Torque Converter Engine Start Control in Hybrid Electric Vehicles
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Solution Overview
Problem
Hybrid electric vehicles without a hybrid starter and generator (HSG) require an effective method to determine an optimal target operating point for the torque converter, considering its performance characteristics, to efficiently start the engine using the motor and torque converter.
Innovation Solution
A method is provided to determine an optimal target operating point for the vehicle driving device by reflecting the characteristics of the torque converter, including determining the target engine starting speed and controlling the engagement and disengagement of the damper clutch, using a control unit to coordinate the motor and engine operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the vehicle is equipped with a torque converter instead of a hybrid starter and generator (HSG), then the vehicle can achieve smoother power transmission and improved comfort, but the method for determining the optimal target operating point becomes more complex and the engine starting control becomes more difficult
Solution Approach 1:
The patent applies preliminary action by pre-establishing the relationship between torque converter output speed and input speed based on characteristic information. The control unit determines the target input speed before engine starting is actually needed, using the formula: target input speed = output speed / speed ratio. This preliminary determination simplifies the real-time control process during engine starting.
Solution Approach 2:
The patent uses the torque converter's speed ratio as an intermediary parameter to bridge the relationship between motor output speed and engine input speed. By introducing this intermediate variable, the control system can indirectly control engine speed through the torque converter without requiring direct mechanical connection, thus simplifying the control logic.
2Productivity
If the target operating point is determined without considering torque converter characteristics, then the control process is simpler, but the engine starting efficiency and fuel economy deteriorate
Solution Approach 1:
The patent applies parameter changes by utilizing the torque converter's characteristic speed ratio parameter to transform the control approach. Instead of directly controlling engine speed, the system controls the torque converter output speed and uses the speed ratio parameter to determine the corresponding input speed. This parameter-based approach improves starting efficiency while keeping the control process manageable.
Solution Approach 2:
The patent implements feedback by continuously monitoring the actual torque converter output speed and comparing it with the target output speed. The control unit adjusts the motor torque command based on the speed difference, creating a closed-loop control system that improves engine starting efficiency while maintaining reasonable control complexity.
Data Source
AI summary
Disclosed herein is a method of controlling a hybrid electric vehicle in which a torque converter is disposed between a motor and a transmission for driving the hybrid electric vehicle comprises, by a control unit, determining a driver demand torque and an output speed of the torque converter based on vehicle driving information, determining a target input speed of the torque converter from the determined output speed of the torque converter based on preset characteristic information of the torque converter and information on the determined driver demand torque, determining the determined target input speed of the torque converter as a target engine starting speed, and performing control to start an engine using torque of the motor when an engine-on mode is determined, and controlling and engine speed to the determined target engine starting speed after startup.