VALVE TRAIN FOR AN INTERNAL COMBUSTION ENGINE

Abstract

 Valve train (1) for an internal combustion engine, comprising:
- at least one rocker arm (2), wherein the at least one rocker arm (2) is mounted at a bearing (3) and wherein the at least one rocker arm (2) can be moved around the bearing (3) by an actuating element (4)
- at least one valve actuating element (5), wherein the at least one valve actuating element (5) can be moved by the at least one rocker arm (2) and wherein at least one valve (6) can be actuated by this movement of the at least one valve actuating element (5),
wherein a fluid element is arranged between the at least one valve actuating element (5) and the at least one rocker arm (2), wherein
- the fluid element comprises at least one cavity (8) for a fluid
- the volume of the fluid in the at least one cavity (8) can be varied by moving a piston and
- the at least one valve actuating element (5) constitutes or is mounted on the piston.

Description

[0001] This invention relates to a valve train for an internal combustion engine with the features of the preamble of claim 1, an internal combustion engine comprising such a valve train and a method for operating a valve train.

[0002] Internal combustion engines, as known from the state of the art, use valve elements to control the intake of fuel and gas to the combustion engine. After the combustion process, wherein the fuel air mixture is burned, further valves are used to control the outlet of exhaust gases produced within the combustion.

[0003] These valves have a clearance between valve and valve seat because during engine operation the valves heat up. On account of the thermal expansion the valve stretches and the clearance between valve and valve seat ensures a save function of the valve train. During the life time of the internal combustion engine the valve seats are strongly loaded by high temperatures and passing by particles. This passing by particles cause abrasive wear on the one side and do deposits on the other hand. The clearance between valve and valve seat is increased or decreased during engine life time. This clearance is also called valve lash. If the clearance between valve and valve seat is too large or to little the fuel consumption increases, the performance decreases, the emissions increase, the compression decreases and/or the temperature of the valve increases until they damage just to name a few examples.

[0004] To ensure that the valve lash does not decrease too much it is necessary to adjust the valve lash after a given period of operating hours.

[0005] This valve lash adjustment requires a great effort in time because each valve has to be adjusted by hand with the help of a feeler gauge. In use of large combustion engines, comprising a plurality of combustion chambers, wherein each combustion chamber is provided with a plurality of valves, the valve lash adjustment can take several hours.

[0006] It is an object of the invention to provide a valve train for an internal combustion engine and an internal combustion engine comprising such a valve train with extended maintenance periods, in other words a valve train which needs a smaller amount of or no maintenance work regarding the valve lash adjustment.

[0007] This object is being accomplished by a valve train for an internal combustion engine having the features of claim 1, by an internal combustion engine comprising such a valve train according to claim 13 and an method for operating a valve train according to claim 14. Advantageous embodiments of the invention are defined in the dependent claims.

[0008] According to the invention there is provided a fluid element between the at least one valve actuating element and the at least one rocker arm, wherein

• the fluid element comprises at least one cavity for a fluid
• the volume of the fluid in the at least one cavity can be varied by moving a piston and
• the at least one valve actuating element constitutes or is mounted on the piston.

Because the valve actuating element can expel fluid from the cavity, the increase in valve wear is counteracted automatically. This system does not have valve lash any more, as valve lash is being replaced by the expelling of fluid. The piston and the cavity are acting like a hydraulically piston/cylinder system.

[0009] The at least one valve actuating element can preferably be a configured to move translationally. Alternatively it can be configured to move in a rotating manner.

[0010] It can be provided that the at least one cavity is in fluid communication with a fluid supplier through a conduct. In a particularly preferred variant it can be provided the conduct is a bore arranged in the rocker arm. It can also be provided that an orifice and a drain are provided instead of the bore.

[0011] It can also be provided that the fluid is a lubricant, preferably oil. In addition it is also possible that the at least one rocker arm is actuating more than one valve.

[0012] In a particularly preferred embodiment it can be provided that the at least one cavity is arranged at least partially, preferably fully, in the at least one rocker arm. It can also be provided that the piston is used as the at least one valve actuating element.

