JPH11141398A - Piston for internal combustion engine and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and surely form a cooling cavity and eliminate a cooling effect from being imparied by fittedly attaching a ring carrier in fitting recess part, by forming the cooling cavity constituted of a circumferential groove, and by connecting the ring carrier to a falling-prevention ring. SOLUTION: A fitting recess part 21 is formed in an outer circumferential face of a top surface 11 side of a main body part 10. The fitting recess part 21 is so formed as to be removed into an L-shape along the outer circumferential edge of the top face 11 and a circumferential groove (a cooling cavity) 22 is formed as being opened in the outer circumferential face of the fitting recess part 21. A ring-shaped ring carrier 23 is fittedly attached in the fitting recess part 21 provided with the cooling cavity 22 in its outer circumferential side. A holding groove 31 is formed in a prescribed position on the outer circumferential face of the fitting recess part 21 and a falling-prevention ring 30 which is held by this holding groove 31 is welded and connected to the ring carrier 23. This constitution can prevent the ring carrier 23 from being fallen.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston for an internal combustion engine and a method for manufacturing the same, and more particularly to a piston for an internal combustion engine having a cooling cavity formed therein.

[0002]

2. Description of the Related Art As pistons for diesel engines have increased in mechanical and thermal loads, pistons made of aluminum alloys and steel pistons having excellent strength and wear resistance have been widely used. Has become.

[0003] The steel piston includes a cast iron integrated piston integrally cast with ductile cast iron, a steel head having a head and a pin boss integrally formed, and an aluminum alloy skirt having a pin hole. And a two-piece piston connected via a piston pin fitted into the piston, and an assembled piston in which a forged steel head and a main body made of steel or aluminum alloy are connected by bolts. Of these three types of pistons, one-piece pistons made of ductile cast iron are widely used in automobiles, construction machines, and small marine diesel engines.

[0004] The ductile cast iron integrated piston is provided with an annular cooling cavity along the circumferential direction inside the vicinity of the piston top surface and near the ring zone, and circulates cooling oil in the cooling cavity. By doing so, the piston head and the ring zone are cooled.

[0005] The cooling cavity as described above is formed by casting an annular sand core with cast iron in a state of being cast inside the piston, and then removing the sand core.

When a cooling cavity is formed in a piston integrated with ductile cast iron, it takes time and effort to fix the above-mentioned sand core to the piston core body. Increase. Further, since the position of the cooling cavity is determined by the position of the sand core, there is a disadvantage that the positional accuracy is deteriorated. Further, since the sand core is wrapped in the molten metal, casting defects are likely to occur around the sand core. Since such a casting defect cannot be visually confirmed from the outside, it is necessary to perform inspection using an expensive inspection device such as a fiberscope or an X-ray inspection device.

In addition, due to design restrictions such as the shape and position of the combustion chamber at the piston head, the shape of the sand core for forming the cooling cavity may be complicated or extremely thin. In such a case, there are problems such as burning of the sand core and difficulty in removing sand from the inside of the piston after casting.

In order to solve such a problem and more easily manufacture a cooling cavity, for example, Japanese Patent Application Laid-Open No. Sho 60-16615.
No. 7 proposes a manufacturing method in which a piston head is divided into a plurality of parts and manufactured, and a cooling cavity is provided in a divided surface, and the parts are joined later by welding. Also, Japanese Patent Application Laid-Open No. 61-169646
Japanese Patent Application Laid-Open Publication No. H11-139,086 also discloses a welded piston crown in which a plurality of divided portions in a portion including a cooling cavity are joined by welding. Japanese Patent Laid-Open No. 60-
JP-A-166157 discloses a method of manufacturing a piston in which divided surfaces including a cooling cavity are joined by a friction welding method.

[0009]

When the cooling cavity forming method disclosed in each of the above-mentioned patent publications is used, it is necessary to cast a sand core for forming the cooling cavity inside the piston. Is eliminated, and casting problems are eliminated. However, another problem arises in joining the divided portions in which the cooling cavities are formed.

When at least one component of the divided portions to be joined is made of ductile cast iron, a large amount of carbon contained in the ductile cast iron causes a hard and brittle metal structure containing carbide when the molten portion is cooled and solidified, that is, Chills occur, which reduces the bonding strength and
Workability deteriorates. In order to solve such problems, a heat treatment for tempering is required.

[0011] Further, the following problem arises as a result of joining the joining surfaces including the cooling cavities. First, in the case of welding, local deformation occurs due to input heat at that time. In addition, the molten portion protrudes into the cooling cavity, obstructing the flow of cooling oil when the product is used, and the cooling cavity does not perform its original function, resulting in poor cooling. In addition, there is a problem that welding powder enters the cooling cavity.

As a countermeasure against the protrusion of the molten portion and the invasion of welding powder, it has been proposed to dispose the joining portion outside the cooling cavity as disclosed in Japanese Utility Model Laid-Open No. 1-78249, for example. . However, such measures inevitably complicate the pre-processing.

[0013] Even when a plurality of joints are joined by friction welding, there is a problem that the melted portion protrudes into the cooling cavity. On the other hand, Japanese Unexamined Utility Model Publication No. 3-65840 discloses a method of forming a flash receiving portion inside a cooling cavity. According to such a piston, it is necessary to remove the protruding molten portion in advance in order to prevent the protruding molten portion from falling into the cooling cavity at the time of using the product and to be mixed into the cooling oil. There is a problem to be solved.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and a cooling cavity is simply and reliably formed, and the cooling effect is not impaired, and the assembling can be performed at low cost. It is an object to provide a piston for an internal combustion engine with a possible cooling cavity and a method for producing the same.

[0015]

According to the present invention, there is provided a main body having at least a top surface and a recess for fitting formed on the outer peripheral surface on the top surface side, and a piston ring groove formed on the outer peripheral surface, A cooling cavity comprising a ring carrier fitted into the fitting recess of the main body, and a circumferential groove formed at least at a joint between the fitting recess of the main body and the inner peripheral surface of the ring carrier. And a drop-off prevention ring held in a holding groove formed in the fitting recess and connected to the ring carrier.

[0016] The main body may be made of cast iron, and the ring carrier and the falling-off prevention ring may be made of steel. Further, the ring carrier and the falling-off prevention ring may be welded and connected by an energy beam irradiated from an outer peripheral side of the ring carrier.

According to still another aspect of the present invention, there is provided a main body having at least a top surface, a fitting concave portion formed on an outer peripheral surface on the top surface side, a piston ring groove formed on the outer peripheral surface, and a circumference. The ring carrier is divided into a plurality of segments in the direction, the split position is melted and joined in a state where the ring carrier is mounted in the fitting recess of the main body, the fitting recess of the main body and the inner peripheral surface of the ring carrier. A cooling cavity formed of a peripheral groove formed on the outer peripheral surface of the fitting concave portion at a joint portion of the ring carrier, and a fall prevention formed in the inner peripheral surface of the ring carrier and engaged with an edge of the peripheral groove. And a projection for an internal combustion engine, comprising:

The fusion bonding of the ring carrier at the division position may be performed by welding, and the welding depth may be adjusted so that the fusion portion does not protrude into the cooling cavity formed by the peripheral groove. Further, at a position above the peripheral groove, the ring carrier may be melt-bonded to the main body along the circumferential direction. Further, the ring carrier may be connected to a drop-off prevention ring that is held on the outer peripheral surface of the fitting concave portion on the top surface side with respect to the peripheral groove.

Still another aspect of the present invention is directed to a main body having at least a top surface and having a fitting recess formed on the outer peripheral surface on the top surface side, and a piston ring groove formed on the outer peripheral surface. A cooling cavity comprising a ring carrier fitted in the fitting recess, a circumferential groove formed in at least one of a joint portion between the fitting recess of the main body portion and an inner peripheral surface of the ring carrier; The present invention relates to a piston for an internal combustion engine, comprising: a wearing recess or an inner peripheral surface of the ring carrier, and a falling-off preventing step portion for preventing the ring carrier from falling off.

A circumferential groove forming the cooling cavity is formed in the fitting recess of the main body, and the falling-off preventing step is formed on the inner peripheral surface of the ring carrier, and the falling-off preventing step is provided. May be engaged with the upper edge of the circumferential groove forming the cooling cavity. The ring carrier may be fitted into the fitting recess of the main body by shrink fitting.

The invention relating to a manufacturing method is characterized in that a fitting recess is formed at least on a top outer peripheral surface of a main body having a top surface, a holding groove is formed in the fitting recess, and the holding groove is formed to prevent falling off. After the ring is fitted, a ring carrier is fitted into the fitting recess, and an energy beam is irradiated from the outer peripheral side of the ring carrier at a portion corresponding to the fall prevention ring held in the holding groove, and The prevention ring and the ring carrier are fusion-bonded, and a cooling cavity is formed inside by a circumferential groove formed on at least one of the joints between the fitting recess and the inner peripheral surface of the ring carrier. The present invention relates to a method for manufacturing a piston for an internal combustion engine, characterized in that it has been made as above.

According to the invention relating to another manufacturing method, a fitting recess is formed at least on a top outer peripheral surface of a main body having a top surface, and a cooling cavity is formed on the outer circumferential surface of the fitting recess. A ring carrier, which is formed into a circumferential groove, is divided into a plurality of segments in the circumferential direction, and has a projection for preventing falling off on the inner peripheral surface, is attached to the fitting recess, and the projection for preventing falling is fitted to the periphery. The present invention relates to a method for manufacturing a piston for an internal combustion engine, wherein the piston is engaged with an edge of a groove to melt-join a split position of the ring carrier.

