JPH02227333A - Power transmission for automobile - Google Patents

Abstract

PURPOSE:To improve accelerability and controllability by compensating a speed differential portion due to a locus difference between front and rear wheels with a first compensating means and a turning center variable portion due to lateral acceleration with a second compensating means, respectively, at time of torque distributing control on the basis of rotational frequency of each wheel. CONSTITUTION:A controller 44 detects each rotational frequency of front wheels 14, 16 and rear wheels 22, 24 with a sensor 46 when a 4WD mode is selected by a mode selector 64, and on the basis of the detected value, it controls the extent of engaging force between front and rear clutches 10, 18, and torque distributing control takes place. At this time, a speed differential portion between these front and rear wheels attributable to a locus difference between the front and rear wheels being found on the basis of a steering angle to be detected by a steering angle sensor 52 and a wheel base between these front and rear wheels is compensated by a first compensating means. In addition, a portion equivalent to a change in the turning center of a vehicle being moved with an increase of lateral acceleration detected by a sensor 50 is compensated by a second compensating means. Thus, accelerability and controllability can be well improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power transmission device for a motor vehicle, particularly a four-wheel drive vehicle.

[Conventional technology]

2. Description of the Related Art In recent years, many four-wheel drive vehicles have been put into practical use that can provide excellent driving force and steering stability even on slippery roads such as snowy roads. In order to further improve acceleration performance and maneuverability on high-μ roads, for example, as shown in Japanese Patent Application Laid-Open No. 63-11431, the driving force distributed to the front wheels and rear wheels is appropriately controlled. Devices configured are known.

In the device disclosed in the above publication, the slip of the front and rear wheels is calculated based on the rotational speed of the front and rear wheels, and also takes into account the rotational speed difference caused by the difference in trajectory between the front and rear wheels, which is determined from the steering angle of the front wheels. It detects the situation and controls the distribution of driving force according to the result.

[Problem to be solved by the invention]

However, with the device disclosed in this publication, it is possible to accurately detect the slip situation of the front and rear wheels even when turning when the lateral acceleration is small, but the trajectory determined from the steering angle of the front wheels is The difference varies depending on the magnitude of the lateral acceleration acting on the vehicle body, so when the lateral acceleration becomes large, accurate detection is difficult.For this reason, the drive force distribution between the front and rear wheels is ideal when turning. There was a problem that there were cases where this did not occur.

[Means to solve the problem]

The present invention has been devised in view of the above, and includes a drive system that transmits the output of the prime mover to the front wheels and rear wheels via a variable transmission torque mechanism, and a drive system that transmits the output of the prime mover to the front wheels and rear wheels through a variable transmission torque mechanism, and a system that transmits the rotational speed of each front wheel and rear wheel detected by a wheel speed sensor. and torque distribution control means for controlling the variable transmission torque mechanism so that the relationship between the slip rate or amount of the front wheels and the slip rate or amount of the rear wheels is a predetermined relationship based on the above. The torque distribution control means includes a steering angle detection means for detecting a steering angle and an acceleration detection means for detecting lateral acceleration acting on the vehicle body, and the torque distribution control means calculates the torque distribution based on the steering angle and the wheel base between the front and rear wheels. a first correction means for correcting an amount corresponding to a difference in rotational speed between the front and rear wheels due to a trajectory difference between the front and rear wheels, and an amount corresponding to a change in the turning center that moves with an increase in the lateral acceleration; This is a power transmission device for an automobile, characterized in that it has a second correction means for correcting.

[Effect]

According to the present invention, the torque distribution control means controls the front and rear wheels by the first correction means when executing the torque distribution control based on the respective rotational speeds of the front wheels and the rear wheels detected by the wheel speed sensor. A change in the center of turning of a vehicle that moves with an increase in lateral acceleration acting on the vehicle body is corrected by an amount corresponding to the difference in rotation speed between the front and rear wheels due to a difference in the trajectory between the front and rear wheels. Correct the amount equivalent to .

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 1 to 12.

FIG. 1 is an explanatory diagram showing the configuration of this embodiment. In the figure, reference numeral 2 denotes an engine, and the output of the engine 2 is transmitted to an output shaft 8 via a clutch 4 and a transmission 6. The power of the output shaft 8 is transmitted to the left and right front wheels 1 via a front clutch 10 and a front differential gear 12.
4.16, and is transmitted to the left and right rear wheels 22.2 via the rear clutch 18 and rear differential gear 20.
4. The slippage of the front clutch 10 and rear clutch 18 varies from 0% (directly connected state) to 100% (disconnected state) depending on the hydraulic pressure acting on the chambers 10a and 18a, respectively.
It is composed of a wet type multi-disc clutch that can take any engagement state up to.

Reference numeral 30 is a hydraulic pump that is driven by the engine 2 or an electric motor and sucks oil in the reservoir 32 and discharges it.
The pressure is regulated by a reservoir valve 34 interposed between the two. In addition, the discharge port of the hydraulic pump 30 is connected to the electromagnetic switching valve 3.
6 to the chamber 10a of the front clutch 10, and is connected to the chamber 18a of the rear clutch 18 via the electromagnetic switching valve 38. These electromagnetic switching valves 3638 are connected to the discharge port of the hydraulic pump 30 via the electromagnetic control valve 40 on one side. The electromagnetic switching valve 36 operates in accordance with a control signal to establish direct communication between the chamber 10a of the front clutch 10 and the hydraulic pump 30 (as shown) and the downstream side of the electromagnetic control valve 40 and the chamber 10a of the front clutch 10. It can take a position that communicates with the other side. Similarly, the electromagnetic switching valve 38 controls the chamber 1 of the rear clutch 18 in response to a control signal.
8a and the hydraulic pump 30, and a position where the chamber 18a of the rear clutch 18 and the downstream side of the electromagnetic control valve 40 are communicated (as shown). The electromagnetic control valve 40 can reduce and adjust the hydraulic pressure downstream of the electromagnetic control valve 40 to any pressure from a maximum hydraulic pressure Pmax equal to the discharge hydraulic pressure of the hydraulic pump 30 to zero in accordance with a control signal. Note that the reference numeral 32a indicates a reservoir for returning oil discharged when lowering the hydraulic pressure on the downstream side of the electromagnetic control valve 40;
Although the reservoir 32a is shown separately from the reservoir 32 for convenience of drawing, it is actually the same as the reservoir 32.

