JPS63258209A - Suspension for vehicle - Google Patents

Abstract

PURPOSE:To make the control conformed to a body attitude so as to be attainable by detecting displacement from a reference space between springing and unspringing at each wheel, discriminating the body attitude in composing the displacement signal, and controlling the feed and discharge of working fluid to an actuator of a suspension according to the body attitude. CONSTITUTION:Displacement from a reference space between springing and unspringing is detected by the displacement sensor 62 set up in each wheel and inputted into a control unit 60 which composes displacement signals of respective wheels to be inputted into this control unit 60 and converts it into a mode signal showing four body attitudes of bound, pitch, roll and warp. And, it operates a mode target flow rate in each mode and distributes the target flow rate of each mode, controlling a flow control valve 48 of each wheel, thus it regulates an actuator 46. For example, controlling it soft to the bound but hard to the roll, respectively. Thus, the control conformed to the body attitude is securable.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a suspension device for a vehicle.

(Prior Art) A common vehicle suspension device is one that combines a spring and a shock absorber. Also,
As a means for providing a vehicle height adjustment device to a suspension device, there is a method using a gas spring, as shown in Japanese Patent Publication No. 14365/1983. In this type of device,
Dynamically, F=kx+Ci where F: load acting on the suspension device X: displacement of the suspension device: displacement speed of the suspension device: spring constant C: damping coefficient.

In other words, the characteristics of the suspension device are the spring constant (k
) and damping coefficient (C), and therefore the spring constant (k) and damping coefficient (C) are set in order to obtain desired characteristics.

However, in a suspension device in which the spring constant (k) and damping coefficient (C) are set to predetermined values, the characteristics are fixed. By changing the orifice diameter of the quad absorber,
As a result, suspension devices with variable characteristics have been put into practical use.

On the other hand, the specification identified by European (EPC) application publication number O114757 includes sprung (vehicle body) and unsprung (wheel)
A suspension device has been proposed in which an actuator is installed between the actuator and the supply and discharge of working fluid to the actuator is feedback-controlled using the above formula: F=kx+C as a control law.

That is, detect F and moxibustion, and based on the above control formula,
This is to find the target displacement xd of the cylinder device. In other words, a system is basically adopted in which each wheel is individually controlled, and as a result, the suspension of all wheels is controlled.

(Problem to be Solved by the Invention) However, when looking at changes in the posture of the vehicle body, it is undesirable that, for example, the vertical vibration (bound) of the vehicle body and the rolling motion are controlled in the same way. , it is necessary to be soft against bouncing in order to improve riding comfort, and on the other hand, it is desirable to be hard in order to suppress rolling.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a suspension device for a vehicle that allows suspension control to be performed in more detailed manner according to the posture of the vehicle body.

(Means and operations for solving the problem) The present invention is designed to determine the suspension characteristics of each wheel by considering the balance of each wheel. In other words, the suspension system for each wheel is based on the recognition that it is just one component of all wheels, and all wheels are controlled comprehensively and comprehensively.

Specifically, assuming a vehicle suspension system that supplies and discharges working fluid to an actuator installed between a sprung mass and an unsprung mass, this is provided for each wheel, and the sprung mass and unsprung mass are connected to each other. a displacement detecting means for detecting a displacement from a reference interval between the wheels; and a mode converting means for receiving a signal from the displacement detecting means, synthesizing the displacement of each wheel, and converting the result into a vehicle body mode signal representing the vehicle body posture; mode-compatible adjustment means that receives a signal from the mode conversion means and adjusts the supply and discharge of working fluid to each actuator according to the vehicle body posture;

This is assumed to be equipped with the following.

With this configuration, the displacement signal from each wheel is first converted into a mode signal that represents the attitude of the vehicle body,
Suspension control can be performed according to the vehicle body posture corresponding to this mode signal.

