JP6241592B2 - Vehicle driving force distribution control device - Google Patents

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 a driving force (torque) from an engine as a driving source to each driving wheel in accordance with the traveling state of the vehicle.
In the drive power distribution control device for a four-wheel drive vehicle (4WD vehicle), a vehicle that employs a 4WD mechanism that controls the drive force of the driven drive wheel (rear wheel) relative to the main drive wheel (front wheel) is the other 4WD. Demand is higher than vehicles that employ mechanisms. 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-A-5-178114

  When the differential adjustment type front and rear wheel driving force distribution control device according to Patent Document 1 is determined that the wheel is in a slip state based on the wheel speed information and the vehicle body speed information, the wheel speed value and the vehicle body speed value are calculated. The differential limit amount is controlled according to the difference between the front wheel (main drive wheel) and the rear wheel (sub drive wheel) to adjust the differential state between the front wheel and the front wheel to control the driving force distribution. is there.

However, in a vehicle that employs a 4WD mechanism that controls the driving force of the driven wheel relative to the main driving wheel, when excessive torque is input to the electronically controlled coupling, the multi-plate clutch in the coupling However, 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, and frequent intervention is a factor that causes a drop in the merchantability, so improvement has been desired.

  Accordingly, the present invention provides a four-wheel drive vehicle equipped with an electronically controlled coupling. When the main drive wheel slips, the engine torque and the coupling torque are limited, thereby reducing the coupling torque to zero ( It is an object of the present invention to provide a vehicular driving force distribution control device that suppresses heat generation of a coupling without being in a 2WD state.

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. A vehicle driving force distribution control device including a coupling control means for performing the engine control when the rotational speed difference detected by the rotational speed difference detection means is greater than or equal to a set value. Run the first reduction control amount engine torque is reduced by means thereafter when said first reduction control is determined to continue to run the first set time or more, the by the coupling control means It is determined that the second reduction control in which the amount of transmission transmitted by the coupling is reduced , and that the second reduction control has been continuously executed for a second set time that is greater than the first set time. In this case, the second reduction control is terminated .

  In this invention, in a four-wheel drive vehicle equipped with an electronically controlled coupling, when the main drive wheel idles, the engine torque and the coupling torque are limited so that the coupling torque is zero (2WD state). Without generating, the heat generation of the coupling can be suppressed.

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 of engine torque reduction start / end control. (Example) FIG. 4 is a time chart of engine torque reduction start / end control. (Example) FIG. 5 is a flowchart of four-wheel drive (4WD) required engine torque instantaneous value calculation control. (Example) FIG. 6 is a time chart of the four-wheel drive (4WD) required engine torque instantaneous value calculation control. (Example) FIG. 7A is an explanatory diagram of a method for determining the smoothing coefficient in the increasing direction in the four-wheel drive (4WD) required engine torque instantaneous value calculation control. FIG. 7B is an explanatory diagram of a method of determining the smoothing coefficient in the decreasing direction in the four-wheel drive (4WD) required engine torque instantaneous value calculation control. (Example) FIG. 8 is a flowchart of coupling command torque control during engine torque reduction. (Example) FIG. 9 is a time chart of coupling command torque control during engine torque reduction. (Example)

  In the four-wheel drive vehicle equipped with the electronically controlled coupling, the present invention limits the engine torque and the coupling torque when the main drive wheel idles, thereby reducing the coupling torque to zero (2WD state). ), The first reduction control is executed to reduce the engine torque when the rotational speed difference between the main drive wheel and the sub drive wheel is greater than or equal to the set value. And when it determines with this 1st reduction control having been performed continuously beyond setting time, it implement | achieves by performing 2nd reduction control by which the transmission amount which a coupling transmits is reduced.

1 to 9 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 4 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. The engine control means 13 controls the engine torque of the engine 2 and, as shown in FIG. 2, on the input side, accelerator opening information, engine speed information, stop lamp switch information, actual engine torque, While obtaining the driver required torque, on the output side, the drive mode information and the 4WD required 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. The coupling control unit 15 includes a 4WD control unit 23, a drive system protection control unit 24, a CAN communication function unit 25, a fail safe control unit 26, and a self diagnosis function unit 27. The coupling control means 15 controls the amount of transmission transmitted by the coupling 9 in accordance with the rotational speed difference 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 28 and a lock (LOCK) switch 29.

