JP2791741B2 - Composite plating method for inner peripheral surface of hollow member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying a composite plating, for example, a nickel 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 an engine cylinder, it is necessary to improve the wear resistance of the inner peripheral surface of the cylinder particularly when the cylinder block is made of an aluminum alloy. By the way, when an opening must be provided on the inner peripheral surface of a cylinder as in a crank scavenging two-stroke engine, it is difficult to fit a sleeve into the cylinder. Composite plating may be applied to the peripheral surface. In order to apply the composite plating 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 mixed in nickel sulfate in the gap. It is known to apply a so-called nicazil plating in which a mixed plating solution is caused to flow and nickel particles are included in nickel.

However, the flow rate of the composite plating solution cannot be made too high 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 laminar. Then, on the upstream side of the composite plating solution, fine particles such as silicon carbide are well contained 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, so that the composite plating layer is reduced. There is a problem that the inclusion amount of the fine particles in the layer decreases, and the composite plating layer becomes non-uniform between the upstream side and the downstream side.

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

[0005]

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

[0006] In view of the above problems, an object of the present invention is to provide a composite plating method capable of uniformly applying a composite plating to the inner peripheral surface of a hollow member.

[0007]

In order to achieve the above-mentioned object, according to the present invention, an electrode is inserted so as to have a gap between itself and the inner peripheral surface of a hollow member, and a composite plating solution is caused to flow through the gap. In the method of performing composite plating on the inner peripheral surface, it is preferable that a gas of 12% to 95% with respect to the volume of the composite plating solution is mixed into the composite plating solution in a bubble state and supplied to the gap. Features.

[0008]

When air is mixed into the composite plating solution, air bubbles adhere to the inner peripheral surface of the hollow member and the electrode, and the air bubbles obstruct the flow of the composite plating solution, forming a vortex behind the bubbles, or When the bubbles are pushed by the liquid flow and move, the composite plating solution containing a large amount of fine particles is pushed to the inner peripheral surface side to stir the composite plating solution. And, due to the stirring action of the composite plating solution due to the mixing of such gas, a fresh composite plating solution is always supplied to the entire inner peripheral surface of the hollow member over the entire inner peripheral surface. Can be applied. However, if the mixing amount of the gas is less than 12%, a sufficient stirring action cannot be exerted. If the mixing amount of the gas exceeds 95%, the entire gap is filled with the gas and the inner peripheral surface and the electrode The gap is insulated by the gas, and no composite plating can be performed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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, which is provided with a cylinder Wc penetrating in a vertical direction, and a space S for air supply and scavenging is provided in the cylinder Wc so as to open. S is sealed from the outside by a cap C. The cylinder block W is mounted on the holding base 1 and is set so that the composite plating solution passage 11 provided in the holding base 1 and the cylinder Wc coincide with each other. An 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. The liquid is set to flow through the gap G. Incidentally, 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 air mixing path 1
A compressor 5 is connected to 3 and an electromagnetic proportional valve 51
A predetermined amount of air is mixed into the composite plating solution in the pipe line 12 through the pipe. The air mixed in this way becomes bubbles 14 together with the composite plating solution.
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 line 32 and is evacuated. Thereafter, the water is sent out to the pipe 12 again by the pump 6.

A bubble sensor 41 is attached to the throttle 11a, and detects the amount B of air mixed in the composite plating solution from the number and size of the bubbles 14 passing through the throttle 11a. The bubble sensor 41 is of a type used for, for example, an ultrasonic flaw detector to capture echoes of transmitted ultrasonic waves, but may be an optical passage sensor or the like. Then, a 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 electromagnetic proportional valve 51 corresponding to the air mixing amount Bo set by the setting device 42.
And the feedback control of the opening D of the electromagnetic 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 and S2), and the set value of the air entrapment amount Bo is input to the controller 4 by the setter 42 (S3). Then, the controller 4 calculates the valve opening D corresponding to Bo, and outputs a signal corresponding to the opening D to the electromagnetic proportional valve 51 (S4). Since the electromagnetic proportional valve 51 reaches the opening degree D, air is actually mixed therein, 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 or not the detected B matches the set value Bo (S6), and B = Bo
Then, the opening degree D at that time is maintained. Also, B> Bo
If so, the opening D is decreased by a predetermined amount α (S7 / S8), and B
If <Bo, the opening D is increased by a predetermined amount α (S7.
S9) The feedback control of the opening D of the electromagnetic proportional valve 51 is performed so that the actually mixed air amount B matches the set value Bo.

