JPH042516A - Damping force variable shock absorber control device - Google Patents

Abstract

PURPOSE:To reduce gate vibration, sensible vibration and fluttering vibration by detecting plural frequency signals from the components of damping force detecting signals to integrate each of frequency signals so that the components of gate vibration, sensible vibration and fluttering vibration can be detected and setting base damping force in accordance with each of components. CONSTITUTION:A damping force detecting means A which detects damping force generated in a shock absorber is provided so that signals with plural frequency components may be detected by a frequency signal detecting means B from the components of damping force detecting signals detected by the damping force detecting means A. An integrating means C integrates each of signals with abovementioned plural frequency components detected by the frequency signal detecting means B to detect respective components of gate vibration, fluttering vibration and sensible vibration, and so a base damping force setting means D sets the base damping force of the shock absorber in accordance with these components.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control device for a shock absorber in which a piezo actuator or the like is installed to vary damping force, and the present invention relates to a control device for a shock absorber that has a piezo actuator or the like installed therein and has variable damping force, and is a control device that realizes stable running and a comfortable ride. Regarding.

[Conventional technology]

Shock absorbers with variable damping force that change the generated damping force by changing the diameter of the restrictive flow path provided in the piston through the operation of a piezo actuator are in practical use, and various attempts have been made to use this to improve the comfort and drivability of vehicles. being done.

Among these, for example, Japanese Patent Application Laid-open No. 64-67407,
A control device has been proposed that detects the damping force change rate of a shock absorber and switches the damping force generated by the shock absorber to a smaller (softer) side when the rate of change exceeds a predetermined threshold.

[Problem to be solved by the invention]

However, with the device proposed above, the damping force can only be set in two stages, hard and soft, and when the damping force is soft, swinging vibrations and fluttering vibrations may occur.
Furthermore, when the damping force is ``heart''', there is a problem that bodily vibrations occur and the riding comfort deteriorates.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control device for a variable damping force shock absorber that generates a damping force that reduces tilting vibration, fluttering vibration, and bodily sensation vibration to realize comfortable driving.

[Means to solve the problem]

As a means for solving the above problems, the present invention includes a damping force detection means for detecting the damping force generated in a shock absorber as shown in FIG. a frequency signal detecting means for detecting a signal of the plurality of frequency components detected by the frequency signal detecting means; an integrating means for integrating each of the signals of the plurality of frequency components detected by the frequency signal detecting means; A control device for a variable damping force shock absorber is proposed, comprising: base damping force setting means for setting the base damping force of the shock absorber according to an integrated value.

[Operation] As a result, multiple frequency signals are detected from the components of the damping force detection signal, and by integrating these multiple frequency signals, the tilting vibration component, the bodily sensation vibration component, and the fluttering vibration component are detected. The base damping force of the shock absorber is arbitrarily set according to the component. Therefore, base damping force can be generated to reduce tilting vibration, bodily sensation vibration, and fluttering vibration.

[Embodiment] FIG. 2 shows the overall configuration of a control device. The control device 1 has a CPU 2 whose operation will be described later, a RAM 4, a ROM 5, an input section 6, and an output section 7 connected to the CPU 2 by a common bus 3. Damping force data is inputted to the input section 6 from a damping force detection circuit 8, and this damping force detection circuit 8 is supplied with the output of each shock absorber 2 (H) provided on the left and right positions of the front and rear wheels. Signals are manually operated.

The input section 6 further receives output signals from a steering sensor 12, a brake sensor 13, a throttle sensor 14, and a wheel speed sensor 15 via a waveform shaping circuit 10.

A drive voltage is output from the output section 7 to a piezo actuator 17 provided inside each shock absorber 20 via a drive circuit 16.

A cross section of a main part of the shock absorber 20 is shown in FIG. In the figure, the cylinder 23 of the Shiyo Noku Absono X20
The inner space is divided into upper and lower hydraulic chambers 20a and 20b by a main piston 24, respectively.The main piston 24 is fixed to a piston rod 25 that is fitted through the center, and the piston rod 25 is connected to a shaft 26 that extends upward. connected to the bottom end.

The main piston 24 has a contraction-side fixed orifice 241 and an extension-side fixed orifice 2 on its outer periphery.
42 are formed, and are opened and closed by plate-shaped check valves 243 and 344 provided on the upper and lower surfaces of the main piston 24, respectively. Inside the piston condo 25, there is a sub-flow path 25 which passes through the center of the loft and exits downward from the surface facing the upper hydraulic chamber 20a.
1 is formed, and the sub-flow passage 251 has its flow passage cross-sectional area changed by an annular groove on the outer periphery of the sprue valve 252 that operates up and down.

