JP2636360B2 - Vehicle traction control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a traction control device for a vehicle which prevents a wheel drive slip (wheel spin).

(Prior Art) As a conventional example of a traction control device for a vehicle, as described in Japanese Patent Application Laid-Open No. 60-179363, for example, a wheel rotational angular acceleration obtained from a wheel rotational angular speed detected at the time of occurrence of a drive slip is a predetermined value (threshold). When the pressure is less than the above, there is one configured to hold (hold) the brake pressure.

(Problems to be Solved by the Invention) However, in the above conventional example, when an appropriate engine torque is obtained by a throttle opening control or the like according to a road surface condition at the time of occurrence of a drive slip, a difference between a drive wheel speed and a driven wheel speed is obtained. When the deceleration is small and the rate of change is negative, a pressure-holding state is established during deceleration. If this pressure-holding state continues for a long time, the throttle opening and the braking force are balanced in that state, and the braking force should be The braking force will continue to be applied even though it is not necessary to apply the braking force. As a result, the lateral force of the tire may decrease over time due to the drive slip caused by the continuation of the braking, and the vehicle traveling direction may be inclined in this direction.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problem by changing the pressure-holding command to a pressure-increasing command for the minimum unit time of the braking control when the duration of the brake-pressure-holding command exceeds the continuation upper limit time.

(Means for Solving the Problems) For this purpose, the traction control device of the present invention travels by driving wheels by power from an engine, as shown in the concept of FIG. In a vehicle in which the wheels are braked by a pressure reduction, pressure holding, pressure increase command with respect to the brake pressure of the brake command means to prevent the drive slip of the wheels, a brake pressure holding pressure command continuation time by the brake command means is measured. And a braking command changing means for changing the holding pressure command to a pressure increasing command for a minimum unit time of the braking control by the braking means when the time exceeds the brake pressure holding command continuation upper limit time. It is characterized by becoming.

(Operation) The vehicle runs by driving the wheels with the power from the engine. Here, when the wheels generate a drive slip, the braking means brakes the wheels based on the pressure reduction, holding pressure, and pressure increase commands with respect to the brake pressure of the brake command means, thereby preventing the drive slip of the wheels.

On the other hand, the timing means measures the duration of the brake pressure holding command by the braking command means, and the braking command changing means, when the time exceeds the brake pressure holding command continuation upper limit time, sends the pressure command to the braking means. Is changed to the pressure increase command only for the minimum unit time of the braking control by.

Therefore, even during deceleration when the difference between the drive wheel speed and the driven wheel speed is small and the rate of change is negative, the brake pressure is maintained for a time until the brake pressure maintenance command continuation upper limit time is reached. Since the pressure is increased only for the minimum unit time of the braking control by the braking means, that is, the pressure is gradually increased, the throttle opening and the braking force are balanced by the gentle pressure increase to escape from a state where the braking is continued. Thus, the problem that the lateral force of the tire decreases with time due to the drive slip caused by the continuation of the braking and the vehicle traveling direction is inclined in this direction can be solved.

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

FIG. 2 is a system diagram showing an embodiment of the traction control device of the present invention, wherein 1L and 1R denote left and right driven wheels (for example, left and right front wheels), and 2L and 2R denote left and right driving wheels (for example, left and right rear wheels). The vehicle travels by being driven by an engine having wheels 2L and 2R shown in the figure, and the engine is controlled in output by a throttle valve 4.

The throttle valve 4 is opened and closed by a step motor 5, and the number of steps (opening degree of the throttle valve 4) is controlled so as to basically correspond to the depression amount of the accelerator pedal 6 depressed by the driver except during traction control. It is controlled by the circuit 7. For this purpose, a signal TH from a throttle sensor 8 for detecting 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 an accelerator sensor 9 for detecting the depression amount Acc of the accelerator pedal 6. Is input to the control circuit 7.

The control circuit 7 comprises a microcomputer 10 and has an A / D converter 11 and an F / V converter 12 in connection with its input side, and a drive circuit 13 and a D / D converter for the step motor 5 in connection with its output side. A converters 14 are provided respectively. The A / D converter 11 converts the throttle opening signal TH and the accelerator signal Acc from analog to digital and inputs them to the microcomputer 10, and converts the voltage signal subjected to frequency-voltage conversion by the F / V converter 12 to a digital signal. Input to microcomputer 10.

Each wheel 1L, 1R, 2L, 2R are equipped wheel cylinders 22L which is operated by the liquid pressure P _M from the brake master cylinder 21 according to the depression force of the brake pedal 20, 22R, 23L, the 23R, operation of these wheel cylinder , The corresponding wheels are individually braked. Thus, hydraulic control valves 24L, 24R for traction control are inserted into the brake hydraulic systems of the drive wheels 2L, 2R, respectively. These hydraulic pressure control valves have the same specifications and the same structure, respectively. The spool 25 is elastically supported by a spring 26 at the leftmost position shown, and the plunger 27 is elastically supported by a spring 28 at the leftmost position shown. .

Hydraulic pressure control valve 24L, 24R are each, is output from the outlet port 30 as the wheel cylinder side hydraulic P _M to the master cylinder side of the inlet port 29 in the normal state shown in the corresponding wheel cylinder, the right line of the spool 25 The time plunger 27 shuts off the port 29, 30 and raises the hydraulic pressure to the wheel cylinder to maintain the rising hydraulic pressure of the wheel cylinder when the spool 25 stops rightward.

The rightward movement of the spool 25 and the stop thereof are controlled by the pressure in the chamber 31, and this pressure is individually controlled by the solenoid valves 40L and 40R, respectively. The same applies to these solenoid valves. When the solenoid 41 is turned off (A), the connection position between the ports shown in FIG.
1 is connected to the drain circuit 42 and cut off from the accumulator 43, and when the solenoid 41 is turned on by a small current (ON), it becomes the connection position between the ports shown in (B), and the chamber 31 is cut off from both the drain circuit 42 and the accumulator 43, When the solenoid 41 is turned on by a large current, it becomes the connection position between the ports shown in FIG.
From the drain circuit 42 and to the accumulator 43.

At the position (A) of the solenoid valves 40L and 40R, the chamber 31 is in a non-pressure state, the spool 25 is brought to the position shown in FIG.
In the position, the chamber 31 is supplied with the constant value Pc of the accumulator 43 to make the spool 25 move rightward in the drawing, and the solenoid valves 40L and 40R (B)
In this position, the supply / discharge of the pressure to the chamber 31 is stopped, and the spool 25 is held at the current right-hand position.

A pump 45 driven by a motor 44 is provided in the accumulator 43.
Is accumulated through the check valve 46, and when the accumulated pressure value of the accumulator 43 becomes a constant value Pc, this is detected and OF
The control circuit 7 stops the motor 44 (pump 45) in response to a signal from the pressure switch 47 which performs F. For this purpose, a signal from the pressure switch 47 is input to the microcomputer 10, and a 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 solenoids 41 of the solenoid valves 40L, 40R are also driven and controlled by the microcomputer 10, and control signals for the solenoids are converted into analog signals by the D / A converter 14 and supplied to the solenoids 41.

Wheel rotation sensor 50 associated with each wheel 1L, 1R, 2L, 2R, respectively.
L, 50R, 51L, the provided 51R, these sensors emit wheel speeds V _FL of the corresponding wheel, V _FR, V _RL, a pulse signal of a frequency corresponding to V _RR, provide these pulse signals to the F / V converter 12 I do. F
The A / V converter 12 converts each pulse signal into a voltage corresponding to the frequency (wheel speed) and inputs the voltage to the A / D converter 11, and the A / D converter 11 converts these voltages into digital signals and converts them into digital signals. Input to the computer 10.

The microcomputer 10 executes the control programs shown in FIGS. 3 to 6 based on various types of input information to perform the normal opening control of the throttle valve 4 and the opening control for traction control, and to control the solenoid valve solenoid 41. , That is, braking control for traction control of the drive wheels, and further, drive control of the pump motor 44 (hydraulic pump 45). 3 to 5 show a constant period ΔT after the engine is started by an operating system (not shown).
FIG. 6 shows a main routine in which a periodic interrupt process is performed every (for example, ΔT = 10 msec). FIG. 6 shows a step motor driving OCI which is processed in a cycle corresponding to the rotation speed of the step motor 5 determined in the main routine. (Output co
mpare interrupt) Indicates interrupt processing.

In FIG. 3, first, in steps 101 and 102, the microcomputer 10 initializes (initializes) the built-in RAM and the like only for the first processing. In the next step 103, the wheel speeds V _FR , V _FL , V _RL , V _RR are read, and based on these, in step 104, the slip ratios S _L , S _R of the left and right driving wheels 2L, 2R are set to S _L =
(V _RL −V _FL ) / V _FL , S _R = (V _RR −V _FR ) / V _FR , and in step 105, the slip rate changing speed _L of the left and right driving wheels 2L, 2R _L = S _L −S _{L -1} (where _SL-1 is the previous left driving wheel slip ratio) and _R = S _R -SR _-1 (where SR _-1 is the previous right driving wheel slip ratio).

