KR100207167B1 - Vehicle suspension controller - Google Patents

Abstract

SUMMARY OF THE INVENTION An object of the present invention is to simultaneously improve the grounding properties of a wheel and to improve the ride comfort. The shock absorber 3 including the damping coefficient changing means 50 and the means for detecting the acceleration in the vertical direction of the vehicle body on the spring. Similarly to 51, the means 52 for detecting the acceleration under the spring and the control means 53 for driving the attenuation coefficient changing means 50 are relative to the road surface and the spring under the acceleration above the spring and the acceleration below the spring. Relative speed estimating means 54 for estimating the speed HV ₀ and target attenuation coefficient Cu for calculating a target attenuation coefficient Cu corresponding to a force proportional to the relative speed under the road surface and the spring. Target attenuation coefficient calculating means 55 for calculating?), And drives the attenuation coefficient of the attenuation coefficient changing means 50 to match the target attenuation coefficient.

Description

Suspension Control Unit of Vehicle

1 is a perspective view of a vehicle showing an embodiment of the invention.

2 is a block diagram illustrating an embodiment of the invention.

3 is a schematic diagram of an acceleration sensor.

4 is a characteristic diagram of an acceleration sensor.

5 is a plan view of the vehicle body showing the arrangement of the acceleration sensor.

6 is a schematic diagram of a vehicle height sensor.

7 is a characteristic diagram of a vehicle height sensor.

8 is a cross-sectional view of the shock absorber.

9 is an enlarged view of part 8a of FIG.

Fig. 10A is a sectional view of the spool showing the relationship between the position of the spool and the flow path.

10B is an explanatory diagram showing the relationship between the position of the spool and the flow path, and showing the relationship between the compression-side flow path and the circular path.

Fig. 11A shows an adjustment state of the damping force, and an explanatory diagram showing a state in which the expansion side is set to hard and the compression side is set to soft.

11B shows an adjustment state of the damping force, and is an explanatory diagram showing a state in which both the expansion and compression sides are set to soft.

11C is an explanatory diagram showing a state in which the damping force is adjusted, and an extension side soft and a compression side are set to hard.

12 is a flowchart showing an example of control.

Fig. 13 shows the relationship between the state of suspension and the time when road unevenness passes, time on the horizontal axis, road displacement X _O , spring displacement X2, relative displacement under the road surface and the spring (X _O -X ₁ ), and damping force (F The dashed line is a graph showing the present embodiment, and the solid line is the case where the attenuation coefficient is fixed.

FIG. 14A is a graph showing the frequency response of the suspension, showing the displacement on the spring / road surface displacement, the broken line showing the present embodiment, and the solid line showing the case where the attenuation coefficient is fixed.

FIG. 14B is a graph showing the frequency response of the suspension, showing a spring / road displacement, a broken line showing the present embodiment, and a solid line showing the case where the attenuation coefficient is fixed.

Fig. 15A shows the frequency response of the suspension to which the skyhook damper control gear is applied, the displacement on the spring / road surface displacement, the broken line shows the case where the skyhook damper control is applied to this embodiment, and the solid line shows the case where the damping coefficient is fixed. .

FIG. 15B shows the frequency response of the suspension to which the skyhook damper control is applied, the displacement / road displacement under the spring, the broken line to show the case where the skyhook damper control is applied to the present embodiment, and the solid line to show the case where the damping coefficient is fixed. .

Fig. 16 is a flowchart showing an example of control of the second embodiment.

17 is a flowchart showing an example of control of the third embodiment.

18 is a flowchart showing an example of control of the fourth embodiment.

19 is a flowchart showing an example of control of the fifth embodiment.

20 is a configuration diagram of the 1/4 vehicle model of the suspension.

21 shows the relationship between the state of suspension and the time of passage of unevenness according to the conventional example, the time on the horizontal axis, the road displacement X _O , the displacement on the spring X2, the relative displacement under the road and the spring (X _O -X _l ). And a graph represented by the damping force (F), wherein the broken line shows the case where the damping coefficient is controlled and the solid line shows the case where the damping coefficient is fixed.

22A is a graph showing the frequency response of a suspension according to the conventional example, showing displacement on the spring / road surface displacement, a broken line showing the present embodiment, and a solid line showing the case where the attenuation coefficient is fixed.

Fig. 22B is a graph showing the frequency response of the suspension according to the conventional example, showing the under-spring / road displacement, and the broken line shows the present embodiment and the solid line shows the case where the attenuation coefficient is fixed.

23 is a block diagram corresponding to any one of claims 1 to 9.

* Explanation of symbols for main parts of the drawings

2FR-2RL: Wheel 3FR-3RL: Shock Absorber

5FR-5RL: Vehicle Height Sensor 6FR-6RL: Acceleration Sensor

7FR-7FR: Actuator 8: Steering Angle Sensor

9: vehicle speed sensor 10: controller

30: control rod 33A, 33B 33C: Euro

34: Spool 35, 36: Compression side flow path

37, 38: expansion side flow path 50: attenuation coefficient changing means

51, 52: acceleration detection means on the spring 53: control means

54: relative speed estimation means under the road spring 55: target attenuation coefficient calculation means

56: relative displacement calculation means 57: differential means

58: speed calculation means on the spring 60: driving state detection means

61: vehicle speed detection means 62: swing detection means

63: road surface detection means 65: stroke detection means

[Industrial use]

The present invention relates to a suspension control device capable of changing the damping coefficient of a vehicle shock absorber.

[Prior art]

Background Art Conventionally, in a vehicle equipped with a shock absorber with an adjustable damping coefficient, it is known to drive the actuator by command of the controller and to variably control the damping coefficient of the shock absorber in order to improve the ride comfort of the wheels. For example, there is an apparatus specified in Japanese Patent Application Laid-open No. Hei 5-1555222.

