JPH0714008Y2 - Variable damping force hydraulic shock absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a damping force variable hydraulic shock absorber for a vehicle such as an automobile, and more specifically, it appropriately controls the damping force according to the turning state of the vehicle body. The present invention relates to a variable damping force type hydraulic shock absorber.

(Prior Art) In recent years, there is a tendency for compatibility between riding comfort and traveling stability to be demanded as the demand for vehicles increases. 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 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 electrons 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, only the magnitude of the hydraulic pressure, that is, the amplitude of the vibration is used as the vibration information, and the vehicle travels. Since the state was determined, it is not possible to determine whether the vehicle is turning or traveling on a rough road when a large-amplitude vibration is input.Therefore, it is not possible to perform appropriate control for turning and traveling on a rough road. There was a point. For example, when the hydraulic pressure exceeds the set value during turning, the damping force is switched to hard, and running stability during turning is satisfied, but when the vehicle starts turning, the shock absorber is actually compressed and becomes hard. Since it switches, it is not possible to perform control at the initial stage of turning, allowing a sudden lean of the vehicle body,
Running stability will be impaired until it is switched to hardware.

On the other hand, when driving on a rough road, if the hydraulic pressure exceeds the set value, the damping force on the compression side and the damping force on the extension side are maintained hard for a predetermined time. It becomes a vibration source, the vibration damping property deteriorates, and the riding comfort deteriorates.
After all, both riding comfort and running stability cannot be achieved at the same time. In other words, in the case of the conventional device, since only the outputs of the piezoelectric elements detected by the four shock absorbers are used as the vibration information and the damping force suppression control is performed based on the magnitude of the hydraulic pressure, The above problems have occurred. The pressure side and the extension side 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 to extend, and may be hereinafter referred to as the pressure stroke and the extension stroke.

(Object of the Invention) Therefore, the present invention detects the hydraulic pressures of the four shock absorbers separately on the pressure side and the extension side, detects the steering state of the steering wheel, and the change speed of the steering state exceeds a predetermined value. When a predetermined turning state is reached, the compression side damping force of the two compressed sides and the extension side damping force of the two extended sides of the four shock absorbers are switched to the hard state, and when the turning state ends, the four By controlling the damping force sequentially with respect to the shock absorber based on the rate of change of the hydraulic pressure on the compression side and the extension side, the damping force is appropriately controlled when the vehicle body leans and when traveling on rough roads, and the running state The purpose is to achieve both riding comfort and running stability.

(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 to detect pressure
Detecting means a, second detecting means b for detecting the hydraulic pressure on the extension side of the variable damping force type shock absorber, steering state detecting means c for detecting the steering state of the steering wheel,
When the speed of change of the steering state exceeds a predetermined value, a turning state determining means d for determining the turning state of the vehicle from the outputs of the first detecting means a and the second detecting means b, and the vehicle is brought into a predetermined turning state. When the transition is made, one or more compression-side damping force on the compressed side and one or more extension-side damping force on the stretched side of the four shock absorbers become a predetermined high damping force, and The value is determined based on the output of the steering state detecting means c, and when the predetermined turning state is completed, the hydraulic pressure is sequentially output to the four shock absorbers from the outputs of the first detecting means a and the second detecting means b. When the rate of change reaches an extreme value, the shock absorber is set to a predetermined high damping force, the value of the high damping force is determined according to the extreme value, and the rate of change falls to a predetermined value. Play a control value to obtain a predetermined low damping force. Of the damping force variable type shock absorber based on the output of the control means e and the first operating means f that exceeds the damping force on the pressure side of the damping force variable type shock absorber based on the output of the control means e. Second operating means g for changing the extension side damping force.

(Operation) In the present invention, the hydraulic pressures on the pressure side and the extension side of the four shock absorbers are detected separately, the steering state of the steering wheel is detected, and when the speed of change of the steering state exceeds a predetermined value, The turning state of the vehicle body is determined based on the hydraulic pressures on the compression side and the extension side, and when a predetermined turning state is reached, the compression side damping force of the two compressed sides and the extension of the two extended sides of the four shock absorbers are determined. When the side damping force is switched to hard and the predetermined turning state is completed, the change rates of the hydraulic pressures on the compression side and the extension side of the four shock absorbers are sequentially obtained, and the change rate exceeds the predetermined dead band and becomes an extreme value. Then, the damping force is switched to hard, and when the rate of change falls to a predetermined value, the damping force is returned to soft. Here, the rate of change corresponds to the speed of vibration, and the initial stage of vibration (near the center)
Takes the maximum value and reaches the peak of the vibration (the boundary between the pressure stroke and the extension stroke) and becomes 0, which is equal to or less than the predetermined value. In addition, the dead zone is provided, for example, over the pressure side and the extension side in consideration of the change in hydraulic pressure due to small vibration when traveling on a rough road, and the damping force is soft to the vibration input in this area. Maintained at.

