JPH0671552A - Manufacture of automobile wheel - Google Patents

Abstract

PURPOSE:To improve the appearance of an automobile wheel by solving such an inconsistent situation where appearance goes down with the amelioration of transparency of a clear coating in a fundamental manner. CONSTITUTION:In the manufacture of an automobile wheel 1 consisting of a die-formed metal material, and formed with a clear coating on a design surface 2 made up into brighteningness, peripheral surface 24a, 24b of buffs 23a and 23b are made to contact with the design surface 2 as supplying an abrasive fluid added with abrasive grains, making this surface bright in a mirror finishing process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an automobile wheel.

[0002]

2. Description of the Related Art Since an automobile wheel constitutes the appearance of an automobile, the appearance of the design surface of the wheel is extremely important in terms of commercial value.

For this reason, conventionally, there has been a technique in which the design surface of an automobile wheel molded by casting or forging is made bright to improve its appearance.

However, since this type of automobile wheel may be damaged by flying stones or the like caused by the running of the automobile, a transparent coating is formed on the design surface in a bright state to protect it from damage. ing.

However, such a transparent film cannot be completely transparent, and it is impossible to make the appearance of the brilliant state of the design surface appear as it is. This transparent film sacrifices the brilliant state of the design surface to some extent. It is supposed to be.

Under these circumstances, the conventional finishing of this kind of design surface is carried out by a finishing machine, and the transparent film formed on the surface finishes it to a bright state sufficient to be visually recognized as a bright state. However, the brilliance is not so good as to be obtained by hand finishing or the like.

[0007]

By the way, recently, the transparency of a transparent coating is being improved due to the progress of the technology for this kind of transparent coating material, and conversely, the transparency of the transparent coating is improved. Small scratches and uneven finish due to the finish of the design itself are visually recognized through the transparent coating, which causes the contradictory situation of impairing the appearance of this type of automobile wheel.

The present invention has been made on the basis of such a background, and it is a contradiction that the appearance is deteriorated as the transparency of the transparent coating is improved even though it is an automobile wheel manufactured by mechanical finishing. The purpose is to fundamentally solve the situation and improve the appearance of automobile wheels.

[0009]

In order to achieve this object, the invention according to claim 1 is an automobile wheel which is made of a molded metal material and has a transparent coating formed on the design surface in a bright state. In the manufacturing method, during the surface finishing step for bringing the design surface into a bright state, the design surface is brought into a bright state by contacting the peripheral surface of the buff while supplying a polishing liquid containing abrasive grains. And

[0010]

According to the first aspect of the present invention, since the buff is used, the buff can flexibly polish its surface according to the unevenness of the surface of the molded product.

Further, this buffing uses a polishing liquid,
Since it is so-called wet buffing, the rotation speed of the buff is slower than that of dry buffing that does not use a polishing liquid, so that the buff deformation can follow the unevenness of the surface well. , The surface is surely polished regardless of the presence of irregularities.

In addition, since the peripheral surface of the buff is brought into contact with the molded product, the contact area between the buff and the molded product is in linear contact and its area is small. Since the abrasive grains can be supplied and foreign matters such as buff residue can be effectively eliminated, a good finished surface can be obtained by buffing the surface of the die-molded product using a machine.

Therefore, the finish of the design surface, which is the base of the transparent coating, becomes good, so that even if the transparency of the transparent coating is improved, there is no contradiction that the appearance of the design surface is deteriorated as in the conventional case, and it is for automobiles. The appearance of the wheel can be improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments shown in the drawings. In this embodiment, the technique of the present invention is applied to an automobile wheel which is a cast product made of an aluminum alloy. In this specification, the design surface means a surface that faces the outside of the vehicle body and constitutes a part of the appearance of the vehicle when the vehicle wheel is mounted on the vehicle.

First, an automobile wheel material 1 as a molded product is cast by pouring a molten aluminum alloy (for example, AC4CH) into a mold having a required shape.

The automobile wheel material 1 thus obtained is taken out of the mold, the weir and the like are removed, and then the shot peening process is first performed.

The processing conditions in this shot peening processing step are shown in Table. Seems like 1.

[0018] Under such conditions, the shot peening process is carried out for about 20 minutes on the entire automobile wheel material 1,
In this embodiment, as will be described later, an automobile wheel material 1
Since the transparent coating 31 is formed on the design surface 2, the shot peening process on the design surface 2 is particularly carefully performed.

The shot peening process is a process having a relatively high degree of freedom, and is a curved design surface 1
A shot can be sprayed on the surface of 2 almost uniformly, and a plastic deformation layer can be formed uniformly.

The surface of the design surface 2 of the automobile wheel material 1 that has been subjected to such shot peening is a fine textured surface having a fine texture, and a plastic deformation layer is formed on the surface layer portion thereof.

Since this plastic deformation layer is formed by the impact of shots, it opens on the design surface 2 of the wheel material 1 for an automobile, and inside it, there are holes such as bubbles containing air and moisture. The cracks have been pressure-bonded and disappeared in the plastically deformable layer, and the air contained in the holes and the like, the water used in the casting work of the automobile wheel material 1, and the like have been discharged to the outside.

Particularly, in the shot peening process in this embodiment, the shot spraying speed is high and the kinetic energy possessed by the shot is high as described above, so that the thickness of the plastic deformation layer is about 1.5 mm to 3.0 mm. Since it is large, substantially no air or water can exist in the plastically deformable layer formed on the surface layer of the design surface 2.

Therefore, even if the preparatory finishing or mirror finishing step described later is performed by wet buffing, there is no problem that moisture remains inside the surface layer of the design surface 2 and hinders the formation of the transparent coating film 31.

Needless to say, shot peening conditions other than the above can be used.

Further, such shot peening processing is
As described above, since the shot is jetted and collides with the surface of the automobile wheel material 1 which is a workpiece, the black skin on the surface of the automobile wheel material 1 which is a workpiece, adhered foreign matter or dirt, etc. The surface can be cleaned by removing it.

After that, the automobile wheel material 1 is machined at a required portion in a machining process to be formed into an accurate predetermined shape as the vehicle wheel material 1.

The design surface 2 of the automotive wheel material 1 is then subjected to the steps shown in FIG. 1, and finally the design surface 2 is a mirror surface in a brilliant state. Obtained as a product.

In the above-mentioned automobile wheel material 1, a large number of irregularities are formed on the design surface 2 by the spoke portion 3, the through hole 4, the hub portion 5, the rim portion 6, etc. due to design requirements. (See Fig. 3, 4 etc.),
A certain amount of black skin remains on this design surface 2.

A black skin removing step is first performed on the design surface 2 having such a black skin remaining.

The black skin removing process of this embodiment is mainly performed in # 100-
It is carried out step by step with a polishing machine using a polishing cloth having # 320 abrasive grains. Depending on the size and shape of the unevenness of the design surface 2, a router of the same degree may be used supplementarily, or hand polishing work may be used in combination.

Further, the black skin removing step is not limited to the one using such an abrasive cloth paper, and other processing method capable of obtaining the same finished surface may be used.

With respect to the design surface 2 of the automobile wheel material 1 from which the black skin has been removed in the black skin removing process,
Next, a rough finishing process is performed.

The rough finishing process of this embodiment is performed in two steps, for example, by so-called dry buffing without using a polishing liquid.

That is, the first stage of this rough finishing process is
Using a sisal buff and a compound for medium finishing, the rotation speed is high, for example, about 2000 rpm.

The second step of the rough finishing process is carried out at the same rotation speed as above using a very good finishing compound on a cotton buff having a rigidity lower than that of the sisal buff.

The surface finishing state of the design surface 2 at the time when such a rough finishing step is completed is the same as the mirror finishing which can be conventionally achieved by mass production of a molded product only by a machine.

In this embodiment, the following preparatory finishing step and mirror finishing step are performed on the design surface 2 of the automobile wheel material 1 on which the rough finishing step has been completed.
With regard to the molded product, it is a mechanical finish that can be achieved only by the manual work of a skilled technician.

The preparatory finishing step and the mirror finishing step are carried out by so-called wet buffing using a polishing liquid, and in this embodiment, they are divided into five stages as shown in FIG.

On the design surface 2 of the automobile wheel material 1 which has been subjected to the rough finishing step of dry buffing as described above, first of all, as the first step of the preliminary finishing step, the electrolytic composite vertical shaft wet buffing is carried out. A processing step is performed.

