JP2927905B2 - Molding method of vanishing model for hollow camshaft - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for molding a vanishing model for a hollow camshaft used in casting a hollow camshaft used in an internal combustion engine.

[Conventional technology]

Conventionally, camshafts used in internal combustion engines are manufactured by forging or casting, but forged steel products are heavier than cast iron products. Not suitable. Therefore, the camshaft is manufactured by casting. In addition, the center of the camshaft is hollowed out. For this purpose, a sand core or a metal tube is disposed at the center of the mold. Among the sand cores and metal pipes, those having a long axis are supported with the sand cores and metal pipes by using kerosene in order to suppress misalignment in the mold. In particular, in order to manufacture a hollow camshaft with one end closed, many special kerens are required to support a sand core and a metal tube.

[Problems to be solved by the invention]

However, in the case where a hollow core is manufactured by casting a molten metal by arranging a sand core or a metal pipe in a mold as described above, the sand core or the metal pipe is formed with a lot of keren as described above. There is a problem that it must be supported and is complicated. In particular, as described above, when a special keren is required, the special keren must be separately manufactured, which increases the cost. Further, when a hollow camshaft is manufactured using a sand core, the hollow camshaft must be vibrated by shot blasting or the like to break and remove the sand core, which is complicated and There was a problem that sand could not be completely removed from the hollow portion.

[Means for solving the problem]

In order to solve such a problem, in the present invention, both ends of the metal tube are supported by supporting portions formed in a model mold, and a disappearing foam material is put in the model mold. The vanishing model of the hollow camshaft in which the metal tube is located at the center is molded. Alternatively, at least one end of the metal tube is supported by the model mold via the disappearing member, and the other end is supported by the support formed in the model mold. The metal tube is placed at the center, and at least one end of the hollow tube is closed by the vanishing member to form a vanishing model of the hollow camshaft.

[Action]

When the lost model is buried in the molding sand in the casting frame and molded, and the molten metal is poured into the lost model from the gate, a hollow camshaft is cast.

Alternatively, the vanishing model whose one end is closed is buried in molding sand to form a mold, and if a molten metal is cast from a gate, a hollow camshaft whose one end is closed is cast.

〔Example〕

Hereinafter, the present invention will be described with reference to the drawings. 1 and 2 are views showing a method for molding a vanishing model for a hollow camshaft according to the present invention.

First, the hollow camshaft is manufactured by a casting method using a vanishing model. In this casting method, a hollow camshaft is manufactured by molding a disappearing model made of expanded polystyrene and casting a molten metal into the disappearing model.

A method for molding a vanishing model for a hollow cam shaft in this casting method will be described. In FIG. 1, reference numerals 1 and 2 denote a pair of model dies, and the shapes of inner wall surfaces 4 and 5 of the model dies 1 and 2 have a shape of a cam shaft used in an internal combustion engine. Support portions 4a, 5 having the same shape as the stainless steel tube 3 are provided at both ends of the inner wall surfaces 4, 5 to support both ends of the stainless steel tube 3.
a, 4b, 5b are formed. Stainless steel pipes 3 are provided in the mold dies 1 and 2, and both ends of the stainless steel pipes 3 are provided.
3a, 3b are supported by the support portions 4a, 5a, 4b, 5b. The stainless steel pipe 3 is coated with graphite (not shown) as a refractory material. After the stainless steel tube 3 is provided, the expanded polystyrene beads 6 are placed in the molds 1 and 2 for the models.

When the model dies 1 and 2 are heated, the beads 6 are foamed to form the disappearing model 7 made of expanded polystyrene having the stainless steel tube 3 inside as shown in FIG. The molds 1 and 2 for the model are opened, and the vanishing model 7 is taken out from the inside, and both ends 3a and 3b of the stainless steel tube 3 protruding from the vanishing model 7 are opened.
Is cut off with a cutter or the like. Next, the lost model 7 is buried in the molding sand in the casting flask and molded.
Has a stainless steel pipe 3 so that no bending occurs during the molding. At this time, if the vanishing model 7 is buried in the casting sand, the stainless steel pipe 3 constituting the hollow portion of the hollow cam shaft is covered by the vanishing model 7, so that there is no need to use conventional keren or the like.

Next, if a molten metal such as spheroidal graphite cast iron is cast into the vanishing model 7 from the gate, a hollow cam shaft is cast, and then the stainless steel pipe 3 is pulled out. In order to prevent the stainless steel pipe 3 from being twisted due to the thermal influence of the molten metal at the time of casting, a stainless steel rod may be inserted into the stainless steel pipe 3. By the way, when a sand core is used to form the hollow portion, it is necessary to vibrate the hollow cam shaft by shot blasting or the like to remove sand from the hollow portion. In such a case, such a work becomes unnecessary and the operation becomes simple.

Next, a second embodiment of the present invention will be described with reference to FIGS. 3 and 4. FIG. The same members as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 3, support portions 4a and 5a are formed at one end of the inner wall surfaces 4 and 5 of the model molds 1 and 2, while the other end is for supporting a disappearing member 11 made of expanded polystyrene or the like. Support portions 4b and 5b are formed.
The disappearing member 11 has a support hole 11a for supporting one end 3b of the stainless steel tube 3. A stainless steel tube 3 having one end 3b closed by a metal stopper 12 is press-fitted into the support hole 11a, and the stainless steel tube 3 to which the disappearing member 11 is attached is arranged in the model dies 1 and 2.

Next, a vanishing model 13 as shown in FIG. 4 is formed in the same manner as in the first embodiment, and the vanishing model 13 has one end closed by the vanishing member 11. next,
When the molten metal is cast as in the first embodiment, a hollow camshaft having one end closed is cast. An oil hole is cut in a cam portion, a journal portion, and the like of the hollow cam shaft by a drill. By introducing lubricating oil into the hollow portion of the hollow camshaft, the lubricating oil is guided from the oil hole to the cam portion and the journal portion. As described above, since it is not necessary to use a conventional special keren in order to cast a hollow camshaft whose one end is closed, it is simple and the manufacturing cost can be reduced.

〔The invention's effect〕

As described above, according to the present invention, both ends of the metal tube are supported by the supporting portions formed in the model mold, and a foaming material for disappearing is put in the model mold so that the metal tube is centered. As the vanishing model of the hollow camshaft located in is designed to be molded, if the vanishing model is buried in casting sand, the stainless steel tube that constitutes the hollow part of the hollow camshaft is enclosed by the vanishing model, so It is not necessary to use Keren or the like.
Further, when a sand core is used to form the hollow portion, there is no need to perform operations such as applying vibration to the hollow cam shaft by shot blasting or removing sand from the hollow portion.

Alternatively, at least one end of the metal tube is supported by the model mold via the disappearing member, and the other end is supported by the support formed in the model mold. The metal pipe is located at the center, and a vanishing model of a hollow cam shaft at least one end of which is closed by the vanishing member is molded. Since the shaft is cast and there is no need to use a conventional special keren, it is simple and the manufacturing cost can be reduced.

[Brief description of the drawings]

1 and 2 are views showing a first embodiment of a method for forming a vanishing model for a hollow camshaft according to the present invention. FIG. 1 is a sectional view of a model die, and FIG. 2 is a vanishing model. FIGS. 3 and 4 are views showing a second embodiment of the method for forming a vanishing model for a hollow camshaft according to the present invention, and FIG. 3 is a cross-sectional view of a model die. The figure is a sectional view of the vanishing model. 1,2 ... model mold, 3 ... stainless steel tube, 4a, 5a, 4b, 5b ... support, 7,12 ... vanishing model, 11 ... vanishing member.

Claims (2)

(57) [Claims] 1. A hollow camshaft in which both ends of a metal tube are supported by supporting portions formed in a model mold, and a vanishing foam material is placed in the model mold so that the metal tube is positioned at the center. A method for molding a vanishing model for a hollow camshaft, wherein the vanishing model is molded. At least one end of the metal tube is supported by a model mold via a vanishing member, and the other end is supported by a support formed in the model mold and vanes into the model mold. Molding a vanishing model for a hollow camshaft, wherein a foaming material is put in and the metal tube is positioned at the center and at least one end is molded by a vanishing model of a hollow camshaft closed by the vanishing member. Method.