JP2012091656A - Travel control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a travel control device for vehicles, in which when both of turning auxiliary control and traction control are executed simultaneously, a reference wheel speed is prevented from becoming an improper value due to failure of a device for detecting a wheel speed and the traction control is prevented from being improperly executed.SOLUTION: The travel control device for vehicles performs the turning auxiliary control for controlling the longitudinal force of a wheel so that the longitudinal force of an inner turning wheel becomes smaller than that of an outer turning wheel and the traction control for reducing the longitudinal force of the wheel, when drive slippage of the wheel is excessive and reducing the drive slippage. When a wheel speed detecting means detects that one wheel other than the inner turning wheel is driven at the wheel speed lower than the actual wheel speed, namely, detects failure and the turning auxiliary control is executed, the reference wheel speed Vwb is set for determining the drive slippage on the basis of the second lowest wheel speed Vmedlo in the wheel speeds of three wheels except for the inner turning wheel.

Description

  The present invention relates to a vehicle travel control device, and more specifically, a turn assist control for controlling the front / rear force of a wheel so that the front / rear force of a turning inner wheel becomes smaller than that of a turning outer wheel, and a driving slip of the wheel is excessive. In some cases, the present invention relates to a travel control device that performs traction control that reduces driving slip by reducing the longitudinal force of the wheel.

  Turning assist control, for example, control for improving turning performance of a vehicle by applying a braking force to a turning inner rear wheel is already known, and is described, for example, in Patent Document 1 below. Further, traction control, for example, control for reducing driving slip by applying braking force to a wheel having excessive driving slip is already well known.

JP 11-49020 A

[Problems to be Solved by the Invention]
Since the wheel to be controlled and the contents of the control of the turning assist control and the traction control are different from each other and do not interfere with each other, both the turning assist control and the traction control may be executed at the same time.

  When traction control is executed in a situation where braking force is not applied by turning assist control, the reference wheel speed for determining drive slip is the lowest of the four wheel speeds. Set to On the other hand, when the traction control is executed in the situation where the braking force is applied by the turning assist control, the reference wheel speed is the three speeds excluding the wheels to which the braking force is applied by the turning assist control. It is set to the lowest wheel speed among the wheel speeds.

  Generally, the wheel speed is detected by a wheel speed sensor, but an abnormality may occur in the wheel speed sensor. When an abnormality occurs in the wheel speed sensor, a situation occurs in which the traction control is inappropriately performed due to the abnormality. For example, let us consider a case where an abnormality in detecting the wheel speed as a value lower than the actual wheel speed occurs in the wheel speed sensors other than the wheel to which the braking force is applied by the turning assist control. In this case, the wheel speed of the wheel to which the braking force is applied by the turning assist control and the wheel speed detected by the abnormal wheel speed sensor become a low value. Therefore, if the reference wheel speed is set to the lowest of the three wheel speeds excluding the wheel to which the braking force is applied by the turning assist control, the reference wheel speed becomes excessively low. Control will be executed improperly.

  The present invention is a case where both the turning assist control and the traction control are executed simultaneously, and the above-described case where an abnormality in detecting the wheel speed as a value lower than the actual wheel speed occurs in the wheel speed sensor. It was made by paying attention to the problem. The main problem of the present invention is that when both the turning assist control and the traction control are executed simultaneously, the reference wheel speed becomes an inappropriate value due to an abnormality in the device for detecting the wheel speed, and the traction control is performed. It is to prevent improper execution.

[Means for Solving the Problems and Effects of the Invention]
According to the present invention, the main problem described above is the structure of claim 1, that is, by reducing the longitudinal force of one turning inner wheel, the longitudinal force of the turning inner wheel becomes smaller than the turning outer wheel so that the longitudinal force of the turning inner wheel becomes smaller. In a four-wheel drive vehicle travel control device that performs turning assist control that controls force and traction control that reduces driving slip by reducing the longitudinal force of the wheel when the driving slip of the wheel is excessive, There is a wheel speed detecting means for detecting the wheel speed of each wheel, the wheel speed detecting means for one wheel other than the turning inner wheel has an abnormality detecting the wheel speed as a value lower than the actual wheel speed, and When the turning assist control is being executed, a reference wheel speed for determining a driving slip of the wheel based on the second lowest wheel speed of the three wheels excluding the turning inner wheel. It is achieved by the travel control apparatus for a vehicle and sets the.

According to said structure, the reference | standard wheel speed for determining the driving slip of a wheel based on the 2nd lowest wheel speed among the wheel speeds of three wheels except a turning inner ring | wheel is set. Therefore, when the wheel speed detecting means has an abnormality detecting the wheel speed as a value lower than the actual wheel speed and the turning assist control is being executed, the reference wheel speed becomes excessively low and the traction control is performed. Inappropriate execution can be prevented.
According to the first aspect of the present invention, the reference wheel speed can be set if the second lowest wheel speed among the wheel speeds of the three wheels excluding the turning inner wheel is found. Therefore, the reference wheel speed can be set without specifying the wheel in which the wheel speed detecting means is abnormal.

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration of claim 1, all wheel speed detection means are normal and the turning assist control is executed. In some cases, the reference wheel speed for determining the driving slip of the wheel is set based on the lowest wheel speed of the three wheels excluding the turning inner wheel.

