JP3301220B2 - Driving force distribution control system for left and right wheels and front and rear wheels - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving force distribution control system for left and right wheels and front and rear wheels applied to a vehicle equipped with a left and right wheel driving force distribution control system and a front and rear wheel driving force distribution control system.

[0002]

2. Description of the Related Art Conventionally, as a driving force distribution control device for a four-wheel drive vehicle for preventing hunting at the time of starting or intermediate acceleration on a road with a low friction coefficient, for example, Japanese Patent Application Laid-Open No. 2-290728 is known.
There is known an apparatus described in Japanese Patent Application Laid-Open Publication No. Hei.

[0003] This conventional reference discloses a normal front and rear wheel rotation speed when wheel spin is detected by a wheel drive detecting means for detecting wheel spin of a clutch engagement drive wheel to which engine driving force is transmitted via a clutch. There is disclosed a technique for performing driving force distribution control corresponding to longitudinal acceleration instead of driving force distribution control corresponding to a difference.

[0004]

However, in the above-mentioned conventional apparatus, the engagement drive wheel spin detecting means detects the engagement drive wheel spin based on the difference between the clutch engagement drive wheel speed and the vehicle body speed based on the average value. If the wheel spin determination threshold is set large to prevent unnecessary wheel spin control,
When starting on a split μ road where one wheel is a high μ road and one wheel is a low μ road, clutch engagement by the average value is achieved because the wheel speed on the high μ road is low even if the wheel speed on the low μ road is high. Driving wheel speed does not increase as when starting on low left and right roads, wheel spin is not detected or wheel spin detection is delayed, and driving force distribution control corresponding to front and rear wheel rotation speed difference is continued However, there remains a problem that control hunting occurs.

Here, the mechanism of occurrence of control hunting when starting on a split μ road will be described.

[0006] In the case of a four-wheel drive vehicle based on a rear wheel drive, the front wheels which are the clutch engagement drive wheels have smaller drive system inertia (inertia) than the rear wheels which are the engine direct drive wheels. Therefore, when the rear wheel spins immediately after the split μ road starts and a front and rear wheel rotational speed difference occurs, the clutch engagement force increases and the driving force is transmitted to the front wheel. Then, the front wheels on the low μ road side with small drive system inertia rapidly increase in rotation and over-rotate, so that the apparent front-rear wheel rotational speed difference decreases and the clutch engagement force decreases. Then,
The front wheels on the low-μ roadside are driven by the increase or decrease in the clutch engagement force, as the front wheels on the low-μ roadside with low drive system inertia grip quickly, causing a difference in front and rear wheel rotational speed again and increasing the clutch engagement force. The spin and the grip are repeated, and as shown in FIG. 6, the ETS torque (clutch engagement force) causes control hunting.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an object to be applied to a vehicle equipped with a left and right wheel driving force distribution control system and a front and rear wheel driving force distribution control system. An object of the present invention is to provide a drive force distribution integrated control device for left and right wheels and front and rear wheels to reliably prevent control hunting based on accurate determination of a split μ road.

[0008]

According to a first aspect of the present invention, there is provided a driving force distribution integrated control device for right and left wheels and front and rear wheels, which achieves the above object, as shown in FIG. A left and right wheel driving force distribution control system a that controls driving force distribution to the left and right wheels based on predetermined input information, and a directly connected driving wheel as the front and rear wheel rotation speed difference detected by the front and rear wheel rotation speed difference detecting means c increases. A front / rear wheel drive force distribution control system b for controlling the drive force distribution to front and rear wheels to reduce the drive force distribution to the clutch engagement drive wheels and reduce the drive force distribution to the clutch engagement drive wheels. Detected by clutch engagement drive wheel speed detecting means d for detecting the clutch engagement drive wheel speed which is the wheel speed of the drive wheel, vehicle body speed detecting means e for detecting the vehicle body speed, and left and right drive wheel rotational speed difference detecting means f. Right and left drive Differential limiting control execution determining means g for determining whether or not control for limiting the differential between the left and right wheel driving wheels is performed based on the occurrence of the wheel rotation speed difference, and the differential between the left and right wheel driving force distribution control system a. At the time of execution of limit control,
In addition, when the deviation between the clutch engagement drive wheel speed and the vehicle body speed exceeds the set deviation, a split μ road determining means h that determines that the road μ is a split μ road with different road surface friction coefficients.
And a split μ road for performing front and rear wheel driving force distribution control by a fixed value obtained by adding a predetermined value to the driving force distribution command value output by the front and rear wheel driving force distribution control system b when the split μ road is determined. Corresponding front and rear wheel drive force distribution control means i
And characterized in that:

