JP4444126B2 - Heating equipment - Google Patents

Description

  The present invention relates to a heating apparatus such as an induction heating cooker that performs cooking while appropriately suppressing the temperature of an object to be heated.

  Conventionally, this type of cooking device stores the control temperature according to the output of the inverter in the memory circuit, and increases and decreases the set output every time the temperature of the thermistor reaches the control temperature according to the set output. Control temperature was also changed according to the output (for example, refer to patent documents 1). In addition, there is a control means for this type of heating cooker that obtains a temperature change of the object to be heated by detecting a time change of the magnetic coupling between the object to be heated and the induction heating coil, and performs an appropriate control. (For example, refer to Patent Document 2).

  FIG. 5 shows a heating cooker described in Patent Document 1. As shown in the figure, an inverter 18 that converts commercial power into high-frequency current, a control circuit 19 that controls the output of the inverter 18, a temperature detection means 21 that detects the temperature of a frying pan 20 that is to be heated, and an inverter 18. An operation unit 22 for setting the output of the control circuit, a storage circuit 23 for storing a control temperature corresponding to the output set by the operation unit 22, and a temperature control unit 24 for controlling the output of the inverter 18. 24, when the temperature detected by the temperature detection means 21 exceeds the control temperature stored in the storage circuit 23, the output of the inverter 18 is stopped or reduced, and the temperature detected by the temperature detection means 21 is the storage circuit 23. When the temperature falls below the stored control temperature, control is performed to increase the output of the inverter 18 to prevent the temperature of the frying pan 20 from becoming abnormally high. To have.

The induction heating cooker of patent document 2 suppresses or stops the output of an inverter according to the time change of the controlled variable of the control means which controls so that the input current of an inverter becomes fixed. The time change of the controlled variable has a correlation with the temperature change of the object to be heated and has high responsiveness, so that the temperature change of the object to be heated can be detected at high speed. In addition, in consideration of the detection result of the temperature change of the temperature detection means, even if the pan bottom as the object to be heated is deformed during heating, it is possible to appropriately control.
JP-A-9-7752 JP 2004-247237 A

  However, in the conventional configuration described in Patent Document 1, the temperature detection means 21 detects the temperature of the frying pan 20 via the heated object mounting table 25, so that the thermal response is slow and appropriate control is difficult. there were. FIG. 6 shows the temperature of the frying pan 20 and the output of the temperature detecting means 21 when cooking the fried food using the frying pan 20. The solid line is the temperature of the frying pan 20 and the broken line is the temperature of the temperature detecting means 21. Although the temperature of the frying pan 20 is drastically lowered by adding the food after the preheating time ty, the output of the temperature detection means 21 is delayed in time and is still in the middle of the rise. For this reason, although the temperature of the frying pan 20 is lowered by the addition of food, and the temperature of the frying pan 20 is not likely to be heated to an abnormally high temperature, the output of the temperature detecting means 21 is due to a time delay. The control temperature stored in the storage circuit 23 is reached and the output of the inverter 18 is stopped or reduced. As a result, the temperature of the frying pan 20 is significantly lower than the target temperature, and there is a problem that sufficient heating power for heating the food cannot be obtained.

  Further, in the conventional configuration described in Patent Document 2, the time change of the control amount of the control means for controlling the input current of the inverter to be constant is not less than a predetermined amount, and the temperature change amount of the temperature detecting means is also the predetermined amount. At the above time, the output of the inverter is suppressed or stopped. For this reason, when heating of the object to be heated is started and stopped once and then heated again, since the object to be heated is already at a high temperature, the time variation of the control amount and the temperature of the temperature detection means There was a problem that the object to be heated would be heated to an abnormally high temperature while the change amount could not be changed more than a predetermined amount.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a heating apparatus that can obtain a sufficient heating power while appropriately suppressing the maximum temperature of an object to be heated regardless of the set output.

In order to solve the conventional problem, the heating device of the present invention includes an inverter to which an induction heating coil is connected and a switching element is provided to convert a commercial power source into a high-frequency current;
Temperature detecting means for detecting the temperature of the object to be heated by the induction heating coil via a top plate on which the object to be heated is placed , an operation unit for setting the output of the inverter, and the switching element. the on-time and long to increase the input current of the inverter to control the inverter so as to constantly maintain each output the input current is set by reducing the input current by shortening the oN time input stop control means, a memory circuit for storing a control temperature corresponding to the output set by the operation unit, the output of the inverter when the temperature detected by said temperature detecting means exceeds a pre-SL control temperature Alternatively smaller and the temperature control means temperature detected by the temperature detecting means is controlled so as to increase the output of the inverter when it becomes less than the control temperature Wherein the temperature control means, said case differential value of the time of the on-time of near zero or negative, even if the temperature detected by said temperature detecting means exceeds the control temperature, stopping the output of the inverter Or it is set as the structure which does not perform the operation | movement to make small .

