JP2016048986A - Vibration actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration actuator capable of generating large torque.SOLUTION: A vibration actuator 10 includes: a stator 13; a rotor 30 which is contacted and supported by the stator 13; a shaft 34 rotatably supporting the rotor 30; a piezoelectric element 17 connected with the stator 13 and serving as a vibration part which applies ultrasonic vibrations to a contact portion between the stator 13 and the rotor 30 to rotate the rotor 30; a connection rod 45, a spring receiving body, and a disc spring 50 connected with the shaft 34 and serving as biasing parts which bias the shaft 34 toward the stator 13 to place the rotor 30 in contact with the stator 13; and bearings rotatably supporting the shaft 34 at both sides of the rotor 30. A recessed part 34a is provided in at least one portion of the shaft 34 which is located between the rotor 30 and the bearing.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a vibration actuator, and more specifically, an object of the present invention is to provide a vibration actuator capable of generating a large torque.

  A conventional vibration actuator is disclosed in, for example, Japanese Patent Application Laid-Open No. 2013-143827 (Patent Document 1). The vibration actuator disclosed in Patent Document 1 rotates a rotor by generating ultrasonic vibration at a contact portion between the stator, a rotor that is in contact with and supported by the stator, a shaft that is integrally rotatable with the rotor, and the rotor and the rotor. Vibrating means and preload means that is connected to the shaft via a bearing and presses the shaft toward the stator to press the rotor and the stator in pressure contact with each other.

JP2013-143827A

  Since the vibration actuator described in Patent Document 1 is configured to take out the rotational force of the rotor as an output through the shaft, a large bearing is used as a bearing that supports the shaft in order to improve the durability of the actuator. There is a need. However, when the diameter of the shaft of the vibration actuator is increased in order to use a large bearing, there is a problem that the torque of the vibration actuator is reduced for the following reason.

  (1) A natural vibration mode of the shaft occurs near the drive frequency of the vibration actuator.

  (2) The displacement amount (deflection amount) of the shaft due to the load of the pressurizing means for pressing the rotor against the stator changes.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to provide a vibration actuator capable of suppressing a reduction in torque even when a large shaft bearing is used. To do.

  A vibration actuator according to one aspect of the present invention includes a stator, a rotor that is contacted and supported by the stator, a shaft that is coupled to the rotor so as to be integrally rotatable, and a contact portion between the stator and the rotor that is coupled to the stator. A vibration unit that applies ultrasonic vibration to the rotor to rotate the rotor, a bearing that rotatably supports the shaft on both sides of the rotor, and a shaft that is coupled to the shaft via the bearing and biases the shaft toward the stator. And a pressurizing portion that pressurizes and contacts the rotor and the stator, and the shaft is provided with a recess at least at one portion in a portion between the rotor mounting portion and the shaft receiving mounting portion.

  In the vibration actuator configured as described above, since the concave portion is provided between the rotor mounting portion and the shaft receiving mounting portion of the shaft, the frequency of the natural vibration mode of the shaft can be shifted from the driving frequency of the vibration actuator. As a result, it is possible to provide a vibration actuator that can suppress a decrease in torque even when a large bearing is used.

  Furthermore, since a recess is provided in the shaft between the rotor mounting portion and the bearing mounting portion, the recess is provided in a portion where a large load is applied. As a result, the natural frequency can be effectively changed.

Preferably, concave portions are provided on both sides of the rotor mounting portion of the shaft.
Preferably, the concave portion is an annular groove formed along the circumferential direction of the shaft.

  A vibration actuator according to another aspect of the present invention includes a stator, a rotor contacted and supported by the stator, a shaft coupled to the rotor so as to be integrally rotatable, and a contact portion between the stator and the rotor. A vibration unit that applies ultrasonic vibration to the rotor to rotate the rotor, a bearing that rotatably supports the shaft on both sides of the rotor, and a shaft that is coupled to the shaft via the bearing and biases the shaft toward the stator. And a pressurizing part that pressurizes and contacts the rotor and the stator, and the shaft includes a cylindrical part provided with a cavity extending in the axial direction at least at a part thereof.

  In the vibration actuator configured as described above, since the shaft is provided with a cavity extending in the axial direction, the drive frequency of the vibration actuator and the frequency of the natural vibration mode of the rotor and the shaft can be shifted. As a result, a vibration actuator capable of generating a large torque can be provided.

  Since the cavity is provided in the shaft, the influence on the strength of the shaft is small even if the mass of the shaft is significantly reduced as compared with the case where the concave portion is provided on the surface of the shaft. As a result, the mass of the shaft can be greatly reduced, and the natural frequency can be effectively changed.

