Abstract:
A compressor apparatus having a check valve ( 70 ) having a first condition permitting downstream flow along the flowpath and a second condition blocking a reverse flow. The valve element includes a resonator ( 112 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to compressors. More particularly, the invention relates to compressors having check valves. 
         [0002]    Screw-type compressors are commonly used in air conditioning and refrigeration applications. In such a compressor, intermeshed male and female lobed rotors or screws are rotated about their axes to pump the working fluid (refrigerant) from a low pressure inlet end to a high pressure outlet end. During rotation, sequential lobes of the male rotor serve as pistons driving refrigerant downstream and compressing it within the space between an adjacent pair of female rotor lobes and the housing. Likewise sequential lobes of the female rotor produce compression of refrigerant within a space between an adjacent pair of male rotor lobes and the housing. The interlobe spaces of the male and female rotors in which compression occurs form compression pockets (alternatively described as male and female portions of a common compression pocket joined at a mesh zone). In one implementation, the male rotor is coaxial with an electric driving motor and is supported by bearings on inlet and outlet sides of its lobed working portion. There may be multiple female rotors engaged to a given male rotor. 
         [0003]    When one of the interlobe spaces is exposed to an inlet port, the refrigerant enters the space essentially at suction pressure. As the rotors continue to rotate, at some point during the rotation the space is no longer in communication with the inlet port and the flow of refrigerant to the space is cut off. After the inlet port is closed, the refrigerant is compressed as the rotors continue to rotate. At some point during the rotation, each space intersects the associated outlet port and the closed compression process terminates. The inlet port and the outlet port may each be radial, axial, or a hybrid combination of an axial port and a radial port. The compression pocket opening and closing (particularly discharge port opening) are associated with pressure pulsations and resulting sound. Sound suppression has thus been an important consideration in compressor design. Many forms of compressor mufflers have been proposed. 
         [0004]    Additionally, various transient conditions may tend to cause reverse flow through the compressor. For example, upon a power failure or other uncontrolled shutdown high pressure refrigerant will be left in the discharge plenum and downstream thereof in the refrigerant flowpath (e.g., in the muffler, oil separator, condenser, and the like). Such high pressure refrigerant will tend to flow backward through the rotors, reversing their direction of rotation. If rotation speed in the reverse direction is substantial, undesirable sound is generated. For some screw compressors, damage to mechanical components or internal housing surfaces can also occur. Accordingly, a one-way valve (a check valve) may be positioned along the flowpath to prevent the reverse flow. Other forms of compressor (e.g., scroll and reciprocating compressors) may include similar check valves. 
       SUMMARY OF THE INVENTION 
       [0005]    A compressor apparatus has a housing having first and second ports along a flowpath. One or more working elements cooperate with the housing to define a compression path between suction and discharge locations along the flowpath. A check valve has a valve element having a first condition permitting downstream flow along the flowpath and a second condition blocking a reverse flow. The valve element includes a resonator. 
         [0006]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a longitudinal sectional view of a compressor. 
           [0008]      FIG. 2  is a partial sectional view of a discharge housing check valve of the compressor of  FIG. 1  in a first condition. 
           [0009]      FIG. 3  is a partial sectional view of the discharge housing check valve of the compressor of  FIG. 1  in a second condition. 
           [0010]      FIG. 4  is a partial sectional view of a second check valve. 
           [0011]      FIG. 5  is a partial sectional view of a third check valve. 
           [0012]      FIG. 6  is an end view of the check valve of  FIG. 5 . 
       
    
    
       [0013]    Like reference numbers and designations in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0014]      FIG. 1  shows a compressor  20  having a housing assembly  22  containing a motor  24  driving rotors  26  and  28  having respective central longitudinal axes  500  and  502 . In the exemplary embodiment, the rotor  26  has a male lobed body or working portion  30  extending between a first end  31  and a second end  32 . The working portion  30  is enmeshed with a female lobed body or working portion  34  of the female rotor  28 . The working portion  34  has a first end  35  and a second end  36 . Each rotor includes shaft portions (e.g., stubs  39 ,  40 ,  41 , and  42  unitarily formed with the associated working portion) extending from the first and second ends of the associated working portion. Each of these shaft stubs is mounted to the housing by one or more bearing assemblies  44  for rotation about the associated rotor axis. 
         [0015]    In the exemplary embodiment, the motor is an electric motor having a rotor and a stator. One of the shaft stubs of one of the rotors  26  and  28  may be coupled to the motor&#39;s rotor so as to permit the motor to drive that rotor about its axis. When so driven in an operative first direction about the axis, the rotor drives the other rotor in an opposite second direction. The exemplary housing assembly  22  includes a rotor housing  48  having an upstream/inlet end face  49  approximately midway along the motor length and a downstream/discharge end face  50  essentially coplanar with the rotor body ends  32  and  36 . Many other configurations are possible. 
         [0016]    The exemplary housing assembly  22  further comprises a motor/inlet housing  52  having a compressor inlet/suction port  53  at an upstream end and having a downstream face  54  mounted to the rotor housing downstream face (e.g., by bolts through both housing pieces). The assembly  22  further includes an outlet/discharge housing  56  having an upstream face  57  mounted to the rotor housing downstream face and having an outlet/discharge port  58 . The exemplary rotor housing, motor/inlet housing, and outlet housing  56  may each be formed as castings subject to further finish machining. 
