Abstract:
An accumulator-dehydrator for use in an air conditioning system. The accumulator-dehydrator has a hollow delivery tube for delivering vaporized refrigerant and entrained oil to the compressor of the air conditioning system. The delivery tube has an expansion chamber and a separator to eliminate noise within the system.

Description:
TECHNICAL FIELD 
     This invention relates to an accumulator-dehydrator assembly for an air conditioning system. This invention specifically relates to an accumulator-dehydrator having a J-tube with an expansion chamber as part of the J-tube and a column separation feature as part of the J-tube. 
     BACKGROUND OF THE INVENTION 
     Vehicle air conditioning systems include a compressor that compresses and superheats refrigerant, which then runs through a condenser, expander and evaporator in turn before returning to the compressor to begin the cycle again. Mixed in with the refrigerant is a small amount of lubricating oil which is entrained within the refrigerant and is needed to ensure smooth performance of the compressor and to prolong the life of the compressor. 
     Interposed between the evaporator and compressor is an accumulator-dehydrator which is designed to accomplish several objectives. The accumulator-dehydrator primarily receives and accumulates the evaporator output effluent. The accumulator-dehydrator serves as a reservoir or separator in which fluid collects at the bottom and vapor at the top. The accumulator ensures that only refrigerant in a vapor stage passes to the compressor. The accumulator-dehydrator also prevents a liquid slug from being pulled or sucked into the downstream compressor. Still further, a desiccant is typically located in the bottom of the accumulator-dehydrator to absorb any water in the refrigerant. 
     Traditionally accumulator-dehydrators are known to use a U-shaped or 
     J-shaped tube more commonly known as a J-tube to collect liquid. The accumulator-dehydrator includes a canister with an inlet connected to the evaporator. The refrigerant enters the inlet as a vapor and liquid mixture. The liquid drops to the bottom of the canister and the vapor rises to the top. The J-tube is connected at one end to the canister outlet, which in turn is connected to the compressor. The J-tube extends down from the outlet to near the bottom of the canister and then turns upward and extends to near the top of the canister. The free end of J-tube, the portion near the canister top, is open to allow the vapor to be drawn into the J-tube and exit to the outlet to the compressor. A small opening is provided in the bottom turn-portion or U-portion of the J-tube to allow the liquid including the oil, to enter the J-tube and be entrained and delivered with the vapor to the compressor. 
     With traditional J-tube accumulator-dehydrators and the compressor disengaged (no flow through the J-tube), the J-tube will fill with liquid to the same level as the liquid in the canister. When the compressor is engaged a large pressure differential quickly occurs across the liquid stored in the J-tube. The large pressure differential causes the liquid in the J-tube to accelerate rapidly and to violently boil off. This rapid liquid acceleration and boiling imparts energy to the accumulator-dehydrator, which is classified as “bump” energy. This “bump” energy is present in all traditional J-tube accumulator-dehydrators. This energy manifests itself as a broad frequency noise known as the “bump”. 
     The energy imparted to the accumulator-dehydrator is a function of the rate of pressure drop across the liquid level in the J-tube within the accumulator-dehydrator. The pressure drop is affected by the compressor displacement, compressor drive ratio, and the amount of internal volume on the suction side of the accumulator-dehydrator. The magnitude and occurrence of noise is dependent on the total energy imparted to the accumulator-dehydrator, the accumulator-dehydrator lines and the extent of accumulator-dehydrator isolation. 
     SUMMARY OF THE INVENTION 
     The accumulator-dehydrator of the present invention has a modified J-tube which contains an expansion chamber. The expansion chamber is a bulge on the J-tube with a predetermined volume. The expanded portion of the lower end of the expansion chamber starts at a point above the liquid line in the modified J-tube. 
     As part of the J-tube there is also a section of side wall which protrudes towards the center of the expansion chamber of the J-tube. This protrusion is called the column separation feature. The column separation feature directs any fluid moving through the J-tube into the expansion chamber. The column separation feature further helps eliminate any liquid slug from being expelled from the accumulator-dehydrator. 
