DESCRIPTION

Air Conditioner

Technical Field

[0001] The present invention relates to an air conditioner that constitutes a refrigerating heat pump cycle for cooling and heating with the use of a refrigerant nd, in particular, to a technology of discharging air within an indoor unit by etecting leakage of a flammable refrigerant in an air conditioner that constitutes the cycle with the use of the flammable refrigerant.

Background Art

[0002] In recent years, global warming is a large issue and a trend toward the use of a refrigerant having a low global warming potential (hereinafter referred to as GWP) becomes conspicuous. In view of this, as an alternative to hydrofluorocarbon (hereinafter referred to as HFC) that has been hitherto used as a refrigerant, a refrigerant such as, for example, a natural refrigerant or
hydrofluoroolefin having a double bond between carbon and carbon has been attracting attention.

[0003] In particular, hydrofluoroolefin (hereinafter referred to as HFO) has been attracting attention as an alternative to an HFC-134a refrigerant and the practical use thereof in automobile air conditioners is promoted. HFO-1234yf has a GWP (100 years) of 4, which is considerably smaller than a GWP of 1430 of HFC-134a or a GWP of 2090 of HFC-410A that is used in, for example, air conditioners. The feature of HFO-1234y of being small in GWP is due to the fact that it has a double bond between carbon and carbon and is accordingly easy to decompose.

[0004] HFCs that have a relatively small GWP and can be used as a refrigerant include slightly flammable HFC-32 (GWP of 675) accounting for 50% of HFC-410A, weakly flammable HFC-152a (GWP of 124) and the like. Also, strongly flammable hydrocarbons have excellent properties as a refrigerant.

[0005] However, because all of those gases are flammable, sufficient attention should be paid when handling during use. Patent Document 1 discloses an air conditioner that has been designed to safely handle a flammable gas.

[0006] The air conditioner as disclosed in Patent Document 1 uses ammonia as a refrigerant. Because ammonia is flammable as with the gasses referred to above and is also toxic, handling thereof is more difficult than, for example, HFC-32. In view of this, the air conditioner of Patent Document 1 is provided with a sensor adjacent to a discharge opening in an indoor unit to detect leakage of a refrigerant.

[0007] If leakage of the refrigerant is detected by the sensor, a damper is operated to close the discharge opening, another damper is operated to open an exhaust opening, and a fan mounted in the indoor unit is driven. By doing so, air drawn into the indoor unit through a suction opening is conveyed together with a leaked refrigerant toward the exhaust opening and discharged outside by the fan.

[0008] Although in the air conditioner of Patent Document 1 the fan in the indoor unit acts to inhale and exhaust air, another fan different from the fan in the indoor unit may be provided to exhaust air, as in an air conditioner disclosed in Patent Document 2. Prior Art Document(s) Patent Document 1: Japanese Patent No. 3291407

• Patent Document 2: Japanese Laid-Open Patent Publication No. 9-324928

Summary of the Invention

Problems to be solved by the Invention

[0009] Because the conventional air conditioner referred to above is provided with only one sensor adjacent to the discharge opening to detect leakage of a refrigerant, if the refrigerant leaks, for example, at opposite end portions of a heat exchanger where an air current is hard to flow, it takes a long time to detect leakage of the refrigerant.

[0010] Also, in the conventional air conditioner, the fan in the indoor unit acts to exhaust air without selecting air inside the indoor unit, the area of the exhaust opening must be increased to ensure a sufficient volume of exhaust air. Because of this, the device itself occupies an increased space and, accordingly, an extensive installation work is required.

[0011] The present invention has been developed to solve the problems inherent in the prior art and is intended to provide a small-sized and easy-to-install air conditioner designed for use of a flammable refrigerant and having a high efficiency of exhausting a leaked refrigerant. Means to Solve the Problems

[0012] In order to solve the conventional problems, the air conditioner according to the present invention uses a flammable refrigerant and includes an indoor unit disposed on an indoor side, at least two refrigerant detecting means mounted in the indoor unit to detect a refrigerant, and an exhaust means for exhausting air inside the indoor unit to outside. When any one of the refrigerant detecting means detects the refrigerant, the exhaust means selectively inhales air having a high refrigerant concentration in the indoor unit to discharge the air outside. Effects of the Invention

[0013] According to the present invention, leakage of the refrigerant can be quickly detected and the leaked refrigerant can be efficiently discharged with a small amount of exhaust air, thus making it possible to realize a small-sized and easy-to-install air conditioner. Brief Description of the Drawings

[0014] The above and other objectives and features of the present invention will become more apparent from the following description of a preferred embodiment thereof with reference to the accompanying drawing, wherein:

[0015] Fig. 1 is a schematic view of an air conditioner embodying the present invention.

Embodiment(s) for Carrying out the Invention

[0016] An air conditioner according to the present invention uses a flammable refrigerant and includes an indoor unit disposed on an indoor side, at least two refrigerant detecting means mounted in the indoor unit to detect a refrigerant, and an exhaust means for exhausting air inside the indoor unit to outside. When any one of the refrigerant detecting means detects the refrigerant, the exhaust means selectively inhales air having a high refrigerant concentration in the indoor unit to discharge the air outside. According to this construction, leakage of the refrigerant can be quickly detected and the leaked refrigerant can be efficiently discharged with a small amount of exhaust air, thus making it possible to realize a small-sized and easy-to-install air conditioner.

[0017] Preferably, the exhaust means includes a suction duct portion, an exhaust blower and an exhaust duct, and the suction duct portion includes a suction port through which a leaked refrigerant is inhaled, a suction port drive unit for moving the suction port, and an extensible suction duct. The suction port drive unit moves the suction port close to a location where a refrigerant concentration is high based on a detection result of the refrigerant detecting means. Such an exhaust means is of a simple construction including just one exhaust blower and just one suction port drive unit and can efficiently discharge the leaked refrigerant with a small amount of exhaust air, thus making it possible to provide a small-sized and inexpensive air conditioner.

[0018] Again, preferably, the refrigerant detecting means are disposed at a lower portion within the indoor unit. By.this configuration, leakage of the refrigerant, which is heavier than air, can be quickly detected, thus making it possible to provide a highly safe air conditioner.

[0019] Preferably, a heat exchanger for use in the indoor unit is a plate fin tube-type heat exchanger and the refrigerant detecting means are located at portions where a tube is exposed at opposite end portions of the heat exchanger. By this configuration, the refrigerant detecting means are disposed at locations where the refrigerant is likely to leak and a leaked refrigerant is likely to remain and, hence, leakage of the refrigerant can be quickly detected, thus making it possible to provide a highly safe air conditioner.

[0020] Preferably, the suction port drive unit is designed to move the suction port substantially in parallel to a straight line connecting the refrigerant detecting means located at the opposite end portions of the heat exchanger. This configuration can simplify the suction port drive unit, thus making it possible to provide a small-sized and inexpensive air conditioner.

[0021] An embodiment of the present invention is described hereinafter with reference to the drawings, but the present invention is not limited to the embodiment. (Embodiment)

[0022] Fig. 1 is a schematic view of an air conditioner embodying the present invention.

[0023] As shown in Fig. 1, an indoor unit 100 of the air conditioner according to this embodiment includes an indoor fan 101 and a plate fin tube-type indoor heat exchanger 102. A gas pipe 112 and a liquid pipe 113 are connected to the indoor heat exchanger 102 and to an outdoor unit (not shown) installed outside a room through a pipe hole 115 defined in a wall 114. The outdoor unit includes a
compressor (not shown), an outdoor heat exchanger (not shown) and the like.

[0024] The air conditioner in this embodiment employs HFO-1234yf as a refrigerant. HFO-1234yf is a gas that has a small global warming potential (GWP) and has been attracting attention as a next-generation refrigerant to replace R134a or R410A. HFO-1234yf has a slightly flammable nature and, for this reason, if HFO-1234yf leaks, it may catch fire.

[0025] In view of this, the air conditioner in this embodiment includes at least two refrigerant detecting means mounted in the indoor unit 100 to detect leakage of the refrigerant and an exhaust means for exhausting air inside the indoor unit 100 to the outside. If any one of the refrigerant detecting means detects a refrigerant, the exhaust means selectively inhales air having a high refrigerant concentration within the indoor unit 100 to discharge it to the outside.

[0026] In this embodiment, the "at least two refrigerant detecting means" are made up of refrigerant detecting sensors 103-105. Also, in this embodiment, the "exhaust means" is made up of an exhaust blower 106, a suction duct 107 and an exhaust duct 110. Each of the suction duct 107 and the exhaust duct 110 is extensible and connected at one end thereof to the exhaust blower 106.

[0027] If at least one of the refrigerant detecting sensors 103-105 detects leakage of the refrigerant, the exhaust blower 106 is driven. The exhaust blower 106 inhales air inside the indoor unit 100 as suction air 116 from a suction port 108 in the suction duct 107 and discharges exhaust air 117 from the exhaust duct 110 to the outside, thereby making it possible to considerably reduce a risk for burning of HFO-1234yf.

[0028] For, example, a semiconductor gas sensor can be used for each of the refrigerant detecting sensors 103-105. The refrigerant detecting sensor 103 and the refrigerant detecting sensor 105 are located at opposite ends of the indoor heat exchanger 102, respectively. More specifically, the refrigerant detecting sensor 103 is disposed below an end portion of the indoor heat exchanger 102 where a refrigerant tube has been bent into a U. The refrigerant detecting sensor 105 is disposed below a welding side end portion of the indoor heat exchanger 102. The U-shaped tube side end portion and the welding side end portion are located opposite to each other with a main body of the indoor heat exchanger 102 interposed therebetween.

[0029] The refrigerant tube (not shown) is exposed at the opposite end portions of the indoor heat exchanger 102 and, hence, when dew condensation occurs on a surface of the refrigerant tube, a hole or holes may be created in the refrigerant tube due to, for example, corrosion. For this reason, the opposite end portions of the indoor heat exchanger 102 are locations having a high chance of causing leakage of the refrigerant. The opposite end portions of the indoor heat exchanger 102 are also locations where an air current from the indoor fan 101 is hard to flow and a leaked refrigerant is accordingly likely to remain.

[0030] The refrigerant detecting sensor 104 is disposed below a central portion of the indoor heat exchanger 102. A location below the central portion of the indoor heat exchanger 102 is a location where a refrigerant leaked from a heat-exchanging portion of the indoor heat exchanger 102 can be easily detected.

[0031] As shown in Fig. 1, the suction duct 107 is provided with a suction port drive unit 109 that moves the suction port 108. The suction port drive unit 109 moves the suction port 108 along a straight line connecting the refrigerant detecting sensor 103, refrigerant detecting sensor 104 and refrigerant detecting sensor 105. In this embodiment, a "suction duct portion" is made up of the suction port 108, the suction port drive unit 109 and the suction duct 107.

[0032] The refrigerant detecting sensors 103-105, the exhaust blower 106 and the suction port drive unit 109 are electrically connected to a controller 111.

The controller 111 determines an appropriate position of the suction port 108 based on signals outputted from the refrigerant detecting sensors 103-105 and controls both the suction port drive unit 109 and the exhaust blower 106.

[0033] According to the air conditioner in this embodiment, because the refrigerant detecting sensors are provided at three locations, leakage of the refrigerant can be quickly detected as compared with a conventional air conditioner having only one refrigerant detecting sensor.

[0034] Also, according to the air conditioner in this embodiment, where in the indoor unit the refrigerant leaks can be determined based on the output signals from the refrigerant detecting sensors 103-105. For example, if the output signal from the refrigerant detecting sensor 104 is extremely greater than the output signal from the refrigerant detecting sensor 103 and that from the refrigerant detecting sensor 105, i.e., a refrigerant concentration in suction air 116 is extremely greater than an average refrigerant concentration within the indoor unit 100, a determination can be made that the refrigerant leaks at the central portion of the indoor heat exchanger 102.

[0035] In this case, as shown in Fig. 1, the suction port 108 is moved to a location adjacent to the refrigerant detecting sensor 104 by the suction port drive unit 109 and the exhaust blower 106 then inhales the suction air 116 to discharge it as the exhaust air 117 to the outside through the exhaust duct 110. By doing so, even if the volume of exhaust air is small, a leaked refrigerant can be efficiently
discharged outside, thereby making it possible to reduce the sizes of the exhaust blower 106, the suction duct 107 and the exhaust duct 110. As a result, the size of the entire indoor unit 100 can be reduced, thus leading to an easy-to-install air conditioner. Also, a reduction in size of the exhaust duct 110 allows the exhaust duct 110 together with the gas pipe 112 and the liquid pipe 113 to be introduced outside through the pipe hole 115 in the wall 114 and, hence, the need for a hole specifically for the exhaust duct 110 can be dispensed with.

[0036] Also, according to the air conditioner in this embodiment, because the refrigerant detecting sensors 103-105 are disposed at a lower portion within the indoor unit 100, leakage of the refrigerant, which is heavier than air and accordingly tends to move down, can be quickly detected.

[0037] According to the air conditioner in this embodiment, because the refrigerant detecting sensor 103 is disposed below the U-shaped tube side end portion of the indoor heat exchanger 102 and the refrigerant detecting sensor 105 is disposed below the welding side end portion of the indoor heat exchanger 102, leakage of the refrigerant can be quickly detected.

[0038] Also, as described above, the locations below U-shaped tube side end portion and the welding side end portion of the indoor heat exchanger 102 are locations where the refrigerant is likely to leak, an air current from the indoor fan 101 is hard to flow, and a leaked refrigerant is likely to remain. Accordingly, if the refrigerant detecting sensors are provided away from such locations, when the refrigerant detecting sensors have detected a refrigerant leaked from those locations, it is likely that a substantial amount of refrigerant has already leaked.

[0039] Further, according to the air conditioner in this embodiment, because the suction duct 107 is provided with the suction port drive unit 109 and the suction port 108 is moved along a straight line connecting the refrigerant detecting sensor 103, refrigerant detecting sensor 104 and refrigerant detecting sensor 105, the suction port 108 can be quickly moved to a site of leakage of the refrigerant that is estimated based on the output signals from the refrigerant detecting sensors 103-105, thus making it possible to quickly discharge air having a highest refrigerant concentration.

[0040] It is to be noted that the present invention is not limited to the above-described embodiment, but practicable in various embodiments. For example, although in the above-described embodiment the suction port 108 in the suction duct 107 provided with the suction port drive unit 109 is moved, the present invention is not limited to such a construction and the suction duct 107 may be fixed.
In this case, the suction duct 107 is provided with a plurality of dampers, opening and closing of which is controlled to change a suction position of a leaked refrigerant.

This construction is as effective as the air conditioner according to the above-described embodiment. However, moving the suction port 108 using the suction port drive unit 109 can minimize the number of drive units and finely control the position of the suction port 108, thus making it possible to enhance an exhaust efficiency.

[0041] Also, although in the above-described embodiment HFO-1234yf is used as a refrigerant, the present invention is not limited to such a refrigerant and another HFO refrigerant such as, for example, HFO-1234ze may be used. Alternatively, a refrigerant mixture including HFO such as HFO-1234yf or HFO-1234ze, a single refrigerant such as HFC-32 or HFC-152a, a refrigerant mixture including HFC-32 or HFC-152a, or a hydrocarbon refrigerant may be used as a refrigerant. This case is also as effective as the air conditioner according to the above-described embodiment.

[0042] Although the present invention has been fully described by way of a preferred embodiment with reference to the accompanying drawing, it is to be noted here that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications otherwise depart from the scope of the present invention as set forth in the appended claims, they should be construed as being included therein. Industrial Applicability

[0043] Because the present invention can enhance an efficiency of exhausting a leaked refrigerant and reduce the size of an air conditioner for easy installation thereof, the present invention does not apply only to the air conditioner, but is broadly applicable to split showcases or refrigerating machines, heat pump water heaters and the like. Explanation of reference numerals

100 indoor unit
101 indoor fan
102 indoor heat exchanger
103,104,105 refrigerant detecting sensor (refrigerant detecting means)
106 exhaust blower (exhaust means)
107 suction duct (exhaust means, suction duct portion)
108 suction port (suction duct portion)
109 suction port drive unit (suction duct portion)
110 exhaust duct (exhaust means)
111 controller
112 gas pipe
113 liquid pipe
114 wall
115 pipe hole
116 suction air
117 exhaust air

CLAIMS

1. An air conditioner designed for use of a flammable refrigerant comprising:

an indoor unit disposed on an indoor side;

at least two refrigerant detecting means mounted in the indoor unit to detect a refrigerant; and
an exhaust means operable to exhaust air inside the indoor unit to outside;

when any one of the refrigerant detecting means detects the refrigerant, the exhaust means selectively inhales air having a high refrigerant concentration in the indoor unit to discharge the air outside.

2. The air conditioner according to claim 1, wherein the exhaust means comprises a suction duct portion, an exhaust blower and an exhaust duct, and the suction duct portion comprises a suction port through which a leaked refrigerant is inhaled, a suction port drive unit operable to move the suction port, and an extensible suction duct, and wherein the suction port drive unit moves the suction port close to a location where a refrigerant concentration is high based on a detection result of the refrigerant detecting means.

3. The air conditioner according to claim 1 or 2, wherein the refrigerant detecting means are disposed at a lower portion within the indoor unit.

4. The air conditioner according to claim 3, further comprising a heat exchanger mounted in the indoor unit and having a tube, wherein the heat exchanger is a plate fin tube-type heat exchanger and the refrigerant detecting means are located at portions where the tube is exposed at opposite end portions of the heat exchanger.

5. The air conditioner according to claim 4, wherein the suction port drive unit moves the suction port substantially in parallel to a straight line connecting the refrigerant detecting means located at the opposite end portions of the heat exchanger.