Two-Phase Stepper Motor Layout for Higher Torque Density
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Solution Overview
Problem
Conventional compact permanent magnet (PM) stepper motors face challenges in achieving high torque and precise angular positioning while maintaining a compact size, with limitations in torque control and speed compared to other types like Variable Reluctance (VR) motors.
Innovation Solution
A compact PM stepper motor design featuring two electromagnetic coils with ferromagnetic stators and a disc-shaped rotor, where the stator teeth are arranged radially to maximize coil volume, allowing for increased winding density and independent winding configuration, enhancing torque without increasing size or current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional PM stepper motors use traditional stator and rotor arrangements, then the motor structure is simple, but the torque output is insufficient and angular positioning precision is limited
Solution Approach 1:
The stator is divided into multiple independent phases (typically four phases) with distinct coil windings, and the rotor is segmented into multiple magnetized teeth with alternating polarity. This segmentation allows independent control of each phase to precisely control rotor position and maximize torque output through sequential activation of different phase combinations.
Solution Approach 2:
The invention transitions from traditional radial magnetization to axial magnetization of rotor teeth, creating a three-dimensional magnetic field distribution. The stator phases are arranged to create magnetic fields that interact with rotor teeth along the axial dimension, enabling more efficient torque generation and finer angular positioning through multi-dimensional field control.
2Volume of moving object
If the motor size is reduced to maintain compact form factor, then the motor remains compact, but the torque and angular positioning capability are compromised
Solution Approach 1:
The invention changes key magnetic parameters including magnetization direction (from radial to axial), pole configuration (increasing number of effective poles through tooth segmentation), and magnetic field distribution patterns. These parameter changes enable higher torque density within a compact volume by optimizing the magnetic interaction efficiency between stator and rotor components.
Solution Approach 2:
The motor employs composite magnetic circuit structures combining ferromagnetic materials with specific permeability characteristics in both stator and rotor. The use of magnetized rotor teeth with alternating polarity patterns creates a composite magnetic field structure that maximizes flux density and torque generation within the limited space of a compact motor design.
3Speed
If VR type motors are used to achieve high speed, then the speed is improved, but the torque control becomes suboptimal
Solution Approach 1:
The motor implements dynamic torque control through sequential activation of different phase combinations, allowing the torque output to be dynamically adjusted during operation. The multi-phase configuration enables smooth transitions between different magnetic field configurations, providing both high-speed capability through rapid phase switching and precise torque control through variable phase activation 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
This design results in a more powerful stepper motor with improved torque and refined angular positioning, maintaining a compact form factor and smoother rotational speed, overcoming the limitations of conventional PM stepper motors.
Implementation Method 1
Two electromagnetic coils, two ferromagnetic stators each accommodating an electromagnetic coil
Implementation Method 2
The rotational movement of the central axis is driven by the angular displacement of the rotor
Implementation Method 3
two ferromagnetic stators each accommodating an electromagnetic coil. Each of the two stators comprises an annular portion arranged around one of the coils and at least two teeth extending from the annular portion
Implementation Method 4
The rotor is positioned between the two stators... PM stepper motors with disc-shaped rotors, wherein the faces of the rotors are magnetised alternatingly
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
The invention concerns a two-phased stepper motor (100) comprising a central shaft (1), two electromagnetic coils (3), two ferromagnetic stators (2A, 2B), each accommodating an electromagnetic coil (3), a rotor (4) rotationally fixed on said central shaft (1) and positioned between the two stators (2A, 2B), said rotor (4) having two faces, each face being magnetized, and a spacer (5) arranged between the stators (2A, 2B) for maintaining the two stators at a fixed minimal distance from each other. The central shaft (1) passes through each of the two coils (3) such as to permit a rotation of said central shaft (1) within said stators (2A, 2B). Each of the two stators (2A, 2B) comprises an annular portion arranged around one of the coils and at least two teeth (250) extending from the annular portion, each tooth comprising a radial portion (251) extending radially between one of the coils (3) and the rotor (4), in direction of the central shaft (1).