Valve Fault Detection in Skip Fire Engines
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Solution Overview
Problem
Internal combustion engines operating in skip fire mode face challenges in identifying valve actuation faults, which can adversely affect engine performance due to unintended high pressure exhaust springs and other valve operation issues, as existing methods lack efficient diagnostic capabilities for real-time fault detection and remedial action.
Innovation Solution
A torque model is used to estimate expected net torque and compare it to actual measured torque, with additional methods such as monitoring crankshaft acceleration, cylinder pressure, and gas properties to detect valve actuation faults, including high pressure exhaust springs, allowing for immediate identification and remedial action to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If skip fire mode is used to improve fuel efficiency and reduce pumping losses, then engine displacement is reduced, but valve actuation faults become harder to detect and engine performance deteriorates
Solution Approach 1:
The system continuously monitors engine parameters (crankshaft acceleration, cylinder pressure, torque) and compares actual values against expected values to detect valve actuation faults in real-time, providing feedback control for reliable operation during skip fire mode
Solution Approach 2:
Traditional mechanical valve train diagnostics are replaced with sensor-based detection systems that measure crankshaft acceleration, cylinder pressure, and torque to identify valve actuation faults, enabling more reliable monitoring during complex skip fire operation
2Reliability
If real-time fault detection is implemented to prevent engine damage, then detection speed is improved, but device complexity increases
Solution Approach 1:
Existing engine sensors (crankshaft position sensor, cylinder pressure sensor, torque sensor) are used for multiple purposes including both normal engine control and valve actuation fault detection, reducing the need for additional dedicated diagnostic hardware
Solution Approach 2:
The engine's own operational parameters (crankshaft acceleration, cylinder pressure, torque) are used to detect valve actuation faults, allowing the system to self-diagnose without requiring external diagnostic equipment
Data Source
AI summary
Methods and systems are described for detecting valve actuation faults in internal combustion engines operating in a skip fire operational mode. In one aspect, a torque model is used to estimate an expected net torque during a selected operating window. The torque model considers an expected torque contribution from each of the cylinders and accounts for the effects of specific skip fire firing decisions that affect the expected torque contribution from each cylinder. A parameter indicative of the actual engine torque is also measured. Valve actuation faults can then be identified based at least in part on a comparison of the measured parameter to an expected parameter value that is based at least in part on the expected net torque. With the described approaches, the occurrence of the valve actuation fault can be made within one engine cycle of the initial occurrence of the fault.