JPH0951687A - Linear ultrasonic motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high efficiecy linear ultrasonic motor with less mechanical loss by configuring a linear motor in standing wave mode. SOLUTION: A linear ultrasonic motor has a pair of diaphragms 7 and 8 with protruding parts 5 and 6 for pinching a guide shaft from sides, piezoelectric elements 9 and 10 which are provided on a reverse side opposite to a surface where the protruding parts 5 and 6 are provided and which are polarized in opposite directions between left and right while pinching the protruding parts 5 and 6, a connection plate 16 for connecting a pair of diaphragms 7 and 8, and a monopoler piezoelectric element 17 which is provided on one main surface of the connection plate 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a completely new linear ultrasonic motor which is driven not in a traveling wave mode but in a standing wave mode, and is used as an actuator for moving an optical pickup device along a guide shaft. It is a useful technique to use.

[0002]

2. Description of the Related Art For example, an ultrasonic motor is used as an actuator used in an automatic focusing mechanism of a camera and is currently in practical use. The ultrasonic motor used for this automatic focusing mechanism uses a traveling wave mode,
The ring-shaped stator and the rotor overlap each other to rotate.

By the way, regarding a method of constructing a linear motor with an ultrasonic motor using the traveling wave mode,
Up to now, no one has been proposed that has sufficiently high efficiency, is easy to adjust and adjust, and has a reasonable preloading method.

Therefore, until now, the rotary type had to be converted into a linear motion with a screw or a rack gear for use.
There was a drawback that the original characteristics of the motor were not utilized. The basic reason is that it is difficult to obtain traveling wave mode resonance by linear motion. That is, the traveling wave overlaps with the reflected wave and becomes a standing wave. There is also a problem that when the motor is downsized, the mechanical loss is relatively increased and the efficiency is extremely deteriorated.

[0005]

Thus, until now, in order to construct a linear motor with an ultrasonic motor using a traveling wave mode, there are the above-mentioned various problems and it cannot be put to practical use. Is.

Therefore, the present invention has been proposed in order to solve the problems of the prior art, and provides a high-efficiency linear ultrasonic motor which constitutes a linear motor in a standing wave mode and has little mechanical loss. With the goal.

[0007]

The linear ultrasonic motor of the present invention is a completely new linear motor that uses a standing wave mode rather than a traveling wave mode. That is, the linear ultrasonic motor of the present invention is a combination of a vibration mode in which the maximum speed is generated and a vibration mode in which the vibrator plate is pressure-bonded to the slide member. A pair of transducer plates having a portion, and a piezoelectric element that is provided on the back surface of each transducer plate on the opposite side of the surface on which the protrusions are provided, and is polarized in opposite directions on the right and left with the protrusions sandwiched therebetween. It has an element. Further, it is configured to include a connecting plate that connects the pair of transducer plates and a piezoelectric element that is provided on one main surface of the connecting plate and has a single pole.

A pair of vibrator plates provided with polarized piezoelectric elements have a vibration mode in which a voltage applied to the piezoelectric elements causes both ends of the vibrator plate and protrusions that sandwich the slide member to become nodes. And generate maximum speed.
On the other hand, when a voltage is applied to the piezoelectric element provided on the connecting plate that connects the pair of vibrator plates, the center portion of the connecting plate is used as a fixed end, and the pair of vibrator plates slide by the primary flexural vibration. The vibration mode is such that the member comes into contact with and separates from the member in a direction toward and away from the member.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described below in detail with reference to the drawings.

In this example, the linear ultrasonic motor of the present invention is applied to a threading motor for moving an optical pickup device incorporated in a reproducing device for a CD-ROM which is a read-only optical disc.

In FIG. 1, an optical pickup device 2 having an objective lens 1 is mounted on a CD-RO by a linear ultrasonic motor 3 along a guide shaft 4 which is a slide member.
An example in which it is movable in the radial direction of M is shown.

The linear ultrasonic motor 3 is an actuator using a standing wave mode, not a traveling wave mode, and has a vibration mode (hereinafter referred to as B mode) for generating a maximum speed. The optical pickup device 2 is moved along the guide shaft 4 by a combination of two modes of a vibration mode in which the vibrator plate is pressure-bonded to the slide member (hereinafter referred to as A mode).

Explaining the B mode in a little more detail, as shown in FIG. 5, it is a vibration mode in which the central portions where the projections 5 and 6 of the vibrator plates 7 and 8 are provided and both ends are nodes. In the mode diagram of FIG. 5, the sine type has one antinode on the left and one on the right with respect to the protrusions 5 and 6, but it may be an odd harmonic mode in which there are a plurality. In this case, there are a plurality of nodes in addition to the center and the vicinity of both ends.

