JP2018170115A - Energization heating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an energization heating apparatus capable of detecting generation of arc discharge between a metal body and an electrode, thereby executing appropriate processing, such as maintenance of the electrode or exchange of the electrode.SOLUTION: Electric power is supplied to a metal body 14 through at least two electrodes 17, 18 for energization heating. While a voltage between the electrodes 17, 18 is being measured by a voltage measurement part 53, when arc discharge is generated between the metal body 14 and the electrodes 17, 18 in contact with the metal body 14, a remarkably high arc voltage is generated, thereby permitting an arc discharge detection part 70a to detect generation of arc discharge between the electrode 17, 18 and the metal 14 on the basis of the voltage value measured by the voltage measurement part 53.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electric heating device.

  2. Description of the Related Art Conventionally, a forming apparatus that heats a metal pipe material that is a metal body and supplies a gas into the metal pipe material to form a metal pipe is known. As such a molding apparatus, for example, Patent Document 1 discloses a pair of molds, an electrode that can be electrically connected to a metal pipe material disposed between the pair of molds, and the electrode is a metal pipe material. A forming apparatus is described that includes a power supply unit capable of energizing a metal pipe material via an electrode in an electrically connected state. This forming apparatus is an energization heating apparatus that heats and molds a metal pipe material by Joule heat generated by energizing the metal pipe material.

JP2015-112608A

  By the way, in the energization heating apparatus as described above, a high current flows and the metal pipe material is energized and heated, so that even if a gap is generated between the metal pipe material and the electrode in contact with the metal pipe material, There is a high possibility that spark (arcing; hereinafter referred to as arc discharge) will occur. If such arc discharge is repeated, the electrode surface will be uneven, which will cause resistance when energized, causing problems such as heating of the electrode itself and hindering temperature rise of the metal pipe material. become. Even if the number of arc discharges is one, there may be a problem if the arc discharge continues for a long time, for example.

  Therefore, the present invention can detect the occurrence of arc discharge between a metal body such as a metal pipe material and an electrode, and as a result, can perform appropriate processing such as electrode maintenance or electrode replacement. An object is to provide an electric heating device.

  An energization heating apparatus according to the present invention is an energization heating apparatus that supplies electric power to a metal body and energizes and heats the metal body, and includes a voltage measuring unit that measures a voltage between the electrodes and at least two electrodes in contact with the metal body. And an arc discharge detector that detects the occurrence of arc discharge between the electrode and the metal body based on the voltage value measured by the voltage measuring unit.

  According to such an energization heating device, while supplying electric power to the metal body via at least two electrodes and energizing heating, the voltage between the electrodes is measured by the voltage measuring unit, and the metal body When an arc discharge occurs between the electrode that contacts the metal body, a very high arc voltage is generated. Therefore, the arc discharge detection unit determines that the voltage between the electrode and the metal body is based on the voltage measured by the voltage measurement unit. The occurrence of arc discharge can be detected. Therefore, thereafter, appropriate processing such as electrode maintenance or electrode replacement can be performed based on the detection result.

  Here, the arc discharge detector may detect the occurrence of arc discharge based on the amount of change in voltage per unit time. According to this, generation | occurrence | production of arc discharge can be detected reliably.

  The arc discharge detector may detect the occurrence of arc discharge based on the difference between the measured voltage value and a predetermined set value. Also by this, generation | occurrence | production of arc discharge can be detected reliably.

  In addition, if a warning device is provided to warn when the occurrence of arc discharge is detected, the operator can be warned that arc discharge has occurred, and whether or not processing such as electrode maintenance or electrode replacement should be performed. Can be recognized.

  Also, if a warning device is provided to warn when the occurrence of arc discharge is detected a plurality of times determined in advance, the operator can be warned that arc discharge has occurred a predetermined number of times, It can be recognized that it is time to replace the electrodes.

  In addition, when the occurrence of arc discharge is detected a predetermined number of times, a warning device that prompts maintenance of the electrode or replacement of the electrode is provided. It is possible to positively warn that it is time for maintenance or electrode replacement, and as a result, it is possible to cause an operator to perform electrode maintenance or electrode replacement.

  According to the present invention as described above, it is possible to provide an electric heating apparatus that can detect the occurrence of arc discharge between the metal body and the electrode and can perform appropriate processing such as electrode maintenance or electrode replacement.

