Cylinder Knock Diagnosis Using Crankshaft Speed Analysis
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Solution Overview
Problem
Identifying and addressing engine knock in multi-cylinder engines without individual cylinder knock sensors is challenging, leading to reduced efficiency and compromised emissions, as current methods require adjusting all cylinders' ignition timing, which is costly and complex.
Innovation Solution
A system using a sensor to measure engine parameters and a controller that applies recursive sum spectral analysis to determine the magnitude of selected frequency components, allowing for diagnosis of engine conditions like knock and adjusting operating parameters accordingly, potentially identifying the specific cylinder affected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual cylinder knock sensors are installed to identify which cylinder is knocking, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent segments the engine into individual cylinders and uses the existing crankshaft position sensor to detect knock in each cylinder sequentially. By dividing the detection task and using the existing sensor for each cylinder's knock detection during its firing cycle, the system achieves cylinder-level identification without adding individual knock sensors to each cylinder.
Solution Approach 2:
The system uses the existing crankshaft position sensor, which is already present for timing purposes, to serve the additional function of knock detection. This self-service approach eliminates the need for dedicated knock sensors in each cylinder, reducing complexity while maintaining identification precision.
2Reliability
If all cylinders have ignition timing adjusted to reduce knocking, then reliability is improved, but productivity and engine efficiency decrease
Solution Approach 1:
The patent applies local quality by identifying the specific cylinder experiencing knock and adjusting ignition timing only for that cylinder rather than all cylinders. This localized adjustment maintains optimal timing for non-knocking cylinders (preserving efficiency) while retarding timing only in the affected cylinder (reducing knock), thus resolving the contradiction between reliability and productivity.
3Device complexity
If a single sensor measures engine parameters and spectral analysis is applied, then device complexity is reduced, but measurement precision for identifying knock may worsen
Solution Approach 1:
The patent exploits mechanical vibration characteristics of engine knock, which manifest as specific frequency components in the signal from the crankshaft position sensor. By applying spectral analysis to identify these characteristic vibration frequencies, the system achieves precise knock detection using a single sensor, resolving the contradiction between device complexity and measurement precision.
Data Source
AI summary
Various systems and methods are provided for identifying cylinder knock. In one example, cylinder knock may be identified based on a knock monitor that identifies knock based on output from a crankshaft speed sensor.