JPH04171365A - Piston pin and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To obtain a piston pin which is lightweight and possesses the superior mechanical strength and sliding performance by constituting the title piston pin from an inner layer part made of the hybrid type fiber reinforced metal and an outer layer part which is closely attached on the surface of the inner layer part made of Ni- containing casted iron. CONSTITUTION:At least one kind of the particles, short fibers, whiskers, or plate shaped small piece bodies which is selected from the heat resistive substance such as ceramics such as silicon carbide, alumina, and silicon nitride, carbon, and glass is interposed in the gap of the continuous fibers 2 in which at least one kind of the continuous fibers 2 which is selected from the ceramics such as silicon carbide, alumina, and silicon nitride, carbon and glass are arranged, keeping a certain interval. The title piston pin is constituted of an inner layer part 1 which is made of the hybrid type fiber reinforced metal which is composite-formed by charging the basic phase metal 4 consisting of aluminium, magnesium, or the alloy thereof, etc., and an outer layer part 9 which is closely attached on the surface of the inner layer part made of the Ni-containing casted iron which possesses the equal or slightly larger thermal expansion coefficient to the hybrid type fiber reinforced metal in the inner layer part 1.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a piston pin used in a piston for an internal combustion engine such as an automobile or a motorcycle, and a method for manufacturing the same.
More specifically, a piston pin that is lightweight and has excellent mechanical strength and slidability and is made of a metal rod-shaped body or a hollow body compositely reinforced with reinforcing fibers and a metal outermost layer covering the metal, and a method for manufacturing the same. It is related to.

[Prior art and its problems]

In order to improve the fuel efficiency of internal combustion engines, efforts are being made to reduce the weight of various parts that make up the internal combustion engine, and in particular, efforts are being made to reduce the weight of piston pins, which are one of the high-speed moving parts. To achieve this weight reduction, fiber-reinforced metal, a material that has recently attracted attention in various fields as a lightweight and high-strength material, has been developed.
FRM) is being considered. Among these, in order to improve compatibility with the sliding counterpart material, FRM with a matrix of aluminum (Affi) or magnesium (Mg) alloy is used for the inner layer, and a metal tube is arranged for the outer layer. A piston pin structure has been proposed (Japanese Patent Laid-Open No. 63-34
No. 368).

However, since the piston pin of this structure uses FRM reinforced only with fibers in the inner layer, there is a lot of contact between the fibers, and the piston pin is vulnerable to shear stress in a plane parallel to the fiber axis of the FRM. Additionally, it is difficult to sufficiently fill the molten matrix metal between the fibers that make up the FRM during manufacturing, resulting in an FRM with many unfilled defects, resulting in an FRM with excellent mechanical strength.
It cannot be set as RM. Therefore, the FRM part does not have sufficient strength against the shear stress generated during operation. In addition, the outer layer metal tube is required to maintain appropriate friction and sliding properties with sliding mating materials (pistons, connecting rods, bushings, etc.), but the metal tubes used in the conventional technology do not meet these requirements. Due to its poor properties, it is necessary to further form a hard coating on the metal tube, which results in a complicated manufacturing process and high costs. Furthermore, there is a problem in that cracks tend to occur at the interface between the metal tube and the FRM part due to mechanical shock or thermal shock.

Therefore, the inventors conducted intensive research to solve the problems of the prior art as described above, and as a result of various systematic experiments, they came up with the present invention.

[Purpose of the invention]

An object of the present invention is to provide a lightweight, high-strength piston pin that has excellent mechanical strength such as shear strength and slidability, and a method for manufacturing the same.

[Description of the first invention] Structure of the invention The piston pin of the first invention is made of at least one type of continuous fiber selected from ceramics such as silicon carbide, alumina, and silicon nitride, and heat-resistant substances such as carbon and glass. At least one particle, short fiber, whisker, or plate selected from ceramics such as silicon carbide, alumina, and silicon nitride, and heat-resistant substances such as carbon and glass is placed between the continuous fibers arranged at intervals of . an inner layer made of a hybrid fiber-reinforced metal that is composited by filling a matrix metal made of aluminum, magnesium, or an alloy thereof with small pieces interposed therein; and a hybrid fiber-reinforced metal of the inner layer. and an outer layer portion formed in close contact with the surface of the inner layer portion made of Ni-containing cast iron and having a coefficient of thermal expansion comparable to or slightly larger than the inner layer portion.

Functions and Effects of the Invention The piston pin of the first invention has excellent mechanical strength such as shear strength and slidability, and is lightweight and high strength.

Although the mechanism by which the piston pin of the first invention exerts the above-mentioned effects is still not fully clear,
It can be considered as follows.

First, the inner layer of the piston pin of the present invention is made of hybrid FRM. This hybrid type FRM has fine whiskers, particles, etc. placed in the gaps between continuous fibers.
The matrix metal is sufficiently filled between the fibers to prevent contact between the fibers. Therefore, by surrounding the fibers with a matrix metal reinforced with whiskers, fine particles, etc., mechanical strength such as shear stress in a plane parallel to the fiber axis and shear stress in a plane perpendicular to the fiber axis can be increased. It can be made to have excellent properties, high strength, and high rigidity. In addition, this structure allows the use of carbon fiber, which has the advantage of being lightweight and has the advantage of being a reinforcing fiber with a low density, but which has traditionally been difficult to use due to poor bonding properties with the matrix and low shear strength. can be made possible.

Further, the outer layer portion is made of Ni-containing cast iron having a coefficient of thermal expansion comparable to or slightly larger than that of the hybrid fiber-reinforced metal of the inner layer portion. Therefore, even if the piston pin is exposed to a high-temperature environment or an atmosphere with a severe temperature difference between high and low temperatures, the inner and outer layers have the same coefficient of thermal expansion, so the inner and outer layers are There are no problems such as peeling of joints or formation of voids. In addition, since the outer layer is made of Ni-containing cast iron, the surface of the cast iron outer layer is dotted with graphite grains, so the piston pin has excellent sliding characteristics and does not damage the sliding counterpart material. Furthermore, since the piston pin itself has excellent wear resistance, there is little wear on the piston pin itself. From this, it is considered that a lightweight, high-strength piston pin with excellent mechanical strength such as shear strength and slidability was obtained.

[Description of the second invention] Below, an invention (second invention) that further specifies the first invention will be described.
invention).

The inner layer of the piston pin of the second invention is made of hybrid FRM.

The continuous fibers of the hybrid FRM are continuous fibers made of at least one material selected from ceramic materials such as silicon carbide, alumina, and silicon nitride, and heat-resistant nonmetallic materials and heat-resistant metal materials such as carbon, boron, and glass. They are fibers, and fibers made of these materials may be used alone or in combination of two or more types of fibers. Further, the properties such as the thickness, length, cross-sectional shape, etc. of the fibers are appropriately selected depending on the material of the outer layer, the intended use, the performance required of the piston pin, etc.

Particles, short fibers, whiskers, or plate-like subtotal bodies interposed between continuous fibers are made of ceramic materials such as silicon carbide, alumina, and silicon nitride, heat-resistant nonmetallic materials such as carbon, boron, and glass, and heat-resistant metal materials. It is at least one kind of substance selected from these materials, and a substance made of these materials may be used alone, or two or more kinds of substances and/or shapes may be used in combination. The amount of the substance to be blended is appropriately selected depending on the application, the performance required of the piston pin, etc. In addition, the shape, size, length, thickness, cross-sectional shape, and other properties of the substance may be determined as appropriate depending on the compatibility and combination with the continuous fibers, the material of the outer layer, the intended use, and the performance required for the piston pin. select.

In addition, the mixing amount of the substance is a volume ratio to continuous fibers,
It is preferably about 1 to 150%.

This is because by setting it within this range, the volume fraction of continuous fibers can be maintained at about 60 to 20%, and the strength of the composite portion of the inner layer can be made to a level that satisfies the required performance.

The matrix metal filled in the gaps between the continuous fibers is a metal such as aluminum, magnesium, or an alloy containing these as main components. As this metal, those commonly used as matrix metals of fiber-reinforced metals can also be used. The content ratio of the base metal and continuous fibers is appropriately selected depending on the type of base metal, the type of continuous fibers, the intended use, the performance required of the piston pin, and the like. Note that the mixing amount is preferably about 35 to 70% by volume in the FRM. This means that the mixing amount is 35% by volume.
If it is less than 70% by volume, the fiber spacing may become narrow and sufficient shear strength may not be obtained, and if it exceeds 70% by volume, the reinforcing fibers will not be able to exhibit the composite reinforcing effect. This is because there is a risk. By keeping it within this range, the inner layer can have sufficient strength and rigidity.

In the piston pin of the present invention, the inner layer portion includes the continuous fibers and the substance consisting of particles, short fibers, whiskers, or small plate-like pieces interposed in the gaps between the continuous fibers, and the substance filled in the gaps between the continuous fibers. It is constituted by a hybrid type FRM consisting of the above-mentioned parent phase metal. By using this hybrid type FRM, the strength in the fiber axis direction of the continuous fibers of the hybrid type FRM is mainly shared by the continuous fibers, and the strength in the direction perpendicular to the continuous fibers is distributed between the continuous fibers. The piston pin of the present invention can be made to absorb shear stress in a plane parallel to the fiber axis and shear stress in a plane perpendicular to the fiber axis by mainly using the particles interposed in the continuous fibers and the matrix metal filled in the gaps between the continuous fibers. It has excellent mechanical strength such as internal shear stress, and can have high strength and high rigidity.

Here, regarding the specific structure of the internal layer of the present invention,
The following embodiments may be adopted.

First, as shown in FIG. 2, the inner layer section 11 of the first embodiment is a hybrid type FRMII in which the entire inner layer group is a rod-shaped body, and is arranged at continuous intervals in the axial direction. It consists of continuous fibers 12, the substance 13 consisting of particles, short fibers, whiskers, or plate-like pieces interposed in the gaps between the continuous fibers, and the matrix metal 14 filled in the gaps between the continuous fibers. Note that this inner layer portion 11 may have a core material at its center.

The inner layer part 21 of the second embodiment is a hybrid FRM 21 with a hollow inner layer part, as shown in FIG.
The substance 23 consists of continuous fibers 22 arranged at continuous intervals in the axial direction, and particles, short fibers, whiskers, or plate-like pieces interposed in the gaps between the continuous fibers.
and the matrix metal 24 filled in the gaps between the continuous fibers.
and a hollow part 25. Note that the portion of the inner layer portion 21 forming the hollow portion 25 may have a hollow cylinder defining the hollow portion.

As shown in FIGS. 4 to 6, the inner layer part 31 of the third embodiment is a rod-shaped or hollow-shaped hybrid FRM 31 in which continuous fibers are continuously arranged in the circumferential direction. , continuous fibers 32 arranged at continuous intervals in the circumferential direction of the core portion 36 , and particles, short fibers, whiskers, or small plate-like pieces interposed in the gaps between the continuous fibers. and the matrix metal 34 filled in the gaps between the continuous fibers. Note that the core portion 36 may have a hollow portion 35. Alternatively, the core portion 36 may be eliminated to form a hollow portion.

Next, the outer layer portion is formed in close contact with the surface of the inner layer portion, and is made of a Ni-containing cast iron metal having a coefficient of thermal expansion comparable to or slightly larger than that of the hybrid fiber-reinforced metal of the inner layer portion. .

Here, Ni in the metal is an element that determines the thermal expansion coefficient of the outer layer portion, and the Ni content is appropriately determined depending on the required thermal expansion coefficient. Further, the graphite content in the cast iron is appropriately determined depending on the characteristics of the surface of the piston pin, such as the sliding characteristics and wear resistance required of the piston pin. Among these, it is preferable that the Ni content is 12 to 22% by weight and the carbon content is 2.5 to 3.2% by weight. By setting the value within this range, the outer layer can have a coefficient of radial thermal expansion that is equal to or slightly larger than the hybrid fiber-reinforced metal of the inner layer, and has excellent sliding properties on the surface of the outer layer. can. Furthermore, the dispersion state of the graphite particles is
It is preferable that they are evenly scattered at least in the sliding portion of the piston pin.

This is because graphite grains themselves have low strength, so if the graphite grains are not distributed uniformly in the sliding part, that is, if they are arranged continuously or unevenly distributed, cracks may occur in the outer layer or stress concentration may occur. This is because there is a risk that this may lead to a decrease in strength.

The specific method of manufacturing the piston pin of the present invention will be briefly explained below.

The method for manufacturing a piston pin of the present invention first includes silicon carbide,
At least one kind of continuous fibers selected from ceramics such as alumina and silicon nitride, and heat-resistant substances such as carbon and glass are arranged at certain intervals, and silicon carbide, alumina, and silicon nitride are arranged in the gaps between the continuous fibers. A fiber material for a composite material is prepared in which at least one type of particles, short fibers, whiskers, or plate-like pieces selected from heat-resistant substances such as ceramics, carbon, and glass are interposed. Next, a Ni-containing cast iron material having a coefficient of thermal expansion comparable to or slightly larger than the coefficient of thermal expansion of the fiber-reinforced metal obtained by the raw material for composite materials and the metal filled between the fibers of the raw material is prepared. Prepare a hollow metal body. Next, the fiber material for composite material is inserted into the hollow part of the hollow metal body to form a piston pin material, and then aluminum, magnesium, or A piston pin is obtained by injecting and filling a matrix metal made of such an alloy, and then cooling and solidifying it.

The piston pin of the present invention has excellent mechanical strength such as shear strength and slidability, is lightweight, has high rigidity, and has high strength.
Taking advantage of this characteristic effect, it is suitable to apply it to members used in harsh environments such as engines with high explosion pressure used in high-temperature atmospheres, such as diesel engines.

[Description of the Third Invention] The third invention relates to a preferred method for manufacturing the piston pin of the first and second inventions.

Structure of the Invention In the method for manufacturing a piston pin according to the third aspect of the present invention, at least one kind of continuous fibers selected from heat-resistant materials are arranged at a certain interval, and in the gaps between the continuous fibers, continuous fibers selected from heat-resistant materials are arranged. at least one type of particles, short fibers,
The coefficient of thermal expansion of the fiber reinforced material for composite materials with whiskers or plate-like small pieces interposed therein is the same as that of the fiber reinforced metal obtained by the fiber material for composite materials and the metal filled between the fibers of the raw material. or a step of preparing a piston pin base material by inserting it into the hollow part of a metal hollow body made of Ni-containing cast iron having a slightly larger coefficient of thermal expansion; A step of joining a thermal stress buffer made of a metal having a melting point higher than that of metal, and a step of joining a thermal stress buffer made of a metal having a melting point higher than that of metal, and adding aluminum, magnesium, an alloy thereof, etc. The method is characterized by a step of manufacturing a piston pin by injecting and filling the base metal, cooling and solidifying the material, and then cutting the thermal stress buffer.

Functions and Effects of the Invention According to the piston pin manufacturing method of the third invention, it is possible to obtain a lightweight, high-strength piston pin that is excellent in mechanical strength such as shear strength and slidability.

The mechanism of why a piston pin having the above-mentioned excellent effects can be easily manufactured by this manufacturing method is not yet fully clear, but it is thought to be as follows.

That is, in the third invention, first, fine whiskers, particles, etc. made of the heat-resistant substance are placed in the gaps between the continuous fibers made of the heat-resistant substance, and a matrix metal is injected and filled between the hindlimb fibers. By using FRM, contact between fibers can be minimized during pouring, and fibers/
The matrix metal can be sufficiently filled between the fibers. Therefore, by surrounding the fibers with a matrix metal reinforced with whiskers, fine particles, etc., mechanical strength such as shear stress in the plane parallel to the fiber axis and shear stress in the plane perpendicular to the fiber axis can be increased. It can be made to have excellent properties, high strength, and high rigidity.

