Method for Operating an Internal Combustion Engine, in Particular of a Motor Vehicle

Abstract

A method for operating an internal combustion engine, which has at least one combustion chamber, at least one intake valve associated with the combustion chamber, and at least one injector associated with the combustion chamber, includes injecting fuel directly into the combustion chamber by the injector in order to operate the internal combustion chamber, where at least one partial stroke of the injector is performed while the intake valve is open.

Claims

1.-9. (canceled)

10. A method for operating an internal combustion engine, wherein the internal combustion engine comprises a combustion chamber, an intake valve associated with the combustion chamber, and an injector associated with the combustion chamber, comprising the steps of: injecting fuel directly into the combustion chamber by strokes of the injector during precisely one inlet stroke of the internal combustion engine and during a warm-up period for heating up the internal combustion engine, wherein a number of the strokes is four or five, wherein the strokes include a first partial stroke while the intake valve is open, and wherein at least one of the strokes is performed while the intake valve is closed.

11. The method according to claim 10, wherein the strokes include a second partial stroke.

12. The method according to claim 10, wherein each of the strokes is a partial stroke.

13. The method according to claim 10, wherein at least one of the strokes is a full stroke.

14. The method according to claim 10, wherein at least two of the strokes differ from one another with regard to a respective injection time.

15. An internal combustion engine which performs the method according to claim 10.

Description

[0038] In the drawings:

[0039] FIG. 1 is a graph to illustrate a method for operating an internal combustion engine, FIG. 1 being used to explain the background of the invention;

[0040] FIG. 2 is a graph to illustrate a method according to a first embodiment for operating an internal combustion engine comprising at least one combustion chamber, at least one intake valve associated with the combustion chamber, and at least one injector associated with the combustion chamber, in which method fuel is injected directly into the combustion chamber by means of the injector in order to operate the internal combustion chamber, the fuel being injected into the combustion chamber by at least one partial stroke of the injector being performed while the intake valve is open;

[0041] FIG. 3 is a graph to illustrate the method according to a second embodiment; and

[0042] FIG. 4 is a graph to illustrate the method according to a third embodiment.

[0043] Identical or functionally identical elements are provided with the same reference signs in the figures.

[0044] FIG. 1 shows a graph 10, on the basis of which a method for operating an internal combustion engine is described. The internal combustion engine is, for example, a component of a motor vehicle which can be driven by means of the internal combustion engine. The internal combustion engine is, for example, designed as a reciprocating internal combustion engine and comprises at least one combustion chamber which is, for example, designed as a cylinder. The cylinder is, for example, formed or delimited at least in part by a first housing element in the form of a cylinder housing of the internal combustion engine. In this case, the cylinder housing forms for example a cylinder wall, by means of which the cylinder is delimited, in particular laterally or in the radial direction.

[0045] The internal combustion engine comprises an output shaft in the form of a crankshaft. The internal combustion engine also comprises a second housing element in the form of a crankcase, it being possible for the second housing element to be integral with the first housing element. Alternatively, it is conceivable for the second housing element to be designed as a component that is formed separately from the first housing element and is connected to the first housing element. The crankshaft is mounted on the crankcase (second housing element) so as to be rotatable about a rotational axis relative to the crankcase. The crankshaft can thus be rotated into different rotational positions about the rotational axis, the rotational positions also being referred to as the crank angle or degree of crank angle. In this case the graph 10 shows an x-axis 12, on which the corresponding crank angle is plotted in degrees.

[0046] A piston is received in the cylinder so as to be translationally movable. The piston is hingedly coupled to the crankshaft by a connecting rod, and therefore the translational movements of the piston are converted into a rotary movement of the crankshaft about the rotational axis thereof relative to the crankcase.

[0047] At least one intake valve is associated with the cylinder. This intake valve is a gas exchange valve which can be moved, in particular in translation, between a closed position and at least one open position. Moreover, at least one injection valve is associated with the cylinder, which injection valve is also referred to as an injector. Fuel, in particular liquid fuel, can be injected directly into the cylinder by means of the injector in order to operate the internal combustion engine.

[0048] The internal combustion engine comprises a third housing element which is designed as a cylinder head. The cylinder head is formed separately from the first housing element and is connected to the first housing element. The piston can be moved in the cylinder between a bottom dead center and a top dead center. The cylinder is delimited, in a direction in which the piston moves on its way to the top dead center, by a combustion chamber roof which is formed by the cylinder head. The intake valve is in this case held on the cylinder head so as to be translationally movable.

[0049] For example, at least one camshaft is provided which is mounted on the cylinder head so as to be rotatable about a rotational axis relative to the cylinder head, for example, and which can be driven by the crankshaft, via a drive system. The intake valve can be moved out of the closed position thereof into the open position thereof by means of the camshaft. This means that the intake valve can be actuated by means of the camshaft. At least one spring is associated with the intake valve, one side of which spring is supported at least indirectly on the cylinder head and the other side of which spring is supported at least indirectly on the intake valve. The spring is tensioned by moving the intake valve out of the closed position into the open position, and therefore the spring provides a spring force which acts on the intake valve that is in the open position. The intake valve is moved out of the closed position into the open position by means of the camshaft and is held in the open position at least temporarily. The intake valve is kept in contact with the camshaft by means of the spring force. The intake valve is also moved out of the open position back into the closed position by means of the spring force.

[0050] At least one intake duct is associated with the intake valve, which intake duct is formed by the cylinder head. As will be described in greater detail in the following, the intake valve is used to control the gas exchange of the cylinder. In particular, the intake valve is used to control, i.e. to set, an inflow of at least air into the cylinder. In the closed position, the intake duct is fluidically shut off by means of the intake valve, and therefore air cannot flow through the intake duct and from the intake duct into the cylinder. In the open position, the intake valve releases the intake duct, and therefore air can flow through the intake duct and from the intake duct into the cylinder.

[0051] Analogously to the intake valve, a further gas exchange valve in the form of an outlet valve is associated with the cylinder. The outlet valve is used to control, i.e. set, an outflow of exhaust gas out of the cylinder. In the closed position, an outlet duct associated with the outlet valve is fluidically shut off by means of the outlet valve, and therefore exhaust gas from a burned air-fuel mixture cannot flow through the outlet duct and from the outlet duct out of the cylinder. In the open position, the outlet valve releases the outlet duct, and therefore exhaust gas can flow through the outlet duct and from the outlet duct out of the cylinder.

[0052] The injector comprises a fuel injection nozzle which defines at least one receiving chamber for receiving the fuel. The injector, in particular the fuel injection nozzle, also has a flow cross-section through which at least one portion of the fuel received in the receiving chamber can be injected out of the injector, in particular the fuel injection nozzle, and can be injected directly into the combustion chamber. This flow cross-section is formed by precisely one injection opening or by a plurality of injection openings in the injector, in particular of the fuel injection nozzle. The relevant injection opening is also referred to as an outlet opening, exit opening, ejection opening, injection hole or through-hole. One side of the relevant injection opening is fluidically connected to the receiving chamber, and therefore fuel can flow out of the receiving chamber through the injection opening. The other side of said injection opening opens into the surroundings and thus, when the internal combustion engine is in a finished manufactured state, opens directly into the combustion chamber, and therefore the fuel received in the receiving chamber can be injected directly into the combustion chamber through the injection opening.

[0053] The injector also comprises a valve element, which is designed as a pin or valve pin. The valve element is received at least in part, in particular at least mostly, in the fuel injection nozzle. In addition, the valve element can be moved, in particular in translation, relative to the fuel injection nozzle. In the process, the valve element can be moved, relative to the fuel injection nozzle, between a dosed position and at least two open positions which are different from one another and from the closed position. In the closed position, the flow cross-section is fluidically shut off by means of the valve element, and therefore fuel cannot be injected into the combustion chamber by means of the injector. In a first of the open positions, the valve element releases at least a first portion of the flow cross-section, and therefore fuel is injected out of the receiving chamber of the injector, through the first released portion, and into the combustion chamber. In particular, the valve element fully releases the injection surface in the first open position.

