Engine Dither Control for Exhaust Temperature and Torque Stability
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Solution Overview
Problem
Existing internal combustion engine control systems face challenges in reducing torque fluctuations while maintaining effective exhaust gas temperature raising capabilities, particularly when prioritizing temperature raising over torque stability.
Innovation Solution
A control device that executes a dither control process by setting specific cylinders to rich and lean combustion modes, with adjustable differences in air-fuel ratios, allowing for reduced torque fluctuations during normal driving while enhancing temperature raising capabilities when necessary, such as during filter regeneration processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the absolute value of the difference between air-fuel ratio of rich combustion cylinder and air-fuel ratio of lean combustion cylinder is increased to enhance temperature raising capability, then the temperature raising effect is improved, but torque fluctuation increases
Solution Approach 1:
The patent applies dynamics by making the dither control executable only under specific conditions (when exhaust gas temperature is below a predetermined threshold and a specific flag is set). This dynamic activation allows the system to adaptively apply large air-fuel ratio differences only when temperature raising is needed, rather than continuously, thus resolving the contradiction between temperature raising capability and torque stability.
Solution Approach 2:
The patent changes the parameter of air-fuel ratio difference dynamically by setting it to a larger absolute value only when dither control is activated. The control device adjusts the injection amount instruction values to create a larger difference between rich and lean cylinders specifically during dither control execution, enabling enhanced temperature raising while limiting torque fluctuation during normal operation.
2Temperature
If dither control is executed continuously to maintain temperature raising capability, then the exhaust gas purifier temperature is maintained, but drivability deteriorates due to constant torque fluctuation
Solution Approach 1:
The patent implements periodic action by executing dither control only intermittently based on temperature conditions and external triggers. The control device checks whether exhaust gas temperature is below a threshold and whether a specific flag (set by external devices at repair shops) is active before activating dither control. This periodic rather than continuous execution maintains temperature capability while minimizing impact on drivability during normal operation.
Solution Approach 2:
The system dynamically switches between dither control execution and non-execution states based on real-time temperature monitoring and external commands. This dynamic on/off control allows the exhaust gas purifier temperature to be maintained when needed while avoiding constant torque fluctuations that would degrade drivability during normal driving conditions.
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 torque fluctuations during normal driving while ensuring sufficient temperature raising capabilities, especially during filter regeneration, without the need for continuous high load operation, thus improving engine performance and efficiency.
Implementation Method 1
a dither control process for operating the fuel injection valves to set at least one of the cylinders as a rich combustion cylinder and to set at least another one of the cylinders that differs from the at least one of the cylinders as a lean combustion cylinder
Implementation Method 2
an exhaust gas purifier, which purifies exhaust gas discharged from a plurality of cylinders
Data Source
AI summary
In a dither control process performed on a fuel injection valve, at least one cylinder is set as a rich combustion cylinder and another cylinder is set as a lean combustion cylinder. A dither control process is executed in a first mode when a vehicle is driven in a normal manner by a user. The dither control process is executed in a second mode on condition that a command signal for performing a temperature raising process on the exhaust gas purifier is input from a device outside the vehicle at a repair shop. The absolute value of the difference between the air-fuel ratio of the lean combustion cylinder and the air-fuel ratio of the rich combustion cylinder obtained by the dither control process is set to be greater in the second mode than in the first mode.