JPS62218889A - Static pressure gas bearing spindle with vacuum suction mechanism - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a hydrostatic gas bearing spindle with a vacuum suction mechanism, and in particular to a hydrostatic gas bearing spindle equipped with a vacuum suction mechanism. A mechanism equivalent to a rotary joint is provided on the 71 housing and the hollow shaft.

[Conventional technology]

Conventionally, this type of spindle has an intake hole provided in a shaft portion of the spindle shaft on the side opposite to the vacuum suction side, and the piping of a vacuum pump is connected to this shaft portion via a rotary joint.

[Problem that the invention seeks to solve]

The conventional hydrostatic gas bearing spindle with vacuum suction mechanism is
Since the rotary joint is connected to the shaft end on the opposite side of the spindle shaft from the vacuum suction side, not only does the axial length of the spindle become longer, but also a large torque is required due to the frictional resistance of the rotary joint's seal. In addition, there is a problem in that the cost of parts for the rotary joint is high and that it is not possible to attach any parts other than the rotary joint to the shaft end of the spindle.

The present invention solves the above-mentioned problems by providing a mechanism as a rotary joint in the housing and hollow shaft of a hydrostatic gas bearing.

[Means for solving problems]

The spindle of the present invention radially supports a hollow shaft having an open end at one end in the axial direction by a pair of hydrostatic gas bearings fitted into the housing at an interval in the axial direction. It is used as a vacuum suction surface for the object to be measured or processed.

At least three locations in the axial direction between the pair of gas bearings are formed with circumferentially continuous grooves on at least one of the inner diameter surface of the housing and the outer diameter surface of the hollow shaft.

The portion between the grooves at both ends in the axial direction has a portion where the gap between the housing and the hollow shaft is equal to or smaller than the radial bearing gap of the gas bearing.

The housing is provided with at least one exhaust hole that communicates between an appropriate number of grooves selected at intermediate positions among these grooves and the outer surface of the housing, and a plurality of exhaust holes that communicate between grooves at both ends in the axial direction and the outer surface of the housing. It has several exhaust holes.

Further, the hollow shaft is provided with a plurality of intake holes that communicate the groove at the intermediate position with the inner surface of the hollow shaft.

The exhaust hole provided at the middle position of the housing described above is an exhaust passage for the air sucked out from the intake hole of the hollow shaft, and the exhaust holes at both axial ends are the exhaust passage for the air supplied to the gas bearing from the air supply hole of the housing. It serves as a discharge passage.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing a first embodiment of the invention.

In the figure, the hollow shaft 10 has a large diameter portion 11 and a medium diameter portion 12.
The large diameter portion 11 is formed into a hollow shape with an open end 11a at one end in the axial direction, and this open end 11a serves as a vacuum suction surface for the object to be measured or the workpiece 40. ing.

This hollow shaft 10 has gas bearings 16. which are made of a pair of porous bodies fitted at intervals in the axial direction of the housing 20.
Both axial ends of the large diameter portion 11 are supported in the radial direction by 18, and gas such as air supplied from the air supply hole 21 of the housing 20 flows into the gas chamber 17 of the gas bearing 16.18.
．． 19, the large diameter portion 11 of the hollow shaft 10 and the gas bearing 16.
The structure is such that it is fed into the radial bearing gap between 18 and 18.

The hollow shaft 10 is rotated by a disk-shaped rotor 36 attached to the end face of the large-diameter section 11 on the side of the medium-diameter section 12 and a disk-shaped stator 38 attached to the side wall of the housing 20 opposite thereto. It's like driving.

In the above hydrostatic gas bearing spindle, the inner diameter surface of the intermediate portion 22 of the housing 20 that separates the pair of gas bearings 16 and 18 is flush with the radial bearing surface of the gas bearings 16 and 18, and this intermediate portion Grooves 23°, 24.25, which are continuous in the circumferential direction, are formed on the inner diameter surface of the groove 22 at three positions at approximately equal intervals in the axial direction.

Of these grooves 23.24.25, the grooves 23.25 located at both ends in the axial direction, that is, adjacent to the pair of gas bearings 16.18, are provided with a plurality of exhaust holes 33.25 on the outside in the radial direction.
35 is provided to open on the outer surface of the housing 20.

In addition, the groove 24 at the intermediate position has at least one exhaust hole 3.
4 is placed on the outside in the radial direction and opened on the outer surface of the housing 20, and the piping of a vacuum pump (not shown) is connected to the threaded portion 50 provided at the open end of the exhaust hole 34 located at the intermediate position. be.

Further, in the large diameter portion 11 of the hollow shaft 10, a plurality of intake holes 15 that penetrate in the radial direction are provided at the same axial position as the intermediate groove 24 provided in the housing 20, facing each other. .

With the above configuration, a portion of the gas introduced into the radial bearing gap from the intake hole 21 of the housing 20 via the gas bearing 16.18 is contained in the gas bearing 16.
The gas that is discharged to the outside from the gap between the hollow shaft 10 on the axially outer side of the gas bearing 16 and the gas bearing 16 and the gas that enters the axially inner side of the gas bearing 16 and the gas bearing 16, 18 flows into the grooves 23 at both ends provided in the middle part 22 of the housing 20. .25, and is discharged to the outside through an exhaust hole 33.35 communicating with this groove 23.25.

Furthermore, when the open end 11a of the large diameter section 11 of the hollow shaft 10 is closed with the object to be measured 40, the air sucked out from inside the large diameter section 11 flows out from the intake hole 15 of the large diameter section 11. It enters a groove 24 at an intermediate position provided in the intermediate part 22 of the housing 20 facing the intake hole 15 at the same position, and this 'a
The gas is discharged to the outside through an exhaust hole 34 which is connected to the exhaust gas 24 by a vacuum pump (not shown).

The gas that is introduced into the radial bearing gap through the gas bearing 16. Since the grooves 23 and 25 have the same dimensions as the radial bearing clearance 18 and are provided at both end positions, negative pressure from the vacuum pump is applied to the groove 24 at the intermediate position of the intermediate portion 22 of the housing 20 and the exhaust hole 34. Even if it is working, the amount sucked out in the axial direction is smaller than the grooves 23.25 at both end positions. Therefore, the negative pressure in the exhaust hole 34 provided in the intermediate portion 22 of the housing 20 is less likely to fluctuate.
The vacuum pressure within the large diameter portion 11 of the hollow shaft 10 can be maintained substantially constant.

As mentioned above, the hollow shaft 10 has a pair of gas bearings 16,18
Even when the hollow shaft 10 is rotating while being supported by
The air sucked out from the intake hole 15 of the large diameter portion 11 of
Since it will be discharged to the outside through the exhaust hole 34 communicating with this groove 24, various parts other than the rotary joint should be placed in the small diameter portion 13, which is the shaft end on the opposite side of the vacuum suction side of the hollow shaft 10. It can be attached and used for various purposes.

In this embodiment, a convex spherical surface is formed on the axial end face of the small diameter portion 13 of the hollow shaft 10, and a plan 42 for removing electrical noise is formed.
are in sliding contact. In this way, the plan 42 makes point contact with the small diameter portion 13 of the hollow shaft 10, so that wear of the plan 42 can be reduced.

Further, in this embodiment, an encoder 4 for an angle reading device of the object to be measured 40 is provided on the outer peripheral surface of the small diameter portion 13 of the hollow shaft 10.
4 is installed.

FIG. 2 shows a second embodiment of the invention, in which a hollow shaft 10,
A case is shown in which the shaft of a unitized encoder 46 is attached to the small diameter portion 13 of the body via a removable coupling 45 on the same central axis.

Since the configuration other than the above is the same as that of the embodiment shown in FIG. 1, the main parts are given the same reference numerals and repeated explanations will be omitted.

FIG. 3 shows a third embodiment of the invention.

In this embodiment, the diameter of the inner diameter surface of the intermediate portion 22 of the housing 20 is smaller than the diameter of the radial bearing surface of the gas bearing 16.18, so that the intermediate portion 22 of the housing 20
The gap between the inner diameter surface of the hollow shaft 10 and the large diameter portion 11 of the hollow shaft 10 is
It is made smaller than the radial bearing clearance of gas bearings 16 and 18.

The rotational drive mechanism of the spindle is the middle diameter portion 12 of the hollow shaft 10.
A cylindrical rotor 36 is attached to the circumferential surface of the housing 20, and a cylindrical stator 38 is attached to the circumferential wall of the housing 20 facing thereto.

In addition, a ball 4 is provided on the axial end surface of the 10th small diameter portion 13 of the hollow shaft.
3 are fitted and attached, and a plan 42 for removing electrical noise is brought into sliding contact with this ball 43.

Since the configuration other than the above is the same as that of the embodiment shown in FIG. 1, the main parts will be denoted by the same reference numerals and repeated explanations will be omitted.

According to this embodiment, the gas introduced into the radial bearing gap from the gas bearing 16.18 is sucked out inward in the axial direction from the grooves 23.25 at both ends provided in the intermediate portion 22 of the housing 20. Since this can be almost completely prevented, the vacuum pressure within the large diameter portion 11 of the hollow shaft 10 can be more effectively maintained.

In addition, between the pair of gas bearings 16 and 18, grooves 23 continuous in the circumferential direction are formed at at least three locations in the axial direction on at least one of the inner diameter surface of the housing 20 and the outer diameter surface of the hollow shaft IO. .24.25 may be provided.

Further, two of the grooves 23, 24, and 25 continuous in the circumferential direction are provided on either the inner diameter surface of the housing 20 or the outer diameter surface of the hollow shaft 10, and at least one other groove is provided in the circumferential direction. The grooves 23, 24, and 25 that are continuous with each other may be provided on the other side.

In each of the embodiments described above, the grooves and exhaust holes provided between the pair of gas bearings 16 and 18 may be provided at more than three locations depending on the axial length of the intermediate portion 22 of the housing. In this case, if the number of grooves is odd, select one or an odd number of grooves in the middle position, provide at least one exhaust hole in this groove, and A plurality of exhaust holes may be provided in each groove, and when the grooves are arranged in an even number, two or an even number of grooves are selected at intermediate positions, and at least one exhaust hole is provided in this groove. , and a plurality of exhaust holes may be provided in each of the grooves other than the groove at the intermediate position.

Furthermore, the intake holes in the large diameter portion of the hollow shaft in the above case shall be provided at positions communicating with an appropriate number of grooves selected at intermediate positions of the housing.

Further, although the hydrostatic moisture bearing of the above embodiment has been described using a porous body, it is also possible to use a material other than a porous material, for example, an orifice-shaped bearing.

The spindle of the present invention can be used for measuring various articles and for processing magnetic disks, aspheric lenses, etc.

〔Effect of the invention〕

As explained above, according to the present invention, a mechanism equivalent to a rotary joint is provided in the housing and the hollow shaft of the hydrostatic gas bearing spindle with a vacuum suction mechanism, so the conventional rotary joint is no longer necessary. Not only can the length of the spindle in the axial direction be shortened, but also the torque during rotation can be reduced because there is no need for a seal to prevent air leakage.

In addition, according to this invention, the cost of the rotary joint is lower than that of conventional spindles of this type, and various parts can be attached to the shaft end as required, so it can be used for a wide range of applications. becomes possible.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of the invention, FIG. 2 is a longitudinal sectional view showing a second embodiment of the invention, and FIG. 3 is a longitudinal sectional view showing a third embodiment of the invention. It is. In the figure, 10 is a hollow shaft, Lla is an open end of the hollow shaft, 15 is an intake hole of the hollow shaft, 16.18 is a static pressure moisture bearing, 20 is a housing, 21 is an air supply hole in the housing, and 22 is a housing hole. Middle part, 23.24° 25 is groove, 33, 34.3
5 is an exhaust hole in the housing. Patent Applicant NSK Ltd. Representative Patent Attorney Tetsuya Mori Patent Attorney Yoshiaki Naito Representative Patent Attorney Tadashi Shimizu Figure 1 Figure 2 Figure 3

Claims (3)

[Claims] (1) A spindle in which a hollow shaft whose one axial end is a vacuum suction surface is supported in the radial direction by a pair of hydrostatic gas bearings fitted into the housing at an axial distance from each other; At least one of the inner diameter surface of the housing and the outer diameter surface of the hollow shaft is located between the pair of gas bearings.
Continuous grooves are formed in the circumferential direction at at least three locations in the axial direction, and the gap between the housing and the hollow shaft is equal to or smaller than the radial bearing gap of the gas bearing in the area between the grooves at both ends in the axial direction. The housing has at least one exhaust hole that communicates between an appropriate number of grooves selected at intermediate positions among these grooves and the outer surface of the housing, and grooves at both axial ends and the outer surface of the housing. In addition, the hollow shaft is provided with a plurality of intake holes that communicate between the groove at the intermediate position and the inner surface of the hollow shaft, and the exhaust hole at the intermediate position of the housing is connected to the intake hole of the hollow shaft. A static pressure device with a vacuum adsorption mechanism, characterized in that the exhaust hole serves as an exhaust passage for air sucked out from the hole, and the exhaust holes at both axial ends of the housing serve as exhaust passages for gas supplied to the gas bearing from the air supply hole of the housing. Gas bearing spindle. (2) A hydrostatic gas bearing spindle with a vacuum adsorption mechanism according to claim 1, wherein a plan for removing electrical noise is disposed in sliding contact with the shaft end surface on the opposite side of the open end of the hollow shaft. . (3) A hydrostatic gas bearing spindle with a vacuum suction mechanism according to claim 1, wherein an encoder of an angle reading device is detachably attached to the shaft end opposite to the open end of the hollow shaft.