JP2000027700A - Cylinder block of internal combustion engine - Google Patents

Abstract

(57) [Problem] To provide a cylinder block of an internal combustion engine in which an anodic oxide film is formed corresponding to a temperature distribution and a pressure distribution on an inner surface of a cylinder bore to sufficiently enhance wear resistance and achieve smooth sliding operation. I do. SOLUTION: A cylinder bore 60 in which a piston slides is provided, a cylinder head is mounted on one end of the cylinder bore, and a crank chamber for accommodating a crankshaft is provided on the other end. In a cylinder block of an internal combustion engine in which an intake port and an exhaust port are provided in a cylinder head and an anodic oxide film is formed on an inner surface of the cylinder bore, the anodic oxide film has a thickness on the cylinder head side with respect to an axial direction of the cylinder bore. Is thicker than the thickness on the crank chamber side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder block of an internal combustion engine, and more particularly to a cylinder block of an internal combustion engine having an anodized film formed on an inner surface of a cylinder bore.

[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.

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 of aluminum alloy or a high-pressure cast or die-cast product,
The piston slides along the inner surface of the cylindrical cylinder bore or the inner surface of the sleeve press-fitted or cast into the cylinder bore. In order to enhance the wear resistance and lubricity of the piston sliding surface of such a cylinder block, it has been proposed to treat the sliding surface with alumite (Japanese Patent Laid-Open No. 61-534).
44, JP-A-6-167243). When anodizing is performed on the cylindrical inner surface of the aluminum alloy base material of the cylinder block, according to the conventional anodizing method, the base material is placed in a stationary bath electrolyte containing an anodization electrolyte. A cylinder block or sleeve is immersed, an electrode on the cathode side is provided in the vicinity of the film formation part, the base material side is connected to the anode, and an anodic oxidation film is formed on the inner surface of the cylindrical cylinder bore of the aluminum alloy base material by the anodic oxidation reaction. It is formed.

Conventionally, no consideration has been given to such a positional film thickness distribution of the anodic oxide film on the inner surface of the cylinder bore.

[0005]

However, distribution of heat load and pressure is generated on the inner surface of the cylinder bore. That is, the inner surface of the cylinder bore has a higher heat load on the cylinder head side where the combustion chamber is formed than the crank chamber side, and also has a higher heat load on the exhaust port side than the intake port side on the cylinder head side. Also, due to the piston side load based on the explosive force and the inertial force, the pressure acting on the inner peripheral surface of the cylinder bore is larger on the side parallel to the crankshaft than on the side perpendicular to the crankshaft. In such a portion where the heat load or pressure is large, the portion is easily worn due to the sliding of the piston. Therefore, when an anodic oxide film is formed on the inner surface of the cylinder bore, the effect of the wear resistance is not sufficiently obtained, and the amount of wear is locally increased, so that a smooth sliding operation may be hindered.

The present invention has been made in consideration of the above points, and forms an anodic oxide film corresponding to the temperature distribution and the pressure distribution on the inner surface of a cylinder bore, thereby sufficiently increasing abrasion resistance and achieving a smooth sliding operation. To provide a cylinder block of an internal combustion engine.

[0007]

In order to achieve the above object, according to the present invention, there is provided a cylinder bore in which a piston slides, a cylinder head is mounted on one end of the cylinder bore, and a cylinder head is mounted on the other side. In a cylinder block of an internal combustion engine, an end portion is provided with a crank chamber for housing a crankshaft, an intake port and an exhaust port are provided in the cylinder head, and an anodic oxide film is formed on an inner surface of the cylinder bore. The present invention provides a cylinder block for an internal combustion engine, wherein the inner peripheral surface of the cylinder bore on the side parallel to the crankshaft is thicker than the inner peripheral surface of the cylinder bore on the side perpendicular to the crankshaft.

According to this configuration, the side pressure acting on the side surface parallel to the crankshaft due to the sliding of the piston corresponds to
Since the thickness of the anodic oxide film on the side where this lateral pressure acts is formed, sufficient wear resistance is secured over the entire circumference of the piston sliding surface, and high wear resistance is maintained over a long period of time to ensure smooth sliding operation. Is achieved.

