JP3325130B2 - Vehicle suspension system - Google Patents

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 control system for controlling a transient roll generated at the time of steering.

[0002]

2. Description of the Related Art Conventionally, as such a vehicle suspension device, for example, Japanese Unexamined Patent Publication No.
No. 624 is known.

[0003] This conventional device is interposed between the vehicle body side and each wheel side, and the extension side is to the hard side. The extension side hard region HS in which the damping force characteristic is variable and the compression side is fixed to the soft characteristic, and the compression side is to the hard side. A damping force characteristic change that has three damping force characteristic switching regions (see Fig. 14): a compression side hard region SH with variable damping force characteristics and the extension side is fixed to soft characteristics, and a soft region SS with soft characteristics on both the extension side and compression side. When the control signal based on the sprung vertical speed detected by the sprung vertical speed detecting means is equal to or more than a positive (upward) threshold value, the shock absorber is controlled to the extension side hard area HS. When the pressure is below the negative (downward) threshold, the shock absorber is controlled to the compression side hard area SH. When the value is between the positive threshold and the negative threshold, the shock absorber is switched to the soft area. Group controlled by SS The roll state of the vehicle body is detected from the control unit and the steering angle detected by the steering angle detection means. When the roll angle exceeds a predetermined threshold, the damping of the shock absorber is performed based on the steering direction at that time. A roll control unit that controls the force characteristics to the extension hard region HS on the steering direction (opposite to the roll direction) side and to the compression hard region SH on the opposite direction (roll direction) to the steering direction. , The roll of the vehicle body is suppressed.

[0004]

However, in the conventional apparatus, in order to obtain a soft ride when traveling straight ahead, when the damping force characteristics on the extension side and the compression side in the soft range are set to be low, the vehicle is not suitable. If the road surface has a slight undulation during the transitional roll based on the cornering of the vehicle, and the hunting of the vehicle body occurs, the reverse stroke side of the shock absorber has a soft characteristic. Therefore, as shown in FIG. Distortion due to hunting of the vehicle body is greatly exhibited, which causes a problem of uncomfortable feeling and a deterioration in cornering performance due to a distorted vehicle posture.

[0005] If the soft characteristics on the extension side and the compression side are set to be higher in order to solve the above-mentioned problems, it becomes impossible to secure a soft riding comfort during straight running.

The present invention has been made in view of the above-mentioned conventional problems, and hunting of a vehicle has occurred during a transitional roll while securing a soft riding comfort of the vehicle during a straight running and a steady roll. It is a first object of the present invention to provide a vehicle suspension device capable of preventing cornering performance by preventing a vehicle posture from being distorted, and furthermore, a transient roll without impairing the riding comfort of the vehicle during straight running and during a steady roll. A second object is to provide a vehicle suspension device that can further enhance the suppression effect.

[0007]

In order to achieve the first object, a vehicle suspension system according to the present invention is interposed between a vehicle body side and each wheel side as shown in the claim correspondence diagram of FIG. A shock absorber b which can be changed to hard, medium and soft damping force characteristics separately on the extension side and the compression side by damping force characteristic changing means a; a sprung vertical speed detecting means c for detecting a sprung vertical speed; When the control signal based on the sprung vertical speed detected by the upper and lower speed detecting means c is equal to or more than a positive (upward) threshold value, the shock absorber b is controlled to have a hard damping force characteristic on the extension side and a soft damping force characteristic on the compression side, When the shock absorber b is equal to or less than the negative (downward) threshold value, the shock absorber b is controlled to have a damping force characteristic of a hard pressure side and a soft extension side, and is a value between a positive threshold value and a negative threshold value. When the shock absorber b is extended A damping force characteristic control means e having a basic control unit d for controlling the damping force characteristics of the soft to the pressure side both,
Transient roll detecting means f for detecting a transient roll state of the vehicle
When the transient roll state of the vehicle is detected by the transient roll detection means f provided in the damping force characteristic control means e,
For the shock absorber b on the outside, the compression side is hard and the extension side is controlled to medium damping force characteristics, and for the shock absorber b on the inside, the expansion side is hard and the compression side is controlled to medium damping force characteristics. And a roll control unit g.

Further, in the vehicle suspension device according to the second aspect,
The damping force characteristic changing means of the shock absorber includes an extension-side hard region in which the extension side is variable to the hard side and the compression side is fixed to the soft characteristic, and the compression side is a variable damping force characteristic to the hard side and the extension side is a soft characteristic. A fixed compression side hard area, a soft area with soft characteristics on both the expansion and compression sides, a compression side hard / extension medium area with characteristics that are hard on the compression side and higher on the expansion side than the soft properties, and a hard property on the expansion side and soft characteristics on the compression side 5 of high-strength hard-side / pressure-side medium area with higher characteristics
This means has two damping force characteristic switching regions.

Further, in the vehicle suspension device according to the third aspect,
In order to achieve the second object, the compression-side damping force in the compression-side hard / extension-side medium area becomes higher than the maximum damping force at the time of control by the basic control unit, and the extension-side attenuation in the extension-side hard / compression-side medium area. The force is made higher than the maximum damping force at the time of control by the basic control unit.

Further, in the vehicle suspension device according to the fourth aspect,
The transient roll detecting means is constituted by a vehicle speed sensor and a lateral acceleration change rate detecting means, and when the vehicle speed and the lateral acceleration change rate each become equal to or more than predetermined values, it is determined that the vehicle is in the transient roll state.

Further, in the vehicle suspension device according to the fifth aspect,
The transient roll detecting means is constituted by a vehicle speed sensor and a steering angular acceleration detecting means, and when the vehicle speed and the steering angular acceleration each become equal to or more than predetermined values, it is determined that the vehicle is in the transient roll state.

Further, in the vehicle suspension device according to the sixth aspect,
The transient roll detecting means is constituted by a vehicle speed sensor and a yaw rate detecting means, and when the vehicle speed and the yaw rate each become equal to or more than predetermined values, it is determined that the vehicle is in the transient roll state.

[0013]

The operation of the vehicle suspension system according to the first aspect of the present invention will be described. The reference numerals in the description correspond to FIG.

First, when the vehicle is running straight (and during steady rolling), the basic control unit d of the damping force characteristic control means e controls switching of damping force characteristics by a direction discriminating code of a control signal based on the sprung vertical speed. As described later, the damping force characteristic control based on the skyhook theory is performed as described later in detail, so that the steering stability and the soft riding comfort of the vehicle can be obtained.

Also, as in the case of cornering of a vehicle,
When the transient roll state is detected by the transient roll detection means f, the transient roll control unit g of the damping force characteristic controls the shock absorber b on the outer side with respect to the turning to the hard pressure side and the extension side to the medium damping force characteristic. The shock absorber b on the inner side of the turn controls the expansion side to be hard and the compression side to have a medium damping force characteristic, thereby controlling the damping force characteristic on each stroke side of each shock absorber b to the hard characteristic. As a result, the transient roll of the vehicle is suppressed, and when the hunting (excessive vertical movement) of the vehicle body occurs during the transient roll, the damping force characteristic on the stroke side opposite to the stroke of each shock absorber b at that time is soft. Since the characteristic is controlled to be higher than the characteristic, the distortion of the roll rate is attenuated (see (b) in FIG. 13). With the cornering performance is improved to stabilize the vehicle attitude.

Further, in the vehicle suspension device according to the third aspect,
The compression-side damping force in the compression-side hard / extension-side medium area is higher than the maximum damping force when controlled by the basic control unit, and the extension-side damping force in the expansion-side hard / compression-side medium area is controlled by the basic control unit. This makes it possible to enhance the transient roll suppressing effect without impairing the soft riding comfort of the vehicle during straight running and during steady rolling.

[0017]

An embodiment 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 an explanatory view showing the configuration of the vehicle suspension system according to the embodiment of the present invention, in which four shock absorbers SA ₁ , SA ₂ , SA ₃ and SA ₄ are interposed between the vehicle body and each wheel.
(Note that in describing the shock absorber, these four are collectively referred to, and when describing these common configurations, they are simply indicated as SA.) A sprung vertical acceleration sensor (hereinafter referred to as a vertical G sensor) 1 (1 ₁ , 1 ₂ , 1 ₃ ) for detecting a vertical acceleration is provided on a vehicle body near a position where each shock absorber SA is mounted on the vehicle body. 1 ₄₎ is provided.
A basic control unit for inputting signals from the vertical G sensor 1 and a vehicle speed sensor 2 (not shown) and outputting a drive control signal to the pulse motor 3 of each shock absorber SA and a transient roll control are provided near the driver's seat. A control unit 4 is provided as a damping force characteristic control means including a portion.

FIG. 3 is a system block diagram showing the above configuration. The control unit 4 includes an interface circuit 4a, a CPU 4b, and a drive circuit 4c. A signal is input.

Next, FIG. 4 shows each shock absorber SA.
In this shock absorber SA, a cylinder 30, a piston 31 defining the cylinder 30 in an upper chamber A and a lower chamber B, and a reservoir chamber 32 on the outer periphery of the cylinder 30 are formed. An outer cylinder 33, a base 34 defining a lower chamber B and a reservoir chamber 32, a guide member 35 for guiding sliding of a piston rod 7 having a lower end connected to the piston 31, and an outer cylinder 33 and a vehicle body. The suspension spring 36 interposed between the bumper rubber 3
7 is provided.

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 A pressure-side damping valve 20 and an extension-side damping valve 12 for opening and closing 31a and 31b, respectively, are provided. A stud 3 penetrating the piston 31 is provided on a bound stopper 41 screwed to the tip of the piston rod 7.
8 is screwed and fixed, and this stud 38 has
A communication hole 39 communicating the upper chamber A and the lower chamber B is formed, and further, an adjuster 40 for changing a flow path cross-sectional area of the communication hole 39 and communication of the fluid in accordance with the direction of fluid flow. Extension side check valve 1 that allows and blocks the flow of hole 39
7 and a pressure side check valve 22 are provided.
The adjuster 40 is rotated by the pulse motor 3 via a control rod 70 (see FIG. 4). The stud 38 has a first port 21, a second port 13, a third port 14,
A fourth port 16 is formed. As shown in the sectional view of FIG. 8, only four second ports 13 are formed at equal circumferential intervals, and the other first port 21, third port 14, and fourth port 16 are Two pieces are formed so as to face each other in the diameter direction.

On the other hand, the adjuster 40 has the hollow portion 19 formed therein, and two lateral holes 24 communicating between the inside and the outside thereof are formed in a state of being diametrically opposed to each other. While the annular groove 25 which always communicates is formed,
Two longitudinal grooves 23 for communicating the annular groove 25 and the fourth port 16 are formed in a state of being diametrically opposed to each other.

Therefore, between the upper chamber A and the lower chamber B, a through-hole 31 is formed as a flow path through which fluid can flow in the extension stroke.
b, the inside of the extension side damping valve 12 is opened to open the lower chamber B
, The second port 13, the annular groove 2
5, an expansion-side second flow path E that opens the outer peripheral side of the expansion-side damping valve 12 through the vertical groove 23 and the third port 14 to reach the lower chamber B, a second port 13, an annular groove 25, There are three flow paths, a third flow path F on the extension side, which opens the check valve 17 on the extension side via the longitudinal groove 23 and the fourth port 16 to reach the lower chamber B. Further, as a flow path through which a fluid can flow in the pressure stroke, the through hole 31 is provided.
a, the pressure-side first flow path H that opens the pressure-side damping valve 20
And a pressure-side second flow path J that reaches the upper chamber A by opening the pressure-side check valve 22 via the hollow portion 19, the lateral hole 24, and the first port 21.

That is, the shock absorber SA is configured such that the damping force characteristic can be changed in multiple steps by rotating the adjuster 40 with the characteristics shown in FIG. 6 on both the extension side and the compression side. That is, as shown in FIG.
When the adjuster 40 is rotated counterclockwise from the soft region SS where the compression side has soft characteristics, the damping force characteristic can be changed in multiple stages to the hard characteristic side only on the extension side, and the compression side is fixed to the soft characteristic. When the adjuster 40 is further rotated counterclockwise, the extension-side damping force characteristic further changes to the hard characteristic side, and the compression-side damping force characteristic changes from the soft characteristic to the medium characteristic side. Changeable expansion side hardware / compression side medium area HM. Conversely, when the adjuster 40 is rotated clockwise, the compression side damping force characteristic can be changed to the hardware characteristic side in multiple steps and the expansion side is fixed to the soft characteristic. Pressure side hard area SM, and adjuster 4
When 0 is rotated clockwise, the compression-side damping force characteristic further changes to the hard characteristic side, and the compression-side damping force characteristic can be changed from the soft characteristic to the medium characteristic side. The structure is as follows.

