DE102004046882B4 - Method for operating an internal combustion engine, and associated computer program, electrical storage medium and control and / or regulating device for detecting a state variable in the exhaust gas of the internal combustion engine - Google Patents

Abstract

A method for operating an internal combustion engine (10) in which particles present in the exhaust gas are retained in a filter device (18) and detected using a first signal from a sensor device (22, 38), the same sensor device (22, 38) delivering a second signal , which is used at least temporarily to determine the exhaust gas temperature (Tex), characterized in that the sensor device (38) is arranged downstream of the filter device (18) and the second signal for monitoring and / or control or regulation of a regeneration of the filter device (18 ) is used and that when the second signal reaches or exceeds a limit value (G2) (90), a possible damage to the filter device (18) by the regeneration is concluded and that if damage to the filter device is detected, a signal (36) a differential pressure sensor (34) which measures a pressure difference (dp) across the filter device (18) h inweg is recorded, adapted (92).

Description

State of the art

The invention initially relates to a method for operating an internal combustion engine, in which particles present in the exhaust gas are retained in a filter device and detected on the basis of a first signal of a sensor device.

The invention further relates to a computer program, an electrical storage medium for a control and / or regulating device of an internal combustion engine, a control and / or regulating device for an internal combustion engine, and a sensor device for detecting at least one state variable in the exhaust gas of an internal combustion engine, with at least one first sensor for detecting particles present in the exhaust gas.

From the market, diesel internal combustion engines are known, which include an exhaust system with a particulate filter that filters soot particles from the exhaust. The filtered-out particles deposit on the filter, which causes the flow resistance of the exhaust gas through the exhaust line to increase over time. The thus increasing so-called "exhaust back pressure" can lead to increased fuel consumption or a reduction in performance of the internal combustion engine.

To prevent this, it is known to regenerate the particulate filter from time to time. In such regeneration, the deposited soot particles are burned. For this purpose, a temperature of more than 650 ° C must be achieved in the particulate filter, which can be effected by various measures. Are known motor measures such as the reduction of boost pressure, a throttling, a shift of an injection timing, additional fuel injection, etc., which all lead to a temporary increase in exhaust gas temperature. An alternative or additional measure is to arrange an oxidation catalyst upstream of the particulate filter in the exhaust line, in which nitrogen dioxide is formed continuously. This can then react in the particulate filter with the soot deposited there to form gaseous nitrogen and carbon dioxide. An exhaust system with a particulate filter is generally from the DE 102 31 620 A1 known.

To detect the loading state of the particulate filter with soot particles and to be able to initiate a regeneration of the particulate filter in time, particle sensor devices are used. Such a particle sensor device is for example in the DE 101 33 384 A1 described. It has a collecting chamber, which is fluidically connected to the exhaust gas flow of the internal combustion engine. On one side of the collection chamber, two electrodes are arranged, which mesh in a comb-like manner ("interdigital"). During operation of the known particle sensor device, soot particles enter the collection chamber and deposit on the electrodes. As a result, the gap between the two electrodes is electrically bridged, so that the impedance of the electrode structure changes. The temporal change of the impedance is a measure of the loading of the exhaust gas flow with soot particles. In order to be able to free the soot particle sensor device from the accumulated soot particles from time to time, it has a heating device, by means of which the soot particles accumulated during operation can be burnt.

Another sensor device is from the DE 101 49 333 A1 known. In this, a resistance measuring structure consisting of interdigital comb electrodes is applied to an electrical insulating support. By addition of soot particles, the electrical resistance of the resistive layer changes.

The not yet published DE 103 53 860 describes a soot particle sensor device, which in addition to the heating element has a temperature detection device, with the signal of which the regeneration of the particle sensor device can be monitored or regulated.

Other relevant methods and devices are in the DE 10209755 A1 , of the DE 103 09 239 A1 and the US Pat. No. 4,656,832 disclosed.

Object of the present invention is to increase the safety in the operation of the internal combustion engine, while low manufacturing and operating costs.

