JPH02141319A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE:To prevent unexpected variation of vehicle height by arranging an adjusting means for adjusting passage area on the communicating passage between a hydraulic cylinder and gas springs of each wheel, and enlarging the spring constant by controlling the adjusting means to minify the passage area at ignition off. CONSTITUTION:Hydraulic chambers 3c delimited with pistons 3b of hydraulic cylinders 3 respectively arranged between respective wheels, front and rear, right and left, and a vehicle body are communicated with gas springs 5 (5FL - 5RR) respectively through communicating passages 4. Each gas spring 5 is provided a plurality of pieces (four pieces), and the above-stated hydraulic chamber 3c is communicated to hydraulic chambers defined by respective diaphragms 5e. In this case, a damping force changeover valve (passage area adjusting means) 26 to adjust passage area is provided on a common communicated passage 4 between a first and second gas springs 5a, 5b. This changeover valve 26 is controlled to minify the passage area at ignition switch off.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a suspension system for a vehicle, and more particularly to an improvement in a hydropneumatic suspension system (HPS system) equipped with a hydraulic cylinder and a gas spring.

(Prior art) This type of suspension device (HPS device) has been used in the past.
For example, as disclosed in Japanese Patent Publication No. 59-14365, each wheel of a vehicle is equipped with a hydraulic cylinder and a gas spring communicating with the hydraulic cylinder, and the gas spring has a low spring constant. The ride quality is good.

(Problem 8 to be solved by the invention) By the way, in the HPS device as described above, if hydraulic pressure is supplied and discharged appropriately to the hydraulic cylinders of each wheel, it can be done in the same way as changing the spring constant of the gas spring appropriately. It is possible to match the suspension characteristics of the vehicle to the driving conditions such as when the vehicle is traveling straight or when turning, and it is possible to further improve ride comfort and driving stability.

However, in that case, when the engine is stopped, the control of supplying and discharging hydraulic pressure to each hydraulic cylinder also stops when the engine is not running, so the spring constant is at the low value that gas springs originally have.

Therefore, in such a situation, for example, when the driver gets out of the vehicle or loads or takes out luggage, the vehicle will move up and down with a low spring constant to compensate for the change in vehicle weight, causing a sudden change in vehicle height. There is.

The present invention has been made in view of the above, and its purpose is to prevent sudden changes in suspension characteristics when the vehicle is running, as well as when the vehicle is stopped and parked with the engine stopped, regardless of changes in vehicle weight. The objective is to prevent vehicle height changes and obtain good suspension characteristics.

(Means for Solving the Problems) In order to achieve the above object, the present invention detects when the engine is stopped by turning off the ignition, and detects the gap between the gas spring and the hydraulic cylinder due to the change in the vehicle type. Reduce the oil flow rate to increase the spring constant.

That is, the specific solution of the present invention is to provide each wheel of a vehicle with a hydraulic cylinder and a gas spring communicating with the hydraulic cylinder, and to supply and discharge hydraulic pressure to and from the hydraulic cylinder of each wheel. The present invention is based on a vehicle suspension system that can vary the suspension characteristics of a vehicle. A passage area adjustment means for adjusting the passage area of the communication passage is disposed in the communication passage between the hydraulic cylinder and the gas spring of each wheel.

Further, an off-time detection means for detecting when the engine ignition is off, and a passage area adjustment means for each wheel so as to reduce the passage area of each communication passage when the ignition is off, as detected by the off-time detection means. The structure includes a control means for increasing the spring constant.

(Function) With the above configuration, in the present invention, when the ignition is turned off and the engine is stopped, the supply and discharge control of the hydraulic pressure to the 'tcli pressure cylinder is stopped, and the passage area adjustment means is controlled so that the gas spring The passage area between the hydraulic cylinders is adjusted to be small. As a result, when the driver, etc. gets out of the vehicle or loads cargo, the air flows between the gas spring and the hydraulic cylinder depending on the change in vehicle weight, but the passage area of the communication path Since the oil flow rate is small, the oil flow rate is also limited, which is equivalent to increasing the spring constant, thereby preventing sudden changes in vehicle height.

(Effects of the Invention) As explained above, the vehicle suspension device of the present invention includes a gas spring and a hydraulic cylinder, and the suspension characteristics can be varied by supplying and discharging hydraulic pressure to the hydraulic cylinder. In this case, when the ignition is turned off, the passage area of the communication passage between the gas spring and the hydraulic cylinder is controlled to a small value to create a situation equivalent to increasing the spring constant of the gas spring, so that it is difficult for the driver to get out of the car or to load luggage. Even when the vehicle weight changes due to factors such as this, sudden changes in vehicle height can be prevented, and suspension performance can be improved.

