US3514225A

US3514225A - Motor driven compressors for refrigerating machines

Info

Publication number: US3514225A
Application number: US738189A
Authority: US
Inventors: Tuneo Monden; Makoto Watanabe
Original assignee: Tokyo Shibaura Electric Co Ltd
Current assignee: Toshiba Corp
Priority date: 1967-06-21
Filing date: 1968-06-19
Publication date: 1970-05-26
Anticipated expiration: 1987-05-26

Description

y 1970 TUNEO MONDEN ETAL 3,514,225

MOTOR DRIVEN COMPRESSORS FOR REFRIGERATING MACHINES Filed June 19. 1968 F I G.

EVAPORATOR INVENTOR5 United States Patent 3,514,225 MOTOR DRIVEN COMPRESSORS FOR REFRIGERATIN G MACHINES Tuneo Monden, Tokyo, and Makoto Watanabe, Kawasakishi, Japan, assignors to Tokyo Shibaura Electric Co., Ltd., Kawasaki-shi, Japan, a corporation of Japan Filed June 19, 1968, Ser. No. 738,189 Claims priority, application Japan, June 21, 1967, 42/ 39,811 Int. Cl. F04c 29/02 US. Cl. 230--207 2 Claims ABSTRACT OF THE DISCLOSURE In a motor driven compressor for a refrigerator comprising a hermetically sealed casing containing the motor compressor and lubricant a suction cup is connected in series with a suction pipe and is maintained in heat exchange relationship with the lubricant.

BACKGROUND OF THE INVENTION This invention relates to a motor driven compressor for a refrigerating machine and more particularly to a motor driven rotary compressor contained in a hermetically sealed casing especially suitable for use in room air conditioners and the like.

In a refrigerating system comprising a motor driven compressor, a condenser and an evaporator the gaseous refrigerant compressed by the compressor is liquidified in the condenser and the liquid refrigerant is then supplied to the evaporator through a capillary tube to be evaporated therein. The gaseous refrigerant in the evaporator is sucked into a cylinder of the compressor through a suction pipe.

In such a refrigerating system, liquid refrigerant in the evaporator may not completely evaporate when the room air conditioner is restarted after a long period of idleness, or the evaporator is excessively cooled, or the quantity of refrigerant sealed in is excessive. In such a case there is a tendency that the liquid refrigerant is entrained in the gaseous refrigerant sucked into the compressor so that so-called liquid compression occurs. As a result, there occur many difficulties such as damage to the discharge valve or other portions of the compressor and seizure of the driving shaft due to excessive compression force. This is especially dangerous in the so-called high pressure type compressor in which the interior of the sealed casing of the motor compressor is maintained at a high pressure because the volume between the suction pipe and the compressor cylinder is extremely small. Further, compression of the gaseous refrigerant in the compressor creates fluctuation in the pressure of the compressed gas in the sealed casing, thus causing noise.

SUMMARY OF THE INVENTION In accordance with this invention, a suction cup having a predetermined volume or space is connected in a suction passage of the gaseous refrigerant to the compressor in such a position that the cup is at least partially immersed in the lubricating oil contained in the bottom of the sealed casing so as to vaporize or separate the liquid refrigerant thus preventing liquid compression and damage of the discharge valve and other portions of the compressor.

As the suction cup has a predetermined volume it can reduce the pressure pulsation caused by the compression of gaseous refrigerant in the cylinder, thus acting as an intake muflier to eliminate noise. It is advantageous to cause the lubricating oil which has completed its lubricating function and is returning from the upper chamber 3,514,225 Patented May 26, I970 "ice to the lower chamber in the sealed casing to drop on the suction cup to effectively cool the lubricant.

BRIEF DESCRIPTION OF THE DRAWING Further object and advantages of the invention can be more fully understood from the following description taken in connection with the accompanying drawing in which:

FIG. 1 shows an elevational view, partly in section, of a motor driven rotary compressor provided with a suct on cup connected in series with a suction pipe; and

FIG. 2 shows a cross-section taken along a line II-II in FIG. 1 and viewed in the direction of arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the accompanying drawing illustrating a preferred embodiment of this invention, a rotary compressor shown in FIG. 1 comprises a hermetically sealed casing 1 consisting of interfitted upper and lower casing halves 2 and 3, an electric motor 4, a frame 5 also acting as a bearing and a compressor 6 contained in the casing. A stator core 8 having a stator coil 7 of the electric motor 4 is secured to the iner wall of the upper casing half as by force fit. The rotor rotating in the stator core 8 with an air gap 9 therebetween is provided with axial air ducts 11 and

spiral oil grooves

13a and 13b are formed on the lower portion of a motor shaft 12. The frame 5 comprises an annular fitting member 15, a horizontal partition 14 and a central bearing member 17 adapted to journal the motor shaft 12 and a flange .16. The fitting member 15 is force fit in the lower portion of the upper casing half 2 beneath the stator core 8, while the flange 16 is fit in the overlapped portion 18 of upper and lower casing halves 2 and 3. The horizontal partition 14 is provided with a perforation 19 intercommunicating the upper chamber containing the motor and the lower chamber containing a compressor 6 and a perforation 20 adapted to interconnect the interior of the upper casing half 2 and a muffler chamber of the compressor to be described later. The compressor comprises a cylindrical rotor 22 fit around an eccentric 21 formed on the lower end of the motor shaft 12 and a hollow cylinder 23 which is securely fixed to the horizontal partition 14 of the frame 5 by means of bolts 25 together with an end plate 24. As shown in FIG. 2 of the cylinder 23 is formed with a cylindrical chamber 26 containing the eccentric 21 of the shaft .12 and rotor 22. Chamber 26 is divided into a low pressure gas chamber 26a and a high pressure gas chamber 26b by means of a slidable blade or vane 30 which is normally urged against the inner periphery of the cylinder by a compression spring 29. A muffler chamber 31 is formed in the cylinder which is communicated with the perforation 20 extending through the horizontal partition 14 and with the high pressure gas chamber 26b through a discharge port 32 which is normally closed by a discharge valve 33, the movement thereof being limited by a stop 34. A body of lubricating oil 35 is contained in the bottom of the lower casing half 5.

One of the features of this invention lies in the provision of a suction cup 36 having a predetermined volume and connected between

suction pipes

27a and 27b which convey gaseous refrigerant to a suction port 28 of the cylinder 23. As shown in the drawing, the suction cup 36 is disposed in a space between cylinder 23 and lower casing half 3 to partially dip in lubricant 35. As shown in FIG. 1, the suction pipe 27a is connected to the lower portion of the suction cup 36 whereas the suction pipe 27b is connected to the upper portion. Further, the suction cup 36 is disposed immediately beneath the perforation 19 extending through the horizontal partition 14.

The compressor of this invention operates as follows: Upon energization of electric motor 4 the eccentric 21 of its shaft 12 rotates eccentrically about the axis thereof. As a result, the rotor 22 is caused to roll along the inner surface of the cylinder so that the gaseous refrigerant is sucked into the low pressure gas chamber 26a and the gaseous refrigerant in the high pressure gas chamber is compressed to a high pressure until finally discharged into the mufller chamber 31 through discharge valve 33. The high pressure gas is then discharged into the upper casing half 2 and supplied to a condenser through a discharge pipe 37.

The lubricating oil 35 contained in the bottom of the lower casing half 3 serves to lubricate movable parts and to provide gastight seal between high and low pressure sides. More particularly, the oil pumped up by the rotation of motor shaft 12 is fed to

spiral oil grooves

13a and 13b through an oil duct 38 extending through shaft 12. The oil supplied to groove 13b is supplied under pressure to the interior of the cylinder 23, especially into the low pressure gas chamber 26a, but major portion of the pumped up oil is supplied to the bearing member 17 through the oil groove 13a, then flows down on the partition wall 14 and finally returns to the bottom of the lower casing half 3 through perforation 19.

The oil supplied into the cylinder 23 via spiral oil groove 13b forms oi lseals in a gap of several tens microns between the rotor 22 and the inner surface of the cylinder and in gaps between the end surfaces of the rotor 22 and the lower surface of partition 14 and the upper surface of end plate 24. Since the oil utilized to form these oil seals is under high pressure it is supplied to the low pressure gas chamber 26a through a slot slidably receiving the blade 30 and through end gaps of the rotor.

Another feature of this invention lies in the provision of the suction cup 36 having a predetermined volume at an intermediate point of the suction pipe to be immersed in the lubricating oil 35. This suction cup serves to vaporize or separate liquid refrigerant entrained in the gaseous refrigerant supplied to the compressor through the suction pipe thereby relieving the compressor from overload while at the same time effectively cools the lubricating oil thus improving lubrication and cooling of the driving motor. Thus the lubricating oil contained in the bottom of the sealed casing is normally maintained at a temperature of from 50 C. to 80 C. so that liquid refrigerant which might be entrained in the gaseous refrigerant from the evaporator operating at a temperature of from C. to 10 C. is vaporized when the compressor is restarted after a long period of idleness, the temperature of the lubricating oil is not sufficiently high. Under this condition, however, as the suction pipe 27b communicated with the compressor is opened in the upper portion of the suction cup 36 the liquid refrigerant would not be introduced directly into the compressor because it is collected in the bottom of the suction cup.

Further, according to this invention the lubricating oil whose temperature has been increased while passing through bearing or moving parts or by contacting with heated portions of the motor can be effectively cooled by the suction cup 35 because heated oil is poured on the suction cup 36 through perforation 19.

Additionally, the suction cup having a considerably large volume acts as an intake mufiler to alienate fluctu- 4 ation in the pressure of the compressed gas thus reducing the noise.

From the foregoing description it will be clear that according to this invention there is provided an improved motor compressor by which liquid refrigerant can be evaporated or separated from the gaseous refrigerant, the lubricant oil is effectively cooled to increase the lubrica-r tion of moving parts as well as the cooling of driving motor and the noise of the compressor can be reduced by providing a suction cup of a predetermined volume in the suction pipe of the compressor and in heat exchange relationship with the lubricating oil.

In accordance with the provisions of the patent statutes, we have explained the principle and operation of our invention and have illustrated and described what We consider to represent the best embodiment thereof. However, we desire to have it understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

' What is claimed is:

1. In a motor driven rotary compressor unit comprising a vertically disposed hermetically sealed cylindrical casing (1). having mounted therein a suction pipe (27a, 27b) for circulating a refrigerant to the exterior and back to the casing, said casing containing a motor (4) towards the upper cylindrical side and a compressor (6) towards the lower cylindrical side connected to the motor by means of a frame (5) separating said motor (4) and said compressor (6), said frame (5) having a bearing member (17) journalling a motor shaft ('12) and wherein a lubricating oil (35) storage zone is located in the bottom of said sealed casing (1), and lubricating oil circulating means (13a, 13b) are provided along said shaft (12) for carrying lubricating oil from said storage zone towards said upper cylindrical side with a perforation (19) in said frame (5) for returning said oil to said storage zone; the improvement therein wherein a suction cup (36) having a relatively large volume is serially inserted in said suction pipe (27a, 2711), said suction cup being least partiallyimmersed in said lubricating oil (35) storage zone and said suction cup (36) being arranged in a position opposite to and under said perforation (19) in said frame (5), whereby hot oil returning to said storage zone from said upper cylindrical side is cooled 'by the refrigerant in said suction cup (36) while any regrigerant in the liquid phase in said suction cup is heated by hot oil to the vapor phase.

2. A rotary compressor. according to claim 1 said suction cup having an upper and a lower section, said compressor (6) including a suction part connected to said suction cup upper section, and, said compressor unit having an external evaporator serially connected to said suction cup lower section.

References Cited UNITED STATES PATENTS 2,096,052 lO/1937 McMahon. 3,066,857 12/1962 McCloy 2 30232 3,311,292 3/ 1967 Conner 23 0-207 ROBERT -M. WALKER, Primary Examiner US. Cl. X.R. 417-410, 902