JPH11147411A - Vehicle suspension unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle suspension unit that can improve the turnability of the vehicle without decreasing the braking performance in both braking and turning. SOLUTION: This vehicle suspension unit is equipped with a damping force characteristic control means e containing a normal state controller d which optimally controls the damping force characteristics of a shock absorber b in the vehicle normal running based on the vertical behavior of the vehicle detected by a vertical vehicle behavior detection means c. The unit is also provided with a braking condition detection means f detecting the braking condition of the vehicle, a turning condition detection means g detecting the turning condition of the vehicle, and a braking and turning correction controller h. When the braking and turning conditions of the vehicle are detected by the braking condition detection means f and the turning condition detection means g, the braking and turning correction controller controls the vehicle in the direction in which the roll stiffness for the fore wheels is lower than that for the rear wheels.

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.
In particular, the present invention relates to a technique for securing steering stability during braking and turning.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension device which controls a damping force characteristic of a shock absorber in order to secure steering stability during braking and turning, for example,
2. Description of the Related Art A vehicle suspension control device described in JP-A-6-64429 is known. This conventional suspension control device for a vehicle includes a traveling state detection unit that detects a traveling state of the vehicle including a steering state detection unit that detects a steering state of the vehicle and a braking state detection unit that detects a braking state of the vehicle. Control means for switching the control characteristics of the suspension device to at least three or more stages based on the detection signal of the traveling state detection means; and turning and braking of which the detection signals of the steering state detection means and the braking state detection means are not less than predetermined levels. The structure includes a determination unit that determines whether the state is in the state, and a prevention unit that prevents switching to a high stage in which the determination result of the determination unit is equal to or more than the first set value. That is, at the time of turning braking of the vehicle, by preventing the control characteristics of the suspension device from being switched to a high step which is equal to or higher than the first set value set in advance, the posture change of the vehicle body is allowed, and Increase in the load sharing amount on the side and decrease in the load sharing amount on the turning inner wheel side can reduce the difference in the load sharing between the inner and outer wheels, suppress the decrease in total cornering power, and improve steering stability. Is to be able to do things.

[0003]

However, in the conventional vehicle suspension control device, as described above, the overall control characteristics of the suspension are deteriorated. Has a problem that braking performance may be reduced due to the increase in the braking force.

The present invention has been made in view of the above-mentioned conventional problems, and provides a vehicle suspension system capable of improving the turning performance of a vehicle without deteriorating the braking performance during braking and turning. It is intended to do so.

[0005]

In order to achieve the above object, in the vehicle suspension system according to the first aspect of the present invention, the damping force characteristic can be changed by being interposed between the vehicle body side and the wheel side. Shock absorber b having damping force characteristic changing means a
A vehicle up / down behavior detecting means c for detecting the up / down behavior of the vehicle; and a damping force characteristic of the shock absorber b during normal running of the vehicle based on the up / down behavior of the vehicle detected by the up / down behavior detection means c. Damping force characteristic control means e having a normal control section d for optimally controlling the vehicle, braking state detecting means f for detecting the braking state of the vehicle, turning state detecting means g for detecting the turning state of the vehicle, and the braking state When the braking state and the turning state of the vehicle are detected by the detecting means f and the turning state detecting means g, the braking / turning correction is performed in such a manner that the roll rigidity of the front wheels becomes lower than the roll rigidity of the rear wheels. And a control unit h. Further, in the vehicle suspension device according to the second aspect, in the first aspect, the braking / turning correction control unit detects the braking state and the turning state of the vehicle with the braking state detecting means f and the turning state detecting means g. In this case, the damping force characteristic of at least the extension stroke side of the left and right rear wheel side shock absorbers b is controlled to a hard characteristic, and the front wheel inner wheel side shock absorber b
By controlling at least the extension stroke side of the front wheel to a soft characteristic and controlling at least the pressure stroke side of the outer wheel side shock absorber b of the front wheel to a hard characteristic, the roll rigidity on the front wheel side becomes lower than the roll rigidity on the rear wheel side. Means configured to be controlled. Further, in the vehicle suspension device according to the third aspect, in the first or second aspect, the braking /
When the turning state correction control unit h detects the braking state and the turning state of the vehicle by the braking state detecting unit f and the turning state detecting unit g, at least the left and right rear wheel side shock absorbers b at least on the extension stroke side. The damping force characteristic is controlled to be a hard characteristic, and at least the extension stroke side of the inner wheel side shock absorber b of the front wheel is controlled to be a soft characteristic than the control characteristic of the normal control unit c.
In the vehicle suspension device according to the fourth aspect, the first to third aspects are provided.
In the above, the braking state detecting means f is provided with a braking initial stage determining means for determining a braking initial stage, and when the braking initial stage determining means determines that the braking is in the initial stage, at least the pressure of the left and right front wheel side shock absorbers b is determined. At least the extended stroke side of the stroke side and the left and right rear wheel side shock absorbers b is controlled to have a hard characteristic.

[0006]

According to the vehicle suspension system of the first aspect of the present invention, since the vehicle is constructed as described above, during normal running of the vehicle (when the braking state and the turning state are not detected), the damping force characteristic control means e is not used. In the normal time control unit d, the optimal control of the damping force characteristic of the shock absorber b is performed based on the up-down behavior of the vehicle detected by the up-down behavior detecting means c. Characteristic control is performed. When the braking state and the turning state of the vehicle are detected by the braking state detecting means f and the turning state detecting means g, the braking / turning correction control unit h sets the ratio of the roll rigidity before and after the vehicle to the front wheel side. By changing the steering characteristic to a lower direction, it is possible to prevent the steering characteristic from being in an understeer state, and to improve the turning performance of the vehicle without deteriorating the braking performance during braking and turning. In the vehicle suspension system according to the second aspect, when the braking state and the turning state of the vehicle are detected by the braking state detecting means f and the turning state detecting means g, the braking / turning correction is performed. In the control unit h, a correction control for controlling the damping force characteristic of at least the extension stroke side of the left and right rear wheel shock absorbers b to a hard characteristic and controlling at least the extension stroke side of the front wheel inner wheel side shock absorber b to a soft characteristic is provided. By doing so, the ratio of the roll stiffness before and after the vehicle is changed in a direction in which the front wheel side becomes lower, thereby preventing the steering characteristic from becoming an understeer state, and improving the vehicle turning performance during braking and turning. Can be. During braking and turning, the front wheel outer shock absorber b
By controlling at least the pressure stroke side to the hard characteristic, the dive of the vehicle at the time of braking and turning can be suppressed and the braking performance can be improved, and the turning performance of the vehicle can be improved. According to a third aspect of the present invention, in the vehicle suspension device according to the first or second aspect, at least the extension stroke side of the inner wheel side shock absorber b of the front wheel is controlled to have a softer characteristic than the control characteristic of the normal control unit c. This allows finer tuning of the roll rigidity balance before and after the vehicle. Further, in the vehicle suspension device according to the fourth aspect, in the first to third aspects, at the initial stage of braking, at least the pressure stroke side of the left and right front wheel side shock absorbers b and at least the extension stroke side of the right and left rear wheel side shock absorbers b. Is controlled to have the hard characteristic, thereby suppressing the dive of the vehicle in the initial stage of braking, suppressing the wheel load variation, and improving the braking performance.

[0007]

Embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a configuration explanatory view showing a vehicle suspension system according to an embodiment of the present invention, and is interposed between a vehicle body and four wheels and is provided with four shock absorbers SA _FL and SA _FL .
_FR , SA _RL , SA _RR (Note that in describing the shock absorber, when these four are collectively referred to and when describing their common configuration, they are simply denoted as SA. Indicates the wheel position, _FL
Indicates front wheel left, _FR indicates front wheel right, _RL indicates rear wheel left, and _RR indicates rear wheel right. ) Is provided. Each wheel position has a vertical acceleration G (G _FL , G _FR , G _RL , G
_RR ) to detect a sprung vertical acceleration sensor
Sensors 1) ( _1FL , _1FR , _1RL , _1RR ) are provided. The steering ST is provided with a steering sensor 2 for detecting a turning state of the vehicle from the steering angle θ. Although not shown in the figure, a brake lamp switch 5 for detecting a brake operation state (braking state) is provided, and further, each of the upper and lower G sensors 1 (1 _FL , 1 _FR , 1 _RL ) is provided near the driver's seat. , 1 _RR ), the steering sensor 2 and the signal from the brake lamp switch 5 are input to each of the shock absorbers SA _FL , SA _FR , S
A control unit 4 for outputting a drive control signal to the pulse motors 3 of A _RL and SA _RR is provided. The above configuration is shown in the system block diagram of FIG. 3, and the control unit 4 includes interface circuits 4a, CP
U4b 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 ), the sprung vertical acceleration G (G _FL , G _FR , G _RL ,
G _RR ) signal, a steering angle θ signal from the steering sensor 2, and a switch signal (ON, OFF) from the brake lamp switch 2, and the control unit 4 receives each shock absorber SA based on these input signals. (SA _FL , SA _FR , SA _RL , SA _RR ) damping force characteristic control is performed.

