JP2576222Y2 - Suspension system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a suspension system for a vehicle such as an automobile, and more particularly to a technique for optimally controlling damping force characteristics.

(Prior Art) Conventionally, as a variable damping force suspension system provided with a hydraulic damper having a variable damping force by a piezoelectric element, for example, a suspension system described in JP-A-61-85210 is known. ing.

The conventional system includes a damping force variable hydraulic buffer having a piezoelectric element that can change a damping force while detecting a hydraulic pressure in a cylinder, and a controller that drives and controls the piezoelectric element, Normally, the controller drives and controls the piezoelectric element so as to give a low damping force characteristic by giving priority to riding comfort, and when a signal indicating a predetermined state such as scat, dive, roll, etc. of the vehicle is input, these are controlled. A predetermined time (for example, about 2
Seconds) Drive control of the piezoelectric element to obtain high damping force characteristics,
Maneuvering stability was to be ensured.

(Problems to be Solved by the Invention) However, in the above-mentioned conventional system, the high damping force characteristic is simply set only at the time of scat, dive, and roll. Is always a constant high damping force, which is not sufficient in terms of achieving both riding comfort and steering stability. In other words, the hydraulic shock absorber is not only the scat dive roll,
A stroke is made by the unevenness of the road surface, and damping force control according to the unevenness of the road surface is also desired. However, the demand cannot be achieved, and at the same time, a constant height is required until the damping force does not need to be increased so much. It becomes a damping force, and the ride quality deteriorates.

Furthermore, according to the above-described conventional system, when it is determined that high damping force characteristics are necessary, the system is controlled to the high damping force characteristics for a predetermined time simply by operating a timer. Therefore, it cannot be said that the damping force characteristic control has been performed. That is, during a predetermined time during which control corresponding to the left roll is being performed, while the vehicle is in the state of the right roll, or while performing control corresponding to the dive,
Conversely, when the vehicle is in the scut state, the riding comfort and the driving stability are rather deteriorated.

As described above, in the conventional system, it is impossible to achieve both the riding comfort and the driving stability of the vehicle at a low level.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a suspension system capable of realizing a high level of compatibility between a vehicle's riding comfort and steering stability at a high level. .

(Means for Solving the Problems) In order to achieve the above object, in the suspension system of the present invention, the valve is opened to allow the flow of the hydraulic fluid along with the extension stroke of the piston, and the volume of the suspension decreases with the stroke. An expansion-side disk valve that generates pressure in the side liquid chamber, and a compression-side disk valve that generates pressure in the compression-side liquid chamber whose volume decreases with the stroke by opening to allow the flow of hydraulic fluid during the compression-side stroke of the piston A hydraulic shock absorber having an expansion-side piezoelectric element and a compression-side piezoelectric element provided so as to change the bending stiffness of each of the expansion-side disk valve and the compression-side disk valve so that the generated damping force can be changed; The expansion-side hydraulic pressure sensor and the compression-side hydraulic pressure sensor that detect the hydraulic pressures of the liquid chamber and the compression-side liquid chamber, respectively, and changes in the hydraulic pressures detected by the expansion-side hydraulic pressure sensor and the compression-side hydraulic pressure sensor, respectively. Finding the extension side change rate and the compression side change rate, which are the chemical conversion rates, and when the extension side change rate becomes an extreme value, while applying a drive voltage set to be smaller as the extreme value is larger for the extension side piezoelectric element, When the extension side change rate becomes 0, the electric charge of the extension side piezoelectric element is discharged, and when the compression side change rate becomes an extreme value, it is set to be smaller as the extremum is larger with respect to the compression side piezoelectric element. And a damping force control unit for discharging the electric charge of the compression side piezoelectric element when the compression side change rate becomes 0 while applying the driving voltage.

(Operation) The operation of the suspension system of the present invention will be described.

In the present invention, when the extension-side piezoelectric element is driven, the rigidity of the extension-side disk valve increases, and the extension-side damping force characteristic becomes hard. On the other hand, when the compression-side piezoelectric element is driven, the rigidity of the compression-side disk valve increases. Thus, the compression characteristic on the compression side becomes hard.

In the hydraulic shock absorber, the hydraulic pressure in the expansion-side liquid chamber or the compression-side liquid chamber increases according to the stroke direction of the piston. This change in hydraulic pressure is proportional to the generated damping force. The hydraulic pressure in the expansion-side hydraulic chamber and the hydraulic pressure in the compression-side hydraulic chamber are detected independently and continuously by the expansion-side hydraulic pressure sensor and the compression-side hydraulic pressure sensor, respectively. The state of generation of the damping force of the shock absorber and the state of stroke of the piston can be detected.

