JPH01202510A - Suspension device - Google Patents

Abstract

PURPOSE:To improve controllability and comfortableness, in a suspension provided with a shock-absorber having variable damping force, by detecting the magnitude of disturbance of pavement during travel and varying the damping force of the shock-absorber. CONSTITUTION:Variation of vehicle height due to variation of pavement condition or load is taken out as a rotary amount of the shaft of a torsion bar 18, then it is transmitted through a link mechanism 19 to a vehicle height sensor 20. The vehicle height sensor 20 provides a vehicle height detection signal to a control unit 24 based on the rotary amount. The control unit 24 obtains a difference of vehicle height during when the vehicle is empty and when the vehicle is traveling and operates the variation of the difference thus providing a control signal for the damping force of shock-absorbers 2R, 2L, 3R, 3L. By such arrangement, control can be made with the magnitude of pavement disturbance being considered, resulting in the improvement of vibration suppressing performance and comfortableness.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a suspension device, and particularly to a suspension device equipped with a variable damping force type shock absorber.

(Prior Art) In recent years, as demands for vehicles have become more sophisticated, there has been a tendency for higher levels of improvement in ride comfort and handling stability to be desired.

In order to meet such demands, suspension devices have already been put into practical use that automatically switch the damping force of a shock absorber according to road surface conditions, steering wheel operation, and vehicle speed.

This type of suspension device is equipped with a shock absorber that can switch the damping force to three levels: soft "S," medium "M," and hard "H," and the damping force can be varied according to road conditions and vehicle conditions. For example, in bottoming control to reduce pitching when going over bumps or steps on the road, if the vehicle height changes by more than a predetermined value, -
After a certain period of time, switch the damping force of each front shock absorber, and after a certain period of time, switch the rear shock absorber to the high damping side (H" or "M"), and then after a certain period of time,
Control is performed to return the damping force to the low damping side ("S").

(Problem to be Solved by the Invention) However, in such conventional suspension devices, changes in vehicle height are judged in binary terms by comparing them with a predetermined reference vehicle height, and changes in the vehicle height are determined in binary terms by comparing them with a predetermined reference vehicle height, and the change in vehicle height is determined in a binary manner by comparing the change in vehicle height with a predetermined reference vehicle height. Since both the switching time and the subsequent time for returning to the low damping side were set to a fixed, predetermined time, it is difficult to believe that the damping force is switched to the appropriate damping force according to changes in the road surface, vehicle body, etc. I couldn't necessarily say that. For example, depending on changes in the load or the size of road surface protrusions, the switched damping force may be too high or too low. There was a problem in that it was too large and deteriorated the riding comfort.

(Purpose of the Invention) Therefore, the present invention aims to improve the damping force of the shock absorber by controlling the damping force of the shock absorber based on the magnitude of the actual road surface disturbance, including the magnitude of road surface protrusions and the magnitude of the load. The aim is to obtain the optimal damping force in response to changing conditions, improving vibration damping performance and ride comfort.

(Means for Solving the Problems) In order to achieve the above object, a suspension device according to the present invention is a suspension device equipped with a shock absorber capable of varying damping force, and includes a detection means for detecting the magnitude of road surface disturbance while the vehicle is running. and a control means for variably controlling the damping force of the shock absorber based on the magnitude of the detected road surface disturbance.

(Function) In the present invention, when conditions such as the size of road surface protrusions and vehicle body load change, this change is detected as the size of road surface disturbance, and the damping force of the shock absorber is controlled according to the size of this disturbance. Ru.

Therefore, the damping force of the shock absorber is selected to be optimal according to actual changes in the road surface, vehicle body, etc.
This will improve distribution performance and ride comfort.

(Example) Hereinafter, the present invention will be explained based on the drawings.

FIG. 1.2 is a diagram showing one embodiment of the present invention, and is an example applied to a vehicle equipped with a shock absorber whose damping force can be continuously varied.