According to still another aspect of the invention, a fitting recess is formed on an outer peripheral surface of a main body having at least a top surface on a top surface side, and a cooling cavity is formed on an outer peripheral surface of the fitting concave portion. A peripheral groove is formed, and a region on an outer peripheral portion of the fitting concave portion and above the peripheral groove is defined as a protrusion for interference, and a shoulder portion is formed on an inner peripheral surface of the ring carrier fitted in the fitting concave portion. Forms a fall prevention step that is engaged with the upper edge of the circumferential groove, and the fall prevention step climbs over the interference projection in a state where the ring carrier is heated and expanded. The ring carrier is fitted into the fitting recess by shrink fitting so as to engage with the upper edge of the peripheral groove, and when the temperature reaches room temperature, the ring carrier is fastened to the fitting recess at the portion of the interference projection. To be worn and to prevent the dropout A process for producing a piston for an internal combustion engine, wherein the shoulder portion is to be fixed is engaged with the upper edge of the circumferential groove.

[0024]

1 to 3 show an internal combustion engine piston according to an embodiment of the present invention. This piston is an integral type piston whose main body 10 is cast from ductile cast iron. It is about improvement. The main body 10 of the piston includes a combustion chamber 12 formed of a concave portion facing the top surface 11, and a portion on the outer peripheral side and a lower end side thereof is constituted by a skirt portion 15. 180 ° in the circumferential direction inside the skirt portion 15
A pair of pin bosses 16 are formed at distant positions, and pin holes 17 are formed in these pin bosses 16.

A fitting recess 21 is formed on the outer peripheral surface of the main body 10 on the top surface 11 side. The fitting recess 21 is formed by removing an L-shaped cross section along the outer peripheral edge of the top surface, and a peripheral groove 22 is formed so as to open on the outer peripheral surface of such fitting recess 21. . The peripheral groove 22 is for forming a cooling cavity. A ring carrier 23 having a ring shape is fitted and attached to an outer peripheral side of the fitting concave portion having the cooling cavity 22. On the ring carrier 23, three piston ring grooves 25, 26, 27 are formed in order from the top.

The ring carrier 23 has a falling-off prevention ring 30 for preventing the ring carrier 23 from falling off. That is, the holding groove 31 is formed at a predetermined position on the outer peripheral surface of the fitting recess 21 as shown in FIG.
The falling-off prevention ring 30 held by the ring carrier 23 is welded and connected to the ring carrier 23, and the falling-off prevention ring 30 prevents the ring carrier 23 from falling off.

Next, a method for manufacturing such a piston will be described in order. First, the main body 10 is manufactured from ductile cast iron. The fitting recess 21 and the holding groove 31 are formed on the outer peripheral surface of the main body 10 by machining. The peripheral groove 22 may be formed by casting in advance, or may be formed by machining later.
Then, into the holding groove 31, for example, as shown in FIG. 4, a two-piece drop prevention ring 30 having the same width as the height direction dimension of the holding groove 31 or a slightly larger thickness is pushed.
Then, processing is performed so that the outer peripheral portion of the falling-off prevention ring 30 pushed into the holding groove 31 becomes a peripheral surface that is continuous with the outer peripheral surface of the fitting concave portion 21.

Next, the ring carrier 23 is fitted with the concave portion 2.
Push into 1. Since the dimensional tolerance of the inner peripheral surface of the ring carrier 23 with respect to the outer peripheral surface of the normal fitting concave portion 21 is a tight fit, the ring carrier 23 is fitted by press fitting. Thereafter, an energy beam, such as an electron beam or a laser beam, is irradiated from the outer peripheral side of the ring carrier 23 at a height corresponding to the falling prevention ring 30 to melt the melting portion 33 of the ring carrier 23 and the falling portion corresponding to the melting portion 33. The portion on the outer peripheral side of the prevention ring 30 is simultaneously melted and fused.
In addition, at the time of this fusion bonding, the holding groove 3
The conditions are set so that the bottom portion 1 and the portion on the inner peripheral side of the falling-off prevention ring 30 are not melt-bonded.

After the drop-prevention ring 30 and the ring carrier 23 are connected to the main body 10 in this manner, finishing is performed to finish the piston.

The ring carrier 23 of such a piston
The drop prevention ring 30 may be made of either carbon steel or alloy steel, and can be appropriately selected.

As shown in FIG. 4, the ring 30 for preventing falling off in the above-described embodiment uses a ring 30 divided at 180 °, but instead of such a ring, as shown in FIG. A ring 30 consisting of a perfect circle
May be used. In this case, it is preferable that the main body 10 is cast in advance at a predetermined position when the main body 10 is cast. The drop-prevention ring 30 may be any shape as long as it can be fixed in the holding groove 31 so as not to move in the vertical direction, and its cross-sectional shape may be any shape such as a rectangle, a circle, and an ellipse.

As shown in FIG. 3, in the above embodiment, a drop-off prevention ring 30 pushed into a single holding groove 31 is used, and such a drop-off prevention ring 30 constitutes a cooling cavity 22. 6, the holding grooves 31 are formed at upper and lower portions of the circumferential groove 22 constituting the cooling cavity 22, respectively, as shown in FIG.
Each of the holding grooves 31 may be provided with a drop prevention ring 30. Also in this case, the falling-off prevention ring 30 is welded from the outside by an energy beam and connected to the ring carrier 23, thereby preventing the falling off of the ring carrier 23.

