CVVT Fastening Bolt Malfunction Detection via PWM Duty Comparison
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Solution Overview
Problem
The release of a fastening bolt in continuous variable valve timing (CVVT) systems leads to vehicle starting issues and DC motor durability problems due to incorrect camshaft position learning, which existing technologies fail to accurately and quickly detect.
Innovation Solution
A method and system that utilize an engine control unit (ECU) to compare PWM duty values for camshaft position and CVVT actuator response speed with set reference values to detect malfunction, determining bolt release by analyzing deviations from these values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing technologies are used to detect fastening bolt release, then the detection process is simple, but the detection accuracy and speed are insufficient
Solution Approach 1:
The system performs preliminary learning of the camshaft's most retarded angle position and CVVT actuator response speed before normal operation. By storing these baseline values and comparing them against actual operating parameters, the system enables early detection of bolt release anomalies without requiring complex additional sensors or detection mechanisms during normal operation.
Solution Approach 2:
The ECU continuously monitors PWM duty values during camshaft position learning and CVVT actuator response speed learning, comparing these values against stored reference values. This feedback mechanism allows the system to detect bolt release by identifying deviations from expected parameter ranges, achieving high detection accuracy through parameter comparison rather than direct mechanical sensing.
2Reliability
If the fastening bolt is not monitored, then the system structure remains simple, but vehicle starting reliability and motor durability are compromised
Solution Approach 1:
The existing ECU and its existing learning functions are utilized to perform bolt release detection. The ECU's existing PWM control and parameter monitoring capabilities are repurposed to detect bolt release by analyzing deviations in camshaft position learning and actuator response speed, eliminating the need for separate dedicated detection hardware while improving reliability.
Solution Approach 2:
The ECU performs multiple functions using the same hardware resources: it controls camshaft position, monitors CVVT actuator response, and detects fastening bolt release status all through the existing PWM control and parameter monitoring infrastructure. This multi-functionality approach maintains simple system structure while achieving enhanced reliability through integrated monitoring.
3Speed
If conventional detection methods are used, then the implementation is straightforward, but the detection speed and response time are slow
Solution Approach 1:
The system performs periodic learning of the camshaft's most retarded angle position and CVVT actuator response speed at defined intervals (e.g., during engine startup or maintenance cycles). By conducting these learning operations periodically and comparing results against reference values, the system achieves rapid detection of bolt release without requiring continuous complex monitoring mechanisms.
Data Source
AI summary
A method for detecting malfunction of a fastening bolt in a continuous variable valve timing (CVVT) includes: deciding whether a camshaft position sensor is operating normally; learning the most retarded angle position of the camshaft using the camshaft position sensor; deciding whether the learning of the most retarded angle position of the camshaft is normal; and comparing a PWM duty value used in the learning with a set first reference value when the learning of the most retarded angle position of the camshaft is normal.