Brennkraftmaschine mit direkter kraftstoffeinspritzung in den brennraum

The invention concerns a Brennkrafimaschine with direct Krafistoffeinspritzung into the combustion chamber, with an exhaust strand, in which a NOx Speicherkatalysator is arranged. An internal-combustion engine of the kind initially specified is from US 5,732,554 A well-known. Foreignignited internal-combustion engines with Direkteinspritzung order due to a better thermal efficiency within the layer range of the engine over a smaller energy entry in the cooling water than fuel glaring machines with mixture sucking in. This slowed down Aut'heizung of the cooling agent drives however in the comparison with mixture-sucking in internal-combustion engines to higher friction achievements of the directinjecting Brennkra machines into engine-warms up. In order to reduce the NOx output with directly injecting Otto engines under the measure required by law, NOx Speicherkatalysatoren are used. Speicheroder adsorbent catalysts have a certain temperature window, in which a NOx conversion takes place. This temperature window in the instrument range of the directly injecting Otto Brennkraftmasehine, in the also over-stoichiometric engine enterprise to be certainly essentially driven cart. When leaving the temperature window the Lambda value must be reduced for the reduction of NOx production, which increases the fuel consumption. Memory catalysts are in addition sensitive to high temperatures and exhibit with Abgasternperaturen, which exceed a specific ageing temperature, a strengthened inclination to an irreversible catalyst aging. In order to avoid this damage, it is well-known to direct for the protection of the catalyst from to high Abgastemperautren the exhaust gas with a bypass system at the adsorbent or switch with exceeding of a certain exhaust gas temperature to strongly unterstöchiometrisehen engine enterprise. This affects however unfavorably the exhaust quality and/or the fuel consumption. Task of the invention is it to avoid and with an internal-combustion engine of the kind initially specified in as simple a way as possible fuel consumption and waste gas emissions reduce these disadvantages. At the same time an effective protection is to be made available for the NOx Speicherkatalysator. According to invention this takes place via that upstream the NOx Speicherkatalysators an exhaust gas cooler is arranged. A particularly good exhaust quality lets itself reach, if the exhaust gas cooler between the NOx Speicherkatalysator an upstream Vorkatalysator and the NOx Speicherkatalysator is arranged. The exhaust gas cooler is attached and on the water side with cooling agent is flowed through in the exhaust strand after dern Vorkatalysator. It is favourable if the exhaust gas cooler into the cooling circuit of the fuel glaring machine is integrated. Alternatively to the fact it can be intended that the exhaust gas cooler is arranged in its own cooling circuit, which is thermally connected by a heat exchanger with the cooling circuit of the fuel glaring machine. Thus different cooling agents can be used for the cooling of the engine and the exhaust gas. In warm up the engine the cooling agent by the energy of the exhaust gas one heats and drives by it to a more rapid Erwärrnung of the directly injecting internal-combustion engine. By the more rapid heating up of the engine the friction achievement can in engine-warms up to be substantially reduced. Further the exhaust gas cooler makes an expansion possible of the instrument range, in which the Brennkraflmaschine can be operated over-stoichiometrically, since the exhaust gas temperature before the NOx Speicherkatalysator can be held by the exhaust gas cooler within the operating window of the NOx Speicherkatalysators. Thus to a certain extent a decoupling of the exhaust gas temperature before the NOx Speicherkatalysator of the exhaust gas temperature at the cylinder withdrawal results, whereby the over-stoichiometric instrument range much be expanded and the fuel consumption can be substantially reduced. The exhaust gas cooler prevents further that the temperature of the exhaust gas flowing in into the NOx Speicherkatalysator exceeds the specific ageing temperature, whereby the exhaust gas cooler offers at the same time an effective protection NR to the NOx Speicherkatalysator. The exhaust gas cooler must be so laid out thereby that the inlet temperature in the NOx Speicherkatalysator in no operating condition of the Brennkraflmaschine can exceed respective ageing temperature. The invention is more near described in the following on the basis the figure. The Fig. schematically an foreignignited directly injecting internal-combustion engine 1 with several cylinders 2 and an exhaust strand 3. the Abgsstrang 3 outgoing from the cylinders 2 shows exhibits a Vorkatalysator 4 and the on memory catalyst 5. Between the Vorkatalysator 4 and the NOx Speicherkatalysator 5 an exhaust gas cooler 6 is arranged, which is attached to the cooling circuit of the Brennkraffmaschine. Alternatively to it the exhaust gas cooler can be arranged 6 also in an own cooling circuit independent of the cooling circuit of the internal-combustion engine, which is thermally connected by a heat exchanger with the cooling circuit of the Brermkraftmaschine. With reference symbol 7 a coolant pump is suggested and with reference symbol 8 a control valve. In warm up the internal-combustion engine 1 the cooling agent across the exhaust gas cooler 6 by the energy of the exhaust gas one heats and leads across the cooling agent cycle of the engine to a more rapid Erwärrnung of the internal-combustion engine 1. as a result of the more rapid heating up of the fuel glaring machine 1 arises the advantage that the friction achievement in engine-warm up and thus the fuel consumption can be reduced. Further the advantage results that over the exhaust gas cooler 6 the exhaust gas flowing in into the NOx Speicherkatalysator 5 is kept at a moderate temperature, so that the exhaust gas temperature exhaust gas of the entering the memory catalyst 5 remains within the operating window of the NOx Speicherkatalysators 5. This quasi decoupling of the exhaust gas temperature after the cylinders 2 and before the NOx Speicherkatalysator 5 drives to a clear extension of the over-stoichiometric instrument range and by it to an additional fuel verb also sinking. In addition it can be guaranteed by suitable dimensioning of the Abgaskühters 6 that the exhaust gas flowing in into the NOx Speicherkatalysator can exceed the critical ageing temperature of the NOx Speicherkatalysators 5 in no engine operating condition. Between the Vorkatalysator the 4 and thus an extremely simple possibility represents 5 arranged exhaust gas coolers 6 to the NOx Speicherkatalysator, the fuel consumption of a lean operated internal-combustion engine 1, in particular with spark ignition and direct injection of improving substantially and of protecting the NOx Speicherkatalysator 5 at the same time against premature aging. Although the invention is described on the basis a petrol internal-combustion engine, their arrangement is possible and favourable also with a Diesel internal-combustion engine. i