Motor Shaft Current Reduction via Pole-Tooth Configuration
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Solution Overview
Problem
Conventional motors connected to internal combustion engines and transmissions face issues with electrolytic corrosion of bearings due to shaft currents, requiring expensive insulation measures and compromising shaft strength and reliability, especially under vibration and load conditions.
Innovation Solution
A motor design with a specific configuration of magnetic poles and teeth, forming an electric conductor circuit between the rotor, bearings, and housing, which compensates circumferential magnetic fluxes to prevent electromotive force generation and reduce shaft currents, using a cost-effective and reliable setup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulation measures (insulating ring, resin coating) are implemented to prevent bearing corrosion, then bearing reliability is improved, but device complexity and cost increase
Solution Approach 1:
The invention extracts and eliminates the source of shaft voltage (circumferential magnetic flux) rather than applying insulation measures to counteract its effects. By removing the harmful electromagnetic induction mechanism through specific pole and tooth configuration, the patent avoids adding insulating rings, resin coatings, or other insulation components, thus improving bearing reliability without increasing device complexity
Solution Approach 2:
The patent converts the potentially harmful shaft current phenomenon into a beneficial configuration constraint. By designing the motor with specific relationships between magnetic poles and teeth (1:1.2 ratio), the circumferential magnetic flux that would normally cause harmful electromotive force is transformed into a design parameter that eliminates the problem at its source, turning a harmful effect into a guiding principle for optimal configuration
2Reliability
If high-permeability portion is provided at shaft to prevent shaft current, then bearing corrosion is prevented, but manufacturing complexity increases
Solution Approach 1:
Instead of modifying the shaft with high-permeability portions to manage shaft current, the invention extracts and eliminates the root cause of shaft voltage generation. By configuring the magnetic poles and teeth to cancel circumferential magnetic flux, no shaft modification is needed, maintaining simple shaft manufacturing while protecting bearings
Solution Approach 2:
The patent replaces mechanical/structural modifications to the shaft (adding high-permeability portions) with an electromagnetic field configuration solution. By adjusting the relationship between magnetic poles and teeth, the harmful electromagnetic induction is eliminated without any mechanical modification to the shaft, simplifying manufacturing
3Reliability
If stator is covered by resin for insulation, then shaft current is prevented, but stator strength decreases
Solution Approach 1:
The invention removes the need for resin coating on the stator by extracting and eliminating the source of harmful electromagnetic induction. Through optimal configuration of magnetic poles and teeth, circumferential magnetic flux is canceled, preventing shaft current without requiring any insulating coating that would compromise stator strength
Solution Approach 2:
The patent converts the design challenge of providing insulation without compromising strength into an opportunity to optimize the magnetic circuit configuration. By using the relationship between magnetic poles and teeth to eliminate harmful flux, the solution provides both electromagnetic protection and maintains full stator structural integrity
4Reliability
If oil film is thinned by vibration or radial force, then lubrication performance decreases, but shaft current increases causing bearing corrosion
Solution Approach 1:
The patent addresses the interaction between vibration-induced oil film thinning and shaft current by eliminating the electromagnetic induction mechanism. Even when vibration thins the oil film and improves electrical contact, the absence of circumferential magnetic flux (achieved through pole-tooth configuration) prevents electromotive force generation, converting a potentially harmful condition into a protected state
Solution Approach 2:
The invention applies preliminary anti-action by pre-configuring the magnetic circuit to eliminate circumferential magnetic flux before vibration and oil film thinning can cause problems. The specific pole and tooth configuration ensures that even under vibrational conditions that improve electrical contact, no electromotive force is generated to drive harmful shaft currents
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 motor effectively reduces shaft currents and enhances bearing reliability by eliminating electromotive forces and maintaining a stable oil film, even under varying loads and vibrations, while minimizing size and complexity.
Implementation Method 1
a rotor 1 and a stator 4 The rotor 1 includes a rotary shaft 2, and the stator 4 is arranged around the rotor 1
Implementation Method 2
the rotary shaft 2 is rotatably held to the housing 8 by a bearing 7a
Data Source
AI summary
A motor, which can reduce a shaft current by a cheap configuration and has a high reliability, is provided. A motor which is provided between an internal combustion engine and a transmission and installed in a housing for connecting the internal combustion engine and the transmission, in which a number of magnetic poles of a rotor is “10×n” (n is a natural number), and a number of teeth of a stator is “12×n” (n is a natural number); and a rotary shaft of the rotor, bearings for supporting the rotary shaft, and the housing are composed of electric conductors; and an electric conductor circuit, which includes the rotary shaft, the bearings, and the housing and is interlinked to the stator, is formed.