JPH0699714A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To restrict active roll in accordance with a rolling direction of a car body using a steering sensor only by determining the rolling direction of the car body based on a direction of a steering angular velocity determined by a steering angle process value passing a low-pass filter, and performing change of a rolling control direction based on this determination. CONSTITUTION:On-spring vertical acceleration sensors 1 are provided in a car body at a close position to four shock absorbers SA1-SA4. In addition, a steering sensor 2 is provided at a steering device as a steering angle detection means to detect a steering angle. A control unit 4 is provided at a close position to a driver's seat, and a low-pass filter 6 is provided inside an interface circuit 4a of the unit 4 to process a signal from the steering sensor 2. This filter 6 has frequency characteristics of an output to an input equivalent to a phase of frequency characteristics of car body rolling relative to the preliminarily measured steering angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension system for a vehicle for optimally controlling the damping characteristics of a shock absorber, and more particularly to a system for controlling roll suppression during steering.

[0002]

2. Description of the Related Art Conventionally, as such a vehicle suspension device, for example, one disclosed in Japanese Utility Model Laid-Open No. 62-70008 is known.

This conventional device calculates the roll angle of the vehicle body from the vehicle speed detected by the vehicle speed detecting means and the steering angle detected by the steering angle detecting means, and when this roll angle exceeds a predetermined threshold value. Is based on the steering direction at that time, and the damping characteristics of the shock absorber are controlled by controlling the extension side to the hard characteristic on the steering direction side and the compression side on the opposite side to the steering direction to set the hard characteristic to roll the vehicle body. Was to suppress.

[0004]

However, in the conventional device, since the apparent roll state is judged based on the steering angle and the steering direction detected by the steering angle detecting means, the steering is performed only once. There is no problem at all when the roll control is performed with respect to the steering angle or when the total steering control is performed with respect to the steering angle, but when a large steering cutback or continuous steering such as slalom is performed, the calculation is performed based on the steering angular velocity. Since a phase difference occurs between the roll angle and the actual roll generated in the vehicle, there is a problem that the damping characteristic is controlled in the direction opposite to the actual roll control direction, and the roll is rather lengthened.

Although the above problems can be solved by using a sensor for detecting the roll direction such as an acceleration sensor or a load sensor in addition to the steering sensor, the cost is high. It causes another problem of getting tired.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a vehicle suspension system capable of active roll restraining control in accordance with a roll direction of a vehicle body only by a steering sensor. I am trying.

[0007]

As shown in the claim correspondence diagram of FIG. 1, a vehicle suspension system of the present invention is interposed between a vehicle body side and each wheel side, and one stroke side of the extension side and the compression side is provided. When controlling to a high damping characteristic, a shock absorber b having a damping characteristic changing means a having a structure in which the reverse stroke side has a low damping characteristic, a steering angle detecting means c for detecting the steering angle of the vehicle, and a vehicle body with respect to the steering angle. A low-pass filter d having an output frequency characteristic with respect to an input having the same phase as the roll frequency characteristic, and the low-pass filter when the steering angle detected by the steering angle detecting means c exceeds a predetermined neutral threshold value. Based on the roll direction of the vehicle body determined from the steering angular velocity direction obtained from the steering angle processing value that has passed through the filter d, the control is switched to a roll control state in which the stroke side damping characteristics of the left and right shock absorbers b are controlled to a higher level. With respect to the subsequent turning back of steering, when the direction of the steering angular velocity obtained from the steering angle processing value that has passed through the low-pass filter d is reversed, the damping characteristics of the left and right shock absorbers b are controlled to be higher. And a roll control means (e) for returning the shock absorber (b) to a normal control state for performing a normal damping characteristic control when the steering angle is reduced to a value less than a predetermined neutral threshold value for a predetermined time. The means to be

[0008]

The function of the present invention will be described. The reference numerals in the description correspond to those in FIG. When a steering operation is performed while the vehicle is running, the vehicle body rolls. At this time, when the steering angle detected by the steering angle detecting means c is less than the predetermined neutral threshold value, the roll hardly occurs, so that the shock absorber b is switched to the normal control state for controlling the normal damping characteristic. Has been. As a result, the riding comfort of the vehicle can be ensured.

