Abstract:
A cylinder barrel inside surface treatment apparatus for providing a uniform treatment finish is disclosed. The treatment apparatus includes a pallet on which a cylinder block is placed with a gasket surface faced upward. A top opening of a cylinder barrel of the cylinder block is covered by a cover member having a concave portion communicating with the top opening. A nozzle having treatment solution spray holes is attached to the cover member. The treatment solution is sprayed toward a wall of the concave portion from the treatment solution spray holes and flows along the wall from a top end to a bottom end of the cylinder barrel inside surface.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an improvement in a technique for causing a treatment solution to come into contact with an inside surface of a cylinder barrel of an engine and treating the cylinder barrel inside surface. 
       BACKGROUND OF THE INVENTION 
       [0002]    An inside surface of a cylinder barrel of an engine is exposed to friction from a piston ring and high heat from combustion of fuel, thus requiring the surface to be strong. A surface treatment is effective for increasing the durability of the surface. With a plating treatment, which is one type of surface treatment, any surface fouling or the like is preferably removed prior to the plating treatment. The process of removing fouling substances before the surface treatment is referred to as pre-treatment. 
         [0003]    An example of a plating pre-treatment will now be described with reference to  FIG. 9  hereof. 
         [0004]    As shown in  FIG. 9 , an etching treatment, an acid activation treatment, a first zincate conversion treatment, a dissolution activation treatment, and a second zincate conversion treatment are performed in the pre-treatment. The etching treatment alone is made up of a plurality of steps including chemical treatment using a treatment solution, primary and secondary rinses for cleaning, and an idler or the like to prevent drying. A specific example of the chemical treatment step as one of these steps is disclosed, e.g., in Japanese Patent Application Laid-Open Publication No. 2008-214730 (JP-A 2008-214730). 
         [0005]    Reference is made next to  FIG. 10  showing the chemical treatment apparatus disclosed in JP-A 2008-214730. 
         [0006]    As shown in  FIG. 10 , a cylinder block  101  is mounted on a pallet  104  provided with a member  103  for closing off a bottom opening, and the bottom opening of the cylinder block  101  is closed off. The pallet  104  is disposed above a pan  105 , and a lid  107  provided with a nozzle  106  is moved as indicated by the arrow ( 1 ) to close off the top opening of the cylinder block  101 . 
         [0007]    A treatment solution is fed to the nozzle  106  from a treatment solution feed channel  108  as indicated by arrow ( 2 ). 
         [0008]    The supplied treatment solution is sprayed at the bottom portion of a cylinder barrel  110  from a treatment solution spray hole  109  as indicated by the arrow ( 3 ), and the treatment solution ascends while coming in contact with an inside surface of the cylinder barrel  110 , as indicated by arrow ( 4 ). 
         [0009]    The treatment solution in the cylinder barrel  110  is discharged mainly from a first drainage passage  111  provided to the pallet  104 , as indicated by arrow ( 5 ), and the remainder of the treatment solution is discharged from a second drainage passage  112  provided to the lid  107 , as indicated by arrow ( 6 ). 
         [0010]    However, cylinder blocks are configured in a variety of ways. The inventors therefore applied the same etching treatment to a cylinder block configured without a crankcase part  102 . 
         [0011]    As shown in  FIG. 11 , a cylinder block  114  is mounted on a pallet  115  so that a gasket surface  113  is facing upward. A step portion  117  of the cylinder block  114  is sealed by a seal member  116 . A top opening  119  of a cylinder barrel  118  is covered by a cover member  121  having a concave portion  120  leading to the top opening  119  of the cylinder barrel  118 . A nozzle  122  for feeding treatment solution to the inside surface of the cylinder barrel  118  is provided to the cover member  121 , and treatment solution spray holes  123  for spraying treatment solution are provided at the bottom of the nozzle  122 . 
         [0012]    The following results were obtained when the treatment solution was fed in the same manner as shown in  FIG. 9  in the cylinder block  114 . Reference characters A, B, and C in  FIG. 11  indicate top, middle, and bottom measurement points, respectively, of the inside surface of the cylinder barrel  118 . 
