JPH0260812A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To prevent water hammer phenomenon from occurring in reflux pipings by providing a pressure attenuating means for attenuating the pressure of working fluid in the reflux pipings, in routes of the reflux pipings. CONSTITUTION:When the liquid pressure chamber 8 of a liquid pressure cylinder 4 is communicated to each of reflux pipings 60F, 60R through operation on a flow rate control valve 52, working fluid in the liquid pressure chamber 8 flows into suddenly and pressure rise in each of the reflux pipings 60F, 60R occurs. But, as return accumulators 62 are respectively provided in routes of reflux pipings 60F, 60R, even if flow in of working fluid is performed suddenly, pressure rise owing thereto in the reflux pipings 60F, 60R is softened by pressure accumulating function of the return accumulators 62. That is to say, the return accumulator 62 comes to function as pressure attenuating means, thereby water hammer phenomenon is prevented from occurring occurs in the reflex pipings 60F, 60R.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention is configured to be able to change suspension characteristics by supplying and discharging working fluid to and from cylinders installed between a vehicle body and wheels. This invention relates to a suspension device.

(Prior Art) A vehicle suspension device generally consists of a combination of a mechanical spring and a shock absorber.
We have also proposed a suspension system in which a cylinder is installed between the vehicle body and the wheels, and by controlling the supply and discharge of working fluid to this cylinder, suspension characteristics such as vehicle height and hardness and softness can be freely changed. being done.

(Problem to be Solved by the Invention) The above-mentioned supply/discharge control in such a suspension device is performed by providing a predetermined control valve in the piping path of the working fluid and controlling the operation of this control valve by a predetermined control means. However, since the working fluid supplied into the cylinder is under high pressure, when the cylinder is connected to the reflux pipe by the operation of the control valve, the working fluid in the cylinder suddenly flows into the reflux pipe. , a pressure increase occurs within the reflux pipe. If such a pressure increase occurs, water hammer phenomena such as abnormal noise and vibration will occur in the reflux pipe, which is undesirable.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a suspension device for a vehicle that can prevent the water hammer phenomenon from occurring in the recirculation pipe.

(Means for Solving the Problems) The vehicle suspension device according to the present invention aims to achieve the above object by providing a predetermined pressure damping means in the return pipe path to alleviate the pressure increase in the return pipe. This is what I did. That is, in a vehicle suspension device configured to be able to change suspension characteristics by supplying and discharging working fluid to and from a cylinder installed between a vehicle body and a wheel, the cylinder is adjusted according to predetermined conditions. A control valve for controlling the supply and discharge of working fluid, and a recirculation pipe connecting the control valve and a reservoir tank, and a pressure damping means for attenuating the pressure of the working fluid in the recirculation pipe in the recirculation piping path. It is characterized by the fact that it is provided.

The above-mentioned "pressure damping means" is not limited to a specific configuration as long as it can dampen the pressure of the working fluid in the reflux pipe, but for example, an accumulator, a throttle, etc. can be adopted. Furthermore, although the position of this "pressure damping means" in the return piping route is not particularly limited, it is preferably located as close to the control valve as possible in order to effectively prevent the water hammer phenomenon.

(Function) As shown in the above configuration, pressure damping means is provided in the reflux piping route, so even if the working fluid suddenly flows into the reflux piping due to the operation of the control valve, the The pressure increase in the reflux pipe is alleviated by the pressure damping means.

(Effects of the Invention) Therefore, according to the present invention, it is possible to prevent the water hammer phenomenon from occurring in the reflux pipe.

(Examples) Examples of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a suspension device for a vehicle according to the present invention, and FIG. 2 is an overall configuration diagram of the suspension device.

In addition, in the diagram, the main elements corresponding to the right front wheel, left front wheel, right rear wheel, and left rear wheel are numbered rFRJ.
rFLJ rRRJ and rRLJ are shown with added symbols, but in the following description, those symbols will be added only when particularly necessary.

As shown in FIG. 2, a hydraulic cylinder 4 is fixed to the vehicle body 2 for each wheel, and a hydraulic chamber 8 is defined by a piston 6 that is slidably inserted into the hydraulic cylinder 4. ing. A wheel 12 is held on a piston rod IO integrated with the piston 6.

A gas spring 14 is communicated with the hydraulic chamber 8 via a hydraulic passage. This gas spring 14 has a gas chamber 18 and a liquid chamber 2 defined by a diaphragm 1B as a movable partition.
0, and this liquid chamber 20 is communicated with the hydraulic pressure chamber 18.

As shown in FIG. 1, three gas springs 14 are provided for the front wheels and two gas springs are provided for the rear wheels, and these springs are arranged in parallel and communicated with each hydraulic cylinder 4. The hydraulic passages 22 communicating with each of these gas springs 14 include
Each is provided with an orifice 24. A unit consisting of such a combination of the hydraulic cylinder 4, the gas spring 14, and the orifice 24 has a buffering effect of the gas spring 14,
The damping effect of the orifice 24 provides the basic function of a suspension device.

