Stationary Yoke XY-Table Drive with Movable Ferromagnetic Bar
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Solution Overview
Problem
Existing XY-table drives for semiconductor manufacturing are cumbersome to integrate and inefficient due to their complex configurations, excessive mass, and the need for cooling and magnetic fields, which are problematic for precise positioning and clean room applications.
Innovation Solution
A 'moving iron' type drive system using a stationary U-shaped yoke and a movable ferromagnetic bar with a magnetic circuit across air gaps, generating vertical reluctance forces and horizontal Lorentz forces, allowing for contactless direct drive with minimal additional mass and no magnetic elements on the moving table, enabling easy integration and precise positioning in all six degrees of freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a planar array of magnets with moving coils is used for XY-table drive, then the table can be moved in all six degrees of freedom, but the drive becomes unnecessarily heavy and requires cooling and magnetic fields that are problematic for precise positioning
Solution Approach 1:
The patent replaces the traditional moving coil or moving magnet system with a stationary U-shaped yoke and a movable ferromagnetic bar. The magnetic field is generated by stationary coils in the yoke, and the ferromagnetic bar responds to this field through magnetic attraction and Lorentz forces, eliminating the need to move heavy electromagnetic components with the table.
Solution Approach 2:
Instead of moving the electromagnetic actuators (coils or magnets) with the table, the patent inverts the configuration by making the electromagnetic components stationary and using a passive ferromagnetic bar that is moved by magnetic forces. This inversion significantly reduces the moving mass while maintaining actuation capability.
2Power
If moving coils are used for magnetic drive, then the table can be actuated, but supply cables and heat generation become problematic for precise positioning
Solution Approach 1:
The patent extracts the electromagnetic actuation components from the moving table and places them in a stationary U-shaped yoke. The ferromagnetic bar on the table is actuated by magnetic fields generated by stationary coils, eliminating supply cables and heat generation from the moving components.
3Measurement precision
If a magnetic bearing system with U-shaped yoke and permanent magnets is used, then vertical positioning and horizontal movement are achieved, but the configuration of moving and non-moving parts becomes complex to integrate
Solution Approach 1:
The patent combines the vertical positioning function (reluctance forces) and horizontal actuation function (Lorentz forces) into a single integrated drive unit consisting of a U-shaped yoke with stationary coils and a movable ferromagnetic bar. This merging reduces the number of separate components and simplifies integration into the XY-table system.
Solution Approach 2:
The ferromagnetic bar serves multiple functions: it responds to vertical magnetic fields for vertical positioning through reluctance forces and to horizontal magnetic fields for horizontal movement through Lorentz forces. This multi-functionality reduces the need for separate actuation mechanisms.
4Power
If traditional magnetic drives with moving coils are used, then actuation is achieved, but additional masses must be moved and the drive is not optimized for swath-by-swath movement patterns
Solution Approach 1:
The patent replaces heavy moving coils or magnets with a lightweight ferromagnetic bar that is actuated by stationary electromagnetic fields. This substitution dramatically reduces the moving mass while maintaining the ability to generate sufficient actuation forces for the required movement patterns.
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 provides a mechanically simple, lightweight, and cost-effective drive system that eliminates the need for gear units and cooling, reduces particle disturbance, and allows for precise positioning with minimal space usage, enhancing the integration and performance of XY-tables in semiconductor manufacturing.
Implementation Method 1
The yoke and the bar carry a magnetic circuit with a flux that takes a path across air gaps between the limbs and the bar, and generates vertical reluctance forces there which counteract the gravitational force of the bar
Implementation Method 2
A plurality of such drives can be connected to an XY-table, to make it possible to adjust all degrees of freedom of the XY-table
Data Source
Figure 1~2
Figure 3~4
Figure 5(a)~5(g)
AI summary
A drive for an XY-table is disclosed, having a stationary, ferromagnetic and U-shaped yoke (1) including a first limb (1.1) and a second limb (1.2) which lie together in one plane (XY), and having a movable ferromagnetic bar (2), the yoke (1) and the bar (2) carrying a magnetic circuit with a flux (Φ) that takes a path across air gaps between the limbs (1.1, 1.2) and the bar (2), and brings about vertical reluctance forces there which counteract the gravitational force of the bar (2). Bar (2) lies parallel to and below the plane (XY) defined by the limbs (1.1, 1.2). An XY-table with such a drive is disclosed. A separate drive to reverse the direction of movement (X) of the table (6) is also disclosed.