JP4443778B2 - Fluid pressure actuator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an actuator for uniaxial driving, and more particularly to a hydraulic actuator suitable for use in a sealed chamber, such as a vacuum chamber in an electron beam exposure apparatus.
[0002]
[Prior art]
The XY table for the electron beam exposure apparatus is used under high vacuum, and the material used for the actuator is limited to non-magnetic materials so as not to affect the magnetic field for controlling the electron beam trajectory. The For this reason, a configuration in which a table using a nonmagnetic material such as alumina ceramics or beryllium copper is guided by a roller bearing and is friction driven is common.
[0003]
As shown in FIG. 6, the actuator by friction drive sandwiches the slider 62 between a driven wheel (not shown) to which a preload P is applied and the drive wheel 61, and the rotational movement of the drive wheel 61 is linearly applied to the slider 62 by friction. It is a structure that transforms into motion. The drive wheel 61 is driven by a servo motor 63. A table 64 is combined with the slider 62 so as to be slidable on the guide surface by a roller bearing guide. The amount of movement of the table 64 is detected by the displacement sensor 65 and sent to the controller 66. The controller 66 controls the servo motor 63 so that the table 64 is positioned at a predetermined target position in response to the detected movement amount.
[0004]
The actuator shown in FIG. 6 has a structure for one axis, and if this is an X-axis actuator, a separate Y-axis actuator is required. The Y-axis actuator has the same configuration as the X-axis actuator, but the X-axis actuator and the table 64 are integrally moved in the Y-axis direction.
[0005]
[Problems to be solved by the invention]
The above-mentioned actuator is characterized in that it can be driven at a high speed as compared with the ball screw drive mechanism. However, it is a problem that the thrust is small because it is driven by a frictional force. Furthermore, since the coefficient of friction between the drive wheel 61 and the slider 62 is unknown, it is often used at low speeds because slipping is undesirable, and the throughput when used in an electron beam exposure apparatus is 15 to 20 semiconductor wafers. / Hr or so. In order to obtain a larger frictional force, a large preload P is required, which is a problem in terms of reliability such as material wear of the actuator, dust generation, and life reduction.
[0006]
Further, the roller bearing guide is a contact type guide, and the guide accuracy is determined by the processing accuracy of the guide surface, and although the guide rigidity is relatively large, there is a problem that it is vulnerable to dust contamination on the contact surface. In addition, a servo motor 63 is used to rotate the drive wheel 61. Since the servo motor 63 has magnetism, it needs to be installed outside the vacuum chamber, and the slider 62 from outside the vacuum chamber that does not affect the magnetic field of the electron beam. Therefore, the configuration of driving the table 64 must be adopted. This is a problem common to both the X-axis and Y-axis actuators. As a result, an increase in the occupied area of the actuator, a deterioration in motion performance due to a decrease in rigidity due to a longer drive shaft, and the like arise as new problems.
[0007]
Accordingly, an object of the present invention is to provide a fluid pressure actuator that does not use a motor.
[0008]
Another object of the present invention is to provide a hydraulic actuator suitable for use in a vacuum chamber.
[0009]
Still another object of the present invention is to provide a fluid pressure actuator that reduces the weight of the movable part.
[0010]
[Means for Solving the Problems]
According to the present invention, seen including a movable tubular slider while accommodating it and the guide shaft extending in the axial direction, the hydraulic actuator for use in a vacuum chamber, wherein the guide shaft, the central portion And a tapered portion between the thick portion and the thinned portion, and the actuator includes the thinned portion of the guide shaft, the periphery of the tapered portion, and the slider. A pressure chamber is formed between the inner wall and a partition that divides the pressure chamber into two cylinder chambers in the axial direction, provided in the slider, and provided in the guide shaft in each of the two cylinder chambers. are constituted by through the supply / discharge passage allowing out of the compressed fluid from said tapered portion, a both sides of the two cylinder chambers, before Between the guide shaft and the slider, there are provided a discharge part for discharging the leaking fluid from the hydrostatic air bearing and the cylinder chamber, respectively, and a discharge passage from the end part to the discharge part is provided in the guide shaft. The fluid pressure actuator is characterized in that the discharge section includes an exhaust section provided on both sides of the hydrostatic air bearing and a vacuum exhaust section provided on the outer side of the hydrostatic air bearing. Provided.
[0013]
Further, connecting portions for supplying / discharging the compressed fluid are provided at both ends of the guide shaft, and a servo valve is provided in a pipe connected to the connecting portion.
