JP7348137B2 - Temperature abnormality determination device and temperature abnormality determination method - Google Patents

Description

The present invention relates to a technique for monitoring the surface temperature of a workpiece that is induction heated.

One of the applications of induction heating is metal die forging. The workpiece (metal) is heated by induction before die forging. During induction heating, the surface temperature of the workpiece is controlled within a predetermined range (for example, 1000°C to 1300°C). If the surface temperature of the workpiece falls below a predetermined range, the press load on the workpiece during die forging will increase, and as a result, the die may be damaged. When the surface temperature of the workpiece exceeds a predetermined range, the crystal grains of the workpiece become enlarged, which may lead to deterioration of the quality of the workpiece (deterioration of the quality of the workpiece causes fatigue failure of the workpiece).

As a technique for monitoring the surface temperature of a workpiece to be heated by induction, there is an induction heating method disclosed in Patent Document 1, for example. In this method, the object to be heated is monitored by one or several thermal recording cameras during heating, and the heating is carried out by adjusting the heating parameters or heating conditions until the desired temperature conditions are obtained for said object. It is characterized by being controlled.

Special Publication No. 2002-532836

A non-contact temperature sensor is usually used to measure the surface temperature of a workpiece. If the measured surface temperature (actual measurement value of surface temperature) is abnormal, there is a possibility that the surface temperature of the workpiece will deviate from the above-mentioned predetermined range. The abnormality occurs due to, for example, oxide scale generated on the surface of the workpiece or a failure of the non-contact temperature sensor. If oxide scale or the like occurs on the surface of the workpiece, the measured temperature will be lower than the actual temperature. If a non-contact temperature sensor fails, it will measure a temperature that is lower or higher than the actual temperature.

An object of the present invention is to provide a temperature abnormality determining device and a temperature abnormality determining method that can determine that the actual value of the surface temperature of a workpiece being induction heated is abnormal.

A temperature abnormality determination device according to a first aspect of the present invention includes a coil that inductively heats a workpiece that is a cylindrical axially long metal member, and a measured value of the surface temperature of the workpiece that is being induction heated by the coil . an acquisition unit that obtains an analysis value of the surface temperature of the workpiece that is being induction heated; and an analysis unit that obtains an analysis value of the surface temperature of the workpiece that is being induction heated; a determination unit that determines that the coil is abnormal; the coil has a length in which the magnetic field is constant in the axial direction at the central portion in the axial direction and a magnetic field distribution occurs only in the radial direction, and the acquisition unit includes: It is a non-contact temperature sensor, and acquires the surface temperature of the workpiece at the center through a hole penetrated through the center .

A temperature abnormality determination method according to a second aspect of the present invention includes an acquisition step of acquiring an actual measured value of the surface temperature of a workpiece , which is a cylindrical axially long metal member that is induction heated with a coil , and the induction heating an analysis step of determining an analysis value of the surface temperature of the workpiece, and a determination step of determining that the actual measurement value is abnormal when the difference between the actual measurement value and the analysis value is not within a predetermined range; The coil has a length in which the magnetic field is constant in the axial direction at the central portion in the axial direction and a magnetic field distribution occurs only in the radial direction, and the acquisition step includes a non-contact temperature sensor measuring the magnetic field in the central portion. The surface temperature of the workpiece at the central portion is obtained through the hole penetrated by the hole .

The present inventors focused on the fact that if the actual measured value of the surface temperature of the workpiece being induction heated is abnormal, the difference between this value and the analytical value of the surface temperature of the workpiece being induction heated becomes large. , have created a temperature abnormality determination device according to the first aspect of the present invention and a temperature abnormality determination method according to the second aspect of the present invention. According to these, when the difference between the measured value and the analytical value of the surface temperature of the workpiece being induction heated is not within a predetermined range, the measured value is determined to be abnormal, so the actual value of the surface temperature of the workpiece is It can be determined that there is an abnormality.

In the above configuration, the analysis unit obtains the analytical value using a coupled analysis of a magnetic field and heat transfer in the workpiece that is being induction heated. Further, in the above configuration, the analysis step obtains the analysis value using a coupled analysis of a magnetic field and heat transfer in the workpiece that is being induction heated.

These configurations are an example of a method for obtaining an analytical value of the surface temperature of a workpiece being induction heated.

