Valve actuation system for an internal combustion engine

Abstract

A valve actuation system for an internal combustion engine The valve actuation system (S) for an internal combustion engine comprises: ⋅a rocker (6) pivotably mounted around a pivot axis (A6), comprising: ⋅a driven end portion (62) for cooperating with a rotating cam including a main bump and at least one smaller auxiliary bump; ⋅an actuating end portion (63) including a piston (8) for opening at least one valve of the engine following the cooperation of the driven end portion (62) with a bump of the cam, the piston (8) being slidably mounted relative to the rocker (6) between a extended position allowing said piston (8) to open said valve when the driven end portion (62) contacts the auxiliary bump, and a retracted position preventing said piston (8) to open said valve when the driven end portion (62) contacts the auxiliary bump; ⋅a fluid circuit for causing the piston (8) to move from its retracted position to its extended position; ⋅a reset circuit comprising a reset valve (99) rotatably mounted relative to the rocker (6), between an inactive position, and an active position in which the reset valve (99) causes the fluid to be drained out of the fluid circuit to allow the piston (8) to move towards its retracted position; ⋅a lever (7) pivotably mounted around a pivot axis (A6), the lever (7) having a driven end portion (72) adapted to cooperate with a rotating reset cam including a bump, and an actuating end portion (73) for rotating the reset valve (99) from its inactive position towards its active position following the cooperation of the lever driven end portion (72) with the bump of the reset cam; ⋅rotational coupling means (75, 95) between the lever (7) and the reset valve (99), said rotational coupling means having a transmission ratio greater than 1.

Claims

1. A valve actuation system for an internal combustion engine, said valve actuation system comprising: a rocker pivotally mounted around a pivot axis, the rocker including: a rocker driven end adapted to engage a rotating cam including a main bump and at least one auxiliary bump having a smaller radial dimension than the main bump; a rocker actuating end equipped with at least one piston adapted to open at least one gas exchange valve of the engine when the cam actuates the rocker driven end, the at least one piston being slidably mounted to the rocker so as to switch between an extended position allowing said at least one piston to open said at least one gas exchange valve when the rocker driven end is actuated by the at least one auxiliary bump, and a retracted position preventing said at least one piston from opening said at least one gas exchange valve when the rocker driven end is actuated by the at least one auxiliary bump; a fluid circuit including a fluid configured to move the at least one piston from the retracted position to the extended position; and a reset circuit including a reset valve rotatably mounted to the rocker, the reset valve configured to switch between an inactive position and an active position in which the fluid drains out of the fluid circuit so as to allow the at least one piston to move towards the retracted position; and a lever pivotally mounted around the pivot axis, the lever including: a lever driven end adapted to engage a rotating reset cam including at least one bump; and a lever actuating end configured to rotate the reset valve via a rotational coupling means for rotating the reset valve from the inactive position towards the active position when the reset cam actuates the lever driven end, wherein said rotational coupling means has a transmission ratio greater than 1.

2. The valve actuation system according to claim 1, wherein the transmission ratio ranges from 2 to 15.

3. The valve actuation system according to claim 1, wherein the reset valve rotates about a reset valve axis which is parallel to the pivot axis.

4. The valve actuation system according to claim 1, wherein the rotational coupling means comprises: a first set of teeth arranged on a cylindrical outer surface of the lever actuating end; and a second set of teeth arranged on a rod of the reset valve, the rod protruding from the rocker towards the lever.

5. The valve actuation system according to claim 1, wherein the lever driven end comprises a leg which protrudes substantially radially away from the pivot axis, said leg having a free end adapted to engage the reset cam.

6. The valve actuation system according to claim 1, further comprising an activation member fixed to the rocker actuating end, wherein said at least one gas exchange valve includes two gas exchange valves, and wherein said activation member is adapted to engage a valve bridge configured to simultaneously open the two gas exchange valves when the main bump actuates the rocker driven end.

7. The valve actuation system according to claim 1, wherein the at least one gas exchange valve is an exhaust valve.

8. The valve actuation system according to claim 7, wherein the at least one auxiliary bump is configured to activate an engine brake function when the at least one piston is in the extended position.

9. An engine arrangement comprising: the valve actuation system according to claim 1; a rocker shaft extending along the pivot axis such that the rocker and the lever are pivotally mounted on said rocker shaft; and a camshaft including the rotating cam and the reset cam, wherein the at least one gas exchange valve includes two gas exchange valves, and wherein the at least one piston is adapted to open at least a first gas exchange valve of said two gas exchange valves.

10. The engine arrangement according to claim 9, further comprising: an activation member fixed to the rocker actuating end; a valve bridge configured to simultaneously open the two gas exchange valves when the activation member actuates the valve bridge; and an opening member secured to an end of the first gas exchange valve, the opening member slidably engaged through a hole of the valve bridge such that only the first gas exchange valve is opened when the at least one piston actuates the opening member.

11. A vehicle comprising the valve actuation system according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

(2) In the drawings:

(3) FIG. 1 is a partial perspective view of an engine arrangement comprising a valve actuation system according to an embodiment of the invention;

(4) FIG. 2 is a perspective view of the valve actuation system of FIG. 1, showing a rocker, a lever and a piston pertaining to said system;

(5) FIG. 3 is a partial perspective view of the engine arrangement of FIG. 1, further showing a camshaft;

(6) FIGS. 4 and 5 are side views of the valve actuation system of FIG. 2, the lever being in two different positions;

(7) FIG. 6 is a sectional view of the valve actuation system showing a fluid circuit for moving the piston;

(8) FIG. 7 is another sectional view of the valve actuation system showing said fluid circuit and a reset circuit;

(9) FIGS. 8 and 9 are sectional views of the valve actuation system showing two operating configurations of the fluid circuit and reset circuit;

(10) FIGS. 10a to 15b schematically show the engine arrangement during various phases of the engine cycle;

(11) FIG. 16 is a diagram showing the evolution of the lifts of the inlet and exhaust valves of the engine arrangement during one engine cycle.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

(12) As this is illustrated in FIGS. 1 to 3, the invention relates to an engine arrangement 1 of a non-represented automotive vehicle.

(13) The engine arrangement 1 comprises a cylinder head 3 of an internal combustion engine of the vehicle, on which cylinder head 3 is secured a bracket 31 for mounting a valve actuation system S, i.e. a camshaft 2. The cylinder head 3 includes openings 32 for receiving the valves of the engine. In this embodiment, each cylinder of the engine is equipped with two inlet valves (not shown), and two exhaust valves 4, 5, namely an inner exhaust valve 4 and an outer exhaust valve 5. The valves have respective axes A4, A5.

(14) Valves 4 and 5 are kept in a closed position by respective springs 41 and 51 (not shown on FIG. 1, but visible on FIGS. 3 and 10a, for example). Each valve 4 and 5 is movable in translation along its respective axis A4, A5 so as to be opened, or lifted. More precisely, translation of valves 4 and 5 opens a passageway between the combustion chamber of the cylinder and an exhaust manifold. Valves 4 and 5 are partly represented on FIGS. 1 and 3, only their respective stems being visible.

(15) The engine arrangement 1 also comprises the camshaft 2 having an axis A2, said camshaft 2 being rotatably mounted around its axis A2 in an opening 33 of the bracket 31. On the camshaft 2 are fastened cams for moving the cylinder valves, among which one cam 21 dedicated to move the exhaust valves 4, 5 of each cylinder. The cam 21 includes a main bump 210 and at least one auxiliary bump having a smaller radial dimension than the main bump 210. The bumps are valve lift sectors where the cam profile exhibits a bigger eccentricity with respect to axis A2 than the base radius of the cam 21. In the disclosed embodiment, the cam 21 comprises two auxiliary bumps 211, 212 (see FIG. 10b). Besides, a reset cam 26 including at least one bump 260 is also fastened on the camshaft 2. The reset cam 26 is offset with respect to cam 21 along axis A2.

(16) With reference to FIG. 1, longitudinal axis X is defined as being parallel to axis A2 of the camshaft, vertical axis Z as being parallel to axes A4, A5 of the valves 4, 5 and transverse axis Y as being orthogonal to axes X and Z. It has to be noted that the term “vertical” is used for simplifying the description, but does not limit the possible orientation of the engine arrangement 1.

