JP2900846B2 - How to pull out resin core - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for extracting and removing a core made of resin from a cast product.

[0002]

2. Description of the Related Art When manufacturing a metal casting, a core is used to form a blank (hollow) portion or an undercut portion which cannot be formed by an outer mold (die). Conventional cores include a sand core and a metal core, but they are selectively used depending on working pressure and the like. In particular, in the die casting method with a high casting pressure (about 100 MPa), the strength of the core is required. Therefore, it is not possible to cope with the sand core, and the metal core is used, or the casting pressure is lowered and the sand core is used. Yes, it is. Sand cores are mainly used in low pressure casting and gravity casting. Recently, a core using a resin has been proposed (for example, JP-A-6-91345).

[0003]

However, the conventional core has the following problems. For sand cores, if a low-strength (low bonding force) core is used, the core will be deformed and broken under high casting pressure conditions such as die casting, so the required quality (shape and precision) will be lower. I can't put it out. When a high-strength core is used, there is a high possibility that foreign matter (sand) remains in the cast-out portion of the product, and if the foreign matter remains, there is a problem that the quality of the product deteriorates. Since the metal core has high strength, it can be used even at a high casting pressure, but there is a problem that the core cannot be removed in some cases. Recently, only a simple resin core having a simple shape is used in consideration of core removal after casting. A core having a complicated shape cannot be removed unless the resin is completely melted, and remains in the product when the resin is melted, and thus is not employed. An object of the present invention is to provide a method of extracting a resin core, which can easily extract a core from a cast product in a softened state (in a state not being a molten state) even if the core has a complicated shape. It is in.

[0004]

The method of the present invention for achieving the above object is as follows. Prepare a resin core having a separation portion that separates when a tensile force is applied, after casting, soften the resin core, apply a tensile force to the resin core,
A method for extracting a resin core, comprising the steps of: separating the resin core by the separating section into a plurality of core portions; and extracting each core portion from a product hole corresponding to the core portion.

[0005]

According to the method of the present invention, the resin core is provided with a separating portion, and after casting, the resin core is separated at the separating portion by applying a tensile force in a softened state of the resin core. Is deformed and pulled out from a hole (for example, a baseboard hole) of a cast product corresponding to the above, so that the core can be easily pulled out even if it has a complicated shape. In this case, since the resin is in a softened state, it can transmit a tensile force, and can be pulled out while the entire resin core is in a continuous state, and does not remain in the product unlike the molten resin.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the method for extracting a resin core of the present invention will be described below with reference to the drawings. The method of drawing the resin core common to all the embodiments of the present invention includes a step of preparing a resin core 1 made of a thermoplastic resin and having a separating portion 3 that separates when a tensile force is applied; The core 1 is softened by heat, a tensile force is applied to the resin core 1 and the resin core 1 is separated at the separation unit 3 into a plurality of parts.
A hole 4 (for example, a hole through which a baseboard for supporting a core passes from a mold) and pulling out. Since the resin core 1 is separated into a plurality of parts and pulled out, the resin core 1 can be taken out from the product 2. Further, since the resin core 1 is pulled out in a semi-hardened softened state before melting, the resin core 1 can transmit the pulling force by itself, and does not become liquid and remain in the product 2, and the separated cores The entire part can be pulled out. In addition, since the resin core 1 is in a softened state, the resin core 1 is deformed and can easily pass through the hole 4.

FIG. 1 shows the relationship between the softening of the resin core and the solidification of the molten metal of the product in terms of temperature and time. What the melt feed start t ₀ of about 700 ° C. are, depending on the product size, with about 30 seconds to 3 minutes, and the temperature drops by about 550 ° C., to complete the coagulation. On the other hand, the temperature of the resin core 1 rises by receiving heat from the molten metal, but has not risen to the resin softening start point (about 200 ° C.) by the time t ₃ at which the solidification of the molten metal is completed. Therefore, the molten metal completes solidification while the resin core 1 is in a hard state. Therefore, the resin core 1 is not deformed even if it receives high pressure from the molten metal, and a cast product 2 with high dimensional accuracy can be obtained. Then, the resin core 1 receives the residual heat of the product and rises in temperature, and the resin softening point (about 200 ° C.)
And the temperature gradually rises. When the temperature of the resin rises to about 250 ° C. due to the residual heat of the product, the melting point is reached in the case of a crystalline resin (for example, polypropylene) and the whole resin is in a molten state, and in the case of an amorphous resin (for example, polycarbonate), Although it does not have a melting point, the degree of softening increases. Mold opening of the mold, later than the freezing completion t ₃ of the molten metal, preferably takes place at a time t ₄ later than the time the resin reaches a softening point. The removal of the resin core 1 from the cast product 2, for example, the drawing, is performed by opening the mold t _4.
This is done later while the resin is in a semi-rigid state, and thus in the case of crystalline resins, before the resin melts. Here means that the semi-rigid in the range of 10 ⁰ to 10 ^-5 GPa in elastic modulus. At this point, the resin is softened but not melted, so that the tensile force can be transmitted by the resin core 1 itself. Withdrawn from product 2. Examples of the thermoplastic resin exhibiting the above-described phase change with temperature include polycarbonate, polypropylene, and a copolymer of propylene and ethylene.

