JP2000026996A - Aluminum pats and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain sufficient lubricity over the whole body of the surface of an anodized layer by forming reticulated cracks on an anodized layer formed on the surface of an aluminum alloy and impregnating a lubricant into the cracks. SOLUTION: On the parts surface of an aluminum alloy, an anodized layer is formed. After the formation of the anodized layer, reticulated cracks are positively formed on this anodized layer, and oil and a solid lubricant are impregnated into this cracks. The formation of the cracks is executed by executing heat treatment by suitable heating, air cooling or the like. Or, by vanishing working of pressing a spherical or cylindrical pressing tool against the object to be worked and compressing it, the reticulated cracks are formed on the anodized layer. In the case the aluminum alloy is incorporated with copper, at the time of forming the anodized film by anodic oxidation treatment, bubbles are generated in the film. With the bubbles as the starting point, the reticulated cracks can efficiently be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aluminum component having an alumite layer formed thereon and a method for producing the same.

[0002]

2. Description of the Related Art It is known to form an alumite film on the surface of an aluminum part by an anodizing method in order to increase the corrosion resistance and hardness of the part. This alumite treatment is performed by immersing an aluminum component in an electrolytic solution tank, connecting the component to the anode side, and performing an electrolytic action. Many pinholes are formed in such an alumite film from the surface toward the inside. These pinholes are formed in accordance with the temperature of the electrolytic solution. When the temperature is high, many pinholes are formed and the alumite film becomes porous.

On the other hand, a piston sliding surface of a cylinder block of an internal combustion engine is required to have heat resistance and wear resistance and to have sufficiently high strength and lubricity at high temperatures.
This cylinder block is usually a low-pressure cast product or a high-pressure cast product of an aluminum alloy, that is, a die-cast product, and a piston slides along an inner surface of a cylindrical cylinder bore or an inner surface of a sleeve press-fitted or cast into the cylinder bore. In order to improve the wear resistance and lubricity of the piston sliding surface of such a piston or a cylinder block, it has been proposed that the sliding surface be anodized to impregnate the pinholes thereof with a solid lubricant. Kaisho 61-5344
No. 4, JP-A-5-25696).

[0004]

However, the pinholes of the alumite film are fine (pore diameter of about 0.01 μm).
m), lubricating oil or solid lubricant cannot be sufficiently impregnated, lubricating properties cannot be maintained for a long time, and as a result, wear resistance cannot be maintained.
In addition, the lubrication of the entire sliding surface cannot be sufficiently enhanced with the scattered pin holes.

[0005] On the other hand, in an internal combustion engine, a vertical groove may be formed in the alumite film in the sliding direction of the piston due to combustion explosion or side pressure of the piston, and oil may enter the vertical groove. Conceivable. However,
Even if such a vertical groove is impregnated with oil, the entire sliding surface cannot be sufficiently covered, and the lubricating property cannot be sufficiently improved.

The present invention has been made in consideration of the above points, and has as its object to provide an aluminum component capable of sufficiently improving the wear resistance and lubricity of the entire sliding surface and a method of manufacturing the same.

[0007]

In order to achieve the above object, the present invention is characterized in that an alumite layer is formed on the surface of a component made of an aluminum alloy, and a network-like crack is formed in the alumite layer. To provide aluminum parts.

According to this structure, a network-like crack is formed in the alumite layer. Therefore, by impregnating the crack with an oil or a solid lubricant, it is possible to obtain sufficient lubricity over the entire surface of the alumite layer. it can.

Further, in the present invention, an alumite forming step of forming an alumite layer on the surface of a component made of an aluminum alloy, and a crack forming step of forming a network-like crack in the alumite layer after the alumite forming step are performed. A method for producing an aluminum component, comprising:

According to this method, after the formation of the alumite layer, a step of positively forming a network-like crack in the alumite layer is provided, and a network-like crack is formed on the surface of the aluminum component. Oil and solid lubricants can be impregnated.

In a preferred configuration example, the crack forming step comprises a heat treatment.

According to this structure, the above-mentioned mesh cracks are formed in the alumite layer by performing appropriate heat treatment such as heating and air cooling.

According to another preferred configuration example, the crack forming step comprises a burnishing process.

According to this configuration, a mesh-like crack is formed in the alumite layer by the burnishing process of pressing and compressing the workpiece using the spherical or cylindrical pressing tool.

In a further preferred configuration example, the aluminum alloy contains copper.

According to this configuration, since the aluminum alloy contains copper, bubbles are generated in the alumite film when the alumite film is formed by the anodic oxidation treatment.
In the crack forming step after the alumite forming step, network-like cracks are efficiently formed in the alumite film starting from the bubbles.

[0017]

FIG. 1 is a schematic configuration diagram of an internal combustion engine to which the present invention is applied. The four-stroke internal combustion engine 1 is configured by connecting a cylinder head 2, a cylinder block 3, and a crankcase 4 formed by low-pressure casting or die-casting of an aluminum alloy. An intake pipe 5 is connected to one side of the cylinder head 2 and an intake opening 5a at an end thereof.
Is fitted with an intake valve 6. An exhaust pipe 7 is connected to the other side of the cylinder head 2, and an exhaust valve 8 is attached to an exhaust opening 7 a at an end thereof. The piston 9 slides along the inner surface of the cylinder bore of the cylindrical cylinder block 3. A piston ring 10 is mounted on a side surface of the piston 9.
The piston 9 includes a piston pin 11, a connecting rod 12
And a crankshaft 14 via a crank arm 13.

The inner surface of the cylinder bore, that is, the cylindrical inner surface of the cylinder block 3 serving as the sliding surface of the piston 9 is of a type in which a sleeve (not shown) made of an aluminum alloy is mounted by press-fitting or casting. Are directly in contact with the cylindrical inner surface of the cylinder block 3. In this embodiment, the alumite treatment is applied to the inner cylindrical surface to reinforce the sliding surface of the piston in any type.

FIG. 2 is a configuration diagram of the alumite processing apparatus according to the embodiment of the present invention. In this embodiment, the inner surface of the sleeve 17 serving as a piston sliding surface mounted on the cylinder block 3 is anodized. The cylinder block 3 is mounted on a support 16 via a gasket 15. The gasket 15 is a sealing material for preventing leakage of the electrolyte and functions as an insulating material for allowing more electrolytic current to flow from the cylinder bore surface. An electrode rod 29 is inserted into the sleeve 17 in the axial direction. The electrode rod 29 is connected to the negative electrode side of a DC power supply 31 converted from an AC power supply 30 to a DC through the rectifier 24 and the control circuit 25. The positive electrode side of the DC power supply 30 is connected to the cylinder block 3 on which the sleeve 17 is mounted. As a result, an anodic oxidation reaction occurs between the negative electrode side electrode rod 29 and the inner surface of the positive electrode side sleeve 17 opposed to the electrode rod 29 at an interval via the electrolytic solution, and the inner surface of the sleeve 17 as described later. Then, an alumite layer which is an anodized film is formed. The upper end of the sleeve 17 is an O-ring 18
Through the cover 19. On the cover 19,
An electrolyte circulation channel 20 is connected and communicates therewith. The lower end (not shown) of the support base 16 is also sealed, and the electrolyte 27 in the electrolyte tank 26 is fed by the circulation pump 28. The electrolyte flows between the sleeve 17 and the electrode rod 29 and circulates in the circulation channel 20. An electrolytic solution tank 26 is arranged in the middle of the circulation flow path 20, and a circulation pump 28 is provided.

On the circulation channel 20, a cooling device 32
Is provided. That is, the electrolytic solution tank 26, the circulating pump 28, the conduit between the electrolytic solution tank 26 and the circulating pump 28, the alumite treatment current passing portion between the sleeve 17 and the electrode rod 29, In any part of the pipeline between the pump 28 and the current passage for alumite treatment, and the pipeline between the current passage for alumite treatment and the electrolyte bath 26, cooling is performed in series or parallel in the flow direction of the treatment liquid. The device 32 is arranged. The cooling device 32 may be, for example, a heat exchanger including a cooling coil 23 that forms an evaporator of a refrigerator to which the refrigerant pipe 22 is connected. Alternatively, cooling water may be circulated through the cooling coil 23. Furthermore, for example, a cooling fin is attached to a pipeline in the middle of the circulation flow path 20, and an air-cooled cooling device that cools with a fan is provided.
After being diverted from the middle of the circulation channel 20 and passed through a cooling device arranged in parallel with the current passage portion for alumite treatment, it may join the circulation channel 20.

For example, a cooling coil through which cooling water passes is immersed in the electrolytic solution tank 26, a water jacket for circulating cooling water is provided in the circulation pump 28 itself, or a cooling water circulation is provided inside the electrode rod 29. The cooling device 32 may be configured such that a cooling jacket is provided. Further, the cooling water may be circulated to the water jacket 3A around the cylinder bore of the cylinder block 3.

A temperature sensor 21 is mounted near the outlet side of the sleeve 17 in the circulation channel 20 to detect the temperature of the electrolyte. The temperature sensor 21 is connected to, for example, a control device (not shown), and when the temperature rises above a set temperature, the cooling device 3
2 is driven or its coolant (cooling water) flow rate is increased to suppress the temperature rise of the electrolytic solution and perform feedback control so as to maintain the temperature at a constant temperature. Along with the temperature control by the cooling device 32, the drive of the circulation pump 28 is controlled to increase the circulation flow rate of the electrolyte when the temperature rises, thereby preventing the reaction speed from decreasing due to the temperature rise due to heat generation in the anodic oxidation reaction. You may. Further, the DC power supply 31 may be controlled to increase the voltage when the temperature rises, thereby increasing the reaction speed.

The cover 19 on the outlet side of the sleeve 17
, The upper side of the sleeve 17 may be completely sealed, a circulation passage may be formed in the center of the electrode rod 29, and the electrolyte may be returned to the electrolyte bath 26 through the circulation passage. In this case, the cooling device 32 can be provided on a pipe on the suction side or the discharge side of the circulation pump 28 to cool the electrolyte.

FIG. 3 is a flowchart showing the steps of manufacturing a sleeveless cylinder block. First, a cylinder block is formed by die casting of an aluminum alloy (step S1). As the material of the cylinder block, any one of ADC1 to ADC14 of the materials shown in Table 1 below is used.

In order to increase the wear resistance, a metal carbide such as SiC or another intermetallic compound may be mixed in addition to the components shown in the table.

[0026]

[Table 1]

After die casting, annealing is performed to remove residual stress (step S2). As an example, the annealing is performed at about 250 ° C. for 4 hours. Next, machining is performed on each part of the cylinder block to adjust its shape (step S3). Subsequently, burnishing is performed on the cylinder bore (step S4), and further, boring processing is performed (step S5), and the inner surface of the cylinder bore, which is the piston sliding surface, is finished by a compression pressing action.
The finishing by the burnishing in step S4 may be omitted.

Next, alumite treatment is performed on the inner surface of the cylinder bore that has been subjected to the finishing process to reinforce the inner surface of the cylinder bore (step S6). Details of the alumite processing conditions will be described later.

Next, the alumite film is subjected to a heat treatment for crack formation (step S7). This heat treatment is performed, for example, by heating the entire cylinder block at 250 ° C. for 30 minutes, and then air cooling. As a result of this heat treatment, cracks are formed in the alumite film in a network-like manner as described later.
This crack occurs because the base aluminum alloy, which is the lower layer of the alumite coating, has a larger thermal expansion coefficient than the alumite coating, so that the alumite coating cannot follow the expansion of the base metal. By forming such cracks, the cracks can be impregnated with oil or a solid lubricant, the frictional resistance of the alumite film surface during sliding of the piston is reduced, and the wear resistance of the sliding surface is improved. .

Next, burnishing is performed to further form a crack on the inner surface of the cylinder bore (step S).
8). The cracks due to this burnishing process have a higher hardness of the alumite film than the aluminum alloy of the base material and a low ductility. Therefore, when pressure is applied to the film by burnishing, even if the base material extends, the film may follow and extend. Cracks cannot be made. In this case, when copper is contained in the base material, the strength of the base material is increased by performing a heat treatment such as T6 treatment or T7 treatment. In such an aluminum alloy containing copper for strengthening the base material, fine bubbles are easily generated in the alumite film formed by the anodic oxidation treatment. Therefore, by performing heat treatment or burnishing after the alumite treatment, cracks can be effectively formed starting from these bubbles.

FIG. 4 shows the shape of such a crack. As shown in FIG. 4A, a network-like crack of about 0.1 to 5 mm is formed on the surface of the alumite film. This crack has a width of 0.1 to 10 as shown in FIG.
It is a size of about 30 to 50 μm with a depth of about 30 μm. By impregnating such mesh-like cracks with a lubricating oil or solid lubricant by applying or the like, the lubricating action is enhanced as compared with pinholes scattered in dots or cracks formed in one direction. Occasionally, the friction resistance of the alumite film surface is greatly reduced, and the wear resistance of the sliding surface is greatly improved. As the solid lubricant, for example, amorphous fluororesin, molybdenum disulfide, tungsten disulfide, graphite, carbon fluoride, boron nitride, and the like can be used.

