Abstract:
An engine block coating system for applying a coating to an engine block includes a work stand, a coating gun, and a first nozzle. The work stand supports the engine block. The coating gun discharges coating on an inner surface of a first cylinder bank. The first nozzle discharges gas from a second cylinder bank to a crankcase side of the first cylinder bank and the second cylinder bank such that the second cylinder bank is shielded from the coating. The coating gun and the first nozzle are arranged relative to each other such that gas discharged by the first nozzle is discharged toward the coating to alter a direction of the coating by the gas discharged by the first nozzle directly contacting the coating such that the coating would otherwise contact the cylinder bore of the second cylinder bank upon stopping discharge of the gas by the first nozzle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional application of U.S. patent application Ser. No. 11/340,416 filed on Jan. 26, 2006. The entire disclosure of U.S. patent application Ser. No. 11/340,416 is hereby incorporated herein by reference. 
         [0002]    This application claims priority to Japanese Patent Application No. 2005-021686, filed on Jan. 28, 2005, and to Japanese Patent Application No. 2005-348463, filed on Dec. 1, 2005. The entire disclosures of Japanese Patent Application No. 2005-021686 and Japanese Patent Application No. 2005-348463 are hereby incorporated herein by reference. 
     
    
     BACKGROUND 
       [0003]    1. Field of the Invention 
         [0004]    The present invention generally relates to a system for coating a cylinder bore of an engine block. 
         [0005]    2. Background Information 
         [0006]    An engine block may be designed to include a coating, e.g., a ferrous material, coated on the inner surface of the cylinder bore. Such a coating may allow engine designs having reduced overall weight of the engine block and enhanced abrasion resistant properties for inner surfaces of the cylinder bores. For example, a coating may be particularly useful for aluminum engine blocks. 
         [0007]    It is desirable to prevent a coating from adhering to a lower portion of an adjacent cylinder bore. For example, if while spraying a coating on one cylinder bore, some amount of spray is directed to an adjacent cylinder bore, the spray in the adjacent cylinder bore will have a lower degree of adhesion. Thereafter, if the adjacent cylinder bore is coated, the coating in that cylinder bore will continue to have a low degree of adhesion to the cylinder bore. This may cause the coating in that cylinder bore to break free during engine operation, which may lead to poor engine performance or even engine failure. 
         [0008]    One method to prevent a coating from adhering to a lower portion of the adjacent cylinder bore requires covering lower parts of the cylinder bore with a masking shield prior to spraying the cylinder bore with a coating. The masking shield protects the lower portion of the cylinder bore when the coating is formed on the inner surface of the engine cylinder bore. After spraying, the masking shield must be removed. 
         [0009]    Removing masking shields is labor-intensive. Further, masking shields are consumable items that contribute to engine manufacturing expenses. In addition, since a coating may have formed a continuous layer connecting an inner surface of a cylinder bore to a masking shield, removal of a masking shield runs the risk of breaking and damaging the coating formed on the inner surface of the cylinder bore. 
       SUMMARY 
       [0010]    Embodiments of the disclosure prevent or reduce adherence of a coating to a cylinder bore without using masking materials by protecting the lower portion of the cylinder bore with a gas gun. Embodiments of the disclosure may be particularly useful for forming a coating on the inner surface of the cylinder bores in one cylinder bank while protecting cylinder bores in an opposing cylinder bank, e.g., in a V-type engine. 
         [0011]    In accordance with a first aspect, an engine block coating system for applying a coating to an engine block comprises a work stand, a coating gun, and a first gas nozzle. The work stand is configured to support the engine block. The coating gun is arranged relative to the work stand to discharge a coating material to form the coating on an inner surface of a cylinder bore of a first cylinder bank of the engine block. The first gas nozzle is arranged relative to the work stand such that gas is discharged by the first gas nozzle from within a cylinder bore of a second cylinder bank of the engine block to a crankcase side of the cylinder bore of the first cylinder bank and the cylinder bore of the second cylinder bank such that the cylinder bore of the second cylinder bank is shielded from the discharged coating material. In addition, the coating gun and the first gas nozzle are arranged relative to each other such that the gas discharged by the first gas nozzle is discharged toward the discharged coating material. Due to this arrangement, the gas discharged by the first gas nozzle directly alters a direction of the discharged coating material by the gas discharged by the first gas nozzle directly contacting the discharged coating material such that the discharged coating material would otherwise contact the cylinder bore of the second cylinder bank upon stopping discharge of the gas by the first gas nozzle. 