         [0013]    When the high-temperature treatment solution is sprayed from treatment solution spray holes  123 ,  123 , the treatment solution accumulates on the pallet  115  and ascends the inside of the cylinder barrel  118  to reach the concave portion  120 . As a result, point C increases in temperature first, then point B, and lastly point A. Moreover, since heat retained by the treatment solution is absorbed by the cylinder barrel  118  before the treatment solution reaches point A, the temperature decreases. As a result, a temperature difference having a maximum T 1  of as much as 25° C. occurs between the temperature increase curve of point A and the temperature increase curve of point C, as shown in  FIG. 12 . 
         [0014]    The surface of the cylinder barrel is etched (corroded) by the treatment solution, but the amount of etching varies according to the temperature. A temperature difference having a maximum T 1  of 25° C. is expected to affect the etching treatment. The amount of etching at each of the points A, B, and C was therefore examined. 
         [0015]    As shown in  FIG. 13A , the etching amount x 1  was adequate at points B and C, but was low at point A. 
         [0016]    When the etching amount is low, i.e., inadequate, adhesion of the plating is expected to decrease. The plating adhesion was therefore studied at each of the points A, B, and C. 
         [0017]    When plating was applied to the pre-treated cylinder barrel, it was apparent that the peel width y 1  of the plating was small at points B and C and large at point A, as shown in  FIG. 13B . This is because a temperature difference on the inside surface of the cylinder barrel causes the treatment to be unevenly performed. Specifically, a technique is needed for treating the inside surface of a cylinder barrel, whereby the surface treatment can be made uniform. 
       SUMMARY OF THE INVENTION 
       [0018]    It is therefore an object of the present invention to provide a technique for treating the inside surface of a cylinder barrel, whereby the surface treatment can be made uniform. 
         [0019]    According to an aspect of the present invention, there is provided a cylinder barrel inside surface treatment apparatus for causing a treatment solution to come into contact with an inside surface of a cylinder barrel provided to a cylinder block of an internal combustion engine and treating the cylinder barrel inside surface, which apparatus comprises: a pallet for supporting the cylinder block with a gasket surface of the cylinder block faced upward, and closing off a bottom opening of the cylinder barrel; a first drainage passage provided to the pallet for discharging a portion of the treatment solution accumulated in the cylinder barrel; a cover member placed on the gasket surface for covering a top opening of the cylinder barrel and having at a bottom thereof a concave portion communicating with the top opening of the cylinder barrel; a nozzle inserted from above downward into and attached to the cover member and having treatment solution spray holes for spraying the treatment solution toward a wall of the concave portion so as to feed the treatment solution to the inside surface of the cylinder barrel along the concave portion wall; and a second drainage passage provided in the cover member for discharging the remaining treatment solution accumulated in the cylinder barrel. 
         [0020]    In the thus-arranged apparatus, since the treatment solution is sprayed in the concave portion rather than being sprayed directly onto the inside surface of the cylinder barrel, it is possible to prevent reaction that is biased toward the portion directly contacted by the treatment solution, so that the reaction can be made uniform. As a result, the inside surface of the cylinder barrel will be uniformly etched, allowing plating adhesion to be improved. 
         [0021]    Preferably, the treatment solution spray holes are positioned upwardly of a top edge of the cylinder block. Since the treatment solution flows along the inside surface of the cylinder barrel from the top end to the bottom end thereof, the inside surface is uniformly etched. 
         [0022]    Desirably, the pallet has on a top surface thereof a positioning pin adapted to be engaged in a hole formed in the cylinder block. The cylinder block is thereby always set on the pallet in a fixed position. 
