Heat calculation program and heat treatment device

Abstract

To provide a heat calculation program and a heat treatment device capable of suppressing a deterioration in calculation accuracy of a heat calculation even if the number of objects increases when analyzing a state of a heated object including an aggregation of the objects.SOLUTION: A computer executes: a calculation step of calculating an amount of heat transfer between objects using a physical quantity indicating heat transfer characteristics of the objects, and calculating a temperature distribution in a space by solving a heat transfer equation including the amount of heat transfer, with respect to a heat transfer model describing heat transfer in the space in which the object to be heated, including an aggregation of the objects, is arranged; and an update step of updating the physical quantity as a manipulated variable of feedback control or feedforward control regarding a temperature using the calculated temperature distribution.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a heat calculation program and a heat treatment apparatus that perform heat calculations based on a heat transfer model that describes heat transfer within a space. [Background technology]

[0002] Analytical techniques for performing thermal calculations using computer simulations have been known for some time. For example, Patent Document 1 discloses a method for optimizing the design of a heat treatment furnace using analysis that takes radiant heat into consideration. Specifically, this document describes determining the pitch of semiconductor wafers so that the in-plane temperature of the semiconductor wafers is approximately uniform when the semiconductor wafers are arranged at equal intervals in multiple stages. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-080613 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, in the case of heat treatment of general machine parts, unlike wafers in semiconductor manufacturing processes, parts with various surface conditions, such as polished surfaces, ground surfaces, and unpolished surfaces, may be present. Therefore, if calculations are performed assuming that the surface conditions of the objects are uniform, errors may occur in the calculation results of the heat transfer amount due to radiation. In particular, when analyzing the condition of a heated object that includes an aggregate of objects, the number of combinations in which heat exchange occurs increases as the number of objects increases, and calculation errors become more apparent.

[0005] The present invention has been made in consideration of such problems, and its purpose is to provide a thermal calculation program and a heat treatment device that can suppress a decrease in the accuracy of thermal calculations when analyzing the state of a heated object that includes an aggregate of objects, even when the number of objects increases. [Means for solving the problem]

[0006] A heat calculation program in a first aspect of the present invention causes a computer to execute the following steps for a heat transfer model describing heat transfer within a space in which a heated object including an aggregate of objects is placed: calculating the amount of heat transfer between the objects using physical quantities that indicate the heat transfer characteristics of the objects, and calculating the temperature distribution within the space by solving a heat transfer equation that includes the amount of heat transfer; and updating the physical quantities as operating variables for feedback control or feedforward control using the calculated temperature distribution.

[0007] In the thermal calculation program according to the second aspect of the present invention, the updating step updates the physical quantity as the manipulated variable of the feedback control based on the relationship between the target temperature value at a specific position in the space and the calculated temperature distribution.

[0008] In the heat calculation program according to a third aspect of the present invention, the updating step updates the physical quantity serving as the manipulated variable of the feedforward control in accordance with a surface area or an energy absorption rate of the surface of the object.

[0009] In the heat calculation program of the fourth aspect of the present invention, the heat transfer model describes a state in which a heater is placed outside the heated object and the heated object is heated by heat generated by the heater, and in the calculation step, the change in temperature over time from the start of heating by the heater until the target temperature is reached is calculated for each object.

[0010] In a fifth aspect of the present invention, the thermal calculation program causes the computer to further execute a determination step of calculating the time required for two or more objects in the collection of objects to reach the target temperature, and determining a control time for heating or cooling the heated object using the two or more arrival times.

[0011] A heat treatment apparatus in a sixth aspect of the present invention is a heat treatment apparatus comprising an apparatus main body that performs heat treatment on a workpiece and a controller that controls the apparatus main body, wherein the apparatus main body comprises an insulating wall that is arranged to surround a heated object including an aggregate of objects as the workpiece, and a heater that heats the inside of a heating chamber formed by the insulating wall, and the controller calculates the amount of heat transfer between objects using physical quantities that indicate the heat transfer characteristics of the objects with respect to a heat transfer model that describes heat transfer within the heating chamber in which the heated object including the aggregate of objects is placed, calculates the temperature distribution within the heating chamber by solving a heat transfer equation that includes the amount of heat transfer, updates the physical quantities as operating variables for feedback control or feedforward control using the calculated temperature distribution, determines a control time for heating within the heating chamber from the time change of the temperature distribution obtained by sequential calculation, and performs heating control on the heater using the control time. [Effects of the Invention]