Incidentally, the adjuster 40 is shown in FIG.
The KK section, the LL section, the MM section, and the NN section in FIG. 5 when arranged at each position of (HM), (MS), (SS), (SM), and (MH). Is shown in FIG.

Next, the control operation of the control unit 4 will be described with reference to the flowchart of FIG. 9 and the time chart of FIG. First, in the flowchart of FIG. 9, in step 101, the vehicle speed detected by the vehicle speed sensor 2 is read.

In step 102, it is determined whether the read vehicle speed is equal to or higher than a predetermined value (30 to 40 km / h).
If YES, the process proceeds to step 103, and if NO, the process proceeds to step 109 to perform the normal control, and ends one control flow. The details of the normal control will be described later.

[0027] At step 103, the value of the sprung vertical acceleration of the vehicle lateral position detected by the front wheel side each vertical G sensor 1 ₁ of the left and right, 1 _2, obtained by computation of the lateral acceleration acting on the vehicle, subsequent step 104 Then, the process proceeds to step 105 after determining the rate of change X of the lateral acceleration. The sprung vertical acceleration is obtained with a positive value in the extension direction and a negative value in the pressure direction, and the rate of change X of the lateral acceleration is a left direction toward the traveling direction (at the time of right steering). Is a positive value, and the right direction (at the time of left steering) is a negative value.

At step 105, the lateral acceleration change rate X
Is greater than or equal to the positive transient roll threshold α, that is,
It is determined whether or not the vehicle is in a transitional roll state to the left.
If S, the process proceeds to step 106, and if NO, the process proceeds to step 107.

In step 106, a transient roll control for suppressing a transient roll in the left direction is performed.
_2, the SA _4, the extension side hard-pressure side Medium area HM
In the shock absorbers SA ₁ and SA ₃ on the left side in the traveling direction, after controlling to the compression-side hard / extension-side medium area MH, one control flow is completed.

In step 107, the lateral acceleration change rate X
Is less than or equal to the negative transient roll threshold -α, that is, to determine whether it is in the transient roll state to the left,
If YES, the process proceeds to step 108, and if NO, the process proceeds to step 109.

In step 108, a transient roll control for suppressing a transient roll to the right is performed, and the right shock absorber SA in the traveling direction is controlled.
_2, the SA _4, the compression side hard extension phase medium area MH
In the shock absorbers SA ₁ and SA ₃ on the left side in the advancing direction, after controlling to the extension-side hard / pressure-side medium area HM, one control flow is completed. One control flow is completed by the above steps, and thereafter, the above steps are repeated.

Next, the control operation of the control unit 4 will be described with reference to the time chart of FIG. (A) Straight running and steady rolling During the straight running and steady rolling of the vehicle, the lateral acceleration change rate X is within the range of the transient roll threshold value -α to α. Normal control is performed in the section.

(B) Transient Rolling At the time of sudden steering or turning back of the steering, a transient roll occurs, and the lateral acceleration change rate X becomes smaller than the transient roll threshold value.
At this time, the transient roll control is performed by the transient roll control unit because the value exceeds the range of α to α.

(A) When the lateral acceleration change rate X is greater than or equal to the transient roll threshold value α, a transient roll to the left has occurred. In the shock absorbers SA ₂ and SA ₄ , the extension side hard / compression side medium region HM is controlled, and although not shown, the shock absorbers SA ₁ and SA ₃ on the left side in the traveling direction of the pressure stroke are: Compression side hard / extension side medium range By controlling to MH, the transient roll is sufficiently suppressed by the extension side or compression side hard characteristic, and the medium characteristic is higher than the soft characteristic on the reverse stroke side for hunting of the vehicle. Thus, it is possible to prevent the vehicle posture from being distorted at the time of hunting, thereby ensuring cornering performance.

(B) When the lateral acceleration change rate X is equal to or less than the transitional roll threshold value -α, a transitional roll to the right has occurred. In the right side shock absorbers SA ₂ and SA ₄ , the compression side hard / extension side medium area MH is controlled, and although not shown, the left side shock absorbers SA ₁ and SA ₃ in the advancing direction of the extension stroke are controlled. By controlling the HM on the extension side and the compression side medium area, the transient roll is sufficiently suppressed by the extension side or compression side hard characteristics, and the medium characteristic is higher than the soft characteristic on the reverse stroke side against hunting of the vehicle. The characteristic prevents the vehicle attitude from being distorted during hunting, thereby ensuring cornering performance.

