JPH1086803A - Driving force control method and driving force control device of four-wheeled vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of durability of a brake device and a driving system by adjusting the driving force transmitted to respective wheels from an engine by brake force on the basis of a brake adjusting parameter, restraining a wheel behavior difference, and reducing output of the engine when the brake force is excessive. SOLUTION: When wheel behavior as an engine output adjusting condition is found (S210) as an engine output adjusting speed difference ΔVE, and an engine output adjusting judgment value VTE is set (S220) according to car body speed VB. A control oil pressure excess corresponding quantity BPE is found (S230) from these values, and a start condition of engine output control is satisfied (S240), and next, when it is judged (S250) as 'NO' such as a finish condition of the engine output control is not satisfied, an electronic throttle ES is driven (S260). Therefore, when brake force is going to become excessive, engine output is reduced, and an increase in a load to a brake device and a driving system is prevented, and the deterioration of these durability can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a driving force control method and a driving force control device for a four-wheel drive vehicle.

[0002]

2. Description of the Related Art Conventionally, four-wheel drive vehicles have been put to practical use in which the driving force from an engine is transmitted to four wheels on the left, right, front and rear to improve the ability to travel on rough roads and rough terrain. However, even in such a four-wheel drive vehicle, when one wheel slips and idles, there is a problem that the driving force is not transmitted to the other wheels and the propulsive force of the vehicle is reduced. That is, in general, in this type of four-wheel drive vehicle, the driving force from the engine is distributed to the front wheel drive shaft and the rear wheel drive shaft via a center differential gear (differential device), Further, the driving force distributed to the front wheel drive shaft is distributed to the left and right front wheels via the front differential gear, and the driving force distributed to the rear wheel drive shaft is distributed to the left and right rear wheels via the rear differential gear. It was to be distributed to the wheels. For this reason, when any one wheel spins, the driving force is not transmitted to the other wheels due to the action of each differential gear.

[0003] As a technique for solving such a problem, for example, Japanese Patent Application Laid-Open No. Sho 60-248440 discloses a technique in which the slip state of each wheel is detected, and a brake device is applied to the wheel where the slip has occurred. It has been proposed that the driving force be transmitted to other wheels by suppressing the slip by providing the wheel. In other words, with this technology,
By reducing the idling of the wheels by a brake, a difference in rotational speed (so-called differential) between the wheels is suppressed.

[0004]

However, since all the rotational speed differences (hereinafter simply referred to as speed differences) are adjusted by the braking force, the higher the engine output, the more the load is substantially unchanged. I got on the brakes. For this reason, the frequency of operation of the actuator for adjusting the wear and heat of the brake pad and the hydraulic pressure in the brake device has increased, and there has been a concern about the durability of the brake device. Further, there is a concern that the drive system (propeller shaft, differential gear, etc.) may be adversely affected.

[0005] There is already known a four-wheel drive vehicle in which the output of the engine is reduced based on the slip ratio (Japanese Patent Laid-Open No. 2-81721). However, in this technology, in order to maintain the running stability of the vehicle, a slip ratio of each wheel is obtained from a difference between a vehicle speed and a wheel speed, and a combination of wheels whose slip ratio is equal to or more than a predetermined value is a special combination ( Specifically, left front wheel-right front wheel, left front wheel-left rear wheel,
Right front wheel-right rear wheel)
Engine output control was being performed.

For this reason, when the combination is different from the above-mentioned combination, the output of the engine is not reduced and an excessive load may be applied to the brake device and the drive system. An object of the present invention is to prevent such an engine output from imposing an excessive load on a brake device or a drive system, thereby reducing the durability thereof. It is another object of the present invention to reduce these loads without sacrificing acceleration performance.

[0007]

SUMMARY OF THE INVENTION One or more inventions are described herein and have the construction and features described below. The driving force control method for a four-wheel drive vehicle according to the present invention determines a difference in wheel behavior between each wheel of the four-wheel drive vehicle and other wheels as a brake adjustment parameter, and transmits the drive transmitted from the engine to each of the wheels. Power
The method is characterized in that the difference in wheel behavior is suppressed by adjusting with a braking force based on the brake adjustment parameter, and the output of the engine is reduced when the braking force is excessive.

According to the present invention, the output of the engine is reduced by catching such an excessive braking force.
As described above, as in the related art, when the engine output is reduced only to a special combination of wheels having a high slip ratio, the load on the brake device or the drive system provided by the engine output cannot be sufficiently prevented. , And a decrease in the durability of the brake device and the drive system can be prevented.

In determining the excessive braking force, the braking force may be measured from a pressure such as a brake oil pressure. For example, a wheel behavior difference between all the wheels is determined as an engine output adjusting parameter, and the engine output adjusting parameter is determined. Excessive braking force may be determined based on the parameter.

That is, the adjustment of the braking force on each wheel is performed based on the brake adjustment parameters. Therefore, an excessive braking force can be determined based on the wheel behavior difference between all the wheels. In addition, since the output of the engine directly affects the driving force of all the wheels, it is determined that the braking force is excessive based on the wheel behavior difference between all the wheels. It can be determined that it is necessary to reduce the output of the engine.

More specifically, for example, when the brake adjustment parameter is larger than a predetermined brake adjustment determination value for each wheel, the brake adjustment parameter and the brake adjustment determination value are determined. The braking force is adjusted according to the difference between the braking force and the engine output adjustment parameter, and when the parameter for engine output adjustment is larger than a predetermined engine output adjustment determination value that is larger than the brake adjustment determination value, the braking force is excessively large. Reducing the output of the engine when the braking force is excessive, by determining that there is, and adjusting the engine output according to a difference between the engine output adjustment parameter and the engine output adjustment determination value. Thus, it is possible to prevent a decrease in the durability of the brake device and the drive system.

Further, since the judgment value for engine output adjustment is larger than the judgment value for brake adjustment, when the wheel behavior difference in all the wheels is further larger than the wheel behavior difference state in which the braking force is adjusted, Adjustments are made to reduce engine power. If the engine output adjustment determination value is set to a value high enough to obtain an appropriate driving force, it is possible to reduce the load on the brake device and the drive system without sacrificing the acceleration performance. .

Here, for example, if the difference between the maximum speed and the minimum speed of all the wheels is used as the engine output adjustment parameter, the engine output can be adjusted for all the wheels. In addition, when the brake adjustment determination value is provided individually for each wheel, for example, the rear wheel side brake adjustment determination value is set to a small value for vehicle running stability. In this case, the engine output adjustment determination value may be set to be larger than the brake adjustment determination value provided for the wheel having the maximum speed by a predetermined value in order to appropriately respond to the braking state of each wheel. .
That is, if the judgment value for brake adjustment is small, the judgment value for engine output adjustment is set to be small accordingly, and if the judgment value for brake adjustment is large, the judgment value for engine output adjustment is set to be large accordingly. May be.

The engine output adjustment parameters include, for example, a wheel behavior difference (for example, a difference between a maximum speed and a minimum speed of all the wheels) among all the wheels.
It may be the same as the brake adjustment parameter for the wheel at the maximum speed. In other words, the same wheel behavior difference is used for both brake adjustment and engine output adjustment,
Only the determination value may be a brake adjustment determination value or an engine output adjustment determination value. However, the parameter used for adjusting the engine output is the parameter for adjusting the brake of the wheel at the maximum speed, so that the output of the engine can be controlled in accordance with the wheel on which excessive braking force is generated, and more accurate High control becomes possible.

The brake adjustment parameters include, for example, the difference between the speed of the own wheel and the speed of the other wheel on the same side in the front and rear direction, and the average value between the own wheel and the other wheel in the front and rear direction. A value obtained by adding a value obtained by subtracting the average value of the velocities of the two wheels on the opposite side can be used, and a wheel behavior difference between each wheel and another wheel can be obtained. If this is represented by a mathematical formula, for example,
The following equations 1 to 4 are obtained.

[0016]

(Equation 1)

Here, △ VFL: a parameter for adjusting the brake of the front left wheel, △ VFR: a parameter for adjusting the brake of the front right wheel, ： VRL: a parameter for adjusting the brake of the rear left wheel, △ V
RR: right rear wheel brake adjustment parameter, VWFL: left front wheel speed, VWFR: right front wheel speed, VWRL: left rear wheel speed, VWRR: right rear wheel speed.

For example, when the engine is an internal combustion engine, the output of the engine is reduced by reducing the amount of intake air of the internal combustion engine or by reducing the amount of fuel supplied to the internal combustion engine. Note that the wheel behavior is not limited to the wheel speed, but may be a wheel acceleration or the like.

When the above-described method for controlling the driving force of a four-wheel drive vehicle is configured as an apparatus, for example, the following configuration can be mentioned. That is, for each wheel of the four-wheel drive vehicle, a difference in wheel behavior with respect to the other wheels is determined as a brake adjustment parameter, and the driving force transmitted from the engine to each of the wheels is determined by the braking force based on the brake adjustment parameter. A driving force control apparatus for a four-wheel drive vehicle having a braking force control means for suppressing the difference in wheel behavior by adjusting the braking force, and determining whether the braking force adjusted by the braking force control means is excessive. Braking force determining means, engine output adjusting means for adjusting the output of the engine, and when the braking force determining means determines that the braking force is excessive, controlling the engine output adjusting means to control the engine output And an engine output control means for reducing the output of the vehicle.

Here, the braking force determining means includes an engine output adjusting parameter calculating means for obtaining a wheel behavior difference between all the wheels as an engine output adjusting parameter, and the engine output calculating means obtaining the engine output adjusting parameter calculating means. Excessive determining means for determining excessive braking force based on an output adjustment parameter may be used.

The brake force control means includes: a brake adjustment parameter determining means for determining whether the brake adjustment parameter is greater than a predetermined brake adjustment determination value; and the brake adjustment parameter determining means. A brake force for adjusting the brake force according to a difference between the brake adjustment parameter and the brake adjustment determination value when it is determined that the brake adjustment parameter is greater than a predetermined brake adjustment determination value; Adjusting means, and the excess determining means determines that the braking force is excessive when the engine output adjusting parameter is larger than a predetermined engine output adjusting determination value larger than the brake adjusting determination value. And the engine output control means determines the If rk in force is determined to be excessive, it can be assumed that decreases the engine output according to the difference between the engine output adjusting decision value and the engine output adjustment parameter.

The engine output adjustment parameters include, for example, the difference between the maximum speed and the minimum speed of all the wheels. If the brake adjustment determination value is provided for each wheel, for example, the engine output adjustment determination value may be a predetermined value based on the brake adjustment determination value provided for the wheel at the maximum speed. One that is set to be large can be mentioned.

[0023] The engine output adjustment parameter may be equivalent to the brake adjustment parameter for a wheel having a maximum speed. The brake adjustment parameter is a difference between the speed of the own wheel and the speed of the other wheel on the same side in the front-rear direction. The value obtained by subtracting the value can be obtained as the added value.

Also, if the engine is an internal combustion engine,
The engine output adjusting means adjusts the intake air amount of the internal combustion engine, and the engine output control means reduces the engine output and reduces the intake air amount of the internal combustion engine by the engine output adjusting means. This can be done by doing Further, the engine output adjusting means includes:
The amount of fuel supplied to the internal combustion engine is adjusted, and the engine output control means can reduce the output of the engine by reducing the amount of fuel supplied to the internal combustion engine by the engine output adjusting means.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] FIG. 1 is a schematic configuration diagram showing an entire control system of a four-wheel drive vehicle according to a first embodiment to which the present invention is applied.

As shown in FIG. 1, each wheel (left front wheel) of the vehicle
FL, front right wheel FR, rear left wheel RL, rear right wheel RR)
Hydraulic brake device (hereinafter referred to as wheel cylinder: W / C) 2FL, 2FR, 2 for applying a braking force to RR
RL, 2RR, and wheel speed sensors 4FL, 4FR, 4RL, 4RR for detecting the rotation speed of each wheel are provided, respectively.

On the other hand, the torque output from the engine (here, an internal combustion engine) 6 via the transmission 8 is transmitted to the front-wheel drive shaft 11F and the rear-wheel drive shaft 11R by the center differential gear 10C. The torque of the drive shaft 11F for the front wheels is further distributed to each of the left and right front wheels FL and FR by the front differential gear 10F, and the torque of the drive shaft 11R for the rear wheels is distributed by the rear differential gear 10R. Left and right rear wheels RL,
It is distributed to each of the RRs.

The engine 6 is provided with a group of sensors 12 for detecting operating conditions such as the rotation speed, intake air amount, cooling water temperature, throttle opening, and the like. Each wheel speed sensor 4FL-4
A detection signal or the like from the RR is input to an electronic control unit (hereinafter, referred to as an ECU) 20.

The ECU 20 controls the fuel injection amount (corresponding to the fuel supply amount) and the ignition timing of the engine 6 based on the detection signal from the sensor group 12, and discharges the brake oil by depressing the brake pedal 32. From master cylinder (hereinafter referred to as M / C) 34 to W of each wheel FL to RR
Hydraulic circuit 4 provided in the hydraulic path from / C2FL to 2RR
Anti-skid control (hereinafter referred to as ABS control) that suppresses slip generated at the time of vehicle braking by controlling various actuators within 0, and each wheel FL
The differential limiting control (hereinafter referred to as driving force control) for suppressing the rotation speed difference between RR and RR is executed.

