JPH06183237A - Vehicle suspension - Google Patents

Abstract

(57) [Summary] [Purpose] To obtain sufficient vibration damping performance against moment of inertia and improve steering stability. [Structure] A shock absorber b interposed between a vehicle body side and each wheel side and capable of changing a damping coefficient by a damping coefficient changing means a, and a sprung vertical speed near a position where each shock absorber b is provided are detected. The sprung vertical speed detecting means c, the pitch rate detecting means d for detecting the pitch rate of the vehicle body, the roll rate detecting means e for detecting the roll rate of the vehicle body, and the damping coefficient of each shock absorber b are Damping coefficient control means f for controlling based on the control signal obtained from the speed, pit rate and roll rate
It is characterized by having and.

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 coefficient of a shock absorber.

[0002]

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

This conventional vehicle suspension system detects the sprung vertical speed and the relative speed between the sprung and unsprung parts. When the two have the same sign, the damping coefficient is made hard, and when the two have different signs, the damping coefficient is set. The damping coefficient control such as softening was performed independently for the four wheels.

[0004]

However, since the above-mentioned conventional apparatus has the above-mentioned structure, when the characteristics of the hardware are suitable when the vehicle body is moving in the bounce direction, With respect to the body movement in which bounce and pitching are coupled, a moment of inertia of the body around the center of gravity of the body is added to the sprung mass, so the damping force (control force) is insufficient and the steering stability is poor. There was a point.

Further, there are known devices for controlling the roll and the pitching, but these are separately and independently controlled, and other sensors such as a steering sensor are required, which simplifies the control and parts. It was also desired to reduce the score.

The present invention has been made by paying attention to the above-mentioned conventional problems. Therefore, it is a first object of the present invention to obtain a sufficient damping property against the moment of inertia and improve the steering stability. The second purpose is to simplify the configuration.

[0007]

Therefore, in the present invention, the control signal is obtained from the sprung vertical velocity, the pitch rate, and the roll rate, and the damping coefficient is controlled based on this control signal to achieve the first object. In addition, the pitch rate and the roll rate are obtained from the sprung vertical velocity to achieve the second object.

That is, the vehicle suspension system according to claim 1 of the present invention is interposed between the vehicle body side and each wheel side, and the damping coefficient is changed by the damping coefficient changing means a, as shown in the claim correspondence diagram of FIG. A possible shock absorber b, a sprung vertical velocity detecting means c for detecting a sprung vertical velocity near a position where each shock absorber b is provided, a pitch rate detecting means d for detecting a pitch rate of a vehicle body, and a vehicle body Roll rate detecting means e for detecting the roll rate of
There is provided damping coefficient control means f for controlling the damping coefficient of each shock absorber b on the basis of a control signal obtained from the sprung vertical velocity, pit rate and roll rate.

A vehicle suspension system according to a second aspect of the present invention is provided with a shock absorber b interposed between the vehicle body side and each wheel side, the damping coefficient of which can be changed by the damping coefficient changing means a, and each shock absorber. The sprung vertical velocity detecting means c for detecting the sprung vertical velocity near the position, the pitch rate detecting means d for detecting the pitch rate of the vehicle body, the roll rate detecting means e for detecting the roll rate of the vehicle body, and the shock absorbers. Relative speed detection means g for detecting the relative speed between the sprung and unsprung portions near the position where b is provided.
And a damping coefficient of each shock absorber b, a control signal obtained by the sprung vertical velocity, the pit rate and the roll rate is obtained. When this control signal and the relative velocity between the sprung and unsprung have the same sign, the damping coefficient is obtained. On the other hand, the damping coefficient control means f for controlling the damping coefficient to the minimum when it has a different sign is provided.

The pitch rate detecting means is means for detecting a pitch rate from a sprung vertical speed difference between the front and rear of the vehicle body based on the sprung vertical speed detected by the sprung vertical speed detecting means. May be means for detecting the roll rate from the difference between the sprung vertical speeds of the right and left of the vehicle body based on the sprung vertical speed detected by the sprung vertical speed detecting means.

In the shock absorber, the expansion side has a variable damping coefficient and the compression side has a low damping coefficient fixed to the expansion side hard area, and the compression side has a variable damping coefficient and the expansion side has a compression side hard area fixed to the low damping coefficient. Both the side and the pressure side are formed in a structure having three regions, a soft region having a low damping coefficient, and the damping coefficient control means sets the shock absorber to the expansion hard region when the control signal is equal to or more than a positive threshold value. The shock absorber is controlled in the pressure side hard area when the control signal is below the negative threshold value, and the shock absorber is controlled in the soft area when the control signal is between the positive and negative threshold values. You may.

Further, in obtaining the control signal,
The sprung vertical velocity uses a signal that has passed through a bandpass filter including the sprung resonance frequencies of the front and rear wheels, the pitch rate uses a signal that has passed through a bandpass filter that includes the pitch resonance frequency, and the roll rate is A band-pass filtered signal containing the roll resonance frequency may be used.

In obtaining the control signal,
The first proportionality constant for multiplying the sprung vertical direction speed, the second proportionality constant for multiplying the pitch rate, and the third proportionality constant for multiplying the roll rate are independently set, and the first proportionality constant is The value according to the direction spring constant
The proportional constant of 1 may be a numerical value according to the pitch rigidity, and the third proportional constant may be a numerical value according to the roll rigidity.

[0014]

When the sprung speed detecting means, the pitch rate detecting means, and the roll rate detecting means detect vertical movement (bouncing), pitching, and roll on the spring, the damping coefficient control means determines the sprung vertical speed and pitch. A control signal is obtained based on the rate and the roll rate, and the damping coefficient of the shock absorber is controlled according to the control signal.

Therefore, sufficient control force can be obtained not only for bounce but also for pitch and roll.

Further, in the apparatus according to the second aspect, the damping coefficient control means increases the damping coefficient when the control signal and the sprung / unsprung relative speed have the same sign, and when both have different signs. Minimizes the damping coefficient. Also in this case, sufficient control force can be obtained not only for bounce but also for pitch and roll.

In the apparatus according to the third aspect, the pitch rate and the roll rate are obtained from the sprung vertical velocity detected by the sprung vertical velocity detecting means. For this reason, the sprung vertical velocity detecting means also serves as the pitch rate detecting means and the roll rate detecting means.

[0018]

Embodiments of the present invention will be described with reference to the drawings. (First Embodiment) First, the structure will be described.

FIG. 2 is a structural explanatory view showing a vehicle suspension system of a first embodiment which is an embodiment of the invention described in claims 1, 3, 4, 5 and 6, and is a vehicle body and four wheels. Interposed between the four shock absorbers SA ₁ , SA ₂ , SA
₃ and SA ₄ (in the explanation of the shock absorber, when these 4 are collectively referred to, and when describing their common configuration, they are simply indicated as SA). A vertical acceleration sensor (hereinafter referred to as vertical G sensor) 1 for detecting vertical acceleration is provided on the vehicle body in the vicinity of each shock absorber SA.
Is provided. In addition, a signal from each sensor 1 is input to a position near the driver's seat so that each shock absorber S
A control unit 4 that outputs a drive control signal to the A pulse motor 3 is provided.

FIG. 3 is a system block diagram showing the above configuration, in which the control unit 4 includes an interface circuit 4a, a CPU 4b, and a drive circuit 4c, and the interface circuit 4a is provided with signals from the above-mentioned respective sensors 1. Is entered. In the interface circuit 4a, a set of five filter circuits shown in FIG. 14 is provided for each upper and lower G sensor 1. That is, LPF1
Is a low-pass filter circuit for removing noise in the high frequency range (30 Hz or higher) from the signals sent from the upper and lower G sensors 1. LPF2 is a low-pass filter circuit LP
It is a low-pass filter circuit for integrating a signal indicating the acceleration passed through F1 and converting it into a sprung vertical velocity. B
PF1 is passed through a frequency range including the sprung resonance frequency bouncing component signal _{v (v 1, v 2,} v 3, v 4 Numerals _{1, 2, 3 and 4} to the position of the shock absorbers SA The same applies to the following.). The BPF 2 passes the frequency range including the pitch resonance frequency to pass the pitch component signal v ′.
It is a bandpass filter circuit that forms (v ₁ ′, v ₂ ′, v ₃ ′, v ₄ ′). The BPF 3 allows the roll component signal v ″ (v
₁ ″, v ₂ ″, v ₃ ″, v ₄ ″). Incidentally, in this embodiment, the sprung resonance, the pitch resonance, and the roll resonance frequencies are different from each other. However, when the resonance frequencies are close to each other, only the BPF 1 is required as the bandpass filter.

Next, FIG. 4 is a sectional view showing the structure of the shock absorber SA.
A is 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, a lower chamber B and a reservoir chamber 32. Which defines the base 34 and the piston 32
A guide member 35 that guides the sliding of the piston rod 7 that is connected to the vehicle, a suspension spring 36 that is interposed between the outer cylinder 33 and the vehicle body, and a bumper bar 37.

Next, FIG. 5 is an enlarged sectional view showing a portion of the piston 31. As shown in FIG. 5, the piston 31 has through holes 31a and 31b formed therein and each through hole. An expansion side damping valve 12 and a compression side damping valve 20 that open and close 31a and 31b respectively are provided. In addition, the stud 38 that is fixed to the tip of the piston rod 7 and penetrates the piston 31 has an upper chamber A
Is formed with a communication hole 39 for communicating the lower chamber B with the lower chamber B. Further, an adjuster 40 for changing the flow passage cross-sectional area of the communication hole 39 and a fluid communication hole 39 depending on the direction of fluid flow are formed.
An expansion-side check valve 17 and a pressure-side check valve 22 that allow and block the flow of the air are provided. The adjuster 40 is rotated by the pulse motor 3 (see FIG. 4). 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, a hollow portion 19 is formed, a first lateral hole 24 and a second lateral hole 25 that communicate the inside and the outside are formed, and a vertical groove 23 is formed in the outer peripheral portion. There is.

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 is constructed so that the damping coefficient can be changed in multiple stages on both the extension side and the compression side with the characteristics shown in FIG. 6 by rotating the adjuster 40. That is, as shown in FIG. 7, when the adjuster 40 is rotated counterclockwise from the state in which both the expansion side and the compression side are soft (in the figure; hereinafter referred to as the soft region SS), the damping coefficient is increased only on the expansion side. A region that can be changed in multiple steps and the compression side is fixed to a low damping coefficient (hereinafter, the extension side hard region HS
Conversely, when the adjuster 40 is rotated in the clockwise direction, the damping coefficient can be changed in multiple steps only on the compression side, and the expansion side becomes a region where the low damping coefficient is fixed (hereinafter referred to as the compression side hard region SH). It has a structure.

By the way, in FIG. 7, when the adjuster 40 is arranged at the positions of, the KK cross section, the MM cross section, and the NN cross section in FIG. 5, respectively, are shown in FIGS. 10 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, each upper and lower G sensor 1,
The vertical acceleration obtained from 1, 1, 1 is applied to each filter circuit L.
This is a step of performing processing by PF1, LPF2, BPF1, BPF2, BPF3 to obtain a bounce component signal v, a pitch component signal v ′, and a roll component signal v ″.

Step 102 uses the following equation 1
This is a step of calculating a control signal V (V ₁ , V ₂ , V ₃ , V ₄ ) for the position of each wheel based on each component signal v, v ′, v ″.

