JP3748684B2 - Control device for hydraulic / pneumatic suspension - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic / pneumatic suspension device for suspending a vehicle, and more particularly to a control device thereof.
[0002]
[Prior art]
Conventionally, the vehicle height is adjusted to improve the driving stability, running performance, ride comfort, and boarding / exiting performance according to changes in the road surface conditions such as flat paved roads, unpaved roads with large unevenness, and load capacity. Adjustment devices are known.
As an example of this type of vehicle height adjusting device, there is a device as shown in FIG. 3 disclosed in Japanese Patent Laid-Open No. 7-164853. In this apparatus, a hydraulic cylinder 1 communicated with an accumulator 2 as a gas spring is interposed between a vehicle body side and a wheel side, and a hydraulic power source 6 and a reservoir tank 8 are connected to the hydraulic cylinder. The on-off valve 7 controlled by the controller 15 is provided in the middle of the hydraulic line connecting the two.
[0003]
This apparatus is provided with a supply / discharge switching valve 11 for controlling the supply / discharge of hydraulic oil to / from the hydraulic cylinder 1 in accordance with the pilot pressure, and one end of a hydraulic cylinder side pilot passage 31 provided in the supply / discharge switching valve 11 is connected to the accumulator 2. Is connected to the communication part 3 between the hydraulic cylinder 1 and the internal pressure of the communication part 3 is set as a pilot pressure, and when the pilot pressure becomes lower than the set pressure, the hydraulic oil from the hydraulic cylinder 1 through the supply / discharge switching valve 11 is supplied. Stop discharging.
[0004]
According to this apparatus, since the supply / discharge switching of the hydraulic oil in the supply / discharge switching valve 11 is performed by the pilot pressure, the switching from the discharge of hydraulic oil to the supply can be adjusted according to the pilot pressure. Further, when the pressure of the hydraulic cylinder 1 becomes equal to or lower than the set pressure, the discharge of the hydraulic oil from the hydraulic cylinder 1 through the supply / discharge switching valve 11 is stopped, so that the internal pressure of the hydraulic cylinder 1 becomes equal to or lower than the set pressure of the accumulator 2. Thus, the so-called zero-down is prevented in which the gas chamber of the accumulator expands and the bladder expands to the maximum extent.
[0005]
[Problems to be solved by the invention]
In Japanese Patent Laid-Open No. 7-164853 described in the prior art, first, the cylinder 1 is configured not to drop below a predetermined pressure by the supply / discharge switching valve 11 shown in FIG. Since the supply / discharge switching valve 11 is configured to control opening and closing between the ports by the movement of the spool 19 in the axial direction, the pressure of the cylinder 1 should not leak to the tank port 28 via the pilot port 32. I can't. That is, since a leak always occurs even when the vehicle is adjusted to a constant vehicle height, correction for returning the vehicle height lowered by driving the hydraulic power source 6 to the original vehicle height must be repeated frequently. In addition, since there is a leak, the accumulator 2 is brought into a zero-down state when the vehicle is left unattended. Therefore, in order to return to the normal vehicle height, the hydraulic oil including the amount for returning the accumulator 2 from the zero-down state. Has to be supplied to the cylinder, which takes a long time.
[0006]
Second, the supply / discharge oil switching valve when the maximum amount of cylinder hydraulic oil is removed is in the state shown in FIG. 3B, and the ports 28 and 29 are closed. In this state, a predetermined pressure remains in the cylinder, but since the ports 28 and 29 are closed, the pressure on the cylinder side is released only by a leak between the ports 29 and 28. The oil supply / discharge valve 7 must be energized for a long time until the cylinder pressure drops to atmospheric pressure due to leakage. If this is not done, the hydraulic fluid pressurized by the gas will blow out from the separate location when the cylinder or pump is removed. In other words, there is a problem that it is difficult to release the pressure of the cylinder and the pipe line.
