Abstract:
A method of modifying a combustion seal of a diesel engine fitted with a cylinder liner having an annular top sealing ridge which is damaged or mispositioned so as to interrupt the combustion seal is provided. The method includes exposing the sealing ridge and, without removing the liner from the engine, clamping and plastically deforming a combustion seal shim against the sealing ridge to perfect the combustion seal.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application Serial No. 60/359,553, filed Feb. 25, 2002. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Technical Field  
           [0003]    This invention relates generally to cylinder liners and particularly to cylinder liners for heavy duty diesel engine applications wherein a combustion seal is maintained between the liners and a metal gasket plates.  
           [0004]    2. Related Art  
           [0005]    Cylinder liners, typically fabricated of cast iron, are installed in engine blocks of heavy duty diesel engines and are formed on their upper edge with a circumferentially extending step for receiving a steel plate. A circumferentially continuous sealing ridge projects up from the step surfaces and makes contact with the underside of the steel plate with sufficient force and sealing quality to establish a gas-tight seal between the steel plate and liners. The steel plate engages the cylinder head on its opposite side when the head is bolted to the block. The seal between the liners of the cylinders and the plate serving to seal off the combustion chambers.  
           [0006]    For various reasons, including improper liner fit and manufacturing tolerances, such a liner may move relative to the block and steel plate during the combustion cycle. Movement of the liner causes the sealing ridge of the liner to wear impairing the ability of the liner to maintain an adequate combustion seal.  
           [0007]    In other situations, it may happen that a liner, through improper installation or manufacturing tolerances is set too low in the block such that the sealing ridge of the liner is not clamped with sufficient force by the steel plate to provide an adequate combustion seal. Such a liner is typically formed with an outer flange that fits into an annular recess machined in the block. When installing the liner, a thin, annular shim is typically installed in the recess of the block and engages the underside of the liner flange to position the sealing ridge at the proper elevation for adequate sealing with the steel plate. In the event the shim turns out to be too thin, such that the liner sits too low for proper sealing, the only known present solution to the problem is to remove the liner and install a thicker shim in the recess of the block, after which the liner is reinstalled. This, of course, can be a costly, inconvenient solution to the problem since the liner needs to be removed and reinstalled, which is particularly troublesome if the problem is discovered after an engine has been built.  
           [0008]    It is an object of the present invention to provide a solution for modifying the combustion seal of a heavy duty liner that is worn, improperly installed, or otherwise arranged to make insufficient contact with the metal plate to establish a suitable combustion seal without having to remove and replace or reinstall the liner.  
         SUMMARY OF THE INVENTION  
         [0009]    According to one aspect of the invention, an annular shim is installed between the sealing ridge of a liner and an overlying steel plate to effectively extend the height of the sealing ridge for establishing a combustion seal between the liner and plate.  
           [0010]    According to a further aspect of the invention, a liner that is installed in an engine block having a damaged or insufficiently tall sealing ridge is fitted with a circumferentially continuous shim between the ridge and plate to make up for the deficiency and material so as to provide a desired combustion seal with an overlying steel plate.  
           [0011]    According to a further aspect of the invention, a liner installed in an engine block having a shim between the liner and the block is provided with a shim between the liner and an overlying steel plate.  
           [0012]    According to still a further aspect of the invention, a method is provided for modifying the combustion seal of a diesel engine block fitted with a liner having either a damaged or mispositioned seal ridge. The method comprises preparing a thin, metal annular shim and installing the shim over the seal ridge of the liner and clamping the shim between the liner and an overlying steel plate to form a gas-tight combustion seal about the circumference of the liner—all without removing the liner from the block. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    A presently preferred embodiment of the invention is disclosed in the following description and in the accompanying drawings, wherein:  
         [0014]    [0014]FIG. 1 is a schematic fragmentary perspective view of a diesel engine fitted with cylinder liners;  
         [0015]    [0015]FIG. 2 is an enlarged, fragmentary sectional view taken generally along lines  2 - 2 , shown with the metal gasket plate and cylinder head in place;  
         [0016]    [0016]FIG. 3 is an enlarged fragmentary plan view of a liner and shim disposed in a block with the head and plate gasket removed; and  
         [0017]    [0017]FIG. 4 is an enlarged fragmentary sectional view taken generally along lines  4 - 4  of FIG. 3 with the head and metal gasket plate in place. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]    A schematic representation of a diesel engine fitted with cylinder liners is shown generally at  10  in FIG. 1 and includes an engine block  12  fitted with a plurality of cylinder liners  14 , a metal plate gasket  16 , and a cylinder head  18  removably mounted to the block  12  by a plurality of fasteners  20  for clamping the plate gasket  16  tightly between the head  18  and liners  14  to establish gas-tight combustion seals around each liner  14  as discussed further below.  
         [0019]    [0019]FIG. 2 is a greatly enlarged, exaggerated sectional view through a portion of one of the liners  14 , showing the manner in which the liner  14  is mounted in the block  12  and how it interacts with the plate gasket  16  and head  18  to provide the gas-tight seal. The liner  14  has an inner cylindrical wall  22  along which a piston (not shown) reciprocates. The inner wall  22  and head  18  define a combustion chamber  24  associated with each liner  14  where combustion of the fuel takes place to drive the piston.  
         [0020]    Each cylinder liner  14  has an upper end surface  26 , an inner cylinder wall  22  and an outer peripheral surface  28 . Spaced radially outwardly from the inner cylinder wall surface  22  is a step  30  formed in the upper surface  26  and extending to the outer surface  28 . The step  30  presents a recessed surface  32  which is spaced axially below the upper surface  26 . An upstanding, annular fire dam  34  extends above the recessed surface  32 , separating the recessed surface  32  from the interior of the liner  14 .  
         [0021]    Referring additionally to FIG. 3, the annular recessed surface  32  is formed with an annular, axially upwardly projecting sealing ridge  36  that extends about and is spaced outwardly of the fire dam  34 . The sealing ridge  36  has an upper annular sealing surface  38  that is preferably flat and planar, as represented by the broken chain line in FIG. 2 but which, for reasons to be explained below, may erode or wear away over time, as represented by solid lines in FIG. 2. The ridge  36  is formed as a one-piece feature with the liner  14 . Liners  14  for heavy duty diesel engines are typically cast from iron and features such as the step  34  and sealing ridge  36  are machined into the liners  14 .  
         [0022]    A mounting flange  40  projects radially outwardly from the sealing ridge  36  and extends about the periphery of the liner  14  at its upper end. The flange  40  has an annular, flat underside mounting surface  42  which fits into a step  44  formed in the block  12  surrounding the cylinder openings  46  in which the liners  14  are installed. The step  44  has an upper annular support surface  48  which underlines the mounting surface  42  of the liners  14 .  
         [0023]    In a typical installation, it is necessary to carefully locate the sealing surface  38  of the ridge  36  relative to the block  12 , such that when the head  18  is bolted to the block  12 , the gasket  16  firmly engages the sealing surface  38  with sufficient force and soundness to create a gas-tight seal about the combustion chamber  24  of each liner  14 . Typically, a spacer or shim  50  is installed on the block support surface  48  prior to installing the liner  14  in the cylinder opening  46 . The shim  50  effectively elevates the mounting surface  42  above the support surface  48 , raising the sealing surface  38  of the ridge  36  to a desired level. In some cases, as illustrated in FIG. 2 by the broken chain line, the spacing of the liner-to-block shim  50  is inadequate, such that the gasket  16  does not contact the sealing surface  38  (shown greatly exaggerated in FIG. 2), or if it does contact, not with sufficient force to produce the desired combustion seal. The step  44  in the block  12  has a cylindrical inner wall surface  52  of fixed diameter which, ideally, closely matches the outer diameter of the mounting flange  40  so as to hold the liners  14  against laterial movement relative to the block  12  and gasket plate  16 . However, as illustrated in FIG. 2, the wall  52  of the step  44  is sometimes made slightly oversized relative to the outer surface of the flange  40  (or the flange  40  made slightly undersized), such that there exists a radial gap  54  between the flange  40  and step wall  52 . The gap  54  permits undesirable lateral movement of the liner relative to the block  12  and plate gasket  16 . Such movement typically occurs under load of combustion forces and causes the sealing ridge  36  to rub against the gasket plate  16 . Over time, the ridge  36  can erode or wear away such that an adequate combustion seal can no longer be maintained between the liners  14  and the gasket plate  16 .  
         [0024]    The invention proposes a solution to the problem of an improperly positioned liner (the liner-to-block shim  50  too thin) and/or a worn sealing ridge  36  without having to remove the liner  14  from the block  12  or having to replace the liner  14 . According to the invention, the head  18  and gasket plate  16  are removed from the block  12 , exposing the liners  14 . An annular washer-like combustion seal shim  56  is disposed over the sealing surface  38  of the ridge  36  radially outboard of the fire dam  34  and inwardly from the outer surface  28  as best shown in FIGS. 3 and 4. The combustion seal shim  56  makes up for the inadequate spacing provided by the shim  50  and/or the material of the ridge  36  lost through wear of the ridge  36  so as to restore the sealing capability of the ridge  36  with the gasket plate  16  without having to remove the liner  14  and replace the inadequate shim  50  or rework or replace a liner having a worn ridge  36 .  
         [0025]    The shim  56  is preferably fabricated of a thin, plastically deformable metal, such as plain carbon steel, heat treatable steel, stainless steel, which may be fully or partially hardened depending upon the requirement of a particular application to provide the desired sealing effect when clamped between the plate  16  and ridge  36 . The selection of material and heat treatment (if any) is thus dependent in part on the needs of each application and may vary accordingly as contemplated by this invention. The thickness of the shim  56  may be on the order of 0.001-0.005 inches and preferably on the order of about 0.002 inches. Of course, the thickness will also depend on the requirements of a particular application and the range given here and those of greater range are thus contemplated by this invention.  
         [0026]    As illustrated best in FIG. 4, the shim  56  has an outer diameter surface  58  that is about the same diameter as that of the outer diameter of the mounting flange  40  of the liner  14 . The shim  56  has an inner diameter surface  60  which is about equal to an inner diameter surface  62  of an opening in the plate  16  surrounding the annular fire dam  34  of the liner  14 . The inner diameter surface  60  is spaced from an outer diameter surface of the fire dam  34 . A plurality of locating tabs or fingers  64  of the shim  56  project radially inwardly from the inner diameter surface  60  of the shim and are relatively sized to engage the outer diameter surface of the fire dam  34  so as to locate the shim  56  on the liner  14  and support the shim  56  against relative lateral movement on the liner  14 . It will be seen from FIG. 4 that a majority of the shim  50  underlies the gasket plate  16 , except for the locating tabs  64 , and is thereby sheltered from the direct heat of combustion passing over the fire dam  34 , protecting the shim  56  against damage or charring from exposure to the heat of combustion.  
         [0027]    Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. The invention is defined by the claims.