First, the configuration will be explained. In Fig. 1, 1 is the vehicle body, and the vehicle body 1 has a front shock absorber 2R1.
2L and the head of the rear shock absorber 3R13L are attached.

These shock absorbers 2R12L, 3R.

Each of the wheels 3L has a wheel attached to its lower end via an axle or the like (not shown), and the wheel elastically supports the vehicle body 1 by a suspension system including a suspension spring (not shown) together with the shock absorbers 2R, 2L, 3R, and 3L. do. Also, shock absorber 2R, 2
L, 3R, and 3L are all used whose damping force can be continuously varied by an electric signal.

FIG. 2 shows a shock absorber 2 to show an example.
It is a figure which shows the principal part cross section of R. Shock absorber 2R
The outer cylinder 4 is attached to the wheel side, the inner cylinder 5 is installed inside the outer cylinder 4, and the inner cylinder 5 is divided into two chambers (chamber A and chamber B) that slide up and down in the figure. The piston part 6 is configured to include a piston part 6 that connects the piston part 6 to the vehicle body, a rod 7 that connects the piston part 6 to the vehicle body, and a bottom valve 8 provided at the bottom of the inner cylinder 5. Possible orifice 9, lO
and a valve body 11 that closes the orifice 9 when the loft 7 exits from the inside of the inner cylinder 5 (so-called expansion side);
A valve body 12 is provided that closes the orifice lO when the rod 7 enters the interior of the inner cylinder 5 (so-called contraction side). Further, the rod 7 is composed of an upper part 7a and a lower part 7b, and the lower part 7b supports the piston part 6, and a variable orifice 13 is formed in the lower part 7b so that both chambers A and B can communicate with each other. ing. The passage area of the variable orifice 13 is continuously changed from opening to closing by the tip of a solenoid plunger 15, and the solenoid plunger 15 is driven by a solenoid part 16 provided inside the upper part 7a. Note that 17 is a cable, and the cable 17 transmits a control signal Sa from a control unit 24, which will be described later, to the solenoid section 16.

Again, in FIG. 1, 18 is a torsion bar;
The torsion bar 18 functions to suppress vertical movement when the left and right wheels move vertically in opposite phases to each other, and
Vertical movement is allowed when they are in the same phase. For example, when the vehicle height changes due to changes in road surface conditions or load, this change in vehicle height is caused by the torsion bar 18 as shown in FIG.
It is expressed as a rotation of the axis. The amount of rotation (amount of change in vehicle height) is transmitted to a vehicle height sensor 20 such as a rotation potentiometer via a link mechanism 19, and the vehicle height sensor 20 converts the amount of rotation into an electrical signal to detect the vehicle height. Signal S.

Bind and output.

Note that the variable orifice 13, solenoid plunger 15, solenoid section 16, and control unit 24 described above have a function as a control means, and the torsion bar 18 and vehicle height sensor 20 have a function as a detection means. .

In FIG. 1, 21 is a vehicle speed sensor that detects vehicle speed ■;
22 is a brake switch that detects depression of the brake pedal 23 and outputs a brake depression signal S□, and a brake depression signal 5IIK, a vehicle speed V, and a vehicle height sensor 2.
The vehicle height detection signal SH from 0 is sent to the control unit 24.
is input. The control unit 24 includes a microcomputer, etc., and controls the damping force of the shock absorbers 2R12L, 3R, and 3L individually or on the front and rear sides based on input signals and other signals (for example, steering signals, etc.). Performs various controls that vary depending on the

Next, the effect will be explained.

In this embodiment, the weight of the vehicle body 1, that is, the vehicle mass m is determined based on the vehicle height detection signal SN, and the magnitude of the damping force of the shock absorbers 2R12L, 3R, and 3L is determined according to the magnitude of this m. ing.

Here, since m changes depending on the load amount and the number of passengers and is not constant, the critical damping coefficient Cc shown by the following equation (2) also changes with the change in m.

