JPH0714007Y2 - Variable damping force hydraulic shock absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a damping force variable hydraulic shock absorber for vehicles such as automobiles, and more specifically, a damping force variable that can vary the damping force for each cycle of road surface vibration. Type hydraulic buffer device.

(Prior Art) Recently, as demands for vehicles have become more sophisticated, both comfort and running stability tend to be required. Therefore, the damping force variable type that adjusts the damping force according to the running state to generate a low damping force that improves riding comfort during normal running and a high damping force that enhances running stability when a vehicle roll occurs. Hydraulic shock absorbers are also popular.

As a conventional damping force variable type hydraulic buffer device of this type, for example, one disclosed in Japanese Patent Application Laid-Open No. 61-85210 is known. In this device, a single piezoelectric element (that is, four elements) provided in each of the four shock absorbers detects the hydraulic pressure in the cylinder generated in response to road surface vibration, and the controller determines the magnitude of the hydraulic pressure. Based on, the voltage is applied to the piezoelectric element to switch the damping force from soft to hard. Switching the damping force between soft and hard is performed at a low vibration frequency that causes displacement of the vehicle body and when the magnitude of the electromotive force generated by two of the four piezoelectric elements exceeds the set value. Maintained for hours.

That is, the damping force is maintained hard within the predetermined time regardless of the pressure stroke and the extension stroke, and the hydraulic pressure is not detected within the predetermined time.

(Problems to be Solved by the Invention) However, in such a conventional damping force variable hydraulic shock absorber, a single piezoelectric element is used as a fluid pressure sensing and an actuator for increasing or decreasing the damping force by applying a voltage. Since the switching force is used and the damping force characteristics are hardened for a predetermined time according to the detection signal, it is not possible to perform sensing within the above specified time, so independent control cannot be performed for each pressure stroke and extension stroke. However, there is a problem that sufficient control cannot be performed for the second and subsequent input vibrations of the continuous input from the road surface. For example, for the input on the pressure side after the first time, a high damping force becomes a vibration source to the contrary, and the vibration damping property deteriorates, and it is not possible to achieve both ride comfort and running stability.

Further, since the magnitude of the hydraulic pressure, that is, the amplitude of the vibration is used as the vibration information and the hydraulic pressure is compared with a constant value regardless of the traveling condition, the hydraulic pressure changes depending on the vehicle speed even if the vibration has the same amplitude. Therefore, in some cases, appropriate control cannot be performed, and riding comfort and traveling stability deteriorate. That is, when high-speed traveling, for example, vibrations with small amplitude (hereinafter referred to as small vibrations) due to small irregularities on the paved road surface are continuously input, the hydraulic pressure remains high, and the damping force is hard for a long period of time. When the pressure input is maintained, the ride comfort is deteriorated by giving a rugged thrusting feeling. On the other hand, when traveling at low speed, the damping force is maintained soft because the hydraulic pressure does not exceed a predetermined value against vibration with large amplitude (hereinafter referred to as large vibration) due to, for example, undulations on the pavement surface or rolls, etc. Swings and the running stability deteriorates. The pressure stroke and the extension stroke refer to the case where the piston moves in the direction in which the piston compresses with respect to the cylinder and the case where the piston moves in the direction in which the piston extends, and may be simply referred to as the pressure side and the extension side hereinafter. .

(Object of the Invention) Therefore, the present invention separately detects the hydraulic pressures on the compression side and the extension side, and when the rate of change exceeds a predetermined dead zone and reaches an extreme value, the damping force is hard-switched and the dead zone is changed. It is set according to the speed of the vehicle, and when the rate of change decreases to a predetermined value, the damping force is softly switched to accurately determine the magnitude of the vibration input, and the damping force control changes appropriately according to the vehicle speed. The purpose of the invention is to make the ride comfort and the running stability compatible with the vibration input regardless of the vehicle speed.

(Means for Solving the Problem) In order to achieve the above object, the damping force variable type hydraulic shock absorber according to the present invention has a basic conceptual diagram as shown in FIG. Second to detect hydraulic pressure
The detection rate of the hydraulic pressure is obtained from the outputs of the detection means b and the first detection means a and the second detection means b. When the change rate reaches the extreme value beyond the predetermined dead zone, the shock absorber is set to the predetermined value. Control means c for calculating a control value for setting a predetermined low damping force when the dead band is set according to the speed of the vehicle and the rate of change decreases to a predetermined value.
And a first operating means d for changing the damping force on the compression side based on the output of the control means c, and a second operating means e for changing the damping force on the extension side based on the output of the control means c. There is.

