JPH09309312A - Damping force control device of suspension system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a damping force control device of a suspension system to improve riding comfortability by restraining car body oscillation, to sufficiently maintain a tire grounding property at the time of quick acceleration and deceleration of a vehicle and to improve a braking and driving property and travelling stability. SOLUTION: A damping coefficient target value computing means 3 to compute a damping coefficient target value of a damping force variable shock absorber 4 is devised to selectively change a basic damping coefficient target value constituting this damping coefficient target value between a large value and a small value in accordance with whether an absolute value of longitudinal acceleration of a vehicle from a longitudinal acceleration detection means 5 is larger than a set value or smaller. Additionally, it is devised to carry out this change-over in accordance with an acceleration indication signal such as, for example, an acceleration pedal angle and brake pedal angle signal from an acceleration indication signal detection means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension system in which a shock absorber capable of variably controlling a damping force and a spring are combined to accurately control the damping force in accordance with a vibration state which changes from moment to moment. The present invention relates to a vehicle that sufficiently maintains a tire ground contact property during acceleration / deceleration of a vehicle and improves braking / driving performance and steering stability.

[0002]

2. Description of the Related Art In a suspension system using a shock absorber having a variable damping force, a damping coefficient is changed according to a vibration state to increase, for example, a damping rate of vibration from above a spring and isolation of vibration from below a spring. Proposals for improving the effect are made by the following references and the like.

Reference 1 ... D. Karnopp et
al. : Vibration Control Usi
ng Semi-Active Force Gene
rats, J. et al. E. FIG. I. ASME, May, 619
/ 626 (1974), Reference 2 ... Takehiko Fujioka, Koji Kido; Study on control method of variable damper (Vehicle vibration control viewed from VSS theory), Preprint 862 197/200 (1989) of the Society of Automotive Engineers of Japan , Reference 3 ... A
n Introduction to Sliding
mode Variable Structure
and Lyapunov Control, 1/2
0, Springer (1994).

Furthermore, the applicant of the present invention filed Japanese Patent Application No. 7-32
In 6169, by adjusting the damping force of the damping force variable shock absorber using signals that are relatively easy to detect, such as the relative speed and relative displacement between the sprung and unsprung, the damping force characteristics as desired can be obtained. There has been proposed a damping force control device that can be used.

[0005]

Generally, in the damping force control device, when the damping characteristic of the suspension is set to be soft, the vibration characteristic of the vehicle body becomes good, but the ground contactability of the tire deteriorates. The steering stability will decrease. On the contrary, if the damping characteristic is set to be harder, the steering stability is improved, but the riding comfort is deteriorated.

The trade-off relationship between the ride comfort and the tire ground contact property is described in the above-mentioned Japanese Patent Application No. 7-32616.
It also occurs in the damping force control device of No. 9. That is, this damping force control device has a large damping effect when the vehicle body vibration is excited by an input from the road surface, but the basic damping constant target value c ₀ is set to balance the ride comfort and the tire ground contact property. It is decided by considering (Japanese Patent Application No. 7-3
In the specification of No. 26169, p. 10), actually, it cannot be said that both the ride comfort and the performance relating to the tire ground contact property are not always sufficiently satisfied.

Focusing on these problems, the present invention suppresses vehicle body vibrations to improve riding comfort, and also maintains sufficient tire ground contact when the vehicle is being accelerated or decelerated, resulting in good braking / driving performance and running stability. It is an object of the present invention to provide a suspension system damping force control device.

