JPH0446830A - Torque distribution control device for four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To prevent the overspeed of an engine when a clutch means is in a loosely engaged condition, by limiting engine output torque as the target of a torque distribution control means, according to transmitted torque with the clutch means kept in the aforesaid condition. CONSTITUTION:When a clutch means 17 for adjusting engine output transmission to four wheels 6 to 9 is in a loosely engaged condition, an output torque limiting means 18 outputs an instruction for limiting target engine output, according to transmitted torque from the clutch means 17 in the aforesaid loosely engaged condition. A torque distribution control means 16 for controlling a torque distribution change means 10 and an engine output change means 15, limits the magnitude of engine output on the basis of the instruction, and performs torque distribution control within a feasible range. According to the aforesaid construction, the overspeed of an engine can be prevented.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a torque distribution control device for a four-wheel drive vehicle.

(Prior art) In a four-wheel drive vehicle that uses engine output to drive four wheels (front, rear, left and right), the torque distribution to each wheel is not always kept equal, but is variably controlled to the optimum distribution according to the driving conditions. Such torque distribution control devices are generally known.

For example, Japanese Patent Laid-Open No. 1-247223 discloses a proposal to divide the turning motion of a vehicle into turning entry, turning, and turning exit, and to distribute torque according to the turning state of the vehicle. In other words, this proposal increases the torque distribution to the rear wheels in order to improve the turning performance of the vehicle, while increasing the torque distribution to the front wheels to improve the straight-line performance when exiting the vehicle.

Furthermore, the movement of the load that occurs as the vehicle moves, such as acceleration and turning, makes the allowable driving force of each wheel unequal. On the other hand, in Japanese Patent Application Laid-open No. 1-247221,
Torque distribution is changed by appropriately applying braking force to each wheel according to the above load shift, and in order to compensate for the decrease in overall drive torque caused by this braking, the target is set according to the drive force that the driver requests from the vehicle. A proposal has been disclosed to increase the engine output by setting an engine output torque as follows.

(Problem to be Solved by the Invention) By the way, when implementing the above-mentioned torque distribution control system in a vehicle with a manual transmission, if a clutch operation is performed for a gear change operation etc. during torque distribution control, the engine may overspeed. This results in

In other words, when controlling torque distribution, if the engine output is increased to compensate for the reduction in overall driving torque caused by applying braking force to the wheels, the clutch is in a disengaged or half-clutch state, so the engine output is increased. This will lead to over rotation.

On the other hand, it is possible to stop the torque distribution control by detecting the clutch disengaged state or half-clutch state, but it is possible to stop the torque distribution control by detecting the clutch disengaged state or half-clutch state. When starting on a hill, it is impossible to deal with the wheel slip that frequently occurs due to a partially engaged clutch.

Therefore, the present invention makes it possible to perform torque distribution control within the possible range without causing overspeed of the engine even in a half-clutch state.

(Means for Solving the Problems) In order to solve such problems, the present invention aims to limit the size of the target engine output when the clutch is in a half-clutch state according to the transmission torque of the clutch means at that time. This prevents engine overspeed while executing torque distribution control to the extent possible.

That is, a torque distribution control device for this purpose is shown in FIG.

In the figure, reference numeral 1 denotes a four-wheel drive vehicle, which is equipped with an engine 2. The output of the engine 2 is transmitted to the left and right front wheels 6.7 and the left and right rear wheels through a center differential 3, a front differential 4, and a rear differential 5. 8.9
This is what is transmitted to each of them.

10 refers to the four wheels 6 to 9, or the front wheels 6 and 7 and the rear wheels 8 and 9.
The torque distribution changing means changes the torque distribution to the four wheels 6 to 9 by applying independent braking forces to the left wheels 6 and 8 and the right wheels 7 and 9.
The above-mentioned torque distribution is changed by operating the brake devices 11 to 14 provided at the brake systems 11 to 9, respectively. Reference numeral 15 denotes an engine output changing means for supplementing the torque required for changing the torque distribution by increasing the engine output. For example, the engine output is changed by changing the throttle opening of the engine 2 using an actuator.

16 is a torque distribution control means for controlling the torque distribution changing means 10 and the engine output changing means 15 according to the driving state of the vehicle. That is, this torque distribution control means 16 controls the torque distribution changing means 10 to change the torque distribution among the four wheels 6 to 9 according to the driving condition of the vehicle, and also controls the torque distribution changing means 10 to change the torque distribution among the four wheels 6 to 9 according to the driving state of the vehicle. The engine output changing means 15 is controlled so that the engine output torque reaches the target engine output torque to compensate for this.

