Refrigerant circulating apparatus

Abstract: In a refrigerant circulating apparatus, a liquid accumulating container (6) for allowing oil droplets to flow out in suspended form is connected between a condenser (4) and a pressure reducing device (5). Thus, refrigerating machine oil which flowed out from a compressor (1) can be reliably returned to the compressor (1), and proper lubricating and sealing functions can be maintained for the compressing elements.

Description: The present invention relates to a refrigerant circulating apparatus having a refrigerant circuit in which a refrigerating machine oil is difficult to dissolve in a refrigerant as in a case where, for example, a hydrofluorocarbon- (HFC-) based refrigerant is used as a refrigerant and an alkylbenzene-based oil as a refrigerating machine oil. In a case where a refrigerating machine oil such as alkylbenzene, which has weak compatibility with respect to a hydrofluorocarbon-(HFC-) based refrigerant, is used as shown in Japanese Patent Application Laid-Open No. 208819/1995, the return of oil from an accumulator provided on the low-pressure side where the solubility of the refrigerating machine oil in the liquid refrigerant declines has hitherto been an important problem in the reliability of a compressor. A conventional refrigeration and air-conditioning cycle apparatus shows a cycle in which an HFC-based refrigerant and an oil having weak solubility are used as a refrigerant and a refrigerating machine oil, respectively, wherein a compressor for compressing a refrigerant gas; a four-way valve having the function of reversing the flowing direction of the refrigerant; a pressure reducing device; an accumulator for accumulating surplus refrigerant; a refrigerating machine oil stored in the compressor to effect the lubrication of sliding portions of the compressor and the sealing of a compression chamber; a condenser for condensing a high-pressure refrigerant gas discharged from the compressor 1; and an evaporator are shown. The refrigerating machine oil with weak solubility used in this refrigeration and air-conditioning cycle apparatus, e.g., alkylbenzene, has nonsolubility or very weak solubility with respect to an HFC-based refrigerant, with its rate of solubility in the liquid refrigerant under the conditions of condensing pressure and condensing temperature being 0.5 - 7 wt%, its rate of solubility in the liquid refrigerant under the conditions of evaporating pressure and evaporating temperature being 0 - 2.0 wt%, and its specific weight in the temperature range of -20°C to +60°C being a value smaller than the specific weight of the liquid refrigerant at the same temperature and under saturated vapor pressure. Next, a description will be given of the behavior of the refrigerating machine oil. The high-pressure refrigerant gas compressed by the compressor is discharged to the condenser. Most of the refrigerating machine oil used for lubricating the compressor and for sealing the compression chamber returns to the bottom of a hermetic container, but the refrigerating machine oil having an oil circulation rate of 0.3 to 2.0 wt% or thereabouts is discharged together with the refrigerant from the compressor. The pipe diameter of the condenser where the refrigerant gas flows is set so as to secure a flow rate of the refrigerant gas sufficient to convey the refrigerating machine oil downstream. Although most of the refrigerant liquefies in the vicinity of an outlet of the condenser and the in-pipe flow rate declines appreciably, since the refrigerating machine oil has weak solubility with respect to the condensed liquid refrigerant, the refrigerating machine oil dissolves in the liquid refrigerant and is conveyed to the pressure reducing device. The temperature and pressure of the refrigerant decline appreciably in a region downstream of the pressure reducing device, and the solubility characteristic of the refrigerating machine oil changes to nonsolubility or very weak solubility with respect to the liquid refrigerant. However, the refrigerating machine oil is conveyed to the accumulator since the flow rate of the refrigerant increases abruptly due to the gasification of part of the liquid refrigerant which occurs in the region downstream of the pressure reducing device, and since the pipe diameter of the evaporator in the next stage is set so as to secure a flow rate of the refrigerant gas sufficient to convey the refrigerating machine oil downstream. Since the solubility of the refrigerating machine oil in the liquid refrigerant under the conditions of evaporating pressure and evaporating temperature is nil or very weak, the refrigerating machine oil forms a separate layer over the liquid refrigerant inside the accumulator. For this reason, the structure provided is such that a plurality of oil returning holes having different heights from a lower end of the accumulator are provided in a lead-out pipe for leading the refrigerant from inside to outside the accumulator, thereby promoting the return of the oil to the compressor. As another example of the conventional refrigeration and air-conditioning cycle apparatus, a refrigeration and air-conditioning cycle apparatus is disclosed in Japanese Patent Application Laid-Open No. 19253/1989. It shows a compressor for compressing a refrigerant gas; a condenser for condensing the high-pressure refrigerant gas discharged from the compressor; a pre-stage pressure reducing device; a receiver for accumulating surplus refrigerant; a post-stage pressure reducing device; the evaporator; and the four-way valve having the function of reversing the flowing direction of the refrigerant. Next, a description will be given of the operation of this refrigeration and air-conditioning cycle apparatus. The high-pressure refrigerant gas compressed by the compressor passes through the condenser while becoming liquefied, is then subjected to pressure reduction by the pre-stage pressure reducing device, and enters the receiver. Here, by controlling the pressure reducing devices disposed respectively before and after the receiver, the surplus refrigerant is accumulated in correspondence with the condition of the load of the apparatus, thereby optimizing the performance and efficiency and ensuring the reliability of the compressor. The liquid refrigerant which flowed out from the receiver is further subjected to pressure reduction to the level of necessary evaporating pressure, then passes through the evaporator, and is sucked into the compressor. In the refrigeration and air-conditioning cycle apparatus cited as a conventional example which uses a hydrofluorocarbon- (HFC-) based refrigerant as a refrigerant and an alkylbenzene-based oil as a refrigerating machine oil, the following problem is encountered in the case where a large amount of surplus refrigerant is accumulated in the accumulator and the liquid level has become high. First, although the refrigerating machine oil which cannot be dissolved in the liquid refrigerant is separated from the liquid refrigerant and is accumulated in an upper layer of the two separated layers, since the force of suction from the upper holes declines as compared with that from the hole provided in a lower end of the lead-out pipe among the oil holes provided in the lead-out pipe inside the accumulator, only the liquid refrigerant in the lower layer flows into the lead-out pipe, and the refrigerating machine oil in the upper layer scarcely flows into the lead-out pipe. Therefore, the refrigerating machine oil is accumulated in a large amount inside the accumulator, with the result that the refrigerating machine oil in the compressor is depleted, possibly causing faulty lubrication. Next, when the liquid level of the liquid refrigerant becomes high, since the liquid refrigerant is sucked from the plurality of oil returning holes in the lead-out pipe, a large amount of liquid refrigerant returns to the compressor which possibly results in a sudden pressure rise in the compression chamber due to the supply of the noncompressive liquid refrigerant to the interior of the compression chamber. In addition, since the liquid refrigerant discharged from the compression chamber is detained in the hermetic container of the compressor, the liquid refrigerant instead of the refrigerating machine oil is supplied to lubricating element portions, which can cause seizure and the like of the bearing of the compressor and sliding portions of compressing elements, thereby leading to a decline in the reliability. In addition, if the diameters of the oil returning holes are set to be small so as to prevent a large amount of liquid refrigerant from returning to the compressor the return of the refrigerating machine oil is further aggravated, and dust, impurities, and the like in the circuit are liable to clog the oil returning holes With the refrigeration and air-conditioning cycle apparatus cited as a conventional example, the apparatus can be operated without a problem in a case where a refrigerating machine oil having compatibility with a refrigerant is used, but if a refrigerating machine oil having noncompatibility or weak compatibility is used, the refrigerating machine oil which is nonsoluble in the liquid refrigerant is separated in an upper layer and is detained inside the receiver under the operating conditions in which the rate of oil circulation is large, and the refrigerating machine oil inside the compressor is depleted, thereby possibly causing faulty lubrication. Conventionally, when an airtight test is performed in the process of manufacturing the compressor using R.22 as a refrigerant, a discharge pipe and a suction pipe are closed by jigs, and the airtight test is performed under the pressure of 28 kgf/cm 2 G. However, in a case where a high-pressure refrigerant such as R.410A is used as the hydrofluorocarbon- (HFC-) based refrigerant, the pressure corresponding to the refrigerant in the case of R.410A is considerably high at 45 kgf/cm 2 G, with the result that there has been a possibility of the jigs from coming off when the airtight test is performed. The present invention has been devised to overcome the above-described problems, and its object is to provide a highly reliable refrigerating and air-conditioning apparatus which is capable of