阅读说明：本技术 活塞式内燃机的可变气门传动机构 (Variable valve drive mechanism of piston type internal combustion engine ) 是由 迪米特里·舍特 哈拉尔德·埃伦特 爱德华·戈洛瓦泰-施米特 于 2018-04-12 设计创作，主要内容包括：本发明涉及活塞式内燃机的可变气门传动机构(1)，其带有每气缸至少一个确定功能的换气气门，其中气门升程分别通过初级凸轮和次级凸轮(7、8)规定，并且通过可切换的气门压杆(10)将气门升程选择性地传递到换气气门上，其中每个初级臂(12)在其端部之间与初级凸轮(7)触碰接触并且每个次级臂(16)与配属的次级凸轮(8)触碰接触并且通过联接元件(15)与初级臂(12)可联接，其中联接元件(15)是在初级臂(12)的横向孔(14)内被引导的联接销，联接销通过在次级臂(16)的横向孔(21)内支承的锁止销(22)可移动到次级臂(16)的联接孔(28)内，以及通过在次级臂(16)的联接孔(28)被引导的解锁销(25)可移回到初级臂(12)的横向孔(14)内，其中锁止销和解锁销(22、25)分别以其轴向外部的端部(23、26)从次级臂(16)伸出，以及分别通过固定在此端部(23、26)上的连接元件(29、30)与切换杆(35)联接，所述切换杆(35)平行于配属的凸轮轴(6)布置，以及通过直线促动器(32)抵抗弹簧元件(37)的回复力地从静止位置(43)可纵向移动到切换位置(45)中。(The invention relates to a variable valve train (1) of a reciprocating piston internal combustion engine, having at least one gas exchange valve of a certain function per cylinder, wherein the valve lift is defined by a primary cam and a secondary cam (7, 8) and is selectively transmitted to the gas exchange valve by a switchable valve lever (10), wherein each primary arm (12) is in contact between the ends thereof with the primary cam (7) and each secondary arm (16) is in contact with an associated secondary cam (8) and is couplable to the primary arm (12) by a coupling element (15), wherein the coupling element (15) is a coupling pin guided in a transverse bore (14) of the primary arm (12) and is movable into a coupling bore (28) of the secondary arm (16) by a locking pin (22) supported in a transverse bore (21) of the secondary arm (16), and is displaceable back into the transverse bore (14) of the primary arm (12) by means of a release pin (25) which is guided in a coupling bore (28) of the secondary arm (16), wherein the locking pin and the release pin (22, 25) each project with their axially outer ends (23, 26) from the secondary arm (16) and are each coupled by means of a connecting element (29, 30) which is fixed on this end (23, 26) to a switching lever (35), which switching lever (35) is arranged parallel to the associated camshaft (6) and is longitudinally displaceable by means of a linear actuator (32) against the restoring force of a spring element (37) from a rest position (43) into a switching position (45).)

1. A variable valve train (1) of a piston internal combustion engine having at least one function-determining gas exchange valve per cylinder, wherein the valve lift of each function-determining gas exchange valve is defined by at least one primary cam (7) and a secondary cam (8) of a camshaft (6) and is transmitted selectively to at least the function-determining gas exchange valves by means of a switchable valve plunger (10) having a primary arm (12) and a secondary arm (16), wherein each primary arm (12) is supported with one end on an associated support element (11) mounted on the housing side and with the other end on the valve stem of the associated function-determining gas exchange valve and is in contact with the associated primary cam (7) between the two ends thereof, wherein each secondary arm (16) is mounted so as to be pivotable on the primary arm (12), The coupling element (15) of each switchable valve lever (10) is designed as a coupling pin which is guided in an axially movable manner in a transverse bore (14) of the primary arm (12), wherein the coupling element (15) of each switchable valve lever (10) is designed as a coupling pin which is guided in an axially movable manner in the transverse bore (14) of the primary arm (12), wherein the coupling pin (15) can be moved into an opposite coupling bore (28) of the secondary arm (16) by means of a locking pin (22) which is mounted in an axially movable manner in a transverse bore (21) of the secondary arm (16), and wherein a release pin (25) which is guided in an axially movable manner in a coupling bore (28) of the secondary arm (16) can be moved back into the transverse bore (14) of the primary arm (12), characterized in that the locking pin (22) and the release pin (25) are each provided with their axially outer ends (23, respectively, 26) Extends from the secondary arm (16) and is each coupled to a switching lever (35) by means of a rod-shaped connecting element (29, 30) fastened to the end (23, 26), the switching lever (35) being arranged above the valve rod (10) parallel to the associated camshaft (6) and being displaceable longitudinally by means of a linear actuator (32) against the restoring force of a spring element (37) from a rest position (43) into a switching position (45).

2. Variable valve train according to claim 1, characterized in that the linear actuator (32) is configured as an electromagnet with an armature (34) guided axially movably in a coil body (33), wherein the armature (34) is in operative connection with the switching rod (35).

3. Variable valve train according to claim 1, characterized in that the linear actuator (32) is configured as a single-acting hydraulic or pneumatic adjusting cylinder with a piston guided axially movable within the cylinder, wherein the piston is operatively connected to the switching rod (35).

4. Variable valve train according to any of claims 1 to 3, characterized in that the switching lever (35) is configured as a flat bar which is arranged with one of its two wider outer sides (38) towards the coupling pin (15) of each switchable valve strut (10).

5. Variable valve train according to claim 4, characterized in that the switching lever (35) is manufactured as a stamped component made of steel sheet or light metal sheet.

6. Variable valve train according to one of claims 1 to 5, characterized in that the connecting elements (29, 30) of each switchable valve lever (10) are designed as leaf springs which are each largely rigidly fixed to the outer ends (23) of the associated locking pin (22) and of the associated unlocking pin (25) and each engage in a slot-shaped opening (39, 40) in the switching lever (35).

7. Variable valve train according to claim 6, characterized in that the leaf springs (29, 30) are fixed in the manner of a guard disc by plugging and engaging, respectively, holes open on the end sides into annular grooves arranged on the axially outer ends (23, 26) of the respective locking pin (22) or the respective unlocking pin (25), which annular grooves are arranged on the respective locking pin (22) or the respective unlocking pin (25).

8. Variable valve train according to claim 6 or 7, characterized in that the axial distance (A) of the openings (39, 40) in the switching lever (35) corresponds to the axial distance between the respective locking pin (22) and the annular groove in the associated unlocking pin (25) when the respective locking pin and the associated unlocking pin rest on the coupling pin (15), and in that the transverse and longitudinal dimensions of the openings (39, 40) in the switching lever (35) are greater than the width and thickness of the leaf springs (29, 30).

9. Variable valve train according to claim 8, characterized in that the switching lever (35) is provided on its wider outer side (38) facing away from each valve strut (10) with an arcuate spring clip (41) on the switching direction side at least on each opening (39) for the leaf spring (29) associated with each locking pin (22), the free end of which spring clip projects in the longitudinal direction into the opening (39) concerned for the elastic support of the associated leaf spring (29).

10. Variable valve train according to any of claims 1 to 9, characterized in that the switching lever (35) is guided axially movably in a plurality of guide openings (42) of the cylinder head (2) which are fixed relative to the housing, and in that at least some of the guide openings (42) for the switching lever (35) are arranged in a bearing cap (5) of the associated camshaft (6).

Technical Field

The invention relates to a variable valve train of a piston internal combustion engine, comprising at least one functional gas exchange valve per cylinder, wherein the valve lift of each functional gas exchange valve is defined by at least one primary cam and a secondary cam of a camshaft, and the valve lift is selectively transmitted to at least the functional gas exchange valve by a switchable valve lever having a primary arm and a secondary arm, wherein each primary arm is supported with one end on an associated support element, which is mounted on the housing side, and with the other end on a valve stem of the associated functional gas exchange valve, and is in contact with the associated primary cam between the two ends, wherein each secondary arm is mounted on the primary arm in a pivotable manner, is in contact with the associated secondary cam, and is couplable to the primary arm by a coupling element adjustable by an adjusting device, the coupling element of each switchable valve lever is designed as a coupling pin which is guided axially movably in the transverse bore of the primary arm and which can be moved into the opposite coupling bore of the secondary arm by means of a locking pin which is mounted axially movably in the transverse bore of the secondary arm and can be moved back into the transverse bore of the primary arm by means of an unlocking pin which is guided axially movably in the coupling bore of the secondary arm.

Background

Switchable valve trains of piston internal combustion engines are known in different designs. The valve drive of the individual cylinders or cylinder groups of the reciprocating internal combustion engine is therefore deactivated by closing the transferable valve lift, and thus the fuel consumption and CO of the reciprocating internal combustion engine are reduced in the partial load operation in combination with the closing of the fuel injection for the cylinder concerned₂Emission and harmful substance emission. On the other hand, the lift time profile that can be transmitted by the valve drive of the intake and/or exhaust valves of the reciprocating internal combustion engine can be varied by means of lift switching and therefore operating parameters that depend on, for example, the engine speed and the engine load are adapted to the current operating state of the reciprocating internal combustion engine, as a result of which the engine output and torque can be increased and the specific fuel consumption of the reciprocating internal combustion engine can be reduced.

In the case of closable valve trains, two components of the switchable lift transmission element, which are movable or rotatable relative to one another, are usually provided in each case, one of which is connected to an associated cam adjustment of the camshaft and the other is connected to a valve stem adjustment of an associated gas exchange valve. The two components are couplable or uncouplable to each other by means of a coupling element, which is usually embodied as a coupling pin. In the coupled state, the valve lift of the associated cam is transmitted to the relevant gas exchange valve, and in the decoupled state, it is not transmitted, so that the gas exchange valve remains closed. The coupling pin is usually guided axially movably in a rotary bore of one component and is movable in a coupling bore of the other component. The coupling pin is held in the rest position by the spring element and is moved into the actuating position by an adjusting force applied against a restoring force of the spring element and is held fixed there. In the case of closable valve trains, the rest position of the coupling pin generally corresponds to the coupled state of the components of the lift transmission element, and the actuating position generally corresponds to the decoupled state of the components. The closable lift transmission element may be a closable cup tappet, a roller tappet, a rocker, a valve rod or a support element.

In the case of switchable valve trains, at least two components of the switchable lift transmission element which can be displaced or rotated relative to one another are provided, one component being coupled to an associated primary cam of a camshaft with a certain valve lift and to a valve stem of an associated gas exchange valve, and the other component being connected to an associated secondary cam of a camshaft with a greater valve lift or with an additional lift. The two components are couplable or uncouplable to each other by means of a coupling element, which is usually configured as a coupling pin. In the disengaged state, the valve lift of the primary cam is transmitted to the gas exchange valve concerned, and in the coupled state, the greater valve lift of the primary cam or the secondary cam is transmitted to the gas exchange valve. The coupling pin is usually guided axially movably in a bore of one component and is movable in a coupling bore of the other component. The coupling pin is held in the rest position by the spring element and is moved into the actuating position and remains fixed there by an adjusting force which is applied against the restoring force of the spring element. In the case of switchable valve trains, the rest position of the coupling pin usually corresponds to the decoupled state of the lift transmission element and the actuating position usually corresponds to the coupled state of the component. The switchable lift transmission element is usually a switchable cup tappet, rocker or valve rod.

The adjustment of the coupling element of the switchable lift transmission element is usually carried out hydraulically, by alternately connecting a switching pressure line to a pressure chamber of the coupling element, for example by means of an electromagnetic switching valve, to an oil pressure source or switching to pressureless. DE 102006057894 a1 discloses a known embodiment of a switchable valve push rod provided with a hydraulically adjustable coupling pin, which is provided in a piston engine for closing the lift of a gas exchange valve. DE 102006023772 a1, on the other hand, describes a switchable valve lever with a hydraulically adjustable coupling pin, which valve lever in a reciprocating piston engine is provided for the lift change of a gas exchange valve.

If the gas exchange valves of the piston internal combustion engine are to be selectively closed or shifted in groups, separate switching pressure lines each with an associated switching valve are required in the case of the hydraulic control of the coupling element. DE 10212327 a1 describes a corresponding hydraulic actuating device for selectively actuating coupling elements of a variable valve train in groups in the case of a piston internal combustion engine with two intake valves and two exhaust valves per cylinder. In this case, the switchable lift transmission element of the valve train is designed as a switchable cup tappet.

However, the adjustment of the coupling elements of the switchable lift transmission element can also be performed electromagnetically, by interacting the coupling elements with the electromagnets, respectively, and switching the electromagnets alternately on and off. A known embodiment of a switchable valve push rod provided with an electromagnetically adjustable coupling pin, which is provided for lift closing of gas exchange valves in piston internal combustion engines, can be derived from US 5544626 a. The coupling pin and the electromagnet (the armature of which is connected to the coupling pin) are arranged in a longitudinally oriented manner in the primary housing of the valve rod, as a result of which a greater structural length of the valve rod and a correspondingly greater width of the cylinder head concerned are obtained.

A variable valve gear mechanism with a series of gas exchange valves is available from JP 2004-108252A. A set of two gas exchange valves is associated with each switchable pivot arm, which has a coupling device running parallel to the camshaft in the primary arm. For loading the coupling devices in the coupling direction, a central switching tube with rigid arms thereon is provided, wherein the shanks are in each case in external contact with a corresponding coupling device on the primary arm.

See DE 10137490 a1 as the closest prior art. It shows a variable valve train for lift switching with switchable valve struts, each consisting of a central primary arm, the shanks of the secondary arms being arranged on both sides of the primary arm. In the transverse bore of the central primary arm, a continuous coupling pin is illustrated, which can be acted upon on one end face by a locking pin and on the other end face by an unlocking pin, which each rest on one of the shanks of the secondary arm. A hydraulic device is provided for the adjustment/displacement of the coupling pin in the direction of the coupling hole, which hydraulic device is guidable by means of a support element in front of the outer end of the locking pin. The return of the coupling pin is effected by the force of a compression spring which is placed in front of the outer end side of the unlocking pin.

It has been established that the arrangement of separate hydraulic or electric switching pressure lines in the cylinder head of a reciprocating internal combustion engine is relatively difficult and expensive due to the limited position conditions.

Disclosure of Invention

The object of the invention is to provide a variable valve train with a quick and reliable operating adjusting device which is simple to construct and requires only a small installation space.

This object is achieved according to the invention in that the locking pin and the unlocking pin each project with their axially outer ends from the secondary arm and are each coupled via a rod-shaped connecting element fixed on this end to a switching lever which is arranged above the valve rod parallel to the associated camshaft and which is longitudinally displaceable from a rest position into a switching position by means of a linear actuator against the restoring force of a spring element.

The actuating device according to the invention therefore has only one single actuator, by means of which the switchable valve lever in question can be changed from a rest position, in which the respective secondary arm is decoupled from the associated primary arm, into a switching position, in which the secondary arm is coupled to the primary arm.

The linear actuator can be arranged and fixed on the cylinder head in a suitable position in the longitudinal direction of the shift lever, in which position the required installation space is available and the energy supply required for the actuation can be advantageously achieved. The actuating device according to the invention, which is switchable purely mechanically, is significantly simpler to construct and more space-saving and can be produced more inexpensively than actuating devices with separate hydraulic or electromagnetic actuators, which can be arranged inside or outside a switchable valve rod. A plurality of such adjusting devices can also be arranged on the cylinder head of the piston engine, so that groups of functionally identical gas exchange valves, for example inlet valves and/or exhaust valves, of all cylinders or only certain cylinders can be selectively changed over, or in the case of a four-valve cylinder head, first and/or second inlet valves and/or exhaust valves can be selectively switched over.

The linear actuator is preferably designed as an electromagnet with an armature guided axially movably in the coil body, wherein the armature is mechanically operatively connected to the shift rod. For the actuation and energy supply of the linear actuator, only a two-wire cable leading from the electronic control device to the coil of the electromagnet is required.

The linear actuator may also be designed as a single-acting hydraulic or pneumatic actuating cylinder with a piston guided axially movably in the cylinder, wherein the piston is mechanically operatively connected to the shift rod. For the actuation and energy supply of the linear actuator, in this embodiment a control pressure line connected to the pressure chamber of the control cylinder is required, which can be selectively connected to a pressure supply line connected to a pressure medium source, or to a pressure-free return line or an exhaust line, for example, by means of a 2-to-3 solenoid valve connected to an electronic control unit.

The switching lever is preferably designed as a flat bar, which is arranged with the one of the two wider outer sides facing the connecting pin of the switchable valve slide. By means of the wide outer side and the outer side orientation, the switching lever has sufficient structural space for the mechanical coupling of the rod-shaped connecting element of the switchable valve push rod. Furthermore, it is possible to simply and inexpensively produce the switching lever as a stamped component made of a steel or light metal sheet.

The connecting element of the switchable valve pressure lever is preferably designed as a leaf spring, which is in each case largely rigidly fixed to the outer end of the associated locking or unlocking pin and in each case engages in a slot-shaped opening in the switching lever. At any time and independently of the current rotational position of the associated camshaft, a change of the valve actuating lever can therefore be initiated for coupling the respective secondary arm to the associated primary arm and for decoupling the secondary arm from the primary arm by an axial displacement of the shift lever.

The change of the valve plunger is immediately effected in that the secondary cam of the valve plunger is just touched by the secondary arm on the base radius. The leaf spring concerned is initially preloaded in or against the switching direction in such a valve slide that its primary cam and secondary cam are just touching outside the base radius. When the associated cam is touched on the base radius as a result of a corresponding rotation of the camshaft, the valve rod concerned is shifted.

In order to ensure simple assembly, it is preferably provided that the leaf spring is fixed in the manner of a protective disk in an annular groove on the locking or unlocking pin by being plugged into and engaging in a bore which is open at the end, the annular groove being arranged on the outer end of the respective locking or unlocking pin.

In order to generate the desired actuating force by a corresponding pretensioning of the leaf spring, the axial distance of the opening in the shift lever preferably corresponds to the axial distance between the respective locking pin and the associated unlocking pin, when they rest on the coupling pin, and the annular groove in the respective locking pin and the associated unlocking pin.

To compensate for the rocking motion of the valve stem and manufacturing tolerances, the transverse and longitudinal dimensions of the opening in the shift lever are preferably greater than the width and thickness of the leaf spring. The leaf spring can thus move without friction in the opening of the switching lever when the reciprocating internal combustion engine is in operation. In this way, manufacturing tolerances in the arrangement of the opening in the switching lever and manufacturing tolerances of the entire switching lever can be compensated in a simple manner by an increased adjustment travel of the linear actuator. The adjusting device according to the invention therefore places relatively low demands on the precision in the production and arrangement of the components and is therefore particularly inexpensive to produce.

The switching lever is preferably provided on its wider outer side facing away from the valve stem, at least on each opening for the associated leaf spring with the locking pin, on the switching direction side, with an arcuate spring clip, the free end of which projects in the longitudinal direction into the opening concerned for the resilient support of the associated leaf spring. In this way, the leaf spring is supported in the opening of the switching lever in a resilient and longitudinally displaceable manner, so that mechanical wear on the contact surface is reduced and the transmission of transverse forces to the locking pin of the valve pressure lever is avoided.

In order to prevent the switching rod from moving outwards or bending under load, the switching rod is preferably guided axially movably in a plurality of guide openings of the cylinder head which are fixed relative to the housing. At least some of the guide openings of the switching lever are preferably arranged in the bearing cap of the associated camshaft, whereby the production of the guide openings is significantly simplified compared to an arrangement in a web of the cylinder head that is fixed relative to the housing.

Drawings

The accompanying drawings are included to provide a further explanation of the invention. Wherein:

fig. 1 shows a preferred embodiment of a valve drive of a reciprocating internal combustion engine according to the invention in a diagrammatic perspective view with three cylinders and four gas exchange valves per cylinder, and with three switchable valve struts in the non-switched state,

fig. 1a shows a segment of the valve drive according to fig. 1, with a side view of the switching lever in the non-switched state,

fig. 1b shows a section of the valve train according to fig. 1, with a longitudinal view of the switchable valve train lever in the non-shifted state,

fig. 1c shows a section of the valve train according to fig. 1, with a transverse view of the switchable valve train lever in the non-shifted state,

fig. 1d shows a section of the valve drive according to fig. 1, with a longitudinal section through the switchable valve train lever in the non-shifted state,

fig. 2 shows a perspective view of a valve train of the internal combustion piston engine according to the invention according to fig. 1, with three switchable valve struts in the non-switched state,

fig. 2a shows a segment of the valve drive according to fig. 2, with a side view of the switching lever in the switched state,

fig. 2b shows a section of the valve train according to fig. 2, with a longitudinal view of the switchable valve train lever in the switched state,

fig. 2c shows a section of the valve train according to fig. 2, with a transverse view of the switchable valve train lever in the switched state,

fig. 2d shows a segment of the valve train according to fig. 2, with a longitudinal section through the switchable valve push rod in the switched state,

fig. 3a shows a side view of a switchable valve lever of the valve train according to fig. 1 to 2d, and

fig. 3b shows a perspective oblique view of a switchable valve train of the valve train according to fig. 1 to 2 d.

Detailed Description

In the diagrammatic perspective view of fig. 1, a valve train 1 of a piston internal combustion engine is partially depicted to the extent required for explaining the invention, with three cylinders arranged in a row and two inlet valves and two exhaust valves per cylinder. The camshaft carrier 2 of the two-part cylinder head of the piston internal combustion engine has four semicircular first plain bearing sections 3 for supporting an intake camshaft, not illustrated, and four semicircular second plain bearing sections 4 for supporting an exhaust camshaft 6. The remaining plain bearing sections for mounting the intake camshaft and the exhaust camshaft 6 are each part of a bearing cap 5, which is placed on the camshaft carrier 2 after the installation of the camshaft and is screwed thereto. Only the bearing cap 5 of the exhaust camshaft 6 is depicted in fig. 1.

The non-depicted first exhaust valve of each cylinder is switchable by the associated switchable valve pressure lever 10 in respect of the transferable lift history of the first exhaust valve, while the likewise non-depicted second exhaust valve of each cylinder has a constant lift transference by the associated non-switchable valve pressure lever. For this purpose, the exhaust camshaft 6 has a centrally arranged primary cam 7 and secondary cams 8 arranged on both sides of the primary cam 7 for the first exhaust valve. For the second exhaust valves, the exhaust camshaft 6 then has in each case only one single cam 9.

Non-switchable valve struts, not shown, are each supported on their lower end side on a support element, which is mounted on the housing side and has an integrated hydraulic valve play compensation element, and on the valve strut of the associated second exhaust valve, in an opposing manner, and are each in contact with the associated cam 9 on their upper side. When the exhaust camshaft 6 rotates, the lift history of the cam 9 concerned is therefore transmitted to the second exhaust valve via the non-switchable valve rod.

As can be seen in the fragmentary side view of fig. 1a, the longitudinal cross-sectional view, the transverse cross-sectional view and the longitudinal cross-sectional view of fig. 1b to 1d, and as can be seen in the side view of fig. 3a and the perspective oblique view of fig. 3b, the switchable gas strut 10 has a primary arm 12 and a secondary arm 16, respectively. The primary arm 12 is largely frame-shaped and is supported on its underside at the end on a support element 11, which is mounted on the housing side and has an integrated hydraulic valve play compensation element, and is supported opposite the valve stem of the associated first exhaust valve. The primary arm 12 is in contact with the associated primary cam 7 on its upper side by way of a contact element 13, which is in this case designed as a rotatably mounted roller. The secondary arm 16 has a frame-shaped configuration surrounding the primary arm 12, and is pivotably supported on the primary arm 12 by a hinge pin 17 arranged on the valve side. The secondary arm 16 has widened web sections as contact elements 19 on both sides, each with an outer sliding surface 20a, 20b, which comes into contact with the cam regions of the two secondary cams 8. Outside this cam region, i.e. in the base circle region of the secondary cam 8, the secondary arm 16 does not come into contact with the secondary cam 8. In this base circle region of the secondary cam 8, the end of the secondary arm 6 remote from the pivot axis is pressed against a stop on the primary arm 12 by the spring force of a compression spring 18, which is designed as a torsion spring.

As a coupling element for the form-locking connection of the secondary arm 16 to the primary arm 12, a coupling pin 15 is provided which is guided axially movably in the transverse bore 14 of the primary arm 12. The coupling pin 15 can be moved into an opposite coupling hole 28 in the secondary arm 16 by means of a locking pin 22 which is mounted axially movably in a transverse hole 21 in the secondary arm 16. In the locked position of the locking pin 22, the locking pin thus locks the primary arm 12 and the secondary arm 16 together with the coupling pin 15. Furthermore, the coupling pin 15 can be moved back into the transverse bore 14 of the primary arm 12 by means of a release pin 25 which is guided axially movably in the coupling bore 28 of the secondary arm 16.

The locking bolt 22 projects with its outer end 23 axially from the secondary arm 16 and is connected to the secondary arm via an upwardly directed rod-shaped connecting element 29 in an adjusting manner to a switching lever 35 of an adjusting device 31. In the same way, the unlocking pin 25 projects with its outer end 26 from the secondary arm 16 and is connected adjustably on the secondary arm to a switching lever 35 of an adjusting device 31 by means of an upwardly directed rod-shaped connecting element 30.

The connecting elements 29, 30 of the switchable valve push rod 10 are in this case designed as leaf springs and are fixed in a not completely visible manner in the manner of a guard disk in an annular groove on the locking or unlocking bolt 22, 25, which is arranged on the outer ends 23, 26 of the respective locking or unlocking bolt 22, 25, by insertion and engagement with a bore which is open at the end.

The switching lever 35 of the actuating device 31 is arranged above the valve rod 10 parallel to the exhaust camshaft 6 and is longitudinally displaceable by the linear actuator 32 against the restoring force of the spring element 37 from a rest position 43 into a switching position 45 (compare fig. 1 and 2). As can be seen from the sectional side view in fig. 1a, the spring element 37 is designed as a helical spring, which is arranged between the bent tongue-shaped end 36 of the switching lever 35 and the adjacent end wall of the camshaft carrier 2. In this case, the switching rod 35 is not rigidly connected to the armature 34, but the switching rod 35 is pressed axially against the armature 34 by a spring element 37. This has the advantage that the armature 34 or the linear actuator 32 can be arranged at a location where there is structural space. The switching rod 35 and the armature 35 therefore do not have to be arranged coaxially with one another, but rather only largely axially parallel. The transmission of force from the armature 34 to the switching rod 35 is effected here by a bent tongue-shaped end 36 of the switching rod 35. The linear actuator 32 is designed, for example, as an electromagnet with an armature 34 guided axially in a coil body 33, the armature 34 of the electromagnet being mechanically operatively connected to an adjusting rod 35 as described.

The switching lever 35 is designed here as a flat bar which is arranged with one of the two wider outer sides 38 facing the connecting pin 15 of the switchable valve slide 10 and is preferably produced as a stamping from a steel or light metal sheet. The switching lever 35 is arranged axially movably in a plurality of guide openings 42 of the camshaft carrier 2 fixed relative to the housing, which are formed in the bearing cap 5 of the exhaust camshaft 6.

The connecting elements 29, 30 of the switchable valve train 10, which are designed as leaf springs, engage with play in slot-shaped openings 39, 40 of the switching lever 35, respectively, the axial distance a of the openings in the switching lever 35 corresponding to the distance of the fastening of the leaf springs 29, 30 on the locking pin 22 and the unlocking pin 25 when the locking pin 22 and the unlocking pin 25 rest on the coupling pin 15. The slot-shaped openings 39, 40 have transverse and longitudinal dimensions greater than the width and thickness of the leaf springs 29, 30. In this way, the leaf springs 29, 30 move without wear in the openings 39, 40 of the switching lever 35 during operation of the reciprocating piston engine. Furthermore, manufacturing tolerances in the formation of the openings 39, 40 in the switching lever 35 and manufacturing tolerances of the entire switching lever 35 can thereby be compensated in a simple manner by an increased adjustment travel of the linear actuator 32.

On the wider outer wall 38 of the switching lever facing away from the valve support lever 10, the switching lever 35 is provided on each opening 39 of the leaf spring 29 for the locking pin 22 on the switching direction side with an arcuate spring clip 41, the free end of which projects in the longitudinal direction into the opening 39 concerned for the elastic support of the associated leaf spring 29. In this way, the leaf spring 29 is supported in the opening 39 of the shift lever 35 in a resilient and longitudinally displaceable manner, so that mechanical wear on the contact surfaces is reduced and the transmission of transverse forces to the latching pin 22 of the switchable valve push rod 10 is avoided.

The switching lever 35 of the actuating device 31 is depicted in fig. 1 and 1a in its rest position 43, in which the secondary arm 16 of the switchable valve train 10 is disengaged from the primary arm 12. This is also visible in the longitudinal view of the disengaged switching state of the switchable valve push rod 10 illustrated in fig. 1b, in which the coupling pin 15 is completely inside the transverse bore 14 of the primary arm 12, as can be seen particularly well in the cross-sectional view of fig. 1 c. In the disengaged state of the primary arm 12 and the secondary arm 16, when the exhaust camshaft 6 is rotated, only the lift path of the primary cam 7 concerned is transmitted to the associated first exhaust valve via the primary arm 12 of the switchable valve strut 10. The lift path of the secondary cam 8 concerned is then only responsible for the resilient compression of the secondary arm 16 relative to the secondary arm 12. This is particularly well visible in the longitudinal sectional view of fig. 1d, in which the primary cam 7 of the exhaust camshaft 6 is just touched by the roller 13 of the primary arm 12 on the base radius, and the secondary cam 8 of the exhaust camshaft 6 is just touched by the sliding surfaces 20a, 20b of the web section 19 of the secondary arm 16 in the region of the additional lift cams.

The switching lever 35 of the adjusting device 31 is depicted in the perspective overview illustration of fig. 2 and in the fragmentary side view of fig. 2a, in its switching position 45, in which it is moved in a switching direction given by the directional arrow 44 by the actuation of the linear actuator 32. In the switching position 45 of the switching lever 35, the coupling pin 15 of the lower valve plunger 10, whose secondary cam 8 is just touched on the base radius, is immediately displaced into the associated coupling hole 28 of the secondary arm 16 by means of the respective leaf spring 29 and the locking pin 22 concerned, since the transverse hole 21 and the coupling hole 28 of the secondary arm 16 are aligned with the transverse hole 14 of the primary arm 12. The secondary arm 16 of the valve plunger 10 concerned is then coupled to the associated primary arm 12.

For a valve actuating lever 10 whose primary cam 7 and secondary cam 8 are just touched by the roller 13 of the primary arm 12 or the sliding surface 20 of the web section 19 of the secondary arm 16 outside the base radius, only an axial pretensioning of the locking bolt 22 in the direction of the coupling bolt 15 is initially achieved by the leaf spring 29. Then, when the primary cam 7 and the secondary cam 8 associated with the respective connecting pin 15 are touched on the base radius, the respective connecting pin 15 is moved into the connecting hole 28 of the secondary arm 16 by means of the respective leaf spring 29 and the locking pin 22.

This is also visible in the coupled switching state of the switchable valve train 10 illustrated in the longitudinal view in fig. 2b, in which the coupling pin 15 is partially located in the coupling bore 28 of the secondary arm 16, which is particularly well visible in the cross-sectional view in fig. 2 c. In the coupled state of the primary arm 12 and the secondary arm 16, during a rotation of the exhaust camshaft 6, the respectively higher lift path of the respective primary cam 7 or of the respective secondary cam 8 is transmitted to the associated exhaust valve via the primary arm 12 of the switchable valve plunger 10 or via the secondary arm 16 and the primary arm 12, respectively. This is particularly well visible in the longitudinal sectional view of fig. 2d, in which the primary cam 7 of the exhaust camshaft 6 is touched by the roller 13 of the primary arm 12 exactly on the base radius and the secondary cam 8 of the exhaust camshaft 6 is touched by the sliding surfaces 20a, 20b of the web section 19 of the secondary arm 16 exactly in the region of the additional lift cams.

By opening and closing the linear actuator 32, the switching lever 35 of the actuating device 31 is moved back into the rest position 43 of the switching lever against the switching direction indicated by the directional arrow 44 under the influence of the tensioned helical spring 37. The leaf spring 30 of the unlocking pin 25 is thereby tensioned, so that the leaf spring axially loads the unlocking pin 25 against the switching direction 44. As a result, the coupling pin 15 of the valve plunger 10 (whose primary cam 7 and secondary cam 8 are just touched by the roller 13 of the primary arm 12 and the sliding surfaces 20a, 20b of the web section 19 of the secondary arm 16 on the base radius) is immediately moved back into the associated transverse bore 14 of the primary arm 12 by the respective leaf spring 30 and the associated unlocking pin 25, since the coupling pin 15, the locking pin 22 and the unlocking pin 25 are not subjected to transverse forces. The secondary arm 16 of the valve plunger 10 concerned is thus decoupled from the associated primary arm 12.

For the valve plunger 10, whose primary cam 7 and secondary cam 8 are touched by the roller 13 of the primary arm 12 and the sliding surface 20 of the web section 19 of the secondary arm 16 just outside the base radius, only an axial pretensioning of the unlocking pin 25 in the direction of the coupling pin 15 is initially achieved by the leaf spring 30. The respective leaf spring 30 and the unlocking pin 25 then move the respective coupling pin 15 into the transverse bore 14 of the primary arm 12, as long as the associated primary cam 7 and secondary cam 8 with the respective coupling pin are touched on the base radius.

The actuating device 31 according to the invention with a valve plunger 10 that can be switched purely mechanically is considerably simpler and more space-saving to construct and can be produced more inexpensively than actuating devices with separate hydraulic or electromagnetic actuators in or on the valve plunger.

List of reference numerals

1 valve drive mechanism

2 camshaft support

3 first plain bearing section

4 second plain bearing section

5 bearing cap

6 exhaust camshaft

7 primary cam

8 primary cam

9 cam

10 switchable valve pressure lever

11 support element

12 Primary arm

13 touching element, roller

14 transverse bore

15 coupling element, coupling pin

16 Secondary arm

17 hinge pin

18 hold-down spring, torsion spring

19 touch element, tab section

20a first sliding surface on the sub-arm

20b second sliding surface on the sub-arm

21 transverse hole

22 locking pin

23 outer end of the locking bolt

25 unlocking pin

26 end of the outer part of the release pin

28 connecting hole

29 first connecting element, leaf spring

30 second connecting element, leaf spring

31 adjustment device

32 linear actuators, electromagnets

33 coil body

34 armature

35 switching rod, flat bar

36 bent tongue-shaped end of switching lever

37 spring element, coil spring

38 wide outer side

39 opening

40 opening

41 spring clip

42 guide opening

43 rest position

44 directional arrow, switching direction

45 switching position

Axial distance A