Hybrid Vehicle Contactor Control for Engine Start
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Solution Overview
Problem
In hybrid vehicles with a motor generator and engine, starting the engine when the battery's State Of Charge (SOC) is below a certain threshold can result in the contactor being turned off, leading to engine failure due to battery degradation, as the contactor is turned off again during cranking, preventing successful engine startup.
Innovation Solution
A hybrid vehicle system that includes a charge state calculation means to determine the SOC, a standard opening and closing means to turn off the contactor when SOC is below a threshold, and an engine startup opening and closing means to maintain the contactor on when an engine startup signal is received if the SOC is above a lower threshold value, allowing the engine to start while minimizing battery degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contactor is turned off when SOC is below the threshold value to protect the battery, then battery degradation is prevented, but engine startability is deteriorated
Solution Approach 1:
The contactor control strategy dynamically adapts based on engine startup conditions. When an engine startup is detected, the system temporarily overrides the standard SOC threshold control, maintaining the contactor in the on-state even when SOC is below the normal threshold, thereby enabling engine cranking while still protecting the battery through controlled discharge limits.
Solution Approach 2:
The system changes the SOC threshold parameter specifically for engine startup scenarios. A lower SOC threshold is applied during engine startup compared to normal operation, allowing the battery to discharge to lower levels temporarily when needed for cranking, while maintaining higher thresholds during regular operation to protect battery health.
2Reliability
If the contactor is turned off due to low SOC during cranking, then battery discharge is limited, but the engine cannot be started
Solution Approach 1:
The system performs preliminary detection of engine startup intent before cranking begins. By detecting the startup signal in advance, the control system prepares by maintaining the contactor in the on-state and adjusting SOC thresholds beforehand, ensuring that sufficient power is available during the critical cranking period without compromising battery protection during subsequent operation.
Solution Approach 2:
The control system acts as an intermediary between the battery protection mechanism and the engine startup requirement. It mediates by temporarily adjusting contactor control parameters and SOC thresholds during startup events, balancing the conflicting demands of battery protection and successful engine cranking through controlled compromises in discharge limits.
Data Source
AI summary
A hybrid vehicle includes: a charge state calculator which calculates a charge state of an electricity storer; a standard opening and closing device which turns off a contactor when the charge state calculated by the charge state calculator is lower than a standard lower-limit value; and an engine startup opening and closing device which maintains the contactor in an on state when an engine startup signal is input even when the charge state calculated by the charge state calculator is a value for turning off the contactor, wherein the contactor turning-on operation executed by the engine startup opening and closing device is executed when the charge state calculated by the charge state calculator is higher than an engine startup lower-limit value set lower than the standard lower-limit value by a predetermined value.