According to a second aspect of the present invention, there is provided a comprehensive control system for driving force distribution between left and right wheels and front and rear wheels according to the first aspect of the present invention. The judging means h determines that the difference between the clutch engagement drive wheel speed and the vehicle speed is equal to or less than the set deviation when the vehicle speed is equal to or less than the set vehicle speed, the left and right wheel driving force distribution control system a determines the execution of the differential limiting control. If it exceeds, it is a means for judging that it is a split μ road having different left and right road surface friction coefficients.

According to a third aspect of the present invention, there is provided a comprehensive control system for driving force distribution between left and right wheels and front and rear wheels according to the second aspect of the present invention. The judging means h determines that the difference between the clutch engagement drive wheel speed and the vehicle speed is equal to or less than the set deviation when the vehicle speed is equal to or less than the set vehicle speed, the left and right wheel driving force distribution control system a determines the execution of the differential limiting control. In the case where the state of exceeding the value exceeds a set time or more, the means is a means for determining that the road is a split μ road having different road surface friction coefficients.

According to a fourth aspect of the present invention, there is provided an integrated driving force distribution control apparatus for left and right wheels and front and rear wheels.
In the driving force distribution integrated control device for the left and right wheels and the front and rear wheels described above, the left and right wheel driving force distribution control system a includes at least a differential high torque corresponding to a difference between left and right driving wheel speeds and a differential restriction torque corresponding to an accelerator opening. The differential limiting control execution determining means g, based on the occurrence of the left and right driving wheel rotation speed difference when the left and right driving wheel speed difference corresponding differential limiting torque is selected, It is a means for determining that the control for limiting the differential of the wheel drive wheels is being executed.

[0012]

The operation of the first invention will be described.

When starting or running, the differential limit control execution determining means g determines the difference between the left and right wheel drive wheels based on the occurrence of the right and left drive wheel rotational speed difference detected by the left and right drive wheel rotational speed difference detecting means f. It is determined whether or not control for restricting the movement is being performed.
At the time of the execution of the differential limiting control in the left and right wheel driving force distribution control system a, the deviation between the clutch engagement drive wheel speed from the clutch engagement drive wheel speed detection unit d and the vehicle body speed from the vehicle body speed detection unit e is determined. When the deviation exceeds the set deviation, it is determined that the road μ is a split μ road having a different friction coefficient between the left and right road surfaces, and the front and rear wheel driving force distribution is determined by the split μ road corresponding front and rear wheel driving force distribution control means i when the split μ road is determined. The front and rear wheel driving force distribution control is performed by a fixed value obtained by adding a predetermined value to the driving force distribution command value output on the control system b side.

As described above, in the vehicle equipped with the left and right wheel driving force distribution control system a, the control for limiting the differential between the left and right wheel driving wheels is performed based on the occurrence of the left and right driving wheel rotation speed difference. Paying attention to the fact that can be used as the estimated information of the split μ road, the uncertainty in the estimated information is compensated for by the deviation information between the clutch engagement drive wheel speed and the vehicle body speed, and the accurate determination of the split μ road is performed.

When it is determined that the vehicle is on the split μ road, the front and rear wheel drive force distribution control is performed by a fixed value obtained by adding a predetermined value to the drive force distribution command value at the time of the determination, so that control hunting is reliably performed. Is prevented.

The operation of the second invention will be described.

In determining the split μ road, the split μ road determining means h determines whether the vehicle speed is equal to or less than the set vehicle speed, and when the right and left wheel drive force distribution control system a determines that the differential limiting control is to be executed. When the deviation between the engagement drive wheel speed and the vehicle body speed exceeds the set deviation, it is determined that the road is a split μ road having different left and right road surface friction coefficients.

That is, since the vehicle speed condition that the vehicle speed is equal to or less than the set vehicle speed is added to the split μ road determination condition in the first invention, the cause of the rattling vibration when the vehicle starts on the split μ road is as follows. Control hunting is prevented.

The operation of the third invention will be described.