         [0012]    Embodiments of the disclosure may provide one or more advantages. For example, since masking materials are reduced or not used, the process of removing the masking material from the engine block may be reduced or eliminated. This also helps to reduce manufacturing expenses by avoiding the use of consumable masking materials to which the spray material adheres. In addition, embodiments of the disclosure prevent damage to an applied coating on the inner surface of the cylinder bore during removal of a masking material. 
         [0013]    The details of one or more embodiments of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Referring now to the attached drawings which form a part of this original disclosure: 
           [0015]      FIG. 1  is a cross-sectional view of A-A in  FIG. 2  showing coating masking techniques in a first exemplary embodiment. 
           [0016]      FIG. 2  is a plain view of the engine block  1  viewed from the side of the mounting surface in the first exemplary embodiment. 
           [0017]      FIG. 3  is a cross-sectional view corresponding to  FIG. 1  showing coating masking techniques in a second exemplary embodiment. 
           [0018]      FIG. 4  is a cross-sectional view corresponding to  FIG. 1  showing coating masking techniques in a third exemplary embodiment. 
           [0019]      FIG. 5  is a cross-sectional view of D-D in  FIG. 4 . 
           [0020]      FIG. 6  is a cross-sectional view similar to  FIG. 1 , showing coating masking techniques in a fourth exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0021]    Selected embodiments will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. Numerical symbols corresponding to the embodiments of the present invention are used for the sake of easier comprehension, but these numerical symbols do not limit the present invention. 
         [0022]    A first exemplary embodiment of coating masking techniques is shown in  FIG. 1 , which is a view of section A-A from  FIG. 2 .  FIG. 2  is a side view of engine block  1  as viewed from the side of the mounting surface. In this example, the engine block  1  represents a V-type engine with the left and right banks  3  and  5 , each bank having three cylinder bores,  7   a,    7   b,    7   c  and  9   a,    9   b,    9   c  respectively, arranged in straight lines toward the axial direction of the crankshaft (not shown). 
         [0023]    The cylinder bores  7   a,    7   b,    7   c  forming the cylinder bank on the left bank  3  and the cylinder bores  9   a,    9   b,    9   c  forming the cylinder bank on the right bank  5  are arranged opposite to one another. Each of the cylinder bores  7   a,    7   b,    7   c  oppose each of the cylinder bores  9   a,    9   b,    9   c  and vice versa. The extensions of central axes SL of the cylinder bores  7   a ,  7   b,    7   c  and SR of the cylinder bores  9   a,    9   b,    9   c  intersect with each other as viewed from the axial direction of the crankshaft, for example, the view shown in  FIG. 1 . 
         [0024]    The engine block  1  may be designed to include a coating, e.g., a ferrous material, coated on the inner surface of the cylinder bore. For example, engine block  1  may be an aluminum engine block. Such a coating may enhance abrasion resistant properties for inner surfaces of the cylinder bores  7   a,    7   b,    7   c  and  9   a,    9   b,    9   c.    
         [0025]    The engine block  1 , as shown in  FIG. 1 , includes crankcase  11  on the lower end of cylinder bores  7   a,    7   b,    7   c  and  9   a,    9   b,    9   c.  The oil pan rail  13   a  of flange  13 , protruding to both sides of the crankcase  11 , is fixed on the hollow center work stand  15  (means for supporting). The crank journal  17  rotationally supports the crankshaft (not shown). 
