JP2014002991A - Joule heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Joule heating device capable of automatically detecting occurrence of heating failures.SOLUTION: A Joule heating device heating food and drink having fluidity as a heated object by Joule heat comprises: a heating unit to which a flow channel is formed, and provided with an electrode pair; and a power supply unit supplying a power to the electrode pair. A controller 26 compares a steady current value at the time when the heated object is heated in a steady state and a detected current value flowing in the heated object with each other, and when the detected current value is different from the steady current value, determines that the heating unit is in a failure state by means of a failure determination part 34. An alarm 35 notifies of failures when it is determined that the heating unit is in the failure state.

Description

  The present invention relates to a joule heating device that heats electricity while continuously feeding a food or drink having fluidity as an object to be heated, and particularly relates to a joule heating device that detects a heating failure.

  Food and drink with low viscosity such as juice, soup, and sometimes eggs, and food and drink with fluidity such as pasty food with high viscosity such as jam and miso, etc. In order to heat by Joule heat while being transported in the flow path formed in Joule, a Joule heating device as described in Patent Document 1 has been developed. The heating unit is provided with a pair of electrodes. By supplying a voltage between the electrodes and passing a current through the object to be heated, the object to be heated generates heat due to Joule heat and is heated. This type of Joule heating device has a form formed by one heating unit and a form formed by connecting a plurality of heating units in series.

  As described in Patent Document 1, the heating unit has a tubular member formed by a plurality of ring-shaped electrodes and a plurality of insulating cylindrical bodies arranged between the electrodes. There is a type having a type, a tubular member having a square cross section, and two plate-like electrodes disposed inside each other so as to face each other. Furthermore, as a form of the heating unit, a type having a tubular member formed of an insulating material and two plate-like electrodes arranged opposite to each other in both end faces of the tubular member, and a tubular member There is a type having a cylindrical electrode disposed on the inner peripheral surface of the tube and a rod-shaped electrode disposed at the center of the tubular member.

  In any type, the temperature of the object to be heated at the inflow portion and the outflow portion of the heating unit is detected by a temperature sensor, and the voltage supplied between the electrodes is feedback controlled according to the temperature difference between the inflow portion and the outflow portion. Thus, the heated object is heated to a set temperature while being conveyed through the flow path of the heating unit.

Japanese Patent No. 4603932

  When energization heating is performed while conveying an object to be heated in the heating unit, the object to be heated may adhere to the inner peripheral surface of the heating unit as a scale in a layered manner over time. When the adhesion amount of the scale increases, the current flowing through the object to be heated decreases and the heating temperature of the object to be heated decreases. When the heating temperature of the object to be heated decreases, the supply voltage to the electrode is increased by feedback control. When the supply voltage is increased, sparks are likely to occur between the scales. When sparks are generated, the object to be heated cannot be heated to the set temperature. Therefore, it is necessary to regularly clean the inner surface of the heating unit and remove the scale to prevent the occurrence of sparks.

  However, the degree of progress of adhesion of the scale to the inner surface of the heating unit differs depending on the type of the object to be heated. There is a tendency for the scale to adhere to the inner surface of the film relatively quickly. If a transparent part is provided on the heating pipe of the heating unit, the degree of scale adhesion to the inner surface of the heating unit can be observed from the outside. However, the operator needs to frequently observe the scale adhesion state, and Joule heating is required. There is a problem that the operability of the apparatus is not good. In particular, when heating multiple types of objects to be heated with a single joule heating device, the degree of progress of the scale differs depending on the type of objects to be heated, and the period during which the heating unit is cleaned is heated. There is a problem that the operability of the joule heating device is not good because it is necessary to make the difference depending on the type of the object. For this reason, in order to improve the operability of the joule heating device, it is desired to automatically detect the occurrence of heating defects such as scales and sparks.

  An object of the present invention is to provide a joule heating device that automatically detects the occurrence of a heating failure.

  The Joule heating device of the present invention is a Joule heating device that heats food and drink having fluidity by Joule heat while continuously transporting food and drinks as heated objects in the channel, and the electrode is formed while the channel is formed. A heating unit provided with a pair, a power supply unit for supplying power to the electrode pair, a current detection means for detecting a current of the electrode pair, and a steady current value when the object to be heated is heated in a steady state And the detected current value flowing through the object to be heated, and the detected current value is different from the steady current value, the failure determining means for determining that the heating unit is in a defective state, and the heating unit is defective And a warning means for warning a fault when the fault determination means determines that the state is in a state.

