JPH0438218A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To prevent generation of an oscillation phenomenon due to the reason that working fluid hardly flows between a hydraulic pressure chamber of a fluid cylinder device and a hydraulic pressure chamber of a gas spring by restraining generation of a damping force in a high frequency oscillation territory where flow velocity of the working fluid is extremely high and the damping force comes to be excessively strong. CONSTITUTION:A restrictor 5j which is a damping force generation means of a gas spring 5 is formed on a free piston 5n supported by a cylinder 5h and a support member 5k through a spring 5m, and a spring force of the spring 5m is set as a value which is smaller than a damping force generated by the restrictor 5j in a high frequency oscillation territory. Accordingly, when fluid is, for example, supplied to a liquid pressure chamber of a fluid cylinder device in the high frequency oscillation territory, the free piston 5n is pushed up by a damping force generated by the restrictor 5j until it makes contact with the bottom face of the support member 5k. It is thus possible to thoroughly absorb high frequency oscillation by the gas spring 5 by way of moving the free piston 5n in the vertical direction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a suspension system for a vehicle, and more particularly to an active suspension system capable of changing suspension characteristics as desired. It is.

Prior Art Suspension devices conventionally called passive suspensions are composed of a hydraulic shock absorber and a damper unit made of a spring such as a coil spring.The suspension characteristics can be adjusted by making the damping force of the hydraulic shock absorber variable. Although it is possible to change it to some extent, the range is small and, in practice, the suspension characteristics of passive suspension devices are set uniformly.

On the other hand, in recent years, a fluid cylinder device having a cylinder and a piston that can slide vertically inside the cylinder is provided between the sprung mass and the unsprung mass, and the cylinder and piston of this fluid cylinder device are By controlling the supply and discharge amount of working fluid to the hydraulic chamber formed by
A suspension device called an active suspension that can change the suspension characteristics as desired has been proposed (for example, Japanese Patent Publication No. 59-143
No. 65, JP-A-63-130418, etc. )
.

Generally, there are three types of vehicle vibration: bounce, pitch, and roll, and such active suspension devices include a fluid cylinder device for each wheel,
In order to improve riding comfort and running stability against these three types of vehicle vibrations, the supply and discharge amount of working fluid to the fluid cylinder device of each wheel is set and controlled according to the vehicle operating condition. The control is performed by controlling the opening degree of the flow control valve of each wheel using a predetermined control gain.

Such an active suspension device includes a cylinder and a free piston that can slide inside the cylinder, and a gas spring with a gas chamber formed on one side of the free piston and a hydraulic pressure chamber formed on the other side is connected to each wheel. 2. Description of the Related Art An active suspension device, called a so-called semi-active suspension device, is known in which a hydraulic pressure chamber of a gas spring and a hydraulic pressure chamber of a fluid cylinder device are connected to each other. In such semi-active suspension devices, the gas springs are supplied with working fluid so that even if the various sensors that detect the displacement of the vehicle fail, the suspension can be controlled using the gas pressure in the gas chamber. A damping force generating means, such as a throttle, is provided for generating a damping force when the fluid flows between the hydraulic pressure chamber of the fluid cylinder device and the hydraulic pressure chamber of the gas spring.

Nodes to be Solved by the Invention As described above, in a semi-active suspension device in which each wheel is equipped with a fluid cylinder device, a gas spring, and a damping force generating means, a damping force generating means such as an aperture is generated. The damping force increases as the flow velocity of the working fluid increases, so when high-frequency vibrations are applied to the vehicle, the damping force becomes excessively large, causing a gap between the hydraulic pressure chamber of the fluid cylinder device and the hydraulic pressure chamber of the gas spring. Fluid may become difficult to flow, and when such a phenomenon occurs, working fluid is supplied to and discharged from the hydraulic pressure chamber of the fluid cylinder device in order to suppress high-frequency vibrations applied to the vehicle. There is a problem in that all pressure fluctuations within the hydraulic pressure chamber of the fluid cylinder device are transmitted to the vehicle body via the piston, resulting in an oscillation phenomenon.

Object of the Invention The present invention provides a fluid cylinder device having a cylinder and a piston that is vertically slidable inside the cylinder between the sprung mass and the unsprung mass of the vehicle for each wheel; It has a cylinder and a free piston that can slide inside the cylinder, and a gas spring that has a gas chamber on one side of the free piston, and depending on the driving condition of the vehicle,
An active suspension device in which suspension characteristics are variable by controlling supply and discharge amounts of working fluid to a hydraulic chamber of the fluid cylinder device formed by the cylinder and the piston, wherein the gas spring With respect to the piston, a hydraulic pressure chamber formed on the opposite side of the gas chamber is configured to communicate with a hydraulic pressure chamber of the fluid cylinder device, and the gas spring is connected to the hydraulic pressure chamber of the fluid cylinder device. A suspension device for a vehicle comprising a damping force generating means for generating a damping force by the working fluid flowing between the hydraulic pressure chamber and the hydraulic pressure chamber of the front gas spring,
It is an object of the present invention to provide a suspension device for a vehicle that can prevent the occurrence of oscillation phenomena in a high frequency vibration region.

Structure of the Invention This object of the present invention is achieved by providing a damping force suppressing means for suppressing the generation of damping force of the damping force generating means in a high frequency vibration region.

Effect of the Invention According to the present invention, since the damping force suppressing means is provided to suppress the generation of damping force of the damping force generating means in the high frequency vibration region, the flow velocity of the working fluid is extremely high and the damping force becomes excessive. In the high-frequency vibration region, the generation of damping force is suppressed, and therefore, the occurrence of oscillation caused by the working fluid becoming difficult to flow between the hydraulic pressure chamber of the fluid cylinder device and the hydraulic pressure chamber of the gas spring is suppressed. It becomes possible to prevent it effectively.

EXAMPLES Hereinafter, examples of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is an overall schematic diagram of a vehicle including a vehicle suspension device according to an embodiment of the present invention.

Although only the left side of the vehicle body 1 is shown in FIG. 1, the right side of the vehicle body 1 is similarly constructed. In FIG. 1, a fluid cylinder device t3 is provided between the vehicle body 1 and the left front wheel 2PL and between the vehicle body 1 and the left rear wheel 2RL.
．． 3 is provided. Inside each fluid cylinder device 3,
A hydraulic chamber 3c is formed by a piston 3b fitted into the cylinder body 3a. The upper end portion of the piston rod 3d connected to the piston 3b of each fluid cylinder 3 is connected to the vehicle body 1, and each cylinder body 3a is connected to the left front wheel 2PL or the left rear wheel 2RL.

The hydraulic chamber 3C of each fluid cylinder device 3 communicates with a gas spring 5 through a communication path 4, and each gas spring 5 is divided into a gas chamber 5f and a hydraulic chamber 5g by a free piston 5e. The hydraulic chamber 5g is connected to the communication path 4 and the piston rod 3.
It communicates with the hydraulic pressure chamber 3C of the fluid cylinder device 3 via d.

FIG. 2 is a schematic longitudinal sectional view showing details of the gas spring 5. FIG.

In FIG. 2, the gas spring 5 includes a cylinder 5h and a free piston 5e that is vertically slidable inside the cylinder 5h.
A hydraulic pressure chamber 5g communicating with the hydraulic pressure chamber 3C of the fluid cylinder device 3 is formed in the upper part thereof, and a gas chamber 5f is formed in the upper part thereof. Immediately above the opening 51 of the communication path 4 to the hydraulic chamber 5g, a throttle 5j that generates a damping force is formed, and the cylinder 5
A free piston 5n supported via a spring 5m is provided on the lower inner surface of the piston h and the lower surface of the support member 5, respectively. The spring force of the spring 5m is set to be smaller than the damping force generated by the aperture 5J in the high frequency vibration region, and the spring 5m constitutes a damping force suppressing means.

A fluid passage IQ connecting the hydraulic pump 8 and each fluid cylinder device 3 so as to be able to supply fluid has a flow rate of fluid supplied to the fluid cylinder device 3 and a flow rate of the fluid supplied to the fluid cylinder device 3.
A proportional flow control valve 9 that controls the flow rate of fluid discharged from the
．． 9 are provided respectively.

The hydraulic pump 8 includes a discharge pressure gauge 1 that detects the discharge pressure of fluid.
2 are provided, and each fluid cylinder device W! A hydraulic pressure sensor 13.13 is provided to detect the hydraulic pressure in the hydraulic pressure chamber 3C of No. 3.

Furthermore, a vehicle height displacement sensor 14.14 is provided which detects the displacement of the vehicle body in the vertical direction relative to each wheel 2FL, 2RL, that is, the vehicle height displacement by detecting the cylinder stroke amount of each fluid cylinder device 3. A vertical acceleration sensor 15.15 detects the vertical acceleration of the wheels 2PL and 2RL, that is, the vertical acceleration of the springs of the wheels 2PL and 2RL.
．． 15 is on a substantially horizontal plane of the vehicle, left and right front wheels 2FL, 2
There are three in total, one each above the PR and one in the center of the left and right rear wheels in the width direction of the vehicle.
A lateral acceleration sensor 16 for detecting acceleration applied in the lateral direction of the vehicle is provided at the center of gravity, and a steering angle sensor 18 is provided at the center of gravity.
and a vehicle speed sensor 19 are provided, respectively.

