Engine Control Method for Gradual Fuel Cut
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Solution Overview
Problem
Existing engine control methods lead to drastic changes in torque, affecting vehicle behavior and drivability due to significant fuel cut-offs, resulting in poor ride comfort and potential over-speed issues.
Innovation Solution
An engine control method that gradually adjusts fuel supply to both cylinders by controlling air-fuel ratios, transitioning from a lean burn in the first step to zero fuel supply in subsequent steps, mitigating torque changes and preventing over-speed by gradually cutting off fuel as engine speed increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fuel supply is cut off abruptly to prevent over-speed, then engine speed is controlled, but torque changes drastically affecting vehicle behavior and ride comfort
Solution Approach 1:
The fuel cut control is divided into three distinct steps based on engine rotation speed thresholds. In the first step (rotation speed ≤ first reference value), fuel supply is maintained. In the second step (first reference value < rotation speed ≤ second reference value), fuel supply to the first cylinder is cut off while the second cylinder continues to receive fuel. In the third step (rotation speed > second reference value), fuel supply to both cylinders is cut off. This segmentation allows gradual transition and prevents abrupt torque changes while effectively controlling engine speed.
Solution Approach 2:
The control system dynamically adjusts fuel supply based on real-time engine rotation speed. The controller continuously monitors rotation speed and switches between different fuel supply strategies (first, second, and third steps) according to the current operating conditions. This dynamic adjustment ensures that fuel cut-off is applied progressively rather than abruptly, maintaining vehicle behavior stability while preventing over-speed.
2Speed
If large fuel cut-off is applied to prevent over-speed, then engine speed is limited, but torque decreases significantly impacting drivability
Solution Approach 1:
The fuel cut control is divided into three distinct steps based on engine rotation speed thresholds. In the first step (rotation speed ≤ first reference value), fuel supply is maintained. In the second step (first reference value < rotation speed ≤ second reference value), fuel supply to the first cylinder is cut off while the second cylinder continues to receive fuel. In the third step (rotation speed > second reference value), fuel supply to both cylinders is cut off. This segmentation allows gradual transition and prevents abrupt torque changes while effectively controlling engine speed.
Solution Approach 2:
In the second step, fuel supply is partially cut off (only to the first cylinder) rather than completely cut off. This partial action reduces the magnitude of torque change while still making progress toward preventing over-speed. The controller applies fuel cut-off progressively, applying more aggressive measures only when necessary (third step), thereby minimizing the impact on drivability while maintaining effective speed control.
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
This approach moderates torque changes, enhancing vehicle stability and ride comfort while preventing excessive engine speed, ensuring smooth transitions and maintaining drivability.
Implementation Method 1
As the fuel burns in the first cylinder and the second cylinder, the engine rotates, and the engine outputs torque
Data Source
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AI summary
There is described an engine control method for controlling an engine (11) provided with a first cylinder (15a) and a second cylinder (15b), including a first step, a second step, and a third step;when a rotation speed (A) is equal to or more than a first reference value (B1) and less than a second reference value (B2), the first step being executed; in the first step, a first amount (Q1) being controlled so that a first air-fuel ratio (D1) being leaner than the theoretical air-fuel ratio, and a second amount (Q2) being controlled so that a second air-fuel ratio (D2) is leaner than the theoretical air-fuel ratio;when the rotation speed (A) is equal to or more than the second reference value (B2) and less than a third reference value (B3), the second step being executed; in the second step, the first amount (Q1) being controlled to zero, and the second amount (Q2) being controlled so that the second air-fuel ratio (D2) is leaner than the theoretical air-fuel ratio; when the rotation speed (A) is equal to or more than the third reference value (B3), the third step being executed; in the third step, the first amount (Q1) being controlled to zero and the second amount (Q2) being controlled to zero.