Method for producing hollow bent component and device for producing hollow bent component

Abstract

Provided is method for producing a hollow bent component comprising a step in which, simultaneously with the formation of a shear bent part, a tensile force in the direction of a velocity intersecting a straight line which is the direction of inclination of a heating means and a cooling means is applied to the shear bent part. Also provided is a device for producing a hollow bent component that is configured such that a control unit thereof controls a conveyance mechanism and / or a bending force application part such that, simultaneously with the formation of a shear bent part, a tensile force in the direction of a velocity intersecting a straight line L1 which is the direction of inclination of a heating means and a cooling means is applied to the shear bent part.

Description

Manufacturing method and device for hollow bent part

[0001] The present invention relates to a method and an apparatus for manufacturing a hollow curved part having a shear bent portion.This application claims priority to Japanese Patent Application No. 2024-062717, filed on April 9, 2024, the contents of which are incorporated herein by reference.

[0002] As is well known, hollow, curved metal strength members, reinforcing members, or structural members used in automobiles, various machines, etc. are required to be lightweight and strong. Conventionally, these types of hollow curved parts have been manufactured by, for example, cold bending, welding of pressed products, punching of thick plates, and even forging. However, there are limits to how much weight and strength can be reduced in hollow curved parts manufactured by these manufacturing methods, and achieving these goals has not been easy.

[0003] In recent years, active consideration has been given to the production of this type of hollow curved part by the so-called tube hydroforming method, as disclosed in, for example, Non-Patent Document 1. However, as described on page 28 of Non-Patent Document 1, the tube hydroforming method has issues such as the development of raw materials and the expansion of the flexibility of the shapes that can be formed, and further development is required in the future.

[0004] In view of this situation, the present inventors previously disclosed an invention relating to a bending apparatus in Patent Document 1. Fig. 5 is an explanatory diagram showing a schematic overview of this bending apparatus 100. As shown in Fig. 5, in this bending apparatus 100, a steel pipe (hereinafter referred to as a hollow material Pm) supported by a pair of support means 101, 101 so as to be freely movable in its axial direction is fed from upstream to downstream in the direction of arrow F by a feeding device (not shown), and bending is performed downstream of the support means 101, 101 to produce a steel hollow bent part Pp. That is, downstream of the support means 101, 101, the hollow material Pm is rapidly heated by a high-frequency heating coil 102 to a temperature range suitable for partial hardening, and the hollow material Pm is rapidly cooled by a water cooling device 103 located downstream of the high-frequency heating coil 102. The position of a movable roller die 104 having at least one pair of rolls 104a, 104a that supports and feeds the hollow material Pm is changed in three dimensions (or in two dimensions in some cases) to apply a bending moment to the heated portion of the hollow material Pm, thereby bending the hollow material Pm. This bending device 100 makes it possible to manufacture high-strength hollow bent parts Pp with high work efficiency.

[0005] International Publication No. WO 2006 / 093006 International Publication No. WO 2011 / 024741

[0006] Automotive Technology Vol. 57, No. 6, 2003, pp. 23-28 Tube Forming, Corona Publishing, 1st Edition, 3rd Printing, November 25, 2002, pp. 51-55

[0007] Hollow bent parts used in automobiles, various machines, and the like come in a variety of shapes. Among these, many hollow bent parts have extremely small bends, such as a bend radius of 1 to 2 times or less the diameter of the metal pipe (or the length of the side in the bending direction in the case of a rectangular cross section). However, when bending a metal pipe using the method of Patent Document 1 to obtain a bend radius of 1 to 2 times or less the diameter of the metal pipe (or the length of the side in the bending direction in the case of a rectangular cross section), wrinkles or folds may occur on the inner periphery of the bend, or the thickness of the outer periphery of the bend may be significantly reduced, resulting in fracture. For this reason, it has been difficult to manufacture hollow bent parts with small bends. Furthermore, as described in Non-Patent Document 2, cold bending of hollow bent parts involves tensile stress acting on the outer periphery of the bend, resulting in a reduction in the plate thickness. Similarly, because the method of Patent Document 1 is also a bending process, a reduction in the plate thickness on the outer periphery of the bend is unavoidable.

[0008] To address these issues, the present inventors disclosed an invention relating to a shear bending apparatus in Patent Document 2. As shown in FIG. 6 , this shear bending apparatus 200 includes a first support means 201, a heating means 202, a cooling means 203, and a gripping means 204. The first support means 201 supports a metal hollow material Pm at a first position A while feeding the hollow material Pm relatively in its longitudinal direction. The heating means 202 partially heats the hollow material Pm at a second position B, which is downstream of the first position A in the feeding direction of the hollow material Pm. The cooling means 203 cools (by forced cooling or natural cooling) the heated portion of the hollow material Pm at a third position C, which is downstream of the second position B in the feeding direction of the hollow material Pm. The gripping means 204 applies shear force to the heated portion of the hollow material Pm by moving the hollow material Pm in two or three dimensions while positioning it at a fourth position D, which is downstream of the third position C along the feed direction of the hollow material Pm. Therefore, this shear bending device 200 makes it possible to shear and heat treat the heated portion of the hollow material Pm. Furthermore, this shear bending device 200 enables reliable mass production of high-strength hollow bent parts with bends having a bending radius of one to two times the diameter of the metal pipe (or the length of the side in the bending direction, in the case of a rectangular cross section), or even less, at low cost.

[0009] The manufacturing method described in Patent Document 2 makes it possible to manufacture hollow bent parts that are high in strength yet have a small bending radius, thereby enabling significant weight reductions for many mechanical parts, including automobiles. However, when designing an integrated hollow bent part as a mechanical part, the product may require a certain level of flatness to ensure the strength and rigidity required for the design. In other words, if wrinkles occur in the product, stress may concentrate at the wrinkled area when a load is applied, which may cause the product to buckle or break prematurely. Furthermore, variations in the size and location of wrinkles that occur during mass production will result in variations in the strength and rigidity of the product. Therefore, it is important to avoid wrinkles in processed products.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a method for manufacturing a hollow curved part that suppresses the occurrence of wrinkles and ensures the strength and rigidity of the product. It is also an object of the present invention to provide a manufacturing device for a hollow curved part that realizes the manufacturing method.

[0011] The gist of the present invention, which was completed based on the above findings, is as follows.

[0012] (1) One aspect of the present invention is a method for manufacturing a hollow bent part, comprising: supporting a long, hollow metal material at a first position while feeding it in a feed direction along its longitudinal direction; partially heating the hollow material at a heated portion using a heating means arranged at a second position downstream of the first position along the feed direction; cooling the hollow material using a cooling means arranged at a third position downstream of the second position along the feed direction; and supporting the hollow material at a fourth position downstream of the third position along the feed direction and moving the support position in two or three dimensions, thereby applying a shear force to the heated portion of the hollow material to form a shear bent portion; and simultaneously with forming the shear bent portion, applying a tensile force to the shear bent portion in a direction intersecting the inclination of the heating means and the cooling means.

[0013] (2) In the above aspect (1), the pulling force may be generated by at least one of slowing down the feed speed of the hollow material at the first position and increasing the movement speed of the support position at the fourth position.

[0014] (3) In the above aspect (1) or (2), the following may be done: when the shear bent portion is formed, the out-of-plane deformation amount of the shear bent portion is measured, and the tensile force is increased or decreased according to the out-of-plane deformation amount.

[0015] (4) Another aspect of the present invention is a manufacturing device for hollow bent parts, comprising: a feeding mechanism that supports a metal hollow material at a first position along a feeding direction, which is the longitudinal direction of the material; a heating means that partially heats the hollow material at a heated portion at a second position downstream of the first position; a cooling means that cools the hollow material by injecting a cooling medium at a third position downstream of the second position; a bending force applying unit that supports the hollow material at a fourth position downstream of the third position and moves the support position in two or three dimensions to apply a shear force to the heated portion of the hollow material to form a shear bent portion; and a control unit that controls the feeding mechanism, the heating means, the cooling means, and the bending force applying unit, wherein the control unit controls at least one of the feeding mechanism and the bending force applying unit to apply a tensile force to the shear bent portion in a direction that intersects with the inclination of the heating means and the cooling means simultaneously with forming the shear bent portion.

[0016] (5) In the above aspect (4), the control unit may generate the tensile force by performing at least one of slowing down the feed speed of the hollow material by the feed mechanism and increasing the movement speed of the support position by the bending force applying unit.

[0017] (6) In the above aspect (4) or (5), the present invention may be configured as follows: the present invention further comprises a deformation amount detection means for measuring the out-of-plane deformation amount of the shear bending portion, and the control unit increases or decreases the tensile force according to the measured out-of-plane deformation amount.

[0018] [Additional Notes] [1] One aspect of the present invention is a method for manufacturing a hollow bent part, which comprises supporting a long, metallic hollow material at a first position while feeding it in a feed direction along its longitudinal direction, partially heating the hollow material at a heated portion by a heating means arranged at a second position downstream of the first position along the feed direction, cooling the hollow material by a cooling means arranged at a third position downstream of the second position along the feed direction, and supporting the hollow material at a fourth position downstream of the third position along the feed direction, and moving the support position in two or three dimensions, thereby applying a shear force to the heated portion of the hollow material, wherein the shear angle of the hollow material formed after the application of the shear force with respect to the feed direction is θ (degrees), the inclination angle of the heating means and the cooling means with respect to the feed direction is α (degrees), and the material feed speed is V ０ , the axial speed at the exit side is V ｘ , the vertical velocity relative to the axial direction on the outlet side is V ｙ , k is a constant, the following formulas 1 to 3 are satisfied.

[0019]

[0020] [2] A hollow curved part manufacturing apparatus for use in a hollow curved part manufacturing apparatus including: a feeding mechanism that supports a metal hollow material at a first position along a feeding direction that is the longitudinal direction of the metal hollow material while feeding the material; a heating coil that heats the hollow material at a second position downstream of the first position; a cooling device that cools the hollow material by injecting a cooling medium at a third position downstream of the second position; and a bending force applying unit that grips the hollow material at a fourth position downstream of the third position and moves the gripping position in two or three dimensions to form a bent part in the hollow material, the hollow curved part manufacturing apparatus including: a mechanism that detects wrinkles on the surface of a processed product, and adjusts an axial speed V on the outlet side to satisfy the following formula 4 based on information about the detected wrinkles: ｘ and the axial and vertical velocity V at the exit ｙ and / or material feed rate V ０ The manufacturing apparatus for hollow curved parts has a means for changing the diameter.

[0021]

[0022] The manufacturing method for a hollow curved part according to each of the above aspects not only enables weight reduction to meet various design needs, but also ensures the flatness of the product. This makes it possible to ensure the strength and rigidity required for the design. Furthermore, because wrinkles are suppressed, early buckling or breaking of the product when a load is applied is less likely to occur, improving product reliability. Therefore, each of the above aspects can provide a manufacturing method for a hollow curved part that suppresses wrinkles and ensures the strength and rigidity of the product. Furthermore, a manufacturing device for a hollow curved part that implements the manufacturing method can also be provided.

[0023] 1 is a longitudinal sectional view schematically showing an apparatus for manufacturing a hollow curved part according to an embodiment of the present invention; FIG. 2 is a view for explaining a method for manufacturing a hollow curved part using the same manufacturing apparatus, and is a partially enlarged view of part X1 in FIG. 1; FIG. 3 is a view showing a hollow curved part manufactured by a conventional manufacturing method using a conventional manufacturing apparatus, and is a partially enlarged view corresponding to FIG. 2; FIG. 4 is a cross-sectional view of the hollow curved part of FIG. 3 taken along line X-X in FIG. 3; FIG. 5 is an explanatory view showing a schematic configuration of a bending apparatus disclosed in Patent Document 1; and FIG. 6 is an explanatory view showing a schematic configuration of a shear bending apparatus disclosed in Patent Document 2.

[0024] A method for manufacturing a hollow curved part according to one embodiment of the present invention and a manufacturing apparatus for the hollow curved part suitable for use in the manufacturing method will be described below with reference to the drawings. The following description will be given by way of example of a case in which the hollow curved part to be manufactured is a hollow square tube made of steel and having a rectangular cross-sectional shape (hereinafter referred to as the hollow material Pm), and a product such as a strength part, reinforcing part, or structural part (hereinafter referred to as the hollow curved part Pp) used in automobiles and various machines is manufactured. First, a manufacturing apparatus for the hollow curved part to which the manufacturing method is applied (hereinafter referred to as the manufacturing apparatus 10) will be described, followed by a description of the manufacturing method.

[0025] [Hollow Bent Part Manufacturing Apparatus] FIG. 1 is an explanatory diagram schematically illustrating a hollow bent part manufacturing apparatus 10 according to the present embodiment. This manufacturing apparatus 10 shears and bends a hollow material Pm to obtain a hollow bent part Pp. The hollow material Pm is a long, rectangular tube having a closed cross-sectional shape perpendicular to its longitudinal direction. The object to be processed in this embodiment is not limited to a rectangular tube, but can also be other steel tubes having, for example, circular, elliptical, or various irregular cross-sectional shapes. Furthermore, the hollow material Pm having a rectangular cross-section can have either a square or rectangular cross-sectional shape. Furthermore, metal tubes other than steel tubes can also be used as the hollow material Pm.

[0026] As shown in FIG. 1 , this manufacturing apparatus 10 includes a feed device 9, a support device 11, a heating device (heating means) 12, a cooling device (cooling means) 13, a shear force applying device (shear force applying section) 14, a control device (control section) 15, and a wrinkle detection means (deformation amount detection means) 50.

[0027] (1) Feeding Device 9 As shown by the arrow F in FIG. 1, the feeding device 9 feeds the hollow material Pm along its longitudinal direction at a predetermined material feeding speed V ０ The feed device 9 is exemplified by a type using an electric servo cylinder, but is not limited to a specific type, and any known type such as a type using a ball screw, a type using a timing belt or a chain, etc. can be used.

[0028] As will be described in more detail later, when the feed device 9 receives an instruction from the control device 15, it can reduce the feed speed as necessary, thereby applying a tensile force to the shear bending portion SB.

[0029] (2) Support Device 11 The hollow material Pm is supported by the support device 11 at the first position A. That is, the support device 11 supports the hollow material Pm, which is fed in its axial direction by the feed device 9, at the first position A.

[0030] In this embodiment, a block is used as the support device 11. The block has a through hole 11a through which the hollow material Pm can be inserted with a gap. Although not shown, the block may be divided into multiple sections, and hydraulic or air cylinders may be connected to clamp and support the hollow material Pm. Furthermore, the support device 11 is not limited to a specific type, and any known support device of this type can be used. For example, as another configuration, one or more pairs of grooved rolls arranged opposite each other can be used side by side. The support device 11 is fixedly disposed on a mounting table (not shown). However, this configuration is not limited to this, and the support device 11 may also be supported by an end effector (not shown) of an industrial robot. After passing through the first position A where the support device 11 is installed, the hollow material Pm is further fed in the direction of arrow F.

[0031] (3) Heating Device 12 The heating device 12 is disposed at a second position B downstream of the first position A along the feed direction of the hollow material Pm. The heating device 12 heats the entire circumference of the cross section of a portion of the hollow material Pm in the longitudinal direction, which is fed from the supporting device 11. An induction heating device is used as the heating device 12. This induction heating device may be any known device as long as it has a coil that can heat the hollow material Pm, for example, by high-frequency induction. The heating coil 12a of the heating device 12 is disposed a predetermined distance from the outer surface of the hollow material Pm, so as to surround the entire circumference of the cross section of the hollow material Pm in the longitudinal direction. The hollow material Pm is then rapidly heated in part by the heating device 12.

[0032] The installation means (not shown) of the heating device 12 can position the heating coil 12a at the second position B so that the inclination angle can be adjusted. That is, the installation means of the heating device 12 can tilt the heating coil 12a at a set angle relative to the feed direction of the hollow material Pm. In the example of FIG. 1 , the heating coil 12a is tilted so that it intersects with the longitudinal direction of the hollow material Pm (the feed direction of the hollow material Pm, indicated by arrow F) at an inclination angle α in a side view. More specifically, as shown in FIG. 1 , when viewed from a cross section including the center line of the heating coil 12a, a line L1 is defined as connecting the widthwise center position of the cross section above the heating coil 12a to the widthwise center position of the cross section below the heating coil 12a. The central axis of the hollow material Pm before reaching the heating coil 12a is defined as a line L2. In this case, if the angle between the lines L1 and L2 is defined as the inclination angle α, the heating coil 12a can be tilted by setting this inclination angle α to an acute angle less than 90°.

