JPH10290578A - Vibration actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration actuator in which the detection accuracy of rotation, rotational speed, and the like, can be varied depending on the application. SOLUTION: A vibration actuator comprises a vibrator 30, a rotary member 20 turnable about a specified rotary axis with a vibrator motion being transmitted at least partially from the vibrator 30, and an output take-out section 24 turning integrally with the rotary member 20 to transmit the rotational motion of the rotary member 20 to the outside wherein the output take-out section 24 can be mounted removably on the rotary member 20 and two or more regions 24b having different electrical, magnetic or optical characteristics, detectable from the outside, are arranged in the circumferential direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration actuator for rotating a rotating member by using a vibration motion of a vibrator.

[0002]

2. Description of the Related Art A vibration actuator is an actuator characterized by small size and high torque, and can directly drive a drive target without using a reduction gear train or the like.
It has been proposed to use it as a drive source for a small device that wants to reduce the size of the entire device by simplifying the mechanism. The electronic timepiece disclosed in Japanese Patent Application Laid-Open No. 60-51478 is an example of the invention in which a vibration actuator is used as a drive source of the timepiece. Is driven to rotate.
By the way, in the vibration actuator, since the moving element is driven to rotate by frictional contact with the vibrating vibrator, the rotation amount / speed of the moving element is reduced due to unevenness of the surface state of the moving element. It may change depending on the rotation angle. Such a change in the amount of rotation or the like becomes a serious obstacle to accurate positioning of the minute hand. Therefore, Japanese Patent Application Laid-Open
In the electronic timepiece disclosed in Japanese Patent No. 51478, a movable element of a vibration actuator is provided with an electrode pattern divided into 60 in the circumferential direction, a rotation angle of the movable element is detected using the electrode pattern, and a feedback of a rotation amount of the movable element is provided. Control is to be performed.

[0003]

However, in the conventional vibration actuator, since the electrode pattern is provided directly on the surface of the moving element, the minimum unit of the detectable rotation angle is determined for each vibration actuator. For example, in the vibration actuator for an electronic timepiece described above, the usage is 6 minutes per minute.
Since the driving source is limited to the minute hand that rotates by degrees, the electrode pattern is provided so as to detect an angle of 6 degrees. For this reason, the application of the vibration actuator is limited.If there is an application with a different rotation speed, for example, an application that makes several tens of revolutions per minute, only the electrode pattern differs according to the application, and the other structure is the same. However, there is a problem that the vibration actuator must be separately manufactured.

On the other hand, as a method for solving the above problem,
It is also conceivable that the movable element is not provided with an electrode pattern, and an independently manufactured encoder is attached to the vibration actuator, thereby detecting the rotation amount and the like of the movable element. However, attaching an encoder that is a completely separate member leads to an increase in the size of the vibration actuator, and there is a possibility that the characteristics of the vibration actuator such as small size and high torque may be lost. In addition, many vibration actuators have a structure that does not have a rotating shaft unlike electromagnetic motors and the like.
There is also a problem that it is difficult to mount an encoder on the assumption that the encoder is mounted on a rotating shaft of a motor.

It is an object of the present invention to provide a small-sized vibration actuator capable of changing the detection accuracy of a rotation amount, a rotation speed, and the like according to an application.

[0006]

According to a first aspect of the present invention, a vibrator and at least a part of a vibrating motion of the vibrator are transmitted to rotate around a predetermined rotation axis. In a vibration actuator comprising a rotating member that rotates and an output take-out part that rotates integrally with the rotary member and transmits the rotational motion of the rotary member to the outside, the output take-out part is detachable from the rotary member. The vibration actuator is characterized in that two or more regions having different electrical, magnetic or optical characteristics that can be detected from the outside are arranged in the circumferential direction.

According to a second aspect of the present invention, in the vibration actuator according to the first aspect, the two or more regions are provided on a surface of the output take-out portion that intersects the rotation axis substantially perpendicularly. This is a characteristic vibration actuator. The invention according to claim 3 is claim 1 or claim 2.
The vibration actuator according to any one of claims 1 to 3, further comprising a detection unit that detects a position of the two or more regions.

