JPH07157896A - Composite plating method of inside surface of hollow member - Google Patents

Abstract

PURPOSE:To apply uniform composite plating on the inner peripheral surface of a hollow member and to regulate an optimum air inclusion quantity as a composite plating liquid is stirred by air bubbles. CONSTITUTION:An 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 composite plating liquid supply path 11. At this time, the quantities of the air bubbles 14 are detected by an air bubble sensor 41 and the opening degree of an electromagnetic valve 51 is so adjusted as to attain the quantities set by a setter 4Z, by which the air inclusion quantity is subjected to feedback control. The air inclusion quantity is adjusted to 12 to 95% of the volume of the composite plating liquid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of applying a composite plating, for example, Nikasil plating, to an inner peripheral surface of a hollow portion 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. In such a case where composite plating is applied to the inner peripheral surface of the cylinder, an electrode is inserted with a gap between the inner peripheral surface of the cylinder, and fine particles of silicon carbide are mixed in nickel sulfate into the clearance. It is known to apply so-called NiCadil plating in which fine particles of silicon carbide are included in nickel by pouring the mixed plating solution.

However, the flow rate of the composite plating solution cannot be increased so much that the fine particles are included 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 is reduced, and thus the composite plating solution is reduced. There is a problem that the amount of fine particles contained in the layer is reduced and the composite plating layer becomes non-uniform on the upstream side and the downstream side.

As a solution to 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.

[0005]

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 method capable of uniformly performing composite plating on the inner peripheral surface of a hollow member.

[0007]

In order to achieve the above object, the present invention inserts an electrode so that there is a gap between the hollow member and the inner peripheral surface, and pours a composite plating solution into the gap. In the method of performing the composite plating on the inner peripheral surface, a gas of 12% to 95% with respect to the volume of the composite plating solution is mixed into the composite plating solution in the form of bubbles and is supplied to the gap. Characterize.

[0008]

When air is mixed in the composite plating solution, air bubbles adhere to the inner peripheral surface of the hollow member and the electrodes, and these air bubbles obstruct the flow of the composite plating solution, forming vortices behind the bubbles, or As the bubbles are pushed by the liquid flow and move, the composite plating liquid containing a lot of fine particles is pushed to the inner peripheral surface side and the composite plating liquid is stirred. Then, due to the stirring action of the composite plating solution due to such gas mixture, fresh composite plating solution is constantly supplied to the entire inner peripheral surface of the hollow member, whereby uniform composite plating is performed on the entire inner peripheral surface of the hollow member. Can be applied. However, if the gas mixture amount is less than 12%, it is not possible to exert a sufficient stirring action, and if the gas mixture amount exceeds 95%, the entire gap is filled with gas and the inner peripheral surface and the electrode are not filled. The space between them is insulated by the gas, making composite plating impossible.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENT An apparatus for carrying out the present invention will be described with reference to FIG. W is a cylinder block of a two-stroke engine made of an aluminum alloy, has a cylinder Wc penetrating in the up-down direction, and a space S for supply and scavenging is provided in the cylinder Wc by opening the space. S is closed to the outside by a cap C. The cylinder block W is placed on the holding table 1, and the composite plating liquid passage 11 provided on the holding table 1 and the cylinder Wc are set to coincide with each other. Further, the electrode 2 is inserted into the cylinder Wc from above, a gap G is formed between the electrode 2 and the inner peripheral surface Wf of the cylinder Wc, and the composite plating liquid channel 11 supplies the composite plating. The liquid is set to flow in the gap G. By the way, the composite plating solution passage 11 is connected to a pump 6 for supplying the composite plating solution via a conduit 12, and an air mixing passage 13 is connected in the middle of the conduit 12. The aeration passage 1
3, a compressor 5 is connected to the solenoid proportional valve 51.
A predetermined amount of air is mixed into the composite plating liquid in the conduit 12 via the. The air thus mixed becomes bubbles 14 together with the composite plating solution and the throttle unit 1
The gas is discharged from 1a, 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 and is discharged. After that, it is sent out to the conduit 12 by the pump 6 again.

A bubble sensor 41 is attached to the narrowed portion 11a to detect the amount B of air mixed in the composite plating solution from the number and size of the bubbles 14 passing through the narrowed portion 11a. The bubble sensor 41 is of a type used for ultrasonic flaw detectors or the like to capture the echo of the transmitted ultrasonic waves, but it may be an optical passage sensor or the like. The detection signal from the bubble sensor 41 is input to the controller 4. A setting device 42 is connected to the controller 4, and the opening D of the solenoid proportional valve 51 corresponding to the air mixing amount Bo set by the setting device 42.
And the feedback control of the opening degree D of the solenoid proportional valve 51 based on the detection signal of the bubble sensor 41.

The operation of the above configuration will be described with reference to FIG. First, the pump 6 and the compressor 5 are operated (S1, S2), and the set value Bo of the air mixing amount is input to the controller 4 by the setting device 42 (S3). Then, the controller 4 calculates the valve opening degree D corresponding to Bo and outputs a signal corresponding to the opening degree D to the solenoid proportional valve 51 (S4). Since the electromagnetic proportional valve 51 becomes the opening D, air is actually mixed, and the actually mixed air amount B is detected by the bubble sensor 41 and input to the controller 4 (S
5). The controller 4 determines whether the detected B matches the set value Bo (S6), and B = Bo
If so, the opening degree D at that time is maintained. Also, B> Bo
If so, the opening degree D is decreased by a predetermined amount α (S7 / S8), and B
If it is <Bo, on the contrary, the opening degree D is increased by a predetermined amount α (S7.
In step S9, the opening degree D of the solenoid proportional valve 51 is feedback-controlled so that the actually mixed air amount B matches the set value Bo.

The state of composite plating when the amount of air mixed is changed in this way will be described with reference to FIGS. 3 to 5. It should be noted that the inclusion amount of silicon carbide in the composite plating layer at each portion of the inner peripheral surface Wf of the cylinder Wc was measured, and the results shown in FIGS.
The vertical axis indicates the content of silicon carbide in% by weight.

FIG. 3 is a development view of the inner peripheral surface Wf of the cylinder Wc. FIG. 4 shows the result of the composite plating process at each point a to p shown in this figure, and FIG. Shown in. Further, a fixed amount of the composite plating liquid is discharged from the pump 6, and the amount of air mixed is shown as a volume% with respect to the discharge amount of the composite plating.

FIGS. 4A to 4C show some examples of the results when the amount of air mixed is increased or decreased.
The amount of mixed air is 0% ・ 12% ・ 27% ・ 61%
And the case of increasing.

In FIG. 5, the maximum value among the measured values of the content of silicon carbide is indicated by x, and the minimum value is indicated by y.

In FIG. 4, in the case of I, the inclusion amount of silicon carbide is lower on the downstream side than on the upstream side (a.b.
・ C ・ d → e ・ f ・ g ・ h and i ・ j ・ k → l ・ m ・
n), after passing through the opening Wo, the inclusion amount of silicon carbide increases again (e · f · g · h → i · j · k). This is the opening Wo
It is considered that the flow of the composite plating solution becomes turbulent once and is agitated, and when the amount of air mixed into II to IV is increased, the composite plating solution is agitated by the air bubbles and the cylinder Wc
It is possible to apply a uniform composite plating over the entire area.

Further, as is apparent from FIG. 5, when air is not mixed in at all, the variation in the contained amount of silicon carbide is large and the minimum value is extremely low as compared with the other conditions. However, when 12% of air is mixed, the minimum value of the inclusion amount of silicon carbide rapidly approaches the maximum value, and the width of variation becomes small. And the amount of air mixed is 20% ・ 2
Even if it is increased to 7%, 61%, and 95%, the width of the variation is small, that is, the circumferential surface Wf can be uniformly subjected to composite plating. If the amount of air mixed in is increased to 99%, the composite plating itself will suddenly become impossible. It is considered that this is because the air fills the gap G too much and the current stops flowing.

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, and a pH value of 4 was used. The composite plating conditions are as follows: the flow speed 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.,
The cathode current density was 28 A / dm ² . The flow rate of the composite plating solution is 264 cm ³ / s.

By the way, although air is mixed in the composite plating solution in the above embodiment, helium gas / argon gas / nitrogen gas or other inert gas may be mixed therein.

[0020]

As is apparent from the above description, according to the present invention, a gas is mixed in the composite plating solution, and the composite plating solution is stirred by the bubbles of the mixed gas, and the inner peripheral surface of the hollow member is It is possible to specify the amount of gas mixed in which the uniform composite plating can be performed.

[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 flow chart showing the operation of the device.

FIG. 3 is a development view of a cylinder Wc

FIG. 4 is a diagram showing the inclusion amount of silicon carbide in the composite plating layer at points a to p.

FIG. 5 is a diagram showing variations in the inclusion amount of silicon carbide in the composite plating layer.

[Explanation of symbols]

 1 Holding Base 2 Electrode 3 Holding Member 13 Air Mixing Channel 14 Bubble G Gap Wc Cylinder WF Inner Surface

Claims (1)

[Claims] 1. A method in which an electrode is inserted so as to leave a gap between the hollow member and the inner peripheral surface, and a composite plating solution is caused to flow into the gap to perform composite plating on the inner peripheral surface. A composite plating method for an inner peripheral surface of a hollow member, characterized in that 12% to 95% of gas relative to the volume is mixed into the composite plating solution in the form of bubbles and supplied into the gap.