Plating Apparatus

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a plating apparatus according to a first embodiment of the present invention;

FIG. 2 is a partial sectional perspective view showing the electrode unit shown in FIG. 1;

FIG. 3 is an exploded perspective view of the electrode unit shown in FIG. 2;

FIG. 4 is an enlarged view of region 4 of FIG. 1;

FIG. 5 is a sectional view showing an example in which the plating apparatus of the first embodiment is placed on a cylinder block;

FIGS. 6A and 6B are schematic views showing an example in which a plating liquid is supplied by the plating liquid supply means according to the first embodiment;

FIGS. 7
a and 7B are schematic views showing the flow of the plating liquid;

FIGS. 8A and 8B are schematic views showing a relationship between the plating liquid and bubbles;

FIG. 9 is a schematic view showing a relationship between the plated coating and the shielding plate according to the first embodiment;

FIG. 10 is a graph showing a relationship between the shielding plate and the plated coating;

FIG. 11 is a sectional view showing the plating apparatus according to a second embodiment of the present invention;

FIG. 12 is a sectional view showing a conventional plating apparatus; and

FIGS. 13A and 13B are schematic views showing a state in which the plated coating is formed by the conventional high-speed plating apparatus of FIG. 12.

BEST MODE FOR CARRYING OUT THE INVENTION

The plating apparatus 10 of the first embodiment shown in FIG. 1 has an electrode unit 15 in which a cylindrical electrode 16 is disposed in a hollow region 12 (refer also to FIG. 5) of a cylinder block (workpiece) 11; plating liquid supply means 18 for supplying a plating liquid 17 to the electrode unit 15; air supply means 21 for supplying air to the plating liquid 17; and electric current supply means 22 for causing an electric current to flow between a cylinder 13 and the cylindrical electrode 16.

The cylinder block 11 has a cylindrical cylinder 13. The hollow region 12 is formed by the inner circumferential wall 14 of the cylinder 13. This cylinder block 11 is a workpiece in which the cylinder 13 and cylinder head part 1 la are formed as an integrated body, and the upper end 12a of the hollow region 12 is substantially sealed off by a cylinder head 11a.

The cylindrical electrode 16 is attached above the inner member 27 disposed in a depression 26 of a support block 25. A ring-shaped introduction channel 28 is formed by the inner member 27 and the depression 26. The introduction channel 28 connects with a pair of vortex-creating channels 29, 29 (refer to FIG. 3). These vortex-creating channels 29, 29 connect with connection channels 30, 30. An outflow channel 31 is formed by a though-hole 27a in the inner member 27 and a through-hole 25a in the support block 25. An upper end 28a of the introduction channel 28 is covered with a porous member 33. A through-hole 16a formed in the cylindrical electrode 16 connects with the outflow channel 31. The shielding plate (shielding member) 35 is attached above an upper end 16b of the cylindrical electrode 16 via attachment means 36.

The cylinder block 11 is mounted on the support block 25. The cylindrical electrode 16 is disposed so that a gap (cylindrical gap) S1 with respect to the hollow region 12 is formed inside the hollow region 12 of the cylinder block 11. The gap S1 forms a cylindrical plating channel 38. The plating channel 38 connects with the introduction channel 28 via the porous member 33. The through-hole 16a of the cylindrical electrode 16 is disposed on the same axis as the outflow channel 31.

The plating liquid supply means 18 supplies the plating liquid 17 in a tank 42 to the connection channels 30, 30 formed in the support block 25 via a supply channel 41 (refer to FIG. 3). Air supply means 21 and a supply pump 46 are provided along the supply channel 41. The outflow channel 31 connects with the tank 42 via a return channel 47. A control valve 48 is provided along the return channel 47.

The air supply means 21 drives an air supply source 51 and supplies air to the supply channel 41 via an air supply channel 52.

In the electric current supply means 22, the positive electrode of a current supply source 23 is connected to the cylindrical electrode 16, and the negative electrode is connected to the cylinder 13 to supply electric current.

The control valve 48 is a valve for adjusting the liquid surface height of the plating liquid 17. The plating liquid 17 is described herein using an example of a composite plating liquid produced by admixing ceramic particles into a plating liquid. A plating liquid used for nickel plating is another example of a plating liquid.

FIG. 2 shows the electrode unit 15 shown in FIG. 1.

The ring-shaped introduction channel 28 is formed from an inner member 27 and a depression 26. The open upper end 28a of the introduction channel 28 is covered with the ring-shaped porous member 33. The cylindrical electrode 16 is attached with a plurality of bolts 54 to the support block 25 via the inner member 27. In this condition, the through-hole 16a formed on the cylindrical electrode 16 is disposed on the same axis as the outflow channel 31.

The cylindrical electrode 16 has a horizontal flat step 56a on the upper end 16b of the inner circumferential region 56 thereof, and also has an inclined surface 56c that gradually increases in diameter from the outer circumferential end 56b of the step 56a toward the upper edge 16c. A shielding plate 35 is affixed to the step 56a via the attachment means 36.

FIG. 3 shows the electrode unit 15 in an exploded perspective view.

The support block 25 has a depression 26 in the center region. The circumferential wall 26a in which the depression 26 is formed is circular. The pair of vortex-producing channels 29, 29 is formed at a spacing of 180° parallel to a tangent to this circumferential wall 26a. Supply openings 29a, 29a of these vortex-producing channels 29, 29 each open onto the circumferential wall 26a.

Thus, the plating liquid 17 is supplied along the circumferential wall 26a of the depression 26 from the supply openings 29a, 29a of the vortex-producing channels 29, 29 (refer to FIG. 1), whereby the plating liquid 17 is caused to flow as a vortex along the circumferential wall 26a.

The support block 25 has attachment holes for accommodating four bolts 54 provided at regular intervals on the bottom part 26b of the depression 26, and also has a through-hole 25a that is formed in the center of the bottom part 26b.

The outside diameter of the inner member 27 is formed so as to be smaller than the inside diameter of the depression 26, and a depression 27b is formed in the center region. A bottom end protrusion 16d on the cylindrical electrode 16 inserts into the depression 27b, and a bottom end 16e of the cylindrical electrode 16 abuts a top surface 27c of the inner member 27.

The inner member 27 has through-holes for accommodating four bolts 54 provided at regular intervals. The through-hole 27a of the inner member 27 is formed on the inside of the depression 27b.

In the condition in which the inner member 27 is attached inside the depression 26 of the support block 25, a top surface 27c of the inner member 27 and a top surface 25c of the support block 25 lie in the same plane (refer to FIGS. 1 and 2).

The porous member 33, for example, is a ring-shaped plate composed of a plurality of mesh members formed from cotton in a network form. In other words, the porous member 33 is a member having a large number of holes (micropores) of a determinate size. The outer circumferential part 33a is disposed in a fitting groove 25d of the support block 25. The inner circumferential part 33b is disposed in a fitting groove 27d of the inner member 27. The porous member 33 covers the upper end 28a of the ring-shaped introduction channel 28 (refer to FIGS. 1 and 2).

A top surface 33c of the porous member 33, the top surface 27c of the inner member 27, and the top surface 25c of the support block 25 lie in the same plane in a state in which the outer circumferential part 33a of the porous member 33 is disposed in the fitting groove 25d of the support block 25, and the inner circumferential part 33b is disposed in the fitting groove 27d of the inner member 27 in this manner (refer to FIGS. 1 and 2).

The cylindrical electrode 16 has the through-hole 16a in the longitudinal direction, and has a bottom protrusion 16d on the bottom end 16e. The cylindrical electrode 16 has a step 56a and an inclined surface 56b on the inner circumferential part 56 of the upper end 16b.

Because the bottom end protrusion 16d inserts into the depression 27b of the inner member 27, the bottom end part 16e of the cylindrical electrode 16 abuts the top surface 27c of the inner member 27.

In this condition, the four bolts 54 insert into the attachment holes of the support block 25 and the attachment holes of the inner member 27. The support block 25, inner member 27, and cylindrical electrode 16 are joined together by causing the threaded parts 54a of the bolts 54 that protrude from the attachment holes of the inner member 27 to threadably engage the screw holes 16f of the cylindrical electrode 16 (refer to FIG. 2).

The shielding plate 35 is formed in the shape of a disk from an insulating material. As shown in FIG. 1, the outside diameter D1 of the shielding plate 35 is formed so as to be smaller than the inside diameter D2 of the inner circumferential wall 14 that forms the hollow region 12 of the cylinder 13. The shielding plate 35 has four attachment holes 61 formed in roughly the center region thereof.

The shielding plate 35 is attached to the upper end part 16b of the cylindrical electrode 16 via a plurality of stud bolds 58 that constitute the attachment means 36. The respective stud bolts 58 have shoulders 58a of height H1. The shoulders 58a have a thread 58b at the bottom ends thereof, and have screw holes 58d in the upper ends 58c.

As shown in FIG. 4, the upper end 16b of the cylindrical electrode 16 is provided with a flat step 56a that is formed on the inner circumferential region 56 of the cylindrical electrode 16, and with an inclined surface 56c formed so that the surface gradually increases in diameter from the outer circumferential end 56b of the step region 56a toward the upper edge 16c. The height from the step 56a to the upper edge 16c is H2.

The shielding plate 35 is attached to the step region 56a via the attachment means 36. Specifically, the attachment means 36 is formed from four bolts 62 and four stud bolts 58 (only the two front bolts are shown in FIGS. 1 to 3).

Four screw holes 57 (only one is shown in the figures) are formed at regular intervals in the step region 56a, and the thread 58b of the stud bolts 58 is threadably engaged with the respective screw holes 57.

The shoulder regions 58a of the stud bolts 58 are at height H1. The height H1 is larger than the height H2 from the step region 56a to the upper end 16c. Specifically, the relationship H1>H2 is satisfied.

The shielding plate 35 is placed on the upper ends 58c of the stud bolts 58, and the bolts 62 are inserted into the attachment holes 61 of the shielding plate 35. The bolts 62 that protrude from the attachment holes 61 of the shielding plate 35 are threadably engaged with the screw holes 58d formed in the upper ends 58c of the stud bolts 58. By this means, the shielding plate 35 is attached to the upper ends 58c of the stud bolts 58.

The height H1 of the shoulder regions 58a of the stud bolts 58 is larger than the height H2 from the step regions 56a to the upper edge 16c. Therefore, the shielding plate 35 is attached above the upper edge 16b of the cylindrical electrode 16 (refer to FIG. 1 as well). A gap H3 is thereby formed between the upper edge 16c of the cylindrical electrode 16 and the shielding plate 35.

In this condition, a lower part 35a of the external circumferential end of the shielding plate 35 is disposed so that this part aligns with the plating boundary position (boundary position) P2 between the surface to be plated 14a and the plating boundary surface 14b (surface above the surface to be plated), or is disposed above the plating boundary position P2.

The term “surface to be plated 14a” refers to the surface of the inner circumferential wall 14 on which the plated coating 66 is to be formed (refer to FIG. 9).

The term “plating boundary surface 14b” refers to the surface above the surface to be plated 14a.

The lower part 35a of the external circumferential end of the shielding plate 35 is disposed so that this part aligns with the plating boundary position P2, or is disposed above the plating boundary position P2. The gap H4 between the lower part 35a of the external circumferential end of the shielding plate 35 and the plating boundary position P2 is set to 0 to 10 mm.

The reason that the gap H4 is set at 0 to 10 mm is discussed below.

Specifically, when the lower part 35a of the external circumferential end of the shielding plate 35 is disposed below the plating boundary position P2, forming the plated coating 66 up to the plating boundary position P2 is difficult to accomplish. Thus, H4 is set to 0 mm or greater so that the plated coating 66 can be formed up to the plating boundary position P2.

