JPS6235947Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention is a hydrostatic gas bearing that supports a rotating shaft in the radial and thrust directions by supplying pressurized gas from the outside into the bearing gap through minute air supply holes. Regarding.

[Conventional technology]

As a static pressure gas bearing that supports the rotating shaft in both the radial direction and the thrust direction, the first
There is something like the one shown in the figure. This bearing has a radial bearing surface 02a of a bearing body 02 that surrounds a rotating shaft 01.
A large number of air supply holes 03 are provided in one or two rows along the periphery of the central portion, and a large number of air supply holes 04 are arranged in a ring shape on the left and right thrust bearing surfaces 02b, and the orifice throttle of the air supply holes 03, 04 Alternatively, the rotating shaft 01 is supported using a self-generating aperture effect.

Other conventional bearings of this type include those that have a large number of fine grooves in the direction perpendicular to the rotational direction of the shaft, as disclosed in Japanese Patent Publication No. 45-21404 and Japanese Patent Publication No. 46-12682, etc. There are surface drawing bearings with.

[Problem that the invention attempts to solve]

In the former type of bearing, the diameter of the air supply holes 03 and 04 cannot be made smaller than 0.1 mm due to processing reasons, so the optimal bearing clearance for maximum load capacity is 30 μm.
That's all there is to it. Therefore, the amount of movement of the bearing when a load is applied to the bearing is large, the stiffness (load/travel) of the bearing, defined as the ratio of the load to the amount of movement of the bearing, is small, and a large number of air supply holes are required. Therefore, it had the disadvantage that the air supply flow rate was large.

Next, the latter type of bearing has the advantage that a high load capacity can be obtained with a minute bearing gap of around 5 μm, so the bearing stiffness is large and the supply air flow rate is small. The drawback was that it was difficult to machine many fine grooves in the right angle direction, and the bearings were quite expensive.

[Means for solving problems]

The present invention was made with the aim of eliminating the above-mentioned drawbacks of conventional hydrostatic gas bearings that support the rotating shaft in both the radial and thrust directions. An exhaust passage is composed of a radial bearing section consisting of a surface and a thrust bearing section formed on both sides of the radial bearing section, and is connected to an exhaust hole leading around the bearing at the boundary between the radial bearing section and the thrust bearing section, and is at ambient pressure. In a hydrostatic gas bearing that supports a shaft in the radial direction and the thrust direction, the bearing has an exhaust groove connected to an exhaust hole that communicates around the bearing between a plurality of radial bearing surfaces and is at ambient pressure. An annular groove having a depth of 2 to 5 times the bearing clearance is formed near both end surfaces of the radial bearing surface and near both ends of the thrust bearing part, and a minute air supply hole for discharging gas is formed in each of the annular grooves. It has three or more openings.

[Effect]

In the present invention, pressurized air passes from the supply pressure Ps through the restriction resistance R ₁ of the air supply hole, expands in the circumferential direction through the annular groove, and then passes through the flow resistance R ₂ in the bearing gap to the exhaust groove. The pressure drops to atmospheric pressure Pa in passageways, etc. Therefore, due to changes in the bearing clearance, the flow resistance R ₂ changes depending on the location, increasing the bearing internal pressure in the narrowing bearing clearance area, and decreasing the bearing internal pressure in the widening bearing clearance area to support the rotating shaft. ing. In particular, the effect of the annular groove allows a pressure distribution that changes slowly in the circumferential direction to be formed, so even if there are as few as three air supply holes in the circumferential direction, it is possible to create a large number of air supply holes with a diameter so small that it is impossible to process them. It has the same effect and can generate pressure to restore the eccentricity of the rotating shaft in any direction. In other words, even if air supply hole rows are provided near the exhaust grooves on both sides, the continuity of the pressure change in the circumferential direction is maintained by the annular groove, and the utilization efficiency of the bearing surface in the circumferential direction does not decrease. A large restoring force can be generated in the wide area between the two annular grooves.

