METHOD AND DEVICE FOR DETERMINING THE LOAD CONDITION OF AN EXHAUST GAS PARTICULATE FILTER

Abstract

The disclosure relates to a method and a device for determining the load condition of an exhaust gas particulate filter that is arranged in an exhaust gas path of an internal combustion engine that is charged by an exhaust gas turbocharger. The behavior of a charging pressure controller or the charging pressure of the exhaust gas turbocharger is analyzed to determine the load condition of the exhaust gas particulate filter.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of International application No. PCT/EP2016/058198, filed Apr. 14, 2016, which claims priority to German patent application No. 10 2015 211 151.2, filed Jun. 17, 2015. The disclosures of the above applications are incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to a method and a device for determining the load condition of an exhaust gas particulate filter.

BACKGROUND

Modern motor vehicles having diesel engines are generally fitted with an exhaust gas particulate filter system for treating exhaust gas in order to be able to comply with legal requirements regarding particulate emissions. However, even in the case of petrol engines legal requirements regarding exhaust gas particulate emissions are expected to become stricter with the result that in the future vehicles having a petrol engine may also have to be fitted with an exhaust gas particulate filter.

Exhaust gas particulate filter systems filter out the soot particulates that are produced during engine combustion. Since the soot particulate storage capability of an exhaust gas particulate filter is limited, it is necessary to regenerate the exhaust gas particulate filter in the case of a correspondingly high load. During this regeneration procedure, soot particulates that have collected in the filter are burned with the result that new soot particulates can be collected in the regenerated exhaust gas particulate filter.

An exhaust gas particulate filter is regenerated typically at a high temperature that either occurs during the practical driving operation or is generated on demand by a corresponding adjustment of engine parameters. Such an artificial regeneration procedure is activated in general in dependence on the load condition of the exhaust gas particulate filter, the load condition being determined typically with reference to the exhaust gas backpressure that increases with an increasing particulate load.

If the exhaust gas backpressure or the differential pressure across the particulate filter exceeds a predetermined threshold value during the operation of the engine, the exhaust gas temperature is increased, by a corresponding adjustment of the engine parameters, to above the temperature at which the soot particulates are combusted, considering further parameters such as, by way of example, the operating temperature and the engine rotational speed.

Determining an increase in the exhaust gas backpressure using exhaust gas pressure sensors that are installed in the exhaust gas system upstream and, where appropriate, also downstream of the exhaust gas particulate filter, or using differential pressure sensors that measure a pressure increase across the filter system is already known.

One disadvantage of this approach resides in the fact that the above mentioned sensors are heavily stressed owing to the high exhaust gas temperature that is associated with the installation position and the contamination caused by the exhaust gas. This results, on the one hand, in high costs for suitable sensors and, on the other hand, in an increased susceptibility to a failure of the sensors.

A known method and a device for controlling the regeneration procedure of a particulate filter may be used in an internal combustion engine that includes an intake air compressor system and is coupled in a fluidically to an exhaust gas post-treatment system that includes a particulate filter. The method includes using engine operating points to determine a steady-state generation rate of the soot that is exiting the engine, setting the steady-state generation rate of the soot that is exiting the engine as a reaction to a transient change in a charging pressure of the intake air compressor system and controlling the regeneration procedure of the particulate filter as a reaction to the set steady-state generation rate of the soot that is exiting the engine. The controlling the regeneration of the particulate filter as a reaction to the set generation rate of the soot that is exiting the engine comprises chronologically integrating the set chronologically steady-state generation rate of the soot that is exiting the engine and ordering regeneration of the particulate filter if the chronologically integrated set generation rate of the soot that is exiting the engine exceeds a predetermined threshold value.

Another known method includes performing a plausibility check on a determined differential pressure value across a particulate filter. This plausibility evaluation is performed using a first measuring unit for determining the differential pressure value and a second measuring unit that determines a charging pressure of the internal combustion engine. A charging pressure value of the internal combustion engine is assigned to each differential pressure value. The two characteristic values are stored in a characteristic diagram storage device. An erroneous differential pressure value is identified if the measured differential pressure value is outside a predeterminable upper and lower threshold value range for the differential pressure value that is stored and allocated to the respective determined charging pressure of the internal combustion engine.

SUMMARY

The disclosure provides a method for determining the load condition of an exhaust gas particulate filter that does not require exhaust gas pressure sensors and nevertheless reliably determines the point in time at which the regeneration procedure of the exhaust gas particulate filter is due.

The method is provided for determining the load condition of an exhaust gas particulate filter that is arranged in the exhaust gas path of an internal combustion engine that is charged by a turbocharger. The behavior of a charging pressure controller of the exhaust gas turbocharger is analyzed in the method to determine the load condition of the exhaust gas particulate filter.

Executing a procedure of indirectly determining the load condition in this manner, makes it unnecessary to measure the exhaust gas pressure upstream and downstream of the particulate filter using exhaust gas pressure sensors. A differential pressure sensor is not required either. Consequently, problems that occur in the case of known methods owing to the arrangement of such sensors in the hot exhaust tract of an internal combustion engine are avoided.

