JPH0699717A - Damping force-changeable shock absorber control device - Google Patents

Abstract

PURPOSE:To restrict unnatural motion of a vehicle in changing damping force without increasing frequency of changing the damping force in a shock absorber. CONSTITUTION:A shock absorber 7 is composed to selectively connect/disconnect an auxiliary passage 50 in a control valve 60 to/from a contraction side passage 56 or an expansion side passage 57 by rotation of the control value 60. Hysteresis is given to a threshold value to a size of vertical speed on spring in transition from a control condition where sizes of damping force on the expansion side and the contraction side are different into a control condition where both the damping forces on the expansion side and the contraction side are small to be zero or close to zero. In changing the damping force from the control condition of the large damping force into the control condition of the small damping force temporarily without increasing frequency of damping force changing, unnatural action in springing is eliminated in the case of performing control of restricting change of an attitude, and a large damping force is more positively used to increase damping effect in the case of performing damping control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber control device capable of switching damping force settings used in a vehicle.

[0002]

2. Description of the Related Art Conventionally, a skyhook damper for generating a damping force proportional to an absolute speed on a spring has been devised in order to improve the riding comfort and steering stability of a vehicle. This skyhook damper is an ideal damper that suspends a damper from a fixed point in space and suppresses vibration of the vehicle body by this damper so as to prevent road irregularities from being transmitted to the vehicle body.

By the way, Karnopp has proposed a control method for realizing a characteristic close to that of a skyhook damper by a semi-active suspension. Ka
In the rnopp method, as shown in FIGS. 16 and 17, when the absolute speed dX2 on the spring and the relative speed dX2-dX1 between the sprung unspring are equal in sign, that is, the vehicle body and the wheels are in opposite directions. The damping force of the shock absorber is increased when the vehicle moves and the wheels move in the same direction and the moving speed of the vehicle is faster than the moving speed of the wheels (when the damping force damps the vehicle body). Enlarge. Further, when the two speeds have different signs, that is, when the vehicle body and the wheels move in the same direction and the moving speed of the wheels is faster than the moving speed of the vehicle body (the damping force excites the vehicle body). Control) to reduce the damping force.

That is, in the Karnopp method, even when the relative speed dX2-dX1 between the sprung unsprung portions is negative (when the shock absorber contracts), when the absolute speed dX2 on the spring is negative (downward). The damping force of the shock absorber was increased. Further, in the conventional device, a sprung acceleration sensor and a stroke sensor are attached to a vehicle, the output signal of the sprung acceleration sensor is integrated to detect the absolute speed dX2 on the spring, and the output signal of the stroke sensor is differentiated. The relative speed between the sprung part and the unsprung part dX2
-DX1 was detected. And the absolute velocity d on the spring
The damping force is changed when the sign of X2 changes and when the sign of the relative speed dX2-dX1 between the sprung part and the unsprung part changes.

The inventors of the present invention have proposed Japanese Patent Application No. 4-144408 "Variable damping force shock absorber and its control device" as a means for simply implementing the above control. In this model, the vertical velocity on the spring is calculated based on the vertical acceleration on the spring detected by the acceleration sensor, and the setting for damping force control of the damping force variable shock absorber is calculated according to the vertical velocity on the spring. The mode is changed appropriately. At this time, the mode switching threshold is constant when the mode is entered and when the mode is exited. (However, there is hysteresis to prevent divergence due to control.) When the sprung mass moves and its speed exceeds a predetermined value on the positive side (hereinafter, referred to as threshold value Vref +), the damping force on the extension side and the contraction side is reduced. Both are small control states (hereinafter,
A transition is made from the S-S mode) to a control state in which the damping force on the extension side is large and the damping force on the contraction side is small (hereinafter referred to as the HS mode). On the other hand, when the sprung mass moves and its speed exceeds a predetermined value on the negative side (hereinafter, referred to as threshold value Vref-), the damping force on the contraction side is large and the damping force on the extension side is small from the SS mode (a control state ( Hereinafter, it will be referred to as S-H mode). In this way, the control device tries to suppress the sprung movement. The vertical speed on the spring is the threshold V
When the value is between ref + and Vref-, the HS mode or S-
Return from the H mode to the S-S mode. Here, the threshold value Vref +
And Vref- may have the same absolute value or different absolute values.

[0006]

Here, for example, paying attention to the sprung front wheel portion at the initial stage of braking, the sprung front wheel portion begins to sink at the start of braking and balances at a fixed position determined by deceleration. That is, when the sinking (negative side) speed exceeds the threshold value Vref-, S-S
The mode is switched to the S-H mode to try to suppress the sinking. Then, when the sinking speed becomes equal to or less than the threshold value Vref-, the damping force is returned to the S-S mode and is reduced on both the extension side and the contraction side. Then, at one end, the vertical velocity on the spring, which was about to stand still, increases again, which may cause an unnatural movement of the vehicle. In order to avoid the unnatural movement of the vehicle, the absolute values of the threshold values Vref + and Vref- may be reduced. However, the frequency of switching between the modes increases, and the control device becomes problematic in terms of durability and power consumption.