The driving force distribution control device 4 according to this embodiment is configured so that the rotational speed difference between the main driving wheels 6L, 6R and the auxiliary driving wheels 11L, 11R detected by the rotational speed difference detecting means 14 (the rotational difference between the front and rear of the coupling 9: When ΔN) is equal to or larger than the set value, the first reduction control in which the engine torque is reduced by the engine control means 13 is executed, and it is determined that the first reduction control is continuously executed for the set time or more. In that case, the second reduction control is executed in which the amount of transmission transmitted by the coupling 9 is reduced by the coupling control means 15.
Further, the driving force distribution control device 4 performs the difference in rotational speed (ΔN) between the main driving wheels 6L, 6R and the auxiliary driving wheels 11L, 11R detected by the rotational speed difference detecting means 14 during the execution of the first reduction control. ) Is less than a set value or when the engine speed detected by the engine control means 13 is less than or equal to a predetermined value continues for a predetermined time, the regulated engine torque is operated toward the end of the first reduction control. Gradually recover to the engine torque required by the user.

Next, driving force distribution control according to this embodiment will be described.
FIG. 3 shows a flowchart of engine torque reduction start / end control.
As shown in FIG. 3, when the program is started (step A01), it is first determined whether or not an engine torque reduction control start condition is satisfied (step A02). This prevents engine torque reduction from operating only in situations where it is necessary to avoid damage to the 4WD mechanism, and prevents engine torque reduction from occurring in other situations. Because. Here, the engine torque reduction control start condition is that the coupling command torque is not less than a specified value, the rotation speeds of the main drive wheels 6L and 6R are not less than a specified value, and the rotation speeds of the auxiliary drive wheels 11L and 11R are Suppose that the condition below the specified value continues for a specified time.
If this step A02 is YES, engine torque reduction control is started (step A03). That is, in this step A03, the first reduction control is executed.
Then, it is determined whether or not an engine torque reduction control end condition (see A in FIG. 4) is satisfied (step A04). This is because the engine torque reduction operation continues only in situations where it is necessary to avoid damage to the 4WD mechanism, and in other situations the engine torque reduction is terminated. Here, the engine torque reduction control end condition is that the state where the 4WD required engine torque is equal to or higher than the driver required engine torque continues for the set time, or the state where the coupling command torque is equal to or less than the specified value is set time. It is assumed that the set time has elapsed since the start of engine torque reduction.
If this step A04 is YES, the engine torque reduction control is terminated (step A05) (see C in FIG. 4).
On the other hand, if step A04 is NO, it is determined whether or not the 4WD request engine torque return start condition (see B in FIG. 4) to the driver request engine torque is satisfied (step A06). This is due to the difference in the rotational speed of the coupling 9 (here, the rotational speed difference (ΔN) between the main drive wheels 6L, 6R and the sub drive wheels 11L, 11R) or the engine rotational speed. This is to determine whether or not the situation should be avoided. Here, the 4WD required engine torque return start condition to the driver required engine torque is a condition in which the front-rear rotational difference (ΔN) of the coupling 9 is equal to or less than a specified value or a state where the engine speed is equal to or less than a specified value. Suppose that it continues.
When this step A06 is NO, it returns to said step A04.
If this step A06 is YES, a 4WD request engine torque return to the driver request engine torque is started (step A07). That is, in step A07, the control is returned to step A04 so that the regulated engine torque is gradually recovered to the engine torque requested by the driver toward the end of the first reduction control.
After the process of step A05, or when step A02 is NO, the program is ended (step A08).

FIG. 5 shows a flowchart of 4WD request engine torque instantaneous value calculation control.
As shown in FIG. 5, when the program is started (step B01), it is determined whether it is within a set time from the start of engine torque reduction control (step B02). This is because the rotation speed of the main drive wheels 6L, 6R often increases in the direction immediately after the start of engine torque reduction, and it is necessary to reverse this in the direction of decrease, which requires a large engine torque reduction instantaneously. This is because of this.
If this step B02 is YES, a 4WD required engine torque instantaneous value is calculated from a torque calculation table centered on the engine torque (step B03) (see A in FIG. 6).
If this step B03 is NO, it is determined whether or not the 4WD required engine torque is being returned to the driver required engine torque (step B04).
When step B04 is YES, the driver request torque is set to the 4WD request engine torque instantaneous value (step B05) (see C in FIG. 6).
If this step B05 is NO, a 4WD required engine torque instantaneous value is calculated from a torque calculation map using the engine torque and the forward / backward rotation difference (ΔN) of the coupling 9 as an axis (step B06) (B in FIG. 6). reference). That is, in step B06, a value that does not stall the engine while suppressing the front-rear rotation difference (ΔN) of the coupling 9 is calculated from the engine torque and the front-rear rotation difference (ΔN).
After the process of step B03, after the process of step B05, or after the process of step B06, the program is returned (step B07).
Note that the 4WD required engine torque is calculated by adding a smoothing to the 4WD required engine torque instantaneous value. This is intended to suppress a sudden change in engine torque and prevent a large behavior change from occurring in the vehicle 1. The above annealing defines the maximum amount of change in the 4WD required engine torque from the previous value to the current value.
Specifically, FIGS. 7A and 7B show a method of determining the smoothing coefficient.
First, from the comparison of the previous value of the 4WD required engine torque and the instantaneous value of the 4WD required engine torque, it is determined whether the direction is increasing or decreasing. Then, the smoothing coefficient is determined from the instantaneous value of the 4WD required engine torque. Thus, by setting the smoothing coefficient based on whether the engine is increasing (see FIG. 7A) or decreasing (see FIG. 7B) and the instantaneous value of the 4WD required engine torque, a sudden engine It is possible to suppress a change in torque, cause a large behavior change in the vehicle 1 and reach the target value as quickly as possible.

FIG. 8 shows a flowchart of coupling command torque control during engine torque reduction.
As shown in FIG. 8, when the program starts (step C01), it is first determined whether or not a set time A has elapsed since the start of engine torque reduction (step C02). This set time A is set to a sufficient time that the difference in forward and backward rotation (ΔN) of the coupling 9 is suppressed by engine torque reduction, and the performance of the 4WD mechanism is not greatly deteriorated even if the maximum coupling command torque is limited. The purpose is to suppress the heat generation of the coupling 9 by limiting the command torque.
When this step C02 is YES, the limitation of the maximum coupling command torque is started (step C03) (see A in FIG. 9). That is, in this step C03, the second reduction control is executed.
Then, it is determined whether or not a set time B longer than the set time A has elapsed since the start of engine torque reduction (step C04). This set time B is a sufficient time for the driver to determine that the vehicle state will not change even if the operation is continued in the current vehicle state. By switching to the 2WD mode, the forward / backward rotation difference of the coupling 9 ( By generating a large ΔN) and making the driver feel a slip state, the driver is encouraged to perform an operation different from the current state, and damage to the 4WD mechanism due to heat generated by the coupling 9 is avoided. It is an object.
When this step C04 is YES, the mode is switched to the 2WD mode, and the maximum coupling command torque limit is terminated (step C05) (see B in FIG. 9). Here, the 2WD mode indicates a state where the coupling command torque is fixed at 0 [Nm].
After step C05, if step C02 is NO, or if step C04 is NO, it is determined whether switching to 2WD mode is being performed and whether the return condition to 4WD mode is satisfied (step C06). ). The return condition to the 4WD mode is that the rotational speed before the coupling 9 is less than the specified value and the rotational speed after the coupling 9 is less than the specified value, or the rotational speed before the coupling 9 is It is assumed that the rotation speed after the coupling 9 is equal to or higher than the specified value and the rotation speed after the coupling 9 is equal to or higher than the specified value.
When this step C06 is YES, it returns to the 4WD mode (step C07) (see C in FIG. 9). 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 the process of step C07 or when the step C06 is NO, the program is returned (step C08).

Generally, in a vehicle that employs a 4WD mechanism that determines the driving force to be distributed to the auxiliary drive wheels (rear wheels) from the running state of the vehicle, etc., when starting on a snowy road or mud road, the side brake is returned. When starting in a forgotten state or when the auxiliary drive wheel (rear wheel) is stuck in a cold region, the main drive wheel (front wheel) is largely idled, so that the torque is transmitted to the auxiliary drive wheel (rear wheel). When a large differential is generated in the electronically controlled coupling, the coupling may generate heat and the 4WD mechanism may be damaged. Further, in order to avoid damage to the 4WD mechanism, fail-safe control is activated, and the 2WD state is entered and the 4WD function may be lost.
For this reason, in the embodiment, in the situation where the main drive wheels 6L and 6R are idling largely, when an excessive torque is input, the engine torque of the engine 2 is optimally controlled and at the same time electronically controlled. The coupling torque of the coupling 9 is optimally controlled to suppress the heat generation of the coupling 9, thereby avoiding damage to the 4WD mechanism and reducing the frequency of fail-safe control operation. Can be maintained.

According to the embodiment of the present invention, when the rotational speed difference (ΔN) between the main drive wheels 6L, 6R and the sub drive wheels 11L, 11R detected by the rotational speed difference detecting means 14 is equal to or larger than a set value, the engine When it is determined that the first reduction control in which the engine torque amount is reduced by the control means 13 and then this first reduction control is continuously executed for the first set time A or longer, the coupling control means 15, the second reduction control in which the transmission amount transmitted by the coupling 9 is reduced is determined, and it is determined that the second reduction control has been continuously executed for a second set time B longer than the first set time A. If so, the second reduction control is terminated .
Thereby, when the idling of the main drive wheels 6L and 6R is detected, the cooperative control of the engine control means 13 and the coupling control means 15 can suppress the heat generation of the coupling 9 while maintaining the 4WD state. it can.
Further, during the execution of the first reduction control, the rotational speed difference (ΔN) detected by the rotational speed difference detecting means 14 is not more than a set value or the engine speed detected by the engine control means 13 is not more than a predetermined value. When the state continues for a predetermined time, the regulated engine torque is gradually recovered to the engine torque requested by the driver toward the end of the first reduction control.
As a result, at the end of the engine torque limit, the regulated engine torque is recovered to the engine torque requested by the driver, so that the driving state requested by the driver can be quickly achieved. Further, the engine torque being regulated can be gradually changed toward the end of the first reduction control, and the behavior change of the vehicle 1 at the end of the first reduction control can be suppressed.

  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 (ECU)
14 Rotational speed difference detection means (ABS)
15 Coupling control means (4WD)
16 Transmission control means (AT)
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

Claims (2)

A vehicle driving force distribution control device for controlling distribution of engine driving force in main and auxiliary driving wheels of a four-wheel drive vehicle,
A coupling that varies a transmission amount of driving force from the engine;
Main driving wheels to which the driving force of the engine is mainly transmitted;
Auxiliary driving wheels to which driving force from the engine is transmitted via the coupling;
Engine control means for controlling engine torque of the engine;
A rotational speed difference detecting means for detecting a rotational speed difference between the main drive wheel and the sub drive wheel;
A vehicle driving force distribution control device comprising: a coupling control unit that controls a transmission amount transmitted by the coupling in accordance with a rotational speed difference detected by the rotational speed difference detection unit;
When the rotational speed difference detected by the rotational speed difference detection means is a set value or more,
Performing a first reduction control in which the engine torque is reduced by the engine control means;
Thereafter, when it is determined that the first reduction control has been continuously executed for the first set time or longer, the second reduction control is executed in which the amount of transmission transmitted by the coupling is reduced by the coupling control means. and,
And when it determines with said 2nd reduction control having been continuously performed more than 2nd setting time larger than said 1st setting time, said 2nd reduction control is complete | finished for vehicles characterized by the above-mentioned. Driving force distribution control device.   During execution of the first reduction control, a state in which the rotational speed difference detected by the rotational speed difference detecting means is not more than a set value or the engine speed detected by the engine control means is not more than a predetermined value continues for a predetermined time. 2. The vehicle driving force distribution control according to claim 1, wherein when the first reduction control is finished, the regulated engine torque is gradually recovered to the engine torque requested by the driver. apparatus.

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