JPH0592712A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To keep a constant pressure accumulation value without using a constant current circuit by realizing feedback of the pressure accumulation value of a main accumulator and correcting the duty ratio for an unload valve of a control means by a correcting means on the basis of the pressure accumulation value. CONSTITUTION:There is provided an expandable fluid cylinder between the upper and the lower parts of vehicle springs which are not shown in the figure, and the suspension characteristics are changed/adjusted by pumping the fluid from a hydraulic pump 8 into/from this fluid chamber. On this case, the pressed fluid is accumulated by means of a main accumulator 22, and a control is made by means of an unload valve 28 so that the pressure accumulation value may be kept constant. In addition, the unload valve 28 is duty-controlled by means of a controller 17. Feedback of the pressure accumulation value is realized, and the duty ratio of the controller 17 to the unload valve 28 is corrected by a correcting means 71 so that the current value of the unload valve 28 may be kept constant on the basis of the pressure accumulation value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention controls the suspension characteristics by supplying / discharging a fluid to / from a fluid chamber of a fluid cylinder installed between a vehicle body (spring) and each wheel (spring) in a vehicle. The present invention relates to the suspension device.

[0002]

2. Description of the Related Art Conventionally, as a suspension device for a vehicle, as disclosed in, for example, Japanese Patent Laid-Open No. 63-130418, a fluid cylinder is provided between a vehicle body and each wheel, and the fluid cylinder of each fluid cylinder is installed. A pressure source such as a pump is connected to the fluid chamber via a fluid passage, and control valves for controlling the supply and discharge of fluid to and from the cylinder fluid chamber are arranged in the middle of each fluid passage, and control of these control valves By supplying and exhausting fluid to and from the fluid chamber of each cylinder to change suspension characteristics, it is possible to achieve both stabilization of the vehicle body posture and improvement of riding comfort, so-called active control suspension device (ACS device). It has been known.

In the ACS system as described above, the pressurized fluid supplied to and discharged from the fluid chamber of the fluid cylinder corresponding to each wheel has its pressure accumulated in the main accumulator. Always approximately constant, that is, considering the lateral acceleration that requires the fluid pressure to be supplied to and discharged from the fluid chamber of the fluid cylinder, for example, 150 k
Control is performed by an unload valve so that the gf / cm ² is maintained.

In this case, the main accumulator and the unload valve are arranged in a high temperature atmosphere in the engine room in order to prevent pressure loss as much as possible near the pump driven by the engine output. In particular, the unload valve is well controlled by the current value held constant from the constant current circuit shielded by the large heat dissipation plate so that the current value for controlling the opening and closing does not change greatly due to heat. I am trying.

[0005]

In this case, the target accumulator value of the main accumulator takes into consideration the lateral acceleration that requires the fluid pressure with respect to the fluid chamber of the fluid cylinder, and 120 kgf during normal running. Since the accumulated pressure value of about / cm ² is sufficient, it is not necessary to strictly maintain the accumulated pressure value of the main accumulator at 150 kgf / cm ² , and even if there is some fluctuation in the accumulated pressure value of the main accumulator, it will be a serious problem. Never. Therefore, instead of the constant current circuit, the accumulated pressure value of the main accumulator is about 15
There is a demand to control the unload valve so that it is maintained at a substantially constant value of about 0 kgf / cm ² .

Further, the provision of the constant current circuit as described above has the drawbacks that it causes problems such as an increase in cost due to an increase in the number of parts and an increase in weight due to a large heat dissipation plate.

The present invention has been made in view of the above circumstances, and it is an object of the present invention that an unload valve has a substantially constant value based on a pressure accumulation value of a main accumulator instead of a constant current value from a constant current circuit. The accumulator value of the main accumulator is controlled to about 150kgf by controlling the current value.
It is intended to maintain a substantially constant value of about / cm ² and to reduce the cost and weight.

