JPH06101567A - Jig for electroplating piston and electroplating method using it - Google Patents

Abstract

PURPOSE:To provide a jig for electroplating only the top land and the skirt portion of an aluminum piston for use in an internal combustion engine and a low-cost electroplating method which uses the jig. CONSTITUTION:A piston is inserted from a piston crown into a jig 11 comprising a head cap 12 to which the crown surface of the piston abuts, a masking ring 12 covering ring grooves and a land portion located between the grooves, and a joint 14 for holding the cap and the ring 13 at an interval equal to the width of a top land, and then the piston crown is made to abut to the head cap and a vinyl chloride band or a round wire 16 is wound to the outer peripheral surface of the masking ring 13 for insulation and electroplating is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jig for electroplating an aluminum piston for an internal combustion engine and a plating method using the jig.

[0002]

2. Description of the Related Art A piston made of an aluminum material for an internal combustion engine is electroplated only on a skirt portion and a top land portion of the piston for the purpose of preventing seizure, and a piston ring groove and a second land or a third land portion between them. The condition is that no coating is attached to the.

FIG. 2 shows the general structure of the internal combustion engine piston 1 and the names of the parts. Reference numeral 2 is a piston crown, 3 is a top ring groove, 4 is a second ring groove, 5 is an oil ring groove, 6 is a top land, 7 is a second land, 8 is a third land, and 9 is a skirt portion.
A piston pin hole 10 is formed in the skirt portion 9.

Conventionally, a method of electroplating only the top land 6 and the skirt portion 9 to prevent the coating film from adhering to the piston ring grooves 3, 4, 5 and the second land 7 and the third land 8 between them is conventionally known. The pistons are connected and held for electroplating, the metal coating is attached to the entire surface, then the piston is removed from the holder, and the piston ring groove, second land part, and third land part that do not require electroplating are unnecessary by polishing. There has been adopted a method of removing the unnecessary plating or a method of preventing the electroplating adhesion by masking the piston ring groove with a filler.

However, in the former method of removing unnecessary plating by polishing, the number of man-hours increases due to duplication of machining, and it is difficult to pursue the accuracy of centering of the work in re-machining.

Further, in the latter method, the masking work relies on human tactics by hand, and not only the work efficiency is extremely poor, but also the masking in the groove is due to poor drainage of the pretreatment liquid and residual. It causes uneven plating and poor adhesion during electroplating, which causes yield deterioration. As the masking material, there are those such as Flon mask or Frontex under the trade name as vinyl chloride paint, and Mask Ace under the trade name as rubber-based paint, which have the advantage of being quick-drying, good peelability and easy to remove. However, there are drawbacks in that repainting is required for each electroplating process, the number of coating steps is increased, and the material cost is increased.

[0007]

SUMMARY OF THE INVENTION The present invention has been conceived in view of the above-mentioned actual situation of a method for electroplating only a necessary portion of a piston, which has been conventionally adopted, and has a high working efficiency and a low cost and piston groove. An object of the present invention is to provide an electroplating jig capable of completely preventing the electroplating from adhering to the land portion between the two and an electroplating method using the same.

[0008]

In order to solve the above-mentioned problems, an electroplating jig according to the present invention comprises a head cap for contacting a piston crown, ring grooves of the piston, and a land portion between them. It is characterized in that it has a plating adhesion preventing ring for covering, and a joint for connecting and holding the above head cap and the above plating adhesion preventing ring with a gap corresponding to the width of the top land.

In the plating method according to the present invention using the jig having the above-mentioned structure, the piston to be plated is inserted into the head cap by inserting the piston crown first, from the ring side of the jig for preventing adhesion of plating. It is characterized in that the dielectric strip-shaped or round wire-shaped member is wound around the outer peripheral surface of the plating adhesion preventing ring to perform plating.

[0010]

The piston for electroplating is inserted into the jig having the above construction from the plating adhesion preventing ring side with the piston crown first, and the piston crown is brought into contact with the head cap. All are exposed from the gap between the cap and the plating adhesion prevention ring, and each ring groove and the second land, third land, etc. between them are covered with the plating adhesion prevention ring. If the outer surface of the plating adhesion prevention ring is wrapped with a dielectric strip-shaped or round wire-shaped member and is electroplated, the plating adhesion prevention ring of the jig will have an insulating effect and will be covered by this on the piston. The plating does not adhere to the ring groove and the land portion between them. Further, since the piston crown is covered with the head cap, plating does not adhere. As a result, the plating adheres only to the top land and the skirt portion of the piston, and it is not necessary to remove the plating adhered to the unnecessary plating portion. Since the dielectric strip-shaped or round wire member wound around the outer peripheral surface of the plating adhesion preventing ring is easy to attach and detach and can be repeatedly used, the processing man-hours and material cost are reduced as compared with the conventional case.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a diagram showing the configuration of an electroplating jig according to the present invention. The jig 11 includes a head cap 12 having a surface for contacting a piston crown of a piston to be electroplated, a masking ring (plating) for masking each ring groove of the piston to be electroplated and a land portion therebetween. Adhesion prevention ring) 13
And connecting the head cap 12 and the masking ring 13 so that a space corresponding to the width of the top land of the piston is formed between the piston crown contact surface of the head cap 12 and the upper end surface of the masking ring 13. It is composed of a plurality of joints 14 to be held.

When electroplating the piston 1, the piston 1 is inserted from the masking ring 13 side of the jig 11 with the piston crown 2 first, and the piston crown 2 is inserted into the piston of the head cap 12 of the jig 11. The piston 1 is attached to the jig 11 by bringing it into contact with the crown contact surface (the lower surface in FIG. 1). In this case, the pin hole 10 of the piston 1 is mounted so as to come to an intermediate position between the adjacent joints 14.

In this state, the entire area of the top land 6 of the piston 1 is exposed between the lower end of the head cap 12 and the upper end of the masking ring 13. Each piston ring groove 3, 4, 5 and the second land portion 7 and the third land portion 8 between the piston ring grooves 3, 4, 5 which do not require the deposition of the coating by electroplating.
Is covered and masked by the masking ring 13. In order to prevent the electroplating from adhering to the piston pin hole 10, it is possible to easily perform masking by inserting a silicon rubber round bar 15 having the same diameter as the pin hole 10.

As shown in FIG. 1, a band-shaped or round wire-shaped member 16 made of a dielectric material such as vinyl chloride is wound around the outer peripheral surface of the masking ring 13 of the jig 11 to produce an insulating effect. A vinyl chloride string is also wound around the joint 14, and further, the masking ring 13 and the head cap 12 are attached at a considerable distance, preferably at a distance of 10 mm or more, and the insulation effect and the thickness of the electroplated film are averaged. To ensure the circularity of the piston outer diameter after electroplating.

In the electroplating method of the present invention, the round wire or strip 16 made of a dielectric material such as vinyl chloride is wound around the masking ring 13 of the jig 11 to mask an unnecessary portion of plating. , Jigs as well as dielectric round wires or strips can be easily attached and detached and can be used semi-permanently, and the above-mentioned vinyl chloride-based or rubber-based insulating paint can be used for each electroplating process. Compared with the method of applying and peeling, the cost can be significantly reduced in terms of the number of working steps and the material cost.

Referring to FIG. 3, the piston 1 is attached to the jig 11 as described above.
The state where is attached is shown. A plurality of sets of a combination of the jig 11 and the piston 1 in this state, an upper part provided with a lower fixing plate 19 provided with a base ring 18 as shown in FIGS. 4 and 5, a piston push screw 20 and a conducting hook 21. As shown in FIG. 6, an electroplating rack 17 in which a fixed plate 22 and a support plate 23 are connected to each other at variable intervals is stacked on a base ring 18 by using a base collar 24, a cap 25, etc. Fix with 20 and insert into electroplating bath. The reference numeral 26 in FIGS. 4 and 6 is an electric line.

When the piston 1 is inserted in the electroplating jig 11 and a plurality of sets are stacked on the rack 17, the gap between the end of the piston skirt and the head cap 12 of the jig 11 should be 0.5 mm or less. Is desirable. The reason for this is to prevent locally excessive adhesion of the skirt end.

Further, since the piston has a vertical direction and the piston crown is on the combustion chamber side of the engine, the piston crown side is generally on the upper side. However, when the piston is mounted on the rack for electroplating, The direction of should be such that the piston crown side is on the lower side. The reason is that, when gas is generated during the electroplating process and the piston crown side is the upper side, the gas is stored above the inside of the piston, and adversely affecting the quality such as discoloration and corrosion of the piston. In order to prevent this, the piston crown side is set to the lower side.

[0019]

As described above, according to the present invention, during the electroplating of the piston, the portions where plating is not required are masked by a jig for electroplating, and a dielectric strip-shaped or round wire-shaped member is used as an insulating material. Since the jig and the above-mentioned members can be semi-permanently used because they are wound around and used, and the attaching / detaching operation is extremely easy, a remarkable effect can be obtained in cost reduction and productivity improvement.

[Brief description of drawings]

FIG. 1 is a front view showing a configuration of an electroplating jig of the present invention.

FIG. 2 is a front view of an example of a piston of an internal combustion engine.

FIG. 3 is a front view showing a state in which the piston is mounted on an electroplating jig.

FIG. 4 is a front view showing an example of an electroplating rack.

FIG. 5 is a side view thereof.

FIG. 6 is a front view showing a state in which a plurality of pistons mounted on the jig are mounted on the electroplating rack.

[Explanation of symbols]

 1 Piston 2 Piston Crown 3, 4, 5 Ring Groove 6 Top Land 7 Second Land 8 Third Land 10 Piston Pin Hole 11 Electroplating Jig 12 Head Cap 13 Masking Ring (Plating Attachment Prevention Ring) 14 Joint 16 Dielectric Band-shaped or round wire-shaped member 17 Rack

Claims (4)

[Claims] 1. An electroplating jig for electroplating only a top land portion and a skirt portion of a piston for an internal combustion engine, in which a head cap is in contact with a piston crown, each ring groove of the piston, and between them. A ring for preventing adhesion of plating for covering the land portion of the above, and a joint for holding the head cap and the ring for preventing adhesion of plating at an interval corresponding to the width of the top land. jig. 2. A method for plating a piston for an internal combustion engine using the jig according to claim 1, wherein the piston to be plated is inserted from the plating adhesion preventing ring side of the jig with the piston crown first. A plating method, wherein a piston crown is brought into contact with a head cap, and a strip-shaped or round wire member made of a dielectric material is wound around an outer peripheral surface of a plating adhesion preventing ring to perform plating. 3. The plating method according to claim 2, wherein a plurality of pistons mounted on the jig are stacked with the crown side down and held in an electroplating rack to perform plating. 4. The plating method according to claim 3, wherein the piston mounted on the jig is plated with the piston crown side down.