(17) The valve actuation system S comprises a rocker 6 which is pivotably mounted around a pivot axis A6 and a lever 7 which is also pivotably mounted around a pivot axis. In the depicted embodiment, the rocker 6 and the lever 7 are pivotably mounted around one and the same pivot axis A6, although their pivoting movements are different. More specifically, a rocker shaft 61 is rotatably mounted around its axis A6 on the bracket 31. The rocker 6 is secured to the rocker arm shaft 61 whereas the lever 7 is able to rotate around the rocker arm shaft 61. A shown on FIGS. 2 and 3, the lever 7 is mounted adjacent a side face of the rocker 6 along axis A6.

(18) The rocker 6 comprises a driven end portion 62 adapted to cooperate with the cam 21, i.e. to follow the peripheral face of said cam 21. The driven end portion 62 can comprise a roller.

(19) The rocker 6 also comprises an actuating end portion 63 located opposite the driven end portion 62 relative to axis A6. As a result, when the driven end portion 62 contacts a bump of the cam 21, the rocker 6 is pivoted such that the driven end portion 62 is moved away from axis A2, substantially along axis Z, and the actuating end portion 63 is moved substantially along axis Z in the opposite direction. The actuating end portion 63 comprises a fixed activation member 64 and a sliding piston 8.

(20) The activation member 64, best shown in FIG. 6, has an axis A64 parallel to the valve axes A4, A5. The activation member 64 comprises a rod 641 the position of which, along Z, can be adjusted relative the rocker 6 by means of an adjusting screw 642. However, in operation, the activation member 64 is fixedly mounted on the rocker 6. The free end of rod 641 facing the cylinder block 3 is equipped with a pad 643 through a ball joint coupling. The activation member 64 is adapted to cooperate with a valve bridge 12 which cooperates with both valves 4, 5, so as to simultaneously open said valves 4, 5 following the cooperation of the driven end portion 62 of the rocker 6 with the cam main bump 210. The valve bridge 12 forms a valve opening actuator, and extends substantially perpendicularly to axes A4 and A5.

(21) The piston 8 has an axis A8 parallel to the valve axes A4, A5. The piston 8 is housed in a chamber 81 of the rocker 6, and can slide inside said chamber 81 along axis A8. The piston 8 comprises a member 82 protruding towards the cylinder block 3. In the depicted embodiment, the piston axis A8 is aligned with the inner valve axis A4. An opening member 40 secured to the valve 4 is slidably engaged in a hole 13 arranged in the valve bridge 12. The opening member 40 is operable by the piston 8, so that the piston 8 is able to open only the inner valve 4, following the cooperation of the driven end portion 62 of the rocker 6 with a bump of the cam 21, as will be explained later. More specifically, as it will be explained below in more detail, the piston 8 is slidably mounted relative the rocker 6, inside chamber 81, between: a retracted position (FIG. 9), in which a gap g1 is provided between the piston 8 and the opening member 40 of valve 4, thus preventing the piston 8 to open the valve 4 when the driven end portion 62 of the rocker 6 contacts an auxiliary bump 211, 212 of the cam 21 (FIGS. 10b, 11b, 12b, 13b, 14b, 15b); and an extended position (FIGS. 8, 10a), in which gap g1 is reduced to g2, i.e. the end of piston 8 has come closer to the opening member 40 of valve 4, thus allowing said piston 8 to open valve 4 when the driven end portion 62 contacts an auxiliary bump 211, 212 of the cam 21. In an embodiment, the piston 8 allows activating an engine brake function when it is in its extended position.

(22) The rocker 6 comprises a fluid circuit for providing a fluid, such as pressurized oil, to chamber 81, in order to cause the piston 8 to move from its retracted position to its extended position. The fluid circuit is internally arranged in rocker 6.

(23) In the shown embodiment, rocker shaft 61 is hollow and defines a duct 611 (FIG. 3) which is connected to a non-shown fluid tank, and to the chamber 81 housing piston 8, via a check valve 97 (FIG. 6). When the engine switches to engine brake mode, check valve 97 is opened so that fluid can flow from duct 611 to the inside of rocker 6 and subsequently to the chamber 81 so as to induce a pressure raise and cause piston 8 to be moved towards its extended position.

(24) The fluid circuit comprises a main duct 103 which is connected to the duct 611 inside rocker shaft 61 via an inlet duct 102 (FIG. 8), and which fluidly links check-valve 97 with the chamber 81. Main duct 103 opens on the outside of rocker 6 and fluid is prevented from going out of rocker 6 by a shutter element 105 screwed into a threaded portion of main duct 103. The main duct successively comprises an enlarged portion 114 (FIG. 6), an intermediate portion 116, and an outlet portion 118 opening in the camber 81.

(25) A seat element 107 is press-fitted into main duct 103, in intermediate portion 116. A ball 109 of check-valve 97 is adapted to cooperate with seat element 107 so as to block passage of fluid from piston chamber 81 back to duct 611, and thus maintain piston 8 in its extended position when the piston 8 is pushing the opening member 40. Ball 109 is biased towards seat element 107 by a spring 111 arranged in the outlet portion 118, and therefore tends to close the check-valve 97. When no control pressure comes from duct 611, ball 109 is kept in open position by a plunger 110 spring-biased by a spring 112 arranged in the enlarged portion 114, the action of the spring 112 being superior to the action of spring 111. The inlet duct 102 is connected to the enlarged portion 114, in an area called chamber 113 which is located on the side of the plunger 110 opposite the spring 112. In other words, fluid coming from duct 611 first flows into chamber 113.

(26) The rocker 6 also comprises a reset circuit for draining the fluid out of the chamber 81 of fluid circuit to allow the piston 8 to move towards its retracted position. The reset circuit comprises a by-pass duct 115 (FIGS. 6 to 9) which originates from main duct 103, more specifically from the outlet portion 118 of main duct 103, i.e. between the ball 109 and the chamber 81, and which opens on the outside of rocker 6, to the rocker shaft 61. In the by-pass duct 115 is arranged a reset valve 99 which is mounted relative to the rocker 6. Thus, an upstream portion 115a of the by-pass duct 115 is defined between the main duct 103 and the reset valve 99, and a downstream portion 115b of the by-pass duct 115 is defined between the reset valve 99 and the outside of rocker 6.

(27) The reset valve 99 is distinct from the check valve 97, and is adapted to rotate around its axis A99 which is parallel to axis A6. The reset valve 99 comprises an inside passage 98 for allowing fluid communication between the upstream portion 115a and the downstream portion 115b of the by-pass duct 115. Thus, reset valve 99 is rotatably mounted relative to the rocker 6 between an inactive position (FIG. 8), in which the main duct 103 and the downstream portion 115b of the by-pass duct 115 are not in fluid communication, and an active position (FIG. 9) in which the reset valve 99 opens the by-pass duct 115 so that the fluid can be drained out of the fluid circuit. The inside passage 98 can be a hollow sector, as shown on FIG. 8 for example, or can comprise two orthogonal bores, as shown on FIGS. 10b, 11b, 12b, 13b. Other implementations can be envisaged.

(28) The lever 7 has a driven end portion 72 adapted to cooperate with the reset cam 26, i.e. to follow the peripheral face of said cam 26. In an embodiment, the driven end portion 72 comprises a leg which protrudes substantially radially away from the pivot axis A6, the free end of said leg 72 being adapted to be in contact with the reset cam 26.

(29) The lever 7 also comprises an actuating end portion 73 for rotating the reset valve 99 from its inactive position towards its active position following the cooperation of the lever driven end portion 72 with the bump 260 of the reset cam 26. In the depicted embodiment, the lever 7 comprises a ring-shaped portion 74 engaged around the rocker shaft 61, and from which protrudes the leg 72. The ring-shaped portion 74 has a cylindrical outer surface on which is provided the actuating end portion 73. More specifically, in an embodiment, said cylindrical outer surface is provided with teeth 75 extending parallel to axis A6.

(30) An elastic member 71, such as represented in FIG. 2, or an elastic member 11, such as represented in FIG. 1, may be provided to ensure the driven end portion 72 is maintained in contact with the reset cam 26. In an embodiment, as shown in FIG. 2, the elastic member 71 can be configured as a leaf having one portion fastened to the leg 72 of lever 7 and one portion secured to the bracket 31. In an alternative, as shown in FIG. 1, the elastic member 11 can be configured as a latch pushing a pin 77 of the lever 7, wherein the pin 77 extends in parallel to the axis A6 and extends from the ring-shaped portion 74.

