JPH01103525A - Suspension for vehicle - Google Patents

Abstract

PURPOSE:To aim at improvement in running stability by selecting damping force of each shock absorber so as to be tightened according to the detected pressure of a fluid spring chamber for rear-wheel side suspension units after level controlling. CONSTITUTION:A control unit 36 feeds or exhausts to or from a fluid spring chamber 3 of respective suspension units FS1, FS2, RS1, RS2 so as to become a desired level by each signal of both front and rear level-control sensors 34F, 34R. Here mean pressure in the fluid spring chamber 3 of these suspension units RS1, RS2 at the rear-wheel side is detected by a pressure sensor 45, and according to this pressure, a step motor 6 is driven and damping force of each shock absorber 1 is selected from the soft side to the medium, hard side by a valve 5a. Running stability is thus improved, especially any possible dancing of a car body at the time of loading on a car is restrainable.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention is a suspension system for a vehicle having a vehicle height adjustment function, in which the suspension is fixed so as to maintain a constant damping ratio when the vehicle is loaded. The present invention relates to a vehicle suspension device that switches damping force.

(Prior art) In a suspension system with a vehicle height adjustment function using an air spring chamber, when the vehicle is empty, the load W is light (and the internal pressure Pa of the air spring chamber is also low. In this way, the spring constant of the air spring chamber is It is generally expressed as Ka - Pa Ao Av /Va, and the internal pressure P
The constant that increases in proportion to a increases.

(Problems to be Solved by the Invention) On the other hand, when the vehicle is loaded, the load W also increases, and the internal pressure of the air spring chamber also increases, so the critical damping force Cc increases. Here, the ratio (damping ratio) between the damping force C of the shock absorber and the critical damping force Cc is expressed as C/Cc-C/2J1ball-. Here, ■ is the spring constant (load)/g.

Here, if the damping force C of the shock absorber remains constant even if the critical damping force Cc increases, then the damping ratio C/
Since Cc decreases, there is a problem that the fit on the spring surface deteriorates.

The present invention has been made in view of the above points, and its object is to change the damping force of the shock absorber to a large extent according to the internal pressure of the air spring chamber when the vehicle height adjustment is completed. To provide a suspension device for a vehicle that can keep Cc constant and improve running stability, especially suppressing the movement of the vehicle body when loaded.

[Structure of the invention] (Means and effects for solving the problem) Vehicle height can be adjusted by supplying and discharging air to fluid spring chambers provided in each suspension unit that supports each wheel. In a vehicle suspension system, a damping force switching means for switching the damping force of each suspension unit into multiple stages, a pressure detection means for detecting the pressure in a fluid spring chamber on the rear wheel side, and a pressure detection means for detecting the pressure detected by the pressure detection means. The suspension device for a vehicle is provided with a damping force switching means for increasing the damping force of each suspension unit by driving the switching means accordingly.

(Example) An example of the present invention will be described below with reference to the drawings. In Figure 1, FSl is a suspension unit for the left front wheel, FS2 is a suspension unit for the right front wheel, R81 is a suspension unit for the left rear wheel, and RS2 is a suspension unit for the left front wheel.
is the suspension unit for the right rear wheel. Each of these suspension units FSI, FS2. RSI, RS
Since the suspension units 2 have similar structures, the suspension units will be described using the reference numeral S, unless the suspension units for the front wheels and those for the rear wheels or for the left wheels and those for the right wheels are explained separately.

The suspension unit S includes a shock absorber 1. This shock absorber 1 includes a cylinder attached to a wheel side, and a piston rod 2 having a piston slidably fitted in the cylinder and having an upper end supported on the vehicle body side. Further, the suspension unit S is provided on the upper part of this shock absorber 1.
An air spring chamber 3 having a vehicle height adjustment function is provided coaxially with the piston rod 2. This air spring chamber 3 is partially formed by a bellows 4, and by supplying and discharging air to and from this air spring chamber 3 through a passage 2a provided in the piston rod 2, the vehicle height can be increased or It can be lowered.

Further, a control rod 5 is disposed inside the piston rod 2 and has a valve 5a at its lower end for adjusting the damping force. The control rod 5 is the piston rod 2
It is rotated by an actuator 6 attached to the upper end of the valve 5a to drive the valve 5a.

By rotating the valve 5a, the damping force of the suspension unit is set to three levels: hard, medium, and soft.

