Gear oil pump for hermetic compressor

Abstract: A gear pump is used in an electrically-operated sealed compressor including a compression mechanism, an electric motor for driving the compression mechanism, and a crankshaft for transmitting the rotational force of the electric motor to the compression mechanism. The gear pump includes a pair of gears being in mesh with each other, one of which is connected to one end of the crankshaft, and a pump casing accommodating only the pair of gears. The pump casing together with the gear pair is disposed on one side of a cover plate, while other elements constituting the gear pump are disposed on the other side of the cover plate. By this construction, the distance between the gear pair and an auxiliary bearing to which the gear pump is secured can be reduced and, hence, an undesirable whirling of one end portion of the crankshaft can also be reduced.

Description: BACKGROUND OF THE INVENTION (Field of the Invention) The present invention relates generally to an electrically-operated sealed compressor such as, for example, a scroll compressor or a rotary compressor for use in air conditioners, refrigerators or the like and, more particularly, to a gear pump mounted in the electrically-operated sealed compressor. (Description of Related Art) Conventionally, an electrically-operated sealed compressor such as a scroll compressor or a rotary compressor is generally used in a cooling apparatus for air conditioners, refrigerators, or the like. This kind of conventional compressor is discussed hereinafter taking the case of a scroll compressor. As shown in Fig. 14, a sealed vessel 10 accommodates a compression mechanism 1, an electric motor 7 including a stator 5 and a rotor 6, a crankshaft 2 for transmitting the rotational force of the electric motor 7 to the compression mechanism 1, a main bearing 3 for supporting one end of the crankshaft 2, and an auxiliary bearing 4a having a bearing holder 4 for supporting the other end of the crankshaft 2. The main bearing 3 has a container 11 attached thereto for temporarily collecting oil which has been supplied to the bearing portions for lubrication thereof. The sealed vessel 10 is provided with a suction pipe 8 for sucking in a low-pressure refrigerant gas and a discharge pipe 9 for discharging a high-pressure refrigerant gas compressed by the compression mechanism 1 to the outside of the sealed vessel 10. The crankshaft 2 has a gear pump 150 attached to that end thereof which is supported by the auxiliary bearing 4a. In the above-described construction, when the rotor 6 of the electric motor 7 rotates, the rotational force thereof is transmitted to the compression mechanism 1 by the crankshaft 2, to thereby compress a refrigerant gas. More specifically, the compression mechanism 1 compresses the low-pressure refrigerant gas drawn through the suction pipe 8 into the high-pressure refrigerant gas, which is in turn discharged into a discharge side space 14 defined in the sealed vessel 10. Thereafter, the high-pressure refrigerant gas passes through a communication hole 12 defined in the main bearing 3 and enters an electric motor side space 17. The main current of the high-pressure refrigerant gas passes through a cutout defined in the stator 5 and enters an auxiliary bearing side space 18 before it is eventually discharged into a refrigerating cycle (not shown) through the discharge pipe 9. On the other hand, the gear pump 150 has a pump casing 151 accommodating or having a pair of gears 52, a strainer 157, a foreign substance storage chamber 155 for storing foreign substances captured by the strainer 157, and an oil suction nozzle 156. The pump casing 151 is covered with a cover plate 153 fastened thereto by a plurality of, for example four, screws 152, and has a recess 60a defined therein so that a gear chamber 60 for accommodating the gear pair 52 therein may be formed by the cover plate 153 and the recess 60a. The fastening force of the screws 152 maintains the tightness between the pump casing 151 and the cover plate 153 to ensure sealing properties to the oil and the refrigerant gas. As shown in Figs. 15 and 16, the pump casing 151 has an oil well 61 defined therein and adjoining the gear chamber 60 so that the gear pair 52 may be supplied with the oil which serves as lubricating and sealing oil at the starting of the pump. The strainer 157 comprises a stainless screen 157a sandwiched between two stainless frames 157b and spot-welded thereto, and a plurality of elastic members or pieces 157c protruding therefrom. As shown in Fig. 16, when the strainer 157 is mounted in the pump casing 151, the elastic members 157c act to bias the strainer 157 against its mounting surface on the pump casing 151 to prevent the foreign substances in the foreign substance storage chamber 155 from entering the gear chamber 60. The gear pump 150 has an insert formed thereon and inserted into an associated portion of the bearing holder 4, and the pump casing 151 is fastened to its seat formed on the bearing holder 4 by a plurality of, for example two, bolts 154. As shown in Fig. 15, the gear pair 52 is comprised of an outer gear 52a and an inner gear 52b in mesh with each other. That end of the crankshaft 2 to which the gear pump 150 is attached has a cutout so as to present a generally D-shaped section and is inserted into a center hole of an inner gear 52b having a corresponding shape. The driving force of the electric motor 7 is transmitted to the inner gear 52b via the D-shaped portion of the crankshaft 2 and that of the inner gear 52b to cause the outer and inner gears 52a and 52b to undergo a mutual rotation for pumping action. When the compressor is in operation, the lubricating oil in an oil sump 15 formed at a lower portion of the sealed vessel 10 is sucked up into the inside of the gear pump 150 through the oil suction nozzle 156, and is then introduced into the space defined between the outer and inner gears 52a and 52b after having passed through the strainer 157 for filtering of foreign substances contained therein. Thereafter, the lubricating oil is fed into an oil passage 153b defined in the cover plate 153 by the pumping action of the gear pair 52, passes through a through-hole defined in the crankshaft 2 along the center line thereof, and is fed to the compression mechanism 1. Most of the lubricating oil acts to lubricate the sliding surfaces of the main bearing 3 and the crankshaft 2 and is then collected in the oil collecting container 11 attached to the main bearing 3. The lubricating oil thus collected in the container 11 is discharged therefrom through a discharge port 11a defined therein and drops by its own gravity to return to the oil sump 15 formed at the lower portion of the sealed vessel 10. The remaining oil together with the high-pressure refrigerant gas is discharged from the compression mechanism 1 into the sealed vessel 10 and is separated from the high-pressure refrigerant gas during movement thereof inside the compressor. This lubricating oil also drops by its own gravity to return to the oil sump 15. According to the above-described conventional compressor, however, because the pump casing accommodates or has the strainer, the foreign substance storage chamber, and the oil suction nozzle in addition to the gear pair, the height of the pump casing becomes large in a direction longitudinally of the compressor, depending on the size required for mounting the strainer, the size appropriate to the volume required for the foreign substance storage chamber, and the size appropriate to the diameter of the oil suction nozzle. On the other hand, the gear chamber accommodating the gear pair and formed in the pump casing is covered with the cover plate screwed to the pump casing, thus inevitably elongating the total longitudinal length of the bearing holder and the gear pair. For these reasons, in the event that the crankshaft undergoes a whirling motion having tilted from the ideal axis of the crankshaft, the gear pair is also affected by the whirling motion of the crankshaft to undergo an eccentric motion relative to the ideal axis of the crankshaft. More specifically, the inner and outer gears forming the gear pair rotate relative to each other with their gear teeth clashing against each other during rotation of the crankshaft then undergoing the whirling motion. Clashing of the gear teeth eventually leads to an abnormal wear of the gear teeth, the wall surface of the gear chamber, the driving portion of the crankshaft for driving the gear pair or the like, or generates abnormal sounds during operation of the compressor, resulting in a lowering in performance and also in reliability of the compressor. To overcome this kind of problem, it is necessary for the conventional compressor to have a relatively large clearance between the gear pair and the gear chamber. In this case, however, the large clearance lowers the sealing properties between the gear pair and the gear chamber, thus reducing the performance of the pump in terms of flow rate and pump head. According to another method of overcoming the above problem, the crankshaft, the bearing holder, and the gear pump are combined with one another after the design tolerances thereof have been strictly determined. This method, however, requires not only highly accurate machining on these elements, but also very careful inspection and management thereof after the machining. Furthermore, as described previously, because the conventional compressor is provided with the pump casing accommodating or having the strainer, the foreign substance storage chamber, and the oil suction nozzle in addition to the gear pair, the projected area of the pump casing becomes large in the longitudinal direction of the compressor. Also, the large height of the pump casing results in an enlargement in the volume of the entire gear pump. On the other hand, to prevent