JP5183131B2 - Ultrasonic motor - Google Patents

Description

  The present invention relates to an ultrasonic motor used for driving an XY stage, a rotary stage, or the like.

  As a driving mechanism such as an XY stage or a rotary stage, two stacked piezoelectric elements that generate expansion / contraction displacement by voltage application are bonded to a head to be in contact with a driven body so that the displacement directions intersect at a certain angle. In addition, an ultrasonic motor having a structure in which these two piezoelectric elements are bonded to a substantially L-shaped holding member is known (for example, see Patent Document 1).

  This ultrasonic motor can be driven by applying a sinusoidal voltage whose phase is shifted by 90 degrees to each of the two piezoelectric elements to cause an elliptical motion in the head, or by using the same phase of the two piezoelectric elements. There is a method of causing the head to generate an elliptical motion by matching the anti-phase resonance modes, and the head is moved in a desired direction by using a frictional force acting between the head and the driven body.

  At this time, in order to reliably apply force from the head to the driven body, the holding member should be firmly made of a hard material such as tungsten carbide so that the displacement of the head will not be absorbed by bending or the like. It is configured.

However, if the holding member is configured to be robust, the displacement amount of the head is substantially limited to the displacement amount of the piezoelectric element, so that a large displacement amount cannot be obtained, and therefore it is difficult to increase the driving speed of the driven body. It is. Further, when the above-described driving method is used, it is necessary to increase the size of the holding member or to fix the holding member so that the holding member does not move in order to prevent the holding member itself from being bent. . Further, the former driving method has a complicated configuration of the driving power source, and the latter driving method has a problem that adjustment of the two resonance frequencies is not easy.
JP 2004-222453 A (paragraphs [0044], [0045], etc.)

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an ultrasonic motor that can be easily driven and can be fixed to a driven body while obtaining a large amount of head displacement. To do.

According to the present invention, the head to be in contact with the driven body, the two piezoelectric elements fixed to the head so that the expansion and contraction direction when a predetermined voltage is applied intersects at a predetermined angle, and the Young's modulus Made of a material of 40 GPa or more and 220 GPa or less, and a concave holding member comprising a first holding portion and a second holding portion for holding the two piezoelectric elements, and a connecting portion for connecting them, and a part of the connecting portion A concave first case part having a bottom wall part for gripping a part, a first side wall part for gripping a part of the first holding part, and a second side wall part for gripping a part of the second holding part, The second side wall portion is pressed against the second holding portion with a predetermined force, so that the first holding portion presses the first side wall portion so that a part of the curved surface is predetermined. Pressed against the fixed surface and the central axis is Comprising a cylindrical member held by the first side wall portion so as to be perpendicular to the displacement plane of the head, and one of the two piezoelectric elements in accordance with the moving direction of the driven body is driven, In this case, an ultrasonic motor is provided that moves the driven body by applying a force to the driven body by moving the head using resonance including the holding member.

  In addition, a concave second case portion for inserting and holding the first case portion and a second side wall portion and a second case portion are provided so as to press the second side wall portion against the second holding portion. It is preferable to further include a first urging member and a second urging member provided between the bottom wall portion and the second case portion so as to press the bottom wall portion against the holding member.

  Specific examples of the material used for the holding member include gray cast iron, stainless steel, aluminum alloy, free-cutting brass, phosphor bronze, and titanium.

  According to the present invention, the displacement of the head can be enlarged by utilizing the resonance of the holding member, and thereby the driving speed of the driven body can be increased. In addition, the holding member can be configured compactly. Since one of the two piezoelectric elements is driven according to the direction of movement of the driven body, adjustment of the driving frequency is extremely easy, and the configuration of the driving power source is simple.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A schematic side view of the ultrasonic motor 100 is shown in FIG. 1, and a schematic cross-sectional view is shown in FIG. Here, as shown in FIGS. 1 and 2, three-dimensional orthogonal coordinates (X axis, Y axis, Z axis) are defined.

  The ultrasonic motor 100 includes an actuator unit 10 and a case unit 20. The actuator unit 10 is fixed to the head 11 so that the head 11 to be in contact with the slider 50 slidably held in the X-axis direction and the expansion / contraction direction when a predetermined voltage is applied intersect at a predetermined angle. Two laminated piezoelectric elements 12a and 12b and a concave holding member 13 for holding the two piezoelectric elements 12a and 12b are provided.

