Evaporative Fuel Handling Apparatus Pump Mode Switching
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Solution Overview
Problem
Existing evaporative fuel handling apparatuses face challenges in reducing size and weight by using a common pump for both forcible purge and leak checking, as the requirements for each operation are substantially different, leading to reduced accuracy in leak checking when a pump designed for forcible purge is used.
Innovation Solution
The apparatus includes a selector device to switch fluid communication between two passages with different pressure loss characteristics, allowing a single pump to perform both forcible purge and leak checking by adjusting the direction of discharge and using a restrictor to modify the pump's characteristic curve for leak checking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a pump is designed for forcible purge operation, then large flow rate is achieved, but the slope of P-Q characteristic curve becomes too large causing reduced accuracy in leak checking
Solution Approach 1:
The pump operates dynamically in two distinct modes: a first operation mode for forcible purge with large flow rate, and a second operation mode for leak checking with controlled flow rate. The controller switches between these modes based on the operational requirement, allowing the pump to adapt its characteristics to achieve both high productivity during purge and high measurement precision during leak checking
Solution Approach 2:
The controller changes the operating parameters of the pump by controlling it to operate at different points on its P-Q characteristic curve. During forcible purge, the pump operates at a point with large flow rate, while during leak checking, it operates at a point with smaller flow rate where the slope of the characteristic curve is smaller, thereby achieving accurate leak detection without requiring a different pump
2Reliability
If separate pumps are used for forcible purge and leak checking, then each operation achieves optimal performance, but the size and weight of the apparatus increase
Solution Approach 1:
A single pump is designed to perform multiple functions: it serves as both the forcible purge pump and the leak checking pump. The controller manages the pump's operation in different modes to satisfy the requirements of both functions, thereby eliminating the need for separate pumps and reducing the overall size and weight of the evaporative fuel handling apparatus while maintaining optimal performance for each operation
3Weight of stationary object
If a common pump is used for both operations, then size and weight are reduced, but the pump characteristics cannot be optimized for both forcible purge and leak checking
Solution Approach 1:
The pump's operating characteristics are made dynamic through controller management. The controller adjusts the pump's operation to match the required characteristics for each function: high flow rate for purge and controlled flow rate for leak checking. This dynamic adaptation allows a single pump to replace what would traditionally require two specialized pumps
Solution Approach 2:
The controller changes the operational parameters of the common pump by selecting different operating points on its P-Q characteristic curve. For forcible purge, it operates at parameters providing large flow rate; for leak checking, it operates at parameters providing appropriate pressure control. This parameter adjustment enables the common pump to achieve adaptability for both functions
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
This solution enables the use of a common pump for both operations, reducing the size and weight of the apparatus, improving accuracy during leak checking, and simplifying construction while maintaining effective forcible purge performance.
Implementation Method 1
A pump is included for producing a pressure difference between the inside and the outside of the purge system
Data Source
AI summary
A fuel handling apparatus with a purge system, a first communication passage, and a second communication passage with a greater pressure loss than the first communication passage. A check device is coupled to the second communication passage for checking a leak of evaporative fuel from the purge system. A pump is included, and a selector device is included for switching fluid communication of the pump between one of the first communication passage and the second communication passage. A controller controls the selector device to allow fluid communication between the first communication passage and the pump and then controls the pump to produce the pressure difference for forcible purging. The controller further controls the selector device to allow fluid communication between the second communication passage and the pump, and then controls the pump to produce the pressure difference and controls the check device for leak checking.