The above apparatus controls the damping coefficient so that the damping force generated in the shock absorber becomes a force proportional to the absolute speed under the spring to increase the grounding properties of the wheel, thereby suppressing free vibration under the spring at the resonance frequency under the spring. Improve the wheel grounding.

[Problems to Solve Invention]

However, in the conventional suspension control device, since the damping force generated in the shock absorber is a force proportional to the absolute speed under the spring, the suppression of free vibration under the spring is accompanied by deformation of the tire, and when the road surface is uneven, There is a problem of deterioration of grounding property due to the increase in the amount of deformation, and the spring in the frequency range of the resonant frequency under the spring at the resonant frequency above the spring and the suppression of vibration under the spring, as in the case of a shock absorber having a fixed damping coefficient. Reduction of the above vibration is contrary. That is, as shown in FIG. 21, in the case of passing the road surface irregularities, the relative displacement (X _O -X ₁ ) of the displacement of the road surface (X _O ) and the displacement under the spring (X ₁ ) by controlling the bottom of the spring as shown by the broken line in the drawing. ) Increases than the fixed attenuation coefficient, so that the amount of deformation of the tire also increases, resulting in poor vehicle grounding.

Also, as shown in Figs. 22A and 22B, when the vibration under the spring is suppressed to the same degree as the shock absorber with the attenuation coefficient fixed, the vibration above the spring in the frequency range of the resonance frequency under the spring and the resonance frequency under the spring (Fig. X ₂ / X ₀ ) is equivalent to fixing the attenuation coefficient, and thus there is a problem that an improvement in ride comfort is not obtained.

Accordingly, an object of the present invention is to provide a suspension control apparatus for a vehicle that can achieve an improvement in ride comfort while improving the foldability of a wheel.

[Means for solving the problem]

As shown in FIG. 23, the first invention includes a shock absorber 3 having a damping coefficient changing means 50 mounted between the spring of each wheel and below the spring to change the damping coefficient. A target attenuation coefficient of the shock absorber 3 is calculated based on the detection values of the acceleration detection means 51 on the spring to detect the acceleration in the vertical direction of the vehicle body and the acceleration detection means in the vertical direction under the spring of each wheel. And a control means (53) for driving the attenuation coefficient changing means (50) so that the attenuation coefficient of the absorber (3) coincides with the target attenuation coefficient. ) Includes target attenuation coefficient calculating means 55 for calculating a target attenuation coefficient Cu _I corresponding to a force proportional to the relative speed below the road at the acceleration above the spring and the acceleration below the spring.

In addition, as shown in FIG. 23, the second invention has a shock absorber (3) having a damping coefficient changing means (50) mounted between a spring and a bottom of each wheel to change the damping coefficient. Acceleration detection means 51 on a spring for detecting acceleration in the up and down direction under the spring, acceleration detection means 52 under a spring for detecting acceleration in the up and down direction under the spring of each wheel, and on these springs And the attenuation coefficient changing means (50) so as to calculate a target attenuation coefficient of the shock absorber (3) based on the detected value of the acceleration detection means under the spring, and to match the attenuation coefficient of the shock absorber to the target attenuation coefficient (50). In a suspension control apparatus for a vehicle having a control means 53 for driving), the driving state detection means 60 for detecting the running state of the vehicle, and the control means 53 are the acceleration and the spores on the spring. Relative speed estimating means 54 for estimating the relative speed HV _O below the road surface and the spring at acceleration below the ring, and a target attenuation coefficient corresponding to a force proportional to the relative speed below the road surface and the spring ( Target attenuation coefficient calculating means 55 for calculating Cu _I ) based on the control gain according to the detected driving state of the vehicle.

Further, in the second invention, in the second invention, as shown in FIG. 23, the driving state detection means 60 includes vehicle speed detection means 61 for detecting a vehicle speed, and the target attenuation coefficient calculation means ( 55) changes the control gain Cu in accordance with the vehicle speed.

According to a fourth aspect of the present invention, in the second invention, as shown in FIG. 23, the traveling state detecting means 60 is constituted by the turning detecting means 62 for detecting the turning state of the vehicle. The coefficient calculating means 55 changes the control gain Cu in accordance with the turning state.

Further, in the second invention, in the second invention, as shown in FIG. 23, the driving state detection means 60 is constituted by road surface state detection means 63 for detecting the state of the road surface, and the target attenuation coefficient. The calculating means 55 changes the control gain Cu in accordance with the road surface state.

Further, in the fifth invention, in the fifth invention, as shown in FIG. 23, the road surface state detecting means 63 is constituted by means 52 for detecting acceleration in the vehicle body up and down direction under the spring, and the target attenuation. The coefficient calculating means 55 changes the control gain Cu according to the acceleration under the spring.

In the seventh invention, in the fifth invention, as shown in FIG. 23, the road surface state detecting means 63 comprises means 65 for detecting the stroke of the shock absorber, and calculating the target attenuation coefficient. The means 55 changes the control gain Cu in accordance with the stroke.

Further, according to the eighth invention, as shown in FIG. 23, the relative speed estimating means 54 under the road spring has a relative displacement Ho under the spring at the acceleration below the acceleration spring above the spring. Relative displacement calculating means 56 for calculating a and differential means 57 for differentiating the relative displacement Ho.

