JP7317291B2 - Vehicle driving force distribution control system - Google Patents

Description

The present invention relates to a vehicle driving force distribution control system, and more particularly to a vehicle driving force distribution control system for controlling the amount of driving force distributed to the front and rear wheels of a four-wheel drive vehicle capable of towing a towed vehicle.

Conventionally, the main drive wheels, to which the torque of the drive source is constantly transmitted, and the operation of the torque coupling, which can change the distribution of driving force according to the vehicle driving conditions, are controlled to adjust the amount of torque transmission distribution to the auxiliary drive wheels. A controlled four-wheel drive vehicle is known (for example, Patent Document 1).

This Patent Literature 1 discloses a technique for determining whether the vehicle is towed based on the driving force and acceleration, and reducing the torque transmitted to the auxiliary drive wheels during towing.

JP 2008-149794 A

Here, in general, in a four-wheel drive vehicle that can control the distribution of driving force between the main drive wheels and the auxiliary drive wheels, the ground contact load state of the front and rear wheels is estimated in each driving scene, including when driving on a low μ road surface. The driving force is distributed so that the tires of the wheels do not slip.

However, the inventors of the present invention have found that when the towing vehicle (four-wheel drive vehicle) pulls the towed vehicle, the greater the acceleration, the greater the force transmitted from the towed vehicle that lifts the rear portion of the towed vehicle. As a result, the ground contact load of the rear wheels is reduced, causing the rear wheels to slip. That is, during acceleration, the inertial force acting on the center of gravity of the towed vehicle generates a force in the pitching direction that causes the towed vehicle to tilt backward. It is transmitted as a lifting force, which reduces the ground load on the rear wheel.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-described problems. It is an object of the present invention to provide a force distribution control system.

In order to achieve the above object, the present invention provides a vehicle driving force distribution control system for controlling the amount of driving force distributed to the front and rear wheels of a four-wheel drive vehicle capable of towing a towed vehicle. a driving force distribution device for distributing driving force to the front and rear wheels of a vehicle; and a driving force distribution control device for controlling the amount of driving force distributed to the front and rear wheels by the driving force distribution device, wherein the driving force distribution control device controls four wheels. The driving force distribution control device comprises traction determination means for determining whether or not the driving vehicle is towing the towed vehicle, and demanded acceleration detection means for detecting the acceleration demanded by the driver in the four-wheel drive vehicle. When the determination means determines that the four-wheel drive vehicle is towing the towed vehicle and the required acceleration detection means detects the driver's requested acceleration, the greater the driver's requested acceleration, the greater the four-wheel drive vehicle's performance. It is characterized in that the driving force distribution device is controlled so as to reduce the amount of driving force distribution to the rear wheels.

According to the present invention configured as described above, when it is determined that the four-wheel drive vehicle is towing the towed vehicle and when the acceleration requested by the driver is detected, the driving force distribution control device The driving force distribution device is controlled so that the driving force distribution amount to the rear wheels of the four-wheel drive vehicle decreases as the required acceleration of the four-wheel drive vehicle increases. As a result, even if the ground load on the rear wheels of the towing vehicle (four-wheel drive vehicle) decreases due to the fact that the towed vehicle leans backward in a side view due to inertial force when accelerating, By reducing the transmitted drive torque, it is possible to suppress the slip of the rear wheels. Therefore, according to the present invention, in a four-wheel drive vehicle, it is possible to suppress the slip of the rear wheels, which reduces the ground contact load, during towing and acceleration.

Further, in the present invention, preferably, the driving force distribution control device determines that the four-wheel drive vehicle is not towing the towed vehicle by the traction determination means and/or determines that the driver's requested acceleration is determined by the requested acceleration detection means. is not detected, the basic driving force distribution ratio determination means for determining the basic driving force distribution ratio between the front and rear wheels of the four-wheel drive vehicle and the towing determination means determine that the four-wheel drive vehicle is pulling the towed vehicle. and when the acceleration requested by the driver is detected by the requested acceleration detecting means, the driving force distribution to the rear wheels is performed with respect to the basic driving force distribution ratio of the front and rear wheels determined by the basic driving force distribution ratio determining means. driving force distribution ratio correcting means for correcting the basic driving force distribution ratio so that the ratio becomes smaller, and the driving force distribution control device detects that the four-wheel drive vehicle is towing the towed vehicle by the traction determining means. and when the required acceleration detection means detects the driver's requested acceleration, calculating the driving force distribution amount to the rear wheels based on the driving force distribution ratio corrected by the driving force distribution ratio correcting means, It is configured to control the drive force distribution device.
According to the present invention configured as described above, the driving force distribution control device suppresses the slip depending on the basic driving force distribution ratio of the front and rear wheels (for example, the road surface μ etc.) at the time of non-traction and/or non-acceleration. Such a distribution ratio, and a distribution ratio that reduces heat generation and energy loss when the driving force distribution device is a coupling device with a plurality of friction plates), and during traction and acceleration, the basic drive The force distribution ratio is corrected, the amount of driving force distributed to the rear wheels is calculated based on the corrected driving force distribution ratio, and the driving force distribution device is controlled, thereby more effectively suppressing rear wheel slippage. can do.

Further, in the present invention, preferably, the four-wheel drive vehicle is a four-wheel drive vehicle in which the front wheels are main driving wheels and the driving force of the front wheels is distributed to the rear wheels by a driving force distribution device. The force distribution control device is configured to control the driving force distribution device so that the greater the acceleration requested by the driver, the smaller the amount of driving force distributed to the rear wheels of the four-wheel drive vehicle.
According to the present invention configured as described above, the front wheels of the four-wheel drive vehicle are the main driving wheels, and the driving force of the front wheels is distributed to the rear wheels by the driving force distribution device, so-called FF (front wheel drive). This is a four-wheel drive vehicle based on a front-drive engine. The greater the acceleration requested by the driver, the smaller the amount of driving force distributed to the rear wheels of the four-wheel drive vehicle, effectively suppressing rear wheel slip. be able to.

