METHOD, COMPUTING UNIT, AND COMPUTER PROGRAM FOR OPERATING AN INTERNAL COMBUSTION ENGINE

Abstract

A method (100) is proposed for operating an internal combustion engine (210), which comprises a lean-burn engine having compression-ignition, having a throttle valve (213) in an air path (212) upstream of the internal combustion engine (210) and an exhaust gas posttreatment system (202) downstream of the internal combustion engine (210), comprising a control of the internal combustion engine (210) according to a present load demand (130) using metering of an amount of fuel in dependence on the present load demand; and if a load demand (130) is absent in a heating operating mode, further comprising partially closing (140) the throttle valve (213) and defining a minimum value for the amount of fuel, which is greater than zero. Furthermore, a computing unit and a computer program for carrying out such a method (100) are proposed.

Claims

1. A method (100) for operating an internal combustion engine (210), which comprises a lean-burn engine, having a throttle valve (213) in an air path (212) upstream of the internal combustion engine (210) and an exhaust gas posttreatment system (202) downstream of the internal combustion engine (210), the method comprising: controlling the internal combustion engine (210) according to a present load demand (130) using metering of an amount of fuel in dependence on the present load demand; and when a load demand (130) is absent in a heating operating mode, partially closing (140) the throttle valve (213) and defining a minimum value for the amount of fuel, which is greater than zero.

2. The method (100) according to claim 1, in which the heating operating mode comprises controlling (140) the internal combustion engine (210) to produce an exhaust gas having an air-fuel ratio less than or equal to 1.

3. The method according to claim 1, wherein the minimum value for the amount of fuel is defined in dependence (120) on a temperature (110) of the exhaust gas posttreatment system (202) and/or in dependence (120) on a function of the exhaust gas posttreatment system (202).

4. The method (100) according to claim 3, wherein the function of the exhaust gas posttreatment system (202) comprises a regeneration of a particle filter and/or a reduction of an exhaust gas component stored in a storage catalytic converter (230).

5. The method (100) according to claim 1, wherein the partial closing (140) of the throttle valve (213) takes place in dependence on a minimum required amount of air.

6. The method (100) according to claim 5, comprising ascertaining (110) the minimum required amount of air in dependence on at least one selected from the group consisting of a stability of the combustion of fuel in the internal combustion engine (210), an acoustic threshold value, and a vibration threshold value.

7. The method (100) according to claim 1, in which the heating operating mode comprises absorbing provided torque by way of an electrical machine and using the absorbed torque to generate electrical energy.

8. The method (100) according to claim 7, wherein the electrical machine is used in a normal operating mode to provide torque according to the load demand and/or to generate electrical energy for use in a power grid.

9. A non-transitory, computer-readable storage medium containing instructions that when executed by a computer cause the computer to control an internal combustion engine (210) according to a present load demand (130) using metering of an amount of fuel in dependence on the present load demand; and when a load demand (130) is absent in a heating operating mode, partially closing (140) a throttle valve (213) and defining a minimum value for the amount of fuel, which is greater than zero.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Further advantages and embodiments of the invention result from the description and the appended drawing.

[0017] The invention is schematically illustrated on the basis of exemplary embodiments in the drawing and is described hereinafter with reference to the drawing.

[0018] FIG. 1 shows an advantageous embodiment of a method according to the invention in the form of a greatly simplified flow chart.

[0019] FIG. 2 schematically shows an arrangement of an internal combustion engine having a throttle valve and an exhaust gas posttreatment system, as can be used in the scope of the invention.

DETAILED DESCRIPTION

[0020] An advantageous embodiment of a method according to the invention is shown in the form of a greatly simplified flow chart in FIG. 1 and identified as a whole with 100. The method 100 is used to control a lean-burn engine having compression-ignition (for example, diesel engine) in selected operating states and is explained hereinafter with reference to FIG. 2, in which an arrangement of an internal combustion engine having a throttle valve and an exhaust gas posttreatment system, as can be used in the scope of the invention, is schematically shown and identified as a whole with 200.

[0021] The arrangement 200 has a supply device 214 for introducing fuel into a combustion chamber or cylinder 211 of an internal combustion engine 210. A throttle valve 213 is situated in an air path 212, via which combustion air is guided into the respective combustion chamber 211. The amount of air can be controlled via the opening angle of the throttle valve 213. Exhaust gas produced in the internal combustion engine 210 is exhausted via an exhaust gas posttreatment system 202, which, in the example shown, comprises a catalytic converter 230 for converting pollutants contained in the exhaust gas into less harmful compounds. Furthermore, the exhaust gas posttreatment system 202 comprises exhaust gas sensors 245, 247 upstream and downstream of the catalytic converter 230, for example, lambda sensors, which can be used to control or monitor a composition of the exhaust gas of the internal combustion engine 210.

[0022] The exhaust gas posttreatment system 202 can also contain further components, for example, further catalytic converters, particle filters, or the like.

[0023] In a first step 110 of the method 100, at least one operating parameter of an internal combustion engine 210 or a component of its exhaust gas posttreatment system 202 is ascertained. In particular, the at least one operating parameter can be a temperature of a component of the exhaust gas posttreatment system 202, for example, of the catalytic converter 230, or the internal combustion engine 210 (for example, coolant water temperature), a speed (crankshaft speed) of the internal combustion engine 210, a fill level of an accumulator for exhaust gas components (catalytic converter), or the like. The ascertainment of the at least one operating parameter can be carried out here using a measuring instrument, for example, a lambda sensor 245, 247 and/or by calculation on the basis of a mathematical model. In particular fill levels of storage catalytic converters can be ascertained in a model-based manner, for example, as described in DE 10 2016 222 418 A1 (in particular for gasoline engine catalytic converters).

[0024] On the basis of the at least one operating parameter, it is determined in a second step 120 of the method 100 whether a heating operating mode or a normal operating mode is to be carried out. If the heating operating mode is selected here, which will be the case in particular if the operating parameter indicates a need for heating, for example, if an ascertained temperature is less than a threshold value or an ascertained fill level of a nitrogen accumulator of the catalytic converter 230 exceeds a predetermined threshold value, the method continues with a step 130, in which a present torque demand is ascertained. The torque demand can be ascertained here in particular by evaluating an accelerator pedal position, a presently used transmission ratio, or other relevant influencing variables.

[0025] In dependence on the ascertained torque demand, in a control step 140, the internal combustion engine 210 is controlled in the heating operating mode to produce a rich exhaust gas and for the most suitable possible torque generation. For this purpose, the throttle valve 213 in the air path 212 upstream of the internal combustion engine 210 is partially closed. The degree to which the throttle valve 213 is closed can be selected here in consideration of the at least one operating parameter and/or further influencing variables so that a stable combustion is ensured in the internal combustion engine 210 and, for example, vibrations are also minimized or acoustic emissions due to the throttled operation do not exceed a specifiable threshold value.

[0026] If it has been ascertained in step 130 that there is no torque demand, in the heating operating mode, fuel is nonetheless metered into the internal combustion engine 210 and combusted with the minimal amount of air to avoid cooling of components of the exhaust gas posttreatment system 202 arranged downstream of the internal combustion engine 210 or to achieve heating of these components. The fuel metering can be set here in particular according to a desired lambda value (for example, close to 1 for minimal emissions or less than 1 for increased heating power).

[0027] As already explained at the outset, the excess torque hereby generated can be used, for example, for current generation. For this purpose, for example, a generator (dynamo) installed in any case, a starter generator, or an electrical machine, which is provided as an electrical drive motor, can be operated as a generator and the current thus generated can be used, for example, to charge a vehicle battery. On the one hand, the generated torque is thus dissipated, on the other hand, the energy is reasonably used, due to which the overall efficiency of an assembly thus operated, for example a motor vehicle, is increased.

[0028] In contrast, if it is ascertained in step 120 that there is no heating demand and therefore the normal operating mode is selected, if a torque demand is absent, the internal combustion engine 210 can be moved into an overrun shutoff operation, in which no fuel is metered. The throttle valve 213, which is usually partially closed for the heating operating mode, is typically completely opened in the normal operating mode. Since this control corresponds to a conventional procedure, it will not be described in more detail here. In the scope of the invention, it can therefore be presumed that the method 100 returns to step 110 until the heating operating mode is required.