JPH03213737A - Variable damping force type shock absorber control device - Google Patents

Abstract

PURPOSE:To prevent the generation of shock and noise caused by change-over by providing a current application control means for stopping current application to a piezoelectric actuator for the fixed time before and after the arrival of an advancing valve body at the specified position. CONSTITUTION:When a current is applied to a piezoelectric actuator 5, the piezoelectric actuator 5 is expanded according to the stored amount of charge, and in association with this, a valve body 4 advances at high speed. A current application control means 6 then stops current application to the piezoelectric actuator 5 when the advancing valve body 4 enters within the fixed time range before reaching the specified position. Even under the current application stopped state, the valve body 4 continues its advance by operating oil, the response delay of the piezoelectric actuator and the inertia of the valve body 4 itself while its advance speed is lowered, and surpasses the specified position. After the lapse of the fixed time, the current application control means 6 resumes current application, so that the expansion speed of the piezoelectric actuator 5 and the operating speed of the valve body 4 are returned to the original speed, and the valve body 4 is operated rapidly toward the set position. In this set position, piston communicating passages 31, 32 have specified opening areas for the flow of operating oil.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for a variable damping force shock absorber, and more particularly to a control device designed to reduce shock when switching damping force.

[Prior Art] Various types of shock absorbers with variable damping force have been proposed. Among them, Japanese Patent Laid-Open No. 61-85210 discloses a system in which a piston sliding in a cylinder is provided with a throttle passage and a communication passage. It has been proposed that the passage is opened and closed by a spool valve driven by a piezo actuator made up of stacked piezoelectric plates to change the magnitude of the generated damping force.

[Problems to be Solved by the Invention] By the way, in the shock absorber having the above structure, when the spool valve is operated at high speed, there is a problem that the hydraulic oil flows rapidly when the communication passage starts to open, causing shock and abnormal noise. Ta. To prevent this, the spool valve may be operated at a sufficiently low speed, but this naturally reduces responsiveness.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a control device for a variable damping force shock absorber that can effectively prevent the occurrence of shocks and abnormal noises when a valve body such as a spool valve operates without reducing responsiveness. do.

[Means for Solving the Problems] To explain the present invention in detail, a control device for a variable damping force shock absorber has a piston 2 that partitions a cylinder 1 (FIG. 1) into a pair of hydraulic chambers 1a and 1b, which has the above-mentioned Both hydraulic chambers 1
A and 1b are formed as communication passages 31 and 1b, and a valve body 4 is provided facing the communication passage 31 and 32 so as to be movable forward and backward, so that when the advanced position of the valve body 4 exceeds a predetermined position, The passage opening area of the communication passages 31 and 32 is made larger than zero according to the amount of advancement, and a piezo actuator 5 is provided to drive the valve body 4 forward and backward, and the valve body 4 advances to the predetermined position. An energization control means 6 is provided for stopping energization to the piezo actuator 5 for a certain period of time before and after reaching the position.

[Operation] In the above configuration, when the piezo actuator 5 is energized, the piezo actuator 5 expands according to the amount of accumulated charge, and the valve body 4 advances at high speed accordingly. The energization control means 6 stops energizing the piezo actuator 5 within the predetermined time period before the valve body 4 advances and reaches the predetermined position. Even if the energization is stopped, due to the response delay of the hydraulic oil and piezo actuator 5 and the inertia of the valve body 4, the valve body 4 moves beyond the predetermined position with a reduced advancement speed. After the predetermined period of time has elapsed, the energization control means 6 starts energizing again, the expansion speed of the piezo actuator 5 and the operating speed of the valve body 4 return to their original values, and the valve body 4 rapidly moves toward the set position. At the set position, piston communication #I31.
32 has a predetermined opening area, hydraulic oil flows therethrough, and the generated damping force becomes small.

Since the advancing speed of the valve body 4 is reduced before and after the predetermined position where the communication passages 31 and 32 begin to open, sudden outflow of hydraulic oil does not occur, and the generation of shocks and abnormal noises is prevented. be done.

In this case, since the operating speed of the valve body 4 is reduced only before and after the predetermined position when advancing, the overall responsiveness is reduced.

[Example] Fig. 1 shows a cross section of the main part of a shock absorber, and a main piston 2 is inserted into the cylinder 1 so as to be able to slide vertically, so that the inside of the cylinder 1 has upper and lower hydraulic chambers 1a,
It is divided into 1b. The main piston 2 is fixed to a piston rod 3 passing through the center, and the piston rod 3 is connected to the lower end of a shaft 7 extending upward.