The control unit 4 includes:
A bounce speed at each wheel position based on a sprung vertical acceleration G (G _FL , G _FR , G _RL , G _RR ) signal from each of the vertical G sensors 1 (1 _FL , 1 _FR , 1 _RL , 1 _RR ). Component, a pitch speed component, and a roll speed component, and a control signal V (V
_FL , V _FR , V _RL , V _RR ) signal processing circuit (FIG. 1)
4) is provided. The details of this signal processing circuit will be described later.

FIG. 4 is a sectional view showing the structure of the shock absorber SA.
A is a cylinder 30, a piston 31 that defines the cylinder 30 in an upper chamber A and a lower chamber B, an outer cylinder 33 in which a reservoir chamber 32 is formed on the outer periphery of the cylinder 30, a lower chamber B and a reservoir chamber 32. Base 34 and 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.

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. A compression-side damping valve 20 and an extension-side damping valve 12 for opening and closing 31a and 31b, respectively, are provided. A stud 38 that penetrates the piston 31 is screwed and fixed to a 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 flow paths (extension-side second flow paths E, expansion-side third flow paths F, bypass flow paths G, and compression-side second flow paths J to be described later) that communicate the upper chamber A and the lower chamber B. A hole 39 is formed.
An adjuster 40 for changing the flow path cross-sectional area of the flow path is rotatably provided in 9. Also, 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. Note that the adjuster 40 is provided with the pulse motor 3.
Is rotated through the control rod 70 (see FIG. 4). Also, studs 38
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, the adjuster 40 has a hollow portion 19, a first horizontal hole 24 and a second horizontal hole 25 communicating between the inside and the outside, and a vertical groove 23 formed in the outer peripheral portion. I have.

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 vertical groove 23,
Via the second port 13, the vertical groove 23, and the fifth port 16 via the fourth port 14, the outer peripheral side of the extension side damping valve 12 is opened to open the outer peripheral side of the extension side damping valve 12 to reach the lower chamber B, and the second port 13, the vertical groove 23, and the fifth port 16. Then, the extension-side check valve 17 is opened to open the extension-side third flow path F leading to the lower chamber B, and a bypass reaching the lower chamber B via the third port 18, the second horizontal hole 25, and the hollow portion 19. There are four flow paths G. In addition, as a flow path through which a fluid can flow during the pressure stroke, the pressure side first valve that opens the pressure side damping valve 20 through the through hole 31a.
Channel 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 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.
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).

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

Next, among the control operations of the control unit 4, each of the upper and lower G sensors 1 ( _1FL , _1FR , _1RL , _1RR )
Sprung vertical acceleration G (G _FL , G _FR , G _RL , G _RR )
Based on the signal, the bounce speed component, the pitch speed component, and the roll speed component at each wheel position are obtained,
The configuration of a signal processing circuit for _obtaining control signals V (V _FL , V _FR , V _RL , V _RR ) at each wheel position from these speed components will be described with reference to the block diagram of FIG.

First, in B1, each upper and lower G sensor 1
From the sprung vertical acceleration G (G _FL , G _FR , G _RL , G _RR ) signal detected at (1 _FL , 1 _FR , 1 _RL , 1 _RR ), the following equation (1),
Based on (2), (3) and (4), the front-wheel-side bounce acceleration component G
Obtaining _BF, the rear wheel side bouncing acceleration component signal G _BR, pitch acceleration component signal G _P, a roll acceleration signal G _R, respectively.

