JP2004230403A - Mold for casting cylinder head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold which can efficiently exhaust gas generated from a port core while precisely positioning the port core. <P>SOLUTION: At a portion corresponding to a core print part 11a of the port core 11 in a center mold 5, a core positioning mechanism 13 so as to insert a positioning pin 15 with a weight 16 in a gas exhausting passage 14, is arranged. When the molds are closed, the core print part 11a and a filter 12 are pushed and positioned with the weights of the positioning pin 15 and the weight 16. At the same time, resin gas generated from the port core 11 by bringing into contact with molten metal, is exhausted to the outer part through the gas exhaust passage 14. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement in a cylinder head casting mold, and in particular, when casting a cylinder head for an internal combustion engine by a low-pressure casting method, accurately positioning a port core arranged at a position to be a supply / exhaust port while accurately positioning the port core. The present invention relates to a structure of a mold capable of efficiently discharging gas generated from a core.
[0002]
[Prior art]
As a technique for positioning a port core in a cylinder head casting mold, for example, a technique described in Patent Document 1 is known. In the technique described in Patent Document 1, the clamp member is moved forward and backward in conjunction with the approaching and separating operations of the horizontal dies that control the casting of the cylinder head itself, and when the clamping of the horizontal dies is completed, the port core is pressed against the lower die. It is designed to be positioned.
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. H5-253663 (FIG. 1)
[0004]
[Problems to be solved by the invention]
The conventional technique described in Patent Document 1 is a method of converting the approach / separation displacement between horizontal dies into the forward / backward displacement of a clamp member in a direction orthogonal thereto, and thus requires a plurality of rods, racks and pinions, and the like. Becomes complicated. Further, in the above-described conventional technique, when a so-called side gate system in which the molten metal is filled with the position immediately adjacent to the baseboard portion of the port core as a gate portion is employed, the port core, which is a sand core, and the molten metal Although the contact area increases and resin gas is generated from the port core, there is no place for the resin gas to escape, and there is still room for improvement. In other words, the resin gas generated from the port core due to the contact between the port core and the molten metal is entangled in the product part, which tends to cause casting defects such as blowholes, shrinkage cavities, and poor running of the molten metal.
[0005]
The present invention has been made in view of the above-mentioned problems, and aims to provide a mold capable of efficiently discharging gas generated from the port core while accurately positioning the port core. Things.
[0006]
[Means for Solving the Problems]
According to the first aspect of the present invention, a port core (sand core) corresponding to an air supply / exhaust port is disposed inside a plurality of mold elements that can be opened and closed, and a baseboard portion of the port core is formed by a plurality of molds. A so-called side gate type mold that casts the cylinder head by filling the molten metal with the position adjacent to the skirting part of the port core as the gate while holding the mold element with pressure. A core positioning mechanism that doubles as a degassing mechanism that discharges gas generated from the port core to the outside, and that presses and positions the baseboard portion of the port core against a specific mold element. I do.
[0007]
The core positioning mechanism is configured with a vertically movable positioning pin having its own weight that can withstand the pressure of the molten metal, and floats by abutting on the baseboard of the port core at the time of mold clamping. The structure shall be such that the baseboard of the port core is pressed against a specific mold element by its own weight.
[0008]
Further, the positioning pin is inserted into the gas vent passage, and the gas vent passage is opened by the floating operation of the positioning pin at the time of mold clamping, or the positioning pin has communication with the gas vent passage. It is desirable that a gas vent hole is formed in the longitudinal direction so as to be constantly maintained.
[0009]
Therefore, in the present invention, when the port cores are clamped together while arranging the port cores on some of the mold elements that constitute the mold, the port cores are the main elements of the core positioning mechanism. It is positioned by a certain positioning pin. Since the positioning pin has its own weight that can withstand the pressure of the molten metal, even if the pressure of the molten metal acts, the positioning state of the port core is held by itself. Also, when filling the molten metal, most of the port core, including the baseboard, comes into contact with the molten metal.Therefore, a large amount of resin gas is generated from the port core, which is a sand core. Is efficiently discharged to the outside with the core positioning mechanism also serving as the gas release mechanism.
[0010]
【The invention's effect】
According to the first aspect of the present invention, the port core can be accurately positioned by the core positioning mechanism having a very simple structure, and the core positioning mechanism also functions as the gas release mechanism. By adopting the gate method, even if a large amount of resin gas is generated from the core of the port, the resin gas can be reliably discharged to the outside. This has the effect of preventing the occurrence of casting defects and improving the quality of the cylinder head.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
1 and 2 are views showing a preferred embodiment of the present invention. In particular, FIG. 1 shows the entire structure of a low-pressure casting type casting apparatus including a so-called two-piece type cylinder head casting mold, and FIG. The details of the main parts of one mold are shown.
