JPH01229721A - Driving power distribution ratio detecting device for four-wheel-drive vehicle - Google Patents

Abstract

PURPOSE:To improve detecting accuracy of ratio correcting theoretical drive power distribution ratio to the actual drive power distribution ratio considering various conditions by calculating front to rear drive power distribution ratio being based on each detection value of clutch connecting power, car speed and a difference between front and rear wheel rotary speeds. CONSTITUTION:A four-wheel-drive vehicle provides a driving system clutch means 1 halfway a driving system distributively transmitting drive power of an engine to front and rear wheels, changing distribution ratio of drive power to the front and rear wheels by adjusting the connecting force of the clutch means 1. In this constitution, each means 2-4, which respectively detects at least clutch connecting force, car speed and a difference between front and rear wheel rotary speeds, is provided as the detecting means. A means 5, which calculates front to rear drive power distribution ratio being based on each detection value from each detecting means 2-4, is provided. In this way, theoretical drive power distribution ratio by the clutch connecting force is corrected to the actual drive power distribution ratio considering a road surface friction coefficient and a tire condition or the like, and detecting accuracy of the drive power distribution ratio is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a driving force distribution ratio detection device for a four-wheel drive vehicle that can change front and rear driving force distribution by increasing or decreasing clutch engagement force.

(Prior Art) As a conventional drive force distribution display device for a four-wheel drive vehicle, for example, a device as described in Japanese Utility Model Application Publication No. 62-47430 is known.

This conventional device detects the driving force distribution ratio based only on detecting the command value of the clutch engagement force that generates the torque transmitted to one of the front and rear wheels, and continuously monitors the driving force distribution situation based on the detected driving force distribution ratio. It is displayed in multiple stages or in multiple stages.

(Problem to be Solved by the Invention) However, in this conventional device, even though it is a driving force distribution situation, it is not suitable to display the clutch engagement force itself assuming that it is the front and rear driving force distribution ratio. Even if it is possible to know the approximate frontal driving force distribution situation, it is not possible to convey to the driver accurate information on the frontal driving force distribution ratio that is actually transmitted from the tires to the road surface. However, there remained the problem that operators were unable to predict changes in vehicle behavior due to changes in the driving force distribution ratio.

In other words, in reality, due to the influence of the road surface friction coefficient, tires, etc.
For example, even if the same clutch engagement force is applied, the driving force transmitted from the tires to the road surface is not constant, and the front-rear driving force distribution ratio also changes sequentially.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and in order to achieve this purpose, the present invention includes the following:
The method described below was adopted.

As shown in the conceptual diagram of the claim in FIG. 1, a drive system clutch means 1 is provided in the middle of an engine drive system that distributes and transmits engine driving force to the front and rear wheels, and the engagement force of the drive system flanch means 1 is increased or decreased to transfer the engine drive force to the front and rear wheels. In a four-wheel drive vehicle in which the driving force distribution ratio is changed, the detection means includes at least clutch engagement force detection means 2 that directly or indirectly detects the clutch engagement force, and vehicle speed detection means 3 that detects the vehicle speed. Front and rear wheel rotation speed difference detection means 4 for detecting the front and rear wheel rotation speed difference
The present invention is characterized in that a longitudinal driving force distribution ratio calculation means 5 is provided which calculates and detects the longitudinal driving force distribution ratio based on the detected values from these detection means.

Here, the drive system clutch means 1 refers to a multi-disc friction clutch that is engaged by externally controlled oil pressure using electronic control, or a viscous clutch that generates transmission torque based on the rotational difference between input and output shafts, etc. The latch means allows the driving force distribution ratio to be changed.

(Function) When detecting the front-rear driving force distribution ratio while driving, the front-rear driving force distribution ratio calculation means 5 uses the clutch engagement force detection means 2, which directly or indirectly detects the clutch engagement force, and detects the vehicle speed. Based on the detected values from the vehicle speed detection means 3 that detects the difference in rotational speed of the front and rear wheels, and the front and rear wheel rotational speed difference detection means 4 that detects the difference in rotational speed of the front and rear wheels, the front and rear driving force distribution ratio is calculated using a predetermined calculation formula that includes at least these detected values. Detected by

Therefore, the vehicle speed and the difference in rotational speed of the front and rear wheels provide indirect information such as the road surface friction coefficient and tire condition, and the theoretical driving force distribution ratio due to the clutch engagement force, the influence of the road surface friction coefficient, the tire influence, etc. are taken into consideration. This is corrected to the actual driving force distribution ratio, and the front-rear driving force distribution ratio can be detected with high accuracy.

