JPH0367713A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To restrict frequent level adjustment caused by load change after stoppage of an engine by providing a sensitivity adjusting part for adjusting a detection signal from a vertical acceleration detecting means for detecting vertical vibration, and controlling to decrease the sensitivity of the sensitivity adjusting part after stopping the engine. CONSTITUTION:A hydraulic cylinder 3 is suspended between a car body 2 and a wheel 2F, 2R respectively, and working fluid from a hydraulic pump 6 is supplied to/discharged from a hydraulic oil chamber 3c connected with a gas spring device 5 through a proportional flow control valve 7. The proportional flow control valve 7 is controlled by a control unit 20 based on outputs of sensors 22 - 26 for expanding/contracting the hydraulic cylinder 3 for supporting the car body stably. In this case, the control unit 20 is provided with a sensitivity adjusting part capable of adjusting a detection signal of a vertical acceleration sensor 24 detecting the vertical acceleration of the vehicle. After stopping an engine, controlling is conducted to decrease the sensitivity of the sensitivity adjusting part for restricting frequent level adjustment caused by load change after stopping the engine.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a cylinder installed between each wheel and a vehicle body.
The present invention relates to an active suspension device that controls supply and discharge of fluid based on the operating state of a vehicle.

[Prior art and its problems] Recently, as a suspension system for a vehicle, a fluid cylinder device is installed between each wheel and the vehicle body, and the supply and discharge of working fluid to and from this fluid cylinder device is controlled based on the driving state of the vehicle. An active type suspension (hereinafter abbreviated as "active suspension") has been proposed, which achieves good ride comfort and running stability by doing so. (Refer to Japanese Unexamined Patent Publication No. 63-130418, etc.) In an active suspension system, a control device controls fluid flow to a fluid cylinder device according to a predetermined control program based on input information from various detection means capable of detecting vehicle conditions. By changing the supply and discharge control pattern of this fluid, its suspension characteristics can be changed as appropriate. Suspension characteristics can be set. Ultimately, it would be ideal to maintain the vehicle body in a stable horizontal state at all times regardless of the displacement of the wheels.

One such active suspension is one in which a cylinder chamber of a fluid cylinder and a gas spring are placed in communication with each other.

According to this configuration, high-frequency vibrations such as road noise can be absorbed by the gas spring, so the fluid supply and discharge control of the fluid cylinder is performed using low-frequency vibrations (for example, 5 Hz or less) such as those caused by rolls caused by manual operation by the driver. This makes it easier to control the vehicle body displacement.

Incidentally, in the above-mentioned active suspension, the pump that supplies the working fluid under pressure is usually configured to be driven by the engine that is the power source of the vehicle.

In this case, when the engine is stopped, the supply of working fluid is stopped, and therefore control becomes impossible. However, this method cannot respond to changes in vehicle conditions after the vehicle has stopped, resulting in various problems.For example, if the sprung weight is reduced by passengers getting out of the car or luggage in the trunk after the engine has stopped. , the fluid cylinder device, whose internal pressure has increased in response to the previous load, suddenly extends to the full stroke of the suspension. In other words, the vehicle height increases.

Therefore, in order to prevent such problems, a pressure accumulating mechanism (accumulator) is provided in the fluid circuit, and the control is continued for a predetermined period of time even after the engine is stopped.

However, even if an accumulator is provided, its capacity is limited, and if control is performed in the same way as when driving, for example, control will be performed in response to vibrations caused by opening and closing of doors, etc. There is a problem in that the pressure stored in the accumulator is consumed, and as mentioned above, the control becomes uncontrollable when it is really needed.

[Object of the Invention] In view of the above circumstances, an object of the present invention is to provide a suspension device for a vehicle as an active suspension that can reliably continue control for a predetermined period of time after the engine is stopped.

[Configuration of the Invention] Therefore, the vehicle suspension head device according to the present invention has the following features:
In addition to being equipped with vertical acceleration detection means for detecting vertical vibration, the control device is also equipped with a sensitivity adjustment section that can adjust the detection signal from the vertical acceleration detection means.