[0012] According to the present invention, when analyzing the state of a heated object including an aggregate of objects, it is possible to suppress a decrease in the accuracy of heat calculation even when the number of objects increases. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic cross-sectional view of a vacuum carburizing furnace as a heat treatment apparatus according to an embodiment of the present invention. [Figure 2] 2 is a flowchart showing an example of a temperature control operation by the controller of FIG. 1. [Figure 3] 3 is a detailed flowchart showing a method for calculating a control time shown in step SP10 of FIG. 2. [Figure 4] FIG. 2 is a diagram illustrating an example of a heat transfer model to be analyzed. [Figure 5] FIG. 2 is a diagram showing an example of a model setting screen displayed on the operation panel of FIG. 1. [Figure 6] FIG. 10 is a diagram showing the temperature characteristics of emissivity in different surface conditions. [Figure 7]FIG. 10 is a diagram illustrating an example of a method for determining a soaking time. [Figure 8] 8A and 8B are diagrams showing an example of temperature changes in a part with a polished surface and a part with a rusted surface, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same components in the drawings will be denoted by the same reference numerals as much as possible, and duplicated descriptions will be omitted.

[0015] [Overall Configuration of Heat Treatment Device 10] 1 is a schematic cross-sectional view of a heat treatment apparatus 10 according to one embodiment of the present invention. The heat treatment apparatus 10 includes a vacuum carburizing furnace 12 (corresponding to the "apparatus main body"), a controller 14 (corresponding to the "computer"), a heating power source 16, and temperature sensors 18, 19, and 20.

[0016] The vacuum carburizing furnace 12 is an apparatus for performing vacuum carburizing using a hydrocarbon gas under high temperature and reduced pressure. The vacuum carburizing furnace 12 includes a furnace body 22 that houses the workpiece W (corresponding to the "object to be processed" or "object to be heated") and a frame 24 attached to the inside of the furnace body 22. Inside the frame 24, there are provided a relatively large, hollow, rectangular parallelepiped insulating member 26, a relatively small, hollow, rectangular parallelepiped insulating member 28, and a plurality of insulating members 30 for connecting the insulating member 26 to the insulating member 28. The insulating members 26, 28, and 30 are made of an insulating material such as ceramic fiberboard. The two insulating members 26 and 28 are spaced apart to form a space 32 that functions as an insulating layer.

[0017] A carburizing chamber 36 for vacuum carburizing is formed inside the furnace body 22, surrounded by a hollow insulating member 30. A hearth 38 is provided in the furnace body 22, extending from the bottom thereof toward the inside of the carburizing chamber 36. A workpiece W is placed on the upper end of the hearth 38.

[0018] A number of heat radiation pipes 40 (corresponding to "heaters") are attached to the top of the furnace body 22 so as to extend inward into the carburizing chamber 36. Each heat radiation pipe 40 is provided in a position that covers a wide area from the top to the bottom of the carburizing chamber 36. This allows the space defined by the carburizing chamber 36 to be heated almost uniformly. The interior of the carburizing chamber 36 is set to a high temperature, for example, exceeding 900°C.

[0019] A plurality of gas introduction nozzles 44 are provided on the top and sides of the furnace body 22 so as to face the position of the workpiece W. By introducing hydrocarbon gas from a gas supply mechanism (not shown) into the carburizing chamber 36 through the gas introduction nozzles 44, the surface of the workpiece W can be carburized.

[0020] An exhaust pipe 46 is provided at the bottom of the furnace body 22, connecting the carburizing chamber 36 to the outside of the vacuum-carburizing furnace 12. The pressure inside the carburizing chamber 36 can be adjusted by operating a vacuum pump (not shown) to exhaust air from an exhaust port 48.

[0021] The controller 14 is a computer that has a processor 50, a memory 52, and an operation panel 54, and controls the operation of each part of the vacuum carburizing furnace 12. The controller 14 reads and executes programs and data stored in the memory 52 to synchronously or in parallel perform the following operations: [1] supply control for supplying hydrocarbon gas into the carburizing chamber 36, [2] pressure control for adjusting the pressure inside the carburizing chamber 36, and [3] heating control for heating the inside of the carburizing chamber 36. To control these operations, a flow rate sensor, a pressure sensor (none of which are shown), and temperature sensors 18 to 20 are connected to the controller 14.

[0022] The processor 50 acquires temperature signals from the temperature sensors 18, 19 and uses the measured temperatures to calculate estimated values ​​for the temperature inside the carburizing chamber 36 and the temperature of the workpiece W. The processor 50 determines the set conditions for the heat treatment of the workpiece W (hereinafter also referred to as "heat treatment conditions") based on the estimated values ​​it has calculated. The processor 50 acquires temperature signals from the temperature sensor 20 and controls the heating of each heat sink 40 by turning the heating power source 16 on and off.

[0023] Here, temperature sensor 18 is installed in a position that contacts the top of furnace body 22, and temperature sensor 19 is installed in a position on the periphery of vacuum carburizing furnace 12. Temperature sensor 20 is installed so as to extend from the top of furnace body 22 toward the inside of carburizing chamber 36. Temperature sensor 20 is composed of, for example, a heat-resistant thermocouple so that it can withstand the high temperatures inside carburizing chamber 36.

[0024] The memory 52 stores setting conditions for the heat treatment of the workpiece W (i.e., heat treatment conditions) and information on a heat transfer model that describes heat transfer within the furnace body 22 (hereinafter also referred to as "model information"). The model information includes: [1] "shape information" regarding the shape of the model elements; [2] "arrangement information" regarding the arrangement of the model elements; [3] "temperature information" regarding temperature constraint conditions; and [4] "physical property information" regarding the physical properties of the model elements.

[0025] The above-mentioned physical property information includes various information related to changes in the surface area or surface energy absorption rate of an object, specifically, the type of material, surface condition, emissivity index, etc. This "surface condition" includes surface roughness, surface color, oxidation progress, coating thickness, surface temperature, etc. The surface condition may be expressed qualitatively or quantitatively. Specific examples of the former include a polished surface, a shot surface, and the presence or absence of rust. Specific examples of the latter include arithmetic mean roughness, maximum height, coating thickness, etc.

[0026] The "radiation index" mentioned above is used to correct a physical quantity that indicates the heat transfer characteristics of an object. This "physical quantity" includes, for example, emissivity, emissivity, heat transfer coefficient, thermal radiation coefficient, and heat flux. The "radiation index" is also used to express an intermediate state between the surface state before heat treatment (hereinafter referred to as the first surface state) and the surface state after heat treatment (hereinafter referred to as the second surface state). For example, when the radiation index η is defined in the range [0, 1], η = 0 corresponds to the first surface state, and η = 1 corresponds to the second surface state.

[0027] The operation panel 54 is an input / output device for an operator to operate. The operation panel 54 includes, for example, a touch panel display, hardware switches, a speaker, etc. This allows the operation panel 54 to display a model setting screen 80 (FIG. 5) for setting a thermal structural model.

[0028] [Controller 14 Operation] <1. Temperature control operation> The heat treatment apparatus 10 in this embodiment is configured as described above. Next, the operation of the heat treatment apparatus 10, more specifically, the temperature control by the controller 14, will be described in detail with reference to the flowchart of FIG.

[0029] 2, the controller 14 calculates various control times included in the heat treatment conditions. Here, the "control time" refers to the time involved in controlling each step constituting a series of heat treatments, and includes [1] the "heating time" required to reach the target temperature, [2] the "soaking time" required to soak at the target temperature, and [3] the "heating time" which is the sum of the temperature rising time and the soaking time.

[0030] In step SP12, the controller 14 sets the heat treatment conditions including the control time calculated in step SP10.

[0031] In step SP14, the controller 14 starts the temperature control operation for the heat radiation pipe 40 in response to the start of the heat treatment.

[0032] In step SP16, the controller 14 performs a series of temperature control operations (e.g., feedback control or feedforward control regarding temperature) on the heat radiation pipe 40 in accordance with the heat treatment conditions set in step SP12. Through these operations, a temperature increase process, a soaking process, a carburizing process, a diffusion process, a furnace cooling process, a quenching and soaking process, and an oil cooling process are performed in sequence.

[0033] <2. Control time calculation operation> Next, the method of calculating the control time in step SP10 in FIG. 2 will be described with reference to the detailed flowchart in FIG.

[0034] 3, the controller 14 acquires model information including a radiation index. Specifically, the controller 14 acquires model information indicating a heat transfer model to be analyzed by reading three-dimensional CAD (Computer Aided Design) data or through an input operation by an operator.

[0035] FIG. 4 shows an example of a heat transfer model to be analyzed, and more specifically, corresponds to a plan view of the interior of the carburizing chamber 36 shown in FIG. 1 viewed from above. The carburizing chamber 36 is equipped with a temperature sensor 20, a hearth 38, a workpiece W on the hearth 38, and multiple heat radiation pipes 40 arranged side by side along both sides of the workpiece W. The workpiece W is composed of a metal part 60 (corresponding to an "object") or a part group 62 (corresponding to an "aggregate of objects") housed in a container (not shown). The hatched heat radiation pipes 40 are positioned closest to the temperature sensor 20.

[0036] 5 is a diagram showing an example of a model setting screen 80 displayed on the operation panel 54 of FIG. 1. The operator can input model information including the above-mentioned shape information, arrangement information, physical property information, and temperature information via the model setting screen 80. For example, when the [Physical Properties] tab 82 is selected, the model setting screen 80 is provided with user controls 84 and 85 related to update settings of the radiation index, user controls 86 to 90 related to the radiation of the workpiece W, a button 92 labeled [Cancel], and a button 94 labeled [Save].

[0037] User control 84 is provided so that feedback control (FF control) regarding the radiation index can be selected to be on or off. User control 85 is provided so that feedback control (FB control) regarding the radiation index can be selected to be on or off. Note that user controls 86 to 90 become active only when "ON" is selected in user control 84.

[0038] User control 86 is provided to allow the user to select the type of material of the component 60 (here, "iron"). User control 87 is provided to allow the user to select the surface condition of the component 60 before heat treatment (here, "condition A"). User control 88 is provided to allow the user to select the surface condition of the component 60 after heat treatment (here, "condition B"). User control 89 is provided to allow the user to select the method for setting the emissivity index (either fixed or variable; here, "fixed"). User control 90 is provided to allow the user to input the value of the emissivity index (0 to 100%; here, "50%").

[0039] When the controller 14 receives a touch operation of the [Cancel] button 92, it terminates the display of the model setting screen 80. On the other hand, when the controller 14 receives a touch operation of the [Save] button 94, it acquires the values ​​most recently input on the model setting screen 80 and stores them as model information in the memory 52 of FIG.

[0040] 3, the controller 14 determines the heat transfer model to be analyzed based on the model information acquired in step SP20. When determining the heat transfer model, the controller 14 determines the initial value of the emissivity of the component 60 using the emissivity index.

[0041] 3, the controller 14 sets a time point to be calculated (hereinafter also referred to as a "sampling time point"). If the initial state is defined as t=0, the first sampling time point is set to t=Δt.

[0042] In step SP26, the controller 14 constructs the heat conduction equation at the sampling time (t = Δt) set in step SP24 for each model element. To calculate the amount of heat transfer by radiation (i.e., heat flux), for example, the Discrete Beam Method (DBM) is used. This "Discrete Beam Method" is a technique that tracks radiation beams to calculate each form factor and uses this form factor to obtain the amount of heat transfer.

[0043] In step SP28, the controller 14 solves the heat conduction equations constructed in step SP26 by联立 or successive connection. As a result, the temperature at each position (i.e., temperature distribution) at the first sampling time (t = Δt) is obtained.

[0044] In step SP30, the controller 14 checks whether the temperature distribution obtained in step SP28 satisfies the end condition of the iterative calculation. This "end condition" is, for example, that the temperatures of n (1 < n ≤ N) out of the N components 60 match the target temperature or are sufficiently close to the target temperature. Since the end condition is not satisfied at the first sampling time (step SP30: NO), the process proceeds to step SP32.

[0045] In step SP32, the controller 14 updates the operation amount (here, the radiation index) of the control regarding the temperature using the temperature distribution calculated in step SP28. This control may be any of [1] feedback control, [2] feedforward control, or [3] both feedback control and feedforward control.

[0046] (1. Feedback control) It should be noted that the Chinese character "联立" in the original text seems to be an incorrect or non-standard term. I translated it as "联立" as it was in the original, but it might need to be verified and corrected if it's a specific error. Also, for the proper technical translation in a patent context, it's advisable to double-check with relevant experts.The controller 14 calculates a feedback term (FB term) based on the relationship between the target temperature value at a specific position in the carburizing chamber 36 and the calculated temperature distribution, and performs feedback control by multiplying the feedback term by a gain value to update the radiation index. The "specific position" is preferably a location where the target temperature value is known, such as the position of the temperature sensor 20 installed in the carburizing chamber 36 or a position nearby. On the other hand, the temperature output value can be selected from the temperature at any position on the temperature distribution. As a rule for updating the radiation index, proportional control (P control), integral control (I control), derivative control (D control), or a combination of these controls is used.

[0047] (2. Feedforward control) The controller 14 performs feedforward control by calculating a feedforward term (FF term) according to the surface area or the energy absorption rate of the object, and multiplying the FF term by a gain value to update the emissivity index. The update amount may be determined, for example, according to a predetermined temperature characteristic of the emissivity.

[0048] Figure 6 shows the temperature characteristics of emissivity for different surface conditions. The horizontal axis of the graph indicates temperature (unit: °C), and the vertical axis of the graph indicates emissivity (unit: dimensionless). As can be seen from this figure, in all of conditions A, B, and C, the emissivity increases as the temperature rises. However, there is a tendency for the emissivity to change depending on the surface condition, and for an arbitrary temperature T, ε A (T)<ε B (T)<ε C (T) is in a magnitude relationship. Here, ε A (T),ε B (T),ε C (T) corresponds to the emissivity of states A, B, and C at temperature T, respectively.

[0049] Here, when the emissivity index is defined as η (0≦η≦1), the corrected emissivity ε(T) is calculated according to the following formula (1).

number

[0050] Returning to step SP24 in FIG. 2, the controller 14 updates the sampling time. As a result, the second sampling time is set to t = 2Δt. Hereinafter, the controller 14 repeatedly executes steps SP24 to SP32 to obtain the temperature distribution at each sampling time (t = mΔt; m is a natural number). When the setting method of the radiation index is "variable", the controller 14 may dynamically change the radiation index η each time the sampling time is updated. For example, by gradually increasing the value of η as the heat treatment progresses, the calculation accuracy of the heat transfer amount can be further improved.

[0051] As the temperature distribution becomes uniform over time and satisfies the above-described end condition (step SP30: YES), the controller 14 proceeds to step SP34 instead of step SP32.

[0052] In step SP34, the controller 14 determines the control time, which is part of the heat treatment conditions, using the time change of the temperature distribution obtained by repeatedly executing step SP28.

[0053] FIG. 7 is a diagram showing an example of a method for determining the soaking holding time. The horizontal axis of the graph indicates the elapsed time (unit: minute), and the vertical axis of the graph indicates the temperature (unit: °C). The three curves indicate the temperatures at different positions P1, P2, and P3 within the work W. As understood from the drawing content of FIG. 4, since there are differences in the degree of heat transfer depending on the position within the work W, the shapes of the curves are different. When defining the arrival times at the target temperatures at positions P1, P2, and P3 as t1, t2, and t3, respectively, the magnitude relationship of t1 < t2 < t3 is satisfied. In this case, the maximum value of the difference (t3 - t1) may be calculated as the soaking holding time.

[0054] FIG. 8(A) is a diagram showing an example of temperature change in a part 60 with a polished surface. FIG. 8(B) is a diagram showing an example of temperature change in a part 60 with a rusted surface. The horizontal axis of the graph indicates elapsed time (unit: minutes), and the vertical axis of the graph indicates [1] temperature (unit: °C) or [2] output rate of the heat sink tube 40 (unit: %). The curve shown by the solid line corresponds to the actual measured value (i.e., the target value) of the temperature at the position of the temperature sensor 20. The two curves shown by the short-dashed line and the dashed-dotted line correspond to the calculated values ​​of the temperature at two different locations.

[0055] As can be seen from FIG. 8(A), the time required to reach the set target temperature is relatively short, so the temperature rise time is set to a small value. However, the temperature rise varies relatively greatly depending on the position of the workpiece W, so the soaking time is set to a large value. Also, as can be seen from FIG. 8(B), the time required to reach the set target temperature is relatively long, so the temperature rise time is set to a large value. However, the temperature rise varies relatively little depending on the position of the workpiece W, so the soaking time is set to a small value. In this way, it is possible to determine a soaking time that is appropriate for the surface condition of the component 60.

[0056] In this way, the controller 14 completes the calculation of the control time (flowchart in FIG. 3). In this way, by appropriately selecting the soaking time so that the end point arrives at the timing when the workpiece W has been soaked, it is possible to achieve both quality and efficiency of the heat treatment.

[0057] [Summary of the embodiment] As described above, in the heat calculation program and method of this embodiment, one or more computers (here, the controller 14) execute a calculation step (SP26, SP28 in FIG. 3) in which, for a heat transfer model describing heat transfer within a space (here, the carburizing chamber 36) in which a heated object (here, the workpiece W) including an aggregate (here, the component group 62) of objects (here, the components 60) is placed, the amount of heat transfer between the components 60 is calculated using physical quantities that indicate the heat transfer characteristics of the components 60, and the temperature distribution within the carburizing chamber 36 is calculated by solving a heat transfer equation that includes the amount of heat transfer; and an update step (SP32) in which the calculated temperature distribution is used to update the physical quantities as manipulated variables for feedback control or feedforward control related to temperature.

[0058] In this way, by updating the physical quantity indicating the heat transfer characteristics of the component 60 as the manipulated variable for feedback control or feedforward control, the calculation error of the heat transfer amount due to radiation is reduced compared to when calculations are performed assuming the physical quantity is unchanged. As a result, when analyzing the state of the workpiece W including the component group 62, it is possible to suppress a decrease in the accuracy of the heat calculation even if the number of components 60 increases.

[0059] In addition, in the updating step, the physical quantity serving as the manipulated variable of the feedback control may be updated based on the relationship between the target temperature value at a specific position in the carburizing chamber 36 and the calculated temperature distribution. Additionally or separately, in the updating step, the physical quantity serving as the manipulated variable of the feedforward control may be updated in accordance with the surface area or the surface energy absorption rate of the object.

[0060] Furthermore, if the heat transfer model describes a state in which a heater is placed outside the workpiece W and the workpiece W is heated by heat generated by the heater, the calculation step may determine the change in temperature over time for each part 60 from the start of heating until the target temperature is reached.

[0061] In addition, the controller 14 may further execute a determination step (SP34 in FIG. 3) in which the controller 14 determines the time required for two or more components 60 in the component group 62 to reach the target temperature, and determines the control time related to heating or cooling the workpiece W using the two or more arrival times.

[0062] Furthermore, when the physical quantity is emissivity and the component 60 changes from a first surface state to a second surface state through heating, the updating step may perform feedforward control to update the emissivity to an intermediate value between the emissivity in the first surface state and the emissivity in the second surface state. Furthermore, the calculation step may calculate the amount of heat transfer between the components 60 using a discrete beam method.

[0063] Moreover, the heat treatment apparatus 10 in this embodiment includes an apparatus main body (here, a vacuum carburizing furnace 12) that performs heat treatment on the workpiece W, and a controller 14 that controls the vacuum carburizing furnace 12. The vacuum carburizing furnace 12 includes an insulating wall (here, insulating members 26, 28, 30) that is arranged to surround the workpiece W including an assembly of objects (here, a group of parts 62), and a heater (here, a heat dissipation pipe 40) that heats the inside of a heating chamber (here, a carburizing chamber 36) formed by the insulating wall.

[0064] The controller 14 then calculates the amount of heat transfer between the parts 60 using physical quantities that indicate the heat transfer characteristics of the parts 60, with respect to a heat transfer model that describes heat transfer in the carburizing chamber 36 in which the workpiece W including the part group 62 is placed, calculates the temperature distribution in the carburizing chamber 36 by solving a heat transfer equation that includes the amount of heat transfer, updates the physical quantities that serve as manipulated variables for feedback control or feedforward control related to temperature using the calculated temperature distribution, determines a control time related to heating in the carburizing chamber 36 from the time change in the temperature distribution obtained by sequential calculation, and uses the control time to control heating of the heat sink pipe 40. This configuration makes it possible to set a control time appropriate for the number and packaging of the parts 60 when heat treating the workpiece W including the part group 62, making it possible to achieve both high quality and efficiency in the heat treatment.

[0065] [Variations] The present invention is not limited to the above-described embodiments, and can be freely modified without departing from the spirit of the present invention. Alternatively, the respective configurations may be arbitrarily combined within the scope of the present invention without causing any technical contradiction.

[0066] In the above embodiment, the controller 14 constituting part of the heat treatment apparatus 10 executes the heat calculation program, but the configuration of the apparatus is not limited to this. For example, a general-purpose computer independent of the vacuum carburizing furnace 12 may execute the heat calculation program for the purpose of computer simulation. [Explanation of symbols]

[0067] 10...heat treatment device, 12...vacuum carburizing furnace, 14...controller (computer), 36...carburizing chamber (heating chamber), 40...heat radiation tube (heater), 50...processor, 52...memory, 60...part (object), 62...group of parts (collection of objects), W...work (object to be heated, object to be treated)

Claims

1. a calculation step of determining physical quantities that indicate the heat transfer characteristics of an object using an index that expresses an intermediate state between the surface state of the object before the heat treatment and the surface state of the object after the heat treatment, for a heat transfer model that describes heat transfer in a space in which an object to be heated, including an aggregate of objects, is placed, calculating the amount of heat transfer between the objects using the physical quantities, and calculating the temperature distribution in the space by solving a heat transfer equation that includes the amount of heat transfer; an updating step of updating the index as a manipulated variable for feedback control or feedforward control related to temperature using the calculated temperature distribution; A thermal calculation program characterized by causing a computer to execute the above.

2. The thermal calculation program according to claim 1, characterized in that in the updating step, the index as the manipulated variable of the feedback control is updated based on the relationship between a target value of the temperature at a specific position in the space and the calculated temperature distribution.

3. A thermal calculation program as described in claim 1 or 2, characterized in that the physical quantity is emissivity, emissivity, heat transfer coefficient, thermal radiation coefficient, or heat flux.

4. the heat transfer model describes a state in which a heater is disposed outside the object to be heated, and the object to be heated is heated by heat generated by the heater; 2. The thermal calculation program according to claim 1, wherein the calculation step obtains, for each object, a change in temperature over time from the start of heating by the heater until the target temperature is reached.

5. The thermal calculation program according to claim 4, further comprising causing the computer to execute a determination step of calculating the time required for two or more of the objects in the collection of objects to reach the target temperature, and determining a control time for heating or cooling the heated object using the two or more time required for the objects to reach the target temperature.

6. A heat treatment apparatus comprising: an apparatus main body that performs heat treatment on a workpiece; and a controller that controls the apparatus main body, The device body includes: a heat insulating wall provided to surround the object to be heated, the object including the aggregate of objects as the object to be treated; a heater for heating the inside of a heating chamber formed by the heat insulating wall; Equipped with The controller With respect to a heat transfer model describing heat transfer within the heating chamber in which the object to be heated is placed, a physical quantity indicating the heat transfer characteristics of the object is obtained using an index for expressing an intermediate state between the surface state of the object before the heat treatment of the object and the surface state of the object after the heat treatment of the object, the amount of heat transfer between the objects is calculated using the physical quantity, and a temperature distribution within the heating chamber is calculated by solving a heat transfer equation including the amount of heat transfer; updating the index as a manipulated variable for feedback control or feedforward control regarding temperature using the calculated temperature distribution; A heat treatment apparatus characterized in that a control time related to heating in the heating chamber is determined from the time change of the temperature distribution obtained by sequential calculation, and the control time is used to perform heating control on the heater.

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