DE102005056521A1 - Internal combustion engine operating method for vehicle, involves temporizing preset time span between end of injection and beginning of ignition, until electrode is immersed into mixture region, and carrying out ignition out within region - Google Patents

Abstract

The The present invention relates to a method for operating a Internal combustion engine (20) with a fuel injection device (25) and a spark plug (26), the spark plug (26) projects into a combustion chamber (29), wherein during a compression tract the internal combustion engine fuel by means of the fuel injection device (27) is injected into the combustion chamber (29) and wherein the fuel is injected into such a way in the combustion chamber (29) that on a Piston (21) an ignitable, patty-shaped mixture area (28) of fuel and air, and between an end of fuel injection and a start of an ignition one is waited for a predetermined period of time, until an electrode area (27) the spark plug (26) in the flat-shaped Mixture area (28) dips, and then an ignition in the Interior of the flat-shaped Mixture area (28) takes place. Furthermore, the invention relates to a appropriately trained internal combustion engine.

Description

State of technology

The The present invention relates to an internal combustion engine for gasoline direct injection and a method for operating such an internal combustion engine.

Internal combustion engines for gasoline direct injection are different from the prior art Embodiments known. Such internal combustion engines are in recently, Time increases used as they lower fuel consumption at lower Have emissions. The known internal combustion engines have in common that they usually having an injection valve in a central position and a spark plug arranged so that it is attached to a spray rim of the combustion chamber Injected fuel lie. The ignition of essentially conical In this case, fuel that is propagating from the injection valve takes place at the edge of the cone, because only here an ignitable air-fuel mixture is present. In practice arise in the positioning of the spark location of the spark plug However, problems, this spark location precisely on the narrow edge zone in the field of ignitable Position fuel-air mixture. This is on the one hand on component tolerances of injector, spark plug and cylinder head and on the other hand also at the scatter of the spray geometry from cycle to cycle, so that the ignitable edge zone may vary to some extent. You can also use the spark plug cyclic scattering of the spark location within the electrode area occur as well as the spray geometry due to age due to deposits or dependent vary from the map of the internal combustion engine. These explained Factors lead on the one hand to a reduced efficiency and on the other hand also to problems with the exhaust gases.

Advantages of invention

The inventive method for operating an internal combustion engine with the features of the claim 1 shows in contrast the advantage that always a safe ignition can be guaranteed. Further can according to the invention an efficiency elevated which results in fuel savings and exhaust emissions be improved. This is inventively achieved in that fuel while a compression stroke of the internal combustion engine in a combustion chamber is injected. The fuel is doing so in the combustion chamber injected, that on the piston an ignitable, patty-shaped mixture area from fuel and air forms. The patty-shaped mixture region is located while on the piston bottom surface of the piston. According to the invention is doing between an end of the fuel injection and a start an ignition with a spark plug a predetermined period of time to wait for the formation of the patty-shaped mixture area to allow on the piston. The time span is chosen in this way until one in the combustion chamber protruding electrode area of the spark plug in the ignitable, patty-shaped mixture area dips in and then an ignition inside the flat-shaped Mixture occurs. According to the invention is thus no longer an ignition on the edge of an injected fuel cloud, but inside a patty-shaped mixture region located on the piston. there is waited for after the injection, until the patty-shaped mixture area on the piston, which is during the compression phase counter to the spray direction of the fuel moved, formed. When the fuel injected into the combustion chamber is injected in the form of a jet, which with increasing Penetration depth evaporated into the combustion chamber, resulting in the jet, in particular in the area of the spray tip, an ignitable shell a gaseous one Fuel-air mixture, which lays like a ruff around a beam center. These gaseous Sheath points essentially the shape of a drop. Because the piston moves against the thus injected fuel, directs the piston the fuel air mixture horizontally to all sides which leads to a further, turbulence-related mixing. Thereby is on the piston head of the ignitable, patty-shaped mixture area according to the invention educated. Thus, during the period after injection and before ignition of the mixture area according to the invention formed on the piston. The patty-shaped mixture region is included from a non-flammable gas mixture, especially air, surrounded. The piston continues to rise in the direction of the spark plug moved, with an ignition only then takes place when the electrode area of the spark plug immersed in the mixture area. Because the spark plasma thus is generated inside the mixture area, a reliable ignition can be made possible. Furthermore, starting from the spark plasma, the flame paths are up to Edge of the mixture range significantly shorter than in comparison with a Ignition point at one edge, so that further achieves faster combustion becomes.

The under claims show preferred developments of the invention.

The injection of the fuel is preferably carried out by a plurality of individual jets, which is generated by means of a multi-hole valve with a number of holes preferably between 7 and 14, or by means of an outwardly opening annular gap valve (A-valve) with an opening angle α between 70 ° ≤ α ≤ 110 °.

preferably, is the time between the end of the fuel injection and the beginning of the ignition chosen so that they a crank angle between 5 ° and 15 °, in particular between 5 ° and 10 ° and especially preferably 7.5 ° corresponds.

Around a faster and safer formation of the patty-shaped mixture region to enable is preferably provided in the piston head a trough in which itself the patenförmig Mixture area forms. The trough is preferably circular and formed symmetrically.

Especially it is preferred to close to or at a central region of the patty-shaped mixture region ignited as possible to have short flame paths through the entire mixture area.

Further Preferably, a projecting nose is formed on the piston head, above which itself the patenförmig Mixture area sets in the patty-shaped mixture area a substantially in the axial direction of the piston projecting area to build. The spark plug immersed in the preceding subsection of the mixture range and then there is an ignition of the flat-shaped Mixture range starting from the above range. Thereby can be achieved that the beginning of the ignition of the patty-shaped mixture area still in the movement section in the direction of top dead center of the piston, so that exactly at top dead center as possible full Ignition of patty-shaped Mixture occurs and then the expansion stroke takes place. Around a positioning of the injector as centrally as possible in the cylinder head To realize, the projecting nose is preferably on one edge the trough arranged on the piston crown.

Preferably the fuel injection takes place in several consecutive Intervals. This ensures that a higher proportion of air in the patty-shaped mixture area exists since between each interval of fuel injection each a small air cushion is located.

Around to achieve a faster formation of the patty-shaped mixture region, A fuel injection is preferably carried out on the piston bottom protruding nose.

The inventive method is preferably in a shift operation of the internal combustion engine applied. Shift operation is understood to mean a mode of operation, to bear in the case of the internal combustion engine only small loads. In shifts while a combustion in the combustion chamber is essentially only by set the injected fuel mass, with a throttle usually wide open is.

Further According to the invention, an internal combustion engine proposed for the direct injection of fuel into a combustion chamber, which is a spark plug, a piston and a fuel injector. Further the internal combustion engine comprises a control device to a ignition timing the spark plug to determine. The controller ignites the spark plug only when the Fuel injection process is completed and reflected on the piston an ignitable patty-shaped mixture area has formed, wherein the electrodes of the spark plug for ignition in the patty-shaped mixture area have to protrude. In other words, passes between the end of the fuel injection process and the beginning of the ignition a predetermined period of time, on the one hand, the formation of the patty-shaped mixture region to enable and on the other hand only then to make an ignition when the Electrodes of the spark plug in the flat-shaped Protrude mixture area. This will ensure that the Mixture area is ignited in its interior, leaving the flame paths are very short.

The Control device determines the ignition timing preferably in dependence from a piston position. The position of the piston can preferably determined by a crank angle by means of a sensor.

Around the formation of the ignitable, patty-shaped mixture area to support, The piston preferably has a piston bottom surface essentially circular Mulde up. The trough is preferably symmetrical to a piston central axis.

Further Preferably, the piston has a projecting nose on the piston bottom surface. The nose may preferably be provided in a circular trough or it is provided at the edge of the hollow. By the above Nose in the area of the trough can be made sure of that the flat-shaped Mixture range also over forms the nose, leaving an area of the mixture area in the direction of movement protrudes the piston. In this case, the spark plug is then preferably such arranged that their electrodes in the projecting area of the Mixture area protrude. As a result, for example, an ignition before the top dead center of the piston can be realized, the ignition anyway safely inside the mixture area.

According to a further preferred embodiment of the invention, the at the piston head surface formed trough an inclined to the central axis of the piston at an angle base. This makes it possible to arrange the spark plug centrally in the cylinder head and still allow a vertical fuel injection to the piston crown.