[0007]
The present invention has been made in view of the above circumstances, and its purpose is to prevent the accumulator from being reduced to zero when the vehicle height is lowered by preventing the cylinder pressure from dropping below a specified value. The hydraulic / pneumatic suspension can prevent hydraulic oil from being discharged from the cylinder to the tank more than necessary, and can prevent the hydraulic oil from blowing out even when pressure remains in the cylinder or accumulator during repair. It is to provide a control device.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the means taken by the present invention is “a hydraulic pump that is located between a vehicle body and an axle and operates as a gas spring, a cylinder having a damping valve, and a hydraulic pump that supplies and discharges hydraulic oil to and from the cylinder. A hydraulic source that connects these element devices to form a control circuit, a leveling valve and a discharge valve that are disposed in the middle of the hydraulic conduit that connects the hydraulic source and the cylinder and that is driven by a controller. In the control device of the hydraulic / pneumatic suspension with
A cock is connected to each of the cylinders branched from the leveling valve, and between the leveling valve and the hydraulic pump, a spring for energizing the valve body facing the seat hole connected to the leveling valve from the back is accommodated. The communication residual pressure valve that maintains a constant differential pressure between the lower chamber communicating with the tank and the upper chamber communicating with the check valve and the discharge valve via the throttle is provided for the hydraulic pump.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of the present invention. First, the structure will be described. A cylinder CY having a damping valve DV and a function of a shock absorber, an accumulator AC that operates as a gas spring, and a cylinder CY are sealed by being closed when removed. Cock KV2, hydraulic pump P for supplying hydraulic oil to cylinder CY when raising vehicle height, discharge valve EV for discharging hydraulic oil from cylinder CY to main tank MT when lowering vehicle height, backflow to hydraulic pump P Check valve CV, which is opened only when the vehicle height is raised or lowered, is normally closed and is disposed between the check valve CV and the check valve CV and the leveling valve LV, and the pressure of the cylinder CY drops below a predetermined pressure. Communication residual pressure valve BV, vehicle height sensor Sh, pressure sensor Sw, vehicle speed sensor Sv, manual operation switch Sm, etc. The controller CNT that drives the hydraulic pump P, the leveling valve LV or the discharge valve EV, the main tank MT that stores hydraulic oil, the sub tank ST that is connected to the main tank MT via the cock KV1, and connects them. It consists of hydraulic lines HL such as piping and rubber hoses. In the circuit diagram, the accumulator AC is provided separately from the cylinder CY, but may be built in the cylinder CY.
[0010]
The cock KV2 that is sealed by closing when removing the cylinder may be integrated with the cylinder as shown in FIG. The cock KV2 is attached to the upper end portion of the hollow hole 201A of the piston rod 201 serving as a hydraulic oil supply / discharge passage to the cylinder 200, and connects or blocks the connection port 202 to the control circuit and the hollow hole 201A. Since it is integrated with the cylinder, it is possible to seal the cylinder by closing the cock when removing the cylinder, so that the operation becomes easy.
[0011]
The main tank MT and the sub-tank ST (hereinafter collectively referred to as a tank if necessary) are constituted by a sealed container, and the inside of the container is shut off from the outside air. Normally, the main tank MT is filled with enough hydraulic fluid to cope with the increase / decrease accompanying the expansion / contraction of the cylinder CY. The sub-tank ST is sealed with hydraulic oil and gas with the cock KV1 connected to the sub-tank ST closed, and when incorporated in the control device, the entire circuit is pressurized by opening the cock KV1.
[0012]
The main tank MT, the hydraulic pump P, the check valve CV, the leveling valve LV, the discharge valve EV, and the communication residual pressure valve BV surrounded by a chain line are units for improving the assembly to the vehicle body and improving the reliability by omitting the piping. It may be an integrated structure. By unitizing, the pressure of the main tank MT can be easily guided to the back surface of the valve body BVc, so that the lower chamber BVe of the communication residual pressure valve BV is not released to the atmosphere. As a result, there is no need for a seal, and hysteresis associated with the operation is reduced, and oil leakage here is eliminated, so that the reliability of operation over a long period can be maintained.
[0013]
The cock KV1 connected between the main tank MT and the sub tank ST is opened after assembling the control device, so that the hydraulic oil in the cylinder CY enters and exits the sub tank ST via the main tank MT. The main tank MT may be omitted if a sufficient volume of the sub tank ST can be secured. Since the communication residual pressure valve BV receives the internal pressure and opens when the internal pressure of the cylinder CY is equal to or higher than the set value, the vehicle height can be adjusted by operating the control device to supply and discharge hydraulic oil to the cylinder CY.
[0014]
Here, pressurization to the control circuit will be described. First, the element devices excluding the sub tank ST and the cock KV1 connected to the sub tank ST and the hydraulic pipes connecting them are assembled to the vehicle body. However, in this state, air is mixed in the component equipment such as the cylinder and the hydraulic pipe, so that normal operation of the component equipment cannot be expected unless the air is removed. Therefore, the controller CNT is driven to operate the leveling valve LV and the hydraulic pump P, and air is released using an air bleeder (not shown) while sending hydraulic oil to the cylinder CY. Thereafter, the cock KV1 connected to the sub-tank ST in which gas and hydraulic oil are sealed in advance is connected to the hydraulic line connected to the main tank MT, and the cock KV1 is opened, whereby the pressure of the gas sealed in the sub-tank ST is controlled. In addition to the whole, the circuit is in a pressurized state.
[0015]
The communication residual pressure valve BV includes a seat hole BVa that communicates with the cylinder CY via the leveling valve LV, and a poppet-shaped valve element BVc that is biased by the spring BVb moves to the upper chamber BVd that communicates with the seat hole BVa. It is accommodated freely and faces the sheet hole BVa. The lower chamber BVe in which the spring BVb is accommodated communicates with the main tank MT, and when the pressure of the control device does not reach the set value, the passage to the leveling valve LV is blocked by the force of the spring. When the hydraulic pump P is actuated to increase the pressure of the control device, the valve body is lifted upward to open a passage to the cylinder CY. That is, in the normal state where the cylinder supports the weight of the vehicle body, the communication residual pressure valve BV is open, and the vehicle height can be adjusted by supplying and discharging hydraulic oil to and from the cylinder CY.
[0016]
The communication residual pressure valve BV is for preventing the pressure of the cylinder CY from dropping below the set pressure, and the so-called valve closing pressure at which the valve body BVc is seated in the seat hole BVa is higher than the gas chamber pressure of the accumulator AC. If set, the communication residual pressure valve BV is closed before the accumulator AC is zero-down, and the circulation from the cylinder CY to the tank is shut off, so that zero-down can be prevented.
[0017]
Further, even if pressure remains in the cylinder CY when the cylinder CY is removed, the cylinder is sealed by closing the cock KV2, so that the hydraulic oil is completely prevented from blowing out. Since the gas pressure acting on the main tank MT side is shut off by the communication residual pressure valve BV and the leveling valve LV, it is possible to prevent the hydraulic oil from blowing out from this side. When only the sub tank ST is removed, it is possible to prevent the hydraulic oil from blowing out by closing the cock KV1 connected thereto.
[0018]
The pressurization of the control device of the hydraulic / pneumatic suspension apparatus according to the present invention is performed by connecting the sub-tank ST in which the gas and the hydraulic oil of a predetermined pressure are sealed to a circuit that has been incorporated in the vehicle body and vented in advance. Even without installing a special device for filling the tank of the hydraulic / pneumatic suspension device in the vehicle body assembly line, the control device is configured to be cut off from the outside air and pressurized only by assembling each component device. be able to.
[0019]
【The invention's effect】
As described above, the communication residual pressure valve BV of the hydraulic / pneumatic suspension apparatus according to the present invention has a communication residual pressure before the accumulator is reduced to zero if the valve closing pressure is set higher than the gas chamber pressure of the accumulator AC. Since the pressure valve BV is closed and the circulation from the cylinder CY to the tank is shut off, zero down can be prevented.
Further, even when pressure remains in the cylinder and the accumulator when the cylinder is removed, the cylinder is sealed by closing the cock KV2, so that the hydraulic oil is completely prevented from blowing out. Since the gas pressure acting on the main tank side is shut off by the communication residual pressure valve and the leveling valve LV, it is possible to prevent the hydraulic oil from blowing out from this side. When only the sub tank ST is removed, it is possible to prevent the hydraulic oil from blowing out by closing the cock KV1 connected thereto.
In addition, equipment such as hydraulic pumps, check valves, discharge valves, leveling valves, and main tanks can be easily united so that the main tank pressure can be easily guided to the back of the valve body. Can be structured not to be released to the atmosphere. As a result, there is no need for a seal, and hysteresis associated with the operation is reduced, and oil leakage here is eliminated, so that the reliability of operation over a long period can be maintained.
[Brief description of the drawings]
FIG. 1 is a control device for a hydraulic / pneumatic suspension according to the present invention.
FIG. 2 is an embodiment in which a cock is integrated with a cylinder.
FIG. 3 is a control device for a hydraulic / pneumatic suspension according to the prior art.
[Explanation of symbols]
P Hydraulic pump AC Accumulator BV Communication residual pressure valve CV Check valve CY Cylinder DV Damping valve EV Drain valve HL Hydraulic line LV Leveling valve MT Main tank NV Throttle ST Sub tank KV1, KV2 Cock CNT Controller BVa Seat hole BVb Spring BVc Valve body BVd Upper part Room BVe Lower room

Claims (1)

An accumulator that operates as a gas spring, a cylinder equipped with a damping valve, a hydraulic source such as a hydraulic pump that supplies and discharges hydraulic oil to the cylinder, and these element devices are connected between the vehicle body and the axle, and a control circuit is connected. In a control device for a hydraulic / pneumatic suspension comprising a hydraulic line to be formed, a leveling valve disposed in the middle of a hydraulic line connecting a hydraulic source and a cylinder and driven by a controller, and a discharge valve,
A cock is connected to each of the cylinders branched from the leveling valve, and between the leveling valve and the hydraulic pump, a spring for energizing the valve body facing the seat hole connected to the leveling valve from the back is accommodated. A hydraulic residual pressure valve that maintains a constant differential pressure between a lower chamber communicating with the tank and a check valve on the hydraulic pump and an upper chamber communicating with the discharge valve via a throttle, respectively. Pneumatic suspension control device.

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