  According to said structure, when all the wheel speed detection means are normal and the said turning assistance control is performed, a reference | standard wheel speed can be set to an appropriate value.

  According to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 1, the wheel speed detection means for one wheel other than the turning inner wheel has an actual wheel speed higher than that. When the turning assist control is being executed in a situation where an abnormality to detect the wheel speed as a high value is occurring, the turning inner wheel and the wheel speed detecting means are the lower of the wheel speeds of the two wheels excluding the abnormal wheels. A reference wheel speed for determining the driving slip of the wheel is set based on the wheel speed of the other side, and the wheel speed detecting means is configured not to determine the driving slip of the wheel for an abnormal wheel (configuration of claim 3) .

  According to the above configuration, the reference wheel speed is set to an appropriate value even when there is an abnormality in detecting the wheel speed as a value higher than the actual wheel speed in the wheel speed detecting means of one wheel other than the turning inner wheel. Can be set to

  According to the present invention, in order to effectively achieve the above main problems, the braking force detecting means for detecting the braking force of each wheel is provided. In the turning assistance control, when the longitudinal force of the turning inner wheel is reduced based on the braking force of the turning inner wheel, all the wheel speed detecting means are normal and the turning assistance control is being executed. Or when the wheel speed detection means of the wheel of the turning inner wheel detects a wheel speed as a value lower than the actual wheel speed and the turning assist control is being executed, The reference wheel speed for determining the driving slip of the wheel is set based on the lowest wheel speed among the wheel speeds of the two wheels.

  According to the above configuration, in the vehicle in which the longitudinal force of the turning inner wheel is reduced by the turning assist control based on the braking force of the turning inner wheel, the reference wheel regardless of whether the wheel speed detecting means is normal or not. Speed can be set to an appropriate value.

  In the present application, the “front / rear force” of the wheel is a braking / driving force in which the traveling direction of the vehicle is positive. The reduction of the longitudinal force not only reduces the longitudinal force in the traveling direction of the vehicle, but also applies a longitudinal force in the direction opposite to the traveling direction of the vehicle to the wheels generating the longitudinal force in the traveling direction of the vehicle. It includes adding.

  Further, in the present application, “turning inner rear wheel” means a turning inner wheel on the rear side with respect to the traveling direction of the vehicle. Accordingly, the “rear wheel” of the “turning inner rear wheel” is the rear wheel of the vehicle when the vehicle moves forward, but is the front wheel of the vehicle when the vehicle moves backward.

[Preferred embodiment of problem solving means]
According to one preferred aspect of the present invention, in the configuration of the above first to fourth aspects, the turning assist control is a control for giving a yaw moment in the turning assist direction to the vehicle by applying a braking force to the turning inner wheel. It is comprised so that it may exist (the preferable aspect 1).

  According to another preferred embodiment of the present invention, in the configuration of the preferred embodiment 1, the turning inner wheel is configured to be a turning inner rear wheel (preferred embodiment 2).

  According to another preferred aspect of the present invention, in the configuration of the first to fourth aspects, the traction control is a control for reducing the driving slip of the wheel by applying a braking force to the wheel to be controlled. (Preferred embodiment 3).

  According to another preferred aspect of the present invention, in the configuration of claims 1 to 3, the turn assist control is configured to reduce the longitudinal force of the turning inner wheel based on the wheel speed ( Preferred embodiment 4).

  According to another preferred aspect of the present invention, in the configuration of the preferred aspect 4, when the wheel speed detecting means of the turning inner wheel is abnormal, the longitudinal force of the turning inner wheel is not reduced by turning assist control. (Preferred aspect 5)

  According to another preferred aspect of the present invention, in the configuration of claim 2, the driving slip is determined for the wheel having the highest wheel speed and the wheel having the second highest wheel speed among the three wheels. (Preferred embodiment 6).

  According to another preferred aspect of the present invention, in the configuration of claim 3, the driving slip is determined for a wheel having a higher wheel speed among the two wheels (preferred aspect 7). ).

  According to another preferred embodiment of the present invention, in the configuration of the first to fourth aspects, the vehicle is configured to be an off-road vehicle (preferred embodiment 8).

  According to another preferable aspect of the present invention, in the configuration of the preferable aspect 8, the turning assist control is configured to apply a braking force to the turning inner rear wheel until the turning inner rear wheel is locked. (Preferred embodiment 9)

1 is a schematic configuration diagram illustrating a first embodiment of a vehicle travel control device according to the present invention. It is a flowchart which shows the routine of turning assistance control in 1st embodiment. It is a flowchart which shows the routine of the traction control in 1st embodiment. 7 is a flowchart showing a calculation routine of a reference wheel speed Vwb and a driving slip ratio Sdri when a braking force is not applied to a turning inner rear wheel by turning assist control in the traction control of the first embodiment. 7 is a flowchart showing a calculation routine of a reference wheel speed Vwb and a driving slip ratio Sdri when a braking force is applied to a turning inner rear wheel by turning assist control in the traction control of the first embodiment. It is a schematic block diagram which shows 2nd embodiment of the traveling control apparatus of the vehicle by this invention. It is a flowchart which shows the routine of the turning assistance control in 2nd embodiment. It is a flowchart which shows the routine of the traction control in 2nd embodiment. 10 is a flowchart showing a calculation routine of a reference wheel speed Vwb and a driving slip ratio Sdri when a braking force is applied to a turning inner rear wheel by turning assist control in the traction control of the second embodiment.

  The invention will now be described in detail with reference to a few preferred embodiments with reference to the accompanying drawings.

First Embodiment FIG. 1 is a schematic configuration diagram showing a first embodiment of a vehicle travel control apparatus according to the present invention.

  In FIG. 1, reference numeral 100 generally indicates a travel control device mounted on the vehicle 102. Reference numeral 10 denotes an engine, and the driving force of the engine 10 is transmitted to the output shaft 16 via the torque converter 12 and the transmission 14. The driving force of the output shaft 16 is transmitted to the front wheel driving shaft 20 or the rear wheel driving shaft 22 by the transfer 18 for switching the driving state. The output of the engine 10 is controlled by the engine control device 24 in accordance with the depression amount of the accelerator pedal 23 operated by the driver.

  The transfer 18 includes an actuator for switching the driving state between the 4WD state and the 2WD state, and the actuator is controlled by the 4WD control device 28 in response to a selection switch (SW) 26 operated by the driver. The selection switch 26 can be switched to the H4 position, the H2 position, the N position, and the L4 position.

  When the selection switch 26 is in the H4 position, the transfer 18 is set to the 4WD position for transmitting the driving force of the output shaft 16 to the front wheel driving shaft 20 and the rear wheel driving shaft 22. On the other hand, when the selection switch 26 is in the H2 position, the transfer 18 is set to the 2WD position where the driving force of the output shaft 16 is transmitted only to the rear wheel driving shaft 22. When the selection switch 26 is in the N position, the transfer 18 is set to a position where the driving force of the output shaft 16 is not transmitted to either the front wheel driving shaft 20 or the rear wheel driving shaft 22. Further, when the selection switch 26 is in the L4 position, the transfer 18 transmits the driving force of the output shaft 16 to the front wheel driving shaft 20 and the rear wheel driving shaft 22 as a driving force for lower vehicle speed and higher torque than in the H4 position. To 4WD position.

  As shown in FIG. 1, the 4WD control device 28 generates a signal indicating whether the command position of the 4WD control device 28 for the transfer 18 is the 2WD position or the 4WD position based on the command signal input from the selection switch 26. Output to the engine controller 24. The engine control device 24 controls the output of the engine 10 according to the command position of the 4WD control device 28.

  The driving force of the front wheel drive shaft 20 is transmitted to the left front wheel axle 32L and the right front wheel axle 32R by the front wheel differential 30, whereby the left and right front wheels 34FL and 34FR are rotationally driven. Similarly, the driving force of the rear wheel drive shaft 22 is transmitted to the left rear wheel axle 38L and the right rear wheel axle 38R by the rear wheel differential 36, whereby the left and right rear wheels 40RL and 40RR are rotationally driven.

  The braking forces of the left and right front wheels 34FL, 34FR and the left and right rear wheels 40RL, 40RR are controlled by controlling the braking pressures of the corresponding wheel cylinders 46FL, 46FR, 46RL, 46RR by the hydraulic circuit 44 of the braking device 42. Although not shown in the figure, the hydraulic circuit 44 includes a reservoir, an oil pump, various valve devices, and the like. The braking pressure of each wheel cylinder is normally controlled by a master cylinder 48 that is driven in response to the driver's depressing operation of the brake pedal 47, and if necessary, by a traveling control electronic control unit 50 as will be described in detail later. Be controlled.

  The electronic control device 50 receives signals indicating the wheel speeds Vi (i = fl, fr, rl, rr) of the left and right front wheels and the left and right rear wheels from the wheel speed sensors 52FL, 52FR, 52RL, 52RR. A signal indicating the vehicle speed V is input from the vehicle speed sensor 54 to the electronic control unit 50, and a signal indicating the steering angle θ is input from the steering angle sensor 56. The steering angle sensor 56 detects the steering angle with the left turning direction of the vehicle as positive.

  The electronic control device 50 receives a signal indicating the position of the transfer 18 from the selection switch 26, and indicates whether or not the turning assist switch is turned on by the turning assist switch 58 operated by the vehicle occupant. A signal is input.

  Further, a signal indicating the accelerator opening Acc is input to the engine control device 24 from an accelerator opening sensor (not shown in FIG. 1) provided on the accelerator pedal 23. Note that the engine control device 24, 4WD control device 28, and electronic control device 50 may actually be constituted by, for example, a single microcomputer including a CPU, a ROM, a RAM, and an input / output device and a drive circuit.

  As will be described later in detail, when the turning assist switch 58 is on, the electronic control unit 50 determines whether or not to apply the control force by the turning assist control. When it is determined that the electronic control unit 50 should be executed, a braking force is applied to the rear turning inner wheel to apply a yaw moment that assists the turning to the vehicle.

  Further, when the vehicle is in a driving state, the electronic control unit 50 calculates a driving slip ratio Sdri (i = fl, fr, rl, rr) for a wheel to be controlled by traction control. When there is a wheel with an excessive driving slip ratio, the electronic control unit 50 applies a braking force according to the driving slip ratio to the wheel, thereby performing traction control to reduce the excessive driving slip.

