JPS63203918A - Orifice type static pressure gas journal bearing - Google Patents

Abstract

PURPOSE:To make the pressure distribution on a bearing surface uniform by forming shallow grooves extending axially and circumferencially, and forcing compressed gas supplied in a bearing gap to flow along the grooves. CONSTITUTION:When compressed air is supplied to an air supply inlet 4, the compressed air flows into a bearing gap 3 through a nozzle 5. Then, the compressed air which flows into the bearing gap 3 flows in both circumferencial and axial directions along grooves 8, and is throttled at the radial stepped parts formed on both axial ends of the grooves 8, and flows outward from both axial ends of the bearing gap 3. The pressure on a bearing surface 9 is thus kept high, while the pressure destribution thereat is uniformalized because the compressed air flows in both circumferencial and axial directions along the grooves 8.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides an orifice that supports a shaft by supplying compressed gas from an air supply hole having an orifice to a bearing gap formed between a shaft and a bearing surface. This relates to type hydrostatic gas journal bearings.

[Conventional technology and its problems]

Orifice-type hydrostatic gas journal bearings have traditionally existed, in which a pocket communicating with an air supply hole is provided on the bearing surface of the bearing member that supports the shaft, and compressed gas is supplied to the bearing clearance through the pocket. The larger the pocket in a bearing, the higher the load capacity of the journal bearing, but on the other hand, pneumatic hammer is more likely to occur due to the compressibility of air, making it impossible to make the pocket larger. For this reason, even if the pressure in the pocket is high (even if the pressure is high, the pressure decreases on the bearing surface away from the pocket, which limits its rigidity and load capacity.

For example, there is an invention described in Japanese Patent Publication No. 134623/1983, which aims to prevent the occurrence of pneumatic hammer as described above and increase rigidity and load capacity.

As shown in FIGS. 9 and 10, the orifice type static pressure gas journal bearing described in the above publication has a plurality of air supply holes 14 having orifices 13 in a bearing member 12 supporting a shaft 11 at equal intervals in the circumferential direction. The bearing surface 15 of the bearing member 12 is provided with an air supply groove 16, and the air supply groove 16 is H-shaped, with circumferential grooves 18 provided at both ends of an axial groove 17.

In the above-mentioned journal bearing, since the air supply grooves 16 are independent from each other, the gas fed into the air supply grooves 16 does not flow in the circumferential direction, and the eccentricity of the shaft 11 due to the load can be accommodated. The advantage is that the load capacity and stiffness can be significantly increased by generating a suitable differential pressure.

However, since there is no circulation of gas in the circumferential direction, the pressure between adjacent air supply grooves 16 becomes low, resulting in an inconvenience that the pressure balance in the circumferential direction is poor.

Furthermore, since it is necessary to provide the air supply grooves 16 on the bearing surface 15 of the bearing member 12 at equal intervals in the circumferential direction, facing each air supply hole 14, there is also the disadvantage that processing is extremely time-consuming.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide an orifice-type hydrostatic gas journal bearing that eliminates the above-mentioned disadvantages, equalizes the pressure on the bearing surface, is easy to process, and can obtain high rigidity and load capacity. The purpose is

[Structure of the invention]

In order to achieve the above object, the present invention forms a bearing gap between a shaft and a bearing member, and provides a plurality of air supply holes each having an orifice in either one of the shaft or the bearing member at a required interval in the circumferential direction. and a shallow groove extending in the axial direction and the circumferential direction is formed on the other surface facing the air supply hole.

[Effect]

With the above configuration, by supplying compressed gas from the air supply hole to the bearing clearance, the compressed gas flows along the groove in the axial and circumferential directions, making the pressure distribution on the bearing surface uniform. Can be done.

In addition, pneumatic hammer is less likely to occur due to the compressed gas going around, and the gas can be narrowed down by the radial step formed at both axial ends of the groove, so the throttling effect of the orifice is combined with the surface at the step. With the addition of a throttling effect, it is possible to maintain high pressure on the bearing surface.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

As shown in FIGS. 1 and 2, a bearing clearance 3 is provided between the shaft 1 and a bearing member 2 that supports it. In the bearing member 2, a plurality of air supply holes 4 are formed in double rows at equal intervals in the circumferential direction, and a nozzle 5 is provided at the tip of each air supply hole 4. Further, an orifice 6 having a smaller diameter than the inner diameter of the nozzle 5 is provided inside the air supply hole 4 .

Here, the orifice 6 may be provided directly on the bearing member 2, or an orifice plate 7 provided with the orifice 6 may be attached to the air supply hole 4 as shown.

The orifice 6 must have a small diameter in order to exhibit a throttling effect. However, it is not easy to directly machine such an orifice 6 into the bearing member 2, and small-diameter drills are often damaged during drilling, and the bearing member 2 is likely to be defective due to the drill damage. . Therefore, by attaching the orifice plate 7 to the air supply hole 4 as shown in the illustrated example, it is possible to effectively eliminate the above-mentioned disadvantages.

The shaft 1 is provided with a shallow groove 8 extending in the axial direction and the circumferential direction on the surface facing the air supply hole 4 .

Here, the depth h of the groove 8 is selected so that the following equation holds true in order to make the area of the orifice constriction smaller than the area of the self-produced constriction by the nozzle 5 and to produce the orifice constriction effect.

π πdi(ho+h)≧□d−・・・・・・■4
dt Here, each symbol is dl... as shown in Figure 3.
...Inner diameter of the orifice d, ...Inner diameter of the nozzle ho...Between the bearing clearance.

The journal bearing shown in the embodiment has the above-mentioned structure, and this journal bearing supports the shaft 1 by supplying compressed gas from the air supply hole 4 to the bearing clearance 3 in the same manner as the conventional journal bearing.

Now, when compressed gas is supplied to the air supply hole 4, the pressure of this compressed gas is increased in the orifice 6 and flows into the bearing gap 3 from the nozzle 5. In addition, the compressed gas that has flowed into the bearing clearance 3 flows in the circumferential direction and axial direction along the groove 8, and is narrowed down at the radial step formed at both axial ends of the groove 8, and is narrowed down in the bearing clearance 3. It flows out from both ends in the axial direction.

As mentioned above, the compressed gas is narrowed down by the orifice 6 and narrowed down at the stepped portion of the groove 8, so in addition to the orifice throttling effect, the compressed gas is subjected to the surface throttling effect.
Since the bearing surface S can be maintained at a high pressure and the compressed gas flows in the circumferential and axial directions along the grooves 8, the pressure distribution on the bearing surface 9 becomes uniform, and the bearing negative capacity and rigidity are improved. can be significantly increased.

FIG. 4 is a graph showing calculation results of bearing stiffness with respect to bearing clearance of the bearing according to the present invention.

Here, the dimensions of each part of the bearing are as follows.

Inner diameter of bearing surface D = 60 m Length of bearing surface L -40 am Groove length l - 30 Depth of crane groove h μm Orifice diameter d + "0.15 m Iris nozzle diameter dz = o, 51 m As is clear from Figure 4 In addition, the rigidity is high when the depth h of the groove 9 is around 8 μm, and the rigidity decreases when the depth h is larger or smaller than that.

Moreover, FIG. 5 is a graph showing the calculation results of the damping coefficient with respect to the bearing clearance of the bearing according to the present invention. The dimensions are the same as the dimensions of each part of the bearing.

As is clear from this Fig. 5, the bearing clearance.

is 8 μm, the damping coefficient decreases as the depth of fs8 increases, but even if the depth h of the groove 8 is 16 μm, the damping coefficient remains positive and stable.

Note that when the damping coefficient becomes negative, pneumatic hammer is more likely to occur.

From FIGS. 4 and 5 above, it is preferable that the bearing clearance ho formed between the shaft 1 and the bearing member 2 is 8 μm.

6 and 7 are graphs showing calculation results of the damping coefficient and bearing rigidity when the inner diameter of the nozzle 5 of the bearing according to the present invention is changed. Here, the bearing clearance ho is 8 μm
It is.

As is clear from FIGS. 6 and 7, in a range where the inner diameter d2 of the nozzle 5 is larger than 111, the bearing rigidity hardly increases even if the inner diameter becomes large, and the damping coefficient tends to become negative. Therefore, in this range, there is little utility value, and the inner diameter d2 of the nozzle 5 is preferably set to 1 ms or less.

In the embodiment shown in FIGS. 1 and 2, the air supply hole 4 is formed in the bearing member 2, and the groove 8 is formed in the shaft 1.
As shown in the figure, the groove 8 may be formed in the bearing member 2 and the air supply hole 4 may be provided in the shaft 1, contrary to the above.

As shown in FIG. 8, the cylinder 1 has a closed end in the air supply hole 4.
0 is fitted, a nozzle 5 is provided at the closed end of the cylinder 10,
By attaching the orifice plate 7 having the orifice 6 inside the cylindrical body 10, the machining of the air supply hole 4 can be made easier.

In the example, a double row of air supply holes 4 arranged at equal intervals in the circumferential direction is provided, but in this case, a land portion at the same height as both ends of the bearing is provided in a part of the axial center of the groove. It may be provided on the circumference. Moreover, the air supply holes may be in a single row.

Effect C] As described above, according to the present invention, the compressed gas supplied to the air supply hole is narrowed by the orifice, flows into the groove facing the air supply hole, and flows in the circumferential and axial directions along the groove. Since the groove is narrowed down at the radial stepped portions provided at both axial ends of the groove, the effect of the surface throttle is added to the effect of the orifice throttle, making it possible to maintain a high pressure on the bearing surface. Therefore, the rigidity and load capacity of the bearing can be improved.

In addition, since gas flows in the axial and circumferential directions of the groove, the pressure distribution on the bearing surface becomes uniform, the number of air supply holes can be reduced compared to conventional models, and it is also effective in preventing the occurrence of pneumatic hammer. can be mentioned.

In addition, an air supply hole is formed in either the shaft or the bearing member,
Since a groove is provided on the other side, manufacturing of the bearing is easy.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional front view showing one embodiment of a journal bearing according to the present invention, Fig. 2 is a longitudinal sectional side view of the same, Fig. 3 is an enlarged sectional view of the same, and Fig. 4 is a bearing clearance of the same. Figure 5 is a graph showing the relationship between the bearing clearance and damping coefficient of the same bearing as above, Figure 6 is a graph showing the relationship between nozzle diameter and rigidity of the same bearing, Figure 7 is the same as above. Graph showing the relationship between nozzle diameter and damping coefficient, FIG. 8 is a longitudinal sectional front view showing another embodiment of the journal bearing according to the present invention, FIG. 9 is a longitudinal sectional front view showing a conventional journal bearing, and FIG. 10 is a longitudinal sectional front view showing the conventional journal bearing. FIG. 1...shaft, 2...bearing member, 3...
... Bearing clearance, 4 ... Air supply hole, 6 ...
... Orifice, 7 Orifice plate, 8...
·groove.

Claims (4)

[Claims] (1) A bearing clearance is formed between a shaft and a bearing member that supports the shaft, and a plurality of air supply holes equipped with orifices that supply compressed gas to the bearing clearance are provided in either one of the shaft and the bearing member in the circumferential direction. an orifice-type hydrostatic gas journal bearing, which is provided at a required interval on the other side, and has a shallow groove extending in the circumferential direction and the axial direction on the surface facing the air supply hole. (2) The orifice type static pressure gas journal bearing according to claim 1, wherein an air supply hole is provided in the bearing member and a groove is formed on the outer diameter surface of the shaft. (3) The orifice type hydrostatic gas journal bearing according to claim 1, wherein an air supply hole is formed in the shaft and a groove is provided in the bearing surface of the bearing member. (4) The orifice type static pressure gas journal bearing according to claim 1, wherein the orifice is provided in an orifice plate fitted into the air supply hole.