JP2012002073A - Method for manufacturing cylinder of internal combustion engine and the cylinder of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce friction between the inner circumference face of a cylinder and a piston by increasing retaining property of a lubricating oil in the inner circumference face of the cylinder, and to improve productivity of the cylinder.SOLUTION: A method for manufacturing the cylinder of an internal combustion engine, in which a plating film 14 is formed on the inner circumferential surface 13 of the cylinder demarcating a bore 12 for housing a piston 11, includes steps of: subjecting the inner circumference face 13 of the cylinder to a boring process to form a plurality of linear boring projections 29A; plating the inner circumferential surface of the cylinder 13 to form a plating layer 31 which includes plating projections 31A where plating metal grows in grains along the boring projections 29A and plating recesses 31B between the plating projections; and forming a plating film 33 by honing the plating projections 31A so that the plating recesses 31B are left to form a smooth plateau face 28 on the plating film and to make the plating recesses 31B function as an oil pocket 27 that irregularly extends and can retain the lubricating oil 35.

Description

  The present invention relates to a cylinder of an internal combustion engine in which an oil pocket capable of holding lubricating oil is provided on a plating film formed on an inner peripheral surface of a cylinder, and a method for manufacturing the same.

  2. Description of the Related Art Conventionally, a cross hatch groove is provided on a cylinder inner peripheral surface of a cylinder of an internal combustion engine, and lubricating oil is held in the groove to lubricate a piston (including a piston ring) and a cylinder inner peripheral surface. However, since the lubricating oil flows out along the cross-hatch groove when the piston slides, the piston between the first piston ring of the piston and the inner peripheral surface of the cylinder is at a part where the piston speed is slow, such as near the top dead center of the piston. The lubrication state becomes boundary lubrication, and there is a problem that friction is increased and the inner peripheral surface of the cylinder is worn. In addition, there is a problem that the lubricating oil that flows out to the combustion chamber side through the cross hatch groove burns with gasoline and is consumed. Furthermore, the cross hatch groove in the combustion chamber expands the clevis volume (unburned gas generation region), and blow-by gas (unburned gas) increases, or blow-by gas flows out through the cross hatch groove to the crankcase side. There are also challenges.

  In order to solve this problem, after forming a plating layer on the inner peripheral surface of the cylinder and honing the plating layer to form a plating film, the surface of the plating film is lubricated with, for example, laser processing. A cylinder of an internal combustion engine in which an oil groove capable of holding the oil is formed has been proposed.

  In addition, the plating film formed on the inner peripheral surface of the cylinder is composed of a chromium plating layer, and micro cracks and micro pores peculiar to the chromium plating layer are used for retaining lubricating oil. A cylinder for an internal combustion engine has been proposed.

  Furthermore, Patent Document 1 discloses a cylinder of an internal combustion engine in which a nickel boron nitride composite plating film having fine through holes (fine holes) is formed on the inner peripheral surface of the cylinder.

  Also, a cylinder of an internal combustion engine in which a concave portion and a convex portion are machined on the inner peripheral surface of the cylinder, and the convex portion is processed to be flat and then plated to form an oil groove capable of holding lubricating oil in the plating film. However, this is disclosed in Patent Document 2.

Japanese Patent Laid-Open No. 4-263095 JP 2008-138811 A

  However, in cylinders of internal combustion engines where oil grooves are formed on the surface of the plating film by laser processing, the retention of lubricating oil on the inner peripheral surface of the cylinder is improved, but special additional processing (laser processing) is performed to form oil grooves. Must be performed, and the productivity of the internal combustion engine is reduced.

  In addition, in a cylinder of an internal combustion engine that uses fine cracks peculiar to the chromium plating layer to hold the lubricating oil, it is difficult to accurately form fine cracks that are effective for holding the lubricating oil. Therefore, also in this case, the productivity of the internal combustion engine is reduced.

  Further, in the cylinder of the internal combustion engine described in Patent Document 1, the plating convex portion on the inner peripheral surface of the cylinder is worn when the piston slides, and friction between the inner peripheral surface of the cylinder and the piston increases or occurs at that time. Wear powder can damage other parts. Furthermore, the presence of minute holes in the combustion chamber expands the clevis volume (unburned gas generation region) and increases the unburned gas. It will be damaged.

