JPH09309311A - Suspension device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure comfortableness and maneuvering stability of a vehicle by controlling each shock absorber to an optimum damping force characteristic corresponding to the vehicle speed at that time at the non-braking time of the vehicle. SOLUTION: At the non-braking time of a vehicle, a basic control part (f) of a damping force characteristic control means (g) controls the damping force characteristic of each shock absorber (b) on the basis of a vehicle behavior signal detected by a vehicle behavior detecting means (c) and a vehicle speed gain depending on the vehicle speed detected by a vehicle speed sensor (d), and comfortableness and maneuvering stability of the vehicle can be ensured by the optimum damping force characteristic corresponding to the vehicle speed. When the braking state of the vehicle is detected by a braking state detecting means (e), a braking time correction control part (h) performs changeover from the vehicle speed gain depending on the vehicle speed in the basic control part (f), to a braking time gain not depending on the vehicle speed. Comfortableness and maneuvering stability of the vehicle can therefore be ensured even at the braking time of the vehicle the actual speed of which cannot be detected.

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 based on vehicle behavior and vehicle speed.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension system for controlling a damping force characteristic of a shock absorber based on a vehicle behavior and a vehicle speed, for example, one disclosed in Japanese Patent Laid-Open No. 4-15117 is known. This conventional vehicle suspension system includes damping force characteristic changing means for performing damping force characteristic control of each shock absorber according to the vehicle traveling state detected by the vehicle traveling state detecting means, and a vehicle speed sensor is provided for detecting the vehicle traveling state. The damping force characteristic is variably controlled according to the vehicle speed including the detected vehicle speed.

[0003]

However, in the conventional device, as described above, the damping force characteristic of the shock absorber is variably controlled according to the vehicle speed, so that the optimum control according to the vehicle speed of the vehicle is achieved. Although it is possible to do so, when the vehicle is being braked (when the anti-skid control is operating), the detected value of the vehicle speed sensor differs from the actual absolute speed of the vehicle body, and since that value fluctuates greatly, It becomes impossible to perform appropriate damping force characteristic control for the vehicle speed,
For this reason, there is a problem that the riding comfort and steering stability of the vehicle may be impaired during vehicle braking.

The present invention has been made by paying attention to the above-mentioned conventional problems, and when the vehicle is not braking, the riding comfort and the steering stability of the vehicle are improved by the optimum damping force characteristics according to the vehicle speed at that time. An object of the present invention is to provide a vehicle suspension device that can ensure the ride comfort and the steering stability of the vehicle even when the vehicle is being braked where the actual vehicle speed cannot be detected.

[0005]

In order to achieve the above-mentioned object, a vehicle suspension system according to claim 1 of the present invention is provided between a vehicle body side and each wheel side as shown in the claim correspondence diagram of FIG. A shock absorber b having a damping force characteristic changing means a interposed between the shock absorber b and the vehicle, a vehicle behavior detecting means c for detecting the vehicle behavior at the position of each shock absorber b, and a vehicle speed of the vehicle. A vehicle speed sensor d, a braking device m for braking the vehicle, a braking state detecting means e for detecting the braking state of the vehicle, a vehicle behavior signal detected by the vehicle behavior detecting means c, and the vehicle speed sensor d. A damping force characteristic control unit g having a basic control unit f that controls the damping force characteristic of each shock absorber b based on the vehicle speed gain that depends on the vehicle speed of the vehicle, and the damping force characteristic control unit g are provided. Further, when the braking state of the vehicle is detected by the braking state detecting means e, a braking correction controller h for switching from a vehicle speed gain dependent on the vehicle speed by the basic controller f to a braking gain independent of the vehicle speed is provided. It was taken as a means. Further, in the vehicle suspension device according to claim 2,
The braking gain that does not depend on the vehicle speed is fixedly set to the vehicle speed gain that depends on the vehicle speed at the time when the braking state of the vehicle is detected. The vehicle suspension system according to claim 3 is a vehicle including an anti-skid control device as the braking device m, and the braking state detecting means e.
Is composed of anti-skid control state detecting means for detecting the braking state from the operation of the anti-skid control device. Further, in the vehicle suspension system according to the fourth aspect, the braking state detecting means e is constituted by a brake switch that detects the braking state from the operation state of the brake pedal. In addition, claim 5
In the vehicle suspension system described above, a brake switch and a wheel speed sensor are provided, and the braking state detecting means e is configured to detect the braking state from the operation state of the brake pedal and the rate of change of the wheel speed. Further, in the vehicle suspension system according to the sixth aspect, the brake fluid pressure detecting means is provided, and the braking state detecting means e is configured to detect the braking state from the brake fluid pressure. Further, in the vehicle suspension system according to the seventh aspect, the vehicle acceleration / deceleration detecting means is provided, and the braking state detecting means e is configured to detect the braking state from the longitudinal acceleration of the vehicle.

