Accumulator

Abstract: In an accumulator, an oil collecting pipe (4,10,16,19,20,23,24,29,30,31,32,35,36,39,40,51-55) is held in a sealed vessel (1,13,27,50) with the lower end thereof closed, the pipe (4,10,16,19,20,23,24,29,30,31,32,35,36,39,40,51-55) has a plurality of oil collecting apertures (4a-4h,10a-10h,16a,19a,20a,29a,30a,30b, 31a,31b,32a,32b,35a,36a,37a,39a,40a,51a-55a) spaced in a vertical direction and a communication port (4i,10i,16b,30c,31c,35b,37b) for communicating with a discharge pipe (3,9,17,18,28,38,49). The communication port (4i,10i,16b,30c,31c,35b,37b) is disposed in the vicinity of the lowermost oil collecting aperture (4a,10a) or to the downstream side of the aperture. Therefore, excessive liquid refrigerant flow from the accumulator is prevented even if a large amount of the liquid refrigerant resides in the sealed vessel (1,13,27,50).

Description: BACKGROUND OF THE INVENTION Field of the Invention: The present invention relates to an accumulator according to the preamble of claim 1. Such an accumulator, which is for example known from US-A-5 347 817, can constitute part of a refrigerating/air conditioning circuit of an air conditioner, refrigerator and the like, in particular for those that use refrigeration machine oil which has little or no solubility in refrigerant or, which if soluble, has a characteristic for separating from refrigerant depending upon temperature conditions. Description of the Related Art: An example of a conventional accumulator will now be described. Fig. 22 is a longitudinal cross sectional view showing the structure of the accumulator disclosed in Japanese Utility Model Publication No. 5-39409. In the drawing, a vessel 101 is provided with a suction pipe 102 and a discharge pipe 103. Liquid refrigerant 104 and refrigeration machine oil 105 reside in the vessel 101. A plurality of oil collecting apertures 103a - 103e are defined in the discharge pipe 103 in a vertical direction and five holes are defined in this example. The discharge pipe 103 is provided with a gas inlet 103f. Symbol U denotes the flow velocity in the discharge pipe 103. In a refrigerating/air conditioning circuit to which the accumulator is assembled, a fluid containing refrigerant gas, the liquid refrigerant 104 and the refrigeration machine oil 105 flows into the vessel 101 through the suction pipe 102. The refrigerant gas is separated from the liquid refrigerant in the space in the vessel 101 and the refrigerant gas flows to the outside of the vessel 101 from the gas inlet 103f through the discharge pipe 103. On the other hand, the liquid refrigerant 104 and the refrigeration machine oil 105 stay in the bottom of the vessel 101. When the refrigeration machine oil 105 is barely soluble or in soluble in the liquid refrigerant 104 are even when it tends to separate from the liquid refrigerant 104 under certain operating conditions. The refrigeration machine oil 105 in the vessel 101 then separates from the refrigerant 104 as shown in the drawing and the refrigeration machine oil 105 with a thickness h floats on the upper layer of the liquid refrigerant 104 having a liquid surface height H. Since the oil collecting apertures 103a - 103e are disposed at a plurality of positions in a vertical direction, the refrigeration machine oil 105 and the liquid refrigerant 104 are sucked into the discharge pipe 103 through the oil collecting apertures 103a - 103e and flow in a mixture with the refrigerant gas. Next, another example of the conventional accumulator will be shown. Fig. 23 is a longitudinal cross sectional view showing the structure of the accumulator disclosed in Japanese Utility Model Laid-Open No. 58-87079 in which the inner arrangement of the accumulator is different from that of the above conventional example. In the drawing, a vessel 106 is provided with a suction pipe 107 and a discharge pipe 108. A plurality of oil collecting apertures 108a - 108e are defined in the discharge pipe 108 in a vertical direction. Liquid refrigerant 109 and refrigeration machine oil 110 reside in the vessel 106. In a refrigerating/air conditioning circuit to which the accumulator is assembled, a fluid containing refrigerant gas, the liquid refrigerant 109 and the refrigeration machine oil 110 flows into the vessel 106 through the suction pipe 107. The refrigerant gas is separated from the liquid refrigerant in the space in the vessel 106 so that the refrigeration machine oil 110 is separated from the liquid refrigerant 109 and the refrigeration machine oil 110 having a smaller specific gravity floats on the upper layer of the liquid refrigerant 109. The oil collecting apertures 108a - 108e are disposed at a plurality of positions in a vertical direction and the refrigeration machine oil 110 and the liquid refrigerant 109 are sucked into the discharge pipe 108 through the oil collecting apertures 108a - 108e and flow in a mixture with the refrigerant gas. Both the above conventional examples operate similarly and have the same problems. The operation of the conventional example shown in Fig. 22 will be described as representing the operation of the above examples and the problems of the example will be described. The amount of the liquid refrigerant flowing into the discharge pipe 103 through the oil collecting apertures 103a - 103e is increased by the increase of the flow velocity U of the gas flowing in the discharge pipe 103 and the increase of the amount of the liquid refrigerant residing in the vessel 101, that is, the increase of the height H of the liquid refrigerant. Fig. 24 shows flow amount characteristics when it is assumed that the gas flow velocity U is set to a given value and the thickness h of the refrigeration machine oil 105 flowing on the upper layer of the liquid refrigerant 104 is fixed. In the drawing, the abscissa represents a liquid refrigerant surface height H (mm) and the ordinate represents an amount (kg/h) of liquid refrigerant flowing into the discharge pipe 103. Further, the dotted lines show the respective amounts of liquid refrigerant flowing from the respective oil collecting apertures 103a - 103e and the dashed line rising to the upper right shows the sum of the liquid refrigerant flowing from the respective oil collecting apertures. As the liquid refrigerant height H increases, the number of oil collecting apertures under the liquid refrigerant 104 increases. At the time, the amount of the liquid refrigerant flowing from the lower oil collecting apertures is greater than that flowing from the upper oil collecting apertures due to the differences in pressures applied thereto. Therefore, the total flow amount of the liquid refrigerant does not increase in proportion to the liquid refrigerant height H but acceleratively increases as the height H increases. That is, as the liquid surface height in the accumulator increases, the amount of the refrigerant 104 sucked into the discharge pipe 103 and flowing from the accumulator increases. Next, the flow amount of oil will be described. The saw-tooth-shaped solid line in Fig. 24 indicating an approximately constant flow amount shows the amount of the refrigeration machine oil 105 which floats on the upper layer and flows into the discharge pipe 103 through the oil collecting apertures. Further, Fig. 25 shows a view explaining the change of the flow amount of the oil. The amount of the refrigeration machine oil is determined by the refrigerating/air conditioning circuit to which the accumulator is assembled. Usually, however, since the diameter of the oil collecting apertures is determined to prevent the excessive refrigeration machine oil from staying in the accumulator, the amount of refrigeration machine oil residing in the sealed vessel 101 of the accumulator barely increases or decreases. Normally, therefore, only one or two oil collecting apertures are positioned with in the thickness h of the refrigeration machine oil although this depends on the intervals between the oil collecting apertures. Fig. 25A shows a case where the refrigeration machine oil 105 stays in the range of the oil collecting apertures 103c and 103d and Fig. 25B shows a case where it stays in the range of the oil collecting aperture 103d although the thickness h of the refrigeration machine oil is the same as that of Fig. 25A. That is, the state shown in Fig. 25A or the state shown in Fig. 25B may be realized depending upon the change of the liquid refrigerant height H. As a matter of course, the difference between both states results in a change of the flow amount of the oil, where the flow amount of the oil in Fig. 25A is greater than that in Fig. 25B. Therefore, even if the thickness h of the refrigeration machine oil is given, the amount of the oil flowing into the discharge pipe 103 is somewhat changed by the change of the liquid refrigerant height H. Actually, although the flow amount of the oil tends to change stepwise as shown Fig. 24, it is constant in average in comparison with the amount of the liquid refrigerant. As is well known, refrigerant gas from the discharge pipe of an accumulator is sucked by a compressor in a refrigerating/air conditioning circuit and discharged after being compressed. When the refrigeration machine oil which separates from the liquid refrigerant is applied to an accumulator having a conventional structure, a phenomena wherein the liquid refrigerant become mixed with the refrigerant gas is caused so that the flow amount of the liquid refrigerant becomes excessive. At this time, the compressor will suck a large amount of liquid refrigerant and compress it. Thus, a liquid compressed state arises, by which abnormally high pressures are generated. Further, since the oil supply pump in the compressor sucks the liquid refrigerant and supplies it to bearings and sliding portions, the bearings will not be sufficiently lubricated. As a result, the sliding portions in the compressor may become abnormally worn or seized. That is, the flow amount of the liquid refrigerant derived from the accumulator assembled to the refrigerating /air conditioning circuit must be smaller than a certain amount and the flow amount of the refrigeration machine oil must be larger than a certain amount for the compressor to operate smoothly. Their limit values depend upon the refrigerating/air conditioning circuit to which the accumulator is assembled. When, for example, the diameter of the oil collecting apertures is made small to reduce the flow amount of the liquid refrigerant in the conventional arrangement, micro-machining may be required which is not suitable large-scale production of the structure. Further, when the apertures have a small diameter, there is an increased possibility that the apertures may become clogged with foreign material. Consequently, the apertures must have a diameter larger than a certain degree and the diameter must be usually set to, for example, about 1.5 mm at the smallest, which, however, cannot reduce the flow amount of the liquid refrigerant. Further, there is the following problem from the view point of the flow amount characteristics of the oil. That is, when it is assumed that the oil collecting apertures are set a small diameter, although the flow amount of the liquid refrigerant can be reduced, the flow amount of the oil is also reduced. Thus it is difficult to obtain the target flow amount of the refrigeration machine oil. In this case, since a large amount of the oil stays in the accumulator vessel, the amount of the oil in the compressor is sharply reduced. As described above, conventional accumulators have problems in that it is difficult to properly control the flow amount of the liquid refrigerant and the flow amount of the refrigeration machine oil. US-A- 5 347 817 discloses an accumulator comprising a sealed vessel, a suction pipe integrally formed with the sealed vessel, a discharge pipe and an oil collecting pipe. The oil collecting pipe has apertures spaced in the vertical direction. At least one communication port is provided. This communication port is provided at the downstream side of the oil collecting aperture. The oil collecting pipe is arranged to surround the discharge pipe. SUMMARY OF THE INVENTION The present invention has been achieved with a view toward solving the problems described above, and it is an object of the present invention to provide an accumulator in which liquid refrigerant is prevented from excessively flowing from the accumulator even if a large amount of the liquid refrigerant resides in an accumulator vessel. Also, refrigeration machine oil staying in the accumulator can be effectively collected into a compressor by machining the diameter of oil collecting apertures to such a size as to present no obstacle in operation so that the flow amount of the liquid refrigerant flowing into the compressor is suppressed while securing the necessary flow amount of the refrigeration machine oil. As a result, the reliability of the refrigerating/air conditioning circuit can be enhanced. This object is solved by an accumulator according to claim 1. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A is a longitudinal cross sectional view showing an accumulator which does not form part of the present invention; Fig. 1B is a cross sectional view taken along the line A - A of Fig. 1A; Fig. 2A is a longitudinal cross sectional view showing another accumulator according to an embodiment of the present invention; Fig. 2B is a cross sectional view taken along the line B - B of Fig. 2A; Fig. 2C is a view explaining the internal flow of liquid refrigerant and refrigeration machine oil; Fig. 3 is a view explaining the internal flow of liquid refrigerant and refrigeration machine oil according to the first embodiment; Fig. 4 is a characteristic graph showing the relationship between the flow amounts (kg/h) of liquid refrigerant and refrigeration machine oil and a liquid refrigerant surface height (mm) ; Fig. 5A is a longitudinal cross sectional view showing an accumulator which does not form part of the present invention; Fig. 5B is a cross sectional view taken along the line D - D of Fig. 5A; Fig. 6A is a longitudinal cross sectional view showing an accumulator which does not form part of the present invention; Fig. 6B is a cross sectional view taken along the live E - E of Fig. 6A; Fig. 7A is a cross sectional view showing the vicinity of the communication port of the accumulator; Fig. 7B is a cross sectional view showing a vicinity of a communication port of an accumulator according to an embodiment of the present invention; Fig. 8A is a longitudinal cross sectional view showing an oil collecting pipe of an accumulator according to an embodiment of the present invention; Fig. 8B is an upper plan view of Fig. 8A; Fig. 9A is a view explaining the flow of liquid refrigerant and refrigeration machine oil in an oil collecting pipe having a thin diameter; Fig. 9B is a view explaining the flow of liquid refrigerant and refrigeration machine oil in an oil collecting pipe having a thick diameter; Fig. 10A is a longitudinal cross sectional view showing an accumulator which does not form part of the present invention ; Fig. 10B is a front elevational view of an oil collecting pipe of Fig. 10A; Fig. 11A is a longitudinal cross sectional