JPH0768608B2 - Carburizing and quenching method of split type joint - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a carburizing and quenching method for a split-type connecting rod, which includes a connecting rod body and a cap fastened to the large end thereof.

(Prior Art) In this type of split connecting rod, as shown in FIG. 2, the large end portion (2) of the connecting rod body (1) is provided with tightening holes (3) on both sides in the diametrical direction of the bearing surface (2a) of the crank pin. And tightening holes (5) on both sides of the bearing surface (4a) of the crankpin in the diametrical direction are formed in the cap (4), and the cap (4) is tightened at both ends (2) at the large end (2). 3) Generally, tightening is performed using a tightening bolt penetrating through (5), and in this case, in order to prevent displacement of the cap (4) with respect to the large end (2), each tightening hole (3) (5) The part on the mating surface (2b) (4b) side of () has a small diameter, and the tightening bolt is press-fitted into this small diameter part (3a) (5a).

By the way, when the connecting rod body (1) and the cap (4) are separated during carburizing and quenching, the connecting rod body (1) is separated.
Of the tightening holes (5) and (5) formed in the cap (4) in the direction in which the large end (2) of the screw tightens the pitch l ₁ of the tightening holes (3) and (3) formed therein. By deforming the pitch l ₂ in a direction that widens it, both tightening holes (3) and (5) are misaligned, and the inner surfaces of the tightening holes (3) and (5) are located on the spot facing surface (2c) (4c) side. Carburizing from the large diameter part (3b) (5b) to the small diameter part (3a) (5a), the hardness of the inner surface of the small diameter part (3a) (5a) becomes high, and its finishing can be done by reaming. It will be difficult.

Therefore, conventionally, as shown in FIG. 3, a cap (4) is fastened to the large end portion (2) of the connecting rod body (1) using a bolt a, and in this state, carburizing and quenching treatment is performed to tighten both ends. To prevent misalignment of the holes (3) and (5), a copper washer c is attached to the head side of the bolt a and the nut b side of the other end, and the tightening holes (3) ( The open end of 5) is sealed so that the inner surfaces of these tightening holes (3) and (5) are not carburized.

(Problems to be Solved by the Invention) In the above-mentioned conventional technique, it takes time to fasten and disassemble the cap (4) before and after the carburizing and quenching treatment, and particularly at the large end (2) and the cap during the carburizing and quenching treatment. A large load may be applied to the threaded portion of the nut b due to the thermal expansion in the axial direction of the hole (4) and the thread may be damaged, making it difficult to remove the nut b. Has become an obstacle.

(Means for Solving the Problems) In order to solve the above problems, the present invention comprises a connecting rod body and a cap fastened to the large end of the connecting rod body, and adjusts the large end and the cap. In a carburizing and quenching method of a split connecting rod, which is formed by forming a stepped tightening hole having a small diameter on the surface side, in the method of carburizing and quenching the large end or the cap, A fixing pin having a length penetrating the small diameter portion of the tightening hole is inserted, and the cap is assembled to the large end portion by fitting the pin into the small diameter portions of the both tightening holes. It is characterized in that the carburizing and quenching treatment is performed in the state.

(Working) The tightening holes on the large end and the cap are held in a centered state by fixing pins fitted to the small diameter parts of both tightening holes, and Misalignment of the both tightening holes is suppressed.

Also, the fixing pin plays the role of a stopper that prevents the processing gas from entering the small diameter part, so that the inner surface of the small diameter part is not carburized, but the inner surface of the large diameter part of the tightening hole is Carburized. Carburizing the inner surface of the large diameter portion effectively functions to increase the strength of the large end portion and the cap.

Furthermore, simply by inserting and removing the fixing pin from one of the tightening holes of the large end and the cap, it is possible to assemble and disassemble the cap without screwing the nut like the prior art, Workability is improved.

(Embodiment) An embodiment of the present invention will be described with reference to FIG. The first
The connecting rod in the figure is the same as that in FIG. 2, and the same reference numerals are given to omit the detailed description of the connecting rod itself.

In FIG. 1, (6) is used to penetrate the tightening hole (5) formed in the cap (4) and the small diameter part (3a) of the tightening hole (3) formed in the large end part (2). A fixing pin formed to have a necessary and sufficient length is shown, and the mating surface (4b) of the cap (4) is butted against the mating surface (2b) of the large end portion (2) in the preceding step of the carburizing and quenching treatment. The fixing pins (6) are inserted into the tightening holes (5) of the cap (4), and the fixing pins (6) are fitted into the small diameter portions (5a) of the tightening holes (5). With the large end (2)
Was fitted in the small diameter portion (3a) of each tightening hole (3), the cap (4) was attached to the large end portion (2), and the carburizing and quenching treatment was performed in this state.

According to experiments, the diameter of the hole fastening (3) pitch l ₁ and fastening holes (3) (5) a defined dimension of the pitch l ₂ of (5) and 49.0 mm, also fixing pin (6) When the small diameter parts (3a) and (5a) were formed by manual press-fitting to such an extent that they could be lightly press-fitted, and l ₁ and l ₂ were measured after carburizing and quenching treatment, both l ₁ and l ₂ were within an allowable range of 49 ± 0.05 mm. It was confirmed that the fixing pin (6) can suppress the misalignment between the tightening holes (3) and (4) to such an extent that there is no practical problem.

Further, the inner surface of the large diameter portion (3b) of the tightening hole (3) of the large end portion (2) which is not closed by the head portion (6a) of the fixing pin (6) is carburized to increase hardness, but has a small diameter. It was also confirmed that the inner surfaces of parts (3a) and (5a) were not carburized.

In the embodiment, since the counterbore surface (2c) of the large end portion (2) is formed close to the mating surface (2b), the corner portion of the counterbore surface (2c) on the bearing surface (2a) side is thick. However, the carburization of the inner surface of the large diameter portion (3b) of the tightening hole (3) effectively functions to compensate the strength reduction of the corner portion.

After the carburizing and quenching treatment, each fixing pin (6) is removed to disassemble the connecting rod body (1) and the cap (4), and the small diameter portions (3a) (5a) of each tightening hole (3) (5) Although the inner surface of the small diameter portions (3a) and (5a) is not carburized as described above, the reaming can be easily performed.

(Effects of the Invention) As described above, according to the present invention, it is possible to suppress the misalignment between the tightening hole formed in the large end portion of the connecting rod body and the tightening hole formed in the cap by the fixing pin during the carburizing and quenching process. At the same time, carburization of the inner surface of the small diameter part of the tightening hole is prevented, which facilitates reaming in the subsequent process, and it is effective in carburizing the inner surface of the large diameter part of the tightening hole to increase the strength of the connecting rod. ,
Moreover, the cap can be assembled and disassembled before and after the carburizing and quenching treatment by simply inserting and removing the fixing pin into and from the tightening hole, which has the effect of improving workability.

[Brief description of drawings]

FIG. 1 is a cross-sectional plan view showing an assembled state of connecting rods during carburizing and quenching treatment by the method of the present invention, FIG. 2 is a cross-sectional plan view showing disassembling of connecting rods, and FIG. 3 is a conventional carburizing and quenching treatment. FIG. 6 is a cutaway plan view showing an assembled state of the connecting rod. (1) …… Connecting rod body, (2) …… Large end (4) …… Cap, (2b) (4b) …… Mating surface (3) (5) …… Tightening hole, (3a) (5a ) …… Small diameter part (6) …… Fixing pin

Claims (1)

[Claims] 1. A connecting rod body and a cap fastened to a large end portion of the connecting rod body, and a stepped fastening hole having a small diameter on a mating surface side is formed in the large end portion and the cap. In the method for carburizing and quenching a split connecting rod, a fixing pin having a length that penetrates from the tightening hole of either the large end or the cap to the tightening hole and the small diameter part of the other tightening hole is formed. The divided connecting rod is characterized in that the cap is assembled to the large end portion by inserting the pin into the small diameter portions of the both fastening holes, and carburizing and quenching treatment is performed in this state. Carburizing and quenching method.