[0006]

Since the vehicle suspension system according to claim 1 of the present invention is configured as described above, when the vehicle is not braked,
In the basic control unit f of the damping force characteristic control unit g, based on the vehicle behavior signal detected by the vehicle behavior detection unit c and the vehicle speed gain dependent on the vehicle speed of the vehicle detected by the vehicle speed sensor d, the shock absorber b of each shock absorber b is detected. Since the damping force characteristic control is performed, the riding comfort and the steering stability of the vehicle can be secured by the optimal damping force characteristic according to the vehicle speed of the vehicle.

Further, when the braking state of the vehicle is detected by the braking state detecting means e, the braking correction control section h changes the vehicle speed gain depending on the vehicle speed by the basic control section f to the braking gain independent of the vehicle speed. The changeover is performed, whereby the riding comfort and the steering stability of the vehicle can be ensured even when the vehicle is being braked where the actual vehicle speed cannot be detected.

Further, in the vehicle suspension system according to claim 5,
By detecting the braking state from the operation state of the brake pedal and the rate of change of the wheel speed, it is possible to control the vehicle immediately in response to the actual vehicle braking state.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) FIG. 2 shows Embodiment 1 of the present invention.
FIG. 2 is an explanatory view showing the configuration of the vehicle suspension device of FIG. 1, which is interposed between a vehicle body and four wheels, and is provided with four shock absorbers S.
A _FL , SA _FR , SA _RL , SA _RR (Note that in describing the shock absorber, these four are collectively referred to, and when describing their common configuration, they are simply indicated as SA. The lower reference numbers indicate the wheel position, _FL indicates the front wheel left, _FR indicates the front wheel right, _RL indicates the rear wheel left, and _RR indicates the rear wheel right.)

At each wheel position, a sprung vertical acceleration sensor (hereinafter referred to as vertical G sensor) 1 (1 _FL , which detects vertical acceleration G (G _FL , G _FR , G _RL , G _RR ))
1 _FR , 1 _RL , 1 _RR ), and wheel speed sensors 2 _FL , 2 for detecting the wheel speeds W _V-FL , W _V-FR of the front wheel side left and right wheels, respectively. _FR is provided, and the rear differential is provided with a wheel speed sensor 2 _RS that detects the wheel speed W _V-RS on the rear wheel side. Also, although not shown in the figure, the vehicle speed Vs of the vehicle is detected. A sensor 5 is provided, and the vertical G sensors 1 are provided near the driver's seat.
(1 _FL , 1 _FR , 1 _RL , 1 _RR ), each wheel speed sensor 2
(2 _FL , 2 _FR , 2 _RS ) and the signals from the vehicle speed sensor 5 are input to each shock absorber SA _FL , SA _FR , S.
A control unit 4 that outputs a drive control signal to the pulse motor 3 of A _RL and SA _RR is provided.

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, and the interface circuit 4a includes the upper and lower G sensors 1 (1).
_FL , 1 _FR , 1 _RL , 1 _RR )
_FL , G _FR , G _RL , G _RR ) signal, wheel speed sensor 2 (2 _FL ,
2 _FR , 2 _RS ) wheel speed W _V (W _V-FL , W _V-FR , W
_V-RS ) signal and the vehicle speed Vs signal from the vehicle speed sensor 5 are input, and the control unit 4 receives the shock absorbers SA (SA _FL , SA _FL , SA _FL) based on these input signals.
The damping force characteristic control of SA _FR , SA _RL , SA _RR ) and the anti-skid control of the braking devices 6 _FR , 6 _FL are performed. It should be noted that description of specific contents of the anti-skid control is omitted.

Further, the control unit 4 includes
The sprung sprung at each wheel position based on the sprung vertical acceleration G (G _FL , G _FR , G _RL , G _RR ) signals from the vertical G sensors 1 (1 _FL , 1 _FR , 1 _RL , 1 _RR ). A signal processing circuit (FIG. 14) for obtaining the vertical speed signal and the sprung unsprung relative speed signal is provided. The contents of each signal processing circuit will be described later.

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 for guiding the sliding of the piston rod 7 connected to the outer cylinder 33, a suspension spring 36 interposed between the outer cylinder 33 and the vehicle body, and a bump rubber 37.

Next, FIG. 5 is an enlarged cross-sectional view showing the 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. 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 periphery of the communication hole 3 in accordance with the direction of fluid flow.
An expansion-side check valve 17 and a compression-side check valve 22 that allow and shut off the flow on the flow path side formed by 9 are provided. It should be noted that this adjuster 40 corresponds to the pulse motor 3
Is rotated through 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, 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.
b, the inside of the extension side damping valve 12 is opened to open 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
, The pressure-side second flow path J that opens the pressure-side check valve 22 to reach the upper chamber A through the air passage, and the bypass flow that reaches the upper chamber A through the hollow portion 19, the second horizontal hole 25, and the third port 18. Road G
And three flow paths.