The damping force control means calculates a change rate of each of the detected hydraulic pressures on the extension side and the compression side, and when the extension side change rate or the compression side change rate corresponding to the stroke direction becomes an extreme value, the extension side piezoelectric element or the compression side piezoelectric element A drive voltage of a smaller value is applied to the piezoelectric element which changes the rigidity of the disk valve in the stroke direction as the magnitude of the extremum increases, and thereafter, when the rate of change becomes zero, the electric charge of the piezoelectric element is discharged.

That is, during the period from when the rate of change of the hydraulic pressure in each of the expansion-side and pressure-side liquid chambers corresponding to the generated damping force reaches an extreme value until the rate of change becomes zero, the elastic force of the suspension mainly increases the stroke speed. In the hydraulic shock absorber, it is in a region where vibration damping is required (hereinafter referred to as a vibration damping region)
During this time, in the present invention, the hydraulic shock absorber is damped with high damping force characteristics. Also, during the period from the time when the change rate of the hydraulic pressure becomes 0 to the extreme value, the elastic force of the suspension mainly acts to reduce the stroke speed. Is in a region that acts to vibrate the vehicle body (hereinafter referred to as a vibration region). In the meantime, in the present invention, the transmission of vibration to the vehicle body is suppressed by setting the hydraulic shock absorber to have a low damping force characteristic.

Therefore, in the case of a single input in which the wheel passes over one protrusion or passes through one hole, the stroke is determined according to the stroke during the stroke from the top dead center or the bottom dead center to the neutral position. The rate of change of the generated hydraulic pressure goes from the extreme value to zero, and during this time, the vibration is damped by being applied to the piezoelectric element and controlled to have high damping force characteristics. After that, when the neutral position is exceeded, the rate of change of the hydraulic pressure generated according to the stroke becomes zero, so that the electric charge of the piezoelectric element is discharged and controlled to a low damping force characteristic, so that the hydraulic shock absorber is controlled. Does not act on the vibration direction of the vehicle body.

Also, while the hydraulic shock absorber is performing the extension side stroke, for example, the wheel falls into the hole, or while the hydraulic shock absorber is performing the compression side stroke, for example, the wheel rides on the protrusion. When a composite input is made to the hydraulic shock absorber as in the case of the above, the composite input is a vibration suppression area (a stroke area from a top dead center or a bottom dead center to a neutral position,
At this time, the rate of change is controlled to a high damping force characteristic according to the extreme value), and the vibration is damped by being already controlled to the high damping force characteristic. The composite input is composed of an excitation area (a stroke area from the neutral position to the top dead center or the bottom dead center, and is controlled to have a low damping force characteristic when the rate of change becomes zero at this time). In this case, the rate of change of the hydraulic pressure becomes an extreme value due to this input, so that the vibration is controlled again according to the high damping force characteristic.

The magnitude of the extreme value of the rate of change of the hydraulic pressure corresponds to the input acceleration to the hydraulic shock absorber. For example, the extreme value increases as the input such as thrust into the vehicle body increases. Thus, in such a case, the input is absorbed by controlling the damping characteristic to be low. Conversely, when the input is small, the damping characteristic is controlled to be high to suppress the vibration of the vehicle body.

Therefore, when the piston acceleration is low (for example, when the vehicle travels at high speed on a road surface with little unevenness, or when the vehicle body rolls, cuts, or dives), a large drive is applied to the piezoelectric element on the stroke direction side in the excitation area. A voltage is applied to control the damping force to a high damping force characteristic, whereby vibration of the vehicle body is suppressed and a sense of tightness is obtained, and high steering stability is obtained.

Conversely, when the piston acceleration is large (for example, when traveling on a rough road with severe unevenness), a small drive voltage is applied to the piezoelectric element in the stroke direction in the excitation area, and the damping force is larger than the above. Is controlled to be low, whereby the shock on the wheel side is absorbed and the vibration is not transmitted to the vehicle body side, and the riding comfort is improved.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

 First, the configuration of the embodiment will be described.

