JP5975742B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to a refrigeration apparatus that includes a plurality of outdoor units and corrects the unevenness of refrigerating machine oil between the outdoor units.

  2. Description of the Related Art Conventionally, there is a refrigeration apparatus that includes a multi-outdoor unit that uses a combination of a plurality of outdoor units (also referred to as outdoor units), and that corrects the unevenness of refrigerating machine oil between the outdoor units. In such a refrigeration apparatus, for example, a plurality of outdoor units including at least a compressor, a condenser, and an accumulator are connected in parallel to an indoor unit (also referred to as an indoor / outdoor unit) including a decompression unit and an evaporator. The refrigeration cycle is formed, and the oil return pipe that returns the refrigerating machine oil stored in the accumulator to the compressor, the oil equalizing pipe that connects the accumulators, and the compressor operation and the oil equalizing pipe are provided. And a control device that controls opening and closing of the electromagnetic valve (see, for example, Patent Document 1).

  Patent Document 1 describes an oil equalizing operation when three outdoor units are combined. For example, when the normal operation time is 1 hour and the oil equalizing operation time is 3 minutes, No. 1 outdoor unit 1a and No. 1 2 outdoor unit 1b has a frequency of 90 Hz, No. 2; The outdoor unit 1c of No. 3 performs at a frequency of 45 Hz. In the oil leveling operation after 2 hours, no. 1 outdoor unit 1a and No. 1 No. 3 outdoor unit 1c has a frequency of 90 Hz, No.3. The second outdoor unit 1b is set to a frequency of 45 Hz. Furthermore, in the oil leveling operation after 3 hours, No. 2 outdoor unit 1b and No. 2 outdoor unit 1b. No. 3 outdoor unit 1c has a frequency of 90 Hz, No.3. The 1 outdoor unit 1a performs at a frequency of 45 Hz. Then, after 4 hours, the operation returns to the beginning, and the oil leveling operation is performed at the same frequency as in the first hour.

  That is, in Patent Document 1, a control device operates a specific compressor at a lower frequency than other compressors while opening all oil equalizing solenoid valves, and performs a low frequency operation for a predetermined time. The oil leveling operation is performed by performing an operation control that causes the compressor to operate at a low frequency at least once. By doing so, in Patent Document 1, the oil amount of the compressor is adjusted to an appropriate oil amount while always ensuring the minimum oil amount in the accumulator.

WO2010 / 113395 (pages 8 to 11)

  The technique described in Patent Document 1 is a configuration in which the operation integration time of the compressor always enters the oil leveling operation (control) in which the amount of oil in the gas-liquid separator that also serves as an oil tank is adjusted every hour. . In particular, refrigeration equipment used in supermarket showcases, convenience stores, refrigerators, freezers, etc., usually performs product temperature management for 24 hours 365 days. In addition, in terms of product temperature management, oil equalization control in which at least one compressor is operated at a low frequency in a refrigeration apparatus including a plurality of outdoor units leads to an increase in the internal temperature. . Therefore, in the technique described in Patent Document 1, the refrigeration capacity is insufficient when the oil equalization control is started, and the internal temperature may become unstable.

  The present invention has been made to solve the above-described problems, and performs oil leveling control that adjusts the oil amount of each outdoor unit only when necessary, while ensuring the quality of the refrigeration apparatus. It aims at providing the freezing apparatus which suppresses the raise of internal temperature as much as possible.

Refrigerating apparatus according to the present invention, at least a compressor, a condenser, includes a accumulator, and connected plurality of outdoor units in parallel, and an indoor unit having at least vacuum means and the evaporator, the connecting piping A refrigeration apparatus for forming a refrigeration cycle, wherein a refrigeration oil stored in the accumulator is returned to the compressor, an oil return pipe that connects between the accumulators, and each compressor Temperature detecting means for detecting the shell temperature of the lower part, operation of the compressor and opening / closing of an electromagnetic valve provided in the oil equalizing pipe based on the shell temperature difference of the lower part of each compressor detected by the temperature detecting means A control device for controlling the temperature of the compressor, and the control device detects a difference in shell temperature at the bottom of each compressor detected by the temperature detection means equal to or greater than a threshold that can be changed according to the season. Each Determines that the deviation has occurred in the refrigerating machine oil cumulants in aerator is for the solenoid valve open.

  The refrigeration apparatus according to the present invention controls the operation of the compressor and the opening and closing of the solenoid valve provided in the oil equalizing pipe based on the temperature difference of the oil in each compressor. Therefore, according to the refrigeration apparatus according to the present invention, the oil leveling control for adjusting the oil amount of each outdoor unit can be executed only when necessary, the in-chamber temperature is prevented from becoming unstable, and the reliability is improved. Improvements can be made.

It is a circuit block diagram which shows roughly an example of the refrigerant circuit structure of the refrigeration apparatus which concerns on embodiment of this invention. It is a refrigerant circuit figure at the time of connecting three outdoor units in parallel in the refrigeration apparatus which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in the following drawings including FIG. 1, the relationship of the size of each component may be different from the actual one. Further, in the following drawings including FIG. 1, the same reference numerals denote the same or equivalent parts, and this is common throughout the entire specification. Furthermore, the forms of the constituent elements shown in the entire specification are merely examples, and are not limited to these descriptions.

  FIG. 1 is a circuit configuration diagram schematically illustrating an example of a refrigerant circuit configuration of a refrigeration apparatus 100 according to an embodiment of the present invention. Based on FIG. 1, the structure and operation | movement of the freezing apparatus 100 which concerns on embodiment of this invention are demonstrated. The refrigeration apparatus 100 is used for, for example, a supermarket showcase, a convenience store, a refrigerator, a freezer, and the like. The refrigeration apparatus 100 corrects the deviation of the refrigeration oil between the outdoor units so as to improve the reliability.

  As shown in FIG. 1, the refrigeration apparatus 100 includes a plurality (two in FIG. 1) of outdoor units 1a and 1b. The outdoor units 1a and 1b are connected in parallel to each other through a liquid pipe 23 and a gas pipe 24 to an indoor unit 20 having an expansion valve 21 and an evaporator 22 as decompression means. In addition, although the case where there are two outdoor units is shown as an example in FIG. 1, three or more outdoor units may be used. In addition, FIG. 1 shows an example in which there is one indoor unit, but usually a plurality of indoor units are connected. Furthermore, in the following description, the outdoor unit may be referred to as an outdoor unit, and the indoor unit may be referred to as an indoor unit.

  The outdoor units 1a and 1b include compressors 2a and 2b, oil separators 3a and 3b, condensers 4a and 4b, accumulators 5a and 5b, and oil regulators 6a and 6b, respectively. In the refrigeration apparatus 100, the condensers 4a and 4b are connected to the liquid piping 23 that communicates with the expansion valve 21, and the accumulators 5a and 5b are connected to the gas piping 24 that communicates with the evaporator 22 via the distributor 25a. By connecting the component devices in this way by piping, a refrigeration cycle is formed, and refrigerant and refrigeration oil contained in the refrigerant circulate in the refrigeration cycle.

  The compressors 2a and 2b compress the refrigerant into a high-temperature and high-pressure refrigerant. The oil separators 3a and 3b are provided on the discharge side of the compressors 2a and 2b, and separate the refrigerating machine oil discharged together with the refrigerant from the compressors 2a and 2b from the refrigerant. The condensers 4a and 4b perform heat exchange between the refrigerant discharged from the compressors 2a and 2b and air supplied from a blower (not shown), for example. The accumulators 5a and 5b are installed on the suction side of the compressors 2a and 2b, and are for storing surplus refrigerant among the refrigerant circulating in the refrigeration cycle. The oil regulators 6a and 6b are for controlling the amount of liquid returned to the compressors 2a and 2b and maintaining the amount of refrigeration oil in the compressors 2a and 2b at a specified amount.

  The expansion valve 21 decompresses and expands the refrigerant circulating in the refrigeration cycle, and may be configured with a valve whose opening degree can be variably controlled, such as an electronic expansion valve. The evaporator 22 performs heat exchange between the refrigerant decompressed by the expansion valve 21 and air supplied from a blower (not shown), for example.

  The distributor 25a distributes the refrigerant and the refrigerating machine oil flowing through the gas pipe 24 to the accumulators 5a and 5b.

  The accumulators 5a and 5b are connected to each other by an oil equalizing pipe 10 in order to correct a deviation in the amount of oil stored in each accumulator. The oil equalizing pipe 10 is provided with an electromagnetic valve 12a for opening and closing the oil flow. Here, the front end portions 10a and 10b of the oil leveling pipe 10 are inserted through the bottoms of the accumulators 5a and 5b, and the end inlet of the oil leveling pipe 10 has a predetermined height from the bottom surface of the accumulators 5a and 5b. It is installed at the same height. Thereby, the minimum amount of oil which can always be secured in the accumulators 5a and 5b can be set. The minimum amount of oil that can always be secured in one of the accumulators is about 1-2 L.

  Gas refrigerant (including refrigerating machine oil that cannot be separated) in the accumulators 5a and 5b is sucked into the compressors 2a and 2b through the gas suction pipes 7a and 7b. The gas suction pipes 7a and 7b are U-shaped at one end inserted into the accumulators 5a and 5b, and have oil return holes 8a and 8b in the U-shaped pipe portions, respectively. However, the U-shaped tube portion inserted into the accumulators 5a and 5b may be a straight tube, and the straight tube portion may not include the oil return holes 8a and 8b. Furthermore, oil return pipes 13a and 13b for returning the oil stored in the accumulators 5a and 5b to the compressors 2a and 2b are connected to the bottoms of the accumulators 5a and 5b at one end, and the other end is an oil regulator. 6a and 6b.

  The oil regulators 6a and 6b and the compressors 2a and 2b are connected by oil suction pipes 14a and 14b and pressure equalizing pipes 15a and 15b. Inside the oil regulators 6a and 6b, there are provided float valves (not shown) that interlock with the float. When the oil level is below the specified height, the float valve is opened and oil is supplied to the compressors 2a and 2b. When the oil level reaches the specified height, the float valve is shut off, and the supply of oil to the compressors 2a and 2b is stopped. The oil separated and stored in the oil separators 3a and 3b is supplied to the compressors 2a and 2b via the gas suction pipes 7a and 7b via a capillary tube (not shown) or directly without the capillary tube. It is supposed to be refueled. A control device 30 controls the operation of the compressors 2a and 2b and the opening and closing of the electromagnetic valve 12a provided in the oil equalizing pipe 10.

  The compressors 2a and 2b are low-pressure shell type inverter compressors in which the inside of a shell such as a scroll has a low pressure, and the compressor oil is held in the compressor shell. In this refrigeration apparatus 100, the required amount of oil is the sum of the appropriate amount of oil in the compressors 2a and 2b and the amount of oil present in each part of the refrigeration apparatus 100. The oil amount is filled more than this oil amount. Excess oil is stored in the accumulators 5a and 5b.

  In the oil stored in the compressors 2a and 2b, the oil take-out amount of the compressor rapidly increases above the oil level, and the compression load increases. Therefore, an appropriate amount of oil in the compressors 2a and 2b is an oil level that has a sufficient amount of oil that does not cause a sudden increase in the amount of oil taken out and that does not exhaust the oil. Further, the compressors 2a and 2b are provided with temperature detection means 50a and 50b each composed of a thermistor or the like capable of detecting the temperature of the shell at the lower part thereof, and accumulated in the lower part of the compressor based on detection information of each temperature detection means. Estimate the amount of oil and determine whether oil leveling control is necessary. Detailed oil leveling control will be described later.

Next, the flow of the refrigerant in the refrigeration apparatus 100 in the present embodiment will be described. The flow of the refrigerant is indicated by solid line arrows in FIG.
The high-temperature and high-pressure gas refrigerant discharged from the compressors 2a and 2b is condensed and liquefied by the condensers 4a and 4b via the oil separators 3a and 3b. Thereafter, the liquefied refrigerant is reduced in pressure by the expansion valve 21 of the indoor unit 20 through the liquid pipe 23 to become a two-phase refrigerant, and is evaporated by the evaporator 22. The gasified refrigerant then enters the accumulators 5a and 5b of the outdoor units 1a and 1b via the gas pipe 24 and the distributor 25a. The refrigerant that has entered the accumulators 5a and 5b and is further evaporated and gasified is sucked into the compressors 2a and 2b through the gas suction pipes 7a and 7b. Thus, a refrigeration cycle in which the refrigerant circulates is formed, and the refrigerant and the refrigeration oil circulate.

Next, the flow of refrigeration oil in the refrigeration apparatus 100 in the present embodiment will be described. The flow of the refrigerating machine oil is indicated by broken-line arrows in FIG.
About 90% of the refrigerating machine oil discharged together with the gas refrigerant from the compressors 2a and 2b is separated by the oil separators 3a and 3b. The separated refrigerating machine oil enters the gas suction pipes 7a and 7b through a capillary tube (not shown) and is returned to the compressors 2a and 2b. The oil that has not been separated by the oil separators 3a and 3b passes through the condensers 4a and 4b, the liquid pipe 23, the expansion valve 21, the evaporator 22, the gas pipe 24, and the distributor 25a in order, and then accumulators 5a and 5b. Flow into.

  In the accumulators 5a and 5b, the refrigerating machine oil and the gas refrigerant are separated, and the separated oil stays at the bottom of the accumulators 5a and 5b. The refrigerating machine oil staying in the accumulators 5a and 5b is supplied from the oil return pipes 13a and 13b to the compressors 2a and 2b via the oil regulators 6a and 6b. In order to make the oil level heights of the oil regulators 6a, 6b and the compressors 2a, 2b equal, pressure equalizing pipes 15a, 15b through which gas flows are connected. Excess oil in the refrigeration apparatus is stored in the accumulators 5a and 5b in the low pressure section.

  In the refrigerant flow from the accumulators 5a and 5b to the compressors 2a and 2b, pressure loss due to friction loss in the piping occurs. The differential pressure corresponding to the pressure loss becomes a driving force for the oil to flow from the accumulators 5a and 5b to the compressors 2a and 2b. Further, the oil level head difference caused by the difference in level between the oil level in the accumulators 5a and 5b and the oil level in the compressors 2a and 2b also affects the oil flow. If the accumulators 5a and 5b have an oil level above the compressors 2a and 2b, the oil supply is promoted, and if the accumulators 5a and 5b are at the lower part, the oil supply is inhibited.

  The oil that has not been separated by the oil separators 3a and 3b travels around the refrigerant circuit and flows into the outdoor units 1a and 1b again. However, generally, when there are a plurality of outdoor units, the oil is not evenly distributed, and the amount of oil returned is different for each outdoor unit. When the refrigeration apparatus 100 according to the present embodiment is operated for a long time, the amount of excess oil stored in the accumulators 5a and 5b is different, and an accumulator in which oil is depleted appears. For example, when the oil in the accumulator 5a is depleted, the oil in the compressor 2a is also depleted, causing the compressor to break.

  An oil leveling method for avoiding compressor breakage due to uneven oil between the outdoor units will be described. The oil equalizing pipe 10 is connected between the accumulator 5a and the accumulator 5b via an electromagnetic valve 12a. Further, the inlet positions (end positions) of the tip portions 10a, 10b of the oil equalizing pipe 10 are set at a predetermined height from the bottom surfaces of the accumulators 5a, 5b.

  During normal operation of the compressors 2a and 2b, the solenoid valve 12a of the oil leveling pipe 10 is closed, and the oil leveling pipe 10 connecting the accumulators 5a and 5b is closed. At this time, when the float valves of the oil regulators 6a and 6b are opened, the oil is sucked into the compressors 2a and 2b, so that the oil in the accumulators 5a and 5b flows through the oil return pipes 13a and 13b. Oil is returned from the regulators 6a and 6b to the compressors 2a and 2b. However, since the oil is not evenly returned to the compressors 2a and 2b, the oil in the accumulators 5a and 5b is also biased, and it is expected that an accumulator in which the oil will eventually be exhausted will appear.

  Therefore, in order to avoid damage to the compressor due to exhaustion of the oil in the accumulator, the oil leveling operation is performed following the normal operation of the compressors 2a and 2b. That is, the normal operation of the compressors 2a and 2b is performed for a certain period of time, and the oil leveling operation is performed to reduce the oil bias in the accumulators 5a and 5b before the oil is depleted. This oil leveling operation is performed by the control device 30 in as short a time as possible. In the oil leveling operation, it is not always necessary to stop the compressor, but the compressor may be stopped.

  Even when a float valve of an oil regulator is shut off, the oil in the accumulators 5a and 5b is biased. For example, when the oil is biased to the outdoor unit 1a and the oil level of the oil regulator 6a becomes a specified height and the float valve is shut off, the oil in the accumulator 5b is compressed through the oil return pipe 13b and the oil regulator 6b. The oil in the accumulator 5b is exhausted. Therefore, the oil leveling operation is performed before the oil is exhausted.

  A timing method for starting the oil equalizing operation in the conventional refrigeration apparatus including the multi-outdoor unit will be described. The method of starting the oil equalizing operation is as follows: normal operation time is 1 hour, oil equalizing operation time is 3 minutes, and oil equalizing operation after 1 hour is No. No. 1 outdoor unit has a frequency of 90 Hz, No. 1 The outdoor unit of No. 2 is set to a frequency of 45 Hz, and in the oil leveling operation after 2 hours, No. 1 outdoor unit has a frequency of 45 Hz, No. 1 The outdoor unit No. 2 has a frequency of 90 Hz, and in the oil leveling operation after 3 hours, it returns to the beginning and is performed at the same frequency as the 1st hour.

  Further, the oil leveling operation may be accompanied by control of the oil return mode. The oil return mode is an operation mode that collects the oil staying outside the outdoor unit system (indoor units, extension pipes, etc.). Recover.

  Here, the oil leveling operation method in the refrigeration apparatus provided with the conventional multi outdoor unit will be described. In addition, about the circuit structure of the freezing apparatus provided with the conventional multi outdoor unit, it shall be the same as that of the freezing apparatus 100, and it demonstrates using the code | symbol similar to the freezing apparatus 100. FIG. During the oil leveling operation, the oil leveling operation is performed by opening the solenoid valve 12a of the oil leveling tube 10 and opening the oil leveling tube 10 connecting the accumulators 5a and 5b. As described above, for example, when the oil in the accumulator 5b is exhausted, surplus oil in the accumulator 5a flows to the accumulator 5b through the oil equalizing pipe 10, and the amount of oil in the accumulators 5a and 5b becomes equal.

  As described above, in the refrigeration apparatus provided with the conventional multi-outdoor unit, the controller 30 operates the specific compressor at a lower frequency than the other compressors while opening the electromagnetic valve 12a, and reduces the frequency within a predetermined time. By changing the compressor that performs the frequency operation and performing the operation control that operates the low frequency operation of all the compressors at least once, the compressor is always compressed while ensuring a minimum oil amount of 1 to 2 L in one of the accumulators. The oil amount of the machine is adjusted to the appropriate oil amount.

  FIG. 2 is a refrigerant circuit diagram when three outdoor units 1a, 1b, and 1c are connected in parallel in the refrigeration apparatus 100. In FIG. 2, the constituent elements of the outdoor unit 1c are the same as the constituent elements of the outdoor units 1a and 1b, and therefore, numerals c or b are sequentially added to numerals representing the respective constituent elements. The flow of refrigerant and refrigerating machine oil is the same as in FIG. In addition, although the specific example of oil equalization control driving | operation is demonstrated based on FIG. 2, oil equalization control driving | operation can be performed similarly also in FIG.

Table 1 shows no. Initially enclosed in compressors 2a, 2b, 2c, oil regulators (O / R) 6a, 6b, 6c and accumulators (ACC) 5a, 5b, 5c in outdoor units 1a, 1b, 1c of 1, 2, 3 An example of the amount of oil is shown.

  The amount in the dead space of Table 1 is the amount of oil that cannot be effectively used in the compressor because oil always remains in the lower part of the compressors 2a, 2b, 2c and the oil separators 3a, 3b, 3c. is there. The initial amount of oil is the amount of oil necessary for the pipe length of the gas pipe 24 (or the liquid pipe 23) to be 0 to 30 m. When the pipe length becomes longer, the oil staying in the gas pipe during operation is increased. Therefore, every time the 10m pipe becomes longer, oil of 0.2L x the number of outdoor units is added to prevent the compressor from running out of oil. However, here, the description will be made assuming that the length of the gas pipe 24 when the initial oil amount is added is 0 m as described above.

  In Table 1, no. The breakdown of the initial oil amount of the outdoor unit 1a is as follows: the compressor 2a has an oil amount of 1.8L including a dead space of 0.5L, the O / R 6a has an oil amount of 0.5L, and within the ACC 5a. The oil amount is 2.7 L, and the oil amount is 0.9 L in the dead space of the oil separator 3a. The initial oil amount of the outdoor unit 1a is 1.8 + 0.5 + 2.7 + 0.9 = 5.9L. However, since the amount in the dead space is 1.4L, in Table 1, it is described as 5.9-1.4 = 4.5L. In addition, No. 1 shows the breakdown of the initial oil amount of the outdoor unit 1a. The same applies to a few outdoor units.

  58 ° C. shown in parentheses in Table 1 indicates the shell temperature at the bottom of the compressor when the refrigeration apparatus 100 is operated at an outside air temperature of 32 ° C., an evaporation temperature of −40 ° C., and an inverter compressor operating frequency of 100 Hz. Yes. The temperature of the shell below the compressor can be detected by the temperature detecting means 50a, 50b, 50c, and data is transmitted to the control device 30 during normal operation and immediately before oil equalizing operation.

  However, Table 1 shows an ideal oil amount distribution when the refrigeration apparatus 100 is operated. In actual operation, the oil distribution is not uniform due to variations in the amount of oil contained in the high-pressure gas refrigerant discharged from the compressors 2a and 2b, variations in the mounting angle generated when the distributors 25a and 25b are assembled, and the like. Absent. Further, the refrigeration apparatus 100 is used at an indoor unit 20 temperature of +15 to -55 ° C and an evaporator 22 evaporation temperature of about +10 to -65 ° C. The fins of the heat exchanger part of the evaporator 22 used in the low temperature region are frosted, and when the amount of frost formation increases, the heat exchange capacity of the evaporator 22 decreases, the internal temperature rises, and is in the internal compartment. Product quality will deteriorate.

  Therefore, when used in a low temperature region, a defrosting operation is performed in which the frost of the evaporator 22 is melted several times a day. The defrosting operation is set to enter several times within a day (the number of times is arbitrarily determined depending on the product in the warehouse and the temperature setting). The details of the single defrosting operation are as follows. Is stopped (about 20 to 30 minutes). In the meantime, with the fan of the evaporator 22 stopped, the attached frost is melted by energizing the heater inside the heat exchanger fins. Methods for melting frost include not only a heater but also a method of flowing a high-temperature and high-pressure refrigerant gas and a method of simply stopping the fan of the evaporator 22.

  Since the inside of the evaporator 22 immediately after melting the frost is at a high temperature, if the fan is immediately rotated, high-temperature air flows into the cabinet, the temperature inside the cabinet rises, or the high-temperature air enters the cabinet. It may be cooled by cold air and re-frost on the product, which may affect the quality of the product. Therefore, the fan of the evaporator 22 is stopped for about 3 to 20 minutes immediately after melting the frost, and the refrigeration apparatus 100 is operated. In about 3 to 20 minutes, the temperature inside the evaporator is cooled, and then the fan of the evaporator 22 is operated to prevent the rise in the inside temperature to a minimum.

  However, while the fan of the evaporator 22 is not operated, the refrigeration apparatus 100 is in an operating state, and heat exchange is not sufficient on the evaporator side. In the refrigeration apparatus 100, the gas cannot be evaporated on the evaporator side and remains a two-phase refrigerant. Of these two-phase refrigerants, particularly the liquid refrigerant, about 10% of each oil that could not be separated by the oil separators 3a, 3b, and 3c (in other words, the oil staying in the gas pipe 24) is all stored in the refrigeration apparatus 100. Will return. All the accumulated oil was subjected to a transient operation in which the temperature inside the chamber was re-cooled by the effect of the above-described variation and the amount of frost that had risen within the melting time. It is conceivable that the outdoor units 1a, 1b, and 1c of 1, 2, and 3 cannot be evenly distributed.

  In this way, in actual operation, no. It is difficult to distribute oil evenly among the 1, 2, and 3 outdoor units 1a, 1b, and 1c. In addition, if the compressors that have a low frequency every 1 h are sequentially changed as in the conventional oil leveling operation, the oil leveling operation in which the oil is further increased in the outdoor unit having a large amount of oil is caused. There is also a high possibility that it will lead to quality degradation. On the contrary, since the outdoor unit with a small amount of oil becomes a soaking operation that reduces oil, there is a high possibility that the quality of the compressor will be reduced due to the exhaustion of the compressor.

  Therefore, only when ensuring the quality of the refrigeration apparatus 100, it is necessary to prevent an increase in the internal temperature as much as possible in the oil leveling operation in which the operation of the compressor is performed at a low frequency. As an optimal oil leveling control method, the amount of oil accumulated in the lower part of the compressor is estimated based on the information detected by the temperature detecting means 50a, 50b, 50c capable of detecting the shell temperature in the lower part of the compressor, This is to determine whether oil leveling control is necessary.

  First, an example of the relationship between the amount of oil in actual operation and the shell temperature at the bottom of the compressor will be described.

Table 2 shows the oil amount after the actual defrosting operation.

  In Table 2, no. The amount of oil is biased toward one outdoor unit 1a, and the shell temperature at the lower part of the compressor 2a is higher than that of other compressors because the amount of oil is increased.

Table 3 shows the oil amount immediately after the oil leveling operation is performed once from Table 2.

  In Table 3, no. The operating frequency of the outdoor unit 1a of No. 1 is controlled to 45 Hz and the other compressors are controlled to 90 Hz. It shows that oil is moved from one outdoor unit 1a to another outdoor unit. The amount of oil that moves is approximately 0 to 1 L in one oil leveling operation, although it varies depending on the operating conditions and the oil distribution state. No. Since the amount of oil in one outdoor unit 1a is reduced, the shell temperature at the lower portion of the compressor 2a is lowered, and conversely, the shell temperature at the lower portion of the compressor is increased by the amount of oil in the other outdoor units.

  Since the control device 30 knows the shell temperatures under the compressors 2a, 2b, and 2c, the outdoor unit that makes the low frequency of the next oil leveling operation has a high shell temperature under the compressor. That is, in Table 3, the second oil leveling operation is the same as the first oil leveling operation. The operating frequency of the outdoor unit 1a of No. 1 is controlled to 45 Hz and the other compressors are controlled to 90 Hz. The control is to move oil from one outdoor unit 1a to another outdoor unit. In one soaking operation, No. Since the amount of oil reduction of one outdoor unit 1a is 0.5 L, the oil leveling operation is performed 4 to 5 times, and the oil amount of all the outdoor units becomes equal.

  In the conventional oil leveling control, for example, the outdoor unit whose frequency becomes low in the second oil leveling operation is No. 1. No. 2 outdoor unit that has a low frequency in the third oil leveling operation is No. 2. No. 3 outdoor unit, and the second and third oil leveling operations from the outdoor unit having a small oil amount to the No. 3 oil amount. The oil has moved to one outdoor unit. Therefore, it is considered that the oil equalizing operation in which all outdoor units are equalized by the conventional oil equalizing control is increased to 12 to 15 times. Actually, since defrosting operation is necessary several times a day, it takes more time until all the outdoor units are equalized.

  Usually, the frequency | count of defrosting of the freezing apparatus used in a low-temperature region is about 1 to 5 times a day. Therefore, it is desirable that the oil leveling operation for equalizing the oil amount of all outdoor units is at least 24 h (1 day) / 5 times (number of defrosting times) = 4.8 h or less. In the refrigeration apparatus 100, as shown in Tables 1 and 2, the oil amount can be adjusted in 4 to 5 oil leveling operations, so that the oil bias can be corrected without impairing the quality of the refrigeration apparatus 100. Therefore, according to the refrigeration apparatus 100, the quality is improved as compared with the conventional oil leveling control.

  If the defrosting frequency is as low as once a day, the oil level has been adjusted from the 6th oil leveling operation, so it is determined that the oil leveling operation is not necessary, and the operation after the next hour To determine whether oil leveling control is necessary. Specifically, the oil leveling operation is performed when the difference between the shell temperatures under the compressors 2a, 2b and 2c immediately before the oil leveling operation is 1.5 ° C or higher in summer and 1 ° C or higher in winter. Make it happen. In summer, the outside air temperature is about 20 to 43 ° C, and in consideration of the increase in the shell temperature due to the influence of the outside air temperature, conversely, in winter, the outside air temperature is about -15 to 20 ° C. Since the shell temperature is low and it may not be possible to properly determine the amount of oil, the threshold value is reduced. Since this threshold varies depending on the amount of oil sealed in the compressor and the outdoor unit, the threshold may be changed according to the specification. Therefore, from the sixth oil equalizing operation, the necessity of the oil equalizing operation can be determined each time based on the threshold value.

  In this way, if it is possible to determine whether or not the oil leveling operation is necessary, it is not necessary to perform the oil leveling operation until it is not necessary to perform the oil leveling operation. Without oil leveling operation, there is no compressor that has a low frequency, so the internal temperature does not become unstable, and the outdoor unit does not run out of oil.

Table 4 shows the assumption of a large number of defrosting times per day in the simulation of the oil leveling operation and the variation in the amount of oil contained in the high-pressure gas refrigerant discharged from the compressor, and the assembly of the distributors 25a and 25b. The oil amount obtained by setting the conditions for the most oil to be returned to the outdoor unit 1a and the conditions for the most oil depletion in the outdoor unit 1c in consideration of the variation in the angle generated and the variation in the separation efficiency. Is.

  In Table 4, no. The amount of oil is biased toward one outdoor unit 1a, and the shell temperature at the bottom of the compressor 2a increases to 85 ° C. as the amount of oil increases. No. The amount of oil in the outdoor unit 1c of No. 3 is reduced, and only 1.9L. This driving situation is No. The amount of oil in the outdoor unit 1a is excessive, and the discharged high-temperature and high-pressure gas refrigerant becomes abnormally high, so that the quality of the compressor cannot be ensured. An abnormal stop will occur. When the shell temperature at the bottom of the compressor is 75 ° C. or lower, the compressor can resume operation again. However, since the shell temperature is about 2 to 4 hours and is about 10 ° C., the abnormal stop at the shell lower temperature of 85 ° C. leads to a temperature rise of the inside temperature.

  No. Since the amount of oil in the outdoor unit 1c of No. 3 is reduced, the compressor 2c has only 1.3L, the O / R 6c has only 0.5L, and the ACC 5c has only 0.1L. Compressor failure due to oil exhaustion. Therefore, determining the oil leveling operation based on the shell temperature at the bottom of the compressor can evenly adjust the amount of oil in each outdoor unit in the case of assuming each variation and transient operation. 100 reliability can be improved.

  As described above, in the refrigeration apparatus 100, the temperature detecting means 50a, 50b, 50c capable of detecting the shell temperature is provided at the lower part of the compressor, the amount of oil accumulated in the lower part of the compressor is estimated, and the oil equalization control is performed. Since it is configured to determine whether it is necessary, the amount of oil in the compressor can be estimated. Therefore, in a refrigeration apparatus having a multi-outdoor unit that uses a combination of a plurality of outdoor units, the temperature difference between the oils is known, so the degree of deviation in the amount of oil in the compressor can be grasped. Therefore, according to the refrigeration apparatus 100, it is possible to determine whether oil leveling control is necessary or not based on the degree of deviation of the oil amount, so that the oil leveling control can be optimized, and the internal temperature can be prevented from becoming unstable. In addition, the effect that the internal temperature is stable and the reliability is improved can be obtained.

  In the above description, the same effect can be obtained as long as the refrigerant and the oil are compatible. Therefore, as the refrigerant, HFC refrigerant, HFC refrigerant mixed refrigerant, HC refrigerant, HC refrigerant mixed refrigerant, HFC refrigerant and HC refrigerant mixed refrigerant, or natural refrigerant such as carbon dioxide, water, etc. The same effect is obtained when using oils that are compatible with these refrigerants, such as ester oils for HFC refrigerants, mineral oils for HC refrigerants, PAG oils for carbon dioxide, etc. Can be obtained.

  1a outdoor unit, 1b outdoor unit, 1c outdoor unit, 2a compressor, 2b compressor, 2c compressor, 3a oil separator, 3b oil separator, 3c oil separator, 4a condenser, 4b condenser, 4c condenser 5a accumulator, 5b accumulator, 5c accumulator, 6a oil regulator, 6b oil regulator, 6c oil regulator, 7a gas suction pipe, 7b gas suction pipe, 7c gas suction pipe, 8a oil return hole, 8b oil return hole, 8c oil return hole, 10 oil equalizing pipe, 10a tip, 10b tip, 10c tip, 12a solenoid valve, 12b solenoid valve, 13a oil return pipe, 13b oil return pipe, 13c oil return pipe, 14a oil suction pipe, 14b oil suction pipe , 14c Oil suction pipe, 15a Pressure equalizing pipe, 15b Pressure equalizing pipe, 15c Pressure equalizing pipe, 20 Indoor unit, 2 An expansion valve, 22 an evaporator, 23 liquid pipe, 24 gas pipe, 25a distributor, 25b distributor, 30 control unit, 50a temperature detector, 50b temperature detecting means, 50c temperature detecting means, 100 refrigeration system.

Claims (2)

And at least a compressor, a condenser, includes a accumulator, connected in parallel to the plurality of outdoor units,
A refrigeration system for forming a refrigeration cycle and the indoor units, the connecting piping comprising at least vacuum means and the evaporator,
A return oil pipe for returning the refrigerating machine oil stored in the accumulator to the compressor;
Oil leveling pipes connecting each accumulator,
Temperature detecting means for detecting the shell temperature at the bottom of each compressor;
A control device for controlling the operation of the compressor and the opening and closing of a solenoid valve provided in the oil equalizing pipe based on a shell temperature difference at the bottom of each compressor detected by the temperature detection means ,
The controller is
When the shell temperature difference at the lower part of each compressor detected by the temperature detecting means is equal to or greater than a threshold that can be changed according to the season, the refrigerating machine oil in each accumulator is biased. And the electromagnetic valve is opened . The controller is
Every time it is judged that the refrigerating machine oil in each accumulator is biased,
While opening all the solenoid valves, the compressor of the highest temperature among the detected temperature by said temperature detecting means than the other compressor in claim 1, characterized in that performing the cause operation control operation in the low frequency The refrigeration apparatus described.

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