(Operation) In the present invention, the fluid pressure on the compression side and the fluid pressure on the extension side are detected separately to obtain the rate of change of the fluid pressure, and when the rate of change exceeds the predetermined dead zone and reaches the extreme value, the damping force is switched to hard. And the dead zone is set according to the speed of the vehicle,
When the rate of change drops to a predetermined value, the damping force is softly switched. The rate of change corresponds to the speed of vibration, becomes maximum at the initial stage of vibration (center of vibration), and becomes 0 when the amplitude reaches the peak of vibration (boundary between pressure stroke and extension stroke). In addition, the dead zone considers the change in hydraulic pressure depending on the vehicle speed.For example, the area is narrowed to distinguish the hydraulic pressure change due to small vibration when traveling at low speed, and the area is widened when traveling at high speed. The region is determined by the softening force, and the damping force is maintained soft for small vibrations having a value within this region regardless of the vehicle speed.

Therefore, if the rate of change is used as vibration information, the damping force is switched to hard for large vibrations where the rate of change exceeds the dead zone and reaches an extreme value, running stability is satisfied, and the rate of change is The damping force is softly maintained for a small vibration with a value within a predetermined dead band to satisfy the riding comfort,
Riding comfort and running stability can be compatible with vibration input regardless of vehicle speed.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

2 to 12 are views showing an embodiment of a variable damping force type hydraulic shock absorber according to the present invention.

First, the configuration will be described. FIG. 2 is an overall configuration diagram of the shock absorber, FIG. 3 is a cross-sectional view of essential parts thereof, FIG. 4 is an overall configuration diagram of the system, and FIG. 5 is a diagram showing a control circuit of one system thereof.

In FIG. 2, reference numeral 1 is a damping force type shock absorber. The shock absorber 1 is a sealed outer cylinder 2
A cylinder 3 contained in the outer cylinder 2, a piston 4 sliding axially on the inner wall of the cylinder 3, a bottom valve 5 provided at the lower end of the cylinder 3, and a piston rod 6 supporting the piston 4. , A reservoir chamber 7 formed by the inner wall of the outer cylinder 2 and the cylinder 3, a rod guide 8 supporting the piston rod 6, a piston seal 9 provided on the upper part of the rod guide 8, and an upper part of the outer cylinder 2 closed. And a stopper plate 10 that operates.

The cylinder 3 has a bottom body 12 having a communication hole 11 at its lower end, and the opening is closed by a rod guide 8.
The inside of the cylinder 3 is divided into two chambers, an upper liquid chamber 14 and a lower liquid chamber 15, by the piston 4, and the hydraulic fluid in the two chambers mutually passes through communication holes 46 to 48 provided in the piston 4 which will be described later. Flow.

The piston 4 has an extension side valve 16 that generates a damping force during the extension stroke.
Further, a spring 17 for urging the extension side valve 16 upward is provided. The lower end of the spring 17 is an adjustment nut.
It is fixed to the piston 4 by means of 18 and a lock nut 19, and an adjust nut 20 is screwed onto the lower end of the piston 4.

The bottom valve 5 is a check valve 21 that opens during the stroke and a port 22 through which hydraulic fluid flows when the check valve 21 opens.
The pressure side valve 23 that opens in the pressure stroke, the orifice 24 that generates a damping force when the pressure side valve 23 opens, the stopper plate 25 that regulates the opening of the check valve 21, and the check valve 21 and the like fixed to the bottom body 12. Caulking pin 26
And are included. During the extension stroke, the hydraulic fluid in the reservoir chamber 7 opens the check valve 21 by the negative pressure in the lower liquid chamber 15 and flows into the lower liquid chamber 15. At this time, the check valve 21 is regulated by the stopper plate 25 so as not to open above a certain level. Further, in the pressure stroke, the hydraulic fluid in the lower liquid chamber 15 opens the pressure side valve 23, and the orifice 24 generates a damping force corresponding to the positive pressure in the lower liquid chamber 15, and passes through the communication hole 11 to the reservoir. It flows into the chamber 7. The pressure in the upper liquid chamber 14 and the lower liquid chamber 15 is generated according to the magnitude of the road surface vibration, and the input state of the road surface vibration, that is, the running state can be detected by detecting the pressure.

Further, a retainer 27 is fixed to the piston rod 6, and the retainer 27, together with an elastic rebound stopper 28 provided on the upper portion, alleviates the collision between the piston 4 and the rod guide 8.

A lower portion of the stopper plate 10 is fitted to the upper end of the cylinder 3, and the piston rod 6 is slidably guided by a bush (not shown) in the central through hole 10a.

