Heat treatment apparatus and method for controlling the temperature of the heat treatment apparatus

Abstract

To provide a heat treatment device with a new constitution capable of continuing temperature control in a zone where a temperature detection part or a temperature adjuster is troubled.SOLUTION: A heat treatment device 1 comprises: a heating chamber 12 heating an object to be treated; a temperature detection part 52, a temperature adjuster 54 and a heating member 59 respectively disposed for plural zones obtained by dividing the inside of the heating chamber 12; and a controller 60 outputting a control signal CS in accordance with an operation amount MV fed from the temperature adjuster 54 in the zone executing temperature monitoring toward the heating member 59, and executes the temperature control of each zone. When the trouble of the temperature detection part 52 or the temperature adjuster 54 is detected in any zone, the controller 60 switches a temperature monitoring zone referred when the control signal CS is outputted to the heating member 59 in which the trouble has been detected from the zone in which the trouble has been detected to the other zone in which a trouble is not detected.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This invention relates to a heat treatment apparatus and a temperature control method for a heat treatment apparatus, and particularly to a heat treatment apparatus that divides a heating chamber into a plurality of zones for temperature control and a temperature control method for a heat treatment apparatus.

Background Art

[0002] A heat treatment apparatus for heat-treating a workpiece includes, as main components, a temperature detection unit such as a thermocouple, a temperature controller, and a heating member such as a heater. The temperature inside the heating chamber is detected by the temperature detection unit, the detected temperature and the set temperature (target temperature) are compared by the temperature controller to calculate an operation amount, and the power supplied to the heating member is controlled. Here, if a failure occurs in the temperature detection unit or the temperature controller, and the power supply to the heating member is stopped, a predetermined heat treatment cannot be performed, and the workpiece being heat-treated becomes a defective product. In addition, when the heat treatment is at a high temperature for a long time, in addition to the generation of defective products, the time loss also becomes large.

[0003] To address such problems, for example, in Patent Document 1 below, it is disclosed that a spare thermocouple is attached to the heating chamber in advance, and when the control thermocouple fails, it is automatically switched to the spare thermocouple to continue the process.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in heat treatment equipment, the heating chamber is sometimes divided into control units called zones, and the internal temperature of the furnace is controlled in order to precisely control the heat applied to the workpiece. In heat treatment equipment that divides the heating chamber into multiple zones and controls them precisely, a temperature detection unit, a temperature controller, and a heating element are required for each zone. If a failure occurs in one of the multiple zones, and temperature control in that zone becomes impossible, the operation of the heat treatment equipment will also become impossible. On the other hand, if, as in the above-mentioned patent document, spare temperature detection units and spare temperature controllers are to be installed in preparation for failures, a large number of temperature detection units and temperature controllers will be required, which will increase equipment costs.

[0006] Against the backdrop of the above circumstances, the present invention aims to provide a novel heat treatment apparatus and a temperature control method for a heat treatment apparatus that can continue temperature control in a zone where the temperature detection unit or temperature controller has failed. [Means for solving the problem]

[0007] The inventors of this invention have conducted extensive research to solve the above problems and have arrived at the present invention as described below. The heat treatment apparatus of the first aspect of this invention is defined as follows: A heating chamber for heating the object to be processed, The heating chamber is divided into multiple zones, each of which is provided with a temperature detection unit, a temperature controller, and a heating element. A control device that outputs a control signal corresponding to the manipulated amount sent from the temperature controller in the temperature monitoring zone toward the heating element, A heat treatment apparatus equipped with and performing temperature control for each zone, If the control device detects a malfunction in the temperature detection unit or temperature controller in any zone, it switches the temperature monitoring zone referenced when outputting the control signal to the heating element belonging to the zone where the malfunction was detected from the zone where the malfunction was detected to another zone where no malfunction has been detected.

[0008] The heat treatment apparatus in the first phase as defined in this manner can continue temperature control of the zone where a failure has been detected using the heating element belonging to the zone where the failure has been detected and the control input from other zones where no failure has been detected.

