JP5308205B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner in which an oil separator that separates oil discharged from a compressor together with refrigerant gas and returns it to the compressor side is provided in a discharge pipe of the compressor.

  A compressor housing applied to an air conditioner is filled with a certain amount of refrigerating machine oil (oil) and is used for lubrication of a sliding portion of the compressor. On the other hand, the refrigerant sealed in the refrigerating cycle of the air conditioner is compatible with the refrigerating machine oil, and when the air conditioner is stopped for a long time, the temperature of the refrigerant in the cycle increases due to the temperature difference. A phenomenon occurs in which the refrigerant moves toward the lower compressor side and is condensed and dissolved in the refrigeration oil. This phenomenon tends to become more prominent as the outside air temperature decreases. When the compressor is started in such a state, oil is discharged from the compressor to the cycle side together with the compressed refrigerant gas, the oil level in the housing is lowered, and the compressor may be poorly lubricated.

  Therefore, an oil separator for separating the oil discharged from the compressor together with the refrigerant gas is provided in the discharge pipe of the compressor, and the separated oil is always returned to the compressor side through the oil return circuit. A method of securing a certain amount of oil and eliminating poor lubrication of the compressor due to lack of refrigeration oil is generally employed. Further, in such a system, if a certain amount of oil is not held in the oil separator, the high-pressure refrigerant gas is bypassed to the compressor via the oil return circuit, or the oil separator at low outside air temperature Since some of the refrigerant is condensed in the interior and the liquid refrigerant is returned to the compressor together with the oil, the refrigeration oil is diluted. Has been proposed.

  For example, in Patent Document 1, an electromagnetic valve is provided in an oil return circuit, and the electromagnetic valve is intermittently opened and closed according to the outside air temperature, thereby suppressing refrigerant condensation in the oil separator at a low outside air temperature. There has been proposed a compressor in which the amount of refrigeration oil in the compressor can be maintained appropriately. In Patent Document 2, a first oil return circuit having a fixed throttle and a second oil return circuit having a solenoid valve and a fixed throttle are connected in parallel between the oil separator and the compressor side, In the figure, an oil return amount can be adjusted as appropriate by opening and closing a solenoid valve while returning a certain amount of oil.

JP 2003-28524 A JP 2008-39332 A

  However, in the technique shown in Patent Document 1, it is necessary to return the oil by normally opening and closing the solenoid valve, and by increasing the opening and closing timing of the solenoid valve as the outside air temperature decreases. The amount of oil in the compressor is kept appropriate. For this reason, the opening and closing frequency of the solenoid valve has to be frequent, and there is a problem that the risk of failure of the solenoid valve or a decrease in the life is increased, leading to a decrease in reliability.

  Further, the technique disclosed in Patent Document 2 is that the oil return amount is increased by opening the electromagnetic valve of the second oil return circuit when the oil rise increases while always returning a constant amount of oil through the first oil return circuit. The amount of oil return can be adjusted according to the operating condition, and the amount of refrigerant dissolved in the oil is large at low outside air temperature, so that the oil is easily discharged from the compressor together with the refrigerant gas. At the start of operation, the solenoid valve was opened to ensure the oil return amount. However, at low outside temperatures, the oil separator itself has become accustomed to low temperatures due to a long stoppage, so a part of the discharged refrigerant gas is condensed in the oil separator and the oil return circuit is put together with oil as liquid refrigerant. After that, it may be returned to the compressor side, which promotes dilution of the refrigerating machine oil in the compressor. As a result, there has been a problem that the risk of the compressor falling into a poor lubrication is increased, as is the case with the oil level drop.

  The present invention has been made in view of such circumstances, and suppresses dilution of refrigeration oil by liquid refrigerant returned from the oil separator to the compressor side through the oil return circuit, and poor lubrication of the compressor. An object is to provide a highly reliable air conditioner capable of reducing risk.

In order to solve the above-described problems, the air conditioner of the present invention employs the following means.
That is, the air conditioner according to the present invention is provided with an oil separator in a discharge pipe of a compressor, a first oil return circuit having a throttle between the oil separator and the compressor side, and an electromagnetic valve And an air conditioner in which a second oil return circuit having a throttle is connected in parallel to each other, until a certain period of time elapses when operation is started after the compressor has been stopped for a predetermined time or longer. or between the oil separator until or discharge superheat temperature exceeds the discharge saturation temperature of up to exceed a predetermined value, e Bei a controller for closing said solenoid valve, said control unit, the outside air temperature is the set temperature The electromagnetic valve is configured to be closed during the above only in the following cases .

If the air conditioner has been stopped for a long time at low outside air temperature, the oil separator is also accustomed to the low temperature state, and when heating operation is started in this state, the refrigerant gas discharged from the compressor A part of the oil is condensed in the oil separator, and the liquid refrigerant may be returned to the compressor through the first oil return circuit and the second oil return circuit together with the oil without being separated from the oil. As a result, dilution of the refrigerating machine oil in the compressor with the liquid refrigerant is further promoted, which causes poor lubrication. According to the present invention, at the start of operation after the compressor has been stopped for a predetermined time or longer, until a certain time elapses or until the temperature of the oil separator exceeds the discharge saturation temperature or the discharge superheat degree is increased. A controller is provided for closing the solenoid valve provided in the second oil return circuit until the constant value is exceeded , and the controller is operated only when the outside air temperature is lower than the set temperature. Therefore, at the start of operation, the outside air temperature is equal to or lower than the set temperature, and a part of the refrigerant gas discharged from the compressor is cooled and condensed in the oil separator. The compressor of the liquid refrigerant condensed by the oil separator is closed only when the liquid refrigerant is returned to the compressor side and there is a high possibility that the refrigeration oil is diluted. By reducing the amount of return to the side, dilution of refrigeration oil can be suppressed Therefore, the risk of poor lubrication of the compressor due to dilution of the refrigeration oil with the liquid refrigerant can be reduced and the reliability can be improved . In other cases, the solenoid valve is appropriately opened and closed as necessary. By ensuring the return amount of the oil separated by the separator to the compressor side, it is possible to reduce the risk of poor lubrication due to a drop in the oil level of the refrigeration oil in the compressor.

Furthermore, the air conditioner of the present invention is the above-described air conditioner, wherein the air conditioner is a multi-type air conditioner in which a plurality of indoor units are connected in parallel to the outdoor unit. Features.

  According to the present invention, since the air conditioner is a multi-type air conditioner in which a plurality of indoor units are connected in parallel to the outdoor unit, refrigerating machine oil or liquid refrigerant stays in a stopped state. Even in a multi-type air conditioner that tends to vary, the oil return circuit from the oil separator to the compressor side functions properly so that the refrigeration oil can be diluted by the extreme liquid refrigerant return from the oil separator. And the oil level can be suppressed. Therefore, the multi-type air conditioner can be operated stably.

According to the present invention, when the outside air temperature is equal to or lower than the set temperature at the start of operation , even if the discharged refrigerant gas is cooled in the oil separator and partially condensed, the solenoid valve of the second oil return circuit is Since it is closed, liquid refrigerant is not returned to the compressor side in large quantities via the oil return circuit from the oil separator side, and dilution of the refrigeration oil in the compressor by the liquid refrigerant can be suppressed, Therefore, the risk of poor lubrication of the compressor due to the dilution of the refrigeration oil with the liquid refrigerant can be reduced, and the reliability can be improved.

It is a refrigerant circuit figure of the air harmony machine concerning a 1st embodiment of the present invention. It is a control flowchart figure of the air conditioner shown in FIG.

Embodiments according to the present invention will be described below with reference to the drawings.
[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 shows a refrigerant circuit diagram of the air conditioner according to the present embodiment. Here, the example at the time of applying to the multi-type air conditioner 1 is shown. The multi-type air conditioner 1 includes one outdoor unit 2, a gas side pipe 4 and a liquid side pipe 5 led out from the outdoor unit 2, and a branching device 6 between the gas side pipe 4 and the liquid side pipe 5. And a plurality of indoor units 7A and 7B that are connected in parallel with each other.

  The outdoor unit 2 heats an inverter-driven compressor 21 that compresses refrigerant, an oil separator 22 that separates refrigeration oil from refrigerant gas, a four-way switching valve 23 that switches a refrigerant circulation direction, and refrigerant and outside air. An outdoor heat exchanger 24 to be exchanged, a supercooling coil 25 configured integrally with the outdoor heat exchanger 24, an outdoor electric expansion valve (EEVH) 26 for heating, a receiver 27 for storing liquid refrigerant, A supercooling heat exchanger 28 that supercools the liquid refrigerant, a supercooling electric expansion valve (EEVSC) 29 that controls the amount of refrigerant diverted to the supercooling heat exchanger 28, and a refrigerant sucked into the compressor 21 An accumulator 30 that separates the liquid component from the gas and causes the compressor 21 to suck only the gas component, a gas-side operation valve 31, and a liquid-side operation valve 32 are provided.

  The respective devices on the outdoor unit 2 side are connected in a known manner via refrigerant pipes such as a discharge pipe 33A, a gas pipe 33B, a liquid pipe 33C, a gas pipe 33D, a suction pipe 33E, and a subcooling branch pipe 33F. The outdoor refrigerant circuit 34 is configured. The outdoor unit 2 is provided with an outdoor fan 35 that blows outside air to the outdoor heat exchanger 24.

  Further, between the oil separator 22 and the suction pipe 33E of the compressor 21, a refrigerating machine oil separated from the discharged refrigerant gas in the oil separator 22 is returned to the compressor 21 side by a predetermined amount. A parallel circuit of a first oil return circuit 37 having a fixed throttle (throttle) 36 and a second oil return circuit 40 having a fixed throttle (throttle) 39 such as an electromagnetic valve 38 and a capillary tube is connected.

  The gas side pipe 4 and the liquid side pipe 5 are refrigerant pipes connected to the gas side operation valve 31 and the liquid side operation valve 32 of the outdoor unit 2, and are connected to the outdoor unit 2 and to it during installation on site. The length is set according to the distance between the indoor units 7A and 7B. An appropriate number of branching devices 6 are provided in the middle of the gas side piping 4 and the liquid side piping 5, and an appropriate number of indoor units 7 </ b> A and 7 </ b> B are connected via the branching devices 6. Thereby, one sealed refrigeration cycle 3 is configured.

  The indoor units 7A and 7B are configured so that the indoor air is passed through the indoor heat exchanger 71 that exchanges heat between the refrigerant and room air for indoor air conditioning, the indoor electric expansion valve (EEVC) 72 for cooling, and the indoor heat exchanger 71. The indoor fan 73 is circulated, and is connected to the branching device 6 through the branch gas pipe 4A and the branch liquid pipe 5A on the indoor side.

In the multi-type air conditioner 1 described above, the cooling operation is performed as follows.
The high-temperature and high-pressure refrigerant gas compressed by the compressor 21 is discharged to the discharge pipe 33A, and the oil separator 22 separates the refrigerating machine oil contained in the refrigerant. Thereafter, the refrigerant gas is circulated to the gas pipe 33B side through the four-way switching valve 23, and is heat-exchanged with the outside air blown by the outdoor fan 35 in the outdoor heat exchanger 24 to be condensed and liquefied. The liquid refrigerant is further cooled by the supercooling coil 25, passes through the outdoor electric expansion valve 26, and is temporarily stored in the receiver 27.

  The liquid refrigerant whose circulation amount is adjusted by the receiver 27 is partly divided into the subcooling branch pipe 33F in the process of being circulated through the supercooling heat exchanger 28 via the liquid pipe 33C, and the supercooling electric expansion is performed. Heat is exchanged with the refrigerant adiabatically expanded by the valve (EEVSC) 29 to give a degree of supercooling. This liquid refrigerant is led out from the outdoor unit 2 to the liquid side pipe 5 via the liquid side operation valve 32, and the liquid refrigerant led out to the liquid side pipe 5 is further branched into the indoor units 7A and 7B by the branching device 6. The flow is diverted to the liquid pipes 5A and 5B.

  The liquid refrigerant divided into the branch liquid pipes 5A and 5B flows into the indoor units 7A and 7B, is adiabatically expanded by the indoor electric expansion valve (EEVC) 72, becomes a gas-liquid two-phase flow, and the indoor heat exchanger 71. Is flowed into. In the indoor heat exchanger 71, the indoor air circulated by the indoor fan 73 and the refrigerant are heat-exchanged, and the indoor air is cooled and provided for indoor cooling. On the other hand, the refrigerant is gasified, reaches the branching device 6 through the branch gas pipes 4A and 4B, and merges with the refrigerant gas from the other indoor units in the gas side pipe 4.

  The refrigerant gas merged in the gas side pipe 4 is returned to the outdoor unit 2 side, reaches the suction pipe 33E via the gas side operation valve 31, the gas pipe 33D, and the four-way switching valve 23, and the refrigerant gas from the branch pipe 33F. After being merged, it is introduced into the accumulator 30. In the accumulator 30, the liquid component contained in the refrigerant gas is separated, and only the gas component is sucked into the compressor 21. This refrigerant is compressed again in the compressor 21, and the cooling operation is performed by repeating the above cycle.

On the other hand, the heating operation is performed as follows.
The high-temperature and high-pressure refrigerant gas compressed by the compressor 21 is discharged to the discharge pipe 33A, and after the refrigerating machine oil contained in the refrigerant is separated by the oil separator 22, the four-way switching valve 23 causes the gas pipe 33D side. It is circulated in. The refrigerant is led out from the outdoor unit 2 through the gas side operation valve 31 and the gas side pipe 4, and is further introduced into the indoor units 7A and 7B through the branching unit 6 and the branch gas pipes 4A and 4B on the indoor side.

  The high-temperature and high-pressure refrigerant gas introduced into the indoor units A and 7B is heat-exchanged with the indoor air circulated by the indoor fan 73 in the indoor heat exchanger 71, and the indoor air is heated and used for indoor heating. The liquid refrigerant condensed and liquefied in the indoor heat exchanger 71 reaches the branching device 6 through the indoor electric expansion valve (EEVC) 72 and the branch liquid pipings 5A and 5B, and is merged with the refrigerant from other indoor units. It returns to the outdoor unit 2 through the liquid side pipe 5. During heating, in the indoor units 7A and 7B, the opening degree of the indoor electric expansion valve (EEVC) 72 is set so that the degree of supercooling of the refrigerant at the outlet of the indoor heat exchanger 71 functioning as a condenser becomes a constant value. It is controlled.

  The refrigerant that has returned to the outdoor unit 2 reaches the supercooling heat exchanger 28 via the liquid side operation valve 32 and the liquid pipe 33C, and is given supercooling as in the case of cooling, and then flows into the receiver 27. Once stored, the amount of circulation is adjusted. This liquid refrigerant is supplied to the outdoor electric expansion valve (EEVH) 26 through the liquid pipe 33C, and is adiabatically expanded there, and then flows into the outdoor heat exchanger 24 through the supercooling coil 25.

  In the outdoor heat exchanger 24, heat is exchanged between the outside air blown from the outdoor fan 35 and the refrigerant, and the refrigerant absorbs heat from the outside air and is evaporated and gasified. This refrigerant is merged with the refrigerant from the subcooling branch pipe 33F from the outdoor heat exchanger 24 via the gas pipe 33B, the four-way switching valve 23, and the suction pipe 33E, and is introduced into the accumulator 30. In the accumulator 30, the liquid component contained in the refrigerant gas is separated, and only the gas component is sucked into the compressor 21. This refrigerant is compressed again by the compressor 21, and the heating operation is performed by repeating the above cycle.

  During the cooling operation and heating operation described above, the refrigerating machine oil separated from the discharged refrigerant gas in the oil separator 22 has a first oil return circuit 37 having a fixed throttle 36 connected in parallel to each other, a solenoid valve 38 and a fixed. It is returned to the compressor 21 side through a second oil return circuit 40 having a throttle 39. As a result, a certain amount of refrigerating machine oil is secured in the compressor 21 and the sliding portion in the compressor 21 is lubricated.

  The solenoid valve 38 provided in the second oil return circuit 40 is opened and closed at an appropriate timing during the normal cooling operation and the heating operation, so that the compressor 21 of the oil separated by the oil separator 22 is operated. The return amount to the side can be adjusted. In addition, in this embodiment, when the operation is started from the state where the compressor 21 has been continuously stopped for a predetermined time or longer by the control unit 41, the temperature of the oil separator 22 is increased until a certain time elapses. The solenoid valve 38 is configured to be closed until the discharge saturation temperature (DST) is exceeded or the discharge superheat degree exceeds a certain value.

  Based on the detection values from the discharge temperature sensor 42, the oil separator temperature sensor 43, the outside air temperature sensor 44, the high pressure sensor 45, and the like, the control unit 41 performs the operation on the solenoid valve 38 according to the control flowchart shown in FIG. The “solenoid valve control at the start of operation” is executed as follows.

  When the operation of the air conditioner 1 is started, first, in step S1, it is determined whether or not the compressor 21 has started operation from a state where it has been continuously stopped for a certain time (for example, 1 hour). . If “NO” is determined here, the process proceeds to “regular solenoid valve control” in step S4. On the other hand, when it determines with "YES", it transfers to step S2, and after closing the solenoid valve 38 of the 2nd oil return circuit 40, it transfers to step S3. In step S3, whether a certain time (for example, 10 minutes) has elapsed since the solenoid valve 38 was closed, or the oil separator temperature detected by the temperature sensor 43 is the discharge temperature sensor 42 or the high pressure sensor 45. It is determined whether or not the discharge saturation temperature (DST) detected in step S1 is exceeded, or whether or not the superheat degree (discharge superheat degree) of the refrigerant gas discharged from the compressor 21 exceeds a certain value.

  If any of the above-mentioned conditions is satisfied in step S3 and it is determined “YES”, the above “solenoid valve control at the start of operation” is terminated, and the next step S4 “solenoid valve at steady state” is continued. “Control”. The “regular solenoid valve control” in this step S4 may be any control, and in addition to a certain amount of oil return through the first oil return circuit 37, for example, from the compressor 21 depending on the operating state. When the amount of oil rising increases, the solenoid valve 38 is opened and the corresponding amount of oil is returned to the compressor 21 side, and the solenoid valve 38 is opened and closed at an appropriate timing, so that the oil return is executed. ing.

In the present embodiment, when “YES” is determined in step S3 and “solenoid valve control at the start of operation” is completed, the process proceeds to “solenoid valve control at steady state” in step S4 as it is. However, once the solenoid valve 38 is opened, the process may proceed to step S4.
Furthermore, in the present embodiment, the detection value of the outside air temperature sensor 44 is input to the control unit 41. Only when the outside air temperature detected by the outside air temperature sensor 44 is equal to or lower than a set temperature (for example, −5 ° C. or lower), the control unit 41 performs “electromagnetic valve control at the start of operation” according to the control flowchart shown in FIG. Is configured to run.

With the configuration described above, according to the present embodiment, the following operational effects can be obtained.
When the air conditioner 1 is stopped for a long time under a low outside air temperature, the liquid refrigerant is dissolved in the refrigeration oil in the compressor 21. The oil separator 22 is also adapted to the low temperature atmosphere. When the compressor 21 is started and the operation is started from such a state, the liquid refrigerant accumulated in the compressor 21 is gasified, and the refrigerant gas in a state where oil is dissolved is discharged from the compressor 21. The

  As a result, the amount of oil contained in the refrigerant gas discharged from the compressor 21 increases, and the amount of oil that is inevitably separated by the oil separator 22 also increases. Further, the discharged refrigerant gas is cooled by the oil separator 22 in a low temperature state, and a part thereof is condensed by the oil separator 22. When this liquid refrigerant and oil are returned to the compressor 21 side through the first oil return circuit 37 and the second oil return circuit 40 together, the oil diluted by the dissolution of the liquid refrigerant is further diluted. Will be.

  However, in the present embodiment, at the start of operation from the case where the stopped state of the compressor 21 has continued for a predetermined time or longer under a low outside air temperature, the temperature of the oil separator 22 is maintained at the discharge saturation temperature until a certain time elapses. The electromagnetic valve 38 provided in the second oil return circuit 40 is closed until (DST) is exceeded or the discharge superheat degree exceeds a certain value. For this reason, even if the refrigerant gas discharged from the compressor 21 is cooled in the oil separator 22 at the start of operation and part of the refrigerant gas is condensed, the solenoid valve 38 of the second oil return circuit 40 is closed. Therefore, a large amount of the liquid refrigerant condensed in the oil separator 22 is not returned to the compressor 21 side via the oil return circuits 37 and 40.

  This eliminates the event that the refrigeration oil in the compressor 21 diluted by the melt of the liquid refrigerant at the start of operation is further diluted by the liquid refrigerant returned from the oil separator 22 via the oil return circuit. Therefore, the risk of poor lubrication of the compressor 21 due to dilution of the refrigeration oil with the liquid refrigerant can be reduced, and the reliability can be improved.

  Further, in the case of the multi-type air conditioner 1 in which a plurality of indoor units 7A and 7B are connected in parallel to the outdoor unit 2, there is variation in the retention of refrigerating machine oil and liquid refrigerant in a stopped state. Although it is likely to occur, the oil return circuits 37 and 40 from the oil separator 22 to the compressor 21 side function properly to dilute the refrigeration oil or reduce the oil level due to the extreme return of the liquid refrigerant from the oil separator 22. Therefore, the multi-type air conditioner 1 can be stably operated.

Furthermore, in this embodiment, only when the outside air temperature is equal to or lower than the set temperature, until a certain time elapses or until the temperature of the oil separator 22 exceeds the discharge saturation temperature or until the discharge superheat exceeds a certain value. Since the solenoid valve 38 is closed, the outside air temperature is, for example, −5 ° C. or less, and a part of the refrigerant gas discharged from the compressor 21 is condensed by the oil separator 22, and the liquid refrigerant Is returned to the compressor 21 side, and only when there is a high possibility that the refrigeration oil is diluted, the electromagnetic valve 38 of the second oil return circuit 40 is closed and returned via the second oil return circuit 40. Dilution of refrigerating machine oil by the liquid refrigerant that is generated can be suppressed.

  Therefore, at the start of operation when the outside air temperature is lower than the set temperature, the risk of poor lubrication of the compressor 21 due to oil dilution can be reliably reduced, and in other cases, the solenoid valve 38 is appropriately opened and closed as necessary. By ensuring the return amount of the oil separated by the oil separator 22 to the compressor 21 side, it is possible to reduce the risk of poor lubrication due to the lowering of the oil level of the refrigeration oil in the compressor 21. .

  In addition, this invention is not limited to the invention concerning the said embodiment, In the range which does not deviate from the summary, it can change suitably. For example, in the above embodiment, an example in which the present invention is applied to the multi-type air conditioner 1 has been described, but the present invention may be applied to a single-type air conditioner in which one indoor unit is connected to one outdoor unit. Of course it is good. In the above embodiment, the example in which the first and second oil return circuits 37 and 40 are connected to the suction pipe 33E of the compressor 21 has been described. However, the first and second oil return circuits 37 and 40 may be directly connected to the housing of the compressor 21. Good.

DESCRIPTION OF SYMBOLS 1 Air conditioner 2 Outdoor unit 7A, 7B Indoor unit 21 Compressor 22 Oil separator 33A Discharge piping 36 Fixed throttle (throttle)
37 First oil return circuit 38 Solenoid valve 39 Fixed throttle (throttle)
40 Second oil return circuit 41 Control unit 42 Discharge temperature sensor 43 Oil separator temperature sensor 44 Outside air temperature sensor 45 High pressure sensor

Claims (2)

An oil separator is provided in the discharge pipe of the compressor, and a first oil return circuit having a throttle and a second oil return circuit having a solenoid valve and a throttle are provided between the oil separator and the compressor side. In air conditioners connected in parallel to each other,
At the start of operation after the compressor has been stopped for a predetermined time or longer, until a certain time elapses, or until the temperature of the oil separator exceeds the discharge saturation temperature, or the discharge superheat exceeds a certain value. during the up, e Bei a controller for closing said solenoid valve,
The controller is configured to close the solenoid valve during the period only when the outside air temperature is equal to or lower than a set temperature . The air conditioner according to claim 1, wherein the air conditioner is a multi-type air conditioner in which a plurality of indoor units are connected in parallel to an outdoor unit.

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