Cylindrical Linear Motor for Downhole Actuation
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Solution Overview
Problem
Existing downhole tools face limitations in efficient motion and actuation due to the geometric constraints and space limitations of boreholes, particularly with conventional linear motors that are not well-suited for the circular geometries and compact spaces found in subsurface applications.
Innovation Solution
The development of a linear motor apparatus with a rotor and cylindrical stator configuration, where the stator has windings flowing current transverse to its long axis, and the rotor has alternating magnetic elements, enabling sliding engagement and relative motion to facilitate advanced motion and actuation in borehole environments, utilizing laminated cores to reduce hysteresis and eddy currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional linear motors are used in downhole applications, then linear motion can be achieved, but the geometric constraints and space limitations of boreholes reduce efficiency and adaptability
Solution Approach 1:
The patent applies spheroidality by configuring the linear motor with a cylindrical stator and a rotor that fits within it, replacing conventional rectangular or planar motor structures. This curved, cylindrical geometry allows the motor to adapt to the circular borehole environment while maintaining efficient electromagnetic interaction between the stator windings and rotor magnetic elements
Solution Approach 2:
The patent implements nesting by placing the rotor inside the cylindrical stator, creating a compact nested structure where the rotor with magnetic elements is contained within the stator with windings. This nested configuration maximizes space utilization within the limited borehole diameter while maintaining the necessary magnetic field interaction
2Force
If the stator has windings flowing current transverse to its long axis, then thrust generation is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by configuring the stator windings to flow current transverse to the long axis specifically in the regions where thrust generation is needed, rather than using a uniform winding pattern throughout. This localized winding configuration optimizes the magnetic field distribution for thrust generation while reducing unnecessary complexity in other areas
Solution Approach 2:
The patent employs asymmetry in the winding arrangement where the current flow direction is deliberately oriented transverse to the long axis rather than parallel, creating an asymmetric current distribution that optimizes the electromagnetic force generation in the radial direction for effective thrust
3Speed
If the rotor has alternating magnetic elements, then relative sliding motion is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies periodic action by arranging magnetic elements on the rotor with alternating polarity in a periodic pattern along the axial direction. This periodic alternation of north and south poles creates a corresponding periodic magnetic field that interacts with the stator windings to generate continuous reciprocating sliding motion
Solution Approach 2:
The patent implements segmentation by dividing the rotor into multiple sections with discrete magnetic elements rather than using a single continuous magnet. This segmentation into individual magnetic elements allows for modular manufacturing and assembly, reducing the overall precision requirements compared to a monolithic magnetic structure
4Loss of energy
If the stator core is formed of laminations, then energy losses are reduced, but device complexity increases
Solution Approach 1:
The patent applies segmentation by constructing the stator core from multiple thin laminations stacked together rather than using a solid block of magnetic material. This segmentation into thin insulated layers breaks up the paths for eddy currents, reducing energy losses while maintaining the necessary magnetic flux conduction
Solution Approach 2:
The patent uses laminations with insulation between layers that provides more than sufficient reduction of eddy currents, applying a slightly excessive measure of insulation to ensure minimal energy loss. This partial over-engineering of the lamination insulation guarantees effective energy loss reduction while the modular lamination structure keeps assembly manageable
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 allows for effective thrust generation and tool positioning within boreholes, enhancing the operational capabilities of downhole devices by providing efficient and controlled linear motion, suitable for various subsurface operations such as drilling, completion, and production activities.
Implementation Method 1
The stator has a winding flowing current in a direction transverse to a long axis of the stator
Implementation Method 2
The polarity of each magnetic element of the rotor is arranged to alternate along a long axis of the rotor... Energizing the winding principally causes relative sliding between the rotor and the stator
Implementation Method 3
The stator has a core formed at least partially of laminations aligned along a plane co-planar with the long axis of the stator
Implementation Method 4
The stator has a core formed at least partially of laminations aligned along a plane co-planar with the long axis of the stator
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3~4
AI summary
An apparatus for use in a borehole includes a rotor (140) having at least one set of magnetic elements (142), wherein a polarity of each magnetic element (142) is arranged to alternate along a long axis of the rotor (140); and a stator (130) in sliding engagement with the rotor (140), the stator (130) having a winding flowing current in a direction transverse to a long axis of the stator (130), the stator (130) having a core formed at least partially of laminations (133) aligned along a plane co-planar with the long axis of the stator (130), wherein energizing the winding causes relative sliding between the rotor (140) and the stator (130), the sliding being principally along the long axis of the rotor (140), and wherein the core includes a plurality of circumferentially distributed planar strips (132), each strip (132) being formed of the laminations (133).