Random Firing Frequency Control for Engine Vibration Reduction
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Solution Overview
Problem
Internal combustion engines face challenges in reducing vibration when cylinders are deactivated, as existing methods do not effectively manage the firing frequency to minimize noise and vibration perception during cylinder deactivation.
Innovation Solution
A system that includes a firing fraction module, an offset generation module, and a firing control module, which determines a firing fraction based on driver torque requests and randomly adjusts the firing frequency by adding an offset to a running total, executing a firing event when the total exceeds a predetermined value, thereby reducing noise and vibration by exciting natural resonances of the vehicle structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If cylinders are deactivated to decrease fuel consumption, then fuel efficiency is improved, but vibration and noise increase
Solution Approach 1:
The patent applies dynamics by randomly varying the firing frequency of active cylinders rather than maintaining a fixed pattern. The control module introduces random offsets to the firing fraction calculation, causing the firing events to occur at dynamically changing intervals. This dynamic adjustment creates a flat frequency distribution that avoids resonant frequencies, thereby reducing vibration and noise while maintaining cylinder deactivation for fuel efficiency.
Solution Approach 2:
The patent changes the parameter of firing frequency from a fixed value to a randomly varied value. By introducing random offsets to the firing fraction and executing firing events based on a running total that includes these random variations, the system creates a non-uniform firing pattern. This parameter change transforms the frequency distribution to be flat across the spectrum, preventing concentration of vibration energy at specific frequencies and thus reducing perceived noise and vibration.
2Object-generated harmful factors
If firing frequency is adjusted to reduce vibration, then noise and vibration are reduced, but engine response to torque requests may be affected
Solution Approach 1:
The patent applies partial action by using a firing fraction that represents only a portion of the full firing cycle. The random offset is added to this partial firing fraction, and firing events are executed selectively based on whether the running total exceeds predetermined thresholds. This approach allows the engine to respond to torque requests with partial firing events rather than requiring full cyclic adjustments, maintaining responsiveness while achieving vibration reduction through the randomized partial actions.
3Object-generated harmful factors
If random offset is added to firing fraction, then frequency distribution becomes flat reducing resonance, but control complexity increases
Solution Approach 1:
The patent applies self-service by using a running total that automatically accumulates the random offsets and firing fractions. The control module simply compares the running total to predetermined thresholds and executes firing events when thresholds are exceeded, then subtracts the firing fraction from the total. This self-regulating mechanism eliminates the need for complex control algorithms or external intervention, achieving flat frequency distribution through simple arithmetic operations that naturally distribute firing events across different frequencies.
Data Source
AI summary
A system according to the principles of the present invention includes a firing fraction module, an offset generation module, and a firing fraction module. The firing fraction module determines a firing fraction based on a driver torque request. The offset generation module randomly generates an offset. The firing control module adds the firing fraction to a running total each time that a crankshaft of an engine rotates through a predetermined angle, adds the offset to the running total, and executes a firing event in a cylinder of the engine when the running total is greater than or equal to a predetermined value.