High Frequency Induction Heating Equipment

Abstract

To measure the temperature of an object to be heated with a smaller error than before.SOLUTION: A high-frequency induction heating device includes a heating coil 1 that receives a high-frequency current and generates an induced current in an object to be heated 11 by high-frequency induction, an oscillator 2 that converts a DC voltage to an AC voltage and supplies a high-frequency current to the heating coil 1, a current sensor 5 that measures a current supplied to the primary side of the oscillator 2, and a temperature calculation unit 6 that calculates an estimated value of a temperature of the object to be heated 11 by inputting the integrated value of the current measured by the current sensor 5 into an equation of the regression line showing the relationship between the integrated value and the temperature of the object to be heated 11.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a high-frequency induction heating device that heats metals and the like by utilizing the principle of electromagnetic induction. [Background technology]

[0002] A high-frequency induction heating device generates a magnetic field by passing a high-frequency current through a heating coil, and generates an induced current in a metallic object to be heated that is placed inside or near the heating coil. This induced current generates Joule heat in the object to be heated, thereby heating the object to be heated (see Patent Document 1).

[0003] For example, when using a high-frequency induction heating device in a manufacturing process in which a metal object to be heated is pressed into a resin part, proper control of the temperature of the object to be heated is an important factor in producing a high-quality product, but it is not possible to attach a temperature sensor to each object to be heated, such as a nut or sleeve. Therefore, conventionally, temperature control has been performed using a radiation thermometer or the like. However, temperature measurement using a radiation thermometer is easily affected by disturbances, and there is a problem that there is a large measurement error of, for example, 50°C to 100°C. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-87807 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made to solve the above-mentioned problems, and has an object to provide a high-frequency induction heating device that can measure the temperature of a heated object to which it is difficult to attach a temperature sensor with an error smaller than that of the conventional device. [Means for solving the problem]

[0006] The high-frequency induction heating device of the present invention is characterized in that it comprises a heating coil configured to receive a high-frequency current and generate an induced current in an object to be heated by high-frequency induction, an oscillator configured to convert a DC voltage to an AC voltage and supply a high-frequency current to the heating coil, a current sensor configured to measure the current supplied to the primary side of the oscillator, and a temperature calculation unit configured to calculate an estimated value of the temperature of the object to be heated by inputting an integrated value of the current measured by the current sensor into a regression line equation showing the relationship between the integrated value and the temperature of the object to be heated.

[0007] Furthermore, one configuration example of the high-frequency induction heating device of the present invention is characterized in that it further includes a judgment unit configured to judge whether or not the estimated value of the temperature of the heated object exceeds a predetermined temperature threshold value. Furthermore, one configuration example of the high-frequency induction heating device of the present invention is characterized in that it further includes a simple regression analysis unit configured to acquire data on the integrated current value for each heating test measured by the current sensor and data on the temperature of the heated object for each heating test measured by a temperature sensor attached to the heated object during multiple heating tests performed before calculating an estimated value of the temperature of the heated object, and to determine an equation for the regression line based on the acquired data.

[0008] The high-frequency induction heating device of the present invention is characterized in that it comprises a heating coil configured to receive a high-frequency current and generate an induced current in an object to be heated by high-frequency induction, an oscillator configured to convert a DC voltage into an AC voltage and supply the high-frequency current to the heating coil, a current sensor configured to measure the AC current supplied to a secondary side of the oscillator, a voltage sensor configured to measure the AC voltage supplied to the secondary side of the oscillator, and a temperature calculation unit configured to calculate an estimated value of the temperature of the object to be heated by inputting an integrated value of the product of the AC current measured by the current sensor and the AC voltage measured by the voltage sensor into a regression line equation showing the relationship between the integrated value and the temperature of the object to be heated.