Thus, in the present invention, when the clutch means 17 that adjusts the transmission of the engine output to the four wheels 6 to 9 is in a half-clutch state, the target engine output torque of the torque distribution control means 16 is transferred to the clutch means 17. The output torque limiting means 18 is provided for limiting the output torque according to the transmission torque of the means 17 in a half-clutch state.

(Function) In the above torque distribution control device, the clutch means 17
is in the connected state, the operation of the torque distribution changing means 10 is controlled by the torque distribution control means 16, and the torque distribution is changed according to the driving condition of the vehicle. The engine output changing means 15 is controlled so as to obtain a target engine output torque to compensate for the accompanying decrease in the overall driving force of the vehicle.

Therefore, when the clutch means 17 is in the half-clutch state, the output torque limiting means 18 limits the target engine output according to the transmission torque of the clutch means 17 in the half-clutch state, thereby preventing unnecessary increases in engine output. This prevents the engine from overspeeding. Even in this case, the torque distribution is changed and the engine output is increased to the extent possible to prevent wheel slippage.

(Effects of the Invention) Therefore, according to the present invention, since the target engine output is limited in accordance with the transmission torque of the clutch means when the clutch is in a half-clutch state, while performing torque distribution control to the extent possible, Overspeeding of the engine can be prevented.

(Example) Embodiments of the present invention will be described below based on the drawings.

Explanation of the overall configuration> Figure 2 shows the overall configuration of the embodiment (note that the first
(The same reference numerals are used for elements corresponding to those shown in the figure.)
.

First, the output of the engine 2 is input via a transmission 31 to a transfer 3 having a center differential that equally transmits the engine output to front wheels and rear wheels. The front differential 4 is connected to the front wheel side output shaft 32 of the transfer 2, and the left and right front wheels 6.7 are connected to the front wheel drive shaft 3.
They are connected via 3. Similarly, the rear differential 5 is connected to the rear-wheel output shaft 34 of the transfer 3, and the left and right rear wheels 8, 9 are connected to the rear differential 5 via a rear-wheel drive shaft 35.

Brake controller 10 as torque distribution changing means
is each brake device 11-1 disposed on the four wheels 6-9.
4 and an actuator thereof. The opening degree of the throttle valve 36 of the engine 2 is adjusted by a throttle motor 37. The engine controller 15 serving as engine output changing means receives an accelerator signal from an accelerator sensor 38 that detects the amount of accelerator operation by the driver and outputs an operation control signal to the throttle motor 37 to correspond to the amount of accelerator operation by the driver. The torque distribution controller 16 as a torque distribution control means adjusts the opening degree of the throttle valve 36 so that
In response to a control signal from the engine, the engine output is changed to obtain the engine output torque necessary to change the torque distribution.

The torque distribution controller 16 is connected to the accelerator sensor 3
In addition to the signals from 8, various signals for measuring the amount of momentum or operation amount for controlling the torque distribution to the four wheels 6 to 9 are input, and outputs control signals to the brake controller 10 and the engine controller 15. The output sources of the various signals mentioned above are as follows.

A steering angle sensor 40 that detects the steering angle. A lateral acceleration sensor 41 that detects the lateral acceleration of the vehicle. A longitudinal acceleration sensor 4 that detects the longitudinal acceleration of the vehicle.
2 Clutch sensor 43 that detects clutch engagement/disengagement and half-clutch state Wheel speed sensor 44 that detects the rotation speed of each wheel 6 to 9 4 Rotation speed sensor 4 that detects engine rotation speed Vehicle speed sensor 4
6 Gear position sensor that detects the gear position (gear stage) of the transmission 25 Boost pressure sensor 48 that detects the boost pressure of the engine 2 Yaw rate sensor 49 that detects the yaw rate of the vehicle a load shift corresponding control section that sets the torque distribution ratio of the four wheels 6 to 9 according to the load shift of the vehicle caused by the generation of acceleration and lateral acceleration; A turning state corresponding control section that sets a torque distribution ratio, a slip state corresponding control section that sets a torque distribution ratio of the four wheels 6 to 9 according to the slip state of the wheels, and a torque distribution ratio correction control section; The engine and brake control section control the engine controller 15 and the brake controller 10 based on the torque distribution ratio obtained by the control.

