METHOD FOR OPERATING A SENSOR FOR DETECTING PARTICLES IN A MEASURING GAS

Abstract

A method for operating a sensor for detecting particles in a measuring gas. The sensor includes a sensor element having an electrically insulating element substrate, a first electrode, and a second electrode. The first electrode and the second electrode is situated at the electrically insulating element. The first electrode and the second electrode carry out a current and/or voltage measurement. The sensor is operated in at least one measuring phase during which a first voltage is applied to the first electrode and the second electrode. A second voltage is applied to the first and second electrode during a predetermined time period outside the measuring phase, the second voltage being lower than a decomposition voltage for water. The presence of water on the sensor element is inferred if the current and/or voltage measurement, with the second voltage being applied, yields a value which exceeds a threshold value for an electric current.

Claims

1-12. (canceled)

13. A method for operating a sensor for detecting particles in a measuring gas, the sensor including a sensor element, the sensor element including at least one electrically insulating element, a first electrode, and a second electrode, the first electrode and the second electrode being situated at the electrically insulating element, the first electrode and the second electrode carrying out a current and/or voltage measurement, the method comprising the following steps: operating the sensor in at least one measuring phase, a first voltage being applied to the first electrode and the second electrode during the measuring phase; applying a second voltage to the first electrode and the second electrode during a predetermined time period outside the measuring phase, the second voltage being lower than a decomposition voltage for water; and based on the current and/or voltage measurement, with the second voltage being applied, yielding a value which exceeds a threshold value for an electric current, inferring a presence of water on the sensor element.

14. The method as recited in claim 13, wherein the particles are soot particles, and the measuring gas in an exhaust gas of an internal combustion engine.

15. The method as recited in claim 13, further comprising: preventing a regeneration of the sensor or preventing a switch into the measuring phase, based on the current and/or voltage measurement, with the second voltage being applied, yielding a value which exceeding a first threshold value for an electric current.

16. The method as recited in claim 15, wherein the regeneration of the sensor or the switch into the measuring phase is enabled when the value of the current and/or voltage measurement, after exceeding the first threshold value, falls below a second threshold value for an electric current.

17. The method as recited in claim 16, wherein the regeneration of the sensor or the switch into the measuring phase is enabled after a predetermined time after a fall below the second threshold value.

18. The method as recited in claim 15, wherein the regeneration of the sensor or the switch into the measuring phase is enabled based on the sensor receiving a dew point end release from outside the sensor.

19. The method as recited in claim 15, wherein the regeneration of the sensor or the switch into the measuring phase is enabled based on the sensor receiving a dew point end release from a control unit.

20. The method as recited in claim 13, wherein the sensor is heated during the predetermined time period outside the measuring phase.

21. The method as recited in claim 20, wherein the sensor is heated to a temperature whose level depends on the value of the current and/or voltage measurement, with the second voltage being applied.

22. The method as recited in claim 13, wherein the sensor is situated in an exhaust tract of an internal combustion engine, the predetermined time period outside the measuring phase being after a cold start of the internal combustion engine, in the case of a missing dew point end release from an engine control unit of the internal combustion engine and/or upon a shortfall of a predetermined temperature in the exhaust tract.

23. The method as recited in claim 13, wherein the second voltage is a value in a range of 0.005 V to 1.2 V.

24. The method as recited in claim 13, wherein the second voltage is a value in a range of 0.05 V to 1.0 V.

25. A non-transitory computer-readable medium on which is stored a computer program for operating a sensor for detecting particles in a measuring gas, the sensor including a sensor element, the sensor element including at least one electrically insulating element, a first electrode, and a second electrode, the first electrode and the second electrode being situated at the electrically insulating element, the first electrode and the second electrode carrying out a current and/or voltage measurement, the computer-program, when executed by a computer, causing the computer to perform the following steps: operating the sensor in at least one measuring phase, a first voltage being applied to the first electrode and the second electrode during the measuring phase; applying a second voltage to the first electrode and the second electrode during a predetermined time period outside the measuring phase, the second voltage being lower than a decomposition voltage for water; and based on the current and/or voltage measurement, with the second voltage being applied, yielding a value which exceeds a threshold value for an electric current, inferring a presence of water on the sensor element.

26. An electronic memory medium on is stored a computer program for operating a sensor for detecting particles in a measuring gas, the sensor including a sensor element, the sensor element including at least one electrically insulating element, a first electrode, and a second electrode, the first electrode and the second electrode being situated at the electrically insulating element, the first electrode and the second electrode carrying out a current and/or voltage measurement, the computer-program, when executed by a computer, causing the computer to perform the following steps: operating the sensor in at least one measuring phase, a first voltage being applied to the first electrode and the second electrode during the measuring phase; applying a second voltage to the first electrode and the second electrode during a predetermined time period outside the measuring phase, the second voltage being lower than a decomposition voltage for water; and based on the current and/or voltage measurement, with the second voltage being applied, yielding a value which exceeds a threshold value for an electric current, inferring a presence of water on the sensor element.

27. An electronic control unit configured to operate a sensor for detecting particles in a measuring gas, the sensor including a sensor element, the sensor element including at least one electrically insulating element, a first electrode, and a second electrode, the first electrode and the second electrode being situated at the electrically insulating element, the first electrode and the second electrode carrying out a current and/or voltage measurement, the electronic control unit configured to: operate the sensor in at least one measuring phase, a first voltage being applied to the first electrode and the second electrode during the measuring phase; apply a second voltage to the first electrode and the second electrode during a predetermined time period outside the measuring phase, the second voltage being lower than a decomposition voltage for water; and based on the current and/or voltage measurement, with the second voltage being applied, yielding a value which exceeds a threshold value for an electric current, infer a presence of water on the sensor element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Additional optional details and features of the present invention are derived from the following description of preferred exemplary embodiments, which are schematically shown in the figures.

[0030] FIG. 1 shows a top view onto a sensor for detecting particles according to one specific example embodiment of the present invention.

[0031] FIG. 2 shows a flowchart of a method for operating a sensor for detecting particles according to one specific example embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0032] FIG. 1 shows a top view onto a sensor 10 for detecting particles in a measuring gas according to one specific embodiment of the present invention. Sensor 10 is designed, in particular, for detecting soot particles in a gas flow, such as an exhaust gas flow, of an internal combustion engine and for installation in an exhaust tract of a motor vehicle. Sensor 10 is designed as a soot sensor, for example, and may be situated downstream or upstream from a soot particulate filter of a motor vehicle including a diesel combustion engine. In the shown example, the measuring gas is exhaust gas of an internal combustion engine. In the shown exemplary embodiment, sensor 10 is designed as a resistive particle sensor.

[0033] Sensor 10 includes a sensor element 12. Sensor element 12 includes an electrically insulating element 14. Electrically insulating element 14 is a substrate. The substrate is a silicon wafer, for example. As an alternative, the substrate is manufactured from a ceramic material. Electrically insulating element 14 has an essentially cuboid design. Sensor element 10 furthermore includes a first electrode 16, a second electrode 18, a first feed line 20 and a second feed line 22. First electrode 16, second electrode 18, first feed line 20 and second feed line 22 are situated on an upper side 24 of substrate 14. First electrode 16 and second electrode 18 are designed as interdigital electrodes. First electrode 16 is connected to first feed line 20. Second electrode 18 is connected to second feed line 22. First feed line 20 and second feed line 22 represent connecting contacts, which are designed to electrically contact first electrode 16 and second electrode 18. First electrode 16 and second electrode 18 are designed to carry out a current and/or voltage measurement. Sensor 10 may optionally include further components, such as a protective tube and/or a heating element, which are not shown in greater detail. The sensor is operated in at least one measuring phase. During the measuring phase, a first voltage of 45 V, for example, is applied to first electrode 16 and second electrode 18. Sensor 10 is connected to an electronic control unit 26. Electronic control unit 26 is an engine control unit of the internal combustion engine, for example. The electronic control unit includes an electronic memory medium 28, such as a chip, on which a computer program is stored. The computer program includes instructions for carrying out a method for operating sensor 10. Such a method is described hereafter in greater detail.

[0034] FIG. 2 shows a flow chart of a method for operating a sensor 10 for detecting particles according to one specific embodiment of the present invention, such as that of sensor 10 shown in FIG. 1. In step S10, the internal combustion engine is started. In step S12, it is checked whether sensor 10 is in a time period outside the measuring phase. The time period outside the measuring phase is, for example, a cold start of the internal combustion engine, a missing dew point end release from an engine control unit of the internal combustion engine and/or upon a shortfall of a predetermined temperature in the exhaust tract. If the check in step S12 yields that it is not a cold start, a dew point end release is present and/or the predetermined temperature in the exhaust tract is exceeded, the presence of moisture at sensor element 12 may be excluded. In this case, the method proceeds to step S14 in which a switch into the measuring phase takes place.

[0035] If the check in step S12 yields that it is a cold start, a dew point end release is not present and/or the predetermined temperature in the exhaust tract falls short, a predetermined time period outside the measuring phase is determined, and the method proceeds to step S16. In step S16, a second voltage is applied to first electrode 16 and to second electrode 18 during the predetermined time period outside the measuring phase, the second voltage being lower than a decomposition voltage for water. The second voltage is a value in a range of 0.005 V to 1.2 V, and preferably 0.05 V to 1.0 V, for example 0.8 V or 1.0 V. In addition to potential enablings from outside sensor 10, a separate check of sensor 10 for the possible presence of water on sensor element 12 takes place. Sensor 10 is heated during the predetermined time period outside the measuring phase. If the current and/or voltage measurement, with the second voltage being applied, yields a value which exceeds a threshold value for an electric current, the presence of water on sensor element 12 is inferred. The first threshold value is 0 A, for example. If the current and/or voltage measurement, with the second voltage being applied, in step S16 yields a value which exceeds a first threshold value for an electric current, the method proceeds to step S18, and a regeneration of sensor 10 or a switch into the measuring phase is prevented. If the first threshold value is not exceeded, water or moisture may be excluded, and the method proceeds to step S14, and a switch into the measuring phase takes place. Subsequent to step S18, step S20 takes place, in which a regeneration of the sensor or a switch into the measuring phase is enabled if the value of the current and/or voltage measurement, after exceeding the first threshold value, falls below a second threshold value for an electric current. The second threshold value may be identical to the first threshold value or may differ therefrom. The enabling thus only occurs after the current at electrodes 16, 18 has decreased. The method then proceeds to step S14, and a switch into the measuring phase takes place.

[0036] The method may be modified as follows. A regeneration of sensor 10 or a switch into the measuring phase is enabled after a predetermined time after a fall below the second threshold value. In other words, a certain time is waited after a current at the electrodes has decayed due to moisture, to also have moisture reliably removed from the deeper ceramic layers of sensor element 12, before sensor element 12 is regenerated or subjected to a measuring voltage. A regeneration of sensor 10 or a switch into the measuring phase is enabled if, in addition to the decrease of the current at electrodes 16, 18, sensor 10 receives a dew point end release from the outside, such as for example the control unit 26. The sensor is heated to a temperature whose level depends on the value of the current and/or voltage measurement, with the second voltage being applied. In other words, the level of the current is evaluated by applying the second voltage during the protective heating, to adapt the protective heating temperature for more rapid drying of the sensor element or for gentler drying of the sensor element. A further modification of the method provides to drastically lowering the protective heating temperature, down to the unheated state, and to utilize the inactive times of the sensor for subjecting electrodes 16, 18 to 1 V, and to determine moisture in the exhaust tract based on the current flowing through, and to make this additional information available to the engine control unit, or to determine the dew point end by measurement and not being dependent on models.