In the piston for an internal combustion engine according to the present embodiment having the above-described configuration, the circumferential groove 22 opened on the outer peripheral surface of the fitting concave portion 21 is closed by the ring carrier 23 to form the cooling cavity 22. Therefore, the cooling oil does not flow out of the cooling cavity 22 more than necessary during operation, and the piston can be sufficiently cooled. In addition, such a structure makes it possible to form the cooling cavity 22 by processing on the outer peripheral surface of the fitting concave portion 21, and it can be formed freely even when the cooling cavity 22 is small. The positioning accuracy of the cooling cavity is also greatly improved.

In general, when the ring carrier 23 is manufactured from a separate steel member for the main body 10 and welding is to be performed later, ductile cast iron forming the main body 10 contains a large amount of carbon. The melted portion is quenched to form a brittle structure containing carbides, ie, chill, and the bonding strength is weak, so that it cannot be used as a piston. Therefore, in the present embodiment, since the fall prevention ring 30 is fitted into the holding groove 31 and only the fall prevention ring 30 is welded to the ring carrier 23, the ductile cast iron and the steel are welded. The above-mentioned problem that sometimes appears can be solved.

Further, since the fitting of the ring carrier 23 to the fitting recess 21 is tight, the combustion gas on the piston top surface 11 does not leak into the cooling cavity 22. Further, the main body 10, the ring carrier 23, and the drop-prevention ring 30 are in close contact with each other, and the frictional force generated between the ring carrier 23 and the fitting concave portion 21 causes the welding connection between the ring carrier 23 and the drop-prevention ring 30. Since the ring carrier 23 acts in addition to the force, the ring carrier 23 can be reliably prevented from coming off the fitting recess 21.

According to the piston according to the present embodiment, the falling-off prevention ring 30 is melt-bonded to the ring carrier 23 by irradiating the energy beam from the outer peripheral side. Local deformation can be prevented, the molten portion does not protrude into the cooling cavity 22, and welding powder does not enter the cooling cavity 22. For this reason, occurrence of cooling failure is prevented.

By controlling the irradiation conditions of the energy beam, the main body 10 made of ductile cast iron can be used when the ring carrier 23 and the drop-prevention ring 30 are welded.
Is not chilled, so that it is not necessary to temper the portion chilled by the heat treatment later. Instead of the energy beam irradiation, the ring carrier 23 and the drop prevention ring 30 may be joined by TIG welding.

According to such a piston for an internal combustion engine, it is not necessary to form the cooling cavity 22 using a sand core or the like. Can be avoided from being deteriorated. In addition, casting defects around the sand core type are avoided, and it is not necessary to check for casting defects.
The inspection step can be omitted. In addition, problems such as design restrictions such as the shape and position of the combustion chamber 12 and complicated work for removing the sand core after casting are avoided.

Next, still another embodiment will be described with reference to FIGS.
It will be explained by. In this embodiment, the fitting recess 21 formed on the outer peripheral surface on the top surface side of the main body 10 is provided.
7 and 8, the ring carrier 23 is divided into a plurality of segments in a circumferential direction, for example, into a pair of 180 ° segments.
A drop-off preventing projection 35 is formed on the inner peripheral surface.

The pair of ring carriers 23 are fitted on the outer peripheral surface side of the fitting recess 21 from both sides thereof.
1. At this time, the protrusions 35 for preventing the falling off of the ring carrier 23 are engaged with the upper and lower edges of the circumferential groove 22 formed on the outer peripheral surface of the fitting recess 21 as shown in FIG. . When the pair of ring carriers 23 is mounted on the outer peripheral surface of the fitting concave portion 21 in this way, as shown in FIG. Welding by energy beam irradiation.

At this time, it is preferable to control the irradiation of the energy beam so as to perform welding so that the welded portion 37 on the joint surface does not protrude into the peripheral groove 22 as shown in FIG. When the division positions are joined to each other by welding as described above, the pair of ring carriers 23 are joined to each other to form a circular ring carrier 23 and are fitted to the fitting recess 21. Moreover, since the falling-off preventing projection 35 is engaged with the edge of the peripheral groove 22, the ring carrier 23 is prevented from falling off.

Thereafter, as shown in FIG. 9, an energy beam is irradiated from the horizontal direction along the circumferential direction on the outer peripheral surface of the ring carrier 23, so that the entire portion of the welded portion 36 is welded. This ring carrier 23
Is welded to a portion on the outer peripheral surface of the fitting concave portion 21 and above the peripheral groove 22. This ensures a seal between the space on the top side of the piston and the cooling cavity formed by the circumferential groove 22.

As described above, in the present embodiment, the segment of the ring carrier 23 having the projection 35 for preventing falling off on the inner peripheral surface to be engaged with the peripheral groove 22 forming the cooling cavity is used as the main body 10. After fitting in the fitting recess 21 of
The butted portions of the ring carrier 23 at the respective divided positions are welded with an energy beam to be integrated as shown in FIGS. At this time, by adjusting the welded portion 37 as shown by oblique hatching in FIG. 11, it is possible to prevent the protruding portion of the molten metal at the time of welding from entering the cooling cavity 22. Ring carrier 23
If the welding at the divided positions is performed by butt electric resistance welding, the entire butt portion can be welded and joined.