         [0017]    Surfaces of the housing assembly  22  combine with the enmeshed rotor bodies  30  and  34  to define inlet and outlet ports to compression pockets compressing and driving a refrigerant flow  504  from a suction (inlet) plenum  60  to a discharge (outlet) plenum  62  ( FIG. 2 ). A series of pairs of male and female compression pockets are formed by the housing assembly  22 , male rotor body  30  and female rotor body  34 . Each compression pocket is bounded by external surfaces of enmeshed rotors, by portions of cylindrical surfaces of male and female rotor bore surfaces in the rotor case and continuations thereof along a slide valve, and portions of face  57 . 
         [0018]      FIG. 2  shows further details of the exemplary flowpath at the outlet/discharge port  58 . A check valve  70  is provided having a valve element  72  mounted within a boss portion  74  of the outlet housing  56 . The exemplary valve element  72  is a front sealing poppet having a stem/shaft  76  unitarily formed with and extending downstream from a head  78  along a valve axis  520 . The head has a back/underside surface  80  engaging an upstream end of a compression bias spring  82  (e.g., a metallic coil). The downstream end of the spring engages an upstream-facing shoulder  84  of a bushing/guide  86 . The bushing/guide  86  may be unitarily formed with or mounted relative to the housing and has a central bore  88  slidingly accommodating the stem for reciprocal movement between an open condition of  FIG. 2  and a closed condition of  FIG. 3 . The spring  82  biases the element  72  upstream toward the closed condition. In the closed condition, an annular peripheral seating portion  90  of the head upstream surface seats against an annular seat  92  at a downstream end of a port  94  from the discharge plenum  62 . 
         [0019]    The opening and closing of the compression pockets at suction and discharge ports produce pressure pulsations. As the pulsations propagate into the gas in the discharge plenum and downstream thereof, they cause vibration and associated radiated sound which are undesirable. This pulsation may be at least partially addressed by modifications involving the check valve. Exemplary modifications involve modifications to the valve head to incorporate one or more resonators tuned to suppress/attenuate one or more sound/vibration frequencies. Exemplary modifications make use of existing manufacturing techniques and their artifacts. Exemplary modifications may be made in a remanufacturing of an existing compressor or a reengineering of an existing compressor configuration. An iterative optimization process may be used to tune the resonator(s). 
         [0020]      FIG. 2  shows one exemplary modification of a basic valve element. This modification involves providing the head  78  with an upstream extending annular wall  100  inboard of the seating portion  90 . The wall has inboard and outboard surfaces  102  and  104 . The exemplary wall  100  extends upstream from a proximal downstream end  106  (joining a remaining portion of the head) to a distal upstream end formed by a rim  108 . The surface  102  of the wall  100  and an upstream-facing surface  109  of a central web portion  110  of the head form a forwardly/upstream open blind compartment/cavity  112  having an upstream port/opening  114  encircled by the rim  108 . Along the compartment  112 , the inboard surface has an essentially constant radius R along a length L. The compartment  112  forms a side branch resonator. Geometric properties of the compartment  112  (e.g., the length and volume) may be tuned to suppress/attenuate one or more sound/vibration frequencies at one or more conditions. An exemplary frequency is that of the compression pockets opening/closing at the designed compressor operating speed and at the designed refrigeration system operating condition. Thus examples of otherwise identical compressors may feature differently-tuned resonators for use in different systems or conditions thereof. Exemplary modifications make use of existing manufacturing techniques and their artifacts. Exemplary modifications may be made in a remanufacturing of an existing compressor or a reengineering of an existing compressor configuration. An iterative optimization process may be used to tune the resonator(s). 
         [0021]      FIG. 4  shows an alternate check valve  170  which may be generally similar to the check valve  70 . Like features of these two valves are shown with like reference numerals. The valve  170  has a valve element  172  wherein the resonator blind compartment/cavity  174  extends downstream into the stem  178  from a port  180  in the head  176  and has a length L 1  and a radius R 1 . These may, respectively be larger and smaller than corresponding parameters of the valve  70  if required to tune the resonator for a corresponding frequency. 
         [0022]      FIGS. 5 and 6  show an alternate check valve  270  which may be generally similar to the check valves  70  and  170 . Like features of these three valves are shown with like reference numerals. The valve  270  has a valve element  272  wherein the resonator compartment/cavity  274  extends upstream within the stem  276  from a port  280  at a stem downstream rim/end  278  toward the head  282  (and potentially into the head). The cavity has a length L 2  and a radius R 2 . These may be similar to corresponding parameters of the valve  170 . 
         [0023]    The relative proximity of the resonator to the discharge plenum is believed advantageous for several reasons. First, the check valve is upstream of components like piping and oil separator that radiate sound due to internal pulsations. Locating a resonator in the check valve therefore cancels pulsations upstream of such components. Second, locating a resonator in the check valve is an effective use of space. Alternative locations might require adding additional material to housing walls. 
         [0024]    Many known or yet-developed resonator configurations and optimization techniques may be applied. The former include, for example, Helmholtz resonators. 
         [0025]    One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, in a reengineering or remanufacturing situation, details of the existing compressor may particularly influence or dictate details of the implementation. Implementations may involve check valves used in other locations in the fluid circuit. The principles may be applied to compressors having working elements other than screw-type rotors (e.g., reciprocating and scroll compressors). Accordingly, other embodiments are within the scope of the following claims.