The compressor 11 compresses atmospheric air taken in from the air cleaner 12 and supplies it to the high pressure reserve tank 15a via the dryer 13 and check valve 14. In other words,
Since the compressor 11 compresses the atmospheric air taken in from the air cleaner 12 and supplies it to the dryer 13, compressed air dried by silica gel or the like in the dryer 13 is stored in the high-pressure reserve tank 15a. The compressor 16 has a suction port connected to a low pressure reserve tank 15b and a discharge port connected to a high pressure reserve tank 15a. Reference numeral 18 denotes a pressure switch that is turned on when the pressure in the low pressure reserve tank 15b exceeds a first set value (for example, atmospheric pressure). When the pressure switch 18 outputs an on signal, the compressor 16 is driven by a compressor relay 17 that is turned on in response to a signal from a control unit 36, which will be described later. As a result, the pressure within the low pressure reserve tank 15b is always maintained below the first set value.

Air is supplied from the high-pressure reserve tank 15a to each suspension unit S as shown by solid arrows in FIG. That is, the compressed air in the high pressure reserve tank 15a is supplied to the air supply flow rate control valve 19, the front air supply solenoid valve 20, the check valve 21, the front left solenoid valve 22. Suspension unit FSI via front useful solenoid valve 23.

Sent to FS2. Similarly, the compressed air in the high pressure reserve tank 15a is supplied to the supply air flow mIIJ control valve 19,
The suspension unit R is connected to the suspension unit R via the rear air supply solenoid valve 24, the air supply solenoid valve 25, the rear water solenoid valve 26, and the rear Ishikawa solenoid valve 27.
81 and R82.

On the other hand, exhaust from each suspension unit S is performed as shown by the broken line arrows in FIG. That is, the compressed air in the suspension units FSI and FS2 is fed into the low pressure reserve tank 15b via the solenoid valve 22.23 and the exhaust direction switching valve 28 consisting of a three-way valve; , exhaust direction switching valve 28, check valve 29, dryer 13
, exhaust solenoid valve 31, check valve 46, and air cleaner 12, and may be exhausted to the atmosphere. Similarly, the compressed air in the suspension units R5I and R82 is supplied into the low pressure reserve tank 15b via the solenoid valves 26, 27 and the exhaust direction switching valve 32, and in the other case, the compressed air is fed into the low pressure reserve tank 15b via the solenoid valves 26, 27 and the exhaust direction switching valve 32. Valve 32, check valve 33, dryer 13, exhaust solenoid valve 31, check valve 4
6 and air cleaner 12, and may be discharged to the atmosphere. Note that a passage is provided between the check valve 29.33 and the dryer 13, which has a smaller diameter than the passage that directly communicates the exhaust direction switching valve 28.32 and the low pressure reserve tank 15b.

In addition, the above-mentioned solenoid valve 22.23°26.2
7.28 and 32, as shown in Figure 2 (A) and (B), the air circulation is as shown by arrow A at 0N (a cloth state), and the air circulation is shown as arrow B when it is OFF (no current). Each allows air circulation. In addition, the air supply solenoid valves 20, 24 and the exhaust solenoid valve 31 are shown in FIGS. 3(A) and (B).
As shown in the figure, when ON (energized state), air circulation is allowed as shown by arrow C, and when OFF (non-energized state), air circulation is prohibited. In addition, when the air supply flow rate control valve 19 is in the off state (not energized), the orifice O as shown in FIG.
Since the air flows through the valve, the air flow rate is small; in the on state (energized), the air flows through the orifice 0 and the large path, as shown in Figure 4 (B), so the air flow rate increases. .

34F is the lower arm 3 of the front right suspension of the vehicle.
5 and the vehicle body to detect the front vehicle height, and 34R is a rear vehicle height sensor installed between the lateral rod 37 of the rear left suspension of the vehicle and the vehicle body to detect the rear vehicle height. It is a sensor. Signals detected by both vehicle height sensors 34F and 34R are supplied to a control unit 36 including a microcomputer.

38 is a vehicle speed sensor built into the speedometer, and supplies a detected vehicle speed signal to the control unit 36. 39 is an acceleration sensor that detects acceleration acting on the vehicle body, and supplies the detected acceleration signal to the control unit 36.

30 is a roll control mode selection switch that selects the roll control mode from SOFT, AUTO, and sport (5 PORTS), and 40 is a steering sensor that detects the rotational speed of the steering wheel 41, that is, the steering angular velocity. 42 is an accelerator opening sensor that detects the depression angle of an accelerator pedal of the engine (not shown). The signals detected by the roll control selection switch 30 and the sensors 40 and 42 are transmitted to the control unit 3.
6.

43 is a compressor relay for driving the compressor 11, and this compressor relay 43 is controlled by a control signal from the control unit 36. 4
4 is a pressure switch that is turned on when the pressure in the high-pressure reserve tank 15a falls below a second set value (for example, 7 kg/aA), and a signal from this pressure switch 44 is supplied to the control unit 36. Then, the control unit 36 controls the pressure switch 18 to be on even if the pressure in the high pressure reserve tank 15a is below the set value and the pressure switch 44 is on, that is, the compressor 1
The compressor 11 is configured to be prohibited from being driven when the compressor 6 is being driven. 45 is a pressure sensor provided in a passage that communicates the solenoid valves 26 and 27 with each other, and is connected to the rear suspension units R81 and R.
The internal pressure of 82 is detected.

In addition, each solenoid valve 19.20.22.2 mentioned above
3.24.26.27.28.31 and 32 are controlled by control signals from the control unit 36.

Next, the operation of the apparatus according to the embodiment configured as described above will be explained. This device has an attitude control function and a vehicle height adjustment function. First, the attitude control function that suppresses attitude changes occurring in the vehicle body will be explained.

When the steering wheel 41 is steered to the right, the vehicle body tends to roll to the left. In response, the control unit 36 turns on the air supply solenoid valve 20.24 for a set period of time, and also turns on the right wheel solenoid valve 23.27.
is turned on, and after the set time has elapsed, the exhaust direction switching valve 32 is turned on. As a result, a set amount of compressed air is supplied from the high-pressure reserve tank 15a to each of the left suspension units FS1 and R81 and the air spring chamber 3, and the right suspension units FS2. R.S.
A set amount of compressed air is discharged from each air spring chamber 3 of No. 2 to the low pressure reserve tank 15b.

This suppresses the displacement of the vehicle body from rolling to the left. In this state, a set amount of compressed air is supplied to each air spring chamber 3 of the left suspension unit FS2, R82, and the right suspension unit FS1
, R81, the state in which a set amount of compressed air is discharged from each air splash chamber 3 is maintained continuously. Then, when the turning operation shifts to straight-line operation and the control unit 36 detects that the steering becomes neutral by the steering sensor 40 or that the lateral acceleration decreases by the acceleration sensor 39, the control unit 36 activates the solenoid valve. 23 and 27 are turned off, and the exhaust direction switching valve 32 is also turned off.

As a result, the air spring chambers of the left and right suspension units are maintained at the same pressure as before the start of control.

On the other hand, when the steering wheel 41 is steered to the left, the vehicle body tends to roll to the right. In response, the control unit 36 turns on the air supply solenoid valve 20.24 for a set period of time, and also turns on the left wheel solenoid valve 22.
．． 26 is turned on, and after the set time has elapsed, the exhaust direction switching valve 32 is turned on. As a result, the right suspension unit FS2. A set amount of compressed air is supplied from the high pressure reserve tank 15a to each air spring chamber 3 of RS2, and the left suspension units FS1 and R
A set amount of compressed air is discharged from each air spring chamber 3 of 8I to the low pressure reserve tank 15b.

This suppresses the displacement of the vehicle body from rolling to the left. Thereafter, the control is performed in the same manner as when the steering wheel 41 is turned to the right as described above.

Next, a description will be given of attitude control in the case of suppressing a nose dive in which the front part of the vehicle body sinks due to negative acceleration acting on the vehicle body when the brake is activated.

When the acceleration sensor 39 detects that negative acceleration in the longitudinal direction of the vehicle exceeds a set value, such as when the brakes are applied, the control unit 36 turns on the air intake solenoid valve 20 for a set time, and turns on the rear wheel. The solenoid valves 26 and 27 are turned on, and after the set time has elapsed, the exhaust direction switching valve 32 is turned on. As a result, the front wheel suspension unit FS1,
A set amount of compressed air is supplied from the high pressure reserve tank 15a of FS2, and a set amount of compressed air is discharged from the rear wheel suspension units R3I and R32 to the low pressure reserve tank 15b. In this way, the nose dive is suppressed. This state continues until the negative acceleration weakens.

Then, when the acceleration sensor 39 detects that the negative acceleration has weakened, the control unit 36 turns on the air intake solenoid valve 22.23 for a set period of time, and turns on the rear wheel solenoid valve 26.2.
Turn off 7. As a result, a set amount of compressed air is discharged from the front wheel suspension units FS1 and FS2 to the low pressure reserve tank 15b, and the high pressure reserve tank 1 is discharged to the rear wheel suspension units RSI and R32.
A set amount of compressed air is supplied from 5a. In this way, each air spring chamber of each suspension unit S is returned to the state before the start of control.

