Patent Description:
In recent years, air conditioners adopting refrigerants having low global warming potential (GWP) (hereinafter, called low GWP refrigerants) in view of environmental protection. Examples of the low GWP refrigerants include a refrigerant disclosed in <CIT>. Further related prior art may be found in <CIT> relating to an indoor unit of an air conditioner using a flammable refrigerant, forming the basis for the preamble of independent claim <NUM>.

It is necessary to install a gas sensor for future refrigerant leakage. When the gas sensor has abnormality, a user or a service person repairs or replaces the gas sensor.

In an indoor unit of a conventional air conditioner including a gas sensor, in view of whether or not a user or a service person can easily attach and detach the gas sensor, a location of the gas sensor is not regarded as being selected to facilitate attachment and detachment.

There is accordingly an object of selecting the location of the gas sensor that can be easily attached and detached by the user or the service person.

The present invention is defined by appended independent claim <NUM>. The dependent claims describe optional features and preferred embodiments.

An indoor unit of a refrigeration apparatus according to a first aspect is to be installed at a ceiling, and includes a casing and a plate-shaped member. The casing has a plurality of blow-out ports and a blow-in port provided in a lower surface. The plate-shaped member is installed below the blow-in port. The casing accommodates a heat exchanger, a control board, a support member, and a gas sensor. The heat exchanger allows a refrigerant larger in specific gravity than air to flow therein. The support member supports the control board. The gas sensor is installed adjacent to the support member, and the gas sensor is configured to detect refrigerant leakage. The gas sensor is detachable and attachable when the plate-shaped member is shifted and a filter is detached.

A user or a service person can attach and detach the gas sensor by shifting the plate-shaped member, so that the indoor unit provides excellent maintainability.

The indoor unit of the refrigeration apparatus according to the first aspect further includes a drain pan installed below the heat exchanger. The drain pan has a first surface facing a bottom of the heat exchanger, and a second surface other than the first surface. The gas sensor is installed at the second surface of the drain pan.

The indoor unit further includes a bell mouth configured to guide air introduced via the blow-in port. The drain pan is installed around the bell mouth.

The indoor unit further includes the filter installed between the blow-in port and the plate-shaped member.

A user or a service person can attach and detach the gas sensor exposed when the filter is detached, so that the indoor unit provides excellent maintainability.

An indoor unit of a refrigeration apparatus according to a second aspect is the indoor unit of the refrigeration apparatus according to the first aspect, in which the casing has a plurality of side walls. The plurality of side walls forms a plurality of corners. The plurality of corners includes a first corner that an end part of the heat exchanger is installed. The support member is disposed along at least one of two side walls forming the first corner of the casing.

An indoor unit of a refrigeration apparatus according to a third aspect is the indoor unit of the refrigeration apparatus according to the first or second aspect, and the indoor unit further includes a plurality of said gas sensors. The plurality of said gas sensors is installed at or adjacent to the support member.

An indoor unit of a refrigeration apparatus according to a fourth aspect is the indoor unit of the refrigeration apparatus according to any one of the first to third aspects, in which the gas sensor is covered with a case having a first opening for ventilation.

The case in the indoor unit can exert two functions of protecting the gas sensor and introducing refrigerant gas as a leaking refrigerant.

An indoor unit of a refrigeration apparatus according to a fifth aspect is the indoor unit of the refrigeration apparatus according to the fourth aspect, in which the case has a ventilation surface facing the plate-shaped member. The ventilation surface is provided with the first opening.

An indoor unit of a refrigeration apparatus according to a sixth aspect is the indoor unit of the refrigeration apparatus according to the fourth or fifth aspect, in which the case has a side surface provided with a second opening.

When the indoor unit has refrigerant leakage, part of refrigerant gas entered via the first opening can flow to a gas sensor <NUM> and the remaining can exit via the second opening. Alternatively, part of refrigerant gas entered via the second opening can flow to the gas sensor <NUM> and the remaining can exit via the first opening.

Description is made herein to an air conditioner <NUM> as an exemplary refrigeration apparatus.

<FIG> is a piping diagram depicting a configuration of a refrigerant circuit C in the air conditioner <NUM> according to an embodiment of the present disclosure. The air conditioner <NUM> depicted in <FIG> cools and heats air in a room. As depicted in <FIG>, the air conditioner <NUM> includes an outdoor unit <NUM> disposed outdoors and an indoor unit <NUM> installed in the room. The outdoor unit <NUM> and the indoor unit <NUM> are connected to each other by two connection pipes <NUM> and <NUM>. The refrigerant circuit C is accordingly constituted in the air conditioner <NUM>. The refrigerant circuit C is filled with a refrigerant that circulates to achieve a vapor compression refrigeration cycle.

The outdoor unit <NUM> is provided with a compressor <NUM>, an outdoor heat exchanger <NUM>, an outdoor expansion valve <NUM>, and a four-way switching valve <NUM>.

The compressor <NUM> compresses a low-pressure refrigerant and discharges a highpressure refrigerant obtained by compression. The compressor <NUM> includes a compression mechanism of a scroll type, a rotary type, or the like driven by a compressor motor 12a. The compressor motor 12a has an operating frequency variable by means of an inverter device.

As depicted in <FIG>, there is provided a discharge pipe <NUM> connecting a refrigerant discharge port of the compressor <NUM> and the four-way switching valve <NUM>. There is further provided a suction pipe <NUM> connecting a suction port of the compressor <NUM> and the four-way switching valve <NUM>.

The outdoor heat exchanger <NUM> is of a fin and tube type. There is installed an outdoor fan <NUM> adjacent to the outdoor heat exchanger <NUM>. The outdoor heat exchanger <NUM> causes heat exchange between air conveyed by the outdoor fan <NUM> and a refrigerant flowing in the outdoor heat exchanger <NUM>.

As depicted in <FIG>, there is provided a first pipe <NUM> connecting a refrigerant inflow port of the outdoor heat exchanger <NUM> and the four-way switching valve <NUM> during cooling operation.

The outdoor expansion valve <NUM> is an electronic expansion valve having a variable opening degree. The outdoor expansion valve <NUM> is installed downstream of the outdoor heat exchanger <NUM> in a refrigerant flow direction in the refrigerant circuit C during cooling operation.

The opening degree of the outdoor expansion valve <NUM> is fully opened during cooling operation. In contrast, during heating operation, the opening degree of the outdoor expansion valve <NUM> is adjusted such that a refrigerant flowing into the outdoor heat exchanger <NUM> is decompressed to pressure enabling evaporation (evaporation pressure) in the outdoor heat exchanger <NUM>.

The four-way switching valve <NUM> has first to fourth ports. At the four-way switching valve <NUM>, a first port P1 is connected to the discharge pipe <NUM> of the compressor <NUM>, a second port P2 is connected to the suction pipe <NUM> of the compressor <NUM>, a third port P3 is connected to the first pipe <NUM> of the outdoor heat exchanger <NUM>, and a fourth port P4 is connected to a gas shutoff valve <NUM>.

The four-way switching valve <NUM> is switched between a first state (state indicated by solid lines in <FIG>) and a second state (state indicated by broken lines in <FIG>). At the four-way switching valve <NUM> in the first state, the first port P1 and the third port P3 communicate with each other and the second port P2 and the fourth port P4 communicate with each other. At the four-way switching valve <NUM> in the second state, the first port P1 and the fourth port P4 communicate with each other and the second port P2 and the third port P3 communicate with each other.

The outdoor fan <NUM> is constituted as a propeller fan driven by an outdoor fan motor 16a. An operating frequency of the outdoor fan motor 16a is variable by means of an inverter device.

The two connection pipes include the liquid connection pipe <NUM> and the gas connection pipe <NUM>. The liquid connection pipe <NUM> has a first end connected to a liquid shutoff valve <NUM> and a second end connected to a liquid connecting pipe <NUM> of an indoor heat exchanger <NUM>. As depicted in <FIG>, the liquid connecting pipe <NUM> is connected directly or indirectly to a refrigerant inlet of the indoor heat exchanger <NUM> during cooling operation.

The gas connection pipe <NUM> has a first end connected to the gas shutoff valve <NUM> and a second end connected to a gas connecting pipe <NUM> of the indoor heat exchanger <NUM>. As depicted in <FIG>, the gas connecting pipe <NUM> is connected directly or indirectly to a refrigerant outlet of the indoor heat exchanger <NUM> during cooling operation.

<FIG> is a longitudinal sectional view of the indoor unit <NUM> of the air conditioner <NUM>. <FIG> is a perspective view from an air blow-in side, of the indoor unit <NUM> with a decorative panel being separated. <FIG> is a plan view from the air blow-in side, of the indoor unit <NUM> with a decorative panel <NUM> being separated.

In <FIG>, <FIG>, and <FIG>, the indoor unit <NUM> according to the present embodiment is of a ceiling embedded type. The indoor unit <NUM> includes a body <NUM>, and the decorative panel <NUM> attached to a bottom of the body <NUM>.

As depicted in <FIG> and <FIG>, the body <NUM> includes a casing <NUM>, the indoor heat exchanger <NUM>, an indoor expansion valve <NUM>, an indoor fan <NUM>, and a gas sensor <NUM>.

The decorative panel <NUM> is attached to the bottom of the body <NUM>. The decorative panel <NUM> includes a panel portion <NUM> and a suction grill <NUM>.

The panel portion <NUM> is provided with a single blow-in flow path <NUM> and four blow-out flow paths <NUM>. As depicted in <FIG>, the blow-in flow path <NUM> is provided at a center of the panel portion <NUM>. The body <NUM> and the blow-in flow path <NUM> interpose a blow-in port 42a. The blow-in flow path <NUM> in the panel portion <NUM> has a lower end provided with an opening 41a corresponding to the blow-in port 42a.

The opening 41a has a quadrilateral shape in a planar view, and the suction grill <NUM> is attached to prevent an interior of the indoor unit <NUM> from being visible via the opening 41a.

The opening 41a and the blow-in port 42a interpose a filter <NUM> configured to capture dust in air sucked via the opening 41a.

The blow-out flow paths <NUM> are provided outside the blow-in flow path <NUM> to surround the blow-in flow path <NUM>. The blow-out flow paths <NUM> respectively extend along four sides of the blow-in flow path <NUM>. The body <NUM> and each of the blow-out flow paths <NUM> interpose a blow-out port 37a. The blow-out flow paths <NUM> in the panel portion <NUM> each have a lower end provided with an opening 43a corresponding to the blow-out port 37a.

The casing <NUM> has a plurality of side walls, and has an octagonal shape obtained by alternately connecting four short sides and four long sides in a planar view. <FIG> depicts a first short side wall 22a as a side wall penetrated by the liquid connecting pipe <NUM> and the gas connecting pipe <NUM> connected to the indoor heat exchanger <NUM>. The first short side wall 22a has a portion that is penetrated by the liquid connecting pipe <NUM> and the gas connecting pipe <NUM> and is bent to be perpendicular to the pipes.

<FIG> depicts a first long side wall 22b, a second short side wall 22c, a second long side wall 22d, a third short side wall 22e, a third long side wall 22f, a fourth short side wall <NUM>, and a fourth long side wall <NUM>, which are disposed clockwise from the first short side wall 22a.

<FIG> is a plan view from the blow-in port 42a, of the indoor unit <NUM> with a drain pan <NUM> being separated from a state of <FIG>. The plurality of side walls depicted in <FIG> forms a first corner <NUM>, a second corner <NUM>, a third corner <NUM>, and a fourth corner <NUM> in the casing <NUM>.

The first corner <NUM> is formed by the first long side wall 22b and the fourth long side wall <NUM>, faces the first short side wall 22a, and an end part 32a of the indoor heat exchanger <NUM> is installed at the first corner <NUM>.

The end part of the indoor heat exchanger <NUM> is connected with the liquid connecting pipe <NUM> and the gas connecting pipe <NUM> that penetrate the first short side wall 22a as described above. The liquid connecting pipe <NUM> is connected with the liquid connection pipe <NUM> and the gas connecting pipe <NUM> is connected with the gas connection pipe <NUM>.

The casing <NUM> accommodates the indoor fan <NUM>, a bell mouth <NUM>, the indoor heat exchanger <NUM>, and the drain pan <NUM>.

The indoor fan <NUM> is a centrifugal fan driven by an indoor fan motor 30a. An operating frequency of the indoor fan motor 30a is variable by means of an inverter device.

As depicted in <FIG>, <FIG>, the indoor fan <NUM> is disposed at a center in the casing <NUM>. The indoor fan <NUM> includes the indoor fan motor 30a and an impeller 30b. The indoor fan motor 30a is supported by a top panel of the casing <NUM>. The impeller 30b is constituted by a plurality of turbo wings arranged in a rotation direction of a drive shaft.

The bell mouth <NUM> is disposed below the indoor fan <NUM>. The bell mouth <NUM> has a circular opening at each of upper and lower ends, and has a tubular shape with an opening area gradually increased toward the decorative panel <NUM>. The bell mouth <NUM> has an arc surface that smoothly connects from the upper end to the lower end and the portion forming the arc surface is called an arc plate 31a.

The bell mouth <NUM> has an internal space communicating with an accommodation space of the indoor fan <NUM>. The bell mouth <NUM> can thus guide air introduced from the opening 41a via the blow-in port 42a into the indoor unit <NUM>.

The indoor heat exchanger <NUM> is of a fin and tube type. The indoor heat exchanger <NUM> is installed adjacent to the indoor fan <NUM>. As depicted in <FIG>, the indoor heat exchanger <NUM> includes a heat transfer tube bent to surround the indoor fan <NUM>.

The indoor heat exchanger <NUM> is installed on an upper surface of the drain pan <NUM> to rise upward. The indoor heat exchanger <NUM> allows passage of air blown laterally from the indoor fan <NUM>. The indoor heat exchanger <NUM> constitutes an evaporator configured to cool air during cooling operation, and constitutes a radiator configured to heat air during heating operation.

The drain pan <NUM> is installed around the bell mouth <NUM>. The indoor heat exchanger <NUM> is installed above the drain pan <NUM> that receives water condensed by the indoor heat exchanger <NUM> and falling downward. The drain pan <NUM> has a first surface 36a facing a bottom of the indoor heat exchanger <NUM>, and a second surface 36b other than the first surface 36a.

The indoor expansion valve <NUM> is connected to a liquid end part of the indoor heat exchanger <NUM> in the refrigerant circuit C. The indoor expansion valve <NUM> is constituted by an electronic expansion valve having a variable opening degree.

The casing <NUM> accommodates an electric component box <NUM>. The electric component box <NUM> is installed at a position visible by a user or a service person when the user or the service person shifts the suction grill <NUM>.

Specifically, the electric component box <NUM> is installed along at least one of the first long side wall 22b and the fourth long side wall <NUM> forming the first corner <NUM> of the casing <NUM>.

The electric component box <NUM> accommodates a control board <NUM> that is also disposed along at least one of the first long side wall 22b and the fourth long side wall <NUM> forming the first corner <NUM> of the casing <NUM>.

The control board <NUM> is equipped with a microcomputer MC that is configured to determine whether or not a refrigerant is leaking in accordance with a signal inputted from the gas sensor <NUM> or the like.

<FIG> is a perspective view of the gas sensor <NUM> to be covered with a case <NUM>. <FIG> is a perspective view of the gas sensor <NUM> covered with the case <NUM>. The gas sensor <NUM> depicted in <FIG> detects refrigerant leakage. The gas sensor <NUM> includes a substrate <NUM>, a sensor unit <NUM>, and a wiring unit <NUM>. The sensor unit <NUM> includes a sensor element 552a, and a cylindrical pipe 552b covering the sensor element 552a.

The sensor element 552a is mounted on the substrate <NUM> and detects whether or not there is refrigerant gas. The cylindrical pipe 552b has an upper end surface provided with a hole 552c allowing entry of refrigerant gas.

The wiring unit <NUM> includes a female connector 553a mounted on the substrate <NUM>, a male connector 553b inserted to the female connector 553a, and a cable 553c connected to the male connector 553b. The wiring unit <NUM> electrically connects the sensor element 552a and the control board <NUM>.

At least the sensor unit <NUM> of the gas sensor <NUM> is covered with the protective case <NUM>. The case <NUM> has a first opening <NUM> for ventilation. The first opening <NUM> is provided in a surface called a ventilation surface 56a.

The ventilation surface 56a according to the present embodiment crosses a side surface 56b provided with a second opening <NUM>.

When a refrigerant leaks, part of refrigerant gas entered via the first opening <NUM> can flow to the sensor unit <NUM> of the gas sensor <NUM> and the remaining can exit via the second opening <NUM>. Alternatively, when the refrigerant leaks, part of refrigerant gas entered via the second opening <NUM> can flow to the sensor unit <NUM> of the gas sensor <NUM> and the remaining can exit via the first opening <NUM>.

According to the present embodiment, the ventilation surface 56a has a plurality of first openings <NUM> and the side surface 56b has a plurality of second openings <NUM>. There may alternatively be provided a single first opening <NUM> and a single second opening <NUM>.

The case <NUM> exerts two functions of protecting the sensor unit <NUM> and introducing refrigerant gas as a leaking refrigerant.

The air conditioner <NUM> according to the present embodiment will be described next in terms of its operation. The air conditioner <NUM> switchingly executes cooling operation and heating operation.

During cooling operation, the four-way switching valve <NUM> depicted in <FIG> is in the state indicated by solid lines, and the compressor <NUM>, the indoor fan <NUM>, and the outdoor fan <NUM> are in an operating state. The refrigerant circuit C thus achieves a refrigeration cycle in which the outdoor heat exchanger <NUM> functions as a radiator and the indoor heat exchanger <NUM> functions as an evaporator.

Specifically, a high pressure refrigerant compressed by the compressor <NUM> flows in the outdoor heat exchanger <NUM> to exchange heat with outdoor air. The high pressure refrigerant radiates heat to the outdoor air in the outdoor heat exchanger <NUM>. A refrigerant condensed by the outdoor heat exchanger <NUM> is sent to the indoor unit <NUM>. The refrigerant in the indoor unit <NUM> is decompressed by the indoor expansion valve <NUM> and then flows in the indoor heat exchanger <NUM>.

In the indoor unit <NUM>, indoor air blown out of the indoor fan <NUM> passes the indoor heat exchanger <NUM> to exchange heat with the refrigerant. The refrigerant in the indoor heat exchanger <NUM> is evaporated by absorbing heat from the indoor air. The indoor air is cooled by the refrigerant.

The air cooled by the indoor heat exchanger <NUM> is supplied into an indoor space. The refrigerant evaporated in the indoor heat exchanger <NUM> is sucked into the compressor <NUM> to be compressed again.

During heating operation, the four-way switching valve <NUM> depicted in <FIG> is in the state indicated by broken lines, and the compressor <NUM>, the indoor fan <NUM>, and the outdoor fan <NUM> are in the operating state. The refrigerant circuit C thus achieves a refrigeration cycle in which the indoor heat exchanger <NUM> functions as a condenser and the outdoor heat exchanger <NUM> functions as an evaporator.

Specifically, a high pressure refrigerant compressed by the compressor <NUM> flows in the indoor heat exchanger <NUM> of the indoor unit <NUM>. In the indoor unit <NUM>, indoor air blown out of the indoor fan <NUM> passes the indoor heat exchanger <NUM> to exchange heat with the refrigerant. The refrigerant in the indoor heat exchanger <NUM> is condensed by radiating heat to the indoor air. The indoor air is heated by the refrigerant.

The air heated in the indoor heat exchanger <NUM> is supplied into the indoor space. The refrigerant condensed in the indoor heat exchanger <NUM> is decompressed by the outdoor expansion valve <NUM> and then flows in the outdoor heat exchanger <NUM>. The refrigerant in the outdoor heat exchanger <NUM> absorbs heat from outdoor air to be evaporated. The refrigerant evaporated in the outdoor heat exchanger <NUM> is sucked into the compressor <NUM> to be compressed again.

The gas sensor <NUM> is accommodated in the casing <NUM>, but is positioned to be detachable and attachable when the suction grill <NUM> is shifted. Specifically, the gas sensor <NUM> is installed at the second surface 36b of the drain pan <NUM> so as to be adjacent to the electric component box <NUM>.

The second surface 36b of the drain pan <NUM> corresponds to the surface excluding the first surface 36a facing the bottom of the indoor heat exchanger <NUM>. In view of maintainability for replacement of the gas sensor <NUM>, the second surface 36b is desirably displaced along the blow-in port 42a.

The present embodiment provides a flat plate 31b disposed adjacent to a lower end of the arc plate 31a of the bell mouth <NUM> so as to surround the lower end. The flat plate 31b is positioned below a bottom wall of the drain pan <NUM>. In order to avoid interference between the flat plate 31b and the bottom wall of the drain pan <NUM>, the bottom wall of the drain pan <NUM> has a step <NUM> to be in contact with the flat plate 31b.

The step <NUM> (<FIG>) includes a horizontal plane 361a in contact with an end part of the flat plate 31b, and a vertical plane 361b standing vertically downward from a terminal end of the horizontal plane 361a.

The gas sensor <NUM> is positioned adjacent to the electric component box <NUM> as depicted in <FIG>, and is attached onto the flat plate 31b in a posture such that the hole 552c of the cylindrical pipe 552b in the sensor unit <NUM> depicted in <FIG> is directed vertically downward.

<FIG> is an enlarged plan view of a location of the gas sensor <NUM>. <FIG> is a side view, along arrow A indicated in <FIG>, of the gas sensor <NUM>. In <FIG>, the ventilation surface 56a of the case <NUM> faces the suction grill <NUM> and is disposed along an opening plane of the blow-in port 42a.

As depicted in <FIG>, the cable 553c of the wiring unit <NUM> is curved to be positioned below the sensor unit <NUM> and is then introduced into the electric component box <NUM>. This configuration prevents any waterdrop adhering to the cable from permeating the substrate <NUM> along the cable 553c.

Most of a refrigerant leaking from the indoor heat exchanger <NUM> accumulates at the drain pan <NUM>, and refrigerant gas as a leaking refrigerant overflown therefrom flows beyond the bell mouth <NUM> and out of the blow-in port 42a to spread to a border between the body <NUM> and the decorative panel <NUM>.

The refrigerant gas is blocked by the filter <NUM> to fill a space between the flat plate 31b and the filter <NUM>. At the gas sensor <NUM>, the refrigerant gas flows from the ventilation surface 56a of the case <NUM>, reaches the sensor unit <NUM> via the first openings <NUM>, and enters the cylindrical pipe 552b via the hole 552c of the cylindrical pipe 552b to come into contact with the sensor element 552a.

The sensor element 552a outputs different voltage values before and after the refrigerant gas comes into contact with the sensor element 552a. The microcomputer MC accordingly determines that refrigerant leakage has occurred in accordance with change in signal voltage inputted to the control board <NUM> via the wiring unit <NUM>.

As depicted in <FIG>, <FIG>, <FIG>, the electric component box <NUM> and the gas sensor <NUM> are installed below the bell mouth <NUM> and above the filter <NUM>. As depicted in <FIG> and <FIG>, the electric component box <NUM> and the gas sensor <NUM> are disposed within a lateral width of the opening 41a. When a user or a service person detaches the suction grill <NUM> from the opening 41a and further detaches the filter <NUM>, the electric component box <NUM> and the gas sensor <NUM> are thus positioned to be visible by the user or the service person and be reached by a hand of the user or the service person.

As described above, the gas sensor <NUM> according to the present embodiment is attached at a position facilitating attachment of the gas sensor <NUM> with excellent maintainability.

(<NUM>-<NUM>)
In the indoor unit <NUM> of the air conditioner <NUM>, the gas sensor <NUM> configured to detect refrigerant leakage is positioned to be detachable and attachable when the suction grill <NUM> is shifted. A user or a service person can thus easily attach and detach the gas sensor <NUM> with excellent maintainability.

(<NUM>-<NUM>)
In the indoor unit <NUM> of the air conditioner <NUM>, the drain pan <NUM> has the first surface 36a facing the bottom of the indoor heat exchanger <NUM> and the second surface 36b other than the first surface 36a, and the gas sensor <NUM> is installed at the second surface 36b.

(<NUM>-<NUM>)
In the indoor unit <NUM> of the air conditioner <NUM>, the drain pan <NUM> is installed around the bell mouth <NUM>.

(<NUM>-<NUM>)
In the indoor unit <NUM> of the air conditioner <NUM>, the end part 32a of the indoor heat exchanger <NUM> is disposed at the first corner <NUM> among the plurality of corners of the casing <NUM>, and the electric component box <NUM> is installed along at least one of the first long side wall 22b and the fourth long side wall <NUM> forming the first corner <NUM>.

(<NUM>-<NUM>)
In the indoor unit <NUM> of the air conditioner <NUM>, the filter <NUM> is installed between the blow-in port 42a and the suction grill <NUM>. The gas sensor <NUM> is exposed when the filter <NUM> is detached, and a user or a service person can thus easily attach and detach the gas sensor <NUM> with excellent maintainability.

(<NUM>-<NUM>)
In the indoor unit <NUM> of the air conditioner <NUM>, a plurality of gas sensors <NUM> is installed at or adjacent to the electric component box <NUM>.

(<NUM>-<NUM>)
In the indoor unit <NUM> of the air conditioner <NUM>, the gas sensor <NUM> is covered with the case <NUM> having the first openings <NUM> for ventilation, and the case <NUM> exerts two functions of protecting the sensor unit <NUM> and introducing refrigerant gas as a leaking refrigerant.

(<NUM>-<NUM>)
In the indoor unit <NUM> of the air conditioner <NUM>, the ventilation surface 56a of the case <NUM> is provided with the first openings <NUM>. The ventilation surface 56a faces the suction grill <NUM>.

(<NUM>-<NUM>)
In the indoor unit <NUM> of the air conditioner <NUM>, the side surface 56b of the case <NUM> is provided with the second openings <NUM>. When a refrigerant leaks, part of refrigerant gas entered via the first openings <NUM> can flow to the sensor unit <NUM> of the gas sensor <NUM> and the remaining can exit via the second openings <NUM>. Alternatively, when a refrigerant leaks, part of refrigerant gas entered via the second openings <NUM> can flow to the sensor unit <NUM> of the gas sensor <NUM> and the remaining can exit via the first openings <NUM>.

The above embodiment provides an aspect of installing the single gas sensor <NUM>. However, the present disclosure should not be limited to this aspect. Alternatively, the indoor unit <NUM> may further include a plurality of gas sensors <NUM> that is installed at a plurality of different positions.

<FIG> is a perspective view from below, of the indoor unit <NUM> according to the first modification example, with the decorative panel <NUM> being detached, depicting locations of the plurality of gas sensors <NUM> being installed. <FIG> depicts three gas sensors <NUM> being installed.

For easier description, assume that the three gas sensors <NUM> include a first gas sensor 55A, a second gas sensor 55B, and a third gas sensor 55C. The first gas sensor 55A is installed at the second surface 36b of the drain pan <NUM>, at a position adjacent to the electric component box <NUM> and also adjacent to the end part 32a of the indoor heat exchanger <NUM>. The second gas sensor 55B is installed at a center of the surface, facing the suction grill <NUM>, of the electric component box <NUM>. The third gas sensor 55C is installed at the second surface 36b of the drain pan <NUM>, at a position adjacent to the electric component box <NUM> and farther than the first gas sensor 55Afrom the end part 32a of the indoor heat exchanger <NUM>.

A refrigerant leaking from the indoor heat exchanger <NUM> accumulates at the drain pan <NUM>, and refrigerant gas as a leaking refrigerant overflown therefrom flows beyond the bell mouth <NUM> and out of the blow-in port 42a to spread to a border between the body <NUM> and the decorative panel <NUM>. The gas sensor <NUM> is thus ideally installed to surround the arc plate 31a of the bell mouth <NUM>. However, in view of economic efficiency and maintainability, the plurality of gas sensors <NUM> is desirably installed at or adjacent to the electric component box <NUM> as described above.

The above first modification example exemplifies the locations of the plurality of gas sensors <NUM>, though there is no need to simultaneously use all the gas sensors <NUM> thus installed. With exemplary reference to <FIG>, only the first gas sensor 55A may be used initially and the second gas sensor 55B may be switchingly used before the first gas sensor 55A terminates its durability life cycle.

The first gas sensor 55A can be switched at timing that can be exemplarily determined in accordance with guarantee years of the gas sensor 55A. The first gas sensor 55A may alternatively be switched to a subsequent gas sensor <NUM> when abnormality different from refrigerant leakage is assumed in accordance with an output signal of the first gas sensor 55A.

In a similar manner, the second gas sensor 55B and the third gas sensor 55C may be used in this order.

The plurality of gas sensors <NUM> may alternatively be installed vertically. <FIG> is a perspective view from below, of the indoor unit <NUM> according to the third modification example, with the decorative panel <NUM> being detached, depicting locations of the first gas sensor 55A and the second gas sensor 55B. The first gas sensor 55A and the second gas sensor 55B depicted in <FIG> are installed vertically.

Assumed examples of a method of use include a first aspect of connecting each of the first gas sensor 55A and the second gas sensor 55B to the control board <NUM>, and a second aspect of connecting only one of the gas sensors.

According to the first aspect, either one of the first gas sensor 55A and the second gas sensor 55B installed vertically detects any refrigerant leakage. Even in a case where any one of the gas sensors is in trouble, the remaining gas sensor detects refrigerant leakage. This configuration achieves quick detection of refrigerant leakage.

Furthermore, according to the first aspect, after elapse of a predetermined period from occurrence of refrigerant leakage, all the gas sensors operating normally detect refrigerant leakage. Any gas sensor not detecting refrigerant leakage after elapse of the predetermined period can thus be determined as being abnormal.

According to the second aspect, only the first gas sensor 55A in the first gas sensor 55A and the second gas sensor 55B is exemplarily connected to the control board <NUM> to be in use, whereas the remaining gas sensor is not in use.

When the first gas sensor 55A is in trouble, a user or a service person has only to connect, in place of the first gas sensor 55A, the second gas sensor 55B stored below the first gas sensor 55A to the control board <NUM> to complete replacement of the gas sensor.

The user or the service person can thus replace the gas sensor even when visiting for repair without carrying any gas sensor for replacement.

(<NUM>-<NUM>)
The embodiment and the modification examples described above exemplify the case where installation conditions of the gas sensor <NUM> are applied to an indoor unit of a ceiling embedded type for full blowoff. However, the present disclosure should not be limited to this case. The installation conditions are exemplarily applicable also to an indoor unit of the ceiling embedded type for four-way blowoff, and an indoor unit of the ceiling embedded type for two-way blowoff.

(<NUM>-<NUM>)
The embodiment and the modification examples described above have no limitation in terms of a refrigerant enclosed in the refrigerant circuit C. All refrigerants, irrespective of incombustible refrigerants or combustible refrigerants, can be adopted. In view of safety, the embodiment and the modification examples described above are useful to combustible refrigerants.

Examples of the combustible refrigerant include refrigerants categorized in Class <NUM> (higher flammability), Class <NUM> (lower flammability), and Subclass <NUM> (slight flammability) in the standards according to ASHRAE <NUM> Designation and safety classification of refrigerant in the U. or the standards according to ISO <NUM> Refrigerants - Designation and safety classification.

Exemplarily adopted as the combustible refrigerant is any one of R1234yf, R1234ze(E), R516A, R445A, R444A, R454C, R444B, R454A, R455A, R457A, R459B, R452B, R454B, R447B, R32, R447A, R446A, and R459A.

The embodiment and the modification examples described above adopt R32 as a refrigerant.

(<NUM>-<NUM>)
The embodiment and the modification examples described above refer to the air conditioner as an exemplary refrigeration apparatus. However, the present disclosure should not be limited to this case. Examples of the refrigeration apparatus include, as well as the air conditioner, a low temperature warehouse storing articles that need to be frozen, refrigerated, or kept at low temperature.

(<NUM>-<NUM>)
In the case <NUM> according to the embodiment and the modification examples described above, the ventilation surface 56a facing the suction grill <NUM> is provided with the first openings <NUM>, and the side surface 56b crossing the ventilation surface 56a is provided with the second openings <NUM>.

The first openings <NUM> and the second openings <NUM> are disposed in a mode that should not be limited to the above. For example, the ventilation surface 56a is provided with the plurality of first openings <NUM>, part of which may serve as a refrigerant gas inflow port and the remaining may serve as a refrigerant gas outflow port. The second openings <NUM> in the side surface 56b can be eliminated in this case.

Claim 1:
An indoor unit (<NUM>) of a refrigeration apparatus to be installed at a ceiling, the indoor unit comprising:
a casing (<NUM>) having a plurality of blow-out ports (37a) and a blow-in port (42a) provided in a lower surface; and
a plate-shaped member (<NUM>) installed below the blow-in port (42a),
wherein the casing (<NUM>) accommodates
a heat exchanger (<NUM>) allowing a refrigerant larger in specific gravity than air to flow therein,
a control board (<NUM>),
a support member (<NUM>) supporting the control board (<NUM>), and a gas sensor (<NUM>),
wherein the indoor unit (<NUM>) is further comprising:
a drain pan (<NUM>) installed below the heat exchanger (<NUM>), wherein the drain pan (<NUM>) has a first surface (36a) facing a bottom of the heat exchanger (<NUM>), and a second surface (36b) other than the first surface (36a); and
a bell mouth (<NUM>) guiding air introduced via the blow-in port (42a), wherein the drain pan (<NUM>) is installed around the bell mouth (<NUM>);
characterized in that
the indoor unit (<NUM>) further comprises a filter (<NUM>) installed between the blow-in port (42a) and the plate-shaped member (<NUM>); wherein
the gas sensor (<NUM>) is detachable and attachable when the plate-shaped member (<NUM>) is shifted and the filter (<NUM>) is detached,
the gas sensor (<NUM>) is installed at the second surface (36b) of the drain pan (<NUM>), and the gas sensor (<NUM>) is installed adjacent to the support member (<NUM>) and the gas sensor (<NUM>) is configured to detect refrigerant leakage filling a space between the bell mouth (<NUM>) and the filter (<NUM>).