JPH0120043Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field This invention relates to a structure for supporting and fixing a sand core to a mold, and is particularly concerned with a core support structure that is effective in low pressure casting methods, such as a cylinder. It can be used in the production field of automobile parts such as heads and road wheels.

PRIOR ART For example, a low pressure casting method is known as an example of a method for manufacturing a cylinder head made of aluminum alloy.As is well known, the low pressure casting method involves inserting a stalk into molten metal in a closed crucible, and A mold is tightly attached to the upper end of the crucible, and compressed air is sent into the crucible to apply pressure to push the molten metal from the stalk into the mold. After the molten metal solidifies in the mold, the pressure in the crucible is released and it solidifies. This is a method of obtaining castings by descending molten metal. Therefore, in the case of horizontally split molds used in the low-pressure casting method, the sprue opens downward, so if it is necessary to remove or insert the sprue near the sprue, it is necessary to remove the casting pin or the insert. must be attached to the bottom of the upper mold. Conventionally, in such cases, metal casting pins and inserts have been fixed to the upper mold by mechanical means such as screws, so that the metal casting pins and inserts have no contact with the casting. Since it was extracted upward, it was necessary to use a tapered cast pin or insert whose width (or radius) became smaller at the bottom in order to obtain the necessary draft angle. However, in the conventional method, the wall thickness near the sprue had to be thicker, in other words, a considerable amount of wasted material was produced, which resulted in galling defects due to overheating of the cast pin, prolongation of the casting cycle, and There were problems such as increased machining allowance on the product.

Purpose of the invention This invention was made in view of the above-mentioned circumstances, and the purpose is to provide a core support structure that can reduce or eliminate the waste material caused by using the core.

Structure and operation of the device This device forms a vent in the upper mold that opens at the location where the core is to be attached, communicates the vent with a low-pressure suction source, and holds the sand core in contact with the open end of the vent. It is characterized in that it is configured to be suctioned and fixed to the upper mold through a vent. Therefore, if the core near the sprue of the low-pressure casting mold is supported as described above, the upper mold and the lower mold will be fixed. After the molten metal solidifies in the cavity thus formed, by releasing the suction on the sand core, the sand core can be pulled out downward relative to the casting. Since the shape can be made to have a larger shape, it is possible to reduce or eliminate wasted meat.

Embodiments Below, embodiments of this invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view showing an embodiment of this invention, and a mold 1 shown here has a horizontally divided upper mold 2. The cavity 4 having the shape shown in the figure is formed by the lower mold 3 and the lower mold 3, and the sprue 5 opening on the lower surface of the lower mold 3 is aligned with the upper end opening of the stalk 6 and is in close contact with the stalk 6. . Said sprue 5
A sand core 7 attached to the center of the lower surface of the upper die 2 is disposed in the center of the upper mold 2. The sand core 7 has a substantially truncated conical shape and is arranged so that the radius becomes larger on the sprue 5 side, that is, so-called reverse draft, and a positioning protrusion 8 is provided on the upper end surface of the sand core 7. In contrast, a positioning recess 9 into which the protrusion 8 of the sand core 7 is fitted is formed at the center of the lower surface of the upper mold 2. In addition, a plurality of (three in the figure) vents 10 are formed in the upper mold 2 and open at locations on the lower surface of the upper mold 2 where the inner surface of the recess 9 and the upper end surface of the sand core 7 come into contact. The other side of the vent 10 communicates with a connecting hole 11 formed in the upper mold 2. Further, the upper die 2 has a second hole connecting the uppermost end of the cavity 4 and the connecting hole 11.
A vent 12 is formed. Note that a filter 13 made of a porous material is inserted into the end of each of these vents 10 and 12 on the cavity 4 side. The connecting hole 11 is connected to a low-pressure suction source 14 such as a vacuum pump, and the gas inside the cavity 4 is sucked through the vents 10 and 12 by the low-pressure suction source 14. Note that the low-pressure suction source 14 only needs to be able to suction the gas inside the cavity 4, and in addition to the vacuum pump, for example, the portion of the connecting hole 11 where the vents 10 and 12 are opened may be used as a ventilator. Alternatively, the pressure may be lowered by increasing the flow rate of the air supplied to the inside of the connecting hole 11 at the ventilate, thereby sucking the gas inside the cavity 4 through the vents 10 and 12. Further, reference numeral 15 in FIG. 1 is a wire mesh, which is placed between the mold 1 and the stalk 6 in order to supplementarily prevent the sand core 7 from falling. Furthermore, the reference numeral 16 in FIG. 1 indicates a nest.