That is, the shock absorber SA is constructed so that the damping force 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.
The state in which both pressure sides are soft (hereinafter, soft area SS
When the adjuster 40 is rotated counterclockwise from
When the damping force characteristic can be changed in multiple stages only on the extension side and the compression side is 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, Only the compression side has a structure in which the damping force characteristic can be changed in multiple stages, and the extension side is a region fixed to the low damping force characteristic (hereinafter referred to as a compression side hard region SH).

Incidentally, 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, in the control operation of the control unit 4, the configuration of the signal processing circuit for obtaining the sprung vertical velocity Δx and the sprung-sprung relative velocity (Δx-Δx ₀ ) is shown in the block diagram of FIG. It will be described with reference to the drawings.

First, in B1, the phase delay compensation formula is used,
Each vertical G sensors _{1 (1 FL, 1 FR,} 1 RL, 1 RR) on each spring is detected by the vertical acceleration _{G (G FL, G FR,} G RL, G RR)
Is converted into a sprung vertical speed signal at each tower position.

The general equation for phase delay compensation can be expressed by the following transfer function equation (1). G _(S) = (AS + 1) / (BS + 1) ... (1) (A <B) And the frequency band (0.5 Hz to 3) required for damping force characteristic control.
Hz), has the same phase and gain characteristics as the case of integration (1 / S), and as a phase lag compensation equation for lowering the gain on the low frequency side (up to 0.05 Hz), the following transfer function equation (2 ) Is used.

G _(S) = (0.001 S + 1) / (10S + 1) × γ (2) Note that γ is a signal and a gain characteristic when the speed is converted by integration (1 / S). Is a gain for matching, and is set to γ = 10 in the first embodiment of the present invention. As a result, as shown in the solid line gain characteristics in FIG. 15A and the solid line phase characteristics in FIG. 15B, the frequency band (0.5 Hz to 3 Hz) required for damping force characteristic control is obtained.
2), only the gain on the low frequency side is reduced without deteriorating the phase characteristics. Note that FIG.
Dotted lines (a) and (b) show the gain characteristic and phase characteristic of the sprung vertical velocity signal that has been velocity-converted by integration (1 / S). In B2, band-pass filter processing is performed to cut off components other than the target frequency band to be controlled. That is, the band-pass filter BPF is composed of a second-order high-pass filter HPF (0.3 Hz) and a second-order low-pass filter LPF (4 Hz), and has a sprung vertical velocity that targets a sprung resonance frequency band of the vehicle. Δx (Δx _FL , Δ
x _FR , Δx _RL , Δx _RR ) signal.

On the other hand, in B3, as shown in the following equation (3),
The vertical acceleration G (G _FL , G _FR , G _RL , G _{RR )} detected by each vertical G sensor 1 using the transfer function Gu _(S) from each sprung vertical acceleration to the relative speed between the sprung and unsprung _portions. ) Signal, the relative speed (Δx
−Δx ₀ ) [(Δx−Δx ₀ ) _FL , (Δx−Δx
₀ ) _FR , (Δx−Δx ₀ ) _RL , (Δx−Δx ₀ ) _RR ] signals are obtained. Gu _(S) =-ms / (cs + k) (3) where m is the sprung mass, c is the damping coefficient of the suspension, and k is the spring constant of the suspension.

At B4, the sprung-unsprung relative velocity (Δx-Δx) at each tower position is calculated based on the inverse proportional map.
₀ ) [(Δx−Δx ₀ ) _FL , (Δx−Δx ₀ ) _FR , (Δ
x-Δx ₀ ) _RL , (Δx-Δx ₀ ) _RR ] The relative speed gain Ku variably set in inverse proportion to the signal is obtained.

That is, according to the first embodiment of the present invention, the vehicle behavior detection in the scope of claims in which the vehicle behavior (spring-vertical vertical velocity) at each wheel position is detected by the vertical G sensor 1 and the signal processing circuit of FIG. The means are configured.

Next, of the damping force characteristic control operation of the shock absorber SA in the control unit 4, the contents of the normal control by the basic control unit will be described with reference to the flowchart of FIG. Note that this normal-time control is performed for each shock absorber SA _FL , SA _FR , SA _RL , SA.
_It is performed for each _RR .

In step 101, the sprung vertical velocity Δx
Is determined to be a positive value. If YES, the flow proceeds to step 102 to control each shock absorber SA to the extension-side hard region HS. If NO, the flow proceeds to step 103.

