Patent Publication Number: US-8110077-B2

Title: Sealing jig and plating treatment apparatus

Description:
This United States Non-Provisional Utility patent application claims priority to and relies for priority upon Japanese Patent Application No. 2008-056341, which was filed on Mar. 6, 2008. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sealing jig or fixture for sealing a cylinder inner peripheral surface which is a surface to be processed of a cylinder block of an engine, for example, at a time when treatment liquid is introduced to an inner peripheral surface of a cylinder and also relates to a plating treatment apparatus provided with such sealing jig for performing pre-plating or plating process to the cylinder inner peripheral surface. 
     2. Related Art 
     Conventionally, there is known a method for sealing a cylinder inner peripheral surface of a cylinder block in an apparatus for performing surface treatment such as plating treatment on the cylinder inner peripheral surface by introducing treatment liquid to the cylinder inner peripheral surface. 
     In a surface treatment apparatus described, for example, in Japanese Patent Application Laid-Open Publication No. 8-199390, diameter of a cylinder is completely expanded by repeating an operation of expanding the diameter of a sealing member and an operation of moving the entire sealing jig including the sealing member within the cylinder, and thereafter, the sealing operation is performed to the cylinder inner peripheral surface. 
     Furthermore, Japanese Patent Application Laid-Open Publication No. 8-144082 discloses a surface treatment apparatus in which an air tube is expanded so as to contact the cylinder inner peripheral surface, thereby sealing the cylinder inner peripheral surface. 
     However, the surface treatment apparatus described in Japanese Patent Application Laid-Open Publication No. 8-199390 has the following drawbacks. That is, when some failure occurs in adjustment of an expanding amount of a sealing member or adjustment of a moving amount of a sealing jig, the cylinder inner peripheral surface to be processed may be damaged, or sealing position with respect to the cylinder inner peripheral surface may be deviated, thus lowering sealing position accuracy. 
     In the surface treatment apparatus described in Japanese Application Laid-Open Publication No. 8-144082, it may become impossible to control a shape or sealing position of the air tube during the expansion because of insufficient positioning of the air tube. Accordingly, in this case, the sealing position accuracy of the cylinder inner peripheral surface may be insufficient. 
     SUMMARY OF THE INVENTION 
     In view of the circumstances encountered in the prior art mentioned above, an object of the present invention is to provide a sealing jig capable of improving sealing position accuracy on a surface to be processed and a plating treatment apparatus including such sealing jig. 
     The above and other objects can be achieved according to one aspect of the present invention by providing a sealing jig for sealing an inner peripheral surface of a cylinder in contact with the cylinder inner peripheral surface as a surface to be processed of a cylinder block at a time of introducing treatment liquid to the cylinder inner peripheral surface, the sealing jig including: 
     a sealing member made of an expandable material and having a ring-buoy shape; 
     a seal support member for supporting one side of the sealing member; and 
     a seal base disposed so as to face the seal support member and adapted to support another side of the sealing member, 
     wherein when the treatment liquid is introduced inward, the sealing member is expanded only in a radial direction under regulation of the seal support member and the seal base so as to come into contact with the cylinder inner peripheral surface. 
     In a preferred embodiment of the above aspect, the seal support member or the seal base may be provided with a fluid flow path including a blowing-off hole for blowing off fluid, the blowing-off hole is closed by the sealing member when the sealing member is expanded in a radial direction and is opened when the sealing member is contracted, and a contacting condition of the sealing member with the cylinder inner peripheral surface is confirmed in accordance with a pressure in the fluid flow path. 
     It may be desired that a plurality of fluid flow paths including the blowing-off hole is formed in a circumferential direction of the sealing member. 
     It may be also desired that fluid supplied to an interior of the sealing member and fluid supplied to an interior of the fluid flow path including the blowing-off hole are air. 
     In another aspect of the present invention, there is also provided a plating treatment apparatus performing a plating treatment to an inner surface of a cylinder, the plating treatment apparatus comprising: 
     an apparatus body provided with an electrode support member; 
     an electrode supported by the electrode support member to be movable; 
     a sealing jig mounted to the electrode; 
     a work support jig holding a work such as a cylinder block; and 
     a treatment liquid supply member supported by the electrode support member for supplying a treatment liquid between the electrode and the sealing jig, 
     the sealing jig including: 
     a sealing member made of an expandable material and having a ring-buoy shape; 
     a seal support member for supporting one side of the sealing member; and 
     a seal base disposed so as to face the seal support member and adapted to support another side of the sealing member, 
     wherein when the treatment liquid is introduced inward, the sealing member is expanded only in a radial direction under regulation of the seal support member and the seal base so as to come into contact with the cylinder inner peripheral surface. 
