CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2021-0024049, filed Feb. 23, 2021, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a launch control method for a vehicle, the method being capable of precisely controlling torque transmission from an engine to driving wheels through control of clutch torque as in a dual clutch transmission (DCT) system or an automated manual transmission (AMT) system.

Description of Related Art

Launch control of a vehicle is a vehicle control technique that accelerates the vehicle from a standing start as fast as possible, and it is mostly found in racing or high-performance vehicles.

In vehicles provided with an automatic transmission (AT) having a torque converter, the torque transmitted to the driving wheels is determined by the torque converter. For the present reason, AT-based vehicles launch control cannot be easily used due to difficulty in precisely controlling the torque transmitted to the driving wheels.

However, in DCT- or AMT-based vehicles, which are provided with a transmission that can precisely control the torque transmitted to the driving wheels from the engine by controlling a clutch torque, it is relatively easy to use the launch control because the transmitted torque may be precisely controlled through the control of the clutch torque.

The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and may not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing a vehicle launch control method that enables an extremely fast acceleration of an AMT- or DCT-based vehicle provided with a transmission that can precisely control a torque transmission from an engine to driving wheels, thereby enhancing customer satisfaction for the vehicle.

To accomplish the objective, various aspects of the present invention are directed to providing a vehicle launch control method including the steps of: [A] when a launch control operation is initiated, adaptively increasing clutch torque of a clutch according to a decrease in braking pressure; [B] when the clutch torque increases to reach or exceed a first reference torque level, maintaining a current level of the clutch torque for a first reference duration; [C] after a lapse of the first reference duration, when a wheel slip ratio exceeds a first reference slip ratio, gradually reducing the clutch torque within a range which is lower than the current level and is equal to or greater than a second reference torque level which is lower than the first reference torque level; [D] when the wheel slip ratio is equal to or less than a second reference slip ratio which is less than the first reference slip ratio or when a second reference duration has elapsed after the clutch torque reaches or exceeds the first reference torque level, gradually increasing the clutch torque until the clutch torque reaches a third reference torque level which is higher than the first reference torque level; and [E] stopping the launch control operation when a period during which a clutch slip remains less than a predetermined critical synchronous slip is equal to or longer than a predetermined critical duration, in which the launch control operation is initiated when a driver selects a launch control option, both an accelerator pedal and a brake pedal are depressed, and an engine speed reaches a predetermined reference engine speed.

The clutch torque may be maintained at a preparation torque level until the engine speed reaches the reference engine speed.

In step [A], the clutch torque may be gradually reduced when the braking pressure is equal to or greater than a second reference braking pressure, and the clutch torque may be linearly increased at a rate corresponding to a first gradient when the braking pressure is lower than the second reference braking pressure.

The clutch torque may be linearly increased at a rate corresponding to a second gradient until the clutch torque reaches the first reference torque level when the accelerator pedal remains depressed down to a position that corresponds to a second APS reference value or more and the braking pressure becomes equal to or lower than a third reference braking pressure which is lower than the second reference braking pressure.

In step [C], the clutch torque may be reduced while a feedback control operation to reduce the wheel slip ratio is performed.

In step [C], the clutch torque may not be reduced but be maintained as it is when the wheel slip ratio is equal to or less than the first reference slip ratio.

In step [D], the clutch torque may be increased while a feedback control operation to reduce the wheel slip ratio is performed.

To accomplish the objective, various aspects of the present invention are directed to providing a vehicle launch control method including the steps of: [A] when a launch control operation is initiated, adaptively increasing clutch torque of a clutch according to a decrease in braking pressure; [B] when the clutch torque increases to reach or exceed a first reference torque level, maintaining a current level of the clutch torque for a first reference duration; [C] after a lapse of the first reference duration, when a wheel slip ratio exceeds a first reference slip ratio, gradually reducing the clutch torque within a range which is lower than the current level and is equal to or greater than a second reference torque level which is lower than the first reference torque level; [D] when the wheel slip ratio is equal to or less than a second reference slip ratio which is less than the first reference slip ratio or when a second reference duration has elapsed after the clutch torque reaches or exceeds the first reference torque level, gradually increasing the clutch torque until the clutch torque reaches a third reference torque level which is higher than the first reference torque level; and [E] stopping the launch control operation when a period during which a clutch slip remains less than a predetermined critical synchronous slip is equal to or longer than a predetermined critical duration, in which after step [D], when the clutch slip is equal to or less than a first reference clutch slip, an average speed of driven wheels is equal to or greater than a first reference speed, and the wheel slip ratio is equal to or less than a third reference slip ratio, a step of increasing the clutch torque toward a fourth reference torque level is performed.

When the average speed of the driven wheels is equal to or greater than a second reference speed or when the period during which the clutch slip remains less than the predetermined critical synchronous slip is equal to or lower than the critical synchronization duration, the launch control operation may be brought into a stop.

In the method, activation of a wheel spin prevention control function for the driving wheels may be prohibited while each of the steps is performed.

The present invention enables an accurate and precise control on vehicle launch, providing an extremely fast acceleration at the time of vehicle launch. This improves the driving performance of a vehicle and makes a driver experience dramatically improved driving comfort, resulting in improved customer satisfaction for the vehicle.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