reliably returning the refrigerating machine oil even in a case where a refrigerant circuit is provided in which the refrigerant and the refrigerating machine oil are difficult to dissolve, and which is capable of accumulating the surplus liquid refrigerant so that a large amount of liquid refrigerant will not return to the compressor. Another object of the present invention is to obtain an apparatus which is inexpensive and highly reliable with a simple arrangement. JP-A-07-208819 discloses a refrigerant circulating apparatus in accordance with the preamble of claim 1. Oil which separates from the refrigerant forms an oil layer in a refrigerant reservoir. A further very close document represents US-A-1 965 198. The object of the present invention is met by the characterizing features of claim 1. In the accompanying drawings: Fig. 1 is a conceptual diagram of a refrigerant circulating apparatus illustrating a first embodiment of the present invention; Fig. 2 is a conceptual diagram of a liquid accumulating container illustrating first and second embodiments of the present invention; Fig. 3 is a conceptual diagram of the refrigerant circulating apparatus illustrating another embodiment of the present invention; Fig. 4 is a conceptual diagram of the refrigerant circulating apparatus illustrating still another embodiment of the present invention; and Fig. 5 is a diagram illustrating the rate of solubility of a refrigerating machine oil in a liquid refrigerant and the relationship between the oil circulation rate and the compressor frequency. Referring now to Figs. 1 and 2, a description will be given of a first embodiment of the present invention. Fig. 1 shows an example of a refrigerant circulating apparatus which is applied to an air conditioner. Reference numeral 1 denotes a compressor for compressing a refrigerant gas; 4, an outdoor heat exchanger for condensing the high-pressure refrigerant gas discharged from the compressor 1; 3, an indoor heat exchanger; 5, a pressure reducing device; 6, a liquid accumulating container for accumulating surplus refrigerant; 8, an inlet pipe connected to the lower side of the container; and 9, an outlet pipe connected to the upper side of the container. Numerals 16 and 17 denote fans for indoor and outdoor heat exchangers, respectively. Next, a description will be given of the behavior of the refrigerant and the refrigerating machine oil in a case where the refrigerant flows in the direction of arrows. The high-pressure refrigerant gas compressed by the compressor 1 is discharged together with the refrigerating machine oil having a weight ratio of 2.0% with respect to the refrigerant, and enters the outdoor heat exchanger 4 which is a condenser for condensing the refrigerant. The refrigerating machine oil is conveyed in the outdoor heat exchanger 4 by the refrigerant gas which has a sufficient flow rate. In the vicinity of the outlet port of the outdoor heat exchanger 4, part of the refrigerating machine oil dissolves in the liquefied refrigerant, while the remaining portion of the refrigerating machine oil is transformed into oil droplets, so that the refrigerating machine oil is conveyed to the liquid accumulating container 6 together with the refrigerant. In the liquid accumulating container where the channel area becomes large, the flow rate of the liquid refrigerant declines, and the refrigerating machine oil which is in the form of oil droplets floats upward in the container since its specific weight is smaller than that of the refrigerant. However, the direction in which the refrigerating machine oil floats upward is the same as the direction of the flow of the refrigerant as indicated by the arrows, and the container is generally in a state of being filled with the liquid except for a period immediately after starting (for about 5 minutes), so that the refrigerating machine oil is conveyed from the outlet pipe 9 to outside the container without being detained in the liquid accumulating container. Since part of the liquid refrigerant is gasified by being subjected to pressure reduction to a necessary pressure level by the pressure reducing device 5, the amount of refrigerant which is present in liquid form is reduced, so that the refrigerating machine oil which dissolved in the gasified liquid refrigerant is separated and forms oil droplets. Nevertheless, since the flow rate of the refrigerant increases abruptly due to the gasification of part of the liquid refrigerant, and the pipe diameter of the indoor heat exchanger 3 which is an evaporator in the next stage for evaporating the refrigerant is set so as to secure a flow rate of the refrigerant gas sufficient to convey the refrigerating machine oil downstream, the refrigerating machine oil is conveyed through the indoor heat exchanger and returns to the compressor 1. Thus, the refrigerating machine oil which flowed out from the compressor can be returned reliably to the compressor, and proper lubricating and sealing functions can be maintained for the compressing elements, so that it is possible to obtain an apparatus in which the reliability of the compressor is high. In addition, the structure is simple, productivity and cost performance are outstanding, and a decline in the performance due to the clogging with dust does not occur. Referring now to Figs. 2 and 3, a description will be given of a second embodiment of the present invention. Fig. 3 shows an example of the refrigerant circulating apparatus which is applied to an air conditioner. Reference numeral 1 denotes the compressor for compressing a refrigerant gas; 2, a four-way valve having the function of reversing the flowing direction of the refrigerant; 18, an extension pipe connecting an indoor unit and an outdoor unit; 3, the indoor heat exchanger; 4, the outdoor heat exchanger; 5, the pressure reducing device; 6, the liquid accumulating container for accumulating surplus refrigerant; 8, the inlet pipe connected to the lower side of the container; and 9, the outlet pipe connected to the upper side of the container. Next, a description will be given of the behavior of the refrigerant and the refrigerating machine oil in a case where heating is effected by the indoor unit. The high-pressure refrigerant gas compressed by the compressor 1 is discharged together with the refrigerating machine oil having a weight ratio of 2.0% with respect to the refrigerant, passes through the four-way valve 2, and enters the indoor heat exchanger 3 which is a condenser. The refrigerating machine oil is conveyed by the refrigerant gas which has a sufficient flow rate, and part of the refrigerating machine oil dissolves in the liquefied liquid refrigerant in the vicinity of the outlet port of the indoor heat exchanger 3, while the remaining portion of the refrigerating machine oil is transformed into oil droplets, so that the refrigerating machine oil is conveyed to the liquid accumulating container 6 together with the refrigerant. In the liquid accumulating container, where the channel area becomes large, the flow rate of the liquid refrigerant declines, and the refrigerating machine oil which is in the form of oil droplets floats upward in the container since its specific weight is smaller than that of the refrigerant. However, the direction in which the refrigerating machine oil floats upward is the same as the direction of the flow of the refrigerant as indicated by the arrows, and the container is generally in a state of being filled with the liquid except for a period immediately after starting (for about 5 minutes), so that the refrigerating machine oil is conveyed from the outlet pipe 9 to outside the container without being detained in the container. Accordingly, the refrigerating machine oil is conveyed to the pressure reducing device 5 without being detained in the liquid accumulating container. Since part of the liquid refrigerant is gasified by being subjected to pressure reduction to a necessary pressure level by the pressure reducing device 5, the amount of refrigerant which is present in liquid form is reduced, so that the refrigerating machine oil which dissolved in the gasified liquid refrigerant is separated and forms oil droplets. Nevertheless, since the flow rate of the refrigerant increases abruptly due to the gasification of part of the liquid refrigerant, and the pipe diameter of the outdoor heat exchanger 4 which is an evaporator in the next stage is set so as to secure a flow rate of the refrigerant gas sufficient to convey the refrigerating machine oil downstream, the refrigerating machine oil is conveyed through the outdoor heat exchanger and returns to the compressor 1. In the case of heating, since the indoor heat exchanger is generally made smaller than the outdoor heat exchanger, the amount of refrigerant can be smaller than in the case of cooling, so that the surplus refrigerant is liable to occur. On the other hand, in a case where cooling is effected by the indoor unit by allowing the refrigerant to flow reversely by changing over the four-way valve, the roles of condensation and evaporation by the indoor and outdoor heat exchangers are changed over, and the refrigerant, in which part of the refrigerant is gasified due to pressure reduction by the pressure reducing device 5 and the liquid and the gas are mixed, flows from the outlet pipe 9 into the container 6. However, since the refrigerant flows from above to below through the container, the refrigerating machine oil is conveyed from the inlet pipe 8 to outside the container without staying therein. For this reason, in the case of cooling in which the refrigerant is used in a large amount, although the liquid accumulating container ceases to function as the liquid accumulating container, there is no need for it, and the refrigerating machine oil which is conveyed together with the refrigerant is conveyed without being detained in the container. Consequently, the refrigerating machine oil discharged from the compressor 1 returns to the compressor 1 without being detained during the cycle. As described above, since the surplus refrigerant can be accumulated even if the required amount of refrigerant differs due to the flowing direction, it is possible to operate the apparatus efficiently irrespective of the flowing direction. At the same time, the