(Example) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In describing this embodiment, we will take as an example a driving force distribution ratio detection device for a four-wheel drive vehicle based on rear wheel drive, in which the driving force distribution is changed by external electronic control.

First, the configuration will be explained.

As shown in FIG. 2, a four-wheel drive vehicle to which the driving force distribution control device of the embodiment is applied includes a transfer device 10, an engine 11, a transmission 12, a transfer input shaft 13, a rear wheel drive shaft 14, and a multi-wheel drive vehicle. Plate friction clutch (drive system clutch means) 15. 16 rear differentials, 17 rear wheels, 18 front differentials, 1 front wheel,
It includes a gear train 20 and a front wheel drive shaft 21.

The multi-disc friction clutch 15 connects the transfer input shaft 13 (directly connected to the rear wheel drive shaft 14) and the front wheel drive shaft 2.
The torque transmitted to the front wheels can be changed by controlling the clutch pressure.

Incidentally, FIG. 3 shows a specific example of the transfer device 10, in which the multi-disc friction clutch 15, gear arrangement, and shaft arrangement are housed in a transfer case 22.

In Figure 3, 159 is a push plate, +5h is a return spring, 24 is a clutch pressure oil input port, 25 is a clutch pressure oil path, 26 is a rear wheel side output shaft, 27 is a lubricating oil path, and 28 is for a speedometer. Binion, 29 is an oil seal, 30 is a bearing, 31 is a needle bearing,
32 is a thrust hair link, and 33 is a joint flange.

Next, as shown in FIG. 4, an electronic control device 40 that controls the clutch oil pressure P for engaging the multi-disc friction clutch 15 and detects the driving force distribution ratio detects the rear wheel rotational speed as a detection means. It includes a sensor 41, a left front wheel speed sensor 42, and a right front wheel speed sensor 43, a control unit 45 as a control processing means, and an electromagnetic proportional relief valve 46 and a driving force distribution ratio display device 60 as an output means. .

Each of the wheel speed sensors 41, 42, and 43 is provided at the left and right front wheel 19 positions or in the middle of the rear drive shaft 14, and detects a sensor rotor fixed to the shaft and changes in magnetic force due to rotation of the sensor rotor. A rotation sensor based on a pickup is used, and each of these sensors 41, 42, and 43 outputs wheel speed signals (nr), (wf,) according to shaft rotation.

(wf2) is output.

The control unit 45 uses a circuit mainly based on an on-vehicle microcomputer, and includes an input interface 451, a RAM 452 . R.O.
M453. CPU454. Output interface 45
5 is biased.

In the electromagnetic proportional relief valve 46, when the output of the command current signal (1) from the control unit 45 is the command current value I" = 0, the clutch oil pressure P = 0, but if the output of the command current signal (1) is When the command current value I*>0, the valve moves in the closing direction, and the line pressure from the hydraulic source 50 is controlled to the clutch oil pressure P according to the magnitude of the command current value ■* by controlling the drain oil amount (fifth (Figure).The relationship between the clutch oil pressure P and the clutch engagement crab is expressed by the following formula (
Figure 6).

P-T/(μ・A・2n-Rm) However, μ: friction coefficient of clutch plate, A: pressure acting area on piston, n: friction disk disc, Rm: torque transmission effective radius of friction disk, When the clutch oil pressure P is increased, the clutch engagement force T also increases proportionally.

The driving force distribution ratio display device 60 is provided in a position visible to the driver inside the vehicle, and is controlled by the control unit 45.
The results of the calculation of the driving force distribution ratio are displayed in digital or analog form.

Next, the effect will be explained.

In describing the operation, the function will be divided into the front-rear driving force distribution control function and the front-rear drive force distribution ratio detection function.

