MICROWAVE HEATING DEVICE AND MICROWAVE HEATING CONTROL METHOD

• US 20120111856A1
• Filed: 06/28/2010
• Published: 05/10/2012
• Est. Priority Date: 07/10/2009
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Nobue, Tomotaka, Oomori, Yoshiharu, Yasui, Kenji, Mihara, Makoto
• Granted Patent: US 9,398,646 B2
• Time in Patent Office: Days
• US Class Current: 219/704
• CPC Class Codes: H05B 2206/044 Microwave heating devices provided with two or more magnetrons or microwave sources of other kind
• CPC Class Codes: H05B 6/686 Circuits comprising a signal generator and power amplifier, e.g. using solid state oscillators
• CPC Class Codes: H05B 6/70 Feed lines
• CPC Class Codes: H05B 6/705 using microwave tuning
• CPC Class Codes: H05B 6/72 Radiators or antennas
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers

Abstract

In order to provide a microwave heating device and a microwave heating control method which are capable of uniformly heating a to-be-heated object in a desired state, by employing plural feeding portions provided in a heating chamber on the basis of information about reflected electric power from the respective feeding portions; a control portion controls to supply microwave electric power from plural feeding portions to a heating chamber by operating a microwave generating portion at a heating frequency for heating a to-be-heated object, estimates a heating state for the to-be-heated object on the basis of per-unit-time increase/decrease change states of detected levels of detection signals detected by electric-power detection portions, and controls the heating frequency and the microwave electric power supplied from the feeding portions to the heating chamber.

Claims

1. A microwave heating device comprising:

a microwave generating portion having a variable frequency function;

a heating chamber for housing an object to be heated;

plural feeding portions for supplying, to the heating chamber, a microwave generated from the microwave generating portion;

an electric-power detection portion for detecting an amount of reflected microwaves which are reflected toward the microwave generating portion from the heating chamber through the feeding portions; and

a control portion for controlling an operation of the microwave generating portion on the basis of a detection signal detected by the electric-power detection portion;

wherein

the control portion is configured to perform control for operating the microwave generating portion at a heating frequency for heating the object to be heated for supplying the microwave electric power from the feeding potions to the heating chamber, estimate a heating state of the object to be heated on the basis of a per-unit-time increase/decrease change state in a detected level of a detection signal detected by the electric-power detection portion, and control the heating frequency and the microwave electric power supplied from the feeding portions to the heating chamber.

2. The microwave heating device according to claim 1, wherein

the microwave heating device is configured that a heating-distribution state of the object to be heated is estimated on the basis of a per-unit-time increase/decrease change state of at least a single amount of reflected microwaves from the electric-power detection portion, and a heating state of the object to be heated is estimated on the basis of per-unit-time increase/decrease change states of all the amounts of reflected microwaves from the electric-power detection portion, whereby the heating frequency and the microwave electric power supplied from the feeding portions to the heating chamber are controlled.

3. The microwave heating device according to claim 2, wherein

the control portion is configured to perform control for causing the microwave generating portion to perform a sweeping operation in a predetermined frequency range, prior to start of an actual heating operation on the object to be heated, for selecting, as a heating frequency, an oscillating frequency at which a total sum of the amounts of reflected microwaves have a minimum value, and for causing the microwave generating portion to operate at the heating frequency for supplying the microwave electric power from the feeding portions to the heating chamber.

4. The microwave heating device according to claim 2, wherein

the control portion is configured to perform control for causing the microwave generating portion to perform a sweeping operation in a predetermined frequency range, prior to start of an actual heating operation on the object to be heated, for selecting, as a heating frequency, an oscillating frequency at which a reflection ratio of a total sum of the amounts of reflected microwaves to a total sum of the amounts of supplied microwaves has a minimum value, and for causing the microwave generating portion to operate at the heating frequency for supplying microwave electric power from the feeding portions to the heating chamber.

5. The microwave heating device according to claim 2, wherein

the respective feeding portions are placed on the same wall surface forming the heating chamber, symmetrically about a center of the wall surface.

6. The microwave heating device according to claim 2, wherein

the control portion is configured to select a heating frequency again, when any of plural amounts of reflected microwaves from the electric-power detection portion has exceeded a preset predetermined value.

7. The microwave heating device according to claim 2, wherein

when the control portion estimates a heating state of the object to be heated on the basis of per-unit-time increase/decrease change states of plural amounts of reflected microwaves from the electric-power detection portion,

the control portion is configured to select a heating frequency again, when at least a single amount of reflected microwaves has a different tendency from others in terms of its increase/decrease change state.

8. The microwave heating device according to claim 3, wherein

when the control portion estimates a heating state of the object to be heated on the basis of per-unit-time increase/decrease change states of all the amounts of reflected microwaves from the electric-power detection portion,

the control portion is configured to continue an actual heating operation, when all the amounts of reflected microwaves have the same tendency, in terms of their increase/decrease change states.

9. The microwave heating device according to claim 3, wherein

when the control portion estimates a heating state of the object to be heated on the basis of per-unit-time increase/decrease change states of all the amounts of reflected microwaves from the electric-power detection portion,

the control portion is configured to estimate that the temperature of the object to be heated falls within the range of 60°

C. to 70°

C., and also calculate a completion time of an actual heating operation, when all the amounts of reflected microwaves have the same tendency in terms of their increase/decrease change states, and also the detected level of the increase/decrease change state of at least a single amount of reflected microwaves has exceeded a threshold value as a determination index.

10. The microwave heating device according to claim 3, wherein

the control portion is configured to perform control for causing the microwave generating portion to operate at a heating frequency selected prior to an actual heating operation on the object to be heated for supplying microwave electric power from the feeding portions to the heating chamber, further to perform the sweeping operation again, for selecting an oscillating frequency for heating the object to be heated, antecedently to the estimation of the heating state and the heating-distribution state of the object to be heated when an amount of reflected microwaves has exceeded a predetermined value, and to update the heating frequency for the object to be heated to the selected oscillating frequency for heating the object to be heated.

11. A microwave heating control method comprising steps of:

performing a sweeping operation over a predetermined frequency range, and detecting an amount of reflected microwaves reflected toward a microwave generating portion from a heating chamber through plural feeding portions, prior to start of an actual heating operation on an object to be heated housed in the heating chamber;

selecting, as a heating frequency, an oscillating frequency at which a detected level of a total sum of detected amounts of reflected microwaves has a minimum value; and

estimating a heating state of the object to be heated on the basis of a per-unit-time increase/decrease change state of a detected level of an amount of reflected microwaves, and controlling the heating frequency and the microwave electric power supplied to the heating chamber from the feeding portions, in a state where microwave electric power is supplied from the feeding portions to the heating chamber at the selected frequency.

12. The microwave heating control method according to claim 11, comprising steps of:

estimating a heating-distribution state of the object to be heated on the basis of a per-unit-time increase/decrease change state of at least a single detected amount of reflected microwaves, estimating a heating state of the object to be heated on the basis of per-unit-time increase/decrease change states of all the amounts of reflected microwaves, and controlling the heating frequency and the microwave electric power supplied from the feeding portions to the heating chamber.

13. The microwave heating control method according to claim 11, wherein the heating-frequency selection step includes selecting, as a heating frequency, an oscillating frequency at which the reflection ratio of a total sum of amounts of reflected microwaves to a total sum of amounts of supplied microwaves has a minimum value.

14. The microwave heating control method according to claim 11, wherein

a heating frequency is selected again, when any of plural detected amounts of reflected microwaves has exceeded a preset predetermined value.

15. The microwave heating control method according to claim 11, wherein

when a heating state of the object to be heated is estimated on the basis of per-unit-time increase/decrease change states of plural detected amounts of reflected microwaves,

a heating frequency is selected again, when at least a single amount of reflected microwaves has a different tendency from others in terms of its increase/decrease change state.

16. The microwave heating control method according to claim 11, wherein

when a heating state of the object to be heated is estimated on the basis of per-unit-time increase/decrease change states of all the detected amounts of reflected microwaves,

an actual heating operation is continued, when all the amounts of reflected microwaves have the same tendency, in terms of their increase/decrease change states.

17. The microwave heating control method according to claim 11, wherein

in an actual heating operation for operating at a heating frequency selected prior to the start of the actual heating operation on the object to be heated for supplying microwave electric power from the feeding portions to the heating chamber,

when an amount of reflected microwaves has exceeded a predetermined value, the sweeping operation is performed again, for selecting an oscillating frequency for heating the object to be heated, antecedently to the estimation of the heating state and the heating-distribution state of the object to be heated, and the heating frequency for the object to be heated is updated to the selected oscillating frequency to thereby heat the object to be heated.