Method for boil detection and induction hob including a boil detection mechanism

Patent metadata

Field	Value
Publication number	US-11330678-B2
Application number	US-201716335722-A
Country	US
Kind code	B2
Filing date	Aug 16, 2017
Priority date	Sep 23, 2016
Publication date	May 10, 2022
Grant date	May 10, 2022

Abstract

The invention relates to a method for boil detection at a heating zone of an induction hob (1), the method comprising the steps of: —disabling (S110) a power control mechanism of the induction hob by setting the frequency of the AC-current provided to an induction coil of the induction hob to a fixed value; —measuring (S120) values of an electrical parameter provided within the induction hob (1); —interpolating (S130) the measured electrical parameter values by gathering a plurality of values of the electrical parameter within a time window and calculating the average value of said gathered plurality of values thereby obtaining interpolated electrical parameter values. —calculating (S140) a gradient measure indicative for the differential change of the interpolated electrical parameter values over time; —determining (S150) the boil point based on the calculated gradient measure.

First claim

The invention claimed is:

1. A method for boil detection at a heating zone of an induction hob, the method comprising the steps of:
disabling a power control mechanism of the induction hob by setting a frequency of AC-current provided to an induction coil of the induction hob associated with the heating zone to a fixed value;
measuring values of an electrical parameter provided within the induction hob;
interpolating the measured electrical parameter values by gathering a plurality of said values of the electrical parameter within a time window and calculating an average value of said gathered plurality of values thereby obtaining interpolated electrical parameter values;
calculating a gradient measure indicative for a differential change of the interpolated electrical parameter values over time;
determining a boil point based on the calculated gradient measure.

2. The method according to claim 1 , wherein the boil point is determined by detecting whether the calculated gradient measure is zero and/or changes in its sign.

3. The method according to claim 1 , wherein the electrical parameter is a peak current of the induction coil, an electrical output power of the induction coil, or a phase delay between the AC current and a voltage provided to the induction coil.

4. The method according to claim 1 , wherein the power control mechanism is disabled after expiry of a certain period of time after starting a cooking process.

5. The method according to claim 1 , wherein determining the boil point is stopped and the power control mechanism is activated if an electrical output power of the induction coil drops below a certain power threshold and the boil point determination process is reinitialized after re-adjusting the electrical output power.

6. The method according to claim 1 , wherein interpolating the measured electrical parameter values is performed by sampling the electrical parameter with a frequency between 1 kHz and 50 kHz and averaging the sampled values within a time window of 1 sec to 10 sec.

7. The method according to claim 1 , wherein criteria for determining the boil point are modified based on elapsed boil-up time and/or based on a relative change of the measured electrical parameter values.

8. The method according to claim 7 , wherein the criteria for determining the boil point are a detection de-bounce time and/or a detection threshold.

9. The method according to claim 1 , wherein a boil detection capability indicator showing a capability of a cookware for being used in boil detection is calculated based on the change of the interpolated electrical parameter values over time.

10. The method according to claim 9 , wherein boil detection is deactivated if said boil detection capability indicator is below a certain threshold value.

11. The method according to claim 1 , wherein the induction coil is powered at boost power level during boil detection, said boost power level having a power level above a highest nominal power level, wherein the induction coil is adapted to be driven at said boost power level only for a limited boost time period.

12. The method according to claim 11 , wherein the boil detection capability indicator is established before said boost time period is elapsed and the boil detection mechanism is stopped and the induction coil is driven in standard boost mode if said indicator shows that a cookware is not capable for being used in said boil detection mechanism.

13. The method according to claim 1 , wherein mains voltage is monitored in order to detect mains voltage fluctuations and the measured electrical parameters are modified based on a compensation formula using said monitored mains voltage.

14. The method according to claim 1 , wherein a change rate of the measured electrical parameter values or interpolated electrical parameter values is monitored and the boil detection is reinitialized if the change rate exceeds a certain threshold value.

15. An induction hob comprising one or more induction coils associated with a heating zone, the induction hob comprising a control entity being adapted to:
disable a power control mechanism by setting a frequency of AC-current provided to the induction coil to a fixed value;
measure values of an electrical parameter provided within the induction hob;
interpolate the measured electrical parameter values by gathering a plurality of values of the electrical parameter within a time window and calculate an average value of said gathered plurality of values thereby obtaining interpolated electrical parameter values;
calculate a gradient measure indicative for a differential change of the interpolated electrical parameter values over time; and
determine a boil point based on the calculated gradient measure.

16. A method for boil detection at a heating zone of an induction hob, the method comprising:
initiating a cooking process by activating a supply of AC current to an induction coil associated with said cooking hob;
during a first time period of said cooking process, maintaining a constant output power level of said induction coil by increasing a frequency of said AC current in order to compensate for increasing resistance in a cookware in said cooking zone as its temperature increases during said first time period;
thereafter, during a second time period of said cooking process, maintaining the frequency of said AC current at a fixed frequency and measuring peak current values of said AC current sampled at a frequency of 5 kHz to 20 kHz and averaging the sampled peak current values within a window of 1 to 10 seconds, interpolating interpolated values of said peak current from the averaged sample values thereof, and determining a first derivative of a time curve of said interpolated peak current values;
detecting when said cookware has reached a boiling point temperature during said second time period based on boiling-point criteria by monitoring when said first derivative of said time curve reaches zero and/or changes sign; and
upon the output power of said induction coil dropping to or below a threshold power level during said second time period, concluding said second time period and resuming maintenance of said constant output power of said induction coil by increasing the frequency of said AC current to again compensate for increasing resistance in the cookware, wherein said boiling-point temperature detection is suspended while the the output power level of said induction coil is maintained at said constant output power level.

17. The method according to claim 16 , said boiling-point criteria being variable between a first criterion applicable during an an initial part of said second time period when a probability of said cookware reaching the boiling point temperature is a first probability, and a second criterion applicable during a subsequent part of said second time period when the probability of said cookware reaching the boiling point temerature is a second probability higher than said first probability, wherein said first criterion is more stringent than said second criterion such that achievement of the boiling point temperature by said cookware is less likely to be detected during the first part of said second time period than during said second part of said second time period under comparable cookware conditions.

18. The method according to claim 17 , further comprising concluding said first part of said second time period upon elapsing of a predetermined period of time, said boiling point criteria comprising a pedetermined length of time during which said first derivativ

Assignees

• Electrolux Appliances AB

Inventors

• Terracciano Nicola
• Jeanneteau Laurent
• Viroli Alex
• Nostro Massimo
• Christiansen Svend Erik

Classifications

• F24C15/106

  electric circuits · CPC title

• H05B2213/07

  Heating plates with temperature control means · CPC title

• H05B6/12

  Cooking devices · CPC title

• H05B1/0269

  For heating of fluids · CPC title

• H05B2213/05

  Heating plates with pan detection means · CPC title