[0014]
Furthermore, before Symbol guide shaft supply passage is provided leading to the hydrostatic air bearings from the end.
[0015]
The actuator is preferably made of a nonmagnetic material except for the slider.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
With reference to FIG. 2, the driving principle of the fluid pressure actuator according to the present invention in the case of a pneumatic actuator will be described. In FIG. 2, the actuator 10 includes a guide shaft 11 having both ends fixed by a support and extending in a uniaxial direction, and a slider 12 movable along the guide shaft 11. The slider 12 is a cylindrical body that can surround the periphery of the guide shaft 11, and a space is formed between the slider 12 and the outer periphery of the guide shaft 11. This space is used as a pressure chamber, and a partition wall 13 that divides the pressure chamber into two cylinder chambers 16 a and 16 b in the axial direction is fixed to the inner wall of the slider 12. The partition wall 13 can also slide along the guide shaft 11 together with the slider 12. Hydrostatic air bearings 14 are provided at both ends of the slider 12, and a bearing air supply system 15 is connected to these hydrostatic air bearings 14. Since the hydrostatic air bearing is well known, a detailed description of the structure is omitted. Cylinder air supply systems 17a and 17b for allowing compressed air to enter and exit from the cylinder chambers 16a and 16b divided into two are connected to both ends of the slider 12, respectively. The cylinder air supply systems 17a and 17b include servo valves 18a and 18b, respectively, and these servo valves 18a and 18b are connected to a compressed air supply source.
[0017]
With such a configuration, when compressed air is supplied to the static pressure air bearing 14, the slider 12 slightly floats with respect to the guide shaft 11. Here, for example, when the servo valve 18a is set to the compressed air supply side and the servo valve 18b is set to the atmosphere release side, the partition wall 13 acts as a piston and the slider 12 moves rightward in FIG. Thus, the slider 12 can be moved to an arbitrary position with respect to the guide shaft 11 by controlling the opening degree of the servo valves 18a and 18b. For the position control system, the same method as described in FIG. 6 can be adopted. That is, the controller described with reference to FIG. 6 may control the opening degree of the servo valves 18a and 18b in accordance with the amount of displacement of the slider 12, and detailed description thereof will be omitted.
[0018]
Next, an example of an actuator 10 using the above driving principle will be described with reference to FIG. In this example, a shaft body having a quadrangular cross section is used as the guide shaft 11, and the slider 12 is also formed into a quadrangular cross section having a square internal section space through which the guide shaft 11 can be inserted. In particular, the gap between the inner wall of the slider 12 and the outer peripheral surface of the guide shaft 11 is slight. In addition, the guide shaft 11 is thinned so that the thick portion and the narrowed portion are tapered so that the pressure chamber can be formed in a region near the center of the guide shaft 11. A partition wall 13 slidable along the guide shaft 11 is fixed to the inner wall of the slider 12 in order to partition the pressure chamber into two cylinder chambers 16 a and 16 b.
[0019]
Below, the structure of the cylinder chamber 16a side among the cylinder chambers 16a and 16b divided into two is demonstrated. The cylinder chamber 16b side has the same structure.
[0020]
In order to allow compressed air to enter and exit the cylinder chamber 16a, an air passage 11-1 is provided in the center of the guide shaft 11 from its end toward the center. The air passage 11-1 is branched into a plurality of portions near the cylinder chamber 16a and communicates with the cylinder chamber 16a at the tapered portion so that the pressure distribution in the cylinder chamber 16a is uniform. An air pipe is connected to the air passage 11-1 at the end of the guide shaft 11, and the servo valve described with reference to FIG. The maximum stroke of the slider 12 is determined by the axial dimensions of the cylinder chambers 16a and 16b.
[0021]
Referring also to FIG. 3, a hydrostatic air bearing 14 is also provided around the guide shaft 11 near the cylinder chamber 16 a, and exhaust portions 19-1 and 19-2 are provided on both sides of the hydrostatic air bearing 14. It is done. Since the cross-sectional shape of the guide shaft 11 is rectangular, the hydrostatic air bearing 14 is provided on its four surfaces. The exhaust parts 19-1 and 19-2 are for exhausting leaked air from the cylinder chamber 16a and air from the static pressure air bearing 14, and are provided with grooves around the guide shaft 11 for easy exhaust. The exhaust gas is exhausted through this groove. The guide shaft 11 is further provided with a vacuum exhaust part 19-3 at a position outside the hydrostatic air bearing 14 in the axial direction. The evacuation unit 19-3 is provided in consideration of use in a vacuum chamber, and the evacuation unit 19-3 also has a groove around the guide shaft 11 in order to facilitate evacuation. It is formed and evacuated through this groove.
