JPH02279409A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE:To obtain a constantly stabilized damping characteristic by controlling a flow control valve for supplying and exhausting oil to a hydraulic cylinder for adjusting a ground clearance and an accumulator according to a first flow control signal based on a ground clearance detection signal and a second flow control signal based on an acceleration detection signal. CONSTITUTION:An axle 2 pivoted on a car body 1 through an arm 4 so that it can freely oscillate, supports the car body 1 through a hydraulic cylinder 5. A flow control valve 9 is provided in order to adjust the amount of oil supplied and exhausted to the hydraulic cylinder 5, and the flow control valve 9 is connected through a piping L1 to a hydraulic pump 6, through a piping L2 to a reservoir-tank 8, through a piping L3 to the hydraulic cylinder 5 respectively, and an accumulator 13 is provided through a restrictor 14 at a middle point of the piping L3. The flow control valve 9 is controlled according to a first flow control signal obtained by multiplying a detection signal from a ground clearance sensor 10 by a first constant, and a second flow control signal obtained by multiplying a detection signal from an acceleration sensor 11 by a second constant.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a vehicle suspension system using an active control method, and particularly relates to a vehicle suspension system that is preferably applied to automobiles.

``Prior Art'' It can be said that the quality of an automobile suspension device is determined by the quality of its vibration damping function. Here, the vibration damping function is a function that suppresses vertical free vibration of the vehicle body and lowers the vibration transmission rate from the road surface to the vehicle body.

Conventionally, as an effective vibration damping method of this type, a method is known in which the vertical absolute velocity of a small body is detected and the value obtained by multiplying it by a negative constant is used as the generated force of a hydraulic cylinder to damp the vibration (Tr
Answer or the ASME, Jou
rnal of Engineering ror
Industry, P619'626 May+
974). However, in this case, it is not possible to directly detect the absolute vertical speed of the vehicle while it is running, so the absolute speed is determined from the detected value of the vertical acceleration of the vehicle, and the hydraulic cylinders are controlled based on the estimated absolute speed. I'm trying to dampen the vibrations. FIG. 7 is a block diagram showing the basic configuration of a conventional active suspension device. In this figure, reference numeral 100 indicates a vehicle body with a mass m, and 101 indicates a vehicle body 10.
This is an acceleration sensor for detecting acceleration in the vertical direction of 0. Further, 102 is a hydraulic cylinder including a hydraulic cylinder, a hydraulic power source, and a flow rate control valve. The hydraulic cylinder supports the vehicle body 100 using hydraulic pressure.

In addition, the above flow rate control valve is connected to the hydraulic pressure 71J from the hydraulic source (
This is a valve that adjusts and controls the amount of oil flowing out (or in the opposite direction). The hydraulic power source is provided with a hydraulic pump for feeding oil to the hydraulic cylinder.

+03 is an accumulator (spring constant K) for absorbing and mitigating impact. Hl is a control circuit that controls the amount of opening and closing of the flow control valve based on detection signals from the acceleration sensors 1 and 01. In the control circuit H1, the acceleration -C1 input from the IJ11 speed sensor 101 is transferred to the transmission element B.
1 and thereby calculates the estimated vertical velocity (2) of the vehicle body 100. At this time, transmission element B1
Was it output from? The IC constant speed n is multiplied by 4 in the feedback element B3 and fed back to the transmission element B1 via the addition point Jl. The estimated speed calculated in this way is transmitted from the transmission element B1 to the multiplication element B2, where it is multiplied by three and transmitted to block 102. Thus, the vibration damping operation is performed based on the vibration damping signal transmitted from the control circuit [ ] 1 to the block 102 based on 3·F.

Further, FIG. 8 is a block diagram showing the state of signal transmission (from the input axle displacement X1 to the output of the vehicle body displacement X) during the vibration damping operation of the active suspension device shown in FIG. The axle displacement X is reversed at the addition point J2 and manually applied to the multiplication element B4. When the multiplication element B4 receives the axle displacement X1, it multiplies it by KG (KG is the spring constant of the accumulator 103) and transmits it to the division element B5.

The division element B5 divides the transmitted signal by the mass of the vehicle body 100, am, and is the acceleration of the vehicle body 100 in the vertical direction.