[0008]

In order to achieve the above-mentioned object, a solution means of the present invention is to provide an extendable and retractable fluid cylinder provided between a sprung portion and an unsprung portion of a vehicle. It is premised on a suspension device for a vehicle in which fluid is supplied to and discharged from the fluid chamber in order to change and adjust suspension characteristics. Then, a main accumulator for accumulating the pressurized fluid to be supplied to and discharged from the fluid chamber of each of the fluid cylinders, an unload valve for controlling the accumulator pressure value to be substantially constant, and the unload valve. The control means for performing duty control on the load valve and the pressure accumulation value of the main accumulator are fed back, and the current value of the unload valve is substantially constant based on the pressure accumulation value with respect to the unload valve of the control means. The configuration includes a correction unit that corrects the duty ratio.

[0009]

With the above-described structure, in the present invention, the accumulated pressure value of the main accumulator is fed back, and the duty ratio for the unload valve of the control means is corrected by the correction means based on the accumulated pressure value, so that the engine output is driven. Even if the unload valve is placed in a high temperature atmosphere in the engine room so that the pressure loss near the pump can be prevented as much as possible, the influence of heat on the current value that controls the opening and closing of the unload valve The current value to the unload valve is maintained at a substantially constant value without being affected, and the accumulated pressure value of the main accumulator is substantially constant, that is, within the range of the accumulated pressure value with some fluctuation of about 150 kgf / cm ^2. Controlled.

Further, since the current value to the unload valve is maintained at a substantially constant value as described above, the constant current circuit can be eliminated, and the cost can be reduced without increasing the number of parts. The weight can be reduced by eliminating the need for a large heat sink.

[0011]

As described above, according to the vehicle suspension device of the present invention, the accumulated pressure value of the main accumulator is fed back, and the duty ratio of the control means to the unload valve is corrected by the correction means based on the accumulated pressure value. As a result, the current value to the unload valve can be kept within a substantially constant accumulated pressure range even if the current value to the unload valve in the high temperature atmosphere in the engine room changes greatly due to heat. Even if the constant current circuit is abolished, it is possible to control the accumulated pressure value in the main accumulator to be substantially constant. Moreover, by eliminating the constant current circuit, it is possible to suppress an increase in the number of parts and to reduce cost and weight.

[0012]

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

FIG. 1 shows the overall schematic structure of the vehicle.

In FIG. 1, reference numeral 1 is a vehicle body member, and 2F and 2R are front and rear wheels, which are wheel member members, respectively, between the vehicle body 1 and the front wheel 2F.
Fluid cylinders 3 are respectively arranged between the rear wheel 2R and the rear wheel 2R. Inside each fluid cylinder 3, the cylinder body 3
A fluid pressure chamber 3c is defined as a fluid chamber by the piston 3b inserted into the inside of a. An upper end portion of a rod 3d connected to each piston 3b is connected to the vehicle body 1, and cylinder bodies 3a and 3a are connected to wheels 2F and 2R, respectively.

In the hydraulic chamber 3c of each of the fluid cylinders 3,
A gas spring 5 is communicatively connected via a communication passage 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 is connected to the fluid passage 3 and the piston 3b of the fluid cylinder 3 through the fluid of the fluid cylinder 3. It communicates with the pressure chamber 3c.

Further, 8 is a hydraulic pump, and
Is a proportional flow rate control valve (flow rate control valve) connected to the hydraulic pump 8 via a hydraulic pressure line 10. The proportional flow rate control valves 9 and 9 are provided for the fluid flow to the fluid cylinders 3 and 3, respectively. It has the function of supplying and discharging and adjusting the flow rate. Further, 12 is a discharge pressure gauge for detecting the oil discharge pressure of the hydraulic pump 8, and 13 and 13 are hydraulic pressure chambers 3 of the respective fluid cylinders 3.
is a hydraulic pressure sensor for detecting the hydraulic pressure of c, and 14, 14 are
A vehicle height sensor for detecting a vehicle height displacement (cylinder stroke amount) with respect to the corresponding wheels 2F, 2R.
Reference numerals 5 and 15 denote vertical accelerations for detecting the vertical acceleration of the vehicle (the sprung accelerations of the wheels 2F, 2R), one each above the left and right front wheels 2F and the rear wheel 2R on a substantially horizontal plane of the vehicle.
One piece (a total of three pieces) is arranged in the center portion in the vehicle width direction between them. Reference numerals 18 and 19 denote a steering angle sensor and a vehicle speed sensor, respectively.

