JPH06247118A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To provide a vehicle suspension device which can improve the maneuvering stability of a vehicle in the steering operation without deteriorating the riding comfortability of the vehicle in the straight running condition. CONSTITUTION:Shock absorbers b provided between a car body side and the wheels side, and the damping charateristics can be converted by a damping characteristics converting means a; a vehicle behavior detecting means c to detect the vehicle behavior; a control means e which has a damping characteristics controller d to control the damping characteristics of the shock absorbers b according to the vehicle behavior signal detected by the vehicle behavior detecting means c; and a yaw rate detecting means f to detect the yaw rate of the vehicle; are provided. And a gain correction controller g provided to the control means e, and to set the control gain of the rear wheel side damping characteristics larger than the control gain of the front wheel damping characteristics, when the direction of the yaw rate detected by the yaw rate detecting means f and the direction of the rate of change of the yaw rate are in the same direction, and to set the control gain of the rear wheel side damping characteristics lower than that of the front wheel side damping characteristics, when the both directions are reverse, is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension system for optimally controlling the damping characteristics of a shock absorber.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension device for controlling the damping characteristic 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, and when the direction discrimination codes of both are the same, the damping characteristic is made hard and the two have different signs. In this case, the damping characteristic control based on the skyhook theory, such as softening the damping characteristic, was performed independently for the four wheels.

In the case of such a system, the attenuation characteristic F when it is hard is generally obtained based on the following arithmetic expression.

F = α × Vn (α: control gain, Vn: sprung vertical velocity)

[0006]

However, since the above-mentioned conventional device has the above-mentioned configuration, when the control gain is set to be suitable for the damping control of the vehicle behavior that occurs during straight traveling. During a steering operation in which a moment of inertia acts on the vehicle, sufficient vibration damping cannot be obtained and the vehicle is in an understeering state, resulting in poor steering stability.

The present invention has been made in view of the above-mentioned conventional problems, and improves the steering stability of a vehicle during steering operation without deteriorating the riding comfort of the vehicle during straight traveling. It is an object of the present invention to provide a vehicle suspension device capable of

[0008]

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. A shock absorber b whose damping characteristic can be changed by the characteristic changing means a and a vehicle behavior detecting means c for detecting the vehicle behavior.
A control means e having a damping characteristic control section d for controlling the damping characteristic of each shock absorber b in accordance with the vehicle behavior signal detected by the vehicle behavior detecting means c; and a yaw rate detecting means f for detecting the yaw rate of the vehicle. And the control means e
When the direction of the yaw rate detected by the yaw rate detecting means f and the direction of the rate of change of the yaw rate are in the same direction, the control gain of the rear wheel side damping characteristic is made higher than the control gain of the front wheel side damping characteristic. And a reverse direction, the gain correction control unit g sets the control gain of the rear wheel side damping characteristic lower than the control gain of the front wheel side damping characteristic.
And, the means provided with.

Further, in the vehicle suspension system according to claim 2,
The yaw rate detecting means is composed of a lateral acceleration detecting means for detecting a lateral acceleration of the vehicle.

Further, in the vehicle suspension system according to claim 3,
The yaw rate detecting means is composed of steering angular velocity detecting means for detecting the steering angular velocity.

Further, in the vehicle suspension system according to claim 4,
As the vehicle behavior detecting means, a sprung vertical velocity detecting means for detecting sprung vertical velocity is used, and in the damping characteristic control section, the damping characteristic of each shock absorber is determined by the bounce rate and the front and rear springs based on the sprung vertical velocity. The control is performed based on the control signal obtained from the pitch rate detected from the upper / lower speed difference and the roll rate detected from the left / right upper sprung speed difference.

[0012]

Since the present invention is configured as described above, the damping characteristic of each shock absorber is optimally controlled according to the vehicle behavior signal detected by the vehicle behavior detecting means when the vehicle is traveling straight ahead. As a result, it is possible to suppress the behavior of the vehicle when traveling straight ahead and secure the riding comfort.

Further, at the time when the vehicle starts to turn from the straight traveling state by the steering operation, the yaw rate direction and the yaw rate change rate direction are in the same direction, and at this time, the control gain on the rear wheel side is The control gain is set to be higher than the control gain on the front wheel side, whereby the front load of the vehicle is increased and the vehicle is in the over-steering state. Therefore, the turning performance during steering can be improved.

