Actuator Piston Position Detection Using Magnetic Field Sensor
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Solution Overview
Problem
Existing injection molding systems face challenges in accurately detecting the position of pistons within actuators, particularly due to the limitations of linear variable differential transformers (LVDTs), which result in unreliable and non-compact measurement systems.
Innovation Solution
The use of a magnetic field detection system comprising a non-magnetic or magnetically permeable actuator housing with a magnetic member and a Hall effect sensor to detect changes in magnetic flux density, allowing for more reliable and compact position measurement of the piston, enabling precise control of valve pin movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linear variable differential transformer (LVDT) is used to detect piston position, then measurement capability is provided, but the system becomes non-compact and unreliable
Solution Approach 1:
The patent replaces the mechanical LVDT system with a magnetic field-based detection system. A magnetic member is embedded in the piston, and a magnetic field sensor mounted on the actuator housing detects changes in magnetic flux density as the piston moves, eliminating the need for complex mechanical transformer coils and ferro-magnetic cores while maintaining measurement capability
Solution Approach 2:
The patent extracts the magnetic sensing function from the mechanical LVDT structure and implements it separately using a magnetic member embedded in the piston and an independent magnetic field sensor mounted on the housing, simplifying the overall system architecture and improving reliability
2Device complexity
If a magnetic field detection system with external sensor is used, then compact arrangement is achieved, but magnetic field transmission through housing must be ensured
Solution Approach 1:
The patent applies local quality by making the actuator housing body portion specifically non-magnetic or magnetically permeable in the region where magnetic field transmission is required, allowing the magnetic field to pass through the housing wall to reach the external sensor while maintaining structural integrity
Solution Approach 2:
The patent changes the material parameter of the actuator housing body portion to be non-magnetic or magnetically permeable, enabling magnetic field transmission through the housing structure and allowing the magnetic sensor to detect piston position from the exterior
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 solution provides a more robust and compact method for detecting piston position, enabling precise control of valve pin movement and improving the reliability of injection molding processes by generating a control signal based on the detected magnetic field changes.
Implementation Method 1
The sensor may comprise a portion of a hall effect circuit, mounted to the outside of the actuator housing, for detecting changes in the magnetic flux density generated by a magnetic member disposed in the piston
Data Source
AI summary
Apparatus and method for detecting a position of an actuator piston driving a valve pin in an injection molding system. The apparatus includes an actuator housing having a body portion, surrounding an axial bore, of a substantially non-magnetic and/or magnetically permeable material, a piston, movable within the axial bore for driving a valve pin, the piston including a magnetic member generating a magnetic field such that axial movement of the piston in the bore modifies the magnetic field according to the position of the piston relative to a detection position, and a magnetic field detector attached to an exterior surface of the body portion at the detection position for detecting the magnetic field associated with the position of the piston and generating an output signal determined by the piston position.