Spool Position Sensing Through a Seal-Free Valve Cap
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Solution Overview
Problem
Existing spool-displacement detection devices require sealing to prevent fluid leakage, which complicates the design and increases the risk of contamination and damage.
Innovation Solution
A spool-displacement detection device with a cap that includes an insertion hole for a displacement member, a magnet, and a detection unit attached to the cap's outer surface, eliminating the need for sealing by using a recessed portion and a magnetic shield to protect the detection unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the magnetic sensor penetrates through the cap to face the pilot chamber, then the detection function is achieved, but sealing complexity increases and fluid leakage risk occurs
Solution Approach 1:
A non-magnetic tube serves as an intermediary component that allows the magnetic sensor to detect the magnet's position through its wall without requiring direct penetration into the fluid chamber. The tube wall acts as a mediator that transmits magnetic field information while maintaining fluid sealing, thus achieving detection functionality without compromising sealing integrity.
2Measurement precision
If the magnetic sensor penetrates through the cap, then detection is enabled, but the risk of fluid leakage and contamination increases
Solution Approach 1:
The non-magnetic tube acts as a protective intermediary barrier between the magnetic sensor and the fluid environment. It allows magnetic field penetration for detection purposes while physically preventing fluid contact with the sensor, thereby eliminating leakage risks and contamination concerns associated with direct penetration designs.
3Device complexity
If the detection unit is attached to the outer surface of the cap, then sealing requirements are eliminated, but the detection distance increases reducing accuracy
Solution Approach 1:
The cap is designed with a localized non-magnetic tube section at the detection area, allowing the magnetic sensor to be positioned close to the magnet through the tube wall. This local modification enables accurate detection without requiring the entire cap structure to be designed for close proximity, thus maintaining detection accuracy while keeping the overall structure simple and seal-free.
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 enhances detection accuracy, reduces the risk of fluid leakage, and simplifies attachment to conventional fluid pressure valve devices while maintaining structural integrity and reducing the device's size.
Implementation Method 1
a magnet provided on the displacement member and configured to be displaced together with the displacement member; and a detection unit configured to detect a change in a magnetic field due to the displacement of the magnet
Data Source
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AI summary
The spool-displacement detection device (100) for detecting the displacement amount of the spool (53) of the fluid pressure valve device (50) serving as the valve device having the housing (51), the accommodating hole (52) formed in the housing (51), and the spool (53) slidably accommodated in the accommodating hole (52) includes: the rod (60) supported at the one end portion by the spool (53); the cap (70) attached to the opening of the accommodating hole (52) at the end surface (51a) of the housing (51); the magnet (65) provided on the rod (60); and the detection unit (80) configured to detect the change in the magnetic field due to the displacement of the magnet (65), the cap (70) is provided with the insertion hole (71) through which the rod (60) is inserted so as to be reciprocatable in the displacement direction and into which the fluid biasing the spool (53) is guided, and the detection unit (80) is attached to the outer circumferential surface (70c) of the cap (70).