JP2502721B2 - Drive force distribution controller for four-wheel drive vehicle - Google Patents

Description

TECHNICAL FIELD The present invention relates to a drive force distribution control device for a four-wheel drive vehicle in which front and rear wheel drive force distribution can be changed.

2. Description of the Related Art Conventionally, as a driving force distribution control device for a four-wheel drive vehicle, for example, a device described in Japanese Patent Application Laid-Open No. 61-154737 is known.

In this conventional device, the clutch engagement force is reduced to the front-rear wheel rotational speed difference ΔN in order to achieve wheel spin prevention during sudden acceleration and start, one-wheel lock prevention during sudden braking, and slip prevention during low μ road traveling. That is, the clutch engagement force is increased as the front / rear wheel rotation speed difference ΔN is increased to change the front / rear drive force distribution to the four-wheel drive direction, and the clutch engagement force is decreased as the front / rear wheel rotation speed difference ΔN is decreased. Is reduced to change the front-rear driving force distribution to the two-wheel driving direction.

(Problems to be Solved by the Invention) However, in such a conventional drive force distribution control device, since the clutch engagement force control is a ΔN feedback control system, the friction clutch is not activated during low μ road acceleration. When the rotational speed detection value of the controlled forest, to which the engine driving force is transmitted via the engine, fluctuates, the fluctuation of the rotational speed detection value of the controlled wheel directly becomes the variation of the front and rear wheel rotational speed difference ΔN which is the control information. However, there is a problem in that control hunting that occurs by repeating the increase and decrease of the clutch engagement force is generated, and noise and rattling vibrations that continue self-excitingly occur.

Here, the mechanism of the control hunting will be explained. For example, a four wheel drive vehicle based on a rear wheel drive has a low μ.
When the road is suddenly accelerated, the slippage of the rear wheels causes a large difference ΔN in the front-rear wheel rotation speed, and the clutch engagement force increases rapidly. When the engine driving force is transmitted to the front wheels, which are the controlled wheels, due to the increase in the clutch engagement force, this time,
The front wheel, whose drive system inertia is smaller than that of the rear wheel, rapidly increases in rotation and becomes over-rotated than the rear wheel. When the front-rear wheel rotation speed difference ΔN suddenly decreases due to the front wheel over-rotation, the clutch engagement force also sharply decreases, so that the front wheel with a small drive system inertia suddenly grips and the front-rear wheel rotation speed difference ΔN again increases rapidly. I will end up.

That is, since the front wheel side has much smaller inertia than the rear wheel side, the wheels easily repeat the wheel spin grip by the driving force distribution control by increasing / decreasing the clutch engaging force, and the control hunting continues.

On the other hand, since the rear wheels are directly connected to the engine and the transmission, the inertia is large and the influence of the driving force distribution control due to the increase / decrease of the clutch engagement force is hardly influenced.

Note that the control hunting becomes more remarkable as the control gain of the clutch engagement force with respect to the front-rear wheel rotation speed difference ΔN is increased in order to improve the control responsiveness.

The present invention has been made by paying attention to the problems as described above, and effectively prevents the control hunting accompanying the rotation speed fluctuation of the controlled wheels during low μ road acceleration while maintaining the ΔN feedback control. The task is to develop a drive force distribution control device for a four-wheel drive vehicle.