Furthermore, since the displacement detection means arranged on each wheel is designed to detect the displacement from the reference interval between the sprung mass and the unsprung mass, the control system described above is a closed system as a result. It also has a feedback function. Therefore, regardless of whether the vehicle is running or stopped, a vehicle height adjustment function is added, and suspension characteristics can be controlled while maintaining this vehicle height adjustment function.

When looking at the present invention from the perspective of vehicle height adjustment, this means that the vehicle height adjustment function can be strengthened or weakened depending on the attitude of the vehicle. This vehicle height adjustment function is also strong or weak, and strengthening the vehicle height adjustment function means that the suspension characteristics are hard, and weakening the vehicle height adjustment function means that the suspension characteristics are soft.

(Example) Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, l is a suspension device, and in this figure, only one wheel is shown to represent all the wheels.

The suspension device 1 has an actuator C installed between a vehicle body A and each wheel B, and a piston 4 is slidably inserted into a cylinder 2 of the actuator C, and a cylinder liquid chamber 6 is inserted into the cylinder 2 of the actuator C.
is defined. The cylinder liquid chamber 6 has oil in the gas spring 8.
The oil passage 10 is connected to the oil passage 10 through an orifice 12.
is provided. The gas spring 8 has a gas chamber 16 defined by a diaphragm 14 as a movable partition wall and a liquid chamber 18, and the liquid chamber 18 communicates with the oil passage 10. The unit 20 consisting of such a combination of the cylinder 2, the gas spring 8, and the orifice 12 has a basic function as a suspension due to the buffering action of the gas spring 8 and the [f action] of the orifice 12.

The characteristics of this pension unit 20 are uniformly determined by the elasticity (spring coefficient) of the gas spring 8 and the throttle resistance of the orifice 12.

On the other hand, an external pipe 22 is connected to the cylinder 2,
Through the supply and discharge passage formed by this external piping 22,
Oil is supplied and discharged into the cylinder 2, that is, into the cylinder liquid chamber 6.

To explain the hydraulic circuit for this cylinder 2,
Reference numeral 30 in the figure is a pump driven by the engine, and the hydraulic fluid pumped up from the reservoir tank 32 by this pump 30 is supplied to the cylinder 2 through the external pipe 22. A flow control valve 48 consisting of a switching valve 42, a check valve 44, an accumulator 46, and a spool valve is installed in the external piping 22 in order from the upstream side to maintain a constant oil pressure in the circuit.
It is said that the amount of hydraulic fluid that passes per unit time, that is, the flow rate of the hydraulic fluid, is adjusted.

Note that the reference numeral 54 in the figure indicates a reflux passage.

Next, the operation of the above hydraulic circuit will be explained. First, when the flow control valve 48 is closed, the suspension unit 20 exhibits characteristics based on the throttle resistance of the orifice 12 and the elastic modulus of the gas spring 8. That is, the amount of change in the load applied to the cylinder 2 is defined by ΔF, the amount of displacement of the piston 4 is defined by ΔX, the throttling resistance of the rewiring device 12, and the elastic modulus of the gas spring 8. Therefore, the suspension unit 20, which is closed as a system, is defined as follows. , forming a so-called passive (pBssimer) control system.

On the other hand, by supplying and discharging hydraulic fluid to and from the cylinder 2 by opening and closing the flow rate control valve 48, the suspension characteristics are made variable, and therefore the suspension unit 20 is opened as a system.

A so-called active (act 1ve) control system is formed.

The flow rate control valve 48 is actuated by a control signal from a control unit 60 composed of a microcomputer, and in order to generate this control signal, the control unit 60 receives a signal from a displacement sensor 62 disposed at each wheel. is input.

Here, the displacement sensor 62 is designed to detect a displacement from a reference Flll distance (reference value) between the sprung portion and the unsprung portion. That is, unsprung displacement X1, sprung displacement x2
Then, the distance between the two is X=X1-X2 Toso(
7) A difference Δx=X−Xo from the reference value Xo is detected.

The signals from each of the circumferential displacement sensors 62 are combined and converted into mode signals representing the four vehicle body postures of bounce, pitch, roll, and warp, and after calculating the mode target flow rate for each of the seven modes, The target flow rate for each mode is distributed to determine the target flow rate for the flow rate control valve 48 for each wheel. If such a control system is represented by a block diagram, it is as shown in Figure 1542. In this figure, the circuit that calculates the mode target flow rate is based on the transfer function GB(S).
, GP(S), GR(S), and Kw. Here, GB(S) is the bounce, GP(S) is the pitch, and GR(
S) is for roll, and Kw is for warp.

Load change amount for ΔF Niji cylinder 2 A: Pressure receiving surface of piston 4 Fluid pressure change in ΔP Niji cylinder 2 ΔPC: Amount of pressure change in liquid spring 8 Squeezing pressure at ΔPN niorifice 12 Amount of change in difference Squeezing resistance of KN Niorifice 12 Oil liquid passing through QN niorifice 12 flow rate of ΔvC two-fluid fluid 8 volume change meter KC: elastic modulus of fluid spring 8 Ke: Sensor characteristics of pressure sensor 62 Δe: Output of pressure sensor 62 The current output from the ΔXX open control circuit 66 Corresponds to the target flow rate of the quantity control valve 48 control current Qv: of oil flowing through the flow control valve 48 flow rate ΔVL Change amount of oil in Niji cylinder 2 △V Niji cylinder 2 (cylinder liquid chamber 6) volume change meter ΔX: Displacement amount of piston 4 FR: Right front wheel FL: Left front wheel RR: Right rear wheel RL: Left rear wheel.

Next, detection of the mode representing the vehicle body posture is performed as follows.

(1) Bound Bound is a posture change mode in the vertical direction of the vehicle body, so the movement directions of all four wheels are the same. From this, detection of bounds is based on the following formula.

ΔeB = ΔeFR+Δ eFL+ΔeRR+ Δ
eRL where, ΔeB: Bound mode detection value ΔeF
R: Output Δe of the right front wheel displacement sensor 62FR FL: Output Δe of the left front wheel displacement sensor 62FL RR: Output Δe of the right rear wheel displacement sensor 62RR RL: Output of the left rear wheel displacement sensor 62RL (2) Pitch pitch is a posture change in which the direction of movement of the front part of the vehicle body and the direction of movement of the rear part of the vehicle body are opposite directions (movement of front rounding or face down). Therefore, pitch detection is based on the following formula.

ΔeP = (ΔeFR+ΔeFL) −(ΔeR
R+ Δe RL) e e meeting (24) Here, ΔeP: Pitch mode detection value (3) Roll Roll is a posture change in which the movement direction of the right side of the vehicle body and the interlocking direction of the left side of the vehicle body are opposite directions (vehicle body longitudinal direction). (rotational motion about an axis extending to ), and therefore, roll detection is based on the following equation:

ΔeR= (ΔeFR−ΔeFL)+(Δe RR−
Δe RL) * * m (25) Here, Δ
eR: Roll mode detection value (4) The torsional moment acting on the warp vehicle body has components in the same direction for the front right wheel (FR) and rear left wheel (RL), and in the opposite direction for other combinations (FL, RR). becomes. From this, the detection of the warp moment is based on the following formula.

Δe 11 = (Δe FR−Δe FL) −(Δe
e RR - Δe RL) Here, Δew: Warb mode detection value ΔeB, ΔeP among mode signals representing each motion mode of bounce, pitch, roll, and warp.

ΔeR is the transfer function GB(S), GP(S), GR(S
), while ΔeW is processed by an arithmetic circuit indicated by a constant KW to determine the mode target flow rate (ΔiB, ΔiP, ΔiR, ΔiW) in the mode.

The target flow rates ΔiB, ΔiP, etc. in each mode obtained in this way are distributed using the same method as the above mode analysis, and converted into target flow rates Δ1FR1ΔiFL, Δ1RR1ΔiRL for each flow rate control valve 48FR, FL, RR, RL. be done.

