JPH02175371A - Vehicle propulsion control method - Google Patents

Abstract

PURPOSE:To reduce the number of times of carrying out brake fluid pressure control and lighten the burden of a brake by setting the threshold value which is the condition of starting/finishing brake fluid pressure control executed to restrain slippage higher as vehicle speed gets higher. CONSTITUTION:The output signals of a driving-wheel speed detecting means 17A and a driven-wheel speed detecting means 17B are inputted into an arithmetic circuit 16A, where the existence of slippage is judged from the difference between the driving-wheel speed and the driven-wheel speed. When the occurrence of slippage is detected at the time of starting or accelerating a vehicle, an engine output control means 15A and/or a brake fluid pressure control means 16B is controlled to restrain the slippage. In such a propulsion force control method, a threshold value which is the condition of starting/finishing brake fluid pressure control is set higher as the vehicle speed gets higher. Thereby, the speed difference taken into the brake fluid pressure control is made larger as the vehicle speed gets higher, to reduce the number of times of carrying out brake fluid pressure control and lighten the burden of the brake.

Description

[Detailed Description of the Invention] [Summary of the Invention] This invention relates to a vehicle propulsion control method that monitors the slip of drive wheels and, when slip is detected, controls brake fluid pressure to suppress the slip. To provide a propulsion force control method for a vehicle that performs brake fluid pressure control, which does not place an excessive burden on the brakes and does not cause problems such as unstable posture of the vehicle during high-speed running. A vehicle that monitors the slip of the drive wheels that occurs when the vehicle starts or accelerates, and when slip is detected, brake fluid pressure is controlled either alone or together with the engine output to suppress the slip. In the propulsion control method B,
The threshold value, which is a condition for starting and ending brake fluid pressure control, is configured to increase as the vehicle speed increases.

[Industrial application field]

The present invention relates to a vehicle propulsion control method for monitoring drive wheel slip and controlling brake fluid pressure to suppress slip when slip is detected.

The system monitors drive wheel slip that may occur when the vehicle starts or accelerates, and when slip is detected, brake fluid pressure and engine output are controlled individually or in combination to suppress slip. There is. The present invention relates to this brake control, particularly to the threshold value for starting the control.

[Conventional technology]

An overview of the propulsion control system for vehicles using automatic transmissions is given in Part 5.
As shown in the figure. In this diagram, IO is the engine, ll is the clutch,
12 is a transmission, and 14 is an accelerator pedal. Reference numeral 15 denotes an electronic control unit that collects information on various parts of the vehicle, such as the amount of depression of the accelerator pedal 14, the position of the selector (shift) lever (not shown), the opening of the engine throttle valve, the engine rotation speed, the vehicle speed, and the engine cooling water. It takes in information such as temperature, clutch position (engagement state B), and transmission input shaft rotation speed, and outputs signals for controlling the engine throttle valve, clutch engagement, and transmission gear shift.

Further, 13a to 13d are vehicle wheels, 17a to 17d are rotation speed detectors, 18a and 1.8b are rear cut valves, 19 is a modulator, 20 is a mask cylinder,
21 is a brake pedal.

Reference numeral 16 denotes a second electronic control device that controls these brake systems, which takes in the outputs of rotational speed detectors 17a to 17d, etc., and controls the modulator 19, rear cut valve 18a,
18b.

The occurrence of slip can be detected when there is a difference of more than a predetermined value between the speeds of the driving wheels 13a, 13b and the speeds of the driven wheels 13e, 13d. In other words, the driven wheel is the vehicle speed (vehicle ground speed)
If the rotational speed of the driving wheel is higher than the rotational speed of the driven wheel, it can be said that slipping has occurred.By the way, slipping means that the driving wheel has no driving force. It is present when the slip is generated, and no driving force can be generated when the slip is zero. However, if the slip is large, the road surface becomes polished and the coefficient of friction decreases, making it easier for the vehicle to slip, making it impossible to start or accelerate. The slip that generates the maximum driving force is 20 to 30% slip,
Anything above that will be subject to suppression.

When a slip to be suppressed occurs, the electronic control device 15,
1.6 adjusts the propulsion force to reduce slip. This may include closing the throttle to reduce engine power, releasing the clutch to reduce wheel drive, or applying the brakes.

FIG. 6 shows a method of performing brake fluid pressure control and engine output control for slip control. In this figure, the target vehicle speed is assumed to be the driven wheel speed, which is constant.

(Problems to be Solved by the Invention) In the propulsion side ill of a conventional vehicle, a threshold value, which is a condition for starting and ending brake fluid pressure control, is set to a constant value. That is, if the driving wheel speed is Vd, the driven wheel speed is Vf, and the L threshold is α, then Vd>Vf+α or Vd−Vf>α.
If so, it was assumed that a slip occurred (to be suppressed).

However, with this method, brake fluid pressure is controlled even when the vehicle is traveling at high speeds in the same way as when traveling at low speeds. For example, α=2Km/
If h is a low speed of 5Kr1/h, if the speed increases by 40% to 7Km/h, slipping of the driving wheels will occur, whereas at a high speed of 60■/h, the speed increases by 3% to 62Km/h.
A slip will occur if this happens. This causes problems such as frequent application of the brakes when driving at high speeds, increasing the load on the brakes, and making the posture of the vehicle unstable while driving at high speeds. If you avoid this and increase α, slip suppression control will not be activated even if excessive slip occurs during low-speed driving such as during startup, which is also a problem.The present invention is capable of suppressing slip reliably. The purpose of the present invention is to provide a method for controlling the propulsion force of a vehicle that performs brake fluid pressure control, which does not place an excessive burden on the brakes, and does not cause problems such as making the vehicle's posture unstable during high-speed driving. It is something to do.

[Means for Solving the Problems] As shown in FIG. 1, the present invention monitors the slip of the driving wheels that occurs when the vehicle starts or accelerates, and when slip is detected, brake fluid pressure is adjusted independently or In vehicle propulsion control that suppresses slippage by controlling along with engine output, the threshold values α and β, which are the conditions for starting and ending brake fluid pressure, are increased as the vehicle speed increases.

Using the threshold values α and β adjusted in this way, and setting the driving wheel speed to Vd and the driven wheel speed to Vf, if Vd>■r×α, slip occurs and brake fluid pressure control starts, and if Vd<Vf×β, slip disappears. , brake fluid pressure control ends. The same applies to engine output control.

[Effect]

By changing the threshold values α and β according to the vehicle speed in this way, it is possible, for example, to cause slip to occur when the driving wheel speed increases by more than α% of the driven wheel speed, and to eliminate slip when the increase is less than β%. This eliminates excessive slippage at low speeds or frequent application of the brakes at high speeds, which would occur if the threshold value is a constant value, making it possible to perform reliable slip control.

〔Example〕

FIG. 2 shows an example of the propulsive force control of the present invention. Since the driven wheel speed can be regarded as representing the desired vehicle speed, the driven wheel speed is calculated from the output of the driven wheel speed detection means 17B. Further, the driving wheel speed is calculated from the output of the driving wheel speed detecting means 17A, and the difference between them is determined. 16A is a circuit that performs such calculations.

Further, the arithmetic circuit ISA determines whether the driving wheel speed - the driven wheel speed>the control start threshold (2). The result of this judgment is Y
If ES, the brake fluid pressure control is performed by the brake fluid pressure control means 16B (2), and then the arithmetic circuit 16A determines whether the driving wheel speed - the driven wheel speed is the control end threshold (2).

The arithmetic circuit 1.6A and the brake fluid pressure control means 16B correspond to the electronic control device 16 in FIG. Further, the engine control means 15A corresponds to the electronic control device 5 in FIG.

In the present invention, the control start threshold value α and the control end threshold value β are increased as the vehicle speed increases, as shown in FIG.

The difference between the driving wheel speed and the driven wheel speed is slip, and there is slip when the car starts and accelerates. However, if excessive slip occurs, the road surface becomes polished and the coefficient of friction decreases, making it more slippery and potentially making it impossible to start or accelerate. For this reason, it is necessary to suppress slip so that propulsive force and steering force can be ensured.

Therefore, α is set to an appropriate value, and if the result of the determination at α is YES, it is determined that a slip to be suppressed has occurred, and the process moves to step (2), where the brakes are applied to the drive wheels. This is■
This process is repeated until the determination result becomes YES.

To explain with Fig. 4, at startup, the drive wheels receive strong driving force from the engine and rapidly increase speed as shown by curve C2.
Since the car has a large inertia, it cannot speed up rapidly, so the driven wheels speed up slowly as shown by the curve (straight line) C+. The difference between the driving wheel speed and the driven wheel speed is slip. Time t
1, this slip gradually exceeds the control start threshold α.

Then, brake fluid pressure control for the drive wheels is started■. This brake fluid pressure control applies the brakes to the drive wheels and reduces the drive wheel speed. Eventually, at time tz, the difference between the driving wheel speed and the driven wheel speed becomes equal to or less than the control end threshold β. Therefore, the result of the determination in (■) is YES, the brake fluid pressure control is completed, and the drive wheels resume speeding up. In other words, the restart of increasing the engine output is performed by the electronic control unit 15 shown in FIG. 5. Note that during brake fluid pressure control, the electronic control device 15 may stop the speed increase control of the drive wheels, and may even actively decelerate (reduce engine output).

When the speed increase of the driving wheels resumes, the speed difference with the driven wheels starts to increase again, and eventually when α is exceeded, brake fluid pressure control is restarted, and the driving wheel speed begins to decrease, causing the difference between the driven wheels and the driven wheels to increase again. When the speed difference becomes less than β, the brake fluid pressure control is stopped and the driving wheel speed increases again, and this process is repeated thereafter. The speed of the drive wheels is increased to a speed corresponding to the opening degree of the accelerator pedal depressed by the driver.

In this method, the threshold values α and β are not constant, but change depending on the speed, so that slip control is not performed uselessly at high speeds, and excessive slip is not allowed at low speeds.

〔Effect of the invention〕

As explained above, according to the present invention, as the vehicle speed increases, the speed difference at which brake fluid pressure control is entered becomes larger, so the number of times brake fluid pressure control is entered is reduced, and the load on the brakes is reduced. In addition, as the vehicle speed decreases, the speed difference that enters brake fluid pressure control becomes smaller, so the number of times brake fluid pressure control is entered increases, and slip is appropriately suppressed, improving the vehicle's starting and acceleration performance. .

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is an explanatory diagram of an example of propulsion control of the present invention, Fig. 3 is an explanatory diagram of control start/end thresholds, and Fig. 4 is a diagram of speed characteristics at startup. FIG. 5 is a block diagram of the vehicle drive/brake control system, and FIG. 6 is a flowchart of slip control using brake and engine output control. Fig. 2 Explanatory diagram of M value for starting/ending driven wheel speed control Fig. 311'1 Fig. 4

Claims (1)

[Claims] 1. Monitoring the slip of the driving wheels that occurs when the vehicle starts or accelerates, and when slip is detected, suppresses the slip by controlling the brake fluid pressure alone or together with the engine output. A method for controlling propulsion force for a vehicle, characterized in that a threshold value serving as a condition for starting and terminating brake fluid pressure control is increased as the vehicle speed increases.