Compact Motor Assembly With Nested Bearings for Shorter Power Tools
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Solution Overview
Problem
Power tools such as impact drivers and impact wrenches often lack sufficient power or are too large to fit into desired locations, necessitating a reduction in size without compromising power performance.
Innovation Solution
A compact brushless motor assembly with a nested bearing configuration and optimized support plate design, allowing for a smaller form factor while maintaining high power output and torque, achieved through the use of a planetary gear set and a rotational impact mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the motor assembly and transmission components are arranged in a conventional configuration, then the power output can be maintained, but the tool length and girth increase making it too large to fit into desired locations
Solution Approach 1:
The patent applies nesting by placing the transmission housing and bearings within the motor envelope. Specifically, the transmission housing is received within the motor envelope, and bearings are positioned within the stator assembly and rotor, allowing compact integration of multiple components in a nested arrangement that reduces overall tool length while maintaining power output
2Power
If the motor assembly and transmission components are arranged in a conventional configuration, then the power output can be maintained, but the tool girth increases making it too large to fit into desired locations
Solution Approach 1:
The patent merges the motor assembly and transmission components into a single integrated unit by receiving the transmission housing within the motor envelope and positioning bearings within the stator and rotor. This consolidation eliminates separate housings and reduces the overall girth of the tool while maintaining the required power output
3Ease of manufacture
If bearings are positioned outside the motor envelope, then the motor assembly is easier to manufacture, but the tool length and girth increase
Solution Approach 1:
The patent positions bearings within the motor envelope, with the first bearing received within the stator assembly and the second bearing received within the rotor. This nested arrangement reduces tool length while the bearings are still accessible for manufacturing and assembly processes
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 solution enables power tools with a maximum power output of at least 430 Watts and 1820 inch-pounds of torque in a length of less than 110 mm, significantly improving power density and fitting into smaller spaces.
Implementation Method 1
a brushless motor received in the housing. The motor includes a rotor configured to rotate about a rotor axis and a stator assembly having a stator core and conductive windings
Implementation Method 2
The transmission may comprise a planetary gear set with the input member including a sun gear rotatably driven by the rotor shaft, the output member including a carrier, and the planetary gear set further including a planet gear rotatably mounted to the carrier and meshed with the sun gear
Data Source
AI summary
A power tool includes a housing and a brushless motor with a rotor and a stator assembly. The motor defines a motor envelope bounded by a rear plane at a rearmost point of the stator assembly and rotor, a front plane at a frontmost point of the stator assembly and rotor, and a generally cylindrical boundary surrounding a radially outermost portion of the stator assembly and rotor. A rotor shaft is rotatably driven by the rotor. A transmission includes an input member rotatably driven by the rotor shaft and an output member. A first bearing supporting the rotor shaft is at least partially received within the motor envelope. A second bearing supporting the rotor shaft or a component of the transmission is at least partially received within the motor envelope. A support plate supporting a component of the transmission may be at least partially received within the motor envelope.