Valvetrain for an internal combustion engine, in particular of a motor vehicle

Abstract

A valvetrain for an internal combustion engine has a camshaft that can be rotated in a direction of rotation around an axis of rotation, at least two cam pieces arranged on the camshaft which each have at least two cams for actuating a respective gas exchange valve and which are rotationally fixedly connected to the camshaft, and an actuator via which the cam pieces can be shifted in the axial direction of the camshaft. A first of the cam pieces has a first rib protruding outwardly from a first base body of the first cam piece in the radial direction of the camshaft and the second cam piece has a second rib protruding outwardly from a second base body of the second cam piece in the radial direction of the camshaft.

Claims

1. A valvetrain for an internal combustion engine, the valvetrain comprising: a camshaft (12) configured to rotate about an axis of rotation (14); a first cam piece (18) rotationally fixed on the camshaft (12), the first cam piece (18) including at least two cams (22, 24) configured to alternately actuate a first gas exchange valve; a second cam piece (20) rotationally fixed on the camshaft (12), the second cam piece (20) including at least two cams (22, 24) configured to alternately actuate a second gas exchange valve; and an actuator (26) wherein configured to axially shift the first and second cam pieces (18, 20) relative to the camshaft (12); wherein the first cam piece (18) further includes a radially outwardly protruding first rib (30) which extends circumferentially about the first cam piece (18) and entirely within a first angle region corresponding to a first half rotation of the camshaft (12); wherein the second cam piece (20) further includes a radially outwardly protruding second rib (36) which extends circumferentially about the second cam piece (20) and entirely within a second angle region corresponding to a second half rotation of the camshaft (12); wherein the actuator (26) engages the first rib (30) and is disengaged from the second rib (36) during the first half rotation so as to axially shift the first cam piece (18); and wherein the actuator (26) engages the second rib (36) and is disengaged from the first rib (30) during the second half rotation so as to axially shift the second cam piece (20).

2. The valvetrain according to claim 1, wherein the first and second cam pieces (18, 20) are each configured to axially shift between a respective first position and a respective second position.

3. The valvetrain according to claim 2, wherein the first and second cam pieces (18, 20) are sequentially shifted from the respective first position into the respective second position within one rotation of the camshaft (12).

4. The valvetrain according to claim 2, wherein the first and second ribs (30, 36) are aligned on a common first plane that extends perpendicular to the camshaft (12) when the first and second cam pieces (18, 20) are simultaneously in the respective first position, wherein the first and second ribs (30, 36) are aligned on a common second plane that extends perpendicular to the camshaft (12) when the first and second cam pieces (18, 20) are simultaneously in the respective second position, and wherein the second plane is axially spaced apart from the first plane relative to the camshaft (12).

5. The valvetrain according to claim 4 further wherein: the actuator (26) is configured to engage the first and second ribs (30, 36) via a first form-fit element (38) and a second form-fit element (40); when the first and second ribs (30, 36) are aligned on the first plane, the first form-fit element (38) is configured to receive the first rib (30) during the first half rotation and to receive the second rib (36) during the second half rotation; when the first and second ribs (30, 36) are aligned on the second plane, the second form-fit element (40) is configured to receive the first rib (30) during the first half rotation and to receive the second rib (36) during the second half rotation; and when the first cam piece (18) is in the respective first position and the second cam piece (20) is simultaneously in the respective second position, the first form-fit element (38 is configured to receive the first rib (30) during the first half rotation and the second form-fit element (40) is configured to receive the second rib (36) during the second half rotation.

6. The valvetrain according to claim 5, wherein the actuator (26) includes an engine (52) configured to drive the actuator (26).

7. The valvetrain according to claim 1, wherein the actuator (26) includes an engine (52) configured to drive the actuator (26).

8. The valvetrain according to claim 1, wherein the first rib extends more than 90 degrees about the first cam piece within the first angle region, and the second rib extends more than 90 degrees about the second cam piece within the second angle region.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1, sectionally, is a schematic side view of a valvetrain according to the invention, wherein cam pieces of the valvetrain are in their first positions;

(2) FIG. 2, sectionally, is a schematic side view of the valvetrain, wherein a first of the cam pieces is in its second position and the second cam piece is in its first position:

(3) FIG. 3, sectionally, is a further schematic side view of the valvetrain, wherein the first cam piece is in the second position and the second cam piece is in the first position; and

(4) FIG. 4, sectionally, is a schematic side view of the valvetrain, wherein the cam pieces are in their respective second position.

DETAILED DESCRIPTION OF THE DRAWINGS

(5) In the Figures, the same or functionally identical elements are provided with the same reference numerals.

(6) Sectionally in a schematic side view, FIG. 1 shows a valvetrain 10 for an internal combustion engine of a motor vehicle, in particular a motor vehicle formed, for example, as a passenger vehicle. The internal combustion engine is formed as a reciprocating piston engine and has at least one or more combustion chambers, wherein the respective combustion chamber is formed, in particular, as a cylinder. At least one gas exchange valve is allocated to the respective cylinder, the gas exchange valve being able to be moved translationally between a respective closed position and at least two open positions different from one another. The respective gas exchange valve can be actuated by means of the valvetrain 10 and can thus be translationally moved from the closed position into the respective open position. To do so, the valvetrain 10 comprises a camshaft 12 also called the wave element, which can be rotated around an axis of rotation 14 in a direction of rotation. In the completely constructed state of the internal combustion engine, the camshaft 12 is rotatably mounted on a cylinder head 16, for example, that can be seen sectionally in FIG. 1 and thus can be rotated around the axis of rotation 14 relative to the cylinder head 16. The valvetrain 10 furthermore comprises two cam pieces 18 and 20 arranged on the camshaft 12 and shiftable in the axial direction of the camshaft 12 relative to it, which cam pieces respectively have at least two cams 22 and 24. Here, the cams 22 and 24 of the cam piece 18 are allocated to a first of the gas exchange valves, wherein the cams 22 and 24 of the cam piece 20 are allocated to a second of the gas exchange valves. This means that the first gas exchange valve can be alternatingly actuated by means of the cams 22 and 24 of the cam piece 18, wherein the second gas exchange valve can be alternatingly actuated by means of the cams 22 and 24 of the cam piece 20. The cam pieces 18 and 20 are rotationally fixedly connected to the camshaft 12 and can thus be rotated with this around the axis of rotation 14 relative to the cylinder head 16.

(7) The valvetrain 10 further comprises an actuator 26 common to the cam pieces 18 and 20 by means of which the cam pieces 18 and 20 can be shifted in the axial direction of the camshaft 12 relative to the camshaft 12. The axial direction of the camshaft 12 here coincides with the axis of rotation 14. The respective cam piece 18 or 20 can be shifted in the axial direction of the camshaft 12 relative to this between a respective first position shown in FIG. 1 and a respective second position shown in FIG. 4. In the first position of the cam piece 18, the first gas exchange valve is actuated by means of the cam 22 of the cam piece 18 when the camshaft 12 and thus the cam pieces 18 and 20 are rotated around the axis of rotation 14. In the second position of the cam piece 18, the first gas exchange valve is actuated by means of the cam 24 of the cam piece 18 when the camshaft 12 is rotated around the axis of rotation 14.

(8) As a result, in the first position of the cam piece 20, the second gas exchange valve is actuated by means of the cam 22 of the cam piece 20, wherein, in the second position of the cam piece 20, the second gas exchange valve is actuated by means of the cam 24 of the cam piece 20. A respective first stroke of the respective gas exchange valve is caused or can be caused by means of the respective cam 22. A respective second stroke of the respective gas exchange valve can be caused or is caused by means of the respective cam 24. Here, the second stroke, for example, is greater than the first stroke, such that the respective gas exchange valve can be opened or is opened further by means of the respective cam 24 than by means of the respective cam 22. The respective gas exchange valve here carries out the respective stroke on its way out of the respective closed position into the respective open position. By carrying out the respective first stroke, the respective gas exchange valve reaches a first of the open positions out of the respective closed position, wherein the respective gas exchange valve reaches the respective second position from the respective closed position by carrying out the respective second stroke. Since the second stroke is greater than the first stroke, the respective first open position is between the closed position and the respective second open position.

(9) Since the different strokes can be moved by means of the cams 22 and 24, a valve stroke switch can be achieved by shifting the respective cam piece 18 or 20 into the respective positions, whereby an efficient and effective operation of the internal combustion engine can be achieved. In order to now be able to keep the installation space requirement of the valvetrain 10 particularly minimal, the cam piece 18 also called the first cam piece has a first rib 30 protruding outwardly from a first base body 28 of the cam piece 18 in the radial direction of the camshaft 12, the rib extending in the direction of rotation into a or across a first angle region of the first cam piece 18. The radial direction of the camshaft 12 runs perpendicularly to the axial direction and is illustrated in FIG. 1 by a double arrow 32. The cam piece 20 also called the second cam piece has a second rib 36 protruding outwardly from a second base body 34 of the cam piece 20 in the radial direction of the camshaft 12, the rib extending in the direction of rotation in a or across a second angle region, attached to the first angle region, of the second cam piece 20. The respective rib 30 or 36 is, for example, shaped like an arc and here is formed, in particular, to be crescent-shaped, such that the respective angle region in the peripheral direction, coinciding with the direction of rotation, of the respective cam piece 18 or 20 or in the peripheral direction of the camshaft 12 is less than 360 degrees and at most 180 degrees, in particular at most 179 degrees.

(10) The actuator 26 is an actuator common to the cam pieces 18 and 20, such that both the cam piece 18 and the cam piece 20 can be shifted out of the respective first position into the respective second position and out of the respective second position into the respective first position by means of the actuator 26. The actuator 26 common to the cam pieces 18 and 20 is coupled in a form-fit manner to the first cam piece 18 via the first rib 30 during a respective first part of a respective rotation of the cam shaft 12 and decoupled from the second cam piece 20, such that—while the actuator is coupled to the cam piece 18 via the rib 30 and decoupled from the cam piece 20—the first cam piece 18 can be shifted via the first rib 30 by means of the actuator 26, while a shifting of the second cam piece 20 caused by the actuator 26 ceases.

(11) During a respective second part, following the first part, of the respective rotation of the camshaft 12, the actuator 26 is coupled to the second cam piece 20 via the second rib 36 and decoupled from the first cam piece 18, such that—while the actuator 26 is coupled to the second cam piece 20 via the rib 36 and decoupled from the first cam piece 18—the second cam piece 20 can be shifted via the second rib 36 by means of the actuator 26, while a shifting of the first cam piece 18 caused by the actuator 26 ceases.

(12) Here, the valvetrain 10 has a first form-fit element 38 and a second form-fit element 40, which is arranged next to the form-fit element 38 in a movement direction 42 running in parallel to the axial direction. The form-fit elements 38 and 40 can here be translationally moved in the movement direction 42 by means of the actuator 26, wherein the form-fit elements 38 and 40 can be translationally moved, i.e., shifted, in a first direction illustrated by an arrow 44 and coinciding with the movement direction and in a second direction illustrated in FIG. 1 by an arrow 46, coinciding with the movement direction and in opposition to the first direction. Here, the cam pieces 18 and 20 can also be shifted in the first direction and in the second direction by means of the actuator 26 via the form-fit elements 38 and 40. The respective form-fit element 38 or 40 has a respective receiver 48 or 50.

(13) The form-fit elements 38 and 40 can here be translationally moved, i.e., shifted, together by means of the actuator 26 in the movement direction between a first position shown in FIG. 1, a second position shown in FIGS. 2 and 3 and a third position shown in FIG. 4. Here, the actuator 26 comprises an engine 52 in particular schematically depicted in the Figures and common to the ribs 30 and 36 and the form-fit elements 38 and 40, by means of which engine the form-fit elements 38 and 40 or the cam pieces 18 and 20 can be shifted. Thus, the engine 52 is an engine common to the form-fit elements 38 and 40 or the cam pieces 18 and 20.