     In a preferred embodiment of this aspect, it may be desired that the seal support member for the sealing jig is installed on the electrode and a communication hole through which the treatment fluid inflows and outflows between the electrode inside and the cylinder inner peripheral surface side is formed in a vicinity of the seal support member. 
     The seal support member may be made of metal and disposed on the electrode through an insulation member, the seal support member has a protrusion having an outer diameter larger than that of the electrode, and an insulating cover is mounted onto the protrusion. 
     The seal support member may include a protrusion having an outer diameter larger than that of an electrode and may be made of an insulation member and installed directly on the electrode or through an insulation member. 
     According to the present invention of the aspects mentioned above, the sealing jig and the plating treatment apparatus including the sealing jig allow a sealing member to be expanded only in a radial direction and come into contact with a cylinder inner peripheral surface during introduction of fluid into the inside, thereby improving sealing position accuracy with respect to the cylinder inner peripheral surface which is a surface to be processed. 
     The nature and further characteristic features of the present invention will be made clearer from the following descriptions made with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is an overall front view illustrating a first embodiment of a plating treatment apparatus according to the present invention; 
         FIG. 2  is a sectional view illustrating a portion around an electrode and an air joint in the plating treatment apparatus in  FIG. 1 ; 
         FIG. 3A  is a sectional view illustrating an expanded state of a sealing member of a sealing jig in  FIG. 2  and  FIG. 3B  is a sectional view illustrating a contracting state of the sealing member; 
         FIG. 4  is a plan view illustrating the sealing member in  FIG. 3 ; 
         FIG. 5  is a sectional view taken along the line V-V in  FIG. 4 ; 
         FIG. 6  is a plan view illustrating a lower plate as the seal support member in  FIG. 3 ; 
         FIG. 7  is a sectional view taken along the line VII-VII in  FIG. 6 ; 
         FIG. 8  is a plan view illustrating a seal base in  FIG. 3 ; 
         FIG. 9  is a sectional view taken along the line IX-IX in  FIG. 8 ; 
         FIG. 10  is a plan view illustrating a sealing jig mounting plate as an insulating member in  FIG. 3 ; 
         FIG. 11  is a sectional view taken along the line XI-XI in  FIG. 10 ; and 
         FIG. 12  is a sectional view illustrating a portion around an electrode and an air joint in a second embodiment of a plating treatment apparatus according to the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will be described hereunder with reference to the accompanying drawings. However, the present invention is not limited to these embodiments. It is further to be noted that terms “upper”, “lower”, “left”, “right” and the like terms are used herein in an illustrated state or in an actually mounted state. 
     First Embodiment 
     FIGS.  1  to  11   
     With reference to  FIGS. 1 and 2 , a cylinder inner peripheral surface  3 , which is a surface to be treated, of a cylinder block  1  of an engine, for example, is pre-plated or plated at high speed by using a plating treatment apparatus  10  illustrated in  FIG. 1  while introducing an treatment liquid (pre-plating liquid or plating liquid) to the cylinder inner peripheral surface  3 . 
     The plating treatment apparatus  10  includes an apparatus body  11 , an electrode  12 , a sealing jig  13 , a work holding jig  14 , an air joint  15 , a clamp cylinder  16 , and an electrode cylinder  17 . In the present embodiment, the cylinder block  1  is a V-type cylinder block for a V-type engine, and the cylinder inner peripheral surface  3  of a plurality of cylinders  2  formed with a predetermined angle in the cylinder block  1  is concurrently pre-plated or plated. 
     The apparatus body  11  is firmly installed on a base  18 . The apparatus body  11  is provided with a work mounting platform  19  for mounting the cylinder block  1 . The cylinder block  1  is mounted on the work mounting platform  19  with a cylinder head surface  4  directed downward. 
     On the apparatus body  11 , the work holding jig  14  is installed above the work mounting platform so as to be vertically movable by the clamp cylinder  16 . The work holding jig  14  is provided with a clamp, not shown. The work holding jig  14  comes into contact with a crankcase surface  5  of the cylinder block  1  mounted on the work mounting platform  19  at a lowered position. At this time, the clamp of the work holding jig  14  clamps the side portion of the crankcase surface  5  of the cylinder block  1  so as to hold the cylinder block  1  between the work mounting platform  19  and the work holding jig  14 . 
     The electrode  12  is supported by an electrode supporting portion  20 , and the electrode supporting portion  20  is mounted on the electrode cylinder  17  installed on the apparatus body  11 . Through reciprocal motion of the electrode cylinder  17 , the electrode  12  is inserted into the cylinder  2  of the cylinder block  1  and is retracted from the cylinder  2  of the cylinder block  1 . 
     In  FIG. 1 , the left side electrode  12  is inserted into the cylinder  2  and in  FIG. 2 , the right side electrode  12  is retracted from the cylinder  2 . When the electrode  12  is inserted into the cylinder  2  of the cylinder block  1 , a seal ring  21  ( FIG. 2 ) made of such as silicon rubber sheet fitted on the electrode supporting portion  20  comes into contact with the cylinder head surface  4  of the cylinder  1  so that the cylinder head surface  4  side of the cylinder inner peripheral surface  3  is sealed. 
     As illustrated in  FIG. 1 , the sealing jig  13  is mounted on an upper end of the electrode  12  and the air joint  15  is installed on the work holding jig  14 . When the electrode  12  is inserted into the cylinder  2  of the cylinder block  1 , the sealing jig  13  comes into contact with the air coupling  15  as illustrated in  FIG. 2 , and air as a fluid is supplied from a main air coupling  22  of the air joint  15  to a sealing member  33  of the sealing jig  13 . Hence, the sealing member  33  is expanded only in a radial direction and comes into contact with the cylinder inner peripheral surface  3  of the cylinder block  1 , and then, the crankcase surface  5  side of the cylinder inner peripheral surface  3  is sealed. 
     To the electrode supporting portion  20  illustrated in  FIG. 1 , a treatment liquid pipe  23  is connected. The treatment liquid pipe  23  is further connected to a liquid supply pump  24  ( FIG. 2 ). In the state of the crankcase surface  5  side in the cylinder inner peripheral surface  3  of the cylinder block  1  sealed by the sealing member  33 , the liquid supply pump  24  introduces a treatment liquid (pre-plating liquid or plating liquid) reserved in a reservoir tank  25  into the electrode  12  through the treatment liquid pipe  23  and the electrode supporting portion  20 . The treatment liquid introduced into the electrode  12 , as illustrated in  FIG. 2 , is introduced into a space  27  partitioned by an outer peripheral surface of the electrode  12  and the cylinder inner peripheral surface  3  of the cylinder block  1  through a slit  26  between a lower plate  34  of the sealing jig  13  and the electrode  12 , and then, the treatment liquid circulates between the space  27  and the reservoir tank  25 . 
     As illustrated in  FIGS. 1 and 2 , the electrode supporting portion  20  is connected to a lead wire  28 , which is connected to a power supply  30 . The power supply device  30  supplies electric power to the electrode  12  through the lead wire  28  and the electrode supporting portion  20  in a state that the treatment liquid fills the space  27 . The power is supplied so that the electrode  12  becomes a negative pole and the cylinder block  1  becomes a positive pole in pre-plating, thereby pre-plating the cylinder inner peripheral surface  3  of the cylinder block  1 . In the plating treatment, the power supply is implemented so that the electrode  12  becomes a positive pole and the cylinder block  1  becomes a negative pole so as to plate the cylinder inner peripheral surface  33  to thereby form a plating film on the cylinder inner peripheral surface  3 . Plating-preprocessing and plating are performed with different treatment liquids and energizing conditions. 
     Although  FIG. 1  illustrates only one air joint  15 , the air joints  15  of the number corresponding to that of the electrodes  12  are provided on the work holding jig  14 . Reference numeral  31  in  FIG. 1  denotes a cleaning shutter which operates when a cleaning liquid is injected into the cylinder  2  of the cylinder block  1  for cleaning after the pre-plating or plating is applied onto the cylinder inner peripheral surface  3  of the cylinder block  1  and the electrode  12  is retracted from the cylinder block  1 . 
     Referring next to  FIGS. 2 to 11 , configurations of the sealing jig  13  and the air joint  15  will be described. 
