JP2006281876A - Variable damping force damper control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect lateral acceleration at the position of a suspension device, and to accurately set a target damping force of a damper. <P>SOLUTION: A value obtained by differentiating the lateral acceleration YG passing through a low-pass filter 31 by a differentiator 32, and a value obtained by multiplying a yaw rate γ passing through a low-pass filter 33 and second-order differentiated by a second-order differentiator 34 by a yaw rate gain, are added by an adding machine 36. Thereby, corrected lateral acceleration at the position of suspension devices of four wheels is calculated. The corrected lateral acceleration is multiplied by a lateral acceleration gain 37 corresponding to vehicle speed and a pushing/drawing gain 40 corresponding to an expanding/contracting direction of the damper, thereby deciding the target damping force of the damper. Therefore, the accuracy of the target damping force can be improved, and steering stability especially in a low speed range can be improved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for a variable damping force damper that variably controls a damping force of a damper provided in a suspension device of a vehicle according to a motion state of the vehicle by a control means.

  As the viscous fluid of the variable damping force damper for the suspension device, a magnetic viscous fluid (MRF: Magneto-Rheological Fluids) whose viscosity is changed by the action of a magnetic field is adopted, and the fluid is applied to the piston that is slidably fitted into the cylinder. Patent Document 1 below discloses a coil provided with a coil for applying a magnetic field to a magnetorheological fluid in a passage. According to this variable damping force damper, the damping force of the damper can be arbitrarily controlled by changing the viscosity of the magnetorheological fluid in the fluid passage by a magnetic field generated by energizing the coil.

Also, during normal times, the damper of the four-wheel suspension system is skyhook controlled to improve riding comfort performance, and when the body roll rate, yaw rate differential value or lateral acceleration differential value exceeds the threshold, the damper damping force Patent Document 2 below discloses that the steering stability performance is increased by increasing the steering angle.
JP-A-60-113711 Japanese Patent Laid-Open No. 11-115440

  By the way, when the target damping force of the damper is set based on the lateral acceleration detected by the lateral acceleration sensor, if the position of each suspension device is separated from the position of the lateral acceleration sensor, the lateral acceleration output from the lateral acceleration sensor is reduced. The value does not coincide with the lateral acceleration at the position of each suspension device. For example, when a lateral acceleration sensor is provided at the center of gravity position of the vehicle, the lateral acceleration sensor detects lateral acceleration associated with turning of the vehicle, but does not detect lateral acceleration associated with yawing around the center of gravity position of the vehicle. The target damping force of the damper cannot be set accurately, and the steering stability performance may deteriorate.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to accurately detect the lateral acceleration at the position of the suspension device and set the target damping force of the damper with high accuracy.

  In order to achieve the above object, according to the first aspect of the present invention, the damping force of the damper provided in the vehicle suspension device is applied to the lateral acceleration detected by the lateral acceleration sensor provided at a predetermined position of the vehicle body. A control device for a variable damping force damper that is determined based on a yaw rate sensor that detects a yaw rate, and determines a lateral acceleration at the position of the suspension device based on the lateral acceleration detected by the lateral acceleration sensor and the yaw rate detected by the yaw rate sensor. A control device for a variable damping force damper is proposed, which calculates and determines the damping force of the damper based on the lateral acceleration.

  According to the invention described in claim 2, in addition to the structure of claim 1, the damping force of the damper is determined based on the time differential value of the lateral acceleration at the position of the suspension device. A control device for damping force damper is proposed.

  According to the above configuration, since the lateral acceleration at the position of the suspension device is calculated in consideration of not only the lateral acceleration accompanying the turning of the vehicle but also the lateral acceleration accompanying the yawing of the vehicle, the damper is generated based on this lateral acceleration. The power damping force can be accurately determined, and the steering stability performance can be improved particularly in the low speed range.

  According to the configuration of the second aspect, since the phase of the temporal differential value of the lateral acceleration is ahead of the rolling phase of the vehicle generated by the lateral acceleration, the damping force of the damper is determined based on the time differential value of the lateral acceleration. By doing so, rolling of the vehicle can be suppressed with good responsiveness.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  1 to 8 show an embodiment of the present invention. FIG. 1 is a front view of a vehicle suspension device, FIG. 2 is an enlarged sectional view of a variable damping force damper, and FIG. 3 is a flowchart of damping force control of the damper. 4 is a map for retrieving a target current from the damper speed and the target damping force, FIG. 5 is a block diagram of a circuit for calculating the target damping force of the damper, and FIG. 6 calculates a corrected lateral acceleration differential value from the lateral acceleration and the yaw rate. FIG. 7 is a map for searching the lateral acceleration gain from the vehicle speed, and FIG. 8 is a graph showing the lateral acceleration differential value and the corrected lateral acceleration differential values on the front and rear sides.

