JP5545822B2 - Cylinder head casting method - Google Patents

Description

  The present invention relates to a cylinder head casting method, and more particularly to a technique for discharging gas generated in a water jacket core during casting to the outside of a mold.

  Manufacture of a cylinder head as an engine part is performed by pouring hot water in a state in which oil jacket cores and water jacket cores are stacked in a predetermined order in a mold by, for example, a low pressure casting method. In view of the complicated shape of the oil jacket and water jacket, the core used at this time is usually a so-called collapsible core formed by bundling shell sand with a resin as a binder. Yes. Therefore, at the time of casting, moisture contained in the core and resin serving as a binder are vaporized by the heat of the molten metal to generate gas.

  This type of gas, in particular, gas generated from a water jacket core surrounded by molten metal, remains as bubbles in the molten metal, thereby forming a casting defect. Therefore, measures are taken to allow the generated gas to escape to the outside of the mold. As an example of this measure, in Patent Document 1 below, a gas suction passage is provided in a baseboard portion of a water jacket core stacked in a mold, and gas generated in the water jacket core is passed through the suction passage. A method of discharging the gas to the outside of the mold by vacuum suction is disclosed.

JP-A-5-146862

  However, as described in Patent Document 1, simply by sucking the gas generated from the water jacket core from the skirting portion of the core, the gas generated inside the water jacket core having a complicated shape, In particular, it is difficult to effectively discharge the gas generated in the center of the water jacket core surrounded by the molten metal. Further, when the gas suction operation is controlled by the suction device, the facilities and control become complicated.

  Therefore, for example, as shown in FIG. 4, a through hole 52 is provided in a portion where a slight gap 56 is formed between the oil jacket core 55 and the water jacket core 57. By providing a gas vent hole 53 communicating with the outside of the upper mold 51 (mold) in the vicinity of the through hole 52 provided in the child 55 (in this figure, the position facing the mold clamping direction) A simple gas venting structure in which the gas generated in the child 57 is discharged to the outside of the mold through the through hole 52 and the gas vent hole 53 can be considered.

  However, in the case of adopting the above configuration, when the molten metal M poured into the cavity 54 enters the gap 56 between the water jacket core 57 and the oil jacket core 55, the molten metal M and the oil There is a risk of entering the gas vent hole 53 of the upper die 51 through the through hole 52 provided in the jacket core 55. In order to prevent the molten metal M from entering, for example, as shown in FIG. 5, it is necessary to provide a vent 58 in the gas vent hole 53 of the upper die 51. (Slit 58a) is closed with the molten metal M. For this reason, it takes time and cost to frequently replace the vent 58, and there remains a problem that practicality (mass productivity) is poor.

  In view of the above circumstances, at the time of casting, the efficiency of discharging the gas generated from the water jacket core can be increased, and the situation where the molten metal enters the gas discharge hole provided in the mold can be prevented, and mass production can be achieved. It is a technical problem to be solved by the present invention to provide an excellent method for casting a cylinder head.

The solution to the above-described problem is achieved by the cylinder head casting method according to the present invention. That is, this casting method is a cylinder head casting method in which hot water is poured in a state where an oil jacket core and a water jacket core are stacked in a mold having an upper mold and a lower mold. The portion of the water jacket core that is closest to or abuts with the water jacket core is provided with a recess that opens to either the upper or lower side, and one of the upper mold and the lower mold has one end at the recess forming portion. opened toward the other end is characterized with a point communicating hole communicates with the outside of the mold are al provided. Incidentally, it intends Kokodei "closest or abutting portion" refers to the range of the laminated portion located inside the mold, the core width wood for placement at a predetermined position in the cavity naturally Is not included in the above range.

