JPH03114914A - Suspension device of automobile - Google Patents

Abstract

PURPOSE:To obtain an under-steer characteristic for an active suspension device, by detecting weight distribution from fluid pressure of each fluid cylinder, and by changing control gain so as to make the quantity of load movement of the front part of a car body larger than that of the rear part, at the time of turning. CONSTITUTION:Fluid pressure of a fluid chamber 3c of each fluid cylinder 3 is detected by a pressure sensor 13, and is inputted to a controller 19, which calculates a weight distributional condition from the detected pressure, and based on the results, fluid to each fluid cylinder 3 is fed and discharged in such a way that the twisting of car body is controlled. In the controlling process, control gain is so changed as to make the quantity of load movement of the front part of the car body larger than that of the rear part at the time of turning. In this structure, an under-steer characteristic can be obtained.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a vehicle suspension device that controls the supply and discharge of fluid to and from a fluid cylinder to vary the suspension characteristics, and in particular, relates to a suspension system for a vehicle that controls the supply and discharge of fluid to and from a fluid cylinder to vary the suspension characteristics. Regarding improvements.

(Prior 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 disposed between a vehicle body and each wheel, and a fluid cylinder is connected to each of the fluid cylinders. The flow rate is controlled independently for each wheel, making the vehicle's suspension characteristics variable depending on the driving conditions. A so-called active control suspension device (AC3 device) is known.

The AC8 device is equipped with a warp control means that controls the flow rate of fluid to and from each fluid cylinder to suppress twisting of the vehicle body based on the output of a pressure sensor that detects the fluid pressure of each fluid cylinder. This warp control is performed based on the hydraulic pressure ratio (pressure ratio) between the left and right wheels on the front wheel side and the hydraulic pressure ratio between the left and right wheels on the rear wheel side. If the hydraulic pressure ratio is the same, it is not possible.

(Problems to be Solved by the Invention) By the way, when the vehicle turns, the center of gravity is located to the front of the center of the vehicle body, and the amount of load movement at the front of the vehicle body is made larger than the amount of load movement at the rear of the vehicle body. It is desirable to cause the rear part of the vehicle body to twist relative to the front part of the vehicle body to obtain understeer characteristics. However, since the weight distribution of the vehicle varies depending on the riding conditions of the passengers and the amount of luggage at the rear of the vehicle, it is not possible to determine the exact location of the center of gravity. The amount of load movement at the rear of the vehicle may become large. In this case,
Since the hydraulic pressure ratio between the rear wheels is greater than the hydraulic pressure ratio between the front wheels, there is a need to perform warp control according to this difference to achieve appropriate understeer characteristics.

The present invention has been made in view of the above, and an object of the present invention is to provide a suspension system for a vehicle that can always provide appropriate understeer characteristics when turning.

(Means for Solving the Problem) In order to achieve the above object, the solving means of the present invention is such that a fluid cylinder is disposed between the vehicle body and each wheel, and the flow rate to and from the merging cylinder is controlled. The present invention is based on a suspension system for a vehicle that changes the suspension characteristics of the vehicle. and a pressure detection means for detecting the pressure of the fluid in each of the fluid cylinders, a weight balance detection means for detecting the weight distribution state of the vehicle body based on the output of each of the pressure detection means, and an output of each of the pressure detection means. and a warp control means for controlling the flow rate of fluid to and from each of the fluid cylinders so as to suppress twisting of the vehicle body. Furthermore,
The warp control means is provided with a control gain changing section that changes the control gain according to the output of the weight balance detection means so that the amount of load movement at the front of the vehicle body during turning becomes larger than the amount of load movement at the rear of the vehicle body. It is structured as follows.

(Function) With the above configuration, in the present invention, the control gain changing unit causes the amount of load movement at the front of the vehicle body during turning to be greater than the amount of load movement at the rear of the vehicle body, depending on the weight distribution state of the vehicle body determined by the weight balance detection means. The control gain is changed so that it becomes larger. In other words, when turning, even if the amount of load movement at the rear of the vehicle is larger than the amount of load movement at the front of the vehicle, the control gain is set so that the amount of load movement at the front of the vehicle is greater than the amount of load movement at the rear of the vehicle. is changed to perform warp control, causing the rear of the vehicle to twist relative to the front of the vehicle, resulting in understeer characteristics.

Moreover, since the weight balance detection means is changed according to the weight distribution state of the vehicle body, the current weight distribution state of the vehicle can be determined very accurately. It is possible to perform warp control in which the control gain is changed according to the distribution state.

(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, and there is a space between the vehicle body 1 and the front wheel 2F, and a space between the vehicle body 1 and the rear wheel 2.
A fluid cylinder 3 is arranged between each R and R.

The merging cylinder 3 has a fluid chamber 3c defined by a piston 3b fitted into a 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 the wheels 2F and 2H, respectively.

Gas springs 5 are connected to the fluid chambers 3c of each of the fluid cylinders 3 through communication passages 4, respectively. Each gas spring 5 is divided into a gas chamber 5r and a fluid chamber 5g by a diaphragm 5e, and the fluid chamber 5g communicates with the fluid chamber 3c of the fluid cylinder 3.

Further, 8 is a hydraulic pump, and 9.9 is a flow control valve interposed in a high pressure line 10 that communicates the hydraulic pump 8 and each fluid cylinder 3. It has the function of supplying and discharging fluid (oil) and adjusting the flow rate.

Further, 12 is a main pressure sensor that detects the oil discharge pressure of the hydraulic pump 8 (more specifically, the pressure of soy sauce in accumulators 22a and 22b, which will be described later), and 13 is a main pressure sensor for each fluid cylinder 3.
a cylinder pressure sensor 1 for detecting the fluid pressure in the fluid chamber 3c;
Reference numeral 4 denotes a vehicle height sensor as a stroke detection means for detecting the vehicle height (cylinder stroke amount of the fluid cylinder 3) of the corresponding wheels 2F, 2H. Further, 15 is a vertical acceleration sensor as a vertical acceleration detection means for detecting the vertical acceleration of the vehicle (spring speed of wheels 2F, 2H); 16;
17 is a lateral acceleration sensor that detects the lateral acceleration of the vehicle; 17 is a steering angle sensor that detects the steering angle of the front wheel 2F, which is a steered wheel; 18 is a lateral acceleration sensor that detects the lateral acceleration of the vehicle;
is a vehicle speed sensor that detects the vehicle speed, and the detection signals of the above sensors are sent to the controller 19 which has a CPU etc. inside.
The controller 19 controls the supply and discharge of fluid to each fluid cylinder 3 based on the outputs of the vehicle height sensor 14, vertical acceleration sensor 15, etc., and variably controls the suspension characteristics. It consists of

Next, a hydraulic circuit for controlling supply and discharge of fluid to and from the fluid cylinder 3 is shown in FIG. In the figure, a hydraulic pump 8 is a variable displacement swash plate piston pump, and a hydraulic pump 21 for a power steering device is driven by a drive source 20.
are connected in two series. The high pressure line 10 connected to this hydraulic pump 8 has three accumulators 22a, 2
2a.

22a are connected to each other at the same point, and at the connection point, the high pressure line 10 is connected to the front wheel side passage 10F and the rear wheel side passage 107? It is branched into. Furthermore, the front wheel side passage 10F is a left front wheel side passage 10PL and a right front wheel side passage 10FR.
and each passage 10FL.

10FR has corresponding wheel fluid cylinders 3PL and 3P.
The fluid chambers 3c of H are communicated with each other. On the other hand, rear wheel side passage 1
One accumulator 22b is connected to 0R, and on the downstream side thereof, it is branched into a left rear wheel passage 10RL and a right rear wheel passage 10RR, each passage 10RL,
l0RR is the corresponding wheel fluid cylinder 3RL,
The fluid chambers 3c of 3RR are communicated with each other.

Each of the above fluid cylinders 3PL, 3PR, 3RL,
Gas springs 5FL, 5PR, 5RL connected to 3RR
, 5RR are each specifically provided with a plurality of pieces (four pieces in the figure), and these gas springs 5a, 5b, 5c,
5d are connected in parallel to the fluid chamber 3C of the corresponding fluid cylinder 3 via the communication path 4. Further, each of the gas springs 5a to 5d is provided with an orifice 25 interposed at the branching part of the communication path 4, and the damping effect at each orifice 25 and the buffering effect of the gas sealed in the gas chamber 5f are It has come to demonstrate both. A damping force switching valve 26 for adjusting the passage area of the communication path 4 is interposed in the communication path 4 between the first gas spring 5a and the second gas spring 5b. , has two positions: an open position where the communicating passage 4 is opened and a constricted position where the passage area is significantly narrowed.

Further, an unload valve 27 and a flow control valve 28 are connected to the high pressure line 10 on the -E flow side of the accumulator 22a. The unload valve 27 has an introduction position where the pressure oil discharged from the hydraulic pump 8 is introduced into the swash plate operation cylinder 8a of the hydraulic pump 8 to reduce the amount of oil discharged from the hydraulic pump 8, and an introduction position where the pressure oil discharged from the hydraulic pump 8 is introduced into the swash plate operating cylinder 8a of the hydraulic pump 8 to reduce the oil discharge amount of the hydraulic pump 8. When the oil discharge pressure of the hydraulic pump 8 exceeds a predetermined upper limit oil discharge pressure (160±10 kgf/c), the discharge position switches to the introduction position, and this state The oil discharge pressure of the hydraulic pump 8 is maintained within a predetermined range (120 to 160 kgf/cJ).
It has the function of holding and controlling.

The flow rate control valve 28 has an introduction position where pressure oil from the hydraulic pump 8 is introduced into the swash plate operating cylinder 8a of the hydraulic pump 8 via the unload valve 27, and an introduction position where the pressure oil in the cylinder 8a is unloaded. and a discharge position for discharging from the valve 27 to the reserve tank 29, and when the oil discharge pressure of the hydraulic pump 8 is maintained within a predetermined range by the unload valve 27, It has a function of keeping the differential pressure between upstream and downstream constant and controlling the oil discharge amount of the hydraulic pump 8 to be constant. Oil is supplied to each fluid cylinder 3 using soy sauce (this oil pressure is referred to as main pressure) from the accumulators 22a and 22b.

On the other hand, on the downstream side of the accumulator 22a of the high-pressure line 10, there are four flow control valves 9, 9, corresponding to the four wheels of the vehicle.・・・
・ is provided. Hereinafter, since the configuration of the parts corresponding to each wheel is the same, only the left front wheel side will be explained, and the explanation of the others will be omitted.

That is, the flow rate control valve 9 consists of an inflow valve 35 and a discharge valve 37. The inflow valve 35 has two positions, a closed position and a fluid supply position (open position) whose opening degree is variable, and is interposed in the left front wheel side passage 10FL of the high pressure line 10. The fluid accumulated in 22a is supplied to the fluid cylinder 3FL from the left front wheel side passage 10PL.

Further, the discharge valve 37 has two positions, a closed position and a fluid discharge position (open position) whose opening degree is variable, and the left front wheel side passage 1
Low pressure line 36 connecting 0PL to reserve tank 29
, and discharges the fluid supplied to the fluid cylinder 3PL at the fluid discharge position to the reserve tank 29 via the low pressure line 36. The inflow valve 35
Both the discharge valve 37 and the discharge valve 37 have built-in differential pressure valves that maintain the fluid pressure at a predetermined value in the open position.

Further, a pilot pressure responsive check valve 38 is interposed in the left front wheel side passage 10FL between the inflow valve 35 and the fluid cylinder 3PL. The check valve 38 receives the hydraulic pressure (that is, the main pressure) in the high pressure line 10 upstream of the inflow valve 35 as a biwatt pressure through a pilot line 39, and this pilot pressure becomes 40) cgf'/
It is provided to close when below c-. In other words, only when the main pressure is 40 kgf/cj or more, pressure oil can be supplied to the fluid cylinder 3 and oil in the fluid cylinder 3 can be discharged.

In FIG. 2, reference numeral 41 indicates a communication passage 42 that communicates the downstream side of the accumulator 22a of the high pressure line 10 with the low pressure line 36.
This is a fail-safe valve installed in the tank, and has the function of switching to the open position in the event of a failure, returning the soy sauce in the accumulators 22a and 22b to the reserve tank 29, and canceling the high pressure state. Reference numeral 43 denotes a throttle provided in the pilot line 39, which has the function of delaying the closing of the check valve 38 when the fail-safe valve 41 is opened. 44 is each fluid cylinder 3 PL on the front wheel side.

This is a relief valve that opens when the oil pressure in the fluid chamber 3C of the 3FR increases abnormally and returns the oil to the low pressure line 36.

Reference numeral 45 denotes a return accumulator connected to the low pressure line 36, which performs a pressure accumulating action when oil is discharged from each fluid cylinder 3.

Next, flow control of each fluid cylinder 3 by the controller 19 will be explained based on FIG. 3.

The figure basically shows a control system A that controls the vehicle height to a target vehicle height based on vehicle height displacement signals X, PR, XFL, XRR, and XRL from the vehicle height sensors 14 to 14 of each wheel, and Vehicle height displacement speed signal YPR obtained from the displacement signal.

Control system B that suppresses vehicle height displacement speed based on YPL, YRR, and YRL, and three vertical acceleration sensors 15°15
．． A control system C that aims to reduce vertical vibration of the vehicle based on the vertical acceleration signals GPR, GFL, and GR of 15, and a pressure signal P of the hydraulic pressure sensors 13, 13, and 13.13 of each vehicle.
It has a control system that calculates the torsion of the vehicle body based on PR, PPL, PRR, and PRL and suppresses the torsion.

In the control system A, 50 is the vehicle height sensor 14.1.
4.14.14 Output XPR of left and right front wheels 2F side
, XPL and the output XR of the left and right rear wheels 2R side.
This is a bounce component calculation unit that calculates the bounce component of the vehicle by summing R and XRL.

Further, 51 is a pitch component calculation unit that calculates the pitch component of the vehicle by subtracting the total value of the outputs XRR and XRL on the left and right rear wheels 2R side from the total value of the outputs XPR and XFL on the left and right front wheels 2F side; 52 is the difference XP between the output of the left and right front wheels 2F side
R-XFL and the difference in output between the left and right rear wheels 2R side XRR-
This is a roll component calculation in which the roll component of the vehicle is calculated by adding the XRL.

Further, 53 inputs the bounce component of the vehicle calculated by the bounce component calculation section 50 and the target average vehicle height TH,
This is a bounce control unit that calculates a control amount for the flow rate control valve 9 of each wheel in bounce control based on the gain coefficient KB+. Further, 54 is a pitch control unit which inputs 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 pitch control based on the gain coefficient KP+. 55 is a roll component calculation unit 5
By inputting the vehicle roll component and target roll displacement amount TR calculated in step 2, each flow rate control valve in roll control is adjusted so that the vehicle height corresponds to the target roll displacement 11TR based on the gain coefficients KRF1 and KRth. This is a roll control unit that calculates the amount of control a of No. 9.

In order to adjust the vehicle height to the target vehicle height, each of the control units 53,
54. Each control amount calculated in 55 is reversed for each wheel (reversed so that the positive and negative signs of the vehicle height displacement signals of the vehicle height sensors 14 to 14 are reversed), and then The bounce, pitch, and roll control amounts are added, and in the control system A, the flow rate signals QFRI of the corresponding proportional flow control valves 9 to 9 are obtained.

