JPS61157819A - Journal slide bearing - Google Patents

Abstract

PURPOSE:To prevent seizure and abrasion of a bearing body by disposing a void or a hole connected to the outside of the bearing body at a portion of the bearing body where the generation of negative pressure is presupposed. CONSTITUTION:A void 4 having a depth about equal to the average radial gap and extending in the longitudinal direction of a bearing body 2 to both end portions is disposed at a portion of the bearing body 2 where the generation of negative pressure is presupposed. Accordingly, lubricating liquid 3 easily flows from both ends of the bearing body 2 into the interior of the bearing, so that negative pressure is not produced at that portion. The pressure at that portion is equal to the base pressure of lubricating oil, so that a difference in pressure between the inner and outer portions of the bearing body 2 relatively becomes zero not to cancel the resultant force of components in the direction of load of static pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to improvements in journal plain bearings used in rotating machines that exist in environments where the ambient pressure is high compared to atmospheric pressure.

[Technical background of the invention and its problems]

In general, there are two types of journal plain bearings: those that supply lubricating liquid such as oil or water locally, and those that lubricate the entire rotating shaft including the bearing by immersing it in lubricating liquid. The base pressure is approximately equal to atmospheric pressure.

By the way, the base pressure of the lubricating fluid in pump motors and the like used inside the pressure vessel or system of a nuclear reactor is equal to the pressure inside the vessel, and the pressure may be extremely high. For example, in an internal pump directly attached to the pressure vessel of a nuclear reactor, the base pressure of the lubricating fluid in the journal sliding bearing reaches as much as 9°Kg/cd.

Therefore, journal sliding bearings used under such high pressures have serious problems in terms of their characteristics. Here, the problem will be explained with reference to Fig. 5 (a> to (f)). Fig. 5 (a) shows that the rotating shaft 1 is supported by the journal sliding bearing body (hereinafter simply referred to as the bearing body) 2. FIG. 3 is a schematic cross-sectional view of a state in which the lubricant is in a state perpendicular to the axis, and shows a state in which pressure is generated when the base pressure of the lubricant is equal to atmospheric pressure.

In theory, negative pressure is generated in this state, but when the absolute pressure becomes negative, cavitation occurs and in reality, almost no negative pressure is generated. In the figure, W indicates the load direction, and in the case of a model machine, the rotor's own weight acts, and in the case of a vertical machine, an unbalanced force or other external force acts.

Here, if the origin of the polar coordinate angle is set at a position 180 degrees opposite to position 3 where the lubricant film thickness is minimum in FIG. 5(a), the pressure distribution will be as shown in FIG. 5(b). hardly ever generates negative pressure. Therefore, the center position of the rotating shaft is determined within the bearing body so that the resultant force of the positive pressure balances the load W, and the locus of the center of the rotating shaft that changes in response to the magnitude of the load is as shown in Figure 5 (C). become. However, the direction in which the load is applied is the vertical direction in the drawing, and the scale is set so that the average radial gap between the bearing body and the rotating shaft is 1.0. According to FIG. 5(C), it can be seen that the center of the rotation axis changes in an arcuate trajectory depending on the load.

On the other hand, when the base pressure of the lubricating fluid becomes high, a relative negative pressure is generated within the bearing body, but the absolute pressure is positive pressure, so cavitation does not occur, and the base pressure is similar to the theoretical calculation. Both positive pressure and negative pressure are generated at the same time. If this situation is drawn in the same manner as in FIGS. 5(a) and (b), it will become as shown in FIG. 5(d), me). That is,
Since the generation distribution of negative pressure has the same shape as that of positive pressure, the resultant force in these load directions cancels out and almost disappears.
Only the resultant force in the direction perpendicular to the load is generated. Therefore, the locus of the rotation axis center corresponding to the magnitude of the load is as shown in FIG. 5(f).

When the base pressure of the lubricant becomes high as shown in Figure 5 (
As is clear from d) to (f), the displacement of the rotating shaft is perpendicular to the direction in which the load is applied, so in this situation the bearing body has extremely large vibrational instability. It turns out. In particular, when used in vertical rotating machinery, bearings cannot exhibit their full bearing capacity against rotational loads such as unbalanced forces, and unstable phenomena called oil whirl and oil whip occur. This causes the shaft to swing around completely in the gap in the bearing body, leading to fatal accidents such as seizure and wear. Furthermore, the accompanying large vibrations have the problem of significantly lowering the reliability of the entire bearing rotating machine system in a wide range of ways, such as loosening of connections and fatigue failure of materials.

[Purpose of the invention]

The present invention was made to solve the above-mentioned problems, and its purpose is to prevent the base pressure of the lubricating fluid from being used under high pressure by preventing negative pressure from occurring inside the bearing body. The purpose of the present invention is to provide a highly reliable journal sliding bearing that can prevent unstable vibrations and eliminate the risk of seizure or further abrasion of the bearing body.

[Summary of the invention]

In order to achieve such an object, the present invention is designed to prevent negative pressure from occurring in the bearing body in advance in a journal slide bearing used in a rotating machine installed in an environment where the surrounding pressure is high compared to atmospheric pressure. The bearing is characterized in that a recess or hole communicating with the outside of the bearing body is provided in a portion that communicates with the outside of the bearing body, and lubricating fluid can flow from the outside of the bearing body through this recess or hole.

In addition, by providing a recess that communicates with the outside of the bearing on the rotating shaft in the area where the direction of rotational load is expected to be applied, the effect can be particularly noticeable when the unbalanced force is large in a vertical rotating machine. It is something.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, and is a schematic cross-sectional view taken in a direction perpendicular to the axis.

In this embodiment, as shown in FIG. 1(a), in the part of the bearing body 2 where negative pressure is expected to be generated, a recess is formed with a depth of about the average radius clearance and a length reaching both ends of the bearing body in the longitudinal direction. 4 is provided.

In this case, if the direction of the load W applied to the rotating shaft 1 is constant and its magnitude is known, the range in which negative pressure is generated can be determined by simple theoretical calculations, and the area corresponding to that range is shown above. What is necessary is to provide such a depression 4.

Therefore, by providing the recess 4 in the bearing body 2, the lubricating fluid 3 can easily flow into the bearing body 2 from both ends thereof, and no negative pressure is generated in this portion.

FIG. 1(b) shows the state of pressure generation in a bearing with such a configuration. If there were no depressions, negative pressure would be generated as shown by the dotted line waveform, but if depressions 4 are provided as shown in this example, negative pressure will be generated. As a result, the pressure in this portion is equal to the base pressure of the lubricating fluid, and the pressure difference between the inside and outside of the bearing body 2 becomes zero, so that the resultant force of the static pressure components in the load direction is no longer canceled out.

Therefore, even the simplest perfect circular bearing can have sufficient vibration stability under high pressure by providing the recess 4 as described above, and at the same time, the load characteristics as a bearing are ensured and there is no worry of seizure or wear. It becomes a journal sliding bearing. A bearing having such a configuration can be used effectively in a horizontal rotating machine or a vertical rotating machine when the direction in which the load is applied is always constant and clearly known.

FIGS. 2 and 3 show second and third embodiments of the present invention.

First, a second embodiment will be described with reference to FIG. Second
In this embodiment, as shown in FIG. 2, a plurality of holes 5 communicating with the outside in the radial direction are provided in a portion of the bearing body 2 where negative pressure is expected to be generated.

Therefore, since the lubricating liquid 3 can flow into the interior from the outside through these holes 5, generation of negative pressure can be prevented. Further, by providing these holes 5 in a concentrated manner in the longitudinal center of the bearing body 2, the effect can be more clearly exhibited.

Next, a third embodiment will be described with reference to FIG.

In the third embodiment, as shown in FIG. 3, a plurality of holes 6 communicating with the outside are provided along the entire circumference of the bearing body 2 at predetermined intervals in the radial direction. Check valve 7
are provided for each.

Therefore, with such a configuration, when positive pressure is generated inside the bearing body 2, the check valve 7 closes to prevent the lubricating fluid from flowing out to the outside, and conversely, when negative pressure is generated, the check valve 7 closes and prevents the lubricating fluid from flowing outside. The check valve 7 opens due to the pressure difference, and lubricating fluid flows in from the outside, thereby preventing the generation of negative pressure. In this case, each hole 6 including the check valve 7 may be provided at one or more locations near the center in the longitudinal direction of the bearing main body, thereby making the effect even more effective. It goes without saying that the same effect as described above can also be obtained by providing the check valve 7 outside the bearing body and connecting it to the hole 6 with a pipe.

Bearings with this configuration are particularly useful in vertical rotating machines where the rotating load is greater than the static load, i.e. where the negative pressure generation position cannot be predicted in advance or changes from moment to moment. I can demonstrate it.

FIG. 4 shows a fourth embodiment of the present invention. In this embodiment, as shown in FIGS. 4(a) and 4(6), a recess 8 is formed on the rotating shaft 1 in a portion where rotational loads are expected to be applied, and the recess 8 communicates with the outside of the bearing.
It is designed to provide a. In this case, the length of the recess 8 is such that it extends slightly outward from the bearing end in the longitudinal direction of the rotating shaft.

Bearings with such a configuration are particularly effective when used in vertical rotating machines where unbalanced forces are large.

In other words, unbalanced force is a rotational load, but if the direction of its action is known in advance and it is used below the primary critical speed of the rotating shaft, negative pressure will be generated in the unbalanced direction of the rotating shaft. The range is determined on the axis. That is, since the whirling direction of the shaft coincides with the direction of unbalance, the minimum lubricant film thickness is formed at a position advanced by an angle e from this direction as shown in the figure. Since there is a region where negative pressure is generated at an angle that is more advanced than this, the recess 8 may be provided with a depth approximately equal to the average radial gap between the shaft and the bearing body.

Therefore, with such a configuration, the lubricating fluid easily flows in from the outside through the recess 8 provided in the rotating shaft 1, so that negative pressure is not generated as shown in FIG. The same effect as in the example can be expected.

【Effect of the invention〕

As described above, according to the present invention, a depression or a hole communicating with the outside of the bearing body is provided in a portion of the bearing body where negative pressure is predicted to be generated in advance, and synovial fluid is drawn from the outside of the bearing body through this depression or hole. This allows for inflow, so even when used in an environment where the surrounding pressure is high compared to atmospheric pressure, relative negative pressure does not occur inside the bearing body, and the pressure is the same as when used under atmospheric pressure. Vibration stability can be obtained, and therefore unstable vibration can be prevented even with a true round bearing with a large load capacity.As a result, there is no need to worry about seizure or abnormal wear of the bearing body, and large vibrations can occur. Therefore, it is possible to provide a journal sliding bearing that can ensure the reliability of the entire rotating machine system including the bearing.

In addition, by providing a recess that communicates with the outside of the bearing on the rotating shaft in the area where rotational loads are predicted, the effect can be fully utilized, especially when the unbalanced force is large in vertical rotating machines. Journal plain bearings can be provided.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) show a first embodiment of the present invention. Distribution map showing the second
3 and 3 are schematic configuration diagrams showing the second and third embodiments of the present invention, respectively, and FIGS. 4(a) to (C) show the fourth embodiment of the present invention, and (a) ) is a schematic configuration diagram taken in a direction perpendicular to the shaft, (b) is a side view showing the rotating shaft with only the bearing body in cross section, (C) is a distribution diagram showing the state of pressure generation, and FIG. (a) to (C) are for explaining the case where only positive pressure is generated in a conventional journal sliding bearing, (a) is a schematic configuration diagram showing a cross section in a direction perpendicular to the axis, and (b) ) is a distribution diagram showing the state of pressure generation, (C) is a diagram showing the locus of the center of the rotating shaft that changes depending on the magnitude of the load, and Figures 5 (d) to (f) are diagrams showing the distribution of pressure in conventional journal plain bearings. This is to explain the case where both positive pressure and negative pressure are generated. (d) is a schematic configuration diagram showing a cross section in the direction perpendicular to the axis, and (e) is a distribution diagram showing the pressure generation state. , (f) are diagrams showing the locus of the center of the rotation axis that changes depending on the magnitude of the load. 1... Rotating shaft, 2... Bearing body, 3... Lubricating fluid,
4°8... recess, 5.6... hole, 7... check valve. Applicant's representative Patent attorney Takehiko Suzue 1st prisoner (a) (b) l Figure 2 Figure 3 Figure 4 (a) (a) (c) (b) (e)

Claims (4)

[Claims] (1) In journal sliding bearings used in rotating machinery installed in environments where the ambient pressure is higher than atmospheric pressure, the portion of the bearing body where negative pressure is expected to be generated communicates with the outside of the bearing body. A journal sliding bearing characterized in that it is provided with a recess or hole. (2) The journal sliding bearing according to claim 1, wherein a plurality of holes communicating with the outside of the bearing body are provided around the entire circumference of the bearing body in the radial direction. (3) The hole communicating with the outside of the bearing body is configured to communicate with the outside by means of a check valve only when negative pressure is generated inside the bearing body. Journal plain bearing. (4) In journal sliding bearings used in rotating machines installed in environments where the ambient pressure is higher than atmospheric pressure, a recess that communicates with the outside of the bearing is installed on the rotating shaft in the area where rotational loads are expected. A journal sliding bearing characterized by: