JP2505229Y2 - 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. for that reason,
Variable damping hydraulic pressure that increases and decreases damping force according to the running state to generate low damping force that improves riding comfort during normal running and high damping force that enhances running stability when rolling of the vehicle body occurs Shock absorbers are also popular.

As this type of conventional damping force variable hydraulic shock absorber,
For example, the one described in JP-A-61-285210 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 between soft and hard damping force is performed at a low vibration frequency that causes displacement of the vehicle body, and when the magnitude of electromotive force generated by two of the four piezoelectric elements exceeds the set value,
It is maintained for a predetermined time.

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 hydraulic pressure sensing device 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, sensing cannot be performed within the above-mentioned predetermined 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.

Moreover, since the low-pass filter is configured to pass the low-frequency component of the detection signal to perform the signal comparison, the damping force is hard-switched against the vibration input in the extremely low-frequency band such as long swell. , Giving a feeling of pushing up to the occupant, which deteriorated the riding comfort. By the way, vibrations in the extremely low frequency range are caused by gentle swells on highways, and if the damping force is selected to be hard in response to the above vibrations, the damping force will be maintained hard for a long time, and driving stability will be improved. Although the performance is improved, it gives the occupant a strong push-up feeling that is rugged against the vibration input on the pressure side.

Therefore, the present invention detects the hydraulic pressures on the pressure side and the extension side separately, and based on the magnitude of the rate of change of the signal component of a predetermined frequency band that does not include the extremely low frequency band among the detection signals, When the rate of change reaches the extreme value, hard is selected, and when the rate of change drops to zero, the mode is switched to soft to accurately determine the magnitude of the vibration input and precisely change the damping force for each cycle of road surface vibration. The purpose is to achieve both riding comfort and running stability for continuous vibration input.

(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. First detecting means a for detecting the pressure, second detecting means b for detecting the hydraulic pressure on the extension side of the variable damping force type shock absorber, and outputs of the first detecting means a and the second detecting means b Among these, the signal processing means c for passing a signal component in a predetermined frequency band, and the change rate of the hydraulic pressure is obtained from the outputs of the first detecting means a and the second detecting means b, and when the change rate becomes an extreme value, The shock absorber is made to have a predetermined high damping force, and when the rate of change is reduced to zero, the control means d for calculating a control value that makes the predetermined low damping force, and the damping on the pressure side based on the output of the control means d The first operation means e for changing the force and the control hand Second operating means f for changing the extension side damping force based on the output of the stage d;
It has.

(Operation) In the present invention, the liquid pressures on the pressure side and the extension side are detected by different detecting means, and only the signal component in the predetermined frequency band of the detection signal is passed to obtain the change rate of the hydraulic pressure. The control value is calculated so that the damping force is hard selected when becomes the extreme value, and the damping force is softly switched when the change rate decreases to zero.

Therefore, the damping force can be increased and decreased independently in real time for vibration input only within the specified frequency band excluding the extremely low frequency range due to a long winding path and the high frequency range due to minute protrusions. Becomes Also,
The rate of change corresponds to the acceleration of continuous vibration, and becomes maximum at the inflection point of the vibration speed, that is, the variation point from the damping range to the vibration range,
Since the velocity becomes zero when it reaches an extreme value, by using the change rate as vibration information, switching to hardware is performed at the extreme value, and when the change rate drops to zero, it returns to soft,
The softness is maintained until the next vibration area is reached, and only the vibration area is effectively damped to satisfy the running stability, while the softness is set in the vibration suppression area to satisfy the riding comfort and continuous vibration. Both riding comfort and running stability can be achieved with respect to input.

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

2 to 5 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 a sectional view showing the overall structure of the shock absorber, FIG. 3 is a sectional view of the essential parts thereof, and FIG. 4 is a diagram showing a control circuit of one system in the overall structure diagram of the system.

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 the lower end.
The rod guide 8 closes the opening. Inside the cylinder 3, the upper liquid chamber 14 is
And the lower liquid chamber 15 are divided into two chambers, and the working liquids in the two chambers flow mutually through communicating holes 46 to 48 provided in the piston 4 which will be described later.