The outer cylinder 2 accommodates the cylinder 3, the rod guide 8 and the piston seal 9 inside, and is formed by swaging the upper end. A main lip 29 that elastically contacts the piston rod 6 and maintains liquid tightness inside and a dust lip 30 that prevents muddy water from the outside are formed on the inner circumference of the piston seal 9. An eye bush 31 and an eye 32 are attached to the lower end of the outer cylinder 2 for attachment to the axle of the vehicle. The wiring 35 drawn from the upper end of the piston rod 6 is connected to the control unit 100.

FIG. 3 shows a cross section around the piston 4, with the upper side in the figure being the vehicle body side and the lower side in the figure being the wheel side. In the figure, a wiring passage 41 for accommodating the wiring 35 is provided in the center of the piston rod 6, and the wiring passage 41 is gradually expanded and screwed with the piston 4 at a screw portion 41a at the lower end. The piston 4 has a main body 42 screwed with the piston rod 6, and a sleeve 43 screwed at the lower end and the upper end of the main body 42. The adjust nut 20 is screwed and fixed to the lower end of the sleeve 43. There is. A seal member 44 made of a low friction material such as Teflon is provided on the outer periphery of the main body 42, and the seal member 44 slides in contact with the inner wall of the cylinder 3. Space 42 in main body 42 and communication hole 4
6 and 47 are formed, and the hydraulic fluid in the upper hydraulic chamber 14 and the lower hydraulic chamber 15 flows through the communication holes 46 and 47. A communication hole 48 is formed in the sleeve 43, and the hydraulic fluid in the space 45 flows through the communication hole 48 while the damping valve 16 generates a damping force. When the hydraulic pressure of the hydraulic fluid passing through the communication hole 48 increases, the expansion side valve 16 overcomes the urging force of the spring 17 and moves downward to generate a damping force for the hydraulic pressure. Further, storage holes 49 and 50 having a circular cross section are formed inside the piston 4, and the storage holes 49 and 50 communicate with the space 45.

Inside the accommodating holes 49, 50 and the space 45, the adjusting mechanism 51, the first piezoelectric element 60, the damping means 70 contacting the lower end of the first piezoelectric element 60, and the first contacting the lower end of the damping means 70. A second piezoelectric element 90, and a cap 94 that supports the second piezoelectric element 90,
Is housed.

The adjusting mechanism 51 is composed of an adjusting screw 52 formed at the upper end of the main body 42 and an adjusting nut 53 screwed to the adjusting screw 52, and is composed of an adjusting nut 53, and the adjusting nut 53 is rotated. And moves in the axial direction to change the axial position of the first piezoelectric element 60.
The adjustment nut 53 contacts the plate 56 via the plate 54 and the cap 55, and the plate 56 is the first piezoelectric element.
It is fixed to the upper end of 60. The first piezoelectric element 60 is supported by the cap 55 and the damping means 70,
Move up and down in 49. The cord 61 of the first piezoelectric element 60,
62 is the wiring 91 together with the cords 91 and 92 of the second piezoelectric element 90
And the wiring 35 is connected to the control unit 100. Further, the first piezoelectric element 60 contacts the slider 71 forming a part of the damping means 70 via the plate 59, and transmits the extension corresponding to the extension side control signal S _A to the damping means 70.

The damping means 70 includes a slider 71, a valve core 72 having a tip portion fitted to a central portion 71a of the slider 71, a valve body 73 attached to the valve core 72, a pressure side valve 74 sandwiched between the valve body 73 and the slider 71. The expansion side valve 75 sandwiched between the valve core 72 and the valve body 73. Orifices 76 and 77 are formed in the valve body 73, and the upper side of the orifice 76 is closed by an elastic compression side valve 74, and the lower side of the orifice 77 is closed by an elastic extension side valve 75. Orif Hess 76
Communicates a space (hereinafter referred to as the first hydraulic pressure) 79 defined by the inner wall of the space 45 and the upper surface of the valve body 73 with the communication hole 47, and when the pressure side valve 74 is bent and opened in the pressure stroke, a predetermined damping is achieved. Generate force. The orifice 76 is closed during the extension stroke so that the hydraulic fluid does not pass through. The orifice 77 is a space defined by the inner wall of the space 45 and the lower surface of the valve body 73 (hereinafter,
The second liquid chamber) 80 and the first liquid chamber 79 are communicated with each other, and a predetermined damping force is generated when the expansion side valve 75 is bent and opened in the extension stroke. The orifice 77 is closed during the pressure stroke, and the hydraulic fluid does not pass through.

The compression side valve 74 and the expansion side valve 75 are formed of a plurality of thin plates and have a predetermined elasticity. The damping means 70 is compressed by the extension of the first piezoelectric element 60 when in the extension stroke,
The opening area of the expansion valve 75 is changed to reduce the opening area of the orifice 77, and a predetermined damping force (hereinafter, soft) is increased to switch to a high damping force (hereinafter, hard).