After the engine is stopped, the control device is configured to reduce the sensitivity of the sensitivity adjustment section.

With this configuration, control is not performed with unnecessary small vibrations when the engine is stopped, and therefore, unnecessary consumption of the accumulated pressure in the accumulator is prevented, and control can be reliably continued for the necessary time.

[Embodiments of the invention] An embodiment of the present invention will be described below based on the drawings.

FIG. 1 is a schematic configuration diagram corresponding to a side view of the entire vehicle to which an embodiment of the vehicle suspension device according to the present invention is applied. FIG. 1 shows only one side (left side) of the vehicle body. The other side is similarly constructed.

In addition, the code rFJ used in the following explanation refers to the front wheel, rRj refers to the rear wheel, rFRJ refers to the right front wheel, rFLJ refers to the left front wheel,
rRRJ means the right rear wheel, rRI, J means the left rear wheel, and when there is no need to particularly distinguish between them, the description will be made without using these identification symbols.

In the figure, vehicle body 1 and wheels 2... (front wheel 2F).

2F or rear wheels 2R, 2R), hydraulic cylinders 3, which are fluid cylinder devices, are installed respectively.

Each hydraulic cylinder 3 is a so-called single-acting operating cylinder,
A hydraulic chamber 3C is defined by the piston 3b fitted into the cylinder tube 3a, and the upper end of the piston rod 3d connected to each piston 3b is connected to the vehicle body 1. 2... is connected to...

The hydraulic chambers 3c of each hydraulic cylinder 3... each have a communication passage 4.
It communicates with a gas spring device 5, which is a gas spring, through.

The gas spring device 5 includes a plurality of gas springs that are divided into a gas chamber 5b and an oil chamber 5c by a diaphragm 5a, and the oil chambers 5c of these gas springs are connected to the communication path 4. Hydraulic cylinder 3 via piston 3b
... is in communication with the hydraulic chamber 3c.

A hydraulic pump 6 is connected to each hydraulic cylinder 3 through a flow path 10, and hydraulic oil is supplied from the hydraulic pump 6.

Proportional flow control valves 7 for controlling the flow rate of hydraulic oil supplied to or discharged from the hydraulic cylinders 3 are provided in the passages 10 connected to the respective hydraulic cylinders 3. .

The hydraulic pump 6 is provided with a discharge pressure gauge 21 for detecting the discharge pressure of hydraulic oil from the hydraulic pump 6, and each hydraulic cylinder 3... is provided with a discharge pressure gauge 21 for detecting the hydraulic pressure in its hydraulic chamber 3C. Oil pressure sensors 22... are provided respectively.

Further, a vehicle height displacement sensor 23... detects the cylinder stroke amount of each hydraulic cylinder 3... and detects the vertical displacement of the vehicle body 1 with respect to each wheel 2..., that is, the vehicle height displacement.
are provided, and vertical acceleration sensors 24 for detecting the vertical acceleration of the vehicle 1, that is, the vertical acceleration on the springs of the wheels 2... Each above 2F - one by one and vq rear wheel 2R
, 2R are provided at a total of three locations, one at the center in the vehicle width direction, and a steering angle sensor 25 and a vehicle speed sensor 26 are provided, respectively.

Each of the above sensors (i.e., discharge pressure gauge 21, oil pressure sensor 2
2..., vehicle height displacement sensor 23..., vertical acceleration sensor 24..., steering angle sensor 25, and vehicle speed sensor 26) are input to a control unit 20 equipped with a CPU, and the control unit 20 performs calculations according to a predetermined program based on these detection signals, and controls the hydraulic pressure supply to each hydraulic cylinder 3 by driving and controlling the proportional flow rate control valves 7 to stabilize the vehicle body. It is to be kept in a safe place.

FIG. 2 is a circuit diagram of a hydraulic circuit that supplies hydraulic oil from the hydraulic pump 6 to the hydraulic cylinders 3 and discharges the hydraulic oil from these cylinders.