(14) FIG. 1 shows a starting state in which the cam pieces 18 and 20 are in their first positions, and the form-fit elements 38 and 40 are in their first sliding position. If the cam pieces 18 and 20 are simultaneously in the first positions, then the first rib 30 interacts in a form-fit manner with the first form-fit element 38 during the first part and the second rib 36 does so during the second part, and a form-fit interaction of the ribs 30 and 36 with the second form-fit element 40 ceases during the rotation, in particular while the form-fit elements 38 and 40 are in their first sliding position. The respective rib 30 or 36 here interacts in a form-fit manner with the form-fit element 38 in such a way that the respective rib 30 or 36 engages in the recess 48 during the respective part. In the starting state, the gas exchange valves are actuated by means of the cam 22, since the cam pieces 18 and 20 are in their first positions. While the rib 30 interacts with the form-fit element 38 and thus with the actuator 26 by the rib 30 engaging in the recess 48, the form-fit elements 38 and 40 are shifted from the first sliding position into a respective second shifting position by means of the actuator 26, in particular by means of the engine 52, wherein the form-fit elements 38 and 40 are shifted to the left by means of the actuator based on the respective image plane of FIG. 1 or 2. Since the cam piece 18 is coupled to the actuator 26 via the rib 30 and the form-fit element 38, the cam piece 18 is shifted together with the form-fit elements 38 and 40, whereby the cam piece 18 is shifted out of its first position into its second position shown in FIG. 2, while a shifting, caused by the actuator, of the cam piece 20 ceases. In order to shift the form-fit elements 38 and 40 from the first sliding position into the second sliding position, the form-fit elements 38 and 40 are shifted together in the first direction by means of the actuator 26, in particular by means of the engine 52.

(15) FIG. 2 shows a first intermediary state, in which the cam piece 18 is in its second position, while the cam piece 20 is in its first position. Furthermore, it can be seen in FIG. 2 that the cam piece 18 is shifted from the first position into the second position, while the cam piece 18 interacts with the actuator 26 via the rib 30 by the rib 30 engaging in the form-fit element 38 or in its recess 48. Here, the rib 36 engages neither in the form-fit element 38 nor in the form-fit element 40, such that the cam piece 20 is decoupled from the actuator 26, while the cam piece 18 is coupled to the actuator 26 via the rib 30.

(16) FIG. 3 shows a second intermediary state following the first intermediary state shown in FIG. 2, in which the cam piece 18 is still in the second position and the cam piece 20 is still in the first position. The difference between the first intermediary state and the second intermediary state is that the camshaft 12 has rotated further in the second intermediary state in comparison to the first intermediary state, in particular by a half rotation, such that, in the first intermediary state, the cam piece 18 is coupled to the actuator 26 via the rib 30 and the cam piece 20 is decoupled from the actuator 26, wherein, in the second intermediary state, the cam piece 20 is connected to the actuator 26 via the rib 30 and the cam piece 18 is decoupled from the actuator 26. In other words, in the second intermediary state, the rib 36 engages in the form-fit element 40, in particular in the recess 50, such that, in the second intermediary state, the cam piece 20 is coupled to the actuator 26 via the rib 36 and the form-fit element 40, while the cam piece 18 is decoupled from the actuator 26. In the second state, i.e., while the cam piece 20 is coupled to the actuator 26 via the rib 36 and the cam piece 18 is decoupled from the actuator 26, the form-fit elements 38 and 40 are shifted further in the first direction and, in doing so, from the second sliding position into a third sliding position by means of the actuator 26, in particular by means of the engine 52. Since here the cam piece 20 is coupled to the form-fit element 40 and thus to the actuator 26 via the rib 36, the cam piece 20 is shifted together with the form-fit elements 38 and 40, whereby the cam piece 20 is shifted from its first position into its second position shown in FIG. 4.

(17) FIG. 4 thus shows an end state, in which the two cam pieces 18 and 20 are simultaneously in the second positions. The end state is a second starting state, starting from which the cam pieces 18 and 20 can be moved back into the first starting state shown in FIG. 1 by means of the actuator 26, in particular via the second intermediary state and via the first intermediary state. For this, the form-fit elements 38 and 40 are shifted in the second direction by means of the actuator 26, in particular by means of the engine 52 and thus moved back from the third sliding position via the second sliding position into the first sliding position.

(18) Overall, it can be seen in FIGS. 1 to 4 that, while the cam shaft 12 is rotated around the axis of rotation 14, firstly the rib 30, for example, comes into engagement with the form-fit element 38, whereby the cam piece 18 is shifted from the first position into the second position by means of the actuator 26, while a shifting of the cam piece 20 ceases. If the camshaft 12 is further rotated, then the rib 30 comes out of engagement with the form-fit element 38, and the rib 36 comes into engagement with the form-fit element 40, such that then the cam piece 20 can be shifted out of the first position into the second position by means of the actuator 26. If the cam pieces 18 and 20 are then simultaneously in the second positions, then the gas exchange valves are actuated by means of the cam 24.

(19) The actuator 26 is, for example, a linear actuator, by means of which the form-fit elements 38 and 40 can be shifted in the movement direction. Furthermore, it is conceivable that the engine 52 is a rotary engine which has, for example, a rotor that can be rotated around the movement direction 42. A threaded spindle, for example, can be driven by means of the rotor and thus can be rotated around the movement direction 42, wherein the form-fit elements 38 and 40, for example, are screwed onto the threaded spindle. Furthermore, the form-fit elements 38 and 40, for example, are secured against a rotation around the movement direction, such that a relative rotation of the threaded spindle between the threaded spindle and the form-fit elements 38 and 40 is converted into a translational movement of the form-fit elements 38 and 40 in the movement direction 42. If thus the rotor and thus the threaded spindle, for example, are rotated in a first direction of rotation, then the form-fit elements 38 and 40 are shifted in the first direction, for example. If, for example, the rotor and thus the threaded spindle are rotated in a second direction opposite to the first direction of rotation, then the form-fit elements 38 and 40, for example, are shifted in the second direction. In this way, the cam pieces 18 and 20 can be shifted forwards and backwards in the movement direction, i.e., in the first direction and in the second direction, by means of the common engine 52.

(20) Overall, it can be seen that, when the cam pieces 18 and 20 are simultaneously in the first positions, the first rib 30 interacts in a form-fit manner with the first form-fit element 38 during the first part and the second rib 36 does so during the second part, and a form-fit interaction of the ribs 30 and 36 with the second form-fit element 40 ceases during the rotation. When the cam pieces 18 and 20 are simultaneously in the second positions, the first rib 30 interacts in a form-fit manner with the second form-fit element 40 during the first part and the second rib 36 does so during the second part, and a form-fit interaction of the ribs 30 and 36 with the first form-fit element 38 ceases during the respective rotation. If the first cam piece is in its first position and if the second cam piece is simultaneously in its second position, the first rib interacts with the first form-fit element during the first part, the second rib interacts with the second form-fit element during the second part, a form-fit interaction of the first rib with the second form-fit element ceases during the rotation and a form-fit interaction of the second rib 36 with the first form-fit element 38 ceases during the rotation.

(21) Furthermore, it can be seen that the two ribs 30 and 36, for example formed as crescent ribs, can be formed to be very narrow in the axial direction, whereby they require only a small construction space on the camshaft 12. Thus, the valvetrain 10 can also be used in such cylinder heads or internal combustion engines, which have a very small cylinder spacing. Moreover, a production of cost-intensive switching connecting links in the cam pieces 18 and 20 can be avoided, such that the valvetrain 10 can be produced cost-effectively.