Expander-compressor unit and refrigeration cycle apparatus having the same

An expander-compressor unit (30) includes: a closed casing (1) holding an oil at a bottom portion thereof; a motor (2) provided in the closed casing (1); a compression mechanism (3) for compressing a refrigerant and discharging it into the closed casing (1), the compression mechanism (3) being disposed below the motor (2) in the closed casing (1); an expansion mechanism (4) disposed below the compression mechanism (3) in the closed casing (1); and a coupling mechanism (50) for coupling a compression mechanism side shaft (5) to an expansion mechanism side shaft (6). An oil supply passage (53) for supplying the oil to the compression mechanism (3) is formed in the compression mechanism side shaft (5). An oil suction port (53A) is provided in a portion of the compression mechanism side shaft (5), the portion being above the expansion mechanism (4).

TECHNICAL FIELD

The present invention relates to an expander-compressor unit applied to a refrigeration cycle apparatuses, such as a refrigerator, an air conditioner, and a water heater, and also relates to a refrigeration cycle apparatus having the expander-compressor unit.

BACKGROUND ART

As a fluid machine forming a part of a refrigeration cycle apparatus, an expander-compressor unit400is known that is constituted by integrating a compression mechanism402for compressing a refrigerant with an expansion mechanism404for allowing a refrigerant to expand and converting into mechanical energy the expansion energy generated during the refrigerant is expanded and decompressed, as shown inFIG. 6(see JP 62(1987)-77562 A). In the expander-compressor unit400, the mechanical energy resulted from the conversion by the expansion mechanism404is utilized as a part of energy for rotating a shaft405of the compression mechanism402. This reduces input to the compression mechanism402from outside, and improves the efficiency of the refrigeration cycle apparatus.

Since the compression mechanism402adiabatically compresses the refrigerant, a temperature of the refrigerant rises in the compression mechanism402. Accordingly, temperatures of components of the compression mechanism402also rise in accordance with the rising temperature of the refrigerant. On the other hand, the expansion mechanism404draws the refrigerant cooled by a radiator, which is not shown, and allows the drawn refrigerant to expand adiabatically. Accordingly, the temperature of the refrigerant lowers in the expansion mechanism404. As a result, temperatures of components of the expansion mechanism404lower in accordance with the lowering temperature of the refrigerant. Thus, mere integration of the compression mechanism402and the expansion mechanism404as described in JP 62(1987)-77562 A allows the heat of the compression mechanism402to transfer to the expansion mechanism404, which heats the expansion mechanism404and cools the compression mechanism402. In this case, in an actual cycle, enthalpy of the refrigerant discharged from the compression mechanism402decreases (see Point B→Point B1) and heating capacity of the radiator deteriorates to be lower than in a theoretical cycle, as shown in the Mollier diagram ofFIG. 7. Moreover, enthalpy of the refrigerant discharged from the expansion mechanism404increases (see Point D→Point D1), and refrigerating capacity of an evaporator deteriorates. The deteriorations in the capacities of the radiator and the evaporator are not preferable because they mean a decrease in the efficiency of the refrigeration cycle apparatus.

Particularly, when the refrigeration cycle apparatus is used as a water heater, it needs to heat water by its radiator to a temperature predetermined for hot reserve water. Accordingly, the refrigerant used for heating, that is, the discharge refrigerant from the compression mechanism402, must have a temperature higher than the predetermined temperature for reserved hot water. However, when a thermal short occurs between the compression mechanism402and the expansion mechanism404, the temperature of the discharge refrigerant from the compression mechanism402lowers, and accordingly, the temperature of the reserved hot water lowers. There is a method of increasing a pressure of the discharge refrigerant from the compression mechanism402in order to compensate the temperature of the discharge refrigerant from the compression mechanism402lowered by the thermal short. In the Mollier diagram ofFIG. 8, Point A→Point B2→Point C2→Point D2shows a theoretical cycle of discharge temperature control, and Point A→Point B3→Point C2→Point D3shows an actual cycle of discharge temperature control. As seen, when the refrigerant is compressed somewhat excessively, the temperature of the discharge refrigerant can be raised, and thereby the temperature of the discharge refrigerant substantially can be maintained at the target temperature. However, this method makes the compression mechanism402perform excessive work, increasing the power consumption at a motor. Therefore, the effect in recovering mechanical power by the expansion mechanism404is reduced.

In order to solve such a problem, a configuration is known in which a heat insulating material504is provided between a compression mechanism501and a expansion mechanism502as shown inFIG. 9(see JP 2001-165040 A). Reference numeral503indicates a shaft coupled to the compression mechanism501and the expansion mechanism502. Since the heat insulating material504is sandwiched between the compression mechanism501and the expansion mechanism502in the configuration shown inFIG. 9, heat transfer between the compression mechanism501and the expansion mechanism502can be reduced. However, such a configuration increases the cost for the heat insulating material504.

