JP3171044B2 - Core molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core molding method,
More particularly, the present invention relates to a method for molding a core having a surface layer of sand having a uniform thickness and a sealed hollow portion surrounded by the surface layer.

[0002]

2. Description of the Related Art A hollow core for casting has conventionally been used. Japanese Patent Publication No. 61-47621 discloses a conventional method for forming a hollow core. FIG. 8 illustrates this conventional method. In FIG. 8, a core forming die 40 is provided on a turntable 42.
The turntable 42 is fixed to the upper end of the rotating shaft 41. Sand supply means 43 such as a sand hopper transfers thermosetting molding sand 45 for the core into the cavity 4 of the core forming die 40.
0a. By rotating the shaft 41 in the direction of the arrow 44 while charging the casting sand 45 from the sand supply means 43 into the cavity 40 a of the heated core forming die 40, the casting The sand 45 is adhered to the wall (the side wall of the core mold 40) forming the cavity 40a in the cavity 40a by the centrifugal force and fired to become a hollow core.

[0003]

However, in the above-mentioned conventional example, since the core forming die has only one rotating shaft, if the core shape becomes complicated, a good quality hollow core is formed. There was a disadvantage that it became difficult. Therefore, an object of the present invention is to eliminate the above-mentioned disadvantages and to form a core having a uniform surface layer of sand even in a core having a complicated shape and a hollow portion surrounded by the surface layer of sand. It is to provide a core forming method capable of forming a core.

[0004]

Means for Solving the Problems To solve the above-mentioned problems, the construction of the invention of the present application is to introduce a curable molding sand into a cavity of a core mold and rotate the core mold to rotate the core. In the hollow core forming method for forming the core, the core forming die is rotated so as to have a plurality of rotating shafts.

[0005]

According to the structure of the present invention, in the process of forming the hollow core, the core forming die is rotated around a plurality of rotation axes as rotation centers. Since the hardening molding sand in the cavity moves in these multiple centrifugal directions, it is possible to homogenize the thickness of the surface molding sand layer and form a hollow core with few defects even for cores with complicated shapes. Become.

[0006]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a process of one embodiment of the present invention, and FIG. 2 shows a cross-sectional structure taken along line AA of FIG. 1 and 2,
The core molding die I0 comprises a fixed die 11 and a movable die 12,
A cavity 14 is formed in the core mold 10.
Reference numeral 15 denotes a baseboard portion of the cavity 14. The blow head 20 is disposed close to and above the opening surface of the cavity 14. Blow nozzle 21 is blow head 2
No. 0 casting sand outlet. First, the blow nozzle 21
The core thermosetting molding sand 30 necessary for securing a predetermined core thickness is blown into the cavity 14. Thereafter, the blow head 20 is pulled up. next,
As shown in FIGS. 3 and 4, the heated lid 13 is pressed against the upper surface 16 of the core mold 10 so as to close the opening surface of the cavity 14. At this time, in order to prevent the molding sand 30 from leaking, the upper surface 16 of the core mold 10 and the lid 13
And the string-shaped heat-resistant sealing material 17 is arranged between the two.

[0007] Next, as shown in FIG.
When the core is rotated in the directions of arrows 17a, 17b, and 17c (clockwise or counterclockwise) around the X axis, the Y axis, and the Z axis by the machine while heating
The casting sand 30 is applied to the wall 14a of the cavity 14 (core mold 1).
0 side wall) and fired to form a hollow core 31 having a predetermined thickness. In this case, the core mold 1
The machine that rotates 0 is driven by a motor and X
A first frame that rotates about an axis, a second frame that is driven by a motor around a Y axis based on the first frame, and a motor that rotates about a Z axis based on the second frame. The core molding die 10 is fixed to the third frame, which is rotated by rotation. The method of rotating the core forming die 10 is determined by the shape of the core 31, and a method of rotating the core forming die 10 suitable for the shape of the core 31 is employed. FIG. 6 shows the relationship between the blow amount of the casting sand 30 and the rotation speed of the core forming die 10 at this time. For example, when the amount of the molding sand 30 is reduced in order to reduce the thickness of the core 31, the rotation speed must be high. On the other hand, as the amount of the molding sand 30 increases, the rotation speed may be reduced, and finally, when there is no hollow, the rotation is unnecessary.

