JPS6283495A - Anodic oxidation treatment of hollow structural body - Google Patents

Abstract

PURPOSE:To form a uniform and thick film on the inside wall of a hollow structural body by respectively water-tightly attaching jigs which can supply and discharge an electrolyte to the hollow structural body and making anodic oxidation while passing the electrolyte through the inside of the hollow part via the above-mentioned jigs. CONSTITUTION:The jigs 2, 3 for supplying and discharging the electrolyte are water-tightly attached by means of 'Teflon(R)' gaskets 4 and rigid PVC bolts 5 to the hollow structural body such as cylinder head 1 made of aluminum having apertures. The electrolyte is passed through the inside or the cylinder head 1 by an electrolyte tank 13, a circulation pump 7, a temp. controller 8, etc., via the above-mentioned jigs 2, 3. The above-mentioned jigs 2, 3 are connected to the cathode of a power source device 6 and the cylinder head 1 is connected to the anode thereof, then the jigs and the cylinder head are energized. The inside wall surface of the above-mentioned cylinder head 1 is thus efficiently subjected to an anodic oxidation treatment with a small amt. of the electrolyte by which the defect-free corrosion resistant film is formed thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in an anodizing treatment method applied to an inner wall of a hollow part of a hollow structure made of aluminum, particularly a hollow structure having an opening.

(Prior art) Conventionally, the anodizing treatment method for aluminum materials is, for example,
Aluminum Processing Technology Handbook, March 5, 1970, Nikkan Kogyo Shimbun, pp. 543-606, [Aluminum Surface Technology Handbook J, October 1980, 17L1 Light Metal Publishing Co., Ltd., pp. 477-712, etc. As such, it is used in many fields as a method of imparting corrosion resistance and decorative properties to aluminum materials. Among the above-mentioned aluminum materials to be treated, for example, cylinder heads made of aluminum castings,
As aluminum hollow structures, such as aluminum hollow parts for automobiles such as inlet manifolds and brake master cylinders made of cast aluminum, are anodized, the anodizing treatment of their inner surfaces becomes more difficult as their shapes become more complex.

For this reason, various proposals have been made and put into practical use, including the above-mentioned document, regarding the composition of the electrolytic solution, the method of applying an electrolytic current, the method of controlling the temperature of the electrolytic solution, the method of suspending the object to be treated, and the like.

(Problems to be Solved by the Invention) However, in such conventional anodizing treatment methods for aluminum hollow structures, it is difficult to anodize the inner surface of the hollow portion, which has a small opening diameter and is deep. For example, on page 557 of the above-mentioned "Aluminum Processing Technology", it is explained that an auxiliary electrode is necessary because the anodic oxide film on the inner wall is 25 to 33% thinner than on the outside. There is a problem. In addition, in order to prevent the electrolyte from reaching a high temperature locally on the surface to be treated, the electrolyte must be vigorously stirred, or fluid anodized as explained in the aforementioned "Aluminum Surface Technology Handbook", pages 501, 504, and 711. Various methods have been devised, including the bubbling method, shower method, roll coater method, flow coater method, mist method, and impeller spray method. However, automotive cylinder heads,
For items with complicated hollow parts, such as suction manifolds, the methods below the shower method are almost impossible to apply to the treatment of the inner wall of the hollow body, where corrosion resistance is most important. Oxidized words make it impossible to achieve the desired thickness of the inner wall, and as a result, unintended areas are treated, which inevitably requires extra electrical energy.
In addition, there is a problem in that a large amount of electrolyte is required for sufficient immersion, resulting in a large economic loss.

(Means for Solving the Problems) The present invention provides a jig capable of watertightly supplying an electrolyte to the hollow structure when anodizing the inner wall of the hollow part of the hollow structure having an opening, and a watertight The present invention relates to an anodizing method characterized in that a jig that can be discharged is attached and electrolysis is performed while an electrolytic solution is caused to flow through the hollow part through the jig.

In anodizing the inner wall of the hollow part of the hollow structure by the method of the present invention, an electrolytic solution is supplied to the hollow structure,
That is, a jig that can be injected and discharged is installed in a watertight manner, and electrolysis is performed while the electrolytic solution flows through the hollow part of the hollow structure through the jig. For example, if the cylinder head of an automobile has a shape and has multiple openings, a jig for supplying electrolyte to at least one opening is attached, and the electrolyte is supplied from these openings. A discharge jig is attached to at least one other opening positioned to permit flow to flow through the hollow space and discharge. Furthermore, if the hollow structure is an elongated hollow body with a relatively large opening at one side end and a closed structure at the other end, such as an automobile brake master cylinder, the opening serves both to supply and discharge electrolyte. Attach a jig, for example, a jig equipped with a liquid supply pipe and a discharge pipe, with the supply pipe extending to the vicinity of the other closed end, and the discharge pipe installed at the opening position to allow the electrolyte to flow through the hollow part. let In this case, other openings are closed with blind plugs, etc., as required.

According to the present invention, as described above, when anodizing treatment is performed with a jig attached, the object to be treated is used as an anode, and the cathode is not separately arranged. The treatment can be carried out using one or both of these as a cathode.

In this manner, the method of the present invention can be used to anodize hollow structures of any shape, such as automotive parts such as aluminum cylinders, brake master cylinders, intake manifolds, and other metal hollow structures that can be anodized. By doing so, a thick coating with a uniform thickness can be formed on the inner wall.

(Example) Next, the present invention will be described by way of examples with reference to the drawings.

An example of a method for treating a cylinder head of an automobile engine, which is a hollow structure, according to the anodizing treatment method of the present invention will be explained with reference to FIG. In FIG. 1, ■ is a cylinder head, 2 is a jig for injecting the electrolyte into the hollow part, and 3 is a jig for discharging the electrolyte from the hollow part. The cylinder head 1 and the jig 2, and the jig 2 and the jig 3 are in contact with each other via a gasket 4 made of Teflon resin, and are further fastened with bolts 5 made of hard vinyl chloride.

In addition to the materials used in this embodiment, the gasket 1 and the bolt 5 may be made of any material as long as it can achieve the main purpose of electrical insulation and watertightness. Further, instead of using the bolts 5, it may be fastened using an insulating clamp. Unnecessary openings in the cylinder head 1 are sealed with blind plugs or the like.

Jig 2 or 3 is used to anodize the hollow part.
, preferably with 2 and 3 as cathodes and the cylinder head 1 as an anode, suspended and electrically connected by an appropriate method to supply an electrolytic current, a pump 7 for circulating an electrolytic solution, and an electrolyzer. A temperature control device v18 for controlling the temperature of the liquid and piping systems 9.10 and 11.12 are arranged as shown.

Alternatively, the temperature of the electrolyte in the electrolyte tank may be independently adjusted using a temperature control device and a pump installed separately. Furthermore, it is desirable that the cylinder head 1, which is the object to be treated, and the piping systems 3 and 11 be electrically insulated.

In anodizing the cylinder head as shown in the figure, the cylinder head 1 is pretreated in advance to purify the hollow inner wall, and the electrolyte tank 13 is connected to the piping, pump, temperature control device, and cylinder head. Fill the tank with enough electrolyte to fully fill the tank, and then operate the pump and temperature control device. That is, first, when a temperature sufficient to stably carry out the anodizing process is reached by the temperature control device 8, the electrolytic process is carried out according to conditions selected from various well-known electrolytic solutions and current loading methods. By continuing to operate the pump 7 during this time, the electrolytic solution does not remain in the cylinder head, and the stirring action is continuously performed.

FIG. 2 is a diagram showing another embodiment for anodizing the cylinder head 1 shown in FIG. 1. In addition to the embodiment shown in FIG.
Furthermore, the branch pipe 1 is connected via the on-off valves 14c and 14d.
6.17 and a storage tank 15 are installed, and any number of branch pipes and storage tanks can be installed together. Further, the opening/closing valve may be operated manually or by remote fusion operation using electricity, hydraulic pressure, or pneumatic pressure.

According to this embodiment, by changing the type of processing liquid in the storage tank 15 or installing branch pipes and storage tanks corresponding to the number of processing liquids, the on-off valve can be switched, and degreasing and chemical polishing can be performed. , anodizing, sealing, rinsing, etc. can be carried out for each step with the object to be treated, such as the cylinder head described in Section 2, still attached to the apparatus. Furthermore, dry air is piped 1
If it is inserted through the branch and opening/closing valve (not shown) provided in 1.3, drying work can be performed as appropriate.

As another example of these methods, by installing an electrolyte injection jig and a discharge jig according to the shape of the brake master cylinder and intake manifold,
The objectives of the invention are achieved.

FIG. 3 shows a cross-sectional view of a workpiece and a jig in an embodiment different from FIGS. 1 and 2 in which a brake master cylinder as a workpiece is anodized according to the method of the present invention. In the drawing, 20 is a brake master cylinder, 21 is a jig that also serves to supply and discharge electrolyte, 2
2 is a blind plug, and 23 is a jig that can electrically insulate the brake master cylinder 20 and the jig 21 and connect them in a watertight manner.

The electrolyte is supplied from a supply pipe attached to the jig 21,
It flows through the inside of the brake master cylinder 20 and is discharged from the discharge pipe f. During this time, anodic oxidation is performed using the brake master cylinder 20 as an anode and the jig 21 as a cathode.

As mentioned above, in this embodiment, by extending the protrusion e between the supply parts as shown in h in the electrolyte supply part, when the electrolyte solution is discharged from the discharge pipe f without providing this protrusion part. It is possible to eliminate the electrolyte stagnation phenomenon that occurs in the section g when the opening i or k is used as a discharge port without installing a blind plug 22 or a blind plug 22.

In this case, since the protrusion functions as an auxiliary electrode, the throwing power and quality of the anodized film are further improved.

Further, by integrating the supply jig and the discharge jig, the number of steps required for mounting the jig can be reduced.

(Effects of the Invention) As explained above, in the anodizing treatment method for a hollow structure of the present invention, a jig that can continuously and watertightly supply an electrolytic solution only to the hollow portion and a watertight discharge method are used. Because the configuration is such that electrolysis is carried out while the electrolyte is flowing through the hollow part by attaching a jig to the hollow part, (a) anodizing can be performed only on the inner wall of the hollow part where corrosion resistance is required, and (b) the inner wall of the hollow part can be anodized. (3) Unlike the immersion method, it can be processed with a small amount of electrolyte;
゛(d) Since the processing liquid is small, it is easy to prepare the liquid material,
The effect is that various pre-treatments and water washing can be carried out with the same equipment and on the object to be treated without any leakage.

[Brief explanation of drawings]

Figures 1 and 2 are system diagrams for anodizing the throats of automobile cylinders by the method of the present invention, and Figure 3 is a brake master for an automobile equipped with a jig for anodizing by the method of the present invention. It is a sectional view of a cylinder. 1-Cylinder head 2-Electrolyte supply jig 3 Electrolyte discharge jig 6-=-Power supply device 7-Circulation pump
8- Temperature adjustment device 13 - Electrolyte tank 20 - Brake master cylinder 21 - Electrolyte supply and discharge jig 23 Fastening jig Fig. 1

Claims (1)

[Claims] 1. When anodizing the inner wall of the hollow part of a hollow structure having an opening, a jig that can supply the electrolyte to the hollow structure in a watertight manner and a jig that can discharge it in a watertight manner are installed. A method for anodizing a hollow structure, characterized in that electrolysis is performed while an electrolytic solution flows through the hollow part through a jig.