If the gap H4 exceeds 10 mm, on the other hand, then the lower part 35a of the external circumferential end of the shielding plate 35 will be too far above the plating boundary position P2, and there is the danger that the plated coating 66 will be formed outside the plating boundary position P2. Thus, the gap H4 is set to 10 mm or less in order to restrict formation of the plated coating 66 to the plating boundary position P2.

The shielding plate 35 is formed in the shape of a disk from an insulating material, and is a member that has an outside diameter D1 that is smaller than the inside diameter D2 of the inner circumferential wall 14 of the cylinder 13, as shown in FIG. 1. By this means, a gap S2 for introducing a plating liquid is formed between the inner circumferential wall 14 and the outer circumference 35b of the shielding plate 35. Specifically, the gap S2 for introducing a plating liquid is set at 0.25 to 5 mm.

The reason that the gap S2 for introducing a plating liquid is set at 0.25 to 5 mm is discussed below.

When the gap S2 for introducing a plating liquid is less than 0.25 mm, the gap S2 is too small, making it difficult for the plating liquid 17 to be conducted into the gap S2. If the plating liquid 17 is not conducted into the gap S2 for this reason, the result is equivalent to a condition whereby the external circumference 35a of the shielding plate 35 is in contact with the inner circumferential wall 14, and there is the danger that flash will be generated at the boundary region of the plated coating as described in the prior art. Consequently, the gap S2 for introducing a plating liquid is set to 0.25 mm or greater, thereby preventing generation of flash at the boundary region 66a of the plated coating 66.

If the gap S2 for introducing a plating liquid exceeds 5 mm, on the other hand, then the gap S2 will be too large, and there is the danger that plating liquid 17 will flow out from the gap S2. If the plating liquid 17 flows out from the gap S2, the plating liquid 17 frequently adheres to regions that are not to be plated. Moreover, the electric current density above the regions to be plated decreases, and the plating thickness in these regions decreases as well. As a result, the gap S2 for introducing a plating liquid is restricted to 5 mm or less, thereby preventing an outflow of the plating liquid 17 from the gap S2.

Because the shielding plate 35 is affixed to the cylindrical electrode 16, the shielding plate 35 can be affixed to the cylindrical electrode 16 by merely using a plurality of stud bolts 58 or bolts 62. Consequently, the members for attaching the shielding plate 35, i.e., the stud bolts 58 or bolts 62, allow the apparatus to be made simpler and smaller, and equipment costs to be reduced.

The method for forming the plated coating on the inner circumferential surface of the cylinder 13 using the plating apparatus 10 of the first embodiment is discussed below in reference to FIGS. 5 to 10.

FIG. 5 shows an example in which the cylinder block 11 is placed on the plating apparatus 10 of the first embodiment.

The cylinder block 11 is placed on the support block 25 of the electrode unit 15 as indicated by the arrow a. At this time, the cylindrical electrode 16 is disposed inside the hollow region 12 (refer to FIG. 1) so that the cylindrical electrode 16 is covered from the side of the bottom end (one end) 12b of the hollow region 12 in the cylinder 13.

The cylinder block 11 is formed with the cylinder head 11a integrated with the cylinder 13, and the upper end 12a of the hollow region 12 is closed off by the cylinder head 11a. For this reason, after placing the cylinder block 11 on the support block 25, the shielding plate 35 cannot be disposed at the prescribed location from the side of the upper end 12a of the hollow region 12.

As a result, the shielding plate 35 is affixed in advance to the upper end 16b of the cylindrical electrode 16. When the cylinder block 11 has been placed on the support block 25, it is possible to dispose the shielding plate 35 in the prescribed position from the side of the lower end 12b of the hollow region 12. Thus, it is possible to use the plating apparatus 10 for cylinder blocks 11 in which only the bottom end 12b of the hollow region 12 is open. Consequently, the range of application of the plating apparatus 10 is not restricted by the shape of the workpiece, allowing the apparatus to be used in a wider range of applications.

FIGS. 6A and 6B are examples wherein the plating liquid 17 is supplied by the plating liquid supply means 18 in the direction of the vortex-producing channel 29.

In FIG. 6A, the supply pump 46 is driven, whereby the plating liquid 17 in the tank 42 is conducted towards the vortex-producing channels 29, 29 (refer to FIG. 6B), as indicated by the arrow b, along the interior of the supply channel 41. Simultaneously, the air supply source 51 is driven to supply air to the supply channel 41 via the air supply channel 52, as indicated by the arrow c. Bubbles 65 (refer to FIG. 7A) are thereby produced by the air in the plating liquid 17 in the supply channel 41.

The plating liquid 17 having the bubbles 65 is conducted to the vortex-producing channels 29, 29 as indicated by the arrow d.

As shown in FIG. 6B, a pair of vortex-producing channels 29, 29 is formed parallel to a tangent to the circumferential wall 26a of the depression 26 formed in the support block 25. Consequently, the plating liquid 17 is supplied along the circumferential wall 26a of the depression 26 from the supply openings 29a, 29a of the vortex-producing channels 29, 29, and the plating liquid 17 flows in an arc along the circumferential wall 26a as indicated by the arrow e.

FIGS. 7A and 7B show the condition in which the plating liquid 17 flows inside the plating apparatus.

In FIG. 7A, the inner member 27 is disposed in the groove 26, whereby a ring-shaped introduction channel 28 is formed by the depression 26 and the inner member 27.

The plating liquid 17 having the bubbles 65 flows in an arc along the ring-shaped introduction channel 28. The plating liquid 17 that flows in an arc along the introduction channel 28 flows into the plating channel 38 via the porous member 33 provided at the upper end 28a of the introduction channel 28.

Thus, the plating liquid 17 in the introduction channel 28 tends to be focused as indicated by the arrow f. Because the plating liquid 17 is conducted into the plating channel 38 via the porous member 33, the flow of the plating liquid 17 is diffused as indicated by the arrows g, and the flow of the plating liquid 17 is adjusted to be uniform.

In addition, in the condition in which the air is supplied to the supply channel 41 from the air supply channel 52 (refer to FIG. 6A), the bubbles 65 in the plating liquid 17 are comparatively large, and the likelihood is high that the size thereof will not be uniform.

The plating liquid 17 having the bubbles 65 is conducted into the plating channel 38 via the porous member 33, whereby the bubbles 65 in the plating liquid 17 are made comparatively small, the size of the bubbles 65 is adjusted to be uniform, and the bubbles 65 are uniformly dispersed.

The uniformly dispersed plating liquid 17 flows upwards helically along the plating channel 38, as indicated by the arrows g in FIG. 7B. The plating liquid 17 includes the bubbles 65 that have been adjusted to be comparatively small and of uniform size.

The mixing of the plating liquid 17 is enhanced because the plating liquid 17 flows helically in the direction of the upper end 38b (upper end of the cylindrical gap) from the lower end 38a (lower end of the cylindrical gap) of the plating channel 38. Consequently, the plating liquid 17 flows uniformly through the plating channel 38. Thus, the plated coating 66 (refer to FIG. 9) is adequately formed at a uniform thickness over the entire inner circumferential wall 14 of the cylinder 13.

FIGS. 8A and 8B show the relationship between the plating liquid and bubbles.

In FIG. 8A, the bubbles 65 in the plating liquid 17 are comparatively small and the size of the bubbles 65 is made uniform, so that the bubbles 65 move smoothly inside the plating liquid 17. Consequently, the plating liquid 17 (i.e., the ceramic particles in the plating liquid 17) are mixed by the bubbles 65 as indicated by the arrows h.

The cylinder 13 and the cylindrical electrode 16 are energized by the electric current supply means 22 (refer to FIG. 6A). Thus, the plating components in the plating liquid 17, as indicated by the arrow i, are uniformly conducted over the entire inner circumferential wall 14 of the cylinder 13, allowing more favorable formation of plated coating 66 at a uniform thickness over the entire inner circumferential wall 14.

Moreover, the plating liquid 17 is dispersed by the porous member 33 (refer to FIG. 7A), and the flow of the plating liquid 17 is adjusted to be uniform by the porous member 33, so that the plating components in the plating liquid 17 are conducted uniformly over the entire inner circumferential wall 14 of the cylinder 13, allowing more favorable formation of the plated coating 66 at a uniform thickness over the entire inner circumferential wall 14.

In FIG. 8B, most of the plating liquid 17 that reaches the upper end 16b of the cylindrical electrode 16 is guided by the shielding plate 35 and introduced into the cylindrical electrode 16 as indicated by the arrow j. The plating liquid 17 that has flown into the cylindrical electrode 16 is conducted to the through-hole 16a of the cylindrical electrode 16.

Meanwhile, the remainder of the plating liquid 17 that has reached the upper end 16b of the cylindrical electrode 16 enters the gap S2 for introducing the plating liquid between the shielding plate 35 and the inner circumferential wall 14 as indicated by the arrow k.

Because the gap S2 is kept at 5 mm or less, an outflow of the plating liquid 17 from the gap S2 is prevented.

As shown in FIG. 6A, the plating liquid 17 that has entered the through-hole 16a in the cylindrical electrode 16 flows as indicated by the arrow m and enters the return channel 47 via the outflow channel 31. The plating liquid 17 that has reached to the return channel 47 as indicated by the arrow n returns to the tank 42 via the control valve 48.

Thus, if there is an appropriate flow of the plating liquid 17, the condition shown in FIG. 9 is produced even without being controlled by the control valve 48. Specifically, the liquid surface height hi of the plating liquid 17 in the gap S2 for introducing the plating liquid can be made approximately equivalent to the upper surface 35d of the shielding plate 35.

If the liquid surface height h1 of the plating liquid 17 in the gap S2 for introducing the plating liquid should be different from the top surface 35d of the shielding plate 35, the height can be adjusted by the control valve 48, and the liquid surface height h1 can thereby be made to approximately correspond with the upper surface 35d of the shielding plate 35.

FIG. 9 shows the relationship between the shielding plate 35 and the plated coating 66.

In the condition in which the plating liquid 17 has been introduced into the gap S2 for introducing the plating liquid between the inner circumferential wall 14 and the outer circumference 35b of the shielding plate 35, the cylindrical electrode 16 and the cylinder 13 are energized by the electric current supply means 22 (refer to FIG. 6a).

In this condition, a constant value A1 is maintained for the electric current density between the plating boundary position P2 and the lower end position P1 of the cylinder 13, and the electric current density between the plating boundary position P2 and the plating upper limit position P3 is made to decrease gradually from the plating boundary position P2 toward the plating upper limit position P3.

The region between the lower end position P1 and the plating boundary position P2 of the cylinder is designated “the surface to be plated 14a,” and the region between the plating boundary position P2 and the plating upper limit position P3 is designated “the plating boundary surface 14b.”

The surface 16g of the cylindrical electrode 16 is opposite and parallel with respect to the surface to be plated 14a on the inner circumferential wall 14. As a result, the electric current density with respect to the surface to be plated 14a is maintained at a constant value A1, and a constant plating thickness t can be ensured for the plated coating 66 formed on the surface to be plated 14a.

On the other hand, the shielding plate 35 is disposed in alignment with the plating boundary position P2 above the plating boundary position P2. This shielding plate 35 is composed of an insulating material. Thus, at the plating boundary surface 14b, the electric current density decreases gradually from the plating boundary position P2 toward the plating upper limit position P3, and becomes zero at the plating upper limit position P3.

By this means, the plating thickness t of the plated coating 66 decreases gradually from the plating boundary position P2 toward the plating upper limit position P3 at the plating boundary surface 14b, and becomes 0 at the plating upper limit position P3.

A uniform plating thickness t can thereby be ensured for the plated coating 66 on the surface to be plated 14a. In addition, because the plating thickness t of the plated coating 66 decreases gradually at the plating boundary surface 14b, an adequate plated coating 66 can be formed.

It is thus possible to prevent separation of the plated coating 66 from the boundary region 66a during machining of the surface of the plated coating 66.

In addition, by providing the shielding plate 35, rising of the plating liquid 17 above the plating surface 14a is inhibited by the shielding plate 35. The plated coating 66 can thereby be reliably formed only on the surface to be plated 14a where the plated coating 66 is necessary.

FIG. 10 is a graph showing the relationship between the position of the shielding plate and the thickness of the plated coating. The vertical axis represents the position P (mm) on the inner circumferential wall of the cylinder, and the horizontal axis represents the plating thickness t (μm). In regard to the position P on the vertical axis, the region between the plating boundary position P2 and the lower end position P1 on the cylinder is designated “the surface to be plated 14a,” and the region between the plating boundary position P2 and the plating upper limit position P3 is designated “the plating boundary surface 14b.”

The graph g1 shows a condition in which a shielding plate 35 is not provided at the plating boundary position P2 (refer to FIG. 9).

Graph g2 shows an example in which a plated coating is formed in a condition in which the gap H4 shown in FIG. 9 is 1 mm and the gap S2 for introducing a plating liquid is set to 5 mm.

Graph g3 shows an example in which a plated coating is formed in a condition in which the gap H4 is 1 mm and the gap S2 for introducing a plating liquid is set to 3 mm.

Graph g4 shows an example in which a plated coating is formed in a condition in which the gap H4 is 1 mm and the gap S2 for introducing a plating liquid is set to 2 mm.

Graph g5 shows an example in which a plated coating is formed in a condition in which the gap H4 is 1 mm and the gap S2 for introducing a plating liquid is set to 1 mm.

Graph g6 shows an example in which a plated coating is formed in a condition in which the gap H4 is 1 mm and the gap S2 for introducing a plating liquid is set to 0.25 mm.

The gap H4 is a gap between the plating boundary position P2 and the lower part 35a of the external circumferential end of the shielding plate 35. The gap S2 for introducing a plating liquid is a prescribed gap between the external circumference 35b of the shielding plate 35 and the inner circumferential wall 14.

The average plating thickness t after the honing process is preferably maintained, for example, at 100 μm (indicated by the broken line) at the surface to be plated 14a on the inner circumferential wall 14 of the cylinder 13.

Plated coatings 66 were formed under the aforementioned conditions of graphs g1, g2, g3, g4, g5, and g6, and an evaluation was made as to whether 100 μm was maintained for the plating thicknesses t at the surfaces to be plated 14a.

The results of the evaluation were made by assigning a judgment of favorable for coatings that were maintained at 100 μm and a judgment of unfavorable for coatings not so maintained.

In graph g1, the average plating thickness could not be maintained at 100 μm in the region between the plating boundary position P2 and the position P4 under the plating boundary position P2. Specifically, in graph g1, 100 μm could not be ensured over the entire region of the surface to be plated 14a. Graph g1 thus provided an evaluation of unfavorable.

In graph g2, 100 μm was maintained on the surface to be plated 14a. Graph g2 thus provided an evaluation of favorable.

In graph g3, as with graph g2, 100 μm was maintained on the surface to be plated 14a. Graph g3 thus provided an evaluation of favorable.

In graph g4, as with graph g2, 100 μm was maintained on the surface to be plated 14a. Graph g4 thus provided an evaluation of favorable.

In graph g5, as with graph g2, 100 μm was maintained on the surface to be plated 14a. Graph g5 thus provided an evaluation of favorable.

In graph g6, as with graph g2, 100 μm was maintained on the surface to be plated 14a. Graph g6 thus provided an evaluation of favorable.

From graphs g2, g3, g4, g5, and g6, it was concluded that a thick plated coating could be increasingly ensured as the gap S2 for introducing a plating liquid decreased.

It was thus confirmed that an evaluation of favorable was obtained when the aforementioned tests were carried out with the gap H4 in the range of 0 to 100 mm and the gap S2 for introducing a plating liquid in the range of 0.25 to 5 mm.

Next, the plating apparatus according to the second embodiment will be discussed in reference to FIG. 11. In the plating apparatus of the second embodiment, the same designations are assigned to the same members as in the plating device of the first embodiment, and descriptions thereof are omitted. The plating apparatus 70 according to the second embodiment, is different from the plating apparatus 10 of the first embodiment shown in FIG. 4 only in terms of the shielding plate 71, but the rest of the structure is the same as that of the plating apparatus 10 according to the first embodiment.

The plating apparatus 70 of the second embodiment shown in FIG. 11 has an insulating shielding plate (shielding member) 71 that is attached via the attachment means 36 above the upper end 16b (over the upper end) of the cylindrical electrode 16. The lower external circumferential surface 71a of the shielding plate 71 is formed so that there is an inclined surface that slants downwards from a proximal location 71c of the outer circumference 71b towards the region below the outer circumferential end 71d. In other words, the region below the external circumferential end 71d is disposed below the lower surface 71e of the shielding plate 71. Consequently, when the region below the external circumferential end 71d is disposed at a gap H4 (0 to 10 mm) from the plating boundary position P2, a large gap H5 can be ensured between the upper edge 16c of the cylindrical electrode 16 and the lower surface 71e of the shielding plate 71.

Consequently, the plating liquid 17 that has reached the upper end 16b of the cylindrical electrode 16 is guided by the shielding plate 71 and is conducted more smoothly from the gap H5 to the through-hole 16a in the cylindrical electrode 16, as indicated by the arrow p.

In the first and second embodiments, the shielding members were described as shielding plates 35 and 71, but this is not the only possible option. The member may also have other shapes such as a block shape, and a device produced by combining a plurality of members may also be used.

In the first and second embodiments, the workpieces were described as cylinder blocks 11, but this is not the only possible option. Any workpiece can be used as long as the workpiece has a hollow region 12 wherein at least one end of the hollow region 12 is open.

Moreover, in the first and second embodiments, cases were described in which the workpiece was a cylinder block 11 having an integrated cylinder head 11a, but this is not the only possible option. The device may be used with types of workpieces in which the cylinder head 11a is separated from the cylinder block 11, i.e., with workpieces in which both ends of the hollow region 12 are open.

In the first and second embodiments, cases were described in which shielding plates 35, 71 were attached to a cylindrical electrode 16, but this is not the only possible option. The invention may also have a configuration in which, as in the prior art, the shielding plates 35 and 71 are detached from the cylindrical electrode 16.

Moreover, in the first and second embodiments, cases were described in which the plating liquid 17 flowed from the bottom to the top side in the gap S1, and the plating liquid 17 that had reached the upper end 16b of the cylindrical electrode 16 was conducted to the through-hole 16a by the shielding plate 35. However, the flow of the plating liquid is not restricted to this option alone. For example, the plating liquid 17 can also flow from the through-hole 16a to the gap S1, and a plurality of small-diameter through-holes may be formed in the wall surface of the cylindrical electrode 16, allowing the plating liquid in the through-holes 16a to pass through the small-diameter through-holes and to flow into the gap S1. In brief, a configuration may be produced in which the plating liquid 17 flows into the gap S1.

In the first and second embodiments, the plated coating 66 was formed using a plating liquid 17 that was produced by mixing bubbles 65 with the plating liquid 17, but this is not the only possible option. The plated coating 66 may be formed using a plating liquid not having admixed bubbles 65.

INDUSTRIAL APPLICABILITY

The present invention can be used in plating apparatuses for forming plated coatings on the inner circumferential walls of cylinders.

Number	Date	Country	Kind
2004-178837	Jun 2004	JP	national
2004-178927	Jun 2004	JP	national

Plating Apparatus

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