Further, according to the ninth invention, as shown in Fig. 23, the target attenuation coefficient calculating means 55 calculates the velocity ZV in the vehicle body vertical direction on the spring based on the acceleration on the spring. A target attenuation coefficient Cu _i corresponding to the force of the force proportional to the road surface and the speed under the spring (HVo) and the force proportional to the force on the spring ZV is provided. Calculate

[Action]

Accordingly, the first invention calculates a target attenuation coefficient Cu _i corresponding to force = damping force proportional to the road surface and the relative speed HVo under the spring estimated based on the acceleration of each wheel and the spring and the acceleration below the spring. The damping coefficient changing means is driven so that the damping coefficient of the absorber 에 matches the target damping coefficient Cu _i , and the spring is improved while the groundability of the wheel is improved by suppressing excessive variation of the relative displacement under the road surface and the spring. Vibration on the spring at the resonant frequency below the spring at the above resonant frequency can be suppressed.

In addition, the second invention detects the target attenuation coefficient Cu _i corresponding to the force = damping force proportional to the road surface and the relative speed HVG under the spring estimated based on the acceleration and the acceleration below the spring of each wheel. It is calculated based on the control gain Cu according to the driving state, and the grounding property of the wheel can be improved while generating the attenuation force according to the driving state.

Further, the third invention changes the attenuation coefficient at low speed by changing the control gain Cu according to the detected vehicle speed, and increases the attenuation coefficient at high speed to secure ride comfort at low speed and to provide the wheel at high speed. Improved grounding can be achieved at the same time.

Further, the fourth invention is changed according to the turning state in which the control gain Cu is detected, so that the attenuation coefficient is decreased when going straight, the attenuation coefficient is increased during turning, ensuring the riding comfort when going straight and the groundability of the wheel while turning. Can be improved simultaneously.

In addition, the fifth invention is changed according to the road surface state where the control gain Cu is detected, and the attenuation coefficient can be changed depending on whether the road surface state is good or bad, thereby ensuring the riding comfort and improving the grounding properties of the wheel.

In addition, the sixth invention is changed according to the acceleration under the spring where the control gain Cu is detected, and when the input on the road surface with less acceleration under the spring is small, the generation of unnecessary damping force is suppressed while the acceleration under the spring is greatly reduced on the road surface. When the input is large, the control under the spring can be executed to secure ride comfort and improve wheel grounding.

In addition, the seventh invention changes according to the stroke of the shock absorber that detects the control gain Cu, and suppresses the generation of undesired damping force when the stroke is small and the input on the road is small, while the stroke is large on the road surface. When the input is large, the control under the spring can be executed to secure ride comfort and to improve wheel grounding.

In addition, the eighth invention makes it possible to obtain the relative minority HVo under the spring by differentiating the road surface and the relative displacement Ho under the spring obtained from the acceleration above the spring and the acceleration below the spring.

In addition, since the ninth invention calculates the attenuation coefficient Cu _i to correspond to the force of the force proportional to the relative speed HVo between the road surface and the spring and the force proportional to the force on the spring ZV. In addition to improving the grounding property, the riding comfort can be improved by suppressing both the vibration above the spring at the resonance frequency above the spring and the vibration below the spring at the resonance frequency below the spring.

EXAMPLE

Best Mode for Carrying Out the Invention Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIGS. 1 to 2, a shock absorber 3FR-3RL and a spring 4 are respectively mounted between each wheel 2FL-2RL and the vehicle body 1, and the vehicle body 1 is mounted on the spring. The wheel (2FR-2RL) constitutes the spring below. In addition, FR represents a right front wheel, FL represents a left front wheel, RL represents a right rear wheel, and RL represents a left rear wheel, respectively.

The shock absorber 3FR-3RL has a damping force adjusting mechanism driven by the actuator 7FR-7RL as a means for changing the damping coefficient as described below, and the controller 10 mainly composed of the microcomputer 100. Each shock absorber 3FR-3RL is set to a target attenuation coefficient by an actuator 7FR-7RL driven in accordance with the command of.

The controller 10 detects the relative displacement between the acceleration sensor 6FR-6R, which detects the acceleration in the up-down direction of the vehicle body 1, that is, the spring position acceleration, the vehicle body 1, and each of the wheels 2FR-2RL. Steering angle of car height sensor (5FR-5RL) and steering wheel ( Skyhook damper control by the detected values from the steering angle sensor 8 for detecting the speed, the speed sensor 9 for detecting the speed V of the wheel, and the brake sensor 11 for detecting on / off of the brake pedal. The attenuation coefficient of each shock absorber (3FR-3RL) is calculated on the basis of the calculation, and the control signal is output to the actuator (7FR-7RL) to change the damping coefficient of the shock absorber (3FR-3RL), respectively. It is.

As shown in FIG. 2, the steering angle at the vehicle height sensor 5FR-5RL, the acceleration sensor 6FR-6R, the steering angle sensor 8, the vehicle speed sensor 9, and the brake sensor 11 ( ), The vehicle speed V, etc. are converted into digital signals through the input interface circuit 111 and the A / D converter 112 and then input to the microcomputer 100.

As described later, the microcomputer 100 calculates a target attenuation coefficient of each shock absorber 3FR-3RL based on the sky hook damper control to convert the attenuation coefficient of each wheel calculated from the target attenuation coefficient into a D / A converter ( 113, the analog signal is converted and amplified through the driver circuit 114, and then output as a control signal to the actuator 7FR-7RL of the shock absorber 3FR-3RL.

Hereinafter, the detection means of each signal input to the controller 10 will be described in detail, and then the damping force adjusting mechanism and control operation of the shock absorber 3FR-3RL will be described in sequence.

[Acceleration sensor]

As shown in FIGS. 3 and 4, the acceleration sensor 6FR-6R which detects the acceleration of the vehicle body up and down on the spring is fixed to the vehicle body 1 side and the semiconductor piezo element is installed in a substantially horizontal direction. The scalpel 61 is provided at the free end of the 60, and the semiconductor piezoelectric element 60 is distorted according to the magnitude of the acceleration applied to the scalpel 61. Is to convert magnitude to voltage.