Description of the brake controller 10 In FIG.
A second hydraulic line for the second hydraulic pressure control valve 2 is provided with first and second brake pressure control valves 61 and 62, each of which controls the supply of brake pressure. In both brake pressure control valves 61 and 62, cylinders 61a and 62a are partitioned into variable volume chambers 61c and 62c and control chambers 61d and 62d by pistons 61b and 62b. The variable volume chambers 61c and 62c transfer the braking pressure generated by the mask cylinder 58 to the brake device 11.
12.

The pistons 61b and 62b are springs 61e.

62e biases the variable volume chambers 61c, 62c in a direction to increase their volumes, and the control chambers 61d, 62
Spring 61e, 62e by the control pressure introduced into d
The variable volume chambers 61c, 62c are moved in a direction to reduce the variable volume chambers 61c, 62c against the urging force of the variable volume chambers 61c, 62c, and check valves 61f, 62f are provided which close the braking pressure inlet of the variable volume chamber 61C162c by moving in the reducing direction. Therefore, the control room 6
1d.

When the control pressure is introduced into 62d and the pistons 61b and 62b move against the springs 61e and 62e, the mask cylinder 58 and the variable volume chamber 61C162c are cut off, and the air inside these chambers 61c and 62c is cut off. The braking pressure generated will be supplied to each brake device 11.12.

On the other hand, in order to operate the brake pressure control valves 61 and 62, the pressure increasing solenoid valves 63a and 64a and the pressure reducing solenoid valve 6 are operated.
First and second actuators 63 and 64 are provided, each of which is composed of actuators 3b and 64b. Pressure increase solenoid valve 63a,
64a is the control chamber 61d, 62d of the brake pressure control valve 61.62 from the oil pump 65 via the relief valve 66.
The pressure reducing solenoid valves 63b and 64b are arranged on the control pressure supply line 69.70 leading to the control chamber 61d.

It is located on the drain line 67.68 leading from 62d. And these solenoid valves 63a.

63b, 64a, and 64b are controlled to open and close by signals from the torque distribution controller 16, and the pressure increasing solenoid valve 63
a, 64a are opened, and the pressure reducing solenoid valves 63b, 64b are opened.
When the brake pressure control 61, 62 control room 61d is shut off,
, 62d, and the pressure increasing solenoid valves 63a, 6
4a is shut off and the pressure reducing solenoid valves 63b, 64b are opened, the control pressure from the control chambers 61d, 62d is discharged.

Further, although the brake devices 13 and 14 for the left and right rear wheels 8 and 9 are not shown, they have the same structure as the brake devices 11 and 12 for the front wheels 6 and 7, and with this structure, each brake It is possible to apply independent braking pressure to the devices 11 to 14.

Next, the torque distribution controller 16 will be explained.

<Explanation of the overall process flow> As shown in Fig. 4, after the start, at a predetermined measurement timing, the accelerator opening, The steering angle, lateral acceleration, longitudinal acceleration, clutch engagement/disengagement, each wheel speed, vehicle speed, gear position, boost pressure, and yaw rate are measured (step S
1. S2).

Then, the judgment of μ of the road surface and the front wheels 6 and 7 according to the load movement are carried out.
and the torque distribution ratio between the left wheel 6°8 and the right wheels 7 and 9 (hereinafter referred to as the left and right distribution ratio as necessary) )
The determination of Q2, the determination of the front-rear distribution ratio R1 and the left-right distribution ratio R2 according to the turning condition, and the determination of the front-rear distribution ratio P1 and the left-right distribution ratio P2 according to the slip condition are sequentially performed (steps S3 to SO).

Next, the torque distribution ratios QL and R1 obtained by each of the above controls are
, PL, Q2. Based on R2 and P2, the front and rear distribution ratio to be executed is 1 and the left and right distribution ratio is 2, which are corrected and determined in accordance with the torque obtained by changing the engine output for changing the torque distribution, and the brake controller 10 and the engine controller 15 control is performed (step S7.
S8).

In this embodiment, the first rank in the front and rear distribution ratio is 0, which means that the front and rear distribution ratio is equal, and +0.5 means that the drive torque for the front wheels 6 and 7 is 0 (maximum drive torque for the rear wheels 8 and 9), -0, 5, the relationship is set to be the opposite. In addition, for the left and right distribution ratio of 2, 0 is equal left and right distribution, +095 is the drive torque O for the left wheels 6 and 8 (maximum drive torque for the right wheels 7 and 9), -0,
5, the relationship is set to be the opposite.

