JPH0461980B2 - - Google Patents

Description

Detailed Description of the Invention Object of the Invention [Industrial Application Field] The present invention provides a damping force detector effective for detecting damping force acting on a vehicle shock absorber, and a damping force detector equipped with the damping force detector. The present invention relates to a shock absorber control device that suitably switches the damping force of a variable damping force type shock absorber based on the detection result of the damping force detector.

[Prior Art] In order to improve the ride comfort of a vehicle and stabilize the vehicle posture, for example, it is necessary to equip the vehicle with a variable damping force type shock absorber to sufficiently respond to rapid changes in the road surface conditions on which the vehicle travels. The variable damping force type shock absorber must be controlled using the variable damping force type shock absorber. To this end, it is necessary to quickly and accurately detect the damping force of the variable damping force type shock absorber, which reflects the road surface condition, and to switch the damping force of the variable damping force type shock absorber at an appropriate time. There is. Conventionally, such technologies include, for example,
The following are proposed. That is, (1) the displacement amount based on the expansion and contraction movement of the variable damping force shock absorber is detected by the displacement amount detection means, and when the damping force of the variable damping force shock absorber is changed by the selection command means, the displacement amount is detected by the damping force detection means. When the previously selected damping force is different from the currently selected damping force, the driving means is activated when the change rate of the displacement amount of the variable damping force shock absorber detected by the change rate detection means first becomes zero or near zero. ``Shock absorber control device'' (Utility Model Application Publication No. 61-67009) that outputs a control signal for switching the damping force of the variable damping force shock absorber.

(2) The detection sensitivity of a damping force signal output from a variable damping force type shock absorber having a damping force sensor is switched according to the damping force setting state of the variable damping force type shock absorber, and is dependent on the damping force setting state. ``Vehicle shock absorber and shock absorber control device using the shock absorber'' that accurately detects road surface conditions and vehicle motion conditions and appropriately sets damping force without Public bulletin).

[Problems to be Solved by the Invention] However, such prior art has the following problems and is still not satisfactory. That is, (1) When detecting the damping force, the amount of displacement based on the expansion and contraction movement of the shock absorber is measured, and the damping force is indirectly calculated from the rate of change of the amount of displacement.
However, even though the relationship between the rate of change in displacement and the damping force is approximately linear, in reality it is a nonlinear relationship, so there is a problem that it is difficult to accurately detect the damping force. Ta.

(2) In addition, the above displacement amount is determined by the fact that a cylindrical cover is integrally attached to the upper end of the piston rod of the shock absorber, and the lower end reaches the cylinder tube and covers it. The relative displacement between the cover and the cylinder tube was measured by a displacement detection coil, a so-called operating transformer, which detected the change in inductance due to a change in the amount of overlap between the cover and the cylinder tube. However, such displacement detection coils have technical issues such as shortening the coil length/stroke ratio, improving versatility, and responsiveness, and cannot be used in harsh environments such as when installed in a shock absorber. It is difficult to apply this method to the damping force sensor used, and in particular, the problem is that its durability and reliability are low.

(3) Furthermore, when using an optical sensor, the light transmittance decreases due to dirt, while when using an ultrasonic sensor, it is not always possible to detect the road surface condition at the actual location where the wheels are traveling. Since there is no,
Neither sensor was suitable for detecting damping force.

(4) Furthermore, as mentioned above, the detection accuracy of the damping force is extremely low, so it is only possible to realize shock absorber control that determines the road surface condition and vehicle motion condition based on the inaccurate damping force, resulting in poor vehicle ride comfort. In addition to deterioration, there was also the problem that maneuverability and stability also deteriorated.

(5) Furthermore, when the detection sensitivity of the output signal of the damping force sensor, which changes depending on the setting state of the damping force, is switched, there is a problem that the circuit configuration of the device becomes complicated.

(6) Furthermore, even if the detection sensitivity of the output signal of the damping force sensor was changed, no consideration was given to the timing of switching the damping force, so if the damping force was changed at an inappropriate time, the damping force Another problem was that the impact caused by the change control caused the vehicle to vibrate. This has emerged as a particularly notable problem, since, for example, when changing from a low damping force to a high damping force, if the timing is not appropriate, the vehicle will experience rolling motion that is uncomfortable for the occupants.

The first purpose is to provide a shock absorber control device that prevents the occurrence of shocks caused by damping force change control by changing the damping force at an appropriate time, thereby preventing the vehicle from being vibrated. be. The second object is to provide a damping force detector that is suitable for determining the appropriate timing to change the damping force and that can directly measure the damping force with a simple configuration, in particular, based on the effect of bending moment. An object of the present invention is to provide a damping force detector that does not erroneously detect damping force.

Structure of the Invention [Means for Solving the Problems] A first invention made to solve the above problems is a shock absorber that is connected to the piston of a cylinder and a piston that is slidably fitted to the cylinder. A piezoelectric element is installed inside the piston rod and generates an electric charge in accordance with the strain transmitted from the outside. a pressure member that transmits strain occurring in the piston rod along the direction to the piezoelectric element;
and the pressure member is composed of two members, a pressure member having a convex surface at one end that makes spherical contact with each other and a pressure member having a concave surface at one end so as to transmit only the strain in the axial direction of the piston rod. The gist of this invention is a damping force detector characterized by the following features.

Here, the piezoelectric element is installed inside the piston rod of the shock absorber, and generates an electric charge corresponding to the strain transmitted from the outside. That is, when pressure or tension is applied, a phenomenon in which electric charges are generated on the end faces of the crystal, the so-called positive piezoelectric effect (piezo effect) is exhibited. For example, it can be realized using piezoelectric ceramics such as lead zirconate titanate (PZT) and barium titanate, crystal, Rosier's salt, and the like.

The pressure member is a member that fixes the piezoelectric element to the piston rod and transmits the strain generated in the piston rod along the sliding direction due to the acting force that expands and contracts the shock absorber to the piezoelectric element. . For example, this can be realized by a fitting member that screws a piezoelectric element disposed in a hole drilled inside the piston rod along its sliding direction. It is constructed by combining two members: a pressure member and a pressure member having a concave surface at one end.

Also, the second work done to solve the above problem
As exemplified in FIG. 1, the present invention provides a shock absorber consisting of a cylinder and a piston that is slidably fitted into the cylinder. a piezoelectric element that generates a corresponding electric charge, and a piezoelectric element that is fixed to the piston rod, and a strain that is generated in the piston rod along the sliding direction due to an acting force that expands and contracts the shock absorber is transmitted to the piezoelectric element. a damping force detector M1 comprising: a damping force changing means M2 for changing the damping force of the shock absorber according to an external command; Damping force signal generating means M3 that stores electric charge and outputs a damping force signal
and a change signal generating means M4 that outputs a change signal according to the time change of the damping force signal outputted by the damping force signal generating means M3, and at least a change signal outputted by the change signal generating means M4 is within a predetermined range. and the damping force signal outputted by the damping force signal generating means M3 is zero,
Alternatively, when the value is close to zero, determining means M5 determines that the high damping force switch is possible, and when the determining means M5 determines that the high damping force switch is possible, the shock absorber The main feature of the present invention is a shock absorber control device comprising: control means M6 for outputting a command to change the damping force of the shock absorber to a higher side to the damping force changing means M2;

Here, the damping force detector M1 is a shock absorber that expands and contracts along the sliding direction of a piston rod connected to the piston of the shock absorber, which is composed of a cylinder and a piston that is slidably fitted into the cylinder. The strain that occurs in the piston rod due to the acting force is transmitted through the pressure member,
The signal is transmitted to a piezoelectric element installed inside the piston rod, and the piezoelectric element generates an electric charge corresponding to the strain. For example, a piezoelectric element made of piezoelectric ceramics such as lead zirconate titanate (PZT) or barium titanate, quartz crystal, Rosier's salt, etc. is disposed inside the piston rod in a hole drilled along the sliding direction. This can be realized by screwing the piezoelectric element with a fitting member. Further, for example, the piston rod may be configured to incorporate a piezoelectric element by combining a convex pressure member and a concave pressure member that are in spherical contact with each other. Furthermore, for example, a pressure-receiving side pressure member that contacts the piezoelectric element, a fixed-side pressure member fixed to the piston rod, and an elastic member interposed between the pressure-receiving side pressure member and the fixed-side pressure member It is also possible to arrange the piezoelectric element on the piston rod by means of a pressure member.

The damping force changing means M2 changes the damping force of the shock absorber according to an external command. For example, a voltage is applied and discharged to a piezo actuator (piezo stack) made up of a combination of multiple piezoelectric elements, which drives a spool valve to open and close a communication hole drilled in the piston of a shock absorber. This can be achieved by Here, a piezoelectric element is a phenomenon in which it expands and contracts when an electric field is applied, the so-called inverse piezoelectric effect (piezo effect).
It is something that causes For example, piezoelectric ceramics such as lead zirconate titanate (PZT), crystal,
Rosier salt etc. Further, for example, the spool valve may be configured to be operated by a well-known electromagnetic valve. Further, for example, a rotary valve may be rotated by a motor or the like to open and close an orifice formed in a piston of the shock absorber.

The damping force signal generating means M3 is the damping force detector M
1 is stored and outputs a damping force signal. For example, it can be realized by an integrating circuit that combines an operational amplifier and a capacitor.

The change signal generating means M4 outputs a change signal corresponding to the time change of the damping force signal. This can be realized by a well-known differentiation circuit that calculates the rate of change of the damping force signal.

The determining means M5 determines that the high damping force switching is possible at least when the change signal is within a predetermined range and the damping force signal is zero or a value near zero. . For example, it can be configured by a comparison circuit that compares the differential signal with threshold values corresponding to both boundary values of a predetermined range, and a comparison circuit that compares the damping force signal with zero. Furthermore, for example, when the change signal is within a predetermined range, the damping force signal is zero or a value near zero, and the shock absorber's expansion/contraction movement shifts from the extension side to the contraction side, the high It can be configured to determine that the damping force can be switched.

The control means M6 outputs a command to change the damping force of the shock absorber to a higher side when it is determined that the high damping force switching is possible. For example, if the differential signal falls below the threshold value,
In addition, it can be configured to output a control signal for switching the damping force of the shock absorber to a high damping force when the damping force signal is zero or a value near zero.

The determination means M5 and the control means M6 are, for example,
This can be realized using independent discrete logic circuits. Also, for example, well-known CPU, ROM,
It may be configured as a logic operation circuit together with RAM and other peripheral circuit elements, and may realize both of the above means according to a predetermined processing procedure.

[Operation] The damping force detector of the first invention causes the piston to move along the sliding direction of the piston due to the acting force that expands and contracts the shock absorber, which is made up of a cylinder and a piston that is slidably fitted into the cylinder. The pressure member transmits the strain generated in the piston rod connected to the piston rod to a piezoelectric element disposed inside the piston rod, and the piezoelectric element operates to generate an electric charge corresponding to the transmitted strain.

That is, the strain caused by the force that expands and contracts the shock absorber, that is, the strain that occurs in response to the damping force, is directly measured.

Here, the pressure member is composed of two members, a pressure member having a convex surface at one end that makes spherical contact with each other, and a pressure member having a concave surface at one end, in order to transmit only the strain in the axial direction of the piston rod. Therefore, even if a bending moment acts on the piston rod, the bending moment only results in slippage at the spherical contact portion and is not transmitted to the piezoelectric element. On the other hand, when an axial force is applied, the force does not cause the spherical contact to slip.
transmitted to the piezoelectric element. Therefore, erroneous detection of the damping force due to the force exerted by the bending moment can be prevented with a simple configuration, and even more accurate damping force detection is possible.

In adopting such a configuration, as a result of adopting the minimum configuration of two members, the escape of the axial pressing force at the spherical contact part can be minimized, and the original detection accuracy can be minimized. do not have.

Therefore, the damping force detector of the first invention always works to accurately detect the damping force of the shock absorber.

Further, as illustrated in FIG. 1, the shock absorber control device of the second invention stores the electric charge generated by the damping force detector M1 in accordance with the strain generated in the piston rod due to the acting force that expands and contracts the shock absorber. When the damping force signal generating means M3 outputs a damping force signal and the change signal generating means M4 outputs a change signal according to the time change of the damping force signal, at least the change signal is within a predetermined range. , and when the determining means M5 determines that the damping force signal is zero or a value close to zero and the high damping force switching is possible, the control means M6 increases the damping force of the shock absorber to a higher value. It works to output a command to change the damping force to the damping force changing means M2.

Therefore, the shock absorber control device of the second invention works to suppress sudden changes in the acting force transmitted through the shock absorber as the damping force of the shock absorber changes.

The technical problems of both inventions are solved by each component of both inventions acting as described above.

[Embodiments] Next, preferred embodiments of both inventions will be described in detail based on the drawings. First, FIG. 4 shows a longitudinal sectional view of a variable damping force type shock absorber incorporating a piezo type damping force sensor as an example that can be used in the second invention.

As shown in the figure, the variable damping force type shock absorber 1FL has a main piston 3 inside a cylinder 2 in the axial direction (indicated by arrows A and B in the figure).
The inside of the cylinder 2 is divided into a first hydraulic chamber 4 and a second hydraulic chamber 5 by the main piston 3. Main piston 3 above
is connected to one end of the piston rod 6, while
The other end of the piston rod 6 is fixed to a shaft 7. The cylinder 2 is housed in an outer shell 2a, and a lower part of the outer shell 2a is attached to a lower arm 2b of the vehicle.
The upper portion 7a of the shaft 16 is fixed to the vehicle body 10 via a bearing 8 and a vibration isolating rubber 9.

The piston rod 6 has built-in a piezo actuator 11FL for switching the damping force of the variable damping force type shock absorber 1FL, and a piezo type damping force sensor 12FL for detecting the damping force of the variable damping force type shock absorber 1FL.

The main piston 3 includes the first hydraulic chamber 4
A fixed orifice 13 on the extension side and a fixed orifice 14 on the contraction side are drilled to communicate the fixed orifice 13 on the extension side and the fixed orifice 14 on the contraction side to communicate with the second hydraulic chamber 5. Plate valves 13a, 14 that limit to
a are arranged respectively. Therefore, when the main piston 3 slides inside the cylinder 2 in the axial direction (indicated by arrows A and B in the figure), the first
Since the hydraulic oil inside the hydraulic chamber 4 and the second hydraulic chamber 5 mutually flow through the expansion side fixed orifice 13 and the contraction side fixed orifice 14,
The cross-sectional area of the hydraulic fluid flow path is relatively small, and its flow rate is also low. Therefore, when the sub flow path 18 is blocked, the damping force characteristic of the variable damping force type shock absorber 1FL becomes a high damping force (HARD) characteristic, as shown in FIG.

By the way, as mentioned above, the piston rod 6 has a hollow part bored in its axial direction, and a piezo actuator, which is an electrostrictive element stack made of piezoelectric ceramics such as PZT, is installed in the hollow part. Built-in 11FL. The piezo actuator 11FL is normally biased by a plate spring 15 in the direction indicated by arrow A in the figure. The lower end surface of the piezo actuator 11FL has an oil-tight chamber 16.
It faces the spool valve 17 via. The spool valve 17 is slidable inside the hollow portion of the piston rod 6 in its axial direction. When a predetermined high voltage is applied to the piezo actuator 11FL, the spool valve 17 moves a predetermined distance in the direction shown by arrow B in the figure. On the other hand, when the predetermined high voltage applied to the piezo actuator 11FL is discharged, the piezo actuator 11FL
The spool valve 17 moves in the direction shown by arrow A in the figure due to the bias of the plate spring 15.
also move in the same direction.

An annular groove 17a is formed on the outer periphery of the lower part of the spool valve 17, and the upper part of the annular groove 17a is shaped into a cylindrical shape. Therefore, the spool valve 17
When the piezo actuator 11FL moves in the direction shown by the arrow A in the figure due to contraction of the piezo actuator 11FL, the annular groove 1 carved on the outer circumference of the lower part of the spool valve 17 moves.
A sub-flow passage 18, which is bored in the piston rod 6 and connects the first hydraulic chamber 4 and the second hydraulic chamber 5, communicates with each other via 7a. Since the first hydraulic chamber 4 and the second hydraulic chamber 5 communicate with each other via the sub-flow passage 18 in this way, the cross-sectional area of the flow passage for the hydraulic oil flowing through the main piston 3 becomes relatively large. The flow rate also increases. Therefore, the damping force characteristics of variable damping force type shock absorber 1FL at this time are as follows:
As shown in the figure, it has low damping force (SOFT) characteristics.

On the other hand, when a high voltage is applied, the piezo actuator 11FL expands by a minute amount, and the spool valve 17 also descends by a predetermined distance in the direction shown by arrow B in the figure, and is shaped into the cylindrical shape of the spool valve 17. The auxiliary flow path 18 is blocked by the cylindrical portion. In this way, the first hydraulic chamber 4 and the second hydraulic chamber 5 are cut off by closing the sub-flow passage 18, so that the cross-sectional area of the hydraulic oil flowing through the main piston 3 becomes relatively small. Its flow rate also decreases. Therefore, the damping force characteristics of the variable damping force type shock absorber 1FL at this time are as shown in Fig. 5.
It has high damping force (HARD) characteristics.

A piezo type damping force sensor 12FL is disposed above the piston rod 6 to detect the magnitude of the damping force acting on the variable damping force type shock absorber 1FL. A piezoelectric element 19FL made of piezoelectric ceramics such as the above piston rod 6 is screwed onto the piston rod 6 by a pressure member 20FL.

Next, the above piezo type damping force sensor 12FL
The structure of will be explained based on FIGS. 2 and 3. As shown in FIG. 2, the piezo type damping force sensor 12FL consists of two thin plates 19FLa and 19FLb each having a disk shape and a through hole in the center, each of which is a piezoelectric element made of piezoelectric ceramics such as PZT, as described above.
Then, a disk-shaped thin plate 21FL, which is a positive electrode and also has a through-hole in the center, is stacked on both sides, and a cylindrical-shaped thin plate 21FL with a through-hole in the center and a threaded part 20FLa on the outer periphery is stacked. Pressure member 20
FL is screwed onto the piston rod 6 which also serves as a negative electrode, and the detection signal is sent to the variable damping force type shock absorber 1FL via a lead wire 22FL disposed in a passage bored inside the piston rod 6. A high voltage is output to the outside, and on the other hand, a high voltage is applied to the piezo actuator 11FL described above via the lead wire 23FL.

A portion of the force generated in response to the axial strain of the piston rod 6 due to the damping force acting on the variable damping force type shock absorber 1FL is transferred to the threaded portion 2.
Piezoelectric element 1 from pressure member 20FL via 0FLa
It is transmitted to 9FLa and 19FLb. In this example,
Even when the piston rod 6 is not strained in the axial direction, a predetermined initial stress is applied to the piezoelectric elements 19FLa and 19FLb by the tightening of the pressure member 20FL. This is the axial tension of the piston rod 6 (the direction shown by the solid arrow in the figure).
This is to detect the strain as a change from the strain due to the initial stress when strain due to compression or compression (in the direction indicated by the broken line arrow in the figure) occurs. Here, the relationships among the various quantities are shown in the following equations (1) to (4).

σ=P/{(A1/K)+A2}...(1) However, K=a-{(a×b)/(l+b)}...(2) a=E2/E1...(3) b={E2 /(EP-1)}×lP...(4) Here, σ is the stress applied to the piezoelectric element, P is the load acting in the axial direction of the piston rod 6, and l is the second
The length of the pressurizing part shown in the figure, A1 is the cross-sectional area of the rod with a built-in piezo type damping force sensor, A2 is the cross-sectional area of the pressurizing member, E1 is the elastic modulus of the piston rod, E2 is the elastic modulus of the pressurizing member, and EP is the piezoelectric The element elastic modulus, lP, is the thickness of the piezoelectric element.

From the above equations (1) to (4), an appropriate pressurizing portion length l is calculated, and the sensitivity of the piezoelectric elements 19FLa and 19FLb to the acting force of the piston rod 6 in the axial direction is determined. Generally, the longer the length l of the pressurizing part, the better the sensitivity; however, due to constraints on mounting dimensions, in this embodiment, the value K in the above equation (2) is set to about 0.5, for example.

By the way, as shown in FIG.
Front and back surfaces of FLa 24FLa, 24FLb, piezoelectric element 19
Silver paste or the like is applied as an electrode material to the front and back surfaces 25FLa and 25FLb of FLb, respectively. The output signals of the piezoelectric elements 19FLa and 19FLb are transmitted from the positive electrode 21FL to the lead wire 22FL shown in FIG.
It is output to the outside via. Further, the piezoelectric elements 19FLa, 19FLb, the positive electrode 21FL, and the pressure member 20FL are connected to the lead wires 2 shown in FIG.
Through holes 26a, 26b, 26 for passing 3FL
c and 26d are drilled respectively.

As explained above, according to this embodiment, the strain generated according to the damping force can be directly measured simply by incorporating the piezo type damping force sensor into the piston rod of the variable damping force type shock absorber, so the structure is simple. Accurate, highly responsive and rapid damping force detection becomes possible.

In addition, since the piezo type damping force sensor is built into the piston rod of the variable damping force shock absorber, problems such as dirt and damage to the sensor are less likely to occur, improving the reliability and durability of damping force detection. can.

Furthermore, piezo type damping force sensors are small and lightweight, which expands the range of their application.
It also increases versatility.

Note that, for example, as shown in FIG.
When composed of FLa and pressure transmission member 27FLb,
Even when a bending moment acts on the piston rod 6, the bending moment causes slippage at the spherical contact portion 27FLc, which causes the piezoelectric element 1 to slip.
On the other hand, only when an axial acting force acts, the acting force is transmitted to the piezoelectric elements 19FLa, 19FLb. Therefore, erroneous detection of the damping force due to the force exerted by the bending moment can be prevented with a simple configuration, making it possible to detect the damping force even more accurately. The damping force detector shown in FIG. 6 corresponds to the first invention.

For example, as shown in FIG. 7, if a flat spring 28FLa and a flat spring receiver 28FLb are interposed between the pressing member 20FL and the piezoelectric element 19FLb, the elasticity of the flat spring 28FLa will cause the pressing member 20FL to move away from the pressing member 20FL. The axial strain transmitted to the piezoelectric element 19FLb is uniformly corrected. Therefore, high precision is not required when processing the flatness, surface roughness, etc. of the contact surface between the pressure member 20FL and the piezoelectric element 19FLb, making manufacturing easier and eliminating the need for fine adjustments during assembly and maintenance work. Moreover, there is also the advantage that compatibility at the parts stage, such as when replacing parts, is improved.

In this example, a so-called piezoelectric element is used.
Although PZT was used, for example, barium titanate,
Alternatively, a substance that produces a piezoelectric effect such as quartz may be used, and the shape of the piezoelectric element is not limited to a disk-shaped thin plate, for example.

Next, FIG. 8 shows a system configuration of a vehicle shock absorber control device according to a first embodiment of the second invention.

As shown in the figure, the vehicle shock absorber control device 30 includes variable damping force type shock absorbers 1FL, 1FR, 1RL, and 1RR, and a stop lamp switch 3 that detects the brake operation state of the vehicle.
1. Vehicle speed sensor 32 that detects the running speed of the vehicle and electronic control device that controls these (hereinafter simply referred to as
It is called ECU. ) 33.

Variable damping force type shock absorber 1FL,
As already mentioned in the embodiment of the first invention, 1FR, 1RL, and 1RR are piezo type damping force sensors that detect the damping force acting on the variable damping force type shock absorbers 1FL, 1FR, 1RL, and 1RR; Force variable shock absorber 1FL, 1FR, 1
It has a built-in piezo actuator that switches the damping force of RL and 1RR.

In addition, the variable damping force type shock absorber 1
FL, 1FR, 1RL, and 1RR are the suspension lower arms 35a and 36 for the left and right front and rear wheels, respectively.
Coil springs 35b, 36b, 37b, and 38b are provided between a, 37a, and 38a and the vehicle body 39.

The detection signals of each sensor and switch listed above are as follows.
The signal is input to the ECU 33, and the ECU 33 outputs a control signal to the piezo actuator described above.

Variable damping force type shock absorber 1FL, 1
Since the structure of FR, 1RL, and 1RR is completely similar to the shock absorber described in the embodiment, the same parts are denoted by the same reference numerals and the explanation will be omitted.

Next, the configuration of the ECU 33 will be explained based on FIG. 9. As shown in the figure, ECU33 is
It is configured as a logical operation circuit centered around the CPU 33a, ROM 33b, and RAM 33c, and the common bus 33
It is connected to an input section 33e and an output section 33f via d, and performs input/output with the outside. Piezo type damping force sensor 12FL, 12FR, 12RL, 12
The RR detection signal is input to the damping force signal detection circuit 41, and is further input to the stop lamp switch 3 via either the damping force switching signal generation circuit 42 or the damping force switching permission signal generation circuit 43.
1 and the detection signals of the vehicle speed sensor 32 are respectively sent from the input section 33e to the CPU 3 via the waveform shaping circuit 44.
3a. On the other hand, the CPU 33a drives the piezo actuators 11FL, 11FR, 11RL, 11RR from the output section 33f through the drive circuit 45.
Outputs a control signal to. Here, the damping force signal detection circuit 41 detects the piezo type damping force sensors 12FL, 12FR, 12 according to the magnitude of the damping force.
Input the charges generated by RL and 12RR and store them,
This is output as a damping force signal. The damping force switching signal generation circuit 42 also includes a differentiating circuit that inputs the damping force signal and outputs its rate of change, and a differential circuit that determines whether or not the rate of change is between an upper limit value and a lower limit value to increase the rate of change. A comparison circuit is provided that outputs a damping force switching signal of either damping force (low level) or low damping force (high level). Further, the damping force switching permission signal generation circuit 43 is composed of a comparison circuit and other logic circuits, and determines when the damping force becomes zero or when the damping force variable shock absorber expands and contracts based on the damping force signal. The period when the damping force becomes zero while transitioning from the extension side to the contraction side,
Alternatively, a signal (high level) that allows switching of the damping force during at least one of the periods when the damping force becomes zero on the contraction side, but prohibits switching of the damping force during other periods. Each signal (low level) is output as a damping force switching permission signal.

Next, the shock absorber control process executed by the ECU 33 will be explained based on the flowchart shown in FIG. This shock absorber control process is started when the ECU 33 is activated.

First, in step 100, a process of reading a damping force switching signal is performed. In the following step 110,
It is determined whether the current damping force is high damping force (HARD), and if the judgment is affirmative, the process proceeds to step 120.
On the other hand, if the determination is negative, the process proceeds to step 140.
In step 120, which is executed when the current damping force is determined to be a high damping force, the step 100 described above is executed.
It is determined whether the damping force switching signal read in is a low damping force (SOFT), and if the determination is affirmative, the process proceeds to step 130, while if the determination is negative, the process returns to step 100. In step 130, which is executed when the damping force switching signal read in step 100 above is low damping force (SOFT), the damping force is changed from high damping force (HARD) to low damping force (SOFT).
After outputting a control signal for switching to the piezo actuators 11FL, 11FR, 11RL, and 11RR, the process returns to step 100.

On the other hand, in step 140, which is executed when it is determined in step 110 that the current damping force is not high damping force (HARD), the damping force switching signal read in step 100 is set to high damping force (HARD).
It is determined whether or not it is, and if the determination is affirmative, the process proceeds to step 150, while if the determination is negative, the process returns to step 100. In step 150, which is executed when the damping force switching signal read in step 100 is a high damping force (HARD), a process of reading a damping force switching permission signal is performed. Next steps
In step 160, it is determined whether the damping force switching permission signal read in step 150 allows switching of the damping force (high level), and if an affirmative determination is made, the process proceeds to step 170; Then, the process returns to step 150 above. In step 170, which is executed when it is determined that the damping force switching permission signal read in step 150 above permits damping force switching (high level), the damping force is changed to low damping force (SOFT).
The control signal for switching from to high damping force (HARD) to the piezo actuators 11FL, 11FR,
After performing the process of outputting to 11RL and 11RR, the process returns to step 100. Thereafter, this shock absorber control process repeats steps 100 to 170.

In the first embodiment of the second invention, the piezo type damping force sensors 12FL, 12FR, 12RL,
12RR is the damping force detector M1, the piezo actuators 11FL, 11FR, 11RL, and 11RR are the damping force changing means M2, the damping force signal detection circuit 41 is the damping force signal generating means M3, and the damping force switching signal generating circuit 42 correspond to the change signal generating means M4. Further, among the processes executed by the ECU 33, step 160 functions as determination means M5, and step 170 functions as control means M6.

As explained above, according to the first embodiment of the second invention, when switching the damping force, the damping force is changed to the low damping force (low damping force) only when the damping force switching permission signal permits switching (high level). Since the damping force is switched from (SOFT) to high damping force (HARD), the damping force can be switched at an appropriate time. That is, the first
As shown in the timing chart in Figure 1, at time T1 when the damping force signal becomes zero, the damping force switching permission signal changes to high level (H), changing the damping force from low damping force (SOFT) to high damping force (HARD). ) is output. In this way, based on the detection results of the piezo type damping force sensor, the damping force is switched from low damping force to high damping force by selecting the time when the damping force of the variable damping force type shock absorber becomes zero, so the damping force It is possible to prevent impact vibration from occurring due to switching. Therefore, the riding comfort of the vehicle is improved, and the maneuverability and stability are also improved.

In addition, the control accuracy of damping force switching control can be improved by appropriately selecting the damping force switching timing.

For example, as shown in the timing chart of FIG. 12, during the transition from the extension side to the contraction side,
At time T2 when the damping force signal becomes zero, the damping force switching permission signal changes to high level (H), and a control signal to switch the damping force from low damping force (SOFT) to high damping force (HARD) is output. , a damping force switching permission signal generation circuit can also be configured. This configuration is particularly effective because the timing for switching damping force from low damping force to high damping force can be optimally selected, and a sudden increase in damping force caused by switching damping force can be prevented.

Further, in the first embodiment of the second invention, the damping force of the shock absorber is changed by the piezo actuator, but for example, as shown in FIG.
The same effect can be obtained by using a variable damping force type shock absorber 1FLS with a built-in 6FL.

Next, a second embodiment of the second invention will be described in detail based on the drawings. The difference between the second embodiment and the first embodiment is that the configuration of the electronic control unit and the shock absorber control processing are different. In addition,
Since the device configuration of the second embodiment is similar to that of the first embodiment described above, the same parts are denoted by the same reference numerals and the explanation will be omitted.

The configuration of the electronic control device that characterizes the second embodiment will be explained based on FIG. 14. As shown in the figure, the ECU 50 includes a CPU 50a, a ROM 50b,
It is configured as a logic operation circuit centered around the RAM 50c, is connected to an input section 50e and an output section 50f via a common bus 50d, and performs input/output with the outside. Piezo type damping force sensor 12FL, 12
The detection signals of FR, 12RL, and 12RR are input to a charge amplifier circuit 51, and one of the damping force signals output from the charge amplifier circuit 51 is output as is, and the other is output as a differentiated signal via a differentiator circuit 52. The detection signals of the vehicle speed sensor 32 are inputted to the CPU 50a from the input section 50e via the waveform shaping circuit 53, respectively. On the other hand, the CPU 50a outputs control signals from the output section 50f to the piezo actuators 11FL, 11FR, 11RL, and 11RR via the drive circuit 54.

Next, the configuration of the charge amplifier circuit 51 is as follows:
This will be explained based on the circuit diagram shown in FIG. As shown in the figure, the charge amplifier circuit 51 includes each of the piezo type damping force sensors 12FL and 12 described above.
4 provided corresponding to FR, 12RL, 12RR
power storage circuits 55FL, 55FR, 55RL, 55
It is composed of RR.

The above power storage circuits 55FL, 55FR, 55RL, 5
Since all 5RRs have the same configuration, the power storage circuit 5
This will be explained using 5FL as an example.

The power storage circuit 55FL is composed of an integrating circuit including an operational amplifier 56 and a capacitor 57, and a resistor 58 connected in parallel with the integrating circuit. When the charge generated by the piezo type damping force sensor 12FL is input to the storage circuit 55FL, the charge is transferred to the capacitor 5 by the action of the operational amplifier 56.
7 is stored. The charge stored in the capacitor 57 is sent to the differentiating circuit 52 as a damping force signal.
and is output to the input section 50e.

The differentiating circuit 52 is composed of circuit elements such as well-known operational amplifiers, and inputs the damping force signal and outputs its time differential value as a differential signal to the input section 50e.

Next, the shock absorber control process executed by the ECU 50 will be explained based on the flowchart of FIG. 16. This shock absorber control process is started when the ECU 50 is started.

First, in step 200, a process of reading a damping force signal is performed. In the following step 210, processing for reading the differential signal is performed. Next step
The process proceeds to step 220, where it is determined whether the absolute value of the differential signal read in step 210 is greater than or equal to a predetermined threshold value.If the judgment is affirmative, the process proceeds to step 230; on the other hand, if the judgment is negative, the process proceeds to step 230. Proceed to step 250. In step 230, which is executed when it is determined in step 220 that the absolute value of the differential signal is greater than or equal to a predetermined threshold value, it is determined whether the current damping force is high damping force (HARD). is determined, and if the determination is affirmative, the process proceeds to step 240, and on the other hand,
If a negative determination is made, the process returns to step 200 above. In step 240, which is executed when the current damping force is determined to be a high damping force, a control signal for switching the damping force from high damping force (HARD) to low damping force (SOFT) is sent to the piezo actuator 11FL. ，
After performing the process of outputting to 11FR, 11RL, and 11RR, the process returns to step 200 above.

On the other hand, in step 250, which is executed when it is determined in step 220 that the absolute value of the differential signal is less than a predetermined threshold value, the current damping force is determined to be low damping force (SOFT). Determine whether or not
If the judgment is affirmative, the process proceeds to step 260, while if the judgment is negative, the process returns to step 200. In step 260, which is executed when the current damping force is determined to be a low damping force, it is determined whether the damping force signal read in the above step 200 is approximately 0, and if the determination is affirmative. Proceed to step 270, while
If a negative determination is made, the process returns to step 200 above. In step 270, which is executed when an affirmative determination is made in step 260, the damping force is set to low damping force (SOFT).
The control signal for switching from to high damping force (HARD) to the piezo actuators 11FL, 11FR,
After performing the process of outputting to 11RL and 11RR, the process returns to step 200 above. Thereafter, this shock absorber control process repeats steps 200 to 270.

In the second embodiment of the second invention, piezo type damping force sensors 12FL, 12FR, 12RL,
12RR is the damping force detector M1, piezo actuators 11FL, 11FR, 11RL, 11RR are the damping force changing means M2, the charge amplifier circuit 51 is the damping force signal generating means M3, and the differentiating circuit 52 is the change signal generating means M4. , each applicable. Also,
Among the processes executed by the ECU 50, step 220,
260 functions as the determination means M5, and step 270 functions as the control means M6.

As explained above, according to the second embodiment of the second invention, even when an impact vibration occurs such as when riding over a bump on the road surface, the damping force is changed from high damping force to low damping force at a suitable time to absorb the impact. At the same time, it is possible to switch from low damping force to high damping force at an appropriate time to suppress vibrations caused by the impact.
That is, as shown in the timing chart of FIG. 17, when a wheel traveling in the direction of arrow C rides over a protrusion 59 on the road surface, the differential signal becomes positive at time T3 when the wheel is about to ride on the protrusion 59. Since the threshold value +Vref is exceeded, the damping force is switched from high damping force (HARD) to low damping force (SOFT) at the same time T3. Therefore, the impact when riding on the protrusion 59 is softened. Eventually, when the wheel gets over the protrusion 59, the differential signal becomes a positive threshold +
It falls within the range of Vref ~ negative threshold value - Vref. Therefore, at time T4 when the damping force signal becomes 0, the damping force is switched from low damping force (SOFT) to high damping force (HARD). For this reason, the protrusion 5
The vibrations generated due to the 9-crossing are suppressed, and the vibrations converge more quickly. Therefore, the riding comfort of the vehicle is improved, and the maneuverability and stability are also improved.

Next, FIG. 18 shows a system configuration of a shock absorber control device according to a third embodiment of the second invention.

As shown in the figure, the vehicle shock absorber control device 60 includes variable damping force type shock absorbers 1FL, 1FR, 61RL, and 61RR, a stop lamp switch 31 that detects the brake operation state of the vehicle, and a stop lamp switch 31 that detects the vehicle running speed. Vehicle speed sensor 32
and an ECU 62 that controls them.

Variable damping force type shock absorber 1FL,
1FR, 61RL, and 61RR are suspension lower arms 35a and 36 for left and right front and rear wheels, respectively.
Coil springs 35b, 36b, 37b, 38b are provided between the vehicle body 63 and the coil springs 35b, 36b, 37b, 38b.

The variable damping force type shock absorbers 1FL, 1FR on the front wheel side are, as described above, equipped with piezo type damping force sensors for detecting the damping force acting on the variable damping force type shock absorbers 1FL, 1FR on the front wheel side. A piezo actuator that switches the damping force of variable damping force type shock absorbers 1FL and 1FR on the side is built-in. On the other hand, the variable damping force type shock absorbers 61RL and 61RR on the rear wheel side are different in structure from the variable damping force type shock absorbers 1FL and 1FR on the front wheel side.
1RL will be explained as an example. As shown in FIG. 19, the variable damping force type shock absorber 61RL on the rear wheel side is interposed between the vehicle body 63 and the rear wheel suspension lower arm 37a, and includes a cylinder 64 connected to the lower arm 37a, and a cylinder 64 connected to the lower arm 37a. A piston 65 that slidably fits into the cylinder 64, a rotary valve 67 that adjusts the opening degree of a variable orifice 66 provided in the piston 65, and a control rod 68 that operates the rotary valve 67.
and a motor actuator 69RL for rotating the control rod 68.
The above motor actuator 69RL is the motor 6
9a, pinion gear 69b, sector gear 69
The motor 69a rotates in response to a control signal from the ECU 62, and the driving force is transmitted in the above order. The cylinder 64 also includes fixed orifices 70a and 70b. Rear wheel variable damping force shock absorber 61 having the above configuration
RL is the motor actuator 69RL that controls the control rod 68 according to the control signal from the ECU 62.
By rotating the rotary valve 67, the rotary valve 67 is switched between a communicating state and a blocking state, and the damping force of the shock absorber is changed between a low damping force and a high damping force.

Next, the configuration of the ECU 62 will be explained based on FIG. 20. As shown in the figure, ECU62
is configured as a logic operation circuit centered on the CPU 62a, ROM 62b, and RAM 62c, and the common bus 6
2d to an input section 62e and an output section 62f, and performs input/output with the outside. Piezo type damping force sensor 12FL installed only on the front wheel side,
The detection signal of 12FR is input to the charge amplifier circuit 71 and converted into a damping force signal, one as a damping force signal, the other as a differential signal via a differentiation circuit 72, and a detection signal of the stop lamp switch 31 and the vehicle speed sensor 32. is the waveform shaping circuit 73
The signals are respectively input to the CPU 62a from the input section 62e. On the other hand, the CPU 62a has an output section 62f.
, to the piezo actuators 11FL and 11FR disposed on the front wheel side via the drive circuit 74, and to the motor actuators 69RL and 69RR disposed on the rear wheel side via the drive circuit 75, respectively. Outputs a control signal.

Next, the shock absorber control process executed by the ECU 62 will be explained based on the flowcharts shown in FIGS. 1, 2, 3, and 4. This shock absorber control process is started when the ECU 62 is activated.

First, in step 300, it is determined whether the current damping force on the front wheel side is high damping force (HARD) or not.
If the judgment is affirmative, the process proceeds to step 310, while if the judgment is negative, the process proceeds to step 500. In step 310, which is executed when the current damping force on the front wheel side is determined to be a high damping force, it is determined whether the current damping force on the rear wheel side is a high damping force (HARD). If the judgment is affirmative, the process proceeds to step 320, while if the judgment is negative, the process proceeds to step 400. In step 320, which is executed when the current damping force on the rear wheel side is determined to be a high damping force, the delay time TD1
It is determined whether or not the above elapsed time has elapsed, and if an affirmative determination is made, the process proceeds to step 370, while if a negative determination is made, the process proceeds to step 330. Steps executed when it is determined that delay time TD1 has not yet elapsed
At 330, processing for reading the differential signal is performed.
In the following step 340, it is determined whether the absolute value of the differential signal read in the step 330 is greater than or equal to a predetermined threshold value, and if an affirmative determination is made, the process proceeds to step 350; Then, the process returns to step 300 above. Steps executed when it is determined in step 340 that the absolute value of the differential signal is greater than or equal to a predetermined threshold value.
On the 350, the damping force on the front wheel side is set to high damping force (HARD).
A process is performed to output a control signal for switching from low damping force to low damping force (SOFT) to the piezo actuators 11FL and 11FR. In the next step 360,
After calculating and setting the delay time TD1, the process returns to step 300 above. Here, the delay time TD1 is obtained by dividing the wheel base of the vehicle by the vehicle speed. In other words, the delay time TD1 is the time equivalent to the time it takes for the rear wheels to run over the obstacle that the front wheels have run over.

On the other hand, the step executed when it is determined in step 320 that the delay time TD1 or more has elapsed.
In 370, the damping force on the rear wheel side is set to high damping force (HARD).
After outputting a control signal for switching from to low damping force (SOFT) to the motor actuators 69RL and 69RR, the process returns to step 300.

On the other hand, in step 400, which is executed when it is determined in step 310 that the current rear wheel damping force is not a high damping force (HARD), a differential signal is read. In the following step 410,
It is determined whether the absolute value of the differential signal read in step 400 is greater than or equal to a predetermined threshold value, and if an affirmative determination is made, the process proceeds to step 420.
On the other hand, if the determination is negative, the process proceeds to step 440. In step 420, which is executed when it is determined in step 410 that the absolute value of the differential signal is greater than or equal to a predetermined threshold value, the damping force on the front wheel side is changed from high damping force (HARD) to low damping force. A process is performed to output a control signal for switching to the force (SOFT) to the piezo actuators 11FL and 11FR. In the following step 430, the process calculates and sets the delay time TD1, and then proceeds to step 440.
In step 440, it is determined whether or not the holding time TD2 or more has elapsed. If the determination is affirmative, the process proceeds to step 450, while if the determination is negative, the process proceeds to step 300.
Return to Here, the holding time TD2 is the time during which the damping force on the rear wheel side is held at a low damping force (SOFT), and the time during which the damping force on the front wheel side is held at a low damping force.
Based on t1, a predetermined function f
(t1), or according to a map that defines the relationship between the time t1 and the retention time TD2. That is, the holding time TD2 is a time period corresponding to the time period during which the damping force on the rear wheel side is maintained at a low damping force when the rear wheel runs over an obstacle that the front wheel has run over.

In step 450, which is executed when it is determined in step 440 that the retention time TD2 or more has elapsed,
After outputting a control signal for switching the rear wheel damping force from low damping force (SOFT) to high damping force (HARD) to the motor actuators 69RL and 69RR, the process returns to step 300.

On the other hand, in step 500, which is executed when it is determined in step 300 that the current front wheel damping force is not high damping force (HARD), the current rear wheel damping force is high damping force (HARD). It is determined whether or not it is, and if the determination is affirmative, the process proceeds to step 510, while if the determination is negative, the process proceeds to step 600.
In step 510, which is executed when it is determined that the current damping force on the rear wheel side is a high damping force, it is determined whether the delay time TD1 or more has elapsed, and if the determination is affirmative, the process proceeds to step 570. , if a negative determination is made, each proceeds to step 520. In step 520, which is executed when it is determined that the delay time TD1 has not yet elapsed, a process of reading the damping force signal and the differential signal is performed. In the following step 530,
Based on the damping force signal read in step 520 above, it is determined whether the damping force on the front wheel side at the time of transition from the extension side to the contraction side is approximately 0, and if an affirmative determination is made, the process proceeds to step 540. , On the other hand, if the determination is negative, the process returns to step 300 above. In step 540, which is executed when it is determined in step 530 that the damping force on the front wheel side at the time of transition from the extension side to the contraction side is approximately 0, the step 540 described above is executed.
It is determined whether the absolute value of the differential signal read in step 520 is greater than or equal to a predetermined threshold value, and if an affirmative determination is made, the process returns to step 300, and on the other hand,
If a negative determination is made, the process proceeds to step 550. In step 550, which is executed when it is determined in step 540 that the absolute value of the differential signal is less than a predetermined threshold value, the damping force on the front wheel side is changed from low damping force (SOFT) to high damping force. The control signal for switching to force (HARD) is sent to the piezo actuator 11 mentioned above.
Processing to output to FL and 11FR is performed. In the following step 560, the above-mentioned holding time TD2 is calculated and set, and then the above-mentioned step 300 is performed.
Return to

On the other hand, the step executed when it is determined in step 510 that the delay time TD1 or more has elapsed.
In 570, the damping force on the rear wheel side is set to high damping force (HARD).
After outputting a control signal for switching from to low damping force (SOFT) to the motor actuators 69RL and 69RR, the process returns to step 300.

On the other hand, in step 600, which is executed when it is determined in step 500 that the current damping force on the rear wheel side is not high damping force (HARD), the holding time is
It is determined whether or not TD2 or more has elapsed, and if a positive determination is made, the process proceeds to step 610, while if a negative determination is made, the process proceeds to step 620. Steps to be executed when it is determined that the retention time TD2 or more has already elapsed
In 610, the damping force on the rear wheel side is set to low damping force (SOFT).
After outputting a control signal for switching from to high damping force (HARD) to the motor actuators 69RL and 69RR, the process proceeds to step 620.
In the following step 620, a process of reading the damping force signal and the differential signal is performed. Next step 630
Based on the damping force signal read in step 620, it is determined whether the damping force on the front wheel side at the time of transition from the extension side to the contraction side is approximately 0, and if an affirmative determination is made, the process proceeds to step 620. The process proceeds to step 640, and if the determination is negative, the process returns to step 300.
In step 640, which is executed when it is determined in step 630 that the damping force on the front wheel side at the time of transition from the extension side to the contraction side is approximately 0, the absolute value of the differential signal read in the above step 620 is ,
It is determined whether or not the threshold value is greater than or equal to a predetermined threshold value, and if an affirmative determination is made, the process returns to step 300,
On the other hand, if the determination is negative, the process proceeds to step 650. In step 650, which is executed when it is determined in step 640 that the absolute value of the differential signal is less than a predetermined threshold value, the damping force on the front wheel side is changed from low damping force (SOFT) to high damping force. A process is performed to output a control signal for switching to the hard force (HARD) to the piezo actuators 11FL and 11FR. In the following step 660, the above-mentioned holding time TD2 is calculated and set, and then the above-mentioned step 660 is performed.
Back to 300. Thereafter, this shock absorber control process repeats steps 300 to 660.

In the third embodiment of the second invention, the piezo type damping force sensors 12FL, 12FR are used as the damping force detector M1, and the piezo actuators 11FL, 11
FR is the damping force changing means M2, the charge amplifier circuit 71 is the damping force signal generating means M3, and the differentiating circuit 7
2 corresponds to the change signal generating means M4. Also, among the processes executed by the ECU 62, the steps
Steps 530, 540, 630, and 640 function as determination means M5, and steps 550 and 650 function as control means M6, respectively.

As explained above, the third embodiment of the second invention is
Piezo type damping force sensor 12FL only on front wheel side,
12FR and piezo actuator 11FL, 1
Variable damping force type shock absorbers 1FL and 1FR with built-in 1FR are installed, and the rear wheel side does not have a damping force detection function, but instead uses a normal motor actuator 69.
The damping force variable type shock absorber 61RL and 61RR with only built-in RL and 69RR were configured. For this reason, the front wheels detect the damping force with high precision and change the damping force with high responsiveness, and the rear wheels change the damping force after the delay time TD1 calculated by dividing the wheel base by the vehicle speed has elapsed. moreover,
The damping force on the rear wheel side is maintained at a low damping force for the holding time TD2 calculated according to the duration time of the low damping force on the front wheel side, so it has a highly accurate damping force detection function and high responsiveness when changing the damping force. Variable damping force shock absorber 1FL, 1FR only for the required front wheel side
Since the rear wheel side only needs to be provided with ordinary variable damping force type shock absorbers 61RL and 61RR, the same effects as those of the above-mentioned embodiments can be achieved with a simple device configuration.

Further, since the number of signals input to the ECU 62 is reduced and the control of the rear wheels becomes relatively easy, the shock absorber control process is also simplified.

Although several embodiments of the inventions have been described above, the inventions are not limited to these embodiments, and may be implemented in various ways without departing from the gist of the inventions. Of course.

Effects of the Invention As detailed above, the damping force detector of the first invention is configured to directly measure the strain caused by the acting force that expands and contracts the shock absorber, that is, the strain that occurs in response to the damping force. . For this reason,
Since the damping force generated in the shock absorber can be accurately measured with a simple structure, it has the excellent effect of dramatically improving the measurement accuracy of the damping force.

Furthermore, since a piezoelectric element is used, the responsiveness of damping force detection is also improved.

Furthermore, since the damping force detector is built into the shock absorber's piston rod, it is less susceptible to contamination or damage even when used in harsh environments, so its reliability and durability can be maintained at a high level.

Furthermore, since the structure is simple and it can be built into the piston rod of the shock absorber, the scope of application of the damping force detector is expanded and its versatility is increased.

In particular, since the pressure member is composed of two members, one having a convex surface at one end that makes spherical contact with the other, and the other having a concave surface at one end, the bending moment acting on the piston rod of the shock absorber is controlled by the piezoelectric element. Since the transmission to the bending moment is blocked by the spherical contact portion, it is possible to prevent the piezoelectric element from erroneously detecting the strain caused by the bending moment as being due to a change in damping force, thereby further improving detection accuracy.

Further, as described above, the shock absorber control device of the second invention increases the damping force when there is no large change in the damping force acting on the shock absorber and when the damping force of the shock absorber is near zero. It is configured to change to the larger side. Therefore, it is possible to prevent the acting force transmitted through the shock absorber from changing suddenly as the damping force of the shock absorber is changed, which is an excellent feature in that the damping force can be changed at an appropriate time. be effective.

Further, along with the above effects, the ride comfort of the vehicle is improved, and the maneuverability and stability are also improved.

Furthermore, since the damping force of the shock absorber is controlled based on the damping force of the shock absorber directly detected by the damping force detector and changes in this damping force, the damping force can be changed accurately and the control accuracy is It also increases.

Note that, for example, if the change signal outputted by the change signal generation means is within a predetermined range, and
The damping force signal outputted by the damping force signal generating means is zero,
Alternatively, if the value is close to zero, and if the configuration is such that it is determined that the shock absorber is in a high damping force switchable state when its expansion/contraction movement shifts from the extension side to the contraction side, the damping force change is not performed. This can be done at the most suitable time. This is particularly effective when performing control to suppress rolling by changing to high damping force after absorbing shocking vibrations caused by single irregularities on the road surface using low damping force. shows.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram conceptually illustrating the contents of the second invention, Fig. 2 is a vertical cross-sectional view of a piezo type damping force sensor, Fig. 3 is an exploded view showing the structure, and Fig. 4 is Similarly, FIG. 5 is a longitudinal cross-sectional view showing the structure of a variable damping force type shock absorber incorporating the piezo type damping force sensor, FIG. 5 is a graph showing the damping force characteristics, and FIG. FIG. 7 is a longitudinal cross-sectional view of a piezo-type damping force sensor which is a further embodiment (corresponding to 1), FIG. 7 is a longitudinal cross-sectional view of a piezo-type damping force sensor which is another embodiment, and FIG. 8 is a first embodiment of the second invention. A system configuration diagram of a shock absorber control device for a vehicle. FIG. 9 is a block diagram showing the configuration of the electronic control device, FIG. 10 is a flowchart showing the control, and FIG. 11 is a flowchart showing the control. Timing chart, FIG. 12 is a timing chart showing the control situation of another embodiment.
FIG. 13 is a longitudinal sectional view showing the structure of another variable damping force type shock absorber, FIG. 14 is a block diagram showing the configuration of the electronic control device of the second embodiment of the second invention, and FIG. 15 is the same charge amplifier. A circuit diagram showing the circuit, FIG. 16 is a flowchart showing the control, FIG. 17 is a timing chart showing the control, and FIG. 18 is a vehicle shock absorber control according to the third embodiment of the second invention. The system configuration diagram of the device, FIG. 19 is a longitudinal sectional view of the variable damping force type shock absorber, FIG. 20 is a block diagram showing the configuration of the electronic control device, and FIG. 21 is a diagram showing the configuration of the electronic control device. This is also a flowchart showing the control. M1... damping force detector, M2... damping force changing means,
M3...damping force signal generation means, M4...change signal generation means, M5...judgment means, M6...control means, 1FL,
1FR, 1RL, 1RR, 1FLS, 61RL, 61
RR...variable damping force shock absorber, 6...piston rod, 11FL...piezo actuator,
12FL...Piezo type damping force sensor, 19FLa,
19FLb...piezoelectric element, 20FL, 27FLa...pressure member, 27FLb...pressure transmission member, 28FLa...disc spring, 28FLb...disc spring receiver, 30, 60...vehicle shock absorber control device, 33, 50, 62
...Electronic control unit (ECU), 33a, 50a, 62
a...CPU, 41...damping force signal detection circuit, 43...
Damping force switching permission signal generation circuit, 51, 71...Charge amplifier circuit, 52, 72...Differentiating circuit.

Claims (1)

[Scope of Claims] 1. A shock absorber consisting of a cylinder and a piston that is slidably fitted into the cylinder;
A piezoelectric element that generates an electric charge corresponding to strain transmitted from the outside, and a piezoelectric element that is fixed to the piston rod and generates electric charge on the piston rod along the sliding direction due to an acting force that expands and contracts the shock absorber. a pressure member that transmits strain to the piezoelectric element; and a pressure member that has a convex surface at one end that makes spherical contact with each other and a concave surface to transmit only strain in the axial direction of the piston rod. 1. A damping force detector comprising two members, a pressure member having a pressure member at one end. 2 installed in a piston rod connected to the piston of a shock absorber consisting of a cylinder and a piston slidably fitted to the cylinder;
A piezoelectric element that generates an electric charge corresponding to strain transmitted from the outside, and a piezoelectric element that is fixed to the piston rod and generates electric charge on the piston rod along the sliding direction due to an acting force that expands and contracts the shock absorber. a pressurizing member that transmits strain to the piezoelectric element; a damping force detector comprising: a damping force changing means that changes the damping force of the shock absorber according to an external command; and a damping force detector that changes the damping force of the shock absorber in accordance with an external command. a damping force signal generating means for storing electric charge generated by the damping force signal and outputting a damping force signal; and a change signal generating means for outputting a change signal according to a time change of the damping force signal outputted by the damping force signal generating means. , at least when the change signal outputted by the change signal generating means is within a predetermined range, and the damping force signal outputted by the damping force signal generating means is zero or a value near zero, high attenuation is achieved. a determination means for determining that the force switch is possible; and when the determination means determines that the high damping force switch is possible, a command to change the damping force of the shock absorber to a higher side is issued to the damping force. A shock absorber control device comprising: a control means for outputting an output to a change means; and a shock absorber control device. 3 The determining means determines that the change signal output by the change signal generating means is within a predetermined range, and the damping force signal output by the damping force signal generating means is zero;
Alternatively, the value is close to zero, and furthermore, when the stretching motion of the shock absorber shifts from the extension side to the contraction side, it is determined that the high damping force switch is possible. Shock absorber control device.