EP3577323B1 - Variable valve drive of a combustion piston engine - Google Patents

Description

The invention relates to a variable valve drive of an internal combustion piston engine with at least one functionally identical gas exchange valve per cylinder, the valve lift of which is predetermined by at least one primary cam and a secondary cam of a camshaft and can be selectively transferred to at least one associated gas exchange valve by means of a switchable rocker arm, which has a primary lever and a secondary lever is, wherein the respective primary lever is supported with its one end on an associated support element mounted on the housing and with its other end on the valve stem of the associated gas exchange valve, the respective primary lever being in tap contact between its two ends with the associated primary cam, and at which the secondary lever is pivotably mounted on the primary lever, is in tap contact with the associated secondary cam, and by means of a coupling element that can be adjusted by an adjusting device can be coupled to the primary lever.

Switchable valve trains of internal combustion piston engines are known in different designs. For example, valve trains of individual cylinders or groups of cylinders of an internal combustion piston engine can be deactivated by switching off the transferable valve lift and thus, in conjunction with switching off the fuel injection for the cylinder in question, the fuel consumption as well as the CO ₂ and pollutant emissions of the internal combustion piston engine can be reduced in partial load operation. On the other hand, the stroke curves over time that can be transmitted through the valve trains of inlet and / or outlet valves of a reciprocating internal combustion engine can be changed by switching the stroke and thus adapted to the current operating state of the reciprocating internal combustion engine as a function of operating parameters such as the engine speed and the engine load. whereby the engine output and the torque can be increased and the specific fuel consumption of the reciprocating internal combustion engine can be reduced.

In the case of disengageable valve trains, two relatively displaceable or rotatable components of a switchable stroke transmission element are usually provided, one component of which is in actuating connection with the associated cam of a camshaft and the other component with the valve stem of the associated gas exchange valve. Both components can be coupled or decoupled to one another via a coupling element, which is mostly designed as a coupling bolt. In the coupled state, the valve lift of the associated cam is transmitted to the gas exchange valve in question, but not in the decoupled state, so that the gas exchange valve then remains closed. The coupling bolt is usually guided in an axially movable manner in a bore of one component and can be displaced into a coupling bore of the other component. The coupling bolt is held in a rest position by means of a spring element and, by the application of an actuating force, is displaced against the restoring force of the spring element into an actuating position and held there. In the case of valve drives that can be switched off, the rest position of the coupling bolt usually corresponds to the coupled state of the components of the stroke transmission element and the actuating position corresponds to the decoupled state of the components. The disengageable stroke transmission elements can be disconnectable bucket tappets, roller tappets, rocker arms, rocker arms or support elements.

In the case of switchable valve trains, at least two relatively displaceable or rotatable components of a switchable stroke transmission element are provided, of which one component is coupled to an associated primary cam of a camshaft with a specific valve lift and to the valve stem of the associated gas exchange valve, and the other component is coupled to an associated one Secondary cam of the camshaft is in control connection with a larger valve lift or with an additional lift. Both components can be coupled or decoupled with one another via a coupling element, which is usually designed as a coupling bolt. In the decoupled state, the valve lift of the primary cam is transferred to the gas exchange valve in question, im In the coupled state, on the other hand, the valve lift of the secondary cam is transmitted to the gas exchange valve. Here, too, the coupling bolt is usually guided in an axially movable manner in a bore in one component and can be displaced into a coupling bore in the other component. The coupling bolt is held in a rest position by means of a spring element and is moved into an actuating position and held there by applying an actuating force against the restoring force of the spring element. In the case of switchable valve drives, the rest position of the coupling pin mostly corresponds to the decoupled state of the components of the stroke transmission element and the actuating position corresponds to the coupled state of the components. Such switchable stroke transmission elements are, for example, switchable bucket tappets, switchable rocker arms or switchable rocker arms.

The adjustment of coupling elements of switchable stroke transmission elements is usually carried out hydraulically, in that a switching pressure line leading to the pressure chambers of the coupling elements is alternately connected to an oil pressure source, for example via a magnetic switching valve, or is switched to a depressurized state. A known embodiment of a switchable rocker arm provided with a hydraulically adjustable coupling bolt, which is provided in an internal combustion piston engine for switching off the stroke of a gas exchange valve, is disclosed in US Pat DE 10 2006 057 894 A1 . In contrast, the DE 10 2006 023 772 A1 a switchable rocker arm described with a hydraulically adjustable coupling pin which is provided in an internal combustion piston engine for switching the stroke of a gas exchange valve.