One aspect of the disclosure provides a method for determining the load condition of an exhaust gas particulate filter that is arranged in the exhaust gas path of an internal combustion engine. The internal combustion engine is charged by an exhaust gas turbocharger. The behavior of a charging pressure controller or the charging pressure of the exhaust gas turbocharger is analyzed to determine the load condition of the exhaust gas particulate filter.

Implementations of the disclosure may include one or more of the following optional features. In some implementations, a long-term observation of the behavior of the charging pressure controller or the charging pressure of the exhaust gas turbocharger is performed to determine the load condition of the exhaust gas particulate filter. In some examples, the charging pressure controller provides control signals for the exhaust gas turbocharger and an evaluation of these control signals is performed in order to determine adaptation values for a pilot control procedure of the exhaust gas turbocharger, and a check is performed as to whether a change in the adaptation values occur in the long term.

In some implementations, a check is performed as to whether a characteristic change in the control signals that are output by the charging pressure controller occurs in the long term. A check may be performed as to whether characteristic deviations occur between a charging pressure desired value and a charging pressure actual value in the long term. In some examples, a point in time directly after the exhaust gas particulate filter has been regenerated is selected as a starting point in time for the analysis of the behavior of the charging pressure controller.

Another aspect of the disclosure provides a device for determining the load condition of an exhaust gas particulate filter that is arranged in the exhaust gas path of an internal combustion engine that is charged by an exhaust gas turbocharger. The device includes a control unit configured to perform the method described above.

The details of one or more implementations of the disclosure are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a block diagram of a device for determining the load of an exhaust gas particulate filter.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

FIG. 1 shows a device for determining the load of an exhaust gas particulate filter. The device includes an internal combustion engine 1, an exhaust gas turbocharger 2 that includes a turbine 3 and a compressor 5, an exhaust gas particulate filter 6, a control unit 7, an operating program storage device 8 and a data storage device 9. The turbine 3 is supplied with the hot exhaust gas of the internal combustion engine 1 and uses said hot exhaust gas to drive a turbine wheel. The turbine wheel is connected in a non-rotatable manner to a shaft 4. The shaft 4 is in turn connected in a non-rotatable manner to a compressor wheel that is arranged in the compressor 5 with the result that rotations of the turbine wheel are transferred to the compressor wheel. The fresh air that is supplied to the compressor is compressed by the rotation of the compressor wheel. The compressed fresh air is supplied to the internal combustion engine 1 and is used to increase the power of the engine.

Furthermore, the illustrated device includes a control unit 7, for example, the control device of the motor vehicle. The control unit 7 is connected to an operating program storage device 8 in which the operating program of the control unit is stored. Furthermore, the control unit 7 is connected to a data storage device 9 in which data is stored that corresponds inter alia to characteristic diagrams that are required by the control unit 7 during operation of the motor vehicle.

The control unit 7 includes a charging pressure controller 7a that is used for controlling the charging pressure of the exhaust gas turbocharger 2 during operation of the exhaust gas turbocharger 2.

The control unit 7 determines and outputs, during operation of the motor vehicle, control signals s1, s2 and s3 that depend on the sensor signals se1 that are supplied to the control unit 7 using the operating program and with the aid of the data that is stored in the storage device 9. The control signals s1 are used to control the internal combustion engine 1, the control signal s2 for controlling the actuators of the turbine 3 and the control signal s3 for controlling the actuators of the compressor 5. A wastegate valve or a variable turbine geometry is associated with the actuators of the turbine 3, and the opening state of the valves is altered on demand by the control signal s2. A bypass valve is associated with the actuators of the compressor 5 and compressed air is supplied via the bypass valve back to the input of the compressor 5 on demand. The opening state of this bypass valve is set by the control signal s3.

The abovementioned control signals se1 include inter alia the output signal of an accelerator pedal sensor that indicates an actuation of the accelerator pedal, the output signal of one or multiple temperature sensors that each provides information regarding a temperature that is measured at a predetermined location on the exhaust gas turbocharger, and the output signal of a pressure sensor that provides information regarding the pressure of the compressed air that is present at the output of the compressor.

Controlling the actuators of the exhaust gas turbocharger 2 is inter alia dependent on the exhaust gas backpressure since the output power of the turbine 3 is determined from the drop in the pressure across the turbine. This drop in the pressure across the turbine is defined by the exhaust gas backpressure downstream of the outlet valve or outlet valves of the internal combustion engine and by the exhaust gas backpressure downstream of the turbine, i.e., the exhaust gas backpressure upstream of the particulate filter 6. In the case of an identical operating point of the internal combustion engine, an increase in the exhaust gas backpressure upstream of the particulate filter 6 as a result of an increased flow resistance in the particulate filter 6 therefore leads to a reduced pressure drop across the turbine. Consequently, the power that is output by the turbine is less than the power that is determined by the control unit 7 using the stored characteristic diagrams, since the stored engine characteristic diagram was created based on the drop in pressure across the turbine in the case of an unloaded exhaust gas particulate filter. During operation of the internal combustion engine the desired charging pressure that is requested by the control unit for the engine operating point that is to be set is not entirely realized with a pilot control procedure that relates to the stored engine characteristic diagram. Consequently, there is a difference between the desired charging pressure and the actual charging pressure, the difference being compensated by the charging pressure controller 7a that is present in the control unit. This leads to a controller deviation that is also dependent upon the load condition of the exhaust gas particulate filter 6.

