US 2981076 A
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United States Patent REFRIGERATING APPARATUS Richard 'S. Gaugler, Dayton, Earl S. Schlotterbeck, Lewisburg, and Raymond F. Schultz, Dayton, Ohio, assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed June 30, 1958, Ser. No. 745,596
'3 Claims. (Cl. 62-208) This invention pertains to refrigerating apparatus and especially to the protection of the refrigerating systems from damage because of insuffic ient circulation of refrigerant and lubricant or because of depletion of the refrigerant and lubricant by leakage or otherwise.
Since automotive air conditioning systems are powered by the same automobile engine used to drive the car, it is not practical to use a hermetically sealed system. Also, such systems are subjected to road shocks and vibration stresses. Consequently, the system is subject to leakage and occasionally such systems do leak. Not only does the refrigerant leak out but some of the oil lubricant also leaks away with it and excessive amounts collect in the evaporator. In such cases, it is necessary to add refrigerant and lubricant to the system. When this is not done and leakage continues, the compressor overheats and may become starved of lubricant and be seriously damaged for lack of proper lubrication.
It is an object of this invention to prevent the operation of the compressor whenever the lubrication thereof is insufficient.
It is another object of this invention to prevent the operation of the compressor whenever the refrigerant charge is depleted a predetermined amount.
It is another object of this invention to prevent the operation of the compressor whenever excessive superheat continues to exist in the suction line.
These and other objects are attained in the form shown in the drawings in which a temperature responsive bulb is clamped to the suction line and connected to one side of a differential fluid motor. The opposite side of the fluid motor is connected to the suction inlet connection of the compressor. The fluid motor is biased by a spring so that it is inoperative until the suction line temperature is more than 60 above the boiling temperature of the refrigerant at the pressure corresponding to the suction inlet pressure. When this excessive super-heat condition, which is indicative of the loss of about one-half the refrigerant charge, is reached, a circuit is closed blowing the fuse to the driving connection for the compressor, which prevents further operation thereof. The car will then be taken to the service station where the proper amount of refrigerant and lubricant will be added so that no damage to the compressor will ensue.
Further objects and advantages of the present invention will be apparent from the following description,
. reference being held to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown. i
In the drawings:
Figure 1 is a diagrammatic representation of an air conditioning refrigerating system for an automobile embodying one form of my invention in normal position; and
Figure 2 is a sectional view through a portion of the control embodying my invention in the position for disconnecting the compressor.
Referring now more particularly to Fig. 1, there is shown an automobile driving engine 20 having a fan 22 ice for circulating air through the condenser 24. The fan shaft also carries a pulley 26 which, through a belt 28, a driving pulley 30 and an electromagnetic clutch 32 drives a compressor 34. This compressor 34 is preferably mounted on the engine 20. The compressor 34 delivers compressed refrigerant through the discharge conduit 36 to the condenser 24 from which the condensed refrigerant flows through a drain conduit 38 to a receiver 40. The receiver 40 is connected by a supply conduit 42 with the thermostatic expansion valve 44 which controls the flow of liquid to the inlet of the air cooling evaporator 46. The thermostatic expansion valve 44 has a thermally operating bulb 48 in heat transfer relation with the suction line 50 connecting the outlet of the evaporator 46 with the inlet of the compressor 34. The thermostatic expansion valve 44 has a diaphragm operating system which is responsive to the dilferent-ial between a pressure corresponding to the temperature of the bulb 48 and the pressure within the evaporator 46. The thermostatic ex-' pansion valve 44 controls the super-heat of the refrigerant leaving the evaporator 46 under normal conditions. A bypass valve 52 is provided in a bypass connection connecting the suction line 50 and the discharge conduit 36 which opens in accordance with reduced refrigeration requirements to reduce the capacity of the refrigerating system. If desired, the electromagnetic clutch 32 may be thermostatically controlled and the bypass connection and valve 52 may be omitted.
The system is charged with a fluorine refrigerant such as difiuorodichloromethane or monochlorodifluoromethane and a mineral oil lubricant. Since the compressor 34 is externally driven, a shaft seal is required for the drive shaft connecting with the driven pulley 30 through the magnetic clutch 32. Also, because of the nature of the installation of the refrigerating system in an automobile it is desirable that the parts be readily removable. It
is therefore more practical to provide removable connections throughout the system so that the parts may be removed whenever necessary. Road shocks and vibrations are apt to affect such connections. As a result, systems of this type are subject to leakage and occasionally serious leaks occur. It was found that in extreme cases of neglect, where the refrigerant charge is almost completely depleted, that excessive amounts of oil lubricant accumulate in the evaporator and there is insufiicient lubrication with the compressor 34. Also, the reduced flow of refrigerant does not supply sufiicient cooling so that the compressor overheats and is damaged. Very often, the compressor is damaged beyond repair.
-We have found that when the valve 44 is' properly set, the super-heat in the suction line 50 is about 23 F. However, this super-heat rises as the refrigerant charge is depleted. This rise in super-heat is particularly rapid when about half of the refrigerant charge has been lost. When'the super-heat exceeds about 60 F., more than half of the refrigerant charge has been lost.
According to this invention, I provide an arrangement wherein the fuse controlling the clutch 32 is blown when ever the super-heat exceeds 60 F. This is provided by a differential fluid motor control which includes a cupshaped body 54 carrying a coaxial electrical terminal 56 threaded within a metal .sleeve 57 embedded in a glass seal 59 within the protruding portion of a spring locator 61 bonded and sealed to the adjacent edges of the aperture in the body 54. The body 54 is provided with an outwardly extending flange 58 on which is seated a thin corrugated metal diaphragm 60. On the opposite side of this diaphragm is a diaphragm cover 62 which is sealed to the shoulder 58 and the edges of the diaphragm 60, The diaphragm cover 62 is connected by a small tube 64 to a thermostatic bulb 66 fastened to the suction line or conduit 50 adjacent the compressor 34. Preferably thethermostatic bulb 66 contains activated charcoal and is charged with carbon dioxide which is absorbed and evolved from the charcoal in accordance with the temperature of the suction line 50.
