JPH03289366A - Torsion coupler ultrasonic motor - Google Patents

Abstract

PURPOSE:To make uniform the characteristic of each piezoelectric element by laminating four sheets of piezoelectric elements into a piezoelectric means and preferably polarizing the piezoelectric element, at once, upon lamination. CONSTITUTION:Four sheets of piezoelectric elements, e.g. piezoelectric ceramics 11-14, are laminated into a piezoelectric section 3. Longitudinal vibration at the piezoelectric section 3 can be made symmetrical by laminating even number of piezoelectric elements 1. When the piezoelectric elements 11-14 are polarized, an upper electrode 1a, a lower electrode 1b and a common electrode 1c2 are connected to the minus side whereas a common electrodes 1c1 and 1c3 are connected to plus side and then the piezoelectric elements 11-14 are polarized simultaneously. Consequently, fluctuation in the characteristics of the piezoelectric elements 11-14 is suppressed resulting in a uniform characteristic.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a torsion coupler type ultrasonic wave generator that generates ultrasonic elliptical vibration by integrally coupling a piezoelectric element and a torsion coupler, for example. It's about morphs.

[Conventional technology]

The ultrasonic motor uses ultrasonic elliptical vibration to rotate a rotor portion that is press-fitted to a stator portion. "The C1 ultrasonic motor requires a vibrator that generates ultrasonic elliptic vibration. For example, there is a device that uses a torsion coupler to generate ultrasonic elliptic vibration. (Special Publication Showa 6l
-0521 (i3 q, JP-A-61-052167)
.

The torsion coupler type ultrasonic morph has a simple structure and can efficiently generate ultrasonic elliptic vibrations.

[Problem to be solved by the invention]

Conventionally, there is a torsion coupling type ultrasonic morph in which a piezoelectric portion is formed by stacking two donut-shaped piezoelectric elements. To drive this ultrasonic motor, an alternating current voltage of at least about 60 V is required since the driving voltage of the ultrasonic motor has a dark value. For this reason, when driving using a commercially available battery, the space of the power supply section becomes large, which poses a problem when downsizing. Further, since the conventional torsion coupling type ultrasonic motor requires a high driving voltage, it is dangerous to the human body, and an improvement has been desired.

The present invention has been made based on the above circumstances, and an object of the present invention is to provide a torsion connector type ultrasonic motor that can be easily reduced in voltage and size.

[Means to solve the problem]

To achieve the above object, the present invention includes a stator section having a piezoelectric means and a torsion coupling means, and a rotor section crimped to the stator section, and the rotor section is moved by the elliptical vibration of the stator section. In the rotating torsion coupling type ultrasonic motor, the piezoelectric means is formed by laminating at least four piezoelectric elements.

Further, it is preferable that the piezoelectric means polarizes the piezoelectric elements at once after laminating the piezoelectric elements.

[Effect]

According to the above structure, the present invention forms a piezoelectric means by forming 11 layers of at least four piezoelectric elements, so that the piezoelectric elements can be connected in parallel and the driving voltage can be lower than that of the conventional one. You can get the output.

Moreover, the piezoelectric means can make the characteristics of each piezoelectric element uniform by polarizing each piezoelectric element at once after laminating the piezoelectric elements.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 3 is a schematic structural diagram of the torsion coupling type ultrasonic motor of the present invention. The torsion coupler type ultrasonic motor of the present invention includes a stator section 30 including a vertical vibrator 10 and a torsion coupler 20, and a rotor section 40. The vertical vibrator 10 includes a piezoelectric portion (piezoelectric means) 3 formed by laminating four piezoelectric elements 1, which will be described later, and an aluminum disc 5.

The torsion coupler type ultrasonic motor having the above configuration converts the longitudinal vibration generated by the vertical vibrator 10 into torsional vibration by the torsion coupler 20, and generates ultrasonic elliptical vibration on the upper end surface of the torsion coupler 20. is generated, and the rotor section 40 is rotated by this ultrasonic elliptical vibration.

FIG. 1 is an enlarged structural diagram of the piezoelectric section 3. As shown in FIG. The piezoelectric section 3 includes four piezoelectric elements (for example, piezoelectric ceramic elements)1. ~1
It is formed by laminating 4.

By forming an even number of eight layers of piezoelectric elements 1 as shown in the figure, the amplitude of the longitudinal vibration of the piezoelectric section 3 can be made symmetrical. Further, 1a is an upper electrode formed on the entire upper surface of the doughnut-shaped piezoelectric element 11, similarly lb is a lower electrode,
IC is a common electrode.

The reason why the electrodes are formed on the entire surface of the piezoelectric element 1 in this way is that the characteristics such as torque of the piezoelectric element 1 are improved compared to the case where the electrodes are formed only partially. Note that the arrow in the figure indicates the direction of polarization.

By the way, when polarizing the piezoelectric element 1, if polarization is performed individually for each piezoelectric element 11 to 14, each piezoelectric element 1 l
” Variations occur in the characteristics of 14.

An ultrasonic motor using the piezoelectric section 3 formed by laminating such piezoelectric elements 11 to 14 can be driven at a low voltage, but its characteristics are slightly inferior to conventional motors.

Therefore, in this embodiment, as shown in FIG.
a, the lower electrode 1b, and the common electrode lcz are connected to the negative side of the DC power supply 6, and the common electrode 1c+ and the common electrode IC3 are connected to the positive side, and each piezoelectric element 1. ~14 at once. This allows each piezoelectric element 11 to
It is possible to suppress variations in the characteristics of No. 14 and make the characteristics uniform. Moreover, when driving each piezoelectric element II to 14,
Each piezoelectric element1. - 14 are connected in parallel to an AC power source (not shown).

