Abstract:
A cylinder liner and piston configuration for an internal combustion engine includes features for improving the cooling of the piston. Specific ratios and dimensions are included to optimize the features of the cylinder liner and piston. Also included are unique piston features that assist in achieving some of the specified dimensions and ratios.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to U.S. Provisional Patent Application No. 61/450,019, filed on Mar. 7, 2011, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to piston and cylinder liner configurations for internal combustion engines. 
     BACKGROUND 
     Internal combustion engines are subject to government regulations and customer expectations. Government regulations include reducing emissions and improving engine efficiency to reduce fuel consumption. Customer expectations include improved engine reliability and longer engine life. While great strides have been made in addressing government regulations and improving the life of internal combustion engines, internal combustion engines are highly complex mechanisms and innovative approaches to engine components may yield life, reliability, and efficiency improvements. 
     SUMMARY 
     This disclosure provides an internal combustion engine comprising an engine body, a cylinder bore, a cylinder liner, and a piston. The cylinder bore is formed within the engine body and has at least one coolant passage located radially outward from the cylinder bore. The cylinder liner is positioned within the cylinder bore and has an internal diameter D. The piston is positioned within the cylinder liner to reciprocate along an axis. The piston includes a top surface, an outside wall having an outer peripheral surface, and a groove positioned an axial distance from the top surface. A ratio of distance B to internal diameter D is less than 0.090. 
     Advantages and features of the embodiments of this disclosure will become more apparent from the following detailed description of exemplary embodiments when viewed in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view through a portion of an internal combustion engine in accordance with an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an internal combustion engine  10  in accordance with an exemplary embodiment of the present disclosure. Engine  10  includes an engine body  12 , only a small portion of which is illustrated, a cylinder head  14  mounted on engine body  12 , at least one cylinder liner  16  positioned in engine body  12 , and at least one piston  18  positioned for reciprocal movement along an axis in cylinder liner  16 . Of course, engine  10  may contain a plurality of cylinder liners  16  and pistons  18 , for example four to eight of each, which may be arranged in a line or in a “V” configuration. As discussed hereinbelow, engine  10  includes various precise configuration parameters that yield certain benefits, such as improved cooling of pistons  18  and cylinder liners  16 , achieving improved life and reliability of engine  10 , and reducing emissions and achieving improved fuel economy and efficiency from engine  10 . 
     Engine body  12  includes at least one cylinder bore  20 . Cylinder liner  16  is positioned within cylinder bore  20 . Cylinder liner  16  includes an internal bore  17 , having an internal diameter D, to locate piston  18 . Piston  18  may be any type of piston so long as it contains the features identified hereinbelow necessary for accomplishing the present invention. For example, piston  18  may be an articulated piston. Liner  16  separates a lubricated portion  22  located at an interior portion of cylinder liner  16  and a combustion chamber  23  positioned at one end of an internal bore  17  between piston  18  and cylinder head  14  from a plurality of coolant passages  26  (e.g.,  26   a ,  26   b ,  26   c ) formed in engine body  12 . A combustion bowl  24  positioned in a proximate, top or upper portion of piston  18  is part of combustion chamber  23 . 
     Combustion bowl  24  may have a plurality of features formed therein. For example, combustion bowl  24  may have a central portion  24   a  that is axially closer to cylinder head  14  than an annular portion  24   b  that extends around central portion  24   a . These features may be related to the characteristics of combustion chamber  23 , which may include fuel flow and how the fuel flow combusts or ignites (not shown). Combustion chamber  23  may have the characteristics of the combustion chamber described in U.S. Pat. No. 6,732,703, issued May 11, 2004, the entire content of which is incorporated by reference in its entirety. 
     Coolant passages  26  may be configured to provide optimal cooling for piston  18 . For example, coolant passage  26   a  may be a high velocity coolant flow and coolant passage  26   b  may be a low velocity coolant flow. Coolant passage  26   c  may be a port that connects one part of fluid passages  26  with another part of fluid passage  26 , such as coolant passage  26   a  with coolant passage  26   b.    