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

In FIG. 1, 1 is a vehicle body, 2F is a front wheel, and 2R is a rear wheel. Hydraulic cylinders 3 are arranged between the vehicle body 1 and the front wheels 2F, and between the vehicle body 1 and the rear wheels 2R. . Inside each hydraulic cylinder 3, a hydraulic chamber 3c is defined by a piston 3b fitted into the cylinder body 3a. The upper end of the rod 3d connected to the piston 3b is connected to the vehicle body 1, and the cylinder body 3a is connected to wheels 21'' and 2R, respectively.

Moreover, in the hydraulic chamber 3c of each hydraulic cylinder 3,
A gas spring 5 is connected through the communication path 4 . Each gas spring 5 is divided into a gas chamber 5f and a hydraulic chamber 5g by a diaphragm 5e, and the hydraulic chamber 5g communicates with the hydraulic chamber 3c of the hydraulic cylinder 3.

Further, 8 is a hydraulic pump, 9.9 is a proportional flow control valve connected to the hydraulic pump 8 via a hydraulic pipe line 10,
It has a function of supplying and discharging hydraulic pressure to each hydraulic cylinder 3P, 3R.

Furthermore, 12 is a discharge pressure needle that detects the oil discharge pressure of the hydraulic pump 8, 13 is a hydraulic gauge that detects the hydraulic pressure in the hydraulic chamber 3c of each hydraulic cylinder 3, and 14 is a corresponding wheel 2F, 2H. Vehicle height sensor that detects high (cylinder stroke amount)
Reference numeral 15 denotes an acceleration sensor for detecting the sprung boat speed of the corresponding wheels 2F and 2R, and these detection signals are manually inputted to a controller 17 having a CPU, etc. inside, and are involved in variable control of suspension characteristics. Ru.

Next, a hydraulic circuit for controlling supply and discharge of hydraulic pressure to the hydraulic cylinder 3 is shown in FIG. In the figure, a hydraulic pump 8 is connected in two series to a hydraulic pump 21 for a power steering device driven by a drive source 20. An accumulator 22 is connected to the discharge pipe 8a of the hydraulic pump 8, and a front wheel side pipe 23F and a rear wheel side pipe 23R are connected in parallel on the downstream side thereof, and a left wheel side pipe 231' is connected to the front wheel side pipe 23F.
L and right wheel side pipe 23PR are connected in parallel, and each pipe 2
3PL, 23r'H corresponds to the hydraulic cylinder 3 of the wheel.
The hydraulic chambers 3c of PL and 31'R are connected in communication. Similarly, the rear wheel side piping 23R has left and right wheel side piping 2.
3RL, 231? I? are connected in parallel, each pipe 2
3RL.

23RI? The hydraulic cylinder 31 of the corresponding wheel? L,
The hydraulic pressure chambers 3c of 3RR are connected in communication.

Each of the above hydraulic cylinders 3FL to 31? I? Gas spring 5PL to 5T connected to? Each R is specifically a plurality of (4
These are connected in parallel to a common communication passage 4 communicating with the hydraulic pressure chamber 3c of the corresponding hydraulic cylinder 3 via branch communication passages 4a to 4d. Also, a plurality of (first to fourth) gas springs 5a for each of the wheels.
5d is equipped with orifices 25a to 25d interposed in the branch communication passages 48 to 4d, and has a basic function as a suspension device due to the damping effect of each of the orifices and the buffering effect of the gas sealed in the gas chamber 5f. Demonstrates functions.

So, gas springs 5FF to 5RI for each wheel? Now, the common communication path 4 between the first spring 5a and the second spring 5b, respectively.
A damping force switching valve (
A passage area adjusting means) 26 is provided. The switching valve 26 has two positions: an open position where the common communication passage 4 is opened, and a throttle position where the passage area is significantly narrowed.

In addition, the discharge pipe 8a of the hydraulic pump 8 has an accumulator to
An unload relief valve 28 is connected near the port 22. The relief valve 28 has an open position and a closed position, and is controlled to be switched to the open position when the oil discharge pressure measured by the discharge pressure gauge 12 is equal to or higher than the upper limit setting value, and the oil from the hydraulic pump 8 is transferred to the reserve tank 29. It has a function of controlling and maintaining the oil pressure value of the accumulator 22 at a set value. Oil is supplied to and discharged from each hydraulic cylinder 3 by storing oil in the accumulator 22.