refrigerating machine oil which flowed out from the compressor can be returned reliably to the compressor, and proper lubricating and sealing functions can be maintained for the compressing elements, so that it is possible to obtain an apparatus in which the reliability of the compressor is high. Referring now to Fig. 4, a description will be given of a third embodiment of the present invention. Fig. 4 shows an example of the refrigerant circulating apparatus which is applied to an air conditioner. In Fig. 4, reference numeral 1 denotes the compressor for compressing a refrigerant gas; 2, the four-way valve having the function of reversing the flowing direction of the refrigerant; 4, the outdoor heat exchanger; 16, an indoor fan; 3, the indoor heat exchanger; 17, an outdoor fan; 5a and 5b, the pressure reducing devices; and 6, the liquid accumulating container for accumulating surplus refrigerant. In general, if a liquid pooling section is provided in a refrigerant circuit, and if a refrigerating machine oil is used which is difficult to dissolve in a refrigerant using hydrofluorocarbon, such as a refrigerating machine oil, alkylbenzene, a mineral oil, an ester oil, an ether oil, or the like which has nonsolubility or very weak solubility with respect to, for example, an HFC-based refrigerant, with its rate by weight of solubility in the liquid refrigerant under the conditions of condensing pressure and condensing temperature being 0.5 - 7 wt%, and its rate by weight of solubility in the liquid refrigerant under the conditions of evaporating pressure and evaporating temperature being 0 - 2.0 wt%, then the oil which is mixed with the refrigerant is detained inside the container in the refrigerant circuit having the liquid pooling section, i.e., the liquid accumulating container for accumulating the surplus refrigerant, where the moving velocity of the refrigerant becomes slow. The rate by weight of solubility of the oil in the refrigerant, in the first place, changes depending on the kinds of refrigerant and oil. For instance, in terms of the rate of solubility of refrigerating machine oil alkylbenzene (viscosity grade VG = 8 - 32), i.e., an HAB oil, in the liquid refrigerant R.407C, i.e., an HFC-based refrigerant, as well as the relationship between the oil circulation rate and the compressor frequency, the refrigerating machine oil exhibits a rate of solubility of 1.0 - 4.0 wt% with respect to the liquid refrigerant in the range of the condensing temperature, but exhibits a very small rate of solubility of 0.2 - 1.8 wt% with respect to the liquid refrigerant in the range of the evaporating temperature. This rate of solubility changes depending on the combinations of various refrigerants and various oils. In general, the oil circulation rate, i.e., a weight ratio of the refrigerating machine oil which flows with the refrigerant from the compressor to the refrigerant, assumes a value of 0.3 - 2.0 wt% or thereabouts, and tends to increase with the rise of the compressor frequency. The refrigerating machine oil circulates in the refrigerant circuit in an amount which is shown by this oil circulation rate, and is particularly liable to be detained in the liquid accumulating container, and the refrigerating machine oil dissolves in the liquid refrigerant inside the container within the range of its rate of solubility at that temperature. However, in a case where the oil circulation rate has become higher than the rate of solubility of the refrigerating machine oil in the liquid refrigerant under the operating conditions at the location where the refrigerant is present, the amount of the refrigerating machine oil which is circulated exceeds an allowable amount of dissolution in the liquid refrigerant. The refrigerating machine oil as lubricating oil for the sliding portions of the compressor is stored in the compressor 1. Although a very small amount of refrigerating machine oil flows out from the compressor to the refrigerant circuit together with the refrigerant, if a refrigerating machine oil is used which scarcely dissolves in a refrigerant using hydrofluorocarbon, such as a refrigerating machine oil, alkylbenzene, a mineral oil, an ester oil, an ether oil, or the like which has nonsolubility or very weak solubility with respect to, for example, an HFC-based refrigerant, with its rate by weight of solubility in the liquid refrigerant under the conditions of condensing pressure and condensing temperature being 0.5 - 7 wt%, and its rate by weight of solubility in the liquid refrigerant under the conditions of evaporating pressure and evaporating temperature being 0 - 2.0 wt%, then the refrigerating machine oil which is mixed with the refrigerant is detained inside the receiver in the refrigerant circuit having the liquid pooling section, i.e., the receiver for accumulating the surplus refrigerant, where the moving velocity of the refrigerant becomes slow. The rate by weight of solubility of the refrigerating machine oil in the above-described refrigerant changes depending on the kinds of refrigerant and refrigerating machine oil. The aforementioned rates by weight of solubility are obtained through various combinations with respect to the various kinds of refrigerating machine oil enumerated above. Fig. 5 shows the rate of solubility of refrigerating machine oil alkylbenzene (viscosity grade VG = 8 - 32) in the liquid refrigerant R.407C, which is an HFC-based refrigerant in this embodiment, as well as the relationship between the oil circulation rate and the compressor frequency. As shown in Fig. 5(a), the refrigerating machine oil exhibits a rate of solubility of 1.0 - 4.0 wt% with respect to the liquid refrigerant in the condensing temperature range of +20°C - +70°C, but exhibits a very small rate of solubility of 0.2 - 1.8 wt% with respect to the liquid refrigerant in the evaporating temperature range of -20°C - +15°C. In addition, the lower the viscosity of the refrigerating machine oil, the greater the rate of solubility in the liquid refrigerant. As shown in Fig. 5(b), the oil circulation rate, i.e., a weight ratio of the refrigerating machine oil which flows with the refrigerant from the compressor to the refrigerant, generally assumes a value of 0.3 - 2.0 wt% or thereabouts, and tends to increase with the rise of the compressor frequency. As described above, since the liquid accumulating container for allowing oil droplets to flow out in suspended form is connected between the condenser and the pressure reducing device, the refrigerating machine oil which flowed out from the compressor can be reliably returned to the compressor, and proper lubricating and sealing functions can be maintained for the compressing elements. Hence, it is possible to obtain an apparatus in which the reliability of the compressor is high. In addition, the structure is simple, productivity and cost performance are outstanding, and a decline in the performance due to the clogging with dust does not occur. In the refrigerant circulating apparatus, since the structure provided is such that the refrigerant is accumulated on the flowing side where the surplus refrigerant occurs, and the liquid accumulating container allows the oil droplets to flow out in suspended form. Therefore, the refrigerating machine oil which flowed out from the compressor can be reliably returned to the compressor, and proper lubricating and sealing functions can be maintained for the compressing elements. Hence, it is possible to obtain an apparatus in which the reliability of the compressor is high. In addition, in a case where the flowing direction of the refrigerant is reverse, since the refrigerant is not accumulated in the container, the refrigerating machine oil is not accumulated, so that the refrigerating machine oil can be returned to the compressor. In the refrigerant circulating apparatus in which the liquid accumulating container is interposed between a pair of pressure reducing devices, the refrigerant can be accumulated irrespective of the flowing direction of the refrigerant.

Claims: Refrigerant circulating apparatus comprising a compressor (1), a condenser (4), a pressure reducing device (5) and evaporator (3), consecutively connected by refrigerant pipes; wherein: a refrigerant and a refrigerating machine oil circulate together while the refrigerant is subjected to a cycle of consecutive compression, condensation, pressure reduction, and evaporation; the refrigerating machine oil exhibits nonsolubility or very weak solubility in the liquid refrigerant, that is, the refrigerating machine oil has a rate by weight of solubility in relation to the liquid refrigerant in the range from 0.5% to 7.0% under the condition of condensing pressure and condensing temperature and has a rate by weight of solubility in relation to the liquid refrigerant in the range from 0% to 2.0% under the condition of evaporating pressure and evaporating temperature; the refrigerating machine oil has a smaller specific gravity than the liquid refrigerant under the condition of the condensing temperature, which is in a range from 20 °C to 70 °C; and comprising a liquid accumulating container (6), between said condenser (4) and said pressure reducing device (5), which has an inlet pipe (8) and an outlet pipe (9) characterised in that : said inlet pipe (8) is disposed at a lower part of said container (6) and said outlet pipe (9) is arranged in such a manner that the refrigerant flows from the inlet pipe (8) to the outlet pipe (9) in a direction from the bottom upwards, which is the same as the direction in which oil droplets float upwards in the liquid refrigerant, so that the oil droplets flow out of the container (6) in the form of a suspension of said oil in said liquid refrigerant. Apparatus according to claim 1, including means (2) for reversing the refrigerant circulating direction. Apparatus according to claim 2, in which the liquid accumulating container (6) is interposed between two pressure reducing devices (5a,5b).

Inventors: AKAHORI YASUSHI, IZAWA TAKESHI, MAKINO HIROAKI, SHIRAFUJI YOSHINORI, YAMASHITA KOJI, AKAHORI, YASUSHI, IZAWA, TAKESHI, MAKINO, HIROAKI, SHIRAFUJI, YOSHINORI, YAMASHITA, KOJI
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1997
Main classification: F25B43
IPC codes: F25B43, F25B31