JPH09226337A - Vehicle suspension device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure driving comfortability and steering stability of a vehicle by restraining sprung behavior at the time of non-braking and to improve a braking effect at the time of braking of the vehicle. SOLUTION: It is furnished with a damping force characteristic control means (e) having a basic control part (d) to carry out damping force characteristic control of each of shock absorbers b1, b2 in accordance with sprung and unsprung behaviors detected by a sprung and unsprung behavior detection means (c) and a braking time correction control part (h) to control a damping force characteristic on the side of extending process on the rear wheel side shock absorber b2 to a hard characteristic while deceleration of a vehicle detected by a deceleration detection means (f) exceeds a specified value and a stroke of the rear wheel side shock absorber b2 detected by a stroke detection means (g) exceeds a specified value on an extending side and to control a damping force characteristic on the rear wheel side shock absorber b2 to extending process side soft characteristic-pressure process side hard characteristic at the time when deceleration of the vehicle exceeds the specified value and the stroke of the rear wheel side shock absorber b2 is lower than the specified value.

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 damping force characteristic control for enhancing a braking effect during braking.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension system for controlling a damping force characteristic of a shock absorber, for example, 3-48 (Anti-dive control column of the Toyota Mark II new vehicle manual) is used.
What is described in the time chart of XD0498) is known. In this conventional vehicle suspension device, when the stop lamp switch is turned on at a vehicle speed of 20 km / h or more, the damping force characteristic of the shock absorber is switched to the hard characteristic, and after holding for a certain period of time, the damping force is restored to the original damping force. However, when the stop lamp switch is turned on and the rate of change in deceleration detected by the ABS speed sensor exceeds a specified value, the damping force is switched to or held at the hard characteristic, and when the amount of change becomes small, the original value is restored after a certain time. It was designed to return to the damping force.

[0003]

However, in the conventional device, as described above, the damping force characteristic of the shock absorber is always a hard characteristic during braking of the vehicle.
Although it is possible to suppress the dive of the vehicle during braking, there is a problem that depending on the road surface input frequency, the wheel load fluctuation becomes large due to the sprung mass behavior, and thus the braking effect may not be improved.

The present invention has been made by paying attention to the above-mentioned conventional problems. When the vehicle is braking, the sprung behavior is suppressed during non-braking to ensure the riding comfort and steering stability of the vehicle. It is an object of the present invention to provide a vehicle suspension system capable of improving the braking effect.

[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. front-wheel-side shock absorbers b ₁ and the rear wheels are interposed when variably controlling the damping force characteristics of one stroke side has a damping force characteristic changing means a damping force characteristic of the opposite stroke side is a soft characteristic The shock absorber b ₂ , the sprung vertical movement detecting means c for detecting the sprung vertical movement at each wheel position, and the shock absorber b on the basis of at least the sprung vertical movement detected by the sprung vertical movement detecting means c _1, b and damping force characteristic control means e having a basic control unit d to perform the damping force characteristic control of _2, and the deceleration detecting means f for detecting the deceleration of the vehicle, of the rear-wheel shock absorbers b ₂ stroke A stroke detecting means g for detecting the click, the deceleration of the vehicle detected by the deceleration detecting means f exceeds the predetermined value, and the stroke of the wheel-side shock absorbers b ₂ after being detected by the stroke detecting means g Is above the predetermined value on the extension side, the damping force characteristic of at least the extension stroke side of the rear wheel side shock absorber b ₂ is controlled to the hard characteristic so that the vehicle deceleration exceeds the predetermined value and the rear wheel When the stroke of the side shock absorber b ₂ is less than or equal to the predetermined value, the rear shock absorber b ₂
The braking-time correction control section h for controlling the damping force characteristics at the extension stroke side soft characteristics / pressure stroke side hard characteristics.

Further, in the vehicle suspension system according to claim 2,
The sprung up / down behavior detecting means c includes at least a sprung up / down speed detecting means for detecting a sprung up / down speed, and the sprung up / down speed calculated by the sprung up / down speed detecting means in the damping force characteristic control means d. When the direction identification code is upward, the damping force characteristic on the extension side of the shock absorber b is shown, and when it is downward, the damping force characteristic on the compression stroke side is shown, and the sprung vertical velocity detected by the sprung vertical velocity detecting means. Based on the variable control.

Further, in the vehicle suspension system according to claim 3,
The deceleration detecting means f is composed of wheel speed sensors provided on the left and right front wheels, and deceleration converting means for obtaining the deceleration of the vehicle body from the wheel speed signals of the left and right front wheels detected by the wheel speed sensors. Further, in the vehicle suspension system according to the fourth aspect, the deceleration detecting means f is constituted by front / rear acceleration / deceleration detecting means for detecting the front / rear direction acceleration / deceleration of the vehicle. Further, in the vehicle suspension system according to claim 5, the deceleration detecting means f is
The brake fluid pressure detecting means detects the brake fluid pressure, and the deceleration estimating means estimates the deceleration of the vehicle from the brake fluid pressure. Further, in the vehicle suspension device according to the sixth aspect, the stroke detecting means g is constituted by a stroke sensor provided at a rear wheel position. Further, in the vehicle suspension system according to claim 7, the stroke detection means g is composed of a sprung vertical acceleration detection means provided at a rear wheel position and a sprung vertical acceleration signal detected by each sprung vertical acceleration detection means. And a stroke estimating means for estimating a stroke.

[0008]

In the vehicle suspension system according to the first aspect of the present invention, since it is constructed as described above, it operates as follows. First, when the deceleration of the vehicle detected by the deceleration detecting means f is less than or equal to a predetermined value, the brake pedal is lightly depressed, or the accelerator pedal is weakened. In such a case, damping force characteristic control of each shock absorber b is performed on the basis of the sprung up / down behavior because it does not require power, so that the ride comfort of the vehicle is improved. And it is possible to secure steering stability.

Further, when the deceleration of the vehicle exceeds the predetermined value and the stroke of the rear wheel side shock absorber b ₂ is less than the predetermined value in the extending direction, a strong braking force is exerted at the initial stage of strong depression of the brake pedal. As a result of the vehicle diving due to sudden braking, the rear side of the vehicle body floats up. At this time, the damping force characteristic on the extension side of the rear wheel side shock absorber b ₂ is controlled to the hard characteristic side. In such a case, the rear wheels are lifted as the rear side of the vehicle body floats up, and as a result, the rear wheel-side ground contact load is released and the braking force is reduced.

Therefore, in such a case, the braking correction control section h controls the damping force characteristics of the rear wheel side shock absorber b ₂ to have soft characteristics on the extension stroke side and hard characteristics on the pressure stroke side. By shifting the center of the wheel load fluctuation on the rear wheel side in the increasing direction, it is possible to enhance the braking effect on the rear wheel side.

Further, when the deceleration of the vehicle exceeds a predetermined value and the stroke of the rear wheel side shock absorber b ₂ exceeds the predetermined value in the extending direction, the rear wheel side shock absorber b ₂ is fully extended. , As a result of the rear wheels being lifted due to the lifting of the rear side of the vehicle body, the rear wheel side ground load will be lost and the braking force will be reduced.
In such a case, the braking correction control unit h controls the damping force characteristic of at least the extension stroke side of the rear wheel side shock absorber b ₂ to a hard characteristic so that the rear wheel side shock absorber b ₂ is fully extended. It is possible to prevent the rear wheel side ground contact load from coming off, and thereby to enhance the braking effect on the rear wheel side.

Further, in the vehicle suspension system according to claim 2,
In the damping force characteristic control means d, when the direction discrimination code of the sprung vertical velocity is upward, the shock absorber b ₁ ,
When the damping force characteristic on the extension stroke side of b ₂ is downward, the damping force characteristic on the compression stroke side is variably controlled based on the sprung vertical speed, while the damping force characteristic on the reverse stroke side is low damping force characteristic, respectively. Therefore, in the damping range where the direction discrimination codes of the sprung vertical velocity and the sprung unsprung relative velocity match, the shock absorbers b ₁ and b ₂ at that time are in a fixed control state. The damping force of the vehicle is increased by variably controlling the stroke side on the high damping force characteristic side, and in the vibration range where the direction discrimination codes of the two do not match, the stroke side of the shock absorbers b ₁ and b ₂ at that time The basic damping force characteristic switching control is performed based on the Skyhook theory, in which the vehicle vibration force is weakened by setting a low damping force characteristic.

[0013]

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.) Each wheel position has a vertical acceleration G (G _FL ,
A sprung vertical acceleration sensor (hereinafter referred to as vertical G sensor) 1 (1 _FL , 1 _FR , G _FR , G _RL , G _RRS ) for detecting
1 _RL , 1 _RR ), and wheel speed sensors 2 _FL , 2 _FR for detecting wheel speeds W _V-FL , W _V-FR of the left and right front wheels, respectively. , The signals from the vertical G sensors 1 (1 _FL , 1 _FR , 1 _RL , 1 _RR ) and the two wheel speed sensors 2 (2 _FL , 2 _FR ) are input to the positions near the driver's seat, and the shock absorbers are input. SA _FL , SA _FR , SA _RL , S
A control unit 4 that outputs a drive control signal to the pulse motor 3 of A _RR is provided.

