JP2001050243A - Structure and manufacture of connecting rod and piston pin for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure and manufacture of a connecting rod and a piston pin with decreasing stress generated at the small end of the connecting rod. SOLUTION: A piston pin 20 is joined to the small end 14 of a connecting rod 10 in an inseparatable and integral manner, thus making the small end 14 thicker. As a result, the small end 14 is less deformed during operating an internal combustion engine to produce a decrease in stress generated at the small end. Manufacture of the connecting rod 10 and the piston pin 20 at the same time and in an integral manner in a series of processes permits simplified manufacturing processes and reduced manufacturing cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a connecting rod and a piston pin of an internal combustion engine and a method of manufacturing the same, and more particularly to a technique for reducing a stress generated at a small end of the connecting rod.

[0002]

2. Description of the Related Art A connecting rod of an internal combustion engine has a function of connecting a piston and a crankshaft and converting an explosive force acting on the piston into a rotational force of the crankshaft. The connection between the piston and the connecting rod is made via a piston pin fitted to the small end of the connecting rod. At this time, since the piston pin is fitted to the small end of the connecting rod by fitting, a minute gap is generated between the two parts.

[0003]

However, in such a structure, when an explosive force acts on the piston top surface, the deformation of the connecting rod small end becomes larger than the deformation of the piston pin, as shown in FIG. In addition, the stress change at the small end portion 1 of the connecting rod becomes large. Here, reference symbol C indicates the stress at the approximate center of the small end portion 1, and reference symbol D indicates the stress at the connecting portion between the small end portion 1 and the main body 2. If the stress at the connecting rod small end 1 exceeds the fatigue strength of the connecting rod material, fatigue breakage may occur from that portion during operation of the internal combustion engine, which may cause a failure.

On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 9-144879, in order to improve the coupling strength between the connecting rod and the piston, instead of the piston pin, a spherical surface formed at the small end of the connecting rod is used. Techniques for connecting the two have also been proposed. However, such a technique complicates the structure of the piston and the connecting rod and increases the weight, so that it is not practical in terms of response and the like.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and by revising the coupling structure between the piston and the connecting rod, the stress generated at the small end of the connecting rod without increasing the weight. It is an object of the present invention to provide a structure of a connecting rod and a piston pin of an internal combustion engine, and a method of manufacturing the connecting rod, in which the number of components is reduced.

[0006]

SUMMARY OF THE INVENTION Accordingly, the invention according to claim 1 relates to a structure of a connecting rod and a piston pin of an internal combustion engine, wherein a piston pin is inseparably and integrally connected to a small end of the connecting rod. It is characterized by having done.

According to such a configuration, the small end and the piston pin are inseparable and integral with each other, so that the thickness at the small end is increased, and the deformation at the small end during operation of the internal combustion engine is reduced. Therefore, the stress generated at the small end of the connecting rod is greatly reduced.

The invention according to claim 2 is characterized in that a through hole through which lubricating oil flows is provided from the inner peripheral surface of the large end to the tip of the small end of the connecting rod. According to this configuration, the lubricating oil is supplied between the crankshaft and the large end of the connecting rod through the lubricating oil passage formed inside the crankshaft, and the lubricating oil passage and the connecting rod inside the crankshaft are supplied to the lubricating oil passage and the connecting rod. When the position matches the formed through hole, lubricating oil is supplied to the through hole of the connecting rod. The lubricating oil supplied to the through hole is jetted from the tip of the small end of the connecting rod toward the back surface of the piston to cool the back surface of the piston. Further, the lubricating oil flows through the through-hole of the connecting rod, so that the connecting rod is also cooled from the inside.

According to a third aspect of the present invention, there is provided a first forging step of forming a connecting rod and a piston pin inseparably and integrally by hot forging using non-heat treated steel as a rough material, and the first forging step. A shot blasting step of performing shot blasting on the connecting rod and the piston pin formed by the above, and a processing step of processing the connecting rod and the piston pin subjected to the shot blasting in the shot blasting step to predetermined dimensions. A method for manufacturing a connecting rod and a piston pin of an internal combustion engine is characterized.

[0010] According to this configuration, the connecting rod and the piston pin are manufactured through the first forging step, the shot blasting step, and the processing step. Therefore, the connecting rod and the piston pin are manufactured in an inseparable and integral manner with fewer steps than the manufacturing method according to the prior art.

