JPH01130840A - Method for molding green sand core - Google Patents

Abstract

PURPOSE:To manufacture a core having the specific strength by adjusting as pressing the special structural sticking rod having impeller in green sand in a cavity. CONSTITUTION:After packing the green sand 86 in the cavity 84, the cylindrical sticking rod 40 and sticking rod 30 providing the impeller 50 as relatively movable in the inner part thereof 40 are pressed in the green sand 86. Successively, under stopping condition of the impeller part 50 to the press-in position, after drawing out the sticking rod body part 40, the impeller 50 is rotated and the green sand 86 beforehand. charged is compressed by pushing in the sticking rod body part 40. By this method, the green sand core having the prescribed strength can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a green sand core molding method applied to manufacturing a casting core.

(Prior art) Conventionally, the shell method, cold box method, etc. using an organic binder have been common as casting core manufacturing methods, but inorganic binders widely used for the main mold have been used. The green sand core molding method used is attracting attention as it is superior in terms of cost and production control.

In this green sand core molding method, first, as shown in FIG. Filled with green sand 6 by blowing from a roller 5.

Thereafter, as shown in FIG. 4B, the piercing rod 7 is press-fitted into the green sand 6 in the cavity 4 to increase the filling density of the green sand and obtain a predetermined core strength. Next, pull out the piercing rod 7t from the mold 3,
Upper mold 1 and lower mold 2f: The molds are opened, and the molds are removed with the hole where the piercing rod 7 was pulled out, leaving a green sand core 8 shaped along the cavity 4 as shown in the figure (C) K. get.

(Problems to be Solved by the Invention) By the way, in the above-mentioned conventional green sand core manufacturing method, the strength of the obtained core is determined by the press-fitting position of the piercing rod, the shape, the press-in force, the press-fitting direction, and the green sand timeability. be done. On the other hand, depending on the shape of the core, there are restrictions on the press-fitting position, shape, and press-fitting direction of the piercing rod. The shape of the core that can be molded is limited, and the result is 1!
+There was a problem that all possible products were restricted.

Additionally, green sand with uniform characteristics is not always used in green sand core production lines, and for this reason, the shape of the piercing rod,
Even if the core is molded by setting conditions such as press force, the strength of each core may vary, and it is not easy to always obtain a core with a constant strength. .

In addition, since the piercing rod is press-fitted by sliding movement in one direction, the portion 9 of the cavity 4 that is in the shadow with respect to the pressing direction of the piercing and the pier, as shown in Fig. 4 (1), A core that does not have the appropriate strength in the relevant area because filling and compaction of green sand is suppressed? There was a problem with the molding.

In addition, Japanese Utility Model Application No. 59-185043 discloses a piercing rod for molding green sand cores with the purpose of obtaining a core having uniform strength throughout.

This piercing rod for molding green sand cores is shown in Figures 5(a) and (b).
), the piercing rod 21 is formed of an elastic member, and the piercing rod 21 is press-fitted into green sand filled in the cavity 23 of the mold 22.
1 is partially expanded, and this expansion increases the strength of the core in the horizontal direction, thereby achieving uniform strength even in the large-diameter stepped hole portion 24, for example.

By the way, in this green sand core molding piercing rod, piercing rod 21
The thrust rod 21 is
partially expands. Therefore, depending on the characteristics of the green sand filled in the cavity 25, the expansion portion and the amount of expansion change. In this case, the characteristics of green sand are particularly the compactability value (C/B value), which indicates the volume ratio before and after compression when green sand is compressed with a constant force. on the other hand,
As mentioned above, the green sand core production line does not necessarily use green sand with uniform characteristics. For this reason, green sand properties may vary depending on the core molding. As a result,
When green sand with a certain C/B value is used, for example, Fig. 5 (
Even if the part located in the large-diameter stepped hole 24 expands as shown in a), if green sand with a different C/B value is used, the large-diameter hole 24 will expand as shown in FIG. 5(b), for example. Expansion occurred in the upper part of the stepped hole 24, and a core metal of appropriate strength could not be obtained. This problem becomes more noticeable as the number of parts where the filling density is to be increased increases, as in the case where there are a plurality of large-diameter stepped holes 24, for example, as shown in FIG.

In addition, the piercing rod 21 has a certain expansion limit depending on the material, and if a flexible material is used to increase the expansion amount depending on the cavity shape, on the contrary, the green sand cannot be sufficiently compressed, and this surface However, there was a problem in that its use was limited depending on the shape of the cavity.

