JP3272546B2 - Manufacturing method of aluminum engine cylinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the formation of a sliding surface applied to a cylinder or the like of an internal combustion engine.

[0002]

2. Description of the Related Art FIG. 2 shows a surface and a cross section of a plated aluminum engine cylinder film according to a conventional technique. In a two-stroke engine cylinder, a chrome plating is applied to a sliding surface with a piston or a piston ring to obtain wear resistance. The usual industrial chromium plating is 250 g / l of chromic acid and sulfuric acid, which is called a sardine bath.
The electrolysis is performed by using an object to be plated as a cathode and a lead alloy or the like as an anode in an electrolytic solution containing 5 g / l. The bath temperature (temperature of the electrolyte) at this time is 50 to 55.
It is generally assumed that the temperature and the current density are 20 to 60 A / dm ² . The hardness of the plating film obtained under these conditions is H
V900. Since the chromium plating cannot be used on the surface of the base material 2 as it is, an inner diameter with a predetermined dimensional accuracy is formed by grinding, and a porous treatment (to be immersed again in a plating tank and reverse electrolysis to form (A process of opening cracks that existed in the above).

In this manufacturing process, 1) it is necessary to increase the thickness of a plating layer in order to obtain dimensional accuracy by grinding. Therefore, the plating time is long. 2) Since the porous process is required after the grinding, the manufacturing process becomes extremely long when combined with the process of 1). 3) Low initial compatibility with the piston ring due to high film hardness. 4) For an attempt to apply honing finishing instead of grinding and porous treatment to shorten the process, the plating film has high hardness, so that the plating film is damaged and cannot be used. There are disadvantages such as.

[0004]

However, when honing is the only finish after plating for the purpose of shortening the process, as described above, the coating does not have toughness at ordinary plating hardness, and thus the coating is deficient or the honing grindstone is not used. The wear will be large and it will be difficult to apply. In order to use only the honing finish, it is necessary to have a tough film that does not cause any damage even by the honing process, and a film hardness that allows little processing of the honing grindstone and allows normal processing. As a gasoline engine, it is a portion where the piston slides, and it is necessary that the film has abrasion resistance and does not deteriorate the engine performance.

It is an object of the present invention to provide the above two items, namely, (1) a plating film capable of honing. (2)
Plating film that does not lower engine performance. It is an object of the present invention to provide an aluminum engine cylinder which forms a plating film satisfying the above, and a method for manufacturing the same.

[0006]

Method for producing aluminum engine cylinder according to the present invention According to an aspect of the aluminum engine cylinder
Chromic acid 250g / l, sulfuric acid 2.5
g / l of a plating solution having a composition of 6
1-65 ° C., current density is 20-60 A / dm ² ,
Chromium plating layer having hardness of HV700-800
And honing the surface of this chrome plating layer
It is characterized in that a cylinder having a predetermined inner diameter is manufactured .

[0007]

[0008]

According to the present invention, the plating bath temperature is raised by about 10 ° C.
The hardness of the coating 1 is HV700 to 800 because
Therefore, with this plating film, there is no loss of the film even after honing, and the initial conformability and wear resistance are good. According to this method, it is possible to set the minimum required plating thickness in the plating step, and since the sliding surface can be formed by honing, the finishing step can be greatly reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a surface and cross-sectional view of a plating film according to a first embodiment, and FIG. 3 is a characteristic diagram showing a relationship between plating bath temperature and plating film hardness. As the first embodiment, prototypes of actual machine parts were manufactured using a two-cycle gasoline engine cylinder. The base material 2 was machined (finished Arasa 3S) on the inner diameter of a cylinder in which a piston slides in a two-cycle gasoline engine cylinder obtained by die-casting an aluminum alloy ADC12 material, and then plated. The plating process is pre-treatment with water washing → alkali etching → water washing → acid activity → water washing → first zinc displacement plating → water washing → acid washing → water washing → second zinc displacement plating, and then enters Cr plating.

The Cr plating 1 has a chromic acid content of 250 g / l,
In a plating bath having a composition of sulfuric acid of 2.5 g / l and generally called a surge bath, the bath temperature was set to 63 ° C. (see FIG. 3), the current density was set to 50 A / dm ² , and the plating time was set to 1 hour. . During plating, there was a concern that the plating solution temperature would locally fluctuate on the plating surface.

However, when the temperature (material temperature and solution temperature) near the plating surface at the time of plating was measured at each part of the plating surface of the component, it was found that the temperature was kept within ± 0.5 ° C.
It was found that the set bath temperature was maintained. After plating was completed, the plating film was examined. As a result, the hardness was HV780, and the film thickness was 25 μm. Thus, the initially targeted plating film was obtained. (Refer to FIG. 1) In the same plating process, the plating bath temperature was set to 65 ° C. and plating was performed.
A plated product having a hardness of 0 was obtained. (See Fig. 3)

Next, the operation of the above embodiment will be described.
The hardness of the plating film 1 from a plating bath temperature of 61 to 65 ° C. is H
V700 to 800, and this plating film has no defects in the plating film even by honing, and has good initial conformability and abrasion resistance. By this method, it is possible to set the minimum required plating thickness in the plating process, to shorten the plating time compared to the conventional method, and to form the sliding surface only by honing finish. Can be greatly reduced.

[0013]

When the honing was applied to the two-stroke gasoline engine cylinders having the two plating hardnesses shown in the above-mentioned embodiment, no film defects were found and good honing was performed. In this case, honing is performed only once. Further, after assembling the parts into a finished engine, a durability operation test was performed. No abnormalities such as peeling of plating and abrasion were observed even after 100 hours.

As a result, about 25 μm of conventional thick plating of about 150 μm, grinding and porous processing are performed.
It was possible to substitute a single honing process with a thin plating of μm, and it was possible to greatly reduce the production process.

[Brief description of the drawings]

FIG. 1 is a surface and cross-sectional view of a plating film by a micrograph according to a first embodiment of the present invention.

FIG. 2 is a surface and cross-sectional view of a plating film by a micrograph of a conventional example.

FIG. 3 is a characteristic diagram showing a relationship between plating bath temperature and plating film hardness.

[Explanation of symbols]

 1 ... plating film, 2 ... base material.

Continued on the front page (72) Inventor Yoshio Kobayashi 1st highway, Iwazuka-cho, Nakamura-ku, Nagoya-shi, Aichi, Japan Nagoya Machinery Works, Mitsubishi Heavy Industries, Ltd. (72) Inventor Shiro Murase, Iwatsukacho, Nakamura-ku, Nagoya-shi, Aichi Road No. 1 Mitsubishi Heavy Industries, Ltd. Nagoya Kiki Seisakusho Co., Ltd. (56) References Shohei Kishi, "Chromium Plating", published by Nikkan Kogyo Shimbun, September 30, 1967, 3rd edition, p. 13, 14, 133-141, 168-171, 182-184, 257-261 (58) Fields investigated (Int. Cl. ⁷ , DB name) C25D 7/00 C25D 3/06 C25D 5/48

Claims (1)

(57) [Claims] 1. An inner diameter sliding surface of an aluminum engine cylinder.
The composition of chromic acid 250g / l and sulfuric acid 2.5g / l
Using a plating solution consisting of
When the flow density is 20 to 60 A / dm ² , HV 700 to 8
A chromium plating layer having a hardness of
Honing the surface of the plating layer
Aluminum engine cylinders
Production method .