Differential Pressure Sensor Spool Rotation Limiting Mechanism
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Solution Overview
Problem
Conventional differential pressure sensors with transversely disposed reed switches experience instability in sensing due to variations in magnetic force, leading to errors in pressure differential measurement.
Innovation Solution
A differential pressure sensor design featuring a spool with a cylindrical flange and front end portion, a rotation limiting mechanism, and a reed switch positioned with its center axis parallel to the casing's axis, preventing spool rotation and ensuring consistent magnetic field interaction, thereby stabilizing pressure sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a reed switch is transversely disposed in the differential pressure sensor, then the device can be manufactured with conventional methods, but the sensing stability deteriorates due to magnetic force variations causing positioning errors
Solution Approach 1:
The patent changes the reed switch from a transverse (asymmetric relative to casing axis) disposition to a longitudinal disposition where its center axis coincides with the casing's center axis. This symmetric alignment ensures that magnetic force variations do not cause positional deviations, thereby improving sensing stability while remaining manufacturable with conventional processes
2Device complexity
If the spool is allowed to move freely in the cavity, then the device structure is simplified, but the sensing precision deteriorates due to rotation causing inconsistent magnetic field interaction
Solution Approach 1:
The patent segments the spool's movement freedom by introducing a rotation limiting mechanism consisting of a rotation limiting portion and a groove portion. This segmentation allows the spool to move only in the axial direction while preventing rotation, thereby maintaining consistent magnetic field interaction between the magnet and reed switch without significantly complicating the overall structure
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 configuration ensures stable and accurate differential pressure sensing by maintaining a consistent positional relationship between the reed switch and magnet, reducing errors caused by magnetic field variations and ensuring reliable operation.
Implementation Method 1
an elastic member for applying a force to the spool in a direction toward the bottom face of the cavity
Implementation Method 2
a magnet provided at a distal end of the front end portion and opposing a bottom face of the cavity; a reed switch having a substantially cylindrical shape and positioned inside the casing to oppose the magnet
Implementation Method 3
When two reed blades within the reed switch are magnetized by a magnetic field of the magnet, the reed switch is brought into a state in which an internal circuit is closed (hereafter, referred to as the 'ON condition')
Data Source
AI summary
A spool, including a substantially cylindrical flange portion and a substantially cylindrical front end portion which is thinner than the flange portion and whose center axis is substantially coincident with the center axis of the flange portion, is provided in a manner capable of slidingly moving in a cavity formed in a casing. The flange portion is inserted in a first cavity which has a center axis substantially coincident with the center axis of the casing and which has an inner diameter that is substantially the same as the diameter of the flange portion in length. The front end portion is inserted in a second cavity which is formed with its center axis being substantially coincident with the center axis of the casing, and which has an inner diameter greater than the diameter of the front end portion and less than the inner diameter of the first cavity in length. The rotation limiting portion, which has a rod-like shape thinner than the front end portion and which is provided along the front end portion in a manner contacting the side surface of the front end portion, is inserted in a groove portion formed on the side face of the second cavity. When the flange portion slidingly moves along the first cavity, the rotation limiting portion slidingly moves along the groove portion.