Hereinafter, since the configurations of the left front wheel, right front wheel, left rear wheel, and right rear wheel are the same, only the left front wheel will be described, and the description of the others will be omitted. That is, the proportional flow rate control valve 9 is interposed in the left front wheel side pipe 23PF. The proportional flow rate control valve 9 has three positions: a stop position where all boats are closed, a supply position where the left front wheel side pipe 23FF is opened, and a discharge position where the hydraulic cylinder 3 side of the left front wheel side pipe 23PF is communicated with the return pipe 32. It has a built-in pressure compensation valve 9a, and the pressure compensation valve 9a
Accordingly, the hydraulic pressure in the hydraulic chamber 3C of the hydraulic cylinder 3 is maintained at a predetermined value at the two positions, the supply position and the discharge position.

In addition, a pilot pressure-responsive on-off valve 33 that opens and closes the left front wheel side piping 231''P is interposed on the hydraulic cylinder 3 side of the proportional flow control valve 9. The on-off valve 33 controls the proportional flow rate. When the solenoid valve 34 that guides the hydraulic pressure of the left front wheel side piping 23PF on the Ura pump 8 side of the control valve 9 is opened, the hydraulic pressure is introduced as a pilot pressure, and when this pilot pressure is equal to or higher than a predetermined value, it opens and operates to control the left front wheel. It has a function of opening the side pipe 23PP and allowing the proportional flow rate control valve 9 to control supply and discharge of hydraulic pressure to the hydraulic cylinder 3.

In the figure, numeral 35 is a relief valve that opens when the hydraulic pressure in the hydraulic chamber 3C of the hydraulic cylinder 3 abnormally increases and returns the hydraulic pressure to the return pipe 32. Further, 36 is an ignition key linked valve connected to the vicinity of the accumulator 22 of the discharge pipe 8a of the hydraulic pump 8, and is controlled to open when the ignition is turned off to return the reservoir of the accumulator 22 to the tank 29 and release the high pressure state. It has the function of Reference numeral 37 designates a relief valve within the pump that returns the oil discharge pressure of the oil pump 8 to the tank 29 to lower the pressure when the oil discharge pressure of the oil pump 8 rises abnormally; It performs a pressure accumulating effect when the pressure is discharged.

Next, the control of the damping force switching valve 26 by the controller 17 will be explained based on the control flow shown in FIG.

After starting, the state of the ignition key is input in step S1, and the 0N10FF state is determined in step S2. When the ignition is on, it is determined that the engine is running, and in step S3 it is further determined whether or not the ignition key is transitioning from OFF to ON. If the ignition is on, it is in operation, so step S4 is performed. The damping force switching valve 26 is controlled according to the driving condition of the vehicle, and when the vehicle turns, it is switched to the throttle position to limit the amount of oil supplied to and discharged from the gas spring 5 and the hydraulic cylinder 3, thereby controlling the variable suspension characteristics. While increasing responsiveness, the system also switches to the open position when driving straight, lowering the spring constant and improving ride comfort.

When it is determined in step S2 that the ignition is off, the damping force switching valve 2 is turned on in step S5 in order to cope with changes in the weight of the vehicle due to the driver getting out of the car, loading luggage, etc.
6 is forcibly switched to the aperture position to increase the spring constant and return.

Then, when the next time the vehicle is driven, when it is determined in step S3 that the ignition is transitioning from OFF to ON, it is determined that it is time to start driving, and the damping force switching valve 26 is turned on in step S6.
After forcibly switching the damping force switching valves 26 to the open position, it is determined in step S7 whether or not the damping force switching valves 26 of all wheels are in the open position, and if they are all in the open position, it is determined that it is normal and the process returns. However, if at least one of them is in the closed position, it is determined in step Ss that a failure has occurred, and countermeasures are taken, such as prompting the vehicle to stop traveling.

Therefore, in the control flow of FIG. 3 above, step S
l*32 constitutes off-state detection means 40 for detecting when the engine ignition is off. Further, in step S5, when the ignition is turned off as detected by the off-time detection means 40, the damping force switching valve (passage area, 1.!J adjustment means) is forcibly switched to the throttle position, and the common communication The control means 41 is configured to reduce the passage area of the passage 4 and increase the spring constant.

Therefore, in the above embodiment, when the engine is running with the ignition on, the ignition switch valve 3
6 is controlled to close, and the oil in the oil pump 8 is supplied to the accumulator 22.
This accumulated pressure value is maintained at a predetermined pressure by the unload relief valve 28.

When the hydraulic pressure in the oil discharge pipe 8a becomes equal to or higher than a predetermined pressure, each pilot pressure-responsive on-off valve 33 is opened to open the pipes 23F[, -23RR to the front, rear, left and right wheels. In this state, the hydraulic chamber 3 of each hydraulic cylinder 3 is controlled to switch to the supply position or discharge position of each proportional flow control valve 9.
By supplying and discharging hydraulic pressure to and from C), the same effect as changing the spring constant of each gas spring 5 and the throttling resistance of each orifice 25 is obtained, and the suspension characteristics can be changed as appropriate according to the operating condition. Make it. In addition, the hydraulic chamber 3c of each hydraulic cylinder 3
The vehicle height is adjusted appropriately by controlling the weight of the vehicle.

On the other hand, when the engine is stopped by stopping the operation and turning off the ignition key, the ignition key interlocking valve 36 is controlled to open, and the accumulated pressure in the accumulator 22 is returned to the tank 29, so that the accumulated pressure value decreases.

Accordingly, the pilot pressure-responsive on-off valve 33 is operated to close, and the pipes 23 PL to 23 RR to the front, rear, left and right wheels are closed. Further, the damping force switching valve 26 is controlled to switch from the open position to the throttle position, and the passage area of each common communication passage 4 is narrowed.

As a result, when the driver or the like subsequently gets out of the vehicle or loads or takes out cargo, the weight of the vehicle changes, and each wheel has the hydraulic chamber 5g of the gas spring 5FF to 5RR and the hydraulic cylinder 3PF to Oil tries to flow between the hydraulic pressure chamber 3C of the 3RR and the common communication path 4, but the pressure of the second to fourth gas springs 5b to 5d is throttled by the damping force switching valve 26, so that the oil does not flow. The flow rate between the pressure cylinder 3 and the pressure cylinder 3 is restricted.
A situation similar to that in which oil flows through only the first spring 5a as usual and the spring constant of the gas spring 5 of each wheel increases is obtained.

As a result, in addition to good suspension characteristics due to hydraulic pressure supply/discharge control while the vehicle was running, the engine stopped. Even when the vehicle is stopped or parked, sudden changes in vehicle height due to changes in vehicle weight are prevented, and good suspension characteristics are obtained even when exiting the vehicle or loading luggage.

Moreover, when you turn on the ignition the next time you get in the car,
Each damping force switching valve 26 is controlled to switch from the throttle position to the open position, and if none of them are in the open position, it is immediately determined that a failure has occurred, so that the failure can be alerted prior to starting.

Therefore, it is possible to prevent the ride comfort and running safety of the vehicle from being deteriorated due to the difference in spring constant between the wheels when the vehicle starts moving without knowing that there is a malfunction.

In the above embodiment, the damping force switching valve 26 is controlled to be switched to the throttle position when the ignition is turned off, but it is of course possible to configure the damping force switching valve 26 to be fully closed.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 41 is a general schematic diagram, FIG. 2 is a hydraulic circuit diagram, and FIG. 3 is a control flowchart. 3FF~3RI? ... Hydraulic cylinder, 3c... Hydraulic pressure chamber, 4... Common communication path, 5FF-5RR... Gas spring, 5f... Gas chamber, 5g... Hydraulic pressure chamber, 9...・Flow rate control valve, 17... Controller, 22... Accumulator, 25a to 25d... Orifice, 26...
・Damping force switching valve (passage area adjustment means), 33...
Pilot-responsive on-off valve, 40... OFF detection means,
41...Control means. 2 others

Claims (1)

[Claims] (1) Each wheel of the vehicle is provided with a hydraulic cylinder and a gas spring communicating with the hydraulic cylinder, and the suspension characteristics of the vehicle are made variable by supplying and discharging hydraulic pressure to the hydraulic cylinder of each wheel. In vehicle suspension equipment,
a passage area adjusting means arranged in a communication passage between the hydraulic cylinder and the gas spring of each of the wheels and adjusting the passage area of the communication passage; an off-time detection means for detecting when the engine ignition is turned off; and control means for increasing the spring constant by controlling the passage area adjusting means for each wheel so as to reduce the passage area of each communication passage when the ignition is turned off, as detected by the off-time detection means. Suspension device.