Therefore, in the mold 1 having the above-mentioned configuration,
With the sand core 7 housed in the cavity 4, the upper mold 2 and the lower mold 3 are brought together and brought into close contact with the upper end surface of the stalk 6, and then gas is sucked from inside the cavity 4 using a low-pressure suction source. For example, the sand core 7 placed in the cavity 4 is sucked up together with the gas toward the upper mold 2 side, and as a result, the protrusion 8 on the upper end surface of the sand core 7 fits into the recess 9 and is positioned. It is suctioned and fixed to the center of the lower surface of the upper mold 2. After setting in this manner, the molten metal is raised from the stalk 6 and supplied into the cavity 4. In that case,
Since the gas in the cavity 4 is forcibly exhausted through the vents 10 and 12, the molten metal quickly spreads throughout the interior of the cavity 4, improving the filling performance of the molten metal. Further, gas generated from the sand core 7 as the molten metal is filled is also exhausted from the vents 10 and 12.
The molten metal in the cavity 4 begins to solidify almost at the same time as the filling is completed, but due to the air cooling effect by continuing to exhaust the gas in the cavity 4 to the upper side of the cavity 4 through the vents 10 and 12, and the cooling effect of the sand core 7. Due to the heat retention effect due to the thermal conductivity being lower than that of the upper mold 2 and lower mold 3, the molten metal gradually solidifies from the upper side of the cavity 4 toward the sprue 5, and therefore solidifies near the sprue 5. It is possible to prevent the stalk from clogging due to the preceding.

When removing the sand core 7 from the obtained casting, the suction via the vent 10 is released and the sand core 7 is removed.
It is sufficient to pull it out from the casting part downward in Fig. 1. In other words, by supporting the sand core 7 as described above, it becomes possible to perform casting using a core with a slope opposite to that of the conventional method, and as a result, waste material near the sprue 5 can be reduced or eliminated. The dimensions indicated by symbols A and B in FIG. 1 are the amount of decrease in wall thickness compared to the conventional example.

Effects of the device As is clear from the above explanation, this device forms a vent in the upper mold that opens at the location where the core is to be attached, connects the vent to a low-pressure suction source, and contacts the open end of the vent. Since the sand core is suctioned and fixed to the upper mold through the vent, if the sand core is supported near the sprue of the mold as described above when performing low pressure casting, the sand core can be easily fixed to the upper mold through the vent. It is possible to set the so-called reverse draft angle, which is opposite to the conventional method, and as a result, it is possible to reduce or eliminate waste when casting out the vicinity of the sprue. In addition, with the core support structure of this invention, suction is carried out from within the cavity until casting is completed, which improves the filling performance of the molten metal, and also due to the air cooling effect of suction and exhaust and the heat retention effect of the sand core. Directional solidification occurs, in which solidification occurs gradually toward the sprue side, and as a result, stalk clogging can be reliably prevented.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of this invention. 1... Mold, 2... Upper mold, 3... Lower mold, 4... Cavity, 5... Sprue, 6... Stoke, 7... Sand core, 10
...Vent, 14...Low pressure suction source.

Claims (1)

[Scope of utility model registration request] A cavity is formed by the upper mold and the lower mold, and a sprue that opens into the cavity is provided in the lower mold, and a vent is provided in the upper mold for suctioning and exhausting air from the cavity. In a mold for low-pressure casting in which a sand core is installed on the same axis as the sprue, another vent is provided on the lower surface of the upper mold at the location where the sand core is butted and installed, and the vent is connected to the low-pressure casting mold. A support structure for a core in a mold, characterized in that the sand core is communicated with a suction source and brought into contact with the open end of the vent, and is suction-fixed to the upper mold via the vent.