Cc=2π mXk ・・・・・・■ However, k: Spring constant of coil spring, etc. Therefore, Cc is the over-damping state when the damping coefficient C of the shock absorber etc. is too large, and the damping state when C is too small. Since this is the boundary between a state of insufficient damping, if the magnitude of the damping force is determined without depending on the magnitude of m as in the past, changes in m will result in over-allocation or under-damping, resulting in worsening ride comfort. Something happened.

FIG. 4 is a diagram in which a vehicle is approximated by a simple vibration model with l degrees of freedom. In Fig. 4, m is the mass of the vehicle body, C is the damping coefficient of the shock absorber, etc., k is the spring constant of the coil spring, etc., X is the displacement of m, υ is the vehicle speed (corresponding to vehicle speed V), and y is the vehicle speed. Travel distance, L is the length of road surface protrusion, 2X
O is the size of the road surface protrusion.

Now, when the vehicle represented by the model in FIG. 4 passes a road surface protrusion represented by the following equation 〇 at vehicle speed υ, its transient response is represented by the following equation 〇 and ■.

(This page, blank space below) (When 0≦t≦t0) λ2 x (t) = 1 −cos ωt −(1−λ
2) 2+(2ζλ)2 [(1-λ2) cosωt+2ζλsinωt, --
hE (when to ≦t) 1 o = - υ λ = □ ωn 2 π υ The above formula ■ indicates that forced displacement is being input, and during this period, forced vibration is dominant, and the damping effect of the damping force by shock absorbers etc. is few.

Furthermore, the above equation (2) indicates the transient vibration after passing over a road surface protrusion, and what influences the amplitude of this vibration is the term (e) in the equation (2)-ζωh. Therefore, if it is assumed that the above-mentioned transient vibration can be allocated and controlled without any discomfort under a predetermined standard condition, for example (ζ-ζ8, ω7=ω7.), then ζω7=ζ1ω, =const...■ The damping force should be determined so that

The above formula ■ is Because 1 , −, c = −C, ...−・■ is obtained.

That is, the damping force of a shock absorber or the like may be increased or decreased in accordance with the rate (m/m) of increase or decrease in vehicle weight.

According to this principle, in this embodiment, the vehicle height detection signal SN in the vehicle stationary state is converted to the vehicle height value HO in the empty vehicle IG state.
From now on, calculate the difference between the vehicle height value H+ while driving and the stored HOO, and calculate this difference by the change in m (rn/m
, ). The vehicle height value H1 while the vehicle is running is obtained by passing the vehicle height detection signal S)l through a low-pass filter of a predetermined frequency (approximately 2 Hz).

The control unit 24 calculates the above-mentioned (m/m1), executes arithmetic processing corresponding to the previous formula
A control signal Sa of an appropriate magnitude for controlling the damping force of R13L is output.

For example, the shock absorber 2R receives the control signal Sa, drives the internal solenoid section 16, and receives the control signal Sa.
The solenoid plunger 15 is moved according to the size of the object. If the amount of movement of the solenoid plunger 15 is small, the variable orifice 13 is almost closed, and in this case the damping force is maximum. Further, when the amount of movement of the solenoid plunger 15 is large, the variable orifice 13 is almost opened, and in this case, the damping force is minimized. Therefore, by varying the cross-sectional area of the variable orifice 13 according to the size of m, the damping force when climbing over bumps, steps, etc. is applied in the right amount, regardless of whether the vehicle is loaded or empty, and the vibrations are sufficiently suppressed. It is possible to suppress this and improve riding comfort.

In this embodiment, m is determined in the same manner as in the first embodiment, and the time T for maintaining the damping force on the high damping side is determined in accordance with the magnitude of m.