The behavior of the charging pressure controller 7a may therefore be used to determine the load condition of the exhaust gas particulate filter 6. Consequently, the point in time of a required regeneration procedure of the exhaust gas particulate filter may be determined using an analysis of the behavior of the charging pressure controller 7a.

There are different possibilities for this analysis of the behavior of the charging pressure controller 7a. In general, the procedure of loading the exhaust gas particulate filter to the point in time at which it is necessary to regenerate the exhaust gas particulate filter takes a relatively longer time. Consequently, it is necessary to perform long-term observation of the behavior of the charging pressure controller 7a and therefore also of the pilot control requirement of the exhaust gas turbocharger 2. An analysis of the required adaptations of the pilot control procedure of the exhaust gas turbocharger is suitable for such long-term observation. Long-term observation of charging pressure overshoots and charging pressure undershoots is also suitable.

A point in time directly after the execution of a regeneration procedure is selected in an advantageous manner as a starting point in time for a long-term observation of this type. At this point in time the above mentioned adaptation values for the pilot control of the turbocharger are reset. Starting from this point in time, new long-term observation of the adaptation values for the preset control procedure of the exhaust gas turbocharger is to be performed.

Alternatively or in addition thereto, it is also possible to perform a check as to whether characteristic changes of the control signals that are output by the charging pressure controller occur in the long term. Furthermore, alternatively or in addition thereto it is possible to perform a check as to whether characteristic deviations occur between the charging pressure desired value and the charging pressure actual value in the long term.

All the above-mentioned checking procedures are performed in dependence on changes that occur in the exhaust gas backpressure.

It follows that the present invention provides a method and a device in which a conclusion is drawn that it is necessary to perform modified pilot control of the exhaust gas turbocharger in response to a change in the drop in pressure across the turbine as a result of an increase in the exhaust gas backpressure in the exhaust gas particulate filter, the increase being caused by increased loading of the exhaust gas particulate filter.

A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.

Claims

1. A method for determining a load condition of an exhaust gas particulate filter arranged in an exhaust gas path of an internal combustion engine, the internal combustion engine is charged by an exhaust gas turbocharger, the method comprising:

analyzing a behavior of a charging pressure controller or the charging pressure of the exhaust gas turbocharger; and

determining the load condition of the exhaust gas particulate filter based on the analyzed behavior of the charging pressure controller or the charging pressure of the exhaust gas turbocharger.

2. The method of claim 1, further comprising:

performing a long-term observation of the behavior of the charging pressure controller or the charging pressure of the exhaust gas turbocharger; and

determining the load condition of the exhaust gas particulate filter based on the long-term observation.

3. The method of claim 1, further comprising:

evaluating control signals provided by the charging pressure controller;

determining adaptation values for a pilot control procedure of the exhaust gas turbocharger based on the evaluated control signal; and

performing a check for determining whether a change in the adaptation values occurs in the long term.

4. The method of claim 3, further comprising performing a check for determining whether a characteristic change in the control signals that are output by the charging pressure controller occurs in the long term.

5. The method of claim 1, further comprising performing a check for determining whether characteristic deviations occur between a charging pressure desired value and a charging pressure actual value in the long term.

6. The method of claim 1, further comprising selecting a point in time directly after the exhaust gas particulate filter has been regenerated as a starting point in time for the analysis of the behavior of the charging pressure controller.

7. A device for determining a load condition of an exhaust gas particulate filter that is arranged in an exhaust gas path of an internal combustion engine that is charged by an exhaust gas turbocharger, the device comprises a control unit configured to execute a method, the method comprising:

analyzing a behavior of a charging pressure controller or the charging pressure of the exhaust gas turbocharger; and

determining the load condition of the exhaust gas particulate filter based on the analyzed behavior of the charging pressure controller or the charging pressure of the exhaust gas turbocharger.

8. The device of claim 7, wherein the method further comprises:

performing a long-term observation of the behavior of the charging pressure controller or the charging pressure of the exhaust gas turbocharger; and

determining the load condition of the exhaust gas particulate filter based on the long-term observation.

9. The device of claim 7, wherein the method further comprises:

evaluating control signals provided by the charging pressure controller;

determining adaptation values for a pilot control procedure of the exhaust gas turbocharger based on the evaluated control signal; and

performing a check for determining whether a change in the adaptation values occurs in the long term.

10. The device of claim 9, wherein the method further comprises performing a check for determining whether a characteristic change in the control signals that are output by the charging pressure controller occurs in the long term.

11. The device of claim 7, wherein the method further comprises performing a check for determining whether characteristic deviations occur between a charging pressure desired value and a charging pressure actual value in the long term.

12. The device of claim 7, further comprising selecting a point in time directly after the exhaust gas particulate filter has been regenerated as a starting point in time for the analysis of the behavior of the charging pressure controller.