JP5858778B2 - Manufacturing method of piston for internal combustion engine - Google Patents

Description

  The present invention relates to a method for manufacturing a piston for an internal combustion engine that includes a piston skirt that is in sliding contact with an inner wall of a cylinder of the internal combustion engine.

  An automobile travels by converting a driving force generated by an internal combustion engine supplied with fuel into a rotational driving force to rotate a tire. Recently, various attempts have been made to improve the fuel consumption rate (fuel consumption) of an internal combustion engine in an automobile having such a configuration. This is because the amount of fuel consumption is reduced, which can save energy and contribute to the protection of the global environment.

  One such attempt is to reduce the sliding resistance between the inner wall of the cylinder of the internal combustion engine (bore or inner wall of the sleeve) and the piston that reciprocates within the cylinder. When the sliding resistance is small, it is easy for the piston to reciprocate. For this reason, the driving force for reciprocating the piston is reduced, which in turn reduces the fuel consumption.

  In order to reduce sliding resistance, it is known to provide a layer containing a highly lubricious substance on the inner wall or piston skirt of the cylinder, thereby improving the lubricating performance of the inner wall or piston skirt. For example, in the patent document 1, the present applicant forms a streak on the sliding contact surface of the piston skirt, and the lubrication film (solid lubricating part) made of silver, silver alloy, copper, or copper alloy. It is proposed to cover with.

International Publication No. 2011/115152 Pamphlet

  In the technique described in Patent Document 1, after an internal combustion engine is assembled using the piston for an internal combustion engine on which the coating is formed, the top of the coating is worn by operating the internal combustion engine. As a result, the top is flattened so as to have a predetermined surface roughness, and as a result, a flat surface that is a substantial sliding contact surface is obtained. Since the surface roughness of the sliding contact surface is small (as flat as possible), the friction loss of the internal combustion engine can be reduced.

  In this case, however, the friction loss is reduced after the top of the coating is worn. That is, a predetermined time is required until the frictional resistance is reduced.

  The present invention has been made to solve the above-described problem, and provides a method for manufacturing an internal combustion engine piston capable of obtaining an internal combustion engine piston capable of reducing friction loss even immediately after the start of operation of the internal combustion engine. The purpose is to provide.

In order to achieve the above object, the present invention provides a method for manufacturing a piston for an internal combustion engine in which a solid lubricating portion is formed in a piston skirt that is in sliding contact with an inner wall of a cylinder of the internal combustion engine.
Applying a paste containing at least one of silver, a silver alloy, copper, or a copper alloy so that the protrusion enters the inside of the protrusion provided on the sliding surface of the piston skirt;
Supplying the fluid medium to the paste applied to the protrusions to flow the paste;
By curing the paste by heating the paste after the flow, silver, silver alloy, looking contains at least any one of copper or a copper alloy, with the top portion is a flat surface, the protrusion A step of covering and obtaining a solid lubricating part into which the convex part has entered ,
It is characterized by having.

  The paste for obtaining the solid lubricating part contains a metal (silver, silver alloy, copper or copper alloy) and has a high viscosity and is difficult to flow. However, when the fluid medium collides, the paste diffuses. Further, when the fluid medium flows on the paste, a part of the fluid medium moves along with the fluid medium. In combination, the flow occurs.

  As a result, the top of the paste is flattened and the maximum height Rz of the paste is reduced. Inevitably, the top of the solid lubrication portion formed by the hardening of the paste becomes as flat as possible, and the maximum height Rz becomes as small as possible.

  The sliding contact portion of the internal combustion engine piston with respect to the inner wall of the cylinder is substantially a solid lubricating portion. As described above, the top of the solid lubrication part is flat, the surface roughness is small, and the maximum height Rz of the solid lubrication part is also small. Therefore, even during the first operation of the internal combustion engine, the sliding resistance of the piston for the internal combustion engine with respect to the inner wall of the cylinder is reduced from the beginning of the operation. For this reason, the friction loss of the internal combustion engine is also reduced.

  As described above, according to the present invention, it is possible to obtain an internal combustion engine with a small friction loss immediately after the start of the first operation.

  If necessary, after applying the paste, vibration may be applied to the paste. For this purpose, for example, vibration may be applied to a piston for an internal combustion engine in which a paste is applied to a piston skirt.

  The paste is flattened by vibration. For this reason, while a top part is further planarized, the solid lubrication part with small small maximum height Rz can be obtained. In this case, it is expected that the friction loss is further reduced.

  The solid lubrication part may be provided on the entire sliding surface of the piston skirt. However, since the solid lubrication part is made of silver, silver alloy, copper or copper alloy, the cost increases and the weight of the piston for the internal combustion engine. Becomes larger. Therefore, it is preferable to form the solid lubrication portion in a linear shape or a dot shape.

  In this case, since the total volume of the solid lubrication part is reduced, the amount of metal (silver, silver alloy, copper, or copper alloy) forming the solid lubrication part is reduced. Therefore, the cost can be reduced. Further, it is possible to avoid a significant increase in the weight of the piston for the internal combustion engine.

  Preferably, the piston skirt is provided with a convex portion, and the solid lubricating portion is selectively provided only on the convex portion.

  In the reciprocating motion of the piston for the internal combustion engine, the convex portion is a substantial sliding contact portion. Therefore, even when the solid lubrication part is provided only on the convex part, sufficient lubrication performance can be obtained. In addition, in this case, the amount of metal (silver, silver alloy, copper or copper alloy) forming the solid lubricating portion is further reduced, which is further advantageous in terms of cost and increases the weight of the piston for the internal combustion engine. This is further suppressed.

  Alternatively, the piston skirt may be a smooth surface. In this case, since it is not necessary to perform the operation of providing the convex portion, the number of steps is reduced and the operation is simplified.

  Furthermore, it is preferable that an intermediate layer containing at least a resin material is interposed between the solid lubricating portion and the piston skirt. The solid lubricating part is firmly bonded to the resin material. For this reason, when the intermediate layer is present, the solid lubrication part is unlikely to fall off from the sliding contact surface. Therefore, friction loss is reduced over a long period.

In addition to the resin material, the intermediate layer may further include a solid lubricant such as MoS ₂ , graphite, or boron nitride. In this case, even if the solid lubrication part falls off and the underlying layer is exposed, the lubrication performance is maintained by the solid lubricant contained in the intermediate layer.

  According to the present invention, after applying the paste for obtaining the solid lubricating portion to the piston skirt, the fluid medium is supplied to the paste. The paste diffuses when the fluid medium collides. Further, when the fluid medium flows on the paste, a part of the fluid medium moves along with the fluid medium. In combination with the above, the paste flows.

  As a result, the top of the paste is flattened and the maximum height Rz of the paste is reduced, so that the top of the solid lubricating part formed by hardening of the paste is as flat as possible. And the maximum height Rz is as small as possible. Therefore, even during the first operation of the internal combustion engine, the sliding resistance of the piston for the internal combustion engine with respect to the inner wall of the cylinder is reduced from the beginning of the operation. For this reason, an internal combustion engine with a small friction loss can be obtained immediately after the start of the first operation.

1 is a schematic overall perspective view of a piston according to a first embodiment of the present invention. It is a side view of the piston shown in FIG. It is a cross-sectional schematic diagram which expands and shows the surface layer part vicinity of the piston skirt which comprises the said piston. It is a cross-sectional schematic diagram which shows the state which has supplied the liquid which is a fluid medium by spray application with respect to the paste apply | coated in order to provide a solid-lubrication part. It is a cross-sectional schematic diagram which expands and shows the solid-lubrication part obtained from the said paste. 6 is a roughness curve of the solid lubrication part shown in FIG. 5. It is a cross-sectional schematic diagram which expands and shows the solid-lubrication part obtained from the paste in which the fluid medium is not supplied. It is a roughness curve of the solid-lubrication part shown in FIG. It is a graph which shows the relationship between the presence or absence of supply of a fluid medium, and the maximum height Rz of a solid-lubrication part. It is a cross-sectional schematic diagram which expands and shows the surface layer part vicinity of the piston skirt which comprises the piston which concerns on the modification of 1st Embodiment. It is a side view of the piston which concerns on 2nd Embodiment of this invention. It is a cross-sectional schematic diagram which expands and shows the surface layer vicinity vicinity of the piston skirt which comprises the piston of FIG. It is a cross-sectional schematic diagram which expands and shows the surface layer vicinity vicinity of the piston skirt which comprises the piston which concerns on the modification of 2nd Embodiment.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of a method for manufacturing a piston for an internal combustion engine according to the present invention (hereinafter sometimes simply referred to as “piston”) in relation to the piston obtained thereby will be described with reference to the accompanying drawings. Details will be described with reference to FIG.

