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. A method, comprising: automatically starting a calibration process for calibrating an oxygen sensor of a household appliance in response to a status parameter of the household appliance reaching or exceeding a predetermined first threshold value; wherein the status parameter comprises a door opening time.

2. The method of claim 1, wherein the household appliance is a steam cooking appliance.

3. The method of claim 1, wherein the oxygen sensor is a lambda probe.

4. The method of claim 3, 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.

5. The method of claim 4, wherein an average value of the fluctuation margin is selected as the reference value of the pump flow.

6. The method of claim 1, wherein the calibration process is automatically started when a plurality of status parameters of the household appliance have reached predetermined-threshold values, respectively.

7. The method of claim 1, wherein the status parameter further comprises a time period elapsing since a last calibration, and the calibration process is automatically started in response to the time period reaching or exceeding a second threshold value, and the door opening time reaching or exceeding the first threshold value.

8. The method of claim 1, wherein the status parameter further comprises a cooking chamber temperature and the calibration process is automatically started in response to the cooking chamber temperature reaching or falling below a third threshold value, and the door opening time reaching or exceeding the first threshold value.

9. The method of claim 1, further comprising discontinuing the calibration process when the calibration process lasts longer than a predetermined threshold value.

10. The method of claim 1, further comprising discontinuing the calibration process when a cooking chamber door of the household appliance is closed.

11. The method of claim 1, further comprising: storing a result of the calibration process; and evaluating the result for a malfunction of the oxygen sensor.

12. The method of claim 11, 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.

13. 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 automatically start a calibration process for calibrating the measured value of the oxygen sensor in response to a status parameter of the household appliance reaching or exceeding a predetermined first threshold value; wherein the status parameter comprises a door opening time.

14. The household appliance of claim 13, wherein the household appliance is a steam cooking appliance, with the treatment chamber representing a cooking chamber configured for application of steam.

15. The household appliance of claim 14, wherein the status parameter further comprises a temperature in the cooking chamber, and the calibration process is automatically started in response to the temperature in the cooking chamber reaching or falling below a second threshold value, and the door opening time reaching or exceeding the first threshold value.

16. The household appliance of claim 13, wherein the oxygen sensor is a lambda probe.

17. The household appliance of claim 13, wherein the data processing device includes a memory device configured to store a result of the calibration process.

18. A method, comprising: automatically starting a calibration process for calibrating an oxygen sensor of a household appliance in response to a status parameter of the household appliance reaching a predetermined threshold value, wherein the oxygen sensor is a lambda probe; measuring, during the calibration process, a pump flow of the lambda probe; and in response to the pump flow remaining 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.

19. The method of claim 18, further comprising: storing the reference value of the pump flow as a result of the calibration process; and evaluating the result for a malfunction of the oxygen sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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.

(2) 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.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE PRESENT INVENTION

(3) 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.

(4) 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 Z-Z0 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.

(5) 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.

(6) 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.

(7) 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%.

(8) In step S4—since all three conditions inquired in steps S1 to S3 are present—the 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.

(9) 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 I.sub.n 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.

(10) 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.

(11) 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 possible—optionally repeatedly—to 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.

(12) The inquiry in step S7 may also relate to whether, before successful execution, the cooking chamber door has been closed again.

(13) 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 values—for example by a comparison of at least one previously determined reference value with the currently measured reference value—to evaluate a malfunction of the oxygen sensor.

(14) Naturally the present invention is not limited to the exemplary embodiment shown.

(15) 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.

(16) Moreover, numerical data may specifically encompass the specified number and a conventional tolerance range, provided this is not explicitly excluded.