Magnetized Piston Rod Sensing for Cylinder Stroke and Velocity
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Solution Overview
Problem
Existing methods for measuring the position and speed of piston rods in hydraulic, pneumatic, or electric cylinders are not sufficiently reliable, particularly due to the complexity of magnetic coding and the need for structural modifications in existing systems.
Innovation Solution
A system involving permanent magnetization of the piston rod and a measuring unit to detect the radial magnetic field component, allowing for easy modification of existing cylinders without structural changes, using a non-zero gradient magnetic field for position measurement and a magnetic field sensor to output varying signals based on the radial component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic coding is used to measure piston rod position, then measurement capability is provided, but the complexity of magnetic coding and structural modification increases
Solution Approach 1:
The patent extracts the magnetic coding complexity from the measurement system by using the piston rod itself as the magnetic carrier rather than adding separate magnetic tapes or codes. The permanent magnetization is applied directly to the piston rod surface, eliminating the need for separate magnetic coding components and their associated installation and alignment complexities.
Solution Approach 2:
The piston rod serves multiple functions: it is both the mechanical actuator and the magnetic field carrier for position measurement. By magnetizing the piston rod itself, the system combines the mechanical function with the measurement function in a single component, reducing overall system complexity while maintaining measurement capability.
2Measurement precision
If magnetic tapes or codes are inserted in pistons to measure cylinder length, then position measurement is enabled, but structural modification of the cylinder assembly is necessary
Solution Approach 1:
The patent eliminates the need for structural modification of the cylinder assembly by extracting the measurement function from the cylinder body and placing it on the piston rod. The permanent magnetization is applied to the piston rod surface, which is already a standard component, avoiding any modifications to the cylinder assembly structure.
Solution Approach 2:
The piston rod is pre-magnetized with a permanent magnetic field before installation into the cylinder assembly. This preliminary magnetization action allows the measurement system to be prepared in advance without requiring structural modifications during the cylinder assembly installation or modification process.
3Measurement precision
If incremental encoders with periodic material measures are used, then position measurement is provided, but the magnetic coding of the piston rod becomes complex
Solution Approach 1:
The patent changes the magnetic field parameter from a periodic pattern (as in incremental encoders) to a permanent magnetization with a non-zero gradient. This parameter change simplifies the magnetic coding by using a monotonic gradient field that directly correlates with position, eliminating the need for complex periodic patterns and their associated decoding complexity.
Solution Approach 2:
The patent replaces the mechanical periodic pattern system of incremental encoders with a permanent magnetic field system. Instead of using mechanical gratings or magnetic tapes with periodic patterns, the system uses a permanently magnetized piston rod with a gradient field, simplifying both the encoding and decoding processes.
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
Enables reliable and simple measurement of piston rod position and speed with a linear relationship between the radial magnetic field component and axial position, reducing measurement interference and allowing for compact, modular implementation.
Implementation Method 1
the piston rod (10) has a permanent magnetic field within an axial region (12) of the piston rod (10), a radial magnetic field component of the permanent magnetic field depending on an axial position having a non-zero gradient
Implementation Method 2
permanent magnetization of the piston rod of the working cylinder
Implementation Method 3
a measuring unit (80) for measuring the radial magnetic field component of the piston rod (10) is provided outside the working cylinder (70)
Data Source
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AI summary
The system (100) according to the invention comprises a working cylinder (70) with a piston rod (10) provided within the working cylinder, wherein the piston rod is axially movable within the working cylinder. The system according to the invention is characterized in that the piston rod has a permanent magnetic field within an axial region (12) of the piston rod, wherein a radial magnetic field component of the permanent magnetic field has a non-zero, in particular constant, gradient as a function of an axial position, and by a measuring unit (80) for measuring the radial magnetic field component of the piston rod, wherein the measuring unit is provided outside the working cylinder.