JPH10154012A - Stage mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively eliminate the adverse influence of shaft deflection to positioning and straight guide precision and the heat generation of a driving motor with a small mechanism by providing two pairs of elastic hinge parts crossing a connection block, holding rigidity in the feed direction of a ball screw and flexibly deforming the mechanism in the direction of shaft shake. SOLUTION: A ball screw nut 9 incorporated in the ball screw 4 is fitted to a feed block 10. The connection block 11 is fitted to the feed block 10 and a sliding table 2. U-shaped groove notches 12 are provided near the fitting part of the sliding table 2 and near the feed block from upper/lower surfaces to the center. Furthermore, U-shaped groove notches 13 from the upper/lower surfaces are provided. A hinge rotating with the base parts 14 of the U-shaped groove notches 12 and 13 as the center is operated. Then, two pairs of elastic hinge parts crossing the connection block 11 by 90 degrees are provided, and rigidity is held in the feed direction. Then, the mechanism flexibly deforms in the shaft deflection direction of the ball screw 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement in straightness of movement of a positioning stage of a device for inspecting dimensions, shapes, and the like.

[0002]

2. Description of the Related Art A positioning stage used in a precision inspection device for dimensions, shapes, etc., needs to position a detector or an object to be measured at a predetermined position. In addition to precise positioning in the direction, so-called pitching in the direction perpendicular to the feed direction,
It is necessary to minimize the yawing error.

[0003] In particular, when it is necessary to have a linear movement accuracy of positioning or feeding within 1 µm for each of the X, Y, and Z axes, X
The guide must be guided with a straightness of 0.5 μm or less on the axis and the Y axis. However, a screw feed mechanism including a ball screw generally used for feeding a table cannot avoid a runout of about 10 μm. However, there is a problem that the straightness of the X-axis and Y-axis movements is adversely affected.

Therefore, conventionally, there has been a method of providing a hydrostatic bearing in a thrust direction between a nut of a feed screw and a table.

According to this method, there is almost no friction in the axial runout direction of the screw, and the influence of the axial runout of the screw can be reduced. However, the apparatus is large and expensive, and cannot be used for a small and low-cost stage. There was a problem.

Another prior art method uses a linear motor instead of a feed screw to avoid the problem of shaft runout of a ball screw. However, this method also has a problem that the linear motor is expensive and the motor that generates heat is mounted on a moving table, so that the positioning tends to be affected by the heat generation.

Next, one known example which solves such a problem will be described with reference to FIGS. 4 and 5. FIG. FIG. 4 is a perspective view of the positioning stage, and FIG. 5 is a perspective view of the nut holder of FIG. 4 and 5, 21 is a stage base, 22 is a top guide surface, 23 is a side guide surface,
24 is a table, 25 is a sliding material, 26 is a ball screw, 2
7 is a ball screw nut, 28 is a nut holder, 29 is a ball screw bearing, 210 is a coupling, 211 is a motor, 212 is a fastening bolt, 213, 214, 217, and 2
18 is a notch, 215, 216, 219 and 220 are elastic hinges, 221 is a nut holder table coupling part, 22
2 is a connecting bolt, 223 is a moving direction of the table 24.

Hereinafter, this operation will be described. The table 24 can be moved in the direction 223 by being guided by the upper surface guide surface 22 and the side surface guide surface 23 finished with high precision via a sliding member 25 fixed to the table 24.

The ball screw 26 is parallel to the upper guide surface 22 and the side guide surface 23 by a bearing 29, is supported in the direction of 223 without play, and is rotatably supported.
0 to the motor 211 and the ball screw 2
Ball nut 26 and nut holder 2
8 is connected to the table 24 via the motor 21
The table 24 is moved in the direction of 223 with one rotation.

At this time, the ball screw 26 is
A shaft runout of about 0 μm is generated, but two cuts 21 are provided at the nut holder 28 at 90 ° intersections with each other.
3,214,217,218, the elastic hinge portions 215, 216, each having a thickness of 0.5 mm at the connecting portion.
The force acting on the nut holder table coupling portion 221 due to the bending of the 219 and 220 becomes extremely small. Considering this operation in detail, if the ball screw is now displaced in the up-down direction, the nut holder 28 is resiliently hinged.
By inclining in the directions opposite to each other with 0 as a fulcrum, the ball screw nut 27 can be allowed to move up and down without the nut holder table coupling portion 221 moving in the vertical direction. In the case where the ball screw causes the axial runout in the horizontal direction, the horizontal deflection of the ball screw nut 27 can be tolerated with the same bending as the elastic hinge portions 215 and 216 serving as a fulcrum. Since the axial runout of the ball screw is the coupling force of the horizontal and vertical axial runouts, the elastic hinge portions 215, 216,
By providing the 219 and 220 at two locations crossing each other at 90 °, shaft runout can be absorbed.

