Internal combustion engine for a motor vehicle, and method for operating such an internal combustion engine

Abstract

An internal combustion engine has a combustion chamber, an intake tract through which air can flow, a first tank for a liquid spark-ignition fuel, a second tank for water, a mixing region, in which the spark-ignition fuel from the first tank is to be mixed with the water from the second tank thereby creating a mixture having the spark-ignition fuel and the water, an injection valve which is allocated to the combustion chamber and by which the mixture can be injected directly into the combustion chamber, and a second injection valve which is allocated to the combustion chamber and provided in addition to the injection valve and by which in relation to the water and the spark-injection fuel, only the spark-injection fuel from the first tank can be injected at a location upstream of the combustion chamber into the intake tract and thus into the air flowing through the intake tract.

Claims

1. An internal combustion engine for a motor vehicle, comprising: at least one combustion chamber having an inlet tract through which flows air and by which the air flowing through the inlet tract is to be conducted into the combustion chamber; a first tank for accommodating liquid gasoline by which the internal combustion engine is operable during fired operation thereof; a second tank for accommodating water; a mixing region in which, to form a mixture which has the gasoline from the first tank and the water from the second tank, the gasoline from the first tank is to be mixed with the water from the second tank; an injection valve which is assigned to the combustion chamber and by which the mixture is injectable directly into the combustion chamber; a second injection valve which is assigned to the combustion chamber and which is provided in addition to the injection valve, and by which, with regard to the water and the gasoline, exclusively the gasoline from the first tank is injectable at a location arranged upstream of the combustion chamber into the inlet tract and thus into the air flowing through the inlet tract; a control unit configured to determine a total gasoline quantity to be delivered from the first tank to the engine; a first fuel partial quantity of the total gasoline quantity to be delivered to the injection valve assigned to the combustion chamber which delivers the mixture of gasoline and water, and a second fuel partial quantity of the total gasoline quantity to be delivered to the second injection valve assigned to the combustion chamber which delivers exclusively gasoline; and a flow dividing valve configured to receive from the first tank the total gasoline quantity and divide the total gasoline quantity into the first partial fuel quantity and the second fuel partial quantity to the second injection valve, output the first fuel partial quantity to the injection valve via a mixing region at which water is mixed with the first fuel partial quantity, and output the second partial fuel quantity to the second injection valve.

2. The internal combustion engine according to claim 1, wherein the internal combustion engine is configured to perform the injection of the mixture by the injection valve as a multiple injection.

3. The internal combustion engine according to claim 2, wherein the internal combustion engine is configured to perform the injection of the gasoline by the second injection valve as a multiple injection.

4. The internal combustion engine according to claim 1, further comprising: at least one exhaust-gas turbocharger which has a turbine, driveable by exhaust gas from the combustion chamber, and a compressor, arranged in the inlet tract and driveable by the turbine, whereby air is compressed.

5. The internal combustion engine according to claim 1, wherein the internal combustion engine is configured to perform the injection of the gasoline by the second injection valve as a multiple injection.

6. A method for operating an internal combustion engine for a motor vehicle, the engine having at least one combustion chamber, an inlet tract which is flowed through at least by air and by which the air flowing through the inlet tract is conducted into the combustion chamber, a first tank in which liquid gasoline is stored by which the internal combustion engine is operable during fired operation thereof, a second tank in which water is stored, a mixing region in which, to form a mixture which has the gasoline from the first tank and the water from the second tank, the gasoline from the first tank is mixed with the water from the second tank, an injection valve by which the mixture is injectable directly into the combustion chamber, a second injection valve in addition to the injection valve by which exclusively the gasoline from the first tank is injectable at a location arranged upstream of the combustion chamber into the inlet tract and thus into the air flowing through the inlet tract, a control unit and a flow dividing valve, the method comprising the acts of: determining a total gasoline quantity to be delivered from the first tank to the engine, a first fuel partial quantity of the total gasoline quantity to be delivered to the injection valve assigned to the combustion chamber which delivers the mixture of gasoline and water, and a second fuel partial quantity of the total gasoline quantity to be delivered to the second injection valve assigned to the combustion chamber which delivers exclusively gasoline; injecting the second fuel partial quantity mixture of gasoline and water via the injection valve directly into the combustion chamber within at least one working cycle of the internal combustion engine; and injecting second fuel partial quantity via the second injection valve into the inlet tract and thus into the air flowing through the inlet tract.

7. The method according to claim 6, wherein the internal combustion engine is operated in stoichiometric operation in which, as a result of the respective injection of the gasoline and of the water, a gasoline-air mixture which has the air and the gasoline and which is stoichiometric with regard to the air and the gasoline is formed in the combustion chamber.

8. The method according to claim 6, wherein the injection of the mixture by the injection valve is performed as a multiple injection within the working cycle.

