JPH065009Y2 - Core pin for mold - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is for a die that is provided in a protruding manner on the cavity surface of the die to form a tap hole or the like in a casting product in die casting. Regarding the core pin, more specifically, a commonly-known stepped core pin in which the shaft diameter of the product forming part that is projected from the mold cavity surface with respect to the insertion part that is inserted into the pin mounting hole of the mold is small. The present invention relates to a so-called mold core pin.

<Prior Art> In this type of mold core pin, the product forming portion protruding from the cavity surface acts in a direction orthogonal to the axial direction due to solidification shrinkage of the molten metal filled in the mold cavity. It is repeatedly affected by bending stress. The bending stress concentrates at the boundary between the insertion part and the product forming part, that is, at the root part of the product forming part, because stress concentration occurs dynamically at the boundary part where the diameters differ for rod-shaped materials. Therefore, there is a problem that the root portion of the product forming portion causes metal fatigue and the core pin is easily broken from the base portion of the product forming portion.

<Problems to be Solved by the Invention> The present invention has been made in view of such a conventional problem, and it disperses and relaxes the stress concentration applied to the base portion of the product forming portion protruding from the cavity surface of the mold. ,as a result,
An object of the present invention is to provide a mold core pin that does not easily break for a long period of time even if it is repeatedly affected by bending stress caused by solidification shrinkage of the molten metal.

<Means for Solving the Problems> A mold core pin of the present invention that achieves such an object is a cavity surface of a mold with respect to an insertion portion that is inserted into a pin mounting hole of the mold. In a mold core pin in which a shaft diameter of a product forming portion to be projected is formed to be small, a concave groove is formed in a circumferential direction on an outer peripheral portion of the inserting portion near the product forming portion. Is.

<Embodiment> An embodiment of the present invention will be described below with reference to the drawings.

In the drawings, A represents a mold core pin according to the present invention, and B represents a mold for molding in which the mold core pin A is mounted.

The mold core pin A according to the present invention is basically inserted into and supported by a pin mounting hole B ₂ formed in the mold B from the cavity surface B ₁ toward the back surface thereof, as in the conventional case. Dress A ₁
The product forming portion A ₂ formed to have a smaller diameter than the shaft diameter of the inserting portion A ₁ and protruding from the cavity surface B _{1 of the} mold B is formed in the same coaxial body, and the inserting portion A ₁ and the product forming portion are formed together. boundary between the part a _2, namely the base portion of the product forming section a _2, to form a rounded to Anaguchi edge of tapped holes or the like formed in the element formation section a ₂ (forming the chamfered portion) for It is formed by forming an arcuate step portion 1.

Then, the tip end side of the insertion portion A ₁ inserted into the pin attachment hole B ₂ of the mold B, that is, the product forming portion A in the insertion portion A ₁ .
_A concave groove 2 is formed in the circumferential direction on the outer peripheral portion nearer to 2.

It grooves 2, because the stress concentration applied to the root portion of the product forming section A ₂ is dispersed relax when subjected to bending stress product forming area A ₂ by the solidification shrinkage of the molten metal filled in the cavity of the mold B The outer peripheral portion of the insertion portion A ₁ closer to the product forming portion A ₂ , more specifically, the outer peripheral portion of the portion located in the vicinity of the mold cavity surface B ₁ in the pin mounting hole B ₂ in the circumferential direction. 1 to a plurality of them are formed.

That is, in the first embodiment shown in FIGS. 1 and 2,
_One wide groove 2 is formed near the product forming portion A ₂ of the insertion portion A ₁ located in the pin mounting hole B ₂ of the mold B. In addition, the second embodiment shown in FIG.
A plurality of (three) recessed grooves 2 are formed in a ring shape along the circumferential direction at the insertion portion A ₁ located in the pin mounting hole B ₂ of the mold B toward the product forming portion A _2, and have the same width and spacing. In addition to the above, the depth of each recessed groove 2 is formed to be gradually shallower substantially along the extended tangent line m of the draft of the product forming portion A ₂ .
In addition, in the second embodiment, it is free to form the recesses 2 with the same depth and to form the recesses 2 with different widths and intervals.

<Effect of the Invention> Since the mold core pin of the present invention is configured in this way, when the bending stress caused by the solidification shrinkage of the molten metal filled in the mold cavity is applied to the product forming part, The stress concentration to be applied to the root portion of the forming portion is dispersed and relaxed by the concave groove. That is, in a rod-shaped material having a different diameter, stress concentration occurs dynamically at a boundary portion having a different diameter, but in the case of the mold core pin according to the present invention, the boundary portion having a different diameter is located at the root portion of the product forming portion and its Since it exists in the concave groove in the vicinity, the stress related to the product forming portion is distributed to the concave groove or the root portion of the product forming portion. As a result, even if the product forming part is repeatedly affected by the bending stress due to the solidification shrinkage of the molten metal filled in the cavity of the mold, the root part of the product forming part is less likely to cause metal fatigue, and the core is This eliminates the risk of the pin breaking from the root of the product forming part.

In addition, Table 1 below shows comparative data in actual operation of the core pin according to the present invention and the conventional core pin (the number of castings until the core pin attached to the mold is broken).

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention assembled in a mold, FIG. 2 is a sectional view taken along line (2)-(2) of FIG. 1,
FIG. 3 is a sectional view showing the second embodiment of the present invention in a state of being assembled in a mold. In the figure, A: core pin A ₁ : insertion part, A ₂ : product forming part B: mold B ₁ : cavity surface, B ₂ : pin mounting hole 1: arcuate step part, 2: concave groove

Claims (1)

[Scope of utility model registration request] 1. A die core pin for a mold, wherein a shaft diameter of a product forming portion which is made to protrude from a cavity surface of the die with respect to an inserting portion inserted into a pin mounting hole of the die is small. A core pin for a die, characterized in that a groove is formed in a circumferential direction in an outer peripheral portion of the insertion portion near the product forming portion.