JP2005144535A - Method for producing bolt with vertical groove - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a bolt with a vertical groove by which the vertical groove having large passage cross-sectional area can easily be formed on the circumferential surface of the shaft part of the bolt with small forming load. <P>SOLUTION: In a production process for the bolt with the vertical groove, at an axial center part of a shaft part 26 in a bolt material 25a, a vertical hole 27 opened to the end surface of the shaft part 26 is formed by a cold-forging. Thereafter, one or a plurality of vertical grooves 28 extended in the longitudinal direction of the shaft part, are formed on the circumferential surface of the shaft part 26 by an opening drawing method (cold-forging) in the shaft part 26. The vertical groove 28 having large passage cross sectional area can easily be formed with the small forming load by the producing method for the bolt with the vertical groove 28 by this opening drawing method. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a vertical groove bolt by cold forging.

  Generally, in a fluid transport passage for transporting a fluid, for example, a lubricating oil supply passage of an automobile engine, a hole-shaped passage formed in a block-shaped member and a tubular shape disposed outside the block-shaped member When connecting to the passage, a joint is used which is inserted or screwed into the hole-like passage on one end side and connected to the tubular passage on the other end side. Conventionally, for example, eyebolts have been widely used as such joints.

  FIGS. 1A and 1B show an example of a connection structure of a fluid transport passage using an eyebolt as a joint. As shown in FIGS. 1 (a) and 1 (b), in this conventional connection structure, a bolt shaft portion with a male thread of an eyebolt 1 is a hole with a female thread formed in a block 2 (block-shaped member). 3 is screwed. A connector 4 is disposed between the head portion of the eyebolt 1 and the block 2. A packing 5 is interposed between the connector 4 and the eyebolt 1 or the block 2. The connector 4 is connected to a hose 8 (tubular passage).

  Here, the hole 3 formed in the block 2 communicates with the hose 8 through the vertical hole 6 and the two horizontal holes 7 formed in the eyebolt 1 and the space in the connector 4. The vertical hole 6 is formed in the axial center of the bolt shaft portion of the eyebolt 1, and is open to the tip surface (lower end surface) of the eyebolt 1. Further, the horizontal hole 7 communicates with the vertical hole 6 and opens to the outer peripheral surface of the bolt shaft portion. Thus, in this connection structure, the fluid flows from the flow path a to the flow path b or in the opposite direction (from the flow path b to the flow path a).

  By the way, in the eyebolt 1 shown in FIGS. 1A and 1B, for example, the vertical hole 6 must be formed in the bolt shaft portion by, for example, plastic working, and further, the horizontal hole 7 must be formed by, for example, punching processing. There is a problem that the manufacturing process becomes complicated and the manufacturing cost increases. Therefore, a longitudinal grooved bolt has been proposed in which a longitudinal groove extending in the longitudinal direction of the axial portion is formed on the peripheral surface of the bolt shaft portion so as to have the same function as the eyebolt (see, for example, Patent Document 1).

2A to 2C show an example of a connection structure of a fluid transport passage using a longitudinal groove bolt as a joint. As shown in FIGS. 2A to 2C, in this conventional connection structure, two vertical grooves 11 are formed on the outer peripheral surface of the bolt shaft portion of the vertical groove bolt 10, and the hole 3 of the block 2 is formed. The space portion in the connector 4 communicates with the vertical groove 11. In such a bolt 10 with a longitudinal groove, the longitudinal groove 11 can be easily formed on the peripheral surface of the shaft portion by, for example, plastic working. In FIG. 2C, L1 indicates a fitting portion between the thread of the male screw of the bolt shaft portion and the screw thread of the female screw of the hole portion 3, L2 indicates the screw outer diameter of the bolt shaft portion, and L3 is The screw inner diameter of the hole portion 3 is indicated, and L4 indicates the root diameter of the bolt shaft portion. The shaded portion indicates a fluid passage formed between the vertical groove 11 and the hole 3. Thus, in this connection structure, fluid flows from the flow path a to the flow path b through the longitudinal groove 11 or in the opposite direction.
Japanese Patent Laid-Open No. 9-4622 (paragraph [0008], FIG. 1)

Such vertical grooved bolts are generally manufactured by the following procedure.
That is, first, as shown in FIGS. 3A to 3C, the bolt material 10b is formed into a bolt shape having the longitudinal grooves 11 by cold forging or the like. Next, as shown in FIGS. 3D to 3F, the male screw 12 is formed on the bolt shaft portion by rolling or the like. Thereby, the bolt 10 with a longitudinal groove is completed.

According to the conventional manufacturing method of the bolt 10 with a longitudinal groove, the longitudinal groove 11 is usually formed by the following procedure by cold forging.
That is, first, as shown in FIGS. 4 (a) and 4 (b), a bolt material 10a having a head portion and a shaft portion and a circular cross section of the shaft portion is formed from a substantially cylindrical groove cold forging die 15. It is arranged at a predetermined upper position. The groove cold forging mold 15 is provided with a hollow portion 16 penetrating in the axial direction, and two groove forming portions 17 bulging inward are provided at the lower portion of the hollow portion 16.

Next, as shown in FIG. 5, the vicinity of the lower end of the shaft portion of the bolt material 10 a is inserted into the space portion 16 of the groove cold forging mold 15. At this time (groove cold forging start time), the portion indicated by R of the shaft portion is not inserted into the space portion 16 and is in an open state not constrained by the groove cold forging die 15. Such a molding technique is generally called open drawing. Then, as indicated by an arrow X1, a forming load is applied to the head of the bolt material 10a.
As a result, as shown in FIG. 6, the bolt material 10 a is pushed into the space portion 16, and the longitudinal groove 11 is formed by the groove forming portion 17 on the peripheral surface of the shaft portion. Thereafter, the bolt material is protruded in the direction indicated by the arrow X2, and the bolt material 10b in which the longitudinal grooves 11 are formed on the outer peripheral surface of the shaft portion as shown in FIGS. 7A and 7B is obtained.

  When the vertical groove 11 is formed by such open drawing, if the load required for forming the vertical groove 11 is larger than the buckling load of the open portion of the shaft portion, the open portion is seated before the formation of the vertical groove 11 is completed. Since it will bend, the vertical groove 11 cannot be formed. For this reason, when the longitudinal groove 11 is formed by open drawing, the limit of the cross-section reduction rate that can be formed is said to be about 25%. In general, the cross-sectional reduction rate is a value defined by the ratio of the total cross-sectional area of the longitudinal groove 11 to the area surrounded by the outer peripheral portion of the shaft portion before molding, as viewed in a cross section perpendicular to the axis of the shaft portion. . 8 (a) and 8 (b), the bolt material 10a before the formation of the longitudinal groove shown in FIG. 8 (a) with respect to the cross-sectional area of the shaft portion (the area of the shaded portion in FIG. 8 (b)). c) The ratio of the cross-sectional area of the vertical groove 11 in the bolt material 10b after forming the vertical groove shown in (d) (the area of the shaded portion in FIG. 8D).

  And when forming the vertical groove 11 by open drawing, since the cross-sectional shape of this vertical groove 11 is unusual, the plastic flow of bolt material becomes non-uniform | heterogenous. As a result, the molding load is increased, and the critical cross-section reduction rate is further reduced accordingly. For this reason, there exists a problem that a channel | path cross-sectional area sufficient to ensure a required flow volume cannot be obtained.

  In addition, a method for manufacturing a bolt with a longitudinal groove is proposed in which a longitudinal groove is formed in a sealed state in a mold before the head portion is formed, and the head portion is formed in a subsequent forging process. Such molding is performed, for example, by the following procedure.

  That is, as shown in FIG. 9A, a substantially cylindrical bolt material 20 a on which no head portion is formed is disposed at a predetermined position above the mold 21. The mold 21 is provided with a hollow portion 22 penetrating through the mold 21 in the axial direction, and a plurality of groove forming portions 23 bulging inward are provided at the lower portion of the hollow portion 22.

  Next, as shown in FIG. 9B, the bolt material 20a is inserted into the space portion 22 of the mold 15 so that there is a region H in which no bolt material exists in the upper portion. That is, the bolt material 20 a is in a sealed state in which it is fully restrained by the mold 21. Such a molding technique is generally called hermetic drawing. Then, as indicated by an arrow X3, a molding load is applied to the bolt material 20a.

  As a result, as shown in FIG. 9C, the bolt material 20a is pushed into the space 22 where the groove forming portion 23 is formed, and the bolt material 20b in which the longitudinal groove is formed on the outer peripheral surface of the shaft portion. Is obtained. Thereafter, a head portion is formed on the bolt material 20b. In such hermetic drawing, it is possible to increase the cross-sectional reduction rate (groove cross-sectional area) as compared to open drawing. However, in order to increase the cross-section reduction rate, the molding load (load / stress applied to the mold) must be increased, and the life of the mold 21 (particularly the groove forming portion 23) is reduced. There is.

  The present invention has been made to solve the above-described conventional problems, and has a longitudinal groove that can easily form a longitudinal groove having a large passage cross-sectional area with a small molding load on the outer peripheral surface of the shaft portion. Providing a method for manufacturing a bolt is a problem to be solved.

  According to the present invention made to solve the above-mentioned problems, a method of manufacturing a bolt with a longitudinal groove in which a longitudinal groove extending in the longitudinal direction of the bolt shaft portion is provided on the outer peripheral surface of the bolt shaft portion is a material for a bolt with a longitudinal groove. Characterized in that a vertical hole is formed in the axial portion of the shaft-shaped portion to be the bolt shaft portion, and a vertical groove is formed in the shaft-shaped portion by cold forging. To do.

  In the above method for producing a bolt with a longitudinal groove, cold forging is performed by pressing (press-fitting) a shaft-like portion into the die in a state where a portion of the shaft-like portion is not restrained by the die. It is preferable to use open drawing. In this case, it is defined by the ratio of the cross-sectional area of the longitudinal groove and the area enclosed by the outer periphery of the shaft-like part before molding (including the area of the part of the vertical hole) as viewed in a cross section perpendicular to the axis of the shaft-like part. It is more preferable to perform open drawing so that the cross-sectional reduction rate is 25 to 50%.

  According to the method for manufacturing a bolt with a longitudinal groove according to the present invention, when forming a longitudinal groove by cold forging, a longitudinal hole opened in the tip surface of the shaft-shaped portion is formed in the shaft core portion of the shaft-shaped portion in advance. Since it is formed, a longitudinal groove having a large passage cross-sectional area can be easily formed on the peripheral surface of the shaft-shaped portion with a very low molding load. That is, the passage cross-sectional area of the longitudinal groove can be increased without causing problems such as buckling of the bolt shaft portion and a decrease in the life of the mold.

  Hereinafter, embodiments of the present invention will be specifically described. The longitudinal grooved bolt manufactured by the method according to the present invention basically has the same configuration as the conventional longitudinal grooved bolt shown in FIGS. 3D to 3F, for example. One or a plurality of (for example, two) longitudinal grooves extending in the longitudinal direction of the bolt shaft portion are formed on the outer peripheral surface of the bolt. However, as will be described later, the passage sectional area of the longitudinal groove, that is, the area of the passage section perpendicular to the axis of the bolt shaft, is larger than that of the conventional longitudinal grooved bolt. And the hole part formed in the block and the hose (tubular passage) provided in the block are connected with a form as shown, for example in Drawing 2 (a) and (b). The longitudinal groove bolt is used, for example, as a joint such as a lubricating oil supply passage or a fuel supply passage of an automobile engine.

  First, the outline | summary of the manufacturing method of the bolt with a longitudinal groove concerning this invention is demonstrated. In this vertical grooved bolt manufacturing method, the vertical grooved bolt material (bolt material) is connected to the axial center portion of the cylindrical shaft-shaped portion to be the bolt shaft portion on the tip surface (bottom surface) of the shaft-shaped portion. A cylindrical vertical hole opening in the end face) is formed. Thereafter, the shaft-shaped portion is subjected to open drawing by cold forging to form vertical grooves on the outer peripheral surface of the shaft-shaped portion. This cold forging is performed by open drawing, in which the shaft-like portion is pushed into the die in a state where a portion of the shaft-like portion is not restrained by the die. According to the manufacturing method of the bolt with a longitudinal groove by this open drawing, a longitudinal groove having a cross-sectional reduction rate of 25 to 50% can be easily formed.

Hereinafter, with reference to FIGS. 10 (a) to (d), “a more specific manufacturing method of the bolt with a longitudinal groove according to the present invention will be described.
In this vertical grooved bolt manufacturing process, first, as shown in FIGS. 10A and 10B, a substantially cylindrical shaft of a bolt material 25a having a head portion 24 (bolt head) formed at one end thereof. A cylindrical vertical hole 27 is formed in the portion 26 by cold forging. The vertical hole 27 is formed in the shaft core portion of the shaft portion 26, and is open to the tip surface of the shaft portion 26 (on the side opposite to the head portion 24). The longitudinal dimension (length) of the longitudinal hole 27 is substantially the same as the longitudinal dimension (length) of the longitudinal groove 28 (see FIG. 10C) formed in the subsequent process. It is.

  The diameter (inner diameter) of the vertical hole 27 is preferably set according to the passage cross-sectional area of the vertical groove 28 to be formed (area of the cross section perpendicular to the axis of the shaft portion). That is, the diameter of the vertical hole 27 is increased when the cross-sectional area of the vertical groove 28 to be formed is increased, and the diameter of the vertical hole 27 is decreased when the cross-sectional area is decreased. The diameter of the vertical hole 27 is preferably set so that the vertical hole 27 substantially disappears when the vertical groove 28 having a desired passage cross-sectional area is formed. That is, the diameter of the vertical hole 27 is set so that the cross-sectional area of the vertical hole 27 is substantially equal to the total cross-sectional area of the vertical groove 28.

  Next, as shown in FIGS. 10C and 10D, one or a plurality of (for example, two) vertical grooves 28 are formed on the outer peripheral surface of the shaft portion 26 by cold forging. At that time, due to the plastic flow of the flesh portion of the shaft portion 26, the vertical hole 27 is almost disappeared and only a small space portion 27 'remains. Thereafter, a screw is formed on the outer peripheral surface of the bolt material 25b by rolling or the like. Thereby, the bolt with a longitudinal groove is completed.

  This cold forging is basically performed by conventional open drawing as shown in FIGS. Thus, since the vertical hole 27 is provided in the axial part 26, in this open drawing molding, the flesh part of the axial part 26 deforms easily plastically. Therefore, the molding load when forming the vertical groove 28 can be significantly reduced. For this reason, even if the passage cross-sectional area of the longitudinal groove 28 is increased, the shaft portion 26 in the open state does not buckle. Therefore, it is possible to easily form the longitudinal groove 28 having a large cross-sectional reduction rate, that is, a large passage cross-sectional area, on the outer peripheral surface of the shaft portion 26 with a very low molding load. That is, the passage area of the longitudinal groove 28 can be increased without causing problems such as buckling of the shaft portion 26 and a decrease in the life of the mold.

  In this embodiment, the vertical grooves 28 are formed by open drawing, but the shaft portion is formed before the head portion is formed by, for example, hermetic drawing as shown in FIGS. A vertical groove may be formed on the surface. Also in this case, the passage cross-sectional area of the longitudinal groove 28 can be increased as in the case of open drawing, and the life of the mold can be improved.

  FIG. 11A shows a cross section of the longitudinal groove 11 of the bolt material 10b manufactured by the conventional manufacturing method (open drawing), and FIG. 11B shows the manufacturing method (open drawing) according to the present invention. The passage cross section of the longitudinal groove 28 of the manufactured bolt material 25b is shown. As is clear from FIGS. 11A and 11B, the bolt material 25b manufactured by the manufacturing method according to the present invention has a depth of the longitudinal groove 28 as compared with the bolt material 10b manufactured by the conventional manufacturing method. Therefore, for example, the passage sectional area of the longitudinal groove 28 can be increased without reducing the fitting peripheral length between the thread of the female screw in the hole and the screw thread of the bolt shaft. In addition, when this fitting peripheral length is short, problems, such as a squeezing at the time of clamping | tightening, generation | occurrence | production of a chip | tip, and the shear stress destruction of a screw thread, will arise.

  As mentioned above, according to the manufacturing method of the bolt with a longitudinal groove concerning the present invention, about the fluid passage defined by the longitudinal groove of the bolt shaft part provided with the external thread, and the inner peripheral surface of the hole part provided with the internal thread, The passage area in the cross section perpendicular to the axis of the bolt shaft portion can be enlarged, the flow rate of the fluid flowing in the longitudinal grooved bolt can be increased, or the pressure loss can be reduced.

(A) is a top view of a conventional eyebolt, and (b) is a partial cross-sectional elevation view of a fluid transport passage connection structure using the eyebolt shown in (a). (A) is a top view of the conventional longitudinal grooved bolt, (b) is a partial sectional elevation view of the connection structure of the fluid transport passage using the longitudinal grooved bolt shown in (a), (c) ) Is a cross-sectional view taken along line AA of FIG. (A), (b), and (c) are a top view, an elevation view, and a bottom view of a bolt material of a conventional longitudinal grooved bolt, respectively, (d), (e), and (f) are They are a top view, an elevation view, and a bottom view of a conventional longitudinal grooved bolt, respectively. (A) is a partial cross-sectional elevation view of a bolt material and a groove cold forging mold of a conventional vertical grooved bolt, and (b) is a cross-sectional view taken along line BB in FIG. 4 (a). It is a partial cross section elevation of a groove cold forging metal mold in the state where bolt material was inserted in the space part. It is a partial cross section elevation view of a groove cold forging metal mold in the state where bolt material was pushed into a space part. (A) And (b) is a partial cross section elevation and bottom view of the conventional longitudinal grooved bolt, respectively. (A) is a partial sectional elevation view of the bolt material before forming the longitudinal groove, (b) is a sectional view taken along the line CC of FIG. 8 (a), and (c) is the bolt after forming the longitudinal groove. It is an elevation view of material, (d) is the DD sectional view taken on the line of FIG.8 (c). (A) is a partial cross-sectional elevation view of the bolt material and mold in hermetic drawing, (b) is a partial cross-sectional elevation view of the mold in a state where the bolt material is inserted into the space, (C) is a partial cross-sectional elevation view of the mold in a state in which the bolt material is pushed into the space. (A) is a partial cross-sectional elevation view of the bolt material after forming the vertical hole, (b) is a cross-sectional view taken along line EE of FIG. 10 (a), and (c) is the bolt material after forming the vertical groove. Fig. 10 (d) is a partial cross-sectional elevation view of Fig. 10 (c). (A) is a figure which shows the channel | path cross section of the vertical groove | channel of the bolt material manufactured with the conventional manufacturing method, (b) shows the channel | path cross section of the vertical groove | channel of the bolt material manufactured with the manufacturing method concerning this invention. FIG.

Explanation of symbols

1 eye bolt, 2 blocks, 3 holes, 4 connector, 5 packing, 6 vertical hole, 7 horizontal hole, 8 hose, 10 vertical grooved bolt, 10a bolt material, 10b bolt material, 11 vertical groove, 12 screw, 15 groove cold Forging mold, 16 space part, 17 vertical groove forming part, 20a bolt material, 20b bolt material, 21 mold, 22 space part, 23 vertical groove forming part, 24 head part, 25a bolt material, 25b bolt material, 26 Shaft, 27 vertical holes, 28 vertical grooves.

Claims (3)

On the outer peripheral surface of the bolt shaft part, there is a method for producing a bolt with a longitudinal groove provided with a longitudinal groove extending in the longitudinal direction of the bolt shaft part,
In the axial groove portion of the shaft-shaped portion to be the bolt shaft portion of the material of the bolt with the vertical groove, a vertical hole that opens to the tip surface of the shaft-shaped portion is formed,
A method of manufacturing a bolt with a longitudinal groove, wherein the longitudinal groove is formed in the shaft-like portion by cold forging.   2. The cold forging is open drawing forming in which the shaft-like portion is formed by being pushed into the die in a state where a part of the shaft-like portion is not constrained by the die. A manufacturing method of the bolt with a longitudinal groove given in 2. The cross-sectional reduction rate defined by the ratio of the cross-sectional area of the longitudinal groove and the area surrounded by the outer periphery of the shaft-shaped portion before molding is 25 to 50% when viewed in a cross section perpendicular to the axis of the shaft-shaped portion. The method of manufacturing a bolt with a longitudinal groove according to claim 2, wherein the open drawing is performed.

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