JP2629303B2 - Vehicle traction control device - 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

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).

2. Description of the Related Art As a conventional example of a traction control device for a vehicle, as described in Japanese Patent Application Laid-Open No. 60-143135, for example, a traction control is performed by braking a driving wheel when a driving slip of a wheel occurs to suppress a driving wheel torque. In some cases, slip is reduced and the differential limiting torque is increased to lock the operation limiting clutch.

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

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problem by making the differential limiting torque variable according to a braking state for preventing driving slip of the left and right driving wheels.

(Means for Solving the Problems) For this purpose, the traction control device of the present invention travels by driving wheels by the power from an engine as shown in the concept of FIG. Traction control braking means provided individually for the wheels brakes the wheels to prevent the wheels from slipping, and clutch control means controls the differential limiting torque of the differential limiting clutch provided between the wheels. A braking state detecting means for respectively detecting a braking state of the left and right driving wheels by the braking means; and a differential limiting torque control condition by the clutch control means according to the braking state. Control condition changing means for changing so that the differential limiting torque decreases as the torque increases. Those were.

(Operation) The vehicle runs by driving the wheels with the power from the engine. Here, when a wheel generates a driving slip, the braking means brakes the driving wheel, thereby preventing the driving slip of the wheel.

On the other hand, the braking state detecting means detects the braking states of the drive wheels by the braking means, respectively, and in accordance with these detection results, the control condition changing means sets the differential limiting torque control condition by the clutch control means as the difference between the left and right braking forces increases. Change so that the differential limiting torque decreases. Therefore, split μ
It is possible to prevent the differential limiting control effect from being duplicated and becoming excessive when a drive slip occurs during road running or turning running, and to improve the running stability of the vehicle by maintaining a balance between left and right driving forces. be able to.

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 driving wheels 2L and 2R by an engine (not shown), 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 relation to its input side, and a drive circuit 13 and a D / D converter for the step motor 5 in relation to its output side. A converters 14 are provided respectively. The A / D converter 11 has a throttle opening signal TH and an accelerator signal Acc.
To analog-digital conversion to a microcomputer 10
At the same time, the voltage signal subjected to the frequency-voltage conversion by the F / V converter 12 is converted into a digital signal and input to the 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 ports 29 and 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 moving to the right.

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 communicates with the drain circuit 42 and is cut off from the accumulator 43. When the solenoid 41 is turned on by a small current, it becomes the connection position between the ports as shown in FIG. 2B, and the chamber 31 is cut off from both the drain circuit 42 and the accumulator 43. At the time of ON due to the large current of 41, the connection position between the ports shown in (C) is
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 and moves the spool 25 rightward in the drawing, and in the position (B) of the solenoid valves 40L and 40R, the supply and discharge of the pressure is stopped and the spool 25 is In the right row position of.

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, which converts these voltages into digital signals and converts them into a microcomputer. Enter 10

Further, in the present invention, a differential limiting clutch (wet multi-plate friction clutch) 55 is provided between the drive wheels 2L and 2R, and these drive shafts are provided.
Limit the differential between 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,
It is engaged by the control oil pressure supplied from the hydraulic pump 45 to increase the differential limiting torque. When the solenoid 56a is not driven, the solenoid proportional pressure reducing valve 56
_Drains the clutch pressure P _cr and supplies the driving current I _c to the solenoid 56a, and the accumulator 43 is generated by the hydraulic pump 45.
The differential pressure limiting torque is increased in proportion to the clutch pressure P _cr by increasing the clutch pressure P _{cr according} to the exciting current I _c using the constant pressure P _c accumulated in the clutch pressure as the base pressure.

The solenoid 56a of the pressure reducing valve 56 is also a microcomputer 10
The control signal (I _c ) for that is converted into an analog signal by the D / A converter 14 and the solenoid 41
To supply. The input to the microcomputer 10 for the differential limiting torque control is the wheel speeds V _FL , V _FR , V _RL ,
V _RR shall be diverted.

The microcomputer 10 executes the control programs shown in FIGS. 3 to 7 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. Position control, that is, braking control for traction control of the drive wheels, drive control of the pump motor 44 (hydraulic pump 45), control of the pressure reducing valve solenoid 56a,
That is, differential limiting torque control is performed. FIGS. 3 to 6 show a main routine in which an interrupt processing is performed at regular intervals ΔT (eg, ΔT = 10 msec) after the engine is started by an operating system (not shown), and FIG. 7 is determined in the main routine. 5 shows an OCI (Output compare interrupt) interrupt process for driving the step motor, which is processed at a cycle corresponding to the rotation speed of the step motor 5.

