Small DC Motor Quadrangular Frame Armature Torque
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Solution Overview
Problem
Small DC motors face limitations in generating torque due to the interposition of field magnets between the motor frame and armature core, which reduces effective magnetic flux and winding capacity, leading to smaller torque output.
Innovation Solution
The motor design increases the outside diameter of the armature assembly by subtracting a minimum air gap from the motor frame's inside diameter, allowing for more effective magnetic flux and increased winding capacity, while maintaining a quadrangular motor frame shape with the same number of corner portions as polarized magnetic poles, thus enhancing torque generation without increasing the motor's size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If field magnets are interposed between the motor frame and armature core to provide necessary magnetization characteristics, then magnetic properties are improved, but the effective magnetic flux per slot of the armature core is lowered and torque is reduced
Solution Approach 1:
The invention extracts the field magnets from the conventional position between the motor frame and armature core, and relocates them to the armature core itself. Specifically, the field magnets are embedded in the yoke of the armature core, allowing the armature core to generate the necessary magnetization characteristics while maximizing the effective magnetic flux and torque output.
2Force
If the outside diameter of the armature assembly is increased to increase effective magnetic flux and winding capacity, then torque is improved, but the motor size increases
Solution Approach 1:
The invention merges the functions of the field magnets and armature core by embedding the field magnets directly into the yoke of the armature core. This integration allows the armature assembly to generate both the magnetization characteristics and the magnetic flux, eliminating the need for separate field magnets in the motor frame and enabling increased torque without increasing motor size.
3Force
If the number of windings around the armature core is increased to increase effective magnetic flux, then torque is improved, but the radial space available for windings is reduced by field magnet thickness
Solution Approach 1:
The invention extracts the field magnets from the motor frame and relocates them to the armature core, thereby eliminating the radial space occupation by field magnets in the motor frame. This creates additional radial space in the air gap that can be utilized for increased winding capacity and effective magnetic flux.
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 increases torque output, minimizes the quantity of expensive magnets used, and reduces the motor's size by optimizing the relationship between the armature core's diameter and the field magnets' dimensions, effectively addressing the limitations of existing small DC motor designs.
Implementation Method 1
field magnets having an arc-shaped surface on an inside thereof and having a cross section in an inside portion that has an arc-shape and in an outside portion that has conformable contact with an inside surface of the motor frame; and an armature assembly including: an armature winding and a shaft and being disposed rotatably within the motor frame
Implementation Method 2
the small DC motor includes an air gap between each of the four sides and a radially outermost surface of the armature assembly
Data Source
AI summary
A small DC motor includes: a motor frame including a cylindrical portion, the cylindrical portion having a constant thickness and having a cross section in a shape that includes 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 including the four sides; field magnets; and an armature assembly, wherein the field magnets are provided so as to be spaced apart from each other, and the small DC motor includes an air gap between each of the four sides and a radially outermost surface of the armature assembly, the air gap being a minimum size needed to rotate the armature assembly.