In the figure, a hydraulic pump 6 is provided in parallel with a hydraulic pump 9 for a power steering device, and is driven by an engine 8, which is a driving source, to discharge hydraulic fluid into a discharge pipe 10A.

The discharge pipe 10A branches into a front wheel side pipe 10F and a rear wheel side pipe 10R on the downstream side of the connection portion of the accumulator 11.

The front wheel side piping 10F is connected to the left front wheel side piping 10FL and the right front wheel side piping 10FH on the downstream side of the branching part with the rear wheel side piping 10R.
Similarly, the rear wheel side pipe 10R branches into a left rear wheel side pipe 10RL and a right rear wheel side pipe 10RH on the downstream side of the branching part.

And each piping 10FL, 10FR.

10RL and 10RR are proportional flow control valves 7, respectively, which will be described later.
(7FL, 7FR, 7RL, 7RR) and the respective wheels 2 (2FL, 2FR, 2RL).

2RR) hydraulic cylinder 3 (3FL, 3FR.

3RL, 3RI'l).

Each proportional flow control valve 7 (7FL, 7FR.

7RL, 7RR) and the reserve tank 19 are return piping 13 (13F (13FL, 13FR), 1
3R (13FL, 13FR)).

Accumulator 1 of discharge pipe 10A from hydraulic pump 6
An unload relief valve 12 is located near the upstream side of the connection part 1.
is connected, and the unload relief valve 12 is switched to the open position when the discharge pressure measured by the discharge pressure gauge 21 is equal to or higher than a predetermined upper limit value, and the unload relief valve 12 is switched to the open position, and the oil discharged from the hydraulic pump 6 is transferred to the reserve tank 19. Return accumulator 11
is controlled so that the accumulated pressure value is maintained at a predetermined value. In this way, oil is supplied to each hydraulic cylinder 3 by the oil in the accumulator 11, which is maintained at a predetermined pressure accumulation value. FIG. 142 shows the unload relief valve 12 in the closed position.

Discharge pipe 10A near the downstream side of the accumulator 11 connection part
and return piping 13 are connected via a fail-safe valve 14, which opens after a predetermined time period when the ignition is turned off to return the oil stored in the accumulator 11 to the reserve tank 19. This is to release the high pressure state within the accumulator 11.

Further, when the discharge pressure of the hydraulic pump 6 increases abnormally, a hydraulic pump relief valve 1 returns the oil in the hydraulic pump 6 to the reserve tank 19 to reduce the oil discharge pressure of the hydraulic pump 6.
Further, return accumulators 13A, 1 are provided in the return distribution v13F, 13L to prevent water hammer when discharging hydraulic oil from the hydraulic cylinders 3...
3A are provided respectively.

Here, the pipes 10FL, 10FR, 10RL.

The hydraulic circuits for each wheel 2 after 10RR (front left wheel 2FL, front right wheel 2FR, rear left wheel 2RL, and rear right wheel 2RR) are configured in exactly the same way, so as an example below, the hydraulic circuits for the left front wheel 2FL, Only the hydraulic circuit will be explained, and the rest will be omitted.

As described above, the left front wheel side piping 10FL is connected to the hydraulic chamber 3C of the hydraulic cylinder 3FL via the left front wheel side proportional flow control valve 7FL.
is connected to.

The proportional flow control valve 7FL is a three-way valve, and has three positions: a closed position where all ports are closed, a supply position where the left front wheel side piping 10FL is opened to the hydraulic pressure supply side, and a discharge position where the hydraulic cylinder 3FL is communicated with the return piping 13F. The proportional flow control valve 7 shown in FIG.
is shown in the closed position.

Moreover, the proportional flow rate control valve 7FL is a pressure compensation valve 7A, 7A.
This pressure compensation valve 7A is equipped with a pressure compensation valve 7A.

7A, the hydraulic pressure in the hydraulic chamber 3c of the hydraulic cylinder 3FL is maintained at a predetermined value when the proportional flow rate control valve 7FL is in the hydraulic pressure supply position or the hydraulic discharge position.