the lubricating oil from being discharged, along with a flow of refrigerant gas, to the outside of the compressor, the auxiliary bearing side space is required to have a sufficiently large volume. For this reason, the gear pump should be a small-sized one of a small volume. In view of this requirement, it is necessary to remove functionally unnecessary pads from the gear pump. To this end, the pump casing and the cover plate become complicated in shape, and screws are frequently used in fastening them. The fastening by the screws causes generation of minute strains in the cover plate which in turn creates a minute gap between the pump casing and the cover plate, resulting in a lowering in sealing properties. As a result, there arises the problem that the refrigerant gas may enter the gear pump, thus reducing the pump performance in terms of flow rate and then reducing the performance and reliability of the compressor. On the other hand, when the operation of the compressor is stopped and the compressor is again started, the gear pair must be supplied with oil to ensure lubrication and sealing thereof for a sufficient pump head. To this end, an oil well is provided so as to adjoin the gear chamber in the pump casing, thus creating a discontinuous plane having a cutout on the cylindrical wall of the gear chamber. Accordingly, when the gear pair undergoes a rotating motion to provide a pumping effect, it slides relative to such cutout to thereby cause an abnormal wear of the gear pair and that of the gear chamber. Worn-out powder thus generated reaches, together with an oil flow, the sliding portions of the compression mechanism and causes seizing thereof, which has a considerably bad influence on the performance and reliability of the compressor. Also, the sliding movement between the gear pair and the cutout generates noise during operation of the compressor. Moreover, the conventional gear pump employs a screen of a rectangular shape. Accordingly, in an attempt to enhance the capability of capturing foreign substances contained in the oil by increasing the screen area, the total length around the strainer becomes longer as compared with an increase in screen area. As a result of this, the height of the pump casing becomes larger. As described previously, because the pump casing should be thin, a sufficient screen area cannot be ensured. Also, because the strainer is caused to adhere to the pump casing by the action of the elastic members attached to and protruding from the strainer frame, the adhesive properties of the strainer to the pump casing vary according to a variation of the elastic force of the elastic members. Furthermore, when the strainer is mounted in the pump casing, the strainer is first inserted into a strainer chamber in the pump casing and an insertion hole is subsequently covered with the cover plate. Because of this, it is likely that a gap is created between the strainer and the cover plate and, hence, the function of the strainer for capturing foreign substances in the oil cannot be completely attained. More specifically, of the foreign substances contained in the oil, very small ones are likely to pass through such gap and reach, along with an oil flow, the sliding portions of the compression mechanism. These very small foreign substances may cause seizing of the sliding portions, which has a very bad influence on the performance of the compressor. In addition, because horizontal type electrically-operated compressors and vertical type ones differ in the arrangement of the oil sump within the sealed vessel, it is necessary to prepare gear pumps of different specifications wherein the position of an oil suction nozzle differs to ensure sufficient oil pumping from the oil sump up to the gear pump. The Japanese patent applications JP 02-030998, 59-060092, 05-164080 and 05-052190 are all directed towards gear pumps for use in a sealed compressor. The Japanese patent application JP-A-02-030998 shows a specific structure that contains a discharge muffler which provides a space to form a housing for the gear pump. JP-A-59-060092 shows a gear pump that is composed by an inner and outer gear, whereas the outer gear also forms the casing of the gear pump. JP-A-05-164080 shows a gear pump, where the shaft, to which one gear is connected, has an auxiliary bearing. The gear pump according to JP-A-05-052190 has a special oil pipe for the particular utilization in a horizontal type compressor. SUMMARY OF THE INVENTION The present invention has been developed to overcome the above-described disadvantages. It is accordingly an objective of the present invention to provide a highly efficient and highly reliable gear pump for use in an electrically-operated sealed compressor. Another objective of the present invention is to provide the gear pump of the above-described type which has a simple construction and can be manufactured at a low cost. These objects are according to the present invention solved by a gear pump for use in an electrically-operated sealed compressor including a compression mechanism, an electric motor for driving the compression mechanism, and a crankshaft for transmitting a rotational force of the electric motor to the compression mechanism, said gear pump comprising: a first gear connected to an end of the crankshaft and a second gear in mesh with the first gear a strainer for capturing foreign substances contained in oil which is introduced to the first and the second gear; and a pump cover for covering the strainer, the pump cover having a shoulder portion in which the strainer is received, the strainer having a height greater than that of the shoulder portion so that the strainer protrudes from one end surface of the pump cover. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objectives and features of the present invention will become more apparent from the following description of preferred embodiments thereof with reference to the accompanying drawings, throughout which like parts are designated by like reference numerals, and wherein: Fig. 1 is a vertical sectional view of that portion of an electrically-operated sealed compressor in which a gear pump according to a first embodiment of the present invention is incorporated; Fig. 2 is a vertical sectional view of a gear pump according to a second embodiment of the present invention; Fig. 3 is a side view of the gear pump of Fig. 2; Fig. 4 is a view similar to Fig. 2, but according to a third embodiment of the present invention; Fig. 5A is a vertical sectional view of an essential portion of a gear pump according to a fourth embodiment of the present invention; Fig. 5B is a side view of the gear pump of Fig. 5A; Fig. 6 is a view similar to Fig. 1, but particularly depicting a modification of a pump cover of the gear pump; Fig. 7 is a view similar to Fig. 1, but particularly depicting another modification of the pump cover; Fig. 8A is a front view of a strainer mounted in the gear pump shown in Fig. 1, 6, or 7; Fig. 8B is a vertical sectional view of the strainer of Fig. 8A; Fig. 9A is a view similar to Fig. 8A, but depicting a modification thereof; Fig. 9B is a vertical sectional view of the strainer of Fig. 9A; Fig. 10A is a view similar to Fig. 8A, but depicting another modification thereof; Fig. 10B is a vertical sectional view of the strainer of Fig. 10A; Fig. 11A is a view similar to Fig. 8A, but depicting a further modification thereof; Fig. 11B is a vertical sectional view of the strainer of Fig. 11A; Fig. 12A is a view similar to Fig. 8A, but depicting a still further modification thereof; Fig. 12B is a vertical sectional view of the strainer of Fig. 12A; Fig. 13 is a vertical sectional view of a vertical type electrically-operated sealed compressor in which the gear pump of the present invention is incorporated; Fig. 14 is a vertical sectional view of a conventional electrically-operated sealed scroll compressor; Fig. 15 is a front view of a conventional gear pump; and Fig. 16 is a vertical sectional view of the conventional gear pump of Fig. 15. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS This application is based on application No. 8-145379 filed in Japan, the content of which is incorporated hereinto by reference. Referring now to the drawings, there is shown in Fig. 1 a gear pump 50 according to a first embodiment of the present invention, which is incorporated in an electrically-operated sealed scroll compressor comprising a sealed vessel 10, a compression mechanism (not shown) accommodated in the sealed vessel 10, an electric motor 7 including a stator 5 and a rotor 6 for driving the compression mechanism, and a crankshaft 2 for transmitting the rotational force of the electric motor 7 to the compression mechanism. As shown therein, the gear pump 50 comprises a pump casing 51 having an insert formed thereon so as to protrude towards the crank shaft 2. This insert is received in an associated portion of a bearing holder 4 of an auxiliary bearing 4a. The pump casing 51 together with a cover plate 53 and a cup-like pump cover 54 is fastened to its seat formed on the bearing holder 4 by means of a plurality of screws 59. The pump casing 51 has a recess 60a defined therein in which only a gear pair 52 comprised of an outer gear 52a and an inner gear 52b in mesh with each other is accommodated. The pump casing 51 together with the gear pair 52 is covered with the cover plate 53 and, hence, a gear chamber 60 in which the gear pair 52 is rotatably mounted is formed by the cover plate 53 and the recess 60a of the pump casing 51. The inner gear 52b has a generally D-shaped center hole defined therein in which one end of the crankshaft 2 having a corresponding shape is engaged so that the rotational force transmitted via the crankshaft 2 may be further transmitted to the inner gear 52b to cause the outer and inner gears 52a and 52b to undergo a mutual rotation for pumping action. On the other hand, the cover plate 53 has an oil communication port 53a defined therein and is interposed between the gear pair 52 and an oil suction nozzle 56 to introduce oil sucked up through the oil suction nozzle 56 to the gear pair 52. The cover plate 53 also has a recessed oil passage 53b defined therein on one surface thereof to introduce the oil having reached the gear pair 52 to an oil passage 16 defined in the crankshaft 2 along the center line thereof. The pump cover 54 is mounted on the cover plate 53 and has a recess defined therein so as to form a foreign substance storage portion 55 and an oil storage portion 58. These storage portions 55 and 58 are delimited by the pump cover 54 and the cover plate 53. The pump cover 54 has a shoulder portion in which a strainer 57 is received having a relatively thin and round frame made of a resin and a screen or meshes made of stainless, brass or iron to which the frame is secured, for example, by injection molding. One end face of the resinous frame of the strainer 57 protrudes slightly beyond one end face of the pump cover 54 in a direction longitudinally of the compressor. In other words, the strainer 57 has a height greater than that of the shoulder portion of the pump cover 54. Because of this, when the pump cover 54 together with the cover plate 53 and the pump casing 51 is fastened to the bearing holder 4 by means of screws, the strainer 57 is sandwiched between the shoulder portion of the pump cover 54 and the cover plate 53 with opposite round faces of the strainer 57 held in contact therewith. Accordingly, the strainer 57 adheres to both the pump cover 54 and the cover plate 53. The cup-like pump cover 54 has a center hole defined in a bottom region thereof with the peripheral lip region thereof inwardly burred to define an inner tube. The oil suction nozzle 56 made of synthetic resin such as, for example, Teflon, has one end inserted inwardly into the inner tube integral with the pump cover 54 and held in tight contact with an inner peripheral surface of the inner tube. The tight contact of the oil suction nozzle 56 with the inner surface of the inner tube of the pump cover 54 can be accomplished by heating that end of the oil suction nozzle 56 to allow it to undergo plastic deformation. The other end of the oil suction nozzle 56 is positioned within an oil sump 15 defined at a lower portion of the sealed vessel 10. The above-construction can shorten the distance between the auxiliary bearing 4a and the gear pair 52, compared with the construction of the conventional gear pumps. Accordingly, when the compressor is in operation, whirling of the end portion of the crankshaft 2 is reduced and, hence, the gear pair 52 mounted thereon smoothly rotates without causing clashing of its teeth within the gear chamber 60. As a result, while no abnormal wear occurs on the gear pair 52 or the wall surface of the gear chamber 60, abnormal sounds are not generated which have been hitherto caused by rotation of the gear pair 52. When the gear pump of the above-described construction is in operation, the oil flows as follows. When the gear pump 50 is in operation, the pumping action of the gear pair 52 introduces oil stored in the oil sump 15 into the foreign substance storage portion 55 through the oil suction nozzle 56. Because the strainer 57 received in the shoulder portion of the pump cover 54 is positioned so as to cover the oil communication port 53a, foreign substances contained in the oil are captured by the strainer 57 when the oil is sucked up by the gear pair 52 through the oil communication port 53a. The oil thus sucked up by the gear pair 52 passes through the oil passage 53b of the cover plate 53 and is introduced into the oil passage 16 of the crankshaft 2 before it is eventually supplied to the compression mechanism 1. Figs. 2 and 3 depict a gear pump 50 according to a second embodiment of the present invention. The function of the gear pump 50 and the oil flow are substantially the same as those in the first embodiment referred to above. In Figs. 2 and 3, the pumping action of the gear pair 52 introduces oil into the foreign substance storage portion 55 formed in the pump cover 54 through the oil suction nozzle 56. The oil then passes through the oil communication port 53a defined in the cover plate 53 and reaches the gear pair 52. Because the oil storage portion 58 is formed by the pump cover 54 and the cover plate 53, even when the gear pump 50 is stopped by stopping the compressor and is again started, the gear pair 52 is supplied with the oil accommodated in the oil storage portion 58 for lubrication and sealing thereof, thus ensuring the pump performance in terms of flow rate. Furthermore, a permanent magnet 61 is mounted in the pump cover 54 to positively capture, by the action of its magnetic force, iron-based foreign substances contained in the oil introduced thereinto so that such foreign substances may be stored in the foreign substance storage portion 55. The pump cover 54 has a rib 54a formed on the entire peripheral edge thereof so as to extend towards the crankshaft 2. Accordingly, even if the pump cover 54 is made thin, the rib 54a rigidifies it, thus ensuring the sealing properties between it and the cover plate 53. Also, a sealing material 62 is interposed between the pump cover 54 and the cover plate 53 to enhance the sealing properties therebetween. Moreover, each of the pump casing 51, the cover plate 53, the sealing material 62, and the pump cover 54 has a flange-shaped external form. More specifically, each of the pump casing 51, the cover plate 53, and the sealing material 62 is generally flat and generally oval-shaped and has a major axis and a minor axis perpendicular to each other, while the pump cover 54 has a generally flat and generally oval-shaped portion having a major axis and a minor axis perpendicular to each other. Accordingly, in assembling the gear pump 50, these elements can be simultaneously fastened to the bearing holder 4 using two screws 59, and a lowering in sealing properties at the sealing surfaces can be minimized which is generally caused by minute strains produced in the pump cover 54 or the cover plate 53 during fastening. Also, because the external form of the gear pump 50 is simplified, it can be made small. In the case where part of the flange-shaped external form is odd- or irregular-shaped, i.e., the pump casing 51, the cover plate 53, the pump cover 54, or the sealing material 62 is asymmetric with respect to one of the major and minor axes thereof, as shown in Fig. 3, an error in the direction in which each element is mounted can be prevented during assemblage of the gear pump 50. Accordingly, generation of a serious defect such as, for example, the reverse pumping action which occurs when the pump casing 51 rotated 180° from its proper position is mounted on the bearing holder 4 can be prevented. In addition, if temporary assemblage is carried out by slightly press-fitting the cover plate 53 into the pump cover 54 with the permanent magnet 61, the strainer 57 and the sealing material 62 accommodated within the rib 54a of the pump cover 54, these elements can be handled together during assemblage, thus enhancing the working efficiency. Fig. 4 depicts a gear pump 50 according to a third embodiment of the present invention. As shown therein, the gear pump 50 comprises a sealing material 62a interposed between the cover plate 53 and the pump casing 51, and another sealing material 62b interposed between the pump casing 51 and the crankshaft 2. These sealing materials 62a and 62b act to enhance the sealing properties of the gear pump 50. The pump cover 54 has a recess 54b defined therein at a lower portion thereof for accommodating foreign substances. This recess 54b acts to reduce clogging of the screen of the strainer by accumulating therein the foreign substances contained in the oil and captured by the strainer. In this embodiment, the strainer frame may be made of a metal and manufactured by a press operation. In this case, it is sufficient if the screen is sandwiched between the pump cover 54 and the strainer frame, with the strainer frame secured to the pump cover 54 by spot-welding or press-fitting. Figs. 5A and 5B depict part of a gear pump 50 according to a fourth embodiment of the present invention. As shown therein, the oil is readily introduced into the gear pair 52 by aligning an oil inlet portion 63 of the gear pair 52 with the oil communication port 53a of the cover plate 53. The oil communication port 53a is generally crescent-shaped to widely cover the oil inlet portion 63 of the gear pair 52. This configuration can sufficiently reduce the resistance of the oil communication port 53a when the oil passes therethrough, making it possible to reduce the load of rotation of the gear pump 50. Furthermore, when the direction in which the cover plate 53 receives the pressure of a press during formation of the oil communication port 53a is made counter to the direction in which the cover plate 53 receives the pressure of the press during formation of the oil passage 53b, the oil communication port 53a and the oil passage 53b can have respective dull or rounded corners on opposite surfaces of the cover plate 53, as shown in Fig. 5A. By so doing, it becomes possible to widen the area of an oil path through which oil in the oil passage 53b is introduced into the oil passage 16 of the crankshaft 2, while it also becomes possible to minimize communication between the oil inlet portion 63 of the gear pair 52 and the oil passage 53b at a location where the gear pair 52 confronts the cover plate 53, to thereby ensure the sealing properties. As shown in Fig. 6, the pump cover 54 may have a slope formed at a bottom portion thereof and an oil suction nozzle 56 integrally formed or processed therewith so as to extend obliquely downwardly therefrom. Also, as shown in Fig. 7, the pump cover 54 may be made of a resin having an oil suction nozzle 56 integrally formed therewith so as to extend downwardly therefrom. Figs. 8A and 8B depict a strainer 57 comprising a cylindrical resinous frame 57b and a screen or meshes 57a secured to one end thereof. Figs. 9A and 9B depict a modification of the strainer 57 having a rib 57d integrally formed with the cylindrical resinous frame 57b and extending outwardly from the other end thereof to rigidify the strainer 57. Figs. 10A and 10B depict another modification of the strainer 57 in which the screen 57a is secured to the internal surface of the cylindrical resinous frame 57b at a central portion thereof. Figs. 11A and 11B depict a further modification of the strainer 57 having a radially extending cross-shaped rib 57d integrally formed with the cylindrical resinous frame 57b to rigidify the strainer 57 and support the screen 57a. Figs. 12A and 12B depict a still further modification of the strainer 57 having a plurality of, for example four, small projections 57e integrally formed with the cylindrical resinous frame 57b and extending outwardly therefrom. When the strainer 57 is slightly press-fitted into the pump cover 54, the projections 57e act to hold the former in the latter. In each of the strainers 57 shown in Figs. 8-12, because the screen 57a is spaced apart from that end face of the cylindrical resinous frame 57b which is held in contact with the cover plate 53, during assemblage the screen 57a does not interfere with or is not damaged by projections which have been formed by press-molding the oil passage 53b on the cover plate 53. Also, each of the strainers 57 shown in Figs. 8-12 has a height considerably smaller than the diameter thereof. It is preferred that the cylindrical frame be made of PBT resin containing 10-50% of graphite. An increase in rigidity of the cylindrical resinous frame makes it possible to reduce pads thereof and enhance the accuracy in shape during molding. It is to be noted here that although in the above-described embodiments the gear pump 50 has been described as being incorporated in the horizontal type electrically-operated compressor, it can be incorporated in vertical type electrically-operated compressor by replacing the oil suction nozzle 56 shown in Fig. 1 with a straight oil suction nozzle, as shown in Fig. 13. It is also to be noted that although in the above-described embodiments the gear pump 50 has been described as comprising an outer gear and an inner gear in mesh with each other, it may comprise two spur gears disposed side by side and being in mesh with each other. It is further to be noted that although the embodiments shown in Figs. 1 to 13 are intended for the electrically-operated sealed scroll compressors, the present invention is also applicable to other electrically-operated sealed compressors such as, for example, sealed rotary compressors.

Claims: A gear pump (50) for use in an electrically-operated sealed compressor including a compression mechanism, an electric motor (7) for driving the compression mechanism, and a crankshaft (2) for transmitting a rotational force of the electric motor (7) to the compression mechanism, said gear pump (50) comprising: a first gear (52a) connected to an end of the crankshaft (2) and a second gear (52b) in mesh with the first gear characterised by a strainer (57) for capturing foreign substances contained in oil which is introduced to the first and the second gear (52a; 52b); and a pump cover (54) for covering the strainer (57), the pump cover (54) having a shoulder portion in which the strainer (57) is received, the strainer (57) having a height greater than that of the shoulder portion so that the strainer (57) protrudes from one end surface of the pump cover (54). The gear pump (50) according to claim 1, further comprising a foreign substance storage (55) portion defined as a portion for storing foreign substances therein; a pump cover (54) mounted on the cover plate (53), wherein the foreign substance storage portion (55) is provided in the pump cover (54); wherein the strainer (57) is interposed between the foreign substance storage portion (55) and the cover plate (53); and wherein the foreign substance storage portion (55) is provided such that the cover plate (53) is interposed between the foreign substance storage portion (55) and the first and second gear (52a; 52b). The gear pump (50) according to claim 2, wherein the strainer (57) has a centre substantially aligned with a longitudinal axis of the compressor crankshaft (2).

Inventors: ABURAYA KIYOJI, AOSHIKA SHOJI, NARITA TSUTAYOSHI, SAKAI MANABU, TAKEUCHI YOSHIHARU, TSUBOKAWA MASAHIRO, YASU TOSHIHARU, ABURAYA, KIYOJI, AOSHIKA, SHOJI, NARITA, TSUTAYOSHI, SAKAI, MANABU, TAKEUCHI, YOSHIHARU, TSUBOKAWA, MASAHIRO, YASU, TOSHIHARU
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1997
Main classification: F04C29
IPC codes: F04C29, F04C18, F04C2, F04C13, F04C23