Piston pin and method of manufacturing the same

Abstract

The invention relates to a piston pin comprising a tubular body made of an iron-based sintered alloy; wherein the piston pin is mounted to penetrate an upper end of a connecting rod and a piston; and wherein the center of gravity of the piston pin is eccentric in the circumferential direction.

Description

Technical Field

[0001] The present invention relates to a piston pin and a method for manufacturing the same, wherein the piston pin is rotatable when the piston is raised by the operation of an engine, thereby providing improved lubrication. Background Technology

[0002] The piston pin is the component that connects the piston and connecting rod in an engine. Due to the acceleration and friction forces applied during the up-and-down movement of the connecting rod, the piston pin rotates slightly irregularly within the bushing at the small end of the connecting rod. Because the uneven force on the piston pin is small and the friction is weak, this rotation approximates conical motion.

[0003] Oil injected into the lower part of the piston from the integral injector impacts the lower surface of the piston and is indirectly supplied to the small end of the connecting rod. If the piston pin does not rotate smoothly, it may not be properly lubricated.

[0004] In addition, low-viscosity oils are now being used in engines to improve fuel economy. Furthermore, combustion pressures are increasing. Therefore, the lubrication environment of the piston pins may deteriorate.

[0005] The information disclosed in this background section is only intended to enhance understanding of the background of the present invention. Therefore, this background section may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] One embodiment provides a piston pin that rotates to improve lubrication when the piston is raised during engine operation.

[0007] Another embodiment provides a method for manufacturing a piston pin, wherein the increase in weight of the piston pin is minimized when an imbalance is artificially applied by another method. This manufacturing method is also advantageous in terms of process and cost, while minimizing the imbalance caused by dimensional deviations due to mechanical errors, resulting in a misalignment between the pin's center of rotation and its center of gravity.

[0008] According to one embodiment, a piston pin includes a tubular body made of an iron-based sintered alloy. The piston pin is mounted to penetrate the upper end of a connecting rod and a piston, and the center of gravity of the piston pin is eccentric in the circumferential direction.

[0009] Iron-based sintered alloys may, based on their total weight, include: 0.4 wt% to 0.8 wt% carbon (C); 0.2 wt% to 3.5 wt% chromium (Cr); 0.1 wt% to 0.3 wt% molybdenum (Mo); 0.2 wt% to 2.0 wt% nickel (Ni), manganese (Mn), copper (Cu), or mixtures thereof; and the balance iron (Fe).

[0010] The piston pin includes a first region and a second region divided along the circumferential direction, and the first region and the second region have different densities.

[0011] The density difference between the first and second regions is 0.05 g / cm³. 3 Or larger.

[0012] The first region occupies an area of ​​30 to 330 degrees in the circumferential direction.

[0013] The dividing line separating the first and second regions forms a 90-degree angle with either the tangent to the outer diameter or the tangent to the inner diameter of the pipe.

[0014] The center of the outer diameter of the pipe is eccentric to the center of the inner diameter of the pipe by 0.1 mm or more.

[0015] The piston pin includes a first region and a second region divided along the circumferential direction, and the first region includes a metal-infiltrated material.

[0016] The piston pin includes a first region and a second region divided along the circumference, and the inner diameter surface of the first region is coated with metal paste.

[0017] Metals include copper (Cu).

[0018] The density difference between the first and second regions is 0.05 g / cm³. 3 Or larger.

[0019] The piston pin includes a first region and a second region divided along the circumferential direction. The first region and the second region have different densities. The center of the outer diameter of the tube and the center of the inner diameter of the tube are eccentric by 0.1 mm or more. The first region includes a metal-infiltrated material, or the inner diameter surface of the first region is coated with metal paste.

[0020] According to another embodiment, a method for manufacturing a piston pin includes the following steps: filling an iron-based alloy powder into a mold, then pressing it to form a tubular shape; and sintering the formed tubular body. This includes an operation that eccentricates the center of gravity of the formed body in the circumferential direction.

[0021] The operation of making the center of gravity of the molded body eccentric in the circumferential direction can be performed by the following steps: filling iron-based alloy powder such that the powder filling height is different in the circumferential direction when the iron-based alloy powder is filled into the mold, and then pressurizing the iron-based alloy powder so that the powder filling height is the same in the circumferential direction when the iron-based alloy powder is pressurized.

[0022] The mold includes: a die having a cylindrical powder-filling space; a core arranged in the center of the powder-filling space and separated from the die; and an upper punch and a lower punch for pressurizing the powder filled between the die and the core, the lower punch including a first lower punch and a second lower punch separated in a circumferential direction.

[0023] The operation of eccentricating the center of gravity of the molded body in the circumferential direction can be performed by the following steps: setting the first and second lower punches to have different heights; filling the mold with iron-based alloy powder; and subsequently pressing the iron-based alloy powder to have the same height in the circumferential direction.

[0024] The operation of making the center of gravity of the molded body eccentric in the circumferential direction is performed by making the center of the core and the center of the powder filling space of the mold eccentric.

[0025] The operation of making the center of gravity of the molded body eccentric in the circumferential direction is performed by the following steps: before sintering, a metal-infiltrating material is coated onto a first region in a first region and a second region divided along the circumferential direction of the molded body, and then sintered.

[0026] The operation of making the center of gravity of the molded body eccentric in the circumferential direction is performed by the following steps: before sintering, metal paste is applied to the inner diameter surface of the first region in the first region and the second region divided along the circumferential direction of the molded body, and then sintered.

[0027] According to the manufacturing method of the piston pin of the present invention, while minimizing the imbalance caused by dimensional deviations due to machining errors, which results in a misalignment between the center of rotation and the center of gravity of the pin, the increase in weight of the piston pin can be minimized when an imbalance is artificially applied by another method. Furthermore, this manufacturing method is also advantageous in terms of process and cost. Attached Figure Description

[0028] Figure 1 An exploded perspective view showing the piston connected to the connecting rod using a piston pin;

[0029] Figure 2 A perspective view of a piston pin according to one embodiment is shown;

[0030] Figure 3 Show Figure 2 A top view of an example piston pin;

[0031] Figure 4 Show Figure 2 A top view of another example of a piston pin;

[0032] Figure 5 The rotation of the piston pin is shown for each piston drive step;

[0033] Figure 6 A top view of a piston pin according to another embodiment is shown;

[0034] Figure 7 Photographs are shown before and after piston pin sintering according to another embodiment;

[0035] Figure 8 A perspective view of a piston pin according to another embodiment is shown;

[0036] Figure 9 A cross-sectional view is shown in the state before pressure is applied to the mold used to manufacture the piston pin, according to another embodiment.

[0037] Figure 10 It shows Figure 9 A cross-sectional view of the mold under pressure.

[0038] Figure label:

[0039] 1: Piston

[0040] 2: Linkage

[0041] 2a: small end

[0042] 3: Snap ring

[0043] 100: Piston pin

[0044] 101: Area Division Line

[0045] 102: outer diameter

[0046] 103: Inner diameter

[0047] 110: First District

[0048] 120: Second Zone

[0049] 130: Metal Penetrant Materials

[0050] 140: Metal Paste

[0051] 200: Casting mold

[0052] 210: Mold

[0053] 220: Core

[0054] 230: Upward punch

[0055] 240: Downward punch

[0056] 241: First punch

[0057] 242: Second punch

[0058] 250: Iron-based alloy powder

[0059] CD: Circumferential direction

[0060] LD: Length direction

[0061] TL0: Tangent to the outer diameter

[0062] TLI: Tangent to the inner diameter

[0063] OC: Center of outer diameter

[0064] IC: Center of inner diameter

[0065] E1: Eccentricity distance

[0066] L1: Height difference of the lower punch Detailed Implementation

[0067] The advantages and features of the invention, as well as the methods of implementing the invention, can be more readily understood by referring to the following detailed description of the embodiments and accompanying drawings. However, the invention can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein. Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. Furthermore, it should be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having the same meaning as in the relevant field and the context of the invention, and should not be construed as having an ideal or overly formal meaning unless expressly defined in this application. Throughout the specification, unless explicitly stated to the contrary, the word "comprising" and variations such as "comprising" or "including" should be understood to imply the inclusion of the stated elements but not exclude any other elements.

