Linear Motor Actuator with Balanced Magnetic Forces
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Solution Overview
Problem
Conventional linear motor actuators face issues with increased load and reduced lifespan due to magnetic attractive forces acting on the slide block, especially when downsized to dimensions like 10 mm width and 40 mm length, leading to early wear of bearing balls and reduced allowable load.
Innovation Solution
The linear motor actuator design arranges stator magnets on the inner side surfaces of the base member's side walls, with coil members mounted to the slide table opposing these magnets, canceling out magnetic attractive forces and allowing for increased thrust force while reducing the load on the slide table, thus enabling downsizing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a core member is provided in the coil member to increase thrust force, then the thrust force is improved, but the magnetic attractive force acting on the slide block increases causing heavier movement and earlier bearing wear
Solution Approach 1:
The linear motor is divided into two independent motor units: one motor unit positioned above the slide block and another below it. Each motor unit has its own stator magnets and coil member. This segmentation allows the magnetic forces to be balanced - the attractive force from the upper motor unit is counteracted by the repulsive force from the lower motor unit, eliminating the continuous unidirectional load on the bearing balls while maintaining thrust capability.
Solution Approach 2:
The lower motor unit acts as a counterbalance to the upper motor unit. When the upper motor unit generates an attractive magnetic force on the slide block, the lower motor unit generates an equal and opposite repulsive magnetic force. This counteracting force system eliminates the continuous unidirectional magnetic attractive force that would otherwise act on the bearing balls, preventing premature wear while maintaining the ability to generate thrust when needed.
2Volume of moving object
If the linear motor actuator is downsized to reduce dimensions, then the device size is reduced, but the allowable load of the linear guide becomes extremely small reducing the useful load capacity
Solution Approach 1:
By segmenting the linear motor into two motor units positioned on opposite sides of the slide block, the patent achieves force balance within the compact structure. The upper and lower motor units counteract each other's magnetic attractive forces, eliminating the need for oversized linear guides to handle continuous unidirectional loads. This allows the use of smaller linear guides with higher allowable loads relative to the actuator size.
Solution Approach 2:
The patent changes the operational parameters of the linear motor by using two motor units that can independently control their magnetic forces. This allows the system to operate with balanced forces during idle states and provide full thrust capability when needed, effectively increasing the allowable load capacity of the downsized linear guide while maintaining compact dimensions.
3Device complexity
If stator magnets are arranged on the bottom plate as in conventional designs, then the structure is simple, but the magnetic attractive force continuously loads the slide block in one direction
Solution Approach 1:
The single motor unit with magnets on the bottom plate is segmented into two motor units: one positioned above the slide block and another below it. Each motor unit has its own stator magnets arranged on opposite sides. This segmentation transforms the force distribution from unidirectional continuous attraction to balanced opposing forces that can be controlled independently.
Solution Approach 2:
Instead of having all stator magnets on one side (bottom plate) as in conventional designs, the patent inverts the arrangement by placing stator magnets on both sides of the slide block - one set above and another below. This inverted symmetric arrangement allows the magnetic forces to counterbalance each other, eliminating the continuous unidirectional load while maintaining structural simplicity.
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 configuration enhances the thrust force and reduces the load on the slide table, extending the lifespan of the linear guide and allowing for a smaller, more efficient linear motor actuator with improved movement capabilities.
Implementation Method 1
a coil member serving as a mover which is electrified by an alternating current to generate a moving magnetic field along an arrangement direction of the magnetic poles of the stator magnets
Implementation Method 2
Owing to cooperation between the moving magnetic field and the stator magnets, a thrust force acts between the mover and the stator magnets
Implementation Method 3
stator magnets having magnetic poles of N poles and S poles alternately arranged on a straight line, for generating magnetic fields
Implementation Method 4
When the coil is energized, each of the teeth becomes an electromagnet. Between each of the teeth and each of the magnetic poles constituting the stator magnets, there is generated a magnetic attractive force or a magnetic repulsive force
Data Source
AI summary
Provided is a linear motor actuator which generates a sufficient thrust force and a retaining force and is remarkably smaller than conventional linear motor actuators. The linear motor actuator includes a base member (1) provided with a bottom plate (10) and a pair of side walls (11) and formed in a channel shape; a track rail (2) laid on the bottom plate along a longitudinal direction of the base member; a slide table (3) moving along the track rail; stator magnets (40) arranged on an inner side surface of each of side walls of the base member; and a pair of coil members (41) mounted to the slide table and opposed to the stator magnets provided to each of the side walls of the base member, thereby constituting a linear motor (4).