Patent Publication Number: US-4549857-A

Title: Hermetic motor compressor having a suction inlet and seal

Description:
BACKGROUND OF THE INVENTION 
     As hermetic motor-compressor units have become increasingly more compact, a number of new problems have been introduced which require solutions. Noise generation has become a major problem resulting from the more compact configurations. As expected, discharge noises are increased in the more compact configurations, but suction side noise generation has reached a noise level requiring a solution especially in view of the noise reduction measures taken on the discharge side. 
     SUMMARY OF THE INVENTION 
     In a two-cylinder reciprocating hermetic compressor, the suction gas supply to each of the two cylinders is via a pair of long slim suction gas supply tubes running through a space between the stator and the cylinder head and into an enclosure surrounding each valve plate. The long slim tubes are integral with the suction seal so as to effectively utilize the space between the cylinder deck and the stator on one side and the cylinder head on the other side. The tubes extend well above the stator core into the cooler suction gas region. The length of the tubes and their cross sectional area are chosen so that the tubes are tuned to minimize the suction gas pulsations. 
     It is an object of the invention to provide pressure pulse attenuation and tuning. 
     It is another object of this invention to provide a suction seal with integral suction gas supply tubes. These objects, and others as will become apparent hereinafter, are accomplished by the present invention. 
     Basically, the suction gas supply tubes are made integral with the seal located between the cylinder head and the cylinder block. The seal effectively fills and seals the space surrounding the valve plate. The suction gas supply tubes extend well above the stator core into the cooler suction gas region and their length is tuned to minimize suction gas pulsations. If necessary, or desirable, additional pressure pulse attenuation may be obtained by providing a resonant chamber on the side or the top of each tube. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the present invention, reference should now be made to the following detailed description thereof taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a sectioned view of a motor-compressor unit employing the present invention; 
     FIG. 2 is an exploded, partially sectioned view of the present invention; 
     FIG. 3 is a horizontal sectional view showing the fluid paths; 
     FIG. 4 is a vertical sectional view showing the fluid paths; 
     FIG. 5 is an isometric partially cutaway view of the suction inlet and seal; and 
     FIG. 6 is a section view taken along line VI--VI of FIG. 5. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIG. 1, the numeral 10 generally designates the hermetic motor compressor unit which is in a shell made up of a lower section 11 and an upper section 12 which are welded together. An electric motor 14 and a compressor 16 are disposed within the shell. The compressor 16 is axially aligned with motor 14 and is disposed therebelow. 
     The motor 14 includes a stator 15 and a rotor (not illustrated) which is operatively connected to drive the crankshaft (not illustrated) which is supported within the cylinder block 20. Referring now to FIGS. 2-4, the cylinder block 20 receives the suction valve guide 40 which, in turn, receives the valve plate assembly 50. The valve plate assembly 50 is received within the suction inlet and seal 60. Cylinder head 80 is separated from seal 60 by gasket 70. The cylinder block 20, valve guide 40, valve plate assembly 50, seal 60, gasket 70 and cylinder head 80 are bolted together as a unit by bolts 90, as is best shown in FIG. 1. 
     Referring back to FIG. 2, it will be seen that cylinder block 20 defines two piston chambers 21 and 22 which are surrounded by the suction plenum. The suction plenum is divided into two parts, 23a and b, by a partition wall 24. The partition wall 24 has two apertures 24a and b formed therein to provide a restricted fluid communication between the two parts of the suction plenum 23a and b. 
     FIGS. 3 and 4 have been taken along several sectional lines in order to show continuity of fluid paths. As best shown in FIG. 3, there are two suction inlets and seals 60 and 61 which define four suction gas supply or inlet tubes 60a-d with tubes 60a and b communicating with plenum 23a and tubes 60c and d communicating with plenum 23b. Apertures 24a and b provide restricted communication between plenums 23a and b. Suction inlets and seals 60 and 61 are identical and surround valve plate assemblies 50 and 51, respectively, and are separated from cylinder heads 80 and 81 by gaskets 70 and 71, respectively. 