  The core used for casting this type of product (cylinder head), as described above, uses a sand-like body that is bound with an appropriate binder (resin) and molded into a predetermined shape. Therefore, it has a so-called porous structure and has a certain air permeability. Also, since the water jacket core is molded integrally with the cast product with the molten metal surrounded by the molten metal, an oil jacket core that cannot be brought close to the original for sand removal after casting. There is a case where a portion close to or in contact with the water jacket core is provided. The present invention has been made paying attention to these points, and is provided with a recess in the portion of the oil jacket core closest to or in contact with the water jacket core, and either the upper mold or the lower mold. Is provided with a so-called vent hole for communicating with the outside of the mold at the other end. With this configuration, the bottom of the recess provided in the oil jacket core can be thinned to the extent that the passage of gas is allowed compared to the thickness around the recess. Moreover, a communicating hole can be arrange | positioned on the extension line | wire of the direction through which gas passes the bottom part of these recessed parts. Therefore, when the mold and the core take the above-described form, the gas generated in the water jacket core at the time of casting is further performed by casting with a thickness that allows gas to pass through the bottom of the recess. It passes through the part where both cores are closest to or abut against each other and the bottom of the recess, and reaches the communication hole provided in one of the upper and lower molds as it is. Therefore, as shown in FIG. 4, the gas generated in the water jacket core can be effectively discharged to the outside of the mold as well as the gas generated in the central portion of the jacket. Moreover, since the gas passes through the bottom of the recess provided in the oil jacket core, the molten metal enters the gap between the cores in the portion where the oil jacket core and the water jacket core are closest to each other. Even in this case, the molten metal that has entered can be blocked from the concave portion, and the molten metal can be reliably prevented from entering the communication hole. Therefore, it is not necessary to provide a vent (see FIG. 5), and it does not take time to replace parts.

  In this case, for example, the concave portion may be opened toward the communication hole, and the bottom portion of the concave portion may be brought closest to or in contact with the water jacket core. By doing in this way, the gas generated in the oil jacket core is also easily collected in the space in the recess through the inner surface of the recess. Therefore, not only the gas generated in the water jacket core but also the gas generated in the oil jacket core can be efficiently discharged out of the mold.

  As described above, according to the casting method of the cylinder head according to the present invention, the molten metal enters the gas discharge hole provided in the mold while enhancing the discharge efficiency of the gas generated from the water jacket core during casting. The situation can be prevented and the mass productivity can be improved.

It is sectional drawing of the casting apparatus which concerns on one Embodiment of this invention. It is AA sectional drawing of the casting apparatus shown in FIG. 1, Comprising: It is the principal part expanded sectional view of the casting apparatus which shows the degassing structure inside a casting_mold | template. FIG. 2 is a plan view of the oil jacket core shown in FIG. It is a figure for demonstrating the content of the invention used as the premise of this invention, Comprising: It is a principal part expanded sectional view of the casting apparatus which shows the degassing structure inside a casting_mold | template. It is a figure for demonstrating the content of the invention used as the premise of this invention, Comprising: It is a principal part expanded sectional view of the casting apparatus which shows the degassing structure inside a casting_mold | template.

  Hereinafter, an embodiment of a casting method of a cylinder head according to the present invention will be described with reference to the drawings. In the following description, a case where a cylinder head is cast by low pressure casting will be described as an example.

  FIG. 1 is a view for explaining an outline of a casting method according to the present embodiment, and shows a cross-sectional view of a main part of a casting apparatus (low pressure casting apparatus) used in the casting method. Here, the left-right direction in FIG. 1 coincides with the longitudinal direction of the cylinder head as a cast product. As shown in the figure, this casting apparatus includes a mold 3 having an upper mold 1 and a lower mold 2, and a cavity 4 formed inside the mold 3 by clamping the mold 3 (upper mold 1 and lower mold 2). The oil jacket core 5 and the water jacket core 7 stacked in a predetermined order inside the mold 3, the pouring ports 8 (two locations in this figure) provided in the lower mold 2, and one end to the pouring port 8 And a stalk portion 9 that is connected and has the other end inserted through a molten metal storage portion (not shown).

  Next, arrangement modes of the oil jacket core 5 and the water jacket core 7 will be described. As shown in FIG. 1, the oil jacket core 5 is installed in the mold 3 in a state of being closer to the upper mold 1 than the water jacket core 7. Here, the oil jacket core corresponds to the spark plug insertion side of the cylinder head. The oil jacket core 5 and the water jacket core 7 are integrally provided with baseboard portions 5a and 7a at both ends in the longitudinal direction. Then, the two cores 5 and 7 are integrally placed on the lower mold 2 in a state where the baseboard parts 5a and 7a are overlapped with each other, and then the upper mold 1 is lowered and overlapped with each other. By sandwiching the combined baseboard portions 5a and 7a between the upper mold 1 and the lower mold 2, the two cores 5 and 7 are held in a state of being positioned in the mold 3, and thereby, a predetermined shape ( A cavity 4 having a shape corresponding to the actual part of the cylinder head) is formed.