The contents of the electrolytic composite vertical axis wet buffing process are as follows (see FIGS. 8 and 3 and 4).

That is, in this electrolytic composite type vertical shaft wet buffing process, the wheel material 1 for an automobile has its center on the rotary table 11 and the center of rotation O of the rotary table 11.
The design surface 2 is fixed in an upward horizontal posture in conformity with the above, and the design surface 2 is polished by the lower end surface 13a of the buff 13 attached to the lower end portion of the rotary shaft 12 hanging from above.

The rotary table 11 is rotationally driven at a low speed during processing, and sequentially displaces the processed portion by the buff 13 in the circumferential direction. The rotary table 11 of this embodiment reverses its rotation direction at appropriate time intervals (for example, 30 seconds).

The buff 13 is made of an extremely flexible material as compared with the conventional buff, and in this embodiment, the sponge material having a high expansion ratio (for example, 3 to 5 times) and continuous cells. It is formed by. The buff 13 is not limited to the sponge material, and a buff made of another material may be used as long as it is flexible to the same degree.

Therefore, this buff 13 has a design surface 2
Despite the unevenness on the surface, as shown in FIG.
The lower end surface can surely maintain the contact state on the design surface 2. The pressing force of the buff 13 on the design surface 2 is
For example, it is as small as 1 kgf / cm ² or less.

Then, on the upper part of the buff 13, the buff 1
An electrode 14 having a shape corresponding to the planar shape of No. 3 is installed (see FIG. 8), and this electrode 14 is used for performing the electrolytic processing function described later.

The rotating shaft 12 for supporting the buff 13 at the lower end is an elevating device 15 composed of a hydraulic cylinder or the like.
The rotation shaft 12 is driven at, for example, 300 rpm so that the rotation speed of the buff 13 is extremely low such as 10 m / sec or less. In the case of this embodiment, The rotation speed of the buff 13 is, for example, 4 m / sec.

This is the buff 13 made of a flexible material.
This is for ensuring that the lower end surface 13a of the above can be deformed following the unevenness while maintaining the contact state with the unevenness of the design surface 2.

The rotation direction of the rotary shaft 12 is driven to rotate in the same direction as the rotation direction of the rotary table 11, and when the rotation direction of the rotary table 11 is reversed. In addition, the rotating shaft 12 is pulled up by the elevating device 15, the buff 13 is separated from the design surface 2 upward, and the rotating direction of the rotating shaft 12 is also reversed.

Therefore, even if the rotating direction of the rotating table 11 is reversed, the rotating direction of the rotating table 11 and the rotating direction of the buff 13 are always maintained in the same direction.

A shaft hole 12a is formed in the rotary shaft 12 (FIG. 8), and a polishing liquid containing abrasive grains is supplied to the central portion of the buff 13 through the shaft hole 12a. It is like this. This polishing solution also functions as an electrolytic solution in the electrolytic processing described later, and in this example, it is an aqueous solution containing alumina having a particle size of 10 μm as abrasive grains and containing a surfactant and an electrolytic substance. .

Further, in this embodiment, as shown by the phantom line in FIG. 3, the polishing liquid nozzle 1 for supplying the same polishing liquid as the above toward the contact portion between the buff 13 and the design surface 2.
6 is provided so that fresh abrasive grains can be reliably supplied to the buff 13.

Since the supply of the polishing liquid from the polishing liquid nozzle 16 is continued even when the rotating direction of the rotary table 11 is reversed, the buff 13 is rotated when the rotary table 11 is reversed. At the time of ascending, the polishing liquid is sprayed toward the portion that was immediately below the buff 13, so that the buff residue and other foreign matter that are interposed between the buff 13 and the design surface 2 can be effectively removed. There is an advantage that can be.

Then, as shown in FIG. 8, the electrolytic processing in the electrolytic composite vertical axial wet buffing process is performed in combination with the vertical axial wet buffing as described above.

That is, the electrolytic processing in this embodiment is performed by the DC power supply 17 and the polishing liquid which are interposed between the electrode 14 and the automobile wheel material 1, and the electrode 14 is On the plus side, the design surface 2 of the automobile wheel material 1 is connected to the minus side.

Between the electrode 14 and the design surface 2, the polishing liquid supplied from the shaft hole 12a of the rotary shaft 12 or the polishing liquid supplied from the polishing liquid nozzle 16 is a continuous-cell sponge material. Since the buff 13 formed in step 1 is infiltrated and exists, the buff 13 is dipped into the buff 13 and the direct current power source 1
An electrolytic circuit from 7 is formed, and on the surface of the design surface 2, electrolytic processing is performed at the same time as buffing with the abrasive grains, and electrolytic composite type buffing is performed.

Therefore, in this electrolytic composite type vertical axial wet buffing process, the processing efficiency is better than that in the normal buffing process.

After the completion of the electrolytic composite vertical axial wet buffing process, the design surface 2 is subjected to the horizontal axial wet buffing process. In the following description, in order to avoid confusion, this horizontal axis wet buffing step will be referred to as a preliminary finishing horizontal axis wet buffing step.

The contents of this preliminary finishing horizontal axis wet buffing process are as follows (see FIGS. 5, 6 and 7).

That is, also in this preliminary finishing horizontal axis wet buffing process, the wheel material 1 for an automobile has the center thereof aligned with the center O of rotation of the rotary table 21 so that the design surface 2 is oriented horizontally. The rotary shaft 22a fixed to the posture and extending from the left and right sides above it,
The design surface 2 is polished by the peripheral surfaces of the buffs 23a and 23b mounted on the 22b.

The rotary table 21 is rotationally driven at a low speed only in a fixed direction during processing, and sequentially displaces the processed portion by the buff 13 in the circumferential direction.

The buffs 23a and 23b are made of a flexible material, and in this embodiment, they are made of a urethane foam material having a high expansion ratio (for example, 3 to 5 times) and closed cells. is there. In addition, these buffs 23a, 2
In 3b, if the material has the same flexibility,
Buffs made of other materials may be used.

Then, the buffs 23a and 23b of this embodiment are
Are attached by penetrating through the rotary shafts 22a and 22b in a laminated state of a plurality of buff members (five in the case shown in the drawing) of appropriate thickness, and setting the peripheral surface shape of the buffs 23a and 23b as a whole. The design surface 2 has a shape similar to the radial cross-sectional shape (see FIG. 6).

Therefore, these buffs 23a, 23b
In spite of the presence of irregularities in the radial direction of the design surface 2, the peripheral surfaces 24a and 24b can surely maintain the contact state with the design surface 2 in the line contact state.

As described above, since the buffs 23a and 23b are in line contact with the design surface 2 in the preliminary finishing horizontal axis wet buffing process, the polishing force by the abrasive grains supplied as described later is large and the electrolytic composite It is possible to effectively eliminate traces of electrolysis caused by the vertical shaft wet buffing process.

In addition, since these buffs 23a and 23b are abscissa and the contact portion with the design surface 2 is arcuate, they are deeply penetrated into the recess formed on the design surface 2 and It is relatively easy to polish (see FIG. 7).

Since the contact between the buffs 23a, 23b and the design surface 2 is in a line contact state, if the buffs 23a, 23b are set on the design surface 2 so as to be preliminarily bent, they will be described later. As described above, since the flexure is also released to the concave portion on the design surface 2, the peripheral surfaces 24a and 24b of the buffs 23a and 23b can be surely brought into contact with each other.

Also in this preliminary finishing horizontal axis wet buffing process, the rotation speed of the rotary shafts 22a and 22b is, for example,
It is a low speed of 0.8 to 10 m / sec at 100 to 500 rpm, and it is ensured that the flexible buffs 23a and 23b come into contact with the inside of the concave portion by releasing the bending, and thus the electrolytic composite type vertical shaft wet type. It is similar to the case of the buffing process.

In this embodiment, the rotation direction of the rotary shaft 22a is designed to rotate in a direction coinciding with the rotation direction of the rotary table 21, and the rotation direction of the other rotary shaft 22b is opposite. Has become.

Then, the design surface 2 of the buffs 23a, 23b which are rotationally driven by the rotary shafts 22a, 22b.
Toward the part on the side where the contact with the polishing liquid starts,
26b are installed respectively.

Incidentally, these polishing liquid nozzles 26a, 26
The polishing liquid sprayed and supplied from b is the same as the above, and is an aqueous solution containing alumina having a particle diameter of 10 μm as abrasive grains and a surfactant added thereto, whereby the buffs 23a and 23b are supplied. The supply of fresh abrasive grains is performed.

In the horizontal axis wet buffing process in which the rotary shafts 22a and 22b are placed in a substantially horizontal posture and buffing is performed on the peripheral surfaces of the buffs 23a and 23b as in the preliminary finishing horizontal axis wet buffing process. As described above, since the contact area between the buffs 23a and 23b and the design surface 2 is linear as described above, fresh abrasive grains can be reliably supplied into the contact area by spraying from the polishing liquid nozzles 26a and 26b. In addition, it can be easily washed away with a polishing liquid sprayed with foreign matter such as buff residue.

For this reason, the design surface 2 has a good finished surface according to the abrasive grains used in the following manner irrespective of the unevenness by the preliminary finishing horizontal axis wet buffing process. be able to.

That is, as shown in FIG. 7, the buff 23
When a required amount of deflection d is given to a and 23b and set,
The lower ends of the peripheral surfaces 24a, 24b of the buffs 23a, 23b can be made to reach a portion lower by an amount corresponding to the amount of bending according to the opening of the bending d.

This is because, when there is unevenness in the circumferential direction of the design surface 2, if the depth of the unevenness is about the dimension d or less, the buffs 23a and 23b also come into contact with each other and the polishing liquid is By supplying, it means that wet buffing is performed also in the recess.

In this embodiment, the buffs 23a and 23b whose rotation directions are opposite to each other are arranged so as to come into contact with the design surface 2. This is because the wheel material 1 for an automobile is rotated by the rotary table 21. By being driven in one direction, the contact of the buffs on both sides in the circumferential direction of the spoke portion 3 extending in the radial direction on the design surface 2 is made uniform, and the buffing state on both sides of the spoke portion 3 is made uniform. This is because

As mentioned above, these buffs 23a, 23
Since b is processed along with the change in deflection d, the buff 23
a, 23b themselves generate heat, but these buffs 23a, 2b
Since the polishing liquid is directly applied to the bent portion of 3b as described above, there is an advantage that it contributes to the extension of the life of the buffs 23a and 23b.

The design surface 2 on which the preliminary finishing horizontal axis wet buffing step has been completed is then subjected to the vertical axis wet buffing step. In the following description, in order to avoid confusion, the vertical shaft wet buffing process will be referred to as prefinishing vertical shaft wet buffing process.

This preliminary finishing vertical shaft wet buffing process is
It is performed by the same device (see FIGS. 3 and 4) used in the electrolytic composite vertical shaft wet buffing process described above, but the electrolytic processing related devices such as the electrode 14 and the DC power supply 17 (FIG. 8) are provided. Only the difference is not.

In the following, the prefinishing axial wet buffing process will be described using the same reference numerals as those common to the above.

That is, in this prefinishing vertical shaft wet buffing process, the lower end of the rotary shaft 12 suspended from above on the design surface 2 of the wheel material 1 for an automobile installed on the rotary table 11 in the same manner as described above. Buff attached to the part 1
The design surface 2 is polished by the lower end surface 13a of 3 and the electrolytic processing as described above is not performed.

Even in this prefinishing vertical shaft wet buffing process, the rotation table 11 is driven at a low speed as in the above case, and it is not possible to reverse its rotation direction every appropriate time (for example, 30 seconds). It is the same.

Further, the buff 13 is made of a material which is extremely flexible as compared with the conventional buff, and in this embodiment, it is also made of the same kind of open cell sponge material having a high expansion ratio. Is.

From these circumstances, although the pressing force of the buff 13 on the design surface 2 is small, for example, 1 kgf / cm ² or less, the buff 13 has unevenness on the design surface 2 in spite of the presence of the unevenness. As shown in FIG. 4, its lower end surface 1
It is also the same that the contact state of 3a can be reliably maintained on the design surface 2.

The rotating shaft 12 supporting the buff 13 at the lower end is driven at a low speed of, for example, about 300 rpm, and the rotation speed of the buff 13 is extremely low at about 10 m / sec or less (for example, 4 m / sec). At the same time, the rotation shaft 12 is held by the lifting device 15, and when the rotation direction of the rotation shaft 12 reverses the rotation direction of the rotary table 11, the lifting device 15 causes the rotation shaft 12 to rotate. The buff 13 is separated from the design surface 2 upward, and the rotation direction of the rotary shaft 12 is also reversed, so that the buff 13 is rotationally driven in a direction coinciding with the rotation direction of the rotary table 11. It is the same.

At the contact portion between the buff 13 and the design surface 2 as described above, alumina having a particle diameter of 10 μm was contained as abrasive grains from the shaft hole 12a of the rotary shaft 12 and the polishing liquid nozzle 16. Wet buffing is performed by supplying a polishing liquid having the same composition.

The reason why the preliminary finishing vertical axis wet buffing step is carried out after the preliminary finishing horizontal axis wet buffing step is that the polishing marks caused by the preliminary finishing horizontal axis wet buffing step are This is because it is erased by a preliminary finishing vertical axis wet buffing process in which polishing is performed in a direction intersecting with.

In this prefinishing vertical shaft wet buffing process, since the buff 13 is flexible and the rotation speed thereof is low, the followability to the irregularities on the design surface 2 is good and the irregularities exist. Regardless, the design surface 2 can be surely polished, and the foreign matter caught immediately below the buff 13 can be effectively removed by the polishing liquid by the elevating operation of the buff 13 when the rotary table 11 is inverted. It has an advantage that a very good finished surface can be surely obtained.

The automobile wheel material 1 for which the preliminary finishing processes up to the preliminary finishing vertical shaft wet buffing process have been completed are then subjected to a mirror finishing process as a mirror finishing process (corresponding to the surface finishing process of the present application). A horizontal axis wet buffing process is performed (see FIGS. 5, 6 and 7).

This mirror finishing horizontal axis wet buffing step is performed in substantially the same manner as the above-mentioned preliminary finishing horizontal axis wet buffing step, except for the polishing liquid, and therefore the apparatus and method thereof are common to those described above. The description thereof will be omitted, and only the matters related to the differences will be described below.

That is, the polishing liquid used in the mirror finishing horizontal axis wet buffing process of this embodiment is an aqueous solution containing alumina having a particle diameter of 1 μm as abrasive grains and a surfactant added thereto.

This mirror finishing horizontal axis wet buffing step is performed subsequent to the prefinishing vertical axis wet buffing step by performing the prefinishing vertical axis wet buffing using abrasive grains having a grain size of 10 μm. This is because the polishing marks in the processing step are erased by using abrasive grains having a particle size of 1 μm to increase the shine. The horizontal axis wet buffing is performed on the peripheral surfaces 24a, 2 of the buffs 23a, 23b.
The polishing power of 4b is large, and even if it is wet buffing using fine abrasive grains, it is possible to efficiently erase the previous polishing marks, and it is possible to obtain a finished surface in a very excellent bright state. Because you can.

In the mirror finishing horizontal axis wet buffing step, for the same reason as in the preliminary finishing horizontal axis wet buffing step, it is in line contact and it is easy to supply fresh abrasive grains. The buffs 23a and 23b can be reliably blown because the polishing power of the abrasive grains is large, the inside of the concave portion of the design surface 2 can be polished, and the polishing liquid can be directly sprayed on the portions of the buffs 23a and 23b where the bending occurs. It has the advantage that it can be cooled to a low temperature.

After that, the automobile wheel material 1 is subjected to a mirror finish finishing axial wet buffing process (see FIGS. 3 and 4), and finally the design surface 2 of the automobile wheel 1 is finished in a mirror state. To be

This mirror-finished vertical axis wet buffing process is
Although only the polishing liquid is different, the prefinishing vertical shaft wet buffing process is performed in substantially the same manner, so that the description of the common apparatus and method etc. will be omitted, and the differences will be related. Only the items to be described will be described below.

That is, the polishing liquid used in the mirror finishing vertical axis wet buffing process of this embodiment contains alumina having a particle size of 1 μm as abrasive grains, and the mirror finishing horizontal axis wet buffing is performed. It is the same as the polishing liquid in the process.

This mirror finishing vertical axis wet buffing process
What is performed after the mirror finishing horizontal axis wet buffing step is that the mirror finishing horizontal axis wet buffing step has a large polishing force, and the minute polishing traces caused by this are the same as those containing abrasive grains of the same particle size. This is for erasing by polishing in the direction intersecting with the previous polishing mark by using the above polishing liquid.

The finished surface of the design surface 2 thus obtained is in a mirror-finished state equivalent to a mirror-finished product finished by a skilled worker by hand, as compared with a conventional molded product.

In this mirror finishing vertical axial wet buffing process, the same flexible buff 13 as in the preliminary finishing vertical axial wet buffing process is used, and the rotation speed is low. The design surface 2 has good followability to the irregularities of the design surface 2, and the design surface 2 can be surely polished by the lower end surface 13a regardless of the presence of the irregularities, and the buff 13 is moved up and down when the rotary table 11 is turned upside down. It is possible to effectively remove the foreign matter caught immediately below 13 with the polishing liquid, and it is possible to reliably obtain a very good finished surface.

On the design surface 2 of the wheel material 1 for an automobile whose design surface 2 is finished as a mirror surface in the bright state as described above, the following coating film forming process is performed, as shown in FIG.
A transparent coating 31 shown in is formed.

In this example, the coating composition used in the film-forming step was a silica-organosilane-based inorganic-organic composite coating composition containing an inorganic material as a main component, a dispersion liquid, an acrylic resin, and a surfactant. Is included.

The coating composition dispersion comprises 20-60% by weight of colloidal silica and 20-60% by weight of organoalkoxysilane partially hydrolyzed condensate, based on the total solids of the coating composition. It will be.

The acrylic resin of this coating composition is
Based on the total solid content of the coating composition, 5 to 40% by weight of a polymer or copolymer of unsaturated ethylenic monomer, and 150 to 5
It is composed of a solvent containing 50% by weight of a glycol derivative as an essential component, and the solvent is a lower aliphatic alcohol such as methanol containing 10% by weight or more of the glycol derivative.

A nonionic surface active agent is added to the surface active agent of the coating composition.

If necessary, a thickener, a defoaming agent, a dye or the like may be added to the coating composition.

In this coating composition, the above-mentioned respective composition components are blended and the above-mentioned blending ratios are provided for the following reasons.

That is, the mixing ratio of the colloidal silica is set to 20 to 60% by weight when the content of the colloidal silica is less than 20% by weight, the hardness of the transparent coating film 31 formed is lowered to 60% by weight.
This is because if it is larger, the impact resistance of the transparent coating 31 is reduced.

The mixing ratio of the partially hydrolyzed condensate of the organoalkoxysilane is set to 20 to 60% by weight. When the content is less than 20% by weight, the adhesiveness of the transparent coating film 31 is lowered and the content is more than 60% by weight. This is because the impact resistance of the transparent film 31 is reduced.

The unsaturated ethylenic monomer or copolymer is contained in an amount of 5 to 40% by weight, which is 5% by weight.
If it is smaller, it is difficult to form the transparent coating 31 having a thickness of more than 20 μm, cracks are likely to occur due to heat shrinkage, etc., and impact resistance and corrosion resistance are deteriorated. On the other hand, if it is more than 40% by weight, the hardness of the transparent coating film 31 is lowered and the scratch resistance and the stain resistance are lowered.

10 to a lower aliphatic alcohol such as methanol
The reason why the solvent containing the glycol derivative in an amount of not less than wt% is used is to enhance the storage stability of the transparent coating 31 and improve the workability of forming the coating and the appearance of the formed transparent coating 31.

The reason why the nonionic surfactant is used as the surfactant is that the storage stability of the transparent film 31 is good.

The transparent coating 31 is formed on the design surface 2 using such a coating composition by a usual method such as spray coating. In this case, since the adhesion of the coating composition to the design surface 2 is excellent, if the design surface 2 is cleaned, the primary treatment is unnecessary.

After applying the coating composition onto the design surface 2,
Automobile wheel 1 in a drying oven etc. at 100-200 ℃ for 10-20
The coating composition is dried and cured by heating for about 3 minutes to give a transparent coating 3
1 is obtained.

The transparent coating film 31 on the design surface 2 thus formed has excellent transparency and good adhesion to the design surface 2, and has high impact resistance and scratch resistance. Is. Therefore, even if the transparent coating 31 on the design surface 2 of the automobile wheel 1 of this embodiment is thinner than the conventional film thickness, for example, about 10 μm, the design surface 2 can be sufficiently protected from damage. .

From this, it means that the transparency of the transparent coating 31 becomes better than before by reducing the film thickness of the transparent coating 31, but the design surface 2 is extremely good as described above. As it has a mirror finish,
Substantially no scratches or irregularities in the finish of the design surface 2 are substantially visible.

Further, since this transparent film 31 has good corrosion resistance and adhesion, it is difficult for rust to occur on the design surface 2, the bright state at this place can be maintained for a long time, and the stain resistance is also good. Therefore, there is also an advantage that stains attached to the surface of the transparent coating film 31 can be easily removed and can be easily maintained in a bright state.

Therefore, in the automobile wheel 1 of this embodiment, the design surface 2 is a very good finished surface, and the transparent coating 31 formed on the design surface 2 also has a very good transparency. Because there is
The excellent bright state of the design surface 2 can be clearly seen from the outside of the transparent coating 31, and the appearance of the automobile wheel 1 becomes extremely good.

The transparent coating 31 may be formed by using an organic paint, but by using a so-called inorganic paint or a coating composition containing an inorganic material as a main component, an aluminum alloy automobile wheel can be obtained. There is an advantage that the occurrence of thread rust can be prevented.

As described above, in this embodiment, an aluminum alloy casting is targeted, and both the preliminary finishing step and the mirror finishing step are performed by wet buffing. The fine pores and pinholes formed on the surface of the product are closed and the diameter is reduced by the contact friction of the buff, which reduces defects on the finished surface of the casting and improves the finish. There is an advantage that the surface can be obtained.

The present invention can be similarly applied to automobile wheels made of not only cast products but also forged products, and the material of the target product is not limited to aluminum alloys, but copper alloys and other mirror surfaces. Any metallic material to be finished can be similarly used.

[0120]

As described above, according to the first aspect of the invention, since the buff is used, the buff can flexibly polish its surface according to the irregularities of the surface of the molded product.

Further, this buffing uses a polishing liquid,
Since it is so-called wet buffing, the rotation speed of the buff is slower than that of dry buffing that does not use a polishing liquid, so that the buff deformation can follow the unevenness of the surface well. , The surface is surely polished regardless of the presence of irregularities.

Moreover, since the peripheral surface of the buff is brought into contact with the molded product, the contact area between the buff and the molded product is linear contact and the area is small. Since the abrasive grains can be supplied and foreign matters such as buff residue can be effectively eliminated, a good finished surface can be obtained by buffing the surface of the die-molded product using a machine.

Therefore, since the finish of the design surface which is the base of the transparent film becomes good, there is no contradiction that the appearance of the design surface is deteriorated as in the conventional case even if the transparency of the transparent film is improved, and it is suitable for automobiles. The appearance of the wheel can be improved.

[Brief description of drawings]

FIG. 1 is a process explanatory diagram of an entire surface finishing process.

FIG. 2 is an explanatory diagram of a polishing process in a preliminary finishing process and a mirror finishing process.

FIG. 3 is a top view for explaining a vertical axial wet buffing process.

4 is a sectional view taken along the line AA of FIG.

FIG. 5 is a top view for explaining a horizontal axis wet buffing process.

6 is a cross-sectional view taken along line CC of FIG.

FIG. 7 is an explanatory diagram of a contact state of a buff with a spoke portion in a horizontal axis wet buffing process.

FIG. 8 is an explanatory diagram of an electrolytic composite vertical shaft wet buffing process in a BB cross section of FIG. 3;

FIG. 9 is a cross-sectional view of a design surface on which a transparent film is formed.

[Explanation of symbols]

 1 Wheel material for automobiles 2 Design surface 23a, 23b Buff 24a, 24b Circumferential surface 31 Transparent coating

Claims (3)

[Claims] 1. A method for manufacturing an automobile wheel, which is made of a molded metal material and has a transparent coating formed on a design surface in a bright state, comprising: A method for manufacturing an automobile wheel, which comprises bringing a peripheral surface of a buff into contact with the design surface to bring it into a bright state while supplying a polishing liquid containing abrasive grains. 2. The method for manufacturing an automobile wheel according to claim 1, further comprising a transparent film to be formed on the design surface in a bright state.
A method for manufacturing an automobile wheel, which comprises forming a composition containing an inorganic material as a main component. 3. The method for manufacturing an automobile wheel according to claim 1, wherein shot peening processing is performed on the design surface prior to the surface finishing step.