     As best shown in FIGS. 3-6, each of the suction inlets and seals 60 and 61 are identical and tubes 60a and d are mirror images of tubes 60b and c respectively. The seals 60 and 61 are molded plastic with tubular steel inserts 62 which minimize creep resulting from clamping forces when seals 60 and 61 are assembled. The plastic chosen should have resistance to creep at high temperatures and resistance to deterioration by refrigerants and oils. A suitable plastic is a 15% glass filled polyester marketed by General Electric Company under the name Valox DR-51. Also, the low thermal conductivity of the plastic minimizes suction gas super heating. Referring specifically to tube 60b as typical, the inlet 68 is flared and of a long, narrow tapering cross section as best shown in FIG. 3. The flare and the long, narrow tapering cross section minimizes flow losses. Referring now to FIG. 5, the passageway defined by each tube terminates in a throat to increase the gas velocity so as to improve gas distribution into the chamber. Specifically, tube 60b has a throat 66 which discharges gas into chamber 64 surrounding valve assembly 50. The throat 66 is restricted at the entrance to chamber 64 by the plastic material surrounding the adjacent tubular steel insert 62. Additionally, the length of tubes 60a-d is such that in combination with the cross sectional area, it provides pressure pulse attenuation and tuning as well as drawing gases from the cooler sections of the motor-compressor unit 10. Further, since the valve plate assemblies 50 and 51 extend out past the cylinder block 20, the seals 60 and 61 serve to seal the gaps between the cylinder block 20 and cylinder heads 80 and 81 and permits the use of inexpensive cylinder head construction such as low cost stamped steel or aluminum die casting. Each one of the tubes 60a-d is in fluid communication with each one of the piston chambers 21 and 22 when the corresponding pistons are on the suction stroke. More specifically, tubes 60a and b discharge into suction plenum 23a while tubes 60c and d discharge into suction plenum 23b. Since suction plenums 23a and b are in fluid communication via apertures 24a and b in partition 24, there is a continuous fluid path between tubes 60a-d and both suction plenums 23a and b. Flow is unidirectional toward the suction plenum that is associated with a piston in the suction stroke. 
     Assuming that the piston associated with piston chamber 21 is on the suction stoke while the piston associated with piston chamber 22 is on the discharge stroke, a suction pressure will be established in suction plenum 23a. Refrigerant in the shell of the hermetic motor compressor unit 10 will then be drawn into tubes 60a and b and pass into the rectangular space 64 surrounding valve plate assembly. Rectangular space 64 is in direct fluid communication with suction plenum 23a. Refrigerant is drawn into piston chamber 21 from space 64 and plenum 23a via inlet openings 52. Because suction plenum 23a is at a vacuum relative to suction plenum 23b, additional refrigerant is drawn into plenum 23a from plenum 23b via apertures 24a and b. This, in turn, creates a vacuum in plenum 23b relative to the interior of the shell of hermetic compressor unit 10 causing refrigerant to be drawn into tubes 60c and d, through rectangular space 65 and into plenum 23b. Since the flow paths from tubes 60a and b to piston chamber 21 are much shorter than the flow paths from tubes 60c and d to piston chamber 21, as well as being unrestricted by apertures 24a and b, and, because of the short stroke duration, flow through tubes 60a and b is much greater than the flow through tubes 60c and d. However, there is flow through each of the tubes 60a-d so that there is no stoppage of flow and the resultant noise. The analogous situation exists when the piston associated with piston chamber 22 is in the suction stroke and the flow is much greater through tubes 60c and d than tubes 60a and b. 
     From the foregoing it is readily apparent that the present invention provides an integral seal and suction gas supply tube construction which provides pressure pulse attenuation and timing for the design speed and supplies suction gas to the chamber surrounding the associated valve assembly as well as to the associated suction plenum. Additionally, a seal is provided which spans and seals the gap between the cylinder block and the cylinder head. 
     Although a preferred embodiment of the present invention has been illustrated and described, other changes will occur to those skilled in the art. For example, resonant chambers can be formed as part of the suction tubes for greater noise attenuation.