JPH0321554A - Traction control device for vehicle - Google Patents

Abstract

PURPOSE:To eliminate the inconvenience of the brake liquid pressure sinking to zero, by sensing the brake liquid pressure supplied to the applicable drive wheel so as to suppress the drive slip, and lowering the decompression speed of the brake liquid pressure when the sensed pressure is low. CONSTITUTION:When a slip is generated at a drive wheel B, a traction control device A suppresses the drive slip by supplying the liquid pressure from liquid pressure source C for traction control as the brake liquid pressure to the drive wheel B, and repeats cycles of decompressing the brake liquid pressure to the drive wheel B at this time of suppression. At this time, the mentioned brake liquid pressure is sensed by a pressure sensor D. When the sensed brake liquid pressure is lower than the specified value, a means E sinks the decompression speed of the brake liquid pressure. This eliminates drop of the brake liquid pressure to zero, and thereby generations of braking noise or vertical vibration of the car body are prevented at the subsequent pressure increase.

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) Conventionally, as a traction control device,
As disclosed in Japanese Patent No. 1-85248, there is a type that prevents spinning by braking the spinning drive wheels.

In this type of device, when a wheel drive slip occurs, the drive slip is suppressed by supplying the hydraulic pressure from a hydraulic pressure source provided for traction control to the drive wheel as brake fluid pressure, and when the drive slip is suppressed, the drive wheel is By repeating the cycle of reducing the brake fluid pressure, drive slip can be prevented most efficiently.

(Problem to be Solved by the Invention) However, in the past, the brake fluid pressure was increased at a constant speed, so depending on the setting of the pressure increase/decrease speed, the pressure decrease cycle may be affected, especially when the brake fluid pressure is low. This brake fluid pressure may be reduced to Okgf/cm2. In this case, the brake fluid pressure will be set to Okg in the next pressure increase cycle.
It is necessary to increase the pressure from f/cm2, but when braking torque is applied from a state where the braking torque is O, it causes braking noise of the drive wheels and vertical vibration of the vehicle body.

This phenomenon occurs as long as the brake fluid pressure is low and braking torque is generated from zero braking torque, and during traction control where the brake fluid pressure is repeatedly increased from zero, pressure increases. The above-mentioned symptoms occur every time the vehicle is cycled, making the occupants uncomfortable.

In view of the above-mentioned circumstances, it is an object of the present invention to solve the above-mentioned problems by lowering the rate of brake fluid pressure reduction compared to normal while the brake fluid pressure is low.

(1000 steps to solve the problem) For this purpose, the present invention, as shown in the concept in FIG. In a vehicle equipped with a traxigon control device that repeats a cycle of suppressing drive slip by supplying brake fluid pressure to the drive wheels as brake fluid pressure, and reducing the brake fluid pressure to the drive wheels when drive slip is suppressed, the brake fluid pressure The pressure sensor is provided with a pressure sensor that detects the brake fluid pressure, and a pressure reduction speed reducing means that reduces the speed of pressure reduction of the brake fluid pressure while the brake fluid pressure is low.

(Function) When wheel drive slip occurs, the traction control device supplies hydraulic pressure from a hydraulic pressure source to the drive wheels as brake hydraulic pressure. As a result, the wheels are braked and their drive slips are suppressed, but when this drive slip is suppressed, the traction control device reduces the brake fluid pressure of the drive wheels to prevent excessive braking. By repeating the pressure increase cycle and pressure decrease cycle of the brake fluid pressure, wheel drive slip is most efficiently prevented.

By the way, in the pressure reduction cycle, the pressure reduction speed reducing means reduces the pressure reduction speed of the brake fluid pressure while the brake fluid pressure detected by the pressure sensor is low.

Therefore, it is possible to prevent the brake fluid pressure from decreasing to 0 kgf/cm'' during the pressure reduction cycle due to the pressure reduction speed being too fast while the brake fluid pressure is low. In the shoes, the brake fluid pressure will not be increased from 0 kgf/cm'' in the next pressure increase cycle, and it is possible to prevent the braking noise of the driving wheels and the vertical vibration of the vehicle body.

(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, where 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). It is assumed that the vehicle travels by driving the wheels 2L and 2R 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 mask 5,
The number of steps (opening degree of the throttle valve 4) is basically controlled by the control circuit 7 to correspond to the amount of depression of the accelerator pedal 6 by the driver except during traction control.

For this purpose, a signal TH from the throttle sensor 8 that detects the opening degree of the throttle valve 4, that is, the number of steps of the motor 5, is fed back to the control circuit 7, and a signal TH from the accelerator sensor 9 that detects the depression IAcc of the accelerator pedal 6 is fed back to the control circuit 7. The signal is input to the control circuit 7.

The control circuit 7 includes a microcomputer 0, and also has 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 13 for the step motor 5 and a D/A converter 14 are provided on the output side. A/D converter l1 receives throttle opening signal T
I 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 wheel IL. IR, 2L, and 2R are wheel cylinders 22L operated by hydraulic pressure PH from the brake master cylinder 2I according to the depression force of the brake pedal 20.
, 22R, 23L, and 23R, and the corresponding wheels are individually braked by the operation of these wheel cylinders. Therefore, the brake fluid pressure systems of the driving wheels 2L and 2R each have a fluid pressure control valve 2 for traction control.
Insert 4L and 24R. These hydraulic pressure control valves have the same specifications and structure, and the spool 25 is elastically supported by a spring 26 at the left limit position shown in the figure, 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 port 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 figure, When moving, the plunger 27 causes the boat 29. 30 and increases the hydraulic pressure to the wheel cylinder, Subur 25
The rising hydraulic pressure in the wheel cylinder shall be maintained when the vehicle stops moving to the right.

The movement of the spool 25 to the right and its stopping are controlled by the pressure within the chamber 3l, and this pressure is individually controlled by electromagnetic valves 40L and 40R, respectively. These solenoid valves are also similar,
When the solenoid 41 is OFF, it is in the port-to-port connection position shown by (8), which connects the chamber 31 to the drain circuit 42 and is cut off from the accumulator 43, and when the solenoid 41 is turned on by a small current, it is in the port-to-port connection position shown in (B). natte room 3
1 is cut off from both the drain circuit 42 and the accumulator 43, and when the solenoid 41 is turned on by a large current, it becomes the port-to-port connection position shown in (C), and the chamber 3l is connected to the drain circuit 42.
It shall be cut off from the air and passed through 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 position shown, and the solenoid valve 40L is turned on.
, 40R, the chamber 31 is supplied with a constant value Pc of the accumulation rake 43, causing the spool 25 to move to the right in the figure.
Solenoid valve 40L. At the (B) position of 40R, the supply and discharge of pressure to the chamber 31 is stopped and the spool 25 is held in the rightward position at that time.

The accumulator 43 accumulates hydraulic pressure from a pump 45 driven by a motor 44 via a check valve 46, and when the accumulated pressure value of the accumulator 43 reaches a constant value PC, a pressure switch 47 detects this and turns OFF. It is assumed that the control circuit 7 stops the motor 44 (pump 45) upon receiving the signal. For this purpose, the signal from the pressure switch 47 is input to the microcomputer IO, 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.

Solenoid valve 40L. The solenoid 4l of 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.

Associated with each wheel IL, IR, 2L, 2R are wheel rotation sensors 50L, 50R. 51L and 51R are provided, and these sensors detect the wheel speed VFLI VF of the corresponding wheel.
R, VRLI Emit pulse signals with a frequency compatible with VRR41m, and convert these pulse signals to F/V converter l2.
supply to. The F/V converter l2 converts each pulse signal into a voltage corresponding to its frequency (wheel rotation speed) and converts it into an A/V converter l2.
The voltage is input to the D converter 11, and the A/LO converter 11 converts these voltages into digital signals and inputs the digital signals to the microcomputer 10.

In addition, the hydraulic pressure of the driving wheel cylinders 23L and 23R,
That is, pressure sensors 60L and 60R are provided to detect drive wheel brake fluid pressures PBL+PIER, respectively, and signals from these are converted into digital signals by an A/D converter 1l and input to the microcomputer IO.

The microcomputer IO executes the control programs shown in FIGS. 3 to 6 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) performs drive control. 3 to 5 are main routines in which an operating system (not shown) performs regular interrupt processing at fixed intervals ΔT (for example, ΔT=10 msec) after the engine is started, and FIG. 6 shows interrupt processing that is determined within this main routine. OCI (Output compare in
interrupt) indicates interrupt processing.

