JPH06247121A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To prevent an unspringing 'tramp, to prevent generation of a noise at a high level, and to improve the riding comfortability, by adapting a damping control by the sky hook theory, not only in the springing condition but also in the unspringing condition. CONSTITUTION:While a drive control signal to drive an actuator d depending on a springing speed, unspringing speed, and the relative speed between the springing and the unspringing speeds, obtained from a behavior detecting means c is formed, a damping characteristics control means e composed by giving weighing coefficients to give different weighings to the springing speed and the unspringing speed respectively, and a coefficient processing means f to form the values of the two weighing coefficients by the signals to give a specific signal process to the condition amounts of the springing and the unspringing conditions, are provided.

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,
In particular, the present invention relates to a control for changing the damping characteristic of a shock absorber based on the skyhook theory.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension system for performing control for changing damping characteristics, for example, Japanese Patent Laid-Open No. 61-16301.
The one described in Japanese Patent Publication No. 1 is known. This conventional vehicle suspension system is a shock absorber that can change the fluid flow path cross-sectional area to change the damping characteristics hard and soft.
The sprung speed detecting means for detecting the sprung vertical speed, the relative speed detecting means for detecting the relative speed between the sprung and unsprung portions, and the sign of the sprung speed and the sign of the relative speed detected by both detecting means are When they match, the damping characteristic of the shock absorber is made hard, and when they do not match, the damping characteristic is made soft, and the damping characteristic control based on the skyhook theory is provided for the four wheels independently. It was

[0003]

In the control as described above, based on the sprung mass and the behavior between the sprung mass and the unsprung mass,
In the sprung resonance point and in the frequency band from the sprung resonance point to the unsprung resonance point, a sufficient effect is observed for the sprung portion. However, when trying to obtain a higher level of effect, in the prior art, unsprung vibration suppression is not controlled at all, and there is a problem to be solved as described below.

That is, if the vehicle runs on a road surface whose main component is near the unsprung resonance point, "fluttering" may occur on the unsprung side where vibration suppression control is not performed.
If this “fluttering” becomes large, the grounding performance of the wheels deteriorates, the steering stability deteriorates, high-frequency sound is generated on the wheel side, and this sound also vibrates the vehicle body to improve riding comfort. There may be a problem of causing deterioration.

The present invention has been made by paying attention to the above-mentioned conventional problems, and by applying the vibration suppression control based on the skyhook theory to the unsprung part, the unsprung part "flutters".
The purpose of this is to improve driving stability, prevent noise, and improve riding comfort at a high level.

[0006]

In order to achieve the above object, in the present invention, as shown in the claim correspondence diagram of FIG. 1, the damping characteristic changing means a is interposed between the vehicle body and each wheel.
Shock absorber b whose damping characteristics can be changed by
A vehicle suspension including a damping characteristic control means e for forming a drive control signal for driving an actuator d for operating the damping characteristic changing means a based on a signal from a behavior detecting means c for detecting the behavior of the vehicle. In the device, the damping characteristic control means e forms a drive control signal based on the sprung speed, the unsprung speed, and the relative speed between the sprung and unsprung portions obtained from the behavior detecting means c, and the drive control signal is generated. In forming, the sprung speed and the unsprung speed are configured to have weighting coefficients for giving different weightings, and the values of these two weighting coefficients are
The configuration is such that the coefficient processing means f for forming a signal obtained by performing a predetermined signal processing on the sprung state and the unsprung state quantity is provided.

When forming the drive control signal, the damping characteristic control means e subtracts the product of the weighting coefficient and the unsprung speed from the product of the weighting coefficient and the unsprung speed to obtain the sprung-unsprung value. When the value obtained by this calculation is positive, a drive control signal having a hard damping characteristic is formed, and when the value obtained by this calculation is negative, a drive control signal having a soft damping characteristic is formed. You may do it.

Also, the coefficient processing means f increases the weighting coefficient of the sprung speed while decreasing the weighting coefficient of the unsprung speed when the value of the sprung resonance frequency band at the input on the spring is large, and vice versa. In addition, when the value of the unsprung resonance frequency band is large, the unsprung weighting coefficient may be increased while the unsprung weighting coefficient may be decreased.

