JPS5918573B2 - Air pads for air bearings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air bearing, and more particularly to an air pad for a thrust type air bearing.

Conventionally, air pads used in thrust-type air bearings either have an air supply hole in the center of the pad and supply air from this air supply hole to a pocket provided on the bottom surface of the pad.
Alternatively, a plurality of air supply holes are provided on a virtual circle centered on the center of the pad, and air is blown out from each of these air supply holes. However, in the case of the former, since the air supply hole is provided in the center of the pad, the machining dimensions of the air supply side hole are required to be 5 mm. This has the disadvantage that although the hole diameter is small, the depth is very deep, making it more difficult to drill a straight drilled hole.

On the other hand, in the latter case, since it is necessary to make the hole diameters 10 of the plurality of air supply holes the same, the air supply hole portion is constructed from a separate member, and this separate member is press-fitted and fixed to the pad body. For this reason,
The press-fitting direction of the member having the air supply hole cannot necessarily be perpendicular to the bottom surface of the pad body, resulting in an inclination.
There is a drawback that the air pad tilts when the float 15 is raised. An object of the present invention is to provide an air pad for an air bearing that is easy to process and has a good floating posture. The present invention provides an air supply hole at a predetermined distance of 20 distance from the center of the air pad body, thereby reducing the depth of the air supply side hole and simplifying machining. A pocket is provided on almost the opposite side of the air supply hole, and this pocket and the air supply hole are connected by a groove passing through almost the shortest distance 25, thereby making the pressure distribution in the air film almost uniform and improving the buoyancy posture. It is an attempt to achieve a goal.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

30. FIG. 1 shows a bottom view of this embodiment, and FIG. 2 shows its cross-sectional view along the line 1--2.

In these figures, the bearing surface, which is the lower surface of the air pad body 1 formed in a disk shape, has a feed length L2 in a direction perpendicular to the lower surface at a position a predetermined distance R from the center O of the air pad body 1. It is drilled at a predetermined depth. The inner end of the air supply hole 2 is communicated with a horizontal air supply hole 3 formed from the side surface of the air pad body 1.

The outer end position VC of this air supply hole 2 is
A circular pocket 4 having a predetermined depth d from the lower surface is provided concentrically with the air supply hole 2, and the diameter of this circular pocket 4 is D1. A circular pocket 5 having a diameter D1 and a depth d is formed on the opposite side of the air pad body 1 across the center O from the air supply hole 2K, that is, at a distance R from the center 0,
This circular pocket 5 and the circular pocket 4 provided concentrically with the air supply hole 2 are connected by a groove 6 passing through the shortest distance.

This groove 6 has the same depth d as the circular pocket 5, and a width B1. Both circular pockets 4 and 5 are connected via groove-shaped pockets 7 and 8, which are formed on both sides of the groove 6 and each formed in a semicircular symmetrical shape with respect to the center 0 of the air cushion body 1, At intermediate positions between these groove-shaped pockets 7 and 8, there are circular pockets 9 and 10, respectively.
is provided.

These groove-shaped pockets 7, 8 have an inner diameter of D2, a width of B2, and a depth of d.
Further, the diameter of the circular pockets 9, 10 located at the intermediate position between the groove-shaped pockets 7, 9 is the same as that of the circular pockets 4, 5.
It has the same diameter D1 and depth d. In addition, the reference numeral 11 in FIG. 2 indicates a receiving member which is opposed to the air butt main body 1 and floats by a predetermined height H, and is composed of a surface plate, a prismatic guide, and the like.

Further, the circular pockets 4, 5, 9, 10, the groove 6, and the groove-shaped pockets 7, 8 are formed by etching. How to use the air pad main body 1 constructed in this way as an air bearing. A member (not shown) to be used to levitate and move the airbud main body 1 is attached to a VC, and compressed air is supplied to the air supply side hole 3 via a pipe (not shown).

This compressed air is supplied to the circular pocket 4 through the air supply hole 2, and is further supplied to the other circular pockets 5, 9, 10 through the groove 6 and groove-shaped pockets 7, 8ffC, and is blown out toward the receiving member 11VC. , the air pad body 1 and the member to which the air pad body 1 is attached are levitated by a height H. At this time, if there were no groove 6, the pressure inside the circular pocket 4 in which the air supply hole 2 was formed would be supplied to the circular pocket 5 on the opposite side via the groove-shaped pockets 7 and 8. In this case, the circular pockets 9 and 10, which have lower air resistance than the groove pockets 7 and 8, are formed in the middle of the groove pockets γ and 8, so the pressure in the circular pocket 5 on the opposite side is equal to that of the circular pocket 9. , 10. However, in this embodiment, circular pockets 4 and 5 are
Since the two are directly connected by the groove 6, the pressure inside the circular pocket 4 is supplied to the circular pocket 5 with almost the same pressure. Furthermore, when compressed air is supplied, the pressure in each circular pocket 4, 5, 9, 10, groove-shaped pockets 7, 8, and groove 6 is equal before the member to which the air pad body 1 is attached floats, and after floating. is each pocket 4,5,7,8
, 9, 10 and the groove 6, but the amount of buoyancy is as small as 10 to 20 μm at most.
1 or width Bl, B2 is 0.1m or? It is made to order, and by setting the dimensions appropriately, such as making the width B1 of the groove 6 wider than the width B2 of the groove-shaped pockets 7 and 8. VC can be supplied to the circular pocket 4 on the opposite side without substantially reducing the pressure inside the circular pocket 4. Furthermore, circular pockets 4, 5, 9, 10 and grooved pockets 7,
Since air is also ejected inward from grooves 8, the pressure is higher than on the outside.
The amount of compressed air ejected from the groove-shaped pockets 7, 8, etc. is smaller than that from the groove-shaped pockets 7, 8, etc., and more air flows into the circular pocket 5 with low resistance, making it possible to maintain the pressure within the circular pocket 5 relatively high. , each pocket 4, 5, 7, 8, 9
, 10, the inside and outside of them are separated by a kind of air curtain, and the air moves so that the pressure difference inside them is canceled out. For the reason, the circular pockets 4, 5, 9, 10
The pressure distribution of the air film inside the groove-shaped pockets 7 and 8 VC becomes almost uniform, and the air pad main body 1 is kept in the correct posture, that is, floated without being tilted. According to this embodiment as described above, the air supply hole 2 is connected to the air pad body 1.
Since it is formed near the outer periphery by a predetermined distance R from the center 0 of the air supply hole 3, the depth of the horizontal air supply hole 3 can be made significantly shallower compared to the conventional hole provided at the center, reducing machining time and reducing the drilling time. It can be processed at high speed and efficiently without paying attention to breakage, etc., and production costs can be significantly reduced.

In addition, since the air supply side hole 3 becomes shorter, the diameter is 200mm.
It is now possible to easily manufacture air pads of a relatively large size, and it is also possible to levitate large members. Furthermore, since only one air supply hole 2 is required, machining time can be reduced, and the hole diameter can be easily managed, which also leads to cost reduction. In addition, since the circular pocket 4 in the air supply hole 2 and the circular pocket 5 on the opposite side are connected by the groove 6, the pressure distribution in the air film on the lower surface of the air pad body 1 can be made uniform.
Improves floating posture. Furthermore, circular pockets 4 and 5
, 9, 10, the grooves 6 and the groove-shaped pockets 7, 8 are formed by etching, it is possible to form relatively shallow recesses with a uniform depth d, which was difficult with conventional machining using end mills, etc. The thickness of the air film formed on the lower surface of the main body 1 is thin and uniform, so that the film thickness and rigidity can be increased, and it can sufficiently cope with changes in load. Further, since it is an etching process, it is possible to process even those with complicated shapes such as the thin pockets 7 and 8, and it is also possible to process hard materials easily. Further, since the circular pockets 4, 5, 9, 10, the groove 6, the thin pockets 7, 8, etc. are shallow and have a small volume,
Pneumatic hammer is less likely to occur, and therefore there is no need to form a damping cavity or the like for preventing pneumatic hammer, and costs can be reduced. According to experiments, when the diameter of the air pad body 1 is about 140TmrL and the supply air pressure is 4Kf/Cd, the diameter D1 of each circular pocket 4, 5, 9, 10 is 5.7TmrL, When the width B1 of the groove 6 is 3'' and the inner diameter D2 of the groove-shaped pockets 7 and 8 is 62 wm, and the width B2 is 1.5 m, the depth d of each circular pocket etc. is varied by 0.15 to 0.5 mVC. If there is a groove 6, a good levitation posture can always be obtained, and the levitation amount, that is, the height H, is 10 to 20 μM,
The slope was 1 to 2 μm as the difference in height at both ends.

On the other hand, even if the dimensions are almost the same, in the case where the groove 6 is not provided, the inclination is too large to be practical. In addition, in implementation,
The shape of the groove-shaped pockets 7, 8 does not have to be circular, but may be square, for example, as long as they are approximately symmetrical about the groove 6. Furthermore, circular pockets 4, 5, 9,
10 etc., the shape and dimensions are not limited to the shapes and dimensions of the above embodiments. Further, the processing of the circular pockets 4, 5, 9, 10, the groove 6, the groove-shaped pockets 7, 8, etc. is not limited to etching as in the above embodiment, but may also be machined using an end mill or the like. If processed by etching, the above-mentioned effect can be obtained. As described above, the present invention has the advantage that it is possible to provide an air pad for an air bearing that is easy to process and has a good floating posture.

[Brief explanation of the drawing]

FIG. 1 is a bottom view of an air pad main body according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line -- in FIG. 1. 1...Air pad body, 2...Air supply hole, 3...Air supply side hole, 4, 5...Round pocket, 6...Groove , 7, 8... 1... Groove pocket.

Claims (1)

[Scope of Claims] 1. An air supply is provided at a position a predetermined distance from the center of the air pad body, a pocket is provided on the opposite side of the air pad body, with the center of the air pad body being interposed between the air supply hole, and the pocket and the air supply hole are provided. An air pad for an air bearing, characterized in that the air pads are connected to each other by a groove that is opened in the bearing surface and passes through almost the shortest distance. 2. In claim 1, a pocket is also provided around the air supply hole, and this pocket and a pocket located on the opposite side of the air supply hole are located approximately on both sides of the groove passing through the shortest distance. An air pad for an air bearing characterized by being connected by symmetrically formed groove-shaped pockets.