In determining the split μ road, the split μ road determining means h determines whether the vehicle speed is equal to or less than the set vehicle speed, and when the right and left wheel driving force distribution control system a determines that the differential limiting control is to be performed. If the deviation between the engagement drive wheel speed and the vehicle speed exceeds the set deviation for more than the set time, the split friction coefficient of the left and right road surface frictions differs.
Road is determined.

That is, the time condition is added to the deviation condition between the clutch engagement drive wheel speed and the vehicle body speed, which is one of the conditions for determining the split μ road in the second invention, so that it is instantaneous due to disturbance or the like. When the deviation condition between the clutch engagement drive wheel speed and the vehicle body speed is satisfied, erroneous determination of the split μ road is prevented.

The operation of the fourth invention will be described.

During traveling, left and right wheel driving force distribution control system a
, The differential limiting torque is applied by at least the select high of the differential limiting torque corresponding to the left and right drive wheel speed difference and the differential limiting torque corresponding to the accelerator opening. Then, when judging the execution of the differential limiting control based on the occurrence of the difference between the left and right driving wheel speeds, the differential limiting control execution determining means g selects the left and right driving wheel speed difference when the differential limiting torque corresponding to the difference is selected. Based on the occurrence of the wheel rotation speed difference, it is determined that the control for limiting the differential between the left and right drive wheels is being executed. Therefore, it is determined that the differential limiting control based on the occurrence of the difference between the left and right driving wheel speeds is performed by a simple determination process only for determining the control mode selected by the left and right wheel driving force distribution control system a. You.

[0024]

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

First, the configuration will be described.

FIG. 2 is an overall system diagram of a rear-wheel drive-based four-wheel drive vehicle to which the integrated driving force distribution control device for the left and right wheels and the front and rear wheels according to the embodiment of the present invention is applied.

In FIG. 2, the driving force from the engine 1 and the transmission 2 is transmitted from the rear propeller shaft 3 to the left and right rear wheels 5 and 6 via the electronically controlled LSD 4.
The power is transmitted from the rear propeller shaft 3 to the left and right front wheels 10, 11 via the ETS transfer 7, the front propeller shaft 8, and the front differential 9.

The electric control LSD 4 includes a hydraulic unit 12.
Left and right rear wheels 5, 6 according to the clutch control pressure applied from
A differential limiting clutch 13 for generating a differential limiting torque between them is built in.

The ETS transfer 7 has front wheels 1 according to the clutch control pressure applied from the hydraulic unit 12.
A transfer clutch 14 for generating a transmission drive torque to 0 and 11 is built in.

The hydraulic unit 12 includes a hydraulic source 15 and an E
It has a TS control valve 16 and an LSD control valve 17.

The ETS control valve 16 operates in accordance with a command from an ETS controller 18a of the controller 18 to generate a clutch control pressure for the transfer clutch 14 (corresponding to the front and rear wheel driving force distribution control system b).

The LSD control valve 17 operates in accordance with a command from an LSD controller 18b of the controller 18 to generate a clutch control pressure for the differential limiting clutch 13 (corresponding to the left and right wheel driving force distribution control system a). .

The controller 18 includes a left front wheel rotation speed NFL from a left front wheel rotation sensor 19, a right front wheel rotation speed NFR from a right front wheel rotation sensor 20, and a left rear wheel rotation sensor 21.
, The right rear wheel rotation speed NRR from the right rear wheel rotation sensor 22, the lateral acceleration YG from the lateral acceleration sensor 23, the accelerator opening θ from the accelerator opening sensor 24, A switch signal from the brake switch 25;
Necessary information such as the longitudinal acceleration XG from the longitudinal acceleration sensor 26 is input.

The controller 18 includes an ETS controller 18a for controlling the driving force distribution of the front and rear wheels and an LSD controller 18b for performing the differential limiting control.
The control information is exchanged between the control unit 18a and the LSD control unit 18b.

Next, the operation will be described.

[Differential Limiting Torque Control Operation] FIG. 3 is a flowchart showing the flow of the differential limiting torque control processing operation performed by the LSD controller 18b of the controller 18, and each step will be described below.

In step 30, the left front wheel speed NFL, the right front wheel speed NFR, the left rear wheel speed NRL, and the right rear wheel speed NRR
And the lateral acceleration YG and the accelerator opening θ are read.

In step 31, the left front wheel speed NFL, the right front wheel speed NFR, the left rear wheel speed NRL, and the right rear wheel speed NRR
From the front left wheel speed VFL, front right wheel speed VFR and rear left wheel speed V
RL and right rear wheel speed VRR are calculated.

In step 32, arithmetic processing of various basic information is performed as follows.

1) The vehicle speed VF is obtained by selecting the smaller one of the front left wheel speed VFL and the front right wheel speed VFR (corresponding to the vehicle speed detecting means e).

2) The difference between the front left and right wheel speeds ΔVF is calculated from the absolute value of the difference between the front left wheel speed VFL and the front right wheel speed VFR.

3) The right and left rear wheel speed difference ΔVR is calculated from the absolute value of the difference between the left rear wheel speed VRL and the right rear wheel speed VRR.

4) The front wheel speed average value VFA is calculated from the average value of the left front wheel speed VFL and the right front wheel speed VFR (corresponding to clutch engagement drive wheel speed detecting means d).

In step 33, a turning trajectory left / right rear wheel speed difference ΔVR ′ generated by a turning trajectory difference between the inner and outer wheels at the time of turning is calculated by the following equation.

ΔVR ′ = K2 · VF / R where
In step 34, K2 is a constant, and R is the turning radius. In step 34, the control right and left rear wheel speed difference ΔVRR is calculated by the following equation that subtracts the turning locus left and right rear wheel speed difference ΔVR 'from the detected right and left rear wheel speed difference ΔVR ( Left and right driving wheel rotational speed difference detecting means f).

ΔVRR = ΔVR−ΔVR 'In step 35, the differential limiting torque TΔn proportional to the difference between the left and right rear wheel speeds is calculated by the following equation.

TΔn = C · ΔVRR Here, C is a constant and is given as a fixed value or a variable value that is a large value in a low vehicle speed range and a small value in a high vehicle speed range.

In step 36, the differential limiting torque TA proportional to the accelerator opening is calculated by the following equation.

TA = K · (θ−θ0) where K is a constant and is given as a fixed value or a variable value that is a small value in a low lateral acceleration range and a large value in a high lateral acceleration range. . θ0 is an accelerator opening offset value, and the differential limiting torque is applied in an accelerator opening region exceeding this value θ0.

In step 37, it is determined whether or not the vehicle speed VF is lower than the set vehicle speed x.

In step 38, VF is determined in step 37.
When it is determined that ≧ x, the differential limiting torque ToLSD is set to the differential limiting torque TA proportional to the accelerator opening.

In step 39, VF is determined in step 37.
When it is determined that x is satisfied, the differential limiting torque TA proportional to the accelerator opening is changed to the differential limiting torque TΔ proportional to the right and left rear wheel speed difference.
It is determined whether it is larger than n (corresponding to differential limit control execution determining means g).

In step 40, TA in step 39
When it is determined that> TΔn, the split μ road flag FMS is set to FMS = 0.

In step 41, the differential limiting torque ToLSD
Is set to the differential limiting torque TA proportional to the accelerator opening.

In step 42, in step 39 TA
When it is determined that ≦ TΔn, the state where the front wheel speed average value VFA exceeds (vehicle speed VF + 0.25 km / h) is 80
It is determined whether or not the continuation is equal to or longer than msec (corresponding to the split μ road determination means h).

In step 43, YES in step 42
Is determined, the split μ road flag FMS is set to FM
S = 1 is set.

In step 44, when it is determined NO in step 42, the split μ road flag FMS is set to FMS.
= 0 is set.

In step 45, the differential limiting torque ToLSD
Is set to the differential limiting torque TΔn proportional to the difference between the left and right rear wheel speeds.

In step 46, steps 38, 41,
A control command for obtaining the differential limiting torque ToLSD set in any one of 45 is output to the LSD control valve 17.

FIG. 5 is a flowchart showing the flow of the front and rear wheel driving force distribution control operation performed by the ETS control unit 18a of the controller 18. Each step will be described below.

In step 50, the left front wheel rotation speed NFL, the right front wheel rotation speed NFR, the left rear wheel rotation speed NRL, and the right rear wheel rotation speed NR
R, lateral acceleration YG, accelerator opening θ, and split μ road flag FMS are read.

In step 51, the left front wheel speed NFL, the right front wheel speed NFR, the left rear wheel speed NRL, and the right rear wheel speed NRR
From the front left wheel speed VFL, front right wheel speed VFR and rear left wheel speed V
RL and right rear wheel speed VRR are calculated.

In step 52, the front and rear wheel rotational speed difference ΔVFR is calculated from the difference between the average rear wheel speed VRA and the average front wheel speed VFA.

In step 53, the ETS clutch torque TΔV is calculated from the gain Kh and the front and rear wheel rotational speed difference ΔVFR.

Here, the gain Kh is set to a high fixed value in the low lateral acceleration region, as shown in a frame 53 ', and decreases in inverse proportion to the magnitude of the lateral acceleration in the high lateral acceleration region. Is set to Further, the ETS clutch torque TΔV is given by a value proportional to the magnitude of the front and rear wheel rotation speed difference ΔVFR, with the gain Kh as an increasing / decreasing slope.

At step 54, it is determined whether or not the split μ road flag FMS is FMS = 1. When FMS = 1, the flow proceeds to step 55 to step 58 (the split μ road corresponding front / rear wheel driving force distribution control). When FMS = 0, steps 59 to 59 are performed.
The flow proceeds to step 61.

In step 55, the FMS counter value C
(FMS) is incremented by one each time the step elapses.

In step 56, the FMS counter value C
It is determined whether (FMS) is C (FMS) = 1.

In step 57, the split μ road corresponding torque T (FMS) is set to 0 and the split μ road flag FMS is set to 0.
ETS clutch torque TΔV when changing from 1 to 1
It is set as a fixed value obtained by adding 0 Kg-m.

In step 58, the ETS clutch torque command value TΔV (n) is changed to the split μ road corresponding torque T (F
MS).

In step 59, the FMS counter value C
(FMS) is reset to C (FMS) = 0.

In step 60, the torque T (FMS) corresponding to the split μ road is set to T (FMS) = 0.

At step 61, the ETS clutch torque command value TΔV (n) is calculated based on the ETS calculated at step 53.
It is set by the value of the clutch torque TΔV.

In step 62, the ETS clutch torque command value TΔV (n) set in step 58 or step 61 is output to the ETS control valve 16.

[Differential Limiting Torque Control] The differential limiting torque control is performed according to a flowchart shown in FIG. When the vehicle suddenly starts on a high μ road or the like, the differential limiting torque ToLSD is set to the differential limiting torque TA proportional to the accelerator opening in step 40, and by this control, the left and right rear wheels 5,
The transmission of the engine driving force to the engine 6 is ensured, and high starting performance is exhibited.

At the time of acceleration running or acceleration turning, the differential limiting torque ToLSD is set at step 38 to the differential limiting torque TA proportional to the accelerator opening. At the time of acceleration running, the engine is supplied to the left and right rear wheels 5 and 6. The transmission of the driving force is ensured, high acceleration performance is exhibited, and the engine driving force is transmitted to the left and right rear wheels 5 and 6 by the engagement of the differential limiting clutch 13 even when the turning inner wheel becomes slightly idle during the acceleration turning. As a result, the response of the accelerator control is improved.

When the vehicle starts on the split μ road, the differential limiting torque ToLSD is set to the differential limiting torque TΔn in proportion to the difference between the left and right rear wheel speeds in step 45, and the idling on the low μ road side of the left and right rear wheels 5, 6 is performed. It can be suppressed by applying the differential limiting torque TΔn.

[Normal Front / Rear Wheel Driving Force Distribution Control] The front / rear wheel driving force distribution control is performed according to the flowchart shown in FIG.
Gain Kh according to lateral acceleration YG and front and rear wheel rotational speed difference Δ
Control for obtaining ETS clutch torque TΔV calculated by VFR is performed. With this control, for example, when turning on a low μ road where the occurrence of the lateral acceleration YG is small, the gain Kh
Is large and the driving force distribution to the front wheels is large with respect to the occurrence of the front and rear wheel rotational speed difference ΔVFR, suppressing oversteer,
Also, when turning on a high μ road where the lateral acceleration YG is large, the gain Kh is small and the distribution of the driving force to the front wheels is small with respect to the generation of the front and rear wheel rotational speed difference ΔVFR, so that tight corner braking and understeer are suppressed. So that
Driving force distribution control is performed so that the steering characteristic at the time of turning keeps a constant characteristic of neutral or weak under, so that steerability is improved.

