DE19633259A1 - Internal combustion engine - Google Patents

Abstract

In familiar internal combustion engines, which also include a fuel vaporization device for individual injection, recondensation of the fuel vapor emitted by the fuel vaporization device can occur in lines of the internal combustion engine, so that it is not possible to meet extremely low emission values. This invention proposes an internal combustion engine (1) which, besides the vaporization device (20) also has a fuel filter (22) mounted after the fuel vaporization device (20) which filters out low volatility fuel components, so that recondensation of the fuel vapor in the fuel vapor lines (27) is nearly completely eliminated. The internal combustion engine is intended for powering motor vehicles.

Description

State of the art

The invention relates to an internal combustion engine according to the Genus of claim 1. It is already one Internal combustion engine known (GB-OS 2 248 087), the one Intake pipe that merges into a manifold from the individual suction pipes to the individual combustion chambers or to the individual cylinders of the Branch off the internal combustion engine. By means of the Individual intake pipes upstream of the intake valves of the Combustion chambers of arranged fuel injection valves can Fuel is dispensed into the individual intake pipes, so too prepare an ignitable fuel-air mixture that flows into the combustion chambers with open intake valves. A electronic engine control unit controls depending on the intake air mass of the internal combustion engine and other engine operating parameters that of the Quantity of fuel delivered by fuel injectors.

In addition to the individual injection The internal combustion engine has fuel injectors another fuel injector that is part of a central  Fuel vaporization device is the fuel vapor can provide the upstream one to Example in the form of a throttle valve Throttle body is discharged into the intake pipe. The feed of fuel vapor using the Fuel vaporization device is on the lower one Load range, especially on the idle range of the Internal combustion engine, limited. In the upper load range, however, especially at full load, deliver exclusively directly to the combustion chambers or the cylinders assigned fuel injectors the required Fuel. By adding vaporous fuel in the intake pipe should during the start phase and subsequent warm-up phase of the internal combustion engine otherwise recondensation of the Fuel vapor on cold walls of the internal combustion engine largely prevented, so as to reduce emissions harmful exhaust gas components, in particular from Hydrocarbons, to be able to reduce significantly.

When switching on the fuel vaporization device the conduits leading between the fuel vapor Fuel vaporization device and the combustion chambers in the Usually colder than the individual dew points of the non-volatile components of the fuel. This has to Consequence that despite the intended fuel evaporation a back condensation of less volatile Fuel components on cold walls, especially on the Walls of the individual intake pipes of the internal combustion engine come can. Store the volatile fuel components on the cold walls of the internal combustion engine can get off the cold walls in an uncontrolled manner detach, so that the subsequent combustion Increase in emissions of harmful exhaust gas components  results. Compliance with extremely low exhaust gas values is therefore not possible. Even smooth running of the Internal combustion engine can not be achieved.

Advantages of the invention

The internal combustion engine according to the invention characteristic features of claim 1 has in contrast the advantage that a back condensation of the fuel vapor or an attachment in particular difficult fuel components in the Lines of fuel vapor leading to the internal combustion engine is almost completely prevented, so that on cold start and the subsequent warm-up phase of the internal combustion engine the emissions of harmful exhaust gas components, especially of hydrocarbons can be lowered.

By the measures listed in the subclaims advantageous developments and improvements in Claim. 1 specified internal combustion engine possible.

In addition to a fuel separator is of particular advantage additionally to provide a mixing device, in particular one upstream of a fuel separator Mixing device, the evaporated fuel air admixed, whereby the partial pressures of the individual Reduce fuel components of the fuel so far that back condensation even at low temperature vaporous fuel leading into the fuel vapor Lines is excluded.  

drawing

Embodiments of the invention are in the drawing shown in simplified form and in the following Description explained in more detail. Show it

Fig. 1 in partial sectional view of an internal combustion engine with fuel evaporation device, mixing device and fuel separator according to a first embodiment of the invention, Fig. 2 in partial cross-section an internal combustion engine with fuel evaporation device, mixing device and fuel separator according to a second embodiment of the invention, Fig. 3 is a structural unit of a Brennstoffabscheiders with mixing device according to a third embodiment of the invention.

