JPH07276953A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To provide a vehicle suspension device able to obtain the turning-round performance of a vehicle and stability in a yawing direction at the steering time. CONSTITUTION:A vehicle suspension device is provided with a damping force characteristic control means (f) having a basic control part (e) for controlling the damping force characteristics of shock absorbers b1, b2 according to a basic control signal based on a sprung behavior signal obtained by a sprung behavior detecting means (c), and a steering time control part (g) provided at the damping force characteristic control means (f) so as to control the damping force characteristic of each shock absorber onto the high side according to a steering time control signal for the specified time after judging the yawing control condition of a vehicle from a yaw rate detected by a yaw rate detecting means (d). In the initial state of steering time control by the steering time control part (g), the damping force characteristic of the rear wheel side shock absorber b2 is controlled to be higher than that of the front wheel side shock absorber b1, and then for the specified time, the clamping force characteristic of the front wheel side shock absorber b1 is controlled to be higher than that of the rear wheel side shock absorber b2.

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 of a shock absorber, and more particularly to a vehicle suspension system for suppressing yawing of the vehicle due to steering.

[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 Laid-Open No. Sho 60 has been proposed.
The one described in Japanese Patent No. 128011 is known. In this conventional vehicle suspension system, during steering control during lane change or slalom, the roll speed frequency is lower than the sprung mass resonance and the roll resonance, so the roll speed and the steering angular velocity detected by the steering sensor are compared. Based on this, the damping force characteristic control of the shock absorber was performed.

[0003]

However, in the above-mentioned conventional device, the behavior of the vehicle in the roll direction is suppressed by controlling the damping force characteristic of the shock absorber based on the steering angular velocity as described above. Is effective to
There is a problem in that the basic characteristics of the vehicle cannot be controlled because the turning performance of the vehicle and the stability in the yaw direction cannot be controlled.

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 obtaining the turning performance of the vehicle and the stability in the yaw direction during steering. To do.

[0005]

In order to achieve the above-mentioned object, the vehicle suspension system of the present invention is interposed between the vehicle body side and each wheel side and damped, as shown in the claim correspondence diagram of FIG. The shock absorbers b ₁ and b ₂ whose damping force characteristics can be changed by the force characteristic changing means a, the sprung behavior detecting means c for detecting sprung behavior, the yaw rate detecting means d for detecting the yaw rate of the vehicle, and the sprung portions. A basic control unit e for performing damping force characteristic control of each shock absorber b according to a basic control signal based on the sprung mass behavior signal obtained by the behavior detection means c.
And a damping force characteristic control means f having the following, and when the yawing control condition of the vehicle is determined from the yaw rate detected by the yaw rate detection means d provided in the damping force characteristic control means f, a steering control signal is sent for a predetermined period thereafter. Accordingly, the steering control unit g for controlling the damping force characteristic of each shock absorber b to be higher.
In the initial stage of the steering control by the steering control unit g, the damping force characteristics of the rear wheel shock absorber b ₂ are controlled to be higher than the front wheel side shock absorber b ₁ .
Thereafter given between was to control than the rear-wheel-side shock absorbers b ₂ to enhance the damping force characteristics of the front-wheel-side shock absorbers b _1.

Further, in the vehicle suspension system according to the second aspect, the steering control by the steering control section g is performed on the front wheel side until the yaw rate exceeds a predetermined threshold after the yawing control condition of the vehicle is judged. The damping force characteristics of the rear wheel side shock absorber b ₂ are controlled to be higher than the shock absorber b ₁ .
Then the front-wheel-side shock absorbers b ₁ than until the yaw rate is 0 cross rear wheel side shock absorbers b ₂
The damping force characteristics of are controlled to be higher.

In the vehicle suspension system according to a third aspect of the present invention, the yaw rate detecting means d is composed of a yaw rate sensor.

According to a fourth aspect of the present invention, the yaw rate detecting means d comprises a pair of front and rear lateral G sensors for obtaining a yaw rate based on a relative lateral acceleration difference between the front and the rear of the vehicle.

