JP5573121B2 - Vibration actuator, lens barrel and camera - Google Patents

Description

  The present invention relates to a vibration actuator, a lens barrel, and a camera.

  There is a vibration actuator that vibrates a vibrator using an electromechanical conversion element such as a piezoelectric element and frictionally drives a relative movement member by the vibration. Conventionally, as the relative movement member, a member having low rigidity such as aluminum is used from the viewpoint of cost and workability. As the vibrator, generally, a highly elastic material, for example, a metal material such as iron or stainless steel is used (see, for example, Patent Document 1).

Japanese Patent Publication No. 1-17354

  However, since aluminum has low rigidity, it is necessary to take measures against friction and wear. In addition, the relative movement member made of aluminum and the vibrator may resonate and drive sound may be generated.

  An object of the present invention is to provide a vibration actuator that has low wear and low driving noise.

The present invention solves the above problems by the following means .

According to the first aspect of the present invention, there is provided a vibrator having a base portion and a tip portion, which is supported by a base portion, and a pair of first electromechanical conversions that drive the base portion in a second direction. An element, a rotationally moving member that rotates and moves along a first direction intersecting the second direction when the transducer is in pressure contact with the tip portion and the vibrator vibrates, and is inserted into the base portion. A support shaft that is provided along a rotation axis of the rotation moving member and supports the rotation movement member, wherein the vibrator includes the pair of first electromechanical transducer elements in the first direction. The base portion is sandwiched along the base portion and is supported by the base portion along the first direction. The density of the rotationally moving member is smaller than that of the vibrator. The Young's modulus is larger than the vibrator. Is a vibration actuator to be.
A second aspect of the present invention is the vibration actuator according to the first aspect, wherein the rotationally moving member is made of ceramic.
The invention according to claim 3 is the vibration actuator according to claim 1 or 2, wherein the vibrator is made of metal.
Invention of Claim 4 is a vibration actuator of any one of Claim 1 to 3, Comprising: The axial maximum thickness of the said rotational movement member is the maximum of the radial direction of the said relative rotational movement member. The vibration actuator is characterized by being larger than the radius.
A fifth aspect of the present invention is the vibration actuator according to the fourth aspect, wherein the rotationally moving member has a rectangular cross-sectional shape parallel to the axis and passing through the axis. Actuator.
Invention of Claim 6 is a vibration actuator of Claim 4, Comprising: The cross-sectional shape which passes along the said axis | shaft in the said rotational movement member is an octagon, The vibration characterized by the above-mentioned. Actuator.
A seventh aspect of the present invention is the vibration actuator according to the fourth aspect of the present invention, wherein a cross-sectional shape that is parallel to and passes through the axis of the rotationally moving member is substantially circular. Actuator.
The invention according to claim 8 is the vibration actuator according to claim 4, wherein the second electric machine is configured to vibrate the tip portion along the first direction between the base portion and the tip portion. The vibration actuator further includes a conversion element.
A ninth aspect of the present invention is a lens barrel including the vibration actuator according to any one of the first to eighth aspects.
A tenth aspect of the present invention is a camera comprising the vibration actuator according to any one of the first to eighth aspects .

  ADVANTAGE OF THE INVENTION According to this invention, a vibration actuator with little abrasion and a small driving sound can be provided.

1 is a conceptual diagram of a lens barrel including a piezoelectric motor according to an embodiment of the present invention and a camera equipped with the lens barrel. It is a front view of a piezoelectric motor. It is sectional drawing of a piezoelectric motor. It is another form of a rotor part, Comprising: (a) shows the case where the cross section containing an axial hole is an octagon, (b) shows the case where the cross section containing an axial hole is substantially circular.

Hereinafter, a piezoelectric motor 100 according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram of a camera 200 to which a lens barrel 300 including a piezoelectric motor 100 according to this embodiment is attached.
The camera 200 includes a camera body 201 having an image sensor 202, and the lens barrel 300 is an interchangeable lens that can be attached to and detached from the camera body 201. In the present embodiment, the lens barrel 300 is an interchangeable lens. However, the present invention is not limited to this. For example, the lens barrel 300 may be a lens barrel integrated with the camera body.