The driving slip ratio Sdri is calculated according to the following equation 1 based on the wheel speed Vi and the reference wheel speed Vwb of the wheel.
Sdri = (Vi−Vwb) / Vwb (1)

  The reference wheel speed Vwb and the wheel to be controlled by the traction control are determined according to the flowcharts shown in FIGS. 3 to 5 as to whether or not the braking force is applied by the turning assist control and any of the wheel speed sensors is abnormal. It is set in a different manner depending on whether or not it has occurred. In the following description, the wheel speeds Vi detected by the wheel speed sensors 52FL to 52RR are Vmin, Vmedlo, Vmedhi, and Vmax in ascending order.

  Further, when the wheel speed detected by the wheel speed sensor is a value that is not possible, it is determined that an abnormality has occurred in the wheel speed sensor. For example, when the vehicle is not in a braking state and the wheel speed detected by another wheel speed sensor is equal to or higher than the reference value for running determination, and the wheel speed detected by one wheel speed sensor is less than the reference value for abnormality determination Further, it is determined that a low output abnormality has occurred in the wheel speed sensor. Typical examples of this abnormality are disconnection of the conducting wire and abnormal fixation of the movable member.

  Also, when the vehicle is not in an accelerated state and the wheel speed detected by another wheel speed sensor is below the reference value for running determination, and the wheel speed detected by one wheel speed sensor is higher than the reference value for abnormality determination Further, it is determined that a high output abnormality has occurred in the wheel speed sensor. A typical example of this abnormality is a short-circuit abnormality.

  The electronic control unit 50 does not apply the braking force by the turning assist control when there is an abnormality in the wheel speed sensor of the rear inner wheel. Further, the electronic control unit 50 does not apply braking force by traction control when abnormality occurs in two or more wheel speed sensors.

  Further, the electronic control unit 50 determines whether or not the vehicle is in an excessive oversteer state or understeer state based on a state quantity of the vehicle detected by a yaw rate sensor or the like not shown in the drawing, that is, a control force by vehicle motion control. It is determined whether or not it is necessary to provide When the electronic control unit 50 determines that the control force needs to be applied, the electronic control device 50 performs oversteer suppression control or understeer suppression control that stabilizes the turning motion of the vehicle by applying a braking force to the control target wheel of the vehicle motion control. Do.

  In particular, in oversteer suppression control, at least a braking force is applied to the outer front wheel of the turn, whereby a yaw moment in the turn suppression direction is applied to the vehicle and the vehicle is decelerated. In the understeer suppression control, the braking force is applied to at least the left and right rear wheels, and the braking force of the inner turning rear wheel is made higher than the braking force of the outer turning rear wheel. A yaw moment in the turning acceleration direction is applied.

  Next, the routine for turning assist control in the first embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is started by closing an ignition switch not shown in the figure, and is repeatedly executed at predetermined time intervals.

  First, in step 50, it is determined whether or not the braking force is applied by the turning assist control, that is, whether or not the braking force is applied to the rear inner wheel. When an affirmative determination is made, the control proceeds to step 300, and when a negative determination is made, the control proceeds to step 100.

  In step 100, it is determined whether or not a condition for permitting the application of braking force by the turning assist control is satisfied. When a negative determination is made, the control is temporarily terminated, and when an affirmative determination is made, the control proceeds to step 150.

In this case, when all the following conditions are satisfied, it may be determined that the condition for permitting the application of the braking force by the turning assist control is satisfied.
(A1) The braking device 42 is normal and the vehicle motion control can be normally executed.
(A2) The selection switch 26 is set to the L4 position.
(A3) The turning assist switch 58 is set to the on position.
(A4) The application of the braking force by the vehicle motion control is not executed.
(A5) The wheel speed sensor of the rear inner wheel is normal.

  In step 150, it is determined whether or not a condition for starting the application of braking force by the turning assist control is satisfied. When a negative determination is made, the control is temporarily terminated, and when an affirmative determination is made, the control proceeds to step 200.

  In this case, when the two conditions (b1) the absolute value of the steering angle θ is not less than the reference value θtas and (b2) the accelerator pedal 23 is depressed, the braking force by the turning assist control is satisfied. It may be determined that the start condition for grant is satisfied. The reference value θtas may be a positive constant, but may be variably set according to the vehicle speed V so that when the vehicle speed V is low, the reference value θtas is larger than when the vehicle speed V is high.

  In step 200, the target increase of the rear inner wheel based on the absolute value of the steering angle θ is set so that the absolute value of the steering angle θ is larger than that when the absolute value of the steering angle θ is small. A pressure gradient ΔPbrint is calculated. The target pressure increase gradient ΔPbrint may be variably set in accordance with the vehicle speed V so that the vehicle pressure V is larger when the vehicle speed V is low than when the vehicle speed V is high.

  In step 250, the braking pressure of the turning inner rear wheel is controlled so that the pressure increasing gradient of the turning inner rear wheel becomes the target pressure increasing gradient ΔPbrint, whereby the application of the braking force to the turning inner rear wheel is started. .

  In step 300, it is determined whether or not a braking force application end condition by the turning assist control is satisfied. When a negative determination is made, control proceeds to step 500, and when an affirmative determination is made, control proceeds to step 400.

In this case, when any of the following conditions is satisfied, it may be determined that the braking force application end condition by the turning assist control is satisfied.
(C1) The absolute value of the steering angle θ is equal to or less than the reference value θtae (positive constant) for the end of control.
(C2) The turning assist switch 62 is switched to the off position.
(C3) It is necessary to apply braking force by behavior control.
(C4) The vehicle motion control cannot be normally executed.
(C5) The wheel speed sensor of the rear inner wheel becomes abnormal.