As shown in Fig. 4, 2.5V is output at 0G, and in Fig. 3, the acceleration at the top in the figure is 4.0V at the size of 1G, and at 1.0G at the acceleration at -1G.

Here, since the acceleration sensor 6FR-6R is provided at three fixed places of the vehicle body 1 as shown in FIG. 5, the acceleration sensor 6FR is located near the right front wheel 2FR, and the vicinity of the left front wheel 2FL. Acceleration sensor 6FL is provided in the vicinity of the right rear wheel PR, and the acceleration sensor 6R is provided, and the acceleration sensors 6FR and 6FL are provided in substantially parallel to the front axle. The acceleration to be detected is ZG ₁ , ZG ₂ and ZG ₃ , respectively. The acceleration on the spring needs to be obtained corresponding to each wheel (2FR-2RL), but since the installation positions of the three acceleration sensors (6FR-6R) are known, three accelerations (ZG ₁ ,) generated on the vehicle body 1 are known. From the ZG ₂ and ZG ₃ ), the controller 10 calculates the accelerations ZG _FR and -ZG _RL occurring on the spring of each wheel 2FR-2RL by the following equation.

L ₁ ; Distance in acceleration direction of acceleration sensors 6FR and 6FL

L ₂ ; Distance in the full length direction of the body of the acceleration sensors 6FR and 6R

L ₃ ; Distance in acceleration direction of acceleration sensors 6FR and 6R

L ₄ , the distance in the vehicle width direction from the axis passing through the acceleration sensors 6FR and 6RR to the acceleration sensor 6FR

L ₅ ; Distance in the vehicle width direction from the axis passing through the magnetic front and rear wheels (2FLR, 2RL) to the acceleration sensor (6FR)

L ₆ ; Distance from the front axle to the acceleration sensor (6FR) in the body length

L ₇ ; Distance in the full length of the vehicle from the rear axle to the acceleration sensor (6FR)

The acceleration ( ₃ ) on the spring corresponding to each wheel (2FR-2RL) at the installation positions of the three accelerations (ZG ₁ , ZG ₂ , ZG ₃ ) and the acceleration sensors (6FR-6R) by the formulas (1)-(4) above. ZG _RF , ZGFL, ZG _RR , ZG _RL ) can be obtained.

[Car height sensor]

The vehicle height sensor 5FR-5RL, which detects the relative displacement above and below the spring, that is, the relative displacement between the vehicle body 1 and the wheels 2FR-2RL, corresponds to each wheel 2FR-2RL, respectively. It is disposed at a predetermined position of the sensor, the signal of the sensor is input to the controller 10 mainly the microcomputer.

The vehicle height sensor 5FR-5RL is composed of, for example, a potentiometer, and as shown in FIG. 6, the base end of the connecting rod 22B is coupled to the shaft of the vehicle height sensor 5FR-5RL. The middle of the arm 21 which supports the wheels 2FR-2RL freely and the free end of the connecting rod 22B are connected by connecting the connecting rod 22A as shown in FIG. 7 to show the wheels 2FR-2RL. And the relative displacement of the vehicle body 1 in the vertical direction as the voltage change according to the angle change of the arm 21.

[Damping force adjustment mechanism]

8 to 11C show the damping force adjusting mechanism of the shock absorber 3FR-3RL, and the actuator 7FR-7RL provided on the vehicle body 1 side of the shock absorber 3FR-3RL is a controller rod 30. As shown in FIG. ), The attenuation coefficient is changed as will be described later. The actuator 7FR-7RL is composed of, for example, a step motor.

The piston 32 constituting the absorber 3FR-3RL is mounted on the inner circumference of the cylinder 31 coupled to the wheel side, and on the inner circumference of the piston 32 a cylindrical stud 33 and A cylindrical spool 34 is coaxially mounted on the inner circumference of the stud 33, and the spool 34 is rotatably supported by the actuator 7FR-7RL in combination with the controller rod 30, while the stud The 33 is integrally fixed to the inner circumference of the piston 32, and the spool 34 connected to the controller rod 30 is capable of relatively rotatable with the piston 32 and the stud 33.

The piston 32 and the stud 33 have the axle-side flow paths 35 and 36 through which the operating oil passes during the compression side stroke of the shock absorber (retraction direction of the spring 4), and the expansion stroke of the shock absorber (spring). Expansion side flow paths 37 and 38 through which the working oil passes are formed in the extension direction of 4). Compression side valves 35A and 35B and expansion side valves 37A and 37B for generating attenuation force are formed in the flow path. It is installed. The stud 33 has a passage hole 33B for connecting the upper surface of the piston 32 and the inner circumference of the stud 33, and a passage hole 33C for connecting the inner circumference of the expansion side flow passage 38 and the stud 33. Is formed.

Here, the spool 34 has a circular flow path 34A and an elliptical flow path 34B formed as a recess at a predetermined position on the outer circumference, and the circular flow path 34A is provided to be replaced with the compression-side flow path 36. And the inner circumference 34C of the spool 34 and the oil chamber 31A through the passage hole 34D. On the other hand, the elliptical flow path 34B is provided at a position that can be replaced with the passage holes 33A-33C of the stud 33, and is configured to interconnect these passage holes 33A-33C.

Here, the damping coefficient of the shock absorber 3FR-3RL is determined in accordance with the rotational position of the spool 34 driven to the actuator 7FR-7RL via the controller rod 30 as shown in FIGS. 10A and 10B. In the case of the compression-side flow path 36, when the spool 34 is rotated in the direction of the arrow in the drawing as shown in FIG. 10B, the circular flow path 34A is rotated to 34A 'and the compression-side flow path 36 and the circular flow path The area of the connection passage part 300 through which the connection 34A overlaps is enlarged, and the attenuation coefficient is changed to the smaller one. The attenuation coefficient may be changed to an arbitrary value according to the area change of the connection passage part 300, and the setting of the attenuation coefficient is almost stepless, and the change may be performed with high responsiveness, but the description is omitted. The same applies to the flow path 34b.

