Valve gear for a combustion engine of a motor vehicle

A valve gear has a cam shaft with a firing cam and a braking cam. A first cam follower is allocated to the firing cam with the first cam follower being provided in a firing operation for actuating a gas exchange valve. A second cam follower is allocated to the braking cam with the second cam follower being provided in a braking operation for actuating the gas exchange valve. A changeover device switches between the operations and has a tilting lever mount having a pivotably mounted mounting element on which a tilting lever belonging to the first cam follower and a tilting lever belonging to the second cam follower are pivotably mounted. The tilting lever mount has two mounting screws respectively having a ball head and the ball heads each form a ball joint together with a ball head receiver of the allocated tilting lever.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a valve gear for a combustion engine of a motor vehicle, in particular a utility vehicle.

A valve gear having at least one cam shaft, which has at least one cam group having at least one firing cam and at least one braking cam, is already known from DE 10 2013 019 000 A1, having at least one cam follower allocated to the firing cam, the cam follower being provided in a firing operation for actuating at least one gas exchange valve, and a cam follower allocated to the braking cam, the cam follower being provided in a braking operation for actuating the at least one gas exchange valve, and having a changeover device, which is provided to switch between the firing operation and the braking operation. The changeover device is provided to convert a torsional moment of the cam shaft into a force for switching between the firing operation and the braking operation.

The known embodiment of the valve gear constitutes a purely mechanical switching between two different valve elevations. The cam followers are functionally allocated to a certain valve elevation, i.e., one cam follower for the fired elevation and another for the braking elevation. The mounting of the cam followers takes place on a common tilting lever axis, which is additionally rotatably mounted in the engine housing. The cam followers themselves are mounted on this axis with a central offset in relation to the rotational axis of the tilting lever axis, such that it leads to a shifting of the tilting lever central axes relatively to the cam shaft axis, when the tilting lever axis is rotated. This rotation causes a counter shifting of the tilting lever mount, such that this alternately comes into contact with the cam shaft. Thus, a switching between different valve elevations is achieved, which are independent of one another and do not have to have a base circle phase.

The synchronous rotation of the tilting lever axis at a certain control point in time is caused by the cam elevation of a cam follower itself, i.e., the mounting force generates a corresponding shifting moment on the tilting lever axis, by means of which this is correspondingly rotated. Since the cam elevation is constant, the tilt lever axis is also hamioniously and continuously adjusted. In addition, the adjustment to the same time interval takes place, in which a regular valve elevation would take place. Switching between the two cam profiles takes place via the unlocking of the end position of the tilting lever axis. In the event of a triggered unlocking, with the next cam elevation, a rotation, which is carried out until reaching the opposite end position and again automatically stops the locking, takes place.

The triggering of the switching process, i.e., the unlocking of the tilting lever axis, is ensured by a cam shaft-synchronous triggering device. This is constructively designed in such a way that the control point in time for switching there and back is shifted by the length of half of the cam elevation. Thus, it is achieved that, when switching from the fired mode, the opening flank of the switching cam used as such of a valve elevation causes the rotation of the tilting lever axis into the braking mode and, corresponding to the down-switching, the closing flank thereof as the switching cam used as such of a valve elevation causes the back-rotation into the fired mode, wherein here either the cam elevation of the braking profile or a return spring causes the corresponding moment on the tilting lever axis.

The object of the invention, in particular, is to provide an advantageously flexible and reliable valve gear.

The invention is based on valve gear having at least one cam shaft, which has at least one cam group having at least one firing cam and at least one braking cam, having at least one cam follower allocated to the firing cam, the cam follower being provided in a firing operation for actuating at least one of the gas exchange valves, and a cam follower allocated to the braking cam, the cam follower being provided in a braking operation for actuating at least one gas exchange valve, and having a changeover device, which is provided to switch between the firing operation and the braking operation. The changeover device has a tilting handle mount having a pivotably mounted mounting element, on which tilting levers belonging to the cam followers are pivotably mounted.

It is provided that the tilting lever mount has two mounting screws each having a ball head, and the ball heads of the mounting screws each form a ball joint together with a ball head receiver of the allocated tilting lever, via which ball joint the corresponding tilting lever is mounted on the tilting lever mount. Preferably, the changeover device is provided to convert a torsional moment of the cam shaft into a force for switching between the firing operation and the braking operation. Thus, the torsional moment and/or the rotational movement of the cam shaft can be used, whereby an actuator system, which provides the force for switching, for example in form of a hydraulic pressure, is no longer necessary. The changeover device is preferably provided for a direct switching between the firing operation and the braking operation for an adjustment of a position of the cam follower. Preferably, the changeover device is provided for a direct switching between the firing operation and the braking operation for an adjustment of the positions of the rotational axes of the cam follower. As a result of the design of the valve gear according to the invention, a mounting of the tilting lever that is particularly independent of position and almost frictionless, in particular, can be achieved. By using a ball joint, the cam followers can abut on the corresponding firing cams or braking cams without an angle offset, such that a punctuate load between cams and cam followers can be avoided, whereby the lifetime can be increased. Furthermore, the friction in a ball joint is particularly minimal.

Here, “cam group” is to be understood as a group of cams, which comprises all the cams provided for one cylinder of the combustion engine, A “firing operation” is be understood, in particular, as a control of the gas exchange valves for a fired operation. A “braking operation” is to be understood, in particular, as a control of the gas exchange valves for a braking operation, in which a compressive action is used inside the cylinder for the braking operation. Here, the firing operation and the braking operation differ, in particular, in terms of control times for the gas exchange valves. In this context, a “changeover device” is to be understood, in particular, as a mechanism which is provided for switching between the firing operation and the braking operation. “Provided” is in particular to be understood as specially configured and/or equipped.

Furthermore, it is provided that the mounting element s provided for receiving the mounting screws, and the mounting screws are respectively formed to be adjustable for setting the valve play relative to the mounting element. Thus, a particularly compact design of the changeover device is advantageously possible.

Furthermore, it is provided that the mounting screws each have an oil channel, and the oil channels are connected to a motor-sided pressure oil supply, and an oil supply line is provided in the ball head receiver, and the oil supply line is in superposition with the oil channel. Advantageously, an oil supply of the tilting lever via the pressure oil supply, the oil channels and the oil supply line into the tilting levers can be guaranteed, and a separate oil supply is not necessary.

It is furthermore provided that the tilting levers respectively have a stopping element, and the stopping element is formed from a spring-loaded ball facing towards the allocated mounting screws, and the stopping element is provided in the ball head receiver along with the oil supply line in the tilting lever. Preferably, the stopping element is integrated in the tilting lever, such that a separate device, for example in the form of a spring acting as a tilting lever, is no longer necessary, whereby a particularly compact device emerges, which can stop the respectively non-actuated tilting lever in a firing operation or in a braking operation.

It is further provided that, in a stopping state of the stopping element, the stopping element is latched into an end of the oil channel facing away from the tilting lever and here covers the oil channel. In a stopping state, the respective tilting levers with their respective cam followers are not in contact with the respective cams, such that the corresponding gas exchange valves are not actuated by the tilting lever in the stopping state, whereby an oil supply is not necessary and the oil provision to the tilting lever is interrupted by the stopping element. Advantageously, an oil flow rate is reduced with the stopping element along with the stopping of a tilting lever not in operation.

In addition, it is provided that the mounting screws on the end of the oil channel on the respective ball head have a conical extension, opening outwards, of the oil channel, Advantageously, a superimposition of the oil channel and the oil supply line is present with the conical extension of the respective tilting levers in a fired operation and in a braking operation in the event of a corresponding pivoting movement of the tilting levers, such that an oil supply is ensured, furthermore, there is a secure latching of the stopping element in which the oil channel is extended.

Further advantages arise from the following description of the Figures. An exemplary embodiment of the invention is depicted in the Figures. The Figures, the description of the Figures and the claims contain numerous features in combination. The person skilled in the art will also necessarily consider the features individually and will integrate them into further worthwhile combinations.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1schematically shows a motor vehicle33. The motor vehicle33is formed from a utility vehicle, in particular from a heavy goods vehicle (HGV). However, in principle, a different design of the motor vehicle33that also seems reasonable to the person skilled in the art would also be conceivable. The motor vehicle33comprises a drive train, via which drive wheels34of the motor vehicle33can be driven. The drive train comprises a combustion engine35. Furthermore, the motor vehicle33has a multi-stage transmission not labelled in more detail. The combustion engine35has a driven crankshaft, which is connected to a transmission gear element of the multi-stage transmission. The multi-stage transmission forms a part of the drive train of the motor vehicle33. The combustion engine35comprises at least one valve gear36. The combustion engine35preferably comprises several valve gears36. The combustion engine35is provided to convert chemical energy into kinetic energy, which serves, in particular, to propel a motor vehicle33.

FIGS. 2 to 13show the valve gear36of the combustion engine35. The valve gear36comprises a cam shaft10, which is provided for a firing operation and a braking operation. The cam shaft10is designed as an outlet cam shaft. The cam shaft10is provided to actuate gas exchange valves15,16for cylinders of the combustion engine35, the cylinders not being depicted in more detail.

In the exemplary embodiment depicted, the combustion engine35comprises two gas exchange valves15,16per cylinder, the gas exchange valves being formed as outlet valves. The cam shaft10comprises at least one cam group having a firing cam11and a braking cam12. The cam shaft10comprises one cam group per cylinder for actuating the two gas exchange valves15,16. In the exemplary embodiment, only the firing cam11and the braking cam12of a cylinder12are depicted. Further cylinders not depicted in more detail have analogously formed cams.

Furthermore, the combustion engine35comprises at least one further gas exchange valve per cylinder, the gas exchange valve being formed as an inlet valve and being actuated by a further valve drive. Two inlet valves are preferably provided for each cylinder, the inlet valves being actuated by an inlet cam shaft. The further valve gear and the inlet valves are not depicted in more detail in the Figures.

The gas exchange valves15,16and the inlet valves are received in a known manner in a cylinder head, not depicted in more detail, of the combustion engine.

The firing cam11is provided to open the gas exchange valves15,16in a firing operation. The braking cam12is provided to open at least one of the gas exchange valves15,16in a braking operation. The firing cam11and the braking cam12have different cam curves. The cam curve of the firing cam11has an elevation, which is provided, in particular, to open the gas exchange valves15,16, while a piston in the corresponding cylinder is moved from a lower dead point into an upper dead point in order to discharge exhaust gas via the gas exchange valves15,16from the cylinder in a discharge cycle. The cam curve of the braking can12is at least provided to open at least one of the gas exchange valves15,16after the piston in the corresponding cylinder was moved from the lower dead point into the upper dead point in order to here emit compressed air or combustion air in a compression cycle via the at least one gas exchange valve15,16. The combustion air is let into the cylinder before the compression cycle in a suction cycle via the inlet valves. The engine braking effect emerges as a result of emitting compressed combustion air at the end of the compression cycle, which can no longer be used in the subsequent work cycle for accelerating a piston from the upper dead point to the lower dead point. The cam curve, depicted inFIGS. 2 to 13, of the braking cam12of the engine braking device according to the invention has two elevations, for example. Here, the elevations are formed as braking elevations and/or boost charging elevations. The valve gear36depicted inFIGS. 2 to 14is thus designed as a 2-stroke engine brake with boost charge. Of course, the valve gear36for a braking operation can also be designed as a 4-stroke engine brake having only one braking elevation and an optional boost charging elevation. The functionality and effect of the braking and boost charging cams are not explained in more detail, since they are adequately known from the prior art.

The valve gear36has a cam follower13allocated to the firing cam11, the cam follower being provided in a firing operation for actuating the gas exchange valves15,16. Furthermore, the valve gear36has a cam follower14allocated to the braking cam12, the cam follower being provided in a braking operation for actuating one of the gas exchange valves15,16. In the exemplary embodiment shown according toFIGS. 2 to 14, only the gas exchange valve16is actuated in the braking operation. The cam follower13which is provided for the firing operation is here only provided for an effective connection to the firing cam11. The cam follower14, which is provided for the braking operation, is only provided for the effective connection with the braking cam12.

Furthermore, the valve gear36has a changeover device17, which is provided to switch between the firing operation and the braking operation. The changeover device17is provided to switch between an actuation of the two gas exchange valves15,16by means of the firing cam11and an actuation of the individual gas exchange valve16by means of the braking cam12. Here, the changeover device17is provided to switch backwards and forwards between a tab of the can curve of the firing cam11by means of the allocated cam follower13and a tap of the cam curve of the braking cam12by means of the allocated cam follower14. The changeover device17is only provided for switching the actuation of the gas exchange valves15,16of the one cylinder. For the further cylinders, the valve gear36can, in principle, have further analogously formed changeover devices.

The valve gear36comprises two tilting levers22,23allocated to the cylinder. In each case, the cam followers13,14are allocated to the tilting levers22,23. The engine braking device comprises two tilting levers22,23respectively having one of the cam followers13,14. The tilting levers22,23can each be pivoted around a tilting lever axis24,25set by a tilting lever bearing21for actuating the gas exchange valves15,16. The one tilting lever22is provided for the firing operation and has the cam follower13, which is provided for the effective connection to the firing cam11. The other tilting lever23is provided for the braking operating and has the cam follower14, which is provided for the effective connection to the braking cam12. The tilting lever22provided for the braking operation acts on the two gas exchange valves15,16. In the exemplary embodiment shown, the tilting lever23provided for the braking operation only acts on the one gas exchange valve16, yet can, in principle, also act on the two gas exchange valves15,16. In the exemplary embodiment shown according toFIGS. 1 to 14, the tilting lever23in the braking operation acts on the gas exchange valve16via a slide shoe37mounted in the tilting lever22in a longitudinally shiftable manner. The two tilting levers22,23are separated from each other in a movement technical manner. Depending on whether the firing operation or the braking operation is switched, the cam shaft10actuates the corresponding tilting lever22,23while the other tilting lever22,23is decoupled from the cam shaft10.

The firing cam11is positioned on the cam shaft substantially centrally between the two gas exchange valves15,16in the axial extension. Furthermore, the tilting lever22is designed to be divided on its end opposite the cam follower13, such that each of the two ends22.1,22.2of the tilting lever22can each actuate one of the two gas exchange valves15,16. Here, the end22.1, allocated to the gas exchange valve15, of the tilting lever22is in direct contact with the gas exchange valve15, while the end22.1, allocated to the gas exchange valve16, of the tilting lever22can act on the gas exchange valve16via the slide shoe37. To do so, the end22.1has a bore22.3, in which the slide shoe37is received in a longitudinally moveable manner. The slide shoe37has a head37.1, which passes into a shaft37.3via a section37.2. The shaft37.3is received in the bore22.3in a longitudinally moveable manner, wherein the end22.2of the tilting lever22is supported on the section37.2during a lifting movement of the tilting lever22in the firing operation and passes the stroke of the firing cam11onto the gas exchange valve16via the head37.1. A cap54can be provided between the head37.1and the gas exchange valve16, the cap being placed onto an end16.1of the gas exchange valve16. The slide shoe37can have a securing element37.4on its shaft37.3opposite the head37.1, which securing element prevents the slide shoe37falling out of the bore22.3when mounting the tilting lever22. Advantageously, the forked tilting lever22is designed to be substantially symmetrical as a result of the central arrangement of the firing cam11between the two gas exchange valves15,16, based on the two ends22.1,22.2of the tilting lever and the firing cam11, such that the two ends22.1,22.2substantially have the same removal from firing cams11, whereby an equal load of the tilting lever22is made possible, and a tilting moment of the cam shaft10is avoided.

The braking cam12is positioned to be spaced apart from the firing cam11on the cam shaft10substantially in alignment with the gas exchange valve16perpendicular to the rotational axis40of the cam shaft10. As a result, the tilting lever23can be designed to be substantially straight, such that an input by transverse forces onto the valve gear36can be avoided, whereby a wear-resistant operation is possible. In the braking operation, the tilting lever23causes a lifting of the braking cam12onto the gliding shoe37via a transmission element55on the end23.1of the tilting lever23. The transmission element55is fixedly connected to the tilting lever23, The longitudinally moveable glide shoe37glides in the bore22.3of the tilting lever22not actuated in the braking operation when transferring the lift of the braking cam12in the direction of the gas valve16and back.

The changeover device17is provided to convert a torsional moment10into a force for switching between the firing operation and the braking operation. The changeover device17comprises an actuator not depicted in more detail for controlling by means of a control and regulation unit not depicted in more detail, by means of which actuator the switching can be triggered. Apart from the actuator, which is only provided for triggering the switching, the changeover device17is formed completely mechanically.

The cam shaft10has a separate switching cam20. The switching cam20is different from the firing cam11and the braking cam12. The switching cam20is formed axially shiftably in relation to the firing cam11and the braking cam12and forms a separate cam contour18. The switching cam20rotates with the cam shaft10. The switching cam20is allocated to the changeover device17. The switching cam20forms an active part of the changeover device17. The switching cam20is coupled to the actuator that is no longer visible, which is provided for triggering the switching. The actuator is controlled by a computing unit of the changeover device17, the computing unit no longer being visible. The computing unit of the changeover device17is formed from a part of the vehicle electronic system of the motor vehicle33. The switching cam20is moveable axially along the cam shaft10via the actuator. For this, the switching cam20is guided in a longitudinal groove10.1of the cam shaft10. The cam shaft10can be substantially designed to be tubular for a shifting of the switching cam20along the cam shaft10and forms a hollow space10.2. The longitudinal groove10.1here penetrates the cam shaft10, wherein the switching cam20having a positioning element20.1is received in the longitudinal groove10.1. For example, an actuator can engage on the positioning element20.1in the hollow space10.2of the cam shaft10and can shift the switching cam20in the longitudinal groove10.1. The switching cam20has two switching positions, wherein a first switching position is allocated to the firing operation and a second switching position is allocated to the braking operation. The cam contour18of the switching cam20is provided in at least one operating state to act directly on the switching element19of the changeover device17, which is provided for a direct switching between the firing operation and the braking operation. The changeover device17has the switching element19. The switching element19is rotatably mounted, wherein the valve gear36is in the firing operation or in the braking operation independently of a pivoting position of the switching element19. The switching cam20is provided for a direct rotation of the switching element19. To do so, the switching element19is rotated via the rotation of the cam shaft10. A mounting axis41of the switching element19extends in parallel to the rotational axis40of the cam shaft10. The mounting axis41of the switching element19is arranged next to the rotational axis40of the cam shaft10. The switching element19is contacted by the switching cam20for a rotation of the switching element19and directly rotated.

The switching element19of the changeover device17is formed from a switching eccentric shaft. The switching element19has a switching portion30that is eccentric in relation to the mounting axis41. The switching element19is here formed in the manner of a crankshaft in the region of the eccentric switching portion30. Furthermore, the switching element19has two switching cams43,44, which are provided for an adjustment of the switching element19. The first switching cam43is here allocated to the firing operation, and the second switching cam44is allocated to the braking operation. The switching cams43,44are arranged one next to other. However, in principle, it would also be conceivable that the switching cams43,44are spaced apart from one another. The first switching cam43is arranged in a plane perpendicular to the rotational axis40of the cam shaft10, in which the switching cam20is also in the first switching position. The second switching cam44is arranged in a plane perpendicular to the rotational axis40of the cam shaft10, in which the switching cam20is also in the second switching position. The switching element19is adjusted via the switching cams43,44, wherein the switching element19is in turn provided for further transferring a switching movement via the eccentric switching portion30. If the switching cam20is in a first switching position and if the valve gear36is in a braking operation, the first switching cam43is in an orbit of the switching cam20and is contacted during a rotation of the switching cam20and shifted out of an orbit of the switching cam20. The switching element19is brought into a firing operation position. If the switching cam20is in a first switching position and if the valve gear36is in a firing operation, the switching cam20and the first switching cam43are contactless. If the switching cam20is in a second switching position and if the valve gear36is in a firing operation, the second switching cam46is in an orbit of the switching cam20and is contacted during a rotation of the switching cam20and shifted out of an orbit of the switching cam40. The switching element19is brought into a braking operation position. If the switching cam20is in a second switching position and if the valve gear36is in a braking operation, the switching cam20and the second switching cam44are contactless (FIGS. 2, 7 and 13).

Furthermore, the switching device17has a tilting lever mount21coupled directly to the switching element19, the tilting lever mount having a first end position allocated to the firing operation and a second end position allocated to the braking operation. The tilting lever mount21is provided for switching the effective connection between the cam shaft10and the cam followers13,14. The tilting lever mount21serves, for example, to mount the tilting levers22,23and, respectively, for the tilting lever22and the tilting lever axis24and for the tilting lever23, fixes the tilting lever axis25different to the tilting lever axis24, around which tilting lever axis25the corresponding tilting lever22,23is pivotably mounted. The tilting lever axes24,25run in parallel to the rotational axis40of the cam shaft10(FIGS. 2 to 11).

The tilting lever mount21comprises a pivotably mounted mounting element28. The tilting lever mount21comprises a mounting element28, on which the tilting levers22,23are mounted (c.f.FIGS. 2, 7 and 12). The mounting element28itself is pivotably mounted. A mounting axis38, around which the mounting element28can be pivoted, is arranged in parallel to the tilting axes24,25. The tilting lever axis24and the tilting lever axis25are provided offset at an angle in relation to each other around a mounting axis38of the mounting element28. The mounting element28is mounted in a housing of the valve gear36, the housing not being depicted in more detail. The housing is attached to the cylinder head. The mounting element28is designed in the shape of a U-shaped frame, wherein ends39,39′ of the mounting element28, which are oriented in parallel to the rotational axis40of the cam shaft10, serve to mount around the mounting axis38, and wherein the tilting levers22,23are attached to a part of the mounting element28, the part running substantially in parallel to the cam shaft10. The ends39,39′ of the mounting element28are designed in the shape of mounting spigots and received rotatably in mounts of the housing that are no longer visible. Furthermore, the switching element19has two ends19.1,19.2opposite each other. The ends19.1,19.2of the switching element19are also formed in the shape of mounting spigots and are received rotatably in further mounts of the housing which are no longer visible. The cam shaft10is also rotatably received in mounts of the housing that are no longer visible. It is also conceivable that the cam shaft is rotatably mounted in the cylinder head in the known manner, and the remaining components of the valve gear36are received in the housing connected to the cylinder head.

The mounting axis38of the mounting element28is oriented in parallel offset relative to the rotational axis40of the cam shaft10. In the first end position, the cam follower13provided for the firing operation is in contact with the firing cam11. In contrast, the cam follower14provided for the braking operation is raised by the braking cam12, whereby the braking cam12runs through below the cam follower14without effect (FIGS. 2 to 6). In the second end position, in contrast, the cam follower14provided for the braking operation is in contact with the braking cam12, while the cam follower13provided for the firing operation is raised by the firing cam11, whereby the firing cam11runs through below the cam follower13without effect. The position of the respective tilting lever axes24,25in relation to the rotational axis40is changed by pivoting the mounting element28from one end position into the other end position. While the one tilting lever axis24,25and the tilting lever22,23belonging to this are in the one end position closer to the rotational axis40of the cam shaft10and provide a contact between the one cam follower13,14having the respective cam11,12, the other tilting lever axis24,25and the corresponding tilting lever22,23in the same end position of the mounting element28is further removed from the rotational axis40of the cam shaft10, whereby there is no prevailing contact between the other cam follower13,14and the respective cam11,12(FIGS. 7 to 11).

A pivoting movement of the mounting element28is limited by two mechanical stops, which define the two end positions of the tilting lever mount21. With a pivoting movement of the mounting element28out of the second end position in the braking operation into the first end position in the firing operation, the stops limit the pivoting movement of the mounting element28. Correspondingly, the stops limit the pivoting movement of the mounting element28out of the first end position in the firing operation into the second end position in the braking operation.

In order to limit the pivoting movement of the mounting element28, the mounting element28of the tilting lever mount21has a switching link29. The switching link29extends perpendicularly to the mounting axis38of the mounting element28. The switching link29is formed from a straight longitudinal recess. However, in principle, a different design that seems significant to the person skilled in the art would also be possible. The eccentric switching portion30of the switching element19of the changeover device17is guided in the switching link29. A position of the mounting element28is set via the switching link29. Depending on a pivoting position of the switching element19, the mounting element28is in the first end position or in the second end position. The eccentric switching portion30is correspondingly on a first end of the switching link29or on the second end of the switching link29depending on a rotational position of the switching element19. In the event of a rotation of the switching element19, the eccentric switching portion30glides through the switching link29from one end to the other, wherein here the mounting element28is rotated from one end position into the other end position (c.f.FIGS. 3, 5, 8, 10 and 12).

The valve gear36has a holding spring56for securing the end positions. The holding spring56is fixed on the mounting element28on its one end56.1by means of a holding element57. The holding element57can be designed in a suitable manner, for example in the shape of a head screw. The holding spring56applies a spring tension, starting from the mounting element28in the direction of the switching portion30. To do so, the holding spring56abuts with its one end56.2in a groove19.3of the switching portion30. The groove19.3is substantially provided between the mounting element28and the switching portion30, wherein the switching portion30is correspondingly held on the first end of the switching link29or on the second end of the switching link29by means of the spring force of the holding spring56depending on the pivoting position of the switching element19. The holding spring56is designed in the shape of a rotational spring, wherein other shapes of a holding spring are also conceivable.

The groove19.3is provided as an at least partially peripheral groove on the end of the switching portion30opposite the switching cam43. The switching portion30is substantially formed in the shape of a cylinder, wherein the switching portion30at least partially passes into the switching cam43.

The adjustment of the engine braking device is thus not constituted by a locking mechanism and the moment necessary for the adjustment from the mounting forces and the eccentric offset of the tilting lever22,23, but via a cinematic coupling of the switching element10and the mounting element28in such a way that the separate cam contour18acts on the switching element19, which, in the context of an individual step of a Maltese cross transmission, causes a rotation of the mounting element28. Thus, the movement of the switching element19is directly coupled to the movement of the mounting element28. Furthermore, the switching point in time is no longer coupled to the outlet cam elevation as a result of the presence of a separate switching cam20, but can be chosen arbitrarily, which constitutes a substantial degree of freedom when shaping the cam. The energy necessary for the switching actuation comes from the cam shaft10, wherein here not the firing cam11via the tilting lever22but the switching cam20is applied by itself. The triggering is represented by an axial shifting of the switching cam20in the cam shaft10. In the embodiment depicted of the switching actuation of an electro-mechanically actuated decompression engine brake, the switching process is represented by the separate switching can20, which is on the cam shaft10, and the switching element19, which acts as a binding member between the cam shaft housing and the rotatably mounted mounting element28. As a result of the arrangement of the switching cam20and switching element19, a cinematic coupling between the rotary cam shaft movement, in particular outlet cam shaft movement, and the rotation of the mounting element28is produced and thus the dependency is raised by the outlet valve elevation.

Furthermore, the tilting lever mount21has two mounting screws26,26′. The mounting screws26,26′ each have a ball head27,27′ for mounting the tilting levers22,23pivotably around the tilting axis24,25. The mounting screws26,26′ are each allocated to one of the tilting levers22,23and serve to mount the tilting levers22,23on the mounting element28. The mounting screws26,26′ are formed identically. However, in principle, an at least partially differing design would also be conceivable. The mounting screws26,26′ are each formed from a ball head screw. A geometric middle point of the ball head27,27′ here respectively defines the tilting lever axis24,25of the respective tilting lever22,23. The ball heads27,27′ of the mounting screws26,26′ each form a ball joint together with a ball head receiver58,58′ of the allocated tilting lever22,23, via which ball joint the corresponding tilting lever22,23is mounted on the tilting lever mount21. The mounted screws26,26′ thus constitute the fixed mounting spigot of the ball head27,27′, i.e., the outer ball, and the respective tilting lever22,23the ball head receiver58,58′. The ball head receiver58,58′ has a peripheral groove58.1,58.1′ on its upper edge, in which groove a retainer ring58.2,58.2′ can be inserted. The retainer ring58.2,58.2′ prevents a detachment of the ball head27,27′ from the ball head receiver58,58′. The rotatably mounted mounting element28is provided for receiving the mounting screws26,26′. The mounting screws26,26′ are each formed adjustably for setting the valve clearance to be limited in relation to the mounting element28. The mounting screws26,26′ are screwed into the mounting element28, wherein a screwing-in depth can be changed. The tilting lever axis24,25of the respective tilting lever22,23can be changed via the screwing-in depth in relation to the mounting element28and can here set a valve play. The mounting screws26,26′ can respectively be secured or countered from an unwanted rotation in the mounting element28for securing the rotation by means of retainer nut60,60′. In order to then carry out the setting of the valve play, the mount central point of the tilting lever22,23now thus shifts the tilting lever axis24,25by means of the respective mounting screws26,26′ in such a way that the spacing of the respective tilting lever22,23in relation to the cam shaft10and the tap on the valve side varies.

The mounting screws26,26′ each have an oil channel31. The oil channels31are each provided to provide an engine-sided pressure oil supply48on the respectively allocated tilting lever22,23depending on a position of the respective mounting screw26,26′ relative to the respectively allocated tilting lever22,23. The oil channels31are each provided to provide the engine-sided pressure oil supply48at required oil points of the respectively allocated tilting, lever22,23, such as a tilting lever roller46,47of the cam follower13,14, via which the tilting lever23,24slides on the firing cam11or the braking cam12, or the contact point between the slide shoe37and the gas exchange valve16depending on a position of the respective mounting screws26,26′ relative to the respectively allocated tilting lever22,23. The mounting screws26,26′ each produce a connection between the engine-sided pressure oil supply48and the tilting lever sided required oil points of the tilting lever roller46,47and of the valve-sided slide shoe contact. The mounting screws26,26′ are rotated relative to the tilting levers22,23when adjusting the operation manner of the fired and braking operations, which allows a control of the oil inflow as a result of the shape of the oil bore position. In turn, this reduces the overall oil requirement for the tilting lever22,23to the activated tilting lever22,23in the respective operating manner. The tilting levers22,23, which are thus not necessary in the current operating state, are excluded from an oil supply. This is carried out, in particular, without additional valves.

By way of example,FIGS. 6 to 11show the oil supply of the tilting levers depending on the operating manner of the combustion engine35. The two Figures show a sectional depiction of the tilting lever23. InFIG. 6, the mounting element28is depicted in its end position for the fired operation. Here, the tilting lever22not shown transfers a stroke of the firing cam11to the gas exchange valves15,16. The tilting lever23shown with its cam follower14is not in contact with the braking cam12and is thus not moved. Furthermore, the pressure oil supply48is connected to the oil channel31in the mounting screw26′. A connection to an oil supply line59to the required oil points is interrupted by the rotation of the mounting screw26′ in relation to the tilting lever23. The oil supply line59is provided in the ball head receiver58,58′ substantially opposite the mounting screw26,26′. InFIG. 11, the mounting element28is depicted in its end position for the braked operation. Here, the tilting lever22not shown does not assign any stroke of the firing cam11to the gas exchange valves15,16, while the tilting lever23shown with its cam follower14is in contact with the braking can12and thus assigns a stroke of the braking cam12to the gas exchange valve16. The pressure oil supply48is connected to the oil channel31in the mounting screw26′, and the oil channel31overlaps the oil supply line59. In order to ensure a sufficient overlap or congruence of the oil channel31and the oil supply line59in the event of a movement of the tilting lever23and thus to enable a constant oil supply in the event of a tilting movement of the tilting lever23, the mounting screw26′ has a conical extension61, opening outwardly, of the oil channel31on the end of the oil channel31on its ball head27. The tilting lever22for the fired operation is designed analogously to the tilting lever23.

Furthermore, the tilting lever23has a stopping element32for the braking operation. The stopping element32is provided for stopping the allocated tilting lever23relative to the tilting lever mount21in at least one position. The stopping element32is provided for stopping the tilting lever23for the braking operation relative to the respectively allocated mounting screw26′ in a deactivated or fired operation. The stopping element32is provided to stop the tilting lever23in a firing operation (FIG. 6). The stopping element32is formed by a spring loaded ball facing towards the allocated mounting screw26′. The stopping element32is provided next to the oil supply line59in the tilting lever22,23in the ball head receiver58.

However, in principle, a different design that seems significant to the person skilled in the art would also be possible. The stopping of the stopping element32can be released non-destructively when applying a defined release force as a result of the switching cam20, which exceeds a stopping force. The stopping element32is provided to hold the tilting lever mount21respectively in the first end position. The stopping element32is directly integrated in the ball joint between the mounting screws26′ and the tilting lever23(c.f.FIGS. 6 and 11).

The stopping element32is further provided to shut off an oil flow of the oil channel31of the mounting screw26′ in a stopping state. An end, facing towards the tilting lever23, of the oil channel31is here covered directly by the ball of the stopping element32. The stopping element32is provided to latch into the oil channel31of the mounting screw26′ in a stopping state. Both a shutting off of the oil channel and a stop take place via the latching. The conical extension61, opening outwardly, of the oil channel31here also forms a corresponding latching cone on the end facing towards the tilting lever23. The stopping element32thus simultaneously shuts off the oil flow in the latched position and releases it again in the activated position (c.f.FIGS. 6 and 11).

The tilting lever22for the fired operation is designed analogously to the tilting lever23.

FIG. 14shows a flow chart of a method for an operation of the valve gear36. The method is analogous to the description and functionality of the valve gear36already explained. In the method, the switching element19of the changeover device17is acted on for a direct switching between the firing operation and the braking operation by means of the separate cam contour18of a cam shaft10of the valve gear36. In the method, the switching cam20is brought into a switching position corresponding to the desired operating state, i.e., a braking operation or a firing operation, in a first method step49. If the valve gear36is already in the corresponding operating state, the switching cam20and the switching element19are contactless in the further method step50. If the valve gear36is still not in the corresponding operating state, the switching cam20contacts the corresponding switching cam43,44of the switching element19in the event of a rotation of the cam shaft10in a second method step51, which is in the same plane and correspondingly rotates the switching element19. The mounting element28in a third method step52changes the end position as a result of the rotation of the switching element19. Subsequently, the tilting lever22,23, which up until now contacted the firing cam11or braking cam12allocated to it, is lifted off from the firing cam11or braking cam12allocated to it by tilting the mounting element28in a fourth method step53, and the tilting lever22,23, which up until now was lifted off from the firing cam11or braking cam11allocated to it, is pressed against the firing cam11or braking cam12allocated to it. Subsequently, a switching between the firing operation and the braking operation is carried out, and the first method step49can be repeated.

LIST OF REFERENCE CHARACTERS