Method and apparatus for manufacturing press component

Abstract

A method and apparatus for manufacturing a press component without generating cracks in a flange on an inner circumferential side of a curved portion includes press working by a free bending method on a blank consisting of an ultra-high tensile strength steel sheet. A press component is manufactured by performing cold press working on a blank of an ultra-high tensile strength steel sheet. By the press working, a material inflow facilitating portion that increases the amount by which a portion of the blank to be formed into an end portion of the press component flows into a portion of the blank to be formed into a flange on an inner circumferential side of the curved portion of the press component is provided in the vicinity of the portion of the blank to be formed into the flange on an inner circumferential side of the curved portion of the press component.

Claims

1. A method for manufacturing a press component, by performing press working on a blank or a pre-formed blank disposed between a die and a die pad, and a punch that is disposed facing the die and die pad, the press component having a top plate extending in a first direction, a convex ridge line connecting to an end portion of the top plate in a direction orthogonal to the first direction, a vertical wall connecting to the convex ridge line, a concave ridge line connecting to the vertical wall, and a flange connecting to the concave ridge line, and also having a curved portion at which the convex ridge line, the vertical wall and the concave ridge line are curved in a plan view that is orthogonal to the top plate, the method comprising, when manufacturing the press component: pressing a portion of the blank to be formed into a part of the top plate by the die pad with an applied pressure of 1.0 MPa or more and less than 32.0 MPa, or subjecting the die pad to approach or come in contact with a portion of the blank to be formed into a part of the top plate while maintaining a gap between the die pad and the punch at a distance that is not less than a sheet thickness of the blank and not more than 1.1 times the sheet thickness of the blank, and forming the vertical wall, the concave ridge line and the flange by relatively moving the die and the punch in directions in which the die and the punch approach each other while causing a portion of the blank that is to be formed into an end portion of the top plate in the first direction to move in-plane over a portion of the die at which the top plate will be formed, wherein, by the press working, in a first portion of the blank to be formed into the flange on an inner circumferential side of the curved portion or a second portion of the blank that is outside the first portion, one or more material inflow facilitating portions are provided, the material inflow facilitating portions increasing an inflow amount of material flowing into the first portion, and the material inflow facilitating portion is formed so as to protrude toward a same side as the top plate or protrude toward an opposite side to the top plate.

2. The method for manufacturing a press component according to claim 1, wherein the method satisfies at least one of the following conditions: the blank comprises an ultra-high tensile strength steel sheet having a tensile strength of 1180 MPa or more; a projection distance of the vertical wall in a product height direction as a height of the press component is 70 mm or more; a radius of curvature of the concave ridge line of the press component is 10 mm or less in side view; and a radius of curvature on the inner circumferential side of the curved portion in the press component is 100 mm or less in the plan view.

3. The method for manufacturing a press component according to claim 1, wherein the method satisfies two or more of the following conditions: the blank comprises an ultra-high tensile strength steel sheet having a tensile strength of 1180 MPa or more; a projection distance of the vertical wall in a product height direction as a height of the press component is 55 mm or more; a radius of curvature of the concave ridge line of the press component is 15 mm or less in side view, and a radius of curvature on an inner side of the curved portion in the press component is 140 mm or less in the plan view.

4. The method for manufacturing a press component according to claim 1, wherein: in the blank, the material inflow facilitating portion is provided at a region that is outside of a region to be formed into the press component.

5. The method for manufacturing a press component according to claim 1, wherein: the concave ridge line has a curved region that is included in the curved portion, and a radius of curvature on an inner circumference of the curved region is 140 mm or less in the plan view, and further wherein when a straight line that is tangent to a center position of the inner circumference of the curved region of the concave ridge line in the plan view is defined as a reference line, and a length of a line passing through a center of the material inflow facilitating portion in a cross-section that is parallel to the reference line in the plan view is defined as a cross-sectional line length, the material inflow facilitating portion has a region in which the cross-sectional line length increases as a distance from the center position increases in the plan view.

6. The method for manufacturing a press component according to claim 1, wherein: the material inflow facilitating portion is a convex bead that is convex toward a same side as the top plate of the press component, or is a concave bead that is convex toward an opposite side to the top plate of the press component.

7. The method for manufacturing a press component according to claim 1, wherein: the material inflow facilitating portion is provided in a stepped shape in a direction parallel to a sheet thickness direction of the blank.

8. The method for manufacturing a press component according to claim 5, wherein: the material inflow facilitating portion has a region in which the cross-sectional line length is constant at positions having different distances from the center position in the plan view.

9. The method for manufacturing a press component according to claim 1, wherein: the press component has a hat-shaped cross-sectional shape.

10. An apparatus for manufacturing a press component by carrying out the method according to claim 1, the apparatus comprising a die and a die pad, and a punch that is disposed facing the die and die pad, wherein: the die and the punch comprise a material inflow facilitating portion forming mechanism which includes a recess provided in the die and a protrusion provided in the punch or a recess provided in the punch and a protrusion provided in the die; and the one or more material inflow facilitating portions by the material inflow facilitating forming mechanism.

11. The apparatus for manufacturing a press component according to claim 10, wherein: the material inflow facilitating portion forming mechanism provides the material inflow facilitating portion at a region of the blank that is outside of a region to be formed into the press component.

12. An apparatus for manufacturing a press component by carrying out the method according to claim 5, the apparatus comprising a die and a die pad, and a punch that is disposed facing the die and die pad, wherein: the die and the punch comprise a material inflow facilitating portion forming mechanism which includes a recess provided in the die and a protrusion provided in the punch or a recess provided in the punch and a protrusion provided in the die; the die and the punch provide the one or more material inflow facilitating portions by the material inflow facilitating portion forming mechanism; and the material inflow facilitating portion forming mechanism forms the material inflow facilitating portion so as to have region in which the cross-sectional line length increases as a distance from the center position increases in the plan view.

13. The apparatus for manufacturing a press component according to claim 10, wherein: the material inflow facilitating portion forming mechanism provides the material inflow facilitating portion, which is a convex bead that is convex toward a same side as the top plate of the press component, or is a concave bead that is convex toward an opposite side to the top plate of the press component.

14. The apparatus for manufacturing a press component according to claim 10, wherein: the material inflow facilitating portion forming mechanism provides the material inflow facilitating portion in a stepped shape in a direction parallel to a sheet thickness direction of the blank.

15. The apparatus for manufacturing a press component according to claim 12, wherein: the material inflow facilitating portion forming mechanism provides the material inflow facilitating portion so as to have a region in which the cross-sectional line length is constant at positions having different distances from the center position in the plan view.

16. The apparatus for manufacturing a press component according to claim 10, wherein: the die, the die pad, and the punch are configured to form the press component, the press component having a hat-shaped cross-sectional shape.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is an explanatory drawing illustrating a configuration example of a manufacturing apparatus according to the present invention.

(2) FIG. 2 is an explanatory drawing partially illustrating an example of a press component that was press-formed by the manufacturing apparatus according to the present invention.

(3) FIG. 3 is an explanatory drawing illustrating the positional relationship between a material inflow facilitating portion forming mechanism and a concave ridge line forming portion of the manufacturing apparatus according to the present invention and a blank.

(4) FIG. 4 is an explanatory drawing illustrating a cross-section in a conventional punch in which a material inflow facilitating portion forming mechanism is not provided, that corresponds to a cross-section A-A in FIG. 1.

(5) FIG. 5 is an explanatory drawing illustrating the positional relationship between a material inflow facilitating portion forming mechanism and a concave ridge line forming portion of the manufacturing apparatus according to the present invention and a blank, and the locations of cross-sections B, C and D.

(6) FIG. 6 is a graph illustrating cross-section line length differences with respect to a conventional punch at a flange forming portion of a punch at the cross-sections B, C and D.

(7) FIG. 7 is an explanatory drawing illustrating a cross-section A-A of a punch in which a material inflow facilitating portion forming mechanism is provided.

(8) FIG. 8 is an explanatory drawing illustrating the positional relationship between a material inflow facilitating portion forming mechanism and a concave ridge line forming portion of the manufacturing apparatus according to the present invention and a blank, and the locations of cross-sections B, C and D.

(9) FIG. 9 is an explanatory drawing that shows the reason why cracking at a portion “a” of a blank is prevented by providing a material inflow facilitating portion forming mechanism constituted by a recess and a protrusion in a die and punch.

(10) FIG. 10(a) to FIG. 10(f) are explanatory drawings that partially illustrate examples of the shapes of protrusions or recesses that are constituent elements of various kinds of material inflow facilitating portion forming mechanisms that are provided in a punch.

(11) FIG. 11(a) and FIG. 11(b) are explanatory drawings that respectively illustrate another press component manufactured by the present invention.

(12) FIG. 12 is an explanatory drawing illustrating an intermediate component (example embodiment of the present invention) for a T-shaped component.

(13) FIG. 13 is an explanatory drawing illustrating an intermediate component (example embodiment of the present invention) for a Y-shaped component.

(14) FIG. 14 is an explanatory drawing illustrating an example of a framework member.

(15) FIG. 15 is an explanatory drawing illustrating an example of a T-shaped component.

(16) FIG. 16(a) and FIG. 16(b) are explanatory drawings illustrating an outline of press working by draw forming, in which FIG. 16(a) illustrates a state prior to the start of forming, and FIG. 16(b) illustrates a state when forming is completed (bottom dead center of forming).

(17) FIG. 17 is an explanatory drawing illustrating an example of a press component manufactured by press working by draw forming.

(18) FIG. 18 is an explanatory drawing illustrating a blank that is a forming starting material for a press component.

(19) FIG. 19 is an explanatory drawing illustrating a wrinkle suppression region of a blank.

(20) FIG. 20 is an explanatory drawing illustrating an intermediate press component as it is in a state in which press working has been performed thereon.

(21) FIG. 21 is an explanatory drawing illustrating an example of the state of occurrence of pressing defects in an intermediate press component.

(22) FIG. 22 is an explanatory drawing that partially illustrates an outline of the patented invention disclosed by Patent Document 1.

DESCRIPTION OF EMBODIMENTS

(23) The manufacturing apparatus and manufacturing method according to the present invention are described hereunder.

(24) In the following description, a case in which a press component 11 to be manufactured by the present invention is an L-shaped component in which a top plate 11a has an external shape that is an inverted L-shape in a plan view that is orthogonal to the top plate 11a is taken an example. However, objects to be manufactured by the present invention are not limited to an L-shaped component, and also include other curved components (T-shaped component and Y-shaped component).

(25) Further, in the following description, a case in which the press component 11 and an intermediate component 11-1 have a hat-shaped cross-sectional shape constituted by the top plate 11a, two convex ridge lines 11b, 11b, two vertical walls 11c, 11c, two concave ridge lines 11d, 11d and two flanges 11e, 11e is taken as an example. However, objects to be manufactured by the present invention are not limited to the press component 11 and the intermediate component 11-1 that have a hat-shaped cross-sectional shape, and also include intermediate components 11-2 and 11-3 for press components having the cross-sectional shapes shown in FIG. 11 set forth below.

(26) 1. Manufacturing Apparatus 20 of the Present Invention

(27) FIG. 1 is an explanatory drawing illustrating a configuration example of a manufacturing apparatus 20 according to the present invention. FIG. 2 is an explanatory drawing partially illustrating an example of an intermediate component 11-1 of a press component 11 that was press-formed by the manufacturing apparatus 20.

(28) As illustrated in FIG. 1, the manufacturing apparatus 20 is a press-forming apparatus that employs bending forming and that uses the free bending method.

(29) The manufacturing apparatus 20 includes a die 21, a die pad 22 and a punch 23. The punch 23 is disposed facing the die 21 and the die pad 22. The die pad 22 is movable up and down together with the die 21, and can also press a part of a blank 24.

(30) The manufacturing apparatus 20 manufactures the intermediate component 11-1 of the press component 11 having the external shape illustrated in FIG. 2 by performing press working as cold or warm working on the blank (developed blank) 24 or on a blank (not illustrated in the drawings) which was subjected to preforming that is minor processing (for example, embossing) that is disposed between the die 21 and die pad 22 and the punch 23.

(31) The sheet thickness of the blank 24 is preferably 0.6 to 2.8 mm, more preferably 0.8 to 2.8 mm, and further preferably 1.0 to 2.8 mm.

(32) The press component 11 or the intermediate component 11-1 has a hat-shaped cross-sectional shape. The hat-shaped cross-sectional shape is a shape that includes a top plate 11a, two convex ridge lines 11b, 11b, two vertical walls 11c, 11c, two concave ridge lines 11d, 11d, and two flanges 11e, 11e.

(33) The press component 11 or the intermediate component 11-1 thereof has a curved portion 13. The curved portion 13 curves so that the external shape of the top plate 11a in a plan view orthogonal to the top plate 11a is an inverted L-shaped.

(34) The top plate 11a extends in a first direction (arrow direction in FIGS. 2 and 17). The two convex ridge lines 11b, 11b connect to both end portions in a direction which is orthogonal (that is, the width direction of the top plate 11a) to the first direction of the top plate 11a. The two vertical walls 11c, 11c connect to the two convex ridge lines 11b, 11b, respectively. The two concave ridge lines 11d, 11d connect to the two vertical walls 11c, 11c, respectively. The two flanges 11e, 11e connect to the two concave ridge lines 11d, 11d, respectively.

(35) The manufacturing apparatus 20 is favorably used in the following first case and second case.

(36) First case: A case satisfying one or more conditions among a condition that the blank 24 is made from an ultra-high tensile strength steel sheet having a tensile strength of 1180 MPa or more, a condition that a projection distance in a product height direction of the vertical wall 11c as a height of the press component 11 or the intermediate component 11-1 thereof is 70 mm or more, a condition that a radius of curvature R.sub.1 of the concave ridge line 11d of the press component 11 or the intermediate component 11-1 thereof is 10 mm or less in side view, and a condition that a radius of curvature R.sub.2 on an inner circumferential side of the curved portion 13 of the press component 11 or the intermediate component 11-1 thereof is 100 mm or less in plan view.
Second case: A case satisfying at least two conditions among a condition that the blank 24 is made from an ultra-high tensile strength steel sheet having a tensile strength of 1180 MPa or more, a condition that a height (projection distance in a product height direction of the vertical wall 11c) of the press component 11 or the intermediate component 11-1 thereof is 55 mm or more, a condition that a radius of curvature R.sub.1 of the concave ridge line 11d of the press component 11 or the intermediate component 11-1 thereof is 15 mm or less in side view, and a condition that a radius of curvature R.sub.2 on an inner side of the curved portion 13 of the press component 11 or the intermediate component 11-1 thereof is 140 mm or less in plan view.

(37) This is because, if press working by the conventional free bending method is performed on the blank 24 in the first case or the second case, cracks will be generated in the flange 11e on the inner circumferential side of the curved portion 13 of the obtained press component 11 or intermediate component 11-1 thereof, and therefore the significance of using the manufacturing apparatus 20 will be recognized.

(38) The die pad 22 presses a portion of the blank 24 to be formed into a part of the top plate 11a at the curved portion 13 of the press component 11 with an applied pressure that is 1.0 MPa or more and less than 32.0 MPa, or comes adjacent to or into contact with the aforementioned portion of the blank 24 while maintaining the distance of a gap with respect to the punch 23 at a distance corresponding to 1.0 to 1.1 times the sheet thickness of the blank 24.

(39) By this means, while out-of-plane deformation at the aforementioned portion of the blank 24 is being suppressed by the die pad 22, the intermediate component 11-1 of the press component 11 is manufactured by performing press working that is described hereunder.

(40) That is, in the press working, in a state in which a portion of the blank 24 to be formed into the end portion 11f in the first direction of the top plate 11a is present on the same plane as a portion of the blank 24 to be formed into the top plate 11a, the die 21 and the punch 23 are relatively moved in directions in which the die 21 and the punch 23 approach each other.

(41) By this means, the vertical wall 11c, the concave ridge line 11d and the flange 11e on the inner circumferential side of the curved portion 13 are formed while the portion of the blank 24 to be formed into the end portion 11f is caused to move in-plane (slide) over a portion of the die 21 at which the top plate 11a will be formed.

(42) In this way, the intermediate component 11-1 of the press component 11 is manufactured.

(43) FIG. 3 is an explanatory drawing illustrating the positional relationship between a material inflow facilitating portion forming mechanism 25 and a concave ridge line forming portion 23b of the manufacturing apparatus 20, and the blank 24.

(44) In addition to performing press working by bending forming using the free bending method disclosed by Patent Documents 1 and 2 and the like, in the manufacturing apparatus 20, as illustrated in FIGS. 1 and 3, a recess 21a and a protrusion 23a as the material inflow facilitating portion forming mechanism 25 for providing a material inflow facilitating portion 19 in the blank 24 are provided in the die 21 and the punch 23, respectively, of the manufacturing apparatus 20. The material inflow facilitating portion forming mechanism 25 is constituted by the recess 21a that is provided in the die 21 and the protrusion 23a that is provided in the punch 23.

(45) At the time of performing the press working, as illustrated in FIG. 2, the manufacturing apparatus 20 uses the material inflow facilitating portion forming mechanism 25 to provide the material inflow facilitating portion 19 in the vicinity (for example, at only the flange, or at the flange and the concave ridge line) of a portion of the blank 24 to be formed into the flange 11e on the inner circumferential side of the curved portion 13 of the intermediate component 11-1.

(46) As illustrated in FIGS. 2 and 3, preferably the material inflow facilitating portion forming mechanism 25 provides the material inflow facilitating portion 19 in a region that is outside a region (hatched region in FIG. 3) of the blank 24 to be formed into the press component 11. By this means, by cutting off the outer edge of the flange 11e of the intermediate component 11-1 as a trim line, it is possible not to leave a trace of the material inflow facilitating portion 19 in the press component 11.

(47) In a case where it is acceptable for a trace of the material inflow facilitating portion 19 to remain in the press component 11, the material inflow facilitating portion 19 may be provided in a region of the blank 24 (hatched region in FIG. 3) to be formed into the press component 11.

(48) Next, the material inflow facilitating portion forming mechanism 25 will be described in more detail.

(49) FIG. 4 is an explanatory drawing illustrating a cross-section in a conventional punch 23-1 in which the material inflow facilitating portion forming mechanism 25 is not provided, that corresponds to a cross-section A-A in FIG. 1.

(50) FIG. 5 is an explanatory drawing illustrating the positional relationship between the blank 24 and the material inflow facilitating portion forming mechanism 25 and concave ridge line forming portion 23b of the manufacturing apparatus 20, and locations of cross-sections B, C and D.

(51) FIG. 6 is a graph illustrating cross-section line length differences (inflow amounts) with respect to a conventional punch at a flange forming portion of the punch 23 at the cross-sections B, C and D. In the cross-sections B, C and D in the graph in FIG. 6, the left side illustrates a case according to the conventional method, and the right side illustrates a case according to the method of the present invention. Further, the cross-sections below the graph in FIG. 6 illustrate the respective shapes of the blank 24 at the cross-sections B, C and D.

(52) FIG. 7 is an explanatory drawing illustrating a cross-section A-A of the punch 23 in which the material inflow facilitating portion forming mechanism 25 is provided.

(53) In the aforementioned first case or second case, if press working of the blank 24 is performed by the free bending method using the conventional punch 23-1, cracking will occur at a portion “a” shown in FIG. 4.

(54) As illustrated in FIGS. 5 and 6, according to the present invention, by providing the material inflow facilitating portion forming mechanism 25 that is constituted by the recess 21a and the protrusion 23a, the material inflow facilitating portion 19 is provided in the intermediate component 11-1 by press working.

(55) The cross-sections B, C and D in FIGS. 5 and 6 are cross-sections in a material inflow direction that is parallel to a straight line that is tangent to a center position (portion “a”) of an inner circumference of the curved portion 13 in a plan view orthogonal to the top plate 11a. The cross-sections B, C and D are cross-sections in a maximum principal strain direction of a deformation of a portion to be formed into the flange 11e on the inner circumferential side of the curved portion 13.

(56) The material inflow facilitating portion 19 is provided so that cross-section line lengths at the cross-sections B, C and D gradually increase with distance from the flange 11e on the inner circumferential side of the curved portion 13.

(57) The cross-sectional shape of the material inflow facilitating portion 19 is not limited to a shape which monotonously increases with distance from the flange 11e on the inner circumferential side of the curved portion 13 of the intermediate component 11-1, and may be a shape that partially includes a portion at which the cross-section line length is constant.

(58) That is, as illustrated in FIG. 6, in comparison to the conventional method in which the material inflow facilitating portion forming mechanism 25 is not provided, the material inflow facilitating portion forming mechanism 25 of the method of the present invention is provided so that a cross-section line length difference (inflow amount) relative to the conventional punch of the flange forming portion of the punch 23 increases at each of the cross-sections B, C and D, and so that the cross-section line length difference (inflow amount) at the cross-section C increases more than the cross-section line length difference (inflow amount) at the cross-section 13, and the cross-section line length difference (inflow amount) at the cross-section D increases more than the cross-section line length difference (inflow amount) at the cross-section C.

(59) In other words, in the present invention, the material inflow facilitating portion forming mechanism 25 having a shape that increases the cross-section line length difference (inflow amount) at each of the cross-sections B, C and D is provided in the die 21 as the recess 21a and is also provided in the punch 23 as the protrusion 23a.

(60) For example, as illustrated in FIG. 7, the material inflow facilitating portion 19 is exemplified as being provided as a protrusion having an external shape that is obtained by connecting the meeting point of the concave ridge line 11d and the flange 11e of the curved portion 13 that is formed, and an end portion 24a of the blank 24 at the time that forming starts.

(61) FIG. 8 is an explanatory drawing illustrating the positional relationship between the blank 24 and the material inflow facilitating portion forming mechanism 25 and concave ridge line forming portion 23b of the manufacturing apparatus 20, and the locations of cross-sections B, C and D.

(62) As described above, a change differential in the inflow amount of the material that is caused by the material inflow facilitating portion forming mechanism 25 increases with distance from the portion “a” of the blank 24 through the cross-section B, the cross-section C and furthermore the cross-section D as indicated by a broad arrow in FIG. 8.

(63) Note that, cracking at the portion “a” of the blank 24 shown in FIG. 4 occurs when a tensile force in the circumferential direction that is not less than the rupture-yield strength of the blank 24 locally arises. Therefore, if a change in the cross-section line length difference is imparted to the portion “a”, cracking at the portion “a” will be more liable to occur. Accordingly, practically no change may be provided in the cross-section line length difference at the portion “a”. Further, it is sufficient to set a region that provides a change in the cross-section line length difference (inflow amount) as a region up to the position at which the blank 24 is present before forming, that is, up to the end portion 24a illustrated in FIG. 7.

(64) Next, the function of the material inflow facilitating portion forming mechanism 25 will be described.

(65) FIG. 9 is an explanatory drawing that shows the reason why cracking at the portion “a” of the blank 24 is prevented by providing the material inflow facilitating portion forming mechanism 25 that is constituted by the recess 21a and the protrusion 23a, in the die 21 and the punch 23.

(66) Cracking at the portion “a” of the blank 24 is attributable to a high tensile force F in the circumferential direction of the concave ridge line 11d that is located at an upper part of the portion “a” in the blank 24. In the present invention, by providing the material inflow facilitating portion forming mechanism 25 in the die 21 and the punch 23 and performing press working, the inflow amount of the blank 24 to an outer side relative to the portion “a” is increased.

(67) By this means, because the inflow amount of the blank 24 increases from around the portion “a”, the inflow amount of the blank 24 to the portion “a” increases. That is, the inflow amount of the blank 24 to the portion of the blank 24 to be formed into the curved portion 13 is increased by means of the material inflow facilitating portion forming mechanism 25. Although the direction of principal strain of a deformation in the portion of the blank 24 to be formed into curved portion 13 does not change significantly, the amount of deformation thereof is reduced.

(68) Thus, according to the present invention, as illustrated by arrows in FIG. 9, the inflow amount of the blank 24 to a portion of the blank 24 to be formed into the flange 11e on the inner circumferential side of the curved portion 13 of the press component 11 increases in comparison to the conventional method in which the material inflow facilitating portion forming mechanism 25 is not provided.

(69) By this means, in the blank 24, since the tensile force F in the circumferential direction of the concave ridge line 11d that is located at the upper part of the portion “a” can be reduced and the deformation load at the portion of the blank 24 to be formed into the curved portion 13 can be decreased, cracking is prevented at the portion “a” of the blank 24.

(70) FIG. 10(a) to FIG. 10(f) are explanatory drawings that partially illustrate examples of the shape of the protrusion 23a or a recess 23c that are constituent elements of various kinds of the material inflow facilitating portion forming mechanism 25 that is provided in the punch 23.

(71) As illustrated in FIG. 10(a), a protrusion that is convex toward the same side as the top plate 11a of the press component 11 that was described above referring to FIG. 7 can be used as the protrusion 23a that is a constituent element of the material inflow facilitating portion forming mechanism 25 provided in the punch 23.

(72) As illustrated in FIG. 10(b), the recess 23c that is convex toward the opposite side to the top plate 11a of the press component 11 may be used instead of the protrusion 23a illustrated in FIG. 10(a). In this case, it need scarcely be said that a protrusion corresponding to the recess 23c is provided in the die 21.

(73) As illustrated in FIG. 10(c), in a case where the blank 24 is small, the protrusion 23a may be provided in a region which is in contact with the blank 24.

(74) As described in the foregoing and as is also illustrated in FIG. 10(d), in a case where it is acceptable for a trace of the material inflow facilitating portion 19 to remain in the press component 11, the protrusion 23a as the material inflow facilitating portion 19 may be provided so as to extend over a region (hatched region in FIG. 3) of the blank 24 to be formed into the press component 11.

(75) As illustrated in FIG. 10(e), two or more of the protrusions 23a that are independent may be provided as constituent elements of the material inflow facilitating portion forming mechanism 25.

(76) In addition, as illustrated in FIG. 10(f), the protrusion 23a may be provided in a stepped shape in a direction parallel to the sheet thickness direction of the blank 12.

(77) Thus, the material inflow facilitating portion forming mechanism 25 provides one or more of the material inflow facilitating portions 19 that increase an inflow amount by which a portion of the blank 24 to be formed into the end portion 11f of the intermediate component 11-1 flows into a portion of the blank 24 to be formed into the flange 11e on the inner circumferential side of the curved portion 13 of the intermediate component 11-1.

(78) FIG. 11(a) and FIG. 11(b) are explanatory drawings that respectively illustrate intermediate components 11-2 and 11-3 of other press components to be manufactured by the present invention.

(79) In the above description, a case of manufacturing the intermediate component 11-1 having the shape illustrated in FIG. 2 by means of the present invention was taken as an example. However, the present invention is not limited to the case described above and is also applicable to a case of manufacturing the intermediate component 11-2 illustrated in FIG. 11(a) and a case of manufacturing the intermediate component 11-3 illustrated in FIG. 11(b), that is, the intermediate components 11-2 and 11-3 that have one of the convex ridge line 11b, the vertical wall 11c, the concave ridge line 11d and the flange 11e, respectively.

(80) 2. Manufacturing Method of the Present Invention

(81) In the manufacturing method of the present invention, basically the intermediate component 11-1 of the press component 11 is manufactured by the free bending method using the manufacturing apparatus 20.

(82) The press component 11 that is taken as the manufacturing object of the present invention preferably satisfies the aforementioned first case or second case. This is because, in the press component 11 that satisfies the first case or second case, cracking occurs at the portion “a” of the blank 24 when manufactured by the conventional free bending method.

(83) That is, a portion (hatched portion 18a in FIG. 22) of the blank 24 to be formed into a part of the top plate 11a of the curved portion 13 of the press component 11 is pressed with an applied pressure that is 1.0 MPa or more and less than 32.0 MPa by the die pad 22, or while maintaining the distance of a gap between the die pad 22 and the punch 23 at a distance corresponding to 1.0 to 1.1 times the sheet thickness of the blank 24, the die pad 22 is brought adjacent to or into contact with the portion (hatched portion 18a in FIG. 22) to be formed into the top plate 11a of the curved portion 13 of the press component 11.

(84) By this means, while suppressing out-of-plane deformation of the portion to be formed into a part of the top plate 11a, the intermediate component 11-1 of the press component 11 is manufactured by performing press working that is described hereunder.

(85) That is, in the press working, in a state in which a portion of the blank 24 to be formed into the end portion 11f in the first direction of the top plate 11a is present on the same plane as a portion of the blank 24 to be formed into the top plate 11a, the die 21 and the punch 23 are relatively moved in directions in which the die 21 and the punch 23 approach each other.

(86) By this means, the vertical wall 11c, the concave ridge line 11d and the flange 11e on the inner circumferential side of the curved portion 13 are formed while the portion of the blank 24 to be formed into the end portion 11f is caused to move in-plane (slide) over a portion of the die 21 at which the top plate 11a will be formed.

(87) By this press working, the material inflow facilitating portion forming mechanism 25 provided in the die 21 and the punch 23 provides at least one material inflow facilitating portion 19 in the vicinity of the portion of the blank 24 to be formed into the flange 11e on the inner circumferential side of the curved portion 13 of the intermediate component 11-1.

(88) According to the present invention, as described in the foregoing referring to FIG. 9, an inflow amount of the blank 24 to a portion of the blank 24 to be formed into the flange 11e on the inner circumferential side of the curved portion 13 of the intermediate component 11-1 increases. Therefore, in the blank 24, the tensile force F in the circumferential direction of the concave ridge line 11d that is located at an upperpart of the portion “a” can be reduced, and by this means cracking at the portion “a” of the blank 24 is prevented.

(89) In a case where there is no unwanted part in the intermediate component 11-1 that underwent press working according to the free bending method by means of the manufacturing apparatus 20, the intermediate component 11-1 serves as it is as the press component 11 that is the end product. On the other hand, in a case where there is an unwanted part in the intermediate component 11-1, the intermediate component 11-1 is made into the press component 11 by cutting off (trimming) the unwanted part including the material inflow facilitating portion 19 by taking the outer edge portion of the flange 11e as a trim line.

Example 1

(90) With respect to each of the intermediate component 11-1 (example embodiment of the present invention) illustrated in FIG. 2 manufactured using the manufacturing apparatus 20 illustrated in FIG. 1, and a press component (comparative example) manufactured using a manufacturing apparatus 14 illustrated in FIG. 20, a maximum sheet thickness reduction ratio at a meeting point “a” portion between the concave ridge line 11d and the flange 11e at a center position in the circumferential direction of the curved portion 13 was analyzed by the finite element method using a computer.

(91) The specifications of the intermediate component 11-1 and the press component that were analyzed are as described hereunder:

(92) Tensile strength and sheet thickness of blanks 24 and 18: 1180 MPa or more, and 1.6 mm

(93) Height (projection distance in product height direction of vertical wall 11c) of intermediate component 11-1 and press component: 60 mm

(94) Radius of curvature R.sub.1 of concave ridge line 11d of intermediate component 11-1 and press component: 20 mm in side view

(95) Radius of curvature R.sub.2 on inner side of curved portion 13 of intermediate component 11-1 and press component: 100 mm in plan view

(96) According to this analysis, if the maximum sheet thickness reduction ratio calculated by the dynamic explicit method using the finite element method was 8% or less, it was determined that there was no cracking at the aforementioned meeting point, while if the maximum sheet thickness reduction ratio that was similarly calculated was more than 13% it was determined that there was cracking at the aforementioned meeting point.

(97) As a result, it was found that the maximum sheet thickness reduction ratio at the aforementioned meeting point “a” portion of the intermediate component 11-1 (example embodiment of the present invention) was 8% and it thus was determined that there was no cracking at the meeting point “a” portion, while in contrast it was found that the maximum sheet thickness reduction ratio at the meeting point “a” portion of the press component (comparative example) was 13% and it was thus determined that there was cracking at the meeting point “a” portion.

(98) According to the present invention, even when press working by the free bending method is performed on the blank 24 in the aforementioned first case or second case, the L-shaped component 11-1 can be manufactured without generating cracking in the flange 11e on the inner circumferential side of the curved portion 13.

Example 2

(99) With respect to intermediate components 11-1 (example embodiments of the present invention) illustrated in FIG. 2 that were manufactured using the manufacturing apparatus 20 illustrated in FIG. 1, and press components (comparative examples) manufactured using the manufacturing apparatus 14 illustrated in FIG. 20, a maximum sheet thickness reduction ratio at a meeting point “a” portion between the concave ridge line 11d and the flange 11e at a center position in the circumferential direction of the curved portion 13 was analyzed by the finite element method using a computer.

(100) Table 1 shows a summary of the specifications of the intermediate components 11-1 and the press components that were analyzed as well as the analysis results.

(101) TABLE-US-00001 TABLE 1 Maximum Sheet Thickness Reduction Ratio % With Material Forming Shape Conditions Inflow Facilitating Top Concave Without Material Portion Surface Ridge Inflow Facilitating (Example Material Formed View Line Portion Embodiment of Strength Height R.sub.2 R.sub.1 (Comparative Cracking the Present No MPa mm mm mm Example) Criterion Invention) 1 1180 60 120 20 13 10 8 2 980 80 120 20 16 15 12 3 980 60 120 5 18 15 13 4 980 60 90 20 17 15 10 5 1180 65 150 20 14 10 9 6 1180 50 150 12 12 10 8 7 980 50 130 12 15 15 12 8 980 65 130 20 15 15 11 9 1180 50 130 20 12 10 6 10 980 65 150 12 15 15 10

(102) According to this analysis, if the maximum sheet thickness reduction ratio of the blank 24 having a tensile strength of 980 MPa that was calculated by the dynamic explicit method using the finite element method was 15% or less it was determined that there was no cracking at the aforementioned meeting point “a” portion, and if the maximum sheet thickness reduction ratio of the blank 24 having a tensile strength of 1180 MPa that was similarly calculated was 10% or less it was determined that there was no cracking at the aforementioned meeting point.

(103) As illustrated in Table 1, according to the present invention, even when press working by the free bending method is performed on the blank 24 in the aforementioned first case or second case, the L-shaped component 11-1 can be manufactured without generating cracking in the flange 11e on the inner circumferential side of the curved portion 13.

Example 3

(104) With respect to an intermediate component 30 (example embodiment of the present invention) of a T-shaped component that is illustrated in FIG. 12 and an intermediate component 31 of a Y-shaped component illustrated in FIG. 13 that were manufactured using the manufacturing apparatus 20 illustrated in FIG. 1, a maximum sheet thickness reduction ratio at a meeting point “a” portion between a concave ridge line and a flange at a center position in the circumferential direction of a curved portion was analyzed by the finite element method using a computer.

(105) Table 2 shows a summary of the specifications of the intermediate components 30 and 31 that were analyzed as well as the analysis results for each. Note that, the term “opening angle” in Table 2 refers to an angle θ shown in FIGS. 12 and 13.

(106) TABLE-US-00002 TABLE 2 Maximum Sheet Thickness Reduction Ratio % Without Material With Material Forming Shape Conditions Inflow Inflow Facilitating Top Concave Opening Facilitating Portion (Example Material Formed Surface Ridge Angle Portion Embodiment of Strength Height ViewR.sub.2 LineR.sub.1 Degree (Comparative Cracking the Present MPa mm mm mm deg. Example) Criterion Invention) Intermediate 1180 60 120 20 90 14 10 9 component 30 for T- shaped component Intermediate 1180 60 120 20 120 11 10 8 component 31 for Y- shaped component

(107) According to this analysis, if the maximum sheet thickness reduction ratio in the case of a material strength of 1180 MPa that was calculated by the dynamic explicit method using the finite element method was 10% or less it was determined that there was no cracking at the aforementioned meeting point.

(108) As illustrated in Table 2, according to the present invention, even when press working by the free bending method is performed on the blank 24 in the aforementioned first case or second case, the intermediate component 30 for a T-shaped component and the intermediate component 31 for a Y-shaped component can be manufactured without generating cracking in the flange 11e on the inner circumferential side of the curved portion 13.