The present invention has been made to solve the above problems, and an object of the present invention is to make a vehicle unnatural when switching the damping force without increasing the frequency of switching the damping force in the shock absorber. It is to suppress such movements.

[0008]

A first feature of the structure of the invention for solving the above-mentioned problems is to have a speed detecting means for detecting a vertical speed on a spring of a vehicle, and to detect the vertical speed on the detected spring. In a damping force variable shock absorber control device for changing a damping force of a shock absorber arranged on each wheel according to a directional speed, a first set of a first threshold value for a vertical speed on the spring is set. Threshold value setting means, second threshold value setting means for setting a pair of second threshold values having an absolute value smaller than the first threshold value with respect to the vertical velocity on the spring to zero or near zero, and on the spring When the vertical speed exceeds the first threshold value, the control state in which the damping forces on the extension side and the contraction side are both small is transited to a control state in which the magnitudes of the damping forces on the extension side and the contraction side are different, and
After the velocity in the vertical direction on the spring exceeds the first threshold value and the control device is in a control state in which the magnitudes of the damping forces on the extension side and the contraction side are different, the vertical velocity on the spring decreases to the second threshold value. And a damping force setting means for making a transition to a control state in which both the damping force on the extension side and the damping force on the contraction side when both are exceeded.

The second feature is that it has first speed detecting means for detecting the vertical speed on the spring of the vehicle and second speed detecting means for detecting the relative speed between the sprung and unsprung parts. A variable damping force shock absorber control device that changes the damping force of a shock absorber arranged on each wheel according to the vertical velocity on the spring and the relative velocity between the sprung unsprung, and the vertical velocity on the spring. And a first threshold value setting means for setting a set of first threshold values for the relative velocity between the sprung and unsprung portions, and the first threshold value for the vertical velocity on the spring and the relative velocity between the sprung and unsprung portions. Second threshold value setting means for setting a second threshold value so as to be closer to zero or near zero, and a damping force control state set by the vertical speed on the spring and the relative speed between the sprung and unsprung parts. Exceeded the first threshold When a control state with a large damping force is changed to a control state with a large damping force, and once the control state with a large damping force is exceeded, when the second threshold value is exceeded, a control state with a large damping force is changed to a control state with a small damping force. And a damping force setting means for controlling the damping force.

[0010]

[Action]

[Operation of First Characteristic] According to the above means, the magnitude of the vertical velocity on the spring exceeds the first threshold value, and the extension side and the contraction side have different damping force magnitudes. After that, the magnitude of the vertical speed on the spring when the damping force on the extension side and the damping force on the contraction side both change to a small value becomes zero or near zero set by the second threshold value. Here, first
The magnitude of the vertical velocity on the spring when the control state in which the damping force on the extension side and the compression side are both small changes to a control state in which the magnitude of the damping force on the extension side and the compression side are different is In order to prevent the vibration from being transmitted to the vehicle body side, it is considered that the first threshold value set to a certain level is exceeded. In the case of this opposite direction, hysteresis is added to the determination of the magnitude of the vertical velocity on the spring as described above, and the magnitude of the vertical velocity on the spring is zero or zero set by the second threshold value. Since the control state is transited in the vicinity, the time for realizing the large damping force of the shock absorber becomes long.

[Operation of Second Characteristic] According to the above means, the control state of the damping force set by the vertical speed on the spring and the relative speed between the sprung and unsprung springs exceeds the first threshold value. The vertical speed on the spring and the relative speed between the sprung and unsprung parts when the damping force is changed to the control state with the large damping force and then the control state with the small damping force is zero or set to the second threshold value. It is near zero. Here, the magnitude of the vertical velocity on the spring and the relative velocity between the sprung and unsprung portions in the transition from the control state in which the damping force is small to the control state in which the damping force is large is determined as follows. In order to prevent the transmission to the side, it is considered that the first threshold value set to a certain size is exceeded. In the case of this opposite direction, as described above, hysteresis is provided in the determination of the relative speed between the vertical speed on the spring and the sprung unsprung, and the vertical speed on the spring and the sprung unsprung are detected. Since the control state transitions when the magnitude of the relative speed is zero or near zero set by the second threshold value, it takes a long time to realize a large damping force of the shock absorber.

[0012]

EXAMPLES The present invention will be described below based on specific examples. FIG. 1 is a block diagram showing the overall configuration of a damping force variable shock absorber control device according to the present invention. Reference numeral 1 denotes a known strain gauge type acceleration sensor, which is attached to a vehicle body near each suspension upper support (not shown) of each wheel. The acceleration sensor 1 detects the vertical acceleration on the spring, and the detection signal is input to the integration circuit 2. The integrating circuit 2 calculates the speed signal V (= dX2) on the spring by integrating the vertical acceleration signal on the spring from the acceleration sensor 1. The control unit 5 inputs a signal from the integration circuit 2 and outputs a control signal to the actuator 6, and is configured as an arithmetic logic circuit. The control valve 60 provided in the shock absorber 7 is driven by the actuator 6.