Calculate. The calculated acceleration ■ is transmitted to the control circuit H1, and as described above in FIG.
Multiplication processing is performed, and the signal obtained as a result of these processing is fed back to the division element B5 via the addition point J3. In this way, the calculated acceleration,
is transmitted from division element B5 to transmission element B6, where 2
The vehicle body displacement X is visually integrated and output. Note that the output vehicle body displacement X2 is fed back to the multiplication element B4 via the addition point J2.

``Problem to be Solved by the Invention J'' By the way, in the method of controlling hydraulic cylinders based on the estimated absolute speed of the prior art described above, estimation means for estimating speed from acceleration are required for four wheels.

This increases the calculation processing time of the control circuit, so
There was a problem that the operation processing was delayed.

Additionally, if a large error occurs in the detected value of the acceleration sensor and the error is largely biased in either the positive or negative direction, the integral value (estimated speed) will be significantly biased in the positive or negative direction. There was a problem with this. Therefore, if the acceleration sensor is defective, good vibration damping characteristics cannot be obtained.

Furthermore, although accumulators have been used in the past, they have not been used organically connected to hydraulic cylinders, and therefore a sufficient shock absorbing effect cannot be expected.

The present invention has been made in view of the above circumstances, and provides a suspension device for a vehicle that can obtain stable and good vibration damping characteristics and has excellent quick response by simplifying the control circuit. The purpose is to

[Means for Solving the Problems J] In order to solve the above problems, the present invention includes a hydraulic cylinder whose volume increases or decreases according to changes in the distance between vehicle axles, and a hydraulic cylinder connected to the hydraulic cylinder and containing gas and gas inside. an accumulator containing oil that can be taken in and out; a vehicle height sensor that detects the distance between the vehicle axles; and an acceleration sensor that detects the vertical acceleration of the vehicle body; and a second flow control signal obtained by multiplying the detection signal of the acceleration sensor and a second constant, to the hydraulic cylinder and the accumulator described in 11i. The present invention is characterized in that it includes a control section that controls a flow rate control valve that supplies and discharges oil to and from the oil supply system.

Effect-1 In the above configuration, oil is supplied to and discharged from the accumulator at a flow rate proportional to the acceleration.Then, the amount of oil accumulated in the accumulator is used as the estimated velocity in the vertical direction of the vehicle body. Since the gas spring of the hydraulic cylinder functions as the gas spring of the first hydraulic cylinder, the above-mentioned estimated speed is directly taken out as the force generated by the hydraulic cylinder.On the other hand, the first
based on the flow control signal and the second flow control signal,
The inflow and outflow of the flow 1 control valve is controlled. Then, this amount of inflow and outflow is added to the second accumulator as a feedback amount.

In this way, even if the second flow rate control signal includes an error and is significantly biased in the positive or negative direction, good and stable vibration damping characteristics can be obtained.

Further, the conventional complicated process of individually estimating the absolute speed of the four wheels from the 1j mouth speed of the four wheels becomes unnecessary. This makes it possible to simplify the configuration of the control circuit, thereby improving quick response.

"Embodiments" Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a vehicle suspension (hereinafter simply referred to as suspension) which is an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a vehicle body length (1 m), 2 an axle, 3 a tire, and 4 an arm pivotally supported at one end by the vehicle body 1 and at the other end by the axle 2. These are part of the vehicle. The mechanical structure of the suspension mounted on the vehicle shown in FIG. 1 is as follows. First, reference numeral 5 denotes a hydraulic cylinder (pressure receiving area A) provided on the axle 2, which supports the vehicle body l. The hydraulic cylinder 5 is connected to the vehicle body 1
It expands and contracts in accordance with the vertical relative displacement (hereinafter referred to as vertical relative displacement) (x, -Xl) between the axle 2 and moves in and out through the pipe L3 accordingly. Here, X represents the displacement of the axle 2, and X represents the displacement of the vehicle body 1 from the base point in the height direction. Further, 6 is a hydraulic pump driven by engine E, 7 is an accumulator that contains gas inside and functions as a gas spring, and 8 is a reservoir tank that stores oil. These hydraulic pump 6, accumulator 7, and reservoir tank 8 constitute a hydraulic system (hydraulic source). Further, reference numeral 9 designates a travel control valve 1 for adjusting oil supply and discharge to and from the Urasho cylinder 5. This flow rate control valve 9 is connected to the hydraulic pump 6 via piping Ll, connected to the J server tank 8 via piping 2, and connected to the hydraulic cylinder 5 via piping 3 (flow control The valve 9 will be described later). Further, an accumulator (spring constant Kc,) 13 having gas inside is provided at the midpoint of the pipe L3 connecting the hydraulic cylinder 5 and the flow rate control valve 9. Furthermore, a throttle with a damping coefficient C is provided between the midpoint of the piping 3 and the accumulator 13. This throttle 14 functions as a piping resistance that suppresses free vibration when the flow rate control valve 9 stops operating. 10 is the vertical displacement between the vehicle body 1 and the axle 2 (11 pair displacement (×).