The Fuel injector is preferably a multi-hole valve with a number of holes between 7 and 14 or an outwardly opening annular gap valve (A-valve), preferably with an opening angle between 70 ° and 110 °.

drawing

following become preferred embodiments the invention with reference to the accompanying drawings in Detail described. In the drawing is:

1 a schematic sectional view of an internal combustion engine according to a first embodiment of the invention,

2a and 2 B schematic representations of the injection of fuel by means of a multi-hole valve,

3 a schematic representation of a spray cloud of an outwardly opening annular gap valve (A-valve),

4a and 4b schematic views of an injection by means of a multi-hole valve according to a further embodiment of the invention,

5 and 6 schematic sectional views of an internal combustion engine according to a second embodiment of the invention,

7 and 8th schematic sectional views of an internal combustion engine according to a third embodiment of the present invention,

9 and 10 schematic sectional views of an internal combustion engine according to a fourth embodiment of the present invention and

11 a schematic sectional view of an internal combustion engine according to a fifth embodiment of the present invention.

description the embodiments

The following is with reference to the 1 and 2 an internal combustion engine 20 described according to a first embodiment of the invention.

As in 1 shown, includes the internal combustion engine 20 a piston 21 with a piston bottom 22 in which a circular trough 23 centrally and symmetrically to a central axis XX of the piston 21 is arranged. The piston 21 moves in a known manner in a cylinder, wherein in a cylinder head 24 an injection device 25 and a spark plug 26 are arranged. The injector 25 is centered in the cylinder head on the center axis XX of the piston 21 arranged and is in this embodiment, a multi-hole valve with ten holes. The arrangement of the holes is out 2a seen. The spark plug 26 is a conventional spark plug and points to its in a combustion chamber 29 protruding end electrodes 27 on.

From the 2a and 2 B is the injection of fuel into the combustion chamber 29 clear. The with the reference numerals 1 to 10 designated individual jets of the injector 25 be in the direction of the oncoming piston 21 in the combustion chamber 29 injected. This results in increasing penetration depth of each individual jet increasing evaporation, so that each injection jet 1 to 10 In particular in the area of the spray syringe of the injected fuel, an envelope of a gaseous fuel air mixture is generated. This is in 2 B with the big circles around every single ray 1 to 10 indicated. The gaseous Krafstoff-Luftgemischhülle puts similar to a ruff around the beam and the tip of the jet is formed by a gaseous fuel-air mixture. How out 2 B can be seen, the fuel-air mixture sheaths of the individual jets are partially overlapped due to turbulence and, because the piston 21 moved against the jet direction and deflects the fuel-air mixture envelope horizontally. This forms an ignitable, patty-shaped mixture area 28 on the piston bottom 22 , The formation of the patty-shaped mixture region 28 is through the intended trough 23 in the piston bottom 22 even stronger. The patty-shaped mixture area 28 has a circular shape with a thickness which decreases, starting from a center in the direction of the outer edge something. The mixture region is a substantially homogeneous gaseous fuel-air mixture having an average lambda between 0.8 and 1.5.

According to the injection of fuel takes place at a crank angle of about 35 ° before top dead center TDC. The holes of the multi-hole valve are to be designed so that each individual jet has a possible bushy shape. For this purpose, a hole diameter of a single hole is preferably between about 130 microns and 200 microns. More preferably, tapered, in particular conical, outwardly opening holes or stepped holes favor a bushy one Spray form with the desired fuel-air mixture gas hoses. As in 2a shown, the beam axes of the holes of the multi-hole valve are chosen such that they have approximately the same space angle distance.

It should be noted that, depending on a distance to be covered by a single jet to the piston crown 22 the hole diameter of the individual holes may be different. Inner rays, at the in 1 shown central arrangement of the injector have the shortest path to the piston, thereby can have a smaller hole diameter, as the circumferentially arranged holes. Due to the smaller holes, the amount of fuel passed therethrough and thus the spray impulse becomes lower, so that even the inner rays are safely vaporized before they reach the piston crown 22 to reach. The choice of hole diameter and opening angle of the spray holes and the number of holes is to be chosen so that the injected fuel is just evaporated when he the piston crown 22 reached. This allows the oppositely moving piston 21 provide a particularly good mixing and homogenization of the ignitable mixture range.

