JPH06106935A - Vehicle suspension - Google Patents

Abstract

(57) [Summary] [Purpose] In a straight running state or a steady turning state, while suppressing vibration transmission to the spring to ensure vibration damping, sufficient control force is generated when an inertial force is applied and a roll occurs. Get it. A suspension unit b interposed between a sprung part and an unsprung part of a vehicle and capable of changing a damping force characteristic by a damping characteristic changing means a, and a vertical behavior for detecting at least a factor relating to a vertical behavior on the spring. Detection means c,
Input means e having a lateral acceleration detecting means d for detecting acceleration in the lateral direction of the vehicle body on the spring, a lateral acceleration and a rate of change of the lateral acceleration obtained from a signal from the lateral acceleration detecting means d, and sprung behavior. The damping force characteristic control means f for controlling the damping force characteristic of each suspension unit b by the control signal obtained by using the signal obtained from the detecting means c is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension system for optimally controlling a damping force characteristic (hard or soft) of a shock absorber, and more particularly to control during rolling of a vehicle.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension system for controlling a damping force characteristic of a shock absorber, for example, Japanese Patent Application Laid-Open No. 61-61600.
The one described in Japanese Patent No. 163011 is known.

This conventional vehicle suspension system detects the sprung vertical velocity and the relative velocity between the sprung and unsprung portions, and when both have the same sign, the damping force characteristic is a hard characteristic, and when both have different signs. The damping force characteristic control based on the skyhook theory, such as making the damping force characteristic soft, was performed independently for the four wheels. As a result, the vibration damping energy can be increased with respect to the vibration energy transmitted to the vehicle body, the vibration of the vehicle body can be suppressed, and an excellent riding comfort can be obtained. It was possible to suppress steering and improve steering stability.

[0004]

However, in the above-mentioned conventional device, when the control gain is determined so as to secure the vibration damping property while suppressing the vibration transmission to the spring on the road surface input, the steering gain, such as during steering, may be reduced. As described above, when an inertial force is applied to the spring to generate a roll, the control force is insufficient by the amount of the inertial force, and a sufficient sprung mass damping effect cannot be obtained.

The present invention has been made by paying attention to the above-mentioned conventional problems. In the straight traveling state and the steady turning state, the vibration transmission to the sprung is suppressed to secure the vibration damping property while the inertia force is applied. The purpose is to obtain sufficient control force when a roll occurs in addition.

[0006]

Therefore, in the present invention, the damping force characteristic of each suspension unit is controlled by the control signal obtained by using the lateral acceleration on the spring and the rate of change of the acceleration to control the spring constant of the suspension. The damping force is applied in the increasing direction to achieve the above-mentioned object.

That is, the vehicle suspension system of the present invention is shown in FIG.
As shown in the claim correspondence diagram, the suspension unit b interposed between the sprung part and the unsprung part of the vehicle and capable of changing the damping force characteristic by the damping characteristic changing means a, and at least the suspension unit b.
Input means e having vertical movement detection means c for detecting factors relating to vertical movement on the spring and lateral acceleration detection means d for detecting acceleration of the vehicle on the spring in the lateral direction.
And each suspension unit b by a control signal obtained by using the rate of change of the lateral acceleration and the lateral acceleration obtained from the signal from the lateral acceleration detecting means d and the signal obtained from the sprung mass behavior detecting means c. The damping force characteristic control means f for controlling the damping force characteristic of is provided.

An acceleration sensor is used as the vertical movement detecting means c, and the acceleration sensors are arranged apart from each other in the left and right directions. The left and right acceleration sensors are respectively inclined with their detection axes toward the center of the vehicle lower direction. Alternatively, the output signals of the left and right acceleration sensors may be used as the left and right accelerations to serve also as the left and right acceleration detecting means.

Further, the suspension unit b is
The expansion side has a variable damping characteristic and the compression side has a fixed low damping characteristic, and the expansion side has a fixed damping characteristic, and the expansion side has a low damping characteristic and the compression side has a low damping characteristic. Both of the side and the pressure side are configured to be able to form three characteristics, a low damping characteristic and a fixed soft characteristic, and the damping characteristic control means f controls the suspension unit when the control signal is positive and exceeds a predetermined threshold value. Is controlled to the extension side hard characteristic, and the control signal is controlled to the soft characteristic when it is within the positive and negative threshold values.
The pressure side hardware characteristic may be controlled when the control signal is smaller than the negative threshold value.

[0010]

When the vehicle travels, a signal from the vertical behavior detecting means for detecting a control factor indicating the vertical behavior on the spring, such as the sprung vertical speed and the sprung / unsprung relative speed, and the lateral acceleration. The damping force characteristic of each suspension unit is controlled by a control signal obtained using the lateral acceleration and the rate of change of the lateral acceleration obtained from the signal from the detection means.

Therefore, at the time of rolling when changing lanes or slalom, it is possible to perform control according to the roll rate by using the rate of change of the lateral acceleration, and to generate by correcting the lateral acceleration. The damping force can be applied in the direction of improving the roll rigidity to increase the spring constant, and thus the roll angle can be reduced.

In the apparatus according to the second aspect, the acceleration (behavior) in the vertical direction is set by the acceleration sensors arranged on the left and right.
On the other hand, the left and right acceleration sensors are attached with the detection axes tilted, and the difference between the left and right output signals is used as the left and right acceleration. Since they are also used, the number of parts can be reduced, and the mounting space and cost can be reduced.

In controlling the damping force characteristic of the suspension unit as described above, in the apparatus according to claim 3, when one stroke direction is controlled to have a high damping force characteristic as the extension side hard characteristic or the compression side hard characteristic, The reverse stroke side is fixed to the low damping force characteristic. Therefore, for example, when the generated damping force is acting in the vibration direction, it is preferable to set the low damping force characteristic in the stroke direction, but in this case, the reverse stroke side is controlled to the high damping force characteristic in the hard characteristic. If so, it is not necessary to switch the characteristics of the suspension unit when the stroke direction of the suspension unit is switched and the generated damping force acts in the damping direction. As a result, high responsiveness is obtained, and
Switching frequency is reduced and durability is improved.

[0014]

Embodiments of the present invention will be described with reference to the drawings. First, the configuration will be described.

FIG. 2 is a structural explanatory view showing a vehicle suspension system of an embodiment of the invention described in each claim, and is interposed between a vehicle body and four wheels, and four shock absorbers (suspension units) are provided. SA ₁ , SA ₂ , SA ₃ , SA
₄ (when describing the shock absorber, when referring to these four collectively, and when describing the common configuration of them, simply referred to as SA). A sprung vertical acceleration sensor (hereinafter referred to as vertical G sensor) 1 _FL , 1 for detecting vertical acceleration is provided on the vehicle body in the vicinity of each shock absorber SA.
_FR , 1 _RL , and 1 _RR are provided (note that these upper and lower G sensors are also simply referred to as the upper and lower G sensors 1 if it is not necessary to specify the positions where they are provided).

Of the four upper and lower G sensors 1,
As shown in FIG. 14, the components provided on the left and right of the front side of the vehicle body are mounted so as to be inclined so that the lower side of the acceleration detection direction gg is directed toward the center of the vehicle. The inclination angle θ ₀ is set to an angle sufficiently larger than the roll angle (0 to 5 °) of the vehicle body (for example, θ ₀ = 25 ° to 30 °).

Then, in the vicinity of the driver's seat, each upper and lower G
A control unit 4 is provided which inputs a signal from the sensor 1 and outputs an operation signal to the pulse motor 3 of each shock absorber SA.

FIG. 3 is a system block diagram showing the above-mentioned configuration. The control unit 4 is provided with an interface circuit 4a, a CPU 4b, and a drive circuit 4c. Signal is input.