[Front-rear driving force distribution control operation 1 First, the overall flow of the driving force distribution control operation in the embodiment is as follows.
This will be explained with reference to the flowchart shown in FIG.

In step a, each sensor 41, 42, 43 detects the left front wheel speed w+1. Right front wheel speed wf 2. The rear wheel rotation speed Nr is read.

In step b, the left front wheel l! read in step a above! ! From Wf1, right front wheel speed w+2, and tire diameter r, vehicle speed Vf, front and rear wheel rotational speed difference ΔN, and left and right front wheel rotational speed difference n are calculated.

The vehicle speed Vf is determined by the following formula from the smaller of the left and right front wheels iJwf + 9wf 2 and the tire diameter r.

Vf=r* (min (wf 1.wf
2)) The vehicle speed Vf may be determined by the average value of the left and right front wheel speeds wfl and wf2, or the absolute vehicle speed may be directly detected.

The front and rear wheel rotational speed difference ΔN is calculated from the contact wheel rotational speed Nr and the average front wheel rotational speed using the following equation.

ΔN=Nr−((wf + +wf 2)/2) Note that this may be directly detected by differential rotation detection of the front and rear wheels.

The left and right front wheel rotational speed difference Δn is determined from the left front wheel speed wf+ and the right front wheel speed wf2 using the following equation.

Δn (=1wf, -wf, l) Note that this left and right front wheel rotational speed difference Δn is for calculating the turning radius R and lateral acceleration Y9, so
The turning radius R may be determined using the steering angle θ, or the lateral acceleration Y9 may be directly detected using a lateral acceleration sensor or the like.

In step C, it is determined whether the front and rear wheel rotational speed difference ΔN obtained in step b is ΔN≧0 or ΔN<O.

Then, from step b, control based on the front and rear wheel rotational speed difference ΔN proceeds to step d (control during constant speed/acceleration) or step e (control during deceleration) based on the judgment in step C, and step f Vehicle speed V advancing to (control at high speed)
Control based on f is executed in parallel.

In the control during constant speed/acceleration in step d, the lateral acceleration Y9 is determined from the left and right front wheel rotational speed difference Δn and the vehicle speed Vf, and the clutch engagement force Tx is calculated from the lateral acceleration Y9 and the front and rear wheel rotational speed difference ΔN. Ru.

Further, details will be described later with reference to FIG. 8 showing the processing contents of (2).

In the control during deceleration of the steering wheel, the clutch engagement force T ne is determined based on the vehicle speed Vf and the absolute value 1△N1 of the difference in rotational speed of the front and rear wheels.
g is calculated. For details, please refer to Section 9 which shows the processing contents of ■.
This will be described later with reference to FIGS.

In the control at high speed in step f, the clutch engagement force Tv is calculated based only on the vehicle speed Vf. Further, details will be described later with reference to FIGS. 12 and 13-, which show the processing contents of (2).

In step 9 and step h, the clutch engagement forces Tx and Tneg on the opposite side are respectively set to 0 (zero).

In step i, the target clutch engagement force T* is determined by selecting the two maximum values among the clutch engagement forces Tx, Tneg, and Tv.

In the "T*=max (Tx, Tneg, Tv) step", the clutch pressure control signal (1) from which the target clutch engagement force T* is obtained is output to the electromagnetic proportional relief valve 46.

Next, the control process (2) during constant speed/acceleration in step d will be explained with reference to the flowchart shown in FIG. 8 (see Japanese Patent Application No. 62-36036).

In step 100, a turning radius R is calculated based on the data obtained in step b.

The calculation formula for the turning radius R is as follows.

In the next steps 101 to 109, a low-pass filter is realized that regulates the rate of change in the direction of decrease and increase in the rate of increase in turning radius.

In step 101, the turning radius R obtained in step 100 and the turning radius date one cycle before. Based on which difference, the amount of change ΔR per unit time is calculated.

In step 102, it is determined whether ΔR is positive or negative, and the turning radius R
A judgment is made as to whether the amount is increasing or decreasing, and the subsequent processing route is changed.