Furthermore, in a hydrostatic bearing, if the number of air supply holes is n, the diameter of the air supply hole is d, and the distance from the air supply hole to the end of the bearing in contact with the exhaust groove or exhaust passage is _l1 , then the optimal bearing clearance that maximizes the load capacity is n・d・It is known that the bearing clearance is proportional to the product of _l1 , and in this invention, the number of air supply holes n, the air supply hole diameter d, and the distance _l1 can all be reduced due to the effect of the annular groove as described above. can be minimized, and consumption of pressurized gas can be extremely reduced.

〔Example〕

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

In FIG. 2, a small diameter portion 1a provided on the rotating shaft 1 and side wall portions 1b at both ends thereof perpendicular to the surface of the small diameter portion 1a.
The bearing body 2 is housed in the groove formed by the above. Radial bearing surface 2 of the bearing body 2 surrounding the small diameter portion 1a
The intersection (boundary) between the left and right thrust bearing surfaces 2b facing the side wall portion 1b is chamfered, and the chamfered portion is formed on the rotating shaft 1 and communicates with the surroundings of the rotating shaft 1. The exhaust hole 3 is connected to constitute an exhaust passage 4 which is at ambient pressure (atmospheric pressure). Radial bearing surface 2 of bearing body 2
An annular exhaust groove 5 is provided in the center of the surface a, and the radial bearing surface 2a is divided into two. An exhaust hole 6 provided in the bearing body 2 and communicating around the bearing body 2 is connected to the annular exhaust groove 5, so that the annular exhaust groove 5 is brought to ambient pressure. A radial annular groove 7 is formed near the exhaust passage 4 and near the annular exhaust groove 5 on the two divided radial bearing surfaces 2a. Inside these radial annular grooves 7, there are third air supply holes 9 with minute diameters that communicate with the gas passages 8 formed in the bearing body 2.
As shown in the figure, there are three openings at equal intervals. Further, in the two thrust bearing surfaces 2b, thrust annular grooves 10 are formed in the vicinity of the outer peripheral surface thereof and in the vicinity of the exhaust passage 4, and within each annular groove 10, as shown in FIG. Air supply hole 1
1 is open. In the drawing, 12 is a base for supplying gas to the gas passage 8.

The gas supplied to the mouthpiece 12 passes through the gas passage 8 and is discharged from each air supply hole 9, 11, and is discharged between the radial bearing surface 2a and the small diameter portion 1a of the rotating shaft 1, and between the thrust bearing surface 2b and the rotating shaft 1. They each flow between the side wall portion 1b and generate a load that supports the shaft.

The first feature of the present invention is that the annular grooves 7, 10 provided near both ends of each bearing surface 2a, 2b are connected to the air supply hole 9,
It is deep enough to guide most of the pressurized gas from No. 11 in the circumferential direction, and shallow enough that in areas where the bearing gap is large enough, most of the gas from the air supply hole immediately flows out to the end of the bearing. . The second feature is that the inner diameters of the air supply holes 9 and 11 provided in the radial annular groove 7 and the thrust annular groove 10 are as small as possible due to machining, for example, about 0.1 mm, and the number of holes in the circumferential direction is 3. ~6 pieces (in this example, 3 pieces at 120 degree intervals). That is, the annular groove 7,
If there is no 10, install many air supply holes (for example, 10 or more)
However, due to the effect of the annular groove, the pressurized gas can be dispersed in the circumferential direction while suppressing the pressure drop. It is possible to obtain the same effect as having a large number of holes in the circumferential direction. Note that with two air supply holes in an annular groove, a restoring force acts when the air supply hole is eccentric in the direction of the air supply hole, but the restoring force becomes weak in any direction such as a direction perpendicular to the direction of the air supply hole, and the restoring force acts on the eccentricity of the rotation axis. I can't go back. Therefore, in order to have a uniform restoring force even if the rotating shaft is eccentric in any direction, it is necessary to
It is necessary to open three air supply holes at intervals.

