JPH08200852A - Refrigerator - Google Patents

Abstract

PURPOSE: To improve the comfortableness of air conditioning by eliminating frequent oil returning. CONSTITUTION: The refrigerator comprises a plurality of outdoor units 2A, 2B, ... and a plurality of indoor units 3A, 3B, ... A plurality of types of coefficients corresponding to the difference of the oil feeding amount fed from a compressing mechanism 21 and the oil returning amount returned to the mechanism 21 are set based on the operating capacity of the mechanism 21, and the coefficient is added corresponding to the capacity of the mechanism 21. When the added value added with the coefficient becomes a predetermined value, the oil returning of a lubricant is executed. Further, when the opening of an indoor motor operated expansion valve 32 is limited, the coefficient is set to a large specific value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus having a plurality of heat source units, and more particularly to a measure for returning oil.

[0002]

2. Description of the Related Art Conventionally, as disclosed in WO94 / 19654, an air conditioner as a refrigeration system has a compressor, a four-way switching valve, an outdoor heat exchanger, and an outdoor electric expansion valve. The two provided outdoor units are connected in parallel to the main liquid line and the main gas line, while the plurality of indoor units provided with an indoor electric expansion valve and an indoor heat exchanger are provided with the main liquid line and the main liquid line. Some are configured to be connected in parallel to the gas line.

During the cooling operation, the refrigerant discharged from the compressor of each outdoor unit is condensed in the outdoor heat exchanger and merges in the main liquid line.
It is decompressed by the indoor electric expansion valve, evaporated by the indoor heat exchanger, divided from the main gas line to each outdoor unit, and returned to the compressor of each outdoor unit.

On the other hand, during the heating operation, the refrigerant discharged from the compressor of each outdoor unit merges in the main gas line and then condenses in the indoor heat exchanger to be diverted from the main liquid line to each outdoor unit. After that, the refrigerant is decompressed by the outdoor electric expansion valve of each outdoor unit, evaporated in the outdoor heat exchanger, and returned to the compressor.

[0005]

In the air conditioner described above, the oil return operation interval is conventionally determined only by the cumulative operation time of the compressor, so that the oil return operation interval is shortened and comfortable air conditioning is achieved. There was a problem that I could not do it.

That is, in the air conditioner equipped with the outdoor unit having one compressor, as shown in FIG. 6, the amount of lubricating oil flowing out from the compressor is proportional to the circulation amount of the refrigerant, That is, it increases as the operating capacity of the compressor increases (see FIG. 6A1). On the other hand, the oil return amount of the circulation amount returning to the compressor increases as the operating capacity of the compressor increases (see Fig. 6B1), but in the region where the operating capacity of the compressor is small, it is slightly smaller than the oil rise amount. When the operating capacity of the compressor becomes larger than the predetermined capacity, it becomes larger than the oil rising amount. Therefore, the oil return operation may be set on the basis of the point M1 at which the oil return amount becomes smaller than the oil upstream amount.

However, in the air conditioner in which a plurality of outdoor units are installed as described above, a plurality of compressors are provided, and in addition, the operating capacity is large and the diameter of the refrigerant pipe is large. As shown in the figure, in a region where the operating capacity of the compressor is small, the oil rise amount is larger and the oil return amount is smaller than that in FIG.

As a result, similar to the above, if the oil return operation is set to be performed on the basis of the point M2 at which the oil return amount is smaller than the oil rising amount, the oil return operation is frequently executed. However, there was a problem that comfort was lost.

The present invention has been made in view of the above points, and an object thereof is to improve comfort of air conditioning by preventing frequent oil return operation.

[0010]

Means for Solving the Problems In order to achieve the above-mentioned object, the means taken by the present invention is one in which the oil return operation interval is made variable in accordance with the relationship between the oil rising amount and the oil returning amount. Is.

Specifically, as shown in FIG. 1, the means taken by the invention according to claim 1 is such that a compression mechanism (21) is first connected to the compression mechanism (21) at one end and branched to the other end. Heat source side heat exchanger (23) to which liquid lines (5L-A, 5L-B, ...) are connected
And a branch gas line (5G-
A, 5G-B, ...) multiple heat source units (2A, 2)
B, ...) are provided. The heat source units (2A, 2B, ...) Are connected in parallel via the branch liquid lines (5L-A, 5L-B, ...) And the branch gas lines (5G-A, 5G-B, ...). Main liquid line (4 L) and main gas line (4 L
G) is provided. Further, a plurality of utilization units (3A) having an expansion mechanism (32) and a utilization side heat exchanger (31) are connected in parallel to the main liquid line (4L) and the main gas line (4G). , 3B, ...) are provided for the refrigerator. A plurality of types of coefficients corresponding to the difference between the amount of oil rising from the compression mechanism (21) and the amount of oil returned to the compression mechanism (21) are set based on the operating capacity of the compression mechanism (21). Coefficient calculation means (81) for adding the above-mentioned coefficient corresponding to the operating capacity of the compression mechanism (21) is provided. In addition, when the added value added by the coefficient calculation means (81) reaches a predetermined value, an oil return operation is executed and the oil return control means (82) resets the coefficient calculation means (81).
Is provided.

The means taken by the invention according to claim 2 is the coefficient calculating means (81) according to the invention of claim 1 above.
However, when the opening degree of the expansion mechanism (32) is limited, the coefficient is set to a large special value.

[0013]

With the above construction, in the invention according to claim 1,
Coefficient calculation means (81) during cooling operation or heating operation
Is a coefficient corresponding to the difference between the amount of oil flowing out from the compression mechanism (21) of each heat source unit (2A, 2B, ...) And the amount of oil returned to the compression mechanism (21). Since a plurality of types are set based on the capacity, the above coefficient will be added according to the operating capacity of the compression mechanism (21). The oil return control means (82) is provided with the coefficient calculation means (81).
When the addition value obtained by adding becomes a predetermined value, for example, when it becomes 100, the oil return operation is executed, and the coefficient calculating means (81).
Will be reset.

In the invention according to claim 2, the coefficient calculating means (81) reduces the refrigerant circulation amount when the opening degree of the expansion mechanism (32) of the utilization unit (3A, 3B, ...) Is limited. Therefore, the coefficient is set to a large special value, and the oil return operation is executed early.

[0015]

Therefore, according to the first aspect of the present invention,
Since the oil return operation is executed at intervals corresponding to the oil rising amount and the oil return amount, the oil return can be reliably performed, so that the operation with high reliability can be executed.

Further, since the interval of the oil return operation is not set on the basis of the state where the oil return is difficult to be performed, the oil return operation is not frequently performed, so that the comfort can be improved.

Further, according to the second aspect of the invention, when the opening degree of the expansion mechanism (32) is set, the interval of the oil return operation can be shortened, so that the oil shortage can be reliably prevented. You can

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

-Overall Structure-As shown in FIG. 2, the air conditioner (10) as a refrigerating device in this embodiment has three outdoor units (2A, 2B,
2C) and three indoor units (3A, 3B, 3C) are connected in parallel to the main liquid line (4L) and the main gas line (4G), respectively.

Each outdoor unit (2A, 2B, 2C) includes a compression mechanism (21), a four-way switching valve (22), and an outdoor fan (23-F).
A heat source unit is configured by including an outdoor heat exchanger (23), which is a heat source-side heat exchanger arranged in close proximity, and an outdoor electric expansion valve (24). The refrigerant pipe (25) is connected to one end on the gas side of the outdoor heat exchanger (23), and the branch liquid lines (5L-A, 5L-B, 5L-C) are connected to the other end on the liquid side. Has been done.

The gas side refrigerant pipe (25) is switchably connected to the discharge side and the suction side of the compression mechanism (21) by a four-way switching valve (22), while the branch liquid line (5L-A) is connected. ， 5L-
B, 5L-C) is provided with the outdoor electric expansion valve (24) and is connected to the outdoor heat exchanger (23) and the main liquid line (4L). And, each of the above branch liquid lines (5L-A, 5L-B,
5L-C) and the main liquid line (4L) are connected to each other by a receiver (11), and the receiver (11) connects the branched liquid lines (5L-A, 5L-B, 5L-C) to each other. Main liquid line (4L)
And are connected.

A branch gas line (5G-A, 5G-B, 5G-C) is connected to the compression mechanism (21) through a refrigerant pipe (25) and a four-way switching valve (22), and the branch Gas line (5G-A, 5G
-B, 5G-C) uses a four-way switching valve (22) to compress the compression mechanism (2
It is switchably connected to the suction side and the discharge side of 1) and is connected to the main gas line (4G). An accumulator (26) is provided in the refrigerant pipe (25) between the suction side of the compression mechanism (21) and the four-way switching valve (22).

Of the three outdoor units (2A, 2B, 2C), the first outdoor unit (2A) is the master unit, and the second outdoor unit (2B) and the third outdoor unit (2C) are the slave units. The first outdoor unit (2A) is replaced by the second outdoor unit (2A).
B) and the third outdoor unit (2C) are configured to be driven in advance, and the first outdoor unit (2A), the second outdoor unit (2B), and the third outdoor unit (2C) are mainly compression mechanisms ( The composition of 21) is different. That is, the compression mechanism (21) of the first outdoor unit (2A) is, as shown in FIG. 3, an inverter-controlled variable capacity upstream compressor (COMP-1) whose capacity is controlled in multiple stages, Constant capacity type downstream compressor (COMP-2) controlled by two types of operation and stop
It is configured as a so-called twin type in which and are connected in parallel.
On the other hand, as shown in FIG. 4, the compression mechanism (21) of the second outdoor unit (2B) and the third outdoor unit (2C) includes an upstream compressor (COMP-1) and a downstream compressor (COMP-2). 2) and 2) are both constant capacity compressors that are controlled to operate and stop, and the upstream compressor (COMP-1) and the downstream compressor (COMP-2) are connected in parallel. It is configured as a so-called twin type. And which outdoor unit (2A, 2B, 2C)
Even in the upstream side compressor (COMP-1)
It is configured to drive prior to MP-2).

On the other hand, each indoor unit (3A, 3B, 3C) is
An indoor heat exchanger (31), which is a usage-side heat exchanger in which an indoor fan (31-F) is arranged in close proximity, and an indoor electric expansion valve (32), which is a usage-side expansion mechanism, constitute a usage unit. ing. The indoor heat exchanger (31) is connected to the indoor liquid pipe (3
L) and the main liquid line (4) via the indoor gas pipe (3G)
L) and the main gas line (4G), and an indoor electric expansion valve (32) is provided in the indoor liquid pipe (3L).

-Structure of Piping Unit- The air conditioner (10) is provided with a piping unit (12) which is a connection circuit section, and the piping unit (12).
Is the branch liquid line (5L) of each outdoor unit (2A, 2B, 2C).
-A, 5L-B, 5L-C) and branch gas lines (5G-A, 5G-B, 5G)
-C) and main liquid line (4L) and main gas line (4L)
G) is connected to.

Specifically, the branch liquid lines (5L-A, 5L-B, 5L
-C) is a branch liquid pipe (5LAa, 5LBa, 5LCa) extending outside from each outdoor unit (2A, 2B, 2C) and the branch liquid pipe (5LA).
a, 5LBa, 5LCa) branch liquid passage (5LAb, 5)
LBb, 5LCb). The branch gas lines (5G-A, 5G-B, 5G-C) are the outdoor units (2A, 2B, 2
Branch gas pipe extending from C) to the outside (5GAa, 5GBa, 5GCa)
And a branch gas passage (5GAb, 5GBb, 5GCb) continuous to the outer end of the branch gas pipe (5GAa, 5GBa, 5GCa).

The main liquid line (4L) is connected to the indoor liquid pipe (3L) of the indoor unit (3A, 3B, 3C), and the main liquid pipe (4L-a). ) And the branch liquid passage (5L) of each outdoor unit (2A, 2B, 2C)
Ab, 5LBb, 5LCb) and the main liquid passage (4L-b) that communicates via the receiver (11). The main gas line (4G) is a main gas pipe (4G-a) connected to the indoor gas pipe (3G) of the indoor unit (3A, 3B, 3C).
And a branch gas passage (5GAb, 5GBb, 5Gb, 5Gb, which is continuous with one end of the main gas pipe (4G-a) and which is provided in each outdoor unit (2A, 2B, 2C).
5GCb) consists of a continuous main gas passage (4G-b).

The piping unit (12) is a branch liquid line (5L-A, 5L) on the side of each outdoor unit (2A, 2B, 2C).
-B, 5L-C) branch liquid passage (5LAb, 5LBb, 5LCb) and branch gas line (5G-A, 5G-B, 5G-C) branch gas passage (5GA)
b, 5GBb, 5GCb), the main liquid passage (4L-b) of the main liquid line (4L) and the main gas passage (4G-b) of the main gas line (4G), and the receiver (11) are integrated. It is formed and unitized.

Further, the piping unit (12) has a first
The gas on-off valve (VR-1) and the second gas on-off valve (VR-2) are integrated into a unit. The first gas on-off valve (VR-1)
Is the branch gas passage (5GBb) on the second outdoor unit (2B) side
The second gas opening / closing valve (VR-2) is provided in the branch gas passage (5GCb) on the side of the third outdoor unit (2C) while the opening / closing mechanism is provided to open and close the branch gas passage (5GBb). Thus, an opening / closing mechanism for opening / closing the branch gas passage (5GCb) is configured.

The first gas on-off valve (VR-1) and the second gas on-off valve (VR-2) are external pressure equalizing type reversible valves and connected to the pilot circuit (50). The pilot circuit (50) has two check valves (CV, CV), a branch gas passage (5GAb) on the first outdoor unit (2A) side, and a first outdoor unit (2A) side described later. The first oil leveling auxiliary passage (77-
A) is provided with a high pressure circuit (51) that is connected to (A) and guides high pressure refrigerant, and has two check valves (CV, CV), and
A branch gas passage (5GAb) on the outdoor unit (2A) side and a first pressure equalizing auxiliary passage (77 on the first outdoor unit (2A) side, which will be described later.
-A) Low voltage circuit (52) connected to and maintaining a low voltage state
It has and.

The pilot circuit (50) includes a high pressure circuit (51) and a low pressure circuit (52) by means of a switching valve (50-S).
And the first gas on-off valve (VR-1) and the second gas on-off valve (VR-
2) is switched and connected to control the first gas on-off valve (VR-1) to be fully closed when the second outdoor unit (2B) is stopped during heating operation, and the third outdoor unit during heating operation. The second gas on-off valve (VR-2) is controlled to be fully closed when the unit (2C) is stopped.

The second outdoor unit (2B) and the third outdoor unit
The outdoor electric expansion valve (24, 24) of the outdoor unit (2C) is not provided in the piping unit (12), but corresponds to the first gas on-off valve (VR-1) and the second on-off valve, It also serves as an opening / closing mechanism that opens and closes each of the branched liquid lines (5L-A, 5L-B, 5L-C), and the second outdoor unit (2B) and the third outdoor unit (2C) during cooling operation and heating operation. ) Is configured to be fully closed when stopped.

-Structure of Pressure Equalizing Line- A pressure equalizing line (60) is connected between the outdoor units (2A, 2B, 2C), and the pressure equalizing line (60) connects the outdoor units ( 2A, 2B, 2C) outdoor heat exchanger (23)
Is connected to the gas side refrigerant pipes (25, 25, 25) and is configured to allow bidirectional refrigerant flow between the outdoor units (2A, 2B, 2C). Furthermore, the pressure equalizing line (60)
Has a pressure equalizing passage (62) continuously formed at the outer ends of pressure equalizing tubes (61-A, 61-B, 61-C) extending outward from the outdoor units (2A, 2B, 2C). Then, the pressure equalizing passage (62)
Is formed in the piping unit (12) and has a first pressure equalizing valve (in the branch pipe portion branched from the first outdoor unit (2A) side to the second outdoor unit (2B) side and the third outdoor unit (2C) side. SVB
1) and the second pressure equalizing valve (SVB2) are provided.

The first pressure equalizing valve (SVB1) is fully closed when the cooling operation of the second outdoor unit (2B) is stopped to prevent the refrigerant from flowing into the second outdoor unit (2B), and the second pressure equalizing valve (SVB1) is closed. (SVB
2) is configured to be fully closed when the cooling operation of the third outdoor unit (2C) is stopped to prevent the refrigerant from flowing to the third outdoor unit (2C).

-Structure of Auxiliary Refrigerant Circuit- Each of the outdoor units (2A, 2B, 2C) has the structure shown in FIGS.
As shown in FIG. 7, an oil return mechanism (70) for returning lubricating oil to the compression mechanism (21) is provided, and the oil return mechanism (70) includes an oil separator (71) and a first oil return pipe (72). ) And the second oil return pipe (7
3) and an oil leveling bypass pipe (74). On the other hand, the downstream compressor (COMP-2) that is a part of the refrigerant pipe (25).
The pressure loss of the suction pipe (25-S) of the compressor is set larger than that of the suction pipe (25-S) of the upstream compressor (COMP-1).
The oil equalizing pipe (75) is connected between MP-1 and COMP-2.
As a result, the lubricating oil is supplied from the upstream compressor (COMP-1) on the high pressure side to the downstream compressor (COMP-2) on the low pressure side.

The oil separator (71) includes an upstream side compressor (COMP-1) and a downstream side compressor (CO) which are a part of the refrigerant pipe (25).
It is arranged at the confluence of the discharge pipe (25-D, 25-D) with MP-2),
The discharge pipes (25-D, 25-D) of each compressor (COMP-1, COMP-2) are equipped with check valves (CV-1, CV-2). Furthermore, between the upper part of the upstream compressor (COMP-1) and the downstream side of the check valve (CV-1) of the discharge pipe (25-D), and the downstream compressor (COMP-
Oil discharge pipes (76, 76) are connected between the upper part of 2) and the downstream side of the check valve (CV-2) of the discharge pipe (25-D). Then, the oil discharge pipes (76, 76) are, for example, discharge pipes (25 -D,
25-D). Further, the check valve (CV-1) of the upstream compressor (COMP-1) has a pipe line to ensure that the lubricating oil is discharged from the discharge pipe (25-D) when the refrigerant circulation amount is small. Resistance is added.

The first oil return pipe (72) is provided with a capillary tube (CP) and has an oil separator (71) and a first compressor (CO).
MP-1) suction pipe (25-S) and oil separator (71)
The lubricating oil accumulated in is constantly returned to the first compressor (COMP-1). Further, the second oil return pipe (73) is
It is equipped with an oil return valve (SVP2) and is connected to the oil separator (71) and the suction pipe (25-S) of the second compressor (COMP-2). The lubricating oil that has been opened to and collected in the oil separator (71) is returned to the suction side of the compression mechanism (21).

The oil equalizing bypass pipe (74) is provided with an oil equalizing valve (SV
O1) and one end of the second oil return pipe (73) is an oil return valve (SV
The other end is connected to the pressure equalizing pipes (61-A, 61-B, 61-C) of the pressure equalizing line (60) upstream of P2). Then, in order to perform an oil leveling operation together with the oil leveling bypass pipe (74), the pressure leveling passage (62) of the pressure leveling line (60) is provided with
1st pressure equalization auxiliary passage (77-A) and 2nd oil equalization auxiliary passage (77-B)
And the third pressure equalization auxiliary passage (77-C) are connected, and the respective pressure equalization auxiliary passages (77-A, 77-B, 77-C) are incorporated in the piping unit (12).

The first pressure equalizing auxiliary passage (77-A) has one end on the first outdoor unit (2A) side of the pressure equalizing passage (62) and the other end on the second outdoor unit (2B) and the third outdoor unit. It is connected to the merging part of the branch gas passage (5GBb, 5GCb) of the unit (2C),
It is equipped with an oil leveling auxiliary valve (SVY1) and a check valve (CV). The second pressure equalizing auxiliary passage (77-B) has a pressure equalizing passage (62) at one end.
On the side of the second outdoor unit (2B), the other end is connected to the branch gas passage (5GAb) of the first outdoor unit (2A), and the second oil auxiliary auxiliary valve (SVY2) and the check valve (CV) are connected. I have it. The third pressure equalizing auxiliary passage (77-C) has one end on the side of the third outdoor unit (2C) of the pressure equalizing passage (62) and the other end of the branch gas passage (5GAb) of the first outdoor unit (2A). And is provided with a third oil leveling auxiliary valve (SVY3) and a check valve (CV).

The oil equalizing valve (SVO1, SVO1, SVO1)
And the first to third oil leveling auxiliary valves (SVY1, SVY2, SVY3) are 2
When performing the oil equalization operation (2 to 3 minutes) once every ~ 3 hours,
Alternatively, it is configured to be opened and closed when the above-described oil-equalizing operation is performed, such as after the end of the oil return operation or after the defrost operation during the heating operation.

The branch gas passage (5GBb) of the second outdoor unit (2B) and the second pressure equalizing auxiliary passage (77-B), and the branch gas passage (5GCb) of the third outdoor unit (2C). ) And the third pressure equalizing auxiliary passage (77-C) have a capillary tube (CP), and the first gas on-off valve (VR-1) is provided during heating operation.
Also, auxiliary refrigerant passages (12-s, 12-s) for releasing refrigerant leaking from the second gas on-off valve (VR-2) are connected.

The outdoor units (2A, 2B, 2C) mentioned above
A liquid injection pipe (2j) is connected to the branch liquid pipes (5LAa, 5LBa, 5LCa) of the liquid injection pipe (2j), and the liquid injection pipe (2j) is branched into two, and the injection valves (SVT1, SVT2) and the capillary are connected. Tube (CP,
CP) to the upstream compressor (COMP-1) and the downstream compressor (COMP-2). The above liquid injection valves (SVT1, SVT2) are used for each compressor (COMP-1, COMP
-2) It is configured to open when the discharge gas refrigerant temperature rises excessively to lower the discharge gas refrigerant temperature.

A hot gas bypass pipe (2h) is connected between the discharge side and the suction side of the compression mechanism (21) in each of the outdoor units (2A, 2B, 2C), and the hot gas bypass pipe (2h). Is equipped with a hot gas valve (SVP1) and is connected to the upstream side of the four-way switching valve (22) and the upstream side of the accumulator (26). The hot gas valve (SVP1) is configured to equalize the discharge side and the suction side of the compression mechanism (21) mainly at the time of starting or the like.

An auxiliary bypass pipe (2b) is connected between the suction side and the discharge side of the compression mechanism (21) in the second outdoor unit (2B) and the third outdoor unit (2C). The bypass pipe (2b) is provided with a check valve (CV) that allows the refrigerant flow only from the suction side to the discharge side of the compression mechanism (21), and the upstream side of the four-way switching valve (22) and the accumulator (26). It is connected to the upstream side. The auxiliary bypass pipe (2b) is provided with a branch gas line (5G-B, when the second outdoor unit (2B) and the third outdoor unit (2C) are stopped during the heating operation.
The refrigerant of 5G-C) is configured to bypass the compression mechanism (21) and be sucked into the first outdoor unit (2A).

Further, the receiver (11) and the pilot circuit (50) low-voltage circuit (52) in the piping unit (12).
A gas vent passage (12-g) is connected between and. The gas vent passage (12-g) is equipped with a gas vent valve (SVTG) and is incorporated in the piping unit (12), and the gas vent valve (SVTG)
Is configured to open for high pressure protection during cooling operation and low pressure protection during heating operation.

-Structure of Sensors-Various sensors are provided in the outdoor units (2A, 2B, 2C) and the indoor units (3A, 3B, 3C).
In each of the outdoor units (2A, 2B, 2C), the outdoor air temperature T1
Outdoor temperature exchanger (23) that detects the outside temperature sensor (Th-1)
An outdoor liquid temperature sensor (Th-2) for detecting the liquid refrigerant temperature T2 of the outdoor heat exchanger (23) is located near the branch liquid line (5L-A, 5L-).
(B, 5L-C), the discharge refrigerant temperature T of the compression mechanism (21)
Discharge temperature sensor (Th31, Th32) that detects 3 sets the suction refrigerant temperature T4 of the compression mechanism (21) to the discharge pipe (25-D, 25-D) of each compressor (COMP-1, COMP-2). A suction temperature sensor (Th-4) for detection is connected to the suction side refrigerant pipe (25) of the compression mechanism (21).
The oil temperature sensor (Th51, Th52) that detects the oil temperature To of the lubricating oil inside each compressor (COMP-1, COMP-2) is connected to each compressor (COMP-
1, COMP-2) is provided below the outdoor heat exchanger (23), and an outdoor gas temperature sensor (Th-6) for detecting the gas refrigerant temperature T6 is provided in each of the gas-side refrigerant pipes (25).

Further, in the first outdoor unit (2A),
The high-pressure pressure sensor (SP-H) that detects the discharge refrigerant pressure PH of the compression mechanism (21) is the discharge-side refrigerant pipe (25) of the compression mechanism (21).
In addition, a low-pressure pressure sensor (SP-L) for detecting the suction refrigerant pressure PL of the compression mechanism (21) is provided in the suction-side refrigerant pipe (25) of the compression mechanism (21), and The high pressure protective switch (H-PS, H-PS) that operates when the discharge refrigerant pressure of (COMP-1, COMP-2) reaches a specified high pressure is used for each compressor (CO
It is installed in the discharge pipe (25-D, 25-D) of MP-1, COMP-2).

Further, since the second outdoor unit (2B) and the second outdoor unit (2B) are provided with the pressure equalizing line (60), the high pressure sensor (SP) like the first outdoor unit (2A) is provided. -H) and low pressure sensor (SP-L) are not provided, and a high pressure protective switch (H-PS) that operates when the discharge refrigerant pressure of each compressor (COMP-1, COMP-2) reaches a specified high pressure. , H-PS)
Is the discharge pipe (25-D, 25-D) of each compressor (COMP-1, COMP-2)
In addition, the high pressure control switch (HPSC) that operates when the discharge refrigerant pressure of the compression mechanism (21) becomes a predetermined high pressure lower than the high pressure protection switch (H-PS, H-PS) discharges the compression mechanism (21). A low-pressure protective switch (L-PS), which operates when the suction refrigerant pressure of the compression mechanism (21) reaches a predetermined low pressure, is provided in each of the side refrigerant pipes (25) in each of the suction side refrigerant pipes (25) of the compression mechanism (21). Has been.

On the other hand, in each indoor unit (3A, 3B, 3C), a room temperature sensor (Th-7) for detecting the indoor air temperature T7 is provided near the indoor fan (31-F), and the indoor heat exchanger (31 ), An indoor liquid temperature sensor (Th-8) for detecting the liquid refrigerant temperature T8 of the indoor heat exchanger (31) detects the gas refrigerant temperature T9 of the indoor heat exchanger (31) in the indoor liquid pipe (3L). ) Is indoor gas piping (3G)
Are provided respectively.

-Control Configuration- The air conditioner (10) is provided with a controller (80), and the controller (80) includes the sensors (Th11 to SP).
-L) and switch (H-PS to L-PS) detection signals are input,
The opening degree of each electric expansion valve (24-32), the capacity of the compression mechanism (21), etc. are controlled based on the detection signal of each sensor (Th11-SP-L).

As a feature of the present invention, the controller (80) is provided with a coefficient calculation means (81) for oil return operation and an oil return control means (82). The coefficient calculation means (81) has a coefficient corresponding to the difference between the oil upstream amount flowing out from the compression mechanism (21) of each outdoor unit (2A, 2B, 2C) and the oil return amount returning to the compression mechanism (21). A plurality of types are set based on the operating capacity of the compression mechanism (21), and the coefficient is added according to the operating capacity of the compression mechanism (21). Further, the coefficient calculating means (81) is configured to set the coefficient to a large special value when the opening degree of the indoor electric expansion valve (32) of the indoor unit (3A, 3B, 3C) is limited. .

The oil return control means (82) executes the oil return operation in the cooling operation cycle when the added value added by the coefficient calculation means (81) reaches a predetermined value, for example, 100, and the coefficient calculation means (82). 81) is configured to reset.

Specifically, first, each outdoor unit (2A, 2
The compression mechanism (21) of (B, 2C) is controlled as shown in Tables 1 and 2 according to the air conditioning load such as the cooling load or the heating load, and the upstream side compressor in the first outdoor unit (2A). The capacity of (COMP-1) is gradually increased and decreased, and other compressors (COMP-1, COMP-2) are operated and stopped.

[0054]

[Table 1]

[Table 2]

Then, as shown in FIG.
As shown in, the oil upflow amount increases with the oil return amount as the capacity of the compression mechanism (21) is increased from step 01 to step 04, and thereafter, the oil upflow amount slightly decreases in step 13 and step 14. However, after that, the amount of oil rising increases again in step 21. Then, thereafter, the amount of returned oil largely increases with respect to the amount of oil rise.

Therefore, the coefficient calculating means (81) is shown in Table 3
The coefficient a is set as shown in, and the compression mechanism (2
The coefficient a corresponding to the capacity of 1) will be added.

[0057]

[Table 3]

Further, when the opening degree of the indoor electric expansion valve (32) is limited by the overload of the cooling, the coefficient calculating means (81) reduces the refrigerant circulation amount.
It is set to 6.

<Operation of Air Conditioning Operation> Next, the control operation of the air conditioning operation in the air conditioner (10) will be described.

First, during the cooling operation, the four-way switching valve (22) is switched to the solid line in FIGS. 3 and 4, and the high pressure discharged from the compression mechanism (21) of each outdoor unit (2A, 2B, 2C). The gas refrigerant is condensed in the outdoor heat exchanger (23) to become a liquid refrigerant,
This liquid refrigerant flows into the main liquid passage (4L) of the piping unit (12).
-Join at b). After that, the liquid refrigerant is decompressed by the indoor electric expansion valve (32) and then evaporated in the indoor heat exchanger (31) to become a low-pressure gas refrigerant. This gas refrigerant is branched into each branch gas in the piping unit (12). The flow is divided into the passages (5GAb, 5GBb, 5GCb), returned to the compression mechanism (21) of each outdoor unit (2A, 2B, 2C), and this circulation operation is repeated.

On the other hand, during the heating operation, the four-way switching valve (22) is switched to the broken lines in FIGS. 3 and 4, and discharged from the compression mechanism (21) of each outdoor unit (2A, 2B, 2C). The high-pressure gas refrigerant flows into the piping unit (12), merges in the main gas passage (4G-b) of the piping unit (12), and then flows into the indoor units (3A, 3B, 3C). Then, this gas refrigerant is condensed in the indoor heat exchanger (31) to become a liquid refrigerant, and this liquid refrigerant is the main liquid passage (4L-
It is branched from b) to the branch liquid passages (5LAb, 5LBb, 5LCb) on the side of each outdoor unit (2A, 2B, 2C). After that, this liquid refrigerant is decompressed by the outdoor electric expansion valve (24), then evaporated in the outdoor heat exchanger (23) to become a low-pressure gas refrigerant, and the compression mechanism of each outdoor unit (2A, 2B, 2C) ( Returning to 21), this circulation operation is repeated.

During the cooling operation and the heating operation,
The controller (80) is an electric expansion valve for each room (32, 32, 32)
And the opening degree of each outdoor electric expansion valve (24, 24, 24) is controlled, and each outdoor unit (2A, 2B,
The capacity of the compression mechanism (21) in 2C) is controlled. Specifically, the controller (80) includes the first outdoor unit (2
The capacity of the upstream compressor (COMP-1) in A) is controlled almost linearly in response to the load by inverter control.
Operate and stop the downstream compressor (COMP-2) of the outdoor unit (2A) and the compressors (COMP-1, COMP-2) of the second outdoor unit (2B) and the third outdoor unit (2C) are doing.
When the load on the indoor units (3A, 3B, 3C) decreases, the operation of the third outdoor unit (2C) and the second outdoor unit (2B) is stopped in this order, and conversely, the indoor units (3A, 3A, 3C) are stopped.
3B, 3C) load increases, the second outdoor unit (2B)
Then, the operation will be started in the order of the third outdoor unit (2C).

Further, in each of the outdoor units (2A, 2B, 2C) operating in both the cooling operation and the heating operation, the first pressure equalizing valve (SVB1) and the second pressure equalizing valve (SVB1)
2) is opened, the high-pressure gas refrigerant flows substantially evenly through the outdoor heat exchangers (23, 23, 23) during the cooling operation, and the low-pressure gas refrigerant flows through the outdoor heat exchangers (23, 23, 23) during the heating operation. 23, 23) will flow almost evenly.

That is, during the cooling operation, for example, when the operating capacity of the third outdoor unit (2C) becomes large with respect to the cooling load, a part of the refrigerant discharged from the compression mechanism (21) is equalized by the pressure equalizing line (60). Through the outdoor heat exchangers (23, 2) in the first outdoor unit (2A) and the second outdoor unit (2B)
It will flow to 3). Conversely, during heating operation,
For example, when the operating capacity of the third outdoor unit (2C) becomes large with respect to the heating load, a part of the refrigerant sucked into the compression mechanism (21) of the first outdoor unit (2A) and the second outdoor unit (2B). Will be sucked into the compression mechanism (21) of the third outdoor unit (2C) through the pressure equalizing line (60).

-Opening / closing operations of various valves-When the cooling operation of the third outdoor unit (2C) is stopped,
The outdoor electric expansion valve (24) and the second pressure equalizing valve (SVB2) are closed to prevent the liquid refrigerant from accumulating in the stopped third outdoor unit (2C), and similarly, for the second outdoor unit (2B). When the cooling operation is also stopped, the outdoor electric expansion valve (24) and the first pressure equalizing valve (SVB1) are closed, and the second outdoor unit (2
The liquid refrigerant is prevented from accumulating in B), and the shortage of the refrigerant amount between the first outdoor unit (2A) and the indoor units (3A, 3B, 3C) is prevented. Since the branch gas lines (5G-A, 5G-B, 5G-C) are in a low pressure state when the cooling operation of the third outdoor unit (2C) and the second outdoor unit (2B) is stopped, The on-off valve (VR-1) and the second gas on-off valve (VR-2) are open.

On the other hand, when the heating operation of the third outdoor unit (2C) is stopped, the outdoor electric expansion valve (24) and the second gas on-off valve (VR-2) are closed to stop the third outdoor unit (2C). )
When the liquid refrigerant does not accumulate in the room and the heating operation of the second outdoor unit (2B) is also stopped, the outdoor electric expansion valve (24) and the first gas on-off valve (VR-1) are closed and stopped. Prevents liquid refrigerant from accumulating in the second outdoor unit (2B) inside, and prevents shortage of the amount of refrigerant between the first outdoor unit (2A) etc. and each indoor unit (3A, 3B, 3C) To do.
The third outdoor unit (2C) and the second outdoor unit (2C
When the heating operation of B) is stopped, the pressure equalizing line (60) communicates with the low pressure side of the first outdoor unit (2A), so the second pressure equalizing valve (SVB2) and the first pressure equalizing valve (SVB1) are open. There is.

Further, immediately after the heating operation of the third outdoor unit (2C) and the second outdoor unit (2B) is stopped, for example, when the third outdoor unit (2C) is stopped, the third outdoor unit (2C) is stopped. The outdoor electric expansion valve (24) and the second gas opening / closing valve (VR-2) are opened for a predetermined time, and
Leave open for 2 minutes. As a result, the high-pressure gas refrigerant from the first outdoor unit (2A), etc. passes through the branch gas line (5G-C) and the auxiliary bypass pipe (2b) of the third outdoor unit (2C) to the branch liquid line (5L-C). ), The liquid refrigerant in the stopped third outdoor unit (2C) flows into the main liquid line (4C).
It is released to L) to prevent a shortage of refrigerant.

Further, during the cooling operation and the heating operation, each oil equalizing valve (SVO1, SVO1, SVO1) and each oil equalizing auxiliary valve (SV)
Y1, SVY2, SVY3) are closed together, while the oil separator (7
The lubricating oil accumulated in 1) always returns from the first oil return pipe (72) to the compression mechanism (21), and at the same time, the oil return valve (SVP)
2) is opened to return the lubricating oil accumulated in the oil separator (71) from the second oil return pipe (73) to the compression mechanism (21).

Further, in both the cooling operation and the heating operation, the oil equalizing valves (SVO1, SVO1, SVO1) and the oil equalizing auxiliary valves (SVY1, SVY2, SVY3) are controlled to open and close as appropriate. The operation is performed so that the amount of lubricating oil in the compression mechanism (21) of each outdoor unit (2A, 2B, 2C) becomes equal.

-Oil Return Operation-During the above-described cooling operation and heating operation, the coefficient calculation means (81) uses the coefficient a set as shown in Table 3 to set the compression mechanism (21) every 10 minutes. The coefficient a corresponding to the capacity of is added. Further, the coefficient calculation means (81) is
When the opening degree of the indoor electric expansion valve (32) is limited due to the overload of the cooling, the coefficient a is set to 16.6. The oil return control means (82) is provided with the coefficient calculation means (8
When the added value added in 1) reaches a predetermined value, for example 100, the oil return operation is executed in the cooling operation cycle, and the coefficient calculation means (81) is reset.

This oil return operation is performed by the outdoor electric expansion valve (24).
Is fully opened, the opening degree of the indoor electric expansion valve (32) is controlled by the oil temperature To, and the operation is performed for, for example, 4 minutes to return the lubricating oil to the outdoor units (2A, 2B, 2C).

-Effects peculiar to the embodiment-As described above, according to this embodiment, the oil return operation is executed at the intervals corresponding to the oil upflow amount and the oil return amount. Since reliable operation can be performed, highly reliable operation can be performed.

Further, since the oil return operation interval is not set on the basis of the state where the oil return is difficult to be performed, the oil return operation is not frequently performed, so that the comfort can be improved.

When the opening degree of the indoor electric expansion valve (32) is set, the oil return operation interval can be shortened, so that oil shortage can be reliably prevented.

-Other Modifications- In the present embodiment, the air conditioner (10) capable of performing the cooling operation and the heating operation has been described, but the present invention is
Of course, the present invention can be applied to an air conditioner dedicated to cooling operation and heating operation.

In this embodiment, the twin type compression mechanism (2
Although 1) has been described, the present invention may have one compressor.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a refrigerant circuit diagram of the air conditioner.

FIG. 3 is a refrigerant circuit diagram of a first outdoor unit.

FIG. 4 is a refrigerant circuit diagram of second and third outdoor units.

FIG. 5 is a characteristic diagram of a lubricating oil amount with respect to a refrigerant circulation amount.

FIG. 6 is a characteristic diagram of the amount of lubricating oil with respect to the refrigerant circulation amount in the case of having one outdoor unit.

[Explanation of symbols]

 10 Air conditioner 2A, 2B, 2C outdoor unit 21 Compression mechanism COMP-1, COMP-2 compressor 22 Four-way switching valve 23 Outdoor heat exchanger 24 Outdoor electric expansion valve 3A, 3B, 3C Indoor unit 31 Indoor heat exchanger 32 Indoor electric expansion valve 4L Main liquid line 4G Main gas line 5L-A, 5L-B, 5L-C Branch liquid line 5G-A, 5G-B, 5G-C Branch gas line 80 Controller 81 Factor calculation means 82 Oil return Control means

Claims (2)

[Claims] 1. A compression mechanism (21) and a compression mechanism (2) at one end.
1) and branch liquid line (5L-A, 5L-B,
...) connected to the heat source side heat exchanger (23), and a plurality of heat source units (2A) to which the branch gas lines (5G-A, 5G-B, ...) are connected to the compression mechanism (21). , 2B, ...) and each heat source unit (2A, 2B, ...) of the branch liquid line (5L-
A, 5L-B,…) and branch gas lines (5G-A, 5G-B,…)
Has a main liquid line (4L) and a main gas line (4G) connected in parallel via the, an expansion mechanism (32) and a use side heat exchanger (31), and the main liquid line (4L) and Multiple usage units (3A, 3B, connected in parallel to the main gas line (4G)
...), the coefficient corresponding to the difference between the amount of oil rising from the compression mechanism (21) and the amount of oil returned to the compression mechanism (21) is the operation of the compression mechanism (21). A plurality of types are set based on the capacity, and a coefficient calculation means (81) for adding the above coefficient corresponding to the operating capacity of the compression mechanism (21), and the addition value added by the coefficient calculation means (81) is a predetermined value. Then, the refrigerating apparatus is provided with an oil return control means (82) for performing an oil return operation and resetting the coefficient calculation means (81). 2. The refrigerating apparatus according to claim 1, wherein the coefficient calculation means (81) is configured to set the coefficient to a large special value when the opening degree of the expansion mechanism (32) is limited. Refrigerating device characterized by.