On the other hand, when the damping means 70 is in the pressure stroke, the second piezoelectric element 90
The expansion of the pressure side valve 74 changes the opening degree of the pressure side valve 74 to reduce the opening area of the orifice 76, and switches the damping force from soft to hard.

Further, the damping means 70 contacts the second piezoelectric element 90 via the plate 88, so that the hydraulic pressure in the first liquid chamber 79 is changed to the second piezoelectric element 90 during the extension stroke.
Of the piezoelectric element 90. The lower end of the second piezoelectric element is in contact with the cap 94, and the upward displacement (corresponding to the hydraulic pressure in the lower liquid chamber 15) transmitted from the cap 94 in the pressure stroke is applied to the damping means and the first piezoelectric element. introduce. The cap 94 receives the hydraulic pressure of the hydraulic fluid flowing in from the hole 95 of the adjust nut 20 on the lower surface in the pressure stroke, and is displaced upward, so that the second displacement occurs.
Of the piezoelectric element 90.

The first piezoelectric element 60 and the second piezoelectric element 90 utilize the piezoelectric effect and the inverse piezoelectric effect (also referred to as an electrostrictive effect) of a predetermined ceramic (hereinafter referred to as a piezoelectric material) and have a thin pair of electrodes. It is formed by laminating a large number of piezoelectric materials (for example, about 100 sheets). The piezoelectric effect is that when a voltage is applied to the electrodes of the piezoelectric material, the piezoelectric material expands and contracts in the vertical direction in the figure according to changes in the applied voltage (hereinafter referred to as mechanical strain).
This is a phenomenon that is unique to piezoelectric materials.

On the other hand, when pressure or displacement is applied to the piezoelectric material in the vertical direction, mechanical strain is generated in the piezoelectric material, and the piezoelectric material generates electromotive force according to the change in mechanical strain. This phenomenon is called an inverse piezoelectric phenomenon, and it is possible to detect the magnitude of the pressure or displacement applied to the piezoelectric material from the magnitude of this electromotive force.

In the extension stroke, the first piezoelectric element 60 expands and contracts when the extension control signal S _A is output from the control unit 100, and displaces the damping means 70 to increase or decrease the damping force. The second piezoelectric element 90 expands and contracts in response to the pressure side control signal S _B in the pressure stroke to give a displacement to the damping means 70 to increase or decrease the damping force.

In the pressure stroke, the first piezoelectric element 60 detects the hydraulic pressure in the lower liquid chamber 15 transmitted from the damping means 70, and outputs the pressure side signal Sp. The second piezoelectric element 90 is a damping means in the extension stroke.
The hydraulic pressure in the first liquid chamber 79 transmitted from 70 is detected, and the extension side signal Ss is output. A vehicle speed sensor (not shown) detects the vehicle speed (hereinafter referred to as vehicle speed) and outputs a vehicle speed signal V _SP .

The first piezoelectric element 60 has a function as first detecting means, and constitutes the second operating means together with the damping means 70. Further, the second piezoelectric element 90 has a function as a second detecting means, and constitutes the first operating means together with the damping means 70. The signals from the first and second piezoelectric elements 60, 90 and the vehicle speed sensor are input to the control unit 100, and the control unit 100 has a function as a control means. Further, the control unit 100 includes the first piezoelectric element 6
Pressure side and extension signals Sp, Ss depending on the presence or absence of signal from 0
Is performed, the change rate of the signal is calculated, and the control signals S _A and S _B are output according to the magnitude of the change rate.

To explain the inside of the control unit 100, FIG. 4 is referred to. In the figure, the control unit 100 is an I / O
It includes a port 101, an input circuit 110, an arithmetic circuit 120, a driving circuit 130, and a driving power supply circuit 140. The shock absorber 1 is connected to the I / O port 101 via a wiring 35, and exchanges signals with the control unit 100.

