Method of operating an exhaust emission control device, and corresponding exhaust emission control device

Abstract

In a method of operating an exhaust emission control device, the presence of an actual pressure loss of a particulate filter is determined, and a model pressure loss is determined as a function of a state variable. On the basis of the actual pressure loss and the model pressure loss a pressure quotient is determined and a condition of the particulate filter is ascertained in a diagnostic mode in response to the pressure quotient.

Claims

1. A method of operating an exhaust emission control device of a motor vehicle, comprising: determining an actual pressure loss across a particulate filter wherein an actual value is associated with the actual pressure loss; determining a model pressure loss as a function of a state variable, wherein a model value is associated with the model pressure loss; forming a model integral value from the model value as a function of time; forming an actual integral value from the actual value as a function of time; determining a pressure quotient as a function of the actual integral value and the model integral value; ascertaining a condition of the particulate filter in a diagnostic mode as a function of the pressure quotient; and communicating the ascertained condition of the particulate filter to a user of the motor vehicle or executing a regeneration mode of the particulate filter when the pressure quotient exceeds a predetermined value.

2. The method of claim 1, further comprising filtering the model value and/or the actual value by a bandpass filter before determining the pressure quotient.

3. The method of claim 2, wherein the bandpass filter has a lower limit of a passband range of 0.1 Hz to 1 Hz and/or an upper limit of the passband range of 1 Hz to 10 Hz.

4. The method of claim 1, further comprising sign correcting or squaring the model value and/or the actual value before determining the pressure quotient.

5. The method of claim 1, further comprising ascertaining a mechanical defect of the particulate filter or a removal of the particulate filter, when the pressure quotient is less than a first limit value.

6. The method of claim 1, further comprising ascertaining a high load of the particulate filter, when the pressure quotient exceeds a second limit value.

7. The method of claim 1, further comprising executing the diagnostic mode when at least one of the following conditions is satisfied: an observation time exceeds a minimum observation time, an integration time period exceeds a minimum integration time period, a drive torque of a drive device exceeds a minimum torque, a drive torque of a drive device is smaller than a maximum torque, a rotation speed of the drive device exceeds a minimum rotation speed, and a rotation speed of the drive device is smaller than a maximum rotation speed.

8. An exhaust emission control device of a motor vehicle, comprising: a particulate filter; and pressure sensors configured to determine an actual pressure loss across the particulate filter, said exhaust emission control device being configured to: determine a model pressure loss as a function of a state variable, wherein an actual value is associated with the actual pressure loss, determine a pressure quotient as a function of the actual pressure loss and the model pressure loss, wherein a model value is associated with the model pressure loss, form a model integral value from the model value as a function of time; form an actual integral value from the actual value as a function of time; ascertain a condition of the particulate filter in a diagnostic mode as a function of the pressure quotient; and communicate the ascertained condition of the particulate filter to a user of the motor vehicle or execute a regeneration mode of the particulate filter when the pressure quotient exceeds a predetermined value.

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 illustration of an exhaust emission control device according to the present invention; and

(3) FIG. 2 is a flow chart of a method of operating an exhaust emission control device according to the present invention.

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 a schematic illustration of an exhaust emission control device according to the present invention, generally designated by reference numeral 100. The exhaust emission control device 100 includes a particulate filter 103 to filter out particles from exhaust gas which flows through the exhaust emission control device 100. The exhaust emission control device 100 can be a component of a drive device which includes an exhaust-producing device 102, such as an internal combustion engine, in addition to the exhaust emission control device 100.

(6) FIG. 2 shows a flow chart of a method of operating an exhaust emission control device according to the present invention.

(7) In a first step 1, provision is initially made to determine an actual pressure loss across the particulate filter 103 with the aid of pressure sensors 104, 105 (FIG. 1). For that purpose, provision can be made to measure the pressure upstream and downstream of the particulate filter 103 and then to determine the actual pressure loss on the basis of a differential between these pressures. In step 1, the determined actual pressure loss 1 is interpreted as equal to an actual value. In a step 2, the actual value is filtered by a band pass filter, i.e. routed through a bandpass filter. The actual value determined in this way is sign-corrected and/or squared in a step 3 and then integrated in step 4 over time to produce an actual integral value.

(8) Integration is executed only when one or more of the following conditions is met: The exhaust mass flow changes, the exhaust temperature exceeds a first temperature threshold value, the exhaust temperature drops below a second temperature threshold value, the exhaust mass flow exceeds a first mass flow threshold value, the exhaust mass flow is smaller than a first mass flow threshold value, an exhaust mass flow integral is greater than a threshold value of an exhaust mass flow integral.

(9) In an analogous manner, a model pressure loss is determined in step 5 on the basis of at least one state variable. The state variable may, for example, be the exhaust mass flow. Another example of a state variable for determination of the model pressure loss may involve the exhaust temperature for example. The model pressure loss is, for example, a function of the exhaust mass flow and/or the exhaust temperature. The model pressure loss is interpreted as model value.

(10) This model value undergoes in step 6 filtering by a bandpass filter, with the bandpass filter having a same passband range, i.e. same lower limit and same upper limit of the passband range, as the bandpass filter used in step 2. The determined model value is sign-corrected and/or squared in a step 7, using a same procedure as applied for the actual value in step 3. The thus determined model value is integrated in step 8 over time to produce a model integral value. Provision may also be made for the model integral value to carry out integration only when at least one of the afore-stated conditions, as applied in the context of the integration of the actual value, is met. Advantageously, integration of the model value is carried out, when integration of the actual value has been executed.

(11) In step 9, a pressure quotient is determined through division of the actual integral value by the model integral value. In response to the determined pressure quotient, a conclusion can be made about the condition of the particulate filter 103. For example, when the pressure quotient is smaller than a first limit value, it follows that a mechanical defect of the particulate filter is present or that the particulate filter has been removed. Conversely, when the determined pressure quotient is greater than a second limit value, it follows that the particulate filter is highly loaded. When the particulate filter 103 is highly loaded, it is provided for example to execute a regeneration mode 106 (FIG. 1). Advantageously, the first limit value is smaller than 1, whereas the second limit value is greater than one. In particular, the second limit value is greater than the first limit value.

(12) The afore-described mode of operation results in a highly reliable diagnostic of the particulate filter so that a high load and/or defect of the particulate filter can be recognized rapidly and efficiently.

(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.