JPS6336864B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for hollow casting a long casting such as a camshaft used in an internal combustion engine for an automobile.

(Background Art) Conventionally, the method of hollowing out a camshaft is to form the entire camshaft from a cast metal and then drill holes later using a machine such as a gun drill, but such machining requires a special processing machine. thing,
It is difficult to process and requires an extremely long time to process, which in combination with the above results in high processing costs, which also affects the camshaft.

Therefore, instead of this, an attempt was made to create a hollow by casting when casting the camshaft, and this was shown in Figure 5.
To explain with FIG. 6, the molding groove 5 between the molds 51 and 52
A core 54 made of a refractory material with relatively high transverse rupture strength, such as a shell core, is vertically inserted into the core 5 and the upper end of the core is held down.
5, the mold is fixed to the mold, molten metal is filled into the molding groove 53 from the runner 56, and hollow casting is performed. In such conventional casting hollow processing, since hollow casting is performed using a core such as a refractory material, 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, so that the core 54 is This causes a problem in that the resulting camshaft after casting has uneven thickness.

(Objective of the Invention) The present invention has been made to improve the above-mentioned problems, and its purpose is to prevent the core from bending during hollow casting using a core, and to prevent hollow camshafts, etc. As a result, 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 method for hollow casting of shaku 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 the hollow casting core. 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.

FIG. 1 is an open front view of the mold with the core set in the mold, and FIG. 2 is a plan view of the mold.

The mold 1 consists of the molds 2 and 3 which are green molds divided as described above, and a molding groove 4 is formed in the mating surfaces of the molds 2 and 3, and when the molds 2 and 3 are combined, a camshaft is molded between the mating surfaces. A groove 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.The upper end of the molding groove 4 is formed with a circular recess 401 that is open upward when combined. A hot water introduction part 402 is formed at the lower end and communicates with the lower end of the runners 5 arranged in parallel through a communication passage 501, and the runners 5 are opened and connected to the sprue 502. Inside the molding groove 4 is a long cylindrical core 6 with the same diameter over the entire length.
The core 6 is made of a refractory material, and the core is hollow and opens upward to provide a passage 604 for degassing.

The core 6 is supported by being inserted into the lowermost part 8 of the mold with the protrusion 7 extending from the lower end 601. Upper part 6 of core 6
02 faces the recess 401, and the bottom 4 of the recess 401
A core support member 9 is inserted into the core support member 9, and the member 9 is disc-shaped and has a vertical support hole 901 in the center, and the upper part 602 of the core 6 is slidably inserted into the support hole 901. When inserted, the upper end 603 of the core 6 protrudes above the branch support member 9, and it is preferable that the member 9 is made of the same material as the core 6. The bottom of the recess 401 has an enlarged diameter portion 4.
04 to support the outer diameter part of the member 9 at this part,
Regulates the vertical direction.

In the above process, the molten metal is poured from the sprue 502, flows into the molding groove 4 from below through the runner 5 communication part 501, gradually increases its level, and fills the groove. The molten metal is filled between the groove 4 and the core 6 to perform casting. At this time, the core 6 expands in its axial direction due to the heat of the molten metal. Core 6 is the upper part 6
02 is supported by the support member 9, but the support hole 901
Because the core 6 is slidably supported in the axial direction, expansion in the elongation direction is allowed, and the thermal expansion is absorbed and the core 6 does not bend, and the elongated state is shown by the chain line A. . Since thermal expansion can be absorbed by elongation, the hollow part formed by the core of a cast camshaft is not deformed straight, but is formed so that the wall thickness around the hollow part is uniform in relation to the camshaft shaft. The Rukoto.

In addition, to give a specific example, RCS as a core
(resin coated sand), using silica sand,
At 1100℃, the linear expansion rate is approximately 1.5% (approximately 60 seconds), and a 400mm camshaft shows an elongation of approximately 6mm, equivalent to 1.5%.
There was no bending in the core, and a clearance between the outer diameter of the core and the inner diameter of the support hole of the support member was 0.6 mm to 1 mm. The supporting members were made of the same material.

FIGS. 3 and 4 show modified embodiments of the core and its supporting member, and FIG. 3 shows an example in which a disc-shaped flange portion 605 is provided on the head of the core 6 described above. A flange portion 60 is provided on the upper surface around the support hole 90 of the support member 9.
5 is suspended and supported, and in the one shown in FIG. 4, the flange part 606 has an inverted truncated conical shape whose diameter gradually decreases downward, and the upper part 90 around the support hole 901 has a conical shape. be.

In the above embodiments, the camshaft is shown, but the present invention can be applied to general hollow casting molding of long casting products.

(Effects of the Invention) As is clear from the above, according to the present invention, a hollow camshaft can be manufactured by hollow casting without requiring a machining process that takes a long machining time, requires a special processing machine, and is disadvantageous in terms of cost. It is possible to obtain long hollow castings such as the one shown in FIG. It has a simple configuration, can be easily obtained, and can be obtained 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 casting machine in a mold split state, 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 addition, in the drawing, 2 and 3 are molds, 4 is a molding groove, 6 is a core,
9 is a core support member.

Claims (1)

[Claims] 1. A long casting product in which a long hollow casting core is inserted and held in a molding groove formed between molds, the molding groove is filled with molten metal, and the core is used to form the hollow part of the casting. In the hollow 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 a long casting, characterized in that thermal expansion of the core due to filling of molten metal into a molding groove is absorbed by the axial elongation movement of the core.