Refrigerant-channel branching component, and refrigeration apparatus including refrigerant-channel branching component

A refrigerant-channel branching component for connecting a connection pipe connected to an outdoor unit with a connection pipe directed toward a plurality of indoor units, the refrigerant-channel branching component includes: an inlet portion; and outlet portions. At least one of the plurality of outlet portions includes: a reference space into which a reference connection pipe with a predetermined outside diameter is inserted; a first space that is adjacent to the reference space and has an inside diameter greater than an inside diameter of the reference connection pipe; and a second space that is adjacent to the first space and has an inside diameter greater than the inside diameter of the first space.

TECHNICAL FIELD

The present invention relates to a refrigerant-channel branching component including a single inlet and a plurality of outlets.

BACKGROUND

Refrigerant-saving air conditioners reduce refrigerant in a pipe by decompressing liquid refrigerant from an outdoor unit once to turn the liquid refrigerant into a gas-liquid two-phase state for transport (to be referred to as “two-phase transport” hereinafter). For example, such an air conditioner is disclosed in Patent Literature 1 (International Publication No. 2015/029160). In the air conditioner, an outdoor liquid-refrigerant pipe, which connects an outdoor heat exchanger with a liquid-refrigerant connection pipe, is provided with a liquid-pressure-regulating expansion valve to decompress refrigerant such that the refrigerant flows through the liquid-refrigerant connection pipe in a gas-liquid two-phase state. This configuration enables two-phase transport of refrigerant in which, when refrigerant discharged from a compressor is passed through the outdoor heat exchanger, the liquid-refrigerant connection pipe, and an indoor heat exchanger in this order, the refrigerant is decompressed by the liquid-pressure-regulating expansion valve into the refrigerant in a gas-liquid two-phase state, and the refrigerant in the gas-liquid two-phase state is delivered from the outdoor unit toward the indoor unit through the liquid-refrigerant connection pipe.

In the above-mentioned air conditioner, refrigerant from the outdoor unit is delivered into a plurality of indoor units in a parallel fashion by the liquid-refrigerant connection pipe. Accordingly, by using a refrigerant-channel branching pipe with a single inlet and a plurality of outlets, the refrigerant is divided into separate streams while splitting the liquid-refrigerant connection pipe into branches. Accordingly, if, for example, a ¼-inch pipe and a ⅜-inch pipe are connected, the contraction ratio of channel cross-sectional area increases, which can cause unwanted noise in the outlet portion.

PATENT LITERATURE

SUMMARY

One or more embodiments of the present invention provide a refrigerant-channel branching pipe capable of reducing noise in its outlet portion.

A refrigerant-channel branching component according to one or more embodiments of the present invention is a refrigerant-channel branching component for connecting a connection pipe connected to an outdoor unit, with a connection pipe directed toward a plurality of indoor units, the refrigerant-channel branching component including an inlet portion and a plurality of outlet portions.

At least one of the outlet portions includes a reference space, a first space, and a second space. A reference connection pipe with a predetermined outside diameter is inserted into the reference space. With the reference connection pipe being inserted in the reference space, the first space is located adjacent to the reference space, and has an inside diameter greater than the inside diameter of the reference connection pipe. The second space is adjacent to the first space, and has an inside diameter greater than the inside diameter of the first space.

With the above-mentioned refrigerant-channel branching component, the channel cross-sectional area in the outlet portion decreases in the order of the second space, the first space, and the reference space. This configuration ensures that the flow of refrigerant is constricted stepwise, and consequently prevents the channel cross-sectional area from being constricted all at once, thus reducing the occurrence of “bubble clogging” and “pressure fluctuations”.

In a refrigerant-channel branching component according to one or more embodiments of the present invention, the reference connection pipe is a ¼-inch pipe. A connection pipe with a large diameter that corresponds to the second space is a ⅜-inch pipe.

With the above-mentioned refrigerant-channel branching component, when it is desired to connect each outlet portion with a ¼-inch pipe, this connection can be achieved by inserting the ¼-inch pipe into the reference space. When it is desired to connect each outlet portion with a ⅜-inch pipe, this connection can be achieved by cutting, at some midpoint, a pipe defining the second space, and inserting the ⅜-inch pipe into the cut pipe.

In a refrigerant-channel branching component according to one or more embodiments of the present invention, the percentage of contraction in channel cross-sectional area from the second space to the first space, and the percentage of contraction in channel cross-sectional area from the first space to the interior of the reference connection pipe are less than the percentage of contraction from the area of a circle with a diameter equal to the outside diameter of the ⅜-inch pipe to the area of a circle with a diameter equal to the inside diameter of the ¼-inch pipe.

With the above-mentioned refrigerant-channel branching component, it allows for gradual contraction of channel cross-sectional area, thus preventing the channel cross-sectional area from being constricted all at once.

In a refrigerant-channel branching component according to one or more embodiments of the present invention, a first pipe portion that forms a pipe defining the first space has an outside diameter of 2.5/8 inch.

With the above-mentioned refrigerant-channel branching component, when refrigerant travels from the second space into the reference connection pipe inserted in the reference space, the refrigerant flows in the same state as when passing through a 2.5/8-inch pipe once. This configuration allows for gradual contraction of the channel cross-sectional area, thus preventing the channel cross-section area from being constricted all at once.

In a refrigerant-channel branching component according to one or more embodiments of the present invention, a second pipe portion that forms a pipe defining the second space, and a first pipe portion that forms a pipe defining the first space are separate from each other.

In this regard, if the second pipe portion and the first pipe portion are formed integrally, the respective dimensions of the second pipe portion and the first pipe portion in the direction of refrigerant flow are subject to manufacturing restrictions. By contrast, with the above-mentioned refrigerant-channel branching component, the second pipe portion and the first pipe portion are formed separately, and thus the respective dimensions of the second pipe portion and the first pipe portion in the direction of refrigerant flow can be set freely irrespective of the manufacturing method used.

In a refrigerant-channel branching component according to one or more embodiments of the present invention, a reference pipe portion that forms a pipe defining the reference space has a dimension in the direction of refrigerant flow greater than the insertion length of the reference connection pipe into the reference space.

In a refrigerant-channel branching component according to one or more embodiments of the present invention, the first space has a dimension of greater than or equal to 10 mm in the direction of refrigerant flow.

In a refrigeration apparatus according to one or more embodiments of the present invention, the refrigeration apparatus includes the refrigerant-channel branching component according to any one of the above-described embodiments of the present invention.

With the above-mentioned refrigeration apparatus, the channel cross-sectional area in the outlet portion of the refrigerant-channel branching component decreases in the order of the second space, the first space, and the reference space. This configuration ensures that the flow of refrigerant is constricted stepwise, and consequently prevents the channel cross-sectional area from being constricted all at once.

In the refrigerant-channel branching component according to the present invention, the channel cross-sectional area in the outlet portion decreases in the order of the second space, the first space, and the reference space. This configuration ensures that the flow of refrigerant is constricted stepwise, and consequently prevents the channel cross-sectional area from being constricted all at once, thus reducing the occurrence of “bubble clogging” and “pressure fluctuations”.

When it is desired to connect the outlet portion with a large-diameter connection pipe having an outside diameter greater than the outside diameter of the reference connection pipe, this connection can be achieved by cutting, at some midpoint, a pipe defining the second space, and inserting the large-diameter connection pipe into the cut pipe.

DETAILED DESCRIPTION

Embodiments of the present invention will be described below with reference to the drawings. The embodiments below are specific examples of the present invention and not intended to limit the technical scope of the present invention.

(1) Configuration of Air Conditioner1

FIG.1illustrates a schematic configuration of an air conditioner1employing a refrigerant-channel branching component according to one or more embodiments of the present invention. The air conditioner1utilizes a vapor compression refrigeration cycle to cool or heat an indoor space of a building or other such structure.

The air conditioner1includes, as its main components, an outdoor unit2, a plurality of (four in this example) indoor units3A,3B,3C, and3D connected in parallel with each other, a liquid-refrigerant connection pipe5and a gas-refrigerant connection pipe6that connect the outdoor unit2with the indoor units3A,3B,3C, and3D, and a control unit19that controls the respective component devices of the outdoor unit2and the indoor units3A,3B,3C, and3D.

A refrigerant circuit10, which is a vapor compression refrigerant circuit of the air conditioner1, is formed by connecting the outdoor unit2with the indoor units3A,3B,3C, and3D via the liquid-refrigerant connection pipe5and the gas-refrigerant connection pipe6. The refrigerant circuit10is filled with a refrigerant such as R32.

The outdoor unit2is installed in an outdoor space of a building or other such structure. The outdoor unit2is connected to the indoor units3A,3B,3C, and3D via the liquid-refrigerant connection pipe5and the gas-refrigerant connection pipe6as described above. The outdoor unit2constitutes a portion of the refrigerant circuit10.

The outdoor unit2includes a compressor21, and an outdoor heat exchanger23as its main components. The outdoor unit2also includes a switching mechanism22. The switching mechanism22switches between a radiation operation state in which the outdoor heat exchanger23is caused to function as a radiator for refrigerant, and an evaporation operation state in which the outdoor heat exchanger23is caused to function as an evaporator for refrigerant.

The switching mechanism22and the suction side of the compressor21are connected to each other by a suction refrigerant pipe31. The suction refrigerant pipe31is provided with an accumulator29for temporarily accumulating the refrigerant to be sucked into the compressor21.

The discharge side of the compressor21and the switching mechanism22are connected to each other by a discharge refrigerant pipe32. The switching mechanism22and the gas-side end of the outdoor heat exchanger23are connected to each other by a first outdoor gas-refrigerant pipe33. The liquid-side end of the outdoor heat exchanger23and the liquid-refrigerant connection pipe5are connected to each other by an outdoor liquid-refrigerant pipe34.

A liquid-side shutoff valve27is provided at the connection of the outdoor liquid-refrigerant pipe34with the liquid-refrigerant connection pipe5. The switching mechanism22and the gas-refrigerant connection pipe6are connected to each other by a second outdoor gas-refrigerant pipe35.

A gas-side shutoff valve28is provided at the connection of the second outdoor gas-refrigerant pipe35with the gas-refrigerant connection pipe6. The liquid-side shutoff valve27and the gas-side shutoff valve28are valves that are opened and closed manually.

The compressor21is a device for compressing refrigerant. An example of the compressor21is a compressor with a hermetically sealed structure with a rotary, scroll, or other type of positive displacement compression element (not illustrated) rotatably driven by a compressor motor21a.

The switching mechanism22is a device capable of switching the flows of refrigerant in the refrigerant circuit10such that, when the outdoor heat exchanger23is caused to function as a radiator for refrigerant (to be referred to as “outdoor radiation state” hereinafter), the switching mechanism22connects the discharge side of the compressor21with the gas side of the outdoor heat exchanger23(see the solid lines inside the switching mechanism22inFIG.1), and when the outdoor heat exchanger23is caused to function as an evaporator for refrigerant (to be referred to as “outdoor evaporation state” hereinafter), the switching mechanism22connects the suction side of the compressor21with the gas side of the outdoor heat exchanger23(see the dashed lines inside the switching mechanism22inFIG.1). The switching mechanism22is, for example, a four-way switching valve.

In cooling operation, the switching mechanism22is switched to the outdoor radiation state, and in heating operation, the switching mechanism22is switched to the outdoor evaporation state.

The outdoor heat exchanger23is a heat exchanger that functions as a radiator for refrigerant, or functions as an evaporator for refrigerant.

The outdoor unit2includes an outdoor fan24. The outdoor fan24supplies the outdoor heat exchanger23with outdoor air serving as a cooling source or heating source for the refrigerant flowing through the outdoor heat exchanger23. The outdoor fan24is driven by an outdoor-fan motor24a.

The outdoor liquid-refrigerant pipe34is provided with an outdoor expansion valve25, and a liquid-pressure-regulating expansion valve26. The outdoor expansion valve25is an electric expansion valve that decompresses refrigerant during heating operation. The outdoor expansion valve25is located in a portion of the outdoor liquid-refrigerant pipe34proximate to the liquid-side end of the outdoor heat exchanger23.

The liquid-pressure-regulating expansion valve26is an electric expansion valve that, during cooling operation, decompresses refrigerant such that the refrigerant flows through the liquid-refrigerant connection pipe5in a gas-liquid two-phase state. The liquid-pressure-regulating expansion valve26is located in a portion of the outdoor liquid-refrigerant pipe34proximate to the liquid-refrigerant connection pipe5. In other words, the liquid-pressure-regulating expansion valve26is located in a portion of the outdoor liquid-refrigerant pipe34between the liquid-refrigerant connection pipe5and the outdoor expansion valve25.

During cooling operation of the air conditioner1, two-phase transport of refrigerant is performed in which, by using the liquid-pressure-regulating expansion valve26, refrigerant in a gas-liquid two-phase state is delivered from the outdoor unit2toward the indoor units3A,3B,3C, and3D through the liquid-refrigerant connection pipe5.

The outdoor liquid-refrigerant pipe34is connected with a refrigerant return pipe41. The refrigerant return pipe41includes, as its main components, a refrigerant return inlet pipe42, and a refrigerant-return outlet pipe43.

The refrigerant return inlet pipe42causes a portion of refrigerant flowing through the outdoor liquid-refrigerant pipe34to branch off from an area between the liquid-side end of the outdoor heat exchanger23and the liquid-pressure-regulating expansion valve26(which in this case is an area between the outdoor expansion valve25and a refrigerant cooler45), and delivers the branched portion of refrigerant to an inlet of the refrigerant cooler45located proximate to the refrigerant return pipe41. The refrigerant return inlet pipe42is provided with a refrigerant-return expansion valve44that regulates the flow rate of refrigerant flowing through the refrigerant cooler45while decompressing refrigerant flowing through the refrigerant return pipe41. The refrigerant-return expansion valve44is implemented by an electric expansion valve.

The refrigerant-return outlet pipe43delivers refrigerant to the suction refrigerant pipe31from an outlet of the refrigerant cooler45located proximate to the refrigerant return pipe41. The refrigerant-return outlet pipe43of the refrigerant return pipe41is connected to a portion of the suction refrigerant pipe31located on the inlet side of the accumulator29.

The refrigerant cooler45is a heat exchanger that, by using refrigerant flowing through the refrigerant return pipe41, cools refrigerant flowing through a portion of the outdoor liquid-refrigerant pipe34located between the outdoor heat exchanger23and the liquid-pressure-regulating expansion valve26. In the refrigerant cooler45, the flow of refrigerant through the refrigerant return pipe41, and the flow of refrigerant through the outdoor liquid-refrigerant pipe34are counter-flows during cooling operation.

(2-8) Various Sensors

The outdoor unit2is provided with a discharge pressure sensor36, a discharge temperature sensor37, a suction pressure sensor39, a suction temperature sensor40, an outdoor heat-exchanger liquid-side sensor38, and a liquid-pipe temperature sensor49.

The discharge pressure sensor36detects the pressure of the refrigerant discharged from the compressor21. The discharge temperature sensor37detects the temperature of the refrigerant discharged from the compressor21. The suction pressure sensor39detects the pressure of the refrigerant to be sucked into the compressor21. The suction temperature sensor40detects the temperature of the refrigerant to be sucked into the compressor21. The outdoor heat-exchanger liquid-side sensor38detects the temperature of the refrigerant at the liquid-side end of the outdoor heat exchanger23. The liquid-pipe temperature sensor49detects the temperature of the refrigerant in a portion of the outdoor liquid-refrigerant pipe34between the refrigerant cooler45and the liquid-pressure-regulating expansion valve26.

The indoor units3A,3B,3C, and3D are installed in an indoor space of a building or other such structure. As described above, the indoor units3A,3B,3C, and3D are connected to the outdoor unit2via the liquid-refrigerant connection pipe5and the gas-refrigerant connection pipe6, and constitute a portion of the refrigerant circuit10.

The configurations of the indoor units3A,3B,3C, and3D will be described below. The indoor unit3A is similar in configuration to the indoor units3B,3C, and3D. Accordingly, only the configuration of the indoor unit3A will be described below. As for the configuration of each of the indoor units3B,3C, and3D, various parts of the indoor unit3B,3C, or3D are designated with a subscript “B”, “C”, or “D” instead of a subscript “A” used to designate various parts of the indoor unit3A, and their description will be omitted. Various pipes in each of the indoor units3B,3C, and3D are designated with a subscript “b”, “c” or “d” instead of a subscript “a” used to designate various pipes in the indoor unit3A, and their description will be omitted.

The indoor unit3A includes, as its main components, an indoor expansion valve51A, and an indoor heat exchanger52A. The indoor unit3A also includes an indoor liquid-refrigerant pipe53athat connects the liquid-side end of the indoor heat exchanger52A with the liquid-refrigerant connection pipe5, and an indoor gas-refrigerant pipe54athat connects the gas-side end of the indoor heat exchanger52A with the gas-refrigerant connection pipe6.

The indoor expansion valve51A is an electric expansion valve that regulates the flow rate of refrigerant flowing through the indoor heat exchanger52A while decompressing the refrigerant. The indoor expansion valve51A is provided to the indoor liquid-refrigerant pipe53a.

The indoor heat exchanger52A is a heat exchanger that functions as an evaporator for refrigerant to cool indoor air, or functions as a radiator for refrigerant to heat indoor air.

The indoor unit3A includes an indoor fan55A. The indoor fan55A causes indoor air to be sucked into the indoor unit3A for heat exchange with refrigerant in the indoor heat exchanger52A, and then supplies the resulting air into the indoor space as supply air. The indoor fan55A is driven by an indoor-fan motor56A.

(3-4) Various Sensors

The indoor unit3A is provided with various sensors. More specifically, the indoor unit3A is provided with an indoor heat-exchanger liquid-side sensor57A that detects the temperature of the refrigerant at the liquid-side end of the indoor heat exchanger52A, an indoor heat-exchanger gas-side sensor58A that detects the temperature of the refrigerant at the gas-side end of the indoor heat exchanger52A, and an indoor air sensor59A that detects the temperature of indoor air sucked into the indoor unit3A.

The liquid-refrigerant connection pipe5includes, as its main components, a junction pipe portion extending from the outdoor unit2, and branch pipe portions5a,5b,5c, and5d, which represent a plurality of (four in this example) branch pipe portions respectively branching off at points before the indoor units3A,3B,3C, and3D.

The gas-refrigerant connection pipe6includes, as its main components, a junction pipe portion extending from the outdoor unit2, and branch pipe portions6a,6b,6c, and6d, which represent a plurality of (four in this example) branch pipe portions respectively branching off at points before the indoor units3A,3B,3C, and3D.

As illustrated inFIG.1, according to one or more embodiments of the present invention, a refrigerant-channel branching component7is used to split the liquid-refrigerant connection pipe5into branches that eventually connect to the branch pipe portions5a,5b,5c, and5d, or to split the gas-refrigerant connection pipe6into branches that eventually connect to the branch pipe portions6a,6b,6c, and6d.

FIG.2is a plan view of the refrigerant-channel branching component7. InFIG.2, the refrigerant-channel branching component7has an inlet portion71, and two outlet portions73. For example, a ⅜-inch pipe is connected to the inlet portion71, and a ⅜-inch pipe or a ¼-inch pipe is connected to each outlet portion73.

FIG.3is a cross-sectional view of each outlet portion73illustrated inFIG.2taken along a line A-A. InFIG.3, the outlet portion73includes a reference pipe portion73a, a first pipe portion73b, and a second pipe portion73cthat differ in their radial dimensions. A reference space730is defined inside the reference pipe portion73a, a first space731is defined inside the first pipe portion73b, and a second space732is defined inside the second pipe portion73c.

In the present case, a ¼-inch pipe with an outside diameter of 6.35 mm is inserted into the reference space730of the reference pipe portion73a. The first pipe portion73bhas an outside diameter of 7.93 mm. The first space731of the first pipe portion73bis a cylindrical space located adjacent to the reference space730and having an inside diameter set to a value (6.33 mm) greater than the inside diameter (4.75 mm) of a ¼-inch pipe. In other words, the first pipe portion73bis a 2.5/8-inch pipe. The dimension of the first space731in the direction of refrigerant flow is set to a value greater than or equal to 10 mm.

The second space732is a cylindrical space located adjacent to the first space731and having an inside diameter set to a value (9.52 mm) greater than the inside diameter of the first space731. This inside diameter allows for insertion of a ⅜-inch pipe.

As described above, the first pipe portion73bcorresponding to a 2.5/8-inch pipe is interposed between the second pipe portion73cand the reference pipe portion73a. This configuration is employed to create the same state as that in which, before refrigerant from the second space732of the second pipe portion73cflows into the ¼-inch pipe inserted in the reference space730of the reference pipe portion73a, the refrigerant passes through a 2.5/8-inch pipe once. This allows for gradual contraction of the channel cross-sectional area, and consequently prevents the cross-sectional area from being constricted all at once, thus reducing the occurrence of “bubble clogging” and “pressure fluctuations”.

For example,FIG.4Ais a cross-sectional view of the outlet portion73when the branch pipe portion5aillustrated inFIG.1is a ¼-inch pipe, and the branch pipe portion5ais inserted in the reference space730of the outlet portion73.FIG.4Bis a cross-sectional view of the outlet portion73illustrated inFIG.4Awith the first space731removed from the outlet portion73.

First,FIG.4Bwill be described below. InFIG.4B, during cooling operation in which gas-liquid two-phase refrigerant passes to the branch pipe portion5a, the refrigerant flows in the outlet portion73of the refrigerant-channel branching component7such that the flow is constricted from the second space732, which is a cylindrical space having a large diameter, into the branch pipe portion5ahaving a small diameter. The channel cross-sectional area is thus constricted all at once.

Accordingly, as refrigerant flows from the second space732into the branch pipe portion5a, a state in which bubbles block the inflow port of the branch pipe portion5a(to be referred to as “bubble-clogging state” hereinafter), and a state in which the blocking bubbles pass through the inflow port (to be referred to as “bubble-released state” hereinafter) are repeated. Each repetition of these states causes pressure fluctuations. Such pressure fluctuations can cause unwanted increase of noise.

By contrast, in the outlet portion73of the refrigerant-channel branching component7illustrated inFIG.4A, the channel cross-sectional area decreases in the order of the second space732, the first space731, and the interior of the ¼-inch pipe. More specifically, the percentage of contraction in channel cross-sectional area from the second space732to the first space731is 69.2%, and the percentage of contraction in channel cross-sectional area from the first space731to the interior of the ¼-inch pipe is 35.9%. These percentages of contraction are less than the percentage of contraction (25%) as illustrated inFIG.4Bfrom the channel cross-sectional area in the second space732(which corresponds to the area of a circle with a diameter equal to the outside diameter of a ⅜-inch pipe) to the channel cross-sectional area in the interior of the ¼-inch pipe (which corresponds to the area of a circle with a diameter equal to the outside diameter of a ¼-inch pipe).

Therefore, during cooling operation in which gas-liquid two-phase refrigerant passes to the branch pipe portion5a, the refrigerant flow is constricted stepwise, thus preventing the channel cross-sectional area from being constricted all at once. This configuration ensures that when refrigerant flows from the first space731into the branch pipe portion5a, the “bubble-clogging state” and the “bubble-released state” are not repeated, thus reducing the occurrence of “pressure fluctuations”.

As described above, when it is desired to connect the outlet portion73with a ¼-inch pipe, this connection can be achieved by inserting the ¼-inch pipe into the reference space730. It may be also desired in some cases to connect the outlet portion73with a ⅜-inch pipe. To this end, according to one or more embodiments of the present invention, the second space732is adapted for a ⅜-inch pipe.

FIG.5is a cross-sectional view of the outlet portion73when connected with a ⅜-inch pipe. Referring toFIG.5, the above-mentioned connection can be achieved by cutting, at some midpoint, the second pipe portion73cdefining the second space732of the outlet portion73, and inserting the ⅜-inch pipe into the cut second pipe portion73c.

The control unit19is communicatively connected with control boards or other components (not illustrated) provided in the outdoor unit2and the indoor units3A,3B,3C, and3D. For the convenience of illustration, the control unit19is depicted inFIG.1as being positioned away from the outdoor unit2and the indoor units3A,3B,3C, and3D.

The control unit19controls various component devices of the air conditioner1(which in this case are the outdoor unit2and the indoor units3A,3B,3C, and3D) based on detection signals or other information obtained by the various sensors mentioned above. In other words, the control unit19controls operation of the entire air conditioner1. Cooling operation will be described below as an example.

(7) Operation of Air Conditioner1

The air conditioner1performs cooling operation and heating operation. In cooling operation, two-phase transport of refrigerant is performed in which, by using the liquid-pressure-regulating expansion valve26provided to the outdoor liquid-refrigerant pipe34, refrigerant in a gas-liquid two-phase state is delivered from the outdoor unit2toward the indoor units3A,3B,3C, and3D through the liquid-refrigerant connection pipe5.

Further, in cooling operation, the following operations are performed by using the refrigerant return pipe41and the refrigerant cooler45: cooling refrigerant in a portion of the outdoor liquid-refrigerant pipe34between the refrigerant cooler45and the liquid-pressure-regulating expansion valve26; and delivering refrigerant to the compressor21. These operations are performed by the control unit19that controls the component devices of the air conditioner1.

In cooling operation, the switching mechanism22is switched to the outdoor radiation state (the state indicated by the solid lines inside the switching mechanism22inFIG.1), and the compressor21, the outdoor fan24, and the indoor fans55A,55B,55C, and55D are driven.

Refrigerant at a high pressure discharged from the compressor21is delivered to the outdoor heat exchanger23through the switching mechanism22. In the outdoor heat exchanger23, the refrigerant is cooled to condense in heat exchange with outdoor air supplied by the outdoor fan24. The resulting refrigerant then leaves the outdoor unit2via the outdoor expansion valve25, the refrigerant cooler45, the liquid-pressure-regulating expansion valve26, and the liquid-side shutoff valve27.

The refrigerant leaving the outdoor unit2is split into separate streams and delivered to the indoor units3A,3B,3C, and3D via the liquid-refrigerant connection pipe5. The refrigerant is then decompressed to a low pressure by each of the indoor expansion valves51A,51B,51C, and51D, and delivered to each of the indoor heat exchangers52A,52B,52C, and52D.

In each of the indoor heat exchangers52A and52B, the refrigerant is heated to evaporate in heat exchange with indoor air supplied from the indoor space by the indoor fan55A,55B,55C, or55D. The refrigerant then leaves each of the indoor units3A,3B,3C, and3D. The indoor air cooled in each of the indoor heat exchanger52A,52B,52C, and52D is delivered to the indoor space to thereby cool the indoor space.

The refrigerant streams leaving the indoor units3A,3B,3C, and3D are combined and delivered to the outdoor unit2via the gas-refrigerant connection pipe6. The resulting refrigerant is then sucked into the compressor21via the gas-side shutoff valve28, the switching mechanism22, and the accumulator29.

During the cooling operation mentioned above, two-phase transport of refrigerant is performed in which, by using the liquid-pressure-regulating expansion valve26, refrigerant in a gas-liquid two-phase state is delivered toward the indoor units3A,3B,3C, and3D through the liquid-refrigerant connection pipe5.

In this case, the liquid-refrigerant connection pipe5is split into branches to deliver refrigerant into a plurality of indoor units connected in parallel. Accordingly, noise may occur due to an abrupt constriction of refrigerant flow in the branching portion. However, according to one or more embodiments of the present invention, the first pipe portion73bcorresponding to a 2.5/8-inch pipe is interposed between the second pipe portion73cand the reference pipe portion73ato allow for gradual contraction of the channel cross-sectional area. This prevents the channel cross-sectional area from being constricted all at once, thus reducing the occurrence of noise.

As a result of research conducted by the present applicant, it has been found that a dimension L, which is the dimension in the refrigerant flow direction of the first pipe portion73bhaving an outside diameter equivalent to 2.5/8 inch, has a large effect on noise reduction.

FIG.6is a graph illustrating the relationship between the dimension L of the second space732in the direction of refrigerant flow, and noise. InFIG.6, noise decreases sharply (by approximately 2.7 dB) when the dimension L of the second space732in the direction of refrigerant flow is in the range from 0 and 10 mm. For values of the dimension L in the range from 10 mm to 25 mm, although the gradient of noise reduction decreases, noise decreases by approximately 1 dB. Further, for values of the dimension L in the range from 25 mm to 50 mm, the gradient of noise reduction decreases even further, and noise decreases by only approximately 0.6 dB. It is thus assumed that at 50 mm or more, noise converges to a constant value.

From these results, the dimension L may be greater than or equal to 10 mm, or greater than or equal to 50 mm

(8) Characteristic Features

In the outlet portion73of the refrigerant-channel branching component7, the channel cross-sectional area decreases in the order of the second space732, the first space731, and the reference space730. The refrigerant flow is thus constricted stepwise. This prevents the channel cross-sectional area from being constricted all at once, thus reducing the occurrence of “bubble clogging” and “pressure fluctuations”.

When it is desired to connect the outlet portion73with a ¼-inch pipe, this connection can be achieved by inserting the ¼-inch pipe into the reference space730. When it is desired to connect the outlet portion73with a ⅜-inch pipe, this connection can be achieved by cutting, at some midpoint, the pipe defining the second space732, and inserting the ⅜-inch pipe into the cut pipe.

The percentage of contraction in channel cross-sectional area from the second space732to the first space731, and the percentage of contraction in channel cross-sectional area from the first space731to the interior of the reference connection pipe are less than the percentage of contraction from the area of a circle with a diameter equal to the outside diameter of a ⅜-inch pipe to the area of a circle with a diameter equal to the inside diameter of a ¼-inch pipe. This configuration allows for gradual contraction of channel cross-sectional area, thus preventing the channel cross-sectional area from being constricted all at once.

The first pipe portion73bdefining the first space731has an outside diameter of 2.5/8 inch. This configuration results in the same state as that in which, when refrigerant from the second space732flows into the reference connection pipe inserted in the reference space730, the refrigerant passes through a 2.5/8-inch pipe once. This allows for gradual contraction of the channel cross-sectional area, thus preventing the channel cross-section area from being constricted all at once.

The dimension L of the first pipe portion73bin the direction of refrigerant flow is set to a value greater than or equal to 10 mm (or, greater than or equal to 50 mm). Noise reduction can be thus achieved.

In the refrigerant-channel branching component7according to the above-mentioned embodiments, the second pipe portion73cdefining the second space732, the first pipe portion73bdefining the first space731, and the reference pipe portion73adefining the reference space730are formed integrally.

However, these pipe portions may not necessarily be formed integrally. As a modification of one or more embodiments, a configuration is proposed in which the second pipe portion73cdefining the second space732, and the first pipe portion73bdefining the first space731are separate from each other.

FIG.7is a cross-sectional view of an outlet portion83of a refrigerant-channel branching component according to the modification. InFIG.7, the outlet portion83has a shape identical to the “shape obtained by cutting the second pipe portion73cat some midpoint” according to the above-mentioned embodiments illustrated inFIG.5. A second space832is defined inside a second pipe portion83c. In other words, one end portion of a ⅜-inch pipe is enlarged into a pipe with “an outside diameter of 11.12 mm and an inside diameter 9.52 mm”.

A first pipe portion83band a reference pipe portion83aare formed integrally. A reference space830is defined inside the reference pipe portion83a, and a first space831is defined inside the first pipe portion83b.

A ¼-inch pipe with an outside diameter of 6.35 mm is inserted into the reference space830of the reference pipe portion83a. The first pipe portion83bhas an outside diameter of 7.93 mm. The first space831of the first pipe portion83bis a cylindrical space located adjacent to the reference space830and having an inside diameter set to a value (6.33 mm) greater than the inside diameter (4.75 mm) of the ¼-inch pipe. In other words, the first pipe portion83bis formed by enlarging one end of the reference pipe portion into a 2.5/8-inch pipe.

If the second pipe portion83cand the first pipe portion83bare formed integrally, the respective dimensions of the second pipe portion83cand the first pipe portion83bin the direction of refrigerant flow are subject to manufacturing restrictions. By contrast, by forming the second pipe portion83cand the first pipe portion83bseparately, the respective dimensions of the second pipe portion83cand the first pipe portion83bin the direction of refrigerant flow can be set freely irrespective of the manufacturing method used.

As described above, when it is desired to connect the outlet portion83with a ¼-inch pipe, this connection can be achieved by inserting the ¼-inch pipe into the reference space830. It may be also desired in some cases to connect the outlet portion83with a ⅜-inch pipe. In this case, the ⅜-inch pipe can be inserted into the second space832of the outlet83as illustrated inFIG.8. This connection is substantially the same as in the above-mentioned embodiments illustrated inFIG.5.

In this modification, as illustrated inFIG.7, the reference pipe portion83adefining the reference space830has a dimension La in the direction of refrigerant flow that is set longer than the insertion length s of the reference connection pipe (¼-inch pipe) into the reference space830to thereby reduce noise.

The present invention can be applied to a wide variety of air conditioners in which an outdoor liquid-refrigerant pipe connecting the liquid-side end of an outdoor heat exchanger with a liquid-refrigerant connection pipe is provided with a liquid-pressure-regulating expansion valve that decompresses refrigerant such that the refrigerant flows through the liquid-refrigerant connection pipe in a gas-liquid two phase state.

REFERENCE SIGNS LIST