FIG. 2 is an overall configuration diagram showing a hydraulic shock absorber used in the suspension unit of one embodiment of the present invention. In FIG. 2, reference numeral 1 denotes a variable damping force type hydraulic shock absorber, It is provided at each of the four wheels. The hydraulic shock absorber 1 includes a sealed outer cylinder 2, a cylinder 3 built in the outer cylinder 2, a piston rod 4 inserted from one end of the cylinder 3, and a cylinder 3 provided at the tip of the piston rod 4. A piston 5 sliding axially on the inner wall of the cylinder 3, a bottom valve 6 provided at the lower end of the cylinder 3, a reservoir chamber 7 formed by the inner wall of the outer cylinder 2 and the cylinder 3,
A rod guide 8 for supporting the piston rod 4, an oil seal 9 provided on the upper part of the rod guide 8,
And a stopper plate 10 that closes the upper part of the device.

The outer cylinder 2 has a bottomed cylindrical shape, houses the cylinder 3, the rod guide 8 and the oil seal 9, and is formed by caulking the upper end. An eye bush 11 and an eye 12 for attachment to a vehicle axle or the like are fixed to a lower end of the outer cylinder 2.

The piston 5 moves the inside of the cylinder 3
And a compression-side liquid chamber 15 whose internal volume is reduced during the compression stroke.

The cylinder 3 has a bottom body 17 having an upper end opening closed by a rod guide 8 and a communication hole 16 at a lower end, and a bottom valve 6 is attached to the bottom body 17. The bottom valve 6 is opened and closed by a check valve 18 that opens during the extension stroke, a port 19 through which hydraulic fluid flows when the check valve 18 opens, a pressure-side disc valve (hereinafter referred to as a pressure-side valve) 20 that opens during the pressure stroke, and a pressure-side valve 20. The orifice 21 includes an orifice 21, a stopper plate 22 for regulating the opening of the check valve 18, and a caulking pin 23 for fixing the check valve 18 and the like to the bottom body 17. In the extension stroke, the hydraulic fluid in the reservoir chamber 7 opens the check valve 18 due to a pressure difference between the hydraulic fluid in the pressure side liquid chamber 15 and flows into the pressure side liquid chamber 15. At this time, the opening of the check valve 18 is regulated by the stopper plate 22. In the pressure stroke, the hydraulic fluid in the pressure side liquid chamber 15 is
And flows into the reservoir chamber 7 through the communication hole 16 while generating a damping force corresponding to the opening. A seal member 24 made of a low friction material such as Teflon is provided on an outer peripheral portion of the piston 5, and the seal member 24 slides in contact with an inner wall of the cylinder 3. The piston rod 4 has a retainer.
25 is fixed, and the retainer 25, together with an elastic rebound stopper 26 provided on the upper portion, reduces the collision between the piston 5 and the rod guide 8.

A piston rod 4 is provided on the inner peripheral portion of the oil seal 9.
A main lip 27 that elastically contacts the inside and maintains liquid tightness inside, and a dust lip 28 that blocks muddy water and the like from the outside are formed.

The lower portion of the stopper plate 10 is fitted to the upper end of the outer cylinder 2. The wiring 30 extended from the upper end of the piston rod 4 is connected to the control unit 100.

FIG. 1 shows a cross section around the piston 5, where the upper side in the figure is the vehicle body side and the lower side in the figure is the wheel side. In the drawing, a wiring passage 41 for accommodating the wiring 30 is formed at the center of the piston rod 4, and the wiring passage 41 is gradually enlarged and fitted and sealed by a seal portion 41a at a lower end. It is screwed with the piston 5 at the portion 41b.

The piston 5 has a main body 42 screwed to the piston rod 4.
And a sleeve 43 screwed to the lower end of the main body 42. An adjust nut 44 is screwed and fixed to the lower end of the sleeve 43. The main body 42 has a hollow part 45, a communication hole 46 for communicating the hollow part 45 with the extension side liquid chamber 14, and a hollow part 45 connected to the pressure side liquid chamber.
A communication hole 47 that communicates with the communication hole 15 is formed.

The sleeve 43 has a communication hole 48 for communicating the hollow portion 45 with the pressure side liquid chamber 15. In addition, piston 5
In the inside of the main body 42 and the sleeve 43, accommodation holes 49, 50 having a circular cross section are formed, and the accommodation holes 49, 50 are formed in the hollow portion 45.
Is in communication with

Inside the hollow portion 45, a valve body 51 is fixedly accommodated between a shoulder portion 42a formed on the inner periphery of the main body 42 and an upper end of the sleeve 43, and the valve body 51 is provided in the hollow portion 45. 45 is partitioned into an upper liquid chamber 52 that communicates with the extension liquid chamber 14 through the communication hole 46 and a lower liquid chamber 53 that communicates with the compression liquid chamber 15 through the communication hole 48.

The valve body 51 has an upper liquid chamber 52 and a lower liquid chamber 53 that are separately communicated with each other, and an expansion channel 54 that is opened and closed by an expansion disk valve 56 and a compression channel that is opened and closed by a compression disk valve 57. 55 are provided. That is,
During the extension side stroke, the hydraulic fluid in the extension side liquid chamber 14 passes through the communication hole 46 to the upper liquid chamber 52 to the extension side flow path 54, opens the extension side disc valve 56, and then passes through the communication hole 48 to the pressure side liquid chamber. Outflow to 15. On the other hand, during the pressure side stroke, the hydraulic fluid in the pressure side liquid chamber 15 is
After the pressure-side flow path 55 to the pressure-side disc valve 57 are opened, the liquid flows out to the extension-side liquid chamber 14 through the upper liquid chamber 52 to the communication hole 46.

The extension side and compression side disc valves 56 and 57 are formed of a plurality of thin plates and have a predetermined bending rigidity.
It changes the opening area of the expansion-side flow path 54 and the compression-side flow path 55 to generate a predetermined damping force in accordance with the opening area. The damping force characteristic of the vessel 1 is configured to change.

An accommodation hole 49 is provided on the inner peripheral upper surface of the compression side disc valve 57.
The lower end of a slider 58 housed therein so as to be slidable up and down is abutted. A first piezoelectric element 80 is provided between the slider 58 and a cap 64 whose upper end is supported by an adjust nut 69 screwed to the upper end of the main body 42.
Is interposed. Here, the first piezoelectric element 80
Utilizing the piezoelectric effect and inverse piezoelectric effect (also called electrostriction effect) of predetermined ceramics (hereinafter, referred to as piezoelectric material),
Many thin piezoelectric materials having a pair of electrodes (for example, 10
The piezoelectric effect means that when a voltage is applied to an electrode of a piezoelectric material, the piezoelectric material expands and contracts in the vertical direction in the figure according to a change in the applied voltage (hereinafter, referred to as “the piezoelectric effect”). On the other hand, the inverse piezoelectric phenomenon is a phenomenon in which when a pressure or a displacement force is applied in the vertical direction of the piezoelectric material, an electromotive force is generated in accordance with the displacement of the piezoelectric material, From the magnitude of the electromotive force, the magnitude of the pressure or the displacement force applied to the piezoelectric material can be detected.

Therefore, when a voltage is applied to the first piezoelectric element 80 to expand it, the slider 58 is pushed downward because the first piezoelectric element 80 has its upper end supported by the adjustment nut 69 via the cap 64. The pressure side disc valve 57
And the bending rigidity of the compression-side disk valve 57 is increased.
In this case, the driving force of the first piezoelectric element 80 is, as described above, the valve body 51 fixed between the shoulder 42a and the sleeve 43.
And is not transmitted to the second piezoelectric element 90.
The initial load applied from the slider 58 to the compression-side disk valve 57 is configured to be adjustable by the adjustment mechanism 67. That is, the adjusting nut 69 is screwed to the upper end of the main body 42 by the adjusting screw 68. When the adjusting nut 69 is rotated, the adjusting nut 69 is displaced in the axial direction, thereby determining the initial load.

In addition, the slider 58 has a lower end outer peripheral inclined surface facing the upper liquid chamber 52, and slides upward by receiving the liquid pressure of the upper liquid chamber 52. Therefore, the first piezoelectric element 80 ,
In the state where no voltage is applied, the displacement occurs in accordance with only the pressing force of the slider 58, that is, the liquid pressure of the upper liquid chamber 52 (= extension liquid chamber 14), and an electromotive force is generated. It will be referred to as signal Ss.

On the other hand, a receiving hole
The outer peripheral shoulder portion of the valve core 59 housed in the 50 so as to be slidable up and down is abutted. And this valve core 59
And an adjustment nut screwed into the lower end of the sleeve 43
A second piezoelectric element 90 similar to the first piezoelectric element 80 is interposed between a cap 65 whose lower end is supported by 44.

Accordingly, when a voltage is applied to the second piezoelectric element 90 to extend it, the valve core 59 is pushed upward because the lower end of the second piezoelectric element 90 is supported by the adjustment nut 44 via the cap 65. The extension-side disc valve 56 is pressed to increase the bending rigidity of the extension-side disc valve 56. In this case, the driving force of the second piezoelectric element 90 is, as described above, the valve body 51 fixed between the shoulder 42a and the sleeve 43.
And is not transmitted to the first piezoelectric element 80. Further, the initial load applied from the valve core 59 to the extension-side disk valve 56 is configured to be adjustable by rotating the adjust nut 44 screwed to the sleeve 43 to move the cap 65 up and down.

A hole 66 is formed in the adjust nut 44, and the cap 65 receives the liquid pressure of the pressure side liquid chamber 15 through the hole 66 and slides upward, so that the second piezoelectric element 90 is , When no voltage is applied, the cap 65
And generates an electromotive force according to only the pressing force of the pressure side, that is, the liquid pressure of the pressure side liquid chamber 15, and this is referred to as a pressure side signal Sp.

A lower end of the piston 5 is provided with an extension valve 70 and a spring 71 for urging the extension valve 70 upward. The lower end of the spring 71 is fixed to the piston 5 by an adjust nut 72 and a lock nut 73. Therefore,
When the expansion stroke is equal to or higher than the predetermined piston speed and the flow rate of the liquid is large, the expansion side is continued between the lower liquid chamber 53 and the compression side liquid chamber 15 downstream of the expansion side disk valve 56 following the expansion side disk valve 56. A differential pressure is generated by the valve 70 to generate a damping force, thereby improving the rise of the damping force.

Also, the cords 81 and 82 of the first piezoelectric element 80 form the wiring 30 together with the cords 91 and 92 of the second piezoelectric element 90, and
Is connected to the control unit 100, and signals from the first and second piezoelectric elements 80 and 90 are
Input to 00.

Turning to FIG. 3, the inside of the control unit 100 will be described. In the figure, the control unit 10
0 is the I / O interface 101, the input circuit 110, and the arithmetic circuit
120, a drive circuit 130, and a drive power supply circuit 140. Each of the piezoelectric elements 80 and 90 in the hydraulic buffer 1 is connected to the I / O interface 101 via the wiring 30, and exchanges signals with the control unit 100.

Turning to FIG. 4, the details will be described. In the figure, a hydraulic buffer 1 has first and second piezoelectric elements therein.
The first and second piezoelectric elements 80 and 90 have one cord 81 and 91 grounded, and the other cords 82 and 92 are connected to the I / O interface 101.

The I / O interface 101 is connected to the input circuit 110 and the drive circuit 130, respectively, and the I / O interface 101 has the extension side signal Ss and the compression side signal from the first or second piezoelectric element 80, 90. The capacitor C for cutting off the DC component of Sp and sending only the AC component to the input circuit 110, and applying and discharging the drive voltage from the drive circuit 130 to the first or second piezoelectric element 80, 90, respectively. Diodes D1 and D2 that constitute a circuit for performing the operations are provided.

The input circuit 110 is a circuit for converting the expansion-side signal Ss pressure-side signal Sp from the first or second piezoelectric element 80, 90 into a signal level that can be received by the arithmetic circuit 120.
As shown, an inverter 112, a diode D4, a resistor R8,
It is composed of a transistor Tr3.

The arithmetic circuit 120 is constituted by, for example, a microcomputer or the like, captures external data according to a program written in the internal memory, and based on the captured data and data written in the internal memory, etc.
Calculating a process value necessary for the variable control of the damping force is output based on the calculation result the compression side control signals S _A or the extension side control signal S _B to the drive circuit 130. Specifically, in the extension stroke,
The compression side signal Ss is input from the second piezoelectric element 90 during the compression side stroke while the expansion side signal Ss is input from the piezoelectric element 80, and the expansion side signal Ss or the compression side signal Sp is input to the arithmetic circuit 120.
Is obtained, and the rate of change K is calculated.
When the extreme value is reached, the piezoelectric element 80 or 90 on the side that does not output both signals Sp and Ss has a higher extreme value, the smaller the extreme value, and the lower the extreme value, the higher the control signal S as a drive voltage. _a or extension side control signal S _B is output to the drive circuit 130,
When the rate of change K becomes 0, the control for outputting the control signals S _A ′ and S _B ′ for discharging the electric charge of the piezoelectric element 80 or 90 on the side not outputting the signals Sp and Ss to the drive circuit 130 is performed. Do.

The drive circuit 130 receives the pressure side control signal S _A from the arithmetic circuit 120,
Upon receiving S _A ′ or the extension side control signals S _B , S _B ′, a driving voltage is applied to the first or second piezoelectric element 80, 90,
Or a circuit for discharging the applied voltage, for example, as shown in FIG. 4, is composed of inverters 131, 132, transistors Tr1, Tr2, Tr4, resistors R1, R2, R3, R5, R6, R7, and a diode D3. The drive circuit 130
Compression side control signals S _A, or the extension side control signal S I / O interface 10 to the driving voltage of the _B driving power source and is the input circuit 140
Via one of the diodes D1 is applied to the first piezoelectric element 80 or the second piezoelectric element 90, switching the damping force of the compression side or extension side from soft to hard, and the compression side control signals S _A to the driving circuit 130 ' Alternatively, when the extension side control signal S _B ′ is input, the charge of the first piezoelectric element 80 or the second piezoelectric element 90 is reduced.
Discharges through diode D2 of I / O interface 101,
Return the damping force from hard to soft.

The driving power supply circuit 140 is formed of, for example, a D / A converter, and outputs a DC high voltage (hereinafter, referred to as a driving voltage) capable of extending the first and second piezoelectric elements 80 and 90.

The position adjustment of the first and second piezoelectric elements 80 and 90 is performed as follows. That is, a predetermined voltage is applied to the first or second piezoelectric element 80, 90 and then discharged, the adjusting nuts 44, 69 are rotated, and the piezoelectric element generated by pressing the expansion-side disk valve 56 or the compression-side disk valve 57 is pressed. The adjustment is made until the voltage from the elements 80 and 90 reaches a certain value.

Next, a method of controlling the damping force characteristics of the hydraulic shock absorber 1 according to the present embodiment will be described based on the time chart of FIG.

FIG. 5 (b) shows the detected values of the pressures of the upper and lower liquid chambers 14 and 15, which are detected by the first and second piezoelectric elements 80 and 90, respectively. Detected by the first piezoelectric element 80, the section gk is the pressure during the pressure stroke, and the second piezoelectric element
Detected at 90. The damping force in FIG. 5A is obtained by multiplying the pressure detection value by the pressure receiving area of each stroke.

In the figures (a) and (b), (Aa), (Gg), (K
k) and (Nn) at each point, the damping force and pressure become “0”,
Of these, A and K become the bottom dead center of the vibration at the point where the damping force shifts from the compression stroke to the extension stroke, and G and M similarly become the top dead center. Between these upper and lower dead centers, there are extreme values of the pressures b, d, f, j, and m. Among them, b, j, and m indicate the neutral position of the piston (the piston when the hydraulic shock absorber 1 is at rest). 5 position).

Also, d and f reach the maximum speed at the neutral position of the piston, and then enter a vibration region (deceleration region) where the piston speed decreases toward the top dead center, and increase the piston speed at the point c. There is an external input, the deceleration is weakened, the minimum value is reached at point d, the piston speed again enters the vibration suppression region (increased speed region), and the vehicle decelerates after reaching the extreme value at f. Is shown.

As described above, the switching between the extension stroke and the pressure stroke can be determined by the pressure signal becoming “0”, but it is difficult to determine the fluctuation of the piston speed due to the external input during each stroke by the pressure signal. .

Therefore, the change rate (corresponding to the acceleration) is obtained by time-differentiating the detection signal shown in FIG. 2B, and the change rate is obtained in FIG. 2C, and the extreme value of the detection signal shown in FIG. Are all “0” at the rate of change shown in FIG. 11C, and the extreme values of the upper and lower dead center and the extreme value due to the external composite input are all “0”.
Can be detected as Further, all the inflection points in FIG. 6B are detected as extreme values in FIG.

That is, a, g, k, and n in FIG. 7B are inflection points at the time of switching the stroke, and c and e are inflection points of the speed due to an external input during the stroke. In the case of c), all are extreme values. Therefore, if the "0" point and the extreme value of the rate of change shown in FIG. 9C are obtained, and the pressure detection signal value shown in FIG. 9B is added to the judgment, all suspension states can be determined, and an appropriate damping force can be obtained. Control becomes possible.

In Fig. 5, the speed increase section (ab), (km), which is the damping range of the extension stroke from the neutral position of the piston to the top dead center
In FIG. 3C, a speed increase section (gj), which is a vibration suppression region of the pressure stroke, is detected as a section in which the rate of change is from an extreme value to “0”. At this time, the actuator is used as an actuator to reduce the piston speed. A voltage is applied to the operable piezoelectric element to control the damping force characteristics to high damping force characteristics (hard). In this embodiment, when a voltage is applied to the piezoelectric element, a drive voltage which is set to be smaller as the magnitude of the extremum is larger and is set to be larger as the magnitude of the extremum is smaller is applied. In this case, since the extremum in FIG. 9C corresponds to the switching of the stroke, the pressures of the upper and lower liquid chambers 14 and 15 in the hydraulic buffer 1 are also switched at the extremum. The piezoelectric element to which a voltage is applied is the piezoelectric element that has been detected so far.

Next, the (jk) section is the section from the neutral position to the bottom dead center, and the (mn) section is the section (excitation area) where the speed from the neutral position to the top dead center decelerates. The element is discharged to make the damping force characteristic of the hydraulic buffer 1 a low damping force characteristic (soft).

The section (bc) is a section of the piston speed from the neutral position to the top dead center as in the section (mn), but the input at the point c decreases the deceleration rate of the piston from the point c. And the velocity curve changes downwardly convexly.
This is detected as an extreme value C '(minimum value) in FIG. 9C, and is caused by a composite input from the next extreme value E' (maximum value) to F 'at which the rate of change becomes "0". In the vibration section, as in the other simple vibration sections described above, the larger the extremal value is, the smaller the magnitude is, and the smaller the extremal magnitude is, the larger the applied driving voltage is applied to the piezoelectric element to reduce the damping force. Perform control.

As described above, in the embodiment of the present invention, the hydraulic shock absorber 1
When a stroke occurs from the top dead center or the bottom dead center to the neutral position during the stroke (damping area), the vibration is damped with high damping force characteristics, while the bottom dead center or the top dead point is set from the neutral position. At the time of vibration toward the point (excitation area), control is performed so as to absorb vibration by controlling to low damping force characteristics, so that vibration can be converged while obtaining good ride comfort,
Further, since the control is switched based on the time when the rate of change K of the hydraulic pressure becomes an extreme value and the time when the hydraulic pressure becomes "0", even when there is a composite input, such vibration suppression and convergence can be accurately achieved. Can be achieved.

Incidentally, in FIG. 5, the extreme value C ′ in the composite input is shown.
Since the section from to the extreme value E 'is a section in which the input acts in the direction of increasing the piston speed, it is actually a vibration suppression area,
Although it is preferable to control to high damping force characteristics in all the sections, in the present invention, control is similarly performed at the time of single input and at the time of composite input, that is, high damping force is applied in a section where the rate of change is from the extreme value to “0”. The control is simplified by controlling the force characteristics. In the section from E to F, the control is performed softly.
Conventionally, high damping force characteristics are not controlled in the section from C to F, and a sufficiently high vibration damping property can be obtained in comparison with this.

In addition, in the present embodiment, the first piezoelectric element 80 functions as a hydraulic pressure sensor for detecting the hydraulic pressure of the extension side liquid chamber 14, and the second piezoelectric element 90 functions as the hydraulic pressure of the compression side liquid chamber 15. Function as a hydraulic sensor to detect pressure, and furthermore, each piezoelectric element 80, 9
While one of the zeros functions as a hydraulic pressure sensor, only the other piezoelectric elements 90 and 80 are controlled to drive and independently control the damping force characteristics in the stroke direction. The number of parts is reduced as compared with the case where the actuator and the sensor for detecting the hydraulic pressure are separately provided, and the hydraulic buffer 1 can be made compact and the manufacturing cost can be reduced.

Further, as described above, the hydraulic pressure on the extension side is the first piezoelectric element 80.
Since the hydraulic pressure on the pressure side is detected by the second piezoelectric element 90, a continuous vibration input can be continuously detected, and a fine damping force corresponding to the fluctuation of the vibration input can be obtained. Control can be performed. In addition, as described above, the damping force on the compression side and the damping force on the extension side can be independently controlled to increase and decrease, so that the riding comfort and steering stability of the vehicle can be realized at a high level.

By the way, the damping force variable hydraulic shock absorber of the conventional system is
One of the sensor function and the actuator function which one piezoelectric element has is operated so as to be selectively switched, and the actuator function is operated so that the damping force variable mechanism has a high damping force characteristic. When switching, the sensor function does not work, so if there is a continuous vibration input from the road surface, for the second and subsequent inputs,
It was difficult to say that the damping force characteristic control could not be performed, and that accurate damping force characteristic control corresponding to the actual vehicle state was performed.

The embodiments of the present invention have been described with reference to the drawings.
The specific configuration is not limited to this embodiment,
Even a design change or the like within a range not departing from the gist of the present invention is included in the present invention.

For example, in the embodiment, the first and second piezoelectric elements 80, 9
Although the case where the damping force variable actuator function and the hydraulic pressure sensor function are operated at 0 has been described, the present invention is not limited to this, and a hydraulic pressure sensor may be provided separately from the piezoelectric element.

The structure and arrangement of the disk valve and the piezoelectric element are also arbitrary. For example, the compression side disk valve 57 and the second piezoelectric element 90 may be provided on the bottom body side.

(Effects of the Invention) As described above, the suspension system of the present invention is provided with the extension-side hydraulic pressure sensor and the compression-side hydraulic pressure sensor for detecting the hydraulic pressures of the extension-side liquid chamber and the compression-side liquid chamber, respectively.
The extension side piezoelectric element and compression side piezoelectric element that change the stiffness of the extension side disk valve and compression side disk valve to change the extension side and compression side damping force characteristics are provided, and the extension side change rate and the compression side change rate of the detected hydraulic pressure are obtained. When the rate of change of the extension side reaches an extreme value, a drive voltage set to a smaller value is applied to the extension-side piezoelectric element as the extreme value increases. When the charge of the element is discharged, and when the compression side change rate becomes an extreme value, a drive voltage set to a smaller value as the extreme value is larger is applied to the compression side piezoelectric element, while the compression side change rate becomes 0. The damping force control means for discharging the charge of the pressure side piezoelectric element is provided, so that when the vibration of the hydraulic shock absorber is in the vibration damping region, it is damped as a high damping force characteristic, and this vibration is applied to the vibration region. Input as low damping force characteristics when Control is achieved, and it is possible to achieve both of ensuring steering stability and improving ride comfort, and to achieve the compatibility by continuously and accurately responding to a composite input during the same stroke. Is obtained.

Further, the drive voltage is applied to the piezoelectric element not during a certain period of time by a timer or the like, but during a period from when the rate of change of the fluid pressure becomes an extreme value to when it becomes zero next time. As described above, the control that promotes the bad behavior of the vehicle body is not performed, and the accurate damping force control is performed to converge the piston to the neutral position corresponding to the actual piston stroke of the hydraulic shock absorber. Is obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a main part of a suspension system according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing an entire configuration of the system of the present invention, and FIG. 3 is a configuration of a control unit of the embodiment system. FIG. 4 is a circuit diagram showing a configuration of a main part of the control unit, and FIG. 5 is an operation explanatory diagram of the suspension system of the embodiment. 1 hydraulic buffer 56 expansion disk valve 57 compression disk valve 80 first piezoelectric element (hydraulic sensor) 90 second piezoelectric element (hydraulic sensor) 100 control Unit (damping force control means)

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shigeru Kikushima 1370 Onna, Atsugi-shi, Kanagawa Prefecture Inside Atsugi Automobile Parts Co., Ltd. (56) References −106131 (JP, A) Fully open 63-54504 (JP, U)

Claims (1)

(57) [Scope of request for utility model registration] An expansion-side disc valve for generating pressure in an expansion-side liquid chamber whose volume decreases with the stroke by opening a valve to allow the flow of hydraulic fluid accompanying the expansion-side stroke of the piston, and a compression-side stroke of the piston. The valve is opened to allow the hydraulic fluid to flow along with the pressure, and the bending stiffness of the compression-side disk valve that generates pressure in the compression-side liquid chamber, whose volume decreases with the stroke, and the expansion-side disk valve and the compression-side disk valve are changed. A hydraulic buffer having a stretching-side piezoelectric element and a compression-side piezoelectric element provided so that the generated damping force can be changed, and a stretching-side hydraulic pressure sensor for detecting the hydraulic pressures of the stretching-side liquid chamber and the compression-side liquid chamber, respectively. And the compression-side hydraulic pressure sensor, the expansion-side change rate and the compression-side change rate, which are the change rates of the respective hydraulic pressures detected by the expansion-side hydraulic pressure sensor and the compression-side hydraulic pressure sensor, are obtained. It became In the meantime, a drive voltage set to be smaller as the extremum value is larger is applied to the extension-side piezoelectric element, and when the extension-side change rate becomes 0, the electric charge of the extension-side piezoelectric element is discharged. When the rate of change reaches an extreme value, a drive voltage that is set smaller as the extreme value increases with respect to the compression-side piezoelectric element is applied. On the other hand, when the rate of change on the compression side becomes 0, the charge of the compression-side piezoelectric element is discharged. A suspension system comprising: damping force control means for causing the suspension system to: