JPH10138728A - Vehicle suspension - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the road surface following property of a tire even when a shock absorber is fully elongated during braking a vehicle, thereby improve the braking effect and the safety of the vehicle. SOLUTION: When a damping force characteristic changing means (a) for a shock absorber (b) variable-controls the damping force characteristic on one process side to the high damping force characteristic side, a process side opposite to the above process side is structured to become a low damping force characteristic, and a braked state detecting means (c) for detecting the braked state of a vehicle, and a fully elongated state detecting means (d) for detecting the fully elongated state of the shock absorber (b), are provided. Then, when the braked state of the vehicle is detected by the braked state detecting means (c), and the fully elongated state of the shock absorber (b) is detected by the fully elongated state detecting means (d), a braking time damping force characteristic control means (e) controls the damping force characteristic changing means (a) so that the elongation side becomes a low damping force characteristic, while the compression process side becomes a high damping force characteristic.

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 improving stability and braking performance when braking a vehicle.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension system for controlling a damping force characteristic of a shock absorber at the time of braking of a vehicle, for example, one described in Japanese Patent Application Laid-Open No. 5-96924 is known. This conventional vehicle suspension device is a suspension system including a suspension controller that receives an ON / OFF signal of a brake switch and appropriately switches a damping force of a damping force switching actuator disposed corresponding to each wheel, wherein the suspension system includes: An ABS controller that outputs an ABS control signal to the suspension controller to prevent the wheels from being locked due to sudden braking or the like is provided.
When the N signal is output, the damping force of each actuator is hardly controlled via the suspension controller, and when the ABS control signal is output in the same state, the damping force of the front wheel actuator is changed to the damping force of the rear wheel actuator. On the other hand, it was configured to control softly.

[0003]

However, in the conventional vehicle suspension system, as described above, the damping force is usually controlled softly, and when the braking state is detected, the damping force is hardly controlled. Since the front wheel side damping force is controlled softly when the ABS is activated thereafter, the suspension is extended and extended at the front and rear wheels when the ABS is not activated during vehicle braking and at the rear wheel when the ABS is activated. As a result, when the tire is separated from the ground and comes into contact with the ground again, the damping force of the shock absorber at that time is small, so that the wheel load is not stabilized and the braking effect may be reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and improves the road following ability of a tire even when the shock absorber is fully extended during braking of the vehicle. It is an object of the present invention to provide a vehicle suspension device capable of improving a braking effect and stability of a vehicle.

[0005]

In order to achieve the above object, a vehicle suspension system according to the first aspect of the present invention, as shown in the claim correspondence diagram of FIG. The damping force characteristic changing means a of the shock absorber b having the interposed damping force characteristic changing means a capable of changing the damping force characteristic variably controls the damping force characteristic on one stroke side to the high damping force characteristic side. At the time, the reverse stroke side has a structure having low damping force characteristics, and includes braking state detecting means c for detecting a braking state of the vehicle, and extended state detecting means d for detecting an extended state of the shock absorber b. When the braking state detecting means c detects the braking state of the vehicle and the extended state detecting means d detects the extended state of the shock absorber b, the damping force characteristic changing means a of the shock absorber b Shin side is a means provided with a braking damping force characteristic control means e for controlling such compression phase at low damping force characteristic is high damping force characteristics. Further, the vehicle suspension device according to the second aspect includes an anti-skid control device, and the braking state detecting means c is configured to detect a braking state from the operation of the anti-skid control device.
Further, the vehicle suspension device according to the third aspect is provided with a brake switch, and the braking state detecting means c is configured to detect a braking state from an operation state of a brake pedal. Further, the vehicle suspension device according to claim 4 is
A brake switch and wheel speed detecting means are provided, and the braking state detecting means c is configured to detect a braking state from an operation state of a brake pedal and a rate of change in wheel speed. Further, the vehicle suspension device according to the fifth aspect includes brake fluid pressure detecting means, and the braking state detecting means c is configured to detect a braking state from the brake hydraulic pressure. Further, the vehicle suspension device according to claim 6 is provided with longitudinal acceleration detecting means, and the braking state detecting means c is configured to detect a braking state from the longitudinal acceleration of the vehicle. Further, in the vehicle suspension device according to a seventh aspect, the extended state detecting means d is configured as a vehicle height sensor. Further, in the vehicle suspension device according to claim 8, the extended state detecting means d determines a stroke using a transfer function from a sprung vertical acceleration detecting means and a sprung vertical acceleration signal detected by the sprung vertical acceleration detecting means. And means for estimating.

[0006]

In the vehicle suspension system according to the first aspect of the present invention, since the vehicle is constructed as described above, the braking state of the vehicle is detected by the braking state detecting means c and the shock is detected by the extended state detecting means d. When the extended state of the absorber b is detected, the damping force characteristic control means e during braking changes the damping force characteristic changing means a of the shock absorber b to a low damping force characteristic on the extension side and a high damping force characteristic on the pressure stroke side. In this manner, the tire can follow the road surface on a concave road when traveling on a concave road due to the low damping force characteristic on the extension stroke side. Can be rapidly increased, so that even when the vehicle jumps during braking and the shock absorber is fully extended, the tires can follow the road surface, thereby improving vehicle stability and braking. It is possible to improve the 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
A sensor (referred to as a sensor) 1 ( _1FL , _1FR , _1RL , _1RR ) is provided, and a stroke sensor 2 ( _2FL , _2FL , _1FL ) for detecting a stroke state of each shock absorber SA is provided between each wheel and the vehicle body. 2 _FR , 2 _RL , 2 _RR ), and a brake switch 5 for detecting a braking state of the vehicle, which is not shown in the figure, is provided. Sensor 1 (1 _FL , 1 _FR , 1 _RL , 1 _RR ),
The signals from the stroke sensors 2 ( _2FL , _2FR , _2RL , _2RR ) and the brake switch 5 are input and driven by the pulse motors 3 of the shock absorbers _SAFL , _SAFR , _SARL , and _SARR. A control unit 4 for outputting a control signal 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 ) signals and strokes S (S) from the stroke sensors 2 (2 _FL , 2 _FR , 2 _RL , 2 _RR ).
_FL , _SFR , _SRL , _SRR ) signals and switch signals (ON, OFF) from the brake switch 5 are input,
In the control unit 4, each of the shock absorbers SA (SA _FL , SA _FR , SA
_RL , SA _RR ).

Further, the control unit 4 includes:
On the basis of the 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 ), the sprung _{mass at} each wheel position is determined. A signal processing circuit (FIG. 14) for obtaining a vertical speed signal and a sprung unsprung relative speed signal 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, and 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 to the lower chamber B, and the bypass to 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).

In FIG. 7, the KK section, the LL section, the MM section, and the NN section in FIG. 5 when the adjuster 40 is arranged at the position of, respectively. 8, 9 and 10 and the damping force characteristics at each position are shown in FIGS.

Next, of the control operation of the control unit 4, the configuration of a signal processing circuit for obtaining the sprung vertical speed Δx and the sprung-unsprung relative speed (Δx−Δx ₀ ) is shown in FIG. Description will be made based on the drawings.

First, in B1, a phase delay compensation equation 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 expression of the phase delay compensation can be represented by the following transfer function expression (1). G _(S) = (AS + 1) / (BS + 1) (1) (A <B) Then, the frequency band (0.5 Hz to 3
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) where γ is a signal and gain characteristic when speed conversion is performed by integration (1 / S). And γ = 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 B2, a band-pass filter process for cutting off components other than the target frequency band to be controlled is performed. 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 ,
Δx _FR , Δx _RL , Δx _RR ) signals are obtained.

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

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 basic control unit will be described with reference to the flowchart of FIG. Note that this normal control is performed by each of the shock absorbers SA _FL , SA _FR , SA _RL , SA
_Performed for each _RR .

In step 101, the sprung vertical speed 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 speed 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 speed Δx is
When the value changes 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 area SS.

When the value of the sprung vertical speed Δx becomes a positive value, the compression-side damping force characteristic is controlled to the extension-side hard region HS to fix the compression-side damping force characteristic to the soft characteristic, while the extension-side damping force characteristic (target The damping force characteristic position P _T ) is changed in proportion to the sprung vertical speed Δx based on the following equation (4). P _T = α · Δx · K (4) where α is a constant on the extension side, and K is a relative speed between the sprung and unsprung (Δx −Δx ₀ ).

When the value of the sprung vertical velocity Δx becomes a negative value, the compression-side hard region SH is controlled to fix the expansion-side damping force characteristic to the soft characteristic while the compression-side damping force characteristic (target damping force) is set. The characteristic position P _C ) is calculated based on the following equation (5).
It changes in proportion to the sprung vertical speed Δx. P _C = β · Δx · K (5) where β is a pressure-side constant.

Next, among the damping force characteristic control operations of the control unit 4, mainly the switching operation state of the control region 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 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 region b, the sprung vertical speed Δx remains a positive value (upward), and the relative speed (Δx−Δx ₀ ) changes from 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 speed Δx at this time, and the stroke of the shock absorber is also the extension stroke. Accordingly, in this region, the extension stroke, which is the stroke of the shock absorber SA at that time, has a hardware characteristic proportional to the value of the sprung vertical speed Δx.

Area c is a state in which the sprung vertical speed Δx is reversed from a positive value (upward) to a negative value (downward), but at this time, the relative speed (Δx−Δx ₀ ) is still positive. (The stroke of the shock absorber SA is on the extension stroke side), and at this time, the sprung vertical velocity Δx
The shock absorber SA is controlled to the pressure side hard region SH based on the direction of the shock absorber SA. Therefore, in this region, the extension stroke which is the stroke of the shock absorber SA at that time has the soft characteristic.

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

As described above, in the embodiment of the present invention, when the sprung vertical speed Δx and the relative speed (Δx−Δx ₀ ) have the same sign (region b, region d), the shock absorber SA at that time is used. And the damping force characteristic control based on the skyhook theory, in which the stroke side of the shock absorber SA is controlled to a hard characteristic, and the stroke side of the shock absorber SA at the time of the different sign (region a, region c) is controlled to a soft characteristic. The same 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 region a to the region b and from the region c to the region d (from the soft characteristic to the hard characteristic), the switching is performed. Since the position of the damping force characteristic on the switching side has already been switched to the hardware characteristic in the previous areas a and c, the switching from the soft characteristic to the hardware characteristic is performed without time delay.

Next, among the damping force characteristic control operations in the control unit 4, the contents of the switching control between the normal control by the normal control unit and the braking control by the braking control unit and the contents of the braking control will be described. This will be described with reference to the flowchart of FIG. 18 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 switch 5 is in the ON state.
It is determined whether the vehicle is in a braking state. If NO (switch signal OFF = non-braking state), step 204
The control is switched to normal control (skyhook control) by the normal control unit, and then one control flow is completed. On the other hand, when the determination in step 201 is YES (switch signal ON = braking state),
Proceed to step 202. In this step 202, it is determined whether or not the stroke S signal of the shock absorber SA detected by the stroke sensor 2 exceeds a predetermined threshold value Ss, so that the shock absorber SA is in an extended state. Is determined, NO
If (S ≦ Ss = non-extended state), step 2
In step 04, the control is switched to the normal control (skyhook control) by the normal control unit, and then one control flow is completed. On the other hand, when the determination in step 202 is YES (S> Ss = extended state),
After proceeding to step 203 to switch to the control during braking (flag ON), one control flow is completed. Thereafter, the above control flow is repeated.

That is, in the braking control by the braking control unit, as shown in FIG. 19, the shock absorber SA is set to the compression side hard area SH and the damping force characteristic on the compression stroke side is set to the maximum position PC _-max . By fixed control,
As shown in FIG. 13, the damping force characteristics on the pressure stroke side are hard characteristics, and the damping force characteristics on the reverse stroke are soft characteristics on the reverse stroke side.

Therefore, even when the stroke of the shock absorber SA is extended beyond the predetermined value and the tire is not sufficiently contacted with the ground, the tire follows the road surface due to the soft characteristic on the extension stroke side when traveling on a concave road surface. In addition, when running on a bumpy road, the wheel load can be rapidly increased due to the hard characteristic on the pressure stroke side, so that the vehicle may jump during braking, for example, and the shock absorber may extend completely. Also improves the tire's ability to follow the road,
Thereby, the stability and the braking performance of the vehicle can be improved.

As described above, the vehicle suspension according to the embodiment of the present invention has the following effects. When the vehicle is not braking, the ride performance and steering stability of the vehicle are ensured by controlling the damping force characteristics of the shock absorber SA based on the skyhook control theory. Can be shortened.

During the braking of the vehicle, the shock absorber S
Even if A is too long, the road surface followability of the tire is improved, and thereby the braking effect and stability of the vehicle can be improved.

In the normal control based on the skyhook control theory, the switching between the soft characteristic and the hard characteristic is performed without time delay, so that a high control response can be obtained, and the switching from the hard characteristic to the soft characteristic is performed by a pulse. This is performed without driving the motor 3, thereby improving the durability of the pulse motor 3 and saving power consumption.

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 within a range not departing from the gist of the present invention, the present invention is not limited thereto. Included in the invention.

For example, in the embodiment of the present invention, an example has been described in which a brake switch is provided as the braking state detecting means, and the braking state is detected from the operation state of the brake pedal. A brake state is detected from the operation of the device, a brake switch and a wheel speed detecting means are provided, and a braking state is detected from an operation state of a brake pedal and a change rate of the wheel speed, and a brake fluid pressure detecting means is provided. Alternatively, the braking state may be detected from the brake fluid pressure, or a longitudinal acceleration detecting means may be provided to detect the braking state from the longitudinal acceleration of the vehicle.

Further, in the embodiment of the present invention, an example in which a stroke sensor is used as the stretched-out state detecting means has been described. In addition, the sprung vertical acceleration signal detected by the vertical G sensor is used to calculate the following equation (6). The stroke of the shock absorber may be estimated using the transfer function shown.

G _(S) =-m / (cs + k) (6) where m is a sprung mass, c is a damping coefficient of the suspension, and k is a spring constant of the suspension.

Further, in the embodiment of the present invention, the soft region SS is controlled only when the sprung vertical speed signal is 0. However, a predetermined dead zone centered on 0 is provided and the spring is controlled within the range of the dead zone. By maintaining the damping force characteristic in the soft region SS while the up-down speed is changing, control hunting can be prevented.

[0047]

As described above, the first aspect of the present invention is as follows.
In the vehicle suspension device described above, as described above, the damping force characteristic changing unit of the shock absorber having a damping force characteristic changing unit that is interposed between the vehicle body side and the wheel side and that can change the damping force characteristic, When the damping force characteristic on one stroke side is variably controlled to the high damping force characteristic side, the reverse stroke side has a low damping force characteristic, and the braking state detecting means for detecting the braking state of the vehicle, and the shock absorber When the extended state is detected by the braking state detecting means, and when the extended state of the shock absorber is detected by the extended state detecting means. Means that the damping force characteristic changing means of the shock absorber is provided with a damping force characteristic control means at the time of braking that controls the extension side to have a low damping force characteristic and the compression stroke side to have a high damping force characteristic. Therefore, even when the shock absorber is fully extended during braking of the vehicle, the ability to follow the road surface of the tire is improved, thereby obtaining an effect that the braking effect and stability of the vehicle can be improved. Can be

[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 sprung vertical speed and a sprung unsprung relative speed 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 braking control by a braking control unit in the vehicle suspension system according to the embodiment of the present invention.

FIG. 19 is a time chart showing details of braking control by a braking 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 braking state detecting means d extension state detecting means e braking damping force characteristic controlling means

Claims (8)

[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, wherein the damping force characteristic changing means includes a damping force on one stroke side. When the characteristic is variably controlled to the high damping force characteristic side, the reverse stroke side has a low damping force characteristic structure, a braking state detecting means for detecting the braking state of the vehicle, and an extension for detecting the extended state of the shock absorber. When the braking state of the vehicle is detected by the braking state detecting means, and when the extended state of the shock absorber is detected by the extended state detecting means, the damping force of the shock absorber is provided. A vehicle suspension device comprising braking damping force characteristic control means for controlling the characteristic changing means such that the extension side has low damping force characteristics and the compression stroke side has high damping force characteristics. 2. A vehicle suspension system according to claim 1, further comprising an anti-skid control device, wherein said braking condition detecting means is configured to detect a braking condition from the operation of the anti-skid control device. . 3. The system according to claim 1, further comprising a brake switch, wherein said braking state detecting means detects a braking state from an operation state of a brake pedal.
The vehicle suspension according to any one of the preceding claims. 4. A braking system comprising a brake switch and wheel speed detecting means, wherein the braking state detecting means is configured to detect a braking state from an operation state of a brake pedal and a rate of change in wheel speed. The vehicle suspension device according to claim 1, wherein 5. The vehicle suspension according to claim 1, further comprising a brake fluid pressure detecting means, wherein the braking state detecting means is configured to detect a braking state from the brake fluid pressure. 6. A vehicle suspension system according to claim 1, further comprising longitudinal acceleration detecting means, wherein said braking state detecting means is configured to detect a braking state from longitudinal acceleration of the vehicle. . 7. The vehicle suspension according to claim 1, wherein said extended state detecting means comprises a vehicle height sensor. 8. The extended state detecting means comprises sprung vertical acceleration detecting means and estimating means for estimating a stroke using a transfer function from a sprung vertical acceleration signal detected by the sprung vertical acceleration detecting means. The vehicle suspension according to any one of claims 1 to 6, wherein: