JPH0245541B2 - KAMUJIKUNOCHUZOHOHO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for casting a camshaft in which the cam portion has high hardness and other portions have excellent machinability and toughness without using a chiller.

The camshaft that opens and closes the intake and exhaust valves in an internal combustion engine is preferably made of a soft material from the viewpoint of ease of machining, but the cam part, which slides and receives the force from the cam follower of the intake and exhaust valve, must be made of a hard material. No. Therefore, in the past, only the shaft part of the camshaft was made of cast iron, which has good workability, and a cam part made of a hard material made by adding chromium, copper, molybdenum, nickel, etc. to cast iron was integrally cast into this shaft part. Alternatively, a method has been adopted in which the cam part is formed of metal sand (chiller) that speeds up the cooling rate of the molten metal, and the cast iron of the cam part is chilled.

However, the method of casting the camshaft in two parts, the shaft part and the cam part, has the disadvantage that the casting work is performed twice and the work efficiency is poor. In addition, in the commonly used chilling method, the metal sand is consumed so much that it often becomes unusable after about three castings, which tends to result in high costs. Moreover, it has the disadvantage that it takes a lot of man-hours because it is necessary to put the metal sand into the sand mold and collect it, and if the hardening caused by the metal sand is too strong, there is a risk that other shaft parts will be hardened as well. . On the other hand, if the hardening with metal sand is insufficient, it is necessary to add a small amount of chromium, copper, molybdenum, nickel, etc. to harden the cast iron, but since it is necessary to cast the shaft and cam parts at the same time, the components are controlled. The process is delicate and requires a high degree of experience and skill.

From this point of view, an object of the present invention is to provide a method for casting a camshaft in which a soft shaft portion and a hard cam portion can be cast simultaneously without using metal sand.

The structure of the first camshaft casting method of the present invention that achieves this object is to form a cylindrical space between the shaft part and the cam part formed in the sand mold of the camshaft, and to prevent rotation and axial displacement. The camshaft is divided by a partition plate provided with a partition plate, and molten metal having different compositions is supplied to the space of the shaft part and the space of the cam part, and the camshaft is cast with the partition plate cast. The second aspect of the camshaft casting method according to the present invention is characterized in that the space between the shaft portion and the cam portion formed in the sand mold of the camshaft is formed into a cylindrical shape and is non-rotating. An addition chamber containing a metal component that increases the hardness of the cam portion is formed in a supply path for molten metal to the space of the cam portion in the sand mold, which is divided by a partition plate provided with an axial shift stopper. Molten metals having different compositions are supplied to the space of the shaft portion and the space of the cam portion, and the camshaft is cast in a state in which the partition plate is cast.

Hereinafter, one embodiment of the method for manufacturing a camshaft according to the present invention will be described in detail with reference to FIG. 1 showing the principle structure of the sand mold and FIG. There is a space 12 in the shaft part of the camshaft and a space 13 in the journal part.
and a space 14 in the cam part, a shaft part feeding path 15 that feeds the molten metal into the journal part space 13 and the shank part space 12, and a cam part feeding path 16 that feeds the molten metal into the cam part space 14. A main feeding path 17 for feeding the molten metal to the shaft feeding path 15 and the cam feeding path 16 is formed, and a cam feeding path 17 is formed in the middle of the cam feeding path 16. An addition chamber 18 is provided in the molten metal flowing through the channel 16 in which metal components for hardening cast iron, such as chromium, copper, molybdenum, and nickel, are stored. Further, a partition plate 20 is interposed between the space 12 of the shaft portion and the space 14 of the cam portion, and has an elliptical cylindrical shape and is provided with a protrusion 19 for preventing displacement in the axial direction.
The space 12 of the shaft part, the space 13 of the journal part, and the space 14 of the cam part are divided into two parts.

Therefore, when molten cast iron is fed from the main feeding path 17, one of the molten metals flows through the shaft feeding path 15 into the space 12 of the shaft and the space of the journal, forming the shaft and journal with good workability. form. Moreover, the other side passes through the cam part feeding path 16 and enters the addition chamber 18 on the way.
The metal components inside mix with the molten cast iron, which flows into the space 14 of the cam part to form a hard cam part. In this case, the shaft feeding path 15 and the cam feeding path 1
Since the molten metal flowing in from 6 and 6 is not mixed with each other by the partition plate 20, the shaft part is made only of cast iron with excellent workability, and the cam part is made of cast iron to which chromium, copper, molybdenum, nickel, etc. are added. It can be made to have high hardness. In this embodiment, metal components such as chromium, copper, molybdenum, and nickel are stored in the addition chamber 18, but ferrosilicon and graphite are added to the white pig iron cast iron to increase the hardness of the cam part. Good too. It is also possible to add a component that increases the hardness of cast iron to the molten metal in advance without providing the addition chamber 18, and to flow the molten metal into the space 14 of the cam part from the cam part feeding path 16.

A partition plate 20 is interposed between the shaft part of the cast camshaft and the cam part, and the end of this partition plate 20 protrudes from the side end surface of the cam part, so it is necessary to cut this part. Although it is necessary to remove it, it can be completed in a very short time by doing this at the same time as the finishing cutting of the shaft, etc. In the present invention, since the shaft portion and the cam portion are integrated through the partition plate 20, it is necessary to prevent the cam portion from rotating relative to the shaft portion, and it is also necessary to prevent the cam portion from rotating relative to the shaft portion. In order to prevent the cam portion from shifting in the axial direction of the shaft portion, it is necessary to provide axial slippage prevention. Therefore, in this embodiment, the partition plate 20 is made into an oval shape to serve as a means for preventing rotation, and a protrusion 19 is formed on the partition plate 20 to prevent the partition plate 20 from slipping in the axial direction. The partition plate 20 may have any shape other than a perfect circle, such as a rectangle or a spline shape, and the axial shift stopper may have any shape as long as the partition plate 20 has at least one step in the axial direction.

As described above, according to the camshaft casting method of the present invention, a cylindrical partition plate is interposed between the shaft space and the cam space of the sand mold, and these are separated so that molten metals with different compositions can be simultaneously poured into each space. Since the camshaft is cast, a camshaft having a shaft portion with good machinability and a cam portion with high hardness can be easily and quickly cast.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing the working principle of an embodiment of the method for casting a camshaft according to the present invention, and FIG. 2 is a sectional view taken along the arrow - 1. In the figure, 11 is a sand mold, 12 is a shaft part. 14 is a space for the cam part, 15 is a shaft feeding path, 16 is a cam feeding path, 17 is a main feeding path, 18 is an addition chamber, 19 is a projection, and 20 is a partition plate.

Claims (1)

[Scope of Claims] 1. A space between a shaft portion formed in a sand mold of a camshaft and a camshaft is divided by a cylindrical partition plate provided with a rotation stopper and an axial shift stopper, A method for casting a camshaft, characterized in that molten metals having different compositions are supplied to a space in the cam part and a space in the cam part, and the camshaft is cast in a state in which the partition plate is cast. 2. The space between the shaft part and the cam part formed in the sand mold of the camshaft is divided by a cylindrical partition plate provided with a rotation stopper and an axial shift stopper, and the space of the cam part in the sand mold is divided. An addition chamber containing a metal component that increases the hardness of the cam part is formed in the supply path of the molten metal to the space, and molten metal having different components is supplied to the space of the shaft part and the space of the cam part, and the partition A method for casting a camshaft, characterized in that the camshaft is cast in a state in which a plate is cast.