[Judgment of split μ road departure] Split μ
The road start determination is performed during the differential limiting torque control processing operation of the LSD control unit 18b.

That is, as shown in the flowchart of FIG. 3, the starting condition of VF <x in step 37, the left and right rear wheel speed difference control condition of TA ≦ TΔn in step 39, and the front wheel speed in step 42 80 msec when the average value VFA exceeds (vehicle speed VF + 0.25 km / h)
If the front wheel speed condition that the vehicle speed continues for c or more is satisfied, at step 43, the split μ road flag FMS is set to FMS = 1.
Is transmitted to the ETS control unit 18a as split μ road information.

That is, in the differential limiting torque control, VF <
x, the accelerator opening proportional differential limiting torque TA and the left and right rear wheel speed differential proportional limiting torque T
Control for applying the differential limiting torque by the select high of Δn is performed. Therefore, when the left and right rear wheel speed difference ΔVR is large when the vehicle starts on the split μ road, the right and left rear wheel speed difference proportional differential limiting torque TΔn is selected by the select high. Conversely, when the right and left rear wheel speed difference proportional differential limiting torque TΔn is selected, it can be estimated that the vehicle is starting on the split μ road.

However, at the time of steering start, etc., the right and left rear wheel speed difference proportional differential limiting torque TΔn may be selected.
Focusing on the fact that the front wheels on the low μ road side are over-rotating when starting on the split μ road, the front wheel average value VFA is calculated as (the vehicle body speed VF + 0.25 k
m / h).

Further, the front wheel speed average value VFA is calculated as (vehicle speed VF).
(+0.25 km / h) on condition that the front wheel speed condition is temporarily satisfied due to disturbances such as wheel lifting, etc., when the vehicle is starting on the split μ road. I try not to judge.

[Front and Rear Wheel Drive Force Distribution Control for Split μ Road Start] When the information of the split μ road flag FMS = 1 is input from the LSD control unit 18b in the ETS control unit 18a, as shown in the flowchart of FIG. Then, from step 54 to step 55 → step 56 → step 5
In step 57, the split μ road corresponding torque T (FMS) is set as a fixed value obtained by adding 10 kg-m to the ETS clutch torque TΔV when the split μ road flag FMS changes from 0 to 1. Is set. Then, in the next control cycle, the flow proceeds from step 54 to step 55 → step 56 → step 58. As long as FMS = 1, the front and rear wheel drive force distribution control by the fixed value is maintained.

That is, front wheel speed, rear wheel speed, ETS torque, LSD torque, FMS
Changes as shown in the time chart of FIG. 5, and the vehicle equipped with the front and rear wheel driving force distribution control system corresponding to the front and rear wheel rotational speed difference reliably prevents control hunting when starting on the split μ road. .

Next, the effects will be described.

(1) In a total driving force distribution control system for left and right wheels and front and rear wheels applied to a vehicle equipped with a differential limiting torque control system and a front and rear wheel driving force distribution control system,
At the time of the differential limiting control in which the left and right rear wheel speed difference proportional differential limiting torque TΔn is applied by the left and right wheel driving force distribution control system, and
Front wheel speed average value VFA is (vehicle speed VF + 0.25 km / h)
, The friction coefficient of the left and right roads is determined to be a different μ road, and the split μ road flag FMS
Is set to FMS = 1, and the front / rear wheel driving force distribution control system side performs the front / rear wheel driving force distribution control by a fixed value obtained by adding 10 kg-m to the ETS clutch torque TΔV output when FMS = 1 is input. Since the apparatus performs the corresponding front and rear wheel drive force distribution control, it is possible to reliably prevent control hunting based on accurate determination of the split μ road.

(2) VF <
Since the start condition x is added, it is possible to prevent control hunting that causes jerky vibration when the vehicle starts on the split μ road.

(3) The front wheel speed average value VFA which is one of the conditions for determining the split μ road is (vehicle speed VF + 0.25 km /
h), the front wheel speed condition that exceeds
By weighting the time condition of continuous msec or more, when the wheel speed condition is satisfied instantaneously due to disturbance or the like, it is possible to prevent erroneous determination as a split μ road.