         [0026]    To create a coating, a coating gun  19 , as shown in  FIG. 2 , enters the cylinder bore  9   a  in one cylinder bank on the right bank  5 , and the center of the spray gun is aligned with the central axis SR of the cylinder bore  9   a.  The spray gun  19  rotates about the central axis SR as it moves along the central axis SR, spraying a coating material  23  from the spray nozzle  21 . In this manner, a coating gun  19  forms a coating on the inner surface of the cylinder bore  9   a.    
         [0027]    Prior to spraying a coating, to protect lower portions of the cylinder bores  9   a ,  9   b  and  9   c,  gas guns  25   a,    25   b,    25   c  are inserted into the cylinder bores  7   a,    7   b  and  7   c , respectively, each opposite to the cylinder bores  9   a,    9   b  and  9   c.  A gas  27  is then discharged out of the gas guns  25   a,    25   b,    25   c.  For example, the gas  27  may consist of air. 
         [0028]    Gas guns  25   a,    25   b,  and  25   c  are substantially similar; however, the following description will only refer to gas gun  25   a,  and cylinder bores  9   a  and  7   a.  The gas gun  25   a  is arranged as the semi-circular shaped gun housing  29 , which is located along the lines of the inner surface of cylinder bore  7   a  at the near side of the cylinder bore  9   a.  The gun housing  29  has an inner portion  31  and an outer portion  33 . The gas nozzle  35  is fixed in the space between inner portion  31  and outer portion  33 . 
         [0029]    The gas nozzle  35  forms gas path  37 , which includes an expansion space  39  prior to multiple outlets  41 . The multiple outlets  41  are arranged along the lines of the semi-circular gun housing  29 . In other words, the outlets  41  of the gas nozzle  35  form a semi-circle along the inner portion  31  of the cylinder bore at the near side of the cylinder bore  9   a.  Gas  27  is supplied from the gas supply equipment  42  to gas path  37 . 
         [0030]    In addition, the gun housing  29  is longer near the wall of the cylinder bore and shorter near the center of the cylinder bore. Thus, the tip  29   a  is wedge shaped, which is aligned with the gas outlets of nozzle  41 . Similarly, the length of the multiple outlets of nozzle  41  is the longest on the side of the cylinder bore  9   a.  The outlet length gradually gets shorter at positions farther from  9   a,  the nozzle located on the left end in  FIG. 1  being the shortest. 
         [0031]    A coating is formed all over the cylinder bore  9   a  inner surface by inserting a coating gun  19  into the cylinder bore  9   a  on the right bank  5 , rotating while advancing it in the direction of the axis, and jetting a coating material  23  from a coating nozzle  21  on its tip. Simultaneously, the gas ventilation equipment  44  suctions out the gas in the engine block  1  from the lower side of the work stand  15  and pulls clean gas  45  in. 
         [0032]    As the coating gun  19  forms the coating, the gas guns  25   a,    25   b,    25   c  are inserted into the cylinder bores  7   a,    7   b,    7   c  on the left bank  3  respectively, opposite to the cylinder bore  9   a,  and the gas supplied from the gas supply equipment  42  is sprayed as the gas  27  from the tip of each outlet  41 . 
         [0033]    In  FIG. 1 , the gas  27  that sprays from each outlet  41  of the gas guns  25   a,    25   b ,  25   c  are arranged between the right and left flange parts  13  in the crankcase, and directed towards a range of angles θbetween arrows B and C. In other words, the direction of the gas spray of each outlet  41  on the gas nozzle  35  is the opening part on the opposite side of the cylinder bore in the crankcase that communicates with the cylinder bore. 