11 is the vertical acceleration of the vehicle body 1 (hereinafter referred to as j speed);
An acceleration sensor 12 detects the vehicle height signal from the middle height sensor 10 (X, 2- This is a control circuit that controls the movement of the oil supply side solenoid 9P and the oil discharge side solenoid 9 of the flow ri1 control valve 9, which will be described later (therefore, the amount of oil supplied and discharged).

Next, the flow control valve 9 will be explained in detail. The control valve 9 has two solenoids (oil supply side solenoid 9 P
, tJF ; Til side solenoid 9R), input/output boat 9a, and these solenoids 9P and 9R,
Three boats (connection ports) are respectively connected to the input/output boat 9a, that is, a refueling boat 9b.

It consists of a holding boat 9c and an oil draining boat 9d. The input/output boat 9a is connected to the piping 3. here,
When current IP is applied from the control circuit 12 to the refueling side solenoid 9P, the refueling boat 9b and input/output boat 9a are opened, the hydraulic pump 6 is activated, and the hydraulic cylinder 5 and the accumulator are supplied from the reservoir tank 8 to the hydraulic cylinder 5 and the accumulator. 1
Oil is supplied to the hydraulic cylinder 3, and a pressurizing force is thereby generated in the hydraulic cylinder 5. On the other hand, when the current IR is applied from the control circuit 12 to the oil drain side solenoid 9R, the oil drain boat 1-9d and the input/output boat 9a are opened.
As a result, oil is drained from the hydraulic cylinder 5 and accumulator 13 into the reservoir tank 8, and the pressure is reduced. In addition, when the control circuit 12 does not energize either the refueling side solenoid 9P or the DF rtt+ solenoid 9R, the holding board 9c and the input/output boat 9a are connected, thereby stopping the supplying port side. In this way, the oil in the hydraulic cylinder 5 is maintained. Figure 2 shows the current-inflow and outflow characteristics of the flow 1 control valve 9, with 0%,
111 side drain/id 9P and oil drain side solenoid 9 P
FIG. 3 is a characteristic diagram showing how q changes. As is clear from FIG. 2, the flow rate control valve 9 has a current value of 1 p, I R
Accordingly, the inflow and outflow mq increases monotonically according to a certain functional condition.

Next, the functions of the control circuit 12 will be explained with reference to FIG. FIG. 3 is a block diagram showing the function of the control circuit 11. In this figure, when the vehicle height sensor 10 detects the vehicle height signal (XI-XI), the vehicle height sensor 10 detects the vehicle height signal (K
2-Xl) is supplied to the control circuit 12. Similarly, when the acceleration sensor 11 detects the acceleration signal , it supplies the acceleration signal to the control circuit 12 . The control circuit 12 uses the supplied vehicle height signal (xy x+) and acceleration signal.

When the amplification element B1 receives the supply of the vehicle height signal (
x2x+) to -2, K +” (X 2X1
), and in the amplification element B2, the acceleration signal is
Multiply - by and get -, and then add these amplified signals at the summing point J1. Then, the flow rate signal q (Q = KI” (X
, XI) Manually input Kz・Ct) to transfer element B3,
The original control valve characteristics are reversely converted (see FIG. 3) so that the flow rate of the flow rate control valve 9 becomes the value of the flow rate signal q, and the oil supply side solenoid 9P or the oil drain side solenoid 9R is energized. At this time, when the flow rate signal q is positive, the following case occurs.

