Abstract:
A rotating type machine including a first moving member having a first surface and a second member having a second surface slidably interfacing with the first surface. The first and second surfaces have relative movement therebetween, and one of the first and second members is supported by the other member through the interface of their respective first and second surfaces. At least one of the first and second surfaces is provided with at least one recess therein. A liquid lubricant is provided between the first and second surfaces, and the lubricant is received in the recess. Relative to the surface in which the recess is provided, the recess has a maximum depth which ranges between about 0.00125 and 0.0060 inches, and a surface area which ranges between about 1.767×10 −4  and 1.963×10 −3  square inches, whereby, during operation of the machine, a pressure spike is created in the lubricant above the recess, and first and second surfaces are hydrodynamically separated from each other by the pressure spike.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit under Title 35, U.S.C. §119(e) of U.S. Provisional Patent Application Serial No. 60/216,044, entitled ROTATING MACHINE HAVING LUBRICANT-CONTAINING RECESSES ON A BEARING SURFACE, filed on Jul. 5, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to rotating type machines including, but not limited to compressors, pumps, transmissions and engines, and particularly to lubricated radial or thrust bearings therein.  
           [0003]    Rotating machines in general have mating axially or radially loaded surfaces such as those at a thrust bearing or radial bearing, respectively, in a compressor. These surfaces tend to be a location of high wear and usually require lubrication. Lubrication between the interfacing bearing surfaces is often facilitated by providing oil to recesses, a groove or clearance space (collectively, recesses) located between these surfaces for retaining oil. Another means of providing an oil retention space between interfacing bearing surfaces is to apply a phosphate coating to one or both of these surfaces, the coating forming micron-sized interstices in which oil is retained. Oil passed over the interfacing bearing surfaces creates a film of lubricant therebetween, which supports the bearing load and reduces the amount of friction, and thus the amount of wear, between the bearing surfaces. The provision of oil retention spaces between the bearing surfaces is intended to help facilitate the formation of this film.  
           [0004]    Previous attempts at using recesses for retaining oil between the interfacing bearing surfaces have yielded unsatisfactory results. These recess were formed having depths on the order of tens of thousands of an inch, and are believed to be too deep for providing a sufficient lubricant film between bearing surfaces. Lubricant captured in these recesses cannot be easily drawn out to lubricate the bearing and establish an oil film to hydrodynamically support the load. Conversely, if the recesses are too small or nonexistent an insufficient amount of lubricant may be received therein to establish the film or a film sufficient to support the bearing load and lubricate the bearing interface. Such a lack of lubricant allows the bearing load to overcome the hydrodynamic pressure provided by the inadequate film, and the oil is forced from between the interfacing bearing surfaces, allowing contact thereof.  
           [0005]    Although the interstices formed in phosphate coatings may allow for adequate oil retention and establishment of the oil film between the bearing surfaces, these coatings do not adhere well to aluminum or powdered metal parts which are common bearing components in rotary machines. Further, during the process of applying the phosphate coating, it may undesirably interface with other parts, causing problems with the operation of the device.  
           [0006]    A means for retaining oil between the interfacing bearing surfaces which is more effective than previously provided, and/or which avoids the problems mentioned hereinabove is desired.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention provides a rotating type machine including a first moving member having a first surface and a second member having a second surface slidably interfacing with the first surface. The first and second surfaces have relative movement therebetween, and one of the first and second members is supported by the other member through the interface of their respective first and second surfaces. At least one of the first and second surfaces is provided with at least one recess therein. A liquid lubricant is provided between the first and second surfaces, and the lubricant is received in the recess. Relative to the surface in which the recess is provided, the recess has a typical depth of 0.002 inches but which may range between about 0.00125 and 0.0060 inches, and an area at the surface which ranges between about 1.767×10 −4  and 1.963×10 −3  square inches, whereby, during operation of the machine, a pressure spike is created in the lubricant above the recess, and first and second surfaces are hydrodynamically separated from each other by the pressure spike.  