The rotating shaft 1 of the bearing having such a structure is the seventh
When pressurized gas is supplied when the bearing is eccentric as shown in the figure (the eccentricity is emphasized in Figure 7), the pressure distribution in the width direction within each bearing will be found in areas where the bearing gap is narrow and where the bearing gap is wide. By the way, the fifth
It becomes a trapezoid like A and A' in figure a. In other words, since the distance between the annular grooves 7 is short, the flow resistance in the bearing width direction is smaller than the flow path resistance in the circumferential direction in the area between the annular grooves 7, so the pressure change in the bearing width direction is small, and the bearing clearance is small. The trapezoidal pressure distribution changes as A' and A, respectively, as
The pressure difference between A' and A works to restore the eccentricity of the rotating shaft 1.

Note that when the bearing width is larger than the bearing diameter, the flow path resistance in the width direction within the bearing cannot be ignored in the circumferential direction. The pressure difference decreases, resulting in a decrease in the load capacity of the bearing.

Therefore, as shown in Fig. 2, an annular exhaust groove 5 with ambient pressure at the center of the radial bearing surface.
The radial bearing surface is divided into two parts by providing an exhaust hole 6 and an exhaust hole 6, and by creating a large pressure difference across all bearing parts as shown by C and C' in Figure 5, the load capacity of the bearing can be increased. has been improved.

Next, FIG. 6 shows pressure distribution characteristics in the circumferential direction along the nine rows of air supply holes on the radial bearing surface 2a. Figure 6 shows the relationship between the angle φ from the maximum clearance position and the pressure when the rotating shaft 1 is eccentric downward when there are three air supply holes 9 as shown in Figure 7, and the depth of the radial annular groove. It is expressed as a parameter. The circumferential pressure distribution characteristics mainly depend on the depth of the radial annular groove 7 opening the air supply hole 9,
When an annular groove with a depth of about 2 to 5 times the bearing clearance is formed, as shown by curve C in Fig. 6,
The pressure in the narrowing gap area (the pressure integrated over the area where the angle φ ranges from 90° to 180° in Figure 6) and the pressure in the widening gap area (the angle in Figure 6 The difference in pressure (integrated pressure over the area where φ is 0° to 90°) is maximum.

If the depth of the annular groove 7 is smaller than this optimum value, the pressurized gas will flow out from the bearing end without being sufficiently filled between the air supply holes 9, so the pressure distribution will become as shown by curve D, and vice versa. If it is larger than this value, the pressurized gas will fill too much in the circumferential direction even within the expanded gap region, and the pressure distribution will become like curve E. Therefore, in either case, the pressure difference decreases and the load capacity of the bearing decreases.

The pressure distribution characteristics in the width direction and circumferential direction shown in FIGS. 5 and 6 are common to both the radial bearing section and the thrust bearing section shown in the embodiment shown in FIG. 2. Therefore, although the bearing of the present invention has a very small number of air supply holes (3 to 6), the effect of the annular groove allows for high pressure generation efficiency within the bearing.
Compared to conventional bearings, the bearing load capacity in the radial direction, thrust direction, and inclination can be increased by more than 50%.

In addition, the bearing of the present invention allows the air supply hole array to be placed near the bearing end due to the effect of the annular groove, and the diameter of the air supply hole is small, around 0.1 mm, and the number of air supply holes can be as small as 3 to 6, resulting in maximum load capacity. The optimum bearing clearance can be reduced to around 5 μm. In other words, according to calculations based on gas lubrication theory, a bearing with the structure shown in Figure 2 has a radial bearing diameter of 50 mm, a total radial bearing width of 50 mm, a thrust bearing outer diameter of 100 mm,
When the number of air supply holes per annular groove is 3, the air supply hole diameter is 0.15 mm, the annular groove width is 1 mm, and the distance between the annular groove and the bearing end is 2 mm, the optimal groove depth on the outer circumferential side of the thrust bearing part is approximately 45μ.
m, the optimum groove depth on the inner circumferential side is about 30 μm, the optimum groove depth on the radial bearing part is about 25 μm, and the optimum bearing clearance for maximum load capacity is about 6 μm. Here, the optimum depth of the annular groove is 2 to 5 times the bearing clearance.

In this way, the bearing of this invention has a small air supply hole diameter,
Since the number of holes is small and the bearing clearance is small, the amount of pressurized gas consumed can be extremely reduced.

The hydrostatic gas bearing assembly of the present invention may have various types other than the embodiment shown in FIG. For example, if the length of the radial bearing part is short, the central exhaust groove 5 and the annular grooves and air supply hole rows on both sides of the central exhaust groove 5 are eliminated;
It is also possible to use a single radial bearing. On the other hand, if you want to increase the load capacity in the radial direction by making the radial bearing part longer, you can use 3 or 4 radial bearing parts with 2 or 3 exhaust grooves.
It is also possible to divide the bearing surface into separate radial bearing surfaces and provide two rows of annular grooves and air supply holes for each bearing surface. In addition, in FIG. 2, the radial bearing surface 2a
In the radial bearing section consisting of a small diameter section 1a surrounded by the radial bearing surface 2a, and the thrust bearing section consisting of a thrust bearing surface 2b and a side wall section 1b opposite thereto, the radial bearing surface 2a and the thrust bearing surface 2b each have an annular shape. Grooves 7, 10, air supply hole 9,
11 is shown as an example, these annular grooves and air supply holes are connected to the small diameter portion 1 on the rotating shaft 1 side.
It is also possible to provide it on the side wall portion a and the side wall portion 1b.

[Effect of idea]

As described above, according to the hydrostatic gas bearing assembly according to the present invention, it is possible to have a high load capacity with a small bearing gap, so that Increased stamina. Furthermore, since the number of air supply holes is small, the air supply flow rate is reduced.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a conventional air supply hole type hydrostatic gas bearing assembly, FIG. 2 is a longitudinal sectional view of an embodiment of the hydrostatic gas bearing assembly according to the present invention, and FIG. FIG. 4 is a side view of the thrust bearing surface of the embodiment shown in FIG. 2, and FIG. 5 is a cross-sectional view along the air supply hole row of the radial bearing in the embodiment shown in FIG. An explanatory diagram showing the pressure distribution characteristics in the direction,
FIG. 6 is a graph showing the difference in pressure distribution in the circumferential direction depending on the depth of the annular groove in the example, and FIG. 7 is a diagram emphasizing the eccentricity of the rotation axis in the example. DESCRIPTION OF SYMBOLS 1... Rotating shaft, 1a... Small diameter part, 1b... Side wall part, 2... Bearing body, 2a... Radial bearing surface,
2b... Thrust bearing surface, 3, 6... Exhaust hole, 4
... Exhaust passage, 5 ... Annular exhaust groove, 7 ... Radial annular groove, 8 ... Gas passage, 9, 11 ... Air supply hole, 10 ... Thrust annular groove.

Claims (1)

[Scope of utility model registration request] It consists of a radial bearing part consisting of one or more radial bearing surfaces and a thrust bearing part formed on both sides of the radial bearing part, and the boundary between the radial bearing part and the thrust bearing part is connected to an exhaust hole that communicates around the bearing to reduce the ambient pressure. It has an exhaust passage that is connected to the exhaust hole that communicates around the bearing between the plurality of radial bearing surfaces, and has an exhaust groove that is at ambient pressure. In the pressurized gas bearing, an annular groove with a depth of 2 to 5 times the bearing clearance is formed near both end faces of the radial bearing surface and near both ends of the thrust bearing part, and a minute air supply hole for discharging gas is formed. A static pressure gas bearing assembly characterized in that each of the annular grooves has three or more openings.