JP2000343974A - Driving force distribution control device for four-wheel drive vehicle - Google Patents

Abstract

(57) [Summary] [Problem] To control the driving force distribution of a four-wheel drive vehicle that achieves both the prevention of tight corner braking and the prevention of torque hunting while using a low-cost system that can use existing in-vehicle sensors. Providing equipment. SOLUTION: When the accelerator opening ACC is in a low opening region where the accelerator opening ACC is less than 1/8 opening,
The transmission torque to the rear wheels 7 and 8 is limited so that the torque distribution tends to be two-wheel drive, and when the accelerator opening ACC is in a high opening region of 1/8 or more, the torque distribution tends to be four-wheel drive. It is a means for controlling to obtain the ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-wheel drive vehicle in which a torque distribution ratio transmitted to front and rear wheels is controlled by a torque distribution actuator provided in a drive system for distributing engine torque to front and rear wheels. Belongs to the technical field of the driving force distribution control device.

[0002]

2. Description of the Related Art Conventionally, as a driving force distribution control device for a four-wheel drive vehicle, for example, a driving force distribution control device described in Japanese Patent Application Laid-Open No. Hei 6-211063 is known.

This publication discloses a clutch torque corresponding to a rotational speed difference corresponding to a front and rear wheel rotational speed difference and a clutch torque corresponding to a yawing momentum for obtaining an optimum yawing momentum in order to suppress driving wheel slip and obtain turning stability. A technique of providing a gain filter processing means for controlling the driving force distribution ratio of the front and rear wheels by giving a clutch engagement force according to the sum of ing.

[0004]

However, in the above-described conventional driving force distribution control device for a four-wheel drive vehicle, the purpose is to prevent control hunting (hereinafter referred to as torque hunting) in which transmission torque repeatedly increases and decreases. Since the filter process with low response is performed regardless of the accelerator opening condition and the vehicle speed condition, when the accelerator opening at the time of starting is in the low opening region, the torque control response is poor, and the torque hardly decreases, that is, The problem is that the distribution ratio of the two-wheel drive side becomes difficult to be obtained, and a tight corner braking phenomenon (a phenomenon in which a braking torque is generated in the directly-coupled drive system due to an average turning radius difference between the front and rear wheels during turning) occurs. There is.

That is, when the torque is controlled by the front-rear rotation difference, for example, when the torque distribution ratio is changed to the four-wheel drive side by increasing the transmission torque due to the generation of the front-rear rotation difference when traveling on a low μ road or the like, the drive slip is reduced. Immediately after that, the transmission torque is reduced because the front-rear rotation difference is suppressed and the difference in the longitudinal rotation is reduced. In the torque distribution ratio state on the two-wheel drive side, a drive slip occurs again to increase the transmission torque, and torque hunting in which the transmission torque increases or decreases occurs. In addition, when the driver performs an operation of repeatedly turning on / off the accelerator, the accelerator-sensitive torque for controlling the torque by the accelerator opening is also determined.
Torque hunting occurs in which the transmission torque increases or decreases according to the change in the accelerator opening. In order to suppress such torque hunting, it is necessary to apply a filter with low response so that the torque does not greatly change in a short time.

The problem to be solved by the present invention is to provide a four-wheel drive vehicle that achieves both the prevention of tight corner braking and the prevention of torque hunting while maintaining a low-cost system that can use existing in-vehicle sensors. Another object of the present invention is to provide a driving force distribution control device.

[0007]

According to the first aspect of the present invention, the front wheels and the rear wheels are controlled by a torque distribution controller for a torque distribution actuator provided in a drive system for distributing engine torque to the front wheels and the rear wheels. In a driving force distribution control device for a four-wheel drive vehicle in which a transmitted torque distribution ratio is controlled, an accelerator opening detecting means for detecting an accelerator opening and a target torque transmitted by fastening the torque distribution actuator are set to an operating state. Target torque calculating means for calculating the calculated target torque, a torque increase / decrease determining means for determining whether the calculated target torque is decreasing or increasing, and when the accelerator opening is in a low opening region less than the set opening. ,
If the target torque tends to decrease, the final target torque is determined by filtering with a high response filter compared to when in the high opening region, and if the target torque tends to increase, the final target torque is determined by filtering with a low response filter. And a final target torque determining means for determining.

According to a second aspect of the present invention, in the driving force distribution control device for a four-wheel drive vehicle according to the first aspect, a vehicle speed detecting means for detecting a vehicle speed is provided, and the final target torque determining means is provided. At extremely low speeds less than and when the accelerator opening is in the low opening range less than the set opening, if the target torque tends to decrease, the final target is processed by a filter with a higher response compared to that in the high opening range. The torque is determined, and if the target torque tends to increase, a means for determining the final target torque by filtering with a low response filter is provided.

According to a third aspect of the present invention, in the driving force distribution control device for a four-wheel drive vehicle according to the first or second aspect, the final target torque determining means is provided with a low accelerator opening condition or an extremely low vehicle speed condition. If the target torque is not decreasing, the final target torque is determined by filtering with a low-response filter that prevents torque hunting if the target torque tends to decrease, and a high-response filter that does not deteriorate responsiveness if the target torque tends to increase. And a means for determining a final target torque by a filtering process.

According to a fourth aspect of the present invention, in the driving force distribution control device for a four-wheel drive vehicle according to any one of the first to third aspects, the target torque calculating means includes a front-rear rotation speed corresponding to at least a front-rear rotation speed difference. It is characterized in that the target torque is a torque selected by the select high among the difference corresponding torque, the vehicle speed corresponding torque corresponding to the vehicle speed, and the accelerator opening corresponding torque corresponding to the accelerator opening.

[0011]

According to the first aspect of the present invention, at the time of starting or running, the target torque calculating means calculates the target torque transmitted by the engagement of the torque distribution actuator according to the driving state, and determines whether the torque is increased or decreased. It is determined whether the calculated target torque is decreasing or increasing. In the final target torque determining means, when the detected accelerator opening is in a low opening region smaller than the set opening, the target torque is determined. If the target torque is decreasing, the final target torque is determined by filtering with a high-response filter compared to the case of the high opening region, and if the target torque is increasing, the final target torque is determined by filtering with a low-response filter. You.

As described above, the accelerator opening information from the accelerator opening sensor used in other in-vehicle control systems such as an engine and an automatic transmission is used as input information, and an expensive steering angle sensor, a lateral acceleration sensor or the like is used. Since the system does not use the turning information, a low-cost simple system that can use existing in-vehicle sensors can be provided.

If the target torque tends to decrease when the accelerator opening is in the low opening range, the final target torque is determined by the filtering process using a high response filter.
The final target torque decreases responsively to the decrease in the target torque, whereby the driving force distribution ratio is changed to the two-wheel drive side at once, thereby preventing the tight corner braking phenomenon and increasing the target torque. If there is a tendency, the final target torque is determined by the filtering process using a low-response filter, so that the final target torque increases slowly with an increase in the target torque, and the two-wheel drive side of the driving force distribution ratio is maintained. This prevents the tight corner braking phenomenon.

When the accelerator opening is in the low opening range, if the target torque tends to increase, the final target torque is determined by a filtering process using a low response filter. When the accelerator opening is in the high opening range, If the target torque tends to decrease, the final target torque will be determined by filtering with a low-response filter compared to when the opening is in the low opening range. Thus, it is possible to prevent torque hunting in which the final target torque increases or decreases in a short time regardless of the magnitude of the accelerator opening.

The reason why the accelerator opening information is used as filter switching information is as follows.

First, when attention is paid to the tight corner braking phenomenon, this phenomenon is easily affected by the road surface, and the driver and the occupant feel uncomfortable at the time of low torque transmission in which no driving torque exceeding the braking torque due to the above phenomenon is generated. give. Whether or not the driving torque is low can be estimated from the accelerator opening from an accelerator opening sensor that is popular as an on-vehicle sensor.

Although the tight corner braking phenomenon does not pose a problem when the vehicle starts straight ahead, the distribution ratio of the two-wheel drive tendency is set in advance when the accelerator opening is smaller than the set opening, so that when the vehicle starts turning, In such cases, the tight corner braking phenomenon can be prevented beforehand.

According to the second aspect of the present invention, in the final target torque determining means, when the vehicle speed is extremely low below the set vehicle speed,
And, when the accelerator opening is in a low opening region less than the set opening,
If the target torque tends to decrease, the final target torque is determined by filtering with a high-response filter compared to the case of the high opening region, and if the target torque tends to increase, the final target torque is determined by filtering with a low-response filter. It is determined.

Here, when attention is paid to the tight corner braking phenomenon, as described above, this phenomenon is applied to a low torque transmission which is easily affected by the road surface and does not generate a driving torque exceeding the braking torque. It gives the most uncomfortable feeling to drivers and occupants at extremely low speeds where vehicle behavior tends to change due to torque.

Therefore, by adding the vehicle speed condition to the filter change condition, the filter change control for preventing the tight corner braking phenomenon can be performed only when the influence on the driver and the occupant by the tight corner braking phenomenon is large.

According to the third aspect of the present invention, in the final target torque determining means, a low response filter for preventing torque hunting if the target torque tends to decrease when the low accelerator opening condition or the extremely low vehicle speed condition is not satisfied. Determines the final target torque, and if the target torque tends to increase, the final target torque is determined by a filtering process using a high-response filter that does not deteriorate the responsiveness.

Therefore, when the low accelerator opening condition or the extremely low vehicle speed condition is not satisfied, the torque distribution ratio of the four-wheel drive is maintained on the decreasing side of the target torque, and the four-wheel driving side is immediately maintained on the increasing side of the target torque. By shifting the torque distribution ratio to
Driving performance can be improved while preventing torque hunting.

According to a fourth aspect of the present invention, in the target torque calculating means, at least a longitudinal speed difference corresponding torque corresponding to the longitudinal speed difference, a vehicle speed corresponding torque corresponding to the vehicle speed, and an accelerator opening corresponding to the accelerator opening degree. The torque selected by the select high among the degree corresponding torques is set as the target torque.

Therefore, the torque corresponding to the front / rear rotational speed difference is dominant during driving in which a drive slip occurs, the vehicle speed corresponding torque is dominant during low speed driving, and the accelerator opening corresponding torque is dominant during driving with a high accelerator opening. Thus, an optimum target torque can be set according to each traveling state.

[0025]

(Embodiment 1) Embodiment 1 is a driving force distribution control device for a four-wheel drive vehicle according to the invention described in claims 1 to 4.

First, the configuration will be described.

FIG. 1 is an overall system diagram showing a driving force distribution control device for a four-wheel drive vehicle according to a first embodiment, wherein 1 is an engine, 2 is an automatic transmission, 3 is a front differential, 4 is a rear differential, and 5 is Right front wheel, 6 left front wheel, 7 right rear wheel, 8 left rear wheel, 9 torque distribution clutch (torque distribution actuator), 10 torque distribution controller, 11 right front wheel speed sensor, 12 left front wheel speed sensor , 13 is a right rear wheel speed sensor, 14 is a left rear wheel speed sensor,
15 is an accelerator opening sensor, 16 is an engine rotation sensor, and 17 is an AT controller.

In the four-wheel drive vehicle to which the invention of the first embodiment is applied, the engine driving force is directly transmitted to the left and right front wheels 5 and 6, and the torque distribution clutch 9 is transmitted to the left and right rear wheels 7 and 8.
Is a front-wheel drive-based four-wheel-drive vehicle to which engine driving force is transmitted via the vehicle. That is, when the torque distribution clutch 9 is in the disengaged state, the front wheel: rear wheel = 100: 0 torque distribution ratio, and if the torque distribution clutch 9 is engaged at a torque equal to or more than ト ル ク of the engine torque. , Front wheel: rear wheel = 50: 50, and the torque distribution ratio transmitted to the front wheels 5, 6 and the rear wheels 7, 8 by the control command from the torque distribution controller 10 to the torque distribution clutch 9 becomes: Front wheel: rear wheel = variable control in the range of 100 to 50: 0 to 50 according to the engagement torque of the torque distribution clutch 9.

The torque distribution controller 10 includes a wheel speed signal from each wheel speed sensor 11, 12, 13, and 14, an accelerator opening signal from an accelerator opening sensor 15, and an engine rotation signal from an engine rotation sensor 16. And a gear position signal and the like from the AT controller 17, perform arithmetic processing according to a determined control law, and transmit a control command based on the arithmetic processing result to the torque distribution clutch 9.
Output to

FIG. 2 is a control block diagram showing a plurality of torque distribution control modes in the torque distribution controller 10 employed in the driving force distribution control device of the first embodiment.

The four-wheel speed calculator 100 calculates the front wheel right wheel speed VwFR, the front wheel left wheel speed VwFL, and the rear wheel right wheel speed VwRR based on the wheel speed signals from the wheel speed sensors 11, 12, 13, and 14. The rear left wheel speed VwRL is calculated. In a vehicle equipped with an anti-skid brake system (ABS), the calculation unit 100 may be omitted by using the calculation result of the ABS controller.

Estimated vehicle speed calculating section 101 (vehicle speed detecting means)
In, the estimated vehicle speed VFF is calculated based on each wheel speed VwFR, VwFL, VwRR, VwRL.

The gain calculator 102 calculates a gain Kh based on the calculated estimated vehicle speed VFF and the gain map.

The front / rear rotation speed difference calculation unit 103 calculates the average value of the left and right front wheel speeds VwFR, VwFL and the left / right rear wheel speed VwFL.
The difference between the front and rear rotation speed ΔVw due to the difference from the average value of wRR and VwRL
Is calculated.

The front-rear rotational speed difference torque calculator 104 calculates a gain KDF from the front-wheel left-right wheel speed difference ΔVwF,
Kh × KDF as the total gain, front-rear rotational speed difference ΔV
The rotational speed difference torque T 数 V corresponding to w is calculated.

In the turning radius calculation unit 105, the left and right rear wheels 7,
The turning radius R is calculated from the tread t, the rear wheel right wheel speed VwRR, and the rear wheel left wheel speed VwRL, which are the wheel intervals of No. 8.

An accelerator opening calculating section 106 (accelerator opening detecting means) calculates an accelerator opening ACC based on a sensor signal from the accelerator opening sensor 15.

The initial torque calculating section 107 calculates an initial torque TV based on the estimated vehicle speed VFF.
The initial torque TV is the highest when VFF = 0, and is given with a smaller torque as the estimated vehicle speed VFF increases.

The driving force map torque calculating section 108 calculates the driving force map torque T based on the estimated vehicle speed VFF and the turning radius R.
Acc is calculated. This driving force map torque TAcc
Is 5 km in a region where the estimated vehicle speed VFF is 20 km / h or less.
/ H, the torque characteristic is such that it peaks at an estimated vehicle speed VFF of around / h, and the turning radius R is used as a parameter. The larger the turning radius, the larger the torque.

The accelerator opening-sensitive torque calculator 109 calculates the accelerator opening-sensitive torque TS based on the accelerator opening ACC and the turning radius R. The accelerator opening sensitivity torque TS increases in a low opening region and is constant in a medium opening region.
The torque is given by the torque characteristic which rises in the high opening range, and the turning radius R is used as a parameter. The larger the turning radius, the larger the torque.

FIG. 3 is a control block diagram showing a process from selection of a target torque to determination of a final output in the torque distribution controller 10 employed in the driving force distribution control device of the first embodiment.

The target torque selecting section 110 (target torque calculating means) selects the target torque T by selecting high among the front-rear rotational speed difference torque T △ V, the initial torque TV, the driving force map torque TAcc, and the accelerator opening sensitivity torque TS.
1 is selected.

The final target torque determining section 111 (final target torque determining means) performs a filtering process of increasing / decreasing the target torque T1 selected by the target torque selecting section 110 to determine the final target torque T. .

In the final target torque-current converter 112,
The current is converted to a current value I corresponding to the final target torque T.

The final output determining section 113 outputs the current value I converted by the final target torque to current converting section 112 to the solenoid in the torque distribution clutch 9 except when the 2WD mode (I = 0) is determined. .

Next, the operation will be described.

[Final Target Torque Determining Operation] FIG. 4 is a flowchart showing the flow of the final target torque determining process performed by the final target torque determining unit 111 of the torque distribution controller 10. Each step will be described below.

In step 40, the target torque selecting section 11
From 0, the target torque T1 is read.

In step 41, the currently read target torque T1 and the previously read target torque of 10 ms
The magnitude of the previous T1 value _T1OLD is compared with the previous value T1 (torque increase / decrease determination means).

In step 42, when the current target torque is decreasing from the previous value in the judgment in step 41, the estimated vehicle speed VFF is less than 5 km / h, and the accelerator opening ACC is 1 / It is determined whether the opening is less than four.

In step 43, when the determination in step 42 is YES, the final target torque T is the value of the target torque T1 read this time and the target torque T1 _OLD read last time.
Is determined by the select high of a value obtained by subtracting 3.8 kgm / 10 ms from the value.

In step 44, when the determination in step 42 is NO, the final target torque T is obtained by subtracting 0.6 kgm / 10 ms from the value of the target torque T1 read this time and the target torque T1 _OLD read last time. Determined by select high.

In step 45, when the target torque is increased in the judgment in step 41, the estimated vehicle speed VFF becomes 5
It is determined whether it is less than km / h and the accelerator opening ACC is less than 1/4 opening.

In step 46, when the determination in step 45 is YES, the final target torque T is the value of the target torque T1 read this time and the target torque T1 _OLD read last time.
Is determined by the select row having a value obtained by adding 0.6 kgm / 10 ms to.

In step 47, when the determination in step 45 is NO, the final target torque T is obtained by adding 1.2 kgm / 10 ms to the value of the target torque T1 read this time and the target torque T1 _OLD read last time. Determined by select row.

In step 48, steps 43, 44,
The final target torque T determined by any of 46 and 47 is output to the final target torque-current converter 112.

Therefore, when the target torque T1 is decreasing and the vehicle speed condition and the accelerator opening degree condition in step 42 are satisfied, a filter having a higher response than when the condition in step 42 is not satisfied. The final target torque T is determined by the filtering process according to the allowable selection, and the target torque tends to increase. When the vehicle speed condition and the accelerator opening condition in step 45 are satisfied, a filter with low response (a small torque increase width is set) The final target torque T is determined by the filtering process based on the selection to restrict the width).

[Tight Corner Breaking Phenomenon Preventing Action] If the target torque T1 tends to decrease when the vehicle speed is in the extremely low vehicle speed range and the accelerator opening is in the low opening range, step 41 in FIG. From 42 to step 43, the final target torque T is determined by the filtering process using a filter having a high response, so that a rapid decrease is permitted as shown by the AD characteristic in FIG. The final target torque T decreases in response to the decrease in the torque T1. As a result, the driving force distribution ratio is changed to the two-wheel drive side at once, thereby preventing the tight corner braking phenomenon.

When the vehicle speed is in a very low vehicle speed range and the accelerator opening is in a low opening range, if the target torque T1 tends to increase,
The flow proceeds from step 41 to step 45 to step 46 in FIG. 4, and the final target torque T is determined by the filtering process using the filter having low responsiveness.
As shown by the AI characteristic in (b), the increase is suppressed to a gradual increase, the final target torque T increases slowly with the increase in the target torque T1, and the two-wheel drive side of the driving force distribution ratio is maintained. Corner braking is prevented.

[Torque Hunting Prevention] If the target torque T1 tends to increase when the vehicle speed is in the extremely low vehicle speed range and the accelerator opening is in the low opening range, the AI characteristic shown in FIG. As described above, the final target torque T is determined by the filtering process using the low response filter, and when the vehicle speed is outside the extremely low vehicle speed range and the accelerator opening is in the high opening range, the target torque T1 tends to decrease. As shown in the BD characteristic of FIG. 5A, the final target torque T is determined by the filtering process using a filter having low response, and in either case, the target torque T1 is either increased or decreased. The filter will work.

Accordingly, it is possible to prevent torque hunting in which the final target torque T increases or decreases in a short time regardless of the vehicle speed or the degree of accelerator opening.

[Regarding Filter Switching Information] First, the reason why the accelerator opening information is used as filter switching information is as follows.

1) When attention is paid to the tight corner braking phenomenon, this phenomenon is easily affected by the road surface, and the driver and the occupant feel uncomfortable at the time of low torque transmission in which no driving torque exceeding the braking torque due to the above phenomenon is generated. give. Whether or not the driving torque is low can be estimated from the accelerator opening from an accelerator opening sensor that is popular as an on-vehicle sensor.

2) The tight corner braking phenomenon is not a problem when the vehicle starts straight ahead, but by setting in advance the distribution ratio of the two-wheel drive tendency when the accelerator opening is less than 1/4 opening, turning At the time of starting, the tight corner braking phenomenon can be prevented.

Next, the reason why the vehicle speed information is used as the filter switching information is that when attention is paid to the tight corner braking phenomenon, this phenomenon is easily affected by the road surface and there is no generation of a driving torque that exceeds the braking torque. One condition is that low torque is transmitted. In addition to this, considering the body sensitivity of the driver and the occupant, the driver and the occupant feel the most uncomfortable at extremely low speeds where the vehicle behavior tends to change due to the braking torque. give.

Therefore, by adding the vehicle speed condition to the accelerator opening degree condition as a filter change condition, the filter change control for preventing the tight corner braking phenomenon is performed only when the influence on the driver and the occupant by the tight corner braking phenomenon is large. Will be able to do that.

[Filter Operation During Normal Running] In the flowchart of FIG. 4, when the low accelerator opening condition and the extremely low vehicle speed condition are not satisfied, if the target torque T1 is decreasing, step 41 → step 42 → step 44. The flow proceeds to step 44. At step 44, a filter process using a low-response filter for preventing torque hunting (FIG. 5)
The final target torque T is determined by the (BD characteristic of (a)), and if the target torque T1 is increasing, step 41
The flow proceeds from step 45 to step 47. At step 47, the final target torque T is determined by a filtering process (BI characteristic in FIG. 5B) using a weak filter that does not deteriorate the response.

Therefore, during normal running that does not satisfy the low accelerator opening degree condition and the extremely low vehicle speed condition, when the target torque T1 tends to decrease, the control is such that the torque distribution ratio on the four-wheel drive side is maintained, and the target torque is reduced. When T1 tends to increase, the torque distribution ratio is immediately shifted to the four-wheel drive side, so that the driving slip is well suppressed by the distribution of the front and rear wheels of the engine driving force, and traveling with high driving performance can be realized. . Of course, torque hunting can also be prevented by a filter function having low response on the torque reduction side.

Next, the effects will be described.

(1) As input information, accelerator opening information from an accelerator opening sensor 15 used in another vehicle-mounted control system such as an engine or an automatic transmission is used, and an expensive steering angle sensor, a lateral acceleration sensor or the like is used. Since the system does not use the turning information, a low-cost simple system that can use existing in-vehicle sensors can be provided.

When the accelerator opening ACC is in a low opening region of less than 1/4 opening, if the target torque T1 tends to decrease, the final target is filtered by a filter having a higher response than in the high opening region. If the torque T is determined and the target torque T1 is increasing, the final target torque T is determined by the filtering process using a low response filter.
It is possible to achieve both the prevention of the tight corner braking phenomenon and the prevention of torque hunting.

(2) In the final target torque determining section 111, when the estimated vehicle speed VFF is at a very low speed of less than 5 km / h and the accelerator opening ACC is in a low opening region of less than 1/4 opening, If the target torque T1 is decreasing, the final target torque T is determined by the filtering process using a high response filter. If the target torque T1 is increasing, the final target torque T is determined by the filtering process using a low response filter. Since the vehicle speed condition is added to the change condition, the filter change control for preventing the tight corner braking phenomenon can be performed only when the influence on the driver and the occupant due to the tight corner braking phenomenon is large.

(3) When the final target torque determination unit 111 does not satisfy the low accelerator opening degree condition or the extremely low vehicle speed condition, if the target torque T1 tends to decrease, a filtering process using a low response filter for preventing torque hunting is performed. , The final target torque T is determined. If the target torque T1 tends to increase, the final target torque is determined by a filtering process using a high-response filter that does not deteriorate the response. Therefore, during normal driving, torque hunting is prevented. The driving performance can be increased while the driving performance is improved.

(4) In the target torque selecting section 110, the front / rear rotational speed difference torque T △ V, the initial torque TV, the driving force map torque TAcc, and the accelerator opening sensitivity torque TS
Of these, the torque selected by the select high is set as the target torque T1, so that the front-rear rotation speed difference torque T △ V is dominant during driving in which a drive slip occurs, the initial torque TV is dominant during starting, and the driving is performed during low-speed driving. The optimal target torque T1 can be set according to each traveling state, such that the force map torque TAcc is dominant and the accelerator opening-sensitive torque TS is dominant during traveling with a high accelerator opening.

(Other Embodiments) In the first embodiment, an example in which the present invention is applied to a front-wheel drive-based four-wheel drive vehicle has been described. However, the present invention can also be applied to a rear-wheel drive-based four-wheel drive vehicle.

In the first embodiment, an example in which the filter is changed according to the vehicle speed condition and the accelerator opening condition has been described. However, the filter is changed only according to the accelerator opening condition (for example, 1/8 opening as the accelerator opening threshold value). The filter may be changed.

[Brief description of the drawings]

FIG. 1 is an overall system diagram showing a driving force distribution control device for a four-wheel drive vehicle according to a first embodiment.

FIG. 2 is a control block diagram showing a plurality of torque distribution control modes in a torque distribution controller employed in the driving force distribution control device according to the first embodiment.

FIG. 3 is a control block diagram showing processing from selection of a target torque to determination of a final output in a torque distribution controller employed in the driving force distribution control device of the first embodiment.

FIG. 4 is a flowchart illustrating a flow of a final target torque determination process performed in a final target torque determination unit of a torque distribution controller of the driving force distribution control device according to the first embodiment.

FIG. 5 is a diagram illustrating filter characteristics on the torque decreasing side and the torque increasing side in the driving force distribution control according to the first embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Automatic transmission 3 Front differential 4 Rear differential 5 Right front wheel 6 Left front wheel 7 Right rear wheel 8 Left rear wheel 9 Torque distribution clutch (torque distribution actuator) 10 Torque distribution controller 11 Right front wheel speed sensor 12 Left front wheel speed sensor 13 Right rear wheel speed sensor 14 Left rear wheel speed sensor 15 Accelerator opening sensor 16 Engine rotation sensor 17 AT controller

Claims (4)

[Claims] 1. A four-wheel vehicle in which a torque distribution ratio transmitted to a front wheel and a rear wheel is controlled by a control command from a torque distribution controller for a torque distribution actuator provided in a drive system that distributes engine torque to a front wheel and a rear wheel. A driving force distribution control device for a driving vehicle, comprising: accelerator opening detection means for detecting an accelerator opening; and target torque calculation means for calculating a target torque transmitted by fastening the torque distribution actuator in accordance with a driving state. A torque increase / decrease determining means for determining whether the target torque is decreasing or increasing, and a high opening if the target torque is decreasing in a low opening region where the accelerator opening is smaller than the set opening. The final target torque is determined by filtering with a higher response filter than in the region, and if the target torque is increasing, a low response filter is used. Final target torque determining means and, driving force distribution control device for a four wheel drive vehicle, characterized in that it comprises a determining the final target torque by filtering by. 2. The driving force distribution control device for a four-wheel drive vehicle according to claim 1, further comprising: vehicle speed detecting means for detecting a vehicle speed, wherein the final target torque determining means is provided when the vehicle speed is extremely low below a set vehicle speed. And, when the accelerator opening is in a low opening region less than the set opening, if the target torque is decreasing, the final target torque is determined by a filtering process using a high-response filter as compared with that in the high opening region. A driving force distribution control device for a four-wheel drive vehicle, characterized in that if the torque tends to increase, the final target torque is determined by filter processing with a low response filter. 3. The driving force distribution control device for a four-wheel drive vehicle according to claim 1, wherein the final target torque determining means is configured to output a target torque when the low accelerator opening condition or the extremely low vehicle speed condition is not satisfied. If the torque is decreasing, the final target torque is determined by filtering with a low-response filter that prevents torque hunting, and if the target torque is increasing, the final target is determined by filtering with a high-response filter that does not degrade responsiveness. A driving force distribution control device for a four-wheel drive vehicle, characterized in that it is means for determining torque. 4. The driving force distribution control device for a four-wheel drive vehicle according to claim 1, wherein the target torque calculating means includes: a torque corresponding to a front-rear speed difference corresponding to at least a front-rear speed difference; A drive force distribution control for a four-wheel drive vehicle, wherein a target torque is selected from among a vehicle speed corresponding torque corresponding to the vehicle speed and an accelerator opening corresponding torque corresponding to the accelerator opening by a select high. apparatus.