JP4477915B2 - Ultrasonic motor - Google Patents

Description

  The present invention relates to an ultrasonic motor having a novel structure.

  As a resonance type ultrasonic motor, as shown in FIG. 7, piezoelectric elements 101a and 101b that generate expansion / contraction displacement are arranged so as to be orthogonal to each other via a head 102, and the piezoelectric elements 101a and 101b are connected with alternating voltages having different phases. An ultrasonic motor 100 that causes elliptical motion in the head 102 by driving is known (see, for example, Patent Document 1). By pressing the head 102 against the side surface of the rotatable rotor 103, the rotor 103 can be rotated and can be stopped at a predetermined position rotated by a predetermined angle.

However, even if the piezoelectric elements 101a and 101b are driven by applying a voltage having a predetermined frequency in the resonance frequency band to drive the piezoelectric elements 101a and 101b and then the voltage application to the piezoelectric elements 101a and 101b is finished, the head 102 The rotor 103 is positioned with high accuracy (for example, nanometers) because the head 102 pushes the rotor 103 because the elliptical motion continues due to inertia or the drive voltage falls for a very short time. Positioning by order) is difficult.
JP 2001-16879 A

  The present invention has been made in view of such circumstances, and an object thereof is to provide a new ultrasonic motor that enables highly accurate positioning.

According to a first aspect of the present invention, a substantially columnar structure including one or more ultrasonic vibration parts;
A plurality of friction sliding portions provided so as to be in contact with the driven body at a predetermined position on a side surface of the structure;
Comprising
The ultrasonic vibration unit generates a flexural vibration in the structure so that an elliptical motion out of phase is generated in the plurality of friction sliding units by continuously changing the direction of the flexure. There is provided an ultrasonic motor, wherein the driven body is moved in a direction perpendicular to the longitudinal direction of the structure.

  In the ultrasonic motor according to the first aspect, two piezoelectric elements are provided as the ultrasonic vibration section at symmetrical positions with respect to the center in the longitudinal direction of the structure, and the two piezoelectric elements are respectively arranged in the longitudinal direction of the structure. It has three drive parts that can be expanded and contracted independently in the direction and have substantially the same shape, and each drive part of the two piezoelectric elements is bent by the expansion and contraction of each drive part of each piezoelectric element. It is preferable that the phase is shifted by 120 degrees so that a large deflection is generated in the structure by combining the two.

According to a second aspect of the present invention, a substantially columnar structure provided with two or more ultrasonic vibration parts;
A plurality of friction sliding portions provided so as to come into contact with the driven body at a predetermined position on a side surface of the structure;
Comprising
The two or more ultrasonic vibration parts respectively generate two or more flexural vibrations that cause the structure to bend in different directions, and the flexural vibrations are combined to generate a longitudinal direction of the structure. An ultrasonic motor characterized in that an elliptical motion out of phase is generated in the plurality of friction sliding portions on a plane orthogonal to the longitudinal direction of the structure to move the driven body in a direction perpendicular to the longitudinal direction of the structure. Is provided.

  In the ultrasonic motor according to the second aspect, as the ultrasonic vibration section, two piezoelectric element groups having two piezoelectric elements are provided at symmetrical positions with respect to the center in the longitudinal direction of the structure, and the piezoelectric element group is provided. The two piezoelectric elements constituting each of the piezoelectric elements have two drive parts that are extendable independently in the longitudinal direction of the structure and that have substantially the same shape with the phases of expansion and contraction reversed. In the element group, the two piezoelectric elements are arranged such that the direction of flexural vibration of the structure due to expansion and contraction of one piezoelectric element is orthogonal to the direction of flexural vibration of the structure due to expansion and contraction of the other piezoelectric element. It is preferable that the structure is configured such that a larger bending vibration is generated in the structure body by combining the bending vibrations of the structure body by the two piezoelectric element groups. In the ultrasonic motor according to the second aspect, it is preferable that the resonance frequencies of two or more flexural vibrations that cause the structure to bend in different directions are matched and driven at the resonance frequency.

  According to the ultrasonic motor of the present invention, the driven body can be moved at high speed by resonant driving, and the driven body can be moved with high accuracy by non-resonant driving.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view of an ultrasonic motor 10 according to the first embodiment. The ultrasonic motor 10 is a substantially columnar structure, and a preferable shape is a cylindrical shape.

  The ultrasonic motor 10 includes a cylindrical (or disc-shaped) first piezoelectric element 11, a cylindrical second piezoelectric element 12, a pivot 13 having predetermined screw grooves formed at both ends, and a concave holding type. The member 14, the first spacer 18 provided between the first piezoelectric element 11 and the second piezoelectric element 12, and the first piezoelectric element 11, the second piezoelectric element 12 and the holding member 14 are provided. It has two second spacers 19 and two fixing members 17 that are screwed into thread grooves formed at both ends of the pivot shaft 13.

  The pivot 13 is inserted through the first and second piezoelectric elements 11 and 12, the first and second spacers 18 and 19, and the holding member 14. The first friction sliding member 16 a that contacts the driven body 5 is provided on the side surface of the first spacer 18 at the longitudinal center of the ultrasonic motor 10, and the second friction sliding member 16 b is the ultrasonic motor 10. Are provided on the side surfaces of the two fixing members 17 at the longitudinal ends.

  The first piezoelectric element 11 and the second piezoelectric element 12 are ultrasonic vibration portions in the ultrasonic motor 10. FIG. 2 is a perspective view showing a schematic structure of the first piezoelectric element 11 and the second piezoelectric element 12. As shown in FIG. 2, the first piezoelectric element 11 includes a cylindrical piezoelectric body 21 and two sets of electrodes that are divided into two at the end face of the piezoelectric body 21 and sandwiched between the piezoelectric bodies 21. That is, the first electrode 22 and the second electrode 23 are provided. As shown in FIG. 2, in the piezoelectric body 21, a portion sandwiched between the first electrodes 22 (hereinafter referred to as “first drive unit 31”) and a portion sandwiched between the second electrodes 23 (hereinafter referred to as “first drive unit 31”). In the “second drive unit 32”), the direction of polarization P is reversed.

  The first electrode 22 and the second electrode 23 are formed on the piezoelectric body 21 so as not to be electrically connected to the pivot 13. In FIG. 2, the first electrode 22 and the second electrode 23 are formed independently, but this is for polarizing the piezoelectric body 21 as shown in FIG. After that, the first electrode 22 and the second electrode 23 may be electrically connected to each end face of the piezoelectric body 21. In FIG. 2, the first electrode 22 and the second electrode 23 are drawn thick for the sake of convenience. The same applies to the third electrode 25 and the fourth electrode 26 of the second piezoelectric element 12 described later.

  The second piezoelectric element 12 has substantially the same structure as the first piezoelectric element 11. That is, the second piezoelectric element 12 is divided into two at the end surface of the cylindrical piezoelectric body 24 and the piezoelectric body 24, and two sets of electrodes formed with the piezoelectric body 24 sandwiched therebetween, that is, the third electrode 25, And a fourth electrode 26. In the piezoelectric body 24, a portion sandwiched between the third electrodes 25 (hereinafter referred to as “third drive unit 33”) and a portion sandwiched between the fourth electrodes 26 (hereinafter referred to as “fourth drive unit 34”). ), The direction of polarization P is reversed.

  In the ultrasonic motor 10, in the first piezoelectric element 11 and the second piezoelectric element 12, the boundary line between the first electrode 22 and the second electrode 23 coincides with the X axis, and the boundary between the third electrode 25 and the fourth electrode 26. The lines are shifted by 90 degrees around the Z axis so that the lines coincide with the Y axis.

  As the first and second spacers 18 and 19, it is preferable to use a material that easily causes flexural vibration described later with reference to FIG. 3, for example, a metal material such as stainless steel, duralumin, or cast iron. Here, since the first piezoelectric element 11 and the second piezoelectric element 12 must be insulated, when a metal material is used for the first spacer 18, the first piezoelectric element 11 and the second piezoelectric element 12 are disposed between the first spacer 18 and the first piezoelectric element 11 and It is necessary to dispose an insulating plate (not shown) between the first spacer 18 and the second piezoelectric element 12. In addition, when the thickness is thin like the 1st spacer 18, it is also preferable to comprise 1st spacer 18 itself with insulating ceramic materials, such as an alumina, a zirconia, silicon nitride, for example.

  Similarly, when a metal material is used for the second spacer 19, in order to insulate the holding member 14 from the first piezoelectric element 11 and the second piezoelectric element 12, a gap between the second spacer 19 and the first piezoelectric element 11 is used. In addition, it is necessary to dispose an insulating plate (not shown) between the second spacer 19 and the second piezoelectric element 12. Of course, the second spacer 19 may be made of an insulating ceramic material such as alumina. However, in this case, since these ceramic materials are less likely to bend than the metal materials described above, the amplitude of the flexural vibration is low. Tend to be smaller. In the following description, unless otherwise specified, the spacer adjacent to the piezoelectric element is assumed to be insulated from the piezoelectric element or itself as an insulator.

  Further, as the pivot 13, the holding member 14, and the two fixing members 17, a metal material such as stainless steel or cast steel is preferably used. The two fixing members 17 have a predetermined force when the first piezoelectric element 11, the second piezoelectric element 12, and the first and second spacers 18 and 19 are inserted through the pivot 13 in the order shown in FIG. Are attached to both ends of the pivot shaft 13 respectively.

  As will be described later, the holding member 14 is attached to the pivot 13 at a position that becomes a node of vibration when the ultrasonic motor 10 generates flexural vibration.

  The first friction sliding member 16a may be integrated with the first spacer 18, or may be bonded to the first spacer 18 with an adhesive or the like. Similarly, the second friction sliding member 16b may be integrated with the fixing member 17, or may be bonded to the fixing member 17 with an adhesive or the like. Preferably, the first friction sliding member 16a and the second friction sliding member 16b are made of the same material so that the wear rates are the same. The positions where the first and second friction sliding members 16a and 16b are provided are positions that become antinodes of vibration when bending vibration is generated in the ultrasonic motor 10, as will be described later.

  A preload mechanism 15 for pressing the first friction sliding members 16 a and 16 b against the driven body 5 with a predetermined force is attached to the holding member 14. As the preload mechanism 15, a coil spring, an air cylinder, a hydraulic cylinder, or the like is used.

Next, the driving method of the ultrasonic motor 10 will be described in the case of driving at the resonance frequency. The first piezoelectric element 11 and the second piezoelectric element 12 are driven with a driving voltage whose phase is shifted by 90 degrees. For example, a drive voltage V ₁ = V ₀ sin 2πft (f: resonance frequency) is applied to the first electrode 22 and the second electrode 23, and a drive voltage having the same phase is applied to the third electrode 25 and the fourth electrode 26. Apply V ₂ = V ₀ cos2πft.

In this case, paying attention only to the first piezoelectric element 11, as shown in FIG. 2, the direction of polarization is reversed in the first drive unit 31 and the second drive unit 32 in the first piezoelectric element 11. Therefore, when an electric field in the same direction as the direction of polarization (hereinafter referred to as “forward electric field”) is applied to one drive unit, the electric field in the direction opposite to the direction of polarization (hereinafter referred to as “reverse electric field”) is applied to the other drive unit. "Electric field"). That is, when the first drive unit 31 extends, the second drive unit 32 contracts. Here, since the boundary between the first drive unit 31 and the second drive unit 32 coincides with the X axis, when the first piezoelectric element 11 is driven with the drive voltage V ₁ = V ₀ sin 2πft, ultrasonic waves are used. The motor 10 will bend and vibrate in the Y direction.

On the other hand, focusing only on the second piezoelectric element 12, the direction of polarization is reversed in the third driving unit 33 and the fourth driving unit 34 in the second piezoelectric element 12, and the third driving unit 33 and the fourth driving unit 34 34 is coincident with the Y-axis, and therefore, when the second piezoelectric element 12 is driven with the drive voltage V ₂ = V ₀ cos 2πft, the ultrasonic motor 10 undergoes flexural vibration in the X direction. Become.

  The ultrasonic motor 10 generates two bending vibrations having different bending directions, such as bending vibration in the Y direction by the first piezoelectric element 11 and bending vibration in the X direction by the second piezoelectric element 12, and these bending vibrations are generated. By synthesizing, the first friction sliding members 16a and 16b are caused to generate an elliptical motion in a plane perpendicular to the Z axis.

  In order to describe the driving mode of the ultrasonic motor 10 in more detail, FIG. 3 shows a schematic diagram showing the bending vibration mode of the ultrasonic motor 10. In FIG. 3, in the first piezoelectric element 11, the first drive unit 31 is positioned on the + Y side, the second drive unit 32 is positioned on the −Y side, and in the second piezoelectric element 12, the third drive unit 33 is positioned on the + X side. In addition, it is assumed that the fourth drive unit 34 is located on the −X side. Further, in the YZ plane views in FIG. 3, the back side of the paper surface is the + X side, and the front side of the paper surface is the −X side. In the XY plane view of FIG. 3, the position of the first friction sliding member 16a is indicated by a point Q, and the position of the second friction sliding member 16b is indicated by a point S.