Also, as shown by reference numeral 36 in FIG. 9, the outer periphery of the ring carrier 23 and the outer periphery of the fitting recess 21 of the main body 10 are welded to each other by applying an energy beam from the outer periphery to thereby reduce the operating time. Leakage of the combustion gas into the cooling cavity 22 is prevented. At this time, the ring carrier 23 is prevented from falling off from the main body 10 by the protrusion 35 for preventing the ring carrier 23 from coming off, so that the outer peripheral portion of the fitting concave portion 21 that is melt-joined to the melting portion 36 by welding is chilled. Even if it becomes brittle, the ring carrier 21 does not fall off.

Next, a modification of the above embodiment will be described with reference to FIGS. In this embodiment, a drop-off prevention ring 30 is further added. That is, a peripheral groove 22 is formed on the outer peripheral surface of the fitting concave portion 21, and a retaining groove 30 is mounted on the peripheral groove 22 by a holding groove, and divided into a plurality of, for example, two in this state. The ring carrier 23 thus mounted is mounted on the outer peripheral surface of the fitting concave portion 21, and the division position is melt-bonded by an energy beam.

When the ring carrier 23 composed of segments whose fusion positions are melt-joined to each other is combined with the ring 30 for preventing falling as described above, when the ring carrier 23 is welded to the main body 10 from the outer peripheral side, The main body 10 is prevented from being locally chilled. Also, it is ensured that the combustion gas generated in the combustion chamber 12 during the operation of the engine is prevented from entering the cooling cavity 22 by the melting portion 36 joining the drop-off prevention ring 30 and the ring carrier 23. Become.

Next, still another embodiment will be described with reference to FIGS.
6 will be described. In this embodiment, the ring carrier 2 is shrink-fitted without using a welding method.
3 is fitted into the fitting concave portion 21 of the main body 10 and the ring carrier 23 is prevented from falling off by the engagement of the drop-off preventing step 38 and the interference projection 43.

As shown in FIG. 14, after casting the piston body 10 made of ductile cast iron, the top surface 11 and the fitting recess 21 are machined to predetermined dimensions. Here, the peripheral groove 22 may be formed by casting or machining.
On the other hand, the ring carrier 23 made of steel is machined to a predetermined size, and the inner periphery thereof is formed as shown in FIGS.
As shown in FIG. 7, a step 38 for preventing falling off is formed.

In such a state, the ring carrier 2
3 is heated to about 500 ° C. so that the inner peripheral surface of the step 38 for preventing the falling off of the ring carrier 23 passes over the outer peripheral surface of the interference projection 43 of the main body 10. Is fitted into the fitting recess 21 as shown in FIG.

When the temperature of the ring carrier 23 becomes room temperature after the fitting, the interference fit between the fitting recess 21 at the portion of the interference projection 43 and the inner peripheral surface of the ring carrier 23 forms a tight fit. 10 and the ring carrier 23 are integrated. At this time, a cooling cavity is formed by the peripheral groove 22 formed on the fitting recess 21 on the inner peripheral side of the ring carrier 23. The piston to which the ring carrier 23 is attached by shrink fitting in this manner is subjected to predetermined machining and then incorporated into the engine.

As described above, in the piston according to the present embodiment, the ring carrier 23 made of the same or different metal as the piston body 10 is attached to the fitting recess 21 of the body 10 by shrink fitting. Here, the interference between the ring carrier 23 and the fitting recess 21 at the interference protrusion 43 is preferably in the range of 1 to 100 μm, more preferably in the range of 1 to 40 μm. The interference between the interference projection 43 and the inner peripheral surface of the ring carrier 23 is caused by the cooling cavity 2.
There may be a light interference between the 2 and the top surface of the piston to keep the air tight. The fitting between the outer peripheral surface of the fitting recess 21 and the inner peripheral surface of the ring carrier 23 at the lower side of the cooling cavity 22 may be a tight fit or a clearance fit.

After shrink fitting, as shown in FIG. 16, a shoulder 39 on the upper end side of a drop-off prevention step 38 provided on the inner peripheral surface of the ring carrier 23 is attached to the outer peripheral surface of the fitting recess 21. The ring carrier 23 is surely integrated with the main body 10 by being engaged with the lower end of the formed interference projection 43. It is necessary to set the size of the outer peripheral portion of the above-mentioned interference projection 43 and the size of the inner peripheral portion of the drop prevention step 38 by combining the materials of the main body 10 and the ring carrier 23. Furthermore, the shrink fitting temperature is properly selected by the combination of the above materials.

According to such a piston for an internal combustion engine,
The circumferential groove 22 is closed by shrink fitting of the ring carrier 23 into the fitting concave portion 21 of the main body portion 10 to form a cooling cavity, and the tightening force of the interference projection 43 and the engagement of the retaining step portion 38 are reduced. By the stopping force, the piston body 10
And the ring carrier 23 are firmly connected.