That is, the bound target flow rate ΔiB is
The pitch target flow rate ΔiP is distributed with the same sign between the front wheels and the rear wheels, and the roll target flow rate Δf
R is distributed between the right wheel and the left wheel under opposite signs, and the warp target flow rate ΔiW is distributed under opposite signs for each combination of wheels located diagonally on the vehicle body. This is the target flow rate of each wheel Δ1ER1Δi FL, Δi RR, ΔiRL
From the side, it is expressed by the following formula.

Δf FR=ΔiB+ΔiP+ΔiR+ΔiWΔ1FL
=(ΔiB+Δ1P) −(ΔiR+ΔiW) Δ1RR=(ΔiB−ΔiP) +(ΔiR−ΔiW) Δ1B=(ΔiB−Δ1P) −(ΔiR−Δi buttocks) And the transmission coefficient i1 G B(S ), G for each mode
The gains of P(S), etc. are set to be different, and here, the gain of transfer coefficient GB(S) for bounce is set small, and the gain of transfer coefficient GP(S), GR(S) for pitching mode and roll mode is set small. ) is considered to be a large gain. Also, the transfer coefficient Kw for warp mode
The gain is set to zero when the vehicle is stopped.

As a result, soft suspension characteristics are obtained against bouncing, which is the vertical movement of the vehicle body, to improve ride comfort, while hard suspension characteristics are obtained against rolls, etc., resulting in the vehicle's posture. In addition, since the warp mode is set to zero while the vehicle is stopped, that is, the control corresponding to warp is stopped, so twisting of the vehicle body can be prevented.

Such control is performed by adding Δ to the displacement signal from the displacement sensor 62.
This is done based on X, and this ΔX is subjected to reference value feedback control.

In other words, the vehicle height is constantly being adjusted.

Therefore, while the vehicle is stopped, the vehicle height is controlled, while while the vehicle is running, the vehicle height is adjusted to maintain the balance of the four wheels, and the suspension characteristics are efficiently controlled. .

Although one embodiment of the present invention has been described above, the present invention is not limited to this and includes the following modifications.

(Depending on the driving condition of the vehicle, the transfer functions GB(S), G
The gains of P(S) and GR(S) may be changed. For example, the vehicle speed and the steering angle may be detected, and when both the vehicle speed and the steering angle are large, the gain of GR(S) may be made larger than when the vehicle speed and the steering angle are small.

(2) The oil to the cylinder 2 may be adjusted by hydraulic pressure.

(Effects of the Invention) As is clear from the above explanation, according to the present invention, the suspension of all wheels is controlled according to the vehicle body posture, so for example, the suspension is soft against bounces and hard against rolls. In this way, more differentiated control becomes possible.

Furthermore, since it also has a feedback function, it is possible to perform suspension control with a vehicle height adjustment function without having to take the trouble to add feedback control separately.

[Brief explanation of drawings] FIG. 1 is an overall system diagram of the embodiment, FIG. 2 is a block diagram of the embodiment. 1: Suspension device 2 Niji Linda 8: Gas spring 30: Pump 46: Accumulator 48-Rate adjustment valve 60: Control unit 62: Displacement sensor GB(S): Bound transfer function GP(S): Pitch transfer function GR(S): Roll transfer function KW: Warb transfer coefficient

Claims (1)

[Claims] (1) In a vehicle suspension system that supplies and discharges working fluid to an actuator installed between the sprung mass and the unsprung mass, a standard is provided for each wheel to determine the standard between the sprung mass and the unsprung mass. a displacement detection means for detecting displacement from the interval; a mode conversion means for receiving a signal from the displacement detection means, synthesizing the displacement of each wheel, and converting it into a vehicle body mode signal representing a vehicle body posture; A suspension device for a vehicle, comprising: mode-compatible adjustment means for adjusting the supply and discharge of working fluid to each actuator according to the vehicle body posture in response to a signal from the vehicle body.