Refrigeration – With indicator or tester – Condition sensing
Patent
1995-04-13
1997-07-15
Tanner, Harry B.
Refrigeration
With indicator or tester
Condition sensing
62126, B60H 132
Patent
active
056472226
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method and a device for diagnosis of the refrigerant quantity in an air conditioning system, in which an evaporator followed by a liquid-separating accumulator, a compressor, a condensor, and a shut-off device are connected in series after one another in a closed circuit for circulation of a refrigerant.
BACKGROUND OF THE INVENTION
Air conditioning systems in vehicles must normally be able to function in greatly varying conditions, for instance regarding ambient temperature and atmospheric humidity. Also, its function depends on the quantity of refrigerant in the closed system.
The most common cause of malfunctions in air conditioning systems is a too high or too low refrigerant quantity. A small leakage in an air conditioning system can be very difficult to discover. If the compressor, over a very long period of time, is forced to function with a too low refrigerant quantity, it might break down.
Even a slight shortage of refrigerant can lead to the following negative consequences:
An excess of refrigerant might, on the other hand, lead to the following negative consequences:
In practice, a shortage as well as an excess of the refrigerant will force the compressor to work more often and during longer time periods than what otherwise would have been necessary.
Up to now, no suitable devices have existed for measuring the refrigerant quantity in a closed system with capillary tubes as a shut-off means, and with a liquid-separating accumulator after the evaporator. For this reason, service and maintenance of cars equipped with air conditioning systems usually mean that the liquid must be evacuated from the system when measuring the quantity of the refrigerant. This evacuation is time consuming, since the system comprises rather long fluid lines with narrow passages. Draining and filling of the refrigerant also lead to risks of discharging substances which are harmful to the environment.
U.S. Pat. No. 4,757,693 describes an air conditioning system with an electronic circuit for detection of malfunctions, for example due to an inaccurate refrigerant quantity. This air conditioning system is however equipped with a tank for the refrigerant between the condensor and the expansion valve. U.S. 4,308,725 describes a detector for indicating the level of the refrigerant in such a storage tank.
SUMMARY OF THE INVENTION
Consequently, a purpose of the present invention is to provide a method and a device for a quick and simple diagnosis of the refrigerant quantity in an air conditioning system which does not have a tank for the refrigerant.
This object is solved in the method according to the invention in that the pressure of the refrigerant is measured between the condensor and the shut-off device, that the temperature of the refrigerant is measured after the compressor and also before the evaporator, and that the measured values are compared with stored set values for determining whether the refrigerant quantity is within, or outside, a reference interval. The device according to the invention is characterized by pressure sensing means for detecting the refrigerant pressure between the condensor and the shut-off device, temperature sensing means for detecting the refrigerant temperature after the compressor and before the evaporator respectively, and by an analysis unit which is arranged to compare input data from the pressure sensing and the temperature sensing means with stored set values.
Advantageous embodiments of the invention will be apparent from the subsequent dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described in greater detail with reference to the accompanying drawings, wherein
FIG. 1 schematically shows an air conditioning system with a diagnosis system, according to a first embodiment of the invention,
FIG. 2 shows in an analogous way a diagnosis system according to a second embodiment of the invention,
FIG. 3 shows a diagnosis system suitable for use in workshops, and
FIG. 4 is a diagram which
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patent: 4220010 (1980-09-01), Mueller et al.
patent: 4677830 (1987-07-01), Sumikawa et al.
patent: 5239865 (1993-08-01), Salzer et al.
patent: 5241833 (1993-09-01), Ohkoshi
AB Volvo
Tanner Harry B.
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