Brushless Motor Insulation Structure for Metal-Cased Work Machines
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Solution Overview
Problem
In electric work machines, such as power tools and lawn mowers, insufficient electrical insulation between the stator core and rotary shaft can lead to electrical issues when a brushless motor is housed in a metal interior case.
Innovation Solution
The implementation of an insulating means, including a bearing-side insulating member and a stator-side insulating member, provides effective electrical insulation between the stator core and the rotary shaft, with the insulating members being integrally formed on the interior case and between the stator core and the housing, respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a brushless motor is housed in a metal interior case, then structural strength and durability are improved, but electrical insulation between the stator core and rotary shaft deteriorates
Solution Approach 1:
The patent introduces insulating members as intermediary elements between the metal interior case and the motor components. Specifically, insulating members are provided between the stator core and the rotary shaft, and between the stator core and the housing, creating a mediating barrier that prevents direct electrical contact while allowing the metal case to provide structural support.
Solution Approach 2:
The patent employs composite construction by combining metal materials for the interior case and housing with insulating materials for the insulating members. This composite approach allows the system to simultaneously achieve the mechanical advantages of metal (strength and durability) and the electrical advantages of insulating materials (electrical isolation).
Data Source
AI summary
An electric work machine, such as a lawn mower includes a motor case (22) fixed inside a main-body housing (10). A brushless motor (21) is housed inside the motor case (22) and includes a stator (23) having a stator core (40), coils (45), and upper and lower insulators (42, 43), and a rotor (24) disposed inward of the stator (23) and having a rotary shaft (25). A spindle (17) is driven by the rotary shaft (25). The motor case (22) holds the stator (23) and axially supports the rotary shaft (25) via bearings (68, 76). One or more insulating members, such as an insulating cap (67) and/or a resin layer (78), provide electrical insulation between the stator core (40) and the rotary shaft (25).