JP3045537B2 - Vehicle suspension device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension system for a vehicle having a hydraulic cylinder between axles of a vehicle body. The present invention relates to a vehicle suspension device that can be stably maintained and that hardly causes full rebound or full bump due to full stroke operation of the hydraulic cylinder when traveling on a road surface having large irregularities.

Conventional technology Conventionally, a hydraulic cylinder is provided between the axles of a vehicle body, and the vertical force of the vehicle body is detected, and the generated force of the hydraulic cylinder is controlled in accordance with a value obtained by multiplying this by a negative constant to reduce the vibration of the vehicle body. There is known an active control type vehicle suspension device for preventing such a problem.

However, this suspension device must calculate the vertical velocity of the vehicle body at each wheel position by integrating the output value of the acceleration sensor provided for each wheel, and this integration calculation for each wheel takes time. In addition to the disadvantage of poor responsiveness, the error of the acceleration sensor is enlarged, so that there is a problem that if there is any error in the acceleration sensor, good vibration damping characteristics cannot be obtained.

Therefore, the applicant has proposed a suspension device in which the above-mentioned problem is solved in Japanese Patent Application No. 1-100590.

That is, a hydraulic cylinder that expands and contracts according to a change in the distance between the vehicle body axles to increase and decrease the volume of the working chamber, an accumulator connected to the working chamber of the hydraulic cylinder and containing gas and oil that can enter and exit, and the accumulator A flow control valve that supplies and discharges oil to and from the cylinder, a vehicle height sensor that detects a distance between the vehicle body axles, and an acceleration sensor that detects vertical acceleration of the vehicle body, and a detection signal of the vehicle height sensor. A first flow rate control signal obtained by multiplying a first amplification rate, and a second flow rate control signal obtained by multiplying a detection signal of the acceleration sensor by a second amplification rate. A control unit for controlling the control valve is provided.

[Problem to be Solved by the Invention] This suspension device is excellent in that it has good vibration damping characteristics and high responsiveness because it does not require the above-described integration operation. In order to stabilize the posture of the vehicle body by absorbing the pressure, the first amplification factor must be set small. Therefore, even if the hydraulic cylinder is near the stroke end, the control amount is small and full rebound or full bump is likely to occur. Had a problem.

Here, the full rebound is a phenomenon in which the hydraulic cylinder extends to the stroke end and the vehicle body rebounds impactfully, and a full bump is a phenomenon in which the hydraulic cylinder contracts to the stroke end and the piston impacts the cylinder end. is there.

The present invention has been made in view of the above-described conventional problems, and can absorb a change in the road surface in a normal road surface traveling and can stably maintain the posture of the vehicle body. It is an object of the present invention to provide a vehicle suspension device in which a full rebound or a full bump due to a full stroke operation of a hydraulic cylinder hardly occurs.

[Summary of the Invention] A suspension device according to claim 1 is connected to a hydraulic cylinder that expands and contracts in response to a change in the distance between vehicle axles to increase or decrease the volume of an operating chamber, and to the operating chamber of the hydraulic cylinder. An accumulator that contains gas and oil that can enter and exit
A flow control valve for supplying and discharging oil to and from the accumulator and the cylinder; and a vehicle height sensor for detecting a change in the distance, wherein a flow control obtained by multiplying a detection signal of the vehicle height sensor by an amplification factor. A control unit that controls the flow control valve based on a signal to return the distance to a neutral state, wherein the control unit is configured such that a magnitude of expansion and contraction of the hydraulic cylinder based on the detection signal is close to a full stroke, and When the direction of expansion and contraction is toward a full stroke, the amplification factor is increased.

According to a second aspect of the present invention, there is provided a suspension device, wherein a hydraulic cylinder which expands and contracts according to a change in a distance between vehicle body axles to increase and decrease the volume of a working chamber, and a gas which is connected to the working chamber of the hydraulic cylinder and is capable of entering and leaving the inside An accumulator including
A flow control valve that supplies and discharges oil to and from the accumulator and the cylinder; and a vehicle height sensor that detects a change in the distance, and a flow signal obtained by multiplying a detection signal of the vehicle height sensor by an amplification factor. A control unit that controls the flow control valve to return the distance to a neutral state based on the control signal, wherein the control unit determines that the magnitude of displacement of the hydraulic cylinder based on the detection signal is close to a full stroke, and When the direction of expansion and contraction is toward a full stroke, the amplification factor is increased in accordance with the operation speed of the hydraulic cylinder based on the detection signal.

