JP2003191049A - Supporting structure of sand core for cylinder block - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To nicely cast a cylinder block having high precision by effectively preventing damage of a sand core at the casting time. <P>SOLUTION: A supporting structure for supporting the sand core in a metallic mold is provided with a first supporting part 26. This first supporting part 26 is constituted of the sand core and provided with an almost triangular-shaped foot part 38 having three flattened surfaces 46a-46c in the cross section shape and the foot part 38 is housed into a recessed part 48 formed in a movable mold 18. Positioning support of the sand core is performed by supporting the flattened surfaces 46a-46c at three parts with flattened projecting parts 50a-50c arranged on the wall surface 48a of the recessed part 48. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sand core which is disposed in a mold for casting a cylinder block and forms a water jacket on a wall surface of the cylinder block. To
The present invention relates to a support structure for a sand core for a cylinder block for supporting in a mold. 2. Description of the Related Art In general, a cylinder block constituting an internal combustion engine is manufactured by high-pressure casting. In this high-pressure casting, a sand core for a cylinder block is used to form a water jacket on the wall surface of the cylinder block. Various proposals have heretofore been made for positioning and supporting this kind of sand core in a mold. For example, a method for holding a sand core disclosed in Japanese Patent No. 2648865 and its holding are disclosed. Devices are known. As shown in FIG. 6, the prior art includes a fixed die 1, movable core dies 2a and 2b, and a movable die 3, and a columnar projection projecting from the movable die 3. The cylinder block cavity 5 is formed by inserting the liner 4 into 3a. [0005] A sand core holding pin 8 is inserted into a hole 7 provided in the movable die 3, and a sand core 9 is held via the sand core holding pin 8. The sand core 9 includes a main body 9a forming a water jacket, a projection 9b for holding the water core in the cavity 5, and a leg 9c. The leg 9c is a communication port of the top deck of the cylinder block. To form In the prior art, the legs 9c of the sand core 9 are provided in parallel with the axial direction of the cylinder bore (the axial direction of the liner 4). The sand core 9 is positioned by inserting the leg 9c into the recess (baseboard) 3b of the movable die 3. At this time, when the gap S between the leg 9c and the concave portion 3b is large, the positioning accuracy of the sand core 9 is reduced. On the other hand, when the gap S is small, the leg 9c It has been pointed out that a problem such as deformation or breakage may occur in the device. SUMMARY OF THE INVENTION The present invention is to solve this kind of problem, and it is possible to reliably prevent damage to a sand core and efficiently cast a high-precision cylinder block. It is an object of the present invention to provide a support structure. In the support structure for a sand core for a cylinder block according to the present invention, a sand core forming a water jacket on the wall surface of the cylinder block is provided with a cylinder bore of the cylinder block. A leg is formed parallel to the axial direction, and the cross-sectional shape of the leg is
It is set to a polygonal shape having three or more flat surfaces. On the other hand, the mold is provided with a recess for accommodating the leg and supporting the leg at three or more points. For this reason, a sufficient gap can be provided between the leg and the recess, and the difference in the filling pressure of the molten metal in the recess can be suppressed to effectively prevent the leg from being broken or the like. It becomes possible to prevent. In addition, since the leg is supported at three or more points in the recess, the leg can be accurately positioned and supported with respect to the recess. Thereby, the positioning accuracy of the sand core is improved, and it becomes possible to cast a cylinder block having a water jacket efficiently and with high accuracy. FIG. 1 is a partially sectional explanatory view of a mold 12 incorporating a support structure 10 for a sand core for a cylinder block according to an embodiment of the present invention. The mold 12 includes a fixed mold 14 and an intermediate movable mold 1.
6a, 16b, and a movable mold 18;
Is provided with a bore pin 20. By covering the sleeve 22 with the bore pin 20, a cylinder block cavity 24 is formed in the mold 12. In the cavity 24, a sand core 34 for forming the water jacket 32 of the cylinder block 30 is disposed via first and second support portions 26 and 28 constituting the support structure 10. As shown in FIGS. 2 and 3, the sand core 34 surrounds each of the cylinder bores 36 of the cylinder block 30, and comprises a plurality of legs 38 constituting the first support portion 26, and a sand core body. 40 are provided integrally. Sun core body 40
On the side (outer surface) 42a opposite to the cylinder bore 36,
A baseboard portion 44 constituting the second support portion 28 is formed. As shown in FIG. 4, the leg 38 has a polygonal cross section, for example, a substantially triangular shape having three flat surfaces 46a, 46b and 46c. Movable mold 18
Has a recess 48 for accommodating the leg 38,
Flat projections 50a, 50b and 50c for supporting the flat surfaces 46a to 46c of the legs 38 are provided on the wall surface 48a of the recess 48. The wall surface 48 of the leg portion 38 and the concave portion 48
a is maintained at, for example, 2 mm, and the width H2 of the flat protrusions 50a to 50c is 2 m.
m, and the flat protrusions 50a to 50c and the flat surfaces 46a to 46c
The gap H3 between 46c is set to 0.5 mm. [0014] As shown in FIG.
It is formed in a substantially semi-ring shape protruding by a predetermined length from 2a. As shown in FIG.
4, the baseboard section 44 and the intermediate movable mold 16
Between the a and 16b, there is provided a basin 52 for allowing the flow of the molten metal. The intermediate movable dies 16a and 16b have a sand core 3