The system block diagram of FIG. 3 shows the above configuration. The control unit 4 comprises an interface circuit 4a, a CPU 4b, and a drive circuit 4c, and the interface circuit 4a is provided with the vertical G sensor 1 (1).
_FL , 1 _FR , 1 _RL , 1 _RR )
_FL , G _FR , G _RL , G _RR ) signals, and wheel speeds W _V (W _V-FL , W) from the two wheel speed sensors 2 (2 _FL , 2 _FR ).
_V-FR ) signal is input, and in the control unit 4,
Based on these input signals, each shock absorber SA
_{(SA FL, SA FR, SA} RL, SA RR) control signal V for performing a damping force characteristic control _{(V FL, V FR, V} RL, V RR)
Is required.

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, and the sprung vertical acceleration G (G _FL ,
G _FR , G _RL , G _RR ) signal processing circuit (Fig. 15 (a)) for determining the stroke of the rear wheel side shock absorbers SA _RL , SA _RR , and wheel speed W _V (W _V-FL , W
A signal processing circuit (FIG. 15B) for obtaining the deceleration of the vehicle body from the _V-FR ) 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 a portion of the piston 31. As shown in FIG. 5, the piston 31 has through holes 31a and 31b formed therein and each through hole. 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 horizontal hole 24 and a second horizontal hole 25 which communicate the inside and the outside are formed, and a vertical groove 23 is formed in the outer peripheral portion. There is.

Therefore, the through hole 31 is provided between the upper chamber A and the lower chamber B as a flow passage through which the 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.
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 constructed so that the damping force characteristic can be changed in multiple stages on both the extension side and the compression side with the characteristic shown in FIG. 6 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).

By the way, in FIG. 7, the KK cross section, the LL cross section, 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, of the damping force characteristic control operation of each shock absorber SA performed by the control unit 4, the basic control operation of the damping force characteristic performed by the basic control unit will be described with reference to the flowchart of FIG. .

At step 101, it is judged if the control signal V exceeds the positive control dead zone V _NC , and if YES, the routine proceeds to step 102, at which each shock absorber SA.
To the extension side hard area HS, and if NO, the process proceeds to step 103.

In step 103, it is judged whether the control signal V is below the negative control dead zone -V _NC , and YES.
If so, the routine proceeds to step 104, where each shock absorber SA is controlled to the compression side hard region SH, and if NO, the routine proceeds to step 105.

In step 105, when NO is determined in steps 101 and 103, that is, the value of the control signal V changes from the negative control dead zone -V _NC to the positive control dead zone V.
This is a processing step when it is within the range up to _NC. At this time, each shock absorber SA is controlled to the soft region SS.

Next, the operation contents of the basic control of damping force characteristics will be described with reference to the time chart of FIG. When the control signal V based on the sprung speed Δx and the relative speed (Δx−Δx ₀ ) changes as shown in this figure, as shown in the figure, the value of the control signal V is from the negative control dead zone −V _NC. When it is within the range up to the positive control dead zone V _NC , the shock absorber SA is controlled to the soft area SS.

Further, the value of the control signal V is a positive control dead zone V.
_{When NC} is exceeded, the expansion side hard region HS is controlled to fix the compression side to a low damping force characteristic, while the expansion side damping force characteristic (= target damping force characteristic position P _T ) is set to the following equation (1). Based on
It is changed in proportion to the control signal V. P _T = (V-V _NC ) / (V _H -V _NC ) ・ Pmax _-T・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (1) In addition, Pmax _-T is the extension side maximum damping force characteristic position, V _NC
Is an extension side control dead zone, and V _H is an extension side proportional range.

Further, the control dead zone where the value of the control signal V is negative is −
_Below V _NC , the compression side hard region SH is controlled to fix the extension side to the low damping force characteristic, while the compression side damping force characteristic (=
The target damping force characteristic position P _C ) is changed in proportion to the control signal V based on the following equation (2). P _C = (V-V _NC ) / (V _H -V _NC ) ・ Pmax _-C・ ・ ・ ・ ・ ・ ・ ・ (2) Pmax _-C is the compression side maximum damping force characteristic position, V _NC
Is a pressure side control dead zone, and V _H is a pressure side proportional range.

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.
Is a state in which the control signal V based on the sprung vertical velocity Δx and the sprung unsprung relative velocity (Δx−Δx ₀ ) is reversed from a negative value (downward) to a positive value (upward). Since the relative speed (Δx−Δx ₀ ) is still a negative value (the stroke of the shock absorber SA is the pressure stroke side), the shock absorber SA is extended based on the direction of the control signal V at this time. It is controlled to the 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 a soft characteristic.

In the region b, the control signal V remains a positive value (upward), and the relative speed (Δx-Δx ₀ ) is a negative value to a positive value (the stroke of the shock absorber SA is the extension side).
At this time, the control signal V
The shock absorber SA is controlled in the extension side hard region HS based on the direction of, and the stroke of the shock absorber is also the extension stroke. Therefore, in this area, the extension side which is the stroke of the shock absorber SA at that time is The hardware characteristic is proportional to the value of the control signal V.