According to a fifth aspect of the present invention, the yaw rate detecting means d comprises a pair of left and right wheel speed sensors for obtaining a yaw rate based on the difference between the right and left relative wheel speeds of the vehicle.

[0010]

Since the vehicle suspension system of the present invention is configured as described above, when the yawing control condition is not judged from the yaw rate detected by the yaw rate detecting means, the yaw rate above a predetermined level does not occur in the vehicle. Therefore, at this time, in the basic control unit of the damping force characteristic control means, the damping force characteristic control of the shock absorber is performed in accordance with the basic control signal based on the sprung mass behavior signal. It is possible to ensure the riding comfort and steering stability of the vehicle.

Further, when the yawing control condition is judged from the yaw rate detected by the yaw rate detecting means, there is a situation in which yawing of a predetermined amount or more occurs in the vehicle. During this period, the damping force characteristic of each shock absorber is controlled to be higher according to the steering control signal, but first, in the initial stage of steering, the damping force characteristic of the rear wheel side shock absorber is made higher than that of the front wheel side shock absorber. This controls the oversteer characteristic to improve the turning ability of the vehicle, and controls the damping force characteristic of the front wheel side shock absorber rather than the rear wheel side shock absorber for a predetermined period thereafter. As a result, the understeer characteristic is obtained, and the stability of the vehicle in the yaw direction is obtained.

Further, in the vehicle suspension system according to claim 5,
By configuring the yaw rate detecting means with a pair of left and right wheel speed sensors that obtain a yaw rate based on the difference between the right and left relative wheel speeds in the vehicle, in a vehicle equipped with an anti-skid brake system, a pair of left and right wheel speed sensors in the system. Since the signal obtained in step 1 can be used, the cost of the entire system can be reduced by omitting the sensor.

[0013]

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

FIG. 2 is a system block diagram showing a vehicle suspension system according to an embodiment of the present invention. Four shock absorbers SA are provided between the vehicle body and four wheels. A vertical acceleration sensor (hereinafter referred to as a vertical G sensor) 1 that detects vertical acceleration is provided on the vehicle body near each shock absorber SA, and the yaw rate generated in the vehicle during steering is detected. A yaw rate sensor 2 is provided, and a control for inputting signals from the vertical G sensor 1 and the yaw rate sensor 2 to a position near the driver's seat and outputting a drive control signal to the pulse motor 3 of each shock absorber SA. A unit 4 is provided.

The control unit 4 includes an interface circuit 4a, a CPU 4b, and a drive circuit 4c. The interface circuit 4a receives signals from the above-mentioned vertical G sensor 1 and yaw rate sensor 2.

A signal processing circuit shown in FIG. 3 is provided in the interface circuit 4a. That is,
This signal processing circuit is provided for each vertical G sensor 1, and the LPF 1 is a low-pass filter for removing high-frequency noise of 30 Hz or higher from the sprung vertical acceleration signal sent from the vertical G sensor 1. . Also, LPF
Reference numeral 2 is a low-pass filter for integrating the acceleration signal processed by the low-pass filter LPF1 and converting it into a sprung vertical velocity. HPF1 is the cutoff frequency
The LPF 3 is a 1.0 Hz high-pass filter and the LPF 3 is a low-pass filter having a cut-off frequency of 1.5 Hz, and both filters form a band-pass filter for obtaining the sprung vertical velocity Vn including the sprung resonance frequency.

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. Defining the base 34 and the piston 31
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 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 the through holes. A compression side damping valve 20 and an expansion side damping valve 12 that open and close 31a and 31b respectively are provided. Further, a stud 38 penetrating the piston 31 is screwed and fixed to the bound stopper 41 screwed to the tip of the piston rod 7, and the stud 38 bypasses the through holes 31a and 31b. Communication for forming a flow path (an expansion-side second flow path E, an expansion-side third flow path F, a bypass flow path G, and a compression-side second flow path J described later) that connects the upper chamber A and the lower chamber B with each other. A hole 39 is formed and this communication hole 3
An adjuster 40 for changing the flow passage cross-sectional area of the flow passage is rotatably provided inside the passage 9. Also, the stud 38
The communication hole 3 is formed on the outer peripheral portion of the communication hole 3 depending on the direction of fluid flow.
An expansion-side check valve 17 and a pressure-side check valve 22 that allow and block the flow passage formed by 9 are provided. It should be noted that this adjuster 40 corresponds to the pulse motor 3
Is rotated via the control rod 70 (see FIG. 4). Also, the stud 38 has
A first port 21, a second port 13, a third port 18, a fourth port 14, and a fifth port 16 are formed in this order from the top.

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 during the extension process.
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 force characteristics 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.
A soft area on both sides (hereinafter soft area SS
When the adjuster 40 is rotated counterclockwise from
Only the extension side can change the damping force characteristic in multiple stages, and the compression side becomes a region fixed to the low damping force characteristic (hereinafter referred to as the extension side hard region HS). Conversely, when the adjuster 40 is rotated clockwise, The damping force characteristic can be changed in multiple steps only on the compression side, and the extension side is a region fixed to the low damping force characteristic (hereinafter, referred to as compression side hard region SH).

Incidentally, in FIG. 7, when the adjuster 40 is arranged at the displacement position of, the KK section, the LL section, the MM section, and the NN section in FIG.
Sections are shown in FIGS. 8, 9 and 10, respectively, and
The damping force characteristics at each displacement position are shown in Figs.
It is shown in 13.

Next, the damping force characteristic control operation in the control unit 4 will be described with reference to the flowchart of FIG. Note that this control is separately performed for each shock absorber SA.

First, at step 101, it is judged whether or not the yaw rate Y detected by the yaw rate sensor 2 is other than 0. If YES (Y ≠ 0), the routine proceeds to step 102, and NO (Y = 0). If so, the process proceeds to step 112.

At step 112, the 0 cross flag is set to O.
After setting the N state, the routine proceeds to step 113, where normal time control is performed. That is, the normal control signal V based on the sprung vertical velocity Vn is calculated by the following equation (1), and the front wheel side and rear wheel shock absorbers SA are calculated based on the normal control signal V by the following equation (2). After obtaining the target damping position P of, the one-time flow is ended.

V = α · Vn (1) P = Pmax (V−V _NC ) / (V _H −V _NC ) ... (2) In the above equation, α is the normal control gain, Pmax
Is the maximum damping position, V _H is the control proportional range, and V _NC is the control dead zone. And the maximum damping position Pmax,
The control proportional range V _H and the control dead zone V _NC are the maximum extension position P for extension when the normal control signal V is a positive value.
max _-T , extension side control proportional range V _HT , and extension side control dead zone V _{NC -T} are set respectively, and when they are negative values, compression side maximum damping position Pmax _-C and compression side Control proportional range V _HC and pressure side control dead zone V _NC-C are set respectively.

Further, steps 102 to 111 are steps for carrying out steering control. First, in step 102, as shown in the following equation (3), the steering gain β is further added to the steering control gain α. After obtaining the hour control signal V ′, the process proceeds to step 103. V '= αVnβ ... (3) In step 103, the yaw rate Y is a predetermined threshold value Y _R centered around 0. And a threshold value Y _B, and if YES (Y _R ≧ Y ≧ Y _B ), the process proceeds to step 104 and NO (Y> Y _R or Y <Y _B ). If there is, go to step 109.

In step 104, it is judged whether or not the yaw rate Y crosses 0, and if YES, step 10
5. If NO, proceed to step 111. In step 105, it is determined whether or not the steering characteristic flag is in the ON state, and if YES, the process proceeds to step 107, where N
If it is O, the routine proceeds to step 106, the steer characteristic flag is turned ON, and then the routine proceeds to step 107.

In step 107, the target damping position P _F of the front-wheel-side shock absorber SA and the rear-wheel-side shock are calculated by the following equations (4) and (5) based on the steering control signal V ′ to which the steering gain β is added. After obtaining the target damping position P _R of the absorber SA, the routine proceeds to step 108.