[0054] The closed position is therefore a first end position of the valve element, the first open position being a second end position of the valve element. The valve element can be moved into the end positions and between the end positions, but the valve element cannot be moved beyond the relevant end position. The valve element can thus be moved relative to the housing within a movement range, the movement range being delimited by the end positions, and the movement range including the end positions.

[0055] The second open position is, based on the movement range, an intermediate position of the valve element, the intermediate position, based on the movement range, being between the end positions. In the second open position, the valve element releases a second portion of the flow cross-section which is smaller by comparison with the first portion, and therefore fuel can be injected out of the injector and directly injected into the combustion chamber, via the second released portion. Since the second open position is between the end positions, the valve element or the injector as a whole opens further in the first open position than in the second open position. However, the valve element or the injector is open in both open positions, since the corresponding portion of the flow cross-section is released.

[0056] A full stroke, denoted VH in the figures, of the valve element and thus of the injector as a whole is caused or performed when the valve element is moved out of the closed position into the first open position and then again out of the first open position back into the closed position. A partial stroke, denoted TH in the figures, of the valve element or the injector as a whole is performed or caused when the valve element is moved out of the closed position into the second open position and then again out of the second open position back into the closed position, the valve element that has moved into the second open position being prevented from moving out of the second open position into the first open position. In other words, when performing a partial stroke TH, the valve element moves out of the closed position merely into the second open position, but not beyond the second open position or at least not out of the second open position into the first open position, but instead the valve element is moved back into the closed position after reaching the second open position, without the valve element moving out of the second open position and further towards the first open position. This means that, when performing the partial stroke, although the valve element is open, i.e. is moved out of the closed position, the valve element is not moved into the first open position, and therefore the valve element does not reach the first open position when moving out of the closed position and back into the closed position again within the context of the partial stroke.

[0057] A timespan during which the valve element or the injector as a whole is open is also referred to as an opening time, injection duration or injection time. During this injection time, the valve element is not in the closed position, and therefore fuel is injected into the combustion chamber by means of the injector during the injection time.

[0058] Overall it can be seen that the valve element performs a stroke when moving out of the closed position into the relevant open position, it being possible for the described full stroke and the described partial stroke of the valve element to be performed or caused.

[0059] The intake valve also performs a stroke, also referred to as a valve stroke, when moving out of the closed position into the open position of the intake valve. This valve stroke is plotted on the y-axis 14 of the graph 10. A curve 16 shown on the graph 10 thus shows the valve stroke and thus the movement of the intake valve out of the closed position into the open position and then back into the closed position again, the closed position of the intake valve being denoted in FIG. 1 by S and the open position of the intake valve being denoted by O.

[0060] Within the context of the method shown in FIG. 1 for operating the internal combustion engine, four injections E1, E2, E3 and E4 are performed by means of the injector, a corresponding amount of the fuel being injected directly into the combustion chamber by means of the injector in each case, within the context of the temporally mutually spaced injections E1-4. The amount of fuel in each case is also referred to as the injection amount. It can be seen from FIG. 1 that all the injections E1-4 are performed by means of the full stroke VH of the injector. It can be seen in FIG. 1 that at least two of the full strokes VH, and thus the injections E1-4 which are part of these two full strokes, differ from one another in their respective injection times, as a result of which different injection amounts are injected directly into the cylinder within the context of these at least two full strokes VH.

[0061] For example, the number of strokes of the injector performed within precisely one intake stroke of the internal combustion engine is within a range of 2 to 8, inclusive. In the method shown by FIG. 1, precisely 4 full strokes VH are performed within the operating cycle and thus 4 temporally mutually spaced injections E1-4 are performed.