G _BF = (G _FL + G _FR ) / 2 (1) G _BR = (G _RL + G _RR ) / 2 _{······················ (2) G P = (} G FL + G FR -G RL -G RR) / 2 ········ ... (3) In the _{G R = (G FR -G FL} + G RR -G RL) / 2 ·········· (4) followed by B2, using the phase lag compensation formula, wherein each front wheel Bounce acceleration component G _BF , rear wheel side bounce acceleration component signal G _BR , pitch acceleration component signal G _P , roll acceleration signal G
_R is the front-wheel-side bounce speed component V _BF , the rear-wheel-side bounce speed component signal V _BR , and the pitch speed component signal V at each tower position.
_P, and converted into a roll velocity signal V _R.

The general expression of the phase delay compensation can be expressed by the following transfer function expression (5). G _(S) = (AS + 1) / (BS + 1) (5) (A <B) Then, a 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 the following transfer function equation (6) is used as a phase lag compensation equation for lowering the gain on the low frequency side (up to 0.05 Hz). ) Is used. G _(S) = ((0.001 S + 1) / (10S + 1)) × r (6) where r is a signal and gain characteristic when the speed is converted by integration (1 / S). This is a gain for matching, and is set to r = 10 in the embodiment of the present invention. As a result, as shown in the gain characteristic of the solid line in FIG. 15A and the phase characteristic of the solid line 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 B3, band-pass filtering is performed to cut off components other than the target frequency band to be controlled. That is, the band-pass filter BPF includes a second-order high-pass filter HPF (0.8 Hz) and a second-order low-pass filter LPF (1.2 Hz), and has a front-wheel-side bounce speed that targets a sprung resonance frequency band of the vehicle. component signal V _BF, the rear wheel side bouncing velocity component signal V _BR, pitch velocity component signal V _P, the roll speed signal V _R determined.

In B4, control signals V (V _FL , V _FR , V _FL , V _FR ) at each wheel position are obtained based on the following equations (7), (8), (9), and (10).
V _RL , V _RR ). _{V FL = K BF · V BF} + K PF · V P -K RF · V R ················· (7) V FR = K BF · V BF + K PF · V _P + K _RF · V _R ·········· (8) V _RL = K _BR · V _BR -K _PR · V _P -K _RR · V _R ··· _{·············· (9) V RR = K} BR · V BR -K PR · V P + K RR · V R ·············· (10) Note that K _BF is the bounce gain on the front wheel side, K _BR is the bounce gain on the rear wheel side, K _PF is the pitch gain on the front wheel side, K _PR is the pitch gain on the rear wheel side, K _RF is the roll gain on the front wheel side, K _RR is a rear wheel roll gain.

Next, of the control operation of the damping force characteristic of the shock absorber SA in the control unit 4, the contents of the normal control by the normal control unit performed when the vehicle is not braked will be described with reference to the flowchart of FIG. . This normal control is performed by each shock absorber S
_{A FL, SA FR, SA RL} , is performed for each SA _RR.

In step 101, it is determined whether or not the control signal V is a positive value.
And move each shock absorber SA to the extension side hard area H
If the answer is NO, the process proceeds to step 103.

In step 103, it is determined whether or not the control signal V is a negative value.
To move the shock absorber SA to the compression side hard area S.
H, and if NO, the process 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 control signal V is 0. In this case, each shock absorber SA is set in the soft area. Control to SS.

Next, the operation of the damping force characteristic control will be described with reference to the time chart of FIG. When the control signal V changes as shown in this figure, as shown in the figure, the control signal V
Is 0, the shock absorber SA is controlled to the soft region SS.

When the value of the control signal V becomes a positive value,
The compression side damping force characteristic is fixed to the soft characteristic by controlling the expansion side hard region HS, and the expansion side damping force characteristic (target damping force characteristic position P _T ) is controlled based on the following equation (11). Change in proportion to V. P _T = (V / V _HT ) × P _T-max (11) where V _HT is the extension-side proportional range, and P _T-max is the extension-side maximum attenuation. This is the force characteristic position. That is, the target damping force characteristic position _PT on the extension side is variably controlled to the hardware characteristic side in proportion to the value of the control signal V.

