Cylinder Malfunction Detection via Retarding Torque Comparison
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Solution Overview
Problem
Existing methods for identifying malfunctioning cylinders in multicylinder combustion engines face challenges such as difficulty in simulating normal driving conditions, engine temperature variations, and interpreting test results due to fuel supply interruptions and cylinder variations.
Innovation Solution
A method involving two test cycles is performed: the first cycle with fuel supply interruption to all cylinders and the second cycle with fuel supply maintained to a single test cylinder, allowing comparison of retarding torque data to determine cylinder functionality, ensuring consistent test conditions and accurate results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If fuel supply is interrupted to all cylinders except one test cylinder, then the test can be performed under normal driving conditions with adequate fuel quantity, but engine temperature variations occur between tests of different cylinders
Solution Approach 1:
The method performs a first test cycle with fuel supply interrupted to all cylinders before performing the second test cycle with fuel supply to the test cylinder. This preliminary action establishes a baseline retarding torque value under identical engine conditions, allowing comparison that compensates for temperature variations between tests of different cylinders.
Solution Approach 2:
The method uses periodic alternation between two test cycles: one with all cylinders cut off and one with the test cylinder active. By repeating these cycles in sequence for each cylinder being tested, the method maintains consistent engine conditions throughout the testing process, eliminating temperature drift effects.
2Speed
If fuel supply is interrupted to only one cylinder, then the engine can run at normal speed with adequate fuel from other cylinders, but the engine may race if fuel quantities are not controlled
Solution Approach 1:
The method extracts the fuel supply to all cylinders except the test cylinder during the second test cycle, isolating the test cylinder's contribution to engine torque. This extraction approach allows the test cylinder to receive adequate fuel quantity while preventing other cylinders from compensating, thereby avoiding engine racing while maintaining normal operating conditions.
3Measurement precision
If the difference in engine speed before and after fuel interruption is measured, then a malfunctioning cylinder can be identified, but the difference is relatively small for engines with several cylinders making identification difficult
Solution Approach 1:
Instead of measuring small engine speed differences that are difficult to detect, the method skips directly to measuring retarding torque by analyzing the rate of engine speed decay during controlled deceleration. This approach amplifies the measurable effect of individual cylinder contribution, making malfunctioning cylinder identification much more precise and less complex.
4Measurement precision
If fuel supply is interrupted to test a cylinder, then torque contribution can be measured, but substantial variations are introduced by other cylinders that may be malfunctioning or have reduced capacity
Solution Approach 1:
The method performs a preliminary first test cycle with all cylinders cut off to establish a baseline retarding torque value. This baseline represents the engine's natural deceleration characteristics without any cylinder contribution. By comparing the second test cycle (with test cylinder active) against this baseline from the same engine state, the method isolates the test cylinder's torque contribution while eliminating interference from other potentially malfunctioning cylinders.
Data Source
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AI summary
A method for identifying a malfunctioning cylinder of a multicylinder combustion engine (1). First and second test cycles are performed after each other when an individual cylinder is to be tested. In both test cycles, the engine speed is allowed to decrease from an upper to a lower engine speed and the engine speed as a function of time during this decrease of the engine speed is recorded. In the first test cycle, no fuel is supplied to the cylinders during the decrease of the engine speed, whereas the test cylinder is supplied with a given fuel quantity during the decrease of the engine speed in the second test cycle. The recorded test data from the first and second test cycles is used in order to establish a test value representing the torque exerted by the test cylinder. This test value is used for establishing whether the test cylinder is malfunctioning.