Then, the detection signals of the respective instruments and sensors are input to a controller 17 having a CPU or the like inside, and the controller 17 controls the proportional flow rate control valves 9, 9 based on these detection signals. Thus, the suspension characteristic is variably controlled.

Next, FIG. 2 shows a hydraulic circuit for controlling supply and discharge of fluid to and from the fluid cylinders 3 to 3.

In FIG. 2, the hydraulic pump 8 is connected to a hydraulic pump 21 for a power steering device driven by a drive source 20 in a high temperature atmosphere in the engine room. In the middle of the discharge pipe 8a of the hydraulic pump 8, an accumulator 22 as a main accumulator for accumulating the fluid pressurized and supplied by the hydraulic pump 8 to and from the hydraulic chamber 3c of each fluid cylinder 3 is provided. Are connected in communication, and the downstream side is connected to the front wheel side pipe 2
It branches to 3F and the rear wheel side pipe 23R. The downstream side of the front wheel side pipe 23F branches into a left wheel side pipe 23FL and a right wheel side pipe 23FR, and the hydraulic cylinders 3FL and 3FR of the corresponding wheels are connected to the respective pipes 23FL and 23FR for communication. Has been done. Similarly, the rear wheel side pipe 23R has its downstream side branched into left wheel side and right wheel side pipes 23RL, 23RR, and the respective pipes 23RL, 23R.
The fluid pressure chambers 3c, 3c of the fluid cylinders 3RL, 3RR of the corresponding wheels are connected to the R for communication.

Each of the gas springs 5FL to 5RR connected to the fluid cylinders 3FL to 3RR is provided with a plurality (four) of gas springs 5a, 5b, 5c and 5d. 5b, 5c, and 5d are connected to the common communication passage 4 that communicates with the hydraulic chamber 3c of the corresponding fluid cylinder 3 via branch communication passages 4a to 4d. Further, the orifice 2 is provided in the branch communication passages 4a to 4d of the plurality of (first to fourth) gas springs 5a to 5d for each wheel.
5a to 25d are provided, and the orifices 25a to 25d are provided.
And the buffering action of the gas sealed in the gas chambers 5f to 5f, the basic function of the suspension device is achieved.

In the gas springs 5FL to 5RR of each wheel, the common communication passage 4 between the first gas spring 5a and the second gas spring 5b has a passage area of the communication passage 4 adjusted to reduce the damping force. A damping force switching valve 26 for switching is provided. The switching valve 26 has two positions: an open position (the position shown in the drawing) that opens the common communication passage 4 and a throttle position that narrows the area of the common communication passage 4.

An unload relief valve 28 is connected to the discharge pipe 8a of the hydraulic pump 8 in the vicinity of the accumulator 22 as an unload valve for controlling the accumulated pressure value in the accumulator 22 to be substantially constant. ing.
This relief valve 28 has an open position and a closed position (the position shown).
And is arranged in the vicinity thereof so that the pressure loss of the accumulator 22 is prevented as much as possible. When the oil discharge pressure measured by the discharge pressure gauge 12 is equal to or higher than the upper limit set value, the relief valve 28 is controlled to switch from the closed position to the open position shown in the drawing, and the oil of the hydraulic pump 8 is directly returned to the reserve tank 29. , The controller 17 performs duty control by the duty ratio T1 on the relief valve 28 so as to control the oil pressure value P of the accumulator 22 to be maintained at the set value P0.
Is done by. In this way, each fluid cylinder 3
The oil is supplied to the accumulator 22 at the set value P0. In this case, the set value P0 is set to about 150 kgf / cm ² in consideration of the lateral acceleration required to supply oil to each fluid cylinder 3 in the most vigorous traveling state.

Since the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel have the same configuration, only the left front wheel side will be described below, and the other description will be omitted.

As described above, the proportional flow control valve 9 is provided in the left front wheel side pipe 23FL. This proportional flow control valve 9 is at a stop position (illustrated position) where all ports are closed.
And a supply position for opening the left front wheel side pipe 23FL to the supply side,
Further, it has three positions, that is, a discharge position where the fluid cylinder 3 of the left front wheel side pipe 23FL communicates with the return pipe 32, and the pressure compensating valves 9a, 9a are built therein. With the pressure compensating valves 9a, 9a, when the proportional flow rate control valve 9 is in two positions of the supply position and the discharge position, the fluid cylinder 3
The hydraulic pressure in the hydraulic chamber 3c is maintained at a predetermined value.

On the fluid cylinder 3 side of the proportional flow control valve 9, a pilot pressure responsive on-off valve 33 for opening and closing the left front wheel side pipe 23FL is provided. This on-off valve 33
Is the left front wheel side pipe 2 on the oil pump 8 side of the proportional flow control valve 9.
When the solenoid valve 34 for guiding the hydraulic pressure of 3FL is opened, the solenoid valve 34
Is introduced as the pilot pressure, and when the pilot pressure is equal to or higher than a predetermined value, the opening / closing valve 33 is opened to open the left front wheel side pipe 23FL, and the flow rate to the fluid cylinder 3 by the proportional flow control valve 9 is increased. It is possible to control. In addition,
The reference numeral 35 denotes an opening operation when the hydraulic pressure in the hydraulic chamber 3c of the fluid cylinder 3 is abnormally increased, so that the fluid in the hydraulic chamber 3c is returned to the return pipe 32.
It is a relief valve that returns to. Reference numeral 36 is an ignition key interlocking valve connected to the vicinity of the accumulator 22 of the discharge pipe 8a of the hydraulic pump, and when the ignition is off, the interlocking valve 36 is controlled to be opened (position shown in the drawing) to store the accumulator 22. The oil is returned to the tank 29 and the high pressure state is released. Further, 37 is an in-pump relief valve that returns the oil to the tank 29 to reduce the pressure when the oil discharge pressure of the oil pump 8 is abnormally increased, and 38 and 38 are return pipes 32.
Is a return accumulator that is connected to the hydraulic cylinder 3 and that accumulates pressure when the pressure of oil discharged from the fluid cylinder 3 is exhausted.

Next, FIG. 3 shows a control block of the suspension characteristic by the controller 17.

In FIG. 3, the vehicle height sensor 14 for each wheel is shown.
Control system A for controlling the vehicle height to the target vehicle height based on the vehicle height displacement signals XFR, XFL, XRR, XRL, and vehicle height displacement speed signals YFR, YFL, YRR, YRL obtained from the vehicle height displacement signals.
And a vertical acceleration signal G of the three vertical acceleration sensors 15, 15, 15 based on
A control system C for reducing vertical vibration of the vehicle based on FR, GFL, GR, and hydraulic pressure sensors 13, 13, 1 for each wheel
A control system D for calculating the twist of the vehicle body based on the pressure signals PFR, PFL, PRR, PRL of 3 and 13 and suppressing the twist.
And are shown. First, in the control system A, 40
Of the vehicle height sensors 14, 14, 14, 14 sums the outputs XFR and XFL of the left and right front wheels 2F, and sums the outputs XRR and XRL of the left and right rear wheels 2R to obtain the bounce component of the vehicle. Is a bounce component calculator that calculates Code 4
Reference numeral 1 denotes a pitch component calculation unit that calculates the total value of the outputs XRR and XRL of the left and right rear wheels 2R from the total value of the outputs XFR and XFL of the left and right front wheels 2F to calculate the pitch component of the vehicle. . Reference numeral 42 is a difference XFR between the outputs of the left and right front wheels 2F.
-X FL and the difference between the left and right rear wheel 2R side outputs XRR-XRL
Is a roll component calculation unit that adds and to calculate the roll component of the vehicle.

The bounce component 43 of the vehicle calculated by the bounce component calculator 40 and the target average vehicle height TH are input to 43, and the flow rate control of each wheel in the bounce control is performed based on the gain coefficient KB1. It is a bounce control unit that calculates a control amount for the valves 9 to 9. Reference numeral 44 is a pitch control unit to which the vehicle pitch component calculated by the pitch component calculation unit 41 is input and which calculates the control amount of each of the flow rate control valves 9 to 9 in the pitch control based on the gain coefficient KP1. Reference numeral 45 is input with the roll component of the vehicle calculated by the roll component calculation unit 42 and the target roll displacement amount TR, and based on the gain coefficients KRF1 and KRR1, the target roll displacement amount T
It is a roll control unit that calculates the control amount of each flow control valve 9 to 9 in roll control so that the vehicle height corresponds to R.

Then, in order to control the vehicle height to the target vehicle height, the respective control amounts calculated by the respective control units 43, 44 and 45 are
The positive / negative of each wheel is inverted (inverted so as to be opposite to the positive / negative of the vehicle height displacement signals of the vehicle height sensors 14 to 14),
After that, the bounce, pitch, and roll control amounts for each wheel are added, and in the control system A, the flow rate signals QFR1, QFL1, QRR1, Q of the corresponding proportional flow rate control valves 9 to 9 are added.
RL1 is obtained. Note that dead band devices 70 to 70 are arranged between the vehicle height sensors 14 to 14 and the calculation units 40, 41, 42, and the dead band devices 70 to 70 are mounted on the vehicle height sensors 14 to 1.
These vehicle height displacement signals XFR, XFL, XRR, XRL are output only when the vehicle height displacement signals XFR, XFL, XRR, XRL exceed the preset dead zones XH to XH.

Next, in the control system B, the vehicle height displacement signals XFR, XFL, XRR and XRL from the vehicle height sensors 14 to 14 are given.
Is input to the differentiators 46 to 46, and the differentiators 46 to 46
Thus, the differential components of the vehicle height displacement signals XFR, XFL, XRR, XRL, that is, the vehicle height displacement speed signals YFR, YFL, YRR, Y
RL is obtained.

The vehicle height displacement speed Y is obtained by Y = (Xn-n-1) / TXn: vehicle height displacement at time t Xn-1: vehicle height displacement at time t-1 T: sampling time ..

Reference numeral 47-1 is an output Y for the left and right rear wheels 2R from the total value of the outputs YFR, YFL for the left and right front wheels 2F.
It is a pitch component calculation unit that calculates the pitch component of the vehicle by subtracting the total value of RR and YRL. Also, 47-2 is a difference YFR-YFL between the outputs of the left and right front wheels 2F and the left and right rear wheels 2F.
It is a roll component calculation unit that calculates the roll component of the vehicle by adding the difference YRR-YRL of the output on the R side.

Numeral 48 is the pitch component calculator 4
The vehicle pitch component calculated in 7-1 is input, and each flow rate control valve 9 in pitch control is based on the gain coefficient KP2.
It is a pitch control unit that calculates the control amounts of 9 to 9. Reference numeral 49
Is a roll control unit that receives the roll component of the vehicle calculated by the roll component calculation unit 47-2 and calculates the control amount of each flow rate control valve 9 to 9 in roll control based on the gain coefficients KRF2 and KRR2. Is.

The positive and negative signs of the control amounts calculated by the control units 48 and 49 are inverted for each wheel (differentiator 4).
6 to 46 are inverted so as to be opposite to the positive / negative of the vehicle height displacement velocity signal, and thereafter, the pitch and roll control amounts for the respective wheels are added, and in the control system B, the corresponding proportional flow control valve. 9-9 flow rate signals QFR2, QFL2, QRR
2, QRL2 is obtained.

Next, in the control system C, reference numeral 50 is 3
Outputs of individual vertical acceleration sensors 15 to 15 GFR, GFL, G
It is a bounce component calculation unit that calculates the bounce component of the vehicle by summing R. Reference numeral 51 designates outputs GFR and G on the left and right front wheels 2F of the three vertical acceleration sensors 15 to 15.
This is a pitch component calculation unit for calculating the pitch component of the vehicle by subtracting the output GR on the rear wheel 2R side from the total value of each half value of FL. Reference numeral 52 denotes a roll component calculation unit that calculates the roll component of the vehicle by subtracting the output GFL on the left front wheel side from the output GFR on the right front wheel side.