Further, according to the present invention, there is provided a cylinder bore in which a piston slides, a cylinder head is mounted on one end of the cylinder bore, and a crank chamber for accommodating a crankshaft is provided on the other end. An intake port and an exhaust port are provided in the cylinder head, and in the cylinder block of the internal combustion engine in which an anodic oxide film is formed on the inner surface of the cylinder bore, the anodic oxide film is formed on the inner peripheral surface of the cylinder bore on the exhaust port side. A cylinder block for an internal combustion engine, wherein the thickness is larger than the thickness of the inner peripheral surface of the cylinder bore on the intake port side.

According to this structure, the thickness of the anodic oxide film on the exhaust port side where the heat load is large and the temperature is high from the intake port side is formed thick, so that the abrasion resistance is sufficient over the entire circumference of the piston sliding surface. , And maintain high wear resistance over a long period of time, and a smooth sliding operation is achieved.

Further, according to the present invention, there is provided a cylinder bore in which a piston slides, a cylinder head is mounted on one end of the cylinder bore, and a crank chamber for accommodating a crankshaft is provided on the other end. An intake port and an exhaust port are provided in the cylinder head, and in the cylinder block of the internal combustion engine in which an anodic oxide film is formed on an inner surface of the cylinder bore, the anodic oxide film is disposed in an axial direction of the cylinder bore. The thickness of the side,
A cylinder block for an internal combustion engine, characterized in that the cylinder block is thicker than the crank chamber side.

[0012] According to this configuration, the thickness of the anodic oxide film on the cylinder head side where the combustion chamber is formed and becomes high temperature is formed larger than the thickness of the anodic oxide film on the crank chamber side. Sufficient wear resistance is secured over the entire length in the axial direction, and high wear resistance is maintained over a long period of time, and smooth sliding operation is achieved.

[0013]

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 cylindrical inner surface (cylinder bore) of the cylinder block 3 serving as a sliding surface of the piston 9 has 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 performed on the inner surface of the cylinder bore to reinforce the sliding surface of the piston in either type.

FIG. 2 and FIG. 3 are configuration diagrams of an alumite processing apparatus according to an 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. That is, the sleeve 1 forming the cylinder bore 60
Anodizing is applied to the inner peripheral surface of 7 to form an alumite film.

The cylinder block 3 is mounted on a support 16 via a gasket 15. The cylinder block 3 is placed on the support 16 with the cylinder head side down and the crankcase side up. 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. Sleeve 17
Inside, an electrode rod 29 is inserted in the axial direction. The electrode rod 29 is connected to the rectifier 24 and the control circuit 2 from the AC power supply 30.
5 is connected to the negative electrode side of the DC power source 31 converted to DC. 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.

In this embodiment, the cylinder bore 60
And the cylindrical electrode rod 29 inserted along the central axis of the cylinder bore 60.
The electrode rod 2 is arranged such that the gap Δr1 on the cylinder head side (lower side in the figure) is narrower than the gap Δr2 on the crank chamber side (upper side in the figure) in the axial direction.
9 are formed. Clearance Δ on cylinder head side
By reducing r1, the current density causing the oxidizing action is increased, and the flow rate of the electrolytic solution is increased to increase the cooling action. As a result, the oxidation reaction is promoted and the thickness of the anodic oxide film is increased. By increasing the film thickness in this way, the wear resistance on the cylinder head side is improved.

The upper end of the sleeve 17 is sealed with a cover 19 via an O-ring 18. An electrolyte circulation channel 20 is connected to the cover 19 and communicates therewith. Support 16
The lower end (not shown) of the circulating pump 28 is also sealed.
The electrolytic solution 27 in the electrolytic solution tank 26 is sent. 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 further provided.
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 cooling water circulation is provided in the circulation pump 28 itself, and a cooling water circulation 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 cross-sectional view of a main part of the anodizing apparatus for more clearly showing the relationship between the electrode rod 29 and the cylinder bore 60 according to the present invention. An imaginary state in which the cylinder head 2 is assembled to the cylinder block 3 is shown by a dashed line. Thereby, the cylinder bore 6
Of 0, the exhaust port side where the temperature tends to rise, and the side where the piston-side pressure load due to the explosive force or inertia force acts due to the adoption of the crank mechanism are clarified. An intake passage 5 and an exhaust passage 7 are formed in the cylinder head 2 for each cylinder, and an intake port 5a and an exhaust port 7a are opened above the respective cylinder bores 60. P indicates a surface on which the crankshaft is arranged, and is on a line connecting the centers of the cylinder bores 60 of the respective cylinders. The intake port 5a and the exhaust port 7a open on opposite sides with respect to the crankshaft P.

