JPH0788134B2 - Active suspension device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention inserts a hydraulic cylinder between a vehicle body and wheels, and adjusts the pressure of the pressure chamber of the hydraulic cylinder according to a command value via a pressure control valve. The present invention relates to an active suspension device that suppresses a change in posture of a vehicle body by controlling it, and particularly to improvement of its hydraulic circuit.

[Conventional technology]

As a hydraulic suspension of an automobile, for example, JP-A-51
There is known a hydropneumatic suspension device as shown in Japanese Patent Laid-Open No. 42215. 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 for vehicle height control.

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. When the switching valve is configured 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 the spool valve type configuration. Therefore, the hydraulic pressure can be completely confined in the hydraulic cylinder and a predetermined vehicle height can be maintained.

However, such a poppet valve type switching valve is an on / off control, and pressure feedback control cannot be performed structurally. 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 to actively change the suspension characteristics.
In a so-called active suspension device, it is unsuitable to adopt a poppet valve type switching valve as a servo valve, and it is unavoidable to use a spool valve type.

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 consisting of a spool valve that controls the pressure of a hydraulic cylinder interposed between the sprung and unsprung parts of a vehicle, and a control device that controls this switching valve according to the relative displacement between the sprung and unsprung parts. When any one of the upper and lower pressure chambers of the hydraulic cylinder is boosted by 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 pressure rising side. By switching the direction of pressure reduction, that is, the direction of cancellation, the vibration input is absorbed by the hydraulic cylinder, and the vibration and swing of the vehicle body are suppressed.

[Problems to be solved by the invention]

However, in such a conventional active suspension device, the switching valve is a spool valve, and in-valve leakage of hydraulic oil is unavoidable. Therefore, when the hydraulic pump driven by the engine is stopped. When stopped, there was an unsolved problem that the pressure of the hydraulic cylinder that had been pressurized up to that point leaked from the switching valve and dropped, resulting in a sudden drop in vehicle height.

The present invention has been made in view of such conventional problems, and it is possible to solve the above conventional problems by securing a predetermined line pressure as necessary even when the hydraulic pump is stopped. The purpose is to provide a possible active suspension device.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention provides a hydraulic cylinder interposed between each wheel and a vehicle body and a command from an attitude change control device by supplying pressure fluid from a hydraulic pressure supply device to the primary side. In an active suspension device including a control valve that controls the fluid returned from the fluid return side to the hydraulic pressure supply device according to the value to control the fluid supplied to the hydraulic cylinder, the primary side of the control valve Is provided with a fluid check means for allowing the fluid to pass only in the output direction of the hydraulic pressure supply device, and is opened on the fluid return side of the control valve when the output of the hydraulic pressure supply device exceeds a predetermined pressure. A fluid closing means for preventing passage of fluid when the pressure falls below a predetermined pressure is provided.

[Action]

In the present invention, while the hydraulic pump of the hydraulic pressure supply device is in operation, the output of the hydraulic pressure supply device is above a predetermined pressure, so the fluid closing means is in the open state and the fluid return side of the control valve is open. In this state, the control valve operates according to a command from the attitude change control device to control the fluid supplied to the hydraulic cylinder and suppress the attitude change of the vehicle body.

Thus, when the engine of the vehicle is stopped and the hydraulic pump of the hydraulic pressure supply device is stopped, the discharge pressure of the hydraulic pump immediately drops. At this time, the check function of the fluid check means provided on the primary side of the control valve works to prevent the reverse flow of the fluid to the hydraulic pump side. On the other hand, on the fluid return side of the control valve, the closing function of the fluid closing means works to prevent the fluid from returning to the oil tank in the hydraulic pressure supply device. As a result, even if the vehicle is stopped, the pressure in the hydraulic cylinder is still maintained, and a sudden change in the posture of the vehicle body can be suppressed. As a result, even if the vehicle is stopped, the pressure in the hydraulic cylinder is still maintained, and a sudden change in the posture of the vehicle body can be suppressed.

〔Example〕

 Embodiments 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, 2 is an engine as a rotary drive source, 3 is an output shaft thereof, and 4 is a hydraulic pump connected to the output shaft 3. The discharge side of the hydraulic pump 4 is connected to the output side hydraulic pipe 5, and the suction side is connected to the tank 6. Further, a branch pipe 7 to the tank 6 is provided in the middle of the output side hydraulic pipe 5, and a relief valve 8 for maintaining the line pressure at the rated pressure is connected.

