Refrigeration – Automatic control – Refrigeration producer
Patent
1997-11-10
1999-05-18
Doerrler, William
Refrigeration
Automatic control
Refrigeration producer
60449, B60H1/32
Patent
active
059040505
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a motor vehicle air conditioning control system.
An all-or-none air conditioning control system that comprises a semi-hermetic compressor linked to an electromagnetic clutch, which are coupled either to the shaft of the heat engine or the propulsion engine or to the distribution outlet, is known. In general, the clutch is driven by the same belt as the one that also drives the alternator. Air conditioning is done during the coupling of the electromagnetic clutch, and the system operates on an all-or-none basis. When there is a need to produce refrigeration, the clutch couples the compressor to the heat engine or the propulsion engine. When the set temperature is reached, the clutch decouples the compressor, which ceases to produce refrigeration as long as the passenger compartment remains in the set temperature range.
Such a system offers the many drawbacks described below:
A semi-hermetic compressor has a performance level coefficient that is not very high for various reasons.
On the one hand, the airtightness of the rotating shaft is ensured by a seal which causes rubbing and wear; these produce microleaks, compromising the sealing of the compressor. These microleaks, which occur at the shaft output, are compensated by the presence of a refrigerating gas reservoir, which requires periodic refills.
On the other hand, the compressor is by necessity located close to the heat engine or the propulsion engine and consequently in a hot environment that is not very favorable to the production of refrigeration. Then, the poor output or the poor performance level coefficient results from the rotation speed of this compressor, which is directly related to the rotation speed of the heat engine or the propulsion engine, which varies between the lowest speed of 800 rpm and the highest speed, which is on the order of 6 to 6500 rpm.
A refrigerating compressor, however, has an output and an optimum refrigeration production for a well-defined nominal speed. This nominal speed of the compressor is generally on the order of 1500 or 1800 rpm.
The compressor is often supposed to produce maximum refrigeration when the speed of the heat engine or the propulsion engine is lowest due to, for example, the need for air conditioning in traffic jams or while idling. It is therefore necessary to size the system to produce the necessary refrigeration or the necessary refrigerating power for the lowest speed. Above this nominal speed, a safety valve system is triggered to create an internal pressure drop.
In addition, the electromagnetic clutch, which ensures the activation of the compressor, draws a great deal of electrical energy. This poses an electric balance problem for the motor vehicle manufacturer. The stress put on the battery by the air conditioning system becomes too great and makes it necessary to resize the capacity of the battery and sometimes even the alternator.
This electromagnetic clutch, which will operate on an all-or-none basis, will also contribute to poor output of the system in that when a compressor is stopped, it is necessary to start the thermodynamic cycle from scratch. With each restart, the thermodynamic irreversibilities are lost, and it is necessary to recompress the gas which, through evaporation, will produce refrigeration.
This all-or-none operation is a major drawback mainly for low-displacement vehicles or low-power vehicles. The torque that is demanded at the beginning of the cycle by the compressor is maximized. When the vehicle is idling, the power that is required, which is the product of torque times speed (power required by the compressor), creates the danger of engine stall. To overcome this drawback, the manufacturers say that, while the air conditioning is in use, the idling speed should be increased to a value generally on the order of 1100 rpm. This will help to increase pollution and raise fuel consumption.
The object of the invention is to overcome one or more of the drawbacks of the prior art.
This object is accomplished by virtue of the fact that the motor veh
REFERENCES:
patent: 2101495 (1937-12-01), Ferris et al.
patent: 5018351 (1991-05-01), Otte
Doerrler William
Technical Maintenance Corporation
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