FIG. 3 is an exploded perspective view of the vibration actuator according to the first embodiment. 2 is a cross-sectional view of a rotor and a shaft used in the vibration actuator according to the first embodiment. FIG. 6 is a perspective view of a vibration actuator according to another aspect of the first embodiment. FIG. 6 is a front view of a shaft and a rotor used in a vibration actuator according to another aspect of the first embodiment. FIG. It is a front view which shows the connection part of a rotor and a shaft. It is a front view which shows the connection part of a rotor and a shaft. 6 is a side view of a shaft used in a vibration actuator according to Embodiment 2. FIG.

  Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. It is also possible to combine the embodiments.

(Embodiment 1)
Hereinafter, the vibration actuator according to the first embodiment will be described with reference to the drawings.

  A vibration actuator 10 shown in FIG. 1 is an ultrasonic actuator that rotates a rotating body using ultrasonic vibration. As shown in FIG. 1, the vibration actuator 10 is connected to a cylindrical base 11, a stator 13, a piezoelectric element 17, a rotor 30 as a rotating body connected to a shaft 34 so as to be integrally rotatable, and the shaft 34. And a disc spring 50 as an urging member.

The base 11 is cylindrical, and a screw hole 12 is formed at the center of the base 11, and the base 11 is connected to the stator 13. The stator 13 includes a shaft portion 14 that can be screwed into the screw hole 12 and a columnar stator main body portion 15 formed on the proximal end side of the shaft portion 14.
A male screw corresponding to the screw hole 12 is formed near the tip of the shaft portion 14.

  Between the base 11 and the stator main body 15, a piezoelectric element 17 is provided as vibration means. The piezoelectric element 17 has a substantially cylindrical shape and has a through hole 18 at the center. By inserting the shaft portion 14 of the stator 13 into the through hole 18 of the piezoelectric element 17, the piezoelectric element 17 is held between the stator 13 and the base portion 11. The piezoelectric element 17 has a structure in which perforated disk-shaped piezoelectric element plates (not shown) that are electrically connected to a drive circuit (not shown) are stacked. The plurality of piezoelectric element plates constituting the piezoelectric element 17 generate ultrasonic vibrations when an AC voltage is applied from the drive circuit.

  A cylindrical stator main body 15 that contacts and supports the rotor 30 is provided on the base end side of the shaft portion 14. At the end of the stator main body 15 on the rotor 30 side, a groove 19 that crosses in the radial direction is formed. The groove part 19 forms a space part in which a part of the connecting member 37 connected to the shaft 34 is accommodated. On both sides of the groove portion 19 in the stator main body portion 15, contact portions 20 having contact surfaces 21 that come into contact with the outer peripheral surface 31 of the rotor 30 are formed. The contact surface 21 corresponds to a contact portion with the rotor 30. The stator 13 has a through hole 22 that passes through the centers of the shaft portion 14 and the stator main body portion 15.

  The rotor 30 includes an outer peripheral surface 31 and a pair of rotor end surfaces 32, and a shaft hole 33 is formed at the center of the rotor 30. A shaft 34 passes through the shaft hole 33 of the rotor 30, and the shaft 34 is fixed to the rotor 30. Thus, when the shaft 34 penetrates the rotor 30, the shaft 34 rotatably supports the rotor. The shaft 34 is fixed to the rotor 30 by adhesion using a set screw, a key, or an adhesive. The outer peripheral surface 31 of the rotor 30 is formed on a surface having the same curvature as the curvature of the contact surface 21 of the contact portion 20 in the stator 13. In the present embodiment, both end portions of the shaft 34 are output ends of the vibration actuator 10, and the rotational force of the shaft 34 is used as an output.

  The shaft 34 is connected to a connecting member 37 via bearings 36 on both sides of the rotor end surface 32. The connecting member 37 is substantially U-shaped when viewed from the front, and includes a pair of connecting portions 38 and a connecting portion 39 that connects the pair of connecting portions 38. A through hole 40 is formed in the connecting portion 38, the shaft 34 is inserted into the through hole 40, and the shaft 34 is supported by the connecting portion 38 via a bearing 36. A portion of the connecting portion 39 and the connecting portion 38 near the connecting portion 39 is a groove inserting portion that is inserted into the groove portion 19 of the stator 13 with almost no gap. The groove inserting portion is set to a dimension corresponding to the width of the groove portion 19. Yes. Incidentally, in this embodiment, the dimension of the connecting member 37 corresponding to the direction of the rotation axis P substantially corresponds to the groove length of the groove portion 19 of the stator main body portion 15, and the connecting member 37 inserted into the groove portion 19 is It only needs to protrude slightly from the groove portion 19.

  In the present embodiment, a gap is formed between the outer peripheral surface 31 of the rotor 30 and the connection portion 39 of the connecting member 37, and a supply body 41 containing lubricating oil as a lubricant is accommodated in this gap. Yes. The supply body 41 corresponds to a lubricating member, and is used to supply lubricating oil to the outer peripheral surface 31 of the rotor 30. The supply body 41 is placed on the surface of the connecting portion 39 between the connecting portions 38 and is not fixed to the connecting member 37. The surface of the connecting portion 39 between the connecting portions 38 corresponds to a facing surface that faces the outer peripheral surface 31 with the rotor 30. In a state in which the connecting member 37 is inserted into the groove portion 19 of the stator 13, the periphery of the supply body 41 is covered with the stator 13, the rotor 30 and the connection member 37, and the supply body 41 does not fall out of the space portion.

  The connecting member 37 is connected to the connecting rod 45. A screw hole 42 is formed in the center of the connecting portion 39 of the connecting member 37. A screw shaft portion 46 corresponding to the screw hole 42 is formed at one end portion of the connecting rod 45. When the screw shaft portion 46 of the connecting rod 45 is screwed into the screw hole 42, the connecting rod 45 and the connecting member 37 are connected to each other. The connecting rod 45 is inserted into the through hole 22 of the stator 13, and the other end of the connecting rod 45 protrudes from the shaft portion 14 of the stator 13. Accordingly, the connecting rod 45 passes through the stator 13 and the piezoelectric element 17. A disc-shaped spring receiver is attached to the protruding end of the connecting rod 45 protruding from the shaft portion 14 via a holder. A disc spring 50 as an urging member is interposed between the spring receiver and the base 11.

  The disc spring 50 has a spring force that opposes the force acting in the direction in which the outer diameter edge and the inner diameter edge of the disc spring 50 approach each other, and the spring force is applied to the connecting rod 45 as a biasing force that brings the shaft 34 closer to the stator 13. Is done. Since the shaft 34 is biased toward the stator 13 via the connecting member 37 by the biasing force of the disc spring 50, the rotor 30 is pressed against the stator 13. In the present embodiment, the connecting rod 45, the spring receiver 49, and the disc spring 50 are elements constituting the preload means. Here, for convenience of explanation, the axial direction of the connecting rod 45 is defined as the Z axis, the X axis is directed in the direction perpendicular to the Z axis, and the Y axis perpendicular to the Z axis and the X axis is set. It shall be. The shaft 34 is provided with a groove-shaped recess 34a.

Next, the operation of the vibration actuator 10 according to this embodiment will be described.
When an AC voltage is applied to each piezoelectric element plate of the piezoelectric element 17 by the drive circuit, each piezoelectric element plate generates ultrasonic vibrations having different vibration directions. By applying alternating voltages having different phases to the piezoelectric element 17, a composite vibration in which the Y-axis direction flexural vibration (lateral vibration) and the Z-axis direction longitudinal vibration are combined is generated in the piezoelectric element 17. The composite vibration of the ultrasonic vibration is transmitted to the stator 13, and an elliptical motion (or circular motion) around the X axis in the Y-axis / Z-axis plane occurs on the pair of contact surfaces 21 in the stator 13. When the rotor 30 receives an elliptical motion (or circular motion) through the contact surface 21, the rotor 30 is rotated about the shaft 34. By the rotation of the rotor 30, a rotational force is obtained as an output at the end of the shaft 34 fixed to the rotor 30. The rotation direction, rotation speed, and torque of the rotor 30 can be controlled by controlling the applied AC voltage, frequency, and the like.

  Since the connecting member 37 is biased in a direction in which the shaft 34 approaches the stator 13 by the connecting rod 45 that receives the biasing force of the disc spring 50, the rotor 30 is pressed against the stator 13. Since the rotor 30 is in pressure contact with the stator 13 by the biasing of the shaft 34 toward the stator 13 by the preloading means, the load due to the pressure contact of the rotor 30 acts equally on the contact surface 21 of the stator 13. The rotor 30 is rotated with high torque. Since the rotor 30 and the stator 13 are in pressure contact with each other, the connecting member 37 does not prevent the vibrating stator 13 and the piezoelectric element 17 from vibrating. For this reason, if a fixed portion for fixing to the installation destination is set in the connecting member 37 and the vibration actuator 10 is fixed to the installation destination via the fixing portion, the fixed vibration actuator 10 is connected to the stator 13 or the piezoelectric element 17. Operates without disturbing vibration. In the present embodiment, it is preferable that a part of the connecting portion 38 of the connecting member 37 is a fixed portion.

