JP2569532B2 - Piezoelectric motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric element motor capable of extracting output using vibration of a piezoelectric element.

[Prior Art] Since a piezoelectric element has a characteristic of being able to convert electric energy and mechanical energy with high efficiency, attention has been paid to research on a motor using the vibration (a so-called ultrasonic motor). ing.

At present, as this type of motor, a vibrator type in which a vibrator with a shoe attached to the tip is rolled in contact with the outer peripheral surface of the rotating body to strike in the circumferential direction, and vibrators are arranged in a disk shape or ring shape Many types are being developed, such as a traveling wave type in which a traveling wave is created by rotating a rotating body placed on the traveling wave.

[Problems to be Solved by the Invention] However, the driving force of any of the conventional devices depends on friction generated between the vibrator and the rotating body. If it is appropriately small, there is an inconvenience that slippage occurs and driving efficiency is reduced. In addition, since the occurrence of slip affects the rotation speed, a complicated feedback mechanism for controlling the slip is required.

An object of the present invention is to solve the slipping problem by reconsidering the driving means, and to realize an efficient and stable motor utilizing the inherent merits of the piezoelectric element.

[Means for Solving the Problems] The present invention employs the following means to achieve the above object.

That is, a backup member having a backup surface, a plurality of piezoelectric elements attached to the backup surface, an elastic body covering the surfaces of these piezoelectric elements to form a rolling surface, and being pressed against the rolling surface. A rotating body, position detecting means for detecting a rolling contact position of the rotating body, and driving for driving the piezoelectric element near the rolling contact position detected by the position detecting means to press the elastic body against the rotating body Means, and an output member for taking out the relative rotation between the backup member and the rotating body as an output.

It is particularly preferable to set the backup surface to an annular or planar surface, or to detect a polarization potential difference generated in the piezoelectric element as position detection means.

[Operation] With such means, it is possible to monitor the rolling contact position of the rotating body through the position detecting means. Since the elastic body is constantly pressed against the rotating body from the vicinity thereof in the traveling direction, the pressing force is more appropriate in the point of application of the force and its direction than in the case where the elastic body is driven by frictional force. Is pressed against the rolling surface, so that the rotating body can be suitably driven without causing slip.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the piezoelectric element motor of this embodiment has a hollow cylindrical housing 1 as a backup member.
The housing 1 is fixed to the outside to set the inner peripheral surface 1a as a backup surface.

A large number of piezoelectric elements 2 are provided along the entire inner peripheral surface 1a. As shown in FIG. 2, the piezoelectric element 2 is formed by laminating a large number of long thin piezoelectric members 2a extending in a cylindrical axis direction in a thickness direction, and a thin plate electrode (not shown) is provided on both end surfaces thereof. It is configured. When a driving voltage is applied between the electrodes, an electrostrictive effect is generated in each of the piezoelectric elements 2, and the piezoelectric elements 2 can expand and contract toward the center of the housing 1 using the inner peripheral surface 1 a as a scaffold. At this time, an appropriate gap 2b is provided between the piezoelectric elements 2 so that the expansion and contraction operation can be performed smoothly. Further, a thin circular elastic ring 3 made of an elastic material is coated on the piezoelectric element 2, and the surface of the elastic ring 3 is used as a rolling surface 3a.

On the other hand, in the elastic ring 3, four identical rollers 4, 5, 5, 5 as shown in FIG. The planetary rollers 5, 5, 5 are configured to be pressed against the rolling surface 3a with a constant force. Specifically, a shaft 6 fixedly supported by the housing 1 is disposed at a center position, a sun roller 4 is rotatably mounted on the shaft 6, and the planetary rollers 5, 5, 5 are symmetrically arranged. The shafts 5a are connected and fixed to a retainer 5b, and each planetary roller revolves around the sun roller 4 while alternately rolling and contacting the sun roller 4 and the rolling surface 3a. In addition, so that each planetary roller 5 is pressed against the rolling surface 3a,
The diameter of each of the rollers 4, 5, 5 and 5 is set slightly larger than 1 / of the inner diameter of the elastic ring 3.

On the other hand, in order to detect the rolling contact position of each of the planetary rollers 5, there is provided a position detecting means 7 in which an input terminal of a judgment circuit 7a is connected to an electrode of the piezoelectric element 2. That is, when the piezoelectric element 2 is compressed and distorted by any one of the planetary rollers 5, the determination circuit 7 can detect a transient polarization potential difference appearing between the electrodes due to the piezo effect as a position signal.

When the position detecting unit 7 detects the roller rolling contact position, the driving unit 8 drives the piezoelectric element 2 in the vicinity thereof to elastically deform and press the elastic ring 3 against the planetary roller 5. Is provided. The driving means 8 has a delay circuit 8a and an amplifier 8b. The input terminal of the amplifier 8b is connected to the judgment circuit 7a via the delay circuit 8a.
Output terminal. That is, the delay circuit 8a that receives the position signal from the determination circuit 7a outputs a drive signal to the amplifier 8b after a delay time corresponding to a rotation speed command appropriately issued from the outside. The output end of the amplifier 8b is connected to both electrodes of the piezoelectric element 2 located rearward with respect to the piezoelectric element 2 that has issued the position signal, based on the direction of arrow movement of the planetary roller 5, and the drive signal Is received, a drive voltage sufficient to produce an electrostrictive effect can be applied to the piezoelectric element 2.

The above-described position detecting means 7 and driving means 8 are provided for all of the attached piezoelectric elements 2, and when applying a voltage, the position detecting lines of the adjacent piezoelectric elements 2 are connected. It is performed using. The sun roller 4 that rotates in accordance with the rotation of the planetary roller 5 functions as an output member of the motor out of the drawing.

 Next, the operation of the present embodiment will be described.

