JPS60196421A - Crankshaft for internal-combustion engine - Google Patents

Abstract

PURPOSE:To secure a crankshaft for an internal-combustion engine being manufacturable in low cost of production while keeping up its strength per area, by casting a web part in a mold solidly in a way of inserting a pin part into a shaft part being bend-molded by means of forging. CONSTITUTION:A pipelike shaft material having a through hole to be turned to an oil passage 12 in its center is bend-molded by means of forging and thereby a rotative central part 9, a pin part 10 and a connecting part 11 are formed in a shaft part 7 of a crankshaft 5. And, as for the shaft part 7, cast iron is cast in a sand mold while energizing and heating the shaft part being set in the sand mold copied from a web part 8 whereby the web part and the shaft part are joined together as one body. Therefore, owing to this manufacturing method, its strength is equal to an average forged crankshaft, though, but its manufacturing cost is largely reducible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement of a crankshaft for an internal combustion engine.

[Prior art]

In general, the crankshaft of an internal combustion engine is generally formed integrally by forging carbon steel or casting high-strength cast iron. Of these two crankshafts,
The former forged product has superior strength compared to the latter cast product, but it requires more machining allowance when dividing the mold,
Cost (1) It had the disadvantage of being high. In particular, when the width between the two webs is narrow and the depth from the 1911 peripheral edge to the crank pin is relatively deep, such as the crankshaft of an internal combustion engine installed in a recent motorcycle, the machining allowance described above is However, it was inevitable that the cost would rise further.

[Purpose of the invention]

An object of the present invention is to provide a crankshaft for an internal combustion engine that can be manufactured at low cost while still having the strength of a forged crankshaft by combining forging and casting techniques.

[Structure of the invention]

In order to achieve the above object, the crankshaft of the present invention is provided by integrally bending and forging the shaft portion of the crankshaft including the pin portion that connects the large end of the connecting rod, and attaching the cylinder to the shaft portion which has been bent and formed. The feature is that the web part is integrally cast between the two parts.

[Embodiments of the invention]

(2) The present invention will be explained below with reference to embodiments shown in the drawings.

Figure 1 shows an internal combustion engine mounted on a motorcycle 17,
is the cylinder body, and 2 is the crankcase. A piston 4 is fitted into each of the four cylinders 3 of the cylinder body 1 so as to be able to reciprocate, and the crankcase 2 has -
A crankshaft 5 is supported so as to be sandwiched between an upper crankcase 2a and a lower crankcase 2b which are separated into F parts. A connecting rod 6 connects the screw 4 and the crankshaft 5.

FIG. 2 shows details of the crankshaft 5,
It is composed of bent shaft parts 7 and 8, and a web part 8 integrally joined to the negative shaft part 7. The shaft portion 7 includes five rotation center portions 9 that are pivotally supported by bearing portions of the crankcase 2, four pin portions 10 that connect the large ends of the four connecting rods 6, and the rotation center portion. 9 and a connecting portion II that diagonally connects the pin portion 10 are bent so as to be integrally continuous, and (3) a lubricating oil passage 12 is provided in the central portion of the shaft portion 7 in a symmetrical manner. It is being The web portions 8 are integrally connected to the connecting portions 11 and 11 on both sides of the shaft portion 7, with the pin portion 10 interposed therebetween.

- When manufacturing the above-mentioned crankshaft 5, the shaft part 7 shown in "2" is formed by bending a pipe-shaped shaft material having a through hole that becomes the lubricating oil passage 12 in the center, and the rotation center part shown in "2" is bent by forging. 9. Pin part 10. The connecting portion 11 is formed so as to be similar to that shown in FIG. When forging the shaft portion 7, it is preferable to fill the through hole with sand or lead in advance and extract it after bending.

The shaft portion 7 bent and formed as described above and the web portion 8 are set in a molded sand mold, cast iron is cast into the sand mold while heating the shaft portion 7 with electricity, and the web portion 8 is integrally joined to the shaft portion 7. let By casting the web portion 8, the crankshaft 5 shown in Fig. 2 is obtained. The electrical heating of the shaft portion 7 is to prevent chill solidification, which is a non-parallel structure of cast iron, and prevents embrittlement of the cast iron structure at the joint with the shaft portion 7 (4). Further, in this electrical heating, it is desirable to use a borax-based flux in combination, and this can prevent oxidation of the shaft portion 7.

- Heating of the shaft portion 7 when casting the web portion 8 described above is not limited to the electric heating described above, but may be performed by placing exothermic thermite material in advance at the location to be joined. You can. Pyrogenic thermi, 1
- Since the material generates heat due to casting of cast iron, the joint portion (connection portion 11) of the shaft portion 7 to the cast iron is heated to prevent the above-mentioned chill solidification.

According to the crankshaft 5 described in -, the web portion 8 only serves as a weight to balance the rotation of the crankshaft 5, so it does not require much strength and can be cast. It can maintain sufficient strength. On the other hand, the shaft portion 7 bears a rotational force of 1-lux or the like, and since the shaft portion 7 is forged, it can maintain sufficient strength to support the rotational force. Therefore, the above-mentioned crankshaft 5 (5) has the same strength as a conventional forged crankshaft, and only the shaft portion 7 is forged, and the straight shaft material is simply bent and formed. Therefore, there is no need for large machining allowances, unlike in conventional forged crankshaft forming. Therefore, waste of materials can be reduced and costs can be reduced.

In addition, in processing the shaft portion 7, it is not necessarily necessary to use a pipe-shaped shaft material as in the above embodiment, and a solid shaft material may be used. However, if a pipe-shaped shaft member is used as in the embodiment, post-processing of the lubricating oil passage 12 is not required, and the lubricating oil can be applied to the entire shaft portion 7, which is difficult to apply T with the conventional post-processing method. The ill tract can be easily formed.

〔Effect of the invention〕

As described above, in the crankshaft of the present invention, the shaft portion of the crankshaft including the pin portion that connects the large end of the connecting rod is integrally bent and formed by forging, and the pin portion is inserted into the bent and formed shaft portion. Since the web part (6) is integrally cast and formed, the strength can be made equal to that of a conventional forged crankshaft. Because it does not require large machining allowances like in the case of I! (Manufacturing is possible at low cost.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view, partially omitted, showing an internal combustion engine for a motorcycle equipped with a crankshaft according to an embodiment of the present invention, FIG. 2 is a front view, partially in section, of the crankshaft; 3
The figure is a view taken along the m-■ arrow in FIG. 5... Crankshaft, 7... Shaft part, 8... Web part, 9... Rotation center part, 10... Pin part,
II...Connection part. Agent Patent Attorney Makoto Ogawa − Patent Attorney No “1 Ken Teru Patent Attorney Kazuhiko Saishita (7)

Claims (1)

[Claims] The shaft part of the crankshaft, including the pin part that connects the large end of the connecting rod, is integrally bent and formed by forging, and the web part is integrally cast and molded with the pin part sandwiched between the bent and formed shaft part. A characteristic feature of the crankshaft of an internal combustion engine.