[0013] In a preferred embodiment of the invention it can be provided that at least one cam shaft is provided, wherein the cam shaft has at least one cam and is rotatable. It can also be provided that at least one cam follower is provided, which cam follower is arranged at the at least one cam, which converts a rotational movement of the cam shaft into a translational movement, which translational movement can be transferred by the cam follower, which works as actuating element or by use of actuating element to transfer, to the rocker arm.

[0014] In accordance with a particularly preferred embodiment it can be provided that a lubrication of the at least one bearing is provided, wherein a fluid for the lubrication of the at least one bearing is provided, which corresponds to the fluid used in the at least one cavity and wherein the lubrication of the bearing serves as the fluid supply.

[0015] Alternatively or additionally it can also be provided that the volume of the fluid in the at least one cavity can be varied in a non-actuated position of the at least one valve.

[0016] In a particularly preferred variant it can be provided that the conduct of the at least one cavity can be closed in such a way, that a volume of the fluid in the at least one cavity can be held essentially constant in an actuated and/or during an actuating movement of the at least one valve.

[0017] In a preferred embodiment of the invention it can be provided at least one valve bridge is provided for actuating at least two valves, wherein the at least one cavity is preferably arranged between the at least one valve bridge and the at least one valve. It can also be provided that the at least one cavity is arranged at least partially, preferably fully, in the at least one valve bridge. In a particularly preferred embodiment it can be provided that a conduct is arranged in the at least one valve bridge to connect the at least one cavity with the fluid supplier. It can also be provided that the conduct can be closed at least partially according to a position of the at least one valve bridge, preferably can be closed in an actuated position of the valve bridge. In this case the activated position is an open position of the at least one valve and the non-activated position is a closed position of the at least one valve.

[0018] In a preferred embodiment of the invention it can be provided that the at least one bearing has a shaft, wherein the bearing allows a rotational movement of the at least one rocker arm around the shaft. This means that the shaft stays in his position (does not rotate) and the at least one rocker arm (mounted on the shaft) could rotate around the shaft axis. In accordance with a particularly preferred embodiment it can be provided that a lubrication is provided between the shaft and the at least one rocker arm, wherein the conduct connects the at least one cavity with the bearing.

[0019] It can also be provided that at the at least one conduct, connecting the at least one cavity with a reservoir, has at least one check valve, wherein the check valve only allows a unidirectional fluid motion.

[0020] It can also be provided that the at least one recess is provided on a surface of the shaft, which is configured to

• connect in a fist position of the rocker arm relative to the shaft the at least one cavity with the lubrication of the bearing by the use of the conduct
• shut off in a second position of the rocker arm relative to the shaft the connection of the at least one cavity with the lubrication of the bearing by the use of the conduct to keep the volume of fluid in the at least one cavity essentially constant.

[0021] These positions (first and second position) are different positions, which can be done by the rocker arm by a rational movement around the shaft.

[0022] Alternatively or additionally it can also be provided that the at least one shaft recess on a surface of the shaft extends over a radial section. In accordance it can be provided that that the extending radial section of the shaft recess tapers axially and the shaft is movable axially with respect to the rocker arm.

[0023] In another example for an embodiment of the present invention a blocking element is provided centrally in the shaft. The shaft has in this embodiment a bore, connecting the blocking element with the at least one conduct leading to the at least one cavity. The blocking element can be moved from a first position to a second position, wherein the blocking element connects the at least one cavity in a first position with a reservoir/fluid supply and wherein the blocking element blocks (interrupts) the fluid communication between the at least one cavity and the reservoir/fluid supply. In a preferred embodiment the blocking element is a rotationally symmetric element arranged in the shaft, which can be rotated between a first and a second position.

[0024] In a particularly preferred variant it can be provided at least one supply-pin is provided, supplying the at least one cavity with fluid. It can be provided that there is a supply pipe inside the supply-pin, supplying the at least one cavity with fluid. In a preferred embodiment of the invention it can be provided that the at least one rocker arm or the at least one valve bridge has at least one supply-pin plunging recess, in which the at least one supply-pin can plunge at least partially. It can also be provided that that the at least one supply-pin serves as fluid supplier. It can be provided that

• in a fist position of the at least one rocker arm or the at least one valve bridge relative to the supply pin the at least one cavity is connected by the conduct with the supply-pin
• in a second position of the at least one rocker arm or the at least one valve bridge relative to the supply pin the at least one cavity is not linked with the supply-pin.

