JP2020093261A - Electric heating device - Google Patents

Abstract

To provide an electric heating device that can reduce variation of temperature distribution in an axial direction of metal pipe materials during heating.SOLUTION: A bypass part 104 is installed to metal pipe materials 14. A bypass part 104 can bypass a portion of an electric current by connecting portions E1, E3 with portions E2, E4 of the metal pipe materials 14 in a position between a first electrode 101 and a second electrode 102. Accordingly, a portion of the electric current flowing in the position can be bypassed to the bypass part 104, even if an area between the portions E1, E3 and the portions E2, E4 among the metal pipe materials 14 is in the vicinity of an inner circumference of the top 14d where the electric current it is easy to be concentrated. As a result, the electric current is prevented from flowing in a concentrated manner in the specific position in the axial direction of the metal pipe materials 14, and thereby a heating value is prevented from increasing in the position.SELECTED DRAWING: Figure 4

Description

The present invention relates to an electric heating device that heats a metal pipe material by applying electric current.

2. Description of the Related Art Conventionally, there has been known a molding apparatus that mold-closes a metal pipe with a molding die and performs blow molding. For example, the molding device disclosed in Patent Document 1 includes a molding die and a gas supply unit that supplies gas into the metal pipe material. In this forming apparatus, the heated metal pipe material is placed in a forming die, and the metal pipe material is expanded by supplying gas from the gas supply unit to the metal pipe material with the forming die closed. Is molded into a shape corresponding to the shape of the molding die.

JP, 2005-112608, A

In the conventional molding apparatus, the metal pipe material is held by the electrode before expansion molding, and the metal pipe material is heated by conducting electricity through the electrode. Here, since various shapes of metal pipes have been required as finished products, various shapes of metal pipe materials have been used accordingly. Here, as the metal pipe material, there is a case where a material that is largely bent is used. However, in the case of a largely bent metal pipe material, the current tends to flow through the metal pipe material in the shortest path, so that the current is concentrated on the inner peripheral side of the bent portion, so that a large amount of heat is generated at that position. .. Therefore, the temperature distribution in the axial direction may be uneven in the metal pipe material during heating.

Therefore, an object of the present invention is to provide an electric heating device capable of reducing unevenness in the axial temperature distribution of the metal pipe material during heating.

An electric heating apparatus according to the present invention is an electric heating apparatus that energizes and heats a metal pipe material, and includes a first electrode that holds the metal pipe material, a second electrode that holds the metal pipe material, and a first electrode that holds the metal pipe material. Between the first electrode and the second electrode, a power supply unit that energizes between the first electrode and the second electrode while holding the metal pipe material by the first electrode and the second electrode. At a position, the bypass portion connects the first portion and the second portion of the metal pipe material to bypass a part of the electric current.

According to this energization heating device, the power supply unit energizes between the first electrode and the second electrode in a state where the metal pipe material is held by the first electrode and the second electrode. Therefore, a current flows through the metal pipe material between the first electrode and the second electrode. A bypass is attached to the metal pipe material. The bypass portion can bypass a part of the current by connecting the first portion and the second portion of the metal pipe material at a position between the first electrode and the second electrode. Therefore, when the current is likely to concentrate in the region between the first portion and the second portion of the metal pipe material, a part of the current flowing at the position can be bypassed by the bypass portion. Accordingly, by suppressing the electric current from concentrating and flowing at a specific position in the axial direction of the metal pipe material, it is possible to suppress an increase in the amount of heat generation at that position. As described above, it is possible to reduce unevenness in the temperature distribution in the axial direction of the metal pipe material during heating.

The electric heating device may further include a first position adjusting part capable of adjusting a mounting position of the bypass part with respect to the metal pipe material. This allows the bypass portion to be attached at an appropriate location on the metal pipe material.

The electric heating device includes a second position adjusting unit capable of adjusting the holding position of the metal pipe material by the first electrode, and a third position adjusting unit capable of adjusting the holding position of the metal pipe material by the second electrode. And a section. This allows the first electrode and the second electrode to hold the proper position of the metal pipe material.

According to the electric heating device of the present invention, it is possible to reduce the unevenness of the temperature distribution in the axial direction of the metal pipe material during heating.