         [0034]    At this point, as shown in  FIG. 1 , a coating gun  19  is located at the terminal end of the cylinder bore  9   a,  and a coating nozzle  21  is directed towards the engine block bulkhead  43 . As a result, some of a coating material  23  that sprays from a coating nozzle  21  flows towards the opposing cylinder bore  7   a  and comes very close to entering the cylinder bore  7   a.  However, the gas  27  that discharges from the gas gun  25   a  alters the direction of this flow downward, thereby preventing or reducing a coating material  23  from adhering to the inner surface of the opposing cylinder bore  7   a.  Likewise, the gas  27  spraying from the gas guns  25   b,    25   c  prevents a coating material  23  from adhering to the cylinder bores  7   b,    7   c  adjacent to the cylinder bore  7   a.    
         [0035]    As shown in  FIG. 1 , the outlets of nozzle  41  are located near the opening on the side of the cylinder bore  7   a  where a coating material  23  may enter the cylinder bore  7   a  to prevent a coating from adhering to the cylinder bore  7   a.  In addition, the outlets  41  are located forming a semi-circular arc covering about half the inner surface of the cylinder bore  7   a  closest to the cylinder bore  9   a  that receives a coating. In particular the outlets of nozzle  41 , are arranged in a half-circle such that each of the set of outlets is substantially equidistant from an interior surface the cylinder bore  7   a.  This arrangement enables the gas  27  that sprays from each outlet  41  to block the spray materials passing below the engine block bulkhead  43 . 
         [0036]    The gas gun  25   a  that is inserted into the cylinder bore  7   a  is located such that the tip  29   a  is behind line L. Line L is an extension of the straight line that connects the spray from nozzle  21  of a coating gun  19  to the end of the engine block bulkhead  43  between the cylinder bore  7   a  and  9   a,  which is on the upper side in  FIG. 1 . As such, gas gun  25   a  is substantially shielded from a coating material  23  by the engine block bulkhead  43 . This prevents a coating material  23  from adhering to nozzle  41 , which may prolong the use of the gas gun  25   a.  In contrast, if gas gun  25   a  projected beyond line L, some of a coating material  23  may adhere to the gas discharging mouth of the outlet  41  and reduce the functional life of gas gun  25   a.    
         [0037]    The direction of the gas discharging from each outlet is set such that the gas  27  and the ventilation gas  45  merge smoothly and flow downwards. Thus, the flow of the ventilation gas  45  is not disturbed much by gas  27 , enabling the spraying process to be performed efficiently. 
         [0038]    As described above, coating masking may be performed by discharging the gas from the same gas supply equipment  42  and inserting the gas guns  25   a,    25   b  and  25   c  into cylinder bores  7   a,    7   b  and  7   c  simultaneously. Thus, coating of cylinder bores  9   a,    9   b  and  9   c  may be performed successively or simultaneously without allowing a coating to adhere to the cylinder bores  7   a,    7   b  and  7   c  during the coating of any of cylinder bores  9   a,    9   b  and  9   c.    
         [0039]    In some embodiments, when spraying the cylinder bore  9   a,  the gas  27  prevents a coating material  23  from adhering to the cylinder bore  7   b  and  7   c.  In such embodiments, the gas  27  may be sprayed only from the gas gun  25   a  rather than from each gas guns  25   a ,  25   b,  and  25   c  during the spraying of the cylinder bore  9   a.  When using the same gas supply source (gas supply equipment  42 ) for the gas guns  25   a,    25   b,    25   c,  a valve may be installed in the middle of the gas piping (not shown) to direct gas only to gas gun  25   a.    
         [0040]    In addition, coating masking may be performed for each of three cylinder bores  9   a,    9   b,    9   c  consecutively, simultaneously or two at a time. In each case, the gas guns  25   a ,  25   b  and  25   c  corresponding to the cylinder bores  7   a,    7   b  and  7   c  that are adjacent to each of the cylinder bores  9   a,    9   b,    9   c  being sprayed should be activated. In some embodiments, all gas guns in cylinder bores opposing a cylinder bore being sprayed may be activated. 