The lens barrel 300 includes a focusing lens 301, a cam barrel 302, a piezoelectric motor 100, a casing 303 surrounding these, and the like.
The piezoelectric motor 100 is disposed in an annular gap between the cam cylinder 302 and the housing 303. In the piezoelectric motor 100, the gear 125 of the rotor portion 120 is disposed in mesh with a gear formed on the outer periphery of the cam cylinder 302, and rotates the cam cylinder 302. Thereby, the focusing lens 301 is driven during the focusing operation of the camera 200.

The cam cylinder 302 is provided in the housing 303 so as to be movable in a direction parallel to the optical axis OA by a rotation operation by the piezoelectric motor 100.
Focusing lens 301 is held by cam barrel 302. The focus is adjusted by moving in the direction of the optical axis OA by the movement of the cam barrel 302 by driving the piezoelectric motor 100.
Although not shown, the lens barrel 300 includes a plurality of lens groups in addition to the focusing lens 301.

  In the camera 200, a subject image is formed on the imaging surface of the imaging element 202 by a lens group including a focusing lens 301 provided in the lens barrel 300. The imaged subject image is converted into an electrical signal by the image sensor 202, and image data is obtained by A / D converting the signal.

Next, the piezoelectric motor 100 will be described. FIG. 2 is a front view of the piezoelectric motor 100. FIG. 3 is a cross-sectional view of the piezoelectric motor 100.
The piezoelectric motor 100 includes a base member 110, a rotor part 120 disposed adjacent to the base member 110, and a support driving part 130 configured on the side of the base member 110 facing the rotor part 120. .

The base member 110 is formed in a hollow cylindrical shape with a metal material such as stainless steel, for example, and a support shaft 115 is inserted and fixed along the central axis C.
At the end of the base member 110 facing the rotor portion 120, there are a plurality of holding recesses 111 for housing the drive mechanism 30 in the support drive portion 130 in the circumferential direction of the base member 110 (that is, the rotational direction of the rotor portion 120) (6 Are provided). The holding recess 111 is formed by passing a thick portion of the annular base member 110 in the radial direction.

  The rotor unit 120 is rotatably supported by a support shaft 115 via a bearing 116 and is disposed on a support driving unit 130. The shape of the rotor part will be described later.

The support drive unit 130 includes six sets of drive mechanisms 30 at equal intervals in the circumferential direction (that is, 60 ° intervals) (only two are shown in FIG. 2).
The drive mechanism 30 includes a lift direction vibrator 31 and a slide direction vibrator 32. Further, a lift piezoelectric body 33 disposed between the lift direction vibrator 31 and the base member 10 and a slide piezoelectric body 34 disposed between the lift direction vibrator 31 and the slide direction vibrator 32 are provided. I have.

  The lift direction vibrator 31 has a rectangular parallelepiped shape and is formed of a light metal such as an aluminum alloy, but is not limited to this, and may be a metal material such as iron or stainless steel. The lift direction vibrator 31 is accommodated in the holding recess 11 in the base member 10. The upper surface protrudes a predetermined amount above the upper surface of the base member 10. The lift piezoelectric body 33 is disposed between the outer surface of the lift direction vibrator 31 before and after the rotation R direction around the central axis C and the inner wall surface of the holding recess 11 before and after the X axis direction. .

  The front and rear lift piezoelectric bodies 33 are formed by a piezoelectric element such as lead zirconate titanate (PZT) into a thin rectangular plate having a predetermined aspect ratio and thickness, and have a piezoelectric effect. The vibration mode is thickness shear vibration, and is formed so as to utilize deformation in the longitudinal direction.

  Each lift piezoelectric element 33 is adhered to the outer surface of the lift direction vibrator 31 with a conductive adhesive, and is adhered to the inner wall surface of the holding recess 11 with an insulating adhesive, with the vibration direction being centered. A direction along the axis C is provided. Each lift piezoelectric body 33 may be bonded to the outer surface of the lift direction vibrator 31 using a non-conductive adhesive. In that case, the lift piezoelectric body 33 and the lift direction vibrator 31 may be bonded so as to provide a portion where the outer surfaces are in direct contact with each other.

  The slide direction vibrator 32 is formed in a hexagonal column shape with a cross section made of stainless alloy steel or the like, and is disposed on the upper surface of the lift direction vibrator 31 via a slide piezoelectric body 34. The upper surface of the sliding direction vibrator 32 is a flat driving surface 32 </ b> A corresponding to the driven surface 121 of the rotor unit 120.

  Like the lift piezoelectric body 33, the slide piezoelectric body 34 is a thin plate-like piezoelectric element having a predetermined aspect ratio and a predetermined thickness, and is provided with a vibration direction as an R direction.

  A drive voltage is applied to each of the lift piezoelectric body 33 and the slide piezoelectric body 34 from a drive circuit controlled by a control device (not shown), and the lift direction vibrator 31 is connected to the ground. The lift piezoelectric body 33 is vibrated by this drive voltage to drive the lift direction vibrator 31 up and down and to drive the slide direction vibrator 32 back and forth.

  That is, the lift piezoelectric body 33 drives the lift direction vibrator 31 to move with a predetermined stroke in the direction along the central axis C with respect to the holding recess 11 by deformation vibration of the piezoelectric element caused by voltage application. Also, the slide piezoelectric body 34 moves the slide direction vibrator 32 with a predetermined stroke in the R direction with respect to the lift direction vibrator 31 (that is, with respect to the base member 10) by deformation vibration of the piezoelectric element due to application of voltage. Move and drive.

  In the piezoelectric motor 100 configured as described above, a drive voltage is applied at a predetermined phase to the lift piezoelectric body 33 and the slide piezoelectric body 34 from the drive device controlled by the control device, and the drive mechanism 30 operates. Then, the rotor unit 120 is rotated in the R direction.

  The six sets of drive mechanisms 30 form groups (first group G1 and second group G2) with three sets of one set (alternate). A drive voltage of the same phase is applied from the power supply unit to the lift piezoelectric body 33 in the drive mechanism 30 constituting each group G1, G2. In addition, a driving voltage having the same phase is applied from the power supply unit to the sliding piezoelectric body 34 in the driving mechanism 30 constituting each of the groups G1 and G2.

  Each drive mechanism 30 is driven such that the slide direction vibrator 32 moves substantially circularly about the central axis C of the base member 110. The drive mechanisms 30 constituting the same group (G1 or G2) operate in the same phase, and the drive mechanisms 30 constituting the group G1 or group G2 operate in different phases. Thereby, the drive mechanism 30 which comprises the group G1 or the group G2 supports the rotor part 120 alternately in a rotating shaft direction, and drives it relatively with respect to the base member 110. FIG. As a result, the support driving unit 130 continuously drives the rotor unit 120 to rotate in the R direction.

  Next, the rotor unit 120 will be described in detail. As shown in FIG. 3, the rotor portion 120 has a substantially rectangular cross section including the support shaft 115, and a gear 125 is formed on the outer peripheral surface. The maximum axial thickness of the rotor portion 120 is larger than the maximum radial radius of the rotor portion 120.

Moreover, the rotor part 120 is solid (the state where the contents are packed), and its material is, for example, a density of 3.6 to 4.0 g / cm ³ and a Young's modulus of 230 to 410 × 10 ⁹ N / m ^2. It is a lightweight and hard ceramic such as alumina. This density is smaller than the sliding direction vibrator 32 made of stainless steel or the like, and the Young's modulus is larger than the sliding direction vibrator 32. Since the rotor part 120 is such a material and shape, it has high rigidity and is not easily worn.

Thus, when a hard ceramic is used for the rotor part 120, it has the following effects.
(1) When the rotor unit 120 is made of a soft material, the driven surface is shaved when frictionally driven with the sliding direction vibrator 32. However, in this embodiment, since the rotor part 120 is a hard ceramic, the wear of the rotor part 120 is reduced and the durability is improved.

(2) Further, the frequency of the primary resonance mode of the rotor unit 120 made of ceramic or the like is sufficiently higher than the drive frequency of the sliding direction vibrator 32 made of stainless steel or the like. For this reason, resonance between the sliding direction vibrator 32 and the rotor unit 120 can be avoided, and it can behave as a rigid body, and generation of sound can be reduced.

(3) The driven surface 121 of the rotor part 120 and the driving surface 32A of the sliding direction vibrator 32 are in pressure contact. If the rigidity of the rotor part 120 is small, the rotor part 120 is deformed by this pressure. Wake up and abnormal noise is generated by this deformation. However, since the rotor part 120 of this embodiment has high rigidity, there is little deformation of the rotor part 120 and the possibility of occurrence of abnormal noise is small.

