Malfunction Diagnostic Device for Evaporative Fuel Leakage Systems
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Solution Overview
Problem
Existing leakage diagnostic devices for evaporative fuel treatment systems cannot accurately distinguish between leaks in the system and malfunctions within the diagnostic device itself, leading to incorrect diagnosis and potential misinterpretation of system issues.
Innovation Solution
A malfunction diagnostic device is introduced, utilizing a pressure sensor, pump current, and air-fuel ratio sensor to diagnose malfunctions in the leakage diagnostic device by analyzing specific parameters and thresholds during various operational states, enabling differentiation between system leaks and diagnostic device failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a leakage diagnostic device is used to detect system leaks, then leakage detection capability is improved, but the ability to distinguish between system leaks and diagnostic device malfunctions deteriorates
Solution Approach 1:
The diagnostic system is segmented into multiple independent diagnostic routines that test different aspects of the system. The malfunction diagnostic routine separates diagnostic device testing from system leak detection, allowing independent evaluation of each component's status and accurate identification of the fault source.
Solution Approach 2:
The malfunction diagnostic routine acts as an intermediary test that isolates the diagnostic device from the system under test. By introducing this intermediate diagnostic layer, the system can determine whether a fault lies in the diagnostic device itself or in the evaporative fuel treatment system, resolving the ambiguity in fault identification.
2Measurement precision
If multiple diagnostic parameters are monitored to improve diagnosis accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The malfunction diagnostic routine utilizes existing sensors and components (pressure sensor, pump, vent valve) for dual purposes: both system leak detection and diagnostic device malfunction testing. This multi-functionality approach improves diagnosis accuracy without requiring additional dedicated hardware, thereby limiting the increase in system complexity.
Solution Approach 2:
The system monitors changes in existing parameters (pressure values, pump current, valve states) under different operational conditions to extract additional diagnostic information. By analyzing parameter behavior rather than adding more parameters, the system achieves higher measurement precision while maintaining relatively simple device architecture.
Data Source
AI summary
A leakage diagnostic device diagnoses leakage of evaporated fuel in an evaporative fuel treatment device. The evaporative fuel treatment device purges evaporated fuel, which is generated in a fuel tank and adsorbed on a canister, to an intake passage. The leakage diagnostic device includes a vent valve that blocks a first atmospheric passage, which connects the canister with an atmospheric opening, and a pump that pressurizes and depressurizes a second atmospheric passage, which is a bypass passage of the first atmospheric passage. The malfunction diagnostic device diagnoses malfunction of the leakage diagnostic device based on an output value of a pressure sensor that detects pressure in a passage connected to the canister.