Variable Displacement Engine Valve Deactivation Diagnostics
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Solution Overview
Problem
Existing methods for detecting non-deactivated intake and exhaust valves in variable displacement engines (VDEs) are not robust enough, particularly in the presence of noise factors, leading to inaccurate identification of lean running engines and increased emissions.
Innovation Solution
A method involving the calculation of variation in exhaust gas oxygen (EGO) sensor signals over multiple engine cycles and comparison with threshold variations, as well as estimating throttle and engine air flow rates, to accurately determine if intake and exhaust valves are deactivated, thereby adjusting engine operation to improve efficiency and reduce emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mean AFR measurement at UEGO sensor is used to detect non-deactivated valves, then detection capability is provided, but robustness to noise factors and accuracy are insufficient
Solution Approach 1:
The patent segments the detection process into multiple independent diagnostic parameters: (1) mean AFR measurement, (2) fast-sampled EGO signal variation analysis, and (3) air flow rate comparison. Each parameter is evaluated separately and combined to make the final diagnostic determination, allowing individual parameters to be optimized independently and reducing the impact of any single noisy measurement.
Solution Approach 2:
The patent applies partial action by using multiple diagnostic measurements beyond the single mean AFR measurement. It performs fast-sampled EGO signal analysis and air flow rate comparisons in addition to mean AFR measurement, using more diagnostic information than traditionally required to compensate for noise and improve detection reliability.
2Loss of energy
If cylinders are deactivated to improve fuel economy, then efficiency increases, but risk of valve malfunction and emissions increases
Solution Approach 1:
The patent implements feedback by continuously monitoring multiple diagnostic parameters (mean AFR, EGO signal variation, air flow rates) during VDE operation and using this information to detect valve non-deactivation malfunctions. The system provides ongoing feedback about the actual state of deactivated cylinders, enabling real-time detection of fresh air leakage into the exhaust system and allowing corrective action to prevent excessive emissions.
3Measurement precision
If fast-sampled EGO signal variation is calculated to detect non-deactivated valves, then detection accuracy improves, but computational complexity increases
Solution Approach 1:
The patent applies local quality by focusing the fast-sampled EGO signal analysis specifically on detecting the characteristic variation pattern caused by non-deactivated valves, rather than analyzing all aspects of the signal. The diagnostic algorithm looks for specific local features (signal variation magnitude and pattern) that indicate valve malfunction, simplifying the analysis compared to comprehensive signal processing.
4Reliability
If air flow rate comparison is used to detect non-deactivated valves, then detection robustness improves, but measurement and estimation complexity increases
Solution Approach 1:
The patent uses air flow rate comparison as an intermediary diagnostic parameter that indirectly indicates valve non-deactivation. Instead of directly measuring valve position or exhaust composition, the system compares throttle air flow rate with engine air flow rate estimates, using the air flow relationship as a mediator to detect the presence of fresh air in the exhaust system caused by non-deactivated valves.
Data Source
AI summary
Methods and systems are provided for a diagnostic routine of a variable displacement engine (VDE) of a vehicle to detect non-deactivated valves of deactivated cylinders due to a degraded valve deactivation mechanism. In one example, a method comprises, during operation of the VDE with one or more cylinders of the VDE deactivated, calculating a variation in a fast-sampled signal outputted by one or more exhaust gas oxygen (EGO) sensors of the VDE over a plurality of engine cycles; determining that the variation is greater than the threshold variation; and in response, indicating that valves of the one or more cylinders are not deactivated. A second method comprises estimating a throttle air flow rate and an engine air flow rate of the VDE; and indicating non-deactivated valves of one or more deactivated cylinders if the throttle air flow rate exceeds the engine air flow rate by a threshold.