Refrigerator

Abstract

The purpose of the present invention is to provide a refrigerator in which the capacity of an oil tank can be made smaller than in the prior art while a foaming phenomenon is addressed. The refrigerator is provided with: a refrigeration cycle which includes a condenser, an evaporator, and an electric compressor having a compression mechanism to be driven by a motor and in which a refrigerant circulates; an oil tank in which a lubricating oil is stored; a heater which is set in the oil tank and which heats the lubricating oil; a lubricating oil supply line which is connected to the oil tank and which supplies the lubricating oil from the oil tank into a housing having the motor housed therein; a lubricating oil discharge line which returns the lubricating oil from the housing back to the oil tank; a pressure equalizing pipe which has one end connected to the oil tank and the other end connected to the refrigeration cycle; and a buffer tank which is set to the pressure equalizing pipe, which receives the refrigerant and the lubricating oil flowing out from the oil tank, and in which the lubricating oil is stored.

Description

TECHNICAL FIELD

[0001] The present invention relates to a chiller.

BACKGROUND ART

[0002] A turbo compressor installed in a centrifugal chiller is configured to include a compression mechanism and an acceleration mechanism. In order to stably operate the turbo compressor, it is necessary to properly and continuously supply a lubricant to a bearing for supporting an impeller of the compression mechanism or a gear of the acceleration mechanism. A lubricant system includes an oil tank and an oil pump. The lubricant stored in the oil tank is supplied to the bearing or the gear of the turbo compressor by the oil pump. The lubricant supplied to the bearing or the gear is returned to the oil tank so as to be repeatedly circulated in the lubricant system.

[0003] In the compression mechanism, the refrigerant system and the lubricant system are not completely independent of each other. Accordingly, the refrigerant dissolves in the lubricant. If the refrigerant dissolves in the lubricant, viscosity decreases. Thus, in order to reduce the dissolving amount of the refrigerant in the oil tank, the oil tank is internally maintained at low pressure. Therefore, for example, a pressure equalizing pipe communicating with a low pressure portion (for example, an evaporator or a compressor suction port) of the refrigerant system is connected to the oil tank.

[0004] PTL 1 below discloses a technique as follows. When the centrifugal chiller is started, the pressure inside the oil tank is lowered, and the refrigerant dissolving in the lubricant is gasified to cause foaming. Accordingly, a target opening degree is provided for a suction capacity control unit for controlling capacity of the refrigerant passing through that the turbo compressor when the centrifugal chiller is started. In addition, PTL 2 below discloses a technique as follows. The other end of the pressure equalizing pipe whose one end is connected to the oil tank is connected to an economizer instead of the evaporator so that the internal pressure of the oil tank and the internal pressure of the economizer are equalized.

CITATION LIST

Patent Literature

[0005] [PTL 1] Japanese Unexamined Patent Application Publication No. 2009-186030

[0006] [PTL 2] Japanese Unexamined Patent Application Publication No. 2009-293901

SUMMARY OF INVENTION

Technical Problem

[0007] The internal pressure is lowered in the oil tank communicating with the refrigerant system, when the centrifugal chiller in which the pressure of the refrigerant system is lowered starts to be operated or is in a transition stage. Here, the transition stage means a time at which an operation state is changed, for example, such as a case of lowering an output of the centrifugal chiller. If the internal pressure of the lubricant system is lowered, such as in a case where the internal pressure of the oil tank is lowered, the refrigerant dissolving in the lubricant no longer dissolves beyond a saturated state, and refrigerant gas is generated, thereby causing a foaming phenomenon in which the lubricant forms bubbles.

[0008] Inside the oil tank where the foaming phenomenon occurs, the oil level rises, compared to a normal time during which the foaming phenomenon does not occur. In addition, if the foaming phenomenon occurs, the supply amount of the lubricant which can be supplied to a bearing or a gear is reduced in the lubricant system. In a case of a low pressure refrigerant (for example, R1233zd), a refrigerant gas specific volume is larger than that of a high pressure refrigerant (for example, R134a). Accordingly, a large volume of the gas is generated during the foaming phenomenon. Therefore, in a case of the low pressure refrigerant, when the oil level rises or the supply amount of the lubricant is reduced, there is a greater difference, compared to the normal time.

[0009] The pressure equalizing pipe connected to the oil tank is connected to an upper portion of the oil tank. However, the lubricant having the foaming is caused to flow into the pressure equalizing pipe due to the oil level rising during the foaming, thereby causing a possibility that the lubricant may flow to the evaporator which is a connecting destination of the pressure equalizing pipe. Therefore, in the related art, in order to cope with the oil level rising during the foaming, a height of the oil tank is increased.

[0010] In addition, while a depth of the oil tank is increased, and the oil pump is located on a bottom surface of the oil tank so that the oil pump does not suction the refrigerant gas during the foaming. In this manner, the oil level when the foaming occurs and a position of the oil pump are separated from each other.

[0011] In any case, it is necessary to increase a size of the oil tank in a height direction, and the large capacity of the oil tank has to be set in order to cope with the foaming phenomenon.

[0012] The present invention is made in view of the above-described circumstances, and an object thereof is to provide a chiller which can cope with a foaming phenomenon and can decrease capacity of an oil tank, compared to that in the related art.

Solution to Problem

[0013] In order to solve the above-described problems, a chiller according to the present invention adopts the following means.

[0014] That is, according to the present invention, there is provided a chiller including a refrigerating cycle that includes an electric compressor having a compression mechanism driven by a motor, a condenser, and an evaporator, and in which a refrigerant is circulated, an oil tank that stores a lubricant, a heater that is installed inside the oil tank so as to heat the lubricant, an oil circulation pipe that is connected to the oil tank so as to supply the lubricant from the oil tank into a housing for accommodating the motor and to return the lubricant from the housing to the oil tank, a pressure equalizing pipe, one end of which is connected to the oil tank, separately from the oil circulation pipe, and the other end of which is connected to the refrigerating cycle, and a buffer tank that is installed in the pressure equalizing pipe, and that receives the refrigerant and the lubricant which flow out of the oil tank so as to store the lubricant.

[0015] According to this configuration, the motor for driving the compression mechanism is accommodated in the housing, and the lubricant is supplied from the oil tank to the housing. Accordingly, a bearing for supporting a rotary shaft of the motor can be lubricated with the lubricant. In addition, one end of the pressure equalizing pipe is connected to the oil tank, and the other end of the pressure equalizing pipe is connected to the refrigerating cycle. Therefore, pressure of a portion connected to the refrigerating cycle and internal pressure of the oil tank are substantially equalized. A portion to which the pressure equalizing pipe is connected in the refrigerating cycle is a portion where the pressure is low in the refrigerating cycle, for example, such as an evaporator and a compressor suction port.

[0016] Furthermore, the refrigerant and the lubricant which flow out of the oil tank are supplied to the buffer tank via the pressure equalizing pipe, and are temporarily stored in the buffer tank. In this manner, even if foaming occurs inside the oil tank and the refrigerant and the lubricant flow out of the oil tank, the lubricant is stored in the buffer tank, and does not flow to the refrigerating cycle. Accordingly, only the refrigerant is guided toward the refrigerating cycle.

[0017] In the above-described invention, the chiller may further include a return pipe, one end of which is connected to the buffer tank, and the other end of which is connected to the oil tank, separately from the pressure equalizing pipe, and that returns the lubricant stored in the buffer tank to the oil tank.

[0018] According to this configuration, one end of the return pipe is connected to the buffer tank, and the other end of the return pipe is connected to the oil tank so that the lubricant stored in the buffer tank is returned to the oil tank. In this manner, the lubricant flowing out of the oil tank and accumulated in the buffer tank is returned to the oil tank without flowing into the refrigerant cycle.

[0019] In the above-described invention, a position where the return pipe is connected to the oil tank may be located on a side close to a position where the oil circulation pipe is connected to the oil tank.

[0020] According to this configuration, the lubricant returned from the buffer tank is returned to the vicinity of the position where the oil circulation pipe is connected to the oil tank. Accordingly, even in a case where the foaming occurs inside the oil inside the oil tank 23, the lubricant returned from the buffer tank is mixed with the lubricant which is not affected by the foaming.

[0021] In the above-described invention, the oil tank may be partitioned by a partition plate, and may be divided into a separation region into which the lubricant returned from the housing flows, and a discharge region through which the lubricant is supplied to the housing.

[0022] According to this configuration, the lubricant having the dissolved refrigerant is supplied to the separation region, and the lubricant having the dissolved refrigerant is separated into the lubricant and the refrigerant in the separation region. Then, the separated lubricant is supplied from the separation region to the discharge region, and is supplied into the housing. The separation region and the discharge region are partitioned by the partition plate. Accordingly, in the separation region, the lubricant flowing into the oil tank is efficiently separated using a difference between the lubricant and the refrigerant or an enclosed space. In addition, even if the foaming phenomenon occurs in the separation region, it is possible to prevent the lubricant having the bubbles formed therein from flowing into the discharge region.

[0023] In the above-described invention, a flow forming plate for guiding a flow of the lubricant stored in the oil tank from an upper portion toward a lower portion or from the lower portion toward the upper portion may be installed in the separation region.

[0024] According to this configuration, it is possible to form a flow guided from the upper portion toward the lower portion inside the stored lubricant, or conversely to form a flow guided from the lower portion toward the upper portion.

[0025] In the above-described invention, the partition plate may be installed away from a bottom surface of the oil tank.

[0026] According to this configuration, the lubricant having the dissolved refrigerant flows to a downstream side without staying in a bottom portion inside the separation region.

Advantageous Effects of Invention

[0027] According to the present invention, it is possible to cope with a foaming phenomenon and to decrease capacity of an oil tank, compared to that in the related art.

BRIEF DESCRIPTION OF DRAWINGS

[0028] FIG. 1 is a configuration diagram illustrating a centrifugal chiller according to an embodiment of the present invention.

[0029] FIG. 2 is a longitudinal sectional view illustrating a turbo compressor of the centrifugal chiller according to the embodiment of the present invention.

[0030] FIG. 3 is a perspective view illustrating an oil tank of the centrifugal chiller according to the embodiment of the present invention.

[0031] FIG. 4 is a perspective view illustrating a modification example of the oil tank of the centrifugal chiller according to the embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

[0032] Hereinafter, a centrifugal chiller 1 according to an embodiment of the present invention will be described with reference to the drawings.

[0033] As illustrated in FIG. 1, the centrifugal chiller 1 includes a turbo compressor 2 which compresses a refrigerant, a condenser 3 which cools and condenses the refrigerant, a sub-cooler 4 which re-cools and applies super-cooling to the refrigerant condensed in the condenser 3, a first pressure-reducing valve 5 which reduces pressure of a high pressure refrigerant to be intermediate pressure, an economizer 6 which applies the super-cooling to the refrigerant, a second pressure-reducing valve 7 which reduces the pressure of the refrigerant to be low pressure, and an evaporator 8 which evaporates a low pressure refrigerant.

[0034] The turbo compressor 2, the condenser 3, the sub-cooler 4, the first pressure-reducing valve 5, the economizer 6, the second pressure-reducing valve 7, and the evaporator 8 configure a refrigerating cycle. The refrigerant is circulated in order of the turbo compressor 2, the condenser 3, the sub-cooler 4, the first pressure-reducing valve 5, the economizer 6, the second pressure-reducing valve 7, and the evaporator 8. The refrigerant is supplied from the economizer 6 to the turbo compressor 2 using a bypass without passing through the evaporator 8.

[0035] The turbo compressor 2 includes a housing 30 configured so that a motor housing 31, an accelerator housing 32, and a compressor housing 33 are combined integrally with each other.

[0036] As illustrated in FIG. 2, a motor 9 driven so that variable speed is allowed by an inverter device is incorporated in the motor housing 31. One end 10a of the motor shaft 10 of the motor 9 protrudes from the motor housing 31 to the accelerator housing 32. The motor 9 includes a stator 20 and a rotor 21. The rotor 21 is fixed to the motor shaft 10, and the rotor 21 is rotated inside the stator 20. The motor shaft 10 is supported by the rolling bearing 14 on the side of the accelerator housing 32. The rolling bearing 14 has a plurality of angular ball bearings, for example. The rolling bearing 14 is installed in the motor housing 31 via a bearing box (not illustrated).

[0037] The compressor housing 33 internally accommodates a compression mechanism 15 having a first stage compression stage and a second stage compression stage. The refrigerant suctioned into the first stage compression stage from the outside and compressed by the first stage compression stage is supplied to the second stage compression stage. Then, the refrigerant, suctioned into the second stage compression stage and compressed by the second stage compression stage is discharged outward.

[0038] A rotary shaft 11 is rotatably installed inside the compressor housing 33. One end 11a side of the rotary shaft 11 has a first stage impeller 12 for the first stage compression stage and a second stage impeller 13 for the second stage compression stage. The rotary shaft 11 is supported by a rolling bearing 14 on a side of the accelerator housing 32. For example, the rolling bearing 14 includes a plurality of angular ball bearings. The rolling bearing 14 is installed in the compressor housing 33 via a bearing box (not illustrated).

[0039] The other end 11b side of the rotary shaft 11 supported by the rolling bearing 14 has a small diameter gear 17. The gear 17 meshes with a large diameter gear 18 disposed in one end 10a of the motor shaft 10. These gears 17 and 18 configure an acceleration mechanism 19. The acceleration mechanism 19 is accommodated in the accelerator housing 32.

[0040] In the rolling bearing 14 and the gears 17 and 18, a lubricant is supplied to each component.

[0041] A lubricant system is configured to include a lubricant supply line 22 and a lubricant discharge line 25.

[0042] The lubricant supply line 22 is a pipe for connecting the oil tank 23 and the turbo compressor 2 to each other. The lubricant is supplied from the oil tank 23 to the motor housing 31 of the turbo compressor 2 and the accelerator housing 32 by an oil pump 36 disposed in the lubricant supply line 22. The lubricant passing through the motor 9 and the acceleration mechanism 19 is returned to the oil tank 23 via the lubricant discharge line 25. An oil cooler 24 is installed in the lubricant supply line 22 and the lubricant discharge line 25 according to the present embodiment.

[0043] The motor housing 31 and the accelerator housing 32 have each lubricant inlet connected to the lubricant supply line 22, and the lubricant is supplied from the lubricant supply line 22 to the turbo compressor 2. The refrigerant extracted from the condenser 3 which configures the refrigerating cycle is supplied to the turbo compressor 2. The motor housing 31 and the accelerator housing 32 have each liquid refrigerant inlet connected to a refrigerant supply line 34, and a liquid refrigerant is supplied from the refrigerant supply line 34.

[0044] The lubricant passing through the inside of the motor housing 31 and the inside of the accelerator housing 32 of the turbo compressor 2 is discharged to the oil tank 23. The motor housing 31 and the accelerator housing 32 have each lubricant outlet connected to the lubricant discharge line 25. The refrigerant and the lubricant are discharged from the motor housing 31 and the accelerator housing 32 to the oil tank 23 via the lubricant discharge line 25.

[0045] In the lubricant discharged to the oil tank 23, the refrigerant dissolves, and the lubricant is diluted by the refrigerant. A heater 27 (refer to FIG. 3) for evaporating the refrigerant in order to increase concentration of the diluted lubricant is installed in the oil tank 23. Since the refrigerant is evaporated, kinematic viscosity of the lubricant returns to a state before the lubricant is diluted. Thus, the lubricant can be repeatedly used as the lubricant for lubricating the gears 17 and 18 and the rolling bearing 14.

[0046] As illustrated in FIG. 3, the oil tank 23 is a container capable of accommodating the lubricant, and the lubricant is stored in a lower portion inside the oil tank 23.

[0047] The oil tank 23 can be roughly divided into a separation region 41 and a discharge region 42.

[0048] The oil tank 23 has a lubricant and refrigerant inlet connected to the lubricant discharge line 25. For example, the heater 27 is installed in a lower portion of the separation region 41 of the oil tank 23. The refrigerant and the lubricant inside the oil tank 23 are heated so as to evaporate the refrigerant. In this manner, refrigerant gas generated by evaporation is guided upward of the oil tank 23, and the lubricant having reduced content of the refrigerant after the refrigerant evaporates flows to a downstream side of the oil tank 23.

[0049] A lubricant outlet connected to the lubricant supply line 22 is formed below the oil tank 23. According to the present embodiment, the oil pump 36 is installed in the lubricant outlet. The lubricant is supplied from the oil tank 23 to the turbo compressor 2 via the lubricant supply line 22.

[0050] In addition, a refrigerant gas outlet connected to the pressure equalizing pipe 29 is formed above the oil tank 23, and the refrigerant gas is supplied from the oil tank 23 to the evaporator 8 via the pressure equalizing pipe 29. In this manner, the refrigerant supplied to the turbo compressor 2 from the condenser 3 and the sub-cooler 4 is returned to the refrigerating cycle.

[0051] In addition, one end of the pressure equalizing pipe 29 is connected to the oil tank 23, and the other end of the pressure equalizing pipe 29 is connected to the evaporator 8 of the refrigerating cycle. Accordingly, pressure of the evaporator 8 in a portion connected to the refrigerating cycle and internal pressure of the oil tank 23 are substantially equalized. A connecting destination of the pressure equalizing pipe 29 is not limited to the evaporator 8, and may be a suction port of the turbo compressor 2, for example.

[0052] It is preferable to adjust the lubricant stored inside the oil tank 23 so as to maintain a predetermined temperature range. For example, the temperature of the lubricant is determined, based on the temperature at which adequate lubrication can be achieved in the gears 17 and 18 and the rolling bearing 14 in the turbo compressor 2 lubricated with the lubricant.

[0053] The temperature of the lubricant stored inside the oil tank 23 is adjusted, for example, by means of heating using the heater 27. The heating using the heater 27 is controlled by the temperature measured by a temperature measuring unit 35 installed in a lower portion of the oil tank 23. Based on the measured temperature, turning on and off of the heater 27 may be controlled so as to adjust the heating of the refrigerant or the lubricant. Alternatively, based on the measured temperature, the setting temperature of the heater 27 may be adjusted.

[0054] The oil tank 23 is partitioned by a partition plate 43, and is divided into the separation region 41 and the discharge region 42. The partition plate 43 is a plate-shaped member, and a side end portion is in contact with an inner surface of the oil tank 23. In this manner, the oil tank 23 is divided into two regions by the partition plate 43 serving as a boundary. The lubricant discharge line 25 side from the partition plate 43 is the separation region 41 into which the lubricant returned from the housing 30 flows. In addition, the lubricant supply line 22 side from the partition plate 43 is the discharge region 42 through which the lubricant is supplied to the housing 30.

[0055] The lubricant having the dissolved refrigerant is supplied from the lubricant discharge line 25 to the separation region 41. The lubricant having the dissolved refrigerant has higher specific gravity than that of the refrigerant alone and the lubricant alone. The concentration is high on a bottom surface of the separation region 41. The refrigerant is heated and gasified by the heater 27 located close to the bottom surface of the separation region 41 having the high concentration of the refrigerant, and the lubricant having the dissolved refrigerant is separated into the lubricant and the refrigerant. Inside the oil tank 23, a space for storing the lubricant is limited by the partition plate 43. Accordingly, the lubricant can be efficiently heated by the heater 27.

[0056] The separation region 41 may have a plurality of flow forming plates 44 other than the above-described partition plate 43. The flow forming plates 44 are installed in the separation region 41. In this way, inside the stored lubricant, it is possible to form a flow in which the lubricant is guided from an upper portion to a lower portion, or conversely to form a flow in which the lubricant is guided from the lower portion to the upper portion. In this manner, the lubricant can be efficiently brought into contact with the heater 27, or the separated and gasified refrigerant can be raised upward.

[0057] The heated and gasified refrigerant rises upward of the lubricant stored in the oil tank 23. Even in a case where a foaming phenomenon occurs, the lubricant having bubbles formed therein rises along the partition plate 43 or the flow forming plate 44. Thereafter, the bubbles are in a state of floating on the liquid lubricant. Therefore, according to the present embodiment, unlike a case where the partition plate 43 and the flow forming plate 44 are not provided, the bubbles formed by the refrigerant gas are less likely to flow to the downstream side inside the liquid lubricant. As a result, the bubbles can be prevented from being suctioned into the oil tank 23.

[0058] The lubricant stored inside the oil tank 23 is caused to flow in one direction by the oil pump 36, that is, to flow from the lubricant and refrigerant inlet side to the lubricant outlet side. In this manner, the lubricant whose refrigerant concentration is lowered by separating the refrigerant flows toward the lubricant outlet side. In addition, in a case where the foaming phenomenon occurs, the bubbles floating on the lubricant also flows toward the downstream side along the flow of the lubricant.

[0059] If the oil level is raised by the bubbles due to the foaming phenomenon, the bubbles pass through the inside of the pressure equalizing pipe 29, and the foamy lubricant falls into the buffer tank 28.

[0060] A lower end portion of the partition plate 43 or the flow forming plate 44 may be in contact with the bottom surface of the oil tank 23, or may be located away from the bottom surface. In a case where the lower end portion is in contact with the bottom surface, a flow from the lower portion to the upper portion is formed in the lubricant. In a case where the lower end portion is located away from the bottom surface, the lubricant having the dissolved refrigerant flows to the downstream side without staying in the bottom portion inside the separation region 41. In this case, the lubricant having the dissolved refrigerant flows along the heater 27. Accordingly, the refrigerant can be efficiently gasified.

[0061] In addition, in the example illustrated in FIG. 3, a case of installing one partition plate 43 and two flow forming plates 44 is illustrated. However, the present invention is not limited to this example. For example, as illustrated in FIG. 4, one partition plate 43 and one flow forming plate 44 may be installed.

[0062] The oil pump 36 is installed in the discharge region 42. For example, the oil pump 36 is an immersion pump, and is installed on the bottom surface of the oil tank 23. The oil pump 36 suctions the lubricant in the bottom portion of the oil tank 23, and supplies the lubricant to the outside, that is, to the housing 30. According to the present embodiment, in a case where the foaming phenomenon occurs, the bubble rises in the separation region 41. Therefore, the oil pump 36 installed in the discharge region 42 is less likely to suction the refrigerant gas.

[0063] The heater 27 may be installed in only the separation region 41 on the upstream side, or may also be installed in the discharge region 42 on the downstream side as illustrated in FIG. 3. Since the heater 27 is installed in the discharge region 42, it is possible to increase the amount of the refrigerant separated from the lubricant. However, in a case where the foaming phenomenon may possibly occur due to the heating using the heater 27 in the discharge region 42, it is preferable not to install the heater 27 in the discharge region 42.

[0064] The buffer tank 28 is installed in the pressure equalizing pipe 29. The buffer tank 28 can store the foamy lubricant flowing out of the oil tank 23, and has capacity not to allow the lubricant to flow out to the pressure equalizing pipe 29 on the downstream side. An upper portion of the buffer tank 28 has an inlet portion connected to the pressure equalizing pipe 29 connected with the oil tank 23. In addition, the upper portion of the buffer tank 28 has an outlet portion formed at a portion separate from the inlet portion. The outlet portion is connected to the pressure equalizing pipe 29 connected to the evaporator 8.

[0065] The refrigerant and the lubricant which flow out of the oil tank 23 are supplied to the buffer tank 28 via the pressure equalizing pipe 29. Then, the lubricant flowing out of the oil tank 23 is temporarily stored in the buffer tank 28. In addition, the gasified refrigerant dissolving in the lubricant flows from the buffer tank 28 to the evaporator 8.

[0066] In this manner, even if the foaming occurs inside the oil tank 23 and the foamy refrigerant and lubricant flow out of the oil tank 23, the lubricant is stored in the buffer tank 28, and does not flow to the refrigerating cycle. Only the refrigerant is guided to the refrigerating cycle.

[0067] The return pipe 26 is connected to below the oil tank 23. In the return pipe 26, for example, one end is connected to the bottom surface of the buffer tank 28, and the other end is connected to the oil tank 23. The return pipe 26 is disposed separately from the pressure equalizing pipe 29, and returns the lubricant stored in the buffer tank 28 to the oil tank 23. In this manner, the lubricant flowing out of the oil tank 23 and accumulated in the buffer tank 28 is returned to the oil tank 23 without flowing to the refrigerant cycle.

[0068] A position where the return pipe 26 is connected to the oil tank 23 is located on a side close to a position where the lubricant supply line 22 is connected to the oil tank 23. In this manner, the lubricant returned from the buffer tank 28 is returned to the vicinity of the position where the lubricant supply line 22 is connected to the oil tank 23, for example, to the discharge region 42. Accordingly, the lubricant returned from the buffer tank 28 is mixed with the lubricant which is not affected by the foaming, even in a case where the foaming occurs inside the oil tank 23.

[0069] Next, a supply method and a cooling method of the lubricant in the centrifugal chiller 1 according to the present embodiment will be described.

[0070] The lubricant is stored in the oil tank 23, and is supplied from the oil tank 23 to the turbo compressor 2 by the oil pump 36. The lubricant supplied to the turbo compressor 2 is supplied to the gears 17 and 18 and the rolling bearing 14 inside the motor housing 31 of the turbo compressor 2 and inside the accelerator housing 32.

[0071] While the lubricant supplied to the gears 17 and 18 and the rolling bearing 14 is used in lubricating the gears 17 and 18 and the rolling bearing 14, the temperature of the lubricant rises due to a friction loss.

[0072] The lubricant passing through the motor housing 31 and the accelerator housing 32 of the turbo compressor 2 is cooled after passing through the oil cooler 24. In this manner, the lubricant passing through the gears 17 and 18 and the rolling bearing 14 inside the motor housing 31 and the accelerator housing 32 of the turbo compressor 2 is cooled by the oil cooler 24.

[0073] Thereafter, the lubricant cooled by the oil cooler 24 and the refrigerant dissolving in the lubricant are discharged to the oil tank 23.

[0074] The lubricant and the refrigerant which are discharged to the oil tank 23 flows to the lower portion in the separation region 41, and is heated by the heater 27 installed in the lower portion inside the oil tank 23 so that the refrigerant evaporates. As a result, the kinematic viscosity of the lubricant diluted by the refrigerant is recovered.

[0075] The lubricant having reduced content of the refrigerant after the refrigerant evaporates flows to the downstream side of the oil tank 23. In addition, the refrigerant gas evaporated by the heater 27 is guided upward of the oil tank 23. The refrigerant gas is supplied from the oil tank 23 to the evaporator 8 through the pressure equalizing pipe 29 and the buffer tank 28.

[0076] In a case of the foaming phenomenon where the pressure inside the oil tank 23 is lowered due to the lowered pressure in the refrigerating cycle and the refrigerant forms the bubbles due to the gasified lubricant, the bubbles formed by the refrigerant and the lubricant rise along the partition plate 43 or the flow forming plate 44. Furthermore, the bubbles floating on the liquid lubricant flow toward the downstream side along the flow of the lubricant.

[0077] If the oil level is raised by the bubbles due to the foaming phenomenon, the bubbles pass through the inside of the pressure equalizing pipe 29, and the bubbles formed by the refrigerant and the lubricant fall into the buffer tank 28. As a result, the lubricant is stored in the lower portion inside the buffer tank 28, and the gasified refrigerant flows to the evaporator 8 via the pressure equalizing pipe 29.

[0078] As described above, according to the present embodiment, the refrigerant and the lubricant which flow out of the oil tank 23 are supplied to the buffer tank 28 via the pressure equalizing pipe 29, and the lubricant is temporarily stored in the buffer tank 28. In this manner, even if the foaming occurs inside the oil tank 23 and the refrigerant and the lubricant flow out of the oil tank 23, the lubricant is stored in the buffer tank 28, and does not flow to the refrigerating cycle. Only the refrigerant is guided toward the refrigerating cycle.

[0079] In addition, the lubricant having the dissolved refrigerant is supplied to the separation region 41 of the oil tank 23, and the lubricant having the dissolved refrigerant is separated into the lubricant and the refrigerant in the separation region 41. Then, the separated lubricant is supplied from the separation region 41 to the discharge region 42, and is supplied into the housing 30. The separation region 41 and the discharge region 42 are partitioned by the partition plate 43. Accordingly, in the separation region 41, the lubricant flowing into the oil tank 23 is efficiently separated using a specific gravity difference between the lubricant and the refrigerant or the increased temperature of the lubricant in a narrow space. In addition, the partition plate 43 is installed. Accordingly, even if the foaming phenomenon occurs in the separation region 41, it is possible to prevent the lubricant having the bubbles formed therein from flowing into the discharge region 42.

[0080] According to the above-described configurations, it is possible to reduce the amount of the lubricant flowing out to the refrigerating cycle such as the evaporator 8. The amount of the refrigerant suctioned by the oil pump 36 is reduced. Therefore, it is possible to prevent the amount of the lubricant circulating in the lubricant system from being reduced.

REFERENCE SIGNS LIST

[0081] 1: centrifugal chiller [0082] 2: turbo compressor [0083] 3: condenser [0084] 4: sub-cooler [0085] 5: first pressure-reducing valve [0086] 6: economizer [0087] 7: second pressure-reducing valve [0088] 8: evaporator [0089] 9: motor [0090] 10: motor shaft [0091] 10a: one end [0092] 11: rotary shaft [0093] 11a: one end [0094] 11b: other end [0095] 12: first stage impeller [0096] 13: second stage impeller [0097] 14: rolling bearing [0098] 15: compression mechanism [0099] 17: gear [0100] 18: gear [0101] 19: acceleration mechanism [0102] 20: stator [0103] 21: rotor [0104] 22: lubricant supply line [0105] 23: oil tank [0106] 24: oil cooler [0107] 25: lubricant discharge line [0108] 26: return pipe [0109] 27: heater [0110] 28: buffer tank [0111] 29: pressure equalizing pipe [0112] 30: housing [0113] 31: motor housing [0114] 32: accelerator housing [0115] 33: compressor housing [0116] 34: refrigerant supply line [0117] 35: temperature measuring unit [0118] 36: oil pump [0119] 41: separation region [0120] 42: discharge region [0121] 43: partition plate [0122] 44: flow forming plate

Claims

1. A chiller comprising: a refrigerating cycle that includes an electric compressor having a compression mechanism driven by a motor, a condenser, and an evaporator, and in which a refrigerant is circulated; an oil tank that stores a lubricant; a heater that is installed inside the oil tank so as to heat the lubricant; an oil circulation pipe that is connected to the oil tank so as to supply the lubricant from the oil tank into a housing for accommodating the motor and to return the lubricant from the housing to the oil tank; a pressure equalizing pipe, one end of which is connected to the oil tank, separately from the oil circulation pipe, and the other end of which is connected to the refrigerating cycle; and a buffer tank that is installed in the pressure equalizing pipe, and that receives the refrigerant and the lubricant which flow out of the oil tank so as to store the lubricant.

2. The chiller according to claim 1, further comprising: a return pipe, one end of which is connected to the buffer tank, and the other end of which is connected to the oil tank, separately from the pressure equalizing pipe, and that returns the lubricant stored in the buffer tank to the oil tank.

3. The chiller according to claim 2, wherein a position where the return pipe is connected to the oil tank is in the vicinity of a position where the oil circulation pipe is connected to the oil tank.

4. The chiller according to claim 1, wherein the oil tank is partitioned by a partition plate, and is divided into a separation region into which the lubricant returned from the housing flows, and a discharge region through which the lubricant is supplied to the housing.

5. The chiller according to claim 4, wherein a flow forming plate for guiding a flow of the lubricant stored in the oil tank from an upper portion toward a lower portion or from the lower portion toward the upper portion is installed in the separation region.

6. The chiller according to claim 4, wherein the partition plate is installed away from a bottom surface of the oil tank.

7. The chiller according to claim 2, wherein the oil tank is partitioned by a partition plate, and is divided into a separation region into which the lubricant returned from the housing flows, and a discharge region through which the lubricant is supplied to the housing.

8. The chiller according to claim 7, wherein a flow forming plate for guiding a flow of the lubricant stored in the oil tank from an upper portion toward a lower portion or from the lower portion toward the upper portion is installed in the separation region.

9. The chiller according to claim 7, wherein the partition plate is installed away from a bottom surface of the oil tank.

10. The chiller according to claim 3, wherein the oil tank is partitioned by a partition plate, and is divided into a separation region into which the lubricant returned from the housing flows, and a discharge region through which the lubricant is supplied to the housing.

11. The chiller according to claim 10, wherein a flow forming plate for guiding a flow of the lubricant stored in the oil tank from an upper portion toward a lower portion or from the lower portion toward the upper portion is installed in the separation region.

12. The chiller according to claim 10, wherein the partition plate is installed away from a bottom surface of the oil tank.

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