US3765191A

US3765191A - Timer circuit-automotive compressor

Info

Publication number: US3765191A
Application number: US00264808A
Authority: US
Inventors: J Canter
Original assignee: General Motors Corp
Current assignee: Motors Liquidation Co
Priority date: 1972-06-21
Filing date: 1972-06-21
Publication date: 1973-10-16
Anticipated expiration: 1990-10-16

Abstract

A compressor protector system in an air conditioning system which includes a compressor driven by an automobile engine through an electromagnetic clutch. When the refrigerant charge level falls below a level necessary for proper compressor cooling and lubrication, a temperature and pressure responsive switch in the compressor causes a relay to close. After a slight delay, a fuse in the electromagnetic clutch circuit is blown. This deactivates the compressor until additional refrigerant can be added to the system.

Description

O United States Patent 1 [111 3,765,191 Canter Oct. 16, 1973 [54] TIMER CIRCUIT-AUTOMOTIVE 3,207,872 9/1965 Nauer 337/95 X COMPRESSOR 3,702,065 11/1972 Jacobs 62/323 X 1 e 3,706,089 12/1972 Huntzinger et al. 337/335 X [7 5 Inventor: James A. Canter, Englewood,

mom?" r Primary Examiner-William F. ODea Asslgneel General Mlftors Corporation, Assistant Examiner-Peter D. Ferguson I Detroit, MlCh. Attorney-W. S. Pettigrew et al. 22 Filed: June 21, 1972 [21] Appl. No.: 264,808 [57] ABSTRACT A compressor protector system in an air conditioning [52] 0.8. CI 62/228, 62/243, 62/323, ystem hich includes a compressor driven by an au- 337/95, 337/99, 337/100, 337/102, 337/104 tomobile engine through an electromagnetic clutch. [51] Int. Cl B60h 3/04 W the fr g r n harge level falls below a level [58] Field of Search 62/228, 243, 323; necessary f r pr per compressor cooling and lubrica- 337/95, 99, 100, 102, 104 tion, a temperature and pressure responsive switch in the compressor causes a relay to close. After a slight [56] Refer s Cit d delay, a fuse in the electromagnetic clutch circuit is UNITED STATES PATENTS blown. This deactivates the compressor until addi- 2,o14,95s 9/1935 Wilhelm 337/101 x tmal refngerfant can be added the System 2,978,879 4/1961 Heidhorn 62/323 X 5 Clams 3 Drawing Figures 2,981,076 4/1961 Gaugler et a1. 62/230 X 3,047,696 7/1962 Heidhom 62/243 3,108,166 10/1963 Baker et a]. 337/102 X TIMER CIRCUIT-AUTOMOTIVE COMPRESSOR This invention relates to a compressor protective system for an automobile air conditioning system.

Automobile air conditioning systems having refrigerant compressors utilize a quantity of oil mixed with refrigerant for compressor lubrication and cooling. A portion of this lubricating oil passes with the refrigerant through the condenser and evaporator. When the refrigerant charge level decreases to a low level due perhaps to leakage, insufficient quantities of refrigerant and oil are available in the compressor for cooling and lubricating.

The present automotive air conditioning system includes a compressor protector which deactivates the compressor when the refrigerant charge level decreases 1 below a quantity found to be insufficient for compressor cooling and lubrication. The compressor is rotated by the automobile engine through an electromagnetic clutch energized by a fused circuit. The circuit also includes a heat biased relay connected between the battery and the fuse and a normally open switch mounted on the compressor. The switch responds to refrigerant temperature and pressure and is adapted to close upon sensing a high refrigerant temperature or a low refrigerant pressure corresponding to operation of the compressor with insufficient quantities of refrigerant in the system. When the switch closes, the relay closes a circuit after a short time delay which causes the fuse to open and deenergize the compressors magnetic clutch. This renders the compressor inoperative until the fuse is replaced and more refrigerant is added to the system.

The relay includes two bimetal arms which are cantilever mounted on a base. The free ends of the arms are connected by a heat insulated link so that both ends are forced to move together. Each bimetal arm has an electric resistance wire heater wound around it which under normal operation of the air conditioning system are both energized. The first resistance heater biases the linked bimetal arms to an open operative position of the relay. The second of the resistance heaters biases the arms to a closed operative position. When both heaters are energized, the relay stays open. When the temperature and pressure responsive switch on the compressor closes, it completes a circuit to bypass the first or opening resistance heater. Energized alone, the second or closing resistance heater causes'the relay to move to a closed position after a short time delay. This grounds the clutch energization circuit and causes a large enough current to flow through the fuse to open it. With the fuse open, the electromagnetic clutch is deenergized and the compressor inoperative.

