Patent Application
20050011480
This application claims the priority of German application 103 32 927.7, filed Jul. 19, 2003, the disclosure of which is expressly incorporated by reference herein.
The present invention concerns a valve drive for an internal combustion engine including a camshaft, and a sliding cam device equipped with cam paths lying next to each other with different cam forms and hoisting curves which function together with actuation elements equipped with control pins for adjustment of the sliding cam device.
A valve drive for an internal combustion engine known from European publication EP 0 798 451 B1 comprises a camshaft with a sliding cam device. The sleeve-type sliding cam device located on the camshaft is equipped with hoisting curves at a distance and cam paths lying next to each other with different cam forms. The hoisting curves work together with actuation elements equipped with control pins for the adjustment of the sliding cam device. This valve drive offers important capabilities in order to realize a highly effective variable valve control with comparably simple means with the goal to improve its performance and consumption.
It is one object of this invention to design a valve drive of this type in such a way that the sliding cam device forms a model construction and switch functions of the different cam paths that are executed via the control pins by actuation elements and a hoisting curve can be performed quickly, safely and exactly.
This object is achieved according to the invention through providing at least one of the hoisting curves of the sliding cam device equipped with the cam paths with different hoisting curve sections for an engaged control pin of a corresponding actuation element. Additional characteristics further developing the invention are specified in dependent claims.
Advantages achieved by this invention include assurance, thanks to the sliding cam device with the hoisting curves having various hoisting curve sections, of a smooth and, therefore, functionally optimal adjustment course of the sliding cam device for the switching of different cam paths. Here the different hoisting curve sections can be represented without any difficulties in the hoisting curves. The sliding cam device with ring elements is a component that can be manufactured by reasonable means, whereby the ring can easily be incorporated into the hoisting curves.
Finally, it is possible to manufacture a sliding cam hub of the sliding cam device and the ring elements in one piece, although assembling the sliding cam hub and the ring elements from several parts is also conceivable.
An embodiment of the invention is shown in the drawings and is described in greater detail below.
Only the valve drive 2 with inlet valves 3 and 4 and outlet valves 5 and 6 (four-valve technology) are represented of an internal combustion engine 1 suited for installation into a motor vehicle, which valves are each located above the combustion chamber of a cylinder, the latter not being represented. A camshaft 6′ driven by a crankshaft actuates the inlet valves 3 and 4 that are surrounded by the valve springs 7 and 8 with an interposition of a roller-type cam follower 9. The camshaft 6′ and the inlet valves 3 and 4 function as a type of variable valve control. For this purpose, the camshaft 6′ is equipped with a sleeve-type sliding cam device 10 that is located on the camshaft 6′ axially mobile in the direction A-A, but is connected torsion-resistant with the latter whereby the sliding cam device 10 functions with the interposition of a positive hub connection 11 that is a multiple groove profile or a serration profile (See
The sliding cam device 10 is equipped with three cam paths 12, 13 and 14 with different cam forms Ni, Nii and Niii that lie next to each other and are combined in a cam block 15. The cam block 15 is bounded by the hoisting curves 16 and 17 on both sides. The actuation elements 22, 23, 24, and 25 having control pins 18, 19, 20 and 21 are used for the adjusting the sliding cam device 10 on the camshaft 6 (which could, for example, be of an electromagnetic or hydraulic type) that are located radially to the sliding cam device 10. Depending on the circuitry of one of the cam paths 12, 13 or 14, the control pins 18, 19, 20 or 21 are engaged with the hoisting curves 16 and 17 that can be formed, for example as U-shaped recesses 26 and 27 as in
The hoisting curves 16 and 17 of the sliding cam device 10 carrying the cam paths 12, 13 and 14 show different hoisting curve sections Hks for the engaged control pins 18, 19, 20 and 21. The hoisting curb sections Hks of the hoisting curves 16 and 17 are formed according to the outer circumferences of the sliding cam device shown in
It can be seen from
After starting the internal combustion engine 1, one of the cam paths 12, 13 or 14 will actuate the roller-type cam follower 9 and with it the inlet valves 3 and 4. Depending on the parameter or the revolution drive pedal position or such of the internal combustion engine 1, the variable valve control is actuated, meaning the actuation elements 22, 23, 24 or 25 are activated and one of the control pins 18, 19, 20 or 21 engages with the cutouts 26 or 27, which leads to an axial movement of the sliding cam device in the direction A-A based on the adjustment section 30 and to a defined switch of one of the cam paths 12, 13 or 14.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 103 32 927.7 | Jul 2003 | DE | national |
