JPS5917286B2 - Hydrostatic journal bearing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydrostatic journal bearing that supports a rotating shaft using the static pressure of a fluid.

Figures 1 and 2 respectively show conventional hydrostatic journal bearings, and Figure 1a shows a type of bearing in which pockets of the same size and lubricant supply holes that also function as fluid throttles are arranged at equal intervals on the bearing surface. Fig. 2a is a vertical sectional view of the bearing having only a supply hole, and Fig. 2b is an exploded view of the bearing surface. 1 is the rotating shaft, 2 is the bearing body, 3 is the pocket, 4 is the supply hole for supplying lubricant such as oil or air, and the hole diameter is 7.
It also serves as a fluid restrictor that changes the pressure of the lubricant supplied by changing the pressure to zero. The supply hole 4 and the pocket 3 or only the supply hole 4 constitute a supply section. 5 is a bearing support frame, 6 is a lubricant reservoir, T is a glue receiving surface, 8 is a bearing clearance, and 9 is a lubricant supply pump 15.

Next, the operating conditions of this bearing will be explained in two cases: a case where the influence of the rotation of the rotating shaft 1 is negligible, and a case where the influence of the rotation is large and whirling vibration becomes a problem.

20 Figure 3 shows the pressure distribution when the rotation speed is slow and the influence of the rotation of the rotating shaft 1 can be ignored, and the rotating shaft 1 rotates eccentrically in the direction of the load.In this case, since there is a supply hole 4, As shown in the figure, the pressure 25 distribution is such that higher pressure is generated where the bearing clearance 8 is smaller.

Therefore, when the load increases and the amount of eccentricity increases, it is necessary to increase the pressure of the lubricant supplied to the bearing.

Figure 4a is a diagram showing the pressure distribution when the rotational speed is high and the rotating shaft 1 is rotating eccentrically in the rotational direction (direction of arrow A) due to the influence of the rotation of the rotating shaft 1. In this case, the load F
An eccentric angular reaction force component Fθ of the bearing corresponding to s is generated.

This is due to the hydrodynamic pressure generated due to the viscosity of the lubricant fluid 35 being added to the static pressure generated as the rotating shaft 1 rotates, resulting in a deviation angle between the load direction and the eccentric direction. This is to generate θ. This eccentric angular direction reaction force component Fθ is a force that tends to cause the rotating shaft 1 to swing,
At a certain rotation speed, the rotating shaft 1 suddenly generates self-excited whirling vibration due to this reaction force component Fθ, and becomes unable to rotate. This phenomenon is considered to be fatal in high-speed fluid journal bearings. To explain in more detail, FIG.
The explanatory diagram of FIG. a shows a situation where the rotating shaft 1 is steadily rotating in the direction of A. 0 is the center of the bearing, σ is the center of the rotating shaft, and F' is the bearing reaction force, which is equal in magnitude to the load FS and opposite in direction since the rotation is normal.

0σ is the amount of eccentricity.

When the above Ff is decomposed into an eccentric direction reaction force component and an eccentric angular direction reaction force component, they become Fε and Fθ, respectively. The reaction force component Fε in the eccentric direction is a force that reduces the amount of eccentricity that attempts to move σ in the direction of O, whereas the reaction force component Fθ in the eccentric angular direction
You can see that it is a force that tries to swing around O. In other words, the eccentric reaction force component Fε does not become a whirling moment about O, whereas the eccentric angular reaction force component Fθ becomes a whirling moment about O.

Therefore, the smaller the reaction force component Fθ in the eccentric angular direction is, the more difficult it becomes for the rotating shaft 1 to swing around. FIG. 5 is a prior art example of this invention suitable for the low speed rotation shown in FIG.
Figure a is a cross-sectional view of the bearing 2, and figure b is a developed view of the bearing surface 7. At the intersection of the load line 10 and the bearing surface 7, there is a pocket 31 with the largest area and the smallest orifice (the orifice with the smallest pressure drop). ), and the pockets 32 to 37 are provided with a supply section that is a combination of a supply hole 41 with a supply hole 41 having a
A supply section is provided, which is a combination of supply holes 42 to 47 whose pressure drop amounts are sequentially increased.

With this configuration, the pressure distribution of the lubricant on the bearing surface 7 will be similar to the pressure distribution shown in FIG. 3 at a position where the rotating shaft 1 is close to concentric with the bearing surface 7. It is supported at a position close to .

However, in the case of the one shown in FIG. 5, the influence of rotation is as large as before, and whirling vibration becomes a problem.

The present invention aims to solve these problems and improve the performance and reliability of the bearing by suppressing the occurrence of whirling vibration, especially during high-speed rotation. FIG. 6 shows an embodiment of the present invention suitable for the high-speed rotation shown in FIG. 4a, in which FIG. 4a is a cross-sectional view of the bearing 2, and FIG.

In this embodiment, no pocket is provided, and the supply hole 4, which is the lubricant supply part, is formed to have the same constriction effect (same diameter, same length) and is centered at the intersection of the eccentric angular reaction force component Fθ and the bearing surface 7. The lubricant is arranged in the vicinity of this point at the highest density, and the lubricant is arranged at a lower density as it moves away from the above-mentioned intersection. With this structure, the pressure distribution of the lubricant on the bearing surface 7 is arranged in the opposite direction in the eccentric angle direction. Since the pressure distribution is such that the force component Fθ is small, the rotating shaft 1 is supported at a position where the deviation angle θ shown in FIG. 4a is small.

Therefore, even if the load is large, the rotary shaft 1 is supported substantially concentrically and does not come into contact with the bearing surface 7 during operation.

Further, since the eccentric angular direction reaction force component Fθ becomes small, the rotating shaft 1 can be stably rotated up to a high rotational speed without whirling.

In the above explanation, in the example shown in FIG. 5, the size of the pocket 3 and the aperture of the supply hole 4 are changed, and in the example shown in FIG. Although configurations with different installation densities have been shown, the example of FIG. 5 can be replaced with the embodiment of FIG. 6.

This invention provides a plurality of lubricant supply sections that open on the bearing surface, and uses these supply sections to supply lubricant at the highest pressure near the intersection of the eccentric angular reaction force component of the bearing and the bearing surface. Or, it is configured or arranged so that the largest amount of lubricant is supplied, and the pressure or amount of lubricant supplied gradually decreases as the distance from the intersection point increases, thereby suppressing the occurrence of whirling vibration of the rotating shaft. Therefore, it is possible to increase the support capacity and stability of the journal hydrostatic bearing, and this can have a great practical effect.

[Brief explanation of drawings]

Figures 1a and 2a are longitudinal cross-sectional views of conventional hydrostatic journal bearings, Figures 1b and 2b are developed views of the bearing surface, and Figure 3 shows the rotation of the rotating shaft ignored. Figure 4a is a diagram showing the pressure distribution during low-speed rotation, where the influence of the rotation of the rotating shaft is large, Figure 4b is an explanatory diagram of Figure 4a, and Figure 5a is a diagram showing the pressure distribution during low-speed rotation. FIG. 5b is a cross-sectional view of a bearing showing an example of the prior art; FIG. 5b is a developed view of the bearing surface; FIG. This is a developed diagram. In the figure, 1 is a rotating shaft, 2 is a bearing, 3, 31-37 are pockets, 4, 41-47 are supply holes, 6 is a lubricating oil reservoir,
7 is a bearing surface, 8 is a bearing clearance, and 9 is a pump.

Claims (1)

[Scope of Claims] 1. A bearing that supports a rotating shaft has a plurality of lubricant supply parts that are distributed and opened on the inner circumferential surface of the bearing, and fluid lubricant is discharged from the supply parts to support the rotating shaft. In the bearing configured to support the bearing, a supply unit is arranged to supply the maximum discharge pressure or the maximum amount of lubricant to the bearing surface located near the intersection of the eccentric angular reaction force component of the bearing and the bearing surface. A hydrostatic journal bearing characterized in that a supply section is provided in which the discharge pressure is gradually decreased as the distance from this position increases, and the supply amount is also gradually decreased. 2. The hydrostatic journal bearing according to claim 1, wherein the supply portion has a pocket formed on the bearing surface with a size corresponding to the discharge pressure of the lubricating oil. 3. The hydrostatic journal bearing according to claim 1 or 2, wherein the arrangement density of the supply holes is changed in accordance with the amount of lubricant to be supplied.