JPH0285050A - Traction controller for vehicle - Google Patents

Abstract

PURPOSE:To maintain the balance between the right and left driving forces and improve the traveling stability of a vehicle by changing the differential restriction torque control condition by a clutch control means so that the differential restriction torque reduces as the difference of the right and left brake powers increases, according to the result of the detection of the brake application state of a driving wheel. CONSTITUTION:If the drive slip of a wheel is generated when the wheel is driven by the power supplied from an engine, a traction controller suppresses the drive slip of the wheel by applying brake onto the wheel by a brake means A for traction control which is installed individually for the right and left driving wheels. Further, the traction controller controls the differential restriction torque of a differential restricting clutch C installed between wheels, by a clutch control means B. In this case, a brake application state detecting means D for detecting the brake application state of the right and left driving wheels by the brake means A is installed. Then, according to the brake application state, the differential restriction torque control condition by the clutch control means B is changed by a control condition changing means E so that the differential restriction torque reduces as the difference between the right and left brake powers increases.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a traction control device for a vehicle that prevents wheel drive slip (wheel spin).

(Prior Art) A conventional example of a traction control device for a vehicle is as described in Japanese Patent Application Laid-Open No. 143135/1983 (
Some systems are designed to brake the drive wheels when a wheel drive slip occurs to suppress the drive wheel torque, thereby reducing the drive slip, and further increasing the differential limiting torque to lock the operation limiting clutch.

(Problem to be Solved by the Invention) However, in the above conventional example, when drive slip occurs when driving on a split μ (friction coefficient) road surface or when turning, the differential limiting control effect due to the braking and the differential limiting system The differential limiting control effect overlaps, resulting in an excessive differential limiting control effect, resulting in an imbalance between the left and right driving forces, which impairs the running stability of the vehicle.

It is an object of the present invention to solve the above-mentioned problem by making the differential limiting torque variable according to the braking state for preventing drive slip of the left and right drive wheels.

(Means for Solving the Problems) For this purpose, the traction control device of the present invention, as shown in the concept in FIG. Braking the wheels by means of braking means for traction control provided individually for the wheels to prevent drive slip of the wheels;
In a vehicle in which a differential limiting torque of a differential limiting clutch provided between the wheels is controlled by a clutch control means, a braking state detection means for detecting a braking state of the left and right driven wheels by the braking means, respectively; and control condition changing means for changing the differential limiting torque control condition by the clutch control means so that the differential limiting torque decreases as the left and right braking force difference increases, depending on the state. It is.

(Operation) A vehicle runs by driving its wheels using power from the engine. If the wheel generates a drive slip, the braking means brakes the drive wheel, thereby preventing the wheel from slipping.

On the other hand, the braking state detecting means detects the braking states of the drive wheels by the braking means, and in accordance with the detection results, the control condition changing means changes the differential limiting torque control condition by the clutch controlling means as the left and right braking force difference increases. Change the differential limiting torque to decrease. Therefore, it is possible to prevent the differential limiting control effect from duplicating and becoming excessive when drive slip occurs when driving on a split μ road surface or when turning, thereby maintaining the balance between left and right driving forces and stabilizing the running of the vehicle. can improve sex.

(Example) Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 is a system diagram showing an embodiment of the traction control device of the present invention. IL and IR are the left and right driven wheels (
For example, left and right front wheels), 2L, and 2R are left and right drive wheels (
For example, left and right rear wheels). The vehicle has 2L wheels.

2R is driven by an engine (not shown), and the output of the engine is adjusted by a throttle valve 4.

The throttle valve 4 is opened and closed by a step motor 5.
The number of steps (opening degree of the throttle valve 4) should be set to correspond to the amount of depression of the accelerator pedal 6 by the driver, except during traction control.
It is controlled by a control circuit 7.

For this purpose, a signal TH from the throttle valve 8 that detects the opening degree of the throttle valve 40, that is, the number of steps of the motor control 5, is fed back to the control circuit 7, and an accelerator sensor that detects the depression amount Acc of the accelerator pedal 6. The signal from 9 is input to the control circuit 7.

The control circuit 7 includes a microcomputer 10 and an A/D converter 11 and an F/D converter 11 on its input side.
A V converter 12 is provided, and a drive circuit I3 for the step motor 5 and a D/A converter 14 are provided on the output side. The A/D converter 11 receives the throttle opening signal T.
H and accelerator signal Acc are analog-to-digital converted and input to the microcomputer 10, and F/V
The converter 12 converts the frequency-voltage converted voltage signal into a digital signal and inputs it to the microcomputer 10.

Each of the wheels IL, IR, 2L, and 2R is a wheel cylinder 22L operated by a hydraulic pressure P from a brake master cylinder 2 corresponding to the depression force of the brake pedal 20.

1. Equipped with 22R, 23L, and 23R. It is assumed that the corresponding wheels are individually braked by the operation of these wheel cylinders. Therefore, the brake hydraulic systems of the driving wheels 2L and 2R each have a hydraulic pressure control valve 24 for controlling the traction cylinder.
1. , 24R is inserted. These hydraulic pressure control valves have the same specifications and the same structure 5, the spool 25 is resiliently supported at the left limit position shown in the figure by a spring 26, and the plunger 27 is supported by a spring 28.
It is configured to be elastically supported at the left limit position shown in the figure.

The hydraulic pressure control valves 24L and 24R output the hydraulic pressures P and 4 to the inlet boat 29 on the master cylinder side as they are to the corresponding wheel cylinder from the outlet port 30 on the wheel cylinder side in the normal state shown in the drawing, and When moving, the plunger 27 isolates the boats 29 and 30 and increases the hydraulic pressure to the wheel cylinder, and when the spool 25 stops moving to the right, the increased hydraulic pressure of the wheel cylinder is maintained.

The right movement of the spool 25 and its stop are controlled by the pressure inside the chamber 31, and this pressure is controlled by the solenoid valves 40L, respectively.

Controlled individually by 40R. These electromagnetic valves are also similar, and when the solenoid 41 is OFF, it is in the port-to-port connection position shown in (A), connecting the chamber 31 to the drain circuit 42 and is cut off from the accumulator 43, and when the solenoid 41 is ON with a small current ( When the solenoid 41 is turned on due to a large current, the chamber 31 is in the port-to-port connection position shown in B) and the chamber 31 is drained. It is assumed that it is cut off from the circuit 42 and communicated with the accumulator 43.

When the solenoid valves 40L and 40R are in the (A) position, the chamber 31 is in a no-pressure state, the spool 25 is in the illustrated position, and the solenoid valve 40L is turned on.
.

At the position (C) of 40R, the chamber 31 is supplied with the constant value Pc of the accumulator 43, causing the spool 25 to move to the right in the figure, and at the position (B) of the solenoid valves 40L and 40R, the pressure supply to the chamber 31 is stopped. to hold the spool 25 in its current rightward position.

Hydraulic pressure from a pump 45 driven by a motor 44 is accumulated in the accumulator 43 via a check valve 46, and when the accumulated pressure value of the accumulator 43 reaches a constant value Pc.

It is assumed that the control circuit 7 stops the motor 44 (pump 45) in response to a signal from the pressure switch 47 which detects this and turns off. For this purpose, the signal from the pressure switch 47 is input to the microcomputer 0, and the motor control signal from the microcomputer 10 is converted into an analog signal by the D/A converter 14 and supplied to the motor 44.

The solenoid 41 of the electromagnetic valves 40L and 40R is also driven and controlled by the microcomputer 10, and the control signal therefor is converted into an analog signal by the D/A converter 14 and supplied to the solenoid 41.

Wheel rotation sensors 50L, 50R, 51L, and 51R are provided in association with each wheel IL, IR, 2L, and 2R, respectively, and these sensors detect wheel speeds VFLI, VFII, and VFII of the corresponding wheels.
It emits pulse signals with frequencies corresponding to I VRLI VIIIILL, and supplies these pulse signals to the F/V converter 12. The F/V converter 12 converts each pulse signal into a voltage corresponding to its frequency (wheel rotation speed) and converts it into an A/D converter.
The voltages are input to the converter 11, and the A/13 converter 11 converts these voltages into digital signals and inputs them to the microcomputer 10.

Furthermore, in the present invention, a differential limiting clutch (wet multi-disc friction clutch) 55 is provided between the drive wheels 2L and 2R to limit the differential movement between these drive wheels 2L and 2R. The clutch 55 is connected to the hydraulic pump 45 via an electromagnetic proportional pressure reducing valve 56 and a check valve 46, and is engaged by control oil pressure supplied from the hydraulic pump 45 to increase differential limiting torque.

When the solenoid 56a is not driven, the electromagnetic proportional pressure reducing valve 56 drains the clutch pressure Pcr of the differential limiting clutch 55 in the normal state shown in the figure, and supplies a drive current to the solenoid 56a. At the time of supply, the clutch pressure Per is increased in accordance with the excitation current IC using the constant pressure PC generated by the hydraulic pump 45 and accumulated in the accumulator 43 as the source pressure, thereby increasing the differential limiting torque in proportion to the clutch pressure Pcr. shall be allowed to do so.

The solenoid 56a of the pressure reducing valve 56 is also driven and controlled by the microcomputer 10, and the control signal (Ic) for this purpose is controlled by the microcomputer 10.
is converted into an analog signal by the D/A converter 14 and supplied to the solenoid 41. It is assumed that the wheel speed VFL+VFR+VRLI VRII is used for the microcomputer 10 for the differential limiting torque control.

The microcomputer 10 executes the control programs shown in FIGS. 3 to 7 based on various human input information to control the normal opening of the throttle valve 4 and the opening for traction control, and also controls the opening of the solenoid valve solenoid 41. position control, that is, braking control for traction control of the driving wheels, and further controls the position of the pump motor 44 (hydraulic pump 4
5), and also controls the pressure reducing valve solenoid 56a.
control, that is, differential limiting torque control. In FIGS. 3 to 6, an operating system (not shown) is used to set a certain period ΔT (for example, ΔT=10 msec) after the engine is started.
), the main routine performs periodic interrupt processing every time
The figure shows 0CI (Output compar.
e 1interrupt) Indicates interrupt processing.

In FIG. 3, first, in steps 101 and 102, the first
Only for the second processing, the microcomputer 10 uses the built-in RA.
Perform initialization of M, etc. The next step 103 is wheel speed V F Rr V F L + V
I L + V Ill is read, and based on these, in step 104, the left and right drive wheels 2L, 2R slip ratio SL is determined.
+ s*St = (v, It VFL)/VFL
, s*=(v**-vr*)/vr* After tJ, in step 105, the slip ratio change speed of the left and right drive wheels 2L and 2R ζL=SL St-+ (however, 5L-1 is the previous left drive wheel Wheel slip rate) and &Eichi 8tt 5l-
1c, where s*-1 is the previous right drive wheel slip rate).

In step 106, the left and right driving wheel slip ratios S, l
Select the smaller of these low slip rates Smi. , set the larger one to select high slip rate S, □.

Next, in step 107, the smaller value of the select low slip rate and the select high slip rate is set to 5h.
The weighting of the slip rate that emphasizes in by the ratio of K (for example, 0.6-0.9) is based on the average value Saw as 5sv=KXS*t
n+(IK)XSIIMX, and the rate of change Sav is determined as 5-v=S-vS-v-+ (where Smv-i is the average value of the previous slip rate weighting).

In step 151, the above slip rate average value 5IIV
Based on the speed of change Sav, the throttle opening TH should be returned to the value corresponding to the depression amount Acc of the accelerator pedal 6 (increase) based on the throttle opening control range data as shown in FIG. The throttle valve 4 should be closed quickly (quickly decreases the throttle opening TH) or slowly closed (overturns the throttle opening TH) to prevent drive slip of the wheels 2L and 2R. Determine whether it is a closed region or a holding region where the throttle opening TH should be kept unchanged. This determination result is used in steps 152-1.
54, go to step 201 in the non-control area, go to step 301 in the slow closing area, go to step 351 in the sudden closing area,
In the holding area, control proceeds to step 401, respectively.

In the non-control area, in steps 201 to 206, the map up counter MA is cleared in step 204 and incremented (stepped) in step 203 or 205.
Each time the PUPC indicates a certain recovery time T, I, the throttle opening map MAP is determined as the previous map (MAPO) -1 in step 206 for each blockage T, and then the control proceeds to step 401. MAP is number 9
As shown in the figure, 20 types are set from the 0th to the 19th map, and the above map up means a command to increase the throttle valve opening to a value corresponding to the accelerator pedal depression amount Acc.

When the control proceeds to step 301 because the throttle is in the slow closing range, first in this step it is checked which throttle control range was used last time. If it was in the uncontrolled area last time, perform the following process 1.
Do it only once. That is, in step 302, the above map up counter MAPUPC is cleared, and in the next step 303
．． At step 304, the brake fluid pressure state of the left and right drive wheels 2L and 2R is checked by determining whether the left or right low pressure flag and the left or right sudden low pressure flag are both 0 force. As described later, these flags indicate the corresponding left and right drive wheels 2L,
If the brake fluid pressure for 2R traction control suddenly decreases for more than a predetermined period of time, or if the pressure decreases suddenly for more than a predetermined period of time, it becomes 0.
If at least one drive wheel is in a state of rapid depressurization, the map drop number MAPDN is set to 1 in step 305; otherwise, MAP[)N is set in step 306.
Set = 2. In step 307, the previous map M
AP O and a predetermined time (T) stored in memory as described below.
, 4 or T,'), whichever is larger than the previous map number PMAP (
Select high map MA (lower throttle opening)
PMAX, and in step 308 this select high-speed map MAPMAX is set as step 305 or 3.
This time, the MAP MA is the one in which the map was dropped by the number of MAPDNs determined in 06 (MAPMAX + MAPDN).
P and commands the throttle opening to be loosely closed. In addition, in steps 309 and 310, the initial map MAPINI obtained when the above MAP first changes from the uncontrolled region to the loosely closed region is
In the following cases, the command is to increase the throttle opening, which is contrary to the intention of slow closing, so MAP-MAPINI
shall be.

If it is determined in step 301 that the previous time was in the slow closing region or rapid closing region, the control proceeds directly to step 401, and if the previous time was in the holding region, in step 311 the previous map MA
This time, map MA is the one in which PO is dropped by 1.
After issuing a command to reduce the throttle opening as P, the control proceeds to step 401.

If the control proceeds to step 351 due to a sudden closing range, the previous throttle opening control range is first checked here. If it was in the non-control area last time, the same processing as steps 302 to 310 is performed in steps 352 to 360, and in step 362, 2 is added to the map obtained by this processing to command a sudden decrease in the throttle opening. Control step 4
Proceed to 01.

If it is determined in step 351 that it was in the sudden closing region from the previous time, the control proceeds directly to step 401, and if it was in the slow closing region or holding region last time, in step 361, the same processing as in step 311 is performed, and then the control is continued to step 401. 401
Proceed to.

If control proceeds to step 401 because of the holding area (same after processing for the non-control area, slow pressure increase area, and rapid pressure increase area), in steps 401 to 404, the MAP value is set to the set map number O ~ shown in FIG. 9. When the value is outside the range of 19, set the MAP value to the nearest limit value 0 or 19. Next step 405.40
At step 6, the brake fluid pressure state of the left and right drive wheels 2L and 2R is checked by checking whether the left and right low pressure flags are both non-zero and whether the left and right sudden low pressure flags are both non-zero. If the pressure is not increased (if the pressure is decreased), in step 407, the throttle control map taken before the corresponding predetermined time I7 is used as PMAP to perform throttle slow/sudden closing control (step 307.35).
7), and if the pressure is increased, in step 408, the map before T and a longer predetermined time TM' is set as PMAP. In the next step 409, the current map MAP is converted to the previous map M.
Store it in memory as AP O and prepare for next time.

After the above processing shown in FIG. 3, the control proceeds to step 5 in FIG.
The program proceeds to step 02, where the accelerator pedal depression amount Acc is read. In the next step 503, the target step number 5TBP of the step motor 5 corresponding to the accelerator pedal depression amount Acc is determined by searching the map based on the opening characteristic map corresponding to the map MAP obtained as described above.

In step 504, the target opening step number 5T of the throttle valve 4 determined in step 503 is determined.
The deviation Dir between EP and the actual opening step number TI is calculated by Dir = 5TEP - TI. Furthermore, in steps 505 and 506, the speed of the step motor 5 is determined, forward rotation/reverse rotation/holding is determined, furthermore, the OCI interrupt period is set, a flag regarding the motor rotation direction, etc. are determined based on the above-mentioned deviation Dir.

Thereafter, in steps 601 to 693, the left drive wheel is braked and released for traction control at an appropriate speed as follows (the right drive wheel is similarly braked and released in steps 695 and 696, which will be described later).

In step 601, the left driving wheel slip rate S is calculated based on the table data corresponding to FIG.

And from the rate of change SL, a region is determined as to whether the left driving wheel brake fluid pressure should be rapidly increased, gradually increased, maintained, overturned, or suddenly decreased. The table data in Fig. 10 shows the control mode of the left drive wheel brake fluid pressure suitable for traction control, and the slip ratio SL (Sli SI2 is the area boundary value) and its rate of change 5L (S!I, 0. S2□ are The higher the area boundary value), the faster the pressure should be increased, and the lower the slip ratio SL and its rate of change SL, the faster the pressure should be reduced. Furthermore, the 10th
The figure also shows the right drive wheel brake fluid pressure control mode, which will be described later.
Therefore, the right driving wheel slip rate S, l and its rate of change S
At is also written.

The above area determination result is determined in steps 602 to 605, and the process branches to the corresponding steps in FIG.

That is, if it is a rapidly increasing pressure area, go to step 611, if it is a slow pressure increasing area, go to step 631, and if it is a holding pressure area, go to step 65.
5, control proceeds to step 661 if the pressure is overturned and depressurized, or to step 681 if the pressure is rapidly reduced.

When step 611 is selected for a sudden pressure increase area, the slow pressure reduction counter, rapid pressure reduction counter, slow pressure increase counter, and promotion counter that are not involved in the sudden pressure increase are cleared, and the no-control flag is set to 1. do. In the next step 612, the previous area is checked, and if it was a depressurized area last time, a loop passing through step 614 is executed only once, and if it was a pressure increasing or holding area last time, a loop passing through step 618 is executed. In the former loop,
First, in steps 614 and 613, it is checked whether the low pressure flag and the sudden low pressure flag are O, that is, whether rapid pressure reduction has been performed for a predetermined time or longer. If there was a sudden pressure decrease last time, the initial pressure increase counter is incremented in step 615 because it is necessary to perform an initial pressure increase faster than 2. pressure increase to eliminate response delay.

Thereafter, in step 691, the solenoid valve 40L is set to the C position.

At this solenoid valve position, the hydraulic pressure control valve 24L increases the left driving wheel brake hydraulic pressure by the movement of the spool 25 in FIG. 2, and brakes the left driving wheel for traction control. If the low pressure flag is not 0 or the sudden low pressure flag is not 0, then the initial pressure increase described above is not necessary, so the rapid pressure counter is incremented in step 616, and step 691 is executed.

Thereafter, step 612 selects step 618, where the low pressure flag is set to 1.

In steps 619 and 620, it is checked whether the above-mentioned initial pressure increase counter is 4 or O, but if step 615 has been executed, the path of steps 619, 620, and 621 is repeated three times, and the pressure is increased in step 691. Next time, step 619 will select steps 622 and 623, and thereafter step 619 will select steps 620 and 623. In step 623, it is checked whether the rapid pressure counter is at a predetermined value TRL, which will be described later.In step 624, it is checked whether the rapid pressure counter is 0 or 1. If step 616 has not been performed, step 623.
The paths 624 and 627 are repeated twice and the pressure is increased by executing step 691 each time, but step 616
If has been executed, the above route is selected only once and step 691 is executed to increase the pressure. After that, step 624 selects step 625, and TR
When L=5, the solenoid valve 40L is activated by executing step 692 three times until the rapid pressure counter reaches 5, and when T++t=7, by executing step 692 five times until the rapid pressure counter reaches 7. Set to B position. At this solenoid valve position, the hydraulic pressure control valve 24L stops moving the spool 25 to maintain the left driving wheel brake hydraulic pressure at the current value. After that, the left drive wheel brake fluid pressure is increased rapidly at a speed corresponding to the duty (duty of 215 or 2/7) where the pressure is increased when the sudden pressure counter is 1.2 and maintained when it is 3 to 5 or 3 to 7. can be pressed.

The above-mentioned sudden pressure increase action will be explained with reference to FIGS. 12 to 14.

As shown in FIG. 12(a), if the low pressure flag = 1 or the sudden low pressure flag = 1 and the pressure reduction area is switched to the rapid pressure area at instant t, then the low pressure flag = 1 until instant t1.
Correspondingly, as will be described later, overpressure depressurization is carried out at 115 days in which one cycle is <50 m5ec and the pressure is reduced by 10 m5ec. Steps 614-616 at instant t1
-691 loop is selected once and then step 618
-619-620-623-624-627-691 loop is selected once, then steps 618-619
The loop containing -620-623-624-625-692 is selected three times when TIIL=5 and five times when TRL=7, so that <275 or 2/
Rapid pressure increase can be performed with a duty of 7.

As shown in FIG. 12(b), instantaneously 1. Assuming that the pressure reduction area switches to the rapid pressure area at , the low pressure flag =
0 and the sudden low pressure flag = 0, the duty is 100% and pressure reduction continues as described below. At instant t1, the loop of steps 614-613-615-691 is 1
times, and then step 618619-620-6
The loop of 21-691 is selected three times, then steps 618-619-622-623-624-627-6
As a result of the loop 91 being selected twice, the initial pressure increase is performed faster than the rapid pressure increase for four times (ΔTX 4 = 40 m5ec) from instant t, resulting in a response delay (Fig. 12(b)). As shown by the middle dotted line, 2 times (ΔTX 2 = 20m
sec). From then on, 275 is the same as described above.
Alternatively, a rapid pressure increase with 2/7 duty can be performed.

As is clear from the above, a rapid pressure increase with a duty of 215 or 2/7 as shown in FIG. 13(a) is performed on a steady basis.

When step 631 in FIG. 5 is selected for the gradual pressure increase area, the unrelated overturning pressure counter, 2, decompression counter, and promotion counter are cleared, and the no-control flag is set to 1.

In the next step 632, the previous area is checked, and if it was the previous decompression area, the loop including step 634 is repeated.
If the previous pressure increase or pressure holding area was the area, a loop including step 638 is executed.

In the former loop, steps 634.633.635.6
In step 36, the same processing as in steps 614, 613, 615, and 616 is performed, but in step 636, a slow pressure increase counter is incremented instead of the rapid pressure increase counter in step 616. Also, at steps 638, 639, 640, 641, and 642, steps 618.
619.620° Perform the same processing as 621 and 622.

However, in step 638, processing for setting the sudden low pressure flag to 1 is added.

In steps 643 and 648, when switching from rapid pressure increase to slow pressure increase, it is checked whether the rapid pressure counter is a predetermined value TIIL, 0, or other than these, in order to set a waiting time for the change. When the rapid pressure counter is other than o and r*, that is, when the rapid pressure is in the middle of rapid pressure, the rapid pressure counter is incremented in step 649, and step 69
2, and when the rapid pressure counter reaches 'r*t, this counter is reset at step 644, and when the rapid pressure counter is O, the process continues at step 645.6.
Perform slow pressure increase control according to 46.647.650.651. This slow pressure increase control is performed in steps 623, 624, and 625.
It is the same as the rapid pressure increase control according to 626.627, but
In step 646 corresponding to step 624, the pressure is increased only when the slow pressure increase counter is 0, so that the pressure can be gradually increased with a smaller duty (115 duty or 1/7 duty) than in the case of sudden pressure increase.

The effect of the above-mentioned gradual pressure increase will be explained with reference to FIGS. 12 to 14.

After instant t1 in Figs. 12(a) and 12(b), the switching from pressure reduction to pressure increase is performed in the same way as during the sudden pressure increase, but as mentioned above, the duty is small, so the changeover is as shown by the solid line in these figures (increase). Pressure time is reduced to 10 m5ec, allowing for gradual pressure build-up.

As is clear from the above, the pressure is steadily increased at a duty rate of 115 or 1/7 as shown in FIG. 13(b).

In addition, if the gradual pressure increase area is switched to the rapid pressure increase area at instant t as shown in FIG. 14(a), the rapid pressure increase starts immediately, but at instant 1 as shown in FIG. When switching from the rapid pressure increase area to the slow pressure increase area, the start of the slow pressure increase is delayed by the waiting time Δt due to the loop including step 643.644.648.649.692 to prevent unnecessary braking. Can be done.

When step 655 in FIG. 5 is selected for the pressure holding area, the initial pressure increase counter, rapid pressure increase counter, and slow pressure increase counter are each cleared here, and then, in step 692, the solenoid valve 40L@B position is maintained. . This allows the left drive brake fluid pressure to be maintained at the current value as required.

When step 661 in FIG. 5 is selected for the overturn and depressurization area, the slow pressure increase counter, rapid pressure increase counter, and initial pressure increase counter are respectively cleared here.

In the next step 662, it is checked whether the pressure has been suddenly reduced for a predetermined period of time or more based on whether the sudden low pressure flag is 0 or not. If so, in step 664, 6 is added to the promotion counter for the purpose described later, and if the pressure has not been rapidly reduced for more than a predetermined period of time, the control proceeds directly to step 663. Step 66
After 3, the pressure reduction speed is gradually increased in the following manner based on the above promotion counter, so that pressure reduction is delayed in the process of eliminating drive slip, and unnecessary braking of the drive wheels or partial effect of braking does not occur. Do it like this.

In other words, while the promotion counter, which is incremented in step 669 every time the overturning pressure counter reaches 5 in step 663, is 3 or less, steps 665-666-670-69
3 is executed once to set the solenoid valve 40L to the A position. At this solenoid valve position, the hydraulic control valve 24 is set to the second position of the spool 25.
The left driving wheel brake fluid pressure is reduced by moving to the left in the figure), and the loop of steps 665-666-667-692 is executed four times to set the solenoid valve 40L to the B position (the left driving wheel brake fluid pressure is maintained). ) Repeat the cycle 4 times. Therefore, as shown in FIG. 13(c), the pressure is reduced at a speed corresponding to the duty of 175 at the initial stage when the promotion counter is 0 to 3.

After that, if the promotion counter is between 4 and 6, step 668-6
Execute the loop of steps 69-670-693 once, and execute the loop of steps 665-671-673-670-693 once.
Execute times 665-671-673-667-
The cycle of executing the loop 692 three times is repeated three times.

Therefore, as shown in FIG. 13(c), when the promotion counter is 4 to 6, the pressure is reduced at a speed corresponding to the 215 duty.

After that, if the promotion counter is between 7 and 9, step 668-6
Run the loop 69-670-693 once and step 665-671-672-675-676-670-6
93 loop twice, steps 665-671-
2 loops of 672-675-676-667-692
Repeat the cycle twice. Therefore, during this time, the first
As shown in FIG. 3(c), the pressure is reduced at a speed corresponding to a duty of <375.

Furthermore, when the promotion counter exceeds 9, step 665-6
The loop 71-672-675-677-693 is executed repeatedly, and the duty becomes 100% as shown in Figure 13(c).
Continuously perform depressurization. Then, in step 672, the low pressure flag is set to O to indicate that the overturning pressure has continued for a predetermined time or more (promotion counter≧7), and in step 677, the no-control flag is reset.

By the way, if step 664 is executed because the pressure was suddenly reduced for more than a predetermined time before moving to the gradual pressure increase area, the pressure reduction corresponding to the promotion counter 6 will be started, and a delay in pressure reduction can be prevented. .

When step 681 in FIG. 5 is selected for the rapid pressure reduction area, the slow pressure increase counter, rapid pressure increase counter, and initial pressure increase counter are respectively cleared here.

Then, since the control always reaches step 693, the 13th
As shown in Figure (d), with a duty of 100%, the pressure is rapidly reduced as requested. During this time, in step 682, the low pressure flag -
It is checked whether the result is 0, that is, whether the pressure has been rapidly reduced for a predetermined period of time or longer. If not, it is checked in step 683 whether the rapid pressure reduction counter incremented in step 684 is indicative of 15 or more. This step 6
At step 83, a sudden pressure reduction counter is used to check whether or not the sudden pressure reduction has continued for a predetermined period of time or more.If the pressure has been rapidly reduced for a predetermined period of time or longer, a sudden low pressure flag is set to O to indicate this in step 685. Even when it is determined in step 682 that the low pressure flag=0, step 685 is executed after adding 15 to the sudden pressure reduction counter in step 686. Then, in step 687, it is checked whether or not there is a long-term sudden decompression such that the sudden decompression counter indicates 30 or more, and if so, the increment of the sudden decompression counter in step 684 is stopped, and the no-control flag is reset in step 689. do.

In the next step 701 in FIG. 6, the wheel speed VIIL+V
From RI, the left and right driving wheel speed difference ΔVR is calculated as ΔV*=V□−V
Calculated by RL, and further calculates the value ΔV one cycle before ΔvR
The deviation ΔvR from R-1 is ΔV = lJv*-ΔVR-1
1, and the differential limiting torque Ta is calculated based on ΔvlI of the lever in step 702 (an example thereof is shown in FIG. 17).
Determine. In steps 703 to 705, the states of the left and right non-control flags are determined, and if either one is O, differential limiting torque control according to the present invention is required, so in step 706 a predetermined value T is determined based on the deviation Δv,I. , ITI
IL is determined to be a value larger than 5, for example 7, by Tst, T*L=f(ΔVR).

On the other hand, if the left and right non-control flags are both O or not 0 in steps 703 to 705, the predetermined value T, TILL is set to 5 in step 707 to perform normal differential limiting torque control.
decided on. T found in these steps 706 and 707
3L+ TRL is used for the aforementioned traction control braking control (steps 623, 643, and 645).

In the next steps 708 and 709, the correction coefficient is determined.

That is, in step 708, the correction coefficient is set based on the deviation ΔV11.
) is determined, and in step 709, a is set to 1. Based on these KT, a differential limiting torque command value T is calculated by T -Kt-Ta in step 710, and in the next step 711, a drive current Ic is applied to the solenoid 56a of the electromagnetic proportional pressure reducing valve so that the command value T is obtained. The differential limiting clutch 55 is operated with the desired differential limiting torque. In addition, since the left and right wheel speed difference ΔV takes positive and negative values, the command value T
, hence the driving current! . are both positive and negative values, and the differential restriction is strengthened on the corresponding wheel side.

The operation of the differential limiting torque control according to the present invention will be explained with reference to FIG. 19.

First, when a drive slip occurs and braking is started on the slip side wheel, resulting in a one-sided brake condition, the differential limiting torque increases as shown by the dotted line in the figure, so the differential limiting effect becomes excessive, and the wheel speed of the driving wheels decreases. In the conventional example, the force decreases as shown by the dotted line in the figure, causing an imbalance between the left and right driving forces. - In the old invention, in that case, the increase in the differential limiting torque is suppressed as shown by the solid line, so the differential limiting control effect becomes appropriate, so the wheel speed of the slip side wheel can be made appropriate as shown by the solid line, and the The driving stability of the vehicle can be improved by maintaining the balance of driving force.

Control similar to the above-mentioned left drive wheel brake fluid pressure (braking) control is also executed for the right drive wheel in steps 695 and 696, and wheel spin of the same drive wheel is similarly prevented. Note that step 695 corresponds to step 601 in FIG.
Step 696 corresponds to the control contents of steps 602 to 693, and TII of steps 623 and 643.
L is TRII, T3L of step 645 is Tsll, TSL+TILL of step 706.707 is TS
It shall be read as ll+TRR.

Thereafter, in steps 751 to 753, the drive control of the hydraulic pump 45 is performed as follows. In step 751, it is checked whether the pressure switch 47 is ON, that is, whether the pressure P of the accumulator 43 has reached a predetermined value. As shown in FIG. 11, the pressure switch 47 has a hysteresis characteristic that turns ON when the accumulator internal pressure PC falls below P1, and turns OFF when it rises above 22. When the pressure switch 47 is turned on, in step 752, the motor 44 is turned on to drive the pump 45 and reduce the accumulator internal pressure P.
Step 753 when increasing C and turning off the pressure switch 47
Then, the pump 45 is stopped by turning off the motor 44, and the rise in the accumulator internal pressure PC is stopped. Therefore, a predetermined pressure P is always stored in the accumulator 43, and the brake fluid pressure increase control for the traction control can be performed.

Next, the 001 interrupt flowchart for opening and closing the throttle valve shown in FIG. 7 will be explained. This program is repeatedly executed at a cycle such that the step motor speed determined in step 505 in FIG. 4 is obtained.
Based on the execution result of step 506 in FIG. 4, it is determined whether the step motor 5 should be rotated in the forward direction, reverse direction, or maintained at the current position. If forward rotation is to be performed, the step motor 5 is set to one-step forward rotation in step 801, and if it is to be reversed, step motor 5 is set to one-step reverse rotation in step 802. If it is to be maintained, steps 801 and 802 are skipped. .

Then, in step 803, a motor drive signal is output to the step motor 5, and the throttle valve 4 is set to the opening degree corresponding to the calculation result in step 503 in FIG.

Hereinafter, the effect of the traction control based on the throttle opening (engine output reduction) control will be explained based on the operation example shown in FIG. 15. In addition, in FIG. 15, the initial map is in the non-control region with MAP=0, and then it becomes a slowly closed region, and the initial map M shown in the figure changes.
It is assumed that the throttle opening degree is controlled by APINI, and then the map is raised by -1 in steps 201 to 206 in FIG. 3 because it is in the non-control region, and at an instant 1+, it becomes the gradual closing region again.

If the low pressure flag or the sudden low pressure flag on either the left or right side is in a depressurized state for more than a predetermined time of O1, that is, the brake fluid pressure for traction control, as shown in FIG. Step 305.307 in Figure 3 based on the previous map value PMAP (see step 407)
．． The process of 308 is performed once, and after instant t1 MAP=M
APMAX+ 1 is set. But TeMAPMAX+
Since l≦MAPINI, in step 310 the 15th
As shown by the dotted line in the figure, < MAP=MAPINI is established, and based on this, the throttle loose/close control for traction control is performed.

By the way, the low pressure flag and sudden low pressure flag are 1 on both the left and right sides.
That is, when the brake fluid pressure for traction control is increased for a predetermined time or longer, the pressure is increased for a predetermined time T,' at the instant t1 as shown in FIG.
However, TM'> TM) based on the previous map value PMAP
In the figure, the processing of steps 306, 307, and 308 is performed once, and after the instant tl, MAP=MAPMAX+2 is set, and based on this, throttle loose/close control for traction control is performed.

Such throttle closing control for traction control is performed in the same manner even when step 154 determines that the vehicle is in the sudden closing region and the control proceeds to step 351.

However, in this quick closing region, execution of step 362 enables quick closing as requested.

By the way, since the above-mentioned predetermined time is changed by +TM° to T according to the drive wheel brake fluid pressure control state for traction control (low pressure flag and sudden low pressure flag), the predetermined time is changed depending on the difference in the braking state for traction control. It will never become inappropriate and will always remain appropriate.

Next, traction control based on the drive wheel braking control of the present invention will be explained based on the operation example shown in FIG. In this example of operation, the explanation will be based on the assumption that the left and right drive wheels are synchronized and spin to the same extent, and the braking of both side drive wheels is simultaneously controlled in the same way.

Up to the instant t1, the slip ratio 5L (S, l) is less than S11, and its rate of change SL (S) is between 0 and 5i11, and as is clear from FIG. 10, it is in the overturning pressure area. Therefore, the brake fluid pressure of both side driving wheels is slowly reduced by the above action, and the braking force of these driving wheels is gradually reduced. Between instants t1 and L2, the slip ratio is between S11 and S+2, and the rate of change is between 0 and SK+, and the 10th
As is clear from the figure, it is in the area of slow pressure increase. Therefore, the brake fluid pressure of both side driving wheels is slowly increased by the above-mentioned action, and the braking force of these driving wheels is gradually increased. Between instants t2 and t3, the slip ratio is between SII+S+Z and the rate of change is 52I or more, or the slip rate is S+2 or more and the rate of change is positive, so as is clear from Figure 10, the situation is in the rapid pressure area. be.

Therefore, the brake fluid pressure of both side driving wheels increases rapidly due to the above-mentioned action, and the braking force of these driving wheels increases rapidly.

Between instants t3 and t4, the slip ratio is S+Z or higher and its rate of change is 0 and S. As is clear from FIG. 10, this value is in the gradual pressure increasing area, and the braking force of both side driving wheels is gradually increased. Between instants t4 and t3, the slip rates are S and Sl! The value is between 0 and 52 □
As is clear from FIG. 10, it is located in the holding pressure area. Therefore, the brake fluid pressure of both side driving wheels is maintained at the value of instant t4 by the above-mentioned action, and the braking force of these driving wheels is maintained.

After the instant t, the brake fluid pressure of both side driving wheels is controlled according to the determination result by the same area determination based on FIG.

The pressure is gradually increased between the instants t7 and t8, the pressure is maintained between the instants t7 and t8, and the overturning pressure is depressurized after the instant tl.

Therefore, traction control is performed by the drive wheel brake fluid pressure control corresponding to FIG. 10, and drive slip of the drive wheels can be prevented.

Furthermore, since the control mode shown in Fig. 10 determines the rate of brake fluid pressure increase and decrease depending on the slip ratio and the rate of change thereof, slips may occur under conditions that cause large drive slips or sudden drive slips. It is possible to increase the braking speed of the drive wheels to match this, to prevent a drop in traction control performance, or to increase the braking release speed to match the fact that drive slip due to braking is quickly settled, to prevent unnecessary braking. Conversely, in situations where the drive slip is small (and occurs slowly), the braking speed may be slowed down to compensate for the occurrence of slip to prevent unnecessary braking, or if the drive slip is suppressed by braking. In accordance with the slow speed, the brake release speed can be slowed down to prevent deterioration of traction control performance.

(Effects of the Invention) As described above, the traction control device of the present invention controls the differential limiting torque so that it decreases as the difference in braking force between the left and right drive wheels increases. It is possible to prevent differential limiting torque from becoming excessive due to overlapping differential limiting control effects when slipping occurs, and it is possible to maintain a balance between left and right driving forces and improve vehicle running stability. .

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of the traction control device of the present invention; FIG. 2 is a system diagram showing an embodiment of the device of the present invention; FIGS. 3 to 7 are flow charts showing the control program of the microcomputer in the same example; Figure 8 is a throttle opening control map for traction control used in the same example, Figure 9 is a map of throttle valve opening versus accelerator pedal depression used in the same example, and Figure 10 is a map of the drive used in the same example. 11 is an ON/OFF diagram of the pump in FIG. 2; FIGS. 12 to 14 are waveform diagrams of the electromagnetic valve drive duty in the device shown in FIG. 2, and FIG. 15 and 16 are operation time charts of traction control by the device of the present invention, and FIG. 17 and 1
FIG. 8 is a diagram illustrating the relationship between the differential limiting torque and the correction coefficient on the same side and the speed difference between the left and right driving wheels, respectively. FIG. 19 is a characteristic diagram showing the differential limiting torque control characteristics in the same example. IL, IR...driven wheels 2L, 2R...
Drive wheel 4... Throttle valve 5... Step motor 6... Accelerator pedal 8
...Throttle sensor 9...Accelerator sensor 10
...Microcomputer 11...A/D converter 12...F/V converter 13...Motor drive circuit 14...D/
A converter 20...brake pedal 21...brake master cylinder 22L, 22R, 23L, 23R...wheel cylinder 24L, 24R...hydraulic pressure control valve 40L,
40R...Solenoid valve 43...Accumulator 45
... Pump 47 ... Pressure switch 50L, 50R, 51L, 51R ... Wheel rotation sensor 55 ... Differential limiting clutch 56 ... Electromagnetic proportional pressure reducing valve QO group Green holding field Fig. 9 Ac 7 Rpeta 7 Pressing t Acc Fig. 1θ Fig. 11 Fig. Pc Kumeregu internal pressure) Fig. 15 (a) (b) Fig. 17 Fig. 18 String candy wheel i - Figure 16 Figure 19 Time

Claims (1)

[Claims] 1. Drives the wheels using power from the engine,
When drive slip occurs in the wheels, the wheels are braked by traction control braking means provided individually for the left and right drive wheels to prevent drive slip of the wheels, and a differential is provided between the wheels by a clutch control means. In a vehicle configured to control differential limiting torque of a limiting clutch, a braking state detection means detects braking states of left and right driven wheels by the braking means, respectively; and differential limiting by the clutch control means according to these braking states. 1. A traction control device for a vehicle, comprising control condition changing means for changing torque control conditions so that differential limiting torque decreases as the difference between left and right braking forces increases.