According to a fourth aspect of the present invention, in the vibration actuator according to the third aspect, the detecting section is provided on a fixed shaft to which the rotating member and the vibrator are attached. It is a vibration actuator. The invention according to claim 5 is the vibration actuator according to claim 3 or 4, wherein the fixed shaft includes the vibrator, the rotating member, and a pressing member that presses the rotating member against the vibrator. And each member is attached in the order of the detection unit.

According to a sixth aspect of the present invention, in the vibration actuator according to any one of the third to fifth aspects, a diameter of a portion of the fixed shaft to which the detection unit is attached is the same as that of the rotating member. Is smaller than the diameter of the part to which the vibration actuator is attached. The invention according to claim 7 is the vibration actuator according to any one of claims 1 to 6, wherein
The number, the shape, or the characteristic of the above-described regions is different depending on the position in the circumferential direction.

[0010]

An embodiment according to the present invention will be described below with reference to the drawings. In the following description, an ultrasonic motor using an ultrasonic vibration region will be described as an example of a vibration actuator.

FIG. 1 is a sectional view showing an embodiment of an ultrasonic motor according to the present invention. As shown in FIG. 1, the ultrasonic motor 10 according to the present embodiment mainly includes a moving element 20 and a stator 30. The moving element 20 includes a stator 30
Is a thick annular or cylindrical member that rotates with the fixed shaft 12 as a rotation shaft by obtaining a driving force from the member. The moving element 20 includes a moving element base material 22 and a sliding member 26 provided on the lower surface of the moving element base material 22. The sliding member 26 is a member that comes into contact with the driving surface D of the stator 30 and slides. Sliding material 2
No. 6 is mainly composed of a polymer material or the like in order to improve the sliding characteristics.

On the other hand, the moving element base material 22 is made of stainless steel,
The member is made of a copper alloy, an aluminum alloy, or the like. The upper end of the moving element base material 22 is a small diameter part having a smaller diameter than other parts, and a gear 24 is detachably fitted to the small diameter part. The gear 24 is for transmitting the rotation output of the moving element 20 to a gear of a driven body (not shown), and is a member corresponding to the output extracting unit according to the present invention.

FIG. 2 shows the movable element 2 with which the gear 24 is fitted.
0 is a top view. As shown in the figure, on the upper surface of the gear 24, a plurality of linear portions 24b are provided at equal intervals in the circumferential direction by plating or the like. Thus, the linear portion 24
The reason for providing b is to change the light reflectance on the upper surface of the gear to obtain an encoder pattern arranged in the circumferential direction as a whole. In addition, the encoder pattern is provided on the upper surface of the gear 24 because the detector for detecting the encoder pattern can be disposed on the upper surface side of the gear 24 instead of the outer peripheral side, thereby increasing the size of the ultrasonic motor in the radial direction. This is in order to prevent that.

As can be seen in FIG. 1, the mover 20 is mounted on the fixed shaft 12 via a bearing 18. The bearing 18 allows the movable member 20 to rotate around a fixed axis, and also serves as a positioning member that positions the movable member 20 at a predetermined position on the fixed shaft 12.

The fixed shaft 12 has a screw portion 12a above the position where the mover 20 is attached, and an adjusting member 14 such as a nut is screwed to the screw portion 12a. In addition, between the adjusting member 14 and the moving element 20,
A pressing member 16 such as a disc spring, a coil spring, or a leaf spring is disposed. The pressing member 16 connects the moving element 20 to the stator 30
Press in the direction of. The moving element 20 receives a pressing force from the pressing member 16 and comes into pressure contact with the driving surface D of the stator 30. On the other hand, the adjusting member 14 appropriately compresses the pressing member 16 by changing the screwed position,
The pressure applied to the mover 20 is adjusted.

