Variable valve mechanism and reciprocating piston internal combustion engine

Abstract

The invention relates to a variable valve train and to a reciprocating-piston internal combustion engine. The variable valve train comprises a slide bar (3) and an actuation assembly for longitudinally actuating the slide bar (3). The slide bar (3) is movably supported in longitudinal direction at a component of the reciprocating-piston internal combustion engine, wherein by a longitudinal movement of the slide bar (3) a coupling element (53) of at least one switchable rocker arm (5) of the variable valve train can be actuated in axial direction, so that the switchable rocker arm (5) can provide different cam lifts. The actuation assembly comprises an electric motor (1) comprising an output shaft, a cam element (2) being mounted anti-rotationally at the output shaft and being abuttable against the slide bar (3), so that a rotational movement of the cam element (2) is converted into a longitudinal movement of the slide bar (3). The reciprocating-piston internal combustion engine comprises the above-mentioned variable valve train.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of vehicle technology. The present application particularly relates to a variable valve train for a reciprocating piston internal combustion engine and to a reciprocating piston internal combustion engine. BACKGROUND

[0002] Currently, it is possible to adjust the intake and / or exhaust of the cylinders of a reciprocating piston internal combustion engine depending on the driving mode of the vehicle by means of variable valve technology, in order to optimize the fuel efficiency of the internal combustion engine and to reduce the emission of carbon dioxide and harmful substances in particular.

[0003] It is known in a variable valve solution for a reciprocating piston internal combustion engine to equip each cylinder of the internal combustion engine with at least one intake valve, the valve stroke of which is determined by a cam of a camshaft and a switchable rocker arm cooperating with the cam, respectively. Such a variable valve train is disclosed, for example, in German patent document DE 102017101792 B4 and in Chinese patent application document CN 110439646 A, wherein the switchable rocker arm has a main arm and a secondary arm which is pivotably supported on the main arm, wherein a coupling and decoupling of the main arm and the secondary arm can be achieved by moving a coupling element in the axial direction of the camshaft. In the different states of coupling and decoupling, the switchable rocker arm provides different valve strokes to the valve stem of the assigned intake valve, respectively, in order to achieve a variable valve stroke of the variable valve train. The axial actuation of the coupling element is achieved by means of a slide bar which is operated by a linear actuator. In this case, the linear actuator can be configured as a hydraulic or pneumatic adjustment cylinder or as an electromagnetic actuator.

[0004] However, in the above-mentioned solution of the hydraulic or pneumatic adjustment cylinder, a corresponding pressure medium duct has to be provided for the adjustment cylinder, whereby the overall structure of the variable valve train is relatively complex. In the current solution of driving the slide bar by means of an electric actuator, a stable input current has to be provided to the electric actuator, for which a current closed-loop channel has to be provided for the motor control unit of the electric actuator, but the current closed-loop channel is not available for the variable valve train due to the lack of additional resources of the current prevailing motor control units. SUMMARY

[0005] It is therefore an object of the present application to provide a variable valve train for a reciprocating piston internal combustion engine, which has a simplified design in particular with regard to the actuation of the coupling element of the switchable rocker arm.

[0006] The object is achieved by a variable valve train for a reciprocating piston internal combustion engine. The variable valve train comprises a slide bar and an actuation assembly for actuating the slide bar in the longitudinal direction, the slide bar being movably supported in the longitudinal direction at a component of the reciprocating piston internal combustion engine, wherein by the longitudinal movement of the slide bar a coupling element of at least one switchable rocker arm of the variable valve train can be actuated in the axial direction, so that the switchable rocker arm can provide different cam lifts. According to the solution of the application, the actuation assembly comprises an electric motor and a cam element, wherein the electric motor has an output shaft, the cam element is mounted anti-rotationally at the output shaft of the electric motor and can act against the slide bar, so that a rotational movement of the cam element can be converted into a longitudinal movement of the slide bar.