The bounce component of the vehicle calculated by the bounce component calculator 50 is input to 53, and the control amount for the flow control valves 9 to 9 of each wheel in the bounce control is calculated based on the gain coefficient KB3. Bounce control unit. Further, 54 is a pitch control unit that receives the pitch component of the vehicle calculated by the pitch component calculation unit 51 and calculates the control amount of each flow rate control valve 9 to 9 in the pitch control based on the gain coefficient KP3. is there. Reference numeral 55 is a roll control unit that receives the roll component of the vehicle calculated by the roll component calculation unit 52 and calculates the control amount of each flow control valve 9 to 9 in roll control based on the gain coefficients KRF3 and KRR3. Is.

Then, the vertical vibration of the vehicle is a bounce component,
In order to suppress the pitch component and the roll component, each control unit 5 described above
The positive and negative of the control amounts calculated in 3, 54, 55 are inverted for each wheel, and then the bounce, pitch, and roll control amounts for each wheel are added, and the control system C responds. Flow rate signal QFR of proportional flow rate control valve 9 to 9
3, QFL3, QRR3, QRL3 are obtained. It should be noted that dead band devices 80 to 80 are arranged between the vertical acceleration sensors 15 to 15 and the calculation units 50, 51, 52, and the dead band devices 80 to 80 are disposed.
˜80 is a dead zone XG in which vertical acceleration signals GFR, GFL, GR from the vertical acceleration sensors 15 to 15 are preset.
Only when XG is exceeded, these vertical acceleration signals G
Outputs FR, GFL, GR.

Next, in the control system D, the warp controller 60 receives the hydraulic signals PFR and PFL of the two hydraulic sensors 13 on the front wheel side, and receives the total hydraulic pressure (PFR + PP) on the front wheel side.
The ratio of the hydraulic pressure difference between the left and right wheels (PFR-PFL) to (FL) (PFR
-PFL) / PFR + PFL) and the same hydraulic pressure ratio (PRR-PR)
L) / (PRR + PRL) for calculating the hydraulic ratio calculation unit 60b on the rear wheel side. Then, after multiplying the hydraulic pressure ratio on the rear wheel side by a predetermined value with a gain coefficient ωF, this is calculated from the hydraulic pressure ratio on the front wheel side, and the result is multiplied by a predetermined value with a gain coefficient ωA.
On the front wheel side, the gain coefficient ωC is multiplied by a predetermined value, and thereafter, the control amount for each wheel is inverted to make the left and right wheels uniform, and in the control system D, the flow rate signals QFR4, QRL4 of the corresponding flow rate control valves 9 to 9, QRR4 and QRL4 are obtained.

As described above, the vehicle height displacement components QFR1 and QFL1 of the flow rate signal determined for each of the flow rate control valves 9 to 9 are determined.
, QRR1, QRL1, vehicle height displacement velocity components QFR2, QFL2,
QRR2, QRL2, vertical acceleration components QFR3, QFL3, QRR
3, QRL3 and pressure components QFR4, QFL4, QRR4,
QRL4 is finally added to obtain final total flow rate signals QFR, QFL, QRR, QRL. In this case,
As shown in FIG. 3, the vehicle height displacement control unit includes a bounce control unit 43 for the bounce component, a pitch component, and a roll component, a pitch control unit 44, and a roll control unit 45. On the other hand, the vehicle height displacement speed control unit has the pitch control unit 48 for the pitch component and the roll control unit 49 for the roll component, but does not have the bounce control unit for the bounce component. .. Therefore, the vehicle height displacement control means and the vehicle height displacement speed control means are downsized to simplify the structure and shorten the processing time.
Further, the vehicle height displacement speed control means is not provided with a bounce control section, but even if there is no bounce control section for this bounce component, there is no great influence on the overall control.