Further, the recess forming the cooling cavity 22 can be cast by an outer mold, and therefore, the cooling cavity 2 can be cast.
When 2 is formed by casting, casting defects are reduced, and the positional accuracy and the shape accuracy of the cooling cavity 22 are improved.

Although the ring carrier 23 is simply joined by shrink fitting, the inertia force at the time of overrun cannot be countered, but a step 38 for preventing falling off is provided.
By engaging the shoulder 39 of FIG. 8 with the edge of the lower end of the interference projection 43, the ring carrier 23 falls out of the fitting recess 21 of the main body 10 even if an inertia force exceeding the interference force acts. Will not be done.

Also, since the core used in the conventional method for forming the cooling cavity and the portion for supporting the core are not required, the inlet hole and the outlet hole for the cooling oil are effectively positioned. Can be placed in In addition, since the core that forms the cooling cavity and the part that supports it are not necessary,
Casting costs will be significantly reduced.

Further, since the piston body 10 and the ring carrier 23 can be made of different materials, a material suitable for the body 10 and a material suitable for the ring carrier 23 are independently selected from each other. It becomes possible to do. For example, by using a material such as niresist cast iron having excellent wear resistance as the ring carrier 23, a piston performance that cannot be obtained with a conventional integrated piston is realized.

[0058]

According to the present invention, there is provided a main body having at least a top surface and a fitting recess formed on the outer peripheral surface on the top surface side, and a piston ring groove formed on the outer peripheral surface to fit the main body. A ring carrier to be fitted in the fitting recess, a cooling cavity comprising a circumferential groove formed in at least one of the joints between the fitting recess in the main body portion and the inner peripheral surface of the ring carrier, and a cooling cavity formed in the fitting recess. And a drop-off prevention ring held in the holding groove and connected to the ring carrier.

Therefore, according to such a piston, the cooling cavity is easily formed by fitting the ring carrier into the fitting recess, and the ring carrier is prevented from falling off by the falling prevention ring. It will surely be prevented.

According to the configuration in which the main body is made of cast iron, and the ring carrier and the falling-off prevention ring are both made of steel,
It is possible to prevent the main body portion made of cast iron from being dropped from the main body portion without melting and joining the ring carrier to the ring carrier.

According to the configuration in which the ring carrier and the drop-prevention ring are welded and connected by the energy beam irradiated from the outer periphery of the ring carrier, the ring carrier is melt-bonded by the energy beam after the assembly. And the drop-off prevention ring can be welded and connected.

According to another aspect of the present invention, there is provided a main body having at least a top surface, a fitting recess formed on an outer peripheral surface on the top surface side, a piston ring groove formed on the outer peripheral surface, and a circumferential direction. The ring carrier is divided into a plurality of segments, and the split position is melt-joined in a state where the ring carrier is attached to the fitting recess of the main body, and the joint between the fitting recess of the main body and the inner peripheral surface of the ring carrier. A cooling cavity comprising a peripheral groove formed on the outer peripheral surface of the fitting concave portion, and a falling-off preventing protrusion formed on the inner peripheral surface of the ring carrier and engaged with an edge of the peripheral groove. The present invention relates to a piston for an internal combustion engine.

Therefore, according to such a piston, the cooling cavity can be easily formed by mounting the ring carrier divided into a plurality of parts into the fitting recess and melting and joining the divided positions. The falling off of the ring carrier is reliably prevented by the falling-off preventing projection formed on the inner peripheral surface thereof.

According to the structure in which the fusion bonding at the split position of the ring carrier is performed by welding and the welding depth is adjusted so that the fusion portion does not protrude into the cooling cavity formed by the circumferential groove, Leakage or protrusion during fusion bonding is prevented from entering the cooling cavity.

According to the configuration in which the ring carrier is melted and joined to the main body along the circumferential direction at a position above the circumferential groove, the combustion gas is prevented from entering the cooling cavity.

According to the configuration in which the ring carrier is connected to the falling-off prevention ring held on the outer peripheral surface of the fitting concave portion and on the top surface side with respect to the peripheral groove, the ring carrier is fusion-bonded to the main body side. In this case, it is possible to use a drop-prevention ring, thereby preventing the main body from being chilled and becoming brittle.

According to still another aspect of the present invention, there is provided a main body having at least a top surface and having a fitting recess formed on the outer peripheral surface on the top surface side, and a piston ring groove formed on the outer peripheral surface to fit the main body. A ring carrier to be fitted into the fitting recess, a cooling cavity comprising a circumferential groove formed on at least one of the joining portions of the fitting recess of the main body and the inner peripheral surface of the ring carrier, and a fitting recess or ring. The present invention relates to a piston for an internal combustion engine, comprising: a drop prevention step formed on an inner peripheral surface of a carrier to prevent a ring carrier from falling.

Therefore, according to such a piston, the cooling cavity is easily formed by fitting the ring carrier into the fitting concave portion, and the falling off of the ring carrier is reliably prevented by the falling prevention step. Will be.

