WO2015154853A1

WO2015154853A1 - Piston for an internal combustion engine

Info

Publication number: WO2015154853A1
Application number: PCT/EP2015/000636
Authority: WO
Inventors: Sebastian Wustl; Björn Schade
Original assignee: Mtu Friedrichshafen Gmbh
Priority date: 2014-04-08
Filing date: 2015-03-25
Publication date: 2015-10-15
Also published as: DE102014005138A1

Abstract

The invention relates to a piston (1) for an internal combustion engine, in particular a diesel engine, having a piston outer diameter (D1) and a piston head (2) which has a cavity (3) having a W-shaped inner cavity area (4) and a toroidal shape in an outer cavity area (5).

Description

MTU Friedrichshafen GmbH

DESCRIPTION Piston for an internal combustion engine

According to the invention, a piston for an internal combustion engine, in particular a

A diesel engine having a piston outer diameter and a piston crown having a trough forming a W-shape in an inner trough region and an outer T-shape in an inner trough region

Muldenbereich a Torusforai has proposed. As a result, a mixture which is introduced into a combustion chamber delimited by the piston crown can be processed particularly well, as a result of which combustion can be improved, in particular in a diesel engine. In particular, in conjunction with charge exchange effects can be achieved that the

Combustion, which emanates from an injection nozzle of the internal combustion engine, is advantageously distributed by the inner trough region, whereby a particularly uniform combustion can be achieved even at low injection pressures. A particular advantage lies in a good transient behavior, by which, in particular during abrupt fuel injections, i. with an increase in the injection pressure at a relative lack of air, soot formation can be improved. A blackening to Bosch can be kept well below 1. In addition, the improved combustion can reduce NOx and particulate emissions. Overall, therefore, by an embodiment of the invention a

Internal combustion engine to be optimized in terms of their operating parameters. A "trough" is to be understood in particular as meaning that the piston head has a surface which forms a depression with respect to the plane which is spanned by the outer diameter of the piston in which the surface has a convex curvature in an inner partial region and a concave curvature in a partial region surrounding the inner partial region. In addition, in the W-shape, a third portion

can be provided, in which the surface has a convex curvature and forms a transition to the outer trough region. In this case, the surface of the piston crown has a smaller depth in the middle subregion than in the surrounding subregion. A "torus fore" is to be understood in particular as meaning that the surface in the trough region has only a concave curvature, in which case a "convex" curvature is understood in particular to mean that the surface is in relation to the plane is spanned by the piston outer diameter, is convexly curved. Accordingly, a "concave" curvature should be understood to mean, in particular, that the surface is concavely curved with respect to the plane defined by the piston outer diameter, in particular, a convex curvature has a center for defining a radius of curvature above the surface of the piston crown. In a concave curvature is correspondingly a center for determining a radius of curvature below the

Surface of the piston crown. A plane which is spanned by the outer diameter of the piston should be understood to mean, in particular, a plane which is stretched out by an outer edge of the piston crown. "Provided" is to be understood in particular to be specially designed and / or equipped.

It is further proposed that the piston crown has a web surrounding the depression. This can further improve the combustion. A "web" is to be understood here in particular as a depression region in which the surface of the piston crown lies in the plane defined by the piston diameter, in particular by a depression region of the surface in which the surface runs perpendicular to an axis of symmetry of the piston crown. An "axis of symmetry" should be understood to mean, in particular, an axis which forms a central axis for the piston diameter. The piston is provided for movement along the axis of symmetry.

Preferably, the web has an inner diameter, based on the

Piston outer diameter has a factor between 1, 0 and 1, 4. The term "between" should be understood here and below as meaning, in particular, a subarea which includes the abovementioned limits with the specified accuracy. "A value" to which the outer diameter of the piston has the stated factor "should be understood in particular to mean that Piston outer diameter is larger by the factor mentioned, as the value to which the factor relates. A "factor of 1, 0" is to be understood in particular as meaning that the outer diameter of the piston corresponds to the inner diameter of the web

Piston outer diameter. Only the outer edge of the piston crown lies in the plane which is spanned by the outer diameter.

In an advantageous embodiment, the outer trough region has an outer diameter to which the outer diameter of the piston has a factor between 1, 0 and 1, 4. In this case, a transition region can be provided between the outer trough region and the web, in which the surface is convexly curved in order to realize an edge-free transition between the web and the outer trough region. Alternatively, the transition area can also be dispensed with.

