WO2004081456A1 - Oven and sensor thereof having pyrolytic function - Google Patents

Oven and sensor thereof having pyrolytic function Download PDF

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Publication number
WO2004081456A1
WO2004081456A1 PCT/TR2003/000012 TR0300012W WO2004081456A1 WO 2004081456 A1 WO2004081456 A1 WO 2004081456A1 TR 0300012 W TR0300012 W TR 0300012W WO 2004081456 A1 WO2004081456 A1 WO 2004081456A1
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WIPO (PCT)
Prior art keywords
sensor
oven
data
pyrolysis
sensor device
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Application number
PCT/TR2003/000012
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French (fr)
Inventor
Burak Aktug
Original Assignee
Gunkol Gunes Enerjisi Ve Klima San. A.S.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Gunkol Gunes Enerjisi Ve Klima San. A.S. filed Critical Gunkol Gunes Enerjisi Ve Klima San. A.S.
Priority to PCT/TR2003/000012 priority Critical patent/WO2004081456A1/en
Priority to AU2003225465A priority patent/AU2003225465A1/en
Publication of WO2004081456A1 publication Critical patent/WO2004081456A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24C—DOMESTIC STOVES OR RANGES ; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
    • F24C14/00—Stoves or ranges having self-cleaning provisions, e.g. continuous catalytic cleaning or electrostatic cleaning
    • F24C14/02—Stoves or ranges having self-cleaning provisions, e.g. continuous catalytic cleaning or electrostatic cleaning pyrolytic type

Definitions

  • This invention relates to an oven having a pyrolytic self-cleaning function and particularly relates to an oven comprising a sensor in the exhaust path thereof for continuously measuring gas concentration and an oven control device receiving the output of the sensor for comparing average value stored in a buffer with an output value for terminating the pyrolysis duration.
  • Gas or electric based ovens are widely used particularly for domestic purposes. During the operation of ovens, some unintended food residues induced by excessive boiling, spilled greases to the walls of the oven accumulate in the cavity of the oven.
  • Pyrolytic function is generally based on increasing the internal temperature of the oven to a predetermined level for a predetermined time pyrolysis function is terminated generally by a timer, which would lead to energy losses and physical deterioration of the components of the oven.
  • the present invention concerns an oven of the kind comprising a cooking chamber, a heating device for heating the cooking chamber, an exhaust flue for discharging the gas induced by burning out food residues, a sensor device for sensing the concentration of the discharging gas, an oven control device for receiving the output signals of the gas sensor and in accordance with the predetermined conditions.
  • Such an oven is known from US 6,392,204 disclosing a heat control device being operable to receive successive gas concentration signal outputs from the gas sensor to determine a gas concentration versus time curve to calculate a gas concentration area representing the area under the gas concentration curve, and to determine the self-cleaning cycle in correspondence with the gas concentration area.
  • US 4,954,694 discloses a pyrolytic oven comprising a heat controlled unit responsive to a gas signal from gas sensor located in the exhaust passage.
  • the heat control samples the gas signal at a given time interval to detect a variation of amount of the gas component and detect a first inflection point from decreasing to increasing and vice versa in a gas component variation and a second inflection point from decreasing to increasing or vice versa in the gas component variation after detection of the first inflection point.
  • the heat control means determines the heating time period for cleaning in correspondence with the second inflection point.
  • US 4,954,694 detection method of the inflection points is based on sampling gas components in predetermined time intervals. Variation of amount of the gas component is given according to an equation constituting subtraction of the recent value from the preceding value. A sign detector is utilized for detecting the sign of the equation i.e. variation of amount of the gas component and then maximum point from increasing to decreasing of the gas component is determined.
  • One apparent disadvantage of US 4,954,694 is the discontinuity in sampling the gas concentration. This is crucial, since the gas concentration values obtained by this discontinuous method are employed in the equation for determining inflection point.
  • sensor types used for sensing gas concentration vary in their nature. In other words according to the sensor employed, the curve representing gas concentration vs. time might be subject to change its characteristic by exhibiting local maximum and minimum points in the curve, which would influence the algorithm proposed by US 4,954,694.
  • the invention seeks to provide an oven having a pyrolytic self-cleaning function of the above-mentioned kind, which evaluates duration for termination of pyrolysis function more effectively.
  • Another object of the present invention is to enhance sensing abilities of sensor device by pyrolytic self cleaning of the sensor device.
  • this object is accomplished in an oven of the above kind in that the oven control device receives sensor outputs continuously and stores them in a buffer for comparing the average value calculated by the oven control device with a recent data output value in the buffer so that the position of gas concentration amount is determined on the sensor output vs. time curve for subsequent determination of pyrolytic self cleaning duration.
  • the algorithm of determining the expiration of the pyrolysis of the oven is based on the logic in which if the recent value of the buffer is greater than the average value then the oven control device proceeds controlling of storing data output of sensor device into the buffer if, however, the average value is greater than the recent value then a predetermined period is held for stability of the curve and then termination time is set by the oven control device.
  • the gas sensor can also be subject to pyrolysis by increasing the heating voltage of the sensor and thus the sensor operation temperature .
  • metal oxide sensors are used in the scope of the instant invention.
  • Figure 1 illustrates the oven with the exhaust pipe and sensor device.
  • Figure 2 illustrates flow chart of pyrolysis termination algorithm.
  • Figure 3 illustrates a typical sensor resistance vs. time curve.
  • Figure 4 illustrates flow chart of sensor device pyrolysis algorithm.
  • Figure 5 illustrates the pyrolysis curve for sensor device.
  • FIG. 1 illustrates an oven (1 ) body comprising a front door for introducing meal therein and walls for forming cavities in the oven (1).
  • the oven is optionally provided with a ventilator or a fan.
  • pyrolytic conditions require the internal temperature of the oven (1) be in the level of 460°C for various kinds of food residues including cheese, caramel, butter etc.
  • a sensor box (3) comprises a sensor in the exhaust pipe (2) for sensing the gas content and a temperature sensor.
  • the sensor is preferably selected from a metal oxide sensor kind or semi conducting kind and the metal oxide sensor preferably comprises the group consisting of SnOa, CTO, WO3, ZnO, V 2 0 5 , Ga 2 O 3) Co 3 0 4 .
  • the metal oxide sensor might be arranged to be sensitive to volatile organic carbons or alternatively to CO.
  • the temperature sensor is provided for measuring the operation temperature of the metal oxide sensor and the temperature sensor is in association with a control circuit for controlling the operation temperature of said metal oxide sensor.
  • the exhaust pipe is provided with a CO (Carbon Monoxide) filter for preventing the CO emissions to the atmosphere.
  • CO Carbon Monoxide
  • An oven control device receives the output data of a sensor device continuously, which is preferably a metal oxide gas sensor, and stores the data into a buffer.
  • the information whether the ventilator is switched on or off is provided by the oven control device, since the gas concentration variation would be affected through the air flow induced by the ventilator.
  • the number of data constituting the data set in the buffer is predetermined and preferably ten.
  • the oven control device calculates the average value of the data stored in the buffer. The average value is compared with the recent data, preferably the last data in the buffer so as to determine the process position i.e. increasing side or decreasing side of the sensor resistance vs. time curve.
  • the increase flag is set to "one" by the oven control device. If, however, the last data is less than the average value then the increase flag is set to "zero" meaning that the position in the decreasing side of the curve and the above-mentioned steps are repeated for achieving the stability condition.
  • the stability condition is checked and the pyrolysis is terminated.
  • Data storing method is based on one step at a time or plurality steps at a time i.e. for pursuing the curve pattern, the first data or first plurality of data in the buffer is / are released and simultaneously all of the remaining data are shifted one stack or plurality of stacks backward position and the recent output data or plurality of data of the sensor is / are stored in the last stack or the last stacks in the buffer. Afterwards, the above-mentioned calculation is performed for determining the position of the sensor resistance data.
  • the sensor resistance vs. time curve follows the pattern namely the sensor output values increases as the time increases and reaches an inflection point (maximum point) and then decreases as the time increases.
  • the sensor resistance pattern shown is typical for so called p-type semiconductors like chromiumtitaniumoxide (Cr2- x Ti x ⁇ 3 +z ).
  • n-type gas sensitive semiconductors like Sn ⁇ 2 perform outputs exhibiting reciprocal pattern i.e. the sensor output decreases as the time increases and reaches an inflection points (minimum point) and then increases as the time increases.
  • the present invention comprises these type of sensors and in this case the pyrolysis expiration algorithm comprises the steps: If the last data is less than the average value then the above-mentioned steps are repeated by the oven control device. In this case, the increase flag is set to "one" by the oven control device. If, however, the last data is greater than the average value then the increase flag is set to "zero" meaning that the position in the increasing side of the curve and the above- mentioned steps are repeated for achieving the stability condition.
  • the stability condition is checked and the pyrolysis is terminated.
  • the algorithm for oven pyrolysis comprises steps for checking the comparison runtime and predetermined timeout period and if runtime is greater than the timeout period, pyrolysis is terminated by the oven control device. According to preferred embodiment of the invention this check is employed during the first steps of the algorithm or in relation to the output of the comparison between the last data read and average value in the buffer or in relation to if increase is zero when last data read is substantially equal to average of the values in the buffer.
  • pyrolysis of the sensor device might be employed before or after the pyrolysis self cleaning of the oven itself.
  • the base line resistance (Ro) during starting up the pyrolysis is set to the resistance of the sensor (R s ) and a threshold resistance (R t ) of the sensor device is predetermined and resistance of sensor (R s ) is normalized by dividing by base line resistance (Ro) i.e. (R s / Ro)for starting the sensor device pyrolysis and sensor device outputs are differentiated with respect to time continuously for having the sign of the derivative or the above-mentioned method is employed for determining the process position of the sensor device outputs as;
  • the termination of the pyrolysis of the sensor device is conditioned to the logic:
  • R s / Ro ⁇ R t and dR s / dt ⁇ 0 or as mentioned above sensor outputs are stored in a buffer and the oven control device calculates the average of the data for comparison with the recent data in the buffer and if the recent data is less than the recent data the oven control determines the position of the process i.e. the decreasing side then the pyrolysis of sensor device is terminated.
  • the algorithm for sensor device pyrolysis comprises predetermined steps for checking the comparison runtime and predetermined timeout period and if runtime is greater than the timeout period, the oven control detects a malfunction associated with the sensor device. So, pyrolysis is terminated.
  • Pyrolysis of the sensor device is preferably initiated and maintained substantially above the temperature 350°C to which the temperature of the metal oxide sensor is heated.
  • the process of sensor device pyrolysis is incorporated with the oven pyrolysis.
  • the sensor device pyrolysis is applied prior to oven pyrolysis or after the oven pyrolysis.

Abstract

A pyrolytic self oven comprising a cooking chamber, a heating device for heating the cooking chamber, an exhaust flue for discharging the gas induced by burning out of food residues, a sensor device for sensing the concentration of the discharging gas, an oven control device for receiving the output signals of the gas sensor and terminating the pyrolysis period wherein the oven control device receives sensor outputs continuously and stores thereof in a buffer having sufficient capacity for comparing the average value calculated by the oven control device with a recent data output value in the buffer so that the position of gas concentration amount is determined on the sensor output vs. time curve for subsequent determination of pyrolytic self cleaning duration.

Description

OVEN AND SENSOR THEREOF HAVING PYROLYTIC FUNCTION
TECHNIC L FIELD
This invention relates to an oven having a pyrolytic self-cleaning function and particularly relates to an oven comprising a sensor in the exhaust path thereof for continuously measuring gas concentration and an oven control device receiving the output of the sensor for comparing average value stored in a buffer with an output value for terminating the pyrolysis duration.
Gas or electric based ovens are widely used particularly for domestic purposes. During the operation of ovens, some unintended food residues induced by excessive boiling, spilled greases to the walls of the oven accumulate in the cavity of the oven.
In order to clean these residues a method known as self-cleaning or pyrolysis is utilized. Pyrolytic function is generally based on increasing the internal temperature of the oven to a predetermined level for a predetermined time pyrolysis function is terminated generally by a timer, which would lead to energy losses and physical deterioration of the components of the oven.
BACKGROUND
The present invention concerns an oven of the kind comprising a cooking chamber, a heating device for heating the cooking chamber, an exhaust flue for discharging the gas induced by burning out food residues, a sensor device for sensing the concentration of the discharging gas, an oven control device for receiving the output signals of the gas sensor and in accordance with the predetermined conditions.
Such an oven is known from US 6,392,204 disclosing a heat control device being operable to receive successive gas concentration signal outputs from the gas sensor to determine a gas concentration versus time curve to calculate a gas concentration area representing the area under the gas concentration curve, and to determine the self-cleaning cycle in correspondence with the gas concentration area.