[0062] It can be seen from FIG. 1 that the full stroke VH that causes the injection E2 is performed at least in part, in particular at least mostly, while the intake valve is open. In the present case, the full stroke VH that causes the injection E1 and the injection E2 is performed while the intake valve is open. The full stroke VH that causes the injection E3 is also performed at least in part, in particular at least mostly or in full, while the intake valve is open.

[0063] In order to achieve an especially favorable operation of the internal combustion engine in terms of consumption and emissions, in each of the embodiments of the method shown by FIG. 2 to 4, the fuel is injected directly into the cylinder by at least one partial stroke TH of the injector being performed while the intake valve is open. FIG. 2 illustrates a first embodiment of the method. In the first embodiment, the respective partial strokes TH that cause the injections E1 and E2 are performed in full while the intake valve is open. Moreover, the partial stroke TH that causes the injection E3 is performed in part, in particular at least mostly, while the intake valve is open. Also in the first embodiment, precisely four injections E1-4 are provided during or within the operating cycle, all of the injections E1-4 being caused by respective partial strokes TH of the injector. Since the four injections E1-4 are provided, a 4-fold injection is provided.

[0064] FIG. 3 shows a second embodiment of the method. In the second embodiment, the injections E1 and E4 are each caused by the full stroke VH of the injector. The injections E2 and E3, however, are each caused by a partial stroke TH of the injector. In total precisely four injections are also provided in the second embodiment, the full stroke VH that causes the injection E1 and the partial stroke TH that causes the injection E2 each being performed in full while the intake valve is open. A first portion of the partial stroke TH that causes the injection E3 is performed while the intake valve is open, and a second portion thereof is performed while the intake valve is closed. In the second embodiment, the full stroke VH that causes the injection E4 is performed in full while the intake valve is closed again. Analogously thereto, in the first embodiment the partial stroke TH that causes the injection E4 is performed in full while the intake valve is closed again. In the second embodiment, a 4-fold injection is thus provided as a combination of two full strokes VH together with two partial strokes TH.

[0065] FIG. 4 lastly shows a third embodiment of the method, in which five injections E1-5 and thus a 5-fold injection are provided. The injections E1 and E2 are caused by a corresponding full stroke VH of the injector, the injections E3-5 each being caused by a partial stroke TH of the injector. In this case, the full strokes VH that cause the injections E1 and E2 and the partial strokes TH that cause the injections E3 and E4 are performed in full while the intake valve is open. Moreover, the partial stroke TH that causes the injection E5 is performed in full while the intake valve is closed again.

[0066] It can be seen from FIG. 2 that the injection time of the partial stroke TH that causes the injection E1 is shorter than the injection time of the remaining partial strokes TH. In the second embodiment, the partial strokes TH each have longer injection times than the full strokes VH, the full stroke VH that causes the injection E4 having a longer injection time than the full stroke VH that causes the injection E1. Moreover, the partial stroke TH that causes the injection E3 has a longer injection time than the partial stroke TH that causes the injection E2.

[0067] In the third embodiment, the partial strokes TH have the same injection time, the injection time of the full stroke VH that causes the injection E2 being shorter than the injection time of the full stroke VH that causes the injection E1. The fact that injection E2 temporally follows injection E1, injection E3 temporally follows injection E2 and injection E1, and injection E4 temporally follows injection E3, injection E2 and injection E1, applies to all embodiments. Furthermore, injection E5 temporally follows injection E4, injection E3, injection E2 and injection E1. Moreover, the respective injections E1-5 are temporally mutually spaced and are thus designed as individual injections. The 5-fold injection provided in the third embodiment is shown as a combination of two full strokes VH together with three partial strokes TH.

[0068] Due to the fact that at least one partial stroke TH for injecting fuel is performed while the intake valve is open, the raw emissions, and in particular the particle emissions, and the fuel consumption of the internal combustion engine can be kept particularly low, since wetting of the intake valve, the cylinder wall, the combustion chamber roof and the piston with fuel can be kept particularly low. In this case it is preferable for the method to be carried out during a warm-up period for heating up the internal combustion engine, it also being possible, however, to carry out the method when the internal combustion engine is already hot.