JP2732270B2 - Temperature control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control method, and more particularly, to a temperature control method for controlling a temperature of a heat treatment furnace used for heat treatment of a substance to a certain value. The present invention also relates to a temperature control method suitable for detecting deterioration of a control thermocouple and outputting a correction or a deterioration alarm to obtain better control accuracy.

2. Description of the Related Art In a conventional temperature control method of this type, a temperature detected by a thermocouple is taken, and compared with an arbitrary set value, the temperature is controlled by heating or cooling so that the difference becomes zero.

Problems to be Solved by the Invention In conventional temperature control, when a thermocouple for detecting temperature deteriorates, there is a disadvantage that the control temperature changes as it is depending on the degree of deterioration. That is, when the deterioration of the thermocouple becomes −5 ° C., the control temperature changes by + 5 ° C. Generally, the deterioration of the thermocouple increases as the operating temperature increases or as the operating time increases. In the example of the R thermocouple, when the thermocouple is used at 1400 ° C. for six months,
There is a report that deterioration at -60 ° C occurs when used at 20 ° C and 1600 ° C for half a year.

The present invention has been made in view of the above-described conventional circumstances, and accordingly, an object of the present invention is to solve the above-described drawbacks inherent in the conventional technology, detect deterioration of a control thermocouple, and perform correction or deterioration alarm. It is an object of the present invention to provide a novel temperature control method that can output and obtain better control accuracy.

Means for Solving the Problems In order to achieve the above object, a temperature control device according to the present invention takes in output signals of a main temperature detecting element and a sub temperature detecting element, and relates to a relation between initial setting values of these temperature detecting elements. A controller for determining the deterioration of the main temperature detecting element from similar data that changes with time based on the data and outputting a correction signal or an alarm signal for the main temperature detecting element, or a furnace wall of a heat treatment furnace. At least one main temperature detecting element and at least two sub-temperature detecting elements, each of which has a protection tube partially fixed to the outside of the furnace and has a fixed support on one side at a predetermined interval in the axial direction of the outer protection tube. A temperature detector configured by sealing a temperature detection element, and output signals of the main temperature detection element and the sub-temperature detection element of the temperature detector are taken in and based on relevant data at the initial stage of installation of these temperature detection elements. And a controller that outputs a correction signal or an alarm signal for the main temperature detecting element based on similar data that changes over time as a standard.

Principle of the Invention When a thermocouple is installed as shown in FIG. 2, a thermal gradient is formed inside and outside the furnace with the furnace wall as a boundary. This thermal gradient is caused by the flow of the heat flow, and is determined when a thermocouple is installed.

The main thermocouple 14, the sub thermocouple 15, and the sub thermocouple 16 measure the thermal gradient, and the sub thermocouple 15 is desirably at an intermediate temperature between the outside air temperature and the furnace temperature. If the temperature of the sub thermocouple 15 is close to the temperature of the main thermocouple 14, the deterioration of the main thermocouple 14 and the deterioration of the sub thermocouple 15 at the same time will make it impossible to detect the deterioration of the main thermocouple 14. Conversely, sub thermocouple
At a temperature where 15 is close to the sub-thermocouple 16, deterioration of the main thermocouple 14 cannot be detected. The secondary thermocouple 15 has a lower temperature than the main thermocouple 14 because of the measurement at a lower temperature than the main thermocouple 14.

In the aging test of R thermocouple for half a year, -60 ℃ at 1600 ℃
There is a report of -20 ° C at 1400 ° C and 1400 ° C.

To adjust the temperature of the sub thermocouple 15 to an intermediate temperature, the length of the thermocouple protection tube 12 inserted into the furnace may be changed by adjusting the thermocouple support 13.

Next, a preferred embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a schematic block diagram showing an embodiment of a temperature control system according to the present invention.

Referring to FIG. 1, reference numeral 1 denotes a heat treatment furnace (for example, an electric furnace) used for heat treatment of an object, and a part of a furnace wall 11 of the heat treatment furnace is exposed outside the furnace (outside air). Protection tube 12
Are fixed by the support portion 13. Inside the heat treatment furnace 1, a heater 2 for heating the furnace is also arranged. From the terminal portion 12a of the protection tube 12, a detection output of a temperature detecting element such as a thermocouple is connected to a controller 4 described later by a signal line 3. The voltage of the power supply 5 is supplied to the heater 2 by the controller 4.
Is controlled. 2 (a) and 2 (b) are a specific configuration diagram and a measured temperature curve diagram in the vicinity of the protection tube 12. FIG. In the illustrated embodiment, a thermocouple is used as a temperature detecting element.

Referring to FIG. 2 (a), reference numeral 11 indicates a furnace wall of a heat treatment furnace used for heat treatment of a substance. The furnace wall 11 has a protective tube 12 having a terminal portion 12a for taking out measurement data. It is supported and fixed by the support portion 13. A part of the protection tube 12 including the terminal portion 12a is exposed to the outside (outside air) of the furnace wall 11.

In the protective tube 12, a main thermocouple 14 for measurement, a sub thermocouple 16 for measuring outside air used by the thermocouple, and a sub thermocouple 15 arranged therebetween are arranged as shown in the figure.

Although various causes of deterioration of the thermocouple have been considered, they are mainly caused by the use temperature and the use time. FIG. 2 (a),
As can be seen from (b), the main thermocouple 14 is exposed to a higher temperature than the other thermocouples (the sub-thermocouples 15 and the sub-thermocouples 16), so that their deterioration is faster.

FIG. 3 is a block diagram showing an embodiment of a controller used in the present invention.

The outputs of the main thermocouple 14 for detecting the temperature and a plurality of sub thermocouples (two of the thermocouples 15 and 16 in the illustrated embodiment) for correcting the deterioration of the main thermocouple 14 are analog multiplexer 41,
The data is input to a microprocessor (μP) 45 via an A / D converter 43 and an I / O interface circuit 44, and initial related data at the time of installing the thermocouple is set and stored in a memory RAM 47. A main thermocouple 14 and two sub thermocouples 1 obtained over time based on the stored initial related data.
The deterioration correction calculation of the thermocouple is performed by the calculation of μP45 from the current related data of 5 and 16. The deterioration signal 8 based on the thermocouple deterioration correction calculation result is output via the I / O interface circuit 44.

The control output h calculated by the PID control system from the temperature and the set value corrected for the thermocouple deterioration is output via the D / A converter 48. The ROM 46 stores programs and the like.

In FIG. 3, the cold junction correction circuits of the main thermocouple 14 and the sub thermocouples 15 and 16 are omitted.

The operation switch 42 is an input switch for setting an initial command signal when the thermocouple is installed, an installation value necessary for temperature control, a PID calculation constant, and the like.

Although the controller shown in FIG. 3 takes in three sets of inputs, a main thermocouple 14 and sub thermocouples 15 and 16, control is performed by the main thermocouple 14, and sub thermocouples 15 and 16 are controlled by the main thermocouple. Used for correction of deterioration of pair 14. That is, the relationship between the main thermocouple 14 and the sub thermocouples 15 and 16 when a new thermocouple is installed is stored in the RAM 47. When the thermocouple is used for a long time at a high temperature and the main thermocouple 14 is deteriorated, the temperature balance between the main thermocouple 14 and the sub-thermocouples 15 and 16 changes from the time when the thermocouple is new (or when the thermocouple is initially installed). An example of these software processes is shown in FIG.

Here, as an example of the processing of the initial related data of the main thermocouple 14 and the two sub thermocouples 15 and 16 and the current related data used for a long time at a high temperature, the correction is performed in a proportional relation as follows. However, the main thermocouple 14, sub thermocouple 15, T _1, the initial value of the sub thermocouple 16 T
₂ , T ₃ , and the degraded values are T ₁ ′, T ₂ ′, T ₃ ′. Here, assuming that the deterioration of the main thermocouple 14 is α and the deterioration of the sub thermocouples 15 and 16 is negligible, (T ₁ −T ₂ ) at the initial value:
If the relationship of (T ₂ −T ₃ ) is represented by the values T ₁ ′, T ₂ ′, T ₃ ′ after deterioration and the deterioration amount α, then ((T ₁ ′ + α) −T ₂ ′): (T ₂ ′) −T ₃ ′)
Becomes That is, the relationship of the expression (1) is obtained.

(T ₁ −T ₂ ): (T ₂ −T ₃ ) = {(T ₁ ′ + α) −T ₂ ′}: (T ₂ ′ −T ₃ ′) (1) Becomes

The correction data displayed in FIG. 4 indicates the deterioration amount α.
It is also possible to obtain α by a method of obtaining the above-mentioned proportional portion or a method of experimentally adding a weight based on the deterioration data, for example, by multiplying by a certain constant to further improve the accuracy of the deterioration data.

In this embodiment, the number of the sub thermocouples is two, but the effect of increasing the accuracy of equal or higher by changing the number of the sub thermocouples can be obtained by calculation.

Further, the thermocouple according to the present invention has been described by enclosing the main thermocouple and the sub-thermocouple in the same protective tube as shown in FIG. 2, but the same thermocouple is obtained by separate thermocouples. It is possible to sell a similar effect with a temperature detector installed in the form.

According to the present invention, it is possible to easily obtain a controller having a function of taking in signals of a main thermocouple and a sub thermocouple, and judging deterioration of the main thermocouple from current data obtained over time based on the initial data.

As a method of using the deterioration data, the present invention shows an example of the thermocouple deterioration correction and the thermocouple deterioration alarm, but only one of them may be used.

In the embodiment described above, a thermocouple is used as the temperature detecting element, but a temperature resistor, a thermistor, or the like can be used instead of the thermocouple.

Effect of the Invention As described above, according to the present invention, an effect is obtained in which deterioration of a temperature detecting element disposed in a heat treatment furnace can be easily and accurately detected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an entire embodiment of a temperature control system according to the present invention, and FIGS. 2 (a) and 2 (b) are enlarged partial block diagrams showing the vicinity of a protection tube fixed to a heat treatment furnace. FIG. 3 is a block diagram showing an embodiment of the controller, and FIG. 4 is an operation flowchart of the present invention. 1 ... heat treatment furnace, 2 ... heater, 3 ... signal line, 4 ...
Controller, 6 Power line, 11 Furnace wall, 12 Protection tube, 13 Support, 14 Main thermocouple, 15, 16 Sub thermocouple, 41 Analog multiplexer, 42 ... Operation switches, 43 ... A / D converters, 44,49 ... I / O interface circuits, 45 ... μP, 46 ... ROM, 47 ... RAM, 48 ... D /
A converter, 50 ... Display panel

Claims (2)

(57) [Claims] 1. A main temperature detecting element, a first sub-temperature detecting element installed in an environment where degradation is negligible, and measuring a portion close to an outside air temperature, the main temperature detecting element and the first sub-temperature detecting element. The output signals of at least two sub-temperature detecting elements of the second sub-temperature detecting element for measuring the intermediate temperature of the temperature detecting elements are fetched, and time based on the detector output data of the initial installation values of these temperature detecting elements is taken as a reference. A temperature control method characterized in that a deterioration amount of the main temperature detecting element is obtained from similar detector output data which changes periodically, and temperature control is performed based on the corrected temperature. 2. A main temperature detecting element, a first sub-temperature detecting element installed in an environment where degradation is negligible and measuring a portion close to the outside air temperature, the main temperature detecting element and the first sub-temperature detecting element. The output signals of at least two sub-temperature detecting elements of the second sub-temperature detecting element for measuring the intermediate temperature of the temperature detecting elements are fetched, and time based on the detector output data of the initial installation values of these temperature detecting elements is taken as a reference. The deterioration amount of the main temperature detection element is obtained from the similar detector output data that changes gradually, the temperature control is controlled by the output of the main temperature detection element, and the deterioration amount is output as a deterioration signal. Temperature control method.