JP3523488B2 - Ultrasonic linear motor and driving device using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for determining a position used in a precision machining machine tool, a semiconductor manufacturing device, a measuring device, and the like with ultra precision, and an ultrasonic linear motor used therein. It is a thing.

[0002]

2. Description of the Related Art In recent years, in machine tools for precision machining, semiconductor manufacturing equipment, measuring equipment, etc., an object to be machined or an object to be measured is placed on a table, and a predetermined driving device is used for positioning. An ultrasonic linear motor is used to drive this device, although it is moved to a position.

7 and 8 show a conventional ultrasonic linear motor 1
7 is a front view of the same, and FIG. 8 is a sectional view taken along the line AA in FIG. 7 (see Japanese Patent Laid-Open No. 7-184382).

In these drawings, reference numeral 2 denotes a rectangular plate-shaped piezoelectric ceramic body made of a piezoelectric material of PZT (lead zirconate titanate). The piezoelectric ceramic body 2 has substantially the same rectangular shape on substantially the entire one main surface thereof. The four electrodes 3, 4, 5 and 6 are attached by point plating so that each electrode occupies a ratio of 1/4 of the one main surface.
The electrodes 4 and 5 arranged diagonally are electrically connected by a lead wire 7, and the electrodes 3 and 6 are electrically connected by a lead wire 8. On the other main surface (back surface in FIG. 7) of this piezoelectric ceramic body 2, the other electrode (not shown) is formed over substantially the entire surface by plating or the like, and is grounded. Then, when an AC voltage is applied to the electrodes 4 and 5, the electrodes 3 and 6 are in a floating state, and when an AC voltage is applied to the electrodes 3 and 6, the electrodes 4 and 5 are in a floating state.

Further, since the piezoelectric ceramic body 2 is formed in a rectangular plate shape, among the four end faces on which no electrodes are formed, the end faces along the longitudinal direction are the long side portions 14 and 15, and the faces along the other short side. When the short side portions 17 and 18 are defined as the short side portions 17, a friction portion 9 made of alumina or zirconia is adhered to the central portion of the short side portion 17, and the guide g is in contact with the friction portion 9.
Moreover, the spring-loaded support body 16 is provided at the center of the short side portion 18.
Is provided in a pressed state, the spring-loaded support body 16 applies pressure between the friction portion 9 and the guide g, whereby the movement of the friction portion 9 is transmitted to the guide g. .

On the other hand, since the long side portion 14 of the piezoelectric ceramic body 2 is provided with the pair of fixed supports 10 and 11, and the long side portion 15 is provided with the pair of spring-loaded support bodies 12 and 13, the piezoelectric ceramic body is provided. The movement of the body 2 is restricted, but these supports 1
0, 11, 12, 13 contact the piezoelectric ceramic body 2 at the zero movement point in the x direction along the pair of long side portions 14, 15 of the piezoelectric ceramic body 2, and therefore the movement in the x direction is restricted. However, these supports 10, 11, 12, 13 are y
The piezoelectric ceramic body 2 can slide in any direction.
Can be moved in the y-direction by pressing with the spring-loaded support 16.

Further, according to the ultrasonic linear motor 1 described above, the movement of the friction portion 9 becomes an elliptic movement having the major axis in the x direction, whereby the guide g is linearly moved (in the x direction). As a result, the guide g can be moved to a desired position and stopped.

The ultrasonic linear motor 1 having the above structure is housed in a case and fixed to a support e. Further, the guide g is pressed in the horizontal direction, and the friction portion 9 is brought into a state of being pressed against the guide g. When the ultrasonic linear motor 1 is used, the guide g is moved by the friction part 9, but the guide n is further conveyed by a predetermined route.
And a linear bearing m form a rail, and a guide g is slidably fitted on the rail.

[0009]

However, according to the ultrasonic linear motor 1 having the above-mentioned structure, when the piezoelectric ceramic body 2 is expanded and contracted by applying an AC voltage to the electrodes 3 to 6, the piezoelectric ceramic body 2 is expanded. There is a problem that heat is generated due to the generated internal stress, and especially when the driving speed is increased, the amount of heat generation is remarkably increased.