If ΔR is positive in step 102, that is, the turning radius R is increasing, it is determined in step 103 whether or not the range of change is larger than the set value A4.
is the value of the low-pass filter when the turning radius increases.

If ΔR is larger than A4 in step 103, the process proceeds to step 104 where filtering is performed, and the turning radius Rx is determined by the calculation formula: RO+A.

Further, if ΔR is smaller than A4 in step 103,
Proceeding to step +05, the calculated turning radius R is directly set as the turning radius Rx.

On the other hand, if ΔR is negative in step 102, that is, the turning radius R is in the decreasing direction, it is determined in step +06 whether the change width is larger than the set value A5, and 5 is set to this set value. This is the value of the low-pass filter when the radius R decreases. Note that the set value A5 is a larger value than the set value A4.

If 1ΔR1 is larger than A5 in step 106, the process proceeds to step 107 where filtering is performed and the turning radius Rx is determined by the calculation formula R8-A3.

If 1ΔR1 is smaller than A5 in step 106, the process proceeds to step +08, and the calculated turning radius R is directly set as the turning radius Rx.

In step 109, the value of the turning radius Rx found in the current control cycle is stored as Ro for calculating ΔR.

In step 110, the lateral acceleration Y9 is determined by the following calculation using the low-pass filtered turning radius Rx and the vehicle speed Vf.

In step 111, a proportional coefficient (gain) is determined using the lateral acceleration Y9 according to the following arithmetic expression.

K=- In step 112, Nx is determined as a correction value for the front and rear wheel rotational speed difference ΔN determined in step b. still,
When ΔN<0, the correction value ΔN× is assumed to be tight] and set to 8Nx=0. When ΔN≧0, the correction value is corrected for the turning trajectory, and ΔNx=ΔN−f (Rx, Vf)
shall be.

In step 113, the clutch engagement force Th (-△Nx) is calculated from the proportional coefficient and the correction value Nx.

In step 114, clutch engagement force T°C (=K·ΔN) is calculated from a predetermined proportional coefficient, °C, and front and rear wheel rotational speed difference ΔN.

In step 115, the larger one of the launch engagement forces Th and TJ2 is selected as the clutch engagement force Tx.

In other words, when Th≧Tj2, Tx=ThTh<
It is set as 8-1\Tx=TJ2 of T°C.

In this way, the clutch engagement force Tx is normally determined by the turning radius R
By applying a filter to the value of , we can indirectly calculate the lateral acceleration Y
The clutch engagement force Th obtained by applying a filter to the value of the proportional coefficient aK determined by 9 is obtained, but in order to avoid an extremely small value, the predetermined clutch engagement force T℃ obtained based on the actual measurement value is I try to at least be able to do it in advance.

Next, the content of the control process (2) during deceleration in step e will be explained with reference to the flowchart of FIG.

In step 120, the gain neg is determined as a function of the vehicle speed Vf. In this gain, neg is the vehicle speed V at which the front and rear wheel rotational speed difference ΔN changes from negative to positive, as shown in FIGS. 10 and 11. Until then, neg=0 and the vehicle speed is V. From vehicle speed V, the value gradually increases until Kneg=O"□Ko, and when the vehicle speed exceeds V1, the value becomes neg-.

In step 12], clutch engagement force T neg is calculated from the gain K neg obtained in step 200 and the absolute value 1ΔN1 of the front and rear wheel rotational speed difference using the following equation.

T neg- to neg * lΔN1 Next, the content of the control processing at high speed in step f will be explained with reference to the flowchart of FIG.

In step 130, the clutch engagement force Tv is calculated as a function of only the vehicle speed V+ using the following equation.

Tv=f (Vf) This multiple function f (Vf) has the content as shown in Fig. 13, and the increase in clutch engagement force due to vehicle speed sensitivity is mainly aimed at stability during high-speed driving, so clutch engagement Power Tv
The vehicle speed at the starting point where is greater than zero is approximately 80 km.
/h, the vehicle speed V reaches the maximum clutch engagement force TVmaX
3 is approximately +20 km/h, which is a range that does not affect turning performance at low to medium speeds.