This object is achieved in a method of the type mentioned in that the same sensor device provides a second signal which is at least temporarily used to determine the exhaust gas temperature.

In a sensor device of the type mentioned, the stated object is achieved in that it has at least one second sensor for detecting the exhaust gas temperature.

Advantages of the invention

The exhaust gas temperature is an important parameter for the control and regulation of an internal combustion engine. Their knowledge enables a low-emission and consumption-optimal operation. The integration of that sensor, which detects the exhaust gas temperature, in the same sensor device, which also is used for detecting particles present in the exhaust gas, reduces the installation effort and the space required for the accommodation of the sensors.

Advantageous developments of the invention are specified in subclaims.

A first preferred embodiment of the method according to the invention is characterized in that the second signal is not used during a regeneration phase of the sensor device for determining the exhaust gas temperature. Such a regeneration phase of the sensor device is usually accompanied by a heating of the sensor device by means of a built-in heating device. This warming naturally also influences the second signal. The inventive measure prevents an exhaust gas temperature is determined which does not correspond to the actual exhaust gas temperature. In this way, the operational reliability of the internal combustion engine, including an associated exhaust aftertreatment system, is improved.

According to the invention, the sensor device is arranged downstream of the filter device and the second signal is used to monitor and / or control or regulate a regeneration of the filter device. Such a regeneration of the filter device is usually associated with a heating of the filter device to a temperature at which the deposited soot particles burn off due to an exothermic reaction. The heating of the filter device required for the initiation of the exothermic reaction can be effected by increasing the exhaust gas temperature, or it can be brought about by a separate heating device. By this heating and the exothermic reaction, the temperature of the exhaust gas downstream of the filter device will be increased accordingly. This can be detected by the sensor device arranged according to the invention, which improves the reliability and quality of the regeneration of the filter device.

In a concrete further development, it is proposed that when the exhaust gas temperature determined from the second signal reaches or exceeds a limit value, a measure for lowering the temperature is initiated, for example by means of engine measures, and / or a shortening of a regeneration phase is determined. Also in this way damage to the filter device is avoided by an excessive temperature. It is further provided according to the invention that, when the second signal reaches or exceeds a threshold value, a possible damage of the filter device due to the regeneration is concluded. As a result, for example, a corresponding entry can be made in a fault memory, so that during maintenance of the internal combustion engine, the filter device can be inspected and possibly replaced. The analysis of the temperature history of the particulate filter also makes it possible to detect possible damage to the same.

Furthermore, it is provided according to the invention that, when a damage to the filter device is detected, a signal of a differential pressure sensor which detects the pressure difference across the filter device is adapted. Such a differential pressure sensor is usually present to also provide a signal by which the loading of the filter device can be determined with particles. However, the interpretation of the signal of the differential pressure sensor is based on a correctly operating filter device. However, if the filter device is damaged, for example by a hole being burnt in at one point by an excessive temperature, the differential pressure sensor possibly supplies a signal which corresponds to a low loading of the filter device, although this is not present per se. By means of the measure according to the invention, misinterpretations of the signal of the differential pressure sensor are avoided. As a result, the reliability increases in the operation of the internal combustion engine.

An alternative embodiment of the inventive method provides that upstream of the filter device in an oxidation catalyst NO _{2 is} generated, that the sensor device is disposed between the oxidation catalyst and the filter device that, taking into account the exhaust gas temperature, a NO ₂ concentration in the exhaust gas determined (estimated, for example ), and that from the NO ₂ concentration on the strength of a continuous regeneration of the filter device is closed. This is based on the following consideration: It is known that the formation of NO ₂ in the upstream oxidation catalyst depends primarily on the exhaust gas temperature. With the device according to the invention, the exhaust gas temperature can be determined in a simple manner and estimated in the sequence of NO ₂ content in the exhaust gas. However, its value is decisive for the degree of continuous regeneration that is possible by the NO ₂ in the particle filter.