On the hydraulic cylinder SFL side of the proportional flow rate control valve 7FL, a pilot pressure-responsive opening/closing valve 15 that can open and close the left front wheel side piping 10FL is provided.

When the solenoid valve 16 that guides the hydraulic pressure of the left front wheel side piping 10FL on the hydraulic pump 6 side of the proportional flow control valve 7FL is opened, the hydraulic pressure of the solenoid valve 16 is introduced as a pilot pressure into the on-off valve 15, and this pilot pressure is When the value exceeds a predetermined value, the on-off valve 1
5 opens the left front wheel side piping 10FL and connects the proportional flow control valve 7F.
This makes it possible to control the flow rate of hydraulic oil to the hydraulic cylinder 3FL by the hydraulic cylinder 3FL.

Furthermore, on the downstream side (hydraulic cylinder 3FL) of the on-off valve 15, there is a return pipe 1 that opens when the oil pressure in the hydraulic chamber 3c of the hydraulic cylinder 3FL rises abnormally and returns the hydraulic oil in the hydraulic chamber 3C.
A gas spring device 5FL is connected via a communication path 4 to the hydraulic cylinder 3FL, which is provided with a relief valve 17 for returning the pressure to the hydraulic cylinder 3FL.

The gas spring device 15FL includes four gas spring units 51.
, 52, 53, and 54 are arranged in parallel, and these gas springs are arranged in parallel.

53 and 54 are branch communication passages 4 branching from the communication passage 4, respectively.
1, 42, 43, and 44. Further, the branch communication passages 41, 42, 43.44 have ori 74 holes 41a, 42a, 43a, respectively.

44a are provided, and these orifices 41a
, 42a, 43a, 44a and the buffering effect of the gas sealed in the gas chamber 5b of each gas spring unit 51, 52, 53.54, the high frequency vibration of the wheel 2FL is absorbed, and the vibration of the vehicle l is absorbed. Efforts are made to reduce vibration.

Each gas spring unit 51 that constitutes the gas spring device 5FL
, 52, 53, and 54, a first gas spring unit 51 provided at a position closest to the hydraulic chamber 3C of the hydraulic cylinder 3FL, and a second gas spring unit 52 adjacent thereto.
The passage area of the communication passage 4 is adjusted by taking an open position in which the communication passage 4 is opened and a closed position in which the passage area is narrowed, thereby reducing overall damping of the gas spring device 15FL. A switching valve 4A is provided that can switch the force into two stages. In FIG. 2, the switching valve 4A is shown in the open position.

FIGS. 3(A) and 3(B) show the control unit 20.
2 is a block diagram of a suspension characteristic control device in the vehicle.

In the figure, the suspension characteristic control device provided in the control unit 20 according to the present embodiment has a suspension characteristic control device for each wheel 2.
A control system A that controls the vehicle height to a target vehicle height based on vehicle height displacement signals X (XFR, XFL, XRR, XRL) from the vehicle height displacement sensors 23 of...

A control system B that controls the vehicle height displacement speed based on the vehicle height displacement speed signal Y (YFR, YH, YRR, YRL) obtained by differentiating the vehicle height displacement signal X, and three vertical acceleration sensors. Vertical acceleration signal G (Gra,
A control system C that aims to reduce the vertical vibration of the vehicle body based on GF (I G*), and a hydraulic sensor 22 for each wheel 2...
Hydraulic signal P (PFR, PFL.

The control system calculates the torsion of the vehicle body based on the torsion of the vehicle (Pu, PR), and controls the torsion of the vehicle body.

Control system A includes vehicle height displacement sensors 23FL and 23FR (7) outputs XFR and XFL for left and right front wheels 2FL and 2FH.
and the vehicle height displacement sensor 23RL for the left and right rear wheels 2RL and 2RR.

