DE19853357A1 - Cylinder head for internal combustion engine, has piston trough on curved wall part of which fuel stream arrives tangentially - Google Patents

Abstract

The cylinder head has an impact element or cylinder trough (6) with a curved wall part and/or piston head (11) on which the fuel jet or fuel (17) arrives at a tangent or along the surface. The wall part is spaced out from the central axis of the piston. Part of the piston head has a sector (13) at a tangent (12) to the surface.

Description

The invention relates to a cylinder head for an internal combustion engine, especially for one Otto engine, with at least one inlet duct, one Exhaust port, one associated with the cylinder head Direct injection device, one an arched Piston recess or an impact element Piston and an ignition device, at least the Central axis of the direct injection device or Main stream of the emerging fuel jet with reference is arranged inclined to the piston roof.

It is already a cylinder head at the beginning known type known (EP 0 558 072 A1), which already shows a piston for an internal combustion engine, which in a concave design on the piston surface Piston well shows an injector and an ignition device is assigned. This directly injecting gasoline engine works according to the so-called wall-guided or wall-distributing Combustion process. Here, the one from the Injector leaking fuel in one approximately right angles to those in the area of Combustion chamber wall lying on the central axis of the piston. The Evaporation of the fuel is caused by the supply of heat supported by the piston. The mixture cloud is over a directional charge movement transported to the spark plug, which are arranged concentrically to the central axis of the piston is. The charge movement is through the inside curved piston bowl and the approximately to the central axis of the  Piston parallel suction channels affected, so that the airflow is moved in one direction, the opposite of the usual direction of rotation of the Flow roller runs. The design of the Piston plate and the required Design of the intake ducts leads to a relative large overall height of the entire engine.

In contrast, the invention is based on the object the fuel jet entering the combustion chamber to align and the piston bowl in such a way to design that a good mixture preparation or Evaporation with a low tendency to deposit or Coking on the spark plug and on the nozzle opening of the Injector is achieved.

This object is achieved in that the piston bowl or (the impact element) a in Curved towards the central axis of the piston has a running wall part and / or a floor, to which the fuel jet or the fuel in strikes tangentially and / or is guided along and the wall part at a distance from the central axis of the Piston is arranged. Because of the advantageous Formation of the introduced into the piston surface, inwardly curved piston bowl or the Impact elements and the corresponding positioning the injector can from the Injector emerging fuel jet or the main stream of the fuel cloud tangential hit and along the piston recess to the spark plug be moved. The charge movement of the tangential incoming air moves along the edge of the Cylinder bore. The injected fuel forms  with the inflowing air an ignitable fuel Air mixture.

For this purpose, it is advantageous that the tangent applied to the first inwardly curved partial bottom section of the piston recess lying in the area of the direct injection device includes an angle of inclination α, α ₁ with the piston surface which is approximately the same size or slightly smaller than that between the central axis, of the ignition device and the piston surface formed inclination angle β, β ₁ . Due to the advantageous design of the piston bowl, in particular the first partial floor section of the piston bowl, the fuel jet emerging from the injection device or the main stream of the fuel cloud impinges tangentially on the first partial floor section or the associated curved wall part of the piston bowl and forms in a very short time with the likewise tangential inflowing air an ignitable fuel-air mixture. The angle of inclination between the longitudinal center axis of the ignition device or the emerging fuel jet can either be the same size or a little smaller than the angle of inclination between the surface of the first partial bottom section of the piston recess and the piston surface.

It is also advantageous that the from the Direct injector emerging fuel jet or fuel or the main stream of the fuel cloud roughly tangential at least to the curved wall part the piston bowl that is closest to the piston skirt lies, strikes and / or guided along this becomes. So that the fuel cloud also tangentially  Edge of the cylinder bore can move, it is advantageous that the curved wall part or the associated bottom of the piston bowl in the immediate vicinity of the piston skirt.

In a further embodiment of the invention, it is advantageous that the two opposite, with Distance from each other arranged wall parts of the crescent-shaped or kidney-shaped Piston recess that extends up to the piston surface extend and form with this edge, a have an average radius of curvature on which approximately the main flow of from the direct injector escaping fuel runs. Since the bottom of the Piston trough and the one adjoining the floor Wall part in approximately the same radius of curvature have, you get an optimal shape of the Piston bowl, in particular also in that a continuous transition between floor and wall part is feasible. It is also advantageous that the floor sections and the adjoining them Wall parts of the piston bowl roughly the same Have radius of curvature.

According to a preferred embodiment of the Finally, the solution according to the invention is provided that the first in the area of direct injection lying partial bottom section of the piston bowl with reference less slope on the piston surface has than that in the area of the ignition device lying second partial bottom section of the piston bowl. This ensures optimal transport of the fuel Air mixture from the piston bowl towards the Spark plug causes.  

It is also advantageous that the radius of curvature Piston bowl in the view from above approximately concentric to the vertical central axis of the piston is arranged and the same or larger Distance A to the central axis than to the piston skirt having.

In connection with the training according to the invention and arrangement of the piston, it is advantageous that the first partial bottom section of the piston bowl Inlet part for receiving the injected fuel and the second partial bottom section of the piston recess Is the outlet part of the fuel mixture, which Inlet part of the piston bowl at least partially below the outlet opening of an inlet channel or Inlet valve is.

It is also advantageous that the partial floor section or the outlet part of the bottom of the piston bowl is below the ignition device.

It is also advantageous that this is curved running impact element on the piston roof or is at least partially integrated in the piston roof its tangential pointing in the direction of the central axis channels or on an impact element, at least the Main stream of the fuel jet, approximately tangential hits.

To implement the process it is necessary to the inlet flow swirls about the central axis produce. Swirl channels are used to generate swirl, Channel shutdown or rotated valve star in  Consideration. The air can be in or opposite to Direction of flow of direct injection leaking fuel executes. So in Connection with the tangentially flowing air through the advantageous embodiment of the inlet channels optimal fuel-air mixture achieved that for Spark plug transported and ignited there. By the transport of the fuel-air mixture Spark plug can be provided there ignitable mixture be filled with air during the rest of the combustion chamber is.

It is also advantageous that at least one part the piston bowl extends above the piston roof and that at least part of the piston bowl is curved and another part forms a flat surface, which in the piston roof runs out and / or on the same level lies like the piston roof.

Further advantages and details of the invention are in the claims and explained in the description and shown in the figures. It shows:

Fig. 1 is a schematic view of the piston of a piston with a vaulted roof inwardly piston recess,

Fig. 2 shows a section of the upper part of the piston with a curved inwardly piston cavity along the line SS in FIG. 1,

Fig. 3 is a plan view of a cylinder head with shown in dashed lines piston recess with an inlet valve,

Fig. 4 is a sectional view of the piston taken along the line AA of Fig. 1,

Fig. 5 is a plan view of a cylinder head of another embodiment with two intake valves and one exhaust valve and a fuel injection and ignition device,

Fig. 6 is a plan view of the piston with an arched roof inwardly trough according to Fig. 7,

Fig. 7 is a sectional view of the upper part of the piston taken along the line AA in FIG. 6,

Fig. 13 is a partial section of the upper part of the piston with the piston cavity of an injection nozzle or injector and an almost upright spark plug in the region of the piston depression,

Fig. 9 shows a further embodiment of a crescent-shaped arrangement of the piston recess in plan view,

Fig. 10 is a partial section of the piston cavity with the injector and the spark plug extending inclined with respect to the piston roof taken along the line SS in FIG. 9,

Fig. 11 is a plan view of the cylinder head with two intake and two exhaust valves,

Fig. 12 is a sectional view of the piston taken along the line AA of FIG. 9,

Fig. 13 shows a further embodiment of a piston provided in the piston recess in section along the line AA of FIG. 14,

Fig. 14 is a plan view of FIG. 13,

Fig. 15 is a sectional view of the upper part of the piston taken along the line SS in Fig. 14,

Fig. 16 shows a further embodiment of a piston provided in the continuous, flat piston recess in section along the line AA of FIG. 17,

Fig. 17 is a plan view of FIG. 16,

FIG. 18 shows a sectional illustration of the upper part of the piston along the line SS according to FIG. 17.