Therefore, an object of the invention is to provide a refrigerant compressor protector which senses an insuft'rcient refrigerant charge level for cooling and lubricating and deactivates the compressor to prohibit further operation.

A further object of the invention is to provide a compressor protector for automobile air conditioning systems including a fuse in the electromagnetic clutch circuit connected to a relay having resistance wire heaters on bimetal arms which move to short circuit the fuse when a switch is closed in response to a high refrigerant temperature or low pressure in the compressor.

A still further object of the invention is to provide a refrigerant compressor protector including a simple and inexpensive time delayed relay with bimetal arms which are held in an open mode when two resistance wire heaters are energized simultaneously and which move to a closed mode when one of the resistance wire heaters is deenergized.

Further objects and advantages of the present invention will be apparent from the following detailed description, reference being had to the accompanying drawings in which a preferred embodiment of the invention is clearly shown.

IN THE DRAWINGS FIG. 1 is a schematic view of an air conditioning protective system;

FIG. 2 is an enlarged view of the switch of FIG. I; and

FIG. 3 is a fragmentary view of another embodiment of the protective system.

In FIG. 1 of the drawings, an automobile air conditioning system is shown including a compressor 10, a condenser 12, a drier-receiver assembly 14, an expansion valve 16, an evaporator 18, and a suction throttling valve 20. The compressor 10 is connected in refrigerant flow relation to the condenser 12 by a high pressure conduit or line 22. The evaporator 18 and throttling valve 20 are connected in refrigerant flow relation to compressor 10 by a suction conduit 24. A temperature bulb 26 and capillary tube 28 sense evaporator outlet temperature to control the expansion valve 16 which regulates the quantity of liquid refrigerant admitted to the evaporator 18 through an inlet conduit 29.

The compressor 10 is rotated by the automobiles engine (not shown) through an electromagnetic clutch 30 which transmits rotation to the compressor whenever a coil 32 is energized. Coil 32 is energized by a battery 34 through a conductor 36, a compressor protective fuse 38 and conductor 40. The coil 32 and battery 34 are grounded respectively by conductors 42 and 44. An on-off switch 46 is manually operated by an automobile occupant to activate the air conditioning system.

As previously stated, it is desirable to deactivate the compressor whenever the refrigerant charge level decreases below a quantity necessary for cooling and lubricating the compressor. When the fuse 38 is open, coil 32 is deenergized until a new fuse can be installed and the refrigerant charge replenished. The fuse 38 is connected by a conductor 48 to one terminal of a relay 50. Another terminal of the relay 50 is connected by a conductor 52 to a temperature and pressure responsive switch 54 mounted in the head 56 of compressor 10. The relay includes a U-shaped bimetal 58 with two cantilever mounted

arms

60 and 62. The free ends of the

arms

60 and 62 are connected by a thermally insulated link 64 so that they must move together with temperature changes.

The

arms

60 and 62 each have a

resistance wire heater

66 and 68 respectively around them in good heat transfer relationship to the arm. Resistance heater 66 around the arm 60 maintains a contact pair 70 open when energized and resistance heater 68 tends to close the contact pair when energized. When both

heaters

66 and 68 are energized simultaneously, the contact pair 70 is maintained open. However, when heater 68 is energized and heater 66 is deenergized, the contact pair 70 closes. When the contact pair 70 closes, the conductor 48 is grounded through a conductor 72. This causes a large electrical current to flow through the fuse 38 which opens it and deenergizes the electromagnetic clutch 30.

Normally, the

resistance heaters

68 and 66 are energized simultaneously by conductor 74 extending between conductor 48 and resistance heater 68, another conductor 76 connecting the two heaters and a conductor 78 to ground. Thus, the circuit extends from the battery 34, through fuse 38, conductors 48, 74, heater I 68, conductor 76, heater 66 and conductor 78 to ground. The resistance of

heaters

66 and 68 is great enough to limit current through the fuse 38 so it will remain closed.