[0068] Furthermore, as used herein, the singular forms “a,” “an,” and “the” are intended to also include the plural forms, unless the context clearly indicates otherwise.

[0069] Figure 1 An exploded perspective view shows the state in which the piston 1 and the connecting rod are connected by using the piston pin 100.

[0070] Reference Figure 1 The piston pin 100 that connects the piston 1 and the connecting rod 2 in the engine can be tubular (i.e., cylindrical).

[0071] The piston pin 100 passes through the small end 2a of the connecting rod 2 and is fixed to the piston 1 by the retaining ring 3 while passing through the piston 1, thereby connecting the piston 1 and the connecting rod 2.

[0072] Meanwhile, the piston pin 100, made of conventional steel, has a high modulus of elasticity (210 GPa), allowing it to be designed to be thinner than piston pins made of other materials. However, when cold-forming the steel, the forming tolerance is ±0.2, so the thickness should be selected based on safety factors. During roughing / finishing in the inner diameter machining, the dimensional tolerance is within ±0.05, increasing costs. Furthermore, compared to materials with low modulus of elasticity such as aluminum, cast iron, and sintered materials that require small inner diameters, steel is more sensitive to elliptical safety factors, resulting in additional eccentricity in addition to machining errors. Even when eccentric machining of the inner diameter is performed after cold forming, the weight increases with width because safety factors must be considered when reducing the inner diameter based on the amount of eccentricity. Additionally, in casting, the density may be uneven due to large shrinkage cavities. In forging, the material has large dimensional tolerances, which is unsuitable in terms of reproducibility.

[0073] Therefore, the piston pin 100 according to the embodiment comprises an iron-based sintered alloy.

[0074] In other words, the piston pin 100 is a sintered piston pin 100 manufactured by sintering iron-based sintered powder using a sintering method, thereby achieving a precise dimensional accuracy of ±0.05 compared to existing steel with a forming tolerance of ±0.2. Therefore, the imbalance caused by dimensional deviations due to forming tolerances, resulting in a misalignment between the pin's center of rotation and center of gravity, can be minimized.

[0075] Iron-based sintered alloys can be manufactured, for example, by sintering Cr-Mo pre-alloy powders containing chromium (Cr) and molybdenum (Mo). Cr-Mo pre-alloys exhibit high gas nitrocarburizing properties and can be used for all sintered materials, with the material selection taking into account factors such as price, dimensional stability, and surface pressure.

[0076] For example, based on the total weight of the iron-based sintered alloy, the iron-based sintered alloy may include 0.4 wt% to 0.8 wt% of carbon (C); 0.2 wt% to 3.5 wt% of chromium (Cr); 0.1 wt% to 0.3 wt% of molybdenum (Mo); 0.2 wt% to 2.0 wt% of nickel (Ni), manganese (Mn), copper (Cu), or mixtures thereof; and the balance iron (Fe).

[0077] Carbon (C) contributes to the formation of bainite and tempered martensite structures because it strengthens the matrix prior to gaseous nitrocarburizing. When the carbon content is less than 0.4 wt%, the strength may deteriorate due to the formation of ferrite, while when the carbon content exceeds 0.8 wt%, carbon segregation and material stability may deteriorate.

[0078] Chromium (Cr) and molybdenum (Mo) contribute to improved wear resistance and fatigue strength by forming compounds and nitrides on the surface and in the pores during gas nitriding. When the chromium (Cr) content is less than 0.2 wt%, fatigue strength may deteriorate, and the gas nitriding effect may be insufficient. When the chromium (Cr) content exceeds 3.5 wt%, formability deteriorates, and nitride formation is difficult due to the formation of chromium oxide on the surface. When the molybdenum (Mo) content is less than 0.1 wt%, fatigue strength deteriorates, and the gas nitriding effect may be insufficient. However, when the Mo content exceeds 0.3 wt%, formability deteriorates, and the price increases.

[0079] It is practically difficult to manufacture when the content of other impurities, such as nickel (Ni), manganese (Mn), copper (Cu), or mixtures thereof, is below 0.2% by weight. When the content of other impurities exceeds 2.0% by weight, the formability may deteriorate.

[0080] Meanwhile, since the sintered piston pin 100 containing iron-based sintered powder has small dimensional tolerances, the imbalance caused by the misalignment of the piston pin 100's center of rotation with its center of gravity is minimized. Therefore, it is necessary to artificially apply the imbalance through other methods. Thus, the piston pin 100 can have a structure in which its center of gravity is eccentric in the circumferential direction.

[0081] Figure 2 A perspective view of the piston pin 100 according to an embodiment is shown. Figure 3 and Figure 4 Show each Figure 2 A top view of an example piston pin 100.

[0082] Reference Figures 2 to 4 The piston pin 100 includes a first region 110 and a second region 120 divided in the circumferential direction CD. The first region 110 and the second region 120 have different densities. Figure 2 As shown, the first region 110 and the second region 120 can extend along the length direction LD. Therefore, the center of gravity of the piston pin 100 is eccentric in the circumferential direction.

[0083] The density difference between region 110 and region 120 can be 0.05 g / cm³. 3 Or even greater. For example, the density difference between the first region 110 and the second region 120 could be 1 g / cm³. 3 Up to 3g / cm 3 When the density difference between the first region 110 and the second region 120 is less than 0.05 g / cm³ 3 At that time, the torque may be weaker.

[0084] For example, the density of a piston pin 100 made of iron-based sintered alloy can be approximately 6.4 g / cm³.3 Up to 6.9 g / cm 3 The density of region 110 in the first area can be 6.4 g / cm³. 3 Above and below 6.65 g / cm 3 Furthermore, the density of region 120 can be 6.65 g / cm³. 3 Up to 6.9 g / cm 3 .

[0085] The first region 110 can occupy an area of ​​30 to 330 degrees in the circumferential direction. For example, as... Figure 3 As shown, the first region 110 can occupy a region of 30 to 90 degrees in the circumferential direction, such as... Figure 4 As shown, the first region 110 can occupy a region of 90 degrees to 330 degrees in the circumferential direction. As described below, in order to ensure the rigidity of the lower punch used to form the first region 110 and the second region 120 with different densities, the first region 110 and the second region 120 must be set at least 30 degrees apart from the central axis of the piston pin 100.

[0086] Furthermore, the dividing line 101 separating the first region 110 and the second region 120 can form a 90-degree angle with the tangent TL0 of the outer diameter of the pipe or the tangent TLI of the inner diameter of the pipe. In other words, in order to minimize the stress concentration at the edge of the lower punch of the mold, the angle formed by the dividing part of the lower punch with the tangent TL0 of the outer diameter of the pipe or the tangent TLI of the inner diameter of the pipe can be perpendicular (90 degrees).

[0087] Figure 5 The rotation of piston pin 100 is shown in each piston drive step. (Refer to...) Figure 5 When the density (weight) along the circumferential direction CD of the piston pin 100 is different, the center of gravity can move along the direction of acceleration. In other words, due to the stroke motion of piston 1 and connecting rod 2, centrifugal force acts along the direction of acceleration, causing piston pin 100 to rotate towards the heavier side.

[0088] Figure 6 A top view of a piston pin 100 according to another embodiment is shown.

[0089] Reference Figure 6 The center OC of the outer diameter 102 and the center IC of the inner diameter 103 of the tube can be eccentric. In other words, the thickness on one side of the tube in the circumferential direction can be greater than the thickness on the other side.

[0090] Therefore, since the center of gravity of the piston pin 100 is eccentric in the circumferential direction, when a centrifugal force is applied in the acceleration direction through the stroke of the piston 1 and the connecting rod 2, the piston pin 100 will rotate towards its heavier side.

[0091] The eccentricity E1 between the center OC of the outer diameter 102 of the tube and the center IC of the inner diameter 103 of the tube can be 0.1 mm or greater, for example, it can be 0.1 mm to 0.5 mm. When the eccentricity E1 between the center OC of the outer diameter 102 of the tube and the center IC of the inner diameter 103 of the tube is less than 0.1 mm, its torque is weak.

[0092] According to another embodiment, the piston pin 100 may include a first region 110 and a second region 120 divided along a circumferential direction, and the first region 110 may include a metal-infiltrated material 130 (e.g., such as...). Figure 7 (As shown).

[0093] Because the first region 110, which contains the metal-infiltrated material 130, has a greater weight than the second region 120, the center of gravity of the piston pin 100 is eccentric in the circumferential direction. When a centrifugal force is applied in the acceleration direction by the stroke of the piston 1 and the connecting rod 2, the piston pin 100 can rotate to its heavier side.

[0094] Figure 7 The photographs show the piston pin 100 before and after sintering the metal-infiltrated material 130. (See reference) Figure 7 Before sintering the piston pin 100, a metal-infiltrating material 130 is coated onto the inner diameter surface of the first region 110. The piston pin 100 is then sintered to form the first region 110 containing the metal-infiltrating material 130.

[0095] Relative to the total weight of the metal penetrant 130, the metal penetrant 130 may include more than 90% by weight of copper (Cu), 2% to 5% by weight of iron (Fe), and the balance being zinc (Zn), manganese (Mn), or a combination thereof.

[0096] Figure 8 A top view of a piston pin 100 according to another embodiment is shown.

[0097] Reference Figure 8 The piston pin 100 includes a first region 110 and a second region 120 divided along the circumferential direction. Metal paste 140 is applied to the inner diameter surface of the first region 110.

[0098] Because the weight of the first region 110 coated with metal paste 140 is greater than the weight of the second region 120, the center of gravity of the piston pin 100 is eccentric in the circumferential direction. When centrifugal force is applied in the acceleration direction through the stroke of the piston 1 and connecting rod 2, the piston pin 100 can rotate to its heavier side.

[0099] Relative to the total weight of the metal paste 140, the metal paste 140 may include more than 90% by weight of copper (Cu), 2% to 5% by weight of iron (Fe), and the balance being zinc (Zn), manganese (Mn), or a combination thereof.

[0100] When the first region 110 includes a metal-permeable material 130 (e.g., such as...) Figure 7 When using (as shown) or metal paste 140, the density difference between the first region 110 and the second region 120 can be 0.05 g / cm³. 3 Or even greater. For example, the density difference between the first region 110 and the second region 120 could be 0.05 g / cm³. 3 Up to 0.2 g / cm 3 When the density difference between the first region 110 and the second region 120 is less than 0.05 g / cm³ 3 At that time, the torque is relatively weak.

[0101] Meanwhile, by combining the above embodiments, the center of gravity of the piston pin 100 according to another embodiment can be eccentric in the circumferential direction.

[0102] In other words, the piston pin 100 may include a first region 110 and a second region 120 divided along the circumferential direction. The first region 110 and the second region 120 may have different densities, or the center OC of the outer diameter 102 of the tube and the center (IC) of the inner diameter 103 of the tube may be eccentric by 0.1 mm or more. The first region 110 may include a metal-infiltrating material 130, or a metal paste 140 may be applied to the surface of the inner diameter 103 of the first region 110, or a combination thereof.

[0103] Figure 9 and Figure 10 A cross-sectional view of a mold used in a method for manufacturing a piston pin, according to another embodiment, is shown. (See also...) Figure 9 and Figure 10 Describe in detail the manufacturing method of the piston pin.

[0104] Reference Figure 9 and Figure 10 The iron-based alloy powder 250 is filled into the mold 200 and then pressed into a tubular shape.