(4) The left and right wheel driving force distribution control system
When the starting condition of VF <x is satisfied, a system for performing a control for applying a differential limiting torque by selecting high among the accelerator opening proportional differential limiting torque TA and the right and left rear wheel speed differential proportional differential limiting torque TΔn. TA ≦ TΔ
With a simple determination process of n, it can be determined that the differential limiting control based on the occurrence of the difference between the left and right drive wheel speeds is being executed.

Although the embodiment has been described with reference to the drawings, the specific configuration is not limited to this embodiment.

For example, in the embodiment, the example of the differential limiting torque control system has been described as the left and right driving force distribution control system. However, a system in which the left and right driving forces are independently controlled by two clutches or the left and right braking forces (negative braking force) The present invention can be applied to a system in which the driving force is independently controlled.

In the embodiment, an example in which the front and rear wheel driving force distribution control system is applied to a four-wheel drive vehicle based on a rear wheel drive has been described. However, the present invention can also be applied to a four-wheel drive vehicle based on a front wheel drive.

[0094]

According to the first aspect of the present invention,
Differential limitation in the left and right wheel driving force distribution control system in the left and right wheel and front and rear wheel driving force distribution comprehensive control device applied to the vehicle equipped with the left and right wheel driving force distribution control system and the front and rear wheel driving force distribution control system A split μ road determining means for determining that the right and left road surface friction coefficients are different μ roads when the control execution is determined and the deviation between the clutch engagement drive wheel speed and the vehicle body speed exceeds a set deviation; Split μ road compatible front / rear wheel drive that performs front / rear wheel drive force distribution control with a fixed value obtained by adding a predetermined value to the drive force distribution command value output on the front / rear wheel drive force distribution control system side when the μ road is determined Since the apparatus is provided with the power distribution control means, an effect is obtained that the control hunting can be reliably prevented based on the accurate determination of the split μ road.

According to the second aspect of the present invention, in the driving force distribution integrated control device for the left and right wheels and the front and rear wheels according to the first aspect, the split μ road determining means determines that the vehicle speed is equal to or less than the set vehicle speed. In the case where the difference between the clutch engagement drive wheel speed and the vehicle body speed exceeds the set deviation at the time of determining the execution of the differential limit control in the left and right wheel driving force distribution control system, the right and left road surface friction coefficients differ. Since the road is determined to be a road, in addition to the above-described effects, an effect is obtained that control hunting that causes jerky vibration when starting on a split μ road can be prevented.

According to a third aspect of the present invention, in the overall driving force distribution control device for the left and right wheels and the front and rear wheels according to the second aspect, the split μ road determining means determines that the vehicle speed is equal to or less than the set vehicle speed. At the time of execution of the differential limit control in the left and right wheel driving force distribution control system, and when the state in which the deviation between the clutch engagement driving wheel speed and the vehicle speed exceeds the set deviation continues for a set time or more, the left and right Since the road friction coefficient is a means for judging a split μ road having a different friction coefficient, in addition to the above effects, when the wheel speed condition is satisfied instantaneously due to disturbance or the like,
This has the effect of preventing erroneous determination that the road is the split μ road.

According to a fourth aspect of the present invention, in the overall driving force distribution control device for the left and right wheels and the front and rear wheels according to the first to third aspects, the left and right wheel driving force distribution control system comprises at least This system applies the differential limiting torque by selecting the differential limiting torque corresponding to the left and right driving wheel speed difference and the differential limiting torque corresponding to the accelerator opening degree. When the dynamic limiting torque is selected, the means for determining that the control for limiting the differential between the left and right drive wheels is performed based on the occurrence of the rotational speed difference between the left and right drive wheels is performed. By the processing, it is possible to determine that the differential limiting control based on the occurrence of the difference between the left and right driving wheel speeds is being performed.

[Brief description of the drawings]

FIG. 1 is a drawing corresponding to a claim showing a total driving force distribution control device for left and right wheels and front and rear wheels according to the present invention.

FIG. 2 is an overall system diagram showing a rear-wheel drive-based four-wheel drive vehicle to which the driving force distribution integrated control device for left and right wheels and front and rear wheels according to the embodiment is applied.

FIG. 3 is a flowchart illustrating a flow of a differential limiting torque control operation performed by an LSD control unit of a controller of the embodiment device.

