KR102267020B1 - Methods for manufacturing pistons with increased wear resistance and insulation and Piston by this manufacturing method - Google Patents

Abstract

The present invention relates to a method for manufacturing a piston with increased wear resistance and thermal insulation and a piston manufactured by the manufacturing method, wherein the piston base material is salt bathed to increase overall hardness, and to increase the local wear resistance of the ring groove to which the piston ring is coupled, while increasing the skirt The purpose is to secure thermal insulation performance in the part.
In the method for manufacturing a piston with increased wear resistance and thermal insulation according to the present invention, a piston having a pinhole formed on its side and connected to a connecting rod by a piston pin inserted into the pinhole, and a crown formed integrally with the skirt. A method comprising: a first step of casting a base material of a piston; a second step of dye bathing the base material prepared in the first step; a third step of forming a carbon film on the sliding surface of the base material after the second step; and a fourth step of forming an insulating film on the surface of the skirt portion of the base material. In the first step, a chamfered edge is formed at the inlet corner of the ring groove of the base material to induce a behavior of the piston ring coupled to the ring groove, and the carbon film is formed over the surface of the edge and the sliding surface. do.

Description

Methods for manufacturing pistons with increased wear resistance and insulation and Piston by this manufacturing method

The present invention relates to a piston for an internal combustion engine, and more particularly, to increase the hardness by salt bathing the piston base material, and to reinforce the ring groove to which the piston ring is coupled and the skirt to which the crankshaft is connected according to their respective functions. It relates to a method for manufacturing a piston and a piston manufactured by the method for manufacturing the same.

This section provides background information related to the subject matter of the present application and is not necessarily prior art.

In general, the engine of an internal combustion engine obtains power by converting the piston lifting motion by the combustion pressure generated when the mixture is burned in the combustion chamber inside the cylinder into rotational motion by the crank mechanism and outputting it. Blocks, pistons, and crank mechanisms.

In order to obtain as much power as possible from the given thermal energy, the cylinder block has the characteristics that the compressed mixture or combusted explosive gas between the cylinder and the piston should not leak, and at the same time, friction and wear due to the sliding of the piston should be low. A separate cylinder liner is applied to the cylinder block in order to solve the difficulties such as precision grinding of the cylinder block.

Conventional cylinder liners are made of special cast iron according to the cylinder block of cast iron is used.

The piston reciprocates in the cylinder of the cylinder block to transmit rotational force to the crank mechanism. The structure consists of a piston head, ring belt (ring groove, oil groove), pin boss, and skirt, and the function is gas generated during power stroke. The basic function is to transmit the explosive pressure of the crankshaft to the crankshaft through the connecting rod so that the crankshaft rotates, and while reciprocating in the cylinder, the airtight between the combustion chamber and the crankcase is maintained through the piston ring, and the piston It functions to quickly transfer the heat transferred to the head to the cylinder wall.

There are various patent documents for increasing hardness with a piston according to the prior art.

Patent Literature (Korean Patent Publication No. 10-2000-0004819) discloses a piston rotating means for rotating a piston in a horizontal state, a cooling-type heating coil inserted into the ring groove of the piston to heat the ring groove at high frequency, and a heated ring A piston ring groove heat treatment device comprising a cooling water pipe for spraying cooling water to the lobes, and an air pipe for scattering the cooling water sprayed from the cooling water pipe by air pressure, and when judged by this device, the ring groove of the piston is heat treated, the piston During the linear reciprocating motion of the piston, it cannot prevent wear at the edge of the piston due to the bending of the piston ring, and there is no technology for insulation.

Patent literature (Republic of Korea Patent Publication No. 10-2009-0098356) is a preparation process (S1) of preparing a processed piston; a polishing process (S2) of polishing the surface of the provided piston; Post-processing comprising a heat treatment process (S3) of heat-treating the polished piston is performed, but the heat treatment process (S3) of the piston includes a cleaning step (G1) of removing oil and foreign substances from the provided piston with a cleaning agent and water; a charging step (G2) of putting the piston assembled in the jig into the furnace; a purging step (G3) of introducing nitrogen gas into the furnace; A preheating step (G4) of raising the temperature inside the furnace to 350°C and maintaining it for at least 8 hours, then raising the temperature again to 570°C, and maintaining it for at least 1 hour and 30 minutes; A softening step (G5) of forming a nitride layer on the piston surface by putting ammonia gas, nitrogen gas, and carbon dioxide into the furnace for 5 to 8 hours, maintaining the furnace internal temperature of 570° C., and the furnace internal pressure of 100 to 250 mmH2O (G5) ); While injecting nitrogen gas into the furnace while maintaining the furnace internal pressure of 500 to 1000 mmH2O, lowering the temperature inside the furnace to at least 120°C, and then taking the piston out of the furnace after cooling and ejecting the piston comprising the step (G6) As a post-processing method, the entire piston is heat-treated in a nitrogen atmosphere, and there is no technology or insulation technology to solve the wear of the piston that occurs when the piston and the piston ring are in contact.

Republic of Korea Patent Publication No. 10-2000-0004819 Republic of Korea Patent Publication No. 10-2009-0098356

The present invention is to solve the above-mentioned problems, the overall hardness is increased by salt bath treatment of the piston base material, wear resistance is secured in the ring groove to which the piston ring is coupled, and the abrasion resistance is secured in the skirt part to which the crankshaft is connected. An object of the present invention is to provide a method for manufacturing a piston with increased thermal insulation properties and a piston manufactured by the manufacturing method.

The method for manufacturing a piston with increased wear resistance and thermal insulation according to the present invention comprises a skirt portion having a pinhole formed on the side and connected to a connecting rod by a piston pin inserted into the pinhole, and a crown portion integrally formed on the upper portion of the skirt portion. A manufacturing method comprising: a first step of casting a base material of a piston; a second step of dye bathing the base material prepared in the first step; a third step of forming a carbon film on the sliding surface of the base material after the second step; It characterized in that it comprises a fourth step of forming a heat insulating film on the surface of the skirt portion of the base material.

In addition, in the present invention, in the first step, a chamfered edge portion is formed at the inlet corner of the ring groove of the base material to induce a behavior of the piston ring coupled to the ring groove, and the carbon film is the surface of the edge portion And it is characterized in that it is formed over the slide surface.

According to the method for manufacturing a piston with increased wear resistance and thermal insulation according to the present invention and the piston manufactured by the manufacturing method, the piston is subjected to salt bath heat treatment as a whole to increase the hardness, and an edge portion is formed at the inlet side of the ring groove as a part requiring wear resistance to form the piston By securing a space for the ring to move and making surface contact with the piston ring, it reduces wear at the inlet of the ring groove to extend the life of the piston, and also improves engine performance by securing insulation performance at the skirt portion in contact with the outside. has the effect of

And, it helps to extend the life of the piston by reducing wear due to the behavior of the piston ring by increasing the hardness of the inner peripheral surface of the piston ring and the inner side of the corresponding ring groove by heat treatment.

1 is a manufacturing process diagram of a piston with increased wear resistance and thermal insulation according to the present invention.
Figure 2 is a cross-sectional view showing the surface reinforcement layer of the abrasion resistance and heat insulation increase piston according to the present invention.
Figure 3 is a view showing the edge portion of the ring groove applied to the abrasion resistance and heat insulation increased piston according to the present invention.
4 is a view showing an edge portion and a hardness increasing portion applied to the abrasion resistance and heat insulation increased piston according to the present invention.

In the following description of the present invention, if it is determined that a detailed description of a related well-known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, the terms described below are terms defined in consideration of functions in the present invention, which may vary according to intentions or customs of users and operators. Therefore, the definition should be made based on the content throughout this specification.

As shown in FIGS. 1 and 2 , the method for manufacturing a piston with increased wear resistance and thermal insulation according to the present invention consists of the following steps: casting - salt bath heat treatment - formation of a carbon film on the sliding surface - formation of a thermal insulation film on the skirt part.

1. Casting.

The base material 11 of the piston is manufactured by pouring molten cast iron into a mold manufactured in the form of a completed piston (eg, assembly of two left and right molds) and hardening. The piston base material 11 refers to a purely cast product without salt bath heat treatment, ring groove heat treatment, and heat insulation treatment.

2. Salt bath heat treatment.

The salt bath heat treatment process is divided into a preheating process, a medium temperature salt bath process, and a cooling process.

end. Preheat.

Put the base material in the preheater (electric furnace, salt bath, etc.) and preheat it at 300℃~400℃ for 30~60 minutes. Through the preheating process, it is possible to shorten the time of the subsequent salt bath heat treatment process.

I. Salt bath (medium temperature salt bath).

Put the preheated base material and salt bath agent (at least one of barium chloride and calcium chloride) in the salt bath, and heat it at a temperature of 850°C to 930°C for 50 to 80 minutes to make austenite. Through such austenitization, carbon is converted into ferrite, so that the carbon concentration becomes uniform and the concentration increases.

