Hybrid Engine Pull-Up Threshold Control via Virtual Impeller Speed
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Solution Overview
Problem
Hybrid vehicle engine pull-up strategies fail to account for the dynamic change in maximum available motor torque due to the opening or slipping of the torque converter bypass clutch during engine starts, leading to torque holes and inefficiencies.
Innovation Solution
A control algorithm that modifies engine pull-up logic by determining an engine pull-up threshold based on maximum available motor torque from a virtual impeller speed, which accounts for changes in motor torque due to the torque converter bypass clutch's opening or slipping, ensuring robust and efficient engine starts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the torque converter bypass clutch is opened or slipped during engine starts to isolate the driveline from torque disturbance, then the engine start reliability is improved, but the maximum available motor torque decreases due to impeller speed increase
Solution Approach 1:
The control algorithm calculates a compensatory torque amount before engine start based on the bypass clutch state, and applies this compensation in advance to the engine pull-up threshold calculation. This preliminary action ensures that the threshold already accounts for the torque reduction that will occur when the bypass clutch opens, preventing torque holes and ensuring reliable engine starts.
2Device complexity
If the engine pull-up threshold is calculated based on current motor torque without accounting for bypass clutch opening, then the control logic is simple, but torque holes occur during engine starts
Solution Approach 1:
The control algorithm continuously monitors the bypass clutch state and uses this feedback to dynamically adjust the engine pull-up threshold calculation. When the bypass clutch is detected to be open or slipping, the algorithm automatically applies torque compensation to the threshold, ensuring accurate engine start control without requiring complex hardware modifications.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides robust and efficient engine starts by dynamically calculating the necessary torque to fill torque holes created by the torque converter's loosening, improving overall vehicle performance and efficiency by accounting for changes in available motor torque.
Implementation Method 1
Opening and/or slipping the torque converter bypass clutch acts like a low pass filter and dampens the torque disturbances from propagating through the driveline
Implementation Method 2
a torque converter having a bypass clutch, and a motor configured to be selectively coupled to the engine
Data Source
AI summary
A system and method for modifying the engine pull-up (EPU) logic within a hybrid vehicle based on max motor torque that accounts for the drop or change in available motor torque due to the opening/slipping of a torque converter bypass clutch during engine starts is disclosed. An engine pull-up threshold is determined from max available motor torque at a virtual impeller speed, where the virtual impeller speed is the impeller speed that would result if the torque converter bypass clutch was open/slipping and transferring the same amount of torque.