Method of operating a drive device and corresponding drive device

Abstract

In a method of operating a drive device, a probe temperature of an exhaust gas exhaust gas probe in an exhaust tract is measured, as the exhaust gas probe is heated by a probe heater. A temperature growth value representative of an increase in temperature of the exhaust gas probe is determined during heating of the exhaust gas probe, and the presence of a defect of the probe heater is recognized, when the temperature growth value deviates from an input value.

Claims

1. A method of operating a drive device of a motor vehicle having an internal combustion engine, said drive device including an exhaust gas probe arranged in an exhaust tract, a probe heater operably connected to the exhaust gas probe for heating the exhaust gas probe, a temperature sensor operably connected to the exhaust gas probe, and a determination device operably connected to the temperature sensor, comprising: measuring a probe temperature of the exhaust gas probe in the exhaust tract using the temperature sensor disposed at the exhaust gas probe, as the exhaust gas probe is heated by the probe heater; determining a temperature growth value representative of an increase in temperature of the exhaust gas probe during heating of the exhaust gas probe by the probe heater using the determination device; checking after elapse of a predefined time interval after start of heating of the exhaust gas probe whether the probe temperature falls below a temperature limit value using the determination device, in response to the measured probe temperature exceeding the temperature limit value, determining a probe temperature gradient as the temperature growth value corresponding to a temperature increase of the exhaust gas probe using the determination device, and in response to both the measured probe temperature gradient falling short of an input gradient limit value and the measured probe temperature falling short of the temperature limit value, recognizing a defect of the probe heater using the determination device only after both conditions have been met.

2. The method of claim 1, wherein the probe temperature gradient is determined by measuring the probe temperature at a first time instance and measuring the probe temperature at a second time instance.

3. The method of claim 1, wherein the probe temperature gradient is determined by ascertaining a time period between reaching of a first temperature value and reaching a second temperature value by the probe temperature.

4. The method of claim 3, wherein the first and second temperature values are selected greater than the probe temperature at a start of heating of the exhaust gas probe.

5. The method of claim 1, wherein the time interval is determined on the basis of the probe temperature at a start of heating of the exhaust gas probe.

6. A drive device of a motor vehicle having an internal combustion engine, comprising: an exhaust gas probe arranged in an exhaust tract; a probe heater operably connected to the exhaust gas probe and configured to heat the exhaust gas probe at least temporarily; a temperature sensor operably connected to the exhaust gas probe and configured to measure a probe temperature; and a determination device operably connected to the temperature sensor and configured to ascertain a temperature growth value representative of an increase in temperature of the exhaust gas probe during heating of the exhaust gas probe by the probe heater, said determination device configured to check after elapse of a predefined time interval after start of heating of the exhaust gas probe whether the probe temperature falls below a temperature limit value, said determination device configured to determine a probe temperature gradient as the temperature growth value corresponding to a temperature increase of the exhaust gas probe in response to the probe temperature exceeding the temperature limit value, wherein the determination device is configured to recognize a defect of the probe heater in response to both the measured probe temperature gradient falling short of an input gradient limit value and the measured probe temperature falling short of the temperature limit value, wherein the defect is recognized only after both conditions have been met.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:

(2) FIG. 1 is a schematic, exemplified illustration by way of a block diagram to illustrate components of a drive device according to the present invention; and

(3) FIG. 2 shows a diagram depicting curves of probe temperatures as a function of time.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(4) The depicted embodiment is to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures may not necessarily be to scale. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

(5) Turning now to FIG. 1, there is shown schematic, exemplified illustration by way of a block diagram to illustrate components of a drive device according to the present invention, generally designated by reference numeral 10. The drive device 10 includes an exhaust gas probe 12 arranged in an exhaust tract and heated, at least temporarily, by a probe heater 14 to increase a probe temperature T of the exhaust gas probe 12. the probe temperature T is measured by a measuring device 16.

(6) FIG. 2 is a diagram depicting respective curves 1, 2, 3 of probe temperatures T of the exhaust gas probe 12 as a function of time t. With reference to the curves 1, 2, 3 the method for recognizing a defect of the probe heater 14 of the exhaust gas probe 12 in accordance with the present invention will now be described.

(7) For example, the operativeness of the probe heater 14 can be checked after elapse of a predefined time interval after start of heating at t.sub.0, by checking whether the probe temperature T has exceeded a temperature limit value T.sub.1. The predefined time interval ends, for example, at time instance t.sub.S. It becomes readily apparent that the probe temperature T according to curve 1 has not, as of yet, reached the temperature limit value T.sub.1. This is an indication that the probe heater 14 is defective. In comparison thereto, the curve 2 shows the probe temperature T at a properly operating probe heater 14. In this case, the temperature limit value T.sub.1 is reached and exceeded at time instance t.sub.3, so that the probe temperature T at time instance t.sub.3, i.e. after elapse of the predefined time interval after start of heating, has a value which significantly exceeds the temperature limit value T.sub.1. The curves 1 and 2 start hereby from a probe temperature T at the start of heating at T.sub.0,1.

(8) When the initial temperature is, however, higher, for example at T.sub.0,2, as this is the case for the probe temperature T according to the curve 3, there may be a situation that the probe temperature T is greater than the temperature limit value T.sub.1 after elapse of the predefined time interval, i.e. at time instance t.sub.S, even though the probe heater is defective. As shown in FIG. 2, based on the higher initial temperature T.sub.0,2, the probe temperature T reaches according to curve 3 the temperature limit value T.sub.1 already at time instance t.sub.5, i.e. prior to the time instance t.sub.S.

(9) To address this scenario and to check more reliably the operativeness of the probe heater 14, it is proposed to determine with a determination device 18 during the heating phase a temperature growth value which corresponds to an increase in temperature of the exhaust gas probe 12. When the temperature growth value deviates from an input value, a defect of the probe heater 14 is indicated. For example, a probe temperature gradient can be used as temperature growth value, whereas the input value is represented by a gradient limit value. When the probe temperature gradient falls short of the gradient time value, then this is an indication that the probe heater 14 is defective.

(10) For example, the probe temperature gradient is determined, when the probe temperature T exceeds the temperature limit value T.sub.1. This is indicated for the curves 1, 2, and 3, respectively. In curve 1, the probe temperature T reaches the temperature limit value T.sub.1 at time instance t.sub.6 so that the probe temperature gradient is determined only at that time instance. In curve 2, the probe temperature gradient is determined already at time instance t.sub.3, whereas in curve 3, the probe temperature gradient is determined at time instance t.sub.5. Comparing the curves 1, 2, 3, it becomes readily apparent that the probe temperature gradients according to curves 1 and 3 are significantly smaller than the probe temperature gradient according to curve 2. Thus, the operativeness of the probe heater 14 can be ascertained on the basis of the magnitude of the probe temperature gradient. When the probe temperature gradient falls short of the gradient limit value, then the probe heater 14 is defective.

(11) In addition, or as an alternative, the temperature growth value may also be represented by a time period between reaching a first temperature value T.sub.2 and reaching a second temperature value T.sub.1 by the probe temperature T. When the time period exceeds a time limit value, used as input value, then this is an indication that the probe heater 14 is defective. For curve 1, the time period lies between the time instances t.sub.4 and t.sub.6, for curve 2, the time period lies between the time instances t.sub.2 and t.sub.3, and for curve 3, the time period lies between the time instances t.sub.1 and t.sub.5. It is readily apparent that the time period for curve 2 is the shortest, whereas the time periods for curves 1 and 3 are significantly longer. Thus, based on the time period, the operativeness of the probe heater 14 can be reliably checked by the determination device 18.

(12) Provision can be made, of course, for all embodiments to compare the probe temperature T with the temperature limit value T.sub.1 after elapse of the predefined time interval, i.e. at time instance t.sub.S, for example. When the probe temperature T falls short of the temperature limit value T.sub.1, then the presence of a defect of the probe heater 14 can be recognized. Provision may be made for this condition to be met in addition to the afore-described criteria. However, it may also be possible to recognize the presence of a defect of the probe heater 14, when only one of the criteria is met. A method according to the present invention is thus able to reliably check the operativeness of the probe heater 14 of the exhaust gas probe 12.

(13) While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.

(14) What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein.