Induction cooker and method of operation

Patent metadata

Field	Value
Publication number	US-9288846-B2
Application number	US-201113642450-A
Country	US
Kind code	B2
Filing date	Jun 10, 2011
Priority date	Jun 10, 2010
Publication date	Mar 15, 2016
Grant date	Mar 15, 2016

Abstract

An induction heating cooker includes a boiling over detecting portion that reduces the heating output of an inverter to a predetermined value when a change amount of an electrostatic capacitance detected by a capacitance detecting portion with respect to a reference value is equal to or greater than a threshold value. The boiling over detecting portion stops a heating action or reduces the heating output to a third set value lower than a second set value when a change rate of the capacitance is equal to or greater than a predetermined change rate, and maintains the heating output at the second set value when the change rate of the capacitance is less than the predetermined change rate, during a boiling over determining period started from the time that the change amount of the capacitance with respect to the reference value is equal to or greater than the output reducing threshold value.

First claim

The invention claimed is:

1. A method for operating an induction heating cooker comprising:
a top panel for mounting a cooking container;
a heating coil provided under the top panel, for heating the cooking container by induction;
an inverter for supplying a high-frequency current to the heating coil;
an electrode provided on a back surface of the top panel adjacent to a periphery of the heating coil;
an electrostatic capacitance detecting portion configured to supply a high-frequency signal to the electrode and detect an electrostatic capacitance of the electrode;
a memory portion configured to store the detected electrostatic capacitance as a reference value;
a control portion that controls the inverter such that heating output of the inverter reaches a first set value; and
a boiling over detecting portion configured to execute a reference value updating process and store the electrostatic capacitance in the memory portion as a reference value when the electrostatic capacitance of the electrode satisfies a predetermined condition, the method comprising:
after a predetermined delay time, the boiling over detecting portion further executes an output controlling action to reduce the heating output of the inverter to a predetermined second set value or stops a heating action, when a change amount of the electrostatic capacitance of the electrode with respect to the reference value is equal to or greater than an output reducing threshold value,
wherein the delay time is the time when the change amount of the electrostatic capacitance with respect to the reference value is equal to or greater than the output reducing threshold value, and does not execute the output controlling action when it is determined that the boiling over is not generated during the delay time, and
wherein the boiling over detecting portion stops the heating action or reduces the heating output to a third set value lower than the second set value when a change rate of the detected electrostatic capacitance is equal to or greater than a predetermined change rate, and
returns the heating output to the first set value when the change rate of the detected electrostatic capacitance is less than the predetermined change rate, during a change rate detecting period that includes a time when the change amount of the electrostatic capacitance of the electrode with respect to the reference value is equal to or greater than the output reducing threshold value.

2. The method of operating an induction heating cooker according to claim 1 , wherein the boiling over detecting portion detects the electrostatic capacitance of the electrode a plurality of times during a first predetermined time, and calculates the change rate with the change amount of an average value of the plurality of detected electrostatic capacitance with respect to the reference value.

3. The method of operating an induction heating cooker according to claim 1 , wherein the boiling over detecting portion updates the electrostatic capacitance detected during a first predetermined time and stores it in the memory portion as the reference value when the change amount of the electrostatic capacitance detected during the first predetermined time with respect to the reference value is less than a reference value update stopping threshold value smaller than the output reducing threshold value, and stops the update of the reference value to the memory portion when the change amount of the electrostatic capacitance detected during the first predetermined time with respect to the reference value is equal to or greater than the reference value update stopping threshold value.

4. The method of operating an induction heating cooker according to claim 1 , wherein the boiling over detecting portion detects the electrostatic capacitance of the electrode a plurality of times during a first predetermined time, and updates an average value of the plurality of electrostatic capacitance detected in the first predetermined time and stores it in the memory portion as the reference value when the change amount of an average value of the plurality of detected electrostatic capacitance with respect to the reference value is less than the reference value update stopping threshold value.

5. The method of operating an induction heating cooker according to claim 1 , wherein the boiling over detecting portion detects the electrostatic capacitance of the electrode a plurality of times during a first predetermined time, and stops the update of the reference value to the memory portion when the change amount of an average value of the plurality of detected electrostatic capacitance with respect to the reference value is equal to or greater than the reference value update stopping threshold value.

6. The method of operating an induction heating cooker according to claim 1 , wherein the induction heating cooker further comprises a plurality of electrodes, and wherein the boiling over detecting portion returns the heating output to the first set value when the change rate of the electrostatic capacitance in any one of the electrodes is equal to or greater than the predetermined change rate, and the change amounts of other electrodes with respect to the reference value all are equal to or greater than a boiling over detecting canceling threshold value that is lower than the output reducing threshold value.

7. The method of operating an induction heating cooker according to claim 1 , wherein the boiling over detecting portion does not execute the output controlling action to be performed when the change amount of the electrostatic capacitance of the electrode with respect to the reference value is equal to or greater than the output reducing threshold value, in a case where a change in high-frequency current, high-frequency voltage, or input current in the inverter or an turn-on time of a switching element of the inverter is not within a predetermined value, during a predetermined period including the time when the change amount of the electrostatic capacitance detected by the electrostatic capacitance detecting portion with respect to the reference value is equal to or greater than the output reducing threshold value.

8. The method of operating an induction heating cooker according to claim 2 , wherein the boiling over detecting portion executes the output controlling action after a predetermined delay time from the time when the change amount of the electrostatic capacitance of the electrode with respect to the reference value is equal to or greater than the output reducing threshold value, and does not execute the output controlling action when the boiling over is not generated during the delay time.

9. The method of operating an induction heating cooker according to claim 3 , wherein the boiling over detecting portion executes the output controlling action after a predetermined delay time from the time when the change amount of the electrostatic capacitance of the electrode with respect to the reference value is equal to or greater than the output reducing threshold value, and does not execute the output controlling action when the boiling over is not generated during the delay time.

10. The method of operating an induction heating cooker according to claim 4 , wherein the boiling over detecting portion executes the output controlling action after a predetermined delay time from the time when the change amount of the electrostatic capacitance of the electrode with respect to the reference value is equal to or greater than the output reducing threshold value, and does not execute the output controlling action when it is determined that the boiling over is not generated during the delay time.

11. The method of operating

Assignees

• Ogasawara Fumitaka
• Takehira Takashi
• Kinoshita Masashi
• Yamamoto Yuji
• Panasonic Ip Man Co Ltd

Inventors

• Ogasawara Fumitaka
• Takehira Takashi
• Kinoshita Masashi
• Yamamoto Yuji

Classifications

• H05B6/062 Primary

  for cooking plates or the like · CPC title