(Means for Solving the Problem) In order to solve the above-mentioned problems, in the drive force distribution control device for a four-wheel drive vehicle of the present invention, as shown in the claim correspondence diagram of FIG. A four-wheel drive vehicle having a direct drive wheel a to which engine driving force is directly transmitted and a controlled wheel c to be transmitted via a friction clutch b that is fastened by an external control force. Outside,
In the driving force distribution control device for a four-wheel drive vehicle, which is provided with a driving force distribution control means d for performing the fastening force increase / decrease control based on the front / rear wheel rotation speed difference information and changing the front / rear wheel driving force distribution, The force distribution control means d includes a direct drive wheel rotational speed detection unit e that detects the rotational speed of the direct drive wheel a, a controlled wheel rotational speed detection unit f that detects the rotational speed of the controlled wheel c, and a vehicle body acceleration. A vehicle body acceleration equivalent value detection unit g for detecting a corresponding vehicle body acceleration equivalent value, a controlled wheel rotational acceleration detection unit h for detecting a rotational acceleration of the controlled wheel c, the vehicle body acceleration equivalent value and rotation of the controlled wheel c. By comparing with the detected acceleration value, the controlled wheel c
Controlled wheel rotational acceleration variation detection unit i that detects that the rotational acceleration of the controlled wheel is in a fluctuating state in which acceleration and deceleration are repeated, and filter processing that controls the change in the rotational acceleration detection value of the controlled wheel c by the controlled wheel rotational speed filter. The controlled wheel rotational speed filter value calculation unit j for obtaining the value and the front and rear wheel rotational speeds when the controlled wheel rotational acceleration fluctuation is detected are replaced with the controlled wheel rotational speed filter values instead of the controlled wheel rotational speed detection values. It is characterized in that it is a means having a front and rear wheel rotation speed difference calculation unit k for calculating the difference.

The controlled wheel rotational speed filter value calculation unit j may be a computing unit that obtains the controlled wheel rotational speed filter value based on the vehicle longitudinal acceleration, or the controlled wheel rotational speed filter value based on the rotational acceleration of the direct drive wheels. It may be a calculation unit for obtaining the wheel rotation speed filter value.

(Operation) During constant speed running or acceleration / deceleration running on a high μ road where acceleration / deceleration of the vehicle body coincides with acceleration / deceleration of controlled wheels and acceleration does not fluctuate, front / rear wheel rotational speed difference calculation of the driving force distribution control means d is performed. In section k, the front and rear wheel rotation speed difference is calculated based on the rotation speed detection value information input from the direct drive wheel rotation speed detection section e and the controlled wheel rotation speed detection section f, and based on this front and rear wheel rotation speed difference information. The clutch engagement force of the friction clutch b is controlled to increase or decrease.

By comparing the vehicle-body acceleration-equivalent value from the vehicle-body acceleration-equivalent value detection section g with the controlled-wheel rotational acceleration detection value of the controlled wheel c from the controlled-wheel rotational acceleration detection section h, the controlled-wheel rotational acceleration fluctuation detection section i Despite the state, when the rotational acceleration fluctuation of the controlled wheel c is detected, which is a fluctuation state in which the rotational acceleration of the controlled wheel c repeats acceleration / deceleration, when the controlled wheel of the front and rear wheels is detected, The controlled wheel rotational speed filter value from the controlled wheel rotational speed filter value calculation unit j is used instead of the rotational speed detection value, and the front and rear wheel rotational speed difference calculation unit k of the driving force distribution control means d uses the front and rear wheel rotational speed difference. Is calculated.

Then, the clutch engagement force of the friction clutch a is controlled to be increased or decreased based on the front-rear wheel rotation speed difference information based on the controlled wheel rotation speed filter value and the directly connected wheel rotation speed detection value.

Therefore, during rapid acceleration on a low μ road, fluctuations in the rotational speed detection value of the controlled wheel are caused by the difference in inertia between the engine directly connected wheel and the controlled wheel to which the engine driving force is transmitted via the friction clutch b. When the above occurs, the control wheel hunting is effectively prevented while maintaining the ΔN feedback control by using the controlled wheel rotation speed filter value instead of the controlled wheel rotation speed detection value.

(Example) Hereinafter, the Example of this invention is described based on drawing.

In describing this embodiment, a drive force distribution control device for a rear wheel-based four-wheel drive vehicle will be taken as an example.

 First, the configuration will be described.