Therefore, the length of the reference scale for positioning measurement changes due to the thermal expansion, and the members constituting the stage are deformed due to the thermal expansion. Therefore, when the semiconductor exposure apparatus, the coordinate measuring machine, or the like is used, heat is generated. In order to reduce the influence, the driving speed must be slowed down, which is not practical.

In order to eliminate the heat generation of the piezoelectric ceramic body 2, a method of directly cooling it with water or the like has been proposed. However, when the water cooling means is used, the cooling effect is reduced unless water is brought into contact with the piezoelectric ceramic body 2 which is a heat source. Therefore, the water cooling means must be used by directly contacting the piezoelectric ceramic body 2. Therefore, the piezoelectric ceramic body 2 did not vibrate ultrasonically.

When an AC voltage is applied to the electrodes 4 and 5, the electrodes 3 and 6 are in a floating state, and when an AC voltage is applied to the electrodes 3 and 6, the electrodes 4 and 5 are in a floating state, and both are not applied simultaneously. Therefore, there is also a problem that the efficiency is reduced.

The present invention has been completed in view of the above circumstances, and an object thereof is to reduce the heat generation of a piezoelectric ceramic body, thereby enabling highly accurate and efficient positioning of an ultrasonic linear motor. To provide.

Another object of the present invention is to increase the driving speed by using the ultrasonic linear motor of the present invention, thereby enabling efficient positioning with respect to a semiconductor exposure apparatus, a coordinate measuring machine or the like. It is to provide a drive device.

[0015]

In the ultrasonic linear motor of the present invention, electrodes are formed on the inner surface and the outer surface, and an alternating voltage is applied between both electrodes to generate a piezoelectric effect. The vibrator is configured by fixing a plurality of shaped bodies by a plurality of supports arranged in parallel on one side and the other side so that the respective end faces are substantially coincident with each other , and the vibrator is fixed to one end of the vibrator.
Via an elastic member is fixed to the casing to the support, and allowed disposed friction portion at the center of the support fixed to the other end
The AC voltage applied to the piezoelectric ceramic cylinder.
On the other hand, by making a difference between one side and the other side,
It is characterized in that the ends are made to move in an elliptical fashion .

Further, the drive device of the present invention conveys the ultrasonic linear motor of the present invention, a guide that comes into contact with the friction portion of the ultrasonic linear motor and moves by the movement of the friction portion, and this guide by a predetermined route. It is characterized in that it is composed of a substrate.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The ultrasonic linear motor of the present invention will be described in detail below with reference to FIGS. FIG. 1 shows a drive device K1 having an ultrasonic linear motor 20 of the present invention as a main component.
2 is a sectional view taken along the section line B-B in FIG. 1, and FIG. 3 is a perspective view of a piezoelectric ceramic tubular body used in the ultrasonic linear motor 20. Further, FIG. 4 is a front view of a driving device K2 mainly composed of another ultrasonic linear motor 20a of the present invention, and FIG. 5 is a section line CC in FIG.
FIG. 6 is a sectional view according to FIG. 6, and FIG. 6 is a schematic view showing an arrangement state of the piezoelectric ceramic cylindrical body.

In the ultrasonic linear motor 20 of the present invention, two cylindrical or pipe-shaped identical piezoelectric ceramic bodies 21, 22 made of PZT (lead zirconate titanate) as the piezoelectric ceramic cylindrical body are parallel to each other. Electrodes 23 and 24 are plated on the outer peripheral surface of each and electrodes 25 and 26 are plated on the inner peripheral surface thereof. These electrodes 2
Lead wires 27, 2 are attached to 3, 24, 25, 26, respectively.
8, 29 and 30 are connected to apply an AC voltage to the electrodes 23 and 25 of the piezoelectric ceramic body 21 and an AC voltage to the electrodes 24 and 26 of the piezoelectric ceramic body 22.