     Cylinder liner  16  includes a top flange portion  28  having an axial or longitudinal thickness A. Cylinder liner  16  also includes an annular wall portion  32  having a radial thickness C that extends axially or longitudinally from top flange portion  28 . Positioned axially further from wall portion  32  may be a protrusion  33  that cooperates with cylinder bore  20  to separate coolant passage  26   a  from coolant passage  26   b . Included on cylinder liner  16  axially further from protrusion  33  may be a stop or step  34 . A wall portion  37  is located on cylinder liner  16  and extends from protrusion  33  to stop  34 . Top flange portion  28  includes an outer annular surface  30  that opposes annular cylinder bore  20 . Coolant passage  26   a  is positioned radially outward from wall portion  32  on one side of cylinder liner  16  and coolant passage  26   c  is positioned radially outward from wall portion  32  on the opposite side of cylinder liner  16  from coolant passage  26   a . Coolant passage  26   a , coolant passage  26   b , and coolant passage  26   c  may be part of a single coolant passage that extends angularly about cylinder liner  16 . 
     Stop  34  located on cylinder liner  16  engages an annular land or stop  35  located on engine body  12 . Stop  34  provides a location that sets the depth or offset of a proximate, near or upper surface  40  of cylinder liner  16  with respect to a top surface  38  of engine body  12 . Stop  34  sets the axial length of the gap between top surface  40  of cylinder liner  16  and cylinder head  14  or a cylinder head gasket  41 . A stop having similarity to stop  34  is described in U.S. Pat. No. 4,294,203, issued Oct. 12, 1981, the entire content of which is hereby incorporated by reference. One or more grooves  42  may also be positioned on an outer wall  36  of cylinder liner  14 . One or more seals  44  may be positioned in each groove  42 . Seals  44  separate lubricated portion  22  from coolant passages  26 . 
     Cylinder liner  16  is inserted into engine body  12  from the top or proximate end of cylinder bore  20 . The outer periphery of cylinder liner  16  is a slip fit with cylinder bore  20  in the area of cylinder liner  16  that includes grooves  42 . As previously noted, seals  44  positioned within grooves  42  prevent lubricant from lubricated portion  22  from contaminating the coolant located in coolant passages  26  and prevent coolant from passages  26  from contaminating the lubricant in lubricated portion  22 . Annular surface  30  of flange portion  28  is a press fit with an inner surface  94  of cylinder bore  20 . The press fit may provide a seal between fluid passages  26  and combustion chamber  23  and secures cylinder liner  16  within engine body  12 . A seal (not shown) may also be located between flange portion  28  and inner surface  94  of cylinder bore  20 . 
     As previously noted, piston  18  is located within internal bore  17 , which has internal diameter D, of cylinder liner  16 . Piston  18  is shown in a top dead center (TDC) position in  FIG. 1 . Piston  18  drives a conventional connecting rod  46  attached to a pin, rod or shaft  48  secured to piston  18 . Connecting rod  18  drives a crankshaft (not shown) of engine  10 . Connecting rod  18  and the crankshaft cause piston  18  to reciprocate along a rectilinear path within cylinder liner  16 . The TDC position is attained when the crankshaft is positioned to move piston  18  to the furthest position away from the rotational axis of the crankshaft. In the conventional manner, piston  18  moves from the TDC position to a bottom dead center (BDC) position when advancing through intake and power strokes. Piston  18  includes a plurality of grooves for piston rings and seals located on a periphery, outside diameter, or outside surface  49  of an outside wall  43  of piston  18 . The plurality of grooves includes a top, upper, proximate, or first groove  50 , a second, center or middle groove  52  and a third, bottom, lower, or distal groove  54 . Top groove  50  includes a first conventional compression ring  56  that assists to prevent combustion gas from combustion chamber  23  from travelling between piston  18  and cylinder liner  16 . An upper side  62  of top groove  50  is positioned a distance B from a top, upper, or proximate surface  64  of piston  18 . Middle groove  52  includes a second conventional compression ring  58 . Third groove  54  includes a conventional oil control ring  60  that limits the amount of oil that moves along internal bore  17  toward the upper or proximate end of piston  18  where combustion bowl  24  is located. 
     Distance B of top groove  50  is important from an emissions perspective. There is a radial gap between exterior or peripheral surface  49  of outside wall  43  of piston  18  and internal bore  17  of cylinder liner  16 . Fuel that is trapped in the region between peripheral surface  49  and internal bore  17  in the region above top ring  56 , which may be called a dead zone, is not combusted. This fuel becomes exposed as piston  18  moves away from the TDC position and the fuel enters an exhaust (not shown) of engine  10 . Unburned fuel contributes to increased emissions and leads to less efficiency of engine  10 . Thus, the ability to decrease distance B decreases emissions and improves fuel efficiency. 
