Method of Manufactring Ring-Shaped Member

Abstract

The yield rate or the percentage of the weight of the ring-shaped member with respect to the weight of the raw material and the yield rate or the percentage of the ring-shaped member with respect to the blank are improved to achieve the cost reduction. A half-finished article 18 having large curved parts 3D obtained by widening the curved parts 3d so as to have a curvature radius larger than the initial curvature radius, and bulge-out parts 3E curved to a circular arc shape at a curvature radius larger than the curvature radius of the curved parts 3d at the linear parts 3b, 3c is molded, and thereafter, the half-finished article 18 is molded into an annular shape to obtain the ring-shaped member 1.

Description

TECHNICAL FIELD

The present invention relates to a method of manufacturing a ring-shaped member.

BACKGROUND ART

A ring-shaped member 1 as shown in FIG. 12 has been conventionally manufactured through a method of punching out a plurality of annular ring-shaped members 1 by one column or a plurality of columns by a pressing device from a raw material 2 having a predetermined plate thickness as shown in FIGS. 13(a) and 13(b).

However, in the conventional manufacturing method, the yield rate or the percentage of the weight of the ring-shaped member 1 with respect to the weight of the raw material 2 is bad, and tends to increase the cost of the ring-shaped member 1.

This is because the material is removed at high percentage of skeleton S1 and slug S2 with respect to the ring-shaped member 1. The “Skeleton” is a frame shaped scrap that remains after punching out a plurality of ring-shaped members 1, and the “slug” is a plurality of scraps punched out and removed with a punch when punching out the plurality of ring-shaped members 1.

A method of molding the ring-shaped member shown in FIGS. 14(a) and 14(b) has thus been proposed (patent document 1).

The method of molding the ring-shaped member described in a patent document 1 includes a step of continuously bending the width of an elliptical ring-shaped raw material into a circular shape while preventing the deformation thereof, and a step of making the raw material formed into a circular shape into a perfect circle.

That is, as shown in FIG. 14(a), inner and outer rollers 103, 104 that freely rotate and move so as to slidably hold in between one width on the minor side of the elliptical ring-shaped raw material 100, and a pair of freely movable bending rollers 105 are arranged, where the inner and outer rollers 103, 104 are rotated in a direction of an arrow F or in the opposite direction thereof to push the pair of bending rollers 105 in the direction of an arrow G while feeding the elliptical ring-shaped raw material 100 in the direction of an arrow L or in the opposite direction thereof, thereby sequentially performing the curvature process on the linear portion of the raw material 100 to be molded into a raw material 101 of circular shape.

Thereafter, as shown in FIG. 14(b), a large diameter inner roller 106 is externally fitted to the inner roller 103 so as to be simultaneously rotatable and inscribed to the raw material 101 formed into a circular shape, and the large diameter inner roller 106 and the outer rollers 103, 104 are rotated in the direction of the arrow F or in the opposite direction thereof to obtain a ring-shaped member 102 molded to a perfect circle.

According to such method of molding the ring-shaped member, the raw material 101 of circular shape is obtained from the elliptical ring-shaped member 100, and thus the material can be removed such that the percentage of the skeleton and the slug with respect to the ring-shaped member 102 of a perfect circle is suppressed lower than the percentage of the skeleton S1 and the slug S2 with respect to the ring-shaped member 1 described in FIG. 13, thereby improving the yield rate or the percentage or the weight of the ring-shaped member 102 with respect to the weight of the raw material, and the cost of the ring-shaped member 102 can be removed.

Patent document 1: Japanese Patent Application Laying-open No. 62-203633

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

However, in the method of molding the ring-shaped member described in the patent document 1, a curved part 107 having a small curvature radius remaining on the circular shaped raw material 101 is pressed and widened from the inner side with a strong pressing force in the direction of an arrow K by the large diameter inner roller 106. When the curved part 107 of small curvature radius is pressed and widened from the inner side, a large “extension” is generated at the radial inner region of small curvature radius in the curved part 107 thereby thinning the relevant region and concentrating stress. Therefore, cracks may be generated at the radial inner region of the curved part 107 in the process of molding the circular shaped raw material 101 into a perfect circular shaped ring-shaped member 102, which degrades the yield rate or the percentage of the perfect circular shaped ring-shaped member 102 with respect to the elliptical ring-shaped raw material 100, and increases the cost.

