Electrostatic Actuator with Electric Field Reduction Area
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Solution Overview
Problem
Conventional actuators for photographic optical modules in digital cameras and portable devices are too large due to the use of electromagnetic actuators, and existing electrostatic actuators that synchronize with piezoelectric vibration for step-driving operations face issues with frictional force control and humidity-induced dielectrophoresis phenomena.
Innovation Solution
An actuator design featuring a fixing member, a vibrator, a vibrating substrate with electrodes separated by an insulating layer, and an electric field reduction area to control electrostatic friction and prevent dielectrophoresis, allowing for efficient step-driving operations even in high-humidity environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If electromagnetic actuators are used for photographic optical modules, then driving force is sufficient, but the device size becomes too large
Solution Approach 1:
The patent replaces the electromagnetic actuation system with an electrostatic actuation system. The electromagnetic motor that drives the mirror holder is substituted by electrostatic attraction forces generated between the mirror holder and the vibration table, eliminating the need for bulky electromagnetic components while maintaining sufficient driving force for optical module operation.
Solution Approach 2:
The patent changes the fundamental actuation mechanism from electromagnetic to electrostatic, utilizing voltage-controlled electrostatic forces instead of current-controlled electromagnetic forces. This parameter change enables miniaturization while providing adequate driving force through high-voltage, low-current operation.
2Volume of moving object
If electrostatic actuators are used to reduce size, then device size is reduced, but frictional force control becomes problematic
Solution Approach 1:
The patent employs periodic vibration of the vibration table at ultrasonic frequencies (20 kHz or higher) to control frictional forces. By synchronizing the electrostatic attraction timing with the vibration cycles, the system achieves precise friction control during the oscillation periods, enabling reliable step-driving operation despite the presence of friction.
Solution Approach 2:
The patent utilizes mechanical vibration of the vibration table as the fundamental operating principle. The table vibrates in the thickness direction at ultrasonic frequencies, and by controlling electrostatic attraction during specific phases of this vibration, the system achieves precise position control and friction management for the mirror holder.
3Force
If high voltage is applied between electrodes for electrostatic adsorption, then electrostatic force is sufficient, but dielectrophoresis occurs in high humidity environments
Solution Approach 1:
The patent applies local quality by creating an electric field reduction area specifically at the edges of the electrodes. The central region maintains full electrostatic attraction force, while the peripheral regions have reduced electric fields. This spatial differentiation of electric field strength prevents dielectrophoresis-induced water accumulation at electrode edges while preserving sufficient electrostatic force in the operational region.
Solution Approach 2:
The patent converts the potential harm of high-voltage operation in humid environments into a benefit by strategically designing the electric field distribution. The high voltage is applied, but the electric field is intentionally reduced at vulnerable edge regions, transforming what would be a harmful condition (high voltage + humidity = dielectrophoresis) into a controlled operation where water accumulation is prevented while maintaining driving force.
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 actuator achieves enhanced driving efficiency by synchronizing electrostatic friction with piezoelectric vibration and prevents dielectrophoresis, ensuring reliable operation under high humidity conditions without compromising electrostatic force.
Implementation Method 1
a vibration generating portion configured to vibrate the vibrating member in the predetermined direction
Implementation Method 2
A potential difference is applied between the movable electrode and the counter electrode to cause an electrostatic force to act
Implementation Method 3
an electric field reduction area configured to shield an electric field occurring between the first and second electrodes by the voltage applied therebetween
Data Source
AI summary
An actuator includes a vibrating substrate having a first electrode on a surface thereof and configured to be reciprocally moved according to a minute displacement of a vibrator, a moving body arranged on the surface of a vibrating substrate and having a second electrode on a surface thereof which faces the first electrode with an insulating layer disposed therebetween, and a controller configured to move the moving body by applying voltage between the first and second electrodes to exert electrostatic adsorptive force therebetween and controlling frictional force between the vibrating substrate and the moving body. The actuator further includes an electric field reduction area configured to shield an electric field occurring between the first and second electrodes by the voltage applied therebetween in a portion which lies outside the first electrode on the surface of the vibrating substrate and faces the moving body.