[0030]

[Equation 1]

Α _f , β _f , γ _f are proportional constants α _r , β _r , γ _r of the front wheels, and proportional constants v ₁ , v ₁ ', v ₁ ″ of the rear wheels: left front wheels sprung mass vertical direction velocity signal _{v 2, v 2 ', v} 2 ": on the front wheel right spring vertical velocity signal _{v 3, v 3', v} 3": the left rear wheel of the spring vertical velocity signal v _4, v ₄ ′, v ₄ ″: sprung vertical speed signals on the right of the rear wheels. In each equation, the first part bound by α _f and α _r is the bounce rate, the part bound by β _f and β _r is the pitch rate, and the part bounded by γ _f and γ _r Is the roll rate. As described above, the bounce rate (spring vertical speed), the pitch rate, and the roll rate are obtained from the signals from the upper and lower G sensors 1, and the portions of the upper and lower G sensors 1 and the control unit 4 that obtain these are claimed. The sprung vertical velocity detecting means, the pitch rate detecting means, and the roll rate detecting means in the range of 4 are constituted.

Step 103 is a step of determining whether or not the control signal V is equal to or more than a predetermined threshold value δ _T , and if YES, the process proceeds to step 104, and if NO, the step 1
Go to 05.

Step 104 is a shock absorber S
This is a step of controlling A to the extension side hard area HS.

Step 105 is a step of judging whether or not the control signal V is a value between a predetermined threshold value δ _T and a threshold value −δ _{C. If} YES, then the routine proceeds to step 106, and if NO. Go to step 107.

Step 106 is a shock absorber S
This is a step of controlling A in the soft area SS.

Step 107 is a step which is displayed for the sake of convenience. When NO is determined in steps 103 and 105, the control signal V is below a predetermined threshold value -δ _C , and in this case, Go to step 108.

Step 108 is a shock absorber S
This is a step of controlling A to the pressure side hard area SH.

Next, the operation of the embodiment apparatus will be described with reference to the time chart of FIG.

When the sprung vertical speed changes as shown by the control signal V in this figure, as shown in the figure, the control signal V
Is a value between the predetermined thresholds δ _T and −δ _C , the shock absorber SA is controlled to the soft region SS.

When the control signal V exceeds the threshold value δ _T , the expansion side hard region HS is controlled to fix the compression side to a low damping coefficient, while the expansion side damping coefficient is made proportional to the control signal V. To change. At this time, the damping coefficient C is C = kV
Control so that.

When the control signal V becomes equal to or lower than the threshold value -δ _{C, the} compression side hard region SH is controlled to fix the extension side to a low damping coefficient, while the compression side damping coefficient is made proportional to the control signal V. To change. Also at this time, the damping coefficient C is C = k
・ V is controlled to be V.

In the first embodiment described above, the effects listed below can be obtained.

Since a sufficient control force can be generated not only for bounce but also for roll and pitch, it is possible to provide a vehicle suspension system that is excellent in riding comfort and steering stability.

In performing the control as described above,
Since only the upper and lower G sensors 1 are used as the detection means, the number of parts can be reduced and the cost can be reduced.
The effect is that the assembly work, the assembly space, and the weight can be reduced.

In obtaining the bounce rate, pitch rate, and roll rate, different constants α,
Since β and γ are used, each rate can be accurately detected based on the sprung vertical velocity even when the sprung resonance frequency, the pitch resonance frequency, and the roll resonance frequency are different in the vehicle.

Next, other embodiments will be described. In describing these embodiments, only the differences from the first embodiment will be described. Also, the first reference numeral
The same reference numerals as those in the embodiment denote the same objects.

(Second Embodiment) In the second embodiment, a part of the control unit 4 is different from that of the first embodiment, that is, in the second embodiment, in obtaining the control signal V, the following mathematical expression is used. The arithmetic expression shown in 2 is used.

[0048]

[Equation 2]

In the second embodiment, the part for obtaining the bounce component v is different, and as the bounce component v, only the component at the position of each shock absorber SA is input. Therefore, the second embodiment is a control in which the bounce component of each wheel is emphasized, as compared with the first embodiment, and has a characteristic in which the vibration damping property with respect to the roll and the pitch is suppressed.

(Third Embodiment) In the third embodiment, as a shock absorber SA of a variable damping coefficient type, when the pulse motor 3 is driven, as shown in FIG. However, both of them have a well-known structure that changes from high attenuation to low attenuation (for example, see Japanese Utility Model Laid-Open No. 63-112914).
This is an example of using the public relations).

