JPH0524425A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE:To improve riding comfortability by preventing damping force from occurring more than it needs. CONSTITUTION:A suspension device for vehicle is provided with a shock absorber 1 and a controller 2. This shock absorber 1 is provided between a sprung part and an unsprung part of a vehicle and is formed so as to change damping coefficient freely. Besides, the controller 2 which controls the shock absorber 1 to its optimum damping coefficient based on data obtained from an acceleration sensor 3 and a load sensor 4, taking as its upper limit the maximum damping coefficient which is set by a maximum damping coefficient setting means which sets the maximum damping coefficient based on the maximum damping coefficient characteristics preliminarily set as well as the sprung oscillation frequency obtained based on the acceleration obtained from the acceleration sensor 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension system for a vehicle, and more particularly to a suspension system having a variable damping coefficient.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension system having a shock absorber with a variable damping coefficient, for example, Japanese Patent Laid-Open No. 64-64-
The one described in Japanese Patent No. 60411 is known.

This conventional device detects the sprung-unsprung relative speed in order to detect the damping force of the shock absorber,
This detected relative speed (damping force) is compared with a predetermined threshold value, and when the relative speed exceeds the threshold value, a high damping coefficient is controlled.

[0004]

However, in the above-described conventional device, the frequency at which the relative velocity (damping force) exceeds the predetermined threshold value increases in the high frequency region where the sprung vibration frequency is equal to or higher than the resonance frequency, The shock absorber will be held at a high damping force. For this reason, there is a problem in that a damping force is generated more than necessary and the riding comfort is deteriorated.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a vehicle suspension system capable of improving a riding comfort by preventing a damping force from being generated more than necessary. .

[0006]

According to the present invention, there is provided maximum damping coefficient setting means for setting the upper limit of the variable damping coefficient corresponding to the sprung mass vibration frequency based on a preset characteristic, and the above-mentioned object is provided. To achieve.

That is, the vehicle suspension system of the present invention is provided between the unsprung portion and unsprung portion of the vehicle and has a shock absorber formed so that the damping coefficient can be changed, and a frequency detecting means for detecting the sprung vibration frequency of the vehicle. A maximum damping coefficient setting means for setting a maximum damping coefficient corresponding to the detected vibration frequency of the frequency detecting means based on a preset maximum damping coefficient characteristic, and a maximum damping coefficient set by the maximum damping coefficient setting means. As the upper limit, a means provided with damping coefficient control means for controlling the shock absorber to an optimum damping coefficient based on data obtained from a predetermined input means.

According to a second aspect of the present invention, the maximum damping coefficient characteristic set in advance by the maximum damping coefficient setting means is such that the sprung vibration frequency is in a higher frequency range than the sprung resonance frequency and the high damping coefficient is present. However, the sprung transmissibility does not change even with a low damping coefficient.The maximum damping coefficient is set to the maximum value when it is lower than the predetermined fixed point frequency, and the higher the damping point frequency, the lower the maximum damping coefficient gradually. The characteristics are as follows.

According to a third aspect of the present invention, the frequency detecting means includes a sprung speed detecting means for detecting a sprung speed of the vehicle, and the sprung speed changes from a peak to 0 or from 0 to a peak. The time until it became measured was measured, and the sprung vibration frequency was detected based on the time.

[0010]

When the sprung portion of the vehicle vibrates due to a road surface input accompanying traveling of the vehicle, the vibration frequency is detected by the frequency detecting means. In the case of the device described in claim 3, the sprung mass oscillation frequency is until the sprung mass velocity obtained by the sprung mass velocity detecting means becomes from 0 to the velocity peak, or from the velocity peak to 0, that is, The time of 1/4 cycle of one stroke is measured, and this time is obtained by quadrupling the reciprocal.

Then, the maximum damping coefficient setting means sets the maximum damping coefficient in accordance with the sprung mass vibration frequency obtained as described above. Incidentally, in the device according to claim 2,
When the sprung vibration frequency is lower than a predetermined fixed point frequency, the maximum damping coefficient is set to the maximum value, and when the sprung vibration frequency is higher than the fixed point frequency, the maximum damping coefficient is set gradually smaller as the frequency increases.

