Evaporative Fuel Treatment System Pressure Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional evaporative fuel treatment systems face inaccuracies in calculating evaporative fuel concentration due to pulsations in intake air passage negative pressure, leading to fluctuations in flow rate or density detection, and may experience delayed or reduced purging due to time-consuming pressure detection processes.
Innovation Solution
An evaporative fuel treatment system with a detection passage having a reduced area portion, a switching device, a depressurizing device, and a pressure detecting device that independently and discontinuously detects cutoff, air, and mixture pressures to calculate the evaporative fuel state, allowing for accurate concentration calculation and timely purging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure detection is performed on a continual basis to ensure accurate evaporative fuel concentration calculation, then measurement precision is improved, but loss of time increases due to delayed purging
Solution Approach 1:
The patent implements periodic action by detecting pressures at specific intervals and stages rather than continuously. The pressure detecting device detects cutoff pressure, air pressure, and mixture pressure at predetermined timing during purge stop and purge execution phases. This periodic detection approach ensures sufficient accuracy for concentration calculation while minimizing time loss and enabling timely purging.
2Measurement precision
If a depressurizing device is used to stabilize differential pressure in the detection passage, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies self-service by utilizing the existing purge mechanism and natural pressure differential to achieve stable detection conditions without requiring a separate depressurizing device. The detection passage is designed to naturally depressurize during purge operations, and the switching device coordinates detection timing with the purge cycle to ensure accurate measurements using already-available system resources.
3Productivity
If the reduced area portion is brought into communication with the canister during purging, then productivity is improved, but measurement precision deteriorates due to pressure fluctuations
Solution Approach 1:
The patent segments the detection process into distinct phases: pressure detection during purge stop (when the reduced area portion is isolated) and purge execution (when communication with the canister is established). The switching device controls the timing to separate these functions, allowing accurate pressure measurement during isolation and high-productivity purging during communication, thereby resolving the contradiction between measurement precision and productivity.
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
The system improves the accuracy of evaporative fuel concentration calculation and ensures timely and increased purging by stabilizing differential pressures and optimizing pressure detection timing, thereby enhancing the quantity and frequency of purged fuel.
Implementation Method 1
a depressurizing device operable for depressurizing the detection passage
Implementation Method 2
a canister into which evaporative fuel is adsorbed
Data Source
AI summary
An evaporative fuel treatment system is disclosed that includes a canister, a detection passage having a reduced area portion, and switching device that switches fluid communication. Also included is a depressurizing device for depressurizing the detection passage coupled to the detection passage on a side of the reduced area portion opposite to the switching device, and a pressure detecting device. Moreover, the system includes an evaporative fuel state calculating device for calculating an evaporative fuel state in the mixture based on a cutoff pressure, an air pressure, and a mixture pressure of a mixture of air and the evaporative fuel. In one embodiment, the cutoff pressure, the air pressure, and the mixture pressure are detected independently and discontinuously. In another embodiment, the cutoff pressure and the air pressure are detected on a continual basis during purge of the evaporative fuel.