JPH1058111A - Core sleeve pin for metallic mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the breakage of a core pin caused by the concn. of stress by fitting a core straight pin in the inner peripheral part having annular groove of a cylindrical pin and forming a step part in a product forming part with the cylindrical pin. SOLUTION: A core sleeve pin 1 for metallic mold fitted to a metallic mold 7 for casting, has double structure, in which the cylindrical pin 2 is fitted into a pin fitting hole 8 in the metallic mold 7, and the straight pin 3 is concentrically fitted in the inside of this cylindrical pin 2. The annular groove 5 is formed along the peripheral direction in the inner peripheral part at the product forming side of this cylindrical pin 2, and a clearance 4 is formed between the inner peripheral surface of the cylindrical pin 2 near a cavity surface 9 from this annular groove 5 and the outer peripheral surface of the straight pin 3. The straight pin 3 fitted to the inner peripheral part of the cylindrical pin 2 reduces the concn. of the stress with this shape, and even if thermal stress, bending stress or resistant force of separation from the mold is loaded, this pin is difficult to break. At the time of loading the bending stress to the product forming part caused by solidified shrinkage force, the stress loaded to the straight pin 3 can be reduced by existence of the annular groove 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core sleeve pin used for die casting.

[0002]

2. Description of the Related Art A product forming portion of a core pin protruding from a cavity surface of a mold has a bending stress, a thermal stress, a product release resistance, etc. due to solidification shrinkage of molten metal filled in the mold cavity. Is received every casting, so that there is a problem in that the pin is easily broken due to fatigue fracture from the pin root at the boundary between the mounting portion where the stress is concentrated and the product forming portion. In particular, as shown in FIG. 2, when the stepped portion 13 is provided near the root of the core pin 10, the stress concentration is increased, so that the fatigue fracture is easily caused. 2, reference numeral 7 denotes a mold, 8 denotes a pin mounting hole, 9 denotes a cavity surface, 11 denotes a mounting portion, and 12 denotes a product forming portion. For this reason, conventionally, the stress applied to the pin is reduced by increasing the radius of curvature of the stepped portion 13, shortening the length of the pin, or increasing the draft angle, and is made of a steel material. Although the fatigue strength has been improved by coating a hard material such as ceramic on the surface of the core pin, it has not been sufficient as a measure for breaking the core pin. In addition, Utility Model Registration No. 2501410 discloses that a pin groove is formed in a circumferential direction in an outer peripheral portion near a product forming portion in a pin mounting portion to be mounted in a pin mounting hole of a mold so that the pin is easily bent. It has been proposed to reduce bending stress and make the pin hard to break.

[0003]

However, even if the groove is provided in the core pin, if the product forming portion has a stepped portion, thermal stress or stress concentration due to release resistance at the time of release acts. Pin breakage cannot be reduced. Therefore, an object of the present invention is to reduce the breakage of the core pin due to the stress concentration described above.

[0004]

In order to achieve the above object, the present invention employs a technical means of fitting a core straight pin into an inner peripheral portion of a cylindrical pin having an annular groove in an inner peripheral portion. . By inserting a straight pin into the inner peripheral part of the cylindrical pin, the stepped part of the product forming part is formed by a cylindrical pin, and the product forming part where the thermal stress, bending stress, and release resistance act is straight pin Therefore, stress concentration can be reduced. In addition, by extruding the cylindrical pin at the time of product release, it is possible to reduce the bending stress caused by the imbalance in the extrusion timing. In addition, since the annular groove is provided in the inner peripheral portion of the cylindrical pin, the straight pin protruding from the product forming portion is easily bent, so that the bending stress itself caused by the solidification shrinkage of the molten metal can be reduced. . Note that the clearance between the straight pin and the cylindrical pin where the product is formed on the product forming side may be set to a size such that burrs are not inserted. The shape of the annular groove 5 and the shape of the tip 6 of the cylindrical pin may be appropriately set according to the shape and dimensions of the product.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a core sleeve pin for a mold of the present invention, and reference numeral 7 denotes a casting mold to which the core sleeve pin is attached. The mold core sleeve pin 1 is a cylindrical pin 2
Is mounted in the pin mounting hole 8 of the mold 7, and the straight pin 3 is fitted concentrically inside the cylindrical pin 2. An annular groove 5 is formed in the inner peripheral portion of the cylindrical pin 2 on the product forming side along the circumferential direction, and an inner peripheral surface of the cylindrical pin 2 closer to the cavity surface 9 than the annular groove 5 and a straight pin. A clearance 4 is formed between the outer peripheral surfaces of 3.
The straight pin 3 attached to the inner peripheral portion of the cylindrical pin 2
In terms of shape, the stress concentration is smaller than that of a pin having a step, so that the pin is less likely to be broken even when subjected to thermal stress, bending stress, and release resistance. The annular groove 5 provided on the inner peripheral portion of the cylindrical pin 2 allows the straight pin to be bent when the product forming portion of the straight pin receives bending stress due to the solidification shrinkage force of the molten metal filled in the cavity of the mold 7. The applied stress can be reduced. That is, since the bending amount of the product forming portion of the straight pin due to the solidification shrinkage of the molten metal is constant, the vicinity of the root of the product forming portion of the straight pin moves within the range of the clearance 4, and the tip 6 of the cylindrical pin 2 becomes a fulcrum. When the straight pin 3 is bent in the annular groove 5 of the cylindrical pin 2, the bending stress applied to the root of the product forming portion of the straight pin is reduced.

[0006] Table 1 shows that a core sleeve pin of the present invention and a conventional pin are mounted on a metal mold to form an aluminum alloy (JIS ADC).
12) shows the number of castings until pin breakage occurs when the chain case is die-cast by using (12 materials) (the casting conditions are the same in all of Examples 1 to 4). In the core pin of the present invention, the outer diameter and inner diameter of the cylindrical pin 2 are 9.5 mm and 6 mm, respectively, and the length L of the product forming portion of the straight pin 3 is 13 mm and 6 m.
The pin has a draft angle of 1.5 ° with respect to the outer diameter of m, the clearance 4 is set to 0.05 mm at which no burr enters, the length of the annular groove 5 in the pin longitudinal direction is 30 mm, and the depth is 0 0.5 mm. In the conventional core pin, the outer diameter of the mounting part 11 to the mold is 9.5 mm, the outer diameter and the length of the product forming part 12 are 6 mm and 13 mm, respectively, and the radius of curvature of the stepped part 13 is 1 mm. . From Table 1, it can be seen that the core sleeve pin of the present invention has a life of about 8 to about 13 times that of the conventional core pin.

[0007]

[Table 1]

[0008]

Since the core sleeve pin for a mold according to the present invention has the above-described structure, thermal stress, bending stress and product separation occur at the product forming portion of the straight pin mounted on the inner periphery of the cylindrical pin. When subjected to a mold force, the straight pin has less stress concentration than a pin having a stepped portion, and moreover,
Since the straight pin easily bends when subjected to bending stress due to the presence of an annular groove in the inner peripheral part of the cylindrical pin, the bending stress itself can be reduced. Breakage due to fatigue failure at the root of the part is reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a state in which a core sleeve pin according to one embodiment of the present invention is incorporated in a mold.

FIG. 2 is a cross-sectional view showing a state where a conventional core pin is assembled in a mold.

[Explanation of symbols]

1 core sleeve pin, 2 cylindrical pin, 3 straight pin, 5 annular groove

Claims (1)

[Claims] 1. A core sleeve pin for a mold, comprising: a cylindrical pin having an annular groove in an inner peripheral portion; and a core straight pin fitted in the inner peripheral portion.