DE10248193A1 - Removal of unburned fuel from vehicle engine following turning-off to reduce emissions, continues engine rotation using electric motor to remove it - Google Patents

Abstract

After switching-off injection, an electric motor (EM) coupled with the engine continues engine turning for a suitable interval, to remove unburned fuel (KF) from the air inlet manifold (AR) and/or cylinders (BR).

Description

The invention relates to a Method of removing unburned fuel from an internal combustion engine after turning it off.

Such a method is in the DE 196 40 166 C2 specified. In this known method, after the internal combustion engine has been switched off, a secondary air pump connected to an exhaust line upstream of a catalytic converter is put into operation for a limited period of time in order to supply hydrocarbons still present in the internal combustion engine to the catalytic converter for conversion. For this purpose, a post-reaction of injected oxygen with the hydrocarbons takes place behind the exhaust valve. If the engine has a valve overlap, a combustion chamber can also be blown out at the rear. However, it is difficult to remove all hydrocarbon residues present in the combustion chamber in this way, and in particular, fuel residues generally remain in the flow channel in front of the combustion chamber after the internal combustion engine has been switched off and are emitted as harmful exhaust gases when the engine is switched off and also during a subsequent start Hydrocarbon emissions in the engine exhaust can contribute.

The invention is based on the object Provide method with which after the engine is turned off Exhaust emissions occurring if possible be largely reduced.

Advantages of invention

This task comes with the characteristics of claim 1 solved. According to this it is provided that time-related for switching off the injection an existing one, which can be coupled or coupled to the internal combustion engine Electric motor to continue rotating over one for removing the unburned Fuel from a relevant intake pipe arrangement and / or suitable time or number of at least one assigned combustion chamber Revolutions is activated.

By continuing to rotate without combustion The internal combustion engine is used in particular as a fuel wall film present unburned fuel by means of the intake air from the intake pipe arrangement and also the combustion chamber into the exhaust line transported. I'm still called It becomes an environmentally friendly catalyst oxidized to carbon dioxide and water. The duration of the further rotation (Time or number of revolutions) can depend on the extraction Volume and the fuel wall film to be broken down. An existing fuel wall film is broken down so that it neither in the shutdown phase, such as an evaporative emission test (SHED test) detectable, still contribute to exhaust emissions at a subsequent start can. Moreover is the air / fuel ratio more reproducible at a subsequent start, since no unknown Wall film amount is present.

Advantageous design variants consist of a starter or starter generator as an electric motor is activated. A starter generator is inexpensive for reasons of comfort and noise.

Other advantageous measures e.g. simply by programming a motor controller accordingly can be made consist of the time or number of revolutions of the revolving depending on the electric motor of assumed or based on empirical values or measurements modeled values of unburned fuel is specified.

Wear to optimize the process the measures at that when specifying the time or the number of revolutions the ambient temperature, the engine temperature, the engine operating temperature, the external air pressure, the suction pipe pressure or a combination of at least two of these Influencing factors taken into account become.

The specification of the time or the number of revolutions in the post-rotation phase is directly dependent of these influencing factors take place or it should be provided that at least one of the influencing variables in assuming or modeling the amount of unburned fuel is taken into account.

Other design options consist of the time or number of revolutions of the revolving dependent on sensor signals of at least one in the intake manifold arrangement and / or of an existing exhaust tract (e.g. a lambda sensor) will draw a conclusion allow for the hydrocarbon content.

For the safe conversion of hydrocarbon vapors can it continues to be cheap be the time or number of revolutions of the revolving dependent on a measured or modeled catalyst temperature is selected.

It is further provided that to remove hydrocarbon vapors stored in a filter of a tank ventilation system during revolving, a throttle valve present in the intake pipe arrangement is closed and a tank ventilation valve positioned between the filter and a position of the intake pipe arrangement downstream of the throttle valve is opened and then - while turning - the throttle valve is at least partially opened again and the tank ventilation valve is closed again, an at least partial emptying of a hydrocarbon filter, in particular an activated carbon filter of the tank ventilation system, can also be incorporated into the method.

The invention is described below of an embodiment explained in more detail with reference to the drawing.

embodiment

The figure shows a schematic Representation of an internal combustion engine with the essential components to carry out the method of removing unburned fuels, especially in Form of a fuel wall film KF in an intake manifold arrangement AR and / or a combustion chamber BR of the internal combustion engine according to their Off.

The fuel wall film KF forms e.g. in the area of the inner wall side of an intake pipe AR in nearby of the EV injection valve and remains when the internal combustion engine is switched off back. This unburned fuel can lead to evaporative emissions during the shutdown phase to lead. Besides, can at the following engine start, if one arranged in an exhaust line AS Catalyst K is still cold, hydrocarbon in the engine exhaust occur strongly increased.