Description of the embodiments

In Fig. 1, a multi-cylinder, spark-ignited internal combustion engine 1 is partially shown in section, which has, for example, four cylinders or four combustion chambers 2 , with only a single cylinder with a combustion chamber 2 being shown in FIGS. 1 and 2. Each combustion chamber 2 has at least one inlet valve 3 and a spark plug 4 and at least one outlet valve, not shown. At least one fuel injection valve 5 is provided upstream of the inlet valve 3 and can discharge fuel into a single intake pipe 6 of the internal combustion engine 1 in the direction of the inlet valve 3 . The, for example, four individual intake pipes 6 of the four-cylinder internal combustion engine 1 are based, for example, on a collective intake pipe 7 , which is part of a further intake pipe 8 of the internal combustion engine 1 . The individual intake pipes 6 , the collective intake pipe 7 and the intake pipe 8 form parts of an intake device of the internal combustion engine 1 . In the intake pipe 8 , a throttle member 9 for controlling the amount of air drawn in by the internal combustion engine 1 is accommodated, which is designed, for example, in the form of a throttle valve and is rotatably mounted in the intake pipe 8 . The air sucked in by the internal combustion engine 1 from the environment flows through an air filter (not shown) in the direction of an arrow 10 shown in FIGS. 1 and 2 into the intake manifold 8 , where it flows further into the manifold intake manifold 7 when the throttle valve 9 is open, in order to remove it to be distributed over the individual intake pipes 6 to the individual combustion chambers 2 of the internal combustion engine 1 .

Upstream of the throttle valve 9 , an idle air line 12 branches off from the intake pipe 8 , which leads to a mixing chamber 14 of a mixing device 15 . To control the amount of air flowing in the idle air line 12 , for example, an idle actuator 16 of a known type can be provided, which can be controlled accordingly by an electronic control unit 32 . The construction of idle actuators is well known to the person skilled in the art, for example from DE-PS 30 01 473. In addition to the idle air line 12 , a fuel evaporator line 17 with a smaller cross section and a connecting line 18 lead to the mixing chamber 14 . All three lines 12 , 17 and 18 have, for example, socket-shaped end pieces 19 which, for example, protrude somewhat into the mixing space 14 . The fuel vaporizer line 17 is connected to a fuel vaporizing device 20 of a known type (GB-OS 2 263 501, DE-OS 44 12 448), which can process fuel vapor that is released into the fuel vaporizer line 17 . For this purpose, the fuel vaporization device 20 has, for example, a central injection valve (not shown in more detail), which is equipped, for example, with a heating attachment. The heating element contains an evaporator structure for liquid fuel that is electrically heatable in a known manner, for example, and for this purpose has resistance heating elements that can have, for example, a positive temperature coefficient (PTC) or a negative temperature coefficient (NTC). The electronic control unit 32 can be provided, for example, to control the resistance heating elements. The resistance heating elements are accommodated in an evaporator housing and are, for example, plate-shaped and optionally have a porous surface.

In the mixing chamber 14 of the mixing device 15 , which enables an increase in the volume of the fuel vapor, the fuel vapor prepared by the fuel evaporation device 20 is introduced via the fuel evaporator line 17 , which then mixes intensively in the mixing room 14 with the air flowing into the mixing chamber 14 from the idle air line 12 , so that it to a decrease in the partial pressures of the individual fuel components and thus the vapor temperature of the fuel. The fuel vapor mixed with air in this way can advantageously only recondense at a much lower temperature than in the unmixed state, since the air added leads to a lowering of the condensation temperature of the newly formed mixture, as a result of which liquid fuel accumulation on cold walls of the internal combustion engine 1 is reliably prevented . The fuel vapor mixed with air in this way then leaves the mixing chamber 14 in the form of a homogeneous fuel-air mixture which is interspersed with the finest droplets and which is fed from the mixing chamber 14 to a fuel separator 22 via the connecting line 18 . To support the mixture formation in the mixing chamber 14 , this can be heated from the outside, for example, by means of an electrical heating device. As shown in FIG. 1, the fuel separator 22 has a relatively strong flow diversion for the fuel flow, which leads to the separation of larger droplets from the fuel-air mixture, which also contains volatile fuel components. The flow deflection is designed in such a way that, for example, a vertical separator line 23 connects at right angles to the horizontal connecting line 18 in order to form a branching point in a T-shape. In this case, a lower end 24 of the vertical separator line 23 opens into a collecting container 30 , which then receives the non-volatile fuel components dripping under the influence of gravity into the collecting container 30 . The upper end 25 of the separator line 23 , which is opposite the lower end 24 , is adjoined by, for example, a horizontally running line section 26 of the fuel separator 22 , which is used for connection to a line system 27 of the internal combustion engine 1 .

The line system 27 is formed, for example, from a plurality of individual lines, which lead in a branched manner from the fuel separator 22 to the individual suction pipes 6 , in order upstream of the inlet valves 3 to contain the fuel air, which is essentially only highly volatile fuel components and has been prepared by the fuel evaporation device 20 , mixing device 15 and fuel separator 22 Mix feed the individual combustion chambers 2 of the internal combustion engine 1 . The fuel-air mixture, which essentially has only volatile fuel components, prevents the fuel-air mixture in the line system 27 from recondensing even at a low temperature.

The lines of the line system 27 preferably consist of tubes or hoses which are made of an elastic material with low thermal conductivity, for example of plastic. As shown in FIG. 1, the lines of the line system 27 are connected or the fuel-air mixture is introduced into the individual intake pipes 6 in the vicinity of the inlet valves 3 of the internal combustion engine 1 . The line system 27 is branched, for example, in such a way that only combustion chambers 2 or cylinders, which are not in direct ignition sequence with one another, are connected in pairs to one another and together with the fuel separator 22 .

The operation of the fuel vaporization device 20 is preferably limited to the lower load range, in particular to the idle range of the internal combustion engine 1 . However, it is also possible to provide for the operation of the fuel vaporization device 20 in the part-load range adjoining the idling range or even until shortly before the full load of the internal combustion engine 1 is reached .

As shown in FIG. 1, for example, an electromagnetically actuated valve 35 is provided for returning the fuel collected in the collecting container 30 , which essentially consists of a condensate of low-volatility fuel components. A valve vent valve, which is usually already present, can be used with the valve 35 and is sufficiently known to the person skilled in the art, for example from DE-OS 40 23 044. The valve 35 is part of a fuel evaporation retention system for a fuel tank of the internal combustion engine 1 and serves to return the fuel vapor volatilized from the fuel tank, which is temporarily stored in an adsorption filter and is released by the latter via the valve 35 into the intake pipe 8 . The via a manifold 36 with the reservoir 30 and the intake manifold 8 connected to valve 35 is actuated, for example in switched off fuel evaporation device 20 of the electronic control unit 32 in a clocked manner, so the collected in the collecting tank 30 the condensate in certain operating states of the internal combustion engine 1 with the aid of the Intake pipe 8 prevailing negative pressure into the intake pipe 8 for subsequent combustion in the combustion chambers 2 of the internal combustion engine 1 .

As shown in FIG. 2, a second exemplary embodiment of the invention, in which all the same or equivalent parts are identified with the same reference numbers in FIG. 1, it is also possible to remove the condensate collected in the collecting container 30 instead of the one shown in FIG 35 to use. 1 provided valve, a pumping device 40. The pumping device 40 is connected via a pump line 41 to the reservoir 30 to again supply during operation of the pumping device 40, the reservoir 30 accommodated in the condensate to a fuel tank 42 of the engine. 1 However, it is also conceivable to arrange the collecting container 30 in good heat-conducting connection with the internal combustion engine 1 , so that when the internal combustion engine 1 is heated, the condensate in the collecting container 30 is heated, which can then evaporate. Separate removal of the condensate by means of valve 35 or pump device 40 can thus be avoided. It would also be possible to heat the collecting container 30 with the aid of an electrical heating device, for example.

In the second exemplary embodiment shown in FIG. 2, the fuel separator 22 has a diaphragm-shaped part 45 for deflecting the flow or for separating the non-volatile fuel components, which is provided in a space 46 , blocking the direct flow path, between the connecting line 18 and line section 26 in the fuel separator 22 . When flowing through the space 46 , the fuel-air mixture is deflected by the orifice-shaped part 45 in such a way that it is in particular on a wall surface 47 of the orifice-shaped part 45 facing the connecting line 18 for separating the non-volatile fuel components in the liquid phase from the fuel-air Mix comes. The non-volatile fuel constituents are deposited on the wall surface 47 in the form of droplets, which then drip under the influence of gravity into the collecting container 30 underneath. The fuel-air mixture emerging from the connecting line 18 into the space 46 is deflected downward by the diaphragm-shaped part 45 and can only reach the further line section 26 after flowing around its lower end 48 . This results in a fuel-air mixture downstream of the diaphragm-shaped part 45 , which essentially has only volatile fuel components, the partial pressure of which is so high that there is no recondensation of the fuel afterwards even at a cold temperature, for example when the internal combustion engine 1 is cold started Air mixture on the cold walls of the internal combustion engine 1 , in particular on the walls of the line system 27 , can come.

However, it is also possible to interchange the order of the mixing device 15 and the fuel separator 22 in a modification of the invention that is not shown in detail. In this case, the fuel vapor prepared by the fuel evaporation device 20 first arrives directly in the separator line 23 of the fuel separator 22 in order to then flow from the fuel separator 22 out of the line section 26 into the fuel evaporator line 17 of the mixing device 15, which is then connected to the line section 26 . The fuel vapor then reaches the mixing chamber 14 of the mixing device 15 from the fuel evaporator line 17 . After the mixing device 15 there is again a fuel-air mixture which essentially has only volatile fuel components which can be discharged via the connecting line 18 into the line system 27 of the internal combustion engine 1 which is then connected to the connecting line 18 .

In Fig. 3, a third embodiment of the invention is disclosed, in which all the same or equivalent parts are identified by the same reference numerals of Figs. 1 and 2. FIG. 3 shows a fuel separator 22 and a mixing device 15 , both of which are accommodated in a common housing 51 and form a structural unit 50 in a construction which saves installation space. The housing 51 is composed, for example, of five parts, an opening in the form of a stepped bore 52 being provided on a first end part 55, which opening represents a part of the fuel evaporator line 17 according to FIGS. 1 and 2, via which the fuel evaporator device 20 processes Fuel vapor flows into the unit 50 . From the bore 52 , the fuel vapor passes through an orifice 53 into the mixing chamber 14 , which is cylindrical, for example, and which is provided in the interior of the housing 51 . The mouthpiece 53 protrudes into a part of the mixing space 14 and ends at a distance from the opposite wall of the mixing space 14 . Air is supplied to the fuel vapor in the mixing chamber 14 via an opening 54 , which is further provided in the mixing chamber 14 , for example circularly, and originates from the idle air line 12 of the internal combustion engine 1, which is not shown in FIG. 3. The opening 54 opens in such a way in the mixing chamber 14 so that the air transversely, that flows to the flow direction of the fuel vapor transversely to the mouth piece 53 and not directed to this in the mixing chamber 14 and is rotated by the cylindrical configuration of the mixing chamber 14 in a swirling motion. This supply of air results in intensive mixing with the fuel vapor, so that a fuel-air mixture permeated with individual droplets is present downstream of the mixing device 15 or the mixing chamber 14 . From the mixing chamber 14 , the fuel-air mixture reaches the fuel separator 22 via the connecting line 18, which is coaxial to the orifice 53 and is designed, for example, in the form of a through hole.

The fuel separator 22 has a flow deflection, which is designed as an aperture-shaped part 45 , in order to, as indicated by an arrow 59 shown in FIG. 3, the U-shaped fuel-air mixture flowing into the space 46 via the through hole 18 first to be deflected downwards and then upwards again so that the deflection leads to the elimination of the low-volatility fuel components from the fuel-air mixture. The non-volatile fuel constituents accumulate in the form of droplets, in particular on the wall surface 47 facing the connecting line 18 on the diaphragm-shaped part 45 , which then drip under the influence of gravity onto the floor of the space 46 and flow from there into a vertically arranged collecting nozzle 62 . The collecting nozzle 62 leads to the collecting container 30 shown in more detail in FIGS. 1 and 2, which holds the non-volatile fuel components. To discharge the fuel-air mixture freed from the non-volatile fuel constituents downstream of the diaphragm-shaped part 45 from the space 46 of the fuel separator 22 , another, for example located somewhat below the through hole 18 , is located transversely to the collecting nozzle 62 on a second end part 64 of the housing 51 substantially horizontally extending connecting piece 66 is provided. The connecting piece 66 represents the line section 26 provided according to FIGS. 1 and 2, which serves to connect the unit 51 to the line system 27 of the internal combustion engine 1 .

Claims (13)

1. Internal combustion engine, with an intake device and with a fuel evaporation device, which provides a fuel-air mixture in certain operating ranges of the internal combustion engine, in particular in the lower load range, for introduction into the intake device, characterized in that a fuel separator ( 20 ) downstream of the fuel evaporation device ( 20 ) 22 ) is provided which separates liquid fuel components from the fuel vapor prepared by the fuel vaporization device ( 20 ). 2. Porridge engine according to claim 1, characterized in that between the fuel evaporation device ( 20 ) and the fuel separator ( 22 ) a mixing device ( 15 ) is provided which has a mixing chamber ( 14 ), in which air is introduced, which is in contact with the the fuel vaporization device ( 20 ) mixes processed fuel vapor. 3. Internal combustion engine according to claim 1, characterized in that the device connected to the fuel evaporation device (20) fuel separator (22) connected to a mixing device (15) having a mixing chamber (14) into which air is introduced, which with the fuel vapor prepared by the fuel separator ( 22 ) mixes in such a way that a fuel-air mixture is formed which is released by the mixing device ( 15 ) into a line system ( 27 ) of the internal combustion engine ( 1 ). 4. Internal combustion engine according to claim 2 or 3, characterized in that the air supplied to the mixing chamber ( 14 ) from an intake device ( 8 ) branching idle air line ( 12 ) of the internal combustion engine ( 1 ) is derived. 5. Internal combustion engine according to one of claims 1 to 3, characterized in that the fuel separator ( 22 ) has an aperture-shaped part ( 45 ) for separating the liquid fuel components. 6. Internal combustion engine according to one of claims 1 to 3, characterized in that the fuel separator ( 22 ) for separating the liquid fuel components has a T-shaped branching point ( 18 , 23 ). 7. Internal combustion engine according to claim 5 or 6, characterized in that a collecting container ( 30 ) is provided for receiving the fuel components separated in the fuel separator ( 22 ). 8. Internal combustion engine according to claim 7, characterized in that means for heating the collecting container ( 30 ) are provided. 9. Internal combustion engine according to claim 7, characterized in that a valve is provided (35) for deriving the deposited in the collecting container (30), fuel components, which in an open position, the outflow of the fuel constituents in the suction present in the collection container (30) (8) Internal combustion engine ( 1 ) releases. 10. Internal combustion engine according to claim 7, characterized in that the valve ( 35 ) is designed to be electromagnetically actuated and can be opened by means of an electronic control unit ( 32 ) emitted signals. In that a pumping device (40) is provided 11. internal combustion engine according to claim 7, characterized in that for the derivation of the deposited in the collecting container (30), fuel components, which conveys the fuel constituents located in the collecting container (30) in a fuel tank (42) of the internal combustion engine (1) . 12. Internal combustion engine according to claim 7, characterized in that the collecting container ( 30 ) is arranged in a thermally conductive connection to the internal combustion engine ( 1 ). 13. Internal combustion engine according to claim 2 or 3, characterized in that the fuel separator ( 22 ) and mixing device ( 15 ) are formed in a structural unit ( 50 ).