That is, when the cylinder head 2 is assembled, the right side in the drawing of the plane P passing through the center of the two cylinder bores 60 is the exhaust port 7a side of the cylinder bore 60, and the plane P
Is the intake port 5a side of the cylinder bore 60. An elliptical electrode rod 29 is inserted into such a cylinder block 3 and anodized in the state shown in FIG. Regarding the clearance between the inner peripheral surface of the cylinder bore 60 and the outer peripheral surface of the electrode rod 29, the clearance C1 on the exhaust port 7a side is smaller than the clearance C2 on the intake port 5a side (C1 <C2). By thus narrowing the gap C1 on the exhaust port side, the electrolytic current density causing an oxidizing action is increased, and the flow rate of the electrolytic solution is increased to increase the cooling action. As a result, the electrolytic reaction is promoted and the anodic oxidation is promoted. The film thickness increases. By increasing the film thickness in this manner, the abrasion resistance of the inner peripheral surface of the cylinder bore on the exhaust port side where the heat load is large increases.

The gaps C1 and C2 between the cylinder bore 60 on the side parallel to the crankshaft (plane P) and the electrode rod 29 are both defined by the cylinder bore 60 on the side perpendicular to the crankshaft (plane P) and the electrode rod 29. Smaller than the gap C3 (C1 <C
2 <C3). A side pressure acts on the inner surface of the cylinder bore parallel to the crankshaft as the piston slides. In the present embodiment, the thickness of the anodic oxide film on the side where the lateral pressure acts is increased corresponding to the lateral pressure. That is, by narrowing the gap between the inner surface of the cylinder bore 60 on the side parallel to the crankshaft and the electrode rod 29, the current density causing the oxidizing action is increased, and the flow rate of the electrolytic solution is increased to increase the cooling action. As a result, the electrolytic reaction is promoted and the thickness of the anodic oxide film is increased. By increasing the film thickness in this manner, the wear resistance of the sliding surface on which the piston side pressure acts is increased.

The electrode rod 29 having an elliptical cross section according to the above-described embodiment is similar to the embodiment shown in FIG. The electrode rod 29 may be formed so that the cylinder head side becomes thicker so that the gap between the electrode rod and the outer surface of the electrode rod becomes narrower. Thereby, in the crankshaft rotation direction, the anodic oxide film is made thicker in accordance with the piston side pressure and the heat load on the exhaust port, and the cylinder head side is formed in accordance with the heat load on the combustion chamber side in the same manner as in the example of FIG. Can be made thicker than the film on the crankcase side. In the case where the side on which the side load from the piston acts on the exhaust port 7a in the explosion process in relation to the rotation direction of the crankshaft 14, the gap between the cylinder bore 60 and the electrode rod 29 is reduced. The thickness of the alumite-treated film is set to be the largest.

FIG. 4 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.

[0029]

[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, anodizing is performed on the inner surface of the finished cylinder bore 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. 5 shows the shape of such a crack. As shown in FIG. 5A, 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.

An 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 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 cracks have 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. 6 is a flowchart showing the steps of manufacturing a cylinder block in which a sleeve is cast.

First, a pipe material of an aluminum alloy 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 wear resistance, a metal carbide such as SiC having a high hardness or other intermetallic compound may be mixed in addition to the components shown in the table.

[0041]

[Table 2]

Next, the pipe material is subjected to 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.

[0043]

[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 into which the sleeve is cast as described above, the cylinder block is
Similar to the sleeveless flow of FIG. 4 described above, each processing of steps S2 to S9, ie, annealing for removing residual stress (step S2), machining of each part of the cylinder block (step S3), burnishing of the cylinder bore Machining (step S4), boring of the cylinder bore (step S5), alumite treatment of the inner surface of the cylinder bore (step S6), heat treatment for crack formation (step S7), and burnishing (step S8);
And finishing honing (step S9). 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. 7 is a flowchart showing a manufacturing process of the cylinder block for press-fitting the 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 is press-fitted, similarly to the above-described sleeveless flow in FIG. 4 and the casting flow in FIG. 6, 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. 8 is a sectional view of a piston ring mounted on the piston 9. 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 4 below shows an example of the ring material of the ring main body 56, and Table 5 shows an example of the treatment of the covering portion 57 obtained by surface-treating the ring material.

[0050]

[Table 4]

[0051]

[Table 5]

In any of the processing examples shown in Table 5, when the coating portion 57 slides on the inner peripheral surface of the cylinder bore subjected to the alumite treatment of the above embodiment, the covering portion 57 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.

Further, as described below, in the case of an alumite film in which Si particles, metal carbide such as SiC having a 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.

The ring main body 56 made of any of the materials shown in Table 4 is mounted in the ring groove of the piston 9 to exhibit a sufficient elastic force for sealing the combustion chamber for a long period of time. Even if the portion 57 is formed by any of the processing examples shown in Table 5, the portion 57 has sufficient bonding properties with the covering portion 57.

FIG. 9 is a detailed flowchart of the alumite processing process (Step S6) in each of the cylinder block manufacturing flows (FIGS. 4, 6, and 7).

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 6 below shows the degreasing conditions of each degreasing method.

[0057]

[Table 6]

After 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 alkali etching are shown in Table 7 below, and the etching conditions for the mixed acid etching are shown in Table 8.

[0059]

[Table 7]

[0060]

[Table 8]

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, if there is a possibility that the surface is not sufficiently removed in the previous degreasing treatment, 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 at the mark where the silicon particles and intermetallic compounds have been removed by the mixed acid etching can be used as a dent for impregnating with oil or a solid lubricant.

Next, the surface of the base material thus etched is subjected to anodizing 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 9 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.

[0065]

[Table 9]

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. A in the figure is A6061
Current density 3A / dm ² (ampere / 100 cm ² ), current waveform: DC, electrolysis time: 20
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.

FIG. 14 is a graph showing the effect of oxalic acid and citric acid concentrations on the film thickness and hardness in a state where the sulfuric acid concentration is maintained at a constant 20 g / l. Other electrolysis conditions are as follows: A6061 for the aluminum alloy to be treated, current density of 3 A / dm ² , current waveform: DC, electrolysis time: 20
The bath temperature is 13 ° C. for 1 minute. Sufficient film thickness, for example, 25
In order to obtain μm or more, the combined concentration of oxalic acid and citric acid needs to be 13 g / l or more.

FIG. 15 is a graph showing the effect of changing the sulfuric acid concentration on the film thickness and hardness using the oxalic acid and citric acid concentrations as parameters. Other electrolysis conditions were as follows: A6061 for the aluminum alloy to be treated, current density of 3 A / dm ² , current waveform: DC, electrolysis time: 20 minutes,
The bath temperature is 13 ° C. When oxalic acid and citric acid are not confused with the electrolytic solution, if the sulfuric acid concentration is 20 g / l or less, it is difficult to form an alumite film under these conditions. Even if it does, the film hardness will be about Hv300,
It cannot be higher than Hv 380 necessary for wear resistance. As can be seen from the figure, by mixing oxalic acid and citric acid in the electrolytic solution, it is possible to form an alumite film even at a wide range of sulfuric acid concentration, and it is necessary to have an Hv of about 380 required for abrasion resistance. Hardness can be obtained. As can be seen from the figure, in this case, the film thickness increases as the sulfuric acid concentration increases, that is, the electrolysis time for obtaining a predetermined film thickness can be shortened.

After the alumite film is formed by the anodic oxidation treatment as described above, the electrolytic solution is removed by washing with water (step S23), and the 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 electrolytic solution 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. 10 and 11 are cross-sectional views of the surface of the base material in each step of the above-described cylinder block manufacturing process. FIG. 10 shows, in order, a flow in which the anodizing process is performed by omitting 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. 10A 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 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. 11A 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.

FIG. 12 is a sectional view showing the state of the base material surface by the mixed acid etching and the alkali etching in the alumite treatment described above. (A) is the same as FIG.
As in (A), the state after the degreasing treatment is shown, and 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. (B) shows a cross section when mixed acid etching is performed after the degreasing treatment.
The silicon particles 41 on the surface of No. 0 are removed by etching to form a dent 45. An alumite treatment is performed in this state, and an alumite film 42 is formed on the surface of the base material 40 as shown in FIG. A depression 45 remains on the surface of the alumite film 42.

FIG. 12D shows a cross section when alkali etching is performed after the degreasing treatment of FIG. As described above, the surface of the base material 40 is removed leaving the silicon particles 41. By subjecting this to alumite treatment, (E)
As shown in (1), the silicon particles 41 protrude from the surface of the alumite film. Thereby, the average hardness of the surface of the alumite film 42 is increased, and the wear resistance is improved.

[0079]

As described above, according to the present invention, the thickness of the anodic oxide film on the side on which the side pressure acts corresponds to the side pressure acting on the side parallel to the crankshaft as the piston slides. Is formed thickly, sufficient wear resistance is secured over the entire circumference of the piston sliding surface, and high wear resistance is maintained over a long period of time to achieve a smooth sliding operation.

Further, since the thickness of the anodic oxide film on the exhaust port side where the heat load is higher than that on the intake port side and becomes high temperature is formed thicker, the wear resistance is sufficiently secured over the entire circumference of the piston sliding surface, and , And a smooth sliding operation is achieved.

Further, since the thickness of the anodic oxide film on the cylinder head side, which becomes high due to the formation of the combustion chamber, is formed to be thicker than the thickness of the anodic oxide film on the crank chamber side, the axial length of the piston sliding surface is increased. The wear resistance is sufficiently ensured over the entirety, and high wear resistance is maintained over a long period of time, and a smooth sliding operation is achieved.

[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 sectional view of a main part of an alumite processing apparatus according to another embodiment of the present invention.

FIG. 4 is a flowchart of a sleeveless cylinder block manufacturing process.

FIG. 5 is an explanatory view of a crack.

FIG. 6 is a flowchart of a sleeve casting cylinder block manufacturing process.

FIG. 7 is a flowchart of a sleeve press-fit cylinder block manufacturing process.

FIG. 8 is a sectional view of a piston ring according to the embodiment of the present invention.

FIG. 9 is a flowchart of an anodizing process.

FIG. 10 is a sectional view sequentially showing the manufacturing process of the aluminum component.

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

FIG. 12 is an explanatory diagram of etching in a pre-process of an alumite process.

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

FIG. 14 is a graph showing the effect of oxalic acid and citric acid concentrations on film thickness and hardness in a state where the sulfuric acid concentration is maintained at a constant 20 g / l.

FIG. 15 is a graph showing the effect of changing the sulfuric acid concentration on the film thickness and hardness using the oxalic acid and citric acid concentrations as parameters.

[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, 56: ring main body, 57: covering portion, 60: cylinder bore.

Claims (3)

[Claims] 1. A cylinder bore in which a piston slides, a cylinder head is mounted on one end of the cylinder bore, and a crank chamber for accommodating a crankshaft is provided on the other end. In a cylinder block of an internal combustion engine in which an intake port and an exhaust port are provided in a cylinder head, and an anodic oxide film is formed on an inner surface of the cylinder bore, the anodic oxide film is formed on an inner peripheral surface of a cylinder bore on a side parallel to the crankshaft. A cylinder block for an internal combustion engine, wherein the thickness is larger than the thickness of an inner peripheral surface of a cylinder bore on a side perpendicular to a crankshaft. 2. A cylinder bore in which a piston slides, a cylinder head is mounted on one end of the cylinder bore, and a crank chamber for accommodating a crankshaft is provided on the other end. In a cylinder block of an internal combustion engine in which an intake port and an exhaust port are provided in a cylinder head, and an anodized film is formed on an inner surface of the cylinder bore, the anodized film has a thickness of an inner peripheral surface of the cylinder bore on the exhaust port side. A cylinder block having a thickness greater than an inner peripheral surface of the cylinder bore on the intake port side. 3. A cylinder bore in which a piston slides, a cylinder head is mounted on one end of the cylinder bore, and a crank chamber for accommodating a crankshaft is provided on the other end. In a cylinder block of an internal combustion engine in which an intake port and an exhaust port are provided in a cylinder head, and an anodized film is formed on an inner surface of the cylinder bore, the anodized film has a thickness on the cylinder head side with respect to an axial direction of the cylinder bore. Characterized in that the cylinder block is thicker than the crank chamber side.