Abstract:
A compressor valve plate ( 80 ) for a reed valve ( 94 ) has a mounting surface portion for mounting a base portion ( 104 ) of a reed ( 100 ). The compressor has a port ( 90 ). A seat ( 150 ) surrounds the port. A trepan ( 154 ) surrounds the seat. A relieved area ( 180, 182 ) less deep than the trepan extends proximally ( 182 ) of and distally ( 180 ) of the trepan. A reciprocating piston compressor comprises a valve assembly having such a compressor valve plate and a reed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    Benefit is claimed of U.S. Patent Application Ser. No. 61/696,729, filed Sep. 4, 2012, and entitled “Reciprocating Refrigeration Compressor Suction Valve Seating”, the disclosure of which is incorporated by reference herein in its entirety as if set forth at length. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to refrigeration compressors. More particularly, it relates to displacement compressors (e.g., reciprocating piston compressors) utilized to compress gases such as low global warming potential (GWP) and natural refrigerants. 
         [0003]    In a reciprocating compressor a piston head is driven between a lower position at which a fluid to be compressed enters the compression cylinder, and an upper or “top” position at which the compressed fluid is driven outwardly of the cylinder. A valve plate is typically placed at the top of the cylinder. The term “top” and “bottom” do not mandate any relative or absolute vertical orientation, but instead only to a relative position in the cylinder. The valve plate carries both inlet and outlet valves for allowing the flow of fluid into the cylinder, and out of the cylinder at appropriate points in the reciprocating movement of the piston. In reciprocating piston compressors and the like, pressure-actuated valves typically open and close once during each shaft revolution of the compressor. 
         [0004]    Various types of valves are known, and various types of valve plates have been utilized. One type of compressor valving structure uses reed valves. A reed valve may cover a plurality of circumferentially spaced ports. When the valve closes, it contacts the valve seat due to valve stiffness and/or pressure actuation, thus sealing flow out of the cylinder for the suction valve, or into the cylinder for the discharge valve 
       SUMMARY 
       [0005]    One aspect of the disclosure involves a compressor valve plate for a reed valve. The plate has a mounting surface portion for mounting a base portion of a reed. The compressor has a port. A seat surrounds the port. A trepan surrounds the seat. A relieved area less deep than the trepan extends proximally of and distally of the trepan. 
         [0006]    In various implementations, there may be a plurality of said ports whose trepans are contiguous. The relieved area may have a span of at least 1.0 mm The relieved area may have a depth of 0.1-0.3 mm The relieved area may have a depth of 40-60% of a trepan depth. 
         [0007]    Another aspect of the disclosure involves a compressor valve assembly comprising such a plate and a reed. The reed has a base mounted to the mounting surface portion and tip over the relieved area distally of the trepan. 
         [0008]    In various implementations, the reed is a single reed mounted to control flow through the plurality of said ports. The tip may protrude over the relieved area by at least 1.0 mm or by at least 15% of a maximum transverse dimension of the port or by at least 75% of a trepan radial span. 
         [0009]    Another aspect of the disclosure involves a compressor comprising such a compressor valve assembly. In various implementations, an electric motor may be within the case coupled to the crankshaft. The valve may be a suction valve. There may be a plurality of said ports whose trepans are contiguous. The reed may be a single reed mounted to control flow through the plurality of said ports. 
         [0010]    A method for using the compressor may comprise running the compressor so that a closing of the reed causes the reed to be at least partially accommodated in the relieved area. 
         [0011]    Another aspect of the disclosure involves a method for manufacturing such a compressor. The valve plate is a replacement for an existing valve plate lacking the relieved area or is formed by reengineering a configuration of such an existing valve plate. 
         [0012]    Other aspects of the disclosure involve a refrigeration system including such a compressor. The refrigeration system may include a recirculating flowpath through the compressor. A first heat exchanger may be positioned along the flowpath downstream of the compressor. An expansion device may be positioned along the flowpath downstream of the first heat exchanger. A second heat exchanger may be positioned along the flowpath downstream of the expansion device. The refrigerant charge may comprise at least 50% carbon dioxide or fluorocarbon by weight. The system may be a fixed refrigeration system. The fixed refrigeration system may further comprise multiple refrigerated spaces. There may be a plurality of said second heat exchangers, each being positioned to cool an associated such refrigerated space. 
         [0013]    The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a side view of a compressor. 
           [0015]      FIG. 2  is a vertical longitudinal sectional view of the compressor of  FIG. 1 . 
           [0016]      FIG. 3  is a partial vertical longitudinal sectional view of a cylinder of the compressor of  FIG. 1 . 
           [0017]      FIG. 3A  is an enlarged view of a valve area of the cylinder of  FIG. 3 . 
           [0018]      FIG. 4  is an underside view of a valve plate and suction valve reed assembly. 
           [0019]      FIG. 5  is a view of the valve plate of  FIG. 4 . 
           [0020]      FIG. 5A  is an enlarged view of a suction port group of the valve plate of  FIG. 5 . 
           [0021]      FIG. 6  is a view of the cylinder of  FIG. 3  in an intermediate position with a compressing condition of the valves shown solid and an expanding/suction condition shown broken. 
           [0022]      FIG. 7  is a schematic view of a refrigeration system. 
           [0023]      FIG. 8  is a schematic view of a fixed commercial refrigeration system. 
           [0024]      FIG. 9  is a partial vertical longitudinal sectional view of a cylinder of a prior art compressor. 
       
    
    
       [0025]    Like reference numbers and designations in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0026]      FIGS. 1 and 2  show an exemplary compressor  20 . The compressor  20  has a housing (case) assembly  22 . The exemplary compressor includes an electric motor  24  ( FIG. 2 ). The exemplary case  22  has a suction port (inlet)  26  and a discharge port (outlet)  28 . The housing defines a plurality of cylinders  30 ,  31 , and  32 . Each cylinder accommodates an associated piston  34  mounted for reciprocal movement at least partially within the cylinder. Exemplary multi-cylinder configurations include: in-line; V (vee); and horizontally opposed. The exemplary in-line compressor includes three cylinders. Each of the cylinders includes a suction location and a discharge location. For example, the cylinders may be coupled in parallel so that the suction location is shared/common suction plenum fed by the suction port  26  and the discharge location is a shared/common discharge plenum feeding the discharge port  28 . In other configurations, the cylinders may share suction locations/conditions but have different discharge locations/conditions. In other configurations, the cylinders may be in series. An exemplary fluorocarbon-based refrigerant is R-410A. An exemplary carbon dioxide (CO 2 )-based (e.g., at least 50% CO 2  by mass/weight) refrigerant is R-744. 
         [0027]    Each of the pistons  34  is coupled via an associated connecting rod  36  to a crankshaft  38 . The exemplary crankshaft  38  is held within the case by bearings for rotation about an axis  500 . The exemplary crankshaft is coaxial with a rotor  40  and stator  42  of the motor  24 . Each piston  30 - 32  is coupled to its associated connecting rod  36  via an associated wrist pin  44 .  FIG. 3  shows the pin  44  as having a central portion  46  mounted for rotation in an aperture  48  in a distal end portion  50  of the connecting rod  36 . The exemplary aperture may be in a bushing (not shown) interference fit in a main piece of the connecting rod. The pin has first and second end portions  52  and  53  mounted in apertures  54  and  55  of associated receiving portions of the piston (e.g., via interference fit such as press fit or via a journaled fit). 
         [0028]    The exemplary piston has a distal end face  60  ( FIG. 3 ) and a lateral/circumferential surface  62 . One or more sealing rings  64  may be carried in corresponding grooves  66  in the surface  62 . The cylinders each have a cylinder wall/surface  70 . 
         [0029]      FIG. 3  shows a cylinder upper end/wall  76  formed by the underside  78  of a valve plate  80  (for a reed valve system). The exemplary valve plate  80  is mounted to the upper face  82  of a cylinder block  84  of the case with a gasket  86  in between for sealing. 
         [0030]    Each cylinder has a plurality of inlet/suction ports  90  and outlet/discharge ports  92  extending through the plate  80  between the upper and lower surfaces thereof. Flows through the ports are controlled by valves. In this example, both inlet valves  94  and outlet valves  96  are reed valves.  FIG. 3  further shows a suction valve reed  100  and a discharge valve reed  102 . Each of the reeds has a proximal/base end portion (base)  104 ,  106  rigidly mounted to the case. Each of the reeds has a distal end portion  108 ,  110  which may shift via flexing of the reed to unblock the associated port and may relax to block the associated port.  FIG. 3  further shows a discharge valve backer  111  to limit the range of flexing of the discharge valve reed. 
         [0031]      FIG. 4  is an underside view of the valve plate with just three suction valve reeds  100  mounted thereto. For ease of illustration, the discharge valve reeds and backers which would be seen below are not included.  FIG. 4  is associated with an exemplary three-cylinder bank of cylinders. There may be one or more such banks of cylinders on a given compressor. Other numbers of cylinders are clearly possible. 
         [0032]      FIG. 5  is a corresponding view of the plate alone. For each cylinder, there are three suction ports  90  (individually labeled as  90 A,  90 B, and  90 C), and three discharge ports  92  (individually labeled as  92 A,  92 B, and  92 C).  FIG. 4  shows each reed  100  as blocking all three associated ports. The base  104  of the reed has an end/edge  130 . The exemplary base  104  comprises a transverse web having a pair of apertures receiving dowel pins  132  for registering the reed with the plate. The pins  132  extend to corresponding apertures in the plate and may be press fitted flush to the reed. The exemplary reed has a pair of arms or branches  134  and  136  extending distally from the base  104  and respectively passing between adjacent discharge ports with  134  passing between  92 A and  92 B and  136  passing between  92 B and  92 C. These branches  134  and  136  rejoin at the distal end portion  108  which is formed with an exemplary three lobes  140 A,  140 B, and  140 C (collectively and individually  140 ) respectively associated with the suction ports. Each of the lobes further comprises a generally circular main portion and a distally-projecting tip portion or tab  142 . The exemplary lobe main portions merge with each other, with the main portions of the lobes  140 A and  140 C respectively merging with the branches  134  and  136  and the lobe  140 B therebetween to join them. 
         [0033]      FIG. 5A  further shows each valve port as having an associated valve seat  150  circumscribing the associated port. The valve seat  150  has a rim  152  which may be formed as an intact portion of the flat lower surface of the original plate (e.g., the plate  80  may be machined from plate stock having two surfaces corresponding to the ultimate upper and lower surfaces). Each of the valve seats is surrounded by a trepan  154 . The exemplary trepans are vertically relieved/machined areas. The exemplary trepans are annular with each trepan just merging with the trepan of the adjacent suction port.  FIG. 3A  shows the trepan as having a base surface  156  and extending from an inboard sidewall  158  (which forms an outer wall of the seat  150 ) to an outer sidewall  160 . A depth of the trepan corresponds to the seat height H T .  FIG. 3A  shows the port as having an axis  540  and a radius R S  at the seat (along seat inner surface  161 ).  FIG. 3  further shows a seat thickness or seat radial span as  D R S . A trepan radial span is seen as  D R T . 
         [0034]      FIG. 6  is a view of the cylinder of  FIG. 3  in an intermediate position with a compressing condition of the valves shown solid and an expanding/suction condition shown broken. In the expanding condition, the underside of the suction reed  100  (position  100 ′) at the tips  142  is bottomed against the bases  210  of stop compartments  212  in the cylinder wall. The trepan limits contact between the valve and the plate (and defines the seat). By establishing a narrow seat, the trepan limits a contact area where there is likely to be an oil film. If there was a broad contact area at the port, the oil would cause stiction. By defining the seat, there is a more limited contact area around the port and much reduced stiction. The trepan width is effective to go slightly beyond the valve lobe planform at least away from the tabs and legs/arms. This helps break stiction when the valve is opening. The closed discharge valve reed is shown in broken line as  102 ′ while shown open in solid line. 
         [0035]      FIGS. 3A and 5A  show a relieved area  180 ,  182  outboard of the trepan.  FIG. 9  shows a baseline valve plate lacking the relieved area. The relieved area may be added in a reengineering of the baseline compressor configuration. Additionally, it may be implemented in the remanufacturing of a compressor such as by replacing the baseline valve plate with the present valve plate. A minimal such reengineering or remanufacturing may preserve all other components. For example, identical reeds might be used in the reengineering or a remanufacturing. 
         [0036]    In the exemplary  FIG. 5A  illustration, there is one relieved area distal portion  180  for each of the seats extending generally distally and of complementary planform to the tab  142  of the associated reed lobe  140 A- 140 C. The relieved area  180  is slightly broader in planform so as to be able to receive the tab when the tab over flexes after snapping back into engagement with the seat from its open condition.  FIG. 3A  shows the areas  180 ,  182  as having a depth H 1  between an intact portion  190  of the plate lower surface and a base surface  192  of the relieved area. The exemplary H 1  is 10-90% of H T , more narrowly, 30-70% or 40-60%. 
