Magnet-Wear Ring Piston Layout for Compact Fluid Pressure Cylinders

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Solution Overview

Problem

Fluid pressure cylinders with magnets attached to pistons have larger axial dimensions, leading to increased overall length, which is undesirable.

Innovation Solution

A fluid pressure cylinder design that incorporates a piston unit with a radially protruding piston body, a ring-shaped magnet, and a wear ring attached to the magnet's outer circumference, where the wear ring and magnet share the same axial position, and the magnet is positioned within the wear ring's axial range, allowing for a reduction in axial dimensions by reducing the magnet's size and thickness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a ring-shaped magnet is attached to the outer circumferential part of a piston, then the piston position can be detected, but the axial dimension of the piston increases

Engineering Contradiction:
Improvepiston position detectionVSAvoidaxial dimension of piston
Core Design Contradiction:
Measurement precisionVSLength of moving object

Solution Approach 1:

The wear ring and ring-shaped magnet are merged into a single integrated component, where the magnet is attached to the outer circumferential part of the wear ring. This combination allows the magnet to be positioned within the axial range of the wear ring, reducing the overall axial dimension while maintaining both the protective function of the wear ring and the position detection function of the magnet.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The magnet is positioned within the axial range of the wear ring rather than extending beyond it, effectively utilizing the axial space already occupied by the wear ring. This dimensional arrangement allows the magnet to be closer to the magnetic sensor without increasing the piston's axial dimension, thereby resolving the contradiction between detection capability and compactness.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Length of moving object

If the axial dimension of the piston is reduced, then the overall length of the fluid pressure cylinder is reduced, but the magnet may be too far from the magnetic sensor for effective detection

Engineering Contradiction:
Improveoverall length of fluid pressure cylinderVSAvoidmagnetic field detection effectiveness
Core Design Contradiction:
Length of moving objectVSMeasurement precision

Solution Approach 1:

By merging the magnet with the wear ring, the magnet is positioned at the outer circumferential part of the wear ring, which is the optimal location for magnetic field detection. This ensures that the magnet remains close to the magnetic sensor mounted on the cylinder tube, maintaining effective detection while keeping the overall length compact.

Inventive Principle:
Principle #5Merging (Combining)

3Ease of manufacture

If the wear ring and magnet are disposed at different axial positions, then each component can be optimized independently, but the axial dimension of the piston body increases

Engineering Contradiction:
Improveindependent component optimizationVSAvoidaxial dimension of piston body
Core Design Contradiction:
Ease of manufactureVSLength of moving object

Solution Approach 1:

The wear ring and magnet are combined into a single integrated component, eliminating the need for separate axial positioning. This merger maintains the functional optimization of both components while reducing the axial dimension, as the magnet is attached to the outer circumferential part of the wear ring and positioned within its axial range.

Inventive Principle:
Principle #5Merging (Combining)

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 design reduces the axial dimension of the piston body and the entire fluid pressure cylinder, while maintaining mechanical strength and enabling closer proximity of the magnet to the magnetic sensor, thereby decreasing the required magnetic force and overall length.

Implementation Method 1

a ring-shaped magnet attached to an outer circumferential part of the piston body

Methodology Applied
Scientific EffectMagnetism: Magnetism

Data Source

PatentEP3770446B1Fluid pressure cylinder
Publication Date: 2023.08.09 SMC CORP
  • EP3770446B1 patent drawingFigure 1
  • EP3770446B1 patent drawingFigure 2
  • EP3770446B1 patent drawingFigure 3

AI summary

A fluid pressure cylinder (10) provided with: a cylinder tube (12) having a sliding hole (13) internally; a piston unit (18) disposed along the sliding hole (13) so as to be capable of moving back and forth; and a piston rod (20) projected in the axial direction from the piston unit (18), wherein the piston unit (18) can shorten the axial dimension of a piston body (40) by mounting a wear ring (44) to an outer circumferential section of a ring-shaped magnet (46) attached to an outer circumferential section of the piston body (40).