Motor Bracket Rib Design for Stiffness and Vibration Control
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Solution Overview
Problem
Reducing the height of a motor's bracket to minimize size and weight leads to reduced stiffness, causing bearing vibrations, which result in commutator wobbling, unstable contact between the commutator and brush, and sparking, thereby shortening the motor's lifespan.
Innovation Solution
A motor design featuring a cylindrical bracket with a rib structure that extends radially outward from the bearing holding portion, providing additional support and maintaining stiffness while allowing for a thinner profile, and a brush card assembly that ensures stable contact between the commutator and brush.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the bracket is reduced to reduce motor size and weight, then the dimension of the bracket in height direction is reduced, but the stiffness of the bracket is lowered
Solution Approach 1:
The patent introduces a rib structure that extends in the radial direction (another dimension) from the bearing holding portion. This adds structural support without increasing the axial thickness of the bracket, thus maintaining reduced size while improving stiffness locally where needed.
Solution Approach 2:
The rib structure provides localized reinforcement at the bearing holding portion where stiffness is critical, rather than uniformly thickening the entire bracket. This allows the bracket to maintain thin overall dimensions while having enhanced stiffness in the specific region that supports the bearing and commutator.
2Volume of moving object
If the bracket stiffness is reduced due to thinner design, then the motor size is reduced, but the bearing begins to vibrate
Solution Approach 1:
The rib extending radially outward from the bearing holding portion provides additional support in the radial direction, stabilizing the bearing without increasing the axial height of the bracket. This dimensional approach allows thin bracket design while maintaining bearing stability.
Solution Approach 2:
The rib structure is designed in advance to prevent bearing vibrations before they occur. By providing preemptive structural support at the bearing holding portion, the design prevents vibration-related issues rather than attempting to correct them after they arise.
3Volume of moving object
If the bearing vibrates, then the motor size remains compact, but the commutator wobbles and separates from the brush
Solution Approach 1:
The radially extending rib provides structural support in the radial direction, preventing commutator wobble caused by bearing vibrations. This allows the motor to maintain compact axial dimensions while ensuring reliable commutator-brush contact through enhanced radial stiffness.
Solution Approach 2:
The rib structure preemptively prevents bearing vibrations that would lead to commutator wobble and brush separation. By addressing the root cause (bearing stability) in advance, the design ensures continuous reliable contact between the commutator and brush throughout operation.
4Weight of stationary object
If the bracket is made thinner to reduce weight, then the motor weight is reduced, but sparking occurs between commutator and brush
Solution Approach 1:
The rib structure extending radially provides the necessary stiffness to prevent commutator wobble and brush separation without increasing the axial thickness or weight of the bracket. This eliminates sparking while maintaining the lightweight advantage of the thin bracket design.
Solution Approach 2:
The rib structure preemptively prevents the chain of events leading to sparking: by stabilizing the bearing and preventing commutator wobble before it occurs, the design eliminates the conditions that would cause brush separation and sparking, thereby preventing harmful effects before they arise.
Data Source
AI summary
A motor may include a shaft, an armature, a commutator, a bearing, a housing, a bracket, and a brush card assembly. The brush card assembly may include a brush contacting the commutator, and a brush card holding the brush. The bracket may include a bracket bottom portion covering at least a portion of a lower side of the brush card, a cylindrical bracket cylindrical portion extending upwardly from a radially outer edge of the bracket bottom portion, a bearing holding portion extending upwardly from the bracket bottom portion at a radially inner side of the bracket cylindrical portion, and holding the bearing, and a rib positioned above the bracket bottom portion, and extending radially outward from the bearing holding portion.