RU2516258C1 - Piezoelectric device with stepped motion - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: in a piezoelectric device with stepped motion that includes a group of at least two piezoelectric elements, each of them is fixed by its end to a carriage moved along a basis and by its other end to a support pressed to the basis, all piezoelectric elements are divided into two subgroups so that ends with fixed supports of the first subgroup and ends with fixed supports of the second subgroup are directed to the opposite directions, at that sawtooth voltage supplied to the piezoelectric elements of the first subgroup is in reversed phase to the voltage supplied to the piezoelectric elements of the second subgroup. Besides, the carriage is fixed to the supports by means of resilient members. Moreover, these resilient members joining the support with the carriage are made in the form of flat springs or flexible joints.

EFFECT: increasing resting base of the motion device with decrease of its dimensions, increasing operating frequency, compensation of spurious heat losses occurring in result of heating of the piezoelectric elements in-built in the device.

3 cl, 4 dwg

Description

The invention relates to the field of electromechanics and can be used in precision positioning systems for linear movement of various objects and devices in nanotechnological equipment and precision instrumentation.

It is known a moving device comprising a base, a carriage, a mover made of two plates interconnected by elastic hinges, with a movable carriage attached to one of the plates, and the other plate pressed against the base and interacting frictionally with it, a piezoelectric element connected by one the end with the edge of one plate, and the other with the opposite edge of the other plate (see RF patent for PM No. 87572, class IPC H01L 41/00, publ. 10.10.2009).

The disadvantage of this device is the use of a plate pressed to the base to increase the support base of the structure. Since the length of the plate must exceed the length of the piezoelectric element used in the device and the plate must have sufficient rigidity, its mass, which cannot be chosen negligible for the above reasons, can significantly reduce the operating frequencies of the device. Another disadvantage of this device is the parasitic displacement of the carriage relative to the base caused by the heating of the piezoelectric element during operation.

A piezoelectric device is known comprising two groups of rod piezoelectric transducers cantilevered in the housing parallel to the axis of the movable element in the form of an output shaft. Each group includes three piezoelectric transducers uniformly spaced around the circumference. An output shaft is fitted with an interference fit between their free ends equipped with friction support elements, the piezoelectric transducers of the two groups facing each other with their free ends. To carry out the movement of the output shaft, the voltage is alternately supplied to the piezoelectric transducers of one and then the second group, moving the ends of the piezoelectric transducers relative to the output shaft in one direction. Then, the electrical voltage from all piezoelectric transducers of both groups is simultaneously removed. As a result, the output shaft moves one step (see patent RU 2045128, IPC 6 H02N 2/02, H01 41/09, publ. 09/27/1995 - prototype).

The disadvantage of this device is its slowness, due to the succession of deformations of the piezoelectric transducers (moving one step consists of 7 separate sequential procedures), in addition, reversing the free ends of the piezoelectric transducers towards each other reduces the support base of the device.

The purpose of the proposed technical solution is to increase the support base of the proposed device while decreasing its overall dimensions, increasing the operating frequency, compensating for spurious thermal drifts caused by heating of the piezoelectric elements built into the device.

This goal is achieved by the fact that in the well-known technical solution for movements (piezoelectric device for step-by-step movement), including a carriage, base, a group of piezoelectric elements, each of which is attached with one end to the carriage and the other against the support pressed to the base, according to the invention, the number of piezoelectric elements in a group of at least two and they are divided into two subgroups so that the ends with attached supports at the first subgroup of piezoelectric elements and the ends with attached supports at the second subgroup of piezoelectric elements and sides opposite from each other, and the sawtooth voltage supplied to the piezoelectric elements of the first subgroup is opposite to the voltage supplied to the piezoelectric elements of the second subgroup.

In addition, the carriage is attached to the supports by means of elastic elements.

In addition, the elastic elements connecting the supports to the carriage are made in the form of flat springs or elastic hinges.

Schematic diagrams of the variants of the proposed device are shown in figures 1-4, where:

1 - carriage;

2 - the first piezoelectric element;

3 - the second piezoelectric element;

4 - the first support;

5 - second support;

6 - base;

7 - flat springs;

8 - magnet;

9 - elastic hinges;

10 - protrusions;

11 - the third piezoelectric element;

12 - the fourth piezoelectric element;

13 - the third support;

14 - the fourth support.

Figure 1 shows the design of a device consisting of a carriage 1, to which one of its ends are attached to the piezoelectric elements 2 and 3, the other ends of which are attached to the supports 4 and 5, respectively. Supports 4 and 5 are pressed to the base 6 (clamping elements not shown) and have frictional contact with it.

