JPH0429575A - Rod-shaped ultrasonic motor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention vibrates a rod-shaped vibrator by supplying electrical energy to an electro-mechanical energy conversion element provided in a rod-shaped elastic body. This invention relates to an ultrasonic motor that frictionally drives a moving body pressed against a vibrator by causing a mass point to move in a circular or elliptical manner.

[Conventional technology]

BACKGROUND ART Conventionally, as an ultrasonic motor, a type that generates bending vibration in a ring and drives a moving body by frictional force has been put into practical use in AF mechanisms for cameras and the like. However, since it is ring-shaped, it is surprisingly expensive as a unit including a pressurizing mechanism, and is disadvantageous in terms of cost for motor applications that do not require a hollow space. Therefore, a rod-shaped ultrasonic motor shown in FIGS. 8 and 9 has been proposed as a solid type motor with an easy configuration such as a pressurizing system.

In FIGS. 8 and 9, 1 is a small diameter shaft portion 1a at the tip.
It is a hollow vibrating body made of a metal round rod with a horn-shaped horn part IC formed between the large-diameter shaft part 1b at the rear end, and a threaded part 1d formed in the shaft hole. Reference numeral 2 denotes a presser body made of a metal round bar formed to have the same outer diameter as the large-diameter shaft portion 1b of the vibrating body 1, and a bolt through hole 2a is formed in the shaft center. 3.
Reference numeral 4 denotes a ring-shaped piezoelectric element plate formed to have the same outer diameter as the large-diameter shaft portion 1b, and is arranged between the vibrating body 1 and the presser body 2 with an electrode plate (not shown) interposed therebetween. . Reference numeral 6 denotes a fixing bolt, which is screwed into the threaded portion 1d of the vibrating body 1 through the bolt through hole 2a of the presser body 2, so that the piezoelectric element plate 3.4 is clamped and fixed between the presser body 2 and the vibrating body 1. The piezoelectric element plates 3.4 have, for example, a common electrode on the negative side and electrodes of different polarities symmetrical with respect to the central axis in the diametrical direction on the other side, so that one piezoelectric element plate 3 and the other piezoelectric element plate 4 are arranged in the same direction, shifted by an angle of 90''.

The two-part electrode surface of one piezoelectric element plate 3 is brought into contact with, for example, the rear end surface of the vibrating body 1, and the other piezoelectric element plate 4 is brought into contact with the other piezoelectric element plate 4 through an electrode plate (not shown), and the common electrode of the other piezoelectric element plate 4 is brought into contact with the front end surface of the presser foot 2. By applying an AC voltage V1 between the electrode plate and the vibrating body 1 and an AC voltage 2 between the electrode plate and the presser body 2, vibrations due to expansion and contraction displacement in the thickness direction of the piezoelectric element plate 3 can be suppressed. , piezoelectric element plate 4
The rod-shaped vibrator A consisting of the vibrating body 1 and the presser body 2 is vibrated by combining with the vibration caused by the expansion/contraction displacement in the thickness direction.

AC voltages V1 and ■2 have the same amplitude and frequency,
The phase has a temporal shift of 90°.

Therefore, the vibrator A performs a circular motion like a skipping rope around the axis. Also, the voltages V1 and V2
If any phase is reversed, the forward and backward rotation of the circular motion will be reversed.

The principle behind this circular motion is described in Japanese Patent Application Laid-open No. 1986-
141980, etc., so the explanation will be omitted.

The vibration mode of the vibration excited in the vibrator A is set so that the peak of vibration is located at the horn IC, and the vibrator 1
Due to the frictional contact between the fitting tip of the rotor R that fits into the tip of the horn section 1c and the antinode of vibration formed in the horn section 1c,
The rotor R is driven to rotate. Reference numeral 5 denotes a spring for bringing the rotor R into pressure contact with the vibrating body 1, and is latched between the tip of the fixing bolt 6 and the tip of the latching dowel 7.

The latch dowel 7 is attached to an inner race portion of a thrust bearing 8 attached to one end of the rotor R, and applies the spring force of the spring 5 to the rotor R.

(Problem to be Solved by the Invention) However, the conventional rod-shaped ultrasonic motor has a piezoelectric element plate of 3.4
When the piezoelectric element was clamped and fixed between the vibrating body 1 and the presser body 2 by bolts 6, as shown in FIG. 10, a difference occurred in the amount of strain in the axial direction of the piezoelectric element.

When holding the piezoelectric element plate, the vibrating body 1 and the presser body 1
This is caused by elastic deformation of the bolt 6 and stress concentration on the inner circumferential side of the bolt 6 near the threaded portion, particularly on the inner circumferential side of the vibrating body 1.

Therefore, when tightening the bolts 6 to clamp the piezoelectric element plate 3.4, the piezoelectric element plate 3.4 made of piezoelectric ceramics
Moreover, since the piezoelectric element plate 3.4 does not come into uniform contact with the vibrating body 1 and the presser body 2, variations in vibration characteristics tend to occur, resulting in a decrease in motor efficiency.

The purpose of the present invention is to solve such conventional problems, to be able to clamp a piezoelectric element plate without causing a difference in the amount of strain, to prevent cracking of the piezoelectric element plate, and to improve vibration characteristics. The object of the present invention is to provide a rod-shaped ultrasonic motor that does not deteriorate.

[Means for resolving issues]

A rod-shaped ultrasonic motor that achieves the object of the present invention includes an electric-mechanical energy conversion element disposed between a rod-shaped vibrating body and a presser body, and a coupling means extending in the axial direction that connects the vibrating body and the presser body. It has a vibrator that clamps and fixes the electro-mechanical energy converting element by coupling and fixing it, and a moving member that is pressed by the vibrating body, and when an AC voltage is applied to the electro-mechanical energy converting element, the vibration is The vibration of the same bending mode is excited in a plurality of different planes with a temporal phase difference, thereby causing the surface particles of the vibrating body to perform circular or elliptical motion, thereby frictionally driving the moving member. In the rod-shaped ultrasonic motor, contact surfaces of the elastic body and the presser body that come into contact with the electro-mechanical energy conversion element, and a position where the coupling force acts on the vibrating body and the presser body by the coupling means are defined. It is characterized by being spaced apart.

(Function) The rod-shaped ultrasonic motor having the above-mentioned configuration is applied to an electric-mechanical energy converting element such as a piezoelectric element plate at a position where a bonding force is applied to clamp and fix the piezoelectric element plate, for example, between the presser body and the vibrating body. By separating the screwing positions of the bolts to be fixed on the vibrating body in the axial direction and also providing a gap in the radial direction, it is possible to make the clamping pressure applied to the piezoelectric element plate uniform.

〔Example〕

Embodiment 1 FIG. 1 is a longitudinal sectional view of a vibrator showing Embodiment 1 of a rod-shaped ultrasonic motor according to the present invention.

Reference numeral 10 denotes a vibrating body, which has a recess 10b formed inside the end surface 10a in contact with the piezoelectric element plate 3, and an inner threaded portion 1 into which the threaded portion of the bolt 6 is screwed on the tip side of the vibrating body 10 from the recess 10b.
0c is formed. In the conventional example shown in FIGS. 8 and 9, the end face of the vibrating body 1 in contact with the piezoelectric element plate 3 and the screw 6
The screw end surfaces of the internal threaded portion of the vibrating body 1 that are screwed together coincide on the same plane, whereas in this embodiment, the internal threaded portion 10c
is separated from the end surface contacting the piezoelectric element plate 3 by a distance equivalent to the depth of the recess 10b, and a gap 10e is created between the inner wall surface of the recess 10b and the outer peripheral surface of the screw 6, which is not engaged with the screw 6. is formed.

The piezoelectric element plate 3.4 is disposed between the end face of the presser body 2 and the end face of the vibrating body 10, and is clamped and fixed by bolts 6, as in the conventional example.

That is, the vibrating body 10 generated by tightening the bolt 6
The corner 10f at the bottom of the recess 10b is where stress concentration is most likely to occur; 3.4 The clamping pressure applied can be made nearly uniform.

As a result, as shown in FIG. 2, the amount of compressive deformation on the inner and outer circumferences of the piezoelectric element plate 3.4 is made uniform, and the contact pressure is also made uniform, so that cracks in the piezoelectric element plate 3.4 are reduced. A vibrator with good vibration characteristics can be obtained.

As described above, in this embodiment, the bonding end surface of the piezoelectric element plate,
By separating the internal threaded end of the vibrating body 1 from the bolt 6 in the axial direction by a gap 10e, and separating the piezoelectric element plate from the part where stress concentration is most likely to occur due to the screw 6, the clamping pressure applied by the piezoelectric element plates 3 and 4 is reduced. We are trying to equalize the

In addition to the embodiment shown in Fig. 1, the structure shown in Figs. There are those shown in Figures 6 and 7.

In the embodiment shown in FIG. 3, a piezoelectric element plate 3.4 is clamped and fixed between the vibrating body 1 and the presser body 2 by using bolts 6' instead of the bolts 6 in the conventional example shown in FIG. are doing.

The bolt 6' is provided with a threaded part 6'a only at the tip, and a gap is formed around the shaft part 6'c between the threaded part 6'a and the head 6'b.

The threaded portion 6'a is set to be inside the end surface of the vibrating body 1 in the tightening position, and the threaded end of the screw and the end surface of the vibrating body 1 are separated by)) in the axial direction. That's what I do.

The embodiment shown in FIG. 4 differs from the conventional example shown in FIG.
A ring-shaped distance plate 40 is interposed between the vibrating body 1 and the piezoelectric element plate 3, so that the end face of the vibrating body 1 and the piezoelectric element plate 3 are spaced apart in the axial direction.

In the embodiment shown in FIG. 5, the vibrating body 51 is integrally provided with a threaded part 53 that is screwed into the presser body 52, and a circumferential groove 54 is formed around the base of the threaded part 53, so that the end surface of the vibrating body 51 is and the base end of the threaded portion 53 are spaced apart in the axial direction. Further, a recess 56 is formed in the presser body 52 in order to separate the end face of the presser body 52 from the end face of the threaded hole 55 into which the threaded portion 53 is screwed.

The embodiment shown in FIG. 6 is opposite to the embodiment shown in FIG.
The presser body 62 is integrally provided with a threaded portion 63 that is screwed into the vibrating body 61.

In the case of this embodiment as well, a circumferential groove 64 is provided in order to position the base end of the threaded portion 63 inward in the axial direction from the end surface of the presser body 62, as in the embodiment shown in FIG. Further, a recess 65 is provided in the vibrating body 61 so that the end face of the vibrating body 61 and the screw end of the screw hole 66 into which the threaded portion 63 is screwed are separated in the axial direction.

In the embodiment shown in FIG. 7, a member 70 with low rigidity, such as felt, rubber, resin, or a flexible board, is provided in the gap 10e of the embodiment shown in FIG.
Positioning of mechanical energy conversion elements, wiring using flexible cables,
etc.

Since the member 70 has low rigidity, even if distortion occurs when the bolt 6 is tightened, the stress does not increase so much, and the same effect as in the first embodiment can be obtained.

FIG. 11 shows a configuration example in which a motor according to the present invention is used to drive a lens barrel of an optical lens.

A gear 12 is coaxially connected to the moving body 8 and transmits rotational output to the gear 13 to rotate a lens barrel 14 having a gear that meshes with the gear 13.

In order to detect the rotational position and rotational speed of the moving body 8 and the lens barrel 14, an optical encoder slit plate 15 is connected to the gear 13.
The photocoupler 16 detects the position speed.

Note that 9 is a spring post, 10 is a bearing, and 11 is a spring.

(Effects of the Invention) As explained above, according to the present invention, the electric-mechanical energy conversion element such as a piezoelectric element plate held between the presser body and the vibrating body can apply a clamping pressure of approximately -. Therefore, it is possible to properly vibrate the vibrator, thereby preventing a decrease in motor efficiency, and also preventing cracking of the piezoelectric element plate.

Further, by using such a motor as a drive source, compact and highly accurate drive becomes possible.

[Brief explanation of drawings]

Figures 1, 3, 4, 5, 6, and 7 are
FIG. 2 is a sectional view of a vibrator showing each embodiment of the rod-shaped ultrasonic motor according to the present invention, and FIG. 2 is a diagram showing the amount of strain in the axial direction of the piezoelectric element plate in the embodiment shown in FIG. Fig. 8 is a perspective view of a conventional rod-shaped ultrasonic motor, Fig. 9 is a sectional view thereof, and Fig. 1
FIG. 0 is a diagram showing the amount of axial strain of the piezoelectric element plate, and FIG. 11 is a sectional view showing the barrel drive mechanism of the optical lens. 1.10, 51.61... Vibrating body 2.5.2.62... Presser body 3.4... Piezoelectric element plate 6.6°... Bolt 70
...low rigidity members Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7

Claims (1)

[Scope of Claims] 1. An electro-mechanical energy converting element is disposed between a rod-shaped vibrating body and a presser body, and the vibrating body and the presser body are coupled and fixed by a coupling means extending in the axial direction. It has a vibrator that clamps and fixes a mechanical energy converting element, and a moving member that is pressed against the vibrating body, and by applying an alternating voltage to the electro-mechanical energy converting element, a bending mode of the same shape is generated in the vibrator. A rod-shaped ultrasonic motor that excites vibrations in a plurality of different planes with a temporal phase difference, thereby causing particles on the surface of the vibrating body to perform circular or elliptical motion, and frictionally driving the moving member. The contact surfaces of the elastic body and the presser body that come into contact with the electro-mechanical energy conversion element are separated from the position where the coupling force acting on the vibrating body and the presser body is applied by the coupling means. rod-shaped ultrasonic motor. 2. A rod-shaped ultrasonic motor characterized in that the coupling means is provided at the axial center of the vibrating body and the presser body. 3. The rod-shaped ultrasonic motor according to claim 2, wherein a gap surrounding the coupling means is formed between the vibrating body of the coupling means and the position where the coupling force is applied on the presser body. 4. A rod-shaped ultrasonic motor characterized in that a member having sufficiently smaller rigidity than the vibrating body and the presser body is provided between the vibrating body of the coupling means and the position where the coupling force is applied on the presser body. 5. An apparatus comprising the rod-shaped ultrasonic motor according to any one of claims 1 to 4, the apparatus having an output member driven by a friction-driven moving member of the rod-shaped ultrasonic motor.