Compact Brushless Sanding Machine Motor Segmentation
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Solution Overview
Problem
Existing electric sanding machines are bulky, difficult to grip with one hand, and prone to interference with the electric network due to their large motor diameter and high harmonic components, necessitating complex and expensive solutions for balance and dust protection.
Innovation Solution
A compact brushless electric motor with a rotor attached to the tool shaft and a stator in the outer housing, utilizing a slotless BLDC motor with external cooling and sensorless control, integrated with a blower for dust extraction and harmonic component management within regulatory limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional electric motor with shaft is used in sanding machines, then the machine can achieve sufficient power, but the machine becomes bulky and difficult to grip with one hand
Solution Approach 1:
The motor is divided into two separate components: the stator remains in the housing while the rotor is detached and attached to the tool shaft. This segmentation eliminates the need for a motor shaft and reduces the overall motor diameter, making the machine compact and easy to grip while maintaining power output.
Solution Approach 2:
The motor configuration transitions from a conventional cylindrical shape to a flattened disc-like shape with the stator in the housing and rotor on the shaft. This dimensional change allows the motor to fit within compact housing constraints while preserving the necessary power delivery capability.
2Power
If the motor diameter is made large to achieve sufficient power, then power output is improved, but the machine becomes difficult to grip and hermetic cooling becomes disadvantageous
Solution Approach 1:
By separating the stator and rotor, the motor diameter is reduced to a compact size that fits comfortably in the hand, while the power output is maintained through the direct coupling of the rotor to the tool shaft, eliminating the need for a large diameter motor.
3Reliability
If a hermetic motor with external cooling is used, then the motor is protected from dust, but cooling efficiency is reduced when air contains dust particles
Solution Approach 1:
The rotor is extracted from the hermetic housing and attached to the tool shaft externally. This allows the stator to remain protected within the sealed housing while the rotor operates in the dust-containing environment, enabling effective cooling without compromising dust protection of the motor components.
4Stability of the object's composition
If the motor is moved to the far end of the arm for wall grinding applications, then balance is achieved, but the machine becomes expensive and difficult to manufacture
Solution Approach 1:
The motor segmentation allows the compact stator-housing assembly to be manufactured separately and easily assembled with the tool shaft-rotor assembly, simplifying production while maintaining balance through the low-profile configuration and proper weight distribution.
5Device complexity
If a simple rectified control unit with large capacitor is used, then the control is simple, but high harmonic components interfere with the electric network
Solution Approach 1:
The control unit parameters are optimized to operate the brushless motor with reduced harmonic distortion. By adjusting the switching frequency and control parameters, the system achieves compliant operation without requiring complex filtering components, maintaining simplicity while eliminating network interference.
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 a lightweight, ergonomic, and hermetic sanding machine that is easy to handle and reduces network interference, eliminating the need for specialized wall grinding machines while maintaining effective power correction and dust management.
Implementation Method 1
an electric drive motor that is brushless and without a shaft of its own, mounted in such a way that the rotor is fastened to the tool shaft and the stator is positioned in the outer housing
Implementation Method 2
The slotless motor has smaller iron losses and a more advantageous price because the iron core of lamination stacks has a simpler form
Implementation Method 3
The cooling air is generated by a blower that is mounted on the tool shaft and can advantageously be integrated in the same vertical direction as the balance weights of the tool shaft. The same cooling air that cools the motor first cools the control unit.
Data Source
AI summary
The present invention particularly relates to a hand-held sanding machine with an outer housing (1), a tool shaft (2) and a brushless electric drive motor. In the present invention, the rotor of the drive motor is fastened to the tool shaft (2) of the sanding machine, and the stator (6) is positioned in the outer housing (1). The present invention also relates to a control method for an electric sanding machine.