JPS58193964A - Screw feeder - Google Patents

Abstract

PURPOSE:To provide the titled feeder free from vibration, stick and slip, having a high axial rigidity and light in the peripheral direction by using a static pressure gas bearing for the bearing of the feed screw. CONSTITUTION:A disc 11 for an oil damper and a disc 12 for a thrust bearing are provided on the same shaft as the shaft of the feed screw. At the disc part of an oil damper is provided an oil basin 13 having a gap slightly wider than the disc part in the diametral direction and thickness direction, and therein the disc rotates together with a feed screw 15 rotated by a DC motor 14. Further, at the part of the thrust disc 12, a bearing 15 having a minute gap in the diametral and thickness directions so as to surround the thrust disc 12, and compressed air is supplied toward the thrust disc from orifices 17 provided at several parts.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a screw feeding device, and particularly to a screw feeding device for precision positioning.

At present, there are many moving tables that require precise positioning, and in these moving tables, the perpendicular direction of movement on the moving side is regulated by various methods (guide mechanism), and positioning is performed by being sent in the direction of movement by a screw feed. The factors governing positioning accuracy vary considerably depending on whether the moving table has a position detection correction mechanism and feeds back the amount of movement to the motor, but it also depends on the accuracy of the screws and nuts, and the fixing force between the nuts and the moving object. law,
These include the n degrees of the upper gear guide mechanism, and the accuracy of the thrust bearing of the screw that keeps the screw itself from moving in the advancing direction even when the screw is fully rotated by a motor or the like and the moving table is moving. Therefore, it is essential that this thrust bearing rotates lightly without stick-slip in the rotational direction, and has high rigidity in the axial direction (a-line direction). Of course, a radial bearing is important for rotating the screw around its center.

As shown in FIG. 1, a conventional precision positioning moving table uses a rolling bearing using rolling elements such as steel balls or rollers, or a sliding bearing using sliding contact in the kite mechanism and screw bearing part. It was common. That is,
When a screw 3 supported by a screw bearing 2 is turned by a motor 1 or by human power, a moving table 5 equipped with a nut 4 that engages with the screw rotates with a rolling element such as a steel ball 6 or a sliding surface. The accompanying rotation is restricted, and the screw moves in the axial direction of the screw with respect to the fixed base 7.

These mechanisms had the following drawbacks.

That is, (1) rolling bearings are not susceptible to so-called rolling motions due to irregularities in steel ball diameters and roller diameters.

(2) Stick-slip is inevitable in sliding bearings,
Fine positioning is not possible.

(3) In both cases, if an attempt is made to increase the rigidity in the axial direction, the load torque will also increase in the rotational direction, which will impede minute positioning.

The above C2) and A3) are particularly large drawbacks in the case of the feedback method. In order to solve these problems, guide mechanisms using air bearings have recently become popular.

The present invention provides a bearing that does not have these drawbacks, that is, a thrust bearing that has no vibration, no stick-slip, has high axial rigidity, and is light in the cylindrical direction (load torque capacity), and also provides a damper effect. The purpose is to provide a tilted thrust bearing.

In order to achieve this object, the present invention is characterized in that a static pressure gas bearing is used as the bearing of the feed screw, and an oil damper is further provided between the set screw and its bearing.

An embodiment of the present invention will be described using a case where the present invention is applied to an optical disk master recording apparatus shown in FIG.

The optical disk recorder is made by coating a glass circular machine with photoresist, rotating it at a few hundred rpm, and continuously irradiating it with a narrow laser beam t#r based on a modulation signal to form unevenness on the glass surface. , it is a device for recording image signals, etc., but due to the stability of the optical system etc.
Both the column and the column move in the radial direction by -14 fMk.

The relationship between the moving table on which the disk rotating device is mounted, the feed screw and nut miniaturized by the can is the same as in Figure 1, but
A disk 11 for an oil damper coaxially with the axis of the feed screw,
A disk 12 is provided for the thrust bearing. On the oil/pa circle number part, there is a blade 1 that is slightly wider in diameter and thickness than the disk. There is an oil reservoir 13 in which a disc is rotated by a DC motor 14 together with a feed screw 15 that can be rotated.

In addition, there is a bearing 16 surrounding the thrust disk 12 with a slight clearance in the diameter and thickness direction, and compressed air is directed toward the thrust disk from orifices 17 provided at several locations. There is no hot water supply. The oil damper was added to remove the drawback of air bearings, such as poor damping ability, and to smoothen the movement when impact force is applied in the rotational or axial direction. This can be adjusted by changing the size of the gap 1 between the oil reservoirs and the characteristics of the oil used. This embodiment has the meaning of countermeasures against impact force caused by splatter caused by disc misalignment and other causes that occur once per rotation of the disc. By applying the present invention described above, the optical disk master recording device (t) of the embodiment has become capable of producing a disk with a highly accurate track pitch.

By using the present invention, the following structural advantages are obtained.

(1) By using an air bearing for the guide of the moving table and a static pressure air bearing for the bearing of the feed screw, there is no stick-slip and the moving table can move smoothly, improving positioning accuracy.

(2) Vibrations such as rolling caused by uneven dimensions of the rolling elements accompanying the rotation of the feed screw are eliminated, and the smooth movement of the feed screw is reflected in the smooth movement of the disk.

(3) By adding an oil damper, the effect of the impact force in the axial direction and movement direction of the feed screw is completely reduced, and the effect of overcoming the disadvantage of poor primary deterioration of the pressure bearing of the feed screw is achieved. I became angry.

Although the present invention is applied to an optical disk master recording device as a practical example, it can also be applied to other moving platforms without impairing the essence of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional screw feeding device fii, and FIG. 2 is a diagram showing an embodiment of the present invention applied to an optical disk master recording device.

Claims (1)

[Claims] 1. By rotating the feed screw by a motor, etc., the movable part of the movable platform, which has a nut that engages with the feed screw, moves relative to the fixed part along a detent guide using a steel ball, etc. A screw feeding device characterized in that a hydrostatic air bearing is used as a bearing of the feeding screw.