A controller 44 includes a CPU, ROM, and RAM necessary for calculation, and an input circuit and an output circuit necessary for human output, although they are not shown. The input circuit of the controller 44 includes a wheel speed sensor 46 that independently detects the rotational speed of each wheel, and a longitudinal acceleration sensor 5 that acts on the center of gravity of the vehicle.
0, Steering sensor 52 that detects the steering condition, Throttle sensor 54 that detects the throttle condition of the engine 2, Engine rotation speed sensor 56 that detects the rotation speed of the engine 2
, a brake sensor 58 that detects the state of the brakes, a shift sensor 60 that detects the shift position of the transmission 6, and a yaw rate sensor 6 that detects the yaw rate of the vehicle body.
2 detection signals are input.

Reference numeral 64 is a mode selector provided on the instrument panel in front of the driver's seat of the vehicle, and switch 6 is used to manually select FF mode, FR mode, and 4WD mode.
6.68 and 70, and switches 72 and 74 for selecting normal mode and sport mode, respectively, which will be described in detail later. Signals indicating the operation status of each switch of the mode selector 64 are also input manually to the input circuit of the controller 44.

Next, the operation of the controller 44 will be explained according to FIGS. 2 to 13.

First, in step M2 of the main routine shown in FIG. 2, the controller 44 initializes each flag and memory area in the RAM necessary for control, that is, sets them to zero. Next, in step M4, the signal from the mode selector 64 is read, and in step M6, it is determined whether or not the signal is on the manual side. If YES is determined in step M6, the process proceeds to step M8, and it is determined which mode the output signal of the mode selector 64 is in. If it is determined in step M8 that it is rFF mode, the process proceeds to step MIO, where the output signal is driven from the output circuit. Outputs a control signal that sets the state to FF mode. In other words, in this case, the controller 44 controls the front clutch 10
The hydraulic pressure in the chamber 10a of the rear clutch 18 is maximized.
In order to make the hydraulic pressure in 8a zero, a control signal is sent to the electromagnetic switching valve 36 so that the switching valve 36 takes a position that directly communicates the chamber 10a and the hydraulic pump 30. A control signal is output to the electromagnetic control valve 40 so that the pressure on the downstream side of the control valve 40 becomes zero. As a result, the front clutch 10 is in a directly connected state and the rear clutch 18 is in a disconnected state, thereby achieving an FF state in which the driving force of the engine 2 is transmitted only to the front wheels 14, 16.

If it is determined in step M8 that the drive state is "rFR mode," the process proceeds to step M12, where the output circuit outputs a control signal that sets the drive state to FR mode. That is, in this case, the controller 44 controls the chamber 10 of the front clutch IO.
In order to zero the oil pressure in the chamber 18a of the rear clutch 18 and maximize the oil pressure in the chamber 18a of the rear clutch 18, the electromagnetic switching valve 36 is positioned so that the switching valve 36 communicates the chamber 10a with the downstream side of the electromagnetic control valve 40. The control signal is sent to the electromagnetic switching valve 38, which is connected to the chamber 1.
8a and the hydraulic pump 30 are output to the electromagnetic control valve 40 such that the pressure on the downstream side of the control valve 40 becomes zero. As a result, the front clutch 10 is in a disengaged state and the rear clutch 18 is in a directly connected state, making it possible to obtain a PR state in which the driving force of the engine 2 is transmitted only to the rear wheels 22 and 24.

Furthermore, if it is determined in step M8 that the drive state is "r 4 W [) mode", the process proceeds to step M14, where the output circuit outputs a control signal that sets the drive state to the direct 4WD mode. That is, in this case, the controller 44 controls each chamber 10a and 18a of the front clutch lO and the rear clutch 18.
In order to maximize the oil pressure in the chambers, control signals are output to the electromagnetic switching valves 36 and 38, respectively, so that the switching valves 36 and 38 take positions that directly communicate the chambers 10a and 18a with the hydraulic pump 30. As a result, the front clutch 10 and the rear clutch 18 are brought into direct connection, respectively, and the front and rear wheels 14, 16 and 2 are connected directly to each other.
Direct connection 4W that transmits the driving force of engine 2 to both 2.24
D state can be obtained.

On the other hand, if the determination in step M6 is "NO", step M
Proceeding to step 16, it is determined whether the output signal of the mode selector 64 is in the normal mode. If rYESJ is determined in step M16, the process proceeds to step M18 to execute the normal mode routine processing described later, and if "NO" is determined.
If so, the program proceeds to step M20 and executes a sports motor routine process which will be described later.

Next, the normal motor routine of step MI8 in the main routine will be explained with reference to FIG.

First, in step 5100, it is determined whether the detection signal from the mode selector 64 was the normal mode last time as well. Immediately after switching to normal mode, this step 510
0, the determination is "NO" and the process advances to step 5102. In step 5102, necessary flags and memory areas necessary for control by this normal motor routine are initialized, that is, set to zero. Next, the process proceeds to step 5104, where control signals are output to the electromagnetic switching valves 36, 38 and the electromagnetic control valve 40 so that the drive state becomes the FF mode. Note that the content of control by this control signal is the same as the content of step MIO described above. Next, in step 5106, flag A is set to "
flag C is set to "0" in step 5108, and the process returns to step M4 of the main routine. This flag A will be explained in detail later, but the front clutch 10
It becomes "1" when both the rear clutches 18 and 18 are in the disengaged state and control is performed such that the driving force is not transmitted to either the front wheels 14, 16 or the rear wheels 22, 24. Flag C also indicates that both the front clutch 10 and the rear clutch 18 have zero slippage, which will be explained in detail later.
In other words, when performing control to transmit driving force to both the front wheels 14.16 and the rear wheels 22.24 in a direct connection state, "1
”.

rYEs'' in step 5100, the detection signals of each sensor are read in step 5110.

Next, in step 5112, it is determined whether flag A is "1", and if the determination is "NO" in step 5112, the process advances to step 5114. In step 5114, flag B
is "1".

This flag B becomes "1" when traction control is being performed, as will be described in detail later. Step 511
If the determination in step 4 is "NO", the process proceeds to step 5116, where it is determined whether flag C is "1". Step 5116
If the determination is "NO", the process advances to step 3118.

In step 5118, it is determined whether the vehicle is in a starting state. The details of this judgment are specifically described below (i) ~
This is to determine whether all conditions (iii) are satisfied.

(i) The vehicle speed V is equal to or lower than the set vehicle speed (for example, 10 km/h).

(ii) The throttle opening θth detected by the throttle sensor 54 is greater than or equal to the set opening (for example, 50%).

(iii) If the steering angle θ of the steering wheel detected by the ti rudder sensor 52 is within the set range (for example, -180°)
≦θ≦180°).

Note that the smallest value among the wheel speeds detected by the wheel speed sensor 46 is adopted as the vehicle speed V under condition (i). If rNOJ is determined in step 5118, the process advances to step 5120.

In step 5120, it is determined whether the difference ΔS between the slip ratio of the front wheels 12.14 (slip ratio of the wheels relative to the road surface) and the slip ratio of the rear wheels 22.24 is larger than a set value (for example, 0.03). Since the FF mode is used when making this determination, a method to calculate ΔS is based on the difference obtained by subtracting the wheel speed of the rear wheel 22.24 from the wheel speed of the front wheel 12.14 detected by the wheel speed sensor 46. However, in order to find the actual slip ratio difference ΔS between the front and rear wheels, it is necessary to correct the difference in turning radius between the front and rear wheels (so-called inner wheel difference) because it occurs during a turn. can be,
Furthermore, due to an increase in the lateral acceleration acting on the vehicle body, the turning center of the vehicle moves forward and the difference between the inner wheels decreases, so it is necessary to correct the decrease.

Therefore, the following calculation is performed in the determination at step 5120.

That is, in the model shown in Fig. 4, f is the front wheel, r is the rear wheel, G is the center of gravity of the vehicle, E is the wheel base, 1r is the distance from the center of the rear wheel f to the center of gravity G, C is the turning center, and Rf
is the distance from the turning center C to the center of the front wheel f, RG is the distance from the turning center C to the center of gravity G, Rr is the distance from the turning center C to the center of the rear wheel r, δ is the steering angle of the front wheel f, and γ is This is the angular velocity of the vehicle center of gravity G around the turning center 6.

Here, according to Atsushiman geometry, Vf-γ・Rf
=(VG/RG) ・RfR"=(1/δ)rrT"
r′r RG = (β/δ) 1+ r
f)2, equation (1) is: V f =VG + 1+ (j!
r/j2)")...(2) Also, Vr=r-Rr= (VG/RG), ・Rr...
・(3) Since Rr=l/δ, equation (3) is Vr=VG/ + r ・−・(4
).

Here, in equation (2), αF= + 1+ (Ilr/i)')
...(5) Then, Vf=af VG -(6)(
4) In formula αr=l/+r...(7
), then Vr=αrl/G...(8)
becomes. (αf, αr near correction coefficients) Therefore, the correction coefficients αf, αr in equations (6) and (8)
can define the characteristics with respect to the steering angle δ as shown in FIG.

On the other hand, as mentioned above, the lateral acceleration G acting on the center of gravity G of the vehicle
As Y increases, the turning center C moves forward and the difference between the inner wheels decreases.Generally, when the lateral acceleration GY is zero, there is a difference between the inner wheels due to the above-mentioned force man correction coefficient, but the lateral acceleration GY When is the set value GYP, the inner ring difference becomes zero, and for lateral acceleration GY between the values, the inner ring difference changes almost in proportion to the size of the lateral acceleration GY, and exhibits a roughly linear shape. has been confirmed. According to experiments, GYP is approximately 0 in a normal passenger car.
．． It has been confirmed that it is 5G. Therefore, as shown in FIG. 6, when GY≦GYP, the characteristic of the correction coefficient αY of the inner ring difference with respect to the lateral acceleration GY is αY - (GY - GYP) + 1. 0 ・
...(9) When GY > GYP, it can be defined as αY=O...(10).

As a result, the slip ratio difference between the front and rear wheels can finally be determined by (11). In addition, in equation (11), ωr is the wheel speed of the front wheel f,
ωr is the wheel speed of the rear wheel r.

As a result, in step 5120, the wheel speed sensor 46
The wheel speed of the front wheel 12.14 and the rear wheel 22.2 detected from
4 wheel speed, the lateral acceleration obtained from the lateral acceleration sensor 50,
Based on the steering angle obtained from the steering sensor 52, the above formula (
9), the slip ratio difference ΔS is calculated, and it is determined whether the slip ratio difference ΔS is larger than a set value (for example, 0°03). In addition, in the calculation, αf, α in equation (11)
For r and αY, formulas (5), (7), (9)
, (10), but instead, it is also possible to create a map of the characteristics shown in FIGS. 5 and 6 and store it in the ROM in the controller 44, and to refer to this map each time to obtain the characteristic.

If the determination in step 5120 is “NO”, step 5
The process proceeds to step 122 to determine whether or not the turning limit is reached. The content of the determination in step 5122 will be explained here. In the model shown in Figure 7, f is the front wheel, r is the rear wheel, m is the vehicle mass, G is the center of gravity of the vehicle, ■ is the yaw moment of inertia around the center of gravity G, L is the wheelbase between the front and rear wheels, and Lf is the front wheel. f
and the distance between the center of gravity G, Lr is the distance between the rear wheel r and the center of gravity G, γ is the yaw rate around the center of gravity G, δ is the steering angle of the front wheel f, UX is the forward speed of the center of gravity G, UY is the lateral speed of the center of gravity G, is the vehicle speed,
GX is the longitudinal acceleration of the center of gravity G, GY is the lateral acceleration of the center of gravity G,
β is the sideslip angle at the center of gravity G, βf is the sideslip angle of the front wheel f, β
r is the sideslip angle of the rear wheel r, Cf is the cornering force of the front wheel, and C is the cornering force of the rear wheel r.

In this model, the lateral motion of the vehicle is m・V(
dβ/d t-1-r)=2Cf+2Cr...(12
) Yawing motion is I-dr/d t=2Lf -Cf-2Lr-Cr...
・It can be expressed as (I3).

Furthermore, if Kf is the equivalent cornering power of the front wheel f and Kr is the equivalent cornering power of the rear wheel r, then cr = f・
βf=Kf・(δ-β-T-Lf/V)...(14
) Cr= to r'βr=Kr・(−β×γ・Lr/V)・・
・(15) becomes.

Now, apply the steady circular turning conditions dβ/dt=o, dr/dt=o, and further γ=
Considering the relationship V/R=GY/V, formula (12) ~
From (15), γ2/δ=GY/L-1/ (1+A-R-GY)...
・(16) However, A = -m/2 ・(Lf・to f−Lr・to r)/
(nif・nir): Stability factor
...(17) can be obtained.

This equation (17) is expressed as the steering angle δ generated with respect to the lateral acceleration GY.
The value of A in the equation can be used to determine whether the turning characteristics are on the US (understeer) side or the O3 (oversteer) side, as shown in FIG.