It is a schematic block diagram which shows the shaping|molding apparatus in which the metal pipe material heated with the electric heating apparatus which concerns on this embodiment is used. It is an enlarged view of an electrode periphery, (a) is a figure which shows the state which the electrode hold|maintains a metal pipe material, (b) is a figure which shows the state which pressed the sealing member to an electrode, (c) is a front view of an electrode. Is. It is a perspective view of the electric heating apparatus which concerns on this embodiment. It is a schematic diagram of the electric heating apparatus which concerns on this embodiment.

Hereinafter, a preferred embodiment of a forming apparatus using a metal pipe material heated by an electric heating apparatus according to the present invention will be described with reference to the drawings. In each figure, the same or corresponding parts will be denoted by the same reference symbols, without redundant description.

<Structure of molding equipment>
FIG. 1 is a schematic configuration diagram of a molding apparatus according to this embodiment. As shown in FIG. 1, a molding apparatus 10 for molding a metal pipe includes a molding die 13 including an upper die 12 and a lower die 11, and a drive mechanism 80 for moving at least one of the upper die 12 and the lower die 11. , A pipe holding mechanism 30 for holding the metal pipe material 14 arranged between the upper mold 12 and the lower mold 11, and a high pressure in the heated metal pipe material 14 held between the upper mold 12 and the lower mold 11. A gas supply unit 60 for supplying gas (gas), and a pair of gas supply mechanisms 40, 40 for supplying gas from the gas supply unit 60 into the metal pipe material 14 held by the pipe holding mechanism 30. And a water circulation mechanism 72 for forcibly cooling the molding die 13 with water, and controlling the drive of the drive mechanism 80, the drive of the pipe holding mechanism 30, and the gas supply of the gas supply unit 60. And are provided.

The lower mold 11, which is one of the molding dies 13, is fixed to the base 15. The lower mold 11 is composed of a large steel block, and has a rectangular cavity (recess) 16 on the upper surface thereof. A cooling water passage 19 is formed in the lower mold 11, and a thermocouple 21 inserted from the bottom is provided at substantially the center. The thermocouple 21 is supported by a spring 22 so as to be vertically movable.

Further, a space 11a is provided near the left and right ends (left and right ends in FIG. 1) of the lower mold 11, and a lower holding member 17 which is a movable part of the pipe holding mechanism 30 and which will be described later is provided in the space 11a. , 18 and the like are arranged so as to be able to move up and down. Then, the metal pipe material 14 is placed on the lower holding members 17 and 18, so that the lower holding members 17 and 18 are arranged between the upper mold 12 and the lower mold 11. Contact material 14.

The lower holding members 17 and 18 are fixed to an advancing/retreating rod 95 that is a movable portion of an actuator (not shown) that constitutes the pipe holding mechanism 30. This actuator is for vertically moving the holding members 17, 18 and the like on the lower side, and the fixing portion of the actuator is held on the base 15 side together with the lower die 11.

The upper die 12, which is the other of the molding dies 13, is fixed to a slide 81, which will be described later, that constitutes the drive mechanism 80. The upper die 12 is formed of a large steel block, has a cooling water passage 25 formed therein, and has a rectangular cavity (recess) 24 on the lower surface thereof. The cavity 24 is provided at a position facing the cavity 16 of the lower mold 11.

A space 12a is provided in the vicinity of the left and right ends (left and right ends in FIG. 1) of the upper mold 12, similar to the lower mold 11, and inside the space 12a is a movable part of the pipe holding mechanism 30, which will be described later. The upper holding members 17, 18 and the like are arranged so as to be vertically movable. Then, in a state where the metal pipe material 14 is placed on the upper holding members 17 and 18, the upper holding members 17 and 18 are moved downward so as to be interposed between the upper die 12 and the lower die 11. Contact the placed metal pipe material 14.

The upper holding members 17 and 18 are fixed to an advancing/retreating rod 96 that is a movable portion of an actuator that constitutes the pipe holding mechanism 30. This actuator is for vertically moving the upper holding members 17, 18, etc., and the fixed portion of the actuator is held together with the upper die 12 on the slide 81 side of the drive mechanism 80.

In the right side portion of the pipe holding mechanism 30, a semi-circular concave groove 18a corresponding to the outer peripheral surface of the metal pipe material 14 is formed on each of the surfaces of the holding members 18, 18 facing each other (see FIG. 2). ), the metal pipe material 14 can be placed so that the metal pipe material 14 just fits into the concave groove 18a. Further, on the front surface of the holding member 18 (the surface in the outer direction of the mold), a tapered concave surface 18b is formed, which is depressed toward the concave groove 18a so that the periphery is tapered. Therefore, when the metal pipe material 14 is sandwiched by the right side portion of the pipe holding mechanism 30 from above and below, the outer circumference of the right side end portion of the metal pipe material 14 can be surrounded so as to be in close contact with the entire circumference. ing.

In the left side portion of the pipe holding mechanism 30, a semi-circular concave groove 17a corresponding to the outer peripheral surface of the metal pipe material 14 is formed on each of the surfaces of the holding members 17, 17 facing each other (see FIG. 2). ), the metal pipe material 14 can be placed so that the metal pipe material 14 just fits into the concave groove 17a. In addition, a tapered concave surface 17b is formed on the front surface of the holding member 17 (a surface in the outer side of the mold), the peripheral surface of which is tapered and concave toward the concave groove 17a. Therefore, when the metal pipe material 14 is vertically sandwiched by the left side portion of the pipe holding mechanism 30, the outer periphery of the left end portion of the metal pipe material 14 can be surrounded so as to be in close contact with the entire circumference. ing.

As shown in FIG. 1, the drive mechanism 80 includes a slide 81 that moves the upper mold 12 so that the upper mold 12 and the lower mold 11 are aligned with each other, and a shaft 82 that generates a driving force for moving the slide 81. And a connecting rod 83 for transmitting the driving force generated by the shaft 82 to the slide 81. The shaft 82 extends in the left-right direction above the slide 81 and is rotatably supported, and has an eccentric crank 82a extending in the left-right direction protruding from the left-right ends at a position separated from the axis thereof. Have The eccentric crank 82 a and the rotary shaft 81 a provided on the upper portion of the slide 81 and extending in the left-right direction are connected by a connecting rod 83. In the drive mechanism 80, the control unit 70 controls the rotation of the shaft 82 to change the vertical height of the eccentric crank 82a, and the position change of the eccentric crank 82a is transmitted to the slide 81 via the connecting rod 83. Thus, the vertical movement of the slide 81 can be controlled. Here, the swing (rotational motion) of the connecting rod 83 that occurs when transmitting the position change of the eccentric crank 82a to the slide 81 is absorbed by the rotary shaft 81a. The shaft 82 rotates or stops according to the driving of a motor or the like controlled by the control unit 70, for example.

Returning to FIG. 1, each of the pair of gas supply mechanisms 40 is connected to a cylinder unit 42, a cylinder rod 43 that moves back and forth according to the operation of the cylinder unit 42, and a tip of the cylinder rod 43 on the pipe holding mechanism 30 side. And a sealing member 44. The cylinder unit 42 is mounted and fixed on the block 41. A taper surface 45 is formed at the tip of the seal member 44 so as to be tapered, and has a shape that fits the taper concave surfaces 17b and 18b of the holding members 17 and 18 (see FIG. 2). The seal member 44 extends from the cylinder unit 42 side toward the tip, and more specifically, as shown in FIGS. 2A and 2B, a gas passage through which the high-pressure gas supplied from the gas supply unit 60 flows. 46 is provided.

The gas supply unit 60 includes a gas source 61, an accumulator 62 that stores the gas supplied by the gas source 61, a first tube 63 that extends from the accumulator 62 to the cylinder unit 42 of the gas supply mechanism 40, and The pressure control valve 64 and the switching valve 65 provided in the first tube 63, the second tube 67 extending from the accumulator 62 to the gas passage 46 formed in the seal member 44, and the second tube 67 The pressure control valve 68 and the check valve 69 are provided. The pressure control valve 64 serves to supply the cylinder unit 42 with a gas having an operating pressure adapted to the pressing force of the seal member 44 against the metal pipe material 14. The check valve 69 plays a role of preventing the high-pressure gas from flowing backward in the second tube 67. The pressure control valve 68 provided in the second tube 67 serves to supply a gas having an operating pressure for expanding the metal pipe material 14 to the gas passage 46 of the seal member 44 under the control of the control unit 70. Fulfill.

The control unit 70 can supply the gas having a desired working pressure into the metal pipe material 14 by controlling the pressure control valve 68 of the gas supply unit 60. Further, the control unit 70 acquires the temperature information from the thermocouple 21 by transmitting the information from (A) shown in FIG. 1, and controls the drive mechanism 80 and the like.

The water circulation mechanism 72 includes a water tank 73 that stores water, a water pump 74 that pumps up the water accumulated in the water tank 73, pressurizes it, and sends it to the cooling water passage 19 of the lower mold 11 and the cooling water passage 25 of the upper mold 12, And a pipe 75. Although omitted, a cooling tower for lowering the water temperature and a filter for purifying water may be provided in the pipe 75.

<Molding method of metal pipe using molding machine>
Next, a method of molding a metal pipe using the molding device 10 will be described. First, a quenchable steel type cylindrical metal pipe material 14 is prepared. The metal pipe material 14 is placed (input) on the holding members 17 and 18 provided on the lower mold 11 side using a robot arm or the like described later. The metal pipe material 14 at the time of charging is in a state of being heated by the electric heating device 100 described later. Since the holding members 17 and 18 are formed with the concave grooves 17a and 18a, the metal pipe material 14 is positioned by the concave grooves 17a and 18a.

Next, the control unit 70 controls the drive mechanism 80 and the pipe holding mechanism 30 to cause the pipe holding mechanism 30 to hold the metal pipe material 14. Specifically, the upper die 12 and the holding members 17, 18 and the like held on the slide 81 side are moved to the lower die 11 side by the driving of the driving mechanism 80, and at the same time, the holding member 17, included in the pipe holding mechanism 30, By actuating an actuator that can move 18 and the like and holding members 17, 18 and the like back and forth, the pipe holding mechanism 30 holds both ends of the metal pipe material 14 from above and below. Due to the presence of the concave grooves 17a and 18a formed in the holding members 17 and 18, this clamping is performed in such a manner that the metal pipe material 14 is in close contact with the entire circumference in the vicinity of both ends thereof.

At this time, as shown in FIG. 2A, the end portion of the metal pipe material 14 on the side of the holding member 18 has a concave groove 18 a and a tapered concave surface of the holding member 18 in the extending direction of the metal pipe material 14. It projects toward the seal member 44 side from the boundary with 18b. Similarly, the end portion of the metal pipe material 14 on the holding member 17 side projects in the extending direction of the metal pipe material 14 toward the seal member 44 side from the boundary between the concave groove 17a and the tapered concave surface 17b of the holding member 17. There is. Further, the lower surfaces of the upper holding members 17 and 18 and the upper surfaces of the lower holding members 17 and 18 are in contact with each other. However, the metal pipe material 14 is not limited to be in close contact with the entire circumference of both ends thereof, and the holding members 17 and 18 may be in contact with a part of the metal pipe material 14 in the circumferential direction.

Then, the molding die 13 is closed with respect to the heated metal pipe material 14 by the control of the drive mechanism 80 by the control unit 70. As a result, the cavity 16 of the lower die 11 and the cavity 24 of the upper die 12 are combined, and the metal pipe material 14 is placed and sealed in the cavity portion between the lower die 11 and the upper die 12.

Then, by operating the cylinder unit 42 of the gas supply mechanism 40, the seal member 44 is advanced to seal both ends of the metal pipe material 14. At this time, as shown in FIG. 2B, the seal member 44 is pressed against the end portion of the metal pipe material 14 on the holding member 18 side, so that the boundary between the concave groove 18a and the tapered concave surface 18b of the holding member 18 is increased. The portion protruding toward the seal member 44 side is deformed into a funnel shape along the tapered concave surface 18b. Similarly, the seal member 44 is pressed against the end of the metal pipe material 14 on the side of the holding member 17, so that the portion of the holding member 17 protruding toward the seal member 44 side from the boundary between the groove 17a and the tapered concave surface 17b. Deforms into a funnel shape along the tapered concave surface 17b. After the sealing is completed, high-pressure gas is blown into the metal pipe material 14 to mold the metal pipe material 14 softened by heating so as to follow the shape of the cavity.

Since the metal pipe material 14 is heated to a high temperature (about 950° C.) and softened, the gas supplied into the metal pipe material 14 thermally expands. Therefore, for example, the supplied gas is compressed air, and the metal pipe material 14 at 950° C. can be easily expanded by the compressed air that is thermally expanded.

The outer peripheral surface of the blow-molded and expanded metal pipe material 14 contacts the cavity 16 of the lower mold 11 to be rapidly cooled, and at the same time, contacts the cavity 24 of the upper mold 12 to rapidly cool (the upper mold 12 and the lower mold 11 are Since the heat capacity is large and the temperature is controlled to be low, the heat of the pipe surface is immediately taken to the mold side when the metal pipe material 14 comes into contact with the metal pipe material 14, and the quenching is performed. Such a cooling method is called mold contact cooling or mold cooling. Immediately after being quenched, austenite transforms to martensite (hereinafter, transformation of austenite to martensite is referred to as martensite transformation). In the latter half of cooling, the cooling rate became smaller, so that the martensite is transformed into another structure (troustite, sorbite, etc.) by recuperation. Therefore, it is not necessary to perform a separate tempering process. Further, in the present embodiment, instead of the mold cooling or in addition to the mold cooling, the cooling may be performed by supplying a cooling medium into the cavity 24, for example. For example, the metal pipe material 14 is brought into contact with a mold (upper mold 12 and lower mold 11) until the temperature at which martensitic transformation starts, and then the mold is opened and a cooling medium (cooling gas) is used as the metal pipe material. The martensite transformation may be generated by spraying on 14.

As described above, the metal pipe material 14 is blow-molded and then cooled, and the mold is opened to obtain a metal pipe having, for example, a substantially rectangular tubular main body.

Next, the electric heating device 100 according to the present embodiment will be described with reference to FIGS. 3 and 4. The metal pipe material 14 used in this embodiment has a bent portion at any position in the axial direction. Here, it has a curved portion 14a that is curved in a mountain shape at the central portion in the axial direction. The electric heating apparatus 100 has a function of holding such a metal pipe material 14 and heating the electric current by electric power. Further, the electric heating device 100 has a function of setting the held metal pipe material 14 in the molding die 13. As shown in FIG. 4, the electric heating apparatus 100 includes a first electrode 101, a second electrode 102, a power supply unit 103, a bypass unit 104, and a control unit 106. Further, as shown in FIG. 3, the electric heating apparatus 100 includes a first position adjusting unit 107, a second position adjusting unit 108, and a third position adjusting unit 109.

As shown in FIG. 4, the first electrode 101 is a member that holds the metal pipe material 14 and energizes the metal pipe material 14 with the second electrode 102. The first electrode 101 includes a holding member 101A and a holding member 101B. The first electrode 101 is held by sandwiching the metal pipe material 14 between the holding member 101A and the holding member 101B. The first electrode 101 holds the metal pipe material 14 near one end 14b in the axial direction. The one holding member 101A is connected to the conductor 110 extending from the power supply unit 103. Of the holding member 101A, at least a portion in contact with the metal pipe material 14 is made of a conductive member. This allows the holding member 101A to pass an electric current to the metal pipe material 14. The holding member 101B may be made of a conductive member, but may be made of an insulating member because the holding member 101A has a function of passing an electric current.

The second electrode 102 is a member that holds the metal pipe material 14 at a position different from that of the first electrode 101 and energizes the metal pipe material 14 with the first electrode 101. The second electrode 102 includes a holding member 102A and a holding member 102B. The second electrode 102 is held by sandwiching the metal pipe material 14 between the holding member 102A and the holding member 102B. The second electrode 102 holds the metal pipe material 14 near the other end 14c in the axial direction. Note that one holding member 102A is connected to the conducting wire 111 extending from the power supply unit 103. At least a portion of the holding member 102A that is in contact with the metal pipe material 14 is formed of a conductive member. As a result, the holding member 102A can pass an electric current to the metal pipe material 14. The holding member 102B may be made of a conductive member, but may be made of an insulating member because the holding member 102A has a function of passing an electric current.

The power supply unit 103 is a device that energizes between the first electrode 101 and the second electrode 102 while the metal pipe material 14 is held by the first electrode 101 and the second electrode 102. The power supply unit 103 includes at least a DC power supply and a switch. The power supply unit 103 is electrically connected to the holding member 101A of the first electrode 101 via the lead wire 110, and is electrically connected to the holding member 102A of the second electrode 102 via the lead wire 111. The control unit 106 can perform control to switch ON/OFF of the switch of the power supply unit 103. Therefore, the control unit 106 can turn on the switch of the power supply unit 103 at a predetermined timing to flow a current through the metal pipe material 14.

The bypass section 104 is a member that bypasses a part of the current at the connection point at a position between the first electrode 101 and the second electrode 102. The bypass section 104 also has a function of holding the metal pipe material 14, and includes a holding member 104A and a holding member 104B. The bypass portion 104 holds the curved portion 14a of the metal pipe material 14 by sandwiching it between the holding member 104A and the holding member 104B. The holding member 104A and the holding member 104B are made of a conductive member.

The holding member 104A has a U-shaped cross section, and contacts the contact portion 104Aa that contacts the metal pipe material 14 and the contact portion 104Ab that contacts the metal pipe material 14 at a position separated from the contact portion 104Ab. And a connecting portion 104Ac that connects the portion 104Aa and the contact portion 104Ab. The contact portions 104Aa and 104Ab have contact surfaces at their tips and extend in a direction opposite to the contact surfaces. The connecting portion 104Ac connects the contact portion 104Aa and the contact portion 104Ab at an end of the contact portion 104Aa and the contact portion 104Ab opposite to the contact surface. In the present embodiment, the contact portion 104Aa of the holding member 104A is in contact with the portion (first portion) E1 of the metal pipe material 14. The contact portion 104Ab of the holding member 104A is in contact with the portion (second portion) E2 of the metal pipe material 14. The portions E1 and E2 are located on both sides of the top portion 14d of the bending portion 14a in the axial direction. With such a configuration, the holding member 104A electrically connects the portion E1 and the portion E2 that sandwich the top portion 14d, and thereby one of the currents flowing between the portion E1 and the portion E2 of the metal pipe material 14 is reduced. Bypass the department.

The holding member 104B has the same configuration as the holding member 104A, and includes a contact portion 104Ba, a contact portion 104Bb, and a connecting portion 104Bc. In the present embodiment, the contact portion 104Ba of the holding member 104B is in contact with the portion (first portion) E3 of the metal pipe material 14. The contact portion 104Bb of the holding member 104B is in contact with the portion (second portion) E4 of the metal pipe material 14. The portions E3 and E4 are located on both sides in the axial direction of the top portion 14d of the bending portion 14a. With such a configuration, the holding member 104B electrically connects the portion E3 and the portion E4 that sandwich the top portion 14d, so that one of the currents flowing between the portion E3 and the portion E4 of the metal pipe material 14 is reduced. Bypass the department. In FIG. 4, the flow of current is indicated by the arrow “EF”.

As shown in FIG. 3, the first position adjusting unit 107, the second position adjusting unit 108, and the third position adjusting unit 109 are configured by a robot arm. For example, the first position adjustment unit 107 includes a robot hand 107a that holds the metal pipe material 14, a movable unit 107b that can change the posture of the robot hand 107a three-dimensionally, and the movable unit 107b and the entire robot hand 107a that are horizontal. It is provided with a pedestal 107c and the like for rotating in the direction. Thereby, the 1st position adjustment part 107 can hold the metal pipe material 14 from all angles and directions. Further, the first position adjusting unit 107 can hold the metal pipe material 14 in any posture, and can hold the held metal pipe material 14 in any position within the range of the movable range. The second position adjusting unit 108 and the third position adjusting unit 109 have the same configuration as the first position adjusting unit 107.

The first position adjusting unit 107 is provided so as to be arranged between the second position adjusting unit 108 and the third position adjusting unit 109. The first position adjusting unit 107 includes a bypass unit 104 at the tip of the robot hand 107a. Accordingly, the first position adjusting unit 107 can adjust the attachment position of the bypass unit 104 with respect to the metal pipe material 14. The second position adjustment unit 108 includes the first electrode 101 at the tip of the robot hand 108a. This makes it possible to adjust the holding position of the first electrode with respect to the metal pipe material 14. The third position adjusting unit 109 includes the second electrode 102 at the tip of the robot hand 109a. This makes it possible to adjust the holding position of the second electrode 102 with respect to the metal pipe material 14.

Each of the position adjusting units 107, 108, and 109 can hold the metal pipe material 14 outside the molding die 13 and convey the metal pipe material 14 to set it in the molding die 13. The position adjusting units 107, 108, and 109 may be controlled by the control unit 106 (see FIG. 4). Therefore, the control unit 106 can hold the metal pipe material 14 in each of the position adjusting units 107, 108, and 109, perform the electric heating, and then dispose the heated metal pipe material in the molding die 13. ..

Next, operations and effects of the electric heating device 100 according to the present embodiment will be described.

First, an electric heating device according to a comparative example will be described. The electric heating apparatus according to the comparative example has the holding member 17 in the above-described embodiment as a first electrode, the holding member 18 as a second electrode, and does not have a bypass portion. In this case, a current flows through the metal pipe material 14 between the first electrode and the second electrode. However, the current tends to flow through the metal pipe material 14 by the shortest path. Therefore, since the metal pipe material 14 is largely bent at the bending portion 14a, current is concentrated near the inner peripheral portion of the top portion 14d of the bending portion 14a, so that large heat is generated at that position. Therefore, the temperature distribution in the axial direction may be uneven in the metal pipe material 14 during heating.

On the other hand, according to the electric heating apparatus 100 according to the present embodiment, the power supply unit 103 holds the metal pipe material 14 with the first electrode 101 and the second electrode 102, and then the first electrode 101. And the second electrode 102 are energized. Therefore, a current flows through the metal pipe material 14 between the first electrode 101 and the second electrode 102. The bypass section 104 is attached to the metal pipe material 14. The bypass portion 104 connects the portions E1 and E3 and the portions E2 and E4 of the metal pipe material 14 at a position between the first electrode 101 and the second electrode 102 to bypass a part of the current. be able to. Therefore, when the region of the metal pipe material 14 between the portions E1 and E3 and the portions E2 and E4 is near the inner peripheral portion of the top portion 14d where the current easily concentrates, a part of the current flowing to the position is bypassed. The part 104 can be bypassed. Accordingly, by suppressing the electric current from concentrating and flowing at a specific position in the axial direction of the metal pipe material 14, it is possible to suppress an increase in the amount of heat generation at that position. As described above, it is possible to reduce unevenness in the temperature distribution of the metal pipe material 14 in the axial direction during heating.

The electric heating apparatus 100 further includes a first position adjusting unit 107 capable of adjusting the mounting position of the bypass unit 104 with respect to the metal pipe material 14. This allows the bypass portion 104 to be attached at an appropriate position on the metal pipe material 14.

The electric heating apparatus 100 is capable of adjusting the position of holding the metal pipe material 14 by the first electrode 101, and the position of holding the metal pipe material 14 by the second electrode 102. And a third position adjusting unit 109. As a result, the first electrode 101 and the second electrode 102 can hold the metal pipe material 14 at appropriate positions.

The present invention is not limited to the above embodiments.

For example, in the above-described embodiment, the bypass unit 104 bypasses the current with both the holding member 104A and the holding member 104B, but may bypass only with one holding member. At this time, the other holding member is made of an insulating member and has a function of only holding the metal pipe material 14.

Further, the first electrode and the second electrode may be provided in the molding device 10. For example, the holding member 17 may be the first electrode and the holding member 18 may be the second electrode. In this case, the first position adjusting unit 107 holds the metal pipe material 14 in the molding die 13 and then holds it by the bypass unit 104 even when the first electrode and the second electrode are energized. To continue.

The shape of the metal pipe material is not limited to the above. For example, the metal pipe material may be bent rather than curved. The metal pipe material may be curved or bent at multiple points. When the metal pipe material is curved or bent at a plurality of points, the bypass portions may be provided in the same number as the number of curved or bent points. However, when the angle of bending/bending is small, the number of bending/bending points and the number of bypass sections do not have to be the same.

Reference numeral 100... Electric heating device, 101... First electrode, 102... Second electrode, 103... Power supply unit, 104... Bypass unit, 107... First position adjusting unit, 108... Second position adjusting unit, 109 ...The third position adjusting unit.

Claims (3)

An electric heating device for heating a metal pipe material by energizing it.
A first electrode holding the metal pipe material;
A second electrode holding the metal pipe material;
A power supply unit for energizing between the first electrode and the second electrode in a state where the metal pipe material is held by the first electrode and the second electrode,
A bypass portion that connects a first portion and a second portion of the metal pipe material at a position between the first electrode and the second electrode to bypass a part of the current. An electric heating device equipped. The electric heating device according to claim 1, further comprising a first position adjusting unit capable of adjusting a mounting position of the bypass unit with respect to the metal pipe material. A second position adjusting unit capable of adjusting the position of holding by the first electrode with respect to the metal pipe material;
The electric heating device according to claim 1 or 2, further comprising: a third position adjusting unit capable of adjusting a position of holding the metal pipe material by the second electrode.

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