[0007] Preferably, the variable valve train comprises a set of switchable rocker arms, the switchable rocker arms preferably being distributed in the axial direction of a camshaft for the reciprocating piston internal combustion engine. The switchable rocker arms can each provide a valve stroke to a respective gas exchange valve in cooperation with a cam at the camshaft. Here, the switchable rocker arms have a main arm and a secondary arm which is pivotably supported at the main arm, wherein by moving the coupling element, preferably in the axial direction of the camshaft, a coupling and decoupling, i.e. a locking and unlocking, of the main arm and the secondary arm can be achieved. In the different states of coupling and decoupling, the switchable rocker arms can provide different valve strokes to the valve stems of the assigned gas exchange valves in cooperation with the camshaft, so that a variable valve stroke of the variable valve train is achieved.

[0008] Preferably, the actuation of the coupling elements of the individual switchable rocker arms is achieved here by means of a common slide bar. That is, a longitudinal movement of the slide bar can here simultaneously actuate the coupling elements of a plurality of switchable rocker arms. In this case, the slide bar is arranged in particular parallel to the camshaft on the cylinder head and is longitudinally slidable relative to the cylinder head. When the slide bar is moved in its longitudinal direction, a coupling and decoupling between the main arm and the secondary arm of the switchable rocker arms can be achieved, thereby providing different valve strokes for the valve stems.

[0009] In the context of this document, "axial direction" means the axial direction of the camshaft and "longitudinal direction" means the longitudinal direction of the slide bar, unless stated otherwise. Here, the longitudinal direction of the slide bar is the axial direction of the camshaft.

[0010] The actuation assembly for actuating the slide bar in the longitudinal direction comprises an electric motor and a cam element. The electric motor is preferably supported at the cylinder head of the reciprocating piston internal combustion engine. The electric motor has an output shaft for outputting a rotational movement. Here, the electric motor is arranged such that the output shaft of the electric motor is inclined, preferably perpendicular, to the longitudinal direction of the slide bar. The cam element can be mounted directly or indirectly at the output shaft of the electric motor and can act directly or indirectly on the slide bar, preferably directly against the longitudinal end of the slide bar, from the rotational movement of the cam element achieved by means of the electric motor a longitudinal movement of the slide bar can be converted.

[0011] In this case, the slide rod can be actuated in the longitudinal direction by driving the cam element in rotation by means of the electric motor. When the slide rod is moved in its longitudinal direction, it can actuate the coupling element in the axial direction directly or indirectly, for example by means of a leaf spring, so that a switchable rocker lever can be switched between the coupled state and the decoupled state, in particular to implement the coupling. Here, a reverse switching of the switchable rocker lever between the coupled state and the decoupled state, in particular the decoupling, can be implemented by means of a reset element, for example a spring element, integrated in the switchable rocker lever. The actuation assembly for the slide rod can thus be constructed simply. On the one hand, the control unit of the electric motor does not need to be provided with a channel for a current loop, simplifying the control unit. On the other hand, the slide rod and its actuation assembly have a simple structure, high mechanical reliability and are easy to arrange in a variable valve train.

[0012] In a preferred embodiment, the electric motor is integrated with a rotation angle sensor, and the rotational movement of the cam element is controlled by means of the rotation angle information of the rotation angle sensor. In particular in the control of the electric motor, the rotation angle feedback function provided by the electric motor itself can thus be fully utilized. Here, no additional sensor needs to be provided for obtaining displacement information of the slide rod, and the variable valve train can be implemented simply and at low cost.

[0013] In a preferred embodiment, the output shaft of the electric motor is arranged perpendicular to the longitudinal direction of the slide rod, so that the rotational movement provided by the electric motor can be converted into the longitudinal movement of the slide rod with a compact structure and high transmission efficiency.

[0014] In a preferred embodiment, the cam element is sleeved on the output shaft of the electric motor by means of an interference fit. In this case, no additional intermediate connecting member needs to be provided, and the variable valve train can be constructed compactly and simply.