After the driver has one Ignition key the Internal combustion engine or the engine has turned off, the injection is via the Injector EV switched off. To break down the fuel wall film KF, an electric motor EM is simultaneously operated via a control device, in particular motor control MS continued to operate. The motor control MS is for programmed and evaluated the operation of this re-turning accordingly suitable received signals from the internal combustion engine. With the electric motor EM is preferably the starter or a e.g. also used as a starter generator or an electric motor Hybrid drives. When turning further, the valves also become one Inlet E and an outlet A in a conventional manner e.g. over a Camshaft operated further. For feeding of air is one that is present in the intake pipe arrangement AR Throttle valve DK, which is also related to the engine control MS, at least partially open.

The figure also shows a fuel tank T, from which the injection valve EV via a corresponding line Fuel supplied will and also with a ventilation system is provided that an activated carbon filter AKF harmful to filter NC vapors and a tank vent valve TEV has over the activated carbon filter to the intake manifold AR between Throttle valve DK and the combustion chamber BR is connected. Depending on execution can the tank ventilation system also include an activated carbon filter shut-off valve AAV.

The post-production period or number of Revolutions can be done by programming the motor control accordingly MS or other control unit that works with the engine control MS related dependent on of different state variables of the Engine, such as engine temperature, engine operating time, intake manifold pressure, Temperature of the catalyst K or the like, and also as a function of external conditions, such as ambient temperature and air pressure. there can this Influencing factors at Specifying the post-rotation duration or number of post-turns is taken into account immediately be or for a modeling of the unburned fuel quantity or the fuel wall film KF in the Intake pipe arrangement AR and / or the combustion chamber BR also used to then become dependent from the modeled unburned fuel quantity or the modeled Fuel wall film KF is the post-production duration or number of post-production runs to determine.

Also the post-production period or Number of revolutions depending be determined by sensor signals from sensors located in the intake manifold or exhaust tract and a conclusion on the hydrocarbon content allow. The possibly considered Catalytic converter temperature can be measured using a catalytic converter temperature sensor TKAT measured or modeled catalyst temperature based.

The tank ventilation system can also be used in the process be included. For this purpose, the throttle valve is turned DK closed, a possible activated carbon filter shut-off valve AAV open and the tank vent valve TEV opened. This turns hydrocarbon vapors from the activated carbon filter AKF and the tank system in the catalyst oxidized. This results in the Advantage that the storage capacity of the activated carbon filter AKF is improved due to this additional flushing. To ensure, that there is still residual hydrocarbons in the flow channel remain between throttle valve DK and catalytic converter, the tank ventilation system in an initial Phase of re-turning over the tank vent valve TEV flushed with throttle valve DK closed and in a subsequent phase of turning the throttle valve DK at least partially opened and the tank vent valve TEV closed, so harmful Hydrocarbon vapors safe removed from the flow channel and be converted in the catalyst K.

Claims (8)

Method for eliminating unburned fuel (KF) from an internal combustion engine after it has been switched off, characterized in that a time-related means for switching off the injection Existing electric motor (EM), which is coupled or can be coupled to the internal combustion engine, for continuing the rotation operation via a time or number of revolutions suitable for removing the unburned fuel (KF) from a relevant intake manifold arrangement (AR) and / or at least one assigned combustion chamber (BR) is activated. A method according to claim 1, characterized in that a starter, starter generator or other electric motor (EM) is activated. A method according to claim 1 or 2, characterized in that that the time or number of revolutions of revolving with the Electric motor (EM) depending of assumed or based on empirical values or measurements modeled values of unburned fuel (KF) is specified. Method according to one of the preceding claims, characterized characterized that when specifying the time or the number of Revolutions the ambient temperature, the engine temperature, the engine operating temperature, the external air pressure, the intake manifold pressure or a combination of at least two of these Influencing factors is taken into account. A method according to claim 4, characterized in that at least one of the influencing factors in the acceptance or the Modeling the amount of unburned fuel (KF) is taken into account becomes. Method according to one of the preceding claims, characterized characterized that the time or number of revolutions of the re-turning dependent on sensor signals of at least one in the intake manifold arrangement (AR) and / or an exhaust tract (AK) existing sensor is also determined, the one or the inference on the hydrocarbon content. Method according to one of the preceding claims, characterized characterized that the time or number of revolutions of the re-turning dependent on a measured or modeled catalyst temperature is selected. Method according to one of the preceding claims, characterized marked that for draining of stored in a filter (AKF) of a tank ventilation system Hydrocarbon vapors while of re-turning an existing one in the intake pipe arrangement (AR) Throttle valve (DK) closed and one between the filter (AKF) and a point downstream of the throttle valve (DK) of the intake manifold assembly (AR) (TEV) opened and then - while still turning - the throttle valve (DK) at least partially opened again and the tank ventilation valve (TEV) is closed again.