US 4,954,694 discloses a pyrolytic oven comprising a heat controlled unit responsive to a gas signal from gas sensor located in the exhaust passage. The heat control samples the gas signal at a given time interval to detect a variation of amount of the gas component and detect a first inflection point from decreasing to increasing and vice versa in a gas component variation and a second inflection point from decreasing to increasing or vice versa in the gas component variation after detection of the first inflection point. The heat control means determines the heating time period for cleaning in correspondence with the second inflection point.
Above-mentioned references bear remarkable advantages for the solution of controlling the duration time of pyrolytic function. However, it is readily identified that there remain disadvantages accompanied with the references cited. For example, in US 6,392,204 termination of pyrolysis is based on calculating the gas concentration vs. time curve and then calculating the area under that curve for the termination. This two-step calculation method leads to superfluous control algorithm of the heat control device.
In US 4,954,694 detection method of the inflection points is based on sampling gas components in predetermined time intervals. Variation of amount of the gas component is given according to an equation constituting subtraction of the recent value from the preceding value. A sign detector is utilized for detecting the sign of the equation i.e. variation of amount of the gas component and then maximum point from increasing to decreasing of the gas component is determined. One apparent disadvantage of US 4,954,694 is the discontinuity in sampling the gas concentration. This is crucial, since the gas concentration values obtained by this discontinuous method are employed in the equation for determining inflection point. Moreover, sensor types used for sensing gas concentration vary in their nature. In other words according to the sensor employed, the curve representing gas concentration vs. time might be subject to change its characteristic by exhibiting local maximum and minimum points in the curve, which would influence the algorithm proposed by US 4,954,694.
It is also known from the prior art references and practice that sensors taking a major role in determining the gas concentration amount are not subject to self cleaning function. This is due to the sensor kind incorporated in the ovens and most of the time the sensors are placed in a predetermined position so that the latter may not be influenced by the temperature within the oven.
Furthermore, in most pyrolytic-based ovens air flow is required for sweeping the gas accumulated in the oven as a result of burning out of the food residues. Since sensor devices are operable in some certain temperature ranges and air flow would affect the temperature of the gas, the efficiency of the sensor devices is inevitably influenced by this temperature level due to direct exposure of the sensor devices to gas temperature in the oven.
Yet another disadvantage accompanied with the present applications is utilizing the infrared (IR) sensors, the outputs of which are decisive for termination of the pyrolysis. Utilization of the IR sensors necessitates a separate chamber in which out coming gas is sampled and prohibiting a continuous measurement.
BRIEF DISCLOSURE OF THE INVENTION
The invention seeks to provide an oven having a pyrolytic self-cleaning function of the above-mentioned kind, which evaluates duration for termination of pyrolysis function more effectively.
Another object of the present invention is to enhance sensing abilities of sensor device by pyrolytic self cleaning of the sensor device.
In accordance with the invention, this object is accomplished in an oven of the above kind in that the oven control device receives sensor outputs continuously and stores them in a buffer for comparing the average value calculated by the oven control device with a recent data output value in the buffer so that the position of gas concentration amount is determined on the sensor output vs. time curve for subsequent determination of pyrolytic self cleaning duration. In principle, the algorithm of determining the expiration of the pyrolysis of the oven is based on the logic in which if the recent value of the buffer is greater than the average value then the oven control device proceeds controlling of storing data output of sensor device into the buffer if, however, the average value is greater than the recent value then a predetermined period is held for stability of the curve and then termination time is set by the oven control device.
Moreover, according to the invention the gas sensor can also be subject to pyrolysis by increasing the heating voltage of the sensor and thus the sensor operation temperature . In order to incorporate this feature into the invention, metal oxide sensors are used in the scope of the instant invention.
DESCRIPTION OF THE FIGURES
Further objects and advantages of the present invention will become apparent upon reading the following description taken in conjunction with the appended drawings wherein:
Figure 1 illustrates the oven with the exhaust pipe and sensor device.
Figure 2 illustrates flow chart of pyrolysis termination algorithm.
Figure 3 illustrates a typical sensor resistance vs. time curve.
Figure 4 illustrates flow chart of sensor device pyrolysis algorithm.
Figure 5 illustrates the pyrolysis curve for sensor device.
REFERENCE NUMBERS OF THE COMPONENTS
1 Oven
2 Exhaust pipe
3 Sensor box
4 CO filter
DISCLOSURE OF THE INVENTION Figure 1 illustrates an oven (1 ) body comprising a front door for introducing meal therein and walls for forming cavities in the oven (1). The oven is optionally provided with a ventilator or a fan. Experiments have shown that pyrolytic conditions require the internal temperature of the oven (1) be in the level of 460°C for various kinds of food residues including cheese, caramel, butter etc.
