Valve stem seal for an internal combustion engine and corresponding internal combustion engine

Abstract

Valve stem seal (4) for an internal combustion engine (1), comprising a sealing element (7) and a sealing housing (8) receiving the sealing element (7), wherein the sealing element (7) bears against an inner circumferential surface (9) of the housing (8), wherein the sealing element (7) bears against the inner circumferential surface (9) of the housing with a sealing outer circumferential surface (16) continuously and, viewed in longitudinal section with respect to a longitudinal central axis (5) of the valve stem seal (4), has an inner circumferential sealing surface (17) on its side facing away from the inner circumferential surface (9) of the housing, wherein the inner circumferential sealing surface (17) has a cylindrical inner circumferential sealing surface area (18), wherein the inner circumferential surface (9) has an inner circumferential sealing surface area (11) that tapers towards an end face (10) of the valve stem seal (4),the sealing element (7) abuts and to which cylindrical inner circumferential surface areas (12, 13) adjoin on both sides, wherein at least one sealing element projection (19) arranged in the axial direction in overlap with the tapered inner circumferential surface area (11) extends radially inwards from the cylindrical inner circumferential surface area (18) to hold the valve stem seal (4) on a valve stem sleeve (3) of a valve guide of a cylinder head (2) of the internal combustion engine (1), characterized in that the tapered inner circumferential surface area (11) extends in longitudinal section with respect to the longitudinal center axis (5) of the valve stem seal (4) over at least 25% of the total extent of the valve stem seal (4) in the axial direction,and that the sealing element projection (19) engages a positive locking projection of the valve stem sleeve (3) in an axial direction to secure the valve stem seal (4) to the valve stem sleeve (3).

Description

[0001] The invention relates to a valve stem seal for an internal combustion engine, comprising a sealing element and a sealing housing accommodating the sealing element, wherein the sealing element bears against a housing inner circumferential surface of the sealing housing, wherein the sealing element bears continuously against the housing inner circumferential surface with a sealing outer circumferential surface and, viewed in longitudinal section with respect to a longitudinal center axis of the valve stem seal, has a sealing inner circumferential surface on its side facing away from the housing inner circumferential surface, wherein the sealing inner circumferential surface has a cylindrical sealing inner circumferential surface region, wherein the housing inner circumferential surface has a housing inner circumferential surface region tapering towards a front end of the valve stem seal, against which the sealing element bears and to which cylindrical housing inner circumferential surface regions adjoin on both sides,At least one sealing element projection, arranged axially in overlap with the tapered housing inner peripheral surface area, extends radially inward from the cylindrical sealing inner peripheral surface area to hold the valve stem seal on a valve stem sleeve of a valve guide of a cylinder head of the internal combustion engine. The invention further relates to an internal combustion engine.

[0002] For example, DE 199 49 248 A1 is known from the prior art. This document describes a valve stem seal on internal combustion engines for vehicles with an elastomeric sealing element mounted on and positioned on the valve stem guide, with a spring-loaded sealing lip resting against the valve stem and a stiffening ring enclosing the sealing element. The sealing element is positioned on the end face of the valve stem guide.

[0003] From the document EP 2 236 867 A1 a sealing device for maintaining a reliable seal between a valve stem seal and a valve stem guide is known, wherein the valve stem seal is separate from a holding region of a valve spring.The valve stem seal comprises a cylindrical metal ring, an elastic rubber lip arranged at one end of the metal ring for sealing the valve stem during displacement on the valve stem, and a sealing element arranged on an inner peripheral surface of the metal ring for sealing an outer peripheral surface of the valve stem guide during attachment to the outer peripheral surface, wherein the sealing device has a metallic attachment portion at which the metal ring is in direct contact with the outer peripheral surface of the valve stem guide, and an elastic rubber attachment portion which is fully held on the inner peripheral surface of the metal ring and in contact with the outer peripheral surface of the valve stem guide.

[0004] The prior art also includes the documents EP 1 749 980 A1 and US 2018 / 0 112 564 A1.

[0005] The object of the invention is to propose a valve stem seal for an internal combustion engine which has advantages over known valve stem seals, in particular enabling simple assembly on a valve stem sleeve and at the same time ensuring a reliable sealing effect or seal.

[0006] This is achieved according to the invention with a valve stem seal for an internal combustion engine having the features of claim 1. It is provided that the tapered housing inner circumferential surface area extends in the axial direction over at least 25% of a total extension of the valve stem seal, viewed in longitudinal section with respect to the longitudinal center axis of the valve stem seal, and that the sealing element projection engages behind a positive-locking projection of the valve stem sleeve in the axial direction for fixing the valve stem seal to the valve stem sleeve.

[0007] Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims.

[0008] The valve stem seal is preferably a component of the internal combustion engine, but can of course also be provided separately. The internal combustion engine particularly preferably serves to drive a motor vehicle and, in this respect, to provide a drive torque directed toward driving the motor vehicle. The internal combustion engine can, in this respect, be a component of the motor vehicle. A motor vehicle is understood, in particular, to be a non-rail vehicle driven by an engine. The motor vehicle can, in this respect, be configured as a motor vehicle, motorcycle, or tractor. The engine for driving the motor vehicle is the internal combustion engine.

[0009] The internal combustion engine preferably has a cylinder crankcase and a cylinder head attached to the cylinder crankcase. The cylinder crankcase contains at least one cylinder bore, which is closed off by the cylinder head. This means that the cylinder bore is open in the direction of the cylinder head in the cylinder crankcase and is only closed when the cylinder head is arranged on the cylinder crankcase. For example, the cylinder bore continues into the cylinder head but does not extend through it.

[0010] The cylinder head also preferably contains at least one gas exchange duct, which is configured, for example, as a fresh gas duct or an exhaust duct. The fresh gas duct opens into the cylinder bore and serves to introduce fresh gas into a combustion chamber of the internal combustion engine, which is formed by the cylinder bore. The exhaust duct extends from the cylinder bore and serves to remove exhaust gas generated during operation of the internal combustion engine from the combustion chamber.

[0011] A gas exchange valve is located in the gas exchange channel, which can be referred to as an intake valve in the case of the fresh gas channel and an exhaust valve in the case of the exhaust gas channel. The gas exchange valve can be a component of the cylinder head. Preferably, at least one fresh gas channel and one exhaust gas channel, with an intake valve and an exhaust valve arranged therein, are configured in the cylinder head for each cylinder. In particular, such a fresh gas channel and such an exhaust gas channel are provided for each cylinder bore, with an intake valve arranged in each of the fresh gas channels and an exhaust valve arranged in each of the exhaust gas channels.

[0012] The aforementioned combustion chamber is partially delimited by the cylinder crankcase, the cylinder head, and a piston that can be moved within the cylinder bore. The combustion chamber therefore has a variable volume. The piston is preferably connected to the crankshaft of the internal combustion engine via at least one connecting rod. With the help of the crankshaft and the at least one connecting rod, a linear movement of the piston in the cylinder bore is converted into a rotary movement of the crankshaft. Naturally, the internal combustion engine preferably has multiple cylinder bores.

[0013] The gas exchange valve has at least one valve stem and one valve plate. It is mounted for linear displacement by means of a valve guide in the cylinder head. For this purpose, the valve stem of the gas exchange valve is accommodated in a valve stem sleeve of the valve guide. The valve stem sleeve allows displacement of the gas exchange valve in the axial direction and, optionally, in the circumferential direction relative to a longitudinal center axis of the valve stem, but fixes the gas exchange valve in the radial direction, at least within the scope of a technically necessary, slight play.

[0014] The valve plate of the gas exchange valve serves as a valve element, which sets different flow cross-sectional areas in different positions of the gas exchange valve. For this purpose, the valve element interacts with a valve seat, which is preferably formed on the cylinder head and / or by the cylinder head. Thus, in a first position of the gas exchange valve, a first flow cross-sectional area exists between the valve element and the valve seat, and in a second position different from the first position, a second flow cross-sectional area different from the first flow cross-sectional area exists.

[0015] During operation of the internal combustion engine, a space, in particular an annular space, located in the radial direction between the valve stem and an inner circumferential surface of the valve stem sleeve is at least temporarily in flow connection with the combustion chamber or the cylinder bore. In order to prevent a fluid from passing through said space or annular space, in particular towards the outside environment of the internal combustion engine, the internal combustion engine has a valve stem seal. This is placed onto the valve stem sleeve and seals around both the valve stem and the valve stem of the gas exchange valve. This means that after the valve stem seal has been mounted on the valve stem sleeve, the valve stem seal forms a sealing contact against both the valve stem sleeve and the valve stem, in particular completely and continuously in the circumferential direction with respect to the longitudinal center axis of the valve stem.

[0016] To achieve a reliable sealing effect, the valve stem seal comprises a sealing element and a sealing housing. The sealing element is made of a material with greater flexibility than the sealing housing, particularly an elastic material. After the valve stem seal is mounted on the valve stem sleeve, the sealing element forms a sealing contact with the valve stem sleeve and the valve stem of the gas exchange valve. The sealing housing, in which the sealing element is arranged, ensures a stable and permanent contact of the sealing element with the valve stem sleeve and the valve stem, particularly over a wide temperature range.

[0017] Preferably, the sealing element is made of plastic, in particular an elastomer or rubber, and / or the sealing housing is made of metal, in particular a metal sheet. Alternatively, however, both the sealing element and the sealing housing can be made of plastic. For example, the sealing element is injection-molded onto the sealing housing. However, it can also be provided that the sealing element is manufactured and subsequently inserted into the sealing housing.

[0018] In order to achieve particularly reliable sealing and simple assembly, the seal housing tapers in a radial direction towards the valve stem sleeve after assembly on the side facing the valve stem sleeve or valve plate, so that an area of ​​the housing's inner peripheral surface tapers towards the front end of the valve stem seal. This area is referred to as the tapered housing inner peripheral surface area. Conversely, the seal housing widens in a radial direction when viewed in longitudinal section, i.e. it has dimensions in the radial direction that increase in the axial direction, namely in the direction away from the front end. The housing inner peripheral surface area can accordingly also be referred to as the widening housing inner peripheral surface area or, more generally, as the dimensional change area.

[0019] Preferably, the radial dimensions of the tapered housing inner circumferential surface region change over its extension in the axial direction by at least 5%, at least 7.5%, at least 10%, at least 12.5%, or at least 15%. A space delimited in the radial direction by the housing inner circumferential surface region, which serves as a receiving space for the sealing element, has, as seen in longitudinal section, first dimensions in the radial direction on a first side of the housing inner circumferential surface region and second dimensions on a second side opposite the first sides, in particular in each case directly adjacent to the housing inner circumferential surface region. The second dimensions are at least 5% larger than the first dimensions.

[0020] Preferably, however, they are at least 10% or at least 15% larger. This achieves a particularly advantageous effect.

[0021] The front end of the valve stem seal refers, in particular, to the side of the valve stem seal facing the valve plate of the gas exchange valve. Particularly preferably, the entire seal housing tapers toward the front end, while also having a constant wall thickness in the area of ​​the inner peripheral surface of the housing. Particularly preferably, the seal housing is designed with a consistently constant wall thickness.

[0022] The housing inner circumferential surface, and in particular the housing inner circumferential surface region, delimit, at least in some regions, a receiving space for the sealing element, in which the sealing element is arranged after the valve stem seal has been installed. Due to the tapering of the housing inner circumferential surface region, the radial dimensions of the receiving space, in particular a diameter of the receiving space, decrease in the direction facing the front end of the valve stem seal. In other words, viewed in longitudinal section, the radial dimensions of the receiving space decrease in the axial direction due to the tapering of the housing inner circumferential surface region.

[0023] The sealing element rests directly against the housing's inner peripheral surface area. Preferably, after the valve stem seal has been installed, the sealing element is clamped between the valve stem sleeve and the housing's inner peripheral surface area, viewed in the radial direction. Such a design of the valve stem seal reliably secures it relative to the valve stem sleeve after installation and prevents accidental removal of the valve stem seal from the valve stem sleeve.

[0024] When the valve stem seal is pushed onto the valve stem sleeve with a specific installation force, a radial force is exerted by the valve stem sleeve via the sealing element onto the seal housing. This deforms the sealing element and influences the installation force, which increases significantly over the installation travel due to the deformation of the sealing element. The installation travel refers to the distance over which the valve stem seal is pushed onto the valve stem sleeve.

[0025] To even out the assembly force required to slide the valve stem seal onto the valve stem sleeve, particularly over the entire assembly path of the valve stem seal, the housing inner circumferential surface area tapered in longitudinal section should extend in the axial direction over at least 25% of the total extension of the valve stem seal. Preferably, an even greater extension of the housing inner circumferential surface area in the axial direction is realized, preferably at least 40%, at least 50%, or at least 60% of the total extension of the valve stem seal.

[0026] As a result, the assembly force required to slide the valve stem seal onto the valve stem sleeve remains largely constant throughout the entire valve stem seal installation process and does not exhibit a drastic increase toward the end of the installation process. Such an increase is the result of an unintentional deformation of the sealing element, which, due to the elastic design of the sealing element, counteracts the sliding action and, after sliding, pushes the sealing element away from the valve stem sleeve, which can lead to an unintentional detachment of the valve stem seal from the valve stem sleeve.

[0027] The tapered housing inner circumferential surface area is, for example, conical in design, i.e. it is present as a surface of revolution of a line, in particular a straight line, around a longitudinal center axis of the valve stem seal. The line is designed and / or arranged such that the housing inner circumferential surface area tapers in the direction of the front end of the valve stem seal when viewed in longitudinal section. For this purpose, the line or an imaginary extension of the line is angled with respect to the longitudinal center axis, i.e. it forms an angle of more than 0° and less than 180° with it. For example, the angle between the line or the imaginary extension and the longitudinal center axis is at least 2° and at most 15°, at least 4° and at most 10°, or at least 5° and at most 7.5°.

[0028] The described design of the valve stem seal ensures simple installation of the valve stem seal, in particular, easy sliding of the valve stem seal onto the valve stem sleeve. At the same time, this results in a permanent attachment of the valve stem seal to the valve stem sleeve and an excellent sealing effect, as compression of the sealing element is achieved without unwanted deformation in the axial direction. As explained, such deformation could result in a counterforce that, on the one hand, counteracts the assembly force during assembly and, on the other hand, forces the valve stem seal off the valve stem sleeve after assembly.

[0029] The invention provides that the housing inner circumferential surface has cylindrical housing inner circumferential surface regions, between which the tapered housing inner circumferential surface region of the housing inner circumferential surface is arranged, viewed in longitudinal section. In the axial direction, cylindrical housing inner circumferential surface regions adjoin the tapered housing inner circumferential surface region on both sides. In the axial direction, there is therefore a first cylindrical region on the one hand of the tapered region and a second cylindrical region on the other hand of the tapered region. The cylindrical housing inner circumferential surface regions are to be understood in particular as circular-cylindrical housing inner circumferential surface regions. In these, the housing inner circumferential surface runs parallel to the longitudinal center axis of the valve stem seal, viewed in longitudinal section.As already explained, such a design enables the excellent sealing effect and reliable attachment of the valve stem seal to the valve stem sleeve.

[0030] A further development of the invention provides that the seal housing, viewed in longitudinal section, has retaining webs extending radially inward at its ends, between which the sealing element is held in a form-fitting manner. The retaining webs are arranged on opposite sides of the tapered inner circumferential surface area of ​​the housing, viewed in the axial direction. The retaining webs can extend the same distance inward in the radial direction. However, their extensions in the radially inward direction are preferably different from one another. For example, the retaining web located on the tapered side of the inner circumferential surface of the housing has a smaller extension than the retaining web located on the opposite side.In this case, it can be provided that the latter retaining web extends further inwards in the radial direction than the former retaining web, so that its free end is closer to the longitudinal center axis than that of the other retaining web.

[0031] The two retaining webs serve to hold the sealing element in a form-fitting manner. Accordingly, they preferably extend radially exactly inward or, viewed in longitudinal section, are inclined towards each other, i.e., converge axially. The housing's inner peripheral surface also extends onto the retaining webs. In the area of ​​the retaining webs, the imaginary planes that completely accommodate the housing's inner peripheral surface are preferably perpendicular to the longitudinal center axis of the valve stem seal. The described design of the valve stem seal ensures, on the one hand, reliable attachment of the sealing element to the seal housing and, on the other hand, eliminates the need for a separate spring element, which would otherwise force the sealing element against the valve stem.Of course, such a spring element can be optional and can encompass the sealing element in such a way that it pushes the sealing element inwards in the radial direction.

[0032] A further development of the invention provides that the retaining webs, viewed in longitudinal section, are located on the sides of the cylindrical housing inner peripheral surface areas facing away from the tapered housing inner peripheral surface area, in particular, they directly adjoin the cylindrical housing inner peripheral surface areas. In other words, one of the cylindrical housing inner peripheral surface areas is located between each of the retaining webs and the tapered housing inner peripheral surface area.

[0033] Preferably, each of the cylindrical housing inner circumferential surface regions directly adjoins the tapered housing inner circumferential surface region on the one hand and one of the retaining webs on the other. However, it can also be provided that the retaining web, viewed in longitudinal section, transitions into the cylindrical housing inner circumferential surface region via a rounded portion or a chamfer. This rounded portion or chamfer is a component of the respective retaining web. This configuration also ensures the uniform distribution of the assembly force required to slide the valve stem seal onto the valve stem sleeve.

[0034] The invention provides that the sealing element bears against the housing inner circumferential surface with an outer sealing circumferential surface and, viewed in longitudinal section, has an inner sealing circumferential surface on its side facing away from the housing inner circumferential surface, wherein the inner sealing circumferential surface has a cylindrical inner sealing circumferential surface region. Viewed in longitudinal section, the sealing element thus has the outer sealing circumferential surface and the inner sealing circumferential surface, which are connected to one another via end faces of the sealing element. The outer sealing circumferential surface of the sealing element bears continuously against the housing inner circumferential surface, in particular completely. The latter means that, viewed in the axial direction, the sealing element is completely accommodated in the seal housing and does not extend beyond it.

[0035] The sealing inner circumferential surface of the sealing element delimits a valve stem sleeve receiving space in the radially outward direction. After the valve stem seal has been mounted on the valve stem sleeve, the valve stem sleeve is arranged in this valve stem sleeve receiving space. The sealing inner circumferential surface is cylindrical in some areas. This area is referred to as the cylindrical sealing inner circumferential surface area. The cylindrical sealing inner circumferential surface area is understood in particular to be a circular cylindrical area. Particularly preferably, the cylindrical sealing inner circumferential surface area is arranged, at least in some areas, in overlap with the tapered housing inner circumferential surface area viewed in the axial direction. The described design of the valve stem seal ensures simple assembly and a reliable sealing effect.

[0036] The invention provides that at least one sealing element projection, arranged in the axial direction and overlapping with the tapered housing inner circumferential surface area, projects radially inwardly from the cylindrical sealing inner circumferential surface area to hold the valve stem seal to a valve stem sleeve of a valve guide of a cylinder head of the internal combustion engine. The sealing element projection projects radially inwardly beyond the sealing inner circumferential surface area and, after assembly of the valve stem seal, projects opposite the valve stem sleeve. On the one hand, it serves to fix the valve stem seal to the valve stem sleeve in the axial direction. For this purpose, it engages behind a form-fitting projection of the valve stem sleeve. On the other hand, it serves - optionally - to ensure a tight fit against the valve stem sleeve, thus achieving a reliable seal between the valve stem seal and the valve stem sleeve.The sealing element projection is preferably designed in a bead-like manner.

[0037] Particularly preferably, viewed in longitudinal section, a vertex of the sealing element projection is arranged on the side of the tapered housing inner peripheral surface area facing the end face. This means that an imaginary plane intersecting the vertex and perpendicular to the longitudinal center axis is at a first distance from an imaginary first plane delimiting the housing inner peripheral surface area on the end face side, and a second distance from an imaginary second plane delimiting the housing inner peripheral surface area on the side facing away from the end face. The first distance is at most as large as the second distance; preferably, it is smaller.

[0038] Preferably, the second distance is greater than the first distance by a factor of at least 1.25, at least 1.5, at least 1.75, or at least 2.

[0039] A further development of the invention provides that a further sealing element projection of the sealing element and / or a sealing lip of the sealing element is arranged in overlap with at least one of the cylindrical housing inner circumferential surface regions, viewed in the axial direction. The further sealing element projection is designed, for example, analogously to the sealing element projection, so that reference is made to the corresponding embodiments. The further sealing element projection is arranged in axial direction in overlap with the cylindrical housing inner circumferential surface regions and preferably lies in sealing contact with the valve stem sleeve after assembly of the valve stem seal. Particularly preferably, there are several further sealing element projections, each of which is provided and designed for sealing contact with the valve stem sleeve.In particular, the further sealing element projections are arranged on opposite sides of the sealing element projection when viewed in longitudinal section.

[0040] The sealing lip of the sealing element is provided and designed to form a sealing contact with the valve stem. After the valve stem seal has been installed, it thus forms a sealing contact with the valve stem. The sealing lip is arranged, at least in some regions in the axial direction, in overlap with one of the cylindrical housing inner circumferential surface areas. Preferably, the further sealing element projection and the sealing lip overlap with different ones of the cylindrical housing inner circumferential surface areas. Such a configuration ensures a reliable sealing effect of the valve stem seal. Particularly preferably, a further sealing lip is present, but outside the seal housing, namely on the side of the seal housing facing away from the end face or the valve plate.In particular, the further sealing lip is encompassed by a spring element, preferably made of metal, particularly preferably made of spring steel, which urges the further sealing lip in the direction of the valve stem.

[0041] A further development of the invention provides that the tapered housing inner circumferential surface region, viewed in longitudinal section, has a constant gradient or is continuously curved over at least 50%, at least 75%, or at least 90% of its extension in the axial direction. In the region of the constant gradient, the tapered housing inner circumferential surface region is, in particular, conical. If, however, it is continuously curved, then it is, for example, spherical in shape in this region. The housing inner circumferential surface region has the aforementioned shape over a large part of its extension in the axial direction, in particular over at least 50% or more.

[0042] For example, the tapered housing inner peripheral surface area is continuously curved from one of the cylindrical seal inner peripheral surface areas to the other of the cylindrical seal inner peripheral surface areas, in particular with a curvature that changes in the axial direction. This allows for a particularly simple adjustment of the assembly force required to install the valve stem seal.

[0043] A further development of the invention provides that the seal housing has a constant wall thickness at least in the region of the tapered inner peripheral surface area and / or the cylindrical inner peripheral surface areas, or throughout. This has already been pointed out. The constant wall thickness enables particularly simple and cost-effective production of the seal housing, for example by forming, in particular by deep drawing.

[0044] The invention further relates to an internal combustion engine having at least one gas exchange valve, the valve stem of which is guided in a valve stem sleeve of a valve guide of a cylinder head of the internal combustion engine, wherein the valve stem sleeve and the valve stem are each sealingly encompassed by a valve stem seal, in particular a valve stem seal according to the above embodiments, which has a sealing element and a sealing housing accommodating the sealing element, wherein the sealing element bears against a housing inner circumferential surface of the sealing housing, wherein the sealing element bears continuously with a sealing outer circumferential surface against the housing inner circumferential surface and, viewed in longitudinal section with respect to a longitudinal center axis of the valve stem seal, has a sealing inner circumferential surface on its side facing away from the housing inner circumferential surface,wherein the seal inner circumferential surface has a cylindrical seal inner circumferential surface region. It is provided that the housing inner circumferential surface has a housing inner circumferential surface region tapering towards a front end of the valve stem seal, against which the sealing element rests and to which cylindrical housing inner circumferential surface regions adjoin on both sides, wherein, starting from the cylindrical seal circumferential surface region, at least one sealing element projection arranged in the axial direction in overlap with the tapered housing inner circumferential surface region projects radially inward for holding the valve stem seal on a valve stem sleeve of a valve guide of a cylinder head of the internal combustion engine.that the tapered housing inner circumferential surface area extends in longitudinal section with respect to the longitudinal center axis of the valve stem seal over at least 25% of a total extension of the valve stem seal in the axial direction, and that the sealing element projection for fixing the valve stem seal to the valve stem sleeve in the axial direction engages behind a positive-locking projection of the valve stem sleeve.

[0045] The advantages of such a design of the internal combustion engine and the valve stem seal have already been pointed out. Both the internal combustion engine and the valve stem seal can be further developed according to the details in this description, so reference is made to these details in this regard.

[0046] The features and feature combinations described in the description, in particular the features and feature combinations described in the following description of the figures and / or shown in the figures, can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the invention. Thus, embodiments are also considered to be encompassed by the invention that are not explicitly shown or explained in the description and / or the figures, but which follow from or can be derived from the explained embodiments.

[0047] The invention will be explained in more detail below with reference to the exemplary embodiments shown in the drawings, without limiting the invention. Fig. 1 a schematic representation of a region of an internal combustion engine, more precisely a schematic longitudinal sectional representation of a valve stem sleeve with a valve stem seal arranged thereon.

[0048] The Fig.1 shows a schematic representation of a region of an internal combustion engine 1, more precisely of a cylinder head 2 of the internal combustion engine 1, namely a schematic longitudinal sectional representation through a valve stem sleeve 3 and a valve stem seal 4 with respect to a longitudinal center axis 5 of both the valve stem sleeve 3 and the valve stem seal 4. The valve stem sleeve 3 serves to linearly guide a gas exchange valve (not shown here). For this purpose, it has a cylindrical guide recess 6, in which a valve stem of the gas exchange valve is displaceably received after assembly of the internal combustion engine 1. For (additional) sealing of the internal combustion engine 1 from the outside environment, the valve stem seal 4 is pushed onto the valve stem sleeve 3.The valve stem seal 4 is in sealing contact with both the valve stem sleeve 3 and the valve stem of the gas exchange valve, namely continuously in the circumferential direction with respect to the longitudinal center axis 5.

[0049] The valve stem seal 4 comprises a sealing element 7 and a sealing housing 8. The sealing element 7 is arranged radially between the sealing housing 8 on the one hand and the valve stem sleeve 3 and the valve stem on the other. It is made of an elastic material, for example, an elastomer. The sealing housing 8, on the other hand, is made of a material that has greater rigidity than the material of the sealing element 7. The sealing housing 8 is preferably made of metal, for example, steel.

[0050] The seal housing 8 has an inner peripheral surface 9 against which the sealing element 7 rests, in particular continuously in the circumferential direction. The inner peripheral surface 9 has at least one inner peripheral surface region 11 tapering toward a front end 10 of the valve stem seal 4. Within this region, the inner peripheral surface 9 tapers from a housing inner peripheral surface region 12 to a housing inner peripheral surface region 13.

[0051] In the exemplary embodiment illustrated here, the housing inner circumferential surface regions 12 and 13 are cylindrical. The housing inner circumferential surface region 12 has larger dimensions in the radial direction than the housing inner circumferential surface region 13. The housing inner circumferential surface regions 12 and 13 are connected to one another in the axial direction by the tapered housing inner circumferential surface region 11. The housing inner circumferential surface region 12 directly adjoins one side of the housing inner circumferential surface region 11, and the housing inner circumferential surface region 13 directly adjoins the other.

[0052] The housing inner peripheral surface area 11 is, for example, conical in shape or, as shown here, continuously curved. For example, the curvature can have a continuous radius of curvature or a radius of curvature that varies in the axial direction. In any case, it is important that the housing inner peripheral surface 9 tapers within the housing inner peripheral surface area 11, so that the distance of the housing inner peripheral surface 9 from the longitudinal center axis decreases.

[0053] Viewed in the axial direction, the tapered housing inner circumferential surface area 11 has dimensions corresponding to at least 25% of a total extension of the valve stem seal 4 in the axial direction, in particular of the seal housing 8. However, a larger extension is preferred, corresponding, for example, to at least 50% or more of the total extension. As a result, the pressing force or assembly force required to push the valve stem seal 4 onto the valve stem sleeve 5 is kept constant or at least nearly constant throughout the assembly path.

[0054] In the exemplary embodiment shown here, the seal housing 8 has retaining webs 14 and 15 formed on its ends. The retaining webs 14 and 15 preferably extend precisely radially inward. The sealing element 7 is held between them in a form-fitting manner. In the initial example shown here, the retaining webs 14 and 15 directly adjoin the cylindrical inner circumferential surface areas 12 and 13 of the housing and are connected to them, for example, via transition radii.

[0055] The sealing element has a sealing outer peripheral surface 16, with which it rests against the housing inner peripheral surface 9 of the seal housing 8. On its side facing away from the sealing outer peripheral surface 16 in longitudinal section, the sealing element 7 has a sealing inner peripheral surface 17. This is cylindrical, at least in some areas, when viewed in the axial direction, so that it has at least one cylindrical sealing inner peripheral surface region 18. A sealing element projection 19, a further sealing element projection 20, and a sealing lip 21 project radially inward beyond this sealing inner peripheral surface region 18.

[0056] The sealing element projection 19 overlaps the tapered housing inner circumferential surface region 11 when viewed in the axial direction, the further sealing element projection 20 overlaps one of the cylindrical housing inner circumferential surface regions 12 and 13, and the sealing lip 21 overlaps the other of the cylindrical housing inner circumferential surface regions 12 and 13. Furthermore, it can be seen that the sealing element 7 also overlaps the retaining webs 14 and 15 when viewed in the axial direction. The sealing element 7 extends in this respect in the axial direction on both sides up to the respective end face of the valve stem seal 4, of which only the end face 10 is designated here.

[0057] A further sealing lip 22 is located axially spaced from the sealing lip 21. This sealing lip 22 is circumferentially encompassed by a spring element 23. The spring element 23 exerts a spring force on the sealing lip 22 and urges it radially inward, particularly toward the valve stem of the gas exchange valve.

[0058] The described design of the internal combustion engine 1 and the valve stem seal 4 has the advantage that, when sliding the valve stem seal 4 onto the valve stem sleeve 3, the assembly force required for sliding it onto the valve stem sleeve 3 remains virtually constant over the entire assembly path. This is achieved by the large extension of the tapered housing inner circumferential surface area 11 in the axial direction. LIST OF REFERENCE SYMBOLS: 1 internal combustion engine 2 cylinder head 3 valve stem sleeve 4 valve stem seal 5 Longitudinal center axis 6 Guide recess 7 Sealing element 8 Seal housing 9 Housing inner peripheral surface 10 front end 11 Housing inner peripheral surface area 12 Housing inner peripheral surface area 13 Housing inner peripheral surface area 14 Holding bridge 15 Holding bridge 16 Seal outer peripheral surface 17 Seal inner peripheral surface 18 Seal inner peripheral surface area 19 Sealing element projection 20 Sealing element projection 21 Sealing lip 22 Sealing lip 23 Spring element

Claims

[1] Valve stem seal (4) for an internal combustion engine (1), comprising a sealing element (7) and a sealing housing (8) accommodating the sealing element (7), wherein the sealing element (7) bears against a housing inner circumferential surface (9) of the sealing housing (8), wherein the sealing element (7) bears continuously with a sealing outer circumferential surface (16) against the housing inner circumferential surface (9) and, viewed in longitudinal section with respect to a longitudinal center axis (5) of the valve stem seal (4), has a sealing inner circumferential surface (17) on its side facing away from the housing inner circumferential surface (9), wherein the sealing inner circumferential surface (17) has a cylindrical sealing inner circumferential surface region (18), wherein the housing inner circumferential surface (9) has a housing inner circumferential surface region (11) tapering towards a front end (10) of the valve stem seal (4),on which the sealing element (7) rests and to which cylindrical housing inner circumferential surface areas (12, 13) adjoin on both sides, wherein from the cylindrical sealing inner circumferential surface area (18) at least one sealing element projection (19) arranged in the axial direction in overlap with the tapered housing inner circumferential surface area (11) projects inwards in the radial direction for holding the valve stem seal (4) on a valve stem sleeve (3) of a valve guide of a cylinder head (2) of the internal combustion engine (1), , characterized bythat the tapered housing inner circumferential surface area (11) extends in the axial direction over at least 25% of a total extension of the valve stem seal (4) as seen in longitudinal section with respect to the longitudinal center axis (5) of the valve stem seal (4), and that the sealing element projection (19) engages behind a positive-locking projection of the valve stem sleeve (3) in the axial direction for fixing the valve stem seal (4) to the valve stem sleeve (3). [2] Valve stem seal according to claim 1, characterized by that the sealing housing (8), seen in longitudinal section, has retaining webs (14, 15) extending radially inwards at the end, between which the sealing element (7) is held in a form-fitting manner. [3] Valve stem seal according to claim 2, characterized bythat the holding webs (14, 15), seen in longitudinal section, are present on the sides of the cylindrical housing inner circumferential surface regions (12, 13) of the housing inner circumferential surface (9) facing away from the tapered housing inner circumferential surface region (11). [4] Valve stem seal according to one of the preceding claims, characterized by that a further sealing element projection (20) of the sealing element (7) and / or a sealing lip (21) of the sealing element (7) is arranged in overlap with at least one of the cylindrical housing inner circumferential surface areas (12, 13) as seen in the axial direction. [5] Valve stem seal according to one of the preceding claims, characterized by that the tapered housing inner circumferential surface area (11) has a constant gradient or is continuously curved over at least 50%, at most 75% or at least 90% of its extension in the axial direction, seen in longitudinal section. [6] Valve stem seal according to one of the preceding claims, characterized by that the seal housing (8) has a constant wall thickness at least in the region of the tapered housing inner circumferential surface region (11) and / or the cylindrical housing inner circumferential surface regions (12, 13) or throughout. [7] Internal combustion engine (1), with at least one gas exchange valve, the valve stem of which is guided in a valve stem sleeve (3) of a valve guide of a cylinder head (2) of the internal combustion engine (1), wherein the valve stem sleeve (3) and the valve stem are each sealingly encompassed by a valve stem seal (4) according to one of the preceding claims.

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