JPH04257658A - Screw compressor for refrigerator - Google Patents

Abstract

PURPOSE:To improve the reliability of a compressor and make it possible to use an oil with low viscosity by a method wherein the performance decrease of a compressor due to temperature rise on a low pressure side gas is essentially prevented from happening, and an oil which is forcibly cooled is fed to required locations. CONSTITUTION:An oil feeding passage 14, by which a low pressure side gas and an oil are heat-changeably provided across a wall, is equipped in a casing 2 to store a pair of rotors 1A, 1B. One end of this oil feeding passage 14 is communicated with an oil tank 8A which is formed on a high pressure side where is sufficiently away from a space which is full of the low pressure side gas in the compressor, and the other end is communicated with at least bearings 1C, 1D of the male rotor 1A and female rotor 1B on the low pressure side. Then, a refrigerant passage 17, which injects a refrigerant with a specified pressure and temperature, is provided on the way of at least one of an oil return passage on the bearing IC side of the male rotor 1A, or a return passage on the bearing 1D side of the female rotor 1B.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil-cooled screw compressor for a refrigerator.

0002

2. Description of the Related Art FIG. 4 shows an oil cooling structure of a conventional screw compressor for a refrigerator disclosed in Japanese Patent Laid-Open No. 60-222585. In this structure, all the oil that lubricated the bearings of the rotors 1A and 1B is returned to the low pressure side space 2A, sucked together with gas into the rotors 1A and 1B, and sent to the high pressure side oil separator.
A cycle is disclosed in which the separated oil is circulated. This reduces the amount of oil, makes the oil separator more compact, and reduces power consumption. However, with this technology,
The oil after bearing lubrication exchanges heat with the low-pressure side gas and heats the gas, resulting in a reduction in compression performance.

On the other hand, in the technique disclosed in Japanese Unexamined Patent Publication No. 2-275086, as shown in FIG.
A and 10B are provided with shaft sealing means 12A, and all oil after lubrication is guided to the tooth grooves of rotors 1A and 1B, thereby solving the problem of reduction in compressive function due to heating of low-pressure side gas.

Furthermore, as shown in FIG.
In the structure according to Publication No. 84, the main casings 2 and 3 are divided into a low pressure section 2A and a high pressure section 8A, thereby achieving miniaturization and improving oil separation performance.

[0005]

[Problem that the invention attempts to solve] However, in 1983-
The techniques of JP-A No. 222585 and JP-A-2-275086 have similar structures and effects in the sense that all of the calorific value of the bearing is transferred (heat exchanged) to the low-pressure side gas or gas at a pressure close to low pressure. are doing. JP-A-2-2
Although the amount of heat exchanged is slightly reduced in Japanese Patent No. 75086, it is difficult to say that this is a substantial improvement, and there is a problem in that a reduction in compression performance is unavoidable.

Furthermore, in the technique disclosed in Japanese Patent Application Laid-Open No. 60-184984, as is clear from FIG. Heat exchange is unavoidable. Although cooling the lubricating oil is favorable for lubrication and the reliability of the slide valve actuator, there is a problem in that an increase in the temperature of the suction gas causes a decrease in compressor performance. In other words, a large amount of lubricating oil is stored in the high-pressure section and is constantly heated by the discharged gas, and this large amount of high-temperature oil and discharged gas with a large heat capacity unnecessarily heats the suction gas, causing the above-mentioned problems. It is.

[0007] Here, the viscosity of oil will be considered. The oil used in a screw compressor dissolves or contains a large amount of refrigerant during its circulation process. The viscosity of oil containing this refrigerant decreases when heated, and also due to an increase in the dissolution rate of the refrigerant (the higher the temperature, the lower the viscosity). For this reason, the method of raising the temperature of oil together with gas to the discharge temperature as in the prior art is preferable in the sense that it lowers the viscosity of the oil itself, but also reduces the dissolution rate of the refrigerant. Therefore, after heating the oil together with the gas to the discharge temperature as described above,
If effective cooling is possible, oil in an optimal state (high viscosity due to low temperature, high viscosity due to low refrigerant dissolution rate) should be able to be used for lubrication, actuator control, etc.

However, in the prior art, no means for forcibly and effectively cooling the oil has been proposed, and combined with the fact that the amount of oil in the oil tank is large, the oil is heated unnecessarily. Oil that had been heated (not sufficiently cooled) and had a low viscosity was being supplied to key locations.

[0009] Excessive reduction in the viscosity of the oil will result in insufficient oil film formation on the sliding parts, reducing the reliability of the bearings, unstable control of the slide valve due to actuator leakage, and problems between the rotors. This was causing seal failure between the rotor and casing. As a countermeasure to this problem, in the prior art, oil having a predetermined viscosity even near the discharge temperature has been supplied. However, this oil has an unnecessarily high viscosity at low temperatures, so it is necessary to increase the capacity of the heater for preheating the oil before starting the compressor, and the oil agitation loss at low temperatures such as during startup is large, so it is not suitable. Met.

The present invention has been proposed in view of the various problems of the prior art described above, and essentially and effectively prevents the performance deterioration of the compressor due to the rise in temperature of the low-pressure side gas, and further improves forced cooling. Our objective is to provide a screw compressor for refrigerators that can improve the reliability of the compressor function by supplying oil to important points, and also allows the use of oil with a lower viscosity than before. There is.

[0011]

[Means for Solving the Problems] A screw compressor for a refrigerator according to the present invention has an oil supply passage provided in a casing housing a pair of rotors so that low-pressure side gas and oil can exchange heat across a wall. The oil supply passage has one end communicating with an oil tank formed on the high pressure side sufficiently far from the space filled with gas on the low pressure side in the compressor, and the other end communicating with at least the bearings of the male and female rotors on the low pressure side. a shaft sealing means for sealing the male and female rotor bearings from low-pressure gas; and an oil return passageway for guiding oil that has finished lubricating the male and female rotor bearings to the rotor tooth grooves. , and has.

Further, the screw compressor for a refrigerator of the present invention has one end communicating with an oil tank formed on the high pressure side sufficiently away from a space filled with gas on the low pressure side in the compressor, and the other end communicating with at least the low pressure gas. an oil passage communicating with the bearings of the male and female rotors on the side; a shaft sealing means for sealing the bearings of the male and female rotors against the low-pressure gas; and an oil passage that communicates with the bearings of the male and female rotors; A refrigerant having a predetermined pressure and temperature is injected into an intermediate portion of at least one of the oil return passage leading to the rotor tooth groove and the oil return passage on the bearing side of the male rotor or the oil return passage on the bearing side of the female rotor. and a refrigerant passage.

In carrying out the present invention, an oil supply passage is provided in the casing housing the pair of rotors, in which the low-pressure side gas and oil are separated by a wall so that heat can be exchanged, and one end of the oil supply passage is provided. It communicates with an oil tank formed on the high pressure side sufficiently far from the space filled with gas on the low pressure side in the compressor, and the other end communicates with at least the bearings of the male and female rotors on the low pressure side, and the bearing side of the male rotor. It is preferable that a refrigerant passage into which a refrigerant having a predetermined pressure and temperature is injected is provided in the middle of at least one of the oil return passage on the bearing side of the female rotor and the oil return passage on the bearing side of the female rotor.

[0014] Furthermore, it is preferable that the oil supply passage is constituted by a space provided with an oil filter.

Furthermore, it is preferable that the other end of the oil supply passage is connected to an actuator of a slide valve for controlling compressor capacity.

In addition, the members connected to the other end of the oil supply passage and supplied with oil include the bearings of the male and female rotors on the low-pressure side and the high-pressure side, the actuators of the slide valves, and the low-pressure side and high-pressure side. Preferably, it is a tooth groove on the side rotor end face.

[0017] Preferably, the oil tank is formed integrally with the lower part of the discharge chamber containing the oil separator.

Further, as the bearing, a rolling bearing, a sliding bearing, or the like can be used, and there is no particular limitation thereto.

[0019] The refrigerant passage and the refrigerant inlet may be formed at only one location, or may be formed at a plurality of locations.

[0020] It is preferable that the oil passage is provided with a throttle member for adjusting the flow rate.

Note that the present invention can also be applied to a heat pump cycle.

[0022]

[Operation] According to the present invention having the configuration as described above,
The oil is sufficiently cooled because it has an oil supply passage provided for heat exchange or a refrigerant passage into which refrigerant having a predetermined pressure and temperature is injected. Here, since the volume of the oil supply passage is sufficiently smaller than that of the suction passage, the oil does not excessively heat the suction gas.

The oil whose viscosity has increased due to cooling improves the formation of an oil film on the sliding parts, improves the reliability of the bearing, and prevents unstable control of the slide valve due to leakage from the actuator and problems between the rotors and between the rotor and the casing. This improves the functionality and reliability of the compressor by preventing seal failures between the compressors.

[0024] In relation to this, compared to the method conventionally used as a countermeasure against low oil viscosity, that is, supplying oil that has a predetermined viscosity even near the discharge temperature but has an excessively high viscosity at low temperatures. , low viscosity oils can also be used.

[0025]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3.

By operating the compressor shown in FIGS. 1 to 3, the pressure within the discharge chamber 8 becomes a discharge pressure, that is, a high pressure, and the oil stored in the oil tank 8A is sent to the oil supply passage 14 via the passage 18. The oil heated to the discharge temperature (high temperature) is filtered by a filter 15 in the oil supply passage 14 .

Here, since the volume of the oil supply passage 14 is sufficiently smaller than that of the suction passage 2A, the oil is sufficiently cooled by heat exchange without excessively heating the suction gas. The oil, whose viscosity has increased due to cooling, improves the performance and reliability of the compressor.

The cooled oil passes through the passage 19 and passes through the male rotor shaft 1C, the female rotor shaft 1D, and the member (
For example, a part of it flows into bearings such as the suction side bearings 10A and 10B and the discharge side bearings 11A and 11B via the gaps 20 between the rotor casing 2 and the discharge casing 8) and the shafts 1C and 1D. The oil that has passed through the bearing is transferred to the shaft sealing means 12.
A. Gas is injected into the tooth spaces of the male rotor 1A and female rotor 1B through the passages 21 and 22 without flowing out to the low pressure side or flowing in from the high pressure side due to the sealing covers 12B and 12C.

A refrigerant passage 17 is provided in the middle of the passages 21 and 22, and a refrigerant (low temperature) having a predetermined temperature and pressure is introduced from the refrigeration system (not shown) through the refrigerant passage to cool the bearing. It is injected into the heated oil via the By injecting this coolant, the gas temperature within the rotor tooth space does not rise unduly.

The oil that has entered the rotor tooth groove is pressurized together with the gas while lubricating and sealing the line contact area between the tooth surfaces of the male and female rotors, that is, the seal line between the rotors, and is discharged via the discharge passage 2B. , flows into the oil separator 9. Then, it is separated from the discharge gas by the oil separator 9, and the suction side (low temperature)
The oil is returned to the oil tank 8A formed sufficiently far from the oil tank 8A. In the illustrated embodiment, the oil tank 8A is formed integrally with the lower part of the discharge chamber 8 which houses the oil separator 9.

The other part of the cooled oil that passes through the passage 19 and passes through the gap 20 is transferred to the male rotor 1A and the female rotor 1B.
is supplied to the end face of the Then, it performs a lubrication and sealing action on the end face, lubricates and seals the seal wire between the rotors, and enters the rotor tooth groove together with the gas. Further, the pressure is increased in the tooth space, flows into the oil separator 9 via the discharge passage 2B, is separated from the discharge gas by the oil separator 9, and returns to the oil tank 8A.

The oil purified and cooled in the oil supply passage 14 is supplied to the pressure chamber 7C or 7D in the actuator 7A of the slide valve 13 via the passage 23.

The oil supplied to the pressure chamber is at high pressure (discharge pressure), and the slide valve is controlled by the differential pressure between the oil and the suction pressure (low pressure). Since various known methods can be used for this control method and flow, detailed description and illustration thereof will be omitted in this specification.

The pressure chamber 7C or 7D communicates with the suction pressure section (low pressure) of the rotor casing 2 via a valve (not shown). Then, the oil released to a low pressure by the valve enters the rotor tooth groove together with the suction gas, lubricates and seals the seal line between the rotors, and increases the pressure together with the gas, and the oil goes into the rotor tooth groove together with the suction gas.
The oil flows into the oil separator 9 via. There, it is separated from the discharged gas and returned to the oil tank 8A.

In the illustrated embodiment, the passage 22 and the refrigerant inlet 17 are provided at one location, but they may be provided at a plurality of locations. Furthermore, the refrigerant inlet may be provided at one or more locations for the plurality of return passages.

Although not shown in the illustrated embodiment, it is extremely useful to provide a throttle member for adjusting the flow rate in any of the oil passages in order to optimize the oil flow rate.

In the illustrated embodiment, oil is supplied to the rotor end face and each bearing through gaps 20 provided between the rotor casing 2 and discharge casing 8 and the rotor shafts 1C and 1D.
However, gaps may be formed between the rings (not shown) fitted into these casings 2 and 8 and the rotor shafts 1C and 1D, and the air may be passed through the gaps.

Furthermore, instead of using the gap 20 in the shaft penetrating portion as an oil passage, an oil passage (not shown) may be bored that directly communicates with each end face of the rotor and each bearing. Of course, it is also possible to combine these modifications.

[0039] In this manner, various modifications of the present invention are possible in addition to the embodiments shown in the drawings. It should be noted that the illustrated embodiments are for illustrative purposes only and do not limit the technical scope of the present invention.

[0040]

As described above, in the present invention, the volume of the oil supply passage is sufficiently smaller than that of the suction passage, and the oil is sufficiently cooled without excessively heating the suction gas. The oil, whose viscosity has increased due to cooling, improves the formation of an oil film on the sliding parts, improving the reliability of the bearing, and preventing unstable control of the slide valve due to actuator leakage and between the rotors and between the rotor and the casing. This prevents seal failures and improves the reliability of compressor functions.

In connection with this, it is no longer necessary to take measures to reduce the viscosity of oil in the prior art, that is, to supply oil that has a predetermined viscosity even near the discharge temperature and has an excessively high viscosity at low temperatures. Viscosity oil can also be used. This makes it possible to reduce the capacity of the oil preheating heater (not shown) before starting the compressor, thereby reducing oil agitation loss at other low temperature times such as during startup.

Furthermore, since the volume of the oil supply passage is sufficiently smaller than that of the suction passage and the suction gas is not heated excessively, the capacity of the compressor does not decrease.

In addition, since the oil tank can be placed sufficiently far from the suction side, the suction gas will not be heated excessively.

[0044] Furthermore, a refrigerant passage is provided in the middle of the oil return passage, and a refrigerant (low temperature) with a predetermined temperature and pressure led from inside the refrigeration system is injected into the heated oil, thereby cooling the rotor tooth space. This prevents the gas temperature from rising unduly and prevents a decrease in compressor performance.

[0045] In the present invention, if the holes drilled in the flesh of the casing etc. are used as oil passages, effects such as manufacturing cost reduction, miniaturization, simplification, and improved reliability of piping against vibrations can be obtained. be.

[Brief explanation of the drawing]

FIG. 1 is a horizontal sectional view of a screw compressor for a refrigerator according to the present invention.

FIG. 2 is a vertical sectional view of a screw compressor for a refrigerator according to the present invention.

FIG. 3 is a schematic diagram showing the flow of oil.

FIG. 4 is a partial cross-sectional view of the prior art.

FIG. 5 is a partial cross-sectional view of another conventional technique.

FIG. 6 is a partial cross-sectional view of yet another prior art.

[Explanation of symbols]

1A, 1B... Rotor 1C, 1D... Rotor shaft 2... Rotor casing 2A... Suction passage 2B... Discharge passage 2C... Casing wall 6A... Suction port 7A... Slide Valve actuators 7C, 7D...Pressure chamber 8...Discharge chamber 8A...Oil tank 8B...Discharge port 9...Oil separator 10A, 10B, 11A, 11B...Bearing 12A...
- Shaft sealing means 12B, 12C...Sealing cover 13...Slide valve 14...Oil supply passage 15...Oil filter 17...Refrigerant inlet 18, 19, 21, 22, 23... Passage 20... gap

Claims (6)

[Claims] Claim 1: An oil supply passage is provided in a casing that accommodates a pair of rotors, in which low-pressure side gas and oil are separated by a wall so that heat can be exchanged; It communicates with an oil tank formed on the high-pressure side sufficiently far from the side gas-filled space, and the other end communicates with at least the bearings of the male and female rotors on the low-pressure side. A screw compressor for a refrigerator, characterized in that it has a shaft sealing means for sealing against side gas, and an oil return passage that guides oil that has finished lubricating the bearings of the male and female rotors to the rotor tooth grooves. . Claim 2: One end thereof communicates with an oil tank formed on the high pressure side sufficiently distant from a space filled with gas on the low pressure side within the compressor, and the other end communicates with at least the bearings of the male and female rotors on the low pressure side. an oil passage, a shaft sealing means for sealing the bearings of the male and female rotors against low-pressure gas, and an oil return passage that guides oil that has finished lubricating the bearings of the male and female rotors to the rotor tooth grooves; A refrigerant passage for injecting a refrigerant having a predetermined pressure and temperature into a midway portion of at least one of the oil return passage on the bearing side of the male rotor and the oil return passage on the bearing side of the female rotor. A screw compressor for refrigerators. 3. The screw compressor for a refrigerator according to claim 1, wherein the oil supply passage is constituted by a space provided with an oil filter. 4. The screw compressor for a refrigerator according to claim 1, wherein the other end of the oil supply passage is connected to an actuator of a slide valve for controlling compressor capacity. 5. The members connected to the other end of the oil supply passage to which oil is supplied include bearings for male and female rotors on the low-pressure side and high-pressure side, actuators for the slide valve, and rotors on the low-pressure side and high-pressure side. The screw compressor for a refrigerator according to any one of claims 1 to 4, wherein the screw compressor has an end face and a tooth groove. 6. The screw compressor for a refrigerator according to claim 1, wherein the oil tank is integrally formed with a lower part of a discharge chamber containing an oil separator.