Further, in the present invention, preferably, the four-wheel drive vehicle is a four-wheel drive vehicle in which the rear wheels are main driving wheels and the driving force of the rear wheels is distributed to the front wheels by a driving force distribution device. The force distribution control device is configured to control the driving force distribution device such that the greater the acceleration requested by the driver, the greater the amount of driving force distributed to the front wheels of the four-wheel drive vehicle.
According to the present invention configured as described above, in a four-wheel drive vehicle, the rear wheels are the main driving wheels, and the driving force of the rear wheels is distributed to the front wheels by a driving force distribution device. Engine rear drive) based 4WD vehicle, and the greater the acceleration requested by the driver, the greater the amount of driving force distributed to the front wheels of the 4WD vehicle, so the amount of driving force distributed to the front wheels was increased accordingly. Accordingly, the amount of driving force distributed to the rear wheels can be reduced, thereby effectively suppressing the slip of the rear wheels.

In the present invention, preferably, the towing determination means of the driving force distribution control device determines that the four-wheel drive vehicle is towing the towed vehicle when the towing mode is selected by the driver.
According to the present invention configured in this manner, when the driver selects the towing mode, driving force distribution control during towing is performed, so that the driver's sense of discomfort can be suppressed.

Further, in the present invention, it is preferable to further include a towed vehicle connection determination device for determining whether or not the non-towed vehicle is connected to a connection portion provided at the rear of the four-wheel drive vehicle. The towing determination means of the control device accepts selection of a towing mode by the driver while the towed vehicle coupling determination device determines that the towed vehicle is coupled, and the four-wheel drive vehicle pulls the towed vehicle. It is determined that
According to the present invention configured in this manner, the towed vehicle is towed while the towed vehicle is connected to the connecting portion of the four-wheel drive vehicle, that is, while the towed vehicle is actually being towed. Therefore, the driving force distribution control during towing can be executed more effectively.

According to the vehicle driving force distribution control system according to the present invention, in a four-wheel drive vehicle, it is possible to suppress the slip of the rear wheels, which reduces the ground contact load, during towing and acceleration.

1 shows a four-wheel drive vehicle as a towing vehicle to which the vehicle driving force distribution control system according to the first and second embodiments of the present invention is applied, and a trailer as a towed vehicle, and forces acting on them during towing; It is a schematic side view for explaining the concept of. 1 is a plan view showing a schematic configuration of a four-wheel drive vehicle equipped with a vehicle driving force distribution control system according to a first embodiment of the present invention; FIG. 1 is a block diagram of a vehicle driving force distribution control system according to a first embodiment of the present invention; FIG. 4 is a flow chart showing control processing executed by the driving force distribution control device of the vehicle driving force distribution control system according to the first embodiment of the present invention; FIG. 4 is a diagram showing the relationship between the amount of driving force distributed to the rear wheels controlled by the driving force distribution control device of the vehicle driving force distribution control system according to the first embodiment of the present invention and the required acceleration; 4 is a time chart showing temporal changes in parameters relating to driving force distribution control in the vehicle driving force distribution control system according to the first embodiment of the present invention; FIG. 2 is a plan view showing a schematic configuration of a four-wheel drive vehicle equipped with a vehicle driving force distribution control system according to a second embodiment of the present invention; FIG. 7 is a block diagram of a vehicle driving force distribution control system according to a second embodiment of the present invention; 8 is a flowchart showing control processing executed by a driving force distribution control device of a vehicle driving force distribution control system according to a second embodiment of the present invention; FIG. 7 is a diagram showing the relationship between the amount of driving force distributed to the front wheels and the required acceleration controlled by the driving force distribution control device of the vehicle driving force distribution control system according to the second embodiment of the present invention; 9 is a time chart showing temporal changes in parameters relating to driving force distribution control in the vehicle driving force distribution control system according to the second embodiment of the present invention;

A vehicle drive force distribution control system according to an embodiment of the present invention will now be described with reference to the accompanying drawings.
First, with reference to FIG. 1, the decrease in the ground load of the rear wheels of the vehicle when the vehicle (traction vehicle) tows the trailer (towed vehicle) and the vehicle is accelerating will be described. FIG. 1 shows a four-wheel drive vehicle that is a towing vehicle to which a vehicle driving force distribution control system according to first and second embodiments of the present invention is applied, and a trailer that is a towed vehicle. is a schematic side view for explaining the concept of force acting on the .

As shown in FIG. 1, the trailer T is connected to the rear of the vehicle V through a coupler H formed by a hitch member provided at the rear of the towing vehicle V and a coupler of the towed vehicle. In this embodiment, it is assumed that the trailer T is a two-axle, four-wheel trailer, and that the center of gravity G thereof is positioned between the two axes in the longitudinal direction of the trailer, as shown in FIG.

When the vehicle V is accelerated, an inertia force acts on the center of gravity G of the trailer T to be towed, causing a load shift on the trailer T, and as a result, a pitching moment around the center of gravity G causing the trailer T to tilt backwards. M is produced. That is, the pitching moment M causes the rear portion of the trailer T to sink and the front portion to rise.
A force FH directed upward in the vertical direction of the vehicle V is applied to the coupler H (hitch point) due to the force that causes the front portion of the trailer _T to rise. This force _FH is transmitted to the rear portion of the vehicle V, and the vehicle V generates a force F2 that causes the rear portion to rise, and a force F1 that causes the front portion to sink relatively. Of these forces, the force F2 that lifts the rear portion of the vehicle V reduces the grounding load of the rear wheels _WR on the road surface, and the reduced amount makes the rear wheels _WR more likely to slip. On the other hand, the ground contact load of the front wheels _WF increases.

