JPS60160384A - Piezoelectric motor - Google Patents

Abstract

PURPOSE:To improve the reproducibility of rotating speed of a piezoelectric motor by converting the deformation of an electrostrictive element to the reciprocation of a rotor, and converting the reciprocation to the rotary motion of the rotational shaft, thereby reducing the variation in the torque. CONSTITUTION:Columnar piezoelectric ceramics 2a-2d are disposed at an angular interval of 90 deg. each other on the outer periphery of a rotor 1. When a voltage is applied between the electrodes of the ceramics 2a-2d, the ceramics 2a- 2d elongate or contract proportionally to the magnitude, and the rotor 1 reciprocates. The inner periphery of the circular hole 5 of the rotor 1 always contacts the peripheral surface of the shaft 3 by the reciprocation, thereby rotatably driving the shaft 3 by the friction therebetween or the engagement of the gears.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a piezoelectric motor that converts deformation of an electrostrictive element into rotational motion of a rotating shaft.

(Prior art) Conventionally, this type of piezoelectric motor, although not specifically shown, has been designed to have friction between an electrostrictive element and a rotor, and to combine the rotation of the rotor with the linear reciprocating motion of the electrostrictive element. It has generally been proposed to maintain the rotation of the rotor by repeating the resulting elliptical motion.

By the way, the piezoelectric motor described above has a problem in that the reproducibility of torque fluctuations and rotational speed deteriorates due to changes in the contact pressure of the electrostrictive element to the rotor and wear of the electrostrictive element and the rotor, resulting in low reliability. .

(Object of the Invention) The present invention has been made to solve the problems mentioned in 2.The purpose of the present invention is to reciprocate in at least two directions a rotor in which an electrostrictive element is arranged around a piezoelectric motor. By bringing the inner peripheral surface of the circular hole at the center of the rotor into contact with the rotating shaft that loosely fits into this circular hole and driving the rotating shaft to rotate, the deformation of the electrostrictive element is temporarily converted into reciprocating motion of the rotor, which is easy to convert. Later, it is converted into the rotational motion of the rotating shaft, eliminating torque fluctuations of the piezoelectric motor and improving the reproducibility of the rotation speed.
The goal is to improve reliability.

(Structure of the Invention) Therefore, the present invention provides a method for reciprocating the rotor in at least two directions by deforming a plurality of pairs of electrostrictive elements disposed around the rotor, and for driving a circle passing through the middle right portion of the rotor. The rotary shaft loosely fitted into the hole contacts the inner circumferential surface of the circular hole by the reciprocating motion of the rotor, and the rotary shaft is rotationally driven.

(Example) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In Figures 1 and 2, 1 is the rotor, 2a+21
1, 2c, and 2d are piezoelectric ceramics as electrostrictive elements,
3 is a rotating shaft, and 4 is a motor case.

The rotor 1, which has a rectangular shape, is made of a material having electrical insulation and rigidity, such as ceramic. The rotor 1 has a circular hole 5 at its center with an inner diameter sufficiently larger than the diameter of the rotating shaft 3, while the piezoelectric ceramic 2a, on the west side surrounding the circular hole 5,
Grooves 6a, 6b into which the tips of 2b, 2c and 2d fit
, 6c and 6d are formed.

Cylindrical piezoelectric ceramics 2a and 2b are arranged on the outer periphery of the rotor 1 at an angular interval of 90 degrees from each other.

2c and 2d are arranged. These piezoelectric sensors 3 = ramics 2a, 2b, 2c, and 2d each have an electrode (not shown) at the tip and rear end, respectively.
It expands and contracts in its axial direction in proportion to the voltage applied between these electrodes.

The piezoelectric ceramics 2a, 2+], 2C and 2d
are fixed to fixing pedestals 7a, 7b, 7c and 7d, which are provided at 90 degree intervals on the inner wall surface of the motor case 4, which has a circular cross-sectional shape. Each groove 6a, 613° 6c and 6d of rotor 1
They are inserted vertically into each. ” - piezoelectric ceramic 2a
, 2b, 2c and 2d have spacers 8a, 8b, 8c and 8d interposed between their respective tips and the bottom surfaces of the grooves 6a, 611.6C and 6d of the rotor 1.

The circular hole 5 of the rotor 1 has a bearing portion 4 of the motor case 4.
a and 41], the rotary shaft 3 rotatably attached is loosely fitted. This rotating shaft 3 includes the piezoelectric ceramic 2a,
No voltage is applied to the electrodes (not shown) between each tip and rear end of piezoelectric ceramics 2a, 21+ of 2b, 2c, and 2d.

=4- When there is no expansion or contraction in 2c and 2d, the axis of the rotating shaft 3 coincides with the center of the circular hole 5 of the rotor 1.

It is preferable that the inner circumferential surface of the circular hole 5 of the rotor 1 and the circumferential surface of the rotating shaft 3 facing the inner circumferential surface be lined with a material having a large coefficient of friction or be geared.

In the piezoelectric motor having the above configuration, a voltage Ea=A sin ωi, E as shown in FIG.
b = AcosωL+ Ec = Asin(ωt+π)
and Ed=Acos(ωt+π) are applied, respectively.

