JPH09330785A - Induction heating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower a heating unit requirement and save energy by providing an arithmetic circuit determining the voltage of prescribed inverters so that the sum of generated power of N inverters may be minimum based on prescribed data. SOLUTION: Before the operation of a heating apparatus, data necessary for the operation, that is, the diameter of a material to be heated and the carrier speed of the material to be heated are inputted by a material to be heated data input device 11. An arithmetic unit 10 calculates the value of a weight to be treated which is calculated by the diameter of the material to be heated and the carrier speed and rough required power by a rough heating unit requirement, based on the data. Next, voltage is determined with repeated calculations by prescribed expressions so that the sum P of generated power of N inverters may be minimum on prescribed conditions. Based on the calculation result, voltage is set to a high frequency inverter 3 for low-temperature and a high frequency inverter 4 for high-temperature. Thus, power which makes the heating unit requirement the smallest is supplied to a heating coil 5 for low-temperature and a heating coil 6 for high-temperature and energy can be saved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating device for forging which can save energy.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of an induction heating device disclosed in Japanese Patent Laid-Open No. 1-313877. In the figure, 1 is a power receiving panel for opening and closing an AC commercial frequency power source, 2 is a power supply transformer, 3 is a high frequency inverter device for low temperature regions, 4 is a high frequency inverter device for high temperature regions, and 5 is for low temperature regions. Is a heating coil for a high temperature range, 7 is a material to be heated which is a steel material, 8 is a pinch roller mechanism for conveying the material to be heated, and 9 is a motor for driving the pinch roller mechanism 8.

The operation of this induction heating device (hereinafter, heating device) will be described below. First, the steady operation will be described. The material 7 to be heated is continuously conveyed at a constant speed through the heating coil 5 for the low temperature region and the heating coil 6 for the high temperature region by the pinch roller mechanism 8 to a predetermined forging temperature (usually 120).
It is heated to about 0 ° C.), discharged from the heating device, and sent to a post process (press device) not shown. During this steady operation, the temperature rise process of the billet (material to be heated) in the heating coil (hereinafter, both the heating coil 5 for the low temperature region and the heating coil 6 for the high temperature region is shown) is normal temperature as shown in FIG. It becomes a curve that rises from to a predetermined temperature.

Here, the electric power output from the high-frequency inverter 3 for the low temperature region and the high-frequency inverter 4 for the high temperature region is determined so as to match the temperature rising curve shown in FIG. The conveyance speed of the material to be heated and the output voltage of the high frequency inverter devices 3 and 4 required for these operations are determined by a control device (not shown) in the heating device.

Next, the case where the treated weight of the material to be heated changes per unit time will be described. The processing weight is the weight of the material to be heated passing through per unit time, and is determined by the diameter of the material to be heated and the conveying speed. When the processing weight is larger than the capacity of the heating device, the electric power generated by the high frequency inverter devices 3 and 4 is set as shown in P1 of FIG. 5, and the temperature rise characteristic in the heating device is the curve of A of FIG. Become. Next, when the processing weight is relatively small, the electric power generated by the high frequency inverter devices 3 and 4 is set as shown by P2L and P2H in FIG. 5, and the temperature rise characteristic in the heating device is the curve of B in FIG. Become.

The reason for this is as follows: As the processing weight becomes smaller, the required power also becomes smaller, but since the heat radiation loss is almost constant, the ratio of the heat radiation loss to the power generated by the high frequency inverter is high in the high temperature zone. growing. Therefore, the electric power that contributes to the temperature rise becomes small in the high temperature zone, and if the electric power of the heating coil 6 for the high temperature region is simply made small, the temperature rise characteristic becomes as shown in FIG. 4B. When the treatment weight is further reduced, the input electric power becomes smaller than the heat radiation loss, and the temperature rise characteristic becomes a curve in which the temperature rises excessively in the high temperature zone as shown in C of FIG. A characteristic such as C in FIG. 4 causes overheating and increases heat dissipation loss, which deteriorates the heating unit.

As an example, let us consider a heating device with a rated power of 1,000 kW.
When the temperature is raised to 1, the total length of the heating coil is about 3,000m.
m, the length of the high temperature region (about 1,100 ° C. or higher) is about 1,000 mm. In this case, the heat dissipation loss in the low temperature region (converted into heating coil power) is only about 10 kW, but the heat dissipation loss in the high temperature region is about 50 kW.
This is because the heat dissipation loss increases as the surface temperature of the material to be heated increases (more accurately, it increases in proportion to the fourth power of the absolute temperature).

At high conveying speeds using rated power,
The power supplied to the low temperature zone is about 800 kW, so even if the transport speed is reduced to 1/5, the power supplied is about 160
Since there is also kW, which is much larger than the heat dissipation loss, the heat dissipation loss can be ignored. On the other hand, in the high temperature zone, the supply power is about 200 kW, so the heat dissipation is larger than the heat dissipation loss at the transfer speed using the rated power, but when the transfer speed is reduced to 1/5, the supply power is reduced to about 40 kW in proportion to it. Lower than the heat dissipation loss. If this condition is left as it is, the temperature will drop in the high temperature region. Therefore, if the supply power is made larger than ⅕ in order to avoid it, overheating such as C in FIG. 4 will occur in the high temperature region.

However, when the low temperature inverter and the high temperature inverter are separately installed as shown in FIG. 3,
It is possible to set such that even if the power of the low temperature range inverter is reduced in proportion to the transport speed when the transport speed is reduced, the power of the high temperature region inverter is not reduced as much as the transport speed is reduced.

Therefore, in order to constantly apply electric power exceeding the heat radiation loss, the heating coil 6 for high temperature range as shown by P3H in FIG.
Apply a relatively large amount of power to. That is, the generated power of the high frequency high frequency inverter device 4 is made higher than that of the low temperature high frequency inverter device 3. By this method
Even in the high temperature zone, the electric power exceeding the heat dissipation loss can be applied, and the temperature rising characteristic is a curve that does not cause overheating like the temperature rising characteristic of a large processing weight (A of FIG. 4) as shown in FIG. 4B.

In the above description, the case where each of the high frequency inverter device and the heating coil is two units is shown, but the same operation is performed even when three or more units (three sections), that is, when the processing weight is small, it is put into the high temperature zone. By making the electric power to be relatively large, overheating can be avoided and a high heating unit consumption can always be obtained.

[0012]

As described above, in the conventional induction heating apparatus, by using a plurality of sections, that is, a plurality of high-frequency inverter devices and heating coils, overheating of the material to be heated can be avoided and a high heating source can be avoided. You can always get credits, but there were the following problems. FIG. 6 shows the temperature characteristics of the surface and center of the material to be heated. In induction heating, an induction current is passed through the surface of the material to be heated, so that the surface temperature first rises and the central temperature catches up due to heat conduction in the high temperature region. In the induction heating device for forging, the smaller the temperature difference between the surface of the material to be heated and the center, the higher the quality of the forged product can be manufactured by pressing in the subsequent process.

Therefore, generally, a large amount of electric power is applied to the first half section (low temperature region) to raise the temperature of the surface first, and a small amount of electric power is applied to the latter half section (high temperature region) to wait for the center temperature to rise. . However,
If a large amount of power is applied in the first half section and the surface temperature is increased in the first half section, heat dissipation loss is increased, and since extra power is applied, the heating unit is deteriorated. That is, reducing the temperature difference between the surface and the center of the material to be heated, that is, soaking has the contradictory problem of deteriorating the heating unit. The conventional induction heating device does not consider the above problems, and has a problem that it is difficult for the user of the induction heating device to use.

The present invention solves the above problems,
The present invention provides a heating device capable of reducing energy consumption and achieving energy saving.

[0015]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems and is divided into N sections for inductively heating a continuously conveyed material to be heated to a predetermined high temperature from room temperature. Heating coil and one to one to the above heating coil
N inverter devices connected to each other to supply high-frequency power, a transport mechanism for continuously transporting the material to be heated from the supply section to the discharge section in the heating coil at a constant speed, and the steady state. In an induction heating device having a voltage setting circuit for setting the voltage of the inverter device according to the speed, the processing weight per unit time of the heated material, the final heating temperature of the heated material, the surface of the heated material , An arithmetic circuit for determining the voltage of the inverter device of the I-th section from the low temperature region so as to minimize the total sum of the generated power of the N inverter devices from the allowable value of the temperature difference between the centers. It is the one.

Further, according to the present invention, in the above arithmetic circuit,
The surface temperature T _{S of} the material to be heated, the center temperature T _{C of} the material to be heated, the allowable value T _D of the temperature difference between the surface of the material to be heated and the center, and the total power P generated by the N inverter devices. Therefore, the voltage determining means for calculating the voltage V _{I of the} inverter device that minimizes the electric power P is provided from the following equations represented by the coefficients K _SI , K _CI , and K _PI .

T _S = Σ _{I = 1} ^N (K _SI × V _I ^J ) T _C = Σ _{I = 1} ^N (K _CI × V _I ^J ) P = Σ _{I = 1} ^N (K _PI × V _I ^J ) │T _S -T _C │ ≦ T _D

Further, according to the present invention, in the above arithmetic circuit,
The treatment weight M of the heated material per unit time, the surface temperature T _{S of} the heated material, the center temperature T _{C of} the heated material, the surface of the heated material, and an allowable value T _D of the temperature difference between the centers, From the sum P of the generated power of the above N inverter devices, the coefficients K _SI , K
_According to the following expressions represented by _SM , K _CI , K _CM , K _PI , and K _PM , a voltage determining means for calculating the voltage V _{I of the} inverter device that minimizes the power P is provided. .

T _S = Σ _{I = 1} ^N (K _SI × V _I ^J ) −K _SM × M T _C = Σ _{I = 1} ^N (K _CI × V _I ^J ) −K _CM × M P = Σ _{I = ^{1 N (K PI × V I}} J) -K PM × M | T S -T C | ≦ T D

According to the present invention having the above-mentioned structure,
In order to determine the applied voltage to each section of the induction heating device, the optimum applied voltage can be calculated from the calculation formula of the final heating temperature and the heating unit.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, 1 to 9 are the same as or equivalent to those shown in FIG. Reference numeral 10 is an arithmetic circuit 11, an input device for data of a material to be heated, 12 is a voltage setter of a high-frequency inverter device for low temperature region, and 13 is a voltage setter of a high-frequency inverter device for high temperature region.

Next, the operation of this device will be described. Applied power of the first half section, that is, high frequency inverter device 3
Of the generated power P _A, the power applied in the latter half section, i.e. power P _B generated by the high-frequency inverter unit 4,
When the total electric power is P _T , the treated weight of the material to be heated is M, and the heating unit is N ₀ , the following formula is obtained.

P _T = P _A + P _B (1) P _T = M × N ₀ (2)

Here, the heating basic unit N ₀ is a value that increases or decreases depending on the temperature rising characteristics as described above, but in a normal heating device, the range of increase or decrease is about ± 10%. The temperature of the material to be heated increases as the electric powers P _A and P _B increase with the same processing weight and as the processing weight M decreases with the same electric power. Therefore, the following formula is established.

Temperature T = K _A × P _A + K _B × P _B −K _M × M (3) Here, K _A , K _B , and K _M are coefficients.

When the above equation is described for the surface temperature T _S and the central temperature T _C of the material to be heated, the following equation is obtained.

T _S = K _SA × V _A ² + K _SB × V _B ² −K _SM × M (4) T _C = K _CA × V _A ² + K _CB × V _B ² −K _CM × M ... (5) _{where, K SA, K SB, K} SM, K CA, K CB, K CM is a coefficient.

Further, as described above, as the power of the first half section is larger than the power of the latter half section, the material to be heated is more likely to be soaked, and the power of the first half section is higher than the power of the latter half section. The smaller the size, the harder it is to heat the material to be heated. Further, since the total length of the heating coil does not change, when the treatment weight M increases, the total heating coil passing time of the material to be heated becomes short, and the temperature difference between the surface and the center of the material to be heated becomes large.

Here, in the induction heating device for forging, the allowable temperature difference T _D between the surface and the center of the final heating temperature is generally 40 to 60 ° C., and there is a problem if it is within this value regardless of the heating curve. Absent. Therefore, the following formula is established.

| T _S −T _C | ≦ T _D (7)

Therefore, the temperature rising curve may be set so that the unit heating rate is the lowest (smallest) so that the allowable temperature difference T _D can be obtained. The temperature rise curve with the smallest heating unit is a curve in which the temperature rise in the first half section is small, and the temperature rise in the second half section is large to reach the predetermined temperature at the outlet of the heating device. The temperature difference between the surface of the material to be heated at the outlet of the heating device and the center is 40 to 6 above.
It should be 0 ° C.

To reduce the temperature rise in the first half section,
It is to reduce the input power of the first half section, and to increase the temperature rise in the second half section, increase the input power of the second half section. Therefore, if the ratio of the applied power P _{A of} the first half section and the applied power P _B of the second half section and P _A / P _B are set to be as small as possible so as to be within a predetermined temperature difference, the heating unit becomes small. That is, the applied voltage V _A of the first half section may be reduced and the applied voltage V _B of the second half section may be increased.

Here, there is the following relationship between the power P, the voltage, and the processing weight M. That is, according to the equation (2), the electric power P is proportional to the treatment weight M, but from the above-mentioned relation,
On the other hand, as the applied voltage V _{A of the} first half section is smaller,
The larger the applied voltage V _{B in the} latter half section, the smaller the required power P becomes. Therefore, the following formula is obtained.

P = K _PA × V _A ² + K _PB × V _B ² + K _PM × M (6) Here, K _PA , K _PB , and K _PM are coefficients.

The control performed in this embodiment will be described below. First, before operating the heating device, the data required for operation, that is, the diameter D of the material to be heated and the transport speed S of the material to be heated are input from the material to be heated data input device 11. Based on the above data, the arithmetic unit 10 calculates the approximate required power P _T from the approximate heating unit based on the value of the treatment weight M calculated from the heated material diameter D and the transport speed S. Next, under the condition of the expression (7), the voltages V _A and V _{B are} repeatedly calculated from the expressions (4) to (6) so that the electric power P is minimized.
To determine.

The coefficients K _SA , K _SB , necessary for the above calculation,
K _SM , K _CA , K _CB , K _CM , K _PA , K _PB , and K _PM can be determined in advance from experimental data and can be stored inside the arithmetic unit 10. Also,
Since the above coefficient changes depending on the diameter of the material to be heated, the memory according to the diameter of the material to be heated is performed.

Based on the above calculation result, the voltage V _A is set in the high frequency inverter device 3 and the voltage V _B is set in the high frequency inverter device 4. By this operation, electric power is supplied to the heating coil 5 for low temperature region and the heating coil 6 for high temperature region so that the heating unit is the smallest. In order to obtain a predetermined temperature difference T _D with respect to S, the operation is performed with a temperature rising curve that minimizes the heating unit.

FIG. 2 shows the result of carrying out the present invention in the following embodiments. In this experiment, a heating device with a rated power of 1,200 kW was installed in the first half section 600 k.
It is divided into two units of W and the latter half section 600 kW, and heats a bar material having a diameter of 44 to 1,200 ° C. According to the experiment, in the data (1) in which the power of the first half section is set to be relatively high and the data (2) in which the power of the first half section is set to be relatively low, the required power of the data (2) is about 8% smaller. became. From this as well, it can be seen that the power required in the first half section is smaller, that is, the energy saving is achieved.

Embodiment 2 In the first embodiment described above, the number of inverter devices is two, but in a heating device that requires a large amount of power, the number may be three or more. Even when three or more units are used, the same control method as the control method described in the first embodiment can be used. That is, the heating unit can be reduced by supplying a small amount of electric power to the section close to the inlet side (first half) of the heating device and a large amount of electric power toward the outlet side (second half). General formulas corresponding to formulas (4) to (6) in this case are as follows.

T _S = Σ _{I = 1} N (K _SI × V _I ² ) −K _SM × M T _C = Σ _{I = 1} N (K _CI × V _I ² ) −K _CM × M P = Σ _{I = 1} N (K _PI × V _I ² ) −K _PM × M where K _SI , K _SM , K _CI , K _CM , K _PI , and K _PM are coefficients.

According to the first and second embodiments, the circuits required for control and calculation can be constructed at a relatively low cost with a commercially available programmable controller or the like.

[0042]

As is apparent from the above description, the induction heating apparatus according to the present invention is divided into N sections for inductively heating the material to be continuously conveyed to a predetermined high temperature from room temperature. A heating coil, N inverter devices connected to the heating coil in a one-to-one relationship to supply high-frequency power, and the material to be heated continuously from the supply portion to the discharge portion in the heating coil. In an induction heating device having a transport mechanism for transporting at a steady speed, and a voltage setting circuit for setting the voltage of the inverter device according to the steady speed, a processing weight of the heated material per unit time, the heated material From the final heating temperature, the allowable temperature difference between the surface of the material to be heated, and the center, the invertor of the I-th section from the low temperature region is set so as to minimize the total sum of the generated power of the N inverter devices. Because you have an arithmetic circuit for determining the voltage of the device, most heating intensity decreases such Atsushi Nobori curve and each section input power can be set, energy saving of the heating apparatus can be achieved.

Further, in the induction heating device according to the present invention, in the arithmetic circuit, the surface temperature T _{S of} the heated material, the central temperature T _{C of} the heated material, the temperature of the surface of the heated material, and the temperature between the centers. From the following equation expressed by the coefficients K _SI , K _CI , and K _PI from the allowable value T _{D of the} difference and the total power P generated by the N inverter devices, the inverter device that minimizes the power P Since a voltage determining means for calculating the voltage V _I of the heating device is provided, the temperature rising curve and the electric power applied to each section can be set so that the heating unit can be minimized similarly to the above, and energy saving of the heating device can be achieved. .

