JPH11190339A - Static pressure fluid bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance characteristics of a static fluid pressure bearing, including a resolution, a responsiveness, a straightness and a positioning reproducibility. SOLUTION: Compressed air is fed through a gap between a first member 1 serving as a guide shaft, and a second member 2 serving as a slider surrounding the first member, and accordingly, the second member 2 as the slider is supported by static pressure in a noncontact manner. An ultrasonic motor 5 incorporating a vibrating member 7 which carries out elliptic oscillation when an ultrasonic vibrator 6 serving as a drive means oscillates is set to the second member 2 so that the vibrating member 7 makes into contact with the first member 1 so as to constitute a static pressure fluid bearing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrostatic bearing having an ultrasonic motor as driving means, and more specifically to a thrust bearing and an air spindle used in a linear guide device and the like. It can be suitably used as a radial bearing.

[0002]

2. Description of the Related Art Conventionally, a hydrostatic bearing has been used as a thrust bearing used for a linear guide device for moving and positioning an object at a predetermined position and a radial bearing used for a spindle for controlling the amount of rotation.

FIG. 7 is a perspective view showing a conventional hydrostatic fluid bearing as a linear guide device. This linear guide device includes a first member 21 forming a guide shaft and a slider surrounding the first member 21. And the second member 22
By supplying a compressed fluid from the fluid supply hole 23 provided in the member 22 to the gap between the first member 21 and the second member 22 to form a hydrostatic fluid layer, the second member 22 as a slider is brought into a non-contact state. Was to be supported.

A nut 24 is attached to a side surface of the second member 22. The nut 24 is connected to a screw shaft 25 rotatably supported by a ball screw system, and the screw shaft 25 is electromagnetically connected. The second member 22 as a slider is moved to a predetermined position by being rotated by the expression motor 26,
Positioning was performed (Japanese Patent Laid-Open No. 58-1939).
No. 64, JP-A-1-135960, JP-A-1
159152).

[0005]

However, in the conventional hydrostatic bearing as described above, the second member 22 as the slider and the electromagnetic motor 26 as the driving means are connected via the power transmission means. Therefore, the coupling portion between the nut 24 and the screw shaft 25 constituting the power transmission means and the screw shaft 25
And the screw shaft 25 at the joint between the motor and the motor 26.
When the second member 22 is moved due to warpage or the like, yawing or pitching occurs, and there is a problem that the second member 22 cannot be moved smoothly.

In recent years, positioning accuracy on the order of nanometers has been required for hydrostatic fluid bearings used for ultra-high precision measurement and ultra-high precision machining. In the conventional hydrostatic bearing used, the backlash between the nut 24 and the screw shaft 25 and between the screw shaft 25 and the motor 26, the nut 24 and the screw shaft 25
And the like, it is difficult to position the second member 22 as a slider at a resolution of the order of nanometers due to the sliding resistance between the ball and a ball (not shown) connecting the second member 22 and the pitch accuracy of the screw shaft 25. There was a point. In addition, due to the effects of the backlash and the sliding resistance, the reproducibility of positioning when the second member 22 is repeatedly moved to a predetermined position is poor.

Further, the electromagnetic motor 26 for rotating the screw shaft 25 has a non-contact between the rotating shaft and the coil in the motor. However, there is a problem that vibration is generated and it cannot be stopped immediately. Therefore, there is a limit in shortening the time from the movement of the second member 22 to the positioning at the predetermined position.

In addition, since the electromagnetic motor 26 has a considerably large magnetism, there are the following problems in the manufacturing process of semiconductor devices and electronic parts.

For example, during exposure processing in a semiconductor manufacturing process, the second member 22 as a slider is used due to the presence of a magnetic field.
The output result of the linear scale for detecting the position of is out of order, the positioning accuracy is reduced, and an accurate exposure process cannot be performed because the electron beam is bent by a magnetic field.

In addition, the conventional hydrostatic bearing requires a nut 24 and a screw shaft 25 as power transmission means to move and position the second member 22 as a slider. There is also a problem that a large space is required for installation.

