OIL LEVEL CONTROL DEVICE FOR A COMPRESSOR

Abstract: A lubricant (L) is stored in a lubricant reservoir (2c) of a casing (2) . One end of a lubricant takeout pipe (15) is in communication with the lubricant reservoir (2c) and the other end thereof is in communication with a suction chamber (14) of a scroll mechanism (3) . An inlet end of the lubricant takeout pipe (15) opens at the same level as an oil-level high-limit point of the lubricant reservoir (2c) in the vicinity of a lower end of a rotor (9b) . When the level of the lubricant (L) moves up to the high-limit point, an excess lubricant is introduced from the lubricant reservoir (2c) into the scroll mechanism (3) , since there is produced a difference in pressure between a lower space (2b) of the casing (2) and the suction chamber (14) . As a result, the level of the lubricant (L) drops.

Description: 1. Technical Field of the Invention This invention relates generally to refrigerating compressors. More particularly, it pertains to an oil-level controller, for use by a refrigerating compressor, for controlling the level of a lubricating oil (hereinafter called a lubricant) stored in the bottom of a compressor casing. 2. Description of the Prior Art Many types of compressors have been proposed. JP Pat. Appln., laid open under Pub. No. 2-305392, discloses one. A compression mechanism is located in an upper space of a casing of the compressor, and located in a lower space thereof is a motor. A crankshaft extends up from the motor for linkage to the compression mechanism. The motor drives the crankshaft, and the crankshaft rotates, and the compression mechanism performs compression operations. A lubricant is stored in the bottom of the casing, and the lower end of the crankshaft lies in the lubricant. The crankshaft lower end is provided with a pump mechanism, e.g., a centrifugal pump. Additionally, a flow passage is formed through the crankshaft. When the motor drives the crankshaft to rotate, the pump mechanism draws up a lubricant from the casing bottom. This lubricant travels through the flow passage to each of slide sections of the compressor for lubrication. In the above-noted compressor, a lubricant is stored by a predetermined amount, and the level of the lubricant is, in any case, maintained to fall within a predetermined range, taking into account the fact that the oil level varies between when the compressor is stopped and when the compressor is driven. In other words, the oil level is high when stopped while it is low when driven. Therefore the oil level is set such that it stays below a rotor of the motor in the stopped state while it stays above the lower end of the crankshaft in the drive state. However, in spite of the above arrangement, the oil level may not fall in the predetermined range depending upon the operating conditions. If a compressor has not been run for a long period of time, or if a compressor is run in humid conditions, then a liquid refrigerant is likely to be mixed with a lubricant stored in a lubricant reservoir. In other words, in addition to the lubricant the liquid refrigerant is now stored in the lubricant reservoir, which may result in increasing the oil level above a predetermined high-limit point. As the oil level goes beyond a predetermined point, the area of the crankshaft that is soaked in the lubricant stored in the lubricant reservoir increases. Additionally the motor rotor, too, is soaked in the lubricant. The crankshaft and the motor rotor must rotate against resistance produced by the lubricant. In this case electrical input must be increased so as to maintain the rotation of the crankshaft constant. This, however, produces input loss. Also, in such a situation, both the crankshaft and the motor rotor stir the lubricant and the temperature of the lubricant increases. This increases the temperature of an entire casing space. As a result the efficiency of compression drops. JP Pat. Appln., laid open under Pub. No. 4-214983, discloses an oil-level control technique known in the art as a forced differential pressure method. In this forced differential pressure method, two compressors are connected together by an oil-level equalizing pipe and there is produced a difference in pressure between the compressors. Most of the lubricant brought back from a refrigerant circulation circuit is introduced into one of the two compressors that is provided on the high-pressure side, and part of the brought-back lubricant is supplied through the oil-level equalizing pipe to the other compressor provided on the low-pressure side because of the aforesaid pressure difference. The above-described organization, however, requires two compressors. In other words, it is difficult to accomplish a forced differential pressure technique with a single compressor. A compressor according to the preamble part of claim 1 is known from JP-A-05/126066. In this compressor there is provided a casing, a compression mechanism, a lubricant reservoir, a drive mechanism and an oil-level controller which is an oil-level lowering means, comprising a discharge mechanism capable of discharging lubricant out of said lubricant reservoir. When the level of said lubricant goes beyond a predetermined high-limit point, said oil-level lowering means brings said excess level down to said predetermined high-limit point. Bearing in mind the above-described problems with the prior art techniques the present invention was made. In accordance with the present invention, the level of a lubricant in a lubricant reservoir can be maintained at a desired point and the increase in the electrical input as well as the increase in the oil temperature can be held as low as possible. DISCLOSURE OF THE INVENTION Accordingly the present invention provides an improved oil-level controller capable of self-level control. In other words, when the oil level goes beyond a predetermined point, it is forced to go downward by means of the self-level control function. The present invention provides a new oil-level controller for use by a compressor, the compressor comprising (i) a casing (2) at the bottom of which is formed a lubricant reservoir (2c) for storing a lubricant (L) , (ii) a compression mechanism (3) for compressing a compression gas, the compression mechanism (3) being housed in the casing (2), and (iii) a drive mechanism (4) for driving the compression mechanism (3), the drive mechanism (4) being housed in the casing (2) (see FIG. 2). The lubricant (L) is applied from the lubricant reservoir (2c) to the compression mechanism (3). More particularly in accordance with the invention of Claim 1, the compressor oil-level controller is an oil-level lowering means (26) whereby when the level of the lubricant (L) goes beyond a predetermined high-limit point the oil-level lowering means brings the excess level down to the predetermined high-limit point. In accordance with the invention of Claim 1, the oil level-lowering means (26) comprises a discharge mechanism (27) capable of discharging a lubricant (L) out of the lubricant reservoir (2c). In accordance with the invention of Claim 1, (i) the discharge mechanism (27) has a displacement pump (20) driven by means of the drive mechanism (4) and a lubricant takeout pipe (15) with an inlet end in communication with an outlet end of the displacement pump (20) , and (ii) a suction passage (20d) formed in the displacement pump (20) has an inlet end that opens in such a way as to face to the predetermined high-limit point (see FIG. 2). In accordance with an aspect of an invention of Claim 2 according to the invention, a lubricant-inflow prevention member (29) is disposed in the vicinity of the inlet end of the suction passage (20d) of the displacement pump (20) , the prevention member (29) preventing a lubricant (L) present in the casing (2) from flowing into the suction passage (20d) (see FIGS. 2 and 4). In accordance with an aspect of an invention of Claim 3 according to the Claim 2 invention, (i) the displacement pump (20) is linked to a drive shaft (10) of the drive mechanism (4) , (ii) the drive shaft (10) is rotatably supported by a bearing member (20e) arranged above the displacement pump (20) , and (iii) a lubricant-inflow prevention member (29) is provided, the lubricant-inflow prevention member (29) being integral with the bearing member (20e) and being formed by a flange (20eD) which laterally extends so as to canopy the suction end of the suction passage (20d) of the displacement pump (20) (see FIGS. 2 and 4). In accordance with an aspect of an invention of Claim 4 according to the invention, (i) a compression gas is directed in such a way as to circle round in the casing (2), (ii) the displacement pump (20) is linked to the drive shaft (10) of the drive mechanism (4) , (iii) the drive shaft (10) is rotatably supported by the bearing member (20e) , (iv) plural fixed legs (20eB) are formed on the bearing member (20e) projecting therefrom for connection to an interior surface of the casing (2) , and (v) the suction end of the suction passage (20d) of the displacement pump (20) is located in the vicinity of the fixed leg (20eB) and is provided on the downstream side of the compression gas circular flow in relation to the fixed leg (20eB) (see FIGS. 2 and 3). In accordance with an aspect of an invention of Claim 5 according to the invention, (i) a suction pipe (5) for suction of a compression gas is linked to the casing (2) , and (ii) the suction end of the suction passage (20d) of the displacement pump (20) is disposed in such a way as to face to an open end of the suction pipe (5) across the center of the drive shaft (10) of the drive mechanism (4) (see FIG. 3). In accordance with an aspect of an invention of Claim 6 according to the invention, (i) a compression gas is directed to circle round in sid casing (2), (ii) the drive mechanism (4) is disposed above the displacement pump (20) , and a vertical lubricant-recovery passage (31) for bringing a lubricant (L) from the compression mechanism (3) back to the lubricant reservoir (2c) , and (iii) the suction end of the suction passage (20d) of the displacement pump (20) is located opposite to a lower end of the lubricant-recovery passage (31) (see FIG. 3.) In accordance with the invention, when the drive mechanism (4) is driven, the compression mechanism (3) compresses a compression gas while at the same time being lubricated by the lubricant (L). During the drive operation, if the oil level goes beyond the predetermined high-limit point, it is forced downward by means of the oil-level lowering means (26) . This prevents the oil level from becoming too high, prevents the lubricant (L) from becoming resistant to the drive mechanism (4) , and prevents the drive mechanism (4) from stirring the lubricant (L) to give rise to an increase in the oil temperature. For example, oil-level rising occurring in a refrigerator is a transition phenomenon due to refrigerant contamination. An excess lubricant (L) is temporarily discharged into a refrigerant circulation circuit until the running conditions become stable, to control the oil level to fall within a predetermined range. In accordance with the invention, when the level of the lubricant (L) stored in the lubricant reservoir (2c) goes beyond the high-limit point, the discharge mechanism (27) discharges a lubricant (L) from the lubricant reservoir (2c) to lower the oil level. As a result of such arrangement, the oil level is controlled to fall within a predetermined range. In accordance with the invention, when the drive mechanism (4) drives the displacement pump (20) and when the level of the lubricant (L) stored in the lubricant reservoir (2c) goes beyond the high-limit point, an excess lubricant oil flows into the displacement pump (20) through the suction passage (20d), thereafter being supplied to the suction section (14) of the compression mechanism (3). As a result, the oil level is lowered, and the oil level can be controlled to fall within the predetermined range. In accordance with the Claim 2 invention, a lubricant that exists in a space other than the lubricant reservoir (2c) is not allowed to flow into the suction passage (20d) of the displacement pump (20) because of the provision of the lubricant-inflow prevention member (29). This ensures that a sufficient amount of lubricant is brought back to the lubricant reservoir (2c). As a result, the compression mechanism (3) is lubricated smoothly. In accordance with the Claim 3 invention, a falling lubricant toward the lubricant reservoir (2c) in the casing (2) is not allowed to enter the suction passage (20d) because of the provision of the flange (20eD) that extends over the suction passage (20d) . This prevents the displacement pump (20) from discharging too much lubricant. In accordance with the Claim 4 invention, on the downstream side of a compression gas circular flow, little or no lubricant oil circles with the compression gas. This prevents a lubricant oil from flowing in the suction passage (20d), thereby preventing the displacement pump (20) from discharging too much lubricant, as in the Claim 3 invention. In accordance with the Claim 5 invention, the suction pipe (5) and the inlet end of the suction passage (20d) are spaced apart. This prevents a lubricant, introduced from the suction pipe (5) into the casing (2) along with a compression gas, from entering the inlet end of the suction passage (20d) . In accordance with the Claim 6 invention, a lubricant, which enters the compression mechanism (3) , passes through the lubricant-recovery passage (31) , and falls towards the lubricant reservoir (2c) , flows with a compression gas circular flow in the casing (2) . This prevents a lubricant from entering the inlet end of the suction passage (20d) disposed below the lubricant-recovery passage (31) . Accordingly advantages of the present invention are as follows. According to the Claim 1 invention, the oil-level lowering means (26) is provided which, when the level of the lubricant (L) stored in the lubricant reservoir (2c) goes beyond a predetermined high-limit point, lowers such an increased oil level. As a result of this arrangement, the level of the lubricant (L) can be kept at a desired point with one compressor. The Claim 1 invention prevents the oil level from becoming too high, prevents the lubricant (L) from becoming resistant to the drive mechanism (4) , and prevents the drive mechanism (4) from stirring the lubricant (L) to give rise to an increase in the oil temperature. As a result, the occurrence of input loss and the drop in compression efficiency can be controlled. According to the Claim 1 invention, the discharge mechanism (27) is provided which discharges an excess lubricant from the lubricant reservoir (2c). The level of the lubricant (L) can be kept at a desired point with one compressor. In accordance with the Claim 1 invention, the inlet end of the displacement pump (20) connected to the lubricant takeout pipe (15) opens in such a way as to face to the high-limit point. This ensures that the oil level is lowered thereby accomplishing reliable oil-level control. In accordance with the Claim 2 invention, the lubricant-inflow prevention member (29) is provided which prevents a lubricant present in the casing's (2) internal space from being discharged by the discharge mechanism (27) . This assures that a sufficient amount of lubricant is brought back to the lubricant reservoir (2c) , therefore preventing the compression mechanism of being short of lubricant. Accordingly highly reliable oil-level control can be accomplished. In accordance with the Claim 3 invention, the flange (20eD) is formed above the inlet end of the displacement pump (20). In accordance with the Claim 4 invention, the inlet end of the displacement pump (20) is located on the downstream side of a compression gas circular flow in relation to the fixed leg (20eB) of the bearing member (20e). In accordance with the Claim 5 invention, the inlet end of the displacement pump (20) and the suction pipe (5) are spaced apart. In accordance with the Claim 6 invention, the inlet end of the displacement pump (20) is located below the lubricant-recovery passage (31) . As a result, with a simple organization, discharge of a lubricant present in the casing's (20) internal space by the discharge mechanism (27) can be prevented. Accordingly highly reliable oil-level control can be accomplished. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a sectional view of a scroll-type compressor which does not form part of the claimed invention. FIGURE 2 is a sectional view of a scroll-type compressor according to the present invention. FIGURE 3 is a top view of a bearing member and its peripheral portions. FIGURE 4 is a sectional view taken along lines V-V of FIG. 4 . FIGURE 5 is an arrow diagram in the direction of arrow VI. DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiment of the present invention is now described below by making reference to the attached drawing figures. FIGURE 1 shows a compressor (1) of a scroll type employing an oil-level controller not being part of the claimed invention. The compressor (1) is included in a refrigerant circulation circuit of a refrigerator, to high-pressure compress a refrigerant gas (i.e., a compression gas). The scroll-type compressor (1) is housed in an enclosed casing (2). The casing (2) accommodates a scroll mechanism (3) and a drive mechanism (4) . A suction pipe (5) is connected to a sidewall central portion of the casing (2) and a discharge pipe (6) is connected to a sidewall upper portion thereof. The scroll mechanism (3) has a fixed scroll (7) and a revolution scroll (8) to form a compression mechanism. The drive mechanism (4) has a motor (9) and a crankshaft (10). The motor (9) is made