         [0037]      FIG. 3A  shows an exemplary spacing S 1  by which the relieved area is broader than the tab. Exemplary S 1  is 0.25-1.0 mm, more narrowly, 0.50-0.75 mm Advantageously, S 1  is large enough so as to provide clearance between the edge of the valve and the valve plate at all possible conditions of misalignment between the two parts based on manufacturing tolerances. Further significant increase merely serves to increase clearance volume and undesirably reduce the volumetric efficiency.  FIG. 3A  shows an exemplary spacing S 2  by which the reed protrudes over the relieved area. Exemplary S 2  at the tip will depend on tip size (in turn determined by the desired tip loading against the stop ( 201  in  FIG. 6 ). Exemplary S 2  at proximal portions will be coincident with the relieved area radial span or other thickness. Exemplary peak S 2  at the tips might be similar subject to the small clearance. Alternatively, such S 2  may be at least 30% of R S  (e.g., 15-40% of the port/seat diameter).  FIG. 3A  shows an exemplary spacing S 3  by which the relieved area is broader than the trepan (extends beyond the trepan). Exemplary S 3  is at least about 75%, more particularly 75-200% of the trepan radial span at the peak relieved area span locations (centrally aligned with the tips and at proximal ends of the lobes) more narrowly, 120-150%. The radial span of the relieved areas is smaller or nonexistent away from the tips/tabs and the proximal regions of the lobes (e.g., adjacent the tabs and along outboard sides of the outboard lobes). The exemplary relived area includes portions isolated at the two cusps between trepans distally thereof and the single proximal region spanning all three trepans. Exemplary S 3  is at least 1.0 mm and exemplary H 1  is 0.1-0.3 mm 
         [0038]    The exemplary relieved area proximal portions  182  are of generally greater planform in the area of the two outboard ports in order to accommodate slight overflexing of the branches. Although the relieved area proximal portions are shown as of the same depth as the distal portions  180 , given the nearer proximity to the base/root, there will be much less overflexing. Accordingly, these relieved areas might be of lower depth than the areas  180 . Additionally, the possibility exists of having a slight variation in depth. 
         [0039]    The relieved areas may serve one or more of several functions. They may improve valve seating by any of several mechanisms. First, they may reduce or eliminate the effect of any gas or lubricant film on portions of the reed away from the seat which might prevent full closing. Similarly, they may reduce the effect of any locally trapped debris. Additionally, wear on the seat and mating portion of the reed upper face might otherwise lead to slapping of the portion of the reed beyond the trepan against the intact surface of the plate (thereby reducing engagement forces with the seat or even leaving gaps). In a baseline compressor, this effect may be observed as wear on the tips of the reed and valve plate. The additional clearance zone, reduced or eliminates this. Additionally, the effects of valve plate and suction valve flatness, and any deflections that can occur due to pressure differentials may be reduced. For example,  FIG. 3A  shows the reed (via broken line upper surface  198 ″) partially accommodated by the relieved area. The exemplary accommodation might be representative of a combination of a general recessing do to wear at the seat and a slight bending at the tip  142 , thereby providing slightly deeper accommodation at the tip. 
         [0040]      FIG. 7  shows an exemplary refrigeration system  220  including the compressor  20 . The system  220  includes a system suction location/condition  250  at the suction port  26 . A refrigerant primary flowpath  252  proceeds downstream from the suction location/condition  250  through the compressor cylinders in parallel to be discharged from a discharge location/condition  254  at the discharge port  28 . The primary flowpath  252  proceeds downstream through the inlet of a first heat exchanger (gas cooler/condenser)  256  to exit the outlet of the gas cooler/condenser. The primary flowpath  252  then proceeds downstream through an expansion device  262 . The primary flowpath  252  then proceeds downstream through a second heat exchanger (evaporator)  264  to return to the suction condition/location  250 . 
         [0041]    In a normal operating condition, a recirculating flow of refrigerant passes along the primary flowpath  252 , being compressed in the cylinders. The compressed refrigerant is cooled in the gas cooler/condenser  256 , expanded in the expansion device  262 , and then heated in the evaporator  264 . In an exemplary implementation, the gas cooler/condenser  256  and evaporator  264  are refrigerant-air heat exchangers with associated fan ( 270 ;  272 )-forced airflows ( 274 ;  276 ). The evaporator  264  may be in the refrigerated space or its airflow may pass through the refrigerated space Similarly, the gas cooler/condenser  256  or its airflow may be external to the refrigerated space. 
         [0042]    Additional system components and further system variations are possible (e.g., multi-zone/evaporator configurations, economized configurations, and the like). Exemplary systems include refrigerated transport units and fixed commercial refrigeration systems. 
         [0043]    An exemplary fixed commercial refrigeration system  350  ( FIG. 8 ) includes one or more central compressors  20  and heat rejection heat exchangers  256  (e.g., rack-mounted outside/on a building  355 ) commonly serving multiple refrigerated spaces  356  (e.g., of retail display cabinets  358  in the building). Each such refrigerated space may have its own heat absorption heat exchanger  264 ′ and expansion device  262 ′ (or there may be a common expansion device). Other rack-mount situations include building heating, ventilation and air conditioning (HVAC). 
         [0044]    The compressor may be manufactured via otherwise conventional manufacturing techniques. The pistons and cylinder block may be cast and machined as may other components. The valve plate may be machined from plate stock. The reeds may be cut from sheet stock. 
         [0045]    Although an embodiment is described above in detail, such description is not intended for limiting the scope of the present disclosure. It will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example, when implemented in the reengineering of an existing compressor configuration, details of the existing configuration may influence or dictate details of any particular implementation. Accordingly, other embodiments are within the scope of the following claims.