JP2791742B2 - 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 of applying a composite plating, for example, a nickel silyl plating, to an 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 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 such a case, in order to solve such a problem, the present applicant disclosed in Japanese Patent Application No. 5-265082, air was mixed in the composite plating solution in the form of air bubbles, and air was mixed in the gaps with air bubbles. A method was proposed in which the plating solution was agitated, and the composite plating solution containing a large amount of fine particles was pushed to the inner peripheral surface side so that uniform composite plating could be applied to the entire inner peripheral surface. It is also conceivable to mix helium gas, argon gas, nitrogen gas and other inert gases in addition to air, but the cost is higher than when air is mixed.

[0005]

By the way, when air is mixed into the composite plating solution, if air bubbles come into contact with the inner peripheral surface before the composite plating layer is applied to the inner peripheral surface, the air is contained in the bubbles. Oxide film may be formed on a part of the inner peripheral surface due to oxygen present. The composite plating layer is finally applied to the portion where the oxide film is formed, but the adhesion between the oxide film and the composite plating layer is lower than the adhesion in the portion where the oxide film is not formed. Therefore, there is a problem that the composite plating layer is peeled off from the portion where the oxide film is formed.

In view of the above problems, the present invention does not form an oxide film on the inner peripheral surface even when air is mixed into the composite plating solution, and improves the adhesion between the inner peripheral surface and the composite plating layer. To provide a composite plating method in which the composite plating layer does not peel off.

[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 applying the composite plating to the inner peripheral surface, only the composite plating solution is allowed to flow for a predetermined time to deposit a thin composite plating layer on the surface of the inner peripheral surface, and then air bubbles are mixed into the composite plating solution. And growing the composite plating layer to a predetermined thickness.

[0008]

In many cases, hollow members such as cylinders are formed of relatively easily oxidizable materials such as aluminum and iron.
On the other hand, nickel or the like which is a base material of the composite plating is relatively hard to be oxidized. Therefore, the composite plating is performed without mixing air for a predetermined time after the start of the composite plating, and the inner peripheral surface is coated with the composite plating layer so that an oxide film is not formed even when bubbles come in contact with the composite plating layer. Mixing to form a uniform composite plating layer. Although the composite plating layer formed without mixing air is not uniform, there is no problem since the composite plating layer formed thereafter becomes uniform by mixing air.

[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, 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. The space S is sealed off 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. When the liquid is in the gap G
It is set to flow inside. 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 13
Is connected to a compressor 5 and is configured to mix a predetermined amount of air into the composite plating solution in the conduit 12 via the electromagnetic proportional valve 51. The air mixed in this way becomes bubbles 14 together with the composite plating solution.
a, flows through the gap G, flows out into the space 31 of the pressing member 3 pressing the upper surface of the cylinder block W, and is returned to the tank (not shown) through the pipe line 32 and is evacuated. Thereafter, the water is sent out to the pipe 12 again by the pump 6.

A power supply 41 is connected between the work W and the electrode 2. A current control circuit 42 for variably controlling the current value is provided between the power supply 41 and the electrode 2, and the current control circuit 42 is controlled by the controller 4. The controller 4 is configured to control the opening and closing of the electromagnetic proportional valve 51 and the operation of the pump 6.

The operation of the apparatus having the above configuration will be described with reference to FIG. When the composite plating is started, first, the pump 6
To make the flow rate of the composite plating solution 845 cm ³ / s (corresponding to the flow rate of 48 cm / s in the gap G).
(Equivalent to 4 A / dm ² ) is applied to perform composite plating. When this state is continued for about 60 seconds, a composite plating layer having a thickness of 2 μm to 3 μm is applied to the surface of the inner peripheral surface Wf. However, since the flow velocity in the gap G is high and the current is small, the composite plating layer deposited at this time hardly contains fine particles of silicon carbide, and only nickel is plated. No oxide film is formed.
Next, the flow rate of the composite plating solution was reduced to 264 cm ³ / s (corresponding to a flow rate of 15 cm / s in the gap G) and the current was reduced to 72 cm ³ / s.
A (corresponding to a cathode current density of 28 A / dm ² ).
Then, when the flow rate of the composite plating solution has settled, the electromagnetic proportional valve 51 is opened to start mixing air. The mixing amount of the air may be 12% to 95% (both volume%) with respect to the flow rate of the composite plating solution, but in this embodiment, 158 cm ³ / s
(Approximately 60%) of air. After this state is continued until the thickness of the composite plating layer becomes about 120 μm, the pump 6 is stopped, the electromagnetic proportional valve 51 is closed, the current is cut off by the current control circuit 42, and the composite plating process is completed. I do. In the case of this embodiment, 400 g of nickel sulfate per liter of water was used as a composite plating solution.
35 g of boric acid and 60 g of silicon carbide fine powder were added, and 2.5 g of saccharin sodium was further added to adjust the hardness to pH = 4.

[0012]

As is apparent from the above description, according to the present invention, the composite plating layer is applied to the inner peripheral surface without mixing air at the initial stage of the composite plating. Even when air is mixed in the composite plating solution, the inner peripheral surface is not oxidized to perform uniform composite plating, and therefore, the adhesion of the composite plating layer to the inner peripheral surface does not decrease.

[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 timing chart showing the operation of the device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Holder 2 Electrode 3 Holding member 4 Controller 5 Compressor 6 Pump 41 Power supply 42 Current control circuit 51 Electromagnetic proportional valve 13 Air mixing path 14 Bubble G Gap Wc Cylinder WF Inner peripheral surface

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) JP-A-7-118894 (JP) , A) Actual opening 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: After flowing for a predetermined time, applying a thin composite plating layer to the surface of the inner peripheral surface, then mixing air bubbles in the composite plating solution to grow the composite plating layer to a predetermined thickness. A composite plating method for an inner peripheral surface of a hollow member.