Further, when the vehicle is in a state where the vehicle is changing its direction from the steady turning state to the straight traveling direction due to the turning back of the steering, the yaw rate direction and the yaw rate change rate direction are opposite to each other. The control gain on the rear wheel side is set to be lower than the control gain on the front wheel side, whereby the front load of the vehicle is reduced and the vehicle is understeered. Therefore, the convergence of the vehicle can be improved. .

Further, in the vehicle suspension system according to claim 4,
When bounce, pitch, and roll are detected by the sprung vertical velocity detection means, the damping characteristic control unit obtains a control signal based on the bounce rate, pitch rate, and roll rate, and the shock absorber damping according to this control signal. It controls the characteristics, so that not only the bounce but also the pitch and roll can be controlled sufficiently.

[0016]

Embodiments of the present invention will be described with reference to the drawings. First, the configuration will be described. FIG. 2 is a configuration explanatory view showing a vehicle suspension system of the embodiment, in which four shock absorbers SA ₁ and SA are interposed between a vehicle body and four wheels.
₂ , SA ₃ and SA ₄ (in the explanation of the shock absorber, when these four are collectively referred to and when a common configuration thereof is explained, they are simply indicated as SA) are provided. A vertical acceleration sensor (hereinafter referred to as a vertical G sensor) that detects vertical acceleration is provided on the vehicle body near each shock absorber SA.
1, a lateral acceleration sensor 2 for detecting the lateral acceleration of the vehicle is provided in the vehicle body near the center of gravity of the vehicle, and each vertical G sensor 1 is provided near the driver's seat.
There is provided a control unit 4 for inputting a signal from the acceleration sensor 2 and a signal from the lateral acceleration sensor 2 and outputting a drive control signal to the pulse motor 3 of each shock absorber SA.

FIG. 3 is a system block diagram showing the above-mentioned configuration. The control unit 4 is provided with an interface circuit 4a, a CPU 4b, and a drive circuit 4c. The vertical acceleration G _T signal, the lateral acceleration G _Y signal from the lateral acceleration sensor 2, and the vehicle speed signal from the vehicle speed sensor 5 are input. The interface circuit 4
A set of five filter circuits shown in (a) of FIG. 14 is provided for each of the upper and lower G sensors 1 in a.
A set of two filter circuits is provided as shown in (b). That is, in (a) of FIG. 14, the LPF 1 is a high frequency region (30 Hz) from the signals sent from the upper and lower G sensors 1.
The LPF 2 is a low-pass filter circuit for removing the above noise, and the LPF 2 is a low-pass filter circuit for integrating a signal indicating the acceleration that has passed through the low-pass filter circuit LPF 1 and converting it into a sprung vertical velocity. Also, 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.), And the BPF 2 passes the frequency range including the pitch resonance frequency to pass the pitch component signal v ′.
A band pass filter circuit that forms (v ₁ ', v ₂ ', v ₃ ', v ₄ '), and the BPF 3 allows the roll component signal v "(v
₁ ″, v ₂ ″, v ₃ ″, v ₄ ″). In addition, in (b) of FIG.
PF is a high-pass filter circuit for differentiating the lateral acceleration G _Y signal sent from the lateral acceleration sensor 2 and converting it into a lateral acceleration change rate (jerk) R, and the LPF 3 is a signal that has passed through the high-pass filter circuit HPF. Is a low-pass filter circuit for removing the noise in the high frequency range. 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. 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 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 is formed. An expansion side damping valve 12 and a compression side damping valve 20 that open and close 31a and 31b, respectively, are provided. 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 horizontal hole 24 and a second horizontal 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, a through hole 31 is provided between the upper chamber A and the lower chamber B as a flow passage through which a 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, both the extension side and the compression side are in the soft state (hereinafter, the soft region S
When the adjuster 40 is rotated counterclockwise from (S), the damping characteristic can be changed in multiple steps only on the extension side, and the compression side becomes a region where the low damping characteristic is fixed (hereinafter referred to as the extension side hard region HS). On the contrary, when the adjuster 40 is rotated clockwise, the damping characteristic can be changed in multiple steps only on the compression side, and the extension side becomes a region where the low damping characteristic is fixed (hereinafter referred to as the compression side hard region SH). There is.

By the way, in FIG. 7, the KK cross section, the LL cross section and 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 operation of the control unit 4 that controls the drive of the pulse motor 3 will be described based on the flowchart of FIG. Note that this control is separately performed for each shock absorber SA.

In step 101, the upper and lower G sensors 1,
In this step, the sprung vertical acceleration G _T obtained from 1, 1, 1 is read, and the lateral acceleration G _Y obtained from the lateral acceleration sensor 2 is read.

