DCT Power-On Down Shift Clutch Torque Control
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Solution Overview
Problem
In vehicles with Dual Clutch Transmission (DCT), power-on down shifts are delayed due to insufficient engine torque when the accelerator pedal is pressed only slightly, leading to delayed and unstable gear shifts.
Innovation Solution
A shift control method that determines if the DCT has entered a power-on down shift inertia phase, controls the release-side clutch by adjusting its torque, and requests engine assistance to increase torque when the clutch torque falls below a minimum, ensuring the engine speed synchronizes with the input shaft speed, thereby stabilizing and accelerating gear shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the release-side clutch is sufficiently released to perform power-on down shift, then the gear shift operation can be performed, but the engine torque may be insufficient to increase engine speed at the required rate, causing delayed synchronization and delayed gear shift
Solution Approach 1:
The TCU performs preliminary determination of whether the DCT has entered the power-on down shift inertia phase before the actual gear shift occurs. By anticipating the need for engine torque assistance in advance and requesting it from the ECU before the clutch torque becomes insufficient, the system ensures that adequate torque is available to maintain the required engine speed change rate throughout the synchronization process, preventing delayed gear shift.
2Ease of operation
If the release-side clutch control torque is reduced to enable gear shift, then the clutch can disengage for the shift operation, but the torque may fall below the minimum control torque required for stable clutch operation
Solution Approach 1:
The TCU continuously monitors the release-side clutch control torque during the gear shift process and performs limit determination to detect when the torque approaches the minimum control torque threshold. Based on this feedback, the TCU requests additional engine torque from the ECU to compensate for the reducing clutch torque, ensuring that the total torque remains sufficient to maintain stable clutch operation throughout the shift process.
3Adaptability or versatility
If the accelerator pedal is pressed with very small amount (ultra-low APS), then the driver's intended acceleration is minimal, but the engine torque becomes insufficient to support the power-on down shift operation
Solution Approach 1:
The TCU acts as an intermediary between the driver's accelerator pedal input and the engine torque delivery. Even when the driver presses the accelerator pedal with a very small amount (ultra-low APS), the TCU determines whether a power-on down shift inertia phase has been entered and, if so, requests additional engine torque from the ECU to compensate for the insufficient torque. This allows the system to maintain proper torque levels for successful gear shift operation regardless of the driver's minimal pedal input.
Data Source
AI summary
A shift control method for the vehicle with a DCT may include a start determining step of determining, by a TCU, whether the DCT may have entered a power-on down shift inertia phase, a clutch control step of controlling a release-side clutch by determining, by the TCU, a release-side clutch control torque, when the DCT enters the power-on down shift inertia phase, a limit determining step of determining whether the release-side clutch control torque is reduced below a predetermined minimum control torque, while the TCU performs the clutch control step, and an engine-assistance requesting step of requesting an ECU to set an engine-torque rise request amount in proportion to a release-side clutch control torque reduction amount that is additionally required by the TCU, when it is determined in the limit determining step that the release-side clutch control torque is reduced below the minimum control torque.