JPS6085848A - Linearly movable table - Google Patents

Abstract

PURPOSE:To improve feed precision and allow high-speed positioning with no speed variation by supporting a table so that a feed screw nut is applied with the degree of freedom only in the radial deflection direction and is restricted in the feed direction and in the rotation direction around the screw axis. CONSTITUTION:In an angular nut 6 coupled with a feed screw 5, both the upper and lower surfaces faced to a frame 15 have a fixed space; both the left and right surfaces are in close contact across needle rollers 16; and both the front and rear surfaces at a right angle to the axis of the screw 5 are pinched by roller bearings 17, 18 of the frame 15; thus motion is restricted in the feed direction of the feed screw 5, in the right-and-left radial deflection direction, and in the rotation direction around the axis; and the degree of freedom is given only to the up-and-down movement. Next, when a linearly movable table 1 is driven by the screw 5 having radial deflection, the up-and-down deflection can be escaped between the nut 6 and the frame 15 and the right-and-left deflection can be escaped between the frame 15 and the table 1, and the degree of freedom is restricted in the feed direction and in the rotation direction around the axis, thereby the linearly movable table 1 can be fed correctly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a support structure for a feed screw nut that requires high-precision feeding, and particularly to a high-precision linear motion table that does not directly transmit radial runout of the screw to the table.

[Background of the invention]

A high Nt degree moving table is indispensable in semiconductor manufacturing equipment such as pattern inspection equipment and exposure equipment, but in recent years, as LSIs have become smaller and more integrated into cylinders, the precision required for moving tables has been increasing. Currently, the required accuracy for these moving tables is that for tables with a stroke of about 200 mm, both linearity and feed accuracy are required to be on the order of submicrons.

FIG. 1 is a diagram showing a conventional general configuration. In the figure, a movable table 1 is guided by a linear guide roller fixed on a pace 2, and is moved linearly by rotating a feed screw 5 by a drive motor 4 and applying feed to a nut B fixed to the movable table 1. It is desirable that the moving table 1 moves with the guidance accuracy of the linear motion guide 30.
As shown in the figure, when the nut 6 is added to the moving table 1 in a solid manner without any degree of freedom, the linear guide accuracy of the linear guide 3, which is relatively easy to obtain, is 1 to 2 μm with a length of about 200 mm. On the other hand, even if the feed screw 5 with a diameter of 16wn and a length of 300 mm is manufactured with high precision, the radial runout is 40 to 50 μm.
Therefore, the radial runout of the feed screw 5 is directly transmitted to the moving table 1, and the original accuracy is not achieved.
There has been a problem in that frictional resistance increases at the joint with the nut 6, impeding smooth operation. Particularly recently, static pressure straight air guides with excellent guidance accuracy have been rapidly increasing.
Although this guiding method is capable of highly accurate straight guiding, it has low rigidity, so the above-mentioned drawbacks of the prior art have become a major problem.

There are two examples shown below as solutions to the problems of the above-mentioned prior art.

First, a first example is shown in FIG. In this example, a nut 6 is supported by a leaf spring 7, and FIG. 2 is a diagram partially showing the supporting portion of the NAND 2 of the vertical and movable table. The nut 6 is arranged in a U-shaped groove provided at the end of the moving table 1 so as to have a certain angle of 94, and one side of the nut 6 and the moving table 1 are connected in two places as shown in a semicircular shape. They are connected by a plate spring 7 which is curved as shown in FIG. According to this embodiment, the radial runout of the feed screw 5 is
It escapes due to the deformation of the leaf spring 7 in the vertical and horizontal directions, and an external force is generated on the movable table 1 according to the amount of deformation. This external force is a much smaller force when compared to the embodiment shown in FIG. 1, so the linear motion table has high guiding rigidity.

However, it is not a sufficient solution for linear motion tables having low rigidity guides, such as those in static pressure linear motion chambers. Further, in the example shown in FIG. 2, since the nut 6 is not restrained in the rotation direction around the axis of the feed screw 5, there is a drawback that accurate positioning with respect to the feed direction of the feed screw 5 cannot be performed. Fig. 3 is a diagram for explaining this defect, and when the feed screw 5 rotates in the direction of the arrow in Fig. 3, the feed screw 5
The nut 6 rotates according to the frictional resistance between the nut 6 and the nut 6.

60 rotations of this nut means a feed error of the feed screw 5,
For example, if the nut 6 is rotated by θ (rad), the feed error will be (torsion)') x (θ/271-).

Furthermore, this means speed fluctuations in a direct-acting table whose only characteristic is constant speed.

Furthermore, the fact that the nut 6 rotates easily due to the frictional resistance with the feed screw 5 means that even if the drive of the feed screw 5 is stopped and the movement of the moving table 1 is stopped, the restoring force of the leaf spring 7 will not attenuate the nut 6. There is also a problem in that it takes a long time for positioning because it vibrates and stops at a predetermined stop position.

A second known example for solving the problems of the prior art is shown in FIGS. 4 to 6. 4 shows the AA cross section in FIG. 6, and FIG. 5 shows the BB cross section in FIG.・The nut 6 has a cylindrical protrusion 11 on one of the two opposing sides.
The movable stage 1 has a circular hole 13 and a square hole 14, and there is a connection between the hole and the MiJ protrusion. The nut 6 and the moving stage 1 are supported via rolling elements 9 and 10, and the structure has a degree of freedom against radial runout of the feed screw 5. FIG. 7 is a diagram for explaining the operating situation in this embodiment, and shows a state in which the feed screw 5 is extended outward by an amount e with respect to the moving stage 1. According to this system, the nut 6 rotates in the radial deflection direction with respect to the radial deflection of the feed screw 5, centering around the contact area between the cylindrical protrusion 11 and the rolling element 9, and further rotates in the radial deflection direction around the contact area between the cylindrical projection 11 and the rolling element 9.
Due to the transfer of 10, the multi-columnar protrusions are moved minutely in the fine direction to avoid radial photography.

However, this method also has the same drawbacks as the first embodiment, as is clear from Figure jA7. That is, the nut 6 rotates with respect to the radial movement of the feed screw 5, causing a feed error or speed fluctuation. The distance between the analytical body insertion spaces narrows in proportion to the rotation, and the contact portion deforms, impeding smooth operation of the nut support.

[Purpose of the invention]

It is an object of the present invention to provide a linear motion table capable of high-speed positioning without transmitting the radial runout of a feed screw to the table, with good feed accuracy, no speed fluctuations, no fluctuations in movement resistance, and little damped vibration when stopped. There is a particular thing.

[Summary of the invention]

In order to achieve the above object, the present invention has a nut of the feed screw that has a degree of freedom only in the direction of two-sial deflection of the feed screw, and is restrained in the feed direction and in the rotation direction of the axial rotation 9 of the feed screw. This is what was supported on the table.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 8 and 9. FIG. 8 is a sectional view taken in the axial direction of the feed screw for explaining this embodiment, and FIG. 9 is a view taken in the direction of arrow C in FIG. 8. As shown in FIG. 9, the square nut 6 engaged with the feed screw 5 has a certain space between its upper and lower surfaces facing the frame 15.

The two left and right sides are closely spaced with the needle roller 16 in between.

The two front and rear surfaces perpendicular to the axis of the feed screw 5 are
It is clamped by a roller 41S7.18 attached to the frame 15, and its movement is restricted in the feeding direction of the feed screw 5, the left and right radial runout direction, and the rotational direction of the axis rotation, and it is free to move only in the vertical direction. It's a matter of discretion. The rolling bearing 17 is attached to the frame 15 by an eccentric shaft 19 so that the nut 6 can be held against the frame 15 without play. Next, the frame 15 has an elastic body 20 in the vertical direction with respect to the movable table 1.
The rollers attached to the frame 15 are connected so as to tightly sandwich the needle rollers 21, and in the feeding direction of the feed screw 5, the rollers attached to the frame 15 sandwich the protrusion 24 of the movable table 1 with the shaft bearings 22 and 23. %, and the feed direction of the feed screw 5,
Movement in the vertical radial deflection direction and rotational direction around the axis is restricted, and freedom is allowed only in left-right movement. The rolling bearing 22 has rollers mounted eccentrically at 25 with respect to the frame 15 in the same way as the 9-roller bearing 17.
The protrusion 24'5 can be held in the frame 15 without play. When the linear motion table with the nut support structure described above is driven by the feed screw 5 having radial runout, the nut 6 and the frame 15 move between the nut 6 and the frame 15 in response to the vertical runout, and the left and right swings move with the frame 15. You can escape at table 1111,
Furthermore, since the degree of freedom is restricted in the feeding direction and the rotation direction around the axis, the movable table 1 can be accurately fed.

In the above explanation, the nut 6 and the frame 15 and the frame 15 and the moving table 1 are connected by roller guides, but the same operation is possible even if they are connected by roller guides.

〔Effect of the invention〕

As described above, according to the present invention, the nut of the feed screw has a degree of freedom only in the radial deflection direction of the feed screw, and is restrained in the feed direction and in the rotational direction of the axis of the feed screw. Since the radial runout of the feed screw is not transmitted to the table, it is now possible to provide a direct-acting table that has good feed accuracy and is capable of high-speed positioning without speed fluctuations or movement resistance fluctuations. In particular, for linear motion tables using the static pressure linear air guidance method with low guiding rigidity, which is expected to increase rapidly in the future, this method will be an effective method that does not impair the excellent guidance accuracy of this method, and will be essential for future linear motion tables. This is a basic technology.

[Brief explanation of drawings]

FIGS. 1 to 7 are diagrams for explaining conventional embodiments and problems, and FIGS. 8 and 9 are diagrams for explaining embodiments according to the present invention. A cross-sectional view taken in the axial direction, FIG. 9 is a view taken along arrow C in FIG. 8. 1...Moving table 2...Base 3...Linear motion guide 4...Driving top 5...Feeding cine slider... ... Nut 7 ... Leaf spring 8 ... Fixing screw 910 ... Rolling element 11 ... Cylindrical protrusion 12 ... Corner Columnar projection 13...Circular hole 14...Square hole 15...Frame 16.21...Needle roller 17, 1B,
22.23...9 roller bearing 1925...
...Eccentric shaft 20...Elastic body 24...Protrusion Fig. 1 4 Fig. 2 Fig. 3

Claims (1)

[Claims] The nut of the feed screw is supported on a table so as to have a degree of freedom only in the radial deflection direction of the feed screw, and to be restrained in the feed direction and the rotation direction around the axis of the feed screw. moving table.