  First, the piston will be described.

  FIG. 1 is a schematic overall perspective view of a piston 10 according to the first embodiment of the present invention, and FIG. 2 is a side view thereof. The piston 10 has a pair of piston skirts 12 and 12 at a lower portion thereof, and wall portions 14 and 14 extending along a substantially vertical direction are interposed between the piston skirts 12 and 12. Each of the wall portions 14 and 14 is provided with pin boss portions 16 and 16 so as to protrude in the horizontal direction, and a piston pin for inserting a piston pin (not shown) into each of the pin boss portions 16 and 16. Holes 17 are formed through. The piston pin is passed through a through-hole formed in a small end portion of a connecting rod (connecting rod) (not shown), thereby pivotally supporting the connecting rod.

  An oil ring groove 18, a first piston ring groove 20, and a second piston ring groove 22 are formed in this order in the upper part of the piston skirts 12 and 12 from the bottom to the top. Of course, the oil ring groove 18, the first piston ring groove 20, and the second piston ring groove 22 are formed so as to go around the head of the piston 10 along the circumferential direction.

  The piston 10 configured as described above is made of AC2A, AC2B, AC4B, AC4C, AC4D, AC8H, A1100 (all aluminum alloys defined in JIS), or an aluminum alloy such as an Al—Cu alloy.

  As shown in an enlarged view in FIG. 3, in the first embodiment, a streak 24 is provided on the sliding contact surface of the piston skirt 12. Here, the arrow X direction in FIG. 3 corresponds to the arrow X direction in FIGS. 1 and 2, and the same applies to the subsequent drawings.

  The streak 24 is a swell having a raised protrusion 26 and a recessed valley 28, and is formed by machining the piston skirt 12 along its circumferential direction. The height H of the protrusions 26 (convex parts) is in the range of 0.001 to 0.1 mm, and the interval between the adjacent protrusions 26 and 26, that is, the pitch P is in the range of 0.1 to 0.5 mm. It is preferable to be within. A more preferable range of the height H is 0.008 to 0.012 mm, and a more preferable range of the pitch P is 0.25 to 0.3 mm.

  Here, in 1st Embodiment, the lubricous buildup part 30 as a solid lubrication part is provided only in the projection part 26 in the streak 24. FIG. That is, the lubricous build-up portion 30 is not provided in the valley portion 28 constituting the streak 24, and extends linearly along the circumferential direction of the piston skirt 12 according to the locus of the protrusion portion 26.

  The lubricity build-up portion 30 is made of any of silver, silver alloy, copper, or copper alloy. Both of these show excellent lubrication performance when the piston skirt 12 is in sliding contact with the inner wall of the bore of the cylinder block or the inner wall of the cylinder sleeve. Note that preferable examples of the silver alloy include an Ag—Sn alloy and an Ag—Cu alloy, and preferable examples of the copper alloy include a Cu—Sn alloy, a Cu—Zn alloy, and a Cu—P alloy.

  When the lubricating build-up part 30 is made of silver or a silver alloy, the purity of silver is preferably 60% by weight or more. If it is less than 60% by weight, the thermal conductivity of the lubricated built-up portion 30 is slightly low, and therefore it is not easy to form a smooth wear surface, thereby reducing the friction loss (Psf) of the internal combustion engine. It tends to be less effective. The purity of silver is more preferably 80% by weight or more.

  On the other hand, when the lubricating build-up part 30 is made of copper or a copper alloy, the purity of copper is preferably 70% by weight or more, particularly preferably 80% by weight or more for the same reason as described above.

  Here, the purity of silver is defined as “% by weight of silver contained in the lubricating buildup 30”. For example, when the lubricous build-up portion 30 made of a silver alloy is formed, the purity of silver is obtained as the weight percentage of silver contained in the lubricous build-up portion 30. Furthermore, when obtaining the lubricity build-up part 30 which consists of a sintered compact after apply | coating a silver particle, the purity of silver is defined as a ratio of the silver particle in a paste. The same applies to the purity of copper.

  In addition, it is not particularly necessary to provide all of the lubricating build-up portion 30 from the same metal. For example, the protruding portion 26 of one streak 24 is covered with a lubricating buildup portion 30 made of silver, and the protruding portion 26 of another streak 24 adjacent to the streak 24 is made of a copper alloy. You may make it provide from another kind of metal, such as coat | covering with the build-up part 30. FIG.

  In addition, the thickness of the lubricating build-up portion 30 is not particularly limited, but if it is too small, the lubricous build-up portion 30 will be worn in a relatively short period of time, and the protrusion 26 that is the base is exposed. Will do. On the other hand, if it is excessively large, the lubricating build-up portion 30 becomes heavy, so that the driving force for reciprocating the piston 10 becomes large. In order to avoid the occurrence of the above inconveniences, it is preferable to set the thickness of the lubricating build-up portion 30 to 0.5 to 100 μm.

  Furthermore, the top part of the lubricating build-up part 30 is flattened as much as possible. For this reason, the surface roughness of the lubricated built-up portion 30 is small, and is preferably 4 μm or less, typically about 2 to 3.1 μm, at the maximum height Rz defined in JIS B 0601 (2001). .

  Moreover, the surface roughness of the top part of the lubricating build-up part 30 is 60 nm or less in arithmetic average roughness Ra prescribed | regulated to JISB0601 (2001).

  The lubricating build-up portion 30 having such a small surface roughness at the top can be obtained by supplying a fluid medium. This will be described in detail later.

  The piston 10 according to the first embodiment is basically configured as described above. Next, the function and effect will be described.

  When the internal combustion engine is assembled and operated, the lubricous build-up portion 30 substantially contacts the inner wall of the cylinder (the inner wall of the cylinder bore or the inner wall of the cylinder sleeve) via the lubricating oil. The top of the lubricous build-up part 30 is flattened in advance, and therefore the maximum height Rz of the lubricous build-up part 30 is preferably 4 μm or less (about 2 to 3.1 μm). The arithmetic average roughness Ra at the top is preferably 60 nm or less.

  Therefore, in this embodiment, the sliding resistance of the piston skirt 12 with respect to the inner wall of the cylinder is reduced. This is because the top portion of the lubricous built-up portion 30 that is a substantial sliding contact portion is flat and the surface roughness (maximum height Rz) of the lubricated built-up portion 30 is also small.

  For this reason, when the top part of the lubricous build-up part 30 is in sliding contact with the inner wall of the cylinder, the top part quickly slides with respect to the inner wall of the cylinder. Therefore, it is difficult for friction to occur between the lubricated built-up portion 30 and the inner wall of the cylinder.

  Further, for example, in the case where the lubricous build-up portion 30 is in sliding contact with the inner wall of the FC (gray cast iron) sleeve or Al sleeve, heat conduction of silver, silver alloy, copper or copper alloy in the lubricous build-up portion 30 is performed. The sum of the temperature and the thermal conductivity of the FC sleeve or Al sleeve is 350 W / (m · K) or more.

  For this reason, even when the top portion of the lubricated build-up portion 30 is in sliding contact with the inner wall of the cylinder, the locally generated heat is easily diffused at each sliding contact portion. In other words, stagnant heat is avoided. Therefore, since the temperature of the sliding contact portion is avoided, the sliding contact portion is easily polished without causing adhesion.

  As a result of the above phenomenon, the piston 10 smoothly reciprocates in the cylinder immediately after the start of operation of the internal combustion engine. For this reason, the friction loss (Psf) of the internal combustion engine is reduced from the initial stage of operation. That is, according to the first embodiment, an internal combustion engine having a sufficiently small friction loss can be provided even immediately after the start of the first operation.

  In addition, in this case, the absolute value of the difference in Young's modulus with respect to the FC sleeve or the Al sleeve of the lubricating build-up part 30 is 10 GPa or more. According to the diligent study by the present inventors, when the difference in the absolute value of the Young's modulus increases in this way, the lubricating oil is satisfactorily held in the minute clearance between the sleeve and the piston skirt 12. For this reason, the occurrence of seizure can be effectively avoided.

