Solid state clutch cycler with charge protection

• US 4,463,576 A
• Filed: 09/27/1982
• Issued: 08/07/1984
• Est. Priority Date: 09/22/1980
• Status: Expired due to Term

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Trissel, Paul E., Butts, Mervin R., Burnett, Dale E.
• Primary Examiner(s): Tanner, Harry B.
• Application Number:
  US06/424,464
• Time in Patent Office: 680 Days
• Field of Search: 62/125, 62/126, 62/127, 62/129, 62/157, 62/158, 62/231, 62/228.1, 62/228.3, 62/226, 62/227, 62/229
• US Class Current: 62/228.3
• CPC Class Codes: B60H 1/00978 Control systems or circuits characterised by failure of detection or safety means; Diagnostic methods
• CPC Class Codes: F25B 2700/04 Refrigerant level
• CPC Class Codes: F25B 49/022 Compressor control arrangements
• CPC Class Codes: G05D 23/1909 whose output amplitude can only take two discrete values

Abstract

A solid state circuit for cycling the refrigerant compressor of an automotive air conditioning system on and off in accordance with a refrigerant vapor condition and for detecting the duration of compressor energization periods as an indication of low refrigerant charge. If a condition of low refrigerant charge is detected, the compressor is disabled and an instrument panel lamp is lit to notify the operator of the vehicle of the low refrigerant charge condition.

Claims

1. In an automotive air conditioning system including an evaporator in which liquid refrigerant is vaporized in effecting heat exchange with a compartment to be cooled, means including a compressor for drawing refrigerant vapor from the evaporator outlet and for supplying refrigerant to the evaporator inlet, the quality of the supplied refrigerant being related to the refrigerant charge level in the system such that the supplied refrigerant is predominantly liquid when the refrigerant charge is at a normal level and predominantly vapor when the refrigerant charge is at an abnormally low level which is insufficient to provide adequate compressor lubrication, and means including a transducer for cycling the compressor on and off according to the pressure of the refrigerant vapor between the evaporator outlet and the compressor such that the compressor is cycled on when such pressure rises above an upper reference value due to vaporization to refrigerant in the evaporator and the compressor is cycled off when such pressure decreases below a lower reference value due to the drawing action of said compressor, the improvement comprising:

sensing means for monitoring the compressor on-time and for signalling the occurrence of an on-time at least as short as a reference on-time which corresponds to system operation wherein the refrigerant supplied to said evaporator is predominantly vapor and wherein the compressor thereby rapidly reduces the pressure of the refrigerant vapor to the lower reference value, whereby said sensing means is effective to detect operation of the compressor with an insufficient refrigerant charge level in said system without necessitating a further transducer for sensing the refrigerant charge level; and

means for counting the number of consecutive cycles for which said sensing means signals the occurrence of an on-time at least as short as said reference on-time and for disabling the compressor when the count reaches a number indicative of a predetermined probability that the amount of refrigerant is insufficient for continued safe operation.

2. In an automotive refrigerant air conditioning system including a transducer responsive to the refrigerant vapor pressure in the system and a compressor which is cycled on and off as a function of such pressure, apparatus for protecting the compressor from damage due to continued operation with insufficient refrigerant without necessitating a further transducer for sensing the amount of refrigerant, the apparatus comprising;

means responsive to the cycling of said compressor effective to generate a reset signal when said compressor is cycled on for a time period greater than a reference time period and for generating a clock signal when said compressor is cycled on for a time period less than said reference time period, said reference time period corresponding to an abnormally short compressor on-time associated with a low refrigerant level in said air conditioning system;

means for incrementing a stored count in response to the generation of a clock signal and for resetting the stored count to zero in response to the generation of a reset signal;

means for generating a disable signal when said stored count exceeds a reference count indicative of a predetermined probability that the amount of refrigerant in said system is insufficient for continued safe operation of said compressor; and

means for disabling said compressor in response to the generation of said disable signal.