         [0023]    According to another aspect of the present invention, there is provided a cylinder barrel inside surface treatment method for causing a treatment solution to come into contact with an inside surface of a cylinder barrel provided to a cylinder block of an internal combustion engine and treating the cylinder barrel inside surface, which method comprises the steps of: placing the cylinder block, with a gasket surface thereof faced upward, on a pallet for closing off a bottom opening of the cylinder barrel; covering, while inserting a treatment solution feeding nozzle into a top opening of the cylinder barrel, the cylinder barrel top opening with a cover member having at a bottom thereof a concave portion communicating with the cylinder barrel top opening; spraying the treatment solution toward a wall of the concave portion from treatment solution spray holes provided to the nozzle so as to feed the treatment solution along the wall of the concave portion to the cylinder barrel inside surface; and discharging a portion of the treatment solution accumulated in the cylinder barrel from a first drainage passage provided to the pallet and discharging a remaining part of the treatment solution accumulated in the cylinder barrel from a second drainage passage provided to the cover member. 
         [0024]    By introducing the treatment solution from above the cylinder barrel and causing the liquid surface to rise back from below to circulate the treatment solution, the difference in temperature between the top and the bottom of the inside surface of the cylinder barrel can be reduced, and the surface treatment can be made uniform. As a result, the inside surface of the cylinder barrel is uniformly etched, and plating adhesion can therefore be improved. 
         [0025]    It is preferred that the treatment solution be fed from a top end to a bottom end of the inside surface of the cylinder barrel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    Certain preferred embodiments of the present invention will be described in detail below, by way of example only, with reference to the accompanying drawings, in which: 
           [0027]      FIG. 1  is a side view showing an apparatus for treating an inside surface of a cylinder barrel, according to an embodiment of the present invention; 
           [0028]      FIG. 2  is a sectional view showing a surface treatment unit of  FIG. 1 ; 
           [0029]      FIGS. 3A and 3B  are cross-sectional views illustrative of a process for positioning a cylinder block; 
           [0030]      FIGS. 4A to 4C  are cross-sectional views illustrative of a process for treating the surface of the cylinder block; 
           [0031]      FIG. 5  is a graph showing the change in temperature of the inside surface of the cylinder barrel of  FIG. 2 ; 
           [0032]      FIG. 6  is a graph showing for comparison the temperature differences of the inside surface of the cylinder barrel in the present embodiment and the prior art; 
           [0033]      FIG. 7  is a graph showing an etching amount in the present embodiment; 
           [0034]      FIG. 8  is a graph showing plating adhesion in the present embodiment; 
           [0035]      FIG. 9  is a view showing a pre-treatment process in conventional plating; 
           [0036]      FIG. 10  is a schematic view illustrating a conventional surface treatment apparatus; 
           [0037]      FIG. 11  is a cross-sectional view showing the conventional surface treatment apparatus as used in a cylinder block having no crankcase part; 
           [0038]      FIG. 12  is a graph showing changes in temperature of the inside surface of a cylinder barrel during conventional surface treatment; and 
           [0039]      FIGS. 13A and 13B  are graphs showing etching amounts and plating adhesion in the conventional surface treatment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0040]    As shown in  FIG. 1 , an apparatus  10  for treating an inside surface of a cylinder barrel according to the present embodiment is provided with a base  12  having adjusters  11 ; lower columns  13  provided upright on the base  12 ; a middle support member  15  provided on the top ends of the lower columns  13 ; a pan  16  for collecting a treatment solution, the pan  16  being supported by the middle support member  15 ; a treatment solution discharge tube  14  for leading the treatment solution collected in the pan  16  to the outside; an enclosure member  17  provided above the pan  16 ; a surface treatment unit  20  provided on the middle support member  15  and surrounded by the enclosure member  17 ; a drainage tube  21  for directing drainage from the top portion of the surface treatment unit  20 , the drainage tube  21  being provided to the surface treatment unit  20 ; a treatment solution detector  22  for monitoring the drainage tube  21 ; middle columns  23  provided upright on the middle support member  15 ; an upper support member  24  provided on the top ends of the middle columns  23 ; upper columns  25  provided upright on the upper support member  24 ; and a top panel  26  provided on the top ends of the upper columns  25 . 
         [0041]    The surface treatment unit  20 , which shall be described in detail hereinafter, is provided with a pallet  31  for supporting a cylinder block  27  subjected to a surface treatment; a cover member  32  for covering a top portion of the cylinder block  27 ; and a second drainage passage  33  provided to the cover member  32  so as to discharge a portion of the treatment solution. 