Therefore, the piston pin can have excellent mechanical strength such as shear stress.

Further, in the method of the present invention, a Ni-containing cast iron hollow body having a thermal expansion coefficient comparable to or slightly larger than the hybrid FRMO thermal expansion coefficient is used, the fiber material for composite material is inserted into the hollow body, and the The piston pin is made by pouring base metal into a hollow body. Normally, when a metal hollow body is used for the outer shell, there is a method such as press-fitting the FRM, but in the method of the present invention, the process of manufacturing the FRM and the process of joining the Ni-containing cast iron hollow body are performed at the same time.
By giving the same thermal history to the contained cast iron hollow body and the FRM, residual stress can be reduced and the process can be simplified. Further, as the hollow metal body forming the outer layer of the piston pin, Ni-containing cast iron having a coefficient of thermal expansion comparable to or slightly larger than that of the hybrid FRM forming the inner layer of the piston pin was used.

As a result, in the step of injecting and filling the parent phase metal made of aluminum, machnesium, or an alloy thereof between the fibers in the hollow metal body of the piston pin base body, and cooling and solidifying the hollow metal body and its interior. It is possible to obtain a piston pin material in which a high-quality hybrid FRM is arranged in the inner layer, without defects such as voids caused by mismatch in thermal expansion coefficient with other materials and poor adhesion at the joint interface.

Further, in the manufacturing method of the present invention, a thermal stress buffer made of a metal having a higher melting point than the filling metal is bonded to the side surface of the outer layer of the piston pin base body, and the metal is poured into the hollow metal body. Become. From this, in the step of injecting and filling the base metal into the piston pin base material having the thermal stress buffer, cooling and solidifying, the solidification shrinkage and/or thermal shrinkage of the molten metal is relaxed, and the hybrid type FRM is formed. Since it is possible to prevent thermal stress from accumulating in the structure, it is possible to form an inner layer made of a high quality hybrid FRM. Further, in the method of the present invention, the piston pin as a product can be easily taken out from the casting after casting by the thermal stress buffer provided on the side surface of the outer layer.

Further, in the piston pin obtained by the manufacturing method of the present invention, the outer layer has a coefficient of thermal expansion of N having a coefficient of thermal expansion comparable to or slightly larger than that of the hybrid fiber-reinforced metal of the inner layer.
Made of i-containing cast iron. Therefore, even if the piston pin is exposed to a high-temperature environment or an atmosphere with a severe temperature difference between high and low temperatures, the inner and outer layers have the same coefficient of thermal expansion. The joint may peel off,
There are no problems such as the formation of voids. In addition, the outer layer has graphite grains scattered on its surface, so it has excellent sliding characteristics for the piston pin, does not damage the sliding partner material, and has excellent wear resistance. There is also less wear on the piston pin itself.

From this, it is believed that by the manufacturing method of the present invention, it is possible to easily manufacture a lightweight, high-strength piston pin that has excellent mechanical strength such as shear strength and slidability.

[Description of the fourth invention] An invention that is a more specific version of the third invention will be described below.

As shown in FIG. 7, the method for manufacturing a piston pin according to the fourth aspect of the present invention begins with at least one continuous material selected from ceramics such as silicon carbide, alumina, and silicon nitride, and heat-resistant materials such as carbon and glass. The fibers 72 are arranged at certain intervals, and in the gaps between the continuous fibers 72, at least one particle selected from ceramics such as silicon carbide, alumina, and silicon nitride, and heat-resistant substances such as carbon and glass,
A fibrillar material 70 for composite material with short fibers, whiskers, or small plate-like pieces 73 interposed therein is prepared (fibrillar material preparation step for composite material). The continuous fibers used in this step, the particles interposed between the continuous fibers, the short fibers, the whiskers, or the substances consisting of plate-like pieces may be the same as those described in the second invention. Note that when short fibers, whiskers, or fine particles are used as the intervening substance, it is preferable to use a heat-resistant nonmetallic material. By using such a material, when the fibrous body and the matrix metal are composited, the fibers can be sufficiently maintained without evaporating or melting even when exposed to high temperatures. In addition, as a method for manufacturing the fiber material for composite materials, the fiber bundle is immersed in a solution in which a predetermined amount of substances that will become inclusions are suspended, without irradiating it with ultrasonic waves, and then pulled up and dried. That's preferable.