The discharge pressure gauge 12 and the hydraulic pressure sensor 13 provided in this way.
13, Vehicle height displacement sensor 14.14, Vertical acceleration sensor 1
5.15.15, Lateral acceleration sensor 16, Rudder angle sensor 18
The detection signals of the vehicle speed sensor 19 and the vehicle speed sensor 19 are input to a control unit (17) having a CPU, etc. inside, and the control unit 17 performs calculations according to a predetermined program based on these detection signals, and operates the proportional flow control valve (9). 9 to variably control suspension characteristics as desired.

FIG. 3 shows a fluid cylinder device 3.3.
FIG. 3.3 is a circuit diagram of a hydraulic circuit for supplying fluid to or discharging fluid from these.

In FIG. 3, the hydraulic pump 8 is a hydraulic pump 21 for a power steering device driven by a drive source 20.
An Akinimulator 22 is connected in communication with a discharge pipe 8a which is connected and arranged in parallel with the Akinimulator 22 and which discharges fluid from the hydraulic pump 21 to the fluid cylinder device 3.3.3.3. On the downstream side of the connection part of
It branches into a front wheel side pipe 23F and a rear wheel side pipe 23R. The front wheel side piping 23F branches into a left front wheel side piping 23FL and a right front wheel side piping 23PR on the downstream side of the branching part with the rear wheel side piping 23R, and the left front wheel side piping 23FL and the right front wheel side piping 23PR are, respectively, It communicates with the hydraulic chambers 3c, 3c of the fluid cylinder device 3FL for the left front wheel and the fluid cylinder device 3FR for the right front wheel. Similarly, the rear wheel side pipe 23R branches into a left rear wheel side pipe 23RL and a right rear wheel side pipe 23RR on the downstream side of the branching part, and the left rear wheel side pipe 23R branches into a left rear wheel side pipe 23RL and a right rear wheel side pipe 23RR.
RL and the right rear wheel side pipe 23RR communicate with the hydraulic chambers 3c, 3c of the fluid cylinder device 3RL for the left rear wheel and the fluid cylinder device 3RR for the right rear wheel, respectively.

These fluid cylinder devices 3FL, 3FR, 3RL.

3RR has gas springs 5FL, 5FR, and 5R, respectively.
L and 5RR are connected, each gas spring 5FL.

5FR, 5RL and 5RR are composed of four gas spring units), 5a, 5b, 5c and 5d.The gas spring units 5a, 5b, 5c and 5d of Sale and Cholera are respectively,
Branch communication passages 4a and 4b are provided in the communication passages 4 communicating with the hydraulic pressure chambers 3c, 3c, and 353c of the corresponding fluid cylinder devices 3FL, 3FR13RL, and 3RR.

4c and 4d. In addition, each gas spring 5
FL, 5FR, 5RL, 5RH branch communication path 4as4
b, 4c and 4d each have an orifice 25a.
125b125CN 2! Dd is provided in the orifices 25a, 25b, 25c.

Damping action of 25d and gas springs 5FL, 5FR, 5R
L.

Due to the buffering effect of the gas sealed in the gas chamber 5f of the 5RR, high frequency vibrations applied to the vehicle are reduced.

Among the gas spring units 5a, 5b, 5c, and 5d in which the gas springs 5FL, 5FR, 5RL, and 5RR are implanted, the gas springs are installed at positions closest to the hydraulic pressure chambers 3C13c, 3c, and 3c of each fluid cylinder device 3FL, 3FR13RL, and 3RR. the first gas spring unit) 5a and the second gas spring unit adjacent thereto.
The communication passage 4 between the gas spring unit 5b and the gas spring unit 5F is adjusted by adjusting the passage area of the communication passage 4 by taking an open position in which the communication passage 4 is opened and a closed position in which the passage area is narrowed.
L, 5FR, 5RL.

Switching valve 26 that switches the damping force of 5RR into two stages
is provided. FIG. 2 shows the switching valve 26 in the open position.

An unload relief valve 28 is connected to the discharge pipe 8 a of the hydraulic pump 8 near the upstream side of the connection part of the accumulator 22 .
If the oil discharge pressure measured at step 2 is a predetermined upper limit value, e.g.
When it is 60 kgf/cat or more, it is switched to the open position and the oil discharged from the hydraulic pump 8 is directly returned to the reserve tank 29.
When it is less than 0 kgf/c++f, it is switched to the closed position, oil is supplied to the accumulator 22, and the hydraulic pressure accumulation value of the accumulator 22 is controlled to be maintained at a predetermined value. In this way, oil is supplied to each fluid cylinder device 3 by the soy sauce in the accumulator 22, which is maintained at a predetermined pressure accumulation value. FIG. 2 shows the unload relief valve 28 in the closed position.

Since the hydraulic circuits for the left front wheel, right front wheel, left rear wheel, and right rear wheel are configured in the same way, only the hydraulic circuit for the left front wheel will be explained below, and the rest will be omitted. do.