P _F = P limit (V′−V _NC ) / (V _H −V _NC ) ... (4) P _R = P max (V′−V _NC ) / (V _H -V _NC ) ... (5) In addition, Plimit is a limit damping position which is set lower than the maximum damping position Pmax by a predetermined position. The maximum attenuation position Pmax, the limit damping position Plimit, control proportional range V _H and the control dead zone V _NC is the maximum attenuation position Pmax _-T for the extension side when steering when the control signal V 'is a positive value, Shin Side mitt damping position Plimit _-T and extension side control proportional range V
_HT and extension dead zone V _NC-T are set respectively,
When the value is negative, the compression side maximum damping position Pma
and x _-C, and the compression side for mitt damping position Plimit _-C, and the compression side control proportional range V _HC, and the compression side control dead zone V _NC-C are respectively set.

At step 108, the 0 cross flag is set to O.
After setting the FF state, this ends one flow. Further, as described above, in step 103, NO (Y> Y _R , Y
If it is determined to be <Y _B ), the routine proceeds to step 109, the steer characteristic flag is turned off, and then the routine proceeds to step 110.

In step 110, the target damping position P _F of the front wheel side shock absorber SA and the rear wheel side shock are calculated by the following equations (6) and (7) based on the steering control signal V'added to the steering gain β. After obtaining the target damping position P _R of the absorber SA, the routine proceeds to step 108.

P _F = P max (V′−V _NC ) / (V _H −V _NC ) ... (6) P _R = P limit (V′−V _NC ) / ( V _H −V _NC ) (7) If NO is determined in step 104 as described above, the process proceeds to step 111 and the steer characteristic flag is set to O.
It is determined whether or not the state is N, and if YES, the process proceeds to step 107, and if NO, the process proceeds to step 110. With the above, one flow is completed, and thereafter, the above flow is repeated.

Next, of the above control operations, the details of the steering control will be described with reference to the time chart of FIG.

First, when the steering of the vehicle is started, the yaw rate Y becomes a value other than 0. At this time, therefore, steering control is performed based on the steering control signal V '. That is, first, when the yaw rate Y becomes a value other than 0, the target damping position of the front wheel side shock absorber SA is kept until the yaw rate Y exceeds the range between the predetermined threshold value Y _R and the threshold value Y _B. The maximum value is set to the limit damping position Plimit, which is lower than the maximum damping position Pmax, as shown by the dotted line in FIG. 15 (g), while the maximum value of the rear wheel side shock absorber SA is set to that in FIG. 15 (g). By setting the maximum damping position Pmax as shown by the solid line,
The oversteer yaw rate characteristic shown by the dotted line in FIG. 15 (c) is used to perform response up control that enhances the turning performance of the vehicle during steering.

Next, the yaw rate Y is set to a predetermined threshold value Y _R.
If the range between the threshold value and the threshold value Y _B is exceeded, the maximum value of the target damping position of the front wheel side shock absorber SA is reversed from that point until the yaw rate Y crosses 0, contrary to the response up control described above. Is set to the maximum damping position Pmax as shown by the dotted line in FIG. 15 (g), while the maximum value of the rear wheel side shock absorber SA is set to a value greater than the maximum damping position Pmax as shown by the solid line in FIG. 15 (g). Is set to a lower limit damping position Plimit,
Switching to the understeer yaw rate characteristic shown by the solid line in FIG. 15 (c) is performed, whereby stable region control that ensures stability in the yaw direction of the vehicle is performed.

Next, the content of the switching control of the damping force characteristic control area in the control unit 4 will be described based on the time chart of FIG. Here, a case where normal control is performed will be described as an example.

As shown in the flow chart of FIG. 16, when the normal control signal V based on the sprung vertical velocity Vn exceeds the extension side control dead zone V _NC-T , each shock absorber SA is in the extension side hard area. The pulse motor 3 is controlled to the HS side, and the pulse motor 3 is drive-controlled toward the target damping position P on the extension side.

When the normal control signal V has a value between the extension side control dead zone V _NC-T and the compression side control dead zone V _NC-C , each shock absorber SA is controlled to the soft region SS. Therefore, the drive of the pulse motor 3 is controlled.