If gas exchange valves of an internal combustion piston engine are to be selectively switched off or switched over in groups, separate switching pressure lines, each with an assigned switching valve, are required for hydraulic adjustment of the coupling elements. A corresponding hydraulic adjusting device for group-wise selective adjustment of the coupling elements of a variable valve drive in an internal combustion piston engine with two inlet valves and two outlet valves per cylinder is for example in the DE 102 12 327 A1 described. The switchable stroke transmission elements of this valve drive are designed as switchable bucket tappets in this case.

The adjustment of coupling elements of switchable stroke transmission elements can, however, also take place electromagnetically, in that the coupling elements are each in operative connection with an electromagnet and the electromagnets are alternately energized or de-energized. A known embodiment of a switchable rocker arm provided with an electromagnetically adjustable coupling bolt, which is provided in an internal combustion piston engine for switching off the stroke of a gas exchange valve, can be the U.S. 5,544,626 A can be removed. The coupling pin and the electromagnet, the armature of which is connected to the coupling pin, are arranged longitudinally in the primary housing of the rocker arm, which results in a greater length of the rocker arm and a correspondingly greater width of the cylinder head concerned.

By contrast, in the not pre-published DE 10 2016 220 859 A1 a valve drive of an internal combustion piston engine with electromagnetically switchable rocker arms described, which is provided in an internal combustion piston engine for switching the stroke of the gas exchange valves concerned. The coupling bolts are each arranged longitudinally in the respective primary lever of the rocker arm and can each be brought into contact with a ramp surface of an armature rod of an associated electromagnet and axially displaced into a coupling position. The electromagnets are arranged with a largely vertical orientation above the rocker arms and the associated camshaft on a carrier plate attached to the cylinder head in question, which results in a greater overall height of the cylinder head.

Further switchable rocker arms with coupling bolts aligned parallel and transversely to the longitudinal extension of the same are from the DE 101 55 801 A1 and the DE 10 2015 221 037 A1 known. In addition, the US 6 499 451 B1 a variable valve drive of an internal combustion engine, in which the switchable rocker arms assigned to each valve can each be actuated by means of a separate actuator. These actuators each act on one arm of a two-armed pivot element pivotably mounted on an axis, the second arm thereof can act on a coupling pin of the associated rocker arm. This valve train, too, is judged to be disadvantageous primarily because of its many separate actuators and adjusting means. The documents too DE 699 23 139 T2 and JP S60 111010 A reveal switchable rocker arms with coupling elements

Finally from the JP 2004-108 525 A1 a variable valve drive with several rocker arms for actuating functionally identical valves of an internal combustion engine is known, the respective actuating device of which manages with only one actuator. The secondary levers and primary levers there are, however, designed separately and arranged next to one another. The secondary levers can be coupled to a directly adjacent primary lever by an axial displacement of a coupling pin mounted in a transverse bore of the respective secondary lever into a coupling bore of the respective primary lever. In the coupled state, the higher lift of the primary and secondary cams of a camshaft is transmitted to the relevant gas exchange valves. The axial displacement of the coupling bolts can only take place if both cams are tapped at the same time in the base circle, since the transverse and coupling bores are only then aligned with one another.

The coupling bolts are actuated by means of an adjusting device which has a shift rod which is arranged parallel to the camshaft of the internal combustion engine and can be linearly displaced by an actuator. Two axial stops are attached to the shift rod for each pair of primary lever and secondary lever. Between two stops, a guide sleeve is arranged on the shift rod, which can be shifted on one side between the two stops by means of a compression spring in the shifting direction, spring-loaded on the shift rod. An arm extends in one piece from the respective guide sleeve and is in actuating contact with the free end face of the coupling bolt mentioned. The respective arms of the respective guide sleeves are designed as rigid metallic levers. The coupling bolt can be returned to its decoupling position by means of a compression spring.

When the shift rod is shifted in the shifting direction, the secondary levers are immediately coupled to the primary levers in the lever pairs that can be shifted. In the case of the pairs of levers that cannot be switched at the moment, the coupling bolts are Tension of the relevant compression springs in the switching direction with a force. The coupling of the secondary levers to the primary levers occurs when the two cams in question of the associated camshaft are tapped in the base circle and the transverse and coupling bores are aligned with one another.

Since the arrangement of separate hydraulic switching pressure lines or electrical switching lines in a cylinder head of an internal combustion piston engine is relatively difficult and expensive due to the limited space available, as well as that from the JP 2004-108 525 A1 known variable valve train was judged as mechanically too complex, the invention was based on the object of proposing a variable valve train of an internal combustion piston engine of the type mentioned with switchable rocker arms for functionally identical gas exchange valves that can be switched by means of a space-saving actuator. For this purpose, only one adjusting device for the rocker switch for actuating functionally identical valves should be used.