[0105] The description of iron-based alloy powder 250 is the same as above, so repeated descriptions are omitted.

[0106] The mold 200 may include a mold 210, a core 220, an upper punch 230, and a lower punch 240.

[0107] Specifically, the mold 210 includes a cylindrical powder filling space, and the core 220 is located in the central part of the powder filling space of the mold 210 and is separated from the mold 210. After the iron-based alloy powder 250 is placed into the powder filling space between the mold 210 and the core 220, the iron-based alloy powder 250 can be formed into a tubular shape by operating the upper punch 230 and the lower punch 240.

[0108] In this case, the molding conditions of the iron-based alloy powder 250 in the mold 200 can be set to meet the physical properties that the piston pin 100 must possess. For example, these physical properties may include a density of 6.6 g / cm³. 3 The above conditions include an elastic modulus of 120 GPa or higher and a rotational bending strength of 280 MPa or higher. In particular, considering the characteristics of sintered materials with lower mechanical properties than steel, such as yield strength, tensile strength, and fatigue strength, the volume that enables an equivalent safety factor and a weight design based on density difference can be used as the forming condition.

[0109] For example, molding conditions can be set such that the density of the piston pin 100 molded in mold 200 is 6.4 g / cm³. 3 Up to 6.9 g / cm 3 Therefore, the physical properties of sintered materials can be improved by promoting the formation of nitrides in and around the pores through subsequent gas nitriding treatment. To this end, the forming conditions can be set to approximately 15% to 35% of the total volume relative to 100% to achieve an elastic modulus of 120 GPa after nitriding treatment.

[0110] Next, the tubular molded body is sintered.

[0111] The chromium (Cr) contained in the iron-based alloy powder 250 is an element that is easily oxidized, therefore sintering must be carried out in a mixed gas atmosphere of hydrogen and nitrogen, in which case hydrogen can be contained in an amount of 10% to 30% by volume. For other materials, an endothermic gas (ENDO) can be used as the general sintering gas.

[0112] Then, optionally, the prepared piston pin 100 is degreased or cleaned by washing, and then subjected to gas-nitrocarburizing.

[0113] Gas nitriding can be performed for 1 to 4 hours at temperatures ranging from 550°C to 590°C. The porous network formed in the piston pin 100 by gas nitriding facilitates the entry and exit of the nitriding gas. Therefore, gas nitriding forms nitrides in the holes extending from the surface of the piston pin 100 to its core. In contrast to the holes that serve as notches to increase fatigue load, the nitrides around the holes partially fill the holes, significantly increasing the fatigue load and reducing the hole size, thereby increasing the elastic modulus.

[0114] Optionally, the prepared piston pin 100 may be initially oil-impregnated. For example, oil impregnation can be achieved by impregnating the piston pin 100 with a low-viscosity oil of 5W30 or higher according to the Society of Automotive Engineers (SAE) standard to improve cold-state (initial start) lubrication. Through oil impregnation, the pores of the piston pin 100 are filled with oil through a pore network.

[0115] Optionally, the prepared piston pin 100 can be subjected to forming processes including centerless machining and ultra-precision machining.

[0116] Centerless machining can remove the black coating from the material surface during the cutting process. Alternatively, for larger machining volumes, it can be performed as follows: roughing by increasing the cutting depth for rapid machining; intermediate cutting to finish the rough surface to near-normal dimensions while cleaning it through roughing; and cutting to fit or meet design specifications.

[0117] During the ultra-precision machining process, fine and soft abrasive particles are applied under low pressure to give the piston pin 100 the designed dimensions and a smooth and high-precision surface.

[0118] Therefore, in the piston pin 100, the gaseous nitride-carbon percolation compound layer (e.g., nitride) deposited on its outer diameter surface is removed. However, the nitride that has penetrated deep along the pore network remains intact, resulting in a large amount of nitride around the holes on the polished surface. More specifically, due to the formation of a diffusion layer around the nitride (compound layer) in the holes, a surface with excellent fatigue strength and wear resistance can be obtained. However, the inner diameter of the piston pin 100 is not machined by centerless machining and superfinishing. This is because the holes are filled with the nitride (compound layer) formed in the inner diameter, which is advantageous in terms of oil impregnation and lubrication.

[0119] Optionally, the piston pin 100 can be cleaned and dried. After degreasing or washing the surface of the piston pin 100 by cleaning, it is dried at 80°C to 120°C.

[0120] Optionally, the piston pin 100 may eventually be immersed in secondary oil.

[0121] For example, secondary oil impregnation can be achieved by impregnating the piston pin 100 with a low-viscosity oil of 5W30 or higher according to SAE standards to improve cold-state (initial start) lubrication. In this case, the porous network formed in the piston pin 100 can enhance the effect of oil impregnation. Through oil impregnation, the pores of the piston pin 100 are filled with oil through the porous network.

[0122] Meanwhile, the manufacturing method of piston pin 100 may include operations for eccentrically positioning the center of gravity in the circumferential direction of the molded body.

[0123] For example, the operation of making the center of gravity eccentric in the circumferential direction of the molded body can be achieved by filling the iron-based alloy powder 250 into the mold 200 with different powder filling heights in the circumferential direction, and then pressing the iron-based alloy powder 250 into a mold with the same height in the circumferential direction.

[0124] Specifically, refer to Figure 9 The lower punch 240 of the mold 200 may include a first lower punch 241 and a second lower punch 242 separated in the circumferential direction. Therefore, when the heights of the first lower punch 241 and the second lower punch 242 are set differently to fill the iron-based alloy powder 250 thereon, the iron-based alloy powder 250 can be filled with different powder filling heights in the circumferential direction. Figure 9 As shown, the height difference can be understood based on the height difference L1 of the lower punches. Then, the iron-based alloy powder 250 can be pressed into having the same height in the circumferential direction, that is, it can be pressed by the upper punch 230, so that the heights of the first lower punch 241 and the second lower punch 241 are the same.

[0125] Therefore, it may include a first region 110 and a second region 120 divided along the circumferential direction. Thus, the piston pin 100 may be made with first regions 110 and second regions 120 having different densities.

[0126] As another example, the operation of eccentricating the center of gravity in the circumferential direction of the molded body can be achieved by eccentricity between the center of the core 220 and the center of the powder filling space of the mold 210. In other words, when the center of the core 220 is eccentric to the center of the powder filling space of the mold 210, a piston pin 100 with eccentricity between the center of the outer diameter 102 of the tube and the center of the inner diameter 103 of the tube can be manufactured.

[0127] As another example, the operation of eccentrically positioning the center of gravity in the circumferential direction of the molded body can be achieved by placing the molded body before sintering, applying the metal-infiltrating material 130 to the first region 110 of the first region 110 and the second region 120 divided along the circumferential direction of the molded body, and then sintering it. Alternatively, this operation can be achieved by standing the molded body upright before sintering to apply the metal paste 140 to the surface of the inner diameter 103 of the first region 110, and then sintering. In this case, the weight of the metal-infiltrating material 130 can be limited so that the metal-infiltrating material 130 does not diffuse throughout the entire piston pin 100.

[0128] Although the invention has been described in conjunction with embodiments now considered practical, it should be understood that the invention is not limited to the disclosed embodiments. Rather, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A piston pin, comprising: The tubular body is made of iron-based sintered alloy. The piston pin is installed to penetrate the upper end of the connecting rod and the piston. The center of gravity of the piston pin is eccentric in the circumferential direction, and in, The piston pin includes a first region and a second region divided along the circumferential direction. The first region and the second region have different densities, and The density difference between the first region and the second region is 0.05 g / cm³. 3 Or larger.

2. The piston pin as claimed in claim 1, wherein, The iron-based sintered alloy, relative to its total weight, comprises: 0.4% to 0.8% by weight of carbon (C); 0.2% to 3.5% chromium (Cr); 0.1% to 0.3% by weight of molybdenum (Mo); 0.2% to 2.0% by weight of nickel (Ni), manganese (Mn), copper (Cu), or mixtures thereof; and The balance of iron (Fe).

3. The piston pin as described in claim 1, wherein, The first region occupies a circumferential area of ​​30 to 330 degrees.

4. The piston pin as claimed in claim 1, wherein, The dividing line separating the first region from the second region forms a 90-degree angle with either the tangent to the outer diameter of the pipe or the tangent to the inner diameter of the pipe.

5. The piston pin as claimed in claim 1, wherein, The center of the outer diameter of the pipe is eccentric to the center of the inner diameter of the pipe by 0.1 mm or more.

6. The piston pin as claimed in claim 1, wherein, The center of the outer diameter of the pipe is eccentric to the center of the inner diameter of the pipe by 0.1 mm or more, and The first region includes a metal-infiltrated material, or the inner diameter surface of the first region is coated with metal paste.

7. A piston pin, comprising: The tubular body is made of iron-based sintered alloy. The piston pin is installed to penetrate the upper end of the connecting rod and the piston. The center of gravity of the piston pin is eccentric in the circumferential direction, and in, The piston pin includes a first region and a second region divided along the circumferential direction. The first region includes a metal-infiltrated material, and The density difference between the first region and the second region is 0.05 g / cm³. 3 Or larger.

8. The piston pin as claimed in claim 7, wherein, The metal permeation material contains copper (Cu).

9. A piston pin, comprising: The tubular body is made of iron-based sintered alloy. The piston pin is installed to penetrate the upper end of the connecting rod and the piston. The center of gravity of the piston pin is eccentric in the circumferential direction, and in, The piston pin includes a first region and a second region divided along the circumferential direction. The inner diameter surface of the first region is coated with metal paste, and The density difference between the first region and the second region is 0.05 g / cm³. 3 Or larger.

10. The piston pin as claimed in claim 9, wherein, The metal paste contains copper (Cu).

11. A method for manufacturing a piston pin, the method comprising the following steps: Iron-based alloy powder is filled into a mold and then pressurized to form a tubular shape. as well as Sintering forms the material into a tubular shape. This includes an operation that causes the center of gravity of the molded body to be eccentric in the circumferential direction, and in, The operation of eccentricating the center of gravity of the molded body in the circumferential direction is performed by the following steps: The iron-based alloy powder is filled such that, when the iron-based alloy powder is filled into the mold, the powder filling height is different in the circumferential direction, and The iron-based alloy powder is then pressurized so that the powder filling height is the same in the circumferential direction when the iron-based alloy powder is pressurized.

12. The manufacturing method as described in claim 11, wherein, The mold includes: A mold having a cylindrical powder-filling space; The core is arranged to be separated from the mold at the center of the powder-filling space; and The upper and lower punches pressurize the powder filled between the mold and the core. The lower punch includes a first lower punch and a second lower punch separated in a circumferential direction.

13. The manufacturing method as described in claim 12, wherein, The operation of eccentricating the center of gravity of the molded body in the circumferential direction is performed by the following steps: The first lower punch and the second lower punch are set to have different heights; The iron-based alloy powder is filled into the mold; and The iron-based alloy powder is then pressed into a shape with the same height along the circumferential direction.

14. The manufacturing method as described in claim 12, wherein, The operation of making the center of gravity of the molded body eccentric in the circumferential direction is performed by making the center of the core and the center of the powder filling space of the mold eccentric.

15. The manufacturing method as described in claim 11, wherein, The operation of eccentricating the center of gravity of the molded body in the circumferential direction is performed by the following steps: before sintering, a metal-infiltrating material is coated onto the first region of the first region and the second region divided along the circumferential direction of the molded body, and then sintered.

16. The manufacturing method as claimed in claim 11, wherein, The operation of eccentricating the center of gravity of the molded body in the circumferential direction is performed by the following steps: before sintering, metal paste is applied to the inner diameter surface of the first region in the first region and the second region divided along the circumferential direction of the molded body, and then sintered.

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