  FIG. 3A shows a state where the ultrasonic motor 10 is stationary. In this state, the first and second friction sliding members 16a and 16b are in overlapping positions when viewed from the Z direction.

In FIG. 3B, sin 2πft = 0 and cos2πft = 1, the driving voltage V ₁ = ₀ is applied to the first piezoelectric element 11, and the driving voltage V ₂ = V ₀ is applied to the second piezoelectric element 12, respectively. Reference numeral 33 denotes a state in which a forward electric field is applied, and a reverse electric field is applied to the fourth drive unit 34. In this case, when the third drive unit 33 expands and the fourth drive unit 34 contracts, bending occurs so that both ends of the ultrasonic motor 10 move in the −X direction. At this time, the first friction sliding member 16a is positioned on the + X side, and the second friction sliding member 16b is positioned on the −X side.

In FIG. 3C, the phase advances 90 degrees from the state shown in FIG. 3B, and sin 2πft = 1 and cos2πft = 0, the drive voltage V ₁ = V _{0 is} applied to the first piezoelectric element 11, and the second piezoelectric element 12 is applied. A driving voltage V ₂ = 0 is applied, and a forward electric field is applied to the first driving unit 31 and a reverse electric field is applied to the second driving unit 32. In this case, when the first drive unit 31 expands and the second drive unit 32 contracts, both ends of the ultrasonic motor 10 move in the −Y direction, and the central portion of the ultrasonic motor 10 is + Y. Deflection that moves in the direction occurs. Accordingly, at this time, the first friction sliding member 16a is positioned on the + Y side, and the second friction sliding member 16b is positioned on the -Y side.

  In addition, since the ultrasonic motor 10 is pressed against the driven body 5 in the Y direction by the preload mechanism 15, the bending in the Y direction is suppressed, whereby the bending amount in the Y direction is larger than the bending amount in the X direction. Becomes smaller.

  In the process of shifting from the state shown in FIG. 3B to the state shown in FIG. 3C, the amount of bending in the −X direction at both ends of the ultrasonic motor 10 decreases and the bending in the −Y direction. Since the amount increases, the second friction sliding member 16b moves from the position shown in FIG. 3B to the position shown in FIG. 3C while drawing an elliptical orbit in the -X / -Y region. Similarly, the first friction sliding member 16a moves from the position shown in FIG. 3B to the position shown in FIG. 3C while drawing an elliptical orbit in the + X / + Y region.

In FIG. 3D, the phase advances 90 degrees from the state shown in FIG. 3C, and sin 2πft = 0 and cos2πft = −1, the drive voltage V ₁ = 0 for the first piezoelectric element 11, and the second piezoelectric element 12 for The driving voltage V ₂ = −V ₀ is respectively applied, and a reverse electric field is applied to the third driving unit 33 and a forward electric field is applied to the fourth driving unit 34. In this case, the third drive unit 33 contracts and the fourth drive unit 34 expands, so that both ends of the ultrasonic motor 10 are in the + X direction and the central part of the ultrasonic motor 10 is in the -X direction. Each of them is bent to move. Accordingly, the first friction sliding member 16a is positioned on the −X side, and the second friction sliding member 16b is positioned on the + X side.

  In the process of shifting from the state shown in FIG. 3C to the state shown in FIG. 3D, the amount of deflection in the −Y direction at both ends of the ultrasonic motor 10 decreases and the amount of deflection in the + X direction. Therefore, the second friction sliding member 16b moves from the position shown in FIG. 3C to the position shown in FIG. 3D while drawing an elliptical orbit in the + X / −Y region. Similarly, the first friction sliding member 16a moves from the position shown in FIG. 3C to the position shown in FIG. 3D while drawing an elliptical orbit in the -X / + Y region.

In FIG. 3E, the phase is advanced by 90 degrees from the state shown in FIG. 3D, and sin 2πft = −1 and cos2πft = 0, the drive voltage V ₁ = −V _{0 is} applied to the first piezoelectric element 11, and the second piezoelectric element 12 shows a state in which the driving voltage V ₂ = 0 is applied to the first driving unit 31 and a reverse electric field is applied to the first driving unit 31 and a forward electric field is applied to the second driving unit 32. In this case, when the first drive unit 31 contracts and the second drive unit 32 expands, both ends of the ultrasonic motor 10 move in the + Y direction, and the central portion of the ultrasonic motor 10 is −Y. Deflection that moves in the direction occurs. Accordingly, at this time, the first friction sliding member 16a is positioned on the -Y side, and the second friction sliding member 16b is positioned on the + Y side.