On the other hand, when the steering angle exceeds the predetermined neutral threshold value, a large roll will be generated in the vehicle body by a large steering, so the roll control means e causes the steering wheel passing through the low-pass filter d. Based on the roll direction of the vehicle body determined from the direction of the steering angular velocity obtained from the angle processing value, the roll control state is controlled in which the stroke side damping characteristics of the left and right shock absorbers b are controlled to be higher. As a result, the stroke of each shock absorber b in the roll direction can be suppressed by the higher damping characteristics, and the roll of the vehicle body can be suppressed from the initial stage of its generation.

Further, during roll control, when the direction of the steering angular velocity obtained from the steering angle processing value that has passed through the low-pass filter d is reversed due to steering back, the damping characteristics of the left and right shock absorbers b are controlled to be higher. The stroke is switched to the reverse stroke side. At this time, since the phase of the frequency characteristic of the output with respect to the input of the low-pass filter d is the same as the phase of the frequency characteristic of the vehicle body roll with respect to the steering angle, it is determined from the steering angle processing value that has passed through the low-pass filter d. The direction of the steering angular velocity substantially coincides with the actual roll direction of the vehicle body. Therefore, only the steering sensor can perform active roll restraining control in accordance with the roll direction of the vehicle body.

During the roll control, when there is a road surface input in the direction opposite to the stroke of the shock absorber b due to the roll of the vehicle body, the road surface input is absorbed by the low damping characteristic on the reverse stroke side. In this way, the road surface input on the reverse stroke side during the roll control can be absorbed with the low damping characteristic to ensure the riding comfort of the vehicle.

Further, this roll control state is maintained until the state where the steering angle is decreased below the predetermined neutral threshold value continues for a predetermined time, and thereafter the shock absorber b is made to have a normal damping characteristic. Return to the normal control state.

[0013]

Embodiments of the present invention will be described with reference to the drawings. First, the configuration of the vehicle suspension system according to the embodiment of the present invention will be described. FIG. 2 is a structural explanatory view showing a vehicle suspension device of an embodiment of the present invention, which is interposed between the vehicle body and each wheel and is provided with four shock absorbers SA ₁ , SA ₂ , SA ₃ , SA ₄
(In describing the shock absorber, when these four are collectively referred to, and when describing the common configuration, they are simply referred to as SA). A sprung vertical acceleration sensor (hereinafter referred to as a vertical acceleration sensor) that detects vertical acceleration is used as a vehicle behavior sensor on the vehicle body in the vicinity of the mounting position of each shock absorber SA.
An up and down G sensor) 1 is provided, a steering sensor 2 as a steering angle detecting means for detecting a steering angle is provided in the steering wheel, and the sensors 1, 2, and A control unit 4 that inputs a signal from a vehicle speed sensor 5 (not shown) and outputs a drive control signal to the pulse motor 3 of each shock absorber SA
Is provided.

The above-mentioned configuration is shown in the system block diagram of FIG. 3, in which the control unit 4 comprises an interface circuit 4a, a CPU 4b and a drive circuit 4c, and the interface circuit 4a is provided with respective sensors 1, 2 and 5. The signal from is input. The interface circuit 4a
A low-pass filter 6 that processes a signal from the steering sensor 2 is provided therein. The low-pass filter 6 has an output frequency characteristic with respect to input that is equivalent to the phase of the frequency characteristic of the vehicle body roll with respect to the steering angle measured in advance (see the characteristic diagram of FIG. 16). Therefore, the roll of the vehicle body can be detected without any phase delay.

Next, FIG. 4 shows each shock absorber SA.
FIG. 3 is a cross-sectional view showing the configuration of the shock absorber SA in which a cylinder 30, a piston 31 that defines the cylinder 30 into an upper chamber A and a lower chamber B, and a reservoir chamber 32 are formed on the outer periphery of the cylinder 30. An outer cylinder 33, a base 34 that defines the lower chamber B and the reservoir chamber 32, a guide member 35 that guides the sliding of the piston rod 7 having a piston 31 connected to the lower end, and an outer cylinder 33 and the vehicle body. The suspension spring 36 interposed between the bumper bar 3 and
7 and 7.

Next, FIG. 5 is an enlarged cross-sectional view showing a portion of the piston 31, and as shown in this figure, the piston 31 has through holes 31a and 31b formed therein and each through hole. A compression side damping valve 20 and an expansion side damping valve 12 that open and close 31a and 31b respectively are provided. In addition, the bound stopper 41 screwed to the tip of the piston rod 7 has a stud 3 penetrating the piston 31.
8 is screwed and fixed, and this stud 38 is
A communication hole 39 that connects the upper chamber A and the lower chamber B is formed, and further, an adjuster 40 for changing the flow passage cross-sectional area of the communication hole 39 and the fluid communication depending on the direction of fluid flow. Extension side check valve 1 that allows and blocks the flow of holes 39
7 and a pressure side check valve 22 are provided.
The adjuster 40 is rotated by the pulse motor 3 via the control rod 70 (see FIG. 4). Further, the stud 38 has a first port 21, a second port 13, a third port 18, and
The fourth port 14 and the 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 which communicate the inside and the outside are formed, and a vertical groove 23 is formed in the outer peripheral portion. There is.

Therefore, the through hole 31 is provided between the upper chamber A and the lower chamber B as a flow passage through which the fluid can flow in the extension stroke.
The inside of the extension side damping valve 12 is opened through b and the lower chamber B
To the extension side first flow path D, the second port 13, the vertical groove 23,
Via 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 fourth port 14, the second port 13, the vertical groove 23, and the fifth port 16. Then, the extension side check valve 17 is opened to reach the lower chamber B by way of the third side flow passage F extending to the lower chamber B and the third port 18, the second lateral hole 25, and the hollow portion 19. There are four channels, channel G. Further, as a flow path through which the fluid can flow in the pressure stroke, the pressure side first valve that opens the pressure side damping valve 20 through the through hole 31a is used.
Flow path H, hollow portion 19, first lateral hole 24, first port 21
Via the pressure side check valve 22 to the upper chamber A, and the bypass flow to the upper chamber A via the hollow portion 19, the second lateral hole 25, and the third port 18. Road G
There are three channels.

That is, the shock absorber SA is constructed so that the damping characteristics can be changed in multiple stages with the characteristics shown in FIG. 6 on both the extension side and the compression side by rotating the adjuster 40. That is, as shown in FIG. 7, when the adjuster 40 is rotated counterclockwise from a region in which both the extension side and the compression side are soft (hereinafter referred to as the soft region SS),
Only the expansion side can change the damping characteristic to the hard side in multiple stages, and the compression side becomes a softly fixed area (hereinafter referred to as the expansion side hard area HS). Conversely, when the adjuster 40 is rotated clockwise, the compression side Only the damping characteristic can be changed to the hard side in multiple steps, and the extension side is softly fixed (hereinafter, compression side hard area SH
That is) the structure.

By the way, in FIG. 7, the KK cross section, the LL cross section, the MM cross section, and the MM cross section in FIG. 8, FIG. 9, and FIG. 10, and the damping force characteristics at each position are shown in FIGS.

Next, the control operation of the control unit 4 will be described with reference to the flowchart of FIG. 14 and the time chart of FIG.

In the flowchart of FIG. 14, step 101 is a step of determining whether or not to start roll control, and the steering angle θ detected by the steering sensor 2 is determined.
Is determined to have exceeded a predetermined neutral threshold value δ, and Y
If ES, the process proceeds to step 102 to start the roll control, and if NO, the process returns to step 101 while maintaining the normal control state.

The steering angle θ is a positive value in the right steering direction,
The left steering direction is given as a negative value.

Step 103 is a step of calculating the initial feeding step S ₁ of the pulse motor 3 based on the following formula.

[Equation 1] S ₁ = f (θP ₀ , V) That is, the roll control start time (the steering angle θ is the neutral threshold δ
Steering angle speed θP ₀ calculated from the value of the steering angle θL that has passed through the low-pass filter 6 and the vehicle speed V
The initial feed step S ₁ is obtained based on the function of

Then, the drive control direction of the pulse motor 3 in each of the left and right shock absorbers SA is determined based on the roll direction of the vehicle body determined from the direction of the steering angular velocity θP ₀ at that time. That is, when the steering angular velocity θP is in the right direction (a positive value), a roll to the left occurs, so that the left shock absorbers SA ₁ and SA _{3 use} the pressure side to suppress the roll to the left. Hard area SH (Fig. 7
Direction), the step directions of the step motors 3 are determined so that the right side shock absorbers SA ₂ and SA ₄ are in the extension side hard region HS direction. Further, when the steering angular velocity θP is in the leftward direction (negative value), a roll in the rightward direction occurs, so that the left shock absorber SA ₁ ,
Set SA ₃ and right shock absorbers SA ₂ and SA ₄ in the direction opposite to the above, in the direction of the hard characteristics on the stroke side.
The step direction of each step motor 3 is determined.

Step 104 is an initial feeding step S ₁
This is a step in which each pulse motor 3 is stepwise driven in the determined direction.

Step 105 is a step of holding the pulse motor 3 at the step position.

In step 106, the steering angle θ is the predetermined time Δ
During T, this is a step of determining whether or not it is within the neutral threshold value δ. If YES, then the process proceeds to step 110, and if NO, then the process proceeds to step 107.

Step 107 is a step of determining whether or not the sign of the steering angular velocity θP calculated from the value of the steering angle θL passed through the low pass filter 6 is reversed.
If S, the process proceeds to step 108, and if NO, the process returns to step 105.

Step 108 is a step of calculating the second and subsequent feeding steps S ₂ , S ₃ , S ₄ of the pulse motor 3 based on the following mathematical expressions.

[Formula 2] S ₂ = f (θP ₁ , θL ₁ , V) S ₃ = f (θP ₂ , θL ₂ , V) S ₄ = f (θP ₃ , θL ₃ , V) That is, a low-pass filter When the sign of the steering angle θL passed through 6 is reversed, when the sign of the steering angular velocity θP ₂ , θP ₃ calculated from the value of the steering angle θL at the time of the sign judgment or the sign of the steering angle θL is not reversed, , The maximum value of the steering angular velocity θP ₁ up to a half cycle before the sign of the steering angular velocity θP reverses,
Steering angles θL ₁ , θ when the sign of the steering angular velocity θP is reversed
Based on the function of L ₂ and θL ₃ and the vehicle speed V, the feeding step S
₂ , S ₃ , S ₄ are calculated.

In step 109, each feeding step S ₂ ,
This is a step in which the pulse motor 3 is step-driven by S ₃ and S ₄ , and then the process returns to step 105.

In step 110, the roll control is OF
This is the step of setting to F.

Step 111 is a step of stopping the roll control calculation and returning to the normal control state.

One control flow is completed by the above steps, and the above steps are repeated thereafter.

Next, the contents of the normal control will be described based on the time chart of FIG.

When the sprung vertical velocity Vn detected by each vertical G sensor 1 changes as shown in this figure, when the sprung vertical velocity Vn is 0, the shock absorber SA
To the soft area SS.

When the sprung vertical velocity Vn becomes a positive value, the expansion side hard region HS is controlled to fix the compression side to the low damping characteristic, while the expansion side damping characteristic is changed to the sprung vertical velocity V.
Change in proportion to n. At this time, the attenuation characteristic C is C =
It is controlled to be k · Vn.

When the sprung vertical velocity Vn becomes a negative value, the compression side hard region SH is controlled to fix the expansion side to a low damping characteristic, while the compression side damping characteristic is changed to the sprung vertical velocity V.
Change in proportion to n. At this time, the damping characteristic C is C
It is controlled so that = k · Vn. Incidentally, k is a proportional constant.