As shown also in FIG. 4, the controller 17 feeds back the accumulated pressure amount P1 of the accumulator 22 by the discharge pressure gauge 12, and the current value to the relief valve 28 is substantially constant based on the change of the accumulated pressure value P1. Therefore, the correction unit 71 for correcting the duty ratio T1 of the relief valve 28 of the controller 17 is provided.

Next, the duty ratio T of the controller 17 with respect to the relief valve 28, which is executed by the correction means 71.
The correction of No. 1 will be described based on the flow of FIG.

First, in step S1, the controller 17 controls the duty ratio T1 of the relief valve 28.
Is output, and in step S2, it is measured by the oil discharge pressure of the discharge pressure gauge 12 whether or not the accumulated pressure value P of oil in the accumulator 22 is 150 kgf / cm ² , which is the set value P0. As a result, if NO, in step S3, the pressure accumulation value P
Change amount dP / dt is the change amount dP0 / d of the set value P0.
It is determined whether or not it is substantially equal to t, and if NO, it is determined in step S4 whether or not the change amount dP / dt of the pressure accumulation value P is smaller than the change amount dP0 / dt of the set value P0.

As a result, if YES, step S5
In the above, while the duty ratio T1 obtained by adding the corrected duty ratio TA to the predetermined duty ratio T10 for the relief valve 28 is output to the relief valve 28, when NO,
In step S6, the duty ratio T1 obtained by subtracting the corrected duty ratio TB from the predetermined duty ratio T10 for the relief valve 28 is output to the relief valve 28,
Control is repeated again.

On the other hand, steps S2 and S
When the determinations of 3 are YES, the duty ratio T1
Is corrected and the previous duty ratio T1 is output to the relief valve 28, and the control is repeated again.

Therefore, in the above embodiment, the change amount dP / dt of the accumulated pressure value P1 of the accumulator 22 is calculated as the discharge pressure gauge 1.
2 is fed back, and the change amount d of the accumulated pressure value P1
P / dt (oil discharge pressure) is the amount of change in set value P0 dP0 / d
The duty ratio T1 with respect to the relief valve 28 of the controller 17 is compared with t, and the duty ratio obtained by adding the correction duty ratio TA to the predetermined duty ratio T10 by the correction means 71 or subtracting the correction duty ratio TB from the predetermined duty ratio T10. Even if the relief valve 28 is arranged in the high temperature atmosphere in the engine room so that the pressure loss in the vicinity of the hydraulic pump 8 driven by the drive source 20 can be prevented as much as possible by correcting to T1. The current value for controlling the opening and closing of the relief valve 28 is not affected by heat, the current value to the relief valve 28 can be maintained at a substantially constant value, and the accumulated pressure value P1 of the accumulator 22 is substantially constant, that is, 150 kgf / It can be maintained within the range of the accumulated pressure value P1 which has a slight variation of about cm ² .

Since the current value to the relief valve 28 can be maintained at a substantially constant value as described above, the constant current circuit can be eliminated and the cost can be reduced without increasing the number of parts. In addition, it is possible to reduce the weight by eliminating the need for a large heat dissipation plate.

[Brief description of drawings]

FIG. 1 is an overall schematic configuration diagram of a vehicle.

FIG. 2 is a circuit diagram of a hydraulic circuit for controlling fluid supply / discharge to / from a fluid cylinder.

FIG. 3 is a control block diagram of suspension characteristics by a controller.

FIG. 4 is a block diagram of correction means.

FIG. 5 is a flowchart showing duty ratio correction control for the relief valve, which is executed by a correction unit.

[Explanation of symbols]

1 Vehicle Body (Spring) 2F, 2R Front Wheel, Rear Wheel (Unsprung) 3-3 Fluid Cylinder 3C-3C Hydraulic Chamber (Fluid Chamber) 17 Controller (Control Means) 22 Accumulator (Main Accumulator) 28 Unload Relief Valve ( Unload valve) 71 Correction means T1 Duty ratio P1 Accumulated value

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] October 23, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

Next, FIG. 3 and FIG. 4 show control blocks of suspension characteristics by the controller 17.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

In FIGS. 3 and 4 , the vehicle height displacement signals XFR, XFL, XRR, X of the vehicle height sensors 14 to 14 of the respective wheels are shown.
A control system A for controlling the vehicle height to a target vehicle height based on RL, and vehicle height displacement speed signals YFR, YFL obtained from the vehicle height displacement signal.
Control system B for suppressing vehicle high displacement speed based on YRR, YRL
A control system C for reducing the vertical vibration of the vehicle based on the vertical acceleration signals GFR, GFL, GR of the three vertical acceleration sensors 15, 15, 15;
A control system D for calculating a twist of the vehicle body based on the pressure signals PFR, PFL, PRR, PRL of 13, 13, 13 and suppressing the twist is shown. First, in the control system A, 40 sums the outputs XFR, XFL of the left and right front wheels 2F of the vehicle height sensors 14, 14, 14, 14, and outputs the outputs XRR, XRL of the left and right rear wheels 2R. In total,
It is a bounce component calculator that calculates the bounce component of the vehicle. Reference numeral 41 is a pitch component calculation unit that calculates the total value of the outputs XRR and XRL of the left and right rear wheels 2R from the total value of the outputs XFR and XFL of the left and right front wheels 2F to calculate the pitch component of the vehicle. is there. Reference numeral 42 indicates a difference XFR-XFL between outputs on the left and right front wheels 2F and a difference XRR between outputs on the left and right rear wheels 2R.
This is a roll component calculation unit that adds -XRL and calculates the roll component of the vehicle.

[Procedure 3]

[Document name to be amended] Statement

[Item name to be corrected] 0040

[Correction method] Change

[Correction content]

Then, as also shown in FIG. 5 , the controller 17 feeds back the accumulated pressure amount P1 of the accumulator 22 by the discharge pressure gauge 12, and the current value to the relief valve 28 is substantially constant based on the change of the accumulated pressure value P1. Therefore, the correction unit 71 for correcting the duty ratio T1 of the relief valve 28 of the controller 17 is provided.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0041

[Correction method] Change

[Correction content]

Next, the duty ratio T of the controller 17 with respect to the relief valve 28, which is executed by the correction means 71.
It will be described with reference to the flow of FIG. 6 for the first correction.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] Brief explanation of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is an overall schematic configuration diagram of a vehicle.

FIG. 2 is a circuit diagram of a hydraulic circuit for controlling fluid supply / discharge to / from a fluid cylinder.

[Figure 3] Part of the suspension characteristics by the controller
It is a control block diagram showing .

[Figure 4] Part of the suspension characteristics by the controller
It is a control block diagram which shows the other part except.

FIG. 5 is a block diagram of correction means.

FIG. 6 is a flowchart showing a duty ratio correction control for the relief valve, which is executed by the correction means.

[Description of Reference Signs] 1 vehicle body (sprung) 2F, 2R front wheel, rear wheel (unsprung) 3 to 3 fluid cylinder 3C to 3C hydraulic chamber (fluid chamber) 17 controller (control means) 22 accumulator (main accumulator) 28 Unload relief valve (Unload valve) 71 Correction means T1 Duty ratio P1 Accumulated value

[Procedure Amendment 6]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

[Procedure Amendment 7]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

[Procedure Amendment 8]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

[Procedure Amendment 9]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Added

[Correction content]

[Figure 6]

Claims (1)

[Claims] 1. An expandable and contractible fluid cylinder is provided between a sprung portion and an unsprung portion of a vehicle, and fluid is supplied to and discharged from a fluid chamber of the fluid cylinder to change and adjust suspension characteristics. In the suspension device for a vehicle described above, a main accumulator for accumulating the pressurized fluid to be supplied to and discharged from the fluid chamber of each fluid cylinder, and an accumulator for controlling the accumulator to have a substantially constant accumulator value. The load valve, control means for performing duty control on the unload valve, and feedback of the accumulated pressure value of the main accumulator so that the current value of the unload valve becomes substantially constant based on the accumulated pressure value. And a correction means for correcting the duty ratio of the means with respect to the unload valve.