A photosensor 44 is mounted on the screw portion 12a above a position where a pressing mechanism such as the adjusting member 14 is mounted. The photo sensor 44 detects whether the linear portion 24b is located at the measurement point or has passed the measurement point based on the amount of light reflected from the gear surface. The output of the photo sensor 44 is connected to a rotation amount / speed calculation device (not shown). The arithmetic unit determines the position of the moving element 2 based on the output signal of the photo sensor 44 and the characteristics of the encoder pattern provided on the upper surface of the gear 24.
A rotation amount, a rotation speed, and the like of 0 are obtained. In addition, the screw portion 12a
Is set smaller than the outer diameter of the fixed shaft 12 at the position where the mover 20 is attached. this is,
This is for facilitating attachment of the moving element, the pressing mechanism, the photo sensor, and the like to the fixed shaft 12.

The stator 30 is a member that generates an elliptical motion on the drive surface D by performing primary longitudinal vibration and secondary torsional vibration. The stator 30 has a thick cylindrical shape, and is fixed to the fixed shaft 12 by passing the fixed shaft 12 through a hollow portion thereof. As shown in the exploded view of FIG. 3, the stator 30 is obtained by sandwiching a layer composed of the electrode plates (55 to 58) between two layers composed of the piezoelectric bodies (51 to 54), and further includes elastic bodies 32 and 34. And a configuration sandwiched between them. In addition, the piezoelectric element, the electrode plate, and the elastic body are bonded to each other with an adhesive.

As shown in FIG. 1, elastic members 32 and 34 are provided.
Are four large diameter portions 30A, 30B, 30C and 30D
And a semi-cylindrical member obtained by vertically dividing a thick-walled cylinder having three small-diameter portions 30a, 30b, and 30c into two, and having a high resonance sharpness such as steel, stainless steel, phosphor bronze, or enriver material. Made of material. Small diameter parts 30a and 3
0c is a small-diameter portion 3 at a position including a node of the secondary torsional vibration.
0b is formed at a position including a node of the primary longitudinal vibration. As described above, the stator 30 is formed into a shape having four large diameter portions and three small diameter portions.
This is for causing the resonance frequency of the longitudinal vibration and the torsional vibration excited to be substantially equal to each other to cause the stator 30 to degenerate.

The stator 30 has four through holes 30E to 30H in the large diameter portions 30A and 30D, respectively, which are parallel to the laminating direction of the piezoelectric bodies (51 to 54). Through hole 30E ~
A bolt 36 is inserted into each of the nuts 30H.
8 fixed. Thus, the elastic bodies 32 and 34 are integrally assembled with the piezoelectric bodies (51 to 54) sandwiched therebetween.

The stator 30 has a through hole 30G in the small diameter portion 30a. The through hole 30G is provided with the spring pin 4
It is a hole for passing 0. The spring pin 40 fixes the stator 30 to the fixed shaft 12 by penetrating through the through hole 30 a of the stator 30 and the through hole 12 b provided in the fixed shaft 12. Stator 3
0 is a member for positioning.

On the other hand, the fixed shaft 12 has two
Positioning members 42 are arranged at various places. The positioning member 42 is an annular or cylindrical member, and is fitted to the fixed shaft 12 from the end face side. The outer peripheral surface of the positioning member 42 is in contact with the inner peripheral surface of the stator 30, whereby the stator 30 is positioned in the radial direction.

As described above, the components constituting the stator 30 2
An electrode plate (55 to 5) is provided between the two elastic bodies 32 and 34.
8) and a layer made of piezoelectric bodies (51 to 54). In FIG. 3, the layers La1, La3,
The four layers La4 and La6 are layers composed of a piezoelectric body, and the layers La2 and La5 are layers composed of electrode plates.

The layer La1 made of piezoelectric material is composed of four piezoelectric materials arranged on the same plane. The four piezoelectric members are a torsional vibration detecting piezoelectric member 51, a torsional vibration piezoelectric member 52, a longitudinal vibration piezoelectric member 53, and a longitudinal vibration detecting piezoelectric member 54, in order from the one near the drive surface D. For torsional vibration piezoelectric element 52, utilizing a piezoelectric constant d _15, a piezoelectric element to excite the torsional vibrations in the stator 30. Here, the torsional vibration refers to a vibration that is displaced around the central axis A. The torsional vibration piezoelectric body 52 is polarized in a direction parallel to the central axis A, and performs a shear deformation in a direction parallel to the central axis A when a voltage is applied in the thickness direction. The torsional vibration detecting piezoelectric element 51 is for detecting torsional vibration excited in the stator 30 by utilizing a piezoelectric effect.