     The sealing jig  13  includes the sealing member  33 , the lower plate  34  and a seal base  35  and serves to seal the cylinder inner peripheral surface  3  in contact with the cylinder inner peripheral surface  3  at the time when the treatment liquid is introduced to the cylinder inner peripheral surface  3  of the cylinder block  1 . 
     The sealing member  33 , as illustrated in  FIGS. 3 to 5 , is made of an expandable material, such as an elastic member like a rubber and is formed into a ring-buoy shape. An inner peripheral portion of the sealing member  33  is opened and provided with an opening portion  49 , and an engaging protrusion  36  is formed on both sides in the vicinity of the opening portion  49 . An outer peripheral portion  33 A of the sealing member  33  is configured to be contactable with the cylinder inner peripheral surface  3  of the cylinder block  1 . 
     The lower plate  34  is formed, as illustrated in  FIGS. 3 ,  6 , and  7 , so that a swelling portion  37  is integrally formed in the center of a disc portion  32 . A ring member  39  formed with a peripheral groove  38  is disposed on an outer periphery of the swelling portion  37 . The swelling portion  37  is formed with main air flow paths  40 C and  40 D communicating with each other. A plurality of, for example, three, main air flow paths  40 D are formed at uniform intervals in a circumferential direction of the lower plate  34 . The main air flow paths  40 D communicate with the peripheral groove  38  in the ring member  39  and further communicate with main air flow paths  40 E formed so as to communicate with the peripheral groove  38 . A plurality of the main air flow paths  40 E, for example three, is formed in the circumferential direction of the ring member  39 . 
     On the disc portion  32  of the lower plate  34 , an engaging groove  41  is formed into a ring shape at a boundary portion to the swelling portion  37 . The engaging protrusion  36  of the sealing member  33  engages with the engaging groove  41 . In addition, a fastening internal thread portion  42  and a bolt through-hole  44  for inserting a bolt  43  are formed on the disc portion  32  and the swelling portion  37 . 
     As illustrated in  FIG. 3 , the lower plate  34  is structured so that the disc portion  32  supports a side surface (a lower side surface  33 C in  FIG. 3 ) of the sealing member  33  in such a state that the opening portion  49  of the sealing member  33  is fitted to the ring member  39  and the engaging protrusion  36  of the sealing member  33  engages with the engaging groove  41 . 
     In the seal base  35 , as illustrated in  FIGS. 3 ,  8 , and  9 , a swelling portion  46  is integrally formed in the middle of the disc portion  45 , and the swelling portion  46  is formed with a seating portion  47  and a main air flow path  40 B. A seal sheet  48  is fitted to the seating portion  47 , and a main air flow path  40 A communicating with a main air flow path  40 B is bored through the seal sheet  48 . The main air flow path  40 B is formed to communicate with a main air flow path  40 C of the lower plate  34 . 
     Further, the disc portion  45  is formed with a recessed portion  50  into which the swelling portion  37  of the lower plate  34  is fitted at a position opposite to the seating portion  47 , and an engaging groove  51  is formed into a ring shape outside the recessed portion  50 . The swelling portion  37  of the lower plate  34  and the engaging protrusion  36  of the sealing member  33  are engaged respectively with the concentric recessed portions  50  and  51 , each in stepped shape, formed on the opposite side of the seating portion  47  of the disc portion  45 . A threaded bolt hole  52  for screwing a bolt  43  is formed through the disc portion  45  and the swelling portion  46 . 
     As illustrated in  FIG. 3 , in a state that the swelling portion  37  of the lower plate  34  is fitted into the recessed portion  50  in the seal base  35 , the opening portion  49  of the sealing member  33  is fitted to the ring member  39  of the lower plate  34 , and the engaging protrusion  36  of the sealing member  33  is fitted into the engaging groove  41  on the lower plate  34 . The engaging groove  51  of the seal base  35 , the sealing member  33 , the lower plate  34  and the seal base  35  are integrated by screwing the bolt  43  into the bolt threaded hole  44  of the lower plate  34  and the threaded bolt hole  52  of the seal base  35 , thus constituting the sealing jig  13 . 
     Under such a condition, the lower plate  34  and the seal base  35  are disposed so as to face each other, and the disc portion  32  of the lower plate  34  supports a side surface (a lower side surface  33 C in  FIG. 3 ) of one side of the sealing member  33 , while the disc portion  45  of the seal base  35  supports a side surface (an upper side surface  33 B) of the other side of the sealing member  33  in surface-contacting state. 
     In addition, the sealing member  33 , the lower plate  34  and the seal base  35  are integrated, and in such state, the main air flow paths  40 A,  40 B,  40 C,  40 D and  40 E communicating with each other communicate with the interior of the sealing member  33 . 
     As illustrated in  FIG. 2 , the sealing jig  13  is installed on an upper end of the electrode  12  through a sealing jig mounting plate  53  as an insulating member. The sealing jig mounting plate  53 , as illustrated in  FIGS. 2 ,  10 , and  11 , is formed into a substantially cruciform shape and an external thread portion  54  for fastening is formed in the center of the sealing jig mounting plate  53 . A front end portion of the approximately cross-shaped sealing jig mounting plate  53  is fixed on the electrode  12  by bolts  55 . The external thread portion  54  of the sealing jig mounting plate  53  is screwed into an internal thread portion  42  in the lower plate  34  of the sealing jig  13 . The sealing jig  13  constructed by integrating the sealing member  33 , the lower plate  34 , and the seal base  35  is installed on the sealing jig mounting plate  53 . 
     The sealing jig mounting plate  53  is made of non-conductive resin and insulates the lower plate  34  and the seal base  35  made of conductive metal from the electrode  12 . The treatment liquid flows toward the slit  26  as shown by an arrow in  FIG. 2  passing through a cut-out portion of the sealing jig mounting plate  53  having a substantially cruciform shape. 
     The air joint  15  illustrated in  FIGS. 1 and 2  includes a main air supply path  56  in addition to the main air coupling  22  as described hereinbefore. The main air coupling  22  is connected to an air supply valve and a compressor, not shown, through a main air supply pipe  57 . 
     When the electrode  12  is inserted into the cylinder  2  of the cylinder block  1 , the air joint  15  comes into contact with the seal sheet  48  of the sealing jig  13  installed on the electrode  12 , and the main air supply path  56  communicates with the main air flow path  40 A of the seal sheet  48 . Air is supplied from the main air supply path  56  to the main air flow path  40 A, and, at this time, air leakage is prevented by the seal sheet  48 . 
     The air supplied from the main air supply path  56  to the main air supply path  40 A is introduced into the sealing member  33  through the main air flow paths  40 B,  40 C,  40 D and  40 E as illustrated in  FIG. 3 . To the sealing member  33 , the upper side surface  33 B is supported by the seal base  35  and the lower side surface  33 C is supported by the lower plate  34  to regulate the expansion of the sealing member  33 . 
     Accordingly, as illustrated in  FIG. 3A , the sealing member  33  expands only in a radial direction, and the outer peripheral portion  33 A of the sealing member  33  comes into contact with the cylinder inner peripheral surface  3  of the cylinder block  1  to thereby seal the crankcase surface  5  side of the cylinder inner peripheral surface  3 . Hence, the plating-preprocessing liquid or plating liquid can be prevented from leaking from the space  27  ( FIG. 2 ) partitioned by the cylinder inner peripheral surface  3  and the outer peripheral surface of the electrode  12  toward the crankcase surface  5  side. 
     When the air supply from the main air coupling  22  to the sealing member  33  is shut down, the sealing member  33  contracts in a radial direction and the outer peripheral portion  33 A thereof is separated from the cylinder inner peripheral surface  3 , as illustrated in  FIG. 3B . 
     A device for confirming the expansion and contraction of the sealing member  33  is provided for the sealing jig  13  and the air joint  15 . The confirming device is composed of a sub-air coupling  58  and a sub air supply path  59  on the air joint  15  side, a sub-air flow path on the seal jig  13  side, an air pressure sensor  61  and a control circuit  62 . 
     A plurality of sub-air couplings  58 , for example three sub-air couplings  58 , is arranged on the air joint  15 . A plurality of sub-air supply paths  59 , for example three sub-air supply paths  59 , is formed on the air joint  15  correspondingly to the sub air couplings  58 , and each of the sub-air supply paths  95  communicates with the sub air coupling  58 . 
     The sub-air flow path  60  is formed on the seal base  35  of the sealing jig  13 . As illustrated in  FIGS. 8 and 9 , a plurality of concentric ring grooves  63 , for example three concentric ring grooves  63 , are formed on a top surface of the swelling portion  46  of the seal base  35  correspondingly to the number of the sub-air supply paths  59 , and each of the concentric ring grooves  63  communicates with each of the sub-air supply paths  59 . A plurality of the sub-air flow paths  60  (e.g. three) are radially formed at uniform intervals correspondingly to the number of the ring grooves  63 . Each of the sub-air flow paths  60  communicates with each of the ring grooves  63 , and is formed with a blowing-off hole  64  at an outer peripheral end portion of the seal base  35 . 
