Serration manufacturing method

Abstract

To provide a serration manufacturing method by which a highly accurate serration can be formed.SOLUTION: A serration manufacturing method includes: a diameter changing step of forming a large diameter portion 2 on one side in an axial direction ad and a small diameter portion 4 on the other side in the axial direction ad, by making a diameter of a part of a cylindrical member 1 relatively smaller than that of the other part; a thickness adjusting step of forming a thick portion 6 on the small diameter portion 4 by inserting a core metal from an end part 3 on a large diameter portion side to the small diameter portion 4 and bringing a thickness of an inner peripheral surface of the small diameter portion 4 closer to an end part 5 on a small diameter portion side; and a serration forming step of forming a serration 7 on the inner peripheral surface of the small diameter portion 4 by inserting a serration tool 19 having a shape corresponding to a teeth shape of the serration 7 into the cylindrical member 1 from the end part 5 on the small diameter portion side.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing serrations for forming serrations on the inner peripheral surface of a cylindrical member. [Background technology]

[0002] In the past, with the aim of producing high-quality outer shafts at low cost, Japanese Patent Application Laid-Open No. 11-247835 discloses a technology in which a drawn portion is formed in a hollow, circular tube-shaped material, and a punch is pressed into the inside of this drawn portion to form female serrations on the inner peripheral surface of the drawn portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-247835 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the technology disclosed in Patent Document 1, when a serration tool for forming serrations is inserted into the drawn portion, as shown in Figure 12 and its enlarged view, the material on the inner circumferential surface near the end 105 of the small-diameter portion (drawn portion), where the serration tool is inserted, escapes downward (in the direction of arrow ar in the figure) and upward (in the direction of arrow al in the figure) in the axial direction ad. Therefore, while the teeth of the formed serrations 107 should have a height h1, as shown by the dashed line in the enlarged view of Figure 12, the tooth height h2 near the end is insufficient, as shown by the solid line. This poses a problem, making it difficult to form serrations 107 with high precision.

[0005] The present invention has been made in view of the above points, and an object of the present invention is to provide a method for manufacturing serrations that can form serrations with high precision. [Means for solving the problem]

[0006] The method for producing serrations of the present invention comprises: a diameter changing step of making a diameter of a part of the cylindrical member relatively smaller than that of the other part to form a large diameter part on one side in the axial direction and a small diameter part on the other side in the axial direction; a thickness adjusting step of inserting a core bar from an end of the large diameter portion to the small diameter portion, and shifting the wall of the inner circumferential surface of the small diameter portion toward the end of the small diameter portion to form a thick portion in a part of the small diameter portion; a serration forming step of inserting a serration tool having a shape corresponding to the tooth profile of the serration into the cylindrical member from the end on the small diameter portion side to form serrations on the inner peripheral surface of the small diameter portion; The present invention is characterized by comprising:

[0007] According to the serration manufacturing method of the present invention, the thickness adjustment step increases the thickness near the end of the small diameter portion, thereby reducing the inner diameter near the end. This prevents the serration teeth from becoming insufficient near the end when the serration tool is inserted, allowing for the formation of highly accurate serrations.

[0008] A preferred example of the method for producing serrations of the present invention is The core bar has a core bar head portion provided at the tip of the core bar and having a diameter equal to or larger than the inner diameter of the small diameter portion, and a core bar shaft portion provided at the base side of the core bar head and having a diameter smaller than the inner diameter of the small diameter portion.

[0009] A preferred example of the method for producing serrations of the present invention is In the thickness adjusting step, the mandrel head is inserted until it penetrates through the end on the small diameter portion side, and then is not returned to the small diameter portion.

[0010] According to these preferred examples of the method for manufacturing serrations of the present invention, the shaft portion of the core is configured to be thinner than the inner diameter of the small diameter portion, thereby reducing resistance when inserting the core into the small diameter portion.

[0011] A preferred example of the method for producing serrations of the present invention is The diameter of the portion of the core that is inserted into the small diameter portion is equal to or larger than the inner diameter of the small diameter portion, and the length of the portion that is inserted into the small diameter portion is equal to or larger than the length of the small diameter portion.

[0012] A preferred example of the method for producing serrations of the present invention is In the thickness adjusting step, the core is inserted until the tip of the core projects from the end on the small diameter portion side, and then returned to the large diameter portion side.

[0013] According to these preferred examples of the method for manufacturing serrations of the present invention, the core is returned to the side of the large diameter portion, so that the thickness adjustment process can be completed by the reciprocating motion of the press mechanism that presses the core.

[0014] A preferred example of the method for producing serrations of the present invention is In the thickness adjusting step, the outer peripheral surface of the small diameter portion is constrained by a die, and an abutment is brought into contact with the end portion on the small diameter portion side without applying back pressure.

[0015] According to a preferred example of the serration manufacturing method of the present invention, in the thickness adjustment process, the outer peripheral surface and end of the small diameter portion are surrounded by the die and the butt. Therefore, when the core is inserted into the small diameter portion, the outer diameter of the small diameter portion does not expand, and the end on the small diameter portion side does not stretch. This improves the accuracy of the inner diameter dimension of the small diameter portion in the thickness adjustment process. Furthermore, although the position of the butt does not move, no back pressure (pressure) is applied when abutting against the end on the small diameter portion side. This simplifies management during manufacturing.

[0016] A preferred example of the method for producing serrations of the present invention is In the serration forming process, the outer peripheral surface of the small diameter portion is restrained by a die, and a butt is brought into contact with the end of the small diameter portion without applying back pressure, and a butt is also brought into contact with the end of the large diameter portion without applying back pressure.

[0017] According to a preferred embodiment of the serration manufacturing method of the present invention, in the serration forming step, the outer peripheral surface and end of the small diameter portion are surrounded by the die and the butt. Therefore, when the serration tool is inserted into the small diameter portion, the material on the inner peripheral surface does not escape toward the end of the small diameter portion. This improves the accuracy of the serration. Furthermore, although the position of the butt does not move, no back pressure (pressure) is applied when the butt is brought into contact with the end of the small diameter portion and the end of the large diameter portion. This simplifies manufacturing management. [Effects of the Invention]

[0018] As described above, the method for manufacturing serrations of the present invention makes it possible to form serrations with high precision. [Brief explanation of the drawings]

[0019] [Figure 1] 10A and 10B are diagrams illustrating a method for manufacturing serrations according to an embodiment of the present invention, and are diagrams illustrating a cylindrical member and a diameter changing process. [Figure 2] FIG. 10 is another diagram illustrating the diameter changing process. [Figure 3] FIG. 10 is another diagram illustrating the diameter changing process. [Figure 4] FIG. 10 is a diagram illustrating a thickness adjusting process. [Figure 5] 10A and 10B are diagrams illustrating a thickness adjusting step and a thick portion formed by the thickness adjusting step. [Figure 6] 10 is a diagram showing the cylindrical member being discharged from the die after the wall thickness adjusting step. FIG. [Figure 7] 10A and 10B are diagrams illustrating a serration forming step. [Figure 8] FIG. 10 is a diagram illustrating a state in which serrations are formed. [Figure 9] 10A and 10B are diagrams illustrating a state in which the cylindrical member is discharged. [Figure 10] 10A and 10B are diagrams illustrating another embodiment of the thickness adjusting step. [Figure 11] 10A and 10B are diagrams illustrating another embodiment of the thickness adjusting step. [Figure 12]FIG. 1 is a diagram illustrating a conventional technique. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of a method for manufacturing serrations according to the present invention will be described in detail with reference to the accompanying drawings. The cylindrical members 1, 100 and their processed products in Figures 1 to 12 are all shown as cross-sectional views. The diagram enclosed by the dashed-dotted line in the upper right of Figure 1 is a plan view of the cylindrical member 1 as viewed from the axial direction ad.

[0021] The method for manufacturing serrations of this embodiment includes a diameter changing step, a thickness adjusting step, and a serration forming step.

[0022] As shown in FIGS. 1 to 3 , the diameter-changing process involves reducing the diameter of a portion of the cylindrical member 1 relative to the diameter of the other portion, thereby forming a large-diameter portion 2 on one side in the axial direction ad and a small-diameter portion 4 on the other side in the axial direction ad. In this embodiment, the cylindrical member 1 is reduced in diameter by forcing it into a die 10, whose inner diameter d4 is the same as the outer diameter d10 of the cylindrical member 1, and a die 11, whose inner diameter d5 is the same as the outer diameter d11 of the small-diameter portion 4 (see FIG. 3 ), using a press cylinder 12. This diameter-reducing process forms the small-diameter portion 4, resulting in the large-diameter portion 2 and the small-diameter portion 4 having relatively different diameters. Furthermore, a butt 16 is disposed at the point where the end 5 on the side that will become the small-diameter portion 4 abuts during the diameter-reducing process. In this embodiment, an end block 16 is used as the butt 16 and may be referred to as the "end block" hereinafter. The end block 16 is also used to eject the cylindrical member 1 after processing is complete. In this embodiment, the large diameter portion 2 and the small diameter portion 4 are formed by reducing the diameter of a portion of the cylindrical member 1, but conversely, the large diameter portion 2 may be formed by expanding the diameter of a portion of the cylindrical member 1. In addition, other dies (not shown) may be used around the cylindrical member 1 as appropriate.

[0023] As shown in FIGS. 4 and 5 , the thickness adjusting process involves inserting the core 13 from the end 3 on the large-diameter side to the small-diameter portion 4. First, the configuration of the core 13 will be described. The core 13 includes a core head 14 and a core shaft 15. The core head 14 is a cylindrical member provided at the tip of the core, with a diameter d2 equal to or greater than the inner diameter d1 of the small-diameter portion 4. In this embodiment, the diameter d2 of the core head 14 is set to be the same as the inner diameter d1 of the small-diameter portion 4. The axial length L1 of the portion of the core head 14 with the largest diameter d2 is approximately 3 to 10 mm, which is approximately 0.2 to 2 times the inner diameter d1 of the small-diameter portion 4. Thus, the length L1 of the core head 14 is configured to be shorter than the length L2 of the small-diameter portion 4. The core shaft 15 is a rod-shaped member provided at the base of the core 13, with a diameter d3 smaller than the inner diameter d1 of the small-diameter portion 4. The mandrel head 14 is inserted from the end 3 on the large diameter side, and the press cylinder 12 is brought into contact with the base side (upper side in the figure) of the mandrel shaft 15 via an adapter or the like (not shown) as appropriate, and the mandrel head 14 is inserted into the small diameter part 4. At this time, the mandrel head 14 is inserted until it passes through the end 5 on the small diameter part.

[0024] The outer peripheral surface of the small-diameter portion 4 is constrained by the die 11 to prevent expansion when the mandrel head 14 is inserted. The end block 16 also abuts against the end 5 on the small-diameter portion side, constraining its axial direction ad. At this time, the end block 16 only abuts against the end 5 on the small-diameter portion side without applying any back pressure, but the position of the end block 16 is fixed and does not move. The end 3 on the large-diameter portion side is not abutted against anything and is left free. After the mandrel head 14 is inserted until it penetrates the end 5 on the small-diameter portion side, the cylindrical member 1 is ejected from the dies 10 and 11 by the end block 16 with the mandrel head 14 still below, as shown in Figure 6. The mandrel 13 is then removed by pushing it up with another knockout (not shown), or by inserting a rod-shaped member (not shown) with a magnet attached to its tip into the dies 10 and 11 to attract and pull up the mandrel 13.

[0025] This thickness adjustment process irons the inner circumferential surface of the small-diameter portion 4, smoothing out any slight irregularities on the inner circumferential surface. Furthermore, as shown by arrow a1 in Figure 4 , the inner circumferential surface of the small-diameter portion 4 is pushed toward the end 5 and its vicinity on the small-diameter portion side. As a result, as shown in the enlarged view of Figure 5 , the thickness t1 (shown by the dashed line) at the end 5 and its vicinity on the small-diameter portion side thickens inward to the thickness t2 (shown by the solid line), forming a thick-walled portion 6 at the end 5 and its vicinity on the small-diameter portion side. This is thought to be because the wall pushed toward the end 5 near the end 5 on the small-diameter portion side elastically deforms, similar to springback, and returns to its original thickness t2, resulting in a smaller inner diameter and the formation of the thick-walled portion 6. Note that the thick-walled portion 6 is exaggerated in the enlarged view of Figure 5 ; in reality, the thick-walled portion 6 does not undergo such dimensional changes. Specifically, the dimensional change in the wall thickness is about 0.01 mm to 0.03 mm for a cylindrical member 1 having a diameter d10 of 20 to 30 mm (see FIG. 1) and a wall thickness t1 of about 3 to 5 mm.

[0026] Here, with reference to FIGS. 10 and 11 , a wall thickness adjusting process according to another embodiment will be described. Here, too, the configuration of the core 20 will be described first. The core 20 used in the wall thickness adjusting process of this embodiment includes a core head 21 and a core shaft 22. The core head 21 is a cylindrical member provided at the tip of the core 20 and has a diameter d20 that is equal to or greater than the inner diameter d1 of the small diameter portion 4. In this embodiment, the diameter d20 of the core head 21 is the same as the inner diameter d1 of the small diameter portion 4. The axial length L20 of the portion of the core head 21 with the largest diameter d20 is longer than the length L2 of the small diameter portion 4. The core shaft 22 is a rod-shaped member provided at the base side of the core 20 and has a diameter d21 that is smaller than the inner diameter d1 of the small diameter portion 4. The mandrel head 21 is inserted from the end 3 on the large-diameter portion side, and the press cylinder 12 is brought into contact with the base side (upper side of the figure) of the mandrel shank 22 via an adapter (not shown) or the like, and the mandrel head 21 is inserted into the small-diameter portion 4 (arrow a20). At this time, the mandrel head 21 is inserted until the tip 23 of the mandrel head 21 protrudes from the end 5 on the small-diameter portion side. Note that the entire length of the mandrel 20 may be the diameter of the mandrel head 21, and the mandrel shank 22 may be eliminated. The outer peripheral surface of the small-diameter portion 4 is restrained by the die 11, and the end 5 on the small-diameter portion side is restrained by the end block 16, as in the above embodiment. The end block 24 also abuts against the end 3 on the large-diameter portion side, but no particular pressure is applied to this either.

[0027] Next, as the press cylinder 12 rises, the core 20 also simultaneously moves toward the large diameter portion 2 and is pulled out from the end 3 on the large diameter portion side (arrow a21). At this time, the end 3 on the large diameter portion side abuts against the end block 24, so the cylindrical member 1 does not rise together with the core 20.

[0028] Furthermore, in another embodiment of the wall thickness adjusting process (not shown), the mandrel heads 14, 21 may be stopped midway through the small diameter portion 4 and pulled back toward the large diameter portion 2. In such a case, the diameters d2, d20 of the mandrel heads 14, 21 are preferably larger than the inner diameter d1 of the small diameter portion 4. In this embodiment, the thick-walled portion can be formed thicker.

[0029] As shown in Figures 7 and 8, the serration forming process involves inserting a serration tool 19, which has a shape corresponding to the tooth profile of the serrations 7, into the cylindrical member 1 from the end 5 on the small-diameter side. In this serration forming process, the die 11 restrains the outer peripheral surface of the small-diameter portion 4 so that it does not expand. The end 5 on the small-diameter side is also restrained by an end block 18 abutting against it in the axial direction ad. Again, the end block 18 abuts against the end 5 on the small-diameter side without applying back pressure, with only its position fixed. Furthermore, the end block 17 abuts against the end 3 on the large-diameter side without applying pressure, and the outer peripheral surface of the large-diameter portion 2 is also surrounded by the die 10. The dimensions of the end block 18 abutting against the end 5 on the small-diameter side are optimized to allow the serration tool 19 to be inserted.

[0030] When the serration tool 19 is inserted into the small-diameter portion 4, the material near the end 5 of the small-diameter portion 4 tends to escape toward the end (downward in the figure) and toward the back of the small-diameter portion 4 (upward in the figure) (see the enlarged view in FIG. 12, arrows ar and al). Regarding downward escape, the end block 18 abuts against the end 5, preventing material from escaping toward the end. Regarding upward escape, the thick-walled portion 6 is formed at and near the end 5 of the small-diameter portion by the wall thickness adjustment process described above. Therefore, there is sufficient wall thickness in the relevant area, and even if material escapes, the tooth height of the serrations 7 will not be insufficient. The serration tool 19 is then withdrawn upward in the figure, completing the serration forming process. Through this serration forming process, the serrations 7 are formed on the inner circumferential surface of the small-diameter portion 4. Then, as shown in FIG. 9, the end block 18 pushes the cylindrical member 1 up and out of the dies 10 and 11, and the cylindrical member 1 is ejected.

[0031] As described above, according to the serration manufacturing method of this embodiment, the thickness adjustment step of inserting a mandrel from the end of the large diameter portion to the small diameter portion allows for the formation of thicker portions at and near the end of the small diameter portion, thereby addressing material loss that occurs during the serration forming step. This allows for the formation of highly accurate serrations while simplifying the manufacturing equipment and manufacturing steps.

[0032] Furthermore, the mandrel is divided into a mandrel head and a mandrel shaft, and the length of the mandrel head is shorter than the length of the small diameter portion. This reduces resistance when inserting the mandrel, thereby reducing the load on the press equipment and mold. Furthermore, in the wall thickness adjustment process, the mandrel head is inserted until it penetrates the small diameter portion, eliminating the need for position adjustment or management of how far into the small diameter portion the mandrel head is inserted and then pulled back, thereby simplifying the manufacturing process. Furthermore, in the wall thickness adjustment process and serration formation process, there is no need to apply back pressure to the end on the small diameter portion side, thereby simplifying the manufacturing equipment and manufacturing process.

[0033] In addition, in an embodiment in which a core bar whose head length is longer than the small diameter portion is used, the core bar can be pushed into the small diameter portion and then pulled out as is, thereby shortening the takt time during manufacturing.

[0034] The above-described method for manufacturing serrations is merely an example of the present invention, and its configuration can be modified as appropriate without departing from the spirit of the invention. For example, the end portion on the large diameter side can be reduced in diameter later to form serrations on the end portion on the large diameter side, or processing other than serrations can be performed. [Explanation of symbols]

[0035] 1,100··Cylindrical member, 2··Large diameter portion, 3··End portion on the large diameter portion side, 4··Small diameter portion, 5,105··End portion on the small diameter portion side, 6··Thick portion, 7,107··Serration, 10, 11·· Die, 12·· Press cylinder, 13·· Core bar, 14·· Core bar head, 15·· Core bar shaft portion, 16, 17, 18·· End block, 19·· Serration tool, 20···Core metal, 21···Core metal head, 22··Core metal shaft portion, 23···Tip, 24···End block, ad··Axial length, h1, h2··Tooth height, d1, d2, d3, d4, d5, d10, d11, d20, d21··Diameter, t1, t2··Wall thickness,

Claims

1. a diameter changing step of making a diameter of a part of the cylindrical member relatively smaller than that of the other part to form a large diameter part on one side in the axial direction and a small diameter part on the other side in the axial direction; a thickness adjusting step of inserting a core bar from an end of the large diameter portion to the small diameter portion, and shifting the wall of the inner circumferential surface of the small diameter portion toward the end of the small diameter portion to form a thick portion in a part of the small diameter portion; a serration forming step of inserting a serration tool having a shape corresponding to the tooth profile of the serration into the cylindrical member from the end on the small diameter portion side to form serrations on the inner peripheral surface of the small diameter portion; A method for manufacturing serrations, comprising:

2. The method for manufacturing serrations described in claim 1, wherein the core bar comprises a core bar head portion having a diameter equal to or larger than the inner diameter of the small diameter portion and provided at the tip of the core bar, and a core bar shaft portion having a diameter smaller than the inner diameter of the small diameter portion and provided at the base side of the core bar head.

3. 3. The method for manufacturing serrations according to claim 2, wherein in the thickness adjusting step, the mandrel head is inserted until it penetrates through the end on the small diameter portion side, and then is not returned to the small diameter portion.

4. 2. The method for manufacturing serrations according to claim 1, wherein the diameter of the portion of the core bar that is inserted into the small diameter portion is equal to or larger than the inner diameter of the small diameter portion, and the length of the portion that is inserted into the small diameter portion is equal to or larger than the length of the small diameter portion.

5. 5. The method for manufacturing serrations according to claim 4, wherein in the thickness adjusting step, the core is inserted until the tip of the core projects from the end on the small diameter portion side, and then returned to the large diameter portion side.

6. 6. The method for manufacturing serrations according to claim 1, wherein in the wall thickness adjusting step, the outer peripheral surface of the small diameter portion is constrained by a die, and a butt is brought into contact with the end portion on the small diameter portion side without applying back pressure.

7. 7. The method for manufacturing serrations according to claim 6, wherein in the serration forming step, the outer peripheral surface of the small diameter portion is constrained by a die, and an abutment is brought into contact with an end portion on the small diameter portion side without applying back pressure, and an abutment is also brought into contact with an end portion on the large diameter portion side without applying back pressure.

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