Fuel Vapor Diagnostic System Using Saturated Pressure
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Solution Overview
Problem
Existing failure diagnostic devices for fuel vapor processing apparatuses require a pressure source to generate positive or negative pressures, necessitating energy for operation and limiting their effectiveness.
Innovation Solution
A diagnostic system that determines saturated vapor pressure characteristics within fuel tanks to diagnose leakage and blockage failures without the need for external pressure sources, using temperature and vapor pressure detection to assess changes over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pressure source is used to generate positive or negative pressure in the diagnostic space, then failure diagnosis can be performed, but energy consumption increases and device complexity increases
Solution Approach 1:
The fuel tank system uses its own saturated fuel vapor pressure to perform self-diagnosis. The ECU monitors pressure changes in the fuel tank without requiring external pressure sources, allowing the system to diagnose itself using naturally occurring vapor pressure differential between the fuel tank and canister.
Solution Approach 2:
The patent replaces the mechanical pressure generation system with a sensor-based monitoring system. Instead of using a pressure source to create positive or negative pressure, the system uses pressure sensors to detect natural pressure changes caused by vaporization and condensation of fuel vapor, substituting mechanical action with electronic detection.
2Reliability
If a pressure source is used to generate positive or negative pressure in the diagnostic space, then failure diagnosis can be performed, but device complexity increases
Solution Approach 1:
The fuel tank system uses its own saturated fuel vapor pressure to perform self-diagnosis. The ECU monitors pressure changes in the fuel tank without requiring external pressure sources, allowing the system to diagnose itself using naturally occurring vapor pressure differential between the fuel tank and canister.
Solution Approach 2:
The patent replaces the mechanical pressure generation system with a sensor-based monitoring system. Instead of using a pressure source to create positive or negative pressure, the system uses pressure sensors to detect natural pressure changes caused by vaporization and condensation of fuel vapor, substituting mechanical action with electronic detection.
3Use of energy by moving object
If saturated vapor pressure characteristics are monitored over time without pressure sources, then energy consumption is reduced, but measurement precision may be affected
Solution Approach 1:
The ECU continuously monitors pressure changes in the fuel tank and compares them against expected vaporization patterns. By using feedback from pressure sensor readings over time, the system can distinguish between normal vapor pressure fluctuations and actual leakage conditions, maintaining measurement precision through continuous monitoring and comparison.
Solution Approach 2:
The system performs preliminary monitoring of pressure changes during normal operation to establish baseline vaporization patterns. This preliminary data collection allows the ECU to later distinguish between normal operational variations and actual failure conditions, improving measurement precision without requiring additional energy-intensive measurements.
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
Enables effective diagnosis of fuel vapor processing apparatus failures by eliminating the need for energy-intensive pressure generation, allowing for accurate detection of leaks and blockages based on vapor pressure changes.
Implementation Method 1
an aspirator that allows the fuel to flow through a narrow flow passage having a passage cross-sectional area narrower than that of an upstream side at a faster flow velocity, thereby generating a negative pressure in a decompression chamber near this narrow flow passage
Implementation Method 2
A saturated vapor pressure characteristic estimating means determines the saturated vapor pressure characteristics of the fuel within the fuel tank
Data Source
AI summary
A failure diagnostic device is configured to determine saturated vapor pressures of a fuel within a fuel tank. In a fuel vapor processing apparatus, some or all of the passages and spaces into which the fuel vapor flows into the fuel vapor processing apparatus are closed to the atmosphere. In this condition, the failure diagnostic device determines a plurality of saturated vapor pressure characteristics over time. The failure diagnostic device is configured to diagnose whether or not a leakage or a blockage failure in the fuel vapor processing apparatus is present. The failure diagnostic device determines a Reid vapor pressure (RVP) based on each of the plurality of determined saturated fuel vapor pressure characteristic and diagnoses whether or not a failure is present in accordance with a change in these RVPs over time.