JPS636238A - Damping force control device of shock absorber - Google Patents

Abstract

PURPOSE:To provide a simple and compact device by furnishing a damping force sensor and a piezo actuator for change of damping force in a rod formed solidly with a piston fitted in an inner cylinder, such that the sensors and actuators are installed laminated one over another. CONSTITUTION:A piston 1 is fitted in an inner cylinder 3 to divide inside of the same into two oil pressure chambers 3a, 3b, and columnar piezo actuator 10 and damping force sensor 11 both consisting of piezo element are laminated solidly one over another in a rod 2 connected to said piston 1. When the piezo actuator 10 is elongated, for ex., a valve 26 is opened through plungers 21, 25, and flow paths 1a, 5a for communication of the two chambers 3a, 3b are opened to lessen the damping force. This current supply to the piezo actuator 10 is controlled via a control means with the detection signal from said damping sensor 1 so that optimum damping force is obtained in accordance with the operating condition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a shock absorber damping force control device for a vehicle using a variable damping force type shock absorber for a vehicle equipped with a damping force detection function.

The vehicle shock absorber damping force control device of the present invention includes:
It is used to variably control the damping force of a shock absorber depending on road surface conditions or vehicle motion conditions to improve the ride comfort of a vehicle.

Note that the road surface condition here refers to whether the road surface is flat or uneven. In addition, the dynamic state of the vehicle refers to the squat phenomenon that occurs when the vehicle starts suddenly, that is, the vehicle's tail-end condition, the nose dive phenomenon that occurs when the vehicle suddenly brakes, that is, the vehicle leans forward, and the roll phenomenon that occurs when the vehicle turns, that is, the vehicle's left-right direction. For example, the state of inclination.

[Conventional technology]

In order to further improve the riding comfort of an automobile, it is preferable to change the damping force of the shock absorber depending on the road surface condition and the motion condition of the vehicle. As a shock absorber for a vehicle having such a variable damping force function, for example, the one described in Japanese Patent Application Laid-open No. 194609/1982 is known. In this shock absorber, two hydraulic chambers are defined by a piston fitted into a cylinder, and a passage is provided to communicate the two hydraulic chambers. changing the damping force.

Conventional methods for adjusting the damping force of shock absorbers according to road surface conditions or vehicle motion conditions use many types of sensors attached to various parts of the vehicle body, such as steering wheel angle sensors, throttle sensors, brake sensors, or ultrasonic waves. The damping force is adjusted by indirectly estimating the road surface condition and vehicle motion condition based on the detection output of the road surface unevenness detection sensor.

(Problems to be solved by the invention) Conventional methods require many types of sensors to detect vehicle motion conditions and road surface conditions, resulting in high costs, and these conditions are determined by estimation. Furthermore, there are problems such as a lack of accuracy due to the use of ultrasonic sensors, and the fact that the detection function of road surface irregularities detected by ultrasonic sensors is degraded by mud splashes and is disadvantageous in terms of cost.

As a method to solve these problems, a method has been proposed in which the road surface condition and the vehicle motion condition are detected by the movement of a total of four shock absorbers attached to the front and rear wheels of the vehicle. This method focuses on the fact that the four shock absorbers exhibit characteristic movements as described below depending on road surface conditions or vehicle motion conditions, and distinguishes each state.

That is, when a squat phenomenon occurs when the vehicle suddenly starts, the front two shock absorbers are expanded, and the rear two shock absorbers are compressed. The opposite is true when a nose type phenomenon occurs during sudden braking. Furthermore, in the event of a roll phenomenon, the expansion and contraction of the left and right shock absorbers are reversed. Furthermore, when the vehicle travels on a significantly uneven road surface, each of the four shock absorbers expands and contracts randomly. Therefore, by knowing the expansion and contraction of the four shock absorbers and their relationship with each other, it is possible to know the vehicle motion state and road surface condition, and based on this information, the optimum vehicle motion state and road surface condition at that time can be determined. The damping forces of the four shock absorbers can be adjusted separately to achieve the desired condition.

When performing damping force control, for example, in order to detect phenomena such as large squat, nose dive, or roll, and control the damping force, it is necessary to detect and control these phenomena at the initial stage. A sufficient effect cannot be expected. The method to detect the expansion and contraction of the shock absorber is as follows:
A possible method is to directly measure the expansion/contraction length of the shock absorber using an expansion/contraction sensor. However, when attempting to detect phenomena such as squat, nose dive, or roll by detecting the expansion and contraction of the shock absorber using a conventional expansion/contraction sensor, it is difficult to determine whether the phenomenon is large enough to require damping force control. Or, it cannot be determined whether the phenomenon is so minor that it is not necessary until the phenomenon has progressed considerably, and therefore, it is difficult to perform effective damping force control using such an expansion/contraction sensor.

As a way to solve this problem, we focused on the fact that phenomena with large amounts of expansion and contraction progress in a short period of time, and calculated the time differential value of the amount of expansion and contraction of the shock absorber to find the expansion and contraction speed.
It is conceivable that this can be used as information, and by using this method, it is possible to make a judgment at the initial stage of a phenomenon such as squatting or nose type as to whether the phenomenon is serious or not.

However, this method requires a process of time-differentiating the output of the telescopic sensor, and a processing circuit is required for that purpose. The problem is that it has a complicated structure as disclosed in the above publication.

Therefore, in view of the above-mentioned technical problems, the present invention is based on the knowledge that the damping force of a shock absorber is set to be generated almost corresponding to the expansion/contraction speed, so it can be substituted for the expansion/contraction speed. Based on the concept of incorporating a damping force detection mechanism into the shock absorber itself, the system quickly and accurately detects the vehicle's motion state or road surface condition, and adjusts the shock absorber's damping force variable mechanism based on these conditions. It is an object of the present invention to provide a shock absorber control device which is accurately driven and has a simple structure in which a detection part and a driving part are integrated.

[Means for solving problems]

In order to solve the above object, the present invention includes a rod member that is slidably fitted into the cylinder, and a rod member that slides in the cylinder integrally with the rod member so that the cylinder is substantially divided into two hydraulic chambers. a damping force variable mechanism that changes the damping force of the shock absorber by changing the area of a wave path formed so as to communicate the two hydraulic chambers with each other, and a damping force variable mechanism provided inside the rod member. a telescopic actuator that is arranged inside the rod member and that expands and contracts in the axial direction of the rod member in response to a drive signal to drive the variable damping force mechanism; A damping force sensor detects damping force and converts it into an electrical detection signal, and a detection signal from the damping force sensor is input, and the telescopic actuator is driven to change the damping force of the shock absorber based on this detection signal. A control means for outputting a signal; and a control means for outputting a signal.

[Effect]

According to the above configuration of the present invention, the damping force generated by the shock absorber is detected by the damping force sensor inside the rod member, converted into an electrical detection signal, and extracted. Since the detection signal of the damping force sensor is approximately proportional to the expansion and contraction speed of the shock absorber, the road surface condition or vehicle movement condition can be determined based on this signal, so the control means can control the shock absorber based on this detection signal. A drive signal is output to the telescopic actuator to change the damping force. The telescopic actuator inside the rod member can drive the damping force variable mechanism to change the damping force of the shock absorber.

〔Effect of the invention〕

According to the present invention, it is possible to provide a shock absorber having a damping force variable mechanism with a damping force detection function.

Further, the shock absorber damping force control device of the present invention includes:
Since the telescoping actuator and the damping force sensor are provided inside the rod member, the structure can be made compact, and the electrical connection between the telescoping actuator and the damping force sensor can be easily made.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a sectional view of a shock absorber for a vehicle as an embodiment of the present invention. In Figure 1,
A piston 1 is slidably fitted into the cylinder (inner cylinder) 3, and the piston 1 substantially divides the cylinder 3 into two hydraulic chambers 3a.

It is classified into 3b. This cylinder 3 has an outer shell (
The outer shell 4 is fixed downward to the axle side. The piston 1 has hydraulic chambers 3a, 3
A throttle channel 1a is formed which communicates the channels b with each other.

Reference numeral 2 denotes a rod 2 connected to the piston 1, and a member 5 that is slidably fitted into an opening 1b provided in the piston 1 is fixed to the distal end side of the rod 2. A cap napft 6 is screwed onto the piston 1 with a coil spring 7 interposed therebetween, so that the piston 1 is pressed in the direction of the rod 2 and attached in a tightened state.

Inside the rod 2, a cylindrical piezoelectric actuator 10 serving as a telescopic actuator and a damping force sensor 11 are integrally stacked and provided, and this will be explained below based on FIG. 2.

A metal housing 12, a piezoelectric actuator 10 and a damping force sensor 11 provided in the housing 12 are housed in a chamber 2C provided in the upper rod 2a.

This piezoelectric actuator 10 is constructed by stacking a large number of disc-shaped piezoelectric elements 10a with electrode plates in between, and every other electrode plate is connected in parallel to form an application electrode 13, and alternate electrode plates are connected in parallel and grounded. It has a structure in which the electrode 14 is used, and is expanded in the axial direction by applying a voltage to the application electrode 13.

An electrode plate 10 connected to a ground electrode 14 is provided on the upper surface of the piezoelectric element 10a at the uppermost end of the piezoelectric actuator 10, and a single piezoelectric element serving as the damping force sensor 11 is laminated on the upper surface of this ground electrode plate. . An insulator case 1 is connected to the top surface of the piezoelectric element of the damping force sensor 11 via a detection electrode plate 15.
6 is provided, and an insulating case 17 is provided on the lower end surface of the piezoelectric actuator 10. In this way, the piezoelectric elements of the piezoelectric actuator 10 and the piezoelectric elements of the damping force sensor 11 are laminated together via one common ground electrode plate,
A laminate is constructed by housing this in cases 16 and 17. The ground electrodes 14 of the piezoelectric actuator 10 and the damping force sensor 11 are commonly grounded via a metal plate 18 interposed between the upper case 16 and the housing 12, the housing 12, and the rod 2.

An application lead wire 19 connected to the application electrode 13 of the piezoelectric actuator 10 and a detection lead wire 20 connected to the detection electrode plate 15 via the upper case of the damping force sensor 11.
is guided out of the absorber from the upper end of the loft 2 through the inside of the rod 2 and connected to the control device 25 . By making the ground electrode plate 1ob common and stacking them together in this way,
The number of lead wires led out to the outside of the absorber can be reduced and can be housed within the rod 2 with a compact structure.

Here, when stress is applied to the piezoelectric elements of the piezoelectric actuator 10 and the damping force sensor 11, an electric charge is generated on the surface based on the stress, and when a voltage is applied to the piezoelectric element in the thickness direction, a charge is generated on the surface according to the voltage. It is an element that expands and contracts in the thickness direction,
For example, it can be constructed from an element exhibiting a piezoelectric effect such as PZT (lead titanium zirconate) or barium titanate.

The attenuation sensor 11 may be a single piezoelectric element as described above, but if a plurality of piezoelectric elements are stacked to increase the charge generated by the sensor, signal processing in the control device becomes easier.

Also, if an odd number of piezoelectric elements are stacked as in this example,
Direct detection lead wire 20 using the uppermost electrode plate as a detection electric scraper
It has the advantage of being able to connect with

The laminated body is held by the housing 12 and the plunger 21 from above and below, and has an upper rod 2a and a lower loft 2b.
Therefore, the load due to the tightening of the upper rod 2a and the lower loft 2b is transferred to the plunger 2.
1. The force is applied in the axial direction of the laminate through the disc spring 22. The load for this tightening is about several tens to hundreds of kilograms.

Next, the damping force variable mechanism driven by the piezoelectric actuator 10 will be explained below. A plunger 2 that can slide inside the lower condo 2b is provided on the lower end side of the piezoelectric actuator 10.
1 is provided, and a pressure chamber 23 is formed between the plunger 21 and the inner wall of the lower rod 2b. The lower end of the pressure chamber 23 is closed by a small plunger 25 that is slidably fitted into a sliding member 24 for preventing wear. A valve 26 is provided at the lower end of the small plunger 25 so as to slide together with the small plunger 25, and the valve 26 has a groove 26a formed along its outer periphery and is pressed upward by a suge ring 27. . The member 5 has a passage 5 that communicates with the hydraulic chamber 3a on one side and the hydraulic chamber 3b on the other side.
a is formed.

Therefore, in the state shown in FIG. 1, the flow path 5a is closed by the valve 26, and when the valve 26 is displaced downward, the groove 2
Hydraulic chambers 3a and 3b communicate with each other via 6a and flow path 5a.

The operation of this variable damping force mechanism will be explained. When no voltage is applied to the application lead wire 19 of the piezoelectric actuator 10, the valve 26 is in the state shown in FIG. 1, and the hydraulic chambers 3a and 3b are in communication via the flow path 5a and the groove 26a. Therefore, when the shock absorber expands and contracts and the rod 2 and cylinder 3 connected to the vehicle body side move relative to each other, hydraulic fluid flows from the hydraulic chambers 3a to 3b, or conversely through the throttle channel 1a. This flow of hydraulic oil creates a pressure difference between the ground pressure chambers 3a and 3b, which applies a load to the rod 2. This load becomes a damping force of the shock absorber, but the damping force generated in this case is relatively large because the hydraulic oil passes only through the flow path 1a.

On the other hand, when a voltage is applied to the lead wire 19 of the piezoelectric actuator 10, the piezoelectric actuator 10 expands. As a result, the plunger 21 is displaced to compress the pressure chamber 23, the small plunger 25 and the valve 26 are displaced downward by an enlarged displacement amount, and the groove 26a of the valve 26 opens the flow path 5a. As a result, the hydraulic chambers 3a and 3b are connected to the throttle flow path 1a.
and communicate through the flow path 5a. At this time, the load applied to the loft 2 according to the speed of expansion and contraction of the shock absorber, that is, the damping force, becomes smaller than in the above case.

In this way, the damping force of the shock absorber can be varied by applying voltage to the piezoelectric actuator 10.

Next, the operation of the MW sensor 11 will be explained.

In a normal state, the damping force sensor 11 is biased with a constant pressing force by tightening the rods 2a and 2b and the disc spring 22. When the shock absorber is compressed and a load in the upward direction of the loft 2, that is, a damping force is applied to the piston 1,
The damping force is determined by the lower rod 2b and the piezoelectric actuator 10.
etc., to increase the pressing force applied to the sensor 11. The damping force sensor 11 thereby generates a positive output voltage, the value of which is proportional to the magnitude of the damping force generated.

On the other hand, when the shock absorber expands, a damping force acts on the piston 1 in the direction of the cap nut 6, and this damping force reduces the magnitude of the pressing force applied to the damping force sensor 11. Therefore, the damping force sensor 11 generates a negative output voltage proportional to the generated damping force. In this way, the damping force sensor 11 generates an output signal corresponding to the fluctuation of the damping force generated by the shock absorber.

FIG. 3 shows a device for controlling the damping force based on the output signal obtained from the damping force sensor of the shock absorber shown in FIG. In the shock absorber shown in Figure 1, the damping force sensor and the piezoelectric actuator that drives the damping force variable mechanism are integrally stacked inside the rod, so when the piezoelectric actuator is driven, the output signal of the damping force sensor There will be an impact. In addition, the damping force of a normal shock absorber is set to be large when the shock absorber is extended and small when it is compressed to improve ride comfort. If you compare the damping force at the same standard level and make the damping force variable, you will feel a sense of discomfort compared to the normal riding comfort.

The third device solves the above problem, and reduces the above effects by temporarily stopping the detection of damping force based on the output signal from the damping force sensor when driving the piezoelectric actuator. .

Furthermore, by comparing the output signals from the damping force sensor at different reference levels when the shock absorber is extended and retracted, it is possible to control the ride so that it approximates normal riding comfort.

In FIG. 3, 30 is the shock absorber shown in FIG. 1, and an output signal from the damping force sensor 11 of this shock absorber is guided to a switching circuit 31. The output signal from the switching circuit 31 is sent to the damping force change determination circuit 3.
2. Delay circuit 34.3 via pulse generation circuit 33
5, the output signals from the pulse generation circuit 33 and the delay circuit 34 are sent to the switching circuit 31 and the delay circuit 34.
The output signal from the circuit 35 is sent to the variable damping force mechanism drive circuit 36.
Piezoelectric actuator 10 of shock absorber 30
guided by.

The switching circuit 31 switches the output from the damping force sensor so as not to guide it to the discrimination circuit 32 at least when the piezoelectric actuator 10 is driven to extend or contract, and the zero discrimination circuit 32 conducts the output signal of the damping force sensor at other times. Determine whether the output signal of the damping force sensor input via the switching circuit 31 is at a level more positive than the first reference level (vl) or more negative than the second reference level (-VX). and outputs a high level signal in either case.

As shown in FIG. 4, the pulse generation circuit 33 outputs a pulse signal of a predetermined time (ts) to the delay circuits 34 and 35 based on the high level signal from the discrimination circuit 32. The delay circuit 34 outputs a delayed pulse signal obtained by delaying the pulse signal by a predetermined time (tl), and the switching circuit 31 outputs a delayed pulse signal that is delayed by a predetermined time (tl), and the switching circuit 31 outputs a delayed pulse signal that is delayed by a predetermined time (tl). Switching is performed so that the output signal of the M attenuation sensor is not guided to the signal processing circuit 32. The delay circuit 35 generates a delayed pulse signal by delaying the pulse signal by a predetermined time (t2), and the drive circuit 36 is activated by this signal, and the damping force variable mechanism is activated to set the damping force to a small value. .

FIG. 5 is a diagram showing a specific circuit of the block diagram of FIG. 3. In FIG. 5, a switching circuit 31 amplifies the output signal from the damping force sensor 11 and outputs it to a signal processing circuit 32, an operational amplifier Q1, resistors R1 and R2, a pulse generation circuit 33, and a switching signal from a delay circuit 34. The circuit includes an aronag switch Q2 which is closed when a current is applied thereto.

The determination circuit 32 includes a first determination circuit 32a that compares the input signal inputted through the resistor R3 with a positive first reference level (Vl''), and a first determination circuit 32a that compares the input signal inputted through the resistor R3 with a positive first reference level (Vl''), and a first determination circuit 32a that compares the input signal inputted through the resistor R3 with a negative second reference level (-Vl'').
Z) and a second determination circuit 32b for comparing with the first. Second
(Or game where the outputs of the judgment circuits 32a and 32b are input)
It consists of Q6. The first determination circuit 32a includes a resistor R4 for determining the first reference level (■,), a comparator Q4, a resistor R6, and a Zener diode D1. The second determination circuit 32b includes a resistor R5 for determining the second reference level (V2), a comparator Q5, a resistor R7, and a Zener diode D2. Comparator Q4 (
Q5) is the voltage V preset by the resistor R4 (R5),
When the input signal becomes higher (lower) than (-vz),
The output signal becomes high level, and the high level signal is outputted to the pulse generation circuit 33 through the OR game Q6. Here, in consideration of riding comfort, the reference voltage is set to V, <V, but depending on the case, it may be 1≧V2.

Further, the reference voltages V, , V, may be changed based on the vehicle speed, and may be changed to be small at low speeds and large at high speeds.

The pulse generation circuit 33 is a known circuit that generates a pulse signal for a predetermined time (t,) based on the high level signal of the discrimination circuit 32. Further, the pulse generating circuit 33 receives control signals unrelated to the control by the damping force sensor from the circuit 37, such as vehicle speed signals, steering angle signals, and other signals indicative of the driving state. Based on these control signals, Predetermined time ts
(the time required to maintain the damping force of the shock absorber in a small state) is determined.

The delay circuits 34 and 35 are composed of inverters Q8 to Q11, resistors R8 and R9, and capacitor C1, each having a delay time Ll+j! is 1. >1. is set to .

- The variable damping force mechanism drive circuit 36a is an operational amplifier Q13.
, transistors Q17 and Q19, and diode D3. An ignition circuit 36a for the thyristor Sl including D4, etc., an inverter Q14, an operational amplifier Q15, a transistor Q16 .
It is constituted by a firing path 36b for thyristor S2 including Q18 and the like.

An output signal from the drive circuit 36 is applied to one electrode of the piezoelectric actuator 10 via a lead wire 19, and the other electrode is grounded.

To explain the operation of the circuit shown in FIG. 5, the output signal from the damping force sensor 11 is amplified by the operational amplifier Q1 of the switching circuit 31 and sent to the discrimination circuit 32. The first and second determination circuits 32a and 32b of the determination circuit 32 determine whether to set the damping force of the shock absorber to low (or high) based on the input signal and each reference level.In this example, the damping force is set to low (or high). When setting, set the output signal to high level, and
When setting a high damping force, the output signal is set to a low level.

When the output signal of the discrimination circuit 32 becomes high level, the pulse generation circuit 33 generates a pulse signal for a predetermined time (t,) determined by the vehicle speed signal or the like. This pulse signal causes delay.
The circuit 34 generates a delayed pulse signal delayed by t, and the OR game 1-Q7 outputs a switching signal from the pulse signal and the delayed pulse signal to the switching circuit 31. The analog switch Q2 of the switching circuit 31 is
It closes in response to a switching signal so that the output signal of the damping force sensor is temporarily (ts+t, time) not guided to the discrimination circuit 32. Further, the pulse signal of the pulse generation circuit 33 is delayed by a predetermined time (t2) by the delay circuit 35 and outputted to the drive circuit 36. This activates the ignition circuit 36a, makes the thyristor S1 conductive, applies a high voltage to the piezoelectric actuator 10, causes it to expand, and the damping force variable mechanism sets the shock absorber to the damping force state # as described above. . After the shock absorber maintains the low damping force state for a predetermined time (T), the pulse signal of the delay circuit 35 disappears, and the ignition circuit 3
6b is actuated, Sairisk S2 becomes conductive, and becomes in a high damping force state again. After a slight delay, the switching signal disappears, and the switching circuit 31 again guides the output signal of the damping force sensor to the discrimination circuit 32.

FIG. 6 shows the relationship between the road surface condition and the output signal from the damping force sensor. Fig. 6 (al shows the unevenness of the road surface and the damping force state of the shock absorber 30 controlled thereby, and Fig. 6 (bl shows the output signal from the damping force sensor via the switching circuit 31). The signal is solid line S
The dotted line Q indicates the output signal from the damping force sensor when the switching circuit 31 is not activated. Note that V, , -V in FIG. 6 indicate the first . The reference levels of the second determination circuit are shown.

In the embodiment described above, the shock absorber is set to a high damping force state during normal times, the damping force sensor detects changes in the damping force of the shock absorber due to uneven road surfaces, and the shock absorber is controlled to a low damping force state when passing through an uneven road surface. As a result, it is possible to suppress impacts such as bumps from the road surface and prevent deterioration of ride comfort due to road surface conditions.

In addition, by holding the shock absorber in a low damping force state for a predetermined period of time and then setting it again in a high damping force state, it is possible to prevent the large shaking of the vehicle that occurs after passing over an uneven road surface, so-called bouncing. Furthermore, according to the above-mentioned control device which sets the shock absorber to a high damping force state during normal operation and a low damping force state when passing through an uneven road surface, it is possible to prevent the squat phenomenon when the vehicle starts, the nose dive phenomenon during sudden braking, or when the vehicle turns. In response to the roll phenomenon, etc., the vehicle posture can be kept stable without the need to particularly control the damping force of the shock absorber. This also has the effect of eliminating the need for many conventional sensors that were provided to detect the above-mentioned phenomenon.

In the above embodiment, the switching circuit 31 is provided to temporarily stop detection of the damping force based on the output signal from the damping force sensor when the piezoelectric actuator is driven. This prevents the output signal of the damping force sensor provided in close proximity to the actuator from being affected when the actuator is driven to extend or contract.

Therefore, instead of the switching circuit 31 described above, detection of the damping force based on the output signal from the damping force sensor is stopped only when the piezoelectric actuator is extended or contracted, and once the piezoelectric actuator is in the extended or contracted state, By using a switching circuit that makes the above detection valid again, it is possible to control the damping force of the shock absorber with higher precision. In addition, the output signal from the damping force sensor is input as a control signal to the pulse generation circuit 33, and based on this signal, the pulse signal is continued for a period of time (t,
), an appropriate predetermined time (t
The pulse signal of 3) can be generated, and the shock absorber can be maintained in a low damping force state for a long period of time when driving on a rough road with continuous uneven road surface conditions.

Next, an example in which the control of the above embodiment is implemented by a microcomputer 70 will be explained with reference to FIG. The microcomputer outputs a switching signal indicating whether or not to input the output signal from the damping force sensor to the switching circuit 31, and also outputs the output signal from the damping force sensor and the signal from the sensor circuit 37 which outputs the vehicle speed signal, etc. Based on this, a holding time t for maintaining the low damping force state is calculated, and a drive command signal is output to the drive circuit 36.

The operation of the microcomputer will be explained based on the flowchart of FIG. 8. In step 81, the damping force sensor 1
In step 82, similarly to the discrimination circuit 32, the signal from the damping force sensor is inputted from the first damping force sensor. Second
It is determined whether the reference voltage level is exceeded, and when the first reference level (V, ) is exceeded, or the second reference level (-VZ
), the process advances to step 83; otherwise, the process returns to step 81. In step 83, the sensor circuit 3
The holding time t for holding the shock absorber in a low damping force state is calculated based on the vehicle speed signal etc. from step 7, and in step 84, a switching signal is output to turn off the switching circuit 31, and an output signal from the damping force sensor is output. Microcomputer 7
Stop typing within 0. In steps 85 and 86, a drive signal is output to the open drive circuit 36 for the holding time t to maintain the shock absorber in a low damping force state.

In step 87, the drive signal is stopped and the shock absorber is placed in a high damping force state again. In step 88, the switching circuit 31 is turned on so that the output signal from the damping force sensor can be input, and the process returns to step 81.

Next, a second embodiment will be explained based on FIG.

In the second embodiment, it is sharply different from the above-mentioned first embodiment,
Normally, the flow path 5a communicates the hydraulic chambers 3a and 3b and is in a low damping force state, and when the piezoelectric actuator 11 extends, the valve 26 is displaced downward, closing the flow path 5a and creating a high damping force state. It is set to be. The other configurations are the same as those in the first embodiment, so their explanation will be omitted.

The second embodiment will now be described based on the flowchart of FIG. 9 as the operation of the microcomputer when the apparatus shown in FIG. 7 is used. The difference from the flowchart described above is in steps 90, 91 and 92, 93, and the other steps with the same numbers are the same as those described above. In the second embodiment, the shock absorber is set to a low damping force state during normal times, so the impact when passing over an uneven road surface is small, but the bouncing after passing over the uneven road surface is large, so this is suppressed. In order to achieve this, the shock absorber is controlled to be in a high damping force state for a predetermined period of time after passing through an uneven road surface. Therefore, after the output signal from the damping force sensor once exceeds the reference level in the first step 82, a determination is made again in the second step 82 after a predetermined time determined by the timer in step 90. If the output signal from the damping force sensor exceeds the reference level in the second step 82, it is assumed that the road surface is in a rough road condition with continuous unevenness, and the process returns to step 90, maintaining the low damping force state. return.

- On the other hand, if the second step 82 is negative, it is assumed that the road has passed through an uneven road surface, and in steps 91, 92 and 93, a signal is output to maintain the shock absorber in a high damping force state for a predetermined period of time, and the above-mentioned process is performed. Suppress housing. In this second embodiment, in order to suppress the squat phenomenon when the vehicle starts, etc., the shock absorber is changed from a low damping force state to a high damping force state based on other control signals such as an accelerator signal and a vehicle speed signal. Set.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a shock absorber according to a first embodiment of the present invention, and FIG. 2 (al and (b) is a damping force sensor (11
) and a partial sectional view and a partial perspective view showing the piezoelectric actuator (10), FIG. 3 is a block circuit diagram showing one embodiment of the damping force control device of the present invention, and FIG. 4 serves to explain the operation of FIG. 3. Timing chart, FIG. 5 is a detailed circuit diagram of FIG. 3, FIG. 6 is a diagram showing the output signal from the damping force sensor and the shock absorber damping force state depending on the road surface condition, and FIG. 7 is the damping force control of the present invention. FIG. 8 is a flow chart showing the operation of the microcomputer (70) in FIG. 7; FIG. 9 is a sectional view of essential parts of the shock absorber according to the second embodiment of the present invention; FIG. The figure is number 9
3 is a flowchart showing the operation of a device that controls the shock absorber shown in the figure. DESCRIPTION OF SYMBOLS 1... Piston, 2... Rod, 3... Cylinder, 10... Piezoelectric actuator, 11... Damping force sensor. 5a...Flow path, 3a, 3b...Hydraulic chamber, 20...
Control circuit, 30... Shock absorber, 31...
Switching circuit, 32... Judgment circuit, 33... Pulse generation circuit, 34.35... Delay circuit, 36.
...Damping force variable mechanism drive circuit. Representative Patent Attorney Takashi Okabe Figure 2 Figure 3 Figure 4 Figure 6 Figure 9

Claims (5)

[Claims] (1) A cylinder, a rod member slidably fitted into the cylinder, and a piston that slides in the cylinder together with the rod member and substantially divides the cylinder into two hydraulic chambers. , a damping force variable mechanism that changes the damping force of the shock absorber by changing the area of a flow path formed to communicate the two hydraulic chambers with each other, and a damping force variable mechanism that is provided inside the rod member and that is driven a telescopic actuator that expands and contracts in the axial direction of the rod member in response to a signal to drive the variable damping force mechanism; and a telescopic actuator that is disposed inside the rod member and detects the damping force that is generated in response to the expansion and contraction of the shock absorber. and a damping force sensor that converts the shock absorber into an electrical detection signal, and inputs the detection signal from the damping force sensor, and outputs a drive signal to the telescopic actuator to change the damping force of the shock absorber based on this detection signal. A damping force control device for a shock absorber, comprising: a control means; (2) The control means includes a drive means that outputs a drive signal based on a detection signal from the damping force sensor, and an input of a detection signal from the damping force sensor based on the drive signal from the drive means. 2. The damping force control device for a shock absorber according to claim 1, further comprising switching means for temporarily stopping the damping force of a shock absorber. (3) The variable damping force mechanism sets the damping force of the shock absorber to a large value when the telescopic actuator is not driven, and sets the damping force of the shock absorber to a small value when the telescopic actuator is driven. A damping force control device for a shock absorber according to scope 1. (4) The damping force sensor is a piezoelectric element that is attached to a portion of the rod member where the load stress changes depending on the damping force of the shock absorber, and outputs a detection signal in accordance with the load stress, and the expansion and contraction actuator is a piezoelectric element that outputs a detection signal in accordance with the load stress. Claim 1, which is a piezoelectric element laminate in which a plurality of piezoelectric elements that expand and contract in response to a drive signal are laminated in the expansion and contraction direction.
Shock absorber damping force control device. (5) The damping force control device for a shock absorber according to claim 4, wherein the damping force sensor is integrally stacked with the telescopic actuator via a common ground electrode plate.