  Further, since silver or silver alloy is generally expensive and heavy, forming a coating made of silver or silver alloy on the entire sliding contact surface of the piston skirt 12 increases the cost and the weight of the piston. However, in the present embodiment, the lubricating build-up portion 30 is selectively provided only on the protruding portion 26. For this reason, since the usage-amount of the metal (silver, silver alloy, copper, or copper alloy) for obtaining the lubricous build-up part 30 reduces, cost is reduced. In addition, since the lubricating build-up portion 30 exists only in the protrusion 26, it is possible to avoid a significant increase in the weight of the piston 10.

  In addition, since the substantial sliding contact portion is the lubricous build-up portion 30, even when the lubricous build-up portion 30 is provided only on the protrusion 26, sufficient sliding characteristics are exhibited in the piston 10.

  As described above, the lubricating build-up portion 30 is selectively provided only on the protruding portion 26, thereby reducing the cost and suppressing the increase in the weight of the piston 10 and exhibiting a sufficient lubricating action. Can do.

  Next, the manufacturing method of the piston 10 according to the present embodiment will be described in relation to the provision of the lubricous built-up portion 30 on the sliding contact surface of the piston skirt 12.

  First, fine particles of silver, a silver alloy, copper or a copper alloy, preferably so-called nanoparticles having an average particle diameter of 1 to 80 nm, more preferably 30 to 80 nm, are dispersed in a dispersion medium. Examples of the dispersion medium include terpineol, nonanol, ethylene glycol, propylene glycol monomethyl ether acetate, methyl ethyl ketone, and the like.

  Further, at least one of carbon materials such as graphite, carbon nanotubes, carbon black and diamond, or carbide ceramics such as silicon carbide, titanium carbide and titanium carbonitride is added to the dispersion medium, and the viscosity is about 10 cp. A paste 32 (see FIG. 4) is prepared. A dispersant or the like may be added to the paste 32.

  Next, the paste 32 is applied to the piston skirt 12. For application, a known application method such as screen printing or pad printing can be employed.

  At this time, the valley portion 28 of the streak 24 is covered with a screen (not shown). As a result, the paste 32 is prevented from being applied to the valleys 28, and as shown in FIG. 4, the paste 32 is selectively applied only to the protrusions 26 that are convex portions.

  The paste 32 containing a large amount of metal (silver, silver alloy, copper or copper alloy) generally has a high viscosity, and the fluidity is not so great. For this reason, the applied paste 32 maintains its position with almost no flow. That is, at this point, the paste 32 hardly moves or falls off.

  Next, a fluid medium is supplied to the applied paste 32. Specifically, for example, the liquid L may be applied. In this case, as the liquid L, those exemplified as the dispersion medium can be selected. Moreover, as a coating method, a method capable of simultaneously supplying the liquid L over a wide range of the paste 32, for example, spray coating is preferable.

  The spray coating device (not shown) includes a coating nozzle 34 as shown in FIG. The liquid L is ejected from the application nozzle 34 toward the paste 32 and eventually collides with the paste 32. The paste 32 is diffused by this collision. Further, the liquid L (fluid medium) after the collision flows on the paste 32. As part of the paste 32 moves along with the flowing liquid L, the paste 32 flows.

  As a result, the top of the paste 32 is crushed and the skirt is expanded. As a result, the top portion is flattened, and the maximum height Rz (value obtained by subtracting the minimum height from the maximum height) of the paste 32 is reduced.

  Next, the paste 32 is heated together with the piston 10. The suitable heating temperature in this case is 160-240 degreeC. As a result, the dispersion medium in the paste 32 and the liquid L used as the fluid medium are volatilized, and the nanoparticles are fused. That is, sintering occurs, and the lubricating build-up part 30 made of a sintered body of nanoparticles is obtained. Since the paste 32 is applied only to the protrusions 26, the lubricating build-up part 30 is also selectively formed only on the protrusions 26.

  When nanoparticles are used, it is possible to sinter in a relatively low temperature range of 160 to 240 ° C. to form the lubricous built-up portion 30 as described above. Therefore, the piston skirt 12 made of an aluminum alloy is avoided from becoming high temperature, and therefore, it is possible to avoid affecting the mechanical strength and the like of the piston skirt 12.

  As described above, the top of the paste 32 is flattened, and the maximum height Rz of the paste 32 is small. For this reason, as shown in FIG. 5, the lubricated built-up portion 30 having a flat top portion, preferably an arithmetic average roughness Ra of 60 nm or less, and a small maximum height Rz, preferably 4 μm or less, is formed. .