This object is achieved in connection with the features of the preamble of claim 1 in that the respective coupling element of the switchable rocker arm is each designed as an axially moveable coupling bolt guided in a transverse bore of the primary lever, that the coupling element by means of a switching bolt mounted axially movably in a transverse bore of the secondary lever is displaceable against the restoring force of a spring element in an opposite coupling bore of the secondary lever, that the respective shift pin protrudes with its axially outer end from the secondary lever, that this axially outer end of the shift pin is connected to a rod-shaped connecting element, which in turn is coupled to a shift rod in an adjusting connection is that the shift rod is arranged above the respective rocker arm parallel to the associated camshaft, that the shift rod by means of a linear actuator against the restoring force of a spring element it is longitudinally displaceable from a rest position into a switching position, and that the connecting elements of the switchable rocker arms are designed as leaf springs.

Advantageous refinements and developments are the subject of the dependent claims.

The invention is therefore based on a per se known variable valve drive of an internal combustion piston engine which has at least one functionally identical gas exchange valve per cylinder. The gas exchange valves with the same function can be inlet valves or outlet valves. The valve lift of these functionally identical gas exchange valves is predetermined by at least one primary cam and a secondary cam of a camshaft and can be selectively transferred to at least one associated gas exchange valve by means of a switchable rocker arm, which has a primary lever and a secondary lever. The primary lever is supported at the end on a support element mounted on the housing side and on the opposite side on the valve stem of the associated gas exchange valve, and in between, for example via a rotatably mounted roller, it is in tap contact with the associated primary cam. The secondary lever is pivotably mounted on the primary lever, for example it is in tap contact with the associated secondary cam via at least one sliding surface, and it can be coupled to the primary lever by means of a coupling element that can be adjusted by an adjusting device. In the coupled state of the rocker arm, the stroke profile of the secondary cam, which usually has a greater stroke height than the primary cam or exerts an additional stroke, is transferred to the associated gas exchange valve. The additional stroke can be, for example, a post-stroke for exhaust gas recirculation or a decompression stroke in the work cycle to increase the engine braking effect.

According to the invention, it is provided in this variable valve drive that the respective coupling element of the switchable rocker arms are each designed as an axially movable coupling bolt guided in a transverse bore of the primary lever an opposite coupling bore of the secondary lever is displaceable, that the respective shift pin protrudes with its axially outer end from the secondary lever, that this axially outer end of the shift pin is connected to a rod-shaped connecting element, which in turn with a shift rod is coupled in an actuating connection, that the shift rod is arranged above the respective rocker arm parallel to the associated camshaft, that the shift rod can be longitudinally displaced from a rest position into a shift position by means of a linear actuator against the restoring force of a spring element, and that the connecting elements of the switchable rocker arms, with which the switching pins can be actuated, are designed as leaf springs.

As an alternative to a hydraulic switchover of the rocker arms with separate switching pressure lines routed to the rocker arms or an electromagnetic switchover of the rocker arms with separate electrical switch lines routed inside or outside the rocker arms, the rocker arms of the functionally identical gas exchange valves can be switched over the switchable rocker arm is each designed as a coupling bolt axially movably guided in a transverse bore of the primary lever, which can be displaced against the restoring force of a spring element into an opposite coupling bore of the secondary lever by means of a switching bolt that is axially movably mounted in a transverse bore of the secondary lever. The transverse bores in the primary levers and the secondary levers of the rocker arms as well as the coupling and switching pins guided therein are thus aligned parallel to the associated camshaft. Each switching pin protrudes with its axially outer end from the secondary lever and is on this via an upwardly directed rod-shaped connecting element with a switching rod in control connection, which is arranged above the rocker arm parallel to the associated camshaft and a linear actuator against the restoring force of a spring element from a Rest position is longitudinally displaceable in a switching position.

According to the invention, the connecting elements of the switchable rocker arms are designed as leaf springs, so that when the shift rod is axially displaced by an actuator, they then build up a pretensioning force on the assigned shift pin when the primary lever and the secondary lever of a shift finger lever cannot be coupled to one another due to their position with respect to one another. This biasing force on the designed as a leaf spring The connecting element is then dismantled by an axial displacement of the associated shift bolt as soon as the primary lever and the secondary lever of the shift lever are aligned with one another in the correct pivoted position.