Further, the maximum clutch engagement force Tvmax is a value that satisfies high-speed straight running stability, and is also a value that is sufficient to make the steering characteristic into a weak understeer characteristic during acceleration turning.

Due to the control operation described above, for example, during constant speed/acceleration at low/medium speeds of 80 km/h or less, the clutch engagement force Tv corresponding to the vehicle speed is almost zero, so the clutch engagement force Tx
is selected as the target clutch engagement force T*.

Furthermore, during deceleration, the clutch engagement force T neg is selected as the target clutch engagement force T* unless the vehicle speed is high.

Also, for example, when driving at high speeds of 80 km/h or more,
The larger value of the clutch engagement force Tx and the clutch engagement force Tv is selected as the target clutch engagement force T*. That is, even when the front and rear wheel rotational speed difference ΔN is small, if the vehicle speed is Vf or high, the value of the clutch engagement force Tv is selected as the target clutch engagement force T*.

Therefore, it is possible to achieve the effect of satisfying all of the requirements of acceleration/deceleration stability at low and medium speeds, stability during high-speed straight running, and optimal steering characteristics during high-speed turning acceleration.

In actual driving, the driving conditions rarely differ clearly as in (a) to (c) above, and each element is complex, but the degree of influence of the clutch engagement force due to each element is By selecting two maximum values that are each one larger, the control will be on the stable side in any case (Patent application 1986-
302473).

[Detection of front-rear driving force distribution ratio] First, the theoretical calculation for determining the driving force distribution ratio from the wheel speed will be described with reference to FIGS. 14 and 15.

However, VLf, Wr: wheel load, Sf, Sr: sling ratio, wf, wr: wheel speed, Of, Or: driving force, Tf, T
r: shaft torque, b: coefficient of friction between tire and road surface, r: tire radius, V: vehicle speed.

Ti=Oi-r Oi=pi-Wi mouth i=ni5i On the other hand, V 1 both V ■ W1= (Si+1) , △N=wr-wf= (Sr-9f) =
12) (+), From (2), front wheel side driving force distribution ratio Tf%=Tf/(Tf+Tr)...
- From (4), the front wheel drive force distribution ratio Tf% can be calculated.

Next, regarding the calculation method of each variable in the above formula (4), the first
This will be explained with reference to Figure 6.

・Front shaft torque Tf Tf=TXif if; Final gear ratio/vehicle speed V ・Wheel load Wf, Wr ・Difference in rotational speed between front and rear wheels ΔN ΔN = w r - w f ・Braking/driving stiffness coefficient An example of calculation based on the above theoretical calculation formula is shown below.

■ In the case of rigid 4WD In the above equation (4), if △N=O, then it becomes, which matches the weight distribution ratio.

■ Is it possible to control the driving force distribution ratio at a constant rate? 9 In the above equation (4), if we solve for ■f% input and Tf output, we get (6), and it is possible to control the driving force distribution ratio at a constant rate.

However, the braking/driving stiffness coefficient changes depending on the road surface friction coefficient and tire condition, and the front and rear wheel rotational speed difference ΔN and the vehicle speed V require turning correction.

Next, the flow of the driving force distribution ratio detection processing operation performed by the control unit 45 based on the above-mentioned theoretical calculation will be explained with reference to the flowchart shown in FIG.

In step 200, the front and rear wheel rotational speed difference ΔN obtained in the driving force distribution control processing operation is determined.

Vehicle speed Vf and turning radius R1 target clutch engagement force T* are read.

In step 201, centripetal acceleration Y9 and longitudinal acceleration x 9 are calculated using the following equations based on the input values at step 200 t'.

Y9=Vf'/R X g= (V+-Vfo)/ΔtVfo is the vehicle speed read before the predetermined control period Δ, and x9 is obtained from the total value of the vehicle speed.

Note that the centripetal acceleration Y9 and the longitudinal acceleration x9 may be directly detected using a G sensor.

In step 202, the front wheel load Wf and the rear wheel load Wr are calculated as a function of longitudinal acceleration x 9 using the following formula.

Wf = (A, -A, -X9) /2W r
−(A 2 + A o·X 9 )/2 Note that the front wheel loads Wf and Wr may be directly detected by a stroke sensor or the like.

In step 203, the braking/driving stiffness coefficient 2kx of the tire is determined as a function of the centripetal acceleration Y9 and the front and rear wheel rotational speed difference ΔN using the following equation.

Here, the braking/driving stiffness coefficient is a value that changes depending on the road surface friction coefficient μ, and as shown in FIG. 18, k,
The relationship is (high-road)>k, (low-μ road).

However, since the road surface friction coefficient μ cannot be directly detected, it is indirectly detected using the centripetal acceleration Y9 and the front and rear wheel rotational speed difference ΔN. That is, one high μ road with large centripetal acceleration, one low exit road with small centripetal acceleration, and furthermore, as shown in Fig. 19, front and rear wheel rotational speed difference - large slip - low μ road front and rear wheel rotational speed difference small → small slip. →Represent the relationship of high μ road as a formula.

kx=f (Y9.ΔN) =A 3 +Aa・Yg Aa・ΔN However, A3. A
,,A, is a constant.

In step 204, the front wheel side driving force distribution ratio Tf% and the rear wheel side driving force distribution ratio Tr% are calculated using the following formula.

Tr%=1-Tf% However, A5 is a constant In step 205, the driving force distribution is changed to inform the driver of the front wheel driving force distribution ratio Tf% and the rear wheel driving force distribution ratio Tr% obtained in step 204. It is output to the ratio display device 60.

Through the above driving force distribution ratio detection processing, the target clutch engagement force T* is used as basic information, and the vehicle speed Vf and the front and rear wheel rotational speed difference ΔN are used as indirect information sources such as the road surface friction coefficient μ and tire condition. The theoretical driving force distribution ratio based on force T* is corrected to the actual driving force distribution ratio in consideration of the influence of road surface friction coefficient, tire influence, etc., and highly accurate front and rear driving force distribution ratios Tf% and Tr% are detected. be done.

Therefore, the driving force distribution ratio detection device of the embodiment provides the following effects.

■ Information on the accurate front-rear driving force distribution ratio Tf% and Tr% is transmitted to the driver by the driving force distribution ratio display device 60, and the driver can confirm the front-rear driving force distribution ratio Tf%.

Changes in vehicle behavior due to Tr% can be accurately predicted.

■ By feeding back the detected front and rear driving force distribution partitions f% and Tr% as input information for driving force distribution control, it is possible to maintain a constant driving force distribution ratio, and to control the front and rear driving force distribution ratio instead of clutch engagement force. Tf%.

Optimal driving force distribution control corresponding to actual driving can be performed with Tr% as a control target.

■ Sensors installed on the vehicle include a contact wheel rotation speed sensor 41, a left front wheel speed sensor 42, and a right front wheel speed sensor 43.
This cost-effective and highly reliable device with only three sensors is capable of not only driving force distribution control but also driving force distribution ratio detection.

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

For example, in the example, the driving force distribution ratio between the front and rear wheels is determined only by a clutch whose engagement force is controlled externally, but a transfer device that combines this electronically controlled clutch with a planetary gear set, etc. In this case, when determining the driving force distribution ratio, the final driving force distribution ratio is determined by considering the distribution ratio by the target clutch engagement force and the distribution ratio by the planetary gear set, etc.

In addition, when a viscous clutch that generates its own engagement force is used as the drive system clutch means, the clutch engagement force T is a function of the rotation speed difference ΔN between the input and output shafts, which is the cause of the generation of the engagement force (
It is obtained by performing an estimation calculation using T=f(ΔN)).

(Effects of the Invention) As explained above, in the driving force distribution ratio detection device for a four-wheel drive vehicle of the present invention, the detection means includes a clutch engagement force that directly or indirectly detects at least a clutch engagement force. a detection means; a vehicle speed detection means for detecting vehicle speed;
and front and rear wheel rotation speed difference detection means for detecting a front and rear wheel rotation speed difference, and front and rear drive force distribution ratio calculation means for calculating a front and rear drive force distribution ratio based on the detected values from these detection means. Since the vehicle speed and front and rear wheel rotational speed differences indirectly provide information such as the road surface friction coefficient and tire condition, the theoretical driving force distribution ratio due to the clutch engagement force has an effect on the road surface friction coefficient. The effect is that the front/rear driving force distribution ratio can be detected with high accuracy by correcting it to the actual driving force distribution ratio taking into account factors such as tire influence and the like.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a claim showing a driving force distribution ratio detection device for a four-wheel drive vehicle according to the present invention, FIG. 2 is a diagram showing a four-wheel drive vehicle to which the embodiment device is applied, and FIG. 3 is a diagram showing the embodiment device. 4 is a flock diagram showing the control unit of the embodiment device, FIG. 5 is a characteristic diagram showing the relationship between clutch oil pressure and clutch engagement force, and FIG. 6 is a diagram showing the relationship between command current value and clutch pressure. 7 is a flowchart showing the flow of driving force distribution control operation in the control unit of the embodiment device; FIG. 8 is a flowchart showing the flow of control processing operation at constant speed/acceleration; FIG. 9 Figure 10 is a flowchart showing the flow of control processing operations during deceleration, Figure 10 is a gain characteristic diagram versus vehicle speed, Figure 11 is a front and rear wheel rotational speed difference characteristic diagram versus vehicle speed, and Figure 12 is a flowchart of control processing operations at high speeds. A flowchart showing the flow, Fig. 13 is a clutch engagement force characteristic diagram with respect to vehicle speed, Fig. 14 is a dynamic model diagram of the drive system during driving, Fig. 15 is a road surface friction coefficient characteristic diagram with respect to slip rate, and Fig. 16 is a vehicle 17 is a flowchart showing the flow of the driving force distribution ratio detection processing operation in the control unit of the embodiment device, and FIG. 18 is a comparison of road surface friction coefficient characteristics on low μ road and high μ road. Figure, 1st
FIG. 9 is a diagram showing the relationship between the front and rear wheel rotational speed difference and the road surface friction coefficient characteristics. 1... Drive system clutch means 2... Clutch engagement force detection means 3... Vehicle speed detection means 4... Front and rear wheel rotational speed difference detection means 5... Front and rear driving force distribution ratio calculation means

Claims (5)

[Claims] (1) A drive system clutch means is provided in the middle of the engine drive system that distributes and transmits the engine drive power to the front and rear wheels, and the drive power distribution ratio to the front and rear wheels is changed by increasing or decreasing the engagement force of the drive system clutch means. In the drive vehicle, the detection means includes at least a clutch engagement force detection means that directly or indirectly detects the clutch engagement force, a vehicle speed detection means that detects vehicle speed, and a front and rear wheel rotational speed difference that detects a front and rear wheel rotational speed difference. A driving force for a four-wheel drive vehicle, comprising: a front-rear driving force distribution ratio calculating means for calculating a front-rear driving force distribution ratio based on detected values from these detecting means. Distribution ratio detection device. (2) The front and rear driving force distribution ratio calculating means calculates the following formula Tf%=f(T,V,ΔN)=T/( 2. The driving force distribution ratio detection device for a four-wheel drive vehicle according to claim 1, wherein the driving force distribution ratio detection device for a four-wheel drive vehicle is means for determining the front wheel side driving force distribution ratio Tf% by: K_1*T+K_2*ΔN/V). (3) In the equation according to claim 2, the front-rear driving force distribution ratio calculating means calculates the following equation in which K_1 and K_2 are functions of front-rear weight distribution of the vehicle: K_1=(1+Wr/Wf) K_2=K_3*Wr , Wf; front weight Wr; rear weight. (4) The driving force distribution ratio detection device for a four-wheel drive vehicle according to claim 3, wherein the longitudinal driving force distribution ratio calculating means is means for calculating K_3 in the equation according to claim 3 by a function of the road surface friction coefficient μ. . (5) The four-wheel drive vehicle according to claim 3, wherein the front-rear driving force distribution ratio calculating means is means for calculating K_3 in the equation according to claim 3 by a function of centripetal acceleration Y_9 and front-rear wheel rotational speed difference ΔN. Driving force distribution ratio detection device.