When the value of the control signal V 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 (target damping force characteristic position P _C ) is set to the control signal V based on the following equation (12). Change proportionally. P _C = (V / V _HC ) × P _C-max (12) where V _HC is the compression side proportional range, and P _C-max is the compression side maximum damping force characteristic. Position. That is, the target damping force characteristic position P _C of the compression side in proportion to the control signal V value is variably controlled in the hard characteristics side.

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

In the time chart of FIG.
Is a state in which the control signal V based on the sprung vertical speed is reversed from a negative value (downward) to a positive value (upward). At this time, the relative speed is still a negative value (the stroke of the shock absorber SA is At this time, the shock absorber S is determined based on the direction of the control signal V.
A is controlled to the extension side hard region HS, and therefore, in this region, the pressure stroke side which is the stroke of the shock absorber SA at that time has the soft characteristic.

An area b is an area in which the control signal V 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 extended). Therefore, at this time, the shock absorber SA is controlled to the extension side hard region HS based on the direction of the control signal V, and the stroke of the shock absorber is also the extension stroke. The extension stroke, which is the stroke of the absorber SA, has hardware characteristics proportional to the value of the control signal V.

Area c is a state where the control signal V is reversed from a positive value (upward) to a negative value (downward).
At this time, the relative speed is still a positive value (shock absorber S
Since the stroke A is the extension stroke side), at this time, the shock absorber SA is controlled to the compression-side hard region SH based on the direction of the control signal V. Therefore, in this region, The extension stroke side of the shock absorber SA has soft characteristics.

The region d is a region in which the control signal V remains negative (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 area SH based on the direction of the control signal V, and the stroke of the shock absorber is also the compression stroke,
Therefore, in this area, the shock absorber SA at that time is
The pressure stroke side, which is the stroke of the above, has hardware characteristics proportional to the value of the control signal V.

As described above, in the embodiment of the present invention, when the control signal V based on the sprung vertical speed and the relative speed have the same sign (region b, region d), the stroke of the shock absorber SA at that time. 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. Further, in the embodiment of the present invention, when the stroke of the shock absorber SA is switched, that is, when shifting from the area a to the area b and from the area c to the area d (from the soft characteristic to the hard characteristic),
Since the damping force characteristic position on the stroke side to be switched has already been switched to the hard characteristic side in the previous areas a and c, the switching from the soft characteristic to the hard characteristic is performed without time delay.

Next, among the damping force characteristic control operations of the control unit 4, the normal control by the normal control unit and the correction control by the correction control unit (initial braking control, steady braking control, and turning braking control). ) Will be described with reference to the flowcharts of FIGS. 18 and 19 and the time chart of FIG.

First, in the flowchart of FIG.
In step 201, it is determined whether or not the switch signal from the brake lamp switch 5 is in the ON state, thereby determining whether or not the vehicle is braking. If NO (switch signal is OFF = non-braking state), Sometimes, step 2
In step 03, the control is switched to the normal control (skyhook control) by the normal control unit, and then one control flow is completed. In this normal control,
As described above, the damping force characteristic control of the shock absorber SA is performed with emphasis on the riding comfort of the vehicle.

On the other hand, the determination in step 201 is YES
If (switch signal ON = during braking), step 2
In step 02, it is determined whether or not it is in the initial stage of braking (the details of the control in step 202 will be described later). If the determination in step 202 is YES (early braking stage), the process proceeds to step 204, where the control is switched to the initial braking stage control, and one control flow is completed.

The determination in step 202 is NO.
If it is (at the time of steady braking), the routine proceeds to step 205. Then, in step 205, by the steering angle theta signal to determine whether it exceeds a predetermined threshold value theta _T, the vehicle is determined whether the turning, YES (and steady braking If it is (turning), the routine proceeds to step 206, where the control is switched to the control at the time of turning braking, after which one control flow is completed.

On the other hand, when it is determined NO (at the time of non-turning steady braking) in step 205, the process proceeds to step 207, where the control is switched to the steady braking control, and one control flow is completed. I do. Thereafter, the above flow is repeated.

Next, in the flowchart of FIG. 18, it is determined whether or not the braking is in the initial stage (step 20).
The control content of No. 2 will be described based on the flowchart of FIG.

Step 301 in the flowchart of FIG.
So after the switch signal from the brake lamp switch 5 is turned ON, by determining whether or not the lapse of a predetermined second T _B, the vehicle is equal to or braking initial stage, NO (predetermined Second T _B ), step 3
03 to determine the initial stage of braking (YE in step 202).
S determination).

Further, when it is YES (the predetermined seconds T _B has elapsed) is whether the process proceeds to step 302, in reality the vehicle pitch rate (pitch velocity component signal V _P) exceeds a predetermined threshold value VP _T by determining, it is determined whether it is necessary to brake the initial stage control, YES (V _P> VP
_T ), the routine proceeds to step 303, where the initial stage of braking is determined (YES determination in step 202), and NO (V
_{If P} ≦ VP _T , the routine proceeds to step 304, where a steady braking judgment (NO in step 202) is made.

Next, in the damping force characteristic control operation of the control unit 4, the normal control by the normal control unit and the correction control by the correction control unit (initial braking control, steady braking control and turning braking control). ) And the contents of each correction control will be described with reference to a time chart of FIG.

(A) Non-braking (Normal control) During normal running of the vehicle (when no braking state is detected),
As the damping force characteristic control of each shock absorber SA, normal control (skyhook control) by the above-described normal control unit is performed, whereby the riding comfort of the vehicle during normal running can be ensured.

(B) Initial stage of braking (correction control) During the initial stage of braking, while the pitch rate of the vehicle exceeds a predetermined value, the left and right front wheel side shock absorbers SA _FL , SA _FL
The damping force characteristics of _FR are fixed to the hard characteristics (soft characteristics on the extension stroke side) in the compression-side hard region SH, and the damping force characteristics of the right and left rear wheel side shock absorbers SA _RL and SA _RR are adjusted to the extension hard. In the region HS, braking initial stage control is performed to fix the extension stroke side to a hard characteristic (the compression stroke side is a soft characteristic), thereby suppressing wheel load fluctuation while suppressing vehicle dive in the initial braking stage. Braking performance can be improved.

(C) At the time of steady braking (correction control) At the time of steady braking in which the pitch rate of the vehicle drops to a predetermined value or less after the initial stage of braking, each shock absorber is compared with the normal control by the normal control unit. Steady braking control is performed to increase the control gain of the damping force characteristic control in SA, thereby suppressing wheel load fluctuations during steady braking and improving braking performance without unnecessarily deteriorating the riding comfort of the vehicle. Can be done.

(D) At the time of braking and turning (correction control) At the time of steady braking in which the pitch rate of the vehicle drops below a predetermined value after the initial stage of braking, and when the vehicle is turning due to steering, , Damping force characteristics of the left and right rear wheel side shock absorbers SA _RL , SA _RR are shown as hard characteristics on the extension side in the extension side hard region HS (soft characteristics on the compression side).
And shock absorber SA for front left and right wheels
Of the _FL and SA _FR , the turning inner wheel side shock absorber SA
While the damping force characteristics of the turning stroke side are controlled to the compression-side hard region SH where the softening characteristic is fixed to the compression stroke side, the damping force characteristics of the turning outer wheel side shock absorber SA are controlled to the compression-side hard region SH and the compression stroke side to the hard characteristic (the compression stroke side Control during turning braking, which is fixed to the soft characteristic.

That is, by controlling the damping force characteristics of the respective shock absorbers SA of the rear wheel side left and right and the front wheel side turning inner wheel as described above, the ratio of the roll stiffness before and after the vehicle is changed in a direction in which the front wheel side becomes lower. Thereby, the steering characteristics can be prevented from being in an understeer state, and the pressure stroke side of the outer wheel side shock absorber SA of the front wheel, which is most loaded at the time of turning, is controlled to the hard characteristic, so that the steering characteristic is controlled during braking and The turning performance of the vehicle can be improved while suppressing the dive of the vehicle at the time of turning and improving the braking performance.