[0008]

A first aspect of the present invention is directed to a sprung and unsprung relative velocity detecting means, a sprung and unsprung relative displacement detecting means, and a relative velocity and relative displacement detected from these. A damping constant target value computing means for setting a damping constant target value of the damping force variable shock absorber as an input, and a damping force variable shock babsaver for inputting the damping constant target value to adjust the damping constant are provided. The force target value calculation means calculates a target value setting means for setting a basic damping constant target value which is a predetermined constant, and a damping constant correction value obtained by correcting the ideal damping force calculated based on the relative speed and relative displacement. A suspension damping force control device that includes a correction value calculation means and outputs a damping constant target value including the basic damping constant target value and the damping constant correction value, and detects the longitudinal acceleration of the vehicle. A longitudinal acceleration detecting means is provided, and the target value setting means selects a small predetermined value as the basic damping constant target value when the absolute value of the longitudinal acceleration is smaller than a set value, and the absolute value of the longitudinal acceleration is the set value. When it is larger than the above, a large predetermined value is selected as the basic damping constant target value.

A second aspect of the present invention is a sprung and unsprung relative velocity detecting means, sprung and unsprung relative displacement detecting means, and a damping force variable shock using the relative velocity and relative displacement detected from these as input. A damping constant target value calculating means for setting a damping constant target value of the absorber, and a damping force variable shock bubbsaver for inputting the damping constant target value to adjust the damping constant are provided, and the damping force target value calculating means is ,
A target value setting means for setting a basic damping constant target value that is a predetermined constant, and a correction value calculating means for calculating a damping constant correction value that corrects the ideal damping force calculated based on the relative speed and the relative displacement are provided. In a suspension damping force control device that outputs a damping constant target value including these basic damping constant target value and damping constant correction value, an acceleration instruction signal for instructing vehicle acceleration and a deceleration instruction signal for instructing vehicle deceleration The target value setting means detects a small predetermined value as the basic damping constant target value according to the magnitude relationship between the acceleration instruction signal and the deceleration instruction signal and a predetermined reference value. Select a large predetermined value.

In a third invention, the acceleration instruction signal is a signal for detecting an accelerator pedal angle, the deceleration instruction signal is a signal for detecting a brake pedal angle, and the target value setting means is the accelerator pedal angle. When both the brake pedal angle and the brake pedal angle are smaller than the set value, a small predetermined value is selected as the basic damping constant target value, and when at least one of the accelerator pedal angle and the brake pedal angle is larger than the set value, the basic value is set. A large predetermined value is selected as the damping constant target value.

[0011]

In the first aspect of the present invention, the damping constant target value input to the damping force variable shock absorber is determined from the basic damping constant target value and the damping constant correction value. When the absolute value of the longitudinal acceleration is smaller than the set value, such as during slow braking or slow acceleration, the basic damping constant target value is set to a small value and the absolute value of the longitudinal acceleration during sudden braking or sudden acceleration is smaller than the set value. When it is large, the target value of the basic damping constant is set to a large value, so while maintaining a good ride comfort due to the soft damping force characteristics during constant speed driving, the ride comfort of the vehicle during sudden braking, sudden acceleration, etc. When it is necessary to place more importance on steering stability than on the other hand, the damping force characteristics can be hardened to improve the ground contact of the tires and improve braking / driving performance and steering stability. Performance and Vertical stability improvements and at the same time can be achieved to the maximum.

In the second aspect of the invention, the target value setting means determines the traveling state according to the magnitude relation between the acceleration instruction signal and the deceleration instruction signal and a predetermined reference value, and when the vehicle is traveling at a constant speed or when braking slowly. , The basic damping constant target value is set to a small value during slow acceleration, and the basic damping constant target value is set to a large value during sudden braking or sudden acceleration. While maintaining good ride comfort with various damping force characteristics, when it is necessary to prioritize steering stability rather than vehicle comfort such as during sudden braking or sudden acceleration, the damping force characteristics should be hardened to improve the tire's ground contact. To improve braking / driving performance and steering stability, and improve the ride comfort of the vehicle.
It is possible to maximize braking / driving performance and steering stability at the same time.