  The Joule heating device of the present invention is a Joule heating device that heats food and drink having fluidity by Joule heat while continuously transporting food and drinks as heated objects in the channel, and the electrode is formed while the channel is formed. A heating unit provided with a pair, a power supply unit for supplying power to the electrode pair, a voltage detection means for detecting the voltage of the electrode pair, and a steady voltage value when the object to be heated is heated in a steady state And the detected voltage value flowing through the object to be heated, and when the detected voltage value becomes higher than the steady voltage value, it is determined that the scale is attached to the inner surface of the flow path of the heating unit. It is characterized by having a failure determination means and an alarm means for alarming a failure when the failure determination means determines that the heating unit is in a failure state.

  According to the present invention, if a heating failure such as scale adhesion occurs on the inner surface of the flow channel of the heating unit in which the flow channel for continuously conveying and guiding the food to be heated is generated, the heating failure has occurred. Since the alarm is automatically notified to the alarm device, the operator does not always need to observe the heating state of the joule heating device frequently, and the operability of the joule heating device is improved.

It is sectional drawing which shows the heating unit of the Joule heating apparatus of this invention. It is a block diagram which shows the power supply unit shown by FIG. It is a block diagram which shows the control circuit of a power supply unit. It is a block diagram which shows the modification of the control circuit of a power supply unit. It is sectional drawing which shows the modification of a heating unit. It is sectional drawing which shows the other modification of a heating unit. It is sectional drawing which shows the other modification of a heating unit.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a heating unit 10 constituting a Joule heating device, and this heating unit 10 has a tubular member having a circular cross section, that is, a heating pipe 12 in which a flow path 11 for guiding an object to be heated is formed. doing. The heating pipe 12 is formed by a plurality of ring-shaped electrodes 13 and a plurality of cylindrical bodies 14 disposed therebetween. The heating unit 10 has a heating pipe 12 composed of an electrode 13 and a cylindrical body 14, and the heating pipe 12 is provided with a pair of electrodes 13. Each electrode 13 is formed of a conductor such as titanium, and each cylindrical body 14 is formed of an insulator such as resin. At both ends of the heating pipe 12, joint members 15 and 16 on the inflow side and the outflow side are attached. A power supply unit 17 is connected to each electrode 13 via a cable, and as shown by an arrow, the power supply unit so that the electrodes 13 adjacent to each other in the flowing direction of the object to be heated have opposite polarities. A high frequency current is supplied from 17.

  Although the heating unit 10 shown in FIG. 1 has eight electrodes 13, the number of electrodes 13 constituting the heating unit 10 is arbitrarily set. Although FIG. 1 shows a joule heating device composed of one heating unit 10, in a form in which a joule heating device is formed by a plurality of heating units 10, a plurality of heating units 10 are connected in series. In any form, the inflow-side joint member 15 is supplied with food and drink having fluidity to be heated as an object to be heated through the inflow-side pipe 18. As described in Patent Document 1, the pipe 18 is connected to a hopper, and an object to be heated is supplied from the hopper to the joint member 15 on the inflow side by a pump. If a preheating device is arranged between the pump and the joint member 15 on the inflow side, the object to be heated supplied to the heating unit 10 is heated to a predetermined temperature in advance. Further, when the heated object heated to a predetermined temperature by the heating unit 10 is held at the heating temperature for a certain time, a hold pipe is connected to the pipe 19 connected to the joint member 16 on the outflow side of the heating unit 10. The The object to be heated that has been held in the hold pipe for a certain period of time and subjected to heat treatment is cooled to a predetermined temperature by the cooling device, and then sent to the recovery tank. An inlet-side temperature sensor 21 is provided in the pipe 18 to detect the temperature of the object to be heated supplied to the heating unit 10, and an outlet-side temperature sensor is used to detect the temperature of the object to be heated after heating. 22 is provided in the pipe 19.

