Fluid sensor, refrigerant leakage detection device, refrigeration system, and refrigerant leakage detection method

A fluid sensor for detecting refrigerant leakage from a refrigerant circuit includes a sensor main body having two electrodes spaced apart from each other. The fluid sensor is configured such that the fluid sensor is connectable to an impedance measurement device to measure impedance between the two electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. National stage application claims priority under 35 U.S.C. §119(a) to Japanese Patent Application Nos. 2007-275537, filed in Japan on Oct. 23, 2007, 2008-010540, filed in Japan on Jan. 21, 2008, and 2008-244470, filed in Japan on Sep. 24, 2008, the entire contents of which are hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a fluid sensor, and particularly relates to a fluid sensor and refrigerant leakage detection device for detecting refrigerant leakage from a refrigerant circuit of a refrigeration system. The present invention also relates to a refrigeration system comprising a fluid sensor and a refrigerant leakage detection device, and to a refrigerant leakage detection method that uses a fluid sensor.

BACKGROUND ART

In one example of a method for detecting refrigerant leakage from a refrigerant circuit of a refrigeration system, a refrigerant quantity charged in a refrigerant circuit is calculated from various operative state quantities, and refrigerant leakage is detected from this calculated refrigerant quantity (See Japanese Laid-open Patent Application No. 2007-163099).

SUMMARY

However, in the method described above, it is difficult to pinpoint the location where refrigerant leakage is occurring.

There is also a demand that in cases in which refrigerant leakage has been detected, the location in the refrigerant circuit where refrigerant leakage is occurring should be pinpointed in order to take the appropriate measures against the refrigerant leakage.

An object of the present invention is to ensure that refrigerant leakage can be detected while pinpointing the location where refrigerant leakage is occurring in a refrigerant circuit of a refrigeration system.

A fluid sensor according to a first aspect of the present invention is a fluid sensor for detecting refrigerant leakage from a refrigerant circuit of a refrigeration system, wherein the fluid sensor comprises a sensor main body having two electrodes spaced apart, and the fluid sensor is configured such that the fluid sensor is capable of being connected to an impedance measurement device for measuring impedance between the two electrodes. The phrase “having two electrodes” herein means having two electrodes that electrically form a pair.

When the sensor main body of the fluid sensor is provided in or in proximity to a portion of the refrigerant circuit where refrigerant leakage detection is performed and impedance between the two electrodes is measured, the effect of the refrigerant or a fluid resulting from refrigerant leakage entering between the two electrodes causes a change in impedance between a case when refrigerant has leaked from the refrigerant circuit and a case when refrigerant has not leaked. With this fluid sensor, it is possible to detect, based on the change in impedance, that refrigerant has leaked from the portion where the sensor main body is provided, i.e., to detect that refrigerant has leaked while pinpointing the location in the refrigerant circuit of the refrigeration system where the refrigerant leakage is occurring. Even if the refrigeration system has already been constructed without a function for detecting refrigerant leakage, if the fluid sensor is custom-installed, refrigerant leakage detection can be enabled by being connected to an impedance measurement device. The phrase “the fluid resulting from refrigerant leakage” herein means refrigerator oil which leaks together with the refrigerant, condensation water formed by refrigerant leakage, or the like.

The fluid sensor according to a second aspect of the present invention is the fluid sensor according to the first aspect, wherein between the two electrodes the sensor main body has a fluid holder for holding a refrigerant or a fluid resulting from refrigerant leakage.

In cases in which the sensor main body of the fluid sensor is configured from only two electrodes, it is difficult to proactively accumulate refrigerant or fluid resulting from refrigerant leakage in between the two electrodes. Therefore, in cases in which the leaked amount is extremely small, for example, situations may arise in which refrigerant leakage cannot be detected.

In view of this, in this fluid sensor, a fluid holder for holding refrigerant or fluid resulting from refrigerant leakage is provided between the two electrodes, and the refrigerant or fluid resulting from refrigerant leakage that enters in between the two electrodes is held and accumulated in the fluid holder. Refrigerant leakage is thereby easily detected and the precision of refrigerant leakage detection can be increased, even if the amount of refrigerant leakage is extremely small.

The fluid sensor according to a third aspect of the present invention is the fluid sensor according to the second aspect, wherein the fluid holder is paper.

In this fluid sensor, refrigerator oil which does not readily evaporate or diffuse can be held and be accumulated by being adsorbed by paper that is the fluid holder even after leakage. Therefore, evidence of refrigerant leakage can be more reliably ascertained than in cases in which refrigerant which readily evaporates or diffuses after leakage is held in the fluid holder, and the precision of refrigerant leakage detection can thereby be increased.

The fluid sensor according to a fourth aspect of the present invention is the fluid sensor according to any of the first through third aspects, wherein the two electrodes in the sensor main body have a multilayered structure.

Since electrodes having a multilayered structure are used in this fluid sensor, the electric capacitance of the sensor main body can be increased, and the precision of refrigerant leakage detection can thereby be increased.

The fluid sensor according to a fifth aspect of the present invention is the fluid sensor according to any of the first through fourth aspects, wherein the sensor main body has a structure which can be mounted so as to surround a pipe or pipe joint constituting the refrigerant circuit.

In this fluid sensor, since the refrigerant or the fluid resulting from refrigerant leakage can be effectively caused to enter in between the two electrodes, evidence of refrigerant leakage can be reliably ascertained, and the precision of refrigerant leakage detection can thereby be increased.

The fluid sensor according to a sixth aspect of the present invention is the fluid sensor according to the fifth aspect, wherein the sensor main body is provided with a latching part for detachably latching to the pipe or pipe joint constituting the refrigerant circuit.

In this fluid sensor, since the sensor main body can be detachably latched to the pipe or pipe joint by the latching part, the operation of attaching and removing the sensor main body is made easier.

The fluid sensor according to a seventh aspect of the present invention is the fluid sensor according to any of the first through fourth aspects, wherein the sensor main body has a flat plate-shaped structure.

In this fluid sensor, since the sensor main body is compact and easily handled, the sensor main body can be easily attached in or in proximity to the portion where refrigerant leakage detection is performed.

The fluid sensor according to an eighth aspect of the present invention is the fluid sensor according to any of the second through sixth aspects, wherein the fluid holder and the electrodes are covered by a casing constituting the sensor main body; and a fluid-guiding member whereby a refrigerant or a fluid resulting from refrigerant leakage is led between the two electrodes is provided to the sensor main body so as to protrude from the casing interior to the casing exterior.

In this fluid sensor, in cases in which refrigerant leakage detection is performed based on the change in impedance caused by a specified fluid among either the refrigerant or fluids resulting from refrigerant leakage, fluids and the like other than the refrigerant and the specified fluid resulting from refrigerant leakage can be prevented to the fullest extent possible from being held in the fluid holder by covering the fluid holder and the electrodes with the casing, and the refrigerant or the specified fluid resulting from refrigerant leakage can be led into the casing and held and accumulated in the fluid holder by providing a fluid-guiding member for leading the refrigerant or a fluid resulting from refrigerant leakage in between the two electrodes so as to protrude from the casing interior to the casing exterior. This can contribute to improving the precision of refrigerant leakage detection.

The fluid sensor according to a ninth aspect of the present invention is the fluid sensor according to the eighth aspect, wherein openings for allowing the fluid-guiding member to protrude from the casing interior to the casing exterior are formed in the casing, and the openings have a smaller opening size than accommodating parts covering the fluid holder and the electrodes.

In this fluid sensor, making the opening size of the openings for allowing the fluid-guiding member to protrude from the casing interior to the casing exterior smaller than the accommodating parts covering the fluid holder and the electrodes makes it possible to prevent fluids and the like other than the refrigerant and the specified fluid resulting from refrigerant leakage from entering through the accommodating parts.

The fluid sensor according to a tenth aspect of the present invention is the fluid sensor according to the ninth aspect, wherein gaps between the openings and the fluid-guiding member are filled with a sealant in a state in which the fluid-guiding member protrudes from the openings.

In this fluid sensor, providing a sealant for filling in the gaps between the openings and the fluid-guiding member in a state in which the fluid-guiding member protrudes from the openings can contribute to preventing fluids and the like other than the refrigerant and the specified fluid resulting from refrigerant leakage from entering through the accommodating parts.

A refrigeration system according to an eleventh aspect of the present invention comprises a refrigerant circuit and the fluid sensor according to any of the first through tenth aspects, the fluid sensor being disposed in or in proximity to a portion in the refrigerant circuit where refrigerant leakage is detected.

With this refrigeration system, since the fluid sensor is provided in or in proximity to a portion in the refrigerant circuit where refrigerant leakage detection is performed, connecting an impedance measurement device to the fluid sensor when refrigerant leakage detection is performed makes it possible to detect that refrigerant has leaked from the portion where the sensor main body is provided, i.e., to detect that refrigerant has leaked while pinpointing the location in the refrigerant circuit of the refrigeration system where the refrigerant leakage is occurring.

The refrigeration system according to a twelfth aspect of the present invention is the refrigeration system according to the eleventh aspect, further comprising an impedance measurement device connected to the fluid sensor.

Since this refrigeration system further comprises the impedance measurement device connected to the fluid sensor, there is no longer a need to connect the impedance measurement device to the fluid sensor when refrigerant leakage detection is performed. It is also possible to contribute to improving the precision of refrigerant leakage detection because a process for storing the results of refrigerant leakage detection and the like can be easily performed. It is also possible to constantly perform refrigerant leakage detection.

The fluid sensor according to a thirteenth aspect of the present invention is a fluid sensor for detecting refrigerant leakage from a refrigerant circuit of a refrigeration system, wherein the fluid sensor comprises a sensor main body having two electrodes spaced apart; and the sensor main body further has an impedance measurement unit for measuring impedance between the two electrodes, a leakage determination unit for determining whether or not refrigerant has leaked based on the impedance value measured by the impedance measurement unit, and a signal output unit for outputting to an external device the result of the refrigerant leakage determination obtained by the leakage determination unit. The phrase “having two electrodes” herein means having two electrodes that electrically form a pair.

When the sensor main body of the fluid sensor is provided in or in proximity to a portion of the refrigerant circuit where refrigerant leakage detection is performed and impedance between the two electrodes is measured, the effect of the refrigerant or a fluid resulting from refrigerant leakage entering between the two electrodes causes a change in impedance between a case when refrigerant has leaked from the refrigerant circuit and a case when refrigerant has not leaked. With this fluid sensor, it is possible to detect, based on the change in impedance, that refrigerant has leaked from the portion where the sensor main body is provided, i.e., to detect that refrigerant has leaked while pinpointing the location in the refrigerant circuit of the refrigeration system where the refrigerant leakage is occurring. Moreover, with this fluid sensor, since the sensor main body has the impedance measurement unit for measuring impedance between the two electrodes, a leakage determination unit for concluding whether or not refrigerant has leaked, and the leakage determination unit for outputting to an external device the conclusion result pertaining to refrigerant leakage, there is no longer a need to connect an impedance measurement device to the fluid sensor when refrigerant leakage detection is performed. The distance between the electrodes and the impedance measurement unit is also shorter than in cases of connecting to an external impedance measurement device or cases of providing an impedance measurement device to the refrigeration system, which therefore contributes to improving the precision of refrigerant leakage detection. Furthermore, since the leakage determination unit and the signal output unit are also provided, even if the refrigeration system has already been installed without a function for detecting refrigerant leakage, refrigerant leakage detection can be enabled merely by custom installing the fluid sensor. The phrase “the fluid resulting from refrigerant leakage” herein means refrigerator oil which leaks together with the refrigerant, condensation water formed by refrigerant leakage, or the like.

A refrigerant leakage detection device according to a fourteenth aspect of the present invention comprises a first sensor, which is the fluid sensor according to any of the first through tenth aspects, a second sensor, a calculation unit, and a detection unit. The second sensor has two electrodes spaced apart, and the second sensor is configured so that refrigerant or a fluid resulting from refrigerant leakage is not held between the two electrodes. The calculation unit calculates, based on a first difference between the output of the first sensor and the output of the second sensor, a change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage. The detection unit determines whether or not refrigerant has leaked based on the change in electrostatic capacitance calculated by the calculation unit.

Besides the refrigerant or the fluid resulting from refrigerant leakage, other possible causes for changes in the impedance (or electrostatic capacitance) of the fluid sensor include humidity (i.e., water vapor), temperature, and changes over time. Therefore, if only one such fluid sensor is provided in or in proximity to each portion in the refrigerant circuit where refrigerant leakage detection is performed, there is a possibility that there will also be effects from causes of changes in electrostatic capacitance based on causes of changes in electrostatic capacitance other than the refrigerant or the fluid resulting from refrigerant leakage. In view of this, the refrigerant leakage detection device is configured having two fluid sensors, which are the first sensor in which the refrigerant or the fluid resulting from refrigerant leakage is held between the two electrodes, and the second sensor in which the refrigerant or the fluid resulting from refrigerant leakage is not held between the two electrodes. Humidity or other causes of changes in electrostatic capacitance thereby act on both the first sensor and the second sensor, but while the refrigerant or the fluid resulting from refrigerant leakage as a cause of a change in electrostatic capacitance does not act on the second sensor, the refrigerant or the fluid resulting from refrigerant leakage as a cause of a change in electrostatic capacitance does act on the first sensor. The calculation unit calculates the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage from the first difference between the sensor outputs, and the detection unit detects refrigerant leakage from the change in electrostatic capacitance. Specifically, with the first sensor and the second sensor, the refrigerant leakage detection device can offset the amount of change in electrostatic capacitance based on humidity or another cause of a change in electrostatic capacitance, and can calculate the amount of change in electrostatic capacitance alone based on the refrigerant or the fluid resulting from refrigerant leakage. It is thereby possible to accurately know whether or not refrigerant leakage has occurred, based solely on the amount of change in electrostatic capacitance of the first sensor based on the refrigerant or the fluid resulting from refrigerant leakage.

The refrigerant leakage detection device according to a fifteenth aspect of the present invention is the refrigerant leakage detection device according to the fourteenth aspect, further comprising a first oscillation unit which oscillates at a frequency corresponding to the electrostatic capacitance of the first sensor, a second oscillation unit which oscillates at a frequency corresponding to the electrostatic capacitance of the second sensor, and an up/down counter which counts up the output of the first oscillation unit and counts down the output of the second oscillation unit. The calculation unit calculates the first difference on the basis of the values counted by the up/down counter.

In this refrigerant leakage detection device, the up/down counter counts up a signal oscillating according to the electrostatic capacitance of the first sensor, and counts down a signal oscillating according to the electrostatic capacitance of the second sensor. Since the values counted by the up/down counter are numbers of pulses equivalent to the difference between a frequency corresponding to the electrostatic capacitance of the first sensor and a frequency corresponding to the electrostatic capacitance of the second sensor, the first difference can be calculated from the counted values. By calculating the change in electrostatic capacitance on the basis of the first difference calculated in this manner, it is possible to accurately single out the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage. Consequently, refrigerant leakage can be detected with greater accuracy.

The refrigerant leakage detection device according to a sixteenth aspect of the present invention is the refrigerant leakage detection device according to the fifteenth aspect, further comprising a selection unit. The selection unit selects either the output of the first oscillation unit or the output of the second oscillation unit. Either the output of the first oscillation unit or the output of the second oscillation unit selected by the selection unit is inputted to the up/down counter.

In this refrigerant leakage detection device, either the output of the first oscillation unit or the output of the second oscillation unit is inputted to the up/down counter. In other words, the output of the first oscillation unit and the output of the second oscillation unit are not inputted to the up/down counter simultaneously. Consequently, the up/down counter is capable of reliably performing the operation of counting up the output of the first oscillation unit and counting down the output of the second oscillation unit, and is also capable of obtaining accurate counted values for calculating the first difference.

The refrigerant leakage detection device according to a seventeenth aspect of the present invention is the refrigerant leakage detection device according to the fifteenth or sixteenth aspect, further comprising a resetting unit for resetting the counted values of the up/down counter in every predetermined cycle.

In this refrigerant leakage detection device, the calculation unit can calculate the first difference between the output of the first sensor and the output of the second sensor from the counted values before resetting.

The refrigerant leakage detection device according to an eighteenth aspect of the present invention is the refrigerant leakage detection device according to the fourteenth aspect, further comprising a first resetting unit for outputting a first reset signal based on a time constant determined by the electrostatic capacitance of the first sensor, a second resetting unit for outputting a second reset signal based on a time constant determined by the electrostatic capacitance of the second sensor, a first counting unit for counting a pulse signal having a predetermined frequency and stopping the counting of the pulse signal on the basis of the first reset signal, a second counting unit for counting the pulse signal and stopping the counting of the pulse signal on the basis of the second reset signal, and a difference calculation unit for calculating a second difference between counted numbers counted by each of the first counting unit and the second counting unit until counting of the pulse signal is stopped. The calculation unit calculates the first difference on the basis of the second difference.

In this refrigerant leakage detection device, the first counting unit counts the pulse signal until resetting is instructed by the first reset signal, and the second counting unit counts the pulse signal until resetting is instructed by the second reset signal. The first reset signal and the second reset signal herein are, respectively, a signal based on a time constant determined by the electrostatic capacitance of the first sensor, and a signal based on a time constant determined by the electrostatic capacitance of the second sensor; therefore, the first counting unit and the second counting unit stop counting at different timings. Specifically, the difference in counted numbers between each of the counting units is equivalent to the difference in electrostatic capacitance between each of the sensors. In view of this, in this refrigerant leakage detection device, the first difference can be derived from the second difference between each of the counted numbers. Consequently, it is possible to accurately single out the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage, and refrigerant leakage can be detected with greater precision.

The refrigerant leakage detection device according to a nineteenth aspect of the present invention is the refrigerant leakage detection device according to the fourteenth aspect, further comprising a first timer unit for outputting a first time duration elapse signal indicating that a time duration determined according to the electrostatic capacitance of the first sensor has elapsed, a second timer unit for outputting a second time duration elapse signal indicating that a time duration determined according to the electrostatic capacitance of the second sensor has elapsed, and an interval calculation unit for calculating the length of time during which either the first time duration elapse signal or the second time duration elapse signal is outputted from the first timer unit or the second timer unit. The calculation unit calculates the first difference on the basis of the length of time calculated by the interval calculation unit.

When the electrostatic capacitances of each of the sensors differ, the time duration determined according to the electrostatic capacitance of the first sensor and the time duration determined according to the electrostatic capacitance of the second sensor are different, and the first and second time duration elapse signals indicating that each of the time durations have elapsed therefore begin to be outputted with different timings. In view of this, in this refrigerant leakage detection device, the first difference is calculated based on the length of time during which either the first time duration elapse signal or the second time duration elapse signal indicating the elapse of a time duration is outputted, i.e., based on the difference between the timing with which the first time duration elapse signal begins to be outputted and the timing with which the second time duration elapse signal begins to be outputted. Specifically, since the above-described length of time is equivalent to the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage, it is possible to accurately single out the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage, and refrigerant leakage can be detected with greater precision.

The refrigeration system according to a twentieth aspect of the present invention comprises a refrigerant circuit and the refrigerant leakage detection device according to any of the fourteenth through nineteenth aspects, the refrigerant leakage detection device being disposed in or in proximity to a portion in the refrigerant circuit where refrigerant leakage detection is performed.

In this refrigeration system, refrigerant leakage detection in the refrigerant circuit is performed by the refrigerant leakage detection device according to any of the fourteenth through nineteenth aspects. Consequently, the same effects as those of the fourteenth through nineteenth aspects can be obtained.

A refrigerant leakage detection method according to a twenty-first aspect of the present invention is a refrigerant leakage detection method for detecting refrigerant leakage from a refrigerant circuit of a refrigeration system, wherein a fluid sensor comprising a sensor main body having two electrodes spaced apart is disposed in or in proximity to a portion in the refrigerant circuit where refrigerant leakage detection is performed, and impedance between the two electrodes is measured by an impedance measurement device. The phrase “having two electrodes” herein means having two electrodes that electrically form a pair.

In this refrigerant leakage detection device, when an impedance measurement device is connected to the fluid sensor provided in or in proximity to a portion of the refrigerant circuit where refrigerant leakage detection is performed and impedance between the two electrodes is measured, the effect of the refrigerant or a fluid resulting from refrigerant leakage entering between the two electrodes causes a change in impedance between a case when refrigerant has leaked from the refrigerant circuit and a case when refrigerant has not leaked. With this refrigerant leakage detection method, it is possible to detect, based on the change in impedance, that refrigerant has leaked from the portion where the sensor main body is provided, i.e., to detect that refrigerant has leaked while pinpointing the location in the refrigerant circuit of the refrigeration system where the refrigerant leakage is occurring. Even if the refrigeration system has already been installed without a function for detecting refrigerant leakage, if the fluid sensor is custom installed, refrigerant leakage detection can be enabled by connecting to an impedance measurement device. The phrase “the fluid resulting from refrigerant leakage” herein means refrigerator oil which leaks together with the refrigerant, condensation water formed by refrigerant leakage, or the like.

DETAILED DESCRIPTION OF EMBODIMENT(S)

Embodiments of a fluid sensor, a refrigerant leakage detection device, a refrigeration system, and a refrigerant leakage detection method according to the present invention are described hereinbelow based on the drawings.

(1) Overall Configuration of Air-Conditioning Apparatus

FIG. 1is a schematic structural diagram of an air-conditioning apparatus1as an embodiment of the refrigeration system according to the present invention. The air-conditioning apparatus1is a so-called separate-type air-conditioning apparatus, comprising primarily a heat source unit2, an utilization unit4, and refrigerant communication pipes5,6for connecting the heat source unit2and the utilization unit4, thus constituting a vapor compression refrigerant circuit10. Charged within the refrigerant circuit10is R12 or another CFC refrigerant, R22 or another HCFC refrigerant, R410A or another HFC refrigerant, propane or another HC refrigerant, carbon dioxide, ammonia, or the like.

The utilization unit4is installed in the back surface of a ceiling, the front surface of a ceiling, a wall surface, or another location in an air-conditioned room, for example, and the utilization unit4has an utilization-side refrigerant circuit10aconstituting part of the refrigerant circuit10. The utilization-side refrigerant circuit10ahas primarily an utilization-side heat exchanger41.

The utilization-side heat exchanger41is a heat exchanger which functions as a refrigerant heater and cools indoor air during a cooling operation, and which functions as a refrigerant cooler and heats indoor air during a heating operation. One end of the utilization-side heat exchanger41is connected to the first refrigerant communication pipe5, and the other end of the utilization-side heat exchanger41is connected to the second refrigerant communication pipe6. The utilization-side heat exchanger41can be a fin-and-tube heat exchanger or the like, configured from numerous fins and heat transfer tubes through which refrigerant flows, for example.

In the present embodiment, the utilization unit4has an utilization-side fan42for drawing indoor air into the unit and supplying the air back into the room after the air has undergone heat exchange and heat exchange can be conducted between the indoor air and the refrigerant flowing through the utilization-side heat exchanger41. The utilization-side fan42is driven by an utilization-side fan motor43.

The utilization unit4also has an utilization-side controller44for controlling the operations of the components constituting the utilization unit4. The utilization-side controller44has a microcomputer, memory, and the like provided in order to control the utilization unit4, and the utilization-side controller44can exchange control signals and the like with a remote controller (not shown) for separately operating the utilization unit4and can also exchange control signals and the like with the heat source unit2.

The heat source unit2is installed outside of the air-conditioned room, for example, and the heat source unit2has a heat source-side refrigerant circuit10bconstituting part of the refrigerant circuit10. The heat source-side refrigerant circuit10bhas primarily a compressor21, a four-way switching valve23, a heat source-side heat exchanger24, an expansion mechanism25, and first and second shutoff valves26,27.

The compressor21is a compressor which has the functions of drawing in a low-pressure gas refrigerant, compressing it into a high-pressure gas refrigerant, and then discharging the high-pressure gas refrigerant. In the present embodiment, the compressor21is a hermetic compressor in which a compressor motor22is installed inside a housing. Also charged within the refrigerant circuit10is refrigerator oil for lubricating the interior of the compressor21.

The four-way switching valve23is a valve which functions as a switching mechanism for switching the direction of refrigerant flow. During the cooling operation, in order for the heat source-side heat exchanger24to function as a cooler of the refrigerant compressed in the compressor21and for the utilization-side heat exchanger41to function as a heater of the refrigerant cooled in the heat source-side heat exchanger24, the four-way switching valve23is capable of connecting the discharge side of the compressor21and one end of the heat source-side heat exchanger24and also of connecting the intake side of the compressor21and the second refrigerant communication pipe6(i.e., the second shutoff valve27) (refer to the solid lines of the four-way switching valve23inFIG. 1). During the heating operation, in order for the utilization-side heat exchanger41to function as a cooler of the refrigerant compressed in the compressor21and for the heat source-side heat exchanger24to function as a heater of the refrigerant cooled in the utilization-side heat exchanger41, the four-way switching valve23is capable of connecting the discharge side of the compressor21and the second refrigerant communication pipe6(i.e., the second shutoff valve27) and also of connecting the intake side of the compressor21and one end of the heat source-side heat exchanger24(refer to the dashed lines of the four-way switching valve23inFIG. 1).

The heat source-side heat exchanger24is a heat exchanger which functions as refrigerant cooler using outside air as a heat source during the cooling operation, and which functions as a refrigerant heater using outside air as a heat source during the heating operation. One end of the heat source-side heat exchanger24is connected to the four-way switching valve23, and the other end of the heat source-side heat exchanger24is connected to the expansion mechanism25. The heat source-side heat exchanger24can be a fin-and-tube heat exchanger or the like configured from numerous fins and heat transfer tubes through which refrigerant flows, for example.

The expansion mechanism25is a mechanism for depressurizing high-pressure refrigerant, and in the present embodiment is an electric expansion valve for depressurizing high-pressure refrigerant during both the cooling operation and the heating operation.

The first and second shutoff valves26,27are valves provided to the ports connecting with external devices and piping (specifically, the first and second refrigerant communication pipes5,6). The first shutoff valve26is connected to the expansion mechanism25. The second shutoff valve27is connected to the four-way switching valve23.

In the present embodiment, the heat source unit2has a heat source-side fan28for drawing outside air into the unit and discharging the air out of the room after the air has undergone heat exchange, and heat exchange can be conducted between the outside air and the refrigerant flowing through the heat source-side heat exchanger24. The heat source-side fan28is driven by a heat source-side fan motor29.

The heat source unit2has a heat source-side controller30for controlling the operations of the components constituting the heat source unit2. The heat source-side controller30has a microcomputer, memory, and the like provided in order to control the heat source unit2, and the heat source-side controller30can exchange control signals and the like with the utilization-side controller44of the utilization unit4. Thus, the heat source-side controller30and the utilization-side controller44together constitute a controller7for controlling the operations of the components of the air-conditioning apparatus1.

(2) Configuration of Fluid Sensor and the Like for Detecting Refrigerant Leakage, and Refrigerant Leakage Detection Method

In the refrigerant circuit10described above, there is a danger that refrigerant will leak out of the refrigerant circuit10from the various devices, pipes, or pipe joints constituting the refrigerant circuit10. When refrigerant leakage has occurred, it is preferable to pinpoint the location where the refrigerant leakage is occurring in the refrigerant circuit10for taking the appropriate measures to deal with the refrigerant leakage.

In view of this, in the air-conditioning apparatus1of the present embodiment, a fluid sensor8is disposed in or in proximity to a portion in the refrigerant circuit10where there is a high danger of refrigerant leakage, and by using the fluid sensor8, it is capable of detecting refrigerant leakage from the refrigerant circuit10of the air-conditioning apparatus1while pinpointing the location in the refrigerant circuit10where the refrigerant leakage is occurring. The following is a description, made usingFIGS. 1 through 7, of the configuration of the fluid sensor8and the like for detecting refrigerant leakage in the present embodiment.FIG. 2is a drawing showing a state in which the fluid sensor8in the present embodiment has been provided in or in proximity to a portion in the refrigerant circuit10where refrigerant leakage is detected.FIG. 3is a view ofFIG. 2as seen in the direction of arrow I.FIG. 4is a perspective view showing the vicinity of a sensor main body8aof the fluid sensor8in the present embodiment.FIG. 5is a perspective view showing an impedance measurement device9used in the present embodiment.FIGS. 6 and 7are schematic structural diagrams of an impedance measurement circuit.

In the air-conditioning apparatus1of the present embodiment, the pipe joints in brazed portions, portions connected by flare nuts, or other portions throughout the refrigerant circuit10are considered primarily to be the components in the refrigerant circuit10where there is a high danger of refrigerant leakage occurring. Therefore, the fluid sensors8are respectively disposed in the pipe joint connecting the first shutoff valve26and the first refrigerant communication pipe5or the proximity thereof, the pipe joint connecting the second shutoff valve27and the second refrigerant communication pipe6or the proximity thereof, the pipe joint connecting the utilization unit4and the first refrigerant communication pipe5or the proximity thereof, and the pipe joint connecting the utilization unit4and the second refrigerant communication pipe6or the proximity thereof, as shown inFIG. 1. In the present embodiment, fluid sensors8are disposed at the aforementioned four locations, but the fluid sensors8are not limited to these locations and may also be disposed in other portions of the refrigerant circuit10. The pipes and pipe joints constituting the refrigerant circuit10are made of copper or another metal.

Next, the specific configuration of the fluid sensor8in the present embodiment will be described. Since the fluid sensors8disposed in the aforementioned four locations all have the same configuration, the fluid sensors8are treated as the same unless otherwise noted.

The fluid sensor8has primarily the sensor main body8aand an electrical wire8b. The sensor main body8ahas primarily two electrodes81,82spaced apart. The electrodes81,82are plate-shaped members made of an electroconductive material, and in the present embodiment, the spacing of the electrodes is maintained by a spacer member83made of an electrically insulated material. Thus, the sensor main body8ain the present embodiment has a flat plate-shaped structure. Copper, iron, aluminum, or another metal or highly electroconductive material is preferred as the electroconductive material used in the electrodes81,82, but any material can be used as long as it is electroconductive. The electrically insulated material used in the spacer member83is preferably a synthetic resin, a ceramic, or another highly electrically insulated material, but any material can be used as long as it is highly electrically insulated.

Connected to the electrodes81,82are the electrical wire8bsuch that it can be connected to an impedance measurement device9(described hereinafter) for measuring impedance between the two electrodes81,82. In the present embodiment, the electrical wire8bis made of a coaxial cable, wherein a BNC connector84ais attached to one end. At the other end of the electrical wire8b, a core84bof the coaxial cable is connected to the electrode82by soldering, and a shield wiring84cof the coaxial cable is connected to the electrode81by soldering. When the shield wiring84cis connected to the electrode81, it is preferable to cover the portion where the shield wiring84cis bundled with a heat-shrinkable tube85and to heat-shrink this portion in advance, in order to avoid contact between part of the shield wiring84cand the core84bor the electrode82as in the present embodiment. It is preferable to use a coaxial cable as the electrical wire8bin view of characteristics such as electrical resistance with respect to the length of the electrical wire as described above, but the electrical wire is not limited to a coaxial cable and various other options are possible. Nor is the connector84aattached to the electrical wire8blimited to a BNC connector, and M, N, F, TNC, and various other types of connecters can be used according to the type and the like of terminal component of the impedance measurement device9to which the wire is connected. Connecting the other end of the electrical wire8bto the electrodes81,82is not limited to soldering, and various other connection methods can be used.

The fluid sensor8having this configuration is arranged in the present embodiment such that the sensor main body8ais adjacent to a pipe joint (a flare nut connected portion in this case), and the electrical wire8bis secured to a refrigerant pipe by a securing member86made of a band, an adhesive tape, or the like so as to preserve this arrangement. Since the sensor main body8ahas a flat plate-shaped structure, the fluid sensor8is compact in size and easy to handle, and it is therefore easy to install the fluid sensor8in proximity to a portion where refrigerant leakage will be detected. As for the timing of providing the fluid sensors8, in cases in which the air-conditioning apparatus1will be newly constructed, the fluid sensors can be provided in advance in the heat source unit2, the utilization unit4, and other components constituting the air-conditioning apparatus1when factory shipping, or the fluid sensors can be provided during onsite installation of the heat source unit2, the utilization unit4, and other components. In cases in which the air-conditioning apparatus1has already been constructed and does not have a function for detecting refrigerant leakage, the fluid sensors can be provided by custom installation during a time such as maintenance.

In the air-conditioning apparatus1provided with such fluid sensors8, the impedance measurement device9is connected to the fluid sensors8and the impedance is measured between the two electrodes81,82of each of the sensor main bodies8aof the fluid sensors8, whereby refrigerant leakage from the refrigerant circuit10of the air-conditioning apparatus1is detected.

First, the principle of refrigerant leakage detection by impedance measurement will be described. As described above, the sensor main bodies8aof the fluid sensors8are provided in or in proximity to portions in the refrigerant circuit10where refrigerant leakage will be detected and the impedance between the pairs of electrodes81,82is measured, whereupon the effect of the refrigerant or the fluid resulting from refrigerant leakage entering into the spaces S between the pairs of electrodes81,82is to cause variation in the impedance between cases in which refrigerant leakage from the refrigerant circuit10occurs and cases in which refrigerant leakage does not occur. The phrase “fluid resulting from refrigerant leakage” refers to refrigerator oil that leaks together with the refrigerant, condensed water produced by refrigerant leakage, or the like. Based on this impedance variation, it is possible to detect refrigerant leakage from the portions where the sensor main bodies8aare provided, i.e., it is possible to detect refrigerant leakage while pinpointing the location in the refrigerant circuit10of the air-conditioning apparatus1where the refrigerant leakage is occurring. In order to allow the effect of the refrigerant or the fluid resulting from refrigerant leakage entering the spaces S between the pairs of electrodes81,82to be clearly observable, it is preferable to dispose the fluid sensors8on the undersides of the portions where refrigerant leakage is detected and thus enable the refrigerator oil or other fluid in liquid form to easily enter the spaces S between the pairs of electrodes81,82as shown inFIG. 2, and also to cover the portions including both the locations of refrigerant leakage detection and the fluid sensors8with films87or the like and thus enable the refrigerant or the fluid resulting from refrigerant leakage to easily pool in the spaces S between the pairs of electrodes81,82as shown inFIGS. 2 and 3.

Next, the impedance measurement device9for measuring impedance between two electrodes81,82will be described. Possible examples of the impedance measurement device9include a device using a measurement system whereby the impedance to be measured is obtained based on the voltage applied to the measured object and the electric current flowing through the object, and a device using a measurement system whereby the impedance to be measured (the impedance between the two electrodes81,82in this case) is obtained based on an element for which the impedance is already known. The impedance measurement circuit shown inFIG. 6is referred to as an LCR meter, which corresponds to the former measurement method, and the impedance measurement circuit shown inFIG. 7is referred to as a bridge circuit, which corresponds to the latter measurement method.

First, to describe the impedance measurement circuit in the example of an LCR meter, the impedance measurement circuit has primarily a power source91, a feedback resistor RS, an op-amp92, and a detector93; and impedance ZX (the sensor main body8ain this case) is connected, thereby constituting a circuit known as a self-balancing bridge. In this impedance measurement circuit, when a voltage is applied from the power source91, since the negative side of the op-amp92is connected to a point P between the impedance ZX and the feedback resistor RS, the voltage at the point P is always zero due to the effect of negative feedback, and the electric current flowing from the power source91through the impedance ZX all flows into the feedback resistor RS. The voltage applied to the impedance ZX is thereupon equal to the voltage of the power source91, and the output voltage of the op-amp92is obtained as a product of the feedback resistor RS and the electric current flowing through the impedance ZX. Therefore, the impedance ZX can be obtained by detecting the two voltages via the detector93and using the product of the feedback resistor RS in the ratio of the voltages.

Next, to describe the impedance measurement circuit in the example of a bridge circuit, the impedance measurement circuit has primarily impedances Z1, Z2, Z3, a detector94, and a power source95; and impedance ZX (the sensor main body8ain this case) is connected, thereby constituting a bridge circuit. In this impedance measurement circuit, the impedance ZX of the sensor main body8acan be obtained by applying a voltage from the power source95and adjusting the impedances Z1, Z2, Z3so that the output in the detector94is zero.

Refrigerant leakage can be detected in the following manner using this type of impedance measurement device9. First, during a state in which no refrigerant is leaking from the refrigerant circuit10(e.g., immediately after the air-conditioning apparatus1has been constructed or the fluid sensor8has been installed), the fluid sensor8is connected to the impedance measurement device9, and the impedance ZX is measured for a state in which no refrigerant is leaking from the portion in the refrigerant circuit10where refrigerant leakage detection is performed. After a predetermined time period has elapsed, the fluid sensor8is once again connected to the impedance measurement device9, the impedance ZX is measured, and this impedance is compared with the impedance ZX measured during the state in which no refrigerant was leaking from the portion in the refrigerant circuit10where refrigerant leakage detection is performed. In cases in which a change exceeding a threshold has occurred, it is concluded that refrigerant is leaking from the refrigerant circuit10and the location of refrigerant leakage is in or in proximity to the portion where the fluid sensor8being measured is placed. In cases in which no changes exceeding the threshold have occurred in any of the fluid sensors8, it is concluded that refrigerant leakage is not occurring in the refrigerant circuit10. Either the LCR meter or the bridge circuit can be used as the impedance measurement device9, but the smaller and more portable LCR meter is more effective than the bridge circuit, which has high measurement precision but is somewhat troublesome to manage and adjust. The smaller and more portable LCR meter is particularly effective in cases such as the present embodiment in which only fluid sensors8are provided to the air-conditioning apparatus1and the impedance measurement device9is connected only when refrigerant leakage detection is performed.

With the fluid sensor8of the present embodiment, it is thereby possible to detect refrigerant leakage while specifying, based on the change in impedance between the two electrodes81,82of the sensor main body8a, that the refrigerant leakage is occurring from the portion where the sensor main body8ais provided, i.e., the location in the refrigerant circuit10of the air-conditioning apparatus1where the refrigerant leakage is occurring. Particularly, since the fluid sensor8is provided in or in proximity to the portion in the refrigerant circuit10where refrigerant leakage detection is performed in the air-conditioning apparatus1of the present embodiment, it is possible to detect refrigerant leakage while specifying that the refrigerant leakage is occurring from the portion where the sensor main body8ais provided, i.e., the location in the refrigerant circuit10of the air-conditioning apparatus1where the refrigerant leakage is occurring by connecting the impedance measurement device9to the fluid sensor8when refrigerant leakage detection is performed. Even if the air-conditioning apparatus1has already been constructed and has no function for detecting refrigerant leakage, if the fluid sensors8are custom installed, it is possible to perform refrigerant leakage detection by connecting the impedance measurement device9thereto.

In the embodiment described above, a space S is merely formed between the two electrodes81,82constituting the sensor main body8aof the fluid sensor8as shown inFIG. 4, and since it is difficult for refrigerant or fluid resulting from refrigerant leakage to actively pool in between the two electrodes81,82in this space S, there are cases in which refrigerant leakage cannot be detected if the amount leaked is extremely small, for example.

In view of this, in the fluid sensor8of the present modification, a fluid holder88for holding the refrigerant or the fluid resulting from refrigerant leakage is provided in the space S between the two electrodes81,82as shown inFIG. 8, and the refrigerant or the fluid resulting from refrigerant leakage entering in between the two electrodes81,82is held and collected in the fluid holder88.

For example, when refrigerator oil is to be the fluid resulting from refrigerant leakage and is actively held between the two electrodes81,82, paper is used as the fluid holder88, the refrigerator oil that has entered between the two electrodes81,82can be held and collected by being soaked up by the fluid holder88. When paper is used as the fluid holder88being highly lipophilic, the refrigerator oil can be effectively held, and reductions in electric capacitance can also be prevented because the fluid holder hardly swell when the oil is soaked up. Furthermore, using a highly water repellent paper makes it possible to prevent condensation water resulting from the refrigerant leakage from being soaked up in the paper and to minimize the effects of condensation water. When condensation water resulting from the surrounding air being cooled by refrigerant leakage is to be the fluid resulting from refrigerant leakage and is actively held between the two electrodes81,82, using a highly hydrophilic fluid holder88made of paper or another substance that hardly swell easily when condensation water is soaked up makes it possible to prevent reductions in electric capacitance caused by effectively holding condensation water or soaking up refrigerator oil, and using a highly oil repellent paper or the like makes it possible to prevent refrigerator oil resulting from refrigerant leakage from being soaked up in the paper and to minimize the effects of the refrigerator oil. When the refrigerant is to be actively held between the two electrodes81,82, an adsorbent that adsorbs the refrigerant (e.g., zeolite or the like) can be used as the fluid holder88, for example, or a substance composed of paper supporting an adsorbent that adsorbs the refrigerant can be used as the fluid holder88. When an adsorbent that adsorbs the refrigerant or paper or another substance supporting the adsorbent is used as the fluid holder88, it is preferable to use an adsorbent that is highly selective with respect to the refrigerant used in the air-conditioning apparatus1. Besides paper, other possible substances that can be used as the fluid holder88include cloth, resins, ceramics and other porous substances, crystalline bodies, films, and the like; and in cases in which refrigerant leakage is detected primarily from the effects of the refrigerator oil, paper is preferably used in view of the cost of the materials, ease of processing, and other factors.

It is thereby possible to increase the precision of refrigerant leakage detection in the fluid sensor8and the air-conditioning apparatus1of the present modification, even if the amount of refrigerant leakage is extremely small. In cases in which paper is used as the fluid holder88, the refrigerator oil, which does not readily evaporate or diffuse, can be held and accumulated by being soaked up by the paper used as the fluid holder88even after the leakage; therefore, it is possible to more reliably ascertain evidence of refrigerant leakage and thereby to further increase the precision of refrigerant leakage detection, in comparison with cases in which the readily evaporating and diffusing refrigerant is held by the fluid holder88after leakage.

In both the embodiment described above and Modification 1, the sensor main body8aof the fluid sensor8was provided to a portion in the refrigerant circuit10where refrigerant leakage detection was performed, but depending on the situation, there are cases in which the sensor main body8amust be placed in proximity to the portion in the refrigerant circuit10where refrigerant leakage detection is performed, yet separate from the portion in the refrigerant circuit10where refrigerant leakage detection is performed.

In such cases, a fluid-guiding member89may be provided for leading refrigerant or fluid resulting from refrigerant leakage from the portion in the refrigerant circuit10where refrigerant leakage detection is performed to the sensor main body8a, and the refrigerant or fluid resulting from refrigerant leakage may be actively led between the two electrodes81,82.

For example, using the fluid sensor8in Modification 1 as an example, one considerable option is to position one end of the fluid-guiding member89in the space S (on the fluid holder88in this case) between the two electrodes81,82as shown inFIG. 9, and to put the other end of the fluid-guiding member89in contact with the portion in the refrigerant circuit10where refrigerant leakage detection is performed. Possible examples that can be used as the fluid-guiding member89include paper, cloth, resins, ceramics and other porous substances, crystalline bodies, films, and the like, similar to the fluid holder88; and a material is used which is suitable for the refrigerant or the fluid resulting from refrigerant leakage that will be led to the space S between the two electrodes81,82. A configuration provided with this type of fluid-guiding member89can also be applied to the sensor main body8ashown inFIG. 4, which has no fluid holder88provided between the two electrodes81,82.

It is thereby possible with the fluid sensor8of the present modification to increase the precision of refrigerant leakage detection even though the sensor main body8amust be placed separate from the portion in the refrigerant circuit10where refrigerant leakage detection is performed, because the refrigerant or fluid resulting from refrigerant leakage can be led between the two electrodes81,82.

In the embodiment described above as well as Modifications 1 and 2, the sensor main body8awith a flat plate-shape structure is used as shown inFIGS. 2 to 4,8, and9, but the sensor main body8amay also have a structure that can be attached so as to wind around the pipes or pipe joints constituting the refrigerant circuit10.

For example, one possibility is to attach a sensor main body having a fluid holder88provided in the space S between the two electrodes81,82so that the sensor main body winds around a pipe, as is the case with the sensor main body8aof the fluid sensor8of the present modification shown inFIGS. 10 and 11. This sensor main body8amay also be attached so as to wind around a pipe joint rather than a pipe.

It is thereby possible with the fluid sensor8of the present modification to effectively lead refrigerant or fluid resulting from refrigerant leakage in between the two electrodes81,82, and it is therefore possible to reliably ascertain evidence of refrigerant leakage and thereby to improve the precision of refrigerant leakage detection.

In the embodiment described above as well as Modifications 1 through 3, there could possibly be cases in which the electric capacitance of the sensor main body8ais small and the precision of refrigerant leakage detection is insufficient, because the electrodes81,82having a single-layer structure are used, wherein only one space S formed by the electrode81and the electrode82is provided as shown inFIGS. 4,8,9, and11.

In view of this, in the fluid sensor8of the present modification, electrodes81,82having a multilayered structure are used, wherein a plurality of spaces formed by the electrode81and the electrode82are provided.

For example, in one possibility shown inFIG. 12, an electrode81, an electrode82, and two fluid holders88are formed into belt shapes, and the fluid holders88are superposed over both surfaces of the electrode82, which is folded over multiple times. The electrode81is folded over multiple times and incorporated from a direction orthogonal to the electrode82with the fluid holders88superposed over both sides, an electrical wire8bis connected to the electrodes81,82by soldering or another method (not shown inFIG. 12), and a heat-shrinkable tube90is then made to cover the arrangement and is heat-shrunk, thereby constituting a flat plate-shaped sensor main body8a. Another possibility is to stack the members multiple times in the following sequence as shown inFIG. 13: an electrode81, a fluid holder88(i.e., space S), an electrode82, the fluid holder88(i.e., space S), etc., wherein the electrodes81are connected to each other, the electrodes82are connected to each other, and the electrical wire8bis connected by soldering or another method to the electrodes81,82(not shown inFIG. 13), thereby constituting a flat plate-shaped sensor main body8a. Another possibility is a configuration in which the members are attached so as to wind multiple times around the refrigerant pipe in the following sequence as shown inFIG. 14: an electrode81, a fluid holder88(i.e., space S), an electrode82, the fluid holder88(i.e., space S). Note that these cases are similar to the embodiment described above as well as Modifications 1 through 3 in that the configuration has two types of electrodes81,82which electrically oppose each other.

It is thereby possible with the fluid sensor8of the present modification to increase the electric capacitance of the sensor main body8aand thereby to improve the precision of refrigerant leakage detection, because the electrodes81,82having a multilayered structure are used.

In Modifications 1 through 4 described above, a structure was presented in which the fluid holder88is provided in the space S between the two electrodes81,82constituting the sensor main body8aas shown inFIGS. 8,9, and11to14, whereby refrigerant or fluid resulting from refrigerant leakage entering in between the two electrodes81,82is held and accumulated in the fluid holder88.

However, in cases in which an attempt to increase the precision of refrigerant leakage detection is made by performing refrigerant leakage detection on the basis of changes in impedance unique to a specified fluid among the refrigerant or fluid resulting from refrigerant leakage, it is preferable to prevent to the fullest extent possible a fluid and the like other than the refrigerant or a specified fluid resulting from refrigerant leakage from entering between the two electrodes81,82, and to thereby prevent a fluid and the like other than the refrigerant or a specified fluid resulting from refrigerant leakage from being held in the fluid holder88. Particularly, in a structure such as Modification 2 wherein the fluid-guiding member89is provided in the sensor main body8aand the refrigerant or fluid resulting from refrigerant leakage is thereby actively led between the two electrodes81,82, there are cases in which the electrodes81,82and the fluid holder88are placed in a location separated from the portion where refrigerant leakage detection is performed, and fluid and the like other than the refrigerant or a specified fluid resulting from refrigerant leakage readily enters in between the two electrodes81,82. It is therefore even more preferable to prevent fluid and the like other than the refrigerant or a specified fluid resulting from refrigerant leakage from being held in the fluid holder88.

In view of this, in the present modification, a fluid holder88and electrodes81,82are covered by a casing101constituting a sensor main body8a, whereby fluid and the like other than the refrigerant or a specified fluid resulting from refrigerant leakage is prevented to the fullest extent possible from being held in the fluid holder88. A fluid-guiding member89for leading the refrigerant or fluid resulting from refrigerant leakage in between the two electrodes81,82is also provided so as to protrude from the interior of the casing101to the exterior of the casing101, whereby the refrigerant or specified fluid resulting from refrigerant leakage can be led into the casing101and held and accumulated in the fluid holder88, and thereby the precision of refrigerant leakage detection can be even further improved.

For example, to make an example of a case in which refrigerator oil is the fluid resulting from refrigerant leakage, the electrodes81,82and the fluid holders88having a multilayered structure are accommodated within accommodating parts102a,102bformed in the casing101which can be attached so as to wind around the pipes constituting the refrigerant circuit10, as shown inFIGS. 15 to 17. The fluid-guiding member89can be made to protrude to the exterior of the casing101through openings103a,103bcommunicated with the accommodating parts102a,102b(Note thatFIG. 17shows only a longitudinal cross-sectional view of a columnar part101aand does not show a columnar part101b, but since the columnar part101bhas the same longitudinal cross section as the columnar part101a, the opening103band other parts formed in the columnar part101bhave the same shapes as the opening103aand other parts formed in the columnar part101a). To describe the structure of the sensor main body8aand the casing101hereinbelow, the sensor main body8ais in a state of being attached so as to wind around a pipe constituting the refrigerant circuit10, wherein the cross section (FIG. 16) of the sensor main body8a(or the casing101) when the refrigerant pipe is cut transversely is a transverse cross section, and the cross section (FIG. 17) of the sensor main body8a(or the casing101) when the refrigerant pipe is cut longitudinally is a longitudinal cross section.

The casing101has the two columnar parts101a,101bwhose transverse cross sections are substantially crescent shapes. The columnar parts101a,101bare composed of a synthetic resin or another electrically insulative material. Inside of each of the columnar parts101a,101bare formed accommodating parts102a,102bwhose transverse cross sections are substantially crescent shapes. Inside of each of the accommodating parts102a,102b, the fluid holder88and the electrodes81,82are accommodated in a multilayered state of being layered with respect to the radial direction of the refrigerant pipe in the following sequence: the electrode81, the fluid holder88, the electrode82, the fluid holder88, the electrode81, the fluid holder88, the electrode82. The electrodes81,82are composed of an electroconductive material as copper, iron, aluminum, or another metal and the like, similar to the embodiment and modifications described above. The fluid holder88is composed of a highly lipophilic material as paper and the like, similar to the embodiment and modifications described above.

Each of the accommodating parts102a,102bopen to the outside of each of the columnar parts101a,101bat one end in the pipe longitudinal direction. In the openings of each of the accommodating parts102a,102bat one end in the pipe longitudinal direction, the opening area when viewed from the pipe longitudinal direction is of a size through which a multilayered stack of the electrode81, the fluid holder88, and the electrode82can be inserted (seeFIG. 17; note thatFIG. 17shows only a longitudinal cross section of the columnar part101a, but the columnar part101bhas the same longitudinal cross section as the columnar part101a). The lead wires of the electrodes81,82are drawn out of the columnar parts101a,101bthrough the openings at one end in the pipe longitudinal direction of each of the accommodating parts102a,102b, and are connected to an electrical wire8b(seeFIG. 17). With the lead wires of the electrodes81,82having been drawn out of the columnar parts101a,101b, the openings at one end in the pipe longitudinal direction of each of the accommodating parts102a,102bare filled in by a sealant104, which can contribute to preventing a fluid and the like other than the refrigerant or a specified fluid resulting from refrigerant leakage (refrigerator oil in this case) from entering the accommodating parts102a,102b. The sealant104herein is composed of a silicon resin or another electrically insulative material.

Openings103a,103bcommunicated with the accommodating parts102a,102bare formed in the columnar parts101a,101b. Each of the openings103a,103bis placed so as to communicate with the opening in the other end of each of the accommodating parts102a,102bin the pipe longitudinal direction. In the openings103a,103b, the opening area when viewed from the pipe longitudinal direction is less than the opening area of each of the accommodating parts102a,102b. Specifically, each of the openings103a,103bis narrowed so as to be smaller in opening size than each of the accommodating parts102a,102bcovering the fluid holder88and the electrodes81,82. The fluid-guiding member89, which leads refrigerant or refrigerator oil as a specified fluid resulting from refrigerant leakage between the electrodes81,82(i.e., to the fluid holder88) inside of each of the accommodating parts102a,102b, protrudes from each of the accommodating parts102a,102bthrough the openings103a,103bto the outside of the columnar parts101a,101b. Specifically, the openings103a,103bare formed in the casing101in order to allow the fluid-guiding member89to protrude from the interior of the casing101to the exterior of the casing101. The fluid-guiding member89is composed of a highly lipophilic material as paper and the like, similar to the fluid holder88. Since the fluid-guiding member89has a portion exposed to the exterior of the casing101, the selectivity of the fluid-guiding member89with regard to the refrigerator oil is preferably higher than that of the fluid holder88covered by the accommodating parts102a,102b. Therefore, a highly water repellent material is preferably used as the fluid-guiding member89. Thus, the opening size of the openings103a,103bfor allowing the fluid-guiding member89to protrude from the interior of the casing101to the exterior of the casing101is less than that of the accommodating parts102a,102bcovering the fluid holder88and the electrodes81,82, whereby fluids (e.g., condensation water) and the like other than the refrigerant or a specified fluid (refrigerator oil in this case) resulting from refrigerant leakage can be hindered from entering the accommodating parts102a,102b. Each of the openings103a,103bis provided with a sealant105for filling in the gaps between each of the openings103a,103band the fluid-guiding member89in a state of the fluid-guiding member89protruding from the openings103a,103b. This can contribute to preventing fluids (e.g., condensation water) and the like other than the refrigerant or a specified fluid (refrigerator oil in this case) resulting from refrigerant leakage from entering the accommodating parts102a,102b. The sealant105herein is composed of an electroconductive material as silicon resin and the like. Somewhat increasing the length of the portion of the fluid-guiding member89exposed outside of the casing101makes it possible to reliably collect the refrigerant leaked out from the detection location (the flare nut portion inFIG. 15) or the specified fluid (refrigerator oil in this case) resulting from refrigerant leakage. A plurality of incisions89arunning in the pipe longitudinal direction (seeFIG. 15) is also formed in the fluid-guiding member89, making it easy for the fluid-guiding member89to be deformed according to the shape of the detection location (the flare nut portion inFIG. 15in this case), and also making it even easier to collect the refrigerant leaked out from the detection location or the specified fluid (refrigerator oil in this case) resulting from refrigerant leakage.

Further, the columnar parts101a,101bare configured so that one pair of ends in transverse cross section are respectively linked together by a hinge101c, while each of the other ends in transverse cross section are capable of moving relative to each other about the hinge101cin the direction of arrow A (seeFIG. 16). In cases in which the columnar parts101a,101bare made of a synthetic resin, the hinge101cthat uses the deformability of the synthetic resin can be integrally molded with the columnar parts101a,101b.

The columnar parts101a,101bare capable of detachably latching together at each of the other ends in transverse cross section via a latching part101d, whereby the sensor main body8acan be detachably latched onto the pipe or pipe joint constituting the refrigerant circuit10. Therefore, the operation of attaching or removing the fluid sensor8is easy. Pawls101e,101fand the like (seeFIG. 16) that enable the other ends of each of the columnar parts101a,101bin transverse cross section to latch together so as to not separate can be used as the latching part101d. In cases in which the columnar parts101a,101bare made of a synthetic resin, the latching part101d(the pawls101e,101finFIG. 16) can be integrally molded with the columnar parts101a,101b.

In the fluid sensor8described above, the sealant104covers the opening at the one ends in the pipe longitudinal direction of the accommodating parts102a,102bof each of the columnar parts101a,101bconstituting the casing101(seeFIG. 17), but this opening may also be covered by lid members106a,106bfor covering the opening at the other ends in the pipe longitudinal direction of the accommodating parts102a,102b(seeFIG. 18;FIG. 18shows only a longitudinal cross section of the columnar part101aand the lid member106a, but the columnar part101band the lid member106bhave the same longitudinal cross sections as the columnar part101aand the lid member106a). In this case as well, the opening at the one ends in the pipe longitudinal direction of the accommodating parts102a,102bis of a size through which a multilayered stack of the electrode81, the fluid holder88, and the electrode82can be inserted, whereby the fluid holder88and the electrodes81,82can be easily inserted through each of the accommodating parts102a,102b.

Another possibility for each of the columnar parts101a,101bis to use parts that do not have an opening in the one ends of the accommodating parts102a,102bin the pipe longitudinal direction. For example, the other ends in the pipe longitudinal direction of the accommodating parts102a,102bare provided with an opening of a size through which a multilayered stack of the electrode81, the fluid holder88, and the electrode82can be inserted, and the fluid holder88and the electrodes81,82are inserted through each of the accommodating parts102a,102b, after which part of the opening in the other ends of the accommodating parts102a,102bin the pipe longitudinal direction may be covered by wedge members107a,107b, thereby forming openings103a,103bthat are smaller than the opening size of the accommodating parts102a,102b(seeFIG. 19;FIG. 19shows only a longitudinal cross section of the columnar part101aand the wedge member107a, but the columnar part101band the wedge member107bhave the same longitudinal cross section as the columnar part101aand the wedge member107a).

In the present modification, the outer shape of the casing101is a substantially cylinder, but is not limited thereto and may be a prismatic column. The spatial shapes of the accommodating parts102a,102bare not limited to arcs; they may assume other shapes.

In Modification 5 described above, a refrigerant pipe constituting the refrigerant circuit10was wound using the casing101having two columnar parts101a,101bwhose transverse cross sections were crescent shapes, but another option is a structure such as the one shown inFIGS. 20 to 22having a casing101made of a synthetic resin, which has primarily a belt-shaped part108substantially shaped as a belt, and a plurality of space-forming parts109formed into L shapes and U shapes in the longitudinal direction of the belt-shaped part108; wherein a plurality of accommodating parts102for covering a fluid holder88and electrodes81,82is formed by the plurality of space-forming parts109and the belt-shaped part108, fluid-guiding members89are made to protrude from the short direction of the belt-shaped part108, and the belt-shaped part108is bent in the directions of the arrows B to wind up the pipe constituting the refrigerant circuit10.

In the present modification, similar to Modification 5, the precision of refrigerant leakage detection can be further improved because fluids and the like other than the refrigerant or the specified fluid resulting from refrigerant leakage are prevented to the fullest extent possible from being held in the fluid holder88, and the refrigerant or the specified fluid resulting from refrigerant leakage can be led into the casing101and held and accumulated in the fluid holder88. Moreover, essentially in the structure of Modification 5, the fluid sensor8must be prepared according to the diameter of the refrigerant pipe, but in the structure of the present modification, the belt-shaped part108is attached by being wound over the refrigerant pipe, and it is therefore possible to more flexibly adapt to the size of the diameter of the refrigerant pipe than in the structure of Modification 5. The operability of winding the belt-shaped part108over the refrigerant pipe can also be improved by forming a thin part108ahaving less thickness in the belt-shaped part108, as shown inFIGS. 20 to 22. In the present modification, similar to Modification 5, latching parts101dcomposed of pawls101e,101for the like may be provided to both longitudinal ends of the belt-shaped part108, and the casing101may be detachably latched to a pipe or pipe joint constituting the refrigerant circuit10.

In the embodiment and its Modifications 1 through 6 described above, fluid sensors8are respectively placed on or in proximity to the pipe joint connecting the first shutoff valve26and the first refrigerant communication pipe5, on or in proximity to the pipe joint connecting the second shutoff valve27and the second refrigerant communication pipe6, on or in proximity to the pipe joint connecting the utilization unit4and the first refrigerant communication pipe5, and on or in proximity to the pipe joint connecting the utilization unit4and the second refrigerant communication pipe6as shown inFIG. 1, but other possibilities for fluid sensor8locations in addition to these areas include refrigerant circuit structural components, such as pressure sensors and capillary tubes.

In this case, in areas where refrigerant leakage is highly likely, such as the joints between pressure sensors and refrigerant pipes or the joints between capillary tubes and refrigerant pipes; pressure sensors, capillary tubes, or other refrigerant circuit structural components provided with fluid sensors8may be prepared in advance in proximity to the joints with each of the refrigerant pipes, and the fluid sensors8may be placed on the refrigerant circuit10at the same time that the pressure sensors, capillary tubes, or other refrigerant circuit structural components are attached to the refrigerant circuit10as shown inFIGS. 23 and 24, rather than being placed after the pressure sensors or capillary tubes have been attached to the refrigerant circuit10.

Discrepancy in the operation of attaching the fluid sensors8is thereby less likely, and detection precision can be improved in comparison with cases in which the fluid sensors8are attached after the pressure sensors or capillary tubes have been attached to the refrigerant circuit10.

In the embodiment and its Modifications 1 through 7 described above, the fluid sensors8alone are provided to the air-conditioning apparatus1and the fluid sensors8are connected to the impedance measurement device9when refrigerant leakage detection is performed as shown inFIGS. 1 and 5, but another possible option is to provide impedance measurement device9(i.e., the impedance measurement circuit such as those shown in FIGS.6and7) connected to the fluid sensors8to controllers7(i.e., the utilization-side controller44or the heat source-side controller30), as shown inFIG. 25.

Thereby, since the air-conditioning apparatus1of the present modification includes impedance measurement device9connected to the fluid sensors8, there is no longer a need to connect the impedance measurement device9to the fluid sensors8when performing refrigerant leakage detection. Processes such as storing the results of refrigerant leakage detection in the utilization-side controller44or heat source-side controller30can also be easily performed, therefore contributing to improving the precision of refrigerant leakage detection. Furthermore, refrigerant leakage detection can be performed constantly.

In the embodiment and its Modifications 1 through 7 described above, since the fluid sensors8are connected to external impedance measurement device9(seeFIG. 5), there arises a need to perform an operation of connecting the impedance measurement device9to the fluid sensors8when refrigerant leakage detection is performed. It is also difficult to apply Modification 8 to an existing air-conditioning apparatus or other refrigeration apparatus that does not have a function for detecting refrigerant leakage.

In view of this, in the present modification, each of the sensor main bodies8aof the fluid sensors8is configured to have an impedance detector8cfor detecting changes in impedance in the electrodes81,82or the like in the embodiment and its Modifications 1 through 7 described above, an impedance measurement unit8dhaving the function of the impedance measurement device9for measuring the impedance between the two electrodes81,82, a leakage determination unit8efor making a determination pertaining to refrigerant leakage on the basis of the impedance value measured by the impedance determination unit8d(more specifically, by comparing with a threshold), and a signal output unit8ffor outputting to an external device the conclusion result pertaining to refrigerant leakage obtained by the leakage determination unit8e. The external device could be the utilization unit4, the heat source unit2, an abnormality warning device, a network connection device, or the like; and, depending on these external devices, an electric current or voltage analog signal or the like can be outputted through wires, a radio wave signal or the like can be outputted wirelessly, or another measure can be used.

In the present modification, unlike the embodiment and its Modifications 1 through 7 described above, there is no longer a need to connect the impedance measurement device9to the fluid sensors8when refrigerant leakage detection is performed. The precision of refrigerant leakage detection can also be improved because the distance between the impedance detector8cand the impedance measurement unit8dof the electrodes81,82or the like is shorter than in cases of connecting to external impedance measurement device9or cases of providing impedance measurement device9to an air-conditioning apparatus or refrigeration apparatus such as the one in Modification 8 described above. Furthermore, since the leakage determination unit8eand the signal output unit8fare included, the input terminal of a controller of an existing air-conditioning apparatus or other refrigeration apparatus can be used, whereby refrigerant leakage detection is made possible merely by custom installing the fluid sensors8even with an existing air-conditioning apparatus or other refrigeration apparatus that does not have a function for detecting refrigerant leakage.

In the embodiment and its Modifications 1 through 9 described above, the fluid sensors8are placed in or in proximity to portions in the refrigerant circuit10where refrigerant leakage is highly likely, and it is possible using these fluid sensors8to detect refrigerant leakage from the refrigerant circuit10of the air-conditioning apparatus1while pinpointing the location in the refrigerant circuit10where the refrigerant leakage is occurring.

However, besides the refrigerant or the fluid resulting from refrigerant leakage, other possible causes for changes in the impedance (or electrostatic capacitance) of the fluid sensors8include humidity (i.e., water vapor), temperature, and changes over time. Therefore, if only one such fluid sensor8is provided in or in proximity to each portion in the refrigerant circuit10where refrigerant leakage detection is performed, there is a possibility that there will also be effects from causes of changes in electrostatic capacitance based on causes of changes in electrostatic capacitance other than the refrigerant or the fluid resulting from refrigerant leakage.

In view of this, the present modification uses a refrigerant leakage detection device207wherein the fluid sensor of the embodiment and its Modifications 1 through 7 described above is a first sensor208in which the refrigerant or fluid resulting from refrigerant leakage is held between two electrodes81,82, two fluid sensors constituting a second sensor209in which the refrigerant or fluid resulting from refrigerant leakage is not held between the two electrodes81,82are included separately from the first sensor208, the change in electrostatic capacitance caused by the refrigerant or fluid resulting from refrigerant leakage is calculated from a first difference between the output of the first sensor208and the output of the second sensor209, and refrigerant leakage is detected via this change in electrostatic capacitance. The refrigerant leakage detection device207according to the present modification is described hereinbelow usingFIGS. 27 and 28.

The refrigerant leakage detection device207according to the present modification comprises primarily the first sensor208, the second sensor209, a first oscillation circuit213, a second oscillation circuit214, an up/down counting circuit215, a resetting circuit216, a calculation unit211, and a detection unit212.

The first sensor208and the second sensor209are placed on or in proximity to a pipe joint of the refrigerant circuit10, similar to the fluid sensor in the embodiment and its modifications described above. The first sensor208and the second sensor209used in the present modification have the same plate-shaped structure (seeFIG. 4) as the fluid sensor in the embodiment described above. Specifically, the first sensor208and the second sensor209both have two electrodes81,82spaced apart from each other. The electrodes81,82are both plate-shaped members made of an electroconductive material, and are maintained as being spaced apart from each other by a spacer member83made of an electrically insulative material in the present embodiment. The first sensor208is covered by a film87, similar to the fluid sensor8in the embodiment described above, and part of the wiring extending from the first sensor208is secured to the refrigerant pipe by a securing member86composed of a band, adhesive tape, or the like. The second sensor209is placed in proximity to the first sensor208, but is not covered by the film87covering the first sensor208. Thereby, in cases in which the refrigerant or fluid resulting from refrigerant leakage is refrigerator oil, as in Modification 1 described above, for example, the refrigerator oil resulting from refrigerant leakage is held between the two electrodes81,82of the first sensor208, but the refrigerator oil resulting from refrigerant leakage is not held between the two electrodes81,82of the second sensor209. Specifically, the first sensor208and the second sensor209are both affected by humidity and other causes of changes in electrostatic capacitance, but the second sensor209is not affected by causes of changes in electrostatic capacitance from the refrigerant or refrigerator oil as a fluid resulting from refrigerant leakage, while the first sensor208is affected by causes of changes in electrostatic capacitance from the refrigerant or refrigerator oil as a fluid resulting from refrigerant leakage. The structure of the first sensor208and the second sensor209is not limited to the flat plate-shaped structure in the embodiment described above, and the structure of the fluid sensor in Modifications 1 through 7 described above (seeFIGS. 8 through 24) may be used.

The first oscillation circuit213is connected to the first sensor208, and the second oscillation circuit214is connected to the second sensor209. The first oscillation circuit213oscillates at a frequency corresponding to the electrostatic capacitance Cx of the first sensor208. The second oscillation circuit214oscillates at a frequency corresponding to the electrostatic capacitance Cn of the second sensor209. Specifically, the first oscillation circuit213oscillates at a frequency corresponding to the electrostatic capacitance Cx of the first sensor208, which changes due to the effects of both the refrigerant or fluid resulting from refrigerant leakage (refrigerator oil in this case) and other causes of changes in electrostatic capacitance, and the first oscillation circuit213outputs a first oscillation signal OS1. The second oscillation circuit214oscillates at a frequency corresponding to the electrostatic capacitance Cn of the second sensor209, which changes due to the effects of causes of changes in electrostatic capacitance other than the refrigerant or fluid resulting from refrigerant leakage (refrigerator oil in this case), and the second oscillation circuit214outputs a second oscillation signal OS2. The first oscillation circuit213and the second oscillation circuit214can be CR oscillation circuits configured primarily from the electrostatic capacitance and resistance of each of the sensors, or LC back-coupling oscillation circuits configured primarily from coils and the electrostatic capacitance of each of the sensors.

The up/down counting circuit215has two input terminals, and each of the input terminals are connected to an output terminal of the first oscillation circuit213and an output terminal of the second oscillation circuit214. The up/down counting circuit215counts up the output of the first oscillation circuit213(i.e., the first oscillation signal OS1) which oscillates at a frequency corresponding to the electrostatic capacitance Cx of the first sensor208, and counts down the output of the second oscillation circuit214(i.e., the second oscillation signal OS2) which oscillates at a frequency corresponding to the electrostatic capacitance Cn of the second sensor209. The up/down counting circuit215repeats this operation at predetermined intervals. The up/down counting circuit thereby counts a number of pulses equivalent to the difference between the frequency of the first oscillation signal OS1, which is based on the first sensor208affected by both the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case) and other causes of changes in electrostatic capacitance, and the frequency of the second oscillation signal OS2, which is based on the second sensor209affected only by causes of changes in electrostatic capacitance other than the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case).

The output terminal of the resetting circuit216is connected to a resetting terminal of the up/down counting circuit215. At predetermined cycles, the resetting circuit216resets a count value according to the up/down counting circuit215. The predetermined cycles are determined in advance based on experimentation, the naturally included electrostatic capacitance in the first sensor208and second sensor209independent of the causes of changes in electrostatic capacitance, or other factors, for example.

Having been reset by the resetting circuit216, the up/down counting circuit215initializes the count value that has been counted up to this point and begins to count up and count down from the beginning.

The calculation unit211is connected to the output terminal of the up/down counting circuit215. Since the number of pulses counted up until the resetting by the up/down counting circuit215is equivalent to the difference between the frequencies of the first and second oscillation signals OS1, OS2, the calculation unit211computes a first difference between the output of the first sensor208and the output of the second sensor209on the basis of the counted value according to the up/down counting circuit215. Based on this first difference, the calculation unit211then calculates the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case), and outputs the calculated result to the detection unit212. The calculation unit211may be configured from a calculation circuit, or from a microcomputer composed of memory and a CPU.

The detection unit212detects refrigerant leakage on the basis of the change in electrostatic capacitance calculated by the calculation unit211. Specifically, if the calculation result from the calculation unit211is “0,” the detection unit212determines that refrigerant leakage has not occurred. If the calculation result by the calculation unit211is not “0,” the detection unit212determines that refrigerant leakage has occurred and computes the amount of leaked refrigerant on the basis of the calculation result. Though the details are not illustrated, the detection result from the detection unit212is sent to the controller7and is used in the controlling of the utilization unit4and the heat source unit2. Similar to the calculation unit211, the detection unit212may be configured from a detection circuit or from a microcomputer composed of memory and a CPU, as long as it is capable of detecting refrigerant leakage.

In this type of refrigerant leakage detection device207according to the present modification, the up/down counting circuit215counts up a signal that oscillates according to the electrostatic capacitance Cx of the first sensor208, and counts down a signal that oscillates according to the electrostatic capacitance Cn of the second sensor209. Since the value counted by the up/down counting circuit215is a pulse number equivalent to the difference between the frequency corresponding to the electrostatic capacitance Cx of the first sensor208and the frequency corresponding to the electrostatic capacitance Cn of the second sensor209, the calculation unit211can calculate the first difference from the counted value. Furthermore, the calculation unit211can accurately single out the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case) by calculating the change in electrostatic capacitance on the basis of the first difference, and the detection unit212can therefore detect refrigerant leakage with greater accuracy.

In the refrigerant leakage detection device207of the present modification, the value counted by the up/down counting circuit215is reset in predetermined cycles by the resetting circuit216. Therefore, the calculation unit211can calculate the first difference between the output of the first sensor208and the output of the second sensor209from the counted value before it is reset.

The up/down counting circuit215in the refrigerant leakage detection device207of the present modification may be configured so as to carry over when the counted result reaches a desired value. With this configuration, the calculation unit211is still capable of computing the first difference in the same manner as described above.

A configuration such as that of a refrigerant leakage detection device307shown inFIG. 29may be used as a refrigerant leakage detection device which uses the first sensor208and the second sensor209as in Modification 10 described above.

The refrigerant leakage detection device307according to the present modification comprises primarily a first sensor208, a second sensor209, a first resetting circuit311, a second resetting circuit312, an oscillation circuit313, a first counting circuit314, a second counting circuit315, a first latch circuit316, a second latch circuit317, a difference circuit318(equivalent to a difference calculation unit), a calculation unit211, and a detection unit212. The first sensor208, the second sensor209, and the detection unit212are the same as the first sensor208, the second sensor209, and the detection unit212in Modification 10 described above and are therefore not described herein.

The first resetting circuit311is connected to the first sensor208, and the second resetting circuit312is connected to the second sensor209. The output terminal of the first resetting circuit311is connected to each of the resetting terminals of the first counting circuit314and first latch circuit316. The output terminal of the second resetting circuit312is connected to each of the resetting terminals of the second counting circuit315and second latch circuit317.

This type of first resetting circuit311outputs a first reset signal Rx, which is based on a time constant determined according to the electrostatic capacitance Cx of the first sensor208, to the first counting circuit314and the first latch circuit316. The second resetting circuit312outputs a second reset signal Rn, which is based on a time constant determined according to the electrostatic capacitance Cn of the second sensor209, to the second counting circuit315and the second latch circuit317. More specifically, the first resetting circuit311outputs the first reset signal Rx for resetting the first counting circuit314and the first latch circuit316in accordance with the electrostatic capacitance Cx changed by both the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case) and another cause of a change in electrostatic capacitance. The second resetting circuit312outputs a second reset signal Rn for resetting the second counting circuit315and the second latch circuit317in accordance with the electrostatic capacitance Cn changed by only another cause of a change in electrostatic capacitance other than the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case). In other words, based on the electrostatic capacitances Cx, Cn of each of the sensors208,209, each of the resetting circuits311,312can determine time durations for holding signals inputted by each of the latch circuits316,317. Based on the electrostatic capacitances Cx, Cn of each of the sensors208,209, each of the resetting circuits311,312can also determine time durations for resetting the counted values of each of the counting circuits314,315. Each of the resetting circuits311,312according to the present modification outputs each of the reset signals Rx, Rn in synchronization with a reference clock. Specifically, each of the resetting circuits311,312at every predetermined timing calculates time constants on the basis of the occasional electrostatic capacitances Cx, Cn of each of the sensors208,209and outputs the reset signals Rx, Rn based on the calculated time constants.

The output terminal of the oscillation circuit313is connected to the input terminals of the first counting circuit314and the second counting circuit315, and an oscillation signal OS3(equivalent to a pulse signal) is outputted to the counting circuits314,315. The oscillation signal OS3is a pulse-form signal having a predetermined frequency as shown inFIG. 30. The predetermined frequency of the oscillation signal OS3is determined in advance through experimentation or the like, irrespective of the electrostatic capacitance Cx of the first sensor208or the electrostatic capacitance Cn of the second sensor209.

The first counting circuit314counts the number of pulses of the oscillation signal OS3and stops the counting of the oscillation signal OS3on the basis of the first reset signal Rx. The second counting circuit315counts the number of pulses of the oscillation signal OS3and stops the counting of the oscillation signal OS3on the basis of the second reset signal Rn. To describe in detail usingFIG. 30, the first counting circuit314counts the oscillation signal OS3while the first reset signal Rx is at “L” indicating that resetting is off (the time period Toff1inFIG. 30), and the first counting circuit314stops counting the oscillation signal OS3when the first reset signal Rx switches to “H” indicating that resetting is on. Similar to the first counting circuit314, the second counting circuit315also counts the oscillation signal OS3if the second reset signal Rn is at “L” and stops counting the oscillation signal OS3if the second reset signal Rn is at “H.”

The length of the time period Toff1during which reset off “L” is outputted as the first reset signal Rx is different from the length of the time period Toff2during which reset off “L” is outputted as the second reset signal Rn, as shown inFIG. 30. This is because each of the reset signals Rx, Rn is determined based on the electrostatic capacitances Cx, Cn of each of the sensors208,209as described above. Specifically, since the time constants used to determine each of the reset signals Rx, Rn are proportionate to the electrostatic capacitances Cx, Cn of each of the sensors208,209, the difference DifA between the length of the time period Toff1during which reset off “L” is outputted as the first reset signal Rx and the length of the time period Toff2during which reset off “L” is outputted as the second reset signal Rn can be said to be equivalent to the difference between the electrostatic capacitances Cx, Cn of each of the sensors208,209. Particularly, inFIG. 30, the time period Toff1during which reset off “L” is outputted as the first reset signal Rx is longer than the time period Toff2during which reset off “L” is outputted as the second reset signal Rn. This is because the electrostatic capacitance Cx of the first sensor208is changed by both the refrigerant or fluid resulting from refrigerant leakage (refrigerator oil in this case) and another cause of a change in electrostatic capacitance, whereas the electrostatic capacitance Cn of the second sensor209is changed based on only another cause of a change in electrostatic capacitance other than the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case). The time period Toff1of the first reset signal Rx is longer than the time period Toff2of the second reset signal Rn by an amount proportionate to the change caused by adsorption of the refrigerator oil.

The first latch circuit316connects through its input terminal to the output terminal of the first counting circuit314, and holds the counted value of the first counting circuit314. The second latch circuit317connects through its input terminal to the output terminal of the second counting circuit315, and holds the counted value of the second counting circuit315. The first reset signal Rx is inputted to the first latch circuit316, and the second reset signal Rn is inputted to the second latch circuit317as described above. Therefore, each of the latch circuits316,317continues to hold the counted values while each of the reset signals Rx, Rn is at reset off “L.” When each of the reset signals Rx, Rn switches to reset on “H,” each of the latch circuits316,317resets each of the counted values being held up to that point.

The difference circuit318has two input terminals, and each of these input terminals is connected to the output terminal of the first latch circuit316and the output terminal of the second latch circuit317. The difference circuit318calculates a second difference between the counted numbers counted by the first counting circuit314and the second counting circuit315respectively until the counting of the oscillation signal OS3was stopped. Since the values counted by each of the counting circuits314,315correlate with the lengths of the time periods Toff1, Toff2during which each of the reset signals Rx, Rn is at reset off “L,” the second difference between the counted value of the first counting circuit314and the counted value of the second counting circuit315as calculated by the difference circuit318can be said to be equivalent to the difference DifA between each of the lengths of the time periods Toff1, Toff2, or to the change in electrostatic capacitance caused by only the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case).

The calculation unit211is connected to the output terminal of the difference circuit318. The calculation unit211calculates the first difference between the output of the first sensor208and the output of the second sensor209on the basis of the second difference calculated by the difference circuit318. The calculation unit211then calculates the change in electrostatic capacitance caused by only the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case) on the basis of the first difference, and outputs the calculated result to the detection unit212. The calculation unit211may be configured from a calculation circuit or from a microcomputer composed of memory and a CPU, similar to Modification 10 described above.

In this type of refrigerant leakage detection device307according to the present modification, the first counting circuit314counts the oscillation signal OS3until resetting is instructed by the first reset signal Rx, and the second counting circuit315counts the oscillation signal OS3until resetting is instructed by the second reset signal Rn. The first reset signal Rx and the second reset signal Rn are, respectively, a signal based on a time constant determined by the electrostatic capacitance Cx of the first sensor208and a signal based on a time constant determined by the electrostatic capacitance Cn of the second sensor209, and therefore the timings whereby the first counting circuit314and the second counting circuit315stop counting are therefore different. In other words, the difference between the counted numbers of each of the counting circuits314,315is equivalent to the difference between the electrostatic capacitances Cx, Cn of each of the sensors208,209. The refrigerant leakage detection device307therefore can calculate the first difference from the second difference of each of the counted numbers. Consequently, it is possible to accurately single out the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case), and refrigerant leakage can be detected with greater accuracy.

A configuration such as a refrigerant leakage detection device407shown inFIG. 31may be used as a refrigerant leakage detection device that uses the first sensor208and the second sensor209, such as those shown in Modifications 10 and 11 described above.

The refrigerant leakage detection device407according to the present modification comprises primarily a first sensor208, a second sensor209, a third resetting circuit411, a first timer circuit412, a second timer circuit413, an EOR circuit414, an oscillation circuit415, a fourth resetting circuit416, a counting circuit417(the EOR circuit414and counting circuit417are equivalent to a time calculation unit), a calculation unit211, and a detection unit212. The first sensor208, the second sensor209, and the detection unit212are the same as the first sensor208, the second sensor209, and the detection unit212of Modification 10 described above and are therefore not described herein.

The output terminal of the third resetting circuit411is connected to each of the resetting terminals of the first timer circuit412and the second timer circuit413. The third resetting circuit411generates a signal for resetting each of the timer circuits412,413and outputs the signal to each of the timer circuits412,413.

The input terminal of the first timer circuit412is connected to the first sensor208, and the input terminal of the second timer circuit413is connected to the second sensor209.

The first timer circuit412first determines a time duration Tx in accordance with the electrostatic capacitance Cx of the first sensor208, which is changed by both the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case) and another cause of changes in electrostatic capacitance, as shown inFIG. 32. After the first timer circuit412has been once reset by the third resetting circuit411, the first timer circuit412begins to measure the time duration. When the measured time duration reaches the time duration Tx, the first timer circuit412outputs a first time duration elapse signal St1indicating the same. The second timer circuit413first determines a time duration Tn in accordance with the electrostatic capacitance Cn of the second sensor209, which is changed by only a cause of changes in electrostatic capacitance other than the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case), and after the second timer circuit413has been once reset by the third resetting circuit411, the second timer circuit413begins to measure the time duration. When the measured time reaches the time duration Tn, the second timer circuit413outputs a second time duration elapse signal St2indicating the same.

The logic of the first time duration elapse signal SU according to the present modification is that the signal is “L” when the time duration measured by the first timer circuit412has not reached the time duration Tx, and the signal is “H” when the time duration Tx has elapsed. Similarly, the logic of the second time duration elapse signal St2is that the signal is “L” when the time duration measured by the second timer circuit413has not reached the time duration Tn, and the signal is “H” when the time duration Tn has elapsed. Each of the time duration elapse signals St1, St2(both “H”) indicating that the time durations Tx, Tn have elapsed are continually outputted until each of the timer circuits412,413are reset by the third resetting circuit411.

Possible examples of the method for determining the above-described time durations Tx, Tn include a first method for determining by multiplying the electrostatic capacitances Cx, Cn by a predetermined coefficient, and a second method for determining by time constants based on the electrostatic capacitances Cx, Cn, similar to Modification 11 described above, but the first method is used in the present modification. Thus, the above-described time durations Tx, Tn are determined by the electrostatic capacitances Cx, Cn, thereby causing a deviation according to the values of the electrostatic capacitances Cx, Cn in the timings at which the first time duration elapse signal St1“H” indicating that the time duration Tx has elapsed and the second time duration elapse signal St2“H” indicating that the time duration Tn has elapsed begin to be outputted respectively. In other words, the difference DifB corresponds to the difference between the electrostatic capacitances Cx, Cn, the difference DifB being the difference between the timing at which the time duration Tx elapses and the first time duration elapse signal St1“H” begins to be outputted and the timing at which the time duration Tn elapses and the second time duration elapse signal St2“H” begins to be outputted. Particularly, the time duration Tx during which the first time duration elapse signal St1is “L” is longer than the time duration Tn during which the second time duration elapse signal St2is “L.” This is because the electrostatic capacitance Cn of the second sensor209changes based on only causes of changes in electrostatic capacitance other than the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case), whereas the electrostatic capacitance Cx of the first sensor208changes not only due to causes of changes in electrostatic capacitance other than the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case), but due to the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case) as well. In other words, the difference DifB between the timings at which each of the time duration elapse signals St1, St2“H” begin to be outputted is equivalent to the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case).

The EOR circuit414has two input terminals, and the output terminals of each of the timer circuits412,413are connected to each of these input terminals. The EOR circuit414is a so-called exclusive OR circuit, which outputs “H” as an enable signal En in cases in which either the first time duration elapse signal St1or the second time duration elapse signal St2outputted from each of the first and second timer circuits412,413is “H,” as shown inFIG. 32. Specifically, the EOR circuit414detects cases in which the time duration Tx based on the electrostatic capacitance Cx has elapsed but the time duration Tn based on the electrostatic capacitance Cn has not elapsed. The EOR circuit414outputs “L” as the enable signal En when the first time duration elapse signal St1and the second time duration elapse signal St2are both “L” or “H.”

The output terminal of the oscillation circuit415is connected to an oscillation signal input terminal of the counting circuit417. The oscillation circuit415outputs an oscillation signal OS4to the counting circuit417. The oscillation signal OS4is a pulse-form signal having a predetermined frequency, as shown inFIG. 32. The predetermined frequency of the oscillation signal OS4, similar to the oscillation signal OS3according to Modification 11 described above, is determined in advance through experimentation or another method, irrespective of the electrostatic capacitance Cx of the first sensor208or the electrostatic capacitance Cn of the second sensor209.

The output terminal of the fourth resetting circuit416is connected to a resetting terminal of the counting circuit417. The fourth resetting circuit416generates a signal for resetting the counting circuit417and outputs the signal to the counting circuit417.

The output terminal of the EOR circuit414is connected to another input terminal of the counting circuit417separate from the oscillation signal input terminal. The counting circuit417counts the number of pulses of the oscillation signal OS4only during the time period DifB in which the enable signal En is “H.” The pulse number counted by the counting circuit417is thereby a value corresponding to the length of the time period DifB.

When a signal for resetting is inputted from the fourth resetting circuit416, the counting circuit417resets the counted value up to that point.

The calculation unit211is connected to an output terminal of the counting circuit417. The calculation unit211calculates the first difference between the output of the first sensor208and the output of the second sensor209on the basis of the pulse number counted by the counting circuit417. The calculation unit211is capable of calculating a first difference because the pulse number counted by the counting circuit417is a value corresponding to the length of the time period DifB and the length of the time period DifB corresponds to the difference between the electrostatic capacitances Cx, Cn of each of the sensors208,209. The calculation unit211then calculates the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case) on the basis of the first difference, and outputs the calculated result to the detection unit212.

The calculation unit211may be configured from a calculation circuit, or from a microcomputer composed of memory and a CPU, similar to Modifications 10 and 11 described above.

In this type of refrigerant leakage detection device407according to the present modification, when the electrostatic capacitances Cx, Cn of each of the sensors208,209are different, the time durations Tx, Tn determined by the electrostatic capacitances Cx, Cn of each of the sensors208,209are also different, and the timings whereby “H” begins to be outputted are therefore also different for the first time duration elapse signal St1and the second time duration elapse signal St2. In view of this, the refrigerant leakage detection device407according to the present modification calculates the first difference on the basis of the length of the time period DifB during which either one of the first time duration elapse signal St1and second time duration elapse signal St2is “H,” i.e., on the basis of the difference between the timing at which “H” begins to be outputted for the first time duration elapse signal St1and the timing at which “H” begins to be outputted for the second time duration elapse signal St2. In other words, since the length of the above-described time period DifB is equivalent to the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case), it is possible to accurately single out the change in electrostatic capacitance caused by refrigerator oil adsorption, and refrigerant leakage can be detected with greater accuracy.

A configuration such as a refrigerant leakage detection device507shown inFIG. 33may also be used as a refrigerant leakage detection device that uses a first sensor208and second sensor209such as those in Modifications 10 to 12 described above.

The refrigerant leakage detection device507according to the present modification differs from the refrigerant leakage detection device207according to Modification 10 by having a selection circuit511instead of the resetting circuit216. Specifically, the refrigerant leakage detection device507comprises primarily a first sensor208, a second sensor209, a first oscillation circuit213, a second oscillation circuit214, a selection circuit511, an up/down counting circuit215, a calculation unit211, and a detection unit212. The first sensor208, the second sensor209, the first oscillation circuit213, the second oscillation circuit214, the up/down counting circuit215, the calculation unit211, and the detection unit212are the same as the first sensor208, the second sensor209, the first oscillation circuit213, the second oscillation circuit214, the up/down counting circuit215, the calculation unit211, and the detection unit212in Modification 10 described above, and are therefore not described herein.

The selection circuit511is a circuit for selecting either the output of the first oscillation circuit213(i.e., the first oscillation signal OS1) or the output of the second oscillation circuit214(i.e., the second oscillation signal OS2) and inputting its selection to the up/down counting circuit215. More specifically, the selection circuit511has a control signal circuit512, a counter circuit513, a logic circuit514having output terminals for enable signals SX, SN, and two NAND circuits515,516.

The control signal circuit512generates a clock signal having a predetermined duty and frequency, and outputs this signal to the counter circuit513. The duty and frequency of the signal outputted by the selection circuit511are determined in advance by the electrostatic capacitances originally included in the first oscillation circuit213and second oscillation circuit214independent of the causes of changes in electrostatic capacitance. The signal outputted by the control signal circuit512is counted in the counter circuit513and then sent to the logic circuit514. The logic circuit514generates two enable signals SX, SN such as those shown inFIG. 34from the counting result of the counter circuit513. The enable signals SX, SN are both signals having the logic “H” or “L,” and the enable signal SX and enable signal SN have exclusive logic. For example, when the enable signal SX has the logic “H,” the enable signal SN has the logic “L.” The enable signal SX is inputted to one of two input terminals of the NAND circuit515, and the enable signal SN is inputted to one of two input terminals of the NAND circuit516. The first oscillation signal OS1is inputted to the other input terminal of the NAND circuit515, and the second oscillation signal OS2is inputted to the other input terminal of the NAND circuit516.

The NAND circuit515described above outputs the first oscillation signal OS1when the logic of the enable signal SX is “H,” and the NAND circuit516outputs the second oscillation signal OS2when the logic of the enable signal SN is “H.” Since the enable signal SX and the enable signal SN never both have the logic “H” but instead alternatively have the logic “H,” either the first oscillation signal OS1or the second oscillation signal OS2is inputted to the up/down counting circuit215(seeFIG. 34). In other words, rather than the first oscillation signal OS1and the second oscillation signal OS2being inputted simultaneously to the up/down counting circuit215, either the first oscillation signal OS1or the second oscillation signal OS2selected by the selection circuit511is inputted. The up/down counting circuit215can, thereby, reliably perform the operation of counting up the first oscillation signal OS1and counting down the second oscillation signal OS2. Consequently, an accurate counted value is outputted from the up/down counting circuit215to the calculation unit211, and the calculation unit211can reliably calculate the first difference, based on the counted value, between the output of the first sensor208and the output of the second sensor209, and can also reliably calculate the change in electrostatic capacitance based on the first difference and caused by the refrigerant or the fluid resulting from refrigerant leakage (refrigerator oil in this case) as a cause of changes in electrostatic capacitance. The change in electrostatic capacitance calculated in this manner by the calculation unit211is outputted to the detection unit212.

Furthermore, in addition to output terminals for the enable signals SX, SN, the logic circuit514in the present modification also has an output terminal for a reset signal Clear (the portion of the logic circuit514having the output terminal for the reset signal Clear is equivalent to a resetting unit). The reset signal Clear has the role of resetting the value counted by the up/down counting circuit215at predetermined cycles. The predetermined cycles are determined in advance based on factors such as the electrostatic capacitance originally included in the first sensor208and the second sensor209independent of causes of changes in electrostatic capacitance, similar to the clock signal outputted by the control signal circuit512. Having been reset by the reset signal Clear, the up/down counting circuit215initializes the values counted up to that point and begins to count up and down from the beginning.

In the refrigerant leakage detection device507according to the present modification, since either the first oscillation signal OS1or the second oscillation signal OS2is inputted to the up/down counting circuit215, the first oscillation signal OS1and the second oscillation signal OS2are not simultaneously inputted to the up/down counting circuit215. Consequently, the up/down counting circuit215can reliably perform the operation of counting up the first oscillation signal OS1and counting down the second oscillation signal OS2, and accurate counted values for calculating the first difference can be obtained.

According to the refrigerant leakage detection device507of the present modification, the values counted by the up/down counting circuit215are reset in predetermined cycles by the reset signal Clear outputted from the logic circuit514. Therefore, the calculation unit211is capable of calculating the first difference between the output of the first sensor208and the output of the second sensor209by the counted values before resetting.

(16) Other Embodiments

An embodiment and modifications of the present invention were described above based on the drawings, but the specific configuration is not limited to the embodiment and its modifications, and changes can be made within a range that does not deviate from the scope of the invention.

(A) In the embodiment and its modifications described above, the present invention was described using as an example a so-called paired air-conditioning apparatus1in which one utilization unit4is connected to one heat source unit2, but the present invention may also be applied to a so-called multi-type air-conditioning apparatus1in which a plurality of utilization units are connected to one heat source unit. In this case, branching parts corresponding to the number of utilization units are formed in the refrigerant communication pipes, and fluid sensors8may therefore be provided to pipe joints or other components in these branching parts.

(B) In the embodiment and its modifications described above, the present invention was described using as an example an air-conditioning apparatus1capable of operating while switching between cooling and heating, but the present invention may also be applied to a cooling-only apparatus, a heating-and-cooling apparatus, a heat storage air conditioner, and various other air-conditioning apparatuses. Moreover, the present invention is not limited to an air-conditioning apparatus, and can also be applied to a refrigeration apparatus that has a refrigerant circuit and is susceptible to refrigerant leakage, such as a heat-pump type water heater.

(C) In Modifications 10 and 13 described above, instead of providing the calculation unit211and the detection unit212ofFIG. 27separately, a determination circuit may be provided in which the calculation unit211and the detection unit212are integrated. In this case, the determination circuit compares the value counted by the up/down counting circuit215with a threshold and determines whether or not refrigerant has leaked according to the comparison result. Even with this configuration, the counted value is equivalent to the difference between the electrostatic capacitance Cx of the first sensor208and the electrostatic capacitance Cn of the second sensor209, i.e., to the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage, and it is therefore possible to accurately single out the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage.

(D) In Modification 11 described above, instead of providing the calculation unit211and the detection unit212ofFIG. 29separately, a determination circuit may be provided in which the calculation unit211and the detection unit212are integrated. In this case, the determination circuit compares the second difference calculated by the difference circuit318with a threshold and determines whether or not refrigerant has leaked according to the comparison result. Even with this configuration, the second difference is equivalent to the difference between the electrostatic capacitance Cx of the first sensor208and the electrostatic capacitance Cn of the second sensor209, i.e., to the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage, and it is therefore possible to accurately single out the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage.

(E) In Modification 12 described above, instead of providing the calculation unit211and the detection unit212ofFIG. 31separately, a determination circuit may be provided in which the calculation unit211and the detection unit212are integrated. In this case, the determination circuit compares the pulse number counted by the counting circuit417with a threshold and determines whether or not refrigerant has leaked according to the comparison result. Even with this configuration, the pulse number is equivalent to the difference between the electrostatic capacitance Cx of the first sensor208and the electrostatic capacitance Cn of the second sensor209, i.e., to the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage, and it is therefore possible to accurately single out the change in electrostatic capacitance caused by the refrigerant or the fluid resulting from refrigerant leakage.

(F) Furthermore, the configuration (various circuits, the calculation unit, and the detection unit) constituting the refrigerant leakage detection device according to Modifications 10 through 13 excluding the sensors208,209may be incorporated into the controller7, similar to Modification 8. The configuration (various circuits, the calculation unit, and the detection unit) constituting the refrigerant leakage detection device according to Modifications 10 through 13 excluding the sensors208,209may also be configured integrally with the sensors208,209, similar to Modification 9.

Industrial Applicability

According to the present invention, it is possible to detect refrigerant leakage while pinpointing the location where the refrigerant leakage is occurring in a refrigerant circuit of a refrigeration system.