FIG. 13 (b) shows the roll rate when the steering angular velocity changes as shown in FIG. 13 (a). The roll rate in the conventional example shown in FIG. In comparison, its distortion has been attenuated,
As described above, it is intended to prevent a sense of incongruity and a collapse of the vehicle posture due to occurrence of hunting of the vehicle body.

Next, the contents of the normal control performed by the basic control section of the control unit 4 will be described with reference to the flowchart of FIG. 11 and the time chart of FIG.
First, in the flowchart of FIG.
In step 1, the control signal V is obtained by multiplying the sprung vertical velocity Vn by a predetermined constant.

[0038] At step 202, the control signal V is equal to or a predetermined extension side threshold [delta] _T or more, the shock absorber SA proceeds to step 203 if YES
To the expansion side hard area MS, and if NO, the process proceeds to step 204.

[0039] At step 204, the control signal V is equal to or less than a predetermined pressure side threshold - [delta _C, YES
If so, the routine proceeds to step 205, where the shock absorber S
A is controlled to the compression side hard area SM, and if NO, the process proceeds to step 206.

[0040] Step 206, if it is determined NO at the step 202 and step 204, i.e., the control signal V has a value between the extension side threshold [delta] _T and the compression side threshold - [delta _C, when the Controls the shock absorber SA in the soft region SS. This completes one control flow,
Thereafter, the above control flow is repeated.

Next, the contents of the normal control will be described with reference to the time chart of FIG. When the control signal V is changed as shown in this figure, when the control signal V has a value between the expansion side threshold [delta] _T and the compression side threshold - [delta _C is the shock absorber SA to the soft region SS By this, when the behavior on the sprung is small, a soft ride comfort of the vehicle can be ensured.

When the control signal V becomes equal to or higher than the extension threshold value δ _T , the compression side is controlled to the extension side hard region MS to fix the compression side to the soft characteristic, while the extension side damping force characteristic C is controlled. Change in proportion to V. At this time, the extension side damping force characteristic C
It is controlled to be C = k _T · V. Note that k _C is an extension-side proportional constant.

When the control signal V becomes equal to or less than the compression side threshold value -δ _C , the compression side is controlled to the compression side hard area SM to fix the extension side to the low damping force characteristic, while controlling the compression side damping force characteristic to the control signal. Change in proportion to V. Also at this time, the pressure side damping force characteristic C is controlled so that C = k _C · V. In addition,
k _C is a pressure-side proportional constant.

That is, when the sprung behavior is large, the damping force characteristics of the respective shock absorbers SA on the stroke side at that time are made to be hard characteristics, so that the vibration damping performance of the vehicle is enhanced, and the steering stability of the vehicle is thereby improved. In addition, by making the damping force characteristics on the reverse stroke side soft characteristics, the road surface input on the reverse stroke side can be absorbed and the riding comfort of the vehicle can be ensured.

In the time chart of FIG.
The area a is a state in which the control signal V based on the sprung vertical velocity Vn is reversed from a negative value (downward) to a positive value (upward). At this time, the relative speed is still a negative value (shock absorber SA). Is a region on the pressure stroke side), and at this time, the shock absorber SA is controlled to the extension side hard region MS based on the direction of the control signal V. Accordingly, in this region, The pressure stroke side, which is the stroke of the shock absorber SA, has soft characteristics. Also,
In the region b, the control signal V based on the sprung vertical speed Vn remains a positive value (upward), and the relative speed is switched from a negative value to a positive value (the stroke of the shock absorber SA is on the extension stroke side). At this time, the shock absorber SA at this time, based on the direction of the control signal V,
, And the stroke of the shock absorber is also the extension stroke. Therefore, in this region, the extension stroke which is the stroke of the shock absorber SA at that time has a hard characteristic proportional to the value of the control signal V.

Area c is a state in which the control signal V based on the sprung vertical velocity Vn is reversed from a positive value (upward) to a negative value (downward). At this time, the relative velocity is still positive. In this case, the shock absorber SA is in the compression-side hard region based on the direction of the control signal V because it is a value range (the stroke of the shock absorber SA is the extension stroke side).
Control is performed by the SM, and therefore, in this region, the extension stroke side, which is the stroke of the shock absorber SA at that time, has soft characteristics.

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

As described above, in this embodiment, when the sprung vertical speed Vn and the relative speed between the sprung and unsprung have the same sign (region b, region d), the stroke of the shock absorber SA at that time is obtained. Side is controlled to a hard characteristic, and when the sign is different (regions a and c), the stroke side of the shock absorber SA at that time is controlled to a soft characteristic, which is the same as the damping force characteristic control based on the skyhook theory. Control will be performed without detecting the sprung and unsprung relative speed. Further, in this embodiment, when shifting from the area a to the area b and from the area c to the area d, the damping force characteristic is switched without driving the pulse motor 3.

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

Also, by making the stroke side in the direction opposite to the stroke of the shock absorber SA at that time soft, the road surface input in the direction opposite to the stroke direction is absorbed, and thereby, during straight running and during steady rolling. The riding comfort of the vehicle can be improved.

Further, as described above, while the soft characteristics of the vehicle are ensured during straight running and steady rolling due to the soft characteristics, even if the hunting of the vehicle occurs during the transient rolling, the stroke of the shock absorber at that time is as follows. With the medium characteristic on the reverse stroke side, it is possible to prevent the vehicle attitude from being distorted and to secure the cornering performance.

As shown in FIG. 7, the compression damping force of the compression side hard / extension side medium area MH is set to be higher than the maximum damping force at the time of normal control by the basic control unit. Medium region HM extension side damping force is set to be higher than that of normal control by the basic control unit to suppress transient rolls without impairing the soft riding comfort of the vehicle during straight running and steady rolling. The effect that the effect can be improved is obtained.

Although the embodiment has been described above, the specific configuration is not limited to this embodiment, and any change in design or the like without departing from the gist of the present invention is included in the present invention.

[0054] For example, in the embodiment, as the transient roll detecting means, a vehicle speed detected by the vehicle speed sensor 2, in operation from left and right vertical G sensors 1 _1, 1 ₂ detected left and right sprung mass vertical acceleration value When the obtained rate of change in lateral acceleration becomes a predetermined value or more, it is determined that the vehicle is in a transient roll state. In addition, the vehicle speed detected by the vehicle speed sensor and the steering angular acceleration detected by the steering sensor are determined. But,
It is determined that the vehicle is in the transitional roll state when it is equal to or more than the predetermined value, or the vehicle speed detected by the vehicle speed sensor and the yaw rate detected by the yaw rate detection means are in the transitional roll state when they are respectively equal to or more than the predetermined value. You may make it determine.

In the embodiment, the characteristics of the medium region in the compression-side hard / extension-side medium region MH and the expansion-side hard / compression-side medium region HM are medium characteristics between the soft characteristics and the hardware characteristics. The characteristics may be enhanced.

[0056]

As described above, the vehicle suspension system according to the present invention can be used when the control signal based on the sprung vertical speed detected by the sprung vertical speed detecting means is equal to or higher than a positive (upward) threshold value. The shock absorber is controlled to have a damping force characteristic of hard on the extension side and soft on the compression side. When the value is between the threshold value and the negative threshold value, damping force characteristic control means having a basic control unit for controlling the shock absorber to soft damping force characteristics on both the extension side and the compression side; The transient roll detecting means is provided in the transient roll detecting means for detecting the roll, and the damping force characteristic controlling means. When the transient roll detecting means detects the transient roll state of the vehicle, the pressure side of the shock absorber outside the turning is hard. The expansion side controls the medium damping force characteristics, and the shock absorber on the inside with respect to the turn has a transient roll control unit that controls the expansion side is hard and the compression side controls the medium damping force characteristics, The soft characteristics ensure that the vehicle has a soft ride during straight running and steady rolls, and the medium characteristics prevent the vehicle from collapsing even when hunting occurs during transient rolls, ensuring cornering performance. Is obtained.

In the vehicle suspension device according to the third aspect,
The compression-side damping force in the compression-side hard / extension-side medium region becomes even higher than the damping force during control by the basic control unit.
By making the extension damping force in the extension hard / compression-side medium area higher than the damping force during control by the basic control unit, the soft ride comfort of the vehicle during straight running and steady rolling is not impaired. The transient roll suppressing effect can be enhanced.

[Brief description of the drawings]

FIG. 1 is a conceptual view of a claim showing a vehicle suspension system of the present invention.

FIG. 2 is an explanatory diagram illustrating a configuration of a vehicle suspension device according to an embodiment of the present invention.

FIG. 3 is a system block diagram showing a vehicle suspension device according to the embodiment.

FIG. 4 is a cross-sectional view showing a shock absorber applied to the embodiment device.

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

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

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

8 is a sectional view taken along the line KK, LL, MM, and N- in FIG. 5 at each position of the adjuster in the embodiment device.
It is N sectional drawing.

FIG. 9 is a flowchart showing a control operation of a control unit in the embodiment device.

FIG. 10 is a time chart mainly showing an operation at the time of transient roll control among control operations of the control unit in the embodiment device.

FIG. 11 is a flowchart showing an operation during normal control among control operations of the control unit in the embodiment device.

FIG. 12 is a time chart showing an operation at the time of normal control among control operations of the control unit in the example device.

FIG. 13 is a time chart showing a steering angular velocity, a roll rate in the embodiment device, and a roll rate in a conventional example.

FIG. 14 is a damping force characteristic diagram corresponding to a step position of a pulse motor of a shock absorber in a conventional example.

[Explanation of symbols]

 a damping force characteristic changing means b shock absorber c sprung vertical speed detecting means d basic control part e damping force characteristic controlling means f transient roll detecting means g transient roll controlling part

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-3-204324 (JP, A) JP-A-5-38920 (JP, A) JP-A-6-183236 (JP, A) JP-A-5-183236 77624 (JP, A) JP-A-6-183237 (JP, A) JP-A-6-219132 (JP, A) JP-A-5-104926 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) B60G 17/015

Claims (6)

(57) [Claims] 1. A shock absorber interposed between a vehicle body side and each wheel side and capable of changing hard, medium, and soft damping force characteristics separately to the extension side and the compression side by damping force characteristic changing means, When the control signal based on the sprung vertical speed detected by the sprung vertical speed detecting means is equal to or higher than a positive (upward) threshold value, the extension side of the shock absorber is hardened. When the compression side controls the soft damping force characteristic, and when the pressure is below the negative (downward) threshold, the shock absorber controls the compression side hard and the extension side controls the soft damping force characteristic. A damping force characteristic control means having a basic control unit for controlling the shock absorber to soft damping force characteristics on both the extension side and the compression side when the value is between the threshold values, and a transient roll detecting a transient roll state of the vehicle. Detecting means, provided in the damping force characteristic control means, wherein when the transient roll detecting means detects a transient roll state of the vehicle, the shock absorber outside the turn is hard on the compression side and medium on the extension side. And a transient roll control unit which controls the shock absorber inside the turn to have a hard damping force characteristic on the extension side and a medium damping force characteristic on the compression side. 2. The damping force characteristic changing means of the shock absorber includes an expansion side hard region in which the extension side is variable to the hard side and the compression side is fixed to the soft side, and a compression side in which the damping force characteristic is variable to the hard side. The compression side hard area where the extension side is fixed to the soft characteristic, the soft area where the extension side and the compression side have the soft characteristic,
Five damping force characteristic switching areas: a compression side hard / extension medium area where the compression side is hard and the extension side is higher than the soft property, and an extension side hard / compression side medium area where the extension side is hard and the compression side is higher than the soft property. The vehicle suspension according to claim 1, further comprising: 3. The compression-side damping force in the compression-side hard / extension-side medium region becomes higher than the maximum damping force at the time of control by the basic control unit, and the extension-side damping force in the extension-side hard / compression-side medium region is controlled by the basic control unit. 3. The vehicle suspension according to claim 2, wherein the maximum damping force during the control is further increased. 4. The transient roll detecting means comprises a vehicle speed sensor and a lateral acceleration change rate detecting means, and when the vehicle speed and the lateral acceleration change rate each become equal to or more than predetermined values, it is determined that the vehicle is in a transient roll state. 2. The method according to claim 1, wherein
The vehicle suspension device according to any one of claims 1 to 3. 5. The transient roll detecting means is constituted by a vehicle speed sensor and a steering angular acceleration detecting means, and when the vehicle speed and the steering angular acceleration become respectively equal to or more than predetermined values, it is determined that the vehicle is in a transient roll state. Claims 1-3
A vehicle suspension device according to any one of the above. 6. The transient roll detecting means is constituted by a vehicle speed sensor and a yaw rate detecting means, and when the vehicle speed and the yaw rate each exceed a predetermined value, it is determined that the vehicle is in a transient roll state. Item 4. The vehicle suspension device according to any one of Items 1 to 3.