As described above, according to the vehicle suspension system of the embodiment of the present invention, the dive of the vehicle in the initial stage of braking is performed during the braking of the vehicle while ensuring the riding comfort of the vehicle during normal traveling. It is possible to improve the braking performance by suppressing the wheel load fluctuations while suppressing the wheel load fluctuations without reducing the ride comfort of the vehicle during the steady braking later than necessary. At the same time, the turning performance of the vehicle can be improved without deteriorating the braking performance during braking and turning.

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 is a design change or the like without departing from the gist of the present invention. Included in the invention.

For example, in the embodiment of the present invention, when the damping force characteristic of one of the expansion stroke and the compression stroke is controlled to the heart characteristic side, the damping force characteristic of the other stroke side is softened. Although an example using a shock absorber with a structure fixed to the characteristics has been shown, the present invention can be applied to a system using a shock absorber with a structure in which the damping force characteristics of the extension stroke and the compression stroke change in the same direction. it can.

In the embodiment of the present invention, the damping force characteristics of the left and right rear wheel side shock absorbers SA _RL and SA _RR are used as the correction control at the time of braking and at the time of turning, by using the extension side hard region HS.
In addition, the extension stroke side is fixed to a hard characteristic (the compression stroke side is a soft characteristic), and the damping force characteristic of the turning inner wheel side shock absorber SA of the left and right front wheel side shock absorbers SA _FL and SA _FR is set to a soft characteristic. And the damping force characteristic of the turning outer wheel side shock absorber SA is set to a hard characteristic on the compression stroke side in the compression side hard region SH (a soft characteristic is provided on the extension stroke side).
However, the correction control of the damping force characteristic may be performed by changing the control gain of the normal control by the normal control unit.

Although the brake lamp switch is used as the braking state detecting means in the embodiment of the invention, the braking state can be detected from the brake fluid pressure and the longitudinal acceleration signal, and the output of the anti-skid control device can be detected. It can also be detected from the signal. Further, in the embodiment of the invention, the determination of the initial stage of the braking is performed by determining the pitch rate of the vehicle as a threshold, but may be performed by determining the rate of change of the acceleration in the longitudinal direction of the vehicle as a threshold. .

Further, in the embodiment of the present invention, an example has been described in which the steering angle signal is judged as a threshold value as the turning state detecting means of the vehicle, but the roll rate or the lateral acceleration signal of the vehicle is thresholded. The value may be determined.

[0054]

As described above, the first aspect of the present invention is as follows.
In the vehicle suspension device described above, as described above, when the braking state and the turning state of the vehicle are detected by the braking state detecting means and the turning state detecting means, the roll rigidity on the front wheel side is smaller than the roll rigidity on the rear wheel side. With the configuration including the braking / turning correction control unit that controls in the lowering direction, it is possible to improve the turning performance of the vehicle without deteriorating the braking performance during braking and turning. The effect is obtained. In the vehicle suspension device according to the second aspect,
As described above, when the braking state and the turning state of the vehicle are detected by the braking state detecting means and the turning state detecting means,
The damping force characteristic of at least the extension stroke side of the right and left rear wheel side shock absorbers is controlled to a hard characteristic, at least the extension stroke side of the front wheel inner wheel side shock absorber is controlled to a soft characteristic, and at least the pressure of the front wheel outer ring side shock absorber is controlled. By controlling the stroke side to hard characteristics, a braking / turning correction control unit that controls the roll stiffness of the front wheel side to be lower than the roll stiffness of the rear wheel side is provided, so that when braking, In addition, it is possible to improve the turning performance of the vehicle while improving the braking performance at the time of turning. Further, in the vehicle suspension system according to the third aspect, when the braking state and the turning state of the vehicle are detected by the braking state detecting means and the turning state detecting means, at least the left and right rear wheel side shock absorbers at least on the extension stroke side. By controlling the damping force characteristic to a hard characteristic and controlling at least the extension stroke side of the inner wheel side shock absorber of the front wheel to a soft characteristic than the control characteristic by the normal time control unit,
Finer tuning of the roll rigidity balance before and after the vehicle becomes possible. In the vehicle suspension device according to the fourth aspect, when the braking initial stage determining means determines that the vehicle is in the initial braking stage, at least the compression stroke side of the left and right front wheel side shock absorbers and at least the extension of the left and right rear wheel side shock absorbers. By controlling the stroke side to the hard characteristic, it is possible to improve the braking performance in which the wheel load fluctuation is suppressed while suppressing the vehicle dive in the initial stage of the braking.