The head 11 is made of a material having excellent wear resistance, for example, a ceramic material such as alumina (Al ₂ O ₃ ), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), or the like on the surface of the metal material. What formed the coating film, such as DLC, is used suitably.

  For bonding the head 11 and the piezoelectric elements 12a and 12b, a hard resin adhesive having a high bonding strength such as an epoxy resin adhesive and excellent in heat resistance is suitably used. As the piezoelectric elements 12a and 12b, a so-called integrally fired laminated piezoelectric element that can obtain a large amount of displacement at a low voltage is suitably used.

  The crossing angle θ in the expansion / contraction direction of the piezoelectric elements 12a and 12b is a parameter for changing the motion trajectory of the head 11, and is appropriately determined so as to obtain a thrust and a feed speed necessary for moving the slider 50. The shape of the head 11 is designed so that the piezoelectric elements 12a and 12b can be bonded to the intersection angle θ.

  The holding member 13 has a substantially concave shape including a first holding portion 13a and a second holding portion 13b having inclined surfaces for holding the piezoelectric elements 12a and 12b, respectively, and a connecting portion 13c for connecting them. ing.

  The piezoelectric elements 12a and 12b are fixed to the first and second holding portions 13a and 13b, respectively, using a resin adhesive in the same manner as the fixing method to the head 11. The angle of the inclined surface to which the piezoelectric elements 12a and 12b are bonded and fixed in the first and second holding portions 13a and 13b is determined by the intersecting angle θ of the piezoelectric elements 12a and 12b.

  The holding member 13 is a monolithic structure and has a Young's modulus of 40 GPa or more and 220 GPa or less, such as gray cast iron (about 101 GPa), stainless steel (about 196 GPa), aluminum alloy (about 71 GPa), free-cutting brass (about 98 GPa). ), Phosphor bronze (about 113 GPa), titanium (about 103 GPa) and the like. However, it is not limited to such materials, and other metals and alloys can be used as long as they have the above properties.

  By using such a material, the holding member 13 is resonated with one of the driven piezoelectric elements 12a and 12b, and the vibration (displacement) is superimposed on the displacement of the head 11, as will be described later. Can be made. When the Young's modulus is less than 40 GPa, the vibration of the piezoelectric elements 12a and 12b is easily absorbed by the holding member 13, while when it exceeds 220 GPa, the vibration amplitude of the holding member 13 is difficult to obtain, and the displacement amount of the piezoelectric elements 12a and 12b. Can only be obtained. The shape of the holding member 13 is appropriately designed according to the shapes of the head 11 and the piezoelectric elements 12a and 12b so that such resonance can be generated.

  The case portion 20 includes a first case portion 21 that directly holds the holding member 13, a second case portion 22 that fits and holds the first case portion 21, a columnar member (hereinafter referred to as “frame”) 23, A first coil spring 24 that is a first urging member and a second coil spring 25 that is a second urging member are provided.

  The first case portion 21 has a concave shape surrounding the holding member 13, and includes a first side wall portion 21a including a claw portion 31a for gripping a part of the outside of the first holding portion 13a, and a second side portion 21a. It is comprised from the 2nd side wall part 21b provided with the nail | claw part 31b for holding a part of the outer side of the holding | maintenance part 13b, and the bottom wall part 21c provided with the nail | claw part 31c which hold | grips a part of connection part 13c. . The first and second side wall portions 21a, 21b and the bottom wall portion 21c are preferably an integral structure from the viewpoint of maintaining high mechanical strength.

  Note that, for example, “the claw portion 31a grips the first holding portion 13a” means that the claw portion 31a sandwiches the first holding portion 13a and uses the friction force acting between the first holding portion 13a. Is held.

  The claw portion 31c will be described as an example. The claw portion 31c is formed by two projections 33a between two projections 33a (see FIG. 1) provided at regular intervals in the Y direction so as to project in the Z direction. And a lower floor portion 33b (see FIG. 2). The surface on the −Z side of the connecting portion 13c is in contact only with this floor surface, and the side surface in the Y direction of the connecting portion 13c is in contact only with the inner surface of the protrusion 33a. The same applies to the claw portions 31a and 31b.

  The holding member 13 is inserted from the upper opening surface of the first case portion 21, and the holding member 13 is inserted between the two protrusions 33a constituting the claw portions 31a to 31c. The shapes (dimensions) of the claw portions 31a to 31c are set so that the holding member 13 is not easily detached in the X, Y, and Z directions after the holding member 13 is inserted.

  Although it is not necessary to bond the holding member 13 to the claw portions 31a to 31c with a resin adhesive or the like, the vibration generated in the piezoelectric elements 12a and 12b and the holding member 13 is not disturbed or is inhibited. If it is a grade which is accept | permitted, the holding member 13 and the contact part of claw part 31a-31c may be adhere | attached. In that case, it is preferable that the holding member 13 is bonded only at the floor portion 33b.

  In this way, by holding a part of the holding member 13 by the claw portions 31 a to 31 c without holding the entire periphery of the holding member 13, the vibration inhibition by the case portion 20 against the resonance generated in the holding member 13 is minimized. Can be suppressed.

  When the piezoelectric elements 12a and 12b are driven, the piezoelectric elements 12a and 12b generate heat. When the driving time is long, the temperature of the holding member 13 rises due to heat conduction from the piezoelectric elements 12 a and 12 b to the holding member 13. The first case portion 21 is preferably made of a resin material having excellent durability against temperature rise and vibration of the holding member 13, and specifically, engineering plastics such as PEEK (polyether ether ketone) are preferably used. .

  The second case portion 22 has a concave shape surrounding the first case portion 21. The second case portion 22 connects the first and second outer wall portions 22a and 22b facing the first and second side wall portions 21a and 21b in the X direction, and the first and second outer wall portions 22a and 22b, respectively. It is comprised from the outer bottom wall part 22c. The first and second outer wall portions 22a and 22b and the outer bottom wall portion 22c may be an integral structure, or may be a structure in which these are connected by bolts or the like.

  A metal material such as aluminum or stainless steel is preferably used for the second case portion 22. A side cover (not shown) may be provided so as to cover the Y direction side surface of the second case portion 22. Further, a cover (not shown) may be provided on the + Z side opening surface of the second case portion 22 so that the head 11 is exposed.

  The first coil spring 24 is disposed between the second side wall portion 21b and the second outer wall portion 22b so as to press the second side wall portion 21b toward the holding member 13 (−X direction). The first coil spring 24 is preferably provided at a position that is back-to-back with the claw portion 31b, so that the holding member 13 can be reliably pressed from the + X side to the −X side.

  A recess for installing the first coil spring 24 is formed on the inner side of the second outer wall portion 22b, and a protrusion 26 for preventing the displacement of the first coil spring 24 in the Z direction is provided on the second side wall portion 21b. It is provided outside.

  The second coil spring 25 is disposed between the bottom wall portion 21c and the outer bottom wall portion 22c so as to press the bottom wall portion 21c against the holding member 13 (connecting portion 13c). A recess for installing the second coil spring 25 is formed in the outer bottom wall portion 22c.

  The second coil spring 25 is preferably provided at a position that is back to back with the claw portion 31c. As a result, the ultrasonic motor 100 is reliably pressed to the + Z side, and the head 11 is pressed against the slider 50. In order to adjust the force with which the head 11 is pressed against the slider 50, it is also preferable to provide a set screw or the like on the outer bottom wall portion 22c for adjusting the expansion and contraction of the second coil spring 25, for example.

  As described above, since the force for pressing the head 11 against the slider 50 can be adjusted by the second coil spring 25, the second case portion 22 is not shown (for example, a device frame for holding a guide or the like). It is easy to set the conditions at that time. That is, the ultrasonic motor 100 can be easily fixed.

  The frame 23 has a central axis (pointing to an axis passing through the center of the cross-sectional circle parallel to the length direction of the frame 23 and perpendicular to this direction) perpendicular to the ZX plane that is the displacement surface of the head 11. It arrange | positions at the 1st side wall part 21a so that it may become parallel. The top 23 is preferably made of a metal material such as stainless steel, brass, aluminum, or cast iron.

  The top 23 is composed of a columnar main body 23a and a columnar protrusion 23b provided at the center of the end surface of the main body 23a. The protrusion 23b serves as a central axis. The top 23 is disposed so that a part of the curved surface of the main body 23a is exposed from the first side wall 21a on the surface of the first side wall 21a opposite to the surface where the claw portion 31a is formed. A recess 27 is formed. The wall parallel to the ZX plane forming the recess 27 is formed with a notch hole 28 for inserting the projection 23b so that the top 23 can be rotatably held. Yes.

  Two frames 23 are arranged side by side in the Z direction. The two frames 23 are preferably provided at a position equidistant from the claw portion 31a. A structure in which only one frame is disposed may be used, but in that case, it is preferable that the frame is disposed at a position that is back to back with the claw portion 31a.

