JPH02211931A - Manufacture of cam shaft with lost foam pattern casting method - Google Patents

Abstract

PURPOSE:To make unnecessity of secondary machining for removing excess thickness, etc., by removing the excess thickness attaching position corresponding to draft developing to the relative position between a cam top position and parting surfaces of dividing molds at forming stage of a lost foam pattern. CONSTITUTION:The parting surfaces 2a, 3a at upper part in one pair of the dividing molds 2, 3 are set on X line passing through the base point 0 and shaft center. The parting surfaces 2c, 3c at lower part of the dividing molds 2, 3 are set so as to pass the cam surface at the lowest position of the cam A. Step difference is arranged to the parting surfaces of the dividing molds 2, 3, and by eliminating interference part (draft) between the ordinary dividing mold 3 and the lost foam pattern 4, parting ability between the dividing molds 2, 3 and the lost foam pattern 4 is secured, and after foaming and solidifying beads under condition of matching both dividing molds 2, 3 obtaining the lost foam pattern removing the excess thickness, the dividing molds 2, 3 are separated. By this method, the lost foam pattern 4 without the excess thickness can be formed and the removal of the excess thickness becomes unnecessary and the machining time can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a camshaft using an investment casting method.

[Conventional technology]

As shown in FIG. 6, the engine camshaft l is -
A plurality of cams A, B,
C, D, E, and F are formed.

In addition, each of these forces, M A, I3. C, D, E, F.

As is well known, the phase angle O of the cam top position of each cam from the base point 0 is shifted by a predetermined amount in accordance with the intake/exhaust cycle of the cylinder to which each cam corresponds. For example, in the case of a 3 cylinder engine.

The phase angle Oa of the cam top position ga of cam A is Da: 1
29°48' (see Fig. 7(a)), and the phase angle Ob of the cam top position 1b of cam B is Ob = 230°11' (
(See Fig. 7(b)), the phase angle Oc of the cam top position C of the cam C is 0c = 9°48' (see Fig. 7(c))
.

The phase angle θd of the cam top position 11d of the cam D is Od:1
10'11' (see Fig. 7(d)), the phase angle Oe of the cam top position 11e of the cam E is 0e = 249'' 4
8' (see Figure 7(e)), cam top position I of cam F! The phase angle Of of f is formed such that Of=350°11' (see FIG. 7(f)).

- On the other hand, as a type of method for manufacturing such a camshaft 1, a camshaft manufacturing method using an investment casting method is known.

As is well known, this manufacturing method involves first forming a pair of split molds 2 and 3 (molds) based on the designed camshaft (see Figure 8 Ca).Next, these split molds 2, Parting surface 2 of 3
With parts a and 3a combined, the piece is filled into a mold, and the piece is heated with steam to foam. As a result, the beads are foamed and solidified along the shape of the mold, and a vanishing model 4 (see Figure 8(b)) of the cam shirt T made of foam is formed.Next, this vanishing model 4 is embedded. A mold 5 (sand mold) is formed, and a predetermined molten metal 6 is poured into this mold 5.
(see Fig. 8(c)), incinerate the vanishing model 4, and form the camshaft material 7 (see Fig. 8(d)).
.

[The problem to be solved by the invention is that the cam top positions of the cams of the camshaft 1 are formed to have different phases from each other as described above. , 3a are set on any normal line passing through the center of the shaft, a part of the cam surface reaching the cam top position of one or two of the cams is not relative to one of the split molds. You will be in a position to dig in and interfere. That is, for example, if the parting surfaces 2a and 3a of the pair of split molds 2.3 are set on the X-ray that passes through the base point O and the shaft center in FIG. 7, the cam surfaces of cam A and cam B A portion of the molds 2 and 3 is inserted into each of the split molds 2 and 3 by the gap g (g = 1.6 mm in the illustrated example) and faces a position where they interfere.

For this reason, in the conventional camshaft manufacturing method described above,
For example, when forming a cam A, as shown in FIG. 8(a), one of the pair of split molds 2 and 3 is placed on the side of the split mold 3 where the cam surface bites and an interference portion occurs.

A clearance 3b was formed in advance to ensure releasability between the split mold 3 and the disappearing model 4.

Therefore, the disappearing model 4 formed by the split molds 2 and 3 has a shape in which extra thickness 4a is formed in the portion corresponding to the cutout allowance 3b of the split mold 3 (see FIG. 8(b)). The camshaft material 7 molded based on this disappearing model 4 has an extra thickness 7a formed therein.

For this reason, the conventional camshaft manufacturing method described above requires extra secondary processing such as grinding just to remove the excess thickness of the molded camshaft material (metal), increasing processing time and costs. There was a drawback.

[Means to solve the problem]

In the above-mentioned vanishing model casting method, the present invention provides a method for forming the vanishing model in the molding stage of the vanishing model by removing excess thickness corresponding to the cutting margin of the split mold caused by the relative position between the cam top position of the camshaft and the parting surface of the split mold. After removing it, the camshaft and material will be cast.

[For production]

According to the method for manufacturing a camshaft of the present invention, the excess thickness portion corresponding to the cut-out allowance of the split mold for molding the vanishing model is removed in the stage of molding the vanishing model.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail, taking as an example the process of molding the cam A shown in FIG. 7(a).

FIG. 1 shows a first embodiment of the present invention.

In FIG. 1, the upper parting surface 2a of the pair of split molds 2 and 3
, 3a are set on the XLA which passes through the base point 0 and the shaft center in FIG. 7(a), as in the conventional case. On the other hand, the lower parting surface 2c of each split mold 2, 3.

3c is set to pass through the cam surface of the lowest portion of the cam A. That is, in this embodiment, by providing a step on the parting surfaces of the 10-piece molds 2 and 3 and eliminating the interference part (cutting margin) between the conventional 1-piece mold 3 and the disappearing model 4, the 10-part molds 2 and 3 disappear. Each of the split molds 2 and 3 is formed so as to ensure the releasability of the model 4 and to obtain a disappearing model with excess thickness removed. therefore.

According to this embodiment, as shown in FIG. 1(a), after the beads are foamed and solidified with the split molds 2 and 3 together,
By separating the split molds 2 and 3 as shown in FIG. 1(b), it is possible to form a disappearing model 4 with no excess thickness.

FIG. 2 shows a second embodiment of the present invention.

In FIG. 2, the upper and lower parting surfaces 2a of the split mold 2 are shown.

2c, the upper parting face 3a of the 6-way split mold 3 is set in the same manner as the conventional split mold, and the lower parting face 3c of the split mold 3 is It is set to be the same surface as the parting surface 3c of the split mold 3 in the embodiment. In addition, a nest 8 is arranged in the gap between the lower parting surface 2c of the 10% mold 2 and the lower parting surface 3c of the 10% mold 3 so as to be able to move forward and backward in the vertical direction. That is, in this example,
By configuring the mold with a nest 8 at a portion corresponding to the interference part between the conventional split mold 3 and the disappearing model 4, releasability from the disappearing model 4 such as the 1-split mold 2 and 3 is ensured. Therefore, according to this embodiment, as shown in FIG. 2(a), each split mold 2,
2(b) after foaming and solidifying the beads with 3 and nest 8 together.

By separating the nest 8 and the split molds 2 and 3 as shown in CC), it is possible to mold the disappearing model 4 with no excess thickness.

FIG. 3 shows a third embodiment of the present invention.

In this embodiment, each split mold 2, 3 has a parting surface 2a,
3a is set almost in the same way as the conventional split mold, but the mold shape ignores the releasability of the split mold 3 and the disappearing model 4, and has a shape that interferes with each other, that is, cam A. It is formed in the designed shape.

In this embodiment, as shown in FIG. 3(a), each split mold 2.
After the beads are foamed and solidified in the state in which the molds 3 are combined, the split molds 2 and 3 are forcibly separated as shown in FIG. 3(b). At this time, the disappearing model 4 is forcibly removed from the interference part 3d of the 10% mold 3.

It is deformed as shown by the five-dashed line in FIG. 3(b), but
Since the gap G of the interference portion 3d is small as described above, the amount of deformation of the vanishing model 4 can usually be kept within the range of elastic deformation.

Therefore, according to this embodiment, the vanishing model 4 with no excess thickness can be molded using an extremely simple split mold.

FIG. 4 shows a fourth embodiment of the invention.

In this embodiment, as shown in FIG. 4(a), a disappearing model 4 with extra thickness 4a is molded by the same method as in the conventional method, and then, as shown in FIG. 4(b), a hot wire By moving the heating wire 9 (heating wire) relative to the cam surface of the vanishing model 4, the excess thickness 4a is removed (cut), and the vanishing model 4 is formed.

FIG. 5 shows a fifth embodiment of the present invention.

In this embodiment, each of the split molds 2 and 3 is formed in the same mold shape as in the third embodiment (see FIG. 5(a)), and these split molds 2° 3 is Fig. 5(b)
As shown in FIG. 3, it is configured to be openable and closable in the direction of the arrow as the center Oxt& axis of a circular arc that is in contact with the tangent between the interference part 3d of the 10% die 3 and the vanishing model 4.

Therefore, according to this embodiment, after the beads are foamed and solidified with the split molds 2 and 3 put together as shown in FIG. 5(a), the beads are foamed and solidified as shown in FIG. 5(b).

By opening each of the split molds 2 and 3 in the direction of the arrow with the center Ox as an axis, it is possible to mold the disappearing model 4 with no excess thickness without causing the interference part 3d of the split mold 3 to interfere with the disappearing model 4. .

As described above, according to the method for manufacturing a camshaft of the present invention, the excess thickness corresponding to the cut-out allowance of the 10% mold is removed at the stage of molding a disappearing model made of a foam that is easy to process and mold. This prevents excess metal from forming during the molding stage of the metal camshaft material, which is highly difficult to process.

〔Effect of the invention〕

According to the present invention, secondary processing such as removing excess thickness of the camshaft material is not necessary, and the processing time and cost i can be reduced.

[Brief explanation of the drawing]

1 is a schematic sectional view of an embodiment of the present invention, FIG. 2 is a schematic sectional view of another embodiment of the invention, and FIG. 3 is a schematic sectional view of yet another embodiment of the invention. 4 is a schematic cross-sectional view of still another embodiment of the present invention, FIG. 5 is a schematic cross-sectional view of still another embodiment of the present invention, and FIG. 6 is a side view of a camshaft in which the present invention is implemented. FIG. 7 is an end view of each cam of the camshaft, and FIG. 8 is a schematic diagram showing a conventional camshaft manufacturing method. l...Camshaft, 2, 3...Split mold, 2a. 2c, 3a, 3c...cutoff surface, 4...disappeared model, 4a...excess material, 5...mold, 6...
Molten metal, 7...camshaft material, 8...nest, 9...hot wire, 0...base point, A,
B, C, D, E, F... cam. at b. j d. I f...Cam top position. Fangtu flood district helmet? Figure Island δ Figure (Kun<d)

Claims (1)

[Claims] In the vanishing model casting method, a camshaft material is cast by forming a vanishing model of the camshaft made of foam using a pair of split molds, and then pouring molten metal into the mold in which the vanishing model is embedded. A cam produced by a vanishing model casting method, characterized in that an area where excess thickness is generated corresponding to the cut-out margin of the split mold caused by the relative position of the cam top position and the cut-off surface of the split mold is removed in the stage of molding the vanishing model. How to manufacture the shaft.