It should be noted that the interface circuit 4a is provided with a circuit for processing the signal g obtained from each of the upper and lower G sensors 1, which are shown in FIGS.
That is, FIG. 15 shows a low-pass filter LPF and a high-pass filter HPF for forming a signal indicating the sprung vertical velocity (hereinafter referred to as vertical velocity) v from the signal g obtained by each vertical G sensor 1. In addition, FIG.
Is a signal g obtained from the upper and lower G sensors 1 _FL and 1 _FR.
An arithmetic circuit 4e for calculating a difference for forming a signal indicating the lateral acceleration change rate ΔG from _FL and g _FR , a high pass filter HPF for differentiation and a low pass filter LPF for cutting high frequency components are shown. Further, FIG. 17 similarly shows a signal g obtained from the front upper and lower G sensors 1 _FL and 1 _FR.
An arithmetic circuit 4e for calculating a difference for forming a signal indicating the lateral acceleration G from _FL and g _FR , a high pass filter HPF for drift prevention and a low pass filter LPF for cutting high frequency components are shown.

Next, FIG. 4 is a sectional view showing the structure of the shock absorber SA.
A cylinder 30, a piston 31 defining the cylinder 30 into an upper chamber A and a lower chamber B, an outer cylinder 33 having a reservoir chamber 32 formed on the outer periphery of the cylinder 30, and a lower chamber B and a reservoir chamber 32 are defined. The base 34, the guide member 35 for guiding the sliding movement of the piston rod 7 connected to the piston 31, the suspension spring 36 interposed between the outer cylinder 33 and the vehicle body, and the bumper bar 37. Reference numeral 7 in the drawing denotes a piston rod, and a control rod 70 rotated by the pulse motor 3 is provided through the piston rod 7.

Next, FIG. 5 is an enlarged sectional view showing a portion of the piston 31. As shown in FIG. 5, the piston 31 is formed with through holes 31a and 31b, and each through hole is formed. An expansion side damping valve 12 and a compression side damping valve 20 that open and close 31a and 31b respectively are provided. A stud 38 penetrating the piston 31 is fixed to the bound stopper 41 screwed to the tip of the piston rod 7 by screwing.
Is a flow path (an expansion side second flow path E, an expansion side third flow path F, a bypass flow path G, a compression side) which communicates the upper chamber A and the lower chamber B by bypassing the through holes 31a and 31b. A communication hole 39 for forming the second flow path J) is formed, and an adjuster 40 for changing the flow path cross-sectional area of the flow path is rotatably provided in the communication hole 39. ing. Also, stud 3
An expansion side check valve 17 and a pressure side check valve 22 are provided on the outer peripheral portion of 8 to allow and block the flow on the side of the flow path formed by the communication hole 39 depending on the direction of flow of the fluid. The control rod 70 is connected to the adjuster 40. In addition, the stud 38 has a first port 21, a second port 13, and a third port in order from the top.
A port 18, a fourth port 14 and a fifth port 16 are formed.

On the other hand, in the adjuster 40, the hollow portion 19 is formed, the first lateral hole 24 and the second lateral hole 25 which communicate the inside and the outside are formed, and the vertical groove 23 is formed in the outer peripheral portion. ing.

Therefore, between the upper chamber A and the lower chamber B, the inside of the extension side damping valve 12 is opened by passing through the through hole 31b as a flow passage through which the fluid can flow in the extension stroke. First side flow path D extending to B, second port 13, vertical groove 2
The expansion side second flow path E which opens the outer peripheral side of the expansion side damping valve 12 to the lower chamber B via the third and fourth ports 14, and the second
The extension side check valve 17 is opened via the port 13, the vertical groove 23, and the fifth port 16 to reach the lower chamber B.
Channel F, third port 18, second lateral hole 25, hollow portion 19
There are four flow paths, a bypass flow path G, which leads to the lower chamber B via. Also, as a flow path through which the fluid can flow in the pressure stroke,
The pressure-side first flow path H that opens the pressure-side damping valve 20 through the through hole 31a and the pressure-side check valve 22 through the hollow portion 19, the first lateral hole 24, and the first port 21 to open the upper chamber A. Pressure side second flow path J leading to the hollow part 19, the second lateral hole 2
5, There are three flow paths, a bypass flow path G reaching the upper chamber A via the third port 18.

