Peizoelectric traveling wave device

Technical field

The invention relates to the field of piezoelectric actuators. It can be used in angular positioning systems, such as controlling microscope tables for positioning objects, chemical / biological media analysis, positioning machined metal / wood products on a software control machine and the like.

State of the art

There is known a device with a piezoelectric actuator in which the movement of the driving circuit is formed by a piezoelectric element having a certain arrangement of electrodes in contact with the driving circuit through abrasion-resistant supports rigidly fixed to the piezoelectric element (see U.S. Patent No. 6,765,335 B2, 2004-07-20). ).

In the device, vibration energy is transmitted to the drive unit from the piezoelectric element through friction-resistant supports, which absorb part of the vibration energy, which reduces the amplitude of oscillation developed by the piezoelectric element and the efficiency of the actuator.

A rotary piezoelectric actuator is known, which comprises a piezoelectric ring with electrodes built into the housing, on which a ring-shaped resilient and abrasion-resistant contact member interacting with a rotor of analogous shape is mounted on a flat surface. The rotor is connected to the drive unit (shaft). The piezoelectric ring electrodes are connected to a high frequency power supply (see U.S. Patent No. 4,562,374, December 31, 1985).

In the above prototype, the rotary motion of the shaft is formed by a traveling wave oscillation generated by an electrically excited piezoelectric ring whose planar surface moves all points along elliptic trajectories. Micrometer-sized row oscillations are transmitted to a ring-shaped elastic and abrasion-resistant contact member as well as to a rotor and drive link (shaft). The ring-shaped elastic and abrasion-resistant contact element used in the design of the device reduces the level of vibration generated by the piezoelectric ring and the efficiency of the piezoelectric actuator.

The essence of the invention

The object of the invention is to increase the torque generated by the device by increasing the amplitude of the traveling wave oscillations generated by the piezoelectric element and reducing the vibration impact on the piezoelectric element by its dynamic contact with the driving circuit and the dynamic effect of the oscillations on the device mounting elements.

The object of the present invention is achieved in that in a piezoelectric traveling wave device comprising a rectangular profile annular piezoelectric element with electrodes connected to a polyphase harmonic oscillator, a contact element and a rotor, wherein the contact element is in the form of a tapered rectangular cylindrical profile. the annular surface is rigidly attached to its wider end, at its northern end, with external forces, a rotor is pressed in, and laterally mounted fasteners. In addition, the tapered contact element L of tapering hollow profile has a length L equal to the half-wave λ / 2 of the excitation oscillating standing wave, with its fastening elements at its node. Also, on the wall of the cylindrical contact member of the tapered hollow profile, triangular holes are formed at the line of the piezoelectric element phase electrodes, and their number is equal to the number of phase electrodes of the piezoelectric element.

Brief description of the drawings

The invention is explained in the following figures.

Fig. 2A shows the construction of a piezoelectric traveling wave device: a is a side section of the device; b is the phase electrode breakdown of the piezoelectric cell for generating a four-phase wave wave.

Fig. 4A is an outline of a hollow cylinder construction of a piezoelectric four-phase traveling wave device with four triangular holes in the wall.

The piezoelectric traveling wave device consists of a rectangular profile annular piezoelectric element 1 with electrodes (sectioned into at least 3 electrodes), a multi-phase harmonic signal generator 2, a rotor 3, a tapered cylindrical contact element, a tapered profile, and a tapered wave element. 5. In order to excite the largest possible amplitudes of resonant oscillations in the cylindrical contact element 4 of the tapered hollow profile, it is made of a material having a high mechanical quality factor. In addition, its mean wall thickness, or triangular apertures 6 parallel to the longitudinal tapered cylindrical profile of the piezoelectric element, may be varied to equalize its longitudinal and bending first-form resonant traveling wave oscillations. 4 for symmetry axis.

Implementation of the invention

The device works as follows.

By applying a high-frequency four-phase electrical signal (Usin (u) t), Usin (o + 9 °), Usin (≤ A) t + 180 ° and Ucos (u) t + 270 ° to the electrodes of the rectangular profile 1 piezoelectric element ), the oscillation phases of the rectangular profile in the annular piezoelectric element 1 differ, depending on its electrode arrangement, and are supplied with corresponding voltages from the polyphase harmonic signal generator 2 (see Fig. 1). In this way, the traveling wave vibrations excited by the annular piezoelectric element 1 of the rectangular profile are transmitted to the rear surface of the rotor 3 via the cylindrical contact element 4 of the tapered hollow profile performing the functions of a waveguide. The rotational motion is formed by the frictional force between the end face of the rotor 3 and the oscillating end of the rectangular profile annular piezoelectric element 1, which is excited by a tapered cylindrical contact member 4 whose circular surface moves at elliptic trajectories caused by a traveling wave effect. In order to increase the amplitude of the traveling wave oscillation of the north end of the contact element, it excites multiphase (at least three phases) longitudinal and bending first-form resonant standing wave oscillations with half-wavelength λ / 2 equal to tapering cylindrical contact element 4 L, ie λ / 2 = L. Due to the tapered cylindrical shape of the contact member 4, the amplitude of the oscillations at its north end increases in proportion to the ratio of the end surface areas. Further forming triangular holes 6 in the wall of the tapered contact member 4 of tapering profile (see FIG. 2), the amplitude of the oscillation of the north end of the contact element 4 is increased and a more precise shape of the excited wave wave is formed, since the influence of the oscillations of the different phases is reduced. Since the contact element 4 of the piezoelectric element 1 is excited by a multiphase standing wave oscillation which at its ends has its maxima and in the plane 00 there is a nodal point of the standing wave oscillation (oscillation amplitude close to zero, see FIG. 1), it is most effective to position the fasteners of the piezoelectric traveling wave device in this plane, since they will be least affected by the vibrations excited by the piezoelectric element 1. When the high-frequency voltage is supplied to the electrodes of the piezoelectric element 1, the rotor 3 is rotated in a direction about the axis of symmetry of the device. In order to change the direction of rotation of the rotor 3 (the propagation direction of the wave traveling in the piezoelectric element 1), the electrical signals of the different phases entering the two electrodes of the piezoelectric element 1 are reversed, e.g. °) phase voltage and vice versa the Usin (u) t) phase voltage is supplied to the electrode provided for the Usin (u) t + 90 °) phase voltage.

Industrial applicability

Compared to the prototype, the new set of structural elements, by virtue of a tapered cylindrical contact member 4, increases the torque and efficiency generated by the device by increasing the amplitude of the traveling wave oscillations generated by the piezoelectric element and decreasing vibration impact on the piezoelectric element , also reduces the dynamic effect of vibrations on the unit's mounting brackets.