The proportional flow control valve 9 is a three-way valve, with a closed position where all ports are closed, a supply position where the left front wheel side piping 23FL is opened to the hydraulic pressure supply side, and a fluid cylinder device 3 of the left front wheel side piping 23FL connected to the return piping 32. It can take three positions with the communicating discharge position. FIG. 2 shows the proportional flow control valve 9 in the closed position. Further, the proportional flow rate control valve 9 includes pressure compensation valves 9a, 9a.
The pressure compensating valves 9a, 9a allow the proportional flow control valve 9 to be in the supply position or the discharge position.
The hydraulic pressure within the hydraulic pressure chamber 30 of the fluid cylinder device 3 is maintained at a predetermined value.

A pilot pressure-responsive opening/closing valve 33 that can open and close the left front wheel side piping 23FL is provided on the fluid cylinder device 3 side of the proportional flow rate control valve 9. When the solenoid valve 34 that guides the hydraulic pressure of the left front wheel side piping 23FL on the hydraulic pump 8 side of the proportional flow rate control valve 9 is opened, the hydraulic pressure of the solenoid valve 34 is introduced as pilot pressure into the on-off valve 33. When is equal to or greater than a predetermined value, the on-off valve 33 opens the left front wheel side pipe 23FL, allowing the proportional flow rate control valve 9 to control the flow rate of fluid to the fluid cylinder device 3.

Further, a relief valve 35 that opens when the hydraulic pressure in the hydraulic pressure chamber 3C of the fluid cylinder device 3 increases abnormally and returns the fluid in the hydraulic pressure chamber 3C to the return pipe 32, and the akinimulator 2
It is connected to the discharge pipe 8a of the hydraulic pump 8 near the downstream side of the 2 connection part, opens when the ignition is turned off, returns the oil stored in the accumulator 22 to the reserve tank 29, and releases the high pressure state in the accumulator 22. An ignition key differential valve 36 that returns the oil in the hydraulic pump 8 to the reserve tank 29 to lower the oil discharge pressure of the hydraulic pump 8 when the oil discharge pressure of the hydraulic pump 8 increases abnormally. Return accumulators 38, 38 are provided, which are connected to the valve 37 and the return pipe 32 and which perform a pressure accumulating action when the fluid is discharged from the fluid cylinder device 3.

4A, 4B, and 4C are block diagrams of a fluid control amount calculation device 90 provided in the control unit 17. FIG.

4A, 4B, and 4C, the fluid control amount calculation device 100 provided in the control unit 17 according to the present embodiment includes a vehicle height sensor 14.1 for each wheel.
4.14 and 140 vehicle height displacement signal XPR% XFL,
Control system A that controls the vehicle height to the target vehicle height based on XRRlXRL, and vehicle height displacement signals XF,, XFL% X1l
ls Vehicle height displacement speed signal Y obtained by differentiating XRL,
A control system B that suppresses the vehicle height displacement speed based on R, Y, . . . YRR and YRL, and three vertical acceleration sensors 1
5. Vertical acceleration signal of 15 and 15 GFl1% GF
A control system C that aims to reduce vertical vibration of the vehicle based on L and G, and a hydraulic pressure sensor for each wheel 13.13.13.1
Based on the pressure signal P□ of 3, PFL% PRRN PRL, the control system calculates and suppresses the torsion of the vehicle body, and the lateral acceleration detection signal G of the lateral acceleration sensor 16 determines the lateral direction of the vehicle. It consists of a control system E that aims to reduce vibration.

Control system A includes vehicle height sensors 14.14.14. for each wheel.
Vehicle height displacement signal XpR%XFL% detected by 14
X11% In order to cut XRL noise, low pass filters 40a140b and 40 cut high frequency components.
c, 40d are provided, and low pass filters 40a, 40
b, left and right front wheels 2FL with high frequency components cut
, 2FR vehicle height sensor 14.14 output XFRSXF
While adding L, low-pass filter 40+:,4
Left and right rear wheels 2 with high frequency components cut by 0d
RL, 2RR vehicle height sensor 14.14 output Xmi,
Adding X+u, r, the bounce component calculation unit 41 that calculates the bounce component of the vehicle, and the added value of the outputs X□ and XFL of the vehicle height sensors 14.14 of the left and right front wheels 2PL and 2PR,
Left and right rear wheels 2RL, 2RR (7) Vehicle height -1znt14
．． 14 outputs X, .

A pitch component calculation unit 42, left and right front wheels 2PL, which calculates a pitch component of the vehicle by subtracting the added value of XRL.

2FR car i1j cent t14.14 output XFISXF
L difference XFI XFL and left and right rear wheels 2RL, 2
．． RR vehicle height sensor 14.14 (D output Xmm,
IL) A roll component calculation unit 43 is provided that calculates a roll component of the vehicle by adding the difference XIR−XIL.

