Compact Brushless Motor Assembly With Nested Transmission Layout
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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 due to their length and girth, necessitating a reduction in size without compromising performance.
Innovation Solution
A compact brushless motor assembly with a nested bearing and transmission design, including a planetary gear set, that allows for a power tool with a maximum power output of at least 430 Watts and a length of less than 110 mm, achieving a power-to-length ratio of 4.5 Watts/mm and torque-to-length ratio of 18.0 inch-pounds/mm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the motor assembly and transmission components are arranged in a conventional layout, then the power tool can achieve sufficient power output, but the length and girth of the tool become too large to fit into desired locations
Solution Approach 1:
The patent applies nesting by placing the transmission assembly inside the motor envelope. The input member is coupled to the rotor shaft and received within the motor envelope, while the output member extends from the housing. This nested arrangement allows the transmission components to occupy space within the existing motor boundaries, reducing the overall tool length while maintaining power transmission capability.
Solution Approach 2:
The patent repositions components from a conventional linear arrangement to a three-dimensional compact layout. The transmission assembly is arranged within the radial and axial space of the motor envelope, utilizing unused volume rather than extending the tool in a single direction. This dimensional optimization reduces the tool's length and girth while preserving power output.
2Power
If the motor assembly and transmission components are arranged in a conventional layout, then the power tool can achieve sufficient power output, but the girth of the tool becomes too large to fit into desired locations
Solution Approach 1:
The transmission assembly is nested within the motor envelope, with the input member received inside the motor boundaries and the output member extending selectively. This nesting consolidates components into a tighter radial arrangement, reducing the tool's girth while maintaining power transmission from the rotor shaft to the output member.
Solution Approach 2:
The patent merges the transmission assembly with the motor assembly by positioning the input member coupled to the rotor shaft and receiving it within the motor envelope. This integration eliminates the need for separate mounting spaces for the transmission, reducing the overall tool girth while maintaining functional separation of components.
3Ease of manufacture
If bearings are positioned outside the motor envelope, then the motor assembly can accommodate standard bearing arrangements, but the overall length of the power tool increases
Solution Approach 1:
The patent positions at least a portion of the bearings within the motor envelope, nesting them inside the existing motor boundaries rather than extending the assembly outward. This allows the bearings to be accommodated within the compact motor space, reducing the overall power tool length while still supporting the rotor shaft and transmission components effectively.
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 compact design maintains high power and torque output while reducing the overall length of the power tool, enabling it to perform effectively in confined 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
A transmission is received in the housing and includes an input member coupled to and configured to be rotatably driven by rotation of the rotor shaft, and an output member configured to be driven by rotation of the input member
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.