Vibration motor

Abstract

A vibration motor (101) includes: a vibration element (102); comprises: an elastic element (106) having a planar or rod-like shape and an X-direction being a longitudinal direction; a piezoelectric element (108) disposed on a first surface (112) of the elastic element (106), the first surface (112) having a normal in a Z direction perpendicular to the X direction; and at least two frictional contact elements (110) protruding from a second surface (112) of the resilient element (106), the second surface (112) being opposite the first surface (110); and a movable element (104) pressed against the frictional contact element (110), in which the vibration element (102) is configured to cause the frictional contact element (110) to generate an elliptical vibration on a ZX plane by applying an alternating voltage signal having a predetermined frequency to the piezoelectric element (108), the friction contact element (110) is arranged in such a way that a tensile vibration that stretches and contracts in the X-direction and a bending vibration that deforms in the Z-direction are caused, and the movable element (104) is designed to be moved in the X-direction and in the-X-direction relative to the friction contact element (110) by the elliptical vibration of the friction contact element (110).

Description

Technical Field

[0001] The present invention relates to a vibration motor. Background Art

[0002] A vibration motor generally includes a vibration element that generates an elliptical vibration and a movable element that presses against the vibration element. The movable element is driven by the friction of the vibration element that generates the elliptical vibration as a driving force. The vibration motor has a simple structure and a small external dimension, and can achieve precise and quiet driving. Therefore, the vibration motor is used as a lens driving mechanism for automatic focusing of a camera, a pivot driving mechanism for a camera platform, and a driving motor for OA equipment. Among such vibration motors, there is a vibration motor that generates an elliptical vibration on a driving transmission element by causing two mutually perpendicular bending vibrations (bending vibrations) on the vibration element, and provides a relative movement of a movable element that is in frictional contact with the driving transmission element (for example, see Patent Publication 1).

[0003] Figure 11 A conventional vibration motor 1101 is shown. As Figure 11 shown in (a) thereof, the vibration motor 1101 includes a vibration element 1102 and a movable element 1104. For example, the vibration element 1102 has a planar structure that extends in the XY plane, with the X direction as the longitudinal direction and the Z direction as the thickness direction. For example, the movable element 1104 has a rod-shaped structure with the X direction as the longitudinal direction. The vibration element 1102 includes: an elastic element 1106 made of an elastic material such as metal; a piezoelectric element 1108 provided on a first surface of the elastic element 1106 perpendicular to the Z direction and made of a piezoelectric material such as PZT; at least two friction contact elements 1110, 1112 provided on a second surface of the elastic element 1106 opposite to the first surface and protruding from the second surface. The movable element 1104 is pressed against the friction contact elements 1110, 1112 by a biasing device such as a spring (not shown). As Figure 11 shown in (b) thereof, two electrodes 1114 are provided on the piezoelectric element 1108, and an alternating current voltage signal (AC voltage signal) can be applied to the electrodes 1114. When in-phase AC voltage signals are applied to the electrodes 1114, the piezoelectric element 1108 and the elastic element 1106 are deformed in phase in the Z direction together (mode A), as Figure 11 shown in (c) thereof. When out-of-phase AC voltage signals are applied to the electrodes 1114, parts of the two electrodes provided on the piezoelectric element 1108 and the elastic element 1106 are deformed out of phase in the Z direction (mode B), as Figure 11As shown in (d) thereof. When the in-phase and anti-phase AC voltage signals are superimposed and simultaneously applied to the electrode 1114, the mode A and the mode B are superimposed, causing a swinging vibration at the tips of the friction contact elements 1110 and 1112, so that the friction contact elements 1110 and 1112 generate an elliptical vibration in the ZX plane. The frictional force generated by the elliptical vibration is transmitted to the movable element 1104 pressed against the friction contact elements 1110 and 1112, so that the movable element moves in the X direction.

[0004] When using Figure 11 the vibration element 1102 shown to configure the vibration motor, it is necessary to cause a swinging vibration on the friction contact elements 1110 and 1112 as described above, so as to cause a reciprocating motion of the movable element 1104 in the X direction. Therefore, in order to amplify the vibration in the X direction, it is necessary to provide the friction contact elements 1110 and 1112 with larger dimensions in the Z direction. These dimensions should be half or more of the entire thickness of the vibration element 1102. In other words, due to the presence of the friction contact elements 1110 and 1112, the thickness of the vibration element 1102 should be twice or more of the elastic element 1106. This hinders the minimization of the vibration motor.

[0005] In addition, since the vibration motor uses the vibration of the vibration element as the driving force of the movable element, it is preferable to support the vibration element without hindering the vibration and prevent the vibration from being transmitted to other elements. Therefore, when the vibration motor uses the vibrations in the above-mentioned mode A and mode B, it is preferable to support the vibration element at the portion where the nodes of the vibrations in the mode A and the mode B are superimposed. However, it is difficult to support Figure 11 the planar vibration element shown. Patent Publication 2 provides planar supports 1204 on both sides of the vibration element 1202 as shown in Figure 12 thereof. The planar supports 1204 are not provided at the nodes of the vibration of the vibration element 1202. Therefore, in order not to hinder the vibration and prevent the vibration from being transmitted to other elements, the planar supports 1204 have a complex shape to buffer the vibration. Such a support structure hinders the minimization of the vibration element and limits the implementation of the vibration element in a device including a vibration motor.

[0006] As described above, there are the following problems: The vibration motor causes elliptical vibration on the drive transmission element through two mutually perpendicular bending vibrations of the vibration element, and causes the movement of the movable element relative to the vibration element (wherein, the movable element is in frictional contact with the drive transmission element). In order to provide reciprocating motion in the X direction in this vibration motor, the frictional contact element protrudes, increasing the thickness of the vibration element. In addition, in order not to interfere with the vibration, a support with a complex structure must be adopted. Such a support has the following problems: It hinders the minimization of the vibration element and limits the implementation of the vibration element in the device including the vibration motor (the vibration motor requires more space in this device).

[0007] Patent Publication 1: Japanese Unexamined Patent Application, First Publication No. 2011-234608

[0008] Patent Publication 2: Japanese Unexamined Patent Application, First Publication No. 2013-187974 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] The present invention solves the problem that the vibration motor requires a large space in the device where the vibration motor is installed.

[0011] Means for Solving the Problems

[0012] The present invention provides a movable element that is driven in the longitudinal direction of a vibration element having a substantially rectangular parallelepiped shape, and provides reciprocating motion of the movable element in the longitudinal direction through a vibration mode in which the vibration element stretches and contracts in the longitudinal direction.

[0013] The vibration motor according to the present invention includes:

[0014] A vibration element, the vibration element including:

[0015] An elastic element having a planar or rod-like shape and having the X direction as the longitudinal direction;

[0016] A piezoelectric element provided on the first surface of the elastic element, the first surface having a normal in the Z direction perpendicular to the X direction (the first surface is parallel to the X direction);

[0017] At least two frictional contact elements protruding from the second surface of the elastic element, the second surface being the surface opposite to the first surface in the Z direction, wherein the Z direction is the thickness direction of the elastic element, and the Z direction is perpendicular to the

[0018] X direction;

[0019] A movable element pressing against the frictional contact element,

[0020] Among them, the vibration element is used to cause the friction contact element to generate an elliptical vibration in the ZX plane (in the Z direction and the -X direction) by applying an alternating voltage signal with a predetermined frequency to the piezoelectric element, thereby causing a tensile vibration that stretches and contracts in the X direction and a bending vibration that deforms in the Z direction.

[0021] Among them, the movable element is used to move relative to the friction contact element in a plane in the X direction (the X direction and the -X direction) by means of the elliptical vibration of the friction contact element.

[0022] In the vibration motor of the present invention, the elastic element has a cuboid shape.

[0023] In the vibration motor of the present invention, the tensile vibration is a vibration in the primary tensile vibration mode of the vibration element, and the bending vibration is a vibration in the secondary bending vibration mode of the vibration element.

[0024] In the vibration motor of the present invention, the piezoelectric element has a planar cuboid shape, the piezoelectric element includes two electrodes on a surface opposite to the first surface, the first surface is in contact with the elastic element, and the piezoelectric element is polarized in the Z direction.

[0025] In the vibration motor of the present invention, the friction contact element is provided at or near both ends in the longitudinal direction of the elastic element.

[0026] The vibration motor of the present invention further includes a support element, and the support element is used to support the elastic element at a portion corresponding to both the node of the tensile vibration and the node of the bending vibration of the vibration element.

[0027] In the vibration motor of the present invention, the ratio of the dimension of the elastic element in the Y direction perpendicular to the X direction and the Z direction to the dimension of the elastic element in the Z direction is greater than or equal to 1.5.

[0028] Alternatively, the vibration motor according to the present invention includes:

[0029] A vibration element, the vibration element includes:

[0030] An elastic element having a planar or rod-like shape and the X direction as the longitudinal direction;

[0031] A piezoelectric element provided on a first surface of the elastic element, the first surface having a normal in the Z direction perpendicular to the X direction (the first surface is parallel to the X direction);

[0032] At least two friction contact elements disposed on a second surface of the elastic element and at or near both ends in a longitudinal direction of the elastic element, the second surface being opposite to the first surface in a Z direction, where the Z direction is a thickness direction of the elastic element and the Z direction is perpendicular to the X direction;

[0033] A movable element pressing against the friction contact element,

[0034] wherein the vibrating element is configured to cause the friction contact element to generate an elliptical vibration in a ZX plane (in the Z direction and the -X direction) by applying an alternating voltage signal having a predetermined frequency to the piezoelectric element, thereby causing a tensile vibration that stretches and contracts in the X direction and a bending vibration that deforms in the Z direction.

[0035] wherein the movable element is configured to move relative to the friction contact element in a plane in the X direction (the X direction and the -X direction) by the elliptical vibration of the friction contact element.

[0036] In the vibrating motor of the present invention, the elastic element has a cuboid shape.

[0037] In the vibrating motor of the present invention, the tensile vibration is a vibration in a primary tensile vibration mode of the vibrating element, and the bending vibration is a vibration in a secondary bending vibration mode of the vibrating element.

[0038] In the vibrating motor of the present invention, the piezoelectric element has a planar cuboid shape, the piezoelectric element includes two electrodes on a surface opposite to the first surface, the first surface is in contact with the elastic element, and the piezoelectric element is polarized in the Z direction.

[0039] In the vibrating motor of the present invention, the friction contact element is an edge line of the elastic element, wherein a surface of the elastic element having a normal in the Z direction and a surface of the elastic element having a normal in the X direction are in contact with each other, and the movable element presses against the friction contact element such that the movable element deforms in a convex manner toward the Z direction.

[0040] The vibrating motor of the present invention further includes a support element configured to support the elastic element at a portion corresponding to both a node of the tensile vibration and a node of the bending vibration of the vibrating element.

[0041] In the vibrating motor of the present invention, a ratio of a dimension of the elastic element in a Y direction perpendicular to the X direction and the Z direction to a dimension of the elastic element in the Z direction is greater than or equal to 1.5.

[0042] Advantages of the Invention

[0043] The present invention advantageously provides a vibration motor with a smaller size. This can miniaturize the device on which the vibration motor is installed. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A side view of a vibration motor according to a first embodiment of the present invention is shown.

[0045] Figure 2 A perspective view of a vibration motor according to a first embodiment of the present invention is shown.

[0046] Figure 3 A vibration mode of a vibration motor according to a first embodiment of the present invention is shown.

[0047] Figure 4 A side view of an alternative example of a first embodiment of the present invention is shown.

[0048] Figure 5 A plan view of a mechanism for supporting a vibration motor according to a first embodiment of the present invention is shown.

[0049] Figure 6 A perspective view of a mechanism for supporting a vibration motor according to a first embodiment of the present invention is shown.

[0050] Figure 7 A perspective view of another mechanism for supporting a vibration motor according to a first embodiment of the present invention is shown.

[0051] Figure 8 A plan view of an alternative example of a first embodiment of the present invention is shown.

[0052] Figure 9 A perspective view of a vibration motor according to a second embodiment of the present invention is shown.

[0053] Figure 10 A side view of a vibration motor according to a third embodiment of the present invention is shown.

[0054] Figure 11 A vibration motor according to the prior art is shown.

[0055] Figure 12 A vibration motor according to the prior art is shown. DETAILED DESCRIPTION

[0056] The vibration motor according to the present invention includes a vibration element and a movable element. Among them, the vibration element includes: an elastic element having a planar or rod shape; a piezoelectric element provided on the elastic element; at least two friction contact elements provided on the elastic element, wherein the movable element presses against the friction contact elements. The vibration motor may include a support element for supporting the vibration element. The elastic element can vibrate in two vibration modes by applying an alternating current (AC) voltage signal to the electrodes provided on the piezoelectric element. One of the vibration modes is a tensile vibration mode in which the elastic element stretches and contracts in the longitudinal direction, and the other is a bending vibration mode in which the elastic element bends in a direction perpendicular to the stretching and contracting direction of the tensile vibration mode. By superimposing these two vibration modes with a time phase difference, elliptical vibration can be caused on the friction contact elements provided on the elastic element. The movable element pressing against the friction contact elements moves relative to the vibration element under the action of the frictional force in the longitudinal direction of the vibration element. This makes the space required for the vibration motor in the device where the vibration motor is installed smaller, and minimizes the device in which the vibration motor is installed.

[0057] Embodiment 1

[0058] Figure 1 A side view of a vibration motor 101 including a vibration element 102 and a movable element 104 according to a first embodiment of the present invention is shown. Figure 2 A perspective view of the vibration element 102 is shown. The vibration element 102 includes an elastic element 106, a piezoelectric element 108, and at least two friction contact elements 110. The device for supporting the vibration motor 101 is not shown in Figure 1 it.

[0059] The elastic element 106 has a planar or rod shape, with its longitudinal direction being the X direction and its short direction being the Y direction. In some embodiments, the elastic element 106 may have a cuboid shape. In some embodiments, the elastic element 106 may be made of an elastic material or the like, or may be made of a metal such as stainless steel (SUS).

[0060] The piezoelectric element 108 is disposed on and bonded to the first surface 112 of the elastic element 106, and the first surface 112 has a normal in the Z direction perpendicular to the X direction. The bonding may include bonding using an adhesive and welding using a solder or brazing material, etc., but is not limited to these aspects. In some embodiments, the piezoelectric element 108 may have a planar rectangular parallelepiped shape. The piezoelectric element 108 may include two electrodes 114a, 114b on the surface opposite to the surface on which the elastic element 106 is disposed. An AC voltage signal is applied to the electrodes 114a, 114b respectively. The surface of the piezoelectric element 108 opposite to the surface on which the electrodes 114a, 114b are disposed may be maintained at a ground potential. The piezoelectric element 108 may be polarized in the Z direction. The piezoelectric element 108 may be made of a piezoelectric material such as lead zirconate titanate (PZT).

[0061] At least two friction contact elements 110 may be disposed on the second surface 116 of the elastic element 106 opposite to the first surface 112. The friction contact elements 110 may be disposed at both ends or near both ends of the elastic element 106 in the X direction. For example, the friction contact elements 110 may have a structure protruding from the second surface 116 in the Z direction. The friction contact elements 110 may be, for example, a cylindrical shape having a circular cross-section or a prismatic shape having a polygonal cross-section in the XY plane. Alternatively, the friction contact elements 110 may have a conical or polygonal pyramid shape, or a frustum shape of a cone or a pyramid. Such a configuration can facilitate the formation of the friction contact elements 110 and can increase the frictional force acting between the friction contact elements 110 and the movable element 104.

[0062] Figure 3 The vibration modes of the vibrating element 102 are shown in the case where various types of AC voltage signals are applied to the electrodes 114a, 114b of the piezoelectric element 108. The vibrating element 102 may vibrate in the primary tensile vibration mode shown in (a) of Figure 3 and the secondary bending vibration mode shown in (b) of Figure 3 etc. These vibration modes may have a primary resonance frequency and a secondary resonance frequency respectively.

[0063] When an AC voltage signal at the primary resonance frequency with the same phase and the same voltage is applied to the electrodes 114a, 114b, the vibrating element 102 may alternately stretch and contract in the X direction at the primary resonance frequency (as shown by the dot pattern in (a) of Figure 3 ), and vibrate in the primary tensile vibration mode. The node 302 of the main vibration mode is located at the center of the vibrating element 102, and no displacement caused by vibration occurs at the node 302.

[0064] When AC voltage signals at the secondary resonance frequency that are inverted and have the same voltage are applied to electrodes 114a and 114b respectively, the vibration element 102 can cause a bending motion at the secondary resonance frequency, such that the two ends of the vibration element 102 in the longitudinal direction are displaced relative to each other in the Z direction, as shown in Figure 3 (b) thereof. Such vibration may be a secondary bending vibration mode. The node 302 is also a node of the secondary bending vibration mode.

[0065] The resonance frequency of the primary stretching vibration mode and the resonance frequency of the secondary stretching vibration mode are roughly inversely proportional to the length (dimension in the X direction) of the vibration element 102. The resonance frequency of the primary stretching vibration mode has no obvious relationship with the width (dimension in the Y direction) and thickness (dimension in the Z direction) of the vibration element 102. On the other hand, the resonance frequency of the secondary bending vibration mode has no obvious relationship with the width of the vibration element 102, but is roughly proportional to the thickness of the vibration element 102. Therefore, an appropriate thickness of the vibration element 102 can be selected, and by utilizing the knowledge that these two resonance frequencies change in different ways when the thickness of the vibration element 102 changes, the resonance frequency of the primary stretching vibration mode and the resonance frequency of the secondary bending vibration mode of the vibration element 102 can be made to roughly match. For example, assume that the length, width, and thickness of the piezoelectric element 108 made of PZT are 3 mm, 1 mm, and 0.3 mm respectively, and the length, width, and thickness of the elastic element 106 made of stainless steel are 3 mm, 1 mm, and 0.66 mm respectively. In this case, the resonance frequency of the primary stretching vibration mode and the resonance frequency of the secondary bending vibration mode are both 745 kHz and match each other. These dimensions and resonance frequencies are just one design change. The dimensions and resonance frequencies can be appropriately selected such that the resonance frequency of the primary stretching vibration mode and the resonance frequency of the secondary bending vibration mode match each other at a preferred value in response to characteristics such as the size and material of the vibration motor, and the operating characteristics of the vibration motor and the device to which the vibration motor is mounted.

[0066] By simultaneously causing these two vibration modes with a 90-degree time phase difference, an elliptical vibration of the friction contact element 110 of the vibration element 102 can be caused in the ZX plane. In other words, an in-phase AC voltage signal and an inverted AC voltage signal are applied to electrodes 114a and 114b in a superimposed manner with a 90-degree time phase difference. These AC voltage signals cause, in a superimposed manner with a 90-degree time phase difference, Figure 3 the vibration in the primary stretching vibration mode that causes the friction contact element 110 to vibrate roughly in the X direction as shown in (a) of Figure 3 (b) thereof, and the vibration in the secondary bending vibration mode that causes the friction contact element 110 to vibrate roughly in the Z direction as shown in (b) of

[0067] The movable element 104 pressed against the frictional contact element 110 that causes elliptical vibration moves in the X direction by the frictional force applied from the frictional contact element 110, and thus transmits the driving force to the outside through an output transmission member (not shown) connected to the movable element 104. The tensile vibration mode in the vibration mode of the vibration element 102 of the vibration motor of the present invention contributes to the movement of the movable element 104. Therefore, the frictional contact element 110 does not need to have a function of amplifying vibration as in the Figure 11 conventional vibration motor shown. The purpose of the protruding structure of the frictional contact element 110 is to limit the transmission of the driving force caused by the elliptical vibration to the portion in contact with the movable element 104. Since there is no need for a function of amplifying vibration, as long as contact between the movable element 104 and the elastic element 106 can be avoided, the length of the frictional contact element 110 in the Z direction can be minimized. In other words, the increase in the thickness of the vibration element 102 caused by the frictional contact element 110 is minimized.

[0068] Alternatively, when an in-phase AC voltage signal and an anti-phase AC voltage signal are applied in a superimposed manner such that the time phase difference is -90 degrees, the rotation direction of the elliptical vibration is reversed. Therefore, the movable element 104 can move in the -X direction. In this way, the reciprocating movement of the movable element 104 in the X direction can be achieved. For example, in the Figure 4 embodiment where the movable element 104 is fixed and the vibration element 102 moves relative to the movable element 104 as shown, the vibration element 102 moves in the longitudinal direction of the vibration element 102 having a substantially rectangular parallelepiped shape. Therefore, as shown in Figure 4 the small area enclosed by the dashed line in the figure is the space required for the vibration motor 101 of the present application, including the space through which the vibration element 102 passes. In addition, the vibration element is thin and small, and the vibration motor of the present invention occupies a small space in the device, so that the miniaturization of the device can be achieved.

[0069] Next, a method for supporting the vibration element of the present invention is discussed. The support of the vibration element preferably does not impede the vibration in the vibration mode for driving, and preferably has stiffness in the driving direction such that the position of the vibration element does not change due to the reaction force of the driving force. The node in the vibration mode for driving the driving force is generally considered a method that does not impede vibration. However, many vibration motors utilize multiple vibration modes, such as the vibration motor 101 of the present invention. Therefore, the position for supporting the vibration element is preferably the node of any vibration mode among the multiple vibration modes.

[0070] In the present invention, the nodes of the primary tensile vibration mode and the secondary bending vibration mode of the vibration element 102 coincide with Figure 3The node 302 shown is matched. Therefore, the vibration element 102 of the present invention is preferably supported at the node 302.

[0071] Figure 5 A plan view showing a method for supporting Figures 1 to 4 the vibration motor 101 shown. Figure 6 A perspective view showing a method for supporting Figures 1 to 4 the vibration motor 101 shown. The support element 502 for supporting the vibration element 102 includes a base 504 and at least two support arms 506 having a rod-like shape and extending from the base 504. Support members 508 are provided at the ends of each support arm 506 and extend perpendicularly from the support arms 506. The support members 508 contact the fixing points 510, 512 of the third surface 514 and the fourth surface 516 of the vibration element 102. Each of the third surface 514 and the fourth surface 516 has a normal in the Y direction. The fixing points 510, 512 correspond to the nodes 302 of the primary tensile vibration mode and the secondary bending vibration mode of the vibration element 102. For example, the support element 502 has a thin plate shape and is made of phosphor bronze. The base 504, the support arms 506, and the support members 508 of the support element 502 can extend in the XY plane. Therefore, the support element 502 is easy to be made from a single plate. Two holes 518 for fixing can be provided in the base 504. For example, screws are inserted into the holes 518 for fixing, and the base 504 can be connected to a fixing member (not shown) to fix and support the vibration element 102.

[0072] The support members 508 can be connected to the vibration element 102 at the fixing points 510, 512. For example, joints can be installed by bonding using an adhesive or welding using solder or brazing material, but are not limited to these solutions. Since the fixing points 510, 512 correspond to the nodes of the primary tensile vibration mode and the secondary bending vibration mode of the vibration element 102, the support members 508 do not interfere with the vibration mode of the vibration element 102. Alternatively, without using bonding or welding, the vibration element 102 can be supported mechanically. For example, pits can be provided at the fixing points 501, 512, and the distance between the two support members 508 can be less than the distance between the bottoms of the pits at the fixing points 510, 512. In this case, the support members 508 can be assembled in the pits and the vibration element 102 can be fixed and supported mechanically. Therefore, the vibration motor 101 is easy to assemble. In addition, Figure 5 and Figure 6 the configuration shown has the advantage of not increasing the thickness (dimension in the Z direction) of the vibration motor.

[0073] Figure 7 A view showing a method for supporting Figures 1 to 4Perspective view of another method of the vibration motor 101 shown. The support element 702 includes a base 704 and at least two support arms 706 having a rod-like shape and extending from the base 704. A support member 708 is provided at the end of each support arm 706 and extends perpendicularly from the support arm 706. The support element 702 is different from Figure 5 and Figure 6 the support element 502 shown in that the support arms 706 extend from the base 704 in the Z direction. The vibration element 102 is supported by the support member 708 in a manner similar to that of the support element 502 discussed with reference to Figure 5 and Figure 6 ; thus, the support method is not explained in detail.

[0074] Since Figure 7 the base 704 of the support element 702 shown is located below the vibration element 102 in the Z direction, it is advantageous that, although the size in the Z direction is large, the projected area of the vibration motor 101 on the XY plane becomes smaller.

[0075] As described above, the support element can be connected to the portion of the vibration element corresponding to the nodes of the primary tensile vibration mode and the secondary bending vibration mode. The shape of the support element can be selected according to the device implementing the vibration motor of the present invention.

[0076] The vibration motor 101 of the present invention simultaneously induces a primary tensile vibration mode and a secondary bending vibration mode with a time phase difference, thereby inducing elliptical vibration in the bending direction (in other words, the thickness direction) of the vibration motor 101 on the friction contact element 110. The friction contact element 110 is provided at or near the end of the elastic element 106. In the primary tensile vibration mode, the vibration element 102 stretches and contracts in the longitudinal direction. In the secondary bending vibration mode, the vibration element 102 bends in a direction perpendicular to the stretching direction of the primary tensile vibration mode. The movable element 104 pressing against the friction contact element 110 moves in the longitudinal direction relative to the vibration element 102 under the action of the frictional force caused by the elliptical vibration of the friction contact element 110. This makes the vibration element thin and small. In addition, this makes the space required for the vibration motor in the device on which the vibration motor is installed smaller and minimizes the device on which the vibration motor is installed.

[0077] In Figures 1 to 4 the embodiment shown, the polarization of the piezoelectric element 108 is the same in the Z direction over the entire surface. In addition, the electrode division pattern provides two electrodes 114a, 114b, as shown in Figure 1 and Figure 2As shown. Therefore, the vibration motor 101 causes vibrations in the primary tensile vibration mode and the secondary bending vibration mode by applying an AC voltage signal that induces the primary tensile vibration mode and the secondary bending vibration mode to the electrodes 114a and 114b in a superimposed manner. However, the polarization pattern of the piezoelectric element, the electrode division pattern, and the method of applying the AC voltage signal are not limited to these aspects, and vibrations in the primary tensile vibration mode and the secondary bending vibration mode can be caused simultaneously.

[0078] Figure 8 The piezoelectric element 808 of the vibration motor 801 having five electrodes according to another embodiment is shown. The polarization of the piezoelectric element 808 in the thickness direction in the regions of the electrodes 814a to 814c is opposite to the polarization of the piezoelectric element 808 in the thickness direction in the regions of the electrodes 814d and 814e. When an AC voltage signal is applied to the terminal Va, tensile vibrations are generated in phase in the X direction of the entire piezoelectric element 808, causing vibrations in the primary tensile vibration mode. When an AC voltage signal is applied to the terminal Vb, tensile vibrations having a phase opposite to the tensile vibrations induced in the regions of the electrodes 814d and 814e are generated in the regions of the electrodes 814b and 814c, causing vibrations in the secondary bending vibration mode. In other embodiments, stacked piezoelectric elements can produce similar effects. Any electrode pattern, polarization pattern of the piezoelectric element, and method of applying the AC voltage signal can be adopted as long as vibrations in the primary tensile vibration mode and the secondary bending vibration mode can be caused simultaneously.

[0079] In addition, the tensile vibration mode and the bending vibration mode may not be limited to the primary vibration and the secondary vibration respectively. Any other order vibration mode can be adopted as long as elliptical vibrations can be caused in the ZX plane.

[0080] In addition, the shape of the elastic element 106 may not be limited to a rectangular parallelepiped shape. The elastic element 106 may have a shape that causes the tensile vibration to cause stretching and contraction in the X direction and causes displacement in the Z direction for the bending vibration. For example, the elastic element 106 may have an octagonal cross-section obtained by cutting the edges of a rectangular parallelepiped shape into bevels.

[0081] Embodiment 2

[0082] Figure 9 A perspective view of the vibration element 902 of the vibration motor 901 according to the second embodiment of the present invention is shown. Figure 9 (a) therein shows the vibration element 902 with a piezoelectric element 108 provided on the side. Figure 9 (b) therein shows the vibration element 902 with a friction contact element 110 provided on the side. Figure 1 and Figure 2In the vibration motor 101 of the first embodiment shown, the same reference numerals denote the same components. Components not shown are also provided, similar to the vibration motor 101 of the first embodiment. Although the size (in other words, the width) of the vibration element 902 in the Y direction of the second embodiment is larger than the width of the vibration element 102 of the first embodiment, other configurations are similar to those of the first embodiment. Although in the first embodiment, the width of the vibration element 102 is substantially the same as the thickness (the size in the Z direction) of the vibration element 102, in the second embodiment, the ratio of the width to the thickness is about 3.

[0083] Generally speaking, the larger the volume of the vibration element, the greater the vibration energy of the vibration element, and the output power of the vibration motor can be increased. The larger vibration energy of the vibration element provides the following advantages: the vibration element is less affected by disturbances and is easy to control.

[0084] As discussed in the first embodiment, the resonance frequencies of the primary tensile vibration mode and the secondary bending vibration mode have no obvious relationship with the width of the vibration element. Therefore, even if the width of the vibration element 902 in the second embodiment is larger than the thickness, the vibration element 902 can be designed such that the resonance frequencies of the two vibration modes match each other. As discussed in the first embodiment, an elliptical vibration can be generated in this way. As long as the layout of the device on which the vibration motor is installed permits, the volume of the vibration element 902 can be increased by increasing the width. Therefore, a vibration motor with a larger output power, less affected by disturbances, and easy to control can be obtained.

[0085] In Figure 9 In the second embodiment shown, the ratio of the width to the thickness is about 3, but this value is not limited thereto. For example, a ratio greater than or equal to 1.5 is advantageous because a larger output power can be obtained.

[0086] Embodiment 3

[0087] Figure 10 A side view of a vibration motor 1001 according to a third embodiment of the present invention is shown. The same reference numerals as those Figure 1 and Figure 2 shown in the vibration motor 101 of the first embodiment denote the same components. Differences from the first embodiment are discussed below.

[0088] The configuration of the vibration element 102 does not correspond to the protruding friction contact element 110 of the first embodiment. Since the movable element 1004 presses against the elastic element 106, the movable element 1004 deforms and bends in a convex manner in the Z direction. The movable element 1004 contacts the end of the elastic element 106 in the X direction. Therefore, the edge between the end of the elastic element 106 in the X direction, or more specifically, the surface of the elastic element 106 having a normal in the Z direction and the surface of the elastic element 106 having a normal in the X direction serves as the friction contact element 1010.

[0089] In the vibration motor 1001 having such a configuration, when the AC voltage signal described in the first embodiment is applied to the electrodes 114a, 114b of the piezoelectric element 108, an elliptical vibration of the friction contact element 1010 is generated in the ZX plane. Therefore, the movable element 1004 pressed against the friction contact element 1010 moves in the X direction relative to the vibration element 102 under the action of the frictional force. Therefore, even if the friction contact element does not have a protruding structure, the end of the vibration element in the longitudinal direction can be used as the friction contact element, which can make the manufacturing of the vibration element easier.

[0090] As referred to Figures 1 to 10 As discussed, the vibration motor of the present invention does not require a large space in the device in which the vibration motor is installed, so the device can be miniaturized. Therefore, the vibration motor of the present invention can be used in small portable devices.

[0091] Although the embodiments of the present invention have been described by way of example, those skilled in the art can easily understand that various modifications and changes can be made without departing from the spirit and scope of the present invention.

[0092] Mark

[0093] 101: Vibration motor

[0094] 102: Vibration element

[0095] 104: Movable element

[0096] 106: Elastic element

[0097] 108: Piezoelectric element

[0098] 110: Friction contact element

[0099] 112: First surface

[0100] 114a, 114b: Electrodes

[0101] 116: Second surface

[0102] 302: Node

[0103] 502: Support element

[0104] 504: Base

[0105] 506: Support arm

[0106] 508: Support member

[0107] 510, 512: Fixing points

[0108] 514: Third surface

[0109] 516: Fourth surface

[0110] 518: Hole for fixing

[0111] 702: Support element

[0112] 704: Base

[0113] 706: Support arm

[0114] 708: Support member

[0115] 801: Vibration motor

[0116] 808: Piezoelectric element

[0117] 814a to 814e: Electrodes

[0118] 901: Vibration motor

[0119] 902: Vibration element

[0120] 1001: Vibration motor

[0121] 1004: Moving element

[0122] 1010: Friction contact element

[0123] 1101: Vibration motor

[0124] 1102: Vibration element

[0125] 1104: Moving element

[0126] 1106: Elastic element

[0127] 1108: Piezoelectric element

[0128] 1110, 1112: Friction contact elements

[0129] 1114: Electrodes

[0130] 1202: Vibration element

[0131] 1204: Planar support

Claims

1. A vibration motor, characterized in that, comprising: a vibration element, the vibration element comprising: an elastic element having a planar or rod-like shape with the X direction as the longitudinal direction; a piezoelectric element provided on a first surface of the elastic element, the first surface being parallel to the X direction; at least two friction contact elements protruding from a second surface of the elastic element, the second surface being a surface opposite to the first surface in the Z direction, wherein the Z direction is the thickness direction of the elastic element and the Z direction is perpendicular to the X direction; a movable element pressing against the friction contact elements, wherein the vibration element is configured to cause the friction contact elements to generate a tensile vibration that stretches and contracts in the X direction and a bending vibration that deforms in the Z direction by applying an alternating voltage signal having a predetermined frequency to the piezoelectric element, wherein the movable element is configured to move relative to the friction contact elements on a plane in the X direction by the vibration of the friction contact elements.

2. The vibration motor according to claim 1, characterized in that, the elastic element has a cuboid shape.

3. The vibration motor according to claim 1 or 2, characterized in that, the tensile vibration is a vibration in a primary tensile vibration mode of the vibration element, the bending vibration is a vibration in a secondary bending vibration mode of the vibration element.

4. The vibration motor according to any one of claims 1 to 3, characterized in that, the piezoelectric element has a planar cuboid shape, the piezoelectric element includes two electrodes on a surface opposite to the first surface, the first surface being in contact with the elastic element, the piezoelectric element is polarized in the Z direction.

5. The vibration motor according to any one of claims 1 to 4, characterized in that, the friction contact elements are provided at or near both ends of the elastic element in the longitudinal direction.

6. The vibration motor according to any one of claims 1 to 5, characterized in that, further comprising a support element configured to support the elastic element at a portion corresponding to both a node of the tensile vibration and a node of the bending vibration of the vibration element.

7. The vibration motor according to any one of claims 1 to 6, characterized in that, a ratio of a dimension of the elastic element in a Y direction perpendicular to the X direction and the Z direction to a dimension of the elastic element in the Z direction is greater than or equal to 1.5.

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