The actuating device with the features of the invention thus has only a single actuator by means of which the switchable rocker arms in question can be switched from the rest position in which the secondary lever is decoupled from the primary lever into the switching position in which the secondary lever is coupled to the primary lever are. The linear actuator can be arranged and fastened in the longitudinal direction of the shift rod at a suitable point on the cylinder head at which the required installation space is available and for which the energy supply required for actuation can be implemented inexpensively. Compared to an actuating arrangement with separate hydraulic or electromagnetic actuators, which can be arranged inside or outside the switchable rocker arms, the actuating device according to the invention with the purely mechanically switchable rocker arms is much simpler and more space-saving and can be manufactured more cost-effectively. Several such actuating devices can also be arranged on the cylinder head of an internal combustion piston engine in order to be able to selectively switch several groups of functionally identical gas exchange valves, such as inlet valves and / or outlet valves of all or only certain cylinders or, in the case of a four-valve cylinder head, of first and second inlet and / or outlet valves.

The linear actuator is preferably designed as an electromagnet with an armature guided in an axially movable manner in a coil body, the armature of which is rigidly connected to the shift rod. For the control and the energy supply of the linear actuator, only a two-wire cable is then required, which is led from an electronic control unit to the coil of the electromagnet.

The linear actuator can, however, also be designed as a single-acting hydraulic or pneumatic actuating cylinder with a piston which is guided in an axially movable manner in a cylinder and whose piston is rigidly connected to the shift rod. For the control and the energy supply of the linear actuator is with this Execution requires a control pressure line connected to the pressure chamber of the actuating cylinder, which can be connected, for example, via a 3/2-way solenoid switching valve connected to an electronic control unit, alternately to a pressure supply line connected to a pressure medium source or to an unpressurized return or vent line.

The switching rod is preferably designed as a flat bar, which is arranged with its wider outer walls at right angles to the switching pin of the switchable rocker arm. Due to the wider outer walls, the switch rod has enough space for mechanical coupling of the rod-shaped connecting elements of the switchable rocker arms.

In addition, this makes it possible to produce the shift rod simply and inexpensively as a stamped component from a sheet steel or a light metal sheet.

The connecting elements of the switchable rocker arms are each largely rigidly attached to the outer end of the associated switch pin and they each engage in a slot-shaped opening in the switch rod. The switchover of the rocker arms can thus be initiated at any time and independently of the current rotational position of the associated camshaft by the axial displacement of the shift rod. At those rocker arms whose primary and secondary cams are currently being tapped by the primary and secondary levers in the base circle radius, the rocker arms are switched over immediately. On those rocker arms whose primary and secondary cams are picked up just outside the base circle radius, the leaf springs in question are preloaded in the switching direction, and the rocker arms in question are switched over when the associated cams are picked up due to a corresponding rotation of the camshaft in the base circle radius.

In order to ensure simple assembly, it is preferably provided that the leaf springs are each pushed on and engaged in the manner of a locking washer a bore open at the end are fastened to the shift pin in an annular groove arranged at the axially outer end of the respective shift pin.

To compensate for the tilting movements of the rocker arms and manufacturing tolerances, the transverse and longitudinal dimensions of the openings in the switching rod are preferably greater than the width and the thickness of the leaf springs. The leaf springs can therefore move in the openings of the shift rod with little wear when the internal combustion piston engine is in operation. Manufacturing tolerances in the arrangement of the openings in the shift rod and the entire shift rod can thus be compensated for in a simple manner by increasing the travel of the linear actuator. The adjusting device according to the invention thus makes relatively low demands on the accuracy in the manufacture and arrangement of the components and is therefore particularly inexpensive to manufacture.

The switching rod is advantageously provided on its wider outer wall facing away from the rocker arms at each opening on the switching direction side with an arcuate spring clip, the free end of which protrudes longitudinally into the opening in question to elastically support the associated leaf spring. As a result, the leaf springs are supported elastically and longitudinally in the openings of the shift rod, which reduces mechanical wear on the contact surfaces and prevents the transmission of transverse forces to the shift pins of the rocker arms.

In order to prevent the shift rod from wandering or buckling under load, the shift rod is preferably guided in an axially movable manner in several guide openings fixed to the housing in the cylinder head.

At least some of these guide openings of the shift rod are preferably arranged in bearing caps of the associated camshaft, which greatly simplifies their manufacture compared to an arrangement in webs of the cylinder head that are fixed to the housing.

