JP2006196343A - Heating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating apparatus capable of obtaining enough heating power suitably restraining maximum allowable temperature of a heated object, irrespective of output setting. <P>SOLUTION: The apparatus is provided with a temperature control means 15 controlling outputs of an inverter 3, so that, in case a temperature detected by a temperature sensing means 13 exceeds a control temperature stored in a storage circuit 14, it stops or weakens an output of an inverter 3, and in the case a temperature detected by the temperature sensing means 13 gets below the control temperature stored in the storage circuit 14, it raises an output of the inverter 3. Actions of the temperature control means are changed so that an input current of the inverter 3 is constant for each output set, by detecting temperature changes of the heated object 12 without delay from changes of control amount with time of an input control means 10 controlling the inverter 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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 the frying pan 20 is used to cook the fried food. 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 above-described conventional problems, a heating apparatus according to the present invention includes an inverter that converts a commercial power source into a high-frequency current, temperature detection means that detects the temperature of an object to be heated, and an operation unit that sets the output of the inverter. Input control means for controlling the inverter so that the input current of the inverter becomes constant for each set output, a storage circuit that stores a control temperature corresponding to the output set by the operation unit, and the temperature When the temperature detected by the detection means exceeds the control temperature stored in the storage circuit, the output of the inverter is stopped or reduced, and the temperature detected by the temperature detection means is less than or equal to the control temperature stored in the storage circuit. And a temperature control means for controlling the output of the inverter to be increased in response to the differential value of the time variation of the control amount in the input control means. It is obtained by a configuration to change the behavior.

  As a result, the time change of the control amount of the input control means correlates with the temperature change of the object to be heated, and the response is high, so that it is grasped 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 detecting means, the temperature of the object to be heated can be appropriately controlled.

  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 inverter for converting a commercial power source into a high-frequency current, temperature detecting means for detecting the temperature of an object to be heated, an operation unit for setting the output of the inverter, and an input current for the inverter are set. Input control means for controlling the inverter to be constant for each output, a storage circuit for storing a control temperature corresponding to the output set by the operation unit, and a temperature detected by the temperature detection means in the storage circuit Stop or decrease the inverter output when the stored control temperature is exceeded, and increase the inverter output when the temperature detected by the temperature detection means falls below the control temperature stored in the memory circuit A temperature control means for controlling, and the temperature control means is a heating device configured to change the operation in accordance with a differential value of the time variation of the control amount in the input control means. As a result, the time change of the control amount of the input control means is correlated with the temperature change of the object to be heated and has high responsiveness, so that it is grasped 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 detecting means, the temperature of the object to be heated can be appropriately controlled.

  According to a second invention, in particular, in the first invention, the input control means controls the input current by driving the switching element of the inverter in a predetermined cycle and changing the on-time of the switching element within the predetermined cycle. As a result, the on-time input control is easy to digitize, it is easy to calculate the differential value of the time change of the on-time, and the circuit configuration that is easy to control combined with information from the temperature detection means using a microcomputer It becomes possible.

  In the third invention, in particular, in the first or second invention, when the differential value of the time variation of the control amount in the input control means is zero or negative, the temperature detected by the temperature detection means is stored in the memory circuit. Although the operation of the temperature control means is changed so as not to stop or reduce the output of the inverter even if the temperature exceeds the control temperature, the temperature of the object to be heated tends to decrease due to the introduction of foodstuffs. The output is not reduced or stopped even when the stored control temperature is exceeded due to the response delay of the temperature detecting means. 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.

  In the fourth invention, in particular, in the first or second invention, when the differential value of the time variation of the control amount in the input control means is zero or negative, the temperature detected by the temperature detection means is stored in the memory circuit. By changing the operation of the temperature control means so that the output of the inverter is not stopped or reduced for a predetermined time even if the control temperature exceeds the control temperature, the temperature of the object to be heated tends to decrease due to the addition of ingredients, etc. Nevertheless, even if the stored control temperature is exceeded due to a response delay of the temperature detecting means, the output is not reduced or stopped for a predetermined time. 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.

  In the fifth invention, in particular, in the first or second invention, when the differential value of the time variation of the control amount in the input control means is zero or negative, the temperature detected by the temperature detection means is stored in the memory circuit. The control temperature is changed to a predetermined value higher so that the temperature of the object to be heated tends to decrease due to the input of food, etc. Even when the control temperature is exceeded, the control temperature is changed to a predetermined value higher and the output is not lowered or stopped. 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 Tc stored in 14 is increased to a predetermined value α and changed to (Tc + 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 Tc + α temperature even when there is a sudden temperature rise. Decrease or stop output. 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 (5)

An inverter that converts commercial power into high-frequency current, temperature detection means that detects the temperature of the object to be heated, an operation unit that sets the output of the inverter, and an input current of the inverter that is constant for each set output An input control means for controlling the inverter, a storage circuit storing a control temperature corresponding to the output set by the operation unit, and a control temperature stored in the storage circuit by the temperature detected by the temperature detection means Temperature control means for controlling the output of the inverter to be increased when the temperature detected by the temperature detection means falls below the control temperature stored in the memory circuit when the output of the inverter is stopped or reduced And the temperature control means changes the operation according to the differential value of the time variation of the control amount in the input control means. The heating apparatus according to claim 1, wherein the input control means is configured to drive the switching element of the inverter at a predetermined cycle and to control the input current by changing the ON time of the switching element within the predetermined cycle. When the differential value of the time variation of the control amount in the input control means is zero or negative, the inverter output is not stopped or reduced even if the temperature detected by the temperature detection means exceeds the control temperature stored in the storage circuit. The heating apparatus according to claim 1 or 2, wherein the operation of the temperature control means is changed. When 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 for a predetermined time even if the temperature detected by the temperature detection means exceeds the control temperature stored in the memory circuit Or the heating apparatus of Claim 1 or 2 which was set as the structure which changes the operation | movement of a temperature control means so that it may not become small. When the differential value of the time variation of the control amount in the input control means is zero or negative, the temperature detected by the temperature detection means is changed to a control value stored in the storage circuit to be higher by a predetermined value. Item 3. A heating apparatus according to Item 1 or 2.

Images