Further, the control system A receives the bounce component of the vehicle calculated by the bounce component calculation unit 41 and the target average vehicle height T8, and controls the fluid cylinder device 3 of each wheel in the bounce control based on the gain K B l. The pitch component of the vehicle calculated by the bounce control B44 which calculates the fluid supply amount and the pitch component calculation unit 42 is input, and the fluid cylinder device 3 of each wheel in pitch control is input based on the gain KPI.
The roll component and the target roll displacement amount Tm calculated by the pitch control section 45 and the roll component calculation section 43, which calculate the amount of fluid supplied to the The vehicle is equipped with a roll control unit 46 that calculates the amount of fluid supplied to the fluid cylinder device 3 of each wheel in roll control so as to achieve a corresponding vehicle height.

In this way, each control amount calculated by the bounce control section 44, the pitch control section 45, and the roll control section 46 has its sign reversed for each wheel, that is, the vehicle height sensor 14.
Letter vehicle height displacement signal detected on 14.14.14
, XF L, Control flow signal Q, , Q, L, , QRR,, Q, to the proportional flow control valve 9
L, is obtained.

Here, each low-pass filter 40a, 40b.

40C, 40d, bounce calculation section 41, pitch calculation section 4
2 and the roll calculation B43, there is a dead band device 47a.
, 47b, 47c, and 47d are provided, and from the vehicle height sensor 14.14.14.14, low puff, 7, f
)I/Evening 40 a, 40 bz 40 C14
Vehicle height displacement signal X-1XFL, X1 input via 0d
ls
Only when the vehicle height exceeds Y, X, , XH, these vehicle height displacements 4 = xva, XFL, X 1m S' It is supposed to be done.

Control system B receives input from vehicle height sensors 14, 14, 14 and 14, and low pass filters 40a140b, 40C.
, 40d, the high frequency component becomes car/ ) sat'Lt
:Car FE displacement signal XFm5XFL% Xl1% XIL
is differentiated, and the vehicle height displacement speed signal YFi is obtained according to the following formula:
s Differentiator 50a15 that calculates YFL, Yo, and YRL
0b, 50c, and 50d.

Y=(X,,X-+)/T Here, Xo is the amount of vehicle height displacement at time t, and Xa is time t
-1 is the vehicle height displacement amount, and T is the sampling time.

Furthermore, the control system B calculates vehicle height displacement speed signals YRL, Y of the left and right rear wheels 2RL, 2RR from the added value of the vehicle height displacement speed signals YFL, Y□ of the left and right front wheels 2PL, 2FR.
A pitch component calculation unit 51 that calculates the pitch component of the vehicle by subtracting the added value of RR, and the left and right front wheels 2PL, 2
Difference YF between vehicle height displacement speed signals YFL and YFn on the PR side
Difference between R-Y F L and vehicle height displacement speed signals YRL and YRR for left and right rear wheels 2RL and 2RR, Y, -YRL
and a roll component calculating section 52 that calculates the roll component of the vehicle by adding the following.

In this way, the pitch component calculated by the pitch component calculation section 51 is manually inputted to the pitch control section 53, and the gain KP is
2, each proportional flow control valve 9 in pitch control
The flow rate control amount is calculated, and the roll component calculation unit 5
The roll component calculated in step 2 is input to the roll control unit 54, and based on the gains KRF2 and KRR2, each proportional flow control valve in the roll control is controlled so that the vehicle height corresponds to the target roll displacement amount T. The flow rate control amount to 9 is calculated.

Each control amount calculated by the pitch control section 53 and the roll control section 54 is further reversed in sign for each wheel, and
That is, differentiators 50a, 50b.

Vehicle height displacement speed signal YF calculated by 50c and 50d
RSy, LSY□, and YRL are reversed so that their positive and negative signs are reversed, and then the pitch and roll control amounts for each wheel are added, respectively, and the proportional flow rate control valve 9 of each wheel in control system B is Flow rate signal Q to
, Q, L2, Q□2, and QIL2 are obtained.

Control system C includes low-pass filters 60a and 60b.

60C, a bounce component calculating unit 61 calculates a bounce component of the vehicle by adding the vertical acceleration sensor 15 and the vertical acceleration detection signal G F L SG a detected by the vertical acceleration sensor 15 and 15 with high frequency components cut off by 60C. and the sum of 1/2 of the output of the vertical acceleration sensor 15.15 installed above the left and right front wheels 2PR12FL (GFR
A pitch component calculation unit 62 that calculates the pitch component of the vehicle by subtracting the output GIII of the vertical acceleration sensor 15 provided at the center of the left and right rear wheels in the vehicle width direction from GFL) /2.
and a roll component calculation unit 6 that calculates the roll component of the vehicle by subtracting the output GFL of the vertical acceleration sensor 15 on the left front wheel side from the output GFit of the vertical acceleration sensor 15 on the right front wheel side.
3, and a bounce control unit 64 which receives the calculated value of the bounce component calculated by the bounce component calculation unit 61 and calculates the control amount of fluid to each proportional flow rate control valve 9 in bounce control based on the gain K113. , a pitch control unit 65 that manually calculates the calculated value of the pitch component calculated by the pitch component calculation unit 62, and calculates the control amount of fluid to the proportional flow rate control valve 9 in pitch control based on the gain K P 3; , the calculated value of the pitch component calculated by the roll component calculation unit 63 is manually applied to the gain,
, , K□3, a roll control unit 66 that calculates the amount of fluid to be controlled to the proportional flow rate control valve 9 in pitch control
It is made up of.