In the area c, the control signal V is reversed from a positive value (upward) to a negative value (downward).
At this time, the relative speed (Δx−Δx ₀ ) is still a positive value (the stroke of the shock absorber SA is on the extension stroke side). Therefore, at this time, the shock absorber is based on the direction of the control signal V. SA is controlled in the compression side hard region SH, and therefore, in this region, the extension stroke side, which is the stroke of the shock absorber SA at that time, has soft characteristics.

In the area d, the control signal V remains a negative value (downward), and the relative speed (Δx-Δx ₀ ) is a positive value to a negative value (the stroke of the shock absorber SA is the extension side).
At this time, the shock absorber SA moves in the compression side hard area SH based on the direction of the control signal V.
Is controlled and the stroke of the shock absorber is also a pressure stroke. Therefore, 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 control signal V.

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

Next, FIG. 14 shows each of the vertical G sensors 1 (1 _FL , 1 _FL ,
1 _FR , 1 _RL , 1 _RR ) sprung vertical acceleration G detected by
Based on the (G _FL , G _FR , G _RL , G _RR ) signals, the sprung vertical velocity Δx (Δx _FL , Δx _FR , Δx at each wheel position.
_RL , Δx _RR ) signal, and relative speed between sprung and unsprung (Δx−Δx ₀ ) [(Δx−Δx ₀ ) _FL , (Δx−Δx)
₀ ) _FR , (Δx−Δx ₀ ) _RL , (Δx−Δx ₀ ) _RR ] is a block diagram showing a signal processing circuit for _obtaining a signal. The sprung vertical acceleration G (G _FL , G _FR , G _RL , G _RR ) signal detected by the G sensor 1 (1 _FL , 1 _FR , 1 _RL , 1 _RR ) is sent to the sprung vertical velocity Δx (Δx _FL , Δx). _FR , Δx _RL , Δ
x _RR ) signal. The general equation for phase delay compensation can be expressed by the following transfer function equation (3). G _(S) = (AS + 1) / (BS + 1) ... (3) (A <B) And the frequency band (0.5 Hz to 3) required for damping force characteristic control.
Has the same phase and gain characteristics as the case of integration (1 / S) at Hz), and the following transfer function equation (4) is used as a phase delay compensation equation for lowering the gain on the low frequency side (up to 0.05 Hz). ) Is used.

G _(S) = (0.001 S + 1) / (10 S + 1) × γ (4) 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 this embodiment. As a result, FIG.
The gain characteristic of the solid line in (a) of 8 and the gain characteristic of FIG.
As shown by the solid line phase characteristics in (b), only the gain on the low frequency side is reduced without deteriorating the phase characteristics in the frequency band (0.5 Hz to 3 Hz) required for damping force characteristic control. . In addition, the dotted lines of (a) and (b) in FIG.
The gain characteristic and the phase characteristic of the sprung vertical velocity signal whose velocity is converted by integration (1 / S) are shown.

At B2, the sprung vertical velocity Δx is increased.
From the (Δx _FR , Δx _FL , Δx _RR , Δx _RL ) signal, bandpass filter processing is performed to cut off components other than the target frequency band to be controlled. That is, this bandpass filter BPF is a second-order highpass filter HPF (0.8 H
z) and a second-order low-pass filter LPF (1.0 Hz), and the sprung vertical velocity V ₁ (V _1-FL , V _1-FR , V _1-RL ) targeting the sprung resonance frequency band of the vehicle. , V _1-RR ) signal is obtained. It should be noted that each of the sprung vertical velocity V ₁ signals is obtained with a positive value in the upward direction and a negative value in the downward direction.

On the other hand, in B3, as shown in the following equation (5),
From the vertical acceleration G (G _FL , G _FR , G _RL , G _RR ) signals on the four-wheel towers, using the transfer function G _{U (S)} of the relative speed between the sprung mass and the sprung vertical acceleration, 4 Relative velocity between unsprung and unsprung at each tower position of wheel (Δx-Δx ₀ )
[(Δx−Δx ₀ ) _FL , (Δx−Δx ₀ ) _FR , (Δx−
Δx ₀ ) _RL , (Δx−Δx ₀ ) _RR ] signal. GU _(S) =-m ₁ s / (c ₁ s + k ₁ ) ... (5) FIG. 19 is an explanatory diagram showing a transfer function calculation model, and is shown in this figure. , X ₁ is the sprung mass input, x ₂
Is an unsprung mass input, x ₃ is a road surface input, m ₁ is an unsprung mass, m ₂ is an unsprung mass, c ₁ is a suspension damping coefficient, c ₂ is a tire damping coefficient, k ₁ is a suspension spring constant, k ₂ is the tire spring constant.