To explain this detail, we turn to FIG. In the figure,
The shock absorber 1 has a pair of piezoelectric elements 60, 90 therein, one cord 61, 91 of the piezoelectric elements 60, 90 is grounded, and the other cord 62, 92 is connected to the I / O port 101. . The first piezoelectric element 60 detects the hydraulic pressure and outputs the pressure side signal Sp, and the capacitor C of the I / O port 101 blocks the DC component of the pressure side signal Sp and passes the AC component. The buffer 112 of the input circuit 110 amplifies the AC component of the pressure signal Sp and amplifies the arithmetic circuit 120.
Output to. The arithmetic circuit 120 is composed of, for example, a microcomputer, takes in external data in accordance with a program written in the internal memory, and based on the taken-in data and the data written in the internal memory, performs a variable control of the damping force. Calculate the required processed value. That is, the arithmetic circuit 120 calculates the change rate of the input signal based on the input signal, and when the change rate reaches the extreme value beyond the dead band, the driving circuit outputs the extension side control signal S _A corresponding to the magnitude of the change rate. Output to 130. When the expansion side control signal S _A is input to the buffer 131, the drive circuit 130 turns on the transistor Tr ₁ and outputs the drive voltage of the drive power supply circuit 140 to the first piezoelectric element via the diode D ₁ of the I / O port 101. Apply to element 60 to switch the damping force from soft to hard. In addition, the drive circuit 130
When the expansion side control signal S _A is input to the buffer 132, the transistor Tr ₂ is turned on, the electric charge of the first piezoelectric element 60 is discharged through the diode D ₂ of the I / O port 101, and the damping force is hardened. Back to soft. The drive power supply circuit 140 is, for example, DC-DC.
A first and second piezoelectric element 60 formed of a converter,
High DC voltage capable of extending 90 (hereinafter referred to as drive voltage)
Is output. The circuits connected to the second piezoelectric element 90 are given the same numbers as above, and the description thereof is omitted.

Further, the position adjustment of the piezoelectric element is performed as follows. That is, after applying a predetermined voltage to the piezoelectric element, the piezoelectric element is discharged, the adjust nut 53 is rotated, and the voltage generated from the piezoelectric element by pressing the damping means 70 is adjusted until it reaches a certain constant value. The same procedure is performed for both the extension side and the compression side.

Next, the operation will be described with reference to FIG.

In the extension stroke as shown in FIG. 7C, the hydraulic pressure in the cylinder 3 generated in response to the external vibration is detected by the second piezoelectric element 90, and the extension side signal Ss is output. At this time, the hydraulic pressure is the first
Since it is not detected by the piezoelectric element 60, the arithmetic circuit 120 determines that it is the extension stroke, and the change rate of the extension side signal Ss is calculated. When the rate of change exceeds the dead band and the rate of change reaches an extreme value as shown in FIG. 7D, the extension side control signal S _A is output to the first piezoelectric element 60, and the damping force is switched to hardware ( (A) section H). When the rate of change decreases to 0, the damping force is softly switched.

On the other hand, in the pressure stroke as shown in FIG.
The piezoelectric element 60 detects the pressure side signal Sp. At this time, since the hydraulic pressure is simultaneously detected by the second piezoelectric element 90, it is determined by the arithmetic circuit 120 that it is a pressure stroke,
When the rate of change of the pressure-side signal Sp exceeds the dead band and reaches an extreme value, the pressure-side control signal S _B is output to the second piezoelectric element 90, and the damping force is switched to hardware. Also, when the rate of change drops to 0, it is switched to software.

FIG. 7 is a flowchart showing a main program for damping force variable control written in the memory of the arithmetic circuit 120, and this program is executed once every predetermined time. In addition, although the case of the pressure stroke will be described here as an example, the same process is performed in the extension stroke.

First, at P ₁ , the pressure side signal Sp and the vehicle speed signal V _SP are read.
The pressure side signal Sp corresponds to the vibration input from the outside, and the cylinder 3
It is detected in real time from the hydraulic pressure inside. Next, the rate of change of the pressure side signal Sp is calculated at P ₂ . The rate of change of the pressure side signal Sp (hereinafter referred to as the rate of change) is obtained by differentiating the pressure side signal Sp with respect to time, and corresponds to the speed of vibration. The speed of vibration becomes maximum at the initial stage (near the center) of vibration with small amplitude, and becomes 0 when the amplitude reaches the peak of vibration. Further, the vibration speed increases as the amplitude increases, and increases as the vibration cycle decreases. Therefore, if the rate of change (speed of vibration) is used as vibration information, it is possible to determine whether or not the amplitude is large at the initial stage of vibration, and the damping force can be appropriately controlled in response to vibration input. . Next, at P ₃ , the dead band width (hereinafter referred to as dead band width) is set according to the vehicle speed. This is because the hydraulic pressure generated by the vibration changes depending on the vehicle speed, and the dead band width is determined by, for example, an experiment or the like in consideration of the hydraulic pressure change due to the vibration with a small amplitude (hereinafter referred to as small vibration). . Here, the setting method is divided into a method of continuously changing the dead band width according to the vehicle speed and a method of changing the vehicle speed when the vehicle speed is in a high speed region (hereinafter referred to as a high speed region). the method of changing the time, further, the front side of the vehicle (hereinafter, F referred _R side) and rear side (hereinafter, referred to as R-side) divided into a case where a case of the same setting, the different setting. Therefore, the next 3
It can be roughly divided into two cases, and these cases will be explained below.

