JP2015006835A - Vehicular drive force distribution control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent excessive rise in a coupling temperature when engine torque reduction control is executed in a vehicular drive force distribution control device for a four-wheel drive automobile, the device including coupling control means for controlling a transmission amount to be transmitted by a coupling in accordance with a rotation speed difference detected by rotation speed difference detection means.SOLUTION: A vehicular drive force distribution control device includes calorific value calculation means (28) for calculating a calorific value of a coupling (9). Further, in the case of an increase amount per unit time of the calorific value calculated by the calorific value calculation means (28) being equal to or more than a set value, a transmission amount controlled by coupling control means (15) 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 controls the distribution of engine driving force in main and auxiliary driving wheels of a four-wheel drive vehicle.

Some vehicles are equipped with a driving force distribution control device that distributes driving force (torque) from an engine as a driving source to driving wheels in accordance with the traveling state of the vehicle.
In the four-wheel drive vehicle (4WD) drive force distribution control device, a vehicle that employs a 4WD mechanism that controls the drive force of the auxiliary drive wheel (rear wheel) with respect to the main drive wheel (front wheel) is another 4WD mechanism. Demand is higher than vehicles that use This is because the electronically controlled coupling acts as a torque limiter against excessive torque input to the 4WD mechanism, thereby making it possible to reduce the weight of the 4WD mechanism, thereby reducing the fuel consumption of other 4WD mechanisms. It is because it is good compared with the vehicle which employs.
As such a driving force distribution control device, there are the following prior art documents.

JP 2013-35378 A

  The driving force distribution device according to Patent Document 1 determines the abnormality of the temperature sensor according to the temperature state and the engine rotation off-time state, and distributes the driving force between the main driving wheel and the auxiliary driving wheel (sub driving wheel). It is intended to stabilize vehicle travel when switching from control to control that distributes driving force only to main drive wheels.

However, in a vehicle that employs a 4WD mechanism that determines the driving force to be distributed to the sub drive wheels from the running state of the vehicle or the like, if excessive torque is input to the electronically controlled coupling, The transmission torque is suppressed by the differential of the plate clutch, but at this time, the multi-plate clutch may generate heat and burn out. For this reason, usually, a control for avoiding damage to the 4WD mechanism is often incorporated by detecting such a state and weakening the coupling force of the multi-plate clutch by the fail-safe function to obtain the 2WD state. However, when the fail-safe function is activated, the original 4WD function is lost, so frequent intervention has been a factor in reducing the merchantability.
For this reason, when excessive torque is input, the engine torque of the engine that is the source of the torque is optimally controlled, and at the same time, the coupling torque of the electronically controlled coupling is optimally controlled. Control that can suppress heat generation, thereby avoiding damage to the 4WD mechanism, reducing the frequency of fail-safe control operation, and realizing maintenance of the 4WD function has been considered.
However, if the forward / backward differential rotation (ΔN) is large and the above control is activated and the heat generation of the coupling cannot be sufficiently suppressed, the 4WD required engine torque is not sufficiently reflected in the engine torque by the engine control. Further, in the case of a failure of a communication circuit with the engine control means, the 4WD mechanism may be damaged, and an improvement has been desired.

  Accordingly, the present invention provides a vehicle driving force distribution control device that prevents an excessive increase in the coupling temperature during execution of engine torque reduction control in a four-wheel drive vehicle equipped with an electronically controlled coupling. Objective.

  The present invention is a vehicle driving force distribution control device that controls the distribution of the driving force of the engine in the main and auxiliary driving wheels of a four-wheel drive vehicle, the coupling for varying the amount of transmission of the driving force from the engine, Main driving wheels to which the driving force of the engine is mainly transmitted; auxiliary driving wheels to which the driving force from the engine is transmitted through the coupling; engine control means for controlling engine torque of the engine; Rotational speed difference detecting means for detecting a rotational speed difference between the main driving wheel and the sub driving wheel, and a transmission amount transmitted by the coupling according to the rotational speed difference detected by the rotational speed difference detecting means is controlled. The vehicle driving force distribution control device includes a coupling control unit that includes a heat generation amount calculation unit that calculates a heat generation amount of the coupling, and is calculated by the heat generation amount calculation unit. When the amount of increase per unit calorific value time is not less than the set value, characterized by a minimum transmission amount that is controlled by said coupling control means.

  The present invention can prevent an excessive increase in the coupling temperature during execution of engine torque reduction control in a four-wheel drive vehicle equipped with an electronically controlled coupling.

FIG. 1 is a schematic configuration diagram of a vehicle equipped with a driving force distribution control device. (Example) FIG. 2 is a control block diagram of the driving force distribution control device. (Example) FIG. 3 is a flowchart for controlling to the 2WD mode when the estimated amount of heat generation from the start of engine torque reduction control is large per unit time. FIG. 4 is a time chart of the driving force distribution control during engine torque reduction. (Example)

  The present invention aims to prevent an excessive increase in the coupling temperature when the engine torque reduction control is executed in a four-wheel drive vehicle equipped with an electronically controlled coupling. This is realized by fixing the transmission amount of the ring torque to the minimum value.

1 to 4 show an embodiment of the present invention.
As shown in FIG. 1, a four-wheel drive vehicle (4WD vehicle: hereinafter referred to as “vehicle”) 1 is equipped with an engine 2 as a drive source and a transmission 3 coupled to the engine 2.
The transmission 3 is connected to a transfer 5 that constitutes a part of a driving force distribution control device 5 that controls the distribution of the driving force of the engine 2.
The transfer 5 is connected to a main drive shaft (front axle) 7 to which a left main drive wheel (left front wheel) 6L and a right main drive wheel (right front wheel) 6R are attached. The driving force of the engine 2 is mainly transmitted to the left main driving wheel 6L and the right main driving wheel 6R.
One end of the propeller shaft 8 is connected to the transfer 5. The other end of the propeller shaft 8 is connected to a differential 10 via a coupling 9. The coupling 9 is an electronically controlled coupling, which is a so-called torque distribution clutch, and varies the amount of driving force transmitted from the engine 2.
The differential 10 is connected to a sub drive shaft (rear axle) 12 to which a left sub drive wheel (left rear wheel) 11L and a right sub drive wheel (right rear wheel) 11R are attached. The driving force from the engine 2 is transmitted to the left auxiliary driving wheel 11L and the right auxiliary driving wheel 11R through the coupling 9.

The vehicle 1 has a configuration that employs a 4WD mechanism that determines a driving force to be distributed to the left auxiliary driving wheel (left rear wheel) 11L and the right auxiliary driving wheel (right rear wheel) 11R from the running state.
Therefore, the vehicle 1 includes an engine control means (ECM) 13, a rotational speed difference detection means (ABS) 14, a coupling control means (4WD) 15, so as to constitute a driving force distribution control device 4. And transmission control means (AT) 16.
The engine control means 13 is connected to the engine 2, the coupling control means 15, an accelerator opening sensor 17 via the engine 2, and a stop lamp switch 18 via the engine 2. This engine control means 13 controls the engine torque of the engine 2 and comprises an engine speed means 13A for obtaining engine speed information as shown in FIG. Degree information, stop lamp switch information, actual engine torque, and driver request torque are obtained, and on the output side, drive mode information and 4WD request engine torque are obtained.
The rotational speed difference detection means 14 includes a coupling control means 15, a left main drive wheel speed detection sensor 19L that detects the rotation speed of the left main drive wheel 6L, and a right main drive that detects the rotation speed of the right main drive wheel 6R. A wheel speed detection sensor 19R, a left sub drive wheel speed detection sensor 20L that detects the rotation speed of the left sub drive wheel 11L, and a right sub drive wheel speed detection sensor 20R that detects the rotation speed of the right sub drive wheel 11R are connected. doing. The rotational speed difference detecting means 14 detects a rotational speed difference (ΔN) between the main driving wheels 6L, 6R and the auxiliary driving wheels 11L, 11R. As shown in FIG. Get information during control execution.
As shown in FIG. 2, the coupling control means 15 is connected to the engine control means 13, the rotational speed difference detection means 14, the coupling 9, the combination meter 21, the drive selection switch 22, and the transmission 3. Transmission control means 16 is connected. Further, as shown in FIG. 2, the coupling control means 15 includes a four-wheel drive control unit 23, a drive system protection control unit 24, a CAN communication function unit 25, a fail safe control unit 26, a self-diagnosis. A functional unit 27, a heat generation amount calculation means 28 for calculating the heat generation amount of the coupling 9, and a storage means 29 for storing an estimated heat generation amount from the start of engine torque reduction control are provided. The coupling control means 15 controls the amount of transmission transmitted by the coupling 9 in accordance with the rotational speed difference (ΔN) detected by the rotational speed difference detection means 14.
The combination meter 21 makes a 4WD auto (AUTO) indicator lighting request and a 4WD lock (LOCK) indicator lighting request.
The drive selection switch 22 includes a 4WD switch 30 and a lock (LOCK) switch 31.

  The driving force distribution control device 4 according to this embodiment is controlled by the coupling control unit 15 when the amount of increase in the heat generation amount calculated by the heat generation amount calculation unit 28 per unit time is equal to or greater than a set value. The transmission amount is set to the minimum value. That is, the temperature of the coupling 9 is estimated from the heat generation amount of the coupling 9 calculated from the coupling torque and the rotational speed difference (ΔN), and when the excessive increase amount exceeds the set value, the 2WD state is achieved by fail-safe control. By switching to, the coupling 9 is prevented from being damaged due to an increase in the coupling temperature.

FIG. 3 shows a flowchart for controlling to the 2WD mode when the estimated amount of heat generation from the start of engine torque reduction control is large per unit time.
As shown in FIG. 3, when the program of the driving force distribution control device 4 is started (step A01), it is determined whether or not the increase amount of the estimated heat generation amount per unit time is equal to or larger than a set value (step A02). That is, in this step A02, the estimated heat generation amount from the start of engine torque reduction control is stored, and a determination is made based on the increase amount from the stored estimated heat generation value. The estimated heat generation amount is calculated from the integrated value based on the coupling torque and the rotational speed difference (ΔN). The set value is a value that does not exceed when damage to the coupling 9 can be avoided and there is no risk of damage.
If step A02 is YES, the mode is switched to the 2WD mode (step A03) (see A in FIG. 4). Thereby, since the coupling command torque is fixed at 0 [Nm], it is possible to suppress an increase in the coupling temperature and to avoid damage to the coupling 9.
After the process of step A03, or when the step A02 is NO, it is determined whether the switching to the 2WD mode is being performed and the return condition to the 4WD mode is satisfied (step A04).
If this step A04 is YES, the mode returns to the 4WD mode (step A05) (see B in FIG. 4). In step A05, the return condition to the 4WD mode is a case where the state where the rotational speed difference (ΔN) is equal to or less than the set value continues for a specified time or longer. This specified time is a time sufficient for the coupling temperature to fall to a range where it can be used regularly. Here, the 4WD mode indicates a state in which the coupling command torque is not fixed at 0 [Nm] and the optimum coupling torque is commanded by the driving force distribution control.
After step A05, or if step A04 is NO, the program is returned (step A06).

As a result, in this embodiment, when the amount of increase in the heat generation amount calculated by the heat generation amount calculation unit 28 per unit time is equal to or larger than the set value, the transmission amount controlled by the coupling control unit 15 is set to the minimum value. And
As a result, when the rise in the coupling temperature is steep, the transmission amount of the coupling torque can be fixed to the minimum value, the rise in the coupling temperature can be suppressed, and damage to the coupling 9 can be avoided. Can do.

  The vehicle driving force distribution control device according to the present invention can be applied not only to a four-wheel drive vehicle but also to various other vehicles such as two-wheel and three-wheel vehicles.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Engine 3 Transmission 4 Driving force distribution control apparatus 5 Transfer 6L Left main drive wheel 6R Right main drive wheel 9 Coupling 10 Differential 11L Left sub drive wheel 11R Right sub drive wheel 13 Engine control means 13A Engine rotation speed detection Means 14 Rotational speed difference detection means 15 Coupling control means 16 Transmission control means 19L Left main drive wheel speed detection sensor 19R Right main drive wheel speed detection sensor 20L Left sub drive wheel speed detection sensor 20R Right sub drive wheel speed detection sensor 28 Calorific value calculation means

Claims (1)

  A driving force distribution control device for a vehicle for controlling distribution of driving force of an engine in main and auxiliary driving wheels of a four-wheel drive vehicle, wherein a coupling for changing a transmission amount of driving force from the engine, and driving of the engine Main driving wheels to which power is mainly transmitted, auxiliary driving wheels to which driving force from the engine is transmitted through the coupling, engine control means for controlling engine torque of the engine, and the main driving wheels A rotational speed difference detecting means for detecting a rotational speed difference between the motor and the auxiliary drive wheel, and a coupling control for controlling a transmission amount transmitted by the coupling in accordance with the rotational speed difference detected by the rotational speed difference detecting means. A vehicle driving force distribution control device comprising: a heating value calculation means for calculating the amount of heat generated by the coupling; and a unit of heating value calculated by the heating value calculation means. If the increase amount per unit time is equal to or more than a set value, the vehicle driving force distribution control apparatus characterized by a minimum transmission amount that is controlled by said coupling control means.

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