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 the change speed av thereof, based on throttle opening degree control range data as shown in FIG. 8 suitable for traction control,
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 (MAP0) -1 by 6
After that, the control proceeds to step 401. Map M
AP sets the 20 different from the 0 th as Figure 9 until 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 gradually reduced for a predetermined time or more and rapidly reduced for a predetermined time or more. If so, at step 305, the number of map omissions MAPDN is set to 1, otherwise, at step 306, MAPDN = 2 is set. 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 reduction to be the map MAP that has just been dropped.

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. 9 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.
Proceed to 502, where the accelerator pedal depression amount Acc is read. In the next step 503, the map M obtained as described above
Based on the opening characteristic map corresponding to the AP, the target number of steps S of the step motor 5 according to the accelerator pedal depression amount Acc
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
Now, based on the table data corresponding to FIG. 10, the left drive wheel brake fluid pressure should be rapidly increased, slowly 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. 10 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 FIG. 10 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, and the promotion counter that are not involved in the rapid pressure increase are cleared, and the non-control flag is set to 1. I do. In the next step 612, the previous area is checked, and if it was the previous pressure reduction area, the loop passing through step 614 is executed only once, and if it was the previous pressure increase or pressure holding area, step 61
Execute the loop through 8. 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. 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 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 value of the sudden pressure increase counter is a predetermined value _TRL described later. In step 624, it is checked whether or not the value of the sudden pressure increase counter is 0 or 1. Step 61
If Step 6 has not been executed, the paths of Steps 623, 624 and 627 are repeated twice, and the pressure is increased by executing Step 691 each time. If Step 616 is executed, the above path is selected only once and Step 691 is selected. To increase the pressure. Thereafter, step 624 selects step 625. When T _RL = 5, the step 692 is executed only three times until the rapid pressure increase counter reaches 5, and when T _RL = 7, the rapid pressure increase counter is 7 times. The position of the solenoid valve 40L is set to the B position by executing step 692 only five times until the time becomes. 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 driving wheel brake fluid pressure is set at a speed corresponding to the duty (duty of 2/5 or 2/7) to be the pressure increase when the rapid pressure increase counter is 1, 2 and the pressure holding when 3-5 or 3-7. Can be rapidly increased.

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

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 Figure 12 (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.
When the loop including −624−625−692 is T _RL = 5, 3 times, T _RL
By selecting five times when = 7, the pressure can be rapidly increased at 2/5 or 2/7 duty as shown by the middle dotted line in FIG. 12 (a).

Assuming that switched to rapid increase area from vacuum area instantaneously t ₁ in a state of low pressure flag = 0 and rapid low flag = 0 as shown in Figure 12 (b), 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. 12 (b). Thereafter, it is possible to execute a rapid pressure increase by the same 2/5 or 2/7 duty as described above.

It should be noted that, as is apparent from the above-described process, the pressure is rapidly increased by 2/5 or 2/7 duty as shown in FIG. 13 (a).

When step 631 in FIG. 5 is selected for the gradual pressure increase area, the irrelevant gradual pressure reduction counter, rapid pressure reduction counter, and promotion counter are first 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 pressure reduction area, the loop including step 634 is executed only once, and if it was the previous pressure increase or pressure holding area, the loop including step 638 is executed. In the former loop, steps 634, 633, 635, 636 perform the same processing as in steps 614, 613, 615, 616,
In step 636, the slow pressure increase counter is incremented in place of the rapid pressure increase counter in step 616.
Also, in steps 638, 639, 640, 641, 642, steps 618, 61
The same processing as in 9,620,621,622 is performed. However, step 638
Then, a process 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, the rapid pressure increase counter checks whether a predetermined value _TRL , which will be described later, is 0 or not. When the rapid pressure increase counter is other than 0 and T _RL , that is, during the rapid pressure increase, while the rapid pressure increase counter is incremented in step 649, the pressure is maintained in step 692, and when the rapid pressure increase counter reaches T _RL , the step is performed. After resetting this counter at 644, if the rapid pressure increase counter is 0, the gradual pressure increase control is performed by steps 645, 646, 647, 650, 651 as it is. This slow pressure increase control is performed in steps 623,624,625,626,
The same as the rapid pressure increase control by 627,
In step 646 corresponding to step (a), the pressure increase is executed only when the slow pressure increase counter is 0, so that the pressure can be gradually increased with a smaller duty (1/5 duty or 1/7 duty) than during the rapid pressure increase.

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

Figure 12 (a), instant t ₁ after the (b), although the switching of the pressure increasing is performed in the same manner as surge pressure time from vacuum, since 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 by a 1/5 or 1/7 duty as shown in FIG. 13 (b).

Further If switched to rapid increase area from Yuruzo圧area instantaneously t ₁ as shown in FIG. 14 (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, the initial pressure increasing counter, the rapid pressure increasing counter, and the slow pressure increasing counter are first cleared here, and then, in step 692, the solenoid valve 40L is maintained at the B position. . As a result, the left drive brake fluid pressure can be maintained at the value at this time as required.

When step 661 in FIG. 5 is selected for the slow pressure reduction area, the slow pressure increase counter, the rapid pressure increase counter, and the initial pressure increase counter are cleared here. Next Step 662
Then, it is checked whether or not the rapid pressure reduction flag is 0 to determine whether or not the pressure has been rapidly reduced for a predetermined time or more. If so, step 66
In step 4, after adding 6 to the promotion counter for the purpose to be described later, if the pressure has not been rapidly reduced for a predetermined time, the control proceeds to step 663 as it is. 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. 13 (c), the decompression 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. 13 (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 thirteenth
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 at 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, first, the slow pressure increase counter, the rapid pressure increase counter, and the initial pressure increase counter are cleared. Then, since the control always reaches step 693, as shown in FIG. 13 (d), a rapid pressure reduction is performed with a duty of 100% as required. During this time, it is checked in step 682 whether or not the low pressure flag is 0, that is, whether or not the pressure has been slowly reduced for a predetermined time or longer.
It is checked in step 683 whether or not it indicates 5 or more. In step 683, the rapid pressure reduction counter checks whether the rapid pressure reduction has continued for a predetermined time or more. If the rapid pressure reduction has occurred for a predetermined time or more, the rapid low pressure flag is set to 0 in step 685 to indicate this. Also in the case where it is determined in step 682 that the low pressure flag = 0, step 685 is executed after adding 15 to the rapid pressure reduction counter in step 686.
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.

Figure 6 during the following step 701 the wheel speed V _RL, V _RR of the driving wheel right wheel speed difference [Delta] V _R is calculated by ΔV _R = V _RR -V _RL, further [Delta] V the value of 1 cycle before the _R [Delta] V _R- the deviation Δ _R of the _{1 Δ
R = | ΔV R -ΔV R-} 1 | by calculating, determining a differential limiting torque T _d based on the [Delta] V _R in step 702 (an example thereof in FIG. 17). Step 703 to 705 makes a determination of the state of the left and right uncontrolled flag in, any of the one requires the differential limiting torque control according to the invention 0, a predetermined value T _SL based on the difference delta _R in step 706 _TSL , _TRL , _TRL
= F (Δ _R ) to determine a value larger than 5, for example, 7.

On the other hand, both the left and right non-control flags are set to 0 in steps 703 to 705.
Alternatively, if both are not 0, the predetermined values T _SL and T _RL are determined to be 5 in step 707 so that the normal differential limiting torque control is performed. The T _SL and T _RL obtained in steps 706 and 707 are the traction control braking control described above (steps 623, 643 and 64).
Use for 5).

In the next steps 708 and 709, the correction coefficient K _T is determined. That is, the correction coefficient K on the basis of the deviation at step 708 delta _R
T (an example of which is shown in FIG. 18 where K _T <1) is determined,
In step 709, _{KT is set} to 1. Based on these K _T , a differential limiting torque command value T is calculated in step 710 by T = _KT · T _d , and in the next step 711 a drive current I _c for obtaining the command value T is determined by an electromagnetic proportional pressure reducing valve. And the differential limiting clutch 55 is operated with a desired differential limiting torque. Note from the left and right wheel speed difference [Delta] V _R takes positive and negative values, the command value T, thus also becomes negative value the drive current I _c, it becomes strengthening the differential limiting respectively corresponding wheel side.

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

In the conventional example, when the torque is evenly distributed to the left and right wheels by the differential device, when the left and right wheels ride on a road surface having a different road surface μ, the tire on the low μ road side slips, and as the slip increases, the wheel slips. The low-μ road side tire torque is transmitted to the high-μ road side (non-slip side) via the differential limiting device.
Transmitted to the tires. Thereafter, in order to suppress the slip, the traction control is activated, and the differential limiting torque applied to the tire increases as shown by the dotted line. (The sum of the torques) acts on the high-μ side tires as a tire driving force and is transmitted to the road surface to generate a turning moment.

On the other hand, in the present invention, before the above-mentioned situation occurs, in order to reduce the increase of the differential limiting torque as shown by the solid line in the drawing, the driving force of the high μ-side tire is only the torque generated by the slip, and the turning moment is reduced. Can be reduced, and the running stability of the vehicle can be improved while maintaining the balance between the left and right driving forces.

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.
6 are those corresponding to the control content of steps 602-693, the T _RL is T _RR of step 623,643, T _SL in step 645
The T _SR, T _SL, T _RL of step 706 and 707 shall be deemed to be replaced in T _SR, T _RR.

Thereafter, in steps 751 to 753, the drive control of the hydraulic pump 45 is performed as follows. In step 751, it is determined whether or not the pressure switch 47 is ON, that is, the pressure of the accumulator 43.
It is checked whether P _c has reached a predetermined value. Pressure switch 47 has a OFF hysteresis characteristic when the accumulator pressure P _c as Figure 11 is ON when reduced to P ₁ below, rises to P ₂ or more. Step 752 when pressure switch 47 is ON
Then, the pump 45 is driven by turning on the motor 44 to increase the accumulator internal pressure _Pc . When the pressure switch 47 is OFF, the pump 45 is stopped by turning off the motor 44 at step 753 to stop the increase of the accumulator internal pressure _Pc . Therefore, accumulator 43
A predetermined pressure _Pc is constantly accumulated in the inside, 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 in FIG. 7 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, the first step forward rotation of the step motor 5 is performed in step 801;
To set the one-step reverse rotation of the step motor 5, and skip 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, it is instantaneously t ₁ following MAP = MAPMAX + 1. Then, due to MAPMAX + 1 ≦ MPAINI, the fifteenth
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-close 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 description will be made assuming that the left and right driving wheels spin in the same manner in synchronization and the two driving 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. 10 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 in the gradual pressure increase area as is clear 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 10 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 A between S ₁₁ and S is a value between ₁₂ and its rate of change 0 and ₂₂ second
As is clear from Fig. 10, it is in the pressure holding area. 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 Figure 10,
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.

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. In addition, the control mode shown in FIG. 10 determines the pressure increase / decrease speed 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 controls the differential limiting torque so as to decrease as the braking force of the left and right driving wheels increases as described above.
When the drive slip occurs during road running or turning, the differential limiting control effect is prevented from overlapping and the differential limiting torque is prevented from becoming excessive. Stability can be improved.

[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 7 are flowcharts showing control programs of the microcomputer in the example, 8 is a map of a throttle opening control for traction control used in the example, FIG. 9 is a map of a throttle valve opening with respect to an accelerator pedal depression amount used in the example, and FIG. 10 is a drive used in the example. FIG. 11 is an ON / OFF diagram of the pump in FIG. 2; FIG. 12 to FIG. 14 are waveform diagrams of the solenoid valve drive duty in the apparatus of FIG. 2; 15 and 16 are operation time charts of traction control by the device of the present invention, and FIGS. 17 and 18 are differential limiting torque and correction in the same example, respectively. FIG. 19 is a graph illustrating the relationship between the coefficient and the difference between the driving wheel left and right wheel speeds. FIG. 19 is a characteristic diagram illustrating the differential limiting torque control characteristic in the example. 1L, 1R ... driven wheel, 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

Claims (1)

(57) [Claims] The vehicle is driven by driving the wheels by power from an engine, and when a driving slip of the wheels occurs, the wheels are braked by traction control braking means provided separately for the left and right driving wheels to drive the wheels. In a vehicle that prevents slippage and controls a differential limiting torque of a differential limiting clutch provided between the wheels by a clutch control unit, a braking state that detects a braking state of left and right drive wheels by the braking unit, respectively. Detecting means; and control condition changing means for changing the differential limiting torque control condition of the clutch control means in accordance with the braking state so that the differential limiting torque decreases as the difference between the left and right braking forces increases. A traction control device for a vehicle, comprising: