Brushless Motor Orientation for Compact Power Tool Design
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Solution Overview
Problem
Existing portable power tools with motors disposed in a way that intersects the impact axis have a large motor housing region, limiting design options for other structural elements and making the tools less compact.
Innovation Solution
The use of a brushless motor with a stator-to-diameter ratio of 1/5 or less and a rotor diameter greater than the stack thickness, allowing for a more compact motor housing and enabling the integration of other components without increasing the tool's overall size, along with a vibration-isolating housing and efficient cooling system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional motor with rotational axis intersecting the impact axis is used, then the motor can provide sufficient power, but the motor housing region becomes large, limiting design options and increasing tool size
Solution Approach 1:
The motor rotational axis is reoriented to be parallel to the impact axis rather than intersecting it, fundamentally changing the spatial dimension of motor placement. This dimensional reconfiguration allows the motor to be positioned at the rear end of the housing, dramatically reducing the motor housing region from extending perpendicular to the impact axis to a compact arrangement along the impact axis direction.
Solution Approach 2:
Instead of the conventional arrangement where the motor rotational axis intersects the impact axis, the invention inverts this relationship by making the rotational axis parallel to the impact axis. This inversion fundamentally changes the motor's spatial footprint and allows for more efficient use of the housing volume.
2Adaptability or versatility
If the motor housing region is made compact, then other structural elements can be arranged more freely, but the motor may not provide sufficient power
Solution Approach 1:
By changing the motor orientation from intersecting to parallel alignment with the impact axis, the invention creates additional spatial freedom in the housing. This dimensional change allows other structural elements to be arranged more freely while maintaining a compact motor housing region, thus achieving both design flexibility and motor power requirements.
3Power
If the stack thickness of the stator is increased to improve power density, then the motor length increases, but if the ratio of stack thickness to diameter is kept at 1/5 or less, the motor becomes more compact
Solution Approach 1:
The invention specifies a parameter constraint where the ratio of stator stack thickness to stator diameter is 1/5 or less. This parameter change transforms the motor from a conventional cylindrical shape to a flat, disc-like structure. By controlling this geometric parameter, the motor achieves high power density through increased diameter while maintaining a compact length, resolving the contradiction between power and size.
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
This configuration reduces the motor housing length, allows for additional components, enhances vibration isolation, and provides effective cooling, resulting in a more compact and efficient power tool design.
Implementation Method 1
The motor-main-body part comprises a stator and a rotor... the motor is preferably configured as a brushless motor
Implementation Method 2
a vibration-isolating housing and efficient cooling system
Data Source
AI summary
A power tool contains a brushless motor that includes a stator having a stack thickness and an outer diameter, a rotor having a diameter, and a motor shaft extending from the rotor and having a rotational axis. A drive mechanism is operably coupled to the motor shaft and is configured to drive a tool accessory in relation to a drive axis. A first housing houses the motor and the drive mechanism. The drive axis does not intersect the brushless motor, but the rotational axis of the motor shaft intersects the drive axis. The outer diameter of the stator is at least five times greater than the stack thickness. Furthermore, the diameter of the rotor is greater than the stack thickness.