JPH0562009B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a connecting rod for an automobile or the like.

(Prior art) Conventionally, in order to manufacture a connecting rod,
First, by forging (including sintering forging), a rough profile 1 similar to a connecting rod as shown in Fig. 6 is produced.
get. The rough section 1 consists of a main body 2, a small end 3 and a large end 4, and holes 5 and 6 are formed in the small end 3 and large end 4, respectively. Next, the rough shaped material 1 is cold coined in the thickness direction. Cold coining is performed on the shaded areas shown in FIG. 6, that is, the ribs of the main body 2, the entire small end 3, and around the hole 6 of the large end 4, thereby improving the flatness and
Dimensional accuracy such as parallelism and thickness is ensured.

Next, the rough section 1 that has been subjected to the cold coining is subjected to machining. In machining, first, the large end 4 of the material 1 is cut within the machining allowance a shown in FIG. It is divided into a cap part 8. Next, the mating surfaces of the divided rod part 7 and the cap part 8 are machined within the machining allowance a, and bolt holes for connection are then drilled in both parts. The part 7 and the cap part 8 are integrated with bolts 9, 9 screwed into the bolt holes, and the large end hole 10 is machined with high precision.

Incidentally, among connecting rods, especially those used for V-type engines, the weight variation is strictly limited, and for this reason, in the final stage of manufacturing, a boss portion previously provided at the rear of the cap portion 8 is attached. 11 is added by cutting from the end face as shown in FIG. 7 to adjust the overall weight.

In addition, in the connecting rod obtained as described above, the rod part 7 and the cap part 8 are once disassembled, the metal is assembled to the inner surface of the large end hole 10, and then the rod part 7 and the cap part 8 are assembled together again with the bolt 9. By doing this, it is assembled to the crankshaft.

(Problems to be Solved by the Invention) However, according to the above-mentioned conventional method of manufacturing a connecting rod, after machining the large end hole 10 and the boss portion 11, the rod portion 7 and the cap portion 8 are
When the rod part 7 and the cap part 8 are disassembled, there is a slight dimensional difference in the hole diameters of the rod part 7 and the cap part 8.
When it is reassembled, a misalignment 10a occurs in the large end hole 10 as shown in FIG. This poses a serious problem of not only reducing engine performance but also reducing fuel efficiency.

Therefore, as a result of various investigations into the causes of the above-mentioned discrepancy, the inventors of the present application have found that the residual stress generated during cold coining is released by subsequent machining, particularly the machining of the boss portion 11, and that its influence is greater on the cap portion 8. The cap portion 8 is exposed to the rod portion 7.
It has become clear that this is caused by expanding the diameter relative to the diameter.

The present invention has been made based on an investigation of this cause, and is designed to minimize the above-mentioned discrepancy by eliminating the influence of residual stress release as much as possible, and to provide a connection that can ensure stable engine performance. The purpose of this invention is to provide a method for manufacturing rods.

(Means for solving the problems) In order to solve the above-mentioned conventional problems, the present invention has the following features:
After cold coining the forged rough section, the cap section is divided from the large end of the forged section, then end face processing and bolt hole machining are performed, and then the cap section is reassembled to form the large end hole. In the method of manufacturing a connecting rod, the final boss part provided at the rear of the cap part is removed to adjust the weight after finishing, and the boss part is removed while ensuring the planar shape of the boss part. The gist is that the weight can be adjusted by

(Function) In the connecting rod having the above structure, when adjusting the weight, the planar shape of the boss part is ensured, so that the remaining thickness of the boss part suppresses a decrease in the rigidity of the cap part, and Expansion of the diameter of the cap portion due to release of residual stress caused by coining is suppressed.

(Example) Hereinafter, an example of the present invention will be described based on the accompanying drawings. For explanation, please refer to the above-mentioned Figure 6~
Also refer to FIG. 7, and the symbols used in these figures apply mutatis mutandis to FIG. 1 and the subsequent figures.

In the method of the present invention, as in the conventional method, the rough shaped material 1 shown in FIG. The cap part 8 is divided from the big end part 4, end face processing and bolt hole machining are performed, and the cap part 8 is reassembled and the large end hole 10 is finished. The weight is adjusted by removing the provided boss portion 11. When adjusting the weight, as shown in FIGS. 1 and 2, the central portion of the boss portion 11 is removed in the form of a groove, leaving a pair of upper and lower ribs 12. That is, the boss portion 11 is processed so as to maintain the predetermined width W and height H of the boss portion 11.

By processing the boss portion 11 as described above, a decrease in the rigidity of the cap portion 8 is suppressed, and an enlargement of the diameter of the cap portion 8 due to the release of residual stress caused by cold coining is suppressed, resulting in a large The offset 10a (FIG. 8) occurring in the end hole 10 is greatly reduced.

Here, as a result of measuring the amount of misalignment of the connecting rod obtained as in the above example, it was found to be 10 μm (n=10) on average. This is the boss part 1
When compared with the conventional method (Fig. 7) in which deletion of 1 was carried out from the end face, in the case of the conventional method,
Similarly, the amount of discrepancy was 50 μm on average, making it clear that the method of the present invention had a significantly smaller amount of discrepancy.

In addition, the cold coining distance for the rough section 1 was varied, and the amount of cap diameter expansion (μm) at A when the boss part 11 was machined as in the above embodiment and B when the boss part 11 was machined as in the conventional method. As a result of investigating the relationship between and the cold coining allowance (mm), as shown in Fig. 3, in case A according to the method of the present invention, the amount of cap diameter expansion does not increase that much even if the cold coining allowance increases. On the other hand, in case B using the conventional method, it has become clear that as the cold coining allowance increases, the amount of cap diameter expansion increases significantly. By the way, the cold coining fee is
The cap diameter is set to 0.4 to 0.6 mm, and when looking at the amount of cap diameter expansion in this range, A by the method of the present invention is 1/4 to 1/5 of B by the conventional method, and the cap part 8 The superiority of the method of the invention for the dimensional stabilization of

In the above embodiment, the boss portion 11 is removed in a groove shape and the rib 12 is left, but instead of this, for example, as shown in FIG. 4, a box-like rib 13 may be left. I can do it. In this case, the rib 13 has a closed cross section, which further suppresses a decrease in the rigidity of the boss portion 11, which is advantageous for suppressing the expansion of the diameter of the cap portion 8. Moreover, this boss portion 11 is
For example, as shown in FIG. 5, by removing the upper and lower surfaces, a solid rib 14 can be left in the center, and in this case, as in the above embodiment,
It becomes possible to suppress a decrease in the rigidity of the boss portion 11.

(Effects of the Invention) As described above in detail, the method for manufacturing a connecting rod according to the present invention is capable of adjusting the weight by removing the boss portion while ensuring the planar shape of the boss portion. As a result, it is possible to suppress a decrease in the rigidity of the cap part, and to significantly reduce the discrepancy between the large end holes caused by the expansion of the diameter of the cap part.As a result, not only the stability of engine performance but also fuel efficiency is improved. It was also effective in achieving improvements in

[Brief explanation of the drawing]

1 and 2 are a plan view and a front view showing the shape of the cap obtained by the method of the present invention, and FIG. 3 is a graph showing the correlation between the cold coining allowance and the amount of cap diameter expansion. , FIG. 4 and FIG. 5 are a side view and a front view showing other aspects of the cap portion obtained by the method of the present invention, FIG. 6 is a plan view showing the shape of the forged rough section, and FIG. This figure is a plan view of a cap portion obtained by the conventional method, and FIG. 8 is a plan view showing misalignment defects that tend to appear in the large end hole. 1... Forged rough section, 4... Big end, 7... Rod part, 8... Cap part, 11... Boss part, 1
2, 13, 14...ribs.

Claims (1)

[Claims] 1. After cold coining the forged rough shape material, divide the cap part from the big end of the rough shape material, then perform end face machining and bolt hole machining, and then reassemble the cap part to form the big end hole. In the method of manufacturing a connecting rod, the boss part provided at the rear of the cap part is removed to adjust the weight, while ensuring the planar shape of the boss part. A method of manufacturing a connecting rod characterized by removing and adjusting weight.