[0025] Alternatively or additionally it can also be provided that the supply-pin is a rotationally symmetrical element and comprises a connecting section between the supply-pin and the at least one rocker arm or the at least one valve bridge and an opening thereon extending in a moving direction of the at least one rocker arm or the at least one valve bridge. By rotating the rotationally symmetrical supply pin clock wise or anti clock wise a duration can be varied, wherein the at least one cavity is connected with the supply/reservoir. It can also be provided that the opening tapers in a direction normal to a moving direction of the at least one rocker arm or the at least one valve bridge and the at least one supply pin is movable in the direction normal to the moving direction of the at least one rocker arm or the at least one valve bridge.

[0026] Furthermore protection is sought for an internal combustion engine, preferably a stationary gas engine comprising a valve train according to the invention

[0027] Protection is also sought for a method for operating a valve train, wherein at least one valve is actuated by at least one valve actuating element and the at least one valve actuating element is moved by at least one rocker arm, wherein the position of the at least one valve actuating element relative to the at least one valve is adjusted by varying a volume of fluid in a fluid element and thereby automatically adjusting valve lash or automatically avoiding valve lash.

[0028] The invention will now be described in greater detail by means of the Figures in which:

Fig. 1

shows a fist embodiment of the invention,

Fig. 2a

shows a cross section of the particular embodiment of Fig. 1,

Fig. 2b

shows the embodiment of Fig. 1 in more detail,

Fig. 3a

shows the embodiment of Fig. 1 in a first position,

Fig. 3b

shows the embodiment of Fig. 1 in a second position,

Fig. 4a

shows a further particular embodiment of the invention in a first position,

Fig. 4b

shows the particular embodiment of Fig. 4a in a second position,

Fig. 5a

shows a particular embodiment of the invention in connection with variable valve timing,

Fig. 5b

shows a particular embodiment of the invention in connection with variable valve timing,

Fig. 6a

shows an exemplary embodiment, wherein a valve bridge is provided,

Fig. 6a

shows an embodiment of the invention, wherein a valve bridge and a supply-pin are provided.

[0029] Fig. 1 shows a fist embodiment of the invention. The shown valve train 1 for an internal combustion engine comprises a rocker arm 2 mounted at a bearing 3. The rocker arm 2 can be moved around the bearing 3 by an actuating element 4. The rocker arm 3 comprises further a valve actuating element 5, which is configured to actuate a valve 6. For reasons of simplicity the valve 6 is not shown Fig. 1. The valve actuating element 5 can be moved by the rocker arm 2 and the at least one valve 6 of the internal combustion engine can be moved by the valve actuating element 5. The bearing 3 is mounted rotationally movable on a shaft 7.

[0030] According to the invention there is also provided a cavity 8 for fluid. In this embodiment this cavity 8 is released as a bore in the rocker arm 2. Together with the valve actuating element 5 in the form of a piston this cavity 8 delimits a volume, which is filled by a fluid. The volume of the cavity 8 can be varied by moving the valve actuating element 5 relative to the rocker arm 2. The cavity 8 is connected by a conduct 9 with the bearing 3 of the rocker arm 2.

[0031] The bearing 3 of the rocker arm 2 is used in this embodiment as fluid supplier. In this way fluid, which is used for the lubrication of the bearing 3, can be used in the cavity 8. The fluid supplier supplies fluid to the cavity 8. If fluid is passed back through the conduct 9 the fuel supplier is used as fluid reservoir. The conduct 9 is released as a bore in the rocker arm 3. The end of the bore, which forms the cavity 9, is closed by a grub screw 10.

[0032] The fluid communication of the cavity 8 with the bearing 3 through the conduct 9 can be cut off by a movement of the rocker arm 2 around the shaft 7, because the conduct 9 connected to the bearing 3 through the bore 11 in the shaft 7 of the bearing 3. If the rocker arm 2 moves rotationally relative to the shaft 7 and the bearing 3. Through such a rotation (in order to activate the valve 6) the conduct 9 is moved away from the supply bore 11. In this situation (where no fluid communication between cavity 8 and fluid supplier is given) the volume of the fluid in the cavity 8 cannot be varied and the valve actuating element 5 cannot be moved relative to the rocker arm 3.

[0033] On the other hand, when the rocker arm 3 is not actuated, and therefore rests in a position where the conduct 9 and the bore 11 are lined up, the fluid communication is present. E.g. through a spring action the actuating element can then be moved to a position without valve lash through a change of the volume of the fluid in the cavity 8.

[0034] In this way it is possible for the valve actuating element 5 to adjust a valve drift (caused by the wear of the valve seat) in a position, wherein the cavity 8 is in fluid communication with the fluid supplier. This position corresponds in this embodiment to a non-actuated position of the valve 6. In all other positions (an actuated or actuating position of the valve 6) a moving of the valve actuating element 5 relative to the rocker arm 3 is prevented by the blocking of the conduct 9, thereby allowing the actuation of the valve 6.

[0035] The cavity 8 is connected to the external environment by an orifice 12. The orifice 12 can be replaced by a sealing element to be installed after system de-airing/bleeding. This avoids special requirements on oil cleanliness if oils are used as fluid.

[0036] In this embodiment a lubrication fluid from the bearing 3 is used for the cavity 8. In particular the lubrication fluid is oil.

[0037] Fig 2a shows cross section of the particular embodiment of Fig. 1. This cross section shown by Fig. 2a gives an example how the lubrication fluid for the bearing 3 (which is also used in the cavity 8) can be supplied. The actuating element 4 contacts the push rod 14. This push rod 14 transmits an alternating transversal movement (created by a camshaft for example) to the actuating element 4. Furthermore the push rod 14 shown can be used as fluid supplier, wherein the push rod 14 has a central bore conveying lubrication fluid to the actuating element 4. The actuating element 4 does also have a central bore leading the lubrication fluid from the push rod 14 to a bore 13 in the rocker arm 2. This bore 13, placed in the rocker arm 2 finally supplies the lubrication fluid to the bearing 3.

[0038] In the embodiments shown by the figures the shaft 7 is fixed, i.e. not rotatable (per definition a pivot pin). The rocker arm 2 is pivoting around this pin.

[0039] Fig. 2b shows in more detail the bore 11 in the bearing 3 which can be used to cut off the fluid communication with the cavity 8. For this a recess 15 is provided on the surface of the shaft 7, which is configured to connect in a first position (shown by Fig 2b and 3a) of the rocker arm 2 relative to the shaft 7 the cavity 8 with lubrication of the bearing 3 by use of the conduct 9. In this example the bearing 3 is provided with a ring (shown in darker gray), which is fixed on the shaft 7 and has a bore 11.

[0040] But it also can be provided that the bearing 3 is released as a hydrostatic bearing, wherein no separate element would be used for the bearing 3, only the pressure of the lubrication would cause a separate layer of lubrication forming the bearing 3 (distance between rocker arm 2 and shaft 7). If the bearing 3 is done by a hydrostatic bearing (also a hydrodynamic bearing would be possible) the conduct 9 would have a tubular element between the inner wall of the rocker arm and the outer surface of the shaft. This would only allow a fluid connection between bearing 3 and cavity 8 if the conduct 9 (with his tubular element) would be positioned in alignment over the recess 15. In all other positions (when the conduct 9 is not positioned over the recess 15) there would be no fluid communication between bearing 3 and cavity 8.

[0041] Fig 3a shows the described embodiment of Fig. 1 and Fig. 2 in a first (non-actuated) position. Fig 3b sows the embodiment of Fig. 1 and 2 in a second (actuated) position. Therefor the rocker arm 2 is rotated around the shaft 7. In this second position of the rocker arm 2 relative to the shaft 7 the connection of the cavity 8 with the lubrication of the bearing 3 by the use of the conduct 9 is shut off to keep the volume of fluid in the at least one cavity 8 essentially constant.

[0042] Fig. 4a and 4b show a further exemplary embodiment of an inventive valve train 1. In this embodiment a helical valve 18 is provided inside the shaft 7. This helical valve 18 is connected to the bearing 3 by a bore 19, which is used as fluid reservoir. With a further bore 17 the helical calve is connected to a flexible pipe 16, which is located inside the conduct 9 and connects the bore 17/the helical valve 18 with the cavity 8.