  FIG. 2 is a block diagram showing the power supply unit 17 shown in FIG. The power supply unit 17 has a rectifier 23 that converts a three-phase AC voltage into a DC voltage. The rectifier 23 is formed by a thyristor SCR and converts an AC voltage of 200 to 400 V supplied from the outside into a DC voltage of 250 to 500 V. The output terminal of the rectifier 23 is connected to the inverter 24, and the voltage converted into direct current is converted into a high frequency voltage of 20 kHz by the inverter 24. The SCR 23 has a function of adjusting the output voltage as described above. The output terminal of the inverter 24 is connected to the transformer 25. The output of the inverter 24 is boosted or depressurized by the transformer 25 and supplied to the electrode 13.

  FIG. 3 is a block diagram showing a control circuit of the power supply unit 17, and output signals from the temperature sensor 21 on the inlet side and the temperature sensor 22 on the outlet side are output to the controller 26. The controller 26 includes a microprocessor that calculates control signals, a memory 27 that stores arithmetic expressions and data, and the like. Based on the temperature difference between the inlet side temperature and the outlet side temperature of the heating unit 10, the controller 26 outputs a control signal to the SCR 23 so that the heating temperature of the heated object flowing out of the heating unit 10 becomes the set temperature. The voltage supplied to the electrode 13 is controlled by the SCR 23. In this way, the voltage supplied to the electrode 13 is feedback controlled based on the temperature difference. The voltage supplied to the electrode 13 by feedback control is set in a range in which the power W supplied from the power supply unit 17 to the electrode 13, that is, the product of the voltage value V and the current value I does not exceed a certain value.

  The controller 26 is connected to an operation board 28 for inputting an energization condition. By operating a key provided on the operation board 28, an energization condition such as a voltage value corresponding to the type of the object to be heated. Is input, and the input energization condition is stored in the memory 27 of the controller 26. A monitor unit, that is, a display unit 29 is connected to the controller 26, and the input energization conditions, the temperature of the heated object during energization heating, and the like are displayed.

  As shown in FIG. 2, a first ammeter 31 and a second ammeter 32 are provided on the secondary side of the transformer 25 as current detection means for detecting the current flowing through the electrode 13. The detection signals of the respective ammeters 31 and 32 are sent to the controller 26 as shown in FIG. The controller 26 has a steady-state current value calculation unit 33. The steady-state current value calculation unit 33 averages the current value over a predetermined time based on the signal from the first ammeter 31, and heats the object to be heated in a steady state. The steady-state current value (RSP value A) is calculated. The controller 26 has a failure determination unit 34, which compares the measured current value, that is, the detected current value (PV value A) and the steady current value (RSP value A) based on the signal from the ammeter 32. Then, it is determined whether or not the heating unit 10 is in a defective state. In FIG. 3, the steady current value calculation unit 33 and the malfunction determination unit 34 are regarded as functional configurations of the controller 26 and are shown as blocks.

  When the heated object is continuously conveyed to the inner surface of the flow channel 11 of the heating unit 10 and energized and heated, a certain amount or more of the scale adheres to the inner surface of the flow channel of the heating unit 10 and the scale is attached. And when a spark generate | occur | produces, it determines with the heating unit 10 being in a heating failure state in any case. When scale adheres to the inner surface of the flow path, the detected current value (PV value A) flowing through the electrode 13 detected by the ammeter 32 gradually decreases as the amount of adhesion increases. The current value of the scale determination value ΔIs is input to the memory 27 in advance, and when the detected current value (PV value A) is lower than the scale determination value ΔIs with respect to the steady current value (RSP value A), the inner surface of the flow path It is determined that the scale attached to the surface exceeds the allowable value, that is, the scale is attached to the inner surface of the flow path. As the scale judgment value ΔIs, the detected current value (PV value A) is set to −3% or less than the steady current value (RSP value A), and the scale is washed and removed when it falls to −3% or less. It is determined that it is in a state where it has adhered to a necessary level.

  If it is determined that the scale is attached, the controller 26 outputs an alarm signal to an alarm device 35 as an alarm means. A lamp or buzzer is used as the alarm device 35. The lamp lights up to indicate that the scale is attached, and the buzzer displays a sound indicating that the scale is attached. One or both of the lamp and the buzzer are connected to the controller 26 as alarm means. One or both of the lamp and the buzzer may be provided on the operation board 28.

  2 and 3, the first ammeter 31 for calculating the steady current value (RSP value A) and the second current for detecting the detected current value (PV value A). 32 in total. On the other hand, the current value in a certain time is averaged by a signal from one ammeter to calculate the steady current value (RSP value A) when the object to be heated is heated in a steady state, and the detected current When the value (PV value A) is detected, the steady current value (RSP value A) and the detected current value (PV value A) are obtained by one ammeter.

  Further, the operator may input the steady current value (RSP value A) and the scale determination value ΔIs in advance by operating the keys on the operation board 28. In that case, the keyed steady current value (RSP value A) and the scale determination value ΔIs are stored in the memory 27, and the failure determination unit 34 stores the steady current value (RSP value A) stored in the memory 27, By comparing the detected current value (PV value A) detected by the ammeter, the malfunctioning state of the heating unit 10 is determined as described above. This form also has one ammeter.

  When a spark occurs on the inner surface of the flow path of the heating unit 10, the detected current value (PV value A) flowing through the electrode 13 detected by the ammeter 32 increases rapidly. A spark determination value ΔIp is input to the memory 27 in advance, and when the detected current value (PV value A) is larger than the spark determination value ΔIp with respect to the steady current value (RSP value A), a spark is generated on the inner surface of the flow path. Is determined to have occurred. As the spark determination value ΔIp, the detected current value (PV value) is set to + 3% or more than the steady-state current value (RSP value A), and a spark is generated when the detected current value increases by 3% or more. judge.

  If it is determined that a spark has occurred, the controller 26 outputs an alarm signal to an alarm device 35 as an alarm means. As the alarm device 35, a lamp or a buzzer is used as in the case of scale adhesion, and heating is stopped when a spark occurs. The spark generation alarm means and the scale generation alarm means described above may be provided separately, and an alarm may be output when any of the malfunction conditions occur.

  As described above, in the power supply unit 17 shown in FIG. 2, both the case where the scale adheres to the inner surface of the flow path 11 of the heating unit 10 and the case where the spark occurs in the flow path as a heating failure of the heating unit 10. For each, an alarm is output. On the other hand, it is good also as a form which outputs a warning only when a scale adheres, and it is good also as a form which stopped a heating and output a warning only when a spark generate | occur | produces.

  As shown in FIG. 2, without providing two ammeters 31 and 32 on the secondary side of the transformer 25, the secondary side of the inverter 24 and the secondary side of the rectifier 23, as shown by a two-dot chain line, May be provided on at least one of them, and an ammeter may be provided on all of them. In the form in which ammeters are provided at a plurality of locations, the failure state may be determined and displayed separately based on each ammeter, or the failure state may be determined based on an average value. Even when ammeters are provided at a plurality of locations, as described above, the steady-state current value (RSP value A) and the detected current value (PV value A) may be obtained from the signals from the respective ammeters. The steady current value (RSP value A) may be input by key operation.

  As mentioned above, based on the temperature difference between the inlet side temperature and the outlet side temperature of the heating unit 10, it is supplied to the electrode 13 so that the heating temperature of the object to be heated flowing out of the heating unit 10 becomes the set temperature. The voltage is feedback controlled. When the scale adheres to the inner surface of the flow path, the temperature on the outlet side of the heating unit 10 becomes lower than the set value, so that the voltage is increased by feedback control. However, the feedback control is set to be performed in a range where the increased voltage does not exceed the feedback limit value with respect to the steady voltage value (RSP value A). When the output side temperature is lowered to such an extent that this feedback limit value is exceeded, the scale attached to the inner surface of the flow path is increased to such an extent that sparks are likely to occur. Therefore, by obtaining the voltage value applied to the electrode 13, it can be detected that the scale is attached.

  FIG. 4 is a block diagram showing a modification of the control circuit of the power supply unit. In FIG. 4, members that are the same as those shown in FIG. 3 are given the same reference numerals. In the control circuit, as described above, it is detected that the scale is attached based on the voltage value supplied to the electrode 13.

  As shown in FIG. 2, a first voltmeter 41 and a second voltmeter 42 are provided on the secondary side of the transformer 25 as voltage detection means for detecting the voltage between the paired electrodes 13. The detection signals of the respective voltmeters 41 and 42 are sent to the controller 26 shown in FIG.

  The controller 26 has a steady voltage value calculation unit 43. The steady voltage value calculation unit 43 averages the voltage value over a predetermined time based on the signal from the first voltmeter 41 and heats the object to be heated in a steady state. The steady-state voltage value (RSP value B) is calculated. The controller 26 has a failure determination unit 44. The failure determination unit 44 compares the measured voltage value based on the signal from the voltmeter 42, that is, the detected voltage value (PV value B) and the steady voltage value (RSP value B). Then, it is determined whether or not the heating unit 10 is in a defective state. Also in FIG. 4, the steady voltage value calculation unit 43 and the failure determination unit 44 are regarded as functional configurations of the controller 26 and are shown as blocks.

  When the scale adheres to the inner surface of the flow path, the voltage supplied to the electrode 13 is controlled by feedback control as the amount of adhesion increases. When the output temperature decreases to the extent that the feedback limit value is exceeded, the scale adhering to the inner surface of the flow path increases to the extent that spark is likely to occur, and the voltage value above the feedback limit value is the scale judgment value. As ΔVs, it is previously input to the memory 27.

  Therefore, when the detected voltage value (PV value B) is higher than the scale determination value ΔVs with respect to the steady voltage value (RSP value B), the scale attached to the inner surface of the flow path exceeds the allowable value, that is, the flow path It is determined that the scale is attached to the inner surface. As the scale determination value ΔVs, the detected voltage value (PV value B) is set to + 5% or more than the steady voltage value (RSP value B), and the scale is attached when it rises by + 5% or more. Is determined.

  If it is determined that the scale is attached, the controller 26 outputs an alarm signal to an alarm device 35 as an alarm means, as in the case described above.

  In the form shown in FIG. 4, a first voltmeter 41 for calculating a steady voltage value (RSP value B), a second voltmeter 42 for detecting a detected voltage value (PV value B), have. On the other hand, a voltage from a single voltmeter is averaged to calculate a steady voltage value (RSP value B) when the object to be heated is heated in a steady state, and the detected voltage When the value (PV value B) is detected, the steady voltage value (RSP value B) and the detected voltage value (PV value B) are obtained by one voltmeter.

  Further, the steady voltage value (RSP value B) may be input in advance by the operator by key operation on the operation board 28. In that case, the steady-state voltage value (RSP value B) input by the key is stored in the memory 27, and the failure determination unit 44 detects the steady-state voltage flow value (RSP value B) stored in the memory 27 by the voltmeter. The detected voltage value (PV value B) is compared, and the malfunction state of the heating unit 10 is determined as described above. This form also has one voltmeter.

  As shown in FIG. 2, the two voltmeters 41 and 42 are not provided on the secondary side of the transformer 25, but the secondary side of the inverter 24 and the secondary side of the rectifier 23, as indicated by a two-dot chain line. It may be provided at least on one side, or a voltmeter may be provided on all. In a form in which voltmeters are provided at a plurality of locations, the failure state may be determined separately based on each voltmeter, or the failure state may be determined based on an average value. Even when voltmeters are provided at multiple locations, the steady voltage value (RSP value B) and the detected voltage value (PV value B) should be obtained from the signals from each voltmeter, as in the case of the ammeter described above. Alternatively, a steady voltage value (RSP value B) may be input by key operation.

  In FIG. 2, the current supplied to the electrode 13 is detected to detect whether or not a scale is attached to the inner surface of the flow path of the heating unit 10 and whether or not a spark is generated. The voltage supplied to 13 is detected to detect whether or not the scale is attached to the inner surface of the flow path of the heating unit 10. In this embodiment, each determination result can be displayed on the display unit 29, or the alarm device 35 can be operated. However, the ammeter shown in FIG. 2 is not required in the form of detecting whether or not the scale is attached only by the voltage.

  FIG. 5A is a longitudinal sectional view showing a modification of the heating unit, and FIG. 5B is a transverse sectional view of FIG. The heating unit 10 includes a heating pipe 12 having a square cross section in which a flow path 11 for guiding an object to be heated is formed. The heating pipe 12 is formed of an insulating material such as resin, and two plate-like electrodes 13 are attached to the inner surface of the heating pipe 12 so as to face each other, and a power supply unit 17 is connected to each electrode 13 by a cable. Has been. At both ends of the heating pipe 12, joint portions 15 and 16 on the inflow side and the outflow side are attached.

