JP2002027768A - Ultrasonic motor and guide apparatus using ultrasonic motor as driving source for movable body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress wear or fracture of a pressing member fitted to an ultrasonic motor, to prolong its life, and to obtain a stable contact with a movable body and an appropriate friction with respect to the movable body. SOLUTION: The pressing member of the ultrasonic motor is made of an alumina ceramic or a single crystal aluminum whose aluminum content is not lower than 99.5 wt.% and Vickers hardness is not lower than 5.2 GPa. The arithmetic means roughness (Ra) of the touching surface of the pressing member with the movably body is not larger than 0.2 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an ultrasonic motor,
The present invention relates to a guide device that drives a movable body that moves linearly or rotationally by an ultrasonic motor, and is particularly suitable as a guide device used for a precision machining machine, a precision measuring device, and a semiconductor manufacturing device.

[0002]

2. Description of the Related Art Ultrasonic motors have the characteristics that the minimum amplitude is as small as nano-order, high-resolution positioning is possible, and the driving force is large due to friction drive. Practical application to a rotary motion system such as a mechanism or a vibration alarm of a wristwatch has been carried out, and recently, application to a linear motion system has been attempted.

For example, as shown in FIGS. 3A and 3B, an example of a conventional ultrasonic motor is shown in FIG.
One main surface of the piezoelectric ceramic plate 32 has four divided electrode films 33a, 33b, 33c, and 33d, and connects the diagonally located electrode films 33a and 33d.
Connecting the electrode films 33b and 33c located at diagonal positions,
On the other main surface, a vibrating body 35 having an electrode film 34 formed on almost the entire surface and a pressing member 36 provided on an end surface of the piezoelectric ceramic plate 32 are provided. The electrode film 33a formed on the one main surface is provided. By applying a voltage having a phase difference of 90 degrees to the electrode film 33b and grounding the electrode film 34 formed on the other main surface, longitudinal vibration and lateral vibration are generated in the piezoelectric ceramic plate 32. Thus, the pressing member 36 is made to perform an elliptical motion by the combination of the vibrations.

FIG. 4 shows an example of a guide device using a conventional ultrasonic motor 31 as a driving source of a movable body. As shown in FIG. 4, this guide device is provided on a base board 11 with a pair of guide members such as a cross roller guide. 12 and these guide members 1
The stage 2 guides the stage 13 as a movable body linearly.

A driving force transmitting member 14 is provided on one side of the stage 13, and a linear scale 15 is provided on the other side of the stage 13, and a measuring head 16 is provided at a position facing the linear scale 15. To provide the position detecting means 17 and the driving force transmitting member 1
4 has an ultrasonic motor 31 perpendicular to its longitudinal direction.
Of the stage 13 and changes according to the deviation between the position information from the position detecting means 17 accompanying the movement of the stage 13 and the reference position information based on the preset movement profile of the stage 13. Based on the parameters, the control unit 18 performs, for example, PID calculation processing, and the driver 1
9 by performing a feedback control for outputting a command signal to the ultrasonic motor 31, the pressing member 36 of the ultrasonic motor 31 performs an elliptical motion according to the command signal, and the frictional drive with the pressing member 36 performing the elliptical motion is performed. Stage 13 by
Is moved along the guide member 12. Reference numeral 20 denotes a case for housing the ultrasonic motor 31. The ultrasonic motor 31 is sandwiched by four springs 21 in the case 20, and is provided between the rear end of the ultrasonic motor 31 and the case 20. The pressing member 36 of the ultrasonic motor 31 is pressed against the driving force transmitting member 14 by the provided spring 22. Reference numeral 23 denotes a load cell for measuring the pressing force of the ultrasonic motor 31.

Since the pressing member 36 of the ultrasonic motor 31 slides while being pressed against the driving force transmitting member 14, it must be formed of a material having excellent wear resistance. There was a glass material such as glass or soda glass, or a ceramic material containing alumina, zirconia, or silicon carbide as a main component (JP-A-7-273384).

[0007]

However, the ultrasonic motor 31 using a pressing member 36 made of a glass material such as quartz glass or soda glass has a small fracture toughness, and when cracks occur, chipping or cracking occurs. There was a problem that it was easy. Therefore, when trying to move the heavy stage 13 by the ultrasonic motor 31 including the glass pressing member 36, the pressing member 36 may be chipped due to the stress applied during the friction driving with the driving force transmitting member 14. Cracks occur,
There was a problem that the guide device had to be stopped each time.

On the other hand, the pressing member 36 of the ultrasonic motor 31
In the case of using ceramics containing alumina, zirconia or silicon carbide as a main component, it is difficult to break as compared with a glass material. There is a problem that the friction coefficient between the driving force transmitting member 14 and the driving force transmitting member 14 is small, and when the ultrasonic motor 31 is vibrated at high speed, slippage occurs and the stage 13 cannot be moved at high speed.

Further, in the case where the zirconia ceramic is used for the pressing member 36, the Vickers hardness is as small as about 12 GPa as compared with other ceramics. There was a problem that it was worn out at home.

Furthermore, although the alumina member ceramics used for the pressing member 36 have relatively high hardness, the alumina ceramics generally used include sintering aids such as calcia, magnesia and silica. Is 1
About 2% by weight is contained, and cracks are generated in the grain boundary layer in the sintered body made of the sintering aid due to the stress acting upon friction driving with the driving force transmitting member 14, thereby causing alumina particles to fall off. Then, the edge of the concave portion in which the threshing occurs causes scratches on the driving force transmitting member 14, or the threshing powder bites between the driving force transmitting member 14 and cuts the pressing member 36 or the driving force transmitting member 14 to cut. There was a problem of causing wear. In addition, the contact state changes when the powdered particles are caught between the driving force transmission member 14 and the stage 1.
There is a possibility that the movement of the third member, the positioning accuracy and the like may be adversely affected, and cracks generated in the pressing member 36 may be developed to further shorten the life.

[0011]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an ultrasonic motor comprising a vibrating body and a pressing member for transmitting the vibration of the vibrating body to the movable body. It is made of alumina ceramic or single-crystal alumina having a content of 99.5% by weight or more and a Vickers hardness of 15.2 GPa or more, and a contact surface in contact with the movable body side has an arithmetic average roughness (R
It is characterized in that it is 0.2 μm or less in a).

In particular, when the pressing member is formed of single-crystal alumina, it is preferable that the crystal orientation of the single-crystal alumina forming the contact surface is the A-plane.

Further, according to the present invention, the pressing member of the ultrasonic motor is arranged in contact with the movable member, and the vibration of the ultrasonic motor is transmitted through the pressing member to thereby frictionally drive the movable member. Thus, the guide device using the ultrasonic motor as the drive source of the movable body is configured.

[0014]

Embodiments of the present invention will be described below.

FIGS. 1A and 1B show an example of an ultrasonic motor according to the present invention, wherein FIG. 1A is a front view and FIG. 1B is a rear view.

This ultrasonic motor 1 is a multi-mode ultrasonic motor, which is divided into four main surfaces of a piezoelectric ceramic plate 2 made of, for example, lead zirconate titanate, barium titanate, lithium niobate or the like. Electrode films 3a, 3b, 3
c, 3d, the electrode film 3a and the electrode film 3 located at diagonal positions.
d, the electrode film 3b and the electrode film 3c located diagonally are connected, and the other main surface is provided with a vibrating body 5 having an electrode film 4 formed on almost the entire surface.
And a pressing member 6 formed of alumina ceramics or single-crystal alumina having an alumina content of 99.5% by weight or more and a Vickers hardness of 15.2 GPa or more, provided on the one main surface. Voltages having phases different from each other by 90 degrees are applied to the formed electrode films 3a and 3b, and the electrode film 4 formed on the other main surface is grounded. Is generated, and the pressing member 6 is caused to perform an elliptical motion in a certain direction by combining these vibrations. By applying voltages whose phases are inverted to the electrode films 3a and 3b, the pressing member 6 is caused to perform an elliptical motion in the opposite direction. It can be made to be.

FIG. 2 is a partially cutaway plan view showing an example of a guide device using the ultrasonic motor 1 of the present invention as a driving source of a movable body. A pair of guide members 12 such as roller guides,
A stage 13 as a movable body is linearly guided by these guide members 12.

A driving force transmitting member 14 is provided on one side of the stage 13, and a linear scale 15 is provided on the other side of the stage 13.
A measuring head 16 is provided at a position opposed to the above to constitute a position detecting means 17, and the pressing member 6 of the ultrasonic motor 1 is brought into contact with the driving force transmitting member 14 perpendicularly to its longitudinal direction. The control unit 18 is based on a parameter that changes according to a deviation between the position information from the position detection unit 17 accompanying the movement of the stage 13 and the reference position information based on a preset movement profile of the stage 13. For example, by performing PID calculation processing and performing feedback control for outputting a command signal to the ultrasonic motor 1 to the driver 19, the pressing member 6 of the ultrasonic motor 1 is caused to perform an elliptical motion according to the command signal, and The stage 13 is moved along the guide member 12 by friction driving between the pressing member 6 of the motor 1 and the driving force transmitting member 14 of the stage 13. That. Reference numeral 20 denotes a case that accommodates the ultrasonic motor 1. The ultrasonic motor 1 is sandwiched between four springs 21 in the case 20 and installed between the rear end of the ultrasonic motor 1 and the case 20. The pressing member 6 of the ultrasonic motor 1 is pressed against the driving force transmitting member 14 by the spring 22. Also,
Reference numeral 23 denotes a load cell for measuring the pressing force of the ultrasonic motor 1.

According to the present invention, the ultrasonic motor 1
Since the pressing member 6 is made of alumina ceramics having an alumina content of 99.5% by weight or more and a Vickers hardness of 15.2 GPa or more, or formed of single crystal alumina, In the friction drive with the driving force transmitting member 14, the pressing member 6
The abrasion and abrasion at the contact surface can be reduced, and the rigidity is high, so that it is not deformed by the stress acting upon friction driving with the driving force transmitting member 14 and the transmission efficiency of the driving force can be increased. it can. Moreover, because of its excellent heat dissipation, heat generated by friction driving with the driving force transmitting member 14 can be effectively released.

Therefore, if the ultrasonic motor 1 of the present invention is used in a guide device using the driving source of the stage 13 as a driving source, the ultrasonic motor 1 is less worn, and the driving force transmitting member 14 as a mating member is worn or scratched. Since the occurrence of scratches can be reduced,
A long-life guide device can be obtained, and the pressing member 6 has very little shedding.
4 can always be stabilized, the movement and positioning accuracy of the stage 13 can be improved, and an appropriate frictional force with the driving force transmitting member 14 can be obtained. Even if it vibrates at a high speed, slippage hardly occurs between the pressing member 6 and the driving force transmitting member 14, and the stage 13 can be moved at a high speed.

That is, when the pressing member 6 is formed of alumina ceramics, the alumina content is 99.5% by weight.
The reason for the above is that when the alumina content is less than 99.5% by weight, calcia (Ca
O), silica (SiO ₂ ), magnesia (MgO), and the like, which constitute a grain boundary layer in the sintered body, account for a large proportion of the sintered body. Cracks occur in the weak grain boundary layer,
This is because the crack progresses from this crack as a starting point, and eventually the alumina particles are shed. If the alumina content is 99.5% by weight or more, the grain boundary layer existing in the sintered body occupies. Since the ratio is small, the occurrence of cracks in the grain boundary layer is small, and even if the cracks occur, the progress of the cracks is small, so that the alumina particles can be prevented from falling. In addition, since the hardness can be increased with the increase in the alumina content, the wear can be reduced, and the specific rigidity can also be increased. 6 is not deformed, and the transmission efficiency of the driving force can be increased. Furthermore, by increasing the alumina content, the thermal conductivity also increases, so that heat generated by friction driving with the driving force transmitting member 14 can be effectively released.

In order to obtain the above alumina ceramics, 99.5% by weight or more of alumina is used, and at least one of calcia (CaO), silica (SiO ₂ ) and magnesia (MgO), which are sintering aids, is mixed with 0%. A slurry of the mixed powder added in a range of not more than 0.5% by weight is prepared, and formed into a predetermined shape by a well-known ceramic forming method such as a uniaxial pressing method, an isopressing method, or an injection molding method. ~ 1
It can be obtained by firing at a maximum temperature of 750 ° C. for about 1 to 10 hours.

When the pressing member 6 is made of single crystal alumina, the single crystal alumina has a Vickers hardness of 16G.
Having a hardness of Pa or higher and higher than the above alumina ceramics, the specific rigidity is high because it is a single crystal,
Since the pressing member 6 is not deformed by the stress applied during friction driving with the driving force transmission member 14, the transmission efficiency of the driving force can be increased. In addition, since there is no grain boundary serving as a starting point of grain removal unlike alumina ceramics, graining does not occur. In addition, since there is no grain boundary layer that hinders heat transfer, it has a higher thermal conductivity than alumina ceramics, and can more effectively release heat generated by friction driving with the driving force transmitting member 14.

Single crystal alumina has A-plane (1120), C-plane (0001), R-plane (1102), etc., depending on the crystal orientation. In particular, the A-plane (1120) has a Vickers hardness of 23 GPa or more. And high hardness, the wear of the contact surface can be further reduced by forming the contact surface with the stage 13 on the A surface.

In order to obtain the above-mentioned single crystal alumina, an EFG method is employed in which a seed crystal is brought into contact with a heated and melted alumina solution, and the seed crystal is pulled up through a crystal growth die having an arbitrary cross-sectional shape. By controlling the crystal orientation of the seed crystal, a single crystal having the same crystal orientation as the seed crystal can be obtained. Further, the single-crystal alumina referred to in the present invention refers to transparent white sapphire, blue sapphire containing titanium oxide and iron oxide, yellow sapphire containing magnesia and nickel oxide, and ruby containing chromium oxide, as described above. Not limited to artificially produced ones, natural single-crystal alumina can also be used.

However, even if the pressing member 6 is formed of the above-mentioned alumina ceramics or single crystal alumina, if the pressing member 6 has a rough surface at the contact surface with the stage 13, it is a mating member in the initial adaptation process. The drive force transmitting member 14 generates scratches and the like, and the wear proceeds rapidly, and the contact surface of the pressing member 6 is severely worn.

Therefore, if the contact surface of the pressing member 6 with the stage 13 is 0.2 μm or less in arithmetic average roughness (Ra), wear of the driving force transmitting member 14 is suppressed and the pressing member 6
Can also be reduced.

In this embodiment, the multi-mode ultrasonic motor 1 has been described as an example. However, a standing vibration type or traveling wave of a single vibration mode, a mode conversion type of a plurality of vibration modes, and a composite vibration type ultrasonic motor 1 are described. It goes without saying that the present invention can be applied to a sound wave motor.

In FIG. 2, a guide device in which the stage 13 moves linearly has been described as an example. However, the present invention can also be applied to a guide device in which the movable body rotates, so long as it does not depart from the gist of the present invention. It goes without saying that various improvements and changes can be made.

[0030]

(Embodiment 1) Here, a pressing member 6 of an ultrasonic motor 1 is manufactured from alumina ceramics having different alumina content and hardness, and these ultrasonic motors 1 are incorporated into the guide device of FIG. An experiment was conducted to examine the amount of wear of the pressing member 6 when the stage 13 was frictionally driven and the amount of wear of the driving force transmitting member 14 as the mating member.

In this experiment, the size of the piezoelectric ceramic plate 2 constituting the vibrating body 5 of the ultrasonic motor 1 was set to a length of 30.
mm, width 7.5 mm, thickness 3 mm, and made of lead zirconate titanate-based piezoelectric ceramics, and the dimensions of the pressing member 6 joined to the piezoelectric ceramic plate 2 are 4.2 mm in length and 3 mm in diameter. As a cylinder,
And the contact surface is a spherical surface having a radius of curvature of 7 mm,
It was formed from alumina ceramics having the alumina content and Vickers hardness shown in Table 1.

The guide member 12 constituting the guide device
The stage 13 having a weight of 5 kg was moved via the guide member 12 using a cross roller guide having a stroke of 100 mm. In addition, a driving force transmitting member 14 that contacts the pressing member 6 of the ultrasonic motor 1
Has stainless steel (SUS304), an alumina content of 99% by weight, and a Vickers hardness of 15.2 GPa.
And the contact surface with the pressing member 6 has an arithmetic mean roughness (Ra) of 0.05 μm.
m.

A moving distance of 100 m is set as a moving profile of the stage 13 which is set in the control unit 18 in advance.
m, an acceleration / deceleration of 0.03 G, and a trapezoidal control with a maximum speed of 100 mm / s, and the ultrasonic motor 1 was driven at a driving frequency of 40 kHz. Then, the wear amount of the pressing member 6 and the wear amount of the driving force transmission member 14 after the stage 13 was driven for 500 km under these conditions were measured.

The results are shown in Table 1.

[0035]

[Table 1]

As a result, as is apparent from Table 1, regardless of the material of the driving force transmitting member 14, the larger the alumina content of the alumina ceramic forming the pressing member 6, the greater the pressing member 6 and the driving force transmitting member 14. It can be seen that the abrasion can be reduced. Then, the sample No. 4 to 7 and sample Nos. 1
As shown in 1 to 14, the pressing member 6 has an alumina content of 9
By using alumina ceramics of 9.5% by weight or more and Vickers hardness of 15.2 GPa or more, the amount of wear of the pressing member 6 can be reduced to single digits and the amount of wear of the driving force transmitting member 14 is significantly reduced. We were able to. Then, when the contact surface of each sample was observed, the sample No. 1 to 3 and sample Nos. Although many abrasions were observed on the contact surfaces of the pressing members 6 of Nos. 8 to 10, the sample Nos. 4 to 7 and sample Nos. 11
On the contact surfaces of the pressing members 6 to 14, almost no shedding was observed.

However, the sample No. 16 to 19, even if the pressing member 6 is formed of alumina ceramics having an alumina content of 99.5% by weight and a Vickers hardness of 15.2 GPa, the arithmetic average roughness (Ra) of the contact surface is obtained. Is larger than 0.2 μm, it can be seen that the amount of wear of both itself and others increases significantly.

From these results, it is clear that the pressing member 6 of the ultrasonic motor 1 is formed of alumina ceramics having an alumina content of 99.5% by weight or more and a Vickers hardness of 15.2 GPa or more, and the arithmetic mean roughness of the contact surface. Sa (Ra)
It can be understood that the wear amount can be significantly reduced for both the self and others by setting the average particle size to 0.2 μm or less. (Example 2) Next, the same experiment as in Example 1 was performed, except that the pressing member 6 of the ultrasonic motor 1 was replaced with sapphire having an arbitrary crystal orientation. The driving force transmitting member 14 has an alumina content of 99% by weight and a Vickers hardness of 1%.
Only one kind of alumina ceramics having 5.2 GPa was used.

The results are as shown in Table 2.

[0040]

[Table 2]

As a result, by using single crystal alumina for the pressing member 6, the pressing member 6 has an alumina content of 99.5.
It can be seen that abrasion can be reduced to a level equal to or higher than that using alumina ceramics having a Vickers hardness of 15.2 GPa or more by weight or more.

Further, by setting the crystal orientation of the single-crystal alumina forming the contact surface of the pressing member 6 to be the A-plane, the amount of abrasion was able to be reduced most by itself and others.

However, as in the case of Example 1, when the arithmetic average roughness (Ra) of the contact surface was larger than 0.2 μm, the amount of wear on both the self and the other was greatly increased.

From these results, it is found that the pressing member 6 of the ultrasonic motor 1 is made of single-crystal alumina and the arithmetic average roughness (Ra) of the contact surface is set to 0.2 μm or less, so that the wear amount of the self and others is reduced. It can be seen that can be greatly reduced. (Embodiment 3) Next, the pressing member 6 of the ultrasonic motor 1 is formed of alumina ceramics or single crystal alumina having an alumina content of 99.5% by weight and a Vickers hardness of 15.2 GPa or more. Driving force transmitting member 1
4 was made of alumina ceramics having different alumina content and hardness as shown in Table 3, and the same experiment as in Example 1 was conducted.

The results are as shown in Table 3.

[0046]

[Table 3]

As a result, if the alumina content of the alumina ceramics forming the driving force transmitting member 14 is increased,
It can be seen that the wear amount can be further reduced for both the self and others.

[0048]

As described above, according to the present invention, in the ultrasonic motor including the vibrating body and the pressing member for transmitting the vibration of the vibrating body to the movable body side, the pressing member has an alumina content. It is made of alumina ceramic or single-crystal alumina having 99.5% by weight or more and Vickers hardness of 15.2 GPa or more, and a contact surface in contact with the movable body side has an arithmetic average roughness (Ra) of 0.2 μm.
By adopting the following, it is possible to reduce degranulation and abrasion on the contact surface of the pressing member in the friction drive with the movable member side. Particularly, when the pressing member is formed of single-crystal alumina, the contact between the pressing member and the movable member can be reduced. By setting the crystal orientation of the contact surface to the A surface having high hardness, wear of the pressing member can be further reduced. In addition, since the above-mentioned alumina ceramics and single crystal alumina have high rigidity, they are not deformed by the stress applied during friction driving, so that the transmission efficiency of the driving force can be increased, and since the heat dissipation is excellent, the friction driving can be performed. The heat generated by the heat can be effectively dissipated.

Therefore, if the ultrasonic motor according to the present invention is used for a guide device using a movable body as a driving source, the ultrasonic motor is less worn, and the abrasion of the movable body as a mating member and the occurrence of scratches are reduced. As a result, it is possible to provide a guide device with a long life, and since the shedding of the pressing member is extremely small, the contact state with the movable body side can be always stabilized, and the movement and positioning accuracy of the movable body can be improved. Since an appropriate frictional force with the movable body side can be obtained, even if the ultrasonic motor is vibrated at a high speed, slipping with the movable body hardly occurs, and the movable body can be moved at a high speed.

[Brief description of the drawings]

FIG. 1 is a view showing an example of an ultrasonic motor according to the present invention;
(A) is the front view, (b) is the back view.

FIG. 2 is a partially broken plan view showing an example of a guide device using the ultrasonic motor of the present invention as a drive source of a movable body.

FIG. 3 is a view showing an example of a conventional ultrasonic motor, and FIG.
Is a front view thereof, and (b) is a rear view thereof.

FIG. 4 is a partially broken plan view showing an example of a guide device using a conventional ultrasonic motor as a drive source of a movable body.

[Explanation of symbols]

1, 31: ultrasonic motor 2, 32: piezoelectric ceramic plate 3a, 3b, 3c, 3d, 33a, 33b, 33c, 3
3d: electrode film 4, 34: electrode film 5, 35: vibrating body 6, 36: pressing member 11: base plate 12: guide member 13: stage
14: Driving force transmitting member 15: Linear scale 16: Measuring head 17: Position detecting means 18: Control unit 19: Driver 20: Case 21: Spring 22:
Spring 23: Load cell

Continued on the front page (72) Inventor Yusaku Ishimine 1-1-1 Yamashita-cho, Kokubu-shi, Kagoshima F-term in the Kyocera Corporation Kagoshima Kokubu Plant (reference) 5H680 AA12 BB13 BC09 BC10 CC02 DD02 DD23 DD39 DD53 DD59 DD65 DD74 GG02 GG42 GG43 GG44

Claims (4)

[Claims] 1. An ultrasonic motor comprising a vibrating body and a pressing member for transmitting vibration of the vibrating body to a movable body, wherein the pressing member has an alumina content of 99.5% by weight or more.
The contact surface which is formed of alumina ceramics having a Vickers hardness of 15.2 GPa or more and is in contact with the movable body side has an arithmetic average roughness (Ra) of 0.2 μm.
An ultrasonic motor characterized by the following. 2. An ultrasonic motor comprising a vibrating body and a pressing member for transmitting the vibration of the vibrating body to the movable body side, wherein the pressing member is formed of single-crystal alumina and is in contact with the movable body side. An ultrasonic motor characterized in that the surface has an arithmetic average roughness (Ra) of 0.2 μm or less. 3. The ultrasonic motor according to claim 2, wherein the crystal orientation of the single-crystal alumina forming the contact surface of the pressing member is the A-plane. 4. The ultrasonic motor according to claim 1 or 2, wherein the pressing member is disposed in contact with a movable body, and the vibration of the ultrasonic motor is transmitted via the pressing member. A guide device using an ultrasonic motor as a drive source of a movable body, wherein the movable body is driven by friction.