According to the suspension device of the first aspect, when a large change in vehicle height occurs such that the hydraulic cylinder operates close to the full stroke, the amplification factor increases in the control unit, and based on the vehicle height, Since the force of the hydraulic cylinder that returns to the state rapidly increases, the occurrence of full rebound and full bump due to the full stroke operation of the hydraulic cylinder is prevented with a very high probability.

In addition, since this amplification factor can be increased only in the range where the hydraulic cylinder is close to the full stroke, the operation of returning the vehicle height to a normal change in vehicle height when traveling on a road surface is performed gently, and The change is not transmitted to the vehicle body as it is, and the posture of the vehicle body does not become unstable.

Further, when the change in the vehicle height is not toward the full stroke of the hydraulic cylinder (that is, there is no possibility that the hydraulic cylinder performs the full stroke operation in this case), even if the vehicle height is in the range close to the full stroke, the amplification is increased. Do not increase the rate. Therefore, full rebound and the like can be prevented, and the posture of the vehicle body can be stably maintained in a wider range.

Further, the suspension device according to the second aspect attempts to return the vehicle height to the original value with a control amount proportional to the speed of the vehicle height change toward the full stroke of the hydraulic cylinder.

As a result, even when the vehicle speed is high, full rebound can be prevented, and when there is a large road surface change, the control amount does not fluctuate due to the reversal of the sign of the vehicle speed and full rebound is smoothly prevented. Is done. Therefore, the suspension device according to claim 3 can more reliably prevent full rebound and the like, and further, there is no possibility that the vehicle body becomes unstable due to this prevention operation.

Embodiments Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 to 3 and FIG.
This will be described with reference to FIG.

FIG. 1 is a block diagram showing a configuration of a vehicle suspension device of the present invention. In FIG. 1, reference numeral 1 denotes a vehicle body (mass m), reference numeral 2 denotes an axle, reference numeral 3 denotes a tire, and reference numeral 4 denotes an arm which is pivotally supported at one end to the vehicle body 1 and at the other end to the axle 2, These are parts of the vehicle.

The configuration of the suspension device mounted on the vehicle shown in FIG. 1 is as follows. First, the axle 2 is indicated by reference numeral 5.
, Which supports the vehicle body 1. The hydraulic cylinder 5 is provided with a vertical relative displacement (hereinafter referred to as a vehicle height) between the vehicle body 1 and the axle 2 (X ₂
−X ₁ ), the oil expands and contracts, and the oil flows in and out through the pipe L3.

Where X ₁ is the axle 2, X ₂ represents a displacement from a reference point of each height direction of the vehicle body 1. The hydraulic cylinder 5
Oil chambers are formed on both sides of the piston 5a.
Is formed with a through-hole for communicating the oil chambers on both sides, and its pressure receiving area A is equal to the cross-sectional area of the rod 5b.

Reference numeral 6 denotes a hydraulic pump driven by the engine E, reference numeral 7 denotes an accumulator that contains gas therein and functions as a gas spring, and reference numeral 8 denotes a reservoir tank that stores oil. From these hydraulic pump 6, accumulator 7, and reservoir tank 8, a hydraulic device (hydraulic source)
Is configured.

Reference numeral 9 denotes a control valve for adjusting the amount of oil supply / discharge to the hydraulic cylinder 5. The flow control valve 9 is connected to the hydraulic pump 6 via a pipe L1, connected to the reservoir tank 8 via a pipe L2, and connected to the hydraulic cylinder 5 via a pipe L3.

An accumulator (spring constant K _G ) 13 having gas therein is provided at a middle point of the pipe L3 connecting the hydraulic cylinder 5 and the flow control valve 9. Further, between the middle point of the pipe L3 and the accumulator 13, a throttle of the attenuation coefficient C is provided. The throttle 14 functions as a pipe resistance that suppresses automatic vibration when the flow control valve 9 stops operating. Reference numeral 10 denotes a vehicle height sensor that detects a vehicle height (X ₂ −X ₁ ), reference numeral 11 denotes an acceleration sensor that detects the vertical acceleration α ₂ of the vehicle body 1, and reference numeral 12 denotes a vehicle height signal from the vehicle height sensor 10 ( X ₂ −X ₁ ) and the acceleration signal α ₂ from the acceleration sensor 11, and based on these signals,
This is a control circuit for controlling the movement amount (therefore, oil supply / discharge amount) of the oil supply side solenoid 9P and the oil discharge side solenoid 9R of the flow rate control valve 9 described later.

Next, the flow control valve 9 will be described in detail. The flow control valve 9 has two solenoids (oil supply side solenoid 9P, oil discharge side solenoid 9R), an input / output port 9a, and three ports which are respectively connected to the input / output port 9a by these solenoids 9P, 9R. I.e. refueling port 9b, holding port
9c and an oil discharge port 9d. The input / output port 9a is connected to the pipe L3.

Here, the current I _P is supplied from the control circuit 12 to the refueling-side solenoid 9P.
Is turned on, the oil supply port 9b and the input / output port 9a are opened, the hydraulic pump 6 is operated, and the hydraulic cylinder 5 and the accumulator are moved from the reservoir tank 8.
Refueling is performed to 13, whereby a pressing force is generated in the hydraulic cylinder 5. On the other hand, if a current I _R is supplied from the control circuit 12 to the oil discharge side solenoid 9R, the oil discharge port
The valve 9d and the input / output port 9a are opened, whereby the oil is drained from the hydraulic cylinder 5 and the accumulator 13 to the reservoir tank 8, and the pressure is reduced. The control circuit 12 is configured to control the oil supply side solenoid 9P and the oil discharge solenoid 9R.
When power is not supplied to any of the above, the holding port 9c and the input / output port a are connected, whereby the supply / discharge oil is stopped and the oil in the hydraulic cylinder 5 is held. The flow control valve 9 is configured such that the inflow / outflow amount Q monotonically increases in accordance with certain functional conditions in accordance with the current values I _P and I _R.

Next, the configuration and function of the control circuit 12 will be described with reference to FIG.

FIG. 2 is a block diagram showing the configuration and functions of the control circuit 12. In this figure, the vehicle height sensor 10 detects the vehicle height signal (X ₂ -X _1), and supplies the vehicle height signal (X ₂ -X ₁₎ to the control circuit 12. Similarly, when detecting the acceleration signal α ₂ , the acceleration sensor 11 outputs the acceleration signal α ₂ to the control circuit.
Supply to 12.

When the control circuit 12 receives the vehicle height signal (X ₂ −X ₁ ) and the acceleration signal α ₂ , the amplification factor B7 adds the vehicle height signal (X ₂ −X ₁ ) to the vehicle height signal (X ₂ −X ₁ ). And outputs a flow signal q (q = K · (X ₂ −X ₁ )). Furthermore, the amplification element B8, multiplied by the constant amplification factor -K ₂ in the acceleration signal alpha _2, and outputs a signal -K ₂ · _{α 2.} And
The output from these amplification factors B7 or amplifying element B8 combined addition in pressurized alignment point J4, the addition flow rate signal Q obtained by the combined _{(Q = K · (X 2} -X 1) -K 2 · α 2) Input to the transmission element B9. Further, in the transmission element B9, the characteristic of the flow control valve is inversely converted so that the flow rate of the flow control valve 9 becomes the value of the flow signal Q, and power is supplied to the oil supply side solenoid 9P or the oil discharge side solenoid 9R. That is, the control circuit 12, when the flow rate signal Q is positive electric current I _P corresponding to the flow rate Q on the oil supply side solenoid 9P, when the flow rate signal Q is negative the flow Q to the oil discharge side solenoid 9R flow the corresponding current I _R.

