METHOD FOR CONTROLLING A PYROLYSIS CLEANING PROCESS IN AN OVEN

Abstract

A method for controlling a pyrolysis cleaning process in an oven includes the steps: a) heating an oven cavity of the oven by switching on a heat source; b) measuring, using an oxygen sensor, an oxygen concentration in the oven cavity or in an exhaust-air conduit configured to discharge fumes from the oven cavity; c) comparing, in an evaluation circuitry of an electrical control unit, the measured oxygen concentration to a predefined limit value stored in a memory; d) operating, if the measured oxygen concentration drops below the limit value, the oven for a predefined first time interval with the heat source switched off, a duration of the first time interval being stored in the memory; and e) repeating steps b) through d) after the first time interval has ended; or f) repeating steps a) through d) if the measured oxygen concentration is equal to or greater than the limit value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention is shown schematically in the drawings and will be described in greater detail below. The drawings show the following:

FIG. 1—a frontal view of an oven in which the method according to the invention is used;

FIG. 2—a sectional view of the oven from FIG. 1; and

FIG. 3—a diagram of the oven cavity temperature and of the oxygen concentration as a function of time.

Claims

1. A method for controlling a pyrolysis cleaning process in an oven, comprising the following steps: a) heating an oven cavity of the oven by switching on a heat source;b) measuring, using an oxygen sensor, an oxygen concentration in the oven cavity or in an exhaust-air conduit configured to discharge fumes from the oven cavity;c) comparing, in an evaluation circuitry of an electrical control unit, the measured oxygen concentration to a predefined limit value stored in a memory;d) operating, if the measured oxygen concentration drops below the limit value, the oven for a predefined first time interval with the heat source switched off, a duration of the first time interval being stored in the memory; ande) repeating steps b) through d) after the first time interval has ended; orf) repeating steps a) through d) if the measured oxygen concentration is equal to or greater than the limit value.

2. The method as recited in claim 1 further comprising alternately switching on the heat source during predefined second time intervals and then switching off the heat source during third time intervals, a duration of the first time interval being the same as a duration of the third time interval, a duration of the second time intervals being stored in the memory.

3. The method as recited in claim 1 wherein the limit value is about 18 vol-%.

4. The method according to claim 1 wherein the pyrolysis cleaning procedure comprises: a heating phase performed until a pyrolysis temperature in the oven cavity has been reached, the pyrolysis temperature being either predefined or automatically determined during the heating phase;a holding phase having a duration corresponding to a fourth time interval, a duration of the fourth time interval being either predefined or automatically determined during the heating phase, the pyrolysis temperature being maintained substantially constant during the holding phase by temperature regulation; anda cooling phase configured to reach a predefined final temperature in the oven cavity;wherein steps a) through f) are performed only during the heating phase.

5. The method as recited in claim 4 wherein at least one of a duration of the fourth time interval and a value of the pyrolysis temperature during the holding phase is automatically determined in the evaluation circuitry as a function of a number of times the heat source was switched off during the heating phase due to the oxygen concentration falling below the limit value.

6. The method as recited in claim 4 wherein at least one of a duration of the fourth time interval and a value of the pyrolysis temperature during the holding phase is automatically determined in the evaluation circuitry as a function of an average oven cavity temperature during a fifth time interval, the fifth time interval having a duration equal to a time period from a first time the heat source was switched off due to the oxygen concentration falling below the limit value until an end of a last time the heat source was switched off due to the oxygen concentration falling below the limit value.

7. The method as recited in claim 4 wherein at least one of a duration of the fourth time interval and a value of the pyrolysis temperature during the holding phase is automatically determined in the evaluation circuitry as a function of a sum of a number times the heat source was switched off during the heating phase due to the oxygen concentration falling below the limit value.

8. The method as recited in claim 7 wherein the duration of the fourth time interval is determined in the evaluation circuitry by adding a sum of the number of times when the heat source was switched off to a predefined minimum duration stored in the memory.