[Brief description of the drawings]

FIG. 1 is a view corresponding to 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 illustrating a vehicle suspension device according to an embodiment of the present invention.

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

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.

FIG. 8 is a perspective view of the shock absorber shown in FIG.
It is -K sectional drawing.

FIG. 9 is a perspective view of the shock absorber shown in FIG.
It is an L sectional view and MM sectional view.

FIG. 10 is a sectional view taken along line NN of FIG. 5 showing a main part of the shock absorber.

FIG. 11 is a damping force characteristic diagram when the shock absorber is on the extension side hard.

FIG. 12 is a damping force characteristic diagram of the shock absorber in a soft state on an extension side and a compression side.

FIG. 13 is a damping force characteristic diagram of the shock absorber in a pressure-side hard state.

FIG. 14 is a block diagram showing a signal processing circuit for obtaining a control signal from a sprung vertical acceleration in the vehicle suspension system according to the embodiment of the present invention.

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 control operation of the damping force characteristic of the control unit in the vehicle suspension system according to the embodiment of the present invention.

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

FIG. 18 is a flowchart showing the contents of switching control between normal control by a normal control unit and correction control by a correction control unit in the vehicle suspension system according to the embodiment of the present invention.

FIG. 19 is a flowchart showing the control content of step 202 of the flowchart of FIG. 18 for determining whether or not it is in the initial stage of braking.

FIG. 20 is a time chart showing the contents of switching control between normal control by the normal control unit and correction control by the correction control unit in the vehicle suspension system according to the embodiment of the present invention.

[Explanation of symbols]

 a damping force characteristic changing means b shock absorber c vehicle vertical behavior detecting means d normal control section e damping force characteristic controlling means f braking state detecting means g turning state detecting means h braking / turning correction control section

Claims (4)

[Claims] 1. A shock absorber having damping force characteristic changing means interposed between a vehicle body side and a wheel side and capable of changing damping force characteristics, and a vehicle vertical behavior detecting means for detecting a vertical behavior of a vehicle. A damping force characteristic control means having a normal time control unit for optimally controlling the damping force characteristic of the shock absorber during normal running of the vehicle based on the vertical behavior of the vehicle detected by the vehicle vertical behavior detecting means; Braking state detecting means for detecting a braking state; turning state detecting means for detecting a turning state of the vehicle; when the braking state and the turning state of the vehicle are detected by the braking state detecting means and the turning state detecting means, A vehicle suspension device comprising: a braking / turning correction control unit that controls the roll rigidity on the front wheel side to be lower than the roll rigidity on the rear wheel side. 2. The braking / turning correction controller, when the braking state detecting means and the turning state detecting means detect the braking state and the turning state of the vehicle, at least the right and left rear wheel side shock absorbers. Controlling the damping force characteristics on the extension stroke side to hard characteristics, controlling at least the extension stroke side of the inner wheel side shock absorber of the front wheels to soft characteristics, and controlling at least the compression stroke side of the outer wheel shock absorbers of the front wheels to the hard characteristics. The vehicle suspension according to claim 1, wherein the control is performed such that the roll rigidity on the front wheel side is lower than the roll rigidity on the rear wheel side. 3. The braking / turning correction control unit, when the braking state detecting means and the turning state detecting means detect the braking state and the turning state of the vehicle, at least the right and left rear wheel side shock absorbers. The damping force characteristic on the extension stroke side is controlled to a hard characteristic, and at least the extension stroke side of the inner wheel side shock absorber of the front wheel is controlled to be a soft characteristic than the control characteristic by the normal time control unit. The vehicle suspension device according to claim 1. 4. The braking state detecting means includes a braking initial stage judging means for judging an initial stage of braking, and when the braking initial stage judging means judges that the vehicle is in the initial braking stage, at least one of the left and right front wheel side shock absorbers. The vehicle suspension device according to any one of claims 1 to 3, wherein at least the extension stroke side of the pressure stroke side and the left and right rear wheel side shock absorbers is controlled to have hard characteristics.