JP2004263995A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air conditioner for improving reliability by improving oil return efficiency to a compressor by surely mixing a liquid refrigerant and oil even in a state of causing separation into two layers of the liquid refrigerant and the refrigerating machine oil in an accumulator. <P>SOLUTION: This air conditioner has the accumulator 6 arranged on the suction side of the compressor 1 for constituting a refrigerating cycle, and introducing and guiding a separated gas refrigerant to the compressor by separating gas and liquid by introducing the refrigerant evaporated in a heat exchanger, and has a hot gas bypass circuit G for separating and introducing a part of hot gas delivered from the compressor to a bottom part of the accumulator, and an opening and closing valve 12 arranged in this hot gas bypass circuit, and controlling opening and closing according to a preset condition. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an air conditioner including an accumulator arranged on a suction side of a compressor.
[0002]
[Prior art]
The accumulator provided in the refrigeration cycle has a tank, an inlet pipe connected to the upper part of the tank and guiding the evaporated refrigerant into the tank, and a gas refrigerant having a substantially U-shaped bent part and gas-liquid separated from the open end of the upper part of the tank. And an oil return hole for returning the refrigerating machine oil accumulated at the tank bottom to the compressor at the bent portion of the outlet pipe.
[0003]
As a prior art, [Patent Document 1] discloses that at least one auxiliary oil return hole is provided vertically along an opening-side pipe wall of an outlet pipe in addition to an oil return hole at the bottom of an outlet pipe, and the presence or absence of liquid refrigerant is provided. Regardless of this, even if the refrigerating machine oil and the liquid refrigerant are separated into two layers, a technique capable of returning the oil to the compressor via the auxiliary oil return hole is disclosed.
[0004]
[Patent Publication 1]
JP-A-11-14201
[0005]
[Problems to be solved by the invention]
However, if the heating operation is performed when the outside air temperature is extremely low, a large amount of liquid refrigerant is temporarily held inside the accumulator at the time of startup. Under such conditions, the liquid refrigerant is sucked not only from the oil return hole but also from the plurality of auxiliary oil return holes, and the amount of liquid back to the compressor increases, which is not preferable in terms of the reliability of the compressor.
[0006]
Further, in the rotary compressor, the refrigerant is directly sucked into the compression chamber, so that the danger is particularly large. Since the amount of oil returned (hole diameter) of the suction cup provided at the compressor suction part is determined, the liquid refrigerant and oil easily accumulate in the suction cup excessively, and the compressor may be damaged by liquid compression / oil compression. There is.
[0007]
Further, in an air conditioner using a refrigerant having a relatively high working pressure such as R32 or R410A, the tank thickness of the accumulator needs to be increased due to pressure resistance design. Simply increasing the thickness of the tank results in an increase in cost. Therefore, it is common practice to increase the height of the tank and increase the height to increase the capacity.
[0008]
Even in such an accumulator, the oil return hole is provided at the lowermost portion of the curved portion of the introduction pipe, so that when the refrigerant oil and the liquid refrigerant are separated into two layers, the oil present on the liquid surface of the liquid refrigerant is compressed. Will not be returned to the machine.
[0009]
If liquid refrigerant or oil is accumulated only at the bottom of the accumulator, the oil return characteristics will be degraded due to the head difference between the tanks. In particular, at a low temperature where the viscosity of the oil becomes high, this tendency becomes remarkable.
[0010]
To remedy this kind of problem, the idea is to increase the flow velocity of the refrigerant flowing in the outlet pipe, increase the differential pressure between the outlet pipe and the outside pipe through the oil return hole, and improve the oil return characteristics. However, on the other hand, there is a problem that the pressure loss in the outlet pipe increases and the coefficient of performance decreases.
[0011]
The present invention has been made in view of the above circumstances, and it is an object of the present invention to reliably mix the liquid refrigerant and the oil even when the liquid refrigerant and the refrigerating machine oil are separated into two layers in the accumulator. Accordingly, it is an object of the present invention to provide an air conditioner in which the efficiency of returning oil to the compressor is improved, thereby improving reliability.
[0012]
[Means for Solving the Problems]
In order to solve the above problems and achieve the object, an air conditioner of the present invention is provided on a suction side of a compressor constituting a refrigeration cycle, and introduces refrigerant evaporated in a heat exchanger to perform gas-liquid separation. A hot gas bypass circuit that includes an accumulator that guides the separated gas refrigerant to the compressor and guides the hot gas discharged from the compressor to a part of the hot gas, and a hot gas bypass circuit that is provided in the hot gas bypass circuit. An on-off valve that is controlled to open and close according to set conditions is provided.
[0013]
By adopting the means for solving such a problem, even when the liquid refrigerant and the oil are separated into two layers in the accumulator, the liquid refrigerant and the oil are surely mixed.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0015]
FIG. 1 is a configuration diagram of a refrigeration cycle of an air conditioner, and FIG. 2 is a cross-sectional view illustrating a structure of an accumulator used in the refrigeration cycle.
[0016]
One port of the four-way switching valve 2 is connected to the refrigerant pipe P connected to the discharge part of the compressor 1, and the outdoor heat exchanger 3 is connected to the refrigerant pipe P connected to the other port of the four-way switching valve 2. An electronic automatic expansion valve 4 and an indoor heat exchanger 5 which are expansion devices are sequentially provided, and are connected to other ports of the four-way switching valve 2.
[0017]
The refrigerant pipe connected to the remaining ports of the four-way switching valve 2 is inserted into the accumulator 6 as an inlet pipe Pa that is a primary side of the accumulator 6 described later. The secondary side of the accumulator 6 communicates with the suction cup 7 provided at the suction part of the compressor 1 as an outlet pipe Pb.
[0018]
Thus, the air conditioner is provided with the heat pump type refrigeration cycle circuit K, and the discharge side refrigerant pipe P of the compressor 1 and the accumulator 6 are communicated with each other by the hot gas bypass circuit G described later.
[0019]
The bypass pipe 11 constituting the hot gas bypass circuit G has one end connected to the compressor discharge side refrigerant pipe P and the other end connected to the bottom of the accumulator tank 10.
[0020]
An on-off valve 12 and a capillary tube 13 are connected in series in the middle of the bypass pipe 11. In particular, the on-off valve 12 includes an electromagnetic coil unit electrically connected to a control unit (control means) 15, and is controlled to open and close based on a control signal from the control unit 15.
[0021]
The accumulator 6 includes a tank 10 having a closed structure, an introduction pipe Pa inserted into the inside of the tank 10 from the top and having an open end located at the top of the tank, and a portion near the bottom of the tank inserted from the top of the tank 10 to the inside. A bent portion b that is bent in a substantially U-shape is provided, and an open end c is provided with an introduction pipe Pb located above the tank 10.
[0022]
The leading ends of the introduction pipe Pa and the discharge pipe Pb are provided at positions not opposing each other. Although the opening at the end of the introduction pipe Pa is closed by a closing plate 16, the refrigerant can be guided into the tank 10 through a hole 17 provided near the end.
[0023]
An oil return hole 18 is provided in the bent portion b of the outlet pipe Pb in the tank 10. The position of the oil return hole 18 is provided at the lowermost part of the curved portion c so that the amount of oil pool is minimized in a normal operation state in which the liquid refrigerant does not pool.
[0024]
As described above, the bottom of the tank 10 forming the accumulator 6 is connected to the bypass pipe 11 forming the hot gas bypass circuit G, and the bypass pipe 11 is provided with the on-off valve 12 and the capillary tube 13.
[0025]
In the air-conditioning apparatus having the above-described configuration, when the cooling operation is selected, the high-temperature and high-pressure refrigerant gas discharged from the compressor 1 is guided as indicated by a solid arrow in the drawing. The refrigerant evaporates in the indoor heat exchanger 5 to absorb the heat of evaporation from the indoor air, dehumidify and lower the temperature of the indoor air, and obtain a cooling effect.
[0026]
When the heating operation is selected, a high-temperature and high-pressure refrigerant gas discharged from the compressor 1 is guided as indicated by a broken line arrow in the figure. The refrigerant is condensed in the indoor heat exchanger 5 to release heat of condensation to the indoor air, thereby increasing the temperature of the indoor air to obtain a heating effect.
[0027]
During both the cooling operation and the heating operation, the evaporated refrigerant is introduced into the accumulator tank 10 via the introduction pipe Pa, and a gas-liquid separation operation is performed. The separated gas refrigerant is sucked into the compressor 1 from the outlet pipe Pb. The separated liquid refrigerant accumulates at the bottom of the tank 10, evaporates and gasifies with the passage of time, and is sucked into the compressor 1.
[0028]
FIG. 3A schematically shows a state inside the accumulator 6 when the heating operation is started under extremely low temperature conditions.
When the compressor 1 is started to perform the heating operation, a large amount of the liquid refrigerant in the refrigeration cycle temporarily accumulates in the accumulator 6. At this time, a large amount of oil is also discharged from the compressor 1 into the refrigeration cycle, and these oils also stay in the accumulator 6 together with the liquid refrigerant.
[0029]
That is, from the relationship of specific gravity, there is a layer R of the liquid refrigerant on the lower side of the tank 10 constituting the accumulator 6, and a layer L of the refrigerating machine oil above the layer R of the liquid refrigerant. Has become.
[0030]
In such a case, the liquid refrigerant and the refrigerating machine oil are sucked from the oil return hole 18 in accordance with the flow differential pressure, but particularly at low temperatures, the head difference due to the height of the accumulator tank 10 and the viscosity of the refrigerating machine oil increase. The return characteristics deteriorate.
[0031]
FIG. 3B is a diagram schematically showing a state inside the accumulator 6 when the on-off valve 12 provided in the hot gas bypass circuit G is opened under the above-described conditions.
[0032]
By opening the on-off valve 12 of the hot gas bypass circuit G connected to the discharge side of the compressor 1, part of the hot gas discharged from the compressor 1 is guided to the accumulator 6 via the bypass pipe 11.
[0033]
The hot gas led to the bypass pipe 11 is injected into the accumulator tank 10 from the bottom thereof in a state of being blown up. The liquid refrigerant layer R and the refrigerating machine oil layer L formed in the tank 10 are efficiently stirred by the injected hot gas, quickly evaporated and gasified, and guided to the compressor 1 via the outlet pipe Pb.
[0034]
That is, by bypassing the hot gas into the accumulator tank 10, the liquid refrigerant in the tank 10 can be quickly discharged to improve the return characteristics, and the reliability of the compressor 1 can be maintained.
[0035]
FIG. 4 shows the oil / refrigerant concentration of the ester oil-based refrigeration oil and the liquid separation characteristics of the refrigerant / refrigeration oil. In the figure, "insoluble" indicates a state in which the oil and the liquid refrigerant are not completely dissolved, and "compatible" indicates that the oil and the liquid refrigerant are almost completely melted and are in a substantially transparent state. "Suspension" refers to a state in which oil is dissolved to some extent in a refrigerant, but there are many portions that do not melt, and the temperature is high and the oil becomes bubbles and becomes cloudy.
[0036]
In a certain region, the refrigerating machine oil and the liquid refrigerant are separated into two layers in the accumulator 6, and the refrigerating machine oil is located above the liquid refrigerant. As it is, it is not possible to suck the refrigerating machine oil unless all the liquid refrigerant is sucked. While the liquid refrigerant is being sucked, the refrigerating machine oil does not return to the compressor at all, and there is a danger that the oil in the compressor 1 runs short and is damaged.
[0037]
Here, the provision of the hot gas bypass circuit G allows the liquid refrigerant to flow due to the stirring effect of the hot gas even if there is an excessive liquid back and the two-layer separation of the refrigerating machine oil and the liquid refrigerant occurs inside the accumulator 6. The evaporation action is promoted, and the oil return to the compressor 1 is improved.
[0038]
Further, since there is no need to provide a plurality of oil return holes as in the prior art [Patent Document 1], the amount of oil returned along with the amount of liquid returned to the compressor does not increase, and the reliability of the compressor does not decrease. .
[0039]
FIG. 5A is a diagram illustrating a structure of an accumulator 6A according to another embodiment, and FIG. 5B is a configuration diagram of a refrigeration cycle of an air conditioner including the accumulator 6A.
[0040]
Since the refrigeration cycle circuit K itself is not particularly changed, the same number is assigned and a new description is omitted. The bypass pipe 11 configuring the hot gas bypass circuit G is connected to a lower part of the side surface of the accumulator tank 10.
[0041]
The accumulator 6A includes a tank 10, an inlet pipe Pa, a lead pipe Pb having a bent part b, and an oil return hole 18 opened in the bent part b of the lead pipe Pb.
[0042]
To further explain the connection position of the bypass pipe 11 to the tank 10 and the position of the oil return hole 18 corresponding thereto, the oil return hole 18 is provided at a position 180 degrees from the connection position of the tank 10 of the bypass pipe 11.
[0043]
That is, as shown in the figure, if the bypass pipe 11 is connected to the lower part of the left side of the tank 10, the oil return hole 18 is located on the right side of the bent part b bent in the left-right direction of the outlet pipe Pb. It is opened.
[0044]
If the bypass pipe 11 is connected to the back side of the tank 10 as shown by a two-dot chain line in the figure, the oil return hole 18 opens to the near side of the bent portion b. In any case, the connection height position Ha of the bypass pipe 11 is selected to be higher than the inner height Hb in the bent portion b of the outlet pipe Pb.
[0045]
With such a configuration, when the on-off valve 12 of the hot gas bypass circuit G is opened and the hot gas is guided to the accumulator tank 10, the hot gas goes upward from the connection position of the bypass pipe 11 due to buoyancy.
[0046]
Therefore, the hot gas that has flowed out of the bypass pipe 11 is not directly sucked into the oil return hole 18 (short circuit), and the liquid refrigerant can be efficiently stirred to avoid two-layer separation.
[0047]
When the refrigerant used in the refrigeration cycle is a high-pressure refrigerant such as R32 or R410A, a pressure-resistant design must be made, and as a result, the thickness of the tank 10 of the accumulator 6 increases, and the cost increases.
[0048]
In order to avoid this, it is easiest to increase the height to increase the capacity by reducing the body diameter. However, when the height is increased, the liquid return characteristic and the oil return characteristic due to the head difference in the tank 10 are increased. Worsens.
[0049]
To remedy this kind of problem, the idea is to increase the flow velocity of the refrigerant flowing in the outlet pipe, increase the differential pressure between the outlet pipe and the outside pipe through the oil return hole, and improve the oil return characteristics. However, on the other hand, there is a problem that the pressure loss in the outlet pipe increases and the coefficient of performance decreases.
[0050]
Here, since the hot gas bypass circuit G is provided as described above, even if the height of the tank 10 is increased, the hot gas is blown upward (that is, in the height direction), and the liquid refrigerant and the refrigerating machine oil are removed. Stirring can be performed efficiently, and the effect can be expected regardless of the tank height.
[0051]
Moreover, in the accumulator tank 10 having a high height, the oil return characteristics deteriorate in the direction in which the head difference increases, but the oil return characteristics can be ensured by the stirring action by the hot gas injection and the reduction of the oil viscosity.
[0052]
FIG. 6 shows a flowchart of an embodiment of the control unit 15 that controls the on-off valve 12 provided in the hot gas bypass circuit G.
[0053]
After starting the compressor 1 in step S1, the outside air temperature To detected by the temperature sensor in step S2 is compared with a set outside air temperature To1 stored in the control unit 15 in advance. If To is higher than To1 (YES), the process proceeds to step S3, and the control unit 15 continues the off (closed) state of the on-off valve 12.
[0054]
When To is lower than To1 (NO), it is determined that a large amount of liquid refrigerant is accumulated in the accumulator 6, and the process proceeds to step S4, where the control unit 15 turns on the on-off valve 12. That is, the opening / closing valve 12 is opened and the hot gas is bypassed to the accumulator 6, so that the above-described effects can be obtained.
[0055]
In either step S3 or step S4, the process proceeds to step S5 to operate the timer and wait for a predetermined time t1 to elapse. After elapse of t1, the process proceeds to step S6, where the temperature Td of the refrigerant pipe P connected to the discharge side of the compressor 1 is detected and compared with the set temperature Td1 of the refrigerant pipe P stored in the control unit 15 in advance.
[0056]
When Td is higher than Td1 (YES), the process proceeds to step S7, and the control unit 15 switches the on-off valve 12 to off. That is, it is determined that the discharge gas temperature of the compressor 1 becomes higher than the set value and the refrigerant temperature rises as a whole, and it is not necessary to cause the accumulator 6 to bypass the hot gas, and the on-off valve 12 is closed.
[0057]
If Td is lower than Td1 (NO), the process shifts to step S8 to calculate the temperature ΔTd of the discharge side refrigerant pipe P of the compressor 1 per unit time, and to calculate the discharge side per unit time in the control unit 15 in advance. This is compared with the set temperature ΔTd1 of the refrigerant pipe P.
[0058]
If the calculated temperature ΔTd of the discharge side refrigerant pipe P of the compressor 1 in the unit time is higher than the set temperature ΔTd1 in the unit time stored in the control unit 15 in advance (YES), the process returns to step S7 and returns to the control unit. Reference numeral 15 keeps the on-off valve 12 in the off state.
[0059]
If the calculated temperature ΔTd of the discharge-side refrigerant pipe P of the compressor 1 in the unit time is lower than the set temperature ΔTd1 of the refrigerant pipe P in the unit time stored in the control unit 15 in advance (NO), the process proceeds to step S9. Then, the control unit 15 switches the on-off valve 12 to on, opens it, and causes the hot gas to bypass the accumulator 6.
[0060]
By performing such control, a state in which the liquid refrigerant or the refrigerating machine oil easily stays in the accumulator 6 can be reliably determined, and the effective use of the hot gas bypass can be achieved.
[0061]
FIG. 7A is a configuration diagram of a refrigeration cycle of an air conditioner including a control unit for a hot gas bypass circuit G according to still another embodiment, and FIG. 7B is an actual control flowchart. .
The refrigeration cycle circuit K and the hot gas bypass circuit G are exactly the same as those described above, and the same reference numerals are given here, and a new description will be omitted.
[0062]
As one means of control, a first temperature sensor 21 is attached to the inlet pipe Pa, which is the primary side of the accumulator 6, and a second temperature sensor 22 is attached to the outlet pipe Pb, which is the secondary side. 21 and 22 are electrically connected to a control unit (not shown).
[0063]
When the compressor 1 is started in step U1, the first temperature sensor 21 detects the temperature of the primary side of the accumulator 6 in step U2 and sends the signal to the control unit.
Further, the second temperature sensor 22 detects the temperature on the secondary side of the accumulator 6 and sends the signal to the control unit.
[0064]
The controller compares the temperature difference (T1−T2) between the primary temperature T1 and the secondary temperature T2 with a set temperature difference ΔTa stored in the controller in advance. If the difference between T1 and T2 is equal to or greater than the set temperature difference value ΔTa (YES), it is determined that the liquid refrigerant or the refrigeration oil has accumulated in the accumulator 6, and the process proceeds to step U3 where the on-off valve 12 is turned on and opened. Hot gas is passed to the accumulator 6.
[0065]
If the difference between T1 and T2 is equal to or smaller than the set temperature difference value ΔTa (NO) in step U2, it is determined that the hot gas bypass is unnecessary in the accumulator 6, and the process proceeds to step U4 to open and close the on-off valve 12 Is turned off and closed.
[0066]
Even after the hot gas is bypassed to the accumulator 6 in step U3, the first temperature sensor 21 and the second temperature sensor 22 continue to perform temperature detection and send a signal to the control unit.
[0067]
The control unit compares the temperature difference value ΔTb set separately in step U5. The set temperature difference value ΔTb is a value slightly exceeding 0, and asks whether a certain temperature difference exists between T1 and T2.
[0068]
If the temperature difference between T1 and T2 is equal to or smaller than the set temperature difference value ΔTb (YES), it is determined that the liquid refrigerant or the refrigerating machine oil in the accumulator 6 has been completely discharged and only the refrigerant gas has been generated. 12 is turned off and closed.
[0069]
If the difference between T1 and T2 is equal to or greater than the set temperature difference value ΔTb (NO) in step 5, it is determined that much of the liquid refrigerant or oil remains in the accumulator 6, and the process proceeds to step U3 to open the on-off valve 6 Turn on and release.
[0070]
By providing such a control means, it is possible to prevent unnecessary supply of hot gas and thereby reduce the coefficient of performance. Then, the on-off valve 12 is actuated immediately in response to a change in the state of the accumulator 6, thereby improving the return characteristics due to agitation / evaporation and preventing liquid back.
[0071]
In addition to the above control means, a means (for example, a pressure sensor 23) for detecting the degree of superheat of the refrigerant is provided in the inlet pipe Pa, which is the primary side of the accumulator 6, so that the superheat reaches the target value on the primary side of the accumulator 6. When it has reached and the difference between T1 and T2 is greater than or equal to the set value ΔTa, the on-off valve 12 may be turned on and opened.
[0072]
In any case, the on-off valve 12 is opened only when the difference between the primary side temperature and the secondary side temperature of the accumulator 6 is equal to or greater than the set temperature difference value. In addition, the state of the liquid pool inside is detected, and the stirring action by the hot gas pipe is obtained only when the liquid refrigerant is retained.
[0073]
FIG. 8 is a configuration diagram of a refrigeration cycle of an air conditioner including a hot gas bypass circuit Ga having a further different configuration. The refrigeration cycle circuit K itself is the same as that described above, and the same numbers are assigned and new explanations are omitted.
[0074]
A bypass pipe 11 is branched from a discharge side refrigerant pipe P of the compressor 1. The bypass pipe 11 is provided with an on-off valve 12 and a first capillary tube 25, and is connected to the bottom of the accumulator tank 10.
[0075]
Further, another bypass pipe 11a is branched from a middle portion of the bypass pipe 11 between the on-off valve 12 and the first capillary tube 15, and a second capillary tube 26 is provided in the bypass pipe 11a. , Is connected to the middle of the outlet pipe Pb, which is the secondary side of the accumulator 6.
[0076]
That is, the hot gas bypass circuit Ga divides a part of the hot gas discharged from the compressor 1 and introduces it to the bottom of the accumulator 6, and divides a part of the hot gas discharged from the compressor. And a circuit to be introduced to the secondary side of the accumulator 6.
[0077]
An on-off valve 12 is provided upstream of each circuit, and capillary tubes (throttle devices) 25 and 26 are provided in each circuit. These capillary tubes 25 and 26 are used to control the flow of refrigerant and to adjust the flow rate.
[0078]
In such a configuration, when the liquid refrigerant or the refrigerating machine oil stays in the accumulator 6, the on-off valve 12 is opened to bypass the hot gas, to promote the stirring and evaporation in the accumulator 6, and to improve the return characteristic and the evaporation characteristic. Improve.
[0079]
In addition, even if the gas refrigerant returning to the compressor 1 via the outlet pipe Pb on the secondary side of the accumulator 6 is cooled, hot gas is guided from the circuit including the second capillary tube 26 to heat the refrigerant. .
[0080]
That is, since the hot gas is directly injected into the suction side of the compressor 1 while maintaining the bypass effect to the accumulator 6, the low-pressure start-up after low-temperature start-up or defrosting (defrosting) operation, and the low-pressure state that is remarkably observed at the time of head dropping piping are observed. It has the effect of preventing abnormal lowering.
[0081]
In addition to the effect of countermeasures against liquid refrigerant evaporation and two-layer separation due to the agitating action on the accumulator 6, the effect of heating the suction of the compressor 1 is obtained at the same time. The reliability can be ensured by preventing the cooling.
[0082]
FIG. 9 is a configuration diagram of a refrigeration cycle of a so-called multi-type air conditioner including a combination of a plurality of outdoor units M1 and M2 and a plurality of indoor units (not shown).
[0083]
Each of the outdoor units M1 and M2 accommodates a plurality of compressors 1, a single oil separator 30, a four-way switching valve 2, an outdoor heat exchanger 3, a liquid tank 31, and an accumulator 6. .
[0084]
Further, the outdoor units M1 and M2 are communicated with each other by a balance circuit B.
The balance circuit B includes a branch circuit that directly communicates with the compressors 1 disposed in the outdoor units M1 and M2, and that communicates with the suction side of the compressor 1, the oil separator 30, and the secondary side of the accumulator 31. ing.
[0085]
The outdoor units M1 and M2 are provided with a bypass pipe 11 branched from the refrigerant pipe P between the oil separator 30 and the four-way switching valve 2 and connected to the accumulator 6. A hot gas bypass circuit G having a capillary tube 13 is provided.
[0086]
The outdoor units M1 and M2 communicate with a plurality of indoor units (not shown) via the gas main refrigerant pipe PG and the liquid main refrigerant pipe PL. Each indoor unit houses an indoor heat exchanger, and these constitute a multi-type refrigeration cycle.
[0087]
Depending on the operating conditions, at least one of the plurality of outdoor units (for example, M1) may continue to operate, and the remaining outdoor units (for example, M2) may stop operating.
[0088]
At this time, in the outdoor unit M2 on the stop side, the refrigerant is recovered from the gas main refrigerant pipe PG at the time of cooling through the balance circuit B as shown by a dashed-dotted arrow in the figure during low-pressure balance and cooling.
[0089]
However, when the stopped outdoor unit M2 is gas-balanced, a large amount of refrigerant stagnating in the low-pressure line stays in a liquid state and stays in the accumulator 6 in the stopped outdoor unit M2.
[0090]
When the stopped outdoor unit M2 is restarted according to the operating conditions, the control unit controls the open / close valve 12 of the hot gas bypass circuit G to open. Part of the hot gas discharged from the compressor 1 is guided to the accumulator 6 via the hot gas bypass circuit G, and quickly evaporates the retained liquid refrigerant.
[0091]
As described above, when the stopped outdoor unit M2 is started in a state where the outdoor unit M2 in which all of the mounted compressors 1 are stopped exists, the open / close valve 12 of the hot gas bypass circuit G is set to a predetermined position. By opening the time and introducing the hot gas into the accumulator 6, it is possible to avoid the liquid compression after the start.
[0092]
【The invention's effect】
As described above, according to the present invention, even in a state where two-layer separation of the liquid refrigerant and the refrigerating machine oil has occurred in the accumulator, these liquid refrigerants and the oil are surely mixed to improve the oil return efficiency to the compressor. Thus, there is an effect that the reliability can be improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a refrigeration cycle of an air conditioner according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the accumulator according to the embodiment.
FIG. 3 is a diagram illustrating different states inside the accumulator according to the embodiment.
FIG. 4 is a characteristic diagram in a state where the refrigerant and the refrigerating machine oil are mixed in the accumulator according to the embodiment.
FIG. 5 is a cross-sectional view and a refrigeration cycle configuration diagram of an accumulator according to another embodiment.
FIG. 6 is a control flowchart for an on-off valve of a hot gas bypass circuit according to still another embodiment.
FIG. 7 is a configuration diagram of a refrigeration cycle and a control flowchart for an on-off valve of a hot gas bypass circuit according to still another embodiment.
FIG. 8 is a configuration diagram of a refrigeration cycle according to still another embodiment.
FIG. 9 is a configuration diagram of a refrigeration cycle on the outdoor unit side according to still another embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Compressor, 6 ... Accumulator, G ... Hot gas bypass circuit, 12 ... Open / close valve, 10 ... Tank, Pa ... Introduction pipe, b ... Bending part, Pb ... Outflow pipe, 18 ... Oil return hole, 15 ... Control Unit (control means).

Claims (6)

An air conditioner provided on the suction side of a compressor constituting a refrigeration cycle, including an accumulator for introducing a refrigerant evaporated in a heat exchanger to separate the refrigerant into gas and liquid, and introducing and guiding the separated gas refrigerant to the compressor. In the device,
A hot gas bypass circuit for diverting a part of the hot gas discharged from the compressor and introducing it to the accumulator,
An on-off valve provided in the hot gas bypass circuit and controlled to open and close according to operating conditions. The accumulator has a tank, an introduction pipe connected to the tank, for introducing and guiding the evaporative refrigerant into the tank, and a bent portion that is bent in a substantially U shape near the bottom in the tank, and has an opening at the top of the tank. An outlet pipe for guiding the gas refrigerant, which has been gas-liquid separated from the opening end, to the compressor, and an oil return hole opened at the bent portion of the outlet pipe for guiding the lubricating oil accumulated at the tank bottom to return to the compressor. With
The connection position of the hot gas bypass circuit to the accumulator tank is located at a position 180 degrees from the oil return hole and at a position higher than the inner height of the bent portion of the outlet pipe. 2. The air conditioner according to 1. The air conditioner according to any one of claims 1 and 2, wherein the refrigerant used in the refrigeration cycle is a high-pressure refrigerant such as R410 or R32. The open / close valve provided in the hot gas bypass circuit, when the outside air temperature is lower than the set temperature at the time of starting the heating operation, or when the temperature change of the compressor discharge side refrigerant pipe after the start is lower than the set temperature change. The air conditioner according to any one of claims 1 to 3, further comprising control means for controlling opening. The open / close valve provided in the hot gas bypass circuit includes a control unit that controls the valve to be opened when a difference between the temperature on the primary side of the accumulator and the temperature on the secondary side becomes equal to or higher than a set temperature value. The air conditioner according to any one of claims 1 to 3, wherein The hot gas bypass circuit includes a circuit for diverting a part of the hot gas discharged from the compressor and introducing it to the bottom of the accumulator, and a circuit for diverting a part of the hot gas discharged from the compressor and accumulating the hot gas. 6. The circuit according to claim 1, wherein a circuit to be introduced to the secondary side is provided in parallel, the on-off valve is provided upstream of each circuit, and a throttle device is provided in each circuit. The air conditioner according to any one of the above.

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