JP2006055868A - Casting method and metallic mold for casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a product provided with an undercut part at a low cost. <P>SOLUTION: Preceding to form a cavity 30 for product by assembling an upper metallic mold 22, a lower metallic mold 24 and a sliding insert 26, a separated piece 28 is fitted from the front part side in the sliding direction to the sliding insert 26. After filling and solidifying molten metal 32 into the cavity 30 for product, when the sliding insert 26 is separated from the product, the separated piece 28 is separated from the sliding insert 26 and remains at the product side. In the case of constituting the separated piece 28 with a general core material, the separated piece 28 can be collapsed and removed with heat-treatment, etc., and then, the cast product having the undercut part can be obtained with a simple mold structure. In the case of constituting the separated piece 28 with a material having high heat-conductivity, the heat of the molten metal 32 is conducted into the sliding insert 26 through the separated piece 28, and the molten metal 32 is efficiently cooled and then, the shortening of time at each one-forming cycle can be attained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for obtaining a product having an undercut portion by die casting.

  Conventionally, as a technique for obtaining a product having an undercut portion using a mold, in a die casting and resin injection molding method, a partial top (placement core) is disposed inside the mold, or A technique that employs a complicated mold division nested structure has been used (see, for example, Patent Document 1 and Patent Document 2). In the case of low pressure casting and gravity casting, an integral product core including an undercut portion has been used. Further, there is a case in which a die-casting or low-pressure casting method is used in which an undercut portion is cast as a surplus and is cut and removed by post-processing.

JP-A-6-122059 ([0007] to [0009], [FIG. 1]) JP-A-9-314301 ([0028] to [0031], [FIG. 1])

However, in a method in which a partial top (placement core) is arranged inside the mold or a complicated mold divided nest structure is adopted, the mold structure is complicated. Molding defects are likely to occur, and malfunctions (stops) of the mold due to mold temperature differences, thermal expansion differences, adhesion of foreign matters, mold wear, etc. are caused, resulting in a decrease in mobility. In addition, an increase in mold cost due to an increase in mold components cannot be avoided.
Also, when using an integral product core that includes an undercut part, the mold cost and core cost are high, and the core area in contact with the molten metal in the mold cavity increases, which is compared with the solidification of the molten metal. It takes a long time, and the product cost increases due to the extension of time for each molding cycle.
Furthermore, the method of cutting and removing the undercut part integrally cast as surplus by post-processing increases the man-hours and cost by machining, and increases the thickness of the product at the time of casting. Casting defects are likely to occur, resulting in a decrease in yield, an increase in mold costs due to the addition of mold cooling means, and an increase in mold maintenance costs.

In addition, in order to meet the recent needs for conversion from cast iron products to aluminum products, the application of the above-described conventional method to aluminum product casting technology has led to a significant increase in product costs.
The present invention has been made in view of the above problems, and its object is to obtain a product having an undercut portion by die casting at a low cost, and in particular, a low pressure casting method and a gravity casting method. Thus, it is possible to obtain a product including an undercut portion at a low cost.

In order to solve the above problems, a casting method according to the present invention forms a product cavity by combining a pair of molds and a slide insert, fills the product cavity with a molten metal, and solidifies the product to obtain a product. In the casting method, prior to the formation of the product cavity, from the slide direction front side with respect to the slide insert, mounted with a product for forming an undercut part of the product, which is made of a material having high thermal conductivity, After the product cavity is formed, the product cavity is filled with a molten metal, the molten metal is cooled through the undercut portion molding piece, and the undercut portion molding piece is removed from the slide insert when the slide insert is released. It is characterized by separating.
The present invention allows the undercut portion molding piece to be separated from the slide insert simultaneously with the mold release of the slide insert by mounting the undercut portion forming piece of the product from the slide direction front to the slide insert. It is possible. In addition, by using a material having high thermal conductivity for the undercut part molding piece, the heat of the molten metal is transmitted to the slide insert through the piece, and the molten metal is efficiently cooled, for each molding cycle. It is possible to shorten the time.

  Further, another casting method according to the present invention for solving the above-mentioned problem is to form a product cavity by combining a pair of molds and a slide insert, and to fill the product cavity with molten metal to solidify. A casting method for obtaining a product, wherein, prior to the formation of the product cavity, a product for forming an undercut portion of the product, which is made of a steel material, is attached to the slide insert from the front side in the sliding direction, and the product After forming the cavity, filling the product cavity with molten metal, casting the undercut part forming piece, and separating the undercut part forming piece from the slide insert when releasing the slide insert It is a feature.

The present invention allows the undercut portion molding piece to be separated from the slide insert simultaneously with the mold release of the slide insert by mounting the undercut portion forming piece of the product from the slide direction front to the slide insert. It is possible. In addition, by using a steel material for the undercut part molding piece and casting the piece, the undercut part molding piece separated from the slide insert together with the product at the time of releasing the slide insert directly It is possible to obtain a cast product having an insert with high mechanical strength and high dimensional accuracy by performing desired machining.
In the present invention, if the contact surface with the molten metal of the piece for forming the undercut portion is configured to have a concavo-convex shape, the molten metal is filled into the concavo-convex shape and solidifies, so that the product and the undercut portion are molded. The bond strength with the piece for use is increased, the release of the piece is promoted, and even after the product is completed, it is possible to more reliably prevent the undercut part forming piece from falling off the product. .
Also in the present invention, if the molten metal is cooled through the undercut portion molding piece, it is possible to efficiently cool the molten metal and shorten the time for each molding cycle.

Moreover, in this invention, it is good also as comprising the said slide insert in the cylindrical shape provided with a draft, and making the said undercut part shaping | molding piece contact | abut over the perimeter of the said slide insert.
According to this configuration, when the undercut part molding piece of the product is mounted on the slide nest from the front side in the sliding direction, the slide nest and the undercut part are configured in a cylindrical shape having a draft angle. By bringing the working piece into contact with the entire circumference, the piece is guided by the draft angle of the slide insert, and positioning in the insertion direction and centering are reliably performed. Therefore, it is possible to cast a high-precision product having a cylindrical inner peripheral wall and having a cylindrical undercut portion on the inner peripheral wall. Moreover, since the undercut part forming piece contacts the entire periphery of the part that becomes the inner peripheral wall of the product during casting, it is possible to increase the cooling efficiency of the entire contact part. Furthermore, when casting the piece, it is possible to promote the mold release of the piece by increasing the draft angle and to provide an insert with high mechanical strength and dimensional accuracy over the entire circumference of the inner peripheral wall of the product. A cast product can be obtained.
In the present invention, if a detent is provided between the undercut portion molding piece and the slide insert, it is possible to reliably position the piece in the rotational direction. Even in the case where a concavo-convex shape is formed at a predetermined position of the product by the outer peripheral portion of the molding piece, the positional accuracy of the concavo-convex shape can be improved.

  Furthermore, if the gas in the product cavity is released from between the piece for molding the undercut portion and the slide insert, it becomes possible to prevent molding defects caused by the gas.

In addition, a casting mold according to the present invention for solving the above-mentioned problems is formed by combining a pair of molds and a slide insert to form a product cavity, and filling the product cavity with molten metal to solidify. A casting mold for obtaining a product, which is attached to the slide insert from the front side in the sliding direction prior to the formation of the product cavity, and separated from the slide insert when the slide insert is released. And an undercut portion molding piece configured to remain on the product side.
According to the present invention, the undercut portion from the slide insert is released simultaneously with the mold release of the slide insert by attaching the undercut portion forming piece of the product to the slide insert from the front in the slide direction with a simple mold structure. Separation of the molding pieces becomes possible.

Further, in the present invention, if the slide insert has a cylindrical shape with a draft, and the undercut portion forming piece abuts over the entire circumference of the slide insert, the slide insert slides against the slide insert. When attaching the undercut part molding piece of the product from the front side in the direction, the slide insert configured in a cylindrical shape with a draft angle and the undercut part molding piece are brought into contact over the entire circumference. Is possible. Therefore, the piece is guided by the draft angle of the slide insert, and positioning in the insertion direction and centering can be reliably performed. Therefore, it is possible to cast a high-precision product having a cylindrical inner peripheral wall and having a cylindrical undercut portion on the inner peripheral wall.
In the present invention, if the anti-rotation convex portion is formed on one of the contact surfaces of the slide insert and the undercut portion forming piece, and the anti-rotation concave portion is formed on the other, the undercut It becomes possible to prevent rotation between the part forming piece and the slide insert. Therefore, positioning of the undercut portion molding piece in the rotational direction is reliably performed, and even if the uneven shape is formed at a predetermined position of the product by the outer peripheral portion of the piece, the positional accuracy of the uneven shape is increased. It becomes possible.

In the present invention, if the undercut part molding piece is made of a material having high thermal conductivity, the heat of the molten metal is transmitted to the slide nest through the piece, and the molten metal is transferred to the slide insert. It is possible to efficiently cool and shorten the time for each molding cycle.
In addition, as described above, when the undercut portion molding piece is in contact with the entire circumference of the slide insert, the entire circumference of the portion where the undercut portion molding piece becomes the inner peripheral wall of the product during casting. Therefore, it is possible to increase the cooling efficiency of the entire contact portion.

Further, in the present invention, if the undercut part forming piece is made of steel, when the slide insert is released, the undercut part forming piece separated from the slide insert together with the product, It is possible to obtain a cast product having an insert with high mechanical strength and high dimensional accuracy by directly performing desired machining.
Furthermore, as described above, when the undercut portion molding piece is in contact with the entire circumference of the slide insert, by increasing the draft, the release of the piece is promoted, and the product A cast product including an insert having high mechanical strength and high dimensional accuracy can be obtained over the entire circumference of the inner peripheral wall.
Also in the present invention, if the molten metal is cooled via the undercut portion molding piece, it is possible to efficiently cool the molten metal and shorten the time for each molding cycle.

  Further, in the present invention, if the uneven surface is formed on the contact surface of the undercut portion molding piece with the molten metal, the molten metal is filled in the uneven shape and solidifies, so that the product and the undercut portion The bonding strength with the molding piece is increased, the release of the piece is promoted, and even after the product is completed, it is possible to more reliably prevent the undercut part molding piece from falling off the product. Become.

  Furthermore, in the present invention, a groove in the sliding direction of the slide insert may be formed on at least one of the contact surfaces of the slide insert and the undercut portion forming piece. According to this configuration, using the groove, it is possible to discharge the gas in the product cavity from between the undercut portion molding piece and the slide insert, thereby preventing a molding defect caused by the gas. Become.

  Since this invention was comprised in this way, it becomes possible to obtain the product provided with an undercut part by die casting at low cost. In particular, by applying to low pressure casting and gravity casting, it is possible to obtain a product having an undercut portion with high accuracy and low cost.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a sectional view showing a case 10 of a differential gear portion of an automobile as an example of a cast product having an undercut portion that can be manufactured by a casting mold according to an embodiment of the present invention. Yes. The mold used when casting the case 10 is such that the upper and lower molds open in directions indicated by arrows A and B, so that the multistage cylindrical hole 12 perpendicular to the direction is slid It becomes the part molded by the insert. Here, since the sliding direction of the slide insert is the direction indicated by the arrow C, the center side opening end portion 14 of the case 10 in the multistage cylindrical hole 12 is an undercut portion.

FIG. 2 shows a die structure for low-pressure casting or gravity casting of the case 10 limited to the periphery of the undercut portion for convenience of explanation. This mold includes a pair of molds including an upper mold 22 and a lower mold 24, and a slide insert 26. The slide insert 26 is accurately slidably guided in the direction of arrow C by the guide key 27A and the guide rail 27B. Furthermore, an undercut part forming piece 28 (hereinafter also referred to as “another piece”) is attached to the slide insert 26.
The slide insert 26 is formed in a multistage cylindrical shape for forming the multistage cylindrical hole 12 (FIG. 1) in the product, and is given a draft angle α. Further, the separate piece 28 is formed in an annular shape, and its inner cylinder portion is given a draft angle α which is the same as the draft angle of the slide insert 26. Therefore, the separate piece 28 is attached to the slide insert 26 as indicated by an arrow E from the front side of the slide insert 26 in the sliding direction. Since the embodiment of the present invention is particularly suitable for the low pressure casting method and the gravity casting method, the material of the separate piece 28 can be selected relatively freely. For example, as with a normal core, it is possible to use a material that satisfies the conditions such as low gas generation, good air permeability, good strength and good disintegration. Further, as the material of the separate piece 28, it is possible to use a material having high thermal conductivity such as a casting material or a copper alloy, or a steel material.

