JPH07157895A - Composite plating device - Google Patents

Abstract

PURPOSE:To apply uniform composite plating on an inner peripheral surface by constituting the composite plating device in such a manner that the composite plating liquid existing in the upper part of the air bubbles sticking to an electrode is moved to the inner peripheral surface side by rising of the air bubbles and the always fresh composite plating liquid is supplied over the entire area of the inner peripheral surface. CONSTITUTION:The electrode 2 is inserted into a cylinder Wc of a cylinder block W from above and the composite plating liquid contg. the air bubbles 14 is passed into the gap G between the electrode 2 and the inner peripheral surface Wf of the cylinder Wc from a discharge port 11a of a composite plating liquid supply pipe 11 so that the air bubbles 14 are made to ascend in the state of sticking to the surface of the electrode 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for applying a composite plating, such as Nikasil plating, to the inner peripheral surface of a hollow member such as an engine cylinder.

[0002]

2. Description of the Related Art For example, since a piston slides inside a cylinder of an engine, it is necessary to improve the wear resistance of the inner peripheral surface of the cylinder especially when the cylinder block is made of aluminum alloy. By the way, it is difficult to fit the sleeve into the cylinder when an opening is required to be provided on the inner peripheral surface of the cylinder as in a crank scavenging two-cycle engine. The peripheral surface may be subjected to composite plating. As a method of performing composite plating on the inner peripheral surface of such a cylinder, an electrode is inserted with a gap between the inner peripheral surface of the cylinder and the fine particles of silicon carbide mixed into nickel sulfate. It is known to perform so-called Nikasil plating in which nickel is mixed with fine particles of silicon carbide by flowing a composite plating solution. However, the flow rate of the composite plating solution cannot be increased so much in order to include the fine particles in the composite plating layer, so that the flow of the composite plating solution in the gap becomes a laminar flow state. Then, on the upstream side of the composite plating solution, fine particles such as silicon carbide are often included in the composite plating layer, but on the downstream side, the content of the fine particles of the composite plating solution near the inner peripheral surface decreases, so that The amount of fine particles contained in
There is a problem that the composite plating layer becomes non-uniform on the upstream side and the downstream side.

To solve such a problem,
For example, Japanese Patent Laid-Open No. 52-93636 discloses a device in which the flow direction of the composite plating solution is reversed at regular intervals.

[0004]

In the above-mentioned conventional one in which the flow direction of the composite plating solution is reversed at regular intervals, the state of composite plating at both end portions of the cylinder can be made the same, but the central portion is at both ends. There is a problem that composite plating is less likely to occur than the cylindrical portion, and this tendency increases as the length of the cylindrical portion increases.

In view of the above problems, it is an object of the present invention to provide a composite plating apparatus capable of uniformly performing composite plating on the inner peripheral surface of a hollow member.

[0006]

In order to achieve the above object, the invention of claim 1 is an apparatus for performing a composite plating on the inner peripheral surface of a hollow member, wherein the generatrix of the inner peripheral surface of the hollow member is vertical. The electrode is inserted so as to have a predetermined gap between it and the inner peripheral surface in a state of being held so as to face, and the discharge port facing below the electrode in the inserted state has an inner diameter of the discharge port. Is provided with a composite plating solution supply pipe having a diameter equal to or smaller than the outer diameter of the electrode, and the composite plating solution containing bubbles is supplied from the discharge port to the gap. .

The invention of claim 2 is characterized in that, in the invention of claim 1, the tip portion of the electrode is formed to have a gradually smaller diameter toward the tip.

[0008]

When bubbles are mixed in the composite plating solution, the rise of the bubbles causes the composite plating solution to be agitated, the flow of the composite plating solution in the gap becomes a turbulent flow, and the downstream portion of the inner peripheral surface is also affected. A composite plating solution containing fine particles is supplied to make the composite plating layer uniform. Further, when the inner diameter of the ejection port is equal to or smaller than the outer diameter of the electrode, all the bubbles contained in the composite plating ejected from the ejection port to the hollow portion once collide with the tip of the electrode. Then, the bubbles adhere to the surface of the electrode and rise in the gap while being adhered to the surface of the electrode. Since the bubbles rise while pushing away the composite plating solution located above the bubbles, the rise of the bubbles displaces the composite plating solution containing many fine particles near the electrode surface toward the inner peripheral surface of the hollow member, thereby The composite plating solution containing a large amount of fine particles is supplied over the entire area of the surface, so that the inclusion amount of the fine particles in the composite plating layer becomes more uniform.

When bubbles adhering to the tip of the electrode rise along the surface of the electrode and the direction of movement of the bubble changes abruptly, the bubble may be separated from the surface of the electrode. Therefore, as described above, the tip portion of the electrode is gradually reduced in diameter toward the tip so that the moving direction of the bubble does not suddenly change and the peeling of the bubble is prevented.