The main piston 2 has a contraction side fixed orifice 21 and an expansion side fixed orifice 22 formed on its outer circumference, which pass through the main piston 2, and are opened and closed by plate-shaped check valves provided on the upper and lower surfaces of the main piston 2, respectively. . piston rod 3
Inside, there are formed a horizontal communication passage 31 that extends horizontally from the side facing the upper hydraulic chamber 1a, and a vertical communication passage 32 that extends downward from this, expands in diameter midway, and connects to the lower hydraulic chamber 1b. The communication path 31 is blocked by a lower end portion of a spool valve 4 disposed within the piston rod 3 so as to be movable up and down. This spool valve 4 is urged upward by a coil spring 43 provided around it.

The details of the spool valve 4 will be explained with reference to FIG. 2. An annular groove 41 of a constant depth is formed on the outer periphery of the upper end of the spool valve 4, and in the illustrated state where the spool valve 4 is in the upper retracted position, Since the position of the annular groove 41 is completely shifted from the horizontal communication path 31, the horizontal communication path 31 is in a blocked state. When the spool valve 4 advances downward by a distance g and reaches a predetermined position, the annular groove 4
The lower surface of the horizontal communication path 31 coincides with the upper surface of the horizontal communication path 31, and the horizontal communication path 31 begins to communicate with the annular groove 41 and open. When the spool valve 4 further advances, the amount by which the annular groove 41 communicates with the horizontal communication passage 31 increases, and the opening area of the passage increases in accordance with the amount of advancement of the spool valve 4.

The lower end of the shaft 7 is formed into a cylindrical shape, and the piezo actuator 5 is provided inside the cylinder.

The piezo actuator 5 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 from an external energization control circuit 6 via a lead wire 51. A piston 52 is provided in contact with the lower end of the vinyl actuator 5, an oil-tight chamber 53 is formed below the piston 52, and a plunger 42 is disposed facing the oil-tight chamber 53 so as to be movable up and down. . This plunger 42 is connected to the spool valve 4.

A load sensor 71 is located at the uppermost end of the cylinder at the lower end of the shaft 7.
The load sensor 71 is composed of stacked piezoelectric ceramic plates sandwiched between electrodes, and emits an output signal corresponding to the damping force generated in the shock absorber.

During the contraction operation in which the main piston 2 moves downward, the sealed oil flows between the hydraulic chambers 1a and 1b through the large-diameter fixed orifice 21 on the contraction side, producing a somewhat small damping force, while the main piston During the extension operation in which the pump 2 moves upward, the sealed oil flows between the hydraulic chambers 1a and 1b via the small-diameter fixed orifice 22 on the extension side, producing a slightly large damping force.

These damping forces can be greatly changed by moving the spool valve 4 forward and backward using the piezo actuator 5 and changing the opening area of the horizontal communication passage 31. line x in the diagram,
The characteristic when the aperture area is reduced in y is shown by the line x- in the same figure.
Indicated by 1y-.

FIG. 4 shows the configuration of the energization control circuit 6.

The energization control circuit 6 includes a CPU 61 whose operation will be described later, and a RAM 63 and a ROM 6 connected to this by a common bus 62.
4, an input section 65, and an output section 66, and damping force change rate data is inputted to the input section 65 from a damping force change rate detection circuit 67. The damping force change rate detection circuit 67 receives an output signal from the load sensor 71 provided inside each shock absorber provided at the left and right positions of the front and rear wheels.

An output signal from a vehicle speed sensor 70 is further input to the input section 65 via a waveform shaping circuit 68. Further, a drive voltage is outputted from the output section 66 via a drive circuit 69 to the piezo actuator 5 installed inside each shock absorber.

As shown in FIG. 5, the damping force change rate detection circuit 67 includes an amplifier circuit 671 with a filter using an operational amplifier and an A/D.
It consists of a converter 672, and the output signal of the load sensor 71 is
After amplification, it is digitally converted into damping force change rate data.

The configuration of the drive circuit 69 is shown in FIG. An extension control signal and a contraction control signal are outputted from the CPU 61 via the output section 66, and are received by the input quadrant 91.692, respectively. Each of the above control signals is a high frequency pulse, and is smoothed through pulse transformers 693 and 694 and supplied to the base of each output transistor 95 and 696. When the output transistor 95 is brought into conduction, a high positive voltage is supplied from a DC-DC converter (not shown) to the piezo actuator 5, and the piezo actuator 5 is charged and extended.

On the other hand, when the output transistor 96 is made conductive, the output transistor 9 passes through the diode 697.
The emitter of 5 becomes a negative voltage, and the piezo actuator 5
is caused to contract by discharge.

The processing procedure within the CPU 61 will be explained below with reference to FIG.

In step 101, data is initialized, and in step 102, a vehicle speed signal is input, and subsequently, in step 1O3, damping force change rate data DFC is input. In step 104, positive and negative threshold values Vrefl and Vref2 are calculated. A correction map is stored in advance for these threshold values Vrefl and Vref2 so that they increase as the vehicle speed increases, as shown in FIG.

In steps 105 and 106, it is determined whether the damping force change rate data exceeds each of the threshold values in the positive or negative direction, and if it does, an extension control signal is output to cause the piezo actuator 5 to extend. , the spool valve 4 is advanced to reduce the damping force generated by the shock absorber, that is, to change it to a soft one (step 107). After this soft damping force is maintained for a time T (step 108)
, a contraction control signal is issued, and the damping force generated by the shock absorber is increased, that is, returned to a hard one (step 109).

To explain step 107 in detail with reference to FIGS. 9 and 10, in step 201, the spool valve 4 is advanced to maintain the damping force generated by the shock absorber in a soft manner for the time T (FIG. 10 (1)). calculate. As shown in FIG. 11, this time T is a constant time T1 in a low vehicle speed region, gradually becomes shorter as the vehicle speed increases beyond this low vehicle speed region, and becomes a constant time T2 in a high vehicle speed region.

Next, the time for outputting the first expansion control signal (about 4 ms) is set in the counter TOH (step 202).
The control signal is output, and the transistor 695 is made conductive until the counter TON becomes 0. As a result, the piezo actuator 5 expands, and the spool valve advances at high speed until it approaches the distance ρ shown in FIG. 2 where the lateral communication passage 31 begins to open.

In step 205, a certain period of time (about 1 ms) for stopping the output of the expansion control signal is set in the counter T OFF.
The output of the extension control signal is stopped and the counter T OF
Transistor 695 is rendered non-conductive until F becomes O.

At this time, due to the response delay of the hydraulic oil and piezo actuator 5 and the inertial force of the spool valve 4, the spool valve 4 continues to advance at a low speed and crosses the above-mentioned path Mρ.

When the counter TOFF becomes 0, the extension control signal is outputted again, the transistor 695 becomes conductive, and the spool valve 4 is operated to advance at high speed again.

The advancing operation of the spool valve 4 is performed until the applied voltage shown in FIG. 10 (2) is saturated, and as a result, the opening area of the communication passage becomes a predetermined size, and the damping force generated by the shock absorber becomes soft. Become.

In this way, for a certain period of time before and after the spool valve 4 starts opening the horizontal communication passage 31, the piezo actuator
By stopping the power supply to the spool valve 4, the speed of the spool valve 4 can be made sufficiently low in this part, preventing rapid flow of hydraulic oil and effectively eliminating the occurrence of shock and abnormal noise. be able to.

In addition, in the above embodiment, application to a shock absorber in which the generated damping force is switched between soft and hard using a spool valve was explained, but as shown in FIG. It can also be applied to shock absorbers that switch between soft and hard force.

. [Effects of the Invention] As described above, according to the variable damping force shock absorber control device of the present invention, when opening the communicating passage and softly switching the generated damping force, the valve body is operated only before and after the opening of the communicating passage is started. The low speed prevents shocks and abnormal noises caused by switching, and since the valve body is operated at low speed only in a limited range, the overall switching response is minimized. It can be suppressed slightly.

[Brief explanation of drawings]

Figure 1 is a sectional view of the main parts of the shock absorber, Figure 2 is an enlarged sectional view of section A in Figure 1, Figure 3 is a diagram showing the damping force characteristics generated by the shock absorber, and Figure 4 is a block of the energization control circuit. Configuration diagram, Figure 5 is a circuit diagram of the damping force change rate detection circuit,
Fig. 6 is a circuit diagram of the drive circuit, Fig. 7 is a program flowchart, Fig. 8 is a diagram showing threshold change characteristics, and Fig. 9 is a diagram showing the change characteristics of the threshold value.
The figure is a program flowchart, Figure 10 is a diagram showing changes in signals over time, Figure 11 is a diagram showing speed dependence of time T, and Figure 12 is a sectional view of main parts of a shock absorber showing another example of the present invention. It is. 1...Cylinder 1a, 1b...Hydraulic chamber 2...Piston 21.22...Orifice 3...Piston rod 31...Horizontal communication passage (communication passage) 32...Vertical communication passage ( Communication path) 4... Spool valve 5... Piezo actuator 6... Energization control circuit (energization control means) Fig. 1 Fig. 2 Fig. 3 (kg) Fig. 4 Fig. 5 Fig. 7 Fig. 6 Figure 7 Figure 8 Figure 10 Figure 1 2 T3 Figure 9

Claims (1)

[Claims] The piston that divides the inside of the cylinder into a pair of hydraulic chambers is provided with a communication passage that communicates the two hydraulic chambers, and a valve body that faces the communication passage and is movable forward and backward, so that the advancing position of the valve body is set at a predetermined position. A piezo actuator is provided so that the opening area of the communication passage increases from zero according to the amount of advancement when the valve body advances beyond the position, and a piezo actuator is provided to drive the valve body forward and backward, and the valve body advances to the predetermined position. A control device for a variable damping force shock absorber, characterized in that it is provided with energization control means for stopping energization to the piezo actuator for a certain period of time before and after the piezo actuator reaches the position.