  FIG. 6 is a roughness curve of the lubricity build-up part 30. From FIG. 6, it can be seen that the top of the lubricating buildup 30 is flattened.

  Here, the lubricous build-up portion 30 formed without supplying the fluid medium is shown in FIG. 7, and its roughness curve is shown in FIG. Further, FIG. 9 shows the maximum height Rz of the lubricous build-up part 30 formed without supplying the fluid medium, and the maximum height Rz of the lubricous build-up part 30 formed by supplying the liquid L by spray coating. It is a graph which shows together.

  By comparing FIGS. 5 and 7, FIGS. 6 and 8, and referring also to FIG. 9, by supplying a fluid medium (liquid L), the top is flat and the maximum height Rz It is clear that a lubricity build-up portion 30 with a small is obtained.

  In addition, after supplying the liquid L (fluid medium) to the paste 32, you may make it provide a vibration with respect to the piston 10 before heating the paste 32. FIG. As a result, the paste 32 is flattened, and as a result, the top portion is further flattened, and the lubricating overlay 30 having a small arithmetic average roughness Ra and a small maximum height Rz can be obtained.

  Of course, vibration may be applied only to the paste 32 instead of the entire piston 10.

  Instead of providing the protrusions with the protrusions 26 of the streak 24, the protrusions may be provided with resin. This will be described as a modification of the first embodiment.

  In this modification, as shown in an enlarged cross section in FIG. 10, the sliding contact surface of the piston skirt 12 is formed as a smooth surface, and the resin layer 40 is fixed to the smooth sliding contact surface. The resin layer 40 is formed with protruding portions 42 so as to form a plurality of linear shapes that circulate around the sliding contact surface. In this case, the convex portion 42 is wide on the bottom side close to the piston skirt 12 and narrow on the top side away from the piston skirt 12. For this reason, a streak shape similar to the streak 24 is formed by the plurality of linear-shaped convex portions 42.

  The resin constituting the resin layer 40 (convex portion 42) is preferably of a type that improves the bonding force between the lubricated built-up portion 30 and the piston skirt 12. Preferable examples of such materials include polyimide resin, polyamideimide resin, epoxy resin, nylon-6 resin, nylon-6,6 resin and the like.

  In this modified example, since the convex portion 42 made of resin is interposed between the sliding contact surface of the piston skirt 12 and the lubricating buildup portion 30, the lubrication buildup portion 30 is formed. The amount of silver, silver alloy, copper or copper alloy used is reduced. As a result, the cost can be reduced and the weight of the piston 10 can be prevented from greatly increasing.

In this modification, when the lubricating build-up portion 30 is formed, as a dispersion medium for obtaining the paste 32, a convex portion 42 (between the sliding contact surface of the piston skirt 12 and the lubricating build-up portion 30 ( It is preferable to select one that can swell the resin. As specific examples, N- methylpyrrolidone, polyvinylpyrrolidone down, trichlorethylene, carbon tetrachloride and the like.

  In this case, the resin swells under the action of the dispersion medium when the paste 32 is applied on the convex portion 42 in order to form the lubricating build-up portion 30. As a result, an intermixed layer in which silver particles diffuse at the interface between the resin and the paste 32 is formed. The mutual mixing layer causes a so-called anchor effect between the convex portion 42 and the lubricous build-up portion 30, so that the bonding force of the lubricous build-up portion 30 to the convex portion 42 is further strengthened.

Of course, also in this modified example, the fluid medium is supplied after the paste 32 is applied. The flow medium, the above N- methylpyrrolidone, polyvinylpyrrolidone down, trichlorethylene, may also be used and carbon tetrachloride, or terpineol, nonanol, ethylene glycol, propylene glycol monomethyl ether acetate, methyl ethyl ketone You may make it use.

  Furthermore, after supplying a fluid medium, you may make it provide a vibration with respect to the piston 10 similarly to the above.

  Next, a second embodiment will be described. The same components as those shown in FIGS. 1 to 4 and 10 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 11 is a side view of the piston 50 according to the second embodiment. In this case, the lubricated build-up part 52 is provided on the sliding contact surface of the piston skirt 12 as a plurality of dot-like shapes. In addition, the lubricous buildup part 52 consists of silver, a silver alloy, copper, or a copper alloy like the lubricous buildup part 30 in 1st Embodiment.

  Although not shown in FIG. 11 for ease of understanding, as shown in an enlarged view in FIG. 12, the striations 24 are formed in the piston skirt 12 also in the second embodiment. On the other hand, the lubricating build-up portion 52 is randomly arranged regardless of whether it is the convex portion (projection portion 26) or the valley portion 28 of the streak 24. That is, in the second embodiment, the formation position of the lubricous build-up portion 52 is not limited to the protrusion 26 (convex portion).

  However, in the second embodiment, since the lubricous build-up portion 52 is provided in a dot shape, the volume of each lubricous build-up portion 52 is small. That is, in the first embodiment, the amount of metal (silver, silver alloy, copper, or copper alloy) used is reduced by providing the lubricated build-up portion 30 only at positions that are involved in actual sliding contact. However, in the second embodiment, the amount of metal used is reduced by reducing the volume of each lubricous build-up part 52, and hence the sum of the volumes of all the lubrication build-up parts 52. .

  For this reason, also in 2nd Embodiment, while the cost can be reduced similarly to 1st Embodiment, the effect that it can avoid that the weight of piston 50 increases greatly is acquired.

  In order to form the lubricity build-up portion 52 in a dot shape, a predetermined portion of the piston skirt 12 is covered with a screen when the paste 32 is applied by a known application method such as screen printing or pad printing described above. You can do it.

Then, after coating the paste 32, to the paste 32, the above-mentioned terpineol, nonanol, ethylene glycol, propylene glycol monomethyl ether acetate, methyl ethyl ketone, N- methyl pyrrolidone, polyvinylpyrrolidone down, trichlorethylene, flow carbon tetrachloride Supply the medium. As a result, the paste 32 diffuses or flows. Therefore, when the paste 32 is cured by heating, the top is flat, preferably the arithmetic average roughness Ra is 60 nm or less, and the maximum height Rz is small. A lubricating build-up portion 52 that is preferably 4 μm or less is provided.

  If necessary, vibration may be applied to the piston 10 after applying the paste 32.

  It is not essential to form the streak 24. That is, the slidable contact surface of the piston skirt 12 may be a smooth surface, and the point-like lubricating buildup portion 52 may be provided on the smooth slidable contact surface. In this case, the recessed part formed between the lubricity build-up parts 52 and 52 plays the role which hold | maintains lubricating oil.

  Furthermore, an intermediate layer may be interposed between the sliding contact surface of the piston skirt 12 and the lubricated build-up portion 52. This will be described as a modification of the second embodiment.

  In this modification, as shown in an enlarged cross section in FIG. 13, the smooth sliding contact surface of the piston skirt 12 is entirely covered with an intermediate layer 54, and a point-shaped lubricating meat is formed on the intermediate layer 54. A raised portion 52 is provided.

The intermediate layer 54 may be formed of an inorganic substance exhibiting good lubricity, such as MoS ₂ or graphite, but may be polyimide resin, polyamideimide resin, epoxy resin, nylon-6 resin, nylon-6,6 resin. You may make it form from resin, such as. In the former case, the lubricating performance is maintained by the intermediate layer 54 even if the lubricating build-up portion 52 should fall off (peel) from the intermediate layer 54. Further, in the latter case, an advantage is obtained that the joining force between the lubricating build-up portion 52 and the piston skirt 12 is improved.

  The intermediate layer 54 may further contain a solid lubricant in addition to the resin material. In other words, the intermediate layer 54 may be a mixed layer of an inorganic substance exhibiting lubricity and the resin as described above.

Known solid lubricants may be blended, and suitable examples thereof include molybdenum disulfide (MoS ₂ ), boron nitride (BN), and graphite (C). In this case, the joining force between the lubricating buildup portion 52 and the piston skirt 12 is improved, and even if the intermediate layer 54 comes into sliding contact with the inner wall of the cylinder, the lubricating performance is maintained by the solid lubricant. The

  As described above, the metal for obtaining the lubricating buildup portion 52 while maintaining the lubricity by the intermediate layer 54 or improving the bonding force between the lubrication buildup portion 52 and the piston skirt 12. The amount of use can be reduced. As a result, the cost can be reduced and the weight of the piston 50 can be prevented from greatly increasing.

