Method for diagnosing deterioration of thermocouple and deterioration diagnosis apparatus

Abstract

To provide a method for diagnosing deterioration of a thermocouple that enables deterioration diagnosis even in a case where two thermocouples have undergone similar deterioration.SOLUTION: A method for diagnosing deterioration of a thermocouple includes detecting a temperature of an atmosphere in a heat treatment chamber 10 by a first thermocouple (13) and a second thermocouple (14), and diagnosing deterioration of the thermocouples based on a difference and magnitude comparison between the detected temperatures. When an absolute value ΔT of the temperature difference is smaller than a first predetermined value ΔTd, if an absolute value |MV-MVstnd| of a difference between a control output value MV of a heater 12 for heating the atmosphere and a reference value MVstnd of the control output value obtained in advance is greater than a second predetermined value ΔMVth, it is diagnosed that both thermocouples (13 and 14) are deteriorated in the same manner (S13, S14, S16).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for diagnosing deterioration of a thermocouple that detects the temperature of an atmosphere in a heat treatment chamber. [Background technology]

[0002] In heat treatment, the temperature of the atmosphere in the heat treatment chamber is detected by a thermocouple, and the atmosphere is controlled to the target treatment temperature based on the detected temperature. Thermocouples deteriorate over long periods of use, causing the detected temperature to be lower than the actual temperature. If the detected temperature deviates, the atmosphere cannot be properly controlled to the target treatment temperature. Therefore, thermocouple deterioration is diagnosed and deteriorated thermocouples are replaced.

[0003] In Patent Document 1, when the difference between the temperatures detected by two thermocouples exceeds a predetermined value, the thermocouples are diagnosed as being deteriorated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-218107 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, if two thermocouples are similarly deteriorated, the difference between the detected temperatures does not increase, and deterioration diagnosis cannot be performed.

[0006] An object of the present invention is to provide a thermocouple degradation diagnosis method and degradation diagnosis device that can perform degradation diagnosis even when two thermocouples are similarly deteriorated. [Means for solving the problem]

[0007] (1) In order to solve the above problem, the thermocouple deterioration diagnosis method of the present invention detects the temperature of the atmosphere in a heat treatment chamber using a first and a second thermocouple, and diagnoses the deterioration of the thermocouple based on a comparison of the difference and magnitude of the detected temperatures. When the absolute value of the difference is smaller than a first predetermined value, if the absolute value of the difference between the control output value of the heater that heats the atmosphere and a reference value of the control output value obtained in advance is greater than a second predetermined value, the two thermocouples are diagnosed as having deteriorated in the same manner.

[0008] (2) In order to solve the above problem, the thermocouple deterioration diagnosis device of the present invention is a device that detects the temperature of the atmosphere in a heat treatment chamber using a first and a second thermocouple, and diagnoses the deterioration of the thermocouple based on a comparison of the difference and magnitude of the detected temperatures. When the absolute value of the difference is smaller than a first predetermined value, if the absolute value of the difference between the control output value of the heater that heats the atmosphere and a reference value of the control output value obtained in advance is greater than a second predetermined value, the device diagnoses that the two thermocouples are similarly deteriorated. [Effects of the Invention]

[0009] The present invention can perform deterioration diagnosis even when two thermocouples are equally deteriorated. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a configuration diagram of a heat treatment system. [Figure 2] FIG. 2 is a functional block diagram of a control device. [Figure 3] 10 is a flowchart of a deterioration diagnosis process for a thermocouple. [Figure 4] 10 is a chart showing the transition of the temperature detected by a thermocouple. [Figure 5] 10 is a chart showing the transition of the temperature detected by a thermocouple and the transition of the control output value. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Heat treatment system configuration] 1 is a diagram showing the overall configuration of a heat treatment system 1. The heat treatment system 1 includes a heat treatment chamber 10, a gas supply unit 20, and a control unit 30.

[0012] The heat treatment chamber 10 is equipped with a fan 11, a heater 12, a control thermocouple (first thermocouple) 13, and a reference thermocouple (second thermocouple) 14. The gas supply device 20 is equipped with a gas tank 21, piping 22, and a valve 23. The workpiece 100 is made of steel and is placed in the heat treatment chamber 10 while being placed in a case or a support table. The control device 30 is electrically connected to the fan 11, the heater 12, the control thermocouple 13, and the reference thermocouple 14.