Now, in the previous equation (■), when (ζ = ζ1, ω7 - ω11), assuming that it is known that it is necessary and sufficient to maintain it on the high attenuation side for t = t 1, then (ζ =
When ζ2, ω7 = ω7□), the same effect as in the above-mentioned known case can be expected by keeping it on the high attenuation side for ζ2ωn2.

Type 0 is becomes.

In other words, by varying the time T during which the damping force of the shock absorber, etc. is maintained on the high damping side according to the rate of increase/decrease in vehicle weight (m2/m1), the optimum high damping can be achieved corresponding to the loading situation at that time. It is possible to set the retention period on the side, and it is possible to attenuate vibrations just the right amount.

In the U-th mouth pupil pre-formula 1■, if it is assumed that the vibration can be damped necessary and sufficiently in the predetermined holding time t1 when X0=X, then the holding time t2 when X0=X is calculated by the following formula. Just set according to ■.

X, 6-””’ =X, e-ζ spider 2,
°, l n X , −ζω, t, = fnXz−ζωn
j! The holding time t2 obtained as shown above is mapped in correspondence with the magnitude of the road surface disturbance that is predicted to be input.
While driving, the damping force of the shock absorber is maintained on the high damping side for a period corresponding to the size of road surface protrusions and the size of the load by looking up the optimal [2] from the map based on road surface disturbances. can improve riding comfort.

In the m-th Masumae equation (■), when xo=X, the predetermined attenuation ratio ζ
1, the vibration can be damped sufficiently (converged to the allowable vibration level) after t1 seconds. When xO=X2, the damping ratio ζ2 that can damp the vibration in the same time t1 is given by the following formula 〇 You can find it according to the following.

X, e −ζ1ω＾ヱ1 : X 2
e −6ωAsu1 00.00. (Φln
X, -ζ, ωn tl = fnXz-ζz6JfiL
1ωFlt.

By mapping the damping ratio ζ2 obtained in this way in correspondence with the magnitude of the road surface disturbance that is predicted to be input, and looking up the optimal ζ2 from the map based on the road surface disturbance while driving, The damping force of the shock absorber can be varied depending on the size of road surface protrusions and the size of the load.

In each of the above embodiments, an example is shown in which the damping force is applied to a shock absorber that can continuously vary the damping force, but the damping force is not limited to this. It may also be applied to a shock absorber whose force can be varied.

(Effects) According to the present invention, the damping force of the shock absorber is controlled based on the magnitude of the actual road surface disturbance, including the magnitude of road surface protrusions and the magnitude of the load. It is possible to obtain an optimal damping force in response to changes in the situation, and it is possible to improve distribution performance and ride comfort.

[Brief explanation of the drawing]

1 to 4 are views common to each of the first to fourth embodiments of the present invention, in which FIG. 1 is an overall configuration diagram thereof, FIG. FIG. 3 is a diagram showing the torsion bar and the vehicle height sensor, and FIG. 4 is a diagram showing a vibration model for explaining the action thereof. 2R, 2L, 3R, 3L... Shock Apsono\, 13... Variable orifice (control means), 15.
... Solenoid plunger (control means), 16.
...Solenoid part (control means), 18...
- Torsion bar (detection means), 20...Vehicle height sensor (detection means), 24...Control unit throat <control means).

Claims (4)

[Claims] (1) In a suspension device equipped with a shock absorber capable of varying damping force, a detection means for detecting the magnitude of road surface disturbance while the vehicle is running, and a detection means for detecting the magnitude of road surface disturbance while the vehicle is running; A suspension device comprising: control means for variably controlling damping force. (2) The detection means detects the magnitude of road disturbance input from a change in vehicle height.
Suspension device as described in section. (3) The suspension device according to claim 1, wherein the detection means detects a magnitude of road disturbance input including a change in vehicle body load. (4) The control means sets a holding time for maintaining the damping force of the shock absorber at a predetermined high damping force based on the magnitude of road surface disturbance. The suspension device according to any of items up to 3.