Method and apparatus for manufacturing hollow bent part, and hollow bent part

Abstract

To provide a method and an apparatus for manufacturing a hollow bent part having a small bending radius and an acute apex angle of a bent part. Another object of the present invention is to provide a hollow bent part manufactured by the method and apparatus for manufacturing a hollow bent part.SOLUTION: In the method and apparatus for manufacturing a bent hollow component, the hollow blank Pm is supported at the first position A while being fed in the feed direction along the longitudinal direction of the hollow blank Pm, the hollow blank Pm is partially heated at the heated portion at the second position B, the hollow blank Pm is cooled at the third position C, and the hollow blank Pm is held at the holding position after passing the third position C and moved in the two-dimension direction or the three dimensional direction to apply a shear force to the heated portion to form the shear-bent portion SB. In the step of forming the shear bending portion SB, the shear angle θ of the shear bending portion SB is set to be more than 90 ° and less than 180 ° by moving the holding position including the moving speed component Vx in the direction opposite to the feeding direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a hollow curved part having a shear bent portion, an apparatus for manufacturing a hollow curved part, and a hollow curved part manufactured by these methods. [Background technology]

[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 manufacturing 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 faces challenges such as the development of raw materials and increasing the degree of freedom in the shapes that can be formed, and further development is required in the future.

[0004] In view of this situation, the present inventors have previously disclosed an invention relating to a bending apparatus in Patent Document 1. Fig. 5 is an explanatory diagram that schematically shows the outline of this bending apparatus 100. 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 the axial direction thereof 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 to a temperature range where partial quenching is possible by a high-frequency heating coil 102, and the hollow material Pm is rapidly cooled by a water cooling device 103 disposed downstream of the high-frequency heating coil 102. Then, 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 apparatus 100 makes it possible to manufacture a high-strength hollow bent part Pp with high work efficiency. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2006 / 093006 [Patent Document 2] International Publication No. 2011 / 024741 [Non-patent literature]

[0006] [Non-Patent Document 1] Automotive Technology Vol.57, No.6, 2003 pages 23-28 [Non-patent document 2] Tube Forming, Corona Publishing, 1st Edition, 3rd Printing, November 25, 2002, pp. 51-55 [Non-patent document 3] Plasticity and Processing,Volume 35,No.398,3-1994,Pages 341-346 Summary of the Invention [Problem to be solved by the invention]

[0007] There are various shapes of hollow bent parts used in automobiles, various machines, etc. Among them, there are many hollow bent parts with extremely small bends, for example, where the bending radius of the bent part is 1 to 2 times or less than the diameter of the metal pipe (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 bending radius that is, for example, 1 to 2 times the diameter of the metal pipe (the length of the side in the bending direction in the case of a rectangular cross section) or less, there is a risk that wrinkles or folds will occur on the inner periphery of the bend, or that the plate thickness on the outer periphery of the bend will be significantly reduced, resulting in breakage. For this reason, it has been difficult to manufacture hollow bent parts with small bends. Furthermore, in the cold bending of hollow bent parts, tensile stress acts on the outer periphery of the bent part, resulting in a reduction in plate thickness, as described in Non-Patent Document 2. Similarly, the method of Patent Document 1 is also a bending process, so a reduction in plate thickness on the outer periphery of the bent part is unavoidable.

[0008] In order to solve these problems, the present inventors have 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 supporting means 201, a heating means 202, a cooling means 203, and a gripping means 204. The first supporting means 201 supports a metal hollow material Pm at a first position A while relatively feeding the hollow material Pm in its longitudinal direction. The heating means 202 partially heats the hollow material Pm at a second position B downstream of the first position A along 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 downstream of the second position B along the feeding direction of the hollow material Pm. The gripping means 204 applies a shear force to the heated portion of the hollow material Pm by positioning the hollow material Pm at a fourth position D downstream of the third position C along the feeding direction of the hollow material Pm and moving it in two or three dimensions. Therefore, it is possible to apply shearing and heat treatment to the heated portion of the hollow material Pm using this shear bending apparatus 200. Furthermore, using this shear bending apparatus 200, it is possible to reliably mass-produce high-strength hollow bent parts at low cost, having bent portions with bending radii that are 1 to 2 times the diameter of the metal pipe (the length of the side in the bending direction in the case of a rectangular cross section), or smaller.

[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, making it possible to significantly reduce the weight of many mechanical parts, including automobiles. However, for example, automotive parts are installed in limited spaces, so it is important to increase the degree of freedom in design to avoid interference with other parts. Non-Patent Document 3 describes cold forming using shear deformation and a method for manufacturing hollow bent parts with small bending radii. Because the hollow bent parts obtained by this manufacturing method are cold-formed products, there is a limit to how much strength can be increased in terms of material ductility. Furthermore, there have been no reported examples of successful manufacturing of hollow bent parts with a bent section having an acute apex angle φ of less than 90°. Furthermore, there have been no reported examples of successful manufacturing of tubes with cross sections other than round ones using cold shear bending. Therefore, there was a demand for a product that was a high-strength hollow bent part having a bend with a bending radius that was 1 to 2 times the diameter of the metal pipe (the length of the side in the bending direction in the case of a rectangular cross section) or less, and in which the apex angle φ of the bend was an acute angle that was greater than 0° and less than 90°.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a method and an apparatus for manufacturing a hollow curved part having a small bending radius and an acute apex angle at the bent portion, as well as a hollow curved part manufactured by the method and apparatus. [Means for solving the problem]

[0011] In order to solve the above problems and achieve the above object, the present invention employs the following aspects. (1) One aspect of the present invention is A long hollow metal material is supported at a first position while being fed in a feed direction along its longitudinal direction, partially heating the hollow material in a heated portion at a second position downstream of the first position along the feeding direction; cooling the hollow blank at a third position downstream of the second position along the feeding direction; The hollow material is gripped at a gripping position after passing through the third position and moved in a two-dimensional or three-dimensional direction, thereby applying a shear force to the heated portion of the hollow material to form a shear-bent portion. A method for manufacturing a hollow curved part, comprising: In the step of forming the shear bent portion, The gripping position is moved with a movement speed component in the opposite direction to the feed direction, so that the shear angle of the shear bending portion is set to be greater than 90° and less than 180°.

[0012] (2) In the method for manufacturing a hollow curved part described in (1) above, The material feed rate V0 and the axial speed V are set to satisfy the following formulas 1 to 3. x and vertical velocity V yAt least one of the above may be controlled.

[0013]

number

[0014] where θ is the shear angle based on the feed direction, and V x is the axial velocity along the feed direction, and V y is the vertical speed perpendicular to the feed direction, α is the inclination angle of the heating coil arranged at the second position to heat the heated portion with respect to the feed direction, V0 is the material feed speed of the hollow blank along the feed direction, and k is a constant equal to or greater than 1.02.

[0015] (3) In the method for manufacturing a hollow curved part described in (2) above, the following method may be used: Measure the out-of-plane deformation of the shear bent portion; By relatively increasing the distance between the heated portion and the gripping position, a tensile force corresponding to the amount of out-of-plane deformation is applied to the shear bent portion.

[0016] (4) Another aspect of the present invention is a feeding mechanism that supports and feeds the metal hollow blank along a feeding direction, which is the longitudinal direction of the blank, at a first position; a heating coil that partially heats the hollow material at a heated portion 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; a bending force applying unit that grips the hollow material at a gripping position after passing the third position and moves it in a two-dimensional or three-dimensional direction to apply a shear force to the heated portion of the hollow material to form a shear-bent portion; a control unit that controls the feeding mechanism, the heating coil, the cooling device, and the bending force applying unit; A manufacturing apparatus for a hollow curved part, comprising: the bending force applying unit has a drive unit that moves the gripping position with a movement speed component including a movement speed component directed in a direction opposite to the feed direction, The control unit controls the drive unit to set the shear angle of the shear bending portion to more than 90° and less than 180°.

[0017] (5) In the manufacturing apparatus for a hollow curved part described in (4) above, the following may be performed: The control unit controls at least one of the feed mechanism and the drive unit so as to satisfy the following formulas 1 to 3.

[0018]

number

[0019] where θ is the shear angle based on the feed direction, and V x is the axial velocity along the feed direction, and V y is a vertical speed perpendicular to the feed direction, α is an inclination angle of the heating coil disposed at the second position and heating the heated portion with respect to the feed direction, V0 is a material feed speed of the hollow blank along the feed direction, and k is a constant equal to or greater than 1.02.

[0020] (6) In the manufacturing apparatus for a hollow curved part described in (5) above, the following may be performed: Further provided is a deformation amount detection means for measuring an out-of-plane deformation amount of the shear bending portion, The control unit controls the drive unit to increase the distance between the heated portion and the gripping position in accordance with the amount of out-of-plane deformation.

[0021] (7) Yet another aspect of the present invention is A one-piece part made of metal, hollow, and having a heat-treated bent portion, The bent portion has a bending radius that is equal to or less than twice the width, which is the dimension between the outer shape of the inner periphery of the bent portion and the outer shape of the outer periphery of the bent portion, and the apex angle φ of the bent portion satisfies the following formula 4.

[0022]

number

[0023] (8) The hollow bending part according to (7) above, It is made of steel, The amount of martensite in the bent portion may be 50% or more. [Effects of the Invention]

[0024] According to the above aspects, it is possible to provide a method and an apparatus for manufacturing a hollow curved part having a small bending radius and an acute apex angle of the bent portion, and also to provide a hollow curved part manufactured by the method and apparatus for manufacturing a hollow curved part. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a vertical cross-sectional view schematically showing a manufacturing apparatus for a hollow curved part according to an embodiment of the present invention. [Figure 2] 2 is a diagram for explaining a method for manufacturing a hollow curved part using the manufacturing apparatus, and is a partially enlarged view of a portion X1 in FIG. [Figure 3] 3 is a diagram for explaining a method for manufacturing a hollow curved part using the manufacturing apparatus, and is a partially enlarged view corresponding to FIG. 2. FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line XX in FIG. 3. [Figure 5] FIG. 1 is an explanatory diagram showing a schematic configuration of a bending device disclosed in Patent Document 1. [Figure 6] FIG. 1 is an explanatory diagram showing a schematic configuration of a shear bending apparatus disclosed in Patent Document 2. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, a manufacturing method and manufacturing apparatus for a hollow curved part according to one embodiment of the present invention, as well as a hollow curved part manufactured by the manufacturing method and manufacturing apparatus, will be described with reference to the drawings. In the following description, an example will be given of a hollow curved part manufactured by the present invention, which is a product (hereinafter, hollow curved part Pp) such as a strength part, reinforcing part, or structural part used in automobiles and various machines, using a hollow square tube made of steel and having a rectangular cross section (hereinafter, hollow material Pm). First, a manufacturing apparatus for hollow curved parts (hereinafter, manufacturing apparatus 10) to which this manufacturing method is applied will be described, followed by a description of this manufacturing method.