During the driving of the motor, the rolling contact state of the planetary roller 5 at an arbitrary location changes in a very short time from (a) to (b) in FIG.
(C). That is, when the roller 5 comes into contact with the central piezoelectric element 2 shown in FIG. 2A, the piezoelectric element 2 is pressed and distorted, causing a potential difference between the electrodes. Since this potential difference appears at the input terminal of the judgment circuit 7a in FIG.
A drive signal is transferred from the output terminal to the delay circuit 8a at the next stage. In the delay circuit 8a, after the time set by the rotation speed command is delayed, the received drive signal is input to the amplifier 8b. As a result, the amplifier 8b immediately applies a drive voltage to the piezoelectric element 2 behind the piezoelectric element 2 that has received the position signal. At this point, the planetary roller 5
Is moved by a minute distance corresponding to the delay time due to inertial running as shown in FIG. 2 (b). Here, the planetary roller 5 and the piezoelectric element 2 (left side in FIG. The positional relationship for the force to work properly has been obtained. Then, the piezoelectric element 2 continues to protrude upward due to the electrostriction effect as shown in FIG. 4C, and the strain stress at this time causes the planetary roller 5 to move from the rear of the rolling contact position through the elastic ring 3 in the traveling direction. Can be urged toward.

And such driving is repeated intermittently,
3a, a progressive traveling wave is formed with time at three points, and each planetary roller 5 is driven to revolve so as to follow the front of the traveling wave.
It is possible to extract the rotation output from.

With the above configuration, since the urging force acts on the planetary roller 5 from an appropriate position and direction, the planetary roller 5 can be suitably driven without causing slip. Since the position detecting means 7 is configured by utilizing the polarization potential difference generated when the piezoelectric element 2 is pressed, simple and reliable sensing is possible.
In such a case, by changing the time constant set value of the delay circuit 7a, an arbitrary rotation speed can be obtained from the sun roller 4.

In the above embodiment, the output may be taken out from the retainer 5b that connects and holds the planetary roller 5. According to this, a rotational output having a different speed and torque can be obtained from the embodiment. Further, the output member can be arbitrarily switched during the rotation driving.
Further, it is also possible to fix the sun roller 4 and relatively rotate the planetary roller 5 and the housing 1 to take out one of the rotations as an output. Further, as the position detecting means, in addition to the above-mentioned ones, a means in which something other than a piezoelectric element is incorporated in the rolling contact surface, or a means which optically senses from a remote position can be considered.

In addition, as shown in FIG. 3, the backup surface 11a is set on the outer periphery of the backup member 11, and as shown in FIG. 4, the backup surface 21a is set on the backup member 21 having a linear plane. However, a suitable effect can be obtained. That is, in FIG. 3, the piezoelectric element 12 is arranged on the outer peripheral surface 11a of the cylindrical backup member 11 fixed at the center, and the hollow cylindrical outer roller 14 and the four intermediate rollers 15 are movable. Configured
The rotation of one of the rollers is connected to the output member. In FIG. 4, the piezoelectric elements 22 are arranged in tandem on a backup member 21 having a linear flat surface 21a, and a linear output can be obtained from an output member 24 and the like supported by a rotating body 25. It is.

FIG. 5 shows a modified embodiment in which an effective combination with a taper roller is used.
An output rotator 29 corresponding to a sun roller is rotated via 27, and an output is taken out from a shaft 30. In this example, the thickness of the shim 28 can be adjusted for the taper roller 27 pressed against the rolling surface.

In addition, various modifications can be made without departing from the spirit of the present invention, such as an arrangement in which the piezoelectric elements are arranged in a staggered manner to increase the element density.

[Effects of the Invention] In the present invention, since the biasing force can be expressed at the optimum position by the above-described configuration, a problem that the driving force is reduced by half or the driving speed becomes uneven due to slippage is caused. Thus, it is possible to provide a piezoelectric element motor capable of obtaining a stable rotation output with high efficiency.

[Brief description of the drawings]

FIG. 1 is a schematic overall view showing one embodiment of the present invention, and FIG.
The figure is a partially enlarged view showing the rolling contact state of the rotating body. Also,
FIGS. 3 to 5 are schematic general views showing other embodiments. DESCRIPTION OF SYMBOLS 1 ... Housing (up-up member) 1a ... Inner peripheral surface (backup surface) 2 ... Piezoelectric element 3 ... Elastic ring (elastic body) 4 ... Sun roller (output member) 5 ... Planetary roller (rotary body) Reference numeral 6: shaft, 7: position detecting means 8: driving means 11, 21, backup member 11a, 21a backup surface 12, 22, 26 piezoelectric element

Claims (5)

(57) [Claims] 1. A backup member having a backup surface, a plurality of piezoelectric elements attached to the backup surface, an elastic body covering the surfaces of the piezoelectric elements to form a rolling surface, and the rolling surface A rotating body pressed against the rotating body, position detecting means for detecting a rolling contact position of the rotating body, and a piezoelectric element near the rolling contact position detected by the position detecting means for driving the elastic body to the rotating body. A piezoelectric element motor comprising: a driving unit that presses the rotation member; and an output member configured to extract a relative rotation between the backup member and the rotating body as an output. 2. The piezoelectric element motor according to claim 1, wherein the backup surface is set on the inner periphery of a hollow cylindrical backup member. 3. The piezoelectric element motor according to claim 1, wherein the backup surface is set on the outer periphery of the cylindrical backup member. 4. The piezoelectric element motor according to claim 1, wherein the backup surface is provided on a backup member having a linear flat surface. 5. The apparatus according to claim 1, wherein said position detecting means comprises a judgment circuit for detecting a polarization potential difference generated in said piezoelectric element.
Item 6. The piezoelectric element motor according to item 5 or 5.