Compact BLDC Motor Assembly With Nested Bearing Layout
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Solution Overview
Problem
Power tools such as impact drivers and impact wrenches often lack sufficient power and are too large to fit into desired locations due to their girth and length, necessitating a reduction in size without compromising performance.
Innovation Solution
A compact brushless motor assembly with a nested bearing and transmission design, including a stator assembly, rotor, and planetary gear set, which allows for a reduced overall length while maintaining high power output and torque.
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 tool becomes too large in length and girth to fit into desired locations
Solution Approach 1:
The patent applies nesting by placing the transmission housing and its components inside the motor envelope. Specifically, the transmission housing is received within the motor envelope, and bearings are nested within the stator assembly and rotor structure. This nested arrangement allows the transmission to occupy space already defined by the motor components, thereby reducing the overall tool length while maintaining both power output and transmission functionality.
2Force
If the motor assembly and transmission components are arranged in a conventional layout, then the power tool can achieve sufficient torque, but the tool becomes too large in girth to fit into desired locations
Solution Approach 1:
The patent merges the motor assembly and transmission housing into a single integrated structure where the transmission housing is received within the motor envelope. The motor envelope is defined by the stator assembly and rotor, and the transmission housing occupies the internal space of this envelope. This merging eliminates the need for separate external transmission housing, reducing the tool's girth while maintaining both motor power and transmission torque capabilities.
3Ease of manufacture
If bearings are positioned outside the motor envelope, then the motor assembly can accommodate standard bearing placements, but the overall tool length and girth increase
Solution Approach 1:
The patent applies nesting by placing the transmission housing and its components inside the motor envelope. Specifically, the transmission housing is received within the motor envelope, and bearings are nested within the stator assembly and rotor structure. This nested arrangement allows the transmission to occupy space already defined by the motor components, thereby reducing the overall tool length while maintaining both power output and transmission functionality.
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 achieves a maximum power output of 430 Watts and a maximum output torque of 1820 inch-pounds in a tool length of less than 110 mm, with a power-to-length ratio of 4.5 Watts/mm and torque-to-length ratio of 18.0 inch-pounds/mm, exceeding expectations for tools of comparable size.
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
Figure 1
Figure 2A
Figure 2B
AI summary
A power tool is provided with a tool housing, a support plate provided within the tool housing, a rear tool cap mounted on a rear end of the tool housing, and a brushless direct-current (BLDC) motor received within the housing. The motor includes a stator assembly having a stator core and stator windings, a front motor bearing supported by the support plate, a rear motor bearing supported by the rear tool cap, and a rotor including a rotor core and a magnet ring mounted around the rotor core. The rotor core defines an annular recess within which at portion of the front bearing and a portion of the support plate are located such that the a radial plane intersects the front bearing, the magnet ring, and the stator core.