  In step 400, the braking pressure of the turning inner rear wheel is reduced, whereby the application of the braking force to the turning inner rear wheel is finished.

  In step 500, the braking slip ratio Sbrin of the turning inner rear wheel is calculated, and it is determined whether or not the turning inner rear wheel is locked based on the braking slip ratio Sbrin. When a negative determination is made, the control is once ended. When an affirmative determination is made, the control proceeds to step 600.

  In step 600, the increase in braking pressure of the rear inner wheel is stopped, whereby the increase in braking force of the rear inner wheel is stopped.

  Next, a traction control routine according to the first embodiment will be described with reference to the flowchart shown in FIG. Note that the control according to the flowchart shown in FIG. 3 is also started by closing an ignition switch (not shown), and is repeatedly executed at predetermined time intervals.

  First, in step 1050, it is determined whether or not braking force is applied by traction control. When an affirmative determination is made, the control proceeds to step 1150, and when a negative determination is made, the control is performed. Proceed to step 1100.

  In step 1100, it is determined whether or not a traction control permission condition is satisfied. If a negative determination is made, the control is temporarily terminated. If an affirmative determination is made, the control proceeds to step 1250. .

In this case, it may be determined that the traction control permission condition is satisfied when all of the following conditions are satisfied.
(D1) The braking device 42 is normal and the traction control can be normally executed.
(D2) The accelerator opening Acc is equal to or greater than a reference value (positive constant) for permission determination.
(D3) No abnormality has occurred in two or more wheel speed sensors.

  In step 1150, it is determined whether or not a traction control termination condition is satisfied. If a negative determination is made, the control proceeds to step 1250. If an affirmative determination is made, the control proceeds to step 1200. move on.

In this case, it may be determined that the traction control end condition is satisfied when any of the following conditions is satisfied.
(E1) The drive slip ratio Sdri is less than or equal to the control end reference value Sdre (positive constant).
(E2) The braking device 42 is abnormal and the traction control cannot be executed normally.
(E3)) The accelerator opening Acc is less than the reference value for the permission determination.
(E4) An abnormality occurred in two or more wheel speed sensors.

  In step 1200, the braking pressure of the wheel to be controlled to which the braking force by the traction control is applied is reduced to 0, whereby the application of the braking force to the wheel to be controlled by the traction control is finished.

  In step 1250, it is determined whether or not a braking force is applied to the rear inner wheel by the turning assist control. When an affirmative determination is made, the control proceeds to step 1400 and a negative determination is made. Sometimes control proceeds to step 1300.

  In step 1300, the reference wheel speed Vwb and the driving slip ratio Sdri (i is fl, fr, rl, when the braking force is not applied to the turning inner rear wheel by the turning assist control according to the flowchart shown in FIG. any one of rr) is calculated.

  In step 1400, the reference wheel speed Vwb and the drive slip ratio Sdri when the braking force is applied to the turning inner rear wheel by the turning assist control are calculated according to the flowchart shown in FIG.

  In step 1600, it is determined whether or not it is necessary to increase the braking pressure of the wheel to reduce the drive slip by determining whether or not the drive slip ratio Sdri is equal to or greater than the reference value Sdrs. When a negative determination is made, the control is temporarily terminated, and when an affirmative determination is made, the control proceeds to step 1700.

  The reference value Sdrs may be a positive constant, but may be variably set according to the vehicle speed V so that when the vehicle speed V is low, the reference value Sdrs is larger than when the vehicle speed V is high.

  In step 1700, the braking pressure of the wheel is increased, thereby reducing the wheel speed of the wheel and reducing the driving slip.

  As shown in FIG. 4, in step 1310, it is determined whether or not all the wheel speed sensors 52FL to 52RR are normal. When a negative determination is made, the control proceeds to step 1340, and when an affirmative determination is made, the control proceeds to step 1320.

  In step 1320, the reference wheel speed Vwb for calculating the drive slip ratio Sdri is set to the lowest wheel speed Vmin among the wheel speeds of all the wheels.

  In step 1330, for three wheels other than the reference wheel, the drive slip ratio Sdri is calculated according to the above equation 1 based on the wheel speed Vi and the reference wheel speed Vwb of the wheel.

  In step 1340, it is determined whether or not the abnormality of the wheel speed sensor is an output reduction abnormality that detects the wheel speed as a value lower than the actual wheel speed. When a negative determination is made, control proceeds to step 1370, and when an affirmative determination is made, control proceeds to step 1350.

  In step 1350, the reference wheel speed Vwb for calculating the driving slip ratio Sdri is the second lowest wheel speed Vmedlo among the wheel speeds of the four wheels (the lowest wheel speed among the wheel speeds of the wheels other than the abnormal wheels). Speed Vmin ′).

  In step 1360, for the wheels other than the abnormal wheel and the reference wheel, the drive slip ratio Sdri is calculated according to the above equation 1 based on the wheel speed Vi and the reference wheel speed Vwb of the wheel.

  In step 1370, the reference wheel speed Vwb for calculating the drive slip ratio Sdri is set to the lowest wheel speed Vmin among the wheel speeds of all the wheels.

  In step 1380, for the wheels other than the abnormal wheel and the reference wheel, the drive slip ratio Sdri is calculated according to the above equation 1 based on the wheel speed Vi and the reference wheel speed Vwb of the wheel.

  As shown in FIG. 5, in step 1410, it is determined whether or not all the wheel speed sensors 52FL to 52RR are normal. When a negative determination is made, control proceeds to step 1440, and when an affirmative determination is made, control proceeds to step 1420.

  In step 1420, the reference wheel speed Vwb for calculating the drive slip ratio Sdri is set to the lowest wheel speed Vmedlo among the wheel speeds of the three wheels excluding the turning inner rear wheel.

  In step 1430, the drive slip ratio Sdri is calculated according to the above-described formula 1 for the wheels other than the turning inner rear wheel and the reference wheel.

  In step 1440, it is determined whether or not the abnormality of the wheel speed sensor is an output reduction abnormality that detects the wheel speed as a value lower than the actual wheel speed. If a negative determination is made, control proceeds to step 1470, and if an affirmative determination is made, control proceeds to step 1450.

  In step 1450, the reference wheel speed Vwb for calculating the drive slip ratio Sdri is set to the lower wheel speed Vmedhi among the wheel speeds of the wheels other than the turning inner rear wheel and the abnormal wheel.

  In step 1460, a wheel other than the inner rear wheel, the abnormal wheel, and the reference wheel, that is, one wheel having the highest wheel speed is driven according to the above formula 1 based on the wheel speed Vi and the reference wheel speed Vwb of the wheel. A slip ratio Sdri is calculated.

  In step 1470, the reference wheel speed Vwb for calculating the drive slip ratio Sdri is set to the lower wheel speed Vmedlo among the wheel speeds of the wheels other than the turning inner rear wheel and the abnormal wheel.

  In step 1480, the wheels other than the turning inner rear wheel, the abnormal wheel, and the reference wheel, that is, the wheel having the second highest wheel speed are driven according to the above formula 1 based on the wheel speed Vi and the reference wheel speed Vwb of the wheel. A slip ratio Sdri is calculated.

  Thus, according to the first embodiment, when it is time to start the turning assist control, a negative determination, an affirmative determination, and an affirmative determination are performed in steps 50, 100, and 150, respectively. In steps 200 and 250, the application of braking force to the turning inner rear wheel is started, and the braking force of the turning inner rear wheel is increased until an affirmative determination is made in step 300 or 500.

  Therefore, a yaw moment in the turning assist direction due to the difference in braking force between the left and right rear wheels is applied to the vehicle, thereby assisting the turning of the vehicle. Accordingly, the turning performance of the vehicle is improved as compared with the case where the braking force is not applied by the turning assist control.

  If the driving slip of any one wheel to be controlled in traction control becomes excessive, negative determination, positive determination, negative determination, and positive determination are performed in steps 1050, 1100, 1250, and 1600, respectively. In step 1700, application of braking force by traction control to the wheel is started, and application of braking force is continued until an affirmative determination is made in step 1150, thereby reducing driving slip of the wheel. The

  Even if the wheel speed sensors 52FL to 52RR for detecting the wheel speed are normal, the setting of the reference wheel speed Vwb and the driving slip ratio Sdri are determined depending on whether or not the braking force is applied to the rear rear wheel by the turning assist control. The operation of must be changed.

  In addition, an abnormality may occur in the wheel speed sensors 52FL to 52RR. When an abnormality occurs in the wheel speed sensor, the setting of the reference wheel speed Vwb and the calculation of the drive slip ratio Sdri must be changed accordingly.

  According to the first embodiment, the setting or the like of the reference wheel speed Vwb is performed according to the flowcharts shown in FIG. 3 to FIG. It changes depending on whether or not it has occurred.

  For example, when the control force is not applied by the turning assist control and the wheel speed sensors 52FL to 52RR are normal, the reference wheel speed Vwb is set to the lowest wheel speed Vmin among the wheel speeds of the four wheels. . And the control object wheel of traction control in this case is three wheels other than a reference | standard wheel.

  In addition, although the application of the control force by the turning assist control is not executed, any one of the wheel speed sensors 52FL to 52RR may be abnormal. In particular, when the abnormality of the wheel speed sensor is a low output abnormality, the reference wheel speed Vwb is set to the second lowest wheel speed Vmedlo among the wheel speeds of the four wheels. In this case, the traction control target wheels are two wheels other than the abnormal wheel and the reference wheel.

  In addition, although the application of the control force by the turning assist control is not executed, when the abnormality of the wheel speed sensor is the high output abnormality, the reference wheel speed Vwb is the wheel speed (Vmin, Vmedlo, Vmedhi) is set to the lowest wheel speed Vmin. In this case, the traction control target wheels are two wheels other than the abnormal wheel and the reference wheel.

  Further, when the control force is applied by the turning assist control and the wheel speed sensors 52FL to 52RR are normal, the reference wheel speed Vwb is the wheel speed (Vmedlo, Vmedhi, Vmax) of the three wheels except the turning inner rear wheel. ) Is set to the lowest wheel speed Vmedlo. In this case, the traction control target wheels are two wheels excluding the reference wheel and the turning inner rear wheel.