The formation of the mixture range 28 takes place in a range between 35 ° before top dead center and about 20 ° before top dead center. 1 shows the position about 20 ° before top dead center, in which the mixture area 28 homogeneous at the piston bottom 22 in the hollow 23 has formed. Ignition by means of the spark plug 26 However, it does not take place until the electrodes 27 into the interior of the mixture area 28 pass. This is at a piston position of about 20 ° before top dead center, as in 1 shown reached.

A control device 34 controls the spark timing of the spark plug 26 depending on the position of the piston 21 , Preferably, the ignition point is at a crank angle of about 20 ° before top dead center. This can ensure that the mixture area 28 is completely ignited at top dead center and a high efficiency of the internal combustion engine 20 is reached. A period of time between an end of the fuel injection and the start of ignition corresponds to a distance traveled by the piston 21 over a crank angle between 5 ° to 10 °, preferably 7.5 °.

By the ignition inside the mixture area 28 are the flame paths through the mixture area 28 significantly reduced in comparison with an ignition at the edge. As a result, on the one hand faster and more complete combustion can be achieved. Furthermore, this results in a particularly stable combustion process, in particular during stratified operation of the internal combustion engine 20 reached. The patty-shaped mixture area 28 results according to the invention thereby by the interaction of the injecting fuel and the piston 21 wherein there is a certain amount of time between the end of the injection and the start of ignition to allow formation of the mixture region and ignition of the mixture region 28 to perform in its interior. Furthermore, due to the internal ignition, the deviations occurring due to tolerances in the components can not lead to uneven combustion. Also, variations in spray geometry from cycle to cycle or scattering of a spark location within the electrode area of the spark plug 26 or map-dependent fluctuations of the spray geometry have no influence on the method according to the invention.

3 shows an alternative embodiment of an injection device 25 in the form of an outwardly opening annular gap valve (A-valve). The annular gap valve shown injects the fuel cone-shaped, so that at the in 3 sectional view shown an annular fuel area 30 results. On both sides of the fuel area 30 each forms a shell 31 and 32 from a fuel-air mixture. An opening angle of the annular gap valve of 3 is preferably between 70 ° and 110 °. The injection by means of the annular gap valve also becomes a homogeneous, patty-like mixture region 28 as in 1 generated on the piston, wherein the piston deflects the impinging fuel-air-gas mixture horizontally both inwardly and outwardly.

The 4a and 4b show a further embodiment of an injection device 25 , which is also designed as a multi-hole valve. This points in the 4a and 4b shown multi-hole valve twelve injection holes 1 to 12 on. The injection holes are distributed on two concentric circles and arranged on the circles offset from one another. This results in the 4b shown spray distribution around the individual beams. The circles again represent the gaseous mixture envelopes. Otherwise, this embodiment corresponds to the first embodiment, so that reference can be made to the description given there.

In the 5 and 6 is an internal combustion engine 20 according to a second embodiment of the invention, wherein identical or functionally identical parts are designated by the same reference numerals. In contrast to the first embodiment is in the internal combustion engine 20 of the second embodiment, the spark plug 26 centrally located on the central axis XX. The injector 25 is the side of the spark plug 26 and arranged at an angle α to the central axis. The injector 25 is again a multi-hole valve, with in 5 schematically three injection jets with a still liquid fuel jet 35 and a forming gaseous shell 36 are shown from a fuel-air mixture. If the individual rays on the piston crown 22 they are completely evaporated, so that only a gaseous fuel-air mixture impinges on the piston crown. As further out 5 It can be seen in the bottom of the piston 22 formed hollow 23 in addition, a protruding nose 37 educated. The protruding nose 37 is central in the hollow 23 arranged on the central axis XX and has substantially the shape of a spherical section. The injection of fuel takes place exactly in the direction of the protruding nose 37 , As in 5 shown, the piston position at the beginning of the injection is about 35 ° before top dead center. When the fuel injection is completed, the piston moves 21 continue towards the spark plug 26 to, which is then due to the deflection at the piston bottom of the homogeneous, ignitable mixture area 28 forms (cf. 6 ). Here is the mixture range 28 also over the prominent nose 37 formed, so that, as in 6 shown the electrodes 27 the spark plug 26 at a piston position of about 20 ° before top dead center into the interior of the mixture area 28 extend. In the 6 shown position of the piston shows the position in which an ignition of the mixture area 28 he follows. As in this embodiment, the spark plug 26 is centrally located on the central axis XX and the center axis XX also has an axis of symmetry for the mixture area 28 is, the flame paths are from the electrodes to the edges of the mixture area 28 particularly short in this embodiment. As a result, a particularly fast and complete combustion can be achieved.

