VALVE TRAIN FOR AN INTERNAL COMBUSTION ENGINE

Abstract

A valve train for an internal combustion engine is provided. The valve train includes at least one rocker arm. The at least one rocker arm is mounted at a bearing. Further, the at least one rocker arm can be moved around the bearing by an actuating element. The valve train also includes at least one valve actuating element, wherein the at least one valve actuating element can be moved by the at least one rocker arm. At least one valve can be actuated by this movement of the at least one valve actuating element. A fluid element is arranged between the at least one valve actuating element and the at least one rocker arm. 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.

Claims

1. A valve train for an internal combustion engine, comprising: at least one rocker arm, wherein the at least one rocker arm is mounted at a bearing, and wherein the at least one rocker arm can be moved around the bearing by an actuating element; at least one valve actuating element, wherein the at least one valve actuating element can be moved by the at least one rocker arm, and wherein at least one valve of an internal combustion engine can be moved by this movement of the at least one valve actuating element; and a fluid element arranged 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, and wherein a volume of the fluid in the at least one cavity can be varied by varying a position of the at least one valve actuating element relative to the at least one rocker arm.

2. The valve train for the internal combustion engine according to claim 1, wherein the at least one cavity is in fluid communication with a fluid supplier through a conduct.

3. The valve train for the internal combustion engine according to claim 2, wherein the conduct is a bore arranged in the rocker arm.

4. The valve train for the internal combustion engine according to claim 2, wherein 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 a fluid supply.

5. The valve train for the internal combustion engine according to claim 4, wherein a piston is used as the at least one valve actuating element.

6. The valve train for the internal combustion engine according to claim 1, wherein 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.

7. The valve train for the internal combustion engine according to claim 2, wherein the conduct of the at least one cavity can be closed so that the 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.

8. The valve train for the internal combustion engine according to claim 1, further comprising at least one valve bridge provided for actuating at least two valves, wherein the at least one cavity is arranged between the at least one valve bridge and the at least one valve.

9. The valve train for the internal combustion engine according to claim 2, further comprising a conduct arranged in the at least one valve bridge to connect the at least one cavity with the fluid supplier.

10. The valve train for the internal combustion engine according to claim 9, wherein the conduct can be closed at least partially according to a position of the at least one valve bridge.

11. The valve train for the internal combustion engine according to claim 3, wherein the bearing has a shaft, wherein the bearing allows a rotational movement of the at least one rocker arm around the shaft, wherein a lubrication is provided between the shaft and the at least one rocker arm, and wherein the conduct connects the at least one cavity with the bearing.

12. The valve train for the internal combustion engine according to claim 1, further comprising at least one supply-pin supplying the at least one cavity with fluid.

13. The valve train for the internal combustion engine according to claim 11, wherein the at least one rocker arm or 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.

14. The internal combustion engine, comprising the valve train according to claim 1.

15. A method for operating the valve train according to claim 1, comprising: actuating at least one valve by at least one valve actuating element, with the at least one valve actuating element moved by at least one rocker arm; and adjusting a position of the at least one valve actuating element relative to the at least one valve by varying a volume of fluid in a fluid element, thereby automatically adjusting valve lash or automatically avoiding valve lash.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The disclosure will now be described in greater detail by means of the Figures in which:

[0032] FIG. 1 shows a first embodiment of the invention;

[0033] FIG. 2A shows a cross section of the particular embodiment of FIG. 1;

[0034] FIG. 2B shows the embodiment of FIG. 1 in more detail;

[0035] FIG. 3A shows the embodiment of FIG. 1 in a first position;

[0036] FIG. 3B shows the embodiment of FIG. 1 in a second position;

[0037] FIG. 4A shows a further particular embodiment of the invention in a first position;

[0038] FIG. 4B shows the particular embodiment of FIG. 4A in a second position;

[0039] FIG. 5A shows a particular embodiment of the invention in connection with variable valve timing;

[0040] FIG. 5B shows a particular embodiment of the invention in connection with variable valve timing;

[0041] FIG. 6A shows an exemplary embodiment, wherein a valve bridge is provided; and

[0042] FIG. 6B shows an embodiment of the invention, wherein a valve bridge and a supply-pin are provided.

DETAILED DESCRIPTION

[0043] FIG. 1 shows a first 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 in 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.

[0044] According to the disclosure 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] In this embodiment a lubrication fluid from the bearing 3 is used for the cavity 8. In particular the lubrication fluid is oil.

[0051] 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.

[0052] 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.

[0053] 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 FIGS. 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.

[0054] 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.

[0055] FIG. 3A shows the described embodiment of FIG. 1 and FIG. 2 in a first (non-actuated) position. FIG. 3B sows the embodiment of FIGS. 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.

[0056] FIGS. 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.

[0057] FIG. 4A shows a first 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.

[0058] 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.

[0059] FIGS. 5A and 5B 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 FIGS. 1 to 3B.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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 FIGS. 5A and 5B) by rotating the supply-pin 24 around its own axis of symmetry.