  Any of the inorganic substances and resins as described above is inexpensive and lightweight. For this reason, even if the entire sliding contact surface of the piston skirt 12 is covered with the intermediate layer 54, the cost increases significantly, and the piston 50 It is avoided that the weight of is excessively large. Moreover, when the entire sliding contact surface of the piston skirt 12 is covered with the intermediate layer 54, the operation is easier and simpler than when the intermediate layer 54 is selectively provided on a part of the sliding contact surface of the piston skirt 12. The advantage is obtained.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

  For example, also in the second embodiment, the lubricating build-up portion 52 may be formed in a dot shape only on the protrusion portion 26 of the streak 24. In other words, in this case, a part of the protrusion 26 that circulates around the sliding contact surface of the piston skirt 12 is covered in a dot shape by the lubricating overlay 52.

  Moreover, you may make it form the intermediate | middle layer 54 in a stripe shape similarly to the modification of 1st Embodiment. In this case, what is necessary is just to form the lubricous buildup part 52 in the shape of a dot in the top part of a streak shape.

  Further, in the modification of the second embodiment, the entire sliding contact surface of the piston skirt 12 is covered with the intermediate layer 54. However, the intermediate layer 54 is selectively applied to a part of the sliding contact surface of the piston skirt 12. Alternatively, the lubricating build-up portion 52 may be selectively provided only on the intermediate layer 54.

  Furthermore, the fluid medium is not limited to the liquid L, and may be a compressed gas such as compressed air. In this case, the supply conditions may be set as appropriate, such as increasing the discharge pressure from the supply nozzle as compared to the discharge pressure from the application nozzle 34 (see FIG. 4).

DESCRIPTION OF SYMBOLS 10, 50 ... Piston for internal combustion engines 12 ... Piston skirt 24 ... Streaks 26 ... Projection part 28 ... Valley part 30, 52 ... Lubrication buildup part 32 ... Paste 34 ... Application nozzle 40 ... Resin layer 42 ... Convex part 54 ... Intermediate layer L ... Liquid

Claims (7)

In a method for manufacturing a piston for an internal combustion engine in which a solid lubricating portion is formed on a piston skirt that is in sliding contact with an inner wall of a cylinder of the internal combustion engine,
Applying a paste containing at least one of silver, a silver alloy, copper, or a copper alloy so that the protrusion enters the inside of the protrusion provided on the sliding surface of the piston skirt;
Supplying the fluid medium to the paste applied to the protrusions to flow the paste;
By heating the paste after flowing, the paste is cured to contain at least one of silver, silver alloy, copper, or copper alloy, the top is a flat surface, and the protrusion is covered. And obtaining a solid lubrication part into which the convex part has entered,
The manufacturing method of the piston for internal combustion engines characterized by having.   The manufacturing method according to claim 1, further comprising a step of forming an intermediate layer including a resin material on the sliding contact surface of the piston skirt, and providing the intermediate layer as a convex portion on the sliding contact surface of the piston skirt, A method of manufacturing a piston for an internal combustion engine, wherein the paste is applied only on the convex portion. In a method for manufacturing a piston for an internal combustion engine in which a solid lubricating portion is formed on a piston skirt that is in sliding contact with an inner wall of a cylinder of the internal combustion engine
Forming a flat intermediate layer containing a resin material on the smooth sliding contact surface of the piston skirt;
On the intermediate layer, a step of applying a paste containing at least one of silver, a silver alloy, copper, or a copper alloy in a dot shape or a linear shape;
Supplying the fluid medium to the paste to cause the paste to flow;
By heating the paste after flowing, the paste is cured to contain at least one of silver, silver alloy, copper, or copper alloy, the top is a flat surface, and is a dot-like or linear shape Obtaining a solid lubricating part having a shape;
The manufacturing method of the piston for internal combustion engines characterized by having. 4. The method for manufacturing a piston for an internal combustion engine according to claim 2 , wherein the intermediate layer is formed of a resin material containing a solid lubricant. 5. The manufacturing method according to claim 4 , wherein at least one selected from the group of molybdenum disulfide, boron nitride, and graphite is selected as the solid lubricant. The method of manufacture according to any one of claims 1 to 5, wherein after supplying the fluid medium, the manufacture of a piston for an internal combustion engine, which comprises applying a vibration to said paste to said paste Method. The method of manufacture according to any one of claims 1 to 6 production method of a piston for an internal combustion engine, which comprises adding a dispersing agent to the paste before application.

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