QPL+, QRR+, and QRL+ are obtained.

In addition, the vehicle height sensors 14 to 14 and the calculation units 50, 51, 52
Dead band devices 80 to 80 are arranged between the vehicle height sensors 14 to 14, and the dead band devices 80 to 80 are arranged in a dead band XH- in which vehicle height displacement signals XFR, XFL, XRR, and XRL from the vehicle height sensors 14 to 14 are set in advance. These vehicle height displacement signals XFR, XFL, XRR, and XRL are output only when XH is exceeded.

Next, in control system B, the vehicle height displacement signals XPR, XPL, XRR, and XRL from the vehicle height sensors 14 to 14 are input to differentiators 56 to 56, and the vehicle height displacement signals Differential components of signals XFR, XFL, XRR, and XRL, that is, vehicle height displacement speed signal YPR.

YFL, YRR, and YRL are obtained.

In addition, the vehicle height displacement speed Y is Y-(Xn-Xn-1)/T Xn: Vehicle height displacement at time t Xn-1: Vehicle height displacement at time t-1 T: sampling time It is determined by

Also, 57-1 is the output V FR of the left and right front wheels 2F side.

From the total value of YFL, the output Y RR of the left and right rear wheels 2R side
.

This is a pitch component calculation unit that calculates the pitch component of the vehicle by subtracting the total value of YRL. In addition, 57-2 is the difference YPR-YFL in the output between the left and right front wheels 2F side, and the difference YPR-YFL between the left and right front wheels 2F side, and the
This is a roll component calculation unit that calculates the roll component of the vehicle by adding the difference YRR-YRL of the R side output.

A pitch control unit 58 inputs the pitch component of the vehicle calculated by the pitch component calculation unit 58-1 and calculates the control amount of each flow rate control valve 9 in pitch control based on the gain coefficient Kp2. Department.

Further, 59 inputs the roll component of the vehicle calculated by the roll component calculation unit 57-2, and calculates the gain coefficient KRF: ,
Kl? R: is a roll control unit that calculates the control amount of each flow rate control valve 9 in roll control based on R:.

Then, each control amount calculated by each of the control units 58 and 59 is reversed in sign for each wheel (inverted so that the sign is opposite to the sign of the vehicle height displacement speed signal of the differentiators 56 to 56). After that, the pitch and roll control amounts for each wheel are added, and in control system B, the corresponding proportional flow control valve 9
~9 flow rate signal QFR2r QPL2 + QRR2+
QRL2 is obtained.

Next, in the control system C, reference numeral 60 is a bounce component calculation unit that calculates the bounce component of the vehicle by summing the outputs GPR, GPL, and GR of the three vertical acceleration sensors 15 to 15. In addition, 61 indicates three vertical acceleration sensors 15 to 15.
Of these, the output GR of the rear wheel 2R side is subtracted from the sum of the half values of the outputs GFR and GFL of the left and right front wheels 2F side.
A pitch component calculating section 62 calculates the pitch component of the vehicle. Similarly, 62 is a roll component calculating section that calculates the roll component of the vehicle by subtracting the output GFL of the left front wheel from the output GFR of the right front wheel.

A bounce control unit 63 inputs the bounce component of the vehicle calculated by the bounce component calculation unit 60 and calculates a control amount for the flow rate control valve 9 of each wheel in the bounce control based on the gain coefficient KBg. Department. Also, 64
65 is a pitch control unit that inputs the pitch component of the vehicle calculated by the pitch component calculation unit 61 and calculates the control amount of each flow control valve 9 in pitch control based on the gain coefficient KP3; similarly, 65 is a roll component. This is a roll control section that inputs the vehicle roll component calculated by the calculation section 62 and calculates the control amount of each flow control valve 9 to 9 in roll control based on the gain coefficient KPR3°KRR3.