     The blowing-off hole  64  is positioned so as to be closed by the sealing member  33  at the time of the expansion of the sealing member  33  and to be opened at the time of the contraction of the sealing member  33 , as illustrated in  FIG. 3 . 
     The air as a fluid introduced from the sub-air coupling  58  provided on the air joint  15  illustrated in  FIG. 2  passes through the sub-air supply path  59  and blows off from the blowing-off hole  64  via the ring groove  63  and the sub air-flow path  60  in the sealing jig  13  ( FIG. 3 ). The air from the blowing-off hole  64  is blown off when the blowing-off hole  64  is opened without being closed by the sealing member  33  at the contraction of the sealing member  33 , as illustrated in  FIG. 3B . At this time, air pressure is decreased in the sub-air flow path  60 , the sub-air supply path  59 , and the sub air coupling  58 . On the contrary, at the time of the expansion of the sealing member  33 , as illustrated in  FIG. 3A , air does not blow off from the blowing-off hole  64  as a result of the blowing-off hole  64  being closed by the sealing member  33  and the air pressure is increased in the sub-air flow path  60 , the sub-air supply path  59 , and the sub-air coupling  58 . 
     The air pressure sensors  61  illustrated in  FIG. 2  are arranged on sub-air supply pipes  65 , for example three sub-air supply pipes  65 , for introducing the air to the sub-air couplings  58 . The air pressure sensor  61  detects air pressure in the sub-air flow path  60 . From the detected values of air pressures, the expansion or contraction of the sealing member  33  of the sealing jig  13  can be confirmed. Specifically, it can be confirmed that the sealing member  33  expands and comes into contact with the cylinder inner peripheral surface  3  of the cylinder block  1  to liquid-tightly seal the cylinder inner peripheral surface  3  or that the sealing member  33  contracts and does not come into contact with the cylinder inner peripheral surface  3  of the cylinder block  1  so that the cylinder inner peripheral surface  3  is unsealed. 
     A detailed example of the confirmation of the sealing by the air pressure will be described below. For example, in a case where the air is supplied to the sub-air flow path  60  with air pressure supplied from the sub-air coupling  58  taken as 0.10 MPa, the air pressure in the sub-air flow path  60  is 0.09 to 0.10 MPa in an expanded state of the sealing member  33 . 
     Although the air pressure in the sub-air flow path  60  may lower due to malfunction or deterioration of the sealing member  33 , when the air pressure is within the range of 0.06 to 0.10 MPa, it can be confirmed that the sealing member  33  expands to contact the cylinder inner peripheral surface of the cylinder block  1 , and the cylinder inner peripheral surface  3  is sealed by the sealing member  33 . On the contrary, when the air pressure in the sub-air flow path  60  is 0.05 MPa or less, it can be confirmed that the sealing member  33  contracts and does not come into contact with the cylinder inner peripheral surface  3  of the cylinder block  1  and the cylinder inner peripheral surface is not sealed by the sealing member  33 , thus confirming that the liquid may leak. 
     The sealing on the cylinder inner peripheral surface  3  of the cylinder block  1  by the expansion and contraction of the sealing member  33  is confirmed over all the circumstance of the sealing member  33  because a plurality of sub-air flow paths  60  are formed at uniform intervals in a circumferential direction of the seal base  35  (i.e., sealing member  33 ), for example three sub-air flow paths  60 , are formed at uniform intervals of 120 degrees in a circumferential direction of the sealing member  33 . 
     Hence, the expanded and contracted states of the sealing member  33  can be confirmed, and thus sealing of the cylinder inner peripheral surface  3  can be confirmed even if deterioration, cracking or breakage occurs at a portion of the sealing member  33  in a circumferential direction, and the sealing member  33  expands normally at any portion except the occurrence portion and expands insufficiently at any failed portion such as cracking and does not come into contact with the cylinder inner peripheral surface  3  of the cylinder block  1 . 
     The control circuit  62  illustrated in  FIG. 2  fetches detected values from the air pressure sensor  61  and controls the driving of the liquid supply pump  24  and the power supply  30 . Specifically, the control circuit  62  determines that when a detected value from the air pressure sensor  61  is higher than a predetermined value, the sealing member  33  of the sealing jig  13  expands and contacts the cylinder inner peripheral surface  3  of the cylinder block  1  and the cylinder inner peripheral surface  3  is sufficiently sealed. At this time, the control circuit  62  starts the liquid supply pump  64  to supply treatment liquid to the space  27  partitioned by the cylinder inner peripheral surface  3  and the outer peripheral surface of the electrode  12 , then drives the power supply device  30  to supply the electric power to the electrode  12  and performs pre-plating or plating on the cylinder inner peripheral surface  3 . 
     The control circuit  62  determines that when a detected value from the air pressure sensor  61  is the predetermined value or lower, the sealing member  33  of the sealing jig  13  does not expands properly and otherwise contracts and does not come into contact with the cylinder inner peripheral surface  3 , and the cylinder inner peripheral surface  3  is sealed incompletely. In this case, the control circuit  62  does not drive the liquid supply pump  24  or the power supply device  30 , or stop the driving of the liquid supply pump  24  and the power supply  30 . 
     According to the present embodiment, the following advantages or effects (1) to (5) will be provided. 
     (1) For the sealing member  33  of the sealing jig  13 , since the upper side surface  33 B is supported by the seal base  35  and the lower side surface  33 C is supported by the lower plate  34 , the expansion of the sealing member  33  is regulated by the lower plate  34  and the seal base  35  at the time of the air introduction into the sealing member  33 , whereby the expansion is caused only in a radial direction and bringing the outer peripheral portion  33 A into contact with the cylinder inner peripheral surface  3  of the cylinder block  1 . Hence, the sealing member  33  coming into contact with the cylinder inner peripheral surface  3  can be precisely positioned. 
     When a plating film is applied to the cylinder inner peripheral surface  3  of the cylinder block  1 , a plating area can be highly precisely controlled according to the present embodiment, whereby the cylinder block  1  having a high-quality plating film can be manufactured. 
     (2) The sub-air flow path  60  provided with a blowing-off hole  64  for blowing off air is formed to the seal base  35  of the sealing jig  13 . The blowing-off hole  64  is closed by the sealing member  33  when the sealing member  33  is expanded in a radial direction and is opened when the sealing member  33  is contracted. The fact whether the sealing member  33  is contacted or not to the cylinder inner peripheral surface  3  is confirmed based on air pressure in the sub-air flow path  60 . Accordingly, only when the sealing member  33  comes into contact with the cylinder inner peripheral surface  3  and the inner-periphery surface  3  is sealed by the sealing member  33 , the treatment liquid is introduced into the space  27  including the inner-periphery surface  3 , thus preventing the liquid from leaking in the space  27 . 
     Furthermore, in a case where the contacting condition between the cylinder inner peripheral surface  3  and the sealing member  33  has been interrupted during a time when the treatment liquid is being introduced into the space  27 , the supply of the treatment liquid to the space  27  is stopped, thereby preventing the liquid from leaking in the space  27 . 
     (3) A plurality of sub-air flow paths  60  having the blowing-off hole  64  for confirming the expansion and contraction of the sealing member  33  are provided to the seal base  35  of the sealing jig  13  along a circumferential direction of the sealing member  33 . Accordingly, even if deterioration, cracking or breakage occurs at a portion of the sealing member  33  and the expansion of the sealing member  33  becomes insufficient as a result at this portion, such a partial failure of the sealing member  33  can be surely detected, whereby defective sealing of the cylinder inner peripheral surface  3  can be surely confirmed. 
     (4) In order to expand and contract the sealing member  33 , air is supplied to the sealing member  33  of the sealing jig  13  from the main air coupling  22  of the air joint  15  through the main air flow paths  40 A,  40 B,  40 C,  40 D and  40 E. For confirmation of such expansion and contraction of the sealing member  33 , air is supplied to the sub-air flow path  60  having the blowing-off hole  64  from the sub-air coupling  58  of the air joint  15 . 
     In a case where a motor-driven mechanism having electric switches and electric wires is used for the expansion and contraction of the sealing member  33  and for the confirmation thereof, electrical malfunction may occur due to the influence of the electrode  12 , and the electric wires may be damaged by highly corrosive treatment liquid such as phosphoric acid or sulfuric acid, and as a result, the durability may be degraded. 