[0012]
As shown in FIG. 1, a two-cavity mold (die) 3 for cylinder head casting is mounted on a lower platen 2 located above a holding furnace 1. Are connected via a hot water supply stoke 4. The mold 3 includes a center mold 5 as a mold element which is shared by a pair of left and right product shape space R1 and R2, and a pair of left and right mold elements as a mold element which can approach and separate from the center mold 5. It is composed of horizontal dies 6A and 6B, and a lower die 7 and an upper die 8 which are also mold elements that can be approached and separated from each other. R2 is formed. Then, the molten metal M is supplied from the stalk 4 to the product shape space R1, R2 via the gate section 18 and the gate section (weir) 9. The holding furnace 1 has a known structure in which the mold 3 is filled with the molten metal M by pressurizing the liquid surface with compressed air pressure introduced from the outside.
[0013]
Here, as shown in FIG. 1 as well as in FIG. 2, the gate portion 9 is open to the side portions of the product shape portion spaces R1, R2, and this gate portion structure is called a side gate type. This side gate method has a higher degree of freedom in setting a water-cooled cooling structure on the lower mold 7 side, as compared with a so-called under gate method in which a gate portion 9 is set on the lower surface side of the product shape space R1, R2. It is said that there is an advantage that the temperature rise of the lower mold 7 can be effectively suppressed.
[0014]
As shown in FIG. 2, port cores (sand cores) 10 and 11 corresponding to supply / exhaust ports are arranged in a mold 3 together with a water jacket core (not shown) and the like. The cores 10 and 11 are clamped and held between the center mold 5 and the lower mold 7 or between the horizontal molds 6A and 6B and the lower mold 7 with the mold elements being clamped to each other. It has become.
[0015]
The baseboard portion 11a of one of the port cores 11 is arranged in the gate portion 9 connected to the gate section 18 and substantially also serves as a part of the gate portion 9; The baseboard portion 11a is pressed and held between the center mold 5 and the lower mold 7 in a state of being integrated in advance with the filter 12 to be disposed in the gate section 9. The use of the port core 11, which also serves as a part of the gate portion 9, can delay the solidification progress in the gate section 18 as compared with the product shape section sections R1, R2 due to the heat retaining property of the core sand. effective. A plurality of core positioning mechanisms 13 also serving as a gas release mechanism are arranged in a portion of the center mold 5 that restricts the baseboard portion 11a of the port core 11.
[0016]
The core positioning mechanism 13 has a stepped positioning pin 15 inserted in a stepped hole-shaped gas vent passage 14 formed in the center mold 5 so as to be vertically movable. A weight 16 is placed on the side. The positioning pin 15 and the weight 16 may be integrated in advance, or may be separate from each other. However, if it is assumed that the weight portion 16 is to be actively replaced with one having a different weight, it is desirable that the weight portion 16 be separate. The gas vent hole 14 is open to the atmosphere with a communication passage 17 connected thereto. The total weight of the positioning pin 15 and the weight 16 is set to a size that can sufficiently oppose the pressure of the molten metal described later, and when the mold 3 is opened, the positioning is performed as shown in FIG. The head 15a of the positioning pin 15 abuts the shoulder, which is a stepped portion of the gas vent passage 14, while the tip of the pin 15 projects slightly (a predetermined amount α) downward, and the positioning pin 15 is positioned at the lower limit position. While the gas vent passage 14 is closed together with the regulation, as shown in FIG. 3B, when the mold 3 is clamped, the positioning pin 15 comes into contact with the baseboard portion 11a of the port core 11 so as to be relatively raised. The baseboard 11a is moved downward to position the baseboard 11a by pressing it downward, and at the same time, the gas vent passage 14 is opened.
[0017]
Here, it is desirable that the positioning pin 15 and the weight 16 have heat resistance due to their functions and have a specific gravity as large as possible. For example, a tungsten pin whose weight can be reduced by about 60% compared to an iron-based metal should be used. If used, a predetermined function can be exhibited even if it is small.
[0018]
Therefore, according to the present embodiment, in addition to the center mold 5, which is a mold (mold) element, with the port cores 10, 11 positioned on the lower mold 7, as shown in FIG. 6A, 6B, the lower mold 7 and the upper mold 8 are clamped respectively. As a result, the regular shaped product shape space R1, R2 is formed in the mold 3, and each of the port cores 10, 11 is located between the lower mold 7 and the center mold 5 or between the lower mold 7 and the horizontal molds 6A, 6B6. And temporary positioning will be performed.
[0019]
When the mold clamping is completed, the tip of the positioning pin 15 abuts on the baseboard portion 11a of the port core 11 and relatively moves upward as shown in FIG. Is added to the baseboard 11a of the port core 11, and the final positioning of the port core 11 is performed by pressing the baseboard 11a of the port core 11 against the lower mold 7 with the total weight of the positioning pins 15 and the weights 16. Will be done. This prevents the port core 11 from lifting. At the same time, the upward movement of the positioning pin 15 as shown in the figure opens the gas vent passage 14 which has been closed by the head 15a, and thereby the portion corresponding to the baseboard portion 11a of the port core 11 Is opened to the atmosphere through the gas vent passage 14 and the communication passage 17.
[0020]
When a molten metal M such as an aluminum alloy is poured in this state, the molten metal M pushed up through the stalk 4 of FIG. 1 is filled into the product shape space R1 and R2 through the gate 18 and the filter 12 which is the gate 9. A cylinder head blank is cast. At this time, even if the pressure of the molten metal M acts on the baseboard portion 11a of the port core 11, the total weight of the positioning pins 15 and the weights 16 is large enough to oppose the molten metal pressure as described above. Since this is set in advance, the positioning pin 15 keeps maintaining the positioning state of the port core 11 in FIG.
[0021]
Further, since the port core 11 contacts the high-temperature molten metal M not only at the port equivalent portion but also at the baseboard portion 11a, for example, phenol resin contained as a binder in the port core 11, which is a sand core, is decomposed. As a result, so-called resin gases G such as phenol, formaldehyde, and ammonia are generated, and these resin gases G are smoothly discharged to the outside of the mold 3 through the gas release passage 14 and the communication passage 17 as shown in FIG. . As a result, the resin gas G does not get caught in the product, and it is possible to prevent the occurrence of casting defects such as blowholes, shrinkage cavities, and poor running water.
[0022]
FIG. 5 is a view showing a second embodiment of the present invention, in which a positioning pin 25 and a weight 26 for forming a core positioning mechanism 13 are integrally formed in advance, and the positioning pin 25 has The gas vent hole 27 penetrating in the center direction is formed. According to this embodiment, there is an advantage that the portion corresponding to the baseboard portion 11a of the port core 11 can always communicate with the gas vent passage 14 and be released to the atmosphere regardless of the floating amount of the positioning pin 25.
[0023]
FIG. 6 is a view showing a third embodiment of the present invention. The suction device 20 is connected to the communication passage 17 on the assumption that the structure is the same as that of the first embodiment shown in FIG. Thus, the resin gas generated from the port core 11 is forcibly sucked, and there is an advantage that the efficiency of sucking and discharging gas harmful to product quality is further improved.
[0024]
FIG. 7 is a view showing a fourth embodiment of the present invention, in which the positioning pin 15 and the weight 36 are separately formed, and the weight 36 is subdivided into a plurality of weight pieces 36a, 36a. The total weight of the weight 36 can be adjusted by using one weight of the weight piece 36a as a unit. Therefore, according to this embodiment, there is an advantage that the positioning pressure to be applied to the baseboard portion 11a of the port core 11 can be easily adjusted.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view showing an example of a casting apparatus using a low-pressure casting method.
FIG. 2 is a view showing the first embodiment of the present invention, and is an enlarged explanatory view of a main part of the mold of FIG. 1;
FIG. 3 is an operation explanatory view of a main part of the mold shown in FIG. 2;
FIG. 4 is a functional explanatory view of a main part of the mold shown in FIG. 2;
FIG. 5 is an enlarged explanatory view of a main part showing a second embodiment of the present invention.
FIG. 6 is an enlarged explanatory view of a main part showing a third embodiment of the present invention.
FIG. 7 is an enlarged explanatory view of a main part showing a fourth embodiment of the present invention.
[Explanation of symbols]
3. Mold (die)
5 ... Center type (die element)
6A, 6B ... horizontal type (mold element)
7. Lower mold (mold element)
8 Upper mold (mold element)
9 Gate parts 10, 11 Port core 12 Filters 10a, 11a Baseboard part 13 Core positioning mechanism (gas release mechanism)
14 gas vent passage 15 positioning pin 16 weight 18 gate 20 suction device 25 positioning pin 26 weight 27 gas vent hole 36 weight

Claims (7)

A port core corresponding to an air supply / exhaust port is arranged inside a plurality of mold elements that can be opened and closed, and a baseboard portion of the port core is pressed and held by the plurality of mold elements. A mold for casting a cylinder head by filling molten metal with a position adjacent to the baseboard portion of the gate as a gate portion,
A core positioning mechanism that doubles as a gas release mechanism that discharges gas generated from the port core when filling the molten metal to the outside, and that presses the baseboard of the port core against a specific mold element to position the core. A cylinder head casting mold characterized by the following. The core positioning mechanism is configured with a vertically movable positioning pin having its own weight that can withstand the pressure of the molten metal. The mold for casting a cylinder head according to claim 1, wherein the baseboard portion of the child is pressed against a specific mold element. 3. The cylinder head casting mold according to claim 2, wherein the positioning pin is inserted into the gas vent passage, and the gas vent passage is opened by a floating operation of the positioning pin at the time of mold clamping. The cylinder head casting mold according to claim 3, wherein a gas vent hole is formed in the positioning pin along the longitudinal direction so as to always maintain communication of the gas vent passage. The cylinder head casting mold according to claim 2 or 3, wherein the positioning pin is divided into a pin body and a weight, and the weight is replaceable with a different weight. The gas venting mechanism includes a gas venting passage and a suction device connected to the gas venting passage, and is configured to forcibly suction at least gas generated from a port core at the time of filling the molten metal. 5. The mold for casting a cylinder head according to any one of 5. The cylinder head casting mold according to claim 5, wherein the positioning pin and the weight are made of a metal material having a large specific gravity.

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