In this way, the bounce control section 64 and the pitch control section 6
5 and the control amount calculated by the roll control unit 66 are reversed for each wheel, and then the bounce, pitch, and roll control amounts for each wheel are added and output from the control system C. Each proportional flow control valve 9
Flow signal to Q□3, Q, L3, QIIR3, QRL3
is obtained.

Note that a low-pass filter 60a cuts high frequency components.
, 60b and 60C and the bounce component calculation section 61, pitch component calculation section 62, and roll component calculation section 63, respectively, are provided with dead band devices 67a, 67b, and 67c. From .15, low-pass filters 60 a, 60 b, 60 c
Vertical acceleration signals G□, G F L, which are input through
G1 is the preset dead zone Xc SXc,
Only when Xc is exceeded, these vertical acceleration signals G□
, GFL, and G1 are output to a bounce component calculation section 61, a pitch component calculation section 62, and a roll component calculation section 63.

In the control system, hydraulic pressure detection signals PFL and PFll detected by the hydraulic pressure sensors 13.13 of the fluid cylinder devices 3 of the left and right front wheels 2FL and 2PR are input, and their high frequency components are filtered by low-pass filters 70a and 70b. After being cut, the difference in hydraulic pressure between the hydraulic pressure chambers 3c and 3c of the fluid cylinder device 3 of the left and right front wheels 2FR and 2PL PFII PFL
and the ratio of these added values P, R+P, L Pt = (
PFI PFL) / (Ppm+PFL) is calculated, and if the calculated hydraulic pressure ratio Pr is -ωL <F', <ω, with respect to the threshold hydraulic pressure ratio ωL, the calculated hydraulic pressure ratio P, is output as is, and on the other hand, P, <-ω
When L or Pt>ω, the front wheel side hydraulic pressure ratio calculation unit 71a outputs the threshold hydraulic pressure ratio −ω or ω.
1 and similarly, the hydraulic pressure detection signal P ILSP IR detected by the hydraulic pressure sensor 13.13 of the fluid cylinder device 3 of the left and right front wheels 2RL, 2RR is input, and its high frequency component is inputted by the low-pass filter 70c, 70d. ,
After being cut, the difference in hydraulic pressure between the hydraulic pressure chambers 3c and 3c of the fluid cylinder device 3 of the left and right front wheels 2FR12PL PRRPIL
Ratio between L and these added values PR1+PRL = Pi =
(Pig-PIIL) / '(P□+PRL), and after multiplying the rear wheel hydraulic pressure ratio P by a predetermined value based on the gain ω, , a warp control unit 7 that subtracts this from the front wheel side hydraulic pressure ratio Pr.
1, the 8 forces of the warp control unit 71 are multiplied by a predetermined value using a gain ω, and then, on the front wheel side, the 8 force of the warp control unit 71 is multiplied by a predetermined value using a gain ω. is used to multiply the fluid supply control amount by a predetermined value, and then reverse one so that the controlled amount of fluid supplied to each wheel is opposite between the left and right wheels, and the flow rate to each proportional flow control valve 9 in the control system is Signals Q, R1, Q, , , Q, , , Q, L are obtained.

Further, the control system E receives a lateral acceleration detection signal applied in the lateral direction of the vehicle detected by the lateral acceleration sensor 16, and after its high frequency component is cut by the low-pass filter 80, the control system E performs control based on the gain Kg. The quantity is calculated, and for the left and right front wheels 2FL and 2FH, it is further multiplied by a predetermined value based on the gain AGF, and then the fluid supply control amount for the left and right wheels is adjusted so that the positive and negative sides are reversed. The fluid supply control amount of the left rear wheel 2PL is reversed, and the fluid supply control amount of the left rear wheel 2FL is reversed so that the positive and negative fluid supply control amounts for the left and right front wheels 2RL and 2RR are reversed. Inversely, the flow signals Q and B to each proportional flow control valve 9 in the control system E
・Q, L5・QR, ・Q, L5 are obtained.

The flow signals to each proportional flow control valve 9 in each control system A, B5C1D, and E obtained as described above are added for each wheel, and are further added to the left and right front wheels 2PL, 2FH.
are multiplied by gain AF to obtain total flow signals Q□, QFLXQ□, and QRL to each proportional flow rate control valve 9.