That is, the shock absorber SA can be changed in characteristics from a low damping force (soft) characteristic to a high damping force (hard) characteristic on both the extension side and the compression side by rotating the adjuster 40. In the embodiment, this characteristic change is proportionally changeable in multiple stages as shown in FIG. 6, so this characteristic is expressed by the term attenuation coefficient.

Further, in the present embodiment, as shown in FIG. 7, the adjuster 40 is rotated counterclockwise from the state in which both the expansion side and the compression side are soft (hereinafter referred to as the soft characteristic SS). And, it is possible to change the damping coefficient in multiple steps only on the extension side,
The compression side has a characteristic that is fixed to a low damping coefficient (hereinafter referred to as the extension side hard characteristic HS). Conversely, when the adjuster 40 is rotated clockwise, the damping coefficient can be changed in multiple steps only on the compression side.
The extension side is configured to have a region where the low damping coefficient is fixed (hereinafter referred to as compression side hard characteristic SH).

By the way, in FIG. 7, when the adjuster 40 is arranged in the position of ,, KK of FIG.
The cross section, the LL cross section, the MM cross section, and the NN cross section are shown in FIGS. 8, 9, and 10, respectively, and the damping force characteristics at each position are shown in FIGS.

Next, the operation of the control unit 4 for controlling the driving of the pulse motor 3 will be described with reference to the flowchart of FIG. Note that this control is separately performed for each shock absorber SA.

In step 101, the vertical velocity v, the lateral acceleration change rate ΔG and the lateral acceleration G obtained by processing the signals from the vertical G sensors 1 are read.

Step 102 is a step of determining whether or not the steering condition is satisfied, that is, a step of determining whether or not the absolute value of (G · ΔG) is larger than a predetermined value K, and YES is determined. The process proceeds to step 103, and if NO, the process proceeds to step 110. Incidentally, FIG. 19 shows a map of the steering condition satisfied region (ON) and the unsatisfied region (OFF). By the way, as for this steering condition, a steering sensor is provided and whether the absolute value of the product of the steering angle θ and the steering angular velocity Δθ is larger than a predetermined value (ON) or not (OF).
The determination may be made in F).

Step 103 is a step for performing processing for setting the flag F = 1.

Step 104 is a step for obtaining the control signal V for each shock absorber SA by the following control formula. When this steering condition is satisfied (ON), the coefficient of the control formula is α _f = α _r = 0, and , A _f = a
_{Let f} , a _r = a _r .

(Control Formula) V _FR = α _f (v ₁ + β _f v ₁ · v _P + γ _f v ₁ · v _R ) + a _f (ΔG + b _f G) V _FL = α _f (v ₂ + β _f v ₂ · _{v P -γ f v 2 · v} R) -a f (ΔG + b f G) V RR = α r (v 3 -β r v 3 · v P + γ r v 3 · v R) + a r (ΔG + b r G) _{V RL = α r (v 4} -β r v 4 · v P -γ r v 4 · v R) -a r (ΔG + b r G) in addition, V _FR is the right front wheel, V _FL left front wheel, V _RR is Right rear wheel, V
_RL represents a control signal for the left rear wheel, but hereinafter, when it does not refer to a specific one, it is simply represented as a control signal V.

Where v ₁ is the sprung vertical speed of the right front wheel, v ₂ is the sprung vertical speed of the left front wheel, v ₃ is the sprung vertical speed of the right rear wheel, and v ₄ is the left rear wheel. Sprung vertical speed,
v _P is the pitch rate and v _R is the roll rate.

Further, the pitch rate v _P is obtained by the difference between the front and rear average vertical velocities as shown in the following equation, and the roll rate v _R is obtained by the average vertical velocities as shown in the following equation.

V _P = (v ₁ + V ₂ −v ₃ −v ₄ ) / 2 v _R = (v ₁ + V ₃ −v ₂ −v ₄ ) / 2 Next, at step 105, the obtained control signal V In the step of judging whether or not the absolute value is larger than the predetermined threshold value δ, the process proceeds to step 106 if YES, and to step 1 if NO.
Proceed to 07.