[0009] The second aspect of this invention is defined as follows: In the first phase, in the specified heat treatment apparatus, the control device has registered the output multiplier for the other zone, and when the temperature monitoring zone is switched to the other zone, it corrects the manipulated amount from the other zone according to the output multiplier. According to the heat treatment apparatus defined in this way, deviations in the manipulated parameters caused by switching the temperature monitoring zone to another zone can be corrected by the output multiplier, thereby suppressing a decrease in uniformity of heat in the heating chamber.

[0010] The third aspect of this invention is defined as follows: In the heat treatment apparatus specified in the first or second phase, the control device has registered priorities for a plurality of other zones, and when it detects a fault in any of the zones, it switches the temperature monitoring zone for the heating element belonging to the zone in which the fault was detected to a zone with a higher priority among the plurality of other zones and in which no fault has been detected. According to the heat treatment apparatus defined in this way, when switching the temperature monitoring zone to another zone, it is possible to switch to another zone that is more suitable from among several other zones (for example, from the viewpoint of suppressing a decrease in uniformity of heat).

[0011] The fourth aspect of this invention, the method for controlling the temperature of a heat treatment apparatus, is defined as follows: A heating chamber for heating the object to be processed, A temperature detection unit, a temperature controller, and a heating element are provided in each of the multiple zones into which the heating chamber is divided. A control device that outputs a control signal corresponding to the manipulated amount sent from the temperature controller in the temperature monitoring zone toward the heating element, A temperature control method for a heat treatment apparatus that includes and controls the temperature of each zone, If a malfunction of the temperature detection unit or temperature controller is detected in any zone, the temperature monitoring zone referenced when outputting the control signal to the heating element belonging to the zone where the malfunction was detected is switched from the zone where the malfunction was detected to another zone where no malfunction has been detected, and temperature control of the zone where the malfunction was detected is continued. According to the temperature control method for the heat treatment apparatus defined in this way, the same effect as in the first phase is achieved.

[0012] The fifth aspect of this invention is defined as follows: In the fourth phase, in the temperature control method for the specified heat treatment apparatus, the output multiplier for the other zones is registered in advance in the control device, and when the temperature monitoring zone is switched to the other zone, the manipulated amount from the other zone is corrected according to the output multiplier. According to the temperature control method for the heat treatment apparatus defined in this way, the same effect as in the second phase is achieved.

[0013] The sixth aspect of this invention is defined as follows: In the fourth or fifth phase, in the temperature control method for the heat treatment apparatus, the priority order for a plurality of other zones is registered in advance in the control device, and when a fault is detected in any of the zones, the temperature monitoring zone for the heating element belonging to the zone in which the fault was detected is switched to a zone among the plurality of other zones that has a higher priority and in which no fault has been detected. According to the temperature control method for the heat treatment apparatus defined in this way, the same effect as the third phase is achieved. [Brief explanation of the drawing]

[0014] [Figure 1] This diagram shows the overall configuration of a roller hearth type heat treatment apparatus according to one embodiment of the present invention. [Figure 2] This is a schematic diagram showing the elements involved in temperature control of the first heating chamber in the heat treatment apparatus shown in Figure 1. [Figure 3] It is a diagram showing an example of the priority order of other zones set for each control target zone. [Figure 4] It is a diagram showing an example of the output magnification of other zones set for each control target zone. [Figure 5] It is a flowchart regarding the temperature control of the first zone in the first heating chamber. [Figure 6] It is a flowchart regarding the temperature control of the first zone following FIG. 5.

Mode for Carrying Out the Invention

[0015] Next, embodiments of the present invention will be described in detail below. FIG. 1 shows a schematic overall configuration of a roller hearth type heat treatment apparatus according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a roller hearth type heat treatment apparatus which continuously heat-treats a workpiece W such as steel or ceramics while placed on a tray 3.

[0016] The heat treatment apparatus 1 includes a substantially cylindrical steel furnace body 5. An inlet 6 for loading is formed on the left side of the furnace body 5 in the figure, and an outlet 7 for unloading is formed on the right side of the furnace body 5 in the figure. Doors 8 and 9 that are opened and closed by air cylinder type opening and closing devices 18 are provided at these inlets 6 and outlets 7, respectively. That is, in this example, the workpiece W loaded from the left side in the figure is conveyed in the right direction in the figure.

[0017] The interior of the furnace body 5 is divided into four sections: a pre-chamber 10, a first heating chamber 12, a second heating chamber 14, and a cooling chamber 16 along the direction in which the workpiece W is conveyed. Air cylinder type opening and closing devices 19 are provided between each chamber to open and close the doors 20, 21, and 22 of the openings formed in each chamber.

[0018] The anteroom 10 is a section that prevents air from entering the heating chambers 12 and 14, and is connected to a degassing pipe 26 connected to a vacuum pump 25 and an N2 gas supply pipe 27 connected to an N2 supply device (not shown). When the material to be processed W is loaded from the inlet 6 and the door 8 is closed, the inside of the anteroom 10 is replaced with an atmospheric gas (N2 gas).

[0019] The first heating chamber 12 and the second heating chamber 14 are sections in which the workpiece W is heated based on a predetermined heat pattern, and each has a heat-resistant insulating material 30 inside, which constitutes an insulating wall 31. Inside the insulating wall 31 is a storage chamber 32 for housing the workpiece W, and an electric heater 56 is provided in the storage chamber 32 as a heating element.

[0020] The cooling chamber 16 is a section for cooling the workpiece W, and is equipped with a cooler 37 for atmospheric gas cooling and a fan (not shown) for circulating the atmospheric gas.

[0021] In the heat treatment apparatus 1 of this example, one set of workpieces W and trays 3 can be accommodated in each of the chambers: the front chamber 10, the first heating chamber 12, the second heating chamber 14, and the cooling chamber 16. Each chamber constituting the heat treatment furnace 1 has conveying rollers 40 arranged in parallel along the conveying direction.

[0022] Multiple rollers 40, positioned in the front chamber 10, the first heating chamber 12, the second heating chamber 14, and the cooling chamber 16, respectively, constitute roller groups 42, 43, 44, and 45. These roller groups 42, 43, 44, and 45 are each driven independently, sequentially transporting the workpiece W on the tray 3 downstream in the transport direction (to the right in the figure), and stopping the workpiece W at a predetermined position in the downstream processing chamber.

[0023] Figure 2 is an explanatory diagram of the components involved in temperature control of the first heating chamber 12. As shown in the figure, in this example, the first heating chamber 12 is divided into a first zone 50a at the upper front, a second zone 50b at the upper center, a third zone 50c at the upper rear, and a fourth zone 50d at the bottom, and temperature control is possible for each zone. Each zone is provided with a temperature detection unit 52, a temperature controller 54, a heater 56 as a heating element 59, and a heater power supply 58. The temperature controller 54 and heater power supply 58 belonging to each zone are connected to the control device 60.

[0024] The temperature detection unit 52 measures the temperature within the installed zone and transmits the temperature information to the temperature controller 54. The type of temperature detection unit 52 is not particularly limited, but known thermocouples, radiation thermometers, etc., can be used, taking into consideration the measurable range and responsiveness.

[0025] The temperature controller 54 displays the temperature of the monitored zone detected by the temperature detection unit 52 as a numerical value, and calculates the manipulated variable MV for the heater 56 by comparing the detected temperature with the set temperature (target temperature) SV. The temperature controller 54 also emits a fault signal FS if a break occurs in the temperature detection circuit, including the temperature detection unit 52, or if the temperature controller 54 itself malfunctions. These manipulated variable MV and fault signal FS are transmitted to the control device 60. In Figure 2, the manipulated variable MV, fault signal FS, set temperature SV, and control signal CS transmitted and received with the control device 60 are distinguished by zone. Therefore, those relating to the first zone 50a are indicated with an 'a' at the end (for example, MVa). Similarly, those relating to the second zone 50b are indicated with a 'b', those relating to the third zone 50c with a 'c', and those relating to the fourth zone 50d with a 'd'.

[0026] The heating element 59 in this example comprises a heater 56 and a heater power supply 58 that supplies power to the heater 56. The heater power supply 58 is a variable power supply comprising a thyristor and the like, and is capable of continuously changing the power supplied to the heater 56 in response to a control signal CS from the control device 60.

[0027] The control device 60 is connected to the temperature controllers 54 and heater power supplies 58 installed in each zone, and outputs a control signal CS to the heater power supply 58 that corresponds to the manipulated variable MV sent from the temperature controller 54 of the zone whose temperature is being monitored. The control device 60 can be implemented, for example, by a PLC (Programmable Logic Controller) equipped with a data processing unit, a storage unit, and a communication interface unit.

[0028] The control device 60 includes a target temperature setting unit 62, a fault detection unit 64, a temperature monitoring zone selection unit 66, and a control signal correction unit 68 as functions related to temperature control of the first heating chamber 12. In addition, the storage unit 61 of the control device 60 stores information regarding the heat pattern for each workpiece, the priority order referenced by the temperature monitoring zone selection unit 66, and the output multiplier referenced by the control signal correction unit 68.

[0029] The target temperature setting unit 62 identifies the current set temperature SV in each zone based on the heat pattern of the object to be processed read from the storage unit 61, and transmits the set temperature SV to the temperature controller 54 for each zone.

[0030] The fault detection unit 64 monitors for the presence or absence of a fault signal FS from the temperature controller 54, and if it detects a fault signal FS, it notifies the temperature monitoring zone selection unit 66 of the zone in which the fault was detected.

[0031] The temperature monitoring zone selection unit 66 selects the temperature monitoring zone to be referenced when outputting a control signal CS to the heating element 59. In this example, four zones 50a, 50b, 50c, and 50d within the first heating chamber 12 are selectable as temperature monitoring zones. When a control signal CS is output to a heating element 59 that belongs to a zone where no fault has been detected (a normal zone), the same zone as the heating element 59 is selected as the temperature monitoring zone. On the other hand, when a control signal CS is output to a heating element 59 that belongs to a zone where a fault has been detected, a different zone from the one to which the heating element belongs is selected as the temperature monitoring zone. Specifically, another zone with a higher priority and where no fault has been detected is selected.

[0032] The method of prioritizing is arbitrary, but prioritization can be determined from the perspective of suppressing a decrease in heat uniformity, for example. Figure 3 shows an example of the priority of other zones set for each controlled zone. According to the example shown in Figure 3, if a fault is detected in the first zone 50a, the temperature monitoring zone will prioritize switching from the first zone 50a to the second zone 50b.

[0033] The control signal correction unit 68 corrects the manipulated input from another zone according to the output multiplier when the temperature monitoring zone is switched to another zone. This is to correct the deviation in the manipulated input caused by switching the temperature monitoring zone to another zone using the output multiplier. For example, if the manipulated input from another zone as the temperature monitoring zone is 50%, and the output multiplier set for that other zone is 0.5, a control signal CS corresponding to a manipulated input of 25% will be output to the heating element 59 of the zone where the fault was detected. Figure 4 shows an example of the output multipliers of other zones set for each controlled zone. K1, K2, K3, ... shown in the figure are the output multipliers. The specific values ​​of the output multipliers are determined in advance during the evaluation.

[0034] Next, the temperature control operation for each zone in the first heating chamber 12 of the heat treatment apparatus 1 will be described. Figures 5 and 6 are flowcharts for the temperature control of the first zone 50a in the first heating chamber 12. The temperature control operation for the other zones 50b, 50c, and 50d is basically the same as that for the first zone 50a, and here the temperature control operation for each zone will be described using the first zone 50a as an example.

[0035] When the temperature control operation in the first heating chamber 12 is started, the temperatures in the four zones 50a, 50b, 50c, and 50d are detected by the temperature detection units 52 belonging to those zones. The temperature controllers 54 belonging to each zone compare the set temperature SV with the detected temperature to calculate the manipulated variable MV for the heater 56 (step S001), and the control device 60 obtains the manipulated variables MVa, MVb, MVc, and MVd from these four zones (step S002).

[0036] Next, the control device 60 determines whether or not there is a fault signal FSa from the first zone 50a (step S003). If there is no fault signal, the first zone 50a is selected as the zone to be monitored for temperature (step S004). The control device 60 then outputs a control signal CSa corresponding to the manipulated variable MVa from the first zone 50a to the heating element 59 belonging to the first zone 50a (step S005). If no fault is detected in the first zone 50a, steps S001 to S005 are repeatedly executed to control the temperature of the first zone 50a.