In step 103, the sprung vertical speed Δx
Is determined to be a negative value. If YES, the routine proceeds to step 104, where each shock absorber SA is controlled to the pressure-side hard area SH, and if NO, the routine proceeds to step 105.

Step 105 is a processing step when NO is determined in steps 101 and 103, that is, when the value of the sprung vertical velocity Δx is 0,
At this time, each shock absorber SA is
To control.

Next, the operation of the damping force characteristic control will be described with reference to the time chart of FIG. The sprung vertical velocity Δx is
When changing as shown in this figure, as shown in the figure, when the value of the sprung vertical velocity Δx is 0, the shock absorber SA is controlled to the soft region SS.

When the value of the sprung vertical velocity Δx becomes a positive value, the extension side hard region HS is controlled to fix the compression side damping force characteristic to the soft characteristic, while the extension side damping force characteristic P is set.
The (target damping force characteristic position P _T ) is changed in proportion to the sprung vertical velocity Δx based on the following equation (4). P = Δx · Ku · αs (4) Note that Ku is the relative speed between the sprung part and the unsprung part (Δx−Δx).
₀ ) is a relative speed gain that is variably set according to ₀ ), and αs is a vehicle speed gain that is variably set according to the vehicle speed Vs, as shown in Table 1 below.

Further, when the value of the sprung vertical velocity Δx becomes a negative value, the compression side hard region SH is controlled to fix the extension side damping force characteristic to the soft characteristic, while the compression side damping force characteristic P is set.
The (target damping force characteristic position P _C ) is changed in proportion to the sprung vertical velocity Δx based on the equation (4).

[0033]

[Table 1]

Next, of the damping force characteristic control operation of the control unit 4, the switching operation state of the control area of the shock absorber SA will be mainly described with reference to the time chart of FIG.

In the time chart of FIG. 17, area a
Is a state in which the sprung vertical speed Δx is reversed from a negative value (downward) to a positive value (upward). At this time, the relative speed (Δx−Δx ₀ ) is still a negative value (shock absorber SA).
Is a pressure stroke side), and at this time, the shock absorber SA is controlled to the extension side hard region HS based on the direction of the sprung vertical speed Δx,
Therefore, in this area, the shock absorber SA at that time is
The pressure stroke side, which is the stroke of, has soft characteristics.

In the region b, the sprung vertical velocity Δx remains a positive value (upward), and the relative velocity (Δx-Δx ₀ ) is a negative value to a positive value (the stroke of the shock absorber SA is the extension stroke). Side), the shock absorber SA is controlled to the extension side hard area HS based on the direction of the sprung vertical velocity Δx at this time, and the stroke of the shock absorber is also the extension stroke. Therefore, in this region, therefore, the extension side, which is the stroke of the shock absorber SA at that time, has a hard characteristic proportional to the value of the sprung vertical velocity Δx.

In the region c, the sprung vertical velocity Δx is reversed from a positive value (upward) to a negative value (downward), but at this time, the relative velocity (Δx-Δx ₀ ) is still positive. Since this is the region where the value of is (the stroke of the shock absorber SA is the extension side), at this time, the sprung vertical velocity Δx
The shock absorber SA is controlled in the compression side hard region SH based on the direction of the above, and therefore, in this region, the extension side, which is the stroke of the shock absorber SA at that time, has a soft characteristic.

In the area d, the sprung vertical velocity Δx remains a negative value (downward), and the relative velocity (Δx-Δx ₀ ) is a positive value to a negative value (the stroke of the shock absorber SA is the extension stroke). Side), the shock absorber SA is controlled to the compression side hard region SH based on the direction of the sprung vertical velocity Δx at this time, and the stroke of the shock absorber is also the pressure stroke. In this region, 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 sprung vertical velocity Δx.

As described above, in the first embodiment of the present invention, when the sprung vertical velocity Δx and the relative velocity (Δx−Δx ₀ ) have the same sign (region b, region d), the shock absorber at that time is obtained. Damping force characteristic control based on the skyhook theory, in which the stroke side of the SA is controlled to the hard characteristic, and when the different sign (area a, area c), the stroke side of the shock absorber SA at that time is controlled to the soft characteristic. The same control as above will be performed. Further, in the first embodiment of the present invention, when the stroke of the shock absorber SA is switched, that is, when the region a shifts to the region b and the region c shifts to the region d (soft characteristic to hard characteristic), Since the damping force characteristic position on the stroke side to be switched is already switched to the hard characteristic side in the previous regions a and c, the switching from the soft characteristic to the hard characteristic can be performed without a time delay.

Next, of the damping force characteristic control operation of the shock absorber SA in the control unit 4, the control contents for switching between the normal control by the basic control unit and the braking correction control by the braking correction control unit, and the braking The contents of the time correction control will be described based on the flowchart of FIG. 18 and the time chart of FIG.

First, in the flow chart of FIG.
In step 201, it is determined whether or not the vehicle is in a braking state based on the anti-skid control operating state. If YES (anti-skid control operating = braking state), the vehicle speed Vs signal from the vehicle speed sensor 5 indicates the actual vehicle absolute speed. since different from, the time proceeds to step 202, sets the switching vehicle speed gain αs braking (during ABS operation) gain alpha _B. The value of the gain α _B during braking is obtained by an experiment. Then, in the following step 204, the target damping force characteristic position P of each shock absorber SA is obtained based on the equation (4) by the switching gain (when ABS is operated) gain α _B , and the actual damping force characteristic position P is obtained. It is possible to ensure the riding comfort and steering stability of the vehicle even when the vehicle speed is not detected and the vehicle is being braked.

Further, the determination in step 201 is NO.
When the anti-skid control is not activated = non-braking state, the vehicle speed Vs signal from the vehicle speed sensor 5 coincides with the actual vehicle absolute speed. At this time, therefore, the routine proceeds to step 203, where the vehicle speed is determined based on Table 1 above. The gain αs is set to the value of the vehicle speed gain α _{0 to} α ₁₀₀ according to the vehicle speed Vs at that time.
Then, in the following step 204, by the vehicle speed gains α _{0 to} α ₁₀₀ set according to the vehicle speed Vs, the above equation (4) is obtained.
Based on the above, each shock absorber SA is variably controlled to have an optimum damping force characteristic according to the vehicle speed of the vehicle at that time, whereby the riding comfort and steering stability of the vehicle when not braking can be secured.

With the above, one control flow is completed, and thereafter, the above control flow is repeated.

As described above, in the vehicle suspension system according to the first embodiment of the present invention, each shock absorber SA is controlled to the optimum damping force characteristic according to the vehicle speed at that time when the vehicle is not braked. As a result, it is possible to ensure the riding comfort and steering stability of the vehicle, and also to secure the riding comfort and steering stability of the vehicle even when the vehicle is being braked for which the actual vehicle speed cannot be detected. The effect is obtained. Next, another embodiment of the invention will be described. In the description of the other embodiments of the present invention, the same components as those of the first embodiment of the invention will be designated by the same reference numerals, and the description thereof will be omitted. Only the differences will be described.

(Second Embodiment of the Invention) A vehicle suspension system according to a second embodiment of the present invention is different from that of the first embodiment of the invention in the way of setting a braking gain during vehicle braking. Hereinafter, the switching control contents between the normal control by the basic control unit and the braking correction control by the braking correction control unit, and the braking correction control contents will be described based on the flowchart of FIG. 20 and the time chart of FIG. To do.

First, in the flow chart of FIG.
In step 301, the vehicle speed Vs signal is read from the vehicle speed sensor 5, and then the process proceeds to step 302.

In this step 302, it is judged whether or not the vehicle is in the braking state based on the operation state of the anti-skid control.
When ES (anti-skid control operation = braking state), the vehicle speed Vs signal detected by the vehicle speed sensor 5 is different from the actual vehicle absolute speed, and at this time, step 303
Advances to, set vehicle speed V _B at the time of braking condition is detected vehicle speed Vs, at the next step 304, based on Table 1, the vehicle speed V _B at the time point when the vehicle speed gain αs the braking state is detected ( In Figure 21, 105km /
vehicle speed gain α _{0 to} α ₁₀₀ corresponding to h) (in FIG. 21,
Fixed to the value of α ₁₀₀ ). And the following step 3
05, the vehicle speed gains α _{0 to} α fixedly set.
The target damping force characteristic position P of each shock absorber SA is obtained from ₁₀₀ on the basis of the equation (4), so that even when the vehicle speed cannot be detected and the vehicle is braked,
It is possible to ensure the riding comfort and steering stability of the vehicle.

On the other hand, the determination at step 302 is NO.
When the anti-skid control is inactive (non-braking state), the vehicle speed Vs signal from the vehicle speed sensor 5 coincides with the actual vehicle absolute speed. At this time, therefore, the routine proceeds to step 304, where the vehicle speed is determined based on Table 1 above. The gain αs is set to the value of the vehicle speed gain α _{0 to} α ₁₀₀ according to the vehicle speed Vs at that time.
Then, in the following step 204, the target damping force characteristic position P of each shock absorber SA is obtained based on the equation (4) by the vehicle speed gains α _{0 to} α ₁₀₀ set according to the vehicle speed Vs at that time. Thus, the vehicle is variably controlled to have the optimum damping force characteristic according to the vehicle speed variation, and thus the riding comfort and the steering stability of the vehicle when the vehicle is not braked can be ensured. Thus, one control flow is completed, and thereafter, the above control flow is repeated.

As described above, in the second embodiment of the present invention, during braking of the vehicle, the vehicle speed gains α _{0 to} α ₁₀₀ corresponding to the vehicle speed V _B at the time when the braking state is detected are fixedly set. It was done.

(Third Embodiment of the Invention) A vehicle suspension system according to a third embodiment of the present invention includes, as braking state detecting means, a brake switch for detecting an operating state (ON-OFF) of a brake pedal, and a wheel acceleration (wheel acceleration). Wheel speed change rate) G
A wheel speed sensor for detecting _W is provided, and the switching control contents between the normal control by the basic control unit and the braking correction control by the braking correction control unit and the braking correction control contents will be described below with reference to FIG. This will be described based on the flowchart of FIG.

First, in the flow chart of FIG.
In step 401, it is determined whether or not the braking state determination flag F _B has been reset to 0, and YES (F _B = 0)
If so, the process proceeds to step 402.

In step 402, it is determined whether the vehicle is in the braking state by determining whether the brake switch is in the ON state and the wheel acceleration G _W is less than the predetermined threshold value G _WT . If YES (braking state), the routine proceeds to step 403, where the braking state determination flag F _B
After setting 1 to 1, the process proceeds to step 406, and N
When it is O (non-braking state), the process proceeds to step 404,
After resetting the braking state determination flag F _B to 0, the process proceeds to step 406.

Meanwhile, in step 401 NO (F _B =
If it is determined to be 1), the process proceeds to step 404, and it is determined whether or not the operation state of the brake pedal is continued by a signal from the brake switch. If YES (the braking state is continuing), the step is directly performed. 406, and if NO (release of braking state), go to step 4 above.
After proceeding to 05 and resetting the braking state judgment flag F _B to 0, the routine proceeds to step 406.

Then, in this step 406,
When the braking state determination flag F _B is set to 1 (when in the braking state), the fixed vehicle speed gain α is set.
_{From 0 to} α ₁₀₀ , the target damping force characteristic position P of each shock absorber SA is obtained based on the above equation (4), so that the ride comfort and the steering stability of the vehicle are stable even during vehicle braking where the actual vehicle speed cannot be detected. It is possible to secure the sex.

When the braking state determination flag F _B is reset to 0 (when the vehicle is in the non-braking state), the vehicle speed gain α ₀ set in accordance with the vehicle speed Vs at that time is determined in step 406. [Alpha] ₁₀₀ , the target damping force characteristic position P of each shock absorber SA is obtained based on the above equation (4), so that it is variably controlled to the optimum damping force characteristic according to the vehicle speed fluctuation. It is possible to ensure the riding comfort and steering stability of the vehicle during braking. Thus, one control flow is completed, and thereafter, the above control flow is repeated.

As described above, in the vehicle suspension system according to the third embodiment of the present invention, the start of the braking correction control is determined based on the operation state of the brake pedal and the wheel acceleration value, and the braking correction control is terminated. By making the determination based on the pedal operation state, it is possible to perform control that immediately corresponds to the actual vehicle braking state.

(Fourth Embodiment of the Invention) A vehicle suspension system according to a fourth embodiment of the present invention is provided with a longitudinal acceleration sensor for detecting a longitudinal acceleration G _L of the vehicle as a braking state detecting means. Hereinafter, the switching control contents between the normal control by the basic control unit and the braking correction control by the braking correction control unit, and the braking correction control contents will be described based on the flowchart of FIG. 24 and the time chart of FIG. 25. .

First, in the flow chart of FIG.
In step 501, by determining whether the longitudinal acceleration G _L of the vehicle is less than a predetermined threshold value G _LT ,
It is determined whether the vehicle is in the braking state, and YES ( _GL <
When G _LT = braking state), the routine proceeds to step 502, where the braking state judgment flag F _B is set to 1, and then the routine proceeds to step 504.

Then, in this step 504,
Since the target damping force characteristic position P of each shock absorber SA is obtained based on the equation (4) by the vehicle speed gains α _{0 to} α ₁₀₀ that are fixedly set, even during vehicle braking when the actual vehicle speed cannot be detected. Therefore, it is possible to secure the riding comfort and the steering stability of the vehicle.

On the other hand, in step 501, NO (G _L ≧
When it is determined that G _LT = non-braking state), step 503
After resetting the braking state determination flag F _B to 0, the process proceeds to step 504.

Then, in this step 504,
Vehicle speed gain α ₀ set according to the vehicle speed Vs at that time
[Alpha] ₁₀₀ , the target damping force characteristic position P of each shock absorber SA is obtained based on the above equation (4), so that it is variably controlled to the optimum damping force characteristic according to the vehicle speed fluctuation. It is possible to ensure the riding comfort and steering stability of the vehicle during braking. Above,
One control flow is ended, and the above control flow is repeated thereafter.