When the normal-time control signal V is less than the pressure side control dead zone V _NC-C , each shock absorber is controlled to the pressure side hard area SH, and the pulse motor 3 is moved toward the target damping position P on the pressure side. Drive controlled.

Further, in the time chart of FIG.
In the region a, the normal-time control signal V based on the sprung vertical velocity Vn is reversed from a negative value (downward) to a positive value (upward), but at this time, the relative velocity is still a negative value (shock). Since the stroke of the absorber SA is on the pressure stroke side), at this time, the shock absorber SA is controlled to the extension side hard area HS based on the direction of the normal control signal V. In the region, the pressure stroke side, which is the stroke of the shock absorber SA at that time, has soft characteristics.

Further, in the region b, the control signal V in the normal state remains the positive value (upward), and the relative speed is switched from the negative value to the positive value (the stroke of the shock absorber SA is the extension stroke side). At this time, the shock absorber SA is controlled to the extension side hard area HS based on the direction of the normal time control signal V, and the stroke of the shock absorber is also the extension stroke. Then, the extension side, which is the stroke of the shock absorber SA at that time, has a hardware characteristic proportional to the value of the normal time control signal V.

In the area c, the control signal V in the normal state is reversed from a positive value (upward) to a negative value (downward), but at this time, the relative speed is still positive (shock absorber SA). Since the stroke is on the extension side), at this time, the shock absorber SA is controlled to the compression side hard area SH based on the direction of the normal time control signal V. Therefore, in this area, The extension side, which is the stroke of the shock absorber SA, has soft characteristics.

The area d is an area in which the normal control signal V remains a negative value (downward) and the relative speed changes from a positive value to a negative value (the stroke of the shock absorber SA is on the extension side). Therefore, at this time, the shock absorber SA is controlled in the pressure side hard region SH based on the direction of the normal time control signal V, and the stroke of the shock absorber SA is also the pressure stroke. Therefore, in this region, The pressure stroke side, which is the stroke of the shock absorber SA, has a hardware characteristic that is proportional to the value of the control signal V during normal operation.

As described above, in this embodiment, when the normal time control signal V based on the sprung vertical velocity Vn and the relative velocity between the sprung and unsprung portions have the same sign (region b, region d), Based on the skyhook theory, the stroke side of the shock absorber SA at that time is controlled to have a hard characteristic, and the stroke side of the shock absorber SA at that time is controlled to have a soft characteristic when different signs (area a, area c) are controlled. The same control as the damping force characteristic control is performed. And further,
In this embodiment, when shifting from the region a to the region b and from the region c to the region d, the damping force characteristics are switched without driving the pulse motor 3.

As described above, in this embodiment, the effects listed below can be obtained. In the initial stage of steering, the oversteer characteristic enhances the turning performance of the vehicle, and thereafter, the understeer characteristic enables the stability in the yaw direction to be obtained.

Compared with the conventional damping force characteristic control based on the skyhook theory, the switching frequency of the damping force characteristic is reduced, so that the control response can be improved and
The durability of the pulse motor 3 can be improved.

Although the embodiment has been described above, the specific configuration 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 extension side hard region in which the extension side has a variable damping force characteristic and the compression side has a low damping force characteristic fixed, and the compression side hard region in which the compression side has a variable damping force characteristic and the extension side has a low damping force characteristic fixed. And a shock absorber having three regions, a soft region with low damping force characteristics on both the extension side and compression side, was used, but it is also possible to control using a shock absorber with a structure in which the damping force characteristics on the extension side and compression side change simultaneously. Can be applied.

Further, in the embodiment, the yaw rate sensor is used as the yaw rate detecting means. However, the yaw rate sensor may be composed of a pair of front and rear lateral G sensors for obtaining a yaw rate based on a relative lateral acceleration difference between the front and the rear of the vehicle, or , For vehicles equipped with an anti-skid brake system, use signals obtained from a pair of left and right wheel speed sensors,
By determining the yaw rate based on the difference between the relative wheel speeds on the left and right, the sensor can be omitted.

