JPH11108039A - Manufacture of connecting rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate division with a small load by forming a notch on a portion of a cap on a large end which is to be broken for division during mechanical finishing of a rod, impregnating the large end with an electrolytic bath, provide the rod with fragility by hydrogen charging followed by breakage and division. SOLUTION: A notch 6 being a V- or U-shaped groove is formed on a portion which is to be broken for dividing a cap 5 on a large end 2, during finishing process of a forged connecting rod 1. Electrolytic solution such as aqueous solvent of sulfric acid having PH of 3.5 is housed in an electrolytic bath. The connecting rod 1 is impregnated with the electrolytic solution until the notch is on a level of the solution. Current is carried with the connecting rod 1 being as a cathode, the electrolytic bath as an anode. Hydrogen charge is applied to the periphery of the notch by cathode electrolysis. The current is controlled by density thereof, voltage and time of electrolysis. The periphery around the notch is hardened to provide a starting point of breakage due to fragility caused by hydrogen. The portion of the notch 6 is thus broken to divide the cap portion 5. It is thus improve division performance, divide the cap with a small breakage load, and improve close fitting performance of the broken surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a connecting rod for an internal combustion engine, in which a cap portion at a large end of the connecting rod is broken and divided.

[0002]

2. Description of the Related Art A connecting rod consisting of a large end, a small end and a rod part connecting them is formed by forging, and then a V-shaped portion is formed at a portion where a cap portion of a large end is to be fractured and split in the middle of mechanical finishing. A connecting rod, which is formed by processing a groove (notch) such as that described above and dividing the groove from the groove, is disclosed in JP-A-61-2.
No. 1414 and Japanese Patent Publication No. 3-18053.

[0003]

When a high-strength member such as a large end of a connecting rod is to be broken, although a V-shaped groove or the like is formed, the breaking load is considerably large, so that a large A breaking device is required, which requires a lot of equipment costs. In order to reduce the breaking load at the large end, it is more effective as the V-shaped groove or the like as the notch function is larger and deeper, but on the other hand, since the fracture split surface is to be used after joining,
At the time of use, the larger the joint area, the stronger and more effective the resistance to lateral displacement. If the notch is deeper and deeper, contradictions such as a smaller joint area occur, and there is a limit to the larger notch.

An object of the present invention is to provide a method for manufacturing a connecting rod, which can improve the fracture splitting ability of a large end portion and can be divided by a small breaking load.

[0005]

According to the first aspect of the present invention, there is provided a connecting rod comprising a forged large end, a small end, and a rod connecting the ends. At the time of finishing, a notch with a V-shaped groove or the like is formed in a portion where the cap portion of the large end is to be split by breaking, and the large end is immersed in an electrolytic cell to a vicinity of the notch, and the notch is formed by hydrogen charging. And embrittlement of the periphery and the inside of the notch, and the notch portion is fractured and split by brittle fracture in a hydrogen intrusion state.

According to a second aspect of the present invention, there is provided a connecting rod comprising a large end, a small end, and a rod connecting between the large end formed by forging. Notch with a V-shaped groove or the like is formed at the portion where the cap portion of the portion is to be split and divided, and the large end is immersed in the electrolytic cell to the vicinity of the notch portion, and the periphery and the inside of the notch portion are fragile by hydrogen charging. And then apply a low-temperature treatment to further embrittle the area around the notch,
In this low-temperature treatment state, the notch portion is broken and divided by brittle fracture.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] In the first embodiment, as shown in FIG.
The connecting rod 1 is manufactured by the manufacturing process (e).

More specifically, FIG. 1A shows a connecting rod 1 formed by forging, comprising a large end 2, a small end 3, and a rod 4 connecting the large end 2 and a rod 5 connecting the large end 2 to a subsequent step. This is a cap part that is divided by breaking.

The forged connecting rod 1 is shown in FIG.
In the finishing step (b), the crank pin insertion hole of the large end 2 and the piston pin insertion hole of the small end 3 are machined, and the cap portion 5 of the large end 2 is to be fractured and split. Then, a notch 6 is formed by a V-shaped or U-shaped groove. The notch 6 may be either the side surface of the large end 2 or the hole for inserting the crankpin.

After the processing and finishing step, a fracture charging step shown in FIG. 1D and a cap portion 5 shown in FIG. It is a bolt assembly process to assemble.

The hydrogen charging step shown in FIG. 1C will now be described. As shown in FIG.
An electrolytic solution 9 such as an aqueous sulfuric acid solution of about 3.5 is accommodated, and the connecting rod 1 is immersed until the notch 6 is positioned at the liquid surface 10 of the electrolytic solution. Then, hydrogen charging is performed around the notch 6 by a cathodic electrolysis method. This hydrogen charge amount is appropriately controlled by the current density A / m2, the voltage V, and the electrolysis time Ks.

Due to this hydrogen charge, hydrogen enters into the lattice gap of iron atoms around the notch 6, hardens by the occurrence of dislocation, becomes hydrogen embrittled, and becomes a starting point of fracture. Even if the material becomes embrittled by hydrogen charging, the hydrogen inside the material disappears and recovers to the hardness before hydrogen charging after the hydrogen is released by the subsequent aging in the atmosphere at room temperature. It does not cause hydrogen embrittlement.

In the hydrogen embrittlement state in which hydrogen has penetrated by the hydrogen charge, the notch 6 is brittlely fractured in the fracture division step shown in FIG. For example, as shown in FIG. 5, the connecting rod 1 is placed in a horizontal state, and the lower surface of the large end 2 is notched.
Are supported at two points S1 and S2 on both sides, and a striking force F is applied near the notch 6 from above. Although not shown,
The cap part 5 can be divided by breaking by inserting a split inner jig into the crankpin insertion hole of the large end 2 and driving the wedge into this to expand the inner jig.

As described above, in the first embodiment, since the periphery of the notch 6 is brittlely fractured in a state in which the periphery of the notch 6 is hydrogen embrittled by hydrogen charging and the cap portion 5 is divided by fracture, the fracture division of the large end portion 2 is improved. However, it is possible to divide by a small breaking load, a small breaking device is sufficient, the adhesion of the fracture surface is improved, and the fatigue strength of the fastening bolt 7 is also advantageous.

[Second Embodiment] In a second embodiment, as shown in FIG. 3, the connecting rod 1 is manufactured by the manufacturing steps (a) to (e).

The second embodiment is the same as the first embodiment except for the step shown in FIG. The step of FIG.
In addition to the hydrogen charge in the vicinity of the above, cooling is performed at a low temperature, and in this low-temperature processing state, the notch 6 is brittlely broken to break and divide the cap portion 5.

The hydrogen charging is performed in the manner shown in FIG. 2 described above, and the low-temperature treatment is performed, for example, as shown in FIG. 4 by a refrigerant 1 in which liquid nitrogen or alcohol is dissolved in dry ice.
Large end 2 of connecting rod 1 in container 11 containing
And cooled to -40 ° C or lower.

As a result, the periphery of the notch 6 at the large end 2 of the connecting rod 1 is synergistically embrittled by low-temperature embrittlement due to low-temperature treatment in addition to hydrogen embrittlement due to hydrogen charging. In the fracture division step d), the cap portion 5 can be fracture-divided by brittle fracture with a smaller fracture load.

[0019] In addition, the hydrogen invading by the hydrogen charge acts to freeze and confine the invading hydrogen by a low-temperature treatment, thereby preventing the early release of hydrogen. And operability in the fracture splitting step is facilitated.

[0020]

As described above, according to the present invention, in the first aspect, the brittle fracture is caused in a hydrogen embrittled state by charging the hydrogen at the fracture splitting portion of the cap portion at the large end of the connecting rod. Therefore, the fracture splitting property is improved, and it can be divided by a small breaking load, a small breaking device is sufficient, and the adhesion of the fracture surface is improved, and the fatigue strength of the tightening bolt is also advantageous. doing.

According to the second aspect of the present invention, the fracture splitting portion of the cap portion at the large end of the connecting rod is hydrogen-charged to cause hydrogen embrittlement and further to brittle fracture in a state of low-temperature embrittlement by low-temperature treatment. Splitting can be performed with a smaller breaking load, and premature release of hydrogen is prevented by freezing due to low-temperature treatment, extending the time of hydrogen embrittlement, facilitating efficient brittle fracture and workability of splitting. There is an advantage to

Furthermore, in any of the first and second aspects, since the fracture splitting property is improved with a small breaking load, the fracture division can be easily performed without making the notch deep, and the joint area of the fracture division is large. In addition, there is an advantage that a connecting rod for an internal combustion engine can be provided, in which resistance to lateral displacement is strongly obtained and strength of a large end portion is improved.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a first embodiment according to the present invention.

FIG. 2 is a sectional view showing hydrogen charging.

FIG. 3 is a manufacturing process diagram of a second embodiment according to the present invention.

FIG. 4 is a cross-sectional view showing low-temperature processing.

FIG. 5 is a sectional view showing an example of a fracture splitting method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Connecting rod 2 Large end 3 Small end 4 Rod 5 Cap 6 Notch 7 Tightening bolt 8 Electrolytic tank 9 Electrolyte 10 Liquid level 11 Container 12 Refrigerant

Claims (2)

[Claims] A V-shaped groove or the like is formed at a portion where a cap portion of the large end portion is to be fractured and divided at the time of mechanical finishing of a connecting rod composed of a large end portion, a small end portion, and a rod portion connecting the forged portions. The large end is immersed in the electrolytic cell up to the vicinity of the notch portion so that the periphery and the inside of the notch portion are embrittled by hydrogen charging, and the notch portion is fractured and split by brittle fracture in a hydrogen intrusion state. A method for manufacturing a connecting rod, comprising: 2. A V-shaped groove or the like is formed at a portion where a cap portion of the large end portion is to be fractured and divided at the time of mechanical finishing of a connecting rod composed of a large end portion, a small end portion, and a rod portion connecting the small end portion by forging. The large end is immersed in the electrolytic cell up to the vicinity of the notch portion, and the periphery and the inside of the notch portion are embrittled by hydrogen charging, and then a low-temperature treatment is applied to further embrittle the periphery of the notch portion. A method for producing a connecting rod, wherein the notch portion is fracture-divided by brittle fracture in the state of the low-temperature treatment.