The 7 and 8th show an internal combustion engine 20 according to a third embodiment of the invention, again and functionally identical parts are denoted by the same reference numerals as in the previous embodiment. The internal combustion engine 20 of the third embodiment substantially corresponds to that of the second embodiment, but with the protruding nose 37 in the third embodiment at an edge of the trough 23 is arranged. This allows the injector 25 centrally on the central axis XX of the piston 21 be arranged and the spark plug 26 becomes so in the cylinder head 24 arranged them over the protruding nose 37 is positioned. This lays the nose 37 and the spark plug 26 essentially on a common, to the central axis XX- parallel axis YY. The injection of fuel takes place directly in the piston in the bottom 22 formed hollow 23 , In cooperation with the Mulde 23 and the movement of the piston opposite to the direction of irradiation 21 becomes after the end of the injection and before the ignition again the mixture range 28 in the hollow 23 formed, the mixture area 28 a prominent area 28a in the area of the prominent nose 27 has (see. 8th ). In a position about 20 ° before top dead center, in 8th is shown, the electrodes dip 27 in the above range 28a of the mixture range 28 a, so that then an ignition of the mixture area 28 can be done. As a result, it is also possible that in comparison with the first embodiment, an earlier ignition of the mixture area 28 allows, as the spark plug in the above range 28a of the mixture range 28 protrudes and thus earlier inside the mixture area 28 located. The central arrangement of the fuel injector also has the advantage of ensuring that no fuel wets the electrodes of the spark plug during the injection of fuel. This ensures a reliable ignition. Otherwise, this embodiment corresponds to the previous embodiments, so that reference can be made to the description given there.

In the 9 and 10 is an internal combustion engine 20 according to a fourth embodiment of the invention, again with identical or functionally identical parts are denoted by the same reference numerals as in the preceding embodiments. The fourth embodiment substantially corresponds to the second embodiment, wherein in the trough 23 in the piston bottom 22 also in the middle a protruding nose 37 is formed. The spark plug 26 is again central to the central axis XX of the piston 21 arranged and the injector 25 at an angle α. In contrast to the second embodiment, however, the piston crown is arranged in the region of the trough inclined to a plane E perpendicular to the central axis XX. The inclination is in the 9 and 10 characterized by the angle β. The slope of the trough 23 is preferably chosen such that a central central injection jet is injected substantially perpendicular to the inclined trough surface. The central injection jet hits in particular on the protruding nose 37 , resulting in a faster formation of the patty-shaped mixture area 28 leads. Like from the 9 and 10 it can be seen, is the spark plug 26 again over the protruding nose 37 arranged so that they are at a position of about 20 ° before top dead center (see. 10 ) in a projecting area 28a of the mixture range 28 lies. Otherwise, this embodiment corresponds to the previous embodiments, so that reference can be made to the description given there.

11 shows a fifth embodiment of an internal combustion engine according to the invention, again with the same or functionally identical parts with are denoted by the same reference numerals as in the preceding embodiments. The fifth embodiment corresponds essentially to the second embodiment, wherein, in contrast to the second embodiment, both the injector 25 as well as the spark plug 26 are arranged at an angle γ and δ to a central axis XX. The inclination angle γ, δ of the injector 25 and the spark plug 26 are the same and differ only by the sign. A protruding nose 37 in the hollow 23 in the piston bottom 22 is again below the spark plug 26 arranged so that there is an asymmetric formation of the trough. The patty-shaped mixture area 28 Forms again with a prominent area 28a over the protruding nose 37 , so in this previous section 28a an ignition of the mixture area 28 he follows. Otherwise, this embodiment corresponds to the previous embodiment, so that reference can be made to the description given there.

It should be noted that, of course, a multiple injection can also be performed in all illustrated embodiments. This has the particular advantage that the mixture area 28 layered, wherein between two fuel-air mixture layers each have a thin layer of air is present. This allows the proportion of air in the mixture area 28 be enlarged.

Another advantage of the method according to the invention in all described embodiments is that for generating the mixture area 28 Injectors can be used, which produce symmetrical spray geometries (without a spray gap for the spark plug). This also eliminates an assignment of the injector to the spark plug. In addition, there is no wetting of the spark plug with liquid fuel, which in particular can reduce the ignitability.

A inventive internal combustion engine can used both in vehicles and stationary.

Claims (18)

Method for operating an internal combustion engine ( 20 ) with a fuel injection device ( 25 ) and a spark plug ( 26 ), the spark plug ( 26 ) in a combustion chamber ( 29 protruding during a compression tract of the internal combustion engine fuel by means of the fuel injection device ( 27 ) in the combustion chamber ( 29 ) is injected, and wherein the fuel into the combustion chamber ( 29 ) is injected on a piston ( 21 ) an ignitable, patty-shaped mixture region ( 28 ) is formed of fuel and air, and is waited between an end of the fuel injection and a start of ignition for a predetermined period of time until an electrode area ( 27 ) of the spark plug ( 26 ) into the patty-shaped mixture region ( 28 ) and then only an ignition inside the patty-shaped mixture area ( 28 ) he follows. A method according to claim 1, characterized in that the injection of the fuel by means of a multi-hole valve with a plurality of injection holes ( 1 - 12 ) or by means of an outwardly opening annular gap valve. Method according to one of the preceding claims, characterized in that the time period between the end of the fuel injection and the start of the ignition corresponds to a time in which the piston ( 21 ) over a crank angle of 5 ° to 15 °, in particular from 5 ° to 10 °, in particular 7.5 °, moves. Method according to one of the preceding claims, characterized in that in the piston head ( 22 ) of the piston ( 21 ) a trough ( 23 ) is formed and the patty-shaped mixture area ( 28 ) in the hollow ( 23 ). Method according to one of the preceding claims, characterized in that the mixture region ( 28 ) is fired as close to or in its center as possible. Method according to one of the preceding claims, characterized in that on the piston ( 21 ) a projecting nose ( 37 ) is formed in the patty-shaped mixture region ( 28 ) an axially projecting area ( 28a ) to build. A method according to claim 6, characterized in that ignition of the mixture area ( 28 ) in the previous section ( 28a ) he follows. Method according to one of the preceding claims, characterized characterized in that the fuel injection in several intervals and / or with multiple injectors. Method according to one of claims 6 to 8, characterized in that the fuel injection in the direction of the projecting nose ( 37 ) in the piston head ( 22 ) he follows. Method according to one of the preceding claims, characterized characterized in that the method is carried out in the stratified operation of the internal combustion engine. Internal combustion engine for direct injection of gasoline, comprising a spark plug ( 26 ), a piston ( 21 ), a fuel injection device ( 25 ), the fuel in a combustion chamber ( 29 ) is injected at a compression stroke in such a way that an ignitable, patty-shaped mixture region ( 28 ) on the piston ( 21 ) and a control device ( 34 ) to an ignition point of the spark plug ( 26 ), the control device ( 34 ) determines the ignition timing such that the spark plug ( 26 ) an ignition signal is transmitted only when an electrode area ( 27 ) of the spark plug ( 26 ) inside the mixture area ( 28 ) is located. Internal combustion engine according to claim 11, characterized in that the control device ( 34 ) determines the ignition timing in dependence on a piston position. Internal combustion engine according to claim 12, characterized in that that the piston position can be determined by determining a crank angle is. Internal combustion engine according to one of claims 11 to 13, characterized in that the piston ( 21 ) at the piston bottom surface ( 22 ) has a substantially circular trough. Internal combustion engine according to one of claims 11 to 14, characterized in that the piston on the piston bottom surface ( 22 ) a projecting nose ( 37 ) having. Internal combustion engine according to claim 15, characterized in that the projecting nose ( 37 ) and the electrode area ( 27 ) of the spark plug ( 26 ) are arranged on a common axis, wherein the common axis parallel to a central axis (XX) of the piston ( 21 ). Internal combustion engine according to one of claims 14 to 16, characterized in that the trough ( 23 ) one to the central axis (XX) of the piston ( 21 ) at an angle (β) inclined base surface. Internal combustion engine according to any one of claims 15 to 17, characterized in that the projecting nose on an edge of the trough ( 23 ) or in the middle of the trough ( 23 ) is arranged.