When switch 54 closes in response to high refrigerant temperature or low pressure,the conductor 52 is connected to ground by conductor 80. This bypasses the resistance heater 66 and causes current to flow through the super heat switch rather than heater 66. With deenergization of the opening resistance heater 66, the closing resistance heater 68 will move the

arms

60, 62 toward a closed position. After a short time delay the contact pair 70 is closed and the conductor 48 is grounded. This causes fuse 38 to open and deenergize the coil 30.

The switch 54 is best shown in FIG. 2. It is mounted in a recess 82 in the compressor head 56. The recess 82 is adapted to accept a cup-shaped member 84 which is held within the recess 82 by an expansion ring 86 which is adapted to fit within a groove 87. A collar 88 is threadably secured to member 84 at 89 to form an interior space 90. A bellows member 92 within the space 90 is supported by the collar 88 and has two cupshaped members 94 and 96 which are joined at their edges 95 to define an expandable chamber 98 therebetween. One of the members 94 is secured to the collar 88 and the other member 96 supports a contact 100 adapted to move with the member 96.

The chamber 98 communicates by port 102 in the collar 88 with the interior of a tube 104 which projects into the suction'cavity of the compressor to sense inlet temperature of refrigerant. After filling chamber 98 with refrigerant, the tube 104 is sealed at its end by a small quantity of solder 106. Ports 108 in the collar 88 communicate the space 90 around bellows 94 with the suction cavity of the compressor. As refrigerant in the compressor. inlet increases in temperature or decreases in pressure, the bellows 94 is expanded causing contact 100 to move toward a contact pin or terminal 110. Pin 110 is mounted within a glass seal 112 to insulate it from the member 84 and the compressor and is electrically connected to the relay 50 by conductor 52.

When enclosed refrigerant within bulb 104 and chamber 98 expands, the contact 100 engages pin 110 and completes a circuit from the relay 50 through conductor 52, pin 110, contact 100, collar 88 and member 84 to the compressor body which is grounded by conductor 80. As previously explained, this deenergizes the opening resistance heater 66 in the relay 50 and after a time delay causes the heater 68 to close contact air 70 and open fuse 38. This de-activates the clutch 30 of compressor 10.

A common refrigerant used in air conditioning systems is dichlorodifluoromethane which has the chemical formula CC1,F,. It has a boiling point at atmospheric pressure of 21.6 F. The refrigerant charge level in a typical General Motors air conditioning system is about 4 pounds of refrigerant. [t has been observed that a charge level less than about one pound of refrigerant may be insufficient for cooling and lubrication of the compressor.

When the charge level of refrigerant is low, the superheat temperature of refrigerant in the compressors suction cavity is significantly increased. Superheat temperature .of refrigerant is the excess of the temperature of the refrigerant vapor over its boiling point for a given pressure. Thus, refrigerant at 116 F. and at atmospheric pressure has a superheat of 10 F. Under normal compressor operation with a full refrigerant charge and a head load on the evaporator, the throttling valve 20 maintains an evaporator pressure of about 30 psig. which corresponds to 32 F. in the evaporator. It does this by restricting the suction line 24 and thus the flow from the evaporator. These conditions represent approximately zero superheat in the evaporator.

When operating the air conditioning system with a heat load on the evaporator such as produced by an ambient temperature of F. and an insufficient refrigerant charge, the temperature of refrigerant in the suction cavity may increase to 140 F. and thus be superheated about 180 F. The switch 56 presently used in General Motors air conditioning systems is set to close at a superheat of 120 F. at zero psig. or a superheat of 141.6 F. Thus, under the aforedescribed conditions, the bellows 92 expands and causes contact to engage the pin and deenergize the clutch 30.

When the heat load on the evaporator becomes relatively small such as with a low ambient temperature near 32 F. and there is insufficient refrigerant in the system, the throttling valve will completely shut off vapor flow through the suction line. When this happens, the suction cavity pressure will drop to near zero psig at which pressure the refrigerants boiling point is about 9 or 10 F. Under a normal 30 psig pressure this temperature is insufficient to close the superheat switch. Because of this low pressure surrounding bellows 92, the switch will close at the lower temperature to prevent further compressor operation.

During some operating conditions of the air conditioning system, the refrigerant superheat in the suction inlet may exceed the closing temperature of the superheat switch even when the system is at full charge. This can occur for instance during rapid acceleration of the automobile or after consecutive starting and stopping of the compressor. The present protective system is insensitive to these transient temperature-pressure conditions because of the aforedescribed time delay built into relay 50.

