JPS59185886A - Screw compressor - Google Patents

Abstract

PURPOSE:To improve sealing property between a rotor and a casing in a screw compressor by disposing a seat capable of floating up a fine amount on the inner peripheral surface of a rotor casing surrounding a compresssion chamber in the latter half of compression stroke. CONSTITUTION:A seat 74 is provided on the inner peripheral surface of a rotor casing body 10 other than the portion in which a suction chamber 52 is provided, and constituted such that lubricating oil is supplied between the seat and the casing. The lubricating oil supplied to an oil groove 76 provided in the rotor casing 10 pushes the seat 74 against rotors 20, 24 with a proper force so that sealing property between the rotor and the casing is improved. Aslo, leak oil lubricates between the seat and the rotor to effect the sealing action so that the sealing property is further improved.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to improved sealing between a rotor and a rotor casing in a screw compressor.

A conventional screw compressor is a compressor equipped with a male rotor having a helical protrusion and a female rotor having a helical groove that engages with the helical protrusion, and when both rotors are rotated within a rotor casing, both rotors and the rotor Gas is compressed by utilizing the change in volume of the space surrounded by the casing, that is, the compression chamber. Although this compressor has the advantage of a simple structure and can be manufactured at low cost, it has the disadvantage that the seal line is long in relation to the volume of the compression chamber, making it difficult to increase volumetric efficiency.

As a means to eliminate this drawback,
Japanese Patent No. 1511 proposes forming a reflective layer or plating layer of soft metal, or a coating layer of synthetic resin, synthetic rubber, etc. on the inner surface of the rotor casing.

In this way, seizing will not occur even if the rotor and rotor casing come into contact, so the clearance between the rotor and the casing can be made smaller than before and the volumetric efficiency can be increased. Even if it is possible to reduce the gap between the rotor and the rotor casing, there are constraints on processing accuracy, and it is necessary to allow for the difference in thermal expansion between the rotor and the rotor casing, so it is not possible to rotate the rotor in close contact with the rotor casing at all times. It is possible.

Purpose of the Invention In view of the above circumstances, the present invention provides a screw compressor that can be operated with no clearance between the rotor and the rotor casing, at least in a region where the pressure inside the compression chamber is high. It was done with the purpose of doing so.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides that, at least in the portion of the inner peripheral surface of the rotor casing surrounding the compression chamber in the second half of the compression stroke, it is possible to lift up a small amount from the inner peripheral surface, but along the inner peripheral surface. The gist of this is that the seat is arranged in such a way that substantial movement in the opposite direction is impossible. This sheet is made of steel.

Various types of rotor casings can be used, such as those made of metal materials such as brass, those made of organic materials such as hard synthetic resin, and those made of composite materials with a synthetic resin coating layer formed on a metal plate. Since it is not fixed to the inner circumferential surface by adhesive or other means, it must be able to maintain a predetermined shape by its own rigidity, at least when it is sandwiched between the rotor casing and the rotor.

The above-mentioned seat is lifted from the inner circumferential surface of the rotor casing and brought into close contact with the rotor by high-pressure fluid that enters the gap between the inner circumferential surface of the rotor casing and the seat.High-pressure fluid is supplied to the gap between the seat and the rotor casing. It is not necessarily necessary to take special measures to achieve this.

As mentioned above, the sheet is not fixed to the inner peripheral surface of the rotor casing, so the high-pressure gas in the compression chamber can be leaked alone or through the small gap between the edge of the sheet on the discharge port side and the rotor casing. This is because it also wraps around to the back side of the sheet and has the effect of lifting the sheet.

However, it is desirable to take measures to actively supply high-pressure fluid to the gap between the seat and the inner peripheral surface of the rotor casing.
For example, one method is to use the discharge pressure to supply lubricating oil, which is separated from the gas discharged from the compression chamber and stored in an oil reservoir, into the gap between the seat and the inner peripheral surface of the rotor casing. Recommended.

In the screw compressor configured as above the effects of the invention,
At least in the portion defining the compression chamber in the latter half of the compression stroke, compression work is performed in a state where there is no substantial gap between the rotor and the seat. Since leakage from the gap between the rotor and the inner circumferential surface of the rotor casing in the second half of the compression stroke greatly affects the volumetric efficiency of the compressor, the volumetric efficiency of the screw compressor can be effectively increased. It is.

Embodiment FIGS. 1 to 4 are diagrams showing a screw compressor for compressing refrigerant gas as an embodiment of the present invention. In the figure, 10 is a rotor casing body, and a front side plate 12 and a rear side plate 14 are shown. Together with this, they constitute the rotor casing.

As is clear from FIG. 2, the rotor casing body 10 is formed with holes having circular cross sections parallel to each other and partially overlapping each other to form a rotor chamber 16. Inside this rotor chamber 16 is a male rotor 2o provided with a spiral protrusion 18.
and a male rotor 24 having a helical groove 22 are disposed, and both rotors mesh with the helical protrusion 18 and the helical groove 22. As is clear from FIG. 1, the male rotor 20 has both side plates 12 on both end surfaces. The shafts 26 and 28 protrude from both end surfaces of the shafts 26 and 28, which are in contact with or in close proximity to the radial bearings 30 by the side plates 12 and 14, respectively.
It is rotatably supported through. Further, a thrust bearing 32 is provided on the shaft 28 side to receive the thrust load of the male rotor 2o. Similarly, the shafts 34 and 36 of the female rotor 24 are supported by the side plates 12 and 14 via a radial bearing 30 and a thrust bearing 32, but the shaft 34 is lengthened so as to be connected to a drive device. Airtightness between the shaft 34 and the boss portion 38 of the front side plate 12 is maintained by a shaft sealing device 40, while a hole formed in the front side plate 12 for supporting the shaft 26 of the male rotor 20 is 0 ring 4
2 and a retaining ring 46.

With the above configuration, a plurality of compression chambers 50 are formed between the male rotor 2o, the m rotor 24, and the rotor casing, and as both rotors 20 and 24 rotate, the compression chambers 50 After the volume increases once, it decreases.

A suction chamber 52 is formed across the front side plate 12 and a portion of the rotor casing body 10 surrounding the compression chamber 50 that is in the process of expansion, and this suction chamber 52 is formed in the casing body 10 as shown in FIG. It is connected to the evaporator of the cooling system through a suction boat 54.

On the other hand, the shafts 28 and 36 are supported on the rear side plate 14.
8 is provided, and a plate 60 is fixed to the end surface of the rib 58 with bolts (not shown), so that the rib 58
A discharge chamber 62 is formed inside. As is clear from FIG. 2, a discharge port 64 is formed in a portion of the rear side plate 14 corresponding to the position where the volume of the compression chamber 50 is smallest, and this discharge port 64 connects the rear side plate 14 to the rotor axis. The rotor chamber 16 and the discharge chamber 62 are communicated with each other by penetrating in a direction parallel to the center.

A rear housing 66 is further placed over the outside of the rear side plate 4, and an oil separation chamber 68 is formed between the two. The discharge port 64 of the rear side plate 14
is covered by a filter 70 fixed to the rear side plate 14 to separate /II oil from the refrigerant gas discharged into the oil separation chamber 68. The separated lubricating oil is stored in the lower part of the oil separation chamber 68. For convenience, this portion will be referred to as an oil reservoir 72. Oil separation chamber 6
8 is connected to a condenser of the cooling device through a discharge port (not shown) formed in the rear housing 66.

A portion of the inner peripheral surface of the rotor casing body 10 other than the portion where the suction chamber 52 is provided is substantially covered by a sheet 74. The sheet 74 is made of polyfluoroethylene synthetic resin such as polytetrafluoroethylene, and is formed in a shape along the inner peripheral surface of the rotor chamber 16, as shown in FIGS. 2 and 3. This sheet 74 covers the inner peripheral surface of the portion of the rotor chamber 16 that accommodates the male rotor 20 (referred to as the male rotor chamber) and the inner surface of the portion that accommodates the female rotor 24 (referred to as the female convex chamber). Although the male rotor chamber and the male rotor chamber are connected to each other at the boundary on the discharge port 64 side, and are formed integrally with the peripheral surface covering portion, as is clear from FIG. 52 side border)
They are separated so that the inner diameter can be easily changed. Although the seat 74 is not fixed to the rotor casing body 10 by adhesive or other means, it is assembled onto the front side plate 1.
2 and the rear side plays 1 and 14, and are prevented from moving in the axial direction, and are also sandwiched between the rotors 20 and 24 and the rotor casing body 10, and are prevented from moving in the circumferential direction. is positioned and held in a predetermined position.

As shown in FIG. 1, a plurality of oil grooves 76 are formed in a portion of the inner peripheral surface of the rotor casing body 10 that is covered with the sheet 74. These plurality of oil grooves 76 are connected to each other by a communication path 78 formed between the rotor casing body 10 and the seat 74 by cutting out the boundary between the male rotor chamber and the female rotor chamber as shown in FIG. In addition, as shown in FIG. 1, the rotor casing body 10 and the rear side plate 14 are connected to each other through a communication passage 80 formed across the rotor casing body 10 and the rear side plate 14 to communicate with the oil reservoir 72. Therefore, the seat 74 is lifted from the inner circumferential surface of the rotor casing body 10 by the high-pressure lubricating oil supplied from the oil sump 72 and brought into close contact with the rotors 20 and 24, but the oil groove 76 is close to the discharge port 64. Since the width of the portion is wide, the portion of the sheet 74 near the discharge port 64 is applied with a large force to the rotor casing body 1.
It will be lifted from the inner peripheral surface of 0.

In the screw compressor configured as described above, when rotational torque is applied to the shaft 34 from the drive device, the female rotor 24 rotates in the direction shown by the arrow in FIGS. 2 and 3.
Along with this, the male rotor 20 is rotated in the direction of the arrow. As a result, the compression chamber 50 is moved from the apparent upper inlet chamber 52 side to the discharge port 64 side in FIG. 1, and the volume increases on the suction chamber 52 side and decreases on the discharge port 64 side. This allows refrigerant gas to flow from the evaporator of the cooling device to the suction port 54 and the suction chamber 5.
2, into the compression chamber 50, and is compressed and discharged through the discharge port 6.
4 into the discharge chamber 62, and after the lubricating oil is separated in the oil separation chamber 68, it is discharged toward the condenser of the cooling device.

On the other hand, the lubricating oil separated from the refrigerant gas and stored in the oil reservoir 72 is supplied to each oil groove 76 via the communication passages 80 and 78 by the pressure of the refrigerant gas in the oil separation chamber 68, and
Highlight 4. This lifting force is applied to the discharge port 6.
As mentioned above, the side closer to 4 is larger, but
The pressure within the compression chamber 50 is also higher near the discharge port 64, so the force with which the sheet 74 is actually pressed against the rotors 20 and 24 is approximately constant over the entire sheet 74, or is close to the discharge port 64. The sheet 74 exerts a moderate force on the rotors 20 and 24, which effectively prevents leakage of refrigerant gas from the compression chamber 50, but creates unnecessary frictional resistance on the rotors 24 and 24. The size is such that it does not give

Moreover, the lubricating oil supplied to the oil groove 76 flows through the gap between the seat 74 and the inner circumferential surface of the rotor casing body 10 as shown by the arrow in FIG.
The contact portions between the sheets 74 and 0 and 24 are lubricated and the sealing effect is improved. As a result, leakage of refrigerant gas from the compression chamber 50 during the compression stroke is reduced, and the volumetric efficiency of the compressor is improved.

In this case, since the seat 74 is in contact with the rotating rotors 20 and 24, it tends to rotate with both rotors, but the part surrounding the male rotor 20 and the part surrounding the female rotor 24 of the seat 74 are in a relationship that prevents each other from moving in the circumferential direction, so the sheet 74 does not actually move.

FIG. 5 shows another embodiment of the invention. This embodiment differs from the previous embodiment in that the seat 84 is provided with a plurality of oil fillers 86. The oil inlet 86 is formed in a portion close to the discharge port 64 so as to communicate with the oil groove 76, and when the compressor is in operation, the oil inlet 86 is connected to the oil groove 76.
6, the lubricating oil is ejected into the rotor chamber 16, which lubricates the seat 84 and the rotors 20 and 24 and improves sealing performance. In this embodiment, the oil well 86 is formed at a position corresponding to the oil groove 76, but it is also possible to form it at a position away from the oil groove 76. In this case, the diameter of the oil well 86 is can be made relatively large, making it easy to process the oil filler 86. In this embodiment, the oil filler 86 can be easily formed by punching or the like, so it has the advantage that the oil filler is easier to form than the conventional oil filler which is formed in the rotor casing body itself. ing.

FIG. 6 is a diagram showing another embodiment of the present invention, in which the sheet 88 is located in the compression chamber 5 in the latter half of the compression stroke.
It is provided only in the part surrounding 0. In this embodiment, the seat 88 is disposed so as to be fitted into a recess 92 formed in a portion of the inner peripheral surface of the rotor casing body 90 near the discharge port 64 so as to be lower than other portions.
The inner surface of the seat 88 and the recess 9 of the rotor casing body 90
The inner peripheral surface of the portion where 2 is not formed forms a substantially continuous cylindrical surface. In this embodiment, the sealing performance near the discharge port where leakage is most likely to occur is intensively improved, and the volumetric efficiency of the screw compressor can be improved while keeping the frictional resistance that the rotor receives from the seat 88 as small as possible. . Furthermore, sheet 8
It is also possible to omit the oil container 86 shown in FIG.

Still another embodiment of the present invention is shown in FIGS. 7 and 8.

This embodiment is characterized in that the rotor casing body 100 does not have an oil groove 76 as in the previous embodiment, and the seat 102 does not have an oil inlet 86. Since the components are the same as those in the embodiment shown in FIGS. 1 to 4, the same parts are given the same reference numerals to indicate the correspondence therebetween, and a detailed explanation will be omitted.

Also in the screw compressor configured in this manner, the seat 102 is lifted from the inner circumferential surface of the rotor casing body 100, and has the effect of improving sealing performance. That is, from the edge of the seat 102 in contact with the rear side plate 14, that is, the edge close to the discharge port 64, the refrigerant gas in the compression chamber 50 flows around to the back side of the seat 102, either alone or together with lubricating oil, and is transferred to the rotor. It is raised from the inner circumferential surface of the casing body 100 and brought into close contact with the rotors 20 and 24. The pressure of the refrigerant gas and lubricating oil that have entered the gap between the seat 102 and the rotor casing body 1 (l) is absorbed by the rear side plate 14 of the seat 102.
The pressure decreases as it moves away from the side edge, but the pressure in the opposing compression chamber 5° also decreases as it moves away from the discharge chamber 64.
The pressing force against 4 is approximately appropriate over the entire sheet 102, that is, the sealing performance is sufficiently improved;
Moreover, the size is maintained so as not to add unnecessary frictional resistance to the rotors 20 and 24.

In this embodiment, no oil grooves are formed on the inner circumferential surface of the rotor casing body 100, and only a communication passage corresponding to the communication passage 80 in the previous embodiment is provided to transfer lubricating oil from the oil reservoir 72 to the seat 102. It is also possible to supply the lubricating oil to the gap between the rotor casing body 100, and in this case, it becomes possible to more actively lift the sheet 102 and supply sufficient lubricating oil into the rotor chamber 16.

Several embodiments of the present invention have been described above, but the present invention can be carried out in other forms with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit of the present invention. Of course it is possible.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of a screw compressor for compressing refrigerant gas, which is an embodiment of the present invention. 2 and 3 are a sectional view taken along the line 1 and 2 in FIG. 1, respectively. FIG. 4 is an enlarged view of section A in FIG. 31. FIG. 5 is a perspective view of a rotor casing body and a seat in another embodiment of the present invention. FIG. 6 is a perspective view of a rotor casing body and a seat in still another embodiment of the present invention. FIG. 7 is a front cross-sectional view of a screw compressor according to yet another embodiment of the present invention, and FIG. 8 is a cross-sectional view taken along the line -■ in FIG. 10.90, 1.00: Rotor casing body 12: Front side plate 14: Rear side plate 18: Spiral projection 20: Male rotor 22: t! l' spiral groove 24: female rotor 5o: compression chamber 52: suction chamber
62: Discharge chamber 64: Discharge port 66: Rear housing 68 Two oil separation chambers 72: Oil reservoir 74, 84, 88, 102 Niji door 6: Oil groove 7'8, 80: Communication path 86: Oil filler

Claims (3)

[Claims] (1) When a male rotor having a helical protrusion and a cross rotor having a helical groove that engages with the helical protrusion are rotated within a rotor casing, the volume of the compression chamber surrounded by both rotors and the rotor casing changes and gas is In a screw compressor configured to suck and compress The seat is arranged in such a manner that it cannot substantially move along the inner circumferential surface, and the inner surface of the seat cooperates with both rotors to perform a sealing action. screw compressor. (2) An oil groove formed along the inner peripheral surface of the rotor casing to be covered by the sheet and communicated with a lubricating oil supply source that supplies lubricating oil at a pressure higher than the pressure inside the compression chamber. Claim 1 comprising:
Screw compressor as described in section. (3) The screw compressor according to claim 2, wherein the sheet is provided with an oil hole passing through the sheet at right angles.