One example of burnishing conditions for forming such a crack is as follows. The cylinder radius before processing is r, the cylinder radius after processing is r + Δr, and the strain generated on the inner surface of the cylinder by processing is ε = Δr / r. Δr × 2 is called a burnish amount. As an example, the range of ε is 0.00
01 to 0.005, and the amount of burnishing on the inner surface of the cylinder having a size of φ70 before processing is 0.01 to 0.315 mm.

Cracks are formed in the alumite film by the above-described heat treatment (Step S7) and burnishing (Step S8). The heat treatment (step S
7) and burnishing (step S8) may be performed only on one of them and the other may be omitted.

Subsequently, the surface of the alumite film on which the crack has been formed is honed to finish the surface (step S9). Thus, the manufacturing process of the sleeveless cylinder block including the alumite treatment on the inner surface of the cylinder bore is completed.

FIG. 5 is a flow chart showing the steps for manufacturing a cylinder block in which a sleeve is cast. First,
An aluminum alloy pipe material serving as a sleeve material is prepared (step S10). As the sleeve material, any of the materials shown in Table 2 below can be used.

In order to increase the abrasion resistance, a metal carbide having a high hardness such as SiC or other intermetallic compounds may be mixed in addition to the components shown in the table.

[0037]

[Table 2]

Next, the pipe material is subjected to a predetermined solution treatment and age hardening treatment by T6 treatment to increase the strength (step S11). Subsequently, the pipe material is machined into a sleeve shape (step S12). Further, T6 processing is performed on the sleeve to increase the strength (step S13). Table 3 below shows the T6 treatment conditions for this sleeve material.

[0039]

[Table 3]

The sleeve thus formed is cast into a cylinder block by die casting (step S14). The materials shown in Table 1 are used for the material of the cylinder block, as in the case of the above-mentioned sleeveless type. After manufacturing the cylinder block in which the sleeve is cast in this way, each processing of steps S2 to S9, that is, the residual stress removal is performed on this cylinder block in the same manner as in the above-described sleeveless flow of FIG. For annealing (step S2), machining of each part of the cylinder block (step S3), burnishing of the cylinder bore (step S4), boring of the cylinder bore (step S5), alumite treatment of the inner surface of the cylinder bore (step S6), crack formation (Step S7) and burnishing (step S7)
8) and finishing honing (step S9)
Is applied. As described above, the manufacturing process of the cylinder block in which the sleeve is cast including the alumite treatment of the inner surface of the sleeve is completed. FIG. 6 is a flowchart showing a process of manufacturing a cylinder block for press-fitting a sleeve. As in the sleeveless case described above, the cylinder block is formed by die casting (step S1), the residual stress is removed (step S2), and each part is machined to form a cylinder block (step S3).

On the other hand, as in the case of the sleeve casting described above, the aluminum alloy pipe material (step S10) is subjected to T6 processing (step S11), machined (step S12), and further subjected to T6 processing (step S13). 2.) Make the sleeve.

Using the separately manufactured cylinder block and sleeve, the sleeve is pressed into the cylinder bore of the cylinder block (step S15). Thereafter, in the cylinder block into which the sleeve has been press-fitted, similarly to the above-described sleeveless flow in FIG. 3 and the casting flow in FIG. 5, each processing in steps S3 to S9, that is, machining of each part of the cylinder block (Step S3), burnishing of the cylinder bore (Step S4), boring of the cylinder bore (Step S5), alumite treatment of the inner surface of the cylinder bore (Step S6), heat treatment for forming cracks (Step S5)
7), burnishing (step S8), and finishing honing (step S9). As described above, the manufacturing process of the cylinder block for press-fitting the sleeve including the alumite treatment on the inner surface of the sleeve is completed.

In each of the embodiments shown in FIGS. 3, 5 and 6, the cylinder block 3 is formed by die casting which is a high pressure casting. However, gravity casting or other low pressure casting may be used instead of the die casting. In that case, any of the materials shown in Table 1 from AC2A to AC4D is used as the material of the cylinder block 3.

FIG. 7 is a flowchart of a piston manufacturing process of the internal combustion engine according to the embodiment of the present invention. First,
A piston material having a rough piston shape is formed by casting or forging an aluminum alloy (step S30).
As the aluminum alloy used as the piston material, any of the alloys shown in Table 4 below can be used.

Incidentally, in order to increase the wear resistance, in addition to the components shown in the table, a metal carbide of high hardness such as SiC or other intermetallic compound may be mixed.

[0046]

[Table 4]

Next, in order to increase the strength, T6 or T7
Is performed (step S31). The T7 treatment is a heat treatment in which the aging treatment after the solution treatment is lengthened and the stabilization is enhanced, as compared with the T6 treatment described above.

Next, each part of the piston is machined (step S32). In this machining process, pin holes for inserting the piston pin, ring grooves for mounting the piston ring, and holding the piston in a holding jig that holds the piston in the electrolytic solution during alumite processing or plating processing described later Processing is performed to obtain the shape to be formed.

Subsequently, an alumite treatment described later is performed on the outer peripheral surface of the piston including the pin hole and the ring groove of the piston (step S33). Next, machining of the outer surface of the piston is performed (step S34). In this outer surface processing step, the shape of the outer peripheral surface of the piston is adjusted. afterwards,
Finishing is performed according to the accurate piston-shaped cam profile (step S35). Finally, the center boss formed on the top surface of the piston for piston processing is deleted.

FIG. 8 is a block diagram of a stationary bath for performing alumite treatment of the piston. The alumite treatment of the piston
In the alumite processing apparatus shown in FIG. 2 described above, a cylindrical electrode tube is disposed instead of the cylinder block 3, and a piston support rod is disposed inside the support base 16 instead of the electrode rod 29. On the inside, instead of the electrode rod 29, a piston is placed on the piston support rod with the head part upward, and the electrode tube is connected to the negative side of the DC power supply 30 and the piston is connected to the positive side of the DC power supply 30, respectively. The present invention may be embodied in such a manner that the electrolytic solution is circulated between the outer peripheral skirt and the electrode tube. Alternatively, a stationary bath in which a piston is immersed in an electrolyte bath as shown in FIG. 8 may be used. As shown in the drawing, an electrolytic solution 51 is accommodated in an electrolytic solution tank 50, and a piston 53 held by a holder 52 is immersed in the electrolytic solution. This holder 52 holds two pistons 53 in two upper and lower holding frames 52a, respectively, and shows a state in which a total of four pistons 53 are held in the drawing. A plurality of such holders 52 may be further immersed in the electrolyte bath 50 in a direction perpendicular to the drawing. Cathode plates 54 are arranged on both sides of the piston 53. The holder 52 for holding the piston is connected to the anode of the DC power supply 55, and the cathode plate 54 is connected to the cathode of the DC power supply 55.
With such a configuration of the stationary bath (electrolyte bath 50), an alumite film is formed on the surface of the piston 53 by anodic oxidation.

In FIG. 8, reference numeral 100 denotes a radiator for cooling the electrolytic solution, 101 denotes a discharge nozzle for discharging a cooling solution of the electrolytic solution, 102 denotes a circulation path for cooling the electrolytic solution, and 103
Is a circulation pump. The low-temperature and low-pressure liquid-phase refrigerant passing through an expansion valve (not shown) is passed through the low-pressure line 104 to the radiator 10.
It is guided to the evaporating coil 104a within zero. Since the temperature of the alumite-treated layer of the piston 53 is prevented from increasing during the alumite treatment, a decrease in the hardness of the alumite layer can be prevented. The temperature is detected by a temperature sensor 105 provided in the lower part of the bathtub 50 or on the piston 53, and the temperature of the control device 10 is controlled.
The higher the temperature, the larger the flow rate of the electrolyte flowing through the circulation path or the higher the discharge pressure of the refrigerant of the compressor (not shown), so as to prevent the temperature of the alumite treatment layer of the piston 53 from increasing as shown in FIG. Alternatively, the temperature of the downstream portion of the radiator 100 may be detected by the temperature sensor 105 ′, and this temperature may be controlled to 30 ° C. or less. Thus, it is possible to more reliably prevent the temperature of the alumite-treated layer from being raised during the alumite treatment, and to more reliably prevent the hardness of the alumite layer from decreasing. Also,
It is preferable to arrange the piston pin holes in the discharge direction of the cooling liquid from the discharge nozzle 101. Further, the radiator 100 may be cooled with groundwater or may be air-cooled.

It should be noted that the piston 53 is generally not subjected to finishing after the alumite treatment. In that case, in consideration of an increase in size due to the alumite treatment, in each machining step shown in FIG. Is applied.

FIG. 9 is a sectional view of a piston ring mounted on the piston. This piston ring includes a ring main body 56 and a covering portion 57 formed by performing a surface treatment on an outer peripheral surface that is a sliding surface thereof. Table 5 below shows an example of the ring material of the ring main body 56, and Table 6 shows an example of the treatment of the covering portion 57 obtained by surface-treating the ring material.

[0054]

[Table 5]

[0055]

[Table 6]

In any of the processing examples shown in Table 6, when the coating portion 57 slides on the inner peripheral surface of the cylinder bore subjected to the alumite treatment of the above-described embodiment, it has good compatibility with the inner peripheral surface of the cylinder bore. In addition, the wear of the alumite treatment layer on the inner peripheral surface of the cylinder bore can be reduced. In particular, cracks are formed as described above after alumite treatment, and when a crack portion is impregnated with a lubricating oil or a solid lubricant, or as described below, mixed acid etching of an intermetallic compound such as Si particles exposed on the inner peripheral surface of the cylinder bore is performed. The effect is remarkable in the case where the alumite treatment is applied to the material removed by the treatment, and the recesses are more positively formed in addition to the cracks so that the lubricating oil or the solid lubricant is more impregnated.

Also, as described below, in the case of an alumite film in which Si particles, metal carbide such as SiC having high hardness, and other intermetallic compounds are exposed on the surface, the hardness of the alumite film side increases. As a result, not only the abrasion of the inner peripheral surface of the cylinder bore is reduced, but also the adaptability to the coating of the coating portion 57 can be improved, and the sealing performance of oil and combustion gas can be improved.

Even if the ring body 56 is made of any of the materials shown in Table 5, the surface of the ring body 56 is subjected to alumite treatment and cracks are formed on the surface by heat treatment or the like. While being kept in the ring groove of the piston 9 in which the concave portion is formed due to the removal of the compound, it constantly collides with the ring groove surface, but lubricating oil or solid lubricant is applied to the crack portion or the concave portion of the ring groove surface. Can be impregnated, ring groove surface, ring body 5
6 can be prevented from being hit and worn. Also,
The ring main body 56 can prevent abrasion of the ring groove surface even when Si particles or an intermetallic compound such as high-hardness SiC is contained in the ring groove exposed on the surface. In any case, by adopting the ring material of the ring main body 56 exemplified in Table 5, the adaptability between the ring groove surface and the ring main body 56 is improved, and oil or combustion gas passes through the back surface of the ring. Can be prevented.

FIG. 10 shows an alumite processing process (step S6) in each of the cylinder block manufacturing flows (FIGS. 3, 5, and 6) and an alumite processing process (step S6) in the piston manufacturing flow (FIG. 7).
It is a detailed flowchart of 33).

First, a degreasing treatment is performed to remove oil on the surface of the base material of the aluminum alloy (step S1).
6). This degreasing treatment includes (1) an acid degreasing method and (2) an alkali degreasing method, and is performed by any one of the degreasing methods. Table 7 below shows the degreasing conditions of each degreasing method.

[0061]

[Table 7]

When the degreasing process is completed, a water washing process is performed to remove the degreasing agent (Step S17).
Next, as necessary, an alkali etching process (Step S18) or a mixed acid etching process (Step S2)
0) is performed, and the base material surface is etched. After each etching process, a water washing process for removing the etchant is performed (step S1).
9, step S21). The etching conditions for the alkaline etching are shown in Table 8 below, and the etching conditions for the mixed acid etching are shown in Table 9.

[0063]

[Table 8]

[0064]

[Table 9]

In the above alkaline etching, the surface of the base material is etched leaving silicon (Si) particles and intermetallic compound particles scattered in the base material of the aluminum alloy, and particles of silicon and intermetallic compounds are projected on the surface. The surface of the base material is removed. On the other hand, in the mixed acid etching, silicon particles and intermetallic compound particles are etched, and concavities are formed on the surface of the base material, where silicon particles and intermetallic compounds are removed.

In such an etching treatment, when there is a possibility that the surface is not sufficiently removed in the degreasing treatment in the preceding step, both the alkali etching and the mixed acid etching are performed to completely remove the surface layer. It is desirable to increase the reliability of the anodic oxidation treatment performed in a later step.

The dent in the trace from which silicon particles and intermetallic compounds have been removed by mixed acid etching can be used as a dent for impregnating oil or a solid lubricant.

Next, the surface of the base material thus etched is subjected to anodic oxidation treatment to form an alumite film (step S22). This anodizing treatment is performed using, for example, the alumite treatment apparatus shown in FIG.
Examples of the alumite treatment are shown in Table 10 below.
(A) is an example in which the alumite treatment is performed on the inner surface of the cylinder bore of the sleeveless cylinder block including the ADC 12 in Table 1 described above, and (B) is an example in which A in Table 2 described above is used.
This is an example in which alumite treatment is performed on the inner surface of the sleeve of a cylinder block into which a sleeve made of 6061 is cast. (C) is an example in which the alumite treatment is performed on the piston made of the alloy 5 in Table 4 described above.

[0069]

[Table 10]

As shown in the table, oxalic acid and citric acid were added in addition to sulfuric acid as an electrolytic solution. Sulfuric acid has a strong film dissolving power and dissolves this anodic oxide film after the anodic oxide film is formed by electrolysis. For this reason, the pinholes formed on the oxide film surface during the anodic oxidation treatment are dissolved and enlarged, and as a result, the surface hardness decreases. However, by adding oxalic acid or citric acid as in this example, the film dissolving power of sulfuric acid is reduced, and the film hardness can be increased. In this case, when the entire electrolytic solution is oxalic acid or citric acid, the electric conductivity of the electrolytic solution, that is, the charge transport function is reduced, and the reaction rate is reduced. However, by including an appropriate amount of sulfuric acid in the electrolytic solution, the electric conductivity is increased, the processing time required to obtain an alumite film of a predetermined thickness is shortened, and the alumite formed due to a small proportion of sulfuric acid is formed. It is possible to prevent the hardness of the film from decreasing due to the dissolving action of the film.

FIG. 13 is a diagram showing the effect of bath temperature on hardness with constant electrolysis conditions. In the figure, a shows current density of 3 A / dm ² (ampere / 100 cm ² ), current waveform: DC, electrolysis time: 20 in A6061 aluminum alloy.
The data are for the case where the alumite treatment was carried out under the conditions of a sulfuric acid concentration: 20 g / l and an oxalic acid + citric acid concentration: 40 g / l, and Hv 380 or more was obtained at a bath temperature of 30 ° C. or lower. In other aluminum alloys of Table 1 and Table 2,
By performing the alumite treatment while controlling the bath temperature to about 30 ° C. or less, the alumite film has a hardness of H which can provide practically sufficient wear resistance as the inner peripheral surface of the cylinder on which the piston slides.
v380 or more. Further, FIG. 2B shows data obtained when the concentration of the sulfuric acid in the electrolytic solution was 20 g / l, the concentration of oxalic acid + citric acid was 0 g / l, and the other conditions were the same as in the case of FIG. Indicates that Hv 380 or more can be obtained.

After the alumite film is formed by the anodic oxidation treatment as described above, a washing treatment is performed to remove the electrolytic solution (step S23), and a secondary electrolytic treatment is performed (step S2).
4). In this secondary electrolytic treatment, a solid lubricant is deposited by electrolytic action on the bottoms of the pinholes formed innumerably on the surface of the alumite film and deposited, and the inside of the pinholes is filled with the solid lubricant from the bottoms. . Thereby, the lubricity of the film surface is further improved, and the wear resistance is further improved.

Subsequently, the electrolyte of the solid lubricant is removed by washing with water (step S25), and the moisture is removed by air blow to dry the cylinder block, thereby completing the alumite treatment (step S26).

FIGS. 11 and 12 are cross-sectional views of the surface of the base material in each step of the above-described cylinder block and piston manufacturing process. FIG. 11 shows, in order, a flow in which the anodizing process is performed without the etching process after the degreasing process. FIG. 12 shows, in order, a flow in which alumite treatment is performed after mixed acid etching is performed.

FIG. 11A shows the state after the degreasing treatment. Silicon particles, metal carbides such as SiC, and other intermetallic compound particles 41 are scattered in the base material 40 made of an aluminum alloy. Dirt such as oil on the surface 40a of the base material 40 is removed by degreasing. After the degreasing treatment, an alumite treatment is performed, and as shown in FIG.
An alumite film 42 is formed on the surface 0. Silicon particles 41 are also scattered in the alumite film 42. Bubbles 43 are generated in the alumite film 42. As described above, the bubbles 43 are often generated when the base material 40 contains a copper component.

Subsequently, heat treatment or burnishing is performed, and cracks 44 are formed in the alumite film 42 as shown in FIG. Next, as shown in FIG. 3D, honing is performed to finish the surface 42a of the alumite film 42.