In a typical FF vehicle, the steering characteristic changes from a weak US characteristic to a strong US characteristic as the lateral acceleration GY increases, as shown in FIG. This characteristic has a tendency that as the driving force increases, the magnitude of the lateral acceleration GY when changing to the strong US characteristic decreases. However, it can be seen that the value increases as the lateral acceleration GY increases, reaches a maximum value, and then rapidly decreases, resulting in an uncontrollable state, and that the maximum value occurs just before the turning limit.

Therefore, the condition for the maximum value that occurs just before this turning limit is d(r''/δ)/dGY=o...(18)
You can get it at

By the way, in actual turning, if the steering angle of the front wheels is on the increasing side, the actual turning limit will be smaller than the value calculated from equation (18), and if the engine throttle is on the depressed side, The actual turning limit is expressed by the formula (1
8) is smaller than the value obtained from 8).

Therefore, in step 5122, it is determined that the turning limit is exceeded when the following (19) is satisfied, based on detection signals from required sensors. When determining according to equation (19), the determination is made based on the detected value of the yaw rate sensor 62, the detected value of the steering sensor 52, the detected value of the lateral acceleration sensor 50, and the detected value of the throttle sensor 54.

Also, instead of formula (19), γ=GY /
By substituting V... (20) can also be adopted. When determining according to this equation (20), the determination is made based on the detected value of the steering sensor 52, the detected value of the lateral acceleration sensor 52, and the detected value of the wheel speed sensor 46. In this judgment, the detection value of the wheel speed sensor 46 (
The smallest value among the four wheels is adopted as the vehicle speed V.
Even if even the wheel with the lowest rotational speed is in a slipping state and its value is larger than the actual value, there is no problem because the error will work on the safe side. Rather, it has a great effect of not requiring the use of the currently expensive yaw rate sensor.

Note that ε1 and ε2 in these equations (19) and (20) are coefficients that are appropriately determined depending on the characteristics of the vehicle. Further, in both equations (19) and (20), the right side is "0", but it is also possible to set the value to an appropriate value depending on the characteristics of the vehicle.

If the determination in step 5122 is "NO", the process advances to step 5104 described above. As a result, in this normal mode routine, after entering the FF mode in step 5104, "NO" is selected in step 5118.
” (the conditions for starting are not satisfied), “NO” in step Sl 20 (the slip ratio difference is small), and “NO” in step 5122 (not at the turning limit), the step 5100.5II0.5112,
5l14, 5L16.5118, 5120, 5122
The processes at 5104, 5106, and 5108 are repeated to maintain the drive state in the FF mode.

On the other hand, if "YES" is determined in step 5122, that is, if it is determined that the vehicle is at the turning limit, the process proceeds to step 5124, where a control signal is output to set the drive state to cut-off mode. That is, in this case, the controller 44 controls the front clutch 10
and a position where the electromagnetic switching valves 36 and 38 communicate the chambers 10a and 18a with the downstream side of the electromagnetic control valve 40 in order to zero the oil pressure in each chamber 10a and 18a of the rear clutch 18. A control signal is output to the electromagnetic control valve 40 so that the pressure on the downstream side of the control valve 40 becomes zero. As a result, the front clutch 10 and the rear clutch 18 are in a disconnected state, and the driving force of the engine 2 is not transmitted to both the front wheels 12.14 and the rear wheels 22.24 at all.

Next, in step 5126, the rotation speed of the engine 2 is controlled. The content of the control is to control the control device 2a of the engine 2 so that the rotation speed of the front wheels 12, 14 (or rear wheels 22, 24) on the engine 2 side of the front clutch 10 (or rear clutch 18) is the same as that of the front wheels 12, 14 (or rear wheels 22, 24). be. For this reason, the target rotation speed of the engine 2 is determined based on the wheel speed obtained from the wheel speed sensor 46 and the shift position obtained from the shift sensor 60, taking into consideration the gear ratio of each power transmission path, and The desired engine rotation speed is fed back and controlled so that the engine rotation speed becomes the target rotation speed. Note that in this embodiment, the control device 2a
As shown in FIG. 10, in addition to the main throttle valve 2b that controls the engine 2 during normal operation, a second throttle valve 2C and a servo device 2d that drives the valve 2C are used. In controlling the rotational speed of the engine 2, the detection signal of the throttle sensor 54 that detects the opening degree of the main throttle valve 2b is also taken into consideration.

Next, in step 5128, a control signal is output to activate the alarm device 76, such as a buzzer or lamp, which gives a warning to the driver, and 7lag A in the memory is set to "1". Therefore, in the next step 5l12, it is determined that rYEsJ, so as long as the flag A is "1", step 51
00.5110.5112,5122. 5124,5
The processes of 126° 512g and 5130 are repeated, and the cutoff mode in which the driving force is not transmitted to either the front wheels 12.14 or the rear wheels 22.24 continues. As a result, front wheel 1
2.14 and rear wheels 22.24 have increased cornering force.

On the other hand, if "YES" is determined in step 3118, that is, if the above-mentioned start-related conditions are satisfied, the process proceeds to step 5132, and a control signal is output to the electromagnetic switching valves 36 and 38 so that the drive state becomes the direct connection 41v'/D mode. . Note that the content of control by this control signal is the same as the content of step M14 described above. Similarly, "YES" in step 5120
If it is determined that this is the case, the process proceeds to step 5132 via the process of step 3121. In addition, in step 5121, the magnitude Gc of the acceleration acting on the center of gravity G at that time (that is, FtTyoff7'') is stored in memory.

When the control signal is output in step 5132, step 5
134, set 7 lag C to "1", then step 8
The process advances to step 136 to determine whether the vehicle is at its turning limit.

The determination in step 5136 is substantially the same as the determination in step 5122 described above, based on the detection signal from the required sensor according to (21) or (22). Note that the determination made in step 8136 is for the direct 4WD mode, so the effect on the turning limit when the steering angle of the front wheels is on the increasing side during turning or when the engine throttle is on the depressed side. This is smaller than the determination made in step 5122 in the FF mode, and therefore the equation (21>,
Coefficient ε1 in (22). Equation (19) for ε2.

Coefficient ε0 in (20). It is set appropriately smaller than ε. Of course, it is also possible to set the right-hand side of both equations (21) and (22) to a numerical value that is appropriately set depending on the characteristics of the vehicle.

If rNOJ is determined in step 5136, the process proceeds to step 5138, where it is determined whether or not there is a longitudinal slip.