As a result, the differential value with respect to the on-time of the switching element is correlated with the temperature change of the object to be heated and has high responsiveness, so whether the temperature of the object to be heated is increasing or decreasing. The temperature of the object to be heated can be appropriately controlled even if there is a delay in the response of the temperature detecting means.

  The heating device of the present invention has a sufficient cooking power and a good cooking performance while appropriately suppressing the maximum temperature of the object to be heated regardless of the set output.

In the first invention, an induction heating coil is connected and a switching element is provided to convert a commercial power source into a high-frequency current, and the temperature of the object to be heated heated by the induction heating coil is adjusted by the object to be heated. The temperature detecting means for detecting through the mounted top plate, the operation unit for setting the output of the inverter, the ON time of the switching element is lengthened to increase the input current of the inverter, and the ON time is increased. an input control means for controlling said inverter so as to constantly maintain each output the input current is set by reducing the input current is shortened, and stores a control temperature corresponding to the output set by the operating unit a memory circuit which the output of the inverter is stopped or reduced when the temperature detected by said temperature detecting means exceeds a pre-SL control temperature And a temperature control unit whose serial detected by the temperature detecting unit temperature is controlled so as to increase the output of the inverter when it becomes less than the control temperature, the temperature control means, the derivative with respect to time of the on-time When the value is close to zero or minus, the heating device is configured so as not to stop or reduce the output of the inverter even if the temperature detected by the temperature detecting means exceeds the control temperature. Therefore , the differential value with respect to the ON time is correlated with the temperature change of the object to be heated and has high responsiveness, so that it is possible to grasp whether the temperature of the object to be heated is increasing or decreasing. Even if there is a delay in the response of the temperature detection means, the temperature of the object to be heated can be appropriately controlled.

If the differential value of the time variation of the control amount in the input control means is zero or negative, the inverter output is stopped or reduced even if the temperature detected by the temperature detection means exceeds the control temperature stored in the storage circuit. Control temperature memorized due to delay in response of temperature detection means even though the temperature of the object to be heated tends to decrease due to the addition of ingredients, etc. The output is not reduced or stopped even when the value exceeds. For this reason, a decrease in the temperature of the object to be heated can be reduced, and during this time, the temperature detection means follows the temperature of the object to be heated, and appropriate control becomes possible.

A second invention is, in particular, in the first invention, temperature control means, if the differential value for the on-time period is near zero or negative, the temperature detected by the temperature detecting means exceeds the control temperature by also has a configuration to avoid the operation temperature detected by said temperature detecting means to stop or reduce the inverter output of a predetermined time from beyond the control temperature, the object to be heated in such ingredients introduced temperature despite declining, the control temperature even if it exceeds the temperature sensing means a predetermined time temperature measured from beyond the control temperature in the response delay of the temperature sensing means decreases the output Or the control which stops is not carried out. For this reason, a decrease in the temperature of the object to be heated can be reduced, and the temperature detection means follows the temperature of the object to be heated within a predetermined time, and appropriate control becomes possible.

A third invention is, in particular, in the first invention, when the differential value of the on-time period is near zero or negative, with the construction of changing to a higher control temperature by a predetermined value, food Even if the temperature of the object to be heated tends to decrease due to the input of heat, etc., even if it exceeds the stored control temperature due to the response delay of the temperature detection means, the control temperature is changed to a higher value by a predetermined value. Does not reduce or stop the output. For this reason, a decrease in the temperature of the object to be heated can be reduced, and during this time, the temperature detection means follows the temperature of the object to be heated, and appropriate control is possible.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIGS. 1-3 has shown the induction heating cooking appliance as a heating apparatus in Embodiment 1 of this invention.

  As shown in FIG. 1, a commercial power source 1 is input to a rectifying / smoothing unit 2, and the rectifying / smoothing unit 2 is composed of a full-wave rectifier composed of a bridge diode and a choke coil and a smoothing capacitor between its DC output terminals. A low-pass filter is connected.

  An inverter 3 that converts the commercial power source 1 into a high-frequency current is connected to the output of the rectifying and smoothing unit 2, and an induction heating coil 4 is connected to the inverter 3. The inverter 3 and the induction heating coil 4 constitute a high frequency inverter. The inverter 3 is provided with a switching element 5 (IGBT in the present embodiment), a diode 6 connected in antiparallel thereto, and a resonance capacitor 7 connected in parallel to the induction heating coil 4.

  The current transformer 8 detects an input current input from the commercial power source 1 of the inverter 3 and inputs it to the control means 9. The control means 9 is provided with input control means 10 for controlling the inverter 3 by turning on and off the switching element 5 so that the input current of the inverter 3 becomes constant for each set output. Further, the control means 9 includes a storage circuit 14 that stores a control temperature tc corresponding to an output set by an operation unit (described later), a time change of a control amount output by the input control means 10, and a plate 11. A temperature control means 15 for controlling increase / decrease / stop of the output based on the result of comparing the detected temperature of the temperature detection means 13 for detecting the temperature of the article 12 to be heated and the control temperature tc of the memory circuit 14 is provided. . The temperature control means 15 stops or reduces the output of the inverter 3 when the temperature detected by the temperature detection means 13 exceeds the control temperature tc stored in the storage circuit 14, and the temperature detected by the temperature detection means 13 Control is performed so as to increase the output of the inverter 3 when the temperature is lower than or equal to the control temperature tc stored in the storage circuit 14, and operates in accordance with the differential value of the control variable in the input control means 10 over time. The configuration is changed.

  The control means 9 is connected to an operation section 16 for setting the output of the inverter 3, and the operation section 16 is provided with at least an output changeover switch 17 and an on / off switch 18 for supporting the start and stop of heating. Yes.

  The operation of the heating device configured as described above will be described.

  The commercial power source 1 is rectified by the rectifying / smoothing unit 2 and supplies power to the high-frequency inverter having the inverter 3 and the induction heating coil 4. The inverter 3 converts the rectified power source into a high frequency power source near 20 kHz by the switching element 5, drives the induction heating coil 4, and heats the object to be heated 12.

  Here, FIG. 2 shows the waveform of the drive signal output from the control means 9 to the switching element 5. The drive frequency is around 20 kHz and the cycle Tc is 50 μsec. The input current is controlled by changing the length of the time Ton when the H signal is output from the control means 9 and the switching element 5 is turned on as the control amount. When the input current is increased, the control amount Ton is lengthened, and when the input current is decreased, the control amount Ton is shortened. The input current is determined according to the output set by the output selector switch 17 of the operation unit 16, and the control amount Ton is controlled so that the current is maintained. The temperature control means 15 stops the output of the inverter 3 when the temperature detected by the temperature detection means 13 exceeds the control temperature tc stored in the storage circuit 14 when the differential value of the time variation of the control amount Ton is positive. Alternatively, the operation is performed so that the output of the inverter 3 is increased when the temperature detected by the temperature detection means 13 becomes equal to or lower than the control temperature tc stored in the storage circuit 14. However, when the differential value of the time variation of the controlled variable Ton is zero or minus, even if the temperature detected by the temperature detecting means 13 exceeds the control temperature tc stored in the storage circuit 14, the inverter 3 The output is not stopped or reduced.

  If it demonstrates based on an actual use condition, FIG. 3 will show the temperature of the to-be-heated object 12, the output of the temperature detection means 13, the control amount Ton time, when cooking the fried food using the to-be-heated object 12. It represents the relationship between the differential value ΔTon of the control amount Ton time and the input current. The solid line is the temperature of the article 12 to be heated, and the broken line is the temperature of the temperature detection means 13. As the temperature of the object to be heated 12 increases, the resistivity of the object to be heated 12 changes (generally, the resistivity increases as the temperature increases). As a result, the magnetic coupling between the induction heating coil 4 and the article to be heated 12 changes and the input current decreases, but the input control means 10 operates to control the control amount Ton in the increasing direction, so that the input current is reduced. Held constant. Further, when the temperature of the article to be heated 12 decreases due to the input of food, the input current increases, and the input control means 10 decreases the control amount Ton and the input current is kept constant. As a result, the change in the control amount Ton represents a change in the temperature of the object to be heated 12 without a time delay. In FIG. 3, the temperature of the object to be heated 12 is drastically decreased by adding the food material after the preheating time ty, whereas the output of the temperature detecting means 13 has a time delay and is still increasing. The control temperature is reached when t1 time elapses. At this time, the temperature of the article to be heated 12 tends to decrease, and the differential value ΔTon of the control amount Ton of the input control means 10 is negative, so that the temperature control means 15 does not decrease or stop the output of the inverter 3. ing. In the present embodiment, the output of the inverter 3 is not reduced or stopped only for a predetermined time tm. Thereby, since an unnecessary output is not reduced or stopped, the temperature of the article 12 to be heated can be reduced and sufficient thermal power can be obtained. In the present embodiment, the temperature detecting means is within a predetermined time tm. 13 follows the temperature of the article 12 to be heated, and appropriate control becomes possible.

(Embodiment 2)
FIG. 4 shows a heating device according to Embodiment 2 of the present invention. The basic configuration of the heating device is the same as that of Embodiment 1, and the description thereof is omitted.

The figure corresponds to FIG. 3 in the first embodiment, and the temperature of the object to be heated 12, the output of the temperature detection means 13, and the control amount when cooking the fried food using the object to be heated 12. The relationship between the Ton time, the differential value ΔTon of the control amount Ton time, and the input current is shown. That is, in the present embodiment, when the differential value ΔTon of the control variable with time in the input control means 10 is zero or negative (between ty and t2), the temperature detected by the temperature detection means 13 is the memory circuit. The control temperature t c stored in 14 is increased by a predetermined value α and changed to ( t c + α).

As a result, the output is not reduced or stopped unnecessarily, so that the temperature drop of the article to be heated 12 can be reduced and the temperature detecting means 13 can reach the temperature t c + α even when there is a sudden temperature rise. The output is reduced or stopped. For this reason, it can prevent that the to-be-heated material 12 becomes abnormally high temperature.

  In the first and second embodiments, the case where the differential value ΔTon of the control amount Ton time is zero or negative has been described, but the temperature rise speed of the object to be heated 12 even if the differential value ΔTon is positive. When the differential value ΔTon is near zero, the same control as in the first and second embodiments may be performed.

  As described above, the heating device according to the present invention can be used in not only a domestic cooking device but also a restaurant kitchen because a sufficient heating power can be obtained while appropriately suppressing the maximum temperature of the object to be heated. It can also be applied to uses such as a commercial cooking device or a heating device other than cooking using induction heating.

The block diagram of the heating apparatus in Embodiment 1 of this invention The figure which shows the waveform of the inverter drive signal output from the control means in the heating apparatus The figure which shows the time change of the temperature of the to-be-heated object of the heating apparatus, and the control amount The figure which shows the time change of the temperature of the to-be-heated object of the heating apparatus in Embodiment 2 of this invention, and control amount. Block diagram of a conventional cooking device The figure which shows the time change of the temperature of the to-be-heated object in the heating cooker.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Commercial power supply 3 Inverter 9 Control means 10 Input control means 12 Heated object 13 Temperature detection means 14 Memory circuit 15 Temperature control means 16 Operation part

Claims (3)

An inverter to which an induction heating coil is connected and a switching element is provided to convert a commercial power source into a high-frequency current, and a top plate on which the object to be heated is placed at the temperature of the object to be heated by the induction heating coil A temperature detecting means for detecting via the inverter, an operation unit for setting the output of the inverter, and increasing the on-time of the switching element to increase the input current of the inverter and shortening the on-time to reduce the input current. It said input control means input current to control the inverter so as to constantly maintain each set output, a memory circuit for storing a control temperature corresponding to the output set by the operation unit by reducing, stopped or reduced and the temperature sensing hand the output of the inverter when the temperature detected by said temperature detecting means exceeds a pre-SL control temperature In a temperature control means for temperature detected is controlled so as to increase the output of the inverter when it becomes less than the control temperature, the temperature control means, the differential value is near zero for the time of the on-time Alternatively, in the case of minus, the heating apparatus is configured such that even if the temperature detected by the temperature detecting means exceeds the control temperature, the inverter is not controlled to stop or reduce the output . Temperature control means, when the differential value for the time of the on-time of near zero or negative, the temperature detected by the temperature detecting means control the temperature even beyond the control temperature detected by said temperature detecting means and the control temperature The heating apparatus according to claim 1, wherein the controller is configured not to perform control to stop or reduce the output of the inverter for a predetermined time after it exceeds the limit. If the differential value for the time of the on-time of near zero or negative, control the heating device according to claim 1, the control temperature was configured to change to a higher predetermined value.

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