[0013] The fan 11 in the heat treatment chamber 10 is an electric motor controlled by the control device 30, and agitates the atmosphere so that the atmosphere is uniformly distributed. The heater 12 heats the atmosphere in the heat treatment chamber 10. The heater 12 heats the atmosphere in the heat treatment chamber 10 to a target treatment temperature T SV The output of the heater 12 is controlled by the control device 30 so that the control output value MV of the heater 12 is set by the control device 30. The control thermocouple 13 is a thermocouple that detects the temperature of the atmosphere in the heat treatment chamber 10 in order to control the temperature of the atmosphere. A The comparison thermocouple 14 is a thermocouple that detects the temperature of the atmosphere for comparison with the control thermocouple 13, and outputs the detected temperature T B is output to the control device 30.

[0014] A gas tank 21 of a gas supply device 20 supplies atmospheric gas to the heat treatment chamber 10 via a pipe 22. The amount of gas supplied is adjusted by a valve 23. The atmospheric gas is appropriately discharged to the outside through an exhaust pipe 15 so as not to become excessive inside the heat treatment chamber 10.

[0015] 2 is a diagram showing the functional blocks of the control device 30. The control device 30 includes a detected temperature difference determination unit 31, a control output value acquisition unit 32, a diagnostic data storage unit 33, a deterioration diagnosis unit 34, and a temperature control unit 35. The temperature control unit 35 adjusts the temperature of the atmosphere in the heat treatment chamber 10 to a target treatment temperature T SV The temperature control unit 35 controls the target processing temperature T SV and the temperature T detected by the control thermocouple 13 A Based on this, the detected temperature T A is the target processing temperature T SV The control output value MV of the heater 12 is set to follow the temperature T A and the temperature T detected by the comparison thermocouple 14 B The absolute value of the difference between the detected temperature difference ΔT and the first predetermined value ΔT d The control output value acquisition unit 32 acquires the control output value MV of the heater 12 set by the temperature control unit 35. The diagnostic data storage unit 33 stores the control output value MV when the temperature of the atmosphere is controlled under predetermined heat treatment conditions as a reference value MV of the control output value MV acquired in advance. stnd The deterioration diagnosis unit 34 stores the detected temperature difference ΔT. d Based on the determination result of the detected temperature difference determination unit 31 that determines whether the detected temperature difference is smaller than the reference temperature difference, the control thermocouple 13 and the comparison thermocouple 14 are diagnosed for deterioration. The control device 30 is configured as a computer and includes a processor, memory, etc. as a hardware configuration, and controls the temperature of the atmosphere in the heat treatment chamber 10. A program for performing deterioration diagnosis processing for the thermocouples (13, 14) is stored in the memory, and the above-mentioned units (31 to 35) are realized by the processor executing the program.

[0016] [Heat treatment process] When the heat treatment is started in the heat treatment system 1, the controller 30 controls the atmosphere in the heat treatment chamber 10 to a target treatment temperature T SV Then, the temperature is raised to the target processing temperature T SV The temperature of the atmosphere is controlled so as to be maintained at the temperature TA The target processing temperature T SV By setting the control output value MV of the heater 12 so that the atmosphere is heated to the target processing temperature T SV Furthermore, in the heat treatment process, the controller 30 performs a deterioration diagnosis process to determine whether the thermocouples (13, 14) have deteriorated. The deterioration diagnosis process is performed for each heat treatment cycle in which the heat treatment system 1 heat-treats the workpiece 100.

[0017] [Deterioration diagnosis processing] 3 is a flowchart of the thermocouple deterioration diagnosis process. The deterioration diagnosis process starts when the ambient temperature reaches the target treatment temperature T SV The temperature is controlled so that the temperature T is stably maintained at the temperature T . A is the target processing temperature T SV After reaching the temperature T A is the target processing temperature T SV Set the time when the temperature is controlled by tracking the detected temperature T A is the target processing temperature T SV After reaching temperature T A is the target processing temperature T SV The time is set to be controlled over a certain period of time so that the temperature stays within a predetermined range of temperature fluctuation.

[0018] When the time comes to perform the deterioration diagnosis process, in step S11, the temperature T detected by the control thermocouple 13 is A and the temperature T detected by the comparison thermocouple 14 B The temperature T A and temperature T B may be the detection values ​​of the control thermocouple 13 and the comparison thermocouple 14 detected at a certain timing, or may be the average value of the detection values ​​of the control thermocouple 13 and the comparison thermocouple 14 detected over a plurality of timings. Alternatively, it may be the time average value of the detection values ​​of the control thermocouple 13 and the comparison thermocouple 14 detected over a certain period of time.