The piston 4 has an extension side valve that generates a damping force during the extension stroke.
A spring 17 for urging the expansion valve 16 and the expansion valve 16 upward is provided. A lower end of the spring 17 is fixed to the piston 4 by an adjusting nut 18 and a lock nut 19, and an adjusting 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,
Port that allows hydraulic fluid to flow in when check valve 21 opens
22, a pressure side valve 23 that opens in the pressure stroke, an orifice 24 that generates a damping force when the pressure side valve 23 opens, a stopper plate 25 that regulates the opening of the check valve 21, a check valve 21 and the like on the bottom body 12. Caulking pin 26 to fix
And are included. In 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 opens the orifice 24.
Then, a damping force corresponding to the positive pressure in the lower liquid chamber 15 is generated and flows into the reservoir chamber 7 through the communication hole 11. 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.

Also, the retainer 27 is fixed to the piston rod 6,
The retainer 27 reduces the collision between the piston 4 and the rod guide 8 together with the elastic rebound stopper 28 provided on the upper portion.

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. Piston body 42
Has a large-diameter portion and a small-diameter portion formed on the outer periphery thereof, and a seal member 44 made of a low-friction member such as Teflon is fitted to the large-diameter portion, whereby the upper and lower liquid chambers 14 and 15 in the cylinder 3 as described above.
It is divided into Further, a male screw is formed at the tip of the small diameter portion, and is screwed to the piston rod 6 as described above. Furthermore, the piston body 42 is hollow,
An adjusting screw 52, to which an adjusting nut 53 is screwed, is formed at the end of the small diameter portion side, and a slightly larger diameter accommodation hole 49 is formed below the adjusting screw 52 following the step portion. A first piezoelectric element 60 sandwiched between a cap 55 and a slider 71 from above and below is fitted into the accommodation hole 49, and the upper portion of the first piezoelectric element 60 is locked to the stepped portion through a length adjusting plate 54. ing. Below the accommodating hole 49, there is a further large-diameter recess 45 having two steps. The valve body 73 is inserted by being pressed against the shoulder having the two steps, and the large-diameter recess 45 ends. The valve body 73 is sandwiched between the stepped portion and the sleeve 43 screwed to the formed female screw portion. A space 79 is defined on the upper surface side of the valve body 73 and communicates with the upper liquid chamber 14 by a communication hole 46 formed in the piston body 42, while a space 80 is defined on the lower surface side with the sleeve 43. Is formed and communicates with the lower liquid chamber 15 through a communication hole 48 formed in the sleeve 43, and the opening on the lower liquid chamber side of the communication hole 48 is the expansion valve.
It is covered with 16. An annular groove 73a is formed on the outer circumference of the valve body 73, and the annular groove 73a communicates with the lower liquid chamber 15 through a communication hole 47 formed in the piston body. Further, the valve body 73 is formed with an orifice 76 that communicates the upper space 79 and the annular groove 73a, and an orifice 77 that communicates the upper space 79 and the lower space 80, and covers these orifices 76 and 77, respectively. Thus, the compression side disc valve 74 is arranged on the upper surface of the valve body 73, and the expansion side disc valve 75 is arranged on the lower surface.

The sleeve 43 is formed in a hollow shape and has a receiving hole.
50 is a valve core 72 and a second piezoelectric element 9 in order from the top.
A cap 94 and a cap 94 are inserted and accommodated in the accommodating hole 50 so as to be vertically movable by an adjusting nut 20 screwed to the lower end of the sleeve 43. The valve core
72 is a hollow shaft portion projectingly provided in the center of the upper surface of a large diameter portion inserted into the accommodation hole 50, the hollow shaft portion penetrating the center hole of the valve body 73, and the center hole of the slider 71 above it. Has penetrated into.