In FIG. 3, in steps 101 and 102, the microcomputer 10 uses the built-in R only for the first processing.
Initialize AM, etc. Next? Step 103 is the wheel speed VFRI VFL, VRLI
VRR is read, and based on these, in step 104, the left and right drive wheels 2L. 2R Nos') Up rate SL + SR to SL
= (VRL VFL)/VFL, SR=(VR
After obtaining R VFR)/VFR, step 10
5 is the slip rate change speed of left and right drive wheels 2L and 2R.
-31SL-1 (however, SL-1 is the previous left drive wheel slip rate) and Le=S*' SR-1 (however, sR-
1 is the previous right drive wheel slip rate).

In step 106, the left and right drive wheel slip ratios SL+S,
Select the smaller of these low slip rates S#L,...
Set the larger one to the select high slip rate S■. Next, in step 107, the smaller value S of the select low slip rate and the select high slip rate is determined.
Weighted average value of slip rate S, v is S, v=KX
S,,,,+(1-K) ,=s. ．． -s. v-
+ <where Sav-+ is the weighted average value of the previous slip rate).

In step 151, the throttle opening Tl1 is adjusted to the depression amount Ace of the accelerator pedal 6 based on the throttle opening control range data suitable for traction control as shown in FIG. is in the uncontrolled range where it should be returned (increased) to the value corresponding to , or the throttle valve 4 is suddenly closed (suddenly decreases throttle opening Tl1) or slowly closed (throttle opening Tl+ gradually decreases) to control wheels 2L, 2R. It is determined whether the throttle opening TH should be kept unchanged in the rapid closing range or the slow closing range in which drive slip should be prevented, or in the holding range in which the throttle opening TH should be kept unchanged. The result of this determination is processed in step 152.
~154, and in the non-control area, go to step 201, in the slow closing area, go to step 7'301, and in the sudden closing area, go to step 35
1 and step 401 in the holding area.

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 2o5.
PUPC has a certain recovery time T. , that is, every TI time, the throttle opening map M is displayed in step 206.
After determining AP as the previous map (MAPO) - 1, control proceeds to step 401. Map MAP is the 8th
As shown in the figure, 201tJtM is set from the 0th sheet to the 19th sheet, and the above map increase means a command to increase the throttle valve opening degree 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 increase counter MAPIIPC is cleared, and in the next step 30
3. In 304, it is determined whether the left or right pressure reduction flag and the left or right sudden pressure reduction flag are both O. As will be described later, these flags indicate that the brake fluid pressure for traction control of the corresponding left and right drive wheels 2L, 2R is in a state of gradual depressurization for a predetermined period of time or more, and that the traction control brake fluid pressure of the corresponding left and right drive wheels 2L, 2R is in a state of gradual depressurization for a predetermined period of time or more'@. O in the reduced pressure state, and if at least one drive wheel is in the tit pressure state, the map drop number MAPDN is set to 1 in step 305,
Otherwise, MAPDN=2 is set in step 306.

In step 307, the larger one (the one with the smaller throttle opening) of the previous map MAP O and the map number PMAP from a predetermined time ago stored in memory as described later is set as the select high manp MAPMAX, and in step 30B, this select High map MAPMAX step 305
Alternatively, the map lowered by the number MAPDN determined in step 306 (MAPMAX + MAPDN) is set as the current map MAP, and a gentle closing/closing of the throttle opening is commanded. In addition, in steps 309 and 310, the initial map M obtained when the above MAP first changes from the non-controlled region to the loosely closed region is
When APIN is less than 1, it means commanding an increase in throttle opening, which goes against the intention of loose closing, so MAP=M
APINI.

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 40'l, and if the previous time was in the holding region, the previous map MAP O is decreased by 1 in step 311. After using this current map as the current map MAP and instructing a reduction in the throttle opening, the control proceeds to step 401.

If the control proceeds to step 351 due to the sudden closing region, first the previous throttle opening control region is checked here. If it was in the non-control range last time, in steps 352 to 360, the same processing as in steps 302 to 310 is performed, 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 the area was in the sudden closing area from the previous time, the control proceeds directly to step 401, and if it was in the gradual closing area or holding area last time, step 36
After performing the same processing as in step 311 in step 1, control proceeds to step 401.

If the 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 number of setting maps is set in the range of 0 to 19 shown in FIG. 8. Set the outer MAP value to the nearest limit value 0 or 19. Next step 405. At step 406, the brake fluid pressure increasing state of the left and right drive wheels 2L and 2H, in which both the left and right pressure reduction flags are not 0 and the left and right sudden pressure reduction flags are not 0, is checked. If the pressure is not increasing (if the pressure is decreasing), the throttle control map from the corresponding predetermined time Tx before is used as PMAP in step 407 for slow throttle closing and quick closing control (steps 307, 357); if the pressure is increasing, the throttle control map is used in step 408. T. The map before the longer predetermined time TM' is defined as PMAP. In the next step 409, the current map MAP is stored as the previous map MAPO in preparation for the 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 STEP of the step motor 5 corresponding to the accelerator pedal depression amount of 8 cc is determined by map searching based on the opening characteristic map corresponding to the map MAP obtained as described above.

In step 504, the target opening step number ST of the throttle valve 4 determined in step 503 is determined.
The deviation Dir between EP and the actual opening degree step number TH is calculated by Dif - STEP - TH. Further, in steps 505 and 506, the speed of the step motor 5 is determined based on the deviation Dir, forward rotation/reverse rotation/holding is determined, and furthermore, the OCI interrupt cycle is set, and the motor rotation direction is determined. Set flags, etc.

In steps 550 to 554, the left driving wheel brake fluid pressure P
1 is the set value p. PIL≧P. Set the low pressure flag to 1 when PL≦PIL<PM, reset the low pressure flag to O when PIL<PL, and set the no-control flag to 0 when PIL<PL.
Reset to .

Thereafter, in steps 601 to 693, the left drive wheel is braked and released for traction control at an appropriate speed as follows. In step 601, based on the table data corresponding to FIG. 9, it is determined whether the left driving wheel brake fluid pressure should be rapidly increased, gradually increased, or held, based on the left driven wheel slip rate SL and its rate of change SL. Determines whether the pressure should be reduced or if the pressure should be suddenly reduced. The table data in Figure 9 shows the control of the left drive wheel brake fluid pressure suitable for traction control, and the slip ratio SL (S
++, Stz is the area boundary value) and its rate of change B, (
S21, O, and St (area boundary values) should be increased at a higher speed, and the lower the slip ratio SL and its rate of change SL, the faster the pressure should be reduced. Note that FIG. 9 also shows the right drive wheel brake fluid pressure control mode, which will be described later, and therefore the right drive wheel slip ratio S, l and its rate of change tR are also shown.

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, the control proceeds to step 661 if the area is a slow decompression area, and to step 681 if the area is a rapid decompression area.

When step 611 is selected for the rapidly increasing pressure area, the slow decreasing pressure counter, rapidly decreasing pressure counter, slowly increasing pressure counter, holding pressure counter, and promotion counter, which are not involved in the sudden pressure increase, are first cleared.

In the next step 612, the previous area is checked, and if it was the previous decompression area, the loop passing through step 614 is changed to 1.
If the pressure was increased or maintained in the pressure area last time, a loop passing through step 61B is executed.

In the former loop, first, in steps 614 and 613, it is checked whether the pressure reduction flag and the rapid pressure reduction flag are O, that is, whether rapid pressure reduction has been performed for a predetermined period of time or longer.

If the previous pressure was in a sudden pressure reduction state, it is necessary to perform an initial pressure increase faster than the sudden pressure increase to eliminate response delay, so the initial pressure increase counter is incremented in step 615. 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 is
2, the left driving wheel brake fluid pressure is increased and the left driving wheel is braked for traction control.

Therefore, if the pressure reduction flag = 0 or the sudden pressure reduction flag = 0, the above-mentioned initial pressure increase is unnecessary, so step 616
Increment the rapid pressure counter at step 691.
Execute.

Thereafter, step 612 selects step 61B, in which the pressure reduction flag is set to 1.

In steps 619 and 620, it is checked whether the above-mentioned initial boost pressure counter is 4 or O, but if step 615 has been executed, steps 619, 620, and 621 are repeated three times, and the pressure is increased in step 691. Next time, step 619 selects steps 622 and 623, and thereafter step 619 selects steps 620 and 623. In step 623, it is checked whether the rapid increase pressure counter is 5 or not, and in step 624 it is checked whether this rapid increase pressure counter is 0 or 1. Step 6
If step 16 has not been executed, steps 623, 624,
The path 627 is repeated twice, each time at step 69.
1 is executed and the pressure is increased, but if step 616 has been executed, the above route is selected only once and step 6 is executed.
91, the pressure is increased. Then step 624
selects step 625, and by executing step 692 three times until the rapid increase pressure counter reaches 5, the solenoid valve 40L is placed in the 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. Thereafter, the left driving wheel brake fluid pressure can be rapidly increased at a speed corresponding to the duty (duty of 2/5), in which the pressure is increased when the sudden increase pressure counter is 1.2, and the pressure is maintained when the sudden increase pressure counter is 3 to 5.

The above rapid pressure effect will be explained with reference to FIGS. 11 to 13.

As shown in FIG. 11(a), if the pressure reduction flag = 1 or the sudden pressure reduction flag = 1 and the pressure reduction area is switched to the rapid pressure reduction area at instant t1, then the pressure reduction flag = 1 until instant t1.
Correspondingly, as will be described later, gradual pressure reduction is performed at a duty of 1/5 in which one period is 50 msec and the pressure is reduced for 10 msec. At instant t1 step 614 -
The loop of 616-691 is selected once and then steps 618-619-620-623-
The loop of 624-627-691 is selected once, then steps 618-619-620-623
By selecting the loop including -624-625-692 three times, rapid pressure increase can be performed with a duty of <275 as shown by the dotted line in the middle of FIG. 11(a).

As shown in FIG. 11(b), if the pressure reduction flag = O and the rapid pressure reduction flag = 0, and the pressure reduction area is switched to the rapid pressure area at instant tl, the pressure reduction flag = 0 until instant t1.
as well as! ．． In response to the M pressure flag = 0, rapid pressure reduction with a duty of 100% is continued as described later. The loop of steps 614-613-615-691 is selected once at instant 1+, then steps 61B-6
The loop 19-620-621-691 is selected three times, then steps 61B-619-622-
As a result of the loop 623-624-627-691 being selected twice, from instant 1 to 4 times (ITX
4 = 40 msec) to eliminate the response delay by increasing the initial pressure faster than the rapid pressure increase, and then increasing the pressure twice (l TX 2 = 20 msec) as shown by the dotted line in Fig. 11(b).
). Thereafter, it is possible to perform a sudden pressure increase with a 2/5 duty similar to that described above.

Note that, as is clear from the above, on a steady basis, a rapid pressure increase is performed at a duty of 2/5 as shown in FIG. 12(a).

When step 631 in FIG. 5 is selected for the slow pressure increase area, the unrelated I1M pressure counter, sudden decrease pressure counter, holding pressure counter, and promotion counter are respectively cleared here. In the next step 632, the previous area is checked, and if the previous area was a depressurized area, a loop including step 634 is executed only once, and if the previous area was an increased pressure or pressure holding area, a loop including step 638 is executed. In the former loop, steps 634, 633, 635, 636
The same processing as in steps 614, 613, 615, and 616 is performed, but in step 636, a slow increase pressure counter is incremented instead of the rapid increase pressure counter in step 616. Also, step 638,
Processes similar to steps 618, 619, 620, 621, and 622 are also performed in steps 639, 640, 641, and 642. However, in step 638, processing for setting the sudden pressure reduction flag to 1 is added.

In steps 643 and 648, when switching from rapid pressure increase to gradual pressure increase, it is checked whether the rapid pressure counter is 5, 0, or other than these in order to set a waiting time for the change. When the surge pressure counter is other than 0.5, that is, during the surge pressure, the surge pressure counter is incremented at step 649, and the pressure is held at step 692, and when the surge pressure counter reaches 5, step 644 is executed. After resetting this counter, if the surge pressure counter is O again, continue with steps 645, 646, 647, 650.
651 to perform slow pressure increase control. This slow pressure increase control is performed in steps 623, 624, 625, 626. 627
is the same as the rapid pressure increase control by step 624
In step 646 corresponding to , the pressure is increased only when the slow increase pressure counter is O, so that the pressure can be gradually increased at a duty of 1/5, which is smaller than that during a rapid pressure increase.

The effect of the above-mentioned gradual pressure increase will be explained with reference to FIGS. 11 to 13.

After the instant tl in Figures 11 (a) and (b), the switching from pressure reduction to pressure increase is performed in the same way as during the sudden pressure increase, but as the duty is small as mentioned above, the pressure is increased as shown by the solid line in these figures. The time is reduced to 10 msec, allowing for a slow pressure increase.

As is clear from the above, the pressure is steadily increased at a 1/5 duty rate as shown in FIG. 12(b).

In addition, if the gradual pressure increase area is switched to the rapid pressure increase area at instant 1 as shown in Fig. 13(a), the rapid pressure increase starts immediately, but at instant h as shown in Fig. 13(b). If the rapid pressure increase area switches to the slow pressure increase area, proceed to step 6.
43, 644, 648, 649, and 692, the start of the gradual pressure increase can be delayed by It, thereby preventing unnecessary braking.

When step 655 in FIG. 5 is selected for the pressure holding area, the initial increase pressure counter, rapid increase pressure counter, and slow increase pressure counter are respectively cleared here, and then step 65
6 to 658, while the holding pressure counter indicates O to 9, that is, J
During the time of tXIO=100 msec, the solenoid valve 40L is kept at the B position in step 692, and during the next cycle time (J
tX 1 =lO msec) At step 691, the solenoid valve 40L is maintained at the C position. As a result, the left drive wheel brake fluid pressure can be maintained at the current value as required while replenishing the amount of fluid leakage.

When step 661 in FIG. 5 is selected for the 11fi pressure area, the slow increase pressure counter, rapid increase pressure counter, holding pressure counter, and initial increase pressure counter are respectively cleared here. In the next step 662, it is checked whether the left driving wheel brake fluid pressure PBL is at a low value of P}I, depending on whether the pressure reduction flag is O or not. If the brake fluid pressure P1 is low, that is, if the brake fluid pressure is reduced to 0 kgf/cm" at a normal pressure reduction speed, causing the above-mentioned problem, the slow pressure reduction period TEL is set in step 663. If the brake fluid pressure PIL is set to a long value 7 and the brake fluid pressure PIL is a high value equal to or higher than PH, the slow pressure reduction period TEL is set to a short value 5 in step 664, thereby performing the following slow pressure reduction speed control.

That is, in step 665, it is checked whether the slow pressure reduction counter has reached the slow pressure reduction period TSL (7 or 5) set as described above. This slow reduction pressure counter is used in step 6.
As long as the no-control flag is determined to be 1 in step 66, that is, as shown in steps 553 and 554 in FIG. As long as control is necessary, it is incremented by 2 in selected steps 673 or 674, and when the set pressure reduction cycles T and L are reached by this increment, it is reset to O in step 675. Further, each time the gradual reduction pressure counter reaches TSL, the promotion counter is incremented in step 676, and after step 674 is executed, the solenoid valve 40L is set to the A position in step 693. At this solenoid valve position, the hydraulic control valve 24L is activated to brake the left driving wheel by moving the spool 25 to the left in FIG. The pressure is reduced to enable re-acceleration after spin suppression of the left drive wheel.

Step 6 until the slow reduction pressure counter reaches TSL.
As long as the no-control flag is determined to be 1 in step 66, the brake fluid pressure is reduced by executing step 693 at a frequency according to the determination result of the low pressure flag (left drive wheel brake fluid pressure) in step 667.

That is, in step 667, the brake fluid pressure is high (P,, ≧
P■), step 672 indicates that while the gradual reduction pressure counter is 0 to 3, regardless of the promotion counter, step 6
93, and the slow pressure reduction counter is 4 to TsL (TsL).
sL is currently set to 5 in step 664), the holding pressure is executed in step 692, and 3/Tst
The brake fluid pressure is reduced at a normal speed corresponding to a duty of =3/5.

In step 667, the brake fluid pressure PIL is low (PIIL
<PH), in the initial stage when the promotion counter is determined to be less than 3 in step 668, step 670 is performed.
Based on the determination result, the pressure is reduced in step 693 while the slow reduction pressure counter is 0~1, and the slow reduction pressure counter is 2~1.
While TSL (TSL is currently set to 7 in step 663), perform the holding pressure according to step 692;
The brake fluid pressure PIIL is reduced at an extremely low speed corresponding to the duty of l/T3L=1/7.

Thereafter, in the middle period until the promotion counter reaches 6 as determined in step 669, based on the determination result in step 671, while the gradual reduction pressure counter is O~2, step 69
3 to T5L (3 to T5L), and 11K pressure counter
to 7), perform pressure holding in step 692,
The brake fluid pressure is reduced at a slightly faster speed corresponding to the duty of 2/Tst=2/7.

Next, after the promotion counter reaches 6, based on the determination result in step 672, the gradual reduction pressure counter becomes 0 to 3.
While , the pressure is reduced in step 693, and while the slow reduction pressure counter is 4 to TsL (4 to 7), the pressure is maintained in step 692, and the speed is faster corresponding to the duty of 3/TsL=3/7. , but the brake fluid pressure is reduced at a slower rate than normal.

Step 662. At 667, the brake fluid pressure PIL is P.
If it is determined that the brake fluid pressure is less than 100 lbs., that is, if the pressure is reduced at the normal slow pressure reduction speed (speed corresponding to 3/5 duty as described above), the brake fluid pressure becomes Okgf/c++" and the next pressure increase cycle is started. Fig. 12(c) shows the above-mentioned gradual pressure reduction effect when the pressure is forced to increase from 0 kgf/cm'' and the above-mentioned disadvantage occurs. That is, in the initial stage when the promotion counter is 0 to 2, T! lL=70
The pressure is reduced for 10 msec during the msec period,
In the middle period when the promotion counter is 3 to 5, T, L = 70
The pressure is reduced for 20 msec during the msec cycle, and after that the promotion counter is 6 or more, TSL = 70 msec.
During the cycle, the pressure is reduced for 39 msec. By making the pressure reduction speed slower than usual in this way, even if the brake fluid pressure pat is low, it is possible to prevent the brake fluid pressure from decreasing to 0 kgf/cm'' in the pressure reduction cycle. Next pressure increase cycle is OK
GF/C-, and it is possible to prevent the braking noise of the driving wheels and the vertical vibration of the vehicle body caused by this. By gradually increasing the pressure reduction speed while in the slow pressure reduction area, it is possible to prevent a pressure reduction delay from occurring.

Note that if it is determined in step 666 that the no-control flag is 0, that is, if the brake fluid pressure PIIL is so low that the pressure reduction speed control described above is unnecessary, step 693 is continued to be executed unconditionally. Brake fluid pressure should be removed quickly.

When step 681 in FIG. 5 is selected because of the rapid pressure reduction area, the slow increase pressure counter, rapid increase pressure counter, holding pressure counter, and initial increase pressure counter are respectively cleared here. Then, the control proceeds directly to step 693, and the pressure is rapidly reduced as requested with a duty of 100% as shown in FIG. 12(d).

Above left driving wheel brake fluid pressure (braking) control (step 5)
Steps 695 and 69 are similar to steps 50 to 693).
6, this is also carried out for the right drive wheel, and wheel spin of the same drive wheel is also prevented. Note that step 695 is the fourth
Although it corresponds to step 601 in the figure, step 55 in the figure
It also includes processes corresponding to steps 0 to 554, and step 696 corresponds to the control contents of steps 602 to 693.

Thereafter, in steps 701 to 703, the drive control of the hydraulic pump 45 is performed as follows. In step 701, it is checked whether the pressure switch 47 is ON, that is, whether the pressure PC of the accumulator 43 has reached a predetermined value. The pressure switch 47 has a hysteresis characteristic that turns ON when the accumulator internal pressure Pe falls below P1 and turns OFF when it rises above P2, as shown in FIG. When the pressure switch 47 is turned on, the motor 44 is turned on in step 702 to drive the pump 45 and reduce the accumulator internal pressure P.
Step 703 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 PC is always accumulated in the accumulator 43, and the brake fluid pressure increase control for the traction control can be performed.

Next, the OCI interrupt flowchart for opening and closing the throttle valve shown in FIG. 6 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, one-step reverse rotation of the step motor 5 is set in step 802, and if it is to be held, step 801. Skip 802.

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.

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

Until instant t, the slip rate SL (SR) is S. and the rate of change SL (SR) is between O and E2, and as is clear from FIG. 9, is it in the INN pressure area? . Therefore, the brake fluid pressure of both drive wheels is slowly reduced by the above action, and the braking force of these drive wheels is gradually reduced. Instant t1~
During t2, the slip ratio is a value between Sl1 and S+z, and its rate of change is between 0 and 521, and as is clear from FIG. 9, it is in the slow pressure increase area. Therefore, the brake fluid pressure of both drive wheels is slowly increased by the above action, and the braking force of these drive wheels is gradually increased. Between instants t2 and t3, the slip rate is between Sth+31■ and the rate of change is S21 or higher, or the slip rate is SIz or higher and the rate of change is positive, so as is clear from Figure 9, the rate of change increases rapidly. In the pressure area.

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

Between instants t and t4, the slip ratio is 81■ or more and the rate of change is between 0 and &2■, and as is clear from Fig. 9, it is in the slow pressure increasing area, and the slip ratio of both drive wheels is Gradually increase braking force. Between instants t4 and t5, the slip rate is S. and 31■, and the rate of change is 0 and 82■
As is clear from FIG. 9, it is located in the holding pressure area. Therefore, the brake fluid pressure of both drive wheels is maintained at {i4 at instant t4 due to the above-mentioned action, and the braking force of these drive wheels is maintained.

After the instant t, the same area determination based on FIG. 9 is performed,
The brake fluid pressure of both drive wheels is controlled according to the determination result, and the pressure is maintained between instants t and t6, the pressure is slowly increased between instants t6 and L, the pressure is maintained between instants t and t8, and after instant t8. and 11M pressure are carried out, respectively.

Therefore, traction control is performed by the drive wheel brake fluid pressure control corresponding to FIG. 9, and drive slip of the drive wheels can be prevented.

However, since the control mode 4B in Fig. 9 determines the rate of brake fluid pressure increase and decrease depending on the slip ratio and its rate of change, it is difficult to prevent slippage in situations where large drive slips or sudden drive slips occur. In order to prevent unnecessary braking, the braking speed of the drive wheels can be increased to compensate for the occurrence of this problem, to prevent a decline in traction control performance, or the brake release speed can be increased to match the fact that the drive slip due to braking is quickly settled, to prevent unnecessary braking. can. On the other hand, drive slip is small,
Moreover, in situations where the slip occurs slowly, the braking speed may be slowed down to compensate for the occurrence of slip to prevent unnecessary braking, or the braking release speed may be slow to accommodate the slowness of the drive slip due to braking. It is possible to prevent deterioration of traction control performance.

(Effects of the Invention) Thus, as described above, the traction control H of the present invention reduces the pressure reduction speed of the brake fluid pressure to a value lower than normal while the drive wheel brake fluid pressure PBL (PIR) is low (
(see steps 663, 668 to 672), the brake fluid pressure does not drop to Okgf/cm2 during the pressure reduction cycle in this low brake fluid pressure state. Therefore, it is possible to avoid inconveniences such as the brake fluid pressure being increased from 0 kgf/cm'' in the next pressure increase cycle and causing braking noise or vertical vibration of the vehicle body.

[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 6 are flow charts showing the control program of the microcomputer in the same example; Figure 7 shows the throttle opening M? for traction control used in the same example. II muff diagram, Figure 8 is a map of throttle valve opening versus accelerator pedal depression used in the same example, Figure 9 is a region map of driving wheel brake fluid pressure control used in the same example, and Figure 10 is Figure 2 shows the ON/OFF diagram of the pump, Figures 11 to 13 are waveform diagrams of the solenoid valve drive duty in the device shown in Figure 2, and Figure 14 is an operation time chart of the traction control by the device of the present invention. be. LL, IR... Driven wheel 2L, 2R...
Drive wheel 4... Throttle valve 5... Step motor 6... Accelerator pedal 8
...Throttle sensor 9...Accelerator sensor 10
...Microcomputer I1...A/D converter 12...F/V converter I3...Motor drive circuit 14...D/
A converter 20...brake pedal 2l...brake master cylinder 22L. 22R, 23L, 23R...Wheel cylinder 24L, 24R...Liquid pressure control valve 40L,
40R...Solenoid valve 43...Accumulator 4
5... Bomb 47... Pressure switch 50L. 50R, 51L, 51R...Wheel rotation sensor 60L, 60R...Pressure sensor Fig. 1 Fig. 10 Fig. 8 Accelerator pedal glance amount ACC Fig. 14

Claims (1)

[Scope of Claims] 1. A hydraulic pressure source for traction control is provided, and when a drive slip occurs in a wheel, the drive slip is suppressed by supplying the hydraulic pressure of the hydraulic pressure source to the drive wheel as brake fluid pressure, In a vehicle equipped with a traction control device that repeats a cycle of reducing brake fluid pressure to drive wheels when suppressing drive slip, the present invention includes a pressure sensor that detects the brake fluid pressure, and a pressure sensor that reduces the brake fluid pressure while the brake fluid pressure is low. A traction control device for a vehicle, comprising a decompression speed reduction means for reducing speed.