A launch control method for a dual clutch transmission

Abstract

A launch control method for a dual-clutch transmission comprises the following steps: 1) setting a brake pressure threshold, a clutch half-engagement point torque, and a speed difference threshold between an engine speed and an input shaft speed for exiting the launch start in a TCU; 2) judging whether to enter a launch start mode; 3) after entering the launch start mode, the TCU controls the clutch to engage to a half-engagement point to eliminate a transmission system gap, and the TCU controls the engine speed to a maximum engine speed to prepare for the launch start; 4) judging whether to start the launch start; 5) during the launch start process, the TCU controls the clutch to engage to the maximum engine torque; by calculating and determining a clutch target torque and an engine target speed, the TCU controls the clutch to the clutch target torque and the engine speed to the engine target speed; 6) judging whether to exit the launch start according to the speed difference between the engine speed and the input shaft speed.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicles, and in particular to a launch control method for a dual-clutch transmission. Background Art

[0002] Launch start is an acceleration technology that uses the gearbox to adjust the engine speed to the output platform of maximum torque, so that the engine starts to output at maximum torque at the moment of starting, achieving the best acceleration. The dual-clutch automatic transmission that is currently widely used is characterized by high transmission efficiency. Most current dual-clutch transmissions do not have a special launch start control program and can only be started through a general start control program. Using a general start control program and stepping on the brake and accelerator at the same time for launch start will increase clutch wear and fail to fully release the power of the engine. The dual-clutch transmission uses a hard connection, and using a general start control program for launch start will cause great damage to the vehicle, especially to the transmission. Summary of the invention

[0003] The purpose of the present invention is to provide a dual-clutch transmission launch control method to address the deficiencies in the prior art, thereby solving the problem of clutch wear and inability to fully release the engine power during launch start of the dual-clutch transmission, causing damage to the transmission and the vehicle.

[0004] The object of the present invention is achieved in that:

[0005] A dual clutch transmission launch control method comprises the following steps:

[0006] 1) Set the brake pressure threshold C for entering the launch mode, the brake pressure threshold S for starting the launch mode, the clutch half-engagement point torque B, and the speed difference threshold R between the engine speed and the input shaft speed for exiting the launch mode in the TCU;

[0007] 2) TCU determines whether to enter the launch mode based on the throttle opening input signal and the brake pressure input signal;

[0008] 3) After entering the launch mode, the TCU controls the clutch to engage to the half-engagement point to eliminate the transmission system gap, and the TCU controls the engine speed to the maximum engine speed to prepare for the launch;

[0009] 4) TCU determines whether to start launch according to the brake pressure input signal;

[0010] 5) During the launch start process, the TCU controls the clutch to engage to the maximum torque of the engine; by calculating and determining the clutch target torque and the engine target speed, the TCU controls the clutch to the clutch target torque and the engine speed to the engine target speed;

[0011] 6) TCU determines whether to exit launch control based on the engine speed signal, the input shaft speed signal, and the speed difference between the engine speed and the input shaft speed.

[0012] In the step 2), the condition for entering the launch mode is that the throttle opening is greater than 99 and the brake pressure is greater than the brake pressure threshold C.

[0013] In step 4), the condition for starting the launch control is that the launch control can be performed when the brake pressure is lower than the brake pressure threshold S.

[0014] In step 5), the calculation steps of the clutch target torque and the engine target speed are as follows:

[0015] S1 calculates the friction torque of the driving wheel:

[0016] T w =T m ·iJ·a0

[0017] Where, T w is the friction torque of the driving wheel, T m is the maximum torque of the engine, J is the moment of inertia of the transmission system and wheels, a0 is the angular acceleration of the driving wheel, and i is the total transmission ratio.

[0018] S2 calculates the clutch target torque:

[0019]

[0020] Where, T is the clutch target torque, T w is the friction torque of the driving wheel, T m is the maximum torque of the engine, J is the moment of inertia of the transmission system and wheels, a0 is the driving wheel angular acceleration, a1 is the driven wheel angular acceleration, and i is the total transmission ratio.