         [0042]    The surface treatment apparatus  10  for the inside surface of a cylinder barrel is also provided with a raising/lowering cylinder  35  for raising and lowering the cover member  32  via a raising/lowering rod  34 , the raising/lowering cylinder  35  being provided to the top panel  26 ; a pivoting part  37  provided so as to be able to pivot about a rotary shaft  36  at a bottom end of the raising/lowering rod  34 ; and a pivot cylinder  41  for causing the pivoting part  37  to pivot via an advancing/retreating rod  38 , the pivot cylinder  41  being provided to the lower portion of the raising/lowering rod  34 . 
         [0043]    The relevant parts of the surface treatment apparatus  10  for the inside surface of a cylinder barrel will next be described. 
         [0044]    As shown in  FIG. 2 , the surface treatment unit  20  is composed of a pallet  31  for supporting the cylinder block  27  so that a gasket surface  42  of the cylinder block  27  faces upward, and closing off a bottom opening  44  of a cylinder barrel  43 ; a first drainage passage  45  provided to the pallet  31  so as to discharge a portion of the treatment solution accumulated in the cylinder barrel  43 ; a step portion seal member  47  provided to the pallet  31  so as to seal a step portion  46  of the cylinder block  27 ; a positioning pin  51  provided to the pallet  31  so as to position a hole  48  of the cylinder block  27 ; a cover member  32  mounted on the gasket surface  42  so as to cover a top opening  52  of the cylinder barrel  43 , the cover member  32  having a concave portion  53  leading to the top opening  52  of the cylinder barrel  43 ; a gasket surface seal member  54  provided to a bottom end of the cover member  32  so as to seal the gasket surface  42 ; a nozzle  57  for feeding treatment solution to the inside surface of the cylinder barrel  43  along a wall  55  of the concave portion  53 , the nozzle  57  being inserted downward from the top of the cover member  32  and attached to the cover member  32 , and having treatment solution spray holes  56  for spraying the treatment solution toward the wall  55  of the concave portion  53 ; a treatment solution feed channel  58  for feeding the treatment solution to the nozzle  57 ; and the second drainage passage  33  provided to the cover member  32  so as to discharge the remaining treatment solution accumulated in the cylinder barrel  43 . 
         [0045]    The treatment solution spray holes  56  formed in the nozzle  57  are positioned higher than the top opening  52  of the cylinder block  27 . The treatment solution therefore flows uniformly from the top end of the inside surface of the cylinder barrel  43  to the bottom end thereof. The treatment solution spray holes  56  are composed of a plurality of holes, and are preferably in a radial arrangement in the radial direction of the nozzle  57  from the treatment solution feed channel  58 , but may also be in a cross arrangement. 
         [0046]    An operation of the surface treatment apparatus  10  described above will next be described based on  FIGS. 3A through 4C . 
         [0047]      FIGS. 3A and 3B  show the process of positioning the cylinder block  27  in the surface treatment apparatus  10 . 
         [0048]      FIG. 3A  shows the process of mounting the cylinder block  27  on the pallet  31 . The cylinder block  27  is mounted on the pallet  31  as indicated by the arrow ( 7 ) so that the gasket surface  42  of the cylinder block  27  faces upward, the pallet  31  closing off the bottom opening  44  of the cylinder barrel  43 . The positioning pin  51  is inserted in the hole  48 , and the cylinder block  27  is thereby properly positioned on the pallet  31  at all times. 
         [0049]      FIG. 3B  shows the process of covering the top opening  52  of the cylinder block  27 . The cover member  32  is moved as indicated by the arrow ( 8 ), and covers the top opening  52  of the cylinder barrel  43  while the nozzle  57  is inserted in the top opening  52  of the cylinder barrel  43 . 
         [0050]      FIG. 4A  shows the process of feeding treatment solution to the nozzle  57 . The treatment solution is fed to the nozzle  57  via the treatment solution feed channel  58 , as indicated by the arrow ( 9 ). The treatment solution fed to the nozzle  57  sprays toward the wall  55  of the concave portion  53  from the treatment solution spray holes  56 . The treatment solution is fed to the inside surface of the cylinder barrel  43  along the wall  55  of the concave portion  53 , as indicated by the arrows ( 10 ). 
