Valve train of an internal combustion engine and corresponding internal combustion engine

Abstract

Valve train (2) of an internal combustion engine (1), comprising at least one camshaft (4) and at least one cam carrier (5) arranged on the camshaft (4) in a rotationally fixed and axially displaceable manner, wherein the cam carrier (5) and / or the camshaft (4) are mounted in a radial bearing (12) formed or at least held by a housing (3) of the valve train (2) and an end stop (14) serving to limit axial displacement of the cam carrier (5) is provided, wherein the end stop (14) is designed as a damping element (15) inserted into the housing (3) of the valve train (2) during assembly, characterized in that the damping element (15) has at least one stop surface (16) for the cam carrier (5) which is provided on a damping wall (17) arranged axially spaced from the radial bearing (12) and / or the housing (3).

Description

[0001] The invention relates to a valve train of an internal combustion engine, comprising at least one camshaft and at least one cam carrier arranged on the camshaft in a rotationally fixed and axially displaceable manner. The cam carrier and / or the camshaft are / is mounted in a radial bearing formed or at least held by a housing of the valve train. An end stop is provided to limit axial displacement of the cam carrier. The end stop is designed as a damping element introduced into the housing of the valve train during assembly. The invention further relates to an internal combustion engine.

[0002] Valve trains of the type mentioned above are known from the prior art. Such valve trains essentially consist of the camshaft and at least one cam carrier. At least one cam is assigned to the cam carrier, which serves, for example, to actuate a valve of the internal combustion engine. The cam has a cam track on which a counter element, which is operatively connected to the valve, runs. Due to its eccentric shape, the cam actuates the valve according to its angular position or the angular position of the camshaft. In order to be able to assign several different cam tracks to the valve, between which switching is possible, for example, depending on the load condition of the internal combustion engine, the cam carrier is arranged on the camshaft so that it can be axially displaced.For example, at least two cams are assigned to the cam carrier, each of which has at least one cam track. By axially displacing the cam carrier, the valve can be brought into operative connection with the different cams or the different cam tracks. To limit the axial displacement of the cam carrier, an end stop is provided. The cam carrier rests against this stop after the displacement has been completed, ensuring a defined axial position of the cam carrier.

[0003] Such a valve train is described, for example, in WO 2004 / 083611 A1. The valve train is associated with an internal combustion engine having a cylinder head and at least one camshaft, on which at least one cam carrier is arranged in a rotationally fixed and axially displaceable manner.

[0004] The publication DE 10 2004 021 375 A1 relates to a valve train of an internal combustion engine with a camshaft on which axially movable cam carriers are arranged. The camshaft and the cam carriers are supported by bearing blocks surrounding the cam carriers, on which stop surfaces forming axial bearings are formed on both sides.

[0005] The prior art documents DE 10 2004 021 376 A1 and DE 20 2006 014 691 U1 are also known.

[0006] In such a valve train, the end stop is usually formed by a valve train housing, in which the camshaft is arranged at least in part. The housing can also simultaneously form the radial bearing for the camshaft or the cam carrier. To limit the displacement of the cam carrier in the axial direction, the end stop interacts, for example, with a projection arranged on the cam carrier or a cam arranged on the cam carrier or the cam carrier itself. A disadvantage of such a valve train design, however, is that the movement of the cam carrier against the end stop causes noises - the underlying vibrations of which are caused, for example, by the gearing between the cam carrier and the camshaft and are generated in particular by alternating torques - which can be perceived as unpleasant.This is particularly the case if the end stop is formed by the radial bearing or the housing of the valve train, because then the structure-borne noise or the corresponding vibration generated by the impact is transmitted via the radial bearing or the housing.

[0007] It is therefore the object of the invention to provide a valve train which does not have the disadvantages mentioned above, but in particular operates with low noise.

[0008] This is achieved according to the invention in that the damping element has at least one stop surface for the cam carrier, which is provided on a damping wall arranged at a distance from the radial bearing and / or the housing in the axial direction. The damping element dampens the noises that usually occur when the cam carrier approaches the end stop or prevents or at least reduces the transmission of structure-borne noise. In this way, a valve train that operates quietly, particularly during the axial displacement of the cam carrier. The end stop is in the form of the damping element. In an embodiment not according to the invention, however, the damping element can alternatively be assigned to the end stop in order to achieve the damping effect.This is especially true if the valve train includes the housing that forms the radial bearing for supporting the cam carrier or camshaft. In this case, the damping element can be assigned to the radial bearing to form the end stop, or the axial bearing can be formed by the damping element assigned to the radial bearing.

[0009] The invention provides that the damping element has at least one stop surface for the cam carrier. Thus, the cam carrier is not merely intended to engage the end stop or damping element at a specific point. Rather, the engagement is to occur over a wide area, with the stop surface of the damping element interacting with a counter-surface of the cam carrier to limit the axial displacement of the cam carrier. It is particularly advantageous if the damping element is present on both sides of the radial bearing, so that it can serve both as an end stop for the cam carrier and for another cam carrier.

[0010] The invention provides that the stop surface is provided on a damping wall arranged at an axial distance from the radial bearing and / or a housing. The damping wall is therefore a component of the damping element or the end stop. The stop surface is provided on the side of the damping wall facing away from the radial bearing, while the side facing the radial bearing is at least partially spaced from it. This axial spacing achieves the damping effect of the damping element. When the cam carrier pushes against the damping element, the damping wall is initially subjected to an impulse, but not the radial bearing or the valve train housing.Thus, the transmission of structure-borne noise in the radial bearing or the housing is at least partially prevented, so that the noises occurring when the cam carrier is displaced or when it moves against the end stop are dampened in volume.

[0011] A further development of the invention provides that the damping wall has at least one spacer designed as a projection for axial spacing from the radial bearing and / or the housing. The spacer is, for example, embossed into the damping wall, so that the projection is formed on the side of the damping element facing the radial bearing and / or the housing. The spacer or projection is therefore provided for supporting the damping element on the radial bearing or the housing in the axial direction. The projection can, in principle, have any desired shape; it is preferably circular to enable simple manufacture by embossing. The projection has a small surface area compared to the stop surface, so that the damping element only comes into contact with the radial bearing or the housing at specific points.Preferably, a fluid film is provided between the damping element and the radial bearing or the housing, which provides additional damping. The spacer can be designed such that it permanently rests against the radial bearing or the housing. In an alternative embodiment, however, it can also be provided that the spacer is spaced from the radial bearing or the housing when the cam carrier is not resting against the end stop. In this case, the spacer is provided to counter the radial bearing or the housing as soon as the cam carrier interacts with the end stop.In this case, the additional fluid film between the damping wall and the radial bearing or the housing provides additional damping because the fluid must first escape from the space formed between the damping wall and the radial bearing or the housing before the spacer can come into contact with the radial bearing or the housing.

[0012] A further development of the invention provides that the damping wall has a radial recess for accommodating the camshaft and / or the cam carrier. The radial recess is intended to accommodate the camshaft or the cam carrier at least in part, so that the damping element surrounds it at least in part. For this purpose, the damping wall can be in the form of an annular section, in particular a circular ring section.

[0013] A further development of the invention provides that the damping element has at least one lubricant supply, via which a lubricant connection is established between the end stop and the radial bearing. To enable reliable operation of the valve train, it is usually necessary to supply both the end stop and the radial bearing with lubricant. It is advantageous if only either the end stop or the radial bearing needs to be supplied with lubricant and the other element is supplied with a sufficient amount of lubricant via the lubricant connection. For this purpose, the lubricant supply is provided, which establishes the lubricant connection or a fluid connection. The lubricant supply can, for example, be present at least partially as a channel or be realized via a recess.

[0014] A further development of the invention provides that the lubricant supply is provided, at least in some areas, as a recess and / or chamfer in the damping element. The recess or chamfer forms (or co-forms) an opening through which the lubricant can pass, thus establishing the lubricant connection between the end stop and the radial bearing.

[0015] A further development of the invention provides that the housing consists of a housing base body and a housing cover that can be placed onto the housing base body, wherein the housing base body and / or the housing cover have a recess for receiving a holding projection functional element in a contact region between the housing base body and the housing cover. The housing therefore consists of at least two elements that form the housing base body and the housing cover. The housing cover can be placed onto the housing base body or connected to it. When the housing cover is placed onto the housing base body, the two elements come into contact with one another in the contact region. The recess for receiving the holding projection is provided in this contact region. The recess can be provided either in the housing body or the housing cover or in certain regions in both.The retaining projection serves to hold the damping element or end stop to the radial bearing or housing. In particular, the retaining projection also ensures the axial spacing of the damping wall from the radial bearing or housing.

[0016] A further development of the invention provides that the retaining projection has at least one spacing projection that vertically separates the retaining projection from the housing base body and / or the housing cover. Analogous to the spacer, which ensures axial spacing between the damping wall and the radial bearing or housing, the spacing projection is provided to separate the retaining projection from the housing base body or housing cover. In this way, the contact surface of the retaining projection or the damping element on the housing base body or housing cover is reduced in order to further dampen structure-borne sound transmission.

[0017] The invention further relates to an internal combustion engine with at least one valve train, in particular according to the above embodiments, wherein the valve train has at least one camshaft and at least one cam carrier arranged on the camshaft in a rotationally fixed and axially displaceable manner, and the cam carrier and / or the camshaft are / is mounted in a radial bearing formed or at least held by a housing of the valve train, and an end stop is provided to limit axial displacement of the cam carrier. It is provided that the end stop is designed as a damping element introduced into the housing of the valve train during assembly. It is further provided that the damping element has at least one stop surface for the cam carrier, which is provided on a damping wall arranged at a distance from the radial bearing and / or the housing in the axial direction.The valve train of the internal combustion engine can be designed or further developed in accordance with the above statements.

[0018] The invention will be explained in more detail below with reference to the exemplary embodiments illustrated in the drawings, without limiting the invention. They show: Fig. 1 a region of a valve train of an internal combustion engine, with a camshaft on which an axially displaceable cam carrier is provided, which is mounted in a radial bearing, Fig. 2 a sectional view of the Fig. 1 known valve train, Fig. 3 a detailed view of a section of the valve train, as in Fig. 2 indicated, Fig. 4 an exploded view of the valve train, showing that a housing of the valve train consists of a housing base body and a housing cover, Fig. 5 a first embodiment of an end stop designed as a damping element, and Fig. 6 a second embodiment of the end stop.

[0019] The Fig. 1 shows a region of an internal combustion engine 1, depicting part of a valve train 2 of the internal combustion engine 1. The valve train 2 has a housing 3. A camshaft 4 is arranged in this housing, at least in part. A cam carrier 5 is arranged or mounted on the camshaft 4 in a rotationally fixed and axially displaceable manner. At least one (here: two) cams 6 and 7 are provided on the cam carrier 5. These each have at least one cam track 8. The cam tracks 8 interact with a respective counter element, which is assigned to a valve (not shown here) of the internal combustion engine 1. The cam tracks 8 are formed eccentrically to the camshaft 4. For this reason, the counter element is subjected to different loads depending on the angular position of the camshaft 4 or of the cams 6 and 7.

[0020] The cams 6 and 7 each have a second cam track 9, which is arranged adjacent to the cam track 8 on the cams 6, 7. The cam tracks 8 and 9 usually have different eccentricities, in particular with regard to a rotational angle position of the maximum eccentricity and / or the height of the maximum eccentricity. By displacing the cam carrier 5, either the cam track 8 or the cam track 9 can be brought into operative connection with the counter element and thus the valve of the internal combustion engine 1. This makes it possible to control the valve of the internal combustion engine 1 differently, for example depending on a load range in which the internal combustion engine 1 is operated.

[0021] To carry out the displacement, the cam carrier 5 has an actuating element 10 on each side, each of which has an engagement track 11. An actuating device can engage in this engagement track 11 to thus displace the cam carrier 5. The cam carrier 5 is mounted in a radial bearing 12, which, in the embodiment shown here, is formed or at least held by the housing 3. The radial bearing 12 ensures radial support of the cam carrier 5 and thus also of the camshaft 4.

[0022] In embodiments of the internal combustion engine 1 known from the prior art, the radial bearing 12 also simultaneously represents an axial bearing 13. However, this is not provided here. Instead, an end stop 14 is provided, which takes over the function of the axial bearing 13. The end stop 14 is designed as a damping element 15 or has a damping element 15. To limit the displacement of the cam carrier 5, the end stop 14 interacts, for example, with the cam carrier 5 itself and / or with a projection arranged on the cam carrier. The projection can, for example, be the cam 6 or 7 arranged on the cam carrier 5. In the embodiment shown here, the damping element 15 is assigned to the radial bearing 12 to form the end stop 14. The axial bearing 13 or the end stop 14 is therefore formed by the damping element 15 assigned to the radial bearing 12.

[0023] The damping element 15 has at least one stop surface 16, which cooperates with the cam carrier 5 or the cam 6 to form the end stop 14 for the cam carrier 5. In the Fig. 1, only the stop surface 16 is visible. The end stop 14 or the damping element 15, however, is designed symmetrically, so that its side facing the cam 7 is designed accordingly. In another embodiment, it can also be provided that the cam carrier 5 is present only on one side of the radial bearing 12. In such an embodiment, the cam carrier 5 can be arranged on one side of the radial bearing 12 and a further cam carrier (not shown here) can be arranged on the other side. The radial bearing 12 serves in particular to support the camshaft 4, and the end stop 14 serves to limit the axial displacement of the cam carrier 5 and the further cam carrier.

[0024] The stop surface 16 is provided on a damping wall 17, wherein the stop surface 16 lies on the side of the damping wall 17 facing the cam 6. The damping wall 17 is spaced apart from the radial bearing 12 or the housing 3 in the axial direction of the camshaft 4. Thus, there is no surface contact between a side surface of the damping wall 17 facing the radial bearing 12 or the housing 3 and the radial bearing 12 or the housing 3. Rather, the spacing is intended to dampen structure-borne noise, so that the counteraction of the cam carrier 5 against the end stop 14 that occurs upon displacement of the cam carrier 5 is dampened. In this way, no noises occur during operation of the internal combustion engine 1 that would be perceived as unpleasant by a user or a driver of a motor vehicle having the internal combustion engine 1.

[0025] The Fig. The housing 3 shown in Figure 1 is made up of several parts, with a housing base body 18 and a housing cover 19 being provided. The housing cover 19 is shown in the illustration of Fig. 1 is shown in section, so that a contact area 20 can be seen, in which the housing cover 19 rests on the housing base body 18. The housing base body and the housing cover 19 are fastened to one another by means of a screw connection, of which only a screw receptacle 21 of the housing base body 18 can be seen here. A recess 22 is formed in the contact area 20, in which a holding projection 23 of the end stop 14 or of the damping element 15 is received. The holding projection 23 is constructed like a bridge in order to connect the two sides of the end stop 14 to one another. In the embodiment shown here, the recess 22 is only provided in the housing base body 18. Alternatively, however, it can also be present at least partially in the housing cover 19.

[0026] The Fig. 2 shows a sectional view of the Fig. 1 known part of the valve train 2 or the internal combustion engine 1. It can be seen that the cam carrier 5 is hollow and accommodates the camshaft 4. In order to fix the cam carrier 5 in its possible displacement positions, a locking device 24 is provided. This consists of a guide channel 25 arranged in the camshaft 4 and a locking element 26 arranged in this guide channel, which is designed here as a ball. The locking element 26 is spring-loaded by a spring 27, whereby it is urged outwards in the radial direction by the spring 27. The locking element 26 interacts with locking tracks 28 provided in the cam carrier 5 to ensure that the cam carrier 5 is held in the respective displacement position.

[0027] In the Fig. 2 also shows that the end stop 14 is designed such that, when the stop surface 16 and the cam carrier 5 interact, a gap 29 remains in the axial direction between the latter and the radial bearing 12. The cam carrier 5 is therefore only in contact with the stop surface 16 or the end stop 14, but not with the radial bearing 12 or the housing 3. This applies to every displacement position of the cam carrier 5. It should be noted again that the end stop 14 is designed symmetrically, although only one side of it will be discussed here. Fig. 2 a section is indicated by a circle III, which is based on the Fig. 3 will be explained in more detail.

[0028] The Fig. 3 shows a section of the sectional view of the Fig. 2. It can be seen that the end stop 14 or its damping wall 17 has at least one spacer 31, which is designed here as a projection to ensure the spacing of the damping wall 17 from the radial bearing 12 or the housing 3. The spacer 31 is produced, for example, by stamping and is therefore in the form of a projection. Consequently, the contact surface between the end stop 14 or the damping element 15 and the housing 3 or the radial bearing 12 is significantly smaller than the contact surface between the cam carrier 5 and the stop surface 16. Effective noise reduction or damping of structure-borne noise is thus achieved.

[0029] The Fig. Figure 4 shows an exploded view of the valve train 2, already known from the above explanations, or the internal combustion engine 1. It can be seen how the end stop 14, or the damping element 15, is designed and how it is inserted into the housing 3 during assembly. The retaining projections 23 of the end stop 14 are inserted into the recesses 22 of the housing base body 18 during assembly. The cam carrier 5, together with the camshaft 4, is then inserted into the radial bearing 12. The housing cover 19 is then placed onto the housing base body 18 so that the radial bearing 20 completely encloses the cam carrier 5 in the circumferential direction and, at the same time, the retaining projections 23 are held in the recesses 22. It can also be seen that the end stop 14, or its damping wall 17, has a radial recess 32 for receiving the camshaft 4 and / or the cam carrier 5. Fig. 4 also shows that at least one receptacle 33 for areas of the end stop 14 is provided in the housing base body 18.

[0030] The Fig. 5 shows a first embodiment of the end stop 14 in a detailed view. In addition to the elements already described above, for which reference is made to the above explanations, it can be seen that the end stop 14 and its holding projections 23 have guide recesses 34, through which the fastening means used for this purpose penetrate when the housing base body 18 and the housing cover 19 are fastened to one another. This serves to further stabilize the damping element 15 in the recesses 22. The damping element 15 and the end stop 14 have four lubricant feeds 35, which in the embodiment shown here are designed as feed recesses 36. Alternatively, a chamfered design can also be provided. A fluid connection or lubricant connection is formed between the end stop 14 and the radial bearing 12 via the lubricant feed 35.In this way, only either the radial bearing 12 or the end stop 14 needs to be supplied with lubricant.

[0031] The Fig. 6 shows a second embodiment of the end stop 14 or the damping element 15. The difference to the Fig. 5 is only in the material thickness, which is the case in the Fig. 6 is significantly lower. The end stop 14 or damping element 15 is therefore designed as a sheet metal component.

[0032] In an alternative embodiment, at least one spacing projection can be provided in the region of the holding projection 23, which spacing the holding projection 23 from the housing base body 18 and / or the housing cover 19 in the vertical direction. LIST OF REFERENCE SYMBOLS 1 fuel engine 2 valve train 3 housings 4 camshaft 5 cam carriers 6 cams 7 cams 8 Cam track 9 Cam track 10 Actuating element 11 intervention lane 12 radial bearings 13 thrust bearings 14 End stop 15 Damping element 16 Stop surface 17 Damping wall 18 Housing clamping bodies 19 Housing cover 20 Contact area 21 screw holder 22 Recess 23 Holding projection 24 locking device 25 guide channel 26 locking element 27 spring 28 Rest track 29 gap 31 spacers 32 Radial recess 33 recording 34 Guide recess 35 Lubricant supply 36 Feed recess

Claims

[1] Valve train (2) of an internal combustion engine (1), with at least one camshaft (4) and at least one cam carrier (5) arranged on the camshaft (4) in a rotationally fixed and axially displaceable manner, wherein the cam carrier (5) and / or the camshaft (4) are / is mounted in a radial bearing (12) formed or at least held by a housing (3) of the valve train (2) and an end stop (14) is provided for limiting an axial displacement of the cam carrier (5), wherein the end stop (14) is designed as a damping element (15) introduced into the housing (3) of the valve train (2) during assembly, characterized by that the damping element (15) has at least one stop surface (16) for the cam carrier (5), which is provided on a damping wall (17) arranged at a distance from the radial bearing (12) and / or the housing (3) in the axial direction. [2] Valve train according to claim 1, characterized bythat the damping wall (17) has at least one spacer (31) designed as a projection for axial spacing from the radial bearing (12) and / or the housing (3). [3] Valve train according to one of the preceding claims, characterized by that the damping wall (17) has a radial recess (32) for receiving the camshaft (4) and / or the cam carrier (5). [4] Valve train according to one of the preceding claims, characterized by that the damping element (15) has at least one lubricant supply (35) via which a lubricant connection is provided between the end stop (14) and the radial bearing (12). [5] Valve train according to claim 4, characterized by that the lubricant supply (35) is present at least in some areas as a recess (36) and / or chamfer of the damping element (15). [6] Valve train according to one of the preceding claims, characterized bythat the housing (3) consists of a housing base body (18) and a housing cover (19) which can be placed on the housing base body (18), wherein the housing base body (18) and / or the housing cover (19) have a recess (22) for receiving a holding projection (23) of the damping element (15) in a contact area (20) of the housing base body (18) and the housing cover (19). [7] Valve train according to claim 6, characterized by that the holding projection (23) has at least one spacing projection which spaces the holding projection (23) in the vertical direction from the housing base body (18) and / or the housing cover (19). [8] Internal combustion engine (1) with at least one valve train (2) according to one of the preceding claims, wherein the valve train (2) has at least one camshaft (4) and at least one cam carrier (5) arranged on the camshaft (4) in a rotationally fixed and axially displaceable manner, and the cam carrier (5) and / or the camshaft (4) are / is mounted in a radial bearing (12) formed or at least held by a housing (3) of the valve train (2), and an end stop (14) serving to limit an axial displacement of the cam carrier (5) is provided, wherein the end stop (14) is designed as a damping element (15) introduced into the housing (3) of the valve train (2) during assembly, characterized by that the damping element (15) has at least one stop surface (16) for the cam carrier (5), which is provided on a damping wall (17) arranged at a distance from the radial bearing (12) and / or the housing (3) in the axial direction.

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