Further, the damping coefficient control means sets the damping coefficient of the shock absorber to the optimum damping coefficient based on the data obtained from the predetermined input means, with the maximum damping coefficient set by the maximum damping coefficient setting means as the upper limit. Control.

Since the upper limit of the damping coefficient of the shock absorber is set in accordance with the sprung mass vibration frequency, the riding comfort can be improved by preventing the damping force from increasing more than necessary.

[0014]

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

First, the structure will be described.

FIG. 1 is an overall view showing a vehicle suspension system according to an embodiment of the present invention, in which 1 denotes a shock absorber 1. In this shock absorber 1, an upper end of a piston rod 1a is supported by a vehicle body, and a lower end of an outer cylinder 1b is connected to a wheel side. And this shock absorber 1
The inside of is configured such that the attenuation coefficient can be changed in multiple stages according to the voltage output from the controller 2. still,
As a configuration for changing this damping coefficient, for example,
Since the structure described in the official gazette presented in the related art can be applied and configured, the description thereof will be omitted. By the way, according to this publication, a center rod having an orifice is configured to be displaced in two steps so that the damping coefficient can be changed between high and low steps. This center rod is displaced in multiple steps. This makes it possible to change the damping force characteristic in multiple stages.

The controller 2 includes an acceleration sensor 3
And the load sensor 4 are connected. This acceleration sensor 3
Is for detecting the vertical acceleration G of the vehicle body on the spring, and is provided for detecting the state of the sprung speed. Further, the load sensor 4 is provided at a portion where the piston rod 1a is attached to the vehicle body, and detects the load W. In order to detect the damping force generated by the shock absorber 1 (corresponding to the sprung-unsprung relative speed). It is provided in.

Next, the control contents of the controller 2 will be described with reference to the flowchart of FIG.

In step 201, the acceleration signal G obtained by the acceleration sensor 3 and the load signal W obtained by the load sensor 4 are read, and the process proceeds to step 202.

In step 202, the load signal W obtained by the load sensor 4 is digitally converted to form the load data D, and the process proceeds to step 203.

In step 203, the load data D formed in step 202 is read and the process proceeds to step 204.

In step 204, the acceleration signal G obtained by the acceleration sensor 3 is converted into digital data to obtain the acceleration data A.
Are formed and the process proceeds to step 205.

In step 205, the acceleration data A is read and the process proceeds to step 206.

At step 206, the acceleration data A is integrated to calculate the sprung mass velocity data V, and then the maximum damping coefficient flow 300 shown in FIG.

In the maximum damping coefficient flow 300, first, in step 301, it is determined whether or not the sprung mass velocity data V has a peak. If YES, the process proceeds to step 302, and if NO, the process proceeds to step 303.
Incidentally, whether or not the sprung mass velocity data V is at the peak can be determined by the sign change of the acceleration data A.

In step 302, the timer counter provided in the controller 2 is cleared, and the flow advances to the next damping coefficient control flow 400.

In step 303, the sprung mass velocity data V
Is 0, and if NO, step 3
If 04, the process proceeds to step 305 if YES.
The sprung speed data 0 can also be obtained by determining whether or not the acceleration data A has a peak.

In step 304, the timer counter starts time measurement. On the other hand, in step 305, the timer counter measured value T at this time is obtained. That is, the sprung speed data V is cleared when the peaks are reached in steps 301 and 302, and the timer counter that starts the measurement based on step 304 at the same time when the peak is passed is the sprung speed data based on steps 303 and 304. The measurement is terminated when V becomes 0, and as a result, 1 / th of one stroke of sprung mass vibration as shown in FIG.
The time T ₀ required for 4 cycles is measured.

The following step 306 is a step for calculating the sprung vibration frequency H _Z , where H _Z = 1 / (4 × T
₀ ) Calculated by the formula.