(1) If both the medium height signal (X, -X,) and the acceleration C7 are negative; (2) Even if the vehicle height signal (X, -X,) is positive, the acceleration C, is negative, and - ni,・te,〉K1・(K2
xl) If the condition (3) is satisfied, even if +JI11 speed C1 is positive, the vehicle height signal (X, ~
, )> K , +Q 2 (7 Ilt !, when the D condition is satisfied, when the signal pressure is 1, the control circuit 12 flows a current IP that sets the flow rate to q to the oil supply side slide/id 9P.

On the other hand, when the signal q is negative, the following case occurs.

(1,) If both the vehicle height signal (XI xl) and the acceleration C2 are positive; (2) Even if the vehicle height signal (X * -・tet> KI・(X,
-X, ) (3) Even if the acceleration C-t is negative, the vehicle height signal (X, -
X) is positive, and K1・(X, −X,)>−,・C
When condition 2 is satisfied, when the dt amount signal q is negative, the control circuit 12 applies a current I to the oil drain side solenoid 9R to set the flow rate to q.

flow.

Next, with reference to the block diagram of FIG. 4, the manner of signal transmission during the control operation of the suspension in this example will be described.

(1) Addition J2 First, at the addition point J2, the displacement signal Xl of the axle 2
-X, and the displacement signal X of the vehicle body 1.

By adding these, a vehicle height signal <X=X,) is obtained.

The vehicle height signal (X, -X,) thus formed is manually input to the transmission element B4.

(2) Differential operation B4 When receiving the vehicle height signal (X, -X,), the transmission element B4 differentiates the signal with respect to time. And this differential value S
is multiplied by 11η to the pressure receiving area of the pressure cylinder 5 to derive the flow rate S-A from the hydraulic cylinder 5 to the accumulator 13.

(3) Integral operation B5 In the transmission element B5, the flow 11 to the accumulator 13
s-A is time-integrated. This integral value 1/S means the amount of oil accumulated in the accumulator 13. Next, this integral value 1/S is multiplied by the spring constant by 6, and then divided by the pressure receiving area A.

The obtained value (]/S)・(K,/A> means the force generated by the hydraulic cylinder 5. In this way,
Divide the required force by the quality of body 1, Jim. In this way, the acceleration of the vehicle body is determined.

(4) Double integration processing B6 Acceleration C of the vehicle body l determined by the transfer element B5! is transmitted to the transmission element B6 and integrated twice, so that the insect body 1
The vertical displacement, X, of

(5) Addition J3 On the other hand, the flow rate f
f1q gets JJO. Part H surrounded by a two-dot chain line in the figure
1 indicates the operation of the control circuit 11 and the switching valve 5. The acceleration -d determined at the transmission element B5 is also transmitted to the feedback element B7. When the feedback element B7 is supplied with an acceleration signal,
With the acceleration signal received, multiply by -7, and the resulting flow rate value - by 1.
I got 7JO in the flow of ffi. This is accumulator 1
3 is integrated as the oil amount, and becomes the force generated by the hydraulic cylinder 5. As a result, it is the same as feeding back the speed (absolute speed) D2 as the force applied to the vehicle body. On the other hand, the vehicle height signal (X, -X
+) is also transmitted to amplification element B8. When the transmission element B8 receives the vertical relative displacement, it receives the vehicle height signal (X).

X, ) is multiplied by -2, and the flow rate value obtained is:
(X, -X,) is added to the flow rate to accumulator 13. This corresponds to the vehicle height adjustment operation of a normal hydraulic suspension system, but it prevents the error k contained in the acceleration d from being integrated and increased in the operation in which the acceleration U is fed back. .

Figure 5 is a characteristic curve diagram showing the characteristics of the vibration damping function of the suspension device in this example. represents the ratio between the frequency f applied to the vehicle body l and the natural vibration If, and the vertical axis represents the amplitude X of the vehicle body l and the amplitude X1 of the axle 2.
, the so-called amplitude ratio. The result of this characteristic curve is almost similar to that of active suspension/jump (when the error of the conventional acceleration sensor 11 is small). FIG. 6 shows the vibration damping characteristics of a conventional passive suspension device consisting of a spring and a damper. Figure 5 (active suspension device) and Figure 6
Comparing with the figure (passive suspension device),
Figure 5 (active suspension device) suppresses vibrations near the natural frequency better, and at frequencies above the natural frequency, the damping force of the damper is as low as when it is zero. , it can be seen that it has an excellent vibration damping function.