Bounce component calculation unit 50° that calculates the bounce component of the vehicle l by adding the outputs XRR and XRL of 23RR Vehicle height displacement sensors 23FL and 23FR for left and right front wheels 2FL and 2FH
From the output of X FR, X FL (7), the vehicle height displacement sensors 23RL, 23RR (
7) Pitch component calculation unit 51 that calculates the pitch component of the vehicle 1 by subtracting the output xRRI XRL(') added value. Vehicle height displacement of left and right front wheels 2FL, 2FH +23FL, 23
FR(1) Difference Xr*-Xrt of output XFIXFL,
Left and right rear wheels 2RL.

2RR vehicle height displacement sensor 23RI, 23RR output X
a roll component calculation unit 52 that calculates the roll component of the vehicle by adding the difference
It is equipped with

Further, the control system A receives the bounce component of the vehicle calculated by the bounce component calculation unit 50 and the target average vehicle height TH,
Each wheel 2 in bounce control based on gain KBI.
Bounce control unit 53 . . . calculates the amount of hydraulic oil supplied to the hydraulic cylinders 3 . The pitch component of the vehicle calculated by the pitch component calculation section 51 is input, and the hydraulic cylinder 3 of each wheel 2 is controlled based on the gain Kp+.
Pitch control unit 54 that calculates the amount of hydraulic oil supplied to...
and target roll displacement amount TR are input, and *r1 is input to the gain.
．． It is equipped with a roll control unit 55 that calculates the amount of hydraulic oil supplied to the hydraulic cylinders 3 of each wheel 2 in roll control so that the vehicle height corresponds to the target roll displacement amount TR based on KRRI. ing.

In this way, the bounce control unit 53. Each control amount calculated by the pitch control section 54 and the roll control section 55 is
The positive and negative values are reversed each time, that is, the vehicle height displacement sensor 2
The vehicle height displacement signal X... detected at 3... is inverted so that its sign is opposite to that of the vehicle height displacement signal X..., and thereafter, each wheel 2...
The bounce, pitch, and mouth control amounts for each wheel are added, and a flow rate signal QFRI + QFLI is sent to the proportional flow control valve 7 of each wheel 2 in the control system A.
, QRRI + QR eyes are obtained.In addition, each vehicle height displacement sensor 23... and bounce component calculation section 50. A dead band device 60 is provided between the pitch component calculation section 51 and the roll component calculation section 52, respectively, and the vehicle height displacement signal X (XFR,
Only when the vehicle height displacement signals (XF, L, XRR, XRL) exceed a preset dead band XH..., these vehicle height displacement signals The information is output to a section 52.

Control system B receives vehicle i displacement signals '14rX (XFR, XFL, XRR) input from vehicle height displacement sensors 23...
, XRL), and calculate the vehicle height displacement signal Y (Y
rR.

Differentiator 56 that calculates YFL, YRR, YRL)...
·have.

Y = (Xn Xn-+) / T where,
Xn is the amount of vehicle height displacement at time t, 1n-1 is the amount of vehicle height displacement at time t-l, and T is the sampling time.

Furthermore, the control system B controls the left and right front wheels 2FL.

The left and right rear wheels 2RL and 2RR side vehicle height displacement speed signal Y are determined from the added value of the 2FR side vehicle height displacement speed signal YF* and Yrt.
A pitch component calculation unit 57A that calculates the pitch component of the vehicle l by subtracting the added values of RR and YRL, and the left and right front wheels 2
The roll component of vehicle l is calculated by adding the difference YFR-YFL between the vehicle height displacement speed signals YFII and YFL on the FL and 2FR sides and the difference YRR-YRL between the vehicle height displacement speed signals YRR and YRL on the left and right rear wheels 2RL and ZRR sides. The roll component calculating section 57B calculates .

In this way, the pitch component calculated by the pitch component calculation section 57A is input to the pitch control section 58, and the gain KP
Each proportional flow control valve 7 in pitch control based on 2.
・The flow rate control to
The pitch component calculated in step B is input to the roll control section 59, and the flow rate control amount to each proportional flow rate control valve 7 in roll control is calculated based on the gain KRF2 + KR112.

