Engine Controller Idle Dither Air-Fuel Ratio Limiting
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Solution Overview
Problem
The existing dither control methods for internal combustion engines cause rotational fluctuation and discomfort due to the difference in torque generated between lean and rich combustion cylinders, particularly noticeable during idling, stopped states, and low engine temperatures or rotational speeds.
Innovation Solution
A controller that executes an idle-time limiting process, reducing the absolute difference in air-fuel ratios between lean and rich combustion cylinders, especially during idling, stopped states, and low engine conditions, to minimize user discomfort by adjusting fuel injection amounts based on engine state and conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If dither control is executed to increase catalyst temperature, then exhaust purification effectiveness is improved, but rotational fluctuation increases causing user discomfort
Solution Approach 1:
The controller dynamically adjusts the air-fuel ratio difference between cylinders based on operating conditions. During idling, the air-fuel ratio difference is limited to prevent excessive rotational fluctuation, while during other operations, a larger difference is allowed to effectively heat the catalyst. This dynamic adjustment resolves the contradiction between catalyst temperature and rotational fluctuation.
Solution Approach 2:
The system changes the air-fuel ratio parameter differently under different operating conditions. By limiting the air-fuel ratio difference during idling and allowing larger differences during other operations, the system optimizes both catalyst heating efficiency and rotational stability according to the specific operating context.
2Temperature
If air-fuel ratio difference between lean and rich cylinders is increased, then catalyst heating efficiency is improved, but torque fluctuation increases
Solution Approach 1:
The controller adjusts the air-fuel ratio parameter based on operating conditions. During idling, the air-fuel ratio difference is limited to maintain torque stability, while during other operations, a larger difference is applied to improve catalyst heating efficiency. This conditional parameter adjustment resolves the contradiction between heating efficiency and torque stability.
3Temperature
If dither control is executed during idling, then catalyst temperature increases, but user comfort deteriorates due to visible vibration
Solution Approach 1:
The controller applies different control strategies dynamically based on whether the engine is idling or operating under other conditions. During idling, the air-fuel ratio difference is limited to maintain user comfort, while during other operations, dither control is applied more aggressively for catalyst heating. This dynamic control strategy resolves the contradiction between temperature increase and user comfort.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces rotational fluctuation and user discomfort by minimizing the torque difference between lean and rich combustion cylinders, particularly during idling and low engine conditions, without excessively reducing the air-fuel ratio difference when the engine is not idling or at higher temperatures/rotational speeds.
Implementation Method 1
an air-fuel ratio in the lean combustion cylinder and an air-fuel ratio in the rich combustion cylinder
Data Source
AI summary
A controller for an internal combustion engine includes processing circuitry configured to execute: a dither control process of operating fuel injection valves to designate at least one of cylinders as a lean combustion cylinder, in which an air-fuel ratio is leaner than a stoichiometric air-fuel ratio, and to designate at least another one of the cylinders as a rich combustion cylinder, in which an air-fuel ratio is richer than the stoichiometric air-fuel ratio; and an idle-time limiting process of causing an absolute value of a difference between the air-fuel ratio in the lean combustion cylinder and the air-fuel ratio in the rich combustion cylinder to be smaller when the internal combustion engine is idling than when the internal combustion engine is not idling.