Step 106 is a step for judging whether or not the control signal V is positive, and if YES, step 108.
And proceeds to step 109 if NO.

Step 107 is a shock absorber S
This is a step of outputting an operation signal to the pulse motor 3 so as to control A to the soft characteristic SS.

Step 108 is a shock absorber S
Pulse motor 3 for controlling A to the extension side hardware characteristic HS
This is a step of outputting an operation signal to. The expansion side damping coefficient at this time is proportional to the magnitude of the control signal V.

Step 109 is a shock absorber S
Pulse motor 3 to control A to pressure side hardware characteristic SH
This is a step of outputting an operation signal to. The compression-side damping coefficient at this time is proportional to the magnitude of the control signal V.

Step 110 is a step of determining whether or not the flag F = 1, and if YES, the process proceeds to step 111, and if NO, the process proceeds to step 114.

Step 111 is a step in which the timer is activated to start measuring the time t.

Step 112 is a step of determining whether or not the timer measurement time t has reached a predetermined time T _{0. If} YES, the process proceeds to step 113, and if NO, step 1
Go to 04.

Step 113 is a step for performing processing for setting the flag F = 0.

In step 114, the steering condition is not satisfied (OF
F) In the step of obtaining a control signal corresponding to time, in this case, the coefficients of the above control equation are set to α _f = α _f , α _r = α _r , and a _f = ar _r = 0.

Next, the operation of the embodiment apparatus will be described.

A) When the steering condition is not satisfied: When the vehicle is traveling straight ahead or is making a constant turn (steady turn), the product of the lateral acceleration G and the lateral acceleration change rate ΔG is small, and the steering condition shown in step 102 is satisfied. Not (OFF).

In such a case, as in step 114, the coefficients of the control equation are α _f = α _f , α _r = α _r , and
The control signal V is calculated with a _f = a _r = 0. In this case, the correction term for the lateral acceleration becomes 0, and the damping coefficient of the shock absorber SA is controlled based on the vertical velocity v, the pitch rate v _P and the roll rate v _R.

The operating state in this case is shown in the time chart of FIG. That is, this time chart
The control signal V (in this case mainly the vertical velocity v
Corresponding to the damping force F, the relative speed between the sprung part and the unsprung part, the control direction of the shock absorber SA, and the operation signal (damping coefficient) output to the pulse motor 3.

As shown in this time chart, when the absolute value of the control signal V does not exceed the threshold value δ, the soft characteristic SS is controlled, and when the absolute value of the control signal V exceeds the threshold value δ, the sign of the control signal V is signified. Is positive, the expansion side hardware characteristic HS is set. Conversely, if the sign of the control signal is negative, the compression side hardware characteristic SH is set. Further, the damping coefficient is controlled according to the magnitude of the control signal V. .

As described above, in the present embodiment, the characteristics are switched based on the sign of the control signal V, but as shown in the time chart, the control signal V and the relative speed substantially corresponding to the vertical speed v are obtained. In the state where the signs of and agree with each other, that is, the damping force generated in the shock absorber SA acts in the damping direction, the stroke direction is controlled to a high damping coefficient, and conversely, In the state where the control signal V and the relative velocity have the same sign, that is, when the damping force acts in the vibration direction, the stroke direction is controlled to a low damping coefficient (that is, skyhook control is performed. ), The road surface input is suppressed and an excellent riding comfort is obtained.

Further, in the time chart, for example, when referring to the case where the control direction of the first shock absorber SA is switched from the pressure side software to the extension side hardware, the pressure side software is controlled as follows.
If the extension side hardware characteristic is switched, it is not necessary to switch the damping force characteristic when the control direction of the shock absorber SA is switched from the compression side software to the extension side hardware.
Therefore, it is characterized by being excellent in operation response and durability.

B) Steering condition satisfied When the lane is changed or the slalom is reached, the product of the lateral acceleration G and the lateral acceleration change rate ΔG becomes large, and the steering condition shown in step 102 is satisfied (ON).