[0009]

[Function] Depending on the behavior of the vehicle body or the input from the road surface,
The amount of state above the spring and the amount of state below the spring change. Therefore, when running on a road surface where the unsprung resonance frequency band is the main component, unsprung "fluttering" appears in the unsprung state quantity,
The coefficient processing means forms the value of the coefficient by weighting the unsprung state quantity. Then, the damping characteristic control means forms the drive control signal with emphasis on the unsprung part by using the weighted weighting coefficient. Therefore, "fluttering" under the spring can be suppressed and the grounding property of the wheel can be improved.

In forming the drive control signal, in the apparatus according to the second aspect, the weighting coefficient and the sprung mass velocity are first calculated.
And the second product of the weighting factor and the unsprung speed,
If the first product is larger, the sprung mass is damped as in the conventional skyhook control, and if the second product is larger, the unsprung mass is damped as described above.

Further, when the coefficient processing means forms the value of the weighting coefficient, in the apparatus of claim 3, if the value of the sprung resonance frequency band at the input on the spring is large, the weighting coefficient of the sprung speed is increased. On the other hand, the unsprung speed weighting coefficient is decreased, and conversely, if the unsprung resonance frequency band is large, the unsprung weighting coefficient is increased while the unsprung weighting coefficient is decreased. .

[0012]

Embodiments of the present invention will be described with reference to the drawings. First, the configuration will be described. FIG. 2 is a configuration explanatory view showing the vehicle suspension system of the embodiment, in which four shock absorbers SA are interposed between the vehicle body and the four wheels. A vertical acceleration sensor (hereinafter referred to as a vertical G sensor) 1 that detects vertical acceleration of the vehicle body as behavior detection means is provided on the vehicle body near each shock absorber SA.
Similarly, between the unsprung member and the unsprung member of the shock absorber SA, a relative displacement between the sprung portion and the unsprung portion is detected in order to detect the relative speed Vpd between the sprung portion and the unsprung portion. A stroke sensor 8 for detecting is provided. Further, at a position near the driver's seat, a signal from each vertical G sensor 1 is input, and a drive control signal mv is output to the pulse motor 3 of each shock absorber SA. Means (corresponding to coefficient processing means).

FIG. 3 is a system block diagram showing the above-mentioned configuration, and the control unit 4 includes an interface circuit 4a, a CPU 4b, and a drive circuit 4c.

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 that guides the sliding of the piston rod 7 that is connected to the vehicle, a suspension spring 36 that is interposed between the outer cylinder 33 and the vehicle body, and a bumper bar 37.

Next, FIG. 5 is an enlarged sectional view showing a portion of the piston 31. As shown in FIG. 5, the piston 31 has through holes 31a and 31b formed therein, and
An extension-side damping valve 12 and a compression-side damping valve 20 that open and close each through hole 31a, 31b are provided.
Further, the bound stopper 41 screwed to the tip of the piston rod 7 has a stud 38 penetrating the piston 31.
Is fixed by screwing, and the upper chamber A and the lower chamber B are bypassed to the stud 38 by bypassing the through holes 31a and 31b.
A communication hole 39 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 pressure-side second flow path J, which will be described later) communicating with the An adjuster 40 for changing the flow passage cross-sectional area of the flow passage is rotatably provided in the communication hole 39. Further, on the outer peripheral portion of the stud 38, an extension side check valve 17 and a pressure side check valve 22 which allow and block the flow on the side of the flow path formed by the communication hole 39 according to the direction of the flow of the fluid are provided. There is. The adjuster 40 is rotated by the pulse motor 3 via the control rod 70 (see FIG. 4). Further, the stud 38 is formed with a first port 21, a second port 13, a third port 18, a fourth port 14, and a fifth port 16 in order from the top.

