JP2006240386A - Vehicle behavior control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle behavior control device capable of improving vehicle motion performance during braking in a turning state, and acceleration while turning on a road with high traveling resistance. <P>SOLUTION: This vehicle behavior control device includes a vehicle motion control ECU 9 which performs ABS control and TRC control, and a steering braking ECU 17 which performs variable transmission ratio control for changing a transmission ratio between a steering wheel 33 and turning wheels 1FR, 1FL. When the vehicle motion control ECU 9 judges that a vehicle travels on a road with high traveling resistance, and a steering state of the vehicle V is an under-steering state, the vehicle motion control ECU 9 sets a target slip ratio of the ABS control or the TRC control for the turning outside front wheels so as to be larger. The steering braking ECU 17 controls a transmission ratio variable mechanism 32 so that the turning angle of each of the turning wheels 1FR, 1FL for the steering angle of the steering wheel 33 may become larger when the target slip ratio of the ABS control or the TRC control is changed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vehicle behavior control device.

On gravel roads and sandy roads with greater running resistance than ordinary paved roads, the anti-lock brake (ABS) mechanism that can arbitrarily control the braking force is used to control the wheels in a tendency to lock. It can be expected that the stop distance will be shortened by entering the gravel road or sandy road. Patent Document 1 discloses ABS control in a gravel road.
JP 2000-233736 A

  On soft unpaved roads such as gravel roads and sandy roads, the turning ability at the time of turning is lower than that on leveling roads, and the vehicle tends to be understeered. According to the above technique, the stopping distance can be shortened by controlling the wheels in a tendency to lock on gravel roads or sandy roads, but the problem of reduced turnability during turning braking cannot be solved. . On the other hand, the traction control (TRC) at the time of turning driving on a soft unpaved road has the same problem.

  The present invention has been made to solve the above-described problems, and provides a vehicle behavior control device capable of improving vehicle motion performance during turning braking or turning driving on a road surface with a large running resistance. For the purpose.

  A vehicle behavior control apparatus according to the present invention includes a control unit that suppresses slipping of each wheel by adjusting a braking force applied to each wheel of the vehicle, and a travel resistance detection unit that detects a travel resistance during travel of the vehicle. And a steer state detecting means for detecting the steer state of the vehicle, and based on the detection result of the travel resistance detecting means, it is determined that the vehicle is traveling on a road surface with a large running resistance, and the detection result of the steer state detecting means When it is determined that the vehicle steer state is an understeer state based on the above, the control means changes the control characteristics so as to delay the intervention of the control on the front outer wheel.

  According to the vehicle behavior control device of the present invention, when the vehicle enters an understeer state when turning on a road surface with a large running resistance, the intervention of the braking control for the front outer wheel is delayed and the front wheel tends to lock (slip). Be controlled. As a result, the turning outer front wheel enters the road surface and a wall is formed on the side surface of the front wheel, thereby increasing the lateral force. As a result, the turning ability of the vehicle can be improved.

  The vehicle behavior control device according to the present invention further includes a transmission ratio variable means for changing a transmission ratio between the steering angle of the steering wheel and the turning angle of the steered wheels, and the control is performed so as to delay the intervention of the control on the front outer wheel. When the characteristic is changed, it is preferable that the transmission ratio variable means changes the transmission ratio so that the turning angle of the steered wheels is larger than the steering angle of the steering wheel.

  In this case, the transmission ratio variable means is controlled in cooperation with the braking control. That is, the transmission ratio is changed so that the turning angle of the steered wheel becomes larger than the steering angle of the steering wheel when the intervention of the braking control for the front outer wheel is delayed. Therefore, the turning outer front wheel is controlled to have a locking tendency and the steered wheel is steered more greatly, so that the turning ability of the vehicle can be further improved.

  According to the present invention, when it is determined that the vehicle is traveling on a road surface having a large traveling resistance and the vehicle steer state is determined to be an understeer state, the intervention of the braking force control for the outer front wheels is delayed. Therefore, it is possible to improve the vehicle motion performance at the time of turning braking or turning driving on a road surface with a large running resistance.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the figure, the same reference numerals are used for the same or corresponding parts. First, the configuration of the vehicle behavior control apparatus according to the embodiment will be described with reference to FIG. FIG. 1 is a main part configuration diagram of a vehicle V equipped with a vehicle behavior control device.

  The brake mechanism of the vehicle V can control the brake hydraulic pressure of each wheel independently. The vehicle behavior control device has an anti-lock brake (hereinafter referred to as “ABS”) function, a traction control (hereinafter referred to as “TRC”) function, and the like. Control.

  The ABS control suppresses the locking of each wheel by adjusting the braking force of each wheel, ensures the braking performance, and ensures the steering performance of the steering wheel and the stability of the vehicle V. The TRC control adjusts the slip ratio of the drive wheel by adjusting the braking force of the drive wheel and the output of the engine 13 to ensure the start acceleration performance and turning stability of the vehicle V.

  The vehicle V includes a right front wheel 1FR, a left front wheel 1FL, a right rear wheel 1RR, and a left rear wheel 1RL (hereinafter, the four wheels 1FR, 1FL, 1RR, 1RL may be collectively referred to as a wheel 1). The right front wheel 1FR and the left front wheel 1FL are steered wheels steered by a steering device. The vehicle V is a four-wheel drive vehicle, and all four wheels 1FR, 1FL, 1RR, 1RL are drive wheels. Each wheel 1 has a wheel speed sensor 2FR, 2FL, 2RR, 2RL for detecting the wheel speed (hereinafter, the four wheel speed sensors 2FR, 2FL, 2RR, 2RL may be collectively referred to as a wheel speed sensor 2). It is attached.

  A brake disc 3 is attached to each wheel 1. A brake caliper 4 incorporating a brake pad and a wheel cylinder is attached to each brake disk 3. Each wheel cylinder is connected to a hydraulic circuit 6 via a brake pipe 5. Each wheel cylinder is also connected to a master cylinder 7 via a brake pipe 5 and a hydraulic circuit 6.

  During normal braking, when the brake pedal 8 is operated by the driver, the pressure in the master cylinder 7 rises, and this pressure rise is transmitted to the wheel cylinder via the brake pipe 5 and the hydraulic circuit 6 so that the pressure in the wheel cylinder is increased. Pressure increases. When the hydraulic pressure in the wheel cylinder is increased, the brake pad is pressed against the brake disc 3, and each wheel 1 connected to the brake disc 3 is braked by the frictional force.

  The hydraulic circuit 6 has a hydraulic pump, an electromagnetic valve, and the like. At the time of ABS control that controls braking force during vehicle braking and suppresses the locking of the wheel 1, the brake pedal 8 is operated to reduce or maintain the brake hydraulic pressure in the wheel cylinder that is raised by controlling the electromagnetic valve. The braking force for each wheel 1 is reduced or maintained. By these controls, the braking force for each wheel 1 is adjusted, and the lock of the wheel 1 is suppressed. That is, the brake disk 3, brake pad, wheel cylinder, brake caliper 4, brake pipe 5, and hydraulic circuit 6 function as control means.

  Also, during TRC control, the brake hydraulic pressure increased by the hydraulic pump of the hydraulic circuit 6 is controlled by an electromagnetic valve and transmitted to or cut off from the wheel cylinder in the brake caliper 4 to increase the braking force for each drive wheel 1. Or maintain. Further, the pressure in the wheel cylinder for each drive wheel 1 can be reduced by controlling the electromagnetic valve. By these controls, the braking force for each drive wheel 1 is adjusted, and the slip of the drive wheel 1 is suppressed.

  The brake system used in this embodiment is a disc brake system, but may be a drum brake system or the like. The hydraulic circuit 6 is connected to a vehicle motion control computer (ECU) 9 that controls the motion state of the vehicle V. The hydraulic pump and electromagnetic valve of the hydraulic circuit 6 are driven by the vehicle motion control ECU 9. Wheel speed sensors 2FR to 2RL are also connected to the vehicle motion control ECU 9. The vehicle motion control ECU 9 is responsible for brake control including ABS control and TRC control.

  The vehicle motion control ECU 9 is also connected to a longitudinal acceleration sensor 10, a lateral acceleration sensor 11, a yaw rate sensor 16, and the like. The vehicle motion control ECU 9 calculates the estimated vehicle body speed necessary for ABS control and TRC control, the slip ratio (amount) of each wheel, and the like based on the output of the wheel speed sensor 2 and the output of the longitudinal acceleration sensor 10.

  Further, the vehicle motion control ECU 9 calculates the estimated wheel acceleration based on the engine torque, the gear stage, and the like, calculates the actual wheel acceleration based on the output of the wheel speed sensor 2, and calculates the estimated wheel acceleration and the actual wheel acceleration. The road running resistance is detected from the degree of deviation. That is, the vehicle motion control ECU 9 also functions as a running resistance detection unit.

  The vehicle motion control ECU 9 is also connected to an engine control computer (ECU) 12. The engine control ECU 12 comprehensively controls the engine 13 and controls injection amount control and ignition timing control.

  The vehicle motion control ECU 9 and the engine control ECU 12 control the slip ratio by adjusting the output of the engine 13 (the driving force of the drive wheels) during TRC control. The output adjustment of the engine 13 is performed by controlling the intake air amount and the fuel injection amount. The throttle valve 21 of the engine 13 is a so-called electronically controlled throttle valve, and the throttle valve 22 can be arbitrarily controlled by a throttle motor 22. Sensors and actuators necessary for this control are connected to the engine control ECU 12. For example, in addition to the throttle motor 22 described above, a throttle position sensor and a rotation speed sensor that detect the throttle valve opening are also connected to the engine control ECU 12.

  The vehicle motion control ECU 9 is also connected to a steering control computer (ECU) 17. The steering control ECU 17 controls the transmission ratio variable mechanism 32 to change the transmission ratio of the steering device, that is, the ratio between the steering angle of the steering handle 33 and the turning angles of the steered wheels 1FR and 1FL. Here, the steering device of the present embodiment will be described.

  The input shaft 30 and the output shaft 31 of the steering device are connected via a transmission ratio variable mechanism 32, and a steering handle 33 is connected to the input shaft 30. The output shaft 31 is connected to a rack shaft 35 via a rack and pinion gear device 34, and steered wheels 1 FR and 1 FL are connected to both ends of the rack shaft 35.

  A steering angle sensor 36 that detects the steering amount of the steering handle 33 is attached to the input shaft 30. A steering angle sensor 37 that detects the rotation angle of the output shaft 31 is attached to the output shaft 31. Here, since the rotation angle of the output shaft 31 corresponds to the stroke position of the rack shaft 35 and the stroke position of the rack shaft 35 corresponds to the turning angle of the steered wheels 1FR and 1FL, the rotation angle of the output shaft 31 is detected. Thus, the turning angles of the steered wheels 1FR and 1FL are detected.

  The transmission ratio variable mechanism 32 connects the input shaft 30 and the output shaft 31 via a gear mechanism, and this gear mechanism is driven by an actuator 38 formed of, for example, a servo motor, whereby the steering angle of the steering handle 33 is increased. And the transmission ratio between the steered wheels 1FR and 1FL. That is, the transmission ratio variable mechanism 32 functions as a transmission ratio variable means. The actuator 38 has an operating angle sensor 39 that detects the operating angle of the actuator 38, and the detected operating angle is output to the steering control ECU 17.

  The drive control of the actuator 38 is executed by the steering control ECU 17. A steering angle sensor 36, a turning angle sensor 37, and an operating angle sensor 39 are connected to the steering control ECU 17, and detection signals of each sensor are input. Further, the steering control ECU 17 receives the steering information of the vehicle V, the control information of the ABS control, the TRC control, and the like from the vehicle motion control ECU 9. The steering control ECU 17 sets a target transmission ratio based on these detection signals and control information, and outputs a control signal corresponding to the target transmission ratio to the actuator 38.

  The mechanism for changing the transmission ratio between the steering angle of the steering handle 33 and the turning angles of the steered wheels 1FR and 1FL is not limited to this embodiment. For example, the steering handle and the rack shaft are mechanically separated, and the steering handle is driven by using a steering device that drives the rack shaft by driving an electric motor or the like based on the detected operation state of the steering handle. The transmission ratio between the steering angle and the turning angle of the steered wheels may be changed.

  As described above, the ABS control and the TRC control are performed by the vehicle motion control ECU 9. Further, according to the vehicle behavior control device, the ABS control, the TRC control and the transmission ratio variable control of the steering device are cooperatively controlled. Here, the vehicle motion control ECU 9 and the steering control ECU 17 constituting the vehicle behavior control device are used. These controls are coordinated. The vehicle motion control ECU 9, the engine control ECU 12, and the steering control ECU 17 store a microprocessor for performing calculations therein, a ROM for storing a program for causing the microprocessor to execute each process, and various data such as calculation results. And a backup RAM in which the stored contents are held by a battery.

  Next, ABS control by the vehicle motion control ECU 9 will be described with reference to FIG. FIG. 2 is a graph showing the relationship between the vehicle body speed, the wheel speed, and the wheel cylinder pressure over time. FIG. 2 shows the state of ABS control when the vehicle is understeered during turning braking on a road surface with a large running resistance.

  In FIG. 2, the difference between the vehicle body speed Vc and the wheel speed Vw is the slip amount. In the present embodiment, as indicated by a fine dotted line in FIG. 2, the normal target slip line is drawn at a portion where a predetermined slip amount has occurred with respect to the vehicle body speed Vc. The slip line referred to here is a line that determines the timing for stopping and increasing the wheel cylinder pressure during ABS control.

  On the other hand, in the present embodiment, when the vehicle is in an understeer state during running on a large running resistance road surface, as shown by the thick rough dotted line in FIG. It is drawn below the normal target slip line (so that the target slip amount or the target slip rate becomes larger than the normal time). At this time, the difference between the vehicle body speed Vc and the slip line becomes the target slip amount, and the slip ratio corresponding to the target slip amount is the target slip ratio. Further, the target slip line of the wheels other than the turning outer front wheel is drawn between the normal target slip line and the target slip line when the running resistance of the turning outer front wheel is large.

  For this reason, in the ABS control when the vehicle V is understeered during turning braking on a large road surface such as gravel road or sandy road, the turning outer front wheel is controlled to the lock side and the turning outer front wheel is set to the road surface. The turning ability can be improved by submerging. When turning right, the left front wheel 1FL corresponds to the outer front wheel, and when turning left, the right front wheel 1FR corresponds to the outer front wheel.

  Further, when the vehicle is in an understeer state during turning driving on the traveling resistance large road surface, the target slip ratio or the target slip amount of the TRC control is set to be larger than normal. As a result, the turning outer front wheel is controlled to easily slip, and the turning outer front wheel enters the road surface, thereby improving the turning ability.

  Next, vehicle behavior control by the vehicle behavior control device will be described with reference to FIG. This vehicle behavior control is realized by ABS control, TRC control, and transmission ratio variable control. FIG. 3 is a flowchart showing a processing procedure of vehicle behavior control by the vehicle behavior control device. This process is executed in cooperation by the vehicle motion control ECU 9 and the steering control ECU 17, and is repeated at a predetermined timing from when the vehicle motion control ECU 9 and the steering control ECU 17 are turned on until they are turned off. Executed.

  In step S100, it is determined whether sensors and actuators related to ABS control, TRC control, and transmission ratio variable control are valid. If these sensors are not valid and step S100 is negative, vehicle behavior control such as ABS control is not performed, and the process exits the flowchart of FIG. On the other hand, if the sensors are valid and step S100 is affirmed, the process proceeds to step S102.

  In step S102, the degree of divergence between the estimated wheel acceleration calculated based on the engine torque, the gear stage, and the like and the actual wheel acceleration calculated from the outputs of the wheel speed sensors 2FR to 2RL and the longitudinal acceleration sensor 10, that is, the road surface A determination is made as to whether the running resistance is greater than or equal to a predetermined value. The predetermined value is set to a value that can distinguish a normal leveling road from a sandy road or a gravel road.

  Here, when the degree of deviation between the estimated wheel acceleration and the actual wheel acceleration is less than a predetermined value, that is, when it is determined that the vehicle is traveling on a normal leveling road where the running resistance is not large, the normal road surface is set in step S104. Combined ABS control or TRC control is performed. In step S106, normal transmission ratio variable control is performed. Thereafter, the process exits from this flow.

  On the other hand, if the degree of deviation between the estimated wheel acceleration and the actual wheel acceleration is greater than or equal to a predetermined value, that is, if it is determined that the vehicle is traveling on a sandy road or gravel road with a large running resistance, the process proceeds to step S108. To do.

  In step S108, a determination is made as to whether or not the steering state of the vehicle V is an understeer state. Here, whether or not the vehicle is understeered is determined, for example, by whether or not the deviation between the target yaw rate calculated from the vehicle speed and the turning angle and the actual yaw rate read from the yaw rate sensor 16 is greater than a predetermined value. . When the actual yaw rate is smaller than the target yaw rate and the deviation is larger than a predetermined value, it is determined that the understeer state.

  When it is determined that the steering state of the vehicle V is not the understeer state, the process proceeds to step S110. On the other hand, when it is determined that the steering state of the vehicle V is the understeer state, the process proceeds to step S114.

  In step S110, the control characteristics are changed so as to delay the intervention of ABS control and TRC control. Specifically, the target slip ratio (or target slip amount) for ABS control and TRC control is set to a value larger than that in the normal state. For this reason, in the ABS control, the wheel 1 is controlled to be locked more easily than when traveling on a normal road surface, and the braking distance is shortened. Further, in the TRC control, the wheel 1 is controlled to slip more easily than when traveling on a normal road surface, thereby improving running performance and suppressing stall.

  In the subsequent step S112, normal transmission ratio variable control is executed. Thereafter, the process exits from this flow.

  When it is determined that the steering state of the vehicle V is the understeer state, in step S114, the control characteristics are changed so as to delay the intervention of the ABS control and the TRC control with respect to the front outer wheel. Specifically, the target slip ratio (or target slip amount) of the ABS control and TRC control for the front outer wheel is set to a value larger than normal. For this reason, in the ABS control, the turning outer front wheel is controlled so as to be easily locked, and the turning ability is improved. Further, the TRW control also controls the turning outer front wheel in a slipping tendency, thereby improving the turning ability.

  In subsequent step S116, the transmission ratio variable mechanism 32 is controlled so that the steered angles of the steered wheels 1FR and 1FL are larger than the steered angle of the steering handle 33. For this reason, the steered wheels 1FR and 1FL are steered more greatly, and the turning performance is further improved.

  According to the present embodiment, for example, when the vehicle V enters an understeer state when turning on a road surface having a large traveling resistance such as a sandy road, the control characteristics are changed so as to delay the intervention of the ABS control and the TRC control with respect to the front outer wheel. Is done. That is, the target slip ratio (or target slip amount) in the ABS control and TRC control is set to a larger value than normal, and the turning outer front wheel is controlled to be locked (slip). Therefore, the turning front of the vehicle V can be improved by the turning outer front wheel entering the road surface and increasing the lateral force of the wheel.

  Moreover, according to this embodiment, transmission ratio variable control is performed in cooperation with ABS control or TRC control. In other words, the transmission ratio variable mechanism 32 controls the steered wheels 1FR and 1FL so that the steered angles of the steered wheels 1FR and 1FL are larger than the steered angle of the steering handle 33 when the intervention of ABS control and TRC control for the front outer wheel is delayed. Is done. Therefore, the turning outer front wheel is controlled to be locked and the steered wheels 1FR and 1FL are steered more greatly, so that the turning ability of the vehicle V is further improved and the vehicle motion performance can be improved.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above embodiment, the road surface is based on the degree of divergence between the estimated wheel acceleration calculated based on the engine torque, the gear stage, and the like and the actual wheel acceleration calculated from the outputs of the wheel speed sensor 2 and the longitudinal acceleration sensor 10. However, the method of detecting the running resistance is not limited to the above embodiment. For example, the running resistance can also be detected based on the wheel speed estimated from the engine speed and the gear speed ratio (gear stage) and the actual wheel speed detected by the wheel speed sensor 2. Further, the running resistance may be detected based on the vehicle body lateral acceleration estimated from the steering angle and the actual lateral acceleration detected by the lateral acceleration sensor 11. Further, the running resistance can be detected based on the hydraulic pressure (estimated longitudinal acceleration) of the master cylinder 7 and the actual longitudinal acceleration detected by the longitudinal acceleration sensor 10. In the case of this method, it is preferable to perform correction using a slope gradient.

  Although a plurality of examples have been given as detection methods for running resistance, the running resistance may be detected only by any one of the detection methods, or two or more detection methods may be used in combination. In addition, a method for detecting a running resistance may be selected depending on a running state such as start acceleration, steady running, turning or braking.

  In the above embodiment, the transmission ratio variable mechanism 32 is controlled so that the turning angle of the steered wheels 1FR and 1FL becomes larger than the steering angle of the steering handle 33, thereby increasing the steered angle of the steered wheels 1FR and 1FL. However, it is also possible to increase the turning angle of the steered wheels 1FR and 1FL by increasing the assist amount of the power steering device.

  Furthermore, in the said embodiment, although the vehicle behavior control apparatus was mounted in the four-wheel drive vehicle, it is also applicable to a front-wheel drive vehicle and a rear-wheel drive vehicle.

It is a principal part block diagram of the vehicle carrying the vehicle behavior control apparatus which concerns on embodiment. It is a figure for demonstrating ABS operation | movement when it will be in an understeer state at the time of driving | running | working resistance road surface driving | running | working. It is a flowchart which shows the process sequence of the vehicle behavior control by the vehicle behavior control apparatus which concerns on embodiment.

Explanation of symbols

  1FR, 1FL, 1RR, 1RL ... Wheels, 2FR, 2FL, 2RR, 2RL ... Wheel speed sensor, 3 ... Brake disc, 4 ... Brake caliper, 5 ... Brake piping, 6 ... Hydraulic circuit, 7 ... Master cylinder, 8 ... Brake Pedal, 9 ... Vehicle motion control ECU, 10 ... Longitudinal acceleration sensor, 11 ... Lateral acceleration sensor, 12 ... Engine ECU, 13 ... Engine, 16 ... Yaw rate sensor, 17 ... Steering control ECU, 32 ... Transmission ratio variable mechanism, 33 ... Steering handle, 36 ... steering angle sensor, 37 ... steering angle sensor, V ... vehicle.

Claims (2)

Control means for suppressing slipping of each wheel by adjusting a braking force applied to each wheel of the vehicle;
Travel resistance detection means for detecting travel resistance during travel of the vehicle;
Steer state detecting means for detecting the steer state of the vehicle,
The control means determines that the vehicle is traveling on a road surface having a large running resistance based on the detection result of the running resistance detection means, and determines that the vehicle steering state is understeer based on the detection result of the steering condition detection means. A vehicle behavior control device characterized by changing a control characteristic so as to delay control intervention for a front outer wheel when turning is determined. A transmission ratio variable means for changing a transmission ratio between the steering angle of the steering wheel and the turning angle of the steered wheels;
The transmission ratio variable means is configured to increase the turning angle of the steered wheels with respect to the steering angle of the steering wheel when the control characteristic is changed so as to delay control intervention on the outer front wheel. The vehicle behavior control device according to claim 1, wherein the transmission ratio is changed.

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