In step 102, the sprung vertical acceleration G _T
Signals shown in (a) of FIG.
The lateral acceleration G _Y obtained from the lateral acceleration sensor 2 is calculated by processing the PF1, BPF2, BPF3, and LPF2 to obtain the sprung vertical velocity bounce component signal v, the pitch component signal v ′, and the roll component signal v ″. This is a step of obtaining the rate of change R of the lateral acceleration by processing with both filter circuits HFP and LPF3 shown in (b) of 14.

In step 103, it is determined whether or not the rate of change R in lateral acceleration is within a range of a predetermined small threshold value (near 0) (-Rx <
If it is YES (within a range of a minute threshold value), the routine proceeds to step 104, where the control gain K _f on the front wheel side and the control gain K _r on the rear wheel side are set to standard values. After setting k ₀ , the process proceeds to step 108, and if NO (outside the minute threshold range), step 10
Go to 5.

In step 105, it is determined whether the direction of the lateral acceleration G _{Y and} the direction of the rate of change R of the lateral acceleration are the same (G _Y × R>
0), and if YES (in the same direction), the routine proceeds to step 106, where the front wheel side control gain K
_{After f} is set to a value k _L that is lower than the standard value k ₀ and the control gain K _r on the rear wheel side is set to a value k _H that is higher than the standard value k ₀ , the process proceeds to step 108 and NO (reverse Direction), the routine proceeds to step 107, where the front wheel side control gain K
_{After f} is set to a value k _H higher than the standard value k ₀ and the rear wheel side control gain K _r is set to a value k _L lower than the standard value k ₀ , the routine proceeds to step 108.

Step 108 uses the following equation 1
Based on the component signals v, v′v ″, the proportional constants α, β, γ, and the control gains K _f , K _r , the control signals V (V ₁ , V ₂ , V ₃ , V of the position of each wheel are obtained. ₄ ) The proportional constants α, β, γ are continuously switched according to the vehicle speed.

Front wheel right V ₁ = K _f (α _f · v ₁ + β _f (v ₁ '-v ₃ ') + γ _f
(v ₁ "-v ₂ ")) Front wheel left V ₂ = K _f (α _f · v ₂ + β _f (v ₂ '-v ₄ ') + γ _f
(v ₂ "-v ₁ ")) Rear wheel right V ₃ = K _r (α _r · v ₃ + β _r (v ₃ '-v ₁ ') + γ _r
(v ₃ "-v ₄ ")) Rear wheel left V ₄ = K _r (α _r · v ₄ + β _r (v ₄ '-v ₂ ') + γ _r
(v ₄ "-v ₃ ")) Note that α _f , β _f , and γ _f are proportional constants α _r , β _r , and γ _r on the front wheel side, and proportional constants on the rear wheel side. 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.

Step 106 is a step of judging whether or not the control signal V is equal to or more than a predetermined threshold value δ _T , and if YES, the routine proceeds to step 107, and if NO, step 1
Go to 08.

Step 107 is a shock absorber S
This is a step of controlling A to the extension side hard area HS and setting the extension side damping characteristic to a value proportional to the control signal V.

Step 108 is a step for 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 109, and if NO, NO. Go to step 110.

Step 109 is a shock absorber S
This is a step of controlling A in the soft area SS.

Step 110 is a step which is displayed for the sake of convenience, and N is omitted in steps 106 and 108.
When it is determined to be O, the control signal V is equal to or lower than the predetermined threshold value −δ _C , and in this case, the process proceeds to step 111,
This is a step of controlling the shock absorber SA to the compression side hard region SH and setting the compression side damping characteristic to a value proportional to the control signal V.

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

When the control signal V based on the sprung vertical velocity changes as shown in this figure, when the control signal V is a value between the predetermined thresholds δ _T and -δ _C , the shock absorber SA is turned on. Control to the soft area SS.

When the control signal V becomes equal to or higher than the threshold value δ _T , the expansion side hard region HS is controlled to fix the compression side to a low damping characteristic, while the expansion side damping characteristic is made proportional to the control signal V. To change. At this time, the attenuation characteristic F is F = θ _T · V
It is controlled so that Note that θ _T is a proportional constant on the extension side.

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 the low damping characteristic, while the compression side damping characteristic is made proportional to the control signal V. To change. Also at this time, the damping characteristic F is F = θ _C
・ V is controlled to be V. Note that θ _C is a proportional constant on the pressure side.

