Small DC Motor Frame Geometry for Compact Torque Output
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Solution Overview
Problem
Existing small DC motors face challenges in reducing size while maintaining driving properties, as altering the thickness of magnets to achieve size reduction often compromises magnetic properties, and existing solutions like quadrangular motor frames with magnets in corners lead to excessive magnet thickness and difficulty in mounting.
Innovation Solution
A small DC motor design featuring a cylindrical motor frame with constant thickness and arc-shaped connecting portions, allowing for a smaller magnet size while maintaining necessary magnetic properties, and incorporating a magnet with a circumferential surface for conformable contact, which can be easily mounted and reduced in size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the magnet is reduced to decrease motor size, then the volume of the motor is reduced, but the magnetic properties of the motor deteriorate
Solution Approach 1:
The motor frame is designed with an asymmetric quadrangular cross-section where the four sides have different lengths, and the corner portions are positioned at specific locations that do not form a regular quadrangle. This asymmetric configuration allows the magnet to be placed in corner portions that are inward from the corners of a regular quadrangle, enabling reduced magnet thickness while maintaining magnetic properties through optimized flux distribution.
Solution Approach 2:
The invention transitions from conventional cylindrical motor frames to a quadrangular cross-section design, adding geometric dimensionality variation. This dimensional change allows the magnet thickness in the radial direction to be reduced while the overall motor volume is decreased, as the quadrangular shape provides more efficient space utilization and magnetic flux paths compared to circular configurations.
2Volume of moving object
If the motor frame is formed into a quadrangular shape with magnets in corner portions to reduce size, then the motor volume is reduced, but the magnet thickness becomes excessive and mounting becomes difficult
Solution Approach 1:
The motor frame employs an asymmetric quadrangular design where the four sides have different lengths and the corner portions are positioned inward from the corners of a regular quadrangle. This asymmetric configuration optimizes the balance between size reduction and mounting ease by preventing excessive magnet thickness while maintaining compact dimensions, making the motor easier to mount in limited spaces.
3Reliability
If the grade of the magnet is upgraded to maintain motor properties during size reduction, then the magnetic properties are maintained, but the manufacturing cost increases
Solution Approach 1:
The invention changes the geometric parameters of the motor frame from conventional cylindrical to quadrangular cross-section with specific side length ratios and corner portion positions. This parameter change allows the use of magnets with lower grade (reduced maximum energy product) while maintaining motor properties, as the optimized quadrangular geometry improves magnetic flux distribution and efficiency, thereby reducing manufacturing cost.
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 design achieves a minimized motor frame cross-sectional area while maintaining sinusoidal magnetic properties, enabling easier mounting and size reduction, and when applied to coreless or slotless motors, increases torque generation while reducing motor size and cost.
Implementation Method 1
A small DC motor includes a motor frame... a magnet... a rotor which is accommodated in a circular cylindrical space in the magnet via a radial gap
Data Source
AI summary
A small DC motor includes a motor frame having a cylindrical portion, the cylindrical portion having a constant thickness and having a cross section in a shape that comprises four sides and connecting portions, each of the connecting portions connecting adjacent two of the four sides and being located inward from a corresponding corner in a quadrangle comprising the four sides; and a magnet having a circumferential surface on an inside thereof and having conformable contact with the motor frame on an outside thereof.