Power Tool Rear End Cap for Rotor-Stator Alignment
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Solution Overview
Problem
Power tools with electric motors face alignment issues between the rotor and stator, leading to potential friction and increased operating temperature, and existing designs either lengthen the tool with end caps or complicate housing molding to avoid misalignment.
Innovation Solution
A power tool design featuring a housing with a main and rear end cap that supports the motor bearing, reducing the overall length and improving manufacturability by allowing the end cap to reside within the housing and directly center the rotor relative to the stator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the air gap between rotor and stator is minimized, then magnetic efficiency is improved, but the likelihood of rotor-stator misalignment and friction increases
Solution Approach 1:
The patent introduces an intermediary alignment mechanism between the rotor and stator, using the motor housing with integrated bearing support as a mediator to maintain precise air gap spacing. The housing acts as a mechanical intermediary that ensures proper positioning while allowing for misalignment compensation, thus maintaining both magnetic efficiency and alignment stability.
2Manufacturing precision
If end caps are added to support rotor bearings, then rotor-stator alignment is improved, but the overall length of the power tool increases
Solution Approach 1:
The patent merges the functions of the motor housing and end caps into a single integrated structure. The motor housing directly supports the rotor bearings and provides alignment features for the stator, eliminating the need for separate end cap components. This consolidation maintains precise alignment while reducing the overall length of the power tool by eliminating the additional length that would be required for separate end caps.
Solution Approach 2:
The motor housing is designed to perform multiple functions: it supports the rotor bearings, provides alignment features for the stator, and serves as a structural component of the power tool. This multi-functional design eliminates the need for dedicated end caps, thereby maintaining alignment precision without increasing tool length.
3Length of moving object
If the housing directly supports rotor bearings to eliminate end caps, then the overall length is reduced, but the alignment between rotor and stator becomes more difficult to achieve
Solution Approach 1:
The patent incorporates preliminary alignment features directly into the motor housing during manufacturing. The housing includes pre-formed bearing support surfaces and stator mounting features that are precisely positioned to ensure correct alignment. This preliminary action during manufacturing eliminates the need for complex post-assembly alignment procedures, achieving both reduced length and high alignment precision.
4Manufacturing precision
If complex housing molding is used to achieve precise alignment, then alignment precision is improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the motor assembly into modular components (motor housing, stator, rotor, bearings) that can be manufactured separately using standard processes. The alignment features are distributed across these modular components rather than requiring complex integrated molding. This segmentation allows each component to be manufactured with simpler, more cost-effective processes while maintaining high alignment precision through precise interface design.
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
A power tool (10) includes a housing (12) and an electric motor (28) supported within the housing (12). The housing (12) includes a main housing portion (14) that defines a rear opening (42). The electric motor (28) includes an output shaft (30) supporting a rotor assembly (44) for rotation about a motor axis (32). The electric motor also includes a stator assembly (46) surrounding the rotor assembly (44), and a rear end cap (18). The rear end cap (18) supports a rear motor bearing (58) that rotatably supports the output shaft (30) at a rear end. A portion of the rear end cap (18) resides within the rear opening (42) to close the rear opening (42).