The following step 307 is a step of setting the maximum damping coefficient value from the sprung vibration frequency H _Z thus obtained. That is, the controller 2 stores in advance the maximum damping coefficient ratio characteristic corresponding to the sprung mass vibration frequency H _z shown in FIG. 6 in the state of an arithmetic expression, and the maximum damping coefficient ratio characteristic is stored based on the maximum damping coefficient ratio characteristic. Set the numerical value MD. By the way, this characteristic is a characteristic in which the maximum damping coefficient value MD is set to the maximum value (1.0) at a frequency lower than the fixed point frequency f _n , and then becomes gradually lower as the frequency becomes higher. It should be noted that this characteristic is composed of three arithmetic expressions according to the frequency domain as shown in the figure, and the inclination of the characteristic becomes gentle as the frequency becomes higher.
Further, the fixed point frequency f _n is, as shown in the sprung transmissivity characteristic diagram of FIG. 7, at a frequency higher than the sprung resonance frequency f _u , a characteristic (solid line) at a high damping coefficient and a low damping. It is the frequency at which the characteristic (one-dot chain line) when it is a coefficient becomes the same characteristic and there is no influence of the damping force.

When the above maximum damping coefficient flow 300 is completed, the processing proceeds to the damping coefficient control flow 400 shown in FIG.

In the damping coefficient control flow 400, first, at step 401, the damping coefficient control point of the shock absorber 1 is indexed from the data map DM from the values of the sprung mass velocity V and the load data D.

Incidentally, this data map DM is tabulated so that the optimum damping coefficient can be obtained from the load data D and the sprung mass velocity data V, and as shown in FIG. The sprung speed data V is taken on the horizontal axis D, and the position of the intersection of the data values at that time indicates the optimum damping coefficient control point. The map is configured to control.
The relationship between the load data D, the sprung speed data D, and the damping coefficient may be, for example, the same as the arithmetic expression described in JP-A-62-181908. The data map DM is indexed for the sake of simplicity. Also, this data map DM
Is set for each control stage of the shock absorber 1, and the optimum damping coefficient to be shifted is slightly different for each control point at that time.

In step 402, the damping coefficient control point is the maximum damping coefficient value M set in the maximum damping coefficient flow 300.
It is determined whether it is D or more, and if YES, step 40
If NO, the process proceeds to step 404.

In step 403, the damping coefficient control point is set to
The maximum damping coefficient value MD set in the maximum damping coefficient flow 300 is set.

In step 404, the drive signal for obtaining the number control points obtained in step 402 or 404 is output to the shock absorber 1.

In the following step 405, step 404
The data map DM corresponding to the control point output in step 3 is read. Therefore, in step 401, this step 405
The data map DM corresponding to the current damping coefficient control point read by the process of
For example, the data map DM shown in the first sheet in FIG.
Is displayed on the left as shown in step 404.
This map is read in step 405 when the drive signal to be the fifth stage attenuation coefficient is output.

In the embodiment apparatus configured as described above, when the sprung vibration frequency H _z is lower than the fixed point frequency f _n , the damping coefficient of the damping coefficient is changed based on the operation of the maximum damping coefficient flow 300 of the controller 2. The upper limit of the variable area is set to the maximum value (1.0) (see FIG. 6). Therefore, based on the operation of the damping coefficient control flow 400 of the controller 2, the shock absorber 1 can be controlled to a high damping coefficient as necessary to suppress the sprung transmission rate and improve the riding comfort.

On the other hand, when the sprung mass vibration frequency H _z becomes the fixed point frequency f _n or more, the damping coefficient control flow 400 of the controller 1 has more opportunities to control the damping coefficient to high damping, but in this case, the controller 1 Based on the operation of the maximum damping coefficient flow 300, the upper limit of the variable region of the damping coefficient is gradually suppressed to a low value according to the frequency, as shown in FIG. Therefore, when the sprung mass vibration frequency H _z is high, it is difficult for the shock absorber 1 to be kept at a high damping coefficient, a damping force is not generated more than necessary, and riding comfort is improved.

As described above, the vehicle suspension system of this embodiment is characterized in that the ride comfort is improved without generating unnecessary damping force.

In addition, in this embodiment, since the damping coefficient is controlled by indexing the data map DM, the structure of the controller 2 can be simplified and the cost can be reduced. Since it is not required, the control time can be shortened and high control responsiveness can be obtained.

Further, in the present embodiment, in obtaining the sprung mass oscillation frequency H _z , the sprung mass velocity data V becomes 0 from the peak, that is, the time T ₀ of 1/4 cycle of one stroke. It is measured and calculated from the reciprocal of this time multiplied by 4. Since the vibration frequency can be detected before the vibration of one stroke is performed, the time required for the detection is short and the control response is high.