FIG. 4 is a flowchart illustrating a flow of a front and rear wheel drive force distribution control operation performed by an ETS control unit of a controller of the embodiment device.

FIG. 5 shows a front wheel speed, a rear wheel speed, an ETS torque, an LSD torque, and an FMS when the vehicle starts on a split μ road.
6 is a time chart showing the respective characteristics of FIG.

FIG. 6 is a time chart showing characteristics of a front wheel speed, a rear wheel speed, and an ETS torque when the vehicle starts on a split μ road.

[Explanation of symbols]

 a left and right wheel driving force distribution control system b front and rear wheel driving force distribution control system c front and rear wheel rotational speed difference detecting means d clutch engagement driving wheel speed detecting means e body speed detecting means f left and right driving wheel rotational speed difference detecting means g differential limiting Control execution determining means h split μ road determining means i split μ road corresponding front and rear wheel drive force distribution controlling means

Continuation of the front page (56) References JP-A-3-164331 (JP, A) JP-A-2-68226 (JP, A) JP-A-6-99762 (JP, A) JP-A-5-16690 (JP) JP-A-2-290728 (JP, A) JP-A-2-290729 (JP, A) JP-A-6-144064 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) B60K 17/28-17/36 F16H 48/00-48/30

Claims (4)

(57) [Claims] 1. A left / right wheel driving force distribution control system for controlling a driving force distribution to left and right wheels based on predetermined input information, and a front / rear wheel rotation speed difference detected by front / rear wheel rotation speed difference detection means is larger. A front / rear wheel driving force distribution control system for controlling distribution of driving force to front and rear wheels that reduces distribution to driving wheels directly connected to the engine and increases distribution to driving wheels for clutch engagement. Clutch engagement drive wheel speed detection means for detecting the clutch engagement drive wheel speed which is the wheel speed of the vehicle, vehicle body speed detection means for detecting the vehicle body speed, and left and right drive wheel rotation speed detected by the left and right drive wheel rotation speed difference detection means A difference limiting control execution determining means for determining whether control for limiting the differential between the left and right wheel drive wheels is performed based on the difference, and a difference between the left and right wheel driving force distribution control system. A split μ road determining means for determining that the right and left road surface friction coefficients are different μ roads at the time of execution of the dynamic restriction control, and when the deviation between the clutch engagement drive wheel speed and the vehicle body speed exceeds a set deviation. When the split μ road is determined, the front / rear wheel driving force distribution control system performs front / rear wheel driving force distribution control by a fixed value obtained by adding a predetermined value to the driving force distribution command value output on the front / rear wheel driving force distribution control system. A driving force distribution control device for left and right wheels and front and rear wheels, comprising: wheel driving force distribution control means. 2. The driving force distribution integrated control device according to claim 1, wherein the split μ road determination means is configured to control the vehicle power when the vehicle speed is equal to or less than a set vehicle speed. When performing the differential limit control, and when the deviation between the clutch engagement driving wheel speed and the vehicle body speed exceeds the set deviation, it is means for judging that the road is a split μ road having different left and right road surface friction coefficients. Driving force distribution control system for left and right wheels and front and rear wheels. 3. The driving force distribution integrated control device for left and right wheels and front and rear wheels according to claim 2, wherein the split μ road determination means is configured to control the driving force distribution control system for left and right wheels when the vehicle speed is equal to or lower than a set vehicle speed. When it is determined that the differential limit control is to be performed, and when the state in which the deviation between the clutch engagement drive wheel speed and the vehicle body speed exceeds the set deviation continues for a set time or more, it is determined that the road is a split μ road having different left and right road surface friction coefficients. A driving force distribution comprehensive control device for left and right wheels and front and rear wheels, which is means for determining. 4. The integrated control system for driving force distribution between left and right wheels and front and rear wheels according to claim 1, wherein the left and right wheel driving force distribution control system includes at least a differential limiting torque corresponding to a left and right driving wheel speed difference. A differential limiting torque is provided by a select high of an accelerator opening-corresponding differential limiting torque, wherein the differential limiting control execution determining means determines whether a left-right driving wheel speed difference-dependent differential limiting torque is selected. A driving force distribution comprehensive control device for left and right wheels and front and rear wheels, which is means for judging that control for limiting differential between left and right driving wheels is executed based on occurrence of a driving wheel rotation speed difference.