Further, in the time chart of FIG.
In the region a, the control signal V based on the sprung vertical velocity 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 absorber SA Since the stroke 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 control signal V,
Therefore, in this area a, the shock absorber S at that time is
The pressure stroke side, which is the stroke of A, has soft characteristics.

In the region b, the control signal V 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 side). At this time, the shock absorber SA is controlled to the extension side hard region HS based on the direction of the control signal V, and the stroke of the shock absorber is also the extension stroke. In this region b, 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 control signal V.

In region c, the control signal V 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. (The stroke of the shock absorber SA is on the extension side). Therefore, at this time, the shock absorber SA is controlled to the compression side hard region SH based on the direction of the control signal V. In c, the extension side, which is the stroke of the shock absorber SA at that time, has soft characteristics.

In the region d, the control signal V 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 side). At this time, the shock absorber SA is controlled to the compression side hard region SH based on the direction of the control signal V, and the stroke of the shock absorber is also the pressure stroke. Then, the pressure stroke side, which is the stroke of the shock absorber SA at that time, has a hardware characteristic proportional to the value of the control signal V.

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, in which the stroke side of A is controlled to have a hard characteristic, and when the different signs (area a, area c) are controlled to the soft side of the shock absorber SA at that time. 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.

Next, the operation of the gain correction control section in the control unit 4 will be described with reference to the time chart of FIG.

(A) At the start of turning At the time when the vehicle starts to turn from the straight traveling state by the steering operation, as shown in FIG. 17, the direction of the lateral acceleration G is the same as the direction of the lateral acceleration change rate R. Therefore, at this time, the control gain K _r (k _H ) on the rear wheel side is set higher than the control gain K _f (k _L ) on the front wheel side, which increases the front load of the vehicle. Then, the over-steering state is set.

Therefore, the turning performance during steering can be improved.

(B) At the time of straight traveling / steady turning When the vehicle is in a straight traveling state or in a steady turning state, the rate of change R in lateral acceleration is near 0 as shown in or of FIG. At this time, the control gains K _f and K _r on the front wheel side and the rear wheel side are set to the standard value k ₀ , and thereby the riding comfort of the vehicle can be improved.

(C) At the time of turning the steering wheel When the vehicle is in a state where the direction is changing from the steady turning state to the straight traveling direction, as shown in FIG. 17, the direction of the lateral acceleration G and the direction of the lateral acceleration change rate R are shown. Therefore, at this time, the control gain K _r (k _L ) on the rear wheel side is set to be lower than the control gain K _f (k _H ) on the front wheel side. Is reduced to the understeering state.

Therefore, the convergence of the vehicle can be improved.

As described above, in this embodiment, the effects listed below can be obtained. It is possible to enhance the damping performance of the vehicle at the time of starting the steering operation and at the time of turning back the steering, and improve the steering stability of the vehicle without deteriorating the riding comfort of the vehicle at the time of straight traveling or at the time of steady turning.

Since 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.

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

As the vehicle behavior, the damping characteristic control based on the skyhook theory can be performed only by detecting the sprung vertical velocity, so that the cost 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.

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 without departing from the gist of the invention.

For example, in the embodiment, the damping characteristic F is made proportional to the control signal V based on predetermined proportional constants θ _T and θ _C ,
Although the control is performed so that F = θ _T · V and F = θ _C · V, it is further proportional to the value of the change rate R of the lateral acceleration, and F = θ _T · R · V, F = It is also possible to control so that θ _C · R · V.

Further, the high value k _H and the low value k _L of the gains K _f and K _r on the rear wheel side in the embodiment are changed according to the value of the change rate R of the lateral acceleration as shown in the map of FIG. It is also possible to variably set based on the correction function to be used.

Further, in the embodiment, the sprung vertical velocity is detected as the vehicle behavior detecting means, but it is based on the conventional skyhook theory combining the sprung vertical velocity and the sprung / unsprung relative velocity. The present invention can be applied to the case where the above control is performed, or to other control methods.

Further, in the embodiment, the bounce rate is independently obtained based on the sprung vertical velocity at each wheel position, but the common bounce rate is obtained based on the average value of the sprung vertical velocity at each wheel position. May be requested.

Further, in the embodiment, the upper and lower G sensors are independently provided at the respective wheel positions, but in order to perform the control for suppressing the bounce and the pitch, at least one pair may be provided on the front wheel side and the rear wheel side. However, only one bounce is required to perform the bounce suppression control.

