VALVE DRIVE FOR AN INTERNAL COMBUSTION ENGINE

Abstract

A valve drive of an internal combustion engine may include a camshaft, at least one cam follower, at least one adjusting device, and a hydraulic actuating element. The camshaft may include at least one first cam structured as a brake cam and a second cam structured as an exhaust cam. The at least one first cam may have a reduced cam lift relative to the second cam. The at least one cam follower may be connected to an exhaust valve of the internal combustion engine via a rocker. The hydraulic actuating element may be adjustable to an extended position and a retracted position. In the extended position, the hydraulic actuating element may be operatively connected to the brake cam providing a braking stroke and, in the retracted position, the hydraulic actuating element may be decoupled from the brake cam providing a cylinder cutout.

Claims

1. A valve drive of an internal combustion engine, comprising: a camshaft and at least one cam follower; the camshaft including at least one first cam non-rotatably coupled on the camshaft and a second cam arranged axially adjacent thereto relative to the camshaft; the at least one cam follower, in a first position, drive-connected to the at least one first cam and, in a second position, drive-connected to the second cam; at least one adjusting device; the second cam structured as an exhaust cam and the at least one first cam structured as a brake cam having, relative to the second cam, a reduced cam lift; wherein the at least one cam follower is connected to an exhaust valve of the internal combustion engine via a rocker; and wherein on one of the rocker and a valve bridge of the exhaust valve a hydraulic actuating element is disposed, the hydraulic actuating element adjustable to an extended position and a retracted position, wherein in the extended position the hydraulic actuating element is operatively connected to the brake cam providing a braking stroke, and in the retracted position the hydraulic actuating element is decoupled from the brake cam providing a cylinder cutout.

2. The valve drive according to claim 1, wherein the hydraulic actuation element is disposed on the rocker, and wherein the hydraulic actuating element includes a plunger extendable in a direction of a valve stem of the exhaust valve.

3. The valve drive according to claim 1, wherein the hydraulic actuation element is disposed on the rocker, and wherein the hydraulic actuating element is integrated in the rocker.

4. The valve drive according to claim 1, wherein the hydraulic actuation element is disposed on the valve bridge, and wherein the hydraulic actuating element includes a plunger extendable in a direction of the rocker.

5. The valve drive according to claim 1, wherein the hydraulic actuation element is disposed on the valve bridge, and wherein the hydraulic actuating element is integrated in the valve bridge.

6. The valve drive according to claim 2, wherein the plunger is adjustable an adjustment distance between the extended position and the retracted position, and wherein the adjustment distance is greater than a cam lift of the brake cam.

7. The valve drive according to claim 1, wherein: the at least one adjusting device includes a first adjustable engagement peg and a second adjustable engagement peg arranged on the at least one cam follower spaced apart from one another; the first engagement peg is configured to interact with a first slotted guide arranged on the camshaft and the second engagement peg is configured to interact with a second slotted guide arranged on the camshaft; the first engagement peg and the second engagement peg are alternately adjustable between a basic position and a shifting position, respectively; and in the basic position, a respective engagement peg of the first engagement peg and the second engagement peg does not contact an associated slotted guide of the first slotted guide and the second slotted guide and, in the shifting position, the respective engagement peg interacts with the associated slotted guide.

8. The valve drive according to claim 1, wherein: the at least one adjusting device includes an adjustable engagement peg configured to interact with a slotted guide including a first slotted track and a second slotted track crossing the first slotted track; the engagement peg is alternately adjustable between a basic position and a shifting position; and in the basic position, the engagement peg does not contact the slotted guide and, in the shifting position, the engagement peg interacts with the slotted guide.

9. The valve drive according to claim 1, wherein the at least one cam follower is axially shiftable relative to the camshaft.

10. The valve drive according to claim 1, wherein the rocker includes a first rocker arm with a first roller and a second rocker arm with a second roller, the second rocker arm couplable to the first rocker arm.

11. An internal combustion engine comprising a valve drive and an exhaust valve, the valve drive including: a camshaft including at least one first cam non-rotatably arranged thereon and a second cam arranged axially adjacent to the at least one first cam relative to the camshaft, the second cam structured as an exhaust cam and the at least one first cam structured as a brake cam, the at least one first cam having a reduced cam lift relative to the second cam; and at least one cam follower drive-connected to the at least one first cam in a first position and drive-connected to the second cam in a second position, the at least one cam follower connected to the exhaust valve via a rocker; wherein a hydraulic actuating element is disposed on one of the rocker and a valve bridge of the exhaust valve, the hydraulic actuating element adjustable to an extended position and a retracted position; and wherein, in the extended position, the hydraulic actuating element is operatively connected to the at least one first cam providing a braking stroke and, in the retracted position, the hydraulic actuating element is decoupled from the at least one first cam providing a cylinder cutout.

12. The internal combustion engine according to claim 11, wherein the hydraulic actuation element is disposed on the rocker, and wherein the hydraulic actuating element includes a plunger extendable in a direction of a valve stem of the exhaust valve.

13. The internal combustion engine according to claim 11, wherein the hydraulic actuation element is disposed on the rocker, and wherein the hydraulic actuating element is integrated in the rocker.

14. The internal combustion engine according to claim 11, wherein the hydraulic actuation element is disposed on the valve bridge, and wherein the hydraulic actuating element includes a plunger extendable in a direction of the rocker.

15. The internal combustion engine according to claim 14, wherein the plunger is adjustable an adjustment distance between the extended position and the retracted position, and wherein the adjustment distance is greater than a cam lift of the at least one first cam.

16. The internal combustion engine according to claim 11, wherein the hydraulic actuation element is disposed on the valve bridge, and wherein the hydraulic actuating element is integrated in the valve bridge.

17. The internal combustion engine according to claim 11, wherein: the at least one adjusting device includes a first adjustable engagement peg and a second adjustable engagement peg arranged on the at least one cam follower spaced apart from one another, the first engagement peg configured to interact with a first slotted guide arranged on the camshaft and the second engagement peg configured to interact with a second slotted guide arranged on the camshaft; the first engagement peg and the second engagement peg are alternately adjustable between a basic position and a shifting position, respectively; and in the basic position, a respective engagement peg of the first engagement peg and the second engagement peg does not contact an associated slotted guide of the first slotted guide and the second slotted guide and, in the shifting position, the respective engagement peg interacts with the associated slotted guide.

18. The internal combustion engine according to claim 11, wherein: the at least one adjusting device includes an adjustable engagement peg configured to interact with a slotted guide including a first slotted track and a second slotted track crossing the first slotted track; the engagement peg is alternately adjustable between a basic position and a shifting position; and in the basic position, the engagement peg does not contact the slotted guide and, in the shifting position, the engagement peg interacts with the slotted guide.

19. The internal combustion engine according to claim 11, wherein the at least one cam follower is axially shiftable relative to the camshaft.

20. The internal combustion engine according to claim 11, wherein the rocker includes a first rocker arm with a first roller and a second rocker arm with a second roller, the second rocker arm couplable to the first rocker arm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] There it shows, in each case schematically

[0019] FIG. 1 shows a valve drive according to the invention corresponding to a first embodiment with axially shiftable cam follower;

[0020] FIG. 2 shows a representation as in FIG. 1, however with a rocker having two rocker arms that can be coupled to one another;

[0021] FIG. 3 shows a lateral view of a valve drive according to the invention with a hydraulic actuating element arranged on a valve bridge in an extended position;

[0022] FIG. 4 shows a representation as in FIG. 3, however with a hydraulic actuating element in its retracted position;

[0023] FIG. 5 shows a hydraulic actuating element arranged on the rocker in an extended position;

[0024] FIG. 6 shows a representation as in FIG. 5, however with a hydraulic actuating element in its retracted position.

DETAILED DESCRIPTION

[0025] According to the FIGS. 1 to 6, a valve drive 1 according to the invention comprises a camshaft 3 of an internal combustion engine 2 which is otherwise not shown in more detail having at least one cam follower 4. The camshaft 3 comprises at least one first cam 5 that is non-rotatably fixed on the camshaft 3 and a second cam 6 that is arranged axially adjacent thereto. Here, the cam follower 4 is drive-connected in a first position to the first cam 5 and in a second position to the second cam 6, wherein cam follower 4 according to FIG. 1 is in its first position and because of this is connected to the first cam 5. According to FIG. 1, a roller pin 7, on which individual rollers 8 are rotatably mounted, is adjustable in the axial direction 9. The valve drive 1 additionally comprises an adjusting device 10 with a first adjustable engagement peg 11 and with a second adjustable engagement peg 12, which are arranged spaced next to one another. In the activated state, the first engagement peg 11 can interact with a first slotted guide 13 arranged on the camshaft 3, while the second engagement peg 12 can interact with a second slotted guide 14 arranged on the camshaft 3. The first engagement peg 11 and the second engagement peg 12 are alternately adjustable between a basic position and a shifting position, wherein in the basic position there is no contact with the associated slotted guide 13, 14, while in the shifting position the respective engagement peg 11, 12 interacts with the associated slotted guide 13, 14.

[0026] Alternatively and not shown it is also conceivable that the adjusting device 10 only comprises a single adjustable engagement peg 11, which interacts with a slotted guide having a first slotted track and a second slotted track crossing the same, wherein the engagement peg 11 is alternately adjustable between a basic position and a shifting position and wherein in the basic position there is no contact with the associated slotted guide 13 and, in the shifting position, the engagement peg 11 interacts with the associated slotted guide 13.

[0027] According to the invention, the second cam 6 is now formed as an exhaust cam 6 and the first cam 5 as a brake cam 5 with, compared with the second cam, a reduced cam lift. Here, the cam follower 4 is itself connected to an exhaust valve 15 (see also the FIGS. 2 to 6) of the internal combustion engine 2 via a rocker 16. According to the invention, a hydraulic actuating element 18 is additionally provided on the rocker 16 or on a valve bridge 17 (see FIGS. 3 and 4), which between an extended position (see the FIGS. 3 and 5) is operatively connected to the brake cam 5, i.e. the first cam 5, and brings about a braking stroke, while in a retracted position (see FIGS. 4 and 6) it is decoupled from the brake cam 5, i.e. from the first cam 5, and brings about a cylinder cutout.

[0028] When the hydraulic actuating element 18 is arranged on the rocker 16, usually has a plunger 19 that is extendable in the direction of a valve stem 20 of the associated exhaust valve 15, wherein the same according to FIG. 5 is shown in its extended position and according to FIG. 6 in its retracted position. The hydraulic actuating element 18 in this case can be screwed to the rocker 16 and thus be formed easily mountable to the same, or the hydraulic actuating element 18 can be integrated in the rocker 16.

[0029] When the hydraulic actuating element 18, alternatively to the situation described in the previous paragraph, is arranged on or integrated in the valve bridge 17 of the exhaust valve 15, it usually comprises a plunger 19 that is extendable in the direction of the rocker 16 (see the FIGS. 3 and 4), wherein the plunger 19 according to FIG. 3 is shown in its extended position, in which an operative connection between the exhaust valve 15 and the brake cam 5, i.e. the first cam 5, is brought about. According to FIG. 4, the piston 19 of the hydraulic actuating element 18 is shown in its retracted position, in which there is no operative connection with the associated cam follower 4, i.e. in the present case the rocker 16 and because of this a cylinder cutout takes place. In this case, the hydraulic actuating element 18 is screwed to the valve bridge 17 or integrated in the same.

[0030] The extendable plunger 19 in this case is adjustable between the retracted position and the extended position by a distance X, which is greater than a cam lift lift.sub.BN of the brake cam 5, i.e. of the first cam 5. By way of this it can be brought about that with completely retracted plunger 19 the clearance x exposed through the retraction movement of the piston 9 is greater than the maximum cam lift of the brake cam 5, i.e. of the first cam 5, as a result of which the cylinder cutout can be brought about.

[0031] The valve drive 1 according to the invention can be employed both with an axially adjustable cam follower 4, as is shown according to FIG. 1, and also with a cam follower 4, i.e. rocker 16, having a first rocker arm 21 with a first roller 8 and a second rocker arm 22 with a second roller 8 (see FIG. 2). In the embodiment of the valve drive 1 according to the invention shown according to FIG. 2, a coupling of the two rocker arms 21 and 22 occurs during the normal operation, so that the cam follower 4, via the roller 8 of the first rocker arm 21, follows the exhaust cam 6. When the roller pin 7 is shifted to the right, the first rocker arm 21 is decoupled from the second rocker arm 22 and the rocker 16 merely follows the brake cam 5, i.e. the first cam 5, via the second roller 8. In this state, a decoupling from the associated exhaust valve 15 can then be additionally effected by actuating the hydraulic actuating element 18, as a result of which the cylinder cutout is brought about.

[0032] Even with a system that is merely a two-stage system per se, which merely makes possible a normal operation via the second cam 6, i.e. the exhaust cam 6, as well as a braking operation via the brake cam 5, i.e. the first cam 5, the valve drive 1 according to the invention thus makes additionally possible a cylinder cutout without further installation space being required for this purpose. In addition, the hydraulic actuating element 18 according to the invention can be installed in a location that is favourable in terms of design. Because of the low complexity of the valve drive 1 according to the invention a comparatively robust design can also be achieved. Through the modular construction and the few components, assembly advantages and cost advantages are additionally attained. The hydraulic actuating element 18 also constitutes a relatively minor moving mass, as a result of which compared with conventional three-stage systems, substantial weight advantages can be achieved.