Here, the amplification factor K is set as follows in each range as shown in FIG.

(I) In the case of h _BST <X ₂ −X ₁ <h _RST (however, except for X ₂ −X ₁ ≒ 0) This is the case where the vehicle is traveling on a normal road surface and the vehicle height ( X ₂ −X ₁ ) is the normal maximum vehicle height h _RST where the hydraulic cylinder 5 is slightly before the full stroke operation of the hydraulic cylinder 5 on the extension side, and a little before the full stroke of the hydraulic cylinder 5 on the compression side. This is a case in which the vehicle height is between the normal minimum vehicle height h _BST which is the vehicle height in the state. Then, in this case, K changes the vehicle height of the suspension device to the neutral position (X ₂ −X ₁ ≒
Utmost small constant value as much as does not disturb the becomes zero position) back function is set to -k _1.

(Ii) In the case of X ₂ −X ₁ ≧ h _RST This is the case where the hydraulic cylinder 5 is extended beyond the position corresponding to the normal maximum vehicle height h _RST . In this case, for example, K = −k ₁ By setting (X ₂ −X ₁ ) / h _RST , the flow signal q (control amount) decreases in a higher-order function as the vehicle height (X ₂ −X ₁ ) increases. ing.

(Iii) In the case of X ₂ −X ₁ ≦ h _BST This is the case where the hydraulic cylinder 5 is contracted beyond the position corresponding to the normal minimum vehicle height h _BST . In this case, for example, K = k ₁ · By setting (X ₂ −X ₁ ) / h _BST , the flow signal q increases in a higher-order function with respect to the decrease in the vehicle height (X ₂ −X ₁ ).

Configured as described above, according to the suspension device, the transfer characteristic of the displacement X ₂ of the vehicle body with respect to the displacement X ₁ axle first
It looks like the block diagram in Figure 12. The small letter s in the block diagram is the Laplace operator.

That is, in Figure 12, the difference between the displacement X ₁ and the vehicle body displacement X ₂ of the axle to be outputted as the vehicle height displacement is represented by the pressurized alignment point J5, the displacement (X ₂ -X ₁ ) Is the movement amount of the piston 5a of the hydraulic cylinder 5 as it is, and the hydraulic cylinder 5 and the accumulator 13 correspond to this movement amount.
The occurrence of oil flow in and out of the space is represented by element B3. That is, a flow rate of the oil is obtained which is obtained by multiplying the value obtained by time-differentiating (s) the movement amount of the piston 5a by the pressure receiving area A of the hydraulic cylinder 5.

The flow rate of the oil flowing into and out of the accumulator 13 depends on the operation of the hydraulic cylinder 5 and the control circuit.
The sum of the supply and discharge through the flow control valve, which operates in response to the command from 12, is added point J6.
Is represented by

Further, a pressure is generated in the accumulator 13 according to the flow rate of the oil flowing into and out of the accumulator 13. That is, in the element B1, the value that the flow rate was time integrating (1 / s) of the oil supplied to and discharged from the accumulator 13 represents the amount of oil accumulated into the accumulator 13, also in the integrated value, the spring constant K _G The value divided by the pressure receiving area A of the hydraulic cylinder 5 is calculated by the pressure in the accumulator 13.
Represents the force generated. Then, the forces generated in the hydraulic cylinder 5 divided by the vehicle mass m is to be equal to the acceleration X ₂ of the vehicle body are represented by the elements B1, the acceleration X ₂ 2-order integration (1 / s ² and a represents an element B2 can) value is displaced X ₂ of the vehicle body. The input of the vehicle height signal (X ₂ −X ₁ ) to the element B7 of the control circuit 12 is represented by an arrow from the output of the addition point J5 to the element B7. The input of the signal (α ₂ ) from the acceleration sensor to B8 is indicated by an arrow from the output of the element B1 to the element B8.

