Linear Motor Cogging Reduction via Asymmetric Tooth Design
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Solution Overview
Problem
Existing linear motors experience cogging issues due to uneven magnetic flux distribution, leading to fluctuations in force acting on the mover when no AC power is supplied.
Innovation Solution
Incorporating a second tooth and magnet outside the first teeth, with specific edge configurations and magnetization directions, to adjust and balance the magnetic flux path, preventing cogging by ensuring equivalent magnetic actions across all magnetic poles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a linear motor uses conventional single-tooth structure, then the structure is simple, but cogging occurs due to uneven magnetic flux distribution
Solution Approach 1:
The single tooth structure is segmented into multiple teeth (first tooth, second tooth, third tooth) with different configurations. Each tooth has specific edge distances from the stator, creating segmented magnetic flux paths that collectively balance the overall magnetic distribution and eliminate cogging forces.
Solution Approach 2:
The patent employs asymmetric tooth design where the first, second, and third teeth have different edge distances from the stator in the protruding direction. This asymmetric configuration creates deliberately unbalanced magnetic flux distribution at individual tooth levels, which when combined, produces balanced overall magnetic action that prevents cogging.
2Ease of operation
If AC power is supplied to coils, then the mover can be driven, but force fluctuations occur when no AC power is supplied due to uneven magnetic flux
Solution Approach 1:
The patent creates equipotential magnetic distribution by configuring multiple teeth with specific edge distances from the stator. This ensures that the magnetic flux density becomes substantially uniform across different tooth positions, making the magnetic potential equivalent throughout the air gap, thereby eliminating force fluctuations during idle movement.
3Device complexity
If outermost first magnetic poles have different magnetic action from other magnetic poles, then the structure is straightforward, but overall cogging occurs
Solution Approach 1:
The patent applies local quality differentiation where the outermost first magnetic poles and other magnetic poles have different local configurations (different edge distances from stator). This local differentiation compensates for the inherently different magnetic actions at outer positions, ensuring that the cumulative magnetic effect across all poles is balanced and cogging-free.
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 effectively reduces overall cogging by aligning magnetic actions of outermost first magnetic poles with the rest, minimizing force fluctuations and enhancing mover stability.
Implementation Method 1
a plurality of coils respectively mounted on the periphery of the plurality of first teeth; a plurality of first magnets respectively buried in the plurality of first teeth
Implementation Method 2
a plurality of first magnets respectively buried in the plurality of first teeth; and a second magnet buried in the second tooth
Data Source
Figure 1
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AI summary
A linear motor 1 includes a stator 10 and a mover 20. The stator 10 has a plurality of salient poles 12. The mover 20 includes a plurality of first teeth 32; a plurality of coils 40 respectively mounted on the periphery of the plurality of first teeth 32; a plurality of first magnets 50 respectively buried within the first teeth 32; a second tooth 33 provided outside the plurality of first teeth 32; and a second magnet 60 buried within the second tooth 33. The second tooth 33 includes a first portion 34 on the opposite side of the first teeth 32 with respect to the second magnet 60; and a second portion 35 close to the first teeth 32 with respect to the second magnet 60. In a protruding direction of the second tooth 33, an edge 34a of the first portion 34 is farther from the stator 10 than an edge 35a of the second portion 35.