Further, in the embodiment, when the damping characteristic on one of the extension side and the compression side is variably controlled, the shock absorber having the structure in which the reverse stroke side is maintained at the predetermined low damping characteristic is used. It is also possible to perform control using a shock absorber having a structure in which the damping characteristics of the compression side and the compression side change simultaneously.

Further, in the embodiment, as the yaw rate detecting means, a lateral acceleration sensor for detecting the lateral acceleration of the vehicle is used, and the control gain correction control is performed by the relative direction discrimination between the lateral acceleration and the change rate of the lateral acceleration. Although the case has been described as an example, as the yaw rate detecting means, a steering sensor for detecting the steering angular velocity is used, and the control gain correction control is performed by the relative direction discrimination between the steering angular velocity and the change rate of the steering angular velocity. Also, in this case, the same action and effect as those of the above-described embodiment can be obtained.

When the change rates of the steering angle and yaw rate, and the change rate of the steering angular velocity and yaw rate are different in phase from the lateral acceleration of the vehicle and the lateral acceleration change rate, respectively, a filtering process is performed using a low-pass filter or the like to perform the phase difference. May be corrected.

[0064]

As described above, in the vehicle suspension system of the present invention, when the direction of the yaw rate detected by the yaw rate detecting means and the direction of the rate of change of the yaw rate are in the same direction, the damping characteristic of the front wheel side is reduced. The control gain of the rear wheel side damping characteristic is set higher than the control gain, and when it is in the reverse direction, the gain correction control unit is set to set the control gain of the rear wheel side damping characteristic lower than the control gain of the front wheel side damping characteristic. As a result, it is possible to improve the steering stability of the vehicle during the steering operation without deteriorating the riding comfort of the vehicle during straight running.

Further, in the vehicle suspension system according to claim 4,
Using the sprung vertical velocity detecting means for detecting the sprung vertical velocity, the damping characteristic control unit detects the damping characteristic of each shock absorber from the bounce rate based on the sprung vertical velocity and the difference between the front and rear sprung vertical velocity. Since control is performed based on the control signal obtained from the pitch rate and the roll rate detected from the vertical speed difference between the left and right springs, sufficient control force can be obtained not only for bounce but also for pitch and roll. Thus, the effect that the riding comfort and the steering stability can be improved can be obtained.

[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 -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 block diagram showing a main part of a control unit in the apparatus according to the embodiment.

FIG. 15 is a flowchart showing a control operation of a control unit in the apparatus of the embodiment.

FIG. 16 is a time chart showing the operation of the damping characteristic control unit in the control operation of the control unit in the embodiment apparatus.

FIG. 17 is a time chart showing the operation of the gain correction control unit in the control operation of the control unit in the embodiment apparatus.

FIG. 18 is a map showing a correction function for correlating the lateral acceleration change rate and the control gain in another embodiment of the device.

[Explanation of symbols]

 a damping characteristic changing means b shock absorber c vehicle behavior detecting means d damping characteristic control section e control means f yaw rate detecting means g gain correction control section

Claims (4)

[Claims] 1. A shock absorber interposed between a vehicle body side and each wheel side and capable of changing a damping characteristic by a damping characteristic changing means, a vehicle behavior detecting means for detecting a vehicle behavior, and a vehicle behavior detecting means for detecting the vehicle behavior. Control means having a damping characteristic control section for controlling the damping characteristic of each shock absorber according to the vehicle behavior signal generated, yaw rate detecting means for detecting the yaw rate of the vehicle, and the yaw rate detecting means provided in the control means. When the direction of the yaw rate and the direction of the rate of change of the yaw rate are in the same direction, the control gain of the rear wheel side damping characteristic is set higher than the control gain of the front wheel side damping characteristic, and when it is in the opposite direction, And a gain correction control section for setting the control gain of the rear wheel side damping characteristic to be lower than the control gain of the front wheel side damping characteristic. Apparatus. 2. The vehicle suspension system according to claim 1, wherein the yaw rate detecting means is a lateral acceleration detecting means for detecting a lateral acceleration of the vehicle. 3. The vehicle suspension system according to claim 1, wherein the yaw rate detecting means is constituted by steering angular velocity detecting means for detecting a steering angular velocity. 4. A sprung vertical velocity detecting means for detecting a sprung vertical velocity is used as the vehicle behavior detecting means, and the damping characteristic of each shock absorber is bounced based on the sprung vertical velocity in the damping characteristic control section. The control is performed based on a control signal obtained from a pitch rate detected from the rate and the vertical speed difference between the front and rear springs and a roll rate detected from the vertical speed difference between the left and right springs. The vehicle suspension system according to claim 2 or 3.