Next, a description will be given of attitude control in the case of suppressing a drift, in which the front part of the vehicle body rises and the rear part of the vehicle body sinks due to acceleration acting on the vehicle body when the vehicle starts and accelerates. When the accelerator opening sensor 43 or the acceleration sensor 39 detects that the vehicle is rapidly accelerating, the control unit 36 turns on the air intake solenoid valve 24 for a set period of time, turns on the front wheel solenoid valves 22 and 23, Further, after the set time has elapsed, the exhaust direction switching valve 32 is turned on. As a result, a set amount of compressed air is discharged from the front wheel suspension units FSI and FS2 to the low pressure reserve tank 15b, and a set amount of compressed air is supplied from the high pressure reserve tank 15a to the rear wheel suspension units RSI and RS2. . In this way, the above-mentioned scattering is suppressed. This state continues until the acceleration weakens. Then, when the control unit 36 detects that the sudden acceleration has weakened by the accelerator opening sensor 42 or the acceleration sensor 39, the control unit 36 controls the intake solenoid valve 20 and the rear wheel solenoid valve 26. .27 is turned on for a set time, and the front wheel solenoid valves 22 and 23 are turned off. This results in
A set amount of compressed air is supplied from the high pressure reserve tank 15a to the front wheel suspension units FS1, FS2, and the rear wheel suspension units Rs1, R8.
A set amount of compressed air is discharged from 2 to the low pressure reserve tank 15b. In this way, each air spring chamber of each suspension unit S is returned to the state before the start of control.

Incidentally, the vehicle height adjustment is performed by supplying/exhausting air to and from the air spring chambers of each suspension unit until the vehicle height detected by the vehicle height sensor 34F (34R) reaches the target vehicle height. When such vehicle height adjustment is completed, the process shown in FIG. 5 is performed. First, the rear internal pressure is read by the pressure sensor 45 that detects the internal pressure of the rear suspension unit (step Sl). Then, it is determined whether the vehicle height adjustment has been completed (step S2), and if the vehicle height adjustment has been completed, the average value of the rear internal pressure read in step S1 is calculated (step S2). S3). Then, in steps 84 to S6, the internal pressure calculated in step S3 and the internal pressures A, B, C (C<
B<A) is compared. Then, if [internal pressure > AJ, the damping force of the shock absorber is I\-de (IIAR
D), [If B≦Internal pressure<AJ, the damping force of the shock absorber is set to medium (MED), [If C≦Internal pressure<BJ, the damping force of the shock absorber is set to medium (MED). If the internal pressure < CJ, the damping force of the shock absorber is set to soft (5OFT).
0). Thereafter, the actuator drive Luzhin is driven, the actuator 6 is driven, and the above steps 87 to S
The damping force of the shock absorber is set to the damping force set in step 10.

In this way, the damping force of the shock absorber is switched according to the rear internal pressure as shown in Fig. 6, and the damping ratio C/C of the shock absorber is changed as shown by a in the figure.
c can be kept constant, and the movement of the vehicle body when loaded can be suppressed.

[Effects of the Invention] As detailed above, according to the present invention, the damping force of the shock absorber can be switched so that the damping ratio C/Cc is constant according to the rear internal pressure when the vehicle height adjustment is completed. According to
It is possible to provide a suspension device for a vehicle that can improve running stability, especially suppressing the movement of the vehicle body when the vehicle is loaded.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a vehicle suspension device according to an embodiment of the present invention, FIG. 2 is a diagram showing a three-way valve in a driven state and a non-driven state, and FIG. 3 is a diagram showing a solenoid valve in a driven and non-driven state. FIG. 4 is a diagram showing the actuation and non-driving states of the intake air flow rate control valve, FIG. 5 is a flowchart showing the operation of an embodiment of the present invention, and FIG. FIG. 3 is a diagram showing set values of damping force of a shock absorber. 6...Actuator, 15a...High pressure reserve tank, 15b...Low pressure reserve tank, 19...Air supply flow rate control valve, 22.23.26.27...Solenoid valve, 36...Control unit, 45
...Pressure sensor. Applicant's agent Patent attorney Takehiko Suzue 1 ToB Figure 2 (A) (B) Figure 3 Figure 4

Claims (1)

[Claims] In a vehicle suspension system that can adjust vehicle height by supplying and discharging air to fluid spring chambers provided in each suspension unit that supports each wheel, the damping force of each suspension unit can be switched in multiple stages. a damping force switching means; a pressure detection means for detecting the pressure of a fluid spring chamber on the rear wheel side; and a damping force of each suspension unit is increased by driving the switching means in accordance with the pressure detected by the pressure detection means. A suspension device for a vehicle, comprising a damping force switching means.