JPH0629045Y2 - Suspension unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a suspension unit for controlling vehicle height and vehicle attitude.

(Prior Art) Conventionally, as a suspension unit capable of controlling a vehicle height and a vehicle attitude, for example, a suspension unit described in JP-A-59-124419 is known.

This conventional suspension unit includes a vehicle height adjusting actuator that is interposed between a vehicle body side and a wheel side and operates by hydraulic pressure, and a hydraulic pressure from a hydraulic pressure source from a controller for the vehicle height adjusting actuator. And a pressure control valve that outputs a fluid pressure in accordance with the control signal.

(Problems to be solved by the invention) However, in such a conventional suspension unit, as soon as the operation of the pump and the pressure control valve is stopped, the hydraulic pressure of the vehicle height adjusting actuator is drained and the vehicle height is increased. The problem is that it lowers the occupant's discomfort and impairs the appearance, and also for the pressure control valve,
Even if the one that can maintain the hydraulic pressure on the output side is used, the liquid pressure leaks from the gap between the spool and the valve hole where the spool slides due to the hydraulic pressure difference. When the vehicle is parked for a time, the hydraulic pressure in the vehicle height adjusting actuator leaks to the drain circuit via the pressure control valve, and the vehicle height is lowered.

Further, if the vehicle height is lowered when the pump is stopped in this manner, the vehicle height is increased to return to the original vehicle height at the next start, which also causes discomfort to the occupant.
There was a practical problem such as being able to run after the vehicle height had increased.

Therefore, as a solution to such a problem, in order to prevent a drain from being formed when the pump is stopped, if the pump stops in the hydraulic pressure supply circuit and the drain circuit,
It is conceivable to provide check valves for shutting off both circuits.

Although the above-mentioned problems can be solved by such means, the following problems to be solved still remain.

That is, when an accumulator is provided in the hydraulic pressure supply circuit for the purpose of reducing the pump capacity, the hydraulic pressure of the accumulator is also enclosed in the closed circuit formed between the check valves, so that the accumulator The hydraulic pressure is transmitted to the vehicle height adjusting actuator via the leak portion of the pressure control valve, and conversely the vehicle height is increased.

An object of the present invention is to solve the above problems and to provide a suspension unit in which the vehicle height does not significantly decrease or rise when the pressure control valve is stopped or started and thereafter. I am trying.

(Means for Solving the Problems) In the present invention for solving the above-mentioned problems, a vehicle height and a vehicle attitude are provided between a vehicle body side and a wheel side, and actuated by hydraulic pressure from an output circuit. An adjustable vehicle height adjusting actuator and a pressure capable of controlling the hydraulic pressure of the output circuit by selectively connecting the output circuit to a hydraulic pressure supply circuit hydraulically supplied from a pump and a drain circuit for drain. Control valve,
Output holding means provided in the pressure control valve for holding the output hydraulic pressure at a predetermined pressure for at least a predetermined time after the drive of the pump is stopped, and the hydraulic pressure supply circuit, which stores the hydraulic pressure from the pump. An accumulator, a first check valve provided in the hydraulic pressure supply circuit at a position between the first accumulator and the pump, and closed when the hydraulic pressure supplied from the pump falls below a predetermined value to prevent backflow, and provided in the drain circuit. And a second check valve that controls the drain by closing the hydraulic pressure of the first accumulator as a pilot pressure and closing the pilot hydraulic pressure below a set value.
A second accumulator provided in the drain circuit upstream of the check valve and having a pressure accumulation operation level set to a pressure lower than the valve closing pilot hydraulic pressure of the second check valve.

The output holding means is a means for continuing the operation of the pressure control valve for at least a predetermined time so that the output hydraulic pressure becomes a predetermined pressure even after the pump is stopped, or the output hydraulic pressure with the operation of the pressure control valve stopped. Is a predetermined fluid pressure (such means can be constituted by a spring force of a return spring, a throttle formed between the spool and the bubble hole, etc.).

(Operation) In the hydraulic suspension of the present invention, when the operation of the pump is stopped, the first check valve is closed due to the decrease in the supplied hydraulic pressure. Even if the hydraulic pressure supply is stopped in this way, the output hydraulic pressure to the vehicle height adjusting actuator is held by the output holding means for at least a predetermined time thereafter, and the vehicle height does not drop significantly.

Then, during this time, if the hydraulic pressure in the accumulator is consumed for maintaining the hydraulic pressure of the vehicle height adjusting actuator or leaks through the pressure control valve and becomes equal to or lower than the set hydraulic pressure, the second check valve is closed. The hydraulic pressure in the first accumulator and the hydraulic pressure in the vehicle height adjusting actuator are sealed between both check valves.

In this way, since the set hydraulic pressure is sealed between both check valves, as a result of the output hydraulic pressure holding being stopped by the output holding means thereafter, the hydraulic pressure is also increased via the pressure control valve due to a leak or the like. As a result of the transmission, the vehicle height adjusting actuator is kept at the set hydraulic pressure, whereby the vehicle height becomes the set vehicle height, and it is possible to prevent the vehicle height from greatly increasing.

By the way, when the second check valve is closed as described above, the drain circuit on the upstream side of the second check valve tries to instantly increase from the atmospheric pressure until then to the set hydraulic pressure. Since the drain circuit of is provided with the second accumulator whose accumulated pressure operation level is set to a pressure lower than this set hydraulic pressure, the hydraulic fluid in the drain circuit is set to the second accumulator before it reaches the set hydraulic pressure. It is stored in the accumulator, and the hydraulic pressure rise in the drain circuit on the upstream side is made with a gentle gradient.

As described above, since the change in the hydraulic pressure in the drain circuit after the second check valve is closed is gradual, the sound and the vibration accompanying the rapid change in the hydraulic pressure do not occur.

Next, when the pump is re-driven and the supplied hydraulic pressure exceeds the set pressure, the first check valve is opened and the hydraulic pressure in the first accumulator is increased.

Due to the increase in the hydraulic pressure of the first accumulator, the second check valve whose pilot pressure is the hydraulic pressure is opened, and the drain circuit upstream of the second check valve is set to the same set hydraulic pressure as the vehicle height adjusting actuator. It tries to drop to atmospheric pressure instantly, but in this second accumulator,
The hydraulic fluid is stored, and the hydraulic fluid is discharged in accordance with the decrease in the hydraulic pressure in the drain circuit on the upstream side. In the drain circuit, the hydraulic pressure is reduced with a gentle pressure gradient.

Therefore, also in this case, the generation of sound and vibration due to a sudden change in hydraulic pressure is prevented.

Then, at the same time when the hydraulic pressure in the drain circuit drops, the pressure control valve becomes in a state where the output hydraulic pressure can be controlled, and control of the vehicle height and the vehicle attitude is restarted. Since the vehicle height hardly changes when the pump is stopped, the vehicle height for returning to the original vehicle height hardly changes when the control is restarted.

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

First, the configuration will be described.

The drawing is an overall view showing a suspension unit according to an embodiment of the present invention. In the drawing, reference numerals 1, 1, 1, 1 denote vehicle height adjusting actuators. Each of the vehicle height adjusting actuators 1 is formed so that its entire length can be changed by hydraulic pressure from the output circuit 2, and is interposed between the front and rear four wheels (not shown) between the axle side and the vehicle body side. By being arranged, the vehicle height at each position is changed by changing the overall length, and thereby the vehicle height and the vehicle attitude can be adjusted. A spring accumulator 2a that constitutes a gas spring is provided in the middle of the output circuit 2 as a part of the suspension.

The output hydraulic pressures of the output circuits 2, 2, 2, 2 are
It is controlled by pressure control valves 3, 3, 3, 3. The pressure control valve 3 has a spool (not shown), and by sliding the spool, the output circuit 2 is selectively connected to the hydraulic pressure supply circuit 4 and the drain circuit 5 to control the pressure. However, detailed description thereof will be omitted.

The operation of these pressure control valves 3 is controlled by the controller 6. The controller 6 includes, for example, a vehicle height sensor and a G sensor for detecting a vehicle height sensor and front-rear, left-right, and lateral gravity accelerations with respect to the vehicle.
An input sensor group 7 including a sensor, a vehicle speed sensor, etc. is connected to perform normal time control and key-off control.

That is, the normal control is to form a target state such as a horizontal state based on the input signal ni from the input sensor group 7,
Further, for example, it is a control for setting a desired vehicle height selected by the driver, and the output hydraulic pressure of each output circuit 2 required to achieve such a vehicle attitude and vehicle height is calculated, and the calculated result is obtained. In response, the control signal si is output to the pressure control valve 3. In addition, the key-off control means that the output circuit 2 maintains the set hydraulic pressure P _s even after the engine E and the pump P are stopped (key-off), so that the set vehicle height H _s can be obtained.
Is a control for activating, that is, it corresponds to the output holding means in the claims. The set vehicle height H _s is
It is considered to be the most average vehicle height for that vehicle.

The hydraulic pressure supply circuit 4 is supplied with hydraulic pressure from a pump P driven by the rotation of the engine E. A pulsation absorbing sub-accumulator 4 is provided in the middle of the hydraulic pressure supply circuit 4.
a and a main accumulator (first accumulator) 4b for accumulating pressure are provided. Further, between the sub accumulator 4a and the main accumulator 4b, there is provided a first check valve 4c which closes when the liquid pressure supplied from the pump P falls below a predetermined level to prevent backflow.

Further, the drain circuit 5 has a tip portion connected to the reservoir tank T, and a second check valve 5a capable of regulating the drain is provided in the middle thereof. This second
The check valve 5a is the main accumulator 4b.
The fluid pressure as a pilot pressure, the main accumulator les - the hydraulic pressure in the motor 4b is configured set pressure P _s follows a closed manner. The set hydraulic pressure P _s is a hydraulic pressure equal to the set hydraulic pressure P _s which is the output hydraulic pressure of the pressure control valve 3 during the key-off control.

Further, the drain circuit 5 upstream of the second check valve 5a has a shock absorbing accumulator (second
An accumulator) 5b is provided. That is, the shock absorbing accumulator 5b is filled with a gas pressure that is considerably lower than the set hydraulic pressure P _{s at} which the second check valve 5a is closed, whereby the accumulator operating level is set to the set hydraulic pressure P _s. When the hydraulic pressure of the drain circuit 5 becomes higher than the gas pressure of the shock absorbing accumulator 5b, it is possible to store the hydraulic fluid in an amount corresponding to the differential pressure. Further, when the hydraulic pressure in the drain circuit 5 decreases, the stored hydraulic fluid can be discharged.

Next, the operation will be described.

(A) Normal time When the pump P is driven, the first check valve 4c is opened by the hydraulic pressure supplied from the pump P, and hydraulic pressure is supplied to the pressure control valve 3 side.

Then, the pressure control valve 3 operates based on a control signal si output from the controller 6 to achieve the target vehicle attitude and vehicle height, and controls the output hydraulic pressure to the output circuit 2.

In this normal time, the hydraulic pressure of the drain circuit 5 is atmospheric pressure.

(B) When the pump is stopped When the engine E is stopped and the drive of the pump P is stopped, the first check valve 4c is closed due to the decrease in the supply hydraulic pressure, and new supply of hydraulic pressure to the main accumulator 4b is stopped. .

Moreover, this starts the controller 6, the key-off control by the stop of the engine E, this in order to hold the engine stop after a predetermined time the vehicle height set vehicle height H _s, the control fluid pressure in the output circuit 2 to the set hydraulic pressure P _s To be done.

Therefore, the feature that the vehicle height does not decrease at the same time when the driving of the pump P is stopped is obtained.

The key-off control causes the hydraulic pressure stored in the main accumulator 4b to be gradually consumed. When the hydraulic pressure in the main accumulator 4b drops below the set hydraulic pressure P _s , this hydraulic pressure is piloted. The second check valve 5a, which is a pressure, is closed, and the hydraulic pressure in the main accumulator 4b and the hydraulic pressure in the vehicle height adjusting actuator 1 are sealed between the check valves 4c and 5a.

As a result, due to a leak or the like through the pressure control valve 3, the hydraulic pressure supply circuit (downstream of the first check valve 4c) 4
The output circuit 2, the vehicle height adjusting actuator 1, and the drain circuit (upstream of the second check valve 5a) 5 each have the set hydraulic pressure P _s. Even if the key-off control is stopped after the passage of, the vehicle height is maintained at the set vehicle height H _s and the vehicle height does not decrease.

In addition, the output hydraulic pressure (vehicle height) when such a pump P is stopped
Is held by the key-off control of the controller 6, the pressure control valve 3 can be the same as the conventional one, and the control content of the controller 6 is simply added, so that the change is easy. To be

By the way, when the second check valve 5a is closed as described above, the drain circuit 5 on the upstream side of the second check valve 5a changes from the atmospheric pressure until then to the set fluid pressure P _s.
However, the drain circuit 5 on the upstream side has a second gas pressure lower than the set hydraulic pressure P _s .
Since the accumulator 5b is provided, the hydraulic fluid in the drain circuit 5 is stored in the second accumulator 5b based on this differential pressure, and the hydraulic pressure increase in the drain circuit 5 on the upstream side is made with a gentle gradient. It

As described above, since the change in the hydraulic pressure of the drain circuit 5 after the second check valve 5a is closed is gradual, the characteristic that no sound or vibration is generated due to the rapid change in the hydraulic pressure is obtained.

(C) At the time of pump re-driving Next, the pump P is re-driving and the supply fluid pressure is set pressure P
_{When s} is exceeded, the first check valve 4c is opened to increase the hydraulic pressure of the main accumulator 4b, and at the same time, the controller 6 starts normal control.

As the hydraulic pressure of the main accumulator 4b rises, the second check valve 5a having this hydraulic pressure as the pilot pressure is opened, and the drain circuit 5 upstream of the second check valve 5a has the same set liquid as the vehicle height adjusting actuator 1. Pressure P
Attempts to instantly decrease from _s to atmospheric pressure, but this second
The hydraulic fluid is stored in the accumulator 5b, and the hydraulic fluid is discharged in accordance with the hydraulic pressure decrease of the drain circuit 5 on the upstream side. In the drain circuit 5, the hydraulic pressure is decreased with a gentle pressure gradient. It

Therefore, also in this case, it is possible to obtain the feature that the generation of sound or vibration due to a sudden change in hydraulic pressure is prevented.

Then, when the hydraulic pressure of the drain circuit 5 is reduced in this way, the pressure control valve 3 becomes a state in which the output hydraulic pressure can be controlled, and control of the vehicle height and the vehicle attitude is restarted. Incidentally, at the time of driving stop of the pump P as described above is maintained at a set vehicle height H _s, car to return from not occurred almost height change compared to the vehicle height at the time of stop, the original vehicle height when the control resumption The characteristic is that a high change hardly occurs.

Although the embodiment has been described with reference to the drawings, the specific configuration is not limited to this embodiment, and even if there is a design change or the like within a range not departing from the gist of the invention, the invention is included in the invention. .

For example, in the embodiment, the key-off control by the controller is shown as the output holding means, but it is not limited to such control means, and the spool shape of the pressure control valve, the return spring for biasing the spring, the port of the valve hole, etc. Means having a structure capable of outputting the set hydraulic pressure when the operation of the pressure control valve is stopped by a mechanical means such as a shape may be used.

(Effect of the Invention) As described above, in the suspension unit of the present invention, the hydraulic pressure supply circuit and the drain circuit are provided with the first and second check valves, respectively, and the second check valve is further provided with the first accumulator. Since it is closed when the pressure drops below the set hydraulic pressure, the vehicle height does not decrease or rise significantly when the pressure control valve is stopped or started, and after that, and the occupant changes due to changes in vehicle height. It is possible to obtain an effect that the user does not feel uncomfortable and the appearance is not impaired.

In addition, since the drain circuit is provided with the second accumulator, when the second check valve that shuts off the drain circuit is opened and closed, a sudden pressure change does not occur in the drain circuit. The effect that vibration does not occur can be obtained.

[Brief description of drawings]

The drawing is an overall view showing a suspension unit according to an embodiment of the present invention. 1 ... Vehicle height adjusting actuator 2 ... Output circuit 3 ... Pressure control valve 4 ... Hydraulic pressure supply circuit 4b ... Main accumulator (first accumulator) 4c ... First check valve 5 ... Drain circuit 5a ... Second check valve 5b ... Shock absorption Accumulator (second accumulator) 6 ... Controller (output holding means) P ... Pump

Claims (1)

[Scope of utility model registration request] 1. A vehicle height adjusting actuator which is interposed between a vehicle body side and a wheel side and which is actuated by hydraulic pressure from an output circuit to adjust a vehicle height and a vehicle attitude; and the output circuit from a pump. Selectively connected to the hydraulic pressure supply circuit that is supplied with hydraulic pressure and the drain circuit for the drain,
A pressure control valve capable of controlling the hydraulic pressure of the output circuit; output holding means provided in the pressure control valve for holding the output hydraulic pressure at the predetermined pressure for at least a predetermined time after the pump is stopped; A first accumulator provided in the supply circuit for accumulating hydraulic pressure from the pump, and a hydraulic pressure supply circuit provided between the first accumulator and the pump, and closed when the hydraulic pressure supplied from the pump falls below a predetermined value. A first check valve for preventing backflow, and a second check valve provided in the drain circuit, which uses the hydraulic pressure of the first accumulator as a pilot pressure and closes when the pilot hydraulic pressure falls below a set value to regulate the drain. And a drain circuit provided upstream of the second check valve and having a pressure accumulation operation level lower than the closing pilot hydraulic pressure of the second check valve. Suspension unit, characterized in that it comprises a second accumulator is set to force the.