Description of μ Determination When the vehicle is running straight, μ is estimated from the change in wheel speed with respect to the change in driving force by utilizing the fact that the driving force becomes O when changing gears. Specifically, as shown in the flowchart of Fig. 5, when the vehicle is traveling straight and there is a shift, μ is determined using the formula μ-(change in slip ratio)/(change in driving force). (Steps SL1-13).

In this case, the amount of change in driving force can be obtained by calculating the engine driving torque from the map shown in Figure 6 based on the accelerator opening degree and engine rotation speed (RPM), and multiplying this by the gear ratio before shifting. can.

On the other hand, the amount of change in slip ratio can be obtained by determining the amount of change in wheel speed due to gear shifting Δ■ and the minimum value V of the wheel speed during shifting, as shown in FIG. can.

Description of control for load movement> This control is executed according to the flow shown in FIG. That is, basically, torque distribution control is performed using the actually measured lateral acceleration Gnat and the actually measured longitudinal acceleration detected by the lateral acceleration sensor 41 and the longitudinal acceleration sensor 42. In addition, when the generation of lateral acceleration is delayed with respect to steering such as on a low μ road surface, an ideal calculated lateral acceleration G, ca that is obtained without delay from steering angle changes and vehicle speed changes obtained on high μ road surfaces etc.
The above-mentioned Glat is corrected by l, and the implementation area of this control is changed according to μ of the road surface.

First, G, cal is calculated according to the following formula (step 5
21).

G, cal-v2/ (1+Av2) ・θ/l■ is the minimum wheel speed determined by the wheel speed sensor 44, θ is the steering angle,
l is the wheel base, and A is a factor for obtaining vehicle behavior characteristics on a high-μ road surface, which is obtained from the characteristic map shown in FIG.

Next, when the above G, cal and Glat are both positive or negative values, if the absolute value of G, cal is smaller than that of Glat, G, cal is used as control Glat, and both of them have opposite positive and negative values. When it is a value, Glat for control is set to O (steps 322 to 525). Then, the load transfer rate Qlat between the left wheels 6, 8 and the right wheels 7, 9 is determined using the control Glat, while the load transfer rate Qlat between the front wheels 6, 7 and the rear wheels 8, 9 is determined using the longitudinal acceleration. The load movement rate Qlon is determined (step 826).

Next, constants GLIM] and GLIM2 for setting the execution range of this control are determined based on the above μ, a torque distribution ratio correction coefficient R is obtained, and this R is applied to the load transfer rate QIon and Q
lat are respectively multiplied to obtain torque distribution ratios Q1 and Q2 (step S27.528).

That is, in a region where longitudinal acceleration and lateral acceleration are low, the correction coefficient R is such that the lower the acceleration, the more the torque distribution ratio Ql, Q
This is a coefficient for correcting so that 2 becomes smaller. GLIMI and GLIM2 are the torque distribution ratios Q1. The upper and lower limits of acceleration for which Q2 is corrected are determined. In this case, GL
At accelerations greater than IMI, the load transfer rates Qlon and Ql
at is directly taken as the torque distribution ratio Ql and Q2 (R-
1) If the acceleration is smaller than that of the GLI blade 2, the torque distribution ratio will be R-0, that is, the torque distribution ratio Ql-0, Q2-0.

Then, as shown in the right figure of step S27, the lower μ becomes, the smaller the values of GLIMI and GLIM2 become, and the difference between them becomes smaller, and as shown by the dashed line in the left figure, the lower μ becomes, the correction coefficient characteristics The line shifts to the left, and the implementation area of this control expands to the low acceleration side, and control is performed with a large torque distribution ratio corresponding to the load transfer rate even at low acceleration. Further, when μ is high, the correction coefficient characteristic line shifts to the right, and the main control is not performed until a relatively high acceleration is reached.

In short, in this control, the above-mentioned Gnat is corrected by the calculated lateral acceleration G, Ca1, so even if a relatively large lateral acceleration remains behind after the end of steering, control based on this lateral acceleration is prevented. , it is possible to prevent extra force from acting on the vehicle through control after the steering is completed.

In addition, since the implementation area of this control is changed according to the μ of the road surface, unnecessary torque distribution control is prohibited on high μ roads, while torque distribution control corresponding to load movement is performed on low μ roads. This means that it is possible.

Description of control corresponding to turning state> This control is executed according to the flow shown in FIG. Basically, the front and rear distribution ratio is R1 based on the sideslip angle of rear wheels 8 and 9.
Determine the left/right distribution ratio R to obtain the target yaw rate.
2.

The distribution ratios R1 and R2 are then corrected depending on the turning state of the vehicle.

First, the turning state of the vehicle is determined from the steering angle and the rate of change of the steering angle obtained from the steering angle sensor 4o, and the next turning state determination flag F is obtained (step 531).

F-0... Straight ahead state; steering angle is less than the predetermined value F-1
...Entering state of turning; steering angle change rate is greater than a predetermined value in the positive direction (increasing direction of rudder angle) F-2...Turning state; steering angle is greater than a predetermined value And the steering angle change rate is less than the predetermined value F-3... Escape from turning; the steering angle change rate is greater than or equal to the predetermined value in the negative direction (steering angle decreasing force direction) and the vehicle is in the turning state. If so, the front/rear distribution ratio R1 is determined based on the slip angle, and the left/right distribution ratio R2 is determined based on the yaw rate (steps 532 to 534). moreover,
In the case of an approach state and an escape state, correction control of the front-rear distribution ratio R1 is performed based on the rudder angle and the rudder angle change rate (step 8).
35-538).

- Determination of front-rear distribution ratio R1 based on slip angle - Rudder angle sensor 40
, using the vehicle speed sensor 46 and the yaw rate sensor 49,
The sideslip angle γ of the rear wheels 8.9 due to the influence of the yaw motion of the vehicle is determined based on the following equation, and the front-rear distribution ratio R1 is determined according to the characteristic map shown in FIG.

7-Yav, r-I/V yav, r; Actual yaw rate g: Distance between the rear wheels and the center of gravity of the vehicle. R1 is determined to increase in the negative direction as it increases in the negative direction. Further, the yaw rate Yaw, r is in a positive direction for a right turn, so the above γ has a plus or minus, and this corresponds to a right turn and a left turn of the vehicle.

Determination of left/right distribution ratio R2 by yaw rate - minimum wheel speed■
, steering angle θ, wheelbase g to calculate the target yaw rate Y, cal corresponding to the high μ road surface, and adjust the left/right distribution ratio so that the target yaw rate Y, cal can be obtained from the difference from the actual 7111 yaw rate) Yav, r. R2 is determined by feedback control. The target yaw rate y and cal are calculated using the following formula.

Y, cal-v/(1+Av2)-θ/gA are factors obtained from FIG.

Then, ΔY-Y, cal-Yaw, r are determined, and the drive torque difference between the left and right wheels corresponding to this deviation ΔY is determined. Next, the ratio between this drive torque difference and the driver's requested torque is determined, and this is calculated as the left-right distribution ratio. This is set as R2. Specifically, it is as follows.

R2- -ΔY/Tr k is a constant for determining the drive torque difference between the left and right wheels corresponding to the deviation ΔY. Tr is the driver required torque, which is the same as the amount of change in driving force for μ determination.

Correction of front-rear distribution ratio R1 - In the state (F-1) of entering a cornering run, step S38 includes a characteristic diagram of correction coefficients a and b and a calculation formula (R1) of correction coefficients a and b.
1-a+b+R1), R1 is corrected to increase as the steering angle increases and as the rate of change in steering angle increases.

On the other hand, in the state of escape from turning (F-3), in step 53g, the characteristic diagram of the correction coefficients a and b and the calculation formula of R1 (
As shown in R1-a+b+R1), as the steering angle increases and as the rate of change in steering angle increases, R1 is corrected to become smaller.

Therefore, in this control, the front and rear distribution ratio R1 is set so that the larger the rear wheel slip angle, the smaller the torque distribution to the rear wheels 8.9.
When the sideslip of the rear wheel increases and the vehicle begins to show a tendency to spin, the rear wheels 8.9
By reducing the driving force of the
It is possible to stabilize cornering on the road surface. Also,
The above R1 is corrected so that it becomes larger when entering a corner depending on the rudder angle and the rate of change of the rudder angle. This increases the grip of the rear wheels and improves driving stability.

Furthermore, since the left-right distribution ratio R2 is feedback-controlled to obtain a yaw rate that targets characteristics on a high-μ road surface, it is possible to obtain a large yaw rate even on a low-μ road surface and improve turning steering performance.

Description of slip state response control> This control calculates the front-rear distribution ratio P1 and the left-right distribution ratio P2 from the slip ratio between the front wheels and the rear wheels and the slip ratio between the left and right wheels.
This is executed according to the flow shown in FIG.

First, the next slip ratios 81 to S4 are determined by the wheel speed sensor 44 of each wheel (step 541).

Sl; (front wheel/rear wheel) slip ratio S2: (rear wheel/front wheel) slip ratio S3; (right wheel/left wheel) slip ratio S4: (left wheel/right wheel) slip ratio In step S41, the meanings of the symbols are as follows.

VFR, right front wheel speed νPL, left front wheel speed WRR, right rear wheel speed WI? L: Wheel speed of the left rear wheel. Then, when the front wheel slip rate S1 is larger than the rear wheel slip rate S2, as this front wheel slip rate 81 increases within a predetermined value of 80 or more, the front and rear distribution ratio P1 is changed to the rear wheel speed. The torque distribution is set to be large (step S42
．． 543).

Conversely, when the rear wheel slip rate S2 is larger than the front wheel slip rate S1, as the rear wheel slip rate 82 increases within the range of 80 or more, the front-rear distribution ratio P1 increases the torque distribution to the front wheels. (Step S42.
544).

On the other hand, when the right wheel slip rate S3 is larger than the left wheel slip rate S4, as the right wheel slip rate 83 increases within the range of 80 or more, the left/right distribution ratio P2 is set such that the torque distribution to the left wheel increases. Set (step S45.
546).

Conversely, when the left wheel slip rate S4 is greater than the right wheel slip rate S3, as the left wheel slip rate 84 increases within the range of 80 or more, the left-right distribution ratio P2 increases the torque distribution to the right wheel. (Step S45.
547).

In short, in this control, slip is suppressed by reducing the torque distribution to the wheel with the larger slip and increasing the torque distribution to the wheel with the smaller slip.

Description of Torque Distribution Ratio Correction Control> This control corrects and determines the front/rear distribution ratio of 1 and the left/right distribution ratio of 2, which are used to execute torque distribution control, according to the possible output torque of the engine. Execute according to the flow shown in Figure 13.

First, the driver's required torque Tr is calculated from the accelerator opening, engine speed, and gear ratio using the map shown in FIG. 6 (step 551).

Then, the torque Ts required to execute the torque distribution control using the front/rear distribution ratio Kl -Ql +R1+IJ, which is the sum of the distribution ratios set by each of the previous controls, and the left/right distribution ratio 2-Q2 +R2+P2, is calculated according to the following formula. This required torque Ts becomes the target torque "rtarg" (step 552).

Ts-4X (IKI l +0.5)X (l
K2 l +0.5 ) xTr Also, the shaft output torque T eng of the transmission 31 is calculated according to the flow shown in FIG. 14 (step 553).

Calculation settings for shaft output torque and target torque - In other words, when it is determined that the clutch is not in a disengaged state or that the transmission 31 is not in neutral based on the outputs from the clutch sensor 43 and gear position sensor 47,
Based on the boost pressure obtained by the boost pressure sensor 48 and the gear ratio, T eng is determined according to the following formula (step S
81. 582).

Teng -AX (Bp-Bs) A correction coefficient K due to friction is determined, and then an actual transmission torque Tc (-TcxK) is determined (steps 583, 584). In this case, in the correction coefficient characteristic diagram described in step S83, Ql is the engine rotational speed (input shaft rotational speed), and ω2 is the average value of the wheel rotational speed/gear ratio (output shaft rotational speed).

Then, the shaft output torque T eng is the transmission torque Tc
If it is larger than , T eng is limited to Tc (steps S85 and 886). That is, the input torque to the transmission 31 is limited because it does not exceed the maximum transmission torque in the half-clutch state.

Furthermore, the target torque T corresponding to the above-mentioned required torque Ts
For targ as well, compare it with Tc, and if Ttarg is larger, this Ttarg
is limited to Tc (step S87.588), that is, the target torque Ttarg is limited so that it does not exceed the maximum transmission torque Tc.

Furthermore, when the clutch is disengaged or the transmission 31 is in neutral, Teng,
T rSTs becomes zero (step 589), and torque distribution control is stopped.

Determination of one distribution ratio--The distribution ratio is determined according to the flow shown in FIG. 13 using the shaft output torque Teng (-Tc) calculated and set according to the clutch state described above.

When the shaft output torque T eng is larger than the required torque Ts, it means that the shaft output torque has a margin to perform torque distribution control (step S'54, Ten
g > T s ) o Therefore, 1 for the front/rear distribution ratio and 2 for the left/right distribution ratio are set as follows, and the above T
s is set as the shaft output torque (step 555),
It will perform engine and brake control (described later).

Kl −Ql +R1+PL K2−Q2 +R2+P2 Next, in the above step S54, T Qng or TS
, when μ is determined to be a low μ road surface smaller than a predetermined value, when entering and exiting a corner (F-1
, 3), select R1, R2, Pi, P2 as the front/rear/left/right distribution ratios as shown below in order to give priority to the turning state response control and the slip state response control, and calculate the necessary Torque Ts is calculated (steps 356-8
58).

Kl-R10PI K2-R2+P2 Then, if Teng>Ts (step 557), in correction calculation step S60, the above corrections of 1 and 2 are performed according to the following equation.

Kl −Kl ・(Teng −Tr) / (T
s -Tr) Kl -2 #(Teng -Tr
) / (T s - T r) That is, as a result of reducing the distribution ratios Ql and Q2 as described above, the shaft output torque T en
Since there is a margin in g, 2 is added to the distribution ratio Kl in step S.
This is a correction to bring the distribution ratio closer to the distribution ratio at step 52. Note that this correction is based on the reduced distribution ratio (in this case, Q
1, Q2) is more preferably carried out in a direction that partially restores it to the extent possible.

Therefore, in step S55, the shaft output torque Teng is set as the required torque Ts.

On the other hand, if Teng>Ts is not determined in step S59, the distribution ratio obtained by deleting the front and rear distribution ratio R1 is set as follows in order to give priority to the left and right distribution control at the time of entering the corner (F-1). The required torque Ts is selected and the required torque Ts at this distribution ratio is calculated (step S61°562).

Kl -PL Kl -R20P2 In addition, if the judgment in step S81 is No, that is, when exiting from turning (F-3), in order to give priority to front-rear distribution control, the left-right distribution ratio R2 is set as follows. The deleted distribution ratio is selected, and the required torque Ts at this distribution ratio is calculated (step 563).

Kl -RL +PL 2-P2 and the above step S[i2. In any of S83, if Teng>Ts (step 564)
Then, the process proceeds to correction calculation step S60, where the above corrections 1 and 2 are performed, and Ts is set in step S55.

Furthermore, in step S84, the shaft output torque T
If eng is smaller than the required torque Ts, the front/rear/left/right distribution ratio is set to P corresponding to the slip ratio as follows.
l and P2 are each selected, and the required torque Ts is calculated (step 565).

Kl -PL 2-P2 In this case, the distribution ratio correction calculation is not performed, and the above Kl,
Kl and TS are used as they are for engine and brake control.

Next, in step S35B, if it is determined that the road surface is high μ, or even if the road surface is low μ, the determination in step S57 is No, that is, the road is traveling straight (F-〇) or the road is turning (F-2). ), it is determined whether or not the vehicle is traveling straight (step 866). If the vehicle is traveling straight, Ql corresponding to the load transfer rate and Pl corresponding to the slip rate are selected as the front/rear distribution ratio, and P2 corresponding to the slip rate is selected as the left/right distribution ratio, as shown below. is selected, and the required torque Ts is calculated (step 56
7).

Kl −Ql +PL 2−P2 Then, if Teng>Ts (step 868), the process goes to correction calculation step S60, and the shaft output torque T e
If ng is smaller than the required torque Ts, the process goes to step S65 described earlier.

On the other hand, if the determination in step 866 is NO, that is, the high μ
When turning on a road surface or when turning on a low μ road surface, Teng>Ts is set so that left and right distribution control is given priority.
Ql, R1, R2, and Q2 are deleted in this order until Teng becomes greater than Ts, and the process proceeds to correction calculation step Sho. If Teng does not become greater than Ts, the process proceeds to step S65. Yes (step 369
~574).

Description of engine and brake control> Based on the required torque Ts (target torque T targ) set as described above and the front/rear and left/right distribution ratios of 1 and Kl, the engine is operated according to the flow shown in FIG. The controller 15 and brake controller 10 are controlled.

That is, the target output torque T targ required of the engine is calculated using the following equation, and the throttle opening THR is determined from the output torque-throttle opening characteristic map (step S91.592).

T targ −T targ/ G iar and
The engine controller 15 sets the throttle opening of the engine 2 to the above THR.
If HR is smaller than the accelerator opening degree ACC operated by the driver, the engine controller 15 is controlled so that the throttle opening degree corresponds to the accelerator opening degree ACC (steps 393 to 595).

Then, based on the distribution ratio Kl, 2, each wheel 6~
Braking torque applied to 9 TBFR (for right front wheel), TB
FL (for left front wheel), TBRR (for right rear wheel) and TB
RL (for the left rear wheel) is calculated according to the following formula, and the brake controller 10 is set so that these braking torques can be obtained.
(Step 89B,
597).

TBFR-Teng-4(0,5-Kl)X
(2 to 0,5+) XTs TBFL=Teng -4(0,5-Kl)X (0
,5-2)'XTs TBRR-Teng -4(0,5+Kl)X (0
,50 to 2) XTs TBRL-Teng -4(0,54 to 1) x (0
, 5-2) When entering and exiting a corner (very small), Kl - R10 Pi and K2 - R2 + P2 are set, and control corresponding to the turning state is given priority over control corresponding to load movement. Therefore, it is possible to give the vehicle a large amount of momentum suitable for cornering, prevent an increase in the amount of steering by the driver, and improve the running stability and maneuverability of the vehicle.

Also, when entering a turn, Kl −Pi, K2−R2+
P2 and priority is given to left and right distribution control, and when exiting a turn, priority is given to front and rear distribution control as Kl -R1 + PI 5K2 - P2, increasing the torque distribution to the outer wheel of the turn to improve vehicle controllability. In addition to being able to
It is possible to reduce the torque distribution to the rear wheels when escaping, thereby suppressing the occurrence of wheel slip or excessive rotational motion, and improving convergence to straight running when escaping from cornering.

On the other hand, on high-μ roads, priority is given to load transfer control or left/right distribution control when cornering, so it is necessary to apply drive torque commensurate with load transfer to each wheel to prevent wheel slip and improve cornering performance. can be achieved.

Therefore, even in a half-clutch state, the shaft output torque T is limited by the clutch transmission torque Tc mentioned above.
Based on eng, the distribution ratio Kl is determined to be 2, and torque distribution control is executed. When the torque Ts (target torque T targ) necessary for distribution ratio control is smaller than the above-mentioned transmission torque Tc, the target torque T targ is limited by this Tc, so that overspeeding of the engine does not occur.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of the present invention, Fig. 2 and subsequent figures show embodiments of the invention, Fig. 2 is an overall configuration diagram, and Fig. 3 is a circuit diagram showing torque distribution changing means (brake controller). 4
The figure is an overall flow diagram of torque distribution control, Figure 5 is a flow diagram for μ determination, Figure 6 is a characteristic diagram showing the relationship between output torque and accelerator opening, and Figure 7 is a diagram showing clutch engagement and disconnection. Figure 8 is a flowchart of load movement response control, Figure 9 is a characteristic diagram showing the relationship between wheel speed and factor A, and Figure 10 is a flowchart of turning state response control. , 1st
Figure 1 is a characteristic diagram showing the relationship between the slip angle difference between the front and rear wheels and the front and rear distribution ratio, Figure 12 is a flow diagram of slip response control, and Figure 13
14 is a flowchart of distribution ratio correction control, FIG. 14 is a flowchart for calculating shaft output torque, and FIG. 15 is a flowchart of engine and brake control. 1...Four-wheel drive vehicle 2...Engine 3...Center differential 4...
Front differential 5...Rear differential 6-9...Wheels 10...Torque distribution changing means 11-14...-Brake device 5... Engine output changing means 6 ... Torque distribution control means 7 ... Clutch means 8 ... Output torque limiting means Fig. 1 ... Four-wheel drive vehicle - Engine 3... Center differential 4... Front differential 5... Rear differential 6 to 9... Wheels 10... Torque distribution changing means 1 to 14. Rebrake device 15... Engine output Changing means 16...Torque distribution control means 17...Clutch means 18...Output torque limiting means] Figure 6 Figure 6

Claims (1)

[Claims] (1) A torque distribution control device for a four-wheel drive vehicle in which four wheels on the front, rear, left and right sides of the vehicle are driven by engine output, and the distribution of drive torque to these four wheels is variable, the device comprising: or torque distribution changing means for changing the distribution of drive torque to the four wheels by applying independent braking forces to the left and right wheels; and engine output changing means for variably controlling the engine output; a clutch means for adjusting the transmission to the wheels; and a clutch means for controlling the torque distribution changing means to change the torque distribution among the four wheels according to the driving condition of the vehicle, and for supplementing the torque necessary for changing the torque distribution. torque distribution control means for controlling the engine output changing means so that the engine output torque becomes a target engine output torque; 1. A torque distribution control device for a four-wheel drive vehicle, comprising: output torque limiting means for limiting the output torque according to the transmission torque in the current state.