KR20210029950A - 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 of manufacturing a piston with enhanced wear resistance and insulation and a piston manufactured thereby. A purpose of the present invention is to increase hardness overall and enhance the local wear resistance of a ring groove combined with a piston ring while securing insulation performance in a skirt part by bathing a piston base material with dye. According to the present invention, the method of manufacturing a piston with enhanced wear resistance and insulation, which is a method of manufacturing a piston comprising a skirt part having a pinhole formed on a side and connected with a connecting rod by a piston pin inserted into the pin hole, and a crown part integrated with the skirt part, includes: a first step of casting a base material of a piston; a second step of bathing the base material manufactured in the first step with dye; a third step of forming a carbon film on a sliding surface of the base material after the second step; and a fourth step of forming an insulation film on the surface of a skirt part of the base material. In the first step, a chamfered edge part is formed in an inlet-side corner part of a ring groove of the base material to induce the behavior of a piston ring combined with the ring groove, and the carbon film is formed throughout the sliding surface and the surface of the edge part.

Description

TECHNICAL FIELD [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, increases the hardness by treating the piston base material with a salt bath, and increases wear resistance and heat insulation by reinforcing the ring groove to which the piston ring is coupled and the skirt to which the crankshaft is connected to each function. It relates to a piston manufacturing method and a piston manufactured by the manufacturing method.

This part provides background information related to the content of the present application, and is not necessarily prior art.

In general, the engine of an internal combustion engine obtains power by converting and outputting the piston lifting motion caused by the combustion pressure generated when the mixer is combusted in the combustion chamber inside the cylinder into rotational motion by the crank mechanism. Such an important component is the cylinder. Blocks, pistons, and crank mechanisms.

The cylinder block has the feature that the compressed mixer or burned explosive gas between the cylinder and the piston does not leak in order to obtain as much power as possible from the given thermal energy, and at the same time, it has the characteristics that friction and abrasion due to the sliding of the piston should be small. A separate cylinder liner is applied to the cylinder block in order to solve the difficulties such as precise polishing of the machine.

Conventional cylinder liners are made of special cast iron to match the cylinder block of cast iron.

The piston reciprocates inside the cylinder of the cylinder block to transmit the rotational force to the crank mechanism.The structure consists of a piston head, a ring belt (ring groove, oil groove), a pin boss, and a skirt, and the function is a gas generated during the power stroke. The explosion pressure of the crankshaft is transmitted to the crankshaft through the connecting rod to make the crankshaft rotate, and while reciprocating in the cylinder, the airtightness between the combustion chamber and the crankcase is maintained through the piston ring, and the piston from the combustion gas. 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.

The patent document (Korean Patent Laid-Open No. 10-2000-0004819) includes a piston rotating means for rotating the piston in a horizontal state, a cooling type heating coil that is inserted into the ring groove of the piston to heat the ring groove at high frequency, and a heated ring g. A piston ring groove heat treatment device comprising a coolant pipe for injecting coolant into the lobe and an air pipe for scattering coolant sprayed from the coolant pipe with air pressure. When judged by this device, it heat-treats the ring groove of the piston. During the linear reciprocating motion of the piston, it does not prevent wear at the edge of the piston due to bending of the piston ring, and there is no technology for insulation.

Patent document (Korean Patent Laid-Open No. 10-2009-0098356) is a preparation step (S1) for preparing a machined piston; A polishing step (S2) of polishing the surface of the provided piston; The post-processing is performed by a heat treatment step (S3) of heat-treating the polished piston, wherein the heat treatment step (S3) of the piston includes: a washing step (G1) of removing oil and foreign substances from the provided piston with a detergent 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, and then raising the temperature to 570°C for at least 1 hour and 30 minutes; Ammonia gas, nitrogen gas, and carbon dioxide are added to the inside of the furnace for 5 to 8 hours, while maintaining a temperature of 570°C and an internal pressure of 100 to 250 mmH2O in the furnace to form a nitriding layer on the piston surface (G5). ); While nitrogen gas is introduced into the furnace, the internal pressure of the furnace is maintained at 500 to 1000 mmH2O, and the temperature inside the furnace is lowered to at least 120°C, and the piston is removed from the furnace by cooling and loading step (G6). As a post-processing method, the entire piston is heat treated in a nitrogen atmosphere, and there is no technology or thermal insulation technology to solve the wear of the piston that occurs when the piston and the piston ring 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-described problems, and the piston base material is entirely salt bathed to increase hardness, and abrasion resistance to secure abrasion resistance in the ring groove to which the piston ring is coupled, and to secure thermal insulation in the skirt portion to which the crankshaft is connected. It is an object of the present invention to provide a method for manufacturing a piston with increased thermal insulation properties and a piston manufactured by the manufacturing method.

The method of manufacturing a piston for increasing wear resistance and heat insulation according to the present invention includes a piston having a pinhole formed on the side and a skirt portion connected to the connecting rod by a piston pin inserted into the pinhole, and a crown portion integrally formed on the top of the skirt portion. A manufacturing method, comprising: a first step of casting a base material of a piston; A second step of treating the base material prepared in the first step with a dye bath; 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 the present invention, the first step is to induce the behavior of the piston ring coupled to the ring groove by forming a chamfered edge portion at the inlet edge of the ring groove of the base material, and the carbon film is the surface of the edge portion It is characterized in that it is formed over the and the sliding surface.

According to the piston manufacturing method for increasing wear resistance and heat insulation according to the present invention and the piston manufactured by this manufacturing method, the piston is entirely salt bath heat treated to increase hardness, and at the same time, the piston is formed with an edge portion at the inlet side of the ring groove as a portion requiring wear resistance. In addition to securing a space for the ring to move, the piston ring is in contact with the piston ring to reduce wear at the inlet of the ring groove, extending the life of the piston, and also improving engine performance by securing insulation performance at the skirt part in contact with the outside. There is an effect.

In addition, it helps to extend the life of the piston by reducing abrasion due to the behavior of the piston ring by increasing the hardness by heat treatment of the inner circumferential side of the piston ring and the inside of the ring groove corresponding to the inner circumferential surface of the piston ring.

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

In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted. In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to the intention or custom of users or operators. Therefore, the definition should be made based on the contents throughout the present specification.

As shown in FIGS. 1 and 2, the method of manufacturing a piston for increasing wear resistance and heat insulation according to the present invention comprises a process of casting-salt bath heat treatment-forming a carbon film on a sliding surface-forming a heat insulating 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 (for example, assembling of two left and right molds) and hardening it. 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 a preheater (electric furnace, salt bath, etc.) and preheat at 300℃~400℃ for 30~60 minutes. Through the preheating process, the time of the subsequent salt bath heat treatment process can be shortened.

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 850℃~930℃ for 50~80 minutes to austenite. Through such austenitization, carbon is expanded to 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 surfaces 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 in the drawings, it is illustrated in a layered structure for better understanding.

In the present invention, the salt bath agent is used together with water, and the 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) of the base material after the medium-temperature salt bath is completed.

3. Formation of a carbon film on the sliding surface.

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

The carbon film is formed by applying (coating) 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 respect to 100 parts by weight of carbon powder of nanoparticles on 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. Forming an insulating film on the skirt part.

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

The heat insulating film 14 is formed on the surface of the salt bath layer 12 of the skirt portion through the above heat insulating treatment.

It is also possible to roughen the surface of the base material before applying the insulation so that the thermal insulation film 14 does not peel off from the base material of the piston, and then apply the insulation material to the rough surface, and since the surface of the base material is in a rough state, the thermal insulation film 14 ) Can be effectively prevented from being peeled off 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 11a for inducing the behavior of the piston ring during linear reciprocating motion of the piston 10 may be configured.

The edge portion (11a) is formed in a chamfered shape 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 slope of the edge portion 11a, thereby reducing fatigue at the edge portion of the ring groove 11b.

That is, when the ring groove 11b is formed with an inner vertical part, a vertical part parallel to each other from the upper and lower parts of the vertical part toward the entrance, and an edge part connected to the slide surface when the ring groove 11b is formed with an inclination extending vertically from the upper and lower horizontal parts, respectively. It consists of (11a). According to this structure, the piston ring 20 is supported on the upper and lower horizontal portions, so that there is no shaking, and it is possible to maintain airtightness, and while inducing the vertical movement of the piston ring 20 through the edge portion 11a on the inlet side, the piston ring It is possible to reduce the wear of the piston 10 by preventing damage to (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 shape to form an edge portion and forming it through a single process of casting, and after manufacturing the inlet of the ring groove in a shape connecting 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 may be worn due to frequent contact with the piston ring 20, and wear is reduced by forming the carbon film 13 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 according to the stroke of the engine, and this linear reciprocation motion is transmitted as a rotational motion through the crankshaft to drive the engine.

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

In addition, during the linear reciprocating motion of the piston 10, the piston ring 20 may not match the motion of the piston 10, so the edge of the piston ring 20 may be bent while contacting the inner circumferential surface of the cylinder bore. 10) The edge part 11a of the piston ring 20 is in surface contact with the piston ring 20 to support the piston ring 20, thus preventing the sharp angle of the piston ring 20 from being bent, extending the life of the piston ring 20 and extending the life of the piston ring 20. It reduces wear at the corners of 20).

On the other hand, when the piston ring 20 behaves as the edge part 15, the inner circumferential side of the piston ring 20, that is, the part corresponding to the inner side of the ring groove 11b, is in the opposite direction to the outer circumferential side of the piston ring 20. 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 bottom of the inner circumferential surface. ) By heat-treating the inner edge of the surface to form a hardness increasing portion (15).

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

That is, the ring groove (11a) is between the edge portion (11a) on the inlet side and the hardness increase portion (15) on the inside, and where the impact from the piston ring (20) is relatively small, only the salt bath layer (12) by salt bath heat treatment There will be.

The method of forming the hardness increasing part 15 is heat treatment by heating the inside of the ring groove 11b through the heating wire in a state in which a heating wire is wound on the inside of the ring groove 11b and insulated by inserting an insulation cover. The heating condition of is 830℃~860℃ as the heating temperature and 10 seconds to 15 seconds as the heating time.

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

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

When the piston 10 descends, the outer circumferential side of the piston ring 20 is directed to the upper end, and the inner circumferential side has a downward force, and the upper edge 11a of the piston 10 is the piston ring 20 While withstanding the force applied from the outer periphery of ), the hardness increasing portion 15 disposed in the inner lower portion reduces abrasion 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 insulating layer, 15: hardness increasing portion
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 the base material of the piston;
A second step of heat-treating a salt bath after preheating the base material prepared in the first step;
A third step of forming a carbon film on a sliding surface of the outer circumferential 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,
The first step is to induce the behavior of the piston ring coupled to the ring groove by forming a chamfered edge portion at the inlet edge of the ring groove of the base material, and the third step is the surface of the edge portion and the sliding surface. A method of manufacturing a piston for increasing wear resistance and heat insulation, characterized in that forming a carbon film over it. The method according to claim 1, wherein the third step comprises forming a hardness increasing part by 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, wherein the ring groove increases hardness from the inside. A piston manufacturing method for increasing wear resistance and heat insulation, characterized in that consisting of a portion, a salt bath layer, and an edge portion. The method according to claim 1, Step 1-1 of preheating the base material to 300 ℃ ~ 400 ℃ 30 minutes to 60 minutes, the base material and the salt bath preheated through the step 1-1 put into a salt bath 850 ℃ ~ 930 A method for manufacturing a piston for increasing wear resistance and heat insulation, characterized in that it comprises a 1-2 step of heating a salt bath by heating at a temperature of °C for 50 to 80 minutes. A piston for increasing wear resistance and heat insulation, characterized in that it is manufactured by the method of manufacturing a piston for increasing wear resistance and heat insulation according to any one of claims 1 to 3.

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