DE10323979B4 - Exhaust treatment device for an internal combustion engine of a motor vehicle - Google Patents

Abstract

Exhaust gas treatment device for an internal combustion engine, in particular of a motor vehicle, with a catalytic converter device and with a heating device arranged in the area of the catalytic converter device, the heating device having a control input into which conversion information about the catalytic converter device can be entered, and wherein the heating device applies heat to the catalytic converter device as a function of the conversion information , characterized by a control device which is set up to predetermine a constant, increased heating output of the heating device if the aging of the catalyst device exceeds a reference value.

Description

The invention relates to an exhaust gas treatment device for an internal combustion engine, in particular of a motor vehicle.

Motor vehicles today usually have an internal combustion engine with a catalytic converter device, which treats the combustion gases originating from the internal combustion engine.

In the prior art, it is known to heat such catalyst devices, especially when the engine is cold, so that their degree of conversion increases. For this purpose, special heaters are provided, as in the WO 01/42713 A1 , In conjunction with a special engine control that of DE 44 00 260 A1 , then unburned fuel or particularly hot combustion gas is conveyed into the exhaust system of the internal combustion engine. As a result, the catalyst is heated effectively and quickly.

This has the disadvantage that the gasoline consumption of the internal combustion engine is increased. On the other hand, the heating of the catalyst is already necessary due to existing emission regulations.

From the DE 43 23 243 A1 is a heating method for a catalyst in the exhaust system of an internal combustion engine, in which from at least two measured values, a signal with respect to the conversion capacity of the catalyst determined and the catalyst is heated depending on the conversion capability.

From the DE 41 33 117 A1 A method for exhaust gas detoxification of internal combustion engines with a preheatable catalyst is known, in which a temperature threshold or the preheating time is controlled in proportion to an aging state of the catalyst.

From the EP 0 718 477 A1 For example, a heating system for a catalyst is known in which a controller for heating a catalyst burns a gas mixture downstream of an internal combustion engine in a separate combustion chamber.

It is an object of the invention to provide a fuel-efficient internal combustion engine, an improved exhaust treatment device, a motor vehicle equipped therewith, and a method for operating such a motor vehicle with an internal combustion engine, with which an appropriate operation is always guaranteed in an economical manner.

This object is solved by the subject matter of the independent patent claims. Advantageous developments emerge from the respective dependent claims.

One of the ideas underlying the invention takes into account that the catalyst unit is heated only to the extent necessary for a proper conversion. For this purpose, information can be used that is incurred during operation of an internal combustion engine according to the invention. These include operating hours of the internal combustion engine and thus the catalyst device or an air quantity integral as a measure of the already converted by the catalyst device amount of combustion gas. In connection with a motor vehicle, running distance information of the motor vehicle can also be used to determine the age of the catalyst device. From the age of the catalyst device results in their capacity for conversion and thus the degree of heating necessary for complete conversion in the cold state of the catalyst device.

The heating device need not be provided in a specially provided part of the motor vehicle or the exhaust gas treatment device. It is also possible to design the heating device as part of an engine control, wherein it emits additional combustion gas or unburned fuel from at least one cylinder of the internal combustion engine into the exhaust gas treatment system for heating the catalyst device. For this purpose, it is possible to provide the ignition timing of a cylinder so late that most of the mixture intended for combustion burns out of the relevant cylinder when it is blown out. This heats the exhaust system more than normal operation. This device is particularly advantageous when the ignition can be changed by an engine electronics.

In a particularly advantageous embodiment of the invention, a conversion diagnostic device is provided on the catalyst device, with which the degree of conversion is determined by the exhaust gas of the catalyst device. From such a conversion diagnostic device, a signal can be obtained, which is supplied to the heater and determines the degree of heating.

Deviating from this, the degree of heating can also be determined as a function of a route measuring device. As a result, a good estimate of the age of the catalyst device can be achieved.

According to the invention, the age determined since the first commissioning of the motor vehicle or the catalyst device running distance. In addition, the conversion capability of the catalytic converter device or the operating time or operating load of the internal combustion engine can also be determined, for example via an air quantity integral. Thereafter, a heating power of the heater is determined. Depending on this, in the case of a cold internal combustion engine, the heating device or the heating is activated, as a result of which the catalyst device is acted upon in the previously determined heating power.

The invention is illustrated in the drawing with reference to two value curves.

1 shows a first course of the change of heating over a covered by a motor vehicle running track and

2 shows a second course of the change in heating over a covered by a motor vehicle running track.

The fuel consumption improvement according to the invention can be realized by a demand-adapted catalyst heating function. The dependency can be regulated by several methods.

First, a demand-adapted catalytic heating over the driven running distance of the motor vehicle is possible, as in 1 is illustrated. The influence of the catalyst heating is given below with a weighting factor or Katalysatorheizfaktor ("KH factor") with respect to a predetermined reference value. The KH factor is here assumed to be "1" for that heating in which an average catalyst achieves a prescribed effect after a running distance of 100,000 km of a motor vehicle within a time predetermined by a standard test. The following value pairs result: Running distance of the vehicle 25,000 50,000 75,000 100000 KH-factor 0.1 0.3 0.6 1.0

This connection is in 1 illustrated. At 0 km no KH moment is provided, because with a new catalyst results in itself an optimal fuel consumption in the cold start. At 25 tkm, 0.1 or 10% of the standard KH torque is effective and at 100 tkm is 1.0 or the full KH torque. The KH factor is multiplied by the applied KH moment.

In addition, a needs-adapted catalytic converter heating via catalytic converter diagnosis is possible. The catalyst diagnosis is a measure of the conversion capability of the catalyst regardless of the running distance. With good correlation of the diagnosis value with the real aging of the catalyst, this is a very sensible solution, since a driver can use the KV advantage for longer by means of gentle driving style ("KV" = "fuel consumption").

When designing a motor control, in fact, recourse is made to values which result in factory endurance tests. A cautious user of a motor vehicle can come to more favorable conditions than in the endurance test.

The invention contemplates increasing fuel prices in conjunction with the automotive industry's goal of reducing CO2 emissions.

Measures that are positive for an early "light-off" (ie 50% of the exhaust gases converted) can generally have a negative impact on fuel economy. The invention adjusts the catalyst heating to the actual need.

• • Die Forderung nach Reduzierung der CO2-Emission (relevant ist derzeit ein ”MVEG-B-Zyklus”)
• • Die Forderung nach sehr schneller Konvertierung des Katalysators nach Kaltstart (zur Erfüllung der gesetzlichen Emissionslimits)

This reconciles two demands on the automotive industry in the design of engine controls:

• • The demand for reducing CO2 emissions (currently relevant is an "MVEG-B cycle")
• • The demand for very fast conversion of the catalytic converter after a cold start (to fulfill the statutory emission limits)

In order to enable a fast conversion through the catalyst, software measures are used in addition to hardware measures (eg close-coupled catalyst), u. a. the so-called "Kat heating". According to the invention, a deterioration of the engine efficiency (later ignition) can be accepted for this purpose. This results in less engine torque and more thermal energy gets into the exhaust system. At the same torque requirement results in a higher throughput with higher exhaust gas temperatures and thus more heat input into the monolith, causing an earlier "light-off" of the catalyst is effected. The once defined KH-moment as standard heating remains the same regardless of the state of the catalyst, only one factor is changed.

The embodiment is based on the following idea. The exhaust emission limits must be complied with according to EU IV over a running distance of 100,000 km. The vote regarding catalytic converter heating depends on the condition of the catalytic converters after a continuous road test (100,000 km DVS). The conversion properties of the catalysts are reduced by thermal, chemical and mechanical aging. Thus, the Kat heating is intensified to ensure a safe compliance with the limits.

The function change only relates to the cat heating moment. Other areas, such as cat heater lambda, are not affected, as KV neutral or KV improving.

The exhaust gas tuning with 100,000 km DVS-Kat results in a certain KH lambda curve, as well as a certain KH torque reserve curve.

This KH torque reserve can be reduced with better-converting catalysts (eg Neu-Kats or 50,000 km Kats), even up to 0% torque reserve, so that the engine is operated even after a cold start with optimum ignition angle and thus with optimum efficiency can be.

With a new catalyst, no or little catalyst heating is necessary. With a "100 tkm DVS catalytic converter" (= aged standard catalytic converter), a corresponding amount of catalytic converter heating is necessary. The applied Kat heating reserve torque is hereinafter referred to as KH.

2 illustrates a variant of the catalyst heating, in which the catalyst is heated intensively when exceeding the standard driving power.

With cat aging of> 120%, kh = 1.10. The increased KH moment is used to make it easier to comply with EOBD limits, even for end-of-life vehicles.

The KV advantage for new catalytic converters is between 1% and 3% of the MVEG consumption with fully active catalytic converter heating, depending on requirements and coordination.

The function according to the invention is easy to implement in existing systems and requires little application effort (low costs). The MVEG consumption for new vehicles and thus the publication value can be reduced without compromising on reaching the emission limits over the running distance.

This results in a fuel consumption advantage in real customer operation, in MVEG consumption (New Kats: 100% KV advantage, 100,000 km Kats: previous fuel consumption level) and KV publication value.

Claims (6)

Exhaust treatment device for an internal combustion engine, in particular of a motor vehicle, with a catalyst device and with a heating device arranged in the region of the catalyst device, the heating device having a drive input into which conversion information can be input via the catalyst device and wherein the heating device applies heat to the catalyst device as a function of the conversion information characterized by a controller adapted to provide a constant increased heating power of the heater if catalyst aging exceeds a reference value. Exhaust treatment device according to claim 1, characterized in that in the region of the catalyst device, a conversion diagnostic device is provided which determines the degree of conversion of exhaust gas in the catalyst device, wherein an output of the conversion diagnostic device is supplied to the heater. An internal combustion engine with an exhaust gas treatment apparatus according to claim 1 or claim 2, wherein in the region of the internal combustion engine, a time measuring device is provided for determining the total operating time of the internal combustion engine and wherein an output signal of the time measuring device is supplied to the heating device. Internal combustion engine according to claim 3, characterized in that the heating device is designed as part of an engine control, which emits for heating the catalyst device additional combustion gas and / or unburned fuel from at least one cylinder of the internal combustion engine and an ignition timing of a cylinder provides such that a part of a burned mixture burns when blowing out of the cylinder. Motor vehicle with an internal combustion engine according to claim 3 or claim 4 and / or with an exhaust gas treatment device according to claim 1 or claim 2, wherein additionally a travel distance measuring device is provided and wherein an output signal of the travel distance measuring device is supplied to the heating device. Method for operating a motor vehicle with an internal combustion engine, which has an exhaust gas treatment device with a catalytic converter device and with a heating device arranged in the region of the catalytic converter device, the method having the following steps after starting the cold internal combustion engine: Determining the running distance covered by the motor vehicle since the first startup of the motor vehicle or since the initial startup of the catalytic converter, the conversion capability of the catalytic converter device or the operating time and / or operating load worked by the internal combustion engine since the first startup of the internal combustion engine or since the first startup of the catalytic converter device . Determining a constant increased heating power of the heater if catalyst aging exceeds a reference value, - Activate the heater and applying the catalyst device with the previously determined heating power.

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