FIG. 7 shows the relationship between the blow amount (blow-out amount) of the casting sand 30 and the thickness of the core 31. Individual core 31
In the case of manufacturing the castings, the blow amount of the molding sand 30 necessary for obtaining the wall thickness required for obtaining the strength, rigidity and the like required for each core is obtained from FIG. At this time, it is necessary to satisfy the condition of FIG. In this manner, in the molding process of the core 31, the plurality of rotating shafts (X
Since the core mold 10 can be rotated about the axis (Y axis, Y axis, and Z axis) as the center of rotation, the direction of the centrifugal force is plural. For this reason, since the molding sand 30 in the cavity 14 moves in the plurality of centrifugal directions, the core 31 having a complicated shape is formed.
In this case, the closed hollow core 31 can be uniformly and sufficiently hollowed. In the above embodiment, the number of rotation axes of the core mold is three, but is not limited to this, and may be two or more. In particular, in the case of a simple-shaped core, the number of rotation axes may be two. The curable molding sand is not limited to thermosetting, but may be gas-curing or self-curing molding sand.

[0009]

As described above in detail, according to the core molding method of the present invention, even in a core having a complicated shape, the core can be hollowed uniformly and sufficiently. A core having a surface layer of natural sand and a hollow surrounded by the surface layer of sand can be formed. Further, there are the following additional effects. That is, the amount of foundry sand can be significantly reduced, which greatly contributes to cost reduction of the hollow core. Although it depends on the shape of the core, the cost can be reduced by about 30% as compared with the conventional case. Since the core forming method according to the present invention forms a closed hollow core, it can be applied to any product. For example, the present invention is also applicable to a core of a water jacket of a cylinder head. For this reason, if all the cores necessary for casting are hollowed, sand removal becomes extremely easy, for example, a sand baking process (heat treatment) carried out to remove sand.
Can be abolished. Therefore, in the process of knocking out sand by directly hitting a cast product (knockout process), which is conventionally performed for sand removal, the impact force can be reduced, and the hitting cracks and residual Problems such as the application of stress are completely eliminated. Further, the noise environment of the work can be improved by reducing the impact force.

Further, since the pre-breakability of sand is remarkably improved, in addition to the above-described effects, sand which could not be completely removed by the conventional sand removal process and the heat treatment process remains in the product, which is an important point which leads to a major problem. The problem of residual sand in the final product can be solved. Further, since the core is significantly reduced in weight, the workability of core delivery can be improved. Specifically, the operation of handling a heavy core is eliminated, and damage due to breakage of the core is reduced, and the casting cycle is shortened. Furthermore, since the core sand is reduced, the core gas pressure (the pressure of the gas generated by the evaporation of the binder of the molding sand) generated during the conventional casting is reduced.
Elimination of hot water wrinkles can be expected, and the quality and stability of cast products can be improved. For this reason, by reducing the absolute amount of the generated gas amount, it is expected that the solid matter (dust) of the gas adhering to the mold machine is reduced and the working environment is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the steps of one embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a front view showing the step, and is a continuation of FIG.

FIG. 4 is a right side view of the one shown in FIG. 3;

FIG. 5 is a perspective view showing the step, and is a continuation of FIG. 3;

FIG. 6 is a graph showing characteristics of the process.

FIG. 7 is a graph showing other characteristics of the process.

FIG. 8 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Core molding die 14 Cavity 17a, 17b, 17c Rotation direction 30 Foundry sand 31 Core X, Y, Z Rotation axis

Claims (1)

(57) [Claims] 1. A hollow core molding method in which a curable molding sand is charged into a cavity of a core molding die, and the core molding die is rotated to form a core. A core forming method, wherein the core is rotated so as to be plural.