The ECU 20 has a CPU, ROM, RA
The microcomputer 20 is mainly configured with a microcomputer including an M and the like. A detection signal from a brake switch 36 that is turned on when the brake pedal 32 is operated is also input to the ECU 20. In the intake system of the engine 6, a driver's accelerator operation is detected by a sensor,
An electronic throttle ES, which is a throttle valve whose opening degree is electronically controlled in accordance with the accelerator operation, is provided. The electronic throttle ES is adjusted by the ECU 20 to a throttle opening smaller than the driver's accelerator operation in order to reduce the output of the engine 6 when the braking force is excessive as described later.

Next, the hydraulic circuit 40 will be described. As shown in FIG. 2, the hydraulic circuit 40 supplies the brake oil pumped from the two oil passages of the M / C 34 to the left front wheel FL and the right rear wheel R
R, right front wheels FR and left rear wheels RL are provided with two hydraulic paths 42 and 44, respectively.

Then, in the hydraulic path 42, the left front wheel FL
The route 42FL to the W / C2FL of the right rear wheel RR and the W / C2
The route 42RR to the RR includes the route 42F
L, 42RR, and a pressure-increasing control valve 46FL, 46 that can be switched between a pressure-increasing position that communicates with the RR and a holding position that interrupts the path.
RR and electromagnetic pressure reducing control valves 48FL, 48RR for discharging brake oil in each W / C2FL, 2RR are provided.

Similarly, in the hydraulic path 44, a path 44FR to the W / C2FR of the right front wheel FR and a W / C2
The route 44RL to the C2RL has its route 4
The electromagnetic pressure-increasing control valve 46FR, 4 which can be switched between a pressure-increasing position for communicating the 4FR, 44RL and a holding position for interrupting the path.
6RL and electromagnetic pressure reducing control valves 48FR, 48RL for discharging brake oil in each W / C2FR, 2RL are provided.

The pressure increase control valves 46FL, 46FR, 46RL,
46RR is normally a pressure increasing position, and is switched to a holding position by energization from the ECU 20. The pressure reduction control valves 48FL, 48FR, 48RL, and 48RR are normally in a shut-off state, and are in a communicating state by energization from the ECU 20, and discharge the brake oil in the corresponding W / C2FL to 2RR.

On the other hand, in the hydraulic path 42, a master cylinder cut valve (hereinafter, referred to as an SM valve) 50a is provided on the path on the M / C 34 side of the pressure increase control valves 46FL and 46RR to connect / disconnect the path. ing. And
In parallel with the SM valve 50a, when the oil pressure on the M / C 34 side is higher than the oil pressure on the pressure increase control valves 46FL and 46RR, the pressure oil output from the M / C 34 is communicated with the pressure increase control valve 46FL. , 46RR are connected to a relief valve 54a to be supplied.

Similarly, in the hydraulic path 44, a path on the M / C 34 side of the pressure increase control valves 46FR and 46RL is also provided.
An SM valve 50b for communicating and shutting off the path is provided. Then, in parallel with the SM valve 50b, when the oil pressure on the M / C 34 side becomes higher than the oil pressure on the pressure increase control valves 46FR, 46RL, the pressure oil outputted from the M / C 34 is increased. Relief valve 5 to supply to valves 46FR and 46RL
4b is connected.

The SM valves 50a and 50b are powered off.
Sometimes the communication state is established, and the state is switched to the cut-off state by energization from the ECU 20. SM valve 50a, 50b
Are connected in parallel with differential pressure valves PRVa and PRVb, respectively.
The flow of brake oil from C34 to the W / C side is prohibited.
The flow of brake oil from the / C side to the M / C 34 is W / C
Is permitted when the brake hydraulic pressure on the side becomes higher than the pressure on the M / C 34 side by a predetermined pressure or more. As the predetermined pressure, 50 at
m to 200 atm, and each differential pressure valve PRVa,
The PRVb protects the pipeline so that the pressure in the pipeline on the W / C side with respect to the SM valves 50a and 50b does not exceed a predetermined pressure when the pumps 60 and 62 described later discharge.

In FIG. 2, the SM valves 50a and 50b are provided with parallel pipes, and the differential pressure valves PRVa and PRVb are provided in these pipes.
, But instead of such a configuration,
Even when a configuration is adopted in which the valve elements at the shut-off positions of the SM valves 50a and 50b are differential pressure valves having a predetermined relief pressure (opening pressure), and the differential pressure valves PRVa and PRVb are built in each of the SM valves 50a and 50b. Good.

Further, in each of the hydraulic paths 42 and 44,
Reservoirs 56 and 58 are provided for temporarily storing the brake oil discharged from the pressure reduction control valves 48FL to 48RR, and the brake oil is further supplied to the SM valve 50a and the pressure increase control valves 46FL and 4FL.
6RR, SM valve 50b and pressure increase control valve 46F
Pumps 60 for pumping to the path between R and RL respectively;
62 are provided. In addition, accumulators 64 and 66 for suppressing the pulsation of the internal hydraulic pressure are provided in the discharge path of the brake oil from the pumps 60 and 62, respectively.

The M / C 34 is provided to each of the hydraulic paths 42 and 44 when a driving force control (differential limit control) described later is executed.
The oil supply paths 42P and 44P for directly supplying the brake oil from the reservoir 68 provided above the M / C 34 to the pumps 60 and 62 through the oil supply paths 42P and 44P are provided in the oil supply paths 42P and 44P, respectively. , A reservoir cut valve (hereinafter, referred to as an SR valve) 70 for communicating and shutting off the path.
a and 70b are provided respectively.

The SR valves 70a and 70b are normally in a shut-off state, and are switched to a communication state by energization from the ECU 20. Also, each pump 60, 62
The motor is driven via the motor 80 when the BS control and the driving force control are executed. Next, the ABS performed by the ECU 20
Control and driving force control will be described.

When the ABS control and the driving force control are not performed, all the solenoid valves of the hydraulic circuit 40 are turned off (OF).
F), and FIG. 2 shows the uncontrolled state. Specifically, as an electromagnetic valve for switching to driving force control, SM valves 50a and 50b = communication positions and SR valves
The valves 70a and 70b are shut-off positions, and the pressure-increasing control valves 46FL to 46RR are communication positions, and the pressure-reducing control valves 48FL to 48RR.
= Set to the blocking position.

ABS Control For example, when a slip occurs on each of the wheels FL to RR due to a sudden braking operation of the driver, as shown in FIG.
The BS control is started, and the SM valves 50a, 50b = communication position (OFF) and the SR valves 70a, 70b = blocking position (OF
F), the motor 80 is driven to drive the pumps 60 and 62.
Is turned on, and the pressure increase control valves 46FL-46RR and the pressure reduction control valves 48FL-48RR are respectively turned ON / OFF (energized / de-energized), so that each W / C2FL according to the slip state of each wheel FL-RR. Reduce the brake oil pressure within 2RR,
The state is appropriately switched to the state of holding and increasing the pressure.

Specifically, when it is determined that the wheels have a tendency to lock, the pressure increase control valves 46FL to 46FL corresponding to the wheels are determined.
RR is shut off (ON) and the pressure reduction control valves 48FL-48
The RR is communicated (ON) to reduce the hydraulic pressure of the corresponding W / C2FL to 2RR to prevent the wheels from being locked. At this time, the amount of oil decompressed from the W / C2FL-2RR is discharged to the reservoirs 56, 58 via the pressure-reducing control valves 48FL-48RR, and further driven by the motor 80 to store the oil in the reservoir 5.
The brake oil accumulated in 6,58 is returned to the normal brake system.

If it is determined that the locking tendency of the wheel has been eliminated during the ABS control, the pressure increasing control valves 46FL to 46RR corresponding to the wheel are communicated (OFF) and the pressure reducing control valves 48FL to 48RR are shut off (OFF). ) To increase the hydraulic pressure of the corresponding W / C2FL-2RR. In this case, if the W / C oil pressure is suddenly increased, the wheels tend to lock, so that both the pressure increase control valves 46FL to 46RR and the pressure decrease control valves 48FL to 48RR are shut off (pressure increase control valve 46 = ON). ,
The pressure reduction control valve 48 is turned off) to create a state in which the W / C hydraulic pressure is maintained. With such control, W / C
Gradually increase the oil pressure to prevent vehicle lock while ensuring vehicle stability.

After the end of the ABS control, the next AB
In order to perform the S control smoothly, the motor 80 is driven for a predetermined period to pump out the brake oil in the reservoirs 56 and 58. Driving force control (differential limiting control of each wheel FL to RR) In this driving force control, when any one of the wheels FL to RR idles in the four-wheel drive vehicle to be controlled, " As described in the section of “Prior Art”, by the action of each of the differential gears 10C, 10F, and 10R,
Since the driving force is not transmitted to the other wheels, in order to prevent such a phenomenon, when the driver performs the accelerator operation to drive the vehicle (the brake operation is not performed), each wheel is not operated. This is performed to detect a rotational speed difference (differential) between FL and RR and suppress the differential.

First, in this driving force control, as shown in FIG. 4, the motor 80 is driven to operate the pumps 60 and 62, and the SM valves 50a and 50b and the SR valves 70a and 70a are driven.
b (turn on). That is, the SM valves 50a, 50
The pump oil can be pumped from the reservoir 68 provided above the M / C 34 to each of the pressure increase control valves 46FL to 46RR by the pumps 60 and 62, where b is the shutoff position and the SR valves 70a and 70b are the communication positions. State.

Further, in the driving force control, each wheel FL to
Depending on the rotational speed difference between RR, pressure increase control valves 46FL-46RR
ON and OFF the pressure reduction control valves 48FL-48RR
By doing so, a braking force is appropriately applied to each of the wheels FL to RR, and the rotational speed difference between each of the wheels FL to RR is suppressed (in other words, the differential between the wheels FL to RR is limited).

Specifically, as in the case of the ABS control,
Pressure increasing control valves 46FL-46RR and pressure reducing control valves 48FL-48RR
To switch the W / C oil pressure of each wheel FL-RR to pressure increase, hold, and pressure reduction as appropriate, thereby changing the braking force of each wheel FL-RR and actually applying the brake force to each wheel FL-RR. The driving force transmitted to the motor is adjusted.

Therefore, hereinafter, EC for controlling the driving force will be described.
The driving force control process (which is a main part of the present embodiment) executed in U20 will be described with reference to the flowchart shown in FIG. The driving force control process is periodically executed at predetermined time intervals when an ignition switch (not shown) of the vehicle is turned on. In the following description, suffixes “FL”, “FR”,
"RL" and "RR" are the numerical values of each wheel FL, FR, RL, RR
Respectively. Therefore,
For example, among the rotation speeds VW, VWFL indicates the rotation speed of the left front wheel FL.

As shown in FIG. 5, when the execution of the driving force control process is started, first, in step (hereinafter simply referred to as "S") 110, it is determined whether the control start condition of the driving force control is satisfied. Determine whether or not. Then, when the control start condition is not satisfied, the driving force control process is temporarily terminated as it is, but when it is determined that the control start condition is satisfied, the process proceeds to S120. The control start condition is as follows:
For example, this holds when the brake switch 36 is not turned on and the driver performs an accelerator operation.

In S120, each wheel speed sensor 4FL
Based on the detection signals from 4RR to 4RR, the rotational speeds VWFL to VWRR of the four wheels FL to RR are calculated, and in S130,
The vehicle speed VB of the vehicle is calculated based on the rotation speeds VWFL to VWRR obtained in S120. This processing is, for example, 4
The minimum speed VWMIN of the rotation speeds VWFL-VWRR of the two wheels FL-RR is calculated from the acceleration limit value Vα obtained by adding a predetermined value to the vehicle speed VB (n-1) obtained last time, from the vehicle speed VB (n-1). Is determined to be within the range from the deceleration limit value Vβ obtained by subtracting the predetermined value from the vehicle speed. If the minimum speed VWMIN is within the range from the acceleration limit value Vα to the deceleration limit value Vβ, the minimum speed VWMIN If the minimum speed VWMIN exceeds the acceleration limit value Vα, this acceleration limit value Vα is set as the vehicle speed VB. If the minimum speed VWMIN is less than the deceleration limit value Vβ, the deceleration limit is set. The value Vβ is set as the vehicle speed VB by a conventionally well-known procedure.

When the vehicle speed VB is obtained in this manner, S
Proceeding to 140, the rotation speed VWFL calculated in S120
Based on VWRR, the above-described equations 1 to 4 are used to calculate the respective brake adjustment speed differences (an example of brake adjustment parameters) △ VFL △△ VRR of the four wheels FLRRRR.

Specifically, for example, the brake adjustment speed difference ΔVFL of the left front wheel FL is, as shown in the above equation 1, the difference between the rotation speed VWFL of the left front wheel FL and the rotation speed VWFR of the right front wheel FR. [VWFL-VWFR] and the rotation speed VWRL of the left and right rear wheels from the average value of the rotation speeds VWFL and VWFR of the left and right front wheels.
, VWRR, which is the difference between the front and rear wheel rotation speeds, which is the value obtained by subtracting the average value [(VWFL + VWFR) / 2− (VWRL + VWRR) / 2]
Is calculated as a value obtained by adding

Further, the speed difference for brake adjustment of the right front wheel FR.
As shown in the above equation 2, VFR is the difference [VWFR−] between the rotation speed VWFR of the right front wheel FR and the rotation speed VWFL of the left front wheel FL.
VWFL], and the difference between the front and rear wheel rotational speeds [(VWFL +
[VWFR) / 2− (VWRL + VWRR) / 2].

On the other hand, the speed difference for brake adjustment of the left rear wheel RL △
As shown in Equation 3, VRL is a difference [VWRL−) between the rotation speed VWRL of the left rear wheel RL and the rotation speed VWRR of the right rear wheel RR.
VWRR], and the rotational speeds VWRL, VWRR of the left and right rear wheels.
Rear wheel rotational speed difference [(VWRL + VWR), which is a value obtained by subtracting the average value of the left and right front wheel rotational speeds VWFL and VWFR from the average value of
R) / 2- (VWFL + VWFR) / 2].

Further, the speed difference for brake adjustment of the right rear wheel RR △
As shown in the above equation 4, VRR is the difference [VWRR− between the rotation speed VWRR of the right rear wheel RR and the rotation speed VWRL of the left rear wheel RL.
VWRL], and the rear-front wheel rotational speed difference [(VWRL +
[VWRR) / 2− (VWFL + VWFR) / 2].

Therefore, the speed difference for each brake adjustment ΔVFL ~
ΔVRR indicates how much the rotation speed VW of the corresponding wheel is higher than the rotation speeds VW of the other wheels. When the brake adjustment speed differences ΔVFL to ΔVRR of the four wheels FL to RR are calculated in S140 in this manner, the subsequent S
At 150, based on the vehicle speed VB determined at S130,
Using the data map of FIG. 7 or FIG.
Brake adjustment determination values VTFL to VTRR for determining the brake adjustment speed differences ΔVFL to ΔVRR are set.

The brake adjustment determination values VTFL to VTFL
TRR is the speed difference for brake adjustment of each wheel FL ~ RRRRVFL ~
It is also a target value for suppressing ΔVRR within the value.
In other words, the speed difference for brake adjustment of each wheel FL ~ RR △ VFL ~
ΔVRR is the corresponding brake adjustment determination value VTFL to VTR
When the pressure becomes larger than R, the W / C hydraulic pressure of the corresponding wheel is increased and the driving force transmitted to the wheel is reduced, as described later. As a result, the brake adjustment speed difference △
VFL to ΔVRR are suppressed within the brake adjustment determination values VTFL to VTRR. Also, as shown in FIG. 7 or FIG.
The brake adjustment determination values VTFL to VTRR are determined by the vehicle speed VB
Is larger, the brake adjustment determination values VTRL, VTRR for the left and right rear wheels RL, RR are better than those for the left and right front wheels FL, FR. It is set to be always smaller than the use determination values VTFL and VTFR. For example, in FIG. 7, the distance is always set smaller by 4 km / h. Therefore, using the data map of FIG. 7, when the brake adjustment speed difference ΔV is smaller for the rear wheels RL and RR than for the front wheels FL and FR, W / C
Pressure increase of the hydraulic pressure (in other words, suppression of slip) is started. In FIG. 7, the respective brake adjustment determination values VTRL, VTRR of the left and right rear wheels RL, RR are set to the same value, and the respective brake adjustment determination values V, of the left and right front wheels FL, FR are set.
Both TFL and VTFR are set to the same value. In FIG. 8, the brake adjustment determination values VTFL, VTFR VTRL, VTRR of all the wheels FL, FR, RL, RR are all set to the same value.

When the brake adjustment determination values VTFL to VTRR for the wheels FL to RR are set in this manner, the process proceeds to S16.
0, and the brake adjustment speed difference ΔV obtained in S140
FL to ΔVRR and brake adjustment determination value V obtained in S150
Using TFL to VTRR, based on the following equations 5 to 8,
Control oil pressure equivalent values BPFL to BPRR for W / C2FL to 2RR of wheels FL to RR are calculated. That is, as shown in the following equations 5 to 8, the control hydraulic pressure equivalent values BPFL to BPRR are obtained by calculating the difference between the brake adjustment speed difference ΔV and the brake adjustment determination value VT for each of the wheels FL to RR. Difference [△ V-VT]
Is multiplied by a predetermined constant α.

[0061]

(Equation 2)

Then, in S170, the motor 80 is driven to drive the pumps 60, 6 as described with reference to FIG.
2 as well as turning on both the SM valves 50a and 50b and the SR valves 70a and 70b,
b = interruption position, and SR valves 70a, 70b = communication position. Further, in S170, the pressure increase control valves 46FL to 46RR and the pressure decrease control valves 48FL to 48RR are driven according to the control oil pressure equivalent values BPFL to BPRR calculated in S160, and the W / The C hydraulic pressure is appropriately switched between pressure increase, hold, and pressure reduction. And, by this, each wheel FL ~ RR
The driving force actually transmitted is adjusted to suppress the brake adjustment speed differences ΔVFL to ΔVRR of the wheels FL to RR within the brake adjustment determination values VTFL to VTRR.

Specifically, based on the brake duty map shown in FIG. 9, the speed difference ΔV for brake adjustment of any of the wheels becomes equal to or larger than the brake adjustment determination value VT, and S1
When the control hydraulic pressure equivalent value BP of the corresponding wheel calculated in step 60 becomes a positive value, the larger the control hydraulic pressure equivalent value BP becomes (ie, the brake adjustment speed difference ΔV greatly exceeds the brake adjustment determination value VT). ), The W of the wheel
The duty of the ON / OFF signal output from the ECU 20 to the pressure increase control valve 46 is controlled so that the / C oil pressure quickly increases.

When the control oil pressure equivalent value BP becomes a negative value, the smaller the control oil pressure equivalent value BP is, the smaller the control oil pressure equivalent value BP is (ie, the more the brake adjustment speed difference ΔV is significantly lower than the brake adjustment judgment value VT). ), The duty of the ON / OFF signal output from the ECU 20 to the pressure reduction control valve 48 is controlled so that the W / C oil pressure of the wheel quickly decreases. The symbol “Front” indicates a map of the front wheels, and “R
"ear" represents the rear wheel map. The symbol “+ G” indicates a map when the wheel is accelerating, and “−G” indicates a map when the wheel is decelerating. BP ≧ 6km / h
In order to match the hydraulic characteristics of W / C, the gradient on the rear wheel side is smaller than that on the front wheel side. Also, BP = 0
Up to 12 km / h, duty (DUTY) = 0%
This part actually holds the W / C hydraulic pressure of the corresponding wheel.