[0027] [Hollow bending part manufacturing equipment] FIG. 1 is an explanatory diagram that schematically shows a manufacturing apparatus 10 for a hollow curved part according to this 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 square tube having a cross section perpendicular to its longitudinal direction that is a closed hollow rectangle. Note that the object to be processed in this embodiment is not limited to square tubes, 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 be either a square or rectangular cross-sectional shape. Furthermore, metal tubes other than steel pipes may be used as the hollow material Pm.

[0028] As shown in FIG. 1, the manufacturing apparatus 10 includes a feeding device 9, a supporting device 11, a heating device 12, a cooling device 13, a shearing force applying device 14, a control device 15, and a wrinkle detecting means 50. (1) Feeder 9 As indicated by an arrow F in FIG. 1, the feeder 9 feeds the hollow material Pm along its longitudinal direction at a predetermined material feed speed V0. The feed device 9 is exemplified by a type that uses an electric servo cylinder, but is not limited to a specific type, and any known type can be used, such as a type that uses a ball screw, a type that uses a timing belt or a chain.

[0029] (2) Support device 11 The hollow material Pm is supported by the supporting device 11 at the first position A. That is, the supporting device 11 supports the hollow material Pm, which is fed by the feeding device 9 in its axial direction, at the first position A. 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 cylinders 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 may be used. For example, as another configuration, one or more sets of a pair of grooved rolls arranged opposite each other may be used side by side. The support device 11 is fixedly disposed on a mounting base (not shown), but is not limited to this configuration, and the support device 11 may be supported by an end effector (not shown) of an industrial robot. The hollow material Pm passes through a first position A where a supporting device 11 is installed, and is then fed further in the direction of arrow F.

[0030] (3) Heating device 12 The heating device 12 is disposed at a second position B downstream of the first position A along the feeding direction of the hollow material Pm. The heating device 12 heats the entire circumference of the cross section of a portion in the longitudinal direction of the hollow material Pm fed from the supporting device 11. An induction heating device is used as the heating device 12. This induction heating device may be any device having a coil that can heat the hollow material Pm, for example, by high-frequency induction heating, and any known device can be used. 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 periphery of the cross section of the hollow material Pm in a portion of the longitudinal direction. The hollow material Pm is then rapidly heated in part by the heating device 12.

[0031] 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. A line L2 is defined as the central axis of the hollow material Pm before it reaches the heating coil 12a. 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°. Since the outer surface of the hollow material Pm on the inside of the bend at the first position A is parallel to the straight line L2, the angle between the outer surface and the straight line L1 is shown as the inclination angle α in Figure 1 and Figure 2 described below.

[0032] The installation means for the heating device 12 can be, for example, an end effector of a well-known industrial robot. However, any known device can 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 heating device 12 may be automatically controlled by the installation means receiving a control signal from the control device 15. In this case, 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 can be stored in the control device 15 in advance, and the tilt angle α of the heating coil 12a can be controlled to a predetermined angle when the feed rate of the hollow material Pm reaches a predetermined feed rate. The tilt angle α is set to be smaller than the apex angle φ, which will be described later.

[0033] Although not shown, one or more preheating devices (for example, small high-frequency heating devices) that can preheat 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.

[0034] (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.

[0035] The cooling device 13 is not limited to a specific type of cooling device as long as it can obtain the desired cooling rate. In general, 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 peripheral surface of the hollow material Pm. In this embodiment, a large number of cooling water spray 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. Then, cooling water from these cooling water spray nozzles 13a is sprayed toward the outer surface of the hollow material Pm. It is desirable to spray the cooling water obliquely in the direction in which the hollow material Pm is fed out, in order not to impede the heating of the hollow material Pm by the heating device 12. Furthermore, by changing and setting 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, it is possible to adjust the axial region of the hollow material Pm that is cooled.

[0036] The portion of the hollow material Pm that has been heated by the heating device 12 is rapidly cooled 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 by appropriately adjusting the starting temperature and cooling rate of water cooling by the cooling device 13. 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.

[0037] 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 minimize the distance between the second position B and the third position C, 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.

[0038] 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 tilt 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 always keeping it the same, the cooling water injection nozzles 13a can be positioned adjacent to each other without interfering with the heating coil 12a.

[0039] 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 the installation means for the cooling device 13 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 for the heating device 12, and control it so that the two devices can be tilted synchronously at the same tilt angle α.

[0040] (5) Shear force applying device 14 The shear force applying device 14 includes a base (not shown), an arm (not shown) supported on the base, and gripping means 14a and 14b, which are chucks supported at the ends of the arms. The base is positioned at a fourth position D, which is downstream of a third position C in the feed direction of the hollow material Pm. The arm has an internal drive unit (motor) (not shown), and the operation of the drive unit is controlled by a control device 15 to move the positions of the gripping means 14a, 14b in two or three dimensions. When a command is received from the control device 15, the gripping means 14a, 14b sandwich and hold the hollow material Pm between them. Therefore, with the gripping means 14a, 14b gripping the hollow material Pm at their gripping positions, the arm can move the positions of the gripping means 14a, 14b to move the gripping positions of the hollow material Pm in two or three dimensions.

[0041] In this way, the shear force applying device 14 applies shear force to the region of the hollow material Pm between the first portion, which is the heated portion heated by the heating device 12, and the second portion, which is the cooled portion cooled by the cooling device 13, thereby shear bending the hollow material Pm. At this time, the shear angle θ shown in Fig. 1 can be adjusted by adjusting the gripping position. This shear angle θ is the angle between the feed direction of the hollow material Pm (more specifically, the direction along the straight line L2) on an imaginary plane including the above-mentioned straight lines L1 and L2, and the outer surface of the hollow material Pm on the outside of the bend after passing through the cooling device 13.

[0042] In the manufacturing apparatus for a hollow curved part of this embodiment, by setting the shear angle θ to be greater than 90° and less than 180°, it is possible to form a shear bent portion SB having an acute apex angle φ greater than 0° and less than 90°, as shown in Fig. 2. Specifically, the control device 15 controls the drive unit to move the gripping position of the hollow material Pm by the pair of gripping means 14a, 14b, including a movement speed component in the direction opposite to the feed direction indicated by arrow F. At this time, the shear angle with the feed direction along the straight line L2 as the reference (0°) is θ (degrees), and the axial speed along the feed direction is V x (mm / min), and the vertical speed perpendicular to the feed direction is V y(mm / min), the inclination angle of the heating coil 12a with respect to the feeding direction is α (degrees), the material feeding speed of the hollow material Pm along the feeding direction is V0 (mm / min), and a constant k is 1.02 or more. The control device 15 controls the driving unit so as to satisfy the following formulas 1 to 3. x As shown in the XY coordinates of FIGS. 1 and 2, the feed direction (mm / min) is a positive value, and the direction opposite to the feed direction is a negative value.

[0043]

number

[0044] In this way, the control device 15 controls the drive unit, and the gripping position by the gripping means 14a, 14b moves toward the right side of the paper in Fig. 1. On the other hand, since the feed direction is the left side of the paper in Fig. 1, when comparing the speed components parallel to the feed direction, the axial speed V x The direction of the speed (mm / min) and the direction of the feed direction are opposite to each other. As a result, as shown in Figure 1, the area including the shear bent portion SB of the hollow material Pm is deformed into an inverted Z shape in side view.

[0045] When this shear bending is performed, a cross section of a portion of the hollow material Pm in the longitudinal direction is heated by the heating device 12, and the deformation resistance is significantly reduced. Therefore, by moving the gripping positions of the gripping means 14a, 14b in three dimensions, it is possible to apply a shear force Ws 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, as shown in FIG. A shearing force Ws acts on the hollow material Pm, forming a shear-bent portion SB (sometimes simply referred to as a "bent portion"). In this embodiment, a shearing 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. This makes it possible to manufacture a hollow bent part Pp having a bent portion with an extremely small bending radius, such as 0.2 to 2 times the cross-sectional width wd (product width), which is the distance between the outer contour curve on the inner periphery and the outer contour curve on the outer periphery of the bent portion.

[0046] 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 the cross-sectional width wd, which was difficult to achieve with conventional technology.

[0047] In this embodiment, the gripping means 14a, 14b are held and moved by the arms, but other configurations may be used as long as the gripping means 14a, 14b can be moved freely in two or three dimensions. However, to be able to manufacture hollow curved parts with an acute apex angle φ, it is necessary to have a function for moving the gripping means 14a, 14b so that the movement speed includes a component of movement in the opposite direction to the feed direction.

[0048] (6) Control device 15 The control device 15 controls all operations of the feed device 9, support device 11, heating device 12, cooling device 13, shear force applying device 14, and wrinkle detection means 50. In particular, the control device 15 of this embodiment controls the drive unit to move the gripping position of the hollow material Pm by the shear force applying device 14 so as to include a moving speed component in the direction opposite to the feed direction, thereby making the shear angle θ of the shear bending portion SB greater than 90° and less than 180°. In addition, the control device 15 of this embodiment determines whether the flatness (wrinkle height, out-of-plane deformation amount) required for the shear bending portion SB exceeds a limit value based on the measurement information of the wrinkle detection means 50. Then, if it is determined that the flatness exceeds the limit value, the control device 15 adjusts the axial speed V x (mm / min), vertical velocity V y Another feature is that the distance between the heated part and the gripping position is increased relative to each other by controlling the material feed rate V0 (mm / min) and the material speed V1 (mm / min), thereby applying a tensile force to the shear bending part SB. The specific control content will be described in detail in the explanation of the manufacturing method.

[0049] (7) Wrinkle detection means 50 The wrinkle detection means 50 is installed downstream of the cooling device 13 and measures the height (flatness, out-of-plane deformation) of wrinkles occurring in the shear bent portion SB. Here, wrinkles occurring in the shear bent portion SB of the hollow curved part Pp will be explained first.

[0050] When designing a one-piece hollow bending part (Pp) as a mechanical part, a certain level of flatness may be required on the outer surface of the product to ensure the strength and rigidity required for the design. In other words, if wrinkles occur on the outer surface of the product, stress will concentrate at the wrinkled area when a load is applied, which can lead to early buckling or breaking of the product. Therefore, it is important to avoid wrinkles in the processed product. The processing targeted in this embodiment is shear bending, not ordinary bending. Therefore, the wrinkles that are to be suppressed during shear bending in this embodiment differ in their formation position and mechanism from those that occur during ordinary bending. This will be explained using FIGS. 3 and 4. FIG. 3 is a diagram illustrating a method for manufacturing a hollow curved part Pp using the manufacturing apparatus 10, and is a partially enlarged view corresponding to FIG. 2. FIG. 4 is a cross-sectional view of the shear bending portion SB taken along line XX in FIG. 3.

[0051] In the case of shear bending, which is the subject of this embodiment, if the processing conditions are not appropriate, concave wrinkles W will occur on a pair of outer surfaces s3 and s4 connecting both side edges of the bent inner surface s1 and the bent outer surface s2 of the shear bent portion SB, as shown in Figures 3 and 4. These wrinkles W are caused by compressive forces acting on the outer surfaces s3 and s4 during shear bending, as indicated by the small arrows in Figure 3. On the other hand, almost no wrinkles will occur on the bent inner surface s1 or the bent outer surface s2. In contrast, in the case of normal bending, wrinkles occur on the bent inner peripheral surface s1 shown 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 it. As explained above, the positions at which wrinkles occur differ between the shear bending process of this embodiment and the normal bending process, and this embodiment is directed to suppressing wrinkles occurring on the outer surfaces s3 and s4.

[0052] First, to detect wrinkles, the manufacturing apparatus 10 is equipped with a wrinkle detection means 50. For example, 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 at the shear bent portion SB can be determined using a contact or non-contact displacement meter. This allows the method of applying the tensile force required to correct the wrinkle height to be acquired in advance as data. 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 determined by processing and digitizing the captured image. Furthermore, the wrinkle height determined in this manner can be sent from the wrinkle detection means 50 to the control device 15 and 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 to increase the tensile force applied to the shear bending portion SB to suppress wrinkles when the wrinkle height is high, and decrease it when the wrinkle height is low.

[0053] [Manufacturing method for hollow bent parts] Next, a method for manufacturing the hollow curved part of this embodiment will be described below. As shown in Figure 1, in this manufacturing method, a long, hollow metal material Pm is supported at a first position A while being fed in a feed direction along its longitudinal direction, the hollow material Pm is partially heated in a heated portion at a second position B downstream of the first position A along the feed direction, the hollow material Pm is cooled at a third position C downstream of the second position B along the feed direction, and the hollow material Pm is gripped at a gripping position after passing through the third position C and moved in a two-dimensional or three-dimensional direction, thereby applying a shear force to the heated portion of the hollow material Pm and forming a shear bent portion SB.

[0054] In this manufacturing method, in the process of forming the shear bending portion SB, the gripping position of the hollow material Pm by the gripping means 14a, 14b is moved including a movement speed component in the direction opposite to the feed direction, so that the shear angle θ of the shear bending portion SB is greater than 90° and less than 180°. That is, in the process of forming the shear bending portion SB, the gripping position is moved including a moving speed component in the direction opposite to the feed direction so that the shear angle θ of the shear bending portion SB satisfies the following formulas 4 and 5. Here, θ is the shear angle (degrees) based on the feed direction, and V x is the axial speed along the feed direction (mm / min), and V y is the vertical speed (mm / min) perpendicular to the feed direction.

[0055]

number

[0056] In addition, in this manufacturing method, the axial speed on the outlet side V x and the vertical velocity V perpendicular to the axial direction of the outlet y and the material feed speed V0, the occurrence of wrinkles is suppressed and the flatness of the hollow curved part is ensured. That is, in the manufacturing method of this embodiment, the control device 15 controls the axial speed V on the outlet side so as to satisfy the following formula 6, which includes a constant k of 1.02 or more (k≧1.02, preferably k≧1.10) in addition to the above formulas 1 and 2. x and the vertical velocity V perpendicular to the axial direction of the outlet y and the material feed speed V0 are controlled, thereby making it possible to suppress the occurrence of wrinkles in the shear bent portion SB and ensure the flatness of the hollow material Pm.

[0057]

number

[0058] The above formula 6 will now be explained. The shear angle of the hollow material Pm formed after the application of shear force with respect to the feeding direction is θ (degrees), the inclination angles of the heating coil 12a and the cooling water injection nozzle 13a with respect to the feeding direction are both α (degrees), and the axial speed along the feeding direction is V x (mm / min), and the vertical speed perpendicular to the feed direction is V y (mm / min), and the material feed speed of the hollow material Pm along the feed direction is V0 (mm / min), V x and V y The relationship is expressed by the following equation 7.

[0059]

number

[0060] On the other hand, the inventors have found that even under processing conditions that cause wrinkles, wrinkles can be reduced by applying elongation strain in the direction perpendicular to the region being heated and processed. Here, the following formula 8 is the condition for applying elongation strain in the direction perpendicular to the region being heated and processed.

[0061]

number

[0062] Here, when a constant k exceeding 1.00 is set, Equation 8 can be expressed as the following Equation 9. Here, the value of the constant k varies depending on the dimensions of the hollow material Pm, particularly the wall thickness of the hollow material Pm, but as a result of repeated various experiments, the inventors have concluded that a good product can be obtained when k≧1.02 (preferably k≧1.10).

[0063]

number

[0064] Based on the above findings, a manufacturing method will be described below in which the shear bending process for forming the shear bent portion SB having an apex angle φ greater than 0° and less than 90° also includes a step of suppressing the occurrence of wrinkles. This manufacturing method will also be described using the manufacturing apparatus 10 shown in Fig. 1 as an example. In this manufacturing method, wrinkle detection means 50 installed downstream of cooling device 13 measures the height of wrinkles in the processed product, i.e., the height of wrinkles W that occur on the outer surfaces s3 and s4 of the shear bent portion SB. If the control device 15 determines that the wrinkle height exceeds a preset limit value as a result of the measurement, the control device 15 does not change the material feed speed V0, but instead changes the outlet axial speed V so as to satisfy the following equation 10: x , the vertical velocity at the exit V y In this way, if the wrinkle height measured by the wrinkle detection means 50 becomes equal to or less than the allowable value as a result of the adjustment to apply the elongation strain, the axial velocity V x and vertical velocity V y is kept at its current value.

[0065]

number

[0066] In the above manufacturing method, the material feed speed V0 is not changed and the axial speed V x and vertical velocity V y However, the present invention is not limited to this. For example, the axial velocity V x and vertical velocity V y Alternatively, the elongation strain may be imparted by decreasing the material feed speed V0 without changing the axial speed V. Specifically, if the control device 15 determines that the wrinkle height exceeds a preset limit value as a result of measurement by the wrinkle detection means 50, the control device 15 may reduce the axial speed V x and vertical velocity V yThe material feed speed V0 is lowered without changing the speed V0. This reduces the amount of material fed into the shear bending section SB, thereby reducing the wrinkle height. If, as a result of this adjustment, the wrinkle height measured by the wrinkle detection means 50 falls below the allowable value, the material feed speed V0 is maintained at its current value.

[0067] Alternatively, the axial velocity V x and vertical velocity V y Specifically, if the control device 15 determines that the wrinkle height exceeds a preset limit value as a result of measurement by the wrinkle detection means 50, the control device 15 reduces the material feed speed V0 while increasing the axial speed V calculated by the following equations 11 and 12. x and vertical velocity V y As a result of this adjustment, the amount of material fed into the shear bending section SB decreases and the amount of material leaving the shear bending section SB increases, so that the wrinkle height decreases significantly. If the wrinkle height measured by the wrinkle detection means 50 becomes equal to or less than the allowable value as a result of this adjustment, the material feed speed V0 and the axial speed V x and vertical velocity V y and are kept at their current values.

[0068]

number

[0069] Alternatively, the axial velocity V x and vertical velocity V y Specifically, if the control device 15 determines that the wrinkle height exceeds a preset limit value as a result of measurement by the wrinkle detection means 50, the control device 15 sets the material feed speed V0 to a value calculated from the formula while satisfying the following formula 13: x and vertical velocity V yOn the other hand, the material feed speed V0 is set so as to satisfy the following formula 14. If the wrinkle height measured by the wrinkle detection means 50 becomes equal to or smaller than the allowable value as a result of this adjustment, the material feed speed V0 and the axial speed V x and vertical velocity V y and are kept at their current values.

[0070]

number

[0071] In the above embodiment, wrinkle height measurement by the wrinkle detection means 50 is performed simultaneously when the shear bent portion SB is formed, but this is not the only embodiment. That is, a configuration in which wrinkle height measurement by the wrinkle detection means 50 is not performed simultaneously when the shear bent portion SB is formed can also be employed. For example, in the case of mass-producing hollow bent parts, the material feed speed V0 and the axial speed V x and vertical velocity V y A prototype is made in a range where the following formulas 15 to 17 are satisfied. At this time, the wrinkle height is not measured at the same time, but is measured after the prototype is made to confirm before mass production that the wrinkle height is within the limit height. Then, in actual mass production, the material feed speed V0 and axial speed V, which have been confirmed as good conditions in the previous prototype, are measured. x and vertical velocity V y The combination of the above is set as the control condition. In this example, although there is the complication of having to carry out a trial production in advance, it is suitable for mass production because it does not require simultaneous measurement of wrinkle height.

[0072]

number

[0073] [Hollow bending parts] The hollow bent part Pp manufactured using the hollow bent part manufacturing apparatus 10 and manufacturing method described above is an integral part made of metal (steel) and having a hollow, heat-treated shear bend portion (bent portion) SB located midway along its longitudinal direction, as shown in Figure 1. As shown in Figure 2, the shear bending portion SB has a bending radius r1 (r2) that is equal to or less than twice the cross-sectional width wd, which is the dimension between the inner peripheral surface s1 (outer peripheral shape) of the shear bending portion SB and the outer peripheral surface s2 (outer peripheral shape) of the shear bending portion SB. The apex angle φ of the shear bending portion SB satisfies the following formula 18.

[0074]

number

[0075] The amount of martensite in the shear bent portion SB is 50% or more. The bending radius r1 of the inner peripheral surface s1 of the shear bent portion SB and the bending radius r2 of the outer peripheral surface s2 of the shear bent portion SB are approximately equal to each other. The thickness of the shear bent portion SB at the inner peripheral surface s1 and the thickness of the shear bent portion SB at the outer peripheral surface s2 are approximately equal to each other. The cross section of the hollow curved part Pp perpendicular to the longitudinal direction thereof may be rectangular, circular, elliptical, or any of various irregular cross sections. The hollow curved part Pp is a steel pipe or other metal pipe. The hollow bent part Pp having the above configuration can be suitably used as an automobile part (for example, a stabilizer or other suspension part) where square tubes are often used, and has the advantages of high design freedom and space efficiency since it can be bent at acute angles. In addition, because it is a one-piece molded part, it has higher mechanical strength and reliability than parts manufactured by welding. [Example]

[0076] The effects of the present invention will be described below based on examples. In each example, the outer surfaces s3 and s4 shown in Fig. 4 may be referred to as "product surfaces." The hollow material Pm used in the manufacturing process was made of 0.2% carbon steel, with a cross-sectional height H of 20 mm, a cross-sectional width wd of 20 mm, and a total length of 1,000 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. The wrinkles on the product surface were then measured, and the quality of the products was judged.

[0077] [Example 1] Table 1 below shows the results of manufacturing hollow bent parts using the manufacturing device 10 with θ = 120° and α = 30°. The wrinkle height on the product surface was measured for each part, and products with a wrinkle height of 0.2 mm or less were judged to be good. The material feed rate V0 was set to 10 mm / min, and the axial speed V x , the vertical velocity at the exit V y was calculated and set using the following formulas 19 and 20. The case where k = 1.00 represents the conventional example, and the results are shown alongside those of the inventive example. The yield rate increased with increasing k, with good results being obtained when k ≥ 1.02. In particular, a significantly high yield rate was obtained when k ≥ 1.05. The radius of the shear-bent portion SB was 2.5 to 3.0 mm. Furthermore, the martensite content of the shear-bent portion SB was 95% to 100%.

[0078]

number

[0079] [Table 1]

[0080] [Example 2] Table 2 below shows the results of manufacturing hollow bent parts Pp using the manufacturing device 10 with θ = 120° and α = 30°. Wrinkles on the product surface were measured for each part, and products with wrinkle heights of 0.2 mm or less were judged to be good. The axial speed V on the outlet side x and the vertical velocity V at the exit y are set constant, the material feed speed V0 is calculated and set using the following equations 21 and 22. The case where k = 1.00 represents the conventional example, and the results are shown alongside those of the inventive example. The yield rate increased with increasing k, and a good hollow bent part Pp with an apex angle φ = 60° was obtained when k ≥ 1.02. In particular, a significantly high yield rate was obtained when k ≥ 1.05. The radius of the shear bent portion SB was 2.5 to 3.0 mm. Furthermore, the martensite content of the shear bent portion SB was 95% to 100%.

[0081]

number

[0082] [Table 2]

[0083] [Example 3] Table 3 below shows the results of manufacturing hollow bent parts Pp using the manufacturing device 10 with θ = 120° and α = 30°. Wrinkles on the product surface were measured for each part, and products with wrinkle heights of 0.2 mm or less were judged to be good. x and the vertical velocity V at the exit y was calculated and set using the following formulas 23 and 24. 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 when k ≥ 1.02, good results with an apex angle φ = 60° are obtained. In particular, when k ≥ 1.05, a significantly high yield rate is obtained. The radius of the shear-bent portion SB was 2.5 to 3.0 mm. Furthermore, the martensite content of the shear-bent portion SB was 95% to 100%.

[0084]

number

[0085] [Table 3]

[0086] [Example 4] Table 4 below shows the results of manufacturing hollow bent parts Pp using the manufacturing device 10 with θ = 130° and α = 25°. Wrinkles on the product surface were measured for each part, and products with wrinkle heights of 0.3 mm or less were judged to be good. The material feed rate V0 was set to 10 mm / min, and the axial speed V x and the vertical velocity V at the exit ywas calculated and set using the following formulas 25 and 26. Note that the case where k = 1.00 is the conventional example, and the results are shown alongside those of the inventive example. As k increases, the yield rate increases, and when k ≥ 1.02, a good hollow bent part Pp with an apex angle φ = 50° was obtained. In particular, when k ≥ 1.05, a significantly high yield rate was obtained. The radius of the shear bent portion SB was 2.0 to 2.5 mm. Furthermore, the martensite content of the shear bent portion SB was 95% to 100%.

[0087]

number

[0088] [Table 4]

[0089] [Example 5] Table 5 below shows the results of manufacturing hollow bent parts Pp using the manufacturing apparatus 10 with θ = 120° and α = 30°. Note that the case where k = 1.00 is a conventional example, and the results of the inventive example are also shown. For each 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 the manufacturing apparatus 10 of this embodiment produced good hollow bent parts Pp with a significantly high yield and an apex angle φ = 60°. In addition, the radius of the shear bent portion SB was 2.5 to 3.0 mm. Furthermore, the martensite content of the shear bent portion SB was 95% to 100%.

[0090] [Table 5] [Explanation of symbols]

[0091] 9 Feeder (feed mechanism) 10 Manufacturing equipment 12 Heating device (heating means) 13 Cooling device (cooling means) 14 Shear force applying device (shear force applying section) 15 Control device (control unit) 50 Wrinkle detection means (deformation amount detection means) A. First position B Second position C Third position D 4th position Pm hollow material Pp hollow bending parts SB shear bending section V0 feedrate α Incline angle θ Shear angle

Claims

1. A long hollow metal material is supported at a first position while being fed in a feed direction along its longitudinal direction; partially heating the hollow material in a heated portion at a second position downstream of the first position along the feeding direction; cooling the hollow blank at a third position downstream of the second position along the feeding direction; The hollow material is gripped at a gripping position after passing through the third position and moved in a two-dimensional or three-dimensional direction, thereby applying a shear force to the heated portion of the hollow material to form a shear-bent portion. A method for manufacturing a hollow curved part, comprising: In the step of forming the shear bent portion, The gripping position is moved including a movement speed component in the direction opposite to the feed direction, so that the shear angle of the shear bending portion is greater than 90° and less than 180°. A method for manufacturing a hollow curved part, comprising:

2. The material feed speed V is set to satisfy the following formulas 1 to 3. ０ and the axial velocity V ｘ and vertical velocity V ｙ and controlling at least one of The method for manufacturing a hollow curved part according to claim 1 . [Equation 1] where θ is the shear angle based on the feed direction, and V ｘ is the axial velocity along the feed direction, and V ｙ is a vertical speed perpendicular to the feeding direction, α is an inclination angle of the heating coil disposed at the second position for heating the heated portion with respect to the feeding direction, and V ０ is the material feed speed of the hollow blank along the feed direction, and k is a constant equal to or greater than 1.

02.

3. Measure the out-of-plane deformation of the shear bent portion; By relatively increasing the distance between the heated portion and the gripping position, a tensile force corresponding to the out-of-plane deformation is applied to the shear bending portion. The method for manufacturing a hollow curved part according to claim 2 .

4. a feeding mechanism that supports and feeds the metal hollow blank along a feeding direction, which is the longitudinal direction of the hollow blank, at a first position; a heating coil that partially heats the hollow material at a heated portion 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; a bending force applying unit that grasps the hollow material at a grasping position after passing the third position and moves it in a two-dimensional or three-dimensional direction to apply a shear force to the heated portion of the hollow material to form a shear-bent portion; a control unit that controls the feeding mechanism, the heating coil, the cooling device, and the bending force applying unit; A manufacturing apparatus for a hollow curved part, comprising: the bending force applying unit has a drive unit that moves the gripping position with a movement speed component including a movement speed component directed in a direction opposite to the feed direction, The control unit controls the drive unit to set the shear angle of the shear bending portion to be greater than 90° and less than 180°. A manufacturing apparatus for hollow bent parts.

5. The control unit controls at least one of the feed mechanism and the drive unit so as to satisfy the following formulas 1 to 3:

5. The apparatus for manufacturing hollow curved parts according to claim 4. [Equation 2] where θ is the shear angle based on the feed direction, and V ｘ is the axial velocity along the feed direction, and V ｙ is a vertical speed perpendicular to the feeding direction, α is an inclination angle of the heating coil disposed at the second position for heating the heated portion with respect to the feeding direction, and V ０ is the material feed speed of the hollow blank along the feed direction, and k is a constant equal to or greater than 1.

02.

6. Further provided is a deformation amount detection means for measuring an out-of-plane deformation amount of the shear bending portion, The control unit controls the drive unit so as to increase the distance between the heated portion and the gripping position in accordance with the amount of out-of-plane deformation.

6. The apparatus for manufacturing a hollow curved part according to claim 5.

7. A one-piece part made of metal, hollow, and having a heat-treated bent portion, The bending portion has a bending radius that is equal to or less than twice the width, which is the dimension between the outer shape of the inner periphery of the bending portion and the outer shape of the outer periphery of the bending portion, and an apex angle φ of the bending portion satisfies the following formula 4. [Equation 3]

8. It is made of steel, The amount of martensite in the bent portion is 50% or more.

8. The hollow curved part according to claim 7.

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