On the other hand, an expander-compressor unit also is known that reduces the heat transfer between the compression mechanism and the expansion mechanism without the heat insulating material (see JP 2005-264829 A). JP 2005-264829 A discloses a configuration in which a compression mechanism602and an expansion mechanism604are disposed spaced apart, and an interior of a closed casing601is filled with a low pressure refrigerant guided from an evaporator to the compression mechanism602, as shown inFIG. 10.

A configuration also is known in which an interior of a closed casing701is partitioned into a low pressure side space752and a high pressure side space751, an expansion mechanism702is provided in the low pressure side space752while a compression mechanism704is provided in the high pressure side space751, as shown inFIG. 11(see JP 2006-105564 A). In the expander-compressor unit ofFIG. 11, the suction refrigerant that will be drawn into the compression mechanism704is guided to the low pressure side space752, and the refrigerant that has been discharged from the compression mechanism704is guided to the high pressure side space751.

In the configuration shown inFIG. 10, the compression mechanism602and the expansion mechanism604are separated from each other, and thereby heat transfer between the compression mechanism602and the expansion mechanism604can be reduced. A surrounding space of the expansion mechanism604is filled with a relatively low temperature refrigerant that will be drawn into the compression mechanism602. This makes it possible to suppress an increase in enthalpy of the refrigerant discharged from the expansion mechanism604. Although the heat transfer occurs also between the compression mechanism602and the suction refrigerant, the refrigerant that has received heat from the compression mechanism602is compressed by the compression mechanism602, and heats the compression mechanism602. Therefore, the discharge temperature of the compression mechanism602does not lower. As a result, a decrease in enthalpy of the refrigerant discharged from the compression mechanism602is suppressed.

However, in the configuration in which the interior of the closed casing601is filled with the low pressure refrigerant as described above, the discharge refrigerant from the compression mechanism602is discharged directly out of the closed casing601via a discharge pipe609. Thus, an amount of the oil discharged out of the closed casing601is larger in this configuration than in the configuration in which the interior of the closed casing601is filled with the discharge refrigerant from the compression mechanism602. The discharged oil adheres to a refrigerant pipe and increases pressure loss of the refrigerant, as well as deteriorates the capacities of the radiator and the evaporator, exerting an adverse effect on the performance of the refrigeration cycle apparatus.

On the other hand, in the configuration shown inFIG. 11, the discharge refrigerant from the compression mechanism704is once released into the high pressure side space751of the closed casing701, and then is discharged from the closed casing701toward the radiator via a discharge pipe709. Since the discharge refrigerant is once released into the high pressure side space751in this way, the oil is separated easily from the discharge refrigerant from the compression mechanism704in the closed casing701. Thus, the discharge refrigerant from the compression mechanism704does not circulate in the refrigeration cycle apparatus together with a lot of oil

However, since the interior of the closed casing701is partitioned into the low pressure side space752and the high pressure side space751, a shaft705coupling the expansion mechanism702to the compression mechanism704needs to penetrate through a partition750. Such a configuration absolutely requires a mechanical seal for preventing the refrigerant from leaking through a clearance between the shaft705and the partition750. There arises a concern that the sliding loss may be increased between the shaft705and the mechanical seal.

As the layout of the compression mechanism, the expansion mechanism, and the motor in such an expander-compressor unit, JP 2003-139059 A proposes four kinds of layouts shown inFIG. 12AtoFIG. 12D. InFIG. 12AtoFIG. 12D, C indicates the compression mechanism, M indicates the motor, E indicates the expansion mechanism, and P indicates an oil pump. However, JP 2003-139059 A does not disclose detailed configuration of each layout. In each configuration shown inFIG. 12AtoFIG. 12D, the oil supplied from the oil pump is supplied to the compression mechanism and the expansion mechanism via an oil supply passage provided in the shaft. That is, the oil passes through one of the compression mechanism and the expansion mechanism, and thereafter passes through the other. This causes the heat transfer to occur between the compression mechanism and the expansion mechanism via the oil.

DISCLOSURE OF INVENTION

In view of the foregoing, the present invention is intended to provide an expander-compressor unit that can suppress a discharge amount of oil, and can reduce the heat transfer between the compression mechanism and the expansion mechanism without increasing mechanical loss.

The expander-compressor unit of the present invention includes: a closed casing having, in a bottom portion thereof, an oil reservoir for holding an oil; a motor provided in the closed casing; a compression mechanism for compressing a working fluid drawn from outside of the closed casing and discharging it into the closed casing, the compression mechanism being disposed below the motor in the closed casing; an expansion mechanism for allowing the working fluid drawn from outside of the closed casing to expand and discharging it out of the closed casing, the expansion mechanism being disposed below the compression mechanism in the closed casing; a shaft extending vertically and being coupled to the motor, the compression mechanism, and the expansion mechanism; and an oil supply passage for supplying the oil held in the oil reservoir to the compression mechanism. An oil suction portion for drawing the oil toward the oil supply passage is located above the expansion mechanism.

In the expander-compressor unit of the present invention, the motor, the compression mechanism, and the expansion mechanism are disposed from top to bottom in the closed casing in descending order of temperature. As a result, a stratified temperature-distribution is formed in the refrigerant and the oil based on the temperature gradient in the closed casing. This makes it possible to reduce heat transfer caused by convection of the refrigerant and the oil in the closed casing.

The oil suction portion of the oil supply passage for supplying the oil to the compression mechanism is disposed at a position above the expansion mechanism. Thus, the relatively high temperature oil present higher than the expansion mechanism is supplied to the compression mechanism, and the relatively low temperature oil present lower than the oil suction portion is supplied to the expansion mechanism. This enables circulation of the high temperature oil, which lubricates the compression mechanism, above the expansion mechanism, and can prevent the expansion mechanism from receiving heat from the high temperature oil. As a result, the heat transfer between the compression mechanism and the expansion mechanism via the oil is suppressed, improving efficiency of the refrigeration cycle apparatus.

The expander-compressor unit of the present invention is a so-called high pressure shell type expander-compressor unit in which the discharge refrigerant from the compression mechanism is once released into an internal space of the closed casing, and then is discharged out of the closed casing. Accordingly, the expander-compressor unit of the present invention can separate sufficiently the oil from the discharge refrigerant from the compression mechanism, and thereby has no possibility of having oil shortage.

Moreover, unlike in the conventional example (seeFIG. 11) in which the interior of the closed casing is partitioned into the high pressure side space and the low pressure side space, the expander-compressor unit of the present invention does not require a special structure around the shaft, such as the mechanical seal for preventing the refrigerant leakage between the high pressure side space and the low pressure side space. Therefore, there arises no problem of an increased mechanical loss of the shaft resulting from the mechanical seal, either.

As described above, the present invention can suppress the discharge amount of oil as well as reduce the heat transfer between the compression mechanism and the expansion mechanism without increasing the mechanical loss.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1is a vertical cross-sectional view of an expander-compressor unit30according to Embodiment 1 of the present invention.FIG. 2shows a refrigeration cycle apparatus90having the expander-compressor unit30.

As shown inFIG. 1, the expander-compressor unit30includes a motor2operating in response to electric power supply from a commercial power source80(seeFIG. 2), a compression mechanism3for compressing a refrigerant, an expansion mechanism4for allowing the refrigerant to expand, and a closed casing1accommodating these elements2,3, and4. The motor2, the compression mechanism3, and the expansion mechanism4are disposed in this order from top to bottom. An oil40for lubricating the sliding parts of the compression mechanism3and the expansion mechanism4is held at a bottom portion of the closed casing1(it should be noted that the “bottom portion” here means a lower side with respect to an arbitrary predetermined position, and does not necessarily mean an absolute position. Accordingly, when the predetermined position is higher than a mid-position of the closed casing1in a vertical direction, a position higher than the mid-position also is included in the “bottom portion”). More specifically, a lower side of the closed casing1is used as an oil reserving portion (an oil reservoir)12.

The motor2has a stator2aattached to an inner peripheral surface of the closed casing1, and a rotor2bdisposed inside of the stator2a. A compression mechanism side shaft5is fixed to the rotor2b. The compression mechanism side shaft5is supported rotatably at a middle portion thereof by a bearing member15. A terminal7is provided at a top portion of the closed casing1. The stator2ais connected to the terminal7via an electric wire21.

The motor2(specifically, the rotor2b) and the compression mechanism3are connected to each other via the compression mechanism side shaft5in such a manner that mechanical power can be transferred therebetween. The compression mechanism3of the present embodiment is a rotary compression mechanism having a cylinder31and a piston32. It should be noted, however, that the compression mechanism3of the present invention is not limited to rotary compression mechanisms, and it may be another rotating type compression mechanism. The specific configuration thereof is not limited in any way. A compression chamber33is formed between the cylinder31and the piston32. A suction passage34for guiding the refrigerant from a suction pipe8to the compression chamber33is formed in the bearing member15. A lower bearing member35is provided below the cylinder31. A muffler space35aand a flow passage35bare formed in the lower bearing member35. The flow passage35bguides the refrigerant compressed in the compression chamber33to the muffler space35a. A discharge passage36extending in the vertical direction is formed in the lower bearing member35, the cylinder31, and the bearing member15. The discharge passage36discharges above the bearing member15the refrigerant in the muffler space35a. A closing plate37is disposed under the lower bearing member35, and closes the muffler space35afrom a lower side thereof.

The expansion mechanism4of the present embodiment is a two-stage rotary expansion mechanism having two cylinders41aand41band two pistons42aand42b. It should be noted, however, that the expansion mechanism4of the present invention is not limited to rotary expansion mechanisms, and it may be another rotating type expansion mechanism. The specific configuration thereof is not limited in any way. A lower bearing member44is disposed below the lower cylinder41a. A partition member43is provided between the lower cylinder41aand the upper cylinder41b. A bearing member45is provided above the upper cylinder41b. The lower bearing member44, the lower cylinder41a, the partition member43, the upper cylinder41b, and the bearing member45are fixed integrally with bolts46. A muffler space44aand a communication port44bare formed in the lower bearing member44. A suction pipe10penetrates through a lower portion of the closed casing1, and is connected to the lower bearing member44. The suction pipe10introduces the suction refrigerant into the muffler space44a. A first expansion chamber47ais formed between the lower cylinder41aand the piston42a. The first expansion chamber47ais in communication with the muffler space44avia the communication port44b. A second expansion chamber47bis formed between the upper cylinder41band the piston42b. A communication passage43ais formed in the partition member43, and the first expansion chamber47aand the second expansion chamber47bare in communication with each other via the communication passage43a. A discharge passage48for guiding the refrigerant from the second expansion chamber47bto a discharge pipe11is formed in the bearing member45. In the expansion mechanism4of the present embodiment, the first expansion chamber47a, the communication passage43a, and the second expansion chamber47bas a whole form one expansion chamber that performs a suction process, an expansion process, and a discharge process of the refrigerant.

In the present embodiment, the upper cylinder41bhas an inner diameter equal to that of the lower cylinder41a, and furthermore, the upper cylinder41bhas a height (a thickness in the vertical direction) larger than that of the lower cylinder41a. Thereby, the second expansion chamber47bhas a volumetric capacity larger than that of the first expansion chamber47a. The configuration for making the volumetric capacity of the second expansion chamber47blarger than the volumetric capacity of the first expansion chamber47ais not limited to this. For example, it is possible to employ a configuration in which the upper cylinder41bhas a height equal to that of the lower cylinder41a, and furthermore, the upper cylinder41bhas an inner diameter larger than that of the lower cylinder41a.

An expansion mechanism side shaft6rotating in accordance with rotation of the pistons42aand42bis provided in the expansion mechanism4. The expansion mechanism side shaft6is coupled to the compression mechanism side shaft5via a coupling mechanism50. Specific configuration of the coupling mechanism50is not particularly limited. For example, a disk-like member suitably can be used to be spline-fitted to each of the compression mechanism side shaft5and the expansion mechanism side shaft6.

The compression mechanism3and the expansion mechanism4are disposed separated from each other in the vertical direction. A buffer space13filled with the oil40is formed between the compression mechanism3and the expansion mechanism4in the closed casing1.

An oil supply passage53for guiding the oil held in the oil reserving portion12to the sliding parts of the compression mechanism3is formed in the compression mechanism side shaft5. The oil supply passage53includes an oil suction port (an oil suction portion)53A, which faces the buffer space13, for drawing the oil at a portion of the compression mechanism side shaft5, the portion being above the coupling mechanism50, a vertical flow passage53B penetrating through a center of the compression mechanism side shaft5, and an oil supply port53C for supplying the oil in the vertical flow passage53B to the sliding parts. Specifically, a through hole is formed in the compression mechanism side shaft5. The through hole extends in an axial direction of the compression mechanism side shaft5. A stopper member53D is inserted into a lower end portion of the compression mechanism side shaft5, and a lower side of the through hole is closed by the stopper member53D. The lateral port53A is formed at a lower side of the compression mechanism side shaft5, and the horizontal port53A constitutes the oil suction port for drawing the oil at the portion above the coupling mechanism50. In the present embodiment, the oil suction port53A opens in a horizontal direction. It should be noted, however, that the opening direction of the oil suction port53A is not limited, and it may open in a direction inclined from the horizontal direction, for example. The vertical flow passage53B has only to open at least downward, not necessarily have to penetrate through the compression mechanism side shaft5.

A flow suppressing plate52is provided in the buffer space13at a position below the oil suction port53A. The flow suppressing plate52is formed in an approximately annular shape, and has an outer diameter slightly smaller than an inner diameter of the closed casing1. Thereby, a clearance70is formed between an outer peripheral surface of the flow suppressing plate52, and the inner peripheral surface of the closed casing1. A hole71into which the compression mechanism side shaft5is inserted is formed at a center of the flow suppressing plate52A. This hole prevents the flow suppressing plate52from interfering with the compression mechanism side shaft5. The flow suppressing plate52is fixed to the compression mechanism3with bolts54, with a spacer55being interposed between the compression mechanisms3and the flow suppressing plate52.

A cylindrical fixing member51is fixed to the closed casing1at a position below the flow suppressing plate52by a method such as welding and shrink fitting. The expansion mechanism4is fixed to the fixing member51with bolts65. A cut-out (not shown) for returning oil is provided in the fixing member51.

An oil supply passage73for guiding the oil to the sliding parts of the expansion mechanism4is provided in the expansion mechanism side shaft6. The oil supply passage73includes an oil suction port73A for drawing the oil from beneath the expansion mechanism side shaft6, a vertical flow passage73B penetrating through a center of the expansion mechanism side shaft6, and an oil supply port73C for supplying the oil in the vertical flow passage73B to the sliding parts.

As shown inFIG. 2, the refrigeration cycle apparatus90includes a main refrigerant circuit91constituted by connecting in a circuit the compression mechanism3of the expander-compressor unit30, a radiator83, the expansion mechanism4, and an evaporator84in this order, as well as a bypass circuit92for bypassing the expansion mechanism4. The compression mechanism3and the radiator83are connected to each other by a first pipe95. The radiator83and the expansion mechanism4are connected to each other by a second pipe96. The expansion mechanism4and the evaporator84are connected to each other by a third pipe97. The evaporator84and the compression mechanism3are connected to each other by a fourth pipe98. A flow rate adjustable valve93is provided in the bypass circuit92. An inverter81is provided between the power source80and the motor2. The compression mechanism side shaft5and the expansion mechanism side shaft6are coupled to each other by the coupling mechanism50so as to constitute a shaft82that rotates integrally.

Next, operation of the expander-compressor unit30of the present embodiment will be described.

Electric power supplied from the commercial power source80is supplied to the motor2via the inverter81and the terminal7. Thereby, the motor2is driven. Rotational mechanical power generated at the motor2is transferred to the compression mechanism3by the compression mechanism side shaft5, and drives the compression mechanism3.

The compression mechanism3draws the low pressure refrigerant via the suction pipe8and compresses it, and then discharges the compressed, high temperature, high pressure refrigerant to the interior of the closed casing1. The refrigerant discharged to the interior of the closed casing1is discharged out of the closed casing1via a discharge pipe9. More specifically, the refrigerant drawn via the suction pipe8is guided to the compression chamber33through the suction passage34, and is compressed in the compression chamber33. The compressed refrigerant flows through the flow passage35b, the muffler space35a, and the discharge passage36in this order, and is discharged above the bearing member15. The refrigerant discharged above the bearing member15flows around the motor2, and then is discharged out of the closed casing1via the discharge pipe9.

The refrigerant discharged via the discharge pipe9is guided to the radiator83through the first pipe95(seeFIG. 2). The refrigerant radiates heat at the radiator83(seeFIG. 2) to be cooled, and is guided to the expansion mechanism4via the second pipe96and the suction pipe10.

The expansion mechanism4allows the refrigerant entering thereinto via the suction pipe10to expand. At this time, the expansion mechanism4converts expansion energy of the refrigerant into rotational mechanical power and recovers it, and rotates the expansion mechanism side shaft6. Since the expansion mechanism side shaft6is coupled to the compression mechanism side shaft5via the coupling mechanism50, the mechanical power of the expansion mechanism side shaft6is transferred to the compression mechanism side shaft5. In this way, the expansion mechanism4superimposes the mechanical power derived from the expansion energy on the mechanical power of the motor2driving the compression mechanism3, via the expansion mechanism side shaft6, the coupling mechanism50, and the compression mechanism side shaft5. Specifically, the refrigerant drawn via the suction pipe10is guided to the first expansion chamber47athrough the muffler space44aand the communication port44b, and expands in the first expansion chamber47a, the communication passage43a, and the second expansion chamber47b. The refrigerant having expanded reaches the discharge pipe11from the second expansion chamber47bthrough the discharge passage48, and is discharged via the discharge pipe11.

The low pressure refrigerant discharged via the discharge pipe11passes through the third pipe97, and then is heated in the evaporator84to evaporate (seeFIG. 2). The refrigerant having flowed out of the evaporator84is guided by the fourth pipe98and the suction pipe8, and again is drawn into the compression mechanism3to be compressed.

The aforementioned operation increases a temperature of the compression mechanism3while decreasing that of the expansion mechanism4. More specifically, since the compression mechanism3adiabatically compresses the refrigerant that has turned into low pressure vapor by passing through the evaporator84, the temperature of the refrigerant during a compression process in the compression mechanism3rises as the pressure increases. This makes the temperature of the compression mechanism3high. On the other hand, since the expansion mechanism4adiabatically expands the refrigerant whose temperature has been lowered by passing through the radiator83, the temperature of the refrigerant during a expansion process in the expansion mechanism4lowers as the pressure decreases. This makes the temperature of the expansion mechanism4low. To the interior of the closed casing1, the high temperature, high pressure refrigerant from the compression mechanism3is discharged. The motor2loses a part of input power due to iron loss, copper loss, etc., and produces heat when generating the rotational mechanical power for driving the compression mechanism3.

In the expander-compressor unit30of the present embodiment, the motor2, which produces heat and has the highest temperature, is disposed at an upper part of the closed casing1, the compression mechanism3, which has a high temperature, is disposed in the middle, and the expansion mechanism4, which has a low temperature, is disposed at a lower part of the closed casing1. More specifically, the motor2, the compression mechanism3, and the expansion mechanism4are disposed from top to bottom in descending order of temperature. Thereby, natural convection of the refrigerant and the oil is suppressed in the closed casing1, and a stratified temperature-distribution is formed in the refrigerant and oil in the closed casing1. Thus, heat transfer via the internal fluid (the refrigerant or the oil) is suppressed among the motor2, the compression mechanism3, and the expansion mechanism4.

In the expander-compressor unit30, the oil suction port53A for the compression mechanism3is provided on the compression mechanism side shaft5located above the coupling mechanism50. Since the oil is temperature-stratified as described above, the oil present higher than the coupling mechanism50has a temperature higher than that of the oil present lower than the coupling mechanism50. Thus, according to the present embodiment, the relatively high temperature oil can be supplied to the high temperature compression mechanism3. This makes it possible to suppress the heat transfer between the compression mechanism3and the expansion mechanism4via the oil.

In the expander-compressor unit30, the oil suction port73A for the expansion mechanism4is provided in the vicinity of a lower end portion of the closed casing1. Thus, the relatively low temperature oil can be supplied to the low temperature expansion mechanism4. This also makes it possible to suppress the heat transfer between the compression mechanism3and the expansion mechanism4via the oil.

In this way, in the expander-compressor unit30, an oil circulation on a side of the compression mechanism3located at the upper part, and an oil circulation on a side of the expansion mechanism4located at the lower part are formed in the closed casing1. More specifically, a circulation is formed on each of the compression mechanism3side and the expansion mechanism4side separately.

In the expander-compressor unit30, the refrigerant compressed by the compression mechanism3is once discharged to the interior of the closed casing1, and then is discharged out of the closed casing1via the discharge pipe9. Accordingly, the oil contained in the discharge refrigerant is separated from the discharge refrigerant while the discharge refrigerant passes through the interior of the closed casing1. As a result, it is possible to suppress the oil contained in the discharge refrigerant from flowing out of the closed casing1, and to avoid oil shortage in the closed casing1.

The expander-compressor unit30does not require the interior of the closed casing1to be partitioned into a high pressure side space and a low pressure side space. Therefore, it is not necessary to provide a special structure around the shaft5, such as a mechanical seal for preventing refrigerant leakage between the high pressure side space and the low pressure side space. There is no possibility for the shaft5to have a mechanical loss resulting from the mechanical seal etc.

In the expander-compressor unit30, the shaft82has the compression mechanism side shaft5and the expansion mechanism side shaft6, and the compression mechanism side shaft5and the expansion mechanism side shaft6are coupled to each other via the coupling mechanism50. This makes it possible to assemble the compression mechanism3with the compression mechanism side shaft5, and assemble the expansion mechanism4with the expansion mechanism side shaft6separately, and thereafter couple them with the coupling mechanism50. Thus, the whole structure can be assembled. This makes the assembly easier, leading to an improved productivity.

In the expander-compressor unit30, the buffer space13filled with the oil is provided between the compression mechanism3and the expansion mechanism4. This makes it possible to prevent the compression mechanism3from contacting the expansion mechanism4directly, avoiding heat conduction between the compression mechanism3and the expansion mechanism4.

Furthermore, since the coupling mechanism50is disposed in the buffer space13in the expander-compressor unit30, the oil in the buffer space13sufficiently can lubricate the coupling mechanism50.

In the expander-compressor unit30, the flow suppressing plate52is provided at a position below the oil suction port53A in the buffer space13. Therefore, even when rotation of the motor2causes a revolving flow of the refrigerant in the closed casing1, and the high temperature oil on the compression mechanism3side flows in accordance with this, mixing of the high temperature oil with the low temperature oil present below the flow suppressing plate52is suppressed. More specifically, even when the high temperature oil present above the flow suppressing plate52flows, there is no possibility that the low temperature oil present below the flow suppressing plate52is stirred strongly because the flow of the high temperature oil is isolated by the flow suppressing plate52. In this way, mixing of the high temperature oil with the low temperature oil can be suppressed, and the heat transfer between the compression mechanism3and the expansion mechanism4via the oil can be suppressed effectively. Furthermore, the oil suction port53A can take in the high temperature oil that is above the flow suppressing plate52.

Moreover, the flow suppressing plate52is a plate of an approximately annular shape having a size that allows the clearance70to be formed between itself and the inner peripheral surface of the closed casing1. The flow suppressing plate52has, at the center thereof, the hole71for avoiding interference with the compression mechanism side shaft5. Since the flow suppressing plate52thus configured is fixed to the compression mechanism3using the bolts54and the spacer55in the present embodiment, the compression mechanism side shaft5can rotate smoothly, and employing the flow suppressing plate52causes no excessive mechanical loss. Also, the heat transfer between the compression mechanism3and the expansion mechanism4can be suppressed with the simple, inexpensive configuration. More specifically, the heat transfer between the compression mechanism3and the expansion mechanism4via the oil can be suppressed by employing the simple, inexpensive configuration in which the approximately circular plate is fixed simply to the compression mechanism3with the bolts54and the spacer55.

The expander-compressor unit30of the present embodiment includes the vertical flow passage53B penetrating through a central axis of the compression mechanism side shaft5, the oil suction port53A communicating with the vertical flow passage53B at the portion of the compression mechanism side shaft5, the portion being above the coupling mechanism50, the oil supply port53C leading from the vertical flow passage53B to the sliding parts of the compression mechanism3, and the stopper member53D for closing a lower end of the vertical flow passage53B. Thus, an oil supply passage to the compression mechanism3can be formed by the simple work of forming laterally the oil suction port53A and the oil supply port53C in the compression mechanism side shaft5having the vertical flow passage53B, and closing the end of the vertical flow passage53B with the stopper member53D. Furthermore, since the stopper member53D closes the end of the vertical flow passage53B, the relatively low temperature oil near the coupling mechanism50and the expansion mechanism side shaft6is not used as the oil for lubricating the compression mechanism3. Thereby, the heat transfer between the compression mechanism3and the expansion mechanism4can be suppressed.

In the expander-compressor unit30, the expansion mechanism4is fixed, with the bolts65, to the cylindrical fixing member51that is fixed to the closed casing1by welding or shrink fitting. This separates substantially the compression mechanism3from the expansion mechanism4. Accordingly, between the compression mechanism3and the expansion mechanism4, the coupling mechanism50and the closed casing1are the only elements of the heat transfer caused by heat conduction. Thereby, influence of the heat transfer caused by heat conduction can be reduced better in this case than in the case of merely fastening the compression mechanism3to the expansion mechanism4with bolts and a spacer. It is desirable for the cylindrical fixing member51to be in contact with the closed casing1in a smaller area. For this purpose, a cut-out(s), or a depression(s) and a projection(s) may be formed in an outer peripheral portion of the fixing member51, for example, so that the fixing member51is in contact with the closed casing1at a point or on a line. The cut-out, or the depression and the projection functions as a flow passage for returning the oil.

The flow suppressing plate52is fixed to the compression mechanism3in the present embodiment. It also is possible, however, to fix the flow suppressing plate52to the expansion mechanism4.

FIG. 3is a vertical cross-sectional view of the expander-compressor unit30according to Embodiment 2 of the present invention. As shown inFIG. 3, the expander-compressor unit30of the present embodiment has almost the same configuration as that of the expander-compressor unit described in Embodiment 1 (seeFIG. 1). Hereinbelow, components having the same functions are indicated by the same reference numerals, and explanations thereof are omitted.

A difference between the present embodiment and Embodiment 1 is the shape of the flow suppressing plate62. The flow suppressing plate62of the present embodiment is a cut-out plate of an approximately annular shape having cut-outs62ain an outer peripheral portion thereof. The cut-outs62aintermittently are formed along the outer periphery of the flow suppressing plate62. The number of the cut-outs62ais not particularly limited. The flow suppressing plate62of the present embodiment also has the hole71at its center in such a manner that the flow suppressing plate62does not interfere with the compression mechanism side shaft5.

The flow suppressing plate62of the present embodiment is fixed to the inner peripheral surface of the closed casing1by shrink fitting or welding. The flow suppressing plate62is not fastened directly to the high temperature compression mechanism3with bolts and a spacer. Accordingly, between the compression mechanism3and the flow suppressing plate62, the closed casing1is the only element of the heat transfer caused by heat conduction in the present embodiment. Thereby, influence of the downward heat transfer caused by heat conduction can be reduced better in this case than in the case of merely fastening the flow suppressing plate62to the compression mechanism3with bolts and a spacer.

Since the cut-outs62aare provided in the outer peripheral portion of the flow suppressing plate62, a contact surface between the flow suppressing plate62and the closed casing1is limited relatively small. Thereby, heat conduction from the closed casing1to the flow suppressing plate62can be suppressed.

In the present embodiment, the flow suppressing plate62is provided with the cut-outs62ain the outer peripheral portion thereof so as to have recessed portions recessed inward in a radial direction. However, the specific shape of the recessed portions is not limited in any way, and a similar effect also can be achieved by forming a depression and a projection in the outer peripheral portion of the flow suppressing plate62. As described above, it is desirable for the flow suppressing plate62to be in contact with the closed casing1in a smaller area. It may be in contact with the closed casing1at a point or on a line.

FIG. 4is a vertical cross-sectional view of the expander-compressor unit30according to Embodiment 3 of the present invention. As shown inFIG. 4, the expander-compressor unit30of the present embodiment has almost the same configuration as that of the expander-compressor unit described in Embodiment 2 (seeFIG. 3). Hereinbelow, components having the same functions are indicated by the same reference numerals, and explanations thereof are omitted.

A difference between the present embodiment and Embodiment 2 is the configuration of the oil supply passage. An oil supply passage63of the present embodiment includes oil grooves63B,63C and63D formed in the outer peripheral surface of the compression mechanism side shaft5, and continuous passages (not shown) bringing them into communication with each other. The oil grooves63B and63D are formed in the outer peripheral surface of the compression mechanism side shaft5, at a portion higher than an eccentric portion of the compression mechanism side shaft5and at a portion lower than the eccentric portion of the compression mechanism side shaft5, respectively. The oil grooves63B and63D extend vertically while being inclined (in a spiral shape, for example). The oil groove63C formed in the outer peripheral surface of the eccentric portion of the compression mechanism side shaft5extends straight in the vertical direction. The continuous passage can be formed, for example, in a lower surface and an upper surface of the eccentric portion, or in the compression mechanism side shaft5. A lower end portion63A of the oil groove63B constitutes the oil suction portion, and faces the buffer space13. Instead of the oil grooves63B and63D, there may be formed an oil groove extending vertically in inner peripheral surfaces of the bearings each disposed above and below the compression mechanism3(each of the bearings has an inner peripheral surface facing the outer peripheral surface of the compression mechanism side shaft5. For example, the bearings are the bearing member15and the lower bearing member37). In this case, a lower end portion of the lower one of these grooves constitutes the oil suction portion.

The present embodiment makes it possible to form the oil supply passage63by the simple, inexpensive work of forming grooves in the outer peripheral surface of the compression mechanism side shaft5or in the bearings. Since the lower end portion63A of the oil supply passage63faces the buffer space13right under the compression mechanism3, it can draw the high temperature oil that is higher than the coupling mechanism50smoothly and reliably.

MODIFIED EXAMPLE

In Embodiment 1 to 3, a configuration as shown inFIG. 5may be employed. Contrary to Embodiment 1 to 3, the lower cylinder41ahas a height larger than that of the upper cylinder41bin the configuration shown inFIG. 5. The first expansion chamber47ais formed between the upper cylinder41band the piston42b. The second expansion chamber47bwith a volumetric capacity larger than that of the first expansion chamber47ais formed between the lower cylinder41aand the piston42a. That is, the second expansion chamber47bis located under the first expansion chamber47a. The discharge pipe11is connected to the lower bearing member44, and the suction pipe10is connected to the bearing member45. The suction passage49for guiding the refrigerant from the suction pipe10to the first expansion chamber47ais formed in the bearing member45.

Locating the second expansion chamber47bunder the first expansion chamber47alike this makes it possible to have a relatively high temperature portion at an upper side while having a relatively low temperature portion at a lower side also in the expansion mechanism4. Thereby, a more preferable temperature distribution can be obtained. The volumetric capacity of the second expansion chamber47bmay be set larger than that of the first expansion chamber47aalso in Modified Example by, for example, making the height of the upper cylinder41bequal to the height of the lower cylinder41a, and furthermore, making the inner diameter of the lower cylinder41alarger than the inner diameter of the upper cylinder41b, as described above.

<<Definition of Term in the Specification>>

In the present invention, “bottom portion” in the phrase “a closed casing having, in a bottom portion thereof, an oil reservoir for holding an oil” means a lower side with respect to an arbitrary predetermined position, and does not necessarily mean an absolute position. Accordingly, when the predetermined position is assumed to be higher than a mid-position of the closed casing in a vertical direction, a position higher than the mid-position also is included in the “bottom portion”.

INDUSTRIAL APPLICABILITY

As having been described, the present invention is useful for expander-compressor units and refrigeration cycle apparatuses having the expander-compressor unit (such as a refrigerator, an air conditioner, and a water heater).