According to the third aspect of the present invention, the signal for detecting the accelerator pedal angle is detected as the acceleration instruction signal and the signal for detecting the brake pedal angle is detected as the deceleration instruction signal. When both the brake pedal angle and the accelerator pedal angle are smaller than the set values, such as during slow braking and slow acceleration, set the basic damping constant target value to a small value and check whether the brake pedal angle is larger than the set value during sudden braking. , When the accelerator pedal angle is larger than the set value, such as during rapid acceleration, the basic damping constant target value is set to a large value, so while maintaining a good ride comfort due to the soft damping force characteristics during constant speed running, When it is necessary to prioritize steering stability rather than vehicle comfort, such as during sudden braking or sudden acceleration, the damping force characteristics should be hardened to improve tire contact and Can to enhance the performance and steering stability, and comfort improve ride vehicle, it is possible to reduce the braking and driving performance and steering stability improvement and the maximally simultaneously.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, 1 is a relative displacement detecting means for detecting the relative displacement of the damping force variable shock absorber 4 between the sprung and unsprung portions, and 2 is the relative speed for similarly detecting the relative velocity of the sprung and unsprung portions. Detecting means 5, a longitudinal acceleration detecting means for detecting a longitudinal acceleration G of the vehicle, 3 calculates a target value of a damping constant on the basis of the relative displacement, relative velocity and longitudinal acceleration, and the result is a damping force variable shock absorber 4 It is a damping constant target value calculation means for controlling to generate a target damping force by inputting into the.

FIG. 2 shows a concrete structure of the damping constant target value calculating means 3. As shown in the drawing, the relative displacement x ₁ between the sprung part and the unsprung part (hereinafter simply referred to as relative displacement), Unsprung relative velocity x ₂ (hereinafter simply referred to as relative velocity),
And a switching input calculation means 11 for calculating a switching input based on a state quantity x _{c of} a filter W _c (s) 13 which will be described later, and a linear input based on a relative speed, a relative displacement and a filter state quantity x _c. A linear input calculation means 12 for calculating, an adder 16 for adding the switching input and the linear input, and a filter W _c (s) for outputting an ideal damping force based on the ideal input which is the output of the adder 16. 13 and filter W
_The correction value calculating means 14 for calculating the correction value of the damping force constant from the ideal damping force output from the _c (s) 13, and the target value setting means 1 for setting the basic damping constant target value from the longitudinal acceleration G.
5 and an adder 17 for adding these outputs and outputting as an attenuation constant target value.

This will be described in more detail below. In the following description, (d / dt) means the first derivative with respect to time, and (d ² / dt ² ) means the second derivative.

The switching input calculation means 11 has a relative velocity, a relative displacement, a filter state quantity x _c , predetermined gains N, M, ρ,
And the constant δ, the switching input u _sw is calculated as follows.

U _sw = ρMx _e / (‖Nx _e ‖ + δ) (1) However, x _e = [x ^T x _C ^T ] ^T and x = [x ₁ x ₂ ] ^T.

The linear input calculation means 12 calculates the linear input u _ln from the control gain L as follows.

U _ln = Lx _e (2) The filter Wc (s) 13 has an ideal input u _ideal = u _sw +
The ideal damping force f _ideal is calculated from u _ln as follows.

(D / dt) x _c = A _c x _c + B _c u _ideal (3) f _ideal = C _c x _c (4) where A _C , B _C , and C _C are filters W _c (s ) 13 is a constant matrix of appropriate dimension that represents the damping characteristic. For example, if the filter W _c (s) is a low-pass filter having a cutoff frequency of 10 [Hz]; W _c (s) = 2π × 10 / (s + 2π × 10), and s is a Laplace operator, then A _C = B _C = 2π × 10 and C _C = 1 may be set.

The damping constant target value calculating means 3 outputs the damping constant target value _{c'according to} c '=-f _ideal / x ₂ + c ₀ (5). Here, c ₀ is a predetermined constant determined from the vibration characteristics in the high frequency band. Note that in relation to the description of the claims, c ₀ corresponds to the basic damping constant target value, and −f _ideal / x ₂ corresponds to the damping constant correction value.

It is assumed that the damping force variable shock absorber 4 receives c'and the generated damping force c is c = c '(6).

Hereinafter, how to derive each control gain will be described.

