Multicylinder rotary compressor

Abstract: A multicylinder rotary compressor capable of performing highperformance capacity control operation without the need for an external piping or for a thicker partition plate which leads to a taller rotary compressing element or a longer bearing span of a bearing. The multicylinder rotary compressor comprises a rotary compressing element housed in a hermetic enclosure; wherein the rotary compressing element is equipped with an intermediate partition plate, cylinders provided on both sides of the partition plate, a rotary shaft having eccentric sections which are shifted against each other by 180 degrees in the angle of rotation, rollers which are fitted onto the eccentric sections of the rotary shaft and which rotate in the cylinders, and bearings which seal the openings of the cylinders. The multicylinder rotary compressor further comprises first apertures provided in the inner walls of the two cylinders, second apertures provided in the two cylinders so that they communicate with the first apertures, and a third aperture provided in the intermediate partition plate so that it communicates with the two second apertures; wherein a gas which is being compressed in one cylinder is allowed to flow, via the first, second, and third apertures, into the other cylinder which is in an intake stroke.

Description: The present invention relates to a multicylinder rotary compressor which is equipped with a plurality of cylinders and which enables capacity control operation. One such multicylinder compressor is known from JP 4241791 and comprises rotary compressing element housed in a hermetic enclosure, said rotary compressing element being equipped with an intermediate partition plate, cylinders provided on both sides of said partition plate, a rotary shaft having eccentric sections which are shifted against each other by 180 degrees in the angle of rotation, rollers which are fitted onto said eccentric sections of said rotary shaft and which rotate in said cylinders and bearings which seal the openings of said cylinders, a delivery passage extending between the cylinders, means for communicating the delivery passage to a source of low or high pressure, an aperture in the intermediate partition plate, an aperture in the delivery passage on either side of the partition plate, and a piston disposed in the delivery passage having biasing means associated therewith and being slidable to a first position when gas at high pressure sufficient to overcome the resilience of the biasing means is supplied to the delivery passage from the source, to position the piston over the apertures in the delivery passage to prevent the flow of gas between the cylinders, and a second position when gas having a pressure which is too low to overcome the resilience of the biasing means is supplied to the delivery passage, in which the piston is no longer positioned over the apertures in the delivery passage thereby allowing gas to flow between the cylinders via the aperture in the intermediate partition plate. A multicylinder rotary compressor is also known from US 5,152,156. Another known type of conventional multicylinder rotary compressor is disclosed in Japanese Patent Publication No. 6-33782, and it will now be described with reference to Figure 7. The multicylider rotary compressor discloses a hermetic enclosure 1 containing an electric element 3 having a rotary shaft 2 located above a rotary compressing element which is driven by the electric element 3. The rotary compressing element 4 comprises an intermediate partition plate 5, cylinders 6 and 7 mounted above and below the plate 5, eccentric sections 8 and 9 which are mounted on the rotary shaft 2 with a 180 degree shift in their angle of rotation, rollers 10, 11 which are mounted for rotation in the cylinders 6,7, respectively, by the eccentric sections, an upper bearing 12 and a lower bearing 13 which seal the openings of the cylinders 6 and 7, respectively, and cup mufflers 14 and 15 mounted on the upper and lower bearings 12,13 respectively. The cup muffler 14 of the upper bearings 12 is provided with a discharge port 21 which opens to a chamber 20 formed between the electric element 3 and the rotary compressing element 4. A discharge tube 22 extends from the top wall of the hermetic enclosure 1. The compressor enables capacity control operation by providing the rotary compressing element 4 with a passage 23 for releasing part of the gas which is being compressed to the low pressure side of an external refrigerant circuit via a connecting tube 24. A control valve 25 is provided in the passage 23. Another type of multicylinder rotary compressor is described in JP 62-7086 and is illustrated in Figures 8 and 9 and has delivery passage 32 and a piston 33 in the partition plate 5. The apertures 30,31 opens to the cylinders 6,7 and the delivery passage 32 communicates with the apertures 30,31 and contains the piston 33 and a coil spring 34 for biasing the piston. A third aperture 35 communicates with the second aperture 32 and is also in communication selectively with the low pressure side or the high pressure side of the external refrigerant circuit. With the arrangement stated above, when low pressure is applied as a back pressure to the piston 33, the piston 33 moves to the right in Figure 8, causing the apertures 30,31 to be in communication with each other via the delivery passage 32 so that a gas flows from the cylinder 6, which is in the compression stroke, to the cylinder 7, which is in the intake stroke, thereby performing capacity control operation. When high pressure is applied as the back pressure to the piston 33, the piston 33 moves to the left as shown in Figure 9, breaking the communication between the first apertures 30,31 and preventing flow of gas through the delivery passage between the cylinders 6,7. The first conventional capacity control unit described above requires a thick piping such as the connecting tube 24 through which gas is taken out of the compressor and also a long pipe to connect the compressor to the pipe on the low pressure side of the external refrigerant circuit. This results in higher manufacturing cost, a more complicated pipe configuration, and low capacity control efficiency because of a larger gas passage resistance. The second conventional capacity control unit described above, is designed so that no gas leaves the compressor during the capacity control. Therefore, the capacity control factor is unaffected when the number or length of the piping is increased. However, the piston 33 and a coil spring 34 provided in the partition plate 5 inevitably add to the thickness of the partition plate. This results in an increase in overall height of the rotary compressing element with a consequent increased height of the compressor and a longer bearing span of bearings 12,13, which leads to deterioration in the strength of the rotary shaft. Accordingly, it is an object of the present invention to provide a multicylinder rotary compressor capable of performing high-performance capacity control operation without the need for an external piping or a thicker partition plate. A multicylinder rotary compressor according to the present invention is characterised in that the piston is formed in two parts, each part being located on opposite sides of the intermediate partition plate such that in use, with the piston in the second position, gas flows between the cylinders via the delivery passage. With this arrangement, the apertures, pistons, spring, etc. required for the capacity control mechanism are arranged in the cylinders so as to reduce the thickness of the partition plate, the height of the rotary compressing element, and the bearing span of the bearings, thus making it possible to provide a compact multicylinder rotary compressor which is capable of implementing a high-performance capacity control operation. In one embodiment, the biasing means extends between each part of the piston through the intermediate partition plate. With this arrangement, the pistons for controlling the capacity can be relatively arranged in the two cylinders to share a single spring, thus reducing the number of components. In addition, coaxial machining is possible for making the second apertures in which the pistons and spring are disposed and the apertures can be positioned more accurately. In one preferred embodiment, the means for communicating the delivery passage with a source of low or high pressure comprises a second aperture at the opposite ends of each delivery passage. With this arrangement, the passages for applying back pressure to the capacity control pistons are configured in the two cylinders with respect to the partition plate so as to evenly apply the back pressure to the two pistons at all times. This makes it possible to simultaneously actuate the two pistons in good balance, leading to improved performance of capacity control. Moreover, the apertures in the delivery passage are formed in the axial direction of the two cylinders, enabling improved workability. According to another embodiment, each part of the piston has a separate biasing means. With this arrangement, the spring can be made shorter and the load applied to the spring can be reduced. The result is greater freedom in the design of the spring and higher reliability of the capacity control unit. Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a longitudinal section view illustrating an essential part of a multicylinder rotary compressor according to the present invention in a capacity control operation mode; Figure 2 illustrates an operation state of the essential part shown in Figure 1 in a normal operation mode; Figure 3 is an enlarged cross-sectional view illustrative of section A of Figure 2; Figure 4 is an enlarged cross-sectional view illustrative of another embodiment of section A; Figure 5 is a longitudinal section view illustrating an essential part of a multicylinder rotary compressor according to another embodiment when it is in the capacity control operation mode; Figure 6 illustrates an operation state of the essential part shown in Figure 5 in the normal operation mode; Figure 7 is a longitudinal cross-sectional view showing a conventional multicylinder rotary compressor; Figure 8 is a longitudinal section view illustrating an essential part of another conventional multicylinder rotary compressor in the capacity control operation mode; and Figure 9 illustrates an operation state of the conventional multicylinder rotary compressor of Figure 8 in the normal operation mode. The present invention will now be described with reference to Figures 1 to 6. The structure which is unrelated to the capacity control unit is identical to that of the conventional example shown in Figure 7. Therefore, the same reference numerals used in Figure 7 are applied and the description thereof is omitted. The capacity control unit has apertures 40,41 provided in the inner walls of the two cylinders 6,7, respectively; a delivery passage 42,43 provided in the cylinders 6,7 and extending between them such that the apertures 40,41 communicate the cylinders 6,7 with the delivery passage 42,43; an aperture 44 in the intermediate partition plate 5 such that the parts of the delivery passage 42,43 on each side of the partition plate 5 are in communication with each other, a piston formed in two parts 45,46 disposed in the delivery passage 42,43 on either side of the partition plate; a coil spring 47 (a leaf spring or bellows may be used as long as it is an elastic body) which extends between the parts 45,46; second apertures 49,50 in the form of recesses 48 formed in the delivery passage (indicated by A in Figure 2; an enlarged view thereof is shown in Figure 3), and a passage 51 for selectively communicating the delivery passage 42,43 with the low pressure side or the high pressure side of an external refrigerant circuit, not shown, through a selector valve or the like. The recesses 48 in the cylinders 6,7 may be formed as recesses 52 at the end surfaces of the bearings 12,13 as shown in Figure 4. When the capacity control unit performs capacity control, as illustrated in Figure 1, the pressure on the low pressure side is applied as the back pressure to the delivery passage 42,43 via the passage 51, the second apertures 49,50, and the recesses 48 to move each part 45,46 of the piston to their top dead centres so as to release the apertures 40,41, thereby allowing the gas, which is being compressed in the cylinder 6, into the cylinder 7, which is in the intake stroke, via the aperture 40 in the wall of one cylinder 6, into the part of the delivery passage 42 on one side of the partition plate, through the third aperture 44 in the partition plate, through the part of the delivery passage 43 on the other side of the partition plate, and through the aperture 41 in the inner wall of the other cylinder 7. For normal operation, as illustrated in Figure 2, the pressure at the high pressure side is applied as the back pressure to the delivery passage 42,43 via the passage 51, the fourth apertures 49,50, and the recesses 48 to move the parts 45,46 of the piston to their bottom dead centers so as to close the apertures 40,41 in the inner walls of the cylinders, thereby preventing gas from moving between the two cylinders 6,7. With this arrangement, the apertures 40,41,44,49 and 50, the delivery passage 42,43, the parts 45,46 of the piston and the spring 47, required for the capacity control mechanism are arranged in the cylinders 6 and 7 so as to reduce the thickness of the partition plate 5, the height of the rotary compressing element 4, and the bearing span of the bearings 12 and 13, thus providing a compact multicylinder rotary compressor which is capable of implementing high-performance capacity control operation. Further, the parts 45,46 of the piston for controlling the capacity can be relatively arranged in each cylinder 6,7 so as to share the spring 47, thus reducing the number of components. In addition, coaxial machining is possible for making the delivery passage 42,43 in which the parts 45,46 and the spring 47 are disposed and the apertures can be positioned more accurately. Furthermore, the second apertures 49,50 for applying the back pressure to the capacity control pistons 45,46 are configured in the two cylinders 6,7 with respect to the partition plate 5 so as to evenly apply the back pressure to parts 45,46 at all times. This makes it possible to simultaneously actuate the parts 45,46 in good balance, leading to improved performance of capacity control. Moreover, the delivery passage 42,43 and the second apertures 49,50 are formed in the axial direction of the two cylinders 6,7, enabling improved workability. Figure 5 and Figure 6 show another embodiment comprising apertures 60,61 provided in the inner walls of the cylinders 6,7; communicating with delivery passages 62,63 provided in the cylinders 6,7, an aperture 64 provided in the intermediate partition plate 5 so that it communicates with the delivery passages 62,63; a piston having two parts 65,66 in the delivery passage 62,63 of the cylinders 6,7; and coil springs 67,68 disposed in the delivery passages 62,63 to bias the parts 65,66; wherein the low pressure or high pressure is selectively applied from an external refrigerant circuit to the delivery passage 62,63 via two piping passages 69,70 to cause each part to move so as to open or close the apertures 60,61 in the inner wall of the cylinders, thereby allowing the gas, which is being compressed in one cylinder 6, 7 to pass into the other cylinder 6, 7, which is in the intake stroke, via the aperture 60 in the inner wall of one cylinder into part of the delivery passage 62 on one side of the partition plate, and via the aperture 64 in the partition plate into the part of the delivery passage 63 on the other side of the partition plate, and through aperture 61 in the inner wall of the other cylinder 7, into the other cylinder 7. With this arrangement, the provision of the two separate coil springs 67,68 enables the respective springs to be made shorter and the load applied to the springs to be reduced, thus enhancing the freedom in designing the springs and also achieving higher reliability of the capacity control unit. Thus, according to the present invention, the structure as described in the claims makes it possible to dispose the apertures, pistons, springs, etc. required for the capacity control mechanism in the cylinders so as to reduce the thickness of the partition plate, the height of the rotary compressing element, and the bearing span of the bearings. The result is a compact multicylinder rotary compressor which is capable of implementing high-performance capacity control operation.

Claims: A multicylinder rotary compressor comprising a rotary compressing element (4) housed in a hermetic enclosure, said rotary compressing element being equipped with an intermediate partition plate (5), cylinders (6,7) provided on both sides of said partition plate (5), a rotary shaft (2) having eccentric sections which are shifted against each other by 180 degrees in the angle of rotation, rollers (10) which are fitted onto said eccentric sections of said rotary shaft (22) and which rotate in said cylinders (6,7) and bearings (12,13) which seal the openings of said cylinders (6,7), a delivery passage (42,43) extending between the cylinders (6,7), means for communicating the delivery passage (42,43) to a source of low or high pressure, an aperture (44) in the intermediate partition plate (15), an aperture (40,41) in the inner wall of the cylinders on either side of the partition plate (5) communicating each cylinder (6,7) with the delivery passage (42,43), and a piston (45,46) disposed in the delivery passage (42,43) having biasing means (47) associated therewith and being slidable to a first position when gas at high pressure sufficient to overcome the resilience of the biasing means (47) is supplied to the delivery passage (42,43) from the source, to position the piston (45,46) over the apertures (40,41) in the inner wall of each cylinder (6,7) to prevent the flow of gas between the cylinders (6,7), and a second position when gas having a pressure which is too low to overcome the resilience of the biasing means (47) is supplied to the delivery passage (42,43), in which the piston (45,46) is no longer positioned over the apertures (40,41) in the inner wall of each cylinder (6,7), thereby allowing gas to flow between the cylinders (6,7) via the aperture (44) in the intermediate partition plate (5), characterised in that the piston (45,46) is formed in two parts, each part being located on opposite sides of the intermediate partition plate (5) such that in use, with the piston (45,46) in the second position, gas flows between the cylinders (6,7) via the delivery passage (42,43). A multicylinder rotary compressor according to claim 1, wherein the means for communicating the delivery passage (42,43) with the low or high pressure side of an external refrigerant circuit comprises second aperture (48) at each end of the delivery passage (42,43). A multicylinder rotary compressor as claimed in claims 1 or 2, wherein the biasing means (47) extends between each part (45,46) of the piston through the intermediate partition plate (15). A multicylinder rotary compressor as claimed in claims 1 or 2, wherein each part has separate biasing means (67,68).

Inventors: KIYOKAWA YASUNORI, SAITO JISUKE, KIYOKAWA, YASUNORI, SAITO, JISUKE
Applicants: SANYO ELECTRIC CO, SANYO ELECTRIC CO., LTD.
Application year: 1996
Main classification: F04C29
IPC codes: F04C29, F04C18, F04C28, F04C23