The state of composite plating when the amount of mixed air is changed in this way will be described with reference to FIGS. In addition, the inclusion amount of silicon carbide in the composite plating layer at each part of the inner peripheral surface Wf of the cylinder Wc was measured, and FIG. 4 and FIG.
The vertical axis indicates the content of silicon carbide in weight%.

FIG. 3 is a developed view of the inner peripheral surface Wf of the cylinder Wc. FIG. 4 shows the result of the composite plating process at each of the points a to p shown in FIG. 3, and FIG. Shown in Further, a fixed amount of the composite plating solution is discharged from the pump 6, and the amount of air mixed therein is shown by volume% with respect to the discharge amount of the composite plating.

I to IV in FIG. 4 show some examples of the results when the amount of mixed air is increased or decreased.
0%, 12%, 27%, 61%
It shows the case where it is increased.

In FIG. 5, the maximum value among the measured values of the contained amount 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
・ Cd ・ 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 (efggh → ijk). This is the opening Wo
It is presumed that the flow of the composite plating solution becomes turbulent and is agitated once, and when the mixed amount of air is increased from II to IV, the composite plating solution is agitated by bubbles and the cylinder Wc
And a uniform composite plating can be applied over the entire area.

Further, as is apparent from FIG. 5, when no air is mixed, the variation in the inclusion amount of silicon carbide is large, and the minimum value is extremely low as compared with the other conditions. However, when air is mixed in by 12%, the minimum value of the inclusion amount of silicon carbide rapidly approaches the maximum value, and the range of variation becomes small. Then, the amount of air mixed is 20% · 2
Even if it is increased to 7% / 61% / 95%, the range of variation is small, that is, uniform composite plating can be applied to the circumferential surface Wf. When the amount of air mixed is increased to 99%, composite plating itself cannot be performed suddenly. This is considered to be due to the fact that the air is filled in the gap G too much and the current stops flowing.

In this embodiment, 400 g of nickel sulfate / 35 g of boric acid / 60 g of fine powder of silicon carbide are added per liter of water as a composite plating solution.
Further, a saccharin sodium of which pH was adjusted to 4 by adding 2.5 g of saccharin sodium was used. The composite plating conditions were as follows: the flow rate of the composite plating solution in the gap G when air was not mixed was 15 cm / s, the temperature of the composite plating solution was 60 ° C.,
The cathode current density was 28 A / dm ² . The flow rate of the composite plating solution is 264 cm ³ / s.

In the above embodiment, air is mixed into the composite plating solution. However, helium gas, argon gas, nitrogen gas, and other inert gases may be mixed.

[0020]

As is apparent from the above description, according to the present invention, a gas is mixed into the composite plating solution, and the composite plating solution is agitated by bubbles of the mixed gas. The amount of gas that can provide uniform composite plating can be defined.

[Brief description of the drawings]

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

FIG. 2 is a flowchart 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 view showing a variation in the inclusion amount of silicon carbide in the composite plating layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Holder 2 Electrode 3 Holding member 13 Air mixing path 14 Air bubble G Gap Wc Cylinder WF Inner peripheral surface

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-52-39535 (JP, A) JP-A-55-54598 (JP, A) JP-A-52-93636 (JP, A) 118894 (JP, A) Jiro 52-111720 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) C25D 7/00-7/12 C25D 15/02

Claims (1)

(57) [Claims] 1. A method of inserting an electrode so as to leave a gap between itself and an inner peripheral surface of a hollow member, flowing a composite plating solution through the gap, and performing composite plating on the inner peripheral surface, comprising: A composite plating method for the inner peripheral surface of a hollow member, wherein a gas of 12% to 95% of the volume is mixed into the composite plating solution in a bubble state and supplied to the gap.