Valve train for an internal combustion engine with a roller rocker arm

Abstract

The invention relates to a valve train (2) for an internal combustion engine (1) with a roller rocker arm (9), with a rocker arm housing (14) on which a rocker arm roller (17) is rotatably mounted about a roller pivot axis (18) and which has, on the one hand, a valve connection point (12) for connection to a gas exchange valve (7) of the valve train (2) on the other hand, a bearing point (10) for mounting on an abutment (11) of the valve train (2) on the other hand, the rocker arm housing (14) has a housing base (15) and housing walls (16) extending from the housing base (15) on both sides of the rocker arm roller (17) and guide projections (21) extending from the housing walls (16) in the direction of the rocker arm roller (17), which are arranged to bear against roller side walls (24) of the rocker arm roller (17).It is provided that the guide projections (21) are only located on one side of the roller axis of rotation (18) facing the valve connection point (12).

Description

[0001] The invention relates to a valve train for an internal combustion engine, comprising a main camshaft on which a valve actuating cam is arranged, and a roller rocker arm for actuating a gas exchange valve by means of the valve actuating cam, wherein the roller rocker arm has a rocker arm housing on which a rocker arm roller is rotatably mounted about a roller pivot axis and which has, on the one hand, a valve connection point for connection to a gas exchange valve of the valve train and, on the other hand, a bearing point for mounting on an abutment of the valve train, wherein the rocker arm housing has a housing base, in particular with a recess that partially receives the rocker arm roller, as well as housing walls extending from the housing base and arranged on both sides of the rocker arm roller, and guide projections extending from the housing walls in the direction of the rocker arm roller.which are arranged for mounting on the roller side walls of the trailing arm roller, wherein the guide projections are only located on one point of the roller rotation axis facing the valve connection point, wherein the valve actuating cam rests at a contact point on the trailing arm roller.

[0002] For example, German patent application DE 10 2010 005 606 A1 is known from the prior art. This document describes a cam follower for actuating a gas exchange valve of an internal combustion engine, comprising a housing and a cam roller mounted in a recess of the housing for tapping a cam of a camshaft. The cam roller is radially mounted on a bearing pin spanning the recess and supported on the housing by means of a needle bearing running in its bearing bore. The width of the needle bearing is significantly larger than the width of the cam roller in the area of ​​cam tapping. Furthermore, the width of the needle bearing is significantly larger than the width of the cam roller in the area of ​​the bearing bore and significantly larger than the clear distance between the roller contact surfaces that define the recess and against which the cam roller axially contacts its end faces.

[0003] Document WO 2019 / 045740 A1 discloses a roller rocker arm with a rocker arm housing comprising two opposing side walls extending from a first end to a second end of the rocker arm housing, each defining a bore, and a bottom wall extending between the side walls of the rocker arm housing, defining a bearing recess defined by two opposing side walls extending between two opposing end walls. A first end and a second end of a bearing pin are received in corresponding pin recesses. A roller bearing comprises an outer ring rotatable about the bearing pin and a plurality of rolling elements arranged between the outer ring and the bearing pin.Each side wall of the bearing recess has a roller guide surface which is located closer to a longitudinal center axis of the rocker arm housing than the remainder of the corresponding side wall of the bearing recess.

[0004] Furthermore, the prior art includes the publication DE 10 2008 034 648 A1.

[0005] The object of the invention is to propose a roller rocker arm for a valve train of an internal combustion engine which has advantages over known roller rocker arms, in particular reducing wear of the rocker arm roller and / or a valve actuating cam of the valve train.

[0006] According to the invention, this is achieved with a roller rocker arm for a valve train of an internal combustion engine with the features of claim 1. It is provided that the contact surfaces of the guide projections facing the rocker arm roller, together with the contact point, lie exclusively within an angular range with respect to the roller's axis of rotation, which has an angle of at most 75°.

[0007] Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims. It should be noted that the exemplary embodiments described in the description are not limiting; rather, any variations of the features disclosed in the description, the claims, and the figures are possible.

[0008] The roller rocker arm is a component of the valve train, but can of course also exist separately from the valve train, particularly until the roller rocker arm is mounted in and / or on the valve train. Similarly, the valve train can be part of the internal combustion engine or exist separately from it. The valve train serves to actuate at least one gas exchange valve of the internal combustion engine. The gas exchange valve is designed, for example, as a gas inlet valve or a gas outlet valve.

[0009] The valve train preferably forms a component of the internal combustion engine together with the at least one gas exchange valve. It comprises a camshaft, which consists of at least one main camshaft and at least one valve actuation cam located on the main camshaft. The camshaft is preferably driven by a crankshaft of the internal combustion engine and is connected to it via a drive mechanism, preferably rigidly and / or permanently. A camshaft adjuster can be provided between the crankshaft and the camshaft, by means of which an angular offset between the crankshaft and the camshaft can be adjusted.

[0010] The camshaft has at least one valve actuating cam, which serves to actuate the gas exchange valve. The actuation of the gas exchange valve by the valve actuating cam is effected via the roller rocker arm, which thus provides at least a temporary drive connection between the valve actuating cam and the gas exchange valve. The roller rocker arm has a contact point which is preferably subjected to an actuating force by the valve actuating cam at least once per revolution of the camshaft. The actuating force causes a deflection of the roller rocker arm, in particular in the form of a rotational movement about a rocker arm axis, by which the roller rocker arm actuates the gas exchange valve.The valve actuating cam thus pushes the contact point and therefore the roller rocker arm away from a rotational axis of the camshaft at least once per revolution of the camshaft, so that the roller rocker arm is deflected to actuate the gas exchange valve.

[0011] The contact point is located on the rocker arm roller, which is rotatably mounted on the rocker arm housing around the roller's axis of rotation. On one side of the rocker arm roller, specifically the contact point, the rocker arm housing has the valve connection point, and on the other side of the rocker arm roller, specifically the contact point, it has the bearing point. The valve connection point is designed and configured to actuate the gas exchange valve during the described deflection of the roller rocker arm, specifically to actuate the gas exchange valve opening. For example, the valve connection point is at least temporarily in contact with a valve stem of the gas exchange valve or is at least in actuation-related communication with the gas exchange valve.

[0012] The bearing point is designed and configured for mounting on the valve train abutment. The abutment is, for example, stationary and / or attached to a valve train housing. In particular, the rocker arm housing rests on the abutment with its bearing point, the abutment supporting the rocker arm housing in the direction away from the camshaft axis of rotation. For example, the abutment rests against a valve lash adjuster, especially a hydraulic valve lash adjuster. The valve lash adjuster can also be referred to as a support element.

[0013] As previously explained, the valve connection point and the bearing point are located on opposite sides of the roller's axis of rotation. Specifically, they are situated on opposite sides of the rocker arm roller. This means that, in a direction perpendicular to the roller's axis of rotation, the valve connection point and the bearing point are positioned between the roller's axis of rotation and the rocker arm roller, respectively. The rocker arm roller is rotatably mounted to the rocker arm housing by means of a bearing. The bearing thus engages the rocker arm roller on one side and the rocker arm housing on the other. Preferably, the bearing is designed as a rolling bearing, more preferably as a roller bearing or a needle bearing. The rocker arm roller completely and continuously surrounds the bearing in the circumferential direction with respect to the roller's axis of rotation. The rocker arm roller is preferably designed as a hollow cylindrical or hollow circular cylindrical shape.

[0014] The rocker arm roller is bounded radially inwards by an inner roller wall and radially outwards by an outer roller wall. The inner roller wall rests against the bearing or rolling bearing. The contact point is located at the outer roller wall, meaning the rocker arm roller periodically comes into contact with the valve actuating cam. The inner and outer roller walls are connected to each other on axially opposite sides by roller sidewalls of the rocker arm roller. These sidewalls extend radially inwards from the inner roller wall and outwards to the outer roller wall. They are preferably ring-shaped. Preferably, the sidewalls lie completely in an imaginary plane that is perpendicular, or at least approximately perpendicular, to the roller's axis of rotation.

[0015] During valve train operation, asymmetrical force application to the rocker arm roller and tolerances in the bearing can cause the rocker arm roller to tilt relative to its axis of rotation. An imaginary plane passing through the center of the roller's axis of rotation will then no longer be perpendicular to the roller's axis, but will form an angle with it other than 90°. This tilting leads to increased wear of the roller rocker arm. For this reason, the roller rocker arm has guide projections located on opposite sides of the rocker arm roller, extending from the housing walls towards the roller's side walls.

[0016] The guide projections are radially aligned with the roller sidewalls relative to the roller's axis of rotation, so that, at least when the trailing arm roller tilts as described, one of the roller sidewalls abuts one of the guide projections. This at least partially prevents or limits the tilting of the trailing arm roller. The guide projections can be permanently in contact with the roller sidewalls. Preferably, however, they have a gap to the roller sidewalls, at least when the trailing arm roller is not tilted. This gap is chosen to be small in order to effectively prevent the trailing arm roller from tilting. For example, the gap, relative to the dimensions of the trailing arm roller in the axial direction, is at most 5%, at most 2.5%, or at most 1%.

[0017] The guide projections extend from the housing walls of the rocker arm housing, which are arranged on opposite sides of the rocker arm roller. The housing walls are connected to each other via the housing base. In particular, the housing base and the housing walls are formed in one piece and made of a single material. For example, they are available as a bent or stamped sheet metal part. Preferably, the housing walls are arranged parallel to each other and angled relative to the housing base. Preferably, the rocker arm housing is U-shaped in cross-section, with the housing base forming a first leg from which second legs in the form of the housing walls extend.

[0018] The use of the guide projections, when the rocker arm roller contacts them, results in a frictional or braking torque on the rocker arm roller. This can cause the rocker arm roller to brake, so that its rolling motion on the valve actuating cam transitions into a sliding motion. In other words, the rocker arm roller no longer rotates at a speed that would allow for pure rolling contact between the rocker arm roller and the valve actuating cam. This can lead to an abrasive effect on the rocker arm roller and / or the valve actuating cam, ultimately resulting in increased wear.

[0019] For this reason, according to the invention, the guide projections are located solely, i.e., exclusively and / or completely, on the side of the roller axis of rotation facing the valve connection point. The guide projections do not extend to the side of the roller axis of rotation facing away from the valve connection point, nor to the side of the roller axis of rotation facing the bearing point, but rather extend at most to the roller axis of rotation or are preferably spaced apart from it. In particular, the guide projections are located exclusively on one side of an imaginary plane that completely encompasses the roller axis of rotation and passes through the contact point, namely on the side of this imaginary plane facing the valve connection point.

[0020] Preferably, the guide projections are the only guide projections; no other projections are present. This means that, apart from the guide projections, the housing walls are consistently further away from the rocker arm roller than the guide projections, particularly in the axial direction. Preferably, the distance between the housing walls increases from the guide projections in opposite directions, preferably continuously and / or steadily. This results in the axial play of the rocker arm roller being smaller on the side of the roller's axis of rotation or the imaginary plane facing the valve connection point than on the side of the roller's axis of rotation or the plane facing away from the valve connection point.

[0021] In other words, due to the guide projections, the housing walls on the side of the roller's axis of rotation facing the valve connection point, or the imaginary plane, are closer to the rocker arm roller than on the side of the roller's axis of rotation facing away from the valve connection point, or the imaginary plane. This creates comparatively small contact surfaces for the guide projections to come into contact with the roller's side walls, thus reducing the braking torque acting on the rocker arm roller in the event of such contact. Consequently, wear on the roller rocker arm is also reduced.

[0022] A further development of the invention provides that a recess produced in the housing base, which partially accommodates the trailing arm roller, has larger dimensions in the axial direction with respect to the roller's axis of rotation than the trailing arm roller. The recess is designed in the housing base such that the trailing arm roller extends into it or passes completely through it. In the latter case, the trailing arm roller is located on both sides of the housing base. The roller's axis of rotation has larger dimensions in the axial direction than the trailing arm roller; in particular, its dimensions are at least 5%, at least 10%, or at least 15% larger than the dimensions of the trailing arm roller in the same direction. This prevents the trailing arm roller from coming into contact with an edge defining the recess when it tilts.Such contact of the roller against the edge could also cause the described braking torque and thus increased wear of the roller roller. This is effectively prevented by appropriately selecting the dimensions of the recess.

[0023] A further development of the invention provides that the rocker arm roller has a central recess in which a rolling bearing is arranged for mounting the rocker arm roller to the rocker arm housing. Such a design has already been mentioned. Preferably, the rocker arm roller rests against the rolling bearing with the aforementioned inner roller wall, or rather, completely and continuously surrounds the rolling bearing in the circumferential direction. The inner roller wall defines the central recess of the rocker arm roller in which the rolling bearing is located. Preferably, the rolling bearing projects axially beyond the rocker arm roller, i.e., extends axially out of the central recess, particularly on both sides of the rocker arm roller. The distances between the housing walls are selected such that even when the rocker arm roller tilts, the rolling bearing is always spaced apart from the housing walls.This also serves to reduce wear on the roller rocker arm.

[0024] A further development of the invention provides that the contact surfaces of the guide projections facing the trailing arm roller have dimensions in the radial direction with respect to the roller's axis of rotation that correspond to at most 50%, at most 30%, or at most 10% of the dimensions of the roller's side walls in the same direction. The contact surfaces are understood to be surfaces of the guide projections against which the trailing arm roller temporarily rests when tilting, i.e., with which it is in contact. In particular, the contact surfaces are understood to be only those surfaces of the guide projections against which the trailing arm roller rests when tilted to its maximum extent.

[0025] The guide projections are dimensioned to be as small as possible in order to ensure reliable guidance of the trailing arm roller while simultaneously achieving this with the lowest possible braking torque. For this reason, the guide projections, viewed axially with respect to the roller's axis of rotation, have dimensions that correspond to at most 50%, at most 30%, or at most 10% of the dimensions of the roller sidewalls in the radial direction. When the roller sidewalls contact the bearing surfaces, the bearing surfaces therefore only partially overlap the roller sidewalls, by at most one of the aforementioned proportions. This results in a particularly low braking torque.

[0026] A further development method involves producing the guide projections by forming, particularly by embossing, the housing walls. For example, the entire rocker arm housing can be formed, and the guide projections are created during this process. Specifically, a blank is first stamped out, which is then formed to create the rocker arm housing. However, it is also possible to initially produce the rocker arm housing without the guide projections and then subsequently form them by forming the housing walls. This can be achieved, for example, by locally forming the housing walls using embossing. This allows for particularly small contact surfaces and thus a low braking torque.

[0027] A further development of the invention provides that the guide projections are formed in certain areas by an edge of the housing walls. The edge of the housing walls is understood to be an edge that defines them on their side facing away from the housing base, thus a free edge of the housing walls. The edge is locally deformed, namely in the axial direction towards the rocker arm roller. This allows for particularly simple manufacturing of the roller rocker arm.

[0028] A further development of the invention provides that the contact surfaces of the guide projections facing the trailing arm roller are convex. The convex shape of the contact surfaces is understood to mean, in particular, a partially spherical, preferably hemispherical, shape. Specifically, the contact surfaces are designed such that the contact between the trailing arm roller and the guide projections is only point contact. This significantly reduces the braking torque. Furthermore, it achieves particularly good lubrication.

[0029] A further method for manufacturing a roller rocker arm for a valve train of an internal combustion engine is disclosed, in particular a roller rocker arm according to the embodiments within the scope of this description, wherein the roller rocker arm has a rocker arm housing on which a rocker arm roller is rotatably mounted about a roller pivot axis and which, on the one hand, has a valve connection point for connection to a gas exchange valve of the valve train on the roller pivot axis and, on the other hand, has a bearing point for mounting on an abutment of the valve train on the roller pivot axis, wherein the rocker arm housing has a housing base, in particular with a recess that partially receives the rocker arm roller, as well as housing walls extending from the housing base and arranged on both sides of the rocker arm roller, and guide projections extending from the housing walls in the direction of the rocker arm roller.which are arranged for mounting on the roller side walls of the trailing arm roller. It is provided that the guide projections are only manufactured on one side of the roller's axis of rotation facing the valve connection point.

[0030] The advantages of such a procedure or such a design of the roller rocker arm have already been mentioned. Both the roller rocker arm and the method for its manufacture can be further developed as described in this document.

[0031] For further information regarding the advantages and possible beneficial developments of the valve train and the roller rocker arm, please refer to the explanations in this description. The main camshaft and the valve actuating cam can be manufactured as a single piece and / or from a single material. However, it is also possible for the valve actuating cam to be positively engaged and / or frictionally engaged on the main camshaft. Particularly preferably, the valve actuating cam is arranged to be displaceable axially with respect to a camshaft axis of rotation, especially such that the roller rocker arm can be actuated by different valve actuating cams.

[0032] The invention provides that the valve actuating cam bears against a contact point on the rocker arm roller, and that the contact surfaces of the guide projections facing the rocker arm roller, together with the contact point, lie at an angle of at most 75° or at most 60° with respect to the roller's axis of rotation. The contact point is located on the rocker arm roller and designates the point at which the valve actuating cam is in contact with the rocker arm roller, at least temporarily, preferably continuously. The contact point is situated at a specific angle of rotation with respect to the roller's axis of rotation.

[0033] Viewed circumferentially, the contact point lies within the angular region in which the contact surfaces of the guide projections are also arranged, in particular entirely. This means that the contact surfaces project beyond the housing walls only within this angular region, and the housing walls, away from the guide projections, preferably continuously, have a greater axial distance from the rocker arm roller than the guide projections. It follows that the guide projections are manufactured close to the contact point, thus reliably preventing tilting of the rocker arm roller. Furthermore, the contact surfaces of the guide projections are designed to be small in order to reduce braking torque.

[0034] The features and combinations of features described in the description, in particular those described in the following figure description and / or shown in the figures, are not only usable in the combinations specified, but also in other combinations or individually, provided that this does not exceed the scope defined by the claims. Thus, embodiments that are not explicitly shown or explained in the description and / or the figures, but which emerge from or can be derived from the explained embodiments, are also to be considered as encompassed by the invention, provided that these embodiments are within the scope of the claims.

[0035] The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawing, without limiting the invention. The drawing shows: Fig. 1 A schematic sectional view through a valve train of an internal combustion engine in the area of ​​a roller rocker arm, which is shown in a first embodiment Fig. 2 a schematic representation of the first embodiment of the roller trailing arm, as well as Fig. 3 a schematic representation of a second embodiment of the roller trailing arm.

[0036] The Fig. Figure 1 shows a schematic cross-sectional view through a section of an internal combustion engine 1, more precisely a valve train 2 of the internal combustion engine 1. The valve train 2 has a camshaft 3, which here, for example, consists of a base camshaft 4 and a valve actuating cam 5 arranged on the base camshaft 4. During operation of the internal combustion engine 1, the camshaft 3 rotates, at least temporarily, in the direction of rotation indicated by arrow 6.

[0037] The camshaft 3, and in particular the valve actuation cam 5, serve to actuate a gas exchange valve 7, of which only a valve stem 8 is indicated here. The actuation of the gas exchange valve 7 by means of the camshaft 3 is effected via a roller rocker arm 9, which is shown here in a first embodiment. The roller rocker arm 9 is supported on one side by a bearing point 10 against an abutment 11, and on the other side by a valve connection point 12 against the valve stem 8. The gas exchange valve 7 is actuated by a spring 13. The spring force pushes the valve stem 8 towards the roller rocker arm 9 and consequently the rocker arm towards the camshaft 3.

[0038] The roller rocker arm 9 has a rocker arm housing 14, on which the bearing point 10 and the valve connection point 12 are provided. In particular, the rocker arm housing 14 has a housing base 15 from which housing walls 16 extend, which are arranged on opposite sides of a rocker arm roller 17. The rocker arm roller 17 is rotatably mounted on the rocker arm housing 14 about a roller pivot axis 18, namely by means of a bearing 19, which is designed as a rolling bearing. The rocker arm roller 17 is arranged and designed such that it comes into contact, at least temporarily, with the camshaft 3 and in particular with the valve actuating cam 5, namely at a contact point 20.

[0039] To prevent or at least limit tilting of the rocker arm roller 17 relative to the rocker arm housing 14, guide projections 21 extend from the housing walls 16 and move towards the rocker arm roller 17 from opposite sides. In cross-section, it can be seen that the contact point 20 and the guide projections 21 are arranged within an angular range around the roller's axis of rotation 18, forming an angle 22. The angle 22 is at most 75°, but preferably smaller.

[0040] The Fig. Figure 2 shows the roller rocker arm 9 in the first embodiment. The two guide projections 21, located on opposite sides of the rocker arm roller 17 and extending from the housing walls 16 towards the rocker arm roller 17, are clearly visible. It can be seen that the guide projections 21 are produced by embossing, so that embossed recesses 23 are present on one side of the housing walls 16 facing away from the rocker arm roller 17.

[0041] Furthermore, it is evident that the guide projections 21 have comparatively small dimensions at their ends facing the trailing arm roller 17. Thus, their ends overlap the trailing arm roller 17 or the roller side walls 24 of the trailing arm roller 17 only to a small extent, preferably in the radial direction with respect to the roller axis of rotation 18 by a maximum of 30%, a maximum of 20%, or a maximum of 10%. The guide projections 21 are spaced apart from the edges 25 of the housing walls 16. The edges 25 are thus located at a greater distance from the trailing arm roller 17 than the guide projections 21.

[0042] The Fig.Figure 3 shows a schematic representation of the roller rocker arm 9 in a second embodiment. This embodiment is fundamentally similar to the first embodiment, so reference is made to the corresponding illustrations, and only the differences are discussed below. These differences lie in the fact that the guide projections 21 are partially formed from the edges 25. The edges 25 are thus deformed axially onto the rocker arm roller 7, in particular by deforming the housing walls 16.

[0043] The sides of the guide projections 21 facing the roller side walls 24, which can also be referred to as contact surfaces 26, are designed to be rounded, for example, partially spherical, in order to achieve a particularly small contact area between the trailing arm roller 17 and the guide projections 21. This enables a particularly significant reduction in friction and a correspondingly low braking torque acting on the trailing arm roller 17 when it contacts the guide projections 21. This significantly reduces wear on the roller trailing arm 9. REFERENCE MARK LIST: 1 internal combustion engine 2 Valve train 3 camshaft 4. Basic camshaft 5 valve actuation cams 6 Arrow 7 Gas exchange valve 8 Valve stem 9 roller rocker arms 10 storage locations 11 abutments 12 Valve connection point 13 spring 14 rocker arm housings 15 Case base 16 case walls 17 Drag lever roller 18 Roller pivot axis 19 warehouses 20 Contact Point 21 Leading lead 22 angles 23 Embossing depression 24 roller side wall 25 Rand 26 Plant area

Claims

[1] Valve train (2) for an internal combustion engine (1), comprising a main camshaft (4) on which a valve actuating cam (5) is arranged, and a roller rocker arm (9) for actuating a gas exchange valve (7) by the valve actuating cam (5), wherein the roller rocker arm (9) has a rocker arm housing (14) on which a rocker arm roller (17) is rotatably mounted about a roller pivot axis (18) and which has, on the one hand, a valve connection point (12) for connection to a gas exchange valve (7) of the valve train (2) on the other hand, a bearing point (10) for mounting on a support (11) of the valve train (2) on the other hand, wherein the rocker arm housing (14) has a housing base (15) and, extending from the housing base (15),Housing walls (16) are arranged on both sides of the rocker arm roller (17), and guide projections (21) extend from the housing walls (16) towards the rocker arm roller (17), which are arranged to bear against roller side walls (24) of the rocker arm roller (17), wherein the guide projections (21) are only present on one side of the roller rotation axis (18) facing the valve connection point (12), wherein the valve actuating cam (5) bears against a contact point (20) on the rocker arm roller (17), characterized by , that the contact surfaces (26) of the guide projections (21) facing the trailing arm roller (17) together with the contact point (20) lie exclusively in an angular range with respect to the roller rotation axis (18) which has an angle (22) of at most 75°. [2] Valve train (2) according to claim 1, characterized by, that a recess produced in the housing base (15) and partially accommodating the trailing arm roller (17) has larger dimensions in the axial direction with respect to the roller rotation axis (18) than the trailing arm roller (17). [3] Valve train (2) according to one of the preceding claims, characterized by , that the rocker arm roller (17) has a central recess in which a rolling bearing (19) is arranged for the mounting of the rocker arm roller (17) on the rocker arm housing (14). [4] Valve train (2) according to any one of the preceding claims, characterized by , that the contact surfaces (26) of the guide projections (21) facing the trailing arm roller (17) have dimensions in the radial direction with respect to the roller axis of rotation (18) that correspond to at most 50%, at most 30% or at most 10% of the dimensions of the roller side walls (24) in the same direction. [5] Valve train (2) according to one of the preceding claims, characterized by, that the guide projections (21) are formed in some areas by an edge (25) of the housing walls (16). [6] Valve train (2) according to any one of the preceding claims, characterized by , that the contact surfaces (26) of the guide projections (21) facing the trailing arm roller (17) are convex.

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