Thus, the compression side disc valve 74 is sandwiched between the lower surface of the slider 71 and the upper surface of the sleeve 43 via the valve body 73, and the set load is adjusted on the upper surface of the valve body 73 according to the adjustment of the adjustment nut 53. . Further, the expansion side disc valve 75 is also sandwiched between the upper surface of the valve core 72 and the shoulder portion of the large-diameter recess 45 of the piston body 42 via the valve body 73, and the valve body 73 is adjusted in accordance with the adjustment of the adjustment nut 20. The set load is adjusted on the bottom surface. Further, an inclined surface 71b is provided at the lower end of the slider 71, and the space 7
The pressure of the upper liquid chamber 14 introduced into 9 is received and the pressure is transmitted to the first piezoelectric element 60. Further, a pressure hole 95 is formed in the lower surface of the adjust nut 20 so that the pressure of the lower liquid chamber 15 is guided to the lower surface of the cap 94, and the cap 94 is pushed to be transmitted to the second piezoelectric element 90.

Thus, the first piezoelectric element 60 or the second piezoelectric element 90
Will be distorted according to the transmitted pressure, and the voltage will be output according to this strain to detect the pressure. Here, the pressure of the upper liquid chamber 14 acts on the piston in an annular cross-sectional area obtained by subtracting the cross-sectional area of the piston rod from the cross-sectional area of the piston, and the extension of the piston is suppressed by the pressure received on this annular surface. Therefore, this is called the extension side damping force. That is, detecting the pressure of the upper liquid chamber 14 is equivalent to detecting the extension side damping force. Similarly, detecting the pressure in the lower liquid chamber 15 is equivalent to detecting the pressure side damping force.

The first and second piezoelectric elements 60, 90 are provided with harnesses 61, 62 and 91, 92, respectively, which are valve cores.
72, piston body 42, cap 55, adjust nut 53
Of the control unit 100, as shown in FIG. 4, the harnesses 61 and 91 are grounded, and the harnesses 61 and 91 are grounded. Connected to / O port 101.

Reference numerals 110 and 110 ′ are arithmetic circuits for amplifying the AC components by the buffers 112 and 112, respectively, by inputting only the AC components of the detection signals from the first piezoelectric element 60 and the second piezoelectric element 90 by the capacitors C and C, respectively. extension phase detection signal S _P 120 is an input circuit for outputting a pressure side detection signal S _S.

The arithmetic circuit 120 is composed of, for example, a microcomputer, captures external data according to a program written in the internal memory, and based on the captured data and the data written in the internal memory,
The processing value required for variable control of damping force is calculated. That is, the arithmetic circuit 120 calculates the change rate of the input signal based on the input signal, and determines the extension side detection signal S _P or S _S and its change rate Δ.
Make a predetermined judgment from S _P or ΔS _S , and depending on the judgment result,
It outputs either the extension side control signal S _A or the compression side control signal S _B. Or nothing is output. For example, the drive circuit 130
When the expansion side control signal S _A is input to the buffer 131, the transistor Tr ₁ is turned on and the drive voltage of the drive power supply circuit 140 is changed to I /
The damping force is switched from soft to hard by applying it to the first piezoelectric element 60 via the diode D ₁ of the O port 101. When the expansion side release signal S ′ _A is input to the buffer 132, the drive circuit 130 turns on the transistor Tr ₂ and discharges the electric charge of the first piezoelectric element 60 via the diode D ₂ of the I / O port 101. And reduce the damping force from hard to soft. The drive circuit
The same applies when the pressure side control signal S _B and the pressure side release signal S ′ _B are input to 130 ′. The drive power circuit 140 is, for example, DC
-First and second piezoelectric elements formed by a DC converter
It outputs a high DC voltage (hereinafter referred to as drive voltage) that can expand 60 and 90.

Next, the flow of hydraulic fluid when the shock absorber expands and contracts, and the functions of detecting and driving the first and second piezoelectric elements 60 and 90 will be described with reference to FIG.