In FIG. 3, another embodiment of the protector is shown utilizing the same U-shaped bimetal 58 with

arms

60 and 62 and link 64. However, only the closing resistance wire heater 68 is used on arm 60. When superheat switch 54 closes, heater 68 is energized through conductors 116, 1 18. This causes the

interconnected arms

60, 62 to move to the left and close contact pair 70. This shorts out the fuse 38 to deactivate coil 32.

While the embodiment of the invention described above is a preferred embodiment, it should be understood that other embodiments may be adapted.

What is claimed is as follows:

1. In an automobile air conditioning system including a refrigerant compressor, a compressor protector comprising: an electromagnetic clutch for interconnecting the automobile engine and said compressor for rotation together when said clutch is energized; circuit means including an electric power source and a fuse for energizing said electromagnetic clutch; compressor protector means for producing a sufficiently large current through said fuse to open it and to deenergize said electromagnetic clutch when the refrigerant charge in said air conditioning system decreases below a level necessary for compressor cooling and lubricating; said compressor protector means including a thermally biased relay which normally holds open a pair of contacts connected between said fuse and ground; said relay having two resistance heaters in circuit with said electric power source and which are normally energized simultaneously to maintain said contact pair open; switch means responsive to the refrigerant temperature and pressure in circuit with said resistance heaters to deenergize one of said resistance heaters when the refrigerant charge level is insufficient for cooling whereby the other of said resistance heaters causes the contact pair to close and pass sufficient current through said fuse to open it and deenergize said compressor.

2. In an automobile air conditioning system including a refrigerant compressor, a compressor protector comprising: an-electromagnetic clutch for interconnecting the automobile engine and said compressor for rotation together when said clutch is energized; circuit means including an electric power source and a fuseifor energizing said electromagnetic clutch; compressor protector means for producing a sufficiently large current through said fuse to open it and to deenergize said electro-magnetic clutch when the refrigerant charge in said air conditioning system decreases below a level necessary for compressor cooling and lubricating; said compressor protector means including a thermally biased relay having two cantilever mounted bimetal arms which are connected at their free ends by a heat insulated link to force said arms to move together with changes of temperature; a resistance wire heater wrapped around each bimetal arm in series connection with each other and with said fuse and said power source; said relay also including a pair of contacts connected between said fuse and ground and adapted when closed to cause sufficient current to flow through said fuse to open it and deenergize said electromagnetic clutch; one of said resistance heaters producing a closing movement of said interconnected arms to close said contact pair when energized separately; the other of said resistance heaters producing an opening movement of said interconnected armsto open said contact pair when energized; switch means in circuit with said resistance heaters responsive to the refrigerant temperature and pressure to deenergize said other resistance heater when the refrigerant charge level is insufficient for cooling leaving only said one resistance heater energized whereby the interconnected bimetal arms are moved into a closed operative position to close said contact pair to cause a relatively large current to pass through said fuse and to open it for deenergizing said compressor.

3. In an automobile air conditioning system including a refrigerant compressor driven by the automobile engine through an electromagnetic clutch which is energized by a circuit having a fuse, a compressor protective system comprising: a thermally biased relay including two cantilever mounted bimetal arms; each bimetal arm supporting a resistance wire heater connected in series with each other and with said fuse; the free ends of said bimetal arms being interconnected by an insulated link to cause said bimetal arms to move together; said relay having a pair of contacts connected between said fuse and ground and adapted to cause a relatively large current to flow through said fuse to open it when the contact pair is closed by a closing movement of said interconnected bimetal arms; the first resistance heater when energized biasing the interconnected bimetal arms toward a closed operative position; the second resistance heater when energized biasing said interconnected bimetal arms toward an open operative position; said contact pair being maintained open by simultaneous energization of both resistance heaters; a temperature and pressure responsive switch in heat transfer relation to refrigerant in the air conditioning system and in circuit with said resistance heaters and ground to cause said second resistance heater to be deenergized when said switch closes whereby said first resistance heater is energized separately and moves said interconnected bimetal arms to the closed position with said contact pair closed thereby opening said fuse and deactivating said electromagnetic clutch and said compressor.

