DE102004064268B3 - Sensor device for detecting particles present in the exhaust gas of an internal combustion engine and for detecting the exhaust gas temperature - Google Patents

Abstract

Sensor device (22, 38) for detecting at least one state variable (dC / dt, Tex) in the exhaust gas of an internal combustion engine (10), with at least one first sensor (24, 40) for detecting particles present in the exhaust gas, characterized in that it has at least a second sensor (26, 42) for detecting the exhaust gas temperature (Tex), that it comprises a heating device (64) with which the first sensor (24, 40) can be burned free of deposited particles, and that the second sensor (26 , 42) is also suitable for detecting the temperature (Tsens) of the sensor device (22, 38) and that it has at least two flat layers (54, 56, 58) adhering to one another and that on the exposed side (59) of the one Layer (54) the first sensor (24, 40), on the exposed side (68) of the second layer (58) the second sensor (26, 42), and between the two layers (54, 58) the heating device (64) ) is arranged.

Description

State of the art

Diesel internal combustion engines are known from the market which comprise an exhaust line with a particle filter which filters out soot particles from the exhaust gas. The particles filtered out are deposited on the filter, which means that the flow resistance of the exhaust gas through the exhaust system increases over time. The so-called “exhaust back pressure” that increases as a result can lead to increased fuel consumption or a reduction in the performance of the internal combustion engine.

To prevent this, it is known to regenerate the particle filter from time to time. During such a regeneration, the deposited soot particles are burned off. For this, a temperature of more than 650 ° C must be reached in the particle filter, which can be achieved by various measures. Engine measures such as reducing the boost pressure, throttling, shifting an injection point in time, additional fuel injection, etc. are known, all of which lead to a temporary increase in the exhaust gas temperature. An alternative or additional measure consists in arranging an oxidation catalytic converter in which nitrogen dioxide is continuously formed upstream of the particle filter in the exhaust system. This can then react in the particle filter with the soot deposited there, forming gaseous nitrogen and carbon dioxide. An exhaust system with a particulate filter is generally from the DE 102 31 620 Al known.

Particle sensor devices are used in order to recognize the state of loading of the particle filter with soot particles and to be able to initiate regeneration of the particle filter in good time. Such a particle sensor device is for example in the DE 10133 384 A1 described. It has a collecting chamber which is fluidically connected to the exhaust gas flow of the internal combustion engine. Two electrodes are arranged on one side of the collecting chamber, which interlock in a comb-like manner (“interdigital”). When the known particle sensor device is in operation, soot particles get into the collecting chamber and are deposited on the electrodes. This electrically bridges the gap between the two electrodes, so that the impedance of the electrode structure changes. The change in impedance over time is a measure of the amount of soot particles in the exhaust gas flow. In order to be able to free the soot particle sensor device itself from time to time from the accumulated soot particles, it has a heating device, through the operation of which accumulated soot particles can be burned.

Another sensor device is from the DE 101 49 333 A1 known. In this case, a resistance measuring structure is applied to an electrically insulating carrier, which consists of interdigital comb electrodes. The accumulation of soot particles changes the electrical resistance of the resistance layer.

The one not yet published on the filing date DE 103 53 860 A1 describes a soot particle sensor device which, in addition to the heating element, has a temperature detection device with whose signal the regeneration of the particle sensor device can be monitored or controlled.

Further sensor devices are from the DE 199 59 870 A1 and the US 2003/0 196 499 A1 known.

The object of the present invention is to increase the safety during the operation of the internal combustion engine while at the same time keeping manufacturing and operating costs low.

In the case of a sensor device of the type mentioned at the outset, the object set 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. Knowing them enables low-emission and consumption-optimized operation. The integration of the sensor that detects the exhaust gas temperature in the same sensor device that is also used to detect particles present in the exhaust gas reduces the installation effort and the space required to accommodate the sensors.

Advantageous further developments of the invention are specified in the subclaims.

According to the invention it is provided that the two sensors are each arranged on exposed surfaces of the device, in particular exposed to the exhaust gas. This means that very dynamic processes can also be reliably recorded.

According to the invention it is provided that the sensor device comprises a heating device with which the first sensor can be burned free of deposited particles, and that the second sensor is suitable for detecting the temperature of the sensor device. The second sensor has a double function because it can be used to monitor the regeneration of the first sensor or the Sensor device can be used as a whole, and outside of these phases it can be used for detecting the exhaust gas temperature. This further reduces the costs and the assembly effort.

The manufacture of the sensor device is simplified by the fact that, according to the invention, it has two flat layers that adhere to one another and that, according to the invention, the first sensor is on the exposed side of one layer, the second sensor is on the exposed side of the second layer, and the heating device is between the two layers is arranged. Such a sensor is also very small and flat and can therefore be arranged at any point in the exhaust line of the internal combustion engine.

The combination according to the invention of particle sensor and temperature sensor for detecting the exhaust gas temperature is particularly advantageous.

Figure list

• 1 eine schematische Darstellung einer Brennkraftmaschine mit mehreren Sensoreinrichtungen und einer Filtereinrichtung im Abgasstrang;
• 2 eine perspektivische Darstellung einer ersten Ausführungsform einer der Sensoreinrichtungen von 1;
• 3 Draufsichten auf drei Teilelemente, aus denen die Sensoreinrichtung von 2 zusammengesetzt ist;
• 4 eine Darstellung ähnlich 2 eines Bereichs einer alternativen Ausführungsform einer Sensoreinrichtung;

Particularly preferred exemplary embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. In the drawing show:

• 1 a schematic representation of an internal combustion engine with several sensor devices and a filter device in the exhaust system;
• 2 a perspective view of a first embodiment of one of the sensor devices of FIG 1 ;
• 3 Top views of three sub-elements that make up the sensor device of 2 is composed;
• 4th a representation similar 2 a portion of an alternative embodiment of a sensor device;

Description of the exemplary embodiments

In 1 an internal combustion engine bears the overall reference number 10 . It includes an engine block 12th and an exhaust system 14th . In the exhaust system 14th seen in the direction of flow are initially an oxidation catalyst 16 and then a particulate filter 18th arranged.

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

Downstream of the filter device 18th is in the exhaust pipe 20th a second sensor device 38 placed, which is identical to the first sensor device 22nd is constructed. Here, too, an exemplary embodiment (not shown) is conceivable in which such a second sensor device is not present. So it also includes a particle sensor 40 as well as a temperature sensor 42 , their signals over lines 44 and 46 to the control and regulation device 32 be directed. A lambda probe 48 is immediately downstream of the oxidation catalyst 16 in the exhaust pipe 20th arranged (the lambda probe cannot be implemented in an embodiment not shown). Their signal comes through a line 50 to the control and regulation device 32 . The control and regulation device 32 is how through 52 is indicated with the engine block 12th connected by signal technology and controls various functions there. These include, for example, ignition and fuel injection.

Because of incomplete combustion in the engine block 12th soot particles can be contained in the exhaust gas. Through the filter device 18th prevents these soot particles, which are harmful to health, from entering the environment. Through the deposition of soot particles in the filter device 18th however, their permeability is reduced. To avoid excessive exhaust back pressure in the exhaust pipe 20th to avoid is the filter device 18th regenerated continuously on the one hand and cyclically on the other hand by oxidizing the accumulated soot particles.

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

The sensor devices 22nd and 38 are constructed identically. In the 2 and 3 is the sensor device 22nd shown as an example. Thereafter, the sensor device comprises 22nd three ceramic layers laminated on top of each other 54 , 56 and 58 , which in the present case are manufactured on an Al ₂ O ₃ or ZrO ₂ basis primarily because of their temperature resistance. The ones in the 2 and 3 upper ceramic layer 54 carries on its exposed outside 59 two electrodes 60 and 62 . The two electrodes 60 and 62 are structured "interdigital" for a resistivity measurement and thus form the particle sensor 24 .

The ones in the 2 and 3 middle ceramic layer 56 carries on their from the location 54 remote side a meandering heating device 64 through which the sensor device 22nd in the area of the particle sensor 24 can be heated. In this way, if necessary, on the sensor device 22nd accumulated soot particles are burned. The ones in the 2 and 3 lower ceramic layer 58 carries a meandering structure made of a thin layer of platinum 66 through which the temperature sensor 26th is formed. The platinum layer is on the exposed side 68 the ceramic layer 58 applied and provided with a thin ceramic protective layer. Due to the arrangement of the platinum layer 66 can the temperature sensor 26th record the temperature of the exhaust gas comparatively precisely. In a first approximation, the temperature of the sensor device 22nd set equal to the exhaust gas temperature.

The temperature of the sensor device, which differs from the exhaust gas, can be used to estimate the influence of the temperature dependency of the soot accumulation (thermophoresis) 22nd can also be estimated using a numerical model or using an estimation method (e.g. an observer method). It is also possible to have a further temperature sensor on the layer, but not shown in the figure 54 facing side of the situation 56 to provide the temperature of the sensor device with its signal 22nd capture.

One in 4th illustrated and even flatter embodiment of a sensor device 22nd consists of only two ceramic layers 54 and 58 . In the 4th The non-visible heating device is on the same lower ceramic layer 58 applied like the platinum layer, which the temperature sensor 26th forms.

Claims (3)

Sensor device (22, 38) for detecting at least one state variable (dC / dt, Tex) in the exhaust gas of an internal combustion engine (10), with at least one first sensor (24, 40) for detecting particles present in the exhaust gas, characterized in that it has at least a second sensor (26, 42) for detecting the exhaust gas temperature (T _ex ), that it comprises a heating device (64) with which the first sensor (24, 40) can be burned free of deposited particles, and that the second sensor ( 26, 42) is also suitable for detecting the temperature (T _sens ) of the sensor device (22, 38) and that it has at least two flat layers (54, 56, 58) that adhere to one another and that on the exposed side (59) one layer (54) is the first sensor (24, 40), on the exposed side (68) of the second layer (58) the second sensor (26, 42), and between the two layers (54, 58) the heating device (64) is arranged. Sensor device (22, 38) after Claim 1 , characterized in that the two sensors (24, 40, 26, 42) are each arranged on exposed surfaces (59, 68) of the device (22, 38) that are exposed to the exhaust gas. Sensor device (22, 38) after Claim 1 or 2 , characterized in that the second sensor (26, 42) is formed by a meandering structure from a thin platinum layer (66) and is provided with a thin ceramic protective layer.

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