JPH0712535B2 - High pressure casting - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high-pressure casting method in which a sand core is fitted into a core holding member for casting, and particularly 800 kg / cm.
^{2 When} casting at a high pressure of about ² and a core holding member,
It almost certainly prevents the occurrence of flash between the sand core and the sand core.

(Prior Art) A conventionally known high-pressure casting method is, for example, Japanese Patent Laid-Open No. 59-23.
Some are disclosed in Japanese Patent No. 2654.

Here, in order to perform high-pressure casting of a cylinder block including a cylinder liner and a water jacket surrounding the cylinder liner, as shown in FIG. 5, a fixed lower mold 1, a movable upper mold 2, and both of these molds are used. A jacket mold 5 mounted on the movable upper mold 2 via a mounting seat 4 between the intermediate mold 3 which is located between and is openable and closable in the left-right direction.
Is projected downward into the cavity 7, and with respect to the jacket mold 5 here, as is apparent from the enlarged view of a part thereof in FIG.
The sand core 9 is fitted into the notch 8 provided in the die peripheral wall 7 extending in the axial direction, and the sand core 9 is
A predetermined gap 11 is left between the upper edge of the jacket mold 5 and the top wall 10 of the jacket mold 5.

Here, in the conventional high pressure casting method, as shown in FIG. 5, 800 kg / cm of molten metal was introduced from the runner 12 into the cavity 6.
After pouring the molten metal at a high pressure of about ² and solidifying the molten metal, the jacket mold 5 and the mold peripheral wall 7 are moved to the sand core 9 into the cylinder block based on the rising operation of the movable upper mold 2. It is carried out by pulling it upward while remaining, according to which, as shown in FIG. 7 which shows a cylinder lock as a cast product in a plan view, the mold peripheral wall 7 is attached to the upper deck thereof.
The opening 13 of the water jacket as the extraction mark of the core and the bridge portion 14 of the required thickness located at the upper portion of the core sand are formed under the action of the gap 11 described above. Compared to the so-called open deck type cylinder block, 14 provides a sufficient improvement in the rigidity of the cylinder block.

(Problems to be Solved by the Invention) However, in such a conventional method, the sand core having the desired shape and size is provided in the notch 8 of the mold peripheral wall 7 as the core holding member. Since the high pressure molten metal is to be poured in the state where 9 is closely fitted,
Under the relationship between the molding accuracy of the sand core 9 and the machining accuracy of the cutout portion 8, there is a gap between the two, and the sand when the sand core 9 is fitted into the cutout portion 8 When a gap is generated between the cores 9 due to cracking or chipping of the core 9, there is a problem in that burrs are generated by inserting the molten metal into the gaps. This is due to the specifications of the cylinder block. By changing the above, as shown in the bottom perspective view in FIG. 8, to the notch 8 provided in the arc-shaped portion of the mold peripheral wall 7,
Mold engaging part whose both ends have a V shape in plan view
9a, which is particularly serious when a sand core 9 having a wall thickness equal to that of the mold peripheral wall 7 is fitted, and such burr is cooled unless it is completely removed. It was virtually impossible to ensure a smooth water circulation.

The present invention advantageously solves the above problems of the prior art, and in particular, by focusing on the deformation of the sand core based on the differential force difference between the molding pressure of the sand core and the pouring pressure, It is intended to provide a high pressure casting method capable of almost certainly preventing the occurrence of flash.

(Means for Solving Problems) The high-pressure casting method of the present invention, when performing casting in a state where the sand core is fitted to the core holding member, the core holding member is
For the action direction of the molten metal pressure, fit a sand core having a size somewhat larger than the required size, and at the time of pouring, deform the sand core to the required size by the melt pressure, and at the same time, It is liquid-tightly adhered to the core holding member.

(Operation) According to this high-pressure casting method, the initial size of the sand core is set to be slightly larger than that required in the direction of action of the molten metal pressure,
The sand core is changed in volume based on the pressure difference between the molding pressure of the sand core and the molten metal pressure of up to 800 kg / cm ² , while the sand core is expanded in the direction in which the molten metal pressure does not act. The dimension, for example, the thickness of the sand core is exactly as intended, and the sand core is liquid-tightly adhered to the core holding member, and the high-pressure molten metal is inserted between them.
It is possible to almost certainly prevent the occurrence of flash.