         [0041]    When a coating is formed on the cylinder bore  9   a,  the gas  27  is supplied because of concern over the entrance of a coating material  23  due to the shape of the opening on the crankcase  11  of the cylinder bores  7   a,    7   b,    7   c  in the cylinder bank opposing the cylinder bore  9   a  that opposes the opening of the cylinder bore  9   a.  However, the cylinder bores  9   a,    9   b,    9   c  are parallel with one another and their openings on the crankcase  11  side are not opposed; therefore, there is no risk of entry of a coating material  23  into cylinder bores  9   b  or  9   c.    
         [0042]    After forming a coating on the cylinder bores  9   a,    9   b  and  9   c  on the right bank  5 , a coating gun  19  forms a coating on the cylinder bores  7   a,    7   b  and  7   c.  This can be performed the same way as described above, by inserting the gas guns  25   a,    25   b  and  25   c  into the cylinder bores  9   a,    9   b  and  9   c  to discharge the gas. This time, a coating from a coating gun  19  is prevented from adhering to the cylinder bores  9   a,    9   b  and  9   c.    
         [0043]    In the first exemplary embodiment described above, the ventilation gas amount Q 1  suctioned by the gas ventilation equipment  44  is larger than the gas flow amount Q 3  that the ventilation gas amount Q 2  supplies to the gas gun  25   a.  This allows the assured draining of a coating material  23  flowing to the crankcase  1  side out of the engine block  1 . 
         [0044]    As described above, in the first exemplary embodiment, when a coating is formed on the cylinder bore  9   a,  a coating does not adhere to the cylinder bores  7   a,    7   b,    7   c  by the gas  27  flowing to the cylinder bores  7   a,    7   b,    7   c.  If a coating is formed to the cylinder bore  9   a  without taking such measures, a coating will adhere to the cylinder bores  7   a,    7   b,    7   c.    
         [0045]    In this case, compared with the cylinder bore  9   a  that actually performs a coating masking, the cylinder bores  7   a,    7   b,    7   c  are arranged further from a coating gun  19 . The degree of adhesion of a coating attached to the cylinder bores  7   a,    7   b,  and  7   c  is lower than that of a coating adhered to the cylinder bore  9   a,  which is problematic. Thereafter, a coating is formed by inserting a coating gun  19  to each of these cylinder bores  7   a,    7   b,    7   c  in the same way as the cylinder bore  9   a.  However, the low degree of adhesion of a coating remains for cylinder bores  7   a,    7   b,    7   c,  and a stable a coating can not be obtained. 
         [0046]    In this case, although unwanted coating can be taken off, the cylinder bore may, by design, have a rough surface from a shot peening process. Such a rough surface increases the degree of adhesion. As a result, it is difficult to completely remove undesirable coating. 
         [0047]    Accordingly, as described in this embodiment, when a coating is formed on the cylinder bore  9   a,  it is possible to increase the degree of adhesion of a coating formed on the cylinder bores  7   a,    7   b,    7   c  later by preventing a coating from adhering to the cylinder bores  7   a,    7   b,    7   c  by flowing the gas  27  to the cylinder bores  7   a,    7   b,    7   c  in the opposing cylinder banks. 
         [0048]    In addition, when a coating is formed on the cylinder bores  7   a,    7   b,    7   c  after forming a coating on the cylinder bores  9   a,    9   b,    9   c,  one can stabilize a coating and also facilitate the subsequent washing of the cylinder bores  9   a,    9   b,    9   c  by preventing a coating from adhering to the cylinder bores  9   a,    9   b,    9   c  on which a coating has been already formed by flowing gas to the side of the cylinder bores  9   a,    9   b,    9   c.    
       SECOND EMBODIMENT 
       [0049]      FIG. 3  is a cross-sectional view corresponding to  FIG. 1  showing coating masking techniques in the second exemplary embodiment of the invention. In this embodiment a gas gun  250  is used instead of the gas guns  25   a,    25   b  and  25   c  described in  FIG. 1 . Except for structure related to the gas gun  250 , the structure and notations for members are the same as that in  FIG. 1 . 
         [0050]    The gas gun  250  in the second exemplary embodiment has a gun housing  290  as a housing having a hollow rectangular shape. Inside the housing, the gas nozzle  350  is provided on the gas path  370  located on the side of rear anchor. The gas path  370  includes an expansion space  390  prior to outlets  410 . Multiple outlets  410  on the side of rear anchor communicate with the expansion space  390 . 
         [0051]    As in the first exemplary embodiment, the direction of the gas spray of each outlet  410  on the gas nozzle  350  is inside the opening on the opposite side of the cylinder bore in the crankcase  11 . The flow of the discharging gas  270  and that of the ventilation gas  45  merge smoothly and head downwards, the flow of the ventilation gas  45  is not greatly disturbed, and the spraying process may be performed efficiently. 
         [0052]    In addition, as in the first exemplary embodiment, the tip of the gun housing  290 , or the gas spray of each outlet  410  of the gas gun  250 , is located on the side in the direction of gas discharging. Thus it is shown on the upper side in  FIG. 3 , located behind line L such that gas nozzle  350  is shielded from a coating material  23  by the engine block bulkhead  43 . Here again, a coating material  23  maybe completely prevented from adhering to the gas spray of the nozzle  410 . Consequently, equipment cost can be reduced by the prolonged use of the gas gun  250 . 
         [0053]    In this second exemplary embodiment, a coating gun  19  is located at the terminal end of the cylinder bore  9   a,  and outlet  21  is directed towards the engine block bulkhead  43 . In this condition, a part of the spray material  23  from outlet  21  sprays towards the opposing cylinder bore  7   a  and comes close to entering it. However, the gas  270  that sprays from the gas gun  250  rectifies this flow downwards. As a result, a coating material  23  that sprays from outlet  21  is prevented from adhering to the inner surface of the opposing cylinder bores  7   a,    7   b,  and  7   c.    
         [0054]    According to the second exemplary embodiment, since the gun housing  290  has a rectangular shape, the whole shape of the gas gun  250  is simplified as compared with the first exemplary embodiment. 
         [0055]    In addition, as shown in  FIG. 3 , the multiple outlets  410  may be formed by slanting some outlets  410  toward the outside rather than forming all the outlets parallel to the central axis of the cylinder bore. This can be easily applied to various engine blocks with different diameters, rendering it versatile. 
       THIRD EMBODIMENT 
       [0056]      FIG. 4  is a cross-sectional view corresponding to the  FIG. 1 , showing the coating masking method of the third exemplary embodiment.  FIG. 5  is a cross-sectional view of D-D in  FIG. 4 . In  FIG. 4  and  FIG. 5 , the same symbols are allocated to the same part or corresponding part of each component in  FIG. 1  and  FIG. 2 . Also  FIG. 4  and  FIG. 5  show an example of forming a coating on the cylinder bore  9   b,  wherein the gas gun  25   b  is inserted into the cylinder bore  7   b  opposing the cylinder bore  9   b.    
         [0057]    The gas gun  25   b  in this embodiment has basically the same structure as that shown in  FIG. 1 . As shown in  FIG. 5 , it also includes the crank journal wall oriented nozzles  51  and  53  that are directed to the crank journal walls  47  and  49  situated in the upper and the lower parts in  FIG. 5  respectively. Furthermore the third exemplary embodiment includes the cylinder bore oriented nozzle  55  directed to the cylinder bore  9   b . The crank journal walls  47  and  49  comprise the crank journal  17  that rotationally supports the crankshaft (not shown). 
         [0058]    The multiple crank journal oriented outlets of nozzles  51  and  53  (four outlets in this embodiment) are arranged along the horizontal direction in  FIG. 5  respectively. These nozzles are oriented to the lower portion of the cylinder bore of the crank journal walls  47  and  49  where a coating can easily adhere. 
         [0059]    The multiple cylinder bore oriented outlets of nozzle  55  (five outlets in this embodiment) are arranged along the circular arc shape of gun housing  29  and are directed to the opening of crankcase  11  of the cylinder bore  9   b.  In particular, the outlets of nozzle  55  are arranged in a half-circle such that each of the set of outlets is substantially equidistant from an interior surface of the cylinder bore  7   b.    