In such a case, as in step 104, the coefficients of the control expression are α _f = α _r = 0 and a _f = a
_The control signal V is calculated with _f , _ar = _ar . In this case, the term relating to the vertical velocity v becomes 0, and the damping coefficient of the shock absorber SA is controlled based on the lateral acceleration change rate ΔG and the lateral acceleration G.

The operating state in this case is shown in the time chart of FIG. This time chart shows the lateral acceleration G and the lateral acceleration change rate ΔG, the control signal V when the steering condition is satisfied (steering control) and the control signal a) when the steering condition is not satisfied (so-called skyhook control) in this order from the top. V'is shown.

That is, when a roll occurs during steering such as when changing lanes or during slalom, the roll rate is determined by the lateral acceleration change rate ΔG and the lateral acceleration G is corrected. Therefore, by performing control using the steering control switching line in FIG. 22, a damping force is applied in a direction to improve roll rigidity, more accurately corresponding to the roll angle and roll rate than in the case of skyhook control. Therefore, the roll angle can be reduced.

Incidentally, FIG. 23 shows the Lissajous waveform of the damping force in the case of the steering control of this embodiment by a solid line. As shown in this figure, the spring constant can be increased. The roll angle can be reduced by the increase. In the figure, the dotted line shows the case where the control signal V is proportional to only the lateral acceleration change rate ΔG, and in this case, the spring constant does not change.

As described above, in the present embodiment, during straight running or during steady turn, vibration is suppressed by suppressing road surface input to obtain a good riding comfort, while at the time of rolling,
The damping force generated in the shock absorber SA acts in the direction of improving the roll rigidity so as to increase the spring constant, and suppresses the roll, so that high steering stability is obtained.

Although the embodiment has been described above, the specific structure is not limited to this embodiment, and the present invention includes a design change and the like without departing from the scope of the invention.

For example, in the embodiment, the extension side hard characteristic H
An example having a suspension unit capable of forming S, a compression side special SH, and a soft characteristic SS was shown, but as shown in the prior art, a suspension unit in which the expansion side and the compression side simultaneously change from hard to soft is provided. You may use. In this case, it is necessary to detect the relative speed when performing the vibration suppression control.

The control formula for obtaining the control signal is not limited to that shown in the embodiment, and the pitch rate and roll rate may be omitted in the term of the speed v.

The suspension unit is not limited to the one shown in the embodiment as long as the damping force characteristic can be changed between hardware and software.

[0062]

As described above, in the vehicle suspension system of the present invention, the damping force characteristic control means is provided with the rate of change of the lateral acceleration and the lateral acceleration obtained from the signal from the lateral acceleration detecting means and the sprung mass. Since the damping force characteristic of each suspension unit is controlled by the signal obtained from the behavior detection means and the control signal obtained by using the signal, the lateral acceleration of the suspension unit can be changed when rolling such as when changing lanes or slalom. By using the rate of change, it is possible to control according to the roll rate, and by adding the correction of the lateral acceleration, it is possible to make the generated damping force act in the direction of improving the roll rigidity and increase the spring constant. The effect that the roll angle can be reduced is obtained.

Further, in the apparatus according to the second aspect, the acceleration sensors arranged on the left and right serve as both the vertical behavior detecting means and the lateral acceleration detecting means. Therefore, the number of parts can be reduced, and the mounting space can be reduced. The effect that the cost can be reduced can be obtained.

Further, in the apparatus according to the third aspect, when the suspension unit is controlled to have a high damping force characteristic in one stroke direction, the suspension unit is formed in a structure in which the reverse stroke side is fixed to the low damping force characteristic, so that the high responsiveness is obtained. It is possible to obtain the effect that the switching frequency is reduced and the durability is improved.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a claim showing a vehicle suspension device of the present invention.

FIG. 2 is a structural explanatory view showing a vehicle suspension device of an embodiment of the present invention.

FIG. 3 is a system block diagram showing a vehicle suspension system of the embodiment.