It is a schematic structure figure showing an energization heating device concerning one embodiment of the present invention. It is an enlarged view of the periphery of the electrode, (a) is a diagram showing a state in which the electrode holds the metal pipe material, (b) is a diagram showing a state in which the seal member is pressed against the electrode, (c) is a front view of the electrode It is. It is a timing chart which shows the electric current and voltage at the time of energization heating, (a) is a figure showing supply current, (b) shows an example of detection of arc discharge which shows change with time of voltage to supply current of (a). It is a figure for demonstrating. FIG. 4 is an enlarged view of a portion IV in FIG. 3. It is a timing chart which shows the electric current and voltage at the time of energization heating, (a) is a figure showing supply current, (b) shows change with time of voltage to supply current of (a), and other detection of arc discharge It is a figure for demonstrating an example.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of an electric heating apparatus according to the invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same part or an equivalent part, and the overlapping description is abbreviate | omitted.

<Configuration of molding equipment>
FIG. 1 is a schematic configuration diagram of a molding apparatus as an electric heating apparatus. As shown in FIG. 1, a molding apparatus 10 for molding a metal pipe moves a blow molding die (mold) 13 including an upper die 12 and a lower die 11 and at least one of the upper die 12 and the lower die 11. Drive mechanism 80, pipe holding mechanism 30 holding metal pipe material 14 disposed between upper mold 12 and lower mold 11, and metal pipe material 14 held by pipe holding mechanism 30 are energized. Heated by a heating mechanism 50, a gas supply unit 60 for supplying high-pressure gas (gas) into the heated metal pipe material 14 held between the upper mold 12 and the lower mold 11, and held by the pipe holding mechanism 30 A pair of gas supply mechanisms 40, 40 for supplying gas from the gas supply unit 60 into the formed metal pipe material 14, a water circulation mechanism 72 for forcibly cooling the blow mold 13 with water, and arc discharge are generated. did A warning device 71 that issues a warning, and the driving mechanism 80, the pipe holding mechanism 30, the heating mechanism 50, the gas supply unit 60, and the warning device 71. And a control unit 70 for controlling each of them.

  The lower mold 11 which is one of the blow molding dies 13 is fixed to the base 15. The lower mold 11 is composed of a large steel block, and includes, for example, a rectangular cavity (concave portion) 16 on the upper surface thereof. A cooling water passage 19 is formed in the lower mold 11 and is provided with a thermocouple 21 inserted from below at a substantially central position. The thermocouple 21 is supported by a spring 22 so as to be movable up and down.

  Further, a space 11a is provided in the vicinity of the left and right ends (left and right ends in FIG. 1) of the lower mold 11, and electrodes 17 and 18 (lower portions), which will be described later, which are movable parts of the pipe holding mechanism 30, are provided in the space 11a. Side electrodes) and the like are arranged so as to be movable up and down. Then, by placing the metal pipe material 14 on the lower electrodes 17 and 18, the lower electrodes 17 and 18 are in contact with the metal pipe material 14 disposed between the upper mold 12 and the lower mold 11. To do. Thus, the lower electrodes 17 and 18 are electrically connected to the metal pipe material 14.

  An insulating material 91 for preventing energization is provided between the lower mold 11 and the lower electrode 17 and under the lower electrode 17, and between the lower mold 11 and the lower electrode 18 and under the lower electrode 18. Each is provided. Each insulating material 91 is fixed to an advance / retreat rod 95 which is a movable portion of an actuator (not shown) constituting the pipe holding mechanism 30. This actuator is for moving the lower electrodes 17, 18 and the like up and down, and the fixed portion of the actuator is held on the base 15 side together with the lower mold 11.

  The upper die 12, which is the other of the blow molding dies 13, is fixed to a later-described slide 81 that constitutes the drive mechanism 80. The upper mold 12 is composed of a large steel block, and has a cooling water passage 25 formed therein, and is provided with, for example, 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 in the same manner as the lower mold 11, and a movable portion of the pipe holding mechanism 30 will be described later in the space 12a. Electrodes 17 and 18 (upper electrodes) and the like are arranged so as to be movable up and down. Then, in a state where the metal pipe material 14 is placed on the lower electrodes 17 and 18, the upper electrodes 17 and 18 are arranged between the upper mold 12 and the lower mold 11 by moving downward. Contact the metal pipe material 14. Thereby, the upper electrodes 17 and 18 are electrically connected to the metal pipe material 14.

  Insulating materials 101 for preventing energization are provided between the upper mold 12 and the upper electrode 17 and above the upper electrode 17, and between the upper mold 12 and the upper electrode 18 and above the upper electrode 18, respectively. Yes. Each insulating material 101 is fixed to an advance / retreat rod 96 which is a movable portion of an actuator constituting the pipe holding mechanism 30. This actuator is for moving the upper electrodes 17, 18 and the like up and down, and the fixed portion of the actuator is held on the slide 81 side of the drive mechanism 80 together with the upper mold 12.

  In the right part of the pipe holding mechanism 30, a semicircular arc-shaped groove 18a corresponding to the outer peripheral surface of the metal pipe material 14 is formed on each of the surfaces where the electrodes 18, 18 face each other (see FIG. 2). The metal pipe material 14 can be placed so as to fit into the concave groove 18a. In the right portion of the pipe holding mechanism 30, a semicircular arc-shaped groove corresponding to the outer peripheral surface of the metal pipe material 14 is formed on the exposed surface where the insulating materials 91 and 101 face each other, like the groove 18a. ing. Further, a tapered concave surface 18b is formed on the front surface of the electrode 18 (the surface in the outer direction of the mold). Therefore, when the metal pipe material 14 is sandwiched from above and below by the right side portion of the pipe holding mechanism 30, the outer periphery of the right end portion of the metal pipe material 14 can be surrounded so as to be in close contact over the entire circumference. ing.

  In the left part of the pipe holding mechanism 30, a semicircular arc-shaped groove 17a corresponding to the outer peripheral surface of the metal pipe material 14 is formed on each of the surfaces where the electrodes 17 and 17 face each other (see FIG. 2). The metal pipe material 14 can be placed so as to fit into the concave groove 17a. In the left portion of the pipe holding mechanism 30, a semicircular arc-shaped groove corresponding to the outer peripheral surface of the metal pipe material 14 is formed on the exposed surface where the insulating materials 91 and 101 face each other, like the groove 18a. ing. In addition, a tapered concave surface 17b is formed on the front surface of the electrode 17 (surface in the outer direction of the mold). Therefore, when the metal pipe material 14 is sandwiched from above and below by the left 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 over 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. An eccentric crank 82a that protrudes from the left and right ends and extends in the left-right direction at a position away from the axis. Have. The eccentric crank 82 a and a rotating shaft 81 a provided in the upper part of the slide 81 and extending in the left-right direction are connected by a connecting rod 83. In the drive mechanism 80, the height of the eccentric crank 82a is changed by controlling the rotation of the shaft 82 by the control unit 70, and the change in the position 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 swinging (rotating motion) of the connecting rod 83 that occurs when the position change of the eccentric crank 82a is transmitted to the slide 81 is absorbed by the rotating 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.

  The heating mechanism 50 includes a power supply unit 55, a bus bar 52 that electrically connects the power supply unit 55 and the electrodes 17 and 18, and a voltmeter 53 as a voltage measurement unit that measures a voltage between the electrodes 17 and 18. . The power supply unit 55 includes a direct current power source and a switch, and can energize the metal pipe material 14 via the bus bar 52 and the electrodes 17 and 18 in a state where the electrodes 17 and 18 are electrically connected to the metal pipe material 14. Has been. Here, the bus bar 52 is connected to the lower electrodes 17 and 18, and the voltmeter 53 is connected to a position near the lower electrode 17 of the bus bar 52 and a position near the lower electrode 18 of the bus bar 52. It is connected to the. The power supply unit 55 supplies power of about 10,000 A20V or more.

  In the heating mechanism 50, the direct current output from the power supply unit 55 is transmitted by the bus bar 52 and input to the electrode 17. The direct current passes through the metal pipe material 14 and is input to the electrode 18. The direct current C is transmitted by the bus bar 52 and input to the power supply unit 55.

  The voltage value measured by the voltmeter 53 (information from (B) shown in FIG. 1) is input to the arc discharge detection unit 70a of the control unit 70. The arc discharge detector 70 a detects the occurrence of arc discharge between the electrodes 17 and 18 and the metal pipe material 14 based on the voltage value measured by the voltmeter 53. When the arc discharge detector 70a detects the occurrence of arc discharge, the controller 70 sends a warning command to the warning device 71. The warning device 71 issues a warning by, for example, a lamp, sound, screen display, or the like.

  Each of the pair of gas supply mechanisms 40 includes a cylinder unit 42, a cylinder rod 43 that moves forward and backward in accordance with the operation of the cylinder unit 42, and a seal member 44 that is coupled to the tip of the cylinder rod 43 on the pipe holding mechanism 30 side. Have The cylinder unit 42 is mounted and fixed on the block 41. A tapered surface 45 is formed at the tip of the seal member 44 so as to be tapered, and is configured to fit the tapered concave surfaces 17b, 18b of the electrodes 17, 18 (see FIG. 2). The seal member 44 extends from the cylinder unit 42 toward the tip, and as shown in detail 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, A pressure control valve 64 and a switching valve 65 provided in one tube 63; a second tube 67 extending from the accumulator 62 to a gas passage 46 formed in the seal member 44; 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 serves to prevent the high pressure gas from flowing back 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 a gas having a desired operating pressure into the metal pipe material 14 by controlling the pressure control valve 68 of the gas supply unit 60. Moreover, the control part 70 acquires temperature information from the thermocouple 21, and controls the drive mechanism 80 grade | etc., By information being transmitted from (A) shown in FIG.

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

<Metal pipe forming method using forming equipment>
Next, a method for forming a metal pipe using the forming apparatus 10 will be described. First, a cylindrical metal pipe material 14 of a hardenable steel type is prepared. The metal pipe material 14 is placed (input) on the electrodes 17 and 18 provided on the lower mold 11 side using, for example, a robot arm or the like. Since the grooves 17a and 18a are formed in the electrodes 17 and 18, the metal pipe material 14 is positioned by the 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 upper electrodes 17 and 18 held on the slide 81 side by the driving mechanism 80 move to the lower die 11 side, and the upper electrode 17 and the upper electrode 17 included in the pipe holding mechanism 30 are moved. By actuating an actuator that allows the 18 and the like and the lower electrodes 17 and 18 to move forward and backward, the vicinity of both ends of the metal pipe material 14 is sandwiched by the pipe holding mechanism 30 from above and below. This clamping is caused to closely adhere to the entire circumference of the metal pipe material 14 near both ends due to the presence of the concave grooves 17a and 18a formed in the electrodes 17 and 18 and the concave grooves formed in the insulating materials 91 and 101. It will be clamped in such a manner.

  At this time, as shown in FIG. 2A, the end of the metal pipe material 14 on the electrode 18 side has a groove 18 a and a taper concave surface 18 b of the electrode 18 in the extending direction of the metal pipe material 14. It protrudes to the seal member 44 side from the boundary. Similarly, the end of the metal pipe material 14 on the electrode 17 side protrudes more toward the seal member 44 than the boundary between the concave groove 17a and the tapered concave surface 17b of the electrode 17 in the extending direction of the metal pipe material 14. The lower surfaces of the upper electrodes 17 and 18 and the upper surfaces of the lower electrodes 17 and 18 are in contact with each other. However, the configuration is not limited to the configuration in which the metal pipe material 14 is in close contact with the entire periphery of the both ends, and a configuration in which the electrodes 17 and 18 are in contact with part of the metal pipe material 14 in the circumferential direction may be employed.

  Subsequently, the control unit 70 heats the metal pipe material 14 by controlling the heating mechanism 50. Specifically, the control unit 70 controls the power supply unit 55 of the heating mechanism 50 to supply power, and performs constant current control of the current value A1 as shown in FIG. Then, the electric power transmitted to the lower electrodes 17 and 18 via the bus bar 52 is supplied to the upper electrodes 17 and 18 and the metal pipe material 14 sandwiching the metal pipe material 14 and exists in the metal pipe material 14. Due to the resistance, the metal pipe material 14 itself generates heat due to Joule heat. Then, the voltage value measured by the voltmeter 53 gradually increases, and energization is terminated when the voltage value reaches a predetermined value.

  Subsequently, the blow 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 mold 11 and the cavity 24 of the upper mold 12 are combined, and the metal pipe material 14 is disposed and sealed in the cavity portion between the lower mold 11 and the upper mold 12.

  Thereafter, the cylinder unit 42 of the gas supply mechanism 40 is operated to advance the seal member 44 to seal both ends of the metal pipe material 14. At this time, as shown in FIG. 2 (b), the seal member 44 is pressed against the end portion of the metal pipe material 14 on the electrode 18 side, so that the boundary between the concave groove 18a and the tapered concave surface 18b of the electrode 18 is exceeded. A portion protruding toward the seal member 44 is deformed in a funnel shape so as to follow the tapered concave surface 18b. Similarly, when the seal member 44 is pressed against the end portion of the metal pipe material 14 on the electrode 17 side, a portion protruding to the seal member 44 side from the boundary between the groove 17a and the tapered concave surface 17b of the electrode 17 is It 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, and the metal pipe material 14 softened by heating is formed so as to follow the shape of the cavity portion.

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

  The outer peripheral surface of the metal pipe material 14 swelled by blow molding is brought into contact with the cavity 16 of the lower mold 11 and rapidly cooled, and at the same time is brought into contact with 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 at a low temperature, if the metal pipe material 14 comes into contact, the heat of the pipe surface is taken away to the mold side at once, and quenching is performed. Such a cooling method is called mold contact cooling or mold cooling. Immediately after being quenched, austenite transforms to martensite (hereinafter, austenite transforms to martensite is referred to as martensite transformation). In the second half of the cooling, the cooling rate was reduced, so that martensite was transformed into another structure (truthite, sorbite, etc.) by recuperation. Therefore, it is not necessary to perform a separate tempering process. In the present embodiment, cooling may be performed by supplying a cooling medium into the cavity 24, for example, instead of or in addition to mold cooling. For example, the metal pipe material 14 is brought into contact with the mold (upper mold 12 and lower mold 11) until the temperature at which martensitic transformation begins, and then the mold is opened and the cooling medium (cooling gas) is used as the metal pipe material. The martensitic transformation may be generated by spraying on 14.

  As described above, blow molding is performed on the metal pipe material 14, and then cooling is performed to perform mold opening, thereby obtaining a metal pipe having a substantially rectangular cylindrical main body, for example.

  Here, when the arc discharge EA is generated between the electrodes 17 and 18 and the metal pipe material 14 during the energization heating described above, a very high arc voltage is generated as shown in FIG. As a result, the voltage value rises sharply.

  The arc discharge detector 70 a detects the occurrence of arc discharge EA between the electrodes 17 and 18 and the metal pipe material 14 based on the voltage value measured by the voltmeter 53. Specifically, as shown in FIG. 4, the occurrence of arc discharge EA is detected based on the amount of voltage change (dv / dt; differentiation) per unit time. More specifically, it is determined that arc discharge EA has occurred when the amount of change in voltage per unit time is equal to or greater than a predetermined value. This predetermined value is a predetermined value, and is a value with which it can be determined that the arc discharge EA has occurred.

  When the controller 70 detects the occurrence of the arc discharge EA, it sends a command to the warning device 71 to generate a warning by, for example, a lamp, sound, screen display, or the like. This warning may be performed when the arc discharge detector 70a detects arc discharge once or when a predetermined number of times is detected. Moreover, when the arc discharge detection unit 70a detects a predetermined number of times, a warning that prompts maintenance of the electrodes 17 and 18 or replacement of the electrodes 17 and 18 may be used.

  As described above, according to the present embodiment, when the electric power is supplied to the metal pipe material 14 via the electrodes 17 and 18 to heat the current and the voltage between the electrodes 17 and 18 is measured by the voltmeter 53. Furthermore, when an arc discharge EA occurs between the metal pipe material 14 and the electrodes 17 and 18 in contact with the metal pipe material 14, a very high arc voltage is generated. Therefore, based on the voltage value measured by the voltmeter 53. The arc discharge detector 70a can detect the occurrence of arc discharge EA between the electrodes 17, 18 and the metal pipe material 14. Therefore, thereafter, appropriate processing such as maintenance of the electrodes 17 and 18 or replacement of the electrodes 17 and 18 can be performed based on the detection result.

  Further, according to the present embodiment, the arc discharge detector 70a detects the occurrence of the arc discharge EA based on the amount of change in the voltage per unit time, and thus can reliably detect the occurrence of the arc discharge EA.

  In addition, since a warning device 71 is provided to warn when the occurrence of arc discharge EA is detected, the operator can be warned that arc discharge EA has occurred, and maintenance of electrodes 17 and 18 or replacement of electrodes 17 and 18 can be performed. It is possible to recognize whether or not to perform such processing.

  Here, the warning device 71 warns when the occurrence of the arc discharge EA is detected a predetermined number of times, specifically, the arc discharge detection unit 70a has predetermined the occurrence of the arc discharge EA. If a warning device that warns in response to a command from the control unit 70 is detected a plurality of times, the operator can be warned that a predetermined number of arc discharges EA have occurred, and maintenance of the electrodes 17 and 18 or the electrodes 17 and 18 can be performed. It is possible to recognize that it is time to exchange.

  Further, when the warning device 71 detects the occurrence of the arc discharge EA a predetermined number of times, a warning device that prompts maintenance of the electrodes 17 and 18 or replacement of the electrodes 17 and 18, specifically, arc discharge detection When the unit 70a detects the occurrence of the arc discharge EA a predetermined number of times, a warning device that prompts maintenance of the electrodes 17 and 18 or replacement of the electrodes 17 and 18 according to a command from the control unit 70 is predetermined for the operator. The number of arc discharges EA generated can be positively warned by, for example, displaying the time when the electrodes 17 and 18 are being maintained or the electrodes 17 and 18 are being replaced. Maintenance or replacement of the electrodes 17, 18 can be performed.

  Here, as another embodiment of the arc discharge detector 70a, as shown in FIG. 5B, the occurrence of arc discharge EA is detected based on the difference between the voltage value measured by the voltmeter 53 and the set value V1. You may make it do. The voltage value V1 as the set value here is a predetermined voltage value, and is a voltage value at which it can be determined that the arc discharge EA has occurred. Then, arc discharge detector 70a determines whether or not arc discharge EA has occurred based on the difference between the measured voltage value and set value V1. Here, it is determined that the arc discharge EA has occurred when the voltage value measured by the voltmeter 53 exceeds the set value V1.

  According to such an arc discharge detector 70a, since the occurrence of arc discharge is detected based on the difference between the measured voltage value and a predetermined set value V1, the occurrence of arc discharge EA can be reliably detected. . When the arc discharge EA is detected in this way, the warning device 71 has the same actions and effects as described above.

  The present invention has been specifically described above based on the embodiment. However, the present invention is not limited to the above embodiment. For example, in the above embodiment, the electrodes 17 and 18 are two. Three or more electrodes may be added by adding electrodes to the inner side in the axial direction from 17 and 18.

  Moreover, in the said embodiment, the arc discharge detection part 70a detects generation | occurrence | production of arc discharge based on the variation | change_quantity of the voltage per unit time in one embodiment, and measured voltage value in other embodiment. The occurrence of arc discharge is detected based on the difference between the predetermined value and the preset value, but the occurrence of arc discharge is detected based on the amount of voltage change per unit time, and the measured voltage value The arc discharge may be detected when the occurrence of the arc discharge is detected based on a difference from a predetermined set value.

  Moreover, in the said embodiment, although the shaping | molding object is made into the metal pipe material 14, it is not limited to the metal pipe material 14, It can apply also to a metal rod-shaped body, a metal plate-shaped body, etc. It can be applied to a metal body that extends to some extent. The forming apparatus can also be a forging apparatus that performs energization heating without supplying gas.

  DESCRIPTION OF SYMBOLS 10 ... Current heating apparatus, 14 ... Metal pipe material (metal body), 17, 18 ... Electrode, 53 ... Voltmeter (voltage measurement part), 70a ... Arc discharge detection part, 71 ... Warning apparatus.

Claims (6)

An electric heating device for supplying electric power to a metal body and energizing and heating the metal body,
At least two electrodes in contact with the metal body;
A voltage measuring unit for measuring a voltage between the electrodes;
An electric heating apparatus comprising: an arc discharge detection unit that detects occurrence of arc discharge between the electrode and the metal body based on a voltage value measured by the voltage measurement unit.   2. The electric heating apparatus according to claim 1, wherein the arc discharge detection unit detects the occurrence of arc discharge based on the amount of change in voltage per unit time.   2. The electric heating apparatus according to claim 1, wherein the arc discharge detector detects the occurrence of arc discharge based on a difference between the measured voltage value and a predetermined set value.   The electrification heating device according to any one of claims 1 to 3, further comprising a warning device that warns when the occurrence of arc discharge is detected.   The electric heating apparatus according to any one of claims 1 to 3, further comprising a warning device that warns when occurrence of arc discharge is detected a plurality of times determined in advance.   The apparatus according to any one of claims 1 to 3, further comprising a warning device that prompts maintenance of the electrode or replacement of the electrode when occurrence of arc discharge is detected a predetermined number of times. Electric heating device.

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