As shown in FIG. 2, the drive system of the four-wheel drive vehicle to which the driving force distribution control device of the embodiment is applied includes an engine 1, a transmission 2, a transfer input shaft 3, a transfer clutch device C, a rear propeller shaft 4, The vehicle includes a rear differential 5, rear wheels 6, a transfer output shaft 7, a front propeller shaft 8, a front differential 9, and a front wheel 10. The engine driving force that has passed through the transmission 2 is directly transmitted to the rear wheels, and is transmitted to the front wheels 10. Is transmitted through a transfer clutch device C provided between the transfer input / output shafts 3 and 7.

Further, outside the transfer clutch device C, a hydraulic pressure control device 20 is provided as a driving force distribution control means for generating a control hydraulic pressure Pc which is a clutch engagement force based on predetermined input information and control content.

The hydraulic control device 20 includes a motor 22 that is driven or stopped by a relief switch 21, a hydraulic pump 24 that is driven by the motor 22 to suck up from a reservoir tank 23, and a pump discharge pressure (primary pressure) from the hydraulic pump 24. An accumulator 26 that stores via a check valve 25, and an electromagnetic proportional pressure table 28 that adjusts a line pressure (secondary pressure) from the accumulator 26 to a predetermined control hydraulic pressure Pc by a command signal control current i ^* from a control unit 27. And is supplied to the control hydraulic port 30 through the control hydraulic pipe 29.

The control unit 27 has an electronic control circuit configuration and includes a front wheel rotation speed sensor 31, a rear wheel rotation speed sensor 32, a control constant setting means 33, a longitudinal acceleration sensor 34, etc. as information input sensors, and is shown in FIG. 3, for example. Such a control constant k
Depending on the torque characteristics, the torque increase / decrease gradient differs depending on
Control is performed so that the clutch engagement force T corresponding to the front-rear wheel rotation speed difference ΔN is obtained, that is, the optimum front-rear wheel driving force distribution ratio is obtained according to the traveling state.

It should be noted that the control unit 27 of the first embodiment includes the front wheels which are the controlled wheels despite the vehicle body acceleration state.
Front wheel rotational acceleration fluctuation detection program that the rotational acceleration of 10 fluctuates in the acceleration direction and deceleration direction, front wheel rotational speed filtering processing program that filters the front wheel rotational speed N _{f based} on the longitudinal acceleration Xg, and rear wheel rotational speed detected value N _r
A front / rear wheel rotation speed difference calculation program for obtaining the front / rear wheel rotation speed difference ΔN based on the front wheel rotation speed filter value N _ff is set.

As shown in FIG. 4, the transfer clutch device C includes a multi-plate friction clutch 60 that is engaged by a pressing mechanism 40 that is operated by a control hydraulic pressure Pc from an external hydraulic control device 20,
A lubricating oil 15 for cooling the clutch provided in the transfer input shaft 3 and in the transfer case 11 and the case cover 12.
To remove the lubricating oil 15 inside the multi-plate friction clutch 60.
And a lubrication pump 70 that guides.

The pressing mechanism 40 of the multi-plate friction clutch 60 includes a cylinder block 41, a piston chamber 42, a piston 43, a piston rod 44, a swing plate 45, a swing pin 46, a fixed pressure plate 47, a bearing 48, a rotary pressure plate.
It is equipped with 49, pressure block 50, and return spring 51.

The multi-plate friction clutch 60 includes a clutch drum 61 that is spline-coupled to the transfer input shaft 3, a drive plate 62 that is spline-fitted to the clutch drum 61,
The driven plate 63 sandwiched between the drive plates 62 and the driven plate 63 are spline-fitted,
Needle bearing 64 for transfer input shaft 3
And a clutch hub 65 rotatably supported by the clutch hub 65.

From the clutch hub 65, the first sprocket 66
→ Chain 67 → Drive torque is transmitted to the transfer output shaft 7 through the second sprocket 68.

The lubrication pump 70 is of a trochoid pump type provided in a pump housing 71 and a pump cover 72 at the inlet of the transfer input shaft 3, and has a suction port 73.
Communicates with a suction tube 75 having a suction port 74, and its discharge port 76 is connected to a radial oil passage 77, an axial oil passage 78, a radial oil passage 79 and a clutch hub 65 formed in the transfer input shaft 3. It communicates with the formed oil holes 80, 81, sucks up the lubricating oil 15 for cooling the clutch in the transfer case 11, guides the lubricating oil 15 to the multi-plate friction clutch 60, and discharges it through the oil hole 82.

The transfer output shaft 7 and the chain 67 to the front wheel 10 provided offset from the transfer input shaft 3 are immersed in the clutch cooling lubricating oil 15 stored in the lower portion of the transfer case 11, Lubrication pump
70 inlets 74 are arranged.

In FIG. 4, 90 is a joint flange, 91, 92, 93 are seals, and 94, 95, 96, 97, 98 are bearings.

 Next, the operation will be described.

First, the flow of the clutch engagement force control processing device executed by the control unit 27 of the first embodiment will be described with reference to the flowchart of FIG.

In step 201, the front wheel rotation speed N _f and the rear wheel rotation speed N _r
Is read.

 In step 202, the longitudinal acceleration Xg is read.

In step 203, the front wheel rotational acceleration _f is calculated by the following equation. _f = (N _f −N _fO ) / dt where N _f ; the front wheel rotation speed this time N _fO ; the front wheel rotation speed one control cycle before dt; the control cycle In step 204, the vehicle is accelerating due to the longitudinal acceleration Xg. Or whether the vehicle is decelerating.

Here, the control hunting occurs when the front wheels 10, which are the controlled wheels, are suddenly accelerated so that wheel spin occurs. Therefore, while the vehicle is decelerating, the clutch control by ΔN control does not cause any problem, and Xg ≦ 0. In case of, the process proceeds to the transient change regulation process step of the front wheel rotation speed calculated value N _ff after the filtering process of step 210 and thereafter.

On the other hand, when Xg> 0 and it is determined that the vehicle is accelerating, the routine proceeds to step 205 and thereafter.

In step 205, it is determined whether the front wheel rotational acceleration _f is in the acceleration direction or the deceleration direction.

In steps 206 and 207, a front wheel deceleration allowable change range Xg 'is set corresponding to the acceleration / deceleration direction of the front wheels 10 as a range in which a change in the front wheel rotation speed is allowed in one control cycle.

For the front wheel acceleration, Xg ′ = Xg + A ₁ , and for the front wheel deceleration, Xg ′ = Xg−A ₂ , and A ₁ and A ₂ are constants indicating the allowable speed range.

When the vehicle is accelerating and the front wheels 10 are in the accelerating direction, the routine proceeds to step 208, where the front wheel rotational acceleration _f is compared with the front wheel speed allowable change range Xg 'to indicate the four-wheel wheel spin state. Whether or not it is determined.

That is, since the front wheel rotational acceleration _f is the front wheel rotational speed change width in one control cycle as is clear from the above equation, the front wheel rotational speed allowable change range is a range in which the change of the front wheel rotational speed is allowed in one control cycle. By comparing with Xg ′, it is possible to determine whether the front wheels 10 are also wheel spin, that is, whether the four wheels are in the wheel spin state.

When _f > Xg ′, the process proceeds to step 209,
The front wheel rotation speed calculation value N _ff obtained by the filtering process is obtained by the following equation.

N _ff = N _ffO + Xg ′ However, N _ffO is the value of the front wheel rotation speed calculation value N _ff one control cycle before.

On the other hand, when _f > Xg ', the routine proceeds to the transient change regulation processing step of gradually matching the front wheel rotational speed calculation value _Nff after the filtering processing in step 210 and subsequent steps with the detected value.

In step 210, the difference _fC between the actual front wheel rotation speed N _f and the filtered value N _ffO of the front wheel rotation speed one control cycle before is calculated.

In step 211, it is determined whether or not | _fC | is larger than the allowable change amount A ₃ .

Here, if | _fC | ≦ A ₃ , the _routine proceeds to step 213, where the detected front wheel rotation speed N _f is directly used as the front wheel rotation speed calculation value N _ff .

On the other hand, when | N _fC |> A ₃ , the calculated front wheel rotation speed N _ff
Is gradually matched with the front wheel rotation speed N _f by the detection.

That is, in step 212, the direction of change is determined from the positive or negative of _fC , and in step 214, N _f > N _ffO , so N _ff = N
_ffO + A _3, and in step 215, N _ff = N _ffO −A ₃ because N _f ≦ N _ffO .

However, A ₃ is a constant indicating the convergence width of the rotation speed in one control cycle.

When the front wheel rotation speed calculation value N _ff is obtained in one of the steps 209 and steps 213 to 215 reached after passing through any of the routes of the above processing, the process proceeds to step 216, and the front wheel rotation speed calculation value is calculated. The front-rear wheel rotation speed difference ΔN is calculated from N _ff and the actually detected rear wheel rotation speed N _r .

Then, in step 217, as shown in FIG. 3, the clutch engagement force T corresponding to the front / rear wheel rotational speed difference ΔN is obtained, that is, the optimum front / rear wheel drive force distribution ratio ΔN is obtained according to the running state. Corresponding control is performed.

Next, the driving force combination control operation in the first embodiment during traveling will be described.

(A) When traveling on a high μ road, etc. When traveling on a high μ road where no four-wheel wheel spin occurs, there is no fluctuation in the front wheel rotation speed N _f due to detection, so
In the flowchart of the figure, step 201 → step 2
The flow proceeds from 02 → step 203 → step 204 (step 208) → step 210 → step 213 → step 216 → step 217, and the rotation speed detection value input from the front wheel rotation speed sensor 31 and the rear wheel rotation speed sensor 32. The front-rear wheel rotation speed difference ΔN is calculated from the information, and the front-rear rotation speed difference ΔN is calculated.
The clutch engagement force of the multi-plate friction clutch 60 is controlled based on N.

Therefore, as the front-rear wheel rotation speed difference ΔN becomes larger, the driving force distribution is gradually increased from the rear-wheel driving force distribution of 100% to the front wheels. In the region of the speed difference ΔN, the driving force distribution control is performed so that the front and rear wheels are distributed in a complete four-wheel drive state, so that optimum traveling performance with suppressed drive wheel slip is exhibited.

(B) When accelerating on a low μ road When driving on a low μ road such as an ice-snow road where acceleration is caused by depressing the accelerator pedal and four-wheel wheel spin occurs, steps 204, 206 and 206 in the flowchart of FIG. The four-wheel wheel spin is detected by step 208, and steps 206, 207 and 209 are performed.
The front wheel rotational speed calculated value N _ff is filtered by the front wheel 10 of the front and rear wheels, which is the controlled wheel, instead of the front wheel rotational speed N _f which is the detected value. The rotational speed difference ΔN is calculated, and based on the front-rear wheel rotational speed difference ΔN, the multi-disc friction clutch 60
The clutch engagement force is controlled to increase or decrease.

Therefore, as shown in FIG. 6, a four-wheel wheel spin state occurs, causing a difference in inertia between the rear wheel 6 which is a direct engine wheel and the front wheel 10 to which the engine driving force is transmitted via the multi-plate friction clutch 60. As shown by the solid line characteristic in FIG. 6, the front wheel rotation speed N _f actually fluctuates greatly, but when such a four-wheel wheel spin state is detected, the front wheel rotation speed is replaced with the front wheel rotation speed detection value. Speed filter value (= N
By using _ff ), the fluctuation range of the front wheel rotation speed can be suppressed to a small value, as shown by the chain line characteristics in FIG.

As a result, control hunting when the detected value of the front wheel rotation speed N _f is used as it is as the calculation information of the front and rear wheel rotation speed difference ΔN is effectively prevented while maintaining the ΔN feedback control, and noise or noise associated with the control hunting is prevented. It is possible to prevent rattling vibrations that continue self-excitingly.

(C) During low-μ road acceleration running → high-μ road running When the transition from low-μ road acceleration running to high-μ road running, in which the four-wheel wheel spin state is eliminated, filtering shown in steps 210 to 215 proceeds to excessively change regulation processing steps of the front wheel rotational speed calculated value N _ff after treatment, the process of matching the front wheel rotational speed N _f by gradually detect the front wheel rotational speed calculated value N _ff is made.

Therefore, when entering a dry road from a snowy road, a sudden change in the front-rear wheel rotational speed difference ΔN and the clutch engagement force T is prevented, a change in vehicle behavior is small, and a smooth transition to ΔN-corresponding control based on the detected value can be achieved. I can.

Next, the control unit 27
The _r and vehicle acceleration equivalent value, setting the front wheel rotational speed filtering processing program to filter wheel rotational speed N _f and the front wheel rotational acceleration detection program for detecting a variation in rotational acceleration of the front wheel 10, a rear wheel rotational acceleration _r as a reference The second embodiment will be described with reference to the flowchart of FIG.

In step 301, the front wheel rotation speed N _f and the rear wheel rotation speed N _r
Is read.

In steps 302 and 303, the rear wheel rotational acceleration _r ,
The front wheel rotational acceleration _f is calculated by the following equation. _r = (N _r −N _rO ) / dt _f = (N _f −N _fO ) / dt) where N _f , N _r ; rotational speed N _fO , N _rO ; rotational speed before one control cycle dt; In the control cycle step 304, the direction of change of the rear wheel rotational acceleration _r is determined.

If _r > 0, the rear wheel is accelerating, and the front wheel rotational acceleration _f is checked in step 305 and thereafter.

If _r ≦ 0, the rear wheels are decelerating, and the front wheel rotational acceleration _f is checked in step 310 and subsequent steps.

In step 305, the changing direction of the front wheel acceleration _f is determined.

If _r > 0 and _f > 0, then step
In 306, a rear wheel rotational acceleration _r as a reference, some tolerance A ₄ front wheel speed allowable variation range in consideration of Xg 'is calculated by the following equation.

Xg '= _r + A ₄ Here, during sudden acceleration, etc., the rear wheels are directly connected to the engine, so wheel spin easily occurs, and the acceleration is usually higher than the front wheels. Therefore, the allowable width A ₄ is set to a small value that allows the difference in rotational acceleration due to the difference in the turning trajectories of the front and rear wheels that occurs when entering a corner at a constant speed.

In step 307, it is determined whether or not the front wheel rotational acceleration _f is within the front wheel speed allowable change range Xg '.

Then, _{if f} > Xg ', the process proceeds to step 308 to regulate the front wheel rotation speed by filtering, and _{if f} ≤Xg', the front wheel rotation speed may not be filtered, but the value after filtering is not necessary. When the difference between N _ff and the actual value N _f is large, the process proceeds to step 316 to step 320 where transitional regulation is performed to prevent a sudden change in the value.

In step 308, the calculated front wheel rotation speed N _ff is calculated by the following equation using the front wheel speed allowable change range Xg ′.

N _ff = N _ffO + Xg ′ On the other hand, if ≦ 0 in step 305, then ≦ 0 and _r > 0. Therefore, in step 309, the calculated front wheel rotation speed N _ff that regulates the decrease in front wheel rotation speed. Is calculated by the following formula.

N _ff = N _ffO −A ₅ On the other hand, if _r ≦ 0 in step 304, step 310
Then, in step 310, the changing direction of the front wheel rotational acceleration _f is determined.

If _r ≤ A and _f <0, then step
In 311, a rear wheel rotational acceleration _r as a reference, some tolerance A ₆ front wheel speed allowable variation range Xg in consideration of the 'is calculated by the following equation.

Xg '=-A _{6 In} step 312, it is judged if the front wheel rotational acceleration | _f | is within the front wheel speed allowable change range | Xg' |.

Then, if | _f |> | Xg ′ |, proceed to step 313 to restrict the front wheel rotation speed by filtering, and if | _f | ≦ | Xg ′ |, perform excessive restriction from step 316 to Go to step 320.

In step 313, the front wheel rotational speed calculation value N _ff is calculated by the following equation using the front wheel speed allowable change range | Xg ′ |.

N _ff = N _ffO − | Xg ′ | On the other hand, if _f ≦ 0 in step 310, then _f ≦ 0 and _r <0.
In 4, the front wheel rotation speed calculation value N _ff that regulates the increase of the front wheel rotation speed is obtained by the following equation.

N _ff = N _ffO + A _{7 Since} the processing steps shown in steps 315 to 320 for gradually matching N _ff with N _f are the same as steps 210 to 215 of the first embodiment, description thereof will be omitted. Also, since step 321 and step 322 correspond to step 216 and step 217 of the first embodiment, the description thereof will be omitted.

Therefore, the same effect as that of the first embodiment can be obtained in the second embodiment, and in addition, the longitudinal acceleration sensor 34 as in the first embodiment is not required, and the existing minimum required for the ΔN corresponding control. Using only the front wheel rotation speed sensor 31 and the rear wheel rotation speed sensor 32, the control hunting is prevented by the filtering processing of the front wheel rotation speed at the time of spinning the four wheels.

Although the embodiment has been described with reference to the drawings, the specific configuration and control contents are not limited to this embodiment.

For example, in the embodiment, an example of application to a drive force distribution control device for a rear wheel-based four-wheel drive vehicle in which the rear wheel side is directly connected to the en-drive is shown. It can also be applied to a drive force distribution control device for a wheel drive vehicle.

Further, in the embodiment, the rotational speed of the front wheels, which are the controlled wheels, is filtered based on the longitudinal acceleration of the vehicle and the rotational acceleration of the rear wheels as a reference to prevent not only control hunting but also high ΔN feedback control accuracy. Although a preferable example that can be maintained is shown, the forced hunting is prevented even if the average value of the detection values obtained in multiple control cycles is taken and the filtering process is performed to regulate the rotational speed change of the controlled theory. The present invention is included as long as the above is achieved.

(Effects of the Invention) As described above, in the drive force distribution control device for a four-wheel drive vehicle according to the present invention, the drive force distribution control means detects the rotation speed of the direct drive wheels. A detection unit, a controlled wheel rotation speed detection unit that detects the rotation speed of the controlled wheel, a vehicle body acceleration equivalent value detection unit that detects a vehicle body acceleration equivalent value that corresponds to the vehicle body acceleration, and a rotational acceleration of the controlled wheel By comparing the controlled wheel rotation speed detection unit with the vehicle body acceleration equivalent value and the rotational acceleration detection value of the controlled theory, the rotational acceleration of the controlled wheel repeats acceleration and deceleration even in the vehicle body acceleration state. Controlled wheel rotational speed filter value calculation by the controlled wheel rotational acceleration fluctuation detection unit that detects that the controlled wheel rotational speed fluctuation value and the controlled wheel rotational speed filter value is calculated by the filtering process that regulates the change in the rotational acceleration detected value of the controlled wheel. Section and a front-rear wheel rotation speed difference calculation unit that calculates the front-rear wheel rotation speed difference using the controlled wheel rotation speed filter value instead of the controlled wheel rotation speed detection value when the controlled wheel rotation acceleration fluctuation is detected. Since it has a means to have, the control hunting accompanying the rotation speed fluctuation of the controlled wheel at the time of low μ road acceleration,
It is possible to effectively prevent the ΔN feedback control while maintaining it, and it is possible to prevent the noise and rattling vibrations associated with the control hunting.

[Brief description of drawings]

FIG. 1 is a diagram showing a drive force distribution control device for a four-wheel drive vehicle according to the present invention, and FIG. 2 shows a drive system and a control system for a four-wheel drive vehicle to which the drive force distribution control device of the embodiment is applied. Figure,
FIG. 3 is a control characteristic diagram of front and rear wheel rotational speed difference of clutch engaging force in the embodiment apparatus, FIG. 4 is a sectional view showing a transfer clutch apparatus used in the embodiment apparatus, and FIG.
FIG. 6 is a flowchart showing a flow of driving force distribution control operation in the control unit of the embodiment, FIG. 6 is a time chart diagram of front wheel rotation speed, rear wheel rotation speed, and vehicle speed during low μ road acceleration traveling, and FIG. It is a flowchart figure which shows the flow of driving force distribution control operation | movement in the control unit of 2nd Example. a: direct drive wheel b: friction clutch c: controlled wheel d: driving force distribution control means e: direct drive wheel rotation speed detection unit f: controlled wheel rotation speed detection unit g: vehicle body acceleration Corresponding value detection unit h: Controlled wheel rotational acceleration detection unit i: Controlled wheel rotational acceleration fluctuation detection unit j: Controlled wheel rotational speed filter value calculation unit k: Front and rear wheel rotational speed difference calculation unit

Claims (3)

(57) [Claims] 1. A four-wheel drive vehicle having, among front and rear wheels, a directly connected drive wheel to which an engine driving force is directly connected and a controlled wheel transmitted via a friction clutch that is engaged by an external control force. Then, outside the friction clutch, a four-wheel drive vehicle is provided with a driving force distribution control means for performing a fastening force increase / decrease control based on the front / rear wheel rotation speed difference information and changing the front / rear wheel driving force distribution. In the driving force distribution control device, the driving force distribution control means includes a direct drive wheel rotational speed detection unit that detects the rotational speed of the direct drive wheel, and a controlled wheel rotational speed detection unit that detects the rotational speed of the controlled wheel. A vehicle body acceleration equivalent value detection unit that detects a vehicle body acceleration equivalent value that corresponds to the vehicle body acceleration, a controlled wheel rotational acceleration detection unit that detects rotational acceleration of the controlled wheel, and the vehicle body acceleration equivalent value and the controlled wheel rotation. Acceleration detection In comparison with the vehicle acceleration state, the controlled wheel rotational acceleration variation detection unit that detects that the rotational acceleration of the controlled wheel is in a fluctuating state in which acceleration and deceleration repeat, and the rotational acceleration detected value of the controlled wheel Of the controlled wheel rotational speed filter value by a filtering process that regulates the controlled wheel rotational speed filter value, and when the controlled wheel rotational acceleration fluctuation is detected, the controlled wheel rotational speed detection value is replaced with the controlled wheel rotational speed detected value. A driving force distribution control device for a four-wheel drive vehicle, comprising: a front-rear wheel rotation speed difference calculation unit that calculates a front-rear wheel rotation speed difference using a control wheel rotation speed filter value. 2. The driving force distribution control for a four-wheel drive vehicle according to claim 1, wherein the controlled wheel rotational speed filter value computing section is a computing section that obtains a controlled wheel rotational speed filter value based on vehicle longitudinal acceleration. apparatus. 3. The four-wheel drive vehicle drive system according to claim 1, wherein the controlled wheel rotational speed filter value computing section is a computing section that obtains a controlled wheel rotational speed filter value based on the rotational acceleration of the direct drive wheels. Power distribution control device.