Furthermore , in the above configuration, the analysis unit subjects the central portion to the coupled analysis, where the magnetic field and temperature satisfy conditions such that the magnetic field and temperature change in the radial direction of the workpiece and are constant in the axial direction of the workpiece, and the The analytical value is obtained using the coupled analysis of the one-dimensional magnetic field and heat transfer in the radial direction of the workpiece. In the above configuration, in the analysis step, the central portion is subject to the coupled analysis, where the magnetic field and temperature satisfy a condition that the magnetic field and temperature change in the radial direction of the workpiece and are constant in the axial direction of the workpiece, and the The analytical value is obtained using the coupled analysis of the one-dimensional magnetic field and heat transfer in the radial direction of the workpiece.

Coupled analysis of a one-dimensional magnetic field and heat transfer can reduce the amount of calculation compared to a three-dimensional or two-dimensional coupled analysis of a magnetic field and heat transfer. Therefore, according to these configurations, the amount of calculation required to calculate the analytical value of the surface temperature of the workpiece can be reduced, and the time required to calculate the analytical value can be shortened.

In the above configuration, a heat generation term that takes as a parameter the measured value of the coil current in the induction heating or the measured value of the surface temperature of the workpiece in the induction heating and indicates the amount of heat generated inside the workpiece in the induction heating; The analysis unit further includes a storage unit that stores in advance data indicating a relationship with a parameter, and the analysis unit acquires the exothermic term corresponding to the parameter acquired during the induction heating from the data, and The obtained exothermic term is applied to a formula that can determine the temperature distribution from the surface to the inside of the workpiece, and the analytical value of the surface temperature is determined using the formula. Further, in the above configuration, a heat generation term indicating the amount of heat generated inside the workpiece during the induction heating, using the actual value of the coil current in the induction heating or the actual measurement value of the surface temperature of the workpiece during the induction heating as a parameter; , further comprising a preparation step of preparing in advance data showing a relationship with the parameter, the analysis step acquiring from the data the exothermic term corresponding to the parameter acquired during the induction heating, The acquired exothermic term is applied to a formula that can determine the temperature distribution from the surface of the workpiece to the inside, and the analytical value of the surface temperature is determined using the formula.

These configurations are other examples of methods for obtaining an analytical value of the surface temperature of a workpiece being induction heated. Coupled analysis of the magnetic field and heat transfer makes it possible to obtain the analytical value of the temperature distribution from the surface of the workpiece to the inside. In this case, it is necessary to calculate the magnetic field and calculate the exothermic term based on the calculated magnetic field, which increases the amount of calculation required to calculate the analytical value. According to these configurations, since the exothermic term is prepared in advance, it is possible to omit the calculation of the magnetic field and the exothermic term when obtaining the analytical value of the temperature distribution from the surface of the workpiece to the inside. Thereby, the amount of calculation necessary for calculating the analytical value can be reduced, and the calculation time for the analytical value can be shortened.

The above configuration further includes a notification unit that provides notification when the actual measured value of the surface temperature is determined to be abnormal. Further, in the above configuration, the method further includes a notification step of notifying when the actual measured value of the surface temperature is determined to be abnormal.

According to these configurations, it is possible to notify the operator that the actual measured value of the surface temperature of the workpiece is abnormal.

According to the present invention, it can be determined that the actually measured value of the surface temperature of the workpiece being induction heated is abnormal.

It is a block diagram showing composition of an induction heating control device and an induction heating device concerning a 1st embodiment. FIG. 3 is a schematic diagram showing the magnetic field at the center in the longitudinal direction of the coil in a state where the coil is tightly wound and the length of the coil is sufficiently large. When the initial value of the surface temperature of the workpiece is 20°C, the analytical value of the temperature distribution from the surface of the workpiece to the inside obtained using the first embodiment and general-purpose software for coupled analysis of magnetic field and heat transfer. This is a graph showing. When the initial value of the surface temperature of the workpiece is 500°C, the analytical value of the temperature distribution from the surface of the workpiece to the inside obtained using the first embodiment and general-purpose software for coupled analysis of magnetic field and heat transfer. This is a graph showing. 3 is a flowchart illustrating a temperature abnormality determination method according to the first embodiment. It is a block diagram showing composition of an induction heating control device and an induction heating device concerning a 2nd embodiment. FIG. 2 is an explanatory diagram illustrating an example of data stored in a database. FIG. 7 is an explanatory diagram illustrating another example of data stored in a database. It is a flow chart explaining the temperature abnormality determination method concerning a 2nd embodiment. It is a graph which shows the analytical value of the temperature distribution from the surface to the inside of a workpiece calculated|required using each of 2nd Embodiment and the general-purpose software of the coupled analysis of a magnetic field and heat transfer.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings. In each figure, components given the same reference numerals indicate the same components, and descriptions of the components that have already been described will be omitted.

FIG. 1 is a block diagram showing the configurations of an induction heating control device 1-1 and an induction heating device 2 according to the first embodiment. The induction heating control device 1-1 has the function of a temperature abnormality determination device, as will be explained later. The induction heating control device 1-1 controls the induction heating device 2. The induction heating device 2 is a device that inductively heats the workpiece W, and includes a conveying section 21, a coil 22, a power source 23, a thermometer 24, and an ammeter 25. The workpiece W is, for example, a cylindrical elongated metal member with a diameter of 200 to 500 mm. The conveyance unit 21 sends out the work W into the coil 22 by moving the work W in the direction indicated by arrow A from one end of the coil 22 to the other end. The length of the coil 22 is, for example, about 2000 mm. Since the length of the coil 22 is shorter than the length of the workpiece W, a portion P (portion shown in gray) of the workpiece W located inside the coil 22 becomes a heating target.

Power supply 23 supplies alternating current to coil 22 . The alternating current flowing through the coil 22 generates magnetic flux around the coil 22. As a result, an eddy current flows through a portion P of the workpiece W located within the coil 22, generating Joule heat, and the portion P is heated for a predetermined period of time. After a predetermined period of time has elapsed, the transport unit 21 moves the workpiece W in the direction of arrow A. As a result, that portion P is sent to the die forging process, and a new portion P of the workpiece W located within the coil 22 is heated for a predetermined time. The above operations are repeated.

The thermometer 24 is a non-contact temperature sensor using a thermocouple, and measures the surface temperature of the workpiece W through a hole penetrated through the center of the coil 22 in the longitudinal direction. Since the heat within the coil 22 is released to the outside from both ends of the coil 22, the temperature at the center of the coil 22 becomes higher than the temperature at both ends of the coil 22. From the viewpoint of avoiding overheating of the work W, the surface temperature of the work W is measured at the center of the coil 22. Temperature data td indicating the surface temperature (actual value of surface temperature) of the workpiece W measured by the thermometer 24 is sent to the induction heating control device 1-1.

The ammeter 25 measures the current flowing through the coil 22 (coil current) during induction heating. Current data id indicating the measured value of the coil current (actually measured value of the coil current) is sent to the induction heating control device 1-1.

The induction heating control device 1-1 includes an arithmetic processing section 11, an IF section 12, an input section 13, and an output section 14. The arithmetic processing unit 11 controls the entire induction heating control device 1-1 and performs processing necessary for the operation of the induction heating control device 1-1. The arithmetic processing unit 11 executes the functions of the arithmetic processing unit 11 and hardware such as a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and an HDD (Hard Disk Drive). Because It is realized by programs and data, etc.

The IF unit 12 is connected to the arithmetic processing unit 11 and inputs and outputs signals and the like to and from external devices under the control of the arithmetic processing unit 11. For example, the IF section 12 receives temperature data td sent from the thermometer 24 and sends it to the arithmetic processing section 11 . In this way, the IF unit 12 (acquisition unit) acquires the actual measured value of the surface temperature of the workpiece W that is being induction heated. Further, the IF section 12 receives current data id sent from the ammeter 25 and sends it to the arithmetic processing section 11 . The IF section 12 sends the control signal s1 generated by the temperature control section 114 of the arithmetic processing section 11 to the power supply 23. The power supply 23 controls the alternating current supplied to the coil 22 based on the control signal s1. The IF unit 12 sends the control signal s2 generated by the transport control unit 115 of the arithmetic processing unit 11 to the transport unit 21. The transport unit 21 controls movement of the workpiece W in the direction of arrow A based on the control signal s2. The IF section 12 is realized by an input/output interface circuit.

The input unit 13 is connected to the arithmetic processing unit 11 and is a device for a user to input various information, data, commands, etc. The input unit 13 is realized by a mouse, a keyboard, a touch panel, etc. The output unit 14 is a device that is connected to the arithmetic processing unit 11 and outputs commands, data, etc. input from the input unit 13 under the control of the arithmetic processing unit 11. The output unit 14 is realized by a liquid crystal display, an OLED display (Organic Light Emitting Diode display), or the like.

The arithmetic processing unit 11 includes an analysis unit 112, a determination unit 113, a temperature control unit 114, and a transport control unit 115 as functional blocks.

The analysis unit 112 uses a coupled analysis of the magnetic field and heat transfer in the work W that is being induction heated to obtain an analytical value of the surface temperature of the work W that is being induction heated.

The determining unit 113 determines whether the actual measured value of the surface temperature of the workpiece W exceeds the upper limit temperature and whether it falls below the lower limit temperature.

The temperature control unit 114 generates a control signal s1 for controlling the temperature of the workpiece W being induction heated when the determination unit 113 determines that the actual value of the surface temperature of the workpiece exceeds the upper limit temperature. , the IF section 12 sends the control signal s1 to the power supply 23. The control signal s1 here is a signal that turns off the power supply 23.

When the power source 23 is turned off, no alternating current is supplied to the coil 22, so induction heating stops and the temperature of the workpiece W gradually decreases. The temperature control unit 114 generates a control signal s1 that controls increasing the temperature of the workpiece W when the determination unit 113 determines that the measured value of the surface temperature is lower than the lower limit temperature, and the IF unit 12 generates a control signal s1 that controls increasing the temperature of the workpiece W. Send it to the power supply 23. The control signal s1 here is a signal that turns on the power supply 23.

The transport control unit 115 generates a control signal s2. The IF unit 12 sends a control signal s2 to the transport unit 21. The transport unit 21 transports the work W into the coil 22 by moving the work W in the direction of arrow A based on the control signal s2.

As described above, the determining unit 113 has a function of determining whether the actual measured value of the surface temperature of the workpiece W exceeds the upper limit temperature and whether it falls below the lower limit temperature. The determining unit 113 further has a function of determining whether the difference between the actual measured value of the surface temperature of the workpiece W and the analytical value of the surface temperature of the workpiece obtained by the analyzing unit 112 is within a predetermined range. .

When the determining unit 113 determines that the difference between the actual measured value and the analytical value of the surface temperature of the workpiece W is not within the predetermined range, the actual measured value of the surface temperature of the workpiece W is considered to be abnormal, and the arithmetic processing unit 11 , the notification is made by displaying a predetermined display on the screen of the output unit 14. This allows the operator to know that the actual measured value of the surface temperature of the workpiece W is abnormal. When the output unit 14 has a function of outputting audio, the notification may be performed using audio or both audio and screen display.

As described above, the induction heating control device 1-1 has the function of a temperature abnormality determination device that determines whether the actual measured value of the surface temperature of the workpiece W being induction heated is abnormal.

How to obtain the analytical value of the surface temperature of the workpiece W will be explained. The analysis unit 112 subjects the part of the work W where the magnetic field and temperature change in the radial direction of the work W and satisfy the condition that they are constant (almost constant) in the axial direction of the work W to be subjected to coupled analysis. The analytical values are obtained using a coupled analysis of the one-dimensional magnetic field and heat transfer in the radial direction. It is a coupled analysis of the magnetic field and heat transfer using only the magnetic field.) The above conditions are, for example, when the length of the coil 22 is sufficiently large relative to the diameter of the workpiece W, the coil 22 is tightly wound, and the length of the coil 22 is sufficiently large.

explain in detail. When the length of the coil 22 is sufficiently large relative to the diameter of the workpiece W, the temperature of the workpiece W in the axial direction of the workpiece W (the longitudinal direction of the coil 22) is constant (approximately constant). In this case, the temperature of the work W changes in the radial direction of the work W. Therefore, it can be considered that a temperature distribution (one-dimensional temperature distribution) occurs only in the radial direction of the workpiece W.

FIG. 2 is a schematic diagram showing the magnetic field at the longitudinal center of the coil 22 in a state where the coil 22 is tightly wound and the length of the coil 22 is sufficiently large. The dotted line indicates the magnetic field. When the coil 22 is tightly wound and the length of the coil 22 is sufficiently large, a magnetic field is generated in the longitudinal direction (z) of the coil 22 in the longitudinal center of the coil 22, and a magnetic field is generated in the radial direction of the coil 22. No magnetic field is generated at (r). In this case, the magnetic field in the longitudinal direction (z) of the coil 22 changes in the radial direction (r) of the coil 22. Therefore, it can be considered that a magnetic field distribution (one-dimensional magnetic field distribution) occurs only in the radial direction of the coil 22 (radial direction of the workpiece W).

From the above, when the length of the coil 22 is sufficiently large relative to the diameter of the workpiece W, the coil 22 is tightly wound, and the length of the coil 22 is sufficiently large, the magnetic field and temperature of the workpiece W are This satisfies the condition that it changes in the radial direction and remains constant (almost constant) in the axial direction of the workpiece W.

The coupled analysis of one-dimensional magnetic field and heat transfer will be explained in detail. Induction heating occurs due to electrical resistance to a current flowing through the workpiece W by electromagnetic induction. The electromagnetic induction phenomenon is explained by the Maxwell equation, and by calculating the magnetic field based on the value of the coil current flowing through the coil 22, the winding density of the coil 22, and the temperature distribution of the workpiece W, the current density in the workpiece W can be calculated. You can find the distribution. Specifically, the strength _HZ of the magnetic field at the longitudinal center of the coil 22 at a point r away from the central axis of the workpiece W in the radial direction is obtained by solving equation (1). σ represents the electrical conductivity of the workpiece W, μ represents the relative magnetic permeability of the workpiece W, f represents the frequency of the coil current, and j represents the imaginary unit.

Equation (1) is called a zero-order Bessel differential equation, and the general solution is expressed by Equation (2).

Here, I ₀ is a Bessel function of the first kind and zero order, K ₀ is a Bessel function of the second kind and zero order, and A and B are constants. An externally applied magnetic field H ₀ is given as a boundary condition for finding equation (2) (that is, finding the values of A and B). The externally applied magnetic field H ₀ is expressed by equation (3). I indicates the value of the coil current (actually measured value of the coil current), and N indicates the winding density of the coil 22.

Since the value I of the coil current (actual measured value of the coil current) is a value that fluctuates from moment to moment, calculation accuracy can be improved by reflecting the current data ID (Fig. 1) sent from the ammeter 25 in equation (3). It is possible to improve Based on the above equations (1) to (3), the strength H _Z of the magnetic field at the longitudinal center of the coil 22 can be determined.

When it is assumed that the magnetic field component is only in the longitudinal direction (z direction) of the coil 22, only the circumferential direction component of the electric field is effective, and by modifying the Maxwell equation, an equation showing the circumferential electric field component E _φ can be obtained. (4) is obtained.

At this time, since the eddy current density i _φ is given by equation (5), the current density distribution inside the workpiece W can be determined from equation (5). The amount of heat q inside the workpiece W is obtained using the current density distribution determined by Equation (5) and Equation (6).

Equation (7) is calculated by using the obtained calorific value q as the exothermic term ΔQ in the heat transfer analysis of Equation (7), and the analytical value of the temperature distribution from the surface to the inside of the workpiece W in the induction heating process is Desired. ρ indicates the density of the workpiece W, c indicates the specific heat of the workpiece W, λ′ indicates the thermal conductivity of the workpiece W, T indicates the analytical value (temperature), and t indicates the time.

As mentioned above, if the target of the coupled analysis is a location on the workpiece W that satisfies the condition that the magnetic field and temperature change in the radial direction of the workpiece W and are constant (almost constant) in the axial direction of the workpiece W, then the primary It will be explained that even in the original coupled analysis of the magnetic field and heat transfer, the analytical value of the surface temperature of the workpiece W is sufficiently reliable. 3 and 4 show the analytical values of the temperature distribution from the surface to the inside of the workpiece W obtained using the first embodiment, and the workpiece obtained using general-purpose software for coupled analysis of magnetic field and heat transfer. It is a graph comparing the analysis value of the temperature distribution from the surface to the inside of W. The value of the current flowing through the coil 22 (actually measured value of coil current) was 4500 A, and the winding density of the coil 22 was 31.5 (1/m). 3 and 4 show cases where the initial temperature of the actual measured value of the surface temperature of the workpiece W is 20° C. and 500° C., respectively. The horizontal axis of the graph indicates the distance (depth) from the surface of the workpiece W. The vertical axis of the graph indicates the analytical value of the temperature of the workpiece W. When the distance from the surface of the workpiece W is 0, an analytical value of the surface temperature of the workpiece is shown.

In FIGS. 3 and 4, the data shown by lines show the analytical values of the temperature distribution from the surface to the inside of the workpiece W obtained using the first embodiment, and the data shown by plots shows the relationship between the magnetic field and heat transfer. The analysis value of the temperature distribution from the surface to the inside of the workpiece W obtained using general-purpose coupled analysis software is shown. Analysis value after 20 seconds after initial temperature measurement, analysis value after 1 minute, analysis value after 5 minutes, analysis value after 10 minutes, analysis value after 20 minutes, analysis value after 40 minutes. It was found that for all of the analytical values, the data shown by the line gave similar results to the data shown by the plot. Therefore, according to the first embodiment, the same analytical values as general-purpose software for coupled analysis of a magnetic field and heat transfer can be obtained, and therefore, the reliability is similar to that of general-purpose software for coupled analysis of a magnetic field and heat transfer.

In the first embodiment, the analytical value of the surface temperature of the workpiece W is determined by coupled analysis of a one-dimensional magnetic field and heat transfer, so that the amount of calculation can be reduced. In fact, the calculation time for the analytical value of the surface temperature of the work W obtained using the first embodiment is about several minutes, and there is no problem in practical use.