[0033] The installation means for the heating device 12 may be, for example, an end effector of a well-known industrial robot, but any known means may be used as long as it is capable of adjusting the tilt angle α as specified. The adjustment of the tilt angle α by the installation means for the heating device 12 may be automatically controlled by the installation means receiving a control signal from the control device 15. In this case, one possible example is to store in advance in the control device 15 the relationship between the position in the longitudinal direction of the hollow material Pm where shear bending is performed and the tilt angle α to be set at that position, and to control the tilt angle α of the heating coil 12a to form the predetermined angle when the feed amount of the hollow material Pm reaches a predetermined feed amount.

[0034] Although not shown, one or more preheating devices (for example, small high-frequency heating devices) capable of preheating the hollow material Pm can be disposed upstream of the heating device 12 along the feeding direction of the hollow material Pm, and the hollow material Pm can be heated using this preheating means in combination with the heating device 12. In this case, it becomes possible to heat the hollow material Pm multiple times.

[0035] (4) Cooling Device 13 The cooling device 13 is disposed at a third position C that is downstream of the second position B along the feeding direction of the hollow material Pm. The cooling device 13 rapidly cools the portion of the hollow material Pm that was heated at the second position B. By being cooled by the cooling device 13, the portion of the hollow material Pm between the first portion heated by the heating device 12 and the second portion cooled by the cooling device 13 reaches a high temperature and a state in which deformation resistance is significantly reduced.

[0036] The cooling device 13 is not limited to a specific type of cooling device as long as it can achieve the desired cooling rate. Generally, it is desirable to use a water-cooling device that cools the hollow material Pm by spraying cooling water toward a predetermined position on the outer circumferential surface of the hollow material Pm. In this embodiment, multiple cooling water injection nozzles 13a are arranged immediately downstream of the heating device 12, spaced apart from the outer surface of the hollow material Pm so as to surround a portion of the cross section of the hollow material Pm in the longitudinal direction. The cooling water from these cooling water injection nozzles 13a is then sprayed toward the outer surface of the hollow material Pm. It is desirable to spray the cooling water obliquely toward the direction in which the hollow material Pm is fed out, so as not to impede the heating of the hollow material Pm by the heating device 12. Furthermore, by changing the distance between each cooling water injection nozzle 13a and the hollow material Pm in a cross section perpendicular to the axial direction of the hollow material Pm, the axial region of the hollow material Pm that is cooled can be adjusted.

[0037] The portion of the hollow material Pm heated by the heating device 12 is rapidly cooled by the cooling device 13. By appropriately adjusting the starting temperature and cooling rate of water cooling by the cooling device 13, it is possible to quench or anneal part or all of the rapidly cooled part of the hollow material Pm. This makes it possible to significantly increase the strength of part or all of the shear bending part of the hollow material Pm, for example, to 1500 MPa or more.

[0038] The installation means for the cooling device 13 is not limited to any specific installation means as long as it can position the cooling device 13 at the third position C. However, in order to manufacture hollow curved parts Pp with high dimensional accuracy using the manufacturing apparatus 10 of this embodiment, it is desirable to set the distance between the second position B and the third position C as short as possible, thereby minimizing the area between the first portion heated by the heating device 12 and the second portion cooled by the cooling device 13. To achieve this, it is desirable to position the cooling water injection nozzle 13a close to the heating coil 12a. Therefore, it is desirable to position the cooling water injection nozzle 13a immediately behind the heating coil 12a. Furthermore, the cooling device 13 may be fixed to the installation means for the heating device 12. In this case, it is possible to tilt both the cooling water injection nozzles 13a and the heating coil 12a at the same tilt angle α while maintaining the relative positional relationship between the cooling water injection nozzles 13a and the heating coil 12a.

[0039] However, this configuration is not limiting, and an installation means for the cooling device 13 may be provided separately from the installation means for the heating device 12. The installation means (not shown) for the cooling device 13 can position each cooling water injection nozzle 13a at the third position C so that the inclination angle can be adjusted freely. That is, the installation means for the cooling device 13 can tilt the cooling device 13 at a set angle with respect to the feed direction of the hollow material Pm. For example, as shown in FIG. 1 , each cooling water injection nozzle 13a can be tilted so that it intersects with the longitudinal direction of the hollow material Pm (the feed direction of the hollow material Pm, indicated by arrow F) at an inclination angle α in a side view. Furthermore, by synchronizing the inclination angle of each cooling water injection nozzle 13a with the inclination angle of the heating coil 12a and keeping it always the same, the cooling water injection nozzles 13a can be positioned adjacent to each other without interfering with the heating coil 12a.

[0040] In this case, the installation means for the cooling device 13 may be, for example, an end effector of a well-known industrial robot, but any known means may be used as long as it can adjust the tilt angle α as specified. The adjustment of the tilt angle α by the installation means for the cooling device 13 may be automatically controlled by receiving a control signal from the control device 15. In this case, one example is to refer to the control signal sent from the control device 15 to the installation means of the heating device 12, and control it so that the two devices can be tilted synchronously at the same tilt angle α.

[0041] (5) Shearing Force Applicator 14 The shearing force applicator 14 is disposed at a fourth position D downstream of the third position C along the feed direction of the hollow material Pm. The shearing force applicator 14 moves in two or three dimensions while positioning the hollow material Pm. In this way, the shearing force applicator 14 applies shear force to a region of the hollow material Pm between the first portion heated by the heating device 12 and the second portion cooled by the cooling device 13, thereby shear bending the hollow material Pm.

[0042] In the example shown in Figure 1, the shear force applying device 14 includes a pair of upper and lower gripping means 14a, 14b. These gripping means 14a, 14b contact the outer or inner surface of the hollow material Pm to determine the support position of the hollow material Pm and move that position. By adjusting this support position, the shear angle θ shown in Figure 1 can be adjusted. This shear angle θ is the angle between the feed direction of the hollow material Pm (more specifically, the direction along line L2) on an imaginary plane including the above-mentioned lines L1 and L2, and the outer surface of the hollow material Pm after it has passed through the cooling device 13.

[0043] The pair of upper and lower gripping means 14a, 14b are held by a moving mechanism (also not shown) that holds them so that they can move freely in two or three dimensional directions.

[0044] A cross section of the hollow material Pm in a longitudinal direction is heated by the heating device 12, significantly reducing its deformation resistance. Therefore, by three-dimensionally moving the positions of the pair of upper and lower gripping devices 14a, 14b at a fourth position D, which is downstream of the third position C along the feed direction of the hollow material Pm, as shown in FIG. 1 , a shear force Ws can be applied to the region of the hollow material Pm between the first portion heated by the heating device 12 and the second portion cooled by the cooling device 13. The shear force Ws acting on the hollow material Pm forms a shear-bent portion. In this embodiment, a shear force is applied to the heated portion of the hollow material Pm, rather than a bending moment, as in the invention disclosed in Patent Document 1. Therefore, a hollow bent part Pp can be manufactured having a shear-bent portion with an extremely small bending radius, such as 0.2 to 2 times the width W (product width), which is the distance between the inner and outer contour curves of the shear-bent portion. The manufacturing method using the manufacturing apparatus 10 of this embodiment can widen the range of possible bending radii by appropriately setting the combination of the shear angle θ and the tilt angle α. Therefore, it is possible to process a large bending radius exceeding twice the bending radius. On the other hand, even when a small bending radius is required for product design reasons, it is possible to obtain an extremely small bending radius of 0.2 to 2 times, which was difficult with conventional technology.

[0045] The shear force applying device 14 may be installed via a mechanism that can freely position the pair of upper and lower gripping means 14a, 14b in two or three dimensions as described above. Such a mechanism is not particularly limited. For example, the gripping means 14a, 14b may be held by an end effector of a well-known industrial robot. For example, a moving device combining a linear guide and a servo motor (not shown) may also be used. As will be described in detail later, the shear force applying device 14 applies a tensile force to the shear-bent portion to be machined in the hollow material Pm when instructed by the control device 15. The direction of this tensile force is a direction intersecting the straight line L1 that forms the inclination angle α, preferably a direction perpendicular (intersecting at 90°).

[0046] (6) Control Device 15 The control device 15 controls all operations of the feeding device 9, the supporting device 11, the heating device 12, the cooling device 13, the shearing force applying device 14, and the wrinkle detecting means 50. In particular, the control device 15 of this embodiment is characterized in that it determines whether the flatness (wrinkle height) required for the shearing bent portion exceeds a limit value based on the measurement information from the wrinkle detecting means 50, and based on the determination result, it can perform at least one of (a) reducing the feeding speed by the feeding device 9 and (b) increasing the pulling speed by the shearing force applying device 14. Specific control contents will be described in detail in the explanation of the manufacturing method.

[0047] (7) Wrinkle Detection Means 50 The wrinkle detection means 50 is installed downstream of the cooling device 13 and measures the height of wrinkles that occur in the shear bent portion. A known non-contact displacement meter can be used as the wrinkle detection means 50. Alternatively, a sample of the hollow bent part Pp can be manufactured and the wrinkle height in the shear bent portion can be determined using a contact or non-contact displacement meter, thereby obtaining data in advance on how to apply the tensile force required to correct the wrinkle height. In this case, the wrinkle height of the sample can be measured using a contact or non-contact displacement meter, and then the wrinkle height of the shear bent portion of the hollow material Pm can be measured using a non-contact displacement meter during actual manufacturing. In this case, a CCD camera or the like can be used as the non-contact displacement meter, and the wrinkle height can be calculated by processing the captured image. Furthermore, the wrinkle height thus determined may be sent from the wrinkle detection means 50 to the control device 15, and may be used as feedback data when the control device 15 controls the feed device 9 and the shear force applying device 14 to correct the wrinkles. In this case, feedback control can be performed such that a higher tensile force is applied when the wrinkle height is high, and a lower tensile force is applied when the wrinkle height is low.

[0048] [Method for manufacturing hollow curved part] Next, a method for manufacturing a hollow curved part according to this embodiment will be described below. As described above, in this manufacturing method, at least one of reducing the feed speed by the feed device 9 and increasing the pulling speed by the shear force applying device 14 is performed based on the measurement information from the wrinkle detection means 50.

[0049] That is, when the limit value of the flatness (wrinkle height) required for the product is exceeded, the material feed speed V ０ and the axial speed V ｘ and vertical velocity V ｙ and change one or both of the axial velocity V ｘ and vertical velocity V ｙ are the moving speed components when the shearing force applying device 14 moves the gripping portion of the hollow material Pm. That is, referring to FIG. 1, the axial speed V ｘ is a velocity component parallel to the straight line L2, which is the central axis of the hollow material Pm. ｙ is the axial velocity V in the imaginary plane including the straight lines L1 and L2. ｘ These axial velocities V ｘ and vertical velocity V ｙ The combined speed is the speed Vn shown in Fig. 2. As shown in Fig. 2, this speed Vn is the pulling speed in a direction intersecting the line L1 which indicates the inclination angle α of the heating device 12 and the cooling device 13. The direction of the speed Vn is preferably close to a direction perpendicular (90°) to the line L1, and most preferably perpendicular (90°).

[0050] Here, we will explain wrinkles that occur in the shear-bent portion of the hollow bent part Pp. First, as described above, the processing in this embodiment is shear bending, not ordinary bending. Therefore, the wrinkles formed in this embodiment differ in their location and mechanism from those formed in ordinary bending. This will be explained using FIGS. 3 and 4 . FIG. 3 is a partial enlargement corresponding to FIG. 2 , showing a hollow bent part subjected to conventional shear bending using a conventional manufacturing apparatus. FIG. 4 is a cross-sectional view of the hollow bent part of FIG. 3 taken along line X-X in FIG. 3 . In the case of shear bending, which is the subject of this embodiment, if the processing conditions are inappropriate, as shown in FIGS. 3 and 4 , concave wrinkles w will occur on a pair of outer surfaces s3 and s4 connecting the both side edges of the bent inner surface s1 and the bent outer surface s2 of the shear bent portion SB. These wrinkles w occur due to compressive forces acting on the outer surfaces s3 and s4 during shear bending, as indicated by the small arrows in FIG. 3 . On the other hand, almost no wrinkles will occur on the bent inner surface s1 and the bent outer surface s2. In contrast, in the case of normal bending, wrinkles occur on the bent inner peripheral surface s1, as indicated by the thick line in Figures 3 and 4. These wrinkles occur as a result of a compressive force acting on the bent inner peripheral surface s1 during normal bending. On the other hand, no wrinkles occur on the bent outer peripheral surface s2 because a tensile force acts on the bent outer peripheral surface s2. As explained above, the positions at which wrinkles occur differ between normal bending and shear bending, and this embodiment is intended to suppress wrinkles w that occur on the pair of outer surfaces s3 and s4 during shear bending.

[0051] The control device 15 performs the above-described control, thereby making it possible to suppress the occurrence of wrinkles w and ensure the flatness of the product. To explain this more specifically, according to the manufacturing method of this embodiment, the axial speed V on the outlet side is adjusted so that (1) the angle (shear angle θ) between the feed direction of the hollow material Pm as the raw material and the traveling direction of the hollow curved part Pp as the product, and (2) the angle (inclination angle α which is the inclination of the heating coil 12a) between the feed direction of the hollow material Pm as the raw material and the heating device 12 satisfy the following formulas 1 to 3: ｘ and the vertical velocity V ｙ and material feed speed V ０By selecting the combination of the above, it is possible to suppress the occurrence of wrinkles in the hollow bent part Pp after the shear bending process and ensure the flatness of the product.

[0052]

[0053] The shear angle formed after the shear force is applied to the hollow material Pm in the feed direction is θ (degrees), the inclination angle of the heating device 12 and the cooling device 13 in the feed direction is α (degrees), and the material feed speed is V ０ and the axial speed on the outlet side is V ｘ and the vertical velocity at the exit V ｙ When V ｘ and V ｙ The relationship between V and V is expressed as the following equation 4. ０ and V ｘ and V ｙ All units are mm / min.

[0054]

[0055] On the other hand, the inventors have found that even under processing conditions that may cause wrinkles w, wrinkles w can be reduced by applying elongation strain in the direction perpendicular to the heated processed region. As a result of repeated experiments, they have found that satisfying the following formula 5 is effective in suppressing the occurrence of wrinkles w.

[0056]

[0057] Therefore, the above equation can be expressed as follows:

[0058]

[0059] The value of k varies depending on the dimensions of the hollow material Pm, particularly the plate thickness, but the inventors have concluded through repeated experiments that a good product can be obtained when k ≥ 1.02, preferably k ≥ 1.10. On the other hand, although there is no particular restriction on the upper limit of the k value, considering the design strength of general products, it is desirable for k to be 4.00 or less.

[0060] An example of a manufacturing method using the manufacturing apparatus 10 will be described. The wrinkle detection means 50 installed downstream of the cooling device 13 measures the height of wrinkles on the hollow bent part Pp, which is the finished product after processing. If the wrinkles exceed a preset limit value, the material feed speed V ０ is not changed, and the axial speed V on the outlet side is set while satisfying the following formula 7. ｘ , vertical velocity V ｙ After that, when the wrinkles to be detected reach the allowable value, V ｘ , V ｙ Stop the increase and keep each at a constant speed.

[0061]

[0062] Or, the axial speed V on the outlet side ｘ , vertical velocity V ｙ Without changing the material feed speed V ０ After that, if the wrinkles that occur become within the allowable value, reduce the material feed speed V ０ Stop the decrease in the material feed speed V and keep it constant. ０ and the material feed rate V ０ The vertical velocity V on the outlet side is calculated using the following equations 8 and 9. ｙ and the axial velocity V ｘ After that, if the wrinkles that occur become within the allowable value, increase the material feed speed V ０ The decrease in speed is stopped and the speed is kept constant.

[0063]

[0064] Alternatively, the axial velocity V on the outlet side while satisfying the following formula 10: ｘ , vertical velocity V ｙ Increase the vertical velocity V ｙ On the other hand, the material feed speed V calculated from the following equation 11 ０ After that, when the wrinkles that occur reach the allowable value, V ０ is held constant.

[0065] By carrying out each of the processes described above, it is possible to produce a hollow curved part Pp with reduced wrinkles and good flatness.

[0066] In addition, when mass-producing a product, the material feed rate V ０ , axial velocity at the outlet V ｘ , vertical velocity V ｙ A prototype is made within the range where the following formulas 12 to 14 are satisfied, and the wrinkle height is measured to confirm that it is within the limit height of the wrinkle. Then, for actual mass production, the material feed speed V that was confirmed as a good condition in the preliminary prototype is used. ０ , axial velocity at the outlet V ｘ , vertical velocity V ｙ Compared to the manufacturing apparatus of the present invention, it is more complicated to have to carry out a trial production in advance, but if mass production is assumed, it is also effective to use the conventional apparatus.

[0067]

[0068] The gist of the present embodiment described above is summarized below. (1) As shown in Figures 1 and 2, one aspect of the present invention is a method for manufacturing a hollow bent part Pp, which includes supporting a long, metallic hollow material Pm at a first position A while feeding it in a feed direction along its longitudinal direction, partially heating the hollow material Pm at a heated portion using a heating device 12 arranged at a second position B downstream of the first position A along the feed direction, cooling the hollow material Pm using a cooling device 13 arranged at a third position C downstream of the second position B along the feed direction, and supporting the hollow material Pm at a fourth position D downstream of the third position C along the feed direction, and moving the support position in two or three dimensions to apply a shear force to the heated portion of the hollow material Pm to form a shear bent portion SB, and simultaneously with the formation of the shear bent portion SB, a tensile force is applied to the shear bent portion SB in a direction of a velocity Vn that intersects with the inclination of the heating coil 12a of the heating device 12 and the cooling water injection nozzle 13a of the cooling device 13.

[0069] (2) In the above aspect (1), the material feed speed V of the hollow material Pm at the first position A ０and the moving speed V of the support position at the fourth position D ｘ , V ｙ The pulling force may be generated by at least one of increasing the speed of the pull rod.

[0070] (3) In the above aspect (1) or (2), the following may be done: when the shear bent portion is formed, the out-of-plane deformation amount of the shear bent portion is measured, and the tensile force is increased or decreased according to the out-of-plane deformation amount.

[0071] (4) Another aspect of the present invention is a manufacturing apparatus 10 for a hollow bent part, comprising: a feeding device 9 that supports a metallic hollow material Pm at a first position A along a feeding direction, which is the longitudinal direction of the hollow material Pm, while feeding the material; a heating coil 12a that partially heats the hollow material Pm at a heated portion at a second position B downstream of the first position A; a cooling device 13 that cools the hollow material Pm by injecting a cooling medium at a third position C downstream of the second position B; a shear force applying device 14 that grips the hollow material Pm at a fourth position D downstream of the third position C and moves the gripping position in two or three dimensions to apply a shear force to the heated portion of the hollow material Pm, thereby forming a shear bent portion; and a control device 15 that controls the feeding device 9, the heating coil 12a, the cooling device 13, and the shear force applying device 14, The control device 15 controls at least one of the feeding device 9 and the shear force applying device 14, so that a tensile force is applied to the shear bending portion SB in a direction intersecting the inclination of the heating coil 12a of the heating device 12 and the cooling water injection nozzle 13a of the cooling device 13 at the same time as the shear bending portion SB is formed.

[0072] (5) In the above aspect (4), the control device 15 controls the material feed speed V of the hollow material Pm by the feed device 9. ０ and the speed V of movement of the support position by the shear force applying device 14 ｘ , V ｙ The pulling force may be generated by performing at least one of the speed increases of the pulley.

[0073] (6) In the above-mentioned aspect (4) or (5), the following configuration may be adopted: the device may further include a wrinkle detection means (50) for measuring the out-of-plane deformation of the shear bending portion, and the control device (15) may increase or decrease the tensile force according to the measured out-of-plane deformation.

[0074] The effects of the present invention will be explained below based on each example. In each example, the outer surfaces s3 and s4 shown in FIG. 4 may be referred to as the "product surface." The hollow material Pm used in the manufacturing process was made of 0.2% carbon steel, had a cross-sectional height H of 20 mm, a cross-sectional width W of 20 mm, and a total length of 1000 mm. The heating temperature of the heated portion by the heating coil 12a was set to 950°C, and 100 pieces of each case were manufactured. Wrinkles on the product surface were measured, and the quality of the product was judged.

[0075] [Example 1] The results of manufacturing hollow bending members using a conventional manufacturing device with θ = 60° and α = 60° are shown in Table 1 below. The wrinkle height on the product surface was measured for each, and products with a wrinkle height of 0.2 mm or less were judged to be good. Material feed speed V ０ = 10 mm / min, and the axial speed on the outlet side V ｘ , vertical velocity V ｙ was calculated and set using the following formulas 15 and 16. The case where k = 1.00 is the conventional example, and the results of the inventive example are also shown. As k increases, the yield rate increases, and good results are obtained when k ≥ 1.02. In particular, a significantly high yield rate is obtained when k ≥ 1.05.

[0076]

[0077]

[0078] [Example 2] The results of manufacturing hollow bending members using a conventional manufacturing device with θ = 60° and α = 60° are shown in Table 2 below. Wrinkles on the product surfaces were measured, and products with wrinkle heights of 0.2 mm or less were judged to be good. The axial speed V on the delivery side ｘ , vertical velocity V ｙ are constant, and the material feed speed V ０was calculated and set using the following formulas 17 and 18. The case where k = 1.00 is the conventional example, and the results of the inventive example are also shown. As k increases, the yield rate increases, and good results are obtained when k ≥ 1.02. In particular, a significantly high yield rate is obtained when k ≥ 1.05.

[0079]

[0080]

[0081] [Example 3] The results of manufacturing hollow bending members using a conventional manufacturing device with θ = 60° and α = 60° are shown in Table 3 below. Wrinkles on the product surfaces were measured, and products with wrinkle heights of 0.2 mm or less were judged to be good. Material feed speed V ０ , axial velocity at the outlet V ｘ , vertical velocity V ｙ was calculated and set using the following formulas 19 and 20. The case where k = 1.00 is the conventional example, and the results of the inventive example are also shown. As k increases, the yield rate increases, and good results are obtained when k ≥ 1.02. In particular, a significantly high yield rate is obtained when k ≥ 1.05.

[0082]

[0083]

[0084] [Example 4] The results of manufacturing hollow bending members using a conventional manufacturing device with θ = 45° and α = 45° are shown in Table 4 below. Wrinkles on the product surfaces were measured, and products with wrinkle heights of 0.3 mm or less were judged to be good. Material feed speed V ０ = 10 mm / min, and the axial speed on the outlet side V ｘ , vertical velocity V ｙ was calculated and set using the following formulas 21 and 22. Note that the case where k = 1.00 is the conventional example, and the results of the inventive example are also shown. As k increases, the yield rate increases, and good results are obtained when k ≥ 1.02. In particular, a significantly high yield rate is obtained when k ≥ 1.05.

[0085]

[0086]

[0087] [Example 5] Table 5 below shows the results of manufacturing a hollow bending member using the manufacturing apparatus of the present invention with θ = 60° and α = 60°. Note that the case where k = 1.00 is the conventional example, and the results are listed alongside those of the inventive example. Wrinkles on the product surface were measured, and products with wrinkle heights of 0.2 mm or less were judged to be good. It was confirmed that a significantly high yield rate was achieved with the manufacturing apparatus of the present invention.

[0088]

[0089] According to the above aspects of the present invention, it is possible to provide a method for manufacturing a hollow curved part that suppresses the occurrence of wrinkles and ensures the strength and rigidity of the product. It is also possible to provide a manufacturing device for a hollow curved part that realizes the manufacturing method. Therefore, the present invention has great industrial applicability.

[0090] 9 Feeding device (feeding mechanism) 10 Manufacturing device 12 Heating device (heating means) 13 Cooling device (cooling means) 14 Shearing force applying device (shearing force applying section) 15 Control device (control section) 50 Wrinkle detecting means (deformation amount detecting means) A First position B Second position C Third position D Fourth position Pm Hollow material Pp Hollow bent part SB Shear bending section V ０ Feed rate α Inclination angle θ Shear angle

Claims

1. A method for manufacturing a hollow bent part, comprising: supporting a long, hollow metal material at a first position while feeding it in a feed direction along its length; partially heating the hollow material at a heated portion using heating means arranged at a second position downstream of the first position along the feed direction; cooling the hollow material using cooling means arranged at a third position downstream of the second position along the feed direction; and supporting the hollow material at a fourth position downstream of the third position along the feed direction, and moving the support position in two or three dimensions to apply a shear force to the heated portion of the hollow material, thereby forming a shear bent portion, wherein simultaneously with forming the shear bent portion, a tensile force is applied to the shear bent portion in a direction perpendicular to the inclination of the heating means and cooling means.

2. The method for manufacturing a hollow curved part according to claim 1, characterized in that the pulling force is generated by at least one of slowing down the feed speed of the hollow material at the first position and increasing the movement speed of the support position at the fourth position.

3. A method for manufacturing a hollow bent part according to claim 1 or 2, characterized in that, when forming the shear bent portion, the amount of out-of-plane deformation of the shear bent portion is measured, and the tensile force is increased or decreased according to the amount of out-of-plane deformation.

4. A hollow bent part manufacturing device comprising: a feeding mechanism that supports a metal hollow material at a first position and feeds it along its longitudinal direction, that is, a feeding direction; a heating means that partially heats the hollow material in a heated portion at a second position downstream of the first position; a cooling means that cools the hollow material by injecting a cooling medium at a third position downstream of the second position; a bending force applying unit that supports the hollow material at a fourth position downstream of the third position and moves the support position in two or three dimensions to apply a shear force to the heated portion of the hollow material to form a shear bent portion; and a control unit that controls the feeding mechanism, the heating means, the cooling means, and the bending force applying unit, wherein the control unit controls at least one of the feeding mechanism and the bending force applying unit to apply a tensile force to the shear bent portion in a direction that intersects with the inclination of the heating means and the cooling means simultaneously with forming the shear bent portion.

5. The hollow bending part manufacturing device according to claim 4, characterized in that the control unit generates the tensile force by performing at least one of slowing down the feed speed of the hollow material by the feed mechanism and increasing the movement speed of the support position by the bending force applying unit.

6. A manufacturing device for a hollow bent part as described in claim 4 or 5, further comprising a deformation amount detection means for measuring the out-of-plane deformation amount of the shear bent portion, and the control unit increases or decreases the tensile force according to the measured out-of-plane deformation amount.

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