JP2020035008A - Temperature control system, temperature control method, and program - Google Patents

Abstract

To prevent the temperature of an electric heating body forming an electric resistance heater from exceeding a predetermined limit temperature.SOLUTION: The present invention relates to a temperature control system that includes an electric resistance heater 20 and a temperature sensor 30 mounted on an object to be heated 90, and controls an energization current to the heater 20 on the basis of the temperature TO of the object to be heated 90 output by the temperature sensor 30. The temperature control unit 40 creates an operation amount MV for controlling the object to be heated 90 to be a predetermined target temperature T target, and causes the energization current according to the operation amount MV to flow to an electric heating body 20x forming the heater 20 to control the temperature TO of the object to be heated 90. During temperature control of the object to be heated 90, electric heating body temperature acquisition units 44, 45 acquire the current temperature TH of the electric heating body 20x. When the current temperature TH of the electric heating body 20x exceeds a predetermined limit temperature T limit, the temperature control unit 40 reduces the operation amount MV to reduce the temperature of the electric heating body 20x to be the limit temperature T limit or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a temperature control system and a temperature control method, and more specifically, includes an electric resistance heater and a temperature sensor mounted on an object to be heated, and controls a current supplied to the electric resistance heater based on an output of the temperature sensor. The present invention relates to a temperature control system and a temperature control method. The present invention also relates to a program for causing a computer to execute such a temperature control method.

  Conventionally, as this type of temperature control system, as disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-053437), for example, an electric resistance heater is provided on an object to be heated (a die for press working). A rod-shaped heater (a commercially available product in which a heating wire is covered with a heat-resistant insulator and housed in a steel pipe) and a temperature sensor for measuring the temperature of the object to be heated are mounted, and the object to be heated reaches a target temperature. As described above, there is known a device that controls a current supplied to the rod-shaped heater based on an output of the temperature sensor.

JP 2003-053437 A

  The present inventor has analyzed a temperature control system including an electric resistance heater similar to that in Patent Document 1, and found that from the start of energization to the electric resistance heater until the target to be heated reaches a target temperature (for example, 200 ° C.). During this time, it was found that the temperature of the heating wire inside the electric resistance heater reached 800 ° C. to 1000 ° C. In addition, although a commercially available electric resistance heater itself does not usually have a built-in temperature sensor, the present inventor specifically analyzed by incorporating a built-in temperature sensor.

  Here, it is said that, for example, one type of nickel chrome wire and two types of nickel chrome wire, which are typical heating wires, are accelerated in deterioration when approximately 700 ° C. or more. In the case of other materials, for example, one type of iron chromium wire and two types of iron chromium wire, the deterioration is accelerated when each exceeds a certain temperature. This situation is not limited to the heating wire, but also applies to the electrotropics. The “heating wire” and the “electrotroph” are collectively referred to as an “heating body”.

  Therefore, an object of the present invention is to provide a temperature control system as described above, which can prevent a temperature of an electric heating element constituting an electric resistance heater from exceeding a predetermined limit temperature. Another object of the present invention is to provide a temperature control method for such a temperature control system, which can prevent a temperature of an electric heater constituting an electric resistance heater from exceeding a predetermined limit temperature. Is to do. Another object of the present invention is to provide a program for causing a computer to execute such a temperature control method.

In order to solve the above-described problems, the temperature control system according to the present disclosure includes:
A temperature control system comprising an electric resistance heater and a temperature sensor mounted on a heating object, and controlling a current supplied to the electric resistance heater based on a temperature of the heating object output by the temperature sensor,
Create an operation amount for controlling the object to be heated to a predetermined target temperature, flow an energizing current according to the operation amount to the electric heating element constituting the electric resistance heater, and set a temperature of the object to be heated. A temperature control unit for controlling
During the temperature control of the heating object, comprising an electric heating element temperature acquisition unit that acquires the current temperature of the electric heating element,
When the current temperature of the electric heating element exceeds a predetermined limit temperature, the temperature control unit reduces the operation amount so as to suppress the electric heating element to a temperature equal to or lower than the temperature limit.

  Throughout this specification, energizing the electric resistance heater means energizing the electric heating element. "Electrification" of the electric heating element is typically performed along the longitudinal direction of the heating wire or the electric tropic forming the electric heating element. Further, the "limit temperature" of the electric heating element is sufficiently higher than the "target temperature" of the object to be heated (otherwise, the electric heating element is used to heat the object to be heated. I can't get it.) Typically, the “target temperature” of the object to be heated is assumed to be 100 ° C. to 200 ° C., and the “limit temperature” of the electric heating element is assumed to be 700 ° C., but is not limited thereto. .

  In the temperature control system according to the present disclosure, the temperature control unit creates an operation amount for controlling the object to be heated to a predetermined target temperature, and generates an operation amount according to the operation amount on the electric heating element that constitutes the electric resistance heater. The temperature of the object to be heated is controlled by passing the supplied current. During the temperature control of the heating target, the electric heating element temperature acquisition unit acquires the current temperature of the electric heating element. When the current temperature of the electric heating element exceeds a predetermined limit temperature, the temperature control unit reduces the operation amount so as to suppress the electric heating element to the temperature equal to or lower than the temperature limit. Thus, according to this temperature control system, it is possible to prevent the temperature of the electric heating element constituting the electric resistance heater from exceeding the limit temperature.

In one embodiment of the temperature control system,
The temperature control unit includes:
A first feedback control unit that creates a first manipulated variable such that a current temperature of the heating target output by the temperature sensor matches the target temperature;
A second feedback control unit that creates a second manipulated variable so that the current temperature of the electric heating element acquired by the electric heating element temperature acquisition unit matches the limit temperature;
A selector that compares the first operation amount with the second operation amount and selects a control unit that gives a smaller operation amount among the first feedback control unit and the second feedback control unit; And characterized in that:

  In the temperature control system according to the embodiment, in the temperature control unit, the first feedback control unit performs feedback control so that a current temperature of the heating target output by the temperature sensor matches the target temperature. First manipulated variable is created. The second feedback control unit creates a second operation amount for feedback control such that the current temperature of the electric heating element acquired by the electric heating element temperature acquisition unit matches the limited temperature. The selection unit compares the first operation amount with the second operation amount, and selects a control unit that gives a smaller operation amount among the first feedback control unit and the second feedback control unit. select. Thus, when the current temperature of the electric heating element exceeds a predetermined limit temperature, the operation amount is reduced so as to suppress the electric heating element to the temperature equal to or lower than the limit temperature.

  That is, the current temperature of the electric heating element is set to the limited temperature from the start of energization to the electric resistance heater (more precisely, the electric heating element; the same applies to the following) until the object to be heated reaches the target temperature. In the following case, by appropriately setting the gains of the feedback control of the first and second feedback control units, the first operation amount (the temperature of the heating target is raised to the target temperature) ) May be smaller than the second manipulated variable (trying to raise the temperature of the electric heating element to the limit temperature). In this case, the selection unit selects the first feedback control unit from the first feedback control unit and the second feedback control unit. Therefore, the temperature control section feeds an energizing current according to the first operation amount to the electric heating element constituting the electric resistance heater, and performs feedback control of the temperature of the heating target (original control).

  On the other hand, when the current temperature of the electric heating element exceeds the limit temperature during a period from the start of energization to the electric resistance heater to the target temperature of the heating object, the first operation amount (the The second manipulated variable (trying to lower the temperature of the electric heating element) may be smaller than that of trying to raise the temperature of the object to be heated. In this case, the selection unit selects the second feedback control unit from the first feedback control unit and the second feedback control unit. Therefore, the temperature control unit can control the temperature of the heating target by flowing an energizing current according to the second operation amount to the electric heating element constituting the electric resistance heater. This control is feedback control such that the current temperature of the electric heating element is made to coincide with the limit temperature. In this way, when the current temperature of the electric heating element exceeds the limit temperature, the operation amount is reduced so as to suppress the electric heating element to the temperature equal to or lower than the limit temperature.

In one embodiment of the temperature control system,
The electric heating element temperature acquisition unit,
During the temperature control of the heating object, a resistance measuring unit that measures the resistance value indicated by the electric heating element as a current resistance value,
During the temperature control of the heating object, an electric heating element temperature calculating unit that calculates a current temperature of the electric heating element according to the current resistance value based on a known temperature-resistance characteristic of the electric heating element. Features.

  In this specification, the term “temperature-resistance characteristic” means a phenomenon (characteristic) in which, when the temperature of the electric heater changes, the resistance value of the electric heater changes accordingly. The “resistance value” here is not limited to the resistance value (unit: Ω) itself, but is a ratio to a resistance value at a predetermined reference temperature (for example, normal temperature such as 23 ° C. or 25 ° C., or 0 ° C.). (Dimensionless). This ratio is typically calculated as (resistance value) / (reference temperature resistance value), but may be a reciprocal.

  In the temperature control system according to the embodiment, during the temperature control of the heating target, the resistance measuring unit included in the electric heating element temperature acquisition unit measures a resistance value indicated by the electric heating element as a current resistance value. . During the temperature control of the heating object, the electric heating element temperature calculation unit calculates a current temperature of the electric heating element according to the current resistance value based on a known temperature-resistance characteristic of the electric heating element. Thus, the current temperature of the electric heating element can be obtained during the temperature control of the heating target. In this case, for example, there is no need to provide an additional temperature sensor for measuring the temperature of the electric heating element inside the case constituting the electric resistance heater. Therefore, as the electric resistance heater, for example, a commercially available product in which an electric heating element is covered with a heat-resistant insulating material and housed in a steel pipe, such as a general rod heater, can be used.

In one embodiment of the temperature control system,
The electric heating element comprises a specific nickel-chromium wire or band having the maximum and minimum temperature-resistance characteristics,
The electric heating element temperature calculating section of the electric heating element temperature obtaining section, during the temperature control of the heating object, when the current resistance value of the electric heating element shows a maximum or a minimum, the current resistance value of the current resistance A temperature control system for calculating a current temperature of the electric heating element according to the maximum or the minimum.

  In the present specification, “a specific nickel chrome wire or band having a maximum versus a minimum in temperature versus resistance characteristics” is, for example, one type of nickel chrome wire for electric heating (abbreviation NCHW1) specified in Japanese Industrial Standards (JISC2520). ) Or one type of nickel chromium band for electric heating (abbreviation NCHRW1).

  For example, as described in the literature (US 2017/0359857 A1), a temperature-resistance characteristic of one type of nickel chrome wire, which is a typical heating wire, is plotted from 0 ° C. (or ordinary temperature) when graphed. It increases as the temperature rises, shows a maximum around 500 ° C., gradually decreases as the temperature rises, shows a minimum around 800 ° C., and rises again when the temperature further rises. The temperature at which the temperature versus resistance characteristic of the particular nickel chrome wire or band exhibits a maximum or minimum is known and determined. Therefore, in the temperature control system of this embodiment, the electric heating element is made of a specific nickel chrome wire or band having the maximum and minimum temperature-resistance characteristics. The electric heating element temperature calculating section of the electric heating element temperature obtaining section, during the temperature control of the heating object, when the current resistance value of the electric heating element shows a maximum or a minimum, the current resistance value of the current resistance A current temperature of the electric heating element according to the maximum or the minimum is calculated. Thus, the current temperature of the electric heating element can be accurately calculated. As a result, it is possible to accurately prevent the temperature of the electric heating element constituting the electric resistance heater from exceeding the limit temperature.

In one embodiment of the temperature control system,
The electric heating element temperature acquisition unit,
An additional temperature sensor provided inside the case constituting the electric resistance heater,
An electric heater temperature measuring unit that measures a current temperature of the electric heater based on an output of the additional temperature sensor during the temperature control of the heating target.

  In the temperature control system of this embodiment, an additional temperature sensor is provided inside a case constituting the electric resistance heater. During the temperature control of the heating target, the electric heating element temperature measuring unit included in the electric heating element temperature acquiring unit measures a current temperature of the electric heating element based on an output of the additional temperature sensor. Thus, the current temperature of the electric heating element can be obtained during the temperature control of the heating target.

In another aspect, the temperature control method of the present disclosure includes:
A temperature control method using an electric resistance heater and a temperature sensor mounted on a heating object, and controlling a current supplied to the electric resistance heater based on a temperature of the heating object output by the temperature sensor,
Create an operation amount for controlling the object to be heated to a predetermined target temperature, flow an energizing current according to the operation amount to the electric heating element constituting the electric resistance heater, and set a temperature of the object to be heated. Control the
During the temperature control of the heating object, obtain the current temperature of the electric heating element,
When the current temperature of the electric heating element exceeds a predetermined limit temperature, the operation amount is reduced so as to suppress the electric heating element to the temperature limit or lower.

  In the temperature control method according to the present disclosure, an operation amount for controlling the object to be heated to a predetermined target temperature is created, and an energizing current according to the operation amount is applied to an electric heating element constituting the electric resistance heater. Thus, the temperature of the object to be heated is controlled. During the temperature control of the object to be heated, the current temperature of the electric heating element is acquired. When the current temperature of the electric heating element exceeds a predetermined limit temperature, the operation amount is reduced so as to suppress the electric heating element to a temperature equal to or lower than the temperature limit. Thus, according to the temperature control method, it is possible to prevent the temperature of the electric heating element constituting the electric resistance heater from exceeding the limit temperature.

  In yet another aspect, a program according to the present disclosure is a program for causing a computer to execute the temperature control method.

  By causing a computer to execute the program according to the present disclosure, the above-described temperature control method can be performed.

  As is clear from the above, according to the temperature control system and the temperature control method of the present disclosure, it is possible to prevent the temperature of the electric heating element constituting the electric resistance heater from exceeding a predetermined limit temperature. The temperature control method can be implemented by causing a computer to execute the program of the present disclosure.

It is a figure showing typically composition of a temperature control system of one embodiment of the present invention. FIG. 2 is a diagram illustrating a hardware configuration of a temperature controller included in the temperature control system. It is a figure showing the flow of the temperature control processing (temperature control method) which the operation part of the above-mentioned temperature controller performs. It is a figure which shows the temperature versus (vs) resistance value characteristic of the heating wire (in this example, two types of nickel chrome wires (abbreviation NCHW2)) which comprises the electric resistance heater contained in the said temperature control system. It is a figure which illustrates the time series change of each of the operation amount of the temperature controller from the temperature control start in the said temperature control system, the temperature of the heating wire which comprises the said electric resistance heater, and the temperature of the said heating object. It is a figure which illustrates each time series change of the operation amount of the temperature controller from the temperature control start in the temperature control system of a comparative example, the temperature of the heating wire which comprises the said electric resistance heater, and the temperature of the said heating object. It is a figure which shows the temperature vs. resistance ratio characteristic when the heating wire which comprises the said electric resistance heater consists of one kind of nickel chrome wire (abbreviation NCHW1). It is a figure showing typically composition of a temperature control system of another embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(1st Embodiment)
FIG. 1 schematically shows a configuration of a temperature control system 200 according to an embodiment of the present invention. The temperature control system 200 includes an electric resistance heater (hereinafter, simply referred to as a “heater”) 20 and a temperature sensor 30 housed or mounted in a housing (indicated by a dashed line) of the object 90 to be heated. A temperature controller 100 is provided for controlling on / off of a current supplied to the heater 20 based on an output of the sensor 30 (object temperature signal TO) and the like.

  In this example, the heater 20 has a case 20a formed of an elongated cylindrical steel pipe forming an outer wall of the heater, and a heating wire 20x disposed inside the case 20a as an example of an electric heating element that is energized and generates heat. are doing. In this example, the type of the heating wire 20x is two types of nickel chrome wires for heating (abbreviated as NCHW2) specified in Japanese Industrial Standard (JISC2520). The heater 20 is connected to a single-phase 200 volt commercial power supply 120 in this example by a pair of wires 121 and 122. A solid state relay (SSR) 110 as a switching element is interposed in one wiring 121. An ammeter 71 including a current transformer (CT) is attached to the other wiring 122. A voltmeter 70 including an instrument transformer (VT) is connected across the wires 121 and 122 on both sides of the heater 20.

  The solid state relay 110 is on / off controlled by an on / off control signal Ctl from the temperature controller 100. In this example, the on / off control signal Ctl is a rectangular wave having a period of 1 second to 2 seconds. The duty of the on / off control signal Ctl (that is, the ratio of the on period in one cycle) is set in accordance with an operation amount described below (this is referred to as MV). Thereby, during the ON period of the solid state relay 110, the heater 20 is energized by the commercial power source 120 (synonymous with energization of the heating wire 20x; the same applies throughout this specification).

  The ammeter 71 detects the current value I of the current supplied to the heater 20. The voltmeter 70 detects a voltage value V of a voltage applied to the heater 20. The current value I detected by the ammeter 71 and the voltage value V detected by the voltmeter 70 are input to the temperature controller 100.

  As shown in FIG. 2, the temperature controller 100 includes, as hardware, in this example, an operation unit 11, a display unit 12, an operation unit 13, a storage unit 14, a data input unit 15, and an output unit 17. , A communication unit 16.

  The operation unit 11 includes a CPU (Central Processing Unit) operated by software (computer program), and executes processing according to a temperature control method described later and other various processing.

  In this example, the operation unit 13 includes a key input switch and a setting switch, and is used for inputting or setting an instruction and data from a user (operator). In this example, the setting switch of the operation unit 13 is set to the target temperature Ttarget at which the heating target 90 is to be heated = 100 ° C., and the limit temperature Tlimit = 500 ° C. for the heating wire 20x constituting the heater 20. Shall be.

  In this example, the display 12 includes an LED (light emitting diode) array, and displays numerical values and the like according to a control signal from the arithmetic unit 11. In this example, the display 12 is used to display the set target temperature Ttarget, the limit temperature Tlimit, and the current temperature TO of the heating target 90.

  In this example, the storage unit 14 includes an EEPROM (electrically rewritable nonvolatile memory) that can temporarily store data and a RAM (random access memory) that can temporarily store data. Contains. The storage unit 14 stores software (computer program) for controlling the operation unit 11. Further, in this example, as shown in FIG. 4, the storage unit 14 stores the temperature-resistance characteristics of the heating wire types (two types of nickel chrome wires (abbreviation NCHW2) in this example) constituting the heater 20. Is stored as a graph C1. As the temperature increases, the resistance values of the two nickel chrome wires (abbreviation NCHW2) monotonically increase. Further, the resistance value indicated by the heating wire 20x is stored in the storage unit 14 as the current resistance value Rs during the temperature control of the heating target 90. These storage contents will be described later in detail.

  The data input unit 15 shown in FIG. 2 includes an AD (analog to digital) converter in this example. The data input unit 15 receives signals representing the current value I from the ammeter 71 and the voltage value V from the voltmeter 70, performs AD conversion, and inputs the result to the arithmetic unit 11.

  The output unit 17 outputs a signal (ON / OFF control signal Ctl) for controlling ON / OFF of the solid state relay 110 according to a control signal from the arithmetic unit 11. Solid state relay 110 conducts or cuts off wiring 121 connected to commercial power supply 120 according to on / off control signal Ctl.

  The communication unit 16 is controlled by the arithmetic unit 11 to transmit predetermined information to an external device, or receives information from the external device and passes it to the arithmetic unit 11. In this example, the communication unit 16 receives an instruction (command signal CM) from an external device.

  As shown in FIG. 1, in this example, a first PID control unit 41 as a first feedback control unit and a second PID control unit as a second feedback control unit are programmed by the arithmetic unit 11. A section 42, a selection section 43, a resistance measurement section 44, a heating wire temperature calculation section 45 as a heating element temperature calculation section, and an output signal creation section 48 are configured. The first PID control unit 41, the second PID control unit 42, and the selection unit 43 constitute a temperature control unit 40. Further, the ammeter 71, the voltmeter 70, the resistance measuring unit 44, and the heating wire temperature calculating unit 45 constitute an electric heating element temperature acquiring unit. The operation of each of these units will be described in the flow of the temperature control process of FIG. 3 described below.

  FIG. 3 shows a flow of a temperature control process (temperature control method) executed by the calculation unit 11 of the temperature controller 100. Immediately before the start of this processing flow, the heater 20 is assumed to be at a predetermined reference temperature, in this example, a normal temperature of 23 ° C. When the user (operator) receives a start instruction via the operation unit 13 shown in FIG. 2 or a start instruction (command instruction CM) via the communication unit 16, the arithmetic unit 11 performs the temperature control process. Start the flow.

  First, as shown in step S1 of FIG. 3, the calculation unit 11 reads a target temperature Ttarget for heating the heating target 90, which is set in advance by the operation unit 13. In this example, it is assumed that the target temperature Ttarget = 100 ° C. In addition, the calculation unit 11 outputs the current temperature of the heating target 90 (this is referred to as the target temperature signal and the target temperature signal) based on the output (target temperature signal TO) of the temperature sensor 30 mounted on the heating target 90 shown in FIG. Is measured and acquired. Further, the arithmetic unit 11 functions as a first PID control unit 41, and performs a first operation for feedback control such that the current temperature TO of the heating target 90 output from the temperature sensor 30 matches the target temperature Ttarget. The quantity MV1 (unit%) is created. The first PID control unit 41 performs PID control (Proportional, Integral and Differential) with a predetermined gain of feedback control so that the current temperature TO of the heating target 90 output from the temperature sensor 30 matches the target temperature Ttarget. Control).

  Next, as shown in step S2 of FIG. 3, the arithmetic unit 11 calculates the current value I measured by the ammeter 71 and the voltage value V measured by the voltmeter 70 shown in FIG. It is input via the data input unit 15 shown therein. Further, the calculation unit 11 functions as the resistance measurement unit 44, and calculates and obtains the resistance value indicated by the heating wire 20x as the current resistance value Rs = V / I.

  Next, as shown in step S3 in FIG. 3, the calculation unit 11 reads a limit temperature Tlimit preset by the operation unit 13 for the heating wire 20x configuring the heater 20. In this example, it is assumed that the limit temperature Tlimit = 500 ° C. In addition, the operation unit 11 functions as the heating wire temperature calculation unit 45, and based on the known temperature vs. resistance characteristic (see FIG. 4) of the heating wire 20x, the current temperature TH of the heating wire 20x corresponding to the current resistance value Rs. Is calculated. For example, if the current resistance value Rs = 10.7Ω, for example, as shown by the auxiliary line Q in FIG. 4, the calculation is performed assuming that the current temperature of the corresponding heating wire 20x is TH = 436 ° C. In this way, the arithmetic unit 11 acquires the current temperature TH of the heating wire 20x during the temperature control of the heating target 90. Further, the calculation unit 11 functions as the second PID control unit 42, and performs the second control for feedback control so that the current temperature TH of the heating wire 20x calculated by the heating wire temperature calculation unit 45 matches the limit temperature Tlimit. Then, an operation amount MV2 (unit%) of No. 2 is created. The second PID control unit 42 performs control for performing PID control with a predetermined gain of feedback control such that the current temperature TH of the heating wire 20x calculated by the heating wire temperature calculation unit 45 matches the limit temperature Tlimit. Department. In this example, it is assumed that the gain of the feedback control of the second PID control unit 42 is at the same level as the gain of the feedback control of the first PID control unit 41.

  Next, as shown in step S4 of FIG. 3, the operation unit 11 acts as the selection unit 43, compares the first operation amount MV1 with the second operation amount MV2, and outputs the first PID control unit 41 And the second PID control unit 42 selects a control unit that gives a smaller operation amount.

  Next, as shown in step S5 of FIG. 3, the calculation unit 11 acts as the temperature control unit 40, and supplies an electric current according to the manipulated variable MV to the heating wire 20x constituting the heater 20. More specifically, the calculation unit 11 functions as the output signal generation unit 48, and generates an on / off control signal Ctl for on / off control of the solid state relay 110 shown in FIG. 1 according to the operation amount MV. Arithmetic unit 11 outputs this on / off control signal Ctl to solid state relay 110 via output unit 17 shown in FIG. As a result, the solid state relay 110 is turned on and off according to the on / off control signal Ctl, and the heater 20 is energized by the commercial power supply 120.

  Thereafter, as shown in step S6 in FIG. 3, unless a stop instruction is received from the user (NO in step S6), the arithmetic unit 11 repeats the processing in steps S1 to S5. When receiving a stop instruction from the user via the operation unit 13 or a stop instruction (command instruction CM) via the communication unit 16 (YES in step S6), the arithmetic unit 11 ends this temperature control process.

  As described above, in the temperature controller 100, the calculation unit 11 selects a control unit that gives a smaller operation amount from the first PID control unit 41 and the second PID control unit 42 (step S5 in FIG. 3). ), An energizing current according to the manipulated variable MV is passed through the heating wire 20x constituting the heater 20 (step S6). Thus, when the current temperature TH of the heating wire 20x exceeds a predetermined limit temperature Tlimit, the manipulated variable MV is reduced so that the heating wire 20x is suppressed to the limit temperature Tlimit or less.

  That is, if the current temperature TH of the heating wire 20x is equal to or lower than the limit temperature Tlimit from the start of energization to the heater 20 until the heating target 90 reaches the target temperature Ttarget, the first and second PID control units 42 By appropriately setting the gain of the feedback control, the first manipulated variable MV1 (which attempts to raise the temperature of the heating target 90 to the target temperature Ttarget) is limited to the second manipulated variable MV2 (the heating wire 20x is limited). (To raise the temperature to the temperature Tlimit). In this case, the selection unit 43 selects the first PID control unit 41 from the first PID control unit 41 and the second PID control unit 42. Therefore, the temperature control unit 40 controls the temperature TO of the heating target 90 by passing an electric current according to the first manipulated variable MV1 to the heating wire 20x constituting the heater 20 (original control).

  On the other hand, when the current temperature TH of the heating wire 20x exceeds the limit temperature Tlimit during the period from the start of energization to the heater 20 to the time when the heating target 90 reaches the target temperature Ttarget, the first operation amount MV1 (the heating target The second manipulated variable MV2 (attempting to lower the temperature of the heating wire 20x) may be smaller than that (tempering to raise the temperature of the heating wire 20x). In this case, the selection unit 43 selects the second PID control unit 42 from the first PID control unit 41 and the second PID control unit 42. Therefore, the temperature control unit 40 can control the temperature TO of the heating target 90 by supplying an electric current according to the second manipulated variable MV2 to the heating wire forming the heater 20. This control is a feedback control such that the current temperature TH of the heating wire 20x matches the limit temperature Tlimit. In this manner, when the current temperature TH of the heating wire 20x exceeds the limit temperature Tlimit, the manipulated variable MV is reduced so that the heating wire is suppressed to the limit temperature Tlimit or less.

  Thus, according to the temperature control system 200, it is possible to prevent the temperature TH of the heating wire 20x constituting the heater 20 from exceeding the limit temperature Tlimit.

(inspection result)
FIG. 5A illustrates a time series change of the operation amount MV of the temperature controller 100 from the start of the temperature control in the temperature control system 200, the temperature TH of the heating wire 20x constituting the heater 20, and the temperature TO of the heating object 90. ing.

i) In FIG. 5A, during the period from the start of the temperature control to 10 seconds, the temperature TO of the heating target 90 is about 50 ° C. or less, and has not yet reached the target temperature Ttarget = 100 ° C. Also, the temperature TH of the heating wire 20x has not yet reached the limit temperature Tlimit = 500 ° C. Accordingly, the first PID control unit 41 is selected during this period (a period from the start of temperature control to 10 seconds). In this example, the operation amount MV during this period (that is, the first operation amount MV1) is 100%.

ii) Subsequently, during a period of 10 to 25 seconds from the start of the temperature control, the temperature TO of the heating target 90 has not yet reached the target temperature Ttarget = 100 ° C. On the other hand, the temperature TH of the heating wire 20x exceeds (has reached) the limit temperature Tlimit = 500 ° C. Accordingly, the second PID control unit 42 is selected during this period (a period of 10 seconds to 25 seconds from the start of the temperature control). In this example, the operation amount MV during this period (that is, the second operation amount MV2) is 0%. Thereby, the temperature TH of the heating wire 20x is suppressed to the limit temperature Tlimit = 500 ° C.

iii) Subsequently, after a lapse of 25 seconds from the start of the temperature control, the temperature TH of the heating wire 20x is lower than the limit temperature Tlimit = 500 ° C. In response, the first PID control unit 41 has been selected. Here, during the period of 25 seconds to 170 seconds from the start of the temperature control, the temperature TO of the heating target 90 overshoots beyond the target temperature Ttarget = 100 ° C., and therefore, in this example, the operation amount MV (that is, The first manipulated variable MV1) = 0%. During a period of 170 seconds to 185 seconds from the start of the temperature control, the manipulated variable MV gradually increases, shows a maximum, and gradually decreases according to the degree that the temperature TO of the heating target 90 falls below the target temperature Ttarget = 100 ° C. In an aspect, it is set variably.

iv) In this example, after 185 seconds have elapsed from the start of the temperature control, the control by the first PID control unit 41 (that is, the first operation amount MV1) is maintained.

  On the other hand, FIG. 5B is a time series change of the operation amount MV of the temperature controller 100, the temperature of the heating wire 20x constituting the heater 20, and the temperature TH of the heating target 90 from the start of the temperature control in the temperature control system of the comparative example. Is exemplified. In the temperature control system of this comparative example, in FIG. 1, the second PID control unit 42, the selection unit 43, the resistance measurement unit 44, and the heating wire temperature calculation unit 45 are omitted, and only the first PID control unit 41 is always included. This is a system for controlling the temperature TO of the object 90 to be heated.

i) In FIG. 5B, during the period from the start of the temperature control to 20 seconds, the temperature TO of the heating target 90 has not yet reached the target temperature Ttarget = 100 ° C. In this example, the operation amount MV during this period (that is, the first operation amount MV1) is 100%. As a result, the temperature TH of the heating wire 20x has reached 800 ° C. to 900 ° C. (that is, the temperature exceeds 700 ° C. at which deterioration is accelerated).

ii) During the period of 25 seconds to 225 seconds from the start of the temperature control, the temperature TO of the heating target 90 overshoots beyond the target temperature Ttarget = 100 ° C. Therefore, in this example, the operation amount MV (that is, 1 (MV1) = 0%. During a period from 225 seconds to 250 seconds from the start of the temperature control, the manipulated variable MV gradually increases, shows a maximum, and gradually decreases according to the degree that the temperature TO of the heating target 90 falls below the target temperature Ttarget = 100 ° C. In an aspect, it is set variably.

iii) In this example, after 250 seconds have elapsed from the start of the temperature control, the control by the first PID control unit 41 (that is, the first operation amount MV1) is maintained.

  As can be seen by comparing FIGS. 5A and 5B above, according to the embodiment (temperature control system 200), the temperature TH of the heating wire 20x constituting the heater 20 exceeds the predetermined limit temperature Tlimit. Can be prevented.

  Moreover, in the temperature control system 200, there is no need to provide an additional temperature sensor for measuring the temperature TH of the heating wire 20x inside the case 20a constituting the heater 20. Therefore, as the heater 20, for example, a commercially available product in which the heating wire 20x is covered with a heat-resistant insulating material and housed in a steel pipe, such as a general rod heater, can be used.

(Modification)
In the above example, as shown in FIG. 4, the types of heating wires constituting the heater 20 are two types of nickel chrome wires (abbreviation NCHW2). However, it is not limited to this. The type of the heating wire constituting the heater 20 may be one type of nickel chrome wire (abbreviation NCHW1) as an example of “a specific nickel chrome wire or band having maximum and minimum temperature versus resistance characteristics”.

  In this example, as shown in FIG. 6, the storage unit 14 stores, for one type of nickel chrome wire (abbreviation NCHW1) which is a heating wire type forming the heater 20, a temperature vs. resistance ratio as a temperature-resistance characteristic. The characteristics are stored as a graph C2. This resistance ratio corresponds to (resistance value) / (reference temperature resistance value) (the reference temperature is normal temperature 23 ° C. in this example). The temperature versus resistance ratio characteristics of one type of nickel chrome wire, when graphed, increase as the temperature rises from 0 ° C. (or room temperature), show a maximum Max near 500 ° C., and gradually decrease as the temperature further rises. It shows a minimum Min around 800 ° C. and rises again when the temperature rises. The temperature at which the temperature-resistance ratio characteristic of one type of nickel chrome wire shows the maximum Max is 500 ° C., and the temperature at which the temperature shows the minimum Min is 800 ° C., which is known and fixed.

  In this example, immediately after the start of the temperature control process, when the heating wire 20x is still at the approximate reference temperature (in this example, normal temperature 23 ° C.), the calculation unit 11 functions as the resistance measurement unit 44 in step S2 in FIG. Then, the current resistance value Rs indicated by the heating wire 20x is determined as the resistance value at the reference temperature (this is referred to as R1), and is stored in the storage unit 14. Further, in step S3 in FIG. 3, the calculation unit 11 functions as the heating wire temperature calculation unit 45, and adds the reference temperature vs. the resistance ratio characteristic (see FIG. 6) of the heating wire 20x stored in the storage unit 14 to the reference temperature. , The current resistance value Rs is obtained every moment, and the current temperature TH of the heating wire 20x according to the current resistance value Rs is calculated.

  Here, in this example, when the arithmetic unit 11 functions as the heating wire temperature calculation unit 45, and the current resistance value Rs of the heating wire 20x indicates the maximum Max or the minimum Min during the temperature control of the heating target 90. , The current temperature TH of the heating wire 20x according to the maximum value Max or the minimum value Min of the current resistance value Rs is calculated. Specifically, when the current resistance value Rs of the heating wire 20x indicates the local maximum Max, for example, as shown by an auxiliary wire Q1 in FIG. 6, the corresponding current temperature of the heating wire 20x is TH = 500 ° C. Calculate that there is. Alternatively, when the current resistance value Rs of the heating wire 20x indicates the minimum value Min, for example, as shown by an auxiliary wire Q2 in FIG. 6, the current temperature of the heating wire 20x corresponding to it is calculated as TH = 800 ° C. I do. As a result, the current temperature TH of the heating wire 20x can be accurately calculated. As a result, it is possible to accurately prevent the temperature of the heating wire 20x constituting the electric resistance heater 20 from exceeding the limit temperature Tlimit.

(2nd Embodiment)
FIG. 7 schematically shows a configuration of a temperature control system 200 'according to another embodiment of the present invention. This temperature control system 200 ′ is an element that constitutes an electric heating element temperature acquisition unit instead of the ammeter 71, the voltmeter 70, the resistance measurement unit 44, and the heating wire temperature calculation unit 45 in the temperature control system 200 of FIG. The difference is that an additional temperature sensor 21 and a heating wire temperature measuring section 46 as an electric heating element temperature measuring section are provided. Otherwise, the configuration is the same as that of the temperature control system 200 in FIG.

  In this example, the additional temperature sensor 21 is a sensor head of a commercially available platinum resistance thermometer, and is provided inside a case 20 a constituting the heater 20. The heating wire temperature measuring section 46 includes a Wheatstone bridge circuit (not shown) provided in a temperature controller (indicated by reference numeral 100 '). The operation unit 11 of the temperature controller 100 ′ acts as a heating wire temperature measuring unit 46, and controls the current temperature of the heating wire 20 x based on the output of the additional temperature sensor 21 during the temperature control of the heating target 90 by a known method. (Indicated by the symbol TH '). The temperature distribution inside the case 20a of the heater 20 is neglected.

  Also in this temperature control system 200 ', when the current temperature TH' of the heating wire 20x exceeds a predetermined limit temperature Tlimit, similarly to the temperature control system 200 of FIG. 1, the heating wire 20x is set to the limit temperature Tlimit. The manipulated variable MV is reduced so as to suppress the following. Thus, according to the temperature control system 200 ', it is possible to prevent the temperature TH' of the heating wire 20x constituting the heater 20 from exceeding the limit temperature Tlimit.

  In the above-described embodiment, the first feedback control unit and the second feedback control unit use the first PID control unit 41 and the second PID control unit 42 that perform PID control (Proportional, Integral and Differential Control), respectively. Yes, but it is not limited to this. For example, as the first feedback control unit and the second feedback control unit, a first P control unit and a second P control unit that simply perform P control (proportional control) may be provided.

  Further, in the above example, the temperature vs. resistance characteristic of the heating wire type constituting the heater 20 is stored as the graph C1 in the storage unit 14, but the present invention is not limited to this. The storage unit 14 stores the temperature and the resistance value of the heating wire type constituting the heater 20 over a certain temperature range (for example, 0 ° C. to 1000 ° C.) at a constant temperature interval (for example, 50 ° C. interval). The correspondence table may be stored as a correspondence table. In this case, for the temperature and the resistance value not listed in the correspondence table, the temperature and the resistance value are associated by a known linear interpolation method (proportional distribution). When the temperature vs. resistance value characteristic is stored as the correspondence table, the storage capacity of the storage unit 14 can be reduced.

  In the above example, the type of the heating wire as the heating element constituting the heater 20 is two types of nickel chrome wire (abbreviation NCHW2) or one type of nickel chrome wire (abbreviation NCHW1), but is not limited thereto. Instead, another line type may be used. For example, one type of iron chrome wire (abbreviation FCHW1), two types of iron chrome wire (abbreviation FCHW2), and the like may be used. The electric heating element constituting the heater 20 may be a heating wire and / or an electric tropic.

  In addition, the above-described temperature control method may be implemented as software (computer program) on a non-transitory recording medium such as a CD (compact disk), a DVD (digital universal disk), or a flash memory. It may be recorded. By installing the software recorded on such a recording medium into a substantial computer device such as a personal computer, a PDA (Personal Digital Assistance), a smartphone, and a PLC (Programmable Logic Controller), the software can be installed in those computer devices. The above-described temperature control method can be executed.

  The above embodiment is an exemplification, and various modifications can be made without departing from the scope of the present invention. Each of the above-described embodiments can be realized independently, but combinations of the embodiments are also possible. In addition, various features in different embodiments can also be independently realized, but combinations of features in different embodiments are also possible.

11 arithmetic unit 14 storage unit 20 heater 20x heating wire 21 additional temperature sensor 70 voltmeter 71 ammeter 100, 100 'temperature controller 200, 200' temperature control system

Claims (7)

A temperature control system comprising an electric resistance heater and a temperature sensor mounted on a heating object, and controlling a current supplied to the electric resistance heater based on a temperature of the heating object output by the temperature sensor,
Create an operation amount for controlling the object to be heated to a predetermined target temperature, flow an energizing current according to the operation amount to the electric heating element constituting the electric resistance heater, and set a temperature of the object to be heated. A temperature control unit for controlling
During the temperature control of the heating object, comprising an electric heating element temperature acquisition unit that acquires the current temperature of the electric heating element,
When the current temperature of the electric heating element exceeds a predetermined limit temperature, the temperature control section reduces the operation amount so as to suppress the electric heating element to the temperature limit or lower. system. The temperature control system according to claim 1,
The temperature control unit includes:
A first feedback control unit that creates a first manipulated variable such that a current temperature of the heating target output by the temperature sensor matches the target temperature;
A second feedback control unit that creates a second manipulated variable so that the current temperature of the electric heating element acquired by the electric heating element temperature acquisition unit matches the limit temperature;
A selector that compares the first operation amount with the second operation amount and selects a control unit that gives a smaller operation amount among the first feedback control unit and the second feedback control unit; And a temperature control system. The temperature control system according to claim 1 or 2,
The electric heating element temperature acquisition unit,
During the temperature control of the heating object, a resistance measuring unit that measures the resistance value indicated by the electric heating element as a current resistance value,
During the temperature control of the heating object, an electric heating element temperature calculating unit that calculates a current temperature of the electric heating element according to the current resistance value based on a known temperature-resistance characteristic of the electric heating element. Characteristic temperature control system. The temperature control system according to claim 3,
The electric heating element comprises a specific nickel-chromium wire or band having the maximum and minimum temperature-resistance characteristics,
The electric heating element temperature calculating section of the electric heating element temperature obtaining section, during the temperature control of the heating object, when the current resistance value of the electric heating element shows a maximum or a minimum, the current resistance value of the current resistance A temperature control system for calculating a current temperature of the electric heating element according to the maximum or the minimum. The temperature control system according to claim 1 or 2,
The electric heating element temperature acquisition unit,
An additional temperature sensor provided inside the case constituting the electric resistance heater,
An electric heating element temperature measuring unit that measures a current temperature of the electric heating element based on an output of the additional temperature sensor during the temperature control of the object to be heated. A temperature control method using an electric resistance heater and a temperature sensor mounted on a heating object, and controlling a current supplied to the electric resistance heater based on a temperature of the heating object output by the temperature sensor,
Create an operation amount for controlling the object to be heated to a predetermined target temperature, flow an energizing current according to the operation amount to the electric heating element constituting the electric resistance heater, and set a temperature of the object to be heated. Control the
During the temperature control of the heating object, obtain the current temperature of the electric heating element,
A temperature control method, wherein when the current temperature of the electric heating element exceeds a predetermined limit temperature, the operation amount is reduced so as to suppress the electric heating element to the temperature limit or lower.   A program for causing a computer to execute the temperature control method according to claim 6.

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