Patent Description:
As disclosed in Patent Literature <NUM>, an air conditioning apparatus for a vehicle is known that performs air conditioning of a vehicular compartment by a refrigeration cycle device that employs carbon dioxide as a refrigerant. The refrigeration cycle device includes an indoor heat exchanger that performs heat exchange between the refrigerant and air of the vehicular compartment.

Additionally, the air conditioning apparatus for a vehicle includes (i) an indoor fan that forms airflow passing through the indoor heat exchanger, (ii) a gas sensor that detects a concentration of carbon dioxide gas at a position located downstream of the indoor heat exchanger with respect to a direction in which the airflow flows, and (iii) a control device that determines, by using a result of the detection by the gas sensor, whether leakage of the refrigerant from the indoor exchanger is occurring.

According to the configuration of the aforementioned air conditioning apparatus for a vehicle, the airflow after passage through the indoor heat exchanger directly hits the gas sensor. This is a factor that leads to a decrease in accuracy of the detection by the gas sensor.

An objective of the present invention is to provide an air conditioning apparatus, for a vehicle, that enables high-accuracy detection of the concentration of carbon dioxide gas due to leakage of refrigerant.

To achieve the aforementioned objective, an air conditioning apparatus for a vehicle according to the present invention includes all the features of claim <NUM>.

According to the aforementioned configuration, the windbreak plate can prevent the airflow from hitting the sensing portion, allowing the first gas sensor to accurately detect the concentration of the carbon dioxide gas due to leakage of the refrigerant.

Hereinafter, air conditioning apparatuses for a railroad vehicle according to Embodiments <NUM>-<NUM>, in which the vehicle is a railroad vehicle, are described with reference to the drawings. In the drawings, components that are the same or equivalent are assigned the same reference sign.

<FIG> is a schematic diagram illustrating a part of configuration of an air conditioning apparatus <NUM> for a railroad vehicle according to the present embodiment. The air conditioning apparatus <NUM> for the railroad vehicle performs air conditioning of a passenger compartment <NUM> that is a vehicular compartment defined in a railroad vehicle <NUM> for human occupancy.

The air conditioning apparatus <NUM> for the railroad vehicle includes an indoor heat exchanger <NUM> having an interior for flow therethrough of a refrigerant containing carbon dioxide that is hereinafter referred to as the "carbon dioxide refrigerant". The indoor heat exchanger <NUM> is a part of a refrigeration cycle device <NUM> that provides a refrigeration cycle by using the carbon dioxide refrigerant.

A refrigerant that contains carbon dioxide as main component, more specifically, a refrigerant corresponding to the refrigerant number "R-<NUM>" and having <NUM> % or more carbon dioxide purity, is preferable as the carbon dioxide refrigerant, from the viewpoint of non-combustibility and a low global warming potential.

Furthermore, the air conditioning apparatus <NUM> for the railroad vehicle includes a casing <NUM> that defines an indoor chamber <NUM> that is a space in which the indoor heat exchanger <NUM> is arranged. The indoor chamber <NUM> communicates with the passenger compartment <NUM>.

Furthermore, the air conditioning apparatus <NUM> for the railroad vehicle includes an indoor fan <NUM> arranged in the indoor chamber <NUM>. The indoor fan <NUM> forms airflow AC by air flowing from the passenger compartment <NUM> into the indoor chamber <NUM>, passing through the indoor heat exchanger <NUM>, and flowing out to return to the passenger compartment <NUM>.

Hereinafter, air that is included in the airflow AC and flows from the passenger compartment <NUM> into the indoor chamber <NUM> to the indoor heat exchanger <NUM> is called the return air RA. Additionally, air that flows out from the indoor chamber <NUM> to the passenger compartment <NUM> after passage through the indoor heat exchanger <NUM> is called the supply air SA.

The return air RA passes through a return duct <NUM> that is a duct communicating with the passenger compartment <NUM>, and flows into the indoor chamber <NUM>. The supply air SA passes through a supply duct <NUM> that is an additional duct communicating with the passenger compartment <NUM>, and flows out from the indoor chamber <NUM> to the passenger compartment <NUM>.

Furthermore, the air conditioning apparatus <NUM> for the railroad vehicle includes (i) a return damper <NUM> that is a damper arranged at a boundary portion between the return duct <NUM> and the indoor chamber <NUM> and (ii) a supply damper <NUM> that is a damper arranged at a boundary portion between the supply duct <NUM> and the indoor chamber <NUM>.

The return damper <NUM> is switchable between (i) an open state in which inflow of air forming the airflow AC, that is, the return air RA, from the passenger compartment <NUM> into the indoor chamber <NUM>, is allowed, and (ii) a closed state in which the inflow is prevented. The return damper <NUM> in the open state can adjust a flow rate of the return air RA.

The supply damper <NUM> is switchable between (i) an open state in which outflow of the airflow AC from the indoor chamber <NUM> to the passenger compartment <NUM> is allowed and (ii) a closed state in which the outflow is prevented. The supply damper <NUM> in the open state can adjust a flow rate of the supply air SA.

Furthermore, the air conditioning apparatus <NUM> for the railroad vehicle includes an exhaust fan <NUM> that exhausts air of the passenger compartment <NUM> to an outside of the vehicle. This "outside of the vehicle" indicates an exterior of the railroad vehicle <NUM> and the casing <NUM>.

Hereinafter, air that is exhausted by the exhaust fan <NUM> from the passenger compartment <NUM> to the outside of the vehicle is called the exhaust air EA. The exhaust air EA is exhausted to the outside of the vehicle through an exhaust duct <NUM> that is a duct communicating with the passenger compartment <NUM>. The exhaust duct <NUM> is a duct that is arranged independently of the return duct <NUM> and the supply duct <NUM>.

For easy understanding of functions of the air conditioning apparatus <NUM> for the railroad vehicle, <FIG> illustrates positions and extension directions of the return duct <NUM>, the supply duct <NUM>, the exhaust duct <NUM>, and the casing <NUM> that are different from actual positions and extension directions thereof. The casing <NUM> may be arranged on a roof of the railroad vehicle <NUM> or may be arranged under a floor of the railroad vehicle <NUM>.

Next, specific arrangement of components in the casing <NUM> is described with reference to <FIG>.

As illustrated in <FIG>, the refrigeration cycle device <NUM> housed in the casing <NUM> includes a first refrigeration cycle device 100a that provides a refrigeration cycle and a second refrigeration cycle device 100b that provides a refrigeration cycle independent of the first refrigeration cycle device 100a.

The first refrigeration cycle device 100a includes (i) a first compressor 110a that compresses the carbon dioxide refrigerant, (ii) a first outdoor heat exchanger 120a that condenses the compressed carbon dioxide refrigerant, (iii) a non-illustrated first expander that expands the condensed carbon dioxide refrigerant, (iv) a first indoor heat exchanger 130a that evaporates the expanded carbon dioxide refrigerant, and (v) a first accumulator 140a that separates liquid from the carbon dioxide refrigerant after passage through the first indoor heat exchanger 130a and causes gas to return to the first compressor 110a.

Furthermore, the first refrigeration cycle device 100a includes first refrigerant piping 150a having an interior for flow therethrough of the carbon dioxide refrigerant. The first refrigerant piping 150a provides, by connecting the first compressor 110a, the first outdoor heat exchanger 120a, the first expander, the first indoor heat exchanger 130a, and the first accumulator 140a, a closed loop in which the carbon dioxide refrigerant flows.

The first compressor 110a, the first outdoor heat exchanger 120a, the first expander, the first accumulator 140a, and the first refrigerant piping 150a, are cooperation devices that are included in the first refrigeration cycle device 100a together with the first indoor heat exchanger 130a.

The second refrigeration cycle device 100b includes (i) a second compressor 110b that compresses the carbon dioxide refrigerant, (ii) a second outdoor heat exchanger 120b that condenses the compressed carbon dioxide refrigerant, (iii) a non-illustrated second expander that expands the condensed carbon dioxide refrigerant, (iv) a second indoor heat exchanger 130b that evaporates the expanded carbon dioxide refrigerant, and (v) a second accumulator 140b that separates liquid from the carbon dioxide refrigerant after passage through the second indoor heat exchanger 130b and causes gas to return to the second compressor 110b.

Furthermore, the second refrigeration cycle device 100b includes second refrigerant piping 150b having an interior for flow therethrough of the carbon dioxide refrigerant. The second refrigerant piping 150b provides, by connecting the second compressor 110b, the second outdoor heat exchanger 120b, the second expander, the second indoor heat exchanger 130b, and the second accumulator 140b, a closed loop in which the carbon dioxide refrigerant flows.

The second compressor 110b, the second outdoor heat exchanger 120b, the second expander, the second accumulator 140b, and the second refrigerant piping 150b, are cooperation devices that are included in the second refrigeration cycle device 100b together with the second indoor heat exchanger 130b.

Furthermore, the air conditioning apparatus <NUM> for the railroad vehicle includes (i) a first indoor fan 310a that facilitates the heat exchange between the first indoor heat exchanger 130a and the air of the passenger compartment <NUM> illustrated in <FIG> and (ii) a second indoor fan 310b that facilitates the heat exchange between the second indoor heat exchanger 130b and the air of the passenger compartment <NUM> illustrated in <FIG>.

The first indoor fan 310a forms airflow AC by which a part of the return air RA passes through the first indoor heat exchanger 130a and then returns as the supply air SA to the passenger compartment <NUM> illustrated in <FIG>. The second indoor fan 310b forms airflow AC by which the rest of the return air RA passes through the second indoor heat exchanger 130b and then returns as the supply air SA to the passenger compartment <NUM> illustrated in <FIG>.

The first indoor fan 310a is arranged at a position located downstream of the first indoor heat exchanger 130a with respect to a flow direction of the airflow AC formed thereby. The second indoor fan 310b is arranged at a position located downstream of the second indoor heat exchanger 130b with respect to a flow direction of the airflow AC formed thereby.

The indoor heat exchanger <NUM> illustrated in <FIG> includes the first indoor heat exchanger 130a and the second indoor heat exchanger 130b. Further, the indoor fan <NUM> illustrated in <FIG> includes the first indoor fan 310a and the second indoor fan 310b. For easy understanding, <FIG> illustrates a single airflow AC as the airflow AC formed by the first indoor fan 310a and the airflow AC formed by the second indoor fan 310b.

Furthermore, the air conditioning apparatus <NUM> for the railroad vehicle includes a first heater 200a arranged in a path of the airflow AC formed by the first indoor fan 310a and a second heater 200b arranged in a path of the airflow AC formed by the second indoor fan 310b.

The first heater 200a is arranged between the first indoor heat exchanger 130a and the first indoor fan 310a. The second heater 200b is arranged between the second indoor heat exchanger 130b and the second indoor fan 310b. Each of the first heater 200a and the second heater 200b heats the return air RA passing therethrough.

Furthermore, the air conditioning apparatus <NUM> for the railroad vehicle includes an outdoor fan <NUM> that facilitates the heat exchange between (i) outside air that is air of the outside of the vehicle and (ii) each of the first outdoor heat exchanger 120a and the second outdoor heat exchanger 120b. The outdoor fan <NUM> forms non-illustrated airflow by passage of the outside air through the first outdoor heat exchanger 120a and the second outdoor heat exchanger 120b and return to the outside of the vehicle.

The casing <NUM> internally defines, in addition to the indoor chamber <NUM> illustrated in <FIG>, (i) an outdoor chamber <NUM> in which the outdoor fan <NUM> is arranged and (ii) an exhaust chamber <NUM> in which the exhaust fan <NUM> is arranged. The indoor chamber <NUM>, the outdoor chamber <NUM>, and the exhaust chamber <NUM>, are disposed so as to be hermetically sealed with respect to each other.

The first compressor 110a, the second compressor 110b, the first outdoor heat exchanger 120a, the second outdoor heat exchanger 120b, the first accumulator 140a, and the second accumulator 140b, are arranged in the outdoor chamber <NUM>, in addition to the outdoor fan <NUM>.

Furthermore, the indoor chamber <NUM> is divided into (i) a first return chamber <NUM> in which the first indoor heat exchanger 130a and the first heater 200a are arranged, (ii) a second return chamber <NUM> in which the second indoor heat exchanger 130b and the second heater 200b are arranged, and (iii) a supply chamber <NUM> in which the first indoor fan 310a and the second indoor fan 310b are arranged.

The first return chamber <NUM> and the supply chamber <NUM> communicate through the first indoor fan 310a. The second return chamber <NUM> and the supply chamber <NUM> communicate through the second indoor fan 310b.

Furthermore, the air conditioning apparatus <NUM> for the railroad vehicle includes (i) a fresh damper <NUM> that is a damper arranged in the first return chamber <NUM> of the indoor chamber <NUM> at a position through which the airflow AC passes and (ii) a fresh damper <NUM> that is a damper arranged in the second return chamber <NUM> of the indoor chamber <NUM> at a position through which the airflow AC passes.

Each of the fresh dampers <NUM> and <NUM> is switchable between (i) an open state in which respective inflow of the outside air into the indoor chamber <NUM> from the exterior of the casing <NUM> or from the exterior of the passenger compartment <NUM> illustrated in <FIG> is allowed and (ii) a closed state in which the inflow is prevented. Hereinafter, the outside air taken in respectively through the fresh dampers <NUM> and <NUM> is called the fresh air FA. Each of the fresh damper <NUM> and <NUM> in the open state can adjust a flow rate of the fresh air FA.

Next, configuration for detecting leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> is described.

As described above, the carbon dioxide refrigerant is used as refrigerant in the refrigeration cycle device <NUM>. Thus, the air conditioning apparatus <NUM> for the railroad vehicle according to the present embodiment is configured so as to enable, even in a case of leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM>, prompt and accurate detection of the leakage. Hereinafter, this configuration is specifically described.

As illustrated in <FIG>, in order to detect leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM>, the air conditioning apparatus <NUM> for the railroad vehicle includes a first gas sensor <NUM> disposed in a path of the airflow AC in the indoor chamber <NUM>. The first gas sensor <NUM> is configured to detect a concentration of carbon dioxide gas in the path of the airflow AC at a position located downstream of the indoor heat exchanger <NUM>.

Specifically, as illustrated in <FIG>, the first gas sensor <NUM> is arranged, in the path of the airflow AC formed by the first indoor fan 310a, at a position located downstream of the first indoor fan 310a. This enables more prompt detection of leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> than in a case of a configuration in which the first gas sensor <NUM> is arranged at a position located upstream of the first indoor fan 310a and the first indoor heat exchanger 130a.

Specifically, the first gas sensor <NUM> is arranged in the supply chamber <NUM> at a position facing the first indoor fan 310a. More specifically, as illustrated in <FIG>, the first indoor fan 310a has an air outlet <NUM> configured to discharge the air included in the airflow AC, and the first gas sensor <NUM> is arranged at a position facing the air outlet <NUM>.

In the case as described above in which the first gas sensor <NUM> is arranged in the path of the airflow AC, a high wind velocity of the airflow AC that hits the first gas sensor <NUM> is a factor that leads to a decrease in accuracy of detection by the first gas sensor <NUM>. In particular, the wind velocity of the airflow AC at the position facing the air outlet <NUM> of the first indoor fan 310a is higher than those of other positions in the path of the airflow AC. Thus, the first gas sensor <NUM> according to the present embodiment has a configuration for suppressing a decrease in accuracy of detection by preventing hitting by the airflow AC. Hereinafter, this configuration is specifically described.

<FIG> is an external perspective view of the first gas sensor <NUM>. The first gas sensor <NUM> includes a sensing portion <NUM> configured to react in accordance with a concentration of carbon dioxide gas, a main body <NUM> configured to output a result of detection of the concentration of carbon dioxide gas based on the reaction by the sensing portion <NUM>, and a windbreak plate <NUM> configured to prevent the airflow AC from hitting the sensing portion <NUM>.

The main body <NUM> is fixed to the casing <NUM> illustrated in <FIG>. Further, the first gas sensor <NUM> includes a protrusion portion <NUM> that protrudes from the main body <NUM> in a vehicle width direction that is an intersection direction intersecting the airflow AC. This "vehicle width direction" indicates a width direction of the railroad vehicle <NUM> illustrated in <FIG>. At the position facing the air outlet of the first indoor fan 310a illustrated in <FIG>, the vehicle width direction is orthogonal to the airflow AC.

The sensing portion <NUM> is disposed at the protrusion portion <NUM>. That is, the sensing portion <NUM> is arranged at a position deviated from the main body <NUM> in a direction orthogonal to the airflow AC. The windbreak plate <NUM> includes a first windbreak plate 513a and a second windbreak plate 513b that each protrude from the main body <NUM> in the vehicle width direction. The first windbreak plate 513a and the second windbreak plate 513b face each other in the direction of the airflow AC. The sensing portion <NUM> is arranged between the first windbreak plate 513a and the second windbreak plate 513b with respect to the direction of the airflow AC.

The first windbreak plate 513a that is a windbreak plate located upstream side among the first windbreak plate 513a and the second windbreak plate 513b with respect to a flow of the airflow AC is arranged between the sensing portion <NUM> and the first indoor fan 310a illustrated in <FIG>. Due to such configuration, the first windbreak plate 513a prevents the airflow AC from hitting the sensing portion <NUM>. This leads to a decrease in the wind velocity of the airflow AC hitting the sensing portion <NUM> and also leads to appropriate stirring of the airflow AC at a position of the sensing portion <NUM>. As a result, accuracy of detection by the first gas sensor <NUM> is improved.

Furthermore, the second windbreak plate 513b that is a windbreak plate located downstream side among a pair of the first windbreak plate 513a and the second windbreak plate 513b with respect to the flow of the airflow AC also serves for the appropriate stirring of the airflow AC at the position of the sensing portion <NUM> and thus contributes to the improvement in the accuracy of detection by the first gas sensor <NUM>. However, the second windbreak plate 513b may be omitted.

A positional relationship between the first gas sensor <NUM> and the first indoor fan 310a with respect to a vertical direction is described with reference to <FIG>. The virtual line VL of <FIG> indicates a central position of the air outlet <NUM> of the first indoor fan 310a in the vertical direction. The first gas sensor <NUM> is arranged below the virtual line VL. That is, the sensing portion <NUM> of the first gas sensor <NUM> is arranged below the central position of the air outlet <NUM> in the vertical direction.

Since carbon dioxide gas is heavier than air, in a case in which the airflow AC includes carbon dioxide gas due to leakage of the carbon dioxide refrigerant, this carbon dioxide gas tries to move downward. Accordingly, arranging the sensing portion <NUM> below the central position of the air outlet <NUM> in the vertical direction enables directing a large portion of the carbon dioxide gas in the air flow AC toward the sensing portion <NUM>. This allows the first gas sensor <NUM> to accurately detect a concentration of carbon dioxide gas.

Again with reference to <FIG>, the air conditioning apparatus <NUM> for the railroad vehicle includes a control device <NUM> configured to make, by using the result of detection by the first gas sensor <NUM>, determination of whether leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> is occurring that is hereinafter referred to as the refrigerant leakage determination. The control device <NUM>, in the case of determining that leakage of the carbon dioxide refrigerant is occurring, performs at least one of emergency control for suppressing an increase in concentration of the carbon dioxide gas in the passenger compartment <NUM> or alert control for issuing an alert indicating the occurrence of the leakage of the carbon dioxide refrigerant.

As described above, according to the present embodiment, the first windbreak plate 513a prevents the airflow AC from hitting the sensing portion <NUM>, allowing the first gas sensor <NUM> to accurately detect a concentration of carbon dioxide gas due to leakage of the carbon dioxide refrigerant. In comparison to conventional techniques, this enables more improvement in accuracy of the refrigerant leakage determination made by the control device <NUM>.

Hereinafter, a preferable modified example of configuration of the first gas sensor <NUM> is described.

As illustrated in <FIG>, in a first gas sensor <NUM> according to the present embodiment, the first windbreak plate 513a protrudes in the vehicle width direction with respect to the protrusion portion <NUM>. Due to such configuration, the first windbreak plate 513a prevents the airflow AC from directly hitting the sensing portion <NUM>. This enables further improvement in accuracy of detection by the first gas sensor <NUM>.

Furthermore, the second windbreak plate 513b also protrudes in the vehicle width direction with respect to the protrusion portion <NUM>. Due to this, the pair of the first windbreak plate 513a and the second windbreak plate 513b causes stirring of the airflow AC at the position of the sensing portion <NUM>. This configuration also contributes to the improvement in the accuracy of detection by the first gas sensor <NUM>. However, the second windbreak plate 513b may be omitted, as described above.

Hereinafter, a specific example of operations by the control device <NUM> illustrated in <FIG> is described. The control device <NUM> executes refrigerant leakage monitor processing in which the aforementioned refrigerant leakage determination is repeatedly made in real time. Hereinafter, the refrigerant leakage monitor processing is described with reference to <FIG> and <FIG>.

As illustrated in <FIG>, the control device <NUM> firstly causes the first gas sensor <NUM> to start detection of the concentration of carbon dioxide gas (step S11). Thereafter, the first gas sensor <NUM> repeatedly detects the concentration of carbon dioxide gas in real time.

Then the control device <NUM> acquires a detection result Cs from the first gas sensor <NUM> (step S12), and compares an increase rate of the detection result Cs and a predetermined threshold Th indicating the occurrence of leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> (step S13). Although the threshold Th is <NUM>,<NUM> [ppm/h] in the present embodiment, no particular limitation is placed on the threshold Th.

The "increase rate of the detection result Cs" indicates (i) a difference between a value of a current detection result Cs and a value of a preceding detection result Cs or (ii) a physical quantity that is proportional to the difference. The "value of a preceding detection result Cs" means a value of the detection result Cs at a time one sampling period beforehand. An initial value of the detection result Cs is taken to be zero.

When the increase rate of the detection result Cs is equal to or smaller than the threshold Th (NO in step S13), the control device <NUM> determines that leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> is not occurring. Then the control device <NUM> returns to step S12 in order to continue monitoring of whether leakage of the carbon dioxide refrigerant is occurring. The loop of step S12 and step S13 is repeated at every sampling period of detection by the first gas sensor <NUM>.

Conversely, when the increase rate of the detection result Cs exceeds the threshold Th (YES in step S13), the control device <NUM> determines that leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> is occurring. Then the control device <NUM> starts the emergency control for suppressing an increase in concentration of carbon dioxide gas in the passenger compartment <NUM> (step S14). Hereinafter, the emergency control is specifically described with reference to <FIG>.

As illustrated in <FIG>, when air conditioning of the passenger compartment <NUM> is currently performed, the control device <NUM> firstly causes stoppage of the air conditioning (step S21). Specifically, the control device <NUM> causes stoppage of the first compressor 110a and the second compressor 110b that are illustrated in <FIG>. This stops circulation of the carbon dioxide refrigerant in the refrigeration cycle device <NUM>, enabling suppression of worsening of the leakage of the carbon dioxide refrigerant. Further, the control device <NUM> also causes stoppage of the first indoor fan 310a, the second indoor fan 310b, and the outdoor fan <NUM> that are illustrated in <FIG>.

Then the control device <NUM> causes the exhaust fan <NUM> illustrated in <FIG> to operate in a state in which the return damper <NUM> illustrated in <FIG> is switched to the closed state and the supply damper <NUM> illustrated in <FIG> and the fresh dampers <NUM> and <NUM> illustrated in <FIG> are each switched to the open state (step S22).

Causing the exhaust fan <NUM> to operate leads to exhausting of the exhaust air EA to the outside of the vehicle through the exhaust duct <NUM>, as illustrated in <FIG>. Since the carbon dioxide gas existing in the passenger compartment <NUM> is also exhausted as the exhaust air EA, an increase in concentration of carbon dioxide gas in the passenger compartment <NUM> is suppressed.

Furthermore, the exhaust fan <NUM> also serves to draw the fresh air FA illustrated in <FIG> into the passenger compartment <NUM>. That is, the atmospheric pressure of the passenger compartment <NUM> decreases due to the exhausting of the exhaust air EA, and due to the decrease in the atmospheric pressure, the fresh air FA illustrated in <FIG> flows into the indoor chamber <NUM> through each of the fresh dampers <NUM> and <NUM> and flows into the passenger compartment <NUM> through the indoor chamber <NUM> and the supply damper <NUM> illustrated in <FIG>. Since the fresh air FA flows into the passenger compartment <NUM> in the aforementioned manner, the increase in the concentration of carbon dioxide gas in the passenger compartment <NUM> is suppressed.

Again with reference to <FIG>, after starting the emergency control as described above (step S14), the control device <NUM> reacquires the detection result Cs from the first gas sensor <NUM> (step S15), and determines whether the increase rate of the detection result Cs exceeds the threshold Th (step S16).

When the increase rate of the detection result Cs exceeds the threshold Th (YES in step S16), since leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> is not yet ended, the control device <NUM> returns to step S15 in order to continue the emergency control. The loop of step S15 and step S16 is repeated at every sampling period of detection by the first gas sensor <NUM>.

Conversely, when the increase rate of the detection result Cs is equal to or smaller than the threshold Th (NO in step S16), since the leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> can be deemed to be ended, the control device <NUM> ends the emergency control (step S17).

Specifically, the control device <NUM> switches the supply damper <NUM> illustrated in <FIG> to the closed state and causes the exhaust fan <NUM> illustrated in <FIG> to stop. The return damper <NUM> illustrated in <FIG> may be switched to the open state, although maintaining in the closed state is preferable in order to disconnect the indoor chamber <NUM> and the passenger compartment <NUM>. Further, each of the fresh dampers <NUM> and <NUM> that are illustrated in <FIG> may be switched to the closed state, although maintaining in the open state is preferable.

Thereafter, the refrigerant leakage monitor processing ends. The control device <NUM> does not restart the air conditioning until completion of repair of the refrigeration cycle device <NUM>.

Although the emergency control according to aforementioned Embodiment <NUM> includes causing the fresh air FA to flow into the passenger compartment through the fresh dampers <NUM> and <NUM>, the fresh dampers <NUM> and <NUM> need not be switched to the open state by the emergency control. Hereinafter, a specific example of such configuration is described.

<FIG> is a flowchart of emergency control according to the present embodiment. In the present embodiment, the control device <NUM> causes stoppage of the air conditioning (step S31), and then causes the exhaust fan <NUM> illustrated in <FIG> to operate in a state in which all of the return damper <NUM> and the supply damper <NUM> that are illustrated in <FIG> and the fresh dampers <NUM> and <NUM> illustrated in <FIG> are switched to the closed state (step S32).

Switching the return damper <NUM> and the supply damper <NUM> to the closed state cuts off the communication between the indoor chamber <NUM> and the passenger compartment <NUM>. Further, since the fresh dampers <NUM> and <NUM> are switched to the closed state, a flow of air from the indoor chamber <NUM> to the vehicle chamber <NUM> is less likely to be formed even upon a decrease in air pressure of the passenger compartment <NUM> that is caused by the exhaust fan <NUM>.

This configuration enables prevention of the carbon dioxide refrigerant leaked from the refrigeration cycle device <NUM> from flowing out from the indoor chamber <NUM> to the passenger compartment <NUM>. Accordingly, an increase in the concentration of carbon dioxide gas in the passenger compartment <NUM> is suppressed.

In a case in which a non-illustrated intake duct leading to the exterior is disposed in the passenger compartment <NUM>, the outside air flows into the passenger compartment <NUM> through this intake duct. In a case in which a non-illustrated window leading to the exterior is disposed in the passenger compartment <NUM>, the outside air flows into the passenger compartment <NUM> through this window. In a case in which a non-illustrated entrance-exit door through which passengers get on and get off is arranged for the passenger compartment <NUM>, the outside air flows into the passenger compartment <NUM> through this entrance-exit door upon arrival of the railroad vehicle <NUM> at a station. Due to this, the concentration of carbon dioxide gas in the passenger compartment <NUM> is reduced.

In aforementioned Embodiments <NUM>-<NUM>, examples of configuration are described in which the determination of whether leakage of the carbon dioxide refrigerant is occurring is made by using the result of the detection by the first gas sensor <NUM>. A second gas sensor may further be arranged at a position located upstream of the indoor heat exchanger <NUM> with respect to the flow direction of the airflow AC, and the determination of whether leakage of the carbon dioxide refrigerant is occurring may be made by using the a result of detection by the first gas sensor <NUM> and a result of detection by the second gas sensor. Hereinafter, a specific example of such configuration is described.

As illustrated in <FIG>, an air conditioning apparatus <NUM> for a railroad vehicle according to the present embodiment includes, in addition to the first gas sensor <NUM>, a second gas sensor <NUM> arranged in the first return chamber <NUM>.

The second gas sensor <NUM> is configured to detect a concentration of carbon dioxide gas, in the path of the airflow AC formed by the first indoor fan 310a, at a position located upstream of the first indoor heat exchanger 130a. The second gas sensor <NUM> has a configuration that is the same as that of the first gas sensor <NUM> illustrated in <FIG> or <FIG>.

In the present embodiment, the control device <NUM> illustrated in <FIG> executes, by using a result of detection by the first gas sensor <NUM> and a result of detection by the second gas sensor <NUM>, the refrigerant leakage monitor processing in which the aforementioned refrigerant leakage determination is repeatedly made in real time. Hereinafter, a specific example is described with reference to <FIG>.

As illustrated in <FIG>, the control device <NUM> firstly causes the first gas sensor <NUM> and the second gas sensor <NUM> to start detection of the concentration of carbon dioxide gas (step S41). Thereafter, each of the first gas sensor <NUM> and the second gas sensor <NUM> repeatedly detects the concentration of carbon dioxide gas in real time at a corresponding position.

The sampling period of detection by the first gas sensor <NUM> and the second gas sensor <NUM> is preferably equal to or less than fifteen seconds, more preferably equal to or less than ten seconds, and still more preferably equal to or less than three seconds.

Then the control device <NUM> acquires a detection result Cs from the first gas sensor <NUM> and acquires a detection result Cr from the second gas sensor <NUM> (step S42),.

Then the control device <NUM> subtracts the detection result Cr of the second gas sensor <NUM> from the detection result Cs of the first gas sensor <NUM>, and determines, by comparing a value of Cs - Cr that is a result of the subtraction and a predetermined first threshold Th1, whether leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> is occurring (step S43).

The control device <NUM> acquires each of the detection result Cs of the first gas sensor <NUM> and the detection result Cr of the second gas sensor <NUM> in real time, and calculates a difference between the detection results Cs and Cr that are detected at the same time.

Hereinafter, the reason is described as to why leakage of the carbon dioxide refrigerant is detectable by the value of Cs - Cr that is a difference between the detection result Cs of the first gas sensor <NUM> and the detection result Cr of the second gas sensor <NUM>.

In <FIG>, in the case in which leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> is not occurring, no factor that causes an increase in concentration of carbon dioxide gas exists between the second gas sensor <NUM> and the first gas sensor <NUM> in the path of the airflow AC formed by the first indoor fan 310a. Due to this, the detection result Cs of the first gas sensor <NUM> and the detection result Cr of the second gas sensor <NUM> indicate the same value or indicate close values. Accordingly, the difference Cs - Cr becomes zero or a small value.

Conversely, in the case of occurrence of leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM>, in particular, from the first indoor heat exchanger 130a or the first refrigerant piping 150a, the detection result Cs of the first gas sensor <NUM> further contains a concentration of carbon dioxide gas that is derived from the leaked carbon dioxide refrigerant. On the other hand, at a time immediately after the occurrence of the leakage, the concentration of carbon dioxide gas that is derived from the leaked carbon dioxide refrigerant is not yet reflected in the detection result Cr of the second gas sensor <NUM> disposed at the position located upstream of the first indoor heat exchanger 130a and the first refrigerant piping 150a. Accordingly, the difference Cs - Cr becomes a large value.

Thus, the control device <NUM> can detect leakage of the carbon dioxide refrigerant by comparing the value of the difference Cs - Cr with the first threshold Th1 that indicates an increase in concentration of carbon dioxide gas in air included in the airflow AC due to the leakage of the carbon dioxide refrigerant.

Again with reference to <FIG>, when the value of the difference Cs - Cr is equal to or smaller than the first threshold Th1 (NO in step S43), since the detection result Cs of the first gas sensor <NUM> and the detection result Cr of the second gas sensor <NUM> indicate the same value or indicate close values, the control device <NUM> determines that leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> is not occurring.