Through the above salt bath heat treatment, the salt bath layer 12 is formed on all surfaces of the base material 11, that is, the surface of the crown portion and the skirt portion. The salt bath layer 12 is formed by heat treatment, and does not form a layered structure separated from the base material 11, but is shown as a layered structure for better understanding in the drawings.

In the present invention, the salt bath agent is used together with water, and a ratio used in a conventional salt bath is used.

All. Cooling.

Natural cooling or forced cooling (cooling by spraying cooling water or blowing cooling air) is performed on the base material after the intermediate temperature salt bath.

3. Formation of carbon film on the sliding surface.

The sliding surface is the outer peripheral surface of the crown part among the outer peripheral surfaces of the base material, excluding the inner peripheral surface of the ring groove to which the piston ring is coupled, and forms a carbon film on the sliding surface.

The carbon film is formed through application (coating) of carbon powder, and is formed by applying a carbon mixture in which 2 to 8 parts by weight of a binder resin is mixed with 100 parts by weight of carbon powder of nanoparticles to the surface of the sliding surface. The thickness of the carbon film can be freely applied within a thickness that does not protrude from the piston ring.

4. Formation of insulation film on skirt part.

An insulating film is formed on the surface of the skirt part (the lower part of the lowermost ring groove) by coating (applying) of an insulating material with excellent thermal insulation performance such as glass fiber. Preferably, as the insulating material of glass fiber, it is possible to use waste glass wool. For example, waste glass wool, a waste in which glass fiber and binder resin are mixed, is processed into fine glass wool through a single process of pulverization or a combined process of melting, cooling and pulverization, and mixed with binder resin (fine glass wool After mixing 2 to 8 parts by weight of the binder resin with respect to 100 parts by weight), the insulating film is formed through the process of applying it to the surface of the skirt part (freely possible within the thickness that does not protrude from the piston ring).

Through the above heat insulation treatment, the heat insulation film 14 is formed on the surface of the salt bath layer 12 of the skirt part.

It is also possible to apply the heat insulating material to the rough surface after roughening the surface of the base material before application of the heat insulating material so that the heat insulating film 14 does not peel off from the base material of the piston, and since the surface of the base material is in a rough state, the heat insulating film 14 ) can effectively prevent peeling from the base material, and even if the surface of the base material is rough, the surface of the insulating film 14 is made of a flat surface without intentional roughness.

In the present invention, an edge portion 11a for inducing the behavior of the piston ring during linear reciprocation of the piston 10 may be configured.

The edge portion 11a is formed in the form of a chamfer at the upper and lower corners of the inlet side of the ring groove 11b, and is formed to be inclined in the direction of movement of the piston ring 20 on both upper and lower sides with the piston ring 20 as the center. As a result, the piston ring 20 moves along the inclination of the edge portion 11a, thereby reducing fatigue in the corner portion of the ring groove 11b.

That is, when the ring groove 11b is formed with an inner vertical portion, an upper and lower horizontal portion parallel to each other from the upper and lower portions of the vertical portion toward the entrance, and an inclination that opens up and down in the upper and lower horizontal portions when viewed in cross section, the edge portion connected to the sliding surface It is composed of (11a). According to such a structure, the piston ring 20 is supported on the upper and lower horizontal portions to ensure airtight maintenance without shaking, and while inducing the vertical movement of the piston ring 20 through the edge portion 11a of the inlet side, the piston ring The wear of the piston 10 can be reduced by preventing the breakage of the 20 and increasing the contact area with the piston ring 20 .

The method of forming the edge portion 11a is a method of forming a mold in a form for forming the edge portion and forming it through a single process of casting, after the inlet of the ring groove is manufactured in a form connected to the upper and lower horizontal portions and the sliding surface A method of forming the edge portion through a separate cutting process is possible.

In addition, the edge portion 11a has a risk of wear due to frequent contact with the piston ring 20, and reduces wear by forming the carbon film 13 up to the surface of the edge portion 11a.

According to the piston according to the present invention, the piston 10 linearly reciprocates the cylinder bore in accordance with the stroke of the engine, and the linear reciprocating motion is transmitted as a rotational motion through the crankshaft to drive the engine.

High-temperature heat and high pressure are generated in the cylinder bore, and the piston 10 is subjected to salt bath heat treatment as a whole to increase the rigidity against heat and pressure, and the sliding surface is treated with the carbon film 13 to further increase the rigidity, thereby reducing deformation.