According to the above configuration, oil is supplied and discharged to and from the accumulator 13 at a flow rate proportional to the acceleration, and
The amount of oil accumulated in the vehicle can be used as the estimated speed. Since the accumulator 13 functions as a gas spring of the suspension device, the flow value which is the estimated speed of the accumulator 13 can be directly taken out as the force generated by the hydraulic linter.

In addition to the feedback of the vertical acceleration signal, the vehicle height signal is also fed back and applied to the flow rate control valve 9, so that the feed bank amount (to the accumulator 13) is determined in the positive direction based on the vertical acceleration signal. Even if an error that is excessively biased in either of the negative directions occurs, it is corrected by the amount of feedback (to the accumulator 13) based on the vehicle height signal, so it is possible to always obtain good and stable vibration damping characteristics. can.

Furthermore, by feeding back the flow rate proportional to the vertical acceleration and vehicle height to the accumulator 13, it is possible to supply and drain oil in accordance with the absolute speed, so the absolute speed of the four wheels can be estimated individually based on the acceleration of the four wheels. The conventional complicated process of calculation becomes unnecessary. Therefore, the configuration of the control circuit can be simplified, and rapid response can be improved.

Furthermore, even if the flow control valve stops operating, the accumulator can function as a normal Banonbu suspension device, so even if the flow control valve fails, a constant vibration damping function can be maintained. I can do it.

[Effect of the Invention J As explained above, in the present invention, the volume increases or decreases in accordance with changes in the distance between the axes of the vehicle body. lit+pressure/linda,
an accumulator connected to the hydraulic cylinder and containing gas therein and an accumulator (M) that can be moved in and out; and the vehicle body axle 17.
a first flow rate obtained by multiplying a detection signal of the vehicle height sensor and a first constant; A flow control valve that supplies and discharges oil to and from the hydraulic cylinder and the accumulator is controlled based on a second flow control signal obtained by multiplying the control signal and the detection signal of the acceleration sensor by a second constant. Since it is equipped with a control section that controls vibration control, it is possible to obtain much better and stable vibration damping characteristics.

Furthermore, the complicated process of individually estimating the absolute speeds of the four wheels from the accelerations of the four wheels, as in the past, is no longer necessary.

As a result, the configuration of the control circuit can be further simplified, and rapid damping response can be obtained.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of a vehicle suspension system which is an embodiment of the present invention, and Fig. 2 shows the current-ura flow/inflow characteristics of the flow 1 control valve applied to the vehicle suspension system. 3 is a block diagram showing the function of the control device applied to the suspension device for the same vehicle. FIG. 4 is a block diagram showing the state of signal transmission during vibration damping operation of the suspension device for the same vehicle. Diagram M: Figure 5 shows the vibration damping characteristics of the suspension system for the same vehicle, Figure 6 shows the vibration damping characteristics of the conventional passive suspension system, and Figure 7 shows the vibration damping characteristics of the conventional active suspension system. A block diagram showing the principle configuration of
FIG. 2 is a block diagram showing how signals are transmitted during vibration damping operation of the active suspension device shown in the figure. )...1g body, 2...1F axis, 5...
...Ura LHH printer, 9...Flow m control valve, 9P...Oil supply side fly/id, 9R...
・Oil drain side solenoid, lO...Vehicle height sensor, 1
1...Acceleration sensor, 12...Control unit (control circuit), 13...Accumulator.

Claims (1)

[Scope of Claims] A hydraulic cylinder whose volume increases or decreases according to changes in the distance between the vehicle body axles; an accumulator connected to the hydraulic cylinder and containing gas and oil that can be taken in and out; and a distance between the vehicle body axles. a first flow rate control signal obtained by multiplying a detection signal of the vehicle height sensor by a first constant; and an acceleration sensor that detects vertical acceleration of the vehicle body. A control unit that controls a flow control valve that supplies and discharges oil to and from the hydraulic cylinder and the accumulator based on a second flow control signal obtained by multiplying the detection signal of the acceleration sensor and a second constant. A vehicle suspension device characterized by: