JPS60258417A - Cam shaft made of cast iron and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture the titled cam shaft made of cast iron having high abrasion resistance and without generation of any sags at its edge part by casting a cam shaft having a chilled layer formed at the end part of the cam part, and remelting and hardening the cam surface to form a chilled layer. CONSTITUTION:In a mold 1 having a cavity 2 consisting of parts for casting a cam part 3, a shaft part 4, and a journal part 5, an agent 6 for promoting the chilling such as Te is coated on the end surface of the part 3 to form said cam part and edge part 3c of parts 3a and 3c for forming the cam surface, and molten iron is filled into the cavity 2 of the mold 1 to cast a cam shaft 8 with a chilled layer 10 formed only on the end part of a cam part 9. Subsequently, the central part of the cam surface is remelted by a plasma arc 12 generated from a plasma torch 11 and then quenched, and a chilled layer 13 which is in contact with said chilled layer 10 or a part of which overlaps the layer 10 is formed by remelting and hardening. The cam shaft 8 made of cast iron and having the cam part 9 having excellent abrasion resistance is obtained in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a cast iron camshaft in which a chilled layer is formed on the cam surface by remelting and hardening treatment, and a method for manufacturing the same.

(Prior art and its problems) The cam surface, which is the surface of the cam portion of the camshaft, comes into sliding contact with the tip of the rocker arm, and therefore is required to have higher wear resistance than other parts.

Therefore, conventionally, when casting a camshaft,
A cooling metal is set in advance on a portion of the mold corresponding to the cam surface, and during casting the molten metal forming the cam surface is rapidly cooled to form a highly hard chilled layer. However, when forming a chilled layer by setting a chilled metal, it is extremely difficult to control the thickness of the chilled layer, and setting the chilled metal is troublesome, as well as causing errors in setting the chilled metal. Therefore, it is necessary to take a large amount of grinding allowance, and when the fine chill is removed, the coarse chill part appears on the sliding surface, reducing the hardness and leading to a decrease in wear resistance.

As a means to eliminate the above-mentioned disadvantages, plasma arc,
By using a high-energy heat source such as an electro beam or laser beam to remelt the cam surface of a camshaft that has been cast, and rapidly cooling this remelted part, a fine chilled layer is formed on the cam surface. is possible.

However, using plasma arc, etc., the entire cam surface can be
If the melt is remelted over the entire width of the cam, sag will occur at the edge, which is the boundary between the end face of the cam part and the cam surface, which not only takes time and effort for later grinding, but also makes it difficult to obtain a chill layer over the entire width of the cam. When grinding, the chill layer becomes thinner. Further, in order to obtain a predetermined chill layer, the effective chilling cam width becomes narrower, causing a problem that the blood pressure at the sliding contact portion of the rocker arm increases.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems, and its purpose is to form a chilled layer on the cam surface by re-melting and hardening treatment, by forming a chilled layer on the cam surface at the time of the raw material. A thin chilled layer is formed all around the cam, without remelting the entire width of the cam, and without causing sagging on the edges. An object of the present invention is to provide a highly abrasive cast iron camshaft and a method for manufacturing the same.

(Structure of the Invention) The structure of the present invention to achieve the above object is to form a chilled layer on the end face of the cam portion of the camshaft by chilling promotion treatment during casting, and to For the parts excepted, a chilled layer was formed by remelting and hardening treatment.

(Embodiments of the Invention) Examples of the present invention will be described below based on the attached drawing ml.

Figure 1 is a diagram showing the inside of a mold for casting a camshaft.A cavity (2) for casting a camshaft is formed in the mold (1).
) consists of a part (3) for casting the cam part of the camshaft, a part (4) for casting the shaft part, and a part (5) for casting the journal part. Moreover, FIG. 2 and FIG. 3, which is a cross-sectional view taken along the line A-A in FIG.
3) consists of a part (3a) that molds the end face of the cam part and a part (3b) that molds the cam surface of the cam part, and these parts (3a).

(3b) includes tellurium, including the edge part (3c);
A chilling (white ironing) accelerator (8) such as the following is applied.

FIG. 4 is a cross-sectional view similar to FIG. 2, showing a part of the mold (1) according to another embodiment on an enlarged scale, and this casting fJ! (1)
The part where the cam part of the cavity (2) is cast (
A chiller (7) which is thinner than a normal chiller and has a simpler plate shape is set in the edge portion (3C) of 3). Note that this entire cooling portion is similar to exposing the pack metal (7a) in the pack metal process as shown in FIG.

Next, a method for manufacturing a camshaft according to the present invention will be described.

First, molten metal is poured into the mold (1) shown in FIGS. 1 to 5 to obtain a camshaft (8) as shown in FIG.

Here, in the cavity (2) of the mold (1), the edge part (3c) which is the boundary between the part (3a) where the end face of the cam part is molded and the part (3b) where the cam surface is molded is Chilling accelerator (6) is applied or chilling metal (7) is 7-2
Chilled! (10) is formed. In addition, the chilled layer has not yet been formed in the central portion (8d) of the cam surface (9b), that is, the portion where the degree of sliding contact with the tip of the rocker arm is greatest.

Next, as shown in FIG. 7, the central part (
9d), the plasma torch (11) is isolated for a predetermined period.
By rotating the camshaft (8) and moving it back and forth in the left and right directions, or by moving the plasma torch (11), the central part of the cam surface is (9d) is remelted and this remelted part is rapidly cooled, so that a chilled layer (13
) to form. Here, in remelting the cam surface (8b) with the plasma arc (12), the cam surface (8b)
A chilled layer (10
) is formed. Therefore, the plasma arc (12
), it is not necessary to remelt up to the edge part (8C), so naturally the edge part does not sag.

FIG. 8 is a sectional view similar to FIG. 7 showing another embodiment,
In this example, the chilled layer formed by the remelting hardening process is the alloy chilled layer (14).

To form such a chilled alloy layer (14), a plasma torch (11) is used which penetrates the shield cap (15) through the introduction tube (16). , i.e. plasma torch (11)
The introduction tube (
Powder (17) of high-hardness metal, such as Cr, Mo, S, etc., is supplied via 16). Then, high hardness metal powder (17
) is confined in the plasma arc (12) and forced into the molten zone by the plasma arc (12). Then, the hard metal powder (
17) is melted or uniformly dispersed in the camshaft base material. After this, the cam part (
A chilled alloy (including solid solution) layer (14) is formed at the center (8d) of the cam surface (9b) of 8). Even in this case, since the chilled layer (10) is previously formed on both edge portions (8c) of the cam surface (9b) during casting prior to remelting, no sag occurs. In particular, the alloy chilled layer cannot be formed by the conventional method using a chilled metal, and it is not recommended to form the chilled layer (10) in advance on the edge portion (8c) as in this example. It is extremely effective in terms of prevention.

1= Incidentally, in the above embodiments, an example was described in which a plasma arc was used as a high-energy heat source, but a laser beam, an electro beam, etc. may also be used.

(Effects of the Invention) As explained above, according to the present invention, when forming a chilled layer on the cam surface by remelting and hardening treatment, dimensional errors or shape errors are avoided without causing sag on the edge portion of the cam surface. It has many effects such as being able to obtain a camshaft that requires less grinding and can be easily ground later, and also being able to easily form a chilled alloy layer in the center of the cam surface where particularly high wear resistance is required. .

[Brief explanation of drawings]

FIG. 1 is a diagram showing the internal structure of a mold for casting a cast iron camshaft according to the present invention, and FIG. 2 is an enlarged view of the main parts of the mold.
Figure 3 is a sectional view taken along line A-^ in Figure 2, Figures 4 and 5 are similar views to Figure 2 showing another embodiment of the mold, and Figure 6 is a part of the cast camshaft. FIG. 7 is a cross-sectional view showing a cast camshaft undergoing remelting and hardening treatment, and FIG. 8 is a cross-sectional view similar to FIG. 7 showing another embodiment. In the drawings, (1) is the mold, (2) is the cavity part (3) is the part of the cavity that molds the cam part, (6) is the chilling accelerator, (7) is the cold metal, and (8) is the mold. is cam shirt), (
9) is a cam portion, (9a) is an end face of the cam portion, (8b) is a cam surface, (8c) is an edge portion (10), (13) is a chilled layer, and (14) is an alloy chilled layer. Patent Applicant Honda Motor Co., Ltd. Agent Patent Attorney 2 1) Production Department Patent Attorney Kuni Ohashi Production Volume Patent Attorney Yu Koyama

Claims (4)

[Claims] (1) A chilled layer is formed on the end surface of the cam part by quenching during casting or by a chilling accelerator, and a chilled layer is formed on the cam surface except for the ends by remelting hardening treatment. Cast iron camshaft. (2) The cast iron camshaft according to claim 1, wherein the chilled layer formed by the remelting hardening treatment is an alloy chilled layer. (3) Chill only the cam end by applying a chilling accelerator to the inner surface of the mold where the end face of the cam part will be formed, or by setting a chilled metal and filling the mold with molten metal. A camshaft with a layer formed thereon is cast, and then the cam surface of this camshaft is remelted and hardened to form a chilled layer that contacts or partially overlaps the chilled layer formed by the casting. A method for manufacturing a cast iron camshaft characterized by: (4) The method for manufacturing a cast iron camshaft according to claim 3, wherein during the remelting, a metal powder different from that of the base material of the camshaft is supplied to the remelting section.