Cast pin

Abstract

To provide a core pin which has no step at the tip of the shaft and is suppressed from breaking. [Solution] A core pin 13 is provided to protrude into a cavity formed between two dies in order to form a through hole in a casting produced by injecting molten metal into the cavity, and is comprised of a core pin body 21 and a cylindrical needle 31 fitted into the hollow part of the core pin body, with a draft angle θ formed at the tip of the needle. The core pin body has a head 23 with a countersunk hole 25, a shaft 24 connected to the head, and a through hole 26 penetrating the shaft from the head, the needle is inserted into the through hole and has a small head 32 that fits into the countersunk hole and a needle part 35 connected to the small head, the needle part has a draft angle at the part protruding from the shaft part of the core pin body, and a C-chamfer is machined at the tip of the shaft part of the core pin body.

Description

[Technical field]

[0001] The present invention relates to a core pin. [Background technology]

[0002] Patent Document 1 discloses a core pin that protrudes into a cavity formed between two dies to form a hole in a casting that is cast by injecting molten metal into the cavity. This core pin has a cylindrical shaft, and a tip is formed by forming a step at the tip of the shaft, and the diameter of the tip is gradually reduced from the shaft toward the tip to make it easier to remove the core pin from the casting. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-183347 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional technology, when molten metal is injected into a cavity to cast a casting, stress is concentrated at a step at the tip of the shaft of the core pin due to seizure, melting, etc., and the core pin may break starting from the step. Breakage of the core pin directly leads to a decrease in productivity of the casting, a decrease in quality, and an increase in cost. The object of the present invention is to prevent breakage of the core pin. [Means for solving the problem]

[0005] The core pin of the present invention is a core pin that is arranged to protrude into a cavity formed between two molds in order to form a through hole in a casting that is cast by injecting molten metal into the cavity.The core pin of the present invention is composed of a core pin body and a cylindrical needle that is fitted into the hollow portion of the core pin body, and a draft angle is formed at the tip of the needle. Effect of the Invention

[0006] In this invention, the core pin is composed of two parts, and the draft angle that protrudes into the cavity is formed at the tip of the cylindrical needle, so there is no step at the tip of the shaft of the core pin, and breakage of the core pin is suppressed. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a diagram showing a part of a mold for casting a casting product. [Diagram 2] FIG. 4 is a diagram illustrating the arrangement of core pins. [Diagram 3] FIG. 1A is a diagram showing a core pin, FIG. 1B is a cross-sectional view showing a core pin body, and FIG. 1C is a diagram showing a cylindrical needle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Embodiment 1] Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. Note that the first embodiment described below is merely an example, and there is no intention to exclude the application of various modifications and techniques not explicitly described in the first embodiment described below.

[0009] This embodiment 1 can be applied to a cast pin for forming a bolt hole in a flange provided on the outer periphery of the end of an automobile transmission casing cast from aluminum in order to connect the casing to other parts (other casings, etc.).

[0010] Fig. 1 is a diagram showing a part of a metal mold for casting a casting product, and Fig. 2 is a diagram for explaining the arrangement of core pins 13.

[0011] As shown in Fig. 1, the mold 1 is composed of two molds, a fixed mold 3 and a movable mold 5. A cavity 7 is formed between the fixed mold 3 and the movable mold 5. The fixed mold 3 includes a main mold 10 and a core 11, and a core pin 13 is arranged in the core 11. 2, the core pin 13 is inserted through the hole 15 of the master mold 10 and placed in the core pin hole 17 of the insert 11. After the core pin 13 is placed in the core pin hole 17, a porcelain enamel set 19 is screwed into the hole 15 of the master mold 10 as shown in FIG.

[0012] [Cast pin configuration] 3A to 3C are diagrams showing the core pin 13. FIG. As shown in the figure, the core pin 13 has a double structure including a hollow core pin body 21 and a cylindrical needle 31 press-fitted into the hollow portion of the core pin body 21 .

[0013] As shown in FIG. 3B, the core pin body 21 includes a head 23 and a shaft portion 24 continuous with the head 23. The head 23 has an outer diameter of 13 mm and a length of 10 mm. The shaft portion 24 has an outer diameter of 5.94 mm and a length of 51.16 mm. The tip of the shaft portion 24 is chamfered. A countersunk hole 25 is formed in the head 23. The countersunk hole 25 has an inner diameter of 9 mm and a length of 7 mm. A through hole 26 is formed in the core pin body 21, penetrating the shaft portion 24 from the bottom of the countersunk hole 25. The through hole 26 has an inner diameter of approximately 4.33 mm.

[0014] The needle 31 is press-fitted into the through hole 26 of the cast pin body 21 . 3C, the needle 31 has a small head portion 32 and a cylindrical needle portion 35 continuing from the small head portion 32. The small head portion 32 of the needle 31 fits into the countersink 25 of the core pin body 21. The needle portion 35 has a cylindrical shaft portion 36 and a substantially cylindrical tip portion 37 that extends continuous with the tip of the cylindrical shaft portion 36 and protrudes into the cavity 7. The diameter of the tip portion 37 is gradually reduced toward the tip in order to facilitate the removal of the core pin 13 from the casting. A draft angle θ is formed in the tip portion 37 in order to facilitate the removal of the core pin 13 from the casting.

[0015] [Action and effect of cast pins] 3A to 3C, the core pin 13 is formed by fitting a cylindrical needle 31 into a through hole 26 of a core pin body 21. At this time, only a tip portion 37 of the needle 31 protrudes from the tip of the core pin body 21. As shown in FIG. 2, the core pin 13 is inserted through a hole 15 in the main mold 10 and disposed in a core pin hole 17 in the insert 11 .

[0016] In this state, the fixed die 3 and the movable die 5 are assembled as shown in Fig. 1, and molten metal is injected into the cavity 7 formed between the fixed die 3 and the movable die 5 to cast a casting. During casting, stress is concentrated on the tip 37 of the needle portion 35 due to seizure, melting, etc.

[0017] In the present embodiment 1, the cylindrical needle portion 35 is a separate member from the cast pin body 21. The needle portion 35 includes a tip portion 37 extending continuously from the cylindrical shaft portion 36, and the tip portion 37 is formed with a draft angle θ. The cylindrical shaft portion 36 has a uniform outer diameter in the longitudinal direction, and there is no step at the boundary between the cylindrical shaft portion 36 and the tip portion 37. When looking at the core pin 13, since there is no step at the boundary between the cylindrical shaft portion 36 and the tip portion 37, no stress concentration occurs at the boundary. Therefore, breakage of the needle portion 35 is suppressed, and thus breakage of the core pin 13 is suppressed.

[0018] The inventors of the present invention have conducted demonstration tests and have found that when the double-structure core pin 13 of the present invention is used, breakage, which frequently occurred in the past, hardly occurs, there is no bending of the needle portion 35, and it can withstand long-term use.

[0019] In the first embodiment, a core pin 13 is provided which protrudes into a cavity 7 formed between two dies 3 and 5 in order to form a hole in a casting which is cast by injecting molten metal into the cavity 7. The core pin 13 is composed of a core pin body 21 and a cylindrical needle 31 which fits into a through hole 26 of the core pin body 21. A draft angle θ is formed at the tip of the needle 31.

[0020] This prevents breakage of the needle portion 35, and therefore prevents breakage of the core pin 13.

[0021] The core pin body 21 includes a head 23 having a countersunk hole 25, a shaft portion 24 continuous with the head 23, and a through hole 26 penetrating the shaft portion 24 from the head 23. The needle 31 is inserted into the through hole 26 and includes a small head portion 32 which fits into the countersunk hole 25, and a needle portion 35 continuous with the small head portion 32, and the needle portion 35 has a draft angle θ at a portion protruding from the shaft portion 24 of the core pin body 21.

[0022] According to this, the core pin 13 can be easily formed by simply press-fitting the needle 31 into the through hole 26 of the core pin body 21. At this time, only the tip portion 37 of the needle 31 protrudes from the tip of the core pin body 21, and there is no step at the tip portion 37 of the needle 31, so that stress concentration is eliminated and breakage of the needle 31 can be suppressed.

[0023] The tip of the shaft portion 24 of the core pin body 21 is chamfered. According to this, when the needle 31 is pressed into the through hole 26 of the core pin body 21, the outer periphery of the tip of the core pin body 21 and the outer periphery of the tip portion 37 of the needle 31 are smoothly continuous, thereby suppressing seizure, melting damage, etc.

[0024] Although the first embodiment of the present invention has been described above, the present invention can be practiced by appropriately modifying the first embodiment. In the above explanation, the present invention has been described as being applied to a cast pin used in manufacturing a casing for an automobile transmission, but the present invention is not limited to the above casing and can be applied to the formation of through holes in various castings. The present invention is not limited to circular through holes formed in a casting, but can also be applied to through holes of other shapes (for example, elliptical). [Explanation of symbols]

[0025] 1. Mold 3 Fixed type 5 Movable type 13 Cast pin 17 Cast pin hole 21 Cast pin body 23 Head 24 Shaft 25 Counterbore 26 Through hole 31 Needle 32 Small head 35 Needle section 36 Cylindrical shaft 37 Tip θ Draft angle

Claims

1. A core pin is provided to protrude into a cavity formed between two dies in order to form a hole in a casting produced by injecting molten metal into the cavity. The core pin is comprised of a core pin body and a cylindrical needle that is fitted into the hollow portion of the core pin body, and a draft angle is formed at the tip of the needle. Cast pin.

2. The core pin body includes a head having a countersunk hole, a shaft portion connected to the head, and a through hole penetrating the shaft portion from the head, the needle is inserted into the through hole, and includes a small head portion fitted into the countersunk hole and a needle portion connected to the small head portion, and the needle portion is provided with the draft angle at a portion of the core pin body protruding from the shaft portion.

2. The core pin according to claim 1.

3. A C chamfer is machined on the tip of the shaft portion of the core pin body. The core pin according to claim 2.

Images