[0037] On the other hand, if the temperature detection system (temperature detection unit 52 or temperature controller 54) fails in the first zone 50a and a fault signal FSa is emitted, in step S003 it is determined that there is a fault signal and the temperature monitoring zone is switched to the second zone 50b, which has priority 1 (step S010). The control device 60 then determines whether or not there is a fault signal FSb from the second zone 50b (step S011). If there is no fault signal, the control device 60 corrects the manipulated variable MVb from the second zone 50b according to the output multiplier K1 (see Figure 4) (step S012), and outputs a control signal CSa corresponding to the corrected manipulated variable toward the heating element 59 belonging to the first zone 50a (step S013). As long as the temperature detection system in the first zone 50a is determined to be malfunctioning and the temperature detection system in the second zone 50b is determined to be normal, steps S001 to S003 and steps S010 to S013 are repeatedly executed to control the temperature in the first zone 50a.

[0038] On the other hand, if both the temperature detection systems in zone 1 50a and zone 2 50b fail and a fault signal is issued, in step S011, it is determined that a fault signal exists, and the temperature monitoring zone is switched to zone 3 50c, which has priority 2 (step S020). The control device 60 then determines whether or not there is a fault signal FSc from the third zone 50c (step S021). If there is no fault signal, the control device 60 corrects the manipulated variable MVc from the third zone 50c according to the output magnification K2 (see Figure 4) (step S022), and outputs a control signal CSa corresponding to the corrected manipulated variable toward the heating element 59 belonging to the first zone 50a (step S023).

[0039] If the temperature detection system in zone 3 50c fails and a fault signal FSc is issued, step S021 determines that a fault signal exists and switches the temperature monitoring zone to zone 4 50d, which has priority 3 (step S030). The control device 60 then determines whether or not there is a fault signal FSd from the fourth zone 50d (step S031). If there is no fault signal, the control device 60 corrects the manipulated variable MVd from the fourth zone 50d according to the output magnification K3 (see Figure 4) (step S032), and outputs a control signal CSa corresponding to the corrected manipulated variable toward the heating element 59 belonging to the first zone 50a (step S033). If a fault signal is detected in step S031, there are no switchable zones, and the control operation will be stopped.

[0040] The temperature control operation for each zone in the first heating chamber 12 has been described above. However, the second heating chamber 14 (see Figure 1) of the heat treatment apparatus 1 has the same configuration as the first heating chamber 12. Therefore, if a failure in the temperature detection system is detected in a zone within the second heating chamber 14, the temperature monitoring zone referenced when outputting the control signal CS to the heating element 59 belonging to the zone where the failure was detected can be switched to another zone within the second heating chamber 14 where no failure has been detected, thereby allowing temperature control of the zone where the failure was detected to be continued.

[0041] As described above, with the heat treatment apparatus of this embodiment, temperature control of the zone where a malfunction has been detected can be continued using the heating element 59 belonging to the zone where the malfunction has been detected and the manipulated variable MV from other zones where no malfunction has been detected.

[0042] In the heat treatment apparatus of this embodiment, the control device 60 has registered output multipliers for other zones, and when the temperature monitoring zone is switched to another zone, the manipulated variable MV from the other zone is corrected according to the output multiplier. Therefore, the deviation of the manipulated variable MV caused by switching the temperature monitoring zone to another zone can be corrected by the output multiplier, and the decrease in uniformity of the heating chamber can be suppressed.

[0043] Furthermore, in the heat treatment apparatus of this embodiment, the control device 60 has priority settings for multiple other zones registered, and if a fault is detected in any of the zones, the temperature monitoring zone for the heating element 59 belonging to the zone where the fault was detected is switched to a zone with a higher priority among the multiple other zones and where no fault has been detected. Therefore, when switching the temperature monitoring zone to another zone, it is possible to switch to another zone that is more suitable from among the multiple other zones (for example, from the viewpoint of suppressing a decrease in uniformity of heat).

[0044] Although embodiments of the present invention have been described in detail above, these are merely examples, and the present invention can be configured in various modified forms without departing from its spirit. (1) For example, in the above embodiment, the control device determines whether or not there is a failure in the temperature detection system in each zone based on the fault signal emitted from each temperature controller. However, it is also possible for the control device to directly receive the detected temperature signal in each zone instead of the fault signal, and for the control device to determine whether or not there is a failure in the temperature detection system in each zone. (2) In some cases, it is also possible to incorporate all the functions of the temperature controllers installed in each zone into the control unit, thereby eliminating the need for separate temperature controllers. (3) Although the heat treatment apparatus in the above embodiment was equipped with a heater as a heating element, the present invention can also be applied to a heat treatment apparatus equipped with a gas burner as a heating element. In that case, the amount of fuel gas supplied to the gas burner can be controlled by outputting a control signal corresponding to the operation amount sent from the temperature controller toward the fuel gas pressure regulator of the gas burner. (4) Although the heat treatment apparatus in the above embodiment was a heat treatment apparatus that continuously processes the workpiece, the present invention is also applicable to batch-type heat treatment apparatuses. [Explanation of Symbols]

[0045] 1 Heat treatment apparatus 12 First heating chamber 14. Second heating chamber 50a Zone 1 50b Zone 2 50c Zone 3 50d Zone 4 52 Temperature detection unit 54 Temperature controller 56 Heater 58 Heater power supply 59 Heating element 60 Control device CS control signal FS fault signal MV manipulated variable W - Workpiece

Claims

1. A heating chamber for heating the object to be processed, The heating chamber is divided into three or more zones, each of which a temperature detection unit, a temperature controller, and a heating element are provided. A control device that outputs a control signal corresponding to the manipulated amount sent from the temperature controller in the temperature monitoring zone toward the heating element, A heat treatment apparatus equipped with and performing temperature control for each zone, The control device, when it detects a malfunction in the temperature detection unit or temperature controller in any zone, switches the temperature monitoring zone referenced when outputting the control signal to the heating element belonging to the zone where the malfunction was detected from the zone where the malfunction was detected to any other zone where the malfunction has not been detected, and uses the control amount of any other zone when determining the control signal to be output to the heating element belonging to the zone where the malfunction was detected.

2. The heat treatment apparatus according to claim 1, wherein the control device has registered output multipliers for the other zones, and when the temperature monitoring zone is switched to the other zone, it corrects the amount of operation from the other zone according to the output multiplier.

3. The heat treatment apparatus according to claim 1 or 2, wherein the control device has registered priorities for a plurality of other zones, and when a fault is detected in any of the zones, the temperature monitoring zone for the heating element belonging to the zone in which the fault was detected is switched to a zone among the plurality of other zones that has a higher priority and in which no fault has been detected.

4. A heating chamber for heating the object to be processed, The heating chamber is divided into three or more zones, each of which a temperature detection unit, a temperature controller, and a heating element are provided. A control device that outputs a control signal corresponding to the manipulated amount sent from the temperature controller in the temperature monitoring zone toward the heating element, A temperature control method for a heat treatment apparatus that includes and controls the temperature of each zone, A temperature control method for a heat treatment apparatus, wherein, when a failure of the temperature detection unit or temperature controller is detected in any zone, the temperature monitoring zone referenced when outputting the control signal to the heating element belonging to the zone in which the failure was detected is switched from the zone in which the failure was detected to any other zone in which the failure has not been detected, and when determining the control signal to be output to the heating element belonging to the zone in which the failure was detected, the temperature control of the zone in which the failure was detected is continued by utilizing the control amount of any other zone.

5. The temperature control method for a heat treatment apparatus according to claim 4, wherein the output multiplier for the other zone is registered in advance in the control device, and when the temperature monitoring zone is switched to the other zone, the amount of operation from the other zone is corrected according to the output multiplier.

6. A temperature control method for a heat treatment apparatus according to claim 4 or 5, wherein the control device pre-registers the priority order for a plurality of other zones, and when a fault is detected in any of the zones, the temperature monitoring zone for the heating element belonging to the zone in which the fault was detected is switched to a zone among the plurality of other zones that has a higher priority and in which no fault has been detected.

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