Engine Control Apparatus for Cold Start Combustion Stability
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Solution Overview
Problem
During engine start-up, especially with heavy fuels of low volatility, the air-fuel ratio can become lean, leading to unstable combustion, decreased engine torque, and increased unburned substances in emissions, as the air-fuel ratio sensor is not immediately activated to perform feedback control.
Innovation Solution
A control apparatus using a crank angle sensor and processor to detect rotational changes in the crankshaft, acquiring specific crank angular velocity differences in defined regions to determine combustion intensity and air-fuel ratio, and adjusting the fuel supply accordingly to prevent lean air-fuel ratios and improve combustion stability before the air-fuel ratio sensor is activated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback control is performed using an air-fuel ratio sensor, then the air-fuel ratio can be accurately controlled, but the sensor cannot detect the air-fuel ratio during the initial period after engine start-up, leading to lean air-fuel ratio and unstable combustion
Solution Approach 1:
The system performs preliminary detection of combustion state using crank angular velocity before the air-fuel ratio sensor becomes active. By monitoring crank angular velocity in the combustion period (e.g., 10-30 degrees after top dead center), the system can detect lean air-fuel ratio conditions and perform fuel amount correction in advance, ensuring stable combustion during the critical warm-up period when the sensor cannot yet provide feedback.
2Ease of manufacture
If heavy fuel with low volatility is used, then the fuel can be stored and handled more easily, but the air-fuel ratio becomes lean during cold start and combustion deteriorates
Solution Approach 1:
The system replaces chemical-based fuel volatility reliance with a physical measurement approach. Instead of depending on fuel vaporization characteristics to achieve proper air-fuel ratio, the system uses crank angular velocity measurement to directly detect combustion state and electronically controls fuel injection amount. This substitution allows heavy fuels to be used without compromising cold-start combustion stability.
3Loss of time
If the air-fuel ratio sensor is activated immediately, then feedback control can start sooner, but the sensor requires warm-up time and cannot provide accurate readings during cold start
Solution Approach 1:
The system introduces crank angular velocity as an intermediary parameter to bridge the gap during sensor warm-up. While the air-fuel ratio sensor is warming up and cannot provide accurate readings, the crank angular velocity serves as a reliable intermediary indicator of combustion quality. The ECU uses this intermediary measurement to control fuel injection, ensuring proper air-fuel ratio control without waiting for sensor activation.
4Reliability
If fuel amount is increased to compensate for lean air-fuel ratio, then combustion stability can be improved, but emission of unburned substances increases
Solution Approach 1:
The system implements a feedback control mechanism using crank angular velocity measurements. The ECU continuously monitors the crank angular velocity during the combustion period and compares it against reference values. When lean air-fuel ratio is detected (indicated by reduced crank angular velocity), the system provides feedback by increasing fuel injection amount. This closed-loop feedback ensures optimal fuel amount is supplied to maintain stable combustion without excessive fuel that would lead to unburned hydrocarbon emissions.
Data Source
AI summary
A control apparatus for an engine includes a crank angle sensor and a processor. The processor acquires a first crank angular velocity difference which is a change in a crank angular velocity in a first region. The first region includes a rotational change correlated with an engine torque output. The processor acquires a second crank angular velocity difference which is a change in the crank angular velocity in a second region. The second region includes a rotational change correlated with a combustion rate attributable to an air-fuel ratio. In a case where the first crank angular velocity difference is less than or equal to a first threshold and the second crank angular velocity difference is less than or equal to a second threshold, the processor performs an increase correction on a fuel amount to be supplied to the engine.