JPH10244819A - Control method for variable-damping force damper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve comfortableness by processing the measured value of the suspended vibration wave-form of a damper device normally set to a high damping characteristic with a band-pass filter, and switching the damper device to a low damping characteristic when the passing signal value is larger than the prescribed threshold value. SOLUTION: Suspended acceleration is read by an acceleration sensor for the measurement of the suspended vibration wave-form signal value of a damper device (ST1), the measured value is processed by a band-pass filter set with the passing frequency band to the region between the suspended and nonsuspended resonance frequencies (ST2), then the processed signal value S is compared with a preset threshold value TH (ST3). The threshold value TH is set to such a value that whether the input deteriorates comfortableness or not can be judged. When the signal value S is judged to be larger than the threshold value TH, a low damping characteristic is set (ST4). When the signal value S is judged to be smaller, a high damping characteristic is set (ST5). A step motor is controlled by the switching signal to rotate it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a damping force variable damper capable of changing a damping characteristic of a vehicle damper device.

[0002]

2. Description of the Related Art Conventionally, there is a damping force variable damper in which a damping force can be changed in a damper device used for an automobile suspension. In such a damping force variable damper, for example, disclosed in Japanese Patent Laid-Open Publication No. 3-42319, at least the damping force can be changed to at least a low damping force and a high damping force, and the sprung speed is adjusted in the direction (reference numeral). When the damping force of the damper acts as vibration suppression, the damping force is switched to a high damping force, and when the damping force acts as an excitation, the damping force is switched to a low damping force to improve ride comfort. When the upper side and the lower side of the sprung part are relatively close to each other, the state is a vibration damping state.

[0003]

However, in the above-mentioned prior art, the ride comfort can be improved near the sprung resonance frequency, but in a region from the sprung resonance frequency to the unsprung resonance frequency, the lower the damping force, the lower the damping force. (Theoretical value is 0) Since it is theoretically clarified that the ride comfort is good, there is a problem that the ride comfort in that region cannot be improved.

[0004]

SUMMARY OF THE INVENTION In order to solve such a problem and to further improve the riding comfort, the present invention provides a damper capable of switching at least to high and low damping characteristics. Normally, the device is set to the high damping characteristic, the sprung vibration waveform of the damper device is measured, and a band set so as to pass a frequency between the sprung and unsprung resonance frequencies of the damper device is set. The measured value is processed by a pass filter, and when the signal value of the measured value that has passed through the band-pass filter is larger than a predetermined threshold value, switching to the low attenuation characteristic is performed.

[0005] In this manner, resonance can be suppressed with high damping characteristics at each of the sprung and unsprung resonance frequencies requiring high damping force. Since zero damping has a higher damping force, when the passing signal value of the band-pass filter that can pass between both resonance frequencies exceeds a predetermined threshold, it switches to low damping characteristics, and damping when vibration is large By increasing the force, it is possible to suitably suppress vibrations that adversely affect ride comfort.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to specific examples shown in the accompanying drawings.

FIG. 1 is a schematic layout view of a main part of a vehicle equipped with a variable damping force damper to which the present invention is applied. As shown in the figure, a variable damping force damper DMP is attached to each of the front and rear wheels together with a spring (not shown). Each of the damping force variable dampers DMP is provided with a step motor 8 for changing the damping force, and a damping force switching signal from the control unit ECU is output to each step motor 8 via the motor driver DRV, and the signal is output. The damping force changes according to the pressure.

Further, acceleration sensors GS are provided in the vicinity of the vehicle body (spring upper side) mounting of the respective damping force variable dampers DMP. In addition, each damping force variable damper DMP
Acceleration sensors G at three places on the vehicle body
S may be attached, and the acceleration at four points of the attachment portion of each damping force variable damper DMP may be calculated.