[0009] Furthermore, one configuration example of the high-frequency induction heating device of the present invention is characterized in that it further includes a judgment unit configured to judge whether or not the estimated value of the temperature of the heated object exceeds a predetermined temperature threshold value. Furthermore, one configuration example of the high-frequency induction heating device of the present invention is characterized in that it further includes a simple regression analysis unit configured to acquire data on the integrated value of the product of the AC current and the AC voltage for each heating test measured by the current sensor and the voltage sensor, and data on the temperature of the heated object for each heating test measured by a temperature sensor attached to the heated object, during multiple heating tests performed before calculating an estimated value of the temperature of the heated object, and to determine an equation for the regression line based on the acquired data. Effect of the Invention

[0010] According to the present invention, by providing a current sensor and a temperature calculation unit, or by providing a current sensor, a voltage sensor, and a temperature calculation unit, it is possible to measure the temperature of a heated object, for which it is difficult to attach a temperature sensor, with an error smaller than that of a conventional radiation thermometer in a process of heating the heated object using a high-frequency induction heating device. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing the configuration of a high-frequency induction heating device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a flowchart illustrating the operation of the high-frequency induction heating device according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is a flowchart illustrating a method for deriving a regression line according to a first embodiment of the present invention. [Figure 4] FIG. 4 shows an example of the change in current and temperature during one heating test. [Diagram 5] FIG. 5 is a diagram for explaining a method for deriving a regression line according to the first embodiment of the present invention. [Figure 6]FIG. 6 is a block diagram showing the configuration of a high-frequency induction heating device according to a second embodiment of the present invention. [Figure 7] FIG. 7 is a flowchart illustrating the operation of the high-frequency induction heating device according to the second embodiment of the present invention. [Figure 8] FIG. 8 is a flowchart illustrating a method for deriving a regression line according to the second embodiment of the present invention. [Figure 9] FIG. 9 is a diagram for explaining a method of deriving a regression line according to the second embodiment of the present invention. [Figure 10] FIG. 10 is a block diagram showing an example of the configuration of a computer that realizes the high-frequency induction heating apparatus according to the first and second embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [Principle of the invention] It has been experimentally demonstrated that the integrated value of the product of the primary side voltage V and the primary side current I during heating in a high-frequency induction heating device has a linear relationship with the temperature of the heated object. The inventors realized that when the primary side voltage V is constant during heating, only the primary side current I changes, and therefore the temperature of the heated object can be determined from the integrated value of the current I during heating.

[0013] [First Example] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a high-frequency induction heating device according to a first embodiment of the present invention. The high-frequency induction heating device includes a heating coil 1 that receives a high-frequency current and generates an induced current in an object to be heated 11 by high-frequency induction, an oscillator 2 that converts a DC voltage V into an AC voltage and supplies a high-frequency current to the heating coil 1, a matching box 3 provided between the oscillator 2 and the heating coil 1, a control unit 4 that controls the oscillator 2, a current sensor 5 that measures a DC current I supplied to the primary side of the oscillator 2, a temperature calculation unit 6 that calculates an estimated value of the temperature of the object to be heated 11 by inputting an integrated value of the current I measured during heating into a regression line equation showing the relationship between the integrated value and the temperature of the object to be heated 11, a display unit 7 that displays the temperature, a judgment unit 8 that judges whether the estimated value of the temperature of the object to be heated 11 exceeds a predetermined temperature threshold value, a judgment result output unit 9 that outputs the judgment result, and a simple regression analysis unit 10 that determines the equation of the regression line based on data obtained during multiple heating tests performed before calculating the estimated value of the temperature of the object to be heated 11.

[0014] As shown in Fig. 1, the object to be heated 11 is placed inside the heating coil 1 (or in the vicinity of the heating coil 1). An example of the object to be heated 11 is a nut or a sleeve that is press-fitted into a resin part in a heated state. The heating coil 1 and the object to be heated 11 need to be mechanically fixed.

[0015] Next, the operation of the high-frequency induction heating device of this embodiment will be described with reference to Fig. 2. The control unit 4 outputs a heating control signal to the oscillator 2 in response to, for example, an instruction to start heating from a user (YES in step S100 in Fig. 2). When the heating control signal is input from the control unit 4, the oscillator 2 starts supplying a high-frequency current to the heating coil 1 via the matching box 3 (step S101 in Fig. 2). The matching box 3 matches the impedance of the oscillator 2 and the heating coil 1 to improve the efficiency of supplying the high-frequency current from the oscillator 2 to the heating coil 1. By supplying a high-frequency current to the heating coil 1, an induced current is generated in the metallic object to be heated 11 placed inside the heating coil 1, and this induced current generates Joule heat in the object to be heated 11.

[0016] The oscillator 2 converts an externally supplied DC voltage V into an AC voltage and supplies a high-frequency current to the heating coil 1. The current sensor 5 measures the current I supplied to the primary side of the oscillator 2. The temperature calculation unit 6 acquires data on the current I measured by the current sensor 5 (step S102 in FIG. 2). The temperature calculation unit 6 acquires data on the current I at regular time intervals until the heating time from the start of heating (start of oscillation) reaches a set value (YES in step S103 in FIG. 2). As a result, the temperature calculation unit 6 records time-series data on the current I.

[0017] When the heating time reaches the set value, the control unit 4 stops outputting the heating control signal. As a result, the oscillator 2 stops supplying high-frequency current to the heating coil 1 (FIG. 2, step S104). As a result, heating of the object 11 to be heated stops.

[0018] When the heating time reaches the set value and the heating is stopped, the temperature calculation unit 6 calculates an estimated value of the temperature of the object 11 by inputting the integrated value of the time series data of the current I acquired from the start of heating to the end of heating into a predetermined regression line equation showing the relationship between the integrated value and the temperature (step S105 in FIG. 2). E , the integrated value of current I is I INTEGRAL , integrated value I INTEGRALand the estimated value of temperature T E If the slope of the regression line showing the relationship between the two is a and the intercept of the regression line is b, the regression line formula is as follows. The method for deriving the regression line will be described later. T E = a × I INTEGRAL +b (1)

[0019] The display unit 7 displays the estimated value T of the temperature T of the object 11 calculated by the temperature calculation unit 6. E In this embodiment, the estimated value T E is displayed, but the estimated value T E The data may be transmitted to the outside.

[0020] The determination unit 8 determines the estimated value T of the temperature T of the object to be heated 11 calculated by the temperature calculation unit 6. E The determination unit 8 determines whether the estimated value T E is the lower limit of temperature T LOWER Less than or equal to the upper temperature limit T UPPER If it exceeds the estimated value T E is the lower limit of temperature T LOWER Above the upper temperature limit T UPPER If it is equal to or less than this, it is determined to be normal.

[0021] The judgment result output unit 9 outputs the judgment result of the judgment unit 8 (step S108 in FIG. 2). The judgment result may be output, for example, by displaying the content notifying the judgment result or by transmitting information notifying the judgment result to the outside.

[0022] In this way, the operation of the high-frequency induction heating device is completed. INTEGRAL and the temperature T of the object to be heated 11, it is possible to measure the temperature of the object to be heated 11, for which it is difficult to attach a temperature sensor, with an error smaller than that of a conventional radiation thermometer.

[0023] Next, the integrated value I of the current I INTEGRALand the estimated value T of the temperature T of the heated object 11 E In this embodiment, before actually manufacturing a product by heating the object 11, a preliminary heating test is performed several times using the same heating coil 1 and object 11 as those used in the manufacturing process, and the integrated value I of the current I is calculated. INTEGRAL The data on the temperature of the object 11 to be heated and the temperature data on the object 11 to be heated are acquired, and a regression line is obtained.

[0024] 3 is a flowchart explaining a method for deriving the regression line. First, a user of the high-frequency induction heating device attaches a temperature sensor such as a thermocouple to the object to be heated 11 placed inside the heating coil 1 (or in the vicinity of the heating coil 1).

[0025] For example, in response to an instruction to start a test from a user (YES in step S200 in FIG. 3), the control unit 4 outputs a heating control signal to the oscillator 2. When the heating control signal is input from the control unit 4, the oscillator 2 starts supplying a high-frequency current to the heating coil 1 via the matching box 3 (step S201 in FIG. 3).

[0026] The simple regression analysis section 10 acquires data on the current I measured by the current sensor 5 (Step S202 in FIG. 3). A temperature sensor attached to the object to be heated 11 measures the temperature T of the object to be heated 11. The simple regression analysis unit 10 acquires data on the temperature T measured by the temperature sensor (step S203 in FIG. 3). The simple regression analysis unit 10 acquires data on the current I and the temperature T at regular time intervals until the heating time from the start of heating reaches a set value (YES in step S204 in FIG. 3). As a result, the simple regression analysis unit 10 records time series data on the current I and time series data on the temperature T.

[0027] When the heating time reaches the set value, the control unit 4 stops outputting the heating control signal, which causes the oscillator 2 to stop supplying high-frequency current to the heating coil 1 (Step S205 in FIG. 3).

[0028] Next, the high frequency induction heating device cools the object 11 to be heated (step S206 in FIG. 3). A cooling device (not shown) is used to forcibly cool the object 11 to be heated. Here, the device may wait for a predefined time, or may wait until the temperature T measured by the temperature sensor becomes equal to or lower than a defined value.

[0029] The simple regression analysis unit 10 waits until the object 11 to be heated cools down, and then changes the heating conditions (step S207 in FIG. 3). The heating conditions include a set value of the heating time and heating efficiency (impedance of the matching box 3). The matching box 3 is equipped with a matching transformer (not shown), and by changing the tap of this matching transformer, the impedance can be changed, and thus the heating efficiency can be changed. The simple regression analysis section 10 changes at least one of the set value of the heating time and the heating efficiency.

[0030] The control unit 4 determines whether the number of heating tests has reached a predetermined number (e.g., two times) (step S208 in FIG. 3), and if the number of heating tests has not reached the predetermined number, returns to step S201 and outputs a heating control signal to the oscillator 2. In this manner, the processes of steps S201 to S207 are repeated until the predetermined number of heating tests are completed. Fig. 4 is a diagram showing an example of changes in current I and temperature T during one heating test.

[0031] After a predetermined number of heating tests are completed, the simple regression analysis unit 10 performs a simple regression analysis based on the recorded time series data of the current I and the time series data of the temperature T, and calculates the slope a and intercept b of the regression line (Step S209 in FIG. 3). Specifically, the simple regression analysis unit 10 calculates an integrated value I of the current I for each heating test. INTEGRALWhen the maximum temperature T for each heating test is obtained as shown in Fig. 5, the least squares method is used to calculate the slope a and intercept b of the regression line L. In the example of Fig. 5, I1 is the integrated value of current I in the first heating test, T1 is the maximum temperature T in the first heating test, I2 is the integrated value of current I in the second heating test, and T2 is the maximum temperature T in the second heating test.

[0032] Then, the simple regression analysis section 10 sets the calculated values ​​of the slope a and the intercept b in the temperature calculation section 6 (Step S210 in FIG. 3). This completes the process in Fig. 3. The process in Fig. 3 is performed before the object 11 is actually heated to manufacture a product, but if the type of at least one of the heating coil 1 and the object 11 is changed, the process in Fig. 3 must be performed again.

[0033] According to this embodiment, the regression line can be derived by a preliminary heating test to automatically set the temperature calculation unit 6, thereby making it possible to realize efficient equipment start-up.

[0034] [Second Example] Next, a second embodiment of the present invention will be described. Fig. 6 is a block diagram showing the configuration of a high-frequency induction heating device according to the second embodiment of the present invention. The high-frequency induction heating device includes a heating coil 1, an oscillator 2, a matching box 3, a control unit 4, a current sensor 5a that measures an AC current Ia supplied to the secondary side of the oscillator 2, a temperature calculation unit 6a, a display unit 7, a judgment unit 8, a judgment result output unit 9, a simple regression analysis unit 10a, and a voltage sensor 12 that measures an AC voltage Va supplied to the secondary side of the oscillator 2.

[0035] Next, the operation of the high frequency induction heating device of this embodiment will be described with reference to Fig. 7. Steps S300 and S301 in Fig. 7 are the same as steps S100 and S101 in Fig. 2. The current sensor 5a measures an AC current Ia supplied to the secondary side of the oscillator 2. The voltage sensor 12 measures an AC voltage Va supplied to the secondary side of the oscillator 2.

[0036] The temperature calculation unit 6a acquires data on the AC current Ia measured by the current sensor 5a and data on the AC voltage Va measured by the voltage sensor 12 (step S302 in FIG. 7). The temperature calculation unit 6a acquires data on the AC current Ia and the AC voltage Va at regular intervals until the heating time from the start of heating (start of oscillation) reaches a set value (YES in step S303 in FIG. 7). As a result, the time-series data on the AC current Ia and the AC voltage Va is recorded in the temperature calculation unit 6a.

[0037] When the heating time reaches the set value and the heating is stopped (step S304 in FIG. 7), the temperature calculation unit 6a calculates an estimated value of the temperature of the heated object 11 by inputting the integrated value of the time series data of the product of the AC current Ia and the AC voltage Va acquired from the start of heating to the end of heating into a predetermined regression line equation showing the relationship between the integrated value and the temperature (step S305 in FIG. 7). E The integrated value of the product of AC current Ia and AC voltage Va is W INTEGRAL , integrated value W INTEGRAL and the estimated value of temperature T E If the slope of the regression line showing the relationship between the two is a and the intercept of the regression line is b, the regression line formula is as follows. The method for deriving the regression line will be described later. T E = a × W INTEGRAL +b (2)

[0038] Steps S306 to S208 in FIG. 7 are the same as steps S106 to S108 in FIG.

[0039] Next, the integrated value W INTEGRAL and the estimated value T of the temperature T of the heated object 11 E A method of deriving a regression line showing the relationship between the heating coil 1 and the object 11 is described below. In this embodiment, before actually manufacturing a product by heating the object 11, a preliminary heating test is performed several times using the same heating coil 1 and object 11 as in the manufacturing process, and the integrated value W INTEGRAL The data on the temperature of the object 11 to be heated and the temperature data on the object 11 to be heated are acquired, and a regression line is obtained.

[0040] 8 is a flowchart for explaining a method for deriving a regression line. Steps S400 and S401 in FIG. 8 are the same as steps S200 and S201 in FIG.

[0041] The simple regression analysis unit 10a acquires data on the AC current Ia measured by the current sensor 5a and data on the AC voltage Va measured by the voltage sensor 12 (Step S402 in FIG. 8). As in the first embodiment, a temperature sensor attached to the object 11 measures the temperature T of the object 11. The simple regression analysis unit 10a acquires data on the temperature T measured by the temperature sensor (step S403 in FIG. 8). The simple regression analysis unit 10a acquires data on the AC current Ia, the AC voltage Va, and the temperature T at regular intervals until the heating time from the start of heating reaches a set value (YES in step S404 in FIG. 8). As a result, the simple regression analysis unit 10a records time-series data on the AC current Ia, the AC voltage Va, and the temperature T.

[0042] When the heating time reaches the set value and the heating stops (Step S405 in FIG. 8), the high-frequency induction heating device cools the object 11 to be heated (Step S406 in FIG. 8). As in the first embodiment, the simple regression analysis unit 10a waits until the object 11 to be heated cools down, and then changes the heating conditions (Step S407 in FIG. 8).

[0043] After a predetermined number of heating tests are completed, the simple regression analysis unit 10a performs a simple regression analysis based on the time series data of the product of the AC current Ia and the AC voltage Va and the time series data of the temperature T, and calculates the slope a and intercept b of the regression line (Step S409 in FIG. 8). Specifically, the simple regression analysis unit 10a calculates an integrated value W of the product of the AC current Ia and the AC voltage Va for each heating test. INTEGRALWhen the maximum temperature T for each heating test is obtained as shown in Fig. 9, for example, the slope a and intercept b of the regression line L are calculated by the least squares method. In the example of Fig. 9, W1 is the integrated value of the product of the AC current Ia and the AC voltage Va in the first heating test, T1 is the maximum temperature T in the first heating test, W2 is the integrated value of the product of the AC current Ia and the AC voltage Va in the second heating test, and T2 is the maximum temperature T in the second heating test.

[0044] Then, the simple regression analysis unit 10a sets the calculated values ​​of the slope a and intercept b in the temperature calculation unit 6a (Step S410 in FIG. 8). Thus, in this embodiment, the same effect as in the first embodiment can be obtained. Note that, although the current sensor 5a and the voltage sensor 12 are provided between the oscillator 2 and the matching box 3 in this embodiment, they may be provided between the matching box 3 and the heating coil 1.

[0045] The control unit 4, temperature calculation unit 6, 6a, display unit 7, judgment unit 8, judgment result output unit 9, and simple regression analysis unit 10, 10a of the high frequency induction heating device explained in the first and second embodiments can be realized by a computer equipped with a CPU (Central Processing Unit), a storage device, and an interface, and a program that controls these hardware resources. An example of the configuration of this computer is shown in FIG.

[0046] The computer includes a CPU 100, a storage device 101, and an interface device (hereinafter abbreviated as I / F) 102. The I / F 102 is connected to an oscillator 2, current sensors 5, 5a, a voltage sensor 12, the hardware of a display unit 7, the hardware of a determination result output unit 9, a temperature sensor, and the like. In such a computer, a program for implementing the method of the present invention is stored in the storage device 101. The CPU 100 executes the processes described in the first and second embodiments in accordance with the program stored in the storage device 101. [Industrial Applicability]

[0047] The present invention can be applied to a high-frequency induction heating device. [Explanation of symbols]

[0048] 1...heating coil, 2...oscillator, 3...matching box, 4...control unit, 5, 5a...current sensor, 6, 6a...temperature calculation unit, 7...display unit, 8...judgment unit, 9...judgment result output unit, 10, 10a...simple regression analysis unit, 11...heated object, 12...voltage sensor.

Claims

1. A heating coil configured to receive a high-frequency current and generate an induced current in an object to be heated by high-frequency induction; an oscillator configured to convert a DC voltage into an AC voltage and supply a high frequency current to the heating coil; a current sensor configured to measure a current supplied to a primary side of the oscillator; and a temperature calculation unit configured to calculate an estimated value of the temperature of the object to be heated by inputting an integrated value of the current measured by the current sensor into a regression line equation showing the relationship between the integrated value and the temperature of the object to be heated.

2. 2. The high frequency induction heating device according to claim 1, The high frequency induction heating device further comprises a determination unit configured to determine whether the estimated value of the temperature of the object to be heated exceeds a predefined temperature threshold value.

3. The high frequency induction heating device according to claim 1 or 2, A high-frequency induction heating device further comprising a simple regression analysis unit configured to acquire data on an integrated current value for each heating test measured by the current sensor and data on the temperature of the heated object for each heating test measured by a temperature sensor attached to the heated object during multiple heating tests performed before calculating an estimated value of the temperature of the heated object, and to determine an equation for the regression line based on the acquired data.

4. A heating coil configured to receive a high-frequency current and generate an induced current in an object to be heated by high-frequency induction; an oscillator configured to convert a DC voltage into an AC voltage and supply a high frequency current to the heating coil; a current sensor configured to measure an alternating current supplied to a secondary side of the oscillator; a voltage sensor configured to measure an AC voltage supplied to a secondary side of the oscillator; and a temperature calculation unit configured to calculate an estimated value of the temperature of the object to be heated by inputting an integrated value of the product of the AC current measured by the current sensor and the AC voltage measured by the voltage sensor into a regression line equation showing the relationship between the integrated value and the temperature of the object to be heated.

5. 5. The high frequency induction heating device according to claim 4, The high frequency induction heating device further comprises a determination unit configured to determine whether the estimated value of the temperature of the object to be heated exceeds a predefined temperature threshold value.

6. 6. The high frequency induction heating device according to claim 4, a simple regression analysis unit configured to obtain data on an integrated value of the product of the AC current and the AC voltage for each heating test measured by the current sensor and the voltage sensor, and data on the temperature of the heated object for each heating test measured by a temperature sensor attached to the heated object, during multiple heating tests performed before calculating an estimated value of the temperature of the heated object, and to determine an equation for the regression line based on the obtained data.

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