As described above, the damping coefficient of the shock absorber 3FR-3RL can be set on the compression side and the expansion side, respectively, as shown in FIGS. 11A to 11C, that is, the shock absorber 3FR-3RL can be moved. According to this, the flow path of the operating oil is converted as follows, and the attenuation coefficient is also set respectively.

[In case of hard reduction factor of expansion attenuation]

As shown in FIG. 11A, the elliptical flow path 34B is displaced to a position not opposed to the passage holes 33A-33C of the stud 33 by the rotational movement of the spool 34, and the operating oil flowing into the oil chamber 32B from 31A is A large damping force is generated by the small flow path cross-sectional area passing through the piston 32, the inlet portion 37C of the compression-side valve 35A, the expansion-side flow path 37, and the expansion-side valve 37A in turn.

[Small (soft) attenuation coefficient on the extension side]

As shown in FIG. 11B, the hydraulic fluid flowing from the oil chamber 31B to 31A by rotating the spool 34 at the position where the elliptical flow passage 34B opposes the passage holes 33A-33C of the stud 33 has a large attenuation coefficient. In this case, the flow passage cross-sectional area is increased by sequentially passing through the inlet portion 37C, the passage hole 33A, the elliptical flow passage 34B, the expansion side flow passage 38, and the expansion side valve 37B on the piston 32. To generate a small damping force.

The expansion-side attenuation coefficient is an optional flow through the flow path 38 through the flow path 37 and by adjusting the overlapping area of the elliptic flow path 34B of the passage holes 33A-33C with the actuator 7FR-7RL. It can be set by the attenuation factor of.

[High attenuation coefficient on the compression side (hard)]

As shown in FIG. 11C, the working oil flowing from the oil chamber 31A to 31B by rotating the spool 34 to the position where the circular flow passage 34A does not face the flow passage 36 of the stud 33 is compressed by the piston 32. Passing through the side flow path 35 and the compression side valve 35A sequentially, a large damping force is generated by a small flow path cross-sectional area.

[High attenuation coefficient on the compression side (hard)]

As shown in FIG. 11A, when the elliptical flow passage 34A rotates the spool 34 at a position opposed to the oil flow passage 35 of the stud 33, the hydraulic oil flowing into the oil chamber 31A to 31B has a large attenuation coefficient. In addition, the flow passage cross-sectional area is increased by sequentially passing through the inner circumference 34C of the spool 34, the passage hole 34D, the circular flow passage 34A, the compression side flow passage 36, and the compression side valve 35B, thereby providing a small damping force. Occurs.

Compression-side attenuation coefficient is an optional attenuation coefficient by selectively passing the passage 36 through the passage 35 and adjusting the overlapping area between the passage 36 and the circular passage 34A with the actuator 7FR-7RL. Can be set to

[Control operation]

The controller 10 calculates a target value of the attenuation coefficient according to the relative speed under the spring calculated based on the acceleration and the relative displacement in the up and down directions above and below the spring where each sensor is detected, and the attenuation coefficient of the target. In response to this, a control signal is output to the actuator 7FR-7RL to change the damping coefficient so that the shock absorber 3FR-3RL generates a predetermined damping force.

12 is a flowchart showing an example of control executed in the controller 10, which is executed at predetermined time intervals by a timer division, etc., and will be described in detail with reference to the flowchart below.

First, the acceleration ZG ₁ , -ZG ₃ and the steering angle sensor 8 and the vehicle speed sensor 9 of the vehicle body 1 detected by the acceleration sensor 6FR-6RL in step S1 are detected. ( ) And the vehicle speed V, respectively, and the relative displacement of the vehicle body 1 and the wheels 2FR-2RL detected by the vehicle height sensor 5FR-5RL in step S2, that is, the shock absorber 3FR-3RL. The stroke is read as the relative displacement (H _FR -H _RL ) above and below the spring.

In step S3, the acceleration ZG _FR -ZG _RL generated on the spring of each wheel 2FR-2RL based on the formula (1)-(4) above the acceleration ZG ₁ -ZG ₃ read in step S1. In step 54, the absolute speeds ZV _FR -ZV _RL are calculated on the springs by integrating the accelerations ZG _FR -2G _RL .

On the other hand, in step S5, the relative speed HV _FR -HV _RL above and below the spring is calculated by differentiating the relative displacement H _FR -H _RL above and below the spring read in step S2.

Based on the absolute speed above the spring (ZV _FR -ZV _RL ) and the relative speed above and below the spring (HV _FR -HV _RL ), in step S6, the target attenuation coefficient C as an ideal target value by the sky hook damper control is obtained. _SFR -C _SRL ) is calculated by the following equation.

Cs denotes the coefficient i of the skyhook damper control i = FR, FL, RR, and RL, and represents the wheel to be focused on (the same).

Subsequently, the SpapS7 compares the magnitude of these target attenuation coefficients Csi with the maximum attenuation coefficient C _max and the minimum attenuation coefficient C _{min which} can be set by the shock absorber (3FR-3RL). C _1FR -C _1RL ) is set as in the following formula (6)-(8).

On the other hand, step S8 differentiates the relative speed HV _F R-HV _{RL of} each wheel 2FR-2RL obtained in step S5, and the relative acceleration above and below the spring at each wheel 2FR-2RL position ( Calculate HG _FR -HG _RL ).

In step S9, the acceleration below the spring (ZC _1FR -ZG _1RL ) in each wheel (2FR-2RL) than the relative acceleration (HG _FR -HG _RL ) and the acceleration on the spring (ZG _FR -2G _RL ) is expressed by the following equation. Calculate

Subsequently, in step S10, the relative displacement (H _OFR -H _ORL ) below the road surface and the spring is measured at the acceleration (ZG _1FR -ZG _1RL ) and the spring acceleration (ZG _FR -ZG _RL ) under the spring of each wheel 2FR-2RL. It is calculated by the following formula.

Provided that M _1i ; Mass under the spring of each wheel

M _2i ; Mass on spring of each wheel

K ₁ ; Bell spring constant of tire

Herein, the road surface of each wheel 2FR-2RL and the relative displacement (H _OFR -H _ORL ) under the spring based on the above equation (10) will be described based on the 1/4 vehicle model shown in FIG. The equations of motion above and below the springs are given by

Provided that X ₀ ; Road displacement

X ₁ ; Displacement under spring

X ₂ ; Displacement on spring

In the above formulas (11) and (12)

Based on the above expression (13), the relative displacement (H _OFR -H _ORL ) under the road surface and the spring is obtained.

Subsequently, in step S11, after calculating the relative displacement (H _OFR -H _ORL ) obtained as described above, the relative speed under the road and the spring (VH _OFR -VH _ORL ) of each wheel 2FR-2RL is calculated. In step S12, the ideal target attenuation coefficient (C _UFR -C _URL ) for the attenuation control under each spring of the wheels (2FR-2RL) is determined by the plaque velocity (HV _oi ) under the road surface and the spring and the relative speed under the spring ( HV ₁ ) is calculated by the following equation.

However, Cu; Attenuation Coefficient Under Spring (= Control Gain) Next, in step S13, the magnitude of the target attenuation coefficient Cu _i can be set in the shock absorber 3FR-3RL and the maximum attenuation coefficient C _max and the minimum attenuation coefficient C _min. ) as compared to the target damping coefficient (C _2FR -C _2RL) of the wheels in accordance with the comparison result, and then the 15-set as expression (17).

In step S14, the skyhook damper control attenuation coefficient C _1FR -C _1RL obtained in step S7 and the target attenuation coefficient C _FR -C _RL obtained in step S13 are calculated.

Then step S15 the damping coefficient (C _i) difference obtained in the attenuation coefficient C _i (n-1) as obtained in the previous processing of the processing geumbeon Calculate each of C _i and in step S16, the difference of the attenuation coefficient The command signal corresponding to the rotation angle δi of the actuator 7FR-7RL according to C _i is outputted to the actuator 7FR-7RL of each wheel 2FR-2RL.

By repeating the above steps S1-S17 every predetermined time, the damping coefficient C _FR -C _RL determined according to the relative speed HV _oi under the road surface and the spring is carried out at the same time to perform the vibration suppression above and below the spring of the vehicle. Can be.

Considering the case in which the vehicle currently driving passes the unevenness of the road surface, as shown in FIG. 13, the damping force F generated by the shock absorber 3FR-3RL is the relative speed HV _Oi under the road surface and the spring. The relative displacement (X ₀ -X _l ) under the road surface and the spring is reduced compared to the fixed attenuation coefficient indicated by the solid line in the drawing because it is set by adding the attenuation coefficient (C2 _FR -C2 _RL ) according to Fig. 21 It is possible to improve the foldability of the wheel compared to the conventional example shown by the broken line at the same time, and at the same time, the displacement on the spring is also reduced as compared with the conventional example, so that the riding comfort of the vehicle can be improved.

In addition, in the above-described conventional example indicated by broken lines in FIG. 21, the damping force of the shock absorber is controlled to be a force compared with the absolute speed in the vertical direction below the spring, so that it is independent of the vertical displacement of the road surface. since the damping force (F) in consideration of the attenuation coefficient (C _2FR = C _2RL) of the relative velocity (HV _Oi) is set, it is possible to secure a jeopjiseong.

In addition, as shown in FIGS. 14A and 14B, in the frequency response of the suspension according to the present invention, the vibration under the spring at the resonance frequency under the spring is reduced, and the frequency range of the resonance frequency under the spring at the resonance frequency above the spring (about 1.5-l0Hz) vibration on the spring is also reduced. The suppression of the vibration below the spring at the resonance frequency below the spring and the reduction of the vibration above the spring in the frequency range of the resonance frequency below the spring at the resonance frequency above the spring can be simultaneously achieved. It is possible to achieve at the same time.

On the other hand, in the frequency response of the conventional example, as shown by the broken lines in Figs. 22A and 22B, the vibration under the spring at the resonance frequency under the spring is reduced, but in the frequency range of the resonance frequency under the spring at the resonance frequency above the spring Vibration on the spring is worse than shock absorbers fixed on the damping coefficient, and is not compatible with suppression of vibration on and under the spring.

Here, the vibration on the spring at the vertical frequency on the spring is a shock absorber having fixed damping coefficients as shown in Figs. 15a and l5b by the skyhook damper control according to the above formulas (5)-(8); Compared with this, it is possible to greatly reduce, and also to promote the damping on and under the spring to enhance the ride comfort.

In addition, in the above embodiment, the outputs of the vertical acceleration sensor 6FL-6R and the vehicle height sensor 5FR-5RL provided with the vertical acceleration under the spring above the spring were obtained by differentiating two layers. The output of the vertical acceleration sensor provided under the spring can be used.

Further, in the up-and-down acceleration below the vertical acceleration spring of the spring seeking the relative displacement (H _oi) below the road surface and the spring, the relative velocity (HV _oi) below the road surface and the spring by differentiating the relative displacement (H _oi) Although calculated | required, you may calculate | require the relative speed (HV _i ) of a road surface and a spring from the derivative value of the up-down acceleration on a spring, and the derivative value of the up-down acceleration under a spring.

In the above embodiment, the sky hook damper control is combined to suppress the vibration on the spring, but may be combined with other damping force control, or may be performed alone.

FIG. 16 is a flowchart showing the second embodiment, wherein the control gain Cu of the formula (14) executed in step S12 shown in FIG. 12 of the first embodiment is varied in accordance with the vehicle speed V to change the step S11. A step S20 for later calculating the control gain Cu is added, which is the same as the other first embodiment.

In FIG. 16, step S20 sets in advance the relationship between the vehicle speed V and the control gain Cu according to the detected value of the vehicle speed sensor 9 to a map or a relationship, and the control gain according to the vehicle speed V ( Calculate Cu).

For example, the control gain Cu has a large input on the road surface at low speed, and the vibration under the spring is less likely to be a problem. On the other hand, it is necessary to ensure the stability of the vehicle at high speeds, so that the control gain Cu is set to a large value as compared with at low speeds so as to improve the foldability of the wheels.

FIG. 17 is a flowchart showing the third embodiment in which the calculation of the control gain Cu executed in step S20 shown in FIG. 16 of the second embodiment is performed according to the turning state of the vehicle. Substituted in step S30, it is similar to the other first embodiment.

In FIG. 17, the stell S30 estimates the turning radius R of the vehicle at the steering angle θ detected by the steering angle sensor 8, and adjusts the control gain Cu as the turning radius R increases. While increasing, the control gain Cu when going straight is set to a small value.

Therefore, the turning side is set to improve the grounding property than when the vehicle is going straight, so that the stability of the vehicle during the turning can be improved, and the occurrence of unnecessary damping force is suppressed at the time of going straight, thereby improving the riding comfort.

The turning state of the vehicle may be estimated from the steering angle speed of the steering, or may be estimated from the steering angle θ and the speed V, the G or the steering angle speed and the vehicle speed V of the steering. In addition, a yaw rate sensor or a sensor for detecting lateral acceleration (acceleration in the vehicle width direction) may be provided to estimate the turning state of the vehicle at yaw rate, yaw acceleration or lateral acceleration, and lateral speed.

18 is a flowchart showing the fourth embodiment. The calculation of the control gain Cu executed in step S20 shown in FIG. 16 of the second embodiment is replaced with step S40 that calculates according to the vertical acceleration under the spring, and is the same as the other first embodiment.

In FIG. 18, step S40 increases the control gain Cu according to the increase of the acceleration under the spring ZG _1FR -ZG _1RL calculated in step S9, and the acceleration under the spring ZG _1FR -ZG _1RL is small. In this case, the input from the road surface is small and vibration under the spring is less likely to be a problem. Therefore, the control gain (Cu) is set to a small value to suppress the occurrence of unnecessary damping force, thereby improving the riding comfort and accelerating under the spring. When (ZG _1FR -ZG _1RL ) is large, the input of the road surface is large, so the control gain (Cu) that suppresses vibration under the spring is set to a large value.

FIG. 19 is a flowchart showing the fifth embodiment, and the control gain (3) according to the stroke of the absorber 3FR-3RL subjected to the first gain Cu operation performed in step S20 shown in FIG. 16 of the second embodiment is shown in FIG. Cu) was replaced with step S50 for calculating Cu, which is the same as in the other first embodiment.

In Fig. 18, step S50 adjusts the control gain Cu in accordance with the increase in the stroke (= relative displacement H _RF -H _RL above the spring and below the spring) of the shock absorber 3FR-3RL read out in step S2. When the stroke of the pressure absorber (3FR-3RL) is small, the input on the road surface is small, and the vibration under the spring is less likely to be a problem. Therefore, the control gain Cu is set to a small value to generate unnecessary damping force. The control gain (Cu) that suppresses the vibration under the spring is set to a large value because the input on the road surface is large when the stroke is large because the riding comfort is improved by suppressing the.

Further, in the above embodiment, the attenuation coefficient (C _FR -C _FL ) of the shock absorber (3FR-3RL) was changed by changing the flow path in accordance with the driving of the actuator (7FR-7RL). bonded to each other to configure a changeable shock absorber the damping coefficient by the viscous fluid, in accordance with the command signal according to the attenuation coefficient (C _i) can be set to a predetermined attenuation coefficient.

[Effects of the Invention]

As described above, the first invention calculates a target attenuation coefficient Cu _i corresponding to a force proportional to the road surface and a relative speed under the spring HV ₀ estimated based on the acceleration above and below the spring of each wheel. By suppressing excessive fluctuations in the relative displacement under the road surface and the spring, it is possible to suppress the vibration on the spring at the resonant frequency under the spring at the resonant frequency above the spring, while improving the grounding properties of the wheels. Can be improved simultaneously.

The second invention relates to a driving state in which a target attenuation coefficient Cu _i corresponding to a force proportional to a road surface and a force proportional to the relative speed HV ₀ under the spring is estimated based on the acceleration above and below the spring of each wheel. According to the control gain (Cu) according to the above, it is possible to improve the grounding properties of the wheel while generating a damping force according to the driving state and to improve the riding comfort.

The third invention is changed according to the vehicle speed at which the control gain Cu is constructed, and the attenuation coefficient is decreased at low speed, and the attenuation coefficient is increased at high speed to secure ride comfort at low speed and to maintain the grounding property of the wheel at high speed. Improvements can be made at the same time.

According to the fourth aspect of the invention, the control gain (Cu) is changed according to the turning state to reduce the attenuation coefficient when going straight, and the attenuation coefficient is increased during the turning to secure ride comfort and improve the grounding property of the turning wheel. Can be achieved at the same time.

According to the fifth aspect of the invention, the control gain Cu is changed in accordance with the road surface state detected to change the attenuation coefficient according to whether the road surface state is good or bad, thereby attaining a riding comfort and improving wheel grounding.

The sixth invention is to change according to the acceleration under the spring detecting the control gain (Cu) to control the occurrence of unnecessary damping force when the acceleration under the spring is small and the input on the road is small, while the input on the road with the large acceleration under the spring is large. At the same time, antistatics can be carried out under the spring to ensure a more comfortable ride and to improve the wheels.

The seventh invention changes according to the stroke of the shock absorber that detects the control gain Cu to control the generation of unnecessary damping force when the stroke is small and the input on the road is small, while the spring when the input on the road with a large stroke is large. The following damping can be carried out to achieve a comfortable ride and to improve the wheels' grounding.

In the eighth invention, the relative speed under the spring and the relative displacement under the spring (H ₀ ) obtained from the acceleration on the spring and the acceleration under the spring can be differentiated to obtain the relative speed HV ₀ under the road and the spring.

The ninth invention calculates the target attenuation coefficient Cu _i to correspond to a force proportional to the road surface and a relative speed under the spring (HV ₀ ) and a force proportional to the spring over speed (ZV). In addition to improving, both the vibration above the spring at the resonance frequency above the spring and the vibration below the spring at the resonance frequency below the spring can be suppressed, thereby improving the grounding property and the ride comfort.

Claims (9)

A shock absorber having a damping coefficient changing means 50 mounted between the spring on each wheel and below the spring to change the damping coefficient, and an acceleration on the spring to detect acceleration of the vehicle body in the vertical direction on the spring of each wheel; On the basis of the detection means of the means 51, the spring acceleration detection means 52 for detecting the acceleration in the up and down direction on the vehicle body under the spring of each wheel, and the detection value of the acceleration detection means 52 above and below the spring. 제어 a suspension control of a vehicle provided with a control means 53 for calculating the target attenuation coefficient of the absorber and driving the damping coefficient changing means 50 to match the attenuation coefficient of the absorber with the target attenuation coefficient; in the apparatus, the control means 53 is in contact under spring road surface estimating the relative velocity (HV ₀₎ below the road surface and the spring in the acceleration and the acceleration under the spring above the spring Estimation means 54 and the road surface and the spring target attenuation coefficients corresponding to a force proportional to the relative velocity of the following (Cu _i) the suspension of the vehicle, characterized in that it includes the operation target damping coefficient calculation means 55 for Control unit. A shock absorber having a damping coefficient changing means 50 mounted between the spring on each wheel and below the spring to change the damping coefficient, and a spring-up acceleration detecting the acceleration in the up-down direction of the vehicle body on the spring of each wheel; On the basis of the detection means of the means 51 and the spring acceleration detection means 52 for detecting the acceleration in the up and down direction of the vehicle body under the spring of each wheel; A suspension control apparatus for a vehicle having a control means 53 for driving the attenuation coefficient changing means 50 so as to calculate a target attenuation coefficient of the absorber and to coincide with the target attenuation coefficient. The driving state detecting means 60 for detecting the driving state of the vehicle, and the control means 53 are relative to the road surface and the spring under the acceleration above the spring and the acceleration below the spring. Figure (HV _0), the road surface estimating a - a spring under the relative velocity estimating means 54, the target damping coefficient (Cu _i) corresponding to said road surface with a force proportional to the relative velocity of the following spring, of the detected vehicle And a target attenuation coefficient calculating means (55) for calculating based on the control gain (Cu) according to the driving state. 3. The driving condition detecting means (60) is composed of vehicle speed detecting means (61) for detecting a vehicle speed, and the target attenuation coefficient calculating means (55) changes the control gain (Cu) according to the vehicle speed. Suspension control device for a vehicle, characterized in that. 3. The driving condition detecting means (60) according to claim 2, wherein the driving state detecting means (60) is constituted by turning detecting means (62) for detecting a turning state of the vehicle, and the target attenuation coefficient calculating means is configured to control the control gain (Cu) according to the turning state. Suspension control device of a vehicle, characterized in that for changing. 3. The driving condition detecting means (60) according to claim 2, wherein the driving state detecting means (60) comprises road surface state detecting means (63) for detecting a state of a road surface, and the target attenuation coefficient calculating means (55) is the control gain in accordance with the road surface state. Suspension control device for a vehicle, characterized in that for changing (Cu). 6. The road surface detection means (63) according to claim 5, wherein the road surface state detection means (63) comprises means for detecting an acceleration in the up and down direction of the vehicle body under the spring, and the target attenuation coefficient calculating means (55) is formed according to the acceleration under the spring. Suspension control device for a vehicle, characterized in that changing the gain (Cu). 6. The road surface detection means (63) according to claim 5, wherein said road surface state detection means (63) comprises means (65) for detecting a stroke of a shock absorber, and said target attenuation coefficient calculating means (55) controls said control gain (Cu) in accordance with said stroke. Suspension control device of a vehicle, characterized in that for changing. The relative speed estimating means (54) according to claim 1, further comprising: a relative displacement calculating means (56) for calculating a relative displacement (H ₀ ) between the road surface and the spring at the acceleration above the spring and the acceleration below the spring; A suspension control device for a vehicle, characterized in that it comprises differential means (57) for differentiating relative displacement (H ₀ ). 3. The road surface according to claim 2, wherein the target attenuation coefficient calculating means (55) is provided with a spring speed calculating means (58) which calculates the speed ZV in the vehicle body vertical direction on a spring based on the spring acceleration. And a target attenuation coefficient Cu _i corresponding to the force of the force proportional to the relative speed HV ₀ below the spring and the force proportional to the speed ZV above the spring. Device.