(31) Moreover, the reset valve 99 comprises a rod 91 (FIG. 7) which protrudes outside the rocker 6 towards the lever 7, parallel to axis A6. Said rod 91 is provided with teeth 95 extending parallel to axis A6. The teeth 75 of the lever 7 and the teeth 95 of the reset valve 99 form rotational coupling means between the lever 7 and the reset valve 99.

(32) Thus, when the leg 72 is in contact with the reset cam 26, not on the bump 260, the lever 7 is in the position shown on FIG. 4, and the reset valve 99 is in the inactive position shown on FIG. 8. When the leg 72 is in contact with the bump 260 of the reset cam 26, the lever 7 has pivoted around axis A6 to the position shown on FIG. 5.

(33) Consequently, via the rotational coupling means, the lever 7 has caused the reset valve 99 to rotate towards its active position shown on FIG. 9.

(34) The rotational coupling means are configured to provide a transmission ratio greater than 1. To ensure an adequate operation of the valve actuation system S in a limited space, the transmission ratio can range from 2 to 15, preferably from 3.6 to 9, said transmission ratio being for example around 5.5.

(35) For example, the valve actuation system S can be dimensioned as follows: radial distance between axis A6 and A99: around 35 mm; pitch radius of rod 91 with teeth 95: around 5.5 mm; pitch radius of ring-shaped portion 74 of lever 7, with teeth 75: around 30 mm; gear module: around 1.2.

(36) In an embodiment, a 10° rotation of lever 7 can lead to a 54° rotation of the reset valve 99, which corresponds to a transmission ratio of 5.4. The maximum rotation of the lever 7 can be around 15°.

(37) With the above described arrangement, on each turn of camshaft 2: cooperation between the main bump 210 of cam 21 and driven end portion 62 of roller 6, on the one hand, and between activation member 64 and valve bridge 12, on the other hand, generate opening of valves 4 and 5 during the corresponding operating phase of the internal combustion engine (exhaust phase); when the engine brake mode is activated, i.e. when the exhaust pipe has been closed by a flap manifold (not represented) located in the exhaust pipe downstream from the turbine of the turbocharger and when the piston 8 has been moved by pressurized fluid towards its extended position, cooperation between the auxiliary bumps 211, 212 of cam 21 and driven end portion 62 of roller 6, on the one hand, and between piston 8 and opening member 40 of valve 4, on the other hand, generate additional and limited openings of valve 4 only, so as to perform an engine brake function at two precise moments during operation of engine; cooperation between the bump 260 of reset cam 26 and driven end portion 72 of the lever 7, on the one hand, and between teeth 75 of the lever 7 and teeth 95 of the reset valve 99, on the other hand, causes opening of the check valve and consequently draining of the fluid circuit, i.e. movement of the piston 8 back to its retracted position.

(38) The dedicated reset cam 26 is adapted to create a relative movement of the lever 7, and thus of the reset valve 99, with respect to the corresponding rocker 6. This relative movement is nevertheless coordinated with the movement of the rocker 6 with respect to the engine housing, so that the reset function is performed at a selected given time within the opening/closing cycle of the valves 4 and 5.

(39) When the engine brake function is not activated (FIG. 9), check valve 97 is in opened position, due to action of the spring biased plunger 110, and piston 8 is retracted in chamber 81. A gap g1 is provided between member 82 of piston 2 and the opening member 40 of valve 4. The driven end portion 62 is in contact with the peripheral face of said cam 21. When the driven end portion 62 comes in contact with one of the auxiliary bump 211, 212 of cam 21, the rocker 6 pivoting movement is not sufficient, because of gap g1, to make member 82 come in contact with opening member 40. The valve opening movement thus only results from the cooperation of activation member 64 and valve bridge 12, following the contact between the rocker 6 and the main bump 210 of cam 21.

(40) The way the invention operates when the engine brake mode is activated, on each turn of camshaft 2, will be described with reference to FIGS. 10a-15b which show the valve actuation system Sat various moments of the engine cycle. FIGS. 10a, 11a, 12a, 13a, 14a, 15a show the position of the lever 7 cooperating with reset cam 26, while FIGS. 10b, 11b, 12b, 13b, 14b, 15b show the position of the rocker 6 cooperating with cam 21 at the respective corresponding moments.

(41) On FIGS. 10a and 10b, the roller 62 of rocker 6 is in contact with the base radius portion of cam 21, and the leg 72 of lever 7 is in contact with the base radius portion of reset cam 26. As piston 8 has moved towards its extended position, because the engine brake mode has been activated, gap g1 is reduced to g2, which is lower than the gap g3 provided between the activation member 64 and the valve bridge 12. Piston 8 is thus ready to cooperate with opening member 40 to open valve 4 when roller 62 comes into contact with one auxiliary bump 211, 212. Reset valve 99 is inactive.

(42) Camshaft 2, cam 21 and reset cam 26 rotate together around axis A2 according to arrow R shown on FIGS. 10a-15b.

(43) In the phase illustrated on FIGS. 11a and 11b, the roller 62 is in contact with one auxiliary bump 211 of cam 21. As a result, rocker 6 pivots and piston 8 pushes opening member 40, causing valve 4 to be slightly opened, to perform an engine brake function. Check valve 97 is closed. Gap g3 has been reduced but a clearance still exists, meaning that activation member 64 and valve bridge 12 do not cooperate. The lever 7 has not pivoted as leg 72 is still in contact with the base radius portion of reset cam 26. Therefore, reset valve 99 is still in its inactive position.

(44) When the roller 62 has passed auxiliary bump 211 it is in contact with the base radius portion of cam 21. Check valve 97 re-opens.

(45) As rotation of camshaft 2 continues, the roller 62 can come in contact with a further auxiliary bump 212 of cam 21 (this phase not being illustrated).

(46) In the position shown in FIGS. 13a and 13b, as roller 62 of rocker 6 comes in contact with the main bump 210 of cam 21, it is pivoted according to a greater range, causing activation member 64 to push the valve bridge 12, and to fully open both valves 4, 5, to perform the exhaust phase of the engine cycle. Springs 41 and 51 are compressed. Check valve 97 is closed.

(47) As shown on FIGS. 14a and 14b, while the roller 62 is progressively coming back in contact with the base radius portion of cam 21, leg 72 of lever 7 remains in contact with the bump 260 of reset cam 26. Indeed, the bump 260 has angular range that angularly extends beyond the main bump 210 of cam 21 and up to a corner 261 of the bump 260. It results from this difference that the rocker 6 rotates with respect to the lever 7, in other words an angular offset is created between the rocker 6 and the lever 7, causing the reset valve 99 to begin to rotate, in function of the pre-determined transmission ratio between the lever 7 and the reset valve 99, around axis A99, towards its active position.

(48) The reset valve 99 begins to open whereas the check valve 97 is still closed and the reset valve 99 reaches its active position, preferably before the roller 62 of rocker 6 comes in contact with the base radius portion of cam 21. As soon as the reset valve 99 begins to open, the fluid circuit starts being drained through the by-pass duct 115 and piston 8 moves back to its retracted position.

(49) Finally, as shown on FIGS. 15a and 15b, the reset valve 99 and the by-pass duct 115 are still opened, but the leg 72 is progressively coming back in contact with the base radius portion of reset cam 26 reducing the angular offset between the rocker 6 and the lever 7. The reset valve 99 is thus rotated towards its inactive position and the piston 8 is moved towards its extended position by fluid pressure inside the fluid circuit. The valve actuation system is then ready for another cycle.

(50) FIG. 16 shows the valve lifts as a function of the camshaft rotation, namely: the inlet valve lift; the outer exhaust lift (valve 5); the inner exhaust lift (valve 4).

(51) CP1 is the cam position corresponding to auxiliary bump 211: owing to the slight opening of valve 4, more air is added in the cylinder chamber at the beginning of the compression phase. CP2 is the cam position corresponding to auxiliary bump 212: owing to the slight opening of valve 4, air is decompressed out of the cylinder chamber in the decompression phase, just before the top dead centre (TDC).

(52) Owing to the lever 7 and its specific movement as previously described, the reset valve 99 allows closing the inner exhaust valve 4 at the same time as the outer exhaust valve 5, i.e. causes an asymmetric movement profile of valve 4. As a result, overlap O is reduced as schematically illustrated by arrow O on FIG. 15. Reducing overlap, i.e. the time period when both the intake and exhaust valves are open, allows improving the engine brake effect.

(53) It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.