The gas content as a result of burning out of the residues is discharged through an exhaust pipe (2) or flue. A sensor box (3) comprises a sensor in the exhaust pipe (2) for sensing the gas content and a temperature sensor. The sensor is preferably selected from a metal oxide sensor kind or semi conducting kind and the metal oxide sensor preferably comprises the group consisting of SnOa, CTO, WO3, ZnO, V205, Ga2O3) Co304.The metal oxide sensor might be arranged to be sensitive to volatile organic carbons or alternatively to CO.
The temperature sensor is provided for measuring the operation temperature of the metal oxide sensor and the temperature sensor is in association with a control circuit for controlling the operation temperature of said metal oxide sensor.
The exhaust pipe is provided with a CO (Carbon Monoxide) filter for preventing the CO emissions to the atmosphere.
Pyrolytic self-cleaning cycle is terminated according to comparing average sensor resistance data with the recent data as illustrated in Figure 2. An oven control device receives the output data of a sensor device continuously, which is preferably a metal oxide gas sensor, and stores the data into a buffer.
The information whether the ventilator is switched on or off is provided by the oven control device, since the gas concentration variation would be affected through the air flow induced by the ventilator.
The number of data constituting the data set in the buffer is predetermined and preferably ten. Once the buffer is stored completely the oven control device calculates the average value of the data stored in the buffer. The average value is compared with the recent data, preferably the last data in the buffer so as to determine the process position i.e. increasing side or decreasing side of the sensor resistance vs. time curve.
In the preferred embodiment of the invention, if the last data is greater than the average value then the above-mentioned steps are repeated by the oven control device. In this case, the increase flag is set to "one" by the oven control device. If, however, the last data is less than the average value then the increase flag is set to "zero" meaning that the position in the decreasing side of the curve and the above-mentioned steps are repeated for achieving the stability condition.
If the average value is approximated to the recent data, in which case the approximation boundaries are predetermined, then the stability condition is checked and the pyrolysis is terminated.
Data storing method is based on one step at a time or plurality steps at a time i.e. for pursuing the curve pattern, the first data or first plurality of data in the buffer is / are released and simultaneously all of the remaining data are shifted one stack or plurality of stacks backward position and the recent output data or plurality of data of the sensor is / are stored in the last stack or the last stacks in the buffer. Afterwards, the above-mentioned calculation is performed for determining the position of the sensor resistance data.
As seen in Figure 3, the sensor resistance vs. time curve follows the pattern namely the sensor output values increases as the time increases and reaches an inflection point (maximum point) and then decreases as the time increases. The sensor resistance pattern shown is typical for so called p-type semiconductors like chromiumtitaniumoxide (Cr2-xTixθ3+z). However, n-type gas sensitive semiconductors like Snθ2 perform outputs exhibiting reciprocal pattern i.e. the sensor output decreases as the time increases and reaches an inflection points (minimum point) and then increases as the time increases. So, the present invention comprises these type of sensors and in this case the pyrolysis expiration algorithm comprises the steps: If the last data is less than the average value then the above-mentioned steps are repeated by the oven control device. In this case, the increase flag is set to "one" by the oven control device. If, however, the last data is greater than the average value then the increase flag is set to "zero" meaning that the position in the increasing side of the curve and the above- mentioned steps are repeated for achieving the stability condition.
If the average value is approximated to the recent data, in which case the approximation boundaries are predetermined, then the stability condition is checked and the pyrolysis is terminated.
The algorithm for oven pyrolysis comprises steps for checking the comparison runtime and predetermined timeout period and if runtime is greater than the timeout period, pyrolysis is terminated by the oven control device. According to preferred embodiment of the invention this check is employed during the first steps of the algorithm or in relation to the output of the comparison between the last data read and average value in the buffer or in relation to if increase is zero when last data read is substantially equal to average of the values in the buffer.
According to the invention as in Figure 4, pyrolytic self cleaning of the sensor device is achieved through the method as elaborated following:
Optionally, pyrolysis of the sensor device might be employed before or after the pyrolysis self cleaning of the oven itself. For sensor device pyrolysis, the base line resistance (Ro) during starting up the pyrolysis is set to the resistance of the sensor (Rs) and a threshold resistance (Rt) of the sensor device is predetermined and resistance of sensor (Rs) is normalized by dividing by base line resistance (Ro) i.e. (Rs/ Ro)for starting the sensor device pyrolysis and sensor device outputs are differentiated with respect to time continuously for having the sign of the derivative or the above-mentioned method is employed for determining the process position of the sensor device outputs as;
If Rs / Ro Rt and dRs / dt > 0 or as mentioned above sensor outputs are stored in a buffer and the oven control device calculates the average of the data for comparison with the recent data in the buffer and if the recent data is greater than the recent data the oven control determines the position of the process i.e. the increasing side then the pyrolysis of sensor device is initiated. Furthermore any other methods enabling the determination of the position of the sensor resistance outputs i.e. in the increasing side of the sensor output vs. time curve can be employed.
The termination of the pyrolysis of the sensor device is conditioned to the logic:
Rs/ Ro < Rtand dRs / dt < 0 or as mentioned above sensor outputs are stored in a buffer and the oven control device calculates the average of the data for comparison with the recent data in the buffer and if the recent data is less than the recent data the oven control determines the position of the process i.e. the decreasing side then the pyrolysis of sensor device is terminated.
The algorithm for sensor device pyrolysis comprises predetermined steps for checking the comparison runtime and predetermined timeout period and if runtime is greater than the timeout period, the oven control detects a malfunction associated with the sensor device. So, pyrolysis is terminated.
Pyrolysis of the sensor device is preferably initiated and maintained substantially above the temperature 350°C to which the temperature of the metal oxide sensor is heated.
Alternatively, the process of sensor device pyrolysis is incorporated with the oven pyrolysis. In this case the sensor device pyrolysis is applied prior to oven pyrolysis or after the oven pyrolysis.

Claims

1. A pyrolytic self cleaning oven comprising a cooking chamber, a heating device for heating the cooking chamber, an exhaust flue for discharging the gas induced by burning out of food residues, a sensor device for sensing the concentration of the discharging gas, an oven control device for receiving the output signals of the gas sensor and terminating the pyrolyis period characterized in that
the oven control device receives sensor outputs continuously and stores thereof in a buffer having sufficient capacity for comparing the average value calculated by the oven control device with a recent data output value in the buffer so that the position of gas concentration amount is determined on the sensor output vs. time curve for subsequent determination of pyrolytic self cleaning duration.
2. An oven according to claim 1 , wherein said oven comprises a ventilating means and information whether the ventilating means is switched on or off is provided with the oven control device.
3. An oven according to claim 1 , wherein a sensor box (3) is provided and said sensor box (3) comprises the sensor device and a temperature sensor for measuring the operation temperature of the sensor device and the temperature sensor is in association with a control circuit for controlling the temperature of said sensor device.
4. An oven according to anyone of the preceding claims, wherein said sensor device is a metal oxide sensor comprising the group consisting of SnO2, CTO, WO3, ZnO, V205> Ga2O3, Co3O4.
5. An oven according to anyone of the preceding claims, wherein said sensor device is a semi conducting sensor.
6. An oven according to claim 1 , wherein said exhaust flue is provided with a CO filter for preventing CO emissions to the atmosphere.
7. An oven according to claim 1 , wherein number of data stored in the buffer is ten.
3. An oven according to anyone of the preceding claims, wherein the recent data is the last data or the plurality of last data stored in the buffer.
9. A method for pyrolytic self cleaning of an oven having a cooking chamber, a heating device for heating the cooking chamber, an exhaust flue for discharging the gas induced by burning out of food residues, a sensor device for sensing the concentration of the discharging gas, an oven control device for receiving the output signals of the gas sensor and terminating the pyrolyis period and comprising the following steps of:
- receiving output data of the sensor device continuously,
- storing the output data into a buffer,
- calculating the average value of the data,
- comparing the average value with a recent data in the buffer,
- determining the process position of the pyrolysis,
- terminating the pyrolysis.
10. A method for pyrolytic self cleaning of an oven according to claim 9, wherein the buffer is stored by releasing the first data or the first plurality of data and shifting the remaining data one stack or plurality of stacks backward and storing the last stack or plurality of last stacks by the recent data.
11. A method for pyrolytic self cleaning of an oven according to claim 9, further comprising the step of:
- repeating preceding steps, afterwards the comparison, in case the recent data is greater than the average data with an increasing flag set to 1.
12. A method for pyrolytic self cleaning of an oven according to claim 9, further comprising the step of:
- repeating preceding steps, afterwards the comparison, in case the recent data is less than the average data with an increasing flag set to O.
13. A method for pyrolytic self cleaning of an oven according to claim 9, further comprising the steps of:
- checking stability conditions, afterwards the comparison, in case the recent data is approximated to the average data with an increasing flag set to 0,
- terminating the pyrolysis.
14. A method for pyrolytic self cleaning of an oven according to claim 9, further comprising the step of:
- repeating preceding steps, afterwards the comparison, in case the recent data is less than the average data with an increasing flag set to 1.
15. A method for pyrolytic self cleaning of an oven according to claim 9, further comprising the step of:
- repeating preceding steps, afterwards the comparison, in case the recent data is greater than the average data with an increasing flag set to 0.
16. A method for pyrolytic self cleaning of an oven according to claim 9, further comprising the steps of:
- checking stability conditions, afterwards the comparison, in case the recent data is approximated to the average data with an increasing flag set to 0,
- terminating the pyrolysis.
17. A method for pyrolytic self cleaning of an oven according to anyone of the claims 9 to 16, further comprising the steps of:
- checking runtime period of the pyrolysis period with a predetermined timeout period in predetermined steps,
- terminating the pyrolysis in case the runtime period is greater than the timeout period.
18. A method for pyrolytic self cleaning sensor device being in association with an oven having a cooking chamber, a heating device for heating the cooking chamber, an exhaust flue for discharging the gas induced by burning out of food residues, a sensor device for sensing the concentration of the discharging gas, an oven control device for receiving the output signals of the gas sensor and terminating the pyrolyis period and comprising the following steps of:
- receiving output data (Rs) of the sensor device continuously,
- determining a threshold resistance (Rt) of the sensor device,
- determining a base line resistance (Ro) of the sensor device during starting up the pyrolysis,
- normalizing the output data (Rs) of the sensor device by dividing thereof by the base line resistance (R0),
- differentiating the output data (Rs) of the sensor device with respect to time for having the sign of the derivative,
- comparing the normalized value with the threshold resistance (Rt) and the differentiation with zero,
- determining the process position of the pyrolysis,
- terminating the pyrolysis.
19. A method for pyrolytic self cleaning of an oven according to anyone of the claims 18, further comprising the steps of: - checking runtime period of the pyrolysis period with a predetermined timeout period in predetermined steps,
- terminating the pyrolysis in case the runtime period is greater than the timeout period.
20. A method for pyrolytic self cleaning sensor device according to claim 18, wherein the pyrolysis is initiated and maintained substantially above 350° C.
21. A method for pyrolytic self cleaning sensor device according to claim 18, wherein the sensor device is a metal oxide sensor.
22. A method for pyrolytic self cleaning sensor device according to claim 18, wherein the pyrolysis of the sensor device is initiated before the pyrolysis of oven as in claim 9.
23. A method for pyrolytic self cleaning sensor device according to claim 18, wherein the pyrolysis of the sensor device is initiated after the pyrolysis of oven as in claim 9.
PCT/TR2003/000012 2003-03-10 2003-03-10 Oven and sensor thereof having pyrolytic function WO2004081456A1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3495742A1 (en) 2017-12-11 2019-06-12 Vestel Elektronik Sanayi ve Ticaret A.S. Arrangement for self-cleaning oven

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US20020014480A1 (en) * 2000-07-12 2002-02-07 Andrea Corda System for controlling the duration of a sefl-clean cycle in an oven
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US4954694A (en) 1989-01-31 1990-09-04 Matsushita Electric Industrial Co., Ltd. Cooking oven having function to automatically clean soils attached to inner walls thereof
US5286943A (en) * 1991-08-19 1994-02-15 Bosch-Siemens Hausgeraete Sensor-controlled oven pyrolysis utilizing fuzzy logic control
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EP1172612A1 (en) * 2000-07-12 2002-01-16 Whirlpool Corporation System for controlling the duration of a self-clean cycle in an oven
US20020014480A1 (en) * 2000-07-12 2002-02-07 Andrea Corda System for controlling the duration of a sefl-clean cycle in an oven
US6392204B2 (en) 2000-07-12 2002-05-21 Whirlpool Corporation System for controlling the duration of a self-clean cycle in an oven
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EP3495742A1 (en) 2017-12-11 2019-06-12 Vestel Elektronik Sanayi ve Ticaret A.S. Arrangement for self-cleaning oven

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