(Example) Below, the Example of this invention is described based on an illustrated example.

FIG. 1 is a longitudinal sectional view illustrating an embodiment of the present invention, in which 21 is a fixed lower mold, 22 is a movable upper mold, and 23 is a movable lower mold.
Indicates an intermediate type interposed between the two types,
The intermediate mold 23 is a mold half 23a that can be opened and closed in the left-right direction in the figure.
With 23b.

Reference numeral 24 denotes a mold holder attached to the movable upper mold 22, and a jacket mold 25 as an example of a core holding member projects downward from the mold holder 24 into the cavity 26.

Here, the mold peripheral wall 27 of this jacket mold 25, particularly the arcuate portion thereof, extends in the axial direction thereof and completely penetrates the wall portion, as shown in the enlarged sectional view of FIG. The cutout portion 28, in other words, a cutout portion having a narrowed portion that contributes to the formation of the bridge portion is provided at the upper end portion, and the cutout portion 28 is positioned below the narrowed portion and curved in an arc shape as a whole, A sand core 30 having a metal mold engaging portion 29 protruding in a V shape at both ends is fitted.

The sand core 30 here is, on the wall surface of the mold peripheral wall 27, the side on which the molten metal pressure acts, the cylinder liner 31 side and the intermediate mold 35 side located in the center of the mold peripheral wall 27 in the figure, respectively. Has a thickness that projects somewhat. The fitting tolerance of the die engaging portion 29 of the sand core 30 and the cutout portion 28 is
It can be similar to that in the prior art.

Under the condition that the sand core 30 is fitted in this way, about 800 k of molten metal is introduced from the runner 33 shown in FIG. 1 into the cavity 26.
When filled at a pressure of g / cm ² , the sand core 30
In the figure, by receiving the molten metal pressure from both inside and outside, based on the differential pressure between the molding pressure and the molten metal pressure, as shown in FIG. 3, until the thickness becomes almost equal to that of the die peripheral wall 27, that is, While the thickness can be reduced until it reaches the required thickness, it will swell in the circumferential direction of the mold peripheral wall 27,
For example, when fitting the sand core 30 to the notch 28,
Sand core even if there is a gap between them
The close contact between the mold 30 and the peripheral wall 27 of the mold is always and surely realized.

Therefore, after the molten metal is solidified, the jacket mold 25 is pulled upward while the sand core 30 remains in the cylinder block based on the rise of the movable upper mold 22, as shown in FIG. Then, the water jacket 32 and the bridge portion 33 having a predetermined size are formed without any flash.

Although the present invention has been described above based on the illustrated example, the present invention can be applied not only to the case where the sand core is subjected to the melt pressure only on one surface thereof, but also to the case where the sand core is subjected to the melt pressure only from the side. It is also possible to apply it when the molten metal pressure is applied from the direction of two or more surfaces adjacent to each other.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view illustrating an embodiment of the present invention, FIG. 2 is a cross-sectional view showing the relationship between a sand core and a core holding member before pouring, and FIG. 3 is a second view after pouring. FIG. 4 is a cross-sectional view showing the same relationship as that of FIG. 4, FIG. 4 is a cross-sectional view of a main part of a cylinder block as a casting, FIG. 5 is a vertical cross-sectional view illustrating a conventional casting mold, and FIG. 6 is a conventional sand core. And FIG. 7 is a plan view of the cylinder block, and FIG. 8 is a bottom perspective view of a jacket mold showing a modification of the specifications. 21 …… Fixed lower mold, 22 …… Movable upper mold 23 …… Intermediate mold, 25 …… Jacket mold 26 …… Cavity, 27 …… Mold peripheral wall 28 …… Notched part, 29 …… Mold engaging part 30 ...... Sunako

Claims (1)

[Claims] 1. When casting is performed with a sand core fitted to a core holding member, the core holding member has a size slightly larger than a required size with respect to a molten metal pressure acting direction. A high-pressure casting method characterized in that a sand core having the above is fitted, and at the time of pouring, the sand core is deformed to a required size by a molten metal pressure and is brought into liquid tight contact with a core holding member.