It is more efficient to wind up the material continuously while dipping it. Inclusions are uniformly attached to the surface of each of the fiber bodies produced in this manner, and the gaps between the fibers are maintained at a constant distance.

Next, as shown in FIG. 8, N has a thermal expansion coefficient comparable to that of the fiber-reinforced metal obtained by the composite material raw material and the metal filled between the fibers of the raw material.
A metal hollow body 80 made of i-containing cast iron is prepared (metal hollow body preparation step). The metal hollow body is made of the same material as the outer layer described in the second invention. Note that since the piston pin moves at high speed in an engine or the like, weight balance is important. Therefore, it is preferable to make the weight distribution uniform in the longitudinal direction and the radial direction.

For the second reason, it is preferable that the metal hollow body 80 has a small misalignment between the inner and outer diameters, and has a shape close to a perfect circle. In addition, the thickness of the outer layer of the piston pin is preferably thick enough to maintain the necessary strength since the thinner the thinner the layer, the lighter the weight.The thickness should be at least 2% of the piston pin's outer diameter. Bye. Therefore, the wall thickness of the metal hollow body may be equal to or more than 2% of the outer diameter of the piston pin plus a machining allowance if necessary. In addition,
Either of the metal hollow body preparation step and the composite material fiber raw material preparation step may be performed first.

Next, the fiber material for composite material is inserted into the hollow part of the metal hollow body to prepare a piston pin material (piston pin material preparation step). At this time, in order to make it easier to take out the piston pin material after casting, a mold release agent containing graphite particles, boron nitride, etc. may be applied to the outer surface of the piston material. Note that the mold release agent may be applied at any time before casting.

Next, as shown in FIG. 9, a thermal stress buffer 98 made of a metal having a higher melting point than the filling metal is bonded to the side surface of the outer layer of the piston body (thermal stress buffer bonding step). . The second thermal stress buffer is installed to prevent residual stress on the outer diameter of the piston pin due to solidification and thermal contraction during casting, so it must be difficult to bond with the base metal and not disappear during casting. suitable. Moreover, the above-mentioned mold release material may be applied to the buffer body in order to weaken the bonding property with the matrix metal. The thermal stress buffer can be simply joined to the side surface of the outer layer of the piston body by welding, and the material for this purpose is preferably steel, stainless steel, or the like. It is preferable that the joining be performed in the normal direction of the side surface of the outer layer part and to cover the entire longitudinal direction of the piston pin original body. The larger the number of bonded buffer bodies, the more effective the effect, but even 1 to 3 bonded buffer bodies can be sufficiently effective.

Next, as shown in FIG. 10, between the fibers in the metal hollow body of the piston pin base body to which the thermal stress buffer was joined,
After injecting and filling the matrix metal 100 made of aluminum, magnesium, or an alloy thereof, the piston pin is manufactured by cooling and solidifying, and then cutting the thermal stress buffer (piston pin manufacturing process). ). At this time, it is preferable to heat the piston pin material in advance.

The preheating temperature is preferably at least the temperature required for the molten metal to penetrate between the fibers of the piston pin material for 20 minutes. Therefore, the preheating temperature is preferably about 500°C or more. When using fibers, it is preferable to use an inert heating atmosphere such as nitrogen.Also, in order to fill the fiber gaps with the matrix metal, after pouring the molten metal, it is
It is preferable to pressurize to kg/cm2 or more. Also,
After the molten metal has solidified, the ingot is taken out and cooled.

Next, the end face and outer peripheral surface of the ingot are finished by machining to obtain a piston pin.

〔Example〕

The present invention will be explained in detail below.

1st Example Carbon fiber (manufactured by Toshi ■: T 300-6000-50B
), silicon carbide fine particles (average particle size: 1
．． After uniformly adhering 8μm), about 1600 bundles were solidified and prepared in advance with an inner diameter of 34mm x length of 90mm.
Nilenst cast iron pipe with wall thickness of 2 mm (Fe-3%C-2
%5i-1.5%Mn-15%Ni-5%Cu-2%C
r, coefficient of thermal expansion: 19 x 10-@/K).

Next, steel fins were welded to the outer periphery of this tube to prevent the generation of thermal stress, and then the tube was heated at 700°C x 30 molecules in a heating furnace and placed in a mold preheated to 300°C. Then,
Immediately, molten AC7A alloy at 750°C was poured and pressurized to 900 kg/cm'' for 120 seconds using a pressure punch.Next, after being pressurized and solidified, it was removed from the mold and cut to form a double structure. A rough piston pin material was obtained.

Next, the outer layer of Niresist cast iron of this rough shape material was made into a 1 mm thick layer.
The screws were cut to a certain extent and finished to predetermined dimensions to obtain screws 1 to 1 according to this example. When the end face of the obtained piston pin was observed under magnification, no problems such as peeling or voids occurred at the interface between the outer layer and the inner layer.

The radial thermal expansion coefficient of the FRM portion of the obtained piston pin was 19°0 x 10-'/.

The obtained screws 1 to 1 pin were put into a diesel engine (39
00cc, 4 cylinders) and a performance evaluation test was conducted. The piston pin obtained in this example was approximately 47% lighter than the piston pin (made of alloy steel) conventionally used in the test engine. In the performance evaluation test, full load operation was performed at the rotation speed at which the maximum torque was generated and at the rotation speed at which the maximum output was generated, but there were no problems and no abnormalities occurred. Furthermore, when the surface shape of the piston pin after the test was measured using a surface roughness meter, no change in surface shape was observed.

Second example carbon fiber (manufactured by Toshiku 4E: M030-6000-50
B and MO40-6000-50B bundled),
Silicon carbide whiskers (average diameter 0
．． 8 μm, average length: 50 μm) and silicon nitride fine particles (average particle size.

1μm) uniformly at a volume ratio of about 1:0.20, about 1,300 bundles were solidified, and prefabricated Niresist cast iron pipes (F e -2, 7% C-1,5%5i-1%M
n-13%Ni-5%Cu-1,7%Cr, coefficient of thermal expansion: 19. 4 x 10-'/K).

Next, steel fins were welded to the outer periphery of this tube to prevent the generation of thermal stress, and then the tube was heated at 600°C x 30 molecules in a heating furnace and placed in a mold preheated to 200°C. Then,
Immediately, molten AC7A alloy at 750°C was poured into the flask and pressurized to 600 kg/cm 2 for 120 seconds using a pressure punch. Next, after being pressurized and solidified, it was taken out from the mold and cut to obtain a double-structured piston pin rough shape.

Next, the outer layer of Niresist cast iron of this rough shape material was made into a 1 mm thick layer.
The piston pin according to this example was obtained by cutting to a certain extent and finishing it to a predetermined size. In addition, F of the obtained piston pin
The radial thermal expansion coefficient of the RM section is 19, 8 x 10-”
It was at /.

The obtained piston pin was used in a diesel engine (390
0cc, 4 cylinders) and a performance evaluation test was conducted.

The piston pin obtained in this example was approximately 40% lighter than the piston pin (made of alloy steel) conventionally used in the test engine. The exam is
When the piston pins were taken out and visually inspected at maximum rotation and after full load operation, no damage was found. Furthermore, when the surface shape of the piston pin after the test was measured using a surface roughness meter, no change in surface shape was observed.

Comparative Example 1 Mild steel (thermal expansion coefficient: 11,
A comparative piston pin was manufactured in the same manner as in the first embodiment described above, except that 8X 10-"/K) was used.
In this comparative piston pin, peeling occurred near the interface between the outer metal tube and the inner layer during processing into the piston pin. Therefore, no performance evaluation test was conducted.

Comparative Example 2 A comparative piston pin was manufactured in the same manner as in Example 2 above, except that a stainless steel pipe (thermal expansion coefficient: 17.3 x 10-6/K) was used instead of the double cyst cast iron pipe. did. At this time, when the molten base metal was poured and solidified, peeling occurred near the interface between the outer layer of the stainless steel pipe and the inner layer.

When the comparative piston pin obtained by finishing was subjected to a performance evaluation test in the same manner as in the second example, a large number of deposits were observed on the outer circumferential surface of the outer layer.

It is thought that this deposit adhered to the sliding mating material or the comparison piston pin during the operation test.

Comparative Example 3 A comparative piston pin was manufactured in the same manner as in Example 1 above, except that silicon carbide fine particles were not interposed between the fibers and the inner layer was made of non-hybrid fiber reinforced metal. The comparative piston pin thus obtained had minimal peeling and voids near the interface between the inner layer and the outer layer. The radial thermal expansion coefficient of this comparative piston pin OFRM section is 20Xl.
It was at O-6/. When this comparative piston pin was subjected to a performance evaluation test in the same manner as in the first example, cracks were found in the FRM of the inner layer in the axial direction.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of the piston pin of the present invention, FIGS. 2 to 6 show embodiments of the inner layer part of the present invention, and FIG.
5 to 5 are perspective views thereof, FIG. 6 is a vertical sectional view of the inner layer portion of FIG. 5, FIG. 7 is a schematic perspective view showing an example of the inner layer portion of the piston pin of the present invention, and FIG. FIG. 9 is a schematic perspective view showing an example of the outer layer portion of the invention, FIG. 9 is a schematic perspective view showing an example of a state in which the thermal stress buffer is welded when producing the piston pin of the invention, and FIG. 10 is the piston of the invention. It is a sectional view explaining an example of a pin manufacturing process. IS II, 21, 31 ... Inner layer part 2.12
．． 22.32.72.92 ... Continuous fiber 13.23.33.73 ... Intervening substance 4.14.
24.34 ... Parent phase metal 25.35 ...
Hollow part 36 ... Core material part 98 ... Thermal stress buffer 9.99 ... Outer layer part

Claims (2)

[Claims] (1) At least one kind of continuous fibers selected from ceramics such as silicon carbide, alumina, and silicon nitride, and heat-resistant materials such as carbon and glass are arranged at a certain interval. Aluminum, magnesium, or any of them with at least one kind of particles, short fibers, whiskers, or plate-like particles selected from ceramics such as silicon, alumina, and silicon nitride, and heat-resistant substances such as carbon and glass. An inner layer made of a hybrid fiber-reinforced metal filled with a matrix metal such as an alloy, and a Ni-containing cast iron having a coefficient of thermal expansion equal to or slightly larger than that of the hybrid fiber-reinforced metal in the inner layer. 1. A piston pin comprising an outer layer formed in close contact with the surface of the inner layer, and is lightweight and has excellent mechanical strength and slidability. (2) At least one kind of continuous fibers selected from a heat-resistant substance are arranged at a certain interval, and at least one kind of particles, short fibers, and whiskers selected from a heat-resistant substance are arranged in the gaps between the continuous fibers. Or, the fiber material for composite materials with plate-shaped small pieces interposed therein is made to have a coefficient of thermal expansion equal to or equal to that of the fiber-reinforced metal obtained by the fiber material for composite materials and the metal filled between the fibers of the material. A step of preparing a piston pin blank by inserting it into a hollow part of a metallic hollow body made of Ni-containing cast iron having a slightly larger thermal expansion coefficient; A step of joining a metal thermal stress buffer having a melting point higher than that of aluminum, magnesium, an alloy thereof, etc. A method for producing a piston pin, comprising the steps of: injecting and filling a matrix metal, cooling and solidifying it, and then cutting the thermal stress buffer to produce a piston pin.