FIG. 2 is a fragmentary overall view of a variable damping force damper to which the present invention is applied. The configuration of the present damper is the same as the configuration described in the specification of Japanese Patent Application No. 8-330546 filed by the same applicant.
A cylinder 2 of a damper is coaxially received and fixed therein, and a piston member 3 is provided in the cylinder 2 so as to be able to reciprocate in the axial direction. The piston member 3
The piston rod 4 coaxially connected to the cylinder 2
From above in the figure.

A dish-shaped bracket 5 connected to the vehicle body is concentrically fixed to an upper portion of the extended portion of the piston rod 4 in the drawing, and is mounted on an outer peripheral surface of an intermediate portion in the axial direction of the casing 1. Is fixed to an annular bracket 6 having a J-shaped cross section. A compression coil spring 7 is coaxially interposed between the brackets 5 and 6.

The step motor 8 is fixed to a support bracket 9 attached to the upper side of the bracket 5 in the drawing, facing the rod end in the direction in which the piston rod 4 extends. One end of a control rod (not shown) received in a through hole provided coaxially in the piston rod 4 is connected to a drive shaft (not shown) of the step motor 8.

In the cylinder 2 chamber, two oil chambers (in the case of an oil damper) 2a are provided in the axial direction by a piston member 3 in the axial direction.
2b, and a damping force is generated by flowing oil from one oil chamber to the other oil chamber in the piston member 3 which is displaced in response to an external force.

Next, the structure of the biston member 3 according to the present invention will be described below with reference to an enlarged sectional view of a main part of FIG. A nut-shaped enlarged portion of a rod end 10 is screwed to an axial end of the piston rod 4 immersed in the cylinder 2, and a cylindrical piston member 3 is attached to a small-diameter cylindrical portion of the rod end 10. Are fitted. A lock nut 11 is screwed to the distal end of the small-diameter cylindrical portion of the rod end 10. The collar 12 is provided at both ends in the axial direction of the piston member 3 to stop the enlarged diameter portion of the rod end 10. The piston member 3 is fixed while being held in the axial direction by the nut 11, and the rod end 10 and the piston member 3 are integrally assembled with each other.

The piston member 3 has an axially intermediate portion whose outer diameter is substantially the same as the inner diameter of the cylinder 2. The inner peripheral surface of the cylinder 2 is connected to the piston member 3 via a low friction material fitted to the outer peripheral surface thereof. Are provided in a liquid-tight manner and slidable in the axial direction. The piston member 3 is opened at an intermediate portion in the axial direction of the outer peripheral surface thereof, and is dug obliquely with respect to the axis in opposite directions so as to easily take in oil by the flow of oil when the damper expands and contracts. The damper extension side flow path 13 and the damper contraction side flow path 14 are formed.

At the time of damper extension, the damper extension side flow path 13
The oil flows in the direction of arrow A in the figure, and when the damper contracts, the oil flows in the direction of arrow B in the figure into the damper contraction side flow path 14. Each channel 13/14
In the piston member 3 through a common flow path on the inlet side,
Flow path 13a for setting the upper limit of damping force of relatively small cross-sectional area
14a and the flow paths 13b and 14b for setting a damping force rise having a relatively large cross-sectional area. The damping force upper limit setting passages 13a and 14a are provided so as to communicate with each other at a relatively small inclination angle with respect to the axis, and each open near the inner peripheral side of the axial end surface of the piston member 3. . Each of the outlets is provided with a main valve 15 or 16 made of an elastic material.

Flow paths 13b and 14 for setting damping force rise
b is a damping force upper limit setting flow path 13a / 14 with respect to the axis.
The piston members 3 are provided so as to communicate with each other at an inclination angle larger than a, and each of the piston members 3 is directed toward the axially central portion of the inner peripheral surface of the piston member 3. A pair of circumferential grooves are provided on the inner peripheral surface of the piston member 3 at the axial center and the axial end, respectively, and each damping force upper limit is set at the axial center of each circumferential groove. The use flow paths 13a and 14a communicate with each other.

In the small-diameter cylindrical portion of the rod end 10, a cylindrical valve body 18 coaxially extended with the control rod 17 is rotatably received. The valve element 18 has two radial through holes 1 arranged in series in the axial direction and separated from each other.
8a and 18b are provided. Each of the radial through holes 18a and 18b is provided with a pair of opening windows 10a and 18a respectively communicating with four small diameter cylindrical sleeve portions of the rod end 10 at four locations corresponding to four circumferential grooves.
The two parts 10b and 10c and 10d are separately connected to each other on the control rod 17 side and the tip side.

These radial through holes 18a and 18b are
As shown in FIG. 4, each of the openings 10a and 10b has a pair of opening windows 10a and 10b as described above. Corresponding to 10c and 10d, the flow path of the valve element 18 is set to the maximum possible.
One of the radial through holes 18a is formed as an elongation-only flow path that can communicate with the damping force rising setting flow path 13b, and the other radial through hole 18b is formed as a damping force rising setting flow path 14b. It is formed as a shrink-only channel that can communicate.

A flow passage communicating with each axial end of a circumferential groove formed in the piston member 3 is provided with a main valve 15.
16 and the piston member 3
In the vicinity of the outer peripheral side of the end face in the axial direction. The damping force upper limit setting passages 13a and 14a are respectively opened at radially inner portions of both end surfaces in the axial direction of the piston member 3, and are provided such that the main valves 15 and 16 open and close the openings. ing. The radially outer portions of both end surfaces in the axial direction of the piston member 3 correspond to the main valve 15.1
6 is formed with a step that is one step higher than the radially inner portion provided with flow passages 13d and 14d in the radially outer portion, from an elastic body that selectively opens and closes each opening. Are provided.

In the damper thus constructed, as described above, the stepping motor 8 is rotated by a predetermined angle in accordance with the output of the damping characteristic switching signal from the control unit ECU, and the valve body 18 is rotated about the axis. Are rotated at the same angle. Due to the position change of the valve element 18 in the rotation direction,
Each opening window 10a provided in the sleeve portion of the rod end 10
-Since the cross-sectional area of the communication passage with 10b and 10c and 10d changes, the damping force can be arbitrarily changed.

Next, the control according to the present invention will be described below with reference to the flowchart of FIG. In the first step ST1, the acceleration sensor GS reads the sprung acceleration as a measurement of the sprung vibration waveform signal value of the damper device. In the next second step ST2, the first step ST1
A process of passing the sprung acceleration measurement value read in step 1 through a band-pass filter (not shown) is performed.

Here, the frequency band (pass band) to be passed by the band-pass filter is set in a region (PB in FIG. 6) between the sprung resonance frequency and the unsprung resonance frequency. FIG. 6 is a diagram illustrating vibration transmission characteristics when the damping force of the damper is infinite (solid line in the figure) and when the damping force is 0 (imaginary line in the figure). As can be seen from the drawing, the infinite damping characteristic is preferable at the sprung resonance point RU and the unsprung resonance point RD, and the zero damping characteristic is good at other points.

As shown in the figure, the frequency at which the above-mentioned zero attenuation characteristic is better is around 5 Hz. S. As can be seen from FIG. 7 showing the resonance curve of the human abdomen according to the study of Clark et al., The human abdominal resonance is around 5 Hz, which also corresponds to the fact that the driver feels strong discomfort particularly in the abdomen especially when riding.

In a third step ST3, the signal value S processed by the band pass filter is compared with a predetermined threshold value TH. Since it is better to have the zero attenuation characteristic as described above in the passband PB, in the case of switching between the low attenuation characteristic and the high attenuation characteristic as in this example, the low attenuation characteristic is set. It is better to do. Therefore, the threshold value TH is set to a value by which it is possible to determine whether the input is a large input that deteriorates the ride quality.