This determination is based on the wheel speed r detected by the wheel speed sensor 46.
The slip ratio in the longitudinal direction is calculated based on ω and the longitudinal acceleration GX detected by the longitudinal acceleration sensor 48, and it is determined whether the slip ratio is equal to or higher than a set value (for example, 1.1). Specifically, (d r w/ d t ) /GX≧1.1 −(
23), it is determined that there is a vertical slip.

If the determination in step 5138 is “NO”, step 5
At step 140, the flag value is set to "zero".

Next, in step 5142, it is determined whether the return conditions for switching from the direct 4WD mode to the FF mode are satisfied. The content of this determination is that the magnitude of the acceleration acting on the center of gravity G (that is, the magnitude of the acceleration acting on the center of gravity G obtained from the longitudinal acceleration GX and lateral acceleration GY detected by the acceleration sensor 50 this time) is "YES" in step 5120. When it is determined that the slip ratio difference ΔS between the front and rear wheels exceeds the set value, the FF
When it is determined that it is necessary to switch from the 4WD mode to the 4WD mode, the magnitude of the acceleration GC acting on the center of gravity G memorized in step 5121 (that is, the value of the fl
TσV), it is determined that the return condition is satisfied.

If “NO” is determined in step 5142, step 5
The process advances to step 144 to determine the state of the brake detected by the brake sensor 58, that is, whether the brake switch (not shown) is on. “NO” at this step 5144
If so, the process returns to step M4 of the main routine.

When the determination in step 8136 is "YES", flag C is set to "0" in step 5146, and step 3
Clear the memory GC at 148, then step 512
Proceeding to step 4, a control signal is output to set the drive state to cut-off mode.

When the determination in step 5138 is "YES", the process proceeds to step 5150 and outputs a control signal for performing traction control to control the drive output of the engine 2 according to the slip ratio of the wheels. Although various well-known methods can be adopted for this traction control method, in this embodiment, the second throttle valve 2c shown in FIG. Therefore, it is preferable to control this servo equipment ff12d to control the output of the engine 2.

When the control signal is output in step 5150, step 5
At step 152, 7lag B is set to "1" and the process returns to step S4 of the main routine. In addition, in relation to this Fudeg B,
rYES" in step 5114, the process is configured to proceed to step 8138.

If it is determined "YES" in step 5142 or 5144, flag C is set to "0" in step 5154,
In step 5156, the GC is cleared and the process returns to step M4 of the main routine.

In this way, in the normal motor routine, after determining "YES" in step 5118 or 5120 and entering the 4WD mode in step 5132, the determination is "NO" in steps 5136, 5138, 5142 and 5144. As long as the driving state is 4WD, the determination in step 5116 is "YES" and the process proceeds to step 5132.
mode. Then, in step 5132, 4W
In the D mode, if the turning limit is reached, it is determined ``YES'' in step 8136, the drive state becomes cut-off mode in step 5124, and if the maneuverability is recovered thereafter, it is determined ``NO'' in step 5122. Step 51
04 becomes FF mode. Also, in step 8138, “Y
ES", traction control is performed in step 5150 while the drive state remains in 4WD mode. Furthermore 4W
When the conditions for returning from the D mode to the FF mode are satisfied, or when the brake switch is turned on, rYESJ is determined in step 5142 or 5144, and the drive state becomes the FF mode.

Next, the sports motor routine of step M20 in the main routine will be explained with reference to FIGS. 11 to 13. In this sports motor routine, processes (steps) having the same contents as those in the normal mode flowchart shown in FIG. 3 are given the same reference numerals as those used in FIG. 3, and detailed explanations thereof will be omitted.

This sports mot routine differs from the normal mot routine shown in FIG. 3 in step 320.
0, 3202, 5204, 3208 and step N2, and these steps will now be explained in order.

In step 5200, it is determined whether or not the detection signal from the mode selector 64 was in the sports mode last time.
If YES, the process advances to step 5110; if NO, the process advances to step 5102. In step 5202, the electromagnetic switching valve 36.
38 and a control signal to the electromagnetic control valve 40. In addition,
The control content by this control signal is as described in step M12 above.
The content is the same as that of

In step 5204, the slip ratio of the rear wheels 22.24 (
It is determined whether the difference ΔS between the slip ratio of the wheels relative to the road surface) and the slip ratio of the front wheels 12.14 is larger than a set value (for example, 0.05). In this step 5204, as in the case of step 5120, the turning radius difference between the front and rear wheels during a turn is calculated based on the difference obtained by subtracting the wheel speed of the front wheel 12.14 from the wheel speed of the rear wheel 22.24. The correction is made for the difference in turning radius which is reduced due to the increase in lateral acceleration acting on the vehicle body. For this reason,
In detail, the calculation is performed according to (24). By the way, in this formula (24), ωr is the wheel speed of the rear wheel r, ωf is the wheel speed of the front wheel, αf, α
r is a correction coefficient determined by the above-mentioned formulas (5) and (7), respectively, and αY is a correction coefficient determined by formulas (9) and (10). Then, if rYEsJ is determined in step 5204, the process proceeds to step 5121 where Gc=
Store X+GY in memory, and if “NO”, step 820
Proceed to step 6.

In step 8206, it is determined whether the turning limit is reached. Here, the content of this determination will be explained.

In connection with step 5122 of the normal motor routine, r"/δ=GY/L・l/(1+A-R-GY)
...(16) and further explained with reference to Fig. 9, but when similarly determining the relationship between lateral acceleration GY and r2/δ for a general FR vehicle, the lateral acceleration is as shown in Fig. 12. As the acceleration GY increases, the steering characteristic changes from a weak US characteristic to a strong O8 characteristic. If we pay attention to the value of γ2/δ, no matter the magnitude of the driving force, its value increases as the lateral acceleration GY increases, and after crossing the 1/L line, it rapidly increases and becomes an uncontrollable state. I know what will happen.

Therefore, the condition that occurs just before this turning limit is d(γ
2/δ)/dGY≧ε, ·(1/L)... (25) It can be obtained as follows. ε is a coefficient appropriately determined depending on the characteristics of the vehicle. Furthermore, in actual turning, if the steering angle of the front wheel f is on the increasing side, the actual turning limit will be smaller than the value calculated from equation (25), and if the engine throttle is on the depressed side, It is also smaller than the value calculated from equation (25).

Therefore, in step 5206, dGY dt dt...
It is determined that the turning limit is exceeded when (26) is satisfied. When determining according to equation (26), the determination is made based on the detected value of the yaw rate sensor 62, the detected value of the steering sensor 52, the detected value of the lateral acceleration sensor 50, and the detected value of the throttle sensor 54.

Also, instead of formula (26), γ=GY /
By substituting V... (27) can also be adopted. When determining according to this equation (27), the determination is made based on the detected value of the steering sensor 52, the detected value of the lateral acceleration sensor 52, and the detected value of the wheel speed sensor 46. In this judgment, the detection value of the wheel speed sensor 46 (
The smallest value among the four wheels is adopted as the vehicle speed V.
Even if even the wheel with the lowest rotational speed is in a slipping state and its value is larger than the actual V, there is no problem because the error will work on the safe side. Rather, it has a great effect of not requiring the use of an expensive yaw rate sensor at present.

Note that ε5. in equations (25) to (27). ε4ε is a coefficient appropriately determined depending on the characteristics of the vehicle.

If rYESJ is determined in this step 5206, the process proceeds to step 5124, and if "NO", step 52
Proceed to 02.

Note that the return condition in step 5142 is satisfied when rYEsJ is determined in step 5204 and stomach 1 is smaller by 1, r stone 17 and stomach 1 than the GC determined in step 5121. In this way, in the sports motor routine, after the FR mode is entered in step 5202, the result is "rNo" in step 5118 (the start condition is not satisfied), and "NO" in step 5204 (the slip ratio difference is small). Yes, and rNO in step 8206.”
As long as it is determined that the vehicle is not at the turning limit, the drive state is maintained in the FR mode. Further, in step 5118 or 5204, it is determined as rYESJ, and the process proceeds to step N2, where the 4WD mode is entered.

Here, the 4WD control routine of step N2 will be explained according to the flowchart shown in FIG.

First, in step 5300, a control signal is output so that the rear clutch 18 is directly connected. That is, in this case, in order to maximize the hydraulic pressure in the chamber 18a of the rear clutch 18, the electromagnetic switching valve 38 is connected to the chamber 18a and the hydraulic pump 3.
A control signal is output that assumes a position that directly communicates with 0. Next, in step 5302, it is determined whether the control method is the first time control method.

This initial control is performed in step 5304, which is proceeded when the answer is "No" in step 5302. Therefore, rYESJ is determined in either step 5116, 5118, or 5204, and the determination is made in step 5302 first. When the answer is "NO". The content of the initial control performed in step 5304 is to control the oil pressure in the chamber 10a of the front clutch 10 to the set oil pressure PS. A control signal is sent to the electromagnetic control valve 40 so that the hydraulic pressure on the downstream side of the control valve 40 is the set hydraulic pressure P.
A control signal that becomes S is output. Then step 5306
The slip ratio difference ΔS obtained by equation (24) is the set value S, (
For example, it is determined whether it is smaller than 0.04). Step 83
06 is "YES", that is, the slip ratio difference ΔS is the set value S
If it is determined that it is smaller than 1, the process proceeds to step 5308, and a control signal is output to the electromagnetic control valve 40 to reduce the oil pressure in the chamber 10a of the front clutch 10 by ΔPo.

“NO” in step 5306, that is, the slip ratio difference Δ
If it is determined that S is greater than or equal to the set value S1, step 53
10, it is determined whether the slip ratio difference ΔS is larger than a set value 32 (for example, 0.06). Step 53
10 is "YES", that is, the slip ratio difference ΔS is the set value S
If it is determined that the pressure is larger than , the process proceeds to step 5312 and a control signal is output to the electromagnetic control valve 40 to increase the oil pressure in the front clutch erotic chamber 10a by ΔP. If “NO” in step 5310, that is, it is determined that the slip ratio difference ΔS is less than or equal to the set value 82, step 5314
The value obtained by differentiating the slip ratio difference ΔS with respect to time is dΔS/
Determine whether dt is greater than or equal to zero. Step 5314
If it is determined that rYESJ, that is, that the slip ratio difference ΔS does not change or tends to increase, step 53
16, a control signal is output to the electromagnetic control valve 40 to increase the oil pressure in the chamber 10a of the front clutch IO by ΔP1. If it is determined in step 5314 that rNOJ, that is, slip ratio difference ΔS, tends to decrease, the process proceeds to step 5318, and a control signal is output to the electromagnetic control valve 40 to reduce the oil pressure in the chamber 10a of the front clutch 10 by ΔP1. . Then, steps 5308.5312.
Upon completion of either 5316 or 5318, the process proceeds to step 5134 in the flowchart of FIG. In addition, in steps 5306 and 5308 for determining the slip ratio difference ΔS, the set value Sl is set to 0°04,
The set value S2 is set to 0.06, which means that the final slip ratio difference ΔS is kept at the target value (0°05) in the 4WD mode, that is, the rear wheel 2 side is lower than the front wheel 12.14 side.
This is to obtain a 4WD mode in which the torque on the 2.24 side is always kept large by a set ratio corresponding to the target value.

Further, in step 5314, the differential value dΔ of the slip ratio difference ΔS is
Determine S/dt and adjust the front clutch l based on the result.
The oil pressure in the chamber 10a of
．． This is because if the pressure is controlled only by 5312, the pressure inside the chamber 10a may become large enough to cause hunting. Therefore, in this modification, ΔP in steps 5316 and 5318
1 is set to a smaller value than ΔP in steps 5308 and 5312.

In addition, in step 5314, it is determined whether dΔS/d t≧0, and if “YES”, the process proceeds to step 5316 “NO”.
”, the process is configured to proceed to step 5318, but between steps 5314 and 8316, dΔS/
It is also possible to provide a step of determining whether dt=0, and to proceed to return when it is determined that rYEsJ in that step.

Then, after entering the 4WD mode, step 5136
, 5138.5142.5144, the driving state is maintained in the 4WD mode. If the turning limit is reached while the 4WD mode is set in step 8132, it is determined as rYEsJ in step 5136, and the drive state changes to cutoff mode in step 5124, and if the maneuverability is recovered thereafter, "NO" is selected in step 5206.
”, and in step 5202, the FR mode is set. If the determination in step 5138 is "YES", traction control is performed in step 5150 while the drive state remains in the 4WD mode. Furthermore, if the conditions for returning from 4WD mode to FR mode are satisfied or the brake switch is turned on, r is set in step 5142 or 5144.
YES” and the drive state becomes FR mode.

According to this embodiment configured as described above, by operating the mode selector 64, not only can the driving state be set to any of the FF mode, FR mode, and 4WD mode as the manual mode, but also the driving state can be set as the normal mode as the auto mode. When driving, the drive state is in FF mode and 4W is applied as necessary.
It is possible to set the normal mode, which switches to D mode, and the sports mode, which changes the drive state to FR mode during normal driving and switches to 4'vVD mode as needed, so the vehicle can be controlled to either normal mode or sports mode. By setting the mode, when 4-wheel drive mode is not required, it becomes 2-wheel drive mode, improving fuel efficiency, and the 2-wheel drive mode can be changed to the drive mode selected according to the driver's preference. This has the effect of maintaining the condition.

In normal mode, as explained according to the flowchart shown in Figure 3, when the turning limit is detected while driving in FF mode, the mode is automatically switched to cutoff mode to increase the cornering force of the tires (front wheels), and at the same time The driver can be alerted to this condition. When the turning limit is restored to a stable side, the FF mode is returned to. However, when it is determined that the turning limit has been exceeded and the switch is switched to the cut-off mode, the rotation speed of the input end of the front clutch 10 and the output side are changed at the same time. Since the engine speed is controlled to match the engine speed, even if the front clutch gear is suddenly engaged when returning from the cutoff mode to the FF mode, it is possible to prevent the shock from occurring. In particular, since the turning limit is determined according to the conditions according to equation (19) or equation (20), it is possible to detect the turning limit with high accuracy, which prevents the situation from becoming uncontrollable during a turn. It can be prevented. Also, if the vehicle is in a starting state while driving in FF mode, or if the front wheels
When it is detected that the slip ratio difference ΔS obtained by subtracting the slip ratio of the rear wheels 22.24 from the slip ratio of the rear wheels 22.24 is greater than the set value (that is, the front wheels 12.14, which are the driving wheels, are in a slip state), Since the vehicle is automatically switched to the 4WD mode and the driving force is transmitted to the road surface through both the front wheels 12.14 and the rear wheels 22.24, slips at the time of starting or on slippery road surfaces are prevented. Note that even when starting, if the steering angle is large, the 4WD mode will not be entered, so the braking phenomenon of so-called direct 4WD can be prevented. Furthermore, since the slip ratio difference ΔS is particularly determined according to the conditions according to equation (11), it is possible to detect the slip ratio difference ΔS with high accuracy and appropriately switch to the 4WD mode. While driving in this 4WD mode, if it detects that the turning limit is reached, it will automatically switch to cut-off mode to ensure steering stability, and if vertical slip (slip in the longitudinal direction of the vehicle body) is detected, it will automatically switch to cut-off mode. Traction control is performed to ensure more reliable driving force on slippery roads. If it is determined from the acceleration acting on the vehicle body while traveling in 4WD mode that it is no longer necessary to travel in 4WD mode, the vehicle can automatically return to FF mode. Furthermore, if it is determined that the brakes are on while driving in 4WD mode, the FF will automatically be turned on.
Since the mode is restored, the operation of the so-called 3-channel type or 4-channel type anti-skid brake device can be prevented from being inhibited.

On the other hand, in sports mode, as explained according to the flowchart shown in Figure 11, when the turning limit is detected while driving in PR mode, the mode is automatically switched to cut-off mode and the cornering force of the tires (rear wheels) is increased to control the steering. It is possible to restore stability and at the same time alert the driver of the situation. When the turning limit is restored to a stable side, the PR mode is returned to. However, when it is determined that the turning limit has been exceeded and the switch is switched to the cut-off mode, the rotation speed of the input end of the rear clutch 18 and the output side are simultaneously changed. Since the rotational speed of the engine 2 is controlled to match the rotational speed of the engine 2, even if the rear clutch 18 is suddenly connected when returning from the cutoff mode to the FR mode, the occurrence of a shock can be prevented. In particular, since the turning limit is determined according to the conditions according to equation (26) or equation (27), the turning limit can be detected with high accuracy, thereby preventing a situation where control is lost during a turn. It can be prevented. Note that by setting the value of the coefficient ε slightly larger than 1 in Equation (26) or Equation (27), it is possible to obtain weak oversteer characteristics with excellent turning response of the vehicle to steering wheel operations. . In addition, while driving in FR mode, the vehicle is in a starting state, or the rear wheels 22.24
When it is detected that the slip ratio difference ΔS obtained by subtracting the slip ratio of the front wheel 12.14 side from the slip ratio of the front wheel 12.14 side is greater than the set value (that is, that the rear wheel 22.24, which is the driving wheel, is in a slip state), Since the vehicle is automatically switched to the 4WD mode and the driving force is transmitted to the road surface through both the front wheels 12.14 and the rear wheels 22.24, slips at the time of starting or on slippery road surfaces are prevented. Note that even at the time of starting, if the steering angle is large, the 4WD mode will not be entered, so the so-called 4WD braking phenomenon can be prevented.

In addition, in particular, since the slip ratio difference ΔS is determined according to the conditions according to equation (24), the slip ratio difference ΔS can be determined with high accuracy.
It is possible to detect S and appropriately switch to 4WD mode. Note that the set value regarding the slip ratio difference ΔS in this PR mode (as a specific example, 0.05) is the same as the set value in the normal mode (as a specific example, 0.03).
), but this is still a slightly larger slip ratio difference Δ when driving in FR mode.
This is to enable the vehicle to run in the FR mode in S mode, thereby allowing the vehicle to be driven into a weak overteer characteristic region in which the vehicle has excellent turning response to steering wheel operations. In particular, in the sports motor routine, if it is determined to be rYESJ in step 5118 or 5204 and the mode is switched to 4WD mode in step N2, the rear wheel 2
Since the driving force is transmitted with the slip ratio on the 12.14 side of the front wheels being larger than the slip ratio on the 12.14 side by the set ratio, acceleration performance is improved, and the steering characteristic approaches the Nicotral characteristic, improving maneuverability.

Also, in this sport mode, when the turning limit is detected while driving in 4WD mode, it can automatically switch to cut-off mode to ensure steering stability, as in the case of normal mode mentioned above. When longitudinal slip is detected, traction control is automatically performed to more reliably obtain driving force on slippery roads. Then, based on the acceleration that acts on the vehicle body while driving in 4WD mode, if it is determined that there is no need to drive in 4'vVD mode, or if it is determined that the brake is on, it will automatically switch to FR mode. Return.