A temperature abnormality determination method according to the first embodiment will be explained. FIG. 5 is a flowchart explaining this. Referring to FIGS. 1 and 5, the induction heating time of the portion P (the portion to be heated) of the workpiece W is a predetermined time (for example, 60 minutes), and during the predetermined time, the IF section 12 Temperature data td (actual measured value of the surface temperature of the workpiece) sequentially sent from the ammeter 25 and current data id (actual measured value of the coil current) sequentially sent from the ammeter 25 are acquired (S1). The IF unit 12 sends the measured value of the surface temperature of the workpiece W to the determination unit 113 and sends the measured value of the coil current to the analysis unit 112.

The analysis unit 112 calculates the strength of the magnetic field _HZ using the measured value of the coil current and equations (1) to (3) (S2). Next, the analysis unit 112 calculates the calorific value q using the magnetic field strength H _Z calculated in process S2 and equations (4) to (6) (S3). Then, the analysis unit 112 performs heat transfer calculation by substituting the calorific value q calculated in step S3 into the exothermic term ΔQ in equation (7) (S4). As a result, an analytical value of the temperature distribution from the surface of the workpiece W to the inside can be obtained.

The determination unit 113 determines whether the difference between the analytical value of the surface temperature of the workpiece W obtained in process S4 and the actual measured value of the surface temperature of the workpiece W obtained in process S1 exceeds a predetermined threshold. It is determined whether or not (S5). When the determination unit 113 determines that the above-mentioned difference does not exceed the threshold value (No in S5), the actual measured value of the surface temperature of the work W is considered to be normal, and the arithmetic processing unit 11 determines that the above-mentioned predetermined time has elapsed. It is determined whether or not (S7).

When the calculation processing unit 11 determines that the predetermined time has elapsed (Yes in S7), the induction heating of the portion P is completed, and when the calculation processing unit 11 determines that the predetermined time has not elapsed (Yes in S7), the induction heating of the portion P is completed. No), the induction heating of the portion P continues, so the IF section 12 executes the process S1.

When the determination unit 113 determines that the difference exceeds the threshold value (Yes in S5), the actual measured value of the surface temperature of the workpiece W is regarded as abnormal, and the arithmetic processing unit 11 displays the value on the screen of the output unit 14. By displaying a predetermined display, it is notified that the actual measured value of the surface temperature of the workpiece W is abnormal (S6). Then, the arithmetic processing unit 11 executes processing S7.

As explained above, according to the first embodiment, when the actual measured value of the surface temperature of the workpiece W is determined to be abnormal during induction heating of the workpiece W, a notification is issued, so that the measurement accuracy of the surface temperature of the workpiece W is improved. It is possible to prevent induction heating in a lowered state.

Regarding the second embodiment, differences from the first embodiment will be mainly described. The second embodiment differs from the first embodiment in how the analytical value of the surface temperature of the workpiece W is determined. In the second embodiment, calculations of equations (1) to (6) are omitted, and an analytical value of the surface temperature of the workpiece W is obtained. FIG. 6 is a block diagram showing the configurations of an induction heating control device 1-2 and an induction heating device 2 according to the second embodiment. The arithmetic processing unit 11 further includes a database 116 and an analysis unit 117 in addition to a determination unit 113, a temperature control unit 114, and a transport control unit 115.

The database 116 stores data indicating the relationship between the measured value of the coil current and the heat generation term in a table format. FIG. 7A is an explanatory diagram illustrating an example of data stored in the database 116. The heat generation term indicates the amount of heat generated inside the workpiece W during induction heating. The heating term is determined in advance by performing magnetic field calculations on the magnetic field generated in the coil 22 under a certain coil current. For example, when the actual value of the coil current is i1, the exothermic term q1 is used, when the actual value of the coil current is i2, the exothermic term is q2, and when the actual value of the coil current is i3, the exothermic term is q3.

Referring to FIG. 6, the analysis unit 117 calculates the current flow from the surface of the workpiece W being inductively heated to the inside based on the current data id (actual measurement value of the coil current in induction heating) sent from the ammeter 25. Obtain the analytical value of temperature distribution. Specifically, the analysis unit 117 uses the current data id (actual measurement value of the coil current) sent from the ammeter 25 as a parameter, and acquires the heat generation term corresponding to this parameter (actual measurement value of the coil current) from the database 116. , the obtained heat generation term is applied to the heat generation term ΔQ in Equation 7, and using Equation 7, the temperature distribution T in the radial direction r of the workpiece W during induction heating (temperature from the surface to the inside of the workpiece W being induction heated) is calculated. analytic value of the distribution).

Another example of data stored in the database 116 will be explained. Another example is data showing the relationship between the measured value of the surface temperature of the workpiece W and the heat generation term. FIG. 7B is an explanatory diagram illustrating another example. The heat generation term indicates the amount of heat generated inside the workpiece W during induction heating. The exothermic term is determined in advance by performing magnetic field calculations on the magnetic field generated in the coil 22 under the actual measured value of the surface temperature of the workpiece W. For example, when the actual value of the surface temperature is t1, the exothermic term is q1, when the actual value of the surface temperature is t2, the exothermic term is q2, and when the actual measured value of the surface temperature is t3, the exothermic term is q3.

In the case of another example of the database 116, the analysis unit 117 calculates the temperature of the workpiece W being induction heated based on the temperature data td (actual measurement value of the surface temperature of the workpiece W during induction heating) sent from the thermometer 24. Obtain the analytical value of the temperature distribution from the surface to the inside. Specifically, the analysis unit 117 uses the temperature data td (actual measured value of surface temperature) sent from the thermometer 24 as a parameter, and acquires the exothermic term corresponding to this parameter (actual measured value of surface temperature) from the database 116. , the obtained heat generation term is applied to the heat generation term ΔQ in Equation 7, and using Equation 7, the temperature distribution T in the radial direction r of the workpiece W during induction heating (temperature from the surface to the inside of the workpiece W being induction heated) is calculated. analytic value of the distribution).

A temperature abnormality determination method according to the second embodiment will be described with reference to FIGS. 6 and 8. FIG. 8 is a flowchart explaining this. The data stored in the database 116 is shown in the example shown in FIG. 7A.

The process S1 is the same as the process S1 shown in FIG. 5, so a description thereof will be omitted. The analysis unit 117 refers to the data shown in FIG. 7A stored in the database 116, and calculates the actual measured value of the coil current obtained in process S1 (the value of the coil current indicated by the current data id sent from the ammeter 25). ) is obtained (S10). The analysis unit 117 performs heat transfer calculation by substituting the exothermic term obtained in step S10 into the exothermic term ΔQ of equation (7) (S4). As a result, an analytical value of the temperature distribution from the surface of the workpiece W to the inside can be obtained. Processing S5 to processing S7 are the same as processing S5 to processing S7 shown in FIG. 5, so explanations thereof will be omitted.

FIG. 9 shows the analytical values of the temperature distribution from the surface of the workpiece W to the inside obtained using the second embodiment, and the surface of the workpiece W obtained using the general-purpose software for coupled analysis of magnetic field and heat transfer. It is a graph comparing the analysis value of the temperature distribution from to the inside. The horizontal axis of the graph indicates the distance (depth) from the surface of the workpiece W. The vertical axis of the graph indicates the analytical value of the temperature of the workpiece W.

Lines (A) to (G) indicate the analytical values of the temperature distribution from the surface to the inside of the workpiece W determined using the second embodiment. The line (A) shows the analysis value 20 seconds after the start of induction heating. The line (B) shows the analysis value 1 minute after the start of induction heating. The line (C) shows the analysis value 5 minutes after the start of induction heating. Line (D) shows the analysis value 10 minutes after the start of induction heating. Line (E) shows the analysis value 20 minutes after the start of induction heating. The line (F) shows the analysis value 40 minutes after the start of induction heating. The line (G) shows the analysis value 60 minutes after the start of induction heating.

The plots (a) to (g) show analytical values of the temperature distribution from the surface of the workpiece W to the inside, obtained using general-purpose software for coupled analysis of magnetic field and heat transfer. The plot in (a) shows the analytical values 20 seconds after the start of induction heating. The plot in (b) shows the analytical values 1 minute after the start of induction heating. The plot in (c) shows the analytical values 5 minutes after the start of induction heating. The plot in (d) shows the analytical values 10 minutes after the start of induction heating. The plot in (e) shows the analytical values 20 minutes after the start of induction heating. The plot in (f) shows the analytical values 40 minutes after the start of induction heating. The plot in (g) shows the analysis values 60 minutes after the start of induction heating.

The analytical value of the temperature distribution from the surface to the inside of the workpiece W obtained using the second embodiment is the same as the analytical value of the temperature distribution from the surface to the inside of the workpiece W obtained using the general-purpose software for coupled analysis of magnetic field and heat transfer. It can be seen that this value almost agrees with the analytical value of temperature distribution.

When calculating the analytical value of the temperature distribution from the surface of the workpiece W to the inside using general-purpose software for coupled analysis of magnetic field and heat transfer, it is necessary to calculate the magnetic field and calculate the heat generation term based on the calculated magnetic field. , the amount of calculation required to calculate the analytical value increases. According to the second embodiment, by using the database 116 storing the data shown in FIG. 7A or 7B, magnetic field calculation and heat generation term calculation can be omitted. Therefore, the amount of calculation required to calculate the analytical value can be reduced, and the time required to calculate the analytical value can be shortened. Specifically, the calculation time for the analytical value of the temperature distribution from the surface to the inside of the workpiece W obtained using the second embodiment is about 1 minute, and there is no problem in practical use.

1-1, 1-2 Induction heating control device 2 Induction heating device 22 Coil 24 Thermometer W Work P Part of the work located inside the coil (part to be heated)
td Temperature data id Current data s1 Control signal s2 Control signal

Claims (6)

A coil that inductively heats a workpiece, which is a cylindrical metal member that is long in the axial direction ,
an acquisition unit that acquires an actual measured value of the surface temperature of the workpiece being induction heated by the coil ;
an analysis unit that obtains an analytical value of the surface temperature of the workpiece that is being induction heated;
a determination unit that determines that the actual measurement value is abnormal when the difference between the actual measurement value and the analysis value is not within a predetermined range;
The coil has a length in which a magnetic field is constant in the axial direction at a central portion in the axial direction and a magnetic field distribution occurs only in the radial direction,
The acquisition unit is a non-contact temperature sensor, and acquires the surface temperature of the workpiece at the center through a hole penetrated through the center,
The analysis unit obtains the analytical value using a coupled analysis of a magnetic field and heat transfer in the workpiece that is being heated by induction,
The analysis unit subjects the central portion to the coupled analysis, where the magnetic field and temperature satisfy the condition that the magnetic field and temperature change in the radial direction of the workpiece and are constant in the axial direction of the workpiece, and determining the analytical value using the coupled analysis of the original magnetic field and heat transfer;
Temperature abnormality determination device. The relationship between a heat generation term indicating the amount of heat generated inside the workpiece in the induction heating and the parameter, using the actual value of the coil current in the induction heating or the actual value of the surface temperature of the workpiece in the induction heating as a parameter. further comprising a storage unit that stores in advance data indicating the
The analysis section includes:
obtaining the exothermic term corresponding to the parameter obtained during the induction heating from the data;
2. The method according to claim 1 , wherein the obtained exothermic term is applied to a formula capable of determining the temperature distribution from the surface to the inside of the workpiece in the induction heating, and the analytical value of the surface temperature is determined using the formula. The temperature abnormality determination device described. The temperature abnormality determination device according to claim 1 or 2 , further comprising a notification unit that notifies when the actual measured value of the surface temperature is determined to be abnormal. an acquisition step of acquiring an actual measured value of the surface temperature of a workpiece , which is a cylindrical, axially long metal member that is induction heated with a coil ;
an analysis step of determining an analytical value of the surface temperature of the workpiece being induction heated;
a determination step of determining that the actual measurement value is abnormal when the difference between the actual measurement value and the analysis value is not within a predetermined range,
The coil has a length in which a magnetic field is constant in the axial direction at a central portion in the axial direction and a magnetic field distribution occurs only in the radial direction,
The acquisition step is to acquire the surface temperature of the workpiece at the central portion through a hole penetrated through the central portion by a non-contact temperature sensor;
In the analysis step, the analytical value is obtained using a coupled analysis of the magnetic field and heat transfer in the workpiece that is being heated by induction;
In the analysis process, the central part is the subject of the coupled analysis, where the magnetic field and temperature satisfy the condition that the magnetic field and temperature change in the radial direction of the workpiece and are constant in the axial direction of the workpiece, and the magnetic field and temperature change in the radial direction of the workpiece. determining the analytical value using the coupled analysis of the original magnetic field and heat transfer;
Temperature abnormality determination method. The relationship between a heat generation term indicating the amount of heat generated inside the workpiece in the induction heating and the parameter, using the actual value of the coil current in the induction heating or the actual value of the surface temperature of the workpiece in the induction heating as a parameter. further comprising a preparation step of preparing in advance data indicating the
The analysis step includes:
obtaining the exothermic term corresponding to the parameter obtained during the induction heating from the data;
5. The method according to claim 4 , wherein the obtained exothermic term is applied to a formula capable of determining the temperature distribution from the surface to the inside of the workpiece in the induction heating, and the analytical value of the surface temperature is determined using the formula. Temperature abnormality determination method described. 6. The temperature abnormality determination method according to claim 4 , further comprising a notification step of notifying when the actual measured value of the surface temperature is determined to be abnormal.