JP2015006834A - Vehicular drive force distribution control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of engine stalling in a case where an engine revolution speed decreases while engine torque reduction control is executed in a vehicular drive force distribution control device including a coupling for varying drive force transmitted to a secondary drive wheel.SOLUTION: A vehicular drive force distribution control device, for use in controlling a transmission amount of drive force a coupling transmitting to a secondary drive wheel in accordance with a rotation speed difference between primary and secondary drive wheels, includes reduction control means for executing engine torque reduction control so that engine control means reduces engine torque in a case where the rotation speed difference detected by rotation speed difference detection means is equal to or more than a set value. Further, in the case of an engine rotation speed detected by engine speed detection means being equal to or less than the set value while the reduction control means executes the engine torque reduction control, a transmission amount of drive force of the coupling controlled by coupling-control means is set at a minimum value.

Description

  The present invention relates to a vehicular driving force distribution control device, and more particularly to a vehicular driving force distribution control device that distributes the driving force of an engine to main driving wheels and sub driving wheels in accordance with a vehicle running state.

A four-wheel drive vehicle that drives all of the front and rear wheels includes a main drive wheel that mainly transmits the driving force of the engine and a sub-drive wheel that transmits the driving force from the engine via the coupling. Many vehicular driving force distribution control devices have been devised that control the amount of driving force transmitted from the coupling to the auxiliary driving wheel in accordance with the difference in rotational speed between the driving wheel and the auxiliary driving wheel.
A conventional vehicle driving force distribution control device is a vehicle driving force distribution control device that distributes driving force to a plurality of wheels at a preset distribution ratio, and the rotation of a wheel braked during downhill traveling. By changing the preset distribution ratio so as to increase the driving force of the wheels below the lower limit rotation speed when the speed becomes the lower limit rotation speed or less, the vehicle speed is avoided while avoiding the wheel lock. A technique that prevents the increase of the value is disclosed.

JP 2007-261666 A

By the way, in the vehicular driving force distribution control device that controls the driving force of the auxiliary driving wheel with respect to the main driving wheel, the transmission amount of the driving force transmitted to the auxiliary driving wheel due to the idling of the main driving wheel is variable. Excessive torque may be input to the coupling. In such a state, the transmission torque is suppressed by the differential of the multi-plate clutch in the coupling. However, at this time, the multi-plate clutch generates heat due to the differential and may be damaged.
Therefore, in the vehicular driving force distribution control device, when such a state is detected, the coupling of the multi-plate clutch is weakened by fail-safe to reduce the driving force transmitted to the auxiliary driving wheels. In many cases, control for avoiding damage to the coupling is incorporated by setting the two-wheel drive state in which the drive force of the drive wheel is increased.

However, when the failsafe for the coupling is activated and the amount of driving force transmitted to the auxiliary drive wheels is reduced, the original four-wheel drive function is lost. This is a factor that causes a decline.
Therefore, when excessive torque is input to the coupling, the torque of the engine that is the source of the torque is optimally controlled, and at the same time, the transmission torque of the coupling is optimally controlled to suppress the heat generation of the coupling. Can be considered. Thereby, damage to the coupling can be avoided, the operation frequency of the fail safe control can be suppressed, and the maintenance of the four-wheel drive function can be realized.
However, in order to control excessive torque input to the coupling to reduce the torque of the engine that is the generation source, depending on the vehicle state, engine torque reduction control may cause a decrease in engine rotation speed. Stalls may occur.

  The present invention provides a vehicular driving force distribution control device having a coupling that varies a driving force transmitted to a sub driving wheel when an engine speed decreases during execution of engine torque reduction control. The purpose is to avoid the occurrence of.

  The present invention is a vehicle driving force distribution control device that controls the distribution of driving force in front and rear wheels of a four-wheel drive vehicle, the coupling for varying the amount of driving force transmitted from the engine, and the driving of the engine Engine control means for controlling torque of the engine, comprising: main drive wheels to which power is mainly transmitted; and sub drive wheels to which drive power from the engine is transmitted via the coupling; An engine rotational speed detecting means for detecting a rotational speed, a rotational speed difference detecting means for detecting a rotational speed difference between the main driving wheel and the sub driving wheel, and a rotational speed difference detected by the rotational speed difference detecting means. And a coupling control means for controlling the transmission amount of the driving force transmitted by the coupling in response to the rotation speed difference detecting means. When the difference in rotation speed is greater than or equal to a set value, the engine control means includes reduction control means for executing engine torque reduction control so that the engine torque is reduced, and the reduction control means is configured to reduce the engine torque reduction control. When the engine rotation speed detected by the engine rotation speed detection means is equal to or lower than a set value during execution of the control, the transmission amount of the coupling driving force controlled by the coupling control means is set to the minimum value. It is characterized by that.

  In the present invention, when the engine rotational speed becomes equal to or lower than the set value during execution of the engine torque reduction control, the engine rotational speed can be increased by minimizing the transmission amount of the coupling driving force. , Engine stall can be avoided.

FIG. 1 is a system configuration diagram of a vehicle driving force distribution control device. (Example) FIG. 2 is a system input / output diagram of the vehicle driving force distribution control device. (Example) FIG. 3 is a flowchart of switching control to the two-wheel drive state. (Example) FIG. 4 is a flowchart of the return control to the four-wheel drive state. (Example) FIG. 5 is a diagram showing a change in engine rotation speed during engine torque reduction control. (Example)

  Embodiments of the present invention will be described below with reference to the drawings.

1 to 5 show an embodiment of the present invention. In FIG. 1, a vehicle 1 has an engine 2 and a transmission 3 mounted horizontally in a front portion, and an inner end of a right front axle 5 and a left front axle 6 is connected to a front differential 4, and a right front axle 5 and a left front axle are connected. A right front wheel 7 and a left front wheel 8 are attached to the outer ends of 6 respectively.
In the vehicle 1, the transfer 9 is connected to the transmission 3, and the front end of the propeller shaft 10 is connected to the transfer 9. The propeller shaft 10 has a rear end coupled to a rear differential 12 via a driving force distribution coupling 11. The rear differential 12 is connected to the inner ends of the right rear axle 13 and the left rear axle 14, and the right rear wheel 15 and the left rear wheel 16 are attached to the outer ends of the right rear axle 13 and the left rear axle 14, respectively. .
The vehicle 1 transmits the driving force generated by the engine 2 to the right front wheel 7 and the left front wheel 8 via the transmission 3, the front differential 4, the right front axle 5 and the left front axle 6, and the right front wheel 7 and the left front wheel 8 are transmitted. Drive as main drive wheel. Further, the vehicle 1 uses the propulsion shaft 10, the coupling 11, the rear differential 12, the right rear axle 13 and the left rear axle 14 to drive the driving force of the engine 2 taken out by the transfer 9 to the right rear wheel 15 and the left rear. This is transmitted to the wheel 16, and the right rear wheel 15 and the left rear wheel 16 are driven as auxiliary driving wheels.
Therefore, the vehicle 1 is a four-wheel drive vehicle that drives all of the front wheels 5 and 6 and the rear wheels 15 and 16 by the driving force of the engine 1.

The coupling 11 has a multi-plate clutch capable of electronically controlling the coupling force, and is connected to the vehicle driving force distribution control device 17. The vehicle driving force distribution control device 17 controls the fastening force of the coupling 11 according to the traveling state of the vehicle 1, and the right rear wheel of the auxiliary driving wheel with respect to the right front wheel 7 and the left front wheel 8 of the main driving wheel. 15 and the driving force of the engine 2 transmitted to the left rear wheel 16 is varied.
As shown in FIG. 2, the vehicle driving force distribution control device 17 includes a four-wheel drive control unit 18, a drive system protection control unit 19, a CAN (in-vehicle LAN) communication function unit 20, a fail-safe control unit 21, and a self-diagnosis. And a functional unit 22.

The drive selection switch 23 is directly connected to the input side of the vehicle driving force distribution control device 17, and the engine control means 24, the transmission control means 25, and the antilock brake system 26 communicate with CAN communication (in-vehicle LAN).
The drive selection switch 23 includes a four-wheel drive switch 27 and a lock switch 28. Four-wheel drive and lock drive selection information is input from the drive selection switch 23.
The engine control means 24 includes an accelerator opening detection means 29 for detecting the accelerator opening of the accelerator pedal, an engine rotation speed detection means 30 for detecting the rotation speed of the engine 2 (engine rotation speed), and a stop lamp switch 31 for the brake pedal. The engine torque detecting means 32 for detecting the actual torque (engine torque) of the engine 2 and the driver required torque detecting means 33 for detecting the torque requested by the driver are provided to control the torque of the engine 2. From the engine control means 24, accelerator opening information, engine rotation speed information, stop lamp switch information, engine torque information, and driver request torque information are input.
The transmission control means 25 has a shift position switch 34 and controls the shift state of the transmission 3. Shift position information is input from the transmission control means 25.
The anti-lock brake system 26 has a right front wheel rotation speed detection means 35, a left front wheel rotation speed detection means 36, a right rear wheel rotation speed detection means 37, and a left rear wheel rotation speed detection means 38. , 15 and 16 are controlled. From the anti-lock brake system 26, wheel rotational speed information of the wheels 7, 8, 15 and 16 detected by the detecting means 35, 36, 37, and 38 and control execution information of the anti-lock brake are input.

Further, the coupling 11 is directly connected to the output side of the vehicle driving force distribution control device 17, and the engine control means 24 and the combination meter 39 are connected by CAN communication (in-vehicle LAN). Yes.
The vehicle driving force distribution control device 17 executes four-wheel drive control by the four-wheel drive control unit 18 based on various pieces of input information, and the CAN communication function unit 20 sends drive selection information and four-wheels to the engine control means 24. Drive request engine torque information is output, and the CAN communication function unit 20 outputs four wheel drive auto indicator light request / lock indicator light request information to the combination meter 39. Further, the drive system protection control unit 19 and the fail safe Processing by the control unit 21 and the self-diagnosis unit 22 is performed.

The vehicle driving force distribution control device 17 includes the coupling 11 that makes a transmission amount of driving force from the engine 2 variable, and the right front wheel 7 that is a main driving wheel to which the driving force of the engine 2 is mainly transmitted. And the left front wheel 8 and the right rear wheel 15 and the left rear wheel 16, which are auxiliary driving wheels to which the driving force from the engine 2 is transmitted via the coupling 11.
The vehicle driving force distribution control device 17 includes the engine control means 24 that controls the torque of the engine 2, the engine rotation speed detection means 30 that detects the rotation speed of the engine 2, and the right that is the main drive wheel. A rotational speed difference detecting means 40 for detecting a rotational speed difference between the front wheel 7 and the left front wheel 8 and the right rear wheel 15 and the left rear wheel 16 as auxiliary driving wheels, and a rotational speed difference detected by the rotational speed difference detecting means 40. And a coupling control means 41 for controlling the transmission amount of the driving force transmitted by the coupling 11 according to the above.
Thereby, the vehicle driving force distribution control device 17 performs the four-wheel drive control by the four-wheel drive control unit 18 according to the traveling state of the vehicle 1, and the right front wheel 7 and the left front wheel 8 that are the main drive wheels. And the distribution of driving force in the right rear wheel 15 and the left rear wheel 16 which are auxiliary driving wheels.
The vehicle driving force distribution control device 17 includes a reduction control means 42. The reduction control means 42 executes engine torque reduction control so that the engine torque is reduced by the engine control means 24 when the rotational speed difference detected by the rotational speed difference detection means 40 is greater than or equal to a set value. . The vehicle driving force distribution control device 17 performs coupling when the engine speed detected by the engine speed detecting means 40 is equal to or lower than the set value while the reduction control means 42 is executing the engine torque reduction control. The transmission amount of the driving force of the coupling 11 controlled by the control means 41 is set to the minimum value.
The vehicle driving force distribution control device 17 transmits the driving force of the engine 2 to the right rear wheel 15 and the left rear wheel 16 which are auxiliary driving wheels by setting the transmission amount of the driving force of the coupling 11 to a minimum value. Instead, the vehicle 1 is brought into a two-wheel drive state by transmitting only to the right front wheel 7 and the left front wheel 8 which are main drive wheels.

Next, the operation will be described.
The vehicle driving force distribution control device 17 avoids engine stall by controlling the vehicle 1 to a two-wheel drive state when the engine rotation speed decreases during execution of engine torque reduction control.
As shown in FIG. 3, the vehicle driving force distribution control device 17 minimizes the amount of transmission of the driving force of the coupling 11 when the program for switching control to the two-wheel driving state starts in the four-wheel driving state (S01). It is determined whether a switching condition for setting the two-wheel drive state as a value is satisfied (S02). The condition for switching to the two-wheel drive state is satisfied when the engine torque reduction control is being executed and the engine rotational speed has dropped below the set value for rotational speed determination (t1 in FIG. 4).
If this determination (S02) is YES, the transmission amount of the driving force of the coupling 11 is switched to the two-wheel drive state with the minimum value (S03), and the process returns to the determination (S02) (S04). If this determination (S02) is NO, the process returns to determination (S02) (S04).
The driving force of the engine 2 is such that the driving force of the engine 2 is not transmitted to the right rear wheel 15 and the left rear wheel 16 which are auxiliary driving wheels by setting the transmission amount of the coupling 11 to a minimum value. It is transmitted only to certain right front wheel 7 and left front wheel 8. At this time, the engine 2 can be freely differentially coupled to the coupling 11, thereby increasing the engine rotation speed and avoiding engine stall.
As a technique for avoiding engine stall, a method of ending engine torque reduction control is also conceivable. However, the end of the engine torque reduction control does not change the transmission amount of the coupling 11, which is a fundamental factor that suppresses the increase in the engine rotation speed, and the engine torque reduction from the end of the engine torque reduction control to a sufficient engine torque that does not stall the engine. Since the time during which the coupling 11 can be freely differentiated after the command torque for coupling the coupling 11 is set to 0 Nm is sufficiently smaller than the return time, the transmission amount of the driving force of the coupling 11 Control with a minimum value is effective in avoiding engine stall.

As shown in FIG. 4, the vehicle driving force distribution control device 17 starts a program for return control to the four-wheel driving state in the two-wheel driving state in which the transmission amount of the driving force of the coupling 11 is minimized ( S05), it is determined whether a return condition for setting the four-wheel drive state with the transmission amount of the driving force of the coupling 11 as an appropriate value is satisfied (S06).
When this determination (S06) is YES, the state is returned to the four-wheel drive state in which the transmission amount of the driving force of the coupling 11 is an appropriate value (S07), and the process returns to the determination (S06) (S08). If this determination (S06) is NO, the process returns to determination (S06) (S08).
In the determination (S06), the differential of the coupling 11 is settled by the information on the rotational speed on the front side of the coupling 11 (input rotational speed) and the rotational speed on the rear side of the coupling 11 (output rotational speed). It is determined whether it is possible to return to the four-wheel drive state. The return condition to the four-wheel drive state is switching to the two-wheel drive state, the input rotation speed of the coupling 11 is less than the input side specified value, and the output rotation speed of the coupling 11 is less than the output side specified value. Alternatively, it is assumed that the input rotation speed of the coupling 11 is equal to or higher than the input side specified value and the output side rotation speed of the coupling 11 is equal to or higher than the output side specified value (t2 in FIG. 4).
The four-wheel drive state here indicates a state in which the command torque for coupling the coupling 11 is not fixed at 0 Nm, and the optimum command torque is commanded to the coupling 11 by the driving force distribution control.

Thus, in the vehicle driving force distribution control device 17, the rotational speed difference between the right front wheel 7 and the left front wheel 8 as the main driving wheels and the right rear wheel 15 and the left rear wheel 16 as the auxiliary driving wheels is equal to or larger than the set value. In this case, engine torque reduction control is executed so that the engine torque is reduced. When the engine speed is equal to or lower than the set value during execution of the engine torque reduction control, the driving force of the coupling 11 is Is the minimum value.
As a result, the vehicle driving force distribution control device 17 sets the transmission amount of the driving force of the coupling 11 to the minimum value when the engine rotational speed becomes a set value or less during execution of the engine torque reduction control. The engine speed can be increased, and the engine stall can be avoided.

  The present invention can avoid an engine stall when the engine rotational speed becomes a set value or less during execution of the engine torque reduction control, and can be applied not only to a four-wheeled vehicle but also to a two-wheeled vehicle.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Engine 3 Transmission 4 Front differential 7 Right front wheel 8 Left front wheel 9 Transfer 10 Propeller shaft 11 Coupling 12 Rear differential 15 Right rear wheel 16 Left rear wheel 17 Vehicle drive force distribution control device 18 Four-wheel drive control unit 24 Engine control device 25 Transmission control device 26 Anti-lock brake system 30 Engine rotation speed detection means 35 Right front wheel rotation speed detection means 36 Left front wheel rotation speed detection means 37 Right rear wheel rotation speed detection means 38 Left rear wheel rotation speed detection means 40 Rotational speed difference detection means 41 Coupling control means 42 Reduction control means

Claims (1)

  A vehicle driving force distribution control device that controls the distribution of driving force in the front and rear wheels of a four-wheel drive vehicle, wherein a coupling that varies a transmission amount of driving force from an engine, and the driving force of the engine are mainly used An engine control means for controlling the torque of the engine; and a rotational speed of the engine, comprising: a main drive wheel to be transmitted; and a sub drive wheel to which a driving force from the engine is transmitted via the coupling. An engine rotational speed detecting means, a rotational speed difference detecting means for detecting a rotational speed difference between the main driving wheel and the sub driving wheel, and the cup according to the rotational speed difference detected by the rotational speed difference detecting means. A vehicle driving force distribution control device including a coupling control means for controlling a transmission amount of the driving force transmitted by the ring, wherein the rotational speed difference detected by the rotational speed difference detection means is When it is equal to or greater than a predetermined value, the engine control means includes a reduction control means for executing engine torque reduction control so that the engine torque is reduced, and the reduction control means is executing the engine torque reduction control. When the engine rotation speed detected by the engine rotation speed detection means is less than or equal to a set value, the transmission amount of the coupling driving force controlled by the coupling control means is set to a minimum value. Vehicle driving force distribution control device.

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