Hybrid Powertrain Shift Timing via Electric Machine Torque Capacity
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Solution Overview
Problem
Hybrid electric automotive powertrains face a torque shortage when restarting the engine and downshifting the transmission, leading to delayed acceleration requests and reduced drivability.
Innovation Solution
A method of controlling the hybrid powertrain that determines the torque capacity of the electric machine and shifting torque required, timing transmission shifts and engine startup to ensure sufficient torque for smooth gear changes, either using the electric machine alone when torque capacity exceeds shifting torque or delaying the shift until the engine is started.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the engine is restarted and transmission is downshifted simultaneously to meet acceleration request, then the acceleration request can be fulfilled, but a torque shortage occurs causing delayed shift completion and reduced drivability
Solution Approach 1:
The controller determines torque capacity and shifting torque requirements before executing the shift, and times the shift completion based on these pre-calculated values. This preliminary assessment allows the system to plan the sequence of engine restart and shift completion to avoid torque shortages, rather than reacting after the problem occurs.
Solution Approach 2:
The system dynamically adjusts the shift timing based on real-time torque capacity of the electric machine and the shifting torque required. The controller can delay shift completion until the engine is running and torque capacity is sufficient, making the shift process adaptive rather than fixed, thereby preventing torque shortages while maintaining acceleration capability.
2Loss of time
If the transmission shift is completed immediately upon receiving shift request, then shift speed is improved, but torque shortage occurs when engine is stopped and machine torque is insufficient
Solution Approach 1:
The controller continuously monitors torque capacity of the electric machine and compares it against the shifting torque required. This feedback mechanism allows the system to detect when torque capacity is insufficient and adjust shift timing accordingly, preventing torque shortages while minimizing delay to shift completion.
Solution Approach 2:
The system changes the timing parameter of shift completion based on torque capacity conditions. When torque capacity exceeds shifting torque, the shift is completed promptly; when torque capacity is insufficient, the shift completion is delayed until the engine starts and torque capacity becomes adequate. This dynamic parameter adjustment resolves the contradiction between speed and force.
Data Source
AI summary
A transmission shift is timed for a hybrid electric powertrain as a function of a torque capacity of an electric machine relative to a shifting torque required to change gearings of a transmission. A vehicle is being propelled by the machine, with an engine stopped, when the shift is requested. If the machine has insufficient torque capacity to change transmission gearings, then the shift request is delayed until the engine has started.