Such voltages Ea, Eb, Ec and E are applied between the electrodes of the piezoelectric ceramics 2a, 21), 2c and 2d.
When d is applied, the piezoelectric ceramics 2a, 2+3.2c and 2d expand and contract in proportion to the magnitude thereof, and the rotor 1 generates a voltage Ea between the electrodes of the piezoelectric ceramics 2a, 2+], 2c and 2d. Eb, Ec and Ec
The state shown in Fig. 4(a) where l is not applied is the third state.
At times Lll L21 L3 and t4 in the figure, the rotor 1 is displaced as shown in FIG. 4 (l]), FIG. 4 (C), FIG. 4 (d), and FIG. The inner circumferential surface of the circular hole 5 is in constant contact with the circumferential surface of the rotary shaft 3, and the rotary shaft 3 rotates due to friction therebetween or meshing of gears.

In the piezoelectric motor described above, the piezoelectric ceramics 2a, 2+].

The expansion and contraction of piezoelectric ceramics 2a, 2+), 2c and 2 are converted into simple reciprocating motion of the rotor 1, and this rotor's movement is converted into rotation of the rotating shaft 3.
This also eliminates the occurrence of torque fluctuations and decreases in the reproducibility of the rotational speed due to changes in the friction coefficient between d and a-1.

In the above embodiment, the piezoelectric ceramic 2a, 2)+.

2c and 2d, for example, as shown in FIG.
Coil springs 11 and 1 serve as piezoelectric ceramics 2b and 2c facing piezoelectric ceramics 2a and 2d, respectively.
2 may be used.

In this way, the piezoelectric motor has two phase voltages Ea and Ed.
It can be driven by torsion.

Also, piezoelectric ceramics 2a, 211.20 and 2d
If the amount of expansion and contraction is small, the piezoelectric ceramics 2a, 21) are placed inside the hydraulic cylinder 13, as shown in FIG.

It is also possible to drive the rotor 1 by means of a piston 14 which is immersed in the pistons 2c and 2d and is attached to the small diameter portion 13a of the hydraulic cylinder 13 so as to be retractable.

Next, another embodiment of the present invention is shown in FIGS. 7 and 8.

The piezoelectric motors shown in FIGS. 7 and 8 can be bent by applying a voltage to the piezoelectric ceramics 2a, 2+), 2c, and 2d instead of the piezoelectric motors described in FIGS. 1 and 2. Piezoelectric bar generated
Immolars 15a, 15b, ISc and l5cl are used as electrostrictive elements, and to avoid duplication, parts corresponding to those in FIGS. 1 and 2 are given the same reference numerals and their explanations will be omitted.

The piezoelectric bimorphs 15a, ISb, 15c and 15
d has its rear end fixed to the motor case 4,
By bending, the tip portion can reciprocate the rotor 1 in exactly the same manner as described using FIGS. 4(a) to 4(e), and rotate the rotating shaft 3.

In the above embodiments, the rotor 1 has a rectangular shape to a hexagonal shape,
It is also possible to form a polygon such as an octagon, etc. and drive it with multiphase voltages.

(Effects of the Invention) As is clear from the detailed description above, the present invention has the following effects:
In a piezoelectric motor using an electrostrictive element, the deformation of the electrostrictive element is converted into a simple reciprocating motion of the rotor, and then this reciprocating motion of the rotor is converted into the rotational motion of the rotating shaft. This can be achieved by obtaining a highly reliable piezoelectric motor that is almost unaffected by friction between the electrostrictive element and the rotor, has little torque fluctuation, and has good rotation speed reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of an embodiment of the piezoelectric motor according to the present invention, FIG. 2 is a cross-sectional view along the line II-II of FIG. 1, and FIG. 3 is a drive voltage waveform diagram of the piezoelectric motor of FIG. 1. , Figure 4(a),
Figure 4(b), Figure 4(C), Figure 4(d) and Figure 4
Figure (e) is an explanatory diagram of the operation of the piezoelectric motor in Figure 1 and Figure 5, respectively.
The figure is an explanatory diagram of a modified example of the piezoelectric motor shown in Figure 1, Figure 6 is an explanatory diagram of a hydraulic cylinder, piston, and piezoelectric ceramic part of an embodiment using hydraulic pressure, and Figure 7 is another embodiment according to the present invention. The vertical cross-sectional view of the example, FIG. 8 is 1v-iv of FIG.
It is a line direction sectional view. 1 =-o-Yu, 2a, 2b, 2c, 2d-Piezoelectric ceramic, deceased...Rotating shaft, 4...Motorket, 5...
Circular hole, 11. 12... Coil spring, 13... Hydraulic cylinder, 14... Piston, 15a, 15b, 15
c, 15d...-Piezoelectric bimorph. Patent Applicant: Murata Manufacturing Co., Ltd. Agent: Former Patent Attorney 2 Baka 8- Figure 5 8d 2d 2 a C C 520 Figure 7 15) 0 2o (2b) (2cX2d)

Claims (1)

[Claims] (1) The rotor is reciprocated in at least two directions by deformation of a plurality of pairs of electrostrictive elements arranged around the rotor, and a rotating shaft loosely fitted in a circle passing through the center of the rotor is connected to the rotor. A piezoelectric motor characterized in that the rotary shaft is rotationally driven by contacting the inner circumferential surface of the circular hole through reciprocating motion of the piezoelectric motor.