[0015] In a preferred embodiment, the cam element comprises an actuation profile section, which provides a cam profile matching the longitudinal stroke of the slide rod. When the cam element abuts against the end of the slide rod with its actuation profile section, the rotational movement of the cam element can be converted into the longitudinal movement required by the slide rod.

[0016] Here, it is particularly preferred that the cam element comprises a holding profile section adjacent to the actuation profile section, which provides a cam profile such that the slide rod maintains its longitudinal position. When the cam element abuts against the end of the slide rod with its holding profile section, the rotational movement of the cam element is not converted into the longitudinal movement of the slide rod, so that the slide rod is prevented from moving beyond its predetermined longitudinal stroke in the case of excessive rotation of the cam element.

[0017] In a preferred embodiment, the region of the cam element for contacting the slide rod is provided with an anti-wear coating, so that the wear of the cam element can be reduced, thereby increasing the service life of the cam element.

[0018] In a preferred embodiment, the slide bar comprises a cam element contact for abutment against the cam element, the cam element contact being configured as a planar section extending parallel to the longitudinal extension of the slide bar. The slide bar is preferably made of sheet metal. In this case, the cam element contact can be configured simply by bending.

[0019] In a preferred embodiment, a leaf spring is fixed to the slide bar, the leaf spring being able to abut against the coupling element of the switchable rocker lever.

[0020] The object of the application can also be achieved by means of a reciprocating piston internal combustion engine comprising a variable valve train configured according to the embodiments described above.

[0021] By means of the solutions provided herein, an actuation assembly for a slide bar can be configured simply. On the one hand, there is no need to provide a control unit for the electric motor with a channel for a current closed loop, simplifying the control unit. On the other hand, the slide bar and its actuation assembly have a simple structure, high mechanical reliability and are easy to arrange in a variable valve train. In particular, it is possible to provide a rotation angle feedback by means of a sensor integrated in the electric motor, in order to control the rotational movement of the cam element or in other words the operation of the electric motor, whereby an optimal implementation, in particular with regard to the control of the electric motor, is possible. BRIEF DESCRIPTION OF DRAWINGS

[0022] Preferred embodiments of the application are schematically illustrated in the following description in conjunction with the attached drawings. The drawings are:

[0023] Figure 1 is a schematic perspective view of a variable valve train according to a preferred embodiment,

[0024] Figure 2 is a partial enlarged view of Figure 1 ,

[0025] Figure 3 is a schematic front view of a cam element of a variable valve train according to Figure 1 ,

[0026] Figure 4 is a schematic partial view of a variable valve train according to Figure 1 in its decoupled state of its switchable rocker lever, and

[0027] Figure 5 is a schematic partial view of a variable valve train according to Figure 1 in its coupled state of its switchable rocker lever. DETAILED DESCRIPTION

[0028] Figure 1A schematic perspective view of a variable valve train according to a preferred embodiment is shown. The variable valve train according to the present embodiment can be used in a reciprocating piston internal combustion engine having four cylinders. Here, each cylinder has two intake and exhaust valves, respectively. The valve stems (not shown) of each valve are each equipped with a corresponding switchable rocker arm 5. The eight switchable rocker arms 5 of the variable valve train are here distributed along an axial direction of a camshaft (not shown) fixed to the cylinder head. Each switchable rocker arm 5 has a coupling element which can be coupled and decoupled by axial movement of the main arm and the secondary arm. The coupling element is here configured as a coupling pin.

[0029] Figure 2 is a partial enlargement of Figure 1 . In conjunction with Figure 1 and Figure 2 it can be seen that the axial movement of the coupling pin of each switchable rocker arm 5 is effected by means of a slide bar 3 which is moved longitudinally by means of an actuation assembly. The slide bar 3 is preferably made of sheet metal. The slide bar 3 is supported in longitudinal movement at the cylinder head of the reciprocating piston internal combustion engine. Here, the slide bar 3 is arranged such that its longitudinal direction is parallel to the axial direction of the camshaft. Fixed to the slide bar 3 is a leaf spring 4 which bears against the coupling pin of each switchable rocker arm 5, respectively, whereby the longitudinal movement of the slide bar 3 can be transmitted to the respective coupling pin by means of each leaf spring 4. For this purpose, each leaf spring 4 is preferably configured in a bent manner.

[0030] In particular as shown in Figure 2 , the actuation assembly for actuating the slide bar 3 in longitudinal direction comprises an electric motor 1 and a cam element 2. The electric motor 1 is supported at the cylinder head of the reciprocating piston internal combustion engine. The electric motor 1 has an output shaft for outputting a rotational movement. Here, the electric motor 1 is arranged such that its output shaft is perpendicular to the longitudinal direction of the slide bar 3. The cam element 2 is in the present embodiment mounted directly to the output shaft of the electric motor 1 by means of an interference fit.

[0031] Figure 3 A schematic front view of the cam element 2 is shown. In conjunction with Figures 1 to 3 it can be seen that the cam element 2 is configured at its outer circumference around its axis of rotation, i.e. the axis of rotation of the output shaft of the electric motor 2, with a profile contour for contacting the slide bar 3. Here, the profile contour of the cam element 2 comprises an actuation profile section 21 which is schematically shown by the line section AB and a holding profile section 22 which is schematically shown by the line section BC. The actuation profile section 21 and the holding profile section 22 are arranged adjacently. The actuation profile section 21 provides a cam profile which matches the longitudinal stroke of the slide bar 3. The holding profile section 22 provides a cam profile which causes the slide bar 3 to maintain its longitudinal position. In order to reduce wear of the cam element 2, an anti-wear coating is provided at the profile contour of the cam element 2, in particular at the actuation profile section 21 and the holding profile section 22.

[0032] To this end, the slide 3 is correspondingly configured at its longitudinal end with a cam member contact for abutting against the profile contour of the cam member 2. As Figure 1 and Figure 2 shown, the cam member contact is configured in the present embodiment as a plane section parallel to the longitudinal extension of the slide 3, for example, by bending. Here, when the cam member 2 abuts with its actuation profile section 21 against the cam member contact of the slide 3, the rotational movement of the cam member 2 can be converted into the required longitudinal movement of the slide 3. When the cam member 2 abuts with its holding profile section against the cam member contact of the slide 3, the rotational movement of the cam member 2 is not converted into a longitudinal movement of the slide 3, thereby preventing the slide 3 from moving beyond its predetermined longitudinal stroke in the event of an over-rotation of the cam member 2.

[0033] Figure 4 and Figure 5 show a schematic partial view of the variable valve train according to the present embodiment in its decoupled state and coupled state of the switchable rocker arm, respectively.

[0034] As Figure 4 shown, when the electric motor 1 is not energized or, respectively, not in operation, the switchable rocker arm 5 of the variable valve train is in the decoupled state. Here, the inner arm 52 acting as a main arm and the outer arm 51 acting as a secondary arm are unlocked from each other, the switchable rocker arm 5 providing a first lift in this case in cooperation with the camshaft to the respective valve stem. At this time, the slide 3 or, respectively, the leaf spring 4 fixedly connected with the slide 3 does not provide an actuation force to the coupling pin 53 of the switchable rocker arm 5 that is able to overcome a restoring force of a restoring member, for example a spring member, integrated in the switchable rocker arm 5, so that the coupling pin 53 does not move axially to switch to the coupled state.

[0035] As Figure 5 shown, when the electric motor 1 is energized such that the output shaft of the electric motor 1 rotates, the cam member 2 rotates with the output shaft, thereby urging the slide 3 to move longitudinally (here to the right of the plane of the drawing). At this time, the slide 3 carries the leaf spring 4 fixedly connected with the slide 3 to move longitudinally, thereby exerting an actuation force to the coupling pin 53 of the switchable rocker arm 5, which moves axially here against the restoring force of a restoring member, for example a spring member, integrated in the switchable rocker arm 5, until the inner arm 52 acting as a main arm and the outer arm 51 acting as a secondary arm are locked to each other. Thereby, the switchable rocker arm 5 of the variable valve train is switched to the coupled state. Here, the switchable rocker arm 5 provides a second lift in cooperation with the camshaft to the respective valve stem, which is different from the first lift.

[0036] While the above description illustrates possible embodiments, it is understood that there exist numerous variations of the embodiments still falling within the scope of the present application, through all combinations of known and otherwise conceivable technical features and implementations. Furthermore, it is understood that the exemplary embodiments are merely presented as an example, and that such embodiments in no way limit the scope of protection, application and construction of the present application. The foregoing description is intended more to provide a technical guide for the skilled person to transform at least one exemplary embodiment, wherein various changes can be made, especially with respect to the functional and structural aspects of the components, without departing from the scope of protection of the claims.

[0037] List of reference signs

[0038] 1 electric motor

[0039] 2 cam member

[0040] 21 actuation contour section

[0041] 22 holding contour section

[0042] 3 slide

[0043] 4 leaf spring

[0044] 5 switchable rocker arm

[0045] 51 outer arm

[0046] 52 inner arm

[0047] 53 coupling element, coupling pin

Claims

1. A variable valve mechanism for a reciprocating piston internal combustion engine, the variable valve mechanism comprising: A slide rod (3), which is longitudinally movably supported at a component of the reciprocating piston internal combustion engine, wherein the longitudinal movement of the slide rod (3) axially actuates at least one coupling element (53) of a switchable rocker arm (5) of the variable valve mechanism, thereby enabling the switchable rocker arm (5) to provide different cam lifts; and An actuation assembly for actuating the slide bar (3) longitudinally. The actuation component is characterized in that it comprises: An electric motor (1) includes an output shaft that is perpendicular to the longitudinal direction of the slide bar (3); A cam element (2) is mounted anti-rotatably at the output shaft and abuts against the slide bar (3), thereby converting the rotational motion of the cam element (2) into the longitudinal motion of the slide bar (3). The cam element (2) includes a retaining profile section (22) that provides a cam profile that allows the slide bar (3) to maintain its longitudinal position.

2. The variable valve mechanism according to claim 1, characterized in that, The electric motor (1) integrates an angle sensor, and the rotational motion of the cam (2) is controlled by the angle information of the angle sensor.

3. The variable valve mechanism according to claim 1, characterized in that, The output shaft of the motor (1) is arranged perpendicular to the longitudinal direction of the slide bar (3).

4. The variable valve mechanism according to claim 1, characterized in that, The cam (2) is fitted onto the output shaft of the motor (1) by an interference fit.

5. The variable valve mechanism according to claim 1, characterized in that, The cam member (2) includes an actuation profile section (21) that provides a cam profile that matches the longitudinal travel of the slide bar (3).

6. The variable valve mechanism according to claim 5, characterized in that, The retaining contour section (22) is adjacent to the actuating contour section (21).

7. The variable valve mechanism according to claim 1, characterized in that, The area of ​​the cam (2) that contacts the slide bar (3) is provided with an anti-wear coating.

8. The variable valve mechanism according to claim 1, characterized in that, The slide bar (3) includes a cam contact portion for abutting against the cam member (2), the cam contact portion being constructed as a planar segment extending longitudinally parallel to the slide bar (3).

9. The variable valve mechanism according to claim 1, characterized in that, A leaf spring (4) is fixed at the slide bar (3), and the leaf spring (4) is able to abut against the coupling element (53).

10. A reciprocating piston internal combustion engine, characterized in that, The reciprocating piston internal combustion engine includes a variable valve mechanism according to any one of claims 1 to 9.

Images