[0021] S3 determines the engine speed corresponding to the clutch target torque according to the clutch target torque and the engine external characteristics. If there are multiple engine speed points, the lower point is taken as the engine target speed.

[0022] In step 6), the condition for exiting the launch control is when the speed difference between the engine speed and the input shaft speed is lower than the speed difference threshold R for exiting the launch control.

[0023] The dual-clutch transmission launch start control method of the present invention does not wear the clutch when the dual-clutch transmission performs a launch start, can fully release the power of the engine, and at the same time ensures the safety and stability of the transmission and the vehicle, thereby ensuring the quality of the entire vehicle while reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A flow chart of a launch control method for a dual clutch transmission;

[0025] Figure 2 Flowchart for calculating clutch target torque and engine target speed. DETAILED DESCRIPTION

[0026] refer to Figure 1 to Figure 2 A dual clutch transmission launch control method comprises the following steps:

[0027] 1) Set the brake pressure threshold C for entering the launch mode, the brake pressure threshold S for starting the launch mode, the clutch half-engagement point torque B, and the speed difference threshold R between the engine speed and the input shaft speed for exiting the launch mode in the TCU;

[0028] 2) TCU determines whether to enter the launch mode based on the throttle opening input signal and the brake pressure input signal; the condition for entering the launch mode is that the throttle opening is greater than 99 and the brake pressure is greater than the brake pressure threshold C.

[0029] 3) After entering the launch mode, the TCU controls the clutch to engage to the half-engagement point to eliminate the transmission system gap, and the TCU controls the engine speed to the maximum engine speed to prepare for the launch;

[0030] 4) TCU determines whether to start launch according to the brake pressure input signal; the condition for starting launch is that launch can be performed when the brake pressure is lower than the brake pressure threshold S.

[0031] 5) During the launch start process, the TCU controls the clutch to engage to the maximum torque of the engine; the clutch target torque and the engine target speed are determined by calculation, and the TCU controls the clutch to the clutch target torque and the engine speed to the engine target speed; the calculation steps of the clutch target torque and the engine target speed are as follows:

[0032] S1 calculates the friction torque of the driving wheel:

[0033] T w =T m ·iJ·a0

[0034] Where, T w is the friction torque of the driving wheel, T m is the maximum torque of the engine, J is the moment of inertia of the transmission system and wheels, a0 is the angular acceleration of the driving wheel, and i is the total transmission ratio.

[0035] S2 calculates the clutch target torque:

[0036]

[0037] Where, T is the clutch target torque, T w is the friction torque of the driving wheel, T m is the maximum torque of the engine, J is the moment of inertia of the transmission system and wheels, a0 is the driving wheel angular acceleration, a1 is the driven wheel angular acceleration, and i is the total transmission ratio.

[0038] S3 determines the engine speed corresponding to the clutch target torque according to the clutch target torque and the engine external characteristics. If there are multiple engine speed points, the lower point is taken as the engine target speed.

[0039] The maximum engine torque T of this embodiment m The torque is 200Nm, the moment of inertia of the transmission system and wheels J is 10kgm, the angular acceleration a0 of the driving wheel is 25 / s2, the angular acceleration a1 of the driven wheel is 1.5 / s2, the total transmission ratio i is 20, and the external characteristics of the engine conform to the following rules:

[0040] Engine torque 50 Nm at 1000 rpm;

[0041] Engine torque 200 Nm at 2000 rpm;

[0042] The engine torque increases linearly from 1000 rpm to 2000 rpm;

[0043] Engine torque 200 Nm at 2000 rpm to 4000 rpm;

[0044] Engine torque 130 Nm at 6000 rpm;

[0045] The engine torque decreases linearly between 4000 rpm and 6000 rpm.

[0046] After calculation, the driving wheel friction torque is 3750 Nm, the clutch target torque is 188.25 Nm, and the engine target speed is 1921.67 rpm.

[0047] 6) TCU determines whether to exit launch control based on the engine speed signal, input shaft speed signal, and the speed difference between the engine speed and the input shaft speed. The condition for exiting launch control is when the speed difference between the engine speed and the input shaft speed is lower than the speed difference threshold R for exiting launch control.

[0048] TCU collects the engine maximum torque signal, engine maximum speed signal, engine external characteristic curve signal, engine speed signal, total transmission ratio signal, input shaft speed signal, transmission system and wheel rotation inertia signal, driving wheel angular acceleration signal, driven wheel angular acceleration signal, throttle opening signal, and brake pressure signal in real time. It determines whether to enter the launch mode according to the brake pressure threshold and throttle opening set in the TCU; the brake pressure threshold determines whether to start the launch; during the launch process, the TCU controls the clutch to engage the maximum torque of the engine; by calculating the clutch target torque and the engine target speed, the TCU controls the clutch to the clutch target torque and the engine speed to the engine target speed; the speed difference threshold R between the engine speed and the input shaft speed determines whether to exit the launch. In this way, the dual-clutch transmission can be launched without wearing the clutch, and the power of the engine can be fully released, while ensuring the safety and stability of the transmission and the vehicle.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A dual clutch transmission launch control method, characterized in that: The following steps are involved: 1) Set the brake pressure threshold C for entering the launch mode, the brake pressure threshold S for starting the launch mode, the clutch half-engagement point torque B, and the speed difference threshold R between the engine speed and the input shaft speed for exiting the launch mode in the TCU; 2) TCU determines whether to enter the launch mode based on the throttle opening input signal and the brake pressure input signal; 3) After entering the launch mode, the TCU controls the clutch to engage to the half-engagement point to eliminate the transmission system gap, and the TCU controls the engine speed to the maximum engine speed to prepare for the launch; 4) TCU determines whether to start launch according to the brake pressure input signal; 5) During the launch process, the TCU controls the clutch to engage to the maximum engine torque; The clutch target torque and the engine target speed are determined by calculation, and the TCU controls the clutch to the clutch target torque and the engine speed to the engine target speed. The calculation steps of the clutch target torque and the engine target speed are as follows: S1 calculates the friction torque of the driving wheel: T w =T m ·i-J·a0 Where, T w is the friction torque of the driving wheel, T m is the maximum torque of the engine, J is the moment of inertia of the transmission system and wheels, a0 is the angular acceleration of the driving wheel, i is the total transmission ratio, S2 calculates the clutch target torque: Where, T is the clutch target torque, T w is the friction torque of the driving wheel, T m is the maximum torque of the engine, J is the moment of inertia of the transmission system and wheels, a0 is the angular acceleration of the driving wheel, a1 is the angular acceleration of the driven wheel, and i is the total transmission ratio; S3 determines the engine speed corresponding to the clutch target torque according to the clutch target torque and the engine external characteristics, and if there are multiple engine speed points, takes the lower point as the engine target speed; 6) TCU determines whether to exit launch control based on the engine speed signal, the input shaft speed signal, and the speed difference between the engine speed and the input shaft speed.

2. The dual clutch transmission launch control method according to claim 1, characterized in that: In the step 2), the condition for entering the launch mode is that the throttle opening is greater than 99 and the brake pressure is greater than the brake pressure threshold C.

3. The dual clutch transmission launch control method according to claim 1, characterized in that: In step 4), the condition for starting the launch control is that the launch control can be performed when the brake pressure is lower than the brake pressure threshold S.

4. The dual clutch transmission launch control method according to claim 1, characterized in that: In step 6), the condition for exiting the launch control is when the speed difference between the engine speed and the input shaft speed is lower than the speed difference threshold R for exiting the launch control.

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