If it is determined in the third step ST3 that the signal value S is larger than the threshold value TH, the process proceeds to a fourth step ST4, where the signal is set to a low attenuation characteristic, and the signal value S is set to the threshold value TH. If it is determined to be smaller than the fifth
The process proceeds to step ST5, where high attenuation characteristics are set. In these fourth and fifth steps ST4 and ST5, a damping characteristic switching signal for rotating the valve body 18 to a position corresponding to each setting is output from the control unit ECU as described above, and the step motor 8 is controlled to Switch to attenuation characteristics.

The above control will be described with reference to FIG. 6. In the frequency region including the sprung resonance frequency lower than the pass band PB and the frequency region including the unsprung resonance frequency higher than the pass band PB, the infinite attenuation characteristic (high Damping characteristic)
In the frequency domain of the passband PB, a zero attenuation characteristic (low attenuation characteristic) having a high damping force is obtained. Therefore, the sprung and unsprung resonance can be suppressed, and the resonance of the human abdomen can be suppressed, so that the riding comfort can be improved.

[0027]

As described above, according to the present invention, resonance can be suppressed by a high damping characteristic at each of the sprung and unsprung resonance frequencies requiring high damping force. Since zero damping has a higher damping force than infinite damping, a pass signal value of a band-pass filter that is allowed to pass between both resonance frequencies is compared with a predetermined threshold value,
By switching to the low damping characteristic when the passing signal value exceeds the threshold value, the damping force when the vibration between the two resonance frequencies is large can be increased, and the vibration that adversely affects the riding comfort can be suitably suppressed. And improve the ride comfort.

Further, when an input exceeding the response frequency of the switching of the damping force occurs, the control for improving the ride comfort becomes unstable, and in such a case, the ride comfort may be deteriorated. According to the present invention, since the high attenuation characteristic is fixed in a frequency region (pass band) other than the frequency region (pass band) that can pass through the band-pass filter, the riding comfort can be stably improved in all frequency regions.

[Brief description of the drawings]

FIG. 1 is a schematic layout view of a main part of a vehicle equipped with a variable damping force damper to which the present invention is applied.

FIG. 2 is an overall cutaway view of a main part of an automobile damper to which the present invention is applied.

FIG. 3 is an enlarged sectional view of a main part showing a piston member of the damper.

FIG. 4 is a fragmentary perspective view showing a valve element.

FIG. 5 is a diagram showing a control flow based on the present invention.

FIG. 6 is a diagram showing infinite damping characteristics and zero damping characteristics in an automobile suspension.

FIG. 7 is a diagram showing a resonance curve of a human abdomen.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Casing 2 Cylinder, 2a, 2b Oil chamber 3 Piston member 4 Piston rod 5 Bracket 6 Ring bracket 7 Compression coil spring 8 Actuator 9 Support bracket 10 Rod end, 10a, 10b, 10c, 10d
Opening window 11 Lock nut 12 Collar 13 Damper extension side flow path 14 Damper compression side flow path 13a / 14a Damping force upper limit setting flow path 13b / 14b Damping force rise setting flow path 13c / 13d / 14c / 14d flow path 15. 16 Main valve 17 Control rod 18 Valve body, 18a / 18b Radial through hole 19/20 Sub valve

 ──────────────────────────────────────────────────の Continuation of front page (72) Inventor Tsukasa Fukusato 1-4-1 Chuo, Wako-shi, Saitama

Claims (1)

[Claims] 1. A damper device capable of switching to at least high and low damping characteristics is normally set to the high damping characteristics, a sprung vibration waveform of the damper device is measured, and a sprung and unsprung spring of the damper device is measured. The measured value is processed by a band-pass filter set to be able to pass a frequency between the respective resonance frequencies, and when the signal value of the measured value that has passed through the band-pass filter is larger than a predetermined threshold value, Is a method for controlling a damping force variable damper, characterized by switching to the low damping characteristic.