Here, a manufacturing procedure of the case 10 using the casting mold according to the embodiment of the present invention will be described with reference to FIGS.
First, as shown in FIG. 2, another piece 28 is attached to the slide insert 26 from the front of the slide insert 26 in the sliding direction. Since the slide insert 26 and the separate piece 28 are provided with the draft angle α, the mounting operation is performed smoothly. In FIG. 2, the slide insert 26 is set in the mold after the upper mold 22 and the lower mold 24 complete the mold clamping. It is good also as taking the procedure which clamps the upper mold | type 22 after setting.

As shown in FIG. 2, after the separate piece 28 is attached to the slide insert 26, a product cavity 30 is formed by combining the pair of molds 24 and 26 and the slide insert 26 as shown in FIG. To do. After the product cavity 30 is formed, the product cavity 30 is filled with a molten metal 32 as shown in FIG.
Here, when a material having high thermal conductivity is used for the separate piece 28, the molten metal 32 can be cooled via the separate piece 28, and the solidification time of the molten metal 32 can be shortened. In this case, the cooling effect can be sufficiently obtained by sufficiently cooling the slide insert 26 before mold clamping. In the case where a steel material is used for the separate piece 28, the separate piece 28 is cast with the molten metal 32.

Then, after the molten metal 32 is solidified, as shown in FIG. 5, when the slide insert 26 is released from the product 34, another piece is separated from the slide insert 26, and the slide insert 26 together with the product 34 is inside the mold. Remain in. Further, FIG. 6 shows a state where the upper mold 22 and the lower mold 24 are opened and the product 34 is taken out from the mold. At this point, the separate piece 28 is integrated with the product 34. However, when the separate piece 28 is formed of a general core material, the separate piece 28 is naturally formed by performing heat treatment on the product 34. It will collapse and be easily removed from the product 34.
On the other hand, when the separate piece 28 is made of a steel material, the separate piece 28 cast into the product 34 is directly machined to give a predetermined dimensional accuracy to the separate piece 28 itself. 7 shows that the case 10 shown in FIG. 1 is obtained by cutting away the machining allowances 36, 38, 40, and 42 of the product 34 when the other piece 28 is removed from the product 34 shown in FIG. be able to.

  The effects obtained by the embodiment of the present invention having the above-described configuration are as follows. First, prior to forming the product cavity 30 by combining the upper mold 22, the lower mold 24 and the slide insert 26, another piece 28 is attached to the slide insert 26 from the front side in the sliding direction, and the product cavity 30 is moved to. When the slide insert 26 is released from the product 34 after the molten metal 32 is filled and solidified, the separate piece 28 is separated from the slide insert 26 and remains on the product 34 side. The separate pieces 28 can be easily separated. In addition, when the separate piece 28 is made of a general core material, the separate piece 28 is collapsed and removed by heat treatment or the like, so that the casting product 10 having an undercut portion is obtained by a simple mold structure. Is possible.

  In addition, the slide insert 26 has a cylindrical shape with a draft angle α, and the separate piece 28 is configured to abut on the entire circumference of the slide insert 26. Positioning of the slide insert 26 in the insertion direction (slide direction C of the slide insert 26) and centering of the separate piece 28 with respect to the slide insert 26 are surely performed when the separate piece 28 is mounted. Become. Therefore, it is possible to cast a high-precision product 10 having multistage cylindrical holes 12 and having a cylindrical undercut portion 14 on the inner peripheral wall.

  As an application example, as shown in FIGS. 8A and 8B, one of the contact surfaces of the slide insert 26 and the separate piece 28 is provided with a protrusion for preventing rotation (the protrusion 26a in FIG. 8A). By forming the convex portion 28b in FIG. 8B on the other side and the concave portion for preventing rotation (the concave portion 28a in FIG. 8A and the concave portion 26b in FIG. 8B), the slide insert 26 and another piece are formed. It is possible to provide a rotation stopper between the two. Therefore, the positioning of the separate piece 28 in the rotational direction with respect to the slide insert 26 is surely performed, and the convex portion 28c formed on the outer peripheral portion of the separate piece 28 has a concave shape (a key groove in the example of FIG. 8) at a predetermined position of the product. Even in the case of forming the concavo-convex shape, it is possible to improve the positional accuracy of the concavo-convex shape.

  Further, if the separate piece 28 is made of a material having a high thermal conductivity, the heat of the molten metal 32 is transmitted to the slide insert 26 via the separate piece 28 to efficiently cool the molten metal 32, It becomes possible to shorten the time for each molding cycle. Moreover, in the present embodiment, since the separate piece 28 is in contact with the entire circumference of the slide insert 26, the separate piece 28 is in contact with the entire periphery of the portion that becomes the inner peripheral wall of the product 32 during casting ( It is also possible to increase the cooling efficiency of the entire contact portion (see FIGS. 4 and 5).

On the other hand, if the separate piece 28 is made of a steel material, when the slide insert 26 is released, the desired piece directly with respect to the separate piece 28 separated from the slide insert 26 together with the product 34 (see FIG. 6) is directly desired. By performing machining, it becomes possible to obtain a cast product including an insert having high mechanical strength and high dimensional accuracy. Therefore, an independent insert press-fitting process is not required, and the manufacturing cost can be reduced.
In addition, when casting another piece 28, the release angle of the separate piece 28 from the slide insert 26 is promoted by setting the angle α of the draft angle of the slide insert 26 and the separate piece 28 to be larger than usual. It is desirable to make it. Further, by forming an uneven shape such as a concave slit or a dimple on the contact surface (outer peripheral portion) of the separate piece 28 with the molten metal 32, the molten metal 32 is filled into the uneven shape and solidifies. The bonding strength with 28 is increased. Therefore, after the slide insert 26 is released from the separate piece 28 and the product 34 is completed, it is possible to more reliably prevent the separate piece 28 from falling off the product.
In addition, even when casting another piece 28, if the molten metal is cooled through the separate piece 28, the molten metal 32 can be efficiently cooled, and the time for each molding cycle can be shortened. Become.

  As a further application example, as shown in FIG. 9, at least one of the contact surfaces of the slide insert 26 and the separate piece 28 is provided with a groove in the slide direction of the slide insert 26 (in the illustrated example, a groove 28d is provided in the separate piece 28). If the above-mentioned groove is used, the gas in the product cavity 30 is discharged from between the separate piece 28 and the slide insert 26 by using such a groove, thereby preventing molding defects caused by the gas. It becomes possible. At this time, if the depth of the groove is 0.2 mm or less, only the gas can be discharged without the molten metal 32 passing through the groove.

  In the embodiment of the present invention, the case 10 of the differential gear portion of an automobile is described as an example of a cast product having an undercut portion. However, the present invention can also be applied to a cast product having another undercut portion. It is. The slide insert 26 is formed in a multi-stage cylindrical shape, and the separate piece 28 is formed in an annular shape. However, the present invention is not limited to this, and the slide insert has a polygonal column shape. May have a polygonal inner cylinder wall, or another piece may partially abut against the entire circumference of the slide nest.

It is sectional drawing which shows the case of the differential gear part of a motor vehicle which can be manufactured with the metal mold | die for casting which concerns on embodiment of this invention. It is principal part sectional drawing which shows the state of the metal mold | die before product cavity formation in the manufacture procedure of the cast product which concerns on embodiment of this invention. FIG. 3 is a sectional view showing a manufacturing procedure subsequent to FIG. 2 in a state where a product cavity of a mold is formed. FIG. 4 is a cross-sectional view illustrating a manufacturing procedure subsequent to FIG. 3 in a state in which a molten metal is filled in a product cavity of a mold. FIG. 5 shows a manufacturing procedure following FIG. 4, and is a cross-sectional view of the main part of the mold when the slide insert is released. FIG. 6 is a cross-sectional view of a main part of a cast product that has been released from the mold, showing a manufacturing procedure following FIG. 5. FIG. 7 is a cross-sectional view of a main part in which a post-processed part is clearly shown in a cast product from which an undercut part forming piece is removed, showing a manufacturing procedure following FIG. It is sectional drawing in the DD line | wire of FIG. 3, and shows the application example of the piece for slide nest | insert and an undercut part shaping | molding. It is sectional drawing in the DD line | wire of FIG. 3, and shows another application example of the piece for slide nest | insert and an undercut part shaping | molding.

Explanation of symbols

10: Case, 22: Upper mold, 24: Lower mold, 26: Slide insert, 28: Piece for molding undercut part, 30: Product cavity, 32: Molten metal, 34: Product

Claims (14)

A casting method for obtaining a product by forming a product cavity by combining a pair of molds and a slide insert, filling the product cavity with molten metal, and solidifying the product cavity,
Prior to the formation of the product cavity, from the slide direction front side with respect to the slide insert, mounted with a product for forming an undercut portion of the product, which is made of a material having high thermal conductivity, and after forming the product cavity, The product cavity is filled with a molten metal, the molten metal is cooled via the undercut portion molding piece, and the undercut portion molding piece is separated from the slide insert when the slide insert is released. Casting method. A casting method for obtaining a product by forming a product cavity by combining a pair of molds and a slide insert, filling the product cavity with molten metal, and solidifying the product cavity,
Prior to the formation of the product cavity, a piece for forming an undercut portion of the product made of steel material is attached to the slide insert from the front side in the sliding direction. After the formation of the product cavity, the molten metal is formed in the product cavity. , Casting the undercut part forming piece, and separating the undercut part forming piece from the slide insert when the slide insert is released. The casting method according to claim 2, wherein an uneven shape is formed on a contact surface of the undercut portion forming piece with the molten metal. The casting method according to claim 2 or 3, wherein the molten metal is cooled through the undercut part forming piece. 5. The slide insert according to claim 1, wherein the slide insert is configured in a cylindrical shape having a draft angle, and the undercut portion forming piece is brought into contact with the entire circumference of the slide insert. 6. Casting method. The casting method according to any one of claims 1 to 5, wherein a detent is provided between the piece for forming the undercut portion and the slide insert. The casting method according to any one of claims 1 to 6, wherein a gas in the product cavity is discharged from between the undercut portion forming piece and the slide insert. A casting mold for obtaining a product by forming a product cavity by combining a pair of molds and a slide insert, filling the product cavity with a molten metal, and solidifying the product cavity,
Prior to formation of the product cavity, the slide insert is attached to the slide insert from the front side in the sliding direction, and is separated from the slide insert when the slide insert is released, and remains under the product side. A casting mold comprising a cut part forming piece. 9. The casting mold according to claim 8, wherein the slide insert has a cylindrical shape with a draft angle, and the undercut portion forming piece abuts over the entire circumference of the slide insert. 10. A casting mold according to claim 9, wherein a rotation stopper convex portion is formed on one of the contact surfaces of the slide insert and the undercut portion molding piece, and a rotation stopper concave portion is formed on the other. . The casting mold according to any one of claims 8 to 10, wherein the undercut portion molding piece is made of a material having high thermal conductivity. The casting mold according to any one of claims 8 to 11, wherein the undercut part forming piece is made of a steel material. The casting mold according to claim 12, wherein an uneven shape is formed on a contact surface of the undercut portion forming piece with the molten metal. The groove | channel of the slide direction of the said slide insert is formed in at least one of the contact surface of the said slide insert and the said piece for undercut part shaping | molding, The any one of Claim 8 to 13 characterized by the above-mentioned. Mold for casting.

Images