Engine Stop Control Threshold Adjustment for Battery Voltage
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Solution Overview
Problem
In vehicles equipped with idling-stop or economy-running functions, the engine restarts before reaching zero engine rotation speed, resulting in a lower load on the starter and less battery voltage drop, potentially allowing insufficient battery voltage to meet the threshold for restarting, leading to restricted engine stop.
Innovation Solution
A control device that adjusts the threshold value for engine stop restriction based on the engine's rotation speed, using different modes for cranking and engaging gears to ensure smooth engagement and higher threshold values at higher rotation speeds, allowing the engine to continue operating even with insufficient battery voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the engine is re-started before the engine rotation speed attains to zero, then the load on the starter is reduced and battery voltage drop is minimized, but the threshold voltage requirement may not be met when battery voltage is insufficient
Solution Approach 1:
The patent applies dynamics by making the threshold voltage value variable rather than fixed. The control unit adjusts the threshold voltage based on the engine rotation speed at the time of restart request: when rotation speed is higher (indicating earlier restart), a higher threshold voltage is required; when rotation speed is lower (indicating later restart), a lower threshold voltage is accepted. This dynamic adjustment resolves the contradiction by adapting the voltage requirement to the actual operating conditions, allowing reliable restarts even when battery voltage is insufficient but rotation speed is still available.
Solution Approach 2:
The patent changes the parameter of threshold voltage based on another parameter (engine rotation speed). By establishing a relationship where threshold voltage increases with engine rotation speed, the system can accommodate varying battery conditions. When the battery is in good condition with sufficient voltage, the threshold is lower; when the battery voltage is insufficient but the engine is still rotating, the threshold is raised to ensure only restarts with adequate rotational energy are permitted, thus maintaining reliability while allowing energy-efficient operation.
2Device complexity
If a fixed threshold voltage is used for engine stop restriction, then the control logic is simple, but it cannot adapt to varying battery voltage conditions and engine rotation speeds
Solution Approach 1:
The patent transforms the static threshold voltage into a dynamic parameter that automatically adjusts according to engine rotation speed. The control unit continuously monitors both the threshold voltage and engine rotation speed, and compares the actual battery voltage against the speed-dependent threshold. This dynamic approach provides adaptability to varying battery conditions without requiring complex control logic, as the threshold adjustment follows a predetermined relationship with rotation speed rather than requiring intricate decision trees or multiple sensors.
Data Source
AI summary
When a predetermined stop condition is satisfied, an engine is stopped. When a predetermined start condition is satisfied, a motor in a starter is driven and the engine is started. When a voltage of a battery for supplying electric power to the motor becomes lower than a threshold value while the motor is driven, stoppage of the engine is thereafter restricted. The threshold value increases as an engine rotation speed at the time when the motor is driven increases.