JPH05185821A - Car suspension system - Google Patents

Abstract

PURPOSE:To provide a car suspension system that is able to improve the extent of riding quality in a car at the time of running on a rough road. CONSTITUTION:This suspension system is provided with a shock absorber (b) being interposed between a body side and each wheel side, and making a damping coefficient changeable by a damping coefficient changing means (a), a sprung vertical acceleration detecting means (c) detecting the extent of sprung vertical acceleration in and around a position where each shock absorber (b) is installed, a high pass filth (d) for cut-offing a low frequency component of less than the unsprung resonance frequency area from sprung vertical acceleration signals being obtained by the sprung vertical acceleration detecting means (c), and a damping coefficient control means (e) controlling the damping coefficient of each shock absorber (b) on the basis of a processing signal value of the sprung vertical acceleration processed by the high pass filter (d), respectively.

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 the damping coefficient of a shock absorber.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension system for controlling a damping coefficient of a shock absorber, for example, Japanese Patent Laid-Open No. 61-
The thing described in 163011 gazette is known.

In this conventional vehicle suspension system, when the direction signs of the sprung vertical speed signal and the sprung / unsprung relative speed signal obtained by processing the signals of the sprung vertical acceleration sensor are the same, the damping coefficient is obtained. Is set to be hard and the damping coefficient is controlled to be soft when the sign is different. The four wheels are independently controlled.

[0004]

However, in the above-mentioned conventional apparatus, when there is a high frequency input from the unsprung part, the control means switches between hard and soft in response to the high frequency, but the control routine time , Depending on the delay of the rising of damping force and the switching time of the actuator,
Since the control response is delayed, the damping performance against low frequency input is improved, but there is a problem that the riding comfort cannot be improved when traveling on a bad road with many high frequency components.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a vehicle suspension system capable of improving the riding comfort of a vehicle when traveling on a rough road. is there.

[0006]

Therefore, in the present invention, the damping coefficient is controlled based on the processing signal of the sprung vertical acceleration that cuts off at least the low-frequency component below the unsprung resonance frequency range. I tried to achieve it.

That is, the vehicle suspension system according to claim 1 of the present invention is interposed between the vehicle body side and each wheel side, and the damping coefficient is changed by the damping coefficient changing means a, as shown in the claim correspondence diagram of FIG. Possible shock absorbers b, sprung vertical acceleration detection means c for detecting sprung vertical acceleration in the vicinity of the position where each shock absorber b is provided, and sprung vertical acceleration signal obtained by the sprung vertical acceleration detection means c. Of the filter circuit d for cutting off at least low frequency components below the unsprung resonance frequency region, and the damping coefficient of each shock absorber b based on the sprung vertical acceleration processed signal processed by the filter circuit d. The damping coefficient control means e for controlling is provided.

A vehicle suspension system according to a second aspect is provided with a shock absorber b interposed between the vehicle body side and each wheel side, the damping coefficient of which can be changed by the damping coefficient changing means a, and each shock absorber b. Sprung vertical acceleration detecting means c for detecting sprung vertical acceleration in the vicinity of the position, sprung vertical speed detecting means f for detecting sprung vertical speed in the vicinity of the position where each shock absorber b is provided, and sprung Of the sprung vertical acceleration signal obtained by the vertical acceleration detecting means c, a filter circuit d for cutting off at least a low frequency component below the unsprung resonance frequency region and a position near each shock absorber b are provided. Relative speed detecting means g for detecting the relative speed between the sprung and unsprung,
The damping coefficient of each shock absorber b is increased when the sprung vertical acceleration and the relative speed between the sprung and unsprung have the same sign, and when the sign is different, the damping coefficient is controlled to the minimum while the sprung mass is controlled. When the processed signal of the vertical acceleration exceeds a predetermined threshold value, the damping coefficient control means e is provided to reduce the damping coefficient until the predetermined time elapses after the processing signal falls below the threshold value. ..

As the filter circuit, a high-pass filter for cutting off low-frequency components below the unsprung resonance frequency region from the sprung vertical acceleration signal obtained by the sprung vertical acceleration detection means, and an unsprung resonance. It may be configured with a low-pass filter that cuts off high-frequency components in the frequency domain and above.

[0010]

The sprung vertical acceleration signal obtained by each sprung vertical acceleration detecting means is passed through the filter circuit to cut off low-frequency components below the unsprung resonance frequency region, whereby the unsprung resonance frequency is reduced. A high frequency component above the region is obtained as a processed value signal.

Since the frequency component in the unsprung resonance frequency region is large when the vehicle travels on a bad road as compared to when the vehicle travels on a good road, the damping coefficient control means determines the shock absorber of the shock absorber in accordance with the processing signal of the sprung vertical acceleration. By performing the damping coefficient control, it becomes possible to improve the riding comfort of the vehicle when traveling on a rough road.

Further, in the apparatus according to the second aspect, the damping coefficient control means increases the damping coefficient when the sprung vertical acceleration and the relative speed between the sprung and unsprung have the same sign, and when the signs are different, the damping coefficient is increased. The coefficient is controlled to the minimum, which can ensure the damping performance on the spring.

On the other hand, even when the sprung vertical acceleration and the relative speed between the sprung and unsprung parts have the same sign and should be controlled to have a high damping coefficient, the processing signal of the sprung vertical acceleration processed by the filter circuit is The damping coefficient is reduced until the specified time elapses after the value falls below the threshold when it exceeds the specified threshold. Can be improved.

[0014]

Embodiments of the present invention will be described with reference to the drawings. (First Embodiment) First, the structure will be described. Figure 2
FIG. 3 is a configuration explanatory view showing a vehicle suspension system of the first embodiment, in which four shock absorbers SA ₁ , SA ₂ , SA ₃ , SA ₄ (shock absorbers are interposed between a vehicle body and four wheels) are provided. In the description, a case where these four are collectively referred to and a case where these common configurations are described are simply referred to as SA.).
A vertical acceleration sensor (hereinafter, referred to as vertical G sensor) 1 for detecting sprung vertical acceleration is provided on the vehicle body near each shock absorber SA. Also,
A control unit 4 that receives a signal from each sensor 1 and outputs a drive control signal to the pulse motor 3 of each shock absorber SA is provided near the driver's seat.

FIG. 3 is a system block diagram showing the above-mentioned configuration. The control unit 4 is provided with an interface circuit 4a, a CPU 4b, and a drive circuit 4c, and the interface circuit 4a is provided with each of the sprung G sensors 1 described above.
A signal from each load sensor (relative speed detecting means between sprung and unsprung) 6 is input. The load sensor 6 is provided at the mounting portion of the shock absorber SA to the vehicle body, and detects the damping force F generated by the shock absorber SA as a load. Also,
In the interface circuit 4a, a set of two filter circuits 4d shown in FIG. 14 is provided for each of the upper and lower G sensors 1. That is, the HPF is a high-pass filter circuit that has a cutoff frequency that is half the unsprung resonance frequency from the sprung acceleration signals sent from the upper and lower G sensors 1, and the LPF is sent from the upper and lower G sensors 1. It is a low-pass filter circuit in which a frequency equal to twice the unsprung resonance frequency is used as a cut-off frequency from among the sprung acceleration signals to be transmitted. Only the frequency component of can be extracted.

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. Which defines the base 34 and the piston 32
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 each through hole. An expansion side damping valve 12 and a compression side damping valve 20 that open and close 31a and 31b respectively are provided. In addition, the stud 38 that is fixed to the tip of the piston rod 7 and penetrates the piston 31 has an upper chamber A
Is formed with a communication hole 39 for communicating the lower chamber B with the lower chamber B. Further, an adjuster 40 for changing the flow passage cross-sectional area of the communication hole 39 and a fluid communication hole 39 depending on the direction of fluid flow are formed.
An extension side check valve 17 and a pressure side check valve 22 that allow and block the flow of the air are provided. The adjuster 40 is rotated by the pulse motor 3 (see FIG. 4). The stud 38 has a first port 21, a second port 13, and a third port in order from the top.
A port 18, a fourth port 14 and a fifth port 16 are formed.

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. There is.

