Sealed Magnet Holder for Reliable Plunger Stroke Sensing
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Solution Overview
Problem
Conventional stroke sensors for plunger/cylinder arrangements in braking systems face challenges with moisture and dirt exposure, leading to reduced reliability and increased complexity due to the need for additional components like separate plungers for magnet holders.
Innovation Solution
A magnet holder with a sleeve enveloping the plunger, a radially protruding magnet mounting, and a cover that allows linear displacement, integrated with a magneto-resistive sensor, providing a sealed chamber for the sensor and magnet to prevent exposure to moisture and dirt, while maintaining sensor accuracy through a rotational interlock and pin/groove engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the stroke sensor is arranged within the cylinder to sense axial displacement, then the sensor can measure displacement directly, but the sensor is exposed to moisture and dirt leading to reduced reliability
Solution Approach 1:
The system is divided into two separate chambers: a first chamber containing the magneto-resistive sensor and magnet holder, and a second chamber (cylinder interior) containing the plunger. A seal divides these chambers, isolating the sensor from the harsh environment while maintaining displacement sensing capability through magnetic field interaction across the seal.
Solution Approach 2:
A magnetic field acts as an intermediary between the protected sensor in the first chamber and the plunger in the second chamber. The magnet mounted on the plunger generates a magnetic field that interacts with the magneto-resistive sensor without requiring direct physical contact, allowing displacement measurement while maintaining environmental isolation.
2Reliability
If a separate sensor chamber with additional plunger is used to protect the sensor, then the sensor is protected from moisture and dirt, but the sensor arrangement becomes more complicated
Solution Approach 1:
The magnet holder and magnet assembly are merged with the plunger structure, eliminating the need for a separate additional plunger. The magnet holder comprises a mounting for the magnet and is integrated such that it moves with the plunger, simplifying the overall arrangement while maintaining sensor protection through the chamber separation.
Solution Approach 2:
The magnet holder serves multiple functions: it mounts the magnet, couples the magnet assembly to the plunger motion, and facilitates the magnetic coupling between the plunger and sensor. This multi-functionality reduces the number of separate components needed while maintaining reliable displacement sensing.
3Reliability
If the magnet holder uses additional plungers with guiding, then the sensor can be protected in a separate chamber, but the manufacturing complexity increases
Solution Approach 1:
The magneto-resistive sensor is extracted from the cylinder interior environment and placed in a separate protected chamber. The magnet holder and magnet assembly are extracted from the need for complex guiding mechanisms by utilizing magnetic field interaction, allowing the plunger to move freely in the cylinder while the sensor remains protected.
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 sensor reliability and simplicity by protecting the magneto-resistive sensor from moisture and dirt, ensuring accurate and linear displacement measurements without additional complex components, thus improving the overall performance of the braking system.
Implementation Method 1
a stroke sensor for a piston with a magneto-resistive element arranged in a cylindrical body, wherein the associated magnet is mounted on the piston. Upon an axial displacement of the piston an electric signal is generated in the magneto-resistive element dependent on the axial position of the piston
Implementation Method 2
Examples for such magneto-resistive sensors uses the Hall-effect, GMR—(giant magneto-resistance), AMR—(anisotropic magneto-resistance), TMR—(tunnel magneto-resistance) effect to generate respective sensor signals
Data Source
AI summary
A magnet holder for a stroke sensor in which the stroke sensor comprises a magneto-resistive sensor with a magnet and is configured to sense a linear displacement of a plunger in a cylindrical body of a plunger/cylinder arrangement. The magnet holder includes a sleeve enveloping the plunger; a mounting for the magnet radially protruding from the sleeve; and a cover for closing the sleeve on one side comprising an opening for allowing the linear displacement of the plunger. The sleeve and the cover move relative to each other, when the plunger performs the linear displacement in the cylindrical body.