     The expansion and contraction of the sealing member  33  and confirmation thereof are pneumatically performed as described above, thereby preventing the failures such as electrical malfunction and degradation of durability mentioned above from causing. 
     (5) Since the sealing jig  13  is installed on an upper end of the electrode  12  through a sealing jig mounting plate  53  as an insulating member, failures such as electrolytic corrosion and adhesion of electrodeposits on the metallic lower plate  34  and seal base  35  of the sealing jig  13  can be prevented from causing. 
     Further, it is to be noted that the present embodiment describes an example of three sub-air flow paths  60  formed on the seal base  35  of the sealing jig  13  in a circumferential direction, but the number of the sub-air flow paths  60  may be increased or decreased as needed. The sub-air flow path  60  may be formed on the lower plate  34  of the sealing jig  13 . 
     Second Embodiment 
     FIG.  12   
       FIG. 12  is a sectional view illustrating a portion around an electrode and an air joint in a second embodiment of a plating treatment apparatus according to the present invention. In the second embodiment, the like reference numerals are added to members or portions corresponding to those in the first embodiment, and duplicated descriptions will be simplified or will not be repeated. 
     Differences of a plating treatment apparatus  70  according to the second embodiment from the plating treatment apparatus  10  reside in that the second embodiment is not provided with a slit  26  (refer to  FIG. 2 ) between the electrode  12  and the lower plate  34  of a sealing jig  74 , that the electrode  12  and the lower plate  34  are proximate each other, that an insulation cover  71  is installed on the lower plate  34 , and that a communication hole  72  is formed on the electrode  12 . 
     Specifically, the lower plate  34  of the sealing jig  74  is made of metal like the seal base  35  and mounted on the electrode  12  through the sealing jig mounting plate  53  made of an insulation material. The lower plate  34  is formed with a protrusion  73  having a diameter larger than the outer diameter of the electrode  12  and the insulation cover  71  is attached to the lower surface of the protrusion  73  and an outer peripheral portion of the disc portion  32 . 
     The insulation cover  71  is made of an insulation material such as non-conductive resin. The electrode  12  is structured so that the upper end thereof comes into contact with the insulation cover  71  attached to the lower plate  34 , and the communication hole  72  is formed in the vicinity of the lower plate  34 . The treatment liquid supplied to the electrode  12  flows into the space  27  including the cylinder inner peripheral surface  3  of the cylinder block  1  through the communication hole  72  as illustrated in  FIG. 12  and is introduced to the inner peripheral surface  3  of a cylinder. The treatment liquid flows into the electrode  12  from the space  27  including the cylinder inner peripheral surface  3  through the communication hole  72 . 
     Accordingly, the present embodiment provides the following advantages or effects (6) and (7) in addition to the advantages (1) to (5) mentioned in connection with the first embodiment. 
     (6) The electrode  12  comes into contact with the insulation cover  71  attached to the lower plate  34  of the sealing jig  74 , and specifically, the electrode  12  is disposed near the sealing member  33  of the sealing jig  74 . Accordingly, a plating film having a uniform thickness is formed up to the end of the crankcase surface  5  side of a plating area in the cylinder inner peripheral surface  3 . 
     (7) In a case where the insulation cover  71  is not attached on the lower plate  34  of the sealing jig  74 , the protrusion portion  73  having a diameter larger than the outside of the electrode  12  is formed, and a distance between the protrusion portion  73  and the cylinder inner peripheral surface  3  of the cylinder block  1  becomes short. Therefore, charges tend to concentrate on the protrusion  73  of the lower plate  34 , which causes abnormal growth of plating such as a flower shaped portion and excessive etching amount in electrically etching the cylinder inner peripheral surface  3 . 
     On the other hand, according to the present embodiment, the insulation cover  71  is attached onto the protrusion  73  of the lower plate  34 , and accordingly, no charges concentrate on the protrusion  73 , thus preventing generation of the above flower shaped portion and excessive etching. 
     Further, in place of attaching the insulation cover  71  onto the lower plate  34  of the sealing jig  74 , the lower plate  34  may be made of an insulation material such as non-conductive resin and may be attached to the electrode  12  through the sealing jig mounting plate  53  or directly onto the electrode  12 . In such case, substantially the same advantages as those attained in a case where the insulation cover  71  is attached to the lower plate  34  will be attained. 
     It is further to be noted that the present invention is not limited to the described embodiments and many other changes and modifications may be made without departing from the scopes of the appended claims.