Table 1 shows an example of the control gain reference map used in each of the control systems A, BSC, D, and E stored in the control unit 17, and seven modes are selected depending on the operating state. It is set.

In Table 1, mode l is the value of each control gain for 60 seconds after the engine has stopped, and mode 2 is the value of each control gain when the ignition switch is on but the vehicle is stopped and the vehicle speed is zero. The value of the control gain, mode 3, indicates the value of each control gain in a straight-ahead state where the lateral acceleration G of the vehicle is 0.1 or less, and mode 4
is the lateral acceleration G of the vehicle when the reverse roll mode is selected by the roll mode selection switch (not shown).
In a slow turning state where L exceeds 0.1 and is below 0.3,
In place of mode 5, it indicates the value of the control gain to be selected, and when the vehicle speed exceeds 120 km/h, it will automatically switch to mode 5 even if the reverse roll mode is selected. , and mode 5 is the lateral acceleration G of the vehicle.

Mode 6 is the value of each control gain when the vehicle's lateral acceleration GL exceeds 0.3 and is in a slow turning state of 0.3 or less. In the control gain mode 7, the lateral acceleration G of the vehicle is 0.
．． The value of each control gain in a sharp turning state exceeding 5 is
Each is shown.

In Table 1, Ql and lAx indicate the maximum flow rate control amount supplied to the proportional flow control valve 9 of each wheel, and P
P 8 indicates the minimum pressure in the hydraulic pressure chamber 3C of the fluid cylinder device 3, and the pressure in the hydraulic pressure chamber 3C of the fluid cylinder device 3 decreases excessively, causing the gas spring 5 to fully extend and break. It is set so that there is no

In Table 1, except for mode 4, each control gain is set such that the larger the mode number is, the more the suspension control is performed with emphasis on driving stability.

In the vehicle suspension system according to the embodiment of the present invention configured as described above, the fluid control amount calculation device 90 calculates each Total flow signals ΩPisQFL, QRR, and QRL to the proportional flow control valves 9 of the wheels are calculated, and according to these signals, a predetermined amount of fluid is supplied from the hydraulic pump 8 to the hydraulic pressure chamber 3C of each fluid cylinder device 3, Alternatively, it is discharged from the hydraulic pressure chamber 3C of each fluid cylinder device 3.

At that time, the hydraulic pressure chamber 3C of the fluid cylinder device 3 of each wheel is
Since the communication passage 4 communicates with the hydraulic pressure chamber 5g of the gas spring 5, fluid flows between the hydraulic pressure chamber 3C of the fluid cylinder device 3 and the hydraulic pressure chamber 5g of the gas spring 5, and A damping force is generated when the piston 5n passes through the throttle 5j formed in the piston 5n. Generating a damping force in this way is essential for the gas spring 5 to perform suspension control when various sensors fail, but in the high-frequency vibration region, it is necessary to Since this is extremely large, the damping force generated when the fluid passes through the throttle 5j correspondingly becomes extremely large at t, causing a phenomenon in which it becomes difficult for the fluid to pass through the throttle 5j.

Therefore, in the past, the throttle 5j was provided at the connection part of the communication path 4 to the gas spring 5, so that a predetermined amount of fluid was supplied to the fluid in the fluid cylinder device 3 in order to suppress high frequency vibrations occurring in the vehicle. When supplying fluid to the pressure chamber 3C or discharging it from the fluid pressure chamber 5C, fluid becomes difficult to flow between the fluid pressure chamber 3c of the fluid cylinder device 3 and the fluid pressure chamber 5g of the gas spring 5.
As a result, high-frequency vibrations occur within the hydraulic pressure chamber 3c of the fluid cylinder device 3, which is transmitted via the piston rod 3d to
There was a problem in that the vibration was transmitted to the vehicle body 1, causing an oscillation phenomenon in the vehicle body 1.

However, according to this embodiment, the throttle 5j, which is the damping force generating means, is formed on the free piston 5n supported by the cylinder 5h and the support member 5k via the spring 5m,
The spring force of the 5m spring is
Since the value is set to be smaller than the damping force generated by The force pushes it up until it abuts the lower surface of the support member 5, and on the other hand,
When the fluid a is discharged from the hydraulic pressure chamber 3c of the fluid cylinder device 3, the free piston 5n is pushed down by the damping force generated by the throttle 5j until it comes into contact with the lower surface of the cylinder 5h. Here, since the amplitude of high-frequency vibrations applied to the vehicle is small, by moving the free piston 5n in the vertical direction in this way, the high-frequency vibrations can be sufficiently absorbed by the gas spring 5. The vibration is transmitted to the car body 1, and the vibration is transmitted to the car body 1.
This can effectively prevent oscillation phenomena from occurring.

The present invention is not limited to the above-mentioned examples, but various modifications can be made within the scope of the invention described in the claims, and these are also included within the scope of the present invention. Needless to say.