Piezoelectric ceramic bodies 21, 22 arranged in parallel
Both ends of the metal such as aluminum, copper, iron, alumina,
Supports 31, 3 made of ceramics such as zirconia
It fixes with 2, and forms the said vibrator by this. And
At the other end of the vibrator, that is, at the center of the support 31, a friction portion 33 made of ceramics such as alumina or zirconia
Are joined.

Regarding one end of the vibrator, a casing 37 made of aluminum for surrounding and supporting the piezoelectric ceramic bodies 21, 22 is attached to an elastic support 38 made of silicon rubber or the like as the elastic body. The guide 34 made of ceramics such as alumina or zirconia is pressed horizontally by the elastic support 38, and the friction portion 33 is pressed against the guide 34. Further, the elastic support 40 is horizontally fixed by a fixed support 39 made of ceramics such as alumina and zirconia and an elastic support 40 made of silicon rubber.
Sliding in the vertical direction is performed by the elastic force of.

The ultrasonic linear motor 2 having the above structure
In order to operate the drive device K1 using 0, the guide 34 is moved by the friction part 33, but the guide 34
A rail is formed by a supporting guide 35 as the base body and a linear bearing 36, which conveys a sheet along a predetermined route, and the guide 34 is slidably fitted into the rail. These supporting guides 35 and linear bearings 3
6 is made of stainless steel, carbide, or ceramics. Reference numeral 42 is a support body for fixing the ultrasonic linear motor 20. Although the elastic support 38 is fixed to the case 37, it may be fixed to the support 42 instead.

Therefore, by making a difference between the voltages applied to both the piezoelectric ceramic bodies 21 and 22, the piezoelectric ceramic body 22 contracts when the piezoelectric ceramic body 21 expands, and a diagonal vector force is generated due to the voltage difference. Friction part 3
The tip of 3 becomes elliptical. That is, when the ultrasonic linear motor 20 is driven, a positive AC voltage is applied to the electrode 23, a negative AC voltage is applied to the electrode 24, and an opposite phase is applied between the electrodes 23 and 24. By the effect (piezo effect), the guide 34 moves to the upper side (+ side). On the other hand, by applying a positive AC voltage to the electrode 24 and applying a negative AC voltage of opposite phase to the electrode 23, the guide 34 moves downward. Move to the side (-side).

Thus, the ultrasonic linear motor 20 of the present invention
According to the above, two cylindrical piezoelectric ceramic bodies 21 and 22 are provided.
By using, it is possible to drive most efficiently even if the ceramic volume arranged between the opposing electrodes is reduced. For example, the piezoelectric ceramic bodies 21 and 22 have a thickness of 0.5 mm and a length of 30 mm. In the case of a cylindrical shape, the displacement in the axial direction of the cylinder can be increased while significantly reducing the capacitance value.
The capacitance of 2 could be reduced to about 10 nF.

Such a cylindrical piezoelectric ceramic body 21, 2
Regarding No. 2, when the radial direction and the axial direction of the cylindrical body are compared, the radial displacement does not contribute to ultrasonic driving, so it is better to reduce the displacement to reduce energy loss. By reducing the thickness, the radial displacement is relatively small, and the radial displacement is as small as about 0.1 relative to the axial displacement, resulting in a significant energy loss. Decrease.

Therefore, by using the piezoelectric ceramic bodies 21 and 22 having a small capacitance value, the energy loss is reduced, and as a result, the heat generation amount is reduced. Moreover, the drive voltage can be set to a large value, for example, 5
It was possible to raise the voltage to about 00V, and therefore a large stage could be driven by a small ultrasonic linear motor. Further, since the piezoelectric ceramic bodies 21 and 22 have a hollow structure, the surface area is more than twice as large as that of the conventional product, and in that respect also, the heat radiation effect is increased, and the harmful effect due to heat generation is reduced. Moreover, it was possible to drive without affecting the surrounding environment even in a vacuum without heat dissipation effect.

Regarding the size of the piezoelectric ceramic bodies 21 and 22, the outer diameter t is 2 to 5 mm, preferably 2 to 4 m.
The range of m is advantageous in that the ultrasonic linear motor 20 can be downsized. It is preferable that the thickness is in the range of 0.5 to 2 mm, preferably 0.5 to 1 mm, because the electrostatic capacity can be reduced. Furthermore, it is preferable that the length p be in the range of 10 to 50 mm, preferably 30 to 50 mm, because the efficiency of the elliptical movement can be maximized.

Regarding the other ultrasonic linear motor 20a of the present invention shown in FIGS. 4 to 6, piezoelectric ceramic bodies 21 and 2 are used.
This is a configuration in which four piezoelectric ceramic bodies such as 2 are arranged. 41 is numbered in the drawing for these piezoelectric ceramic bodies, and 41a, 41b, 41c, 41 in FIG.
The arrangement relationship is represented by each number of d. Other configurations are the same as those of the ultrasonic linear motor 20 shown in FIGS. 1 to 3, and the same portions are denoted by the same reference numerals.

In this ultrasonic linear motor 20a, the piezoelectric ceramic bodies 41a and 41c are paired and the piezoelectric ceramic bodies 41b and 41d are paired, and a positive AC voltage is applied to the piezoelectric ceramic bodies 41a and 41c to apply the piezoelectric ceramics. A negative AC voltage is applied to the bodies 41b and 41d to create a voltage difference between the pair of the bodies 41b and 41d, thereby causing the tip of the friction portion 33 to make an elliptical motion. Such elliptical motion can improve the motion performance as compared with the case where the two piezoelectric ceramic bodies described above are used. Moreover, in order to improve the motion performance in this way, it is better to drive two smaller piezoelectric ceramic bodies than to increase the size of one piezoelectric ceramic body, so that the electrostatic capacity decreases, the surface area increases, and the driving voltage decreases. As a result, it was possible to efficiently enhance the exercise performance while reducing the heat generation amount.

[0029]

[Experimental example] Next, an experiment was conducted to compare the heat generation state of the ultrasonic linear motor 20 of the present invention with the heat generation state of the conventional ultrasonic linear motor 1.

The piezoelectric ceramic body 21 used in the present invention,
22 has an outer diameter of 3 mm, an inner diameter of 2 mm, and a length of 30.
mm. The size of the conventional piezoelectric ceramic body 2 is 10 m
It is a plate-like body of m × 3 mm × 30 mm. Both are Physik
Instrumente (PI) PZ of PT130.0 made by Gmbh & Co.
T (lead zirconate titanate) was used.

Then, when the temperature changes of the piezoelectric ceramic body, the guide and the guide support were measured when the ultrasonic linear motor was continuously driven, the following results were obtained. The temperature at the start of the experiment was 20
The temperature was 0 ° C., and the temperature immediately after driving for 1 hour was performed by attaching a thermocouple.

As a result, the ultrasonic linear motor 2 of the present invention is
The piezoceramic bodies 21 and 22, the guide 34, and the guide support 35 of 0 are 1.0 ° C., 0.5 ° C., and 0.1 ° C., respectively.
On the other hand, in the conventional ultrasonic linear motor 1, the piezoelectric ceramic body 2, the guide g, the guide support n
Are 5.0 ° C., 5.0 ° C., and 1.2 ° C., respectively, and thus it can be seen that in the present invention, the degree of temperature rise is low for all members.

The calorific value of the piezoelectric ceramic body is proportional to the AC voltage, and the calorific value rises when the AC voltage is increased (when the driving speed is increased). The amount of heat generation is also proportional to the capacitance value C of the piezoelectric ceramic body, and the amount of heat generation increases when a material having a large capacitance value is used, and this amount of heat generation P is P = Kt
It is represented by an δ · f · C · U ² . Here, K is a proportional constant, tan δ is an angular loss (about 0.05), f is a driving frequency (40 kHz), C is a capacitance, and U is a driving voltage.

By the way, in the conventional ultrasonic linear motor, the piezoelectric ceramic body 2 is a bulk body, and when the dimension of PZT is calculated from the driving ability, it is 30 mm × 10 mm ×
A piezoelectric ceramic of 3 mm is required, but since the bulk-shaped piezoelectric ceramic has a capacitance value of 50 nF, the amount of heat generated is large.

Further, the piezoelectric ceramic body 2 according to the present invention
When the changes in temperature of the piezoelectric ceramic body, the guide 34, and the guide support 35 were measured with various changes of Nos. 1 and 22, the results shown in FIG. 9 were obtained.

In the figure, the black squares represent the temperature changes of the piezoelectric ceramic bodies 21 and 22, and the black triangles represent the guide support 3.
5 shows the temperature change, and the white square shows the temperature change of the guide 34.

If the temperature change of the guide support is 0.1 ° C. or less, it is the allowable value of the temperature difference in the current semiconductor product device, and therefore the positioning device is not affected. As a reference, the piezoelectric ceramic bodies 21 and 22 may be 10 nF or less.

The present invention is not limited to the above-described embodiments, and various modifications and improvements may be made without departing from the scope of the present invention. For example, the piezoelectric ceramic body has a cylindrical shape or a pipe shape, but this shape may be a cylindrical body having an elliptical cross section or a rectangular cross section, and electrodes may be formed on the inner surface and the outer surface.

[0039]

As described above, according to the ultrasonic linear motor of the present invention, since the vibrator made of the piezoelectric ceramic cylindrical body is used, the heat generation amount is remarkably reduced. There was no measurement error due to heat generation, and this enabled highly accurate and efficient positioning.

Further, the ultrasonic linear motor of the present invention is used to increase the driving speed, and thereby the driving device for ultra-precision determining the positions used in precision machining machine tools, semiconductor manufacturing equipment, measuring equipment and the like. In, the positioning can be performed easily and quickly, and as a result, the production cost can be reduced.

[Brief description of drawings]

FIG. 1 is a front view of a drive device of the present invention.

2 is a cross-sectional view taken along the section line BB in FIG.

FIG. 3 is a perspective view of a piezoelectric ceramic tubular body.

FIG. 4 is a front view of another drive device of the present invention.

5 is a cross-sectional view taken along the section line C-C in FIG.

FIG. 6 is a schematic view showing an arrangement state of a piezoelectric ceramic tubular body.

FIG. 7 is a front view of a conventional drive device.

8 is a cross-sectional view taken along the section line AA in FIG.

FIG. 9 is a diagram showing changes in temperature of the piezoelectric ceramic body, the guide, and the guide support body with respect to the capacitance of the piezoelectric ceramic body.

[Explanation of symbols] 1, 20, 20a Ultrasonic linear motor K, K1, K2 drive 2, 21, 22, 41 Piezoelectric ceramic body 23, 24, 25, 26 electrodes 9,33 Friction part g, 34 guide e Support n, 35 support guide m, 36 linear bearing 31, 32 support 37 cases 38, 40 elastic support 39 fixed support

Claims (2)

(57) [Claims] 1. A electrodes formed on inner and outer surfaces, both of the alternating voltage between the electrodes by applying the same which is adapted piezoelectric effect occurs piezoelectric ceramic tubular body, such that each end face is substantially aligned Meanwhile By a plurality of supports arranged side by side on the other side
Fixed to form a vibrator and fixed to one end of the vibrator
The support is fixed to the inside of the casing through an elastic body, and the friction part is arranged at the center of the support fixed to the other end.
AC voltage applied to the piezoelectric ceramic cylinder.
By making a difference between the pressure on one side and the pressure on the other side,
Ultrasonic linear motor , characterized in that the tip of is moved in an elliptical motion . 2. The ultrasonic linear motor according to claim 1, a guide that abuts on a friction portion of the ultrasonic linear motor and moves by the movement of the friction portion, and a base body that conveys the guide along a predetermined route. Drive.