Therefore, between the upper chamber A and the lower chamber B, the inside of the extension side damping valve 12 is opened by passing through the through hole 31b as a flow passage through which the fluid can flow in the extension stroke. First side flow path D extending to B, second port 13, vertical groove 2
An expansion side second flow path E reaching the lower chamber B by opening the outer peripheral side of the expansion side damping valve 12 via the third and fourth ports 14;
The extension side check valve 17 is opened via the port 13, the vertical groove 23, and the fifth port 16 to reach the lower chamber B.
Channel F, third port 18, second lateral hole 25, hollow portion 19
There are four flow paths, the bypass flow path G, which leads to the lower chamber B via the. Also, as a flow path through which the fluid can flow in the pressure stroke,
The pressure-side first flow path H that opens the compression-side damping valve 20 through the through hole 31a, and the pressure-side check valve 22 through the hollow portion 19, the first lateral hole 24, and the first port 21 to open the upper chamber A. Pressure side second flow path J leading to the hollow part 19, the second lateral hole 2
5, there are three flow paths, a bypass flow path G reaching the upper chamber A via the third port 18.

That is, the shock absorber SA is constructed so that the damping coefficient can be changed in multiple stages on both the extension side and the compression side with the characteristics shown in FIG. 6 by rotating the adjuster 40. That is, as shown in FIG. 7, both the expansion side and the compression side are in the soft state (hereinafter, the soft region S
When the adjuster 40 is rotated counterclockwise from (S), the damping coefficient can be changed in multiple steps only on the expansion side, and the compression side becomes a region where the damping coefficient is fixed to a low damping coefficient (hereinafter referred to as the expansion side hard region HS). On the contrary, when the adjuster 40 is rotated clockwise, the damping coefficient can be changed in multiple steps only on the compression side, and the extension side becomes a region where the low damping coefficient is fixed (hereinafter referred to as the compression side hard region SH). There is.

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

Next, the operation of the control unit 4 for controlling the driving of the pulse motor 3 will be described. In addition,
This control is separately performed for each shock absorber SA.

First, the rough road judgment flow will be described with reference to the flowchart of FIG. 17 and the time chart of FIG.

In step 201, the sprung vertical acceleration obtained from each vertical G sensor 1 is converted into each filter circuit HPF,
This is a step of performing a process of obtaining a processed signal V ₀ of the sprung vertical acceleration that is cut off in a region other than the unsprung resonance frequency region by passing through the LPF.

Step 202 is a step of judging whether or not the processed signal V ₀ of sprung vertical acceleration exceeds a predetermined threshold value V _S , and if YES, the routine proceeds to step 203,
If NO (less than the threshold value V _S ), the process proceeds to step 204.

In step 203, the threshold crossing flag F is set.
This is a step of turning on lag1 and then proceeds to step 205 to turn on the rough road flag.

In step 204, the threshold crossing flag F is set.
This is a step of turning off lag1, and then proceeds to step 206.

Step 206 is a step of judging whether or not the previous processed signal V ₀ of sprung vertical acceleration exceeds a predetermined threshold value V _S , and if YES, step 20
7. Go to 7 and step 2 if NO (less than the previous threshold value V _S )
Go to 08.

Step 207 is a step of clearing the timer count, and then the process proceeds to step 210.

Step 208 is a step for judging whether or not the timer count exceeds the control delay time T _{S. If} YES, the process proceeds to step 211, and if NO (less than the control delay time T _S ), the process proceeds to step 209.

Step 209 is a step in which 1 is added to the timer count, and then the process proceeds to step 210.

Step 210 is a delay flag Fla.
This is the step of turning on g2, and then step 20
Go to 5.

In step 211, the delay flag Fla is set.
This is the step to turn off g2, and then step 2
Proceed to 12 and turn off the rough road flag.

That is, in this rough road judgment flow, the threshold crossing flag Flag1 or the delay flag Fla is detected.
When at least one of g2 is ON, it is judged as a bad road and the bad road flag is turned ON, and in other cases, the bad road flag is turned OFF.

Next, the damping coefficient control operation of the control unit 4 will be described with reference to the flowchart of FIG. 15 and the time chart of FIG.

In step 101, the sprung vertical velocity signal V
Is a step of determining whether or not the sprung / unsprung relative speed F has the same sign. If YES, the process proceeds to step 103, and if NO (different sign), the process proceeds to step 102.