According to a fourth aspect of the present invention, there is provided a second forging step of forming a connecting rod and a piston pin inseparably and integrally by hot forging using low carbon steel as a rough material, and the second forging step. A roughing step of roughly processing the formed connecting rod and piston pin to predetermined dimensions, a carburizing step of subjecting the connecting rod and piston pin processed in the roughing step to carburization, and a carburizing step. A heat conditioning treatment step of subjecting the carburizing-treated connecting rod and piston pin to heat conditioning treatment, and a heat treatment treatment of the connecting rod and piston pin subjected to the heat treatment treatment by the heat treatment treatment step. A shot peening step of performing shot peening; and shot peening is performed by the shot peening step. Characterized in that to constitute a manufacturing method of a connecting rod and piston pin of an internal combustion engine includes a finishing step of processing the connecting rod and the piston pin to final dimensions, the.

According to such a configuration, the connecting rod and the piston pin are provided in the second forging step, the roughing step,
It is manufactured through a carburizing process, a thermal conditioning process, a shot peening process, and a finishing process. Here, by using low-carbon steel as a rough material in the second forging step, forging and machining are facilitated because the amount of carbon contained in the rough material is small. Further, through the carburizing process, the heat conditioning process, and the shot peening process, the surface strength and wear resistance of the connecting rod and the piston pin are improved.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the attached drawings. FIG. 1 shows an embodiment of the structure of a connecting rod and a piston pin according to the present invention.

The connecting rod 10 includes a large end 12, a small end 14, and a main body 16, as shown in the drawing. The large end 12 is divided substantially at the center of the large end hole 12a, and is rotatably connected to a pin of a crankshaft by a high tension bolt 12b and a nut 12c in a state where a half-split plain bearing (not shown) is inserted. You.
The large end 12 is not limited to the configuration shown in FIG. 1. For example, the large end 12 may be provided with a female thread to eliminate the nut, or may be divided obliquely for the convenience of assembly, or use an assembled crank. Instead, a needle bearing or the like may be used.

A substantially cylindrical piston pin 20 is inseparably and integrally connected to the small end 14. That is, the piston rod having a separate structure is fitted into the small end hole of the connecting rod 10 by press-fitting or the like, and is not integrated.
The small end 14 and the piston pin 20 are inseparable and integrally formed.

The main body 16 has a substantially I-shaped cross section and is interposed between the small end 14 and the large end 12 so as to connect the small end 14 and the large end 12. Be linked. According to the structure of the connecting rod 10 and the piston pin 20 having such a configuration, the small end portion 14 and the piston pin 20
Is integrated, the thickness at the small end 14 is increased, and the deformation at the small end 14 is reduced. Therefore, as shown in FIG.
4 greatly reduces the risk that the stress exceeds the fatigue strength of the connecting rod material, and prolongs the fatigue life of the connecting rod. Note that reference numerals C and D in FIG.
Indicate the same parts as C and D in FIG.

FIG. 3 shows a configuration in which lubricating oil is supplied to the connecting rod 10 and the piston pin 20 on the back surface of the piston to cool the piston 30 in the previous embodiment.

It is known that the temperature of the piston 30 of an internal combustion engine rises during explosive combustion, causing a decrease in strength. For this reason, it is common practice to forcibly supply lubricating oil to the back surface of the piston by an oil gallery or an oil jet, and to cool the back surface of the piston by the lubricating oil to suppress a rise in temperature. However, when the in-cylinder pressure at the time of the explosion further increases, the piston temperature increases more than the current state, so that further cooling is required.

Therefore, as shown in FIG. 3, the connecting rod 10 in which the small end portion 14 and the piston pin 20 are integrated is moved from the inner peripheral surface of the large end portion 12 slidably in contact with the crankshaft 40 to the small end portion 14. An oil hole (through hole) 18 through which lubricating oil flows to the tip is formed. In this case, the piston pin 20 is not formed in a substantially cylindrical shape, and the piston pin hole 20 is formed so as to leave a flesh at the center of the piston pin 20 so that lubricating oil does not leak from the piston pin 20.
a must be formed.

According to the structure of the connecting rod 10 and the piston pin 20 having such a configuration, when lubricating oil is supplied to the outer peripheral surface of the pin portion 40b through the oil hole 40a formed in the crankshaft 40, the pin portion 40b And the connecting rod large end hole 12a is lubricated. At the same time, the pin portion 40b and the large end hole 12a rotate relatively, and the oil hole 40 of the crankshaft 40 is rotated.
When “a” matches the oil hole 18 of the connecting rod 10, lubricating oil is supplied from the crankshaft 40 to the oil hole 18 of the connecting rod 10. The lubricating oil supplied to the oil hole 18 of the connecting rod 10 gushes from the oil hole opened at the tip of the small end portion 14,
Hit the back of the piston. Then, the back surface of the piston is cooled by the lubricating oil, the temperature of the piston decreases, and a decrease in piston strength due to heat can be suppressed. Also,
At the same time, since the connecting rod 10 is also cooled from the inside thereof, a decrease in the thermal strength of the connecting rod 10 can be suppressed.