[0043] Fig. 4a shows a fist position (a non-actuated position) of the helical valve 18 and the valve train 1, wherein the valve 6 of the internal combustion engine is closed. In this first position the of the rocker arm 3 relative to the shaft 7 the cavity 8 is connected with the fluid supply (in this example the bore 19 together with the bearing 3) through the conduct 9, more specifically through the flexible pipe 16 placed inside the conduct 9.

[0044] Fig. 4b shows a second position (an actuated or actuating position) of the helical valve 18 and the valve train 1, wherein the valve 6 of the internal combustion engine is opening or open. In this second position the rocker arm 2 and/or the helical valve 18 have been rotated around the shaft 7 (relative to Fig 4a). The connection between the cavity 8 and the fluid supply (in this example the bore 19 together with the bearing 3) through the conduct 9, more specifically through the flexible pipe 16 placed inside the conduct 9, has been shut off by the helical valve 18.

[0045] Fig. 5a and 5b are show an embodiment of the invention, wherein the recess 15 on the surface of the shaft 7 extends over a radial section and tapers axially. The shaft 7 is axially movably mounted with respect to the shaft 7 and the bearing 3. This gives the possibility of variable valve timing. An opening time of the valve 6 can be varied by moving the shaft 7 axially. In a position as shown in Fig. 5a the recess 15 has a small extension on the surface of the shaft 7. If the rocker arm 2 rotates around the shaft 7 from a first (non-actuated) position into a second (actuated or actuating) position this would correspond to the already described functionality of Fig. 1 to 3b.

[0046] But if the shaft is moved axially into a position as shown by Fig. 5b the fluid connection between the cavity 8 and the fluid supplier (in this case the bearing 3) through the conduct 9 can be extended from the first (non-actuated) position. This connection can be kept till the conduct 9 leaves the last position in alignment with the recess 15 through the rotational movement of the rocker arm 2 relative to the shaft 7 during an actuating movement. Even if the rocker arm 2 is at the start of the actuating movement in movement the valve 6 is still not moved, because fluid can still leak form the cavity 8 through the conduct 9 into the bearing 3 by the help of the recess 15. The valve 6 presses the valve actuating element 5 into cavity 8. So to say the movement of the rocker arm 2 is compensated by the movement of the valve actuating element 5 into the cavity 8 till the conduct 9 moves over the recess 15.

[0047] Fig. 6a shows an exemplary embodiment, wherein a valve bridge 20 is provided for actuating at least two vales 6. In this embodiment the cavity 8 is arranged in the valve bridge. The cavity 8 is closed in a similar way to the above described embodiments by a valve actuating element 5. The valve bridge 20 is activated by a rocker arm 2. Inside the valve bridge 20 a conduct 21 is provided to connect the cavity 8 with a fluid supplier (in this case the fluid supplier is a conduct 9 inside the rocker arm 2). The opening and shutting off of the connection between the cavity 8 and fluid supplier in Fig. 6a is performed according to the same principle as described in connection with Fig 4 or 5. A valve bridge guide 22 is provided to guarantee the position of the valve bridge 20. This valve bridge guide 22 can plunge into the valve bridge 20 depending on the actual position of the valve bridge 20.

[0048] Fig. 6b shows an embodiment, wherein the valve bridge guide 22 from Fig. 6a is used as supply-pin 24, supplying the cavity 8 with the help of the supply-pin conduct 25. This supply-pin conduct 25 leads in a non-actuated position (first position) of the valve bridge 20 into the conduct 21, which is connected to the cavity 8. If the valve bridge 20 is moved into an activated position the supply-pin 24 plunge into the valve bridge 20 and the connection between conduct 21 and supply-pin conduct 25 is shut off.

[0049] It can be provided that the supply-pin 24 is a rotational symmetrical element comprising an opening on a connection section between the supply-pin 24 and the at valve bridge 20 (as shown by the detail supply-pin cross section 23), extending in a moving direction of the valve bridge 20 and tapering in a direction normal to a moving direction of the valve bridge. In this way the valve opening times can be variated (as already explained in connection with Fig. 5a and 5b) by rotating the supply-pin 24 around its own axis of symmetry.

List of used reference signs:

[0050] 

1

valve train

2

rocker arm

3

bearing

4

actuating element

5

valve actuating element

6

valve

7

shaft

8

cavity

9

conduct

10

grub screw

11

bore

12

orifice

13

bore

14

push rod

15

recess

16

pipe

17

bore

18

helical valve

19

bore

20

valve bridge

21

conduct

22

valve bridge guide

23

supply-pin cross section

24

supply-pin

25

supply-pin conduct

Claims

1. Valve train (1) for an internal combustion engine, comprising:

- at least one rocker arm (2), wherein the at least one rocker arm (2) is mounted at a bearing (3) and wherein the at least one rocker arm (2) can be moved around the bearing (3) by an actuating element (4)

- at least one valve actuating element (5), wherein the at least one valve actuating element (5) can be moved by the at least one rocker arm (2) and wherein at least one valve (6) of an internal combustion engine can be moved by this movement of the at least one valve actuating element (5)

characterized in that a fluid element is arranged between the at least one valve actuating element (5) and the at least one rocker arm (2), wherein
the fluid element comprises at least one cavity (8) for a fluid,
wherein the volume of the fluid in the at least one cavity (8) can be varied by varying the position of the at least one valve actuating element (5) relative to the at least one rocker arm (2).

2. Valve train for an internal combustion engine according to claim 1, characterized in that the at least one cavity (8) is in fluid communication with a fluid supplier through a conduct (9).

3. Valve train for an internal combustion engine according to claim 2, characterized in that the conduct is a bore arranged in the rocker arm (2).

4. Valve train for an internal combustion engine according to any of claims 2 - 3, characterized in that a lubrication of the at least one bearing (3) is provided, wherein a fluid for the lubrication of the at least one bearing (3) is provided, which corresponds to the fluid used in the at least one cavity (8) and wherein the lubrication of the bearing (3) serves as the fluid supply.

5. Valve train for an internal combustion engine according to preceding claim, characterized in, that the piston is used as the at least one valve actuating element (5).

6. Valve train for an internal combustion engine according to any of the preceding claims, characterized in that the volume of the fluid in the at least one cavity (8) can be varied in a non-actuated position of the at least one valve (6).

7. Valve train for an internal combustion engine according to any of the claims 2 - 6, characterized in that the conduct (9) of the at least one cavity (8) can be closed in such a way, that a volume of the fluid in the at least one cavity (8) can be held essentially constant in an actuated and/or during an actuating movement of the at least one valve (6).

8. Valve train for an internal combustion engine according to any of the preceding claims, characterized in that at least one valve bridge (20) is provided for actuating at least two valves (6), wherein the at least one cavity (8) is preferably arranged between the at least one valve bridge (20) and the at least one valve (6).

9. Valve train for an internal combustion engine according to claim 2 as well as 8 characterized in, that a conduct (21) is arranged in the at least one valve bridge (20) to connect the at least one cavity (8) with the fluid supplier.

10. Valve train for an internal combustion engine according to claim 9, characterized in that the conduct (21) can be closed at least partially according to a position of the at least one valve bridge (20), preferably can be closed in an actuated position of the valve bridge (20).

11. Valve train for an internal combustion engine according to claim 3 and 5, characterized in that the at least one bearing (3) has a shaft (4), wherein the bearing (3) allows a rotational movement of the at least one rocker arm (2) around the shaft (4) and wherein a lubrication is provided between the shaft (4) and the at least one rocker arm (2), wherein the conduct (9) connects the at least one cavity (8) with the bearing (3).

12. Valve train for an internal combustion engine according to any of the preceding claims, characterized in, that at least one supply-pin (24) is provided, supplying the at least one cavity (8) with fluid.

13. Valve train for an internal combustion engine according to claim 11, characterized in, that the at least one rocker arm (2) or the at least one valve bridge (20) has at least one supply-pin plunging recess, in which the at least one supply-pin (24) can plunge at least partially.

14. Internal combustion engine, preferably a stationary gas engine comprising a valve train (1) according to any of the preceding claims.

15. Method for operating a valve train (1), in particular according to at least one of the claims 1 to 12, wherein at least one valve (6) is actuated by at least one valve actuating element (5) and the at least one valve actuating element (5) is moved by at least one rocker arm (2), characterized in that the position of the at least one valve actuating element (5) relative to the at least one valve (6) is adjusted by varying a volume of fluid in a fluid element and thereby automatically adjusting valve lash or automatically avoiding valve lash.

Drawing