If, on the one hand, the possible degree of regeneration and, on the other hand, the particle content in the exhaust gas are known, which is both possible by the method proposed here and the corresponding sensor device, it is possible in turn to deduce the current loading of the filter device with increased precision. The inventive method thus allows a simple Assessment of the current state of the filter device. This is laid down in a further advantageous embodiment of the method according to the invention, according to which the current loading of the filter device is concluded by using the first signal and the second signal. This has far-reaching positive effects: If temperature peaks during regeneration can be avoided by a more precise knowledge of the amount of soot contained in the particle filter, then a less thermally stable, but more cost-effective filter material can be used.

The precision in determining the load is thereby increased by the fact that the temperature of the sensor device is at least approximately detected and / or determined and / or estimated, and that the difference between the exhaust gas temperature and the temperature of the sensor device at least indirectly in determining the current loading of the filter device is taken into account. In this way, the "thermophoretic effect" can be included in the determination of Rußanlagerung: The Rußanlagerung on the sensor device depends namely on the temperature difference between the sensor device and the exhaust gas. If the exhaust gas is significantly hotter than the sensor device (which is generally the case), more soot is deposited on the sensor device than at a lower temperature difference or even in the opposite case that the sensor device is hotter than the exhaust gas. With knowledge of the actual temperature conditions, it is therefore possible to deduce the actual soot content in the exhaust gas and consequently the soot load of the particulate filter from the detected soot accumulation on the sensor device with even higher accuracy.

It is particularly advantageous if from a signal of a differential pressure sensor, which detects the pressure difference across the filter device away, on the current load of the filter device is closed, and if this result is compared with the determined from the second signal load. The second signal, which determines the temperature of the exhaust gas, allows a more accurate knowledge of the volumetric flow, which in turn allows optimization of the differential pressure sensor. If the determined loads differ by more than a certain limit value, there is a problem, so that, for example, a corresponding entry into a fault memory can be made and the problem during maintenance can be investigated. This facilitates maintenance and improves the emission and consumption quality of the internal combustion engine.

Analogous to the method specified above, it is also proposed that, depending on the result of the comparison, the signal of the differential pressure sensor be adapted. The accuracy in the interpretation of the signal of the differential pressure sensor is thereby increased.

In the same direction aims that development in which the second signal is monitored by means of a third signal of another temperature detection device.

In the case of a sensor device, it is particularly advantageous if the two sensors are each arranged on exposed surfaces of the device exposed to the exhaust gas. As a result, even very dynamic processes can be detected reliably.

Furthermore, the sensor device may comprise a heating device with which the first sensor can be burned free of deposited particles, and the second sensor may be suitable for detecting the temperature of the sensor device. In this case, the second sensor has a dual function, because it can be used on the one hand for monitoring the regeneration of the first sensor or the sensor device as a whole, and outside these phases it can be used for the detection of the exhaust gas temperature. This again reduces the costs and installation costs.

The manufacture of the sensor device is simplified in that it has two flat and adhered layers and that on the exposed side of the one layer, the first sensor, on the exposed side of the second layer, the second sensor, and between the two layers, the heater is arranged , Such a sensor also builds very small and flat and can therefore be placed anywhere in the exhaust system of the internal combustion engine.

The combination of particle sensor and temperature sensor for detecting the exhaust gas temperature is particularly advantageous when it is used to carry out a method of the above type.

drawing

Hereinafter, particularly preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings.

In the drawing show:

1 a schematic representation of an internal combustion engine having a plurality of sensor devices and a filter device in the exhaust system;

2 a perspective view of a first embodiment of the sensor devices of 1 ;

3 Top views of three sub-elements, from which the sensor device of 2 is composed;

4 a representation similar 2 a portion of an alternative embodiment of a sensor device;

5 a flowchart for operating sensor devices of 1 ;

6 a flowchart of a first method for monitoring the regeneration of the filter device of 1 ;

7a a diagram in which the temperature of the filter device of 1 during regeneration is plotted over time;

7b a diagram in which a differential pressure across the filter device of 1 is applied over time;

8th a flowchart of a second method for monitoring a cyclic regeneration of the filter device of 1 ; and

9 a flowchart of a method for predicting the loading of the filter device of 1 ,

Description of the embodiments

In 1 an internal combustion engine carries the reference numeral 10 , It includes an engine block 12 and an exhaust system 14 , In the exhaust system 14 are seen in the flow direction, first an oxidation catalyst 16 and then a particle filter 18 arranged.

