CALIBRATING AN OXYGEN SENSOR OF A DOMESTIC APPLIANCE

Abstract

A method for calibrating an oxygen sensor of a household appliance includes a calibration process which is automatically started when at least one status parameter of the household appliance has at least reached a predetermined threshold value. The household appliance can be a steam cooking appliance, and the oxygen sensor can be a lambda probe.

Claims

1-15. (canceled)

16. A method, comprising: starting a calibration process for calibrating an oxygen sensor of a household appliance when a status parameter of the household appliance has at least reached a predetermined threshold value.

17. The method of claim 16, wherein the household appliance is a steam cooking appliance.

18. The method of claim 16, wherein the oxygen sensor is a lambda probe.

19. The method of claim 16, wherein the calibration process is automatically started when a plurality of status parameters of the household appliance have reached predetermined threshold values, respectively.

20. The method of claim 16, wherein the status parameter comprises a time period elapsing since a last calibration and the calibration process is automatically started when the time period has reached or exceeded the threshold value.

21. The method of claim 16, wherein the status parameter comprises a door opening time and the calibration process is automatically started when the door opening time has reached or exceeded the threshold value.

22. The method of claim 16, wherein the status parameter comprises a cooking chamber temperature and the calibration process is automatically started when the cooking chamber temperature has reached or fallen below the threshold value.

23. The method of claim 18, further comprising: measuring during the calibration process a pump flow of the lambda probe; and when the pump flow remains for a predetermined time period within a predetermined fluctuation margin, selecting a value of the pump flow from the fluctuation margin as a reference value of the pump flow.

24. The method of claim 23, wherein an average value of the fluctuation margin is selected as the reference value of the pump flow.

25. The method of claim 16, further comprising discontinuing the calibration process when the calibration process lasts longer than a predetermined threshold value.

26. The method of claim 16, further comprising discontinuing the calibration process when a cooking chamber door of the household appliance is closed.

27. The method of claim 16, further comprising: storing a result of the calibration process; and evaluating the result for a malfunction of the oxygen sensor.

28. The method of claim 27, further comprising: measuring during the calibration process a pump flow of the lambda probe; when the pump flow remains for a predetermined time period within a predetermined fluctuation margin, selecting a value of the pump flow from the fluctuation margin as a reference value of the pump flow; and using the reference value of the pump flow as the result.

29. A household appliance, comprising: a treatment chamber; an oxygen sensor; and a data processing device for determining a moisture content in the treatment chamber based on a measured value of the oxygen sensor, said household appliance being configured to start a calibration process for calibrating the measured value of the oxygen sensor when a status parameter of the household appliance has at least reached a predetermined threshold value.

30. The household appliance of claim 29, wherein the household appliance is a steam cooking appliance, with the treatment chamber representing a cooking chamber configured for application of steam.

31. The household appliance of claim 29, wherein the oxygen sensor is a lambda probe.

32. The household appliance of claim 30, wherein the status parameter comprises a temperature in the cooking chamber temperature, with the calibration process being automatically started when the temperature in the cooking chamber has reached or fallen below the threshold value.

33. The household appliance of claim 30, further comprising a door for opening and closing the cooking chamber, wherein the status parameter comprises an opening time of the door, with the calibration process being automatically started when the opening time of the door has reached or exceeded the threshold value.

34. The household appliance of claim 29, wherein the data processing device includes a memory device configured to store a result of the calibration process.

Description

[0042] The above-described properties, features and advantages of this invention and the manner in which they are achieved will become more clear and more easily comprehensible in connection with the following schematic description of an exemplary embodiment which is described in more detail in connection with the drawings.

[0043] FIG. 1 to this end shows a possible flow diagram of a method for calibrating measured values of an oxygen sensor of a steam cooking appliance.

[0044] The household appliance in the form of a steam cooking appliance 1 comprises a cooking chamber 2 to which steam is able to be applied, an oxygen sensor in the form of a lambda probe 3 and a data processing device 4. The data processing device 4 is designed to determine a moisture content in the cooking chamber 2 based on measured values of the lambda probe 3. The data processing device 4 is further designed to execute the method. The data processing device 4 may be a central control device for operating the steam cooking device 1.

[0045] In the method, the data processing device 4 monitors in a first step S1 whether a status parameter in the form of a time period ZZ0 since the time Z0 of a last calibration is greater than a threshold value in the form of a predetermined time period Zg. In other words, in step S1 it is monitored whether from the last calibration executed at the time Z0 to the current time Z, the time period Zg has already elapsed. Zg may, for example, be 30 hours. If this is not the case, step S1 is repeated at a later time. Step S1 may be executed regularly by the data processing device 4. If this is the case, however, step S2 is executed. The times Z and Z0 and/or the time period Zg may, for example, be detected by means of an operating time hour meter of the steam cooking appliance 1.

[0046] In step S2 it is monitored whether a door opening time t of a cooking chamber door has exceeded a threshold value in the form of a predetermined time period tg, in this case for example a time period tg of 60 seconds. If this is not the case (n), step S2 is repeated. If, however, this is the case (y), step S3 is executed.

[0047] In step S3 it is monitored whether a cooking chamber temperature T has fallen below a threshold value in the form of a predetermined limit temperature Tg, here for example a limit temperature Tg of 50 C. If this is not the case (n) step S3 is repeated. Alternatively, for example, it is possible to return to step S2. However, if this is the case (y) step S4 is executed.

[0048] By the three steps S1 to S3, the probability is very high that the lambda probe 3 is surrounded by fresh ambient air with an oxygen component of approx. 20.95%.

[0049] In step S4since all three conditions inquired in steps S1 to S3 are presentthe calibration process is automatically started by the data processing device 4. To this end, in step S4, the lambda probe 3 is initially prepared for recording measurements, for example heated up.

[0050] In step S5, a pump flow I of the lambda probe 3 is then measured. Namely, initially a first measured value I.sub.1 is recorded. In the following measurements which, for example, are carried out at intervals of five seconds, the associated measured values L are examined by the data processing device 4 as to whether they are all within a fluctuation margin around the first measured value I.sub.1, by way of example of I.sub.1+/1%. The step S5 may be executed for a predetermined time period, for example for 30 seconds.

[0051] If step S5 is successful (y), in a following step S6 the first measured value I.sub.1 is regarded as a new reference value of the pump flow I for an oxygen concentration of 20.95%. The calibration process is thus terminated.

[0052] If step S5 is unsuccessful (n), as a result in a step S7 an inquiry may be made as to whether the calibration process is to be discontinued. If this is the case (y), it is possible to proceed to the monitoring of step S1. If not (n), it is possibleoptionally repeatedlyto return to step S5. For example, a predetermined number (for example a maximum of four times) of calibrating attempts according to step S5 may be executed and/or attempted, to complete step S5 successfully within a specified time period (for example with a threshold value of two minutes) before proceeding to step S7.

[0053] The inquiry in step S7 may also relate to whether, before successful execution, the cooking chamber door has been closed again.

[0054] The data processing device 4 may also be designed to store the reference values and thus to compile a history of these reference values. The data processing device 4 may also be designed to use the reference valuesfor example by a comparison of at least one previously determined reference value with the currently measured reference valueto evaluate a malfunction of the oxygen sensor.

[0055] Naturally the present invention is not limited to the exemplary embodiment shown.

[0056] Generally one may be understood as a single number or a plurality thereof, in particular within the meaning of at least one or one or more, etc. provided this is not explicitly excluded, for example by the expression just one, etc.

[0057] Moreover, numerical data may specifically encompass the specified number and a conventional tolerance range, provided this is not explicitly excluded.

LIST OF REFERENCE CHARACTERS

[0058] 1 Steam cooking appliance [0059] 2 Cooking chamber [0060] 3 Lambda probe [0061] 4 Data processing device [0062] S1-S5 Method steps [0063] t Door opening time [0064] tg Predetermined time period [0065] T Cooking chamber temperature [0066] Tg Limit temperature [0067] Z Current time [0068] Z0 Time of last calibration [0069] Zg Predetermined time period [0070] I.sub.1 First measured value of pump flow [0071] I.sub.n nth measured value of pump flow