JPH0582907B2 - - Google Patents

Description

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

[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]

Conventional hydrostatic gas bearing spindles with vacuum suction mechanisms have a rotary joint connected to the shaft end on the opposite side of the spindle shaft from the vacuum suction side, which not only increases the axial length of the spindle, but also increases the In addition to requiring a large torque due to the frictional resistance of the joint's seal, the rotary joint is expensive due to the cost of parts, and there is also the problem that parts other than the rotary joint cannot be attached to the shaft end of the spindle.

The present invention solves the above-mentioned problems by providing a mechanism serving 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 static pressure type gas bearings fitted into a housing at intervals in the axial direction, and the hollow shaft has an open end. The end serves as a vacuum suction surface for the object to be measured or processed.

At least 3 in the axial direction between a pair of gas bearings
A circumferentially continuous groove is formed in 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, a hollow shaft 10 includes a large diameter part 11, a medium diameter part 12, and a small diameter part 13, and the large diameter part 11 is formed into a hollow shape with one end in the axial direction being an open end 11a. The open end 11a serves as a vacuum suction surface for the object to be measured or the object to be processed 40.

This hollow shaft 10 is radially supported at both axial ends of the large diameter portion 11 by a pair of gas bearings 16 and 18 made of porous bodies fitted at intervals in the axial direction of the housing 20. The gas such as air supplied from the air supply hole 21 of the housing 20 passes through the gas chambers 17 and 19 of the gas bearings 16 and 18 to the large diameter portion 11 of the hollow shaft 10 and the gas bearings 16 and 18.
It is configured to be fed into the radial bearing gap between the

The above-mentioned hollow shaft 10 has a medium diameter portion 12 of a large diameter portion 11.
A disc-shaped rotor 36 attached to the side end face
and a disk-shaped stator 38 attached to the side wall of the housing 20 opposite thereto.

In the above-described 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
The inner diameter surface of the intermediate portion 22 is provided with grooves 2 continuous in the circumferential direction at three positions at approximately equal intervals in the axial direction.
3, 24, and 25 are formed.

Out of these grooves 23, 24, 25, a plurality of exhaust holes 33, 35 are provided on the outside in the radial direction in the grooves 23, 25 located on both axial end sides, that is, in positions adjacent to the pair of gas bearings 16, 18. housing 2
It is opened on the outer surface of 0. Also, the groove 2 at the intermediate position
4, at least one exhaust hole 34 is provided on the outside in the radial direction and opens on the outer surface of the housing 20, and a vacuum pump (not shown) is connected to a threaded portion 50 provided at the open end of the exhaust hole 34 at an intermediate position. The pipes are connected.

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 part of the gas fed into the radial bearing gap from the intake hole 21 of the housing 20 via the gas bearings 16 and 18 is in the hollow space outside the gas bearings 16 and 18 in the axial direction. The gas discharged to the outside through the gap between the shaft 10 and the gas bearings 16 and 18 enters the inside of the gas bearings 16 and 18 in the axial direction through the grooves 23 and 25 provided at both ends of the intermediate portion 22 of the housing 20. The gas is discharged to the outside from exhaust holes 33 and 35 that communicate with the exhaust holes 23 and 25.

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

The gap between the inner diameter surface of the intermediate portion 22 of the housing 20 and the large diameter portion 11 of the hollow shaft 10 is the gap between the gas bearing 1
Since the dimensions are the same as those of the 6 and 18 radial bearing gaps (generally 5 to 20 μm on one side in the radial direction), the resistance to gas flowing through such a small gap is extremely large. Moreover, in this type of spindle, the pressure of the bearing gas fed into the gas bearings 16 and 18 is higher than the pressure of the air sucked from inside the large diameter portion 11 of the hollow shaft 10, so that the gap between the radial bearing gap and the gap Compared to the pressure difference of the bearing gas flowing out to the grooves 23, 25 which communicate with the exhaust holes 33, 35 through the grooves 23, 25,
The pressure difference between the air sucked in is much smaller.

Therefore, even if negative pressure from the vacuum pump is applied to the gap between the groove 24 provided at the intermediate position of the intermediate portion 22 of the housing 20 and the grooves 23 and 25 at both ends, the gas will not flow out from the gas bearings 16 and 18. It is difficult for the bearing gas to flow over the grooves 23 and 25 through the gap to the groove 24, and the amount sucked into the exhaust hole 34 is small. For this reason, housing 2
The negative pressure in the exhaust hole 34 provided in the intermediate portion 22 of the hollow shaft 10 does not fluctuate much;
The vacuum pressure inside can be maintained almost constant.

As mentioned above, the hollow shaft 10 is connected to the pair of gas bearings 1
6 and 18, the air sucked out from the intake hole 15 of the large diameter portion 11 of the hollow shaft 10 flows into the intermediate portion 22 of the housing 20 without drawing in much of the bearing gas. Exhaust is discharged to the outside through a groove 24 at an intermediate position provided and an exhaust hole 34 communicating with this groove 24, and the housing 2
0 and the hollow shaft 10, a vacuum suction mechanism equivalent to this is provided instead of the conventional vacuum suction mechanism using a rotary joint. Since it is possible to generate vacuum pressure, various parts other than the rotary joint can be attached to the small diameter portion 13, which is the shaft end on the opposite side of the vacuum suction side of the hollow shaft 10, as necessary, so that it can be used for various purposes. It becomes possible to use it for

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 the brush 42 for removing electrical noise is brought into sliding contact therewith. In this way, since the brush 42 makes point contact with the small diameter portion 13 of the hollow shaft 10, wear of the brush 42 can be reduced.

Further, in this embodiment, the small diameter portion 1 of the hollow shaft 10 is
An encoder 44 for an angle reading device of the object to be measured 40 is attached to the outer peripheral surface of the object 3.

FIG. 2 shows a second embodiment of the present invention, in which an encoder 46 is integrated into a small diameter portion 13 of a hollow shaft 10 via a removable coupling 45.
This shows the case where the shafts of are installed on the same central axis.

The configuration other than the above is the same as the embodiment shown in FIG.
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 made smaller than the diameter of the radial bearing surfaces of the gas bearings 16 and 18, so that the inner diameter surface of the intermediate portion 22 of the housing 20 and the hollow shaft 10 are The gap between the large diameter portion 11 and the gas bearings 16, 18
radial bearing clearance.

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

Further, a ball 43 is fitted and attached to the axial end face of the small diameter portion 13 of the hollow shaft 10, and a brush 42 for removing electrical noise is brought into sliding contact with the ball 43.

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

According to this embodiment, the resistance of the gas flowing through the gap between the intermediate portion 22 of the housing 20 and the large diameter portion 11 of the intermediate shaft 10 is greater than that in the first and second embodiments. Bearing 16,1
The gas introduced into the radial bearing gap from 8 is
Since it is possible to almost completely prevent the vacuum pressure inside the large diameter portion 11 of the hollow shaft 10 from being sucked out in the axial direction from the grooves 23 and 25 at both ends provided in the intermediate portion 22 of the housing 20. retention becomes more effective.

In addition, at least one of the inner diameter surface of the housing 20 and the outer diameter surface of the hollow shaft 10 is provided with at least 300 mm in the axial direction between the pair of gas bearings 16 and 18.
Circumferentially continuous grooves 23, 24, 25 may be provided at the locations.

Further, grooves 23, 24, 25 continuous in the circumferential direction
Two of the grooves 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 23, 2 is provided continuous in the circumferential direction.
4 and 25 may be provided on the other side.

In each of the above embodiments, a pair of gas bearings 16,
Depending on the axial length of the intermediate portion 22 of the housing, more than three grooves and exhaust holes can be provided between the housings. 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 static pressure type gas bearing of the above embodiment has been described using a porous body, it is also possible to use a material other than a porous body, for example, an orifice type bearing.

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

In each of the above embodiments, the small diameter portion 1 of the hollow shaft 10
As the part to be attached to the shaft end of No. 3, a rotational drive part of the spindle such as a pulley or a drive shaft can also be attached.

〔Effect of the invention〕

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

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, 11a is an open end of the hollow shaft, 15 is an intake hole of the hollow shaft, 16 and 18 are static pressure type gas bearings, 20 is a housing, 21 is an air supply hole in the housing, and 22 is an air supply hole in the housing. Middle part, 23,2
4 and 25 are grooves, and 33, 34, and 35 are exhaust holes of the housing.

Claims (1)

[Claims] 1. A hollow shaft with one axial open end serving as a vacuum suction surface is supported in the radial direction by a pair of static pressure type gas bearings fitted into the housing at an interval in the axial direction. In the spindle, continuous grooves 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 and the outer diameter surface of the hollow shaft at a location between the pair of gas bearings. However, 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, and the housing has a portion between these grooves. At least one exhaust hole that communicates between an appropriate number of grooves selected at intermediate positions and the outer surface of the housing, and a plurality of exhaust holes that communicate between the grooves at both ends in the axial direction and the outer surface of the housing, and a 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 used as an exhaust passage for air sucked out from the intake hole of the hollow shaft and the shaft of the housing. A hydrostatic gas bearing spindle with a vacuum suction mechanism, characterized in that exhaust holes at both ends in the direction serve as exhaust passages for gas supplied to the gas bearing from an air supply hole in the housing. 2. A hydrostatic gas bearing spindle with a vacuum suction mechanism according to claim 1, wherein a brush for removing electrical noise is disposed in sliding contact with the shaft end surface opposite to 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.