JP2006180589A - Ultrasonic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To build a position detector (encoder) and a scale directly in the structure of a rod-like ultrasonic motor without enlarging the profile of the motor. <P>SOLUTION: A supporting member for securing a rod-like vibrator is provided with a means for detecting the amount of movement of a moving element (rotor) and a rotation output member is provided with a scale integrally. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic motor using a rod-shaped vibrator, and more particularly to a structure of a rod-shaped ultrasonic motor that realizes miniaturization in an optical device such as a camera and office equipment such as a printer.

  Ultrasonic motors have been applied to products such as camera lens drive applications, and there are two types, an annular type and a rod type.

  FIG. 7 shows the structure (a) of the rod-like vibrator and its vibration mode (b), and FIG. 8 shows a configuration diagram of an ultrasonic motor currently used for driving a camera lens or the like (FIGS. 7 and 8 show rotation). It is a sectional view in a plane including an axis of symmetry).

  1 is a first elastic body, 2 is a second elastic body, 3 is a laminated piezoelectric element (or a laminated body of single-plate piezoelectric elements), 4 is a shaft, 5 is a nut, and parts 1 to 3 are the shaft. 4 and the nut 5 are tightened to give a predetermined clamping force.

  One surface of the rotor 7 has a structure with a small contact width and an appropriate spring property, and this surface contacts the friction surface 6 of the vibrating body. On the other surface of the rotor 7, a convex portion (or concave portion) is formed so as to engage with the concave portion (or convex portion) of the gear 8 that rotates together with the rotor and transmits the output of the motor. . Further, the position of the gear 8 is fixed in the thrust direction of the shaft 4 by a flange 10 for mounting the motor, and a pressure spring 15 for applying pressure to the rotor 7 is interposed between the gear and the rotor. Is provided.

  Here, in the laminated piezoelectric element 3 (or a laminated body of single-plate piezoelectric elements), electrodes are grouped into two electrode groups, and an AC electric field having a different phase is applied to each electrode group from a power source (not shown). In the vibrator, two orthogonal bending vibrations are excited. By adjusting the phase of the applied electric field, a 90-degree temporal phase difference can be given between the two vibrations. As a result, the bending vibration of the rod-shaped vibrator rotates around the axis of the vibrator.

  As a result, a circular motion is formed on the upper surface of the first elastic body in contact with the rotor 7, and the rotor 7 pressed against the wear-resistant member 6 is frictionally driven. The pressure spring 15 rotates as a unit.

A power transmission system switching gear (hereinafter abbreviated as a shift gear) connected to the gear and a position closer to the output shaft of the reduction gear mechanism than the shift gear does not transmit power (that is, from the motor to the lens). (Not in the mechanical coupling mechanism), and a known encoder plate (scale) is attached to the gear, and the coding pattern formed on the encoder plate is an electric signal. Position detection and speed detection are performed based on a signal from a position detector (encoder) for replacement (for example, see Patent Document 1).
JP-A-5-268780

  The rod-shaped ultrasonic motor as shown here is much smaller than the previous ring-type vibration wave motor, and has a simple design so as to minimize the cost of processing parts.

  However, there are demands in the world for digitalization and further miniaturization, and there is a desire to make it even smaller, cheaper, and more accurate than current bar-shaped ultrasonic motors. In order to meet this demand, proposals have been made separately for a motor structure that shortens the length of the motor or reduces the cost of a piezoelectric element that is relatively expensive (small diameter, thin) to achieve low cost. In addition, there is a problem that the structure using a scale attached to a gear that does not transmit power separately from the ultrasonic motor as described in the prior art cannot be sufficiently reduced in size.

  Accordingly, an object of the present invention is to realize a miniaturization and high accuracy by incorporating a position detector (encoder) and a scale directly into the structure of a rod-shaped ultrasonic motor without increasing the shape of the motor. It is to provide a sonic motor.

  In order to achieve the above object, the ultrasonic motor has the following configurations (1) to (5).