In the A mode, as shown in FIG. 5, the connecting plate 1
This is a vibration mode in which the center portion of 6 is a fixed end, and the pair of transducer plates 7 and 8 are brought into contact with and separated from the guide shaft 4 in a direction toward and away from the guide shaft 4 by a primary flexural vibration. This A
As with the B mode, the mode may be a higher-order mode as long as it is a centrally symmetric mode.

As shown in FIGS. 2 and 3, the portion for generating the B mode is a pair of vibrator plates 7 and 8 having protrusions 5 and 6 that sandwich the guide shaft 4 from both sides, and the protrusion 5 , 6 are piezoelectric elements 9 and 10 provided on the back surface opposite to the surface on which the piezoelectric elements 9 and 6 are provided.

The vibrator plates 7 and 8 are formed as plate-shaped bodies having a substantially rectangular shape in plan view, and are made of a material in which vibration is easily sustained.
For example, stainless steel, phosphor bronze, aluminum, carbon steel and the like are preferable, and among them, stainless steel that is readily available is preferable. Then, the main surfaces 7a, 8a of the transducer plates 7, 8 are
Protrusions 5 and 6 for sandwiching the guide shaft 4 from both sides are provided in the central part of the.

The projections 5 and 6 are for transmitting vibrations to the guide shaft 4, and as shown in FIG. 4, are provided perpendicularly to the main surfaces 7a and 8a of the vibrator plates 7 and 8. And is formed integrally with the vibrator plates 7 and 8. The tips of the protrusions 5 and 6 stabilize the contact position with the guide shaft 4, and the preload spring 1
The surface contacting the guide shaft 4 is inclined so as to have the effect of uniformly receiving the force of 1.

On the surface contacting the guide shaft 4,
Friction members 12 and 13 are provided in order to efficiently transmit the vibration to the guide shaft 4 and to have a function of sandwiching the guide shaft 4. Friction member 1
As 2 and 13, friction plates made of synthetic resin such as rubber or plastic are used. This friction member 12,
In order to provide 13 on the tips of the protrusions 5 and 6, for example, a method of adhering or coating with an adhesive can be used.

The friction members 12 and 13 may be formed on the guide shaft 4. If the friction members 12 and 13 are formed on the guide shaft 4, the protrusions 5 and 6 are formed.
The same effect as the one formed at the tip of is obtained.

Further, the vibrator plates 7 and 8 are provided with elongated holes 14 and 15 which are openings for making the A mode and the B mode independent as described above. This long hole 14,1
5 is formed as a hole penetrating the thickness of the vibrator plates 7 and 8 between the lower ends of the protrusions 5 and 6 and the connecting plate 16 described later.

The piezoelectric elements 9 and 10 are provided on the back surfaces 7b and 8b opposite to the surfaces 7a and 8a on which the projections 5 and 6 of the vibrator plates 7 and 8 are provided. Such piezoelectric elements 9, 10
Is a piezoelectric ceramic made of, for example, lead zirconate titanate or the like and provided with electrodes, and is polarized in opposite directions on the right and left sides with the projections 5 and 6 interposed therebetween. In this example, the right side portion is the positive pole and the left side portion is the negative pole with the protrusions 5 and 6 in FIG. 2 as the center. Therefore,
The piezoelectric elements 9 and 10 facing each other have positive poles on the right side and negative poles on the left side.

On the other hand, the portion for generating the A mode is shown in FIG.
As shown in FIG. 4 and FIG. 4, the connecting plate 16 connects the pair of transducer plates 7 and 8, and the piezoelectric element 17 provided on one main surface 16 a of the connecting plate 16.

The connecting plate 16 forms a pair of vibrator plates 7 and 8 in parallel, and connects the base ends of the vibrator plates 7 and 8 so as to be symmetrical with respect to the guide shaft 4. It is provided. The connecting plate 16 is formed as a rectangular plate-shaped body, and is integrally formed of the same material as the vibrator plates 7 and 8 described above. Further, on the connecting plate 16, motor mounting portions 18, 1 for fixing the linear ultrasonic motor 3 to the optical pickup device 2 by screwing.
9 are provided. This motor mounting portion 18, 19
Has circular through holes 20 and 21 through which fastening members such as screws are inserted, and is provided on both sides with the connecting plate 16 interposed therebetween.

The piezoelectric element 17 is provided on the surface 16a of the connecting plate 16 opposite to the side where the guide shaft 4 is provided. This piezoelectric element 17 is the same as the piezoelectric elements 9 and 10 provided on the vibrator plates 7 and 8 described above, in which electrodes are provided on piezoelectric ceramics made of lead zirconate titanate or the like. The piezoelectric element 17 is the same as the previous piezoelectric elements 9 and 1.
Unlike 0, it has only a single pole. In this example, it is a positive pole.

In the linear ultrasonic motor 3 having such a structure, as shown in FIG.
AC power sources 22 and 23 are connected to the piezoelectric elements 9, 10 and 17 provided in 8 and 16, respectively. The AC power supply 22 connected to the piezoelectric elements 9 and 10 provided on the pair of vibrator plates 7 and 8 is a common power supply. And
These AC power sources 22 and 23 cause the vibrator plates 7 and 8 to generate a vibration of Csin ωt by a voltage, and the connecting plate 16 to generate a vibration of Cos ωt by a voltage. Note that C is the amplitude of vibration, ω is an angular frequency that is 2π times the frequency f, and t is time.

Then, the vibrator plates 7 and 8 and the connecting plate 16 are
The operation as shown in FIG. 5 is performed. First, when ωt = 0, as shown in FIG. 5A, the maximum speed Vmax is generated in the protrusions 5 and 6 of the vibrator plates 7 and 8. This maximum speed V
Since max is provided at the node at the center of the vibration mode, the vibration output take-out protrusions 5 and 6 are generated in the protrusions 5 and 6. On the other hand, the connecting plate 16 is curved with the center as a fulcrum, and the projections 5 and 6 provided on the pair of transducer plates 7 and 8 are in a state of maximum contact with the guide shaft 4.

When ωt = π / 2, as shown in FIG. 5 (b), both ends of the vibrator plates 7 and 8 and the protrusions 5 and 6 become a vibration mode, and the velocity V is zero. Become. On the other hand, the connecting plate 16 is brought into a contact end state with the guide shaft 4.

When ωt = π, as shown in FIG. 5C, the maximum velocity Vmax is generated in the projections 5 and 6 of the vibrator plates 7 and 8 in the opposite direction to the case where ωt = 0. . On the other hand, the connecting plate 16 is also curved in the opposite direction to the case where ωt = 0, and the protrusions 5 and 6 are separated from the guide shaft 4.

When ωt = 3π / 2, as shown in FIG. 5 (d), both ends of the vibrator plates 7 and 8 and the protrusions 5 and 6 which are 90 ° out of phase with respect to ωt = π / 2. However, the phase is 9 for ωt = π / 2.
The shape is offset by 0 °. The speed V at this time is zero. The connecting plate 16 is in a state of initial contact with the guide shaft 4.

By repeating such a mode,
The optical pickup device 2 moves in the direction indicated by X in FIG. When moving in the opposite direction,
The oscillator plates 7 and 8 generate −C sin ωt vibration by voltage, and the connecting plate 16 generate Cos ωt vibration by voltage.

In the above example, the central portion of the connecting plate 16 is used as the fixed end by being supported by the preload spring 11. However, when the motor mounting portions 18 and 19 are not provided, free vibration occurs. In the middle of 16, two positions are symmetrical.

The specific embodiments to which the present invention is applied have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made. In the above example, the present invention is applied to the threading motor that moves the optical pickup device along the guide shaft.
The present invention is not limited to this, and it can be used as a drive source for linearly moving any object such as an opening / closing drive source such as a curtain or a slide drive source for a chair of an automobile or the like.

[0033]

As is apparent from the above description, according to the linear ultrasonic motor of the present invention, it is possible to drive in the standing wave mode, and the rotary motion is linearly moved by using a screw or a rack gear. There is no waste of converting to, and the original characteristics of the linear motor can be utilized. Further, in the linear ultrasonic motor of the present invention, since it has a simple structure and is extremely small, it is possible to significantly reduce the cost, reduce mechanical loss, and improve efficiency.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example in which a linear ultrasonic motor of the present invention is applied to a threading motor that moves an optical pickup device.

FIG. 2 is an exploded perspective view of a linear ultrasonic motor.

FIG. 3 is a plan view of a linear ultrasonic motor.

FIG. 4 is a configuration diagram of a drive system of a linear ultrasonic motor.

FIG. 5 is a schematic diagram showing an operation of a linear ultrasonic motor.

[Explanation of symbols]

 2 Optical pickup device 3 Linear ultrasonic motor 4 Guide shaft 5,6 Projection part 7,8 Transducer plate 9,10,17 Piezoelectric element 14,15 Long hole 16 Connection plate

Claims (5)

[Claims] 1. A pair of transducer plates having protrusions for sandwiching the slide member from both sides, and a pair of transducer plates provided on the back surface opposite to the surface on which the protrusions of each transducer plate are provided, and sandwiching the protrusions. A piezoelectric element that is polarized in opposite directions on the right and left, a connecting plate that connects the pair of transducer plates, and a piezoelectric element that is provided on one main surface of the connecting plate and has a single pole. A linear ultrasonic motor. 2. The linear ultrasonic motor according to claim 1, wherein the protrusion is provided at a node position in the vibration mode. 3. The linear ultrasonic motor according to claim 1, wherein a friction member is provided at a portion of the protrusion that contacts the slide member. 4. The linear ultrasonic motor according to claim 1, wherein a portion of the protrusion contacting the slide member is inclined. 5. The linear ultrasonic motor according to claim 1, wherein the vibrator plate is formed with an opening for making the vibration modes independent.