Wireless Fuel Level Sensor with Self-Powered Isolated Circuit
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Solution Overview
Problem
Conventional liquid surface level sensors in fuel tanks face issues with fuel ingress due to deteriorating seals, leading to potential galvanic corrosion from alcohol-based fuels, which affect sensor performance.
Innovation Solution
A liquid surface level sensor design with a magnet outside the housing, an arm converting float movement into magnet rotation, and a self-powered circuit unit isolated within the housing, using generating coils to produce power and wireless communication for level detection, eliminating the need for external power wires and reducing corrosion risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wires are routed from outside to inside the housing for electrical connection, then the sensing element can be electrically connected to the power source and external electronic devices, but fuel can enter the housing through the boundary between the wires and housing, causing deterioration of sealing performance and galvanic corrosion
Solution Approach 1:
The patent removes the wires and external power source from the system, extracting the harmful element that creates the sealing boundary. Instead of routing wires through the housing, the invention uses a wireless communication unit to transmit data externally, eliminating the physical penetration point where fuel could ingress.
Solution Approach 2:
The patent replaces the mechanical electrical connection system (wires and connectors penetrating the housing) with a wireless electromagnetic communication system. The sensing element remains isolated inside the housing, communicating data wirelessly to external devices, thus eliminating the mechanical breach in the housing seal.
2Object-affected harmful factors
If a molded member is used to seal the boundary between wires and housing, then fuel ingress can be prevented, but the molded member deteriorates after long-time exposure to fuel and loses adhesion strength due to thermal expansion and contraction
Solution Approach 1:
The patent completely removes the molded sealing member and wire assembly from the system. By eliminating the wires that require sealing, the complex molded seal structure is no longer needed, removing the component subject to fuel deterioration and thermal cycling.
Solution Approach 2:
The patent introduces wireless electromagnetic waves as an intermediary for data transmission between the isolated sensing element and external devices. This intermediary replaces the physical wire connection, allowing communication without compromising the housing seal integrity.
3Reliability
If alcohol fuel containing water adheres to metal portions of elements and circuits, then galvanic corrosion occurs between dissimilar metals and metal portions are electrolytically corroded, but wireless communication eliminates this risk by isolating the circuit unit
Solution Approach 1:
The patent extracts the circuit unit and sensing element from the fuel environment by enclosing them in a sealed housing. The wireless communication unit transmits data externally, allowing the electronic components to remain isolated from the corrosive alcohol-fuel-water mixture that would cause galvanic and electrolytic corrosion.
Solution Approach 2:
The housing creates an inert protective environment around the circuit unit and sensing element, isolating them from the corrosive fuel atmosphere. This physical barrier prevents contact between the metal portions of electronic components and the electrolytic alcohol-fuel mixture, eliminating galvanic and electrolytic corrosion risks.
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 solution effectively prevents fuel ingress and corrosion by generating power internally and transmitting data wirelessly, ensuring reliable operation and reducing electrical consumption.
Implementation Method 1
a float located on a liquid surface of the liquid due to buoyancy
Implementation Method 2
a generating element that generates electric power based on a change in magnetic flux caused by the rotation of the magnet
Data Source
AI summary
A liquid surface level sensor includes a housing, a float located on a liquid surface, a magnet that rotates in accordance with up-and-down movement of the float, an arm joined with the float and the magnet, and a circuit unit. The circuit unit includes a sensing element that detects rotation of the magnet, and a wireless communication circuit that outputs a liquid surface level detected by the sensing element to a device installed in a vehicle. The circuit unit includes generating element that generate electric power from a change in magnetic flux caused by the rotation of the magnet, and a generation circuit that supplies electric power generated by the generating element to the sensing element and the wireless communication circuit as drive electric power. The circuit unit is included inside the housing in a state isolated from the outside.