Transmission Clutch Characterization via Torque Threshold Adjustment
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Solution Overview
Problem
In hybrid vehicles, unknown or inaccurate operating characteristics of the transmission clutch can lead to driveline torque disturbances during gear shifts, which are objectionable to occupants, especially under high torque demand conditions.
Innovation Solution
Adjusting the torque threshold of the electric machine via a controller in response to immature transmission clutch characterization, allowing for characterization of the clutch during gear downshifts to reduce torque disturbances, and applying or releasing the clutch based on this characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transmission clutch characterization is performed during normal operation, then clutch operating characteristics improve, but driveline torque disturbances increase during gear shifts
Solution Approach 1:
The patent applies preliminary action by adjusting the torque threshold before clutch characterization is complete. The controller proactively limits the electric machine's regenerative braking torque to values below the threshold during immature characterization phases, preventing potential torque disturbances before they occur. Once characterization is complete, the threshold is adjusted upward to restore full regenerative braking capability.
2Measurement precision
If regenerative braking torque threshold is reduced during clutch characterization, then opportunity to characterize clutch improves, but regenerative braking performance deteriorates
Solution Approach 1:
The patent applies partial action by implementing regenerative braking at a reduced level rather than fully limiting it. The controller allows regenerative braking torque up to the threshold value during characterization, which is below the maximum capability but sufficient to enable clutch learning. This partial utilization maintains some energy recovery while creating safe operating conditions for characterization.
3Measurement precision
If transmission gear downshift is used for clutch characterization, then clutch operating characteristics improve, but gear shift smoothness may deteriorate
Solution Approach 1:
The patent applies preliminary anti-action by preemptively limiting the electric machine's regenerative braking torque during the downshift process. The controller detects the downshift event and actively constrains torque demands to prevent disturbances that would otherwise occur during clutch engagement. This counter-measure is applied in advance and during the critical transition period to maintain smooth shifting while enabling characterization.
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
This approach improves the characterization of transmission clutches, reduces driveline torque disturbances, and allows for regenerative braking even during clutch characterization, enhancing the smoothness of gear shifts and maintaining opportunities for regenerative braking.
Implementation Method 1
The electric machine may convert the vehicle's kinetic energy into electric energy while it is providing the regenerative braking torque
Data Source
AI summary
Systems and methods for operating a vehicle that includes an engine and an electric machine are described. In one example, an actual total number of transmission gear downshifts are counted to determine whether or not a transmission clutch characterization is immature. The transmission clutch characterization may be adjusted if it is determined to be immature.