     When the compressor starts its cycle and begins to draw refrigerant into the compressor the expansion chamber in the J-tube lengthens the time of the pressure drop upon engagement of the compressor. The velocity of the liquid extracted from the J-tube is decreased and the liquid begins to boil or flash much easier because the expansion chamber provides for more room and a lower pressure. 
     In the preferred embodiment, the accumulator-dehydrator of the present invention uses a J-tube, which is manufactured out of plastic. This allows for economical and cost effective manufacturing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
     FIG. 1 is a schematic side view of the accumulator-dehydrator containing the J-tube showing the expansion chamber and column separation feature. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, the accumulator-dehydrator of the present invention is generally shown at  10 . The accumulator-dehydrator includes a two piece casing having cup-shaped members  20 , 22  sealingly joined by an annular weld. These two cup shaped members  20 , 22  form a canister  21  when welded together. Inlet fitting  26  and outlet fitting  28  are attached near the top  49  of the canister  21 . The accumulator-dehydrator  10  is connected through the fittings  26  and  28  to the refrigerant line  24  between the evaporator  18  and compressor  12 . 
     The air conditioning system is shown schematically at  11  and includes compressor  12  and evaporator  18  as well as condenser  14  and value  16 . 
     Liquid and vapor refrigerant enter the accumulator-dehydrator through the inlet fitting  26 . Vaporous refrigerant collects at the top  49  of canister  21  and liquid refrigerant collects at the bottom  48  of canister  21 . 
     A delivery tube or J-tube  30  is mounted internally in canister  21 . The J-tube is affixed to the outlet fitting  28  located near the top  49  of the canister. J-tube  30  has a flared opening  33  to draw in vaporized refrigerant from the upper portion of canister  21 . Mounted on the bottom of the J-tube  30  is a filter screen assembly  42 . Refrigerant and oil flow through the filter and into the J-tube  30  through a small hole  60  located in the bottom of the J-tube  30 . The liquid levels in the J-tube  30 , and in the canister  21 , are generally at the same level when the air conditioning system is idle. The J-tube may or may not include a pressure equalization hole  41 . Pressure equalization hole  41  is preferably located between the outlet  36  and the sidewall of the canister  21 . The pressure equalization hole equalizes the pressure in the J-tube  30  with that in the canister  21 . This arrangement insures that if liquid does accumulate in the J-tube, it will not be pulled into the compressor by refrigerant migration. 
     Expansion chamber  32  is disclosed as a large chamber, which protrudes away from the outer wall  31  of J-tube  30  into the canister  21 . In the disclosed embodiment chamber  32  generally fills the space within the upper portion of canister  21  between the inner walls  34  of J-tube  30 . In this way, a greater volume of expansion can be achieved. The disclosed chamber  32  has an outlet  36 , which is mechanically attached to outlet  28 . As will be appreciated, other attachment methods could be used. 
     To help direct the liquid into the expansion chamber  32  there is a column separation feature  35 . The column separation feature  35  is a protrusion that extends from the side wall  31  of the J-tube  30  into the main diameter of the J-tube  30  in the direction of the expansion chamber  32 . As the suction of the compressor pulls liquid (both oil and refrigerant) from the reservoir into the J-tube the column separation feature  35  helps stop a liquid slug from being passed on to the compressor  12 . The column separation feature  35  interferes with and directs any liquid flowing upward into the center of the expansion chamber away from the outlet  28  of the canister  21 . This redirection assists in the vaporization of the liquid by dispersing the liquid towards the large compartment of the expansion chamber  32 . 
     In the disclosed embodiment, a desiccant shown generally at  58  is provided to absorb moisture within the canister  21 . As illustrated, the desiccant  58  is mounted above the refrigerant and oil liquid level to absorb moisture from the vaporized refrigerant. 
     The invention has been described in an illustrative manner, and it is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for convenience and are not to be in any way limiting, the invention may be practiced otherwise than as specifically described.