(I) when continuous change (II) at the time the change in the high speed range (F _R side, the same set R side both) (III) when changes in the high speed range (F _R side, different settings for R side) (I) During continuous change This setting is based on the vehicle speed signal V _SP at that time from the dead band width pattern stored in the memory of the arithmetic circuit 120.
The dead band width is read and obtained. The dead band width pattern is shown in FIG. 8 and is stored in the memory of the arithmetic circuit 120, for example, in the form of a data map.

(II) When changing in the high speed range (F _R side and R side have the same setting) To make the explanation easier to understand, move on to the subroutine here. In Figure 9, it is determined whether the vehicle speed at P ₂₁ is in the high speed range, the dead zone width in P ₂₂ when in a high speed region F
The second predetermined width X ₂ is set for both the _R side and the R side. here,
Similar to (I), the above determination is performed by reading the dead band width corresponding to the vehicle speed according to the dead band width pattern shown in FIG. 10, and a predetermined hysteresis is provided for setting the dead band width. On the other hand, setting the dead zone width to a first predetermined width X ₁ in P ₂₃ when the vehicle speed is not in the high speed region. The first and second predetermined widths are determined by, for example, experiments, and are stored in the form of a data map together with the corresponding vehicle speed.

(III) upon changes in the high speed range (F _R side, different settings for R side) in the subroutine shown in FIG. 11, it is determined whether the vehicle speed at P ₃₁ is in the high speed region, the vehicle speed is in the high speed region Sometimes
Moves to P _32, is set to a value of dead zone width was different between F _R side and R side P _32. That is, the F _R side is set to the _second predetermined width X ₂ , and the R side is set to the first predetermined width X ₁ . The reason for this setting, the F _R side concentrates the weight of such engines, because the 70 to 80% of the weight of the vehicle weight is applied. Further, in the case of a front-wheel drive vehicle, the front wheels (F _R side) function as steering wheels and drive wheels, and the ground contact of the tires has a great influence on the steering function and power performance. Similar to (II), the above setting is also performed by reading the dead band width corresponding to the vehicle speed according to the dead band width pattern shown in FIG. On the other hand, if the vehicle speed is not in the high speed range at P ₃₁ , P
Moves to ₃₃ and sets the dead zone width in P ₃₃ F _R side, the first predetermined width X ₁ to R side both.

As described above, in this embodiment, the dead zone width is set according to the vehicle speed, so that the influence of the change in hydraulic pressure due to the vehicle speed can be eliminated and the magnitude of the small vibration can be accurately determined regardless of the vehicle speed. In other words, in the low speed range
The dead band width is set narrow because the hydraulic pressure inside is kept low, and the dead band width is set wide because the hydraulic pressure increases at high speeds.

By setting the dead band width in this way,
Returning to the main program shown in the figure, it is determined at P ₄ whether the rate of change is within the dead band width. The reason for making this determination is to determine a small vibration. By the way, small vibrations are generated, for example, by small irregularities on the paved road surface, and can be softly and sufficiently damped. When switched to hard, a feeling of push-up is generated and riding comfort deteriorates. Moves to P ₅ when it exceeds the dead band, the change rate P ₅ determines whether it is extreme. The reason for making this determination is to determine a vibration with a large amplitude (hereinafter referred to as a large vibration) that progresses in a short time (short cycle), and the large vibration includes, for example, a roll, a squat (a bottom descent phenomenon), and a dive ( This means vibration such that the vehicle body suddenly tilts and the running stability is impaired, such as the phenomenon of front turning. When the rate of change is not the extreme value, it is determined that the pressure stroke has not ended, and this routine is ended. If the pressure stroke has not ended, the damping force set in the previous routine is used to damp the vibration, and switching of the damping is not performed.

On the other hand, when it is an extreme value at P ₅ , the pressure side control signal S _B is output at P ₆ , and the driving voltage is applied to the second piezoelectric element 90 to switch the damping force from soft to hard. Here, the value of the high damping force (hard) corresponds to the drive voltage, and it can be made stepless depending on the setting of the drive voltage. Then, it is determined whether or not reached application level P _7, does not reach the application level, returns to P _6, ends the current routine when a driving voltage is applied again at P _6, it reaches the application level To do. Here, the applied level means a voltage value when a driving voltage is applied and the damping force is switched to a hard one. Step P ₅
By executing the steps from ~ P ₇ , it is possible to determine a large vibration in the initial stage of the vibration, and unlike the conventional example, the damping force can be immediately switched to the hard condition to satisfy the running stability. That is, in this embodiment, the initial responsiveness to vibration is improved as compared with the conventional example in which control is performed based on the magnitude of hydraulic pressure, and the damping force can be appropriately controlled to follow the vibration input.

On the other hand, when the change rate P ₄ is within the dead zone width is moved to P ₈ is determined that the small vibration is inputted, it determines whether the rate of change P ₈ is zero. When the shock absorber 1 is compressed and the amplitude reaches the apex (the boundary between the compression stroke and the extension stroke) or the vibration on the extension side is input, the speed of the vibration, that is, the rate of change becomes zero. Therefore, if the above determination is performed, it is possible to determine whether or not the pressure stroke has ended, and independent control can be performed for the pressure stroke and the extension stroke of the vibration cycle. When the rate of change is not 0, it is determined that a small vibration has been input, and this routine ends. That is, when a small vibration is input regardless of the vehicle speed, the software is maintained and the vibration is damped. Therefore, unlike the conventional example in which hard is selected for small vibrations when traveling at high speeds, the present embodiment can eliminate the occupant's feeling of thrusting up for small vibrations, and provides a comfortable ride for small vibrations regardless of vehicle speed. Both running stability can be achieved.

On the other hand, proceeds to P ₉ determines that enough stroke if 0 is the rate of change in P ₈ has ended, and outputs the compression side control signals S _B at P _9, discharges the electric charge of the second piezoelectric element 90. Then, at P ₁₀ , the pressure side signal Sp
Is compared with a predetermined value, the process returns to P ₉ be below a predetermined value, P ₉
Then, the electric charge is discharged again, and when the discharging is sufficiently performed, the routine of this time is ended. Here, the predetermined value means a voltage value at which the length of the piezoelectric element returns to the original length and the damping force returns from hard to soft, and the second piezoelectric element 90 detects that the charge is equal to or less than the predetermined value. Restore function as a means. When the damping force is soft from the beginning, the damping force does not change.

Step P ₈ or more stroke has been completed by the execution of ~P _10,
Alternatively, it is determined that the vibration on the extension side has been input, and the damping force can be controlled independently in the pressure stroke and the extension stroke of the road surface vibration. That is, by switching between hard in the pressure stroke and soft in the extension stroke, recovery from the compressed state can be accelerated while satisfying the ride comfort. Further, in this embodiment, since the dead band width is set according to the vehicle speed, small vibration and large vibration can be accurately distinguished regardless of the vehicle speed, and appropriate control can be performed for small vibration and large vibration. It can be carried out. In other words, hard is selected for large vibrations where the rate of change exceeds the dead band width and becomes an extreme value, and running stability is satisfied, while soft is maintained for small vibrations where the rate of change is within the dead band width. As a result, the ride comfort can be satisfied, and the ride comfort and the running stability can be compatible with continuous vibration input regardless of the vehicle speed. As described above, in the present embodiment, the damping force is finely changed based on the magnitude of the rate of change.Therefore, the initial response is improved and the continuous large vibration and small vibration are input in real time. It can be controlled appropriately.

A concrete timing chart of this is shown in FIG. In the figure, the horizontal axis corresponds to the center of vibration and the vertical axis corresponds to the amplitude of vibration. As shown in FIG. 7C, when a large vibration is input at point A and the rate of change exceeds the dead zone and reaches an extreme value, the damping force is immediately switched from soft to hard (section H). At this time, the hydraulic pressure (detection signal) in the cylinder 3 rises by the amount of increase in the damping force (driving voltage) as indicated by the alternate long and short dash line, and changes in the same manner as the software indicated by the dotted line (see FIG. 7B). . Therefore, the movement of the piston 4 is restricted by a high damping force, that is, a high flow resistance, and its amplitude is reduced as compared with the conventional example in which the softness is maintained up to the point B. Further, at the point F, the rate of change becomes 0, the damping force in the pressure stroke is softly switched, and the piston quickly returns to the center of vibration due to low flow resistance (section FG). Therefore, in the present embodiment, the expansion of the shock absorber 1 due to the road surface vibration is less than in the conventional example, and the shock absorber 1 recovers more quickly, the inclination of the vehicle body is suppressed in advance, and the traveling stability is improved (section AG).

Further, in the present embodiment, unlike the conventional example in which the hard condition is continuously maintained after the point B in order to ensure traveling stability, continuous vibration is generated even during the period in which the extension damping force is hard maintained (section AG). The damping force on the pressure side can be made soft with respect to the input, and vibration characteristics can be improved to improve riding comfort (section BC).
This is because the spring can sufficiently absorb the vibration due to the low flow resistance, and the compression side damping force is generally set lower than the extension side damping force.