         [0060]    The outer gas nozzles  57  and  59  are arranged on the work stand  15  that is located downward of the cylinder bore  9   b  on which a coating is formed. These nozzles are gas discharging nozzles that spray gaseous gas upward in  FIG. 4 . 
         [0061]    The outer gas nozzle  57  sprays the gas  61  toward the cylinder bore  9   b  along the inner wall  11   a  of the crankcase  11 . It is formed so as to open from within the wall of the work stand  15  to within the crankcase  11 . 
         [0062]    The multiple gas outlets of nozzle  59  (three outlets in this embodiment) are arranged inside of the work stand  15  along the horizontal direction in  FIG. 4  and discharge the gas  63  and  65  toward the crank journal walls  47  and  49  shown in the  FIG. 5 . These multiple outer gas outlets of nozzle  59  are arranged on the pipes extending in the perpendicular direction, and the lower end of the nozzle is communicated with the pipe  67  extending to the horizontal direction. 
         [0063]    The gas supply pipe  67  is connected to the continuous hole  15   a,  adjacent to the lower end of the outer gas nozzle  57 . The outside of the continuous hole  15   a  also connects with the gas supply piping  69 . The gas is supplied from a gas source (not shown). 
         [0064]    The outer gas nozzle  59  may be oriented to focus gas on both of the crank journal walls  47  and  49  simultaneously. In other embodiments, outer gas nozzle  59  may focus gas on only crank journal walls  49 , and a different outer gas nozzle may focus gas on crank journal walls  47 . 
         [0065]    In the third exemplary embodiment, the gas  71  discharging from the cylinder bore oriented nozzle  55  prevents a coating material  23  from flowing to the opposing cylinder bore  7   b  and entering the cylinder bore  7   b  by altering the direction. Consequently, it can prevent some of a coating material  23  discharged from a coating nozzle  21  from adhering to the inner surface of the opposing cylinder bores  7   b  and  7   a,    7   c.    
         [0066]    In addition, the gas  73  and  75  discharging from the crank journal wall oriented nozzles  51  and  53  flow to the crank journal walls  47  and  49  respectively. This prevents a coating material  23  from adhering to the crank journal walls  47  and  49 . 
         [0067]    Moreover, similarly to the previously described gas  73  and  75 , the gas  63  and  65  discharging from the outer gas nozzle  59  flow to the crank journal walls  47  and  49  respectively. This prevents a coating material  23  from adhering to the crank journal walls  47  and  49 . 
         [0068]    Also, the gas  61  discharging from the outer gas nozzle  57  flows along the inner wall  11   a  of the crankcase  11 . This prevents a coating material  23  from adhering to the inner wall  11   a  of the crankcase  11 . 
         [0069]    The speed and amount of the gas  61 ,  63 ,  65  discharging from the outer gas nozzles  57  and  59  are set such that a coating material  23  draining into the crankcase  11  does not flow back to the cylinder bore  9   b.    
         [0070]    In the third exemplary embodiment shown in  FIG. 4 , the ventilation gas amount Q 1  is determined so that the gas amount Q 2  entering the cylinder bore  9   b  exceeds the total gas amount Q 3  supplied to the gas gun  25   a  and the gas amount Q 4  supplied to the gas supply piping  69 . This ensures a coating material  23  flowing out to the crankcase  11  is directed out of the engine block  1 . 
         [0071]    Since the outer gas nozzles  57  and  59  are arranged on the work stand  15  where the engine block  1  is installed, the gas  61 ,  63 , and  65  can be discharged accurately to the inner surface  11   a  of the crankcase  11  and the crank journal wall  47  without adjusting the position of the outer gas nozzle  57  and  59 , by installing the engine block  1  in the specified position on the work stand  15 . 