  FIG. 6 is a longitudinal sectional view showing another modification of the heating unit. The heating unit 10 includes a heating pipe 12 having a circular cross section in which a flow path 11 for guiding an object to be heated is formed. The heating pipe 12 is formed of an insulating material such as a resin. Plate-like electrodes 13 are attached to both end faces of the heating pipe 12 so as to face each other, and a power supply unit 17 is connected to each electrode 13 by a cable. At both ends of the heating pipe 12, joint portions 15 and 16 on the inflow side and the outflow side are provided. In this type of heating unit 10, the heating pipe 12 may have a square cross section.

  FIG. 7 is a longitudinal sectional view showing another modification of the heating unit. The heating unit 10 includes a heating pipe 12 having a circular cross section in which a flow path 11 for guiding an object to be heated is formed, and both ends of the heating pipe 12 are closed by end plate portions 20. The plate portion 20 is formed of an insulating material such as resin. A cylindrical electrode 13 a is fixed to the inner surface of the heating pipe 12, and both ends of the rod-shaped electrode 13 b disposed at the center of the heating pipe 12 are fixed by end plate portions 20. A power supply unit 17 is connected to both cylindrical and rod-shaped electrodes 13a and 13b by cables, and inflow and outflow side joint portions 15 and 16 are provided at both ends of the heating pipe 12, respectively.

  In the heating unit 10 shown in FIGS. 5 to 7, there are a form in which a Joule heating device is configured by a single heating unit and a form in which a Joule heating device is configured by connecting a plurality of heating units in series. is there.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 10 Heating unit 11 Flow path 12 Heating pipe 13 Electrode 14 Cylindrical body 15 Joint member 16 Joint member 17 Power supply unit 21 Temperature sensor 22 Temperature sensor 23 Rectifier 24 Inverter 25 Transformer 26 Controller 27 Memory 28 Operation board 29 Display part 31, 32 Current Total 33 Steady-state current value calculation unit 34 Defect determination unit 35 Alarm 41, 42 Voltmeter 43 Steady-state voltage value calculation unit 44 Defect determination unit

Claims (8)

A Joule heating device for heating by Joule heat while continuously transporting food and drink having fluidity as an object to be heated in a flow path,
A heating unit in which the flow path is formed and an electrode pair is provided;
A power supply unit for supplying power to the electrode pair;
Current detecting means for detecting the current of the electrode pair;
The heating unit malfunctions when the detected current value is different from the steady current value by comparing the steady current value when the heated object is heated in a steady state with the detected current value flowing through the heated object. A failure determination means for determining that the state is present;
A joule heating device comprising alarm means for alarming a malfunction when the malfunction determination means determines that the heating unit is in a malfunction state.   The Joule heating device according to claim 1, wherein when the detected current value is lower than the steady current value, it is determined that a scale adheres to the inner surface of the flow path of the heating unit. apparatus.   The joule heating device according to claim 1, wherein when the detected current value is higher than the steady current value, it is determined that a spark is generated on the inner surface of the flow path of the heating unit. apparatus.   The joule heating device according to any one of claims 1 to 3, further comprising a storage unit that stores the steady-state current value, wherein the failure determination unit includes the steady-state current value stored in the storage unit and the storage unit. A joule heating device characterized by comparing a detected current value.   The joule heating apparatus according to any one of claims 1 to 3, wherein an average value of the detected current values at a predetermined time by the current detecting means is set to the steady current value, and the failure determining means is set. A joule heating device that compares the steady current value with the detected current value. A Joule heating device for heating by Joule heat while continuously transporting food and drink having fluidity as an object to be heated in a flow path,
A heating unit in which the flow path is formed and an electrode pair is provided;
A power supply unit for supplying power to the electrode pair;
Voltage detection means for detecting the voltage of the electrode pair;
When the detected voltage value is higher than the steady voltage value by comparing a steady voltage value when the heated object is heated in a steady state and a detected voltage value flowing through the heated object, the heating unit A failure determination means for determining that a scale is attached to the inner surface of the flow path;
A joule heating device comprising alarm means for alarming a malfunction when the malfunction determination means determines that the heating unit is in a malfunction state.   7. The joule heating device according to claim 6, further comprising storage means for storing the steady voltage value, wherein the failure determination means compares the steady voltage value stored in the storage means with the detected voltage value. A joule heating device.   7. The joule heating device according to claim 6, wherein an average value of the detected voltage values at a predetermined time by the voltage detecting means is set to the steady voltage value, and the failure determining means is configured to set the steady voltage value and the detected voltage. A joule heating device characterized by comparing values.

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