The longitudinal vibration piezoelectric element 53, utilizing a piezoelectric constant d _31, a piezoelectric element to excite longitudinal vibration in the stator 30. Here, the longitudinal vibration refers to a vibration that is displaced in a direction parallel to the central axis A. The piezoelectric body 53 for longitudinal vibration is polarized in the plate pressure direction, and when a voltage is applied in the plate thickness direction, the piezoelectric body 53 expands and contracts in the plane direction. The longitudinal vibration detecting piezoelectric body 54 is for detecting the longitudinal vibration excited in the stator 30 using the piezoelectric effect.

The layer La3 has the same structure as the layer La1. However, the polarization directions of the torsional vibration piezoelectric body 52 and the longitudinal vibration piezoelectric body 53 are opposite to each other in the layer La1 and the layer La3 (see broken arrows in FIG. 4). on the other hand,
The layer La2 arranged between the layers La1 and La3 is 4
Two electrode plates, that is, an electrode plate 55 for torsional vibration detection, an electrode plate 56 for torsional vibration, an electrode plate 57 for longitudinal vibration, and an electrode plate 58 for longitudinal vibration detection are arranged on the same plane. The torsional vibration electrode plate 56 is arranged between the torsional vibration piezoelectric bodies 52 of the layers La1 and La3, and is an electrode plate for simultaneously applying a drive signal (frequency voltage) to these two piezoelectric bodies.

Similarly, the longitudinal vibration electrode plate 57 is disposed between the two longitudinal vibration piezoelectric members 53, and is for applying drive vibration to these piezoelectric members simultaneously. on the other hand,
Electrode plate 55 for detecting torsional vibration and electrode plate 58 for detecting longitudinal vibration
Are disposed between two torsional vibration detecting piezoelectric bodies 51 or two longitudinal vibration detecting piezoelectric bodies 54, respectively, so that voltages generated in the piezoelectric bodies can be detected. The layer La4
La6 are layers La1 to La3 around the central axis A of the stator 30.
It is obtained by rotating La3 by 180 degrees,
It has the same configuration as 1 to La3. Therefore,
Here, the description is omitted.

FIG. 4 is an explanatory view showing the arrangement of the piezoelectric body in the stator 30 and the vibration mode excited by the stator 30. 4A is a diagram illustrating a side surface of the stator 30 and the like, FIG. 4B is a cross-sectional view of the FF of the stator 30, and FIG. 4C is a diagram illustrating a vibration mode excited by the stator 30. FIG.
As shown in (c), the primary longitudinal vibration and the secondary torsional vibration are excited in the stator 30. Further, as shown in FIG. 4A, the small diameter portions 30a and 30c of the stator 30 are provided.
Is provided at the position of the node of the torsional vibration,
0b is provided at the position of the node of the longitudinal vibration.

On the other hand, the torsional vibration piezoelectric body 52 is
0a, that is, so as to straddle the one closer to the drive surface D among the two nodes of the torsional vibration. Further, the piezoelectric body 53 for longitudinal vibration is arranged at a position including the small diameter portion 30b, that is, so as to straddle a node part of longitudinal vibration. The reason why the piezoelectric body is disposed so as to straddle the nodes of the vibrations is that each vibration can be efficiently excited by applying a force to the elastic body at the nodes.

When a positive voltage is applied to the electrode plate 56 with respect to the potential of the elastic body (32, 34), the shear deformation shown by an arrow in FIG. The direction of the shear deformation is opposite between the piezoelectric bodies of the layers La1 and La3 and the piezoelectric bodies of the layers La4 and La6. Due to the shear deformation of the torsional vibration piezoelectric body 52, the stator 30 is twisted in a direction indicated by an arrow m in FIG. When a negative voltage is applied to the electrode plate 56, the direction of the shear deformation of the piezoelectric body 52 and the direction of the torsion of the stator 30 are reversed. Therefore, the electrode plate 56
When a frequency voltage is applied to the stator 30, torsional vibration is excited in the stator 30.

On the other hand, when a positive voltage is applied to the electrode plate 57, all of the four longitudinal vibration piezoelectric members 53 are parallel to the central axis A of the stator 30 as shown by arrows in FIG. Elongation and deformation when a negative voltage is applied. Therefore, when a frequency voltage is applied to the electrode plate 57, longitudinal vibration is excited in the stator 30.

Next, the operation of the ultrasonic motor according to this embodiment will be described with reference to FIG. FIG.
FIG. 4 is an explanatory diagram schematically showing the operation of FIG. In the figure, ω represents the angular frequency (ω = 2πf) when the drive frequency is f.
When drive signals (frequency voltages) having a phase difference of 90 ° are input to the piezoelectric body 53 for longitudinal vibration and the piezoelectric body 52 for torsional vibration, the phases of the longitudinal vibration and torsional vibration generated in the stator 30 are 90 °. On the driving surface D, an elliptical motion combining these vibrations is generated.

Specifically, first, at time t = 0,
The displacement of the torsional vibration is maximum on the left side, and the displacement of the longitudinal vibration is zero. In this state, the moving element 20 is in contact with the driving surface D of the stator 30 by the pressing member 16. From this state, from t = 0 to (4/4) × (π / ω), the torsional vibration is displaced from the maximum on the left to the maximum on the right. On the other hand, the longitudinal vibration is displaced from zero to an upper maximum and returns to zero again. Therefore, the driving surface D of the stator 30 rotates rightward while pressing the moving member 20, and the moving member 20 is driven.

Next, t = (4/4) × (π / ω)-(8
/ 4) × (π / ω), the torsional vibration is displaced from the maximum on the right to the maximum on the left. On the other hand, the longitudinal vibration is displaced from zero to a lower maximum and returns to zero again. At this time, the moving element 20
Is the pressing member 1 even if it is pressed by the pressing member 16.
Since the natural frequency of 6 is lower than the ultrasonic vibration range, it cannot follow the contraction of the stator. Therefore, the rotor and the moving element 20 are not driven leftward on the driving surface D of the stator 30 while moving away from the moving element 20. As described above, in the present embodiment, when a drive signal having a phase difference of 90 ° is input to the piezoelectric body for longitudinal vibration 53 and the piezoelectric body for torsional vibration 52, elliptic motion occurs on the drive surface D, and further, the drive surface D Since a part of the elliptical motion is transmitted to the movable element 20, the movable element 20 performs a rotational movement in a certain direction.

As described above, in the present embodiment, the rotation amount and the rotation speed of the movable element are detected by using the encoder pattern of the gear attached to the movable element and the photo sensor attached to the fixed shaft. You are going to. Therefore, by attaching gears provided with different encoder patterns to the mover, it is possible to easily change the detection resolution such as the rotational speed in accordance with the use mode of the ultrasonic motor, and to change one ultrasonic motor into many different ones. Can be used for applications.

(Other Embodiments) The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the scope of the claims of the present invention. It is included in the technical scope of the invention.

1) In the above embodiment, the case where the first-order longitudinal vibration and the second-order torsional vibration are excited in the elastic body has been described. It may be to excite those. 2) In the above embodiment, the case where the piezoelectric body is used as the vibration source that excites the torsional vibration or the longitudinal vibration in the elastic body has been described as an example. It is not meant to be limiting. The vibration source may be any source that can apply predetermined vibration to the elastic body, and an element (electrostrictive element) that excites the elastic body by converting electric energy, magnetic energy, heat energy, or the like into mechanical displacement. , Magnetostrictive elements, etc.). 3) In the above embodiment, the case where linear portions are provided at equal intervals in the circumferential direction on the upper surface of the gear 24, that is, the case where the encoder pattern is a so-called incremental type, has been described. The characteristic such as the interval, the number, the shape, or the reflectance of the linear portions may be changed in accordance with the position in the circumferential direction. In addition, the encoder pattern is not limited to one that uses a change in light reflectance, that is, a change in optical characteristics, and may use a change in electrical or magnetic characteristics. 4) In the above embodiment, the case where the output take-out unit is a gear has been described as an example, but this may be a cam or the like.

[0037]

As described above in detail, according to the first aspect of the present invention, the output take-out portion has two or more regions having different characteristics arranged in the circumferential direction. , Rotation speed, etc. can be easily detected. In addition, since the output take-out unit is detachable, by attaching the output take-out unit having a different arrangement of the area to the rotating member, it is possible to easily change the detection accuracy such as the rotation amount of the rotating member.

According to the second aspect of the present invention, since the two or more regions are provided on the surface of the output take-out section which intersects substantially perpendicularly to the rotation axis, the positions of these regions are parallel to the rotation axis. It is possible to detect from the direction, by installing a detector to detect the position of those areas,
The vibration actuator can be prevented from increasing in size in the radial direction.

According to the third aspect of the present invention, since there is also provided a detecting section for detecting the positions of two or more areas provided in the output take-out section, it is possible to detect the rotation amount and the rotation speed of the rotating member by itself. It has become possible to provide a simple vibration actuator. According to the invention according to claim 4, since the detection unit is installed on the fixed shaft to which the rotating member and the vibrator are attached, it is not necessary to prepare a new mechanism or member for installing the detection unit. In addition, the installation of the detection unit does not significantly reduce the size of the vibration actuator.

According to the fifth aspect of the present invention, since the vibrator, the rotating member, the pressurizing unit, and the detecting unit are attached to the fixed shaft in this order, the detecting unit is attached to and detached from the fixed shaft. In addition, there is no need to attach / detach the pressurizing unit or readjust the pressing force generated by the pressurizing unit. According to the invention according to claim 6, since the diameter of the fixed shaft is smaller than the diameter of the portion to which the rotating member is attached, it is easy to attach the rotating member to the fixed shaft. is there.
According to the invention according to claim 7, the number, shape, or characteristics of the two or more regions differ depending on the circumferential position.
By detecting the number, shape, or characteristics, the absolute rotation angle of the rotating member can be confirmed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an ultrasonic motor according to the present invention.

FIG. 2 is a top view of the moving element 20 to which the gear 24 is fitted.

FIG. 3 is an exploded perspective view showing a vibrator 30.

FIG. 4 is an explanatory diagram showing an arrangement of piezoelectric bodies in a vibrator 30 and a vibration mode excited by the vibrator.

FIG. 5 is an explanatory diagram schematically showing an operation of a vibrator 30.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Ultrasonic motor 12 Fixed axis 20 Moving element 22 Moving element base material 24 Gear 24b Encoder pattern 26 Sliding material 30 Vibrator 32, 34 Elastic body 44 Photosensor 51-54 Piezoelectric body 55-58 Electrode plate

Claims (7)

[Claims] 1. A vibrator, a rotating member to which at least a part of a vibration motion of the vibrator is transmitted, and which rotates around a predetermined rotation axis; and a rotating member which rotates integrally with the rotating member to rotate the rotating member. An output actuator for transmitting a motion to the outside, wherein the output extractor is detachable from the rotating member and has at least two different electrical, magnetic or optical characteristics detectable from the outside. Are arranged in the circumferential direction. 2. The vibration actuator according to claim 1, wherein the two or more regions are provided on a surface of the output take-out section that intersects substantially perpendicularly to the rotation axis. 3. The vibration actuator according to claim 1, further comprising a detection unit configured to detect the positions of the two or more regions. 4. The vibration actuator according to claim 3, wherein the detection unit is provided on a fixed shaft to which the rotating member and the vibrator are attached. 5. The vibration actuator according to claim 3, wherein the fixed shaft has the vibrator, the rotating member, a pressing member that presses the rotating member against the vibrator, and the detection. A vibration actuator, wherein each member is attached in the order of the parts. 6. One of claims 3 to 5
The vibration actuator according to claim 1, wherein a diameter of a portion of the fixed shaft to which the detection unit is attached is smaller than a diameter of a portion of the fixed shaft to which the rotating member is attached. 7. One of claims 1 to 6
The vibration actuator according to claim 1, wherein the number, the shape, or the characteristic of the two or more regions is different depending on a circumferential position.