The pressure,-therefore, betweenthe diaphragm cover 62 and the diaphragm 69 is responsive to the temperature of the suction line 50 at the point Where the bulb 66 is clamped. The valve body 54 is connected by the tubular connection 68 with the suction gauge connection 70 of the compressor 34 so that it is responsive to the pressure within the suction conduit 50. The diaphragm 60 bears against a cup-shaped member 72 surrounding the inner end of the terminal 56. The cup-shaped member 72 is provided with a flanged guide ring 74 which guides the movement of the cup-shaped member 72 within the housing 54. Within the cup-shaped member 72 there is provided a compression type coil spring 78 which extends between the interior of the cup-shaped member 72 and the portion of the Wall of the valve body 54 surrounding the electrode 56. This spring acts with suificient force to move the cup-shaped member 72 toward the diaphragm cover 62.
The pressure in the chamber between the diaphragm 60 and the diaphragm cover 62 responds to the temperature of the suction line 50 at the location of the bulb 66. The pressure Within the chamber containing the cup-shaped member 72 is responsive to the suction inlet pressure of the compressor 34 which is substantially the same as the pressure within the suction line 59 adjacent the bulb 66. The spring 78 bears with sufficient force on the interior of the cup member 72 that a super-heat of more than 60 at the thermostatic bulb 66 is required before it collapses. When the spring 78 collapses, the cup member 72 will rest upon the tip of the electrode 56, as shown in Fig. 2.
This will close a circuit from the ground 80 through the body 54, the spring 78, the cup member 72 to and through the electrode 56. The electrode 56 is connected by the conductors 82 and 84 to the fuse 36 which completes a circuit through the manual off-on switch 86 and the battery 90 to the ground 92. Since this is a virtual short-circuit, the fuse 86 will be blown to prevent operation of the compressor 34. To prevent false operation of this protection device when the system is started under high temperature conditions, a thermistor 9 1 is provided in the conductor 82 providing a short time delay before the fuse 86 is blown. The blowing of the fuse 86 will also cut off the supply of current from the battery 90 to the fan motor 94 which drives the evaporator fan 96 for forcing the air into the interior of the automobile. The blowing of the fuse 86 will also deenergize the compressor clutch 34 to prevent the connection of the compressor to the engine 26. When the owner finds that the car is not providing refrigeration, he will take the car to a service station for addition of refrigerant and lubricant to the system and the replacement of the fuse 36 to restore normal operating conditions, under which the compressor 34 will not be damaged.
While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.
What is claimed is as follows:
1. Refrigerating apparatus containing a refrigerant and including a compressor, a condenser connected to the compressor, a flow control device and an evaporator connected to said condenser, a suction line connecting said evaporator and said compressonmeans for driving said compressor, an electrically operated clutch connecting said driving means and said compressor, a fuse connected in electrical series circuit with and having one terminal connected to one terminal of said electrically operated clutch, a source of electrical energy connected to a second terminal of said fuse and a second terminal of said electrical device, switch means connected in parallel circuit with said electrically operated clutch having one electrical connection to said source and one electrical connection to said one terminal of said fuse, and means responsive to excessive superheat of the refrigerant in said suction line for closing said switch means for blowing said fuse to declutch said compressor from said driving means.
2. Refrigerating apparatus containing a refrigerant and including a compressor, a condenser connected to the compressor, a flow control-device-and an, evaporator connected to said condenser, a suction line connecting said evaporator and said compressor, means including an electrical device for driving said compressor, a fuse in series with and having one terminal connected to one terminal of said electrical device, a source of electrical energy connected to a second terminal of said fuse and a secondterminal of said electrical device, a thermostatic device providing a pressure responsive to the temperature of the refrigerant in the suction line, a fluid motor operated switch connected in parallel circuit With said electrical device having an electrical connecton to said source and an electrical connection to said one terminal of said fuse, said fluid motor operated switch having one fluid motor connected to said thermostatic device and a second fluid motor connected to said suction line, said fluid motors being arranged in opposing relation to close said switch to blow said fuse for preventing operation of said compressor, and a thermistor time delay device connected in electrical series circuit with said switch.
3. Refrigerating apparatus containing a refrigerant and including a compressor, a condenser connected to the compressor, a flow control device and an evaporator connected to said condenser, a suction line connecting said evaporator and said compressor, means for driving said compressor, a clutch connecting said driving means and said compressor, electrical means controlling said clutch, a fuse connected in serieselectrical circuit with said electrical means, said fuse and electrical means each having one terminal connected together, a fluid motor operated switch for blowing said fuse for controlling said electrical means, a source of electrical energy connected to a second terminal of said fuse and a second terminal of said electrical means, said switch being connected in parallel circuit with said electrical means and having one electrical connection to said source and one electrical connection to said one terminal of said fuse, said switch having a fluid motor responsive to the temperature of the refrigerant in said suction line and to the pressure of the refrigerant in said suction line.
References Cited in the file of this patent UNITED STATES PATENTS 1,750,336 Terry Mar. 11, 1930 1,768,558 Andrews July 1, 1930 1,768,602 Hull July 1, 1930 2,621,487 Warren Dec. 16, 1952 2,752,760 Kaufman July 3, 1956 2,779,163 Jacobs Ian. 21, 1957