Consider the suspension system shown in FIG. The equation of motion on the spring of this system can be written as

M ₂ (d ² / dt ² ) z ₂ = −k ₂ (z ₂ −z ₁ ) −c ₂ [(d / dt) z ₂ − (d / dt) z ₁ ] m ₁ (d _{^{2 / dt 2) z 1 =}} k 2 (z 2 -z 1) + c 2 [(d / dt) z 2 - (d / dt) z 1] -k 1 (z 1 -z 0) ... (7) Here, m ₁ is the unsprung mass, k ₁ is the unsprung mass, m ₂ is the unsprung mass, k ₂ is the spring rigidity, c ₂ is the shock absorber damping constant, and (d ² / dt ² ) z ₂ is the unsprung mass. Vertical acceleration with respect to absolute coordinates of (d ² / dt ² ) z ₁ is vertical acceleration with respect to absolute unsprung coordinates, z ₀ is disturbance displacement, z ₁ is unsprung displacement, and z ₂ is sprung displacement. This is a simplified model of an automobile suspension, for example m ₁ →
The following argument holds even if 0, k ₁ → ∞. The purpose of the suspension system is to damp the motion on the spring in the presence of the disturbance z ₀ .

The relative displacement between the sprung part and the unsprung part is x ₁ = z ₂ −z
₁ , the relative speed of sprung and unsprung is x ₂ = (d / dt) z ₂
If-(d / dt) z ₁ is set,

[0029]

[Equation 1]

Is obtained. This equation (8) is rewritten as follows.

[0031]

[Equation 2]

However, c ₂ = c ₀ + c _u and u = [0-c _u ] x. c _u is a variable damping coefficient of the variable damping force shock absorber 4. c ₀ is determined in consideration of the vibration characteristic in the high frequency band and the longitudinal acceleration G detected by the longitudinal acceleration detecting means 5, as will be described later, regardless of the actual variable amount of the shock absorber.

U is generated via the filter W _c (s) as follows: u (s) = W _c (s) u _ideal (10) Thus, for example, if by W _c (s) is a low pass filter which attenuates high frequency components of u (s), the high frequency _{band, u ≒ 0⇒c u ≒ 0⇒c 2} ≒ c 0 ... (11) Become. This effect will be described later.

When u is generated as in the equation (10), the suspension system and the filter expansion system can be expressed as follows.

[0035]

(Equation 3)

The acceleration (d ² / dt ² ) z ₂ is (d ² / dt ² ) z ₂ = [C _P0 C _c ] x _e (13) Here, x _e = [x ^T x _c ^T ] ^T.

Below, the control gain is derived based on the sliding mode control theory.

Equation (12) is given by T ₁ B _c = [0 B ₂ ^T ] ^T , B ₂
Is a regular matrix, and a similarity transformation using T _{1 such} that

[0039]

(Equation 4)

According to

[0041]

(Equation 5)

Can be rewritten as

When u _ideal is generated as in equation (19) described later, the sliding mode is switched within a sufficiently short time from the start of control for practical use; σ = 0, σ = Fy ₁ + y ₂ (15) ) Can be generated. That is, the state quantity of the expansion system is constrained to the plane of σ = 0 [see Reference 3]. At this time, the motion of the expanding system is (d / dt) y ₁ = A ₁₁ y ₁ + A ₁₂ y ₂ + B ₁₁ (d ² / dt ² ) z ₁ y ₂ = −Fy ₁ (16) That is, (d / dt) y ₁ = (A ₁₁ −A ₁₂ F) y ₁ + B ₁₁ (d ² / dt ² ) z ₁ (17)

To meet the control objective, the state may be constrained to the desired switching surface. In other words, the expression (17) may be expressed as a preferable vibration characteristic. This is equivalent to the problem of damping the system represented by (d / dt) y ₁ = A ₁₁ y ₁ + A ₁₂ v with state feedback v = −Fy ₁ . In order to design such a feedback gain F (switching surface), the following known method may be used.

When the state is restricted to the switching surface σ = 0, the following evaluation function

[0046]

(Equation 6)

The switching surface that minimizes σ _∞ = 0, σ _∞ = F _∞
y ₁ + y ₂ can be designed from the equation (16) by H _∞ optimization. Here, Q is a positive definite symmetric weight matrix, y = [y ₁
y ₂ ] ^T and γ are constants determined by the characteristics of the suspension system and the characteristics of the filter. Alternatively, if (d ² / dt ² ) z ₁ is assumed to be an impulse function or white noise, Slidein
The following evaluation function when gMode is generated;

[0048]

(Equation 7)

The switching surface that minimizes σ ₂ = 0, σ ₂ = F ₂ y ₁
+ Y ₂ can be designed by H ₂ optimization [see Reference 3].

Here, for example, the sprung vertical acceleration (d ² /
To suppress dt ² ) z ₂ , (d ² / dt ² ) z ₂ may be put in the evaluation function, and (d ² / dt ² ) z ₂ = [C _P0 C _c ] x _e , T ₂ x _e = Y (18), Q = Q ₀ + ([C _P0 C _c ] T ₂ ^-1 ) ^T ([C _P0 C _c ] T ₂ ^-1 ) ... (18a). However, x _e = [x ^T x _c ^T ] ^T , and Q ₀ is Q
Is a matrix for satisfying the positive definite symmetry of.

The ideal input u _ideal for realizing the sliding mode may be generated as u _ideal = Lx _e + ρMx _e / (‖Nx _e ‖ + δ) (19). Here, the control gains L, M, and N are the appropriate matrices shown in the above-mentioned reference document 3, and are obtained as follows. First, Σ, Θ, and Φ are defined as follows.

Σ = A ₁₁ −A ₁₂ F Θ = FΣ−A ₂₂ F + A ₂₁ Φ = FA ₁₂ + A _{22 From} these, L, M and N are L = −B ₂ ⁻¹ (Θ Φ−Φ ′ ′) T ^{_{3 T 2 M = -B 2 -1}} (0 P 2) T 3 T 2 N = (0 P 2) becomes T ₃ T _2. Here, P ₂ is a positive definite symmetric solution of the following Lyapunov equation.

[0053] In the ^{_{P 2 Ф '+ Ф' T}} P 2 = -I Ф ' and ρ is the design parameters, respectively Sliding
A stability matrix that determines the speed of convergence to the mode, and a positive constant that determines the size of u _sw . Also,

[0054]

(Equation 8)

Is as follows.

Δ ≧ 0 is a design parameter, which is a positive constant for preventing chattering. The response of the damping constant is fast enough,
In addition, when the relative displacement and the relative velocity can be detected sufficiently fast, if δ = 0, u _sw becomes a discontinuous switching input, and the state can be reliably restrained to the switching surface.

From u _ideal , the ideal damping force is generated as previously shown: f _ideal (s) = W _c (s) u _ideal (s). With ideal damping force, f _sabs that can be generated by the shock absorber is -f _ideal / x ₂ = c ″ ≧ 0, f _sabs = −c ″ x ₂ (20) and when −f _ideal / x ₂ ≧ 0. Limited Here, it is not always guaranteed that −f _ideal / x ₂ ≧ 0, but the filter W
_{If c} (s) and the switching surface σ = 0 are properly set, a sufficient control effect can be expected in the practical area. From this, the target value of the damping constant of the damping force variable shock absorber is as shown in equation (5) in consideration of the fixed component c ₀ of the damping force, as shown in equation (5): c ′ = c _u + c ₀ , c _u = −f _ideal / X ₂ is sufficient.

Next, the effect of the basic damping constant target value c ₀ will be described.

In the present invention, as will be described below, as the basic damping constant target value c ₀ , for example, two large and small predetermined values are set, and these absolute values of the longitudinal acceleration G |
By switching according to the magnitude of G│,
In the high frequency band, soften the damping force characteristics of the suspension system to suppress the vertical acceleration on the springs to improve the ride comfort, or harden the damping force characteristics of the suspension system to suppress the vertical accelerations on the unsprung area. It is possible to select whether to improve the braking / driving performance and the steering stability by increasing the ground contact property of the tire.

First, the motion equation (7) of the suspension system is rewritten as follows.

M_Two(D^Two/ Dt^Two) Z_Two+ C_Two(D / dt) z_Two+ K_Twoz_Two= C_Two(D / dt) z₁+ K _Two z₁ (21) Here, considering that the vibration to be damped is the vibration on the spring,
z₁, (D / dt) z₁Is a disturbance, k_Two, C_TwoEach
It can be seen that this is the input gain. This thing
La c_TwoDistortion (d / dt) z by decreasing the value of₁The effect of
Therefore, the vibration characteristics in the relatively high frequency band are blocked.
It will be improved, but then the damping on the left side will be insufficient,
Resonance frequency (k_Two/ M_Two)^1/2Vibration near the
You.

However, in the control method described above, for example, if the filter W _c (s) is a low-pass filter and c ₀ is a sufficiently small value, then c ₂ ≈ at high frequencies as described in equation (11). c ₀ , the disturbance blocking property is improved, and Sliding Mo is used in the low frequency band.
The effect of de control appears and the damping of the suspension system can be improved.

Therefore, when the absolute value │G│ of the longitudinal acceleration G is smaller than a predetermined set value G ₀ (│G│ <G ₀ ), such as when the vehicle is traveling at a constant speed, at the time of slow braking, or at the time of slow acceleration. Since it is necessary to mainly suppress the sprung vertical acceleration and improve the riding comfort, if the basic damping constant target value c ₀ is switched to a smaller predetermined value and the damping force characteristic is set softly, As shown in the graph (A) of FIG. 4, a good sprung vertical acceleration characteristic in a high frequency band can be obtained.

On the other hand, when the absolute value │G│ of the steering speed G is larger than the predetermined set value G ₀ (│G│> G ₀ ), such as during sudden braking or sudden acceleration of the vehicle, the basic damping constant By switching the target value c ₀ to the larger predetermined value, the damping force characteristic of the shock absorber 4 is made harder. As a result, as shown in the graph (B) of FIG. 5, the unsprung vertical acceleration is suppressed and the tire ground contact property is enhanced, so that the braking / driving performance and the steering stability are improved.

Since the damping constant variable amount c _u which is the output from the corrected calculation value setting means 14 does not change, the vibration characteristic of the suspension system does not change in the low frequency band where this c _u is effective. .

As described above, according to the present invention, the vertical vibration of the vehicle body can be suppressed by using the signal which is relatively easy to detect, and the basic damping constant is determined according to the state of the vehicle judged by the longitudinal acceleration G. By switching the target value c ₀ , the damping force of the shock absorber in the high frequency band is switched, and when the vehicle is traveling at a constant speed,
While suppressing the sprung vertical acceleration to improve the riding comfort, it is possible to suppress the unsprung vertical acceleration mainly to enhance the steering stability when the vehicle is suddenly braked or suddenly accelerated. As a result, the most effective suspension characteristics can be obtained according to the driving situation of the vehicle, so that the riding comfort of the vehicle is improved, and the braking / driving performance and the steering stability are improved.
At the same time, it can be maximized.

6 and 7 show another embodiment of the present invention.

As shown in FIG. 6, in this embodiment,
Acceleration / deceleration instruction signal detection for detecting an acceleration instruction signal (accelerator pedal angle λ _{A in} this embodiment) and a deceleration instruction signal (brake pedal angle λ _{B in} this embodiment) instead of the steering speed detection means 5 in FIG. Means 6 is provided, and the damping constant target value determining means 3 is configured such that the sprung and unsprung relative displacement from the relative displacement detecting means 1, the sprung and unsprung relative speeds from the relative speed detecting means 2, and acceleration / deceleration instruction The target value of the damping constant is calculated based on the acceleration instruction signal and the deceleration instruction signal from the signal detection means 6, and the result is input to the damping force variable shock absorber 4 so that the target damping force is generated. .

That is, as shown in the concrete configuration of the damping constant target value calculating means 3 in FIG. 7, the accelerator pedal angle λ _{A as the} acceleration instruction signal and the brake pedal angle λ _{B as the} deceleration instruction signal are the target values. The basic damping constant target value c ₀ is switched according to the accelerator pedal angle λ _A and the brake pedal angle λ _B which are input to the setting means 15.

Specifically, for example, at the time of constant speed running, slow acceleration, slow braking, etc., both the accelerator pedal angle λ _A and the brake pedal angle λ _B have their respective set values λ _A0 ,
When smaller than λ _B0 (when λ _A <λ _A0 and λ _B <λ _B0 )
In order to suppress the vehicle body vibration in the high frequency band by suppressing the sprung vertical acceleration by softening the damping force characteristic of the suspension system by setting the basic damping constant target value c ₀ to a small predetermined value, Improves ride comfort.

On the other hand, when at least one of the accelerator pedal angle λ _{A and the} brake pedal angle λ _B is larger than the respective set values λ _A0 and λ _B0 (λ _A > λ _A0 or In the case of λ _B > λ _B0 ), the damping force characteristic of the suspension system is made stiff with a large predetermined value of c ₀ to mainly suppress unsprung vertical acceleration, and the damping force characteristic is stiff even in the high frequency band. Will improve the ground contact of the tires and improve braking / driving performance and steering stability.

As a result, according to the present invention, the most effective suspension characteristics can be obtained according to the driving condition of the vehicle, the riding comfort of the vehicle is improved, and the braking / driving performance and the steering stability are improved. Can be maximized at the same time.

[0073]

According to the first aspect of the present invention, the damping constant target value input to the damping force variable shock absorber is determined from the basic damping constant target value and the damping constant correction value. When the absolute value of the longitudinal acceleration is smaller than the set value, such as during constant speed driving, slow braking, or slow acceleration, the basic damping constant target value is set to a small value and the absolute value of the longitudinal acceleration during sudden braking or sudden acceleration is reduced. When the value is larger than the set value, the target value of the basic damping constant is set to a large value, so while maintaining a good riding comfort due to the soft damping force characteristics, such as during constant speed driving, during sudden braking, sudden acceleration, etc. When it is necessary to focus on driving stability rather than riding comfort of the vehicle, the damping force characteristics can be hardened to improve the ground contact of the tires, improving braking / driving performance and driving stability, and improving the riding comfort of the vehicle. And braking It can be achieved to maximize performance and steering stability improved and at the same time.

According to the second invention, the target value setting means is
The running state is determined according to the magnitude relationship between the acceleration instruction signal and the deceleration instruction signal and a predetermined reference value, and the basic damping constant target value is small during constant speed traveling, slow braking, slow acceleration, etc. Since the target value of the basic damping constant is set to a large value during sudden braking or sudden acceleration, a soft damping force characteristic keeps a good ride comfort while driving at a constant speed. When it is necessary to prioritize steering stability rather than riding comfort of the vehicle during braking or sudden acceleration, the damping force characteristics can be hardened to improve the ground contact of the tires and enhance braking / driving performance and steering stability. In addition, it is possible to maximize the improvement of the riding comfort of the vehicle and the improvement of braking / driving performance and steering stability at the same time.

According to the third invention, the signal for detecting the accelerator pedal angle is detected as the acceleration instruction signal, and the signal for detecting the brake pedal angle is detected as the deceleration instruction signal. When both the brake pedal angle and the accelerator pedal angle are smaller than the set values, such as during slow braking, slow braking, and slow acceleration, the basic damping constant target value is set to a small value, and the brake pedal angle is less than the set value during sudden braking. If the accelerator pedal angle is larger than the set value, such as during large acceleration, the target value for the basic damping constant is set to a large value, while maintaining a good ride comfort due to the soft damping force characteristics during constant speed driving. Then, during sudden braking,
When it is necessary to prioritize steering stability rather than riding comfort of the vehicle, such as during sudden acceleration, the damping force characteristics can be hardened to improve the ground contact of the tires and enhance braking / driving performance and steering stability. It is possible to maximize the riding comfort and the braking / driving performance and the steering stability at the same time.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a damping force calculation means.

FIG. 3 is a model diagram showing a suspension system of the same.

FIG. 4 is a characteristic diagram similarly showing a vibration damping effect.

FIG. 5 is a characteristic diagram similarly.

FIG. 6 is a block diagram showing another embodiment of the present invention.

FIG. 7 is a block diagram showing a damping force calculating means.

[Explanation of symbols]

 1 Relative Displacement Detecting Means 2 Relative Velocity Detecting Means 3 Damping Constant Target Value Calculating Means 4 Shock Absorbers 5 Longitudinal Acceleration Detecting Means 6 Acceleration / Deceleration Instruction Signal Detecting Means 11 Switching Input Calculating Means 12 Linear Input Calculating Means 13 Filters 14 Correction Value Calculating Means 15 Target value setting means

Claims (3)

[Claims] 1. A sprung and unsprung relative velocity detecting means, a sprung and unsprung relative displacement detecting means, and a damping constant of a damping force variable shock absorber using the relative velocity and relative displacement detected from these as input. A damping constant target value calculating means for setting a target value, and a damping force variable shock babsaver for inputting the damping constant target value to adjust the damping constant are provided, and the damping force target value calculating means is a predetermined constant. A target value setting means for setting a basic damping constant target value that is, and a correction value calculating means for calculating a damping constant correction value that corrects the ideal damping force calculated based on the relative speed and relative displacement,
In a suspension system damping force control device that outputs a damping constant target value including these basic damping constant target value and damping constant correction value, a longitudinal acceleration detecting means for detecting longitudinal acceleration of the vehicle is provided, and the target value setting means is When the absolute value of the longitudinal acceleration is smaller than a set value, a small predetermined value is selected as the basic damping constant target value, and when the absolute value of the longitudinal acceleration is larger than the set value, a large predetermined value is set as the basic damping constant target value. A suspension damping force control device characterized by selecting a value. 2. A sprung and unsprung relative velocity detecting means, a sprung and unsprung relative displacement detecting means, and a damping constant of a damping force variable shock absorber using the relative velocity and relative displacement detected from these as input. A damping constant target value calculating means for setting a target value, and a damping force variable shock babsaver for inputting the damping constant target value to adjust the damping constant are provided, and the damping force target value calculating means is a predetermined constant. A target value setting means for setting a basic damping constant target value that is, and a correction value calculating means for calculating a damping constant correction value that corrects the ideal damping force calculated based on the relative speed and relative displacement,
In a suspension damping force control device that outputs a damping constant target value including these basic damping constant target value and damping constant correction value, an acceleration instruction signal for instructing vehicle acceleration and a deceleration instruction signal for instructing vehicle deceleration are provided. The target value setting means includes an acceleration / deceleration instruction signal detecting means for detecting, and the target value setting means has a small predetermined value or a large value as the basic damping constant target value according to a magnitude relationship between the acceleration instruction signal and the deceleration instruction signal and a predetermined reference value. A damping force control device for a suspension system, wherein a predetermined value is selected. 3. The acceleration instruction signal is a signal for detecting an accelerator pedal angle, the deceleration instruction signal is a signal for detecting a brake pedal angle, and the target value setting means is the accelerator pedal angle and the brake pedal angle. When any of the above is smaller than the set value, a small predetermined value is selected as the basic damping constant target value, and when at least one of the accelerator pedal angle and the brake pedal angle is larger than the set value, the basic damping constant target value is selected. The damping force control device for a suspension system according to claim 2, wherein a large predetermined value is selected as.