Brushless Motor Rotor Shaft Interference Fit for Axis Alignment
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Solution Overview
Problem
The manufacturing process of brushless motors can lead to undesirable bending of the rotor shaft and misalignment of the rotational axes, resulting in reduced performance due to insufficient rotation-fixing force between the rotor core and shaft, which is more critical in brushless motors than brushed motors.
Innovation Solution
A rotor shaft design with thicker-diameter and thinner-diameter force-fitting segments, each with different interference fits, ensures a rigid fixation by surface contact, minimizing bending and misalignment during assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If linear protuberances are used to force-fit the rotor shaft into the rotor core, then the rotor shaft can be fixed in position, but the rotor shaft may bend during manufacturing and the rotational axes may become misaligned
Solution Approach 1:
The rotor shaft is divided into multiple force-fitting segments (first, second, and third segments) with different diameters, each providing interference fit at different locations. This segmentation allows distributed fixation points that prevent bending and maintain alignment better than a single linear protuberance
Solution Approach 2:
Different segments of the rotor shaft have different diameters (first diameter for first segment, second diameter for second segment, third diameter for third segment) to create varying interference fit strengths at different locations. This local variation in geometry optimizes the force distribution to prevent misalignment while maintaining rotational balance
2Strength
If a one-step force-fitting process is used, then the manufacturing process is simple, but the rotation-fixing force between rotor core and rotor shaft is insufficient
Solution Approach 1:
The force-fitting process is segmented into multiple steps, with each step inserting a different diameter segment into the rotor core. This multi-step approach builds cumulative rotation-fixing force that exceeds what a single-step process could achieve
Solution Approach 2:
Smaller diameter segments are force-fitted into the rotor core before larger diameter segments. This preliminary action creates initial fixation points that guide and support subsequent larger segments, ensuring proper alignment and maximizing the cumulative rotation-fixing force
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 prevents degradation in rotational balance and performance by ensuring a secure fit between the rotor core and shaft, reducing manufacturing defects and vibration in brushless motors.
Implementation Method 1
a thicker-diameter force-fitting segment, which is force-fit into the shaft hole with a first amount of force-fitting interference; and a thicker-diameter force-fitting segment, which is disposed at a location different (axially spaced apart) from that of the thicker-diameter force-fitting segment in a front-rear (axial) direction parallel to (or colinear with) the rotational axis and which is force-fit into the shaft hole with a second amount of force-fitting interference that is larger than the first amount of force-fitting interference
Data Source
AI summary
A brushless motor (6) includes: a rotor (25), which rotates about a rotational axis (AX); and a stator (24), which is disposed around the rotor and comprises one or more coils (29). The rotor comprises a rotor core (31) and a rotor shaft (33), which is disposed in a shaft hole (60) of the rotor core. The rotor shaft includes: a thinner-diameter force-fitting segment (82), which is force-fit into the shaft hole with a first amount of force-fitting interference; and a thicker-diameter force-fitting segment (79), which is disposed at a location different from that of the thinner-diameter force-fitting segment in a front-rear direction parallel to the rotational axis and which is force-fit into the shaft hole with a second amount of force-fitting interference that is larger than the first amount of force-fitting interference.