In addition, it is advantageous if the outer trough region has a maximum angle, which is in a vertical between 25 degrees and 35 degrees. Under an "angle in one

Vertical "is to be understood in particular as meaning an angle which the symmetry axis and a surface tangent of the piston crown enclose." An angle in a horizontal "is to be understood in particular as meaning an angle perpendicular to the symmetry axis and a surface tangent of the piston crown. In this case, a "maximum angle" is to be understood as meaning, in particular, the angle at a point at which the surface has its maximum gradient, whereby the angle at which the plane is perpendicular to the axis of symmetry and the surface tangent of the piston crown at this point are to be understood, the slope corresponding to the angle of the surface in the vertical at that point.

Preferably, the outer trough region has a maximum depth which is between 5 mm and 10 mm. A "depth" is to be understood in particular as meaning a distance between the plane spanned by the piston outer diameter and a point on the surface along a direction which is oriented parallel to the axis of symmetry The plane spanned by the outer diameter has preferably a height of 0 mm.

Moreover, it is advantageous if the outer trough region has an inner diameter to which the outer diameter of the piston has a factor between 1, 2 and 2. An "inner diameter of the outer depression region" is intended in particular to mean a

Diameter are understood that limits the defined by its convex curvature outer trough portion relative to the axis of symmetry radially inward.

In addition, it is proposed that the piston head has a transition angle between the inner trough portion and the outer trough portion, which is in a horizontal between 0 degrees and 10 degrees. Under a transition angle is intended in particular Angle at a point at which the convex curvature of the outer trough portion in a concave curvature as a transition into the inner trough area passes over.

It is further proposed that the inner trough region has a turning point diameter, to which the outer diameter of the piston has a factor between 3 and 6. A turning point diameter is to be understood as meaning, in particular, a defined diameter through the inflection point which separates the inner subregion and the subregion of the depression region surrounding the inner subregion. In addition, it is advantageous if the inner trough region has a maximum depth which is between 10 mm and 20 mm. A "maximum depth" is to be understood in particular as meaning a depth in the concavely curved partial area which surrounds the inner partial area

Horizontal is between 20 degrees and 30 degrees. In particular, an angle which a surface tangent with the plane perpendicular to the axis of symmetry encloses in the inflection point, which encloses the inner subregion and the subregion surrounding the inner subregion, is to be understood by a "inflection point angle".

In addition, it is proposed that the inner trough portion has a central depth which is between 4 mm and 9 mm. In this context, a "central depth" should be understood to mean, in particular, a depth in a middle of the inner subarea Further, an internal combustion engine with at least one piston according to the invention is proposed, whereby an internal combustion engine with optimized operating parameters can be provided.

Further advantages will become apparent from the following description of the figures. In the figures, an embodiment of the invention is shown. The figures, the description of the figures and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations. Fig. 1 shows schematically an internal combustion engine with a plurality of cylinders.

Fig. 2. shows a piston of the internal combustion engine in a cross section.

1 shows an internal combustion engine having a plurality of cylinders 7, 8, 9, 10, which in each case have a combustion chamber 11, 12, 13, 14 and a piston 1, 15, 16, 17 guided in the corresponding combustion chamber 11, 12, 13, 14 exhibit. The internal combustion engine is designed as a diesel engine, i. an ignitable mixture of air and fuel present in the cylinders 7, 8, 9, 10 spontaneously ignites upon compression. The respective pistons 1, 15, 16, 17 and the corresponding combustion chamber 11, 12, 13, 14 delimit a combustion chamber in which, depending on a mixture distribution, the ignition of the mixture gradually spreads. In a typical mixture distribution, the mixture burns in particular along a combustion jet, which extends starting from a cylinder head side in the direction of the piston 1, 15, 16, 17 centered within the corresponding combustion chamber 11, 12, 13, 14. Fig. 2 shows the piston 1 in a cross section. The remaining pistons 15, 16, 17 are formed equivalent. For deflecting this combustion jet, the piston 1 has a piston head 2, which has a trough 3. The piston 1 has a piston outer diameter Dj, which is defined by an outer edge 18 of the piston 1. The edge 18 spans a plane on which, relative to the piston head 2, the trough 3 forms in its center. The edge 18 is circular. With respect to the edge 18 is thus an axis of symmetry 19th

definable, which in the following forms a reference axis for the description of the piston crown 2. With respect to the axis of symmetry 19, the piston head 2 is rotationally symmetrical. The symmetry axis 19 extends in the vertical direction. In one operation, the piston 1 is displaced along the symmetry axis 19. In this case, the combustion chamber 11 has a running surface 20 provided for guiding the piston 1, which is likewise rotationally symmetrical with respect to the axis of symmetry 19.