[0051]

As described above, the vehicle suspension system according to the present invention is basically designed to perform damping force characteristic control of each shock absorber in accordance with a basic control signal based on the sprung mass behavior signal obtained by the sprung mass behavior detecting means. A damping force characteristic control unit having a control unit and a steering control signal for a predetermined period thereafter when the yawing control condition of the vehicle is determined from the yaw rate detected by the yaw rate detection unit provided in the damping force characteristic control unit. According to the steering control section for controlling the damping force characteristic of each shock absorber to a higher value, the damping force characteristic of the rear wheel side shock absorber is more than that of the front wheel side shock absorber in the initial stage of the steering control by the steering time control section. Is controlled to be higher, and then the damping force characteristic of the front wheel side shock absorber is controlled to be higher than the rear wheel side shock absorber for a predetermined period. By the, to increase the vehicle turning property by oversteer characteristics in the initial stage of steering, then the effect is obtained that it is possible to obtain the yaw direction stability by understeer characteristics.

Further, in the vehicle suspension system according to claim 5,
By configuring the yaw rate detecting means with a pair of left and right wheel speed sensors that obtain a yaw rate based on the difference between the right and left relative wheel speeds in the vehicle, in a vehicle equipped with an anti-skid brake system, a pair of left and right wheel speed sensors can be used. Since the signal can be used, the cost of the entire system can be reduced by omitting the sensor.

[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 system block diagram showing a vehicle suspension device according to an embodiment of the present invention.

FIG. 3 is a block diagram showing a signal processing circuit in the apparatus 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 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 a flowchart showing a damping force characteristic control operation of the control unit in the embodiment apparatus.

FIG. 15 is a time chart showing the contents of steering control in the damping force characteristic control operation of the control unit in the embodiment apparatus.

FIG. 16 is a time chart showing the details of switching control of the damping force characteristic control region during normal control in the damping force characteristic control operation of the control unit in the embodiment apparatus.

[Explanation of symbols]

a damping force characteristic changing means b ₁ shock absorber b ₂ shock absorber c sprung behavior detecting means d yaw rate detecting means e basic control section f damping force characteristic control means g steering control section

Claims (5)

[Claims] 1. A shock absorber interposed between a vehicle body side and each wheel side and capable of changing a damping force characteristic by a damping force characteristic changing means, a sprung behavior detecting means for detecting sprung behavior, and a yaw rate of a vehicle. A yaw rate detecting means for detecting, and a damping force characteristic control means having a basic control section for performing damping force characteristic control of each shock absorber according to a basic control signal based on the sprung behavior signal obtained by the sprung behavior detecting means, The damping force characteristic control means is provided, and when the yawing control condition of the vehicle is judged from the yaw rate detected by the yaw rate detecting means, the damping force characteristic of each shock absorber is increased in response to the steering control signal for a predetermined period thereafter. The steering control unit for controlling the steering wheel is provided, and in the initial stage of the steering control by the steering control unit, the rear wheel side shock absorber is set from the front wheel side shock absorber. Controlled to increase the damping force characteristics of the click absorber, then given between the vehicle suspension system and controlling than the rear-wheel-side shock absorbers to enhance the damping force characteristics of the front-wheel-side shock absorbers. 2. The damping force of the front-wheel-side shock absorber from the front-wheel-side shock absorber until the yaw rate exceeds a predetermined threshold after the yaw-rate control condition of the vehicle is judged by the steering-time control section. 2. The vehicle according to claim 1, wherein the characteristics are controlled to be high, and thereafter the damping force characteristics of the front wheel side shock absorber are controlled to be higher than the rear wheel side shock absorber until the yaw rate crosses 0. Suspension system. 3. The vehicle suspension system according to claim 1, wherein the yaw rate detecting means is a yaw rate sensor. 4. The vehicle suspension system according to claim 1, wherein the yaw rate detecting means is composed of a pair of front and rear lateral G sensors that obtain a yaw rate based on a relative lateral acceleration difference between the front and the rear of the vehicle. 5. The vehicle suspension system according to claim 1 or 2, wherein the yaw rate detecting means is composed of a pair of left and right wheel speed sensors that obtain a yaw rate based on a left and right relative wheel speed difference in the vehicle.