5 becomes zero. Therefore, the pilot operated check valve 18 functions as a check valve because its pilot piston returns to the spring. Therefore, the circuit (low pressure side) of the return side flow path 17 connected to the return port 21c of the pressure control valve 11 is closed, and the flow of the hydraulic oil returning from the hydraulic cylinder 14 to the tank 6 is blocked.

Thus, the pressure in the hydraulic circuit from the check valve 9 to the pilot operated check valve 18 via the hydraulic cylinder 14 is maintained at about the pressure before the engine 2 is stopped, and thus the hydraulic pressure is stopped at the same time as when the engine is stopped as in the conventional case. The phenomenon in which the pressure chamber 14a of the cylinder 14 is opened and the vehicle height suddenly drops does not occur.

In this case, if the pilot operated check valve 18 functions as a check valve while the engine 2 is stopped and the internal pressure of the accumulator 10 is still sufficiently high, the location of the hydraulic oil leaked from the pressure control valve 11 will be reduced. Then, the pressure in the hydraulic cylinder 14 tries to rise excessively. At that time, the relief valve VR provided in the bypass passage 17a of the return side passage 17 functions. That is, if the set pressure Pa rises abnormally,
Relief valve VR opens, releasing excess pressure. As a result, the pressure of the circuit extending from the return port 21c of the pressure control valve 11 to the pilot operated check valve 18 is held, but the magnitude of the holding pressure is controlled to be equal to or lower than the set pressure Pa.

Further, the relief valve VR prevents abnormal boosting of the hydraulic circuit due to malfunction of the pilot operated check valve 18.

That is, in the unlikely event that the hydraulic pump 4 is generating high pressure while the vehicle is traveling, the pilot operated check valve 18
However, if it operates as a check valve due to, for example, a failure of the pilot flow path 19 or sticking of the valve, the hydraulic circuit becomes overpressure. Even in that case, the relief valve VR functions similarly to the above to control the pressure of the hydraulic circuit to the set pressure Pa smaller than the rated pressure Ps, so that the phenomenon that the vehicle height suddenly rises to the full rebound during traveling is prevented. be able to.

Here, if any abnormality occurs in the pressure control valve 11, it acts as follows. That is, the pressure control valve
Pressure control valve abnormality detection device 27 based on output signal U from 11
At, it is determined that the operation of the pressure control valve 11 is abnormal. At this time, the output signal W is sent from the pressure control valve abnormality detecting device 27 to the electromagnetic relief valve 8, and the electromagnetic relief valve 8 is switched based on the output signal W, so that the hydraulic pump 4
The discharged oil of (1) is communicated with the tank 6 through the branch pipe 7. As a result, the pressure in the pilot passage 19 becomes zero, so that the pilot operated check valve 18 acts as a check valve. In this state, the pressure in the hydraulic cylinder 14 is maintained at a predetermined pressure Pa or higher by the action of the check valve 9 and the pilot operated check valve 18. Since hydraulic oil is not supplied from the hydraulic pressure supply device 1 to the pressure control valve 11, even if the pressure control valve 11 is operating abnormally, there is no particular effect, and the hydraulic cylinder 14 is It performs the same function as a conventional hydropneumatic suspension. Therefore, improper pressure control in the hydraulic cylinder 14 due to abnormality of the pressure control valve 11 will not occur.

In the above embodiment, the case where the pressure control valve 11 is applied as the control valve of the hydraulic suspension has been described, but the present invention is not limited to this, and other flow control servo valves and the like can be applied. is there.

Further, the abnormality detecting means does not have to detect the abnormality based on the input / output pressure of the pressure control valve, but may be based on the displacement of the spool or the like. Further, the posture change suppression control device and the abnormality detection means may be provided as separate control units.

[Effect of device]

As described above, according to the present invention, the supply side flow path connecting the hydraulic pressure supply device and the pressure control valve is provided with the fluid check means for passing the fluid only in the output direction of the hydraulic pressure supply device, and the pressure control valve is provided. The output pump of the hydraulic pressure supply device has a fluid closing means for preventing passage of the fluid only when the output of the hydraulic pressure supply device falls below a predetermined pressure in the return side flow path connecting the hydraulic pressure supply device and In the suspension control device, it is possible to secure a predetermined line pressure even when stopped, and to completely prevent the phenomenon that the vehicle height suddenly drops when the vehicle is stopped. By providing the abnormality detecting means for detecting an operation abnormality of the pressure detecting means and the pressure adjusting means for decreasing the output of the hydraulic pressure supply device to a predetermined pressure or less based on the output signal from the abnormality detecting means, Even if the control valve malfunctions for some reason while the vehicle is running, that is, while the hydraulic pressure supply device is operating normally, and the original proper pressure control in the hydraulic cylinder cannot be performed, the vehicle attitude changes significantly during running. To prevent
The effect that the steering stability can be ensured is obtained.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention, FIG. 2 is a sectional view showing an example of a pressure control valve applicable to the present invention, and FIG. 3 shows control characteristics of the pressure control valve of FIG. It is a graph shown. In the figure, 1 is a hydraulic pressure supply device, 2 is an engine, 5 is a supply side flow path, 8 is an electromagnetic relief valve (pressure adjusting means), 9 is a check valve (fluid check means), 11 is a pressure control valve, 12 Is a vehicle body, 13 is a wheel, 14 is a hydraulic cylinder, 17 is a return passage, 18 is a pilot operated check valve (fluid closing means), 19 is a pilot passage, 26 is a posture change suppression control device, and 27 is pressure. It is a valve abnormality detection device (abnormality detection means).

Claims (1)

[Scope of utility model registration request] 1. A hydraulic cylinder interposed between each wheel and a vehicle body, a hydraulic supply device that operates using an engine of the vehicle as a drive source to supply a working fluid to the hydraulic cylinder, and a running state of the vehicle. And a posture change suppression control device that outputs a command value that suppresses a posture change of the vehicle body, and is connected to the hydraulic pressure supply device via a supply side flow path and a return side flow path,
A pressure control valve that is connected to each of the hydraulic cylinders via a supply / discharge passage, and that can individually control the working fluid supplied to the hydraulic cylinders according to a command value from the posture change suppressing device; A fluid check valve that allows a working fluid to pass only in the output direction of the hydraulic pressure supply device is provided in the supply-side flow passage, and the return-side flow passage is provided when the output of the hydraulic pressure supply device drops below a predetermined pressure. In an active suspension device provided with fluid closing means for preventing passage of a working fluid, an abnormality detecting means for detecting an operation abnormality of the pressure control valve, and an output of the hydraulic pressure supply device based on an output signal from the abnormality detecting means. And a pressure adjusting means for reducing the pressure below the predetermined pressure.