However, in this example, a rotation force 224 acts on the nut holder with the rotation of the screw.

This force is transmitted to the table via the nut holder, and the rotation of the table is stopped by a guide such as an air slide.

At this time, the nut holder is twisted, and at the same time, the nut slightly rotates, so that a slight lost motion occurs in the axial movement. In order to reduce this tendency, the nut holder may be made rigid, but the rigidity also becomes rigid in the horizontal and vertical directions, and the accuracy of the true point guidance of the movement tends to deteriorate.

In the present invention, the rotational force acting on the nut holder is blocked by the second linear guide mechanism, and only the force in the moving direction of the moving block and the deviation of the shaft and the true point guide error are transmitted to the connecting block. , More accurate stage can be made.

[0015]

The above-mentioned prior art has the drawback that the apparatus is large and expensive, and that the positioning and straight guiding accuracy due to heat are easily affected.

The known examples shown in FIGS. 4 and 5 also have the above-mentioned problems.

The present invention eliminates these drawbacks, and provides a compact, low-cost positioning stage that does not have an adverse effect on the positioning and straight guide accuracy due to the axial deviation of the feed screw and the heat generated by the drive motor. The purpose is to do.

[0018]

According to the present invention, in order to achieve these objects, a connecting block for connecting a nut of a screw feed mechanism and a moving table is provided.
° Two pairs of intersecting elastic hinges are provided to maintain rigidity in the feed direction of the ball screw and to flexibly deform in the direction of the shaft runout of the ball screw.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

A slide table 2 is incorporated in the air slide guide 1 and is supplied with compressed air of 0.5 Mp from an air supply port 3 so that a space between the guide surface of the slide table 2 and the guide surface of the air slide guide 1 is provided. About 10μ
The air slide table 2 is supported by the air slide guide 1 so as to be able to move with high straight guide accuracy by forming an air bearing while maintaining a gap of m.

On the other hand, a ball screw 4 is supported beside the air slide guide 1 by support bearings 5 and 6 so as to be parallel to the air slide guide 1 and to be rotatable and not displaced in the axial direction. Have been. The ball screw 4 is driven to rotate by a motor 8 via a shaft coupling 7. Further, a ball screw nut 9 is incorporated in the ball screw 4, and the ball screw nut 9 is attached to the feed block 10. The feed block 10 and the slide table 2 have a connection block 11 having a cross section of 8 mm square.
Is attached to the connection block 11 near the mounting portion of the slide table 2 and near the feed block.
A U-shaped groove-shaped cut 12 is provided from both upper and lower surfaces toward the center,
Furthermore, adjacent to the U-shaped groove-shaped cut 12 from both upper and lower surfaces,
A U-shaped groove-shaped cut 13 is provided from both left and right sides toward the center. The cross section of the bottom portion 14 of the U-shaped groove-shaped cuts 12 and 13 is 0.6 mm × 8 mm, and functions as a hinge that rotates around this portion.

Under the ball screw 4, a linear motion guide block 15 of a ball circulation type linear motion guide is disposed parallel to the air slide guide 1 and parallel to the air slide guide 1. The linear motion guide block 15 has a bearing. The block 16 is incorporated, and the feed block 10 is fixed to the bearing block 16. When the ball screw 4 rotates, the rotation of the ball screw nut 9 causes the feed block 10 to rotate.
0, since it is blocked by the linear motion guide block 15 via the bearing block 16 and guided only in the axial direction, it moves in the axial direction according to the amount of rotation.

This operation is performed when the motor 8 is driven to rotate by a predetermined amount by a control device and a motor driver (not shown).
The ball screw 4 rotates via the shaft coupling 7. At this time,
Since the ball screw 4 is supported by the support bearings 5 and 6, it is not displaced in the axial direction but moves only in the rotational direction. When the ball screw 4 rotates, the ball screw nut 9
And linear motion guide 15 bearing unit 1
By the action of 6, the feed block 10 moves in the axial direction according to the lead angle of the ball screw 4.

The movement of the feed block 10 is transmitted to the slide table 2 via the connection block 11. At this time, if the ball screw 4 has a shaft runout of 10 μm and the linear motion guide 15 has a straight guide error of 10 μm, the straightness of the axial movement of the feed block 10 is also about 10 μm due to the mixing of the two errors. Error.

When the feed block 10 is displaced in the vertical direction due to this error, as shown in an exaggerated manner in FIG. 2, the bottom portions 14 of the two vertical U-shaped groove-shaped cuts 12 are symmetrically deformed. In the case of displacement in the horizontal direction, as shown in an exaggerated manner in FIG.
Is deformed symmetrically. The force that attempts to displace the table 2 by this deformation increases the distance between the bottoms 14 by 5
Approximately 10gf when 0mm, bearing rigidity 20kg
The effect on the slide table 2 having f / μm is theoretically a displacement of 5 × 10 to ⁵ μm, which is within the straightness error of the movement of the slide table 2.

Actually, no effect of the movement of the slide table 2 on the straight guide error was recognized.

In the embodiment of the present invention, the slide table 2
Since it is a stage mechanism for precisely measuring the height of the object to be measured (not shown) mounted and fixed on the vertical direction, the vertical movement accuracy needs to be higher than the horizontal movement accuracy,
The distance between the U-shaped grooved cuts 12 in the horizontal direction is longer than the distance between the U-shaped grooved cuts 13 in the vertical direction, so that the influence on the slide table 2 is reduced.

Since no twisting force acts on the connecting block of the present invention, there is no possibility of breakage due to twisting even when an excessive torque is applied to the ball screw (which often occurs during adjustment).

Further, since the torsional rigidity does not need to be considered in the connecting block of the present invention, the hinge interval l can be increased, and the rigidity in the feed direction and the rigidity in the horizontal and vertical directions can be easily optimized.

Compared with FIGS. 4 and 5, in the present invention, it is not necessary to consider the effect of torsional rigidity, and it is also possible to increase the hinge interval in the horizontal or vertical direction that requires accuracy, so that the bearing rigidity can be increased. However, even with an air bearing of 10 kg / μm, a true point guidance accuracy of 0.05 μm was sufficiently realized.

Since the air bearing is non-contact, it has a long life and no change in frictional resistance.

[0032]

As described above, according to the present invention, a U-shaped groove-shaped notch is formed in the nut portion of the motor-driven screw and the table of the high-precision guide portion so as to form an elastic hinge crossing 90 °. Only by connecting with a connecting rod, it is possible to substantially eliminate the influence of the shaft runout of the ball screw, and there is almost no thermal displacement because the table is separated from the motor that generates heat.

Therefore, it is possible to obtain a small, low-cost, high-precision stage which does not adversely affect the positioning by heat and the accuracy of straight guide.

Further, depending on the direction in which more accuracy is required,
Since the distance between the U-shaped groove-shaped cuts can be set, the degree of freedom in design is high.

[Brief description of the drawings]

FIG. 1 is an external view showing an embodiment of the present invention.

FIG. 2 is an external view illustrating the operation of the embodiment of the present invention in an exaggerated manner.

FIG. 3 is an explanatory view showing the outer shape of the operation of the embodiment of the present invention in an exaggerated manner.

FIG. 4 is a perspective view of a conventional example.

FIG. 5 is a perspective view of a conventional nut holder.

[Explanation of symbols]

1: Air slide guide, 2: Slide table, 4:
Ball screw, 10: feed block, 11: connection block, 12: vertical U-shaped grooved cut, 13: horizontal U-shaped grooved cut.

Claims (3)

[Claims] 1. A straight guide block, a moving block guided by the straight guide block, a feed screw installed parallel to the straight guide block, and a second linear guide block installed parallel to the feed screw. A second moving block guided by the linear guide block, a feed block to which a nut of the feed screw is attached, and a feed block attached to the second movable block, and the feed block and the high-precision moving block. A connecting block to be connected, wherein the connecting block is symmetrically formed in a U-shaped cross-section from both outer diameter surfaces of the connecting block at a total of two locations near the moving block and the feed block toward the center. A first rectangular cross section is formed by the bottoms of the two U-shaped groove-shaped cuts.
And two elastic hinge portions, one each,
And two second elastic hinges each having the same shape as the first elastic hinge are provided adjacent to the elastic hinges, and a U-shaped groove-shaped cut in section of the second elastic hinge is provided. Direction is first
A stage mechanism intersecting the elastic hinge at 90 °. 2. A stage mechanism according to claim 1, wherein said feed screw is a ball screw. 3. A stage mechanism according to claim 1, wherein a cross section of said connecting block is circular.