JP6418873B2 - Bending method - Google Patents

Description

  The present invention relates to a bending method.

  For example, Patent Document 1 describes a vehicle including a metal frame on which an engine, a cab, and the like are mounted. This metal frame is long and has a U-shaped cross section perpendicular to the longitudinal direction, and has a bent portion in the middle in the longitudinal direction so that it can be placed away from the engine installation location. ing. For example, the bent portion is formed by bending a metal frame material having a U-shaped cross section along a predetermined planned bending line. This bending process is performed, for example, in a state where one side and the other side of the planned bending line are sandwiched by pads (clamping members).

JP-A-2005-75018

  In general, a metal frame as described in Patent Document 1 is painted to form a coating film on the surface. As a method of obtaining such a metal frame, a method of bending a metal frame material having a U-shaped cross section and then coating the metal frame material after the bending process is conceivable. However, in this case, by having the bent portion, the transportability of the metal frame material after the bending process to the coating process is lowered, and the work efficiency may be lowered.

  On the other hand, after the metal frame material is painted, a method of bending the painted metal frame material is also conceivable. However, if the metal frame material after coating is bent, there is a possibility that the coating film peels off at the deformed portion. Therefore, in order to prevent the occurrence of peeling of the coating film, it is also conceivable that the metal frame material is preheated before bending to keep the coating film soft. However, in this case, since the coating film of the sandwiched portion by the pad is also heated and softened, there is a possibility that the coated film of the sandwiched portion is depressed and the quality of the painted surface is lowered when sandwiched by the pad.

  This invention is made | formed in view of the said situation, and it aims at providing the bending method which can maintain the quality of a coating surface, suppressing generation | occurrence | production of coating film peeling.

  The bending method according to the present invention is a bending method for bending a long metal frame material, and the metal frame material has a bottom plate and a pair of side plates that stand up from the bottom plate and face each other. The metal frame material having a coating film on the surface and inductively heating at least a part of the metal frame material that deforms during bending, and the metal frame material sandwiched by the sandwiching member A bending step of bending the bottom plate along a planned bending line extending in a direction intersecting the longitudinal direction.

  According to this bending method, since the deformed portion at the time of bending is locally heated by induction heating, the coating film of the deformed portion can be softened to suppress the occurrence of coating film peeling and It is possible to suppress the heating of the coating film and make it difficult to generate the dent. This makes it possible to maintain the quality of the painted surface while suppressing the occurrence of coating film peeling. Moreover, since it heats locally by induction heating, energy efficiency is high, it can heat to desired temperature in a short time, and can improve work efficiency.

  In the bending method according to the present invention, in the heating step, at least a part of the portion that is deformed when the side plate is bent may be induction-heated. According to this bending method, since the deformation part of the side plate where the amount of deformation during bending is large and the coating film is easily peeled is locally heated, the occurrence of coating film peeling can be effectively suppressed. Moreover, by this, the force clamped by the clamping member is large, and it is possible to suppress heating of the bottom plate in which a dent is likely to occur in the coating film, and it is possible to further prevent the dent from being generated.

  In the bending method according to the present invention, the coating film may be formed of a highly rigid paint. According to this bending method, the surface of the metal frame after bending can be prevented from being damaged by a coating film formed of a highly rigid high-rigidity paint. Further, according to this bending method, it is possible to suppress the occurrence of coating film peeling even when a high-rigidity coating that is difficult to stretch and easily peels off during bending is used.

  ADVANTAGE OF THE INVENTION According to this invention, the bending method which can maintain the quality of a coating surface can be provided, suppressing generation | occurrence | production of coating film peeling.

It is a perspective view which shows the metal frame which concerns on embodiment. It is a perspective view which shows metal frame material. It is the schematic explaining the heating process of the bending method which concerns on embodiment. It is the schematic explaining the bending process of the bending method which concerns on embodiment, (a) is a side view, (b) is sectional drawing seen from the longitudinal direction.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted. In the following description, “longitudinal direction” refers to the longitudinal direction of the metal frame 1 and the metal frame material 30.

  FIG. 1 is a perspective view showing a metal frame according to the embodiment. The metal frame 1 is used as a vehicle body frame on which various components such as a cab, an engine, and a loading platform are mounted in a vehicle such as a truck.

  The metal frame 1 is a long metal frame, and is made of, for example, steel. The metal frame 1 has a thickness of about 5 to 10 mm, for example. The metal frame 1 has a bottom plate 11 and a pair of side plates 13. The pair of side plates 13 are formed in the same shape, and stand vertically from the bottom plate 11 and face each other. Thereby, the metal frame 1 has a substantially U-shaped cross section perpendicular to the longitudinal direction. Such a metal frame 1 is formed, for example, by bending a flat steel plate in the width direction.

  The metal frame 1 has two bent portions 21 at a predetermined interval at an intermediate portion in the longitudinal direction. The bending part 21 is provided, for example, in order to arrange the metal frame 1 on the vehicle body while avoiding the installation location of the engine. In FIG. 1, the bending center 23 of the bending portion 21 is indicated by a broken line. In this example, the bending center 23 is orthogonal to the longitudinal direction of the metal frame 1. The two bent portions 21 are formed by bending the bottom plate 11 at the bending center 23, and are formed by bending in directions opposite to each other. The bending angle of the bending part 21 is set to a predetermined angle of about 5 to 10 °, for example.

  The metal frame 1 has a coating film on the entire surface. This coating film is formed by powder coating, for example, and has a thickness of, for example, about 50 μm. In addition, this coating film is formed of, for example, a polyester-based high-rigidity paint in order to effectively suppress scratches on the surface of the metal frame 1.

  Next, the bending method according to the embodiment will be described. FIG. 2 is a perspective view showing a metal frame material. FIG. 3 is a schematic diagram illustrating a heating process of the bending method according to the embodiment, and FIG. 4 is a schematic diagram illustrating the bending process. In this bending method, the metal frame 1 is obtained by bending the metal frame material 30. The metal frame material 30 is the metal frame 1 before the bending part 21 is formed, and a coating film is formed on the surface by the previous process. In this bending method, the bent portion 21 is formed by bending the bottom plate 11 along a planned bending line 35. The planned bending line 35 coincides with the bending center 23 of the bent portion 21, and in this example, extends perpendicular to the longitudinal direction of the metal frame material 30.

  When the bottom plate 11 is bent along the planned bending line 35, the bottom plate 11 is bent and deformed, and the side plate 13 is deformed larger than the bottom plate 11. 2-4, the deformation | transformation centerline 37 used as the center of a deformation | transformation in the side plate 13 when the baseplate 11 is bent by the bending expected line 35 is shown with the dashed-two dotted line. Moreover, in FIG. 2, the deformation | transformation part 39 which is a part which deform | transforms at the time of a bending process is shown by hatching. The side plate 13 contracts and deforms around the deformation center line 37 when the bottom plate 11 is bent in the direction indicated by the arrow A in FIG. 4A, and deforms when the bottom plate 11 is bent in the direction indicated by the arrow B. It extends and deforms around the center line 37. In either case, the amount of deformation increases as the distal end of the side plate 13 is farther from the center of bending. The maximum width of the deformed portion 39 in the longitudinal direction, that is, the width of the deformed portion 39 at the tip of the side plate 13 is, for example, about 120 to 160 mm.

  Thus, at the time of bending, the deformation amount of the side plate 13 becomes larger than the deformation amount of the bottom plate 11, and the deformation amount of the side plate 13 becomes larger toward the tip side. In places where the amount of deformation at the time of bending is large, coating film peeling tends to occur. For this reason, in this embodiment, at least a part of the deformed portion 39 during bending of the side plate 13, particularly at least a part of the deformed portion 39 of the tip end portion 13 </ b> A of the side plate 13, is preliminarily heated to suppress occurrence of coating film peeling. . The tip portion 13A is, for example, a portion having a length that is about half of the length of the side plate 13 in the standing direction.

  In this bending method, for example, the metal frame material 30 is conveyed along a longitudinal direction on a conveyance path (not shown), and two bent portions 21 are sequentially formed by a heating process and a bending process. A heating process is performed at one position on the conveyance path, and a bending process is performed at another position.

  Hereinafter, a heating process and a bending process are demonstrated concretely. First, the configuration of the heating device 40 used in the heating process will be described. The heating device 40 is used for induction heating of the deformed portion 39 of the tip portion 13A of the side plate 13. As shown in FIG. 3, the heating device 40 includes a pair of coils 41, a high-frequency current transformer 43, a high-frequency power source 45, and a cooling water circulation unit 47.

  The coil 41 generates a high-density eddy current near the surface of the object to be heated by flowing an alternating current, and heats the object to be heated by Joule heat. The pair of coils 41 is bent so that the distal end portion is substantially U-shaped, and has an inner portion 41A on the distal end side and an outer portion 41B continuous from the inner portion 41A. The width in which the coil 41 extends in the longitudinal direction of the metal frame material 30 is, for example, about 30 to 50 mm. The coil 41 is movable up and down between a heating position on the conveyance path shown in FIG. 3 and a standby position outside the conveyance path located below the heating position. When the coil 41 is in the heating position, the inner portion 41A extends along the inner surface of the deformed portion 39 of the tip 13A of the side plate 13, and the outer portion 41B extends along the outer surface of the deformed portion 39. To do. Thereby, when an alternating current is passed through the coil 41, at least a part of the deformed portion 39 of the front end portion 13A of the side plate 13 is induction-heated.

  A proximal end portion of the coil 41 is connected to the high-frequency current transformer 43. The high frequency current transformer 43 converts the power from the high frequency power supply 45 supplied via the feeder 49 into a high frequency current and supplies it to the coil 41. The coil 41, the high frequency current transformer 43, and the high frequency power supply 45 are cooled by the cooling water supplied from the cooling water circulation unit 47.

  In the heating step, first, the metal frame material 30 is positioned at a predetermined position on the conveyance path. In parallel with this, or after that, the coil 41 is moved from the standby position to the heating position, and the deformation center line 37, that is, the deformation portion 39 of the front end portion 13A of the side plate 13 is positioned between the inner portion 41A and the outer portion 41B. . At this time, the center line and the deformation center line 37 in the longitudinal direction of the metal frame material 30 of the inner part 41A and the outer part 41B are aligned. In this state, a high-frequency current is passed through the coil 41 to inductively heat the deformed portion 39 of the front end 13A of the side plate 13 to a predetermined temperature.

  Next, the bending process will be described. In the bending step, as shown in FIG. 4, the metal frame material 30 is sandwiched by the sandwiching member 50 on one side and the other side in the longitudinal direction with respect to the planned bending line 35 (deformation center line 37), and the sandwiching member 50 is held in this state. By inclining each other, the bottom plate 11 is bent at a predetermined angle along a planned bending line 35. At this time, the temperature of the deformed portion 39 of the tip 13A of the heated side plate 13 is preferably equal to or higher than a predetermined temperature (for example, 60 ° C.).

  Each clamping member 50 has a first clamping member 50A, a pair of second clamping members 50B, and a pair of third clamping members 50C. The bottom plate 11 is clamped between the first clamping member 50A and one side surface of the pair of second clamping members 50B, and between the third clamping member 50C and the other side surface of the second clamping member 50B. The side plate 13 is sandwiched. Since the bottom plate 11 is bent, the magnitude of the force for sandwiching the bottom plate 11 by the first sandwiching member 50A and the second sandwiching member 50B is such that the side plate 13 by the second sandwiching member 50B and the third sandwiching member 50C. It is larger than the magnitude of the force to pinch.

  In the present embodiment, the distance in the longitudinal direction of the metal frame material 30 between the holding member 50 on one side and the holding member 50 on the other side is, for example, about 15 to 30 mm. Since this interval is smaller than the extending width of the coil 41, in this example, the sandwiched portion between the second sandwiching member 50B and the third sandwiching member 50C has a deformation of the distal end portion 13A of the heated side plate 13. A portion 39 is included. In consideration of the occurrence of dents on the coating surface, it is preferable that the sandwiched portion does not include the heated portion as much as possible, but a part of the heated portion may be included as in this example.

  According to the bending method of the embodiment described above, the deformed portion 39 of the metal frame material 30 at the time of bending is locally heated by induction heating. Generation | occurrence | production of peeling can be suppressed and it can make it difficult to generate | occur | produce a hollow by suppressing that the coating film of the clamping part by the clamping member 50 is heated. This makes it possible to maintain the quality of the painted surface while suppressing the occurrence of coating film peeling.

  As other heating methods, it is conceivable to perform heating with warm air heating in a drying furnace or a heating device using infrared rays, microwaves, etc. In this case, the entire metal frame material 30 is heated and sandwiched. Since the coating film of the clamping part by the member 50 is also heated and becomes soft, there is a possibility that a dent will be generated in the coating film of the clamping part when it is clamped by the clamping member 50. Moreover, it becomes a large sized facility or a specialized facility, which may increase the cost. Moreover, there is a possibility that it cannot be heated to the target temperature in a short time.

  On the other hand, according to the bending method of the embodiment, since the heating is locally performed by induction heating, the coating of the sandwiched portion by the sandwiching member 50 is suppressed from being heated, and the dent is hardly generated. Can do. Further, the heating device 40 can be realized with simple equipment, and the cost can be reduced. Moreover, since energy efficiency is high and it can heat to desired temperature in a short time, working efficiency can be improved. Further, by changing the shape of the coil 41, it is possible to easily cope with the difference in shape and size of the metal frame material 30. Moreover, the temperature at the time of heating can be easily controlled by controlling the current flowing through the coil 41.

  Moreover, according to this bending method, since the deformation | transformation part 39 of the side plate 13 with which the deformation | transformation amount at the time of a bending process is large and a coating-film peeling tends to generate | occur | produce locally, generation | occurrence | production of coating-film peeling is suppressed effectively. it can. In addition, this suppresses heating of the bottom plate 11 where the force that is sandwiched between the sandwiching members 50 (the first sandwiching member 50A and the second sandwiching member 50B) is large and the coating film is likely to be depressed. Further, it is possible to make the depression more difficult to occur.

  Also, according to this bending method, the deformation amount during bending is larger, and the deformed portion 39 of the tip portion 13A of the side plate 13 where the coating film peeling is likely to occur is locally heated. Can be more effectively suppressed.

  Moreover, according to this bending process method, the damage | wound etc. of the surface of the metal frame 1 after a bending process can be suppressed with the coating film formed with the highly rigid highly rigid coating material. Further, according to this bending method, it is possible to suppress the occurrence of coating film peeling even when a high-rigidity coating that is difficult to stretch and easily peels off during bending is used.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. The present invention is not limited to the scope described in the claims and can be modified or applied to other embodiments. May be.

  For example, in the above-described embodiment, the front end portion 13A of the side plate 13 has been described as being heated. However, the present invention is not limited to this, and any unit that locally heats the deformed portion 39 at the time of bending may be used. The side plate 13 including the deformed portion 39 may be heated. In addition to this, the deformed portion 39 of the bottom plate 11 may be heated. In these cases, for example, the coil 41 may be shaped to extend along the deformation center line 37 and the planned bending line 35.

  Moreover, in the said embodiment, the bending expected line 35 should just cross | intersect the longitudinal direction of the metal frame material 30, and may cross | intersect at angles other than orthogonal. Moreover, a heating process and a bending process may be performed in the same position on a conveyance path. Moreover, the coating film on the surface of the metal frame 1 may be formed by electrodeposition coating or the like.

DESCRIPTION OF SYMBOLS 1 ... Metal frame, 11 ... Bottom plate, 13 ... Side plate, 13A ... Tip part, 21 ... Bending part, 23 ... Bending center, 30 ... Metal frame material, 35 ... Planned bending line, 37 ... Deformation center line, 39 ... Deformation part , 40 ... heating device, 41 ... coil, 43 ... high frequency current transformer, 45 ... high frequency power supply, 47 ... cooling water circulation unit, 49 ... feeder, 50 ... clamping member, 50A ... first clamping member, 50B ... second. Clamping member, 50C ... 3rd clamping member.

Claims (3)

A bending method for bending a long metal frame material,
The metal frame material has a bottom plate and a pair of side plates standing upright from the bottom plate and facing each other, and has a coating on the surface,
A heating step of inductively heating at least part of a portion of the metal frame material that is deformed during the bending process;
It said metal frame material while pinched by pinching member, seen including and a step bend bending the bottom plate scheduled line bend extending in a direction crossing the longitudinal direction of the metal frame material,
In the heating step, the bottom plate is not heated, and at least a part of the side plate that is deformed during the bending is induction-heated . 2. The bending method according to claim 1, wherein, in the heating step, the base end portion of the side plate is not heated, and at least a part of the tip portion of the side plate that is deformed during the bending is induction-heated .   The bending method according to claim 1, wherein the coating film is formed of a highly rigid paint.

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