DE102015004356A1 - Piston crown for internal combustion engines - Google Patents

Abstract

The present disclosure relates to a piston crown (110) for internal combustion engines. The disclosed piston crown (110) has a piston skirt (114) having a central axis (112), a piston skirt (116) delimiting the piston skirt (114) and consisting of a piston crown edge (118) and a piston crown (120) and one in the piston crown (116) recessed valve pocket unit (131) with at least two valve pockets (132, 134) whose sectional profile in a plane perpendicular to the central axis (112) plane with respect to the central axis (112) is curved outward in each case. The valve pocket unit (131) additionally comprises a transition lateral surface (137) which connects the first lateral surface (133) to the second lateral surface (135) and has a rectilinear sectional profile in a plane perpendicular to the central axis (112). 112) perpendicular to the section of the first lateral surface (133) and in the sectional profile of the second lateral surface (135) merges tangentially.

Description

Technical area

The present invention relates to a piston crown and a piston for internal combustion engines.

background

Pistons for internal combustion engines may have a piston skirt which is connected to a piston crown and a connecting rod. The piston crown defines a combustion chamber together with a cylinder or cylinder liner in which the piston reciprocates and the cylinder head.

The piston crown has an outer circumferential surface, which is bounded at the top by a piston crown, which is formed by a piston bottom edge and a piston crown. The piston bottom recess forms part of the combustion chamber.

For example, used in a gasoline engine piston with different Kolbenmuldenformen. Thus, pistons are known with roof-shaped piston crown, which is designed for combustion processes with gas-rinsed prechamber such that the torch jets meet as late as possible on the combustion chamber walls. In addition, pistons are known with trough-shaped piston bottom, which is designed so that a Tumbleströmung generated on the inlet side is maintained. There are also pistons with omega piston crown, in which the piston crown is designed for diesel operation for optimal direct injection and is used for cost reasons and for simplicity, unchanged in the gas Otto engine. The latter regardless of a possibly worse combustion result. In addition, pistons are known with a pot-piston bottom wells, in which the piston head can be designed such that a squish flow (squish flow) arises in the radial direction between the piston edge and the cylinder head. In addition, the swirl flow can be amplified in the pot-piston bottom tray.

For engines with swirl inlet ducts and chamber candles pistons with pot-piston bottom wells are very well suited. During the compression stroke, the mixture is displaced above the piston bottom edge (squish edge) of the piston into the pot piston bottom recess. During the expansion stroke, the mixture is sucked out of the pot bottom of the piston. This process leads to strong pinch currents, especially near top dead center.

In addition to the squish flow, the pot bottom of the pot also leads to an acceleration of the swirl flow generated on the inlet side. Due to the angular momentum conservation, the rotational speed of the swirl flow increases when the mixture is displaced inwardly into the pot bottom of the pot bottom.

From the DE 10 2010 018 930 A1 a piston for an internal combustion engine is known, which has four valve pockets within the piston head, which ensure a clearance of the exhaust and intake valves.

From the DE 10 2012 103 212 A1 is a piston of an internal combustion engine is known in which the height of the piston crown with the depth of the valve pockets in a certain relationship to each other.

The present disclosure is directed, at least in part, to improving one or more aspects of known systems.

Summary of the Revelation

According to one aspect of the present disclosure, a piston crown for internal combustion engines is disclosed, which is connectable to a piston skirt for forming a piston. The piston crown has a piston skirt having a center axis, a piston crown bounding the piston skirt, which is formed by a piston bottom edge and a piston bottom recess, and a valve pocket unit embedded in the piston bottom edge and having a first valve pocket and a second valve pocket. The valve pocket unit comprises a curved first lateral surface assigned to the first valve pocket, whose sectional profile is curved outward in a plane perpendicular to the central axis with respect to the central axis, a curved second lateral surface assigned to the second valve pocket, the sectional profile of which is in a plane perpendicular to the central axis with respect to the central axis is curved outwards, and a transition surface area, which connects the first lateral surface with the second lateral surface. The transitional lateral surface has, in a plane perpendicular to the central axis, a rectilinear cutting profile which merges tangentially in the plane perpendicular to the central axis into the section of the first lateral surface and into the section of the second lateral surface.

In another aspect, a piston for internal combustion engines is disclosed having a piston skirt and a piston crown attached to the piston crown in accordance with the present disclosure.

Other features and aspects of this disclosure will become apparent from the following description and the accompanying drawings.

Brief description of the drawings

1 shows a plan view of a piston crown of a piston for an internal combustion engine, having an exemplified piston crown,

2 shows a sectional view through the piston of 1 along the line II-II,

3 shows a further sectional view through a piston having a further embodiment of the valve pockets.

Detailed description

The following description is a detailed description of exemplary embodiments of the present disclosure. The exemplary embodiments described herein and illustrated in the drawings are intended to teach the principles of the present disclosure, to enable those skilled in the art to practice them, and to utilize the present disclosure in various environments and for various applications. Therefore, the exemplary embodiments are not intended and should not be construed to be a limiting description of the scope. Rather, the scope of the present disclosure is defined by the appended claims.

In the context of the present disclosure, a surface curved outwards with respect to the reference axis in a reference plane perpendicular to a reference axis means that this surface, viewed from the reference axis, is substantially convex in the reference plane. In contrast, in the context of the present disclosure, an inwardly curved surface in the reference plane with respect to the reference axis means that, viewed from the reference axis, this surface is substantially concave in the reference plane.

In the context of the present disclosure, a pocket describes a recess formed in a body, which has a lateral surface and a bottom surface adjoining the lateral surface. The bottom surface of the bag can be provided in any form. For example, the bottom surface partially flat, partially curved, inclined relative to the lateral surface or provided in any other way.

The present disclosure is based at least in part on the idea that the valve pockets let into the piston head merge into one another in such a way that almost no sharp edges are present on the piston crown. In addition, the present disclosure is based at least in part on the idea that almost all combustion chamber side interconnected surfaces of the piston crown are provided by rounding with predetermined radii or bevels, so that the partially defined by the piston crown cavity combustion chamber is only slightly rugged. The combustion chamber provided thereby has a geometry that can reduce the turbulences introduced into the combustion mixture and thus provide a more homogeneous combustion mixture within the combustion chamber. This can lead to lower emissions and higher combustion efficiency.

Further, the present disclosure is based on the idea that, by providing valve pockets that connect and simultaneously make fillets into the piston crown, a combustion chamber can be created in which uniform combustion can take place. In addition, it can be prevented that local temperature peaks (so-called hot spots) form at any concave areas or edges.

The example in the 1 and 2 illustrated piston 100 has a piston crown 110 and a piston shirt 140 on. The piston crown 110 is by means of at least one screw 102 with the piston shirt 140 releasably connected. The piston 100 is adapted to be guided by a cylinder or a cylinder liner of an internal combustion engine. The internal combustion engine is, for example, an Otto gas engine, a diesel engine, a two-fuel engine that can be operated with liquid as well as with gas fuel, or a Trikraftstoffmotor that can be operated, for example, heavy fuel oil, diesel fuel or gas fuel.

The piston crown 110 has one around a central axis 112 extending piston skirt 114 and a piston skirt 114 upwards limiting piston crown 116 on. The piston bottom 116 is from a piston bottom edge 118 and one coaxial with the central axis 112 extending piston bottom well 120 educated. The piston bottom recess 120 has a the piston crown 120 downwardly delimiting piston bowl bottom 122 and one on the piston bowl bottom 122 subsequent piston bowl wall 124 on.

In the embodiment illustrated in the drawings, the piston shown by way of example is shown 100 adapted to be used in an internal combustion engine, the two cylinders per cylinder Inlet poppet valves 12 . 14 (shown in dashed lines) and two Ausstellstellerventile 16 . 18 (shown in dashed lines). Thus, the piston crown exemplified in the drawings has 110 a valve pocket unit 131 with a total of four valve pockets 132 . 134 . 136 . 138 on, so in the piston bottom edge 118 are provided that these the positions of the respective associated inlet or Auslasstellerventils 12 . 14 . 16 . 18 correspond. Preferably, the valve pocket unit 131 with the valve pockets 132 . 134 . 136 . 138 symmetrical about the central axis 112 are arranged. According to the 1 form the four valve pockets 132 . 134 . 136 . 138 in plan view, essentially a rectangle with rounded corners.

It should be noted, however, that the number of valve pockets of the valve pocket unit is not limited to four. If, for example, the internal combustion engine has only one inlet valve and only one outlet valve per cylinder, then only two valve pockets are provided in the piston bottom edge.

Like in the 1 shown is the valve bag 132 at least partially circular arc-shaped and has a curved lateral surface 133 with a first radius R1, whose section in a direction to the central axis 112 vertical plane with respect to the central axis 112 curved outwards. The first radius R1 is at least partially greater than the radius of the associated inlet valve 12 so that this easily in the valve bag 132 can be included when the piston 100 located at top dead center.

Furthermore, the valve pocket 134 at least partially circular arc-shaped and has a curved lateral surface 135 with a second radius R2, whose section in a direction to the central axis 112 vertical plane with respect to the central axis 112 curved outwards. The second radius R2 is at least partially greater than the radius of the associated Einlasstellerventils 14 so that this easily in the valve bag 134 can be included when the piston 100 located at top dead center.

Similarly, the valve pockets include 136 . 138 each curved lateral surfaces with predetermined radii whose sectional shape in one to the central axis 112 vertical plane with respect to the central axis 112 each outwardly curved. The curved lateral surfaces of the valve pockets 136 . 138 are not provided with a reference numeral in the drawings for the sake of simplicity. The radii of the valve pockets 136 . 138 are at least partially larger than the respective radius of the associated Auslasstellerventils 16 . 18 so that these are easily in the associated valve pocket 136 . 138 can be absorbed when the piston 100 located at top dead center.

In the 1 is shown that all valve pockets 132 . 134 . 136 . 138 in diameter direction not over the piston bottom edge 118 go out and thus have an outer contour that is at least partially rectangular. In further embodiments, however, it may be preferred that the valve pockets 132 . 134 . 136 . 138 in the diameter direction over the piston bottom edge 118 go out and thus have a discontinuous outer contour.

The Indian 1 shown in plan view of the valve pocket unit 131 is substantially rectangular and is at its corners by the radii R1, R2 of the valve pockets 132 . 134 . 136 . 138 rounded.

For example, in the embodiment shown in the drawings, the radii R1, R2 of all lateral surfaces of the valve pockets 132 . 134 . 136 . 138 same size.

The valve pocket unit 131 also has a transition surface 137 on that the lateral surface 133 with the lateral surface 135 connects and in one to the central axis 112 vertical plane has a straight line cutting. In particular, the cutting profiles of the lateral surface go 133 and the lateral surface 135 in one to the central axis 112 perpendicular plane each tangent in the transitional surface area 137 above. This can be in the piston bottom edge 118 a transitional pocket that holds the valve bag 132 with the valve bag 134 connects and the transitional surface area 137 having. In the 1 become the lateral surface 133 , the transitional lateral surface 137 and the lateral surface 135 graphically distinguished from each other by cross strokes.

Due to the tangential to the first lateral surface 133 and the second lateral surface 135 extending transition lateral surface 137 have the valve pockets embedded in the piston edge 132 . 134 . 136 . 138 no concave areas and thus form part of the combustion chamber, which is only slightly rugged.

Each of the valve pockets 132 . 134 . 136 . 138 has a depth T (see 2 ), wherein in the example shown in the drawings, each valve pocket 132 . 134 . 136 . 138 has an identical depth T. Also, the transition pocket, the transitional area 137 can have a depth that is the depth of the valve pockets 132 . 134 equivalent. In further embodiments, for. For example, the valve pockets associated with the inlet valve valves have a first depth and the outlet valve valves associated with the valve pockets have a second depth which differs from the first depth. In such an embodiment, the transition pocket smoothly compensates for the difference in level.

The depths of the valve pockets 132 . 134 . 136 . 138 are each selected such that a predetermined distance to the associated intake or Ausstellstellerventil 12 . 14 . 16 . 18 can be complied with.

In the 2 is further shown that the combustion chamber facing, upper edge of the lateral surface 133 the valve bag 132 is rounded with a fourth radius R4 and the brennraumabgewandte, lower edge of the lateral surface 133 the valve bag 132 is rounded with a fifth radius R5. The fourth radius R4 and the fifth radius R5 each have a value that is, for example, between about 5 mm and about 15 mm.

Similarly, the combustion chamber facing, upper and the combustion chamber facing away, lower edges of the lateral surfaces of the valve pockets 134 . 136 . 138 also be rounded with radii. In addition, the combustion chamber facing, upper and the brennraumabgewandten, lower edges of the transition surfaces can also be rounded with radii.

Instead of the radii R4 and R5 can in alternative embodiments, all combustion chamber facing upper and brennraumabgewandte lower edges of the lateral surfaces of the valve pockets 132 . 134 . 136 . 138 and the transitional shell surfaces 137 be provided with chamfers, which contribute to the through the piston crown 120 and the valve pockets 132 . 134 . 136 . 138 be provided formed part of the combustion chamber of the internal combustion engine such that it is only slightly rugged.

In the 2 is further shown that the combustion chamber facing, upper and the combustion chamber facing away, lower edge of the piston bowl wall 124 the piston bottom recess 120 also rounded with radii R6 or R7. Instead of the radii R6 and R7 chamfers may alternatively be provided.

The piston bottom recess 120 has a height h that is about 5 mm to about 40 mm. The depth T of the valve pockets 132 . 134 . 136 . 138 is about 10% to about 80% of the height h of the piston crown 120 , The ratio of the height h of the piston crown 120 to the diameter D of the piston crown 116 or the piston diameter D is about 0.03 to about 0.2, wherein the diameter D is between about 180 mm to about 500 mm. The ratio of the bowl diameter d to the diameter D of the piston crown 116 is about 0.3 to about 0.8.

The radius R1 is approximately 10% to 40% of the diameter D of the piston crown 116 and the radius R2 is about 10% to about 40% of the diameter D of the piston crown 116 ,

In one in the 3 shown further embodiment, the valve pockets 132 . 134 . 136 . 138 have a valve pocket bottom with a surface normal, wherein the surface normal of at least one of the valve pockets 132 . 134 . 136 . 138 at an angle α inclined to the central axis 112 is arranged. The angle α may be, for example, about 1 ° to about 25 °, the depth T to the piston crown 120 grows up. Instead of a plane and with respect to the central axis 112 inclined surface, the valve pockets bottoms can also be connected. The fillets can preferably be designed such that the through the valve pockets 132 . 134 . 136 . 138 and the piston bottom tray 120 formed part of the combustion chamber is convex. That is, the fillets with respect to the central axis 112 are curved outwards.

Thus, the valve pockets 132 . 134 . 136 . 138 , as already explained above, at least in certain areas, that is to say in particular in the region of the piston bottom cup wall 124 to be trained a little deeper. The valve bag bottoms may be flat, concave, convex or have a hybrid form of the above basic shapes. The surface normal represents at least one zone or only one point on the valve pocket bottom.

In the 2 is further shown that the piston crown 110 at least part of an outer cooling channel 142 of the piston 100 and at least part of an internal cooling chamber 144 of the piston 100 having, with the outer cooling channel 142 over cross holes 146 connected is. The part of the outer cooling channel 142 is at least partially below the piston bottom edge 118 and at least partially provided below the valve pocket bottoms and adapted to the piston bottom edge 118 and at least partially cool the valve pockets bottoms. The inner cooling chamber 144 is below the piston bowl bottom 122 arranged and adapted to the piston bowl bottom 122 to cool. The outer cooling channel 142 is referred to as outer shaker space and the inner cooling chamber 144 is called an inner shaker space.

In further embodiments, the outer cooling channel 142 be equipped with cooling holes, resulting in a bore-cooled piston.

Industrial Applicability

By providing the valve pockets 132 . 134 . 136 . 138 , each with each other with the transitional shell surfaces 137 are connected and whose upper and lower edges are provided with radii R4, R5 and bevels, respectively, is provided by the piston crown 110 a part of the combustion chamber shown, which is slightly rugged and has only a few concave areas. This can help make that through the intake valve valves 12 . 14 admitted gas fuel-air mixture is only slightly influenced in the optimal turbulence and maintains its predominantly laminar flow component. This can result in optimal and near-complete combustion, with emissions kept lower at higher efficiency

By the piston crown according to the invention 110 For example, providing the radii R4 to R7 or corresponding chamfers can avoid localized glow points and reduce the risk of knocking, which can result in more efficient and complete combustion ,

By providing the radii R4 to R7, the gas fuel-air mixture is only slightly influenced in the optimum turbulence and maintains its predominantly laminar flow component. This in turn can further optimize and complete the combustion. It can further reduce emissions and increase combustion efficiency.

Although the preferred embodiments of this invention have been described herein, improvements and modifications may be incorporated herein without departing from the scope of the following claims.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010018930 A1 [0007]
• DE 102012103212 A1 [0008]

Claims (12)

Piston crown ( 110 ) for internal combustion engines equipped with a piston skirt ( 140 ) for forming a piston ( 100 ) is connectable, wherein the piston crown ( 110 ) has a central axis ( 112 ) having piston skirt ( 114 ), a piston skirt ( 114 ) limiting piston crown ( 116 ), which consists of a piston bottom edge ( 118 ) and a piston bottom trough ( 120 ) is formed, and one in the piston bottom edge ( 118 ) and a first valve pocket ( 132 ) and a second valve pocket ( 134 ) having valve pocket unit ( 131 ) with: one of the first valve pocket ( 132 ) associated curved first lateral surface ( 133 ) whose section in a direction to the central axis ( 112 ) vertical plane with respect to the central axis ( 112 ) is curved outwards, one of the second valve pocket ( 134 ) associated curved second lateral surface ( 135 ) whose section in a direction to the central axis ( 112 ) vertical plane with respect to the central axis ( 112 ) is curved outwards, and a transition surface ( 137 ), the first lateral surface ( 133 ) with the second lateral surface ( 135 ) and in one to the central axis ( 112 ) vertical plane has a straight line profile, which in the center axis ( 112 ) vertical plane in the section of the first lateral surface ( 133 ) and in the section of the second lateral surface ( 135 ) passes tangentially. Piston crown ( 110 ) according to one of the preceding claims, wherein in the piston crown edge ( 118 ) a total of four valve pockets ( 132 . 134 . 136 . 138 ) which are symmetrical about the central axis ( 112 ) are arranged. Piston crown ( 110 ) according to one of the preceding claims, wherein the valve pockets ( 132 . 134 . 136 . 138 ) have a depth (T) which is equal to the depth (T) in the region of the transition surface ( 137 ). Piston crown ( 110 ) according to one of the preceding claims, wherein in a direction to the central axis ( 112 ) vertical plane of the curved section of the first lateral surface ( 133 ) is at least partially circular arc-shaped with a first radius (R1) and in a direction to the central axis ( 112 ) vertical plane of the curved section of the second lateral surface ( 135 ) is at least partially circular arc-shaped with a second radius (R2). Piston crown ( 110 ) according to claim 4, wherein the first radius (R1) and the second radius (R2) are each about 10% to 40% of the diameter (D) of the piston head ( 116 ) amount. Piston crown ( 110 ) according to one of the preceding claims, wherein the first lateral surface ( 133 ), the second lateral surface ( 135 ) and / or the transition surface area ( 137 ) has at the combustion chamber facing edge a rounding with a radius (R4) and at the combustion chamber remote edge has a rounding with a radius (R5). Piston crown ( 110 ) according to one of the preceding claims, wherein at least one of the valve pockets ( 132 . 134 . 136 . 138 ) has a valve pocket bottom with a surface normal inclined by an angle (α) to the central axis ( 112 ), wherein the depth (T) of the valve pockets ( 132 . 134 . 136 . 138 ) to the piston crown ( 120 ) grows. Piston crown ( 110 ) according to claim 7, wherein the angle (α) is about 1 ° to about 25 °. Piston crown ( 110 ) according to one of the preceding claims, further comprising at least part of an outer cooling channel ( 142 ) of the piston ( 100 ) and at least part of an inner cooling chamber ( 144 ) of the piston ( 100 ) connected to the outer cooling channel ( 142 ) via transverse bores ( 146 ) connected is. Piston crown ( 110 ) according to one of the preceding claims, wherein the piston bottom diameter is about 180 mm to about 500 mm. Piston ( 100 ) for internal combustion engines, comprising: a piston skirt ( 140 ) and one on the piston shirt ( 140 ) attached piston crown ( 110 ) according to any one of the preceding claims. Piston according to claim 11, wherein the piston skirt ( 140 ) with the piston crown ( 110 ) by means of at least one screw ( 102 ) connected is.

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