In addition, in the above embodiment, step 5 is performed in both the normal mot routine and the sports mot routine.
144 uses the detection signal of the brake sensor 58 to detect whether the brake switch is on or not, but instead it uses the detection signal of the brake sensor 58 to detect whether the brake switch is on or not. When it is detected by the brake sensor 58 and it is determined that the anti-skid brake device has operated for anti-skid based on the detection signal, the mode changes from 4WD mode to FF mode or FF mode.
It is also possible to configure the device to switch to R mode.

Further, in the above embodiment, the determination of the turning limit in steps 5122 and 3136 in FF mode or 4WD mode is performed using equation (19) or (20), equation (21) or (22), respectively.
), only the turning limit on the US side is targeted, and the determination of the turning limit in step 8206 during FR is performed using the formula (2
6) or (27) for only the turning limit on the O8 side, preferably step 5122.313
In the determination of step 6, formula (26) or (27) is also incorporated as a determination condition, and in the determination of step 3206, formula (19) or (20), or formula (21) is
Or, by also incorporating (22) as a determination condition, these steps 5122. 5136 or 52
With $06, both the US side turning limit and the O8 side turning limit can always be determined.

FIG. 14 is a modification of the main routine shown in FIG. 2 in the above embodiment. This modification differs from the flowchart shown in FIG. 2 in that step M22 is added after step M18 in FIG. 2, and step M24 is added after step M20.

This step M22 sets any of the flags A, B, C to "1" in the normal motor routine of step M18.
” is set. At step M22, ``YE''
If the answer is "S", the process advances to step M18, ie, step 5100 of the normal motor routine; if the answer is "NO", the process returns to step M4.

Similarly, step M24 sets flags A and B in the sports motor routine of step M20.

It is determined whether any of C is set to "1".

If rYESJ is determined in step M24, step M20;
That is, the process advances to step 5100 of the sports motor routine, and if "NO", returns, that is, returns to step M4.

Therefore, in the normal moat routine of step M18, as long as any of flags A, B, and C is set to "1", the process of the normal mote routine is continued. In other words, if flag 8 is "l", the cutoff mode continues until it is determined to be "NO" in step 5122 of the normal motor routine, and if flag B is "1", until it is determined to be rNOJ in step 5138. Traction control is continued, and if flag C is "1", 4WD mode is continued until a "NO" determination is made in step 5142 or 5144.

Also in the sports mot routine of step M20, as long as any of the flags A, B, and C is set to "1", the sports mot routine continues. In other words, if flag A is "1", the cut-off mode will continue until it is determined as "NO" in step 8206 of the sports motor routine, and if flag B is "1", the traction mode will continue until rNOJ is determined in step 5138. The control continues, and if the flag C is "1", the control is continued until "NO" is determined in step 5142 or 5144.
Processing of the WD control routine continues.

As a result, when the normal mode or sport mode is selected and the cut-off mode is executed to restore maneuverability, the 4WD mode or 4WD control routine is activated to improve the transmission of driving force to the road surface. In addition, when traction control is being executed, that control mode will be executed until maneuverability is restored or until the driving force is reliably transmitted to the road surface, so even if the control mode is Even if another mode is selected by the mode selector 64, that signal will be ignored.

Therefore, according to this modification, for example, when the cut-off mode is being executed to restore maneuverability, the crew member may accidentally select one of the manual modes and become unable to control the vehicle again. 4WD mode or a mode based on the 4WD control routine to improve the transmission of driving force to the road surface on a slippery road surface, or a mode based on the 4WD control routine, or even if the occupant accidentally selects manual mode while traction control is being executed. It is possible to avoid a situation where the transmission of driving force to the road surface is reduced.

In addition, in the above embodiment, [Effect of the Invention] As described above, according to the present invention, the torque distribution control means operates based on the rotational speeds of the front wheels and rear wheels detected by the wheel speed sensor. When executing torque distribution control,
The first correction means corrects the difference in rotational speed between the front and rear wheels due to the difference in trajectory between the front and rear wheels, and the second correction means corrects the amount corresponding to the difference in rotation speed between the front and rear wheels due to the difference in trajectory between the front and rear wheels. Since the system corrects the amount corresponding to the change in the turning center of the moving vehicle, it is possible to almost accurately detect the slip situation of the front and rear wheels even when turning, where large lateral acceleration is acting on the vehicle body. This brings about the effect that the driving force distribution between the front and rear wheels can be brought close to the ideal one, and acceleration performance and maneuverability are significantly improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the entire system showing one embodiment of the present invention;
FIG. 2 is a flowchart showing the control of the embodiment of FIG. 1;
Fig. 3 is a flowchart showing the normal motor routine of Fig. 2, Fig. 4 is an explanatory diagram for explaining the determination of the slip ratio difference in the flowchart of Fig. 3, and Fig. 5 is a flowchart showing the normal motor routine of Fig. 2. Figure 6 is a characteristic diagram showing the relationship between lateral acceleration GY and correction coefficient αY, and Figure 7 is a characteristic diagram showing the relationship between Atsushi Man correction coefficient α' and αr. An explanatory diagram for such explanation, FIG. 8 is an explanatory diagram showing the relationship between r"/δ and GY related to the determination of the turning limit, FIG. 9 is a characteristic diagram for a general FF vehicle,
FIG. 10 is an explanatory diagram showing details of the control device 2a in FIG. 1;
Fig. 11 is a flowchart showing the sports motor routine in Fig. 2, Fig. 12 is a characteristic diagram for a typical FR vehicle, Fig. 13 is a flowchart showing the 4WD control routine in Fig. 11, and Fig. 14 is a flowchart showing the 4WD control routine in Fig. 2. 12 is a flowchart showing a modification of the flowchart (main routine) of FIG. 2...Engine, 10...Front clutch, 12
...Rear clutch, 44...Controller, 50.
... Lateral acceleration sensor, 52... Steering sensor

Claims (1)

[Claims] A drive system that transmits the output of the prime mover to the front and rear wheels via a transmission torque variable mechanism, and a slip rate or amount of slip for the front wheels and the rear wheels based on the rotational speed of the front and rear wheels detected by the wheel speed sensor. A power transmission device comprising a torque distribution control means for controlling the variable transmission torque mechanism so that a relationship with a wheel slip rate or slip amount is a set relationship, a steering angle detection means for detecting a steering angle; , acceleration detection means for detecting lateral acceleration acting on the vehicle body; a first correction means for correcting an amount corresponding to the difference in rotational speed between the two; and a second correction means for correcting an amount corresponding to a change in the turning center that moves with the increase in the lateral acceleration.
A power transmission device for an automobile, characterized in that it has a correction means.