Then the control device <NUM> returns to step S42 in order to continue monitoring of whether leakage of the carbon dioxide refrigerant is occurring. The loop of step S42 and step S43 is repeated at every sampling period of detection by the first gas sensor <NUM> and detection by the second gas sensor <NUM>.

Conversely, when the value of the difference Cs - Cr exceeds the first threshold Th1 (YES in step S43), since this indicates that the detection result Cs of the first gas sensor <NUM> contains a concentration of carbon dioxide gas that is derived from the carbon dioxide refrigerant, the control device <NUM> determines that leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> is occurring.

Thus, the control device <NUM> starts the emergency control for suppressing an increase in concentration of carbon dioxide gas in the passenger compartment <NUM> (step S44). Specific content of this emergency control is the same as that indicated in <FIG> or that indicated in <FIG>.

Then the control device <NUM> acquires the detection result Cs from the first gas sensor <NUM> (step S45) and compares the detection result Cs of the first gas sensor <NUM> and a predetermined second threshold Th2 (step S46). The second threshold Th2 is a value that is sufficiently small as to allow the leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> to be considered to be ended.

That is, step S46 indicates a determination that is hereinafter referred to as the end determination and is a determination of whether to end the emergency control. As described above, after starting the emergency control, the control device <NUM> makes the end determination by using, among the detection result Cs of the first gas sensor <NUM> and the detection result Cr of the second gas sensor <NUM>, only the detection result Cs of the first gas sensor <NUM>.

This is because, at a time of the end determination in step S46, the return damper <NUM> is in a state of being switched to the closed state, and therefore almost no airflow AC is formed around the second gas sensor <NUM>, and the detection result Cr of the second gas sensor <NUM> is unlikely to change even after ending of leakage of the carbon dioxide refrigerant. On the other hand, since the fresh air FA passed through the indoor heat exchanger <NUM> flows through the position of the first gas sensor <NUM>, whether leakage of the carbon dioxide refrigerant is ended is detectable by using the detection result Cs of the first gas sensor <NUM>.

When the detection result Cs of the first gas sensor <NUM> exceeds the second threshold Th2 (YES in step S46), since the leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> is not yet ended, the control device <NUM> returns to step S45 in order to continue the emergency control. The loop of step S45 and step S46 is repeated at every sampling period of detection by the first gas sensor <NUM>.

Conversely, when the detection result Cs of the first gas sensor <NUM> is equal to or smaller than the second threshold Th2 (NO in step S46), since the leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> can be deemed to be ended, the control device <NUM> ends the emergency control (step S47).

According to the embodiment described above, the effects below are obtainable.

In the case in which leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> is not occurring, the detection result Cs of the first gas sensor <NUM> and the detection result Cr of the second gas sensor <NUM> indicate the same value or indicate close values, and in contrast, in the case of occurrence of leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM>, the detection result Cs of the first gas sensor <NUM> at the time of the occurrence of the leakage becomes larger than the detection result Cr of the second gas sensor <NUM> at the time of the occurrence of the leakage. Due to this, the control device <NUM> can accurately detect leakage of carbon dioxide gas by using the value of the difference Cs - Cr.

Furthermore, in step S43, the control device <NUM> can cancel out from the detection result Cs of the first gas sensor <NUM> the concentration of carbon dioxide gas derived from expired human breath existing in the passenger compartment <NUM>, by subtracting the detection result Cr of the second gas sensor <NUM> from the detection result Cs of the first gas sensor <NUM>. That is, even in a case in which concentration of carbon dioxide gas derived from the expired human breath changes in accordance with a change in a passenger load factor of the passenger compartment <NUM>, this change is unlikely to produce an effect on Cs - Cr that is the difference between the detection result Cs of the first gas sensor <NUM> and the detection result Cr of the second gas sensor <NUM>.

Thus, there is no necessity for changing the strictness of determination of whether leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> is occurring depending on a change in concentration of carbon dioxide gas derived from expired human breath. This enables easy detection of leakage of the carbon dioxide refrigerant.

Although a determination of whether leakage of the carbon dioxide refrigerant is occurring is made based on Cs - Cr that is the difference between the detection result Cs of the first gas sensor <NUM> and the detection result Cr of the second gas sensor <NUM> in aforementioned Embodiment <NUM>, the physical quantity used for the determination is not limited to the difference Cs - Cr.

As illustrated in <FIG>, in the present embodiment, after step S42 described above, the control device <NUM> determines, by comparing an increase rate of the difference Cs - Cr and a predetermined third threshold ThA, whether leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> is occurring (step S51).

The "increase rate of the difference Cs - Cr" indicates (i) a difference between a value of a current difference Cs - Cr and a value of a preceding difference Cs - Cr or (ii) a physical quantity that is proportional to the difference. The "value of a preceding difference Cs - Cr" means a value of the difference Cs - Cr at a time one sampling period beforehand.

In the case in which leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> is not occurring, since almost no temporal change occur in the value of the difference Cs - Cr, the increase rate of the difference Cs - Cr becomes zero or a value close to zero. Conversely, in the case of occurrence of leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM>, the increase rate of the difference Cs - Cr becomes a large value, since this rate represents severity of the leakage of the carbon dioxide refrigerant.

When the increase rate of the difference Cs - Cr is larger than or equal to the third threshold ThA indicating the occurrence of leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> (YES in step S51), the control device <NUM> proceeds to step S44.

Conversely, when the increase rate of the difference Cs - Cr is smaller than the third threshold ThA (NO in step S51), the control device <NUM> returns to step S42 due to the inability to say in this case that leakage of the carbon dioxide refrigerant from the refrigeration cycle device <NUM> is occurring.

Furthermore, in the present embodiment, after step S45 described above, the control device <NUM> determines, by comparison as to whether an increase rate of Cs is equal to or smaller than a predetermined fourth threshold ThB, whether the leakage of the of the carbon dioxide refrigerant is ended (step S52).

The "increase rate of Cs" indicates (i) a difference between a value of a current Cs and a value of a preceding Cs or (ii) a physical quantity that is proportional to the difference. The "value of a preceding Cs" means a value of Cs at a time one sampling period beforehand.

When the leakage of the carbon dioxide refrigerant is ending, the increase rate of a leakage amount of the carbon dioxide refrigerant indicates a negative value. Thus, the control device <NUM> proceeds to step S47 when the increase rate of Cs is equal to or smaller than the fourth threshold ThB that is a negative value indicating that leakage of the carbon dioxide refrigerant is ending (YES in step S52), or returns to step S45 when the gradient of Cs is larger than the fourth threshold ThB (NO in step S52). Other configuration and functional effects are similar to those of Embodiment <NUM>.

Although <FIG> illustrates an example of configuration in which the second gas sensor <NUM> is arranged in the indoor chamber <NUM>, the second gas sensor <NUM> may be arranged in the passenger compartment <NUM>.

As illustrated in <FIG>, in the present embodiment, the second gas sensor <NUM> is arranged inside the passenger compartment <NUM> at a location other than a location that is directly hit by the supply air SA. Since specific gravity of carbon dioxide gas is larger than specific gravity of air, the second gas sensor <NUM> may be arranged on the floor of the passenger compartment <NUM>, at a lower part of a seat, or the like. Other configuration and functional effects are similar to those of Embodiment <NUM>.

Although Embodiments <NUM>-<NUM> are described above, modifications as described below may be made.

Although <FIG> relating to aforementioned Embodiments <NUM> and <NUM> illustrate the second windbreak plate 513b facing the first windbreak plate 513a, the second windbreak plate 513b may be omitted.

Although aforementioned Embodiment <NUM> describes making the determination of whether leakage of the carbon dioxide refrigerant is occurring based on the value of the difference Cs - Cr and aforementioned Embodiment <NUM> describes making the determination of whether leakage of the carbon dioxide refrigerant is occurring based on the increase rate of the difference Cs - Cr, the physical quantity used for the determination of whether leakage of the carbon dioxide refrigerant is occurring is not limited to the difference Cs - Cr and increase rate of the difference Cs - Cr. Any physical quantity dependent on the difference Cs - Cr is usable for the determination of whether leakage of the carbon dioxide refrigerant is occurring.

The railroad vehicle as used herein is not limited to a train but includes a bullet train, a monorail, and other vehicles that travel along a track. Further, the vehicle in which the casing <NUM> is installed is not limited to a railroad vehicle and may be a bus or other automobile-type vehicle.

The foregoing describes some example embodiments for explanatory purposes. Although the foregoing description has presented specific embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the invention as defined by the claims. Accordingly, the description and drawings are to be regarded in an illustrative rather than a restrictive sense. This detailed description, therefore, is not to be taken in a limiting sense, and the scope of the invention is defined only by the claims.

Claim 1:
An air conditioning apparatus (<NUM>) installed on a vehicle (<NUM>), the air conditioning apparatus (<NUM>) comprising:
a casing (<NUM>) installed on the vehicle (<NUM>) and defining an indoor chamber (<NUM>), the indoor chamber (<NUM>) communicating with a vehicular compartment (<NUM>) of the vehicle (<NUM>);
an indoor heat exchanger (<NUM>) arranged in the indoor chamber (<NUM>) and having an interior for flow therethrough of a refrigerant containing carbon dioxide;
a cooperation device (110a, 110b, 120a, 120b, 140a, 140b, 150a, 150b) included in, together with the indoor heat exchanger (<NUM>), a refrigeration cycle device (<NUM>) for circulation therethrough of the refrigerant; the cooperation device (110a, 110b, 120a, 120b, 140a, 140b, 150a, 150b) comprising a compressor (110a;110b), an outdoor heat exchanger (120a;120b), an expander, an accumulator (140a; 140b) and a refrigerant piping (150a; 150b);
an indoor fan (<NUM>) arranged in the indoor chamber (<NUM>) and configured to form airflow, the airflow being formed by air flowing from the vehicular compartment (<NUM>) into the indoor chamber (<NUM>), passing through the indoor heat exchanger (<NUM>), and flowing out to return to the vehicular compartment (<NUM>); and
a first gas sensor (<NUM>) to detect a concentration of carbon dioxide gas in a path of the airflow at a position located downstream of the indoor heat exchanger (<NUM>), wherein
the first gas sensor (<NUM>) includes:
a sensing portion (<NUM>) configured to react in accordance with the concentration of the carbon dioxide gas,
a main body (<NUM>) fixed to the casing;
a protrusion portion (<NUM>) that protrudes from the main body (<NUM>) in a vehicle width direction indicating a width direction of the vehicle (<NUM>), the sensing portion (<NUM>) is disposed at the protrusion portion (<NUM>), and
a windbreak plate (<NUM>) extending in the vehicle width direction and configured to prevent the airflow AC from directly hitting the sensing portion (<NUM>),
said vehicle width direction is an intersection direction intersecting the airflow AC.