Each hydraulic cylinder 4 has high pressure piping 26F or 28
R is connected, and hydraulic fluid is supplied to and discharged from the hydraulic cylinder 4 through this piping.

The pump 28 that supplies this hydraulic fluid is a vane pump driven by an engine, and is connected to a reservoir tank 30.
The hydraulic fluid 32 is pumped up from the common high-pressure pipe 26, and the hydraulic fluid 32 is passed through the high-pressure pipes 28F for the front wheels and the rear wheels.
, 26R. This common high pressure pipe 26 is provided with a filter 36, a check valve 38, a main accumulator 40 that functions to accumulate pressure, and a system oil pressure gauge 42 in this order from the upstream side. Further, inside the pump 28, an in-pump relief valve 44 is provided which allows the discharged hydraulic fluid 32 to flow back to the suction side when the pressure on the discharge side increases abnormally.

The high-pressure pipe 26F for the front wheel is branched into a high-pressure pipe 26FR for the right front wheel and a high-pressure pipe 26FL for the left front wheel, and each of these pipes 26F R and 26F L is connected to a hydraulic cylinder 4FR for the right front wheel and a hydraulic cylinder 4FL for the left front wheel, respectively. The hydraulic pressure chambers 8 are connected to each other. The same applies to the rear wheels. Further, pilot passages 46F and 46R are branched from each of the high pressure pipes 26F and 28R, and these pilot passages 4
6F and 46R are connected to an electromagnetic on-off valve 48, respectively. Each of the above high pressure piping 26FR.

26FL, 26RR, and 28RL are provided with a flow control valve 52 having a built-in pressure guarantee valve 50, a pressure-operated on-off valve 54, a relief valve 56, and a hydraulic pressure gauge 58 in this order from the upstream side. The relief ports of each of the relief valves 56 are as follows:
It is connected to the reflux pipe 80F or 80R.

Further, each hydraulic fluid return port of the pressure guarantee valve 50 and the electromagnetic on-off valve 48 is also connected to the above-mentioned return pipe 60F or 60R. A return accumulator 62 is installed near the flow control valve 52 of these return pipes 60F and 60R, respectively, to perform a pressure accumulation function.

The front wheel side reflux pipe 60F and the rear wheel side reflux pipe 60R are connected to a common reflux pipe 60 that reaches the reservoir tank 32 via a cooling circuit 64. The common reflux pipe 60 and the common high pressure pipe 26 are communicated with each other by relief pipes 66 and 68, and an unload relief valve 70 and an ignition switch interlocking valve 72 are provided in the relief pipes 66 and 68, respectively. Connections between the relief pipes 66 and 68 and the common high pressure pipe 26 are made on the upstream and downstream sides of the check valve 38, respectively.

Next, the operation of the suspension device having the above configuration will be explained.

The operations of the unload relief valve 70, the ignition switch interlocking valve 72, the electromagnetic on-off valve 48, and the flow rate control valve 52 are controlled by a control unit 74 (see FIG. 2) comprising, for example, a microcomputer. This control unit 74 includes the system oil pressure gauge 4.
2. Oil pressure gauge 58 provided for each hydraulic cylinder 4, acceleration sensor 7B for detecting sprung acceleration for each wheel 12FR, 12FL, 12RR, 12RL, and similarly for each wheel 12FR, 12FL, 12RR, 12RL. Vehicle height(
In other words, the vehicle height sensor 78 detects the cylinder stroke)
(In Fig. 2, the output of the left rear wheel 12RL is input.)
(Only the oil pressure gauge 58, acceleration sensor 76, and vehicle height sensor 78 corresponding to the above are shown). The control unit 74 controls supply and discharge of the hydraulic fluid 32 based on the cylinder internal pressure, sprung mass acceleration, and vehicle height indicated by the oil pressure gauge 58, acceleration sensor 76, and vehicle height sensor 78, respectively.

That is, first, when the electromagnetic on-off valve 48 is closed by the control unit 74, even if the pump 28 etc. are operating normally, the hydraulic fluid 3 in the pilot passage 46
2, the supply to the activated on-off valve 54 is cut off at this electromagnetic on-off valve 48. The pressurized on-off valve 54 connected to the pilot passage 46 normally remains closed and opens only when a predetermined operating pressure is received at the operating pressure receiving port 54a. Therefore, when the supply of the hydraulic fluid 32 to the operating pressure receiving port 54a is cut off as described above, the operating pressure receiving port 54a is in a closed state. When the pressurized on-off valve 54 is thus closed, the suspension device exhibits characteristics based on the elastic modulus of the gas spring 14 and the throttling resistance of the orifice 24. That is, at this time, the suspension device becomes a so-called passive suspension.

On the other hand, when the electromagnetic on-off valve 48 is opened by the control unit 74 while the pump 28 etc. are operating normally, the pressure of the hydraulic fluid 32 is applied to the operating pressure inlet 54a of the pressurized on-off valve 54. This opens the on-off valve 54. In this way, when the pressure-operated on-off valve 54 is opened and the flow control valve 52 is opened to the opening specified by the control unit 74, the piston 10 is displaced upward (to the left in FIG. 1), for example. When the hydraulic fluid 32 is supplied to the hydraulic chamber 8 of the hydraulic cylinder 4 while the piston 6 is being moved, the displacement of the piston 6 is suppressed by the supplied hydraulic fluid 32. The constant changes in the direction of increasing. By supplying and discharging the hydraulic fluid into the hydraulic cylinder 4 in this way, the same effect as changing the throttling resistance of the orifice 24 and the elastic modulus of the gas spring 14 can be obtained, and the suspension device functions as a so-called active suspension device. do. It is also possible to control the vehicle height for each wheel by controlling the amount of hydraulic fluid in the hydraulic chamber 8 of the hydraulic cylinder 4.

In the above control, since the hydraulic fluid supplied to the hydraulic chamber 8 of the hydraulic cylinder 4 is in a high pressure state, the flow control valve 5
2, the hydraulic chamber 8 of the hydraulic cylinder 4 is connected to the reflux pipe 6.
When connected to 0F and 60R, the working fluid in the hydraulic pressure chamber 8 suddenly flows into the reflux pipes 60F and 80R, causing a pressure increase in the reflux pipes 80F and 80R. When such a pressure increase occurs, the reflux pipe 80F,
Water hammer phenomena such as abnormal noise and vibration occur in the BUR, which is undesirable.

However, in this embodiment, the reflux pipe 60F,
There is a return accumulator 6 in each path of 60R.
2 is provided, even if the working fluid suddenly flows into the reflux pipes 60F, 80R due to the operation of the flow control valve 52, the pressure increase in the reflux pipes 60F, 80R due to this will be suppressed by the return accumulator 62. This will be alleviated by the pressure accumulation effect. In other words, the return accumulator 62 functions as a pressure damping means,
Thereby, it is possible to prevent the water hammer phenomenon from occurring in the reflux pipes 60F and 60R.

Note that when the pressure in the high pressure piping 26 indicated by the system oil pressure gauge 42 exceeds the set value, the control unit 74 opens the unload relief valve 70, thereby returning the hydraulic fluid 32 to the reservoir tank 3G and releasing the high pressure piping. This prevents an abnormal rise in pressure within 26. Further, the control unit 74 controls the ignition switch interlocking valve 72 to be closed only when the ignition switch is ON.
As a result, after the engine is stopped, the ignition switch interlocking valve 72 is opened and the high pressure state in the high pressure pipe 26 is released.

As mentioned above, if the hydraulic pressure (supply pressure) upstream of the flow rate control valve 52 drops abnormally due to, for example, damage to the high-pressure piping 26, even if the electromagnetic on-off valve 48 is open, the pressure will not be increased. The predetermined operating pressure is not applied to the pressure-operated on-off valve 54. As a result, the on-off valve 54 automatically enters the closed state, and at this time the suspension device enters the aforementioned passive state. Of course, even in this state, the basic function of the suspension device is maintained, so there is no problem with the running of the vehicle. Furthermore, when the engine is stopped when the vehicle is parked, the pump 28 is stopped and the ignition switch interlocking valve 72 is opened, so that the predetermined operating pressure is not applied to the operating pressure inlet 54a of the pressurized on-off valve 54. Therefore, in this case, even if the electromagnetic on-off valve 48 fails and is left open, the pressurized on-off valve 54 will remain closed, so the hydraulic fluid 32 will flow out little by little from the hydraulic cylinder 4. A situation in which the vehicle height becomes low is reliably prevented.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a vehicle suspension system according to the present invention, and FIG. 2 is an overall configuration diagram of the suspension system. 2... Vehicle body 4... Hydraulic cylinder 6.
... Piston 8 ... Hydraulic pressure chamber 10 ... Piston rod 12 ... Wheel 14 ... Gas spring
16...Movable bulkhead 18...Gas chamber
20...Liquid chamber 26...High pressure piping 28.
... Pump 30 ... Reservoir tank 32 ... Hydraulic fluid (working fluid) 52 ... Flow rate control valve (control valve) 60 ... Reflux piping 62 ... Return accumulator (pressure damping means) 7
4...Control unit

Claims (1)

[Scope of Claim] A suspension device for a vehicle configured to be able to change suspension characteristics by supplying and discharging working fluid to and from a cylinder installed between a vehicle body and a wheel, according to predetermined conditions. a control valve that controls the supply and discharge of working fluid to and from the cylinder, and a reflux pipe that connects the control valve and a reservoir tank, and attenuates the pressure of the working fluid in the reflux pipe during the reflux piping route. A suspension device for a vehicle, characterized in that it is provided with pressure damping means.