By the way, in the ultrasonic motor, the electric field strength of the piezoelectric element E=V
When /d (where ■ is the drive voltage and d is the thickness of the piezoelectric element) changes, its torque and other characteristics change. According to the piezoelectric section 3 having the above configuration, four piezoelectric elements are stacked and each piezoelectric element l is connected in parallel and driven, so the thickness, inner diameter and outer shape of the piezoelectric section 3 are the same as those of the conventional one. In this case, even if the driving voltage V applied to each piezoelectric element 1 is reduced by about half, the electric field strength E of each piezoelectric element 1 can be made equal to that of the conventional one. In this way, the ultrasonic motor using the piezoelectric section 3 of this embodiment can maintain the electric field strength E of each piezoelectric element 1 the same as the conventional one even if the driving voltage V is reduced to about half compared to the conventional motor. Therefore, in principle, the same rotation speed and torque as a conventional ultrasonic motor should be generated.

The present inventors prototyped an ultrasonic motor using a piezoelectric part 3 formed by laminating four donut-shaped piezoelectric elements 1 with a thickness of 0.5-1, an inner diameter of 3 m, and an outer diameter of 15 m, and conducted experiments. . As a result of measurement by connecting each piezoelectric element II to 14 in parallel and applying a drive voltage of approximately 25V, it was found that the conventional 2u piezoelectric element (1u
The output was approximately the same as that obtained when a motor having a motor (formed by stacking two thick piezoelectric elements) was driven with an AC voltage of 100V.

The inventors also prototyped and experimented with an ultrasonic motor using a piezoelectric part 3 formed by laminating B donut-shaped piezoelectric elements with a thickness of 0.25M, an inner diameter of 3M, and an outer diameter of 15M. .

As a result of measurement by connecting each piezoelectric element in parallel and applying a driving voltage of about 13 V, in this case as well, substantially the same output as the above-mentioned conventional one was obtained.

In the above cases, the resonance Q value was somewhat low in both cases. Furthermore, although the piezoelectric element of this example is not disk-shaped but doughnut-shaped, the conventional piezoelectric element and this example are compared using the electromechanical coupling coefficient (Kp) used for the disk-shaped piezoelectric element. As a result, the Kp value of this example was approximately the same as that of the conventional one. Further, by stacking and forming piezoelectric elements, the admittance can be made smaller than that of a single piezoelectric element. Furthermore, the maximum value of admittance was approximately 95% of the total admittance value of each piezoelectric element l.

According to the embodiment described above, it is possible to reduce the driving voltage to .12 .mu. or less, and when the device is driven by a battery, it can be easily miniaturized.

Furthermore, according to the above embodiment, since the drive voltage can be lowered, even if the power supply section is touched by mistake, the drive voltage can be reduced.
The ultrasonic motor can be made without causing any harm to the human body.

Furthermore, since the driving voltage is lowered, insulation may be simpler, and therefore 1!1 edge processing becomes easier, manufacturing costs are lowered, and further miniaturization becomes possible.

Note that the thinner the piezoelectric element 1 is, the more laminated it can be.
Since the number of sheets increases, it becomes possible to drive at a lower voltage. However, if the thickness of the piezoelectric element 1 is made too thin, the Q value will decrease and the mechanical strength will become weaker, making it more likely to break. Practically preferred.

Furthermore, when a large number of piezoelectric elements are stacked, those connected in series may be connected in parallel.

Furthermore, an ultrasonic motor using a piezoelectric part formed by laminating four piezoelectric elements with a thickness of 11 mm and a conventional one made by stacking two piezoelectric elements with a thickness of 2 μ are operated at the same driving voltage (60 V AC). When we drove it and measured the characteristics of both, we found that the rotational speed and torque of this ultrasonic motor were about twice that of conventional motors. In this way, in this embodiment, the characteristics of the ultrasonic motor can be improved by keeping the drive voltage the same as the conventional one.

〔Effect of the invention〕

As explained above, according to the present invention, by stacking at least four piezoelectric elements to form a piezoelectric means, it is possible to obtain the same output as before even at low voltage, and also to use existing batteries. Therefore, it is possible to provide a helical coupling type ultrasonic motor that can be easily miniaturized when driven by a coil.

[Brief explanation of drawings]

Fig. 1 is an enlarged structural diagram of the piezoelectric part, Fig. 2 is a diagram for explaining polarization of the piezoelectric element, and Fig. 3 is a schematic structure of a helical coupling type ultrasonic motor which is an embodiment of the present invention. It is a diagram. 11-14... Piezoelectric element, 1a... Upper electrode, 1b
... lower electrode, IC ... common electrode, 3 ... piezoelectric part, 5 ... aluminum disk, 10 ... Langevin oscillator, 40 ... torsion coupler, 30 ... stator section, rotor section.

Claims (3)

[Claims] (1) A torsion coupling type comprising a stator section having a piezoelectric means and a torsional coupling means, and a rotor section crimped to the stator section, the rotor section being rotated by longitudinal vibration and torsional vibration of the stator section. A torsion coupling type ultrasonic motor, wherein the piezoelectric means is formed by laminating at least four piezoelectric elements. (2) The torsion coupling type ultrasonic motor according to claim 1, wherein the piezoelectric means polarizes the piezoelectric elements at once after laminating the piezoelectric elements. (3) The torsion coupling type ultrasonic motor according to claim 1, wherein the piezoelectric means is formed by laminating ten or less piezoelectric elements.