FIG. 4 is a cross-sectional view showing a shock absorber (suspension unit) applied to the apparatus of the embodiment.

FIG. 5 is an enlarged cross-sectional view showing a main part of the shock absorber.

FIG. 6 is a damping force characteristic diagram corresponding to the piston speed of the shock absorber.

FIG. 7 is a damping force characteristic diagram corresponding to the step position of the pulse motor of the shock absorber.

FIG. 8 is a K of FIG. 5 showing a main part of the shock absorber.
FIG.

FIG. 9 is an L of FIG. 5 showing a main part of the shock absorber.
It is a -L cross section and a MM cross section.

FIG. 10 is a sectional view taken along line NN of FIG. 5, showing a main part of the shock absorber.

FIG. 11 is a damping force characteristic diagram of the shock absorber when the extension side is hard.

FIG. 12 is a damping force characteristic diagram of the shock absorber in a soft state on the extension side and the compression side.

FIG. 13 is a damping force characteristic diagram of the shock absorber in a compression side hard state.

FIG. 14 is an explanatory diagram showing a main part of the device according to the embodiment.

FIG. 15 is a circuit diagram showing a main part of the device according to the embodiment.

FIG. 16 is a circuit diagram showing a main part of the device according to the embodiment.

FIG. 17 is a circuit diagram showing a main part of the device according to the embodiment.

FIG. 18 is a flowchart showing the control operation of the control unit of the embodiment apparatus.

FIG. 19 is a diagram showing a map for determining whether or not a steering condition of the embodiment apparatus is satisfied.

FIG. 20 is a time chart showing the operation of the embodiment apparatus when the steering condition is not satisfied.

FIG. 21 is a time chart showing the operation of the embodiment apparatus when the steering conditions are satisfied.

FIG. 22 is a diagram showing a control switching line during steering of the embodiment apparatus.

FIG. 23 is a diagram showing a Lissajous waveform of the damping force in the case of steering control of the embodiment apparatus.

[Explanation of symbols]

 a damping force characteristic changing means b suspension unit c vertical behavior detecting means d lateral acceleration detecting means e input means f damping force characteristic controlling means

Claims (3)

[Claims] 1. A suspension unit interposed between a sprung part and an unsprung part of a vehicle and capable of changing a damping force characteristic by a damping characteristic changing means; and a vertical behavior for detecting at least a factor relating to a vertical behavior on the spring. An input means having a detection means and a lateral acceleration detection means for detecting a lateral acceleration of the vehicle body on the spring; a rate of change of the lateral acceleration and the lateral acceleration obtained from a signal from the lateral acceleration detection means; A vehicle suspension device, comprising: damping force characteristic control means for controlling the damping force characteristic of each suspension unit by a control signal obtained by using a signal obtained from the up-down direction behavior detecting means. 2. An acceleration sensor is used as the up-and-down behavior detecting means, the acceleration sensors are arranged apart from each other in the left and right directions, and the left and right acceleration sensors are respectively inclined with their detection axes toward the center of the vehicle downward direction. The vehicle suspension device according to claim 1, wherein the vehicle suspension device is mounted as a horizontal acceleration detecting unit by using the difference between the output signals of the left and right acceleration sensors as the horizontal acceleration. 3. The suspension unit has an expansion side hard characteristic in which the expansion side damping characteristic is variable and the compression side damping characteristic is fixed to a low damping characteristic, and a suspension side damping characteristic is variable and the expansion side damping characteristic is low damping. It is configured to be able to form three characteristics, a compression side hard characteristic fixed to the characteristic and a soft characteristic fixed to both the extension side and the compression side to a low damping characteristic, and the damping characteristic control means is set to a predetermined value when the control signal is positive. When the threshold value is exceeded, the suspension unit is controlled to the extension side hard characteristic, when the control signal is within the positive and negative threshold values, it is controlled to the soft characteristic, and when the control signal is smaller than the negative threshold value, the pressure side is controlled. The vehicle suspension system according to claim 1 or 2, wherein the vehicle suspension system is controlled to have a hardware characteristic.