Next, the structure of the shock absorber 7 is shown in FIG.
~ It demonstrates using FIG. Figure 2 shows the shock absorber 7
It is a longitudinal cross-sectional view showing. The middle space of the cylinder 10 of the shock absorber 7 is vertically divided by the main piston 20 into an upper chamber 2a and a lower chamber 2b, respectively. The main piston 20 is fixed to a piston rod C36 penetrating the center of the main piston 20 by a nut 37 via a spacer or the like. The piston rod C36 is screwed and fixed to the piston rod A30 together with the piston rod B35 by a threaded portion of the lower end cylindrical portion of the piston rod A30. Also, piston rod A
A communication chamber 56b is formed between 30 and the piston rod B35 in an oil-tight manner via two O-rings 90. The piston rod A30 and the piston rod B35 are provided with a pair of communication holes 56a and a plurality of communication holes 56c, and together with the communication chamber 56b, a contraction-side dedicated channel 56 having a relatively large channel area is formed. Also, piston rod A3
0 and the piston rod B35 between the spring 54
And a plate check valve 58. The upper end of the spring 54 abuts on the piston rod A30, the lower end abuts on the plate check valve 58, and the spring 54 urges the plate check valve 58 downward. Therefore, the contraction-side flow path 56 is opened and closed by the plate check valve 58 that allows only the outflow from the direction of the control valve 60 to the upper chamber 2a.

Piston rod B35 and piston rod C
36, there is a spring chamber 57b which is oil-tightly formed through three O-rings 90 and accommodates the spring 55 and the plate check valve 59. The upper end of the spring 55 abuts on the piston rod B35, and the lower end abuts on the plate check valve 59, and the spring 55 urges the plate check valve 59 downward. The piston rod A30 and the piston rod C36 have a pair of communication holes 57a and a plurality of communication holes 57.
c is provided, and together with the spring chamber 57b, an extension-side dedicated flow channel 57 having a relatively large flow channel area is formed. Therefore, the extension-side dedicated flow path 57 is connected to the control valve 6 from the upper chamber 2a.
It is opened and closed by a plate check valve 59 that allows only the inflow in the 0 direction.

The main piston 20 has an upper chamber 2a,
A contraction-side main flow channel 41 and an extension-side main flow channel 42, which have a relatively small flow channel area and communicate with the lower chamber 2b, are formed. The contraction side main flow passage 41 is opened / closed by a plate check valve 48 provided on the upper surface of the main piston 20, and the extension side main flow passage 42 is opened / closed by a plate check valve 49 provided on the lower surface of the main piston 20. In the piston rod C36, the sub-flow passage 5 that allows the working oil to flow between the upper chamber 2a and the lower chamber 2b.
0 is formed.

The lower end portion of the piston rod A30 is formed in a tubular shape, and a control valve 60 is oil-tightly and rotatably fitted in the tubular portion. The upper portion of the control valve 60 is in the shape of a solid thin rod, and its upper end is connected to the actuator 6 (not shown). The upper rod-shaped portion of the control valve 60 may be made separately and press-fitted into the lower tubular portion of the control valve 60. Also, member 3
1, 32 are press-fitted and fixed to the piston rod A30, and the inner diameter portion thereof is rotatably fitted to the small diameter portion of the control valve 60. O-ring 9 disposed under the member 31
0 is to maintain oil tightness with the outside. Therefore, the control valve 60 is rotatable about the central axis of the piston rod A30 by driving the actuator 6.

FIG. 3 is a vertical sectional view of the control valve 60.
The lower end of the control valve 60 has a hollow structure as shown in the drawing, and forms a part of the sub-flow path 50. 4A is a cross-sectional view taken along the line AA of FIG. 2, and FIG. 4B is a cross-sectional view taken along the line BB of FIG. Control valve 6
A pair of polygonal contraction-side holes 66 is formed at 0, and the sub-flow passage 50 and the contraction-side dedicated passage 56 can be connected or disconnected by rotating the control valve 60. Further, the control valve 60 is formed with a pair of polygonal expansion-side exclusive holes 67, and the sub-flow passage 50 is rotated by the rotation of the control valve 60.
And the extension-side dedicated flow channel 57 can be communicated or blocked. The communication hole 56a and the contraction side dedicated hole 66 are formed to face each other, and the communication hole 57a and the extension side dedicated hole 67 are formed to face each other. As shown in FIG. 5, communication is performed based on the change of the rotation angle θ of the control valve 60. The area S can be changed. Here, the communication area S _N represents the maximum communication area on the expansion side, and determines the minimum damping force on the expansion side. Also, the communication area S _T
Represents the maximum communication area on the contraction side, and determines the minimum damping force on the contraction side. The relationship between the communication areas S _{N and} S _T is arbitrary, and the path from the communication area S of zero to S _N or S _T with respect to the control valve rotation angle θ may be a straight line as shown in the figure. It may be a curve.

Therefore, when the control valve 60 is at the position shown in FIGS. 4 (a) and 4 (b), the contraction side dedicated flow passage 56 and the sub flow passage 50 and the expansion side dedicated flow passage 57 and the sub flow passage 50 are Both are opened by the control valve 60. Therefore, when the hydraulic oil flows from the upper chamber 2a to the lower chamber 2b, it mainly passes through the expansion-side dedicated channel 57 having a large channel area, and when it flows from the lower chamber 2b to the upper chamber 2a, the channel area mainly. Through the dedicated flow path 56 on the large contraction side. This results in a small damping force on both the extension side and the contraction side. Moreover, the control valve 60 is shown in FIGS. 4 (a) and 4 (b).
When rotated by 45 ° in the clockwise direction from the position shown in, the contraction-side dedicated channel 56 and the sub-channel 50 remain in communication with each other, but the extension-side dedicated channel 57 and the sub-channel 50 are connected to each other. Is cut off. Therefore, when the hydraulic oil flows from the upper chamber 2a to the lower chamber 2b, it passes through the extension side main flow passage 42 having a small flow passage area,
When flowing from the lower chamber 2b to the upper chamber 2a, it passes through the contraction-side dedicated channel 56 having a large channel area, as in the previous case. As a result, the extension side has a large damping force and the contraction side has a small damping force. On the other hand, when the control valve 60 rotates about 45 ° in the counterclockwise direction from the position shown in FIGS. 4 (a) and 4 (b), the contraction-side dedicated flow path 56 and the sub-flow path 50 are shut off and expanded. The side-only flow channel 57 and the sub-flow channel 50 remain in communication with each other. Therefore, when the hydraulic oil flows from the upper chamber 2a to the lower chamber 2b, it passes through the expansion-side dedicated flow passage 57 having a large flow passage area and passes through the lower chamber 2b.
When passing from the upper chamber 2a to the upper chamber 2a, it passes through the contraction side main flow channel 41 having a small flow channel area. As a result, the extension side has a small damping force, and the contraction side has a large damping force.

As described above, the actuator 6 operates the control valve 60, and the sub-flow passage 50, the contraction-side dedicated passage 56, and the extension-side dedicated passage 5 in the control valve 60 are operated.
By changing the communication area of 7, it is possible to largely change the damping force of the other side while keeping either one of the damping force of the extension side or the damping force of the contraction side always a smaller damping force.

As described above, the vertical acceleration signal on the spring from the acceleration sensor 1 is integrated by the integrating circuit 2 to calculate the speed signal V (= dX2) on the spring. The control unit 5 sets the relationship between the absolute speed dX2 on the spring and the damping force for controlling the damping force of the shock absorber 7 so as to obtain the characteristic diagram shown in FIG. Here, for the shock absorber 7, the absolute velocity on the spring dX2
Is increased in the upward (+) direction, the threshold for entering the HS mode from the SS mode is Vref2 +, and the threshold for returning to the SS mode from the HS mode after entering the HS mode is zero. It is set to Vref1 + in the vicinity. Also, the absolute speed dX2 on the spring increases in the downward (-) direction, and the S-S mode changes to the S-mode.
The threshold for entering the -H mode is Vref2-, and the threshold for returning from the S-H mode to the S-S mode after entering the S-H mode is Vref1- near zero. Where threshold V
The absolute values of ref2 + and Vref2- may be the same or different, and the same applies to the absolute values of the threshold values Vref + and Vref-.

FIG. 7 is an explanatory view showing a state of an operation (abbreviated sprung speed dX2) at the time of damping control in the apparatus of this embodiment. As an example, consider a case where a posture change (squat, dive, roll) actually occurs on a flat road surface. For example, paying attention to the sprung front part when the vehicle speed becomes zero due to braking, there is a phenomenon that the sprung front part that has been sunk until then rises and returns to the neutral position. At this time, the upward sprung absolute velocity dX
When 2 exceeds the threshold value (Vref2 +), the mode is switched to the HS mode to try to suppress the floating speed. Then, when the upward sprung mass absolute speed dX2 becomes equal to or lower than the threshold value (Vref1 +), the mode is switched to the SS mode. At this time, since the sprung part is already in the neutral position and is almost stationary, it is possible to avoid an unnatural behavior such as further movement. In this case, the frequency of switching the damping force in the shock absorber does not increase as in the conventional case.

Next, as another example, referring to FIG.
Consider a case where vibration suppression control is performed on a rough road surface. When the vertical speed on the spring exceeds the threshold value (Vref2 +), the HS mode is set to suppress the sprung behavior. Then, when the vertical velocity on the spring becomes equal to or lower than the threshold value (Vref1 +), the SS mode is set. On the other hand, when the vertical velocity on the spring exceeds the threshold value (Vref2-), the SH mode is set to suppress the sprung behavior. Then, when the vertical speed on the spring becomes equal to or higher than the threshold value (Vref1-), the SS mode is set.

Here, in the conventional control device, the vertical speed on the spring is equal to or less than the threshold value (Vref2 +) or the threshold value (Vref2 +).
-) When it becomes the above, it switches to SS mode immediately. On the other hand, in the control device of the present invention, the threshold value (Vref
The vibration damping effect is increased by the amount that a large damping force can be maintained up to 1+). In this way, H-S mode or S-H
By setting the switching threshold from the mode to the S-S mode to zero or near zero, the unnatural behavior on the spring is eliminated when the posture change suppression control is performed, and the large damping is performed when the vibration suppression control is performed. The idea is to use the force more positively to enhance the anti-vibration effect. Even in this case, the frequency of switching the damping force in the shock absorber does not increase as in the conventional case.

Next, a case will be described in which the damping force variable shock absorber control apparatus according to the present invention is provided with a means for changing the threshold value according to a parameter such as a vibration frequency in the above-mentioned control and the control is simultaneously performed. The means for changing the threshold value is achieved by the control unit 5 described above, and FIG. 8 is a block diagram showing its concrete configuration. The acceleration sensor 1 detects the vertical acceleration on the spring, and the detection signals are HPF (high-pass filter) and LPF.
Input to each (low pass filter). And
A high frequency component is extracted from the HPPF, and a low frequency component is extracted from the LPF. A high frequency vibration level V _{H is obtained} from the extracted high frequency component, and a low frequency vibration level V _L is similarly obtained from the low frequency component. This V _H and V
_The vibration frequency parameter P is obtained by substituting _L into the following equation.

## EQU1 ## P = (aV _H ) / (bV _L ), where a and b are weighting coefficients.

For example, as shown in FIG. 9, when the vibration frequency parameter P is relatively high, the width of the SS mode is widened so that a large damping force is less likely to occur and the high frequency vibration is transmitted to the spring. Suppress. Further, when the vibration frequency parameter P is relatively low, the width of the S-S mode may be narrowed so that a large damping force is easily generated to suppress the tilt on the spring. Note that FIG. 9A shows the case where the threshold value is continuously changed according to the vibration frequency parameter P.
FIG. 6 is a characteristic diagram showing a case where the threshold value is changed in two steps according to the vibration frequency parameter P. When performing such control and the control in the above-described embodiment at the same time,
Only Vref2 + and Vref2- in FIG. 6 may be changed according to the vibration frequency, and Vref1 + and Vref1- may be set to zero or near zero regardless of the vibration frequency. Here, the magnitude of the damping force for damping can be adjusted by appropriately changing the control valve rotation angle θ as shown in FIG. 5 to increase or decrease the communication area S on the extension side or the contraction side depending on the situation. Is.

Next, a plurality of thresholds are set for the absolute velocity dX2 on the spring in the above-described embodiment, and the control valve rotation angle θ is changed so as to change the communication area S on the expansion side and the contraction side.
The case of controlling is described. As an example, a case will be described here where the damping force mode is switched to seven levels. In this case, the control unit 5 controls the absolute velocity d on the spring for controlling the damping force of the shock absorber 7.
The relationship between X2 and the damping force is set so that the characteristic diagram shown in FIG. 10 is obtained. As shown in FIG. 5, the control valve rotation angle θ is changed from 0 ° to the positive (+) side on the extension side and to the negative (−) side on the contraction side to gradually reduce the communication area S and reduce the damping force. The sizes are H _1, H _{2 and} H ₃ . The modes at the time of damping force control when the absolute velocity dX2 on the spring is positive (+) are called H ₁ -S mode, H ₂ -S mode, and H ₃ -S mode, respectively. The absolute speed dX2 sprung negative (-), respectively S-H ₁ mode mode when the damping force control when the, S
-H ₂ mode, called S-H ₃ mode. Also in this control device, in order to maintain a large damping force until the vertical velocity on the spring is zero or close to zero, and the vibration damping effect can be enhanced, the H ₁ -S mode or the S-H ₁ mode to the S-S mode Only the switching thresholds (Vref1 +, Vref1-) for switching to 0 are set to zero or near zero. In this case, other thresholds are also provided with some hysteresis for the purpose of preventing divergence due to control. This makes it possible to eliminate the unnatural behavior on the spring when controlling the posture change suppression, and to use the large damping force more positively when performing the vibration damping control to enhance the vibration damping effect. Even in this case, the frequency of switching the damping force when returning to the S-S mode in the shock absorber does not increase as in the conventional case.

Next, the structure of the simplified shock absorber 7'will be described with reference to FIGS. The same components as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted. In FIG. 11, the piston rod C36 is screwed and fixed to the piston rod A30 by the threaded portion of the lower end cylindrical portion of the piston rod A30. Further, between the piston rod A30 and the piston rod C36, there is a spring chamber 57b accommodating a spring 55 and a plate-like check valve 59 which are oil-tightly formed via two O-rings 90. . Piston rod A3
0 and the piston rod C36 are provided with a pair of communication holes 57a and a plurality of communication holes 57c, and the spring chamber 57b.
Together with this, the extension-side dedicated flow channel 57 is formed. The extension-side dedicated flow passage 57 is opened and closed by a plate check valve 59 which allows only the inflow from the upper chamber 2a toward the control valve 63.

The main piston 20 communicates with the upper chamber 2a and the lower chamber 2b, and the contraction side main flow passage 41 'having a relatively large flow passage area and the expansion side main flow passage 4 having a relatively small flow passage area.
2'is formed. The contraction side main flow passage 41 ′ is opened and closed by a plate check valve 48 having a relatively thin plate provided on the upper surface of the main piston 20, and the extension side main flow passage 42 ′ has a relatively plate thickness provided on the lower surface of the main piston 20. It is opened and closed by a thick plate-like check valve 49. A sub passage 50 is formed in the piston rod C36 to allow the working oil to flow between the upper chamber 2a and the lower chamber 2b.

The lower end portion of the piston rod A30 is formed in a tubular shape, and a control valve 63 is oil-tightly and rotatably fitted in the tubular portion. The control valve 63 is rotatable about the central axis of the piston rod A30 by driving the actuator 6. FIG. 12 is a vertical sectional view of the control valve 63. The lower end of the control valve 63 is
It has a hollow structure and forms a part of the sub-flow path 50. FIG. 13 is a cross-sectional view taken along the line AA of FIG. The control valve 63 is formed with a pair of polygonal expansion-side exclusive holes 67, and the sub-flow passage 50 and the expansion-side exclusive passage 57 can be connected or disconnected by rotating the control valve 63. The communication hole 57a and the expansion-side dedicated hole 67 are formed to face each other, and the communication area S can be changed based on the change in the rotation angle θ of the control valve 63, as shown in FIG. Here, the communication area S _N represents the maximum communication area on the expansion side, and determines the minimum damping force on the expansion side. Further, the path from the communication area S to zero to S _N with respect to the control valve rotation angle θ may be a straight line or a curved line as shown in the figure.

Therefore, when the control valve 63 is at the position shown in FIG. 13 (a), the expansion side dedicated flow channel 57 and the sub flow channel 50 are blocked by the control valve 63. Therefore, when the hydraulic oil flows from the upper chamber 2a to the lower chamber 2b, it passes through the expansion-side main flow passage 42 'having a small flow passage area, and when the hydraulic oil flows from the lower chamber 2b to the upper chamber 2a, it has a large flow passage area It passes through the side main flow channel 41 '. As a result, the expansion side has a large damping force, and the contraction side has a small damping force. Also, the control valve 63
Is rotated about 90 ° from the position shown in Fig. 13 (a).
At the position shown in (b), the extension-side dedicated channel 57 and the sub-channel 50 communicate with each other. Therefore, when the hydraulic oil flows from the upper chamber 2a to the lower chamber 2b, it mainly passes through the auxiliary flow passage 50 having a large flow passage area, and when it flows from the lower chamber 2b to the upper chamber 2a,
As in the case described above, the contraction side main flow path 4 having a large flow path area
Pass 1 '. This results in a small damping force on both the extension side and the contraction side.

As described above, while the damping force on the contraction side is always set to a small damping force, the control valve 63 is actuated by the actuator 6 and the auxiliary flow passage 50 and the expansion-side dedicated flow passage 57 in the control valve 63 are operated. It is possible to change the damping force on the extension side by changing the flow path area of and.

In the control device of the present embodiment, it is only necessary to consider the case where dX2 in FIG. 6 of the above-mentioned embodiment is positive (+), and therefore the threshold values Vref1-, Vref2 on the negative (-) side.
-Is unnecessary. That is, only the threshold Vref1 + from the HS mode to the SS mode may be set to zero or near zero. In this control device, the setting of a plurality of threshold values to control the damping force is the same as in the above-described embodiment, and the description thereof is omitted.

The operation of the damping force variable shock absorber according to this embodiment and the control by the control unit 5 having the above-mentioned structure will be described. Here, each state quantity (displacement of vehicle body, wheel, tire, speed and acceleration) is positive in the upward direction. In the control of the present embodiment, when the vehicle body has an upward velocity and the damping force of the shock absorber has a damping effect on the movement of the vehicle body, that is, when the damping force of the shock absorber acts downwardly on the vehicle body. To increase the damping force. Further, when the vehicle body has an upward speed and the damping force excites the motion of the vehicle body, that is, when the damping force of the shock absorber acts upwardly on the vehicle body, the damping force is reduced. On the other hand, when the vehicle body has a downward speed, the damping force is kept small in preparation for an unexpected passage through the road surface projection. Specifically, when the absolute velocity on the spring is positive, the expansion side damping force of the shock absorber may be increased and the contraction side damping force may be decreased. That is, as shown in FIG. 13 (a), the control valve 63 is set to a position where the expansion-side dedicated flow path 57 and the sub-flow path 50 are shut off, and the expansion-side damping force of the shock absorber is greatly reduced. It should be small. On the contrary, when the absolute velocity on the spring is negative, the control valve 63 is rotated to connect the extension-side dedicated flow channel 57 and the sub-flow channel 50 to each other, and a small damping force is applied to both the extension side and the contraction side.

Also in the control device using the simplified shock absorber described above, the damping effect can be enhanced by maintaining a large damping force until the upward velocity on the spring is zero or near zero. As a result, the unnatural behavior on the spring can be eliminated when the posture change suppression control is performed, and a large damping force can be more positively used when the vibration suppression control is performed to enhance the vibration isolation effect. Even in this case, the frequency of switching the damping force in the shock absorber does not increase as in the conventional case.

Next, the conventionally proposed Karno
An example of the case in which the present invention is applied to the pp control method (FIGS. 16 and 17) will be described with reference to FIG. 15. Ka
In the case of the control method of rnopp, the transition between the control state with the large damping force and the control state with the small damping force is based on the relative speed between the sprung and unsprung portions regardless of the extension side or the contraction side as in the above-described embodiment. Done. The boundary for switching from the control state having a small damping force to the control state having a large damping force is indicated by a dotted line, and the threshold value of this boundary is indicated by Vrefa2 +, Vrefa2-, Vrefb2 +, Vrefb2-. Also, a boundary for switching from a control state with a large damping force to a control state with a small damping force is a chain line, and the threshold value of this boundary is Vrefa1.
+, Vrefa1-, Vrefb1 +, and Vrefb1- are shown. This control device also has the same effects as those of the above-described embodiment.

The structure of the shock absorber for realizing the characteristics shown in FIG. 15 will be described. The structure of the main flow path in this case is the same as that shown in FIG. 2, but the structure of the sub flow path is different. That is, in order to realize the characteristics of FIG. 15, it is not necessary that the expansion-side dedicated flow path and the contraction-side dedicated flow path be separately configured, and a sub-stream that can be distributed to either the expansion side or the contraction side. Any road is fine. Therefore, the plate-like check valves 58, 59, springs 54, 55, etc. shown in FIG. 2 are not necessary, and the control valve 60 can also have a simple structure capable of only opening and closing the sub-flow passage 50.

Regarding the operation, as shown in FIGS. 16 and 17, basically, the damping force is increased when the vehicle body is to be damped and the damping force is reduced when the vehicle body is to be excited. Take control. Specifically, dX2,
When the vehicle state represented by dX1 exceeds the broken line from the origin side, the second quadrant, and the fourth quadrant, the damping force is switched from small to large. That is, the sub flow path is changed from the open state to the closed state. Further, when the vehicle state crosses the one-dot chain line and returns to the origin side, the second quadrant, and the fourth quadrant, the damping force is switched from large to small. That is, the sub flow path is changed from the closed state to the open state. Also in this method, by setting the threshold values Vrefa1 +, Vrefa1−, Vrefb1 +, Vrefb1− when returning from a control state with a large damping force to a control state with a small damping force to zero or near zero, the same effect as that shown in FIG. 6 can be obtained. can get.

[0038]

【The invention's effect】

"First Effect" The present invention is configured as described above, and transits from a control state in which the magnitudes of the damping forces on the extension side and the compression side are different to a control state in which the damping forces on the extension side and the compression side are both small. In such a case, the magnitude of the vertical velocity on the spring can be set to zero or in the vicinity of zero to prolong the time for realizing a large damping force of the shock absorber. That is, the damping force of the shock absorber can be switched depending on the magnitude of the vertical velocity on the spring and the direction of its change. As a result, in the damping force variable shock absorber control device of the present invention, a large damping force can be used until the sprung mass is in the neutral position and almost stopped, so that the unnatural behavior of the sprung member immediately before it stops can be eliminated. There is. Moreover, since the frequency of switching the damping force in the damping force variable shock absorber control device of the present invention is no different from the conventional one, there is no problem in terms of durability and power consumption.

[Second Effect] The present invention is configured as described above, and in the case where the control state in which the damping force is large is changed to the control state in which the damping force is small, the vertical velocity on the spring and the sprung force are increased. By setting the magnitude of the relative velocity between the unsprung parts to zero or near zero, it is possible to lengthen the time for realizing a large damping force of the shock absorber. That is, the damping force of the shock absorber can be switched depending on the magnitude of the vertical velocity on the spring and the relative velocity between the sprung and unsprung mass, and the direction of the change. As a result, in the damping force variable shock absorber control device of the present invention, a large damping force can be used until the sprung mass is in the neutral position and almost stopped, so that the unnatural behavior of the sprung member immediately before it stops can be eliminated. There is. Moreover, since the frequency of switching the damping force in the damping force variable shock absorber control device of the present invention is no different from the conventional one, there is no problem in terms of durability and power consumption.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a damping force variable shock absorber control device according to a specific embodiment of the present invention.

FIG. 2 is a vertical sectional view showing a structure of a shock absorber according to the embodiment.

3 is a vertical cross-sectional view of the control valve of FIG.

FIG. 4 is a cross-sectional view of the main part of the shock absorber taken along the line AA and the line BB of FIG.

FIG. 5 is a characteristic diagram showing a relationship between a rotation angle and a communication area of the control valve according to the embodiment.

FIG. 6 is a characteristic diagram showing the relationship between the absolute velocity on the spring and the damping force according to the embodiment.

FIG. 7 is an explanatory diagram showing an operation state during vibration suppression control according to the embodiment.

FIG. 8 is a block diagram showing the overall configuration of the damping force variable shock absorber control device according to the present invention when the vibration frequency is fetched.

FIG. 9 is a characteristic diagram showing a case where the threshold value according to the device of the embodiment is changed according to the vibration frequency.

FIG. 10 is a characteristic diagram showing the relationship between the absolute velocity on the spring and the damping force according to the embodiment.

11 is a vertical cross-sectional view showing a simplified configuration of the shock absorber of FIG.

12 is a vertical cross-sectional view of the control valve of FIG.

13 is a cross-sectional view taken along the line AA of FIG.

14 is a characteristic diagram showing a relationship between a rotation angle and a communication area of the control valve of FIG.

FIG. 15 is a characteristic diagram showing the relationship between the absolute velocity on the spring and the relative velocity between the unsprung sprung and the damping force when the damping force variable shock absorber control device of the present invention is applied to the Karnopp control method. .

FIG. 16 is an explanatory diagram showing a method of controlling the damping force of Karnopp.

FIG. 17 is a characteristic diagram showing the relationship between the absolute velocity on the spring and the relative velocity between the sprung unsprung portion and the damping force in Karnopp control.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Acceleration sensor 2 ... Integration circuit 5 ... Control part (1st threshold value setting means, 2nd threshold value setting means, damping force setting means) 6 ... Actuator 7 ... Shock absorber 10 ... Cylinder 20 ... Main piston 60 ... Control valve 2a ... upper chamber 2b ... lower chamber

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kinji Hohei, 1-1, Showa-cho, Kariya city, Aichi prefecture

Claims (2)

[Claims] 1. A damping device which has speed detecting means for detecting a vertical speed on a spring of a vehicle, and which changes a damping force of a shock absorber arranged on each wheel according to the detected vertical speed on the spring. In the variable force shock absorber control device, a first threshold value setting means for setting a set of first threshold values for the vertical speed on the spring, and an absolute value from the first threshold value for the vertical speed on the spring. And a second threshold value setting means for setting a second threshold value set to zero or near zero, and a damping force on the extension side and the contraction side when the vertical velocity on the spring exceeds the first threshold value. Is changed to a control state in which the magnitudes of the damping forces on the extension side and the contraction side are different from each other, and once the vertical velocity on the spring exceeds a first threshold value, damping on the extension side and the contraction side. Control with different magnitude of force And a damping force setting means for making a transition to a control state in which both the extension side and the contraction side damping forces are small when the vertical velocity on the spring exceeds the second threshold value. Variable damping force shock absorber control device. 2. A vertical direction on the detected spring having first speed detecting means for detecting a vertical speed on a spring of the vehicle and second speed detecting means for detecting a relative speed between the sprung and unsprung parts. In a damping force variable shock absorber control device that changes the damping force of a shock absorber arranged on each wheel according to the speed and the relative speed between the sprung and unsprung portions, the vertical speed on the spring and the unsprung portion Threshold value setting means for setting a set of first threshold values with respect to the relative speed of, and zero or near zero from the first threshold value with respect to the relative speed between the vertical speed on the spring and the sprung unspring. A second threshold value setting means for setting a second threshold value so that the control state of the damping force set by the vertical speed on the spring and the relative speed between the sprung and unsprung springs is set to the first threshold value. Damping force is small when exceeding A damping force setting for transitioning from a control state having a large damping force to a control state having a large damping force and then transitioning from a control state having a large damping force to a control state having a small damping force when the second threshold value is exceeded. And a damping force variable shock absorber control device.