  Further, in the cylinder of the internal combustion engine described in Patent Document 2, since the oil groove formed in the plating film is an inclined cross-hatch groove, the friction increases and the consumption of lubricating oil as described at the beginning of the background art. Problems such as increase in volume and generation of blow-by gas are inevitable.

  The object of the present invention has been made in consideration of the above-mentioned circumstances, and can improve the retention of the lubricating oil on the cylinder inner peripheral surface to reduce the friction between the cylinder inner peripheral surface and the piston, and improve the productivity of the cylinder. An object of the present invention is to provide a cylinder manufacturing method for an internal combustion engine and a cylinder for the internal combustion engine that can improve the efficiency.

  A cylinder manufacturing method for an internal combustion engine according to the present invention is a cylinder manufacturing method for an internal combustion engine in which a plating film is formed on a cylinder inner peripheral surface defining a bore in which a piston is accommodated. A plurality of linear pre-processed convex portions are formed by processing, and then plating treatment is performed on the inner peripheral surface of the cylinder so that a plating metal grows along the pre-processed convex portions. And forming a plating film by honing the plating convex part so as to leave the plating concave part, and smoothing the plating film. While forming a plateau surface, the said plating recessed part is functioned as an oil pocket which extends irregularly and can hold | maintain lubricating oil.

  The cylinder of the internal combustion engine according to the present invention is a cylinder of an internal combustion engine in which a plating film is formed on a cylinder inner peripheral surface that defines a bore that accommodates a piston, and the plating film is formed on the cylinder inner peripheral surface. The plating convex portion is honed so as to leave the plating concave portion among the plating convex portion and the plating concave portion between the plating convex portions where the plating metal grows along the linear pre-processed convex portion formed in It is formed by processing, and the plating recess in the plating film is configured to function as an oil pocket that extends irregularly and can hold lubricating oil.

  According to the cylinder manufacturing method of an internal combustion engine and the cylinder of the internal combustion engine according to the present invention, the oil pocket capable of holding the lubricating oil is formed in the plating film on the inner peripheral surface of the cylinder. Retention is enhanced, and friction between the cylinder inner peripheral surface and the piston can be reduced.

  In addition, honing is applied to the plating protrusions so as to leave the plating recesses, and a plating film is formed. The plating recesses function as oil pockets, so no additional work is required to form the oil pockets. Productivity can be improved.

Sectional drawing which shows the cylinder to which one Embodiment in the cylinder of the internal combustion engine which concerns on this invention was applied with a part of piston. The expanded sectional view which shows the piston ring periphery of FIG. The expanded sectional view which expands and shows the piston ring periphery of FIG. 2 further. The expanded view of the cylinder internal peripheral surface provided with the oil pocket shown in FIG.1 and FIG.3. FIG. 2 is a cross-sectional view of a cylinder showing rough boring marks formed on a piston sliding surface on an inner circumferential surface of the cylinder in FIG. 1. Sectional drawing of the cylinder shown with the plating layer formed in the cylinder internal peripheral surface (piston sliding surface) of FIG. FIG. 7 is an enlarged cross-sectional view similar to FIG. 7A, in which the plating layer of FIG. 6 is shown enlarged, (A) is an enlarged cross-sectional view, and (B) is a process of grain growth of a plating metal. The surface view which shows the surface property of the plating layer of FIG. The expanded sectional view corresponding to FIG. 7 (A) which shows the plating layer by the plating process given to the fine boring process trace formed in the combustion chamber inner surface of the cylinder internal peripheral surface of FIG. The surface view which shows the surface property of the plating layer of FIG. Sectional drawing of the cylinder shown with the plating film formed by honing the plating layer of FIG.6 and FIG.7. The expanded sectional view of the plating film which expands and shows a part of FIG.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, the present invention is not limited to this embodiment.

  A plating film 14 is formed on a cylinder inner peripheral surface 13 that defines a bore 12 in which a piston 11 is accommodated in the cylinder 10 of the internal combustion engine shown in FIG. Thus, the wear resistance of the cylinder inner peripheral surface 13 is enhanced. In addition, a cylinder head 16 including a combustion chamber 15 is installed on the upper portion of the cylinder 10. The piston 11 reciprocates (slids) while slidingly contacting the cylinder inner peripheral surface 13 in the bore 12, sucks a mixture of fuel and air into the combustion chamber 15 (intake), and compresses the mixture. Explode and exhaust the exhaust gas.

  As shown in FIG. 2, the piston 11 includes a first piston ring 18, a second piston ring 19, and an oil ring 20 that are sequentially fitted on the upper portion of the piston body 17, so that the airtightness between the piston 11 and the cylinder inner peripheral surface 13 is achieved. Sexuality is enhanced. A skirt portion 21 is provided at the lower portion of the piston body 17.

  The plating film 14 provided on the cylinder inner peripheral surface 13 of the cylinder 10 is a plating film using nickel-phosphorus containing SiC particles as a metal for plating. The plating film 14 has, for example, a hardness of HV550 to 700, a film thickness of 20 to 100 μm, a content of SiC particles of 1 to 3.5 wt%, an average particle size of SiC particles of 1.5 to 3 μm, Excellent wear resistance.

  As will be described later, the plating film 14 is bored with the cylinder inner peripheral surface 13 of the cylinder 10 as a pre-processing, and a plating layer is formed on the boring processing surface through a plating pre-treatment to form a plating layer. Formed by honing. Among these, a part of the pre-plating process (electrolytic etching process or the like) and the plating process are performed, for example, at one end part (end part on the cylinder head 16 side) 22 and the other end part (crankcase) of the cylinder inner peripheral surface 13 of the cylinder 10. Side end) 23, an electrode (not shown) is disposed in the bore 12 of the cylinder 10, and a treatment liquid (pre-plating treatment liquid, plating treatment liquid) is circulated and guided to the cylinder inner peripheral surface 13. A high-speed plating process in which a plating pretreatment (such as an electrolytic etching process) and a plating process are performed on the inner circumferential surface 13 of the cylinder is employed.

  The cylinder inner peripheral surface 13 of the cylinder 10 includes a piston sliding surface 24 on which the piston 11 slides and a combustion chamber surface 25 that forms part of the combustion chamber 15 without the piston 11 sliding. The The piston sliding surface 24 is a region from the other end 23 of the cylinder inner peripheral surface 13 to the top dead center position 26 (FIGS. 2 and 3) of the first piston ring 18. The combustion chamber inner surface 25 is a region from the top dead center position 26 of the first piston ring 18 to the one end 22 of the cylinder inner peripheral surface 13.

  And the oil pocket 27 which can hold | maintain the lubricating oil 35 (FIG. 3) is formed in the plating film 14 (after-mentioned plating film 33) corresponding to the piston sliding surface 24. FIG. Further, the plating film 14 (the plating film 34 described later) corresponding to the combustion chamber inner surface 25 is formed on a smooth surface having no oil pockets 27, for example, having a surface roughness Rz of 1 μm or less.

  As shown in FIGS. 1 and 4, the oil pocket 27 is irregularly discontinuous or partially continuous in a direction orthogonal to the sliding direction A of the piston 11 (that is, the axial direction O of the cylinder 10). Are arranged in the sliding direction A of the piston 11 and are formed in a striped pattern. The oil pocket 27 has a depth t of 3 to 50 μm, a width W of 20 to 80 μm, a length L of 20 to 5000 μm, and an interval (pitch) P of 100 to 500 μm, for example. A smooth plateau surface 28 is formed between these oil pockets 27, that is, between the oil pockets 27 adjacent in the sliding direction A of the piston 11 and between the oil pockets 27 adjacent in the direction orthogonal to the sliding direction A of the piston 11. It is formed.

  Next, the manufacturing method of the cylinder 10 in which the oil pocket 27 is formed in the plating film 14 (plating film 33) corresponding to the piston sliding surface 24 of the cylinder inner peripheral surface 13 will be described.

  First, as shown in FIGS. 1, 3, and 5, the cylinder inner peripheral surface 13 is bored to form a rough boring mark 29 on the boring surface of the piston sliding surface 24 of the cylinder inner peripheral surface 13. To do. The rough boring marks 29 are formed with a plurality of boring protrusions 29A extending in the direction orthogonal to the sliding direction A of the piston 11 and arranged in the sliding direction A of the piston 11. A boring recess 29B is formed between the portions 29A. Further, in this boring process, for example, by changing the spindle feed speed of the cutting blade slowly, a fine boring mark 30 is formed on the boring surface of the combustion chamber inner surface 25 of the cylinder inner peripheral surface 13.

  Next, the boring surface of the cylinder inner peripheral surface 13 having the rough boring marks 29 and the fine boring marks 30 is subjected to a pre-plating process and then subjected to a plating process, as shown in FIGS. 3, 6, and 7. As described above, the plating layer 31 includes the plating convex portion 31A in which the metal for plating (nickel and phosphorus) grows along the boring convex portion 29A of the rough boring trace 29 and the plating concave portion 31B between the plating convex portions 31A. Form. Further, on the combustion chamber inner surface 25 of the cylinder inner peripheral surface 13, as shown in FIGS. 3 and 9, the unevenness of the fine boring marks 30 becomes very fine due to the plating pretreatment. Therefore, even in the plating layer 32 formed on the fine boring marks 30, the surface irregularities become very fine.

  Next, honing is performed on the plating layers 31 and 32. In the honing process, as shown in FIGS. 3, 11, and 12, in the plating layer 31, the plating convex part 31 </ b> A is honed so as to leave the plating concave part 31 </ b> B to form a plating film 33. A smooth plateau surface 28 is formed on the film 33, and the plating recess 31 </ b> B is made to function as an oil pocket 27 that can hold lubricating oil. Further, by performing this honing process on the plating layer 32 (FIGS. 3 and 9), a plating film 34 having a smooth surface is formed. With these plating films 33 and 34, the plating film 14 is formed on the cylinder inner peripheral surface 13.

  Thus, the plating film 14 (plating film 33) corresponding to the piston sliding surface 24 of the cylinder inner peripheral surface 13 is used for plating along the linear boring convex portion 29A formed on the piston sliding surface 24. Of the plating protrusions 31A where the metal grains grow and the plating recesses 31B between the plating protrusions 31A, the plating protrusions 31A are formed by honing so as to leave the plating recesses 31B. 31B functions as an oil pocket 27 that can hold the lubricating oil.

  Hereinafter, a cylinder block manufacturing method for manufacturing the cylinder block 9 including the cylinder 10 having the oil pocket 27 on the plating film 14 (plating film 33) on the cylinder inner peripheral surface 13 will be described in detail.

  A cylinder block 9 shown in FIG. 1 includes a cylinder 10 of a single cylinder or a plurality of cylinders, and uses an aluminum alloy material such as a low pressure casting material (AC4B, AC4C, etc.) or a die casting material (ADC10, ADC12, etc.). In this embodiment, a cylinder block 9 having an in-line three-cylinder cylinder 10 made of ADC12 material is used.

  The cylinder block 9 after casting is subjected to heat treatment (T5 treatment) or the like in order to reduce deformation of the bore 12 during engine operation, and thereafter, boring processing is performed on the cylinder inner peripheral surface 13 as pre-processing. In this boring process, a cutting blade (not shown) is fed from one end 22 of the cylinder 10, and the spindle feed speed of the cutting blade is slowed at the combustion chamber inner surface 25 and fast at the piston sliding surface 24. The surface roughness Rz of 25 is as fine as 2 to 5 μm, and the surface roughness Rz of the piston sliding surface 24 is as coarse as 15 to 30 μm. At this time, fine boring marks 30 on the combustion chamber inner surface 25 and rough boring marks 29 on the piston sliding surface 25 are continuously formed in the circumferential direction of the cylinder inner peripheral surface 13 by the cutting blades, and the cylinder inner peripheral surface. 13 are formed at equal intervals in the axial direction O.

  In this embodiment, by setting the spindle feed speed of the cutting blade to 200 mm / min for the combustion chamber inner surface 25 and 340 mm / min for the piston sliding surface, the cylinder inner peripheral surface 13 (boring surface) after the boring is obtained. The combustion chamber inner surface 25 was formed to have a surface roughness Rz of 3 μm and an interval of boring marks of 0.1 mm, and the piston sliding surface 24 was formed to have a surface roughness of Rz 22 μm and an interval of boring marks of 0.2 mm. Further, as shown in FIG. 5, as the surface roughness of the piston sliding surface 24 on the cylinder inner peripheral surface 13 is increased, the contact area between the aluminum alloy substrate constituting the cylinder 10 and the plating film 14 increases. The piston sliding surface 24 is improved in plating adhesion.

  Next, a plating pretreatment is performed on the cylinder 10 of the cylinder block 9 shown in FIG. This pre-plating process includes a degreasing / heating process and an electrolytic etching process. First, the cylinder block 9 is sequentially subjected to a degreasing process, a water washing process, and a preliminary heating process.

  In the degreasing treatment, an aqueous solution of a degreasing agent of 20 to 50 g / l is used as a treatment liquid, and the entire cylinder block 9 is immersed in the treatment liquid at a liquid temperature of 40 to 80 ° C. and a treatment time of 0.5 to 3 minutes. During this immersion, the cleaning effect can be enhanced by swinging the cylinder block 9 and using an ultrasonic oscillator. Oil and dirt of the cylinder block 9 can be removed by this degreasing treatment. In the water washing treatment, water at room temperature to 80 ° C. is used, and the entire cylinder block 9 is immersed in washing water for 0.5 to 3 minutes for washing. In the preliminary heating process, warm water of 50 to 90 ° C. is used, and the entire cylinder block 9 is immersed in warm water for 0.5 to 3 minutes for heating. By performing this preliminary heating, the entire cylinder block 9 is uniformly heated to a predetermined temperature, so that the electrolytic etching processing time can be shortened and the etching amount can be made uniform.

The detailed conditions of the electrolytic etching treatment are phosphoric acid 100 to 500 g / l as a treatment solution, the solution temperature 60 to 90 ° C., the treatment time 0.5 to 3 minutes, the liquid flow rate 10 to 50 cm / second, and the energization condition 10 to 80A. Process at / dm ² . By performing this electrolytic etching treatment, impurities and oxide films adhering to the cylinder inner peripheral surface 13 are removed, and eutectic silicon in the aluminum alloy is projected to the surface, and the cylinder inner peripheral surface 13 is further roughened. The adhesion of plating is improved by the anchor effect. Under this condition, a rough boring mark 29 remains on the piston sliding surface 24 of the cylinder inner peripheral surface 13 in particular. After this electrolytic etching process, the cylinder block 9 is cleaned and transported to the plating process.

  Next, the cylinder 10 of the cylinder block 9 is plated. In this plating process, the plating film 14 is applied to the cylinder inner peripheral surface 13 by a high-speed plating process in which the plating solution is flowed into the bore 12 of the cylinder block 9 in which the cylinder inner peripheral surface 13 has been subjected to the plating pretreatment. Form. At this time, the plating film 14 is formed so that the surface roughness Rz of the combustion chamber inner surface 25 of the cylinder inner peripheral surface 13 is 10 to 30 μm and the surface roughness Rz of the piston sliding surface 24 is 40 to 70 μm.

In this plating process, electricity is supplied in three steps: weak, medium, and strong. That is, the treatment liquid uses nickel sulfate 300 to 700 g / l, the liquid temperature is 40 to 80 ° C., the treatment time is 3 to 10 minutes, the liquid flow rate is 50 to 80 cm / second, and the energization condition is 10 to 30 A / dm ² ×. Process by sequentially changing 0.5 to 1 minute (weak step), 30 to 70 A / dm ² × 0.5 to 1 minute (medium step), 80 to 120 A / dm ² × 2 to 8 minutes (strong step) I do. Thereby, a plating film 14 having a uniform film thickness is formed on the cylinder inner peripheral surface 13 of the cylinder 10 in the cylinder block 9. The surface roughness of the plating film 14 at this time is Rz 20 μm for the combustion chamber inner surface 25 and Rz 55 μm for the piston sliding surface 24.

  In the above-described plating treatment, the plating metal has a characteristic of growing in a granular form, and the grain growth of the plating metal is promoted at the convex portion of the surface to be plated. Therefore, as shown in FIG. 7, in the piston sliding surface 24 of the cylinder inner peripheral surface 13 where the rough boring marks 29 are formed by boring, grain growth of the plating metal is promoted at the boring convex portions 29A. Thus, the plating layer 31 is formed. Then, on the surface of the plating layer 31, as shown in FIG. 8, plating convex portions 31 </ b> A in which coarse particles of plating metal are arranged in a streak shape are along a direction orthogonal to the sliding direction A of the piston 11. A plating recess 31B is provided between the plating protrusions 31A.

  Further, as shown in FIG. 9, in the combustion chamber inner surface 25 of the cylinder inner peripheral surface 13 where the fine boring marks 30 are formed by boring, the metal particles for plating are fine at the convex portions of the fine boring marks 30. The plating layer 32 is formed by dense growth. Therefore, as shown in FIG. 10, dense particles of the plating metal are uniformly dispersed on the surface of the plating layer 32.

  Next, the plating layers 31 and 32 formed on the cylinder inner peripheral surface 13 of the cylinder 10 shown in FIG. 3 are subjected to plateau honing (that is, finish honing). In the plating layer 31 formed on the piston sliding surface 24 of the cylinder inner peripheral surface 13, as shown in FIGS. 11 and 12, coarsely grown plating convex portions 31 </ b> A are plateau honed to form a smooth plateau surface 28. A polished plating film 33 is formed. At this time, the plating recesses 31B between the plating protrusions 31A remain, and the plating recesses 31B are formed in the plating film 33 as irregular oil pockets 27 that are discontinuous or partially continuous. Further, in the plating layer 32 formed on the combustion chamber inner surface 25 of the cylinder inner peripheral surface 13 shown in FIG. 3, the surface of the densely grown plating layer 32 is plateau honed to form a plating film 34. The surface of the plating film 34 is provided on a smooth surface (plateau surface) without unevenness.

In this plateau honing, a diamond grindstone (length 70 mm, length: 70 mm, particle size # 3000 to 1000 (average particle diameter 5 to 15 μm), concentration 30 to 50% (1.3 to 2.2 ct / cm ² ) is used. Honing was carried out using 6 pieces having a width of 3 mm and an expansion pressure of 3 to 15 kgf / cm ² . The machining allowance is 40 to 60 μm in diameter. In particular, in the plating layer 31 formed on the piston sliding surface 24 of the cylinder inner peripheral surface 13, only the plating convex portion 31A is polished. For this reason, this plateau honing has a high cutting efficiency, and the time required for machining is 20 to 60 seconds per one cylinder inner peripheral surface 13, and the conventional honing process in which rough honing, thinning honing and finishing honing are sequentially performed. Compared to the case, the time can be greatly reduced.

  In this way, the plating film 33 (plating film 14) formed on the piston sliding surface 24 of the cylinder inner peripheral surface 13 of the cylinder 10 has a depth t of 3 to 3, as shown in FIGS. Oil pockets 27 having a width of 50 μm, a width w of 20 to 80 μm, a length L of 20 to 5000 μm, and a distance P of 100 to 500 μm are formed, and a smooth plateau surface 28 is formed between these oil pockets 27. Further, the plating film 34 (plating film 14) formed on the combustion chamber inner surface 25 of the cylinder inner peripheral surface 13 has no oil pocket 27, and the plating film 34 has a smooth surface with a surface roughness Rz of 1 μm or less. Formed.

  With the configuration as described above, according to the present embodiment, the following effects (1) to (7) are obtained.

  (1) Since the oil pocket 27 capable of holding the lubricating oil 35 is formed in the plating film 33 (plating film 14) formed on the piston sliding surface 24 of the cylinder inner peripheral surface 13, the cylinder inner peripheral surface 13 The retention of the lubricating oil is enhanced, and the friction between the cylinder inner peripheral surface 13 and the piston 11 can be reduced.

  (2) The plating convex portion 31A is plateau honed so as to leave the plating concave portion 31B of the plating layer 31 formed on the piston sliding surface 24 of the cylinder inner peripheral surface 13 to form the plating film 33, and the plating concave portion 31B is oiled. Since it functions as the pocket 27, there is no need for additional processing such as laser processing after the plateau honing for forming the oil pocket 27. As a result, the productivity of the cylinder 10 and consequently the productivity of the cylinder block 9 are improved. Can be made.

  (3) Since the oil pocket 27 extending in the direction orthogonal to the sliding direction A of the piston 11 is formed in the plating film 14 (plating film 33) of the cylinder inner peripheral surface 13, the first piston ring of the piston 11 18, the sealing performance of the lubricating oil 35 by the second piston ring 19 and the oil ring 20 is improved. For this reason, since it is possible to prevent the lubricating oil 35 from flowing out into the combustion chamber 15 through the oil pocket 27, the consumption of the lubricating oil 35 can be reduced. Furthermore, it is possible to prevent blow-by gas from flowing through the oil pocket 27 to the crankcase side.

  (4) Since a smooth plateau surface 28 is formed between the oil pockets 27 on the plating film 14 (plating film 33) on the cylinder inner peripheral surface 13 of the cylinder 10, the first piston ring 18 of the piston 11, the second piston ring 19. The amount of wear of the plating film 14 (plating film 33) by the oil ring 20 can be reduced. For this reason, the engine equipped with this cylinder 10 does not require a running-in operation, and the friction between the piston 11 and the cylinder inner peripheral surface 13 is reduced from the beginning of the engine start, and the fuel consumption can be improved.

  (5) The plating film 34 formed on the combustion chamber inner surface 25 of the cylinder inner peripheral surface 13 of the cylinder 10 is formed on a smooth surface having no oil pocket 27 and having a surface roughness Rz of 1 μm or less. For this reason, since the oil film of the lubricating oil on the surface of the plating film 34 in the combustion chamber inner surface 25 of the cylinder inner peripheral surface 13 can be thinned, the consumption amount of the lubricating oil 35 can be reduced. Further, the plating film 34 on the combustion chamber inner surface 25 of the cylinder inner peripheral surface 13 forming the combustion chamber 15 is formed on a smooth surface having no oil pocket 27 and having a surface roughness Rz of 1 μm or less. The clevis volume (unburned gas generation region) is reduced, and the generation of blow-by gas itself can be reduced.

  (6) The honing process of the plating layers 31 and 32 is a plateau honing process that particularly hoses the plating convex portions 31A of the plating layer 31, and does not require rough honing and decimation honing, so the honing process can be reduced. Furthermore, the allowance for plateau honing can be reduced. As a result, the honing time can be shortened, and the productivity of the cylinder 10 and thus the cylinder block 9 can be improved from this point.

  (7) On the plating film 33 formed on the piston sliding surface 24 of the cylinder inner peripheral surface 13, oil pockets 27 are discontinuous or partially continuous in a direction orthogonal to the sliding direction A of the piston 11. A plateau surface 28 is formed between these oil pockets 27. Therefore, it is possible to prevent the first piston ring 18 and the second piston ring 19 of the piston 11 extending in the direction orthogonal to the sliding direction A of the piston 11 from entering the oil pocket 27 and being caught.

  As mentioned above, although this invention was demonstrated based on the said embodiment, this invention is not limited to this.

  For example, in the plating film 33 formed on the piston sliding surface 24 on the cylinder inner peripheral surface 13 of the cylinder 10, oil provided near the top dead center of the piston 11 (that is, near the top dead center position 26 of the first piston ring 18). The pocket 27 may be formed to have a depth t deeper than the oil pocket 27 provided in another portion and the interval P may be narrow. In the vicinity of the top dead center of the piston 11, the oil film of the lubricating oil 35 is likely to be cut off due to the influence of the combustion pressure. However, as described above, the depth t of the oil pocket 27 is increased near the top dead center of the piston 11 and the interval P is set. By forming it narrowly, the retainability of the lubricating oil 35 can be improved.

  Moreover, the oil pocket 27 provided in the plating film 33 of the piston sliding surface 24 on the cylinder inner peripheral surface 13 of the cylinder 10 may be formed to extend in different directions for each formation position. For example, in the plating film 33 in which the skirt portion 21 (FIG. 1) of the piston 11 is slidably contacted, the direction of the oil pocket 27 is formed parallel or oblique to the sliding direction A of the piston 11 so that the lubricating oil 35 is disposed on the inner circumferential surface of the cylinder. 13 may be prevented from flowing out in the circumferential direction, and friction between the skirt portion 21 of the piston 11 and the cylinder inner peripheral surface 13 (plating film 33) may be reduced.

  As for the pretreatment for plating, when a low pressure casting material such as AC4B material is used for the cylinder block 9, anodizing treatment is performed after the electrolytic etching treatment. Low-pressure cast material has a larger surface area of eutectic silicon protruding by electrolytic etching because the eutectic silicon in the aluminum alloy is coarser than die-cast material, but by performing anodization after electrolytic etching This is because a porous anodic oxide layer can be formed on the surface of the aluminum alloy substrate, thereby improving plating adhesion.

DESCRIPTION OF SYMBOLS 10 Cylinder 11 Piston 13 Cylinder inner peripheral surface 14 Plating film 18 First piston ring 24 Piston sliding surface 25 Combustion chamber inner surface 27 Oil pocket 28 Plateau surface 29A Boring processing convex part (pre-processing convex part)
31 Plating layer 31A Plating convex part 31B Plating concave part 33 Plating film 35 Lubricating oil A Piston sliding direction

Claims (7)

A cylinder manufacturing method for an internal combustion engine in which a plating film is formed on an inner peripheral surface of a cylinder that defines a bore in which a piston is accommodated,
Pre-processing the cylinder inner peripheral surface to form a plurality of linear pre-processing projections,
Next, a plating process is performed on the inner peripheral surface of the cylinder to form a plating layer including a plating convex portion in which a plating metal grain grows along the pre-processed convex portion and a plating concave portion between the plating convex portions. ,
Next, the plating protrusion is honed so as to leave the plating recess to form a plating film, a smooth plateau surface is formed on the plating film, and the plating recess is irregularly extended and lubricated. A cylinder manufacturing method for an internal combustion engine, which functions as an oil pocket capable of holding A cylinder of an internal combustion engine in which a plating film is formed on an inner peripheral surface of a cylinder that defines a bore that accommodates a piston;
The plating coating includes the plating recesses among the plating protrusions in which the plating metal grows along the linear pre-processed protrusions formed on the inner peripheral surface of the cylinder and the plating recesses between the plating protrusions. The plating convex part is formed by honing so as to leave
A cylinder of an internal combustion engine, wherein the plating concave portion in the plating film extends irregularly and functions as an oil pocket capable of holding lubricating oil. The cylinder inner peripheral surface is formed by a piston sliding surface on which the piston slides and a combustion chamber surface that does not slide on and forms a part of the combustion chamber, and corresponds to the piston sliding surface. The cylinder of the internal combustion engine according to claim 2, wherein an oil pocket is formed in the plating film to be formed, and a plating film corresponding to the inner surface of the combustion chamber is formed on a smooth surface without the oil pocket. The cylinder of the internal combustion engine according to claim 2, wherein the oil pocket extends in a direction perpendicular to the sliding direction of the piston and is formed in a stripe shape. The cylinder of the internal combustion engine according to claim 2, wherein a smooth plateau surface is formed between the oil pockets on the plating film. The cylinder of the internal combustion engine according to claim 2, wherein the oil pocket provided in the vicinity of the top dead center of the piston is provided with a deeper depth and a smaller interval than oil pockets at other positions. The cylinder of the internal combustion engine according to claim 2, wherein the oil pocket provided in the plating film on the inner peripheral surface of the cylinder extends in a different direction at each formation position.