DE2732303A1 - Hydrostatic axial and radial bearing - has ring segments located in external groove of rotor disc used in semiconductor wafer prodn. - Google Patents

Abstract

The disc shaped rotor (1) has a semicircular groove on its outside dia. and is located by three equally spaced ring segments (3) which engage the rotor groove (2). This produces a single contact area which provides axial and radial bearing support. Compressed air which is forced into the gap between rotor groove and bearing segments produces a hydrostatic action that creates frictionless bearings. A disc (8), coaxial to the rotor and of larger dia. has its outside edge located inside the slot of a linear drive motor (9).

Description

Hy @ rostatisches Auslat @ trossel- @ amer

The present invention relates to the routing of annular and disk-shaped la @ e @ n, where @as is the ratio of the length of the shaft to the diameter the elle se @ is small. Such disk-shaped bearings are used in the Storage of turntables with very large diameters, particularly advantageous for Storage of so-called inner diameter saws and ring-shaped bearings that are used for machining of non-rotating salts. It is a matter of such applications those inside the rotating disc require a large axial passage is.

The invention relates to a suitable pneumatic bearing for this purpose ? ll to absorb radial uni axial loads with the highest demands at the same time on ten @ slow running at higher speeds and on the accuracy of the bearing. @as camp necessarily consists of a housing with the disc rotatably arranged in it. Using known technology, support points for receiving tiltable bearing segments provided, the supply of the pressure medium to the bearing gap is carried out by the storage locations distributed around the circumference.

The use of a disk-shaped bearing is particularly important here Project to manufacture large-area silicon wafers, which are essential today Ausgan @ sprodukt at. the production of semiconductors and integrated circuits, described.

The production of large-area wafers is extremely tricky and Costly process, with today l @@, 125 and even 150 in diameter than must be absolutely welcome. With a thickness of only °, S mm, these disks are required with regard to flatness, micro-roughness and purity of individual defects such as pore scratches and grooves, meet the highest requirements.

It is known that air storage is used to advantage in the case of grinding, here using an inner diameter saw, a surface to get, which is so smooth as a result of the advantages of the air storage that one of speaks an opiate cut. the elimination of rolling vibrations, chatter vibrations (it or vibrations caused by the drive side, nh.solot is required to achieve a To obtain surface, which pral-table to generate the necessary polishing a high gloss only to a very small extent and as little loss of material as possible requires.

Another application example are ring-shaped bearings, their inner axial passage is so large that it is about roller bodies for the purpose of machining them can be pushed away. For the purpose of machining or grinding The ring-shaped bearing takes over the rotation, while the Ealze is stationary remain. The method offers great advantages because of the drop in imbalance Vibrations in the roller.

So here we are dealing with applications in which the direction of delivery is predominantly radial, while there is less load in the axial direction.

B @ knows are segment bearings and multi-surface plain bearings, each of which individual surface is biased separately. In the known bearings of this type However, mostly two bearing surfaces are used, e.g. with the shaft bearings with two conical ring surfaces that can be both outward and inward.

In the embodiment of a disk-shaped bearing according to the invention only a single rotationally symmetrical support surface is used, which is slightly in high precision can be produced with simple means and which are statically determinate Location requires storage shoes that can only be delivered in one clearing.

It is known that spherical spherical bearings can be used more radial and at the same time axial loads can be used.

Deviating from this and yet while maintaining the advantages more spherical Geometry carries a disk in the embodiment of the bearing according to the invention its circumference a rage with a circular cross-section. Air bearing shoes dip into the toroidal groove a, wherein the air gap between the bearing shoe and disk in the circumferential direction as is circular arc-shaped in the tangential direction. This geometry allows the bearings according to the invention take full advantage of the support provided by spherical domes be used. It should be noted that this advantage is that when pairing spherical surface sections, this is important for the air bearing function Pocket formation takes place automatically, i.e. the outlet throttling at the periphery the segment-shaped bearing shoes takes place.

Further features and advantages of the invention can be found in the following Description of some exemplary embodiments and the drawings in the figures.

Fig. 1 shows a cut and a view of the disk-shaped bearing Annular gap with toroidal bearing gap.

Fig. 2 explains the geometry of the bearing shoe.

Figure 3 shows a possible solution for driving the bearing.

The bearing shown in Fig. 1 consists of the ring body 1, the A groove with a circular cross-section, radius Rl, worked in at point 2 on the circumference Has.

At least three bearing shoes 3 are arranged on the circumference, these Shoes can be delivered individually by screws and inside by balls are supported four-way tilt, which is known technology in itself.

The bearing shoes 3 are supported by the balls 4 on one Place where the bearing shoe both around the radius Rl (small radius) and around the Radius R2 (large radius) can tilt. When using three support points the well-known advantages of the .f) three-point bearing.

Another advantage of the storage described is that the high-precision guidance takes place on the outermost circumference of the rotating disk and then the area of use, be it for a rotating diamond, be it for a diamond-coated inner diameter saw, on a smaller scale. In the event of any vibrations still occurring despite air storage, this results in the absolute deflection at the start of processing reduced.

Another characteristic of the storage according to the invention is Art of the drive, which can also be used as a brake. This drive is fully integrated with the storage, which is anyway when using air bearings the desired embodiment of the drive is. As shown in Fig. 1, a disk armature 8 is used, which is known in the art by a linear motor 9 in rotation versetst host. Since when using mains frequency, the use of Tinear feed motors achieve a speed of 1.5 m / sec in synchronous operation, It may be necessary to adapt the diameter of the disc 8 to the desired speed. If this is not possible, the drive system can also be operated with a frequency converter will. This known eddy current drive using the disk d allows namely the attachment of mechanical Brernsen, which is required in practice are. It has been shown that the braking of a ring bearing nit large mass electrical path alone is insufficiently possible. The remaining braking to a standstill expediently takes place via a mechanical claw brake. This is graphically here not set out.

2 shows the possible embodiment of the bearing shoes 3.

'; ie with the well-known flat and conical bearing shoes, must the surfaces of the tread and the shoe must be adapted to one another. In the present Case is a possible embodiment of the bearing shoe that.sowohl radius Rl and radius R2 are equal to the corresponding values of the disk-shaped hotor are. By a slight 7, reset of the bearing shoe results This creates a safe space in both directions, which is suitable for the Air forms the required pocket. In another embodiment of the Pocket can be highlighted more in the circumferential direction. The nature of the camp is hereby qualified as a so-called outlet throttle storage.

The novelty of the following embodiment is that the Bearing shoe the bearing function due to its biaxial spherical curvature takes over in the radial and axial direction.

Claims (1)

P a t e n t a n s p r a c h e Claim 1 Hy trostatic in radial Outlet throttle bearing for a disc-shaped shaft, bearing in the axial direction in a housing, in which the radial distance corresponding to the air gap trei or several Iagerglieder used tiltable in the manner of multi-flattened tilting segment bearings are, which in turn @ a passages to the gas-filled annular gap have between tilting segments and elle by which the @elle @ is supported by marked that the Semmente, bearing shoes, with the @elle a spherical @gap both in the direction of the circumference of the shaft and at the same time across an angular zone at least 170 ° perpendicular to the circumferential direction - i.e. in the direction of the surface line the shaft - form, the running surface of the rotatable shaft being toroidal Surface with an outwardly pointing radius and the support of the cell by the toroidal surface in both axial and radial weighting by only one the only contiguous running surface is given. Claim 2: bearing according to claim 1, characterized in that let a such is used to accommodate inner diameter saws, the cut material from the one Side is fed and the cut slice is discharged on the other side will. Claim 3: bearing according to claim 1, characterized in that let the End face tool holder attached sinl to accommodate cutting tools that serve to overturn stationary rollers.