FIGS. 2 and 3 show an example of the relationship between a cast product 2 and a resin core 1 to which the method of the present invention is applied. 2 and 3 show a state in which the resin core 1 is still included in the cast product 2 in a state after casting, and the resin core 1 has to be withdrawn from the cast product 2 from now on. However, in this state, the resin core 1 extends annularly in the cast product 2 over the entire circumference, so that the resin core cannot be pulled out from the baseboard hole 4. In order to pull out the resin core from the baseboard 4, the resin core 1 must be separated into at least two pieces in the circumferential direction. For this purpose, the resin core 1 is provided with a separating portion 3 that separates when a tensile force is applied at the stage of setting the resin core in the mold. The resin core 1 can take various structures depending on the structure of the separating portion 3. In the present invention, the resin core 1 is divided into a combined resin core and a notch-type integrated resin core according to the structure of the separating portion 3, and the combined resin core is composed of an adhesive resin core and a non-adhesive resin core. And divided into Hereinafter, these will be described as examples of the present invention.

First Embodiment A resin core that cannot be easily removed from the baseboard hole 4 is divided and molded, and a core used in combination before casting is referred to as a combined resin core. This combination includes a method using an adhesive and a method using no adhesive. The first embodiment of the present invention employs a resin core bonded with an adhesive (hereinafter, referred to as a resin core).
(Referred to as an adhesive resin core 1A). The outline of the adhesive resin core 1A is shown in FIGS.
The core separating section 3 divides the core into a plurality of core portions,
A convex portion 3a having a narrower tip side on the joint surface of one core portion
Is received on the joint surface of the other core portion,
A concave portion 3b having a wide exit side is formed, and the convex portion 3a and the concave portion 3b are engaged with each other, and are bonded with an adhesive 7 on a joint surface. It is desirable to provide a small protrusion 5 and a small groove 6 as shown in FIG. 5 on at least one of the joining surfaces of the core portion. FIG. 6 shows the state of FIG. 4 in which the concave and convex portions are engaged with each other and bonded with an adhesive 7, and FIGS.
The case where the concave-convex engagement / adhesion structure of the first embodiment is applied to the core is shown. By providing the groove 6, the surface area of the concave-convex engaging surface can be increased, the effect of the adhesive 7 can be more effectively obtained, and the adhesion of the core can be strengthened. Also, protrusion 5
Is intended to seal the joint surface by using the elasticity of the resin when the core mating surfaces are joined together at the time of bonding. This prevents the adhesive 7 from jumping out of the joint surface and preventing the molten metal (eg, aluminum alloy) from being inserted into the joint surface during casting, thereby improving the quality of the cast product. In addition, the concavo-convex structure positions the divided cores when they are combined with each other, and maintains the dimension and shape of the cores with high accuracy. By using the combination core as described above, in the core removal step after casting, the resin core 1 is softened (either softened by residual heat of the product or softened by heating; the same applies hereinafter). When a tensile force is applied to the core 1, the core 1 is separated at the separation portion 3 formed of the joining surface, so that the core 1 is easily removed through the baseboard hole 4 without leaving resin or foreign matter in the product. it can.

Second Embodiment A second embodiment of the present invention relates to a method of extracting a resin core (hereinafter, referred to as a non-adhesive resin core 1B) which is combined without using an adhesive among the combined resin cores. It is related. 8 to 11 show the non-adhesive resin core 1B. The separation part 3 of the core divides the core into a plurality of core parts, and a convex part 3c having a thicker tip side is provided on a joint surface of one core part and a convex part is formed on a joint surface of the other core part. A joint surface of any one of the core portions, which is formed by forming a concave portion 3d having a narrow outlet for receiving the concave portion 3c and engaging the convex portion 3c and the concave portion 3d in a hard core state so as not to be detached. 9 and 10, a projection 5 is formed, and the projection 5 has a sealing function of preventing the molten metal from entering the joining surface. As shown in FIG. 11, a ridge 8 may be provided on at least one of the side surfaces of the convex portion 3c and the concave portion 3d. This ridge 8
Has a function of preventing the convex portion 3c and the concave portion 3d from shifting. After the casting is performed using such a non-adhesive combination resin core 1B, in the core removal step, the resin core 1
When a tensile force is applied to the resin core 1 in the softened state, the convex portion 3c and the concave portion 3d are deformed, and the core 1 is separated into a plurality of core portions at the separating portion 3, and the core portion is separated. Can be easily removed through each skirting hole. Since the resin is not in a molten state, that is, in a softened state and can transmit a tensile force, it can be pulled out without leaving the core in the product.

