JPS60199545A - Hollow hole casting method of long-sized casting - Google Patents

Abstract

PURPOSE:To prevent bending of a core for hollow hole casting and to form a long-sized casting having no thickness deviation by hollow hole casting by supporting freely slidably the core to a core supporting material provided to have the gap to permit elongation of the core owing to thermal expansion at one end of a casting mold. CONSTITUTION:The molten metal poured through a sprue 502 is filled through a runner 5 and a communicating part 501 into a molding groove 4 to perform hole casting with a core 6. The core 6 is thermally expanded by the heat of the molten steel so as to elongate axially. The upper part 602 of the core 6 is supported by a supporting member 9 and since said part is supported freely axially slidably by a supporting hole 901, the expansion in the elongating direction is permitted and the thermal expansion is absorbed. The cast can shaft is thus formed in such a way that the wall thickness around the hollow part thereof is made uniform in relation with the shaft part thereof without bending of the core 6 while the hollow part is maintained straightforward without deformation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a hollow casting method for long castings such as camshafts used in internal combustion engines for automobiles.

(Background Art) Conventionally, the method of hollowing out a camshaft is to form the entire camshaft by casting and then drill the holes using a gun drill or other machine tool, but such machining requires a special processing machine. However, it is difficult to process and requires an extremely long time to process, resulting in high processing costs, which also affects the camshaft.

Therefore, instead of this, an attempt was made to perform hollow casting during casting of the camshaft, and this is explained in Figures 5 and 6. A core (5
4) is inserted vertically, the two ends of the core are fixed in the mold with the holding body (55), molten metal is filled into the molding groove (53) from the runner (56), and hollow casting is performed. . In such conventional casting hollow processing, hollow casting is performed using a core such as a refractory material, so the core (54) is restrained and held in the mold by the molten metal pressure during casting and the thermal expansion of the refractory material. (541), and as a result, the camshaft obtained after casting has a problem of uneven thickness.

(Objective of the Invention) The present invention has been made to improve the above, and its purpose is to prevent the bending of the core during hollow casting using a core, and to prevent hollow camshafts etc. from being cast by hollow casting. In addition, it is possible to obtain a hollow cast product with no uneven thickness, uniform thickness in each part, and good quality accuracy at an advantageous cost. The purpose of the present invention is to provide a hollow casting method for castings.

(Structure of the Invention) In order to achieve the above object, the present invention provides a core support member having a gap at one end of the mold to allow elongation due to thermal expansion of a hollow casting core, and the core support member The gist is that the core is slidably supported and cast.

(Embodiment) Next, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 is a front view of the mold with the core set in the mold, Figure 2
The figure is a plan view of the mold.

The mold (1) is made up of molds (2) and (3) which are green molds divided as described above, and molding grooves (4) are formed on the mating surfaces of the molds (2) and (3). By combining (2) and (3), a camshaft is created between the mating surfaces! Iln will be formed. The molding groove (4) is vertically long because the mold is vertically elongated, and is formed by a recess that forms the outer shape of the camshaft, and the molding groove (0) has a circular recess (401) that opens upward when assembled at the upper end. A hot water introduction part (402) is formed at the lower end of the molding groove (4) and communicates with the lower end of the runner (5) arranged in parallel through a communication passage (501).
5) The upper end is open and connected to the sprue (502).

A long cylindrical core (6) having the same diameter over the entire length is inserted into the molding groove (4), and the core (8) is made of a refractory material.
The core is hollow with a passageway (Boo) open upwards.
Perform degassing action.

The core (6) is a keren (7) with the lower end (801) extended.
Insert it into the bottom part of the mold (8) and support it. The upper part (802) of the core (6) faces the recess (401), and
A core support member (8) is fitted into the bottom (403) of 1), and the member (9) has a disc shape with a support hole (+1
01) is installed vertically, and the upper part (802) of the core (6) is slidably inserted into the support hole (901), and the upper end (803) of the core (6) is placed above the support member (8). The member (8
) is preferably molded from the same material as the core (6).The bottom of the recess (401) is provided with a swollen diameter part (400), and this part supports the outer diameter part of the member (9). regulate.

In the above process, molten metal is poured from the sprue (502), flows into the molding groove (4) from below through the runner (5) communication part (501), and gradually increases its level to fill the groove. Ru. The molten metal is filled between the groove (0) and the core (6), and casting is performed. At this time, the core (6) expands in its axial direction due to the heat of the molten metal. The core (8) is at the top (802)
is supported by the support member (9), but since it is supported slidably in the axial direction in the support hole (901), the ai in the elongation direction
1 bulge is allowed, the thermal expansion is absorbed, the core (8) does not bend, and the elongated state is 11
Indicated by il line (A).

In this way, thermal expansion can be absorbed by elongation, so that the hollow part formed by the core of the cast camshaft does not deform straight, and the wall thickness around the hollow part becomes uniform in relation to the camshaft shaft. It will be molded.

To give a specific example, RCS (resin coated sand) and silica sand were used as the core, and the line *n! Rate approx. 1.5$ (approx. 80 seconds), 400mm
(1) The camshaft shows an elongation of approximately 6WI layers equivalent to 1.5%, there is no bending in the core, and the outer diameter of the core and the inner diameter of the support hole of the support member is 0.6" to 1". It was taken as intestinal clearance. The supporting members were made of the same material.

Figures 3 and 4 show modified embodiments of the core and its supporting members, and Figure 3 shows an example in which a disc-shaped flange (805) is provided on the head of the core (8) described above. With this, the support member (
8) on the upper surface around the support hole (901).
) is suspended and supported, and the one in Figure 4 has an inverted truncated conical flange part (eoe
), and the upper surface part ([2)] around the support hole (901) is conical.

Although a camshaft has been shown in the above embodiments, the present invention can be implemented in general hollow casting molding of long casting products.

(Effects of the Invention) As is clear from the above, according to the present invention, the machining process takes a long time, requires a dedicated processing machine, and is disadvantageous in terms of cost.
Long hollow castings such as hollow camshafts can be obtained by hollow casting without the need for hollow casting, and the hollow castings obtained also have a hollow part that is straight in the axial direction and no uneven thickness between the surroundings. Thus, a long hollow casting having excellent quality and precision can be easily obtained with a simple configuration and extremely advantageously in terms of cost.

The present invention has many advantages as described above.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is an explanatory front view of the mold side of the casting device, FIG. 2 is a plan view, and FIGS. 3 and 4 are main parts of a modified embodiment. , and FIG. 5 are the same views as FIG. 1 of the conventional example, and FIG. 6 is the same plan view. In the drawings, (2) and (3) are the mold, (0 is the molding groove, (8) is the core, and (8) is the core support member. Patent applicant Honda Motor Co., Ltd. agent Patent attorney 2 1) Patent Attorney Kuni Ohashi, Patent Attorney Koyama Right Hand 1 Figure 2 Figure 4 Figure 5 Figure 6 Figure 6 56':)l

Claims (1)

[Claims] A long hollow casting core is inserted and held in the molding groove formed between the molds, the molding groove is filled with molten metal, and the core is used to form the hollow part of the casting. In the casting method, a core support member having a gap that allows elongation due to thermal expansion of the core is provided at one end of the mold, and the core is slidably supported by the core support member; A method for hollow casting of a long casting, characterized in that heat W11N of the core due to filling of the molten metal into the molding groove is absorbed by the axial elongation movement of the core.