• Fig. 1 eine bevorzugte Ausführung eines erfindungsgemäßen Ventiltriebs eines Verbrennungskolbenmotors mit drei Zylindern und vier Gaswechselventilen pro Zylinder mit drei schaltbaren Schlepphebeln im nicht umgeschalteten Zustand in einer perspektivischen Übersichtsdarstellung,
• Fig. 1a einen Ausschnitt aus dem Ventiltrieb gemäß Fig. 1 mit einer Längsansicht eines schaltbaren Schlepphebels im nicht umgeschalteten Zustand,
• Fig. 1b einen Ausschnitt des Ventiltriebs gemäß Fig. 1 mit einer Querschnittsansicht eines schaltbaren Schlepphebels im nicht umgeschalteten Zustand,
• Fig. 1c einen Ausschnitt des Ventiltriebs gemäß Fig. 1 mit einer Längsschnittansicht eines schaltbaren Schlepphebels im nicht umgeschalteten Zustand,
• Fig. 2 den erfindungsgemäßen Ventiltrieb eines Verbrennungskolbenmotors gemäß Fig. 1 mit den drei schaltbaren Schlepphebeln im umgeschalteten Zustand in einer perspektivischen Übersichtsdarstellung,
• Fig. 2a einen Ausschnitt des Ventiltriebs gemäß Fig. 2 mit einer Längsansicht eines schaltbaren Schlepphebels im umgeschalteten Zustand,
• Fig. 2b einen Ausschnitt des Ventiltriebs gemäß Fig. 2 mit einer Querschnittsansicht eines schaltbaren Schlepphebels im umgeschalteten Zustand,
• Fig. 2c einen Ausschnitt des Ventiltriebs gemäß Fig. 2 mit einer Längsschnittansicht eines schaltbaren Schlepphebels im umgeschalteten Zustand,
• Fig. 3a einen schaltbaren Schlepphebel des Ventiltriebs gemäß den Figuren 1 bis 2b in einer Seitenansicht, und
• Fig. 3b den schaltbaren Schlepphebel des Ventiltriebs gemäß den Figuren 1 bis 2b in einer perspektivischen Schrägansicht von oben.

To illustrate the invention, the description is accompanied by a drawing with an exemplary embodiment. In this shows

• Fig. 1 a preferred embodiment of a valve drive according to the invention of an internal combustion piston engine with three cylinders and four gas exchange valves per cylinder with three switchable rocker arms in the non-switched state in a perspective overview,
• Fig. 1a a section of the valve train according to Fig. 1 with a longitudinal view of a switchable rocker arm in the non-switched state,
• Figure 1b a section of the valve train according to Fig. 1 with a cross-sectional view of a switchable rocker arm in the non-switched state,
• Figure 1c a section of the valve train according to Fig. 1 with a longitudinal sectional view of a switchable rocker arm in the non-switched state,
• Fig. 2 the valve train according to the invention of an internal combustion piston engine according to Fig. 1 with the three switchable rocker arms in the switched state in a perspective overview,
• Fig. 2a a section of the valve train according to Fig. 2 with a longitudinal view of a switchable rocker arm in the switched state,
• Figure 2b a section of the valve train according to Fig. 2 with a cross-sectional view of a switchable rocker arm in the switched state,
• Figure 2c a section of the valve train according to Fig. 2 with a longitudinal sectional view of a switchable rocker arm in the switched state,
• Fig. 3a a switchable rocker arm of the valve train according to the Figures 1 to 2b in a side view, and
• Figure 3b the switchable rocker arm of the valve train according to the Figures 1 to 2b in a perspective oblique view from above.

In the perspective overview of Fig. 1 a valve drive 1 of a reciprocating internal combustion engine with three cylinders arranged in series and two inlet valves and two outlet valves per cylinder is partially shown, but only to the extent necessary to explain the invention. A camshaft carrier 2 of a two-part cylinder head of the reciprocating internal combustion engine has four semicircular first slide bearing sections 3 for mounting an intake camshaft, not shown, and four semicircular second slide bearing sections 4 for Storage of an exhaust camshaft 6. The remaining slide bearing sections for mounting the inlet camshaft and the outlet camshaft 5 are each part of bearing caps 5, which are placed on the camshaft carrier 2 after the camshafts have been inserted and are screwed to it. In Fig. 1 only the bearing caps 5 of the exhaust camshaft 6 are shown.

While the first exhaust valves of each cylinder, not shown, can be switched via assigned switchable rocker arms 10 with regard to their transferable stroke profile, the second exhaust valves of each cylinder, also not shown, are assigned to non-switchable rocker arms 11 for constant lift transfer. To this end, the exhaust camshaft 6 has a centrally arranged primary cam 7 for each of the first exhaust valves and two secondary cams 8 arranged on both sides of the primary cam 7. In contrast, the exhaust camshaft 6 has only a single cam 9 for each of the second exhaust valves.

The non-switchable rocker arms 11, not shown in detail, are each supported on their underside at the ends on a support element 13 with an integrated hydraulic valve lash adjuster (HVA) mounted on the housing and at their other end on the valve stem of the associated second outlet valve. In addition, they are in tap contact with the associated cam 9 between these two ends on their upper side. When the exhaust camshaft 6 rotates, the stroke profile of the relevant cams 9 is transmitted to the second exhaust valves via the non-switchable rocker arms 11.

As in the longitudinal, cross-sectional, and longitudinal sectional views of Figures 1a to 1c as well as in the side view of Fig. 3a and in the perspective oblique view of Figure 3b As can be seen, the switchable rocker arms 10 each have a primary lever 14 and a secondary lever 19. The primary lever 14 is largely frame-shaped and supported on its underside at the end on a support element 12 with an integrated hydraulic valve lash adjuster (HVA) mounted on the housing side and at the other end on the valve stem of the associated first outlet valve.

On its upper side, the primary lever 14 is in tap contact with an associated primary cam 7 via a tap element 15, which in the present case is designed as a rotatably mounted roller. The secondary lever 19 has a frame-like shape that encompasses the primary lever 14, and it is pivotably mounted on the primary lever 14 via a hinge pin 20 arranged on the valve side. Like in particular the Figures 3a and 3b show, the secondary lever 19 has a widened web section on both sides of its longitudinal extension as tap elements 22, each with an outer sliding surface 23, which are in tap contact with the associated secondary cams 8 due to the spring force of a compression spring 21 designed as a leg spring.

As a coupling element 17 for the positive connection of the secondary lever 19 to the primary lever 14, an axially moveable coupling bolt guided in a transverse bore 16 of the primary lever 14 is provided which, via a switching bolt 25 axially displaceably mounted in a transverse bore 24 of the secondary lever 19, counteracts the restoring force of a spring element 18 designed as a helical spring is displaceable in an opposite coupling bore 28 of the secondary lever 19. The shift pin 25 protrudes with its outer axial end 26 from the secondary lever 19 and is in an actuating connection there via an upwardly directed rod-shaped connecting element 29 with a shift rod 34 of an actuating device 30.

The connecting elements 29 of the switchable rocker arms 10 are in the present case designed as leaf springs and are fastened to the associated switching pin 25 in the manner of a locking washer and inserting its end-open bore into an annular groove formed at the axial end 26 of the switching pin 25.

In order to limit the adjustment travel of the respective switching pin 25 to the outside and to protect the connection of the switching pin 25 to the respective leaf spring 29, the secondary levers 19 each have one, in particular one in Figure 3b easily recognizable bracket 27, which comprises the outer end 26 of the associated shift pin 25. The switching rod 34 of the adjusting device 30 is arranged above the rocker arms 10, 11 parallel to the exhaust camshaft 6 and can be longitudinally displaced from a rest position 39 into a switching position 41 via a linear actuator 31 against the restoring force of a spring element 42. In the present case, the linear actuator 31 is designed, for example, as an electromagnet with an armature 33 guided in an axially movable manner in a coil body 32, the armature 33 being rigidly connected to the shift rod 34.

The switching rod 34 is in the present case designed as a flat bar, which is arranged with its wider outer walls 35 at right angles to the switching pin 25 of the switchable rocker arm 10, and which is preferably made as a stamped component from a sheet steel or light metal sheet. The shift rod 34 is guided so as to be axially movable in a plurality of guide openings 38 in the camshaft carrier 2 which are fixed to the housing and which, in the present case, are arranged in the bearing caps 5 of the exhaust camshaft 6.

The connecting elements 29, designed as leaf springs, of the switchable rocker arms 10 each engage, with play, in a slot-shaped opening 36 of the switching rod 34, the transverse and longitudinal dimensions of which are greater than the width and the thickness of these connecting elements 29 Move in the openings 36 of the shift rod 34 with little wear. In addition, manufacturing tolerances in the arrangement of the openings 36 in the shift rod 34 and the entire shift rod 34 can be compensated for in a simple manner by an increased travel of the linear actuator 31. On its wider outer wall 35 facing away from the rocker arms 10, 11, the switching rod 34 is provided with an arcuate spring clip 37 on the switching direction side at each opening 36, the free end of which protrudes longitudinally into the relevant opening 36 for elastic support of the associated leaf spring 29. As a result, the leaf springs 29 are supported elastically and longitudinally displaceably in the openings 36 of the shift rod 34, which reduces mechanical wear on the contact surfaces and prevents the transmission of transverse forces to the shift pins 25 of the shiftable rocker arms 10.

In Fig. 1 the switching rod 34 of the actuating device 30 is shown in its rest position 39, in which the secondary levers 19 of the switchable rocker arms 10 are decoupled from the primary levers 14. This decoupled switching state of a switchable rocker arm 10, in which the coupling bolt 17 is located completely within the transverse bore 16 of the primary lever 14, is particularly good in the cross-sectional view of FIG Figure 1b recognizable. In the uncoupled state of the primary lever 14 and the secondary lever 19, when the exhaust camshaft 6 rotates, only the stroke profile of the relevant primary cam 7 is transmitted via the primary lever 14 of the switchable rocker arm 10 to the associated first exhaust valve. The stroke profile of the relevant secondary cams 8 then only ensures a compression of the secondary lever 19 in relation to the primary lever 14. This is good in the longitudinal sectional view of FIG Figure 1c It can be seen in which the primary cam 7 of the exhaust camshaft 6 is picked up by the roller 15 of the primary lever 14 just in the base circle radius and the secondary cams 8 of the exhaust camshaft 6 are picked up by the sliding surfaces 23 of the web sections 22 of the secondary lever 19 just in the area of an additional lift cam.

In the perspective overview of Fig. 2 the switching rod 34 of the actuating device 30 is shown in its switching position 41, into which it is shifted by actuation of the linear actuator 31 in the switching direction indicated by a directional arrow 40. In the switching position 41 of the switching rod 34, the coupling pins 17 of those rocker arms 10, the primary and secondary cams 7, 8 of which are tapped by the roller 15 of the primary lever 14 and the sliding surfaces 23 of the web sections 22 of the secondary lever 19 just in the base circle radius, via the respective leaf spring 29 and the relevant switching pin 25 are immediately moved into the associated coupling bore 28 of the secondary lever 19, since the transverse bore 24 and the coupling bore 28 of the secondary lever 19 are then aligned with the transverse bore 16 of the primary lever 14. The secondary levers 19 of the rocker arms 10 in question are then coupled to the primary lever 14 in question (see FIG Figure 2b ).

In those rocker arms 10, the primary or secondary cams 7, 8 of the roller 15 of the primary lever 14 or the sliding surfaces 23 of the web portions 22 of the Secondary lever 19 are tapped just outside the base circle radius, the leaf springs 29 initially only bias the switching pins 25 in the switching direction 40. The coupling pins 17 in question are then moved into the coupling bore 28 of the secondary lever 19 via the respective leaf spring 29 and the switching pin 25 as soon as whose associated primary and secondary cams 7, 8 are tapped in the base circle radius.

This also in the longitudinal view of Fig. 2a The illustrated coupled switching state of a switchable rocker arm 10, in which the coupling pin 17 is located within the coupling bore 28 of the secondary lever 19, is particularly good in the cross-sectional view of FIG Figure 2b recognizable. In the coupled state of the primary lever 14 and the secondary lever 19, when the exhaust camshaft 6 rotates, the higher stroke profile of the respective primary cam 7 is transferred via the primary lever 14 or the relevant secondary cam 8 via the secondary lever 19 and the primary lever 14 of the switchable rocker arm 10 to the assigned first Transfer exhaust valve. This is particularly good in the longitudinal section view of FIG Figure 2c It can be seen in which the primary cam 7 of the exhaust camshaft 6 is picked up by the roller 15 of the primary lever 14 just in the base circle radius and the secondary cams 8 of the exhaust camshaft 6 are picked up by the sliding surfaces 23 of the web sections 22 of the secondary lever 19 just in the area of an additional lift cam.

In comparison to an actuating arrangement with separate hydraulic or electromagnetic actuators in or on the rocker arms, the actuating device 30 according to the invention with the rocker arms 10, which can be switched purely mechanically, has a significantly simpler and more space-saving design and can be manufactured more cost-effectively.

List of reference symbols

1

Valve train

2

Camshaft carrier

3

First plain bearing section

4th

Second plain bearing section

5

Bearing cap

6th

Exhaust camshaft

7th

Primary cam

8th

Secondary cam

9

cam

10

switchable rocker arm

11

non-switchable rocker arm

12th

Support element

13th

Support element

14th

Primary lever

15th

Pick-up element, role

16

Cross hole

17th

Coupling element, coupling bolt

18th

Spring element, coil spring

19th

Secondary lever

20th

Hinge pin

21

Compression spring, leg spring

22nd

Pick-up element, web section

23

Sliding surface

24

Cross hole

25th

Switch pin

26th

Outside end

27

hanger

28

Coupling hole

29

Connecting element, leaf spring

30th

Adjusting device

31

Linear actuator, electromagnet

32

Bobbin

33

anchor

34

Shift rod, flat bar

35

Wider outer wall

36

opening

37

Spring clip

38

Guide opening

39

Rest position

40

Direction arrow, switching direction

41

Switch position

42

Spring element

Claims (10)

1. A variable valve drive (1) of an internal combustion piston engine having at least one functionally identical gas exchange valve per cylinder, the valve stroke of which is specified by at least one primary cam (7) and a secondary cam (8) of a camshaft (6) and can be selectively transmitted to at least one associated gas exchange valve by means of a switchable cam follower (10), which has a primary follower (14) and a secondary follower (19), wherein the respective primary follower (14) is supported, with its one end, on a associated supporting element (12) mounted on the housing and, with its other end, on the valve stem of the associated gas exchange valve, wherein the respective primary follower (14) is in following contact between its two ends with the associated primary cam (7), and in which the secondary follower (19) is pivotably mounted on the primary follower (14), with the associated secondary cam (8) in following contact, and can be coupled to the primary follower (14) by means of a coupling element (17) which can be adjusted by an adjusting device (30), and wherein the respective coupling element (17) of the switchable cam follower (10) is designed as a coupling bolt guided in a transverse bore (16) of the primary follower (14) in an axially movable manner are such that the coupling element (17) can be moved into an opposite coupling bore (28) of the secondary follower (19) against the restoring force of a spring element (18) by means of a switching bolt (25) which is axially movable in a transverse bore (24) of the secondary follower (19), that the respective switching bolt (25) protrudes with its axially outer end (26) from the secondary follower (19), that this axially outer end (26) of the switching bolt (25) is connected to a rod-shaped connection element (29), which in turn is connected to a switching rod (34) in an adjusting connection that the switching rod (34) is arranged above the respective cam follower (10) parallel to the associated camshaft (6), that the switching rod (34) can be moved longitudinally from a rest position (39) into a switching position (41) by means of a linear actuator (31) against the restoring force of a spring element (42), and that the connection elements (29) of the switchable cam followers (10) are formed as leaf springs.
2. The variable valve drive according to claim 1, characterised in that the linear actuator (31) is formed as an electromagnet with an armature (33) that is axially movably guided in a coil body (32) and the armature (33) of which is rigidly connected to the switching rod (34).
3. The variable valve drive according to claim 1, characterised in that the linear actuator (31) is formed as a single-acting, hydraulic or pneumatic actuating cylinder with a piston that is axially movably guided in a cylinder and piston of which is rigidly connected to the switching rod (34).
4. The variable valve drive according to any one of claims 1 to 3, characterised in that the switching rod (34) is formed as a flat bar, which is arranged with its wider outer walls (35) at right angles to the switching bolts (25) of the switchable cam followers (10).
5. The variable valve drive according to claim 4, characterised in that the switching rod (34) is produced as a stamped component from sheet steel or light sheet metal.
6. The variable valve drive according to any one of claims 1 to 5, characterised in that the connection elements (29) of the switchable cam followers (10) are respectively substantially rigidly attached to the axially outer end (26) of the associated switching bolt (25) and respectively engage in a slot-shaped opening (36) in the switching rod (34).
7. The variable valve drive according to claim 6, characterised in that the leaf springs (29) are fastened to the switching bolt (25) in the manner of a locking washer, respectively by fitting and engaging a bore open at the end in an annular groove arranged at the axially outer end (26) of the respective switching bolt (25).
8. The variable valve drive according to claim 6 or 7, characterised in that the transverse and longitudinal dimensions of the openings (36) in the switching rod (34) are greater than the width and the thickness of the leaf springs (29).
9. The variable valve drive according to claim 8, characterised in that the switching rod (34) is provided with an arcuate spring clip (37)on its wider outer wall (35) facing away from the cam followers (10) at each opening (36) on the switching direction side, the free end of which arcuate spring clip protrudes into the relevant opening (36) in the longitudinal direction for the elastic support of the associated leaf spring (29).
10. The variable valve drive according to any one of claims 1 to 9, characterised in that the switching rod (34) is axially movably guided in several guide openings (38) fixed to the housing of the cylinder head (2), and in that at least some guide openings (38) for the switching rod (34) are arranged in bearing covers (5) of the associated camshaft (6).

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