         [0072]    While the third exemplary embodiment includes the gas  61 ,  63 , and  65  sprayed on the inner wall  11   a  of the crankcase  11  and the crank journal walls  47  and  49  to prevent adhesion of the coating, it is not always necessary to prevent adhesion of the coating on inner wall  11   a  of the crankcase  11  and the crank journal walls  47  and  49 . For example, even if some of a coating material  23  adheres to the inner wall  11   a  of the crankcase  11  and the crank journal walls  47  and  49 , the degree of adhesion of a coating to the inner wall  11   a  of the crankcase  11  and the crank journal walls  47  and  49  is lower than that to the cylinder bore  9   a.  The distance between a coating gun  19  and the inner wall  11   a  of the crankcase  11  and the crank journal walls  47 ,  49  is greater than that between a coating gun  19  and the cylinder bore  9   a.  Furthermore, inner wall  11   a  of the crankcase  11  and the crank journal walls  47 ,  49  are not generally textured. Also, the inner wall  11   a  of the crankcase  11  and the crank journal walls  47 ,  49  are not processed after cast molding as cylinder bores, and an oxide film remains, resulting in an even lower level of adhesion. For all of these reasons, a coating adhering to the inner surface  11   a  of the crankcase  11  and the crank journal walls  47 ,  49  can be removed, e.g., by subsequent washing. 
       FOURTH EMBODIMENT 
       [0073]      FIG. 6  is a cross-sectional view, showing the coating masking method of the engine block in the fourth exemplary embodiment of the invention. In  FIG. 6 , the same symbols are allocated to the same part or corresponding part of each component in  FIG. 1 . 
         [0074]    The gas gun  25   a  in this embodiment has basically the same structure as that shown in  FIG. 1 ; however, the supply source that supplies gas to the gas gun  25   a  is cooling gas supply equipment  77  instead of the gas supply equipment  42  in  FIG. 1 , and the entire gas gun  25   a  or a portion thereof is insulated to reduce or prevent condensation. 
         [0075]    As compared to previously described embodiments, the cooling gas supplied from the cooling gas supply equipment  77  further decreases the adhesion of a coating material  23  to the cylinder bore  7   a,  the crank journal walls  47  and  49 , and the inner surface  11   a  of the crankcase  11 . 
         [0076]    Since the degree of adhesion of a coating decreases at low temperature, a coating adhering in this condition can be more easily removed by subsequent washing. For example, a coating temporally adhering to the cylinder bore  7   a  and the crank journal walls  47 ,  49  or the inner wall  11   a  of the crankcase  11  can be removed. 
         [0077]    However, the cooling gas into the gas gun  25   a  may result in condensation and water drops. When water drops appear, these water drops flow out to the crankcase  11  side and this has adverse effects in forming a coating on the cylinder bore  9   a  due to the steam generated within the engine block  1 . However, it is possible to prevent condensation on the outer wall surface of the gas gun  25   a  by insulating the entire gas gun  25   a,  including the gas nozzle  35  or a portion thereof. 
         [0078]    Cooled gas may be used in conjunction with any of the described embodiments. For example, the gas  61 ,  63 ,  65  discharged from the outer gas nozzles  57 ,  59  may be substituted with cooling gas. In addition, the entire outer gas nozzles  57 ,  59  or a portion thereof may be insulated. 
         [0079]    Various embodiments of the invention have been described. However, various modifications can be made within the spirit of the invention. For example, in each of the above described embodiments, a V-type engine was described. The invention can be applied to any engines and is particularly applicable to any arrangement including opposing cylinders. For example, an engine may include additional cylinder banks or other arrangement of cylinders. In such cases, opposing cylinders may be masked using the described techniques to prevent undesirable adhesion of the coating. Furthermore, the described embodiments may be readily adapted to mask additional portions of an engine block. In addition, in each of the above described embodiments, the operation of a coating gun  19  and the gas guns  25   a,    25   b,    25   c,  and  250  may be automated with a robotic mechanism, be carried out by manual operation of workers, or by a combination thereof. These and other embodiments are within the scope of the following claims.