JP5654795B2 - Ultrasonic drive mechanism - Google Patents

Description

  The present invention relates to a drive mechanism using an ultrasonic motor, and more particularly to an ultrasonic drive mechanism in which a driven member is driven by frictional contact with a contact at the tip of a vibrator of the ultrasonic motor.

With the rapid development of electronic and information technology, there is a need for further miniaturization and higher integration of precision parts, and an ultra-precision positioning device that supports nano-order (10 ^-9 m) inspection and ultra-fine processing. It is necessary. In medical and biological research, the development of applied technology by controlling proteins and cells is progressing, and the need for a microscope stage that can be positioned in a finer region is increasing. Further, in recent years, along with the demand for higher precision, as the objects for inspection, processing, measurement, etc. become smaller, the positioning device and its drive source are also required to be smaller and lighter.

  As a driving device for dealing with such a fine region in the nano-order, an ultrasonic motor using a piezoelectric vibrator as described in Patent Documents 1 to 3 has been developed in place of the conventional electromagnetic motor. Each of these ultrasonic motors is a driving device based on a driving principle that is completely different from that of an electromagnetic motor, and has excellent features such as low speed, high torque, silence, and position retention when stopped. Further, since the structure of the vibrator is simple, it is advantageous for downsizing and is expected as a small actuator.

  While the ultrasonic motor has various excellent features as described above, there are various problems regarding the material, hardness, friction characteristics, etc. of the pressing member (contactor) at the tip of the vibrator and the driven member that is in frictional contact with the contactor. It has been pointed out that many attempts have been made to solve these points. In Patent Document 1, the contact material at the tip of the vibrator is made of alumina ceramic or single crystal alumina having an alumina content of 99.5% by mass or more and a Vickers hardness of 15.2 GPa or more. While suppressing as much as possible, moderate frictional force is ensured between the driven member.

  Also, in Patent Document 2, the contact surface of the ultrasonic motor vibrator tip and the contact surface of the driven member are respectively formed of dense ceramics or cermet, and either of the contact surfaces is hard on either side. An ultrasonic driving device provided with a wear-resistant layer made of carbon is disclosed. Further, in Patent Document 3, the tips of vibrators arranged in a substantially V shape are coupled by a coupling member, a projection-shaped protection member is provided on a driven member that is in frictional contact with the coupling member, and the length of the projection member is Discloses an ultrasonic motor having a diameter of 2 mm or less along the moving direction of the driven member.

JP 2002-27768 A Japanese Patent Laid-Open No. 11-136968 JP 2004-304894 A

  In an ultrasonic motor, it is necessary that the operation characteristics are stable, the wear between the vibrator and the driven member is small, and the contact area on the vibrator side should be constant even when worn. In the above-mentioned Patent Document 1, although measures are taken to reduce the amount of wear such as the material, surface roughness, mechanical strength of the contact at the tip of the vibrator, it is a configuration that exclusively prevents wear and degranulation on the contact side. On the other hand, there is a problem that wear on the driven member side is increased.

  In Patent Document 2, excellent wear resistance is ensured in high-speed friction drive by forming a wear-resistant layer made of hard carbon with extremely high wear resistance on both the contact and driven member of the vibrator tip. However, since both the contactor and the driven member are made of a material having high hardness, the operation is not stable, and there is a problem in terms of stationary holding property. Further, in Patent Document 3, a semi-cylindrical or hemispherical or columnar protrusion is provided at the contact portion of the driven member, and the contact area with the contact increases due to wear, so that the operating characteristics change and stable operation is achieved. There was a possibility that it could not be obtained.

  The present invention solves the above-described problems, provides an ultrasonic drive mechanism that is stable in operation, has a high bending strength of the driven member, easily obtains a good mirror surface of the driven member, and is less likely to be warped or deformed during firing. The purpose is to provide.

  The present invention also provides an ultrasonic drive mechanism that maintains a stable speed, thrust, and stable resonance frequency by maintaining the initial operating state by the shape of the contact at the tip of the vibrator, and that provides stable operating characteristics over a long period of time. The purpose is to provide.

  In order to achieve the above object, an ultrasonic drive mechanism (1) according to the present invention includes an ultrasonic motor and a driven member that is driven in frictional contact with a contact of the ultrasonic motor. The contact is formed of partially stabilized zirconia, and the contact portion of the driven member with the contact is formed of alumina zirconia.

  According to one aspect of the present invention, in the ultrasonic drive mechanism described in (1) above, the alumina zirconia is mixed with 90 to 97% by mass of alumina powder and 2 to 9% by mass of partially stabilized zirconia powder, and An ultrasonic drive mechanism (2) which is a sintered body obtained by adding 0.5 to 3% by mass of a sintering aid to the sintered body is provided. In this embodiment, an ultrasonic drive mechanism (alumina zirconia, which is a sintered body in which 94% by mass of alumina powder and 5% of partially stabilized zirconia powder are mixed and 1% by mass of a sintering aid is added thereto and fired) 3) is preferred.

According to another aspect of the present invention, the ultrasonic drive mechanism (1) to (3), wherein the sintering aid, CaO10～16 mass%, MgO20～26 wt%, SiO ₂ 60 to 65 An ultrasonic drive mechanism (4) which is a powdery composition composed of mass% is provided. In this embodiment, an ultrasonic drive mechanism (5), in which the sintering aid is a powdery composition comprising CaO 13% by mass, MgO 24% by mass, and SiO ₂ 63% by mass, is preferable.

  Furthermore, according to another aspect of the present invention, in the ultrasonic driving mechanism of the above (1) to (5), the contact of the ultrasonic motor has a mirror finish with a surface roughness Ra <0.05, and the driven member An ultrasonic drive mechanism (6) is provided in which the contact surface with the contact is a mirror-finished surface with a surface roughness Ra <0.04.

  Furthermore, according to the other form of this invention, in the ultrasonic drive mechanism of said (1)-(6), the cross section perpendicular | vertical to the axial direction of this contactor has the same shape and the same shape along the axial direction. An ultrasonic drive mechanism (7) formed in the cross-sectional area is provided.

  Furthermore, according to the other form of this invention, in the ultrasonic drive mechanism of said (1)-(7), the ultrasonic drive mechanism (8) whose said contactor is a pin-shaped contactor is provided.

  In the present invention, the contact is formed of partially stabilized zirconia, and the driven member is formed of alumina zirconia, so that the operation of the driven member is stable and the bending strength is high, and the driven member side Abrasion is suppressed, and the yield of the driven member product is increased and the quality is improved without warping or distortion due to the addition of a sintering aid.

  Further, in the present invention, even if the contact at the tip of the vibrator of the ultrasonic motor is worn, the contact area with the driven member is constant, and the operation characteristics are stabilized. Further, chipping at the ridge portion of the contact is unlikely to occur, damage to the contact is suppressed, and an ultrasonic drive mechanism having a long life can be realized.

It is the figure which showed the change of the moving speed (mm / s) and the resonant frequency (KHz) with respect to the drive distance of the driven member in the Example (driven member: alumina zirconia, contactor: partially stabilized zirconia) of this invention. It is the figure which showed the change of the moving speed (mm / s) and resonance frequency (KHz) at the time of using the conventional alumina as a driven member and using partially stabilized zirconia as a contact. It is the figure which showed the moving speed (mm / s) and resonance frequency (KHz) with respect to the drive distance at the time of forming a contactor and a driven member by partially stabilized zirconia. It is the figure which showed the bending strength with respect to the calcination temperature of the various alumina zirconia which comprises the driven member by the Example of this invention. It is the figure which showed the curvature amount in the baking process with respect to the baking temperature of the various alumina zirconia which comprises the driven member by the Example of this invention. It is the figure which showed the relationship between the amount of zirconia substitution of alumina zirconia, and bending strength. It is the figure which showed the relationship between the amount of zirconia substitution of alumina zirconia, and thermal conductivity. It is the top view (A) and side view (B) of the vibrator | oscillator for ultrasonic motors by the Example of this invention. FIG. 8 is a perspective view showing a state in which wear progresses with a contact (pin-shaped member) at the tip of the vibrator shown in FIG. 7. It is an enlarged plan view of a prismatic pin-shaped contact according to an embodiment of the present invention. It is a figure which shows the operating principle of the ultrasonic motor to which this invention is applied typically.

  Next, an ultrasonic drive mechanism according to an embodiment of the present invention will be described with reference to the drawings. FIGS. 11A and 11B are diagrams schematically showing the operating principle of an ultrasonic drive mechanism to which the present invention is applied. The ultrasonic drive mechanism includes a vibrator 1 and a driven member 2, and the vibrator 1 is composed of a piezoelectric vibration element. By applying an electrode (not shown) provided on the side surface, the expansion and contraction operation and the bending operation can be performed simultaneously. Each of them is generated independently, and by the combination, at least a part thereof, in particular, the contact 3 at the tip of the vibrator that is in frictional contact with the driven member 2 performs an elliptical motion to move the driven member 2 intermittently. For example, the point p (center point of the left end surface of the vibrator) in FIG. 11A draws a locus shown in FIG. 11B through the four states (a) to (d). In the figure, x is an axis in the longitudinal direction of the vibrator, and y is an axis perpendicular to the upper and lower side surfaces 1a of the vibrator.

  A contact 3 is fixed (adhered) to the tip of the vibrator 1 that is elliptically moving. The elliptical motion of the vibrator 1 is transmitted to the driven member 2 through the contact 3 and becomes a driving force for operating the driven member 2. In the example of FIG. 11, the driven member 2 can cause a rotational motion around the guide 4 by repeating this elliptical motion. Further, if the driven member 2 is formed in an annular shape, it is possible to cause a rotational movement around the guide 4. The magnitude of the elliptical motion is controlled by the input voltage to the electrode of the piezoelectric vibration element 1.

Next, 99% alumina and yttrium oxide (Y ₂ O ₃ ) were added in the order of 3 mol% as materials of the contactor and the driven member, and the crystal structure of zirconia (Z ₂ O ₃ ) was partially stabilized. Table 1 shows the experimental results of the operational stability and the amount of wear when a preliminary experiment was performed by combining zirconia fluoride, polyphenylene sulfide resin (PPS), and alumina zirconia in which a part of alumina was replaced with partially stabilized zirconia.

  This preliminary experiment was performed with a driving distance of 1000 m and continuous driving (total). The vibrator length was 30 mm, the contact was hemispherical, the pressing spring pressure was 40 N (however, the pressing pressure for PPS was 15 N only). )). The wear amount (μm) in the table is the wear amount of the contact. In this preliminary experiment, among the combinations of materials of the contactor and the driven member, three kinds that are considered to be relatively good were selected, and this experiment was performed for a driving distance of 100 km. From the results of Table 1 in the preliminary experiment, it is considered that the contactor-driven member is made of (A) partially stabilized zirconia-alumina zirconia, and (B) partially stabilized zirconia-99% alumina. And (C) Partially Stabilized Zirconia-Partially Stabilized Zirconia were selected, and this experiment was performed for each. The results are shown in FIGS.

  As a result of this experiment, the best result was obtained when the driven member was formed of alumina zirconia and the contact at the tip of the vibrator contacting the driven member was formed of partially stabilized zirconia. In the above preliminary experiment, when the material of the contactor and the driven member is partially stabilized zirconia-alumina zirconia, the wear amount of the contactor is extremely small so that it cannot be measured in the range of the driving distance of 1000 m. Has been confirmed to be the most stable. FIG. 1 shows the experimental results when the material of the contact and the driven member according to the present invention is partially stabilized zirconia-alumina zirconia. This shows the driving distance. FIG. 2 shows the moving speed and resonance frequency of the driven member when alumina is used as the driven member and the contact is made of partially stabilized zirconia. FIG. 3 is a diagram showing the moving speed (mm / sec) and the resonance frequency (KHz) with respect to the driving distance when both the contactor and the driven member are made of partially stabilized zirconia.

The alumina zirconia in the example of FIG. 1 is a sintered body obtained by mixing and firing 94% by mass of alumina powder, 5% by mass of zirconia powder, and 1% by mass of a sintering aid to be described later. For example, a powdery composition composed of 13% by mass of CaO, 24% by mass of MgO, and 63% by mass of SiO ₂ is used for preventing warpage of the driven member. Further, as the partially stabilized zirconia, the specific surface area (SA) consisting of 97.4 mol% of zirconia (ZrO ₂ ) and 2.6 mol% of yttrium oxide (Y ₂ O ₃ ) has an average of 7.8 m ² / g. A commercial product (manufactured by Daiichi Rare Elements) having a particle size (D ₅₀ ) of 0.52 μm was used. In FIG. 1, the pressing spring pressure that presses the contact against the driven member is 20 N, the stationary holding force is 6 N, and the surface roughness Ra of the driven member is 0.05 μm. The alumina zirconia used in this example has a bending strength (MPa) of 600, a Vickers hardness (Hv) of 1552, and a density (g / cm ³ ) of 4.038. In the firing of the sintered body, zirconia (made of the first rare element) having a specific surface area (SA) of 13.1 m ² / g and an average particle diameter (D ₅₀ ) of 0.5 μm as a raw material in firing at 1550 ° C. ), A tendency to slightly improve the strength is recognized.

On the other hand, in the conventional alumina driven member in the example of FIG. 2, the bending strength (MPa), Vickers hardness (Hv), and density (g / cm ³ ) are 200, 1429, and 3.785, respectively. . The partially stabilized zirconia driven member has a bending strength (MPa) of 1200, a Vickers hardness (Hv) of 1280, and a density (g / cm ³ ) of 6.099. In the present invention, the length of the vibrator is 30 mm, the contact is a pin shape of 0.5 mm diameter (with a 2 mm diameter pin base), the stationary holding force is 6 N, and the total driving distance in repeated reciprocating operations is 100 km. Tested to ~ 300Km. On the other hand, in the case of the conventional example shown in FIG. 2, the vibrator has a length of 30 mm, a contact diameter of 0.8 mm (with a 2 mm diameter pin base), a static holding force of 10 N, and a driving distance of 200 km to 800 km. Tested. In the example of FIG. 3, the length of the vibrator and the contact diameter are the same as in FIG. 2, but the pressing spring force is 20 N, the stationary holding force is 15 N, and the surface roughness Ra of the driven member is 0.05 μm. It was.

  In FIG. 1, the change in the speed and resonance frequency at the start of drive start is steep because it takes time for the contact surface and the surface of the driven member to contact each other at the time of start-up. It can be resolved by aging.

  As can be seen from comparison of these figures, in the case of the present invention, both the moving speed and the resonance frequency are constant and stable movement over the entire driving distance, but in the conventional example of FIG. Further, the resonance frequency also shows a large variation between the moving distances of 1 to 300 km. In the case of the present invention, the amount of wear of the contact at a driving distance of 1000 km is 5 μm, which is extremely small compared to the conventional case. Wear on the driven member side is even smaller than this, and is hardly measurable. The resonance frequency is measured as a change in impedance, and the value fluctuates when the wear is large. It is assumed that the variation in the resonance frequency of the conventional example shown in FIG. 2 is large because of wear. In the example of FIG. 3 as well, a large variation in resonance frequency can be seen in the driving distance range of 200 km to 1000 km.

Next, the results of various experiments conducted on the bending strength (MPa) and the warping amount (mm) of alumina zirconia constituting the driven member in the ultrasonic driving mechanism according to the example of the present invention are shown in FIG. The alumina zirconia used as a sample described with reference to FIG.
A: A mixture of 95% by mass of alumina (Al ₂ O ₃ ) and 5% by mass of partially stabilized zirconia (ZrO ₂ ) and calcined (without using a sintering aid),
B: A mixture of 94% by mass of alumina (Al ₂ O ₃ ) and 5% by mass of partially stabilized zirconia (ZrO ₂ ), and fired with the sintering aid as 1% by mass,
C: 92% by mass of alumina (Al ₂ O ₃ ), 5% by mass of partially stabilized zirconia (ZrO ₂ ), and 3% by mass of the sintering aid,
D: 90% by mass of alumina (Al ₂ O ₃ ), 5% by mass of partially stabilized zirconia (ZrO ₂ ), and 5% by mass of the sintering aid were used.
The bending strength (MPa) when the firing temperature was 1500 ° C., 1530 ° C., and 1580 ° C. was measured for the above A to D. According to the measurement results shown in FIG. 4, the above-mentioned B having 0% of the auxiliary A and 1% by mass of the auxiliary B is excellent in bending strength, and good in the firing temperature range of 1500 ° C to 1530 ° C. Showed a good value. However, since the warpage is large at 0% by mass of the auxiliary agent and it is practically difficult to fire without using the auxiliary agent, the above-mentioned B type is the best.

FIG. 5 is a diagram showing the maximum amount of warp (mm) per 6 inches (15.24 cm) when the samples A to D are fired at a firing temperature of 1530 to 1560 ° C. FIG. From this figure, it can be seen that B to D having 1 to 5 mass% of auxiliary agent have a small amount of warping (maximum value) during firing. From these results, as a driven member of the present invention, 1% by mass of a sintering aid was added to the above-mentioned composition of B, that is, a mixture of 94% by mass of alumina and 5% by mass of partially stabilized zirconia (ZrO ₂ ). It can be seen that the product has a high bending strength and a small amount of warpage upon firing. Therefore, in the present invention, it is most preferable to use alumina zirconia having the composition B in which the above-mentioned auxiliary agent is 1% by mass as the driven member.

Next, changes in bending strength and thermal conductivity when the content of partially stabilized zirconia in alumina zirconia (partially stabilized zirconia substitution amount) is changed will be described with reference to FIGS. FIG. 6 is a graph showing the relationship between the partially stabilized zirconia substitution amount of alumina zirconia and the bending strength. The firing temperature is 1550 ° C. From this measurement result, it is understood that the bending strength shows a constant value of about 700 MPa when the partially stabilized zirconia substitution amount is 5% by mass or more. As for the relationship between the amount of zirconia substitution of alumina zirconia and the thermal conductivity, as shown in FIG. 7, in the case of partially stabilized zirconia having a specific surface area of 7.8 m ² / g and an average particle size of 0.52 μm, it is partially stable. As the zirconia fluoride substitution amount increases, the thermal conductivity decreases. The reason why the thermal conductivity is evaluated is to evaluate the heat dissipation of frictional heat and to provide a driving device with a small thermal drift. From the above results, the alumina zirconia according to the present invention is a sintered body in which 94% by mass of alumina and 5% by mass of zirconia are mixed, and 1% by mass of a sintering aid is added thereto, followed by firing. Good.

  In the present invention, the contact on the vibrator side and the contact member of the driven member are polished so as to have a mirror finish. In an unpolished state with a surface roughness Ra of about 0.3, the contact of the contact at the tip of the vibrator is severely worn and the movement becomes unstable. Therefore, in order to obtain a stable operation, in the present invention, the surface roughness Ra of the contactor is mirror-finished polishing with Ra <0.05, and the surface roughness Ra of the driven member is mirror-finished with Ra <0.04. By doing so, wear of the driven member is prevented together with the material of the driven member.

  Next, the state of wear of the transducer tip in the ultrasonic motor of the ultrasonic drive mechanism according to the embodiment of the present invention will be described with reference to FIGS. 8 and 9, a cylindrical pin base 5 is fixed to the tip of the vibrator 1, and a cylindrical pin contact 6 that is in frictional contact with the driven member is provided at the tip of the pin base 5. . The pin-shaped contact 6 is formed in a cylindrical shape whose cross section has the same outer diameter along the axial direction. In the present invention, as described above, the contact of the ultrasonic motor is made of a material (partially stabilized zirconia) having higher wear than the driven member (alumina zirconia), and the contact is worn more than the driven member. The contact 6 wears due to frictional contact with the driven member, and as shown in FIG. 9, even if the wear progresses from the initial state (a) to (b), (c), the length is reduced and the driven member is driven. The contact area with the member does not change, so that the initial operation is continued and a stable speed, thrust, and resonance frequency are maintained.

  The pin base 5 to which the contact 6 is fixed is not limited to a cylindrical shape, and may be a prismatic shape. The pin-shaped contact 6 may also be a prism having a rectangular cross section. FIG. 10 is an enlarged plan view of the prismatic pin-shaped contact 7. In this case, the four side portions 7 a of the prism are R-chamfered. The length of one side of the prism in this embodiment may be approximately the same as the diameter of the cylindrical pin contact described above. In the case of a prismatic shape, the pin length is preferably 2 mm or less. If R-chamfering is not performed on the prismatic ridge, chipping occurs at the ridge during frictional contact, and wear is accelerated at this part, making it difficult to maintain the initial operation. , There is no need to worry about such problems.

DESCRIPTION OF SYMBOLS 1 Vibrator 2 Driven member 3 Contact 4 Guide 5 Pin stand 6 Pin type contact 7 Pin shape contact of prism shape

Claims (8)

In an ultrasonic drive mechanism having an ultrasonic motor and a driven member that is driven in frictional contact with a contact of the ultrasonic motor, the contact is formed of partially stabilized zirconia, and the contact of the driven member The contact portion is made of alumina zirconia , and the shape of the contact is formed in a cross section perpendicular to the axial direction in the same shape and cross-sectional area along the axial direction .   The alumina zirconia is a sintered body obtained by mixing 90 to 97% by mass of alumina powder and 2 to 9% by mass of partially stabilized zirconia powder and adding 0.5 to 3% by mass of a sintering aid thereto. The ultrasonic drive mechanism according to claim 1.   3. The ultrasonic wave according to claim 2, wherein the alumina zirconia is a sintered body obtained by mixing 94% by mass of alumina powder and 5% of partially stabilized zirconia powder, and adding 1% by mass of a sintering aid thereto and firing the mixture. Drive mechanism. The sintering aid, CaO 10 to 16 wt%, MgO 20 to 26 wt%, the ultrasonic drive according to claim 1 in powder form composition comprising SiO ₂ 60 to 65 wt% mechanism. The ultrasonic drive mechanism according to claim 4, wherein the sintering aid is a powdered composition comprising 13 mass% CaO, 24 mass% MgO, and 63 mass% SiO ₂ . The contact of the ultrasonic motor has a mirror finish with a surface roughness Ra <0.05, and the contact surface of the driven member with the contact has a mirror finish with a surface roughness Ra <0.04. The ultrasonic drive mechanism in any one of -5. Ultrasonic driving mechanism according to any of claims 1-6 wherein the contact is a pin-shaped contact which is provided on a stand. The ultrasonic drive mechanism according to claim 7, wherein the pin-shaped contact is a cylinder or a prism having a rounded chamfer .

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