[0011]

SUMMARY OF THE INVENTION In view of the above problems, the present invention comprises a first member and a second member surrounding the first member, and a gap between the first member and the second member is provided. In a hydrostatic fluid bearing formed by supplying a compressed fluid to form a hydrostatic fluid layer and moving or rotating the first member or the second member in a non-contact state, the elliptical shape is caused by the vibration of the ultrasonic vibrator. An ultrasonic motor having a vibrating body is disposed on the second member, and the driving force of the ultrasonic motor moves or rotates the first member or the second member.

[0012]

According to the present invention, since the first member and the second member are statically supported in a non-contact state, there is almost no sliding resistance at the time of movement or rotation, and the first member or the second member has no sliding resistance. The second member can be smoothly moved or rotated. Then, an ultrasonic motor is used as a driving unit, and the ultrasonic motor is vibrated in a state where the ultrasonic motor is in contact with the first member.
Because a driving force can be directly applied to the first member or the second member by the frictional resistance between the members and can be moved or rotated, high-resolution positioning is possible,
Straightness and positioning reproducibility can be greatly improved. In addition, since a conventional power transmission means such as a ball screw system is not required, the entire bearing can be made compact.

Further, the ultrasonic motor used as the driving means does not generate vibration when stopped, unlike an electromagnetic motor, and can be stopped in a short time, so that the time required for positioning can be shortened. In addition, the responsiveness can be improved, and since it is non-magnetic, it can be used also in a manufacturing process of a semiconductor device or an electronic component, which does not want to generate a magnetic field.

[0014]

Embodiments of the present invention will be described below. FIG. 1 is a perspective view showing an example in which the hydrostatic bearing according to the present invention is used for a linear guide device, and includes a first member 1 forming a guide shaft and a second member as a slider surrounding the first member 1.
A static pressure fluid layer is formed by supplying a compressed fluid to a gap between the first member 1 and the second member 2 from a fluid supply hole 3 provided on a side surface of the second member 2; The second member 2 as a slider is supported without contact with the first member as a guide shaft.

As shown in FIG. 2, the inner surface of each of the wall plates 2A to 2D constituting the second member 2 has a main groove 2a communicating with the fluid supply hole 3 and connecting the wall plates 2A to 2D. T-shaped shallow throttle grooves 2b communicating with the main grooves 2a are provided, respectively, and the compressed fluid supplied to the fluid supply holes 3 is supplied to each wall through the main grooves 2a and the throttle grooves 2b. Board 2A
2D, and forms a hydrostatic fluid layer in the gap between the first member 1 and the second member 2.

The linear guide device is an ultrasonic motor 5 comprising an ultrasonic vibrator 6 made of a rectangular parallelepiped piezoelectric material and a columnar vibrator 7 attached to an end face of the ultrasonic vibrator 6. The ultrasonic motor 5 is disposed on the second member 2 in a state where the vibrating body 7 is in contact with the first member 1.

As shown in FIG. 3, the fixing structure of the ultrasonic motor 5 is provided with a recess in the wall 2C of the second member 2, and a case 4 is fixed to the wall 2C so as to surround the recess. . The ultrasonic vibrator 6 of the ultrasonic motor 5 is housed in the case 4, and the elastic support 8 is disposed between the ultrasonic vibrator 6 and the case 4 to form the ultrasonic vibrator 6. A pin 9 provided through the case 4 is brought into contact with the surface of the ultrasonic vibrator 6 on the side opposite to the vibrator 7, and the distal end of the pin 9 is supported. By interposing the coil 10 between the flange portion 9a provided in the case and the case 4, the vibrating body 7 of the ultrasonic motor 5 is moved to the first position.
It is in contact with the member 1.

A linear encoder or the like can be used to detect the position of the second member 2, and although not shown, a linear scale is provided on the lower surface of the first member 1 and the wall plate 2B of the second member 2 is provided. The position information may be detected by arranging a detection head at the position and reading the scale of the linear scale with the detection head.

In order to operate the linear guide device, an alternating voltage is applied to the ultrasonic motor 5 to cause the ultrasonic vibrator 6 to elliptically vibrate, so that the frictional resistance between the vibrating body 7 and the first member 1 is increased. The slider 2 can move the second member 2 as a slider in the direction of the arrow, and the position detection means such as a linear scale detects that the second member 2 has reached a predetermined position, and energizes the ultrasonic motor 5. Is closed, the frictional resistance between the vibrating body 7 and the first member 1 sharply increases, so that the second member 2 as a slider immediately does not generate vibration.
Can be stopped and positioned at a predetermined position.
Note that the phase of the AC voltage applied to the ultrasonic motor 5 is 90
The second member 2 as a slider can be moved in the direction opposite to the arrow by shifting the angle.

According to the present invention, the ultrasonic motor 5 is used as the driving means, and the vibrating body 7 of the ultrasonic motor 5 is moved to the first position.
Since it is arranged in a state of being in contact with the member 1 and the driving force is directly applied to the second member 2 by frictional resistance between them, pitching and yawing during movement of the second member 2 are suppressed, Straightness can be improved, and high-resolution positioning on the order of nanometers by the ultrasonic motor 5 and the time required to move the second member 2 to a predetermined position can be significantly reduced. it can.

Further, unlike the conventional linear guide device, power transmission means such as a ball screw type is not required, so that the entire device can be made compact and the ultrasonic motor 5 can be used.
Since it is non-magnetic, it can be used in the process of manufacturing semiconductor devices and electronic components that dislike generating a magnetic field.

On the other hand, the problem with the use of the ultrasonic motor 5 is that, when the ultrasonic motor 5 is driven, the ultrasonic vibrator 6 generates heat, and the heat changes the vibration characteristics. In addition to adversely affecting characteristics such as straightness and positioning reproducibility, the first member 1 and the second member 2 are minute due to frictional heat generated by frictional resistance between the vibrating body 7 of the ultrasonic motor 5 and the first member 1. According to the present invention, the ultrasonic motor 5 and the ultrasonic motor 5 are always subjected to the thermal deformation due to the compressed fluid supplied to the gap between the first member 1 and the second member 2, which may adversely affect the measurement accuracy and the processing accuracy. Since the drive unit of the ultrasonic motor 5 can be cooled, the vibration characteristics of the ultrasonic motor 5 deteriorate due to heat generation and the first characteristic due to frictional heat.
Thermal deformation of the member 1 and the second member can be suppressed.

Thus, by using the linear guide device of the present invention, high-resolution positioning can be performed, and responsiveness, straightness, and positioning reproducibility can be greatly improved. It can be suitably used for high precision machining.

Next, another embodiment of the present invention will be described.
FIG. 4 is a perspective view showing an example in which the hydrostatic bearing according to the present invention is used for an air spindle, and includes a first member 11 serving as a column-shaped rotating shaft, and a cylindrical member surrounding the first member 11. A second member 12 forming a fixed body;
A compressed fluid is supplied to a gap between the first member 11 and the second member 12 through a fluid supply hole 13 provided on the side surface of the second member 12 to form a hydrostatic fluid layer, and the first member 11 as a rotation axis is fixed. The second member 12 as a body is supported in a non-contact state.

As shown in FIG. 5, a porous body 2a made of metal or ceramics is embedded in the inner surface of the second member 12, and the compressed fluid supplied to the fluid supply hole 13 is supplied to the porous member 2a. By spraying the first member 11 from the body 2a, a hydrostatic fluid layer is formed in the gap between the first member 11 and the second member 12.

This air spindle is provided with an ultrasonic motor 15 comprising an ultrasonic vibrator 16 made of a rectangular parallelepiped piezoelectric material and a columnar vibrator 17 attached to an end face of the ultrasonic vibrator 16. The vibration member 17 of the ultrasonic motor 15 is disposed on the second member 12 in a state where the vibration member 17 is in contact with the outer peripheral surface of the first member 11.

As shown in FIG. 6, a structure for fixing the ultrasonic motor 15 is provided with a concave portion in a part of the second member 2, and a case 14 is fixed so as to surround the concave portion. Then, the ultrasonic vibrator 16 of the ultrasonic motor 15 is housed in the case 14. An elastic support 18 is disposed between the ultrasonic vibrator 16 and the case 14, and the ultrasonic vibrator 16 Of the ultrasonic vibrator 16
A pin 19 provided through the case 14 is in contact with the surface on the opposite side of the vibrating body 17. A coil 19 is provided between a flange 19 a provided at the tip of the pin 19 and the case 14. 20 so that the ultrasonic motor 1
The fifth vibrating body 17 is in contact with the first member 11. The second member 12 has a through hole 1 communicating with the case 14.
The compressed fluid supplied to the gap between the first member 11 and the second member 12 is also guided from the through hole 12b to increase the cooling efficiency of the ultrasonic motor 15.

To drive this air spindle,
AC voltage is applied to the ultrasonic motor 15 and the ultrasonic vibrator 1
6 can be rotated in the direction of the arrow by applying a driving force to the first member 11 as a rotating shaft by frictional resistance between the vibrating body 17 and the first member 11 by causing the first member 11 to rotate in the direction of the arrow. When it is detected that the member 11 has rotated to a predetermined position and the power supply to the ultrasonic motor 15 is closed, the vibration body 17 and the first
Since the frictional resistance between the first member 11 and the member 11 increases rapidly, the first member 11 serving as the rotating shaft can be stopped immediately without vibration to control the rotation amount to a predetermined value. Note that the phase of the AC voltage applied to the ultrasonic motor 15 is 90
If it is shifted, the first member 11 as a rotation axis can be rotated in the direction opposite to the arrow.

According to the present invention, the ultrasonic motor 15 is used as the driving means, and the vibrating body 17 of the ultrasonic motor 15 is used.
Are arranged in contact with the first member 11, and the driving force is directly applied to the first member 11 by frictional resistance therebetween, so that the first member 11 can be smoothly rotated. Besides, it is possible to control the rotation amount with high resolution by the ultrasonic motor 15 and improve the responsiveness of the first member 11.

Thus, the use of the air spindle of the present invention makes it possible to control the amount of rotation with high resolution, and it can be suitably used as a spindle requiring position control.

In the hydrostatic bearing shown in FIGS. 1 and 4, the materials constituting the first members 1, 11 and the second members 2, 12 are lightweight, have a small coefficient of thermal expansion, and are processed with high precision. Preferably, ceramics such as alumina, zirconia, silicon carbide, silicon nitride, and aluminum nitride can be used.

The fixing structure of the ultrasonic motors 5, 15 is not limited to those shown in FIGS. 3 and 6, and the vibration members 7,
Any structure can be used as long as it can fix the first member 17 so as to be in contact with the first members 1 and 11.

(Experimental Example) Here, the hydrostatic bearing of the present invention shown in FIG. 1 and the conventional hydrostatic fluid bearing shown in FIG. 7 were prepared, and an experiment for comparing the performance was performed.

In this experiment, the first members 1 and 21 as the guide shafts constituting the hydrostatic bearing were used in a cross section of 60 × 6.
The second members 2 and 21 serving as sliders each have a width of 110 mm and a length of 150 m.
m, two wall boards 2B and 2D having a thickness of 20 mm and a width of 60 m
m, 150 mm long, 25 mm thick two wall plates 2A,
What joined 2C and 2C was used. Each of the first members 1 and 21 and the second members 2 and 22 has a purity of 9%.
It was formed of 9.5% alumina ceramics.

Then, the moving stroke is set to 300 mm, the moving time of the second members 2 and 21 as the slider,
Positioning resolution and straightness accuracy were measured.

The results are as shown in Table 1.

