Valve drive for an internal combustion engine

Abstract

A valve drive is suited for an internal combustion engine that has a camshaft with a sliding cam device. The sliding cam device is 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 the adjustment of the sliding cam device. For optimization of the valve track, at least one hoisting curve of the sliding cam device carrying the cam paths is equipped with different hoisting curve sections for the engagement of the control pin of the corresponding actuation element.

Description

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.

BACKGROUND AND SUMMARY OF THE INVENTION

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.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an inclined view of a valve drive of an internal combustion engine according to the invention with a slide cam device,

FIG. 2 illustrates a longitudinal section through the sliding cam device of FIG. 1,

FIG. 3 illustrates a section along line III-III of FIG. 2,

FIG. 4 illustrates hoisting curves of the sliding cam device, and

FIG. 5 illustrates a schematic detail X of FIG. 4 on a larger scale.

DETAILED DESCRIPTION OF THE INVENTION

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 FIG. 3).

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 FIG. 2.

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 FIGS. 4 and 5 and are connected through the inlet section 28, a first centering section 29, an adjustment section 30 and a second centering section 31 to the outlet section 32. An area of the cutouts 26 and 27 for the control pins 18, 19, 20 and 21 between the start of the inlet section 28 and the end of the second centering 31 is designated with AfdS as shown in FIG. 5. The inlet section 28 tapers off in the direction of the first centering station 29 like the funnel 33. A first adjustment section 34 is located upstream from the funnel 33. In addition, a locking section 35 and a second adjustment section 36 are located downstream from the second centering section 21. A locking device 37 serves for the correct positional arrangement of the cam paths 12, 13 and 14 in relation to the inlet valves 3 and 4 as seen in FIG. 2 comprising three radial grooves 39, 40 and 41 at the inner circumference plane 38 of the sliding cam device, whereby the camshaft 6′ is equipped with a cylindrical recess 42 for a locking ball 43 and a spiral spring 44 in the area of the grooves 39, 40 and 41.

It can be seen from FIG. 2 that ring elements are provided on both sides of the cam block 15 in the form of a cam hub 45 carrying the cam paths 12, 13 and 14, which protrude from the cam block 15. The hoisting curves 16 and 17 are located in the ring elements 46 and 47. Radial webs 48 and 49 of the ring elements 46 and 47 border on the cam paths 12, 13 and 14 of the cam block 15. The ring elements 46 and 47 and the cam hub 45 are made in one piece. Finally, it is also conceivable that the ring elements 46 and 47 and the cam hub can consist of several parts.

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.

Claims

1. A valve drive for an internal combustion engine comprising:

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,

wherein at least one of the hoisting curves of the sliding cam device equipped with the cam paths is equipped with different hoisting curve sections for an engaged control pin of a corresponding actuation element.

2. The valve drive according to claim 1, wherein the hoisting curve sections of the at least one of the hoisting curves are formed by an inlet section, a first centering section, an adjustment section and a second centering section.

3. The valve drive according to claim 2, wherein an outlet section is attached to the second centering section.

4. The valve drive according to claim 2, wherein the inlet section tapers off in the direction of the first centering section in the form of a funnel.

5. The valve drive according to claim 1, wherein the sliding cam device has a cam block forming a cam hub carrying the cam paths on both sides and equipped with ring elements as a type of a hollow body that protrude over the cam block.

6. The valve drive according to claim 5, wherein the ring elements are equipped with the hoisting curves.

7. The valve drive according to claim 5, wherein the ring elements include radial webs which border on the cam paths.

8. The valve drive according to claim 5, wherein the ring elements and the cam hub consist of one part.

9. The valve drive according to claim 5, wherein the ring elements and the cam hub are assembled from several parts.

10. The valve drive according to claim 6, wherein the ring elements and the cam hub consist of one part.

11. The valve drive according to claim 7, wherein the ring elements and the cam hub consist of one part.

12. The valve drive according to claim 6, wherein the ring elements and the cam hub are assembled from several parts.

13. The valve drive according to claim 7, wherein the ring elements and the cam hub are assembled from several parts.

14. An internal combustion engine comprising:

a valve drive having a camshaft and a sliding cam device equipped with cam paths lying next to each other with different cam forms and hoisting curves, and

actuation elements equipped with control pins adapted to function together with the hoisting curves for adjustment of the sliding cam device,

wherein at least one of the hoisting curves of the sliding cam device equipped with the cam paths is equipped with different hoisting curve sections for an engaged control pin of a corresponding actuation element.

15. The internal combustion engine according to claim 14, wherein the hoisting curve sections of the at least one of the hoisting curves are formed by an inlet section, a first centering section, an adjustment section and a second centering section.

16. The internal combustion engine according to claim 15, wherein an outlet section is attached to the second centering section.

17. The internal combustion engine according to claim 15, wherein the inlet section tapers off in the direction of the first centering section in the form of a funnel.

18. The internal combustion engine according to claim 14, wherein the sliding cam device has a cam block forming a cam hub carrying the cam paths on both sides and equipped with ring elements as a type of a hollow body that protrude over the cam block.

19. The internal combustion engine according to claim 18, wherein the ring elements are equipped with the hoisting curves.

20. The internal combustion engine according to claim 18, wherein the ring elements include radial webs which border on the cam paths.

21. The internal combustion engine according to claim 18, wherein the ring elements and the cam hub consist of one part.

22. The internal combustion engine according to claim 18, wherein the ring elements and the cam hub are assembled from several parts.