  FIG. 2 is an AA cross-sectional view of the casting apparatus shown in FIG. 1 and shows an enlarged view of the gas vent structure inside the mold 3. As shown in FIG. 2, the water jacket core 7 disposed at a position farther from the upper mold 1 than the oil jacket core 5 has a protruding portion 7b protruding toward the upper mold 1 side in the thickness direction. Is provided. Further, a receiving portion 5b for receiving the protruding portion 7b is provided on the lower surface of the oil jacket core 5 so as to be depressed by one step from the periphery. The oil jacket 5 and the water jacket core 7 are overlapped to form the mold 3. In the state installed inside, the protrusion part 7b and the receiving part 5b are mutually fitted. In this case, the protruding portion 7 b and the receiving portion 5 b form a portion that is closest or abuts between the oil jacket core 5 and the water jacket core 7. The protrusion 7b is provided for sand removal after casting, for example, and has a substantially columnar shape. In this embodiment, as shown in FIG. 3, portions 5 d and 5 d of the oil jacket core 5 corresponding to the spark plug insertion holes (the spark plug insertion holes are formed by pin portions provided in the upper mold 1. ) Is provided, and the gap 10 as the closest part is formed between the receiving part 5b and the protruding part 7b (see FIG. 2). As will be described later, the gap 10 is preferably set to such a size that the molten metal poured into the cavity 4 does not enter.

  The receiving portion 5 b of the oil jacket core 5 is provided with a concave portion 11 that opens toward either the upper or lower side of the mold 3. In this embodiment, the concave portion 11 has an opening shape toward the upper mold 1 and is formed in a bottomed cylindrical shape with the same central axis as the receiving portion 5b (see FIGS. 2 and 3). . Therefore, the bottom portion 5c of the recess 11 constitutes the lowermost portion of the receiving portion 5b as a part of the oil jacket core 5, and the lower surface thereof has a gap 10 between the lower surface of the receiving portion 5b (the protruding portion 7b). And the same plane).

  Further, the thickness of the bottom 5c is set to such a thickness that allows gas generated in the water jacket core 7 during casting to pass toward the upper mold 1. As a result, the bottom portion 5 c is the thinnest portion of the oil jacket core 5. As a specific example, when the composition of the oil jacket core 5 is granular: silica sand (average particle diameter φ0.3 mm), binder: phenol resin, the bottom 5c has a thickness of 1.0 mm or more and 2.0 mm. Set to:

  At the position of the upper mold 1 facing the recess 11 in the mold clamping direction, a communication hole 12 having one end opened toward the recess 11 and the other end communicating with the outside of the mold 3 is formed. In this embodiment, as shown in FIG. 2, the concave portion 11 and the central axis are made the same so as to penetrate the upper mold 1 vertically. As shown in FIG. 2, there is a predetermined gap 13 between the upper mold 1 and the oil jacket core 5, but naturally the molten metal does not enter the gap 13.

  The cavity 4 is formed by installing the oil jacket core 5 and the water jacket core 7 having the above configuration in the mold 3 and clamping the mold. Then, by using a pressure adjusting means (pressurizing means or pressure reducing means) (not shown), the stalk portion 9 connected to the molten metal reservoir is increased by relatively increasing the pressure in the molten metal reservoir relative to the pressure in the cavity 4. The molten metal is supplied into the cavity 4 through the pouring port 8 (see FIG. 1). Thereby, the molten metal is filled around the water jacket core 7 installed in the cavity 4, and the water jacket core 7 is heated, whereby the resin serving as the binder of the water jacket core 7 is vaporized, Or the water | moisture content inside evaporates. When the pressure of the gas generated from the water jacket core 7 exceeds the liquid pressure of the surrounding molten metal, there is a possibility that the gas is released into the molten metal as bubbles.

  Here, in this casting apparatus, the water jacket core 7 in which the gas is generated is provided with a protruding portion 7b, and a receiving portion 5b adjacent to the protruding portion 7b at a minimum distance is provided in the oil jacket core 5, and A recess 11 that opens toward the upper mold 1 is formed in the receiving portion 5b, and the thickness of the bottom 5c is set to a size that allows the gas to pass toward the upper mold 1. Therefore, the gas generated in the water jacket core 7 flows preferentially toward the bottom portion 5c of the receiving portion 5b that requires less pressure to flow than in the molten metal. Further, at the position of the upper mold 1 facing the concave portion 11 in the mold clamping direction, a communication hole 12 having one end opened toward the concave portion 11 and the other end communicating with the outside of the mold 3 is provided. The gas flowing into 5c passes through the bottom 5c toward the communication hole 12 having a relatively low atmospheric pressure, and further passes through the recess 11 to flow into the communication hole 12. As a result, the gas generated in the water jacket core 7 can be discharged to the outside of the mold 3 without being released into the molten metal, thereby avoiding a situation in which the gas remaining in the molten metal causes casting defects such as a nest. Casting quality can be improved. In particular, in this embodiment, the recess 11 is provided between the portions 5d and 5d of the oil jacket core 5 corresponding to the spark plug insertion holes (see FIG. 3). The protruding portion 7 b of the water jacket core 7 that fits with the receiving portion 5 b can be disposed at a substantially central portion of the water jacket core 7. Therefore, most of the gas generated inside the water jacket core 7 can be efficiently discharged to the outside of the mold 3 (via the bottom 5c, the concave portion 11, and the communication hole 12). Further, in this embodiment, since the concave portion 11 is opened toward the upper mold 1 and formed in a bottomed cylindrical shape, the gas generated in the oil jacket core 5 is also sucked effectively into the concave portion 11, It can be discharged out of the mold 3 through the communication hole 12.

  Further, the bottom portion 5c of the concave portion 11 connected to the communication hole 12 includes a gap 10 between the receiving portion 5b of the oil jacket core 5 and the protruding portion 7b of the water jacket core 7, as shown in FIG. 11 is partitioned. Therefore, as described above, the gap 10 connected to the cavity 4 is preferably small so that the molten metal does not enter. However, even if the molten metal enters the gap 10 for some reason, the molten metal that has entered the molten metal has entered. Can be reliably blocked from the recess 11 to prevent the molten metal from adhering to the communication hole 12.

  As mentioned above, although one Embodiment of the casting method of the cylinder head based on this invention was described, this casting method is not limited to the form of the said illustration of course, and can take arbitrary forms within the scope of the present invention. Is possible.

  For example, in the above-described embodiment, the configuration in which the concave portion 11 is opened toward the upper mold 1 is illustrated, but conversely, the configuration in which the concave portion 11 is opened toward the water jacket core 7 can be taken (not shown). ). In this case, as long as the bottom 5c of the recess 11 is set to a thickness that allows the gas generated in the water jacket core 7 to pass toward the upper mold 1, the same effects as in the above embodiment ( Degassing action and action of preventing molten metal from entering the communication hole 12). Moreover, the bottom part 5c of the recessed part 11 may be provided in the thickness direction one end part of the receiving part 5b as mentioned above, and may be provided in the intermediate part of the thickness direction. In this case, although not shown, the two concave portions 11 and 11 sharing the bottom 5c may be formed so as to open to the upper mold 1 and the water jacket core 7, respectively.

  Further, the formation position of the recess 11 is not particularly limited to the above position. For example, the recess 11 can be formed at an arbitrary plane position of the oil jacket core 5 except for some exceptions (parts whose shape cannot be changed due to the function of the cylinder head) such as a part corresponding to the valve insertion hole. . In short, the concave portion 11 can be formed at a portion that is closest or in contact with the water jacket core 7.

  Of course, other specific forms can be adopted for matters other than the above as long as the technical significance of the present invention is not lost.

DESCRIPTION OF SYMBOLS 1 Upper mold | type 2 Lower mold | type 3 Mold 4 Cavity 5 Oil jacket core 5a, 7a Base board part 5b Receiving part 5c Bottom part 5d, 5d The part corresponding to a spark plug insertion hole 7 Water jacket core 7b Protrusion part 8 Pouring port 9 Stalk Part 10 Clearance 11 Recess 12 Communication hole 13 Clearance 51 Upper mold 52 Through hole 53 Hole 54 Cavity 55 Oil jacket core 56 Clearance 57 Water jacket core 58 Vent 58a Slit M Molten metal

Claims (2)

In a casting method of a cylinder head that performs pouring in a state where an oil jacket core and a water jacket core are stacked in a mold having an upper mold and a lower mold,
A portion of the oil jacket core that is closest to or in contact with the water jacket core is provided with a recess that opens to either the upper or lower side,
Cylinder to either one of the upper and lower molds has one end opened toward the forming portion of said recess, and wherein the other end is a communication hole communicates with the outside of the mold has been found provided Head casting method. The water jacket core is provided with a protruding portion that protrudes in the thickness direction thereof, and the oil jacket core is provided with a receiving portion for receiving the protruding portion in a state of being depressed one step from the periphery thereof. ,
The receiving portion and the projecting portion constitute a portion of the oil jacket core that is closest to or abuts with the water jacket core, and the concave portion is formed at the portion of the receiving portion that is closest to or abuts. The method for casting a cylinder head according to claim 1, which is provided .

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