EP3173593B1 - Variable valve drive with a rocker arm - Google Patents

Description

The invention relates to a variable valve train for a lift valve, in particular for a charge exchange valve of an internal combustion engine, which is periodically movable between a closed and an open position by a cam via a rocker arm. It is known to operate gas exchange valves of an internal combustion engine variable with different opening and closing times and with different valve opening strokes. Such variable valve trains offer the advantageous possibility of targeted adjustment of the course of the valve lift over the cam angle as a function of operating parameters of the device equipped with the respective lift valve, that is, for example, depending on the speed, load or temperature of an internal combustion engine. In particular, it is known to generate a plurality of different lift curves for a lift valve in that a plurality of cams are present for the actuation of this lift valve, and that in each case the contour of only one cam effects the lift progression. To switch to another stroke course is switched to the contour of another cam. Such a valve control is from the DE 42 30 877 A1 previously known. In this case, a camshaft block with two different cam contours is rotatably but axially displaceably arranged on a camshaft. According to the axial position of the cam block is a cam contour via an intermediate member (transmission lever) with the lifting valve in operative connection. The axial displacement of the cam block to change the valve parameters takes place during the Grundkreisphase against the action of a return spring by means of a pressure ring.

From the DE 195 19 048 A1 is a variable valve train for an internal combustion engine previously known, in which also two differently shaped in their cam contour cams are arranged directly adjacent to each other on the camshaft. The change of the cam engagement is effected by an axial displacement of the camshaft with the cam located on it.

Furthermore, from the DE 195 20 117 C2 a valve train of an internal combustion engine previously known, in which on the camshaft rotationally fixed an axially displaceable cam block is arranged with at least two different cam tracks. The adjustment of the cam block via an adjusting member, which is guided inside the camshaft. By a frontal side arranged on the camshaft double-acting hydraulic or pneumatic piston-cylinder unit, the adjusting member is moved inside the camshaft. The adjusting member is connected to a driving piece, which penetrates an axially arranged in the camshaft slot and opens into a bore of the cam block.

A disadvantage of the cited prior art is that different opening and closing times and different valve opening strokes are not infinitely adjustable. Another disadvantage is that it is not possible with these known approaches to convert an existing valvetrain without variability to a valvetrain with variability, without requiring changes to surrounding components, other than those needed immediately for the realization of variability become.

To solve these problems are from the EP 0 717 174 A1 and US 2007/0125330 A1 Valve controls known, which additionally have a rotatably mounted transmission lever between the camshaft and valve lever. By shifting the transmission lever axis, the contact point of the valve lever roller can be changed on the contour surface of the transmission lever, whereby a continuous adjustment of the valve lift is made possible. However, a disadvantage is the high space requirement for the adjusting devices for displacing the axis of the transmission lever.

It is an object of the invention to provide an improved variable valve train with a rocker arm, with which disadvantages of conventional techniques can be avoided. The object of the invention is in particular to provide a variable valve train, which allows a continuous change of the valve opening and closing times and the valve opening strokes.

These objects are achieved by a variable valve train with the features of the independent claim. Advantageous embodiments and applications of the invention are the subject matter of the dependent claims and are explained in more detail in the following description with partial reference to the figures.

According to the invention, a variable valve drive is provided for a lift valve. The lift valve is between a closed and an open position, in particular against the force of a return spring, indirectly movable by a cam of a camshaft periodically. The lift valve is preferably a charge exchange valve of an internal combustion engine.

According to general aspects of the invention, the valve train comprises a switchable rocker arm arrangement for actuating the lift valve. A switchable rocker arm arrangement is understood to mean a rocker arm arrangement which can be changed by a switching device or actuator in its transmission properties relating to the transmission of the cam movement to the lift valve such that a valve opening and / or closing time and / or a height of the valve opening travel is variable.

The rocker arm assembly comprises a first rocker arm, hereinafter referred to as transfer rocker arm, and a second rocker arm, hereinafter referred to as a valve rocker arm, which are mounted pivotably on different rocker arm shafts, which are each parallel to the camshaft axis. In this case, the valve rocker arm is in operative contact with the lifting valve at a first end and has a roller, in particular a pressure roller, on a second end. The transfer rocker arm is associated with a cam of the camshaft at a first end, ie, engages the cam to pick up the cam movement. According to the cam movement, the transmission lever tilts. At a second end of the transfer rocker arm over a contour surface, in particular a Ventilhubvorgebende contour surface, with the role of Ventilkipphebels in operative connection, such that a tilting movement of the transfer rocker generates a corresponding tilting movement of the valve rocker, wherein the roll of the valve rocker rolls on the contour surface. Due to the tilting of the transmission lever, the roller of the rocker arm thus rolls on the contour surface, and the resulting tilting movement of the valve rocker arm causes a corresponding valve lift. In this sense, transmission lever and valve lever are connected in series.

The contour surface is a surface of the transfer rocker arm on which the role of the valve rocker lever in the transmission of the cam movement back and forth to the lift valve and so transmits the movement of the transfer rocker arm to the valve rocker arm or coupled. Due to the design of the surface shape of the contour surface, z. B. the slope in unwinding, the course of the valve lift can be set.

The variable valve drive comprises an actuating device for switching the rocker arm arrangement, by means of which the contour surface is rotatable about the rocker arm axis of the transfer rocker arm in order to produce a displacement of a rolling region of the roller of the valve rocker arm on the contour surface. Preferably, the adjusting device is designed to generate a rotation of the contour surface or of the contour surface of the comprehensive part of the transfer rocker arm relative to the valve rocker arm. As a result, the region of the contour surface tapped by the roller of the valve rocker arm and thereby also the resulting valve lift and / or the valve opening or closing times change.

An advantage of the variable valve train according to the invention is that the construction of rocker arm and camshaft can remain unchanged - with respect to a conventional non-variable valve train. Another advantage is that the variable valve train manages the valve actuation with little moving masses, since the valve rocker arm tilts up and down as usual, the transmission rocker also tilts up and down and rotates the camshaft as usual.

Furthermore, the variable valve train allows a very robust solution for fully variable control, especially for commercial vehicle and industrial engines.

According to a preferred embodiment, the contour surface has a first rolling region which does not generate a valve lift when the roller of the valve rocker roll rolls on the first rolling region. In particular, the first rolling area forms a base circle contour and is also referred to below as the base circle area. The roll-off points on the base circle region have a preferably constant radial distance to the rocker arm axis of the transmission lever.

According to this preferred embodiment, the contour surface further has a second rolling region adjoining the first rolling region, which has a ramp contour. A ramp contour predetermines a valve lift such that the further the roller of the valve rocker roll rolls off the first roll-off area on the second roll-off area, the greater the valve lift. A ramp contour is thus understood to mean a region which has an increasing radial distance to the rocker arm axis of the transmission lever in a direction of movement of the roller. In the opposite direction of movement of the roller, the radial distance on the second rolling area consequently decreases.

A rolling region is understood to be a region of the contour surface on which the roller of the valve rocker arm can be unrolled during a tilting movement of the transmission rocker arm. The extent to which the roll actually rolls in a tilting movement on a certain rolling area, depends on the adjusting device set twisting position of the contour surface.

In an advantageous variant of this embodiment, the contour surface has a third rolling region adjoining the second rolling region. The third roll-off region preferably generates a valve position with a predetermined constant valve lift, for example a valve position with maximum valve lift, when the roller of the valve rocker roll rolls on the third roll-off region. The roll-off points on the third rolling range preferably have a constant radial distance to the rocker arm axis of the transmission lever. However, the radial distance of the third rolling area is greater than that of the first rolling area.

The area of the contour surface unrolled by the rocker roller remains constant in the angular amount. Due to the rotation of the contour surface by means of the adjusting device relative to the valve rocker arm, however, the area of the contour surface actually tapped from the roller will be moved, that is, unrolled. For example, if the contour surface is rotated by means of the adjusting device relative to the valve rocker arm so that the rocker arm rolls a smaller distance on the first area and instead a greater distance on the second area, the valve lift increases. By a suitable embodiment of the dimensions and / or gradients or gradient courses of the rolling regions, the valve lift and / or the valve opening and closing times, which result from the rolling of the valve rocker arm on the contour surface, can be set. Depending on the setting or change of the rolling range, the lifting valve can be kept completely closed, for example, for example, if the role of the valve rocker only on the first Abrollbereich back and forth. There is also the possibility of a valve operation in which the lift valve is kept open for a short time on the maximum valve lift. This can be achieved, for example, if the contour surface is fixed by the adjusting device in a twisting position, in which the rolling movement of the roller of the valve tilting lever also at least partially surrounds the third region. During unwinding on the third area, the lift valve is briefly kept open at the maximum valve lift.

In a further advantageous variant of this embodiment, the contour surface has a fourth rolling region adjoining the third rolling region, which in turn forms a ramp contour, and a fifth region, which adjoins the fourth rolling region. The roll-off points on the fifth Abrollbereich have a constant radial distance to the rocker arm axis of the transmission lever. The radial distance of the fifth Abrollbereichs is greater than the radial distance of the third Abrollbereichs and greater than the radial distance of the first Abrollbereichs. In this embodiment with five Abrollbereichen the third area forms a middle position in which the lift valve kurzeitig, d. H. is kept open during the rolling of the roll on the third area, in an opening position with a constant lifting height, which is smaller than the maximum lifting height.

According to a preferred embodiment, the transfer rocker arm comprises a first lever, which engages the cam of the camshaft, and a second lever, comprising the contour surface which is in operative connection with the roller of the valve rocker arm. The first lever and the second lever are coupled to each other in movement, in particular such that a tilting movement of the first lever generated by the cam leads to a corresponding tilting movement with the same angular amount of the second lever about the tilt lever axis of the transfer rocker arm. Furthermore, by means of the adjusting device a twisting position of the second lever relative to the first lever changeable to change a Abrollbereich the role of the valve rocker arm on the contour surface. In the rotational position which can be adjusted by means of the adjusting device, the first lever and the second lever are then coupled to each other again so that they are jointly pivoted back and forth about the rocker shaft axis when excited by the cam. Thereby, a robust adjustable transmission mechanism for variably transmitting the cam movement to the valve rocker arm can be provided.

It is particularly advantageous if the adjusting device is designed to continuously change a rotational position of the second lever relative to the first lever. Alternatively, the adjusting device may be designed to change a rotational position of the second lever relative to the first lever into two or more predetermined positions, so that two or more different rolling regions on the contour surface and thus valve strokes are switchable.

An advantageous possibility of the realization according to the invention provides that the adjusting device is designed as a hydraulic switching unit. For example, the actuating device may comprise a hydraulically actuable and / or actuated shift pin, which is attached at its first end to the first lever and is attached to a second end on the second lever of the transfer rocker arm, wherein an extension of the shift pin is a rotational position of the second lever relative to the first Lever changed.

Alternatively, the adjusting device may be designed as an electrical and / or mechanical adjusting device, for example, to actuate the switching pin electrically and / or mechanically.

Furthermore, the first lever and the second lever can be coupled to one another via a driver. The driver can also form a receptacle for the shift pin and thus form a dual function.

According to a further embodiment of the transfer rocker arm may be biased by means of a return spring, such that the transmission lever is pressed against the camshaft. As a result, a secure tapping of the cam movement is made possible. For example, the first lever of the transmission lever may be biased by means of a return spring, such that the transmission lever is pressed against the camshaft.

In the context of the invention, there is also the possibility that the valve rocker arm has at its valve-side end a receptacle in which a hydraulic valve clearance compensation element or a screw with elephant foot is added.

The rocker arm may further on its underside, d. H. the cylinder head facing side, have a geometry for axial fixation on a bearing block. For example, the rocker arm may have a mounting for attachment to a Kipphebellagerbock on which the rocker shaft is arranged, on which the rocker arm with an associated bore is pivotally mounted and held by an axial position assurance, wherein the axial position securing a guide connection as an engagement element counter-element connection between the bearing block and the rocker arm, in which a transversely aligned to the axial direction engagement element, for. B. in the form of an annular web, engages pivotally in an associated counter element with axial flank support.

Another aspect of the invention relates to a motor vehicle, in particular a commercial vehicle, with a variable valve train, as described in this document.

Figur 1

eine Seitenansicht eines Ventiltriebs gemäß einer Ausführungsform der Erfindung;

Figur 2

eine perspektivische Seitenansicht eines Ventiltriebs gemäß einer Ausführungsform der Erfindung;

Figur 3

eine Detailansicht der Kopplung zwischen Ventilkipphebel und Übertragungskipphebel gemäß einer Ausführungsform der Erfindung;

Figur 4

eine Seitenansicht eines zweiten Hebels des Übertragungskipphebels gemäß einer Ausführungsform der Erfindung;

Figur 5

eine Seitenansicht eines zweiten Hebels des Übertragungskipphebels gemäß einer weiteren Ausführungsform der Erfindung;

Figur 6

eine Illustration verschiedener einstellbarer Hubkurven des Hubventils;

Figur 7

eine perspektivische Darstellung des Übertragungskipphebels in einem ersten Schaltzustand gemäß einer Ausführungsform der Erfindung; und

Figur 8

den Übertragungskipphebel aus Figur 7 in einem zweiten Schaltzustand.

The preferred embodiments and features of the invention described above can be combined with one another as desired. Further details and advantages of the invention will be described below with reference to the accompanying drawings. Show it:

FIG. 1

a side view of a valve train according to an embodiment of the invention;

FIG. 2

a side perspective view of a valve train according to an embodiment of the invention;

FIG. 3

a detailed view of the coupling between the valve rocker arm and transfer rocker arm according to an embodiment of the invention;

FIG. 4

a side view of a second lever of the transfer rocker arm according to an embodiment of the invention;

FIG. 5

a side view of a second lever of the transfer rocker arm according to another embodiment of the invention;

FIG. 6

an illustration of various adjustable lift curves of the lift valve;

FIG. 7

a perspective view of the transfer rocker arm in a first switching state according to an embodiment of the invention; and

FIG. 8

off the transfer rocker arm FIG. 7 in a second switching state.

Identical parts are provided in the figures with the same reference numerals, so that the different views of the valve train shown in the figures are also self-explanatory.

The FIGS. 1 and 2 show a side view and a side perspective view of a variable valve train 1 according to an embodiment of the invention. The valve train 1 is used for actuating charge exchange valves (not shown) of an internal combustion engine, which are periodically movable between a closed and an open position by a cam 2 of a camshaft 3.

The valve drive 1 comprises a switchable rocker arm arrangement for actuating the lift valves. The rocker arm assembly comprises a first rocker arm (valve rocker arm) 20, which is pivotally mounted about a rocker shaft 23, and a second rocker arm (Übertragungskipphebel) 10 which is pivotally mounted on a further rocker shaft 13. The two rocker shafts 13, 23 are spatially separated, but both parallel to the axis of the camshaft third

The valve rocker arm 20 is in operative contact with a valve-side end 21, ie with its valve-side lever arm 21, with two lift valves (not shown). The valve-side lever arm 21 of the valve rocker arm 20 is designed for this purpose as a two-valve lever arm to actuate two charge exchange valves simultaneously. For this purpose, the valve-side lever arm 21 is fork-shaped, which in FIG. 2 is recognizable. As in FIG. 2 can be seen, two such Ventilkipphebelanordnungen 10, 20 are arranged in the axial direction of the camshaft one behind the other to actuate four globe valves. At each valve-side end of the lever arm 21, a receptacle 24 is arranged. The receptacle 24 can be used for mounting a known hydraulic lash adjuster element 25. Instead of a hydraulic valve clearance compensation element, a screw with elephant foot can be received in the receptacle 24 with appropriate processing, by means of which a valve clearance can be readjusted manually.

Hydraulic valve clearance compensation elements (HVA) in internal combustion engines are known per se and serve, in particular the length dimensions which change over the service life the charge exchange valves compensate so that in the base circle phase of the valve-actuating cam safe valve closing is ensured. On the other hand, the cam lobe should be transferred without loss to the valve and thus converted into a valve lift. The operation of such hydraulic valve clearance compensation elements, which are arranged in the power flow of a valve control, in particular an internal combustion engine, is assumed to be known.

The valve rocker arm 20 is mounted on a rocker arm bearing block (not shown), wherein the rocker arm shaft 23 is disposed on the rocker arm bearing block, on which the valve rocker arm 20 is pivotally mounted with an associated bore and held by an axial position assurance. In the present embodiment, the axial position assurance is designed as an engagement element counter-element connection between the bearing block and the rocker arm, wherein a transversely aligned to the axial direction engagement element, for. B. in the form of a ring land 27, in an associated counter-element (not shown) engages pivotally with axial flank support. However, the axial position assurance can also be done in a conventional manner via contact surfaces on the Kipphebelflanken. These flanks can be created for example by calibration of the forging blank or by mechanical processing. Bearing side, the fixation can also be done on appropriately machined surfaces and by means of washers and retaining rings. Next axial position locks between a rocker arm and the axle are known. For example, has an area of the axis, which is enclosed by the bore of the rocker arm, an annular groove in which a snap ring extends, which runs at the same time with its outer ring portion in an annular groove of the rocker arm.

At its opposite with respect to the tilting axis 23 end 22, d. H. on the camshaft-side lever arm 22, a roller 26 is disposed at the distal end of the lever arm 22.

The transfer rocker arm 10 is engaged with the cam 2 of the camshaft 3 at a cam shaft side end 11. For this purpose, a roller 18, z. B. a pressure roller, arranged, which rolls on the cam 2 of the camshaft 3 and thus picks up the cam movement. The transfer rocker arm 10 is also operatively connected to the roller 26 of the valve rocker arm 20 at the other end 12 with respect to the rocker arm shaft 13 via a stroke-defining surface, ie, the roller 26 of the valve rocker arm 20 rolls at one of the cam movement generated tilting movement of the transfer rocker arm 10 on the contour surface 16, whereby a corresponding tilting movement of the valve rocker arm 20 is generated. The transfer rocker arm 10 transmits by its tilting movement, the cam movement on the valve rocker arm 20, which in turn generates the valve lift by its corresponding resulting tilting movement. Transfer rocker arm 10 and valve rocker arm 20 are connected in series in this manner. Camshaft 3 and valve rocker arm 20 can be designed for this purpose in a conventional manner and are coupled to each other in motion by the transmission lever 10 arranged therebetween.

The contour surface 16, on which the Ventilkipphebelrolle 26 is supported, serves as Abrollbereich on which the Ventilkipphebelrolle 26 back and rolls in the transmission of the tilting movement of the transfer rocker arm 10 on the valve rocker 20 and. Due to the configuration of this contour surface 16 serving as a rolling surface, the stroke behavior of the lifting valve can thus be predetermined and also varied.

FIG. 3 shows a detailed view of the coupling between the valve rocker arm 20 and the transfer rocker arm 10 on the contour surface 16. The contour surface 16 has in this embodiment, three different areas 16a, 16b and 16c, which can serve as Abrollbereiche for the roller 26.

The first rolling area 16a forms the base circle contour, i. H. when the roller 26 rolls on this area, the valve rocker arm 20 generates no valve lift. The distance of the points on the first rolling surface 16a to the rocker shaft 13, d. H. their radial distance R1, is constant. The contour surface 16 furthermore comprises a second rolling region 16b immediately adjacent to the first rolling region 16a, which has a ramp contour. The radial distance of the roll-off points increases on the second rolling range, starting from a value R1 up to a value R2. Thus, when the roller 26 rolls on the second portion 16b from the first portion 16a, the more the roller 26 rolls on the second rolling portion 16b, the more the valve rocker 20 tilts. Consequently, the further the roller 26 of the valve rocker arm 20 rolls off the first rolling region 16a on the second rolling region 16b, the greater the generated valve lift is.

Connected to the second rolling region 16b is a third rolling region 16c, which has a constant radial clearance R2 and produces a valve position with maximum valve lift when the roller 26 of the valve rocker arm 20 rolls on the third rolling region 16c.

The valve drive 1 further comprises an actuating device 30 for switching the rocker arm assembly 10, 20, by means of which the contour surface 16 about the rocker shaft 13 of the transmission rocker arm 10 is rotatable to produce a displacement of a Abrollbereichs the roller 26 of the valve rocker arm 20 on the contour surface 16. As a result, the region of the contour surface 16 that has been unrolled or tapped from the roller of the valve rocker arm changes, and thereby also the resulting valve lift and / or the valve opening or closing times.

For this purpose, the in FIG. 1 shown embodiment of the transfer rocker arm 10, a first lever 14, hereinafter referred to as a cam follower lever, which is connected via a roller 18 with the cam 2 of the camshaft 3 in engagement. The transfer rocker arm 10 further comprises a second lever 15, hereinafter referred to as a contour lever, which has the contour surface 16 which is in operative connection with the roller 26 of the valve rocker arm 20.

The cam follower lever 14 and the contour lever 15 are coupled to each other such that a tilting movement of the cam follower lever 14 generated by the cam 2 results in a corresponding tilting movement of the contour lever 15 about the rocker arm axis 13 of the transfer rocker arm 10. By means of an adjusting device 30, however, a rotational position of the contour lever 15 relative to the cam follower lever 14 is variable to change a Abrollbereich the roller 26 of the valve rocker arm 20 on the contour surface. In each of the different adjustable rotational position cam follower lever 14 and contour lever 15 are then again motion-coupled with respect to a pivoting movement (tilting movement) about the rocker shaft 13th

The adjustable different Abrollbereiche are in FIG. 4 illustrated. FIG. 4 shows a side view of the contour lever 15 of the transfer rocker arm 10 according to an embodiment of the invention.

For example, the adjusting device, the below still using the FIGS. 7 and 8th explained in more detail, be executed to set two different rotational positions of the contour lever 15 relative to the cam follower lever 14, resulting in two different Abrollbereiche a1 and a2 for the roller 26 of the valve rocker arm 10.

In a first set rotational position, the roller 26 reciprocates on a first rolling-off area a1 when the tilting movement of the transmission rocker arm 10 or contouring lever 15 is almost the whole of the first rolling-off area 16a and a first partial area of the second rolling area 16b includes. In a second set On the other hand, in the case of a tilting movement of the transfer rocker arm 10 or the contour lever 15 generated by the cam 2, the roller 26 rolls back and forth on the second rolling area a2, which comprises almost the entire second rolling area 16b and a partial area of the third rolling area 16c.

If the valve drive 1 is switched over from the rolling area a1 to the rolling area a2, the valve lift that can be generated by the camshaft 3 increases. As in FIG. 4 can be seen, the radial distance at the right end of the area a2 is still equal to the radial distance in the first Abrollbereich 16a, so that at this point a closed position of the globe valves is generated.

The adjusting device can be designed so that it can set a rotational position of the second lever relative to the first lever in two predetermined positions, so that two different, predetermined Abrollbereiche on the contour surface 16 and thus valve strokes are switchable. Alternatively, the adjusting device can also be designed so that more than two predetermined Verdrehpositionen are adjustable or the rotational position is infinitely variable within predetermined limits. In the latter variant, the valve lift can be varied continuously.

FIG. 5 shows a side view of the contour lever 515 of the transfer rocker arm 10 according to another embodiment of the invention. In this embodiment, the contour lever has a contour surface 516 with five different rolling areas 16a-16e. The first rolling roller 16a again forms the base circle contour with a constant radial distance R1 to the axis 13. The subsequent second Abrollbereich 16b again forms a ramp contour, with increasing radial distance, which has risen to the value R2 at the end of the second Abrollbereichs. The adjoining third rolling region 16c again forms an area with a constant radial distance R2.

At this third Abrollbereich 16c is now followed in the unwinding a fourth Abrollbereich 16d, which in turn forms a Rampenkontur. At the end of the fourth rolling range 16d, the radial distance has increased to the value R3. The fourth area is now followed by a fifth rolling area 16e, which in turn has a constant radial distance. The unwind points on the fifth Abrollbereich 16e have a constant radial distance to the rocker arm axis of the transmission lever. The radial distance R3 of the fifth rolling region 16e is greater than the radial distance R2 of the third rolling region 16c and greater than the radial distance R1 of the first rolling region 16a. In this embodiment With five Abrollbereichen the third region 16c forms a middle position in which the lift valve is kept open, ie during the rolling of the roller 26 on the third region 16c, in an open position with a constant lift height, which is smaller than the maximum lift height.

FIG. 6 illustrates various stroke curves that can be adjusted with the valve train. The abscissa axis corresponds to the rotational angle α of the camshaft 3. The ordinate axis corresponds to the valve lift d. The curves 61 to 64 show four different adjustable valve lift curves as a function of the angle of rotation of the camshaft. Each of the four curves 61 to 64 corresponds to a specific set by means of the adjusting device rotational position from the second lever 15 to the first lever 14 of the transfer rocker arm 10. Here, the curve 61 corresponds to a set rotational position, which produces the largest valve lift and the shortest valve closing times, while the curve 65 on the other hand produces the lowest valve lift and the longest valve closing times.

The FIGS. 7 and 8th illustrate the operation of the hydraulic actuator. This shows FIG. 7 a perspective view of the two-part construction of the transfer rocker arm 10 in a first switching state.

It has already been explained above that the transfer rocker arm 10 has a two-part construction. Here, the transfer rocker arm 10 includes a first lever (cam follower lever) 14, which engages with the cam 2 of the camshaft 3, and a second lever (contour lever) 15 having the contour surface 16 which is operatively connected to the roller 26 of the valve rocker arm 20 stands.

The cam follower lever 14 and the contour lever 15 are coupled to each other via the driver 32, which presses against the stop surface 19, such that a tilting movement of the cam follower lever 14 generated by the cam 2 to a corresponding tilting movement of the contour lever 15 about the Kipphebelachse 13 of the transfer rocker 10th leads. This movement coupling of cam follower lever 14 and contour lever 15 can be realized instead of the driver shown by other positive or hydraulic connections, z. B by an internal toothing, a swing motor principle, etc. and can be attached to a location other than the one shown.

By means of a hydraulic adjusting device 30, however, a rotational position of the contour lever 15 relative to the cam follower lever 14 is variable to change a Abrollbereich the roller 26 of the valve rocker arm 20 on the contour surface 16.

For this purpose, the hydraulic adjusting device 30 comprises a hydraulically actuated pin 31, also referred to in this document as a shift pin 31 which is attached at one end to the cam follower lever 14 and disposed at another end on the contour lever 15.

As in the FIGS. 7 and 8th can be seen, the cam follower lever 14 for this purpose a bolt receptacle 33 for holding the shift pin 31, in which a pressurizable with a hydraulic fluid pressure chamber is arranged (not shown). The hydraulic lines for supplying the pressure chamber and the control lines of the actuator 30 are not shown. The other end of the shift pin is held in a receptacle on the contour lever 15, wherein the recording simultaneously forms the driver 32.

When switching the adjusting device, the pressure chamber is acted upon by hydraulic fluid, whereby the shift pin 31 from the in FIG. 7 shown retracted state in the in FIG. 8 shown extended state moves.

By extending the shift pin 31, the contour lever 15 rotates clockwise in a different rotational position relative to the cam follower lever 14. As a result, the contour surface 16 also rotates clockwise. Thus, the Abrollbereich for the roller 26 of the valve rocker arm 20. Depending on the design of the actuator 30 can be adjusted by controlling the pressure level in the pressure chamber different extension positions of the shift pin 31 and thus different Verdrehpositionen.

The cam follower lever 15 is biased by means of a return spring 17 via a Rückstellfederanschlagpunkt 17 a, so that the entire transfer rocker arm 10 is pressed by the spring force of the return spring against the camshaft 3.

Although the invention has been described with reference to particular embodiments, it will be apparent to those skilled in the art that various changes may be made and equivalents may be substituted for without departing from the scope of the invention. In addition, many modifications can be made without leaving the associated area. Accordingly, the invention should not be limited to the disclosed embodiments, but should include all embodiments which fall within the scope of the appended claims. In particular, the invention claims also protection for the subject matter and the features of the subclaims independently of the claims referred to.

LIST OF REFERENCE NUMBERS

1

Variable valve train

2

cam

3

camshaft

10

Übertragungskipphebel

11

First end

12

Second end

13

Rocker shaft of the transfer rocker arm

14

First lever or cam follower lever

15, 515

Second lever or contour lever

16, 516

contoured surface

16a, 16b, 16c, 16d, 16e

Abrollbereiche

17

Return spring

17a

Lifting point for return spring

18

role

19

stop surface

20

rocker

21

First end or valve-side lever arm

22

Second end or camshaft-side lever arm

23

Rocker shaft of the valve rocker arm

24

admission

25

Hydraulic valve clearance compensation element

26

role

27

ring land

30

setting device

31

Hydraulic shift pin

32

takeaway

33

bolt Hole

61 - 65

Ventilhubverlaufskurve

a1

First roll-off area

a2

Second roll-off area

R1, R2, R3

Radial distance of Abrollbereichs of the rocker shaft

Claims (13)

1. Variable valve drive (1) for a lifting valve, in particular for a charge-exchange valve of an internal combustion engine, which is periodically movable between a closed position and an open position indirectly by way of a cam of a camshaft, comprising

   a switchable rocker lever arrangement for the actuation of the lifting valve, having a transmission rocker lever (10) and a valve rocker lever (20) which are mounted so as to be pivotable on different rocker lever axles (13, 23) which are each parallel to the camshaft axis,

   wherein the valve rocker lever (20), at a first end (21), is in operative contact with the lifting valve and, at a second end (22), has a roller (26),

   wherein the transmission rocker lever (10), at a first end (11), is in engagement with a cam (2) of the camshaft (3) and, at a second end (12), is operatively connected, by way of a contour surface (16; 516), to the roller (26) of the valve rocker lever (20), in such a way that a rocking movement of the transmission rocker lever (10) generates a rocking movement of the valve rocker lever (20), during which the roller (26) of the valve rocker lever (20) rolls on the contour surface (16); and

   an actuating device (30) for the switching of the rocker lever arrangement, by way of which actuating device the contour surface (16; 516) can be rotated about the rocker lever axle (13) of the transmission rocker lever (10), in order to generate a displacement of a rolling region (a1, a2) of the roller (26) of the valve rocker lever (20) on the contour surface (16; 516).
2. Variable valve drive (1) according to Claim 1, characterized in that the contour surface (16)

   (a) has a first rolling region (16a) which forms in particular a base circle contour which generates no valve lift when the roller (26) of the valve rocker lever (20) rolls on the base circle contour, and

   (b) has a second rolling region (16b) which adjoins the first rolling region (16a) and which has a ramp contour.
3. Variable valve drive according to Claim 2, characterized in that the contour surface (16) has a third rolling region (16c) which adjoins the second rolling region (16b) and which generates a valve position with maximum valve lift when the roller (26) of the valve rocker lever (20) rolls on the third rolling region (16c).
4. Variable valve drive (1) according to Claim 2 or 3, characterized in that the transmission rocker lever (10) has a first lever (14), which is in engagement with the cam (2) of the camshaft (3), and a second lever (15; 515), having the contour surface (16; 516) which is operatively connected to the roller (26) of the valve rocker lever (20), wherein the first lever (14) and the second lever (15; 515) are coupled to one another such that a rocking movement of the first lever (14) generated by the cam (2) leads to a corresponding rocking movement of the second lever (15; 515) about the rocker lever axle (13) of the transmission rocker lever (10), wherein, by way of the actuating device (30), a rotational position of the second lever (15; 515) relative to the first lever (14) can be varied in order to vary a rolling region of the roller (26) of the valve rocker lever (20) on the contour surface (16; 516).
5. Variable valve drive according to Claim 4, characterized

   (a) in that the actuating device is designed to vary a rotational position of the second lever relative to the first lever in continuously variable fashion; or

   (b) in that the actuating device is designed to vary a rotational position of the second lever relative to the first lever into two predetermined positions, such that switching is possible between two different valve lifts.
6. Variable valve drive according to Claim 4 or 5, characterized

   (a) in that the actuating device (30) is designed as a hydraulic switching unit; and/or

   (b) in that the actuating device (30) has a hydraulically actuated switching pin (31) which, at one end, is fastened to the first lever (14) and, at another end, is fastened to the second lever (15), wherein a deployment of the switching pin (31) varies a rotational position of the second lever (15) relative to the first lever (14).
7. Variable valve drive according to Claim 4 or 5, characterized in that the actuating device is designed as an electrical or mechanical actuating device.
8. Variable valve drive according to one of Claims 4 to 7, characterized in that the first lever (14) and the second lever (15) are coupled to one another by way of a driver (32).
9. Variable valve drive according to one of the preceding claims, characterized in that the transmission rocker lever (10) is preloaded by way of a restoring spring (17) such that the transmission rocker lever (10) is pushed against the camshaft (3).
10. Variable valve drive (1) according to one of Claims 4 to 9, characterized in that the first lever (14) of the transmission rocker lever (10) is preloaded by way of a restoring spring (17) such that the transmission rocker lever (10) is pushed against the camshaft (3).
11. Variable valve drive (1) according to one of Claims 3 to 10, characterized in that the contour surface (516) has a fourth rolling region (16d), which adjoins the third rolling region (16c) and which forms a ramp contour, and a fifth rolling region (16e), which adjoins the fourth rolling region (16d), wherein the fifth rolling region (16e) has a constant radial spacing (R3) to the axis of the rocker lever axle (13) of the transmission lever (10), which spacing is greater than the radial spacing (R2) of the third rolling region (16c) and than the radial spacing (R1) of the first rolling region (16a).
12. Variable valve drive (1) according to any of the preceding claims, characterized in that the valve rocker lever (20) has, at its valve-side end (21), a receptacle (24) in which a hydraulic valve play compensation element (25) or a screw with elephant foot is received.
13. Motor vehicle, in particular utility vehicle, having a variable valve drive (1) according to one of the preceding claims.

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