Patent Grant
8844581
This is a §371 of International Application No. PCT/JP2009/067129, with an international filing date of Sep. 24, 2009, which is based on Japanese Patent Application No. 2008-245464, filed Sep. 25, 2008, the subject matter of which is incorporated by reference.
This disclosure relates to a press forming method for manufacturing a closed structure part having a closed section by press-forming a metal plate using a press forming die and fixing flange portions formed at a pair of joint ends of the metal plate to each other by hemming, a press forming apparatus used for the press forming method, a closed structure part manufactured using the press forming method, and a closed structure part with welded flanges.
For example, to manufacture a structural part having a closed section (a closed structure part), such as a side member or a side door of a vehicle (e.g., a motor vehicle), a plurality of sub-parts of the closed structure part are formed from a metal plate (e.g., a steel plate) using press forming (i.e., press sub-parts). Thereafter, one of the press-formed sub-parts is attached to another press sub-part, and the two press sub-parts are fixedly joined to each other by, for example, hemming or welding. In this way, a closed structure part is manufactured from a plurality of press sub-parts.
An example of such a closed structure part is a door structure of a vehicle described in Japanese Unexamined Patent Application Publication No. 2007-176361. The door structure of a vehicle described in JP 2007-176361 includes an inner panel and an outer panel each having a concave shape. The inner panel has, in an edge portion thereof, a hemming flange bent towards the outer panel. The hemming flange is bent to sandwich the edge portion of the outer panel. In this way, the inner panel is hemming joined to the outer panel.
In addition, Japanese Unexamined Patent Application Publication No. 5-228557 describes a hemming machine for joining an outer panel to an inner panel by hemming (press hemming) (refer to Paragraphs [0002] and [0003] and FIGS. 5 through 10). To join an outer panel to an inner panel, the hemming machine places the inner panel and the outer panel so that the inner panel and the outer panel overlap each other, brings a pre-hemming steel into contact with the top end portion of the hemming flange of the outer panel, and urges the top end portion in the diagonally downward direction to bend the top portion. Thereafter, the hemming machine moves the pre-hemming steel downward to further bend the hemming flange. The edge portion of the inner panel is sandwiched by the hemming flange of the outer panel. In this way, the outer panel is joined to the inner panel by hemming (hemming joint).
In addition, to manufacture a front side member, which is a closed structure part used for absorbing a shock occurring when the vehicle collides with an object, the flange portions formed for a plurality of press parts are firmly joined with one another using welding, such as spot welding, laser welding, or arc welding.
When manufacturing the above-described closed structure part having a closed section, a plurality of press sub-parts of the closed structure part are formed from, for example, a steel plate by pressing. Thereafter, the press sub-parts are placed to overlap one another. The flange portions of the press sub-parts are joined by hemming or welding. Thus, a plurality of press sub-parts are assembled into the closed structure part.
However, in general, the weight of a closed structure part having a closed section increases as the number of press sub-parts of the closed structure part increases. That is, if the number of the press sub-parts increases, a connection flange portion is needed for each of the press sub-parts. In addition, such a flange portion needs to be formed on either end of the press sub-part with an inner space therebetween. Accordingly, as the number of the press sub-parts increases, the ratio of the weight of the flange portions to the entire weight of the closed structure part increases. As a result, the weight of the closed structure part is increased.
In addition, such a closed structure part is manufactured through at least a press step to form a plurality of press sub-parts of the closed structure part using dedicated press forming dies and a hemming step to join the press sub-parts to one another by hemming. In recent years, to reduce the manufacturing cost of closed structure parts, it has been required to manufacture closed structure parts more efficiently than ever.
Accordingly, it could be helpful to provide a method and an apparatus capable of reducing the number of sub-parts of a closed structure part and the number of steps for manufacturing the closed structure part and, therefore, efficiently manufacturing the closed structure part. It could also be helpful to provide a lightweight closed structure part by reducing the number of sub-parts.
We thus provide a method for manufacturing a closed structure part having a closed section using a metal plate by press-processing the metal plate using a press forming die and fixing a pair of flange portions made into a pair of joint ends of the metal plate to each other is provided. The method is characterized by including a pre-hemming step of bending a hemming prong protruding from a top end of the flange portion towards the flange portion, a closing step of, after the pre-hemming step is completed, urging a pair of insert guide surfaces formed on the press forming die against the top of the flange portion having the hemming prong therein, moving the press forming die in a predetermined pressing direction so that the two flange portions are brought closer to each other due to a force component perpendicular to the pressing direction that is generated by each of the insert guide surfaces, and guiding the pair of the flange portions into a slit clearance formed between the pair of insert guide surfaces of the press forming die, and a hemming press step of, after the closing step is completed, further moving the press forming die in the pressing direction, inserting the pair of flange portions into the slit clearance, simultaneously bending the hemming prong using a pressing force transferred from an inner surface portion of the slit clearance to a top portion of the hemming prong so that the other flange portion is sandwiched by the hemming prong and the flange portion is fixed to the flange portion and, simultaneously, pressing the metal plate using a press forming surface formed outside of each of the insert guide surfaces of the press forming die and press-forming outer portions of the pair of the flange portions of the metal plate into predetermined shapes.
In the method for manufacturing a closed structure part according to [1], after the pre-hemming step is completed, the closing step is performed. In the closing step, the pair of insert guide surfaces formed on the press forming die are urged against the top of the flange portion having the hemming prong therein. Simultaneously, the press forming die is moved in a predetermined pressing direction so that the two flange portions are brought closer to each other due to a force component perpendicular to the pressing direction that is generated by each of the insert guide surfaces, and the pair of the flange portions are guided into a slit clearance formed between the pair of insert guide surfaces of the press forming die. Thus, the pair of flange portions can be brought closer to each other against the deformation resistance (springback) of the metal plate serving as the material used for the closed structure part, and the distance between the pair of the flange portions can be set to correspond to the opening width of the slit clearance. Accordingly, if the opening width of the slit clearance is appropriately determined in accordance with the allowable value for the distance between the pair of flange portions, the distance between the pair of flange portions can be sufficiently reduced and can be maintained in the slit clearance.
In addition, in the method for manufacturing a closed structure part according to [1], after the closing step is completed, the hemming press step is performed. In the hemming press step, the press forming die is further moved in the pressing direction, and the pair of flange portions is inserted into the slit clearance. Simultaneously, the hemming prong is bent so that the flange portion is sandwiched by the hemming prong and the flange portion is fixed to the other flange portion. At the same time, the metal plate is pressed using a press forming surface formed outside of each of the insert guide surfaces of the press forming die, and press-forming outer portions of the pair of the flange portions of the metal plate are press-formed into predetermined shapes. Accordingly, the distance between the pair of flange portions can be sufficiently decreased. Thereafter, one of the flange portions can be fixed to the other flange portion using the hemming prong (hemming joint). At the same time, the outer portions of the pair of flange portions can be press-formed into a predetermined shape.
Therefore, according to the method for manufacturing a closed structure part described in [1], a closed structure part having a closed section can be manufactured using a single metal plate. In addition, since an operation for hemming joint of the pair of flange portions of the closed structure part and an operation for press-forming the outer portions of the flange portions can be performed at the same time, the number of sub-parts of the closed structure part and the number of steps for manufacturing the closed structure part can be reduced and, therefore, the closed structure part can be efficiently manufactured.
Furthermore, according to [2], the method for manufacturing a closed structure part described in [1] is characterized by further including a welding step of, after the hemming press step is completed, fixing one of the flange portions to the other flange portion by welding.
According to [3], a press forming apparatus for use in the method for manufacturing a closed structure part described in [1] or [2] is provided. The apparatus is characterized by including the press forming die and driving means for moving the press forming die in the pressing direction when the closing step and the hemming press step are performed. The press forming die has a pair of press forming surfaces having a shape corresponding to the outer portion of the pair of flange portions of the closed structure part, a pair of insert guide surfaces disposed on the outer sides of the press forming surfaces in a direction perpendicular to the pressing direction and oblique to the pressing direction and the direction perpendicular to the pressing direction, and the slit clearance formed between the pair of insert guide surfaces in the direction perpendicular to the pressing direction.
In the press forming apparatus used for manufacturing a closed structure part according to [3], by mounting a single metal plate in the press forming die and moving the press forming die in a predetermined pressing direction using the driving means, the distance between the pair of flange portions can be sufficiently decreased. Thereafter, one of the flange portions can be fixed to the other flange portion using the hemming prong (hemming joint). At the same time, the outer portions of the pair of flange portions of the metal plate (the closed structure part) can be press-formed into a predetermined shape. Therefore, a closed structure part having a closed section can be manufactured from a single metal plate. In addition, since an operation for hemming joint of the pair of flange portions of the closed structure part and an operation for press-forming the outer portions of the flange portions can be performed at the same time, the number of sub-parts of the closed structure part and the number of steps for manufacturing the closed structure part can be reduced and, therefore, the closed structure part can be efficiently manufactured.
In addition, according to [4], the press forming apparatus used for manufacturing a closed structure part is characterized in that in the press forming apparatus used for manufacturing a closed structure part described in [3], the depth of the slit clearance with respect to the insert guide surfaces is greater than or equal to 3 mm and less than or equal to 50 mm, and an opening width of the slit clearance in the direction perpendicular to the pressing direction is greater than or equal to 2 times a thickness of the metal plate serving as the material used for the closed structure part and less than or equal to 10 times the thickness of the metal plate.
According to [5], a closed structure part manufactured using the method for manufacturing a closed structure part described [1] or [2] is provided. The closed structure part is characterized by including a body having a closed section, a flange portion formed in each of a pair of joint ends of the body, and a hemming prong protruding from a top end of one of the flange portions, where the hemming prong is processed by hemming so that the one of the flange portions is fixed to the other flange portion.
In the closed structure part according to [5], the body, the flange portion, and the hemming prong are formed from a single metal plate. In addition, a hemming prong protruding from one of a top end of the flange portions is processed by hemming so that the one of the flange portions is fixed to the other flange portion. Thus, one of the flange portions is fixed to the other flange portion (hemming joint). In this way, the body, the pair of flange portions, and the flange prong, which are main components of the closed structure part, are integrally formed from a single metal plate. In addition, by joining the joint ends of the body with each other using only the pair of flange portions, the body can have a closed section. Accordingly, the number of sub-parts of the closed structure part can be reduced, and the ratio of the weight of the flange portions to the entire weight of the closed structure part can be reduced, as compared with a closed structure part including two or more independent sub-parts. Thus, the weight of the closed structure part can be efficiently reduced.
In addition, according to [6], a closed structure part is characterized in that in the closed structure part described in [5], a plurality of the hemming prongs are provided in the one of the flange portions in a width direction of the flange portion with a predetermined separation distance PH therebetween, and a width of each of the hemming prongs is set to a value greater than or equal to 2 times a thickness of the metal plate and less than or equal to a product length of the closed structure part. A protruding length of the hemming prong from the top end of the flange portion is set to a value greater than or equal to 1 time the thickness of the metal plate serving as the material used for the closed structure part and less than or equal to 1.5 times a flange height, and the separation distance PH is set to a value greater than or equal to 5 mm and less than or equal to a value obtained by subtracting the widths of the hemming prongs from the product length.
As described above, a method for manufacturing a closed structure part and a press forming apparatus used for manufacturing a closed structure part can reduce the number of sub-parts of the closed structure part and the number of manufacturing steps. As a result, a closed structure part can be efficiently manufactured.
In addition, the number of sub-parts of the closed structure part can be reduced and, thus, the weight of the closed structure part can be reduced.
A method for manufacturing a closed structure part, a manufacturing apparatus used in the method, and the closed structure part manufactured using the method according to examples are described below with reference to the accompanying drawings.
(Structure of Closed Structure Part)
Each of the closed structure parts 10 to 16 includes a main body 18 that has a closed section extending in a direction perpendicular to the length direction. Flange portions 20 and 22 are integrally formed as the pair of joint ends of the main body 18. The main body 18 and the pair of flange portions 20 and 22 are formed from a single high-tensile steel plate by press forming.
The main bodies 18 of the closed structure parts 10 to 16 have a variety of shapes in cross section in accordance with a required installation space and the required strength of the body of the vehicle. More specifically, for example, the main body 18 of the closed structure part 10 (refer to
Note that the cross-sectional shape of the main body 18 is not limited to the shapes shown in
The pair of flange portions 20 and 22 are formed as the upper portions of each of the closed structure parts 10 to 16 in the vertical direction (a direction indicated by an arrow HP). The two flange portions 20 and 22 have symmetrical shapes in the width direction (a direction indicated by an arrow WP). The two flange portions 20 and 22 are formed by bending either of the end portions (a pair of joint ends) of the main body 18 in a direction perpendicular to the length direction upwards. In the states (finished states) indicated by
To manufacture a side member using one of such closed structure parts 10 to 16, high stiffness cap members fixedly cap the ends of the closed structure parts 10 to 16 in the length direction of the closed structure parts 10 to 16 by insertion. Thereafter, a reinforcement member for reinforcing one of the closed structure parts 10 to 16 or a bracket, a bolt, or a nut for connecting the closed structure part to the vehicle is attached to the outer periphery or the inner periphery of the closed structure part as needed. In this way, a side member, which is a component of the body of the vehicle, is manufactured.
(Apparatuses for Manufacturing Closed Structure Part)
As shown in
The lower surface of the punch 34 serves as a press forming surface 44. In the middle of the press forming surface 44 in the width direction (a direction indicated by an arrow WM), a press convex portion 46 that protrudes with respect to both ends in a convex shape is formed. The cross-sectional shape of the press convex portion 46 along the width direction is substantially trapezoidal to correspond to the cross-sectional shape of the press concave portion 40. The press convex portion 46 includes slope surfaces 48 at either end thereof in the width direction. The slope surfaces 48 correspond to the slope surfaces 42 of the press concave portion 40.
The hydraulic actuator 36 includes a cylinder 50 and a plunger 52 disposed on the inner peripheral side of the cylinder 50. The cylinder 50 is fixed to a support frame (not shown) of the first press forming apparatus 30. The plunger 52 is supported by the cylinder 50 in a slidable manner along the height direction (a direction indicated by an arrow HM). The lower end of the plunger 52 is joined to the upper middle portion of the punch 34. Under hydraulic control of a hydraulic control unit (not shown), the hydraulic actuator 36 moves the punch 34 between a press position (refer to
As shown in
The punch 64 has a substantially rectangular shape in cross section having a length direction that coincides with the height direction (indicated by the arrow HM). The lower end surface of the punch 64 includes the press forming surfaces 74 that form a convex shape and that correspond to the press forming surfaces 68 that form a concave shape.
The hydraulic actuator 66 includes a cylinder 76 and a plunger 78 disposed on the inner peripheral side of the cylinder 76. The cylinder 76 is fixed to a support frame (not shown) of the second press forming apparatus 60. The plunger 78 is supported by the cylinder 76 in a slidable manner along the height direction. The lower end of the plunger 78 is joined to the upper middle portion of the punch 64. Under hydraulic control of a hydraulic control unit (not shown), the hydraulic actuator 66 moves the punch 64 between a press position (refer to
As shown in
The supporting pad 86 has a blank supporting surface 94 formed from a pair of slope surfaces that form a concave shape on the upper surface side. The shape of the blank supporting surface 94 corresponds to the shape of a bottom plate portion 54 of the main body 18. In addition, the punch 84 has two press forming surfaces 96 at either end of the punch 84 in the width direction of the lower surface. The two press forming surfaces 96 have a shape that corresponds to the shape of a shoulder portion 26 that is an outer portion of the flange portions 20 and 22.
In contrast, the insert core 82 has, as the upper surface, a press forming surface 98 formed from slope surfaces that correspond to the two press forming surfaces 96. In addition, the insert core 82 has, as a bottom surface, a convex blank supporting surface 100 that corresponds to the blank supporting surface 94 of the supporting pad 86. In addition, the side surface of each of the pressure cams 88 on an inner side in the width direction serves as a pressure surface 89 corresponding to a side portion 83 of the insert core 82.
As shown in
Each of the two insert guide surfaces 104 is formed as a convex curved surface having a constant radius of curvature. The insert guide surface 104 smoothly connects the side end portion of the press forming surface 96 to the lower end portion of the slit clearance 102. In this instance, RG denotes the radius of curvature of the insert guide surface 104. Then, the radius of curvature RG may be 0 mm (a right angle) or may have a value greater than 0. The radius of curvature RG can be set to any value as appropriate.
The hydraulic actuator 90 includes a cylinder 106 and a plunger 108 disposed on the inner peripheral side of the cylinder 106. The cylinder 106 is fixed to a support frame (not shown) of the hemming press apparatus 80. The plunger 108 is supported by the cylinder 106 in a slidable manner along the height direction. The lower end of the plunger 108 is joined to the upper middle portion of the punch 84. Under hydraulic control of a hydraulic control unit (not shown), the hydraulic actuator 90 moves the punch 84 between a press position (refer to
A pair of the cam drive mechanisms 92 operates in conjunction with the operation performed by the hydraulic actuator 90. Each of the cam drive mechanisms 92 moves the pressure cam 88 between a standby position (refer to
While the above-described apparatus shown in
(Method for Manufacturing Closed Structure Part)
A method for manufacturing the closed structure part 12 (a method for manufacturing a closed structure part) using the above-described manufacturing apparatus is described next.
In one method for manufacturing a closed structure part, a first press step using the first press forming apparatus 30 shown in
In this method for manufacturing a closed structure part, a preliminary hemming step is performed using a general-purpose press forming apparatus (not shown) after the first press step has been completed. An example of the general-purpose press forming apparatus is a press forming apparatus that can bend the end portion of a planar high-tensile steel plate at a substantially right angle. In addition, as shown in
In this instance, PH denotes the separation distance between the protruding portions 27 in the length direction and LH denotes the protruding length of the plurality of protruding portions 27 from the side end of the blank 24. The separation distance PH is appropriately set to a value greater than or equal to 5 mm and less than or equal to a length obtained by subtracting the hemming prong widths from the product length. In addition, the protruding length LH is appropriately set to a value greater than or equal to 1 time the thickness of the blank 24 and less than or equal to 1.5 times the flange height. Furthermore, a width BH is appropriately set to a value greater than or equal to twice the thickness of the plate and less than or equal to the product length.
In the preliminary hemming step (not shown), the plurality of protruding portions 27 that are formed in the blank 24 in the first press step shown in
In one method for manufacturing a closed structure part, a second press step using the second press forming apparatus 60 shown in
In one method for manufacturing a closed structure part, a closing step and a press hemming step are performed using the hemming press apparatus 80 after the second press step has been completed. In the closing step and press hemming step, as shown in
Subsequently, as shown in
As shown in
In one method for manufacturing a closed structure part, after the hemming press step has been completed, a welding step is performed using a general-purpose welding apparatus, such as a spot welding apparatus, a laser welding apparatus, or an arc welding apparatus. During the welding step, the flange portions 20 and 22 joined using the hemming prongs 28 are welded together using spot welding, laser welding, or arc welding. Thereafter, if, like a part, such as a front side member, the flange portions are not used for another purpose, the top end of the welded portion of the flange portions 20 and 22 is cut off by shearing or meltdown to further reduce the weight. However, for a portion (e.g., a locker) that needs to be joined to another part (joining of the locker and a floor in the case of the locker), the flange portion is not cut off and can be used as a joint flange for joining another part. Thus, the closed structure part 12 shown in
Note that the closed structure parts 10, 14, and 16 other than the closed structure part 12 can be manufactured through the steps that are substantially the same as those for the closed structure part 12 by simply mounting the dies 32 and 62, the punches 34, 64, and 84, the supporting pad 86, the pressure cams 88, and the insert core 82 that correspond to the shape of the closed structure part to be manufactured into the first press forming apparatus 30, the second press forming apparatus 60, and the hemming press apparatus 80 and appropriately adjusting, for example, the strokes of the hydraulic actuators 36, 66, and 90 and the cam drive mechanism 92.
In addition, as shown in
The hemming press step of one method for manufacturing a closed structure part is described in more detail next with reference to
As described above, through the preliminary hemming step, the plurality of hemming prongs 28 protruding from the top end of the flange portion 20, which is one of the two flange portions, are bent towards the flange portion 22, as shown in
In the closing step and the hemming press step, as shown in
Subsequently, as shown in
As shown in
As shown in
If the flange portions 20 and 22 are joined together by hemming, the hemming press apparatus 80, as shown in
(Operations)
In one method for manufacturing a closed structure part, after the preliminary hemming step has been completed, the closing step is performed. In the closing step, the two insert guide surfaces 104 of the punch 84 are urged against the top end of the flange portion 20, and the punch 84 is lowered towards the press position. Thus, the flange portions 20 and 22 are brought closer to each other due to a force component generated by each of the two insert guide surfaces 104, and the flange portions 20 and 22 are guided into the slit clearance 102 of the punch 84. In this way, the flange portions 20 and 22 can be brought closer to each other against the deformation resistance (springback) of the blank 24, and the distance between the flange portions 20 and 22 can be set to correspond to the opening width WA of the slit clearance 102. Accordingly, if the opening width WA of the slit clearance 102 is appropriately determined in accordance with the allowable value for the distance between the flange portions 20 and 22, the distance between the flange portions 20 and 22 can be sufficiently reduced and can be maintained in the slit clearance 102.
In addition, in one method for manufacturing a closed structure part, after the closing step has been completed, the punch 84 is further lowered towards the press position in the hemming press step. Thus, the flange portions 20 and 22 are inserted into the slit clearance 102 and the hemming prongs 28 are bent to sandwich the flange portion 22. In this way, the flange portion 20, which is one of the two flange portions, is joined to the other flange portion 22. At the same time, the metal plate is pressurized by the two press forming surfaces 96 of the punch 84 and, thus, the two shoulder portions 26 of the blank 24 are press-formed into a predetermined shape. Accordingly, the distance between the flange portions 20 and 22 can be sufficiently decreased. Thereafter, the flange portion 20 can be fixed to the flange portion 22 using the hemming prongs 28 (hemming joint). At the same time, the two shoulder portions 26 of the blank 24 can be press-formed into a predetermined shape.
Thus, in one method for manufacturing a closed structure part, a single high-tensile steel plate serving as the blank 24 can be manufactured into any one of the closed structure parts 10 to 16. In addition, the hemming joint operation of the flange portions 20 and 22 of one of the closed structure parts 10 to 16 and the press-forming operation of the two shoulder portions 26 of the blank 24 can be performed at the same time. Accordingly, the number of sub-parts of each of the closed structure parts 10 to 16 and the number of steps for manufacturing the closed structure part can be reduced and, therefore, the closed structure parts 10 to 16 can be efficiently manufactured.
In addition, according to the hemming press apparatus 80, which is one apparatus for manufacturing the closed structure part, a single metal plate serving as the blank 24 is mounted on the insert core 82 and the punch 84. The punch 84 is lowered from the standby position to the press position using the hydraulic actuator 90. Thus, the distance between the flange portions 20 and 22 can be sufficiently reduced in the slit clearance 102. Thereafter, the flange portion 20, which is one of the two flange portions, can be fixed to the flange portion 22 using the hemming prongs 28 (hemming joint). At the same time, the two shoulder portions 26 of the blank 24 can be press-formed into a predetermined shape. Accordingly, any one of the closed structure parts 10 to 16 having a closed section can be manufactured using the single metal plate serving as the blank 24. In addition, the hemming joint operation of the flange portions 20 and 22 of each of the closed structure parts 10 to 16 and the press-forming operation of the two shoulder portions 26 of the blank 24 can be performed at the same time. Accordingly, the number of sub-parts of each of the closed structure parts 10 to 16 and the number of steps for manufacturing the closed structure part can be reduced and, therefore, the closed structure parts 10 to 16 can be efficiently manufactured.
Furthermore, according to one of the closed structure parts 10 to 16, the main body 18, the two flange portions 20 and 22, and the hemming prongs 28 are formed from a single high-tensile steel plate (the blank 24). Hemming is performed so that the hemming prongs 28 protruding from the top portion of the flange portion 20, which is one of the two flange portions, sandwich the other flange portion 22. Thus, the flange portion 20 is fixed to the flange portion 22 (hemming joint). In this way, the main body 18, the flange portions 20 and 22, and the hemming prongs 28, which are main components of each of the closed structure parts 10 to 16, can be integrally formed from the single blank 24. In addition, joint ends of the main body 18 can be joined together using only the flange portions 20 and 22 so that the main body 18 can have closed section. Accordingly, the number of sub-parts of each of the closed structure parts 10 to 16 can be reduced, and the ratio of the weight of the flange portions 20 and 22 to the entire weight of the closed structure part can be reduced, as compared with a closed structure part including two or more independent sub-parts. Thus, the weight of each of the closed structure parts 10 to 16 can be efficiently reduced.
(Hemming Press Apparatus)
The dimensions of the main components of the punch 84 of the hemming press apparatus 80 and the reason for selecting the dimensions are described next as an example.
As described above, the opening width WA of the slit clearance 102 of the punch 84 is appropriately set to a value greater than or equal to twice the thickness of the blank 24 that is the material used for the closed structure part 10 and less than or equal to ten times the thickness. This is because if the opening width WA is set to a value less than twice the thickness of the blank 24, the friction resistance between the slit clearance 102 and each of the flange portions 20 and 22 is excessively increased when the punch 84 is lowered and, therefore, fracturing or cracking may occur in the blank 24. In contrast, if the opening width WA is set to a value greater than ten times the thickness of the blank 24, the hemming prongs 28 cannot be urged against the other flange portion 22 in hemming even if the punch 84 is lowered to the press position. Thus, a gap may be formed between the flange portions 20 and 22 (backlash may occur).
In addition, the depth DG of the slit clearance 102 of the punch 84 is appropriately set to a value greater than or equal to 3 mm and less than or equal to 50 mm. This is because the depth DG of the slit clearance 102 needs to be greater than the protruding length of each of the flange portions 20 and 22. If the depth DG is set to a value less than 3 mm, the height of each of the flange portions 20 and 22 is too small and, thus, it is difficult to join the flange portions 20 and 22 together by welding after the hemming joint is performed. In contrast, if the depth DG is set to a value greater than 50 mm, it is difficult to maintain the stiffness of the punch 84.
(Hemming Prong)
The dimensions of the hemming prongs 28 of each of the closed structure parts 10 to 16 and the reason for selecting the dimensions are described next as an example.
As described above, the protruding length LH of the hemming prongs 28 is appropriately set to a value greater than or equal to 1 time the thickness of the blank 24 and less than or equal to 1.5 times the flange height. This is because if the protruding length LH is less than 1 time the thickness of the blank 24, it is difficult to sufficiently increase the joint strength between the flange portions 20 and 22 that are joined using the hemming prongs 28. Thus, it is difficult to reliably join the flange portions 20 and 22 together by hemming. In contrast, if the protruding length LH is greater than 1.5 times the flange height, the ratio of the weight of the hemming prongs 28 to the entire weight of each of the closed structure parts 10 to 16 becomes too large. Thus, the weight of each of the closed structure parts 10 to 16 is disadvantageously increased.
In addition, the separation distance PH of the hemming prongs 28 is appropriately set to a value greater than or equal to 5 mm and less than or equal to a length obtained by subtracting the hemming prong widths from the product length. This is because if the separation distance PH is less than 5 mm, the ratio of the weight of the plurality of hemming prongs 28 to the entire weight of each of the closed structure parts 10 to 16 is excessively increased and, therefore, the weight of each of the closed structure parts 10 to 16 is increased. In addition, the separation distance PH can be less than or equal to a length obtained by subtracting the length of the hemming prong from the product length.
If the hemming prong width is less than 2 times the thickness of the plate, it is difficult to sufficiently increase the joint strength between the flange portions 20 and 22 and, therefore, it is difficult to reliably join the flange portions 20 and 22 together by hemming. In addition, the hemming prong width can be smaller than or equal to the product length.
Closed structure parts manufactured using the method for manufacturing a closed structure part are described next as Examples 0 to 4. In addition, closed structure parts manufactured using a method for manufacturing a closed structure part that does not meet our conditions are described below as comparative examples 1 to 4.
In comparative example 1, a cold-rolled steel having a thickness of 1.2 mm and a tensile strength of 1180 MPa is employed as the blank 24. Such a blank 24 is subjected to a process performed in a hemming press step using the hemming press apparatus 80. Thus, as shown in
The closed structure part 120 has a substantially rectangular cross section. A width B of the closed structure part 120 is 120 mm. A height H of the closed structure part 120 is 80 mm. The entire length of the closed structure part 120 is 800 mm. However, the closed structure part 120 does not have the two flange portions and hemming prongs. Accordingly, even when the hemming press step is performed on the blank 24, hemming is not performed on hemming prongs. Accordingly, the presence or absence of the insert guide surface 104 and the slit clearance 102 in the punch 84 has no impact on, for example, the shape of the closed structure part 120.
In addition, in comparative example 2, a cold-rolled steel having a thickness of 1.2 mm and a tensile strength of 1180 MPa is employed as the blank 24. Such a blank 24 is subjected to the processes in the closing step and hemming press step using the hemming press apparatus 80. Thus, as shown in
The closed structure part 122 has a substantially rectangular cross section. A width B of the closed structure part 122 is 120 mm. A height H of the closed structure part 122 is 80 mm. The entire length of the closed structure part 122 is 800 mm. In addition, the protruding length LF of the flange portions 20 and 22 is set to 15 mm. However, the closed structure part 122 does not have a hemming prong. Accordingly, when the closing step and hemming press step are performed on the blank 24, the closing process for bringing the flange portions 20 and 22 close to each other is performed. However, hemming is not performed on hemming prongs.
In addition, the punch 84 including the slit clearance 102 having a depth DG of 30 mm and an opening width WA of 5 mm and the insert guide surfaces 104 having a radius of curvature RG of 30 mm is employed.
In contrast, in comparative example 3, a cold-rolled steel having a thickness of 1.2 mm and a tensile strength of 1180 MPa is employed as the blank 24. Such a blank 24 is subjected to the processes performed by the hemming press apparatus 80 in the closing step and the hemming press step. Thus, as shown in
The closed structure part 124 has a substantially rectangular cross section. A width B of the closed structure part 124 is 120 mm. A height H of the closed structure part 124 is 80 mm. The entire length of the closed structure part 124 is 800 mm. In addition, the protruding length LF of the flange portions 20 and 22 is set to 15 mm. The flange portion 20, which is one of the two flange portions, integrally includes a plurality of hemming prongs 28 protruding from the top portion of the flange portion 20. The hemming prongs 28 are processed in a preliminary hemming step before the blank 24 is mounted in the hemming press apparatus 80 and are preliminary bent.
Herein, the width BH of the hemming prong 28 is set to 10 mm. The protruding length LH of the hemming prongs 28 is also set to 10 mm. In addition, the separation distance PH of the hemming prongs 28 is set to 250 mm.
In addition, as shown in
In contrast, in comparative example 4, a cold-rolled steel having a thickness of 1.2 mm and a tensile strength of 1180 MPa is employed as the blank 24. Such a blank 24 is subjected to the processes performed by the hemming press apparatus 80 in the closing step and the hemming press step. Thus, as shown in
The closed structure part 126 has a substantially rectangular cross section. A width B of the closed structure part 126 is 120 mm. A height H of the closed structure part 126 is 80 mm. The entire length of the closed structure part 126 is 800 mm. In addition, the protruding length LF of the flange portions 20 and 22 is set to 15 mm. The flange portion 20, which is one of the two flange portions, integrally includes a plurality of hemming prongs 28 protruding from the top portion of the flange portion 20. The hemming prongs 28 are processed in a preliminary hemming step before the blank 24 is mounted in the hemming press apparatus 80 and are preliminary bent.
Herein, the width BH of the hemming prong 28 is set to 10 mm. The protruding length LH of the hemming prongs 28 is set to 1 mm. In addition, the separation distance PH of the hemming prongs 28 is set to 780 mm.
In addition, as shown in
In contrast, in comparative example 0, a cold-rolled steel having a thickness of 1.2 mm and a tensile strength of 1180 MPa is employed as the blank 24. Such a blank 24 is subjected to the processes performed by the hemming press apparatus 80 in the closing step and the hemming press step. Thus, as shown in
The closed structure part 128 has a substantially regular hexagonal cross section. The length of a side S of the hexagonal cross section is 40 mm. The entire length of the closed structure part 128 is 800 mm. In addition, the protruding length LF of the flange portions 20 and 22 is set to 15 mm. The flange portion 20, which is one of the two flange portions, integrally includes a plurality of hemming prongs 28 protruding from the top portion of the flange portion 20. The hemming prongs 28 are processed in a preliminary hemming step before the blank 24 is mounted in the hemming press apparatus 80 and are preliminary bent.
Herein, the width BH of the hemming prong 28 is set to 10 mm. The protruding length LH of the hemming prongs 28 is set to 10 mm. In addition, the separation distance PH of the hemming prongs 28 is set to 250 mm.
In addition, as shown in
In contrast, in Example 1, a cold-rolled steel having a thickness of 1.2 mm and a tensile strength of 1180 MPa is employed as the blank 24. Such a blank 24 is subjected to the processes performed by the hemming press apparatus 80 in the closing step and the hemming press step. Thus, as shown in
The closed structure part 130 has a substantially rectangular cross section. A width B of the closed structure part 130 is 120 mm. A height H of the closed structure part 130 is 80 mm. The entire length of the closed structure part 130 is 800 mm. In addition, the protruding length LF of the flange portions 20 and 22 is set to 15 mm. The flange portion 20, which is one of the two flange portions, integrally includes a plurality of hemming prongs 28 protruding from the top portion of the flange portion 20. The hemming prongs 28 are processed in a preliminary hemming step before the blank 24 is mounted in the hemming press apparatus 80 and are preliminary bent.
Herein, the width BH of the hemming prong 28 is set to 10 mm. The protruding length LH of the hemming prongs 28 is also set to 10 mm. In addition, the separation distance PH of the hemming prongs 28 is set to 250 mm.
In addition, as shown in
In contrast, in Example 2, a cold-rolled steel having a thickness of 1.2 mm and a tensile strength of 1180 MPa is employed as the blank 24. Such a blank 24 is subjected to the processes performed by the hemming press apparatus 80 in the closing step and the hemming press step. Thus, as shown in
The closed structure part 132 has a substantially regular hexagonal cross section. The length of a side S of the hexagonal cross section is 40 mm. The entire length of the closed structure part 132 is 800 mm. In addition, the protruding length LF of the flange portions 20 and 22 is set to 15 mm. The flange portion 20, which is one of the two flange portions, integrally includes a plurality of hemming prongs 28 protruding from the top portion of the flange portion 20. The hemming prongs 28 are processed in a preliminary hemming step before the blank 24 is mounted in the hemming press apparatus 80 and are preliminary bent.
Herein, the width BH of the hemming prong 28 is set to 10 mm. The protruding length LH of the hemming prongs 28 is also set to 10 mm. In addition, the separation distance PH of the hemming prongs 28 is set to 250 mm.
In addition, as shown in
In contrast, in Example 3, a cold-rolled steel having a thickness of 1.2 mm and a tensile strength of 1180 MPa is employed as the blank 24. Such a blank 24 is subjected to the processes performed by the hemming press apparatus 80 in the closing step and the hemming press step. Thus, as shown in
The closed structure part 134 has an irregular hexagonal cross section. The width B of the bottom plate portion 54 of the closed structure part 134 is 120 mm. A width BS of a slope portion 58 that connects the side plate portion to the top plate portion is 30 mm, and a height H of the closed structure part 134 is 70 mm. The entire length of the closed structure part 134 is 800 mm. In addition, the protruding length LF of the flange portions 20 and 22 is set to 15 mm. The flange portion 20, which is one of the two flange portions, integrally includes a plurality of hemming prongs 28 protruding from the top portion of the flange portion 20. The hemming prongs 28 are processed in a preliminary hemming step before the blank 24 is mounted in the hemming press apparatus 80 and are preliminary bent.
Herein, the width BH of the hemming prong 28 is set to 10 mm. The protruding length LH of the hemming prongs 28 is also set to 10 mm. In addition, the separation distance PH of the hemming prongs 28 is set to 250 mm.
In addition, as shown in
In contrast, in Example 4, a cold-rolled steel having a thickness of 1.2 mm and a tensile strength of 1180 MPa is employed as the blank 24. Such a blank 24 is subjected to the processes performed by the hemming press apparatus 80 in the closing step and the hemming press step. Thus, as shown in
The closed structure part 136 has an irregular octagonal cross section. Each of the widths B of the bottom plate portion 54 and the side plate portions 56 of the closed structure part 136 is 60 mm. Each of the width BS of a slope portion 301 and a width BN of two top plate portions 59 located outside the flange portions 20 and 22 is 30 mm. In addition, the protruding length LF of the flange portions 20 and 22 is set to 15 mm. The flange portion 20, which is one of the two flange portions, integrally includes a plurality of hemming prongs 28 protruding from the top portion of the flange portion 20. The hemming prongs 28 are processed in a preliminary hemming step before the blank 24 is mounted in the hemming press apparatus 80 and are preliminary bent.
Herein, the width BH of the hemming prong 28 is set to 10 mm. The protruding length LH of the hemming prongs 28 is also set to 10 mm. In addition, the separation distance PH of the hemming prongs 28 is set to 250 mm.
In addition, as shown in
A method for evaluating the closed structure parts 120, 122, 124, and 126 according to the comparative examples and the closed structure parts 128, 130, 132, 134, and 136 according to the examples is described next. A gap distance GB (a maximum value) between the flange portions 20 and 22 (between two joint ends for the closed structure part 120) immediately before the blank 24 was subjected to a hemming press process using the hemming press apparatus 80 and a gap distance GA (a maximum value) between the flange portions 20 and 22 (between the two joint ends for the closed structure part 120) immediately after the blank 24 was subjected to the hemming press process were measured. In such a case, to increase the welding performance, it is desirable that the gap distance GA be minimized. If the gap distance GA is about 0.3 mm, the flange portions 20 and 22 can be reliably welded together without externally holding the flange portions 20 and 22.
Evaluation for the closed structure parts 120, 122, 124, and 126 and the closed structure parts 128, 130, 132, 134, and 136 is shown in the following TABLE 1.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-245464 | Sep 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/067129 | 9/24/2009 | WO | 00 | 3/23/2011 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2010/035887 | 4/1/2010 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3909919 | Miyabayashi et al. | Oct 1975 | A |
| 4055133 | Wessely | Oct 1977 | A |
| 4238550 | Burgess et al. | Dec 1980 | A |
| 4395900 | Saurenman | Aug 1983 | A |
| 4441241 | Hoeffken | Apr 1984 | A |
| 4466267 | Casler et al. | Aug 1984 | A |
| 4734971 | Dupasquier | Apr 1988 | A |
| 8365411 | Saito et al. | Feb 2013 | B2 |
| 20070131015 | Matsumura et al. | Jun 2007 | A1 |
| 20070145767 | Saitoh et al. | Jun 2007 | A1 |
| 20110174868 | Higai et al. | Jul 2011 | A1 |
| Number | Date | Country |
|---|---|---|
| 955541974 | Feb 1976 | JP |
| 57-184520 | Nov 1982 | JP |
| 5-228557 | Sep 1993 | JP |
| 2000-515432 | Nov 2000 | JP |
| 2006-247748 | Sep 2006 | JP |
| 2007-7176361 | Jul 2007 | JP |
| 0242019 | May 2002 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20110174409 A1 | Jul 2011 | US |