T _S = Σ _{I = 1} ^N (K _SI × V _I ^J ) T _C = Σ _{I = 1} ^N (K _CI × V _I ^J ) P = Σ _{I = 1} ^N (K _PI × V _I ^J ) │T _S -T _C │ ≦ T _D

Further, in the induction heating device according to the present invention, in the arithmetic circuit, the treatment weight M of the material to be heated per unit time, the surface temperature T _{S of} the material to be heated, and the central temperature T _{C of the} material to be heated. , The allowable value T _D of the temperature difference between the surface of the material to be heated and the center, and the total power P generated by the N inverter devices, the coefficients K _SI , K _SM , K _CI , K _CM , K _PI , and K _Since the voltage determining means for calculating the voltage V _{I of the} inverter device that minimizes the electric power P is provided from the following expression represented by _PM , the heating unit unit that minimizes the heating unit is the same as above. The temperature curve and the power input to each section can be set to save energy in the heating device.

T _S = Σ _{I = 1} ^N (K _SI × V _I ^J ) −K _SM × M T _C = Σ _{I = 1} ^N (K _CI × V _I ^J ) −K _CM × M P = Σ _{I = ^{1 N (K PI × V I}} J) -K PM × M | T S -T C | ≦ T D

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing an implementation result in the first embodiment.

FIG. 3 is a block diagram showing a conventional induction heating device.

FIG. 4 is a diagram showing a temperature rise curve.

FIG. 5 is a diagram showing input power.

FIG. 6 is a diagram showing changes in surface temperature and center temperature of a material to be heated.

[Explanation of Codes] 1 power receiving panel, 2 transformer, 3 high frequency inverter for low temperature range, 4 high frequency inverter for high temperature range, 5 heating coil for low temperature range, 6 heating coil for high temperature range, 7 heated material (steel material), 8 Pinch roller mechanism, 9 drive motor, 10
Arithmetic device, 11 input device, 12 voltage setting device, 13
Voltage setting device.

Claims (3)

[Claims] 1. A heating coil divided into N sections for inductively heating a continuously conveyed material from room temperature to a predetermined high temperature, and high-frequency power connected to the heating coil in a one-to-one correspondence. Inverter units for supplying the heating target material, a transport mechanism for continuously transporting the material to be heated from the supply unit to the discharge unit in the heating coil at a steady speed, and the inverter device according to the steady speed. In an induction heating device having a voltage setting circuit for setting the voltage of, the processing weight per unit time of the heated material, the final heating temperature of the heated material, the surface of the heated material, the temperature difference between the center of It has an arithmetic circuit for determining the voltage of the inverter device of the I (≦ N) th section from the low temperature range so as to minimize the total sum of the generated power of the N inverter devices from the allowable value. That the induction heating device. 2. The arithmetic circuit comprises a surface temperature T _{S of} the material to be heated, a center temperature T _{C of the} material to be heated, a surface temperature of the material to be heated, a permissible value T _D of the temperature difference between the centers, and N. From the sum P of the generated power of the individual inverter devices, the coefficients K _SI , K _CI ,
The induction heating device according to claim 1, further comprising a voltage determining unit that calculates a voltage V _{I of the} inverter device that minimizes the electric power P from the following expression represented by K _PI . [Formula 1] T _S = Σ _{I = 1} ^N (K _SI × V _I ^J ) T _C = Σ _{I = 1} ^N (K _CI × V _I ^J ) P = Σ _{I = 1} ^N (K _PI × V _I ^J ) | T _S −T _C | ≦ T _D 3. The arithmetic circuit comprises a processing weight M of the heated material per unit time, a surface temperature T _{S of} the heated material, a central temperature T _{C of} the heated material, a surface of the heated material, and a center of the heated material. From the allowable value T _D of the temperature difference between them and the total P of the generated power of the above N inverter devices, the coefficients K _SI , K _SM , K _CI , K _CM , and K
The induction heating device according to claim 1, further comprising a voltage determining unit that calculates a voltage V _{I of the} inverter device that minimizes the electric power P from the following expressions represented by _PI and K _PM . [Formula 2] T _S = Σ _{I = 1} ^N (K _SI × V _I ^J ) −K _SM × M T _C = Σ _{I = 1} ^N (K _CI × V _I ^J ) −K _CM × M P = Σ _{I ^{= 1 N (K PI × V}} I J) -K PM × M | T S -T C | ≦ T D