In an exhaust pipe 20 is between the oxidation catalyst 16 and the filter device 18 a first sensor device 22 placed, which is a particle sensor 24 and a temperature sensor 26 includes (wherein the sensor means 22 basically also in other places in the exhaust pipe 20 can be arranged). The signal of the particle sensor 24 is over a line 28 , the signal of the temperature sensor 26 over a line 30 to a control and regulating device 32 directed. In the area of the filter device 18 is a differential pressure sensor in the embodiment shown here 34 arranged, its signal via a line 36 to the control and regulating device 32 is directed. In an embodiment not shown, such a differential pressure sensor is dispensed with.

Downstream of the filter device 18 is in the exhaust pipe 20 a second sensor device 38 placed, which are identical to the first sensor device 22 is constructed. Again, a not shown embodiment is conceivable in which such a second sensor device is not present. So it also includes a particle sensor 40 and a temperature sensor 42 whose signals are transmitted via lines 44 and 46 to the control and regulating device 32 be directed. A lambda probe 48 is immediately downstream of the oxidation catalyst 16 in the exhaust pipe 20 arranged (and the lambda probe may not be realized in an embodiment not shown). Their signal passes over a line 50 to the control and regulating device 32 , The control and regulating device 32 is how through 52 is indicated with the engine block 12 signal technically connected and controls there various functions. These include, for example, ignition and fuel injection.

Due to incomplete combustion in the engine block 12 may be included in the exhaust soot particles. Through the filter device 18 Prevents these soot particles that are harmful to health, get into the environment. By the deposition of soot particles in the filter device 18 however, its permeability is reduced. Too high exhaust back pressure in the exhaust pipe 20 to avoid, is the filter device 18 regenerated on the one hand continuously and on the other cyclically by the accumulated soot particles are oxidized.

The continuous regeneration takes place by means of NO ₂ , which in the upstream oxidation catalyst 16 is produced. The cyclic regeneration of the filter device 18 is brought about by an increase in the exhaust gas temperature, which together with a provided in the present embodiment, but not shown in the figure catalytic coating of the filter device 18 causes an exothermic reaction. The increase in the exhaust gas temperature can be effected, for example, by engine measures, for example the post-injection of fuel. The regenerations of the filter device 18 can by means of the two sensor devices 22 and 38 be monitored.

The sensor devices 22 and 38 are identical. In the 2 and 3 is the sensor device 22 exemplified. Thereafter, the sensor device comprises 22 each three laminated ceramic layers 54 . 56 and 58 , which are produced in the present case mainly because of the temperature resistance based on Al ₂ O ₃ or ZrO ₂ . The in the 2 and 3 upper ceramic layer 54 is wearing on her exposed outside 59 two electrodes 60 and 62 , The two electrodes 60 and 62 are structured "interdigitally" for a resistivity measurement and thus form the particle sensor 24 ,

The in the 2 and 3 middle ceramic layer 56 carries on her from the situation 54 opposite side a meandering heater 64 through which the sensor device 22 in the area of the particle sensor 24 can be heated. In this way, if necessary, at the sensor device 22 accumulated soot particles are burned. The in the 2 and 3 lower ceramic layer 58 carries a meandering structure of a thin platinum layer 66 through which the temperature sensor 26 is formed. The platinum layer is on the exposed side 68 the ceramic layer 58 applied and provided with a thin ceramic protective layer. By the arrangement of the platinum layer 66 can the temperature sensor 26 detect the temperature of the exhaust gas comparatively accurate. In a first approximation, the temperature of the sensor device 22 be set equal to the exhaust gas temperature.

For the estimation of the influence of the temperature dependence of the Rußanlagerung (Thermophorese) can different from the exhaust temperature of the sensor device 22 also be estimated by means of a numerical model or by means of an estimation method (for example an observer method). It is also possible, another, but not shown in the figure, temperature sensor on the location 54 facing side of the situation 56 provide, with its signal, the temperature of the sensor device 22 capture.

An in 4 illustrated and even shallower building embodiment of a sensor device 22 consists of only two ceramic layers 54 and 58 , In the 4 invisible heating device is on the same lower ceramic layer 58 Applied as the platinum layer, which the temperature sensor 26 forms.

Out 5 shows how the signal of the temperature sensors 26 and 42 the two sensor devices 22 and 38 is used: After a start block 70 will be in a block 72 queried, if just a regeneration of the first sensor device 22 or the second sensor device 38 takes place. Such regeneration includes startup of the respective heater 64 for burning the respective sensor device 22 respectively. 38 , Is the answer in the block 72 No, the signal from the temperature sensor 26 or the temperature sensor 42 used to determine the exhaust gas temperature T _ex (block 74 ). It is considered by a not shown in the figure delay element that from the signal of the temperature sensors 26 and 42 not only during the actual operation of the heater 64 but also during a subsequent cooling phase, the exhaust gas temperature can not be determined with the desired accuracy. Is the answer in the block 72 Yes, in the block 76 the signal of the temperature sensor 26 respectively. 42 for determining the temperature T _{sens of} the sensor device 22 respectively. 38 used, which allows conclusions about the accumulated amount of soot. The procedure ends in the block 78 ,

As indicated above, it is alternatively possible to place two temperature sensors so that one senses the exhaust gas temperature and the other senses the sensor temperature. On the basis of the temperature difference, a thermophoretic effect of Rußanlagerung on the sensor device 22 respectively. 42 and thereby increases the accuracy in determining the amount of soot actually contained in the exhaust gas and deposited in the particulate filter.

A procedure for monitoring the regeneration of the filter device 18 is in 6 shown using the signal of the second sensor device 38 , Will a cyclic regeneration of the filter device 18 For example, by increasing the exhaust gas temperature initiated (block 80 in 6 ), thereby becomes in the filter device 18 an exothermic reaction set in motion (block 82 in 6 ), which leads to an increase in the exhaust gas temperature downstream of the filter device 18 leads. This is done by the temperature sensor 42 detected, and the corresponding temperature T _ex is sent to the control and regulating device 32 directed. By a corresponding reduction or increase in the exhaust gas temperature can by the control and regulating device 32 Influence on the exothermic reaction in the filter device 18 be taken. If, for example, the temperature T _{ex exceeds} a limit value, the control and regulating device 32 initiated a decrease de exhaust gas temperature to reduce the extent of the exothermic reaction.

We out 7a However, the exothermic reaction can run so hard that a limit G2 of the temperature sensor 42 detected exhaust gas temperature T _{ex is} exceeded. The limit value G2 is chosen so that when exceeded, it can be assumed that in the filter device 18 a permissible temperature has been exceeded and a damage to the structure of the filter device 18 For example, a hole has occurred. If such a hole occurs, a signal dp of the differential pressure sensor falls 34 ( 7b ) very quickly, since the exhaust gas through the hole in the filter device 18 with little resistance, although in other places the filter device 18 the soot particles are not completely burned down. In the control and regulating device 32 therefore becomes the signal of the differential pressure sensor 36 adapted in such a case. A corresponding method is in 8th shown:
After a starting block 84 is in 86 checked whether the exhaust gas temperature T _ex detected by the temperature sensor is greater than a limit value G1. If this is the case, it will be in a block 90 queried whether the exhaust gas temperature T _{ex is} greater than a limit G2 (G2> G1). If this is also the case, is in a block 92 the signal dp of the differential pressure sensor 34 adapted. Otherwise 88 becomes the exothermic reaction in the filter device 18 and thus their regeneration in the block 88 slowed down. The procedure ends in an end block 94 ,

The upstream of the filter device 18 arranged first sensor device 22 can predict the loading of the filter device 18 and used to monitor their continuous regeneration. This goes out 8th forth: By means of the lambda probe 48 or from stored map data is an oxygen content (block 96 ) and by means of the temperature sensor 26 an exhaust gas temperature T _ex (block 98 ). This will be in 100 in the oxidation catalyst 16 Nitrogen amount determined or estimated with the aid of stored map data. This results in the block 102 again a strength -dC / dt of the possible degradation of in the filter device 18 deposited soot particles. Due to the signal of the particle sensor 24 is in 104 a strength + dC / dt of the possible increase of accumulated soot particles determined.

In 106 a balance is created from which a possible current loading Cload1 of the filter device 18 with soot particles. From the signal of the differential pressure sensor 34 and the differential pressure dp (block 108 ) is in 110 also a current loading Cload2 of the filter device 18 determined with soot particles. The two in the blocks 106 and 110 determined loads are in one block 112 compared to each other. Depending on the comparison is in the block 114 the signal of the differential pressure sensor 34 adapted.

Claims (12)

Method for operating an internal combustion engine ( 10 ), in the exhaust gas particles in a filter device ( 18 ) and based on a first signal of a sensor device ( 22 . 38 ) are detected, wherein the same sensor device ( 22 . 38 ) supplies a second signal, which is at least temporarily used for determining the exhaust gas temperature (T _ex ), characterized in that the sensor device ( 38 ) downstream of the filter device ( 18 ) and the second signal for monitoring and / or controlling a regeneration of the filter device ( 18 ) and that when the second signal reaches or exceeds a limit value (G2) ( 90 ), on possible damage to the filter device ( 18 ) is closed by the regeneration and that when a detected damage of the filter device, a signal ( 36 ) of a differential pressure sensor ( 34 ), which a pressure difference (dp) via the filter device ( 18 ), adapted ( 92 ). A method according to claim 1, characterized in that the second signal during a regeneration phase of the sensor device ( 22 . 38 ) is not used to determine the exhaust gas temperature (T _ex ). A method according to claim 1, characterized in that when the exhaust gas temperature (T _ex ) determined from the second signal reaches or exceeds a limit value (G1) ( 86 ), a measure for lowering the temperature is initiated and / or a shortening of a regeneration phase is determined ( 88 ). Method according to one of claims 1 to 3, characterized in that upstream of the filter device ( 18 ) in an oxidation catalyst ( 16 ) NO _{2 is} generated, that the sensor device ( 22 ) between the oxidation catalyst ( 16 ) and the filter device ( 18 ) is arranged that, taking into account the exhaust gas temperature (T _ex ), a NO ₂ concentration in the exhaust gas is determined ( 100 ), and that from the NO ₂ concentration on the strength (-dC / dt) of the possible regeneration of the filter device ( 18 ) is closed ( 102 ). Method according to Claim 4, characterized in that, using the first signal and the second signal, the current load (Cload1) of the filter device ( 18 ) is closed ( 106 ). A method according to claim 4, characterized in that the temperature of the sensor device at least approximately detected and / or determined and / or estimated, and that takes into account the difference between the exhaust gas temperature and the temperature of the sensor device at least indirectly in determining the current load of the filter device becomes. Method according to one of claims 4 to 6, characterized in that from a signal ( 36 ) of a differential pressure sensor ( 34 ), which determines the pressure difference (dp) via the filter device ( 18 ) to the current load (Cload2) of the filter device ( 18 ) is closed ( 110 ) and that this result is compared with the load (Cload1) determined from the second signal ( 112 ). Method according to Claim 7, characterized in that, depending on the result of the comparison, the signal ( 36 ) of the differential pressure sensor ( 34 ) is adapted ( 114 ). Method according to one of the preceding claims, that the second signal is monitored on the basis of a third signal of another temperature detection device. Computer program, characterized in that it is programmed for use in a method according to one of the preceding claims. Electrical storage medium for a control and / or regulating device of an internal combustion engine, characterized in that a computer program for use in a method of claims 1 to 9 is stored on it. Control and / or regulating device for an internal combustion engine, characterized in that it is programmed for use in a method according to one of claims 1 to 9.

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