Therefore, it is possible to accurately determine whether the vehicle is turning or traveling on a rough road based on the steering state of the steering wheel.
The damping force on both the compressed side and the expanded side of the shock absorber in the book is switched to hard, which prevents the leaning of the vehicle body in advance and ensures running stability. The damping force on the compression side and the damping force on the extension side are appropriately controlled with respect to the vibration input to satisfy the riding comfort, and the riding comfort and the running stability can be achieved regardless of the running state.

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

2 to 8 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 push (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 peripheral portion 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. The adjusting nut 53 moves in the axial direction when rotated, and The position of the piezoelectric element 60 in the axial direction is changed. The adjustment nut 53 abuts the plate 56 via the plate 54 and the cap 55, and the plate 56
Is fixed to the upper end of the first piezoelectric element 60. The first piezoelectric element 60 is supported by the cap 55 and the damping means 70, and moves up and down in the accommodation hole 49. The cords 61 and 62 of the first piezoelectric element 60 are the cords 91 of the second piezoelectric element 90,
The wiring 35 is formed together with 92, and the wiring 35 is connected to the control unit 100. Further, the first piezoelectric element 60 abuts the slider 71 which constitutes a part of the damping means 70 via the plate 59, and attenuates the extension according to the extension side control signal S _A.
Propagate to 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 held between the valve body 73 and the slider 71. , And an extension side valve 75 held between a valve core 72 and a 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. Orifice 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 does not allow hydraulic fluid to 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.

In the extension stroke, the damping means 70 is compressed by the extension of the first piezoelectric element 60, changes the opening degree of the extension side valve 75 to reduce the opening area of the orifice 77, and provides a predetermined damping force (hereinafter referred to as software). Increase and switch to a high damping force (hereinafter referred to as "hard"). On the other hand, the damping means 70 is pressed by the expansion of the second piezoelectric element 90 in the pressure stroke, changes the opening 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 and transmits the hydraulic pressure in the upper liquid chamber 14 to the second piezoelectric element 90 during the extension stroke. The lower end of the second piezoelectric element contacts 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 damped by the damping means 70 and the first piezoelectric element. Propagate to 60. 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 thereof and is displaced upward and transmits the displacement to the second 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 side 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 compression side 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 upper liquid chamber 14 transmitted from 70 is detected, and the extension side signal Ss is output. A steering state detecting means 150 is provided around the steering wheel inside the vehicle (not shown), and the steering state detecting means 150 detects the steering angle of the steering wheel and outputs a steering angle signal Sd.

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 steering state detecting means 150 are input to the control unit 100, and the control unit 100 has a function as a turning state determining means and a controlling means. Further, the control unit 100 discriminates the pressure side and extension side signals Sp and Ss based on the presence / absence of a signal from the first piezoelectric element 60, calculates a change rate of the signal, and outputs a control signal corresponding to the magnitude of the change rate.
Output S _A and S _B.

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. Four shock absorbers 1 and a steering state detecting means 150 are connected to the I / O port 101, and exchange 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. Further, the steering state detecting means 150 detects the steering direction and the steering angle of the steering wheel and outputs the steering angle signal Sd. The buffer 114 of the input circuit 110 amplifies the steering angle signal Sd and outputs it to the arithmetic circuit 120. Arithmetic circuit 120
Is composed of, for example, a microcomputer, acquires external data according to a program written in the internal memory, and performs processing necessary for variable control of damping force based on the acquired data and the data written in the internal memory. Calculate the value.