Then, the vertical vibration of the vehicle is divided into bounce component, pitch component,
In order to suppress the roll component, each of the above control units 63, 64, 6
After each control amount calculated in step 5 is reversed for each vehicle, the bounce, pitch, and roll control amounts for each wheel are added, and in control system C, the corresponding proportional flow rate control valve is 9 to 9 flow rate signals QFR3, GFL3.
QRR3+ QRL3 is obtained.

In addition, vertical acceleration sensors 15 to 15 and calculation units 60 and 61
．． 62, dead band devices 85-85 are arranged, and the dead band devices 85-85 receive the vertical acceleration signals GPR from the vertical acceleration sensors 15-15.

These vertical acceleration signals GPR only when GFL, GR exceed a preset dead band, XG-XG.

Output GFL and GR.

Next, in the control system, 70 inputs the hydraulic pressure signals PFR, PFL of the two hydraulic pressure sensors 13, 13 on the front wheel side,
The ratio of the hydraulic pressure difference between the left and right wheels (P PR - P PL) to the total hydraulic pressure on the front wheels (P FR + P FL) (PFR - P
A hydraulic pressure ratio calculating section 70a on the front wheel side calculates the hydraulic pressure ratio (FL) / CPPR+pPL), and a similar hydraulic pressure ratio calculating section 70a on the rear wheel side.
The warp control section 70 includes a rear wheel side hydraulic pressure ratio calculation section 70b that calculates PRL)/(PRR+PRL). Then, after multiplying the rear wheel side hydraulic pressure ratio by a predetermined value by a gain coefficient ωF, this is subtracted from the front wheel side hydraulic pressure ratio, and the result is multiplied by a predetermined value by a gain coefficient ωA, and for the front wheels by a predetermined gain coefficient ωC. After that, the control amount for each wheel is reversed to equalize it between the left and right wheels, and in the control system, the flow rate signal QFRa + of the corresponding flow rate control valves 9 to 9 is
QRL4 + QRR4+ QRL4 is obtained.

As described above, the vehicle height displacement components QPR+, QFL+, of the flow signal determined for each flow control valve 9 to 9 are
QRRl, QRL+, vehicle height displacement speed component QPR:
.

QFL; , QRR21QRld, vertical acceleration component QPR3°QFLs, QRR3, QRLs, and
Pressure component QPRa.

GFL4 * QRRs + QRL4 are finally added to give the final total flow signals QFR, QPL,
QRR and QRL are obtained.

In the vehicle suspension system according to the embodiment of the present invention, the warp control section 60 of the control system shown in FIG.
The gain coefficient ωF, which multiplies the rear wheel side hydraulic pressure ratio calculated in the internal (rear wheel side hydraulic pressure ratio calculating section 60b) by a predetermined value, is set to be changeable. That is, the weight distribution state of the vehicle is detected by the pressure values from the pressure sensors acting on the front wheel 2F side and the rear wheel side 2R, and according to this detected value, the amount of load transfer at the front of the vehicle when the vehicle turns is The control gain is changed so that it becomes larger than the load movement amount.

The suspension system for a vehicle according to an embodiment of the present invention will be described below based on the flowchart in FIG.
The cylinder pressure sensor 13 reads the pressures PFL, PPR, PRL, and PRR acting on the fluid cylinders 3 of 2PR, 2RL, and 2RR. Next, in step S2, each fluid cylinder 3PL on the front wheel 2F side,
The average pressure on the front wheel side PF' is calculated by dividing the sum of pressures acting on 3PH PFL+PFR by 2, and in step S3, the sum of the pressures acting on each fluid cylinder 3RL and 3RR on the rear wheel 2R side PRL+
By dividing PRR by 2, the rear wheel side average pressure PR- is calculated.

Thereafter, in step S4, the average pressures PF'' PR- on the front wheel side and the rear wheel side are respectively controlled by the controller 19.
and waits until one minute has elapsed in step S5.

Then, when one minute has elapsed, in step S6, based on the front wheel side average pressure PF' and the rear wheel side average pressure PR- stored in the controller 19 for one minute in step S4, the front wheel 2P side and the rear wheel Calculate the reference average pressures PP and PR on the 2R side. Thereafter, in step S7, the reference average pressure PR on the rear wheel 2R side for one minute is subtracted from the reference average pressure PF on the front wheel 2P side for one minute to calculate a pressure subtraction value P1.

Then, in step S8, the pressure subtraction value P1 calculated in step S7 is within the absolute value of the reference value PO - PO≦
Is P1≦Po, that is, is the center of gravity of the vehicle located on the front side due to the weight distribution state of the vehicle, and is the amount of load movement at the front of the vehicle when the vehicle turns within the allowable range greater than the amount of load movement at the rear of the vehicle? If the pressure subtraction value P1 is within the allowable range (YES), the gain coefficient ωF is set to 1 in step S9.

On the other hand, if the determination in step S8 is No, meaning that the pressure subtraction value P1 is outside the allowable range, in step Slj, the pressure subtraction value P1 is close to the reference value -PO side -PO≦P
I%, that is, whether the center of gravity of the vehicle is located on the rear side due to the weight distribution of the vehicle, and the amount of load movement at the front of the vehicle when the vehicle turns is outside the allowable range, which is smaller than the amount of load movement at the rear of the vehicle. If the pressure subtraction value P1 is close to the reference value -PO side, the gain coefficient ωF is set to 2 (K2 < Kl) in step Sl+.

On the other hand, if the determination in step SIO is No that the pressure subtraction value P1 is close to the reference value po, the gain coefficient ωF is set to 3 (Kl < Kl) in step S+z.

Therefore, in this embodiment, steps 81 to S of the above flow
7 constitutes a weight balance detection means 91 that receives the output of the pressure sensor 13 and detects the weight distribution state of the vehicle, and calculates the weight of the vehicle based on the pressure subtraction value P1 obtained by the weight balance detection means 91. The distribution state can be obtained.

Further, in steps S8 and Sle, the control gain is changed as appropriate according to the output of the weight balance detection means 91 so that the amount of load movement at the front of the vehicle during turning becomes larger than the amount of load movement at the rear of the vehicle. Change part 9
2 are configured.

Therefore, in the above embodiment, the pressure subtraction value P1 is within the absolute value of the reference value PO -PO≦P1≦PO, and the center of gravity of the vehicle is located on the front side due to the weight distribution state of the vehicle, and when the vehicle turns. If the amount of load movement at the front of the vehicle is within the allowable range, which is greater than the amount of load movement at the rear of the vehicle, the gain coefficient ωF is set to 1, and the vehicle body twists when the vehicle turns. Wave control section 7
0, warp control is performed and appropriate understeer characteristics are obtained.

In addition, the pressure subtraction value P1 is outside the allowable range and the reference value -po
-PO≦P1 near the side. If the center of gravity of the vehicle is located on the rear side due to the weight distribution state of the vehicle, and the amount of load movement at the front of the vehicle when the vehicle turns is outside the allowable range, which is smaller than the amount of load movement at the rear of the vehicle, the gain coefficient ωF (however, K2<Kl), the warp control unit 70 changes the rear wheel side hydraulic pressure ratio to be smaller than the front wheel side hydraulic pressure ratio, that is, changes the hydraulic pressure ratio of the front part of the vehicle when the vehicle turns. The amount of load movement is changed to be larger within an allowable range than the amount of load movement at the rear of the vehicle, and in this case as well, appropriate understeer characteristics can be obtained.

Furthermore, the pressure subtraction value P1 is outside the allowable range and the reference value po
P1≦PO near the side. If the center of gravity of the vehicle is located far to the front due to the state of the vehicle's weight distribution, and the amount of load transfer at the front of the vehicle when the vehicle turns is significantly larger than the amount of load transfer at the rear of the vehicle, it is outside the allowable range. Since the gain coefficient ωF is set to 3 (however, K<Kl), the hydraulic pressure ratio on the rear wheel side of the warp control unit 70 is the hydraulic pressure ratio on the front wheel side, and the amount of load movement at the front of the vehicle when the vehicle turns is The amount of load movement at the rear of the vehicle is changed to be larger within an allowable range, and in this case as well, appropriate understeer characteristics can be obtained.

In these cases, the pressure subtraction value P1 is the average pressure PP on the front wheel 2F side and the rear wheel 2R side in one minute based on the front wheel side average pressure PF - and the rear wheel side average pressure PR -.
, PR, and then calculate the average pressure PF on the rear wheel 2R side for 1 minute from the average pressure PF on the front wheel 2F side for this 1 minute.
Since the pressure subtraction value P1 is calculated by subtracting the pressure, a very accurate current weight distribution state of the vehicle can be obtained, and the gain is calculated based on the accurate weight distribution state at the current time, such as when the vehicle is running. Let the coefficient ωF be , , .

Warp control is performed to appropriately change Kl, and this warp control causes the rear part of the vehicle to twist relative to the front of the vehicle, resulting in very appropriate understeer characteristics, thereby making it possible to optimize the steering characteristics.

In the above embodiment, the reference average pressures PP and PR on the front wheel 2F side and the rear wheel 2R side for one minute are calculated based on the front wheel side average pressure PF' and the rear wheel side average pressure PR- stored in the controller 19 for one minute. Although these calculations were made, the average pressure on the front wheel side and the average pressure on the rear wheel side before the vehicle starts may be used as the reference average pressure on the front wheel side and the rear wheel side.

Further, in the above embodiment, the present invention is applied to a suspension device equipped with a gas spring 5, but the present invention can also be applied to a suspension device that does not include a gas spring and only includes a fluid cylinder 3 to make the suspension characteristics variable. Of course, it can be applied.

(Effects of the Invention) As described above, according to the vehicle suspension device of the present invention, the amount of load movement at the front of the vehicle body during turning is controlled by the control gain changing unit according to the weight distribution state of the vehicle body determined by the weight balance detection means. The control gain is changed so that it is larger than the amount of load movement at the rear, so the load at the front of the car is adjusted according to the difference between the amount of load movement at the front of the car body and the amount of load movement at the rear of the car body, which is very accurate. Warp control is performed so that the amount of travel is greater than the amount of load movement at the rear of the vehicle, and this warp control allows the rear of the vehicle to twist relative to the front of the vehicle, resulting in very appropriate understeer characteristics. It is possible to optimize the characteristics.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a general schematic diagram, FIG. 2 is a hydraulic circuit diagram, FIGS. 3A and 3B are control block diagrams showing variable control of suspension characteristics by a controller, and FIG. The figure is a flowchart showing the change of the gain coefficient within the warp control section of the control system. 1... Vehicle body 2PL to 2RR... Wheels 3PL to 3RR... Fluid cylinder 9... Flow rate control valve 13... Pressure sensor (pressure detection means) 91... Warp control means 92... Control Gain changing section D...warp control means

Claims (1)

[Claims] (1) A fluid cylinder is arranged between the vehicle body and each wheel,
A suspension device for a vehicle that changes the suspension characteristics of a vehicle by controlling the supply and discharge of a flow rate to each of the fluid cylinders, comprising a pressure detection means for detecting the pressure of the fluid in each of the fluid cylinders; weight balance detection means for detecting the state of weight distribution of the vehicle body based on the output; and supply/discharge control of the flow rate of fluid to each of the fluid cylinders so as to suppress twisting of the vehicle body based on the outputs of the respective pressure detection means. warp control means, the warp control means changing a control gain so that the amount of load movement at the front of the vehicle body during turning becomes larger than the amount of load movement at the rear of the vehicle body in accordance with the output of the weight balance detection means. 1. A suspension device for a vehicle, comprising a control gain changing section.