  Moreover, the application of the control force by the turning assist control is executed, and any one of the wheel speed sensors 52FL to 52RR other than the turning inner rear wheel may be abnormal. In particular, when the abnormality of the wheel speed sensor is an output reduction abnormality, the reference wheel speed Vwb is set to the lower wheel speed Vmedhi of the wheel speeds (Vmedhi, Vmax) of the two wheels other than the abnormal wheel and the turning rear rear wheel. The In this case, the control target wheel of the traction control is the wheel having the higher wheel speed among the two wheels other than the abnormal wheel and the turning inner rear wheel.

  In addition, when the control force is applied by the turning assist control and the wheel speed sensor abnormality is a high output abnormality, the reference wheel speed Vwb is the wheel speed (Vmedlo) of two wheels other than the abnormal wheel and the turning inner rear wheel. , Vmedhi), the lower wheel speed Vmedlo is set. In this case, the control target wheel of the traction control is the wheel having the higher wheel speed among the two wheels other than the abnormal wheel and the turning inner rear wheel.

  Therefore, according to the first embodiment, the reference wheel speed Vwb is appropriately set depending on whether braking force is applied by the turning assist control and whether or not an abnormality has occurred in the wheel speed sensor. Can do. In particular, when the control force is applied by the turning assist control, and the wheel speed sensors of the wheels other than the turning inner rear wheel have an abnormal output decrease, the reference wheel speed Vwb is prevented from being set to the wheel speed Vmedlo. In addition, it is possible to prevent the traction control from being performed inappropriately.

  Further, according to the first embodiment, the condition a5 is set as one of the permission conditions in step 100. Therefore, when the wheel speed sensor of the turning inner rear wheel is abnormal, it is determined that the permission condition for turning assist control is not satisfied even if a request to apply braking force to the turning inner rear wheel is generated by the turning assist control. The Therefore, in a situation where the wheel speed sensor of the turning inner rear wheel is abnormal, it is possible to prevent application of braking force by turning assist control to the turning inner rear wheel.

Second Embodiment FIG. 6 is a schematic configuration diagram showing a second embodiment of the vehicle travel control apparatus according to the present invention, and FIGS. 7 and 8 respectively show the turning assist control and the traction control in the second embodiment. It is a flowchart which shows a routine.

  In FIG. 6, the members corresponding to those shown in FIG. 1 are denoted by the same reference numerals as those in FIG. 7 and 8, the steps corresponding to the steps shown in FIGS. 2 and 3 are assigned the same step numbers as those shown in FIGS. 2 and 3, respectively. .

  In the second embodiment, as shown in FIG. 6, the braking pressure Pbi (i = fl, fr, rl, rr) is detected for each wheel, that is, the pressure in the wheel cylinders 46FL to 46RR. Pressure sensors 60FL to 60RR are provided. The braking force applied to the turning inner rear wheel by the turning assist control is controlled by controlling the braking pressure of the turning inner rear wheel to the target braking pressure.

  As shown in FIG. 7, the turning assist control is executed in the second embodiment in the same manner as in the first embodiment. However, in step 100, it is determined that the turning assist control permission condition is satisfied when all of the above-described a1 to a4 are satisfied. That is, the above-mentioned a5 is not one of the permission conditions for the turning assist control in the second embodiment.

  In step 500, the target of the rear wheel on the inside of the turn is set based on the absolute value of the steering angle θ so that the absolute value of the steering angle θ is larger than that when the absolute value of the steering angle θ is small. The braking pressure Pbrint is calculated. Then, it is determined whether or not the braking pressure Pbrin of the turning inner rear wheel has reached the target braking pressure Pbrint. Further, when a negative determination is made, the control is temporarily terminated, and when an affirmative determination is made, the control proceeds to step 600.

  Further, as shown in FIG. 8, the traction control in the second embodiment is executed in the same manner as in the first embodiment. However, if a negative determination is made in step 1250, the control proceeds to step 1300, but if an affirmative determination is made, the control proceeds to step 1500.

  In step 1500, the reference wheel speed Vwb is set and the driving slip ratio Sdri (i is fl, fr) when the braking force is applied to the rear inner wheel by the turning assist control according to the flowchart shown in FIG. , Rl, or rr).

  As shown in FIG. 9, steps 1510 to 1530 and steps 1540 to 1580 of the traction control are executed in the same manner as in the first embodiment. However, if an affirmative determination is made in step 1510, control proceeds to step 1520, but if a negative determination is made, control proceeds to step 1532.

  In step 1532, it is determined whether or not the wheel whose wheel speed sensor is abnormal is the rear turning inner wheel. When a negative determination is made, control proceeds to step 1540, and when an affirmative determination is made, control proceeds to step 1534.

  In step 1534, the reference wheel speed Vwb for calculating the drive slip ratio Sdri is set to the lowest wheel speed Vmin 'among the wheel speeds of the three wheels excluding the turning inner rear wheel.

  In step 1536, the drive slip ratio Sdri is calculated according to the above-described equation 1 for the two wheels other than the turning inner rear wheel and the reference wheel.

  Therefore, according to the second embodiment, as in the case of the first embodiment, the reference is based on whether braking force is applied by the turning assist control and whether an abnormality has occurred in the wheel speed sensor. The wheel speed Vwb can be set optimally. In particular, when the control force is applied by the turning assist control, and the wheel speed sensors of the wheels other than the turning inner rear wheel have an abnormal output decrease, the reference wheel speed Vwb is prevented from being set to the wheel speed Vmedlo. In addition, it is possible to prevent the traction control from being performed inappropriately.

  Further, according to the second embodiment, a5 in the first embodiment is not one of the permission conditions in Step 100. Therefore, if the pressure sensor of the rear inner wheel is normal even when the wheel speed sensor of the rear inner wheel is abnormal. A braking force is applied to the rear rear wheel by the turning assist control.

  In addition, when the control force is applied by the turning assist control and the wheel speed sensor of the turning inner rear wheel is abnormal, a negative determination and an affirmative determination are performed in steps 1510 and 1532, respectively. In step 1534, the reference wheel speed Vwb is set to the lowest wheel speed Vmin ′ among the wheel speeds of the three wheels excluding the turning inner rear wheel.

  Therefore, when the control force is applied by the turning assist control, and the wheel speed sensor of the turning inner rear wheel is abnormal, the reference wheel speed Vwb is prevented from being set to the wheel speed Vmedhi, and the traction control is performed. Inappropriate operation can be prevented.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

  For example, in the first embodiment described above, the turning assist control applies a braking force to the turning inner rear wheel until the turning inner rear wheel is locked. It may be modified so that the braking force is applied until the slip amount or the braking slip ratio reaches the reference value.

  In each of the above-described embodiments, the target pressure increasing gradient ΔPbrint of the rear turning inner wheel is calculated based on the absolute value of the steering angle θ, so that the target pressure increasing gradient corresponds to the absolute value of the steering angle θ. However, the target pressure increase gradient may be constant.

  In each of the above-described embodiments, the wheel speed of the predetermined wheel is set to the reference wheel speed of the traction control, but at the center of gravity of the vehicle based on the wheel speed of the predetermined wheel. The vehicle body speed may be calculated, and the vehicle body speed may be set to the reference wheel speed. Alternatively, the vehicle body speed at the position of the control target wheel may be calculated based on the vehicle body speed at the center of gravity of the vehicle, and the vehicle body speed may be set as the reference wheel speed of the corresponding control target wheel.

  In each of the above-described embodiments, the reduction of the wheel longitudinal force in the traction control is performed by applying a braking force to the wheel. However, the driving force can be reduced or the driving force can be reduced. And may be performed by applying a braking force.

  Further, in each of the above-described embodiments, the turning assist control applies a braking force to the turning inner rear wheel, but may apply a braking force to the turning inner front wheel. Further, a braking force may be applied to one turning inner wheel and a driving force may be applied to the turning outer wheel.

  In each of the above-described embodiments, oversteer suppression control and understeer suppression control are performed as vehicle motion control. However, these controls may not be performed.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 18 ... Transfer, 24 ... Engine control device, 26 ... Selection switch, 28 ... 4WD control device, 30 ... Front wheel differential, 36 ... Rear wheel differential, 42 ... Braking device, 50 ... Electronic control device for driving control, 52FL to 52RR ... wheel speed sensor, 54 ... vehicle speed sensor, 56 ... steering angle sensor, 58 ... turn assist switch, 60FL-60RR ... pressure sensor

Claims (4)

  Turning assist control for controlling the longitudinal force of the wheel so that the longitudinal force of the inner turning wheel becomes smaller than that of the outer turning wheel by reducing the longitudinal force of one turning inner wheel, and the wheel when the driving slip of the wheel is excessive In a four-wheel drive vehicle travel control device that performs traction control to reduce drive slip by reducing the longitudinal force of the vehicle, the vehicle has wheel speed detection means for detecting the wheel speed of each wheel, other than the turning inner wheel When the wheel speed detection means of one of the wheels has an abnormality in detecting the wheel speed as a value lower than the actual wheel speed, and the turning assist control is being executed, the three wheels except for the turning inner wheel A vehicle travel control device that sets a reference wheel speed for determining a driving slip of a wheel based on a second lowest wheel speed among wheel speeds.   When all the wheel speed detection means are normal and the turning assist control is being executed, to determine the driving slip of the wheel based on the lowest wheel speed of the three wheels excluding the turning inner wheel. The vehicle traveling control device according to claim 1, wherein a reference wheel speed is set.   When the turning assist control is being executed in a situation in which the wheel speed detecting means of one wheel other than the turning inner wheel detects a wheel speed as a value higher than the actual wheel speed, the turning inner wheel is being executed. And the wheel speed detecting means sets a reference wheel speed for determining the driving slip of the wheel based on the lower wheel speed of the two wheels excluding the abnormal wheel, and the wheel speed detecting means is abnormal. 2. The vehicle travel control apparatus according to claim 1, wherein a drive slip of the wheel is not determined for the wheel.   Braking force detection means for detecting the braking force of each wheel; in the turning assist control, the longitudinal force of the turning inner wheel is reduced based on the braking force of the turning inner wheel, and all wheel speed detection means are When the turning assist control is normal and the turning assist control is being performed, or the wheel speed detecting means of the turning inner wheel has an abnormality detecting the wheel speed as a value lower than the actual wheel speed, and the turning assistance The reference wheel speed for determining the driving slip of the wheel is set based on the lowest wheel speed among the wheel speeds of the three wheels excluding the turning inner wheel when the control is being executed. The vehicle travel control apparatus according to any one of 1 to 3.

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