JPH01244954A - Traction control method for vehicle - Google Patents

Abstract

PURPOSE:To restrain the sudden change of a driving wheel speed by reducing the degree of a brake fluid pressure rise accompanying with an increase in slip amount in the system where brake fluid pressure for a driving wheel is controlled on the basis of the slip thereof detected upon the start and the like of a vehicle. CONSTITUTION:Among wheel speed signals obtainable from outputs of each rotational speed sensor 24L, 24R, 25L and 25R for each pair of driving and driven wheels right and left, the acceleration and deceleration of the wheel speed of each driving wheel are operated 35 and 36, and inputted to a control logic circuit 30. Also, a larger value is selected 37 from the wheel speeds of each driven wheel for use as a pseudo-body speed and the predetermined value is added thereto, thereby setting 38 a threshold value. This value is inputted to the control logic circuit 30. Furthermore, the slip of the driving wheel is detected with the circuit 30 and brake fluid pressure for the driving wheel is compressed, decompressed or retained for controlling the slip. In this case, the brake fluid pressure is so controlled as to reduce the degree of the pressure rise thereof with the increase of the slip amount.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a traction control method for a vehicle, which detects the slip of the drive wheels that occurs when the vehicle starts or accelerates, and brakes the drive wheels based on this detection. The present invention relates to a vehicular traction control method for controlling and suppressing slip of drive wheels.

(Prior Art) Conventionally, especially when a vehicle runs on a road surface with a low coefficient of friction such as an icy road, snowy road, or muddy road, it is possible to prevent the drive wheels from slipping that occurs when the vehicle starts or accelerates. BACKGROUND ART Traction control devices that improve running stability and acceleration are known. Such a traction control device detects the slip state of each of the left and right drive wheels, and if the degree of slip exceeds a predetermined value, it adjusts the pressurization conditions based on the amount of slip or acceleration of the drive wheels. Normally, the brake fluid pressure for the brake device of the drive wheel is increased to perform braking control.

However, in traction control, engine output is controlled in parallel with brake fluid pressure control, so
If pressurization conditions are set simply based on the amount of slip or acceleration of the drive wheels, the brake fluid pressure will rise too much, leading to sudden deceleration of the drive wheels, worsening ride comfort and impairing acceleration performance. was there.

(Object of the Invention) Therefore, the present invention provides a traction control method that suppresses excessive rise in brake fluid pressure when pressurizing brake fluid pressure, prevents sudden deceleration of wheels, and facilitates control. The purpose is to

(Structure of the Invention) The present invention is characterized in that the brake fluid pressure is controlled so that the degree of increase in the brake fluid pressure decreases as the slip amount of the drive wheels increases.

(Effects of the Invention) According to the present invention, sudden changes in drive wheel speed during traction control can be suppressed, and smooth traction control becomes possible.

(Example) Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a traction system 11 applied to the implementation of the present invention.
A system diagram of 11 devices is shown. In the figure, reference numeral 10 indicates a brake pedal as a brake applying member, and this brake pedal 10 operates a tandem type mask cylinder 11 having two pressurizing chambers (not shown). A reservoir 12 is attached to the upper part of the mask cylinder 11, and a pump 13 is supplied from the reservoir 12.
is configured to draw up brake fluid and store it in an accumulator 14 at high pressure.

One pressurizing chamber 11a of the mask cylinder 11 is a normally open type 1
Liquid passage 15 equipped with gate valve GV consisting of 1M1 valve
The liquid passage 15 is connected to the wheel cylinder 21 of the brake that brakes the front right wheel 20R, which is the driving wheel, and the liquid passage 15 is connected to the wheel cylinder 21 of the brake that brakes the rear left wheel 22L, which is the driven wheel. It is connected via a cant valve C■ consisting of a type t valve. The other pressurizing chamber 11b of the mask cylinder 11 is connected to a wheel cylinder 21 of a brake that brakes the left front wheel 2OL, which is a driving wheel, through a liquid passage 16 equipped with a gate valve GV consisting of a normally open electromagnetic valve. In addition, the liquid passage 16 is connected to a cut valve Cv, which is a normally open electromagnetic valve, in a wheel cylinder 21 of a brake that brakes the right rear wheel 22R, which is a driven wheel.
connected via. A normally closed T! is provided between the liquid passage 15 and the accumulator 14 and between the liquid passage 16 and the accumulator 14, respectively. A build pulp BV consisting of a magnetic valve is connected, and a liquid passage 15 and a reservoir 12 are connected.
A decay valve DV, which is a normally closed electromagnetic valve, is connected between the liquid passage 16 and the reservoir 12. Each build pulp BV has a function of supplying high-pressure brake fluid accumulated in the accumulator 14 to the wheel cylinder 21 or cutting off the supply by its opening or closing operation, and the decay valve DV has the function of
By its opening or closing operation, the wheel cylinder 2
It has the function of discharging the brake fluid in the reservoir 12 to the reservoir 12 or blocking the discharge.

These gate valve GV, cut pulp Cv1 build pulp BV, and decay valve DV are composed of solenoid valves, and are also used for anti-lock control during braking of a vehicle, and are controlled by commands from a control device 23 mainly composed of a microcomputer. Opening/closing controlled. Then, when traction control for the left and right driving wheels 2OL and 20R is started, the gate valve GV and the cut valve C■ are closed, and the wheel cylinders 21 of the driving wheels 20L and 20R are separated from the mask cylinder 11. The wheel cylinders 21 of the driving wheels 22L and 22H are in the liquid passage 1.
5.16. By closing the gate valve GV and the car/ ) valve Cv, the brake fluid pressure in the wheel cylinder 21 of the brakes of the driven wheels 22L, 22R is maintained at a pressureless state, and the driving wheels 20L,
The brake fluid pressure in the wheel cylinder 21 of the 2OR brake is determined by the open state of the build valve BV and the decay valve DV.
is pressurized in the closed state of the build pulp BV and the decay valve DV is held in the closed state,
And, the closed state of the build pulp BV and the decay valve DV
The pressure is reduced in the open state.

On the other hand, the control device 23 includes each wheel 20L, 20R122.
Rotational speed sensors 24L, 24R, and 25L for detecting the rotational speeds of L and 22R, respectively.

25R, a brake switch 26 that detects that the brake pedal 10 is depressed, and an accelerator depression amount sensor 28 that detects the y3 depression amount of the accelerator pedal 27 are connected. Based on the information supplied from these sensors, the control device 23 drives the engine throttle control mechanism 29 to control the engine output, and also controls the gate valve GV.
, cut valve CV2, build pulp BV, and decay valve DV are opened and closed to control the brake fluid pressure of the wheel cylinders 21 of the driving wheels 20L and 20R.

Furthermore, when the brake switch 26 is actuated, traction control is immediately terminated.

FIG. 2 shows the mechanism of the control device 23, and shows the drive wheels 20L, 2.
The rotational speed of 0R is detected by the rotational speed sensors 24L and 24R, respectively, and the wheel speeds v, L, and vJ of the driving wheels are calculated by the calculation circuits 31 and 32, respectively. Wheel speed V
, L, V, 'R are input to the control logic circuit 30.

Furthermore, the rotational speeds of the left and right driven wheels 22L, 22R are detected by rotational speed sensors 25L, 25R, respectively, and the wheel speeds V, IL, V of the left and right driven wheels are detected by the calculation circuits 33.34.
, R are calculated.

In addition, the wheel speeds ■IIL and vDR of the left and right driving wheels are respectively given to acceleration/deceleration calculation circuits 35 and 36,
Acceleration/deceleration of wheel speed V, L, VゎR V, L, V,
R is calculated and input to the control logic circuit.

On the other hand, the wheel speed VNL of the left and right driven wheels 22L and 22R,
The VNR is given to a high select circuit 37, and the higher wheel speed among these wheel speeds V, L, V, and R is selected, and a speed close to the actual vehicle speed is calculated as a pseudo vehicle speed VV. This speed Vv is given to a threshold setting circuit 38 which is made up of an adding circuit. This threshold setting circuit 38 adds a constant value Vk to the pseudo vehicle speed Vv to obtain a first threshold value Vt1 (=V
v+Vk). This threshold value vB is input to the control logic circuit 30. In addition, the control logic circuit 30
The output from the placket inch 26 is input to the .

The control device 23 drives the throttle control ELTL 129 based on the above-mentioned signals to control the accelerator opening when the vehicle starts and accelerates, and also controls the build valve B.
Traction control is performed by controlling the opening and closing of V, decay valve DV, and other pulps to control the brake fluid pressures of the wheel cylinders 2I of the left drive wheel 20L and right drive wheel 2OR, respectively.

Next, a first embodiment of traction control according to the present invention will be described with reference to FIG. 3, which shows a timing chart of control in each status, and FIG. 4, which shows a flowchart of control. The brake fluid pressure in the present invention is controlled individually for the left and right drive wheels, but here, the brake fluid pressure is controlled by the wheel speeds V, L, V, R of the left and right drive wheels.
We will collectively express them in Vw.

In the first embodiment of the present invention, each pressurization time gradually decreases in repetition of small pressurization and holding of the brake fluid pressure, which starts when the wheel speed Vw during acceleration exceeds the threshold value vt1. It is controlled as follows. That is, first, the initial pressurization time t1 and holding time t2 are set based on the acceleration VW when the wheel speed Vw reaches the threshold value Vtl, and the next holding time t! Set only the next pressurization time to be shorter than tl by Δt without changing , and then set the next pressurization time to be further shortened by Δt so that each pressurization time gradually decreases. It is something to control.

First, before starting traction control, the wheel speed Vw is below the threshold value vt1 (Vw<Vt1), the build valve BV is closed, the decay valve DV is closed, and the gate valve GV and cut valve C■ are both open. can be,
The brake fluid pressure pw is in the maximum reduced pressure state.

If the wheel speed Vw reaches the threshold value vB during acceleration (
In steps S1 and S2 in FIG. 4, the gate pulp Gv and the cut pulp Cv are closed from that point A, and the brake fluid pressure is increased stepwise by opening and closing the build valve BV little by little.

In that case, the first pressurization from time A is for a preset pressurization time T=t corresponding to the acceleration Vw when the wheel speed Vw reaches the threshold value Vtl.

and holding time t2 (step S3).

If the wheel speed Vw is greater than the threshold value Vtl and has not reached the high peak (steps S4, S5
'), the next pressurization time T is changed to t-Δ ((where t is the previous pressurization time) in step S6), and the next pressurization time T and holding time t2 are changed (step S6).
7), return to step S4. In this way, the pressurization time T
The brake fluid pressure is increased stepwise while decreasing the brake fluid pressure one after another.

From time B when the wheel speed Vw reaches a high peak, the build valve Bv is closed to maintain the brake fluid pressure Pw, and from time C when the wheel speed Vw falls below the threshold value Vtl, the decay valve DV is opened and closed in small increments until the low peak. The brake fluid pressure pw is reduced stepwise.

As a result, the degree of increase in brake fluid pressure Pw decreases as shown by the solid line in Figure 3, and the wheel speed Vw gradually decelerates as shown by the solid line in Figure 3, making smooth traction control possible. . However, when the brake fluid pressure is increased in a stepwise manner with a constant machining time t1 and a holding time t2 from when the wheel speed Vw exceeds the threshold value vB until it reaches a high peak as in the past, the third It can be seen that smooth traction control cannot be performed because the wheel speed Vw suddenly decelerates as shown by the broken line in the figure. In addition, in the control method shown in FIG. 4, by decreasing each pressurization time T as the wheel speed Vw approaches a high peak, the ratio (duty ratio) of each pressurization time to each holding time is decreased. However, instead of this, the duty ratio may be decreased by keeping the pressurization time constant and increasing the holding time.

Next, FIG. 5 is a flowchart showing a traction control method according to a second embodiment of the present invention.

In the case of this embodiment, in addition to the threshold Vtl, a second threshold Vt2, which exceeds the threshold Vtl by a certain value Vk', and a second threshold Vt2. A third threshold value vt3 is set in advance so that the wheel speed exceeds the threshold value Vk' by a certain value Vk', and each pressurization time t is controlled to decrease each time the wheel speed Vw exceeds the thresholds Vt2 and Vt3. It is.

In FIG. 5, steps Sll to 515 are the same as steps 81 to s5 in FIG. 4. and step S
In step S16, it is determined whether the wheel speed Vw exceeds the second threshold value Vt2, and further in step S17, it is determined whether the wheel speed Vw exceeds the third threshold value Vt3. While the determination in step S16 is rNOJ, each pressurization time t is not changed, and the determination in step S16 is rYE.
sJ, and if the determination in step 317 is "NO", each pressurization time is decreased to [1-Δt. Also, the determination in step S16 and the stay.

If both of the determinations in block 317 are rYEsJ, each pressurization time is further reduced to, for example, t and -2Δt.

It is clear that the same effects as in the first embodiment described above can be achieved by controlling each pressurization time in this manner.

In addition, in this case, each pressurization time is kept constant, and only each holding time is set when the wheel speed Vw is the threshold value Vt2, vt3.
Needless to say, it may be decreased each time the value exceeds .

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a truck system control device applied to the implementation of the present invention, FIG. 2 is a block diagram showing the configuration of the control circuit, and FIG. 3 is a brake fluid pressure control according to a first embodiment of the present invention. FIG. 4 is a flowchart of the pressurization control, and FIG. 5 is a flowchart of the pressurization control according to the second embodiment of the present invention. 10-Brake pedal 11--Master cylinder 12-Reservoir 13-Pump 14-Accumulator 20L,
20R...Drive wheel 21--Wheel cylinder 22L, 22R-Driven wheel 23...-Control j1 device 24L, 24R125L, 25R-----One wheel rotation speed sensor 26-Brake switch 27-Accelerator Pedal 28 - Accelerator depression amount sensor 29 - Throttle control mechanism 30 - Control logic circuits 31 to 34 - Wheel speed calculation circuit 35.36 - Acceleration/deceleration calculation circuit 37 - High select circuit 38 - L threshold setting circuit

Claims (7)

[Claims] 1. The slip of the drive wheels that occurs when the vehicle starts or accelerates is detected, and based on this detection, the brake fluid pressure for the drive wheels is controlled to be pressurized, depressurized, or maintained, and the brake fluid pressure of the drive wheels is A traction control method for a vehicle that suppresses slip, characterized in that the brake fluid pressure is controlled so that the degree of increase in the brake fluid pressure decreases as the amount of slip of the drive wheels increases. traction control method. 2. The slip of the drive wheels that occurs when the vehicle starts or accelerates is detected, and based on this detection, the brake fluid pressure for the drive wheels is controlled to be pressurized, depressurized, or maintained, and the brake fluid pressure of the drive wheels is In a vehicle traction control method that suppresses slip, a threshold higher than the vehicle speed is determined based on the vehicle speed, and the wheel speed of the driving wheels reaches a high peak after exceeding the threshold. The brake fluid pressure is increased stepwise by repeating small pressurization and holding until the brake fluid pressure is increased, and each pressurization time is A traction control method for a vehicle, characterized in that the ratio is decreased as the wheel speed of the driving wheels approaches a high peak. 3. In the method according to claim 2, when the brake fluid pressure rises stepwise, the ratio of each pressurization time to each holding time is decreased by keeping each holding time constant and reducing each pressurization time. The method is characterized in that it is carried out by causing. 4. In the method according to claim 2, when the brake fluid pressure rises stepwise, the ratio of each pressurization time to each holding time is decreased by keeping each pressurizing time constant and increasing each holding time. The method is characterized in that it is carried out by causing. 5. The slip of the drive wheels that occurs when the vehicle starts or accelerates is detected, and based on this detection, the brake fluid pressure for the drive wheels is controlled to be pressurized, depressurized, or maintained, and the brake fluid pressure of the drive wheels is In a vehicle traction control method for suppressing slip, a plurality of threshold values higher than a vehicle body speed are respectively set based on the vehicle body speed, and the wheel speed of the driving wheels is set to a value higher than the plurality of threshold values. After the lowest threshold value is exceeded until reaching the high peak, the brake fluid pressure is increased stepwise by repeating small pressurization and holding of the brake fluid pressure, and the brake fluid pressure is increased stepwise. 1. A traction control method for a vehicle, characterized in that a ratio of each pressurizing time during a rising period is decreased each time the wheel speed of the drive wheel exceeds the threshold value. 6. In the method according to claim 5, when the brake fluid pressure rises stepwise, the ratio of each pressurization time to each holding time is decreased by keeping each holding time constant and reducing each pressurization time. The method is characterized in that it is carried out by causing. 7. In the method according to claim 5, when the brake fluid pressure rises stepwise, the ratio of each pressurization time to each holding time is decreased by keeping each pressurizing time constant and increasing each holding time. The method is characterized in that it is carried out by causing.