Now, when the vehicle body bounces due to the wheels riding on protrusions or the like and the piston rod 6 moves downward relative to the cylinder 3, the hydraulic fluid in the lower fluid chamber 15 penetrates into the piston rod 6 and becomes an integral volume. It flows into the upper liquid chamber 14. That is,
The pressure side disk valve 74 is pushed open from the lower liquid chamber 15 through the communication hole 47, the annular groove 73a and the orifice 76, and flows into the upper liquid chamber 14 through the space 79 and the communication hole 46. At this time, the pressure side disc valve 74 bends according to the flow rate passing therethrough, so that the amount of bending in the hydraulic fluid before and after passage opens the gap between the valve body 73 and the pressure side disc valve 74, and this opening forms the orifice. The upper and lower liquid chambers 14, 15 are formed in the process in which the working fluid of the lower liquid chamber 15 passes through this orifice and moves to the upper liquid chamber 14.
A pressure difference is generated between the two, and the lower liquid chamber 15 has a correspondingly high pressure, which acts on the pressure receiving surface (corresponding to the cross-sectional area of the piston) and acts as a pressure side damping force. Since the pressure of the lower liquid chamber 15 is introduced from the pressure hole 95 to the lower surface of the cap 94, as described above, the second piezoelectric element 90 is distorted according to the pressure, and the voltage according to the strain is applied to the pressure side detection signal S _S. As control unit 10
Output to 0.

At this time, since the valve body 73 is locked to the shoulder portion of the large-diameter recess 45, the force is not transmitted to the upper first piezoelectric element 60 even when pressed from below. Therefore, at this time,
The piezo-electric element 60 of (1) is ready to operate as an actuator. Further, if the pressure side detection signal S _S input to the control unit 100 is calculated and the rate of change ΔS _S is maximum and the pressure side detection signal S _S is zero, the piston rod 6 in the pressure stroke becomes the lowest point. This means that the piston rod 6 has reached the maximum compression state, and the piston rod 6 moves to the extension stroke at the next moment. At the same time, the fact that the pressure side detection signal S _S is zero means that the second piezoelectric element 90
Also, the pressing force from the lower liquid chamber 15 is released and the distortion is eliminated. At this time, when it is determined that the damping force needs to be hardened, the pressure side control signal S _B is output to the second piezoelectric element 90 and the extension strain corresponding to the applied voltage is applied to the second piezoelectric element 90. Then, the valve core 72 is pressed upward to increase the set load of the expansion side disc valve 75 and increase the valve opening resistance. Thus, contrary to the pressure stroke described above, the hydraulic fluid flowing from the upper liquid chamber 14 to the lower liquid chamber 15 generates a higher differential pressure before and after the expansion side disc valve 75, and the expansion side damping force is hard. become. At this time, the slider 71 is urged upward by the pressure of the space 79 and the first piezoelectric element.
60 is distorted and a voltage corresponding to the pressure is output to the control unit 100 as the extension side detection signal S _P.

The above is the case where the change rate ΔS _S is maximum and the pressure side detection signal S _S is zero, but the pressure side detection signal may not be zero even if the change rate ΔS _S is maximum. This is the case for complex inputs, such as when the shock absorber is in the pressure stroke and the wheel rides on a further protrusion.

In such a case, when the control unit 100 determines that the damping force needs to be hardened, the extension side control signal S _A is output to the first piezoelectric element 60. Here, as described above, since the first piezoelectric element 60 is not subject to expansion / contraction strain during the pressure stroke, extension strain is generated according to the applied voltage corresponding to the extension side control signal S _A , which causes the slider to move.
71 is pressed to more strongly clamp the compression side disc valve 74 between it and the valve body 73 to increase the set load and make it hard.

At this time, since the valve body 73 is supported on the upper end of the sleeve 43 screwed to the piston body, it does not affect the second piezoelectric element 90 acting as the detection means.

As described above, by the first and second piezoelectric elements 60 and 90, it is possible to always act as the detecting means or the actuator regardless of the single input or the composite input.

Further, in the present embodiment, among the detection signals obtained by detecting the pressure side and the extension side hydraulic pressures in real time, only the signal component in the predetermined frequency band is passed. For this reason, it is possible to prevent switching to the vibration input in the extremely low frequency band and the high frequency band, and it is possible to improve the riding comfort as compared with the conventional example in which the thrust is generated.

Further, in the case of hard control, the extreme value is used as a reference, which corresponds to the fact that the speed is at the inflection point when the rate of change is the extreme value. The fact that the velocity is an inflection point means that the vibration changes from the damping region to the exciting region, and by controlling the damping force hard from here, the vibration is damped more effectively, and When the rate of change decreases to zero, it returns to soft and is effectively damped only in the vibration range to satisfy running stability.In the vibration control range, soft is set to satisfy the riding comfort, and for continuous vibration input. Both riding comfort and running stability can be achieved.

The control of the damping force of the damping force variable hydraulic shock absorber having the above-mentioned configuration and the basic action will be described with reference to FIG.

Figure (a) shows the controlled damping force, where the upper side from the center line is the extension side, that is, the damping force in the extension stroke in which the piston rod changes from the most compressed position to the most extended position, and the lower side is the compression side.
That is, it is the damping force of the compression stroke in which the piston rod is displaced from the most extended position to the most compressed position.

FIG. 9B shows a detection signal obtained by detecting the damping force shown in FIG. 9A by the first and second piezoelectric elements 60 and 90, and is shown by a chain line. The broken line in this figure is a soft detection signal that is assumed when a drive voltage is not applied to the piezoelectric element on the actuator side.

Figure (c) is a time differential of the detection signal of Figure (b). Since the detection signal is a pressure that represents a damping force, it relates to speed, and if this speed is time differentiated, it represents acceleration. Become.

Then, from the extreme value to zero of the rate of change is the vibration excitation range, and from zero to the extreme value is the vibration suppression range. Therefore, in the vibration areas AB, CD, EF, GI, and JK, the piezoelectric element that is not detected at that time is driven as an actuator, and the hard H is used to effectively damp the vibration.

Further, since the AG section and the JL section are the extension strokes and the detection is performed by the first piezoelectric element 60, the AB section, the CD section, the EF section,
In the JK section, the second piezoelectric element 90 acts as an actuator, and conversely, the GI section in the pressure stroke is detected by the second piezoelectric element 90, so in the GI section, the first piezoelectric element 60 is driven as an actuator. .

(Effect) According to the present invention, the pressure side and the extension side hydraulic pressures are detected by different detecting means, and only the signal component in the predetermined frequency band of the detection signal is passed to obtain the hydraulic pressure change rate. The damping force is hard selected when the rate of change reaches the extreme value, and the control value is calculated so that the damping force is softly switched when the rate of change falls to zero.

Therefore, the damping force can be increased and decreased independently in real time for vibration input only within the specified frequency band excluding the extremely low frequency range due to a long winding path and the high frequency range due to minute protrusions. Becomes Also,
The rate of change corresponds to the acceleration of continuous vibration, and becomes maximum at the inflection point of the vibration speed, that is, the variation point from the damping range to the vibration range,
Since the velocity becomes zero when it reaches an extreme value, by using the change rate as vibration information, switching to hardware is performed at the extreme value, and when the change rate drops to zero, it returns to soft,
The softness is maintained until the next vibration area is reached, and only the vibration area is effectively damped to satisfy the running stability, while the softness is set in the vibration suppression area to satisfy the riding comfort and continuous vibration. Both riding comfort and running stability can be achieved with respect to input.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 5 are views showing an embodiment of a variable damping force type hydraulic shock absorber according to the present invention, and FIG. 2 is the entire shock absorber thereof. FIG. 3 is a cross-sectional view showing the configuration, FIG. 3 is a cross-sectional view of the main part thereof, FIG. 4 is a circuit diagram showing a part of the system configuration diagram, and FIG. 5 is a diagram showing its operation. DESCRIPTION OF SYMBOLS 1 ... Shock absorber, 60 ... 1st piezoelectric element (1st detection means, 2nd operation means), 90 ... 2nd piezoelectric element (2nd detection means, 1st operation means), 100 ... Control Unit (control means),

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Emura 1370, Onna, Atsugi City, Kanagawa Prefecture Atsugi Motor Parts Co., Ltd. (56) References JP 62-198513 (JP, A) JP 61- 85210 (JP, A)

Claims (1)

(57) [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) signal processing means for passing a signal component of a predetermined frequency band among outputs of the first detecting means and the second detecting means, and d) liquid from the outputs of the first detecting means and the second detecting means. A control that calculates the rate of change of pressure and calculates a control value such that the shock absorber has a predetermined high damping force when the rate of change has an extreme value, and a predetermined low damping force when the rate of change decreases to zero. Means, e) first operating means for changing the compression side damping force based on the output of the control means, and f) second operating means for changing the extension side damping force based on the output of the control means. A damping force variable hydraulic shock absorber characterized by the above.