KR101429363B1 - Oil-cooled two-stage compressor and heat pump - Google Patents

Abstract

The present invention is a oil-type two-stage compressor and a heat pump which can ensure the circulation of oil even when the suction pressure and the discharge pressure change, and does not deteriorate the performance. The oil-type two-stage compressor of the present invention comprises: a first end compressing section for sucking gas from a suction passage and compressing the gas together with oil and discharging the oil into an intermediate pressure space; An oil supply passage for supplying oil to the bearing on the discharge side of the second stage compression section and an oil flowing out from the bearing on the discharge side of the second stage compression section during the compression of the first stage compression section And an oil return path for returning the oil to the closed space.

Description

[0001] The present invention relates to an OIL-COOLED TWO-STAGE COMPRESSOR AND HEAT PUMP,

The present invention relates to a water-cooled two-stage compressor and a heat pump.

In the oil-type compressor, oil is supplied for cooling, lubrication, and sealing of the rotor to the closed space isolated from the suction flow path and the discharge flow path by the rotor, which is a space in the rotor chamber. do. As a result, not only oil is contained in the gas discharged from the compressor but oil also flows out from the shaft portion or the bearing portion. For example, Japanese Utility Model Application Laid-Open No. 6-22587 discloses a method of controlling the oil flow rate of oil flowing out from the shaft bar portion to a predetermined pressure, which is substantially equal to the pressure of the oil, To the inside of the space. Specifically, in the oil-type compressor, the oil flowing out from the shaft rod portion on the discharge side is returned to the closed space.

However, depending on the use of the compressor, the suction pressure and the discharge pressure may fluctuate independently of each other, and it is not possible to specify a portion that becomes a pressure equivalent to the pressure of the oil flowing out from the shaft end portion or the bearing portion on the discharge side. In this case, the oil flowing out from the shaft end portion or the bearing portion on the discharge side is configured to be returned to the suction flow path.

In a heat pump (including a freezer) for circulating a refrigerant by using a compressor, the suction pressure of the compressor depends on the evaporation temperature of the refrigerant in the evaporator, and the discharge pressure of the compressor is set to a temperature of condensation of the refrigerant in the condenser It depends. In general, when the two-stage compressor is used as the heat pump, the oil discharged from the shaft rod portion or the bearing portion of the second stage discharge side is discharged into the intermediate pressure space, that is, the discharge passage of the first stage compressor, And is refluxed.

The pressure (intermediate pressure) in the intermediate pressure space is usually determined by the suction pressure and the compression ratio of the first-stage compressor in a heat pump or the like. Therefore, depending on the conditions of the heat source (or the cooling load) and the heat source of the cooling source (or the heat load), the suction pressure at the first stage may rise and the intermediate pressure may become higher than the discharge pressure at the second stage. Then, in the conventional two-stage compressor, the circulation of the oil through the shaft rod or the bearing of the second-stage discharge side is delayed, and the bearing or the like is damaged.

When the oil flowing out from the shaft rod portion or the bearing portion of the second stage discharge side is returned to the first stage suction flow path, the circulation of oil can be ensured. However, when the difference between the oil pressure and the suction pressure is large, The pressure of the oil is lowered, and the gas dissolved in the oil is released (degassed). The glass of this gas raises the groove pressure and causes the performance of the compressor to deteriorate. Generally, since the refrigerant used in the heat pump is apt to dissolve in oil, the problem of performance deterioration due to deaeration of the refrigerant is likely to become present.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a two-stage oil-type compressor and a heat pump which can ensure the circulation of the oil even when the suction pressure and the discharge pressure are varied.

In order to solve the above problems, the oil-based two-stage compressor according to the present invention comprises: a first stage compression section for sucking gas from a suction passage and compressing the same with oil and discharging the oil into an intermediate pressure space; An oil supply passage for supplying oil to at least one of the shaft structure and the bearing on the discharge side of the second end compressing portion; And an oil returning passage for returning the oil flowing out from at least one of the shaft rod structure on the discharge side of the compression section and the bearing to the closed space which is a space during the compression of the first end compression section.

According to this configuration, the oil is refluxed into the closed space having a lower pressure than the intermediate pressure space even if the axial rod structure on the discharge side of the second stage compression section and the pressure of the oil flowing out from the bearing decrease with the decrease of the discharge pressure. And it is possible to prevent the bearings from being damaged or the like. Further, since the pressure in the closed space is higher than the suction pressure, the pressure difference against the pressure of the oil does not become excessively large, so that the performance deterioration that may occur due to the release of the gas dissolved in the oil when the discharge pressure is high can be suppressed.

In the oil-type two-stage compressor of the present invention, the oil return passage is branched and connected to the intermediate pressure space. The oil return passage includes a low-pressure opening / closing valve capable of shutting off the oil passage to the closed space, Pressure open / close valve capable of shutting off the flow path to the intermediate pressure space, and when the pressure of the oil supply path is higher than the pressure of the oil return path, the low-pressure on-off valve is closed and the high- And a flow control device for opening the low-pressure on-off valve and closing the high-pressure on-off valve when the pressure of the oil supply passage is equal to or lower than the pressure of the oil return passage.

According to this configuration, when the axial rod structure on the discharge side of the second-stage compressing section or the pressure of the oil flowing out of the bearing is high, the oil is refluxed into the intermediate pressure space of higher pressure. Thus, the performance deterioration due to the glass of the gas dissolved in the oil Can be further suppressed. Further, when the pressure of the oil to be discharged is low, circulation of the oil can be ensured by refluxing into the closed space.

Further, the heat pump according to the present invention has the above-described oil-type two-stage compressor.

Further, in view of the conditions expected when the oil-type two-stage compressor of the present invention is applied to a heat pump for producing cold water and hot water using R245fa as a refrigerant, It is preferable that the space is set to 1.1 times.

1 is a configuration diagram of a heat pump according to a first embodiment of the present invention;
2 is a configuration diagram of a heat pump according to a second embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, Fig. 1 shows the structure of a heat pump which is a first embodiment of the present invention. The heat pump device of the present embodiment is a heat pump device of the present invention as well as an oil type two-stage screw compressor 1, an oil separator 2, a condenser 3, an expansion valve 4, And an evaporator 5 interposed therebetween, and encloses the refrigerant (for example, R245fa) to constitute the closed refrigerant circulating flow path 6. [

The oil-type two-stage screw compressor 1 compresses a gas refrigerant, but at this time, the refrigerant is compressed by mixing the oil for cooling, lubrication and sealing. The refrigerant discharged from the oil-type two-stage screw compressor (1) is introduced into the oil separator (2), and the refrigerant and oil are separated. The separated oil in the oil separator 2 is refluxed to the oil-type two-stage screw compressor 1 by the discharge pressure of the oil-type two-stage screw compressor 1.

The oil-removed refrigerant in the oil separator 2 is introduced into the condenser 3. The condenser (3) is a heat exchanger that performs heat exchange between a refrigerant and water, and produces hot water by heating water. In the condenser (3), the refrigerant condenses to become a liquid.

The refrigerant condensed in the condenser 3 is depressurized by the expansion valve 4 and supplied to the evaporator 5. The evaporator (5) is a heat exchanger that performs heat exchange between a refrigerant and water, and cools water to produce cold water. In the evaporator (5), the refrigerant evaporates and becomes a gas. In the evaporator (5), the evaporated refrigerant is supplied again to the oil type two-stage screw compressor (1).

In the oil-type two-stage screw compressor (1), the first stage compressing section (8) and the second stage compressing section (9) are formed in the housing (7).

The first stage compression section 8 includes a pair of male and female screw rotors 11 housed in a rotor chamber 10 formed in a housing 7 and is connected to a suction flow path 12 and discharges the refrigerant into the intermediate pressure space 14 formed in the housing 7 through the discharge passage 13. [ The screw rotor 11 divides the space in the rotor chamber 10 to form a plurality of closed closed spaces 15 and compresses the refrigerant by reducing the volume of the closed space 15 with rotation. At this time, the first-stage compression section (8) sucks the oil together with the refrigerant. This oil seals and lubricates between the housing 7 and the screw rotor, between the screw rotor 11 and between the screw rotor 11 and the inner wall of the rotor chamber 10.

The second stage compression section 9 also includes a pair of male and female screw rotors 17 housed in a rotor chamber 16 formed in the housing 7 in the same manner as the first stage compression section 8, Sucks and compresses the refrigerant from the intermediate pressure space 14 through the suction passage 18 and discharges the refrigerant to the refrigerant circulation passage 6 through the discharge passage 19. [ One of the screw rotor 11 of the first stage compression section 8 and one of the screw rotors 17 of the second stage compression section 9 is integrally connected to the output shaft of the motor 20 .

The shaft of the screw rotors 11 and 17 is supported by the bearings 21, 22, 23, and 24. The intermediate pressure space 14 is integral with the space for accommodating the bearings 22 and 23 as well as the flow path for the refrigerant connecting the first stage compression section 8 and the second stage compression section 9, And is also a flow path for supplying oil for lubrication to the oil chambers 22 and 23. Similarly, bearing spaces 25 and 26 are formed on the suction side of the first stage compression section 8 and on the discharge side of the second stage compression section 9. The bearing spaces 25 and 26 also serve as oil passages for lubricating the bearings 21 and 24.

Oil is supplied from the oil separator 2 through the oil supply passage 27 to the bearing 24 on the discharge side of the second-stage compression section 9 for lubrication. The oil that lubricates the bearing (24) flows out into the bearing space (26). The oil-type two-stage screw compressor 1 is provided with an oil return path (oil return path) for connecting the discharge space-side bearing space 26 of the second stage compression section 9 and the closed space 15 of the first stage compression section 8 28). The pressure of the refrigerant in the closed space 15 at the position where the oil return path 28 is connected to the closed space 15 is about 1.1 times the pressure of the refrigerant in the suction path 12. [

The pressure of the oil flowing out into the bearing space 26 is substantially equal to the supply pressure of the oil from the oil separator 2, that is, the discharge pressure of the oil type two-stage screw compressor 1 (second compression section 9) And becomes a pressure slightly lower than the pressure loss in the bearing 24. The discharge pressure of the oil-based two-stage screw compressor 1 is determined by the condensation temperature in the condenser 3. As a presumed operating condition in the present embodiment, there is a possibility that the discharge pressure of the oil type two-stage screw compressor 1 is lowered to 0.61 MPa. The suction pressure of the oil-based two-stage screw compressor 1 (first-stage compression section 8) is determined by the evaporation temperature in the evaporator 5. In the present embodiment, it is assumed that the evaporation temperature reaches 66 占 폚 at the maximum. In this case, the suction pressure is 0.54 MPa. The pressure in the closed space 15 of the first end compressing section 8 to which the oil return path 28 is connected is equal to the lowest value of the discharge pressure 0.61 MPa and the circulation of the oil through the oil return path 28 Can be secured.

As described above, in this embodiment, even if the condensation temperature in the condenser 3 is low and the evaporation temperature in the evaporator 5 becomes high, the oil is discharged from the bearing space 26 through the oil return path 28 So that the supply of fresh oil to the bearing 24 can be ensured. Since the pressure in the closed space 15 is higher than that in the suction passage 12, the pressure drop of the oil flowing through the oil return passage 28 is minimized. Thus, the amount of refrigerant liberated by the pressure drop of the oil is reduced to suppress the performance deterioration of the oil-type two-stage screw compressor (1).

2 shows the structure of a heat pump according to a second embodiment of the present invention. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. In the heat pump of the present embodiment, the oil return path 28 branches and is also connected to the intermediate pressure space 14. The oil return path 28 includes a low pressure opening and closing valve 29 capable of shutting off the oil flow path to the closed space 15 and a high pressure opening and closing valve 30 capable of shutting off the oil flow path to the intermediate pressure space 14. [ . The oil-type two-stage screw compressor 1 according to the present embodiment is provided with a discharge pressure sensor 31 for detecting the oil pressure Pd supplied from the oil separator 2, And a flow control device 33 for opening and closing the low pressure open / close valve 29 and the high pressure open / close valve 30 in accordance with the detection values of the discharge pressure sensor 31 and the intermediate pressure sensor 32 ).

The flow control device 33 compares the pressure Pd detected by the discharge pressure sensor 31 with the pressure Pm detected by the intermediate pressure sensor 32. When the pressure Pd detected by the discharge pressure sensor 31 is lower than the pressure Pd detected by the intermediate pressure sensor 32, Closing valve 29 is closed and the high-pressure on-off valve 30 is opened while the pressure Pd detected by the discharge pressure sensor 31 is higher than the pressure Pm detected by the intermediate pressure sensor 32 When the detected pressure Pm or lower, the low-pressure on-off valve 29 is opened and the high-pressure on-off valve 30 is closed.

That is, in the present embodiment, when the discharge pressure Pd is high, the oil that has flowed out to the bearing space 26 on the discharge side of the second stage compression section 9 flows into the closed space 15 To the intermediate pressure space 14 having a pressure higher than that of the intermediate pressure space 14. As a result, the amount of refrigerant liberated from the oil decreases with the decrease in the oil pressure, and the performance deterioration when the discharge pressure of the oil-type two-stage screw compressor 1 is high is reduced. In the present embodiment, when the discharge pressure Pd is low, the oil that has flowed out into the bearing space 26 on the discharge side of the second stage compression section 9 is supplied to the first stage compression section 8 to the closed space 15, thereby ensuring circulation of the oil.

In the embodiment described above, the oil flowing out of the bearing 24 is refluxed into the closed space 15 through the oil return path 28. However, the oil supplied from the oil supply path 27 The oil flowing out from the shaft end structure on the discharge side of the second stage compression section 9 may be returned to the closed space 15 through the oil return path 28. [

Claims (4)

A first end compressing section for sucking gas from the suction passage and compressing the gas together with the oil, and discharging the gas into the intermediate pressure space;
A second end compressing section for sucking the gas from the intermediate pressure space and compressing the gas together with the oil,
An oil supply passage for supplying oil to at least one of an axial rod structure on the discharge side of the second stage compression section and a bearing,
And an oil returning passage for returning the oil flowing out from at least one of the shaft rod structure on the discharge side of the second stage compression section and the bearing to a closed space which is a space during the compression of the first stage compression section,
Wherein the oil reflux passage is branched and connected to the intermediate pressure space,
Wherein the oil reflux passage includes a low pressure opening / closing valve capable of shutting off the flow path to the closed space and a high pressure opening / closing valve capable of shutting off the flow path to the intermediate pressure space,
Close valve is closed and the high-pressure on-off valve is opened when the pressure of the oil supply passage is higher than the pressure of the oil return passage, and when the pressure of the oil supply passage is equal to or lower than the pressure of the oil return passage, And a flow control device that opens the low-pressure on-off valve and closes the high-pressure on-off valve. delete The method according to claim 1,
Wherein the closed space is a space in which the pressure is 1.1 times the pressure of the suction passage. A heat pump having the oil-type two-stage compressor according to any one of claims 1 to 3.

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