The present invention, in view of solving the above problems, aims to provide a method of manufacturing a ring-shaped member that improves the yield rate or the percentage of the weight of the ring-shaped member with respect to the weight of the raw material, and improves the yield rate or the percentage of the ring-shaped member (correspond to ring-shaped part molded into a perfect circle described in the patent document 1) with respect to a longitudinal annular blank (correspond to elliptical ring-shaped raw material described in the patent document 1), even though the method can achieve a cost reduction.

Means for Solving the Problems

The present invention relates to a method of manufacturing a ring-shaped member in which an annular ring-shaped member is obtained from a longitudinal annular blank having curved parts at both ends in a longitudinal direction, wherein the longitudinal annular blank is molded to a half-finished article having a pair of large curved parts widened so as to have a curvature radius larger than the curvature radius of the curved parts and a pair of bulge-out parts curved to a circular arc shape at a curvature radius larger than the curvature radius of the curved parts, and thereafter, the half-finished article is molded into the annular ring-shaped member.

According to such configuration, the annular ring-shaped member is obtained from the longitudinal annular blank, and thus the material can be removed such that the percentage of the skeleton and the slug with respect to the ring-shaped member is suppressed low compared to the case shown in FIG. 13, and the yield rate or the percentage of the weight of the ring-shaped member with respect to the weight of the raw material can be improved.

Prior to molding the longitudinal annular blank into an annular shape, a half-finished article including a pair of large curved parts having a curvature radius larger than the curvature radius of the curved parts and a pair of bulge-out parts curved to a circular shape at a curvature radius larger than the curvature radius of the curved parts is molded in advance, and such half-finished article is molded into an annular ring-shaped member, and thus “extension” of the radial inner region of the large curved parts and the bulge-out parts having a large curvature radius is suppressed as much as possible, the thinning of the thickness of the radial inner region is avoided, and stress concentration of the radial inner region is alleviated when molding the half-finished article into an annular shape. As a result, cracks are not generated at the large curved parts and the bulge-out parts, and the yield rate or the percentage of the ring-shaped member with respect to the longitudinal annular blank can be improved.

The present invention relates to a method of manufacturing a ring-shaped member in which an annular ring-shaped member is obtained from a longitudinal annular blank, wherein the longitudinal blank has linear parts facing each other at both sides in the width direction and a pair of curved parts for continuing both ends in the longitudinal direction of the linear parts; and the blank is molded into a blank having a dimension in the width direction widened from the dimension in the width direction of the blank by widening the linear parts outward in the width direction, the blank whose dimension is widened in the width direction is molded into a half-finished article having a pair of large curved parts obtained by widening the curved parts so as to have a curvature radius larger than the initial curvature radius and a pair of bulge-out parts curved into a circular arc shape at a curvature radius larger than the curvature radius of the curved parts at the linear parts, and thereafter, the half-finished article is molded to the annular ring-shaped member.

According to such configuration, the annular ring-shaped member is obtained from the longitudinal annular blank, and thus the material can be removed such that the percentage of the skeleton and the slug with respect to the ring-shaped member is suppressed low compared to the case shown in FIG. 13, and the yield rate or the percentage of the weight of the ring-shaped member with respect to the weight of the raw material can be improved.

Prior to molding the longitudinal annular blank into an annular shape, a step of molding into a half-finished article including large curved parts obtained by widening the curved parts so as to have a curvature radius larger than the initial curvature radius and bulge-out parts curved to a circular arc shape at a curvature radius larger than the curvature radius of the curved parts at the linear parts is performed after the step of widening the linear parts outward in the width direction and molding into a blank of dimension in the width direction wider than the dimension in the width direction of the blank, and thus “extension” of the radial inner region of small curvature radius at the curved parts is suppressed as much as possible, thinning the radial inner region is avoided, and stress concentration of the radial inner region is alleviated in the step of molding to the half-finished article, whereby the curved parts are readily molded into the large curved parts of large curvature radius without generating cracks at the curved parts.

After the step of molding to the half-finished article, the half-finished article is molded into an annular ring-shaped member, and thus “extension” of the radial inner region of the large curved parts and the bulge-out parts having a large curvature radius is suppressed as much as possible, thinning the radial inner region is avoided, and stress concentration of the radial inner region is alleviated when molding into an annular shape. As a result, cracks are not generated at the large curved parts and the bulge-out parts, and the yield rate or the percentage of the ring-shaped member with respect to the longitudinal annular blank can be improved.

EFFECTS OF THE INVENTION

According to the present invention, the yield rate or the percentage of the weight of the ring-shaped member with respect to the weight of the raw material is improved by removing the material such that the percentage of the skeleton and the slug with respect to the ring-shaped member is suppressed low, and the cost of the ring-shaped member can be reduced. Furthermore, “extension” of the radial inner region at the curved parts of the longitudinal annular blank is suppressed as much as possible, thinning the radial inner region can be avoided, and stress concentration of the radial inner region is alleviated, whereby cracks are not generated at the curved parts of the longitudinal annular blank, and the yield rate or the percentage of the ring-shaped member with respect to the longitudinal annular blank can be advantageously improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a first embodiment of a step of punching out blanks from a raw material.

FIG. 2 is an enlarged front view showing the blank punched out from the raw material of FIG. 1.

FIG. 3 is a plan view showing an embodiment of a state in which the blank is set in a first shaping device.

FIG. 4 is a plan view showing an embodiment of a state in which the deformed blank is molded by the first shaping device.

FIG. 5 is a plan view showing an embodiment of a state in which the deformed blank is set in a second shaping device.

FIG. 6 is a plan view showing an embodiment of a state in which a half-finished article is molded by the second shaping device.

FIG. 7 is a plan view showing an embodiment of a state in which the half-finished article is set in a third shaping device.

FIG. 8 is a plan view showing an embodiment of a state in which the right half portion of the half-finished article is molded into a semicircle by the third shaping device.

FIG. 9 is a plan view showing an embodiment of a state in which the half-finished article is molded into a ring-shaped member by the third shaping device.

FIG. 10 is an enlarged front view showing a second embodiment of a blank.

FIG. 11 is a plan view showing another embodiment of a step of punching out the blank from the raw material.

FIG. 12 is a front view showing one example of the ring-shaped member.

FIG. 13 is a plan view showing the conventional steps of punching out the blank from the material, where 13(a) shows punching out one column, 13(b) shows punching out in parallel.

FIG. 14 is an explanatory view of a method of molding the ring-shaped member described in the patent document 1.

DESCRIPTION OF NUMERAL REFERENCES

• 1 ring-shaped member
• 3 longitudinal annular blank
• 3 b, 3c linear part
• 3A blank which width dimension is widened
• 3D large curved part
• 3 d curved part
• 3E bulge-out part
• 18 half finished-article

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the method of manufacturing the ring-shaped member according to the present invention will now be described based on the drawings.

As shown in FIG. 1, a plurality of longitudinal annular blanks 3 is punched out in series at a predetermined spacing 1 in the feeding direction by the pressing device while feeding the raw material 2 of a predetermined plate thickness in the longitudinal direction of the raw material 2 as shown by an arrow X. The raw material 2 used may be that formed in to a plate shaped body by rolling the metal rod material such as copper, aluminum, iron, stainless steel and the like, or that formed as a plate shaped body from the beginning. The longitudinal annular blank 3 may be obtained by performing press work such as cutting and punching, casting and the like on the metal rod material instead of being obtained by punching out the raw material 2 of plate shaped body.

The longitudinal annular blank 3 includes linear parts 3b, 3c on the left and right sides facing each other so as to sandwich a longitudinal hole 3a having a small width dimension w1 on the inner side, and a pair of curved parts 3d continuing both ends in the longitudinal direction of the linear parts 3b, 3c, as shown in FIG. 2, and the longitudinal annular blank 3 is set in a first shaping device 4, as shown in FIG. 3.

The first shaping device 4 includes a moving plate 5 and a pair of front and back guide plates 6, where the moving plate 5 is guided by the guide plates 6 to move forward and backward in the left and right direction (direction of arrow X1, X2) by a forward/backward movement mechanism (not shown). The moving plate 5 includes a main body part 5a, and collar parts 5b, 5b formed on both ends in the front and back direction of the main body part 5a, where the collar parts 5b, 5b slidably go under the lower side of the edges 6a, 6a at the side facing the opponent in the guide plate 6, and a vertical step difference surface 5c formed at the boundary of the main body part 5a and the collar parts 5b, 5b is arranged so as to slidably contact the end surface 6b at the side facing the opponent in the guide plate 6. An inner die 8-1 having a boat shape in a projected plane is projected upward at the central part of the main body part 5a in the moving plate 5 on the line Y orthogonal to line X. The width dimension w2 of the inner die 8-1 is set to a size slightly smaller than the width dimension w1 of the longitudinal hole 3a so as to fit into the longitudinal hole 3a of the blank 3.

A pair of front and back positioning projections 8-2, and two pairs of front and back positioning/deformation tolerating projections 9 are arranged on the guide plate 6 in the first shaping device 4. As mentioned below, the pair of positioning projections 8-2 is provided to prevent the longitudinal annular blank 3 from moving in the direction of the arrow Y1, Y2 and to position the longitudinal annular blank 3 at an appropriate position when the longitudinal annular blank 3 is set in the first shaping device 4, and furthermore, is arranged at symmetrical positions with the line X in between so as to face each other on the line Y orthogonal to the line X, where the distance in between is set to a value slightly larger than the dimension in the longitudinal direction of the longitudinal annular blank 3 to enable the setting of the longitudinal annular blank 3.

As mentioned below, the two pairs of front and back positioning/deformation tolerating projections 9 are provided to prevent the longitudinal annular blank 3 from moving in the direction of the arrows X1, X2 and to position the longitudinal annular blank 3 at an appropriate position as well as to tolerate the deformation of the longitudinal annular blank 3 by an inner die 8-1 when the longitudinal annular blank 3 is set in the first shaping device 4, and is further arranged at symmetrical positions with the line X and the line Y passing through the center of the moving plate 5 in between, where the distance in between in the direction of the line X is set at a value slightly larger than the dimension in the width direction of the longitudinal annular blank 3 to enable the setting of the longitudinal annular blank 3. Each positioning/deformation tolerating projection 9 has a circular arc shaped deformation tolerating surface 9b formed in continuation to the positioning surface 9a that is parallel to the line Y.

As shown in FIG. 3, when the longitudinal annular blank 3 is set in the first shaping device 4, an upper die 10 shown by a double-chain dashed line is lowered from above. The upper surfaces of the guide plate 6, the positioning projection 8-2, and the positioning/deformation tolerating projection 9 are thereby pressed by the lower surface of the upper die 10, and the upper surfaces of the blank 3 and the inner die 8-1 face the lower surface of the upper die 10 by way of an extremely small gap (small gap allowing slide movement) thereby preventing a warp of the blank 3.

The moving plate 5 is moved in the direction of the arrow X2 in this state. The inner die 8-1 presses and energizes the linear part 3c on the right side of the longitudinal annular blank 3 in the direction of the arrow X2 from the inner side to bend in the direction of the arrow X2 as shown in FIG. 4, and subsequently, the moving plate 5 is moved in the direction of the arrow X1 so that the inner die 8-1 presses and energizes the linear part 3b on the left side (see FIG. 3) of the longitudinal annular blank 3 in the direction of the arrow X1 from the inner side to bend in the direction of the arrow X1 as shown in FIG. 4, where a longitudinal annular blank 3A in which the dimension in the width direction is widened and deformed from the dimension in the width direction of FIG. 3 is molded. In the process of molding, the widening deformation of the linear parts 3b, 3c on both left and right sides of the longitudinal annular blank 3 shown in FIG. 3 is tolerated since the outer surface in the width direction of the region near the curved part 3d of the linear parts 3b, 3c is widened until contacting the circular arc shaped deformation tolerating surface 9b of each of the two pairs of positioning/deformation tolerating projection 9, and thinning the widened and deformed part in time of widening deformation can be suppressed since the deformation tolerating surface 9b is formed into a circular arc shape.

In the next step, the deformed longitudinal annular blank 3A shown in FIG. 4 is set in a second shaping device 11 shown in FIG. 5.

The second shaping device 11 includes a pair of left and right molding outer dies 12, and a pair of front and back regulating dies 13, where the molding outer die 12 is guided by a guide groove 14 and is moved forward and backward in the left and right direction (direction of arrows X1, X2) on the base 15 by a forward/backward movement mechanism (not shown).

The molding outer die 12 includes a mounting surface 12a and a pressing surface 12b projecting vertically upward from the mounting surface 12a and having the projected plane which is depressed into a circular arc shape, where the curvature radius of the pressing surface 12b is set to a value larger than the curvature radius of the outer peripheral surface of the curved part 3d in the deformed longitudinal annular blank 3A. The regulating die 13 is formed at the end face on the side facing the opponent with a regulating surface 13a having the projected plane which is depressed into a circular arc shape. Furthermore, a holding inner die 16 projecting upward from the upper surface at the central part of the base 15 and having a boat shape in projected plane view is arranged extending in the direction of the line X, where the width dimension of the holding inner die 16 is set to a dimension slightly smaller than the width dimension of the longitudinal hole 3e so as to be fitted to the longitudinal hole 3e of the deformed longitudinal annular blank 3A. A circular arc shaped holding surface 16a is arranged vertically at both ends on the line X of the holding inner die 16, and a cut-out part 16b is formed on the lower side of the holding surface 16a and the vicinity thereof.

As shown in FIG. 5, after the longitudinal annular blank 3A is set in the second shaping device 11 with the holding inner die 16 sandwiched by the linear parts 3b, 3c of the deformed longitudinal annular blank 3A and the curved part 3d and the vicinity of the blank 3A mounted on the mounting surface 12a of the molding outer die 12, an upper die 17 shown by a double chain-dashed line is lowered from above. As a result, the upper surfaces of the regulating die 13 and the holding inner die 16 are pressed by the lower surface of the upper die 17, and the upper surfaces of the longitudinal annular blank 3A and the molding outer die 12 face the lower surface of the upper die 17 by way of an extremely small gap (small gap allowing slide movement) thereby preventing the warp of the blank 3A.

The molding outer dies 12 are moved in the direction of the arrows X1, X2 in this state. The pressing surface 12b of the molding outer die 12 thereby presses and energizes the outer side of the curved part 3d of the deformed longitudinal annular blank 3A towards the curved part 3d on the opponent side. In this case, the mounting surface 12a of the molding outer die 12 enters the cut-out part 16b of the holding inner die 16. Therefore, as shown in FIG. 6, both curved parts 3d are deformed along the pressing surface 12b when the radial outer surface of large curvature radius is pressed inward from the outer side by the pressing surface 12b depressed into a circular arc shape of the molding outer die 12 in a state wherein the radial inner surface is slightly pressed and widened by the circular arc shaped holding surface 16a of the holding inner die 16 and positioned with the movement in the directions of the arrows X1, X2 regulated, thereby molding into a large curved part 3D having a curvature radius which is larger than the curvature radius of the curved parts 3d, and thus “extension” is generated in the radial outer region of the large curved part 3D having large curvature radius and “extension” in the radial inner region is suppressed as much as possible, thinning the radial inner region is avoided, and furthermore, flow of material that thickens the large curved part 3D is generated so as to alleviate stress concentration at the radial inner region. As a result, both curved parts 3d can be molded to the large curved part 3D having a larger curvature radius than the initial curvature radius and being advantageous in manufacturing the ring-shaped member 1 without generating cracks at the curved part 3d, and thus the yield rate or the percentage of the ring-shaped member 1 with respect to the longitudinal annular blank 3A can be improved.

In the process of molding into the large curved part 3D having a curvature radius larger than the curvature radius of both curved parts 3d, the linear parts 3b, 3c in the deformed longitudinal annular blank 3A shown in FIG. 5 are widened in the direction of the arrows Y1, Y2 thereby forming a pair of bulge-out-parts 3E curved to a circular arc shape at a curvature radius larger than the initial curvature radius of the curved part 3d at the central part, as shown in FIG. 6, where the deformed longitudinal annular blank 3A (see FIG. 5) is regulated from widening in excess in the direction of the arrows Y1, Y2 when the outer surface of the bulge-out part 3E contacts the regulating surface 13a depressed into a circular arc shape of the regulating die 13, and a half-finished article 18 including a pair of large curved parts 3D of large curvature radius and a pair of bulge-out parts 3E curved to a circular arc shape at a large curvature radius, and having the large curved parts 3D and the bulge-out parts 3E continued by way of four short linear parts 3F is molded.

The half-finished article 18 shown in FIG. 6 is further set in a third shaping device 19 shown in FIG. 7 in the next step.

The third shaping device 19 includes a base 20, and an upper plate 21 for blocking the upper surface of the base 20 by way of a spacing in the height direction, where a guide groove 22 is formed in the base 20 on the line X passing through the center, and a moving plate 23 that freely moves forward and backward in the direction of the arrows X1, X2 is fitted into the guide groove 22. The moving plate 23 moves forward and backward in the direction of the arrows X1, X2 by a forward/backward moving mechanism (not shown). The upper surface of the moving plate 23 is in plane with the upper surface of the base 20, and a finishing inner die 24 having an elliptical shape in a projected plane view is arranged at the central part so as to project upward on a line Y passing through the center of the base 20 and being orthogonal to the line X. The finishing inner die 24 faces a window part 25 of a substantially perfect circle formed on the upper plate 21, and the inner peripheral surface of the window part 25 functions as an outer die.

As shown in FIG. 7, when the half-finished article 18 is set in the third shaping device 19, an upper die 26 shown with a double chain-dashed line is lowered from above. The upper surface of the upper plate 21 is thereby pressed by the lower surface of the upper die 26, and the upper surfaces of the half-finished article 18 and the finishing inner die 24 face the lower surface of the upper die 26 by way of an extremely small gap (small gap allowing slide movement) thereby preventing the warp of the half-finished article 18.

The moving plate 23 is moved in the direction of the arrow X2 in such a state. As a result, the finishing inner die 24 presses and energizes the right half portion of the half-finished article 18 in the direction of the arrow X2 from the inner side and presses the outer peripheral surface of the right half portion against the inner peripheral surface of the right half portion in the window part 25 of a substantially perfect circle, as shown in FIG. 8, thereby molding the right half portion of the half-finished article 18 into a semicircle. Subsequently, the moving plate 23 is moved in the direction of the arrow X1. The finishing inner die 24 thereby presses and energizes the left half portion of the half-finished article 18 in the direction of the arrow X1 from the inner side and presses the outer peripheral surface of the left half portion against the inner peripheral surface of the left half portion in the window part 25 of a substantially perfect circle as shown in FIG. 9, thereby molding the left half portion of the half-finished article 18 into a semicircle to manufacture a ring-shaped member 1 shown in FIG. 9 and FIG. 12. In molding the half-finished article 18 into an annular ring-shaped member 1, “extension” in the radial inner region of the large curved part 3D and the bulge-out part 3E having a large curvature radius is suppressed as much as possible, thinning of the radial inner region is avoided, and concentration of stress on the radial inner region is alleviated. As a result, cracks are not generated at the large curved part 3D and the bulge-out part 3E.

Therefore, according to the present invention, the ring-shaped member 1 shown in FIG. 9 and FIG. 12 is manufactured by punching out a plurality of longitudinal annular blanks 3 from a raw material 2 shown in FIG. 1, and pressing and widening the longitudinal annular blanks 3 to be molded into an annular shape by first to third shaping devices 4, 11, 19. Therefore, the yield rate or the percentage of the weight of the ring-shaped member 1 with respect to the weight of the raw material 2 can be improved, and the cost of the ring-shaped member 1 can be reduced by removing the material such that the percentage of the skeleton S1 and the slug S2 of FIG. 1 with respect to the ring-shaped member 1 is suppressed lower than the percentage of the skeleton S1 and the slug S2 with respect to the ring-shaped member 1 described in FIG. 13.

Furthermore, each curved part 3d is deformed along the pressing surface 12b and molded into the large curved part 3D of large curvature radius when the radial outer surface is pressed inward from the outer side by the pressing surface 12b depressed into a circular arc shape of the molding outer die 12 with the radial inner surface slightly pressed and widened by the circular arc shaped holding surface 16a of the holding inner die 16 and positioned with the movement in the directions of the arrows X1, X2 regulated by pressing and energizing the outer side of the pair of curved parts 3d of the deformed longitudinal annular blank 3A towards the curved part 3d on the opponent side by the pressing surface 12b depressed to a circular arc shape of the molding outer die 12 by the second shaping device 11, and thus “extension” in the radial outer region having large curvature radius is suppressed as much as possible, thinning the radial inner region is avoided, and furthermore, flow of material that thickens the large curved part 3D is generated and alleviates stress concentration at the radial inner region. As a result, both curved parts 3d can be molded into a large curved part 3D having a large curvature radius and being advantageous in manufacturing the ring-shaped member 1 without generating cracks at the curved part 3d, and thus the yield rate or the percentage of the ring-shaped member 1 with respect to the longitudinal annular blank 3A can be improved and the cost of the ring-shaped member 1 can be reduced.

In the above embodiment, the longitudinal annular blank 3 having a small width dimension w1 of the longitudinal hole 3a is punched out, and such blank 3 is pressed and widened to manufacture the ring-shaped member 1, as shown in FIG. 2, but as shown in FIG. 10, a longitudinal annular blank 27 having a longitudinal hole 27a of oval shape in which the width dimension w3 is sufficiently larger than the width dimension w1 of FIG. 2 may be punched out, and such blank 27 may be pressed and widened through the same procedures as the above embodiment to be molded into the ring-shaped member 1. In this case as well, the yield rate or the percentage of the ring-shaped member 1 with respect to the longitudinal annular blank 27 can be improved and the cost of the ring-shaped member 1 can be reduced, similar to the above embodiment.

Moreover, in punching out a plurality of longitudinal annular blanks 3, 27 from the raw material 2 of a predetermined width, the outer end faces of the linear parts 3b, 3c in the longitudinal annular blank 3, 27 may be formed using both ends faces 2a in the width direction of the raw material 2, and the raw material 2 may be cut by the pressing device to form a pair of curved parts 3d continuing the pair of linear parts 3b, 3c to each other at both ends in the longitudinal direction, as shown in FIGS. 11(a) and 11(b). Therefore, the material can be removed such that the percentage of scraps with respect to the longitudinal annular blanks 3, 27 is suppressed to a minimum. In other words, the scraps are reduced to the slug S1 punched out and removed by punch in time of punching out the longitudinal hole 3a or the longitudinal hole 27a of oval shape, and an end plate part 2x of drum shape existing between the longitudinal annular blanks 3 or blanks 27 arrayed in the longitudinal direction and to be separated away from the raw material 2. As a result, the yield rate or the percentage of the weight of the ring-shaped member 1 with respect to the weight of the raw material 2 further can be improved.

The method of manufacturing the ring-shaped member of the present invention also has the following features.

The longitudinal annular blank 3 is molded to an annular shape by pressing the curved part 3d at both ends in the longitudinal direction towards the opponent side from the outer side. The material can be removed such that the percentage of the skeleton and the slug with respect to the ring-shaped member 1 is suppressed low, and the yield rate or the percentage of the weight of the ring-shaped member 1 with respect to the weight of the raw material can be improved. Furthermore, since the curved parts 3d at both ends in the longitudinal direction are pressed towards the opponent side from the outer side, the “extension” of the radial inner region having a small curvature radius at the curved part 3d can be suppressed as much as possible, thinning of the radial inner region is avoided, and furthermore, the flow of material that thickens the curved part 3d is generated and alleviates the stress concentration of the radial inner region. As a result, cracks are not generated at the curved part 3d, and the yield rate or the percentage of the ring-shaped member 1 with respect to the longitudinal annular blank 3 can be improved.

The longitudinal annular blank 3 is desirably molded into an annular shape by shaping devices 11, 19 including an inner die 16, 24 and an outer die 12, 25. The ring-shaped member 1 of high quality is thereby efficiently manufactured and cost can be reduced.

Moreover, the longitudinal annular blank 3 includes linear parts 3b, 3c facing each other at both sides in the width direction with the longitudinal hole 3a on the inner side, and curved parts 3d for continuing both ends in the longitudinal direction of the linear parts 3b, 3c, where the dimension in the width direction of the longitudinal annular blank 3 is widened by pressing and energizing the linear parts 3b, 3c by the inner die 8-1 fitted in the longitudinal hole 3a, and thereafter, the outer side of the curved parts 3d is pressed and energized towards the curved part 3d on the opponent side with the molding outer die 12 with the holding inner die 16 fitted into the longitudinal hole 3a whose dimension in the width direction is widened, thereby pressing and widening the curved parts 3d to large curved parts 3D having a large curvature radius.

Therefore, after widening the dimension in the width direction of the longitudinal annular blank 3 by the inner die 8-1 fitted into the longitudinal hole 3a and pressing and energizing the outer side of the curved part 3d toward the curved part 3d on the opponent side by the molding outer die 12 with the holding inner die 16 fitted into the longitudinal hole 3a whose dimension in the width direction is widened, the curved parts 3d are pressed inward from the outer side by the molding outer die 12 while being positioned with the movement towards the curved part 3d on the opponent side regulated by the holding inner die 16, whereby “extension” of the radial inner region having a small curvature radius in the curved part 3d is suppressed as much as possible, thinning of the radial inner region is avoided, and stress does not concentrate at the radial inner region, so that both curved parts 3d are readily molded into the large curved parts 3D having a large curvature radius without generating cracks at the curved parts 3d.

Claims

1. A method of manufacturing a ring-shaped member in which an annular ring-shaped member is obtained from a longitudinal annular blank having curved parts at both ends in a longitudinal direction, wherein the longitudinal annular blank is molded into a half-finished article having a pair of large curved parts widened so as to have a curvature radius larger than the curvature radius of the curved parts and a pair of bulge-out parts curved to a circular arc shape at a curvature radius larger than the curvature radius of the curved parts, and thereafter, the half-finished article is molded into the annular ring-shaped member.

2. A method of manufacturing a ring-shaped member in which an annular ring-shaped member is obtained from a longitudinal annular blank, wherein the longitudinal annular blank has linear parts facing each other at both sides in the width direction and a pair of curved parts for continuing both ends in the longitudinal direction of the linear parts; andthe blank is molded into a blank having a dimension in the width direction widened from the dimension in the width direction of the blank by widening the linear parts outward in the width direction, the blank whose dimension in the width direction is widened is molded into a half-finished article having a pair of large curved parts obtained by widening the curved parts so as to have a curvature radius larger than the initial curvature radius and a pair of bulge-out parts curved into a circular arc shape at a curvature radius larger than the curvature radius of the curved parts at the linear parts, and thereafter, the half-finished article is molded into the annular ring-shaped member.