The lower end of the shaft 26 is shaped into a cylinder, and a piezo actuator 17 is provided inside the cylinder. The piezo actuator 17 is constructed by laminating a large number of piezoelectric ceramic plates such as PZT, and expands and contracts in accordance with a drive voltage supplied through a lead wire 211. A piston 212 is provided in contact with the lower end of the piezo actuator 17, an oil-tight chamber 213 is formed below the piston 212, and a plunger 214 is disposed facing the nuclear oil-tight chamber 213 so as to be movable up and down. This plunger 214 is the spool valve 2
52.

At the uppermost end of the cylinder at the lower end of the set 26 described above, there is a vinyl '7'.
A sensor 9 is provided, which is made by stacking the piezo sensor 9 and a piezoelectric ceramic plate with electrodes in between, and generates an output signal corresponding to the rate of change of the damping force generated in the absorber 20.

Therefore, when the main piston 24 moves downward during the contraction operation, the sealed oil flows between the hydraulic chambers 20a and 2Ob through the large-diameter fixed orifice 241 on the contraction side, producing a slightly small damping force. 24 is -L
During the extension operation of moving in the direction, the sealed oil flows between the hydraulic chambers 2a and 2b through the small-diameter fixed orifice 242 on the extension side, producing a slightly large damping force.

These damping forces can be continuously changed by operating the spool valve 252 by the piezo actuator 17 and continuously changing the flow passage cross-sectional area of the sub-flow passage 251.

That is, as shown in FIG. 4, any damping force can be generated between the characteristics x, y when the cross-sectional area of the flow path is increased and the characteristics x' and y′ when the cross-sectional area of the flow path is decreased.

Here, the length of the piezo actuator 17 changes due to thermal expansion when the ambient temperature changes.

Further, the volume of the sealed oil increases due to thermal expansion, and a considerable amount of the sealed oil leaks from the oil-tight chamber 213, and the volume decreases due to this leakage. Therefore, even if the piezo actuator is energized under the same conditions, the amount of movement of the spool valve 252 fluctuates due to the influence of ambient temperature and oil leakage, and the damping force may not be uniquely determined.

Therefore, in this embodiment, the piezo actuator 17 is caused to perform expansion and contraction operations at predetermined intervals (for example, every 10 minutes), and the sealed oil is introduced into the oil-tight chamber 213 via the check valve 30. As a result, the oil-tight chamber 213 is filled with sealed oil when the piezo actuator I7 contracts, and the volume reduction due to oil leakage is corrected. Furthermore, even if the length of the piezo actuator 17 changes due to temperature changes, the oil-tight chamber 21
The amount of oil sealed in the piezo actuator 17 is offset by the amount of oil sealed in the piezo actuator 17, so that a damping force corresponding to the amount of current applied to the piezo actuator 17 can be obtained at all times.

FIG. 5 shows the configuration of the drive circuit 1G. The above CPU2 (
The digital control signal output from the D/A converter 191 is converted into an analog signal by the low-pass filter 1.
99 and is input to the comparator 192. A comparator 192 compares the control signal voltage with the voltage of a piezoelectric charge amount detection capacitor 198 that is foot-hacked via a Hanfa 196. When the control signal voltage is large, the comparator 192 outputs the IJ level signal, the photocoupler 193A is turned off, and the output FET1 is disconnected.
94A conducts, DC/DC core Hark 197
The high voltage generated by the piezo actuator 17
is applied to charge this.

The charging current at this time is kept constant by the current feed bank circuit 195A.

When the voltage of the actuator 17 increases and the foot bank voltage exceeds the control signal voltage, the output signal of the comparator 192 becomes "oJ level. When the comparator signal reaches [oJ level, the photocamera 193B is extinguished and disconnected, the output FET 194B becomes conductive, and the piezo actuator 17 is discharged.The discharge current is kept constant by the current feed hack circuit 195B.

In this way, the amount of charge stored in the actuator 17, that is, the amount of its extension, corresponds to the signal level of the control signal, and the damping force generated by the shock absorber 20 is continuously changed by the control signal.

The operation of this embodiment will be explained based on the flowchart of FIG.

Steps 8100 to 5106 are processes for gradually increasing the damping force when a change in attitude occurs in the vehicle. First, in step 5IO1, the lateral C (-C,) applied to the vehicle is determined by the signals from the vehicle speed sensor 11 and the steering sensor 12.
is estimated using the following formula.

G=k・θ・vl・4 (k is a proportional constant, θ is the steering angle of change, and ■ is the vehicle speed) In addition, in step 5102, the signals from the brake sensor 13, throttle sensor 14, and wheel speed sensor 15 cause the vehicle to The before and after G (=G2) is estimated and calculated. Next, in step 5103, step 5101 and step 510
2, the sum of the absolute values of G and G2 I GII +
To calculate l Gzl and determine whether the vehicle can cause a posture change that can be felt by humans, the sum 1c, l + 1c2
1 and a predetermined value ε. When the sum 1G, l+1G21 is larger than the predetermined value ε, it is determined that the vehicle is capable of causing a posture change that can be felt by humans, and the process proceeds to step 5104, where the current base damping force F' is held. Step 8105
~5106 is the current damping force (base damping force Fi) when increasing the damping force according to the sum l Gr l + l czl.
This step is to find the increase in damping force for .

First, in step 5I05, the attitude control coefficient K, which corresponds one-to-one to the sum)G+lG21, is determined from the map of IC,l+021 and K. This attitude control coefficient takes a value of O~1 and is set so that l (g l + l
Then, in order to gradually increase the damping force in accordance with the posture change, that is, 1G, :→1Gzl, the damping force increase amount Δd for increasing the base damping force F' is determined by the following calculation formula.

ΔF=K ・(Fmax −F′) (A
) F' is the current base damping force, K is the attitude control coefficient, F
wax is the maximum damping force.

FIG. 7 is a diagram showing the temporal change in the damping force when the damping force is controlled according to the posture changes l G, l + l czl, and (A) 2 will be explained based on this diagram.

Letting the current Haese damping force F' be point A (F=F'), take the difference (HA) between the maximum damping force F max and this F' and multiply it by the attitude control coefficient K corresponding to 1c+l+:czl. Then, the damping force increase K·(Fmax-F') is calculated. This damping force increase corresponds to IA', and the addition of the base damping force F' to this increases the damping force, which becomes the next damping force.At this time, the damping force is switched from point A to point A' to increase the damping force.

When the change in vehicle attitude is large, that is, l GIl +
When l Gz l is large, the attitude control coefficient is also large, so the damping force increase K·(Fmax-F') becomes large, and the damping force changes rapidly.

Also, when the -1-s damping force is small, Fmax-F' becomes large, so the damping force increase K.multidot.(Fmax-F') becomes large, and the damping force quickly switches to a large damping force.

7 in FIG. 7 represents a change in damping force when the attitude change of 1G, 1±lG21, which is the same as in ■, occurs and the base damping force is smaller than in ■. At this time, damping force increase K・(Fmax
-F') takes a larger value than ■.

(K is the same for both ■ and ■) That is, the damping force increase from point B to B' is larger than that from point A-A', and the response to the desired damping force is improved. In other words, when the base damping force is small and when posture changes are large, increase the damping force with emphasis on responsiveness, and when the base damping force is large, the emphasis is on preventing shocks and noise caused by sudden changes in damping force rather than responsiveness. Emphasis is placed on reducing the increase in damping force.

Also, if the attitude change becomes smaller after the damping force increases, that is, if :G, :T1G, : becomes smaller, the attitude control coefficient will also become smaller, so the damping force increase K・(Fmax −
F') also decreases, and the damping force approaches the Heiss damping force.

At this time, the amount of decrease in the damping force increase increases as the base damping force F' decreases. When there is no change in attitude, the damping force increase becomes zero.

The damping force is calculated by adding the damping force increase ΔF obtained above to the base damping force F'.

This damping force is used as a damping force command signal at the time of posture change, and this signal drives the piezo actuator via the drive circuit 16 of the output section to control the damping force of the shock absorber.

If lG, l+lG, l is smaller than the predetermined value ε in step 5103, that is, if it is determined that the vehicle does not cause a posture change that can be perceived by humans, the process proceeds to step 5107;
The hold on the base damping force F' is released and a new base damping force F' is set in steps 8108 to 5112 below.

First, in step 5108, the output signal of the piezo sensor 9, which is a damping force detection signal, is input. and step 51
In 09, the piezo sensor signal is passed through three types of band-pass filters that serve as frequency signal detection means to detect the spring top resonance frequency signal (1 to 1.3H2)/\, the spring intermediate resonance frequency signal (2 to 6H2) B, and the bottom resonance. Frequency signal (9~12H
2) Separate C into three resonance frequency signals. Next, in step 5110, the three frequency signals A, B, and C obtained in step 5109 are integrated into an integrating means in order to obtain the vehicle's tilting vibration, bodily sensation vibration, and fluttering vibration.
^ Accumulate each voltage using an integrator and calculate the integrated values A, B, and C△. At this time, A is a vibration component, B is a perceptible vibration component, and C is a fluttering vibration component.

Next, in step 5111, go to the sum of A and C and C of B. Find the relative value (A+CL/B).

Step 3112 is a step to reduce the tilting vibration component, the bodily sensation vibration component, and the fluttering vibration component (calculating the base damping force).

It is set from a map of base damping force F' corresponding to /B and (A+C)/B.

^ By the way, A and C can be reduced by increasing the damping force, and B can be reduced by decreasing the damping force.

A △ △ As the map between the relative value (A+C)/B and the damping force goes up, the relative value becomes larger and the damping force corresponding to the relative value becomes larger. Also, as the weight increases, the relative value decreases, and the damping force corresponding to the relative value ΔA/% decreases. As described above, the heel damping force F' is calculated in order to reduce A, B, and C.

The base damping force F' calculated by the above operation is used as the damping force during normal running.

The next step 5114 is a step of determining whether or not there is a protrusion on the road surface. When it is determined that there is no protrusion, that is, when G<GO, the base damping force of the protrusion in step 5112 is set as the damping force command signal.

Here, the presence or absence of a protrusion on the road surface is detected in step 5113. First, the threshold value G is roughly set based on the input signal from the piezo sensor 9. When the threshold value is exceeded, it is detected that there is a protrusion on the road surface.

Also, if G≧00 in step 5114, that is, if there is a protrusion on the road surface, the process advances to step 5115, and the process proceeds to step 511.
The base damping force F' calculated in step 2 is switched to soft. Then, the soft damping force is used as a damping force command signal.

As described above, the piezo actuator is driven via the output section 7 and the drive circuit 16 using the damping force command signals from steps 5106, 5113, and 5l14, thereby controlling the damping force of the shock absorber.

By the way, the hand in this example is threshold G. is set to a predetermined value, but may be made variable depending on the unevenness of the road surface or changes in the attitude of the vehicle.

(Effects of the Invention) As described above, in the present invention, a plurality of frequency signals are detected from the components of the damping force detection signal, and each of these frequency signals is integrated to detect the tilting vibration component, the bodily sensation vibration component, and the fluttering vibration. The components are detected and the Haese damping force of the shock absorber is arbitrarily set to eliminate these components.This reduces tilting vibration, bodily sensation vibration, and fluttering vibration, improving ride comfort and realizing comfortable driving. This has an excellent effect.

[Brief explanation of drawings]

Figure 1 is a complaint response diagram, Figure 2 is a block diagram of the overall configuration of the control device, Figure 3 is a sectional view of the main parts of the shock absorber, Figure 4 is a characteristics diagram of the shock absorber, and Figure 5 is the circuit of the drive circuit. 6 is a flowchart showing the operation of the embodiment of the present invention, and FIG. 7 is a diagram showing the change in damping force over time. ■...Control device, 2...CPtJ, 3...Damping force detection circuit, 4...Piezo sensor, 17...Piezo actuator. Attorney Takashi Okabe

Claims (4)

[Claims] (1) a damping force detection means for detecting the damping force generated in the shock absorber; a frequency signal detection means for detecting signals of a plurality of frequency components from the components of the damping force detection signal detected by the damping force detection means; an integrating means for integrating each of the plurality of frequency component signals detected by the frequency signal detecting means; and setting a base damping force of the shock absorber according to an integrated value of the plurality of frequency signals integrated by the integrating means. A control device for a variable damping force shock absorber, comprising a base damping force setting means. (2) The frequency signal detection means detects a sprung mass resonance frequency signal, a spring intermediate resonance frequency signal between the sprung mass and the sprung mass, and an unsprung mass resonance frequency signal from the components of the damping force detection signal. The control device for a variable damping force shock absorber according to claim 1. (3) A damping force switching means for softly switching the damping force of the shock absorber from the base damping force when the damping force signal exceeds a predetermined threshold value. Alternatively, the variable damping force shock absorber control device according to 2. (4) longitudinal acceleration detection means for detecting longitudinal acceleration applied to the vehicle; lateral acceleration detection means for detecting lateral acceleration applied to the vehicle; and increasing the damping force in accordance with the sum of the longitudinal acceleration and the lateral acceleration. 2. The control device for a variable damping force shock absorber according to claim 1, further comprising a damping force increase calculation means for calculating a damping force increase to be added to the base damping force.