In addition, during the linear reciprocating motion of the piston 10, the piston ring 20 does not match the motion of the piston 10, so the edge of the piston ring 20 may be bent while in contact with the inner circumferential surface of the cylinder bore, and at this time, the piston ( 10) The edge portion 11a of the piston ring 20 and the surface contact with the piston ring 20 to support the piston ring 20, so prevent the abrupt bending of the piston ring 20 to extend the life of the piston ring 20, the piston ( 20) to reduce wear at the corners.

On the other hand, when the piston ring 20 behaves as the edge portion 15, the inner circumferential side of the piston ring 20, that is, the portion corresponding to the inside of the ring groove 11b is the outer circumferential side of the piston ring 20 in the opposite direction. A force may be generated, that is, when the outer circumferential surface of the piston ring 20 is directed upward, a load may be applied to the inner circumferential edge of the ring groove 11b toward the inner circumferential side toward the bottom, and to solve this, the ring groove 11b ) to form a hardness increasing part 15 by heat-treating the inner edge surface.

The hardness increasing portion 15 is a portion in which three surfaces (a vertical surface and an upper and lower horizontal surface) are connected inside the ring groove 11b and is formed so as not to overlap the carbon film 14 .

That is, the ring groove 11a is between the inlet side edge portion 11a and the inner hardness increasing portion 15, and only the salt bath layer 12 by salt bath heat treatment is located where the impact from the piston ring 20 is relatively small. there will be

In the method of forming the hardness increasing part 15, a heating wire is wound on the inside of the ring groove 11b and the heat treatment is performed by heating the inside of the ring groove 11b through the heating wire in a state insulated by inserting an insulating cover, at this time For the heating conditions, 830℃~860℃ is the heating temperature and 10 seconds to 15 seconds is the heating time.

The heating wire has a diameter corresponding to the area of the hardness increasing part 15 , and the heat insulating cover is sized to cover a space in the ring groove 11b excluding the space occupied by the heating wire.

The edge portion 11a and the hardness increasing portion 15 are in an organic relationship,

When the piston 10 is lowered, the outer periphery of the piston ring 20 is directed toward the upper end and the inner periphery of the piston 10 has the opposite downward force, and the upper edge 11a of the piston 10 moves to the piston ring 20 ) while withstanding the force applied from the outer periphery, the hardness increasing portion 15 disposed on the inner lower portion reduces wear due to the force applied from the inner periphery of the piston ring 20 .

10: piston, 11: base material
11a: edge portion, 11b: ring groove
12: salt bath layer, 13: carbon film
14: heat insulation layer, 15: hardness increase part
20: piston ring,

Claims (4)

A method of manufacturing a piston comprising a skirt portion having a pinhole formed on a side surface and connected to a connecting rod by a piston pin inserted into the pinhole, and a crown portion integrally formed on the upper portion of the skirt portion,
A first step of casting and processing the base material of the piston;
a second step of preheating the base material prepared in the first step and then heat-treating the salt bath;
a third step of forming a carbon film on the sliding surface of the outer peripheral surface of the base material after the second step;
Including a fourth step of forming a heat insulating film on the surface of the skirt portion of the base material,
In the first step, a chamfered edge is formed at the inlet corner of the ring groove of the base material to induce a behavior of the piston ring coupled to the ring groove, and the third step is on the surface and sliding surface of the edge portion. A method of manufacturing a piston with increased wear resistance and thermal insulation properties, characterized in that the carbon film is formed over it. The method according to claim 1, wherein the third step comprises heat-treating an inner edge surface of the ring groove opposite to the inner circumferential surface of the piston ring so as not to overlap the carbon film to form a hardness increasing portion, wherein the ring groove increases in hardness from the inside. A method of manufacturing a piston with increased wear resistance and heat insulation, characterized in that it consists of a part, a salt bath layer, and an edge part. The method according to claim 1, wherein the second step is a step 2-1 of preheating the base material to 300 ° C. to 400 ° C. for 30 minutes to 60 minutes, and the base material and the salt bath agent preheated through the step 2-1 in a salt bath furnace. A method of manufacturing a piston for increasing wear resistance and heat insulation, characterized in that it comprises a second-2 step of putting in and heating at a temperature of 850 ° C. to 930 ° C. for 50 to 80 minutes to perform a salt bath treatment. A piston with increased wear resistance and thermal insulation, characterized in that it is manufactured by the method for manufacturing a piston with increased wear resistance and thermal insulation according to any one of claims 1 to 3.

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