[0039] In subsequent B4, as shown in (c) of FIG. 20, the direction discrimination code (extension phase is positive, compression phase is minus) of the relative velocity ([Delta] x-[Delta] x _0), the relative velocity ([Delta] x-[Delta] x ₀ ) The peak value XP _T on the extension side and the peak value XP _C on the compression side are detected respectively, and the peak value XP on the extension side XP
_The extension side processed signal XP ′ _T and the pressure side processed signal XP ′ _C that hold the peak value XP _C on the _T side and the peak side XP _C respectively are generated until the next peak values are detected.

[0040] followed in B5, the extension side processed signal XP _'T and the compression side processed signals XP' respectively inversely the extension side reprocessed signals KUS _-T to _{C (KUS -FR-T, KUS} -FL-T, KUS -RR _-T , KUS
_-RL-T ) and pressure side reprocessing signal KUS _-C (KUS _-FR-C , KUS
_-FL-C , KUS _-RR-C , KUS- _{RL -C} ). That is,
In the embodiment of the present invention, as shown in the following equations (6) and (7), the expansion _- side reprocessed signal KUS- _T and the pressure-side reprocessed signal KUS- _C are obtained by using an inverse proportional function. KUS _-T = 1 / XP ' _T・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (6) KUS _-C = 1 / XP' _C・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (7) However, When the value of the expansion side processed signal XP ' _T or the compression side processed signal XP' _C is less than or equal to the specified minimum value MIN (XP ' _T , XP' _C ≤ MIN
) Is the extension side reprocessed signal KUS _-T and the compression side reprocessed signal KUS _-C
Set the value of to the maximum value MAX (KUS _-T , KUS _-C = MAX
(1.0, 0.9)) is performed. This has the meaning of preventing the processed signal XP _'T, XP' denominator side reprocessed signals KUS _-T as the value of _C is close to 0, that the value of KUS _-C diverges to infinity.

Subsequently, in B6, the extension side reprocessed signal KUS- _T (KUSFR _-T , KUSFL _-T , KU) obtained in B5 is obtained.
S _RR-T , KUS _RL-T ) and pressure side reprocessing signal KUS _-C (KU
S _FR-C , KUS _FL-C , KUS _RR-C , KUS _RL-C ) is subjected to averaging processing to obtain the averaged re-processed signal K
U- _T (KU _FR-T , KU _FL-T , KU _RR-T , KU _RL-T ) and pressure side reprocessing signal KU _-C (KU _FR-C , KU _FL-C , KU _RR-C ,
KU _RL-C ). The pressure side reprocessed signal KU- _C is obtained as an absolute value.

Then, the control signal V which is the basis of the damping force characteristic positions P _T and P _C of each of the shock absorbers SA is obtained by the following equations (8) and (9). Expansion side V = g ・ V ₁・ KU _-T・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (8) Pressure side V = g ・ V ₁・ KU _-C・ ・ ・ ・ ・ ・ ・(9) Note that g is a proportional constant.

That is, according to the first embodiment of the present invention, when the control signal V is formed, the expansion side processing signal is added at B5.
XP ' _T and pressure side processed signal XP' _C are once converted into inverse proportional signal KUS _-T for expansion side reprocessed signal and pressure side reprocessed signal KUS _-C (and state KU _-T averaged in B6) , KU _-C ) is applied to the sprung vertical velocity signal V ₁ so that the control signal V can be prevented from being divided by 0.

Next, FIG. 20 is a time chart showing the formation state of the control signal V in the signal processing circuit.
For low-frequency fluctuations of the sprung vertical velocity Δx as shown in FIG. 9 (a), relative velocity (Δx−Δx
₀ ) shows the case where it fluctuates at high frequency.

As shown by the black dots in FIG. 6C, the extension side peak value XP _T and the pressure side peak value XP _C at the relative speed (Δx−Δx ₀ ) are detected, respectively, and as shown by the solid line in (c), until the next peak value respectively the peak value XP _C of the peak values XP _T and the compression side of the extension side is detected by performing signal processing to be held, high-frequency relative The velocity (Δx-Δx ₀ ) signal is converted into the extension side processed signal X
It can be deformed to a low frequency signal P _'T and the compression side processed signal XP' _C.

Therefore, as shown in the above equations (8) and (9), the fluctuation waveform of the control signal V calculated based on the low frequency signal is also
As shown in (d) of the same figure, it can be obtained in a low frequency state, so that even if the response of the pulse motor 3 is not so high, as shown in (e) of the figure, the damping force characteristic position P The switching can be made to follow the change of the control signal V.

Next, FIG. 15A shows the stroke of the rear wheel side shock absorbers SA _RL , SA _RR from the sprung vertical accelerations G _RL , G _RR signals detected by the rear wheel side vertical G sensors 1 _RL , 1 _RR. FIG. 9 is a block diagram showing a signal processing circuit for _obtaining S _RL and S _RR . As shown in the following equation (10), the transfer function G _{S (S)} of the stroke with respect to the sprung vertical acceleration is used, and The strokes S _RL and S _RR signals of the rear wheel side shock absorber are obtained from the acceleration G _RL and G _RR signals.

G _{S (S)} = − m ₁ / (c ₁ s + k ₁ ) ... (10) Next, FIG. 15B shows the both wheel speed sensor 2 (2 _FL , 2
Wheel speed detected by the _{FR) W V (W V-} FL, from W _V-FR) signal, a block diagram showing a signal processing circuit for obtaining a vehicle body deceleration during braking of the vehicle, first, in C1, Average wheel speed of the left and right front wheels (= (W _V-FL + W _V-FR )
/ 2) is obtained, and at C2 that follows, noise reduction processing is performed on this with a second-order low-pass filter LPF (1.0 Hz), and then the deceleration (acceleration) G _B of the vehicle body is obtained by differentiating at C3 that follows.

Next, on the basis of the strokes S _RL and S _RR signals of the shock absorbers SA and the deceleration G _{B of the} vehicle body obtained as described above, the damping force characteristics are controlled by the braking correction controller of the control unit 4. The braking correction control is performed. The contents of the braking correction control will be described below with reference to the flowchart of FIG. 21 and the time chart of FIG.

First, in the flow chart of FIG.
In step 201, it is judged whether or not the deceleration G _{B of the} vehicle exceeds a predetermined threshold value G _T , and YES (G _B > G
_T ), the process proceeds to step 202, sets the deceleration flag F _G to 1, and then proceeds to step 204, and when NO (G _B ≤G _T ), proceeds to step 202 and reduces After resetting the speed flag F _G to 0, the routine proceeds to step 204.

In this step 204, it is judged whether or not the stroke S of the shock absorber SA exceeds a predetermined threshold value S _T , and when YES (S> S _T ),
After advancing to step 205 and setting the stroke flag F _S to 1, advancing to step 207, NO (S ≦
S _T ), the routine proceeds to step 206, where the stroke flag F _S is reset to 0, and then the routine proceeds to step 207.

In step 207, the deceleration flag F
It is determined whether _G is set to 1 and NO (F _G
= 0), the routine proceeds to step 211, where the basic control unit performs basic control of damping force characteristics.

YES in step 207 (F _G = 1)
If it is determined that the stroke flag F _S is set to 1, it is determined in this step 208 that if YES (F _G = 1), the step 209 is performed. Proceed to and shock absorber S
Set the target damping force characteristic position P of A to the extension side hard area HS.
If NO (F _S = 0), the routine proceeds to step 210, where the target damping force characteristic position P of the shock absorber SA is controlled to the pressure side hard region SH. Thus, one control flow is completed, and thereafter, the above control flow is repeated.

Next, the content of the braking correction control by the braking correction control unit as described above will be described with reference to the time chart of FIG. (A) When the deceleration is small When the deceleration G _{B of the} vehicle is less than or equal to a predetermined threshold value G _T , the brake pedal is lightly depressed, or the accelerator is depressed in a weakening direction. Since it does not require a very strong braking force like the above, in such a case, control that suppresses sprung mass behavior by basic control of damping force characteristics based on the skyhook theory by the basic control unit as described above. This ensures the ride comfort and steering stability of the vehicle.

(B) When the deceleration is large and the stroke is short, the deceleration G _{B of the} vehicle exceeds the predetermined threshold value G _T ,
When the strokes S _RL , S _{RR of the} rear wheel side shock absorbers SA _RL , SA _RR are less than or equal to a predetermined threshold value S _T in the extension direction, a strong braking force is required at the initial stage of strong depression of the brake pedal. However, as a result of the vehicle diving due to sudden braking, the rear side of the vehicle body rises, and at this time, the rear wheel side shock absorbers SA _RL , S
If the damping force characteristic on the extension side of A _RR is controlled to the hard characteristic side, the rear wheel is lifted along with the lifting of the rear side of the vehicle body, and as a result, the rear wheel side ground load is released and the braking force is increased. Will be lowered.

Therefore, in such a case, by controlling the damping force characteristics of the rear wheel side shock absorbers SA _RL and SA _RR to the pressure side hard region SH in which the extension side has a soft characteristic and the compression side has a hard characteristic, the rear wheel side is controlled. By shifting the center of the wheel load fluctuation in the increasing direction, the braking effect on the rear wheel side can be enhanced.