Further, in the time chart of FIG.
Region a is a sprung vertical velocity Vn based on the sprung vertical velocity.
Is a state in which it is reversed from a negative value (downward) to a positive value (upward), but at this time, the relative speed is a negative value (the stroke of the shock absorber SA is the pressure stroke side). Therefore, at this time, the shock absorber SA is controlled in the extension side hard region HS based on the direction of the sprung vertical velocity Vn. Therefore, in this region, the pressure stroke side, which is the stroke of the shock absorber SA at that time, has a soft characteristic. Becomes

In the region b, the sprung vertical velocity Vn based on the sprung vertical velocity remains a positive value (upward), and the relative velocity is from a negative value to a positive value (the stroke of the shock absorber SA is the extension stroke). The shock absorber SA is controlled to the extension side hard region HS based on the direction of the sprung vertical velocity Vn at this time, and the stroke of the shock absorber is also the extension stroke. Therefore, in this region, therefore, the extension side, which is the stroke of the shock absorber SA at that time, has a hard characteristic proportional to the value of the sprung vertical velocity Vn.

In region c, the sprung vertical velocity Vn based on the sprung vertical velocity is reversed from a positive value (upward) to a negative value (downward), but at this time, the relative velocity is still positive. Value (shock absorber SA stroke is on the extension side)
At this time, the shock absorber SA is controlled to the compression side hard region SH based on the direction of the sprung vertical velocity Vn, and therefore, in this region, the stroke of the shock absorber SA at that time is controlled. A certain stretch side has soft characteristics.

In the area d, the sprung vertical velocity Vn based on the sprung vertical velocity remains a negative value (downward), and the relative velocity is from a positive value to a negative value (the stroke of the shock absorber SA is the extension stroke). Side), the shock absorber S at this time is based on the direction of the sprung vertical velocity Vn.
A is controlled in the compression side hard region SH, and the stroke of the shock absorber is also the pressure stroke. Therefore, in this region, the pressure stroke side, which is the stroke of the shock absorber SA at that time, becomes the value of the sprung vertical velocity Vn. It has proportional hardware characteristics.

As described above, in this embodiment, when the sprung vertical velocity and the relative velocity between the sprung portion and the unsprung portion have the same sign (region b, region d), the shock absorber S at that time.
Attenuation characteristic control based on the skyhook theory, that is, the stroke side of A is controlled to have a hard characteristic, and when the signs are different (area a, area c), the stroke side of the shock absorber SA at that time is controlled to have a soft characteristic. The same control will be performed without detecting the relative speed between sprung and unsprung. Further, in this embodiment, when the region a is shifted to the region b and the region c is shifted to the region d, the damping characteristics are switched without driving the pulse motor 3.

As described above, in the vehicle suspension system according to the present embodiment, the frequency of switching the damping characteristic is reduced as compared with the conventional damping characteristic control based on the skyhook theory, so that the control response can be improved and The durability of the pulse motor 3 can be improved.

Further, when the steering angle is large, the stroke side damping characteristic of each shock absorber SA is controlled to be high based on the roll direction predicted from the direction of the steering angle θ, so that the shock absorber SA expands and contracts. The speed and stroke are suppressed, so that the roll of the vehicle body due to a large steering operation can be suppressed from the initial stage of the roll generation.

Further, the stroke side in the direction opposite to the stroke of the shock absorber SA at that time has a predetermined low damping characteristic to absorb the road surface input in the direction opposite to the stroke direction based on the roll,
As a result, the riding comfort of the vehicle during roll control can be improved.

Further, regarding turning back of the steering, the steering angle processing value θL passed through the low-pass filter 6 having the output phase frequency characteristic with respect to the input equivalent to the phase frequency characteristic of the vehicle body roll with respect to the steering angle θ measured in advance is used as a reference. Then, when the sign of the steering angular velocity θP obtained from the steering angle processing value θL is reversed, the roll control direction is switched, so that only the steering sensor 2 is used to adjust the active roll in accordance with the roll direction of the vehicle body. The restraint control becomes possible, and the roll of the vehicle can be restrained accurately even in continuous steering such as slalom, and the steering stability can be secured.

Also, for correction of steering sawing and the like, the signal passed through the low-pass filter 6 is used,
The high-frequency component of the waveform is licked, which makes it possible to eliminate the malfunction of switching the attenuation characteristics.

