JPH0827086B2 - Screw compressor for refrigerator - Google Patents

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 into the rotors 1A and 1B together with the gas, and sent to the high pressure side oil separator.
A cycle of circulating the separated oil is disclosed. As a result, the amount of oil is reduced, the size of the oil separator is reduced, and the power consumption is reduced. However, in this technique, the oil after bearing lubrication exchanges heat with the low-pressure side gas to heat the gas, so that the compression function force is reduced.

On the other hand, in the technique disclosed in Japanese Patent Laid-Open No. 275086/1990, as shown in FIG.
By providing the shaft sealing means 12A on A and 10B and guiding all the oil after lubrication to the tooth spaces of the rotors 1A and 1B, the problem of reduction in compression functional force due to heating of the low pressure side gas is attempted to be solved.

Furthermore, Japanese Patent Laid-Open No. 60-1849 shown in FIG.
In the structure according to Japanese Patent Laid-Open No. 84, the main casings 2 and 3 are divided into a low pressure portion 2A and a high pressure portion 8A to reduce the size and improve the oil separation performance.

[0005]

[Problems to be Solved by the Invention] However, JP-A-60-
In the technology of JP-A-222585 and JP-A-2-275086, there is a similar structure and operational effect in the sense that all the calorific value of the bearing is transmitted (heat exchange) to the low pressure side gas or the gas having a pressure close to the low pressure. are doing. JP-A-2-
In Japanese Patent No. 275086, the amount of heat exchanged is slightly reduced, but it cannot be said to be an essential improvement, and there is a problem that a reduction in compression function force is unavoidable.

Further, in the technique disclosed in Japanese Patent Laid-Open No. 60-184984, as is clear from FIG. 6, the low-pressure portion having a low temperature and the high-pressure portion having a high temperature are in contact with each other with one wall separated from each other. Heat exchange is unavoidable. Although cooling of the lubricating oil is preferable for lubrication and reliability of the slide valve actuator, there is a problem that the compressor performance is deteriorated due to the temperature rise of the suction gas. That is, a large amount of lubricating oil is stored in the high-pressure portion and is constantly heated by the discharge gas, and the large amount and large heat capacity of the high temperature oil and the discharge gas unnecessarily heat the suction gas, causing the above problems. Of.

Here, the viscosity of oil is considered. The oil used in the screw compressor dissolves or contains a large amount of refrigerant in the process of its circulation. The oil containing this refrigerant has a low viscosity due to heating, and also has a low viscosity due to an increase in the rate of dissolution of the refrigerant (smaller at higher temperatures). For this reason, the method of raising the temperature of the oil to the discharge temperature together with the gas as in the prior art is preferable in the sense that the viscosity of the oil itself is decreased, but the dissolution rate of the refrigerant is decreased. Therefore,
If effective cooling is possible after heating the oil to the discharge temperature together with the gas as described above, lubricate the oil in the optimum state (viscosity is large at low temperature, viscosity is large due to small refrigerant dissolution rate) and It should be usable for control, etc.

However, in the prior art, no means for forcibly and effectively cooling the oil has been proposed, and because of the large amount of oil in the oil tank, heating is unnecessarily performed. The oil that had been reduced in viscosity (not sufficiently cooled) and had a low viscosity was being supplied to important points.

If the viscosity of the oil becomes excessively low, the formation of an oil film on the sliding portion becomes insufficient, which lowers the reliability of the bearing, causes unstable control of the slide valve due to leakage of an actuator, and This caused defective sealing between the rotor and casing. As a countermeasure against this, in the prior art, oil having a predetermined viscosity even near the discharge temperature was supplied. However, since the viscosity of this oil is unnecessarily high at low temperatures, it is necessary to increase the capacity of the oil preheating heater before starting the compressor, and the oil agitation loss at the time of low temperatures such as startup is large, so it is not suitable. Met.

As another prior art, Japanese Patent Laid-Open No. 55-8
Japanese Patent No. 5863 discloses a technique in which an oil cooling means (oil cooler) is provided in an oil supply passage.
Japanese Patent No. 500 (Japanese Utility Model Publication No. 51-307605) discloses a technique for cooling oil flowing in an oil supply passage by a low pressure gas that separates the wall from the oil supply passage. Also,
Japanese Unexamined Patent Publication (Kokai) No. 60-40794 discloses an entire structure of a compressor and an oil filter. In the microfilm of Japanese Patent Application No. 59-74458 (Japanese Utility Model Application No. 60-187872), an oil is used for an actuator of a slide valve. A technique in which the supply passages are connected is disclosed. However, the actual application Sho 49-1
The means for cooling the oil disclosed in the microfilm of No. 10500 (Japanese Utility Model Publication No. 51-307605) is for injecting the cooled oil from the oil injection port into the gas during compression, It cannot be discussed in the same row as the oil supply passage of the present invention provided for cooling the oil before it is supplied to the bearing. Further, in all of these conventional techniques, only cooling by heat exchange is performed, but it is difficult to lower the temperature of the heated oil to a predetermined temperature only by cooling by heat exchange. The present invention has been proposed in view of the above-mentioned various problems of the prior art, and essentially and effectively prevents the performance deterioration of the compressor due to the temperature rise of the low pressure side gas, and further forcibly cools the oil. The purpose of the present invention is to provide a screw compressor for a refrigerating machine which can improve the reliability of the compressor function by supplying the oil to important points and can use oil having a viscosity lower than that of the conventional one.

[0011]

In a screw compressor for a refrigerator of the present invention, an oil supply passage is provided in a casing accommodating a pair of rotors so that the low-pressure gas and oil are heat-exchanged with a wall therebetween. The oil supply passage has an upstream end communicating with an oil tank formed on a high pressure side sufficiently separated from a space filled with low pressure gas in the compressor, and a downstream end of the oil supply passage has at least a low pressure male part. And bearings of the female rotor, and shaft sealing means for sealing the bearings of the male and female rotors against the low-pressure side gas, and oil for which lubrication of the bearings of the male and female rotors has been completed. And an oil return passage leading to the oil return passage, and 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 injects a refrigerant having a predetermined pressure and temperature. The refrigerant passages communicate with each other.

With respect to the oil supply passage, the phrase "upstream side" means the side of the oil tank that is the oil supply source, and the "downstream side" refers to the side of various members to which the oil is supplied. I mean.

[0013]

Further, it is preferable that the oil supply passage is constituted by a space provided with an oil filter.

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

In addition to this, the members connected to the other end of the oil supply passage and supplied with oil include male and female rotor bearings on the low pressure side and the high pressure side, the actuator of the slide valve, the low pressure side and the high pressure side. The rotor end surface on the side is preferably a tooth groove.

It is preferable that the oil tank is formed integrally with the lower portion 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.

The refrigerant passage and the refrigerant inlet may be formed at only one place, or may be formed at a plurality of places.

It is preferable that a throttle member for adjusting the flow rate is provided in the oil passage.

The present invention can also be applied to a heat pump cycle.

[0022]

According to the present invention having the above-mentioned structure,
Since the oil supply passage provided for heat exchange or the refrigerant passage for injecting the refrigerant having a predetermined pressure and temperature is provided, the oil is sufficiently cooled. Here, since the volume of the oil supply passage is sufficiently smaller than that of the suction passage, the oil does not overheat the suction gas.

The oil whose viscosity is increased by cooling improves the formation of an oil film in the sliding portion, improves the reliability of the bearing, and causes unstable control of the slide valve due to leakage of the actuator and between the rotors and between the rotor and the casing. Prevents a defective seal between them and improves the function and reliability of the compressor.

In relation to this, as compared with the conventional method for reducing the viscosity of oil, that is, to supply an oil having a predetermined viscosity near the discharge temperature, but having an excessively high viscosity at a low temperature. Low viscosity oils can also be used. Further, according to the present invention, a refrigerant passage is provided in the middle of the oil return passage, and the refrigerant having a predetermined temperature and pressure introduced from the inside of the refrigeration system (low temperature)
By injecting into the heated oil, the gas temperature in the rotor tooth groove can be suitably lowered. as a result,
It is possible to prevent the performance of the compressor from being deteriorated due to the increase in the gas temperature in the rotor tooth space. That is, according to the present invention, not only the cooling by heat exchange but also the cooling of the oil is performed by injecting the low temperature refrigerant into the heated oil, so that the cooling is suitably and reliably performed.

[0025]

Embodiments of the present invention will be described below with reference to FIGS.

By the operation of the compressor shown in FIGS. 1 to 3, the pressure in the discharge chamber 8 becomes the discharge pressure, that is, the 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 the filter 15 in the oil supply passage 14.

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 overheating the suction gas. The oil whose viscosity is increased by cooling improves the function and reliability of the compressor.

The cooled oil passes through the passage 19 and a gap between the male rotor shaft 1C and the female rotor shaft 1D, the members (for example, the rotor casing 2 and the discharge casing 8) through which these penetrate, and the shafts 1C and 1D. 20 through the suction side bearings 10A, 10B, discharge side bearings 11A, 11B
Etc. into the bearing. The oil that has passed through the bearing is the shaft sealing means 1
2A, sealed covers 12B, 12C do not flow out to the low pressure side, and gas does not flow in from the high pressure side,
It is injected into the tooth spaces of the male rotor 1A and the female rotor 1B through the passages 21 and 22.

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 inside of a refrigerating system (not shown) through the refrigerant passage to allow the bearing It is injected into the heated oil via. By the injection of this refrigerant, the gas temperature in the rotor tooth space will not unduly rise.

The oil that has entered the rotor tooth groove is pressurized together with the gas while the tooth surfaces of the male rotor and the female rotor lubricate and seal the line contact portion, that is, the seal line between the rotors, and passes through the discharge passage 2B. , Into the oil separator 9. Then, it is separated from the discharge gas by the oil separator 9, and the suction side (low temperature)
Is returned to the oil tank 8A which is formed sufficiently far from the. In the illustrated embodiment, the oil tank 8A is integrally formed under the discharge chamber 8 containing the oil separator 9.

The other portion of the cooled oil that passes through the passage 19 and the clearance 20 is the male rotor 1A and the female rotor 1B.
Is supplied to the end face of. Lubrication and sealing are performed on the end faces, and the seal line between the rotors is lubricated and sealed to enter 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 has a high pressure (discharge pressure), and the slide valve is controlled by the pressure difference with the suction pressure (low pressure). Various well-known control methods and flows can be used, so detailed description and illustration thereof will be omitted in this specification.

The pressure chamber 7C or 7D communicates with a suction pressure portion (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, and is pressurized with the gas while lubricating and sealing the seal line between the rotors, and the discharge passage 2B.
Through the oil separator 9. There, it is separated from the discharged gas and returned to the oil tank 8A.

Although the passage 22 and the refrigerant inlet 17 are provided at one place in the illustrated embodiment, they may be provided at a plurality of places. Also, the coolant inlet may be provided at one or more locations for the plurality of return passages.

Although not shown in the illustrated embodiment, providing a throttle member for adjusting the flow rate in any of the oil passages is extremely useful in optimizing the oil flow rate.

In the illustrated embodiment, the oil is supplied to the rotor end surface and each bearing by a gap 20 provided between the rotor casing 2 and the discharge casing 8 and the rotor shafts 1C and 1D.
However, a gap may be formed between a ring (not shown) fitted in these casings 2 and 8 and the rotor shafts 1C and 1D, and the gap may be passed through.

Instead of using the oil passages as the gaps 20 in the shaft penetrating portions, oil passages (not shown) may be drilled that directly communicate with the end faces of the rotor and the bearings. Of course, it is also possible to combine these modifications.

As described above, in the present invention, various modifications other than the illustrated embodiment can be considered. Further, it should be noted that the illustrated embodiments are for the purpose of illustration 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 in the sliding part, improves the reliability of the bearing, and causes unstable control of the slide valve due to actuator leakage and between the rotor and between the rotor and the casing. Prevents defective sealing and improves the reliability of the compressor function.

In connection with this, it is not necessary to adopt the conventional technique for reducing the viscosity of oil, that is, the method of supplying the oil having a predetermined viscosity even near the discharge temperature and having an excessively high viscosity at a low temperature. Viscous oils can also be used. This makes it possible to reduce the capacity of the oil preheating heater (not shown) before the compressor is started, and it is possible to reduce the oil agitation loss at the time of starting or at other low temperatures.

Furthermore, the capacity of the compressor is not reduced in connection with the fact that the volume of the oil supply passage is sufficiently smaller than that of the suction passage and the suction gas is not excessively heated.

In addition to this, since the oil tank can be arranged sufficiently far from the suction side, the suction gas is not excessively heated.

Further, a refrigerant passage is provided in the middle of the oil return passage, and a refrigerant (low temperature) having a predetermined temperature and pressure introduced from the inside of the refrigeration system is injected into the heated oil so that the rotor groove inside Without unduly raising the gas temperature,
The deterioration of the compressor performance is prevented.

In the present invention, if the holes formed in the meat portion of the casing or the like are used as the oil passages, the manufacturing cost can be reduced, downsizing, simplification, and the reliability of the pipe against vibration can be improved. is there.

[Brief description of drawings]

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 a conventional technique.

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 actuator 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 (5)

[Claims] 1. A casing for accommodating a pair of rotors is provided with an oil supply passage in which low-pressure gas and oil are provided so that heat can be exchanged across a wall, and the upstream end of the oil supply passage is compressed. It communicates with an oil tank formed on the high pressure side that is sufficiently distant from the space filled with the low pressure side gas in the machine, and the downstream end communicates with at least the low pressure side male and female rotor bearings,
A shaft seal means for sealing the bearings of the male and female rotors against the low pressure side gas; and an oil return passage for guiding the lubricated oil of the bearings of the male and female rotors to the rotor tooth space. A refrigerant passage for injecting a refrigerant having a predetermined pressure and temperature is communicated with at least one of the oil return passage on the bearing side of the rotor and the oil return passage on the bearing side of the female rotor. Screw compressor for refrigerator. 2. The screw compressor for a refrigerator according to claim 1, wherein the oil supply passage is formed by a space provided with an oil filter. 3. 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 compressor capacity control slide valve. 4. A member connected to the other end of the oil supply passage and supplied with oil includes male and female rotor bearings on the low pressure side and the high pressure side, an actuator for the slide valve, and a rotor on the low pressure side and the high pressure side. The screw compressor for a refrigerator according to claim 1, wherein the screw compressor is an end face and a tooth groove. 5. The screw compressor for a refrigerator according to claim 1, wherein the oil tank is integrally formed with a lower portion of a discharge chamber containing an oil separator.