That is, the arithmetic circuit 120 determines the turning state of the vehicle based on the input signal, and when the vehicle turns into a predetermined turning state, the vehicle 4
Side 2 of book shock absorber 1 that is compressed during turning
The pressure side and extension side control signals S _A and S _B are output to the book and the two sides to be extended. Further, the arithmetic circuit 120 calculates the rate of change of the input signal when the turning state ends, and when the rate of change is an extreme value, the extension side control signal S _A corresponding to the magnitude of the rate of change is calculated.
Is output to the drive circuit 130. The drive circuit 130 is a buffer 131
ON the extension side control signal S _A is input transistor Tr ₁ in
Then, the drive voltage of the drive power supply circuit 140 is applied to the first piezoelectric element 60 via the diode D ₁ of the I / O port 101, and the damping force is switched from soft to hard. In addition, the drive circuit 13
When 0, 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 hard Back to soft. The driving power supply circuit 140 is formed of, for example, a DC-DC converter, and includes the first and second piezoelectric elements 60, 90.
It outputs a high DC voltage (hereinafter referred to as a drive voltage) capable of expanding the signal. 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 from the piezoelectric element generated by pressing the damping means 70 is adjusted to a certain value. Adjust the same procedure for both the extension and compression sides.

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

In the extension stroke as shown in FIG. 6C, 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.

7 (a) and 7 (b) are flowcharts showing a damping force variable control program written in the memory of the arithmetic circuit 120, and FIG. 7 (a) is a posture control program for the vehicle body, and FIG. FIG. 6B shows a program for the damping force variable control, and this program is executed once every predetermined time.

When the vehicle is in a normal running condition where vibration with a relatively small amplitude (hereinafter referred to as small vibration) is input, the vehicle is running at a low speed but with large amplitude (hereinafter referred to as large vibration), resulting in poor riding comfort. When traveling on a bad road, when the traveling speed is relatively high, the vehicle body is tilted by steering the steering wheel. When the vehicle turns, it is further divided into a right turn (hereinafter, right turn) and a left turn. It is divided into turns (hereinafter referred to as left turns) and is shown as follows.

(I) When turning (right turning) (II) When turning (left turning) (III) When traveling on a rough road (IV) When traveling normally Hereinafter, these cases will be described separately.

(I) When turning (right turn) First, at P ₁ , the steering angle signal Sd and the pressure side and extension side signals Sp and Ss are read. Here, reading of the compression side signals and the expansion side signals Sp, Ss is performed for the four shock absorbers 1. Then, calculates the rate of change of the steering signal Sd at P _2, is compared with a predetermined value change rate P _3, proceeds to P ₄ when the change rate exceeds a predetermined value. The above determination is performed to determine a predetermined turning state, and the above predetermined value is determined by an experiment or the like. Incidentally, the predetermined turning state means a state in which the vehicle body leans in the left-right direction due to turning with a low damping force, and the vehicle body suddenly leans to the left side to impair the running stability. When changing to the turning state, the changing speed of the steering angle shows a large value. Then, at P ₄ , the steering angle signal
The absolute value of Sd is compared with a set value theta, when the Sd ≧ theta moves to P _5, it is determined whether or not the rightward steering based on the steering signal Sd at P _5. Here, the set value θ is determined by experiments or the like so that the turning state can be discriminated. When steering to the right
Of the four shock absorbers 1 at P ₆ , 2 on the left side of the vehicle body
This is to determine whether it is more stroke, moves to P ₇ as long as stroke, two vehicle body right side P ₇ it is determined whether or not a more Nobuyuki. The above determination is performed to accurately determine a predetermined turning state (right turning). When the vehicle turns right to reach a predetermined turning state, the left side 2 of the vehicle body among the four shock absorbers 1
The book is compressed and the right two are expanded. If enough Nobuyuki moved to P ₈ to determine that the predetermined turning state, the compression side control signals to the shock absorber 1 of the vehicle body of the left two at P ₈
S _B is output and a drive voltage is applied to the second piezoelectric element 90 to switch the compression side damping force from soft to hard. Then P ₉
Then, the extension side control signal S _A is output to the shock absorber 1 of the two right side of the vehicle body, and the driving voltage is applied to the first piezoelectric element 60 to switch the damping force to hard. Here, the value of the high damping force (hard) corresponds to the changing speed of the steering angle signal Sd, and changes steplessly according to the turning state. Then P ₁₀
In to determine whether reached application level, does not reach the application level, returns to P _8, the driving voltage is applied again at P _8, P _9, and ends the current routine reaches the application level .

By the execution of Step P ₂ to P _10, the predetermined turning state can be determined precisely, four shock absorber 1
It is possible to immediately switch the two compression side damping forces on the right side of the compression side and the two extension side damping forces of the extended side to the hard side. Therefore, due to the high flow resistance, the leaning of the vehicle body can be prevented and the running stability can be satisfied.

(II) When turning (left turning) If it is not right steering in P ₅ , it is determined whether it is left steering in P ₁₁ and if it is left steering, 4 shock absorbers 1 in P ₁₂
Of the two on the left side of the car body, it is determined whether or not it is the extension stroke,
Moves to P ₁₃ as long as Nobuyuki, two the right side of the vehicle body at P _13, it is determined whether or not as stroke. The above determination is performed to accurately determine a predetermined turning state (counterclockwise turning), and when the vehicle turns to a predetermined turning state, the four shock absorbers 1
Of these, the right two of the vehicle body are compressed and the left two are extended. If more stroke is determined that the predetermined turning state (left turn), and outputs the expansion side signal S _A with respect to the vehicle body of the left two at P _14, the extension side damping force by applying a driving voltage switched to hard, then the compression side signal S _B with respect to the right side of the vehicle body 2 by P ₁₅
Is output and the compression side damping force is switched to hard. Then
It is determined whether or not reached application level P _16, returns to P ₁₃ does not reach the application level, it ends the current routine when applied again driving voltage at P _14, P ₁₅ reaches the application level To do.

Step P ₅ to P ₁₆ predetermined turning state (left turn) by the execution of the can be determined accurately, it is possible to prevent leaning of the vehicle body from occurring by switching immediately damping force hard. That is, in this embodiment, since the damping force is controlled based on the output of the steering state detecting means 150, it is possible to accurately determine the turning state regardless of the turning direction, and the conventional example in which the switching to the hardware is delayed. Differently, it is possible to satisfy the predetermined turning state and switch the damping force to satisfy the traveling stability.

Incidentally, the condition determination in Step P ₁ to P _16, all when the condition is not satisfied, the process proceeds to the program shown in Figure 7 to determine not the predetermined turning state (b).

FIG. 7 (b) is a flow chart showing a program for performing damping force control during normal traveling and traveling on rough roads.
The shock absorbers 1 of the book are sequentially performed. 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.

(III) when running on a rough road is first read the compression side signal Sp detected in real time from the hydraulic pressure in the cylinder 3 at P _17, calculates a rate of change of the pressure side signal Sp at P _18. 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 small-amplitude vibration, and becomes 0 at the peak of large-amplitude vibration. Also, the speed of vibration increases as the amplitude increases,
The shorter the cycle of vibration, the larger the vibration. Therefore, by using the rate of change (speed of vibration) 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 determined based on the rate of change. You can control. Next, at P ₁₉ , it is determined whether the rate of change is the extreme value. The reason for determining the extreme value is to determine a vibration with a large amplitude (large vibration) that advances in a short time (short cycle). Here, the large vibration means a vibration in which the vehicle body is suddenly tilted to impair traveling stability, for example, when traveling on a rough road. The driving stability is best when the vehicle body is horizontal, and the maneuverability is good. When the vehicle body has a large inclination or the vehicle body suddenly leans, the maneuverability becomes worse. P _{20 for} extreme values
Output the pressure side control signal S _B determined according to the extreme value at
A driving voltage is applied to the piezoelectric element 90 to switch the damping force from soft to hard. Here, the value of the high damping force (hard) corresponds to the extreme value, and changes steplessly according to the amplitude (extreme value) of the vibration input from the road surface. That is, in this embodiment, the value of the high damping force (hard) changes in accordance with the magnitude of the amplitude,
It is always appropriate for vibration input, improving vibration control. Then determines whether the reached application level P _21. Here, the applied level means the voltage value of the pressure-side signal Sp when the damping force is switched to hard. If not reached application level, returns to _{P. 2O,} a driving voltage is applied again with _{P. 2O,} it reaches the application level and ends the current routine.

Step P ₁₇ to P by executing ₂₁ can determine a large vibration in the early stages of vibration, it is possible to immediately switch the damping force hard. Furthermore, since the value of the high damping force is determined according to the extreme value, the damping force can be appropriately controlled to follow the vibration input, and the damping performance is improved to improve running stability and riding comfort. Can be compatible. That is, in this embodiment, the initial responsiveness to vibration is improved as compared with the conventional example in which control is performed according to the magnitude of hydraulic pressure, and the damping force can be appropriately controlled during traveling on a rough road.

On the other hand, proceeds to P ₂₂ when the rate of change in P ₁₉ is not extreme, P ₂₂
Determines whether the rate of change is 0. When the amplitude of the vibration reaches the peak (the boundary point between the pressure stroke and the extension stroke), the speed of the vibration, that is, the rate of change becomes zero. Therefore, by determining whether or not the change rate is 0, 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. That is, in the extension stroke, the damping force can be returned to soft to accelerate the recovery from the compressed state. If the rate of change is not 0, it is determined that the pressure stroke has not ended, and this routine is ended. When the pressure stroke is not completed, vibration is damped by the damping force set in the previous routine, and the damping force is not switched.

On the other hand, proceeds to P ₂₃ it is determined that enough stroke if 0 is the rate of change in P ₂₂ is completed, it outputs a compression side control signals S _B at P _23, the second
The electric charge of the piezoelectric element 90 is discharged. Then, by comparing the pressure side signal Sp and the predetermined value P _24, if less than a predetermined value returns to P _23, and discharges the electric charge again P _23, the discharge ends sufficiently carried out when the current routine. Here, the predetermined value refers to 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.
The piezoelectric element 90 of 1 restores the function as the detecting means. When the damping force is soft from the beginning, the damping force does not change.

By the execution of step P ₁₉ to P _24, stroke as it is determined that the vibration of the or the extension side has been completed is input, can be controlled independently damping force in pressure stroke and the extension stroke of the road surface vibration. In other words, the pressure stroke is switched to hard and the extension stroke is switched to soft, and in combination with the improvement of the initial response, the leaning of the vehicle body is made smaller than in the conventional example, and the running stability is improved.

By executing the (IV) normal running time of the step P ₁₇ to P _24, the damping force can always be made to correspond to vibration input can fill the riding comfort and driving stability.

As described above, in this embodiment, since the damping force is finely changed based on the magnitude of the rate of change, independent control can be performed for the pressure stroke and extension stroke of the vibration cycle, and continuous road surface It can respond appropriately to vibration. Further, in the present embodiment, the value of the high damping force is determined according to the extreme value, so that a large value is used when the amplitude is large, and a small value is used when the amplitude is small. As a result, the vibration damping property is improved, and both riding comfort and running stability can be achieved.

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.

When traveling on a rough road As shown in FIG. 6 (c), when a large vibration is input at point A and the rate of change reaches an extreme value, the damping force is immediately switched from soft to hard (section (H)). Therefore, the hydraulic pressure (detection signal) in the cylinder 3 increases by the amount of increase in the damping force (driving voltage) as indicated by the one-dot chain line, and changes in the same manner as the software indicated by the dotted line (see (b) in the figure). . At this time, the movement of the piston 4 is restricted by the high damping force, that is, the high flow resistance, and the amplitude thereof is reduced as compared with the conventional example in which the piston 4 is maintained soft up to the point B. Therefore, in this embodiment, the expansion of the shock absorber 1 due to the vibration of the road surface is smaller than that in the conventional example,
Inclination of the vehicle body is suppressed and driving stability is improved (section AG).

Further, in the present embodiment, since the hydraulic pressures on the compression side and the extension side are separately detected in real time, the damping force is appropriate for continuous vibration input at the time of traveling on a rough road in combination with the improvement of the initial response. Can be controlled. That is, unlike the conventional example in which the extension side damping force is maintained hard to secure the running stability (section AG), unlike the conventional example in which the extension side damping force is maintained hard after point B, the vibration input to the pressure side The rate of change becomes 0, and the damping force on the compression side can be softened, and vibration characteristics can be improved to improve riding comfort (sections BC and DE). This is because the flow resistance is reduced and the vibration can be sufficiently absorbed by the spring, and the compression side damping force is generally set lower than the extension side damping force.

As described above, in this embodiment, the hydraulic pressures on the compression side and the extension side are detected in real time, and the damping force is controlled based on the rate of change of the hydraulic pressure. On the other hand, the damping force can always be made appropriate, and the ride comfort can be satisfied.

At the time of turning When the output and the changing speed of the steering angle signal Sd at a point G exceed a predetermined value and a predetermined turning state is reached, the damping force is immediately switched from soft to hard. At this time, the movement of the piston 4 is restricted by the high damping force, that is, the high flow resistance, and the amplitude thereof is reduced as compared with the conventional case. Further, at the point J, the predetermined turning state ends and the rate of change becomes 0, the damping force in the extension stroke is softly switched, and the piston quickly returns to the center of vibration due to low flow resistance (section JK).
Therefore, in the present embodiment, the expansion of the shock absorber 1 at the time of turning is less than that in the conventional example and the speed is quickly recovered, and the inclination of the vehicle body is suppressed in advance and the traveling stability is improved (section GK).

As described above, in this embodiment, the steering state of the steering wheel is detected, and the predetermined turning state is determined from the steering state and the hydraulic pressures on the pressure side and the extension side of the shock absorber. It is possible to accurately determine, and it is possible to achieve both riding comfort and running stability regardless of the running state.

It should be noted that the predetermined value referred to in the utility model registration claim is a concept including 0, and the predetermined value is set to 0 in the present embodiment, but the present invention is not limited to this, and an upper limit value and a lower limit value, such as a dead zone, are set. It may be all values within a predetermined range having a value.

Further, in the present 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 present 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 predetermined dead zone is set to the predetermined range extending from the pressure side to the extension side, but the present invention is not limited to this, and a predetermined range of change rate 0 from the pressure side or the opposite thereof may be used. Of course it's good.

Although the steering state detecting means 150 detects the steering angle of the steering wheel in the present embodiment, the present invention is not limited to this.
The steering amount may be detected, and the invention is not limited to the above embodiment as long as the steering state of the steering wheel can be detected.

(Effect) In the present invention, the hydraulic pressures on the compression side and the expansion side of the four shock absorbers are detected separately, the steering state of the steering wheel is detected, and the change speed of the steering state is set to a predetermined value based on these outputs. When the predetermined turning state is reached, when the predetermined turning state is reached, the compression side damping force of the two compressed sides and the extension side damping force of the two extended sides of the four shock absorbers are hardened. When the turning state is completed, the damping force is sequentially controlled for the four shock absorbers based on the rate of change of the hydraulic pressure. Therefore, it is possible to accurately determine whether the vehicle is turning or traveling on a rough road. When the vehicle turns, the vehicle body is prevented from tilting to ensure running stability, and when driving on rough roads, the damping force for the vibration input can be controlled independently for the compression side and the extension side to provide a comfortable ride. It is possible to achieve both riding comfort and running stability regardless of the running state.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 8 are diagrams showing one 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. 7 (a),
(B) is a flowchart showing a program for the damping force variable control, and FIG. 8 is a diagram for explaining its 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), 90 ... second piezoelectric element (second detecting means, first operating means), 100 ... control unit (control means, turning state determining means), 101 ... I / O port,
110: input circuit, 120: arithmetic circuit, 130: drive circuit, 140: drive power circuit, 150: steering state detection means.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Junichi Emura 1370, Onna, Atsugi City, Kanagawa Prefecture Atsugi Motor Parts Co., Ltd. (56) References JP-A-52-81823 (JP, A) JP-A-61-75007 (JP, A) Actual Kaihei 1-161102 (JP, U)

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. And c) steering state detecting means for detecting the steering state of the steering wheel, and d) the vehicle based on the outputs of the first detecting means and the second detecting means when the speed of change of the steering state exceeds a predetermined value. Of the four shock absorbers when the vehicle shifts to a predetermined turning state, one or more compression side damping forces on the compressed side and one on the expanded side. The extension side damping force equal to or more than a predetermined number is set as a predetermined high damping force, the value of the high damping force is determined based on the output of the steering state detecting means, and when the predetermined turning state is completed, the four shock absorbers are compared. The first inspection The rate of change of the hydraulic pressure is obtained from the outputs of the output means and the second detection means, and when the rate of change reaches the extreme value, the shock absorber is made to have a predetermined high damping force, and the value of the high damping force becomes the extreme value. And a control means for calculating a control value such that a predetermined low damping force is obtained when the rate of change decreases to a predetermined value, and f) damping on the pressure side of the damping force variable shock absorber based on the output of the control means. A damping force, comprising: a first operating means for changing the force; and g) a second operating means for changing the extension side damping force of the damping force variable shock absorber based on the output of the control means. Variable hydraulic buffer.