Camera Module SMA Motor With Magnetic Centering Against Eccentricity
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Solution Overview
Problem
Conventional shape memory alloy motors used in camera modules for autofocus and optical image stabilization suffer from significant eccentricity issues when powered off, leading to reduced product yield and accuracy due to the loose positioning of the rotor, which affects the camera module's appearance and functionality.
Innovation Solution
Incorporating an eccentricity-prevention magnetic assembly with magnetostatic forces between a first eccentricity-prevention member and a second eccentricity-prevention member, which keeps the central axes of the base and support base aligned even when the motor is powered off, and utilizing shape memory alloy actuators for movement when powered on, assisted by an elastic structure for improved centering and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If shape memory alloy wires are used to suspend the rotor and achieve AF and OIS functions, then the motor structure is simplified and costs are reduced, but the rotor position deviates significantly from the central position when powered off, causing large eccentricity
Solution Approach 1:
The patent introduces a magnetic assembly as an intermediary component between the rotor and stator. This magnetic assembly generates magnetic attraction force to pull the rotor toward the center position when the motor is powered off, compensating for the lack of active control and reducing eccentricity without adding complex mechanical structures.
Solution Approach 2:
The patent utilizes the change in magnetic force parameters based on the motor's power state. When powered on, the magnetic assembly is deactivated or its force is overcome by the drive mechanism; when powered off, the magnetic assembly's attraction force automatically engages to center the rotor, dynamically adapting to operational conditions.
2Force
If the rotor is suspended only by shape memory alloy wires, then the motor achieves large thrust and long stroke, but the position and posture of the rotor become relatively free and may vary with gravity direction, resulting in large deviation from central position
Solution Approach 1:
The magnetic assembly acts as a counterbalancing mechanism that provides a restoring force opposite to the gravitational effect and positional deviation. When the rotor moves away from the central position due to gravity or other forces, the magnetic attraction force pulls it back, stabilizing the rotor position without counteracting the useful thrust during operation.
Solution Approach 2:
The magnetic assembly provides self-centering functionality automatically when the motor is powered off, without requiring external intervention or complex control systems. The system uses its own magnetic field to correct positional deviations and maintain stability.
3Measurement precision
If conventional OIS apparatuses use voice coil motors or other electromagnetic devices, then precise control is achieved, but electromagnetic interference occurs and costs increase
Solution Approach 1:
The patent replaces electromagnetic drive mechanisms with a shape memory alloy-based mechanical system for the primary driving function. The magnetic assembly used for centering is a passive magnetic field system that does not generate significant electromagnetic interference, thus eliminating the harmful effects associated with conventional electromagnetic OIS apparatuses while maintaining control precision through the shape memory alloy's responsive mechanical properties.
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 solution effectively reduces eccentricity, enhances product yield, and maintains accurate centering of the camera module, ensuring improved performance and appearance by ensuring the motor's axes remain aligned both in powered-on and powered-off states.
Implementation Method 1
the shape memory alloy actuator is configured to drive the support base to move relative to the base
Implementation Method 2
a first central axis of the base coincides with a second central axis of the support base under the action of magnetostatic forces between the first eccentricity-prevention member and the second eccentricity-prevention member
Data Source
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AI summary
Disclosed are a motor (20, 40, 50, 60, 70, 80), a camera module (100), and a mobile terminal (200). A motor (20, 40, 50, 60, 70, 80) includes a base (21, 41, 51, 61, 71, 81), a support base (23, 43, 53, 63, 73, 83), and a shape memory alloy actuator (25). The shape memory alloy actuator (25) is fixedly connected between the base (21, 41, 51, 61, 71, 81) and the support base (23, 43, 53, 63, 73, 83), and the shape memory alloy actuator (25) is configured to drive the support base (23, 43, 53, 63, 73, 83) to move relative to the base (21, 41, 51, 61, 71, 81). The motor (20) further includes an eccentricity-prevention magnetic assembly (27, 47, 57), the eccentricity-prevention magnetic assembly (27, 47, 57) includes a first eccentricity-prevention member (271, 471, 571, 771, 871) and a second eccentricity-prevention member (273, 473, 573, 773, 873), the first eccentricity-prevention member (271, 471, 571, 771, 871) is disposed on the base (21, 41, 51, 61, 71, 81), the second eccentricity-prevention member (273, 473, 573, 773, 873) is disposed on the support base (23, 43, 53, 63, 73, 83), and when the motor is in a powered-off state, a first central axis of the base (21, 41, 51, 61, 71, 81) coincides with a second central axis of the support base (23, 43, 53, 63, 73, 83) under the action of magnetostatic forces between the first eccentricity-prevention member (271, 471, 571, 771, 871) and the second eccentricity-prevention member (273, 473, 573, 773, 873), to resolve the problem of eccentricity of the motor (20, 40, 50, 60, 70, 80).