Power Transmission Control for Electric Motor Overspeed
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Solution Overview
Problem
Existing power transmission systems face issues with overspeed of the first electric motor when there is a malfunction in the electrical transmission mechanism, leading to potential deterioration of drivability during normal conditions.
Innovation Solution
A control apparatus that includes a malfunction determination unit, engine operation control unit, and shift control unit to determine and address overspeed by causing the mechanical transmission mechanism to upshift when a malfunction is detected, thereby preventing overspeed without compromising drivability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the vehicle is restricted to avoid traveling ranges that lead to overspeed of the first electric motor when engine rotation is stopped, then the first electric motor overspeed risk is prevented, but vehicle acceleration performance and drivability are deteriorated
Solution Approach 1:
The control apparatus performs preliminary action by causing the mechanical transmission mechanism to upshift before the engine rotation is completely stopped. This proactive shift timing ensures that when the engine stops, the input rotating member rotation speed is already reduced, preventing first electric motor overspeed without requiring permanent restriction of traveling ranges, thus maintaining vehicle acceleration performance during normal operation.
2Reliability
If the mechanical transmission mechanism is caused to upshift when malfunction is detected and engine operation is stopped, then the first electric motor rotation speed is reduced, but the complexity of the control system increases
Solution Approach 1:
The control apparatus merges the malfunction determination function, engine operation control function, and shift control function into a single integrated control system. By combining these previously separate control functions, the system achieves coordinated control for protecting the first electric motor during malfunctions while minimizing the increase in overall system complexity through functional integration.
3Reliability
If the first electric motor operating state is uncontrollable due to malfunction, then the electrical transmission mechanism cannot be properly controlled, but restricting vehicle traveling ranges deteriorates normal drivability
Solution Approach 1:
The control apparatus executes preliminary action by immediately causing the mechanical transmission mechanism to upshift upon detecting a malfunction and stopping engine operation. This preliminary shift action reduces the input rotating member rotation speed before it can cause overspeed of the first electric motor, ensuring protection without requiring permanent restrictions on vehicle traveling ranges, thus preserving ease of operation during normal conditions.
Data Source
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AI summary
When an electrical continuously variable transmission (30) malfunctions and the operation of an engine (14) is stopped, an automatic transmission (20) is caused to upshift. Therefore, when the rotation of the engine (14) is stopped as a result of a stop of the operation, an AT input rotation speed (Ni) is decreased as compared to that before it is determined that there is a malfunction in the electrical continuously variable transmission (30). Thus, an MG1 rotation speed (Ng) is decreased in absolute value as compared to when the automatic transmission (20) is not caused to upshift, so an overspeed of a first electric motor (MG1) is prevented.