JPH0238128A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To prevent a back flow of working fluid and prevent comfortableness in riding in a vehicle from becoming worse being attended therewith, etc. by stopping the working fluid from being supplied to a cylinder interposed between the body of a vehicle and each of its wheels when the inner pressure of the cylinder rises near the supply pressure of the working fluid. CONSTITUTION:A vehicle body 11 is provided with a plurality of liquid hydraulic cylinders 12 which include respective piston rods 15 each having each wheel 10 supported thereto and also respective liquid pressure rooms 14 each having each gass spring 21 communicated therewith. And each of the liquid hydraulic cylinders 12 has each high-pressure piping 31F, 31R connected thereto, whereby supply or discharge of working fluid thereto/from is possible under the control by a control unit 45. In this case, sensors 38, 55 detect the pressure of working fluid located on the side of its pressurizing source and that of working fluid on the side of each of the liquid hydraulic cylinders 12, respectively, and also the differential pressure between them. When the differential pressure becomes less than its predetermined value, the control unit 45 controls supply of the working fluid to each of the hydraulic cylinders 12 so that it is stopped.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a vehicle suspension system, and more specifically, to improving suspension characteristics by supplying and discharging working fluid to and from a cylinder installed between a vehicle body and a vehicle. This invention relates to a suspension device that can be changed.

(Prior art) For example, European (EPC) application publication number 0114757
As shown in the specification specified in , by installing a cylinder between the vehicle body and the wheels and controlling the supply and discharge of working fluid to this cylinder, suspension characteristics such as vehicle height and hardness and softness can be freely adjusted. Modifiable vehicle suspension systems are known.

The above suspension devices generally have a return port between the pressurized source of the working fluid and the cylinder to return the working fluid to the reservoir tank, thereby controlling the flow rate to control the supply and discharge of the working fluid to and from the cylinder. A valve is provided, and the cylinder internal pressure is controlled within a range lower than the fluid pressure (supply pressure) on the pressure source side than the flow rate control valve.

(Problems to be Solved by the Invention) However, in the above-mentioned conventional suspension device,
For example, when controlling the supply and discharge of the working fluid to control the roll angle during turning, supplying a large amount of working fluid to the outer cylinder may cause an abnormal increase in the internal pressure of this cylinder.

In this case, the difference between the supply pressure from the working fluid pressurizing source and the cylinder internal pressure becomes extremely small, but if the vehicle runs over a protrusion in this state, the working fluid in the cylinder will leak from the working fluid pressurizing source such as a hydraulic pump. The air flows backwards to the sides, impairing ride comfort and making the vehicle's posture unstable.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a suspension device for a vehicle that can prevent the above problem from occurring.

(Means and Effects for Solving the Problems) A suspension device for a vehicle according to the present invention includes a working fluid pressurizing source, a flow rate control valve, and a cylinder as described above, and supplies and discharges working fluid to and from the cylinder. In the suspension device configured to control the flow rate control valve, a differential pressure detection means detects a differential pressure between each fluid pressure on the working fluid pressurization source side and the cylinder side relative to the flow rate control valve; The present invention is characterized by being provided with a supply regulating means for stopping the supply of working fluid to the cylinder when the differential pressure becomes equal to or less than a predetermined value.

In the above configuration, the cylinder internal pressure and hydraulic fluid supply pressure (
In other words, as the pressure difference between the flow rate control valve and the pressure source (pressure on the pressure source side) becomes abnormally small, working fluid will not be oversupplied to the cylinder. is prevented from flowing backwards.

Another suspension device according to the present invention is a suspension device that also includes the above-mentioned working fluid integral pressurizing source, a flow rate control valve, and a cylinder, and controls the supply and discharge of working fluid to and from the cylinder. A pressure detection means for detecting fluid pressure on the cylinder side of the flow control valve, with a pressure guarantee means for maintaining the fluid pressure on the side of the pressure source of the working fluid within a reference range from the valve; The present invention is characterized by further comprising supply regulating means for stopping the supply of working fluid to the cylinder when the pressure detected by the means exceeds a predetermined value lower than the reference range.

In the above configuration, the working fluid supply pressure is maintained within the reference range by the pressure guarantee means, so by stopping the working fluid supply when the pressure on the cylinder side of the flow control valve exceeds a predetermined value, The more the differential pressure between the supply pressure and the cylinder internal pressure becomes abnormally small, the less the working fluid will be oversupplied.

Therefore, in this case as well, backflow of the working fluid is prevented in the same manner as described above.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 2 shows a vehicle suspension device according to an embodiment of the present invention, and FIG. 1 shows a hydraulic circuit used in this suspension device. 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, respectively.
The symbols rRRJ and rRLJ are added and shown,
In the following explanation, these symbols will be added only when it is particularly necessary.

As shown in FIG. 2, a hydraulic cylinder 12 is fixed to each shaft layer of the vehicle body 11, and a hydraulic chamber 14 is defined by a piston 13 that is slidably inserted into the hydraulic cylinder 12. has been done. A wheel 10 is held on a piston rod 15 that is integrated with the piston 13. A gas spring 21 is communicated with the hydraulic pressure chamber I4 via a hydraulic passage. The gas spring 21 has a gas chamber 25 defined by a diaphragm 23 as a movable partition wall and a liquid chamber 27, and the liquid chamber 27 is communicated with the hydraulic pressure chamber 14. In addition, as shown in detail in FIG. 1, in this embodiment, the gas spring 21
Two of them are provided for each width, and they are connected to the hydraulic cylinder 12 in a parallel relationship with each other. An orifice 29 is provided in each of the hydraulic passages 18 that communicate with each of these gas springs 21 . The unit consisting of such a combination of the hydraulic cylinder 12, the gas spring 21, and the orifice 29 has a basic function as a suspension device, with the buffering action of the gas spring 21 and the damping action of the orifice 29. Become.

The above-mentioned hydraulic cylinder 12 has a high pressure pipe 31F or 3
1R is connected, and hydraulic fluid is supplied to and discharged from the hydraulic cylinder 12 through this piping.

A hydraulic circuit for supplying and discharging this hydraulic fluid will be described below with reference to FIG. 1. The vane pump 32 driven by the engine pumps up the hydraulic fluid 44 from the reservoir tank 33 and pumps the hydraulic fluid 44 through the common high-pressure pipe 34 to the high-pressure pipes 31F and 31R for the front wheels and the rear wheels. This common high pressure pipe 34 is equipped with a filter 35 and a check valve 3B in this order from the upstream side.

A main oil pressure regulator 37 and a hydraulic pressure gauge 38 are provided to perform a pressure accumulating function. Also, inside the pump 32,
Hydraulic fluid 44 discharged when the discharge side pressure increases abnormally
An in-pump relief valve 30 is provided to recirculate the water to the suction side.

The high pressure pipe 31F for the front wheel is the high pressure pipe 31FR1 for the right front wheel.
It is branched into a high-pressure pipe 31FL for the left front wheel, and these pipes 31F R, 3LF L are communicated with the respective hydraulic pressure chambers 14 of the front right wheel hydraulic cylinder 12FR and the front left wheel hydraulic cylinder 12FL, respectively. Further, a pilot passage 39F branches off from the high pressure pipe 31F, and this pilot passage 39F is connected to a front wheel electromagnetic on-off valve 50F. The high-pressure piping 31FR for the right front wheel includes a pressure holding valve 51FR, a flow control valve 52FR1, a pressure-operated on-off valve 5, sequentially from the upstream side.
3FR, relief valve 54FR.

A hydraulic pressure gauge 55FR is provided. On the other hand, a pressure guarantee valve 51FL is also installed in the high pressure piping 31FL for the left front wheel from the upstream side.
, a flow rate control valve 52FL, a pressurized on-off valve 53FL, a relief valve 54FL, and a hydraulic pressure gauge 55FL are interposed.

Further, the pilot passage 39F on the downstream side of the above-mentioned electromagnetic on-off valve 50F is branched into two systems, and each operating pressure inlet 58F R,
Connected to 56FL. and relief valve 54F
Each of the relief ports R, 54F and L is connected to the reflux pipe 40F. Further, the hydraulic fluid return ports of the pressure guarantee valves 51FR, 51FL and the electromagnetic on-off valve 50F are also connected to the above-mentioned return pipe 40F. A return rate humulator 59F that performs a pressure accumulating function is attached to this recirculation passage 40F.

Exactly the same elements as the front wheel elements described above are also provided on the rear wheel high pressure pipe 31R side. In FIG. 1, the front wheel element and the rear wheel element, which are equivalent to each other, are distinguished by the symbols rFJ and rRJ added next to their respective numbers.

The front wheel side reflux pipe 40F and the rear wheel side reflux pipe 4°R are connected to a common reflux pipe 41 leading to the reservoir tank 33. The common reflux pipe 41 and the common high pressure pipe 34 are communicated through a relief pipe 42, and an unload relief valve 43 is interposed in the relief pipe 42.

Next, the operation of the suspension device having the above configuration will be explained. The operations of the unload relief valve 43, the electromagnetic on-off valve 50, and the flow rate control valve 52 are controlled by a control unit 45 (see FIG. 2) consisting of, for example, a microcomputer. This control unit 45 includes the hydraulic pressure gauge 38, a hydraulic pressure gauge 55 provided for each hydraulic cylinder 12, and each wheel 10FR, 10FL, 10RR, 1
an acceleration sensor 57 that detects sprung acceleration every 0RL;
and similarly each wheel 1OFR, l0FL, l0RR, l
The output of a vehicle height sensor 58 that detects the vehicle height (that is, cylinder stroke) is input every 0RL (in FIG. 2, an oil pressure gauge 55, an acceleration sensor 57, and a vehicle height sensor 58 corresponding to the left rear wheel 10RL) are input. (only shown).

First, the control unit 45 controls the electromagnetic on-off valve 5.
0 is closed, the hydraulic fluid 44 flowing through the pilot passage 39 is returned to the recirculation passage 40 at this electromagnetic on-off valve 50 even if the pump 32 and the like are operating normally.

Pressure-operated on-off valve 53 connected to pilot passage 39
is normally kept closed and opens only when a predetermined operating pressure is received at the operating pressure receiving port 56. Therefore, when the supply of the hydraulic fluid 44 to the working pressure receiving port 5B is cut off as described above, it is in the closed state. In this way, the on-off valve 53
When closed, the suspension device exhibits properties based on the elastic modulus of the gas spring 21 and the throttling resistance of the orifice 29. That is, this suspension device becomes a so-called passive suspension.

On the other hand, when the electromagnetic on-off valve 50 is opened by the control unit 45 while the bomb 32 etc. are operating normally, the pressure of the hydraulic fluid 44 is applied to the operating pressure inlet 56 of the pressurized on-off valve 53. This opens the on-off valve 53. In this way, when the on-off valve 53 is opened and the flow rate control valve 52 is opened to the opening specified by the control unit 45, for example, when the piston 13 is displaced upward (to the left in FIG. 1), When the hydraulic fluid 44 is supplied into the hydraulic cylinder 12, the supplied hydraulic fluid 4
As a result of the movement of the piston 13 being suppressed by 4, the dynamic spring constant of the suspension device changes in the direction of increasing. By supplying and discharging the hydraulic fluid into the hydraulic cylinder 12 in this way, the throttle resistance of the orifice 29 and the gas spring 2
The same effect as changing the elastic modulus of 1 is obtained, and the suspension device functions as a so-called active suspension device. It is also possible to control the vehicle height for each axis by controlling the amount of hydraulic fluid in the hydraulic cylinder 12.

As described above, the control unit 45 controls the cylinder internal pressure, sprung mass acceleration, and vehicle pressure indicated by the oil pressure gauge 55 provided for each hydraulic cylinder 12, the acceleration sensor 57 provided for each axle layer, and the vehicle height sensor 58, respectively. The supply and discharge of the hydraulic fluid 44 is controlled based on the height. Further, when the pressure in the high pressure pipe 34 indicated by the system oil pressure gauge 38 exceeds a set value, the control unit 45 opens the unload relief valve 43. As a result, the hydraulic fluid 44 is returned to the reservoir tank 33, and an abnormal rise in pressure within the high pressure pipe 34 is prevented.

The control unit 45 basically controls the supply and discharge of the hydraulic fluid 44 as described above, but the hydraulic pressure detected by a certain hydraulic pressure gauge 55 and the hydraulic pressure gauge 38, which naturally has a higher value, When the differential pressure with the detected hydraulic fluid supply pressure is below a predetermined value, the flow control valve 52 corresponding to the oil pressure gauge 55 (for example, the flow control valve 52FR for the oil pressure gauge 55FH) is Irrespective of the basic control, the supply of the hydraulic fluid 44 to the hydraulic cylinder 12 is set to be cut off. This prevents the hydraulic fluid 44 from being oversupplied to each hydraulic cylinder 12 to the extent that the cylinder internal pressure becomes extremely close to the hydraulic fluid supply pressure. If this is the case, the hydraulic fluid 44 will flow from the hydraulic cylinder 12 to the pump 3 due to the vehicle riding on a protrusion or the like under this oversupply condition.
This prevents the flow from flowing backwards to the second side.

In the present invention, in addition to detecting the differential pressure between the working fluid upstream and downstream of the flow control valve 52 as described above, the pressure guarantee valve 51 and the like are provided as in the above embodiment to supply the working fluid. When the pressure is maintained within the reference range, only the hydraulic pressure on the side of the hydraulic cylinder 12 rather than the flow control valve 52 is detected, and the supply of working fluid is regulated based on this. Good too. In other words, in that case, the hydraulic pressure detected by the oil pressure gauge 55 is equal to or higher than a predetermined value that is lower than the above reference range (this predetermined value is different from the predetermined value of the differential pressure).
The control unit 45 is configured to stop the supply of the hydraulic fluid 44 when the condition reaches . In this case, too, the differential pressure between the supply pressure of the hydraulic fluid 44 and the internal pressure of the hydraulic cylinder will not become abnormally small, so that the hydraulic fluid 44 will flow back from the hydraulic cylinder 12 to the pump 32 side. can be prevented from happening.

(Effects of the Invention) As explained in detail above, the suspension device of the present invention is configured to stop supplying working fluid to the cylinder when the cylinder internal pressure rises to a point where it becomes extremely close to the supply pressure of working fluid. With this device, the working fluid that is oversupplied to the cylinder will not flow back from there to the working fluid pressurizing source, and this backflow will prevent the riding comfort from being impaired or the vehicle posture from becoming unstable. It can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a hydraulic circuit used in a suspension device according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing the suspension device. 10... Wheels 11... Vehicle body 12...
・Hydraulic cylinder 13...Piston 14...Hydraulic pressure chamber of the hydraulic cylinder

Claims (2)

[Claims] (1) In a vehicle suspension device configured to change suspension characteristics by supplying and discharging a working fluid to and from a cylinder installed between a vehicle body and a wheel, the pressurized source of the working fluid and the cylinder are provided. A flow control valve having a return port for returning the working fluid to the reservoir tank and controlling the supply and discharge of the working fluid to the cylinder is provided between the cylinder and the working fluid pressurizing source side of the flow control valve. and differential pressure detection means for detecting the differential pressure of each fluid pressure on the cylinder side, and stopping the supply of working fluid to the cylinder when the differential pressure detected by the differential pressure detection means becomes a predetermined value or less. A suspension device for a vehicle, characterized in that a suspension device for a vehicle is provided with a supply regulating means. (2) In a vehicle suspension device configured to change suspension characteristics by supplying and discharging a working fluid to and from a cylinder installed between a vehicle body and a wheel, the pressurized source of the working fluid and the cylinder a flow control valve that has a return port for returning the working fluid to the reservoir tank and controls the supply and discharge of the working fluid to the cylinder; pressure ensuring means for maintaining the fluid pressure within the reference range, pressure detection means for detecting fluid pressure on the cylinder side of the flow control valve, and pressure detected by the pressure detection means being lower than the reference range. A suspension device for a vehicle, comprising: a supply regulating means for stopping the supply of working fluid to the cylinder when the fluid reaches a predetermined value or more.