[0037]

[Table 1]

As a result, in the conventional hydrostatic bearing, 1 mm
It took 1 second to move ± 0.1 μm, while the hydrostatic bearing of the present invention took only 0.2 seconds.

The positioning resolution is 0.1 μm in the conventional hydrostatic bearing, whereas the hydrostatic bearing of the present invention has a resolution of 1/20 of 0.005 μm.

Further, in the straightness accuracy, the conventional product was 0.3 μm / 300 mm in both the horizontal and vertical directions due to the influence of whirling of the screw shaft 25, whereas the product of the present invention was 0.1 μm / 300 mm. It had an excellent straightness accuracy of 300 mm.

When the sizes of the hydrostatic bearings were compared, the width of the nut 24 and the screw shaft 25 was 10 in the conventional product.
Since there is also 0 mm, the entire width needs to be 210 mm. On the other hand, the present invention only needs to have a space for the case accommodating the ultrasonic motor 5. It was enough.

[0042]

As described above, according to the present invention, the first member and the second member surrounding the first member are provided, and the compressed fluid is supplied to the gap between the first member and the second member. Forming a hydrostatic fluid layer, and moving or rotating the first member or the second member in a non-contact state, in a vibrating body that elliptically vibrates with the vibration of the ultrasonic vibrator The ultrasonic motor provided with the second member is disposed on the second member, and the driving force of the ultrasonic motor moves or rotates the first member or the second member.
High-resolution positioning of the member or the second member is possible, and straightness, responsiveness, and positioning reproducibility can be significantly improved. In addition, since a power transmission means such as a ball screw system as in a conventional hydrostatic fluid bearing is not required, the entire bearing can be made compact.

Further, since the ultrasonic motor and the drive section of the ultrasonic motor can be constantly cooled by the compressed fluid supplied to the gap between the first member and the second member, the heat generated by the ultrasonic motor and the ultrasonic wave can be reduced. Immediately dissipates frictional heat in the motor drive, preventing deterioration of vibration characteristics and thermal deformation, and since the ultrasonic motor is non-magnetic, dislikes the generation of a magnetic field as in the semiconductor device manufacturing process. Can be used in such places.

Therefore, if the hydrostatic bearing of the present invention is used, it can be suitably used as a thrust bearing or a radial bearing for ultra-high precision measurement or ultra-high precision machining.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example in which a hydrostatic bearing according to the present invention is used in a linear guide device.

FIG. 2 is a partially broken perspective view showing only a second member of FIG. 1;

FIG. 3 is a sectional view showing a fixing structure of an ultrasonic motor provided in the hydrostatic bearing of FIG. 1;

FIG. 4 is a perspective view showing an example in which the hydrostatic bearing according to the present invention is used for an air spindle.

FIG. 5 is a partially cutaway perspective view showing only a second member of FIG. 4;

FIG. 6 is a sectional view showing a fixing structure of an ultrasonic motor provided in the hydrostatic bearing of FIG. 4;

FIG. 7 is a perspective view showing a conventional hydrostatic bearing as a linear guide device.

[Explanation of symbols]

1 1st member 2 2nd member 2A-2D ...
・ Wall plate 2a ・ ・ ・ Main groove 2b ・ ・ ・ Throttle groove 3 ・ ・ ・ Fluid supply hole 4 ・ ・ ・ Case 5 ・ ・ ・ Ultrasonic motor 6 ・ ・ ・ Ultrasonic vibrator 7 ・ ・
・ Vibrator 8 ・ ・ ・ Elastic support 9 ・ ・ ・ Pin 10 ・ ・ ・ Coil

Claims (1)

[Claims] A first member that surrounds the first member and a second member that surrounds the first member; a compressed fluid is supplied to a gap between the first member and the second member to form a hydrostatic fluid layer; In a hydrostatic bearing in which a first member or a second member is moved or rotated in a non-contact state, an ultrasonic motor including a vibrating body that performs an elliptical vibration with the vibration of an ultrasonic vibrator is provided by the second member. Wherein the first member or the second member is moved or rotated by the driving force of the ultrasonic motor.