Step 102 is a shock absorber S
The damping coefficient of A is controlled so that both the extension and the pressure have the lowest damping coefficient. That is, the shock absorber SA is controlled to the soft area SS (area in FIG. 7).

Step 103 is a step of determining whether or not the rough road flag is ON, and if YES, step 104
If NO (bad road flag is OFF), the process proceeds to step 105.

Step 104 controls to a predetermined medium damping coefficient. That is, the shock absorber SA is controlled to the extension side hard region HS or the compression side hard region SH so that the stroke side, which is the same as the direction of the sprung speed at that time, has a predetermined middle damping coefficient and the reverse stroke has the minimum damping coefficient. ..

In step 105, the damping force is F = k · V.
(Note that k is a proportional constant.) The damping coefficient is proportionally controlled. That is, the shock absorber SA is set to the extension side hard region HS (see FIG. 3) so that the stroke side, which is the same as the direction of the sprung speed at that time, has a high damping coefficient proportional to the sprung vertical velocity V and the reverse stroke has the minimum damping coefficient. 7 side) or the pressure side hard area SH (the side of FIG. 7).

Next, the operation of the embodiment apparatus will be described with reference to the time chart of FIG.

(A) During normal road traveling When the vehicle travels on a normal road, the value of the sprung vertical acceleration near the unsprung resonance frequency is small and the sprung vertical acceleration signal value V ₀ is a predetermined threshold value V _{0. Since} it is less than _S , when the sprung vertical velocity V and the relative speed F have the same sign, that is, when the damping force acts in the damping direction, a shock in the same direction as the sprung vertical velocity V at that time is generated. Control the stroke side of the absorber SA to a high damping coefficient proportional to the sprung vertical velocity V, and to the lowest damping coefficient when the sign is different, that is, when the damping force acts in the vibration direction. As a result, the vibration of the vehicle body at the time of inputting a low frequency can be suppressed and the steering stability of the vehicle can be ensured.

(B) When traveling on a bad road When the vehicle travels on a bad road, the value of the sprung vertical acceleration near the unsprung resonance frequency becomes large and the sprung vertical acceleration signal value V ₀ becomes a predetermined threshold value V _{0. Because} it exceeds _S , at this time,
After that, the control delay time T decreases after falling below the threshold value.
_The sprung vertical velocity V and relative velocity F until _S elapses.
Even if the same sign is used, the ride comfort of the vehicle at high frequency input is improved by controlling the stroke side of the shock absorber SA in the same direction as the direction of the sprung vertical velocity V at that time to a medium damping coefficient M. You can

As described above, in the vehicle suspension system of the first embodiment, it is possible to improve the riding comfort of the vehicle when traveling on a rough road while ensuring the steering stability of the vehicle when traveling on a normal road. It has the feature that

Next, the second embodiment will be described. In describing this embodiment, only the differences from the first embodiment will be described. The same reference numerals as those used in the first embodiment indicate the same objects.

The second embodiment is a shock absorber S
As A, a variable damping coefficient type, as shown in FIG. 19, when the pulse motor 3 is driven, a well-known structure in which both the expansion side and the compression side change from high damping to low damping (for example, (Refer to the public announcement of Shokai 63-112914)
It is an example using.

In the second embodiment, as shown in the time chart of FIG. 20, the damping coefficient of the shock absorber SA is set to a high damping coefficient H, a medium damping coefficient M, and a minimum damping coefficient S. It is designed to switch to three stages.

Although the embodiment has been described above, the specific configuration is not limited to this embodiment, and the present invention includes a design change and the like within a range not departing from the gist of the invention.

For example, in the embodiment, as an example of reducing the damping coefficient at the time of traveling on a rough road, the case of controlling the intermediate damping coefficient between high and low is shown, but the damping coefficient is controlled to the minimum damping coefficient. You can

Further, in the embodiment, one set of filter circuit is used for the HPF and the LPF, but the LPF may be omitted.

[0051]

As described above, in the vehicle suspension system of the present invention, a high-pass filter is used to select from among the sprung vertical acceleration signals obtained by the sprung vertical acceleration detection means.
By controlling the damping coefficient of each shock absorber based on the processed signal value of the sprung vertical acceleration that is cut-off processed for low-frequency components below the unsprung resonance frequency range, the ride comfort of the vehicle on rough roads can be improved. It is possible to obtain the effect of being able to improve.

According to the second aspect of the present invention, the damping coefficient of each shock absorber is increased when the sprung vertical acceleration and the relative speed between the sprung and unsprung portions have the same sign, and the damping coefficient has a different sign. While sometimes controlling the damping coefficient to the minimum, when the processing signal of the sprung vertical acceleration processed by the filter circuit exceeds a predetermined threshold value, after that, it decreases from below the threshold value until a predetermined time elapses. By providing a damping coefficient control means for reducing the damping coefficient,
While ensuring the steering stability of the vehicle when traveling on normal road,
It is possible to improve the riding comfort of the vehicle when traveling on a rough road.

[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 the first embodiment of the present invention.

FIG. 3 is a system block diagram showing a vehicle suspension system of the first embodiment.

FIG. 4 is a sectional view showing a shock absorber applied to the device of the first embodiment.

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 an attenuation coefficient characteristic diagram corresponding to the step position of the pulse motor of the shock absorber.

FIG. 8 is a part of the shock absorber shown in FIG.
FIG.

FIG. 9 is an M of FIG. 5 showing a main part of the shock absorber.
FIG.

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 pressure side hard state.

FIG. 14 is a block diagram showing a main part of a control unit of the first embodiment.

FIG. 15 is a flowchart showing the control operation of the control unit of the first embodiment device.

FIG. 16 is a time chart showing the operation of the first embodiment device.

FIG. 17 shows a control operation of the control unit,
It is a flowchart which shows operation | movement of the rough road judgment flow part.

FIG. 18 is a time chart showing the control operation of the rough road judgment flow portion.

FIG. 19 is a damping coefficient characteristic diagram of the shock absorber of the second embodiment device.

FIG. 20 is a time chart showing the control operation of the control unit of the second embodiment device.

[Explanation of symbols]

 a damping coefficient changing means b shock absorber c sprung vertical acceleration detecting means d filter circuit e damping coefficient controlling means f sprung vertical speed detecting means g sprung / unsprung relative speed detecting means

Claims (3)

[Claims] 1. A shock absorber which is interposed between a vehicle body side and each wheel side and whose damping coefficient can be changed by a damping coefficient changing means, and a sprung vertical acceleration near the position where each shock absorber is provided is detected. The sprung vertical acceleration detection means, a filter circuit for cutting off at least low frequency components below the unsprung resonance frequency region from the sprung vertical acceleration signal obtained by the sprung vertical acceleration detection means, and a shock absorber of each shock absorber. A vehicle suspension system, comprising: a damping coefficient control means for controlling a damping coefficient based on a processing signal of sprung vertical acceleration processed by a filter circuit. 2. A shock absorber which is interposed between the vehicle body side and each wheel side and whose damping coefficient can be changed by a damping coefficient changing means, and a sprung vertical acceleration near the position where each shock absorber is provided is detected. The sprung vertical acceleration detection means, the sprung vertical speed detection means for detecting the sprung vertical speed near the position where each shock absorber is provided, and the sprung vertical acceleration signal obtained by the sprung vertical acceleration detection means From this, a filter circuit for cutting off at least low-frequency components below the unsprung resonance frequency region, and a relative speed detection means for detecting the relative speed between the sprung and unsprung portions near the position where each shock absorber is provided, Increase the damping coefficient of each shock absorber when the sprung vertical acceleration and the relative speed between sprung and unsprung have the same sign. When the sign is different, the damping coefficient is controlled to the minimum, while when the sprung vertical acceleration processed signal processed by the filter circuit exceeds the specified threshold value, the value falls below the threshold value and the specified time elapses. Until then, a vehicle suspension system comprising: damping coefficient control means for reducing the damping coefficient. 3. The filter circuit includes a high-pass filter that cuts off low-frequency components below the unsprung resonance frequency region from the sprung vertical acceleration signal obtained by the sprung vertical acceleration detection means, and an unsprung resonance. The vehicle suspension system according to claim 1 or 2, wherein the vehicle suspension system is configured by a low-pass filter that cuts off high-frequency components in a frequency range or higher.