For example, in the embodiment described above, the gas spring 5 is arranged such that the gas chamber 5f is located above the hydraulic pressure chamber 5g, but conversely, the hydraulic pressure chamber 5g is located above the gas chamber 5f. It may be arranged as follows.

Effects of the Invention According to the present invention, it is possible to provide a suspension device for a vehicle that can prevent oscillation phenomena in a high frequency vibration region.

[Brief explanation of drawings]

FIG. 1 is an overall schematic diagram of a vehicle including a vehicle suspension device according to an embodiment of the present invention. FIG. 2 is a schematic longitudinal sectional view of the gas spring. FIG. 3 is a circuit diagram of a hydraulic circuit that supplies fluid from a hydraulic pump to a fluid cylinder device or discharges fluid therefrom. FIGS. 4A, 4B, and 4C are block diagrams of a fluid supply amount calculator provided in the control unit. 1...Vehicle body, 2PL...Left front wheel, 2FR...Left rear wheel, 2
RL...right front wheel, 2RR...right front wheel, 3
...Fluid cylinder device, 3FL...Fluid cylinder device for left front wheel, 3FR...
-Fluid cylinder device for right front wheel, 3RL...Fluid cylinder body for left rear wheel, 3RR...Fluid cylinder device for right rear wheel, 3a...Cylinder body, 3b...Piston, 3c... ... Hydraulic pressure chamber, 3d... Piston rond, 4... Communication path, 4a, 4b, 4c, 4d... Branch connection i1.5... Gas spring, 5FL... Gas spring for left front wheel , 5FR... Gas spring for the right front wheel, 5RL... Gas spring for the left rear wheel, 5RR... Gas spring for the right rear wheel, 5a, 5b, 5c, 5d... Gas spring unit, 5e
...free piston, 5f...gas chamber of gas spring, 5g...hydraulic pressure chamber of gas spring, 5h...cylinder, 5''...throttle, 5k...
...Support member, 5m...Spring, 5n...Free piston, 8-Hydraulic pump, 8a...Discharge pipe, 9...
Proportional flow control valve, 9a...Pressure compensation valve, 10...Fluid passage, 12...Discharge pressure needle, 1
3... Hydraulic pressure sensor, 14... Vehicle height displacement sensor, 15... Vertical acceleration sensor, 16... Lateral acceleration sensor, 17... Control unit, 18... Rudder angle sensor, 19.・Vehicle speed sensor,
20... Drive source, 21... Hydraulic pump for power steering device, 22
...Akinimureta, 23F...Front wheel side piping, 23R...Rear wheel side piping, 23FL...Left front wheel side piping, 23PR...Right front wheel side piping, 23RL...Left rear wheel side Piping, 23RR...right rear wheel side piping, 25a, 25b, 25c, 25d-orifice, 26.
...Switching valve, 28...Unload relief valve, 29...Reserve tank, 33...Opening/closing valve, 34...Solenoid valve, 35...
...Relief valve, 36...Ignition key chain valve, 37...Hydraulic pump relief valve, -Return akinimulator, 1...Bounce component calculation section, 2...Pitch component calculation section, 3... Roll line segment calculation unit, 4... Bounce control unit, 5... Pitch control unit, 6... Roll control unit, Oa, 50b, 50c, 50d... Differentiator, 1...・
Pitch component calculation unit, 2... Roll component calculation unit, 3... Pitch control unit, 4... Roll control unit, 1... Bounce component calculation unit, 2... Pitch component calculation unit, 3. ...Roll line segment calculation section, 4.. Bounce control section, 5.. Pitch control section, 6.. Roll control section, 1.. Warp control section, 1a.. Front wheel side hydraulic pressure ratio calculation section. , 71b... Rear wheel side hydraulic pressure ratio calculation unit, 90... Fluid control amount calculation device. i

Claims (1)

[Claims] For each wheel, between the sprung weight and the unsprung weight of the vehicle, there is provided a fluid cylinder device having a cylinder and a piston that can slide vertically inside the cylinder, and a cylinder and the inside of the cylinder. a gas spring having a slidable free piston and a gas chamber on one side of the free piston; An active suspension device in which suspension characteristics can be varied by controlling the amount of supply and discharge of working fluid to a hydraulic pressure chamber, the active suspension device having a suspension on the opposite side of the gas chamber with respect to the piston of the gas spring. The formed hydraulic chamber is configured to communicate with the hydraulic chamber of the fluid cylinder device, and the gas spring is arranged between the hydraulic chamber of the fluid cylinder device and the hydraulic chamber of the gas spring. The suspension device for a vehicle is equipped with a damping force generating means that generates a damping force by the working fluid flowing through the vehicle, and further comprising a damping force suppressing means that suppresses the generation of damping force of the damping force generating means in a high frequency vibration region. A vehicle suspension device featuring: