Patent Publication Number: US-6039552-A

Title: Rotary compressor

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a rotary compressor for compressing various types of fluids, for use as pumps or superchargers for internal combustion engines. 
     2. Description of the Related Art 
     Such a rotary compressor hitherto known comprises, as described in, e.g., Japanese Utility Model Registration Laid-open Publication No. 59-181284, a casing having an inflow port and an outflow port for a fluid which open on its inner surface, a cylindrical outer rotor rotatably housed in the casing, a cylindrical inner rotor rotatably supported at an eccentric position within the outer rotor, and a plurality of vanes slidably attached, in the radial direction, to grooves formed in the outer peripheral surface of the inner rotor, wherein a fluid is sucked through the inflow port of the casing into a space between the outer rotor and the inner rotor partitioned by the vanes, the fluid being discharged through the outflow port of the casing. 
     However, due to the structure of the conventional rotary compressor in which the tips of the vanes whirl in contact with the inner peripheral surface of the outer rotor, the loss attributable to mechanical friction is significant, making difficult the use in high-speed rotations, as in the case of use as, e.g., an automobile supercharger. 
     SUMMARY OF THE INVENTION 
     The present invention was conceived in view of the above problems. It is therefore an object of the present invention to provide a rotary compressor capable of significantly reducing the loss attributable to mechanical friction. 
     According to an aspect of the present invention, there is provided a rotary compressor comprising a casing having an inflow port and an outflow port for a fluid which open on its inner surface, a cylindrical outer rotor rotatably housed in the casing, and a cylindrical inner rotor rotatably supported at an eccentric position within the outer rotor, the rotors being rotated in a predetermined direction to introduce the fluid from the inflow port into a space between the rotors, the fluid being discharged through the outflow port, the improvement wherein the outer rotor has an inner peripheral surface provided with one or more protruding portions for partitioning which are radially inwardly raised and are circumferentially spaced apart from one another; and the inner rotor has an outer peripheral surface provided with one or more recessed portions for partitioning which are radially inwardly recessed and are circumferentially spaced apart from one another; and wherein the outer rotor and the inner rotor are connected to each other in such a manner that the protruding portions for partitioning of the outer rotor move circularly in a non-contact manner along inner surfaces of the recessed portions for partitioning of the inner rotor. 
     According to the present invention, rotations of the rotors allow a non-contact circular movement of the protruding portions for partitioning of the outer rotor along the inner surfaces of the recessed portions for partitioning of the inner rotor, with the result that a fluid from the inflow port is sucked into a space between the rotors partitioned by the protruding portions and the recessed portions for partitioning, the fluid being discharged through the outflow port. Thus, the loss arising from mechanical friction is reduced to a large extent, making it possible to deal with the use in high-speed rotations, which is extremely advantageous to, e.g., superchargers for internal combustion engines. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other aspects, objects, advantages and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings, in which: 
     FIG. 1 is a sectional side elevation of a rotary compressor showing an embodiment of the present invention; 
     FIG. 2 is a sectional view taken along a line 5--5 of FIG. 1; 
     FIG. 3 is a front elevational view of the rotary compressor; 
     FIG. 4 is an exploded perspective view of the major parts of the rotary compressor; 
     FIG. 5 is an explanatory diagram of the action of the rotary compressor; 
     FIG. 6 is a sectional plan view of a rotary compressor showing another embodiment of the present invention; 
     FIG. 7 is a sectional view taken along a line 15--15 of FIG. 6; and 
     FIG. 8 is a sectional view taken along a line 16--16 of FIG. 6. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 to 5 illustrate an embodiment of the present invention. A rotary compressor according to this embodiment comprises a casing 1 constituting a compressor body, an outer rotor 2 rotatably housed in the casing 1, an inner rotor 3 rotatably supported at an eccentric position within the outer rotor 2, and a plurality of connecting plates 4 connecting the outer rotor 2 and the inner rotor 3 in a freely turnable state relative to each other. 
     The casing 1 is in the form of a hollow cylinder having one end which is opened and the other end which is provided with a bearing portion 1a for supporting the outer rotor 2. The one end of the casing 1 is fitted with a casing cover 1b carrying a support shaft 1c for providing a support for the inner rotor 3. The case cover 1b includes an inflow port 1d and an outflow port 1e which open into the interior of the casing 1, the inflow 1d and outflow 1e ports being connected to the exterior by way of a suction pipe 1f and a discharge pipe 1g, respectively. 
     The outer rotor 2 is in the form of a hollow cylinder having one end which is opened and the other end at which the outer rotor 2 is rotatably supported via a bearing 2a by the bearing portion 1a of the casing 1. The outer rotor 2 has a support shaft 2b extending through its hollow and rotatably supported via a bearing 2c by the support shaft 1c of the casing cover 1b. In this instance, the support shaft 1c of the casing cover 1b is offset radially from the rotational center of the outer rotor 2. The outer rotor 2 has on its inner peripheral surface a plurality of radially inwardly extending partition pieces 2d which are circumferentially spaced apart from one another in the shape of protruding portions for partitioning, the tip of each partition piece 2d being circular in section. 
     The inner rotor 3 is in the form of a hollow cylinder having open opposed ends and has the inner peripheral surface supported via a bearing 3a by the support shaft 1c of the casing cover 1b. The outer peripheral surface of the inner rotor 3 is formed with a plurality of radial partition grooves 3b which are circumferentially spaced apart from one another in the shape of recessed portions for partitioning, with each partition groove 3b extending axially up to one end surface of the inner rotor 3. The interior of each partition groove 3b is of a circular section, with part of its peripheral surface extending up to the outer peripheral surface of the inner rotor 3. 
     Each of the connecting plates 4 is in the form of a disk having an outer diameter equal to the inner diameter of the partition grooves 3b in the inner rotor 3. Each plate 4 has at its one end a support shaft 4a rotatably connected via a bearing 4b to the interior of each partition groove 3b on the other end side thereof. Each plate 4 has at its other end a pin 4c connecting to each partition piece 2d of the outer rotor 2 and rotatably supported by a bearing 4d, with the pin 4c being disposed on a predetermined circle around the support shaft 4a. Thus, rotations of the connecting plates 4 result in circular movements of the tips of the partition pieces 2d within the associated partition grooves 3b along the inner surfaces of the partition grooves 3b in a non-contact manner. In this instance, extremely minute gaps are kept between the partition pieces 2d and the associated partition grooves 3b. 
     In case of the thus constructed rotary compressor, when the outer rotor 2 is rotated by external rotational force, the inner rotor 3 also rotates together with the outer rotor 2 in the same direction since the outer rotor 2 is coupled via the connecting plates 4 to the inner rotor 3. At that time, the rotors 2 and 3 rotate at positions offset relative to each other, so that the partition pieces 2d of the outer rotor 2 describe a circle within the associated partition grooves 3b of the inner rotor 3 while turning the connecting plates 4. Thus, as shown in FIG. 5, the rotors 2 and 3 rotate together, with at least two partition pieces 2d turning all the time along the inner surfaces of the associated partition grooves 3b in a non-contact manner, so that a fluid from the inflow port Id flows into a space A between the rotors 2 and 3 partitioned by the partition pieces 2d and the partition grooves 3b, the fluid being finally discharged through the outflow port 1e. 
     Thus, according to the rotary compressor of this embodiment having a structure in which a fluid is sucked into and discharged from the space between the outer rotor 2 and the inner rotor 3 which rotate at positions offset relative to each other, the plurality of partition pieces 2d formed on the inner peripheral surface of the outer rotor 2 are caused to perform circular movement in a non-contact manner along the inner surfaces of the plurality of partition grooves 3b formed in the outer peripheral surface of the inner rotor 3 so that the space between the rotors 2 and 3 can be partitioned without allowing the partition pieces 2d and the partition grooves 3b to come into contact with one another, thereby making it possible to remarkably reduce the loss arising from mechanical friction and to deal with the use in high-speed rotations. Furthermore, the outer rotor 2 and the inner rotor 3 are coupled together by means of the connecting plates 4 so that the rotations of the connecting plates 4 allow circular movement of the partition pieces 2d of the outer rotor 2 along the inner surfaces of the partition grooves 3b of the inner rotor 3, with the result that application of rotational force to the outer rotor 2 can cause a rotation of the inner rotor 3. 
     Although the above embodiment is provided with a plurality of partition pieces 2d and a plurality of partition grooves 3b, it may have a single partition piece 2d and a single partition groove 3b. 
     FIGS. 6 to 8 illustrate another embodiment of the present invention. A rotary compressor according to this embodiment comprises a casing 10 constituting a compressor body, an outer rotor 11 rotatably housed in the casing 10, an inner rotor 12 rotatably supported at an eccentric position within the outer rotor 11, and a pair of gears 13 and 14 for interlocking the outer rotor 11 and the inner rotor 12. 
     The casing 10 includes a bearing portion 10a and a support shaft 10b arranged at one end and the other end thereof, respectively, for providing a support for the inner rotor 12, and includes bearing portions 10c and 10d arranged at the other end thereof and internally at substantially the middle position, respectively, for providing a support for the outer rotor 11. The casing 10 further includes in its peripheral surface an inwardly opened inflow port 10e and outflow port 10f which are circumferentially spaced apart from each other. 
     The outer rotor 11 is provided with one end 11a and the other end 11b which are disk-shaped and axially confront each other, and with a plurality of partition pieces 11c in the shape of protruding portions for partitioning which extend between the one end 11a and the other end 11b and are circumferentially spaced apart from one another. The one end 11a of the outer rotor 11 is rotatably supported via a bearing 11d by the bearing portion 10d of the casing 10, the other end 11b being rotatably supported via a bearing 11e by the bearing portion 10c of the casing 10. The plurality of partition pieces 11c are inwardly raised from the inner peripheral surface of the outer rotor 11, with their tips being circular in section. A gear 11f is provided on the outer rotor 11 at the side of its one end 11a. 
     The inner rotor 12 has at its one end a support shaft 12a which is rotatably supported via a bearing 12b by the bearing portion 10a of the casing 10. The inner rotor 12 has at its other end a bearing portion 12c which is rotatably supported via a bearing 12d on the support shaft 10b of the casing 10. In this instance, the inner rotor 12 is supported to be radially offset from the rotational center of the outer rotor 11. The outer peripheral surface of the inner rotor 12 is formed with a plurality of partition grooves 12e which are radially recessed for partitioning and are circumferentially spaced apart from one another, the interior of each partition groove 12e being of a circular section. A gear 12f is provided on the support shaft 12a of the inner rotor 12. In this instance, the support shaft 12a of the inner rotor 12 extends through the one end 11a of the outer rotor 11, with the gear 12f of the inner rotor 12 being coaxial with the gear 11f of the outer rotor 11. 
     Gears 13 and 14 are provided axially integrally with each other, with the both ends thereof being rotatably supported via bearings 13a and 14a, respectively, within the casing 10. That is, the gears 13 and 14 mesh with the gear 11f of the outer rotor 11 and the gear 12f of the inner rotor 12, respectively, so that the outer rotor 11 and the inner rotor 12 are rotated by way of the gears 13 and 14, respectively. In this instance, the outer rotor 11 and the inner rotor 12 are designed to have the same speed reduction ratio. That is, arrangement is such that rotations of the outer rotor 11 and the inner rotor 12 cause circular movement of the tips of the partition pieces 11c within the partition grooves 12e while being in close proximity to the inner surfaces of the partition grooves 12e. In this instance, an extremely minute gap is secured between the partition pieces 11c and the partition grooves 12e. 
     According to the thus constructed rotary compressor, when the inner rotor 12 is rotated by external rotational force, the outer rotor 11 can rotate in the same direction together with the inner rotor 12 since the outer rotor 11 is coupled via the gears 13 and 14 to the inner rotor 12. At that time, the rotors 11 and 12 rotate at positions offset relative to each other, so that the partition pieces 11c of the outer rotor 11 perform circular movement along the inner surfaces of the partition grooves 12e of the inner rotor 12 in a non-contact manner. Thus, in the same manner as the preceding embodiment, a fluid is sucked through the inflow port 10e of the casing 10 into the space between the rotors 11 and 12 partitioned by the partition pieces 11c and the partition grooves 12e, the fluid being finally discharged through the outflow port 10f to the exterior. 
     While the present invention has been described with relation to certain presently preferred embodiments, those skilled in this art will recognize other modifications of the present invention which will still fall in within the scope of the invention, as expressed in the accompanying claims.