EP0859907A1

EP0859907A1 - Internal combustion engine with a fuel vaporization device

Info

Publication number: EP0859907A1
Application number: EP97924919A
Authority: EP
Inventors: Winfried Moser; Klaus Joos; Gerhard Benz; Nikolaus Simon; Jörg Lange; Anwar Abidin; Andreas Eichendorf; Christof Vogel; Georg Mallebrein
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1996-08-17
Filing date: 1997-05-28
Publication date: 1998-08-26
Also published as: JPH11514069A; DE19633259A1; WO1998007977A1

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

INTERNAL COMBUSTION ENGINE WITH A FUEL EVAPORATION DEVICE

State of the art

The invention relates to an internal combustion engine according to the preamble of claim 1. An internal combustion engine is already known (GB-OS 2 248 087)

Has intake pipe, which merges into a collective intake pipe, branch off from the individual intake pipes to the individual combustion chambers or to the individual cylinders of the internal combustion engine. By means of the individual intake pipes upstream of intake valves of the

Combustion chambers of fuel injectors arranged can deliver fuel into the individual intake pipes in order to prepare an ignitable fuel-air mixture that flows into the combustion chambers when the inlet valves are open. An electronic engine control unit controls the amount of fuel emitted by the fuel injection valves depending on the intake air mass of the internal combustion engine and other engine operating parameters.

In addition to the individual injection

Fuel injection valves, the internal combustion engine has another injection valve, which is part of a central Is fuel vaporization device that can provide fuel vapor, which is then discharged upstream of a throttle body, for example in the form of a throttle valve, into the intake pipe. The supply of fuel vapor by means of the

Fuel vaporization device is limited to the lower load range, in particular to the idle range of the internal combustion engine. In the upper load range, in particular at full load, however, only the fuel injection valves directly assigned to the combustion chambers or the cylinders deliver the required fuel. Through the supply of vaporous fuel in the intake pipe during the starting phase and the subsequent warm-up phase of the internal combustion engine, an otherwise recondensation of the

Fuel vapor on cold walls of the internal combustion engine can be largely prevented, so as to reduce the emissions of harmful exhaust gas components, in particular from

Hydrocarbons, to be able to reduce significantly.

When the fuel vaporization device is switched on, the fuel vapors are conduction paths between the

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 the consequence that despite the intended fuel evaporation to a recondensation it is less volatile

Fuel components can come on cold walls, especially on the walls of the individual intake pipes of the internal combustion engine. The non-volatile fuel components accumulate on the cold walls of the internal combustion engine and can detach themselves from the cold walls in an uncontrolled manner, so that an increase in emissions of harmful exhaust gas components occurs in the subsequent combustion results. It is therefore not possible to maintain extremely low exhaust gas values. Even the internal combustion engine cannot run smoothly.

Advantages of the invention

The internal combustion engine according to the invention with the characterizing features of claim 1 has the advantage that a back condensation of the fuel vapor or an accumulation of particularly volatile fuel components in the fuel vapor leading lines of the internal combustion engine is almost completely prevented, so that the emissions during the cold start and the subsequent warm-up phase of the internal combustion engine harmful exhaust gas components, especially hydrocarbons, can be further reduced significantly.

The measures listed in the dependent claims advantageous refinements and improvements of the internal combustion engine specified in claim 1 are possible.

In addition to a fuel separator, it is particularly advantageous to provide a mixing device, in particular a mixing device connected upstream of a fuel separator, which mixes air with the vaporized fuel, as a result of which the partial pressures of the individual fuel components of the fuel decrease to such an extent that even at low temperature, vapor fuel recondenses into the Lines carrying fuel vapor is excluded. drawing

Embodiments of the invention are shown in simplified form in the drawing and explained in more detail in the following description. 1 shows a partial sectional view of an internal combustion engine with fuel vaporization device, mixing device and fuel separator according to a first exemplary embodiment according to the invention, FIG. 2 shows a partial sectional view of an internal combustion engine with fuel vaporization device, mixing device and fuel separator according to a second exemplary embodiment according to the invention, FIG. 3 shows a structural unit of a

Fuel separator with mixing device according to a third embodiment of the invention.

Description of the embodiments

In FIG. 1, a multi-cylinder, externally ignited internal combustion engine 1 is partially shown in a sectional view, which has, for example, four cylinders or four combustion chambers 2, only one 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 one spark plug 4 and at least one outlet valve, not shown. Upstream of the inlet valve 3, at least one fuel injector 5 is provided, the fuel in a single intake pipe 6 of the internal combustion engine 1 in the direction of the inlet valve 3 can. 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 manifolds 6, the collective intake manifold 7 and the intake manifold 8 form parts of an intake device of the internal combustion engine 1. In the intake manifold 8, a throttle element 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 rotatable in the intake manifold 8 is stored. 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 the individual intake pipes 6 to be divided into the individual combustion chambers 2 of the internal combustion engine 1.

One branches upstream of the throttle valve 9

Idle air line 12 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 smaller cross section leads to the mixing chamber 14

Fuel evaporator line 17 and a connecting line 18. All three lines 12, 17 and 18 have, for example nozzle-shaped end pieces 19 which, for example, protrude somewhat into the mixing space 14. The fuel evaporator line 17 is connected to a

Fuel vaporization 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 evaporator 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). to

Control of the resistance heating elements, for example, the electronic control unit 32 can be provided. The resistance heating elements are housed in an evaporator housing and are, for example, plate-shaped and may 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 vaporization device 20 is introduced via the fuel evaporator line 17, which then mixes intensively in the mixing chamber 14 with the air flowing into the mixing chamber 14 from the idle air line 12, so that there is a decrease in the partial pressures of the individual fuel components and thus the vapor temperature of the fuel. The so with

Air mixed fuel vapor can advantageously only at a significantly lower temperature than in Recondense 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 individual 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. At the upper end 25 of the separator line 23, which is opposite the lower end 24, a line section 26, for example, runs horizontally

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 intake pipes 6 in order to upstream the inlet valves 3 from the

The fuel vaporization device 20, the mixing device 15 and the fuel separator 22 are supplied to the individual combustion chambers 2 of the internal combustion engine 1, and the fuel / air mixture is prepared and contains essentially only volatile fuel components. 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 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 Figure 1, the connection of the lines of the line system 27 or the introduction of the fuel-air mixture into the individual intake manifolds 6 takes place in relative proximity to the inlet valves 3 of the internal combustion engine 1. The line system 27 is branched, for example, such that only combustion chambers in each case 2 or cylinders, which are not in direct ignition order to one another, are connected in pairs to one another and jointly to 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. But it is also possible to operate the Fuel vaporization device 20 to be provided 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. Valve 35 is part of a fuel evaporation retention system for one

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 released by the latter via the valve 35 into the intake pipe 8. The valve 35, which is connected to the collecting tank 30 and the intake pipe 8 via a collecting line 36, is actuated in a clocked manner, for example when the fuel vaporization device 20 is switched off, in order to determine the condensate collected in the collecting tank 30 at certain times

To guide operating states of the internal combustion engine 1 with the aid of the negative pressure prevailing in the intake pipe 8 into the intake pipe 8 for subsequent combustion in the combustion chambers 2 of the internal combustion engine 1.

As in Figure 2, a second invention

Exemplary embodiment of the invention is shown, in which all Identical or equivalent parts with the same reference numerals of FIG. 1, it is also possible to use a pump device 40 instead of the valve 35 provided in FIG. 1 to discharge the condensate collected in the collecting container 30. The pump device 40 is connected via a pump line 41 to the collecting container 30 in order to feed the condensate received in the collecting container 30 back to a fuel tank 42 of the internal combustion engine 1 when the pump device 40 is operating. 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 diverting 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 diaphragm-shaped part 45 in such a way that it in particular on a wall surface 47 of the diaphragm-shaped part 45 facing the connecting line 18 for separating the liquid phase, non-volatile fuel components come from the fuel-air mixture. The most volatile

Fuel components 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 it is even at cold temperature, for example when starting the cold

Internal combustion engine 1, after which no recondensation of the fuel-air mixture on the cold walls of internal combustion engine 1, in particular on the walls of line system 27, can occur.

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 one prepared by the fuel vaporization device 20 arrives

Burn off steam first directly into the separator line 23 of the fuel separator 22, and then from

Fuel separator 22 to flow from 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 passes from the fuel evaporator line 17 into the mixing space 14 of the mixing device 15. After the mixing device 15 again a fuel-air mixture is present 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.

FIG. 3 discloses a third exemplary embodiment of the invention, in which all the same or equivalent parts are identified by the same reference numerals from FIGS. 1 and 2. FIG. 3 shows a fuel separator 22 and a mixing device 15, both in a common housing

51 are housed and form a structural unit 50 in a space-saving design. The housing 51 is composed, for example, of five parts, with 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 vaporization device 20 processes it

Fuel vapor flows into the unit 50. From the hole

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 projects into a part of the mixing space 14 and ends with

Distance in front of the opposite wall of the mixing chamber 14. Air is supplied to the fuel vapor in the mixing chamber 14 via an opening 54 which is further provided, for example circular, in the mixing chamber 14 and which is not shown in FIG

Idle air line 12 of the internal combustion engine 1 originates. The opening 54 opens into the mixing chamber 14 in such a way that the air flows into the mixing chamber 14 transversely to the direction of flow of the fuel vapor, that is to say transversely to the orifice piece 53 and not directed towards it, and through the cylindrical configuration the mixing chamber 14 is set in a swirl movement. 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 a diaphragm-shaped part 45, in order, as indicated by an arrow 59 shown in FIG. 3, to initially flow through the through hole 18 into the space 46 in a U-shaped fuel-air mixture to deflect downwards and then upwards again, so that the deflection leads to the elimination of the non-volatile fuel components from the fuel-air mixture. The low-volatility fuel components 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 greater 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 components downstream of the diaphragm-shaped part 45 from the space 46 of the

Fuel separator 22 is provided transversely to the collecting nozzle 62 on a second end part 64 of the housing 51, for example a substantially horizontally extending nozzle 66 located somewhat below the through hole 18. The support 66 represents the one according to FIGS and 2 provided line section 26, which serves to connect the unit 51 to the line system 27 of the internal combustion engine 1.

Claims

claims

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, the liquid fuel components from the

Fuel vaporization device (20) separates processed fuel vapor.

2. Internal combustion 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), into which air is introduced, which mixes with the fuel vapor prepared by the fuel evaporation device (20).

3. Internal combustion engine according to claim 1, characterized in that the to

Fuel evaporation device (20) connected fuel separator (22) is connected to a mixing device (15) which has a mixing space (14) into which air is introduced, which mixes with the fuel vapor prepared by the fuel separator (22) such that a fuel -Air mixture arises, 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, 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 (35) is provided for discharging the fuel components separated in the collecting container (30), which in an open position allows the outflow of the in the collecting container (30)

Releases fuel components in the intake device (8) of the internal combustion engine (1).

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.

11. Internal combustion engine according to claim 7, characterized in that a pump device (40) is provided for deriving the fuel components separated in the collecting container (30), which pumps the fuel components located in the collecting container (30) into 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).