As it can be seen from the block diagram of the Figure 12, according to the first embodiment the suspension device, discharge feed flow control circuit 12 is obtained by amplifying the acceleration signal alpha ₂ to the accumulator 13, the sheet The amount of oil in the accumulator 13 increases or decreases in accordance with the discharged flow rate, and becomes a force generated by the hydraulic cylinder 5. As a result, the acceleration applied to the vehicle body is fed back as a force applied to the vehicle body, and as an active suspension device Good vibration damping characteristics can be obtained, and excellent responsiveness can be obtained because calculation for integrating the acceleration signal is not required.

Further, the control circuit 12 also supplies and discharges the flow rate obtained by amplifying the vehicle height signal by the amplification factor K to the accumulator 13, so that the hydraulic cylinder 5 always returns the change in vehicle height to the original. Such a force is generated, and this suspension device has a vehicle height adjusting function.

In addition, since the amplification factor K is as small as possible in a change in vehicle height when traveling on a normal road surface as described above, the change in vehicle height is moderated by this suspension device, and the change in road surface is not changed. And the posture of the vehicle body is not unstable. On the other hand, when large unevenness such as large undulations is present on the road surface and a large change in vehicle height occurs, the amplification factor K sharply increases as described above, and the force of the hydraulic cylinder 5 for returning the vehicle height to the original value is reduced. Because of the rapid increase, the occurrence of full rebound (FR) and full bump (FB) due to the full stroke operation of the hydraulic cylinder 5 is prevented with a very high probability.

Next, a second embodiment will be described with reference to FIGS.

The suspension device of the second embodiment differs from the suspension device of the first embodiment in a part of the control circuit 12.

In other words, this amplification elements 7B of the control circuit 12 of the suspension device, and the velocity signal V ₂₁ obtained by the detection signal and the detection signal of the vehicle height sensor 10 is differentiated by the derivative element B10 is input. The amplification element B7 outputs the vehicle height signal (X ₂ −
X ₁ ) and the amplification factor K changed by the speed signal V ₂₁ are multiplied by the vehicle height signal (X ₂ −X ₁ ), and the flow rate signal q (q = K · (X ₂ −
X ₁ )) is added and input to the matching point J4. More specifically, as shown in FIGS. 5 and 6, the gain K is set as follows in each range. (I) h _BST <
In the case of X ₂ −X ₁ <h _RST (however, except for X ₂ −X ₁ ≒ 0) As in the first embodiment, the amplification factor K is set to the smallest possible constant value −k ₁ .

(Ii) When X ₂ −X ₁ ≧ h _RST When the speed signal V ₂₁ ≦ 0, K = −k _{1. When} the speed signal V ₂₁ > 0, for example, K = −k ₁ · (X ₂ −X ₁ )
By setting / h _RST , the flow signal q decreases in a higher-order function as the vehicle height (X ₂ −X ₁ ) increases.

(Iii) When X ₂ −X ₁ ≦ h _BST When the speed signal V ₂₁ ≧ 0, K = −k _{1. When} the speed signal V ₂₁ <0, for example, K = k ₁ ( X ₂ −X ₁ ) / h
By setting _BST , the flow signal q increases in a higher-order function with respect to a decrease in the vehicle height (X ₂ −X ₁ ).

In the suspension device of the second embodiment, the block diagram representing the signal transmission is obtained by adding the differential element B10 to the block diagram of FIG. Works almost the same as the device,
The operation differs in the vehicle height adjustment function for a large vehicle height change.

That is, when the normal vehicle height change is exceeded (see (ii) above).
Even if the (iii)), if not the direction in which the direction of vehicle height change at that time the hydraulic cylinder 5 is operated full stroke, the amplification factor K is as much as possible with a small constant value -k _1, return to the neutral position It is done slowly.

Therefore, when the vehicle height exceeds the normal value and the hydraulic cylinder 5 is close to the stroke end, but the vehicle body is about to return toward the neutral point (that is, in this case, there is no possibility of full rebound or the like). The problem that the vehicle body is likely to be unstable due to the increase of the amplification factor K can be avoided.

Therefore, like the suspension device of the first embodiment, the suspension device of the second embodiment has a low possibility of full rebound and the like, and stabilizes the posture of the vehicle body in a wider range than the first embodiment. It has the feature that it can be kept in place.

Next, a third embodiment will be described with reference to FIGS.

The suspension device of the third embodiment is also different from the suspension device of the first embodiment in the control circuit.
Twelve elements B7 are different.

That is, the element B7 of the control circuit 12 of this suspension device operates as shown in the flowchart of FIG. 7 to input the flow rate signal q to the addition point J4. Hereinafter, this flowchart will be described for each step.

[Step A, Step B] The vehicle speed V ₂₁ is obtained from the vehicle height signal (X ₂ −X ₁ = X ₂₁ ),
Proceed to step C.

[Step C] In Step C, it is determined whether or not the current state is in a state where full stroke (full rebound, full bump) is likely to occur. That is, if | X ₂₁ | ≧ X _SES and X ₂₁ · V ₂₁ > 0, since the vehicle height X ₂₁ is close to the stroke end and the hydraulic cylinder 5 is displaced toward the stroke end, a full stroke is easy. It proceeds to step D, otherwise proceeds to step E.

Here, X _SES is an absolute value when the absolute value of the above-mentioned regular maximum vehicle height h _RST and the regular minimum vehicle height h _BST is set to be equal. In this case, h _RST = X _SES , h _BST = −X _SES It is.

[Step D] The following equation is calculated and the process proceeds to step F.

q = − (X ₂₁ −X _SES ) · V ₂₁ · K _SES −X _SES · K _{1 In the} above equation, the value of − (X ₂₁ −X _SES ) · V ₂₁ · K _SES indicates the ease of full stroke. and requests, but to calculate the flow rate signal q based on this value, this time, in order to have a continuous sense of normal relative displacement feedback, and added -X _SES · K _1.

Also, K _SES is an amplification factor which increases with respect to X ₂₁ as shown in FIG. 8 are set as in Example similar example the formula described above.

K _SES = k ₁ · X ₂₁ / X _SES [Step E] The following equation is calculated and the process proceeds to Step F.

q = −X ₂₁ · K ₁ [Step F] The flow rate signal q obtained by the calculation in Step D or Step E is added and output to the joining point J4.

The suspension device of the third embodiment operates substantially the same as the suspension device of the first embodiment or the second embodiment, but differs in operation in a vehicle height adjustment function for a large vehicle height change. . That is, the flowchart in particular as apparent from the step D, relative to the vehicle height change toward the stroke end of the hydraulic cylinder 5, which tends to return to the original vehicle height control amount in proportion to the velocity V _21.

Therefore, unlike the first embodiment or the second embodiment in which full rebound cannot be prevented when the vehicle height changes at a high speed, full rebound can be prevented even when the vehicle speed is high.

Further, for example, when there is a road changes as shown in Figure 10 (a), according to the suspension apparatus of the second embodiment, as shown in the inverted by the 10 view of the sign of the velocity V ₂₁ (b) The flow signal q fluctuated. However, according to the suspension device of the third embodiment, since the amplification factor is adjusted according to the vehicle speed, the flow rate signal q changes smoothly as shown in FIG. Etc. are prevented.

Therefore, the suspension device of the third embodiment has an excellent feature that the full rebound and the like can be more reliably prevented, and the vehicle body is not likely to be unstable due to this prevention operation.

The above three examples, increases the predetermined value (i.e., regular maximum vehicle height h _RST, etc.) the amplification factor K and the boundary of the vehicle height to prevent full rebound or the like (X ₂ -X ₁₎ Let me
For example, as shown in FIG. 11, it may be increased so as to form a curve that can be expressed by one higher-order function expression.

Further, according to the present invention, the acceleration α
_{The present} invention is not limited to a suspension device that feeds back ₂ and any suspension device that has a need to restore the vehicle height based on a vehicle height signal has the same effect.

[Effect of the Invention] According to the suspension device described in claim 1, the occurrence of full rebound and full bump is prevented with a very high probability, and the vehicle is not affected by a change in vehicle height when traveling on a normal road surface. The effect that the operation of returning the height is performed gently and the change in the road surface is not transmitted to the vehicle body as it is and the posture of the vehicle body becomes unstable is exerted.

In addition, it is possible to prevent full rebound, etc., and even if there is a large change in vehicle height, the posture of the vehicle body can be stably maintained when the vehicle body is displaced toward the original position. To play.

Further, the suspension device according to the second aspect can reliably prevent full rebound and the like even when the vehicle body speed is high, and there is a large change in the vehicle height similarly to the suspension device according to the second aspect. Also, when the vehicle body is displaced toward the original position, the posture of the vehicle body can be stably maintained, and the effect of preventing the full rebound or the like is performed very smoothly. .

[Brief description of the drawings]

1 to 12 are views for explaining an embodiment of the present invention. FIGS. 1 to 3 and 12 are views for explaining the first embodiment, FIG. 1 is a block diagram showing the overall configuration of a suspension device, and FIG. FIG. 3 is a block diagram showing the relationship between the vehicle height and the control amount, and FIG. 12 is a block diagram showing the transfer characteristics of the entire suspension device. 4 to 6 are diagrams for explaining the second embodiment. FIG. 4 is a block diagram showing the configuration and function of the control unit, and FIG. 5 is a vehicle height and an amplification factor. A graph showing the relationship of
FIG. 6 is a graph showing the relationship between the vehicle height and the control amount. 7 to 10 are diagrams for explaining the third embodiment, FIG. 7 is a flowchart showing the operation of the control unit, and FIG. 8 shows the relationship between the vehicle height and the amplification factor. Graph showing, ninth
The figure shows the relationship between the vehicle height and the stroke of the hydraulic cylinder, FIG. 10 (a) shows the road surface change, and FIGS. 10 (b) and 10 (c) show the vehicle height signal with respect to the road surface change, respectively. FIG. 5 is a diagram showing changes in the control amount and the control amount. FIG. 11 is a diagram for supplementary explanation of the present invention, and is a graph showing the relationship between the vehicle height and the amplification factor. 1 ... body, 2 ... axle, 9 ... flow control valve, 10 ... vehicle height sensor, 12 ... control unit, 13 ... accumulator, X
₂₁ (X ₂ −X ₁ ): variation in distance between vehicle axles, q: flow rate signal (control amount) K: amplification factor.

Continuation of the front page (72) Inventor Hidekatsu Ozaki 1-3-6 Fujimi, Kawasaki-ku, Kawasaki-shi, Kanagawa Tokiko Corporation (56) References JP-A-4-100717 (JP, A) JP-A-4-100711 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60G 17/015

Claims (2)

(57) [Claims] 1. A hydraulic cylinder, which expands and contracts in accordance with a change in the distance between vehicle body axles to increase and decrease the volume of a working chamber, and an accumulator connected to the working chamber of the hydraulic cylinder and containing gas and oil capable of entering and leaving. A flow control valve that supplies and discharges oil to and from the accumulator and the cylinder, and a vehicle height sensor that detects a change in the distance, wherein a flow rate obtained by multiplying a detection signal of the vehicle height sensor by an amplification factor. A control unit that controls the flow rate control valve based on the signal to return the distance to a neutral state, wherein the control unit is configured such that a magnitude of expansion and contraction of the hydraulic cylinder based on the detection signal is close to a full stroke, and The vehicle suspension device according to claim 1, wherein the amplification factor is increased when the direction of expansion and contraction is toward a full stroke. 2. A hydraulic cylinder, which expands and contracts in response to a change in the distance between vehicle body axles to increase or decrease the volume of a working chamber, and an accumulator connected to the working chamber of the hydraulic cylinder and containing gas and oil capable of entering and leaving. A flow control valve that supplies and discharges oil to and from the accumulator and the cylinder, and a vehicle height sensor that detects a change in the distance, wherein a flow rate obtained by multiplying a detection signal of the vehicle height sensor by an amplification factor. A control unit that controls the flow rate control valve based on the signal to return the distance to a neutral state, wherein the control unit is configured such that a magnitude of expansion and contraction of the hydraulic cylinder based on the detection signal is close to a full stroke, and A vehicle that increases the amplification factor in accordance with the operating speed of the hydraulic cylinder based on the detection signal when the direction of the expansion and contraction is toward a full stroke. Suspension system.