Abstract:
A hermetic compressor assembly includes a compressor housing having a quantity of liquid lubricant therein. A compressor mechanism is provided within the compressor housing and a drive shaft is selectively rotatable and operably connected to the compressor mechanism. A liquid lubricant displacement element is engaged to the drive shaft and a support member is attached to the compressor housing. A pivotable magnetic member is provided between the liquid lubricant displacement element and the support member and includes a suction port provided therein. The liquid lubricant displacement element is in fluid communication with the quantity of liquid lubricant through the suction port in the magnetic member. At least a portion of any ferrous particles contained in the liquid lubricant are attracted to and retained by the magnetic member as the liquid lubricant is passed through the suction port of the magnetic member.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to hermetic compressors having positive displacement liquid lubricant pumps to supply liquid lubricant to bearing surfaces. More specifically, the present invention relates to compressors including liquid lubricant pumps having cavities disposed within the pump and drive shaft to trap debris by magnetic and centrifugal force. 
     2. Description of the Related Art 
     Compressor lubrication systems often include a positive displacement lubrication pump to supply liquid lubricant to bearing surfaces within the compressor. Liquid lubricant, or oil, often contains debris in the form of metallic particles circulating throughout the lubrication system. The particles detrimentally affect bearing surfaces by causing premature wear, and consequently, compressor performance is compromised. It is known to provide cartridge type or screen filters to capture debris, however an inherent disadvantage of cartridge and screen filters is that they clog and consequently block circulation of oil to bearing surfaces which significantly shortens the life of the compressor. Responsive to this clogged filter effect, compressor assemblies have been adapted with bypass valving, for example, which routes the oil around the filter when the filter becomes clogged to effectively maintain an adequate oil supply to the bearing surfaces. However, the circulating oil remains debris-laden which may cause an abrasive attack on the bearing surfaces resulting in bearing seizure and imminent failure of the compression mechanism. 
     Hermetic compressor assemblies are susceptible to oil-entrained debris, the most destructive being the fine powdered debris, which may not be captured by standard cartridge and filtering methods. The fine powders entrained in the oil are often composed of ferrous material which is attracted to a magnet. While previous compressor assemblies have utilized magnets to attract entrained metallic particles, these compressors have proven to do so inefficiently. Typically, magnets are randomly placed within the interior of the compressor housing, producing marginal particle accumulation performance. Therefore, the marginal benefits provided by these types of compressors, in view of the substantial costs associated with installing magnets to attract ferrous particles, have limited their practicality. 
     Further, with evolving and more demanding environmental standards, the hydrocarbon based oils and refrigerants traditionally used are yielding to environmental friendly substitutes. However, it is not fully understood whether these substitute lubricants are equally effective in providing comparable levels of lubrication and durability to the compressor mechanism. Thus, improving the ability to remove foreign particles from liquid lubricant, without a substantial compressor assembly cost increase, would be highly desirable. 
     Yet another problem associated with the use of impeller type pumps in compressor assemblies is one of drive shaft misalignment, relative to the pump housing, during the assembly process. Traditionally, misalignment of the drive shaft and pump housing was avoided by providing the pump housing, compressor mechanism assembly and impeller pump assembly with precise tolerances. A significant labor and handling cost is associated with parts having precise tolerances. What is desired is an impeller type pump assembly structure which requires significantly less labor to manufacture and assemble compared to previously employed structures. 
     An inexpensive oil pump assembly which includes the ability to trap debris suspended in the oil while continuously providing an ample supply of oil to bearing surfaces is highly desired. Further, an oil pump assembly which provides further cost reduction attributable to avoiding precise part tolerances in preventing drive shaft and pump housing misalignment is desired. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the disadvantages of prior compressor assemblies by providing a hermetic compressor assembly which includes a compressor housing including a quantity of liquid lubricant therein, a compressor mechanism provided within the compressor housing, a drive shaft selectively rotatable and operably connected to the compressor mechanism, a liquid lubricant displacement element engaged to the drive shaft and a support member attached to the compressor housing, a pivotable magnetic member provided between the liquid lubricant displacement element and the support member provided with a suction port therein. The liquid lubricant displacement element is in fluid communication with the quantity of liquid lubricant through the suction port in the magnetic member. At least a portion of any ferrous particles contained in the liquid lubricant are attracted to and retained by the magnetic member as the liquid lubricant is passed through the suction port of the magnetic member. 
     The present invention further provides a hermetic compressor assembly including a compressor mechanism and a quantity of liquid lubricant provided in a compressor housing, a selectively operable drive shaft driveably connected to the compressor mechanism, a liquid lubricant displacement element supported by a support member and engaged to the drive shaft. The compression mechanism and the liquid lubricant displacement element are in fluid communication through a passage provided in the drive shaft. A centrifugal particle trap cavity is defined by a wall of the passage within the drive shaft and a portion of the liquid lubricant displacement element. A magnetic member is pivotably supported by the support member and a thrust member is superposed with the magnetic member. A magnetic particle trap cavity is provided within a lateral face of the thrust member and is partially enclosed by a lateral surface of the magnetic member. The liquid lubricant is urged from the sump to the compression mechanism through the passage in the drive shaft and any debris in the liquid lubricant is successively retained by the magnetic particle trap cavity and the centrifugal particle trap cavity prior to the lubricants introduction to the compression mechanism. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a sectional view of a hermetic compressor assembly provided with an oil pump assembly in accordance with the present invention; 
     FIG. 2A is an exploded view of a first embodiment of an oil pump assembly in accordance with the present invention, viewing the pump from the bottom; 
     FIG. 2B is an exploded view of the thrust plate and magnetic disk assembly of a second embodiment of an oil pump assembly in accordance with the present invention, viewing the assembly from the bottom; 
     FIG. 3A is an exploded view of the oil pump assembly of FIG. 2A, viewing the pump from the top; 
     FIG. 3B is an exploded view of the thrust plate and magnetic disk assembly of FIG. 2B, viewing the assembly from the top; 
     FIG. 4 is a sectional view of the oil pump assembly taken along line  4 — 4  of FIG. 11, however shown in an operational mode, illustrating a flow of oil therethrough and particles being trapped in respective magnetic and centrifugal traps; 
     FIG. 5 is a sectional view of the oil pump assembly taken along lines  5 — 5  of FIG. 11, however shown in a non-operational mode; 
     FIG. 6 is a plan view of the bottom of the impeller of the oil pump of FIG. 2A, showing the plurality of impeller blades; 
     FIG. 7 is a plan view of the bottom of the thrust plate of the oil pump of FIG. 2A, showing the pair of arcuate slots and the magnetic particle trap cavity; 
     FIG. 8 is a plan view of the bottom of the magnetic disk of the oil pump of FIG. 2A; 
     FIG. 9 is a plan view of the top of the pump housing of the oil pump of FIG. 3A; 
     FIG. 10A is a fragmentary sectional view of the oil pump assembly according to the present invention enclosed within the circular portion shown as line  10 A— 10 A of FIG. 11, showing the engagement between the frustoconical surfaces of the pump housing and magnetic disk; 
     FIG. 10B is a fragmentary sectional view of a third embodiment of the oil pump assembly according to the present invention showing the engagement between the spherical surfaces of the pump housing and magnetic disk; and 
     FIG. 11 is a bottom view of the oil pump assembly of FIG.  2 A. 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, compressor assembly  10  includes hermetically sealed housing  12 , having base  17  provided at a lower end thereof. Motor assembly  14 , enclosed within housing  12 , includes rotor  11  and stator  13  and is directly connected to, and operatively drives, compression mechanism  15 . Compression mechanism  15  may constitute a reciprocating piston-type compression mechanism, as shown, which includes cylinder block  16  having reciprocating piston  18  therein. Alternatively, compression mechanism  15  may be a rotary or scroll type mechanism. Drive shaft or crankshaft  20 is driveably coupled to motor assembly  14  and extends vertically from a lowermost portion of compressor assembly  10  upwardly towards compression mechanism  15 . Upper end of crankshaft  20  is rotatably supported by main bearing  22  and is generally hollow, including inner passage  23  extending axially, and continuously, along the length of crankshaft  20 . Arrows  25  illustrate flow of liquid lubricant (e.g., oil), which is directed through passage  23  of crankshaft  20 , to supply oil to bearing surfaces, such as rod bearing  24 , and to wrist pin  27 , as shown. Oil pump assembly  42  is positioned at lower end  36  of crankshaft  20  to urge oil from oil sump  30  to upper end  38  of crankshaft  20 . Support member  43 , provided within lower portion  28  of housing  12  to support pump  42 , includes a plurality of arms  33  equidistantly spaced and radially extended between pump  42  and inner surface  35  of housing  12 . Oil sump  30 , formed by lower portion  28  of housing  12 , contains surplus oil to supply pump assembly  42  with oil. Oil level  32  within sump  30  is preferably maintained above oil pump assembly  42 , as shown, such that a continuous supply of oil is pumped to bearing surfaces by pump assembly  42 . 
     Referring to FIGS. 2A and 3A, shown is oil pump assembly  42 , engaged with lower end  36  of crankshaft  20 . Lower end  36  of crankshaft  20  includes end face  50  and outer surface  46 . Lower end  36  of crankshaft is attached to oil displacement element or impeller  52 . Alternatively, oil displacement element  52  may include a gerotor or gear type element to transfer oil from sump  30  to compression mechanism  15  (FIG.  1 ). It may be seen that counterbore  40  (FIG. 2A) is formed in lower end  36  of crankshaft  20  to receive stem  56  of impeller  52 . End face  50  of crankshaft  20  includes angled counterbore or chamfer  44  provided in counterbore  40  of crankshaft  20  (FIG.  2 A). A pair of diametrically opposed slots  48  (FIG. 2A) radially extend from counterbore  40  of crankshaft  20  toward outer surface  46  of crankshaft  20  to engageably receive tangs  60  of impeller  52 . Tangs  60  axially extend from disk shaped drive portion  54  and are attached to a periphery of impeller stem  56  (FIG.  3 A). 
     Impeller stem  56  axially extends from drive portion  54  and includes circumferentially disposed groove  58  (FIGS.  4  and  5 ), having a U-shaped cross section and O-ring  62  is received therein. O-ring  62  provides a liquid seal between the outer periphery of impeller stem  56  and counterbore  40  of drive shaft  20  (FIGS.  4  and  5 ). Drive portion  54  of impeller  52  includes a plurality of radially arranged impeller blades  66 . Each impeller blade  66  is separated from an adjacent impeller blade  66  by circumferential spaced groove  65  (FIG.  6 ). As best seen in FIGS. 2A and 6, impeller  52  includes annular groove  68  located substantially centered on lower surface of drive portion  54  of impeller  52 . Impeller  52  includes center portion  69  provided with generally planar surface  71  which is coextensive with surface  73  of each respective impeller blade  66  (FIG.  6 ). Hole  64  extends axially through impeller  52 . Surfaces  71  and  73  form thrust face  70  (FIGS. 4-5) of impeller  52 . 
     Referring again to FIGS. 2A and 3A, shown is thrust member or thrust plate  72  having thrust face  74  which rotatably supports thrust face  70  of impeller  52  (FIGS.  4 - 5 ). It may be seen that a clearance “c” exists between main bearing  22  and shoulder portion  75  of crankshaft  20  such that the weight of crankshaft  20  and displacement element  52  urges displacement element  52  into engagement with face  74  of thrust plate  72  (FIG.  1 ). Those having ordinary skill will understand that the combined weight of crankshaft  20 , and displacement element  52 , bearing down on face  74  of thrust plate  72  prevents a significant and detrimental loss of lubricant through an interface provided by displacement element  52  and face  74  of thrust plate  72 . 
     Thrust plate  72  includes outer radial surface  76  and lateral surface  77  (FIG.  7 ). Lateral surface  77  is provided with lower faces  78   a ,  78   b  and  78   c  which collectively form a planar support surface which abuts upper face  86  of magnetic member or disk  84  (FIGS.  2 A and  7 ). Thrust plate  72  is provided with central hole  80  which is aligned with central hole  64  of impeller  52  (FIGS.  4  and  5 ). As best seen in FIGS. 2A and 4, thrust plate  72  includes extended annular nose portion  81 , split into two arcuate halves, each of which axially extend from lower face  78   b . The two halves of nose portion  81  are engaged with recess  94  in magnetic disk  84  to center thrust plate  72  relative to magnetic disk  84  (FIG.  3 A). 
     Magnetic disk  84  includes upper face  86 , lower face  88  and peripheral surface  90 , and as best seen in FIGS. 3A and 8, is provided with semi-circular notch  92  which receives semi-circular protrusion  82  (FIG. 7) axially extended from thrust plate  72 . Protrusion  82 , extended into notch  92 , prevents rotation between magnetic disk  84  relative to thrust plate  72 . Lower face  88  of magnetic disk  84  includes three projections  96  intersected at centerline axis  85  and radially extended towards peripheral surface  90  of magnetic disk  84  (FIGS.  2 A and  11 ). Referring to FIG. 11, radial projections  96  are engaged with three circumferentially spaced slots  116  (FIG. 9) located in pump housing  104  to prevent rotation between magnetic disk  84  and pump housing  104 . Housing  104  is fixed to support member  43  by, for example, a press fit engagement between outer surface  106  of housing  104  and counterbore  105  located in support member  43  (FIG.  1 ). Alternatively housing  104  may be eliminated and in its place support member  43  may be provided with identically internal characteristics as that of housing  104 . 
     Magnetic disk  84  may be manufactured from a magnetized metallic material through, for example, a sinterized powder metal process. The magnetic properties of magnetic disk  84  attract ferrous particles  87  (FIG. 4) entrained or suspended in the oil as described below. Impeller  52  and thrust plate  72  may be made of an abrasion resistant moldable plastic, such as a phenolic material for example, through an injection molding process. Crankshaft  20  may be preferably made from a carbon steel and formed through a forging process to produce high durability and abrasion resistant properties. 
     An alternate thrust plate and magnetic disk engagement is shown in FIGS. 2B and 3B. As best seen in FIG. 2B, magnetic disk  84 ′ includes a pair of through holes  98  aligned with a pair of holes  99  in thrust plate  72 ′. Holes  99  are engaged by a pair of fasteners  100 , which may include, for example, brads, to secure magnetic disk  84 ′ to thrust plate  72 ′. 
     Referring to FIGS. 2-5, pump housing  104  is provided with cylindrical outer surface  106  and cylindrical inner surface  108  (FIGS.  3 - 5 ). Housing  104  and support member  43  may be made from an aluminum alloy through a die cast molding process or a powder metal process, for example. As best seen in FIG. 10A, lower end  109  of housing  104  includes annular platform  110  which provides support for magnetic disk  84 . Platform  110  includes inwardly angled frustoconical surface  112  providing support for outwardly angled frustoconical surface  102  (FIG. 8) provided on lower face  88  of magnetic disk  84  (FIGS. 4,  5  and  10 ). Lower end  109  of housing  104  includes through hole  114  extended axially through housing  104  to provide an inlet for oil to be drawn into pump  42  by the oil displacement element, i.e. impeller  52 . Frustoconical surface  112 , provided on annular platform  110 , forms a frustoconical engagement with frustoconical surface  102  of magnetic disk  84 . The frustoconical engagement provides a degree of self alignment of the abutting faces of impeller  52  and thrust plate  72 , despite angular variations in the housing centerline relative to the shaft centerline. As a result, reliance on close manufacturing and assembling tolerances of impeller  52 , crankshaft  20  and thrust plate  72 , traditionally employed, are not required with oil pump  42 . 
     Referring to FIG. 10B, a third embodiment of a lubricant pump is shown and includes mating hemispherically shaped surfaces  102 ′,  112 ′ of magnetic member and housing  104 ′,  84 ′ respectively. As an alternative to frustoconical surfaces  102 ,  112  shown, in FIG. 10A, hemispherical surfaces  102 ′,  112 ′ shown in FIG. 10B provide increased pivoting mobility between magnetic member  84 ′ relative to housing  104 ′ to remedy the angular variations in the housing centerline relative to the shaft centerline. 
     The flow of oil through oil pump assembly  42  will now be described. Referring to FIG. 4, oil is drawn through suction port or hole  114  of housing  104  from sump  30  and into a pair of arcuate suction ports  120  formed in magnetic disk  84  (FIGS. 4,  8  and  11 ). Arcuate suction ports  120  extend completely through the magnetic disk from lower face  88  to upper face  86  (FIG.  8 ). Similarly, arcuate suction port  122  extends completely through thrust plate  72  between thrust face  74  and lower face  78   a  thereof (FIG.  7 ). Arcuate suction port  122 , provided in thrust plate  72 , is radially aligned with the, pair of arcuate suction ports  120  in magnetic disk  84 . It may be seen that thrust plate  72  includes a pair of U-shaped discharge slots  126  provided in outer periphery  76  of thrust plate  72  (FIG.  3 A). Slots  126  are oppositely located relative to one another and axially extend into a pair of arcuate channels  130  formed in thrust plate  72  (FIGS. 2A,  7 ). Channels  130  are provided in lateral surface  77  of thrust plate  72  as described below. 
     As best seen in FIG. 7, each channel  130  includes transverse wall  132 , first sidewall  136 , and second sidewall  138 . Transverse wall  132  is substantially planar and is formed within lateral surface  77  of thrust plate  72 . First sidewall  136  is arcuate and extends from its respective discharge slot  126  to hole  80  in thrust plate  72 . Each second side wall  138  of channel  130  includes U-shaped slot  140 . A portion of oil received by slots  126  from impeller  52  flows into channels  130  and into central hole  80  in thrust plate  72 . The other portion of oil flows into magnetic particle trap cavity  142  as described below. 
     Lateral surface  77  of thrust plate  72  is provided with crescent-shaped magnetic particle trap cavity  142 . First sidewall  144  of magnetic particle trap cavity  142  includes a plurality of circumferentially spaced semi-circular inclusions  146  (FIG.  7 ). Second sidewall  148  of magnetic particle trap cavity  142  is generally smooth and continuous. Magnetic particle trap cavity  142  includes transverse wall  150  provided in lateral surface  77  of thrust plate  72 . Magnetic particle trap cavity  142  is enclosed by upper face  86  of magnetic disk  84  (FIGS.  4  and  5 ). 
     In operation, pump  42  is activated by motor driven shaft  20  urging rotation of impeller  52  and oil in sump  30  (FIG. 1) is drawn, illustrated by arrows  149  in FIG. 4, into suction port  120  of magnetic disk  84 . Thereafter, oil enters suction port  122  provided in thrust plate  72 . It is well understood that over time a compressor assembly generates debris which becomes entrained in the oil and frequently a portion of the debris is in the form of ferrous particles. Ferrous particles, which may be included in the present invention lubricant pump  42 , are attracted to and retained by magnetic disk  84  before the oil enters suction port  122  of thrust plate  72 . Oil then enters annular groove  68  within impeller  52  and is centrifugally flung radially outward through radially positioned grooves  65  between impeller blades  66 . The oil is then urged downwardly into U-shaped discharge slots  126  in thrust plate  72 , and thereafter, a portion of the oil is urged into the pair of arcuate channels  130  which extend toward central hole  80  of the thrust plate  72 . Oil entering central hole  80  of thrust plate  72  via channels  130  is urged upwardly through hole  64  in impeller  52 , into passage  23  of crankshaft  20 , and is ultimately received by the bearing surfaces within the compressor mechanism. 
     The portion of oil which does not travel through arcuate slots  130  enters magnetic particle trap cavity  142  and is slow moving due to the debris entrained therein. The oil entering magnetic particle trap cavity  142  is flung radially outward into the plurality of inclusions  146  in first sidewall  144 . Oil circulates through magnetic particle trap cavity  142 , entering one of the U-shaped slots  140  and exiting the other U-shaped slot  140 . Since thrust plate  72  is symmetrical, pump  42  may operate in either rotational direction with similar particle trapping results, i.e., pump  42  is reversible. 
     Referring to FIGS. 4 and 5, it may be seen that upper face  86  of magnetic disk  84  overlays arcuate channels  130  and magnetic particle trap cavity  142  of thrust plate  72 . Ferrous particles  87  entering magnetic particle trap cavity  142  are carried with the oil and are attracted to and trapped by upper face  86  of magnetic disk  84  under the influence of magnetic force established by magnetic disk  84  (FIG.  4 ). Additionally, oil flowing through channels  130  includes ferrous particles which pass over magnetic disk  84  and become attracted and attached to face  86  of magnetic disk. Additional particles and debris, which may include ferrous or non-ferrous particles, are caught within inclusions  146  of magnetic particle trap cavity  142  as oil flows through cavity  142 . Therefore, magnetic particle trap cavity  142  and face  86  of magnetic disk  84  provide a two-stage debris retaining structure, the first stage provided by inclusions  146  within thrust plate  72 , trapping a portion of the debris therein, and a second stage, provided by face  86  of magnetic disk  84 , trapping additional debris, in the form of ferrous particles  87 . 
     As best seen in FIG. 4, drive shaft  20  is provided with centrifugal particle trap cavity  155  radially located within a wall defining passage  23 . Specifically, centrifugal particle trap cavity  155  is bound by counterbore  40  and frustoconical surface  156  of impeller stem  56 , on one axial end, and frustoconical surface  160  of the other axial end. Thus, it may be seen that annular, frustoconical surfaces  156 ,  160 , and a portion of counterbore  40  in crankshaft  20 , form centrifugal particle trap cavity  155  to capture debris  162 , as it is transported by the oil flowing through passage  23 , shown by flow arrow  149  (FIG.  4 ). Particles  162 , under the influence of centrifugal force as crankshaft  20  is rotated by motor assembly  14 , are flung into centrifugal particle trap cavity  155  as oil moves through passage  23 . Particles  162  are thereby centrifugally trapped in centrifugal particle trap cavity  155  during compressor operation, and are prevented from thereafter continuing with the oil upwards through passage  23 . 
     Referring to FIG. 5, it may be seen that once shaft  20  ceases rotation, at least a portion of particles  162  travel downwardly and rest upon conical surface  156  formed by impeller stem  56 . The remaining particles continue downwardly from second chamber  155  and accumulate at center portion  164  of magnetic disk  84  and some particles may eventually flush back through oil pump  42  and into oil sump  30  or magnetic particle trap cavity  142 . Those having ordinary skill in the art will understand that an abundance of debris entrained in the oil will not plug inventive pump  42 . Rather, magnetic and centrifugal particle trap cavities  142 ,  155  are so positioned within the oil circuit such that oil is allowed to pass through pump  42  regardless of whether the magnetic and centrifugal particle trap cavities are replete with debris. Since hermetically sealed compressor assembly  10  of the present invention is manufactured to be non-maintainable, i.e., not to be disassembled for maintenance purposes, it is particularly important that oil pump  42  continues to perform even if a significant amount of debris is accumulated within magnetic and centrifugal particle trap cavities  142 ,  155 . 
     Referring to FIGS. 2-5, gas vent  166  extends from chamfer  44  of crankshaft  20  to outer surface  46  of crankshaft  20  to provide an escape path for refrigerant gases flashed from the oil in pump  42 . Gases or vapor which are not vented may be detrimental to proper lubricant flow, inasmuch as it may cause an insufficient amount of oil being delivered to the bearing surfaces. Vent  166  provides an escape for these gases to avoid bearing damage. 
     While this invention has been described as having exemplary designs, the present invention may be further modified within the spirit and scope of this disclosure. Therefore, this application is intended to cover any variations, uses, or adaptations of the invention using its general principles. For example, aspects of the present invention may be applied to compressors other than reciprocating piston compressors such as rotary and scroll compressor assemblies, for example. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.