A circumferential groove forming the cooling cavity is formed in the fitting concave portion of the main body, and a step for preventing falling is formed on the inner peripheral surface of the ring carrier, and the step for preventing falling forms the cooling cavity. According to the configuration in which the ring carrier is engaged with the upper edge of the peripheral groove to be formed, the falling-off preventing step comes into contact with the upper edge of the peripheral groove of the cooling cavity, thereby preventing the ring carrier from falling off.

According to the configuration in which the ring carrier is fitted to the fitting recess of the main body by shrink fitting, the ring carrier is fitted and fixed to the fitting recess of the main body by shrink fitting by shrink fitting. .

The invention relating to a manufacturing method is characterized in that a fitting recess is formed at least on the outer peripheral surface on the top surface side of a main body having a top surface, a holding groove is formed in the fitting recess, and a drop-off prevention ring is provided in the holding groove. After the fitting, the ring carrier is fitted into the fitting concave portion, and an energy beam is irradiated from the outer periphery of the ring carrier at a portion corresponding to the falling-off prevention ring held in the holding groove, and the falling-off prevention ring and the ring carrier are applied. Are melt-bonded, and a cooling cavity is formed inside by a circumferential groove formed on at least one of the joints between the fitting recess and the inner peripheral surface of the ring carrier.

Therefore, according to such a manufacturing method, the piston for an internal combustion engine having an excellent cooling effect according to the first invention can be efficiently manufactured at low cost.

According to another invention relating to another manufacturing method, a fitting recess is formed at least on a top outer peripheral surface of a main body having a top surface, and a cooling cavity is formed on the outer peripheral surface of the fitting recess. A groove is formed, a ring carrier that is divided into a plurality of segments in the circumferential direction, and has a projection for preventing falling on the inner peripheral surface is mounted in the fitting recess, and the projection for preventing falling is formed with the edge of the circumferential groove. The ring carrier is melt-joined at the split position.

Therefore, according to such a method, it is possible to efficiently manufacture the piston for an internal combustion engine according to the another aspect of the present invention having an excellent cooling effect at a low cost.

The invention relating to still another manufacturing method is characterized in that a fitting recess is formed at least on a top outer peripheral surface of a main body having a top surface, and a cooling cavity is formed on the outer peripheral surface of the fitting recess. A groove is formed, and an outer peripheral portion of the fitting recess and a region above the circumferential groove is used as a closing protrusion, and a shoulder portion of the circumferential groove is formed on an inner circumferential surface of the ring carrier fitted in the fitting recess. A drop-prevention step that is engaged with the upper edge is formed, and the drop-prevention step crosses over the interference projection and engages with the upper edge of the circumferential groove when the ring carrier is heated and expanded. Then, the ring carrier is fitted into the fitting recess by shrink-fitting, and when the temperature reaches room temperature, the ring carrier is fastened to the fitting recess at the portion of the protruding portion for tightening, and the shoulder portion of the drop-off prevention step portion is formed. The upper edge of the circumferential groove is locked and fixed Than it is.

Therefore, according to such an invention, it is possible to efficiently manufacture the piston excellent in the cooling effect according to the another invention at a low cost.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a piston for an internal combustion engine.

FIG. 2 is a longitudinal sectional view taken along a center line of a pin boss of the piston.

FIG. 3 is an enlarged vertical sectional view of a main part showing attachment of a ring carrier.

FIG. 4 is a perspective view of a drop prevention ring.

FIG. 5 is a perspective view of another drop-off prevention ring.

FIG. 6 is an enlarged sectional view of a main part of another embodiment.

FIG. 7 is a longitudinal sectional view showing an exploded state of a piston for an internal combustion engine according to another embodiment.

FIG. 8 is a perspective view of the ring carrier.

FIG. 9 is a longitudinal sectional view of the assembled state of the internal combustion engine piston.

FIG. 10 is a plan view of the same.

FIG. 11 is a cross-sectional view of a joining surface showing a state of welding at a butt position of the ring carrier.

FIG. 12 is a longitudinal sectional view showing a piston for an internal combustion engine according to a modification.

FIG. 13 is an exploded perspective view showing a ring carrier and a drop-off prevention ring used for the piston.

FIG. 14 is an exploded longitudinal sectional view showing a piston for an internal combustion engine according to still another embodiment.

FIG. 15 is a perspective view of a ring carrier.

FIG. 16 is an enlarged longitudinal sectional view showing attachment of a ring carrier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Main body part 11 Top surface 12 Combustion chamber (recess) 15 Skirt part 16 Pin boss 17 Pin hole 21 Fitting concave part 22 Circumferential groove (Cooling cavity) 23 Ring carrier 25-27 Piston ring groove 30 Drop prevention ring 31 Holding groove 33 Dissolution part by welding 35 Protrusion for drop-off prevention 36 Dissolution part by welding 37 Welded part 38 Step part for prevention of drop-off 39 Shoulder 40 Escape groove 43 Protrusion for tightening allowance

Claims (13)

[Claims] 1. A main body having at least a top surface and a fitting recess formed on an outer peripheral surface on a top surface side, and a piston ring groove formed on an outer peripheral surface, wherein a fitting recess of the main body is formed. A ring carrier to be fitted; a cooling cavity comprising a circumferential groove formed in at least one of a joining portion between the fitting recess of the main body portion and an inner peripheral surface of the ring carrier; and a cooling cavity formed in the fitting recess. A drop-off prevention ring held in the holding groove and connected to the ring carrier. 2. A piston for an internal combustion engine according to claim 1, wherein said main body is made of cast iron, and said ring carrier and said falling-off prevention ring are made of steel. 3. The ring carrier according to claim 1, wherein the ring carrier and the falling-off prevention ring are welded and connected by an energy beam irradiated from an outer peripheral side of the ring carrier. Pistons for internal combustion engines. 4. A body having at least a top surface and having a fitting recess formed on the outer peripheral surface on the top surface side, a piston ring groove formed on the outer peripheral surface, and a plurality of circumferentially extending piston ring grooves. A ring carrier that is divided into segments and is melt-joined at a dividing position in a state where the ring carrier is attached to the fitting concave portion of the main body portion; and a joint portion between the fitting concave portion of the main body portion and the inner peripheral surface of the ring carrier. A cooling cavity formed of a peripheral groove formed on an outer peripheral surface of the fitting concave portion; and a falling-off preventing protrusion formed on an inner peripheral surface of the ring carrier and engaged with an edge of the peripheral groove. A piston for an internal combustion engine, comprising: 5. The fusion welding of the ring carrier at a split position is performed by welding, and a welding depth is adjusted so that a fusion portion does not protrude into a cooling cavity formed by the peripheral groove. The piston for an internal combustion engine according to claim 4, wherein 6. The piston for an internal combustion engine according to claim 4, wherein the ring carrier is fusion-bonded to the main body along the circumferential direction at a position above the circumferential groove. 7. The ring carrier according to claim 4, wherein the ring carrier is connected to a fall-off prevention ring which is held on the outer peripheral surface of the fitting recess and on the top surface side with respect to the peripheral groove. A piston for an internal combustion engine according to the above. 8. A main body having at least a top surface and having a fitting recess formed on an outer peripheral surface on the top surface side, and a piston ring groove formed on the outer peripheral surface. A ring carrier to be fitted, a cooling cavity comprising a circumferential groove formed in at least one of a joint portion between the fitting recess of the main body portion and an inner peripheral surface of the ring carrier; A piston for an internal combustion engine, comprising: a step formed on an inner peripheral surface of a ring carrier for preventing the ring carrier from falling off. 9. A peripheral groove forming the cooling cavity is formed in a fitting recess of the main body, and a step for preventing falling is formed on an inner peripheral surface of the ring carrier. The piston for an internal combustion engine according to claim 8, wherein a step is engaged with an upper edge of a peripheral groove forming the cooling cavity. 10. The piston for an internal combustion engine according to claim 8, wherein the ring carrier is fitted in the fitting concave portion of the main body by shrink fitting. 11. A fitting recess is formed at least on a top outer peripheral surface of a main body having a top surface, a holding groove is formed in the fitting recess, and a drop-prevention ring is fitted into the holding groove. After that, a ring carrier is fitted into the fitting concave portion, and an energy beam is irradiated from an outer peripheral side of the ring carrier at a portion corresponding to the fall prevention ring held in the holding groove, and the fall prevention ring is The ring carrier is melt-bonded, and a cooling cavity is formed inside by a circumferential groove formed on at least one of a joint portion between the fitting recess and an inner peripheral surface of the ring carrier. A method for manufacturing a piston for an internal combustion engine, comprising: 12. A fitting recess is formed on an outer peripheral surface on a top surface side of a main body having at least a top surface, and a circumferential groove forming a cooling cavity is formed on an outer peripheral surface of the fitting concave portion. A ring carrier divided into a plurality of segments in the circumferential direction and having a projection for preventing falling on the inner peripheral surface is mounted in the fitting recess, and the projection for preventing falling is engaged with an edge of the circumferential groove. A method for manufacturing a piston for an internal combustion engine, wherein the ring carrier is welded at a split position. 13. A fitting recess is formed on an outer peripheral surface on a top surface of a main body having at least a top surface, and a peripheral groove forming a cooling cavity is formed on an outer peripheral surface of the fitting concave portion. An outer peripheral portion of the fitting recess and a region above the peripheral groove is defined as a protrusion for interference, and a shoulder portion of the ring carrier to be fitted into the fitting concave portion has an upper portion above the peripheral groove. Forming a fall prevention step to be engaged with the edge, wherein the fall prevention step crosses over the interference projection in a state where the ring carrier is heated and expanded to form an upper edge of the circumferential groove; The ring carrier is fitted into the fitting recess by shrink fitting so as to engage with each other. When the temperature of the ring carrier reaches room temperature, the ring carrier is fastened to the fitting recess at the portion of the interference protrusion, and The shoulder of the preventing step is the upper edge of the circumferential groove A method for manufacturing a piston for an internal combustion engine, wherein the piston is locked and fixed to a piston.