Innovative solutions that give consideration to the high conscience for costs are demanded in industries such as medical engineering. The aim is the increase of the feed-in quality, while maintaining a justifiable costliness. An example of such a solution is the standardized, piezoelectric motor. The production of this multifunctional miniature motor costs only a tenth to a hundredth in comparison to a conventional piezo drive.
A standardized, high-precision piezoelectric motor makes it possible to produce the smoothest movements in all types of industrial products, such as automobiles and consumer goods. The advantages of this fully developed and cheap technology are the high dynamics, the high positioning accuracy, the noiseless operation, the minor mass, and the continuously variable speed.
There have been piezoelectric motors for more than 35 years. Compared to traditional models, a standardized piezomotor is constructed in a much easier way and has a very positive influence on price.
This type of motor, such as the Elliptecmotor, produces rotary and linear movements with a speed of 0-300 mm/sec and feeding forces up to 0.4 Newton. Higher forces can be realized with the aid of simple lever mechanisms or the use of several motors.
The core of the motor is piezo ceramic, which activates the oscillating of a vibratory element — the resonator — with approximately 100 KHz, whereby a wheel or a driving rod can be activated. Thanks to its minor fitting dimension and mass, this type of piezo motor can be easily integrated into a large number of products.
The motor is able to directly produce slow movements. This special advantage is effective where, due to a low installation space or due to costs, no gear can be used. It is possible to adjust any speed with the aid of software. Therefore the motor needs — in comparison to the electronics of a stepper motor — a much less number of electronic components. The supply voltage can be between 2.4 V (operation with batteries) and 30 V.
Nearly every conventional electric motor is operated by a magnetic field and has a rotation axle. The standardized, high-precision piezoelectric motor, on the other hand, is operated on the base of a micro-subtle driving movement, whereas the driven element is moved in thousands of small steps. These micro-steps are produced by the resonator that is excited to oscillate by the piezo ceramic. Piezo ceramics expand by 0.1 percent of their dimension when an electronic voltage is created and shorten again after removal of the voltage. The piezo element is installed into the resonator that is approximately 2 cm long and manufactured by aluminum. Due to a special form of the resonator, the tip oscillates in an elliptic path.
In order to move the motor in a continuously linear or rotary movement, the tip of the motor will be pushed against the driven element. Due to the preload force between the motor tip and the driven element, a force transmission by friction appears. By each movement of the motor the tip of the motor pushes the driven element some amount of micro-meters. Due to the high operational frequency of the motor, a steady movement emerges. It is also possible to operate it as a stepper motor.
The robust, gear-less motor consists of four parts: The piezo ceramic, the circumjacent aluminum frame (resonator), a clip fixed at the frame, and the connection cables.
One place that the motor is particularly useful is in medical applications. (See adjacent article.) Due to its precision and its functional principle, as well as its noiseless operation, the minor construction volume, and a weight of 1.2 g, it is suitable for an energy-saving application in medical metering units.
But there are other applications where it is also useful. The heavily reduced costs, thanks to a new patented production method, make this miniature motor interesting for several types of applications.
Dirk van Vinckenroye works for German-based Elliptec AG and specializes in high-precision piezoelectric motors. More information is available at www.elliptec.com or by calling 610-687-2277.
Pull-Quote : There have been piezoelectric motors for more than 35 years. Compared to traditional models, a standardized piezomotor is constructed in a much easier way and has a very positive influence on price.
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