Crankshaft Phase Variation Analysis for Combustion Stability
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Solution Overview
Problem
Existing methods for estimating a stable combustion state in internal combustion engines face challenges due to the damping effect of inertia around the crankshaft, leading to a degraded signal-to-noise ratio and increased costs from the use of pressure sensors, which are also prone to degradation in harsh environments.
Innovation Solution
An internal combustion engine control device that calculates the time-series crank rotational speed, phase, and cycle-to-cycle variation of the phase to accurately estimate the stable combustion state without relying on pressure sensors, using a rotational speed calculation unit, phase calculation unit, and cycle variation calculation unit to control engine parameters like EGR rate and air-fuel ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the variation amount of crank rotational speed is used to detect combustion stability, then the detection cost is low, but the signal-to-noise ratio deteriorates due to the large moment of inertia around the crankshaft
Solution Approach 1:
The patent transitions from analyzing the magnitude of crank rotational speed variation to analyzing the phase relationship between crank rotational speed variations and combustion events. By examining the timing (phase) rather than just the amplitude of speed variations, the system can detect combustion instability before it is masked by the inertial damping effect, thereby maintaining low cost while improving measurement precision.
Solution Approach 2:
The system performs preliminary analysis of crank rotational speed data to identify patterns and trends that indicate combustion instability early in the combustion cycle. By detecting phase shifts in the rotational speed signal that precede significant torque variations, the system can alert operators or adjust parameters before the inertia of the crankshaft system masks the underlying combustion problems.
2Measurement precision
If a pressure sensor is installed in the combustion chamber to detect combustion variation state, then the detection accuracy is high, but the cost increases and the sensor degrades due to harsh environment
Solution Approach 1:
The patent uses the crank angle sensor and crank rotational speed data as an intermediary to indirectly measure combustion variation state. Instead of placing a pressure sensor directly in the harsh combustion chamber environment, the system uses the rotational speed variations of the crankshaft as a mediator that reflects combustion stability, thereby achieving accurate detection without exposing expensive sensors to degrading conditions.
Solution Approach 2:
The patent replaces the mechanical pressure sensing system with an electrical/electronic measurement system based on crank angle sensing and rotational speed analysis. By substituting a robust mechanical pressure sensor with an electronic system that measures crankshaft rotation characteristics, the invention achieves comparable or superior detection accuracy while eliminating the cost and reliability issues associated with pressure sensors in harsh environments.
Data Source
AI summary
Provided is an internal combustion engine control device that is capable of accurately estimating a stable combustion state at low cost. An internal combustion engine control device according to one aspect of the present invention includes: a rotational speed calculation unit 122a that calculates a time-series value of a crank rotational speed of an internal combustion engine; a rotational, speed phase calculation unit 122b that calculates a phase of the crank rotational speed from the time-series value of the crank rotational speed calculated by the rotational speed calculation unit; and a cycle variation calculation unit 122c that calculates the magnitude of variation between cycles of the phase of the crank rotational speed calculated by the rotational speed phase calculation unit.