Induction heat cooking apparatus

• US 4,638,135 A
• Filed: 01/07/1985
• Issued: 01/20/1987
• Est. Priority Date: 01/20/1984
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Aoki, Masayuki
• Primary Examiner(s): Leung, Philip H.
• Application Number:
  US06/689,338
• Time in Patent Office: 743 Days
• Field of Search: 219/10.77, 219/10.49 R, 219/10.55 B, 219/497, 219/499, 219/494, 219/506
• US Class Current: 219/627
• CPC Class Codes: H05B 6/062 for cooking plates or the like

Abstract

In an induction heat cooking apparatus of the invention, an electromagnetic field is generated by a heating coil, and the generated electromagnetic field is supplied to a load so that the load is inductively heated. The cooking apparatus includes an exciter circuit for exciting the heating coil to generate the electromagnetic field; a temperature set circuit for providing a temperature set signal which designates a given target temperature of the load; and a temperature measure circuit for measuring the temperature of the load to generate a temperature measure signal which represents the measured temperature of the load. The cooking apparatus further includes a difference detector circuit for detecting a difference between the temperature set signal and the temperature measure signal and generating a difference signal. The exciter circuit receives the difference signal so as to control heat power for the heating coil.

Claims

1. An induction heat cooking apparatus, comprising:

a heating coil for providing an electromagnetic field, when excited to inductively heat a load;

exciter means for exciting said heating coil to cause variable amount of heating power to be output therefrom;

temperature setting means for providing a temperature set signal which designates a desired target temperature of said load;

temperature measuring means for measuring a temperature of said load to generate a temperature measure signal indicative thereof; and

difference detector means, coupled to said temperature measuring means, said temperature setting means and said exciter means, for detecting a difference between said temperature set signal and said temperature measure signal and generating a difference signal indicative of said difference, and for supplying a difference signal to said exciter means to control the degree of excitation thereof, said heating power for said heating heating coil being continuously controlled to variable power levels in accordance with said difference signal so that said heating power is maintained at a first constant power level until said load temperature reaches a first value, and said heating power is then decreased at a definite rate until said load temperature reaches a second value greater than said first value, said rate being less than infinity to cause said heating power to gradually decrease as a function of time, so that when said load temperature approaches said set temperature, said heating power has been lowered from said first constant level, and therefore a rate of temperature increase of the load has been lowered to thereby maintain said load temperature close to said set temperature by varying said heating power to minimize an amount of temperature overshoot.

2. An induction heat cooking apparatus according to claim 1, further comprising:

judging means, coupled to said difference detector means, for judging whether said the value of said difference signal falls within a predetermined range of values; and

means for indicating the result of the judgment.

3. An induction heat cooking apparatus according to claim 2, wherein said difference detector means includes comparator means being responsive to a given comparison signal, for comparing said difference signal with said given comparison signal, and reducing said heat power when the magnitude of said difference signal corresponds to said given comparison signal, thereby substantially avoiding a temperature increase of said load above said desired target temperature.

4. An induction heat cooking apparatus according to claim 1, wherein said difference detector means includes comparator means, being responsive to a given comparison signal, for comparing said difference signal with said given comparison signal, and reducing said heat power when the value of said difference signal is within a predetermined range around said given comparison signal, thereby substantially avoiding a temperature increase of said load above said desired target temperature.

5. An induction heat cooking apparatus according to claim 1, wherein said temperature measuring means includes:

temperature to voltage converter means, thermally coupled to said load, for converting the measured temperature of said load to a temperature voltage; and

circuit means, coupled to said temperature/voltage converter means and being responsive to a given reference voltage, for generating said temperature measure signal in accordance with the difference between said temperature voltage and said reference voltage.

6. An induction heat cooking apparatus according to claim 5, wherein said temperature measure means includes voltage source means for generating a plurality of fixed voltages, and one of the plural fixed voltages is used for said given reference voltage.

7. An induction heat cooking apparatus according to claim 1, wherein said difference detector means includes program control means being implemented by a microcomputer for providing data corresponding to said difference signal.

8. An induction heat cooking apparatus comprising:

a resonance circuit of a heating coil and capacitor for generating an electromagnetic field for supply to a load so that the load is indictively heated;

inverter means for driving said resonance circuit so that the electromagnetic field is generated;

temperature setting means for providing a temperature set signal which designates a given target temperature of the load;

temperature sensor means for sensing a temperature of the load to generate a load temperature signal; and

actuator means, coupled to said inverter means, said temperature setting means, and said temperature sensor means, for comparing said load temperature signal with said temperature set signal, and actuating said inverter means in accordance with the results of the comparison, so that (1) said inverter means intermittently energizes said resonance circuit when the temperature of said load is higher than said given target temperature, and (2) said inverter means continuously energizes said resonance circuit when the temperature of said load is lower than said given target temperature,

said actuator means including load detector means, coupled to said resonance circuit, for generating a load condition signal by comparing the magnitudes of a voltage and current applied to said resonance circuit; and

indicator means, coupled to said load detector means, for indicating whether a proper load is set.

9. An induction heat cooking apparatus according to claim 8, wherein the condition that the temperature of said load is higher than said given target temperature represents a condition that said load temperature signal corresponds to said temperature set signal, and wherein the condition that the temperature of said load is lower than said given target temperature represents a condition that said load temperature signal does not correspond to said temperature set signal.

10. An induction heat cooking apparatus according to claim:

8, wherein said load detector means includes;

voltage detector means, coupled to said resonance circuit, for detecting a voltage of said heating coil to generate a voltage signal;

current detector means, coupled to said resonance circuit, for detecting a current of said heating coil to generate a current signal; and

condition detector means, coupled to said voltage detector means and to said current detector means, for detecting in accordance with said voltage and current signals a condition that a proper load is placed in the induction heat cooking apparatus, and generating said load condition signal.

11. An induction heat cooking apparatus according to claim 8, wherein said actuator means includes:

comparator means, coupled to said temperature set means and to said temperature sensor means, for comparing said load temperature signal with said temperature set signal, and generating a switch signal when said load temperature signal corresponds to said temperature set signal;

pulse generator means for generating a pulse train having a given pulse width; and

gate circuit means, coupled to said comparator means and to said pulse generator means, for providing a power control signal which has a pulsate signal component corresponding to said pulse train and serves to effect the intermittent energization of said resonance circuit when said switch signal is generated, the pulse width of said pulsate signal component being selected such that said load detector means is enabled to generate said load condition signal during the period of the pulse width of said pulsate signal component.

12. An induction heat cooking apparatus according to claim 8 actuator means includes:

comparator means, coupled to said temperature set means and to said temperature sensor means, for comparing said load temperature signal with said temperature set signal, and generating a switch signal when said load temperature signal corresponds to said temperature set signal;

pulse generator means for generating a pulse train having a given pulse width;

gate circuit means, coupled to said comparator means and to said pulse generator means, for providing a power control signal which has a pulsate signal component corresponding to said pulse train and serving to effect the intermittent energization of said resonance circuit when said switch signal is generated, the pulse width of said pulsate signal component being selected such that said load detector means is enabled to generate said load condition signal during the period of the pulse width of said pulsate signal component.

13. An induction heat cooking apparatus according to claim 8, wherein said actuator means includes program control means being implemented by a microcomputer for performing the comparing and actuating operation of said actuator means.

14. An induction heat cooking apparatus in which an electromagnetic field is generated from a resonance circuit of a heating coil and capacitor, and the generated electromagnetic field is supplied to a load so that the load is inductively heated, said cooking apparatus comprising:

inverter means for energizing said resonance circuit so that said electromagnetic field is generated;

temperature set means for providing a temperature set signal which designates a given target temperature of said load;

temperature measure means for measuring temperature of said load to generate a temperature measure signal which represents the measured temperature of said load;

difference detector means, coupled to said temperature measure means and to said temperature set means, for detecting a difference between said temperature set signal and said temperature measure signal to generate a difference signal;

actuator means, coupled to said inverter means, said difference detector means, and said temperature measure means, for comparing said temperature measure signal with said difference signal, and selectively actuating said inverter means, so that said inverter means intermittently energizes said resonance circuit when the temperature of said load is higher than said given target temperature, and said inverter means continuously energizes said resonance circuit when the temperature of said load is lower than said given target temperature;

load detector means, coupled to said resonance circuit, for generating a load condition signal in accordance with a comparison between the magnitudes of a voltage and current applied to said resonance circuit; and

indicator means, coupled to said load detector means, for indicating in accordance with said load condition signal whether or not a proper load is set.

15. An induction heat cooking apparatus according to claim 14, further comprising:

judge/indicator means, coupled to said difference detector means, for judging whether said difference signal falls within a predetermined range and for indicating this result.

16. An induction heat cooking apparatus comprising:

a heating coil for providing, when excited, an electromagnetic field to inductively heat a load;

exciter means for exciting said heating coil;

temperature setting means for providing a temperature set signal which designates a desired target temperature of the load;

temperature measuring means for measuring a temperature of the load to generate a temperature measure signal indicative thereof;

difference detector means, coupled to said temperature measure means, said temperature setting means and said exciter means, for detecting a difference between said temperature set signal and said temperature measure signal to generate a difference signal indicative of such difference, and supplying said difference signal to said exciter means to control the degree of excitation thereof so that heat power for said heating coil is continuously controlled in accordance with said difference signal; and

limiter means within said difference detector means for limiting the maximum magnitude of said difference signal that can be supplied to said exciter means, so that the upper limit of heat power for said heating coil is restricted to a predetermined maximum value.

17. An induction heat cooking apparatus in which an electromagnetic field generated by a heating coil is supplied to a load so that the load is inductively heated, said cooking apparatus comprising:

exciter means for exciting said heating coil to generate said electromagnetic field;

temperature setting means for providing a temperature set signal which designates a desired target temperature of said load;

temperature measuring means for measuring a temperature of said load to generate a temperature measure signal indicative thereof; and

difference detector means, coupled to said temperature measuring means, said temperature setting means and said exciter means, for detecting a difference between said temperature set signal and said temperature measure signal and generating a difference signal indicative of said difference, said difference signal being coupled to said exciter means to control the degree of excitation thereof so that heat power for said heating coil is continuously controlled in accordance with said difference signal, including selector means, coupled to said temperature setting means, for selecting either one of said difference signal and said temperature set signal, and supplying the selected signal to said exciter means so that the heat power for said heating coil is controlled in accordance with said selected signal.

18. An induction heat cooking apparatus according to claim 17, wherein said heating coil is combined with a capacitor to form a resonance circuit, and

wherein said exciter means includes:

signal generator means for generating a sawtooth-wave signal;

modulator means, coupled to said signal generator means and to said selector means, for pulse-width-modulating said sawtooth-wave signal according to the selected one of said difference signal and temperature set signal, and providing a pulse-width-modulated signal; and

inverter means, coupled to said resonance circuit and to said modulator means, for exciting the resonance circuit of said heating coil in accordance with said pulse-width-modulated signal to generate said electromagnetic field.

19. An induction heat cooking apparatus in which an electromagnetic field generated by a heating coil is supplied to a load so that the load is inductively heated, said cooking apparatus comprising:

exciter means for exciting said heating coil to generate said electromagnetic field;

temperature setting means for providing a temperature set signal which designates a desired target temperature of said load;

temperature measuring means for measuring a temperature of said load to generate a temperature measure signal indicative thereof;

difference detector means, coupled to said temperature measuring means, said temperature setting means and said exciter means, for detecting a difference between said temperature set signal and said temperature measure signal and generating a difference signal indicative of said difference, said difference signal being coupled to said exciter means to control the degree of excitation thereof so that heat power for said heating coil is continuously controlled in accordance with said difference signal;

judging means, coupled to said difference detector means, for judging whether the value of said difference signal falls within a predetermined range of values, including;

(a) first level means for providing a first level which defines the upper limit of said predetermined range; and

(b) second level means for providing a second level which defines the lower limit of said predetermined range;

means for indicating the result of the judgment; and

level comparator means, coupled to said indicator means, said first level means, said second level means, and said difference detector means, for comparing the signal level of said difference signal with each of said first and second levels, and for actuating said indicator means to indicate the results of said judgment when the signal level of said difference signal is higher than said second level but lower than said first level.