In this third embodiment, as shown in FIG. 18, load sensors (sprung / unsprung relative speed detecting means) 6, 6, 6, 6 are provided as input means. In addition,
The load sensor 6 is provided at the mounting portion of the shock absorber SA to the vehicle body, and detects the damping force (corresponding to the relative speed) F generated in the shock absorber SA as a load.

Control unit 304 of the third embodiment
19 will be described with reference to the flowchart of FIG. 19, the step 301 is the damping force F detected by the load sensor 6.
Is a step of reading, and after this processing, steps 101 and 102 similar to those in the first embodiment are performed, and then the process proceeds to step 302.

In step 302, the damping force F and the control signal V
YES in the step of determining whether and are the same sign
Then, the process proceeds to step 303, and if NO (different sign), the process proceeds to step 304.

In step 303, the damping force F is F = k
The damping coefficient is changed so that V becomes V.

In step 304, the damping coefficient of the shock absorber SA is controlled so that both the extension and the pressure have the minimum damping coefficient.

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 within a range not departing from the gist of the invention.

For example, in the embodiment, the pitch rate is obtained by the difference between the front and rear sprung vertical velocities, and the roll rate is obtained by the difference between the left and right sprung vertical velocities. A sensor that detects a change in pitch angle or a sensor that detects a change in roll angle may be used.

[0058]

As described above, in the vehicle suspension system of the present invention, the damping coefficient control means obtains the control signal from the sprung vertical velocity, the pitch rate and the roll rate, and the shock absorber damping is performed based on this control signal. Since the coefficient is controlled, sufficient control force can be obtained not only for bounce, but also for pitch and roll. This has the effect of improving ride comfort and steering stability. . Further, in the apparatus according to the third aspect, the pitch rate and the roll rate are obtained from the sprung vertical speed detected by the sprung vertical speed detecting means, so that the sprung vertical speed detecting means detects the pitch rate detecting means and the roll rate detecting means. Since it also serves as a means, the number of parts is reduced, and this has the effect of simplifying the configuration and reducing the cost, assembly time, and weight.

[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 the first embodiment of the present invention.

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

FIG. 4 is a sectional view showing a shock absorber applied to the device of the first 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 an attenuation coefficient 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 M of FIG. 5 showing a main part of the shock absorber.
FIG.

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 a block diagram showing a main part of a control unit of the first embodiment.

FIG. 15 is a flowchart showing the control operation of the control unit of the first embodiment device.

FIG. 16 is a time chart showing the operation of the first embodiment device.

FIG. 17 is a damping coefficient characteristic diagram of the shock absorber of the third embodiment device.

FIG. 18 is a system block diagram showing a device of a third embodiment.

FIG. 19 is a flowchart showing the control operation of the control unit of the third embodiment device.

[Explanation of symbols]

 a damping coefficient changing means b shock absorber c sprung vertical speed detecting means d pitch rate detecting means e roll rate detecting means f damping coefficient controlling means g sprung / unsprung relative speed detecting means

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] May 8, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

Next, FIG. 5 is an enlarged sectional view showing a portion of the piston 31. As shown in FIG. 5, the piston 31 has through holes 31a and 31b formed therein and each through hole. An expansion side damping valve 12 and a compression side damping valve 20 that open and close 31a and 31b respectively are provided. A communication hole 39 that communicates the upper chamber A and the lower chamber B is formed at the tip of the piston rod 7 that penetrates the piston 31, and the flow passage cross-sectional area of the communication hole 39 is changed. There is provided an adjuster 40 for this purpose, and an extension side check valve 17 and a pressure side check valve 22 that allow and block the flow of the fluid through the communication hole 39 depending on the direction of flow of the fluid. The adjuster 40 is rotated by the pulse motor 3 (see FIG. 4).
Further, at the tip of the piston rod 7, the first
A port 21, a second port 13, a third port 18, a fourth port 14 and a fifth port 16 are formed. Reference numeral 38 in the drawing denotes a retainer on which the pressure side check valve 22 is seated.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

[0030]

[Equation 1]

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

Α _f , β _f , γ _f are proportional constants of the front wheels α _r , β _r , γ _r are proportional constants of the rear wheels v ₁ , v ₁ ′, v ₁ ″: right front wheels Spring sprung vertical speed signal v ₂ , v ₂ ', v ₂ ″: Front wheel left sprung vertical speed signal v ₃ , v ₃ ′, v ₃ ″: Rear wheel right sprung vertical speed signal v ₄ , v ₄ ′, v ₄ ″: sprung vertical velocity signals on the left of the rear wheel.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction content]

[0048]

[Equation 2]

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

[Procedure correction 6]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

Claims (6)

[Claims] 1. A shock absorber which is interposed between a vehicle body side and each wheel side and whose damping coefficient can be changed by a damping coefficient changing means, and a sprung vertical velocity in the vicinity of the position where each shock absorber is provided is detected. The sprung vertical velocity detecting means, the pitch rate detecting means for detecting the pitch rate of the vehicle body, the roll rate detecting means for detecting the roll rate of the vehicle body, the damping coefficient of each shock absorber, the sprung vertical velocity, the pit rate and the roll rate. And a damping coefficient control means for controlling based on a control signal obtained from the rate and the vehicle suspension device. 2. A shock absorber which is interposed between the vehicle body side and each wheel side and whose damping coefficient can be changed by a damping coefficient changing means, and a sprung vertical velocity in the vicinity of the position where each shock absorber is provided is detected. A sprung vertical speed detecting means, a relative speed detecting means for detecting a relative speed between sprung and unsprung portions in the vicinity of a position where each shock absorber is provided, a pitch rate detecting means for detecting a pitch rate of a vehicle body, and a vehicle body The roll rate detecting means for detecting the roll rate of each of the shock absorbers and the damping coefficient of each shock absorber are obtained by the control signal obtained by the sprung vertical velocity, the pit rate and the roll rate. When the speed has the same sign, the damping coefficient is increased, and when the speed has the different sign, the damping coefficient control means for controlling the damping coefficient to the minimum is provided. Vehicle suspension system, characterized in that there. 3. The pitch rate detecting means is means for detecting a pitch rate from a sprung vertical speed difference between front and rear of a vehicle body based on the sprung vertical speed detected by the sprung vertical speed detecting means, and the roll rate detecting means. 3. The vehicle suspension system according to claim 1 or 2, wherein said means is means for detecting a roll rate from a difference between the sprung vertical speeds on the left and right of the vehicle body based on the sprung vertical speed detected by said sprung vertical speed detecting means. . 4. The shock absorber includes an expansion side hard region in which the expansion side is variable and the compression side is fixed at a low damping coefficient, and a compression side hard region is in which the compression side is variable and the expansion side is fixed at a low damping coefficient. The damping coefficient control means controls the shock absorber in the extension side hard area when the control signal is equal to or higher than the positive threshold value, by forming the structure having three areas, that is, the soft area having the low damping coefficient on both the side and the compression side. However, when the control signal is below the negative threshold, the shock absorber is controlled in the pressure side hard area, and when the control signal is between the positive and negative thresholds, the shock absorber is controlled in the soft area. The vehicle suspension system according to claim 1, wherein: 5. In obtaining the control signal, the sprung vertical velocity is a signal passed through a bandpass filter including the sprung resonance frequencies of the front and rear wheels, respectively.
3. The pitch rate uses a signal that has passed a bandpass filter including a pitch resonance frequency, and the roll rate uses a signal that has passed a bandpass filter that includes a roll resonance frequency. The vehicle suspension system described. 6. In obtaining the control signal, a first proportional constant applied to the sprung vertical velocity, a second proportional constant applied to the pitch rate, and a third proportional constant applied to the roll rate are independently provided. The first proportional constant is a numerical value according to the vertical spring constant, and the second proportional constant is a numerical value according to the pitch rigidity,
The vehicle suspension system according to claim 1 or 2, wherein the third proportionality constant is a numerical value according to roll rigidity.