Furthermore, at the coupler H, which is the hitch point, as shown in FIG. If it is greater, the force _FH directed upward in the vertical direction of the vehicle V on the hitch H (hitch point) will be greater. That is, when the height of the hitch member of the vehicle V and the height of the coupler of the towed vehicle T are combined and connected in the vertical direction, an additional force _FH due to the height difference and/or the weight difference. ' is added to the connector H. This force F _H ' has a constant value during running, and the rear portion of the vehicle V is lifted by that amount.

In the first and second embodiments of the present invention described below, the vehicle driving force distribution control system 1 (see FIGS. 2 and 7) applied to the four-wheel drive vehicle 2, 102 controls such a vehicle V The slip of the rear wheels W _R , 8, 108 due to the reduction of the ground load of the rear wheels W _R , 8, 108 is suppressed. As a modified example of the trailer T, if it is a trailer that applies an upward force to the coupler H during acceleration, a trailer that does not have the two axles and four wheels described above, and a trailer that does not have the center of gravity position described above. It may be a trailer.

Next, referring to FIG. 2, a schematic configuration of a four-wheel drive vehicle equipped with a vehicle driving force distribution control system according to the first embodiment of the present invention will be described. FIG. 2 is a plan view showing a schematic configuration of a four-wheel drive vehicle equipped with a vehicle driving force distribution control system according to the first embodiment of the present invention.
As shown in FIG. 2, a vehicle driving force distribution control system 1 according to the present embodiment is applied to a four-wheel drive vehicle 2. As shown in FIG.

First, the four-wheel drive vehicle 2 has left and right front wheels 6 as main drive wheels and left and right rear wheels 8 as auxiliary drive wheels. It is a so-called FF (front engine front drive) based four-wheel drive vehicle that distributes power to the rear wheels 8 by
Here, the coupling device 10 is controlled by an ECU (Electronic Control Unit) 4 (see FIG. 3 etc.). It corresponds to the "driving force distribution device" in the present invention. Control of the coupling device 10 is executed by a circuit within the ECU 4 .

Next, the four-wheel drive vehicle 2 includes an engine 12 as a driving source, a transmission 14, and a front-wheel differential 18 that distributes the driving force transmitted from the engine 12 to the left and right front wheels 6 via a front-wheel drive shaft 16. and
The four-wheel drive vehicle 2 further includes a transfer 22 that distributes the driving force of the engine 12 to the rear wheels 8 through the propeller shaft 20, a coupling device 10 connected to the propeller shaft 20, and the coupling device 10. A rear wheel differential 26 is also provided, which is connected and distributes the driving force distributed by the coupling device 10 to the left and right rear wheels via a rear wheel drive shaft 24 .

The coupling device 10 has a wet-type multi-plate clutch (not shown) that disconnectably connects a propeller shaft 20 and a rear wheel differential 26, the input side of which is connected to the propeller shaft 20 and the output side of which is connected to the propeller shaft 20. It is connected to the rear wheel differential 26 . In this embodiment, the coupling device 10 is an electronically controlled coupling whose operation is controlled by the ECU 4. By controlling the fastening force between a plurality of friction plates of the wet multi-plate clutch, the front wheels 6 and the rear wheels 8 driving force (driving torque) distribution amount is controlled.
Torque distribution (front wheels:rear wheels) in this embodiment is controlled from the basic 100:0 to, for example, 50:50 according to the slip state of the front and rear wheels.

Here, a basic control concept of driving force distribution control by the coupling device 10 according to this embodiment will be described.
First, in the present embodiment, the driving force is distributed to the front and rear wheels 6 and 8 according to the slip state of the front and rear wheels with respect to the road surface in such a manner that such a slip state is suppressed. there is In this embodiment, the slipping state means that the front and rear wheels 6 and 8 slip on the road surface, such as when driving on a low μ road surface such as a snowy road or a wet road surface, when driving uphill or downhill, or when escaping from a concave road surface. It is assumed that idling will occur.
As a modification, for example, the energy loss at the front wheel 6 caused by the slip of the front wheel 6, the energy loss at the rear wheel 8 caused by the slip of the rear wheel 8, and the energy loss at the rear wheel 8 through the coupling device 10 The amount of driving force distributed to the front and rear wheels 6 and 8 may be controlled so that the total amount of the three energy losses of the mechanical energy loss of the driving system due to transmission of the driving force to the front and rear wheels 6 and 8 is reduced.
As a further modification, in order to prevent excessive heat generation of the coupling device 10, the amount of driving force distributed to the front and rear wheels 6, 8 is controlled in consideration of energy loss due to heat generation of the plurality of friction plates of the coupling device 10. may

Next, control blocks of the vehicle driving force distribution control system according to the first embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram of a vehicle driving force distribution control system according to the first embodiment of the present invention.
As shown in FIG. 3, the ECU 4 has a microcomputer, memory, I/F circuit and the like (not shown).
In this embodiment, the ECU 4 includes an output signal relating to ON/OFF of the traction mode from a traction mode switch 30 which is provided near the driver's seat of the vehicle and which can be manually selected by the driver, and an accelerator pedal from an accelerator opening sensor 32. An output signal regarding the degree of opening, an output signal for detecting the slip state of the front wheels 6 from the front wheel speed sensor 34 that detects the number of rotations of the front wheels 6, and an output signal from the rear wheel speed sensor 36 that detects the number of rotations of the rear wheels 8. An output signal for detecting the slip state of the wheel 8, an output signal for determining whether or not the towed vehicle is coupled from the actual traction sensor 38, which is the energization sensor of the coupler H, and the engine speed sensor 40. An output signal related to the rotation speed of the engine 12 from, an output signal related to the rotation speed of the input shaft of the transmission 14 from the transmission input shaft rotation speed sensor 42, and an output signal relating to the rotation speed of the input shaft of the transmission 14 from the transmission output shaft rotation speed sensor 44 Output signals relating to the number of revolutions of the output shaft are respectively input.

The output signal regarding the degree of opening of the accelerator pedal is a signal that outputs a numerical value corresponding to the amount of depression of the accelerator pedal by the driver, and the ECU 4 calculates the required acceleration of the driver based on this output signal.
The ECU 4 also calculates a value related to the reduction ratio in the transmission 14 based on output signals from the transmission input shaft rotation speed sensor 42 and the transmission output shaft rotation speed sensor 44 .
The ECU 4 is connected to the coupling device 10 and controls the coupling device 10 based on each output signal, as will be described later. That is, the ECU 4 outputs to the coupling device 10 a command value relating to the driving force distribution between the front and rear wheels (torque distribution ratio between the front and rear wheels). It is controlled to distribute the driving force. As will be described later, the ECU 4 also calculates the coupling transmission torque in the coupling device 10 based on the command value related to this driving force distribution.

Next, the control contents of the vehicle driving force distribution control system according to the first embodiment of the present invention will be described with reference to FIGS. 4 to 6. FIG. FIG. 4 is a flowchart showing control processing executed by the driving force distribution control device of the vehicle driving force distribution control system according to the first embodiment of the present invention, and FIG. FIG. 6 is a diagram showing the relationship between the amount of driving force distributed to the rear wheels and the required acceleration controlled by the driving force distribution control device of the driving force distribution control system of FIG. 2 is a time chart showing temporal changes of parameters relating to driving force distribution control in the driving force distribution control system of FIG. In FIG. 4, S indicates each step.

First, as shown in FIG. 4, the ECU 4 (driving force distribution control device) acquires output signals from the switches/sensors 30, 32, 34, 36, 38, 40, 42, and 44 in S1. . The ECU 4 also acquires, as a signal, a command value relating to the distribution of driving force to the front and rear wheels, which is output from the ECU 4 to the coupling device 10 at S1. In S1, the ECU 4 reads the vehicle weight, the front wheel radius, and the rear wheel radius as vehicle specifications (fixed values) stored in the memory of the ECU 4 . Further, the ECU 4 reads engine specifications that define the relationship between the engine speed and the engine torque, stored in the memory within the ECU 4 .

Next, in S2, the estimated ground contact load of the rear wheels is calculated.
Specifically, in S2, the ECU 4 first calculates the value of the engine torque output from the engine 12 from the engine speed and engine specifications acquired in S1. The ECU 4 further calculates the gear ratio value of the transmission 14 from the rotation speeds of the input shaft and the output shaft of the transmission 14 obtained in S1. The ECU 4 further calculates the torque output from the transmission 14 based on the calculated engine torque value and gear ratio value. The ECU 4 further calculates the coupling transmission torque in the coupling device 10 based on the output torque from the transmission 14 and the command value regarding the driving force distribution to the front and rear wheels obtained in S1.
Then, in S2, the ECU 4 calculates the estimated ground load of the rear wheels based on the calculated value of the coupling transmission torque and each value of the vehicle specifications read out in S1.

Next, in S3, it is determined whether or not the four-wheel drive vehicle 2 is towing the towed vehicle T (see FIG. 1). This determination is basically performed based on whether or not an output signal relating to ON/OFF of the traction mode by the driver's operation of the traction mode switch 30 is detected. In this embodiment, the presence or absence of an energization signal from an energization sensor 38 (actual traction sensor 38 in FIG. 3) provided at the coupler H (hitch point) is further detected. When the vehicle T to be towed is connected, it is determined that the towed vehicle T is being towed by receiving an ON signal by the operation of the towing mode switch 30 by the driver.
In this embodiment, in this manner, when the driver selects the towing mode, the correction processes of S4 and S5 are performed, thereby suppressing the driver's sense of incongruity and actually towing the vehicle. It is determined that the towed vehicle is being towed while the towed vehicle is being towed, so that the processing of S4 and S5 during towing is executed more effectively.

Next, in S3, if it is determined that the vehicle is being towed, the process advances to S4 to determine a towing correction coefficient as a process for towing. This towing correction coefficient is a coefficient for correcting the estimated ground contact load calculated in S2 (correction is performed in S5).
In S4, the first correction coefficients are the vehicle weight (fixed value), the vehicle wheel base (fixed value), the distance between the rear wheels and the coupler H (hitch point), the weight of the towed vehicle T. (fixed value) and the driver's requested acceleration of the vehicle to determine the correction factor.

In the first embodiment, as shown in FIG. 5, by such a correction coefficient, the basic driving force distribution amount to the rear wheels 8 in the normal state (during non-traction) indicated by the one-dot chain line is changed to that indicated by the solid line. Further, the amount of driving force distributed to the rear wheels 8 is corrected to decrease as the driver's requested acceleration increases. As an example, when a certain required acceleration A is obtained, a towing correction amount B that reduces the amount of driving force distribution to the rear wheels is obtained. It should be noted that the amount of driving force distributed to the rear wheels 8 as shown in FIG. 5 is determined in S7.

Here, the above-described basic driving force distribution amount is the driving force appropriately determined by the ECU 4 based on road surface conditions, heat generation of the coupling device 10, etc., for example, during normal running when being towed and/or when not accelerating. It is a distribution amount, and for example, in the following, front wheels:rear wheels=80:20.

Next, as a second correction coefficient, when the acceleration requested by the driver is 0, the correction coefficient is set to 1, and as shown in FIG. so that

Next, as the third correction coefficient, the correction coefficient was already determined during the previous processing of S4, and the driver's requested acceleration during the previous processing is If the requested acceleration of the driver has increased or decreased, determine the incremental correction coefficient to obtain the increased correction amount or decreased correction amount corresponding to the difference in the requested acceleration with respect to the previous correction amount (B) You may
Further, as the fourth correction coefficient, the correction coefficient is already determined at the time of the previous processing of S4 as described above, and the driver's requested acceleration at the time of the previous processing is compared with the acceleration requested by the driver at the time of the current processing. If the required acceleration has not changed, the correction coefficient may be set to 1 to obtain the same correction amount (B) as in the previous process.

Although FIG. 5 linearly shows the degree of decrease in the driving force distribution amount with respect to the required acceleration during towing in order to clarify the concept of the correction amount during towing, the vehicle specifications and suspension of the four-wheel drive vehicle 102 are not shown. It may be non-linear depending on the characteristics of the device, the specifications of the vehicle T to be towed, the magnitude of the required acceleration, and the like.

Next, in S5, the estimated ground load of the rear wheels calculated in S2 is multiplied by the towing correction coefficient determined in S4. That is, in S5,
Estimated ground load after correction (S5)=Estimated ground load (S2)×Correction coefficient (S4)
and calculation.

Next, in S6, the estimated slip limit load of the rear wheels is calculated. Specifically, the corrected estimated ground contact load calculated in S5 is multiplied by a slip limit gain, which is a predetermined value determined by experiment or the like, to calculate the estimated slip limit load of the rear wheels. The slip limit gain is stored in the ECU 4 as a map corresponding to the road surface μ.

Next, in S7, the driving force distribution amount of the rear wheels 8 that does not exceed the estimated slip limit load of the rear wheels calculated in S6 is determined, and the cups are adjusted so as to obtain the determined driving force distribution amount of the rear wheels 8. Control the ring device 10 . In S7, the driving force distribution amount for the rear wheels 8 is determined based on the driving force distribution ratio during traction (for example, front wheels:rear wheels=90:10).

On the other hand, if it is determined in S3 that it is not towing, in S6 the estimated ground contact load of the rear wheels calculated in S2 is multiplied by the slip limit gain described above to obtain the estimated slip limit load of the rear wheels. In S7, a driving force distribution amount for the rear wheels that does not exceed the estimated slip limit load of the rear wheels calculated in S6 is determined, and the coupling device is adjusted so as to obtain the determined driving force distribution amount for the rear wheels. control 10. In S7, the amount of driving force to be distributed to the rear wheels is determined based on the normal basic driving force distribution ratio (for example, front wheels:rear wheels=80:20).

Next, as shown in chart (a) of FIG. 6, when the driver's requested acceleration starts to increase from a certain time t1, as shown in chart (b), the towed vehicle The load F _H received from T also increases, and due to the increase in the load F _H , the dynamic ground contact load of the rear wheels decreases.
On the other hand, in the present embodiment, as described above, the greater the acceleration requested by the driver, the smaller the amount of driving force distributed to the rear wheels 8. are trying to reduce This prevents the rear wheel 8 from slipping even if the dynamic ground load is reduced.
Incidentally, as shown in chart (d), the driving force of the front wheels is increased by the amount corrected so that the amount of driving force distribution to the rear wheels 8 is reduced.

Next, with reference to FIG. 7, a schematic configuration of a four-wheel drive vehicle equipped with a vehicle driving force distribution control system according to a second embodiment of the present invention will be described. FIG. 7 is a plan view showing a schematic configuration of a four-wheel drive vehicle equipped with a vehicle driving force distribution control system according to a second embodiment of the present invention. In the second embodiment described below, the same components as in the first embodiment described above are denoted by the same reference numerals.
As shown in FIG. 7 , a vehicle driving force distribution control system 1 according to the second embodiment includes a four-wheel drive vehicle 102 and an ECU (driving force distribution control device) 104 .

First, the four-wheel drive vehicle 2 includes left and right rear wheels 108 as main drive wheels and left and right front wheels 106 as auxiliary drive wheels. It is a so-called FR (Front Engine Rear Drive) based four-wheel drive vehicle in which power is distributed to the front wheels 106 by means of 110 .
As in the first embodiment described above, the coupling device 110 is controlled by an ECU (Electronic Control Unit) 104. The ECU 104 corresponds to the "driving force distribution control device" in the present invention, and the coupling device 110 corresponds to a "driving force distribution device" in the present invention. Control of the coupling device 110 is performed by a circuit within the ECU 104 .

Next, the four-wheel drive vehicle 102 includes an engine 112 as a driving source, a transmission 114, and a transfer 122 for transmitting the driving force of the engine 12 to the rear wheels 8 through a rear wheel propeller shaft 120. , and a rear-wheel differential 126 connected to the rear-wheel propeller shaft 120 and distributing the transmitted driving force to the left and right rear wheels via a rear-wheel drive shaft 124 .

The four-wheel drive vehicle 102 is further connected to a rear-wheel propeller shaft 120, and a coupling device 110 that distributes the driving force transmitted to the rear wheels 108 to the front wheels 106; A front wheel propeller shaft 111 for transmitting the distributed driving force to the front wheel side and a front wheel differential 118 for distributing the transmitted driving force to the left and right front wheels 106 via the front wheel drive shaft 116 are provided.

Coupling device 110 has a wet-type multi-plate clutch (not shown) that disconnectably connects rear-wheel propeller shaft 120 and front-wheel propeller shaft 11 , and the input side thereof is connected to rear-wheel propeller shaft 120 . , and the output side is connected to the front wheel propeller shaft 111 . This coupling device 10 is an electronically controlled coupling whose operation is controlled by the ECU 104, as in the first embodiment described above. The amount of driving force (driving torque) distributed to the rear wheels 108 and the front wheels 106 is controlled.
The torque distribution (front wheels:rear wheels) in this embodiment is controlled from 0:100 in the basic to 50:50, for example, according to the slip state of the front and rear wheels.

Here, in the second embodiment, as in the above-described first embodiment, the front and rear wheels are distributed with a driving force distribution amount that suppresses such a slip state according to the slip state of the front and rear wheels with respect to the road surface. The driving force is distributed to 6 and 8.
As a modification, for example, the energy loss at the front wheel 6 caused by the slip of the front wheel 6, the energy loss at the rear wheel 8 caused by the slip of the rear wheel 8, and the energy loss at the rear wheel 8 through the coupling device 10 The amount of driving force distributed to the front and rear wheels 6 and 8 may be controlled so that the total amount of the three energy losses of the mechanical energy loss of the driving system due to transmission of the driving force to the front and rear wheels 6 and 8 is reduced.
As a further modification, in order to prevent excessive heat generation of the coupling device 10, the amount of driving force distributed to the front and rear wheels 6, 8 is controlled in consideration of energy loss due to heat generation of the plurality of friction plates of the coupling device 10. may

Next, with reference to FIG. 8, control blocks of a vehicle driving force distribution control system according to a second embodiment of the present invention will be described. FIG. 8 is a block diagram of a vehicle driving force distribution control system according to a second embodiment of the present invention.
As shown in FIG. 8, in the ECU 4, similarly to the above-described first embodiment, an output signal relating to ON/OFF of the traction mode from the traction mode switch 30 that can be manually selected by the driver, and an output signal from the accelerator opening sensor 32 , an output signal for detecting the slip state of the front wheels 6 from the front wheel speed sensor 34 that detects the rotation speed of the front wheels 6, and a rear wheel speed sensor 36 that detects the rotation speed of the rear wheels 8. An output signal for detecting the slip state of the rear wheels 8 from, an output signal for determining whether or not the towed vehicle is connected from the actual traction sensor 38, which is the energization sensor of the coupler H, and the engine rotation An output signal related to the rotation speed of the engine 112 from the number sensor 40, an output signal related to the rotation speed of the input shaft of the transmission 114 from the transmission input shaft rotation speed sensor 42, and a shift from the transmission output shaft rotation speed sensor 44. An output signal relating to the number of revolutions of the output shaft of the machine 114 is input respectively.

The output signal regarding the degree of opening of the accelerator pedal is a signal that outputs a numerical value corresponding to the amount of depression of the accelerator pedal by the driver, and the ECU 104 calculates the required acceleration of the driver based on this output signal.
ECU 104 also calculates a numerical value related to the reduction ratio in transmission 114 based on the output signals from transmission input shaft rotation speed sensor 42 and transmission output shaft rotation speed sensor 44 .
The ECU 104 is connected to the coupling device 110 and controls the coupling device 110 based on each output signal, as will be described later. That is, the ECU 4 outputs a command value regarding the distribution of driving force to the front and rear wheels to the coupling device 110, and the coupling device 110 is controlled to distribute the driving force to the front and rear wheels 106, 108 based on this command value. be. As will be described later, the ECU 104 also calculates the coupling transmission torque in the coupling device 110 based on the command value related to this driving force distribution.

Next, the control contents of the vehicle driving force distribution control system according to the second embodiment of the present invention will be described with reference to FIGS. 9 to 11. FIG. FIG. 9 is a flow chart showing the control processing executed by the driving force distribution control device of the vehicle driving force distribution control system according to the second embodiment of the present invention, and FIG. FIG. 11 is a diagram showing the relationship between the amount of driving force distributed to the rear wheels and the required acceleration controlled by the driving force distribution control device of the driving force distribution control system of FIG. 11, and FIG. 2 is a time chart showing temporal changes of parameters relating to driving force distribution control in the driving force distribution control system of FIG. In FIG. 9, S indicates each step.

First, as shown in FIG. 9, the ECU 104 (driving force distribution control device) controls the above-described switches/sensors 30, 32, 34, 36, 38, 40, 42 and 44, the signal of the command value regarding the driving force distribution to the front and rear wheels is acquired, and the values of the vehicle specifications and the engine specifications are read out. Calculate the estimated ground load.

Next, in S3, it is determined whether or not the four-wheel drive vehicle 2 is towing the towed vehicle T (see FIG. 1), as in the first embodiment described above. If it is determined that the vehicle is towed, the process advances to S4, and as processing for towing, first, a correction coefficient for towing is determined. This towing correction coefficient is a coefficient for correcting the estimated ground contact load calculated in S2 (correction is performed in S5).
In S4, the first correction coefficients are the vehicle weight (fixed value), the vehicle wheel base (fixed value), the distance between the rear wheels and the coupler H (hitch point), the weight of the towed vehicle T. (fixed value) and the driver's requested acceleration of the vehicle to determine the correction factor.

In the second embodiment, as shown in FIG. 10, with respect to the basic driving force distribution amount to the front wheels 106 in the normal state (when not towing) indicated by the one-dot chain line, the greater the acceleration required by the driver, the more the amount of power to the front wheels 106. Correction is made so that the driving force distribution amount is increased. As an example, when a certain required acceleration A is obtained, a towing correction amount C that increases the driving force distribution amount to the front wheels is obtained. Incidentally, the driving force distribution amount for the front wheels 106 is determined in S7.

More specifically, since the second embodiment is the driving force distribution control system 1 applied to the FR-based four-wheel drive vehicle 102, for example, the basic distribution ratio of front wheels:rear wheels=0:100 Therefore, by increasing the amount of driving force distributed to the front wheels 106, the distribution of the driving force to the rear wheels 108 is relatively reduced. He is trying to suppress the slip of 108.

The basic drive distribution amount in the second embodiment is a drive force distribution amount appropriately determined by the ECU 104 during normal running, for example, when being towed and/or not accelerated, as in the first embodiment described above. For example, in the following, front wheels:rear wheels=0:100.

Next, as a second correction coefficient, when the acceleration requested by the driver is 0, the correction coefficient is set to 1, and as shown in FIG. be.

Next, as the third correction coefficient, the correction coefficient was already determined during the previous processing of S4, and the driver's requested acceleration during the previous processing is If the requested acceleration of the driver has increased or decreased, the incremental correction coefficient is determined to obtain an increased correction amount or a decreased correction amount corresponding to the difference in the requested acceleration from the previous correction amount (C). You may
Further, as the fourth correction coefficient, the correction coefficient is already determined in the previous processing of this S4 as described above, and the acceleration requested by the driver in the previous processing is compared with the acceleration demanded by the driver during the current processing. is not changed, the correction coefficient may be set to 1 and the same correction amount (C) as in the previous process may be obtained.

In order to clarify the concept of the correction amount during towing, FIG. It may be non-linear depending on the characteristics of the device, the specifications of the vehicle T to be towed, the magnitude of the required acceleration, and the like.

Next, as in the first embodiment described above, in S5, the estimated rear wheel ground load calculated in S2 is multiplied by the correction coefficient determined in S4, and in S6, the estimated rear wheel slip limit is calculated. Calculate the load.

Next, in S7, in the second embodiment, the rear wheel drive force distribution amount that does not exceed the estimated slip limit load of the rear wheels 108 calculated in S6 is first determined, and the determined rear wheel drive force distribution is determined. From the amount, the amount of driving force distribution to the front wheels 106 is determined. Then, in S7, the coupling device 110 is controlled so that the determined driving force distribution amount for the front wheels 106 is obtained. In this S7, the driving force distribution amount for the front wheels 106 is determined based on the driving force distribution ratio during traction (for example, front wheels:rear wheels=10:90).

On the other hand, if it is determined in S3 that the vehicle is not towing, in S6 the estimated ground contact load of the rear wheels calculated in S2 is multiplied by the slip limit gain to calculate the estimated slip limit load of the rear wheels, In S7, the amount of driving force distribution to the front wheels is determined so that the amount of driving force distribution to the rear wheels does not exceed the estimated slip limit load of the rear wheels calculated in S6, and the determined driving force distribution amount to the front wheels is obtained. Coupling device 110 is controlled so that In S7, the amount of driving force to be distributed to the front wheels 106 is determined based on the normal basic driving force distribution ratio (for example, front wheels:rear wheels=0:100).

Next, as shown in chart (a) of FIG. 11, when the acceleration requested by the driver starts to increase from a certain time t1, the load F _H ( reference), and due to the increase in the load _FH , the dynamic ground contact load of the rear wheel 108 decreases as shown in chart (b).
On the other hand, in the second embodiment, as described above, the greater the acceleration requested by the driver, the greater the amount of driving force distributed to the front wheels 106 (chart (d)). He is trying to reduce the driving force (chart (c)). This prevents the rear wheel 108 from slipping even if the dynamic ground load of the rear wheel 108 decreases.

Next, functions and effects according to the embodiment of the present invention will be described.
A vehicle driving force distribution control system 1 according to the first and second embodiments of the present invention is a driving force distribution device for distributing driving force to front and rear wheels 6, 8, 106, 108 of a four-wheel drive vehicle V, 2, 102. 10, 110, and an ECU (driving force distribution control device) 4, 104 for controlling the amount of driving force distributed to the front and rear wheels by this driving force distribution device. A traction determination means for determining whether or not the towing vehicle is being towed, and a demanded acceleration detection means for detecting the acceleration demanded by the driver in the four-wheel drive vehicle. When it is determined that the vehicle is being towed and the acceleration requested by the driver is detected, the amount of driving force distributed to the rear wheels 8 and 108 of the four-wheel drive vehicle becomes smaller as the acceleration requested by the driver increases. It is configured to control the drive force distribution device.
As a result, when the towed vehicle (four-wheel drive vehicle) V, 2, 102 is accelerated, the towed vehicle T is tilted backward in a side view due to the inertia force, and the front part of the towed vehicle T is lifted up. Accordingly, even if the rear portion of the connected four-wheel drive vehicle V, 2, 102 is lifted and the ground load of the rear wheels 8, 108 is reduced, the greater the acceleration required by the driver, the greater the force on the rear wheels 8, 108. By reducing the driving force distribution, the driving torque transmitted from the rear wheels 8, 108 to the road surface can be reduced. Therefore, it is possible to suppress the slip of the rear wheels 8, 108, which reduces ground contact load, during towing and acceleration.

Further, according to the first and second embodiments of the present invention, the ECU (driving force distribution control device) 4, 104 controls the basic driving force distribution ratio of the front and rear wheels (for example, a distribution ratio that suppresses a slip that depends on the road surface μ, a distribution ratio that reduces heat generation and energy loss when the driving force distribution devices 10 and 110 are coupling devices with a plurality of friction plates, etc.) is determined, and during traction and acceleration, the basic driving force distribution ratio is corrected, the driving force distribution amount to the rear wheels 8, 108 is calculated based on the corrected driving force distribution ratio, and the driving force distribution device 10 and 110 are controlled, the slippage of the rear wheels 8 and 108 can be suppressed more effectively.

Further, according to the first embodiment of the present invention, the four-wheel drive vehicle V, 2 has the front wheels 6 as the main driving wheels, and the driving force of the front wheels is transferred to the rear wheels 8 by the driving force distribution device 10. It is a so-called FF (front engine front drive) based four-wheel drive vehicle, and the greater the acceleration required by the driver, the smaller the amount of driving force distributed to the rear wheels 8 of the four-wheel drive vehicle. , the slip of the rear wheel 8 can be suppressed.

Further, according to the second embodiment of the present invention, the four-wheel drive vehicle V, 102 has the rear wheels 108 as the main driving wheels, and the driving force of the rear wheels is transferred to the front wheels 6 by the driving force distribution device 110. This is a so-called FR (Front Engine Rear Drive) based four-wheel drive vehicle. By increasing the amount of driving force distributed to the rear wheels 108, it is possible to reduce the amount of driving force distributed to the rear wheels 108, thereby effectively suppressing the slippage of the rear wheels 108.

V four-wheel drive vehicle (tow vehicle)
T trailer (towed vehicle)
G Center of gravity of towed vehicle H Coupler (connecting part)
F Force, load M Moment 1 Driving force distribution control system for vehicle 2, 102 Four-wheel drive vehicle 4, 104 ECU (driving force distribution control device)
6, 106, W _F front wheels 8, 108, W _R rear wheels 10, 110 Coupling device (driving force distribution device)

Claims (6)

A vehicle driving force distribution control system for controlling the amount of driving force distributed to front and rear wheels in a four-wheel drive vehicle capable of towing a towed vehicle,
a driving force distribution device that distributes the driving force to the front and rear wheels of the four-wheel drive vehicle;
a driving force distribution control device for controlling the amount of driving force distributed to the front and rear wheels by the driving force distribution device;
The driving force distribution control device is
traction determination means for determining whether or not the four-wheel drive vehicle is towing the towed vehicle;
and a required acceleration detecting means for detecting the required acceleration of the driver in the four-wheel drive vehicle,
When the traction determination means determines that the four-wheel drive vehicle is pulling the towed vehicle, and the required acceleration detection means detects the driver's requested acceleration, The driving force of a vehicle, wherein the driving force distribution device is configured to control the driving force distribution device so that the driving force distribution amount to the rear wheels of the four-wheel drive vehicle decreases as the driver's requested acceleration increases. Distribution control system. The driving force distribution control device is
When the traction determination means determines that the four-wheel drive vehicle does not tow the towed vehicle and/or the required acceleration detection means does not detect the driver's requested acceleration, the four-wheel drive vehicle basic driving force distribution ratio determination means for determining a basic driving force distribution ratio of the front and rear wheels;
When the traction determining means determines that the four-wheel drive vehicle is pulling the towed vehicle and the required acceleration detecting means detects the driver's requested acceleration, the basic driving force distribution ratio determining means driving force distribution ratio correction means for correcting the basic driving force distribution ratio so that the driving force distribution ratio to the rear wheels becomes smaller than the basic driving force distribution ratio of the front and rear wheels determined by
When the traction determination means determines that the four-wheel drive vehicle is pulling the towed vehicle, and the required acceleration detection means detects the driver's requested acceleration, 2. The driving force distribution device according to claim 1, wherein the driving force distribution amount to the rear wheels is calculated based on the driving force distribution ratio corrected by the driving force distribution ratio correcting means, and the driving force distribution device is controlled. vehicle driving force distribution control system. The four-wheel drive vehicle is a four-wheel drive vehicle in which the front wheels are main driving wheels and the driving force of the front wheels is distributed to the rear wheels by the driving force distribution device,
The driving force distribution control device is configured to control the driving force distribution device so that the driving force distribution amount to the rear wheels of the four-wheel drive vehicle decreases as the driver's requested acceleration increases. 3. A driving force distribution control system for a vehicle according to claim 1 or 2. The four-wheel drive vehicle is a four-wheel drive vehicle in which the rear wheels are main driving wheels and the driving force of the rear wheels is distributed to the front wheels by the driving force distribution device,
2. The driving force distribution control device is configured to control the driving force distribution device so that the driving force distribution amount to the front wheels of the four-wheel drive vehicle increases as the acceleration requested by the driver increases. 3. The vehicle driving force distribution control system according to claim 2. 5. The traction determining means of the driving force distribution control device according to any one of claims 1 to 4, wherein the towing determination means determines that the four-wheel drive vehicle is towing the towed vehicle when the towing mode is selected by the driver. A driving force distribution control system for a vehicle according to any one of the preceding paragraphs. Further comprising a towed vehicle connection determination device for determining whether or not the non-towed vehicle is connected to a connecting portion provided at the rear of the four-wheel drive vehicle,
The traction determining means of the driving force distribution control device accepts selection of a traction mode by the driver while the towed vehicle coupling determination device determines that the towed vehicle is coupled, and the four-wheel drive mode is selected. 6. The vehicle traction distribution control system of claim 5, wherein the vehicle determines that the vehicle is towing a towed vehicle.

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