  During the rotation of the rotor 30, the lubricant oil of the supply body 41 is applied to the outer peripheral surface 31 of the rotor 30, and the pressure contact state between the outer peripheral surface 31 of the rotor 30 and the contact surface 21 of the stator 13 is high. A torque rotational force can be obtained and high durability is achieved. That is, the lubricating oil maintains an appropriate pressure contact state between the outer peripheral surface 31 of the rotor 30 and the contact surface 21 of the stator 13.

  Referring to FIG. 2, the rotor 30 is fixed to the shaft 34 and rotates together with the shaft 34. The shaft 34 is provided with recesses 34 a and 34 b on both sides of the rotor 30. In this example, two recesses 34a and 34b are provided. However, two recesses are not necessarily provided, and one or more recesses may be provided.

  In this embodiment, the recesses 34a and 34b are provided in an annular shape, but the recesses 34a and 34b may be provided in a C shape instead of in an annular shape.

  Referring to FIG. 3, rotating member 110 may be attached to shaft 34. The rotating member 110 is a gear, a pulley, a finger member, or the like. When the shaft 34 rotates, the rotating member 110 also rotates together with the shaft 34. 3 is the same as that shown in FIG. 1 except that the shape of the connecting member is different from that shown in FIG.

  A shaft 34 is provided so as to penetrate the rotor 30, and the shaft 34 is rotatably supported by the needle bearing 101. The shaft 34 may be rotatably held by a ball bearing or a fluid bearing instead of the needle bearing 101.

  FIG. 1 shows an exploded view of each member of the vibration actuator 10, and FIG. 3 shows a view in which the members of the vibration actuator 10 are assembled. The shaft 34 is pulled downward by the spring force of the disc spring 50 through the needle bearing 101. As a result, the rotor 30 connected to the shaft 34 is also urged downward. As a result, the rotor 30 is pressed against the supply body 41 side.

  Referring to FIG. 4, rolling regions 34 c and 34 d that are in contact with the rolling elements of needle bearing 101 cannot be processed. As a result, a recess is provided between the rolling regions 34 c and 34 d and the rotor 30. The outer diameter D2 of the rotor 30 is larger than the outer diameter D1 of the shaft 34, and the width W1 of the shaft 34 is larger than the width W2 of the rotor 30. The width W1 of the shaft 34 cannot be changed for the convenience of the assembly member. The outer diameter D1 of the shaft 34 is determined by the inner diameter of the bearing.

  Referring to FIGS. 5 and 6, in order to adjust the natural frequency of the rotor 30 and the shaft 34, there are generally two methods of changing the (dimension) and changing the material. However, it is difficult to change the material from the viewpoint of the load and durability of the shaft 34. Therefore, it is necessary to change the dimension (shape) in order to adjust the natural frequency. However, as shown in FIG. 4, there is a region where the shape cannot be changed. Since the rotor 30 and the shaft 34 are bonded, the width W2 and the outer diameter D2 of the rotor 30 are designed to obtain bonding strength. Although it is possible to increase the width W2 and the outer diameter D2, it is not preferable because the rotor 30 needs to be changed. Comparing the dimensional change A shown in FIG. 5 with the dimensional change B shown in FIG. 6, the dimensional change B shown in FIG. 6 is larger than the dimensional change A shown in FIG. Therefore, in the structure shown in FIG. 6, the natural frequency changes more greatly than in the structure shown in FIG.

  Even when the recess is formed only on one side of the rotor 30, the natural frequency of the rotor 30 and the shaft 34 can be changed. However, in this case, since the strength of the shaft 34 of the rotor 30 is different, the rotor may not uniformly contact the vibrator.

  That is, the vibration actuator 10 as an ultrasonic motor is connected to the stator 13, the rotor 30 that is contacted and supported by the stator 13, the shaft 34 that rotatably supports the rotor 30, and the stator 13, and the stator 13 and the rotor. The piezoelectric element 17 as a vibration part that rotates the rotor by applying ultrasonic vibration to the contact portion with the rotor 30, and the rotor 30 and the stator 13 that are connected to the shaft 34 and bias the shaft 34 toward the stator 13. The connecting rod 45, the spring receiver 49, and the disc spring 50 as urging portions that contact the rotor 30 and the needle bearing 101 that rotatably supports the shaft 34 on both sides of the rotor 30 are provided. Recesses 34a and 34b are provided in at least one position of the shaft 34 between To have. The recess is a groove, and recesses 34 a and 34 b are provided on both sides of the rotor 30.

  By adopting such a configuration, the strength of the shaft can be reduced by the recess even when the outer diameter of the shaft 34 is increased. As a result, the shaft 34 can be greatly bent. That is, the amount of deflection can be the same as when the small-diameter shaft 34 is used.

  Furthermore, since the natural frequency of the shaft 34 and the rotor 30 can be shifted from the frequency of the vibration actuator, unnecessary vibration can be suppressed. As a result, a vibration actuator having high durability and capable of generating a large torque can be provided.

(Embodiment 2)
Referring to FIG. 7, a part of the shaft 34 is a cavity 34e. If the shaft 34 has a cylindrical hollow shape, the strength of the shaft 34 can be reduced as compared with the case where the shaft 34 is solid. As a result, the shaft can be greatly bent. Thereby, since the natural frequency of the shaft 34 and the rotor 30 can be shifted from the frequency of the vibration actuator, unnecessary vibration can be suppressed. As a result, a vibration actuator having high durability and capable of generating a large torque can be provided.

  The hollow 34e having a hollow shape may be provided so as to penetrate the shaft 34 in the axial direction, or may be provided so as not to penetrate.

  The vibration actuator 10 as an ultrasonic motor includes a stator 13, a rotor 30 that is contacted and supported by the stator 13, a shaft 34 that rotatably supports the rotor 30, and a stator 13 and the rotor 30 that are coupled to the stator 13. The piezoelectric element 17 serving as a vibrating portion that rotates the rotor by applying ultrasonic vibration to the contact portion of the rotor 30 and the rotor 30 and the stator 13 are connected to the shaft 34 and urge the shaft 34 toward the stator 13. A disc spring 50 as an urging portion to be contacted, and a needle bearing 101 that rotatably supports the shaft 34 on both sides of the rotor 30, and the shaft 34 is provided with a cavity 34 e extending in the axial direction. At least a part of the shaft 34 is cylindrical.

  In the vibration actuator configured as described above, since the shaft is provided with the cavity 34e extending in the axial direction, the drive frequency of the vibration actuator and the frequency of the natural vibration mode of the rotor and the shaft can be shifted. . As a result, a vibration actuator capable of generating a large torque can be provided.

  The present invention is not limited to these exemplifications, but is defined by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

  The present invention can be used in the field of vibration actuators.

  DESCRIPTION OF SYMBOLS 10 Vibration actuator, 11 Base, 12, 42 Screw hole, 13 Stator, 14 Shaft part, 15 Stator main body part, 17 Piezoelectric element, 18, 40 Through-hole, 19 Groove part, 20 Contact part, 21 Contact surface, 22 Through-hole, 30 rotor, 31 outer peripheral surface, 32 rotor end surface, 33 shaft hole, 34 shaft, 34a, 34b recess, 34c, 34d rolling region, 34e cavity, 34y groove, 36 bearing, 37 connecting member, 38 connecting portion, 39 connecting portion , 41 Supply body, 45 Connecting rod, 46 Screw shaft part, 49 Spring receiver, 50 Belleville spring, 101 Needle bearing, 110 Rotating member.

Claims (4)

A stator,
A rotor contacted and supported by the stator;
A shaft coupled to the rotor to be integrally rotatable;
A vibration unit connected to the stator and rotating the rotor by applying ultrasonic vibration to a contact portion between the stator and the rotor;
A bearing rotatably supporting the shaft on both sides of the rotor;
A pressurizing portion coupled to the shaft via the bearing and urging the shaft toward the stator to press-contact the rotor and the stator;
The shaft is a vibration actuator in which a concave portion is provided in at least one portion in a portion between the rotor mounting portion and the shaft receiving mounting portion.   The vibration actuator according to claim 1, wherein the concave portion is provided on both sides of the rotor mounting portion of the shaft.   The vibration actuator according to claim 1, wherein the recess is an annular groove formed along a circumferential direction of the shaft. A stator,
A rotor contacted and supported by the stator;
A shaft coupled to the rotor to be integrally rotatable;
A vibration unit connected to the stator and rotating the rotor by applying ultrasonic vibration to a contact portion between the stator and the rotor;
A bearing rotatably supporting the shaft on both sides of the rotor;
A pressurizing portion coupled to the shaft via the bearing and urging the shaft toward the stator to press-contact the rotor and the stator;
The said shaft is a vibration actuator provided with the cylindrical part by which the cavity extended in the axial direction was provided in at least one part.

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