Next, a method of manufacturing a connecting rod and a piston pin according to the present invention will be described. First,
In order to clarify the difference between the present invention and the prior art, a method for manufacturing a connecting rod and a piston pin according to the prior art will be described.

In the prior art, as shown in FIG. 7, the connecting rod and the piston pin are manufactured in different processes. That is, as shown in FIG. 7A, the connecting rod is manufactured by hot forging a coarse material, removing burrs and scales by shot blasting, and performing a finishing process after a roughing process. . On the other hand, the piston pin
As shown in FIG. 7 (B), it is manufactured by roughly processing a rough material, hardening the surface by carburizing treatment, performing heat conditioning treatment such as quenching and tempering, and then performing finishing processing.

As described above, in the conventional manufacturing method, many steps must be performed to manufacture the connecting rod and the piston pin, and it is difficult to reduce the manufacturing cost. Further, since the manufactured connecting rod and piston pin are assembled to the piston and the crankshaft, respectively, the assembling process is complicated, and it has been difficult to reduce the cost of the assembling work.

Therefore, in one embodiment of the method of manufacturing the connecting rod according to the present invention, the connecting rod 10 and the piston pin 2 are passed through the steps shown in FIG.
0 was adopted.

First, as a first step, the connecting rod 10 and the piston pin 20 are formed into a shape in which the connecting rod 10 and the piston pin 20 are inseparable and integrated by hot forging using a connecting rod material of non-heat treated steel as a rough material. I do. The first
The process corresponds to a first forging process.

In the second step, the connecting rod 10 and the piston pin 2 formed by the first step are made of small particles of metal called a shot by shot blasting.
The projection is performed at high speed on the surface of No. 0 to remove burrs and scale. Note that the second step corresponds to a shot blast step.

In the third step, the connecting rod 10 and the piston pin 20 are processed to predetermined dimensions by rough processing. In addition, you may process the hole part 20a of the piston pin 20 by forging etc. as needed. The hole 20a of the piston pin 20 can be pierced over the entire length of the piston pin, or two types of processing, that is, leaving the meat at the center thereof, can be considered.

As a fourth step, the connecting rod 10 and the piston pin 20 are processed to final dimensions by finishing. Here, the oil hole 18 for cooling the piston back surface shown in FIG. 3 may be formed using a drill or the like in the third step or the fourth step.

The third step and the fourth step correspond to processing steps. According to the first to fourth steps described above,
The connecting rod 10 and the piston pin 20
It will be manufactured through two processes. For this reason, it is manufactured in fewer steps than in the conventional case, the manufacturing steps can be simplified, and the manufacturing cost can be reduced.

The connecting rod 10 and the piston pin 20 may be manufactured by the steps shown in FIG. That is, as a first step, a low carbon steel such as chromium steel or chromium molybdenum steel is used as a rough material, and the rough material is formed into a shape in which the connecting rod 10 and the piston pin 20 are inseparable and integrated by hot forging. I do. Here, by using low-carbon steel as a rough material, the amount of carbon contained in the rough material is small, forging and machining are facilitated, and the tool life of a mold and a machine tool can be extended. Note that the first step corresponds to a second forging step.

In the second step, the connecting rod 10 and the piston pin 20 are roughly machined to predetermined dimensions by rough machining. In this step, similarly to the first embodiment, the hole 20a of the piston pin 20 is
You may process by forging etc. The second step corresponds to a rough processing step.

As a third step, carbon is infiltrated from the surfaces of the connecting rod 10 and the piston pin 20 by carburizing to harden the surface layer. The third
The process corresponds to a carburizing process.

As a fourth step, the connecting rod 1
By subjecting the piston pin 20 and the piston pin 20 to heat conditioning such as quenching and tempering, the crystal grains of the coarse material are refined to homogenize the material, thereby improving ductility and toughness. The fourth
The process corresponds to a heat conditioning process.

In the fifth step, small particles of a metal called a shot are projected at high speed onto the surfaces of the connecting rod 10 and the piston pin 20 by shot peening.
Work hardening occurs on the surface and residual stress compression occurs on the surface. In addition, connecting rod 10
Also, fine cracks and flaws on the surface of the piston pin 20 are crushed by the impact of shot projection. For this reason, the fatigue strength of the connecting rod 10 and the piston pin 20 can be improved. Note that the fifth step corresponds to a shot peening step.

In the sixth step, the connecting rod 10 and the piston pin 20 are processed to final dimensions by finishing. Note that the sixth step corresponds to a finishing step. Here, the oil hole 18 for cooling the piston back surface shown in FIG. 3 may be formed using a drill or the like in the second step or the sixth step.

According to the first to sixth steps described above, in addition to the operation and effect of the above-described embodiment, the residual stress compression occurs on the surface of the connecting rod 10 due to shot peening, which is generated during the operation of the internal combustion engine. Therefore, the fatigue life of the connecting rod 10 can be further improved.

[0037]

As described above, according to the first aspect of the present invention, the stress generated at the small end of the connecting rod is greatly reduced, and the danger of the stress exceeding the fatigue strength of the connecting rod material is dramatically reduced. And the fatigue life of the connecting rod can be prolonged.

According to the second aspect of the present invention, the back surface of the piston is cooled by the lubricating oil jetted toward the back surface of the piston, so that the temperature of the piston is reduced and the decrease in the strength of the piston due to heat can be suppressed. At the same time,
Since the connecting rod is also cooled from inside,
A reduction in the thermal strength of the connecting rod can also be suppressed.

According to the third aspect of the present invention, the connecting rod and the piston pin can be manufactured in fewer steps than the manufacturing method according to the prior art, so that the manufacturing steps can be simplified and the manufacturing cost can be reduced. Can be.

According to the fourth aspect of the invention, in addition to the functions and effects of the manufacturing method of the third aspect, forging and machining are facilitated by using low carbon steel as a rough material in the second forging step. And the tool life of the mold and the machine tool can be extended. Further, through the carburizing process, the heat conditioning process, and the shot peening process, the surface strength and wear resistance of the connecting rod and the piston pin can be improved.

[Brief description of the drawings]

FIG. 1 shows the structure of a connecting rod and a piston pin according to the present invention, wherein (A) is a front view and (B) is a top view.

FIG. 2 is an explanatory view of the effect of reducing the stress generated at the small end of the connecting rod by the above.

FIG. 3 is a structural view in which a mechanism for cooling a piston is added to the connecting rod of the above.

FIG. 4 is a process chart showing one embodiment of a method for manufacturing a connecting rod and a piston pin according to the present invention.

FIG. 5 is a process chart showing another embodiment of a method for manufacturing a connecting rod and a piston pin according to the present invention.

FIG. 6 is an explanatory view of stress generated at a small end of a connecting rod according to a conventional technique.

7A and 7B show a manufacturing process of a connecting rod and a piston pin according to a conventional technique, wherein FIG. 7A is a manufacturing process diagram of a connecting rod, and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Connecting rod 12 Large end 14 Small end 18 Oil hole 20 Piston pin

Claims (4)

[Claims] 1. A structure of a connecting rod and a piston pin of an internal combustion engine, wherein a piston pin is inseparably and integrally connected to a small end of the connecting rod. 2. A connecting rod and a piston pin for an internal combustion engine according to claim 1, wherein a through hole through which lubricating oil flows is provided from the inner peripheral surface of the large end to the tip of the small end of the connecting rod. Construction. 3. A first forging step in which a connecting rod and a piston pin are formed inseparably and integrally by hot forging using non-heat treated steel as a rough material, and a connecting rod formed by the first forging step. And a shot blasting step of performing shot blasting on the piston pin, and a processing step of processing the connecting rod and the piston pin on which the shot blasting has been performed in the shot blasting step to predetermined dimensions. And a method of manufacturing a connecting rod and a piston pin of an internal combustion engine. 4. A second forging step of forming a connecting rod and a piston pin inseparably and integrally by hot forging using low carbon steel as a rough material, and a connecting rod formed by the second forging step; A roughing step of roughing the piston pin to a predetermined size, a carburizing step of carburizing the connecting rod and the piston pin processed in the roughing step, and a carburizing step of the carburizing step. A heat conditioning process for performing a heat conditioning process on the connecting rod and the piston pin; and a shot peening for performing shot peening on the connecting rod and the piston pin subjected to the thermal conditioning process in the heat conditioning process. And a connecting rod subjected to shot peening by the shot peening step. Method for producing a connecting rod and piston pin of an internal combustion engine, characterized in that it is configured to include a finishing step of processing the de-and piston pin to final dimensions, the.