In the embodiment, the sprung vibration frequency H
_{When z} is _{equal to} or higher than the fixed point frequency f _n , the maximum damping coefficient value MD is gradually decreased as the frequency becomes higher, so that the damping characteristics do not change suddenly and the deterioration of the riding comfort due to the rapid changes in characteristics can be prevented.

Although the embodiment has been described above, the specific configuration is not limited to this embodiment. For example, in the embodiment, the damping coefficient control of the shock absorber is performed by the data map index. , Other means such as control based on calculation may be used. Further, in the embodiment, in the frequency range above the fixed point frequency, the maximum attenuation coefficient is gradually lowered in proportion to the frequency, but it may be lowered stepwise, on the other hand, below the fixed point frequency. The maximum attenuation coefficient may be changed even in the frequency range of. Further, in the embodiment, the sprung vibration frequency is calculated from the time of 1/4 cycle of vibration, but, for example,
Other well-known ones such as converting the vibration stroke on the spring into a voltage and detecting it may be used.

[0045]

As described above, in the vehicle suspension system of the present invention, the maximum damping coefficient is set corresponding to the vibration frequency detected by the frequency detecting means based on the preset maximum damping coefficient characteristic. Means provided with damping coefficient setting means and damping coefficient control means for controlling the shock absorber to an optimum damping coefficient based on data obtained from a predetermined input means, with the maximum damping coefficient set by the maximum damping coefficient setting means as an upper limit. Therefore, the upper limit of the damping coefficient of the shock absorber is set in accordance with the sprung mass vibration frequency, so that the riding comfort can be improved by preventing the damping force from becoming unnecessarily high.

In addition, according to the invention of claim 2,
Since the maximum damping coefficient is set to gradually decrease as the sprung mass vibration frequency increases, it becomes more difficult to increase the damping coefficient more than necessary, and it becomes more difficult for sudden changes in damping force characteristics to occur, resulting in a more comfortable ride. Is improved.

Further, according to the third aspect of the invention, the sprung vibration frequency is detected in a quarter cycle of one stroke of the sprung vibration. It is possible to obtain the effect of being able to increase.

[Brief description of drawings]

FIG. 1 is an overall view showing a vehicle suspension device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an operation flow of a controller of the embodiment apparatus.

FIG. 3 is a flowchart showing a maximum damping coefficient flow which is a part of the operation of the controller.

FIG. 4 is a flowchart showing a damping coefficient control flow that is part of the operation of the controller.

FIG. 5 is an explanatory diagram when detecting a sprung vibration frequency.

FIG. 6 is a characteristic diagram of a maximum damping coefficient value.

FIG. 7 is a characteristic diagram of sprung mass transfer rate.

FIG. 8 is a diagram showing a data map.

[Explanation of symbols]

1 shock absorber 2 controller (frequency detection means, maximum damping coefficient setting means, damping coefficient control means) 3 acceleration sensor (frequency detection means, sprung speed detection means) 4 load sensor (input means)

Claims (3)

[Claims] 1. A shock absorber provided between a sprung part and an unsprung part of a vehicle, the damping coefficient of which can be changed, a frequency detecting means for detecting a sprung vibration frequency of the vehicle, and a preset maximum damping coefficient. Based on the characteristics, the maximum damping coefficient setting means for setting the maximum damping coefficient corresponding to the detected vibration frequency of the frequency detecting means, and the maximum damping coefficient set by the maximum damping coefficient setting means as an upper limit, from a predetermined input means A vehicle suspension system comprising: a damping coefficient control means for controlling the shock absorber to an optimum damping coefficient based on the obtained data. 2. The maximum damping coefficient characteristic preset by the maximum damping coefficient setting means is transmitted on the sprung mass regardless of whether the sprung mass vibration frequency is higher than the sprung mass resonance frequency and whether the damping coefficient is high or low. The maximum damping coefficient is set to the maximum value when the frequency is lower than the predetermined fixed point frequency where the rate does not change, and the characteristic is that the maximum damping coefficient gradually decreases as the frequency becomes higher than this fixed point frequency. The vehicle suspension system according to claim 1. 3. The frequency detecting means comprises a sprung speed detecting means for detecting a sprung speed of a vehicle, and measures a time until the sprung speed becomes 0 from a peak or 0 to a peak, The vehicle suspension system according to claim 1 or 2, wherein the sprung vibration frequency is detected based on the time.