[0019] In step S12, the control output value MV of the heater 12 set by the temperature control unit 35 is acquired. The control output value MV may be a set value set by the temperature control unit 35 at a single timing, or may be an average value of set values ​​set by the temperature control unit 35 over multiple timings. Alternatively, the control output value MV may be a time average value of set values ​​set by the temperature control unit 35 over a certain period of time.

[0020] In step S13, the temperature T detected by the control thermocouple 13 obtained in step S11 is A and the temperature T detected by the comparison thermocouple 14 B The absolute value of the difference between the detected temperature difference ΔT and the first predetermined value ΔT d It is determined whether the detected temperature difference ΔT is smaller than the temperature T A and temperature T B The absolute value of the difference between A -T B The first predetermined value ΔT d is set as a threshold value for making the judgment based on the detected temperature difference ΔT0, which is the absolute value of the difference in the detected temperatures between the control thermocouple 13 and the comparison thermocouple 14, acquired in advance at a point in time during which it is determined that the new control thermocouple 13 and comparison thermocouple 14 have not substantially deteriorated since their installation. Note that the first predetermined value ΔT d For example, the allowable temperature difference ΔT that can be tolerated as an error when there is no deterioration with respect to the detected temperature difference ΔT0. tor That is, ΔT d =ΔT0+ΔT tor ΔT is set based on ΔT0 obtained at the reference time point. d is stored in the diagnostic data storage unit 33.

[0021] In step S13, the detected temperature difference ΔT is equal to or exceeds the first predetermined value ΔT d If it is determined that the temperature is not smaller than the temperature T A and temperature T B Compare the magnitudes of the temperature T AIf it is determined that the temperature T is not larger (NO in step S17), the control thermocouple 13 is diagnosed as being deteriorated in step S18. A If it is determined that the difference is larger (YES in step S17), the comparison thermocouple 14 is diagnosed as being deteriorated in step S19. In either case, the administrator of the system 1 is notified by displaying the diagnostic information on a monitor, for example.

[0022] In step S13, the detected temperature difference ΔT is equal to or exceeds the first predetermined value ΔT d If it is determined that the control output value MV is smaller than the reference value MV (YES in step S13), the control output value MV is compared with the reference value MV in step S14. stnd The absolute value of the difference between the output value |MV-MV stnd | is the second predetermined value ΔMV th If it is determined in step S14 that it is greater than the reference temperature (YES in step S14), it is diagnosed in step S16 that the two thermocouples (control thermocouple 13 and comparison thermocouple 14) have deteriorated in the same manner. Also, in step S14, the output value difference |MV-MV stnd | is the second predetermined value ΔMV th If it is determined that the reference value MV is not greater than the reference value MV (NO in step S14), it is determined in step S15 that neither of the two thermocouples (the control thermocouple 13 and the comparison thermocouple 14) has deteriorated. In either case, the system 1 administrator is notified by displaying the diagnostic information on a monitor, for example. stnd Regarding the control output value MV, the control output value MV when the temperature of the atmosphere is controlled under the predetermined heat treatment conditions is acquired in advance during the period when it is judged that the new control thermocouple 13 and the comparison thermocouple 14 have not substantially deteriorated after installation, and this is used as the reference value MV. stnd The diagnostic data is stored in the diagnostic data storage unit 33 as the above.

[0023] The deterioration diagnosis is not limited to an automatic diagnosis by the control device 30, but may be performed by an operator or manager of the heat treatment system 1. In this case, the temperature T A and temperature T B The target processing temperature T SV and the first predetermined value ΔT dAlso, the control output value MV is displayed on the monitor together with the reference value MV stnd and the second predetermined value ΔMV th The operator can determine the detected temperature difference ΔT and the first predetermined value ΔT based on the display. d and the output value difference |MV-MV stnd | and the second predetermined value ΔMV th By comparing the measured values ​​with the measured values, the deterioration state of the control thermocouple 13 and the comparison thermocouple 14 is diagnosed.

[0024] 4(A) and 4(B) show the temperature T A and temperature T B 4A shows the case where the control thermocouple 13 has deteriorated, and FIG. 4B shows the case where the comparison thermocouple 14 has deteriorated. As shown in FIG. 4(A), when the control thermocouple 13 is deteriorated, the temperature T A is lower than the actual temperature. A The ambient temperature is controlled based on the target processing temperature T SV While the temperature T B is the target processing temperature T SV The temperature becomes higher than the reference temperature, and the detected temperature difference ΔT becomes larger. As shown in FIG. 4B, when the comparison thermocouple 14 is deteriorated, the temperature T B is lower than the actual temperature. A The ambient temperature is controlled based on the target processing temperature T SV While the temperature T B is the target processing temperature T SV The temperature becomes lower than the reference temperature, and the detected temperature difference ΔT becomes larger.

[0025] 5(A) and 5(B) show the temperature T A , temperature T B5A shows the transition of the control output value MV of the heater 12, and the control output value MV of the heater 12. Fig. 5A shows the case where the control thermocouple 13 and the comparison thermocouple 14 have deteriorated in the same manner. As shown in FIG. 5(A), the temperature T A and the temperature T detected by the comparison thermocouple 14 B The temperature remains approximately the same as that of the temperature of the heater, and the detected temperature difference ΔT does not increase. However, the reference value MV stnd By comparing the control output value MV with the control thermocouple 13, it can be determined that the control thermocouple 13 and the comparison thermocouple 14 have deteriorated in the same manner.

[0026] [Device] In terms of device configuration, the control device 30, which serves as a device for diagnosing deterioration of a thermocouple that detects the temperature of the atmosphere within the heat treatment chamber 10, executes the processing program of steps S11 to S19 in Figure 3, thereby configuring the device as one in which a detected temperature difference judgment unit 31, a control output value acquisition unit 32, a diagnostic data storage unit 33, a deterioration diagnosis unit 34, and a temperature control unit 35 are constructed.

[0027] [Effects of this embodiment] According to this embodiment, even if the two thermocouples (control thermocouple 13 and comparison thermocouple 14) deteriorate in the same manner, and the detected temperature difference ΔT between control thermocouple 13 and comparison thermocouple 14 is almost zero, and deterioration diagnosis based on the detected temperature difference ΔT cannot be performed, the control output value MV of heater 12 and the previously acquired reference value MV stnd The absolute value of the difference between the output value |MV-MV stnd By making a judgment based on |, it is possible to perform a deterioration diagnosis of the control thermocouple 13 and the comparison thermocouple 14.

[0028] [Variations] In the above-described embodiment, the thermocouple 13 is used as a control thermocouple and the thermocouple 14 is used as a comparison thermocouple. However, a configuration may also be implemented in which the thermocouples 13 and 14 are switched between being used for control and comparison during heat treatment or in heat treatment cycle units. Furthermore, in the above-described embodiment, a form in which a thermocouple degradation diagnosis is performed when the temperature of the atmosphere in the heat treatment chamber is detected by only two thermocouples is exemplified, but a form in which a thermocouple degradation diagnosis is performed when the temperature of the atmosphere in the heat treatment chamber is detected by three or more thermocouples may also be implemented. [Industrial Applicability]

[0029] The present invention can be widely applied as a deterioration diagnosis method and deterioration diagnosis device for a thermocouple that detects the temperature of the atmosphere in a heat treatment chamber. [Explanation of symbols]

[0030] REFERENCE SIGNS LIST 1 heat treatment system, 10 heat treatment chamber, 11 fan, 12 heater, 13 control thermocouple (first thermocouple), 14 comparison thermocouple (second thermocouple), 15 exhaust pipe, 20 gas supply device, 21 gas tank, 22 piping, 23 valve, 30 control device, 31 detected temperature difference determination unit, 32 control output value acquisition unit, 33 diagnostic data storage unit, 34 deterioration diagnosis unit, 35 temperature control unit, 100 treatment object

Claims

1. A method for diagnosing deterioration of a thermocouple by detecting the temperature of an atmosphere in a heat treatment chamber with a first thermocouple and a second thermocouple and comparing the difference and magnitude of the detected temperatures, comprising: a method for diagnosing deterioration of a thermocouple, wherein, when the absolute value of the difference is smaller than a first predetermined value, if the absolute value of the difference between the control output value of the heater that heats the atmosphere and a reference value of the control output value obtained in advance is larger than a second predetermined value, the method diagnoses that the two thermocouples are similarly deteriorated.

2. An apparatus for diagnosing deterioration of a thermocouple by detecting the temperature of an atmosphere in a heat treatment chamber with a first thermocouple and a second thermocouple and comparing the difference and magnitude of the detected temperatures, When the absolute value of the difference is smaller than a first predetermined value, if the absolute value of the difference between the control output value of the heater that heats the atmosphere and a reference value of the control output value obtained in advance is larger than a second predetermined value, the thermocouple deterioration diagnosis device diagnoses that the two thermocouples are similarly deteriorated.

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