Form rolling flat die and form rolling method using the same

Abstract

To provide a form rolling flat die and form rolling method that, in form rolling for a workpiece, without adding pre-processing prior to the form rolling, enable: suppressing deformation of a hollow hole portion after the form rolling even in the case of the same machining cycle as that of a solid cylindrical workpiece; and obtaining excellent form rolling precision.SOLUTION: A form rolling flat die of the present invention comprises, at least, a biting portion comprising a plurality of forming teeth to perform form initial rolling on a workpiece, and a finishing portion comprising a plurality of forming teeth to perform subsequent form rolling. In a cross-sectional view perpendicular to a longitudinal direction of the form rolling flat die: flat portions 51B and 52B are respectively arranged extending from edges of both right and left sides toward a center side in a width direction of the form rolling flat die; and a ridge line at each of tips of the forming teeth of the biting portion and the finishing portion is formed in a convex shape from one end sides of the flat portions on both right and left sides toward the center side.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a rolling die for rolling splines, knurls, gears, etc., on a workpiece, and a rolling method using the rolling die. [Background technology]

[0002] Conventionally, in the rolling process using flat dies for rolling, various flat dies for rolling and rolling methods using them have been disclosed (see Patent Documents 1 and 2). However, these flat dies are intended for solid cylindrical workpieces, and when rolling hollow cylindrical workpieces, there is a problem in that the hollow hole portion is significantly deformed by the large load during rolling.

[0003] Therefore, several rolling methods for hollow cylindrical workpieces have been disclosed. For example, Patent Document 3 discloses a rolling method using a round die. Also, Patent Document 4 discloses a rolling method for hollow cylindrical workpieces using a mandrel in the hollow portion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-106286 [Patent Document 2] Publication number 2-27950 [Patent Document 3] Japanese Patent Application Publication No. 5-69074 [Patent Document 4] Patent No. 5183116 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the rolling process using a round die as disclosed in Patent Document 1, the rolling machine used becomes larger, leading to increased costs and lead times. Furthermore, in the rolling process using a mandrel as disclosed in Patent Document 2, a process of removing the mandrel after the process is completed is required, which also increases the processing time. At the same time, there is a possibility that the diameter of the hollow portion will widen, and in order to ensure the diameter of the hollow portion, certain restrictions are imposed on the material and thickness of the workpiece.

[0006] Therefore, the present invention aims to provide a flat die for rolling that can suppress deformation of the hollow hole portion after rolling, even with a processing cycle similar to that for solid cylindrical workpieces, and can obtain good rolling accuracy in rolling workpieces (especially hollow cylindrical workpieces), without adding a pre-process (so-called preparation process) before rolling, and a rolling method using the flat die for rolling. [Means for solving the problem]

[0007] The flat rolling die of the present invention has at least a chamfering portion with a plurality of teeth that initially rolls the workpiece, and a finishing portion with a plurality of teeth that are formed contiguous with the chamfering portion and subsequently roll the workpiece, and in a cross section perpendicular to the longitudinal direction of the flat rolling die (a cross section parallel to the width direction), the die has flat portions extending from both left and right edges toward the center in the width direction of the die, and the ridges of the tips of the teeth of the chamfering portion and the finishing portion are formed in a convex shape extending from one end of the flat portions toward the center. Note that the convex ridges may be formed from a plurality of straight ridges or curved ridges.

[0008] Next, with regard to the invention of the rolling method using flat rolling dies, the two aforementioned flat rolling dies are set as a set, and the processing teeth of the set of flat rolling dies are aligned to face each other, and the workpiece is sandwiched between these processing teeth and then the set of flat rolling dies is moved in opposite directions (first processing step).

[0009] Next, when the workpiece reaches the end of the finishing section of the pair of rolling dies, the movement of the pair of rolling dies is stopped (second processing step). After that, the pair of rolling dies is moved again from the finishing section toward the chamfer section (third processing step). That is, in the first processing step, the pair of rolling dies is advanced while rolling the surface of the workpiece, and in the second processing step, the movement of the pair of rolling dies is temporarily stopped, and in the third processing step, the pair of rolling dies is retracted while rolling the surface of the workpiece again. [Effects of the Invention]

[0010] The flat rolling die of the present invention can suppress deformation of the hollow hole during rolling of a hollow cylindrical workpiece, thereby achieving good rolling accuracy, and at the same time, can significantly reduce the overall length of the flat rolling die (die length). [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic front view of a flat die for rolling 1 of the present invention. [Figure 2] 2 is an enlarged view of a portion A of the flat die for rolling 1 shown in FIG. [Figure 3] 2 is an enlarged view of a portion B of the flat die for rolling 1 shown in FIG. [Figure 4] 1 is a schematic plan view of a flat die for rolling 1 of the present invention. [Figure 5] 5 is a cross-sectional view of the flat die for rolling 1 taken along line XX in FIG. 4. [Figure 6] FIG. 1 is a schematic plan view of a conventional flat die 100 for rolling according to an embodiment. [Figure 7] 7 is a cross-sectional view of the flat rolling die 100 taken along line YY shown in FIG. 6. [Figure 8] 1 shows rolling test data using the flat die for rolling of the present invention. [Figure 9] This is rolling test data using a conventional flat die for rolling. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the rolling die of the present invention will be described with reference to the drawings. Fig. 1 shows a schematic front view of a rolling die 1 according to one embodiment of the present invention, Fig. 2 shows a schematic enlarged view of part A of the rolling die 1 shown in Fig. 1, Fig. 3 shows a schematic enlarged view of part B of the rolling die 1, Fig. 4 shows a schematic plan view of the rolling die 1 of the present invention, and Fig. 5 shows a cross-sectional view of the rolling die 1 shown in Fig. 4 taken along line XX.

[0013] As shown in Fig. 1, the flat rolling die 1 of the present invention is divided into three sections, from the front side (right side in Fig. 1) to the rear side (left side in Fig. 1) in the direction of movement during rolling: a chamfering section 10 equipped with a plurality of working teeth that first perform rolling on the workpiece, a finishing section 20 formed contiguous with the chamfering section 10 and equipped with a plurality of working teeth that subsequently perform rolling on the workpiece, and a relief section 30. Furthermore, on both the left and right sides of the width direction of the flat rolling die 1 (the vertical direction in Fig. 4), flat sections 51 (51A to 51C), 52 (52A to 52C) having a predetermined width from the front end to the rear end of the flat rolling die 1 are formed as shown in Fig. 4.

[0014] As shown in Fig. 2, the chamfering portion 10 of the flat rolling die 1 of the present invention has the teeth 61A-61E and 62A-62E gradually increasing in height from the leading edge toward the rear. Accordingly, the height of the flat portions 51A-51E also increases. Furthermore, as shown in Fig. 3, the finishing portion 20 of the flat rolling die 1 has the teeth 61P-61S and 62P-62S of a constant height from the chamfering portion toward the relief portion (not shown). Similarly, the height of the flat portions 51P-51S is also constant.

[0015] 4 and 5, the processing teeth 61B (61), 62B (62), 63B (63) in the chamfering portion 10 of the flat rolling die 1 are arranged so as to be sandwiched between the flat portions 51B (51), 52B (52) formed on both the left and right sides of the flat rolling die 1. In other words, the shape of the tip of the processing tooth in the chamfering portion 10 is formed so as to be convex upward (toward the workpiece side) of the flat rolling die. [Example]

[0016] A gear rolling test (hereinafter referred to as the "test") was conducted on the outer circumferential surface of a workpiece using two types of flat rolling dies: a flat rolling die according to the present invention (hereinafter referred to as the "invention") and a conventional flat rolling die (hereinafter referred to as the "conventional product"). The test results are described below with reference to the drawings. For both the invention and the conventional flat rolling dies, the rolling process was carried out using a method including the first to third processing steps described above. The inventive flat rolling die used in the test was the flat rolling die shown in Figures 1 to 5. A schematic plan view of the conventional flat rolling die (conventional product) 100 used in the test is shown in Figure 6, and a cross-sectional view of the flat rolling die 100 shown in Figure 6 taken along line YY is shown in Figure 7.

[0017] This test was carried out on the workpiece under the following processing conditions, and then the difference in diameter in the longitudinal direction of the workpiece after rolling was measured. ·Material of workpiece: Carbon steel (S45C) Shape of workpiece: Hollow cylinder with diameter 54mm x length 120mm Gear specifications for the processed part: module 0.4, pressure angle 45°, number of teeth 134 Rolling speed: 20m / min

[0018] After the test, the diameter of the workpiece was measured again to confirm the difference in the diameter in the longitudinal direction of the workpiece before and after the test. Figure 8 shows the rolling test data when the flat rolling die of the present invention was used, and Figure 9 shows the rolling test data when a conventional flat rolling die was used. In each graph of Figures 8 and 9, the horizontal axis (X axis) represents the measurement position from the end of the workpiece (a total of five positions: 7.5 mm, 30 mm, 60 mm, 90 mm, and 112.5 mm from the end), and the vertical axis (Y axis) represents the diameter (unit: mm) of the workpiece measured at each measurement position after the test. The size of the workpiece was also measured in both the horizontal direction (X direction) and the vertical direction (Y direction) before and after the test.

[0019] The test results when the inventive product was used showed that the difference in diameter in the longitudinal direction of the workpiece was in the range of 3 to 34 μm in the X direction and 7 to 14 μm in the Y direction, as shown in Figure 8. In contrast, the test results when the conventional product was used showed that the difference in diameter in the longitudinal direction of the workpiece was in the range of 22 to 55 μm in the X direction and 6 to 69 μm in the Y direction, as shown in Figure 9, meaning that the difference in diameter in the longitudinal direction was increased by 1.4 to 4 times. Therefore, it was found that rolling using the inventive product can reduce the change in size (diameter) of the workpiece in the longitudinal direction by 40 to 80% compared to the results of rolling using the conventional product. [Explanation of symbols]

[0020] 1. Flat die for rolling 10. Feeding section 20 Finishing Section 30 Relief 51A~51E Flat part 51P~51S Flat part 52A~52C Flat part 61A~61E Chamfering teeth 61P~61S Chamfering teeth 62A~62E Chamfering teeth 62P~62S Chamfering teeth 63A Chamfering teeth

Claims

1. A flat rolling die having at least a chamfering portion with a plurality of processing teeth that initially performs rolling on the workpiece, and a finishing portion with a plurality of processing teeth that are formed continuous with the chamfering portion and subsequently perform rolling on the workpiece, characterized in that, when viewed in a cross section perpendicular to the longitudinal direction of the flat rolling die, the chamfering portion and the finishing portion each have a flat portion extending from the left and right edges of the flat rolling die in the width direction toward the center, and the ridge lines of the tips of the processing teeth of the chamfering portion and the finishing portion form a convex shape from one end of the flat portions on the left and right sides toward the center.

2. 2. The flat die for rolling according to claim 1, wherein the convex ridgeline is formed by a plurality of linear ridgelines.

3. 3. A rolling method using the flat rolling dies according to claim 1 or 2, comprising: a first processing step in which a workpiece is sandwiched between a pair of flat rolling dies with their processing teeth facing each other in opposite directions, and then the pair of flat rolling dies is moved in opposite directions to roll the workpiece using the chamfering portions; a second processing step in which, after the first processing step, the movement of the pair of flat rolling dies is stopped when the workpiece reaches the end of the finishing portion of the pair of flat rolling dies; and a third processing step in which, after the second processing step, the pair of flat rolling dies is moved again from the end of the finishing portion toward the chamfering portions.

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