(4) The rotor unit 120 is ceramic and non-conductive. Therefore, even when the drive mechanism 30 (sliding direction vibrator 32) has the role of an electrode, it can be used.
(5) Since the rotor part 120 is lightweight, inertia force is small. For this reason, it is easy to operate and the efficiency of control increases.

(Deformation)
The present invention is not limited to the above-described embodiment, and various modifications and changes as described below are possible, and these are also within the scope of the present invention.
(1) FIG. 4 shows another form of the rotor part 120. FIG. 4 (a) shows an octagonal rotor part 120A including a shaft hole 115A through which the support shaft 115 passes, and FIG. A rotor portion 120B having a substantially circular cross section including the hole 115B is shown. In these figures, gears are omitted. As shown in the figure, the rotor portion is not limited to a rectangle, but may be a pentagon or more polygon or a circle. However, when the rotor section 120 having a rectangular cross section as described in the embodiment and the rotor sections 120A and 120B having other shapes in FIG. 3 are compared, the rotor section 120 having a rectangular cross section has the same cross section. However, it is preferable because the moment of inertia of the cross section becomes large. When the cross-sectional shape is the same, the cross-sectional secondary moment increases as the cross-sectional area increases.
(2) The material of the rotor part 120 is not limited to alumina, for example, silicon carbide having a specific gravity of 3.1 to 3.2 g / cm ³ and a Young's modulus of 340 to 410 × 10 ⁹ N / m ^2. Also good.
(3) In the above-described embodiment, the piezoelectric motor 100 including the plurality of drive mechanisms 30 each having the lift direction vibrator 31 and the slide direction vibrator 32 has been described. However, the present invention is not limited to this, and the piezoelectric element. The present invention may be applied to a piezoelectric motor in which a relative movement member is driven by elliptical vibration of an elastic body excited by.
(4) In the above-described embodiment, the solid rotor portion has been described. However, the present invention is not limited to this, and may be hollow as long as the Young's modulus is large.
In addition, although embodiment and a deformation | transformation form can also be used in combination as appropriate, detailed description is abbreviate | omitted. Further, the present invention is not limited to the embodiment described above.

  32: Slide direction vibrator, 33: Piezoelectric body for lift, 34: Piezoelectric body for slide, 100: Piezoelectric motor, 115: Support shaft, 120: Rotor part, 200: Camera, 300: Lens barrel

Claims (10)

A vibrator having a base portion and a tip portion, supported by the base portion;
A pair of first electromechanical transducers for driving the base along a second direction;
A rotationally moving member that rotates and moves along a first direction intersecting the second direction by pressurizing and contacting the tip, and the vibrator vibrates;
A support shaft that is inserted through the base portion and provided along the rotation axis of the rotation moving member, and supports the rotation movement member;
The vibrator is supported by the base portion with the pair of first electromechanical transducers sandwiching the base portion along the first direction, and is also supported by the base portion along the first direction. Arranged,
A vibration actuator, wherein the density of the rotationally moving member is smaller than that of the vibrator, and the Young's modulus of the rotationally moving member is larger than that of the vibrator. The vibration actuator according to claim 1,
The vibration actuator, wherein the rotationally moving member is made of ceramic. The vibration actuator according to claim 1 or 2,
A vibration actuator, wherein the vibrator is made of metal. The vibration actuator according to any one of claims 1 to 3 ,
Axial direction of maximum thickness before Symbol rotary moving member, vibration actuator, wherein, larger than the maximum radius of the radial direction of the relative rotational movement member. The vibration actuator according to claim 4,
The vibration actuator according to claim 1, wherein a cross-sectional shape of the rotary moving member parallel to the axis and passing through the axis is a rectangle. The vibration actuator according to claim 4,
A vibration actuator characterized in that a cross-sectional shape passing through and passing through the axis of the rotationally moving member is an octagon. The vibration actuator according to claim 4,
A vibration actuator characterized in that a cross-sectional shape parallel to and passing through the axis of the rotationally moving member is substantially circular. The vibration actuator according to claim 4,
A vibration actuator, further comprising: a second electromechanical transducer that vibrates the tip along the first direction between the base and the tip. A lens barrel, characterized in that, with a vibration actuator according to any one of claims 1 to 8. Providing the vibration actuator according to any one of claims 1 to 8, a camera according to claim.

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