[0010]

EXAMPLES Referring to FIG. 1, W is made of an aluminum alloy 2
It is a cylinder block of a stroke engine, has a cylinder Wc penetrating up and down, and a space S for supply and scavenging is provided in the cylinder Wc so that the space S is opened to the outside by a cap C. Are sealed. The cylinder block W is placed on the holding table 1, and the composite plating solution supply pipe 11 provided on the holding table 1 and the cylinder Wc are set to coincide with each other. Further, an electrode 2 having a substantially hemispherical tip is inserted into the cylinder Wc from above, and a gap G is formed between the electrode 2 and the inner peripheral surface Wf of the cylinder Wc to perform composite plating. The composite plating solution supplied from the solution supply pipe 11 is set to flow in the gap G. Here, if the diameter of the electrode 2 is D and the inner diameter of the discharge port 11a of the composite plating solution supply pipe 11 facing the tip of the electrode 2 is d, then in the case of this embodiment D
> D.

By the way, the composite plating solution supply pipe 11 is connected to a pump (not shown) for supplying the composite plating solution through a pipe line 12, and an air mixing passage 1 is provided in the middle of the pipe line 12.
3 is connected. A compressor (not shown) is connected to the air mixing path 13 so that a predetermined amount of air is mixed into the composite plating solution in the conduit 12. The air thus mixed becomes bubbles 14 and rises in the composite plating solution supply pipe 11 together with the composite plating solution, and the discharge port 11
It is discharged from a into the cylinder Wc. Then, it flows through the gap G, flows out into the space 31 of the holding member 3 holding the upper surface of the cylinder block W, and is returned to the tank (not shown) via the pipe 32. Then, after being degassed in the tank, it is sent again to the conduit 12 by the pump.

According to the above configuration, as shown in FIG.
Since> d is set, all the bubbles 14 in the composite plating solution ejected from the ejection port 11a collide with the tip of the electrode 2 and adhere to the surface of the electrode 2. Since the tip of the electrode 2 is formed in a substantially hemispherical shape, the bubbles 14 adhering to the surface of the electrode 2 do not separate but rise while adhering to the surface. This time,
The composite plating liquid, which is located on the upper portion P of the bubble 14 adhering to the surface of the electrode 2 and contains sufficient fine particles, is pushed away toward the inner peripheral surface Wf as the bubble rises. Since the bubbles 14 rise along the surface of the electrode 2 to a portion corresponding to the upper end of the cylinder Wc, the composite plating solution containing a large amount of fine particles from the electrode 2 side toward the inner peripheral surface Wf over the entire inner peripheral surface Wf. Is supplied to obtain a uniform composite plating layer.

In this embodiment, 400 g of nickel sulfate, 35 g of boric acid, and 60 g of fine powder of silicon carbide were added to 1 liter of water as a composite plating solution.
Further, 2.5 g of saccharin sodium was added to adjust the hardness to pH = 4, and composite plating called nickel plating containing nickel particles containing silicon carbide was performed. The composite plating conditions are that the flow rate of the composite plating solution in the gap G when air is not mixed is 15 cm / s, the temperature of the composite plating solution is 60 ° C., and the cathode current density is 28 A / dm ² . Although the inner diameter d of the discharge port 11a is smaller than the diameter D of the electrode 2, both may be set to have the same size, and even in that case, all the bubbles 14 can be attached to the surface of the electrode 2. it can.

By the way, although air is simply mixed in the above-mentioned embodiment, when the size of bubbles is reduced, air is mixed through a porous material or a composite plating solution is provided upstream of the discharge port. It suffices to stir to break up the bubbles. Further, in the above-mentioned embodiment, the tip of the electrode 2 is formed in a substantially hemispherical shape, but it may have a tapered shape or any other shape as long as the shape gradually becomes smaller toward the tip. Further, although air is mixed in the composite plating solution, helium gas, argon gas, nitrogen gas, or other inert gas may be mixed.

[0015]

As is apparent from the above description, according to the present invention, the composite plating solution containing a large amount of fine particles in the vicinity of the electrode surface is generated by raising the bubbles mixed in the composite plating solution along the electrode. Since it is supplied to the entire peripheral surface, uniform composite plating can be applied to the inner peripheral surface.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an apparatus for carrying out the present invention.

FIG. 2 is a partially enlarged view showing details of bubbles attached to the electrode surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Holding table 2 Electrode 3 Holding member 11a Discharge port 13 Air mixing path 14 Bubble D Electrode diameter d Discharge port inner diameter G Gap Wc Cylinder Wf Inner peripheral surface

Claims (2)

[Claims] 1. An apparatus for performing composite plating on an inner peripheral surface of a hollow member, wherein the hollow member is held with the generatrix of the inner peripheral surface facing in the vertical direction, and a predetermined interval is provided between the hollow member and the inner peripheral surface. Supplying a composite plating solution having an electrode inserted with a gap and an ejection port facing below the electrode in the inserted state, the inner diameter of the ejection port being the same as or smaller than the outer diameter of the electrode A composite plating apparatus comprising a pipe and supplying a composite plating liquid containing bubbles from the discharge port to the gap. 2. The composite plating apparatus according to claim 1, wherein the tip portion of the electrode is formed to have a gradually smaller diameter toward the tip.