  As shown in FIG. 1, a suspension device S that suspends a wheel W of a four-wheeled vehicle has a suspension arm 13 that supports a knuckle 12 in a vertically movable manner on a vehicle body 11, and a variable damping that connects the suspension arm 13 and the vehicle body 11. A force damper 14 and a coil spring 15 connecting the suspension arm 13 and the vehicle body 11 are provided. The electronic control unit U that controls the damping force of the damper 14 includes a signal from the sprung acceleration sensor Sa that detects the sprung acceleration, a signal from the damper displacement sensor Sb that detects the displacement (stroke) of the damper 14, and A signal from the lateral acceleration sensor Sc that detects the lateral acceleration of the vehicle, a signal from the yaw rate sensor Sd that detects the yaw rate of the vehicle, and a signal from the vehicle speed sensor Se that detects the vehicle speed are input.

  It is assumed that the center of yawing of the vehicle is the position of the center of gravity of the vehicle, the distance from the position of the center of gravity of the vehicle to the front wheel suspension devices S, S is Lf, and the distance from the rear wheel suspension devices S, S to The distance is Lr (see FIG. 6).

  As shown in FIG. 2, the damper 14 includes a cylinder 21 whose lower end is connected to the suspension arm 13, a piston 22 that is slidably fitted into the cylinder 21, and an upper wall of the cylinder 21 that extends upward from the piston 22. And a free piston 24 that is slidably fitted to the lower part of the cylinder, and is partitioned by the piston 22 inside the cylinder 21. An upper first fluid chamber 25 and a lower second fluid chamber 26 are partitioned, and a gas chamber 27 in which a compressed gas is sealed in a lower portion of the free piston 24 is partitioned.

  A plurality of fluid passages 22a are formed in the piston 22 so that the upper and lower surfaces thereof communicate with each other, and the first and second fluid chambers 25 and 26 communicate with each other through these fluid passages 22a. The magnetorheological fluid sealed in the first and second fluid chambers 25 and 26 and the fluid passages 22a is a dispersion of magnetic fine particles such as iron powder in a viscous fluid such as oil. By aligning the magnetic fine particles along the magnetic field lines, it is difficult for the viscous fluid to flow, and the apparent viscosity increases. A coil 28 is provided inside the piston 22, and energization of the coil 28 is controlled by the electronic control unit U. When the coil 28 is energized, a magnetic flux is generated as indicated by an arrow, and the viscosity of the magnetorheological fluid changes due to the magnetic flux passing through the fluid passages 22a.

  When the damper 14 contracts and the piston 22 moves downward with respect to the cylinder 21, the volume of the first fluid chamber 25 increases and the volume of the second fluid chamber 26 decreases. Passes through the fluid passage 22a of the piston 22 and flows into the first fluid chamber 25. Conversely, when the damper 14 extends and the piston 22 moves upward relative to the cylinder 21, the volume of the second fluid chamber 26 increases. Since the volume of the first fluid chamber 25 decreases, the magnetorheological fluid in the first fluid chamber 25 passes through the fluid passage 22a ... of the piston 22 and flows into the second fluid chamber 26, and at that time, the fluid passage 22a The damper 14 generates a damping force due to the viscous resistance of the magnetorheological fluid passing through.

  At this time, if the coil 28 is energized to generate a magnetic field, the apparent viscosity of the magnetorheological fluid existing in the fluid passage 22a of the piston 22 increases and it becomes difficult to pass through the fluid passage 22a. Damping force increases. The amount of increase in the damping force can be arbitrarily controlled by the magnitude of the current supplied to the coil 28.

  When a shocking compressive load is applied to the damper 14 to reduce the volume of the second fluid chamber 26, the free piston 24 descends while the gas chamber 27 is contracted to absorb the impact. Further, when a shocking tensile load is applied to the damper 14 to increase the volume of the second fluid chamber 26, the impact is absorbed by the free piston 24 rising while the gas chamber 27 is expanded. Further, when the piston 22 descends and the volume of the piston rod 23 accommodated in the cylinder 21 increases, the free piston 24 descends so as to absorb the increase in the volume.

  Thus, the electronic control unit U detects the sprung acceleration detected by the sprung acceleration sensor Sa, the damper displacement detected by the damper displacement sensor Sb, the lateral acceleration detected by the lateral acceleration sensor Sc, the yaw rate detected by the yaw rate sensor Sd, and the vehicle speed. Based on the vehicle speed detected by the sensor Se, the damping force of a total of four dampers 14 of each wheel W is individually controlled, thereby suppressing the vehicle shake when overcoming road irregularities and improving the ride comfort. Ride comfort control such as skyhook control and steering stability control that suppresses rolling during turning of the vehicle and pitching during sudden acceleration and deceleration of the vehicle are selectively executed according to the driving state of the vehicle.

  FIG. 3 is a flowchart for explaining the operation of the steering stability control that suppresses rolling by increasing the damping force of the dampers 14 when the vehicle turns.

  First, a target damping force Ft to be generated by the damper 14 is calculated based on the lateral acceleration YG detected by the lateral acceleration sensor Sc in step S1, the yaw rate γ detected by the yaw rate sensor Sd, and the vehicle speed V detected by the vehicle speed sensor Se. To do. Details of the calculation of the target damping force Ft will be described later. In the subsequent step S2, the damper speed Vp is calculated by differentiating the damper displacement detected by the damper displacement sensor Sb with respect to time. In the following step S3, the target current It is searched by applying the target damping force Ft and the damper speed Vp to the map of FIG. In step S4, the target current It is supplied to the coil of the damper 14 to generate the target damping force Ft, thereby suppressing rolling of the vehicle and improving the steering stability performance.

  FIG. 4 is a map for retrieving the target current It from the target damping force Ft and the damper speed Vp. When the damper speed Vp is constant, the target current It increases as the target damping force Ft increases. When the force Ft is constant, the target current It decreases as the damper speed Vp increases. For example, when the target damping force Ft is Ft1 and the damper speed Vp is Vpt, the target current is It5, but when the damper speed Vp increases to Vpt1, the target current decreases to It4 and the damper speed Vp decreases to Vpt2. Then, the target current increases to It6.

  Next, the process of calculating the target damping force Ft of the damper 14 from the lateral acceleration YG, the yaw rate γ, and the vehicle speed V in step S1 will be described.

  As shown in FIG. 5, the electronic control unit U includes a low-pass filter 31, a differentiator 32, a low-pass filter 33, a second-order differentiator 34, a yaw rate gain 35, an adder 36, a lateral acceleration gain 37, a vehicle speed map 38, a sign determination. And a push / pull gain 40.

The lateral acceleration YG detected by the lateral acceleration sensor Sc passes through the low-pass filter 31, and at that time, the lateral acceleration during normal traveling that does not depend on steering is blocked. The lateral acceleration YG that has passed through the low-pass filter 31 is time-differentiated by a differentiator 32 to calculate a lateral acceleration differential value dYG / dt. The differentiator 32 of the lateral acceleration YG includes a front wheel WFL, WFR and a rear wheel WRL, WRR. The lateral acceleration differential value is also a value (dYG / dt) _F for the front wheels WFL, WFR and a rear wheel WRL, A value for WRR (dYG / dt) _R is calculated.

On the other hand, the yaw rate γ detected by the yaw rate sensor Sd passes through the low-pass filter 33, and at that time, the yaw rate during the normal traveling that does not depend on the steering is cut off. The yaw rate γ that has passed through the low-pass filter 33 is subjected to second-order time differentiation by the second-order differentiator 34 to calculate the yaw rate second-order differential value d ² γ / dt ² . Subsequently, the yaw rate second-order differential value d ² γ / dt ² and the yaw rate gain 35, that is, the distance from the center of gravity position of the vehicle to the suspension devices S, S of the front wheels WFL, WFR is Lf, or the suspension devices of the rear wheels WRL, WRR. The distance to S and S is multiplied by Lr, so that the correction value d ² γ / dt ² × Lf of the lateral acceleration differential value at the position of the front wheels WFL and WFR accompanying the yawing of the vehicle, and the rear following the yawing of the vehicle A correction value d ² γ / dt ² × Lr of the lateral acceleration differential value at the position of the wheels WRL and WRR is calculated.

Then, the front side lateral acceleration differential value (dYG / dt) _F and the front side lateral acceleration differential value correction value d ² γ / dt ² × Lf are added by the adder 36, thereby correcting the front side corrected lateral force. The acceleration differential value
Calculated as (dYG / dt) _F + d ² γ / dt ² × Lf, and the corrected lateral acceleration differential value (dYG / dt) _R and the corrected lateral acceleration differential value d ² γ / dt ² × Lr And the adder 36 add the corrected lateral acceleration differential value on the rear side,
(DYG / dt) _R + d ² γ / dt ² × Lr

  FIG. 7 shows a vehicle speed map 38 of the lateral acceleration gain using the vehicle speed V detected by the vehicle speed sensor Se as a parameter. The front side and rear side gains retrieved from the vehicle speed map 38 are corrected to the front side corrected lateral acceleration. Multiply the differential value and the corrected lateral acceleration differential value on the rear side. Further, the sign of the output of the adder 36 is determined by a sign determination unit 39, and a different push / pull gain 40 is further multiplied depending on the damper 14 on the contraction side and the damper 14 on the expansion side by the lateral acceleration acting on the vehicle. Is output as the target damping force Ft on the front and rear sides.

In FIG. 8, the lateral acceleration differential value dYG / dt at the center of gravity of the vehicle is a solid line, and the corrected lateral acceleration differential value (dYG / dt) _F + d ² γ / dt ² × Lf at the positions of the front wheels WFL and WFR. Is a broken line, and a corrected lateral acceleration differential value (dYG / dt) _R + d ² γ / dt ² × Lr at the positions of the rear wheels WRL and WRR is indicated by a chain line.

  As described above, the target damping force of the damper 14 is set using not only the lateral acceleration generated by turning of the vehicle but also the lateral acceleration corrected by adding the lateral acceleration generated by yawing of the vehicle to the front wheel WFL. , WFR position, or the target damping force of the damper 14 that accurately reflects the lateral acceleration at the rear wheel WRL, WRR position can be set. Steering stability can be improved. In addition, the lateral acceleration of the vehicle is not used as it is, but the target damping force is set using the time differential value of the lateral acceleration whose phase is advanced from that of the lateral acceleration. Control responsiveness can be further improved.

  The ride comfort control when the above-described steering stability control is not performed is the well-known skyhook control, and when the sprung speed (upward is positive) and the damper speed (extension direction is positive) are the same direction. The dampers 14 are controlled to increase the damping force. When the sprung speed and the damper speed are opposite directions, the dampers 14 are controlled to decrease the damping force. The sprung speed can be obtained by integrating the sprung acceleration detected by the sprung acceleration sensor Sa, and the damper speed can be obtained by differentiating the damper displacement detected by the damper displacement sensor Sb.

  Although the embodiments of the present invention have been described above, various design changes can be made without departing from the scope of the present invention.

  For example, in the embodiment, the target damping force is set based on the time differential value of the lateral acceleration of the vehicle, but the target damping force may be set based on the lateral acceleration of the vehicle.

  In the embodiment, the damping force of the dampers 14 is variably controlled using a magnetorheological fluid, but any method for variably controlling the damping force is arbitrary.

Front view of vehicle suspension system Expanded sectional view of variable damping force damper Flow chart of damper damping force control Map to search for target current from damper speed and target damping force Block diagram of the circuit for calculating the target damping force of the damper Explanatory drawing of the principle of calculating corrected lateral acceleration differential value from lateral acceleration and yaw rate Map to search lateral acceleration gain from vehicle speed A graph showing the lateral acceleration differential value and the corrected lateral acceleration differential values on the front and rear sides

Explanation of symbols

14 Damper S Suspension device Sc Lateral acceleration sensor Sd Yaw rate sensor YG Lateral acceleration γ Yaw rate

Claims (2)

A variable damping force damper that determines a damping force of a damper (14) provided in a suspension device (S) of a vehicle based on a lateral acceleration (YG) detected by a lateral acceleration sensor (Sc) provided at a predetermined position of the vehicle body In the control device of
A yaw rate sensor (Sd) for detecting the yaw rate (γ) is provided, and the suspension device (S) is based on the lateral acceleration (YG) detected by the lateral acceleration sensor (Sc) and the yaw rate (γ) detected by the yaw rate sensor (Sd). ), And the damping force of the damper (14) is determined based on the lateral acceleration. The control device for a variable damping force damper according to claim 1, wherein the damping force of the damper (14) is determined based on a time differential value of the lateral acceleration at the position of the suspension device (S).

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