view showing an accumulator according to another embodiment of the present invention; Fig. 11B is a cross sectional view taken along the line F - F of Fig. 11A; Fig. 12 is a characteristic graph showing the relationship between the flow amounts (kg/h) of liquid refrigerant and refrigeration machine oil and a liquid refrigerant surface height (mm) according to the embodiment of the present invention; Fig. 13A is a longitudinal cross sectional view showing an accumulator according to another embodiment of the present invention; Fig. 13B is a cross sectional view taken along the line G - G of Fig. 13A; Fig. 14A is a longitudinal cross sectional view showing an accumulator according to another embodiment of the present invention; Fig. 14B is a cross sectional view taken along the line H - H of Fig. 14A; Fig. 14C is a view explaining the internal flow of liquid refrigerant and refrigeration machine oil of Fig. 14A; Fig. 15A is a longitudinal cross sectional view showing an accumulator according to another embodiment of the present invention: Fig. 15B is a cross sectional view taken along the line I - I of Fig. 15A; Fig. 16A is a longitudinal cross sectional view showing an accumulator according to another embodiment of the present invention; Fig. 16B is a cross sectional view taken along the line J - J of Pig. 16A; Fig. 17 is a longitudinal cross sectional view showing an accumulator which does not form part of the present invention; Fig. 18A is a view showing the arrangement of a main portion of the accumulator of Fig. 17; Fig. 18B is a cross sectional view taken along the line K - K of Fig. 18A; Fig. 19A is a view explaining the operation of the accumulator according to Fig. 17; Fig. 19B is a view explaining the operation of the accumulator according to Fig. 17; Fig. 20 is a characteristic graph showing the relationship between the flow amounts (kg/h) of liquid refrigerant and refrigeration machine oil and a liquid refrigerant surface height (mm); Fig. 21A is a longitudinal cross sectional view showing an accumulator which does not form part of the present invention; Fig. 21B is a cross sectional view taken along the line L - L of Fig. 21A; Fig. 22 is a longitudinal cross sectional view showing an example of a conventional accumulator; Fig. 23 is a longitudinal cross sectional view showing another example of the conventional accumulator; Fig. 24 is a characteristic graph showing the relationship between the flow amounts (kg/h) of liquid refrigerant and refrigeration machine oil and a liquid refrigerant surface height (mm) according to the conventional accumulator; Fig. 25A is a view explaining the change of the flow amount of oil of the conventional accumulator; and Fig. 25B is a view explaining the change of the flow amount of oil of the conventional accumulator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments according to the present invention will now be described with reference to the accompanying drawings. The embodiments of the accumulator shown in Figs. 1A, 1B, 5A, 5B, 6A, 6B, 10A, 10B, 17, 18A, 18B, 19A, 19B, 21A and 21B do not form part of the present invention. Fig. 1A is a longitudinal cross sectional view showing an accumulator. Fig. 1B is a cross sectional view taken along the line A - A of Fig. 1A. In the drawings, a sealed vessel 1 is provided with a suction pipe 2 and a discharge pipe 3 having a refrigerant gas inlet 3a and a communication port 3b. An oil collecting pipe 4 is disposed in the sealed vessel 1 and provided with a plurality of oil collecting apertures 4a - 4h disposed in a vertical direction and a communication port 4i communicated with the discharge pipe 3. Liquid refrigerant 5 and refrigeration machine oil 6 resides in the sealed vessel 1. The oil collecting pipe 4 is fixed to the discharge pipe 3 through a reinforcing member 7. The communication port 3b and the oil collecting apertures 4a - 4h are arranged to have, for example, an orifice structure and basically formed to a circular shape, although they are arranged likewise when they are not formed in a circular shape. The communication port 3b is disposed in the vicinity of the lowermost oil collecting aperture 4a or nearer to the downstream side of the refrigerant passage than the aperture 4a. Fig. 2A is a longitudinal cross sectional view showing an accumulator according to an embodiment of the invention. Fig. 2B is a cross sectional view taken along the line B - B of Fig. 2A. Fig. 2C is a view explaining the internal flow of liquid refrigerant and refrigeration machine oil. In the drawings, a suction pipe 8 is connected to a sealed vessel 13. A discharge pipe 9 is inserted into the sealed vessel 13 and is provided with a refrigerant gas inlet 9a and a communication port 9b. An oil collecting pipe 10 is fixed to the discharge pipe 9 and provided with oil collecting apertures 10a - 10h and a communication port 10i with the discharge pipe 9. Liquid refrigerant 11 and refrigeration machine oil 13 resides in the sealed vessel 1. In Figs. 1A to 2B, the diameter of the oil collecting apertures defined in the oil collecting pipes is set to about 1 - 3 mm which causes no obstacle in machining. The operation of the embodiment will be described as to the accumulator arranged as shown in Fig. 2, The accumulator functions to temporarily store refrigerant circulating in a refrigerating/air conditioning circuit. The refrigerant gas flowing from the suction pipe 8 is separated from the liquid refrigerant, the liquid refrigerant 11 is stored in the sealed vessel 13 to prevent it from being supplied to a compressor (not shown) and the refrigerant machine oil 12 stored in the sealed vessel 13 is returned to the compressor. Fig. 2A shows a state where the fluid of the liquid refrigerant 11 and the refrigerant machine oil 12 mixed with the refrigerant gas from the suction pipe 8 is separated therefrom in the sealed vessel 13 and the liquid refrigerant 11 and the refrigerant machine oil 12 stay in the sealed vessel 13. Since the liquid refrigerant 11 and the refrigerant machine oil 12 have little solubility, they stay in the lower portion of the sealed vessel 13 in a separated state. Usually, since the specific gravity of the refrigerant machine oil 12 is less than that of the liquid refrigerant 11, the refrigerant machine oil 12 floats on the upper layer of the liquid refrigerant 11. One function of the accumulator is returning the refrigerant machine oil 12 to the compressor by sucking it into the discharge pipe 9 regardless of the amount of liquid refrigerant 11 residing therein, that is, even if the height of the liquid refrigerant 11 varies. In this embodiment, the plurality of oil collecting apertures 10a - 10h are vertically disposed along the axis of the oil collecting pipe 10 to collect the refrigerant machine oil 12 floating on the liquid refrigerant 11 into the oil collecting pipe 10. As shown in Fig. 2B, the communication port 10i disposed to the lower portion of the oil collecting pipe 10 is made to communicate with the communication port 9b disposed in the discharge pipe 9 so that the liquid refrigerant 11 and the refrigerant machine oil 12 in the oil collecting pipe 10 can be sucked into the discharge pipe 9. As seen from Fig. 2C, the liquid refrigerant 11 in the oil collecting pipe 10 is mixed with the refrigerant machine oil 12 therein and the refrigerant machine oil 12 entering the oil collecting pipe 10 is accompanied by the flow of the liquid refrigerant 11 in the oil collecting pipe 10, passes through the communication ports 10i, 9b and is further sucked into the discharge pipe 9. The refrigerant machine oil 12 floating on the upper layer of the liquid refrigerant 11 in the sealed vessel 13 is sucked into the discharge pipe 9 as described above. Next, the flow amount characteristics of the liquid refrigerant 11 and the refrigerant machine oil 12 will be described. Fig. 3 shows the internal flow and the liquid surface height in the discharge pipe 9 and the oil collecting pipe 10, wherein Fig. 3A shows a case where the liquid surface height H in the sealed vessel 13 is low and Fig. 3B shows a case where the liquid surface height H is high. In the drawings, symbol L denotes the liquid surface height in the oil collecting pipe 10, symbol L1 corresponds to the case where the liquid surface height is low (Fig. 3A) and symbol L2 corresponds to the case where the liquid surface height is high (Fig. 3B). The pressure in the communication port 10i drops by Δ P as compared with that in the sealed vessel 13 due to the refrigerant gas flowing in the discharge pipe 9. The total flow amount Q of the liquid refrigerant 11 and the refrigerant machine oil 12 which flow in the communication port 10i is shown by Q ∝ √ (Δ P + ρ gL), where ρ represents liquid density and g represents gravity acceleration. The number of oil collecting apertures (10a - 10e) into which the liquid refrigerant 11 and the refrigerant machine oil 12 flow is increased by the increase in the liquid surface height H in the sealed vessel 13 to increase the liquid surface height L in the oil collecting pipe 10 accordingly. The total flow amount Q of the liquid refrigerant 11 and the refrigerant machine oil 12 which flow in the communication port 10i is determined by Q ∝ √ (Δ P + ρ gL), so that the total flow amount characteristics Q shown in Fig. 4 can be obtained. Next, the ratio between the flow amount of the liquid refrigerant and that of the refrigeration machine oil will be described. In the oil collecting pipe 10 arranged as described above, when the oil collecting apertures have the same size and are disposed at the same intervals, the inflow at the respective oil collecting apertures is approximately the same. As a result, where an oil collecting aperture 10a and oil collecting aperture 10b are disposed as shown in Fig. 3A the liquid refrigerant 11 and the refrigerant machine oil 12 respectively flow in approximately equal amounts. Further, in Fig. 3B, where four oil collecting apertures 10a - 10d are disposed into which the liquid refrigerant 11 flows the one oil collecting aperture 10e is disposed into which the refrigerant machine oil 12 flows, the flow amount of the refrigerant machine oil 12 is approximately one fifth the total flow amount Q. The flow amount characteristics of the refrigerant machine oil 12 and the liquid refrigerant 11 are determined as described above. Thus the flow amount of the liquid refrigerant and the flow amount of the refrigeration machine oil shown in Fig. 4 can be obtained. In Fig. 4, the abscissa represents the liquid surface height H (mm) of the liquid refrigerant and the ordinate represents the flow amount from the oil collecting pipe 10 to the discharge pipe 9. When the flow amount characteristics of the liquid refrigerant obtained by the embodiment are compared with the flow amount characteristics of the liquid refrigerant of the conventional accumulator shown in Fig. 24, the former characteristics are clearly different from the latter characteristics and this embodiment can greatly reduce the increase of the flow amount of the liquid refrigerant caused by an increase of the liquid surface height H. As described above, since this embodiment is provided with the oil collecting pipe having the plurality of oil collecting apertures vertically spaced therein and the oil collecting pipe is made to communicate with the discharge pipe through the single orifice-shaped communication aperture, even if the height of the liquid refrigerant in the sealed vessel 13 increases, the amount of the liquid refrigerant sucked into the discharge pipe 9 is not increased as in the conventional example. Thus excessive flow of the liquid refrigerant from the accumulator can be prevented and the refrigeration machine oil remaining, the accumulator can be effectively collected to the compressor. Therefore, the amount of the liquid refrigerant flowing into the compressor can be suppressed and the necessary flow amount of the refrigeration machine oil can be secured. As a result, the reliability of the refrigerating/air conditioning circuit can be improved. The arrangement of an oil collecting pipe of another accumulator which does not form a part of the invention will now be described. Fig. 5A is a longitudinal cross sectional view showing an accumulator. Fig. 5B is a cross sectional view taken along the line D - D of Fig. 5A. This accumulator makes the reinforcing member for supporting the oil collecting pipe in the arrangement of Fig. 1A unnecessary for simplification. In the drawings, an oil collecting pipe 16 is provided with a plurality of oil collecting apertures 16a, a communication port 16b. Also, the oil collecting pipe 16 is fixed to a discharge pipe 17 at the communication port 16b and a fixed point 16c. The oil collecting pipe 16 is connected to the discharge pipe 17 through the communication ports 16a, 17a defined in them, respectively. When the plurality of oil collecting apertures 16a have the same size and are disposed at the same intervals, an advantage similar to that of the first embodiment can be obtained. In addition, since the oil collecting pipe 16 can be fixed without the provision of the reinforcing member 7 in Fig. 1A, the arrangement can be simplified. Next, the structure of an oil collecting pipe of another accumulator which does not form part of the present invention will be described. Fig. 6A is a longitudinal cross sectional view showing an accumulator. Fig. 6B is a cross sectional view taken along the line E - E of Fig. 6A. In the drawings, a discharge pipe 18 is inserted into the sealed vessel 1 and provided with a communication port 18a and a gas inlet 18b. An oil collecting pipe 19 is provided with a plurality of oil collecting apertures 19a. The communication port 18a is located at a high position nearer to the downstream side of a refrigerant passage than the oil collecting aperture disposed to the lowermost Position of the J-shaped oil collecting pipe 19. It also communicates an the J-shaped discharge pipe 18 side with the oil collecting pipe 19 at a high position nearer to the downstream side of the refrigerant passage than the lowermost portion of the discharge pipe 18. The operation will be described below. The disposition of the communication port 18a at the position shown in the drawing increases the distance from the gas inlet 18b of the discharge pipe to the communication port 18a, by which the pressure loss Δ P generated in the pipe within the above range is made larger than that in the first embodiment. As described above, since the total flow amount Q of the liquid refrigerant 5 and the refrigerant machine oil 6 flowing through the communication port 18a in; determined by Q ∝ (ΔP + ρ gL), the total flow characteristics Q in this embodiment are increased over those in the first embodiment. Since the ratio of the refrigeration machine oil contained in the total flow amount Q is the same, the flow amount of the refrigeration machine oil is also increased by the increase of the total flow amount Q. Although there is an obstacle when the total flow amount Q is excessively increased as described above, the total flow amount Q in this accumulator does not increase acceleratively as in the conventional example. Also, there is an advantage in that the refrigeration machine oil can be increased. The total flow amount Q of the liquid refrigerant and the refrigeration machine oil can be adjusted by changing the position where the communication port is connected to the discharge pipe as described above. That is, the communication port 18a need not be always disposed at the lowermost portion of the discharge pipe as found in the first embodiment and the characteristics of the flow mount to the discharge pipe 18 can be adjusted by communicating the oil collecting pipe 19 with the discharge pipe 18 in the vicinity of the lowermost oil collecting aperture or at any arbitrary position on the downward stream side therefrom. As a result, this embodiment has an advantage in that the operating conditions of the refrigerating/air conditioning circuit to which the accumulator is assembled can be optimized as well as advantages similar to the first embodiment. The arrangement and operation of an accumulator according to a another embodiment of the present invention will be described below. This embodiment relates to the shape of a communication port and reduces the effect of an flow amount caused by the viscosity of the fluid flowing the communication port. Fig. 7A shows an arrangement where the diameter of the communication port 16b of an oil collecting pipe 16 is the same as the diameter of the communication aperture 17a of a discharge pipe 17. When the oil collecting pipe 16 and the discharge pipe 17 have the same wall thickness, the length of the passage in the flow direction corresponds to twice the wall thickness t of the pipe. Further, Fig. 7B shows an arrangement where the diameter of the communication port 16c of the oil collecting pipe 16 is larger than the diameter of the communication port 17a of the discharge pipe 17, in which the length of the passage in the flow direction corresponds to the wall thickness t of the pipe. In a comparison of the arrangement of Fig. 7A with that of Fig. 7B, although the cross sectional areas of the communication ports are the same, the length of the passage in the flow direction is longer in Fig. 7A. Therefore, when, for example, refrigeration machine oil having a high viscosity flows in the arrangement of Fig. 7A, the resistance of the passage is increased, thus reducing the flow amount. On the other hand, when the diameter of one of the communication ports 16b or 17a is made larger than that of the other to substantially reduce the length of the passage as in Fig. 7B, the change of passage caused by the effect of viscosity can be suppressed. Although the diameter of communication port 16c is larger than that of communication port 17a in Fig. 7B, the diameter of communication port 17a may be larger than that of communication port 16c. The structure of an oil collecting pipe of an' accumulator according to a further embodiment of the present invention will be described below. This embodiment is arranged to more effectively feed the refrigeration machine oil flowing into the oil collecting pipe. Fig. 8A is a longitudinal cross sectional view showing an oil collecting pipe of an accumulator according to this embodiment of the present invention. Fig. 8B is an upper plan view of Fig. 8A. The oil collecting pipe 20 is provided with a plurality of oil collecting apertures 201. A columnar member 21 is held in the vicinity of the center of the oil collecting pipe 20 and an annular space 22 is defined between the inner wall of the oil collecting pipe 20 and the side surface of the columnar member 21. Figs. 9A and 9B are views explaining the operation of the oil collecting pipes, wherein Fig. 9A shows a case where the oil collecting pipe 23 has a thin diameter of about 4 - 5 mm and Fig. 9B shows a case where the oil collecting pipe 24 has a thick diameter of about 10 mm. In the drawings, symbol Δ P denotes a pressure difference acting on the oil collecting pipes 23, 24 where the lower portions of the pipes are under low pressure to communicate with the discharge pipes. Next, how the flowing state changes in relation to the diameter of the oil collecting pipe will be described with reference to Fig. 9. The minimum diameter of an oil droplet 26 is determined by the surface tension of the refrigeration machine oil 26 and the liquid refrigerant 25. Fig. 9A shows an arrangement where the diameter of the droplet 26 is approximately the same as the inside diameter of the pipe and the liquid refrigerant 25 flows so as to push out the droplet 26. Since the pressure difference Δ P acts on the droplet 26 in this state, the droplet 26 and liquid refrigerant 25 form a continuous flow. Since there is a difference between the specific gravity of the refrigeration machine oil and that of the liquid refrigerant, the droplet 26 flows by being pushed downward by the liquid refrigerant 25 although buoyancy acts on the droplet 26. On the other hand, since the droplet 26 can move freely in the arrangement of Fig. 9B in which the oil collecting pipe 24 has a large diameter, the falling flow velocity of the droplet 26 is slower than that in Fig. 9A. As described above, when the diameter of the flow passage of the oil collecting pipe is approximately as small as the droplet, the state shown in Fig. 9A can be created, which permits the droplet 26 to more easily flow downward. Fig. 8 shows a structure in which the above idea is specifically realized in the accumulator. In Fig. 8, the shape of a flow passage is changed from a cylindrical pipe to the annular space 22. To achieve the arrangement, for example, where the cross sectional area of the annular space 22 serving as the flow passage is equal to the cross sectional area of a circular pipe having an inside diameter of 10 mm, a pipe having an inside diameter of 11. 7 mm, for example, is used as the oil collecting pipe 20 and a columnar member having an outside diameter of 6 mm is fixed therein. At the time, the diameter of a droplet capable of passing through the annular space 22 is 2.9 mm. That is, the slight increase in diameter of the oil collecting pipe 20 and the provision of the columnar member 21 therein permit the space in the flow passage to be adjusted to correspond to the diameter of the droplet of the refrigeration machine oil while maintaining a large cross sectional area of the pipe. Therefore, the flowing state of the droplet 26 will be near the state shown in Fig. 9A, so that a state where the droplet can easily flow against buoyancy can be realized. The structure of an oil collecting pipe of an accumulator which does not form part of the present invention will be described below. This embodiment is arranged to effectively feed the refrigeration machine oil flowing into the oil collecting pipe. Fig. 10A is a longitudinal cross sectional view showing this accumulator. Fig. 10B is a front elevational view of the oil collecting pipe of Fig. 10A. In the drawings, a discharge pipe 28 is inserted into a sealed vessel 27. A communication port 28a is disposed to the lower portion of the discharge pipe 28. A cylindrical oil collecting pipe 29 is disposed to surround the discharge pipe 28 to define an annular space between itself and the discharge pipe 28. A plurality of oil collecting apertures 29a are disposed in the side surface of the oil collecting pipe 29. The operation of this accumulator will be described below. As in the embodiment described with respect to Fig. 8, the liquid refrigerant 11 and the refrigerant machine oil 12 flowing into the cylindrical oil collecting pipe 29 through the oil collecting apertures 29a flow downward through the annular space formed between the inner wall of the cylindrical oil collecting pipe 29 and the side surface of the discharge pipe 28. They flow into the discharge pipe 28 through the communication port 28a disposed to the lower portion. The oil can easily flow through the annular space against buoyancy because the space is made to be approximately as small as the diameter of an droplet in the flow passage. Thus, the flow amount of the refrigerant machine oil 12 is increased and the amount of the refrigerant machine oil 12 collected into the compressor can be increased. In addition, since the length of the communication port 28a in the direction of flow can comprise the wall thickness of the discharge pipe 28, as described in Fig. 7B, flow amount characteristics of the liquid refrigerant 11 and the refrigerant machine oil 12 which depend little on viscosity can be realized. The arrangement of an oil collecting pipe of an accumulator according to a further embodiment of the present invention will be described below. This embodiment is arranged to relatively increase the amount of refrigeration machine oil to be collected in a state where a large amount of the liquid refrigerant and the refrigeration machine oil resides in the accumulator to increase the amount of refrigeration machine oil supplied to the compressor so that the reliability of the compressor is enhanced. Fig. 11A is a longitudinal cross sectional view showing an accumulator according to this embodiment of the present invention. Fig. 11B is a cross sectional view taken along the line F - F of Fig. 11A. In the drawings, an oil collecting pipe 30 is provided with a plurality of oil collecting apertures 30a and 30b. The diameter of the oil collecting apertures 30b are smaller than those of the oil collecting apertures 30a. For example, the cross sectional area of an oil collecting aperture 30b is about one fourth the cross sectional area of the oil collecting aperture 30a. The operation will be described below. When the diameter of the upper oil collecting apertures 30a is larger than that of the lower oil collecting apertures 30b, the ratio of the amount of the liquid refrigerant flowing from the lower oil collecting apertures 30b is relatively reduced, so that the flow amount characteristics shown in Fig. 12 are obtained. In Fig. 12, the abscissa represents a liquid surface height H (mm) and the ordinate represents the flow amount (kg/h) of the fluids flowing into the discharge pipe 28 through a communication port 30c. The solid line in the drawing shows the flow amount characteristics obtained by this embodiment and the dotted line shows the flow amount structure when all the oil collecting apertures have the same diameter. As is apparent from Fig. 12, according to the arrangement of this embodiment, both reductions in the flow amount of the refrigeration machine oil and increases in the flow amount of the liquid refrigerant can be eased in the region where the liquid surface height H is high. As a result, even if a large amount of the liquid refrigerant and the refrigeration machine oil remain, the refrigeration machine oil can be stably supplied to the compressor and the reliability of the compressor can be enhanced. Further, by changing the diameters of the oil collecting apertures in the upper and lower portions, the flow amount characteristics of the liquid refrigerant 11 and the refrigerant machine oil 12 flowing into the oil collecting pipe 30 can be adjusted. The structure of an oil collecting pipe of an accumulator according to another embodiment of the present invention will be described below. This embodiment is arranged to relatively increase the amount of refrigeration machine oil to be collected in a state where a large amount of the liquid refrigerant and the refrigeration machine resides in the accumulator to increase the amount of refrigeration machine oil supplied to the compressor so that the reliability of the compressor is enhanced. Fig. 13A is a longitudinal cross sectional view showing an accumulator according to this embodiment of the present invention. Fig. 13B is a cross sectional view taken along the line G - G of Fig. 13A. In the drawings, an oil collecting pipe 31 is provided with oil collecting apertures 31a and 31b. The interval Y between adjacent oil collecting apertures 31b is made narrower than the interval X between adjacent oil collecting apertures 31a. For example, the interval between the oil collecting apertures 31b is set to be about 2 cm and the interval between the oil collecting apertures 31a is set to about 3 cm. The flow amount characteristics of the liquid refrigerant 11 and the refrigerant machine oil 12 flowing into the oil collecting pipe 31 can be adjusted by the arranging the intervals between the upper oil collecting apertures 31b to be narrower than the intervals between the lower oil collecting apertures 31a as described above. For example, when a large amount of the liquid refrigerant 11 remains, that is, when the height H of the liquid refrigerant 11 is high, there is a characteristic that a large amount of the refrigerant machine oil 12 will flow because the number of the oil collecting apertures 31b located in the layer of the refrigerant machine oil increases. Therefore, similar to the flow amount characteristics shown by the solid line of Fig. 12, the drop in the flow amount of the refrigeration machine oil in communication ports 31c and 28a can be reduced in the region where the liquid surface height H is high. As a result, a reduction of the amount of refrigerant machine oil 12 returned to the compressor can be prevented so that the reliability of the compressor can be enhanced. The structure of an oil collecting pipe of an accumulator according to a further embodiment of the present invention will be described below. This embodiment is arranged to more promptly feed the refrigeration machine oil in the oil collecting pipe. Fig. 14A is a longitudinal cross sectional view showing an accumulator according to this embodiment of the present invention. Fig. 14B is a cross sectional view taken along the line H - H of Fig. 14A. Fig. 14C is a view explaining the internal flow of liquid refrigerant and refrigeration machine oil of Fig. 14A. In the drawings, an oil collecting pipe 32 is provided with the oil collecting apertures 32a and 32b. These apertures 32a and 32b are disposed opposite from each other an the same peripheries in a plurality of combinations: Liquid refrigerant 33 and refrigeration machine oil 34 remain in the sealed vessel 27. The operation of the embodiment will be described. A plurality of oil collecting apertures 32a and 32b, two in this case, are disposed an opposite side of the same periphery of the oil collecting pipe 32. The liquid refrigerant 33 flows from the respective oil collecting apertures 32a and 32b collide as shown in Fig. 14C. Since the collision is caused in the flow with in the oil collecting pipe 32, a turbid state is created in the liquid refrigerant 33 and the refrigeration machine oil 34 entering from the oil collecting apertures 32a, 32b to thereby accelerate the atomization of the refrigeration machine oil 34. Since the refrigeration machine oil 34 will easily flow downward together with the flow of liquid refrigerant 33, when it has a smaller particle size, the refrigeration machine oil can be fed easily so that the flow amount of the refrigeration machine oil 34 can be increased. As a result, reductions in the flow amount of the refrigeration machine oil 12 to be returned to the compressor can be prevented so that the reliability of the compressor can be enhanced. The structure of an oil collecting pipe of an accumulator according to a further embodiment of the present invention will be described below. This embodiment is arranged to more promptly feed the refrigeration machine oil in the oil collecting pipe. Fig. 15A is a longitudinal cross sectional view showing an accumulator according to this embodiment of the present invention. Fig. 15B is a cross sectional view taken along the line I - I of Fig. 15A. In the drawings, an oil collecting pipe 35 has an upper cross sectional wall area larger than the lower cross sectional area. For example, the oil collecting pipe 35 is composed of a taper-shaped pipe whose inside diameter is about 5 mm at the upper end and about 10 mm at the lower end. A plurality of oil collecting apertures 35a are defined in the oil collecting pipe 35. Next, the operation of the embodiment will be described. Although the refrigeration machine oil 34 flowing into the oil collecting pipe 35 flows together with the liquid refrigerant 33, generally speaking, as the flow velocity of the liquid refrigerant 33 in the pipe is higher than the oil, the droplets of the refrigeration machine oil 34 can be fed more easily. When the oil collecting pipe 35 is formed to have a uniform inside diameter as in the first embodiment, the flow amount of the liquid refrigerant in the oil collecting pipe 35 is greater in the lower portion of the pipe than in the upper portion thereof so that its flow velocity in the pipe is increased. However, since the pressure loss in the oil collecting pipe 35 is increased when the flow velocity of the liquid refrigerant in the pipe is high, the flow amount of the refrigeration machine oil 34 flowing from the upper oil collecting apertures is reduced by the pressure loss. Although a suitable pressure loss must be produced in the orifice-shaped communication ports 28a, 35b to control the total amount of the liquid refrigerant flowing to the discharge pipe 28, an excessive increase in pressure loss in the oil collecting pipe 35 must be prevented and the flow velocity in the lower portion of the oil collecting pipe 35 must be lowered. In this embodiment, the change of the inflow velocity to the oil collecting pipe 35 can be reduced and the increase of the pressure loss in the pipe can be prevented by changing the inside diameter of the pipe in the vertical direction thereof in correspondence with the flow amount of the liquid refrigerant 33 in the pipe. More specifically, for example, when the oil collecting pipe 35 is composed of a taper-shaped pipe having a diameter gradually increasing from the upper end to the lower end as shown in Fig. 15, the flow velocity at the lower portion of the oil collecting pipe 35 can be reduced. As a result, a drop in the flow amount of the refrigeration machine oil 34 flowing into the oil collecting pipe 35 can be prevented. Note, since floating droplets cannot be fed if the flow velocity in the pipe is below a limit value, it is necessary to secure a certain flow velocity in the pipe, that is, an inside diameter of the pipe, which permits the droplets of the refrigeration machine oil 34 to be fed. The structure of an oil collecting pipe of an accumulator according to another embodiment of the present invention will be described below. This embodiment promptly feeds the refrigeration machine oil in the oil collecting pipe by a simple arrangement. Fig. 16A is a longitudinal cross sectional view showing an accumulator according to this embodiment of the present invention. Fig. 16B is a cross sectional view taken along the line J - J of Fig. 16A. In the drawings, an oil collecting pipe 36 is connected to the upper portion of an oil collecting pipe 37. The oil collecting pipe 36 has a smaller inside diameter than that of the oil collecting pipe 37. That is, the oil collecting pipe is composed of, for example, pipes arranged in two stages so that the inside diameter of the lower pipe is larger than that of the upper pipe. A plurality of oil collecting apertures 36a and 37a are respectively defined in the oil collecting pipes 36 and 37. Next, the operation will be described. The taper-shaped pipe such as the oil collecting pipe of the previous embodiment presents some difficulties in machining. To cope with this problem, the oil collecting pipe of this embodiment is arranged by connecting pipes 36, 37 having different diameters as an example of a more simple structure. In the oil collecting pipe 37 arranged as described, since the cross sectional area of the lower portion is larger than that of the upper portion, there is an advantage in that the flow velocity in the lower pipe is reduced to thereby decrease the pressure loss in the pipe. Therefore, this embodiment achieves an advantage similar to that of the embodiment described with respect to Fig. 15. As a result, a drop in the amount of refrigeration machine oil flowing into the oil collecting pipes 36, 37 can be prevented. The structure of an oil collecting pipe of an accumulator which does not form part of the present invention will be described below. This accumulator provides a plurality of oil collecting pipes and controls the flow amount of the liquid refrigerant by opening and closing a communication port with a float structure. Fig. 17 is a longitudinal cross sectional view showing an accumulator. Fig. 18A is a view showing the arrangement of a main portion of the accumulator of Fig. 17. Fig. 18B is a cross sectional view taken along the line K - K of Fig. 18A. In the drawings, a discharge pipe 38 is provided with a communication port 38a. A first oil collecting pipe 39 has a plurality of oil collecting apertures 39a. A second oil collecting pipe 40 also has a plurality of oil collecting apertures 40a. A float 41 is disposed in the sealed vessel 1. Further, the float 41 moves upward and downward depending upon the height of the refrigeration machine oil 46 and the liquid refrigerant 47. A float arm 42 having a pin hole 42a is fixed to the float 41. A pin 43 is inserted into the pin hole 42a and serves as the fulcrum of the float arm 42. A pin 44 is disposed at the end of the float arm 42. A communication port opening/closing rod 45 is coupled with the pin 44 and executes an upward/downward motion in association with the motion of the float arm 42. A communication port opening/closing unit 45a is located in lower portion of the communication port opening/closing rod 45 and has a function as an opening/closing mechanism. A recess 45b is formed in the communication port opening/closing rod 45 to remove the portions in contact with the oil collecting apertures 39a to prevent the clogging thereof. The refrigeration machine oil 46 floats on the liquid refrigerant 47. The first oil collecting pipe 39 and the second oil collecting pipe 40 are held at a different height and the upper end of the oil collecting pipe 39 held at a lower portion is closed. Further, the first oil collecting pipe 39 communicates with the discharge pipe 38 at the lower end thereof through the communication port 38a and the second oil collecting pipe 40 communicates with the discharge pipe 38 at the lower end thereof through a communication port (not shown) likewise. The communication port opening/closing unit 45a constituting the opening/closing mechanism and the float 41 constituting a control mechanism for actuating the opening/closing mechanism in accordance with the liquid surface height are mounted on the first oil collecting pipe 39 to open/close the flow passage of refrigerant flowing in the first oil collecting pipe 39. The operation of this accumulator will be described. Fig. 19A shows a case that the refrigeration machine oil 46 and the liquid refrigerant 47 have a low liquid surface level, whereas Fig. 19B shows a case that they have a high liquid surface level. In Fig. 19A, the float 41 falls and the communication port opening/closing rod 45 coupled with it rises so that the communication port 38a is opened. On the other hand, in Fig. 19B, the float 41 rises by floating on the refrigeration machine oil 46 and the communication port opening/closing rod 45 coupled with it falls so that the communication port 38a is closed. The amount of the liquid refrigerant 47 flowing into the discharge pipe 38 is changed by the opening and closing of the communication port 38a. Fig. 20 shows the flow amount characteristics when the height of the liquid refrigerant 47 changes. In the drawing, the abscissa represents the height H (mm) of the liquid refrigerant surface, the ordinate represents the amount (kg/h) of the fluid flowing from the oil collecting pipes 39, 40 through the communication port 38a and H' denotes the height of the lowermost oil collecting aperture 40a defined in the second oil collecting pipe 40. When the height H of the liquid refrigerant 47 is below H', the liquid refrigerant 47 flows into the discharge pipe 38 through the communication port 38a as in the first embodiment. As the height H of the liquid refrigerant increases, the number of the oil collecting apertures in the liquid increases so that the flow amount of the liquid refrigerant increases. When the height H of the liquid refrigerant 47 reaches H', the communication port 38a is closed. As a result, the flow amount of the liquid refrigerant 47 becomes 0 as shown in the drawing. On the other hand, the refrigeration machine oil 46 flows into the discharge pipe 38 from the oil collecting aperture 40a of the second oil collecting pipe 40 at the time it reaches the liquid surface height H of the liquid refrigerant 47. Thus, the characteristic as shown in the drawing is obtained. Since the communication port 38a is closed when the height H of the liquid refrigerant 47 rises and H' < H is established, the liquid refrigerant 47 flows only from the second oil collecting pipe 40. Therefore, the flow amount of the liquid refrigerant 47 increases as the height H of the liquid refrigerant 47 increases. The flow amount of the refrigeration machine oil 46 gradually decreases as the height H of the liquid refrigerant 47 increases. That is, since the flow of the liquid refrigerant into the discharge pipe 38 is suppressed when the height H of the liquid refrigerant 47 is high, the reliability of the compressor is improved. Note, the number of the oil collecting pipes is not limited to two. When three or more are provided, the amount of the liquid refrigerant flowing into the discharge pipe 38 can be more minutely controlled. Further, although the communication port 38a is closed by the rod 45 connected to the float 41 in the above arrangement, the oil collecting aperture 39a may be closed. The structure of an oil collecting pipe of an accumulator which does not form part of the present invention will be described below. The accumulator of this embodiment is arranged to collect the refrigeration machine oil by providing a plurality of oil collecting pipes having different lengths and a pipe for gathering the respective pipes. Fig. 21A is a longitudinal cross sectional view showing an accumulator of this embodiment. Fig. 21B is a cross sectional view taken along the line L - L of Fig. 21A. In the drawings, a suction pipe 48 is connected to the upper portion of a sealed vessel 50. A discharge pipe 49 having a communication port 49a is inserted into the sealed vessel 50. Five oil collecting pipes 51 - 55 having different lengths are disposed in the sealed vessel 50. The oil collecting pipes 51 - 55 have open portions 51a - 55a at their upper ends. Further, the lower ends of the oil collecting pipes 51 - 55 are gathered into the gathering pipe 56 which communicates with the communication port 49a. Liquid refrigerant 57 resides in the sealed vessel 50. Refrigeration machine oil 58 floats on the upper layer of the liquid refrigerant 57. Next, the operation of the embodiment will be described. The height of the liquid refrigerant 57 is determined by the amount there of in the accumulator and the amount of the liquid refrigerant 57 in the accumulator is determined by the operating conditions of the refrigerating/air conditioning circuit. Usually, since the operating conditions cover a wide range of pressure and temperature conditions, the height of the liquid refrigerant 57 is not fixed. Therefore, the height of the refrigerant machine oil 58 floating on the upper layer of the liquid refrigerant 57 is not also fixed. Even in such a case, since the lengths of the oil collecting pipes 51 - 55 are formed stepwise, the refrigerant machine oil 58 may be sucked from any of the oil collecting pipes. That is, as shown in the drawing, when the refrigerant machine oil 58 is in the vicinity of the upper end of the oil collecting pipe 53, the refrigerant machine oil 58 flows into the oil collecting pipe 53 from the open end 53a thereof. Further, the liquid refrigerant 57 also flows into the oil collecting pipes 51, 52 from the open ends 51a, 52a thereof. The refrigerant machine oil 58 and the liquid refrigerant 57 flowing into the oil collecting pipes also flows into the gathering pipe 56 with a pressure loss generated in the communication port 49a similar to the first embodiment. The flow amount of the liquid refrigerant is therefore controlled so that it is not excessively sucked into the discharge pipe 49. As described above, since a plurality of oil collecting pipes each having a different length are provided and the fluid flowing into the oil collecting pipes is permitted to flow into the discharge pipe from the one communication port, even if the surface of the refrigeration machine oil is indefinite, the flow amount of the refrigeration machine oil can be secured so that the refrigeration machine oil can be collected from the accumulator into the compressor. As a result, reductions in the oil in the compressor can be prevented and the reliability of the compressor can be secured.

Claims: An accumulator, comprising : a sealed vessel (13, 27, 50) for temporarily storing refrigerant (11) circulating in a refrigerating/air conditioning circuit; a suction pipe (8) for introducing the refrigerant into said sealed vessel; a discharge pipe (9, 28, 49) having a refrigerant gas inlet (9a) for discharging the refrigerant in said sealed vessel; and an oil collecting pipe (10, 30, 31, 32, 35, 36, 37) held in said sealed vessel with the lower end thereof closed and having a plurality of oil collecting apertures (10a-10h, 30a, 30b, 31a, 31b, 32a, 32b, 35a, 36a, 37a) spaced in a vertical direction and a communication port (10i; 30c, 31c 35b, 37b) for communicating with said discharge pipe, said communication port being disposed in the vicinity of the lowermost oil collecting aperture of said oil collecting pipe or to the downstream side of said lowermost aperture; characterized in that the refrigerant gas inlet (9a) of the discharge pipe is located higher than the top portion of the oil collecting pipe; and the discharge pipe (9, 28, 49) and the oil collecting pipe (10, 30, 31, 32, 35, 36, 37) are disposed outside of each other.

Inventors: IIJIMA HITOSHI, IZAWA TAKESHI, KODA TOSHIHIDE, SHIMOJI MIHOKO, SUGIHARA MASAHIRO, TANAKA NAOKI, TOYOSHIMA MASAKI, IIJIMA, HITOSHI, IZAWA, TAKESHI, KODA, TOSHIHIDE, SHIMOJI, MIHOKO, SUGIHARA, MASAHIRO, TANAKA, NAOKI, TOYOSHIMA, MASAKI
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1997
Main classification: F25B43
IPC codes: F25B43