JP2006297414A - Method and device for holding collapsible sand core - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for holding a collapsible sand core and a holding device, wherein even in the case of being the sand core having poor collapsibility, the removal of the sand from the opening hole of a cast product is made to easy and also, the invasion of molten metal between the collapsible sand core and a projecting part for holding the core, is prevented at the casting time. <P>SOLUTION: When the sand core 10 is held in a cavity 1a demarcated in a metallic mold 1 composed of a movable metallic mold 21 and a fixed metallic mold 22, pins 4 for holding as cast, projected from the movable metallic mold 21 are inserted into at least one holding hole 12 formed in the sand core 10. The pins 4 for holding as cast, are projected from a flattened surface 21A of a basic seat 3 forming an opening hole part in the cast product by arranging the basic seat at the position of the cavity surface 21A of the movable metallic mold 21, and the sand core 10 is held by abutting the flattened surface 31 on the whole circumference of the peripheral part 11a of the sand core 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for holding a collapsible sand core and a collapsible sand core holding device, and more particularly, to a method for holding a collapsible sand core and a collapsible sand core holding device that suppress the occurrence of extra-wall protrusions.

  In Patent Document 1, a collapsible sand core is not provided with a skirting board, but a core holding projection is protruded from a mold, and the core is held in a holding hole formed in the collapsing sand core. A technique for inserting a protrusion and holding a collapsible sand core in a cavity is disclosed.

In collapsible sand cores for die casting, it is common to use a high-strength phenolic resin as a binder to prevent damage to the sand core even when injection molding a molten metal such as aluminum at high speed and high pressure. is there. However, when using a collapsible sand core containing phenol resin as a binder, the disintegration property is inferior, and therefore it is necessary to provide an opening in the cast product to facilitate sanding.
Japanese Patent No. 3274669

  When the opening is provided, the core holding protrusion protrudes from the opening to hold the collapsible sand core. In this case, a part of the cast molten metal is from the periphery of the opening. In some cases, a gap (clearance) between the core holding protrusion and the collapsible sand core may enter. As a result, surplus protrusions with some core sand adhering to the vicinity of the opening of the cast product are generated. Since the surplus protrusions in which the core sand and aluminum are coagulated are extremely hard, they are removed by cutting with an ultra-hard cutting tool, but the cutting work requires a great deal of labor.

  In addition, when the collapsible sand core becomes large, for example, when the number of core holding projections is 5 or more, if the temperature rise of the casting mold is slightly different from the predicted value, the pitch of the core holding projections Will not match the pitch of the collapsible sand core. In this case, it was difficult to hold the collapsible sand core in the mold cavity with high accuracy.

  Therefore, the present invention facilitates sand removal from the opening of the cast product even if the sand core is inferior in collapsibility, and between the collapsible sand core and the core holding projection during casting. It is an object of the present invention to provide a collapsible sand core holding method and a collapsible sand core holding device capable of preventing intrusion of molten metal and holding the collapsible sand core in a mold cavity with high accuracy.

  In order to achieve the above object, the present invention provides a core holding projection 4 projecting from a fixed mold 22 or a movable mold 21 in at least one holding hole 12 formed in the collapsible sand core 10. In the method for holding a collapsible sand core, wherein the collapsible sand core 10 is held in a cavity 1 a defined by the fixed mold 22 and the movable mold 21, The part 4 protrudes from the flat surface 31 of the pedestal 3 that forms an opening in the cast product. The collapsible sand core is brought into contact with the flat surface 31 and the entire periphery of the holding hole opening peripheral portion 11A. A method for holding a collapsible sand core is provided.

  In the above holding method, it is preferable that a groove 31b filled with molten metal is formed at a position where the flat surface 31 contacts the collapsible sand core 10.

  A plurality of the core holding projections 4 and the holding holes 12 are provided, and clearances 41a and 42a are formed between the core holding projection 4 and the inner surface of the holding hole 12, The clearance 41a, 42a has a size in a direction perpendicular to the protruding direction of the core holding projection 4 at least two different values in the plurality of core holding projections 4 and the holding holes 12. Is preferred.

  In order to achieve the above object, the fixed mold 22 and the movable mold 21 that define the cavity 1a, the pedestal 3 that is provided in the fixed mold 22 or the movable mold 21 and defines a part of the cavity 1a, A collapsible sand core 10 provided with at least one core holding projection 10 projecting from the pedestal 3 and having a holding hole 12 formed in the holding hole 12. 4 is a collapsible sand core holding device 1 that inserts 4 into the cavity 1a and holds the core holding projection 4 at the base of the core holding projection 4 of the pedestal 3. A flat surface 31 having a plane perpendicular to the projecting direction and contacting the collapsible sand core 10 is provided, and the flat surface 31 has an area larger than the opening area of the holding hole 12 and the holding hole. The collapsible sand core holding device 1 arranged so that 12 is in the region of the flat surface 31 Subjected to.

  According to the method for holding a collapsible sand core according to claim 1 of the present invention, since the core holding projection protrudes from the flat surface of the pedestal that forms the opening, a sand core that is inferior in collapsibility is provided. Sanding can be easily performed even when used. In addition, since the flat surface and the peripheral edge of the holding hole are in contact with each other over the entire circumference to hold the collapsible sand core, the molten metal is added to the clearance formed between the core holding protrusion and the inner surface of the holding hole. The part can be prevented from entering. Even if a part of the molten metal enters and a surplus protrusion is formed, it can be easily punched with a press die or punch chisel together with a burr formed between the flat surface and the peripheral edge of the holding hole. Can be removed.

  According to the method for holding a collapsible sand core according to claim 2, a part of the molten metal can flow into the groove. As a result, burrs are formed at the flat surface position of the cast product. Therefore, even if the sand of the collapsible sand core that is in contact with the flat surface is detached when the cast product is removed, the sand is taken out together with the burrs and flat. Residual sand can be suppressed on the surface.

  According to the method for holding a collapsible sand core according to claim 3, since the clearance values of the core holding projections and the holding holes are different, the position of one core holding projection with respect to one holding hole And the error of the position of the other core holding projection with respect to the other holding holes can be set to different values. Therefore, even if the distance between the one holding hole and the core holding projection and the other holding hole and the core holding projection has an unexpected error with respect to the design value, for example, the one holding hole and the core holding projection By making the clearance of the core holding projection larger than the clearances of the other holding holes and the core holding projection, errors can be absorbed in one holding hole and the core holding projection. Therefore, even when the collapsible sand core is automatically inserted by a robot or the like, it can be stably and accurately held in the cavity.

  According to the collapsible sand core holding device according to claim 4 of the present invention, since the core holding projection protrudes from the flat surface of the pedestal forming the opening, the sand core inferior in collapsibility is provided. Sanding can be easily performed even when used. In addition, since the flat surface and the peripheral edge of the holding hole are in contact with each other over the entire circumference to hold the collapsible sand core, the molten metal is added to the clearance formed between the core holding protrusion and the inner surface of the holding hole. The part can be prevented from entering. Even if a part of the molten metal enters and a surplus protrusion is formed, it can be easily punched with a press die or punch chisel together with a burr formed between the flat surface and the peripheral edge of the holding hole. Can be removed.

  A collapsible sand core holding method and a collapsible sand core holding device according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG. 1 is a cross-sectional view of a mold 1 that is a collapsible sand core holding device. The mold 1 is a die-cast mold, and a sand core 10 that is a collapsible sand core is held in a cavity 1 a defined in the mold 1. The mold 1 includes a movable mold 21 and a fixed mold 22. The movable mold 21 has a cavity surface 21A that defines the cavity 1a on its dividing surface, and the fixed mold has a cavity surface 22A that defines the cavity 1a on its dividing surface. The movable mold 21 is moved to the fixed mold 22 side and comes into contact with the divided surface of the movable mold 21 so as to face the divided surface of the fixed mold 22. The cavity surface 21A and the cavity surface 22A are also formed in an L shape so that the cavity 1a is formed in an L shape corresponding to an L shape that is the shape of the sand core 10 described later. .

  The sand core 10 is formed in a substantially L shape by combining sand with a binder (FIG. 2), and a plurality of holding holes 12 are formed on one surface 11 thereof. Each of the plurality of holding holes 12 has substantially the same shape, and has an opening on one surface 11. The depth of the holding hole 12 drilled: L is a value obtained by subtracting L from T with respect to the thickness: T of the sand core 10 is at least 3 mm, preferably 5 mm or more. The value obtained by dividing T by L is preferably 2/3 or more and 9/10 or less. Further, the opening peripheral edge portion 11 </ b> A that is the peripheral edge portion of the opening of the one surface 11 is configured to be a plane that is substantially orthogonal to the direction in which the holding hole 12 is drilled.

  A plurality of pedestals 3 are provided at the position of the cavity surface 21 </ b> A of the movable mold 21. The pedestal 3 is formed in a truncated cone shape so as to have a draft without undercut, and a substantially smooth flat surface 31 is provided on the top of the pedestal (FIG. 4A). Further, portions other than the flat surface 31 on the outer peripheral surface of the base 3 together with the cavity surface 21A define a cavity 1a.

  On the flat surface 31, a holding core pin 4 that protrudes in a direction substantially orthogonal to the flat surface 31 is a protruding core holding pin 4. The holding core pin 4 has a length from the position of the flat surface 31 that is the base to the tip thereof slightly shorter than the depth L of the holding hole 12, and a diameter orthogonal to the protruding direction is slightly smaller than the inner diameter of the holding hole 12. It is configured. There are two types of holding core pins 4 depending on their diameters. The holding core pin 4 having a smaller diameter serves as a holding core pin 41 for auxiliary fitting, and the holding core pin 4 having a larger diameter has a larger diameter. Is a retaining pin 42 for precision fitting.

  The sand core 10 is held in the cavity surface 21 </ b> A of the movable mold 21 with the auxiliary fitting holding core pin 41 and the precision fitting holding core pin 42 inserted into the holding hole 12. Yes. The auxiliary fitting holding core pin 41 and the precision fitting holding core pin 42 are both smaller in diameter than the holding hole 12, and therefore, between the auxiliary fitting holding core pin 41 and the holding hole 12, and As shown in FIG. 1, a first clearance 41a and a second clearance 42a are formed between the precision fitting holding core pin 42 and the holding hole 12, respectively. However, since the holding fitting pin 41 for auxiliary fitting is smaller in diameter than the holding casting pin 42 for precise fitting, the value of the second clearance 42a (0.05 mm to 0.20 mm) is the value of the first clearance 41a. It is slightly smaller than (0.20 mm to 0.50 mm). The value of the first clearance 41a and the value of the second clearance 42a are the sizes in the direction orthogonal to the protruding direction of the holding core pin 4, respectively.

  The mold 1 is generally made in consideration of dimensional changes due to thermal expansion, but since the atmosphere differs depending on the season, it may be slightly different from the dimensions considered in advance. The sand core 10 also has a subtle dimensional change between the lots. However, with the precision fitting holding core pin 42 as a reference position, the dimensional error is absorbed by the first clearance 41 a in the auxiliary fitting holding core pin 41, so that the sand core 10 can be attached to the mold 1. High accuracy can be maintained.

  Since the protruding amount of the auxiliary fitting holding core pin 41 and the precision fitting holding core pin 42 is smaller than the drilling depth of the holding hole 12, the opening peripheral edge portion 11A has a flat surface 31 over the entire circumference thereof. Abut. In this case, the size of the base 3 is determined so that the distance from the opening of the holding hole 12 to the outer peripheral position of the flat surface 31 is at least 2 mm, and preferably 4 mm or more.

  FIG. 2 shows a plan view of a split surface on which the cavity surface 21A of the movable mold 21 is provided. As shown in FIG. 2, the movable mold 21 is formed with a runner having a plurality of gates opened in the cavity surface 21A and an injection port 21a communicating with the runner. In the cavity surface 21A, a pedestal 3A, a pedestal 3B, a pedestal 3C, and a pedestal 3D are arranged on the long side portion of the L-shape, and the L-shaped long side and the short side cross each other. A pedestal 3E is disposed, and a pedestal 3F is disposed on the short side portion of the L shape. Among these, the direction from the pedestal 3A to the pedestal 3B and the direction from the pedestal 3C to the pedestal 3D are substantially parallel, and are substantially orthogonal to the L-shaped long side direction of the cavity surface 21A. In the long side direction of the L-shape of the cavity surface 21A, between the holding core pin 4 protruding from the base 3A and the base 3B, and the holding core pin 4 protruding from the base 3C and the base 3D, and The pitch between the holding core pin 4 protruding from the base 3C and the base 3D and the holding core pin 4 protruding from the base 3E is the length of the L-shaped long side direction of the sand core 10, respectively. : L × 0.3 to 0.5.

  With respect to the pedestal 3A to the pedestal 3D, one holding cast pin 4 protrudes from one pedestal, and for the pedestal 3E and pedestal 3F, two holding cast pins 4 protrude from the one pedestal. ing. One holding cast pin 4 of the pedestal 3A, pedestal 3C, pedestal 3E, and one of the pedestal 3F is a holding cast pin 41 for auxiliary fitting, and the pedestal 3B, the other of the pedestal 3D, the other of the pedestal 3E, and the pedestal. The other holding core pin 4 of 3F is a holding core pin 42 for precision fitting.

