JP2016079877A - Screw compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sealing performance in a region showing a high pressure difference between a protrusion end surface clearance and a bearing chamber, in particular, in regard to leakage of compressed gas through clearance between a female rotor shaft and a male rotor shaft.SOLUTION: This invention relates to a screw compressor composed of a pair of male and female rotors engaged and rotated to each other, and a casing storing these rotors and having a function capable of supplying liquid to the clearance between the rotor shafts and the casing, the inner surface of the casing storing at least any one of the make and female rotor shafts is provided with an annular groove and there is provided a portion where a groove depth shows the minimum value in a range from a line connecting the center of the rotor shaft with a discharging start position to a line connecting the center of the rotor shaft with the final contact point between the male rotor and the female rotor.SELECTED DRAWING: Figure 1

Description

The present invention relates to a screw compressor formed by a tooth groove and a casing of a male and female rotor meshing with each other.

  FIG. 2 shows a conventional screw compressor. The screw compressor 1 includes a male rotor 2 and a female rotor 3 that rotate while meshing with each other with a twisted lobe, a casing 4 that accommodates them, and a suction-side bearing 5 for rotatably supporting the male and female rotors and a discharge. A side bearing 6 is used. Generally, the male rotor 2 is connected to an external rotational drive source (not shown) via a rotor shaft at the suction side end (left side of the drawing).

  The male rotor 2 that is rotationally driven by the rotational drive source rotationally drives the female rotor 3, and the working space formed by the tooth grooves of both the male and female rotors and the inner wall surface of the casing 4 that surrounds them expands and contracts. Then, a fluid such as air is sucked from the suction port 7, compressed to a predetermined pressure, and then discharged from the discharge port 8.

  FIG. 3 shows an enlarged view of a portion A in FIG. A discharge end face gap 9 exists between the male rotor 2 and the female rotor 3 and the wall surface of the casing 4 facing the end faces thereof. A male rotor shaft gap 12 and a female rotor shaft gap 13 also exist between the rotor shaft 10 of the male rotor 2 and the rotor shaft 11 of the female rotor 3 and the wall surface of the casing 4 containing the rotor shaft 10. Therefore, the compressed gas leaked from the working space and the discharge port 8 into the discharge end face gap 9 leaks into the bearing chamber 14 through the male rotor shaft gap 12 and the female rotor shaft gap 13 due to a pressure difference with the bearing chamber 14. To do. This leakage phenomenon may cause a reduction in compressor efficiency.

For the purpose of preventing leakage of compressed gas through the male and female rotor shaft gaps, for example, an oil supply type screw compressor described in Patent Document 1 is disclosed. In Patent Document 1, a simple gap seal with a constant gap between the screw shaft and the casing is provided between the screw rotor discharge side end face and the discharge side bearing, and a bearing oil supply hole is formed in the casing on the opposite side of the seal to the rotor. doing. The lubricating oil supplied from the bearing oil supply port into the simple gap seal seals the compressed air leaking from the working space via the screw rotor end face.

JP 2001-323887 A

  FIG. 4 shows a B section passing through the discharge port in FIG. The pressure distribution of the compressed gas in the gap 9 between the discharge end faces is not uniform due to the change in the pressure in the working space with the rotation of the male and female rotors and the influence of the discharge port 8, and is particularly high in the vicinity of the discharge port 8. Therefore, it is considered that the amount of compressed gas leakage in the male rotor shaft gap 12 and the female rotor shaft gap 13 increases in the discharge port vicinity region 15.

  In the oil supply type screw compressor described in Patent Document 1, since the gap in the seal is uniform, the pressure distribution peculiar to the rotor shaft gap of the screw compressor is not taken into consideration. There is no effect of effectively preventing leakage in a region with a large amount of leakage.

The object of the present invention is to improve the sealing performance in the vicinity of the discharge port where the pressure difference between the discharge end surface gap and the bearing chamber is large, with respect to the leakage of compressed gas through the male and female rotor shaft gaps. To realize a compressor.

  In order to achieve the above object, the present invention comprises a pair of male and female rotors that rotate in mesh with each other and a casing that houses them, and has a function of supplying liquid between the rotor shaft and the casing. The screw compressor has an annular groove on the inner surface of the casing that accommodates at least one of the male and female rotor shafts, and from the line connecting the rotor shaft center and the discharge start position of the discharge port, the rotor shaft center and the male and female rotors In the range up to the line connecting the final contact points, there is a portion where the groove depth is minimized.

Further, the groove depth is discontinuously enlarged in the rotation direction of the rotor shaft in a portion where the groove depth is minimized.

According to the present invention, since the pressure of the liquid in the groove is the highest in the vicinity of the portion where the groove depth is the smallest, particularly in a region where a large amount of compressed gas leaks from the gap between the discharge end faces to the outside of the compression chamber. The liquid film can be effectively sealed. This makes it possible to increase the efficiency of the screw compressor.

It is a vertical sectional view of a screw compressor in the 1st example of the present invention. It is a vertical sectional view of a general screw compressor. It is an enlarged view of the A section in FIG. It is B sectional drawing in FIG. It is C sectional drawing as described in FIG. 1 in 1st Example of this invention. It is a lubricating oil pressure distribution map inside the male side sealing groove | channel in 1st Example of this invention. It is C sectional drawing as described in FIG. 1 in 2nd Example of this invention. It is a lubricating oil pressure distribution map inside the male side sealing groove in 2nd Example of this invention.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1, 5, and 6. FIG. In addition, a present Example is related with the screw type air compressor which compresses air. Further, since the configuration is the same as the configuration shown in FIGS. 2, 3, and 4, the same reference numerals are given and description thereof is omitted.

  In this embodiment, the difference from FIGS. 2, 3, and 4 is that an annular male sealing groove 16 and female sealing are formed on the inner surface of the casing 4 that forms the male rotor shaft gap 12 and the female rotor shaft gap 13. The groove 17 is provided, and the male side oil supply hole 18 and the female side oil supply hole 19 for supplying lubricating oil thereto are provided.

  FIG. 5 shows a C cross-sectional view in FIG. The groove depth of the male-side shaft sealing groove 16 in the angular range between the discharge start position 20 of the male rotor 2 and the final contact point 21 of both male and female rotors when the discharge of the working space is completed with respect to the axial center of the male rotor 2 There is a position 22 where the distance is minimized. In addition, the female-side shaft sealing groove 16 has an angular range between the discharge start position 23 of the female rotor 3 and the final contact point 21 of the male and female rotors when the discharge of the working space is completed with respect to the axial center of the female rotor 3. There is a position 24 where the groove depth is minimized.

FIG. 6 shows the pressure distribution of the lubricating oil in the male side sealing groove 16 in the present embodiment. Since the groove depth changes in the rotation direction of the male rotor 2 and the male rotor shaft 10 rotates, the pressure in the male-side sealing groove 16 is highest at the position 22 where the groove depth is the smallest due to the wedge effect. . In this embodiment, the position 22 where the groove depth is the smallest is the discharge start position 20 of the male rotor 2 and the final contact point 21 of the male and female rotors when the discharge of the working space is completed with respect to the axial center of the male rotor 2. It is the angle range between them, that is, the discharge port vicinity region 15. Accordingly, the pressure of the lubricating oil in the male-side sealing groove 16 becomes high in the discharge port vicinity region 15 where the pressure at the discharge end face gap 9 is the highest and the compressed air leakage rate at the male rotor shaft gap 12 is the highest. This effect is the same in the female side sealing groove 17. As described above, it is possible to effectively suppress the leakage of compressed air in the male rotor shaft gap 12 and the female rotor shaft gap 13 and realize high efficiency of the compressor.

  Hereinafter, a second embodiment of the present invention will be described with reference to FIG. 1, FIG. 7, and FIG. In addition, a present Example is related with a screw type air compressor similarly to Example 1, and it attaches | subjects and demonstrates the same code | symbol about the same location as Example 1. FIG.

  A C cross-sectional view in FIG. 1 is shown in FIG. This embodiment is different from the first embodiment in that the positions 22 and 24 where the groove depths of the male side sealing groove 16 and the female side sealing groove 17 are the smallest are the respective positive rotations compared to the first embodiment. It is in the direction and the depth of each groove discontinuously expands at that position.

  FIG. 8 shows the pressure distribution of the lubricating oil in the male side sealing groove 16 in the present embodiment. When the pressure downstream of the discharge port 8 is smaller than the compression ratio of the screw compressor 1, the pressure of the compressed air in the working space 25 immediately before the completion of discharge is higher than the pressure of the compressed air at the discharge port 8. Become. Accordingly, there is a concern that the leakage flow rate of the compressed air in the male rotor shaft gap 12 is larger in the vicinity of the working space 25 immediately before the completion of discharge than in the vicinity of the discharge port 15. Therefore, the position 22 where the groove depth of the male side shaft sealing groove 16 is the smallest is provided at a position in the positive rotational direction from the line segment connecting the axis center of the male rotor 2 and the axis center of the female rotor 3. Further, by increasing the groove depth discontinuously at the position 22 where the groove depth of the male side shaft sealing groove 16 is the smallest, the pressure of the lubricating oil in the male side sealing groove 16 is reduced to the smallest. It is possible to enlarge locally at the position 22. These configurations and effects are the same in the female side shaft sealing groove 17.

As described above, when the influence of the pressure in the working space 25 immediately before the completion of discharge is larger than the influence on the downstream side of the discharge port 8 with respect to the leakage amount of the compressed air in the male rotor shaft gap 12 and the female rotor shaft gap 13. Also, by providing the position of the portion where the groove depth of the male side shaft sealing groove 16 and the female side shaft sealing groove 17 is minimum at the position in the positive rotation direction with respect to the line segment connecting the axial centers of the male and female rotors, In the rotor shaft gap 12 and the female rotor shaft gap 13, it is possible to effectively seal a particularly large area where the amount of compressed air leaks, and to increase the efficiency of the compressor.

DESCRIPTION OF SYMBOLS 1 ... Screw compressor 2 ... Male rotor 3 ... Female rotor 4 ... Casing 5 ... Suction side bearing 6 ... Discharge side bearing 7 ... Suction port 8 ... Discharge port 9 ... Clearance at discharge end surface 10 ... Male rotor shaft 11 ... Female rotor shaft 12 ... male rotor shaft gap 13 ... female rotor shaft gap 14 ... bearing chamber 15 ... discharge port vicinity region 16 ... male side sealing groove 17 ... female side sealing groove 18 ... male side oil supply hole 19 ... female side oil supply hole 20 ... male Discharge start position of rotor 2 21. Final contact point of both male and female rotors upon completion of discharge 22 Position where groove depth of male side shaft sealing groove 16 is smallest 23 ... Discharge start position of female rotor 3 24 ... Female side shaft seal Position where groove depth of groove 17 is the smallest 25. Working space immediately before completion of discharge

Claims (2)

In a screw compressor comprising a pair of rotating male and female rotors and a casing for storing them, and having a function of supplying a liquid between the rotor shaft and the casing,
A line that has an annular groove on the inner surface of the casing that houses at least one of the male and female rotor shafts, and that connects the rotor shaft center and the final contact point of the male and female rotors from the line connecting the rotor shaft center and the discharge start position of the discharge port A screw compressor characterized in that there is a portion where the groove depth is minimum in the range up to a minute. 2. The screw compressor according to claim 1, wherein the groove depth discontinuously expands in the rotational direction of the rotor shaft at a portion where the groove depth is minimized.