Further, each control W amount calculated by the pitch control section 58 and the roll control section 59 is reversed in sign for each wheel 2..., that is, the vehicle height displacement speed signal calculated by the differentiator 46... Y... is reversed so that its sign is opposite, and then the pitch and roll control amounts for each wheel 2... are added, respectively, and each wheel 2... in control system B is inverted. Flow rate signal GFR2* Qr to the proportional flow control valve 7...
T? + QRR2+ QR12 is obtained.

The control system C includes a vertical acceleration sensor 24 (24FR,
24FL, 24R) output GFR, GFL.

A bounce component calculation unit 70 that adds GR and calculates a bounce component of the vehicle, and the left and right front wheels 2FL.

Vertical acceleration sensor 24FL installed above 2FH
, the sum of 1/2 of the output of 24FH (GF*+GFL)/
a pitch component calculating section 71 that calculates the pitch component of the vehicle by subtracting the output of a vertical acceleration sensor 24R provided at the center of the left and right rear wheels 2RL and 2RR in the vehicle width direction from 2; and a vertical acceleration sensor for the right front wheel 2FH. A roll component calculation unit 72 that calculates the roll component of the vehicle by subtracting the output of the vertical acceleration sensor 24FL of the left front wheel 2FL from the output of the left front wheel 2FL, and a bounce component calculation value calculated by the bounce component calculation unit 70 are input, A bounce control unit 73 that calculates the control amount of hydraulic oil to each proportional flow rate control valve 7 in bounce control based on the gain 83, and a pitch component calculation unit 7.
A pitch control unit 7 receives the calculated value of the pitch component calculated by 1 and calculates the control amount of hydraulic oil to the proportional flow rate control valve 7 in pitch control based on the gain KP3.
4, and the calculated value of the pitch component calculated by the roll component calculation unit 72 are input, and the gains KRF3 and KRR3 are input.
In this embodiment, the bounce control section 73 is configured with a roll control section 75 that calculates the control amount of hydraulic oil to the proportional flow control valve 7 in roll control based on the above-mentioned bounce control section 73.
．． By changing the respective gains Kaz, Kp3°KBF4, and KRR3 in the P2CH control section 74 and the roll control section 75, each control amount can be adjusted and changed. This is what makes up the .

4, the bounce control unit 73. Pitch control section 7
4 and the control amount calculated by the roll control unit 75, its sign is reversed for each wheel 2..., and then bounced for each wheel 2....

A flow signal GF to each proportional flow control valve 7, which is outputted from the control system C by adding up each control amount of pitch and roll.
R3+GFL3+QRR3, Q[3] is obtained.

In addition, the vertical acceleration sensor 24... and the bounce component calculation section 70... Pitch force calculation unit 71 and roll component calculation unit 72
Dead band devices 90... are provided between the vertical acceleration sensors 24... and the vertical acceleration signals G (GFR, GFL, GR) output from the vertical acceleration sensors 24... These vertical acceleration signals G . It is also possible to adjust the control amount by changing the dead band XG of this dead band device 90, and therefore, this dead band device 90 also has a function as a sensitivity adjustment section.

The control system includes the left and right front wheels 2FL, 2FH hydraulic cylinder 3FL, and 3FR hydraulic sensor 22FL.

The oil pressure detection signals PrR and Prt of 22FR are input.

Difference in oil pressure in the oil pressure chambers 3c of the hydraulic cylinders 3 of the left and right front wheels 2FL and 2FH, PFR-PFL, and their addition value P
FR+P The ratio Pf to FL is Pt = (PFR
-PFL) / (PFR+PFL), and this oil pressure ratio Pf is -ωL < with respect to the threshold oil pressure ratio ωL.
If Pf <ω[, the calculated hydraulic pressure ratio Pf is output as is; on the other hand, if Pr<-ωL or Pt>ω, the threshold hydraulic pressure ratio -ω[or ωL is output. Front wheel side hydraulic pressure ratio calculating section 101. And, similarly, the left and right rear wheels 2RL, 2RR hydraulic cylinders 3RL.

Oil pressure detection signals PRR and PRL are input from the oil pressure sensors 22RL and 22RR of 3RR, and the left and right rear wheels 2RL, 2
Difference in oil pressure between hydraulic chambers 3c of hydraulic cylinders 3RI and 3RR of FIR PRR-PRL and their sum PRR+PR
The ratio Pr to L is Pr = (PRR-PRL) / (PRR+PRL
) and a rear wheel side hydraulic pressure ratio calculation unit 102,
The warp control unit 100 is provided, which multiplies the oil pressure ratio Pr on the rear wheels 2RL and 2RR side by a predetermined value based on the gain ωF, and then subtracts this from the oil pressure ratio Pf on the front wheels 2FL and 2FR sides. The output is multiplied by a predetermined value using the gain ω^, and then the gain ω is applied to the front wheels 2FL and ZFR.
Multiply by a predetermined value using C, and then reverse the left and right wheels 2 so that the control amount of hydraulic oil supplied to each wheel 2 is opposite in positive and negative, and then set the control system. Flow rate signals QFRI, QrLa to each proportional flow control valve 7...
.

QRR4 and QRLI are obtained. The flow rate signal (QFRI + QFLI) to each proportional flow control valve in each control system obtained as above.

QRRI, QRLI, QFR2+ QFL
2 + QRR2+QRL2. QF fee 3, QF
L3 + Q! lR3, QRL3.

QFRJ + QFL4 + QIIRJ + QRL
4) is each wheel 2 (2FR, 2FL, 2RL, 2R
R), and the final total flow signals QFR, QFLI Q**+ QRL to each proportional control valve are obtained.

Table 1 shows an example of the control gain map described above used in each control system A, B, C, and D stored in the control unit 2o, and shows seven modes depending on the operating state. It is set.

Table 1 (L = liters/minute) In Table 1, mode 1 indicates the value of each control gain during a predetermined time (60 seconds in the example) after the engine has stopped, and mode 2 indicates the value of each control gain when the ignition switch is turned on. The value of each control gain in a state where the vehicle is stopped and the vehicle speed is rOJ,
Mode 3 is the value of each control gain in a straight-ahead state where the vehicle's lateral acceleration G is 0.1 or less, and mode 4 is each control gain value in a slow turning state where G is more than 0.1 and 0.3 or less. gain value,
Mode 5 is the value of each control gain in a small turning state where G exceeds 0.1 and 0.3 or less, Mode 6 is the value of each control gain in a sharp turning state where G exceeds 0.5, are shown respectively. Mode 7 is selected in place of mode 4 when the reverse roll mode is selected by a roll mode selection switch (not shown) and in a slow turning state where the lateral acceleration G of the vehicle is more than 0.1 and less than 0.3. When the vehicle speed exceeds 120 km/h, the mode is automatically switched to mode 4 even if the reverse roll mode is selected.

In Table 1, QMAX is the proportional flow control valve 7 of each wheel 2...
... is the maximum flow rate control amount supplied to..., PNAX is the maximum pressure in the hydraulic chamber 3c of the hydraulic cylinder 3..., and
Ps+M indicates the minimum pressure in the hydraulic chamber 3c of the hydraulic cylinder 3, respectively. PNAX is hydraulic cylinder 3.
In order to prevent hydraulic oil from flowing back into the accumulator 11 from the hydraulic chambers 3c of the hydraulic cylinders 3...・They are set so that they will not be damaged due to overstretching.

Note that the column indicated by an arrow in the table indicates that the control gain is set to the same value as the numerical value indicated by the arrow.

In Table 1, each control gain is set so that, with the exception of mode 7, the larger the mode number is, the more the suspension control is performed with emphasis on driving stability.

The control unit) 20 selects a mode according to the driving state, sets each control gain to the values shown in Table 1, and performs suspension control.
After the engine is stopped (c), as shown in the flowchart of FIG. 4, control is performed by setting each control gain to the value of mode 1 shown in Table 1.

That is, first, detect ON-OFF of the ignition,
If it is rONJ, normal control (that is, control by selecting one of modes 2 to 7) is performed, and rOFF J
At this time, each control gain is set to a value determined for mode 1, and control is performed until a predetermined time (60 seconds) has elapsed or the main pressure becomes below a predetermined value (lOOkgf/cm2).

When either one of the conditions is met, the fail-safe valve 14 is opened to return the oil stored in the accumulator 11 to the reserve tank 19, and the control is stopped.

Here, in mode 1, vertical acceleration signals G (GFR, GFL) from the vertical acceleration sensors 24...

Each gain value (KO2, K
P3. KRF3, KRR3) are set low to reduce the sensitivity to the signals, thereby slowing down the control.

That is, the bounce component calculation unit 7 in the bounce control unit 73
The gain for the bounce component calculation value due to 0 is 83. Gain KP3 for the pitch component calculation value by the pitch component calculation unit 71 in the pinch control unit 74. and a gain KRF3 for the pitch component calculation value by the roll component calculation unit 72 in the roll control unit 75. KRR3, respectively decreased (KB3 = 5, KP3 = 5.KRF3 = 5.KR
R3=5), and the dead band device 90
Increase the dead band XG of

As a result, the amount of control output from the control system C for bounce, pitch, and roll is reduced, and therefore, some shaking caused by opening/closing the door or raising and lowering the occupant is allowed, and the consumption of hydraulic pressure is reduced.

As a result, the controllable time is extended.

In addition, in mode 1 in this embodiment, each vehicle height displacement sensor 23 . . . of the control system A and the bounce component calculation unit 50 .
The dead band XH of the dead band device 6o provided between the pitch component calculating section 5 and the roll component calculating section 52.
is set to high < (XH=5) to make the control by the control system A dull, and the gain KP2 for the pitch component calculated by the pitch component calculation unit 57A in the pitch control unit 58 of the control system B is set to rOJ. (When stopping, which is the stage before turning off the ignition, it is controlled by mode 2, and in this mode 2, KP2 = 0.05, so
This is to clear this. Furthermore, in mode 2, KP2=
The reason why it is set to 0.05 is to prevent a so-called squat dive, where the vehicle body momentarily sinks when selecting the D range in a vehicle with an automatic transmission.

Furthermore, by adjusting the opening degree of the proportional flow rate control valve 7, the maximum control flow rate indicated by QM^X in the table can be adjusted to 184 mm.
The speed is reduced from 1/sin to 5/min. By restricting the flow rate in this way, it is also possible to extend the control time.

After the control is stopped and the fail-safe valve 14 is opened, check whether the main pressure has decreased using the discharge pressure gauge 21, and if the main pressure has not decreased, it is assumed that the fail-safe valve 14 is malfunctioning. It is stored in the storage device that is installed.

[Effects of the Invention] As described above, according to the vehicle suspension device according to the present invention, control can be reliably continued for a predetermined period of time even after the engine has stopped, and malfunctions caused by changes in load after the engine has been stopped can be prevented. It is.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram equivalent to a side view of an entire vehicle to which an embodiment of the present invention is applied, Fig. 2 is a circuit diagram of a hydraulic circuit, and Figs. 3 (A) and (B) are a diagram of a suspension characteristic control device. The block diagram, FIG. 4, is a control flowchart. 20... Control unit (control device) 24
(24FR, 24FL, 24R)... Vertical acceleration sensor (vertical acceleration detection means) 73... Bounce control section (
Sensitivity adjustment section) 74...Pitch control section (sensitivity adjustment section) 7
5... Roll control section (sensitivity adjustment section) 90... Dead band device (sensitivity adjustment section)

Claims (1)

[Claims] This is a suspension system installed between the wheels of a vehicle and the vehicle body, in which a control device supplies fluid to fluid cylinders installed between each wheel and the vehicle body based on detection signals from various sensors. In an active suspension device that controls supply and exhaust, the control device includes a vertical acceleration detection means for detecting vertical vibration, and the control device includes a sensitivity adjustment unit capable of adjusting a detection signal from the vertical acceleration detection means, and after the engine is stopped. The suspension device for a vehicle is characterized in that the control device is configured to perform control to reduce the sensitivity of the sensitivity adjustment section.