The trough 3 is formed by a superposition of two basic shapes. The trough 3 itself has an inner trough region 4, in which the trough 3 has a W-shape, and an outer trough region 5, in which the trough 3 has a toroidal shape. The piston crown 2 has a surface whose geometric configuration in the inner depression region 4 and the outer depression region 5 are each rotationally symmetrical with respect to the

Symmetry axis 19 is. The outer trough region 5 completely surrounds the inner trough region 4. In addition, in the exemplary embodiment illustrated, the piston head 2 has a web 6 surrounding the depression 3. The web 6 has a surface perpendicular to the

Symmetry axis 19 is oriented. In a region in which the piston head 2 has the web 6, the piston head 2 is almost flat. In this area, the piston head 2 has an average curvature which is zero.

The web 6 has an outer diameter which corresponds to the piston outer diameter Di. Based on the piston outer diameter Di, the web 6 has an inner diameter D ₂ , to which the piston outer diameter Di has a factor between 1, 0 and 1.4. On the web 6 can therefore be dispensed basically.

Based on the piston outer diameter Di, the outer trough region 5 has a

Outside diameter D ₃ , to which the piston outer diameter Di also has a factor between 1.0 and 1.4. In the illustrated embodiment, the

Inner diameter D _{2 of} the web 6 about a factor of 1.03 larger than that

Outer diameter D _{3 of} the outer trough region 5. Between the web 6 and the outer trough region 5, the piston head 2 has a transition region 21, in which the

Surface of the web 6 steadily, ie edge-free, merges into the outer trough area 5. The inner diameter D _{2 of} the web 6 is 118 mm. The outer diameter D _{3 of} the outer trough portion 5 is 115 mm.

The inner diameter D _{2 of} the web 6 is defined as a diameter at which the web 6 merges into the trough 3. In the inner diameter D _{2 of} the web 6, the surface of the

Piston bottom 2, starting from the piston outer diameter Di, for the first time a convex curvature. The transition region 21 is completely convexly curved. By doing

illustrated embodiment, the transition region 21 has a minimum

Radius of curvature R ₅ between 2 mm and 4 mm. The outer diameter D _{3 of} the outer well region 5 is defined as a diameter at which the surface of the piston head 2 has a point of inflection 22. In the outer

Trough region 5 itself, the surface of the piston crown 2 is completely concave curved. Starting from the outer edge 18 of the piston crown 2, the surface is initially flat. At the planar web 6 of the transition region 21 connects, in which the surface is a convex Curvature has. The convex curvature of the transition region 21 is adjoined by the outer trough region 5, in which the surface has the concave curvature. To the

Turning point 22, which defines the outer diameter D _{3 of} the outer trough region 5, thus passes over the concave curvature of the transition region 21 into the convex curvature of the outer trough region 5.

At the turning point 22 between the transition region 21 and the outer trough region 5, the outer trough region 5 has a maximum angle W ₂ , which is in a vertical between 25 degrees and 30 degrees. In the turning point 22 is the angle that the

Includes surface of the piston crown 2 with the plane perpendicular to the axis of symmetry 19, maximum. The surface of the piston crown 2 has its greatest slope in the point of inflection 22.

In a transition between the outer trough region 5 and the inner trough region 4, the surface again has a point of inflection 23. The turning point 23, at which the

Curvature of the surface from concave to convex, defines an inner diameter D ₄ , the outer trough region 5 has. At the inflection point 23 at which the outer trough region 5 merges into the inner trough region 4, the outer trough region 5 has a maximum depth H ₂ which is between 5 mm and 10 mm. The outer trough portion 5 has a minimum radius of curvature R4 between 3 mm and 9 mm. Of the

Radius of curvature R4 becomes minimal approximately in the middle between the two turning points 22, 23.

The piston head 2 has between the inner bowl portion 4 and the outer

Trough region 5, that is, at the inflection point 23, where the outer trough region 5 merges into the inner trough region 4, a transition angle W ₃ , which is in a horizontal between 0 degrees and 10 degrees. In the illustrated embodiment, the surface thus runs almost parallel to the plane which is oriented perpendicular to the axis of symmetry 19. In the region of the point of inflection 23 at which the outer trough region 5 merges into the inner trough region 4, the curvature of the surface is almost zero.

Based on the piston outer diameter Di, the outer trough region 5 has a

Inner diameter D ₄ , to which the piston outer diameter Di has a factor between 1, 2 and 2. The inner diameter D ₄ corresponds to an outer diameter of the inner trough region 4. The outer trough region 5 and the inner trough region 4 are continuous into each other, ie the surface of the piston crown 2 is free from edges in a transition from the outer trough region 5 into the inner trough region 4.

The outer trough region 4 extends annularly around the inner trough region 4. The inner trough region 4 extends over an entire area enclosed by the inner diameter D _{4 of} the outer trough region 5. The inner trough region 4 has a total of three partial regions 26, 27, 28, which are curved in different directions. The inner trough region 4 thus has a total of two inflection points 24, 25 which separate the partial regions 26, 27, 28 from each other

In the first partial region 26, which lies radially outward with respect to the axis of symmetry 19, the surface has a convex curvature. The surface has a minimum radius of curvature R ₃ between 2 mm and 4 mm. In the second subregion 27, which lies with respect to the axis of symmetry 19 between the two other subregions 26, 28, the surface has a concave curvature. The surface has in the central portion 27 a minimum radius of curvature R ₂ between 3 mm and 9 mm. In the third portion 28, which lies with respect to the symmetry axis 19 within the two other portions 26, 27, the surface again has a convex curvature. The

Surface has in the inner portion 28 a minimum radius of curvature R] between 2 mm and 4 mm. The radii of curvature R _1? R _{3 of} the surface in the first portion 26 and in the third portion 28 are thus the same size on average. The second portion 27 is less curved than the other two portions 26, 28th

In the inner trough area 4, the trough 3 has its lowest point over its entire extension. The inner trough region 4 in this case has a maximum depth K _\ , which is between 10 mm and 20 mm. Its maximum depth Hi reaches the inner trough area 4 in the central portion 27.

Relative to the piston outer diameter D _\ , the inner trough region 4 in the

Turning point 25, in which the second portion 27 merges into the third portion 28, a turning point diameter D ₅ , based on the piston outer diameter Di has a factor between 3 and 6. In this turning point 25, the inner trough portion 4 has a turning point angle W] which is in a horizontal between 20 degrees and 30 degrees. The inner bowl portion 4 has a central depth H ₃ , which is between 4 mm and 9 mm.

Claims

1. piston (1) for an internal combustion engine, in particular a diesel engine, with a piston outer diameter (D and with a piston head (2) having a trough (3) in an inner trough region (4) a W-shape and in a outer trough region (5) has a toroidal shape.

2. piston (1) according to claim 1,

characterized in that

the piston head (2) has a web (6) surrounding the depression (3).

3. piston (1) according to claim 1 or 2,

characterized in that

the web (6) has an inner diameter (D ₂ ), based on the

Piston outer diameter (DO has a factor between 1.0 and 1.4.

4. piston (1) according to any one of the preceding claims,

characterized in that

the outer trough region (5) has an outer diameter (D ₃ ) to which the outer diameter of the piston (DO has a factor between 1.0 and 1.4.

5. Piston (1) according to one of the preceding claims,

characterized in that

the outer trough portion (5) has a maximum angle (W ₂ ) which is in a vertical between 25 degrees and 35 degrees.

6. piston (1) according to any one of the preceding claims,

characterized in that

the outer trough region (5) has a maximum depth (H ₂ ) which is between 5 mm and 10 mm.

7. piston (1) according to any one of the preceding claims,

characterized in that

the outer trough region (5) has an inner diameter (D ₄ ) to which the outer diameter of the piston (Di) has a factor between 1.2 and 2.

8. piston (1) according to any one of the preceding claims,

characterized in that

the piston head (2) has a transition angle (W ₃ ) between the inner trough region (4) and the outer trough region (5), which is between 0 degrees and 10 degrees in a horizontal plane.

9. piston (1) according to any one of the preceding claims,

characterized in that

the inner trough area (4) has a turning point diameter (D ₅ ), to which the outer diameter of the piston (Di) has a factor between 3 and 6.

10. piston (1) according to any one of the preceding claims,

characterized in that

the inner trough portion (4) has a maximum depth (Hi) which is between 10 mm and 20 mm.

11. Piston (1) according to one of the preceding claims,

characterized in that

the inner trough portion (4) has a turning point angle (W) which is in a horizontal between 20 degrees and 30 degrees.

12. Piston (1) according to one of the preceding claims,

characterized in that

the inner trough portion (4) has a central depth (H ₃ ) which is between 4 mm and 9 mm.

13. Internal combustion engine with at least one piston (1) according to one of the preceding claims.