(C) When the deceleration is large and the stroke is large, the deceleration G _{B of the} vehicle exceeds the predetermined threshold G _T ,
When the strokes S _RL , S _{RR of the} rear wheel side shock absorbers SA _RL , SA _RR exceed the predetermined threshold value S _T in the extending direction, the rear wheel side shock absorbers SA _RL , SA
_{When the} rear wheel is lifted on the rear side of the vehicle due to the full extension of _RR, the rear wheel side ground load is released and the braking force is reduced. By controlling the damping force characteristics of the side shock absorbers SA _RL , SA _RR to the extension side hard area HS where the extension side has a hard characteristic and the compression side has a soft characteristic, the rear wheel side shock absorbers SA _RL , SA _RR are fully extended. It is possible to prevent the side ground load from coming off, thereby enhancing the braking effect on the rear wheel side.

As described above, the vehicle suspension system according to the first embodiment of the present invention has the following effects. It is possible to suppress the sprung behavior by controlling the damping force characteristic based on the skyhook theory during non-braking to ensure the riding comfort and steering stability of the vehicle, while improving the braking effect during vehicle braking. become.

Even if an inexpensive pulse motor 3 having a relatively low responsiveness that cannot respond to the unsprung resonance frequency component included in the relative speed between unsprung parts is generated, a control force based on the ideal skyhook theory is generated. It is possible to let

Although the embodiments of the present invention have been described above, the specific structure 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 embodiment of the invention, the deceleration detecting means determines the deceleration of the vehicle body from the wheel speed sensors provided on the left and right front wheels and the wheel speed signals of the left and right front wheels detected by the wheel speed sensors. Although an example constituted by the deceleration conversion means is shown, in addition to this, a front-rear acceleration / deceleration detection means for detecting the vehicle front-rear direction acceleration / deceleration, a brake fluid pressure detection means for detecting a brake fluid pressure, It may also be configured with a deceleration estimating means for estimating the deceleration of the vehicle from the brake fluid pressure.

Further, in the embodiment of the invention, the stroke detecting means is a sprung vertical acceleration detecting means provided at the rear wheel position, and a stroke is calculated from the sprung vertical acceleration signals detected by the sprung vertical acceleration detecting means. An example of the stroke estimating means for estimating is shown, but a stroke sensor provided at the rear wheel position may be used instead.

[0063] Further, in the embodiment of the invention, at B9 of the signal processing circuit, and the extension side processed signal XP _'T and the compression side processed signal XP' extension side reprocessed signal is inversely proportional to _C KUS _-C and the compression side reprocessed signals As a means of forming KUS _-T , the inverse proportional function equation (6),
Although (7) is used, an inverse proportional map can also be used.
Further, the proportional constant g of the above equations (8) and (9) for obtaining the control signal V
May be changed according to the vehicle speed.

[0064]

As described above, the first aspect of the present invention is as follows.
In the vehicle suspension system described above, as described above, when the damping force characteristic of one stroke side is interposed between the vehicle body side and each wheel side and is variably controlled, the damping force characteristic of the reverse stroke side is soft. A front wheel side shock absorber and a rear wheel side shock absorber having damping force characteristic changing means, a sprung vertical movement detecting means for detecting sprung vertical movement at each wheel position, and at least the sprung vertical movement detecting means. Damping force characteristic control means having a basic control part for performing damping force characteristic control of each shock absorber based on the detected sprung up / down behavior, deceleration detecting means for detecting deceleration of the vehicle, and the rear wheel side shock. Stroke detection means for detecting the stroke of the absorber, the deceleration of the vehicle detected by the deceleration detection means exceeds a predetermined value, and the stroke detection means While the stroke of the rear wheel side shock absorber detected in step 6 exceeds the predetermined value on the extension side, the damping force characteristic of at least the extension side of the rear wheel side shock absorber is controlled to the hard characteristic to reduce the vehicle deceleration. When the stroke exceeds the specified value and the stroke of the rear wheel side shock absorber is less than the specified value, during braking in which the damping force characteristics of the rear wheel side shock absorber are controlled to the extension stroke side soft characteristics and the pressure stroke side hard characteristics. With the configuration including the correction control unit, the sprung behavior is suppressed during non-braking to secure the riding comfort and steering stability of the vehicle, while the braking effect is improved during vehicle braking. The effect of being able to do is obtained.

Further, in the vehicle suspension system according to claim 2,
The sprung vertical movement detecting means includes at least a sprung vertical speed detecting means for detecting a sprung vertical speed, and the damping force characteristic control means determines the direction of the sprung vertical speed calculated by the sprung vertical speed detecting means. Based on the sprung vertical velocity detected by the sprung vertical velocity detecting means, the damping force characteristic on the extension side of the shock absorber when the code is upward, the damping force characteristic on the compression stroke side when the code is downward, By performing variable control, the stroke side of the shock absorber at that time can be variably controlled on the high damping force characteristic side in the damping range where the direction discrimination codes of the sprung vertical velocity and the sprung sprung relative velocity In this way, the damping force of the vehicle is increased and the stroke side of the shock absorber at that time is made to have a low damping force characteristic in the vibration range where the direction discrimination codes of the two do not match. And in weakening the excitation force of the vehicle, such as it is possible to perform the switching control of the basic damping force characteristic based on skyhook theory.