up of a stator (9a) fixed to an interior surface portion of the casing (2) and a rotor (9b) rotatably disposed in the stator (9a) . The crankshaft (10) runs through the center of the rotor (9b) to form a drive shaft extending towards the scroll mechanism (3). Whereas the fixed scroll (7) is formed by forming in front of an end plate (7a) a lap (7b) in an involute fashion, the revolution scroll (8) is formed by forming in front of an end plate (8a) a lap (8b) in an involute fashion. With the front of the end plate (7a) of the fixed scroll (7) and the front of the end plate (8b) of the revolution scroll (8) facing each other, the fixed scroll (7) and the revolution scroll (8) are disposed in vertical, parallel relationship. The lap (7b) and the lap (8b) are engaged with each other. A side of the lap (7b) is in contact with a side of the lap (8b) at plural points. Formed between such contact sections is a compression chamber (3a) . Formed at the center of the end plate (7a) of the fixed scroll (7) is a refrigerant outlet end (7c) in communication with the compression chamber (3a) as well as in communication with an upper space (2a) of the casing (2) . The fixed scroll (7) has a mount portion (7d) dependent from a peripheral edge of the end plate (7a) . The fixed scroll (7) is fixed, at the mount portion (7d) , to an interior surface portion of the casing (2) . Mounted at the rear of the end plate (8a) of the revolution scroll (8) is a scroll shaft (8d) with a bearing hole (8c) at the center thereof. A stationary frame (11) , which is located on the rear side of the revolution scroll (8) , is fixedly displaced in the center of the casing (2) . The crankshaft (10) vertically penetrates the frame (11) through a bearing (12). The crankshaft (10) has a crank main shaft (10a) attached to the rotor (9b) of the motor (9) and a coupling pin (10b) off-centered from the axis (01) of the crankshaft (10). The coupling pin (10b ) is inserted, through a bearing (8e), into the bearing hole (8c) of the scroll shaft (8d). Therefore the scroll shaft (8d) (the axis (02)) and the crankshaft (10) are not co-axial. A peripheral portion of the frame (11) is fixed to an interior surface portion of the casing (2) . A peripheral upside of the frame (11) and an underside of the mount portion (7d) of the fixed scroll (7) are joined together. The end plate (8a) of the revolution scroll (8) is mounted on an upside of the frame (11) and the revolution scroll (8) is supported by the frame (11). Mounted between the frame (11) and the end plate (8a) of the revolution scroll (8) is an Oldham's mechanism, not shown in the figure, whereby the revolution scroll (8) moves in a circular orbit without rotating, with respect to the fixed scroll (7) . A suction chamber (14) is defined between the laps (7b, 8b) and the mount portion (7d) of the fixed scroll (7). Located below the frame (11) is a balancer (10c) of the crankshaft (10). A lubricant reservoir (2c) for storing a lubricant (L) is formed at the bottom of a lower space (2b) of the casing (2) . An oil feed passage (not shown) is formed extending through the crankshaft (10) . This oil feed passage extends from the lower end of the crankshaft (10) to the upper end of the coupling pin (10a). The lower end of the crankshaft (10) is soaked in the lubricant (L) stored in the reservoir (2c) . A centrifugal pump (10d) is mounted at the lower end of the crankshaft (10). As the crankshaft (10) rotates, the centrifugal pump (10d) operates, and the lubricant (L) is supplied via the oil feed passage to the bearings (8e, 12) and to the scroll mechanism (3). An advantage of this construction is a lubricant takeout pipe (15) that is connected to an exterior sidewall portion of the casing (2) . The lubricant takeout pipe (15) extends vertically. The lubricant takeout pipe (15) has an outlet end (15a) (i.e., the upper end) and an inlet end (15b) (the lower end). The outlet end (15a) , on the one hand, is in communication with the suction chamber (14) via the casing (2) and the mount portion (7d) of the fixed scroll (7). The inlet end (15b) , on the other hand, is in communication with the lower space (2b) of the casing (2) via a portion of the casing (2) under the motor (9) . The position of the inlet end (15b) of the lubricant takeout pipe (15) is described in detail. The inlet end (15b) is located slightly below the rotor (9b) of the motor (9) . In other words, when the level of the lubricant (L) stored in the lubricant reservoir (2c) goes up to a point close to the lower end of the rotor (9b) indicated by imaginary line L2 of FIG. 1 (hereinafter called the high-limit point), the inlet end (15b) of the lubricant takeout pipe (15) becomes flush with the level of the lubricant (L). An oil-level lowering means (26) acting as a discharge mechanism (27) of the present invention is implemented by the lubricant takeout pipe (15). As shown in FIG. 1 , a lubricant-recovery passage (16) for bringing a lubricant reaching the upper space (2a) of the casing (2) back to the lubricant reservoir (2c) is formed so as to pass through the mount portion (7d) of the fixed scroll (7) and a peripheral portion of the frame (11) . The upper space (2a) of the casing (2) is provided with a demister (17) for collecting a lubricant (L) flowing in the lubricant-recovery passage (16). The operation of the scroll-type compressor (1) is explained. When the motor (9) is activated to rotate the crankshaft (10) , the revolution scroll (8) moves in a circular orbit without rotating, with respect to the fixed scroll (7) . A refrigerant is first introduced through the suction pipe (5) into the casing (2). The refrigerant then passes through the suction chamber (14) to reach the compression chamber (3a) of both the scrolls (7, 8) where the refrigerant is compressed. The refrigerant is discharged from a refrigerant outlet end (7c) of the fixed scroll (7) to, via the upper space (2a) of the casing (2) , the discharge pipe (6) out of which the refrigerant is discharged to a refrigerant circulation circuit. During the compression operation a lubricant (L) is supplied to each bearing (12, 8e) and to the scroll mechanism (3) , via the foregoing oil feed passage of the crankshaft (10). The advantage of this construction is demonstrated when the level of the lubricant (L) stored in the lubricant reservoir (2c) goes up. This is explained below. Under the normal running conditions the level of the lubricant (L) stored in the lubricant reservoir (2c) is in line with imaginary line L1 of FIG. 1 . However, when the compressor (1) has been put out of service for a long time, a liquid refrigerant is likely to "fall asleep". Additionally, when the compressor (1) is run under humid atmosphere conditions, a liquid refrigerant returns to the compressor (1) to be mixed with the lubricant (L) stored in the lubricant reservoir (2c) . As a result, the level of the lubricant (L) moves up to near the lower end of the rotor (9b) of the motor (9) . If the oil level goes beyond the high-limit point indicated by imaginary line L2 of FIG. 1 , then the inlet end (15b) of the lubricant takeout pipe (15) becomes ready for accepting an excess lubricant. The suction chamber (14) in communication with the outlet end (15a) of the lubricant takeout pipe (15) is in a high negative pressure atmosphere resulting from revolution movement by the revolution scroll (8) . The suction chamber (14) is in a low pressure state in comparison with the lower space (2b) of the casing (2) in communication with the inlet end (15b) of the lubricant takeout pipe (15) . Because of such a difference in pressure between the chamber (14) and the space (2b) , part of the lubricant (L) (i.e., a surface lubricant) flows into the lubricant takeout pipe (15) and climbs up therethrough. The lubricant (L) is supplied from the lubricant takeout pipe (15) to the suction chamber (14) . With the compression operation of the refrigerant, the lubricant (L) is discharged, along with a high-pressure refrigerant, from the compression chamber (3a) to the discharge pipe (6) , via the refrigerant outlet end (7c) and the upper space (2a) . To sum up, of the lubricant (L) stored in the lubricant reservoir (2c) an excess lubricant automatically flows into the inlet end (15b) of the lubricant takeout pipe (15) and is discharged into a refrigerant circulation circuit of the refrigerator. The level of the lubricant (L) of the lubricant reservoir (2c) is lowered accordingly. The repetition of such operations prevents the level of the lubricant (L) stored in the lubricant reservoir (2c) from going beyond the inlet end (15b) of the lubricant takeout pipe (15a). Accordingly the level of the lubricant (L) is kept at a desired point. Particularly for the case of refrigerators, an increase in the oil level is just a transition phenomenon created by, for example, refrigerant contamination. Therefore the oil level can be controlled to fall within a predetermined range by temporarily discharging an excess lubricant to a refrigerant circulation circuit until the refrigerator goes in the stable running conditions. Since the lubricant level will not go beyond a predetermined point, this prevents the area of the crankshaft (10) that is soaked in the lubricant (L) from increasing and the rotor (9b) is not soaked in the lubricant (L) . As a result of this, the lubricant (L) is no longer a cause of producing resistance against the rotation of the crankshaft (10) and the rotor (9b) , and extra input to keep the rotation of the crankshaft (10) constant becomes unnecessary. Neither the crankshaft (10) nor the rotor (9b) stirs the lubricant (L) . The increase in the oil temperature can be suppressed, so that the increase in the temperature in the entire interior space of the casing (2) can be suppressed. Therefore the drop in the compression efficiency becomes avoidable. THE PREFERRED EMBODIMENT The preferred embodiment of the present invention is now explained by making reference to FIG. 2. Referring now to FIG. 2, therein is illustrated the scroll-type compressor (1) of the preferred embodiment. Provided at the lower end of the crankshaft (10) is a trochoid pump (20) (i.e., a displacement pump). The trochoid pump (20) includes a pump casing (20b) in which a pump chamber (20a) is formed and an impeller (20c) which is housed in the pump casing (20b) and which rotates with the crankshaft (10) . The trochoid pump (20) performs predetermined pump operations as the impeller (20c) rotates. Located above the pump casing (20b) is a bearing member (20e) for supporting the lower end of the crankshaft (10). Defined between the bearing member (20e) and the pump casing (20b) is the foregoing pump chamber (20a). A suction passage (20d) is formed in the trochoid pump (20) , penetrating the bearing member (20e) . As the suction passage (20d) goes up, it inclines outwardly. The suction passage (20d) opens at one end near the upper-end square section of the bearing (20e) . The upper end of the suction passage (20d) acting as an inlet end is located below the rotor (9b) of the motor (9) . When the level of the lubricant (L) of the lubricant reservoir (2c) goes up to near the lower end of the rotor (9b) (i.e., line L2 of FIG. 2), the lubricant (L) flows into the inlet end of the suction passage (20d). A coupling pipe (15c) is connected between the lubricant takeout pipe (15) and the trochoid pump (20) . In this way, the oil-level lowering means (26) acting as a discharge mechanism (27) is implemented by the trochoid pump (20) and the lubricant takeout pipe (15). How in the preferred embodiment a lubricant is discharged is explained below. During the drive operation of the compressor (1) the impeller (20c) of the trochoid pump (20) is rotated in the pump chamber (20a) by the crankshaft (10) , whereupon a fluid, introduced at the inlet end of the suction passage (20d) , is discharged to the coupling pipe (15c) . In such a situation, the level of the lubricant (L) in line with line L1 of FIG. 2 may go up to near the lower end of the rotor (9b) of the motor (9) because of liquid refrigerant contamination. If the oil level goes beyond the high-limit point (line L2 of FIG. 2), part of the lubricant (L) flows into the inlet end of the suction passage (20d) . The lubricant (L) then flows into the lubricant takeout pipe (15) via the pump chamber (20a) and the coupling pipe (15c). Thereafter the lubricant (L) climbs up the lubricant takeout pipe (15) and is supplied to the suction chamber (14) from the outlet end (15a) of the lubricant takeout pipe (15). Then the lubricant (L), with the compression operation of a refrigerant, is discharged to the discharge pipe (6) together with a high-pressure refrigerant, by way of the refrigerant outlet end (7c) and the upper space (2a) . Because of the repetition of such operations the present invention prevents input loss due to an excess oil-level and the drop in compression efficiency due to an oil temperature increase. In accordance with the present embodiment, the oil level is lowered by the discharge operation of the trochoid pump (20) , which ensures that the oil-level is lowered adequately. This accomplishes reliable oil-level control. MODIFICATION OF PREFERRED EMBODIMENT A modification of the preferred embodiment using the trochoid pump (20) will be described below. This modification is intended to prevent a falling lubricant (L) towards the lubricant reservoir (2c) in the casing (2) or a mist-like lubricant (L) flowing with a refrigerant that circles in the casing (2) , from entering the pump chamber (20a) of the trochoid pump (20) . The trochoid pump (20) is originally provided to discharge an excess lubricant from the lubricant reservoir (2c) of the casing (2) . If, however, a lubricant (L) on the way back to the lubricant reservoir (2c) or a lubricant (L) flowing in the casing (2) is discharged outside, then the lubricant reservoir (2c) will be short of lubricant. As a result, the oil level becomes too low. This may produce the problem that the scroll mechanism (3) is not lubricated smoothly. To prevent the occurrence of the above-noted problem, the following four structures are proposed with respect to the discharge mechanism (27) . Before starting describing these four structures, how the bearing member (20e) in which the suction passage (20d) is formed is explained. FIGURE 3 is a top plan view showing the bearing member (20e) and its peripheries. FIGURE 4 is a sectional view taken along lines V-V of FIG. 3. As seen from FIGS. 3 and 4, the bearing member (20e) has a tubular bearing body (20eA) and three fixed legs (20eB, 20eB, 20eB). These three fixed legs (20eB, 20eB, 20eB), spaced at 120 degrees, extend radially from a peripheral surface of the bearing body (20eA) and are fixed to interior surface portions of the casing (20) . A bering hole (20eC) is formed through the bearing body (20eA) . The crankshaft (10) is inserted into the bearing hole (20eC) extending therethrough. Provided between the underside of the bearing member (20e) and the pump casing (20b) is a spacer (30) . The pump chamber (20) is formed within the pump casing (20b) . The foregoing prevention means for preventing the trochoid pump (20) from discharging a falling lubricant (L) or a flowing lubricant in the casing (2) are explained in detail. The scroll-type compressor (1) is designed as follows. A refrigerant, introduced from the suction pipe (5) , flows counterclockwise (arrow A) within the casing (2) , and the refrigerant is introduced into the suction chamber (14) of the scroll mechanism (3) , and a mist-like lubricant (L) flows with the refrigerant that circles in the casing (2). PREVENTION MEANS 1 A first prevention means is described. As shown in FIG. 4, the first prevention means is formed by a flange (20eD) of the bearing member (20e). The flange (20eD) is a rim extending outwardly from an upper end portion of the bearing member (20e) . The flange (20eD) is formed all around the bearing member (20e) . In other words, the bearing body (20eA) has an upper section with a greater diameter than the remaining other sections thereof. The suction passage (20d) has a vertical section (20dA) which vertically extends through the bearing body (20e) and whose lower end is connected, via the spacer (30), to the pump chamber (20a), and a lateral section (20dB) which extends in a lateral, outward direction from the upper end of the vertical section (20dA). The lateral section (20dB) has an inlet end located near and below the flange (20eD) of the bearing body (20eA) . In other words, the flange (29eD) canopies the inlet end of the lateral section (20dB) . The flange (20eD) constitutes a lubricant-inflow prevention means (29) of the present invention. The flange (29eD) prevents a lubricant (L) , which falls towards the lubricant reservoir (2c) after lubricating the scroll mechanism (3), from entering the lateral section (20dB) of the suction passage (20d) (see dot-dash line arrow of FIG. 4). That is, the trochoid pump (20), only when the level of the lubricant (L) stored in the lubricant reservoir (2c) of the casing (2) reaches the inlet end of the lateral section (20dB) (line L2 of FIG. 4), discharges an excess lubricant. As a result, unnecessary discharge of the lubricant (L) can be prevented. Second to fourth prevention means are explained. In these prevention means, the suction passage (20d) is formed in a different location and the positional relationship of the suction passage (20d) with the other members is modified. PREVENTION MEANS 2 The second prevention means is directed to the inlet end of the suction passage (20d). More specifically, as shown in FIGS. 3 and 5, the inlet end of the lateral section (20dB) of the suction passage (20d) is located next to a counterclockwise sidewall in FIG. 3 in relation to the fixed leg (20eB). Because of the above-described structure, during the drive operation, the circular flow of a refrigerant introduced from the suction pipe (5) into the casing (2) branches out, around the fixed leg (20eB), into an upper flow that flows over the fixed leg (20eB) (arrow B of FIG. 5) and a lower flow that flows under the fixed leg (20eB) (arrow C). As a result, there is little or no flow of the refrigerant around the inlet end of the lateral section (20dB) located next to the fixed leg (20eB) . Accordingly a mist-like lubricant (L) that flows with a refrigerant is controlled not to enter the suction passage (20d). In other words, the fixed leg (20eB) constitutes the lubricant-inflow prevention member (29). The trochoid pump (20), only when the level of the lubricant (L) stored in the lubricant reservoir (2c) of the casing (2) reaches the inlet end of the lateral section (20dB) (line L2 of FIG. 4), discharges an excess lubricant. As a result, unnecessary discharge of the lubricant (L) can be prevented. PREVENTION MEANS 3 The third prevention means relates to the formation location of the suction passage (20d). As shown in FIG. 3, the suction passage (20d) is formed such that the suction passage (20d) and the suction pipe (5) face each other across the center (0) of the casing (2). In other words, the inlet end of the lateral section (20dB) of the suction passage (20d) and the suction pipe (5) are spaced apart. As a result of such an arrangement that the suction pipe (5) is separated from the inlet end of the lateral section (20dB) , a mist-like lubricant (L) , introduced into the casing (2) from the suction pipe (5) together with a refrigerant, is controlled not to enter the lateral section (20dB). No lubricant other than the lubricant (L) stored in the lubricant reservoir (2c) of the casing (2) is likely to enter the lateral section (20dB) of the suction passage (20d). Unnecessary discharge of the lubricant (L) can be prevented. PREVENTION MEANS 4 The fourth prevention means is directed to the formation location of the suction passage (20d). As represented by imaginary line of FIG. 3, the stator (9a) of the motor (9) disposed above the bearing member (20e) has on its peripheral edge four notches (9c, 9c, 9c, 9c) . Each notch (9c) works to bring a lubricant (L), which goes down in the casing (2) after lubricating the scroll mechanism (3), back to the lubricant reservoir (2c) . The upper and lower spaces of the motor (9) are connected together by the notches (9c, 9c, 9c, 9c). In other words, the provision of the notches (9c, 9c, 9c, 9c) form lubricant-recovery passages (31, 31, 31, 31) . In accordance with the fourth prevention means, the inlet end of the lateral section (20dB) of the suction passage (20d) and a lubricant-recovery passage (31) are disposed at circumferentially the same location. In other words, the inlet end of the lateral section (20dB) and the lubricant-recovery passage (31) face each other in the radial direction of the casing (2) . During the drive operation, a lubricant (L) , which falls towards the lubricant reservoir (2c) from the scroll mechanism (3) through the lubricating recovery passage (31) opposite to the inlet end of the lateral section (20dB), flows counterclockwise because a refrigerant circles in the casing (2) (arrow D of FIG. 3). As a result, the lubricant (L) is controlled not to flow into the suction passage (20d) at the inlet end of the lateral section (20dB). The trochoid pump (20), only when the level of the lubricant (L) stored in the lubricant reservoir (2c) of the casing (2) reaches the inlet end of the lateral section (20dB) (line L2 of FIG. 4), discharges an excess lubricant. As a result, unnecessary discharge of the lubricant (L) can be prevented. As described above, the first to fourth prevention means each prevent a falling lubricant towards the lubricant reservoir (2c) or a flowing lubricant that flows with a refrigerant that circles in the casing (2), from entering the pump chamber (20a) of the trochoid pump (20) . Accordingly the scroll mechanism (3) can be lubricated smoothly, since it is assured that a sufficient amount of lubricant is brought back to the lubricant reservoir (2c) thereby preventing the level of the lubricant (L) from becoming too low. In comparison with a technique that uses the trochoid pump (20) of FIG. 2 to lower the oil level, each prevention means can provide more effective oil-level lowering operations. More reliable oil-level control is accomplished. The preferred embodiment of the present invention has been described in the event of refrigerating compressors. However, the present invention may be practiced in a compressor mounted on a different types of apparatus. Further, the present invention may be useful for rotary piston-type compressors. The preferred embodiment has been described in terms of a refrigerator with a single scroll-type compressor (1). However, the present invention may be applicable in a refrigerator with plural compressors in parallel relationship. In such a case, a plurality of compressors each having lubricant takeout pipes (15, 22) of the present invention are connected together in parallel relationship and oil-level control of each of the compressors can be accomplished. Accordingly, unlike a forced differential pressure method that produces the problem that the drop in internal pressure with the loss of suction pressure occurs, the present invention provides the advantage that the drop in performance of a compressor provided on the low-pressure side can be prevented. The present invention provides a high-performance refrigerator which has a structure free from the loss of suction pressure and which accomplishes improved oil-level control. INDUSTRIAL APPLICATION The present invention finds applications in refrigerating compressors, particularly in a compressor in which the oil level varies due to a liquid stream.

Claims: Compressor, including a casing (2), a compression mechanism (3) for compressing a compression gas, said compression mechanism (3) being housed in said casing, a lubricant resevoir (2c) for storing a lubricant (L), said lubricant reservoir (2c) being formed at the bottom of said casing (2) and said lubricant (L) being applied from said lubricant reservoir (2c) to said compression mechanism (3), a drive mechanism (4) for driving said compression mechanism (3), said drive mechanism (4) being housed in said casing (2), and an oil-level controller which is an oil-level lowering means (26), comprising a discharge mechanism (27) capable of discharging said lubricant (L) out of said lubricant reservoir (2c), whereby when the level of said lubricant (L) goes beyond a predetermined high-limit point said oil-level lowering means brings said excess level down to said predetermined high-limit point, characterized in that said discharge mechanism (27) has a displacement pump (20) driven by means of said drive mechanism (4) and a lubricant takeout pipe (15) with an inlet end in communication with an outlet end of said displacement pump (20) and in that a suction passage (20d) formed in said displacement pump (20) has an inlet end that opens at the same level as said predetermined high-limit point. Compressor according to claim 1, characterized in that a lubricant-inflow prevention member (29) is disposed in the vicinity of said inlet end of said suction passage (20d) of said displacement pump (20), said prevention member (29) preventing a lubricant (L) present in said casing (2) from flowing into said suction passage (20d). Compressor according to claim 2, characterized in that said displacement pump (20) is linked to a drive shaft (10) of said drive mechanism (4), said drive shaft (10) is rotatably supported by a bearing member (20e) arranged above said displacement pump (20) and said lubricant-inflow prevention member (29) is integral with said bearing member (20e) and is formed by a flange (20eD) which laterally extends so as to canopy said suction end of said suction passage (20d) of said displacement pump (20). Compressor according to any one of claims 1-3, characterized in that a compression gas is directed in such a way as to circle round in said casing (2), said displacement pump (20) is linked to said drive shaft (10) of said drive mechanism (4), said drive shaft (10) is rotatably supported by said bearing member (20e), plural fixe legs (20eB) are formed on said bearing member (20e) projecting therefrom for connection to an interior surface of said casing (2), said suction end of said suction passage (20d) of said displacement pump (20) is located in the vicinity of said fixed leg (20eB) and is provided on the downstream side of said compression gas circular flow in relation to said fixed leg (20eB). Compressor according to any one of claims 1-4, characterized in that a suction pipe (5) for suction of a compression gas is linked to said casing (2), said suction end of said suction passage (20d) of the displacement pump (20) is disposed in such a way as to face to an open end of said suction pipe (5) across the center of said drive shaft (10) of said drive mechanism (4). Compressor according to any one of claims 1-5, characterized in that a compression gas is directed to circle round in said casing (2), said drive mechanism (4) is disposed above said displacement pump (20), and a vertical lubricant-recovery passage (31) for bringing a lubricant (L) from said compression mechanism (3) back to said lubricant reservoir (2c), said suction end of said suction passage (20d) of said displacement pump (20) is located opposite to a lower end of said lubricant-recovery passage (31).

Inventors: KITAURA HIROSHI, KOMORI KEIJI, MATSUURA HIDEKI, KITAURA, HIROSHI, KOMORI, KEIJI, MATSUURA, HIDEKI, KITAURA, Hiroshi, Rinkai Factory, Sakai Plant,, KOMORI, Keiji, Rinkai Factory, Sakai Plant,, MATSUURA, Hideki, Rinkai Factory, Sakai Plant,
Applicants: DAIKIN IND LTD, DAIKIN INDUSTRIES, LTD.
Application year: 1995
Main classification: F04C29
IPC codes: F04C29, F04B39, F04C28