(Fifth Embodiment of the Invention) A vehicle suspension system according to a fifth embodiment of the present invention is provided with a brake fluid pressure sensor for detecting a brake fluid pressure P _B as a braking state detecting means. Switching control contents between normal control by the basic control unit and braking correction control by the braking correction control unit,
The contents of the braking correction control will be described with reference to the flowchart of FIG. 26 and the time chart of FIG.

First, in the flow chart of FIG.
In step 601, it is determined whether or not the vehicle is in a braking state by determining whether or not the brake fluid pressure P _B exceeds a predetermined threshold value P _T , and YES (P _B > P _T =
In the braking state), the routine proceeds to step 602, where the braking state judgment flag F _B is set to 1 and then step 604
Proceed to.

Then, in this step 604,
Since the target damping force characteristic position P of each shock absorber SA is obtained based on the equation (4) by the vehicle speed gains α _{0 to} α ₁₀₀ that are fixedly set, even during vehicle braking when the actual vehicle speed cannot be detected. Therefore, it is possible to secure the riding comfort and the steering stability of the vehicle.

On the other hand, at the step 601, NO (P _B ≤
When it is determined that P _T = non-braking state), step 603
After resetting the braking state determination flag F _B to 0, the process proceeds to step 604.

Then, in this step 604,
Vehicle speed gain α ₀ set according to the vehicle speed Vs at that time
[Alpha] ₁₀₀ , the target damping force characteristic position P of each shock absorber SA is obtained based on the above equation (4), so that it is variably controlled to the optimum damping force characteristic according to the vehicle speed fluctuation. It is possible to ensure the riding comfort and steering stability of the vehicle during braking. Above,
One control flow is ended, and the above control flow is repeated thereafter.

Although the embodiments of the present invention have been described above, the specific configuration is not limited to the embodiments of the present invention, and even if there are design changes and the like within the scope not departing from the gist of the present invention, Included in the invention. For example, in the first embodiment of the invention, the wheel speed sensors are provided at the left and right wheel positions on the front wheel side, but may be provided at the left and right wheel positions on the rear wheel side.

In the third embodiment of the invention, the brake pedal operating state (ON-O) is used as the braking state detecting means.
Comprising a brake switch for detecting FF), a wheel speed sensor for detecting a wheel acceleration (rate of change of wheel speed) G _W,
The start of the braking correction control is determined by the operation state of the brake pedal and the wheel acceleration, and the end is determined only by the operation state of the brake pedal, but both the start and the end are determined by only one of them. May be.

Further, in the embodiment of the invention, as the damping force characteristic changing means in the shock absorber, when the damping force characteristic on one stroke side is variably controlled, the damping force characteristic on the reverse stroke side becomes a soft characteristic. However, the present invention can also be applied to the case where a structure in which the damping force characteristics of the extension stroke and the compression stroke change at the same time is used.

Further, in the embodiment of the invention, the soft region SS is controlled only when the sprung vertical velocity signal is 0, but a predetermined dead zone centered at 0 is provided and the spring is controlled within this dead zone. Control hunting can be prevented by maintaining the damping force characteristic in the soft region SS while the upper and lower velocities are changing.

[0071]

As described above, the first aspect of the present invention is as follows.
In the vehicle suspension system described above, as described above, the damping force characteristic control of each shock absorber is performed based on the vehicle behavior signal detected by the vehicle behavior detection means and the vehicle speed gain depending on the vehicle speed of the vehicle detected by the vehicle speed sensor. A damping force characteristic control means having a basic control section for performing the above, and a vehicle speed dependent on the vehicle speed by the basic control section provided in the damping force characteristic control means when the braking state of the vehicle is detected by the braking state detection means. With the configuration that includes the braking correction control unit that switches from gain to braking gain that does not depend on vehicle speed, each shock absorber has the optimum damping force characteristics according to the vehicle speed at that time when the vehicle is not braking. Control and by this
It is possible to obtain the effect of being able to ensure the riding comfort and steering stability of the vehicle, and also to secure the riding comfort and steering stability of the vehicle even when the vehicle is being braked where the actual vehicle speed cannot be detected. To be

In the vehicle suspension system according to the fifth aspect,
By providing a brake switch and a wheel speed sensor, and the braking state detecting means is configured to detect the braking state from the operation state of the brake pedal and the rate of change of the wheel speed, control that responds immediately to the actual vehicle braking state Is possible.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram showing a vehicle suspension device of the present invention.

FIG. 2 is a configuration explanatory view showing a vehicle suspension device according to the first embodiment of the present invention.

FIG. 3 is a system block diagram illustrating the vehicle suspension device according to the first embodiment of the present invention.

FIG. 4 is a sectional view showing a shock absorber applied to the vehicle suspension system according to the first embodiment of the present invention.

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 a perspective view of the shock absorber shown in FIG.
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 signal processing circuit for obtaining a sprung vertical velocity and a sprung unsprung relative velocity signal from sprung vertical acceleration.

FIG. 15 is a diagram showing a gain characteristic (a) and a phase characteristic (b) of the sprung vertical velocity signal converted by using the phase lag compensation equation.

FIG. 16 is a flowchart showing a normal-time control operation of damping force characteristics of the control unit according to the first embodiment of the present invention.

FIG. 17 is a time chart showing a damping force characteristic normal control operation of the control unit according to the first embodiment of the present invention.

FIG. 18 is a flowchart showing the contents of switching control between normal control and braking correction control by the basic control unit of the control unit according to the first embodiment of the present invention and braking correction control unit.

FIG. 19 is a time chart showing the contents of switching control between normal control and braking correction control by the basic control unit of the control unit according to the first embodiment of the present invention and braking correction control unit.

FIG. 20 is a flowchart showing the contents of control for switching between normal control and braking correction control by the basic control unit of the control unit in the vehicle suspension system according to the second embodiment of the present invention and braking correction control unit.

FIG. 21 is a time chart showing the contents of switching control between normal control and braking correction control by the basic control unit of the control unit in the vehicle suspension system according to the second embodiment of the present invention.

FIG. 22 is a flowchart showing the contents of switching control between normal control and braking correction control by the basic control unit of the control unit in the vehicle suspension system according to the third embodiment of the present invention and braking correction control unit.

FIG. 23 is a time chart showing the contents of switching control between normal control and braking correction control by the basic control unit of the control unit in the vehicle suspension system according to the third embodiment of the present invention.

FIG. 24 is a flowchart showing the contents of switching control between normal control and braking correction control by the basic control unit of the control unit in the vehicle suspension system according to the fourth embodiment of the present invention and braking correction control unit.

FIG. 25 is a time chart showing the contents of switching control between normal control and braking correction control by the basic control unit of the control unit in the vehicle suspension system according to the fourth embodiment of the present invention and braking correction control unit.

FIG. 26 is a flowchart showing the contents of switching control between normal control and braking correction control by the basic control unit of the control unit in the vehicle suspension system according to the fifth embodiment of the present invention.

FIG. 27 is a time chart showing the contents of switching control between normal time control by the basic control unit of the control unit and the braking correction control by the braking correction control unit in the vehicle suspension system according to the fifth embodiment of the present invention.

[Explanation of symbols]

 a damping force characteristic changing means b shock absorber c vehicle behavior detecting means d vehicle speed sensor e braking state detecting means f basic control unit g damping force characteristic control means h braking correction control unit m braking device

Claims (7)

[Claims] 1. A shock absorber, which is interposed between a vehicle body side and each wheel side and has damping force characteristic changing means capable of changing the damping force characteristic, and a vehicle behavior for detecting a vehicle behavior at each shock absorber position. Detecting means, a vehicle speed sensor for detecting the vehicle speed of the vehicle, a braking device for braking the vehicle, a braking state detecting means for detecting the braking state of the vehicle, and a vehicle behavior signal detected by the vehicle behavior detecting means Damping force characteristic control means having a basic control portion for performing damping force characteristic control of each shock absorber on the basis of the vehicle speed gain dependent on the vehicle speed detected by the vehicle speed sensor, and the damping force characteristic control means. However, when the braking state of the vehicle is detected by the braking state detecting means, the vehicle speed gain depending on the vehicle speed is changed from the vehicle speed gain by the basic control unit to the braking time gain not depending on the vehicle speed. Vehicle suspension system characterized in that it comprises a braking correction control unit, the changing Ri. 2. The vehicle suspension according to claim 1, wherein the vehicle speed gain that does not depend on the vehicle speed is fixedly set to the vehicle speed gain that depends on the vehicle speed at the time when the braking state of the vehicle is detected. apparatus. 3. A vehicle provided with an anti-skid control device as the braking device, wherein the braking state detecting means comprises anti-skid control state detecting means for detecting a braking state from the operation of the anti-skid control device. The vehicle suspension system according to claim 1 or 2, wherein the vehicle suspension system is provided. 4. The vehicle suspension system according to claim 1, wherein the braking state detecting means is composed of a brake switch that detects the braking state from the operating state of the brake pedal. 5. A brake switch and a wheel speed sensor are provided, and the braking state detecting means is configured to detect the braking state from the operation state of the brake pedal and the rate of change of the wheel speed. The vehicle suspension device according to claim 1 or 2. 6. A brake fluid pressure detecting means is provided, and the braking state detecting means is configured to detect a braking state from the brake fluid pressure.
The vehicle suspension device described in. 7. The longitudinal acceleration detecting means is provided, and the braking state detecting means is configured to detect the braking state from the longitudinal acceleration of the vehicle. Vehicle suspension system.