In addition, as shown in FIG. 7, the cavity forms a large-diameter stepped hole 241 that corresponds only to a part of the circumferential direction of the axis of the piercing rod 21, and the portion where the filling density should be increased is the portion of the piercing rod 21. If the core does not spread uniformly in the circumferential direction of the axis, the compression and contraction forces will not be spread evenly and it will not be possible to obtain a core with uniform strength.

In addition, with this piercing rod 21, for example, as shown in FIG. 5(a), a thin wall portion 25 is partially formed in the core, resulting in a weak portion in terms of strength, and a core with uniform strength is obtained in the same manner as described above. I couldn't do that.

As described above, the above-mentioned piercing rod for making green sand cores has various problems, and it has not been a sufficient solution to improve the problems of the above-mentioned conventional green sand core making method. .

The present invention has been made in view of the above-mentioned problems, and is capable of securing strength and strength without being limited in shape, and is suitable for use in various products (
C. It is an object of the present invention to provide a method for molding green sand cores that can be used in a wide range of processes and that can mold cores having a predetermined strength without being affected by the characteristics of green sand.

(Means for Solving the Problems) The configuration of the present invention to achieve the above object is shown in FIG. 1(a).
, (b) , To explain with reference to FIGS. 2 and 3, the method of the present invention is to fill the green sand 86 into the cavity 84 of the mold 83 by blowing, and then to fill the green sand 86 with:
A stabbing rod 3 comprising a cylindrical stabbing rod main body 40 and an impeller section 50 disposed within the stabbing rod main body 40 so as to be relatively movable.
0, then pull out the stabbing rod main body 40 with the impeller section 50 held in the press-in position, and then rotate the impeller section 50 to remove the raw material previously stored in the stabbing rod main body 40. The gist is to compress the green sand 86 in the cavity 84 by extruding green sand of the same type as the sand 86.

(Function) With the above configuration, the present invention allows the green sand previously stored in the internal space of the piercing rod main body to be discharged at a predetermined pressure by the plate portion, and the discharged green sand to be filled in advance into the cavity. As the green sand that was filled in is compressed,
The green sand can be compressed according to the shape of the cavity and the characteristics of the green sand, and as a result, it is possible to create a core that always has the specified strength regardless of the characteristics of the green sand, and has uniform strength regardless of the shape. Can be molded.

(Example) Hereinafter, a green sand core molding method according to an example of the present invention will be described with reference to the accompanying drawings. In addition, in this example, FIG.
4. (b) Prepare the piercing rod 30 as shown in FIGS. 2 and 3 in advance.

The piercing rod 14isa includes a piercing rod main body portion 40 and an impeller portion 5.
It is composed of 0.

The stab rod main body 40 has a substantially cylindrical shape, and an inner wall 42 defining an internal space 41 is formed with a guide groove (not shown) extending in the axial direction. A substantially cylindrical impeller portion 50i is housed in the internal space 41.

The impeller portion 50 has a substantially conical tip portion 51 and a shaft portion 52 with a small diameter, and a plate portion 53 connected to the tip portion 51 via the shaft portion 52, and a plate portion 53 that is slightly shorter in diameter than the inner wall 42. The impeller shaft part 54 has a diameter of a paddle and is connected to the shaft part 52.

A longitudinal projection (not shown) is formed on the outer circumferential surface of each of the tip portion 51 and the impeller shaft portion 54 to fit into a guide groove formed in the inner wall 42 of the stab rod main body portion 4o. and the piercing rod main body 40 can mutually move in the axial direction with the protrusion fitted into the guide groove, and can also rotate together in the circumferential direction.

A plate 55 is provided on the shaft portion 52 of the plate portion 56. When the impeller portion 5o is rotated in the direction of arrow A in FIG.
(in the direction of arrow B) at a predetermined pressure.

The impeller shaft portion 54 is provided with a through hole 57 that connects the space portion 56 formed in the plate portion 53 and the external space. Green sand of the same type as green sand 86, which will be described later, is previously stored in the space 56 by blowing through the through hole 57.

Next, the manufacturing process procedure of this example is shown in FIG. 1(a).

(b) Explain based on K. As shown, 81.82
are an upper mold and a lower mold, respectively, and the upper mold 81 and the lower mold 82 are overlapped at the parting surface to form a mold 83. Type 83
A cavity 84 is formed therein. Further, a blow port 85 is connected to the cavity 84 and is formed along the parting surface.

First, the inside of the cavity 84 ((green sand 86) is filled with blow ink from the blow port 85.Next, the piercing rod 30 configured as described above is press-fitted into the green sand 86 in the cavity 84 from the blow port 85. .