  A process of manufacturing a cast product by holding the sand core 10 in the cavity 1a of the mold 1 having the above configuration will be described. First, in the movable die 21 shown in FIG. 2, the holding fitting pin 42 for precision fitting is used as a reference and inserted into the corresponding holding hole 12, and the holding die pin 41 for auxiliary fitting is corresponding. The sand core 10 is held by being inserted into the holding hole 12 as shown in FIGS. At this time, the entire circumference of the opening peripheral edge portion 11 </ b> A of each holding hole 12 abuts on the flat surface 31 of each pedestal 3.

  In this state, the movable mold 21 and the stationary mold 22 are brought into contact with each of the divided surfaces, and the molten metal is poured into the cavity 1a from the injection port 21a. At this time, since the flat surface 31 and the opening peripheral edge portion 11A are in contact with each other, a part of the molten metal is prevented from entering the first clearance 41a and the second clearance 42a. Even if the molten metal enters the first clearance 41a and the second clearance 42a and a surplus protrusion is generated, the surplus is made via a burr formed in a thin plate shape between the flat surface 31 and the opening peripheral edge 11A. Protrusions and castings are connected. Since this burr is formed along the flat surface 31 and has a flat plate shape perpendicular to the opening direction of the opening of the cast product, it can be easily punched with a press die or punch chisel etc. At this time, the excess protrusion is also removed.

  The collapsible sand core holding method and the collapsible sand core holding device according to the present invention are not limited to the above-described embodiments, and various modifications and improvements can be made within the scope described in the claims. For example, as shown in FIGS. 4B and 4C, grooves 31 b formed in a series in the circumferential direction and grooves 31 c formed radially are arranged around the holding core pin 4 on the flat surface 31. Also good. Since the flat surface 31 is a portion that directly contacts the sand core 10, by manufacturing a cast product using the sand core 10, the binder of the sand core 10 is melted by the heat of the molten metal. There is a case where the sand at the opposite position leaves the sand core 10 and remains on the flat surface 31. In this case, when the next sand core 10 for casting is inserted, the holding position of the sand core 10 may be shifted by the amount of sand remaining on the flat surface 31. However, by forming the groove portions 31b and 31c on the flat surface 31, a part of the molten metal enters the groove portions 31b and 31c to form burrs. By forming this burr, the sand of the sand core 10 can be taken out together with the cast product without leaving and remaining, and the possibility of the sand remaining on the flat surface 31 is extremely reduced. it can.

  However, in order to prevent the sand core 10 from floating in a direction away from the flat surface 31 when the molten metal is poured, an area of 20% or more of the total area of the flat surface 31 is applied to the sand core 10. It is desirable to touch.

  Moreover, about a holding | maintenance casting pin, as FIG. 5 shows, you may provide the vent holes 143a-143c in the holding | maintenance casting pins 143A-143C, respectively. Since the sand core 110 is hardened with a binder (organic binder), gas may be generated when the binder is heated. Since the gas generated in this case may be mixed into the cast product to cause a gas defect, gas vent holes 143a to 143c are provided, and the gas in the clearances 144a to 144c is discharged to the outside of the mold 101 to cause the gas defect. To prevent. The mold 101 includes a movable mold 111 composed of a movable holder 111A and a movable die 111B, and a fixed mold 112 composed of a fixed holder 112A and a fixed die 112B. An exhaust passage 101a is formed between the movable holder 111A and the fixed holder 112A and communicates with the atmosphere.

  In the holding core pin 143A, the gas vent hole 143a is a through-hole drilled from the front end to the rear end of the main body of the holding core pin 143A, the front end opens to the clearance 144a, and the rear end communicates with the exhaust passage 101a. As a result, the gas in the clearance 144a is extracted.

  In the holding core pin 143B, the gas vent hole 143b is formed so as to open to a position 103B facing the clearance 144b of the pedestal 103 integral with the movable die 111B. A gas vent space 121b communicating with the exhaust passage 101a is formed around the holding core pin 143B of the movable die 111B and continuing to the gas vent hole 143b, and the clearance is formed via the gas vent hole 143b and the gas vent space 121b. The gas in 144b is extracted.

  For the holding core pin 143C, the movable die 111B is provided with a bush 123 that supports the holding core pin 143C and serves as the pedestal 103. The vent hole 143c is formed at a position 103C facing the clearance 144c of the base 103 portion of the bush 123. A degassing space 121b communicating with the exhaust passage 101a is formed at a position around the holding core pin 143C of the bush 123 and continuing to the degassing hole 143c, and a clearance 144c is formed via the degassing hole 143c and the degassing space 121c. The gas inside is exhausted.

  In the present embodiment, the position of the sand core 10 is determined only by the holding core pin 4 in the cavity 1a without using the baseboard, but the present invention is not limited to this, and a baseboard may be used in combination. When the total length of the sand core 10 is increased, only the holding core pins 4 at both ends in the longitudinal direction are used as the holding core pins 41 for precision fitting, and the other holding core pins 4 are the holding core pins for auxiliary fitting. 42 may be used. Moreover, in the pitch of the holding | maintenance punching pin 4, when there exists a shape restriction | limiting of a cast product, you may set the pitch suitably with sand core full length: Lx0.2-0.6. In the present embodiment, the holding core pin 4 is projected from the pedestal 3 of the movable mold 21. However, the present invention is not limited to this, and the pedestal 3 is provided on the fixed die 22 and the holding core pin is provided from the pedestal 3. 4 may be projected. In the present embodiment, the length of the holding core pin 4 is slightly shorter than the depth L of the holding hole 12, but the holding core pin 4 may penetrate the sand core 10. In this case, a pedestal having a hole into which the tip of the holding core pin 4 is inserted may be provided at a position where the tip of the holding core pin 4 faces.

Sectional drawing of the holding | maintenance apparatus of the collapsible sand core which concerns on embodiment of this invention. The perspective view which shows the holding | maintenance apparatus of the collapsible sand core which concerns on embodiment of this invention, and the relationship of a sand core. The perspective view of the state which attached the sand core to the holding | maintenance apparatus of the collapsible sand core which concerns on embodiment of this invention. (A) The perspective view which showed the state of the base of the holding | maintenance apparatus of the collapsible sand core which concerns on embodiment of this invention, and a holding core pin. (B) The perspective view which showed the example of a change (state in which the circumferential groove | channel was formed in the base) of embodiment of this invention. (C) The perspective view which showed the example of a change (state which formed the radial groove | channel in the base) of embodiment of this invention. Sectional drawing which shows the holding | maintenance core pin shape which concerns on the example of a change of the holding | maintenance apparatus of the collapsible sand core which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 101 .... Mold 1a .. Cavity 3 .... Base 4 .... Holding core pin 10 ... Sand core 11A ... Opening edge part 12 ... Holding holes 21, 111 ... Movable molds 22, 112 .. Fixed mold 31.. Flat surface 31 b.

Claims (4)

By inserting a core holding projection projecting from a fixed mold or a movable mold into at least one holding hole formed in the collapsible sand core, the collapsible sand core is attached to the fixed mold and the fixed mold. In a method for holding a collapsible sand core held in a cavity defined by a movable mold,
The core holding projection protrudes from a flat surface of a pedestal that forms an opening in the cast product, and the flat surface and the entire periphery of the holding hole opening peripheral portion are brought into contact with each other in the collapsible sand. A method for holding a collapsible sand core, characterized by holding a child.   The method for holding a collapsible sand core according to claim 1, wherein a groove portion filled with a molten metal is formed at a position where the flat surface is in contact with the collapsible sand core.   A plurality of the core holding projections and the holding holes are provided, and a clearance is formed between the core holding projection and the inner surface of the holding hole, and the core holding projection of the clearance is formed. 3. The collapse according to claim 1, wherein the size in a direction perpendicular to the protruding direction of the plurality of cores is at least two different values in the plurality of core holding protrusions and the holding holes. To hold a natural sand core. A fixed type and a movable type that define cavities;
A pedestal provided in the fixed mold or the movable mold and defining a part of the cavity;
A collapsible sand core having a holding hole formed therein, and inserting the core holding protrusion into the holding hole. A collapsible sand core holding device for holding in a cavity,
The base of the core holding projection of the pedestal is provided with a flat surface having a flat surface perpendicular to the protruding direction of the core holding projection and abutting the collapsible sand core,
The collapsible sand core holder characterized in that the flat surface is arranged so that the area thereof is larger than the opening area of the holding hole and the entire circumference of the holding hole is in the region of the flat surface. apparatus.

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