         [0051]      FIG. 4B  shows the process whereby the treatment solution is discharged from the first drainage passage  45 . A portion of the treatment solution accumulated in the cylinder barrel  43  is discharged from the first drainage passage  45 , as indicated by the arrow ( 11 ). The amount of treatment solution fed is greater than the amount discharged from the first drainage passage  45 . The treatment solution therefore accumulates in the cylinder barrel  43 , as indicated by the arrows ( 12 ). The nozzle  57  extends downward past the cylinder barrel  43 , and the volume of the space formed by the inside surface of the cylinder barrel  43  and the outside surface of the nozzle  57  is thereby reduced. The ascent of the treatment solution is therefore accelerated, and the number of steps involved in the treatment can be reduced. 
         [0052]      FIG. 4C  shows the process whereby the treatment solution is discharged from the second drainage passage  33 . The remainder of the treatment solution accumulated in the cylinder barrel  43  is discharged from the second drainage passage  33 , as indicated by the arrow ( 13 ). Monitoring the drainage through the use of the treatment solution detector  22  ( FIG. 1 ) enables the surface treatment to be reliably performed. 
         [0053]    The inventors investigated the change in temperature at points A, B, and C shown in  FIG. 2 , and the obtained results will be described using  FIG. 5 . 
         [0054]    As shown in  FIG. 5 , the temperature immediately increased when the high-temperature treatment solution was fed at points B and C in the middle and lower portions of the cylinder barrel  43 . The results also showed that the temperature increase was also rapid at the upper point A as compared with the prior art example shown in  FIG. 12 . This is because the retained heat of the treatment solution is transferred first to point A by the high-temperature treatment solution being fed from above the inside surface of the cylinder barrel  43 , and the first temperature increase thus occurs at point A. The reference symbol T 2  refers to the maximum temperature difference. 
         [0055]    The temperature difference in the present embodiment shown in  FIG. 2  and the temperature difference in the prior art example shown in  FIG. 10  were then compared. The results of this comparison are described using  FIG. 6 . 
         [0056]    As shown in  FIG. 6 , the maximum temperature difference T 1  in the prior art example was 25° C., whereas the maximum temperature difference T 2  in the present embodiment was 12° C. At the time immediately after the feeding of the treatment solution started, the temperature difference between different positions on the inside surface of the cylinder barrel in the present embodiment was 15° C. or less; i.e., small. It is apparent that the temperature of the inside surface of the cylinder barrel is more uniform in the present embodiment than in the prior art example. 
         [0057]    Reducing the temperature difference to 15° C. or less is also expected to minimize any effect on the etching treatment. The amount of etching at each of the points A, B, and C was therefore examined. The results are described using  FIG. 7 . 
         [0058]    As shown in  FIG. 7 , the etching amount x 2  was 2.5 μm or more at all of points A, B, and C; and was adequate. The plating adhesion was expected to improve when the etching amount was adequate. The plating adhesion at each of the points A, B, and C was therefore examined. The results are described using  FIG. 8 . 
         [0059]    As shown in  FIG. 8 , when the pre-treated cylinder barrel was plated, the peel width y 2  of the plating was small at all of the points A, B, and C. This indicates that the absence of large temperature differences on the inside surface of the cylinder barrel allows the treatment to be evenly performed. 
         [0060]    An example was described in the embodiment in which the technique for treating a cylinder barrel surface according to the present invention was applied to pre-treatment for plating, but a pre-treatment for plating is not given by way of limitation; the invention may be applied to another surface treatment process provided that the surface treatment is performed on an inside surface of a cylinder barrel. 
         [0061]    The technique for treating an inside surface of a cylinder barrel according to the present invention can be used in a plating pre-treating of an inside surface of a cylinder barrel. 
         [0062]    Obviously, various minor changes and modifications of the present invention are possible in light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.