(1) An electro-mechanical energy conversion element is sandwiched between elastic members, and the elastic members are fastened and integrated by fastening means, and an alternating current having a predetermined phase difference in time with respect to the electro-mechanical energy conversion element. By applying a voltage, by combining bending vibrations excited in different planes including the axis, a rod-like vibrator that forms a circular or elliptical motion on the surface particles of the drive surface, and a drive surface of the rod-like vibrator A movable member that is in pressure contact; a rotation output member that rotates integrally with the movable member; and a support member that fixes the rod-shaped vibrator, and the movable body is moved by a circular or elliptical motion formed on the rod-shaped vibrator. In an ultrasonic motor that drives friction,
An ultrasonic motor comprising: a supporting member for fixing the rod-like vibrator; a moving amount detecting means for detecting a moving amount of the moving body; and a rotary output member integrally provided with a scale. .

  (2) In the ultrasonic motor according to (1), the moving amount detection means for detecting the moving amount of the moving body on the support member that fixes the rod-shaped vibrator is a reflective optical encoder, An ultrasonic motor characterized in that an optical scale is integrally provided on the rotation output member.

  (3) The ultrasonic motor according to (2), wherein the optical scale is a micro roof mirror array scale.

  (4) In the ultrasonic motor according to (1), the movement amount detection means for detecting the movement amount of the moving body on the support member that fixes the rod-shaped vibrator is a magnetic sensor, and the rotation An ultrasonic motor, wherein an output member is integrally provided with a magnetic scale.

  (5) In the ultrasonic motor according to (1), two movement amount detection means for detecting the movement amount of the moving body are arranged on a support member that fixes the rod-shaped vibrator, and the two movement amounts An ultrasonic motor, characterized in that the detection means are arranged at positions facing each other about the rotation axis.

  According to the present invention, since a scale for detecting the position of the motor is attached, a position position detector is directly attached to the structure of the rod-shaped ultrasonic motor without disposing a separate gear and without increasing the shape. By incorporating an (encoder) and a scale, it is possible to provide an ultrasonic motor that achieves miniaturization and high accuracy.

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

(First embodiment)
FIG. 1 shows a first embodiment according to the present invention. The figure is a cross-sectional view including a rotational symmetry axis.

  In this figure, 1 is a first elastic body (metal material), 2 is a second elastic body (a wear-resistant material such as alumina), and 3 is a laminated piezoelectric element (or laminated single-plate piezoelectric element). Body), 4 is a shaft, and 5 is a nut. The first elastic body 1 and the shaft 4 are integrally coupled by press-fitting to form an elastic body shaft unit component, and laminated with the second elastic body 2. The piezoelectric element 3 is clamped by the elastic shaft unit component and the nut 5 so that a predetermined clamping force is applied, thereby constituting a vibrator.

  One surface of the rotor 7 has a structure with a small contact width and an appropriate spring property, and this surface contacts the friction surface of the vibrator (the upper surface of the second elastic body 2). Further, the other surface of the rotor 7 is provided with a convex portion (or concave portion) formed in the radial direction, and the lower surface of the gear 8 facing this is provided with a concave portion (or convex portion) formed in the radial direction. When the convex portions (or concave portions) of the rotor 7 and the concave portions (or convex portions) of the gear 8 are coupled, the rotor 7 and the gear 8 are constrained in the circumferential direction and rotate integrally, and the rotational force of the rotor 7 is changed to the gear. 8 is transmitted. Further, the gear 8 (FIG. 2 is a view seen from the upper side) has a micro roof mirror array reflector 20 (hereinafter referred to as MRA) arranged as an encoder scale on the upper side, and a shaft 4 by a flange 10 for mounting a motor. The position is fixed in the thrust direction, and a pressure spring 15 for applying pressure to the rotor 7 is provided between the gear and the rotor. In addition, one (or two) encoder heads 21 that efficiently extract detection signals from the MRA are integrally disposed as a mass body on the upper side of the flange 10 (FIG. 3 is a view seen from the upper side). Yes.

  Here, only the difference between the encoder using the MRA effect and the normal reflection scale will be described with reference to FIG. 4 (detailed description of the encoder using the MRA effect is described in JP-A-2002-323347). ).

  FIG. 4A shows the locus of light when a normal reflection scale is used. As can be seen from the figure, the light from the point light source is divergent light and diverges after being reflected by the scale. Therefore, when the distance between the light source and the scale is increased, almost no light returns to the light receiving sensor provided at substantially the same position as the light source.

  FIG. 4 (b) shows the locus of light when a scale using an MRA reflector is used. As can be seen from the figure, the light from the point light source returns to the light receiving sensor provided at substantially the same position as the light source via the MRA scale. Here, since the scale using the MRA reflector is used, the light collection efficiency from the light source is improved. Further, since the light is condensed and returned by the effect of the scale using the MRA reflector, the amount of light is not drastically reduced even if the distance between the light source and the scale is increased.

  As described above, as a merit of the reflector having the MRA shape, the absolute light quantity guided to the light receiving portion can be larger than that of the conventional reflector, and the light quantity changes with respect to the reflection scale and sensor distance (gap) fluctuation. There is little and becomes 1 / distance relationship.

  Here, in the laminated piezoelectric element 3 (or a laminated body of single-plate piezoelectric elements), electrodes are grouped into two electrode groups, and when an AC electric field having a different phase is applied to each electrode group from a power source (not shown). In the vibrator, two orthogonal bending vibrations are excited. By adjusting the phase of the applied electric field, a 90-degree temporal phase difference can be given between the two vibrations. As a result, the bending vibration of the rod-shaped vibrator rotates around the axis of the vibrator.

  As a result, a double circular motion is formed on the upper surface of the first elastic body in contact with the rotor 7, and the rotor 7 pressed by the wear-resistant member is frictionally driven. The pressure spring 15 rotates as a unit.

  As described above, MRA is arranged on the motor gear and the encoder head is integrally arranged on the flange as a mass body, so that the motor can be further enlarged without providing a separate gear for detecting the position. Therefore, it is possible to provide an ultrasonic motor that realizes miniaturization and high accuracy. In this embodiment, MRA is used as the encoder. However, if the mounting accuracy of the gear and the flange portion is high, it can be realized even in a normal reflection encoder.

  In the present embodiment, one encoder head 21 is attached to the upper side of the flange 10, but the second encoder head is arranged on the dotted line portion (opposite side) in FIG. It is possible to extract a highly reliable detection signal.

(Second Embodiment)
FIG. 5 shows a second embodiment according to the present invention. The figure is a cross-sectional view including a rotational symmetry axis.

  In these drawings, 1 is a first elastic body (metal material), 2 is a second elastic body (metal material), 3 is a laminated piezoelectric element (or a laminated body of single-plate piezoelectric elements), 4 is a shaft, Reference numeral 5 denotes a nut, and the components 1 to 3 are tightened by the shaft 4 and the nut 5 so that a predetermined clamping force is applied, thereby constituting a vibrator.

  One surface of the rotor 7 has a structure with a small contact width and an appropriate spring property, and this surface contacts the friction surface 6 of the vibrator. Further, the other surface of the rotor 7 is provided with a convex portion (or concave portion) formed in the radial direction, and the lower surface of the gear 8 facing this is provided with a concave portion (or convex portion) formed in the radial direction. When the convex portions (or concave portions) of the rotor 7 and the concave portions (or convex portions) of the gear 8 are coupled, the rotor 7 and the gear 8 are constrained in the circumferential direction and rotate integrally, and the rotational force of the rotor 7 is changed to the gear. 8 is transmitted. Furthermore, the gear 8 (FIG. 6 is an enlarged view) has a known magnetic scale 22 arranged as an encoder scale on the upper side, and is fixed in the thrust direction of the shaft 4 by a flange 10 for mounting a motor. A pressure spring 15 for applying pressure to the rotor 7 is provided between the gear and the rotor. In addition, one (or two) magnetic sensor heads 23 that extract detection signals from the scale are integrally disposed on the upper side of the flange 10 as a mass body. Since the magnetic sensor and the scale are known, detailed description thereof is omitted.

  Here, in the laminated piezoelectric element 3 (or a laminated body of single-plate piezoelectric elements), electrodes are grouped into two electrode groups, and an AC electric field having a different phase is applied to each electrode group from a power source (not shown). In the vibrator, two orthogonal bending vibrations are excited. By adjusting the phase of the applied electric field, a 90-degree temporal phase difference can be given between the two vibrations. As a result, the bending vibration of the rod-shaped vibrator rotates around the axis of the vibrator.

  As a result, a circular motion is formed on the upper surface of the first elastic body in contact with the rotor 7, and the rotor 7 pressed against the wear-resistant member 6 is frictionally driven. The pressure spring 15 rotates as a unit.

  As described above, an ultrasonic motor that achieves miniaturization and high accuracy without increasing the size of the motor by integrally arranging the magnetic scale on the gear of the motor and the magnetic sensor head as a mass on the flange. Can be provided.

1 is a configuration diagram of an ultrasonic motor according to a first embodiment of the present invention. The upper side enlarged view of the gear in 1st Embodiment in this invention The upper side enlarged view of the flange in 1st Embodiment in this invention The figure showing the locus | trajectory of light when using the normal reflection scale of the 1st Embodiment in this invention, and the locus | trajectory of light when using the scale using the MRA reflector (b). The block diagram of the ultrasonic motor in 2nd Embodiment in this invention The upper side enlarged view of the gear in 2nd Embodiment in this invention The figure showing (a) the structure of a rod-shaped vibrator and (b) its vibration mode in the prior art example. Configuration diagram of an ultrasonic motor used for camera lens drive, etc.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st elastic body 2 2nd elastic body 3 Laminated piezoelectric element 4 Shaft 5 Nut 6 Friction surface 7 Rotor 8 Gear 9 Bearing
10 Flange 11 Nut 15 Pressure spring 20 Micro roof mirror reflector (MRA)
21 Encoder head 22 Magnetic encoder scale 23 Magnetic sensor head

Claims (5)

The electro-mechanical energy conversion element is sandwiched between elastic members, and the elastic members are fastened and integrated by fastening means, and an alternating voltage having a predetermined phase difference is applied to the electro-mechanical energy conversion element. By combining bending vibrations excited in different planes including the axis, a rod-like vibrator that forms circular or elliptical motion on the surface particles of the drive surface, and pressure contact with the drive surface of the rod-like vibrator And a rotation output member that rotates integrally with the moving member and a support member that fixes the rod-shaped vibrator, and frictionally drives the moving body by a circular or elliptical motion formed on the rod-shaped vibrator. In ultrasonic motors,
An ultrasonic motor comprising: a supporting member for fixing the rod-like vibrator; a moving amount detecting means for detecting a moving amount of the moving body; and a rotary output member integrally provided with a scale. .   2. The ultrasonic motor according to claim 1, wherein the moving amount detecting means for detecting the moving amount of the moving body on the support member that fixes the rod-shaped vibrator is a reflective optical encoder, and the rotation output member. An ultrasonic motor characterized in that an optical scale is integrally provided.   3. The ultrasonic motor according to claim 2, wherein the optical scale is a micro roof mirror array scale.   2. The ultrasonic motor according to claim 1, wherein the moving amount detecting means for detecting the moving amount of the moving body on the support member fixing the rod-shaped vibrator is a magnetic sensor, and the rotating output member is magnetically connected. An ultrasonic motor comprising an integrated scale.   2. The ultrasonic motor according to claim 1, wherein two movement amount detection means for detecting the movement amount of the moving body are arranged on a support member that fixes the rod-shaped vibrator, and the two movement amount detection means are mutually connected. An ultrasonic motor, wherein the ultrasonic motor is disposed at a position facing each other about a rotation axis.