Next, another embodiment of the present invention will be described. In the description of this embodiment, the same elements as those in the above embodiment are designated by the same reference numerals, and the description thereof will be omitted. Only the differences will be described.

In this embodiment, in the flow chart of FIG. 14 showing the control operation of the control unit 4, the second and subsequent feeding steps S ₂ , S ₃ , S of the pulse motor 3 are carried out.
₄ ... A part of step 108 for obtaining ... Is different from the above embodiment.

That is, in this embodiment, as shown in the time chart of FIG. 18, when the feed steps S ₂ , S ₃ , S _4, ... If a predetermined threshold value δ ₁ is provided for the steering angular velocity θP, and the maximum value of the steering angular velocity θP up to a half cycle before the sign of the steering angular velocity θP is reversed exceeds the predetermined threshold value δ ₁ , As in the case of the above embodiment, the feed steps (S ₁ , S ₂ , S ₄ , S ₅ , S of the step motor 3 are calculated based on the equation ( ₂₎ .
₇ , S ₉ ) is calculated, but if it is not exceeded, the steering angular velocity θP is very small and the feed step becomes too small according to Equation 2. In such a case, the same step as the previous feed step number ( S ₃ = S ₂ , S ₆ = S ₅ , S ₈
= S ₇ ).

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.

[0055]

As described above, the vehicle suspension system of the present invention is provided with the low-pass filter having the frequency characteristic of the input and the frequency characteristic of the same phase of the frequency characteristic of the vehicle body roll with respect to the steering angle measured in advance, By determining the roll direction of the vehicle body from the direction of the steering angular velocity obtained from the steering angle processing value that has passed through this low-pass filter, and switching the roll control direction based on this determination, the steering sensor alone Active roll suppression control that matches the roll direction is possible, and the effect that the roll of the vehicle can be accurately suppressed even for continuous steering such as slalom, and steering stability can be secured can get.

[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 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 characteristic diagram corresponding to a step position of a 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 LM sectional view.

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 characteristic diagram of the shock absorber in a soft state on the expansion side / compression side.

FIG. 13 is a damping characteristic diagram of the shock absorber when the pressure side is hard.

FIG. 14 is a flowchart showing a roll control operation of the control operations of the control unit in the apparatus according to the embodiment.

FIG. 15 is a time chart showing the roll control operation of the control operations of the control unit in the apparatus of the embodiment.

FIG. 16 is a phase frequency characteristic diagram of a vehicle body roll with respect to a steering angle.

FIG. 17 is a time chart showing an operation during normal control among the control operations of the control unit in the apparatus of the embodiment.

FIG. 18 is a time chart showing the roll control operation of the control unit in the apparatus of another embodiment.

[Explanation of symbols]

 a damping characteristic changing means b shock absorber c steering angle detecting means d low-pass filter e roll controlling means

Claims (1)

[Claims] 1. A damping characteristic changing means which is interposed between a vehicle body side and each wheel side and has a structure such that when one of the extension side and the compression side stroke side is controlled to have high damping characteristics, the reverse stroke side has low damping characteristics. A shock absorber having a steering angle detecting means for detecting a steering angle of the vehicle, a low-pass filter having a frequency characteristic of an output with respect to an input having the same phase as a frequency characteristic of the vehicle body roll with respect to the steering angle, and the steering angle detecting means. When the steering angle detected by the means exceeds a predetermined neutral threshold value, each of the left and right shocks is determined based on the roll direction of the vehicle body, which is determined from the steering angular velocity direction obtained from the steering angle processing value that has passed through the low-pass filter. Switching to a roll control state in which the damping characteristic on the stroke side of the absorber is controlled to a higher level, and for subsequent steering back, from the steering angle processing value that has passed through the low-pass filter, When the direction of the obtained steering angular velocity is reversed, the strokes for controlling the damping characteristics of the left and right shock absorbers to a higher degree are switched, and when the state where the steering angle falls below the predetermined neutral threshold value continues for the predetermined time, A vehicle suspension system, comprising: a roll control means for returning the shock absorber to a normal control state in which normal damping characteristic control is performed.