9. The method according to claim 8, wherein the injection of the gasoline by the second injection valve is performed as a multiple injection within the working cycle.

10. The method according to claim 6, wherein at least one exhaust-gas turbocharger is provided which has a turbine, which is driven by exhaust gas from the combustion chamber, and a compressor, which is arranged in the inlet tract and which is driven by the turbine, whereby the air is compressed by the compressor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic illustration of an internal combustion engine according to an embodiment of the invention.

(2) FIG. 2 is a flow diagram for illustrating a method according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(3) FIG. 1 shows, in a schematic illustration, a spark-ignition internal combustion engine 1, designed preferably as a gasoline engine, for a motor vehicle, in particular for a motor car designed for example as a passenger motor car. The internal combustion engine 1 has a motor housing 2, which is designed for example as a cylinder housing, in particular as a cylinder crankcase, and by means of which multiple combustion chambers in the form of cylinders 3 of the internal combustion engine 1 are formed. Here, the internal combustion engine 1 is designed as a reciprocating-piston engine, such that a piston is accommodated in translational movable fashion in the respective cylinder 3. Here, the internal combustion engine 1 has an output shaft 4 which is designed for example as a crankshaft and which is rotatable about an axis of rotation relative to the motor housing 2. Here, the pistons are articulatedly connected to the output shaft 4 via respective connecting rods, such that the translational movements of the piston in the cylinders 3 are converted into a rotational movement of the output shaft 4.

(4) In the context of a method for operating the internal combustion engine 1, the internal combustion engine 1 is operated in fired operation which comprises multiple chronologically successive working cycles of the internal combustion engine 1. Here, the respective working cycle encompasses exactly two complete rotations of the output shaft 4, wherein the internal combustion engine 1 is designed for example as a four-stroke engine. During the fired operation, within the respective working cycle, a gasoline-air mixture, also referred to as fuel-air mixture, is formed in the respective cylinder 3, which mixture is ignited by applied ignition and burned. As a result, an exhaust gas is generated in the respective cylinder 3, which exhaust gas can flow out of the respective cylinder 3. For this purpose, the internal combustion engine 1 comprises an exhaust tract 5 through which the exhaust gas can flow and by means of which the exhaust gas is discharged from the respective cylinder 3.

(5) Here, the internal combustion engine 1 furthermore has an intake tract 6, which can be flowed through by air and which is also referred to as an induction tract and by means of which the air flowing through the intake tract 6 is to be conducted or is conducted into the respective cylinder 3. Furthermore, the internal combustion engine 1 has an injection system which is denoted as a whole by 7 and by means of which a liquid fuel in the form of liquid gasoline is introducible or introduced into the respective cylinder 3 for the operation of the internal combustion engine 1 in fired operation. The air flowing into the respective cylinder 3 via the intake tract 6 forms the respective abovementioned gasoline-air mixture with the gasoline introduced by means of the injection system 7 into the respective cylinder 3. Since the respective gasoline-air mixture is burned within the respective working cycle, and since the fired operation comprises multiple successive working cycles, in each case multiple combustion processes take place in the cylinders 3 during the fired operation, by means of which combustion processes the pistons, and, via these, the output shaft 4, are driven.

(6) The internal combustion engine 1 has, for each cylinder 3, a first injection valve 8 also referred to as first injector or high-pressure injector, such that the respective injection valve 8 is assigned to exactly one respective cylinder of the cylinders 3. Furthermore, the internal combustion engine 1 has a first tank 9 for accommodating exclusively the liquid gasoline, by means of which the internal combustion engine 1 is operable during the fired operation thereof. In other words, in the context of the abovementioned method, exclusively the gasoline is accommodated in the first tank 9.

(7) Furthermore, a second tank 10 is provided in addition to the first tank 9 and which is separate from the first tank 9, and in which exclusively water can be or is accommodated. In particular, it is for example the case that pure water is accommodated in the tank 10. Here, the first tank 9 is a tank which is common to the injection valves 8, wherein the second tank 10 is also a tank which is common to the injection valves 8 if—as will be discussed in more detail further below—the injection valves 8 are supplied both with the gasoline from the tank 9 and with the water from the tank 10.

(8) The internal combustion engine 1 has a mixing region 11 which is illustrated in particularly highly schematic form in FIG. 1 and in which, to form a mixture which has the gasoline from the first tank 9 and the water from the second tank 10, the gasoline from the first tank 9 is to be mixed or is mixed with the water from the second tank 10. In the flow direction of the gasoline from the tank 9 in the direction of the injection valves 8 and in the flow direction of the water from the tank 10 in the direction of the injection valves 8, the mixing region 11 is arranged for example downstream of the respective tank 9 or 10 and upstream of the injection valves 8. Here, the mixing region 11 is a mixing region which is common to the injection valves 8. It is alternatively conceivable that a dedicated mixing region for mixing the gasoline from the tank 9 with the water from the tank 10 is provided for each injection valve 8, wherein, then, the respective mixing region is for example accommodated in the respective injection valve 8.

(9) For example, by means of a conveying device which is not illustrated in FIG. 1, the gasoline from the tank 9 and the water from the tank 10 are conveyed into the mixing region 11, wherein the conveying device has for example a first pump for conveying the gasoline from the tank 9 and a second pump for conveying the water from the tank 10. From the mixing region 11, the mixture can flow for example to the injection valves 8. It can be seen from FIG. 1 that the mixture is injectable or injected by means of the respective injection valve 8 directly into the respectively associated cylinder 3.

(10) In the exemplary embodiment illustrated in FIG. 1, a distributing element 12 is provided which is common to the injection valves 8 and which, for example, is also referred to as a rail or pipe. Here, the mixture flows for example firstly into the distributing element 12 and can be temporarily stored in the distributing element 12. By means of the distributing element 12, the mixture accommodated in the distributing element 12 is firstly distributed between the injection valves 8, such that the injection valves 8 can be supplied with the mixture by means of the distributing element 12. By means of the conveying device, the mixture can be brought to a predefinable first pressure, wherein the mixture can be stored at the first pressure in the distributing element 12. By means of the distributing element 12, the mixture which has the first pressure can be distributed to the injection valves 8, by means of which the mixture is then injected at the first pressure directly into the cylinders 3. The first pressure is for example at least 350 bar. The direct injection of the mixture is also referred to as DWI concept or DWI operation and effected, that is to say performed, by means of the injection valves 8.

(11) In order to now be able to implement operation of the internal combustion engine 1 with low fuel consumption and low pollutant emissions, the respective cylinder 3 is assigned a second injection valve 13 which is provided in addition to the respective injection valve 8 and by means of which, with regard to the water and the gasoline, exclusively the gasoline, also referred to as petrol, from the first tank 9 is injectable or injected, at a respective location S, into the intake tract 6 and thus into the air flowing through the intake tract 6. It can be seen from FIG. 1 that the respective location S is arranged upstream of the cylinder 3 in the flow direction of the air flowing through the intake tract 6, such that the respective injection of the gasoline at the respective location S, which can be or is effected by means of the respective second injection valve 13, is an intake pipe or channel injection. By contrast, the respective injection of the mixture, which can be or is effected by means of the respective first injection valve 8, is a direct injection. The injection of the gasoline at the respective location S, which is or can be effected by means of the respective injection valve 13, is also referred to as MPI operation or as MPI concept.

(12) For example with regard to the water accommodated in the tank 10 and with regard to the gasoline accommodated in the tank 9, exclusively the gasoline accommodated in the tank 9 is conveyed by means of the conveying device from the tank 9 to the injection valves 13, such that exclusively the gasoline is injected by means of the injection valves 13 into the intake tract 6. In order to be able, for example, to supply the gasoline from the tank 9 both to the injection valves 8 and to the injection valves 13, a valve device 14 is provided. By means of the conveying device, in particular by means of the second pump, it is for example the case that a total stream of the gasoline is conveyed from the tank 9 firstly to the valve device 14. By means of the valve device 14, the total stream is divided for example into a first partial stream and a second partial stream, wherein the first partial stream flows for example to the injection valves 13 and the second partial stream flows to and in particular into the mixing region 11. The second partial stream can then be mixed with the water from the tank 10, whereby the above-described mixture is formed.

(13) In particular, a second pressure of the gasoline is effected by means of the conveying device, wherein the gasoline is injected at the second pressure by means of the injection valves 13 into the intake tract 6. Here, the internal combustion engine 1 comprises a further distributing element 15 which is common to the injection valves 13 and which is referred to for example as a rail or pipe. The gasoline flows for example from the valve device 14 to and in particular into the distributing element 15 and can be stored at the second pressure in the distributing element 15. The injection valves 13 are supplied with the gasoline at the second pressure by means of the distributing element 15, such that the injection valves 13 inject the gasoline at the second pressure into the intake tract 6. Here, the second pressure is significantly lower than the first pressure, such that the respective injection valve 13 is for example also referred to as low-pressure injector. It can furthermore be seen that the injection valves 8, the injection valves 13 and the distributing elements 12 and 15 are constituent parts of the injection system 7, because the gasoline and the water can be correspondingly injected by means of the stated constituent parts.

(14) FIG. 2 shows a flow diagram for illustrating the abovementioned method for operating the internal combustion engine 1. In a first step S1 of the method, a total quantity of the gasoline that is to be introduced into the respective cylinder 3 within the respective working cycle is determined, in particular calculated, for example, by means of an electronic processing device 16, which is illustrated in particularly highly schematic form in FIG. 1, of the internal combustion engine 1. In a second step S2 of the method, the total quantity is divided by means of the electronic processing device 16, which is also referred to as a control unit, into a first partial quantity, which is to be injected by means of the respective first injection valve 8 directly into the respective cylinder 3, and a second partial quantity, which is to be injected by means of the respective second injection valve 13 into the intake tract 6 at the respective location S, wherein the first partial quantity and the second partial quantity collectively result in the total quantity.

(15) In a third step S3 of the method, within the respective working cycle, the first partial quantity is injected by means of the respective first injection valve 8 directly into the respective cylinder 3. Here, the respective first partial quantity is a constituent part of the respective mixture which is injected by means of the respective injection valve 8 directly into the respective cylinder 3. Furthermore, in the third step S3, the respective second partial quantity is injected by means of the respective second injection valve 13 into the intake tract 6.

(16) The injection of the mixture and/or the injection of the gasoline can be performed as a multiple injection which has multiple chronologically successive and mutually spaced-apart individual injections within the respective working cycle. During the respective individual injection, a respective individual quantity of the mixture or of the gasoline is correspondingly injected by means of the respective injection valve 8 or 13.

(17) In particular, in the context of the method, it is provided that the internal combustion engine 1 is operated in lambda-1 operation. This means that, by means of the injection of the mixture which is or can be effected by means of the respective injection valve 8, and by means of the respective injection of the gasoline which is or can be effected by means of the respective injection valve 13, the respective gasoline-air mixture is formed in the respective cylinder 3 as a stoichiometric fuel-air mixture, such that the combustion air ratio, also referred to as lambda (λ), during the fired operation amounts to 1. In this way, it is possible to avoid an enrichment for the purposes of component cooling, such that the fuel consumption can be kept at a particularly low level, in particular even at high loads of the internal combustion engine 1.

(18) As can be seen from FIG. 1, the internal combustion engine 1 has at least one exhaust-gas turbocharger 17 which has a turbine 18 arranged in the exhaust tract 5. The turbine 18 has a turbine wheel 19 which is drivable by the exhaust gas flowing through the exhaust tract 5. Furthermore, the exhaust-gas turbocharger 17 comprises a compressor 20 which is arranged in the intake tract 6 and which has a compressor wheel 21 for compressing the air flowing through the intake tract 6. The exhaust-gas turbocharger 17 furthermore comprises a shaft 22 which is connected rotationally conjointly both to the turbine wheel 19 and to the compressor wheel 21. In this way, the compressor wheel 21 can be driven by the turbine wheel 19 via the shaft 22. In other words, if the turbine wheel 19 is driven by the exhaust gas flowing through the exhaust tract 5, then the compressor wheel 21 is consequently driven by the turbine wheel 19 via the shaft 22, whereby the air flowing through the intake tract 6 is compressed. In this way, energy contained in the exhaust gas is utilized for compressing the air, such that it is possible to realize operation with particularly low fuel consumption. Alternatively or in addition, the internal combustion engine 1 could have at least one electric compressor for supplying compressed air to the respective cylinder 3, or the internal combustion engine 1 is designed as a naturally aspirated engine.

(19) Furthermore, in the exhaust tract 5, there is arranged at least one exhaust-gas aftertreatment device 23 which is arranged downstream of the turbine 18 in the flow direction of the exhaust gas flowing through the exhaust tract 5. The exhaust-gas aftertreatment device 23 comprises at least one exhaust-gas aftertreatment element, which may be designed for example as a catalytic converter, in particular as a 3-way catalytic converter. Alternatively or in addition, it is conceivable for an exhaust-gas aftertreatment device to be arranged in the exhaust tract 5 upstream of the turbine 18, wherein this constitutes a close-coupled exhaust-gas aftertreatment device. By means of the combination of DWI operation with MPI operation as shown in FIG. 1 and described above, it is possible to avoid excessively high temperatures of the exhaust-gas aftertreatment device 23 and of the turbine 18 without additional fuel being injected for the purposes of component cooling. In other words, the exceedance of component limit temperatures can be avoided even during the above-described lambda-1 operation, such that the fuel consumption and thus the CO.sub.2 emissions of the internal combustion engine 1 can be kept particularly low.

LIST OF REFERENCE DESIGNATIONS

(20) 1 Internal combustion engine 2 Motor housing 3 Cylinder 4 Output shaft 5 Exhaust tract 6 Intake tract 7 Injection system 8 First injection valve 9 First tank 10 Second tank 11 Mixing region 12 Distributing element 13 Second injection valve 14 Valve device 15 Distributing element 16 Electronic processing device 17 Exhaust-gas turbocharger 18 Turbine 19 Turbine wheel 20 Compressor 21 Compressor wheel 22 Shaft 23 Exhaust gas aftertreatment device S Location S1 First step S2 Second step S3 Third step