In the drawing, a cylinder head 1 of a gasoline engine is schematically shown in Fig. 3, which is equipped with an intake valve 2 and an exhaust valve 3 . Below the inlet valve 2 there is a piston recess 6 , indicated in dashed lines, which is illustrated in more detail in FIGS. 1, 2 and 4. The inlet valve 2 and an outlet opening of the associated inlet channel, which is not shown in the drawing for the sake of simplicity, is located above the piston recess 6 . The cross-sectional area of the inlet valve covers a large area of the piston bowl 6 . The inlet channel or the associated outlet opening 24 with the inlet valve 2 , which is not shown in the drawings, can be arranged such that the largest part of the surface of the piston recess 6 according to FIG. 3 is covered by the outlet opening or the inlet valve 2 . It should be noted that the swirl is generated during the piston extraction stroke. The air flows tangentially into the cylinder space through appropriate design of the inlet channels. Instead of a charge movement, the axis of which is perpendicular to the cylinder axis (tumble), the charge movement can also be generated with an axis in the cylinder direction (swirl). By switching off the channel it is also possible to positively influence the mixture formation. As is apparent from FIGS. 1 and 2 of the first embodiment, there is a piston cavity 6 of two with spaced wall portions 16 and 19 which extend from a bottom 11 of the piston recess 6 to a piston surface and a piston top 15, while edges 20 and form 21 , which lie on an average radius of curvature 22 . The average radius of curvature 22 is arranged concentrically at a distance from the vertical central axis 23 of the cylinder head 1 , the distance A between the central axis 23 and the radius of curvature 22 depending on the exemplary embodiment being smaller, the same size or greater than the distance B between the radius of curvature 22 and a piston skirt 18 can be.

Referring to FIG. 1, the edge 21 extends the wall portion 16 in approximately parallel to the piston shell 18. However, it is also possible to choose a smaller or larger radius of curvature.

In Fig. 2 the piston recess 6 is shown in section along the line SS of FIG. 1. The base 11 likewise has a curved course, a first partial base section 13 being formed in the area of a direct injection device 4 or an injector, which is defined by a radius R ₁ and a second partial base section 14 in the area of an ignition device 8 by a radius R ₁ , R ₁ 'is defined. The radius R ₁ is significantly larger than the radius R ₂ , R ₂ '. The partial floor section 13 can also run on a straight line and continuously merge into a partial floor section 14 . A tangent 12 applied at R ₁ 'forms with the piston roof 15 an angle α, which in the exemplary embodiment according to FIG. 2 is smaller than the angle β between the piston roof 15 and a central axis 10 of the direct injection device 4 or an emerging fuel jet 17 , so that the fuel jet 17 emerging from the nozzle of direct injection strikes the piston recess 6 tangentially and is guided approximately tangentially along the bottom 11 and / or the wall parts 16 , 19 of the piston recess 6 in its main flow direction according to the arrow and with the charge movement (fuel cloud) which is also tangential can be imported, is transported. For example, it is advantageous if the channels are designed as swirl channels.

The much stronger, curved partial floor section 14 ends directly in the area and / or below the ignition device 8 . This partial floor section is determined by the radius R ₂ . However, it is also possible to design the partial floor sections 13 and 14 and the floor 11 so that they are defined by numerous increasingly curved partial floor sections.

The partial floor section 14 that runs into the piston roof 15 or a tangent 26 applied to the edge 21 of the partial floor section at R ₂ ′ forms an angle δ with the piston roof 15 that is greater than the angle α or α ₁ ′ between the piston roof 15 Tangent 12 at R ₁ 'or 12 at R ₁ . The angle σ between a central axis 9 of the ignition device 8 and the piston roof 15 is substantially larger than the angle δ between the tangent 26 and the piston roof 15 , so that the main stream 25 of the fuel cloud is transported in the direction of the spark plug of the ignition device 8 and there is an ignitable Fuel-air mixture forms.

In the embodiment according to FIGS. 5 to 8 is the cylinder head with an outlet valve 3 'and two intake valves 2, 2' is shown, with the piston cavity 6 also may extend substantially below the inlet valve 2 and the direct injector 4 in the area of the sub-bottom section 13 and the ignition device 8 is located in the region of the partial floor section 14 of the piston recess 6 . The course of the floor 11 corresponds approximately to the course of the floor according to FIG. 2, the last section of the partial floor section 14 , which merges into the piston roof 15 , being curved much more than the partial floor section 14 according to FIG. 2. A tangent 26 ′ forms in the area of the edge 21 with the piston roof an approximately right angle δ. As a result, the fuel-air mixture of the spark plug is supplied to the ignition device 8 in an optimal manner.

According to FIG. 6, as in the exemplary embodiment according to FIG. 3, the piston recess 6 is kidney-shaped or sickle-shaped in the view from above. The distance A between the vertical central axis 23 of a piston 5 and the mean radius of curvature 22 is approximately equal to the distance B between the piston skirt 18 and the mean radius of curvature 22 .

In the exemplary embodiment according to FIGS. 9 to 12, the cylinder head 1 is provided with two intake valves 2 , 2 'and two exhaust valves 3 , 3 '. In this example, the piston recess 6 , which is indicated in broken lines in FIG. 11, is arranged essentially below the inlet valve 2 and somewhat below the outlet valve 3 . According to FIG. 10, the shape of the bottom 11 of the piston recess 6 also corresponds to the shape of the bottom according to FIG. 2. The same also applies to the arrangement of the direct injection device 4 and the ignition device 8 .

In Fig. 12, the piston recess 6 in the section AA is shown in FIG. 9 size. In this exemplary embodiment, the piston recess 6 is designed to be substantially narrower, the angle μ 'between a tangent 27 and the piston roof 15 between 20 ° and 30 ° and the angle between a tangent 28 and the piston roof 15 approximately between 30 ° and 100 ° preferably Is 90 °. This results in very steeply rising wall parts 19 and 16 , each of which runs into the piston roof 15 . It can also be advantageous if the greatest width of the depression 6 is greater than or the same size as the greatest depth of the depression 6 .

According to a further exemplary embodiment according to FIGS. 13 to 15, instead of the inwardly curved piston recess 6, the piston roof 15 can also have an elevation 29 or a curved impact element, the wall element 16 of which is also curved in the direction of the vertical central axis 23 of the piston 5 , whereby the wall elements 19 , 16 can have a strong concave surface and thereby form an upstanding piston recess 6 . A part of the piston bowl is molded into the piston roof 15 , and another part of the piston bowl 6 protrudes as a wall part 16 on the piston roof 15 by the dimension C.

It is advantageous that in all of the exemplary embodiments the fuel jet 17 emerging from the direct injection device 4 or the fuel strikes the piston recess 6 approximately tangentially and with its main flow direction according to arrow 25 on the surface of the bottom 11 and the curved wall parts 16 adjoining it Piston recess 6 is guided along. It is advantageous that the outlet opening of the direct injection device 4 lies above the partial floor section 13 of the piston recess 6 or the inlet part of the piston recess 6 , while the ignition device 8 is provided in the region of the second partial floor section 14 or the outlet part of the piston recess 6 . Due to the required configuration of the piston recess 6 in connection with the direct injection device 4 and the ignition device 8 , the longitudinal movement of the fuel or the fuel cloud in connection with the tangentially flowing air (swirl movement) in the direction of the spark plug is favored, as already mentioned, in such a way that optimal mixture preparation (evaporation) results in low soot emissions, while at the same time the tendency for deposits (coking) on the spark plug or on the nozzle opening can be reduced to a minimum. The correspondingly arranged inlet channels or swirl channels allow the incoming air to rotate in the combustion chamber and, as mentioned, achieve a very good mixture preparation. The swirl can run counterclockwise or clockwise.

In Figs. 16 to 17 a further embodiment of a flat piston recess 6 is shown lying on the same plane in such as the piston top 15 of the piston 5. The flat piston bowl 6 has an edge 21 which is curved with respect to the vertical central axis 23 of the piston 5 and which lies in the region of the piston jacket 18 . Starting from this edge 21 , the base 11 of the piston recess 6 extends in the direction of the central axis 23 .

As in the example according to FIG. 13, the edge 21 lies above the piston roof 15 . The piston recess 6 begins in the region of the edge 21 and then gradually changes into an approximate straight line 30 or flat surface 30 ′ of the piston roof 15 . The surface 30 ′ can lie approximately on the same plane as the piston roof 15 .

The direct injection device 4 can be arranged, for example, in the direction of flow or opposite to the tangentially flowing air.

The edges 20 , 21 shown in FIGS. 6 to 17 do not lie on an arc, but form a curved line. However, it is also possible to form them in the form of a circular arc.

Claims (12)

1.Cylinder head for an internal combustion engine, in particular for a gasoline engine, with at least one intake port, one exhaust port, a direct injection device ( 4 ) assigned to the cylinder head, a piston ( 7 ) with an arched piston recess or an impact element ( 6 ) and an ignition device ( 8 ), at least the central axis ( 10 ) of the direct injection device ( 4 ) or the main stream of the emerging fuel jet being arranged inclined with respect to the piston roof, characterized in that (the impact element) the piston recess ( 6 ) or one in the direction of the The central axis ( 23 ) of the piston ( 7 ) has a curved wall part ( 16 ) and / or a base ( 11 ) on which the fuel jet or the fuel ( 17 ) strikes approximately / tangentially and / or is guided along and the wall part ( 16 ) is arranged at a distance from the central axis ( 23 ) of the piston. 2. Cylinder head according to claim 1, characterized in that the at the first inwardly curved, in the area of the direct injection device ( 4 ) lying bottom section ( 13 ) of the piston recess ( 6 ) applied tangent ( 12 , 12 ') with the piston surface ( 15 ) an inclination angle α, which is approximately the same size or slightly smaller than the inclination angle β, β ₁ formed between the central axis ( 9 ), the ignition device ( 8 ) and the piston surface ( 15 ). 3. Cylinder head according to claim 1, characterized in that the fuel jet or fuel ( 17 ) or the main stream of the fuel cloud emerging from the direct injection device ( 4 ) is approximately tangential at least on the curved wall part ( 16 ) of the piston recess ( 6 ), the is closest to the piston skirt ( 18 ), strikes and / or is guided along it. 4. Cylinder head according to claim 1 or 2, characterized in that the two opposite, spaced wall parts ( 16 , 19 ) of the crescent-shaped or kidney-shaped piston recess ( 6 ) which extend to the piston surface ( 15 ) and with this Form edges ( 20 , 21 ), have an average radius of curvature ( 22 ) on which the main flow of the fuel ( 17 ) emerging from the direct injection device ( 4 ) runs. 5. Cylinder head according to claim 1, characterized in that the first in the area of the direct injection device ( 4 ) lying partial bottom portion ( 13 ) of the piston bowl ( 6 ) with respect to the piston surface ( 15 ) has a lower inclination than that in the area of the ignition device ( 8 ) lying second partial floor section ( 13 ) of the piston recess ( 6 ). 6. Cylinder head according to one of the preceding claims, characterized in that the radius of curvature ( 22 ) of the piston recess ( 6 ) in the view from above is arranged approximately concentrically to the vertical central axis ( 23 ) of the piston ( 5 ) and an equal or greater distance A to the central axis ( 23 ) than to the piston skirt ( 18 ). 7. Cylinder head according to claim 1, characterized in that the first partial bottom section ( 13 ) of the piston recess ( 6 ) is the inlet part for receiving the injected fuel ( 17 ) and the second partial bottom section ( 14 ) of the piston recess ( 6 ) is the outlet part of the fuel mixture, wherein the inlet part of the piston recess ( 6 ) is at least partially below the outlet opening of an inlet channel or inlet valve ( 2 ). 8. Cylinder head according to claim 7, characterized in that the partial bottom section ( 14 ) or the outlet part of the bottom ( 11 ) of the piston recess ( 6 ) is below the ignition device ( 8 ). 9. Cylinder head according to claim 1, characterized in that the curved impact element ( 6 ) is integrated on the piston roof ( 15 ) or at least partially in the piston roof ( 15 ), on the wall element ( 16 ) pointing in the direction of the central axis ( 23 ). at least the main stream of the fuel jet ( 17 ) strikes approximately tangentially. 10. Cylinder head according to claim 1 and 9, characterized in that at least one inlet duct is designed as a swirl duct and the air emerging from the outlet opening ( 24 ) of the inlet duct has a swirl movement about the central axis ( 23 ) counterclockwise or in or opposite to the flow direction ( 25 ) of the fuel ( 17 ) emerging from the direct injection ( 4 ). 11. Cylinder head according to claim 1 and 9, characterized in that at least part of the piston recess ( 6 ) extends above the piston roof ( 15 ). 12. Cylinder head according to claim 1 and 9, characterized in that at least part of the piston recess ( 6 ) is curved and another part forms a flat surface ( 30 ') which runs out into the piston roof ( 15 ) and / or on the same Level lies like the piston roof ( 15 )