Cam Profile Switching Diagnostic Emissions Control
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Solution Overview
Problem
Existing diagnostic methods for cam profile switching in internal combustion engines often result in increased undesirable emissions due to momentary changes in exhaust constituents during the diagnostic process, which can indicate incorrect operation and require frequent checks to ensure compliance with emission regulations.
Innovation Solution
A diagnostic method that compares exhaust gas constituents before and after a camshaft condition change while adjusting fuelling, allowing for correct operation indication without altering combustion conditions, thereby minimizing emissions. This method uses a control logic to determine if the camshaft switching system is functioning correctly by maintaining substantially unchanged combustion conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a momentary forced change of camshaft condition is performed for diagnostic purposes, then correct cam switching operation can be confirmed, but undesirable emissions increase due to change in exhaust constituents
Solution Approach 1:
The patent applies parameter changes by adjusting the fuel injection quantity in response to camshaft position changes during diagnostic operation. When the camshaft switches between high-lift and low-lift profiles, the fuel amount is modified to compensate for changes in intake air quantity, thereby maintaining substantially constant exhaust gas composition and preventing emission increases while still enabling diagnostic detection of cam switching operation
Solution Approach 2:
The patent implements feedback control by using oxygen sensors to detect exhaust gas composition and comparing it between different camshaft operating conditions. The detected oxygen concentrations are fed back to the control unit, which then adjusts fuel injection quantities to maintain consistent exhaust composition across camshaft profile changes, enabling emission-free diagnostic operation
2Object-generated harmful factors
If closed loop feedback control is used to maintain stoichiometric air:fuel ratio, then emissions are minimized, but catalyst storage capacity may be exceeded during large disturbances
Solution Approach 1:
The patent applies preliminary action by proactively adjusting fuel injection quantities before and during camshaft profile switching operations. By anticipating the change in intake air quantity that occurs during camshaft switching and pre-adjusting the fuel amount, the system prevents large disturbances in the air:fuel ratio, ensuring catalyst storage capacity is not exceeded and emission control reliability is maintained
3Productivity
If diagnostic is performed for minimum time period, then diagnostic efficiency is improved, but emission increase still occurs
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting fuel injection quantities throughout the diagnostic process, not just at the beginning or end. This continuous parameter adjustment ensures that exhaust gas composition remains constant even during the brief momentary diagnostic operation, eliminating emissions increases while maintaining diagnostic efficiency
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
The method reduces the occurrence of undesirable emissions during diagnostics, ensuring accurate camshaft switching system operation without increasing emissions, and allows for reliable recording of diagnostic results, enhancing compliance with emission regulations.
Implementation Method 1
an oxygen sensor in the exhaust tract determines whether the exhaust gases have an oxygen content indicative of non-stoichiometric combustion
Implementation Method 2
catalytically coated substrates in each exhaust system to minimize tailpipe emissions
Data Source
AI summary
A diagnostic routine momentarily forces an engine to an alternative operating condition, and at the same time adjust fuelling of the engine so as to be appropriate to the alternative operating condition (31). In one embodiment substantially unchanged exhaust constituents (32) indicate correct adoption of the alternative operating condition. In another embodiment a substantial change in a calculated measure is indicative of correct adoption of the alternative condition. The invention allows better control of undesired exhaust emissions during operation of the diagnostic.