JPS61103013A - Device for fixing outer race of thrust bearing or screw compressor - Google Patents

Abstract

PURPOSE:To reliably fix an outer race of a bearing by providing a spigot joint structure on a pressing plate for fixing an outer race of a thrust bearing to a casing. CONSTITUTION:The form of a pressing plate 13 for fixing an outer race of a combined angular ball bearing 4 to a casing 3 is of spigot joint structure. Therefore, a spigot joint 13A is disposed, thereby to stop the radial movement of the pressing plate 13. Thus, the outer race can be prevented from causing eccentricity to reduce eccentric load, bearing clearance and to eliminate a factor such as pre-pressure or the like related to the life of the bearing.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to thrust bearings for screw compressors.

The present invention relates to a shaft fixing method, and particularly to an outer ring fixing device for a thrust bearing of a dry screw compressor.

[Background of the invention]

Figure 1 shows a cross-sectional view of the main body of the dry screw compressor.

In a dry screw compressor, a male rotor 1 and a female rotor 2 are rotated without contact with each other by a timing gear 9 while maintaining a small gap between them. JP-A-59-93-83 has a structure in which roller bearings are arranged on the suction side and discharge side to support the radial load, and a combination angular ball bearing is arranged on the discharge side to support the thrust load. During steady operation of the compressor, gas pressure is acting on the rotor in the direction indicated by the arrow in FIG. 1A, and a load is acting on the combined angular contact ball bearing in the direction of pulling it toward the suction side. However, when the load condition changes, there is a possibility that the rotor shaft moves toward the discharge side (opposite to the arrow). For example, in a high-pressure stage of a two-stage compressor, the discharge pressure is released to the atmosphere during no-load operation, and the suction side is closed at the same time. However, this operation does not occur completely simultaneously, and a pressure state opposite to normal may occur temporarily.

To suppress such movement, a combination angular contact ball bearing or a four-point contact ball bearing is used, and the outer ring is usually designed to be loose with respect to the casing in order to extend the life of the bearing. Therefore, the outer rings of these bearings must be fixed to the casing so that they do not move in the axial direction (thrust direction). FIG. 2 is a detailed view of a known angular contact ball bearing.

The plate is placed against the outer ring of the bearing and is secured to the casing by bolts. In this example, it is fixed with three bolts, but in the process of tightening the bolts one by one, it is difficult to tighten the three bolts evenly even if you manage the tightening load with torque, as shown in Figure 6. The elastic deformation of the presser plate generates a force that moves the outer ring in the radial direction. Axial and radial clearances exist inside a ball bearing, but during the process of fastening the outer ring, the outer ring is forcibly moved, and the radial clearance is twice the design value (see Figure 6). There were problems such as areas where there was no clearance (X area in Fig. 6), or areas where preload was generated when an unbalanced load was applied.

[Object of the Invention] An object of the present invention is to provide a method for reliably fixing an outer ring of a thrust bearing of a dry screw compressor without reducing the life of the bearing.

[Summary of the Invention] A feature of the present invention is that the retaining plate for fixing the outer ring of the thrust bearing to the casing has a spigot structure.

[Embodiments of the invention]

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

In this figure, the shape of the presser plate 13 is a structure in which a spigot is provided. The above-mentioned phenomenon in which the outer ring becomes eccentric is due to the eccentric movement of the retainer plate itself, which moves in the radial direction to the opposite side of the tightened bolt as the bolt is tightened together with the eccentric load of the retainer plate. Therefore, by providing the spigot 13A on the presser plate 13 and thereby stopping the movement of the presser plate 13 in the radial direction, it is possible to prevent the above-mentioned phenomenon from occurring. Practically speaking, a gap must be provided between the spigot 13A and the casing. The smaller the gap, the better, but it is desirable to make it at least equal to or smaller than the radial gap of the combination angular contact ball bearing.

One way to simply fix the bearing outer ring evenly in the axial direction is to use wave springs 16 as shown in Figure 7. In this case, the vibration system in the thrust direction including the rotor and bearings is mounted on a bearing as shown in Figure 8. A spring system with a spring constant that is very small (loose) even when compared to its own spring constant of 1 is loaded, especially in dry screw compressors that are operated at high speed and with a small gap. This is because complex vibration phenomena tend to occur during transient conditions when operating conditions change.

It is not preferable for the thrust bearing to have such a structure because it may cause fatal phenomena such as contact between the rotor's discharge side end face.

〔Effect of the invention〕

As described above, according to the present invention, factors that lead to a reduction in bearing life, such as unbalanced load, reduction in bearing clearance, and preload, can be eliminated, and the life of a thrust bearing can be extended as calculated.

It is particularly effective when applied to high-speed rotating bodies such as dry screw compressors.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a dry screw compressor, Figure 2 is a cross-sectional view of a conventional thrust bearing, and Figure 3 is A in Figure 2.
4 is a sectional view of the thrust bearing portion of the present invention, FIG. 5 is a view along the B-B arrow in FIG. 4, FIG. 6 is a supplementary explanatory view of FIG. 2, and FIG. is a sectional view of another embodiment, No. 8
The figure is a supplementary explanatory diagram of FIG. 7. 1... Male rotor, 2... Female rotor, 3... Casing, 4... Combined angular contact ball bearing (thrust bearing), 5... Cylindrical roller bearing (suction side) 6... Cylindrical roller Bearing (discharge side), 7... Oil seal, 8... Air seal, 9... Timing gear, 1o... Pinion gear, 11... Oil supply nozzle, 12... Water cooling jacket, 13... Osae plate, 14...bearing oil supply nozzle,
15...Volt, 16...Wave spring. pierce 1 kakui 20 arithmetic 3 figure

Claims (1)

[Claims] A fixing device for a thrust bearing outer ring of a screw compressor using an angular ball bearing as a thrust bearing, characterized in that a presser plate for fixing the outer ring is provided with a spigot structure.