JP4089037B2 - Oil-cooled two-stage screw compressor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an oil-cooled screw compressor that uses oil for cooling a rotor, and more particularly to a two-stage oil-cooled screw compressor that includes a low-pressure stage and a high-pressure stage.
[0002]
[Prior art]
In a conventional oil-cooled two-stage screw compressor, a low-pressure stage rotor, a high-pressure stage rotor, and a casing are arranged in tandem as described in JP-A-8-10987. Further, as described in JP-A-48-21806, a high-pressure stage rotor and a low-pressure stage rotor are housed in one casing. Furthermore, as described in Japanese Utility Model Laid-Open No. 6-1790, a high-pressure stage rotor and a low-pressure stage rotor are disposed above the input shaft.
[0003]
[Problems to be solved by the invention]
A large oil-cooled screw compressor uses a two-stage compressor that can obtain high efficiency because of high power consumption. However, when a two-stage machine is adopted as the screw compressor, the structure of the machine becomes nearly double that of a single-stage machine, the structure becomes complicated, the size is increased, and space saving is difficult to realize. In addition, a grease lubrication motor used as a prime mover becomes large, and a great deal of labor and time is spent on maintenance work such as replenishment and replacement of grease. In particular, a crane may be used for a large motor, and in a coupling structure machine, operations such as centering of the apparatus increase.
[0004]
In the one described in JP-A-8-10987, a low-pressure stage and a high-pressure stage compressor are coupled in tandem to save space. Furthermore, the low-pressure stage rotor shaft is extended, and the motor rotor is attached to this extended portion. However, the one described in this publication has a long axial length of the compressor, and when the motor and the compressor are installed on a common base, the occupied area of the base increases. If equipment is arranged on the upper part of the compressor, maintenance work becomes difficult, the space above the compressor cannot be used, and the compactness and compactness of the product itself of the screw compressor are impaired. Moreover, since the screw rotor is directly connected to the motor shaft, it is necessary to make all the specifications of the rotor different according to the difference in drive frequency (50 Hz, 60 Hz) and the difference in capacity. It is insufficient in terms of sharing.
[0005]
In the one described in Japanese Patent Laid-Open No. 48-21806, the low-pressure stage rotor and the high-pressure stage rotor are housed in one casing to shorten the axial length of the compressor. However, the one described in this publication needs to connect the drive shaft and the motor by coupling, in which case the axial length is not much different from that described in the above-mentioned JP-A-8-10987, Or more. Furthermore, since the motor is grease-lubricated, as described above, a great amount of time and cost are required for motor maintenance.
[0006]
The one described in Japanese Utility Model Laid-Open No. 6-1790 can prevent leakage of lubricating oil from the outside of the machine while ensuring the performance of the shaft seal portion, but the motor and the compressor stage are juxtaposed. The axial length of the screw compressor is increased due to the presence of the gear device between the compressor stages. Further, the maintenance of the motor has the same problems as in the above known example.
[0007]
The present invention has been made in view of the above problems of the prior art, and an object thereof is to realize a small and compact oil-cooled screw compressor. Another object of the present invention is to provide a two-stage oil-cooled screw compressor equipped with a highly reliable motor. Still another object of the present invention is to provide a two-stage oil-cooled screw compressor that facilitates the common use of rotor series design and parts. Another object of the present invention is to facilitate maintenance in a two-stage oil-cooled screw compressor.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the first feature of the present invention is:
Two pairs of male and female rotors are rotatably housed in one casing, one set being a low-pressure stage compressor, the other set being a high-pressure stage compressor, and the suction port of the low-pressure stage compressor being the casing In the oil-cooled two-stage screw compressor provided at the top of
The low-pressure stage compressor is arranged in the upper part and the high-pressure stage compressor is arranged in the lower part, and is sandwiched between the low-pressure stage compressor and the high-pressure stage compressor, and the discharge side of the low-pressure stage compressor It has an intermediate passage that communicates with the suction side of the high-pressure compressor,
A driven gear is attached to the male rotor of the low-pressure stage compressor and the high-pressure stage compressor ,
A drive shaft configured integrally with the motor shaft and the drive gear shaft provided with a motor rotor extending opposite the respective rotor has a drive gear meshed with the driven gear at one end, two of the said A gear casing that houses the drive gear and the drive gear and is adjacent to the casing; a first bearing that supports the drive shaft and is positioned at a shaft end portion of the drive gear; and that supports the drive shaft and the drive gear; A second bearing located between the motor rotor ,
In the cross section perpendicular to the rotor, the drive shaft center is disposed within a quadrangular range connecting the four points of the low pressure stage male rotor center, the low pressure stage female rotor center, the high pressure stage male rotor center, and the high pressure stage female rotor center,
The motor rotor portion of the drive shaft is overhung supported by the first bearing and the second bearing.
[0010]
And preferably, either holds the first bearing casing, and holds the formic ya casing. Furthermore, it is desirable that the first bearing and the second bearing be oil lubricated.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, some embodiments of the present invention will be described with reference to the drawings. 1 is a longitudinal sectional view of a first embodiment of a two-stage oil-cooled screw compressor according to the present invention, and FIG. 2 is a front view thereof, and FIG. 2 is a top view of the embodiment shown in FIG. It is a figure.
[0013]
In the two-stage oil-cooled screw compressor, the low-pressure stage portion is disposed at the upper part of the casing 1. The low-pressure stage has a low-pressure stage male rotor 2 and a low-pressure stage female rotor 3. The rotors 2 and 3 are rotatably supported by a cylindrical roller bearing 7 on the suction side and an angular ball bearing 13 on the discharge side, and the bearings 7 and 13 are held by the casing 1.
[0014]
The suction gas is sucked into a space formed between the male rotor 2 and the female rotor 3 of the low-pressure stage disposed horizontally from a suction port 6 provided in the upper part of the casing 1. Oil is injected into the sucked gas during the compression process in the low pressure stage. The working gas compressed in the low pressure stage is discharged from the discharge port of the low pressure stage, and then flows into the intermediate stage passage 10 which is a space between the low pressure stage and the high pressure stage of the casing 1. Oil is also injected into the intermediate passage 10 to cool the working gas. The working gas cooled in the intermediate stage passage 10 is sucked into a space formed by the high pressure stage male rotor 4 and the high pressure stage female rotor 5.
[0015]
The high-pressure stage male rotor 4 and the high-pressure stage female rotor 5 included in the high-pressure stage are disposed in the lower part of the casing 1. These rotors 4 and 5 are rotatably supported at the suction side shaft portion by the cylindrical roller bearing 12 and are rotatably supported at the discharge side shaft portion by the angular ball bearing 14. The bearings 12 and 14 are held in the casing 1 similarly to the low-pressure stage. The high-pressure stage rotors 4 and 5 are also horizontally arranged in the same manner as the low-pressure stage rotors 2 and 3.
[0016]
The working gas is further pressurized to a predetermined pressure in a compression working chamber formed by the high-pressure stage male rotor 4 and the high-pressure stage female rotor 5, and then discharged from a discharge port formed in the high-pressure stage D casing 18.
[0017]
A low-pressure stage driven gear 20 and a high-pressure stage driven gear 21 are attached to the low-pressure male rotor 1 and the high-pressure male rotor 4, respectively. Further, a drive gear 19 is attached to the drive shaft 23, and the drive gear 19 is engaged with the low-pressure stage driven gear 20 and the high-pressure stage driven gear 21. It is transmitted from the drive shaft. These gears 19, 20, 21 are accommodated in a gear casing 22.
[0018]
The drive shaft has a tapered roller bearing 25 mounted on one side and a cylindrical roller bearing 8 mounted on the other side across a portion where the drive gear 19 is mounted, and is rotatably supported by both the bearings 8 and 25. ing. The drive shaft 23 has a motor rotor 26 and then a motor cooling fan 28 mounted on the shaft end side of the tapered roller bearing 25 so as to overhang. A motor stator 27 is attached to a motor casing 29 so as to face the motor rotor 26. When the drive shaft is assembled in this embodiment, the outer ring of the cylindrical roller bearing 8 that supports the drive shaft is held in the casing 1, and then the drive shaft 23 to which the inner ring of the bearing 8 is attached is inserted into the outer ring of the bearing 8. According to the present embodiment configured as described above, the rotational speeds of the high pressure stage and the low pressure stage can be freely set by a combination of gears, so that the rotor can be easily shared.
[0019]
An oil seal 24 is attached to a fixed member between the tapered roller bearing 25 and the motor rotor 26. The oil seal 24 prevents the lubricating oil in the gear casing 22 from flowing out from the gear casing 22 side to the motor casing 29 side while being in contact with the driving shaft 23 while the drive shaft 23 is rotating.
[0020]
The bearings 8 and 25 that support the drive shaft 23 are accommodated in the gear casing 22. These bearings 8 and 25 are supplied with clean oil filtered through a filter in the same manner as the bearings 7, 12, 13 and 14 in the compressor, and are forcedly lubricated and cooled. Therefore, compared to conventional motors that require replenishment and replacement of grease, maintainability can be improved, and lubrication and cooling failure due to grease exhaustion or grease deterioration can be prevented, improving motor reliability. Can do.
[0021]
According to the present embodiment, the drive shaft 23 is a shaft in which the motor shaft and the drive gear shaft are integrally formed, so that coupling means for connecting the motor and the gear shaft is not necessary. This eliminates the need for centering work between the motor shaft and the drive gear shaft, and improves maintainability. Combined with the high pressure stage and low pressure stage rotors being housed in the same casing, it is possible to reduce the size of the compressor, in particular, to significantly reduce the axial length.
[0022]
Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a diagram corresponding to FIG. 1 of the first embodiment, and FIG. 4 is a diagram corresponding to FIG. FIG. 5 is a cross-sectional view taken along the line AA in FIG. In these drawings, parts that are the same as those described in the first embodiment are denoted by the same reference numerals. The second embodiment is different from the first embodiment in that the cylindrical roller bearing 8 that supports the drive shaft 23 is held in the gear casing 22.
[0023]
In both the first and second embodiments, as shown in FIG. 5, the low pressure stage male rotor center o, the low pressure stage female rotor center p, the high pressure stage male rotor center q, and the high pressure stage female rotor center. The drive shaft center s is disposed within a rectangular range connecting the four points r. As a result, a space is formed between the four bearings of the male rotor suction side bearing 7, the female rotor suction side bearing 9, the high pressure stage male rotor suction side bearing 12, and the female rotor suction side bearing of the low pressure stage rotor. The cylindrical roller bearing 8 attached to the drive shaft 23 is disposed in this space, and the distance between the five bearings is made as small as possible, thereby minimizing the height dimension of the compressor. It becomes possible to suppress.
[0024]
As shown in the first embodiment, when the cylindrical roller bearing 8 that supports the drive shaft 23 is disposed in the casing 1, the axial dimension of the gear casing 22 can be shortened. However, it is necessary to arrange so that the outer rings of the four bearings 7, 9a, 9, 12 on the suction side of the compressor main body and the outer rings of the bearing 8 do not interfere with each other. Therefore, the distance between the high pressure stage and the low pressure stage is determined from the size of this bearing. In consideration of maintenance and assembly, the drive shaft 23 must be inserted into the outer ring of the bearing 8 held by the casing with the tapered roller bearing 25 and the like assembled to the drive shaft 23. This point is improved in the second embodiment.
[0025]
In FIG. 3, since the cylindrical roller bearing 8 is installed in the gear casing, the axial length of the compressor is slightly longer than in the first embodiment. However, since the axial positions of the four bearings 7, 9, 9a, 12 on the suction side of the compressor and the cylindrical roller bearing 8 are different from each other, the range of the compressor is within a range that does not cause resistance to the outflow of drained oil from the bearings. The bearing 8 can be arranged at a free position with respect to the four bearings on the suction side. In other words, the four bearings and the bearing 8 can be disposed at positions where they can interfere with each other within the cross section perpendicular to the rotor axis. Therefore, the member 30 that holds the outer ring of the cylindrical roller bearing 8 is disposed in the vicinity of the flange surface of the gear casing 22 on the casing 1 side. Further, the support members 30, 31, 32, and 33 are provided so as to hold the member 30 in the gear casing 2 without interference between the low pressure stage driven gear 20 and the high pressure stage driven gear 21.
[0026]
Therefore, in this embodiment, the rotor shaft interval between the high-pressure stage and the low-pressure stage can be made shorter than that in the first embodiment, particularly when the vertical height of the screw compressor has to be lowered. effective. Further, at the time of maintenance or assembling, it is only necessary to assemble the parts related to the drive shaft 23 into the gear casing 22 and then assemble them into the rotor and the gear casing 1 to improve workability.
[0027]
According to each of the above-described embodiments, in the two-stage oil-cooled compressor including the motor, the rotor axial dimension can be significantly shortened compared to the tandem arrangement that has been widely used in the past, and the compressor can be downsized. . In addition, it becomes possible to shorten the distance between the total of five bearings, that is, four bearings provided on the suction side of each rotor and one bearing supporting the drive shaft, which support the low-pressure stage and the high-pressure stage rotor. The height dimension of the compressor can be reduced. Further, no grease is required for lubrication of the motor portion, and the motor bearing is forcibly lubricated and cooled with clean oil in the same manner as the compressor bearing, so that motor lubrication failure can be prevented and reliability can be improved. Since no coupling is required, there is no work such as centering and maintenance is easy. Furthermore, since the rotational speed of the rotor can be set freely only by combining the drive shaft and the gears attached to the end portions of the rotors, series design and sharing of rotor parts becomes easy.
[0028]
【The invention's effect】
As described above, according to the present invention, since the motor has an overhang structure, a small and compact oil-cooled screw compressor can be realized. In addition, since the motor is oil-lubricated, a two-stage oil-cooled screw compressor provided with a highly reliable motor can be provided. Furthermore, since the connection between the drive shaft and each rotor is a gear connection, the rotor series design and parts can be easily shared. Furthermore, since each shaft is inserted into the casing from one direction and a gear is attached to the end thereof, maintenance is facilitated.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a front view of a first embodiment of an oil-cooled screw compressor according to the present invention.
FIG. 2 is a cross-sectional view of the top view of the embodiment shown in FIG.
FIG. 3 is a sectional view showing a front view of a second embodiment of the oil-cooled screw compressor according to the present invention.
4 is a cross-sectional view of the top view of the embodiment shown in FIG. 3;
5 is a cross-sectional view taken along line AA in FIG.
[Explanation of symbols]
1; casing, 2; low-pressure stage male rotor,
3; low-pressure stage female rotor, 4; high-pressure stage male rotor,
5; high-pressure stage female rotor, 6; suction port,
7, 8; cylindrical roller bearings,
10: Intermediate stage passage, 12: Cylindrical roller bearing,
13, 14; angular contact ball bearings,
17; low pressure stage D casing, 18; high pressure stage D casing,
19; drive gear, 20; low-pressure driven gear,
21; high-pressure driven gear, 22; gear casing,
23; drive shaft, 24; oil seal,
25; tapered roller bearing, 26: motor rotor,
27; motor stator, 28; cooling fan,
30; bearing holding member, 31-34; support member.

Claims (4)

Two pairs of male and female rotors are housed in one casing so as to be rotatable. One set is a low-pressure stage compressor, the other is a high-pressure stage compressor, and the suction port of the low-pressure stage compressor is the casing. In the oil-cooled two-stage screw compressor provided at the top of
The low-pressure stage compressor is disposed in the upper part, the high-pressure stage compressor is disposed in the lower part, and is sandwiched between the low-pressure stage compressor and the high-pressure stage compressor. Provided with an intermediate passage communicating with the suction side of the high-pressure compressor,
A driven gear is attached to the male rotor of the low-pressure stage compressor and the high-pressure stage compressor,
A drive shaft having a drive gear meshing with the driven gear on one end side and extending on the opposite side of each rotor and having a motor shaft and a drive gear shaft integrally formed ; and the two driven gears. A gear casing that houses the drive gear and the drive gear and is adjacent to the casing; a first bearing that supports the drive shaft and is located at a shaft end portion of the drive gear; and that supports the drive shaft and the drive gear; A second bearing located between the motor rotor ,
In the cross section perpendicular to the rotor, the drive shaft center is disposed within a quadrangular range connecting the four points of the low pressure stage male rotor center, the low pressure stage female rotor center, the high pressure stage male rotor center, and the high pressure stage female rotor center,
An oil-cooled two-stage screw compressor, wherein a motor rotor portion of the drive shaft is overhang supported by the first bearing and the second bearing . The drive shaft is, before Symbol oil-cooled two-stage screw compressor according to claim 1, wherein the first bearing, characterized in that held in the casing. The drive shaft is, before Symbol oil-cooled two-stage screw compressor according to claim 1, wherein the first bearing, characterized in that held in the gear casing. The oil-cooled two-stage screw compressor according to any one of claims 1 to 3 , wherein the first bearing and the second bearing are oil-lubricated.

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