The hydraulic pressure supply device 1 is provided further downstream of the output hydraulic line 5.
Check valve 9 (for example, a simple in-line type spring-loaded check valve may be used) as a fluid check means for passing the pressure oil discharged from the hydraulic pump 4 of FIG. An accumulator 10 and a pressure control valve 11 are connected in this order. Further, a hydraulic cylinder 14 constituting an active suspension interposed between the vehicle body 12 and the wheels 13 is connected to the end of the pressure control valve 11 via a hydraulic pipe 5A. An accumulator 15 is attached to the hydraulic pipe 5A via a throttle 16.

A return pipe is provided between the pressure control valve 11 and the tank 6.
17 is connected to the tank 6 for returning oil from the hydraulic cylinder 14.
I am going to return it to. A pilot operated check valve 18 is mounted in the middle of the return pipe 17 as a fluid closing means for preventing passage of return oil only when the output of the hydraulic pressure supply device 1 drops below a predetermined pressure. The pipe 19 is connected to the output side hydraulic pipe 5 upstream of the check valve 9.

The pilot operated check valve 18 has a well-known structure in which, for example, a pilot piston is incorporated in an ordinary spring-loaded check valve, and a poppet, which is a valve body, is pressed against a valve seat to allow fluid flow in only one direction. To pass through and block the flow in the opposite direction. However, when pilot pressure is applied, the tip of the poppet is pushed by a spring-return type pilot piston to push the poppet up from the valve seat, allowing the fluid to flow backward.

An oil cooler 20 is connected to the return pipe 17.

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 the spring 24 interposed between the spool 22 and the rod 23 and the pressing force of the spring 24 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 is connected to the insertion hole 21a and the other end is connected to the input port 21b connected to the output side hydraulic pipe 5 of the hydraulic pressure supply device 1 and the tank 6 of the hydraulic pressure supply device 1. An output port 21c connected via a return pipe 17 and an input / output port 21d communicating with the pressure chamber 14a of the hydraulic cylinder 14 via a hydraulic pipe 5A are provided.
The output port 21c is connected to drain passages 21e and 21f that communicate with the output port 21c and the upper and lower ends of the spool 22.

A land 22a facing the input port 21b and a land 22b facing the output port 21c are formed on the spool 22, and the land 2 having a smaller diameter than both the lands 22a and 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, and the exciting coil 25b is based on detection signals such as lateral acceleration, vertical acceleration and longitudinal acceleration of the vehicle. , The command value V from the attitude change suppression control device 26 that outputs a command value that suppresses the attitude change of the vehicle body
Is being supplied. Here, command value V and input / output port 21
The relationship with the hydraulic pressure P output from d is as shown in FIG. That is, when the command value V is zero,
When a predetermined offset pressure P ₀ is output and the command value V increases in the positive direction from this state, the output pressure P increases with a predetermined proportional gain K _{1 to} the rated pressure P of the line pressure of the hydraulic pressure supply device 1. _When it reaches _S , it saturates, and when the command value V increases in the negative direction, the output pressure P decreases in proportion to this.

The pressing force by the proportional solenoid 25 of this pressure control valve 11 is
The pressure is applied to the spool 22 via the spring 24, and the pressing force of the spring 24 and the pressure of the pressure control chamber C are balanced. In this state, when a vibration input of a relatively low frequency corresponding to the upward sprung resonance frequency range of the vehicle due to passage of a convex portion of the road surface (or a downward vibration input due to passage of a 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 increases (or decreases).
In this way, when the pressure in the pressure chamber 14a rises (or decreases), the pressure chamber 14a, the hydraulic pipe 5A, and the input / output port are responded accordingly.
The pressure in the pressure control chamber C communicated via the 21d and the pilot passage 21g rises (or falls), and the balance with the pressing force of the spring 24 is lost. Then, the spool 22 moves upward (or downward) and changes in the direction of closing (or opening) between the input port 21b and the input / output port 21d, so that part of the pressure in the pressure chamber 14a enters. It is discharged from the output port 21d to the tank 6 through the output port 21c and the return pipe 17 (or from the hydraulic pressure supply device 1 to the input port 21b, the input / output port).
The hydraulic pressure is supplied to the pressure chamber 14a via 21d and the hydraulic pipe 5A). As a result, the pressure in the pressure chamber 14a of the hydraulic cylinder 14 is reduced (or increased), and the pressure in the pressure chamber 14a is increased by the upward vibration input (or the pressure chamber 1 is generated by the downward vibration input).
(Pressure reduction of 4a) is suppressed, and the vibration input transmitted to the vehicle body 12 can be reduced.

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 passage without unevenness, and the vehicle height value is also within an appropriate range.

While the engine 2 is operating, the hydraulic pump 4 is driven and the hydraulic pressure of the output hydraulic pipe 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 through the pilot pipe 19. As a result, the function of the pilot operated check valve 18 as a check valve is canceled, so that the fluid can freely flow from the return pipe 17 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 an excited state, the spool 22 is set to a predetermined neutral position, and the pressure chamber 14a of the hydraulic cylinder 14 is pressurized. Is also maintained at the offset pressure P ₀ . 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 its 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 output port 21c opens, part of the pressure oil in the pressure chamber 14a is discharged to the return pipe 17, and the pilot operation type in the open state. It is discharged to the tank 6 via the check valve 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 to the right, a lateral acceleration is generated in the vehicle body depending on the vehicle speed and the steering angle at that time, which causes the vehicle body to roll to the lower left. . When the vehicle rolls in this way, the vehicle body is
The right side position of 12 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) arranged at the right position, and a positive vertical acceleration detection signal is output from the vertical acceleration detector (not shown) arranged at the right 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 performs a calculation based on these signals and outputs a negative command value V to the hydraulic cylinder 14 _R corresponding to the right wheel 13 _R , while outputting to the left wheel 13 _L. for the corresponding hydraulic cylinder 14 _L outputs a positive command value V.

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

In addition, not only when the vehicle rolls, but also when the vehicle pitches in the front-back direction or when the vehicle bounces in the up-down direction, it is possible to suppress the change in the attitude of the vehicle body in the same manner.

When the vehicle stops from the running state and the engine 2 stops, the hydraulic pump 4 of the hydraulic 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 output-side hydraulic pipe 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 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 pipe 19 branched from the upstream side of the check valve 9 in the output side hydraulic pipe 5 becomes zero. Then, the pilot piston springs back, and the pilot operated check valve 18 functions as a check valve. Therefore, the circuit of the return pipe 17 connected to the output 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. The phenomenon in which the pressure chamber 14a of the hydraulic cylinder 14 is opened and the vehicle height suddenly drops does not occur.

In this case, the engine 2 stops and the accumulator
If the pilot-operated check valve 18 functions as a check valve while the internal pressure of 10 is still sufficiently high, the hydraulic oil leaking from the pressure control valve 11 will disappear and the pressure in the hydraulic cylinder 14 will rise. possible. At that time, it is conceivable to provide an orifice for delaying the operation of the pilot operated check valve 18 until the internal pressure of the accumulator 10 decreases on the pilot pipe 19 side of the pilot operated check valve 18.

Further, in the above embodiment, the case where the rotational driving force of the hydraulic pump 4 is obtained from the engine has been described, but the present invention is not limited to this, and it goes without saying that another rotational driving source can be applied. Yes.

Furthermore, the control valve of the hydraulic suspension is not limited to the pressure control valve 11 described above, and other flow control servo valves or the like can be applied.

〔The invention's effect〕

As described above, according to the present invention, the primary side of the control valve is provided with the fluid check means for allowing the fluid to pass only in the output direction of the hydraulic supply device, and the fluid return side of the control valve is provided with the hydraulic check device. It is opened when the output exceeds a predetermined pressure, and it is necessary even when the output pump of the hydraulic pressure supply device stops because the fluid closing means is provided to prevent the passage of the fluid when the output falls below the predetermined pressure. It is possible to secure a predetermined line pressure in accordance with the above, and it is possible to obtain the effect of completely preventing the phenomenon that the vehicle height suddenly drops when the vehicle is stopped.

[Brief description of drawings]

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 supply device, 2 is an engine, 5 is an output side hydraulic pipe, 9 is a check valve (fluid check means), 11 is a pressure control valve, 12 is a vehicle body, 13 is a wheel, and 14 is a hydraulic cylinder. Reference numeral 17 is a return pipe, 18 is a pilot operated check valve (fluid closing means), 19 is a pilot pipe, and 26 is a posture change control device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yosuke Akatsu 2 Takara-cho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (56) Reference JP-A-61-215105 (JP, A) JP-B-53-45046 (JP, B2)

Claims (1)

[Claims] 1. A hydraulic cylinder interposed between each wheel and a vehicle body, and pressure fluid from a hydraulic pressure supply device is supplied to the primary side, so that the fluid return side responds to a command value from an attitude change control device. An active suspension device including a control valve for controlling the fluid to be returned to the hydraulic cylinder by controlling the fluid returned to the hydraulic cylinder from the output of the hydraulic supply device to the primary side of the control valve. Is provided with a fluid check means for allowing the fluid to pass only in the direction, and is opened on the fluid return side of the control valve when the output of the hydraulic pressure supply device exceeds a predetermined pressure, and when the output falls below the predetermined pressure. An active suspension device comprising a fluid closing means for preventing passage of a fluid.