Brushless Screen Actuator Geometry for Low-Noise Torque
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Solution Overview
Problem
Electromechanical actuators for screens in home automation face challenges in minimizing noise generation while maintaining sufficient torque and being economical, particularly in applications where the actuator is inserted into a winding tube with a small diameter, such as 40 mm, and must operate variously sized screens effectively.
Innovation Solution
The design of a brushless electric motor with a stator and rotor positioned coaxially, featuring a ratio of external to internal stator diameter less than 1.7 and axial length to external diameter greater than 1.5, increasing the motor's length and air gap to reduce noise and improve robustness, using ferrite permanent magnets for high torque with reasonable production costs, and a six-pole stator configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the actuator diameter is reduced to fit in a 40 mm winding tube, then the actuator can be installed in standard rollable screens, but the torque capability is reduced
Solution Approach 1:
The patent transitions from a conventional short and wide motor configuration to an elongated cylindrical configuration by increasing the length-to-diameter ratio. This dimensional change allows the motor to fit within a 40 mm diameter winding tube while maintaining sufficient torque capability through increased axial length, effectively trading radial space for axial space to resolve the contradiction between compact diameter and torque capability.
Solution Approach 2:
The patent modifies key geometric parameters of the motor, specifically setting the ratio between external stator diameter and internal stator diameter to less than 1.7, and the ratio between axial length and external diameter to greater than 1.5. These parameter changes optimize the motor's torque density and allow it to deliver adequate torque within the constrained 40 mm diameter envelope required for standard rollable screen installations.
2Weight of moving object
If lightweight motors are used to reduce actuator mass, then the actuator can be made more compact and economical, but noise generation increases due to vibrations
Solution Approach 1:
The patent employs ferrite permanent magnets in the rotor, which provide high torque output relative to their weight. This material choice allows the motor to maintain low mass while generating sufficient electromagnetic force, and the ferrite material properties contribute to reduced vibrations and noise compared to lighter materials that would require higher operating currents.
Solution Approach 2:
The elongated cylindrical motor design serves multiple functions: it reduces noise by increasing mass and reducing vibrations, maintains compact dimensions for installation in 40 mm winding tubes, and provides sufficient torque for screen operation. The single design configuration simultaneously addresses weight, noise, and space constraints that would otherwise require separate design compromises.
3Force
If the motor length is increased to provide sufficient torque, then the torque capability improves, but the actuator becomes wider than it is long
Solution Approach 1:
The patent fundamentally changes the motor's geometric proportions by increasing the length-to-diameter ratio to greater than 1.5. This dimensional transformation allows the motor to achieve adequate torque through increased axial length rather than radial expansion, ensuring the motor remains compact enough for installation in standard 40 mm diameter winding tubes while providing sufficient torque capability.
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 results in a motor with reduced specific power, increased robustness, and lower noise levels, allowing effective operation within small diameters while maintaining sufficient torque for winding screens, and is more cost-effective than conventional designs.
Implementation Method 1
The rotor includes a rotor body provided with magnetic elements, such as permanent magnets, distributed on the outer surface of the rotor
Implementation Method 2
The magnetic elements of the rotor are surrounded by the stator. The stator is formed by a stator core comprising pole elements supporting windings
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
This electromechanical actuator configured for controlling screens comprises an electronically-commutated, brushless, DC electric motor (16), a rotor (13) and a stator (14) of the electric motor (16) being positioned coaxially around an axis of rotation (X), the rotor (13) comprising a rotor body (31) provided with magnetic elements (32) distributed over the outer surface of the rotor (13), the magnetic elements (32) of the rotor (13) being surrounded by the stator (14), said stator being formed by a stator core comprising a circular peripheral wall and pole elements supporting windings, the pole elements being distributed on the inside of the peripheral wall. The ratio between the outer diameter (D3) of the stator (14) and the inner diameter (D4) of same is less than 1.7. Further, the ratio between the axial length (L14) of the stator and the outer diameter (D3) of the stator is greater than 1.5.