Spark Ignition Engine Intake Valve Timing Control
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Solution Overview
Problem
In spark ignition type internal combustion engines, the variation in air-fuel ratio among cylinders during cold start is significant due to excessive blowback of the air-fuel mixture, leading to uneven fuel concentration and reduced engine efficiency.
Innovation Solution
A spark ignition type internal combustion engine with a variable closing timing mechanism for the intake valve and a throttle valve in the engine intake passage, where the closing timing of the intake valve is advanced during cold operation, and the throttle valve is reduced in opening degree, to control the amount of intake air and minimize blowback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the closing timing of the intake valve is retarded to reduce the amount of intake air, then the heat efficiency is improved, but the blowback of air-fuel mixture becomes excessive causing deviation in air-fuel ratio among cylinders
Solution Approach 1:
The patent applies dynamic adjustment of intake valve closing timing based on engine operating conditions. The ECU varies the closing timing according to engine speed and load, advancing it during cold starts and low-speed operations to prevent excessive blowback, and retarding it during high-speed operations to improve heat efficiency. This dynamic control resolves the contradiction by adapting the valve timing to specific operating conditions rather than using a fixed timing strategy
Solution Approach 2:
The patent changes the parameter of intake valve closing timing based on engine operating conditions. During cold starts and low-speed operations, the closing timing is advanced to reduce blowback and maintain uniform air-fuel ratio. During high-speed operations, the closing timing is retarded to reduce intake air amount and improve heat efficiency. This parameter change strategy allows the system to optimize for different priorities depending on operating conditions
2Reliability
If the closing timing of the intake valve is advanced to reduce blowback, then the air-fuel ratio uniformity is improved, but the amount of intake air increases reducing heat efficiency
Solution Approach 1:
The system dynamically adjusts the intake valve closing timing based on real-time engine operating conditions. During cold starts and low-speed operations, the timing is advanced to ensure uniform air-fuel distribution. During high-speed operations, the timing is retarded to optimize heat efficiency. This dynamic adaptation allows the system to prioritize air-fuel uniformity when needed and heat efficiency when needed
Solution Approach 2:
The patent implements parameter changes in the intake valve closing timing based on engine speed and load conditions. The ECU advances the closing timing during cold starts and low-speed operations to prevent excessive blowback and maintain uniform air-fuel ratio. During high-speed operations, the closing timing is retarded to reduce intake air amount and improve heat efficiency, thus optimizing the parameter according to operating conditions
Data Source
AI summary
A spark ignition type internal combustion engine of the present invention is provided with a variable closing timing mechanism which can change a closing timing of an intake valve after suction bottom dead center wherein the amount of intake air fed into a combustion chamber is controlled mainly by changing the closing timing of the intake valve. At the time of engine cold start, the closing timing of the intake valve is advanced compared with the time of engine warm operation. At the time of engine cold start, the air-fuel mixture which is taken into a combustion chamber is blown back into the engine intake passage whereby the air-fuel ratio varies among cylinders, but according to the spark ignition type internal combustion engine of the present invention, it is possible to suppress such variation in the air-fuel ratio among cylinders.