After executing the processing of S170, the output control processing of the engine 6 (S200) is performed. FIG. 6 shows a flowchart of the output control process of the engine 6. First, in order to view the wheel behavior as an engine output adjustment condition in terms of wheel speed, an engine output adjustment speed difference (an example of an engine output adjustment parameter)
The calculation of ΔVE is performed as in the following Expression 9 (S210).

[0066]

(Equation 3)

The wheel behavior may be wheel acceleration or the like. Here, MAX () is an operator for extracting the maximum value, and MIN () is an operator for extracting the minimum value. Therefore, the difference between the maximum speed and the minimum speed among all the wheels FL to RR is set as the engine output adjustment speed difference ΔVE. Since the maximum speed has already been obtained in step S130, that value may be used.

Next, the engine output adjustment determination value VTE is set according to the vehicle speed VB using the data map of FIG. 7 or 8 (S220). As can be seen from FIG. 7 or FIG. 8, the engine output adjustment determination value VTE is always set to a value larger than the brake adjustment determination values VTFL to VTRR by a predetermined value. For example, in FIG. 7, the left and right front wheels FL,
8km longer than FR brake adjustment judgment values VTFL and VTFR
/ H (judgment value VTRL for brake adjustment of left and right rear wheels RL, RR,
It is set to be 12 km / h larger than VTRR. In FIG. 8, the brake adjustment determination values VTF for all the wheels FL to RR are shown.
It is set to be 12 km / h larger than L to VTRR.
Therefore, the engine output is not reduced while the acceleration is insufficient, so that the acceleration performance is maintained.

Next, the control hydraulic pressure excess equivalent amount BPE is given by the following equation (1).
It is calculated as 0 (S230).

[0070]

(Equation 4)

Next, it is determined whether a condition for starting the engine output control is satisfied (S240). This start condition is determined based on whether or not BPE> 0. If the start condition of the engine output control is not satisfied ("NO" in S240), the engine output control process ends as it is.

If the start condition of the engine output control is satisfied ("YES" in S240), it is determined whether or not the end condition of the engine output control is satisfied (S25).
0). The termination condition is determined based on whether BPE is lower than a termination condition determination value set sufficiently lower than 0, or whether BPE ≦ 0 has been maintained for a predetermined time. Alternatively, the determination may be made based on whether or not the controlled throttle opening is equal to the opening indicated by the driver's accelerator operation.

If "YES" in step S240 and "NO" in step S250, the electronic throttle ES is driven (S260). That is, control is performed to reduce the throttle opening degree designated by the driver by the opening degree corresponding to the control oil pressure excess amount BPE obtained in step S230.

For example, a decrease θd in the throttle opening is obtained by a predetermined calculation or a table from the control oil pressure excess amount BPE, and the control opening obtained by subtracting the decrease θd from the throttle opening θ0 indicated by the driver. The electronic throttle ES is adjusted so that the degree becomes θE.

As a result, when an excessive wheel speed difference (an example of a wheel behavior difference) is generated between the wheels FL and RR and the braking force is going to be excessive, the output of the engine 6 can be reduced. As a result, it is possible to prevent the frequency of actuator operation for brake pad wear and heat generation and hydraulic pressure adjustment in the brake device from increasing, and to prevent the load on the drive system from increasing. The drop can be prevented. Further, since the engine output adjustment determination value VTE is set at a position where the engine output is sufficiently higher than the brake adjustment determination values VTFL to VTRR, the acceleration performance is sacrificed even if the engine output is reduced. Never be.

It should be noted that the engine output control (S20
When 0) is completed, the driving force control process is terminated once, and after a predetermined time has elapsed, the execution is started again from the process of S110. Next, as a specific example, FIG. 8 shows a case where the driving force control is performed by the left front wheel FL and the left rear wheel RL slipping during acceleration on a straddle road or the like having different friction coefficients on the right and left sides of the road. An example using a map is shown in FIG.
This will be described based on the timing chart shown in FIG.

First, since the left front wheel FL and the left rear wheel RL have started to slip, their speeds VWFL, VWRL (in this example, the maximum speed is represented by VWMAX) are rapidly increased, and the other wheels FR are increased. , RR, VWFR, VWRR (in this example, the minimum speed is represented by VWMIN.) And rises (time t0), and ΔVF obtained from the above equations (1) and (3).
L and ΔVRL are the brake adjustment determination values VTFL and
When it exceeds VTRL, the control oil pressure equivalent values BPFL and BPRL set based on the equations (5) and (7) exceed 0 (time t1).

Therefore, after this time t1, the pump 60,
The brake hydraulic pressure generated by the drive of 62 is W / C2F
In addition to L and 2RL, the hydraulic pressure rises, and the braking of the left front wheel FL and the left rear wheel RL is started by the braking force.

At time t2, the value of VWMAX-VWMIN,
That is, since ΔVE exceeds the engine output adjustment determination value VTE, the control hydraulic pressure excess equivalent amount BPE> 0, and BPE
The control for reducing the output of the engine 6 by reducing the opening degree of the electronic throttle ES in accordance with the value of is started.

As described above, since the output of the engine 6 is reduced, the driving force of the wheels is reduced. Therefore, the speed VWF of the left front wheel FL and the left rear wheel RL with particularly high brake oil pressure is
As shown by the solid lines, the rises of L and VWRL are suppressed and further decreased. As a result, the control oil pressure equivalent value BPF
Since the increase of L and BPRL is suppressed and decreased, the increase of the brake oil pressure is suppressed as shown by the solid line.

If the output of the engine 6 is not reduced, the control oil pressure equivalent values BPFL, BPRL and the brake oil pressure change as shown by the broken line, and the brake oil pressure is further increased and the actuator processing for applying the brake oil pressure is performed. For a long time, the wear of the brake pads and the drive frequency of the actuator increase, the durability of the brake device decreases, the load on the drive system increases, and the durability of the drive system decreases. In the present embodiment, such a problem does not occur. These results are shown in FIG.
The same applies to the case where the data map is used.

In the present embodiment, steps S120 to S170 in the driving force control processing correspond to processing as braking force control means, and steps S160 and S170
Correspond to brake adjustment parameter determination means and brake force adjustment means, and are equivalent to steps S120, S210 to S2.
40 corresponds to a process as a braking force determining unit, step S210 corresponds to a process as an engine output adjustment parameter calculating unit, steps S220 to S240 correspond to a process as an excessive determining unit, and the electronic throttle ES.
Corresponds to engine output adjusting means, and step S260 corresponds to processing as engine output control means.

When the data map of FIG. 7 is used, the brake adjustment determination values VTRL, VTR for the left and right rear wheels RL, RR are used.
TRR is the brake adjustment judgment value VTFL for the front left and right wheels FL and FR.
, VTFR is set to a value smaller than
As a result, the right / left rear wheels RL and RR are smaller than the left and right front wheels FL and FR when the brake adjustment speed difference ΔV is smaller than the W / C ratio.
The increase of the hydraulic pressure is started. Therefore, when a rotational speed difference occurs between both the left and right front wheels FL and FR and between the left and right rear wheels RL and RR, the rotational speed difference between the left and right front wheels FL and FR is larger than the rotational speed difference between the left and right front wheels FL and FR. The rotation speed difference is preferentially suppressed. As a result, it is possible to preferentially prevent the behavior of the vehicle from becoming oversteer (spin tendency) due to a difference in rotational speed between the left and right rear wheels RL, RR, and the running stability is impaired. While preventing
The propulsion of the vehicle can be reliably maintained.

In this embodiment, the left and right front wheels FL, FR
Rotation speed difference [VWFL-VWFR], [VWFR-V
WFL], the front and rear wheel rotational speed difference [(VWFL + VWFR) / 2
− (VWRL + VWRR) / 2] is added to the left and right front wheels.
The speed difference for brake adjustment between FL and FR is △ VFL, 、 VFR, and the rotational speed difference between the left and right rear wheels RL, RR [VWRL-VWRR],
[VWRR-VWRL] is added to the rear front wheel rotational speed difference [(VWRL +
VWRR) / 2- (VWFL + VWFR) / 2], and calculate the speed difference {VRL,} for the brake adjustment of the left and right rear wheels RL, RR.
VRR. Therefore, as the total rotational speed [VWFL + VWFR] of the left and right front wheels FL and FR becomes larger than the total rotational speed [VWRL + VWRR] of the left and right rear wheels RL and RR, the left and right front wheels F
When the speed difference ΔVFL, ΔVFR for each brake adjustment of L, FR becomes a large value, and when both speed difference ΔVFL, ΔVFR for both brake adjustments exceed the judgment value VTFL, VTFR for brake adjustment, the left and right front wheels FL, FR , A braking force is applied to both of them, thereby suppressing a difference in rotational speed between the front and rear wheels.

Conversely, as the total rotational speed [VWRL + VWRR] of the left and right rear wheels RL and RR becomes larger than the total rotational speed [VWFL + VWFR] of the left and right front wheels FL and FR, the left and right rear wheels R
When each of the brake adjustment speed differences △ VRL and △ VRR of L and RR becomes a large value, and both brake adjustment speed differences △ VRL and △ VRR exceed the brake adjustment determination values VTRL and VTRR, the left and right rear wheels RL and A braking force is applied to both of the RRs, thereby suppressing a difference in rotational speed between the front and rear wheels. Therefore, it is possible to suppress the difference in rotational speed between the front and rear wheels while preventing running stability from being impaired, and to more reliably maintain the propulsion of the vehicle.

In this embodiment, the wheel speed sensor 4
Based on the detection signals from FL to 4RR, the speed difference for brake adjustment △ VFL to △ VRR and the speed difference for engine output adjustment ΔVE of each wheel FL to RR are determined, so that the structure is simple and accurate. The driving force and the engine output transmitted to each of the wheels FL to RR can be controlled. For example, by monitoring the differential state of each of the front differential gear 10F and the rear differential gear 10R, the left and right front wheels FL, FR Rotation speed difference [VWFL-VWF
R], [VWFR-VWFL] and the rotational speed difference [VWRL-VWRR], [VWRR-VWRL] between the left and right rear wheels RL, RR, and further monitors the differential state of the center differential gear 10C. , Front and rear wheel rotation speed difference [(VWFL + V
WFR) / 2- (VWRL + VWRR) / 2] and rear front wheel rotational speed difference [(VWRL + VWRR) / 2- (VWFL + VWFR) /
2], the brake adjustment speed differences ΔVFL to ΔVRR of the wheels FL to RR and the engine output adjustment speed difference ΔVE may be obtained.

On the other hand, in the present embodiment, the braking force is generated on each of the wheels FL to RR and the opening degree of the electronic throttle ES of the engine 6 is controlled to decrease, so that the driving force transmitted to each of the wheels FL to RR Therefore, the above-described effects can be obtained by using most of the existing brake system and engine control system mounted on the vehicle, and the device can be simplified and the weight of the vehicle can be reduced. be able to.

Specifically, as a brake system,
Normally, to perform ABS control, the hydraulic circuit 40 of FIG.
, The SM valves 50a, 50b and the relief valves 54a,
A circuit configuration excluding 54b and the SR valves 70a and 70b is required, but it is only necessary to add the SM valve, relief valve, and SR valve to this configuration. Also, as the engine control system, step S200
It is only necessary to add the control program of

[Others] In the above embodiment, even when the data map of FIG. 7 is used as the brake adjustment determination value, the engine output adjustment determination value VTE is only one as shown in FIG. The engine output adjustment determination value VTE may be switched and used depending on whether the maximum speed wheel is the front wheel or the rear wheel. For example, as shown in FIG. 11, an engine output adjustment determination value VTEF when the front wheel is at the maximum speed is provided at a position shifted upward by a predetermined value from the brake adjustment determination values VTFL, VTFR for the front wheels. A determination value VTER for adjusting the engine output when the rear wheel is at the maximum speed may be provided at a position shifted upward by a predetermined value from the adjustment determination values VTRL, VTRR. When such a determination value is used, the output of the engine can be controlled in accordance with the wheel on which excessive braking force is generated, so that more precise control can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an entire control system of a four-wheel drive vehicle according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a configuration of the hydraulic circuit.

FIG. 3 is a timing chart illustrating ABS control performed by an ECU.

FIG. 4 is a timing chart illustrating driving force control performed by an ECU.

FIG. 5 is a flowchart illustrating a driving force control process executed by the ECU.

FIG. 6 is a flowchart illustrating an engine output control process executed by the ECU.

FIG. 7 is a configuration explanatory diagram of an example of a data map used when executing a driving force control process.

FIG. 8 is a configuration explanatory diagram of another example of the data map used when executing the driving force control process.

FIG. 9 is an explanatory diagram of a configuration of a brake duty map used when executing a driving force control process.

FIG. 10 is a timing chart for explaining an operation example of the embodiment.

FIG. 11 is a configuration explanatory diagram of another example of the data map used when executing the driving force control process.

[Explanation of symbols]

FL: Left front wheel FR: Right front wheel RL: Left rear wheel RR
... right rear wheel ES ... electronic throttle 2FL, 2FR, 2RL, 2RR ... brake device (wheel cylinder: W / C) 4FL, 4FR, 4RL, 4RR ... wheel speed sensor 6 ... engine 8 ... transmission 10C ... center differential gear 10F: Front differential gear 10R: Rear differential gear 11F: Drive shaft for front wheels 11R: Drive shaft for rear wheels
12 Sensor group 20 ECU 32 Brake pedal 34 Master cylinder (M / C) 36 Brake switch 40 Hydraulic circuit 42, 44 Hydraulic path 46 (46FL, 46FR, 46RL, 46RR) ... Pressure increase control valve 48 (48FL, 48FR, 48RL, 48RR) ... pressure reducing control valve 50a, 50b ... SM valve 54a, 54b ... relief valve 56, 58 ... reservoir 60, 62 ... pump 64, 66 ... accumulator 68 ... reservoir 70a, 70b ... SR valve 80 …motor

Claims (18)

[Claims] A wheel behavior difference between each wheel of a four-wheel drive vehicle and other wheels is determined as a brake adjustment parameter, and a driving force transmitted from an engine to each wheel is determined as the brake adjustment parameter. A driving force control method for a four-wheel drive vehicle, characterized in that the difference in wheel behavior is suppressed by adjusting the braking force based on the braking force, and the output of the engine is reduced when the braking force is excessive. 2. The method according to claim 1, wherein a wheel behavior difference between all wheels is determined as an engine output adjustment parameter, and the excessive braking force is determined based on the engine output adjustment parameter. A driving force control method for a wheel drive vehicle. 3. When the brake adjustment parameter is greater than a predetermined brake adjustment determination value for each wheel, a brake is applied in accordance with a difference between the brake adjustment parameter and the brake adjustment determination value. While adjusting the force, when the engine output adjustment parameter is larger than a predetermined engine output adjustment determination value that is larger than the brake adjustment determination value, it is determined that the braking force is excessive, The driving force control method for a four-wheel drive vehicle according to claim 2, wherein the engine output is adjusted according to a difference between an engine output adjustment parameter and the engine output adjustment determination value. 4. A driving force control method for a four-wheel drive vehicle according to claim 2, wherein said engine output adjustment parameter is a difference between a maximum speed and a minimum speed of all wheels. 5. The method according to claim 1, wherein the determination value for brake adjustment is provided for each wheel, and the determination value for engine output adjustment is set to a predetermined value larger than the determination value for brake adjustment provided for a wheel having a maximum speed. The driving force control method for a four-wheel drive vehicle according to claim 3, wherein 6. The driving force control method for a four-wheel drive vehicle according to claim 5, wherein said engine output adjustment parameter is equal to said brake adjustment parameter for a wheel having a maximum speed. 7. The brake adjustment parameter includes a difference between a speed of the own wheel and a speed of another wheel on the same side in the front-rear direction, and an average value between the own wheel and the other wheel on the opposite side in the front-rear direction. The driving force control method for a four-wheel drive vehicle according to any one of claims 1 to 6, wherein a value obtained by adding a value obtained by subtracting the average value of the two-wheel speed is added. 8. The engine according to claim 1, wherein the engine is an internal combustion engine, and the output of the engine is reduced by reducing an intake air amount of the internal combustion engine. A driving force control method for a wheel drive vehicle. 9. The engine according to claim 1, wherein the engine is an internal combustion engine, and the output of the engine is reduced by reducing an amount of fuel supplied to the internal combustion engine. A driving force control method for a wheel drive vehicle. 10. A wheel behavior difference between each wheel of a four-wheel drive vehicle and other wheels is determined as a brake adjustment parameter, and a driving force transmitted from the engine to each wheel is determined as the brake adjustment parameter. A driving force control device for a four-wheel drive vehicle having a braking force control means for adjusting the braking force based on the braking force to suppress the wheel behavior difference, wherein the braking force adjusted by the braking force control means is excessive. A braking force determining unit that determines the output of the engine; and an engine output adjusting unit that adjusts the output of the engine. When the braking force determining unit determines that the braking force is excessive, the engine output adjusting unit controls And an engine output control means for reducing the output of the engine by a driving force control device for a four-wheel drive vehicle. 11. An engine output adjustment parameter calculation means for obtaining a wheel behavior difference between all wheels as an engine output adjustment parameter, and the engine output obtained by the engine output adjustment parameter calculation means. Based on the tuning parameters,
The driving force control device for a four-wheel drive vehicle according to claim 10, further comprising: an excessive determination unit configured to determine an excessive braking force. 12. The brake force control means, comprising: a brake adjustment parameter determining means for determining whether the brake adjustment parameter is greater than a predetermined brake adjustment determination value; and the brake adjustment parameter determining means. When it is determined that the brake adjustment parameter is larger than a predetermined brake adjustment determination value, the brake force is adjusted according to a difference between the brake adjustment parameter and the brake adjustment determination value. A braking force adjusting unit, and the excessive judging unit, when the engine output adjusting parameter becomes larger than a predetermined engine output adjusting judging value larger than the brake adjusting judging value, The engine output control means determines that the power is excessive, and the engine output control means 12. The method according to claim 11, wherein when it is determined that the braking force is excessive, the engine output is reduced according to a difference between the engine output adjustment parameter and the engine output adjustment determination value. Of four-wheel drive vehicle. 13. The engine output adjustment parameter,
13. The driving force control device for a four-wheel drive vehicle according to claim 11, wherein the difference is a difference between a maximum speed and a minimum speed of all the wheels. 14. A method according to claim 1, wherein the determination value for brake adjustment is provided for each wheel, and the determination value for engine output adjustment is set to a predetermined value larger than the determination value for brake adjustment provided for a wheel having a maximum speed. The driving force control device for a four-wheel drive vehicle according to claim 12, wherein 15. The engine output adjusting parameter is:
The driving force control apparatus for a four-wheel drive vehicle according to claim 14, wherein the parameter is equal to the brake adjustment parameter for a wheel having a maximum speed. 16. The brake adjustment parameter includes a difference between the speed of the own wheel and the speed of another wheel on the same side in the front-rear direction, and the difference between the average value between the own wheel and the other wheel in the front-rear direction. The driving force control device according to any one of claims 10 to 15, wherein a value obtained by adding a value obtained by subtracting the average value of the speeds of the two wheels is added. 17. The engine is an internal combustion engine, the engine output adjusting means adjusts an intake air amount of the internal combustion engine, and the engine output control means controls a decrease in the output of the engine. The driving force control device for a four-wheel drive vehicle according to any one of claims 10 to 16, wherein the output adjustment means reduces the amount of intake air of the internal combustion engine. 18. The engine is an internal combustion engine, the engine output adjusting means adjusts the amount of fuel supplied to the internal combustion engine, and the engine output control means controls a decrease in the output of the engine. The driving force control device for a four-wheel drive vehicle according to any one of claims 10 to 16, wherein the output adjustment means reduces the amount of fuel supplied to the internal combustion engine.