  When the first coil spring 24 presses the second side wall portion 21 b against the holding member 13, the first side wall portion 21 a is pressed against the first outer wall portion 22 a via the holding member 13. Thus, a part of the curved surface of the top 23 exposed from the first side wall portion 21a is pressed against the first outer wall portion 22a. Since the contact area between the top 23 and the first outer wall portion 22a is a strip shape that is long in the Y direction and narrow, the frictional force in the Y direction between the top 23 and the first outer wall portion 22a increases. Since the top 23 is difficult to slide in the Y direction due to this frictional force, the occurrence of shaking of the actuator unit 10 in the Y direction is suppressed.

  Further, the displacement of the frame 23 in the Y direction is suppressed by the structure of the frame 23 and the holding form of the frame 23 by the concave portion 27 and the cutout hole portion 28, so that the vibration of the actuator unit 10 in the Y direction is also suppressed by this. Occurrence is suppressed.

  Furthermore, since the holding member 13 is stably held in the X direction by the biasing force of the first coil spring 24, the occurrence of shaking of the actuator unit 10 in the X direction is also suppressed. Thus, when the piezoelectric elements 12a and 12b are driven, the occurrence of shake of the actuator unit 10 in the X direction and the Y direction is suppressed. Therefore, when one of the piezoelectric elements 12a and 12b is driven, the head 11 is driven. Can perform a motion to draw a stable trajectory.

  Due to such a structure, in the ultrasonic motor 100, it is difficult for the head 11 to vary in the magnitude of the thrust applied to the slider 50, and the slider 50 can be driven stably with high accuracy. Further, by using the first case portion 21 and the second case portion 22, the assembly of the ultrasonic motor 100 can be performed very easily.

  Next, the driving method of the ultrasonic motor 100 and the resonance of the holding member 13 will be described. FIG. 1 simply shows a connection form between the ultrasonic motor 100 and a power source. The power supply 40 outputs a sinusoidal driving voltage having a constant frequency, and this driving voltage is selectively output to one of the piezoelectric elements 12a and 12b by the switch 41. That is, the ultrasonic motor 100 does not drive the piezoelectric elements 12a and 12b at the same time.

  Since the piezoelectric elements 12a and 12b having substantially no difference in driving characteristics are used, the frequency of the driving voltage output from the power source 40 is the holding member 13 when driving either one of the piezoelectric elements 12a and 12b. Is set to a frequency that causes resonance. This frequency setting is extremely easy because the piezoelectric elements 12a and 12b are not simultaneously driven to resonate.

  3A and 3B schematically show how the piezoelectric element 12a and the holding member 13 vibrate (displace) when the piezoelectric element 12a is driven. 3A shows a state in which the piezoelectric element 12a is expanded, and FIG. 3B shows a state in which the piezoelectric element 12a is contracted. The end point Q on the second holding portion 13b side is set as a fixed point.

  Simultaneously with the expansion / contraction of the piezoelectric element 12a, the connecting portion 13c bends, and this displacement amount is superimposed on the displacement amount of the head 11, so that a displacement and thrust larger than the displacement amount of only the piezoelectric element 12a can be obtained.

  The shape of the holding member 13 is designed according to the shapes of the head 11 and the piezoelectric elements 12a and 12b so that such resonance can be generated. At this time, the holding member 13 and the first case portion 21 are designed. The gap between the first case portion 21 and the second case portion 22 is designed so that the displacement generated in the holding member 13 is not offset by the displacement of the piezoelectric element 12a.

  Further, when the head 11 is pressed against the slider 50 with a constant force and either one of the piezoelectric elements 12a and 12b is driven, the balance between the force applied by the head 11 to the slider 50 and the vibration (deflection) generated in the holding member 13 is achieved. Is determined in consideration of the moving speed required for the slider 50.

  The movement of the head 11 is considered to be basically a linear motion in the expansion / contraction direction of the piezoelectric element to be driven (it may be considered that a slight elliptical locus is drawn due to restraint by a piezoelectric element that is not driven), and the head 11 strikes the slider 50. Use frictional force and impact force. Therefore, a drive voltage is applied to the piezoelectric element 12a to move the slider 50 to the + X side, and a drive voltage is applied to the piezoelectric element 12b to move the slider 50 to the -X side. Thus, in order to drive either one of the piezoelectric elements 12a and 12b, it is not necessary to apply the two resonance frequencies of the same phase and the opposite phase together or to shift the phases as in the prior art. In addition, it is easy to set the drive frequency, and the power supply 40 can be configured easily.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to such a form. For example, although the form using the first coil spring 24 and the second coil spring 25 as the first urging member and the second urging member has been described, a leaf spring can be used instead. Further, the top is not limited to one made of a metal material, and one made of an elastic body such as rubber can also be used. Further, a linear guide can be used instead of the frame.

  As the frame, a simple cylindrical shape can be used. In that case, it is preferable that the first side wall portion 21a is provided with a through-hole through which the frame can be inserted in the Y-axis direction so that a part of the curved surface of the frame is exposed to the outside of the first side wall portion 21a. It is preferable to prevent the frame from falling off by reducing the tolerance between the outer diameter of the frame and the inner diameter of the hole as much as possible or by providing a cover on the side surface in the Y direction.

  In the above-described embodiment, the structure in which the first case portion 21 is fitted and held in the second case portion 22 has been described. However, in the linear stage and the XY stage, the device frame has a shape equivalent to that of the second case portion. Therefore, the actuator portion 10, the first case portion 21, the frame 23, the first coil spring 24, and the second coil spring 25 may be directly attached to such a recess.

  In the above embodiment, the configuration in which the ultrasonic motor 100 is fixed and the slider 50 is moved in the X direction has been described. However, if the head 11 is brought into contact with the side surface of a disk that is rotatably installed, The disc can be rotated. Further, if the ultrasonic motor 100 and the bearing are arranged on the same substrate so as to sandwich the guide rail fixed by the bearing and the head 11 of the ultrasonic motor 100, a linear motor that causes the ultrasonic motor 100 to self-run. It can deform | transform into the structure of.

The schematic side view of an ultrasonic motor. The schematic sectional drawing of an ultrasonic motor. The figure which shows typically the deformation | transformation aspect of the holding member at the time of expansion | extension of a piezoelectric element. The figure which shows typically the deformation | transformation aspect of the holding member at the time of shrinkage | contraction of a piezoelectric element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Actuator part, 11 ... Head, 12a * 12b ... Piezoelectric element, 13 ... Holding member, 13a ... 1st holding part, 13b ... 2nd holding part, 13c ... Connection part, 20 ... Case part, 21 ... 1st case Part, 21a ... first side wall part, 21b ... second side wall part, 21c ... bottom wall part, 22 ... second case part, 22a ... first outer wall part, 22b ... second outer wall part, 22c ... outer bottom wall part, 23 ... Top (cylindrical member), 24 ... First coil spring, 25 ... Second coil spring, 26 ... Projection, 27 ... Recess, 28 ... Notch hole, 31a, 31b, 31c ... Claw, 33a ... Projection, 33b ... floor, 40 ... power supply, 41 ... switch, 50 ... slider, 100 ... ultrasonic motor.

Claims (3)

A head to be in contact with the driven body;
Two piezoelectric elements fixed to the head such that the expansion and contraction directions when a predetermined voltage is applied intersect at a predetermined angle;
A concave holding member made of a material having a Young's modulus of 40 GPa or more and 220 GPa or less, comprising a first holding portion and a second holding portion for holding the two piezoelectric elements, respectively, and a connecting portion for connecting them,
A concave mold having a bottom wall part for gripping part of the connecting part, a first side wall part for gripping part of the first holding part, and a second side wall part for gripping part of the second holding part. A first case portion of
It has a columnar shape, and the second side wall portion is pressed against the second holding portion with a predetermined force, so that the first holding portion presses the first side wall portion and a part of the curved surface is fixed to a predetermined level. A cylindrical member that is pressed against the surface and held by the first side wall so that its central axis is orthogonal to the displacement surface of the head;
Comprising
Either one of the two piezoelectric elements is driven in accordance with the direction of movement of the driven body, and at that time, the head is moved using resonance including the holding member to apply force to the driven body. An ultrasonic motor characterized by moving the driven body. A concave second case portion for inserting and holding the first case portion;
A first biasing member provided between the second side wall portion and the second case portion so as to press the second side wall portion against the second holding portion;
According to claim 1, characterized by further comprising a second biasing member provided between the between the bottom wall portion and the holding member in pressing manner the bottom wall portion and the second case portion Ultrasonic motor. The holding member is gray cast iron, stainless steel, aluminum alloy, free-cutting brass, phosphor bronze, ultrasonic motor according to claim 1 or claim 2, characterized in that it consists of one of titanium.

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