US3548612A

US3548612A - Refrigerating compressor with oil cooler

Info

Publication number: US3548612A
Application number: US794096*A
Authority: US
Inventors: Mamoru Mitsubayashi; Yasuhiko Muraishi; Kazuichi Nishitsuji
Original assignee: Tokyo Shibaura Electric Co Ltd
Current assignee: Toshiba Corp
Priority date: 1969-01-27
Filing date: 1969-01-27
Publication date: 1970-12-22
Anticipated expiration: 1987-12-22

Description

United States Patent O 3,548,612 REFRIGERATING COMPRESSOR WITH OIL COOLER Mamoru Mitsubayashi, Yasuhiko Muraishi and Kazuichi Nishitsuji, Numazu-shi, Shizuoka-ken, Japan, assignors, by mesne assignments, to Tokyo Shibaura Denki Kabushiki Kaisha, also known as Tokyo Shibaura Electric Co., Ltd., Kawasaki-shi, Kan-agawa-ken, Japan, a jointstock company of Japan Filed Jan. 27, 1969, Ser. No. 794,096 Int. Cl. F25!) 43/02 US. Cl. 62469 3 Claims ABSTRACT OF THE DISCLOSURE In a hermetically sealed type compressor, an oil cooler is provided to cool the lubricant contained in a casing which encloses the compressor, and a portion of a liquid refrigerant is circulated through the oil cooler from the condenser to cool the lubricant and compressor. In a modified embodiment an ejector is connected between the compressor and condenser to enhance circulation of the refrigerant through the oil cooler.

BACKGROUND OF THE INVENTION This invention relates to refrigerating apparatus and more particularly to an improved device for preventing overheating of hermetically enclosed type refrigerant compressors.

A recent trend in refrigerating apparatus requires compressors of small size, light weight and high efficiency. To meet these requirements, compressor driving motors have been changed from four-pole to two-pole type to double their speed and to decrease piston displacement per cylinder thus decreasing their physical size. In compressors driven by four-pole motors, temperature rise during operation of the refrigerator is not excessive because the speed of motors and compressors is relatively low, and, hence, the quantity of heat generated thereby is small, and because the motor compressors are relatively massive and, hence, have a large heat dissipating surface. However, in high-speed compressors driven by two-pole type motors, as the quality of heat generated is increased and as their physical size is greatly reduced, the temperature rise of the compressors is much higher than that of compressors driven by four-pole type motors, so that under certain operating conditions, they are overheated, thus causing defective operation of failure. Especially in compressors used in low-temperature refrigerating apparatus operating at temperatures as low as 40 C. or lower, the temperature of the compressors rises excessively due to the relatively small quantity of gaseous refrigerant circulating through the refrigerating system and high compression ratio of the refrigerant, thus giving rise to such trouble as decrease in the compressor efficiency, deterioration of the lubricating oil for the compressors, which in turn causes seizure of bearings, damage to valves, burning out of driving motors, etc.

A conventional motor-driven compressor is sealed in a casing, and the motor-compressor assembly is resiliently supported in the casing by spring means. A quantity of lubricant is contained in the bottom of the casing to lubricate rotary parts of the motor and compressor. Usually a heat exchanger or an oil cooler is provided in the body of the lubricant. Cooling water is circulated through the oil cooler in parallel with a condenser for the compressed refrigerant whereby overheating of the compressor is prevented. The cooling effect of the oil cooler, however, gradually decreases due to accumulation of scale therein. In household refrigerators, as the overall size of the motor compressor has been decreased by the adoption of high-speed machines, the size of the oil cooler is also limited. For this reason, a small accumulation of scale greatly reduces the cooling effect, thus causing overheating. When the refrigerator is not used, as in winter, the cooling water remaining in the oil cooler often freezes to break the oil cooler. To prevent this, it is usually to provide a drain cock for the oil cooler. However, as the oil cooler is disposed in the bottom of the compressor casing, such a drain cock must be positioned beneath the compressor casing, which requires difficult work. Even when such a drain cock is provided the user may often forget to operate the drain cock.

SUMMARY OF THE INVENTION It is therefore an object of this invention to provide a new and improved refrigerating apparatus in which the above mentioned defects are eliminated.

Another object of this invention is to provide a novel refrigerator wherein the lubricant for a motor-driven compressor contained in a sealed casing is cooled by the evaporation of a portion of the liquified refrigerant.

Still another object of this invention is to provide an improved lubricant cooler for a sealed type compressor including means to create forced circulation of the liquid refrigerant through the lubricant cooler.

According to this invention a portion of the liquid refrigerant condensed in the condenser is caused to circulate through the oil cooler contained in a sealed casing accommodating a motor compressor. According to a modified embodiment of this invention, an ejector is included in a conduit between the compressor and the condenser to induce forced circulation of the refrigerant through the oil cooler. Where the quantity of refrigerant circulating through the refrigerating system is small, as in the case of low temperature operation, the ejector is positioned at substantially the same level as the oil cooler to enhance circulation of the refrigerant through the oil cooler. In this case a capillary tube is connected in parallel with the ejector to prevent back flow of the liquid refrigerant to the compressor.

BRIEF DESCRIPTION OF THE DRAWING The invention can be more fully understood from the following description taken in conjunction with the accompanying drawing in which:

FIG. 1 is an elevation, in vertical section, of a sealed type motor compressor provided with an oil cooler;

FIGS. 2, 3 and 4 are diagrams of three different embodiments of this invention; and

FIG. 5 is a longitudinal section of an ejector utilized in the embodiments shown in FIGS. 3 and 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1 which shows a vertical section of a sealed type motor compressor 1 for household refrigerators. A compressor 20 and its driving motor 21 are resiliently supported in a hermetically sealed casing 18 by means of suitable supporting springs 19 (only one is shown). To lubricate bearings, cylinders and other sliding parts 22, a quantity of lubricating oil 23 is contained in the bottom of casing 18, and an oil cooler 8 in the form of a spiral coil is immersed in lubricating oil 23.

As diagrammatically shown in FIG. 2, a high-temperature, high-pressure gaseous refrigerant compressed by motor compressor 1 is conveyed to a condenser 3 via a conduit 2. Condenser 3 is cooled by suitable means such as a water cooled coil 9. Condensed refrigerant then passes to an evaporator 6 via a conduit 4 and a through or expansion valve 5. Gaseous refrigerant generated in the evaporator then passes to motor compressor 1 and Dec. 22, 1970 MAMQRU WTSUBAYASHI ET AL 3,54%,632

REFRIGERATING COMPRESSOR WITH OIL COOLER Filed Jan. 27', 1969 MAMORU MITSUBAYASHI, YASUHIKO MURAISHI and KAZUICHI NISHITSUJI,

INVENTORS ATTORNEY