[0022]
In order to supply compressed air to the static pressure air bearing 14, a plurality of air passages 11-2 extending from the end portion to the static pressure air bearing 14 are provided in the guide shaft 11. In the guide shaft 11, a plurality of exhaust passages 11-3 extending from the end portions to the grooves of the exhaust portions 19-1 and 19-2 are also provided. Further, an exhaust passage 11-4 extending from the end of the guide shaft 11 to the groove of the vacuum exhaust section 19-3 is provided. The exhaust passage 11-4 is preferably provided with holes in the groove of the vacuum exhaust part 19-3 for each of the four surfaces of the guide shaft 11 and communicates with the holes. In FIG. 3, for convenience, a plurality of types of passages provided in the guide shaft 11 are all shown by solid lines, but it goes without saying that these passages are provided at different positions in the circumferential direction in the guide shaft 11. Yes.
[0023]
An air pipe is connected to the plurality of air passages 11-2 at the end of the guide shaft 11, and a compressed air supply source is further provided. Similarly, an air pipe is connected to the plurality of exhaust passages 11-3 at the end of the guide shaft 11, and an exhaust pump is further provided. An air pipe is connected to the exhaust passage 11-4 at the end of the guide shaft 11, and a vacuum exhaust pump is further provided.
[0024]
Note that both end portions of the guide shaft 11 penetrate the side walls so as to be supported on the side walls of the vacuum chamber 1 as shown in FIG. Therefore, the connection of the air pipes at both ends of the guide shaft 11 is performed outside the vacuum chamber 1.
[0025]
When the actuator is used under a high vacuum such as a vacuum chamber in an electron beam exposure apparatus, the material of each component is made to be a slider 12 so as not to affect the magnetic field that controls the electron beam trajectory. A non-magnetic material such as alumina ceramics or beryllium copper is used. On the other hand, titanium is preferable for the slider 12. This is because if the thickness of the slider 12 is reduced in order to reduce the weight of the movable portion, that is, a material such as alumina ceramic or beryllium copper, the slider 12 is easily deformed by compressed air, which adversely affects movement. It is. Titanium is suitable for weight reduction because it has a large mechanical strength even if it is thinner than the above materials.
[0026]
FIG. 4 shows another example of the actuator. In this example, the guide shaft 11 ′ has the same cross-sectional shape with respect to the axial direction. On the other hand, the cylindrical member which connects slider 12 ', covering two members 12-1 and 12-2 through which guide shaft 11' is inserted, and covering these two members 12-1 and 12-2 The pressure chamber is formed around the central portion of the guide shaft 11 ′. Furthermore, by fixing the partition wall 13 'to the guide shaft 11' in the pressure chamber, the pressure chamber is divided into two cylinder chambers 16a and 16b. The two members 12-1 and 12-2 are movable along the guide shaft 11 ′ together with the cylindrical body 12-3, and the inner wall of the cylindrical body 12-3 forming the pressure chamber is a partition wall 13. It can slide on the outer periphery of ′. The structure for allowing compressed air to enter and exit the cylinder chambers 16a and 16b, the static pressure bearing part 14, the exhaust parts 19-1 and 19-2, the vacuum exhaust part 19-3 and the structure around them are the same as the above example. The same is good.
[0027]
Also in this example, the slider 12 ', which is a movable part, in particular, the cylindrical body 12-3 can be made of titanium, and the weight of the movable part can be reduced, and the other fixed parts are made of the non-magnetic material described above. Is done.
[0028]
Although this actuator differs from the example of FIG. 1 in that, for example, when compressed air is introduced into the cylinder chamber 16a ′, the slider 12 ′ moves to the left in FIG. 4, the operating principle is exactly the same.