Next, the stab rod main body section 40 is pulled out while the impeller section 50 is kept at the insertion position, and when the tip thereof passes through the plate section 55, the withdrawal is stopped.

Next, when the stabbing rod body 40 is held in the hand and rotated in the direction of the arrow, the plate 53 also rotates, and the green sand stored in the space 56 is moved by the rotational force of the plate 55. It is discharged in the direction of arrow B, which is the outer circumferential direction. As a result, the green sand 86, which has been filled in the cavity 84 in advance, is compressed under a predetermined pressure together with the green sand, thereby increasing the packing density. In this way, Figure 4 (
In the conventional methods as explained in a), (b), and (C), even the portions where the compression force was incomplete can be compressed with an appropriate force to mold a core with uniform packing density.

After that, the rotation of the impeller part 50 is stopped and the impeller part 50 is stopped.
0 and the stab rod main body 40 are pulled out from the mold 83 all at once, and the upper mold 81 and the lower mold 82 are opened to remove the core.

Subsequently, when molding a new core, the cavity 84 is first filled with green sand 86 in the same way as described above, and the core is then molded in the same procedure as described above, but the filled green sand 86 If the characteristics of the green sand 86 are different from those in the previous core molding, the rotational force of the impeller section 50 is adjusted to compress the green sand 86, and filling is performed according to the characteristics of the green sand 86. In this way, even if green sand with different characteristics is used in the core production line, cores with a predetermined strength can always be molded.

In addition, in this example, as shown in FIG. 1(b) 7i:
Although we have taken as an example a case in which the rotational force of the plate 55 is directed in the direction of arrow B as the impeller portion 50 rotates in the direction of arrow A, it is possible to
For example, it can be directed in the direction of arrow C. By changing the direction of the rotational force in this way, the green sand in the area in that direction becomes easier to compress.

Further, in this embodiment, two cases are described in which the impeller section 50 is manually rotated, but a separate motor may be installed and the impeller section 50 may be configured to be rotated by this motor. In this case, higher compression force can be obtained compared to manual operation, and
By controlling the speed, the compression force can be adjusted over a wider range compared to manual compression.

Further, in this embodiment, the case where one continuous plate 55 is provided in the plate portion 53 is taken as an example, but the number is not limited to -, and a plurality of plates may be provided.

(Effects of the Invention) As explained above, the present invention involves filling the cavity of a core molding mold with green sand by blowing, and in this green sand,
The cylindrical main body has an impeller part movable relative to the main body and provided with a plate in the internal space of the main body, and a piercing rod in which green sand of the same type as the green sand is stored in advance in the installation space of the plate. Press fit, then pull out the piercing rod main body while keeping the impeller inside, and then rotate the impeller to compress the green sand in the cavity, so uniform strength can be ensured regardless of the shape. It has the effect that it can be used for a wide variety of products, and that cores having a predetermined strength can be molded without being affected by the properties of green sand.

[Brief explanation of the drawing]

The first factor <a), (b) is a cross-sectional view showing a mold and a piercing rod to which a green sand core molding method according to an embodiment of the present invention is applied;
Fig. 2 is a sectional view taken along the line l-11 in Fig. 1, Fig. 3 is a schematic perspective view showing the plate portion of the stabbing rod, Fig. 4(a),
(b) and (C) are schematic diagrams showing the molding process of an example of the conventional green sand core molding method, and Figures 5 (a) and (b) are molds to which the conventional green sand core molding method is applied. 6 is a sectional view showing another mold cavity to which the same molding method is applied, and FIG. 7 is a sectional view showing another mold cavity to which the same molding method is applied. It is. 30... Pierce rod, 40... Pierce rod main body, 41...
・. Internal space, 50... Impeller part, 53... Plate part, 55... Plate, 56... Space part, 83...
・Mold, 84...Cavity, 86...Green sand. Patent applicant: Toyota Motor Corporation its 1 Figure " (b) 'zr'J 2 Figure 3 Figure 4 (G) (C) Only Figure 5 (Q) (b) 6th do:
Miya 7

Claims (1)

[Claims] The cavity of the core molding mold is filled with green sand by blowing, and then a cylindrical main body and a single sheet are placed in the green sand so as to be movable relative to each other in the internal space of the main body. Press-fit the impeller with the above-mentioned plate, then pull out the impeller with the impeller fixed, and then rotate the impeller and attach it to the impeller in advance. A green sand core molding method characterized by compressing green sand in a cavity by extruding green sand of the same type as the stored green sand.