The device operates as follows.

A sawtooth voltage is applied antiphase to piezoelectric elements 2 and 3. During the slow phase of the saw, piezoelectric element 2, for example, slowly compresses, and piezoelectric element 3 slowly expands, while the forces acting on the side of the piezoelectric elements 2 and 3 are less than the rest forces between the base 6 and the supports 4 and 5, respectively, therefore the supports 4 and 5 will remain stationary relative to the base 6, and the carriage 1 will shift to the left by the deformation of the piezoelectric elements 2 and 3. During the fast phase of the saw, the piezoelectric elements 2 and 3 sharply return to their original state, while the supports 4 and 5 from the side of the piezoelectric elements 2 and 3 with tvetstvenno acting force exceeding the static frictional force between them and the base 6, whereby the supports 4 and 5 are shifted to the left, and the carriage 1, thanks to its inertia, is practically remains stationary.

At the next sawtooth pulse, the process of moving the carriage 1 will be repeated, and it will move to the left one more step.

To move the carriage 1 to the right, you must either change the sequence of the slow and fast phases of the supplied sawtooth voltage, or change its polarity.

The frequency of repetition of steps is regulated from single steps to comparable with the natural frequencies of piezoelectric elements 2 and 3, because the masses of supports 4 and 5 can be chosen smaller than the masses of the piezoelectric elements 2 and 3 themselves.

Due to the fact that the ends of the piezoelectric elements 2 and 3 with the supports 4 and 5 attached to them are respectively directed in opposite directions from each other, the stability of the entire structure increases due to the increase in the support base, and the heating of the piezoelectric elements 2 and 3 when the device is operating at high frequencies does not to parasitic displacement of the carriage 1 relative to the base 6.

Figure 2 shows a variant of the device in which the carriage 1 is attached to the supports 4 and 5 by means of elastic elements made in the form of flat springs 7. In this embodiment, the supports 4 and 5 are pressed to the base 6 using a magnet 8 located on the carriage 1, wherein the base 6 or a part thereof is made of a material having magnetic properties.

Figure 3 presents a variant of the device in which the carriage 1 is attached to the supports 4 and 5 by means of elastic hinges 9, and the piezoelectric elements 2 and 3 are located one above the other and are attached to the protrusions 10 of the carriage 1, and the piezoelectric element 2 passes through the hole in the protrusion 10.

The number of piezoelectric elements in the proposed piezoelectric device of stepwise movement, depending on the requirements for it in terms of traction and stability (support base), may be more than two.

Figure 4 shows a variant of the device, in which along with the piezoelectric elements 2 and 3 to the protrusions 10 of the carriage 1 are attached the piezoelectric elements 11 and 12 with supports 13 and 14, respectively (the figure shows a view of the carriage 1 from the side of the base 6), while on the piezoelectric elements 2 and 12, the common-mode voltage is applied, which is out of phase with the voltage supplied to the piezoelectric elements 3 and 11.

Since antiphase voltage (of different polarity) is supplied to the piezoelectric elements during operation of the device, its value should not exceed the values leading to the depolarization of the piezoelectric elements.

The range of movement of these device options is limited only by the linear dimensions of the base.

Thus, the use of the invention will increase the support base of the moving devices, making their linear dimensions comparable with the length of the piezoelectric elements used in them, which is important in the manufacture of miniature step positioners, and will also increase the operating frequencies of the device and avoid parasitic carriage displacement due to thermal expansion of the piezoelectric elements due to their heating when operating in silent mode at high frequencies.

Claims (3)

1. A piezoelectric device of step-by-step movement, comprising a carriage, a base, a group of piezoelectric elements, each of which is attached to the carriage with one end and the support pressed to the base with the other, characterized in that the number of piezoelectric elements in the group is at least two and they are divided into two subgroups so that the ends with attached supports for the first subgroup of piezoelectric elements and the ends with attached supports for the second subgroup of piezoelectric elements are directed opposite to each other, and the sawtooth voltage applied to the piezoelectric elements of the first subgroup , out of phase with the voltage supplied to the piezoelectric elements of the second subgroup. 2. The piezoelectric device according to claim 1, characterized in that the carriage is attached to the supports by elastic elements. 3. Piezostroy according to claims 1 and 2, characterized in that the elastic elements connecting the supports to the carriage are made in the form of flat springs or elastic hinges.

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