JPS6345898B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for casting a casting for a hollow camshaft, and particularly for casting a casting for a hollow camshaft in which the diameter of one end of the camshaft is smaller than the other end. Concerning a suitable casting method.

Conventionally, in response to the demand for lighter weight and higher speed internal combustion engines, the use of hollow camshafts has increased, where the camshaft is made hollow to reduce weight, or where lubricating oil is passed through the hollow part to cool and lubricate the cam part. are doing.

As a method of manufacturing this type of hollow camshaft by casting, a method of casting a ceramic pipe or steel pipe as a core has been proposed. However, when a ceramic core is used, gas defects are likely to occur in the casting due to the poor ventilation of the core, and it requires many man-hours to remove the ceramic core after casting, resulting in high costs. It is extremely difficult to cast a hollow camshaft using a ceramic core, especially since the shaft diameter of the camshaft becomes smaller at the end. Further, when a steel pipe is used as the core, there is a problem that if the core is long, the steel pipe will be heated during casting and will be softened and bent, making it difficult to form a hollow portion along the axis.

In particular, according to the conventional method of making the hollow part of the camshaft approximately the same diameter over its entire length, the shaft diameter of the pulley mounting part that transmits power to the camshaft becomes thicker, and as a result, the shaft diameter of the pulley mounting part becomes larger. In addition, there are problems such as going against the desire for weight reduction or increasing the number of man-hours required for processing the mounting portion.

In view of the above, the present invention provides a method for casting hollow camshaft castings that does not cause gas defects during casting and allows for easy removal of the core after casting, and in particular a method for casting a hollow camshaft in which the shaft diameter of the camshaft becomes narrower at the end. The purpose of the present invention is to provide a method suitable for casting hollow camshaft castings, in which a combination mold having a cylindrical hole along the center line of the dividing surface is placed inside the hole along its axis. The first step is to prepare a mold for making a shell mold having a cylindrical space around the mandrel in which the mandrel is assembled.After filling the cylindrical space of the mold heated to a predetermined temperature with shell sand, the mold is A second step of dividing and extracting the mandrel to obtain a cylindrical shell mold; one end of the cylindrical shell mold has a baseboard piece protruding from one end, and the rest of the mandrel is The removal trace is removed in the third step of obtaining a hollow core, in which the end of the baseboard bar piece at one end of the core and the other end of the core are used as a baseboard, and the core is used as a main body for camshaft casting. A fourth step of assembling a mold for casting a hollow camshaft by installing it in the mold cavity. After pouring molten cast iron into the mold and solidifying it, the mold is separated, and the cylindrical shell mold or cylindrical shell mold of the core and the rod are separated. The present invention relates to a method for casting a hollow camshaft casting having a smaller diameter at one end, which comprises a fifth step of removing a piece to obtain a camshaft casting.

Next, embodiments of the present invention will be described with reference to the accompanying drawings. In FIG. 1, a shell molding mold 1 is composed of a combination of divided pieces 2 and 3, which can be divided vertically in the plane of the paper at a dividing plane (or mating plane) 7, and in the assembled state, the center line of the dividing plane A cylindrical hole 4 is formed along the cylindrical hole 4, and a mandrel 5 is inserted into the cylindrical hole 4 through a mandrel hole 8 provided in the dividing surface of the upper and lower mold pieces as shown in FIG. A cylindrical space 6 is formed around the . Although not shown in the drawings, the shell mold making mold 1 is provided with holes and vents for blowing shell sand as usual.

The above-mentioned shell mold making mold 1 is heated as usual, and shell mold sand is blown into it through the shell mold sand injection hole.Once the shell mold sand filling the cylindrical space is solidified, the mold 1 is divided. By removing the mandrel 5, a hollow cylindrical shell mold 9 as shown in FIG. 3 is obtained. Although either the mold division or the mandrel removal may be performed first, it is better to perform the mold division after the mandrel removal from the viewpoint of preventing damage to the cylindrical shell mold.

Next, as shown in FIG. 4, a cylindrical shell mold 9 is formed.
A baseboard steel bar piece 1 is attached to one end of the central through hole 10 of
1 to obtain a core 12 in which a steel bar piece 11 protrudes from the end of the cylindrical shell mold 9.

As another means of obtaining the core, as shown in FIGS. 5 and 6, the shell molding mold 1 can be divided into two by a cylindrical hole 4 formed along the center line of the dividing surface. After the mandrels 5 and 5a were inserted concentrically and molded in the same manner as described above, the shell mold molding mold 1 was divided and one mandrel 5 was removed, and the other mandrel 5a was attached to the cylindrical shell mold 9. If it is left as it is, there is no need to insert another baseboard rod piece 11 into the central through hole 10 as described above, and the rod piece 5a, that is, 11 is protruded from one end of the cylindrical shell mold 9 as it is. The core 12 is obtained, the number of man-hours is reduced, and the work becomes easy and slow.

The rod piece 11 or the mandrel 5a becomes the core of the pulley mounting part, but its end also serves as a baseboard when the core is assembled into the main mold for camshaft casting, which will be described later, so it must have sufficient strength. It may be made of metal, a sand mold, a solid body, or a hollow body, and its shape and material are not limited.

Next, the core 12 is placed in the cavity 14a of the main mold 13 for casting a camshaft manufactured by a normal manufacturing method, and the tip portion of the baseboard piece 11 or mandrel 5a and the shell-shaped end portion 15 at the other end are used as a baseboard. The camshaft casting mold 14 is then installed (see FIG. 7).

Note that a core 1 is placed on the split surface of the camshaft casting mold 14.
The ventilation hole 13 is connected to the central through hole 10 of No. 2.
If a is formed, gas release during casting can be further improved.

Molten cast iron for the camshaft is poured into the casting mold 14 in the usual manner, and then the mold is dismantled and the shell mold sand of the core is removed to form the end of the camshaft as shown in FIG. Steel bar piece 11 or mandrel 5a
A hollow camshaft casting 16 having a protruding shape is obtained.

The baseboard steel bar piece 11 or mandrel 5a protruding from the end of the camshaft can be cut in a later processing step, or the outer surface of the core steel bar piece 11 or mandrel 5a can be coated in advance and then cast. It is also possible to extract the camshaft later from the casting and form a hole 19 penetrating the camshaft as shown in FIG.

In the present invention, the main body of the core for casting the camshaft is a hollow cylindrical shell type. Therefore, since the core has good air permeability, a camshaft casting without casting defects can be obtained, and furthermore, the core can be easily removed from the camshaft casting after casting. Further, since the core used in the method of the present invention has a narrow diameter portion from which a steel rod piece or mandrel protrudes at the end, the diameter of the shaft of the camshaft is narrowed at the end. It is possible to easily obtain a casting for a hollow camshaft with a camshaft, and the mounting part of the pulley that transmits the driving force to the camshaft will not have an unnecessarily thick diameter, or the pulley etc. can be made smaller and the camshaft It is highly effective in promoting weight reduction.

[Brief explanation of drawings]

Figure 1 is a sectional view of the shell molding mold, Figure 2 is a sectional view showing the state in which the mandrel is inserted, and Figure 3 is a sectional view of the shell molding mold.
The figure is a partially fragmented front view showing the cylindrical shell type.
The figure is a partially fragmented front view showing a state in which a steel bar piece is inserted, FIG. 5 is a cross-sectional view of another mold similar to FIG. 2, showing a state in which another mandrel is inserted, and FIG. Partially fragmented front view showing the cylindrical shell type, No. 7
The figure is a sectional view of a mold for casting a hollow camshaft with a core attached, FIG. 8 is a sectional view of an example of a casting for a hollow camshaft obtained by the method of the present invention, and FIG. It is a sectional view showing an example. 1... Mold for shell molding, 4... Hole, 5...
...Mandrel, 6...Cylindrical space, 7...Dividing surface, 9...
... Cylindrical shell mold, 11 ... Steel bar piece, 12 ... Core, 13 ... Main mold for camshaft casting, 14 ... Mold for camshaft casting, 15 ... Shell mold core end, 16 ...
...Casting for hollow camshaft, 17...Pulley mounting part,
18...Hollow part.

Claims (1)

[Scope of Claims] 1. A shell mold having a cylindrical space around it, in which a mandrel is installed along the axis of the combination mold having a cylindrical hole along the center line of the dividing surface. The first step is to prepare a mold for molding. After filling the cylindrical space of the mold heated to a predetermined temperature with shell sand, the mold is divided and the mandrel is extracted to obtain a cylindrical shell mold. Step 2: On the center line of the cylindrical shell mold, one end has a mandrel baseboard piece protruding, and the remaining mandrel removal trace is used as a third step to obtain a core with a hollow hole. Step: Using the end of the baseboard bar piece at one end of the core and the other end of the core as a baseboard, the core is installed in a main mold cavity for camshaft casting to form a hollow camshaft casting mold. a fourth step of assembling the molten cast iron; a fifth step of assembling the camshaft by injecting and solidifying the molten cast iron into the mold, then breaking the mold, and removing the cylindrical shell mold or the cylindrical shell mold and the rod piece of the core to obtain a camshaft casting; A method for casting hollow camshafts in which one end has a smaller diameter. 2 The mandrel in the first step is a mandrel divided into two parts,
The mandrel removal in the second step is the removal of the split mandrel on the large diameter end side of the camshaft, and the baseboard bar pieces of the mandrel in the third step are the split mandrels of the two-divided mandrel, and the cylindrical shell is removed. 2. A method for casting a hollow camshaft casting having a small diameter at one end according to claim 1, which is the mandrel left on the small diameter end side of the camshaft of the mold.