Third Embodiment A third embodiment of the present invention relates to a resin core 1 which cannot be easily removed from a baseboard hole 4 is provided with notches at a plurality of positions, and the notch portion is formed when a tensile force is applied. The present invention relates to a core drawing method using a resin core (hereinafter, referred to as a notch-type integrated resin core 1C) which can be separated and pulled out by using a core. The outline of the notch integrated resin core 1C is as follows.
This is shown in FIGS. The separating portion 3 of the core is composed of a plurality of notches 3e formed in the resin core 1, and when a tensile force is applied, the resin core is separated at the notch 3e and divided into a plurality of core portions. It has become. Notch 3e
Is, for example, a V notch, preferably a core.
It is provided in correspondence with the position on the outer peripheral surface. FIG. 12 shows a case where the core which is not easily removed as shown in FIGS. 2 and 3 is formed from a notch-type integral resin core 1C. FIG. 13 shows a case where a water jacket core of a cylinder block of a four-cylinder internal combustion engine is constituted by a notch-type integral resin core 1C. FIG. 14 shows a case where a water jacket core of a cylinder head of a four-cylinder internal combustion engine is a notch type. Integrated resin core 1C
Are shown. In FIGS. 13 and 14, reference numeral 3 denotes a separating portion formed of a notch, and reference numeral 4 denotes a portion corresponding to a baseboard hole. After performing casting using the notch-type integral resin core 1C as described above, in the core removal step, when a tensile force is applied to the resin core 1 in a softened state of the resin core 1, the core becomes The core can be easily removed by separating at the notch 3e into a plurality of core portions and pulling out each core portion using the respective baseboard holes 4. Further, since the core is not in a molten state, the entire core portion is integrally pulled out, and the core resin does not remain in the product.

[0012]

According to the present invention, a separation portion is provided in advance in the resin core, and the core is separated from the casting product at the time of pulling out from the cast product, so that the core can be easily pulled out. Can be pulled out. Further, since the core resin is pulled out when it is in a softened state, the resin does not remain in the cast product unlike the molten resin.

[Brief description of the drawings]

FIG. 1 is a temperature characteristic diagram of a resin material of a resin core applicable to any embodiment of the present invention.

FIG. 2 is a perspective view of a cast product including a resin core.

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a partial perspective view of a resin core showing a separating portion in the first embodiment of the present invention.

FIG. 5 is a sectional view taken along line 5-5 in FIG. 4;

6 is a cross-sectional view when the resin cores of FIG. 3 are combined and adhered.

FIG. 7 is a perspective view of the case where the separation unit structure of FIG. 4 is applied to the core of FIG. 2;

FIG. 8 is a partial perspective view of a resin core showing a separating portion according to a second embodiment of the present invention.

9 is a sectional view taken along line 9-9 in FIG.

FIG. 10 is a sectional view when the resin core of FIG. 8 is combined.

11 is a side view of a separation portion of the resin core of FIG.

FIG. 12 is a perspective view of a resin core showing a separating portion in a third embodiment of the present invention.

FIG. 13 is a perspective view of a case where the separation unit structure of FIG. 12 is applied to a cylinder flock water jacket core of an internal combustion engine.

FIG. 14 is a perspective view showing a case where the separating portion structure of FIG. 12 is applied to a water jacket core of a cylinder head of an internal combustion engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core 1A Adhesive combination resin core 1B Non-adhesion combination resin core 1C Notch-type integral resin core 2 Casting product 3 Separation part 3a Convex part 3b Concave part 3c Convex part 3d Concave part 3e Notch 4 Baseboard hole

──────────────────────────────────────────────────の Continuation of the front page (72) Inventor Shuichi Tomita 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-7-284902 (JP, A) (58) Fields investigated (Int.Cl. ⁶ , DB name) B22C 9/10 B22D 17/22 B22D 29/00

Claims (1)

(57) [Claims] 1. A resin core having a separating portion that separates when a tensile force is applied is prepared. After casting, the resin core is softened, a tensile force is applied to the resin core, and the resin core is removed. A method for extracting a resin core comprising the steps of: separating the core into a plurality of cores in the separation section; and extracting each core from a product hole corresponding to the core.