FIG. 12A shows a state after the mixed acid etching process. The silicon particles 41 on the surface of the base material 40 are removed by etching to form a dent 45. In this state, an alumite treatment is performed, and as shown in FIG.
An alumite film 42 is formed on the surface of the base material 40. A depression 45 remains on the surface of the alumite film 42. Subsequently, heat treatment or burnishing is performed to form cracks 44 in the alumite film 42 as shown in FIG. Next, as shown in FIG. 3D, a honing process is performed and the surface 42a of the alumite film 42 is formed.
Is finished. In this case, the alumite film 42
Since the depressions 45 are formed by the mixed acid etching together with the cracks 44, the impregnation amount of the oil or the solid lubricant can be increased.

When the acid-resistant intermetallic compound particles 41 are exposed on the surface, they are not eluted by mixed acid etching, but are exposed on the surface of the alumite film 42 after the alumite treatment.
Alternatively, the silicon particles 41 that are not exposed on the surface of the alumite film 42 are exposed on the surface of the alumite film 42 by honing. As described above, the intermetallic compound particles 4 having a high hardness such as silicon particles and SiC are obtained after all the processes.
When 1 is exposed on the surface, the average hardness of the surface of the alumite film 42 is increased, and the wear resistance is improved.

Further, in the case of performing alkali etching, heat treatment or burnishing after the degreasing treatment and then honing, the silicon particles 4 are subjected to the alkali etching.
Since the surface of the base material 40 is removed except for 1, silicon particles protrude from the surface of the alumite film 42, and the silicon particles are exposed on the surface of the alumite film 42 even after honing in the final step. Further, since silicon particles hidden under the surface of the alumite film 42 are also exposed by the honing, the average hardness of the surface of the alumite film 42 is increased, and the wear resistance is improved.

[0080]

As described above, in the present invention, since network-like cracks are formed in the alumite layer, by impregnating the cracks with oil or a solid lubricant, sufficient cracks can be obtained over the entire surface of the alumite layer. Lubricity can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an internal combustion engine to which the present invention is applied.

FIG. 2 is a configuration diagram of an alumite processing apparatus according to an embodiment of the present invention.

FIG. 3 is a flowchart of a sleeveless cylinder block manufacturing process.

FIG. 4 is an explanatory view of a crack.

FIG. 5 is a flowchart of a sleeve casting cylinder block manufacturing process.

FIG. 6 is a flowchart of a sleeve press-fit cylinder block manufacturing process.

FIG. 7 is a flowchart of a piston manufacturing process.

FIG. 8 is a configuration diagram of a still bath in which a piston is anodized.

FIG. 9 is a sectional view of a piston ring according to the embodiment of the present invention.

FIG. 10 is a flowchart of an anodizing process.

FIG. 11 is a sectional view sequentially showing a manufacturing process of the aluminum component.

FIG. 12 is a sectional view sequentially showing another manufacturing process of the aluminum component.

FIG. 13 is a graph showing the effect of bath temperature on the hardness of alumite.

[Explanation of symbols]

1: internal combustion engine, 2: cylinder head, 3: cylinder block, 4: crankcase, 5: intake pipe, 5a: intake opening, 6: intake valve, 7: exhaust pipe, 7a: exhaust opening,
8: exhaust valve, 9: piston, 10: piston ring, 1
1: piston pin, 12: connecting rod, 13: crank arm, 14: crankshaft, 15: gasket, 16:
Support stand, 17: sleeve, 18: O-ring, 19: cover, 20: circulation channel, 21: temperature sensor, 22: refrigerant pipe, 23: cooling coil, 24: rectifier, 25: control device, 26: electrolyte Tank, 27: electrolyte, 28: circulation pump, 29: electrode rod, 30: AC power supply, 31: DC power supply,
32: cooling device, 40: base material, 41: silicon particles, 4
2: alumite film, 43: bubble, 44: crack, 4
5: recess, 50: electrolytic solution, 51: electrolytic solution, 52: holder, 53: piston, 54: cathode plate, 55: DC power supply,
56: ring main body, 57: covering part.

Claims (5)

[Claims] 1. An aluminum part, wherein an alumite layer is formed on the surface of a part made of an aluminum alloy, and a network-like crack is formed in the alumite layer. 2. An alumite forming step for forming an alumite layer on the surface of a component made of an aluminum alloy, and a crack forming step for forming a network-like crack in the alumite layer after the alumite forming step. Manufacturing method of aluminum parts. 3. The method according to claim 2, wherein said crack forming step comprises a heat treatment. 4. The method according to claim 2, wherein said crack forming step comprises a burnishing process. 5. The method according to claim 2, wherein the aluminum alloy contains copper.