4. In an automobile air conditioning system including a refrigerant compressor, a compressor protector comprising: an electromagnetic clutch for interconnecting the automobile engine and said compressor for rotation together when said clutch is energized; circuit means including an electric power source and a fuse for energizing said electromagnetic clutch; compressor protector means for producing a sufficiently large current through said fuse to open it and to deenergize said clutch when the refrigerant charge in said air conditioning system decreases below a level necessary for compressor cooling and lubrication; said compressor protector means including a thermally biased relay which normally holds open a pair of contacts between said fuse and ground; said relay having two bimetal arms which are cantilever mounted with their free ends interconnected for movement together by an insulative link; one of said contacts being mounted near the free end of one bimetal arm; a resistance wire heater around one of said bimetal arms which will cause the arms to move and close said contact pair when energized; switch means in circuit with said resistance wire heater and responsive to refrigerant temperature and pressure for energizing resistance wire heater when the refrigerant charge level is insufficient for cooling whereby the contact pair is closed and the large current flowing through said fuse causes it to open and deenergize said clutch.

5. In an automobile air conditioning system including a refrigerant compressor, a compressor protector comprising: an electromagnetic clutch for interconnecting the automobile engine and said compressor for rotation together when said clutch is energized; circuit means including an electric power source and a fuse for energizing said electromagnetic clutch; compressor protector means for producing a sufficiently large current through said fuse to open it and to deenergize said clutch when the refrigerant charge in said air conditioning system decreases below a level necessary for compressor cooling and lubrication; said compressor protector means including a thermally biased relay which normally holds open a pair of contacts between said fuse and ground; said relay having two bimetal arms which are cantilever mounted with their free ends interconnected for movement together by an insulative link; one of said contacts being mounted near the free end of one bimetal arm; a resistance wire heater coacwhereby when the refrigerant charge level is insufficient for cooling the contact pair is closed and the large current flowing through said fuse causes it to open and deenergize said clutch.

Claims

2. In an automobile air conditioning system including a refrigerant compressor, a compressor protector comprising: an electromagnetic clutch for interconnecting the automobile engine and said compressor for rotation together when said clutch is energized; circuit means including an electric power source and a fuse for energizing said electromagnetic clutch; compressor protector means for producing a sufficiently large current through said fuse to open it and to deenergize said electro-magnetic clutch when the refrigerant charge in said air conditioning system decreases below a level necessary for compressor cooling and lubricating; said compressor protector means including a thermally biased relay having two cantilever mounted bimetal arms which are connected at their free ends by a heat insulated link to force said arms to move together with changes of temperature; a resistance wire heater wrapped around each bimetal arm in series connection with each other and with said fuse and said power source; said relay also including a pair of contacts connected between said fuse and ground and adapted when closed to cause sufficient current to flow through said fuse to open it and deenergize said electromagnetic clutch; one of said resistance heaters producing a closing movement of said interconnected arms to close said contact pair when energized separately; the other of said resistance heaters producing an opening movement of said interconnected arms to open said contact pair when energized; switch means in circuit with said resistance heaters responsive to the refrigerant temperature and pressure to deenergize said other resistance heater when the refrigerant charge level is insufficient for cooling leaving only said one resistance heater energized whereby the interconnected bimetal arms are moved into a closed operative position to close said contact pair to cause a relatively large current to pass through said fuse and to open it for deenergizing said compressor.

5. In an automobile air conditioning system including a refrigerant compressor, a compressor protector comprising: an electromagnetic clutch for interconnecting the automobile engine and said compressor for rotation together when said clutch is energized; circuit means including an electric power source and a fuse for energizing said electromagnetic clutch; compressor protector means for producing a sufficiently large current through said fuse to open it and to deenergize said clutch when the refrigerant charge in said air conditioning system decreases below a level necessary for compressor cooling and lubrication; said compressor protector means including a thermally biased relay which normally holds open a pair of contacts between said fuse and ground; said relay having two bimetal arms which are cantilever mounted with their free ends interconnected for movement together by an insulative link; one of said contacts being mounted near the free end of one bimetal arm; a resistance wire heater coactive with one of the bimetal arms which will cause the arm to move and close said contact pair; switch means coactive with said resistance wire heater and responsive to refrigerant temperature and pressure for regulating the energization of the resistance wire heater whereby when the refrigerant charge level is insufficient for cooling the contact pair is closed and the large current flowing through said fuse causes it to open and deenergize said clutch.