On the other hand, in the adjuster 40, a hollow portion 19 is formed, a first lateral hole 24 and a second lateral hole 25 which communicate the inside and the outside are formed, and a vertical groove 23 is formed in the outer peripheral portion. ing. Therefore, the upper chamber A and the lower chamber B are
And a first expansion-side flow path D that opens the inside of the expansion-side damping valve 12 through the through hole 31b and reaches the lower chamber B as a flow path through which the fluid can flow in the expansion stroke, Expansion side damping valve 12 via 2 port 13, vertical groove 23, and 4th port 14
An expansion side second flow path E that opens the outer peripheral side of the valve to reach the lower chamber B,
An extension-side third flow path F that opens the extension-side check valve 17 through the second port 13, the vertical groove 23, and the fifth port 16 to reach the lower chamber B, a third port 18, and a second lateral hole. 25, there are four flow paths of a bypass flow path G reaching the lower chamber B via the hollow portion 19. The pressure side first flow path H that opens the compression side damping valve 20 through the through hole 31a, the hollow portion 19, the first lateral hole 24, and the first port 21 are used as the flow path through which the fluid can flow in the pressure stroke. The pressure-side second flow path J that opens the pressure-side check valve 22 to reach the upper chamber A and the bypass flow path that reaches the upper chamber A via the hollow portion 19, the second lateral hole 25, and the third port 18 There are three channels to G.

That is, in the shock absorber SA, by rotating the adjuster 40 to switch the position, the damping coefficient (the damping force characteristic with respect to the piston speed is a coefficient as shown in FIG. 6 on both the extension side and the compression side. It is configured to be changeable in multiple stages because it changes like the above. That is, as shown in FIG. 7, when the adjuster 40 is rotated counterclockwise from a state in which both the expansion side and the compression side are soft (hereinafter referred to as the soft position SS), only the expansion side has multiple damping coefficients. It can be changed and the compression side becomes a region where the damping coefficient is fixed to a low damping coefficient (hereinafter referred to as extension side hard area HS). On the contrary, when the adjuster 40 is rotated clockwise, only the compression side can change the damping coefficient in multiple stages. The side has a structure in which the region is fixed to a low damping coefficient (hereinafter referred to as the pressure side hard region SH).

Incidentally, in FIG. 7, the KK cross section, the LL cross section and the MM cross section, and the MM cross section in FIG. 8, FIG. 9, and FIG. 10, and FIG. 11, 12, and 1 show the damping force characteristics when arranged in each position.
3 shows.

Next, the configuration of the control unit 4 for controlling the drive of the pulse motor 3 will be described in detail.
Reference numeral 4 denotes a configuration of a main part of the CPU 4b, which is a low-pass filter LPF1 for performing integration for converting a sprung acceleration signal g input from the vertical G sensor 1 into a sprung vertical speed Vup.
(0.05 Hz) and the range of A ₁ Hz to A ₂ Hz including the sprung resonance frequency band from the sprung vertical velocity Vup (see FIG. 15)
A ₃ Hz ~A ₄ Hz including a high-pass filter HPF1 and the low pass filter LPF2 for forming a first coefficient control signals S ₁ composed of a low-frequency component, the sprung mass vertical velocity Vup to the spring under the resonance frequency band of the The high pass filter HPF2 and the low pass filter LPF3 for forming the second coefficient control signal S ₂ composed of the high frequency components in the range (see FIG. 15). The second coefficient control signal S ₂ forms the unsprung vertical speed Vud from the sprung-unsprung relative speed Vpd and the sprung vertical speed Vup, and then the high-pass filter HPF2 and the low-pass filter HPF2 as shown in FIG. The filter LPF3 may extract and form frequency components in the range of A ₃ Hz to A ₄ Hz. Further, these coefficient control signals S ₁ and S ₂ are formed by taking out the signals in the above frequency band not from the sprung or unsprung speed as in the present embodiment but from the sprung or unsprung acceleration. Good.

Next, the operation of the control unit 4 will be described with reference to the flow chart of FIG. 17. Step 101 is a step of forming the first coefficient control signal S ₁ according to the configuration shown in FIG. Similarly, 102 is a step of forming the second coefficient control signal S ₂ by the configuration shown in FIG.

In step 103, both coefficient control signals S ₁ ,
A step of setting the first and second weighting coefficients α and β from S ₂ with reference to a previously input map shown in the figure, wherein the map includes the first coefficient control signal S _{As 1} increases, the first weighting coefficient α increases, while the second weighting coefficient β decreases, and conversely, as the second coefficient control signal S ₂ increases, the second weighting coefficient α increases.
While the weighting coefficient β increases, the first weighting coefficient α
Is set to be small.

In step 104, Vs = (αVup−βV
ud) · Vpd is a step of calculating the control signal Vs by an arithmetic expression. Note that Vpd is the relative speed between the sprung portion and the unsprung portion, and is calculated from the change in relative displacement between the sprung portion and the unsprung portion detected by the stroke sensor 8 per unit time.

In step 105, it is judged whether or not the control signal Vs is positive, and if YES, the routine proceeds to step 106, where N
If O, the process proceeds to step 107.

Step 106 is a step of calculating an optimum damping force step (corresponding to the number of switching steps of the pulse motor 3) u by the following arithmetic expression (1). u = K (αVup−βVud) / (Vpd) (1) Note that K is a control gain.

Step 107 is the damping force step u.
Is a step of setting to a minimum min (soft position SS).

Step 108 is the step 106,
In accordance with the damping force step u obtained in 107, the pulse motor 3
Is a step of outputting the drive control signal mv.

Next, the operation of the embodiment will be described. FIG.
Is a schematic diagram showing vibration of a vehicle degree of freedom system, where m ₁ is unsprung weight, m ₂ is unsprung weight, x ₁ is unsprung displacement, and x ₂ is unsprung displacement.

In the above-mentioned Skyhook theory, the product of the sprung vertical velocity Vup and the sprung-unsprung relative velocity Vpd: Vup · Vpd is positive because of the vibration suppression on the spring. When the product: Vup · Vpd is negative, the switching control is performed so as to have a low damping coefficient. On the other hand, when performing unsprung vibration suppression, unsprung vertical velocity Vud
And a relative speed Vpd between the sprung and unsprung: a low damping coefficient when Vud · Vpd is positive, and a high damping coefficient when this product: Vud · Vpd is negative. Become.

As described above, in both the sprung mass damping and the unsprung mass damping, the sprung vertical speed Vup or the unsprung vertical speed Vud is different from the sprung-unsprung relative speed Vpd.
The optimum damping coefficient is obtained based on the value obtained by multiplying by
The relationship between the damping coefficient and this value is opposite between the sprung and unsprung parts. Therefore, in the device of this embodiment,
The arithmetic expression u of the above (1) u = K (αVup−βVud) / (Vp
Using d), weighting is performed in the term of αVup−βVud to give priority to sprung mass damping or unsprung mass damping.

That is, in the behavior of the vehicle, the components of the low frequency band (S ₁ ) of A _{1 to} A ₂ Hz including the resonance frequency on the spring and the high component of A _{3 to} A ₄ Hz including the resonance frequency on the unsprung part. Whether the sprung mass damping priority or the unsprung mass damping priority is determined depending on which one of the components of the frequency band (S ₂ ) is large. As shown in the map of step 103 in FIG. When the first coefficient control signal S ₁ in the frequency band is large, the value of the first weighting coefficient α is large, and conversely, when the second coefficient control signal S ₂ in the high frequency band is large, the value of the second weighting coefficient β is large. Grows larger.

Therefore, in the device of this embodiment, when the vehicle runs on a road surface whose main component is near the unsprung resonance point, A ₃ to
As the second coefficient control signal S _{2 in} the high frequency band of A ₄ Hz becomes large, a large value is set as the second weighting coefficient β, while a small value is selected as the first weighting coefficient α. When calculating the damping coefficient u, the calculation with emphasis on the unsprung vibration suppression is performed. Therefore, "fluttering" under the spring can be suppressed and the grounding property of the wheel can be improved.

Further, when the main component of the sprung resonance is vertical movement in the vehicle body, the first coefficient control signal S _{1 in} the low frequency band of A _{1 to} A ₂ Hz becomes large, which is contrary to the above. While a large value is set as the first weighting coefficient α, a small value is selected as the second weighting coefficient β, and control that focuses on damping on the spring can be performed by skyhook control similar to the conventional one. Done.

As described above, in the device of this embodiment, the vibration on the sprung resonance frequency band can be suppressed on the sprung portion according to the skyhook theory similar to the conventional one. In response to the input of, the "fluttering" under the spring is prevented from being transmitted to the spring, improving the steering stability, preventing the generation of high frequency noise on the wheel side, and improving the riding comfort. What you can do,
It has the characteristic that both steering stability and riding comfort can be achieved at a higher level than before.

Although the embodiment has been described above, the specific structure is not limited to this embodiment, and even if there is a design change or the like within the scope not departing from the gist of the invention, it is included in the invention. In the embodiment, when one of the extension side and the compression side is controlled to be highly damped, the other is fixed to be low damping, but the damping characteristic changing means is shown. Although it is advantageous that the number of times of switching is reduced, it is possible to use a well-known structure in which the expansion side and the compression side simultaneously have high damping and low damping.

[0035]

As described above, the vehicle suspension system of the present invention forms the drive control signal based on the sprung speed, unsprung speed, and relative sprung-unsprung speed obtained from the behavior detecting means. At the same time, in forming this drive control signal, there is provided damping characteristic control means having weighting factors for giving different weights to the sprung mass velocity and the unsprung mass velocity, respectively. Since a value is provided with coefficient processing means for forming a signal by subjecting the sprung and unsprung state quantities to predetermined signal processing, the sprung weighting of the sprung side is applied to the input of the sprung resonance frequency band. The coefficient can be increased to suppress the sprung mass according to the skyhook theory similar to the conventional one, and the unsprung weighting is applied to the input of the unsprung resonance frequency band. By increasing the coefficient to prevent unsprung "fluttering" from being transmitted to the spring, it is possible to prevent high-frequency noise from being generated on the wheel side and improve riding comfort. At the level, it is possible to obtain the effect that both the driving stability and the riding comfort can be achieved.

[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 structural explanatory view showing a vehicle suspension device of an embodiment of the present invention.

FIG. 3 is a system block diagram showing an apparatus according to an embodiment.

FIG. 4 is a cross-sectional view showing a shock absorber applied to the apparatus of the embodiment.

FIG. 5 is an enlarged cross-sectional view showing a main part of the shock absorber.

FIG. 6 is a damping force characteristic diagram corresponding to the piston speed of the shock absorber.

FIG. 7 is a damping force characteristic diagram corresponding to the step position of the pulse motor of the shock absorber.

FIG. 8 is a K of FIG. 5 showing a main part of the shock absorber.
FIG.

FIG. 9 is an L of FIG. 5 showing a main part of the shock absorber.
It is a -L cross section and a MM cross section.

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

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

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

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

FIG. 14 is a block diagram showing a main part of a control unit in the apparatus according to the embodiment.

FIG. 15 is a characteristic diagram showing an example of transmissibility characteristics in the device of the embodiment.

FIG. 16 is a block diagram showing another example of the main part of the control unit.

FIG. 17 is a flowchart showing control of the controller unit of the embodiment apparatus.

FIG. 18 is a schematic diagram showing vibration of a vehicle degree of freedom system.

[Description of Reference Signs] a damping characteristic changing means b shock absorber c behavior detecting means d actuator e damping characteristic controlling means f coefficient processing means

Claims (3)

[Claims] 1. A shock absorber which is interposed between a vehicle body and each wheel and whose damping characteristic can be changed by a damping characteristic changing means, and the damping characteristic change based on a signal from a behavior detecting means for detecting the behavior of the vehicle. A damping characteristic control means for forming a drive control signal for driving an actuator for operating the means, wherein the damping characteristic control means has a sprung speed, an unsprung speed, and a spring obtained from the behavior detecting means. A drive control signal is formed based on the relative speed between the unsprung part and the unsprung part, and in forming the drive control signal, there is a weighting coefficient for giving different weights to the unsprung speed and unsprung speed. Coefficient processing for forming the values of these weighting coefficients by signals obtained by subjecting the sprung and unsprung state quantities to predetermined signal processing. A vehicle suspension device characterized by being provided with a processing means. 2. The damping characteristic control means sets a value obtained by subtracting a product of a weighting coefficient and an unsprung speed from a product of a weighting coefficient and an unsprung speed to form a drive control signal. When a value obtained by this calculation is positive, a drive control signal having a hard damping characteristic is formed, and when the value obtained by this calculation is positive, a drive control signal having a soft damping characteristic is formed. The vehicle suspension system according to claim 1, wherein 3. The coefficient processing means increases the weighting coefficient of the sprung speed while decreasing the weighting coefficient of the unsprung speed when the value of the sprung resonance frequency band at the input on the spring is large, and vice versa. 3. The vehicle suspension system according to claim 1, wherein if the value of the unsprung resonance frequency band is large, the unsprung weighting coefficient is increased while the unsprung weighting coefficient is decreased. .