[0029]
FIG. 5 shows still another example of the actuator. In this example, the guide shaft is composed of two shaft bodies 21a and 21b having one end portions opposed to each other at a predetermined distance so that the central axes coincide with each other. The two shaft bodies 21a and 21b preferably have a rectangular cross-sectional shape. On the other hand, the slider 22 includes a space (pressure chamber) formed between one end portions of the two shaft bodies 21a and 21b facing each other and a region of a predetermined distance from the one end portion toward the other end portion. It is made up of a cylindrical body having an internal space with a rectangular cross section. Furthermore, the Rukoto provided a partition 13 for partitioning a space formed between the one end into two in the axial direction on the inner wall of the slider 22, the end face of the one end of the shaft 21a, 21b, the inner wall of the slider 22 And the partition wall 13 form two cylinder chambers 16a and 16b . The slider 22 is movable along the guide shafts 21a and 21b. The structure for allowing compressed air to enter and exit the cylinder chambers 16a and 16b, the static pressure bearing portion 14, the exhaust portions 19-1 and 19-2, the vacuum exhaust portion 19-3, and the surrounding structure are shown in the example of FIG. Same as ok.
[0030]
In this example, the slider 22 and the partition wall 13 are made of titanium, and the other fixing members are made of a nonmagnetic material.
[0031]
In this actuator, for example, when compressed air is introduced into the cylinder chamber 16a, the slider 22 moves to the right in FIG. 5 as in the example of FIG. Therefore, the operating principle is exactly the same as in the example of FIG.
[0032]
In the above description, the case of a pneumatic actuator using compressed air has been described. However, not only compressed air but also other fluids such as nitrogen gas or fluids such as water may be used.
[0033]
【The invention's effect】
As described above, since the actuator according to the present invention has a structure in which the slider is guided in a non-contact manner with respect to the guide shaft, problems due to friction between them, that is, material wear, dust generation, Problems such as a decrease in service life can be solved. Further, by forming the movable portion from titanium, the thickness can be reduced and the weight can be reduced. Furthermore, elements other than the compressed air supply source and the pump for evacuation can be arranged in the vacuum chamber, and the occupied area in the vacuum chamber can be reduced. The actuator according to the present invention is particularly suitable for use in a vacuum chamber such as an electron beam exposure apparatus by constituting each component with a nonmagnetic material.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing a structure of an actuator according to the present invention.
FIG. 2 is a diagram for explaining a driving principle of the actuator shown in FIG. 1;
3 is an enlarged cross-sectional view showing a static pressure air bearing portion, an exhaust portion, and a vacuum exhaust portion in FIG. 1 and a passage provided in a guide shaft for connecting them to an air pipe.
FIG. 4 is a sectional view showing another example of an actuator according to the present invention.
FIG. 5 is a sectional view showing still another example of the actuator according to the present invention.
FIG. 6 is a view showing an example of a conventional actuator by friction drive.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vacuum chamber 10 Actuator 11, 21a, 21b Guide shaft 12, 22 Slider 13 Partition 14 Static pressure air bearing 16a, 16b Cylinder chamber 18a, 18b Servo valve 19-1, 19-2 Exhaust part 19-3 Vacuum exhaust part

Claims (4)

Look including a movable tubular slider and the guide shaft extending in the uniaxial direction while accommodating this, the hydraulic actuators used in the vacuum chamber,
The guide shaft has a thinned portion at the center thereof, and has a tapered shape between a thick portion and a thinned portion,
The actuator forms a pressure chamber between the narrowed portion of the guide shaft, the periphery of the tapered portion, and the inner wall of the slider, and divides the pressure chamber into two cylinder chambers in the axial direction. A partition wall is provided on the slider, and each of the cylinder chambers divided into two is configured to allow compressed fluid to enter and exit from the tapered portion through a supply / discharge passage provided in the guide shaft ,
On both sides of the two cylinder chambers, between the guide shaft and the slider, there are provided a hydrostatic air bearing and a discharge portion for discharging leaking fluid from the cylinder chamber, respectively, Provide a discharge passage from its end to the discharge part,
The fluid discharge actuator according to claim 1, wherein the discharge part includes an exhaust part provided on both sides of the static pressure air bearing and a vacuum exhaust part provided on the outer side of the static pressure air bearing . 2. The fluid pressure actuator according to claim 1 , wherein a connecting portion for supplying / discharging the compressed fluid is provided at each end of the guide shaft, and a servo valve is provided in a pipe connected to the connecting portion. Fluid pressure actuator. The fluid pressure actuator of claim 1, wherein, before Symbol guide shaft hydraulic actuator, characterized in that a supply passage leading to the hydrostatic air bearings from the end. The fluid pressure actuator according to any one of claims 1 to 3 hydraulic actuator, characterized in that the actuator was constructed except for the slider in the non-magnetic material.

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