     A scraper ring  39  may be positioned in cylinder liner  16  at an interior portion of top flange portion  28 . Scraper ring  39  has an inner diameter that is smaller than the diameter of internal bore  17 . Scraper ring  39  reduces the volume of the dead zone described hereinabove as well as helping to remove deposits on surface  49  of piston wall  43  above top groove  50 . Thus, scraper ring  39  helps remove deposits above top or first compression ring  56 . 
     Piston  18  is fabricated from two separate portions. An upper, proximate, or top portion  66  is joined to a lower, distal, or bottom portion  68  along a first joint  70  and a second joint  72 . First joint  70  includes a surface  74  located on lower portion  68  and a matching surface  76  located on upper portion  66 . First joint  70  is positioned between top groove  50  and second groove  52 . Second joint  72  includes a surface  78  located on upper portion  66  and a surface  80  located on lower portion  68 . Second joint  72  is axially displaced from first joint  70  in a direction that is further from combustion chamber  23  than first joint  70 . By having second joint  72  in this position, a wall or rib  88 , which is described in more detail hereinbelow, is readily accessible from a radial direction to form features therein, such as fluid passages (not shown). Top portion  66  and bottom portion  68  are affixed to each other through a conventional spin welding process. By fabricating piston  18  as two separate pieces, a gallery  82  may be extended, or positioned closer to top surface  64  during the fabrication of upper portion  66  since the interior of upper portion  66  is accessible prior to attaching or welding upper portion  66  to lower portion  68 . 
     Gallery  82  has a lower portion  82   a  having a radial extent and an upper portion  82   b  having a radial extent that is less than the radial extent of lower portion  82   a . Lower portion  82   a  extends radially from a radial distance from the central axis of piston  18 , and upper portion  82   b  extends radially from a radial distance that is further from the central axis of piston  18  than lower portion  82   a  because upper portion  82   b  follows the contour of combustion bowl  24 . Because upper portion  82   b  follows the contour of combustion bowl  24 , the uppermost portion of portion  82   b  of gallery  82  may be located at a distance equal to the wall thickness of combustion bowl  24  from top surface  64  of combustion bowl  24 . The position of the uppermost portion of portion  82   b  enables top groove  50  to be in a closer position at distance B from top surface  64  than is possible in conventional piston designs, as will be explained in more detail hereinbelow. Positioning top groove  50  at distance B provides an advantage in that heat travels a shorter distance in piston  18  before reaching a cooling fluid than in a conventional piston design. The faster access to a cooling fluid reduces heat buildup in piston  18 , decreasing the stress on piston  18 , which therefore increases the life of piston  18 . Oil splash from connecting rod  46  goes through a plurality of piston passages  84  into gallery  82  and then back out piston passages  84  into lubricated portion  22 . 
     Hollowing out the interior of a conventional piston to form a gallery similar to gallery  82  is not possible because the top surface of a conventional piston would be unable to withstand the stresses in an associated combustion chamber. The reason a conventional piston is unable to withstand these stresses is because there would be insufficient support within a conventional piston to withstand the combustion pressure exerted on the top surface of a convention piston. Piston  18  overcomes this difficulty by fabricating upper piece or portion  66  and lower portion  68 , forming gallery  82  into at least upper portion  66 , and then welding the two portions together via a spin welding process. The outer surface or diameter  49  of piston  18  may then be machined, ground and/or honed to a desired dimension, removing any unevenness left by the spin welding process. 
     Passages  84  may be located in lower or distal portion  68  during casting or may be machined into lower portion  68  after casting. Wall or rib  88  located in proximate portion  66  is contiguous with a wall or rib  86  located in distal portion  68 . Wall or rib  88  and wall or rib  86 , because of the spin welding process, form a contiguous or continuous wall or rib that extends from a combustion bowl wall  90 , which is part of combustion bowl  24 , to a sidewall portion  92 , which is axially below bottom groove  54 . Sidewall portion  92  is part of sidewall, exterior wall, or outside wall  43  of piston  18 . Thus, piston  18  has the ability to provide cooling to a peripheral portion of the top of piston  18  in a region between combustion bowl  24  and outside wall  43  of piston  18  while maintaining the strength of a conventional piston because of the two-piece piston design. 
     To obtain the maximum cooling, emissions and efficiency benefit from the aforementioned features, certain ratios are applicable. A first ratio is quantified in equation (1), which specifies a limit for the ratio of the top ring distance B from top surface  64  of piston  18  to piston bore diameter D. This ratio applies to piston bores having a diameter that meets the requirements of equation (2).
 
 B/D&lt; 0.090  (Equation 1)
 
275 mm≧ D≧ 165 mm  (Equation 2)
 
Distance B and diameter D are sized and dimensioned to result in a maximum ratio of 0.090, as described by equation (1), and preferably a maximum ratio of 0.085. The range of diameter D that achieves these ratios is as listed in equation (2) with a preferable range provided in equation (3).
 
275 mm≧ D≧ 175 mm  (Equation 3)
 
Meeting the requirements of equation (1) is critical to optimizing emission and reducing fuel consumption. It is apparent from equation (1) that distance B should be as close to top surface  64  of piston  18  as possible while maintaining the strength of piston  18 . However, gallery  82  needs to extend to a location closer to top surface  64  of piston  18  than top groove  50 . Otherwise, cooling of piston  18  in the area of top groove  50  will be inadequate, leading to excessive heating of compression ring  56 , which leads to wear and early failure of cylinder liner  16 . Thus, top groove  50  can be no closer to top surface  64  than gallery  82 , which can only be as close to top surface  64  as the required strength of combustion bowl wall  90 .
 
     Improved cooling of piston  18  is achieved by two aspects of the present disclosure. First, distance B of top groove  50  with respect to thickness C of cylinder liner  16  in wall portion  32  determines, in part, the adequacy of cooling of piston  18 . The relationship between distance B and thickness C is defined in equation (4).
 
 B/C&lt; 1.30  (Equation 4)
 
Distance B and thickness C are sized and dimensioned to result in a maximum ratio of 1.30 and preferably a maximum ratio of 1.25. As in equation (1), equation (4) indicates that distance B should be relatively small, at least in comparison to thickness C of wall portion  32  of cylinder  16 . As previously noted, while distance B should be as small as possible, this distance is limited by the ability to cool top groove  50 , which is limited by the ability to extend gallery  82  as close to top surface  64  of piston  18  as possible. The second aspect of cooling is determined by a ratio of thickness A of top flange  28  to distance B, specified in equation (5).
 
 A/B&lt; 0.80  (Equation 5)
 
Thickness A and distance B are sized and dimensioned to result in a maximum ratio of 0.80 and preferably a maximum ratio of 0.80. Thickness A of top flange  28  determines how close coolant passage  26   a  comes to top surface  40  of cylinder liner  16 , which also limits distance B since thickness A must be no more than 0.75 times distance B. By having thickness A meet this condition, coolant is able to provide optimal cooling for top groove  50 . However, thickness A has a minimum thickness determined by the ability to withstand the pressures from combustion chamber  23  and by the ability to press fit top flange  28  into cylinder bore  20 . Thus, distance B is limited by two factors, the minimum thickness of top flange  28  and by the ability to make gallery  82  extend close to surface  64  of piston  18 .
 
     Considering now equations (1)-(5), it is apparent that optimal cooling of piston  18  is achieved by meeting the requirements of equations (4) and (5), and minimum emissions and best efficiency is achieved by meeting the conditions of equations (1)-(3). The key to cylinder liner, piston ring, and piston longevity is minimizing the top ring reversal temperature. The top ring reversal temperature is the temperature of top compression ring  56  when piston  18  is at TDC and about to change direction from an upward stroke to a downward stroke. If the top ring reversal temperature is too high, then excessive wear of cylinder liner  16  and piston ring  56  occurs, shortening the life of cylinder liner  16  and piston ring  56 . However, groove  50 , which holds ring  56 , can only be moved higher by enabling cooling of ring  56 . The present disclosure describes a configuration that enables a much higher position for groove  50  and ring  56  than in conventional designs when the conditions of equations (1)-(5) are met, which improves the life and reliability of piston  18  as well as decreasing emissions and improving engine  10  efficiency. 
     While various embodiments of the disclosure have been shown and described, it is understood that these embodiments are not limited thereto. The embodiments may be changed, modified and further applied by those skilled in the art. Therefore, these embodiments are not limited to the detail shown and described previously, but also include all such changes and modifications.