[Brief description of drawings]

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

FIG. 2 is a 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 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.
It is -K sectional drawing.

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 diagram showing a vehicle suspension device according to the first embodiment of the present invention, in which the extension side reprocessed signal and the pressure side reprocessed signal are averaged based on the sprung vertical acceleration, the sprung vertical speed, and the sprung unsprung relative speed signal. It is a block diagram which shows the signal processing circuit which calculates | requires a processed signal.

FIG. 15 is a block diagram showing a signal processing circuit for obtaining (a) stroke from vertical sprung acceleration and (b) vehicle body deceleration from wheel speed in the vehicle suspension system according to the first embodiment of the present invention.

FIG. 16 is a flowchart showing a damping force characteristic basic control operation of the control unit in the vehicle suspension system according to the first embodiment of the present invention.

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

FIG. 18 is a diagram showing a gain characteristic (a) and a phase characteristic (b) of the sprung vertical velocity signal converted using the phase delay compensation formula in the vehicle suspension system according to the first embodiment of the present invention.

FIG. 19 is an explanatory diagram showing a transfer function calculation model in the vehicle suspension system according to the first embodiment of the present invention.

FIG. 20 is a time chart showing a control signal forming state of the signal processing circuit in the vehicle suspension system according to the first embodiment of the present invention.

FIG. 21 is a flowchart showing the operation contents of the damping force characteristic braking correction control of the control unit in the vehicle suspension system according to the first embodiment of the present invention.

FIG. 22 is a time chart showing an operation content of the damping force characteristic braking correction control of the control unit in the vehicle suspension system according to the first embodiment of the present invention.

[Explanation of symbols]

a damping force characteristic changing means b ₁ front wheel side shock absorber b ₂ rear wheel side shock absorber c sprung vertical movement detecting means d basic control section e damping force characteristic controlling means f deceleration detecting means g stroke detecting means h braking correction control Department

Claims (7)

[Claims] 1. A damping force characteristic change which is interposed between a vehicle body side and each wheel side, and 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. Front wheel side shock absorber and rear wheel side shock absorber having means, sprung up / down behavior detecting means for detecting sprung up / down behavior at each wheel position, and at least sprung up / down behavior detected by the sprung up / down behavior detecting means. A damping force characteristic control means having a basic control portion for performing damping force characteristic control of each shock absorber based on the above, a deceleration detection means for detecting a deceleration of the vehicle, and a stroke for detecting a stroke of the rear wheel side shock absorber. The detection means and the vehicle deceleration detected by the deceleration detection means exceed a predetermined value, and the rear wheel side shear detected by the stroke detection means. During the stroke of the Kkuabusoba exceeds a predetermined value of the extension side controls the damping force characteristics of at least the extension phase in the hard characteristic at the rear wheel side shock absorbers,
When the deceleration of the vehicle exceeds a specified value and the stroke of the rear wheel side shock absorber is less than the specified value, the damping force characteristics of the rear wheel side shock absorber are extended side soft characteristics / pressure stroke side hard characteristics. A vehicle suspension system, comprising: 2. The sprung vertical movement detecting means includes at least a sprung vertical speed detecting means for detecting a sprung vertical speed, and the sprung vertical speed detecting means in the damping force characteristic control means calculates the sprung vertical speed. When the direction discriminating code of the vertical speed is upward, the damping force characteristic of the shock absorber on the extension stroke side, when it is downward, the damping force characteristic of the pressure stroke side,
2. The vehicle suspension system according to claim 1, wherein variable control is performed based on the sprung vertical velocity detected by the sprung vertical velocity detecting means. 3. The deceleration detecting means comprises a wheel speed sensor provided on the left and right front wheels, and a deceleration converting means for obtaining the deceleration of the vehicle body from the wheel speed signals of the left and right front wheels detected by the wheel speed sensor. The vehicle suspension system according to claim 1 or 2, which is configured. 4. The deceleration detection means applies a vehicle longitudinal direction
The vehicle suspension system according to claim 1 or 2, comprising front and rear acceleration / deceleration detection means for detecting deceleration. 5. The deceleration detecting means is composed of a brake fluid pressure detecting means for detecting a brake fluid pressure and a deceleration estimating means for estimating a deceleration of a vehicle from the brake fluid pressure. The vehicle suspension system according to claim 1 or 2. 6. The vehicle suspension system according to claim 1, wherein the stroke detection means is composed of a stroke sensor provided at a rear wheel position. 7. A sprung vertical acceleration detecting means provided at a rear wheel position, and a stroke estimating means for estimating a stroke from a sprung vertical acceleration signal detected by each sprung vertical acceleration detecting means. The vehicle suspension device according to any one of claims 1 to 5, wherein