Furthermore, since the dead zone width is changed according to the vehicle speed in the present embodiment, it is possible to eliminate the influence of the change in hydraulic pressure due to the vehicle speed, and for the small vibration in which the rate of change is within the dead zone width regardless of the vehicle speed. You can maintain both softness and comfort while riding (section DF).

In this embodiment, the first piezoelectric element 60 and the second piezoelectric element 90 are switched to the first and second detecting means and the first and second operating means, but the invention is not limited to this, and The configuration method and position of the second detection means and the first and second operation means are not limited to the above-mentioned embodiment, and it goes without saying that they may be provided separately, for example.

In the present embodiment, the dead zone extends from the pressure side to the extension side, but the present invention is not limited to this, and it is of course possible to use only the pressure side or vice versa.

In this embodiment, when the speed of the vehicle is in the high speed range, the dead zones are set differently by the shock absorbers before and after the vehicle, but the present invention is not limited to this, and in the case of continuously changing according to the speed of the vehicle. Of course, the dead zones may be set differently for the front, rear, left and right shock absorbers of the vehicle.

(Effect) According to the present invention, the hydraulic pressure on the compression side and the hydraulic pressure on the extension side are detected separately to obtain the rate of change of the hydraulic pressure, and when the rate of change exceeds the predetermined dead zone and reaches the extreme value, the damping force is switched to hard. With
The dead band is set according to the speed of the vehicle, and the damping force is softly switched when the rate of change drops to a predetermined value, so the influence of the change in hydraulic pressure due to the vehicle speed can be eliminated, and the rate of change can be set to a predetermined value. The damping force is switched to hard for large vibrations that reach the extreme value beyond the dead band of the above, and running stability is satisfied, and the damping force is softened for small vibrations where the rate of change is within the above dead band. The ride comfort can be maintained by maintaining the above, and the ride comfort and the running stability can be compatible with respect to the vibration input regardless of the vehicle speed.

[Brief description of drawings]

FIG. 1 is a basic conceptual view of the present invention, FIGS. 2 to 12 are views showing an embodiment of a damping force variable type hydraulic shock absorber according to the present invention, and FIG. 2 is a diagram showing the overall structure of the shock absorber. Sectional view shown in FIG. 3, FIG. 3 is a cross-sectional configuration diagram of relevant parts, FIG. 4 is an overall configuration diagram of the system, FIG. 5 is a partial circuit diagram thereof, and FIG. 6 is a diagram for explaining its operation. FIG. 7 is a flow chart showing the main program of the damping force variable control,
FIG. 8 is a diagram showing speed characteristics of the dead band, and FIG. 9 is a flowchart showing a subroutine for setting the dead band.
FIG. 10 is a diagram showing speed characteristics of the dead band, FIG. 11 is a flowchart showing a subroutine for setting the dead band,
FIG. 12 is a diagram for explaining the operation. 1 ... Shock absorber, 3 ... Cylinder, 4 ... Piston, 60 ... First piezoelectric element (first detecting means, second
Operating means), 70 ... damping means (first operating means, second operating means)
Operating means), 71 ... slider, 72 ... valve core, 73
...... Valve body, 74 ...... Pressure side valve, 75 ...... Extension side valve, 76 ...... Orifice, 77 ...... Orifice, 90 ...... Second
Piezoelectric elements (second detecting means, first operating means), 94 ...
Cap, 100 Control unit (control means), 101 I / O port, 110 input circuit, 120 arithmetic circuit, 130 drive circuit, 140 drive power circuit.

Front Page Continuation (56) References JP-A-52-81823 (JP, A) JP-A-61-89111 (JP, A) JP-A-60-199710 (JP, A) JP-B-63-44565 (JP , B2)

Claims (1)

[Scope of utility model registration request] 1. A) first detecting means for detecting a hydraulic pressure on the pressure side of a variable damping force type shock absorber, and b) second detecting means for detecting a hydraulic pressure on the extending side of a variable damping force type shock absorber. C) The rate of change of the hydraulic pressure is obtained from the outputs of the first and second detecting means, and when the rate of change exceeds the predetermined dead zone and reaches the extreme value, the shock absorber is set to the predetermined high damping force. In addition, the dead zone is set according to the speed of the vehicle, and when the rate of change decreases to a predetermined value, a control means for calculating a control value that provides a predetermined low damping force, and d) the output of the control means. A damping force variable comprising: a first operation means for changing the compression side damping force based on the above; and e) a second operation means for changing the extension side damping force based on the output of the control means. Type hydraulic shock absorber.