In step 106, the smaller one of the left and right driving wheel slip rates S _L and S _R is set as the select low slip rate S _min , and the larger one is set as the select high slip rate S _max . Next step
At 107, the smaller value _Smin of the select low slip ratio and the select high slip ratio is set to K (for example, 0.
6-0.9) weighted average value of the slip ratio to be emphasized in the ratio
S _{av is obtained} by S _av = K × S _min + (1−K) × S _max , and the change speed _av is _av = S _av −S _av−1 (where S
_av-1 obtains the previous slip rate weighted average value).

In step 151, based on the slip ratio average value S _av and its change speed _av , based on throttle opening control range data as shown in FIG.
Throttle opening TH to the back toward the value corresponding to the depression amount A _cc of the accelerator pedal 6 (to be increased) uncontrolled area or, (sharp decrease the throttle opening TH) Kyu閉the throttle valve 4 or Yuru閉(Throttle The opening degree TH is gradually reduced) to determine whether it is a rapid closing area or a gentle closing area in which the drive slip of the wheels 2L, 2R is to be prevented or a holding area in which the throttle opening TH is kept constant. The determination result is determined in steps 152 to 154, and the control proceeds to step 201 in the non-control area, to step 301 in the gentle closed area, to step 351 in the sharply closed area, and to step 401 in the holding area.

In the non-control area, in steps 201 to 206, step 20
4 is cleared in step 20 each time showing a map up counter MAPUPC a certain recovery time T _R to be incremented (increment) at step 203 or 205, for each ie T _R Time
The throttle opening map MAP is changed to the previous map (MAPO) -1 at 6.
After that, the control proceeds to step 401. Map M
Set 20 different from the 0 th as Figure 8 to the AP until the 19 th, the above map up is a command to increase to a value corresponding to the throttle valve opening degree to the accelerator pedal depression amount A _cc Means that.

When the control has proceeded to step 301 because of the gradual closing area, first, in this step, it is checked which throttle control area was the last time. If it was the last non-control area, the following processing is performed
Do it only once. That is, the map raising counter MAPUPC is cleared in step 302, and in the next steps 303 and 304, both the left or right low pressure flag and the left or right sudden low pressure flag are set to 0.
By determining whether or not the brake fluid pressure of the left and right drive wheels 2L, 2R is checked. As will be described later, these flags become 0 when the brake fluid pressure for traction control of the corresponding left and right drive wheels 2L and 2R is low for a predetermined time or more and is rapidly reduced for a predetermined time or more. If it is in the state, the number of map drops MAPDN is set to 1 in step 305, and otherwise, MAPDN = 2 is set in step 306. In step 307, the previous map
MAP0 a predetermined time which has been memory as described later (T _M or
T _M ′) The larger of the previous map number PMAP (the smaller the throttle opening) is set as the select high map MAPMAX, and in step 308 this select high map MAPMAX is mapped by the number MAPDN determined in step 305 or 306. What was dropped (MAPMAX + MAPDN) was set as the map MAP this time,
Command the slow opening and closing of the throttle opening. Step 309,
In 310, when the above MAP is equal to or less than the initial map MAPINI obtained at the time of the first slow-closed area from the non-control area, it means that a command to increase the throttle opening is given. MAPINI.

If it is determined in step 301 that the previous time is a gentle closed area or a rapid closed area, the control proceeds directly to step 401, and if it is a previous holding area, the previous map MAP0 is set to 1 in step 311.
The control is advanced to step 401 after instructing the throttle opening range as the current map MAP with the map dropped this time.

If the control has proceeded to step 351 due to the sudden closing area, first, the previous throttle opening control area is checked here. If the previous time was in the non-control range, the same processing as in steps 302 to 310 is performed in steps 352 to 360, and in step 362, 2 is further added to the map obtained by this processing to instruct the throttle opening to sharply decrease. Control proceeds to step 401.

If it is determined in step 351 that the area was abruptly closed from the previous time, the control proceeds directly to step 401.
After performing the same processing as described above, the control proceeds to step 401.

If the control proceeds to step 401 because of the holding range (the same applies after the processing for the non-control range, the gradual pressure increase range, and the rapid pressure increase range), step 4
When the MAP value falls outside the range of the set map numbers 0 to 19 shown in FIG. 8 from 01 to 404, the MAP value is set to the closer limit value 0 or 19. In the next steps 405 and 406, the brake hydraulic pressure state of the left and right driving wheels 2L and 2R is checked based on whether both the left and right low pressure flags are not 0 and whether both the left and right sudden low pressure flags are not 0. If the pressure is not increased (if the pressure is reduced), the throttle slow-closing and rapid-closing control (step 407) is performed using the throttle control map corresponding to the predetermined time T _M before as the PMAP in step 407 (step
307, 357), if the pressure is increasing, the map before the predetermined time T _M ′ longer than T _M is set as PMAP in step 408. In the next step 409, the current map MAP is stored as the previous map MAP0 and prepared for the next time.

After the above processing shown in FIG. 3, the control proceeds to the step shown in FIG.
Proceeds to 502, reads the accelerator pedal depression amount A _CC here. In the next step 503, the map M obtained as described above
Based on the opening characteristic map corresponding to the AP, the target step number S of the step motor 5 corresponding to the accelerator pedal depression amount A _CC
Determine TEP by searching the map.

In step 504, the difference Dif between the target opening step number STEP of the throttle valve 4 determined in step 503 and the actual opening step number TH is calculated by Dif = STEP-TH. Further, in steps 505 and 506, the speed of the step motor 5 is determined, forward rotation / reverse rotation / holding is determined based on the above-mentioned deviation Dif, and further, an OCI interrupt cycle is set, and a flag is set for the motor rotation direction.

Thereafter, in steps 601 to 693, the left driving wheel is braked and released for traction control at an appropriate speed as follows (the right driving wheel is also described later in step 69).
Braking and braking release are similarly performed at 5,696). Step 601
Based on the table data corresponding to FIG. 9, the left drive wheel brake fluid pressure should be rapidly increased, gradually increased, maintained, or gradually reduced based on the left drive wheel slip ratio _SL and its change speed _L. Area (area) to be decompressed or depressurized
judge. The table data in FIG. 9 is a control mode of the left driving wheel brake hydraulic pressure suitable for traction control.
Slip ratio S _L (S _11, S ₁₂ is the area boundary value) and its change rate _{L (21,} 0, ₂₂ the area boundary value) boosts fast higher, lower slip ratio S _L and the change rate _L The pressure should be reduced at a higher speed. Note Figure 9 is also a right drive wheel brake fluid pressure control mode will be described later, thus also the right driving wheel slip ratio S _R and its change rate _R are also shown.

The above area determination result is determined in steps 602 to 605, and the process branches to the corresponding step in FIG. That is, if the area is a sudden increase in pressure, step 611 is performed.
The control proceeds to step 655 for the pressure holding area, to step 661 for the gentle pressure reduction area, or to step 681 for the rapid pressure reduction area.

When step 611 is selected for the rapid pressure increase area, first, the slow pressure reduction counter, the rapid pressure reduction counter, the slow pressure increase counter, the holding counter, and the promotion counter that are not involved in the rapid pressure increase are cleared, and the no control flag is set. Set to 1. In the next step 612, the previous area is checked, and if it was the previous pressure reduction area, the loop through step 614 is executed only once, and if it was the previous pressure increase or pressure holding area, the loop 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 0, that is, whether the rapid pressure reduction has been performed for a predetermined time or more. If it was in the rapid pressure reduction state last time, the initial pressure increase counter is incremented in step 615 because it is necessary to execute the initial pressure increase faster than the rapid pressure increase to eliminate the response delay. Then, in step 691, solenoid valve 4
Set 0L to the C position. At this solenoid valve position, the hydraulic pressure control valve 24L raises the left driving wheel brake hydraulic pressure by the rightward movement of the spool 25 in FIG. 2 to brake the left driving wheel for traction control. If the low pressure flag is not 0 or the sudden low pressure flag is not 0, the initial pressure increase is unnecessary, so that the rapid pressure increase counter is incremented in step 616 and step 691 is executed.

Thereafter, step 612 selects step 618, in which the low pressure flag is set to 1. Step 61
At 9,620, it is checked whether the initial pressure increase counter is 4 or 0. If step 615 is executed, step 61 is executed.
The pressure increase is repeated in step 691 while repeating the path of 9,620,621 three times, and next step 619 selects steps 622 and 623, and then step 619 selects steps 620 and 623. In step 623, it is checked whether or not the rapid pressure increase counter is 5, and in step 624, it is checked whether or not the rapid pressure increase counter is 0 or 1. If step 616 has not been executed, the path of steps 623, 624, 627 is repeated twice, and the pressure is increased by executing step 691 each time.
If step 616 has been executed, the above path is selected only once, and pressure is increased by executing step 691. After that, step 624 will select step 625,
The solenoid valve 40L is set to the B position by executing step 692 only three times until the rapid pressure increase counter reaches 5. At this solenoid valve position, the hydraulic pressure control valve 24L stops the movement of the spool 25 and maintains the left drive wheel brake hydraulic pressure at the value at this time. Thereafter, the left drive wheel brake fluid pressure can be rapidly increased at a speed corresponding to the duty (duty of 2/5) for which the rapid pressure increase counter is 1, 2 for pressure increase and 3 to 5 for holding pressure.

The above-described rapid pressure increasing operation will be described with reference to FIGS. 11 to 13.

Assuming that switched to rapid increase area from vacuum area instantaneously t ₁ at low pressure flag = 1 or sudden low flag = 1 state as shown in FIG. 11 (a), up to instant t ₁ corresponds to the low-pressure flag = 1 As will be described later, gentle depressurization is performed at 1/5 duty in which 50 msec is defined as one cycle and pressure is reduced by 10 msec. Instantaneous t ₁
First, the loop of steps 614-616-691 is selected once, then the loop of steps 618-619-620-623-624-627-691 is selected once, and then the steps 618-619-620-623 are selected.
By selecting the loop including −624−625−692 three times, the pressure can be rapidly increased at 2/5 duty as shown by the dotted line in FIG. 11 (a).

Assuming that switched to rapid increase area from vacuum area instantaneously t ₁ in the state of FIG. 11 low as shown in (b) flag = 0 and rapid low flag = 0, until instant t ₁ low flag = 0 and sudden low Duty 10 corresponding to flag = 0 as described later
0% rapid decompression is continued. Step in an instant t ₁ 614-61
3-615-691 loop is selected once, then step 6
18-619-620-621-691 loop is selected three times, then the result of the loop of steps 618-619-622-623-624-627-691 is selected twice, the instant t ₁ 4 times ([Delta] T × 4
(= 40 msec) to eliminate the response delay by performing an initial pressure increase faster than the rapid pressure increase, and then increase pressure twice (ΔT × 2 = 20 msec) as shown by the middle dotted line in FIG. 11 (b). Thereafter, the same rapid increase in pressure by 2/5 duty as described above can be executed.

It should be noted that, as is apparent from the above-described process, the pressure is rapidly increased by 2/5 duty as shown in FIG. 12 (a).

When step 631 in FIG. 5 is selected for the slowly increasing pressure area, first, the unrelated slow pressure reduction counter, the rapid pressure reduction counter, the holding counter, and the promotion counter are cleared, and the no control flag is set to 1. I do. In the next step 632, the previous area is checked, and if it is the previous decompression area, the loop including step 634 is executed only once,
If it was the pressure increase or pressure holding area last time, a loop including step 638 is executed. In the former loop, steps 634,633,
In steps 635, 636, the same processing as in steps 614, 613, 615, 616 is performed, but in step 636, the slow pressure increasing counter in step 616 is incremented by a slow pressure increasing counter. Steps 638, 639, 640, 641, 642 also perform the same processing as steps 618, 619, 620, 621, 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,
In order to set a waiting time for the switching, it is checked whether the above-mentioned rapid pressure increase counter is 5 or 0, or other than these. When the rapid pressure increase counter is other than 0,5, that is, during the rapid pressure increase, the pressure is maintained in step 692 while incrementing the rapid pressure increase counter in step 649, and when the rapid pressure increase counter reaches 5, the flow proceeds to step 644. After resetting this counter, if the rapid pressure increase counter is 0, step
Slow pressure increase control by 645, 646, 647, 650, 651 is performed. This gradual pressure increase control is the same as the rapid pressure increase control in steps 623, 624, 625, 626, and 627, except that in step 646 corresponding to step 624, pressure increase is performed only when the gradual pressure increase counter is 0, so that 1 / The pressure can be increased slowly with 5 duties.

The operation of the gradual pressure increase will be described with reference to FIGS. 11 to 13.

Figure 11 (a), instant t ₁ after the (b), but switched to the pressure increase from the pressure reduction is carried out in the same manner as surge pressure time, because as the duty of the small, increased as shown in these diagrams the solid lines The pressure time is reduced to 10 msec, enabling a gradual increase in pressure.

Note that, as is apparent from the above-described process, the pressure is gradually increased at a 1/5 duty as shown in FIG. 12 (b).

Further If switched to rapid increase area from Yuruzo圧area instantaneously t ₁ as shown in Figure 13 (a), even immediately surge pressure is started, the instant t _1, as shown in FIG. (B) If the pressure is switched from the rapid pressure increase area to the slow pressure increase area, steps 643, 64
Unnecessary braking can be prevented by delaying the start of gentle pressure increase by the waiting time Δt by the loop including 4,648,649,692.

When step 655 in FIG. 5 is selected for the pressure holding area, first, the initial pressure increasing counter, the rapid pressure increasing counter, and the slow pressure increasing counter are respectively cleared, and in the present invention, the holding counter is reset in the next step 657. Determine whether or not 9
If it is not 9, the holding counter is incremented in step 658, and in step 692, the solenoid valve 40L is kept at the B position.
As a result, the left drive brake fluid pressure can be maintained at the value at this time as required. On the other hand, when the holding counter reaches 9, the control proceeds from step 657 to step 659 to clear the holding counter, and then the pressure is increased in step 691.

The gradual pressure increase effect by the combination of the above pressure holding and pressure increasing will be described with reference to FIG. 14. When the holding counter acting as a timer for counting the duration of the brake pressure holding command is 0 to 8 (continuous upper limit time). The loop of steps 657-658-692 is selected to hold the pressure, and when the holding counter is 9, step 65
The loop of 7−659−691 is selected and the pressure is increased only by 1/10 duty to increase the pressure by the minimum unit time of the braking control by 10 msec. A decrease in force can be prevented.

When step 661 in FIG. 5 is selected for the slow pressure reduction area, first, the slow pressure increase counter, the rapid pressure increase counter, the holding counter, and the initial pressure increase counter are cleared. In the next step 662, it is checked whether or not the rapid pressure reduction flag has been set to 0 to determine if the rapid pressure reduction has been performed for a predetermined time or more. If so, step 664 sets the up / down counter at 6 for the purpose described below.
After the addition, if the pressure has not been rapidly reduced for a predetermined time or more, the control directly proceeds to step 663. After step 663, the pressure reduction speed is gradually increased under the above-mentioned promotion counter as follows, and the pressure reduction is delayed in the process of eliminating the drive slip, and unnecessary braking of the drive wheels and the one-sided braking effect may occur. Not to be.

That is, every time the slow pressure reduction counter becomes 5 in step 663, the promotion counter incremented in step 669 becomes 3
During the following period, the loop of steps 665-666-670-693 is set to 1
Step 665 to set the solenoid valve 40L to the A position (at this solenoid valve position, the fluid pressure control valve 24 reduces the left drive wheel brake fluid pressure by the left row of the spool 25 in FIG. 2), and Steps 665-666-667
The −692 loop is executed four times, and the cycle of setting the solenoid valve 40L to the B position (holding the left driving wheel brake fluid pressure) is repeated four times. Accordingly, as shown in FIG. 12 (c), the pressure reduction is performed at a speed corresponding to 1/5 duty in the initial stage of the promotion counter of 0 to 3.

Thereafter, if the promotion counter is between 4 and 6, steps 668-669
The loop of −670−693 is executed once, and step 665−671−
The loop of 673−670−693 is executed once, and steps 665−67 are performed.
The cycle to execute the loop of 1−673−667−692 three times is 3
Repeat several times. Therefore, as shown in FIG. 12 (c), the pressure of the promotion counter is reduced at a speed corresponding to 2/5 duty between 4 and 6.

Thereafter, while the promotion counter is between 7 and 9, steps 668-669.
The loop of −670−693 is executed once, and step 665−671−
The loop of 672-675-676-670-693 is executed twice, and the loop of step 665-671-672-675-676-667-692 is executed twice.
The cycle of execution is repeated twice. Therefore, during this period
The pressure is reduced at a speed corresponding to 3/5 duty as shown in FIG.

Further, when the promotion counter exceeds 9, steps 665-671
The loop of −672−675−677−693 is repeatedly executed, and pressure reduction is continuously performed with a duty of 100% as shown in FIG. Then, in step 672, the low pressure flag is set to 0 so as to indicate that the gentle pressure reduction has continued for a predetermined time or longer (promotion counter ≧ 7), and in step 677, the no-control flag is reset.

By the way, when step 664 is executed due to rapid pressure reduction for a predetermined time or more before shifting to the gradual pressure increase area, pressure reduction corresponding to the promotion counter 6 is started, and pressure reduction delay can be prevented. .

When step 681 in FIG. 5 is selected for the rapid pressure reduction area, the slow pressure increasing counter, the rapid pressure increasing counter, the holding counter, and the initial pressure increasing counter are cleared here. Then, since the control always reaches step 693, as shown in FIG. 12 (d), the pressure is rapidly reduced by the duty of 100% as required. During this time, it is checked in step 682 whether or not the low pressure flag = 0, that is, whether or not the pressure has been slowly reduced for a predetermined time or longer. If not, it is determined in step 684 whether or not the rapid decompression counter incremented indicates 15 or more. Check in step 683. This step 683 is for checking whether or not the rapid decompression has continued for a predetermined time or more by the rapid decompression counter.
At 5, the rapid low pressure flag is set to 0 to indicate this. In the case where it is determined in step 682 that the low pressure flag = 0, step 6
Step 685 after adding 15 to the rapid decompression counter by 86
Execute Then, in step 687, it is checked whether or not the rapid decompression counter indicates a long-term rapid decompression indicating 30 or more. If so, the increment of the rapid decompression counter in step 684 is stopped, and the no control flag is reset in step 689. I do.

The same control as the above left drive wheel brake fluid pressure (braking) control is also executed for the right drive wheel in steps 695 and 696,
Wheel spin of the drive wheels is similarly prevented. Step 695 corresponds to step 601 in FIG.
Reference numeral 6 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, whether the pressure switch 47 is ON or not is determined by the pressure P _{c of the} suspension accumulator 43.
Check if has reached a predetermined value. Pressure switch 47 has a OFF hysteresis characteristic when the accumulator pressure P _c as Fig. 10 is turned ON when reduced to P ₁ below, it rises to P ₂ or more. When the pressure switch 47 is ON, the pump 45 is driven by turning on the motor 44 in step 702 to increase the accumulator internal pressure _Pc, and when the pressure switch 47 is OFF, the pump 45 is stopped by turning off the motor 44 in step 703 to stop the accumulator internal pressure _Pc. Stop rising _c . Therefore, the predetermined pressure _Pc is always accumulated in the accumulator 43, and the traction control brake fluid pressure increase control can be performed.

Next, the OCI interrupt flowchart for opening and closing the throttle valve in FIG. 6 will be described. This program is repeatedly executed in a cycle such that the step motor speed determined in step 505 in FIG. 4 can be obtained. First, in step 800, whether the step motor 5 should be rotated forward or backward based on the execution result of step 506 in FIG. It should be determined whether to maintain the current position. If it is to be rotated forward, step 801 is performed by one step forward rotation of the step motor 5 in step 801;
Sets the one-step reverse rotation of the step motor 5, and skips steps 801 and 802 if it should be held. 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 corresponding to the calculation result in step 503 in FIG.

Hereinafter, the operation of the traction control by the throttle opening (engine output reduction) control will be described based on the operation example of FIG. In FIG. 15, the initial map MAPINI is shown in the non-control area where MAP = 0 at first, and then gradually closed.
By the throttle opening control is performed, then the third map raised -1 increments by drawing steps 201 to 206 for the non-control region is made, and that a re-slow closed instantaneously t _1. If the low pressure flag or the sudden low pressure flag is 0 on both the left and right sides, that is, if the traction control brake fluid pressure is reduced for a predetermined time or more, a predetermined time T _M (see FIG. 3) at instant t ₁ as shown in FIG. Step 407) Previous map value P
Processing of FIG. 3 in step 305,307,308 based on MAP is performed once, is instantaneously t ₁ hereinafter MAP = MAPMAX + 1. Then, at step 310, MAPMAX + 1 ≦ MAPINI.
As shown by the dotted line in the figure, MAP is set to MAPINI, and throttle slow-close control for traction control based on this is performed.

Incidentally, the left and right both low flag and rapid low pressure flag is 1, that is, when the pressure increasing state for a predetermined time or more of the traction control brake fluid pressure, FIG. 15 (b) the predetermined time T _M 'instant t ₁ as shown in (a Refer to step 408 in 3
T _M ′> T _M ) Steps in FIG. 3 based on the previous map value PMAP
Processing of 306, 307, 308 is performed once, instant t ₁ subsequent MAP = MAPM
AX + 2, and throttle slow closing control for traction control based on this is performed.

In the throttle closing control for such traction control, step 154 determines that the area is abruptly closed, and control is performed in step 3.
The same applies when proceeding to 51. However, in this suddenly closed area, execution of step 362 enables rapid closing as requested.

By the way, the above-mentioned predetermined time is changed as T _M , T _M ′ according to the drive wheel brake fluid pressure control state for traction control (low pressure flag and sudden low pressure flag).
The predetermined time does not become inappropriate due to a difference in the traction control braking state, and is always maintained appropriately.

Next, traction control by the drive wheel braking control of the present invention will be described based on the operation example of FIG. In this operation example, the left and right drive wheels are synchronized and the wheels spin about the same,
The description will be made assuming that both drive wheels are simultaneously brake-controlled in the same manner.

Until instant t ₁ is the slip ratio S _L (S _R) is in a clear manner gentle vacuum area from FIG. 9 there between the change rate _{L (R)} is 0 and ₂₁ and less than S _11. Therefore, the brake fluid pressure of both drive wheels is slowly reduced by the above-described action,
The braking force of these drive wheels is gradually reduced. Instant t ₁ ~t ₂ between the slip ratio at a value between S ₁₁ and S _12, the change rate of 0 and ₂₁
And is in the gradual pressure increase area as is apparent from FIG. Therefore, the brake fluid pressure of both drive wheels is gradually increased by the above-described operation, and the braking force of these drive wheels is gradually increased. Between the instants t _{2 and} t ₃ , the slip rate is a value between S ₁₁ and S ₁₂ , and the change rate is ₂₁ or more, or the slip rate is S ₁₂ or more and the change rate is positive. It is in a sudden pressure increase area. Therefore, the brake fluid pressure of both drive wheels is rapidly increased by the above-mentioned action, and the braking force of these drive wheels is rapidly increased. During instant t ₃ ~t ₄ is slip ratio is in Yuruzo圧area as a value is clear from Figure 9 between the change rate of 0 and ₂₂ in S ₁₂ above, the two drive wheels Gradually increase braking force. During instant t ₄ ~t ₅ is slip ratio is a value a is and clear pressure-holding area as from Figure 9 A between the change rate of 0 and ₂₂ between S ₁₁ and S _12. Therefore, the brake fluid pressure of both drive wheels are pressed coercive the value of the instantaneous t ₄ by the action, it holds the braking force of the drive wheels.

Instantaneous t ₅ later a similar area determination based on FIG. 9,
Determination result brake fluid pressure control of both drive wheels in response to is made, instantaneous t ₅ ~t ₆ between the pressure-holding, instant t ₆ ~t ₇ between the Yuruzo圧instantaneous
During t ₇ ~t ₈ is holding pressure, instant t ₈ thereafter slow decompression are respectively executed.

Accordingly, 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. Further, the control mode of FIG. 9 determines the pressure increase and decrease speeds of the brake fluid pressure according to the slip ratio and the change speed thereof. Therefore, in a situation where a large drive slip or a sudden drive slip occurs, the slip may be generated. Therefore, the braking speed of the drive wheels can be increased to prevent the traction control performance from deteriorating, and the braking release speed can be increased in accordance with the quick elimination of the drive slip due to the braking, thereby preventing unnecessary braking.
On the other hand, in a situation in which the drive slip is small and occurs slowly, the braking speed may be reduced to prevent unnecessary braking to match the occurrence of the slip, or the drive slip due to braking may be slowed down. At the same time, the braking release speed is also slowed, so that a decrease in traction control performance can be prevented.

(Effect of the Invention) As described above, the traction control device of the present invention, when the brake pressure holding command continuation time exceeds the brake pressure holding command continuation upper limit time, applies the pressure holding command to the minimum value of the braking control by the braking means. Since the pressure is changed to the pressure increase command for the unit time and the pressure is gradually increased, the throttle opening and the braking force are balanced by the slow pressure increase, and it is possible to escape from a state in which the braking is continued. It is possible to prevent the lateral force of the tire from decreasing with the lapse of time due to the drive slip caused by the continuation, thereby ensuring the running stability of the vehicle.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of the traction control device of the present invention, FIG. 2 is a system diagram showing one embodiment of the device of the present invention, FIGS. 3 to 6 are flowcharts showing control programs of the microcomputer in the example. 7 is a map of a throttle opening control for traction control used in the example, FIG. 8 is a map of a throttle valve opening with respect to an accelerator pedal depression amount used in the example, and FIG. 9 is a drive used in the example. FIG. 10 is an ON / OFF diagram of the pump in FIG. 2, FIG. 11 to FIG. 14 are waveform diagrams of solenoid valve drive duty in the apparatus of FIG. 2, respectively. FIG. 15 and FIG. 16 are operation time charts of traction control by the device of the present invention. 1L, 1R ... driven wheel, 2L, 2R ... drive wheel 4 ... throttle valve 5 ... step motor, 6 ... accelerator pedal 8 ... throttle sensor 9, 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

Claims (1)

(57) [Claims] The vehicle travels by driving the wheels with the power from an engine, and when a driving slip of the wheels occurs, the braking means brakes the wheels in accordance with pressure reduction, pressure holding, and pressure increase commands with respect to the brake pressure of the brake command means. A vehicle for preventing wheel drive slip; a timer for measuring the duration of the brake pressure holding command by the braking command means; and when the time exceeds the brake pressure holding command continuation upper limit time, the holding is performed. A traction control device for a vehicle, comprising: braking command changing means for changing a pressure command to a pressure increasing command for a minimum unit time of braking control by the braking means.