           [0008]    The present invention also provides a rotating machine including a rotating element, a sliding member having first and second surfaces, the rotating element engaging the sliding member and inducing a moment thereon, and a slotted member having third and fourth surfaces slidably interfacing with and moving relative to the first and second surfaces, respectively. At least one of the surfaces is provided with at least one recess therein, and liquid lubricant is provided between the interfacing surfaces, the lubricant being received in the recess. Relative to the surface in which the recess is provided, the recess has a maximum depth which ranges between about 0.00125and 0.0060 inches, and a surface area which ranges between about 1.767×10 −4  and 1.963×10 −3  square inches, whereby, during operation of the machine, a pressure spike is created in the lubricant above the recess, the interfacing surfaces are hydrodynamically separated from each other by the pressure spike, and the moment is at least partially counteracted by the spike.  
           [0009]    The present invention further provides a method of elastohydrodynamically separating a pair of slidably interfacing surfaces including: slidably interfacing a first member having a first surface and a second member having a second surface; relatively moving the first and second surfaces; collecting a quantity of lubricant in a recess located in one of the first and second surfaces; creating a pressure spike in the lubricant above the recess and between the first and second surfaces; and elastohydrodynamically separating the first and second surfaces with the pressure spike.  
           [0010]    The rotating machine may be, but is not limited to, a compressor, pump, transmission or engine. The dimples or recesses may be, for example, spherically shaped, but other shapes (e.g., cylindrical, parallelepiped) may be employed provided that the depth of the recess and its area at the surface in which it is located are suitably selected in accordance with the present invention. The prescribed size and depth of the dimple produces, in the oil above the dimple, a pressure spike which supports the bearing load; the oil also lubricates the interfacing bearing surfaces.  
           [0011]    In accordance with the present invention, the oil-receiving recesses or dimples may be incorporated into either thrust type bearings, radial type bearings, or planar sliding surfaces to reduce wear of the surfaces, thereby increasing the life of the parts and efficiency of the machine. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The above mentioned and other features and objects 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:  
         [0013]    [0013]FIG. 1 is a longitudinal sectional view of a first embodiment of a rotary compressor in accordance with the present invention;  
         [0014]    [0014]FIG. 2 is a plan view of the outboard bearing of the rotary compressor of FIG. 1;  
         [0015]    [0015]FIG. 3 is a sectional view of the outboard bearing of FIG. 2 along line  3 — 3  thereof;  
         [0016]    [0016]FIG. 4 is a fragmentary sectional view of a second embodiment of rotary compressor in accordance with the present invention;  
         [0017]    [0017]FIG. 5 is a sectional view of another embodiment of a thrust bearing according to the present invention, also showing the end of a rotating shaft abutting same;  
         [0018]    [0018]FIG. 6 is a sectional view of the compression chamber in the rotary compressor of FIG. 1;  
         [0019]    [0019]FIG. 7A is a view of a first side of the roller of the compressor of FIG. 1;  
         [0020]    [0020]FIG. 7B is an end view of the roller of FIG. 7A;  
         [0021]    [0021]FIG. 7C is a view of the second end surface of the roller of FIG. 7A;  
         [0022]    [0022]FIG. 8 is a an enlarged fragmentary view of the compressor of FIG. 6 showing the forces acting upon the vane;  
         [0023]    [0023]FIG. 9A is a plan view of a first side of the vane of the compressor of FIG. 6;  
         [0024]    [0024]FIG. 9B is a side view of the vane of FIG. 9A;  
         [0025]    [0025]FIG. 9C is a plan view of the second side of the vane of FIG. 9A;  
         [0026]    [0026]FIG. 10 is a longitudinal sectional view of an embodiment of a scroll compressor in accordance with the present invention;  
         [0027]    [0027]FIG. 11 is a sectional side view of the frame of the scroll compressor of FIG. 10;  
         [0028]    [0028]FIG. 12 is a plan view of the frame of FIG. 11;  
         [0029]    [0029]FIG. 13 is a longitudinal sectional view of a first embodiment of a reciprocating piston compressor in accordance with the present invention;  
         [0030]    [0030]FIG. 14 is a partially sectioned side view of the crankcase of the reciprocating piston compressor of FIG. 9;  
         [0031]    [0031]FIG. 15 is a plan view of the crankcase of FIG. 10;  
         [0032]    [0032]FIG. 16 is a longitudinal sectional view of a second embodiment of a reciprocating piston compressor in accordance with the present invention;  
         [0033]    [0033]FIG. 17 is a sectional side view of the crankcase of the reciprocating piston compressor of FIG. 16;  
         [0034]    [0034]FIG. 18 is a plan view of the crankcase of FIG. 17;  
         [0035]    [0035]FIG. 19 is a plan view of an embodiment of a connecting rod in accordance with the present invention;  
         [0036]    [0036]FIG. 20 is a sectional view of the connecting rod of FIG. 19 along the line  20 — 20 ;  
         [0037]    [0037]FIG. 21 is a plan view of a second embodiment of a thrust bearing in accordance with the present invention;  
         [0038]    [0038]FIG. 22 is a sectional view of the thrust bearing of FIG. 21 along line  22 — 22 ; and  
         [0039]    [0039]FIG. 23 is an enlarged, fragmentary sectional view of the thrust bearing of FIG. 22.  
         [0040]    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.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0041]    In accordance with the present invention, radial bearing, thrust bearing and planar sliding surfaces of the depicted machines are provided with recesses or dimples  20  which facilitate increased elastohydrodynamic separation forces between, and lubrication of, the interfacing bearing surfaces. Oil received between the bearing surfaces is captured within dimples  20 , and above each of the dimples, a pressure spike is created in the oil which acts on the interfacing bearing surfaces, ensuring separation and sufficiently reducing wear of the surfaces. Dimple  20  may be machined into its bearing surface, depressed into its bearing surface, or otherwise integrally formed into its bearing surface.  
         [0042]    Dimples  20  may be applied to bearing surfaces in several types of rotating machines, such as hermetically sealed rotary compressor  22  shown in FIG. 1. Rotary compressor  22  includes thrust or outboard bearing  24  having dimples  20  on thrust surface  26  thereof. The general concept of a rotary compressor is disclosed, for example, in U.S. Pat. Nos. 5,829,960 to Dreiman, 6,171,076 to Gannaway, and 6,195,889 to Gannaway, the disclosures of which are expressly incorporated herein by reference. With reference to FIGS. 2 and 3, outboard bearing  24  has bore  28  therethrough for receiving end  30  of crankshaft  32 , and surface  26  which is in contact with lower surface  34  of cylinder block  54 . Surface  26  of outboard bearing  24  is also in contact with surface  38  of eccentric  40 , integrally formed in crankshaft  32 , and annular surface  42  of roller piston  44  which surrounds the crankshaft eccentric. Oil is provided to surface  26  in any conventional way for lubrication and/or sealing of eccentric surface  38  and piston surface  42  relative to surface  26 . Formed in surface  26  about bore  28  are dimples  20 . As depicted, a pair of individual concentric annular arrays of dimples  20  surround bore  28  in an equally distributed manner. Notably, the dimples of one array are located circumferentially between a pair of circumferentially adjacent dimples of the other array. It is to be understood, however that the number of dimple arrays, whether one, two (as shown), or more, may be varied to accommodate different loads exerted on surface  26 . The oil in each of dimples  20  creates a pressure spike which elastohydrodynamically supports the load exerted on surface  26  by the crankshaft or the piston. The more dimples within each array, or the more arrays, the more pressure spikes are created and thus the greater the load which can be accommodated. By thus separating eccentric  40 , piston  44  and outboard bearing  24 , wear of surfaces  26 ,  38  and  42 , indeed their direct contact during compressor operation, is nearly eliminated and the efficiency of compressor  22  is increased. Notably, dimples  20  may be located on either or both of the interfacing bearing surfaces, but dimples  20  are preferably located on the non-rotating surface.  
         [0043]    A second embodiment of a rotary compressor according to the present invention is shown in FIG. 4. Rotary compressor  50  includes main bearing  52 , cylinder block  54 , and thrust or outboard bearing  56 . Crankshaft  58  is rotatably supported in main bearing  52  and has eccentric  60  located within cylinder block  54 . Roller piston  62  is disposed about eccentric  60 . Compressor  50  may be otherwise substantially similar to compressor  22 , but its crankshaft  58  is provided with shoulder  64  having axial surface  65  which is in axially abutting engagement with thrust surface  66  of outboard bearing  56 . Oil in dimples  20  provides elastohydrodynamic lubrication and thrust support to crankshaft  58  through shoulder  64 . Annular axial surface  68  of piston  62  also slidably abuts surface  66 . Dimples  20  are provided in thrust surface  66  of outboard bearing  56  and form an annular array as described above with respect to compressor  22 . During operation of rotary compressor  50 , however, dimples  20  are cyclically covered and uncovered by the respective interfacing axial surfaces  65  and  68  of shoulder  64  and piston  62 . Although it is possible to configure these thrust bearings such that the array(s) of dimples is wholly covered by the surface which interfaces the surface in which the dimples are provided, as shown in FIG. 4, shoulder surface  65  covers approximately half of dimples  20  in an array, and oil may be received in dimples  20  while uncovered.  
         [0044]    Referring now to FIG. 5, there is shown another embodiment of a thrust bearing according to the present invention. Thrust bearing  74 , which may also be adapted for use in hermetic compressors, is provided with an annular array of dimples  20 , as described above, and the end of shaft  70  interfaces and rotates in place relative to surface  72 , in which the dimples are located. As described above, the relative motion of shaft  70  and surface  72  causes the oil in each of dimples  20  to create a pressure spike, and shaft  70  is axially supported elastohydrodynamically on the film of oil. Notably, longitudinal axis  75  of shaft  70  and the annular array of dimples  20  are concentric.  
         [0045]    Referring now to FIG. 6, there is shown the roller and vane of the compression chamber of a rotary compressor. First and second annular axial surfaces  68 , and  68 ′ of eccentric roller  62  (FIGS.  7 A- 7 C), driven by crankshaft  32 , seal against compression chamber surfaces  66  and  66 ′. Eccentric roller  62  also engages cylindrical compression chamber surface  67  at a discrete movable line on its outer periphery. Vane  69  maintains contact with roller  62  in the usual, known manner, thereby creating a pressurized zone within the compression chamber.  
         [0046]    Referring now to FIGS. 7A, 7B, and  7 C, there is shown roller  62  of FIGS. 4 and 6 in accordance with the present invention. The roller ends  68 , and  68 ′ are provided with an annular array of dimples  20 , as described above. The compression chambers annular axial surface  66 ,  66 ′ and roller ends  68 ,  68 ′ slidably interface and rotate relative one another. As described above, the relative motion of roller ends  68 ,  68 ′ and the compression chambers annular axial surfaces  66  and  66 ′, cause the oil in each of dimples  20  to create a pressure spike. The roller ends are prevented from contacting the compression walls by the hydrodynamic force created by the pressure spike resulting in less wear of the surfaces and greater efficiency of the compressor.  
         [0047]    Referring now to FIG. 8, there is shown vane  69  of FIGS. 4 and 6. The vane maintains contact with roller  62 , which rotates within the compression chamber, as described above. The contact between the roller and the vane creates force F, acting upon the vane tangential to the direction of roller rotation which induces a moment on the vane. This creates reactionary force R 1  on the vane at the end of the vane entering the compression cylinder, on the opposite surface that the force was applied, and a reactionary force R 2  on the vane, at the end of the vane which remains within the vane slot of the compression chamber. Referring to FIGS. 9A, 9B and  9 C, each of the vane load sites, located on opposite planar sides of the vane and near opposite ends of the vane, are supplied with dimples  20 . As described above, the relative motion of the vane and the slot walls cause the oil in each of dimples  20  to create a pressure spike. The vane load sites are prevented from contacting the slot walls by the hydrodynamic force created by the pressure spike resulting in less wear of the surfaces and greater efficiency of the compressor. The spikes formed on the opposite sides of the vane form reactionary forces R 1  and R 2  which counteract the moment induced by force F.  
         [0048]    Referring now to FIG. 10, there is shown scroll compressor  76  into which dimples  20  have been incorporated for supporting a thrust load. The general concept of a scroll compressor is disclosed, for example, in U.S. Pat. Nos. 4,875,838 to Richardson, Jr., 6,139,294 to Haller, 6,139,295 to Utter et al., 6,146,118 to Haller et al., and 6,196,814 to Cooksey et al., the disclosures of which are expressly incorporated herein by reference. Scroll compressor  76  includes housing  78  and crankshaft  80  which is rotatably mounted in bearings  82  and  83 . Orbiting scroll member  84  is mounted on an eccentric located at one end of shaft  80  and is provided with an involute wrap operatively engaged with the wrap of fixed scroll member  86  as shown, compression spaces being defined between the scroll members. Orbiting scroll member  84  is slidably disposed on, and held in axial compliance with fixed scroll member  86  by, frame  88 , which is shown in greater detail in FIGS. 11 and 12. Frame  88  has cavity  90  into which fixed scroll member  86  is fitted, cavity  90  partially defined by annular surface  100 , in which a pair of concentric annular arrays of dimples  20  are provided (FIG. 12). Underside surface  102  of frame  88  interfaces surface  100 . Oil is provided between surfaces  100  and  102  in any suitable way. For example, with reference to FIG. 11, an arrangement of oil delivery channels  92  may be provided in frame  88  which delivers oil pumped therethrough to surface  100  and/or to one or more of dimples  20 . Alternatively, oil may be delivered upward from oil sump  96  through bore  94  in crankshaft  80  by means of an oil pump provided at the end of the crankshaft and immersed in sump  96  (FIG. 10), and/or under the influence of centrifugal force by means of bore  94  being disposed at an angle relative to the axis of rotation of the shaft, in the well known manner. Oil may then be delivered from bore  94  into chamber  99  defined between frame  88 , the exterior surface of orbiting scroll member hub  97 , and surface  100  of the scroll member. The oil delivered to chamber  99  may be communicated to surface  100  and/or at least one dimple  20  through channels  92  (FIG. 11). The oil in chamber  99  may be under sufficient pressure to provide axial compliance between the orbiting and fixed scroll members in a manner well-known in the art. Moreover, the oil pressure spikes which separate surfaces  100  and  102  elastohydrodynamically on a film of oil may also contribute to the axial compliance of the scroll members, the oil pressure spikes counteracting the axial separation forces between the scrolls which are induced by the pressures of gases being compressed thereby.  
         [0049]    Referring now to FIG. 13, there is shown a first embodiment of reciprocating piston compressor according to the present invention. The general concept of a reciprocating piston refrigeration compressor is disclosed, for example, in U.S. Pat. Nos. 5,160,247 to Kandpal and 5,554,015 to Dreiman et al., the disclosures of which are expressly incorporated herein by reference. Compressor  106  has a pair of concentric annular arrays of dimples  20  provided in thrust surface  104 , which interfaces with thrust washer  107  disposed about crankshaft  114 , adjacent rotor  124 . Shaft  114  and rotor  124  are elastohydrodynamically supported by a film of oil provided between washer  107  and surface  104  through oil pump groove  130  provided on the exterior of shaft  114 . Annular thrust surface  104  is provided on the upper end of bearing shaft  132 , integrally formed on crankcase  110 , as shown in FIGS. 14 and 15.  
         [0050]    [0050]FIG. 16 illustrates a second embodiment of a reciprocating piston compressor according to the present invention. Compressor  108  also employs dimples  20  in accordance with the present invention, located on annular thrust surface  102  of bearing  150 , which is integrally formed on crankcase  110 ′ (FIG. 18). Thrust surface  102  interfaces with annular surface  136  of a flange formed on crankshaft  114 ′ (FIG. 16). Oil is provided between surfaces  102  and  136  in any conventional way, as by means of a centrifugal oil pump having a oil conveyance bore (not shown) which extends longitudinally through shaft  114 ′, the bore having an angle relative to the crankshaft axis of rotation and opening into the oil sump  128 ′ at the bottom of the compressor housing, the oil delivered to the interface between surfaces  102  and  136  through a cross bore (not shown) which communicates with the oil conveyance bore. As shown in FIG. 18, surface  102  is provided with a pair of concentric annular arrays of dimples  20 , as described above. Shaft  114 ′ and rotor  124 ′ are axially supported elastohydrodynamically by the pressure spikes created in the film of oil above each dimple  20  in surface  102 . As noted above, a single array of dimples in surface  102  may suffice, depending on the load to be supported.  
         [0051]    In each of compressors  106  and  108  (FIG. 13, and  16 ), connecting rod  118  engages eccentric crankpin  116  or  116 ′ respectively formed on crankshaft  114  or  114 ′. Connecting rod  118  is attached at its opposite end to piston  122  via wrist pin  120 . Each end of connecting rod  118  comprises a radial bearing. Piston  122  is received within cylinder bore  125  or  125 ′, in which it reciprocates.  
         [0052]    Referring now to FIGS. 19 and 20, interior cylindrical surface  138 , which defines large opening  140  at rod strap end  142  of connecting rod  118  is provided with a pair of circumferentially arranged arrays of dimples  20  (FIG. 20). Surface  138  interfaces with the cylindrical outer surface of crankpin  116  or  116 ′, and thus a radial bearing is formed therebetween. Dimples  20  in surface  138  receive oil from respective sump  128  or  128 ′ of compressor  106  or  108  in the way oil may usually be delivered to rod strap/crank pin interface, and oil pressure spikes are established above each dimple  20  as the outer surface of eccentric crankpin  116  or  116 ′ and rod surface  138  slide relative to each other, thereby providing elastohydrodynamic radial support, and lubrication therebetween. Notably, connecting rod  118  could easily be used in an engine as well as in a compressor.  
         [0053]    Referring now to FIGS.  21 - 23 , there is shown a second embodiment of a thrust bearing according to the present invention. Bearing  152 , which has the form of a thrust washer, has flat annular surface  154  in which is provided a pair of concentric annular arrays of dimples  20 , as described above. One of dimples  20  in bearing  152  is shown in greater detail in FIG. 23, and is illustrative of all dimples  20  discussed hereinabove, in thrust bearing applications as well as in radial bearing applications. In the depicted embodiments, dimples  20  are spherically shaped. The shape of dimples  20 , however, is not critical to practicing the present invention. Rather, it is the area of the dimple at the surface in which it is located (e.g., surface  154  or  138 ) and its depth below that surface which are important to providing the proper development of the pressure spike through the oil film which provides the desired elastohydrodynamic surface separation and lubrication. The distribution and number of dimples or arrays of dimples may be varied to accommodate different design loads, as explained above. The pattern of dimples  20  is also variable, and determined by the shape and location of the bearing interface. It is thought that any array will provide satisfactory performance which provides a total dimple area, at the surface in which dimples are located, which, in conjunction with the magnitude of the pressure spikes formed, provides a force suitable to offset the bearing load and separate the interfacing bearing surfaces.  
         [0054]    Maximum depth d of each dimple  20  (FIG. 23) is kept very shallow, having a range between about 0.00125 and 0.0060 inches below the surface in which the dimple is provided. In the embodiments described above, maximum depth d is approximately 0.002 inches. In the embodiments described above, diameter D of each dimple  20  is approximately  0 . 031  inches, thereby yielding an area of approximately 7.548×10 −4  square inches at the surface in which the dimple is provided. This diameter may have a range between about 0.015and 0.050 inches. These dimensions are recommended for the rotating devices discussed above, but may vary slightly depending on the relative speed of the interfacing bearing surfaces, the type of the lubricant, and its normal operating temperature and pressure. In the above described compressors, for example, an oil such as Emery 2942 (POE) may be used, and may have normal operating temperatures and pressures which range from between 180 and 280 degrees Fahrenheit, and between 78 and 645 psig. In the above described embodiments, each dimple  20  is expected to produce a pressure spike of approximately 25 psig. Thus, based on the above-cited area of 7.548×10 −4  square inches, each dimple  20  is expected to yield a thrust or radial force of approximately 0.1 pounds.  
         [0055]    While this invention has been described as having a exemplary designs, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. 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.