Hybrid Vehicle EV Mode Control for Coolant Temperature Limits
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Solution Overview
Problem
In hybrid vehicles, maintaining a low state of charge for the battery while preventing performance degradation of heating and defrosting devices is challenging, as continuous engine stoppage leads to decreased engine coolant temperature, necessitating engine restarts that can hinder battery charge reduction and degrade device performance.
Innovation Solution
A control method that adjusts the duration of electric vehicle mode based on estimated engine coolant temperature, continuing EV mode if the temperature remains above a threshold and shortening it if the temperature falls below, to maintain performance while reducing battery state of charge before reaching a destination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the hybrid vehicle continues to travel in EV mode to reduce battery state of charge, then the state of charge is reduced, but the engine coolant temperature decreases below the lower limit value
Solution Approach 1:
The patent applies dynamics by making the EV mode execution duration variable rather than fixed. The controller dynamically adjusts the EV mode termination timing based on real-time engine coolant temperature monitoring. When the temperature approaches the lower limit threshold, the controller automatically terminates EV mode and switches to engine operation, thereby adapting the charge reduction process to thermal conditions and preventing temperature from dropping below the functional threshold.
Solution Approach 2:
The patent changes the operational parameters by introducing temperature-based control logic. The system monitors engine coolant temperature as a key parameter and uses it to determine when to transition from EV mode to engine mode. This parameter-driven approach allows the system to optimize the trade-off between battery charge reduction and maintaining adequate coolant temperature for heating device functionality.
2Temperature
If the engine is restarted when coolant temperature reaches lower limit, then the coolant temperature is maintained, but the state of charge cannot be lowered as intended
Solution Approach 1:
The patent applies preliminary action by proactively managing the EV mode duration to prevent temperature from reaching the critical lower limit in the first place. Rather than waiting for temperature to drop and then restarting the engine, the controller predicts temperature trends and terminates EV mode in advance when temperature approaches the threshold. This preventive approach allows the system to maintain temperature without requiring engine restarts, thereby enabling continued charge reduction.
3Quantity of substance
If the engine stopping state is maintained after coolant temperature reaches lower limit, then the state of charge continues to be reduced, but the performance of heating device or defroster device is degraded
Solution Approach 1:
The patent implements feedback control by continuously monitoring engine coolant temperature and using this information to adjust EV mode execution. The controller receives temperature feedback and automatically terminates EV mode when the temperature approaches the lower limit threshold. This closed-loop control ensures that charge reduction actions do not compromise the reliability of heating and defroster devices, as the system responds to thermal conditions in real-time.
Data Source
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AI summary
A method for controlling a hybrid vehicle is a method for controlling a hybrid vehicle including an engine, a power generating motor generator, a traveling motor generator, and a battery. A controller executes a state of charge reducing control in which a state of charge of the battery at a time point at which the hybrid vehicle reaches a destination is lower than an upper limit state of charge by providing a section for executing an EV mode until the hybrid vehicle reaches the destination. During execution of the state of charge reducing control, if an estimated value of a lowest temperature of an engine coolant until the hybrid vehicle reaches the destination, assuming that the EV mode is continued to the destination, is equal to or higher than a first threshold value, the controller starts the EV mode when the EV mode is continuable to the destination and executes the EV mode until the hybrid vehicle reaches the destination, and if the estimated value of the lowest temperature is lower than the first threshold value, the controller shortens a section for executing the EV mode compared to when the estimated value of the lowest temperature is equal to or higher than the first threshold value.