The pin member 54 supporting the 4 corresponds to the hot water dispenser 52,
It is fixed by welding or screwing. The pin member 54 is formed of the same material as the intermediate movable dies 16a and 16b, and engages with the pedestal portion 56 fixed to the intermediate movable dies 16a and 16b and the baseboard portion 44 of the sand core 34. And is integrally formed with the cylindrical portion 58. The operation of the support structure 10 thus configured will be described below. First, as shown in FIG. 1, in a state where the mold 12 is clamped, a molten metal such as molten aluminum is supplied to the cavity 24 through a runner and a gate (not shown).
Is filled in. Then, the molten metal in the cavity 24 becomes 8
High pressure casting is performed at a pressure of about 5 MPa to 100 MPa, and solidification of the molten metal is started. At this time, a high pressure acts on the sand core 34, and the sand core 34 contracts. Specifically, as shown in FIG. 5, the surface 42b of the sand core 34 on the cylinder bore 36 side is used.
, A casting pressure F1 acts outward, while a casting pressure F1 acts inward on a side surface 42a of the sand core 34 opposite to the cylinder bore 36 side. In this case, in the second support portion 28, the sand core 3
In the baseboard portion 44 of the bath 4, a hot-water supply portion 5 allowing the flow of the molten metal is provided.
2, and a pin member 54 that engages with the baseboard portion 44 corresponding to the hot water supply portion 52 is provided on the intermediate movable molds 16a and 16b. For this reason, on the side surface 42a of the sand core 34,
A substantially uniform casting pressure F1 acts on the entire surface, and the casting pressure F1 is balanced with the casting pressure F1 acting on the surface 42b of the sand core 34. Therefore, it is possible to reliably prevent the sand core 34 from being partially deformed. On the other hand, in the first support portion 26, as shown in FIG. 4, the cross-sectional shape of the leg portion 38 is changed to three flat surfaces 46a-46.
c and a movable mold 18
The flat surfaces 46a to 46c are connected to the flat projections 50a to 50c.
A concave portion 48 for supporting three points at 0c is formed. A gap H1 of, for example, about 2 mm is provided between the outer peripheral surface of the leg portion 38 and the wall surface 48a of the concave portion 48, and the flat surfaces 46a to 46c and the flat protrusions 5 are provided.
A gap H3 of, for example, about 0.5 mm is provided between 0a to 50c. Thereby, the molten metal can be reliably filled around the leg portion 38. Therefore, the leg 3
There is no difference in filling pressure around 8, and damage such as breakage of the leg 38 can be reliably prevented. Further, the leg 38 has flat surfaces 46a-46.
c and the flat protrusions 50a to 50c are supported at three points. Accordingly, the leg 38 can be easily and reliably positioned and supported with respect to the concave portion 48, and the sand core 34 can be positioned with high accuracy in the cavity 24. Therefore, in the present embodiment, an effect is obtained that the cylinder block 30 having the water jacket 32 having a desired shape can be manufactured efficiently and with high accuracy. In the present embodiment, the cross-sectional shape of the leg 38 is set to be substantially triangular. However, the present invention is not limited to this. And so on. In the support structure for a sand core for a cylinder block according to the present invention, the sand core forming the water jacket on the wall surface of the cylinder block has a polygonal shape having a flat surface having a cross section of 3 or more. Is formed, and this leg is accommodated in a recess provided in the mold and supported at three or more points. For this reason, a sufficient gap can be provided between the leg and the concave portion to suppress the difference in the filling pressure of the molten metal, and it is possible to effectively prevent the leg from being broken or the like. Moreover, since the leg is supported at three or more points in the recess, the leg can be accurately positioned and supported with respect to the recess. This makes it possible to cast a cylinder block having a water jacket efficiently and with high precision.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross-sectional explanatory view of a mold incorporating a support structure for a sand core for a cylinder block according to an embodiment of the present invention. FIG. 2 is a schematic perspective explanatory view of a sand core placed in the mold. FIG. 3 is an explanatory plan view of the sand core. FIG. 4 is an explanatory plan view of a first support portion constituting the support structure. FIG. 5 is an explanatory view when a casting pressure acts on the sand core in the mold. FIG. 6 is a schematic explanatory view of a holding device for a sand core according to a conventional technique. [Description of Signs] 10 ... Support structure 12 ... Mold 14 ... Fixed mold 16a, 16b ...
Intermediate movable mold 18 Movable mold 20 Bore pin 22 Sleeve 24 Cavities 26 and 28 Support 30 Cylinder block 32 Water jacket 34 Sand core 36 Cylinder bore 38 Leg 40 Sand core body 44 Baseboards 46a to 46c: Flat surface 48: Depressions 50a to 50c: Flat protrusions 52: Hot water supply

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02F 1/10 F02F 1/10 D (72) Inventor Shigemitsu Nakabayashi 1-10- 1 Honda Engineering Co., Ltd. F term (reference) 3G024 AA26 AA38 CA05 DA18 FA14 GA04 GA05 GA06 GA36 4E093 QA01 QB05 QD01 QD10 UA02

Claims (1)

Claims: 1. A sand core, which is provided in a mold for casting a cylinder block and forms a water jacket on a wall surface of the cylinder block, is supported in the mold. The sand core support structure for a cylinder block, wherein the sand core has legs formed in parallel with an axial direction of a cylinder bore constituting the cylinder block, and the cross-sectional shape of the legs is A polygonal shape having three or more flat surfaces, wherein the mold is provided with a recess for accommodating the leg and supporting the leg at three or more points. Core support structure.