  In the process of transition from the state shown in FIG. 3D to the state shown in FIG. 3E, the amount of bending in the + X direction at both ends of the ultrasonic motor 10 decreases and the amount of bending in the + Y direction decreases. Therefore, the second friction sliding member 16b moves from the position shown in FIG. 3D to the position shown in FIG. 3E while drawing an elliptical orbit in the + X / + Y region. Similarly, the first frictional sliding member 16a moves from the position shown in FIG. 3D to the position shown in FIG. 3E while drawing an elliptical orbit in the -X / -Y region.

  When the phase further advances by 90 degrees from the state shown in FIG. 3 (e), the state returns to the state shown in FIG. 3 (b). In this process, since the + Y deflection amount at both ends of the ultrasonic motor 10 decreases and the −X deflection amount increases, the second frictional sliding member 16b is drawn while drawing an elliptical orbit in the −X / + Y region. It moves from the position shown in 3 (e) to the position shown in FIG. 3 (b). Similarly, the first frictional sliding member 16a moves from the position shown in FIG. 3E to the position shown in FIG. 3B while drawing an elliptical orbit in the + X / −Y region.

  In this way, in the ultrasonic motor 10, the bending vibration is generated by repeating FIG. 3B → FIG. 3C → FIG. 3D → FIG. 3E → FIG. The first friction sliding member 16a and the second friction sliding member 16b are caused to generate an elliptical motion in a plane orthogonal to the Z axis. Thereby, the driven body 5 can be moved in the + X direction. In order to move the driven body 5 in the −X direction, in the example of FIG. 3, for example, the driving voltage of the second piezoelectric element 12 is left as it is, and the phase of the driving voltage applied to the first piezoelectric element 11 is changed. What is necessary is just to shift 180 degrees.

  In the ultrasonic motor 10, since the phases of the elliptical motions of the first friction sliding member 16a and the second friction sliding member 16b are shifted by 180 degrees, they are driven so as to kick the driven body 5 alternately. 5 is driven by friction, so that the driven body 5 can be moved at high speed.

  In addition, the ultrasonic motor 10 can be driven not only at the above-described resonance drive but also at a non-resonance frequency lower than the resonance frequency. The form of flexural vibration of the ultrasonic motor 10 at that time is shown in FIG. The same as the thing. For this reason, when the ultrasonic motor 10 is driven non-resonantly, the driven body 5 can be moved at a low speed, thereby reducing the moving inertia of the driven body 5 and the vibration of the ultrasonic motor 10 itself. Since the inertia is also reduced, the driven body 5 can be moved with high accuracy.

  Next, a second embodiment will be described. FIG. 4 is an explanatory diagram showing a schematic structure of an ultrasonic motor 50 according to the second embodiment. FIG. 4 is a schematic sectional view of the ultrasonic motor 50 and a perspective view showing the arrangement of the first and second piezoelectric elements 11 and 12 included in the ultrasonic motor 50.

  The ultrasonic motor 50 includes two piezoelectric element groups 51 and 52 that use the first piezoelectric element 11 and the second piezoelectric element 12 described above as one piezoelectric element group. The two first piezoelectric elements 11 are arranged at symmetrical positions with respect to the longitudinal center of the ultrasonic motor 50. Similarly, the two second piezoelectric elements 12 are arranged at symmetrical positions with respect to the longitudinal center of the ultrasonic motor 50. ing. Thereby, the vibration in the resonance mode shown in FIG.

  Further, the ultrasonic motor 50 includes a pivot 53 having predetermined screw grooves formed at both ends, a holding member 54, a first spacer 55 provided between the two first piezoelectric elements 11, and a first piezoelectric element. 11, two second spacers 56 provided between the holding member 54, two third spacers 57 provided between the second piezoelectric element 12 and the holding member 54, and both ends of the pivot 53. Two metal fixing members 59 screwed into the screw grooves and a fourth spacer 58 made of an insulating material provided between the second piezoelectric element 12 and the fixing member 59 are provided. The first friction sliding member 60 a that contacts the driven body 5 is provided on the side surface of the first spacer 55, and the second friction sliding member 60 b is provided on the side surface of the fixed member 59.

The arrangement form of the first piezoelectric element 11 and the second piezoelectric element 12 in the piezoelectric element groups 51 and 52 is as shown in FIG. Similarly to the ultrasonic motor 10 described above, the ultrasonic motor 50 is driven by, for example, driving voltage V ₁ = V ₀ sin 2πft applied to the first piezoelectric elements 11 of the first and second piezoelectric element groups 51 and 52. And the drive voltage V ₂ = V ₀ cos2πft is applied to each second piezoelectric element 12 of the first and second piezoelectric element groups 51 and 52.

  Since the form of the flexural vibration of the ultrasonic motor 50 at this time is the same as that of the ultrasonic motor 10, detailed description thereof is omitted here. In the ultrasonic motor 50, the bending vibration generated by the piezoelectric element group 51 and the bending vibration generated by the piezoelectric element group 52 are combined to generate a larger bending vibration than in the ultrasonic motor 10. For this reason, a torque larger than that of the ultrasonic motor 10 can be generated.

  Next, a third embodiment of the present invention will be described. FIG. 5 is an explanatory diagram showing a schematic structure of an ultrasonic motor 70 according to the third embodiment. FIG. 5 is a schematic sectional view of the ultrasonic motor 70 and a perspective view showing the arrangement of the piezoelectric elements 71 included in the ultrasonic motor 70.

  The ultrasonic motor 70 is also a columnar structure. The ultrasonic motor 70 includes a cylindrical piezoelectric element 71, a pivot 72, a concave holding member 73, two spacers 74 provided between the piezoelectric element 71 and the holding member 73, and both ends of the pivot 72. And two fixing members 75 to be screwed into the thread grooves formed in the. The pivot 72 is inserted through the piezoelectric element 71, the spacer 74, and the holding member 73. The first friction sliding member 76 a that contacts the driven body 5 (not shown in FIG. 5) is provided on the side surface of the piezoelectric element 71, and the second friction sliding member 76 b is provided on the side surface of the two fixing members 75. ing.

  As shown in FIG. 5, the piezoelectric element 71 includes a piezoelectric body 81 and three sets of electrodes (a first electrode 82, a second electrode 83, a third electrode 84, and the like) formed with the piezoelectric body 81 interposed therebetween. And). The piezoelectric body 81 is uniformly polarized in the thickness (length) direction. The first to third electrodes 82 to 84 may be formed by dividing the electrode formed to polarize the piezoelectric body 81 by dicing after polarization, or may be divided into three from the beginning. Good. Hereinafter, a portion sandwiched between the first electrodes 82 is a first drive unit 85, a portion sandwiched between the second electrodes 83 is a second drive unit 86, a portion sandwiched between the third electrodes 84 is a third drive unit 87, And

In the ultrasonic motor 70, the first electrode 82, the second electrode 83, and the third electrode 84 have a drive voltage whose phase is shifted by 120 degrees (2π / 3 radians), for example, the first electrode 82 has V ₁ = V _0. sin (2πft + 2π / 3), V ₂ = V ₀ sin2πft is applied to the second electrode 83, and V ₃ = V ₀ sin (2πft-2π / 3) is applied to the third electrode 84, respectively. Thereby, the expansion / contraction timings of the first drive unit 85 to the third drive unit 87 are shifted, and the bending vibration substantially the same as the bending vibration in which the direction of the bending continuously changes as shown in FIG. 3 is generated. The driven body 5 (not shown) can be moved by the elliptical motion of the first and second friction sliding members 76a and 76b.

  In the ultrasonic motor 70, since the first friction sliding member 76 a is provided on the piezoelectric element 71 that causes expansion and contraction, the first friction sliding member 76 a may be separated from the piezoelectric element 71. Therefore, when an ultrasonic motor is configured using the piezoelectric element 71, it is preferable that the piezoelectric element 71 is provided with an even number.

  For example, FIG. 6 shows an explanatory diagram showing a schematic structure of an ultrasonic motor 90 according to the fourth embodiment provided with two piezoelectric elements 71. In FIG. 6, a perspective view showing an arrangement form of the piezoelectric elements 71 is shown in parallel with the schematic cross-sectional view of the ultrasonic motor 90.

  In the ultrasonic motor 90, the two piezoelectric elements 71 are disposed at symmetrical positions with respect to the center in the longitudinal direction of the ultrasonic motor 90 so that flexural vibration is easily generated. The ultrasonic motor 90 also includes a pivot 91, a holding member 92, a first spacer 93 provided between the two piezoelectric elements 71, and two piezoelectric elements 71 and the holding member 92. There are two second spacers 94 provided, and two fixing members 95 that are screwed into thread grooves formed at both ends of the pivot shaft 91. The pivot 91 is inserted through the two piezoelectric elements 71, the first spacer 93 and the holding member 92. A first friction sliding member 96 a that contacts the driven body 5 (not shown in FIG. 6) is provided on the side surface of the first spacer 93, and a second friction sliding member 96 b is provided on the side surfaces of the two fixing members 95. It has been.

  In the ultrasonic motor 90, the two piezoelectric elements 71 are arranged so that the first driving portions 85 of the two piezoelectric elements 71 overlap when viewed from the Z direction. That is, the second driving units 86 of the two piezoelectric elements 71 overlap when viewed from the Z direction, and the third driving units 87 also overlap when viewed from the Z direction.

For example, the two first driving units 85 are driven by V ₁ = V ₀ sin (2πft + 2π / 3), the two second driving units 86 are driven by V ₂ = V ₀ sin 2πft, and the two third driving units 87 are driven. Is driven with V ₃ = V ₀ sin (2πft−2π / 3), the bending vibrations generated by the two piezoelectric elements 71 can be combined to generate a larger bending vibration. Further, since the first frictional sliding member 96a is attached to the first spacer 93, it is difficult to peel off even if the first frictional sliding member 96a is attached to the first spacer 93 by adhesion. The friction sliding member 96 a can be provided integrally with the first spacer 93.

As mentioned above, although embodiment of this invention has been described, this invention is not limited to such a form. For example, as a driving form of the ultrasonic motor 10, a case where a driving voltage having a maximum voltage (amplitude) of ± V ₀ is applied to both the first piezoelectric element 11 and the second piezoelectric element 12 has been described. The maximum voltage applied to the element 11 and the maximum voltage applied to the second piezoelectric element 12 may be different. In this case, the elliptical locus generated in the first and second friction sliding members 16a and 16b changes according to the magnitude of the voltage.

  Further, using the first piezoelectric element 11 and the second piezoelectric element 12 constituting the ultrasonic motor 10, for example, a structure in which one second piezoelectric element 12 is sandwiched between two first piezoelectric elements 11 via a spacer, Even when an ultrasonic motor having a structure in which two first piezoelectric elements 11 and three second piezoelectric elements 12 are alternately arranged via spacers is formed, the flexural vibration described with reference to FIG. 3 occurs. Can be made.

  Further, the ultrasonic motor 50 including two piezoelectric element groups each including the first piezoelectric element 11 and the second piezoelectric element 12 provided in the ultrasonic motor 10 has been described. It can also be set as the structure prepared so that the bending vibration by an element group might be synthesize | combined and a bigger bending vibration might generate | occur | produce.

In the first piezoelectric element 11 constituting the ultrasonic motors 10 and 50, the direction of the polarization P in the piezoelectric body 21 is opposite in the first drive unit 31 and the second drive unit 32. For example, the polarization in the piezoelectric body 21 the P orientation and uniform, and, by independently of the first electrode 22 and second electrode 23, for example, simultaneously with the application of a _V 1 _{= V} 0 _sin2πft the first electrode 22, _{V 1} to the second electrode 23 '= -V ₀ sin2πft may be applied.

  In the ultrasonic motor 70, the three first to third driving units 85 to 87 that are substantially equivalent to the piezoelectric element 71 are provided. However, the number of such driving units may be four or more. In this case, the phase of the drive voltage applied to each drive unit is shifted according to the number of drive units. For example, it may be shifted by 90 degrees when there are four driving sections and by 60 degrees when there are six driving sections. Further, even when the ultrasonic motor 70 includes three or more piezoelectric elements constituting the ultrasonic motor 70 as if the ultrasonic motor 70 was transformed into the ultrasonic motor 90, the bending vibration shown in FIG. 3 can be generated. .

  In the above description, the piezoelectric element has a structure made of cylindrical piezoelectric ceramics. However, the thickness of the piezoelectric element can be reduced as long as a predetermined amount of displacement is obtained. That is, the piezoelectric element may be an annular plate. Moreover, although what consists of innocent piezoelectric ceramics was shown as a piezoelectric element, the piezoelectric element may be a multilayer element formed by alternately laminating a plurality of piezoelectric ceramic layers and electrodes (internal electrodes).

  The present invention is suitable as a driving device for an XY stage apparatus mounted on a semiconductor manufacturing apparatus or the like.

1 is a schematic sectional view of an ultrasonic motor according to a first embodiment. The perspective view which shows schematic structure of the 1st piezoelectric element and 2nd piezoelectric element which comprise the ultrasonic motor shown in FIG. The schematic diagram which shows the form of the bending vibration of the ultrasonic motor shown in FIG. Explanatory drawing which shows schematic structure of the ultrasonic motor which concerns on 2nd Embodiment. Explanatory drawing which shows schematic structure of the ultrasonic motor which concerns on 3rd Embodiment. Explanatory drawing which shows schematic structure of the ultrasonic motor which concerns on 4th Embodiment. Explanatory drawing which shows the structure of the conventional ultrasonic motor.

Explanation of symbols

5; driven body 10, 50, 70, 90; ultrasonic motor 11; first piezoelectric element 12; second piezoelectric element 13; pivot 14; holding member 15; preload mechanism 16a; first friction sliding member 16b; 2 Friction sliding member 17; Fixed member 18; First spacer 19; Second spacer 21; Piezoelectric body 22; First electrode 23; Second electrode 24; Piezoelectric body 25; Third electrode 26; 1 drive part 32; 2nd drive part 33; 3rd drive part 34; 4th drive part 51 * 52; Piezoelectric element group 53; Pivot 54; Holding member 55; 1st spacer 56; 2nd spacer 57; 58; fourth spacer 59; fixed member 60a; first friction sliding member 60b; second friction sliding member 71; piezoelectric element 72; pivot 73; holding member 74; spacer 75; fixing member 76a; Member 76b 2nd friction sliding member 81; Piezoelectric body 82; 1st electrode 83; 2nd electrode 84; 3rd electrode 85; 1st drive part 86; 2nd drive part 87; 3rd drive part 91; 93; first spacer 94; second spacer 95; fixed member 96a; first friction sliding member 96b; second friction sliding member 100; ultrasonic motors 101a and 101b; piezoelectric element 102; head 103;

Claims (6)

A substantially columnar structure including one or more ultrasonic vibrators;
A plurality of friction sliding portions provided so as to come into contact with the driven body at a predetermined position on a side surface of the structure;
Comprising
The ultrasonic vibration unit generates a flexural vibration in the structure so that an elliptical motion out of phase is generated in the plurality of friction sliding units by continuously changing the direction of the flexure. An ultrasonic motor characterized in that the driven body is moved in a direction perpendicular to the longitudinal direction of the structure. Two piezoelectric elements as the ultrasonic vibration part are provided at symmetrical positions with respect to the longitudinal center of the structure,
Each of the two piezoelectric elements can be extended and contracted independently in the longitudinal direction of the structure, and has three driving parts having substantially the same shape,
The drive portions of the two piezoelectric elements are driven with a phase shift of 120 degrees so that the flexures generated in the structure are combined by the expansion and contraction of the drive portions of the piezoelectric elements to produce a large flexure in the structure. The ultrasonic motor according to claim 1. A substantially columnar structure including two or more ultrasonic vibration parts;
A plurality of friction sliding portions provided so as to come into contact with the driven body at a predetermined position on a side surface of the structure;
Comprising
The two or more ultrasonic vibration parts respectively generate two or more flexural vibrations that cause the structure to bend in different directions, and the flexural vibrations are combined to generate a longitudinal direction of the structure. An ultrasonic motor characterized in that an elliptical motion out of phase is generated in the plurality of friction sliding portions on a plane orthogonal to the longitudinal direction of the structure to move the driven body in a direction perpendicular to the longitudinal direction of the structure. . As the ultrasonic vibration unit, two piezoelectric element groups having two piezoelectric elements are provided at symmetrical positions with respect to the longitudinal center of the structure,
The two piezoelectric elements constituting the piezoelectric element group can be expanded and contracted independently in the longitudinal direction of the structure, and two substantially identical drive units with the phases of expansion and contracting reversed are respectively provided. Have
In the piezoelectric element group, in the two piezoelectric elements, the direction of flexural vibration of the structure due to expansion and contraction of one piezoelectric element is orthogonal to the direction of flexural vibration of the structure due to expansion and contraction of the other piezoelectric element. Arranged as
The ultrasonic motor according to claim 3, wherein a bending vibration of the structure body by the two piezoelectric element groups is combined to generate a larger bending vibration in the structure body.   The ultrasonic motor according to claim 3 or 4, wherein resonance frequencies of two or more flexural vibrations that cause the structure to bend in different directions are made to coincide with each other and driven at the resonance frequencies. The ultrasonic motor according to claim 5, further driven at a non-resonant frequency lower than the resonance frequency.

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