Patent Application
20200291830
This application claims priority to German Application No. DE 10 2019 203 429.2 filed on Mar. 13, 2019, the contents of which are hereby incorporated by reference in its entirety.
The present invention relates to a slotted guide comprising two guide tracks, which cross one another in a crossing region, for guiding a switching pin of a cam follower of a valve train. The invention furthermore relates to a valve train comprising a slotted guide of this type as well as to an internal combustion engine comprising a valve train of this type.
A generic slotted guide is generally used in the case of a valve train of an internal combustion engine, in the case of which the inlet times or the outlet times of an inlet or outlet valve are to be influenced. The switchover from a normal cam profile to a brake cam profile is also conceivable in this context, whereby a braking operation of an internal combustion engine equipped therewith can be controlled, To be able to thereby change between the different cam profiles, whereby a turn-off of a cylinder can, for example, also be made possible, a so-called displacement bolt system is often provided, in the case of which a switching pin of a cam follower is guided in a generic slotted guide comprising two guide tracks, which cross one another in a crossing region.
It may be disadvantageous thereby, however, that in the case of functionally optimized cam contours, the ejection of the switching pin and thus the transfer into the other guide track are made more difficult or are not possible at all. The reason for this is the reduced time or distance, respectively, which is available in the case of a slotted guide comprising two guide tracks, which cross one another. This is so, because the ejection of the switching pin has to thereby take place immediately after the lift switch-over, whereby the tilt lever, together with switching pin, is already in an upwards movement immediately after the profile switch-over in the case of a functionally optimized selection of a brake cam profile, which prevents the ejection of the switching pin from the respective guide track comprising a conventional ejection contour.
The present invention thus deals with the problem of specifying an improved or at least an alternative embodiment for a slotted guide of the generic type, which in particular overcomes the disadvantages known from the prior art.
This problem is solved according to the invention by means of the subject matter of the independent claim(s). Advantageous embodiments are subject matter of the dependent claims.
The present invention is based on the general idea of providing a radial projection at the slotted guide, which protrudes from the actual switching contour plane and which newly creates, increases, or extends, respectively, an ejection contour by means of this material application, whereby an ejection of the switching pin is also made possible in response to an upwards movement of the tilt lever or of the cam follower, respectively, thus in the case of a smaller immersion depth of a switching pin into the corresponding guide track. The slotted guide according to the invention thereby has two guide tracks, which cross one another in a crossing region, for guiding the switching pin of the cam follower or of the tilt lever, respectively, of a valve train of an internal combustion engine, wherein each guide track can have lateral edges. Each guide track furthermore has an on-track region, a crossing region located in the region of a crossing point, as well as an off-track region, wherein a depth of the guide track can increase from the on-track region up to the crossing region and can then decrease again up to the off-track region. According to the invention, at least one radial projection, which protrudes beyond the slotted guide in the radial direction, is now provided in or downstream from the off-track region (in the direction of rotation) of at least one guide track, whereby the switching pin can be ejected more easily and more reliably even in response to an upwards movement of the cam follower or of the tilt lever, respectively. In particular a reliable mode of operation of a valve train, which is equipped with a slotted guide of this type, and thus of an internal combustion engine, which is equipped with a valve train of this type, can be attained thereby, without requiring larger structural changes or higher costs for that purpose. With the radial projection according to the invention, a special structural feature in the case of an X-groove can be considered, namely that only a small angular range is available for the ejection of the switching pin, so that the ejection has to take place later. The tilt lever is already raised by the beginning cam lift in the corresponding angular range, the positive radial (ejection) projection thereby additionally supports an ejection of the switching pin.
In the case of an advantageous further development of the invention, the radial projection connects directly to the off-track region of at least one guide track, so that the projection represents an extension of the off-track region. An ejection of the switching pin, which is guided in the guide track, is thereby also possible in the case of an immersion depth, which is small or not present, in the corresponding guide track. The radial projection is arranged at a base of the guide track in the off-track region in this case.
A width and an axial position of the at least one radial projection on the bolt advantageously corresponds to a width and an axial position of at least one guide track, so that the switching pin, which is guided in the guide track, can come into contact with the projection in and downstream from the off-track region on the front side. The radial projection is thus arranged so as to be essentially aligned with the respective guide track in the circumferential direction.
In the case of an alternative embodiment, a width of the radial projection downstream from the off-track region is larger than the width of the corresponding guide track. The radial projection thus does not only continue in alignment with the guide track in the circumferential direction, but can also continue in alignment in the edges, which laterally limit this guide track. A widened and thus also improved ejection option is thereby created for the switching pin.
Again in the alternative, it can be provided that the radial projection extends over the entire width of the slotted guide, that is, the axial length of the slotted guide, and is interrupted by maximally one guide track, so that the number of the resulting undercuts is minimized. A simplified machining, e.g. of forging blank, which already has the projection, can be made possible thereby, in that the same projected outer contour is always at hand, if possible, in the case of lateral top view onto the part.
Advantageously, it is possible that the radial projection is only located on at least one edge in the off-track region of at least one guide track, and that the switching pin, which is guided in the guide track, has a shoulder, which can come into contact with the projection on the edge of the guide track. An improved ejection option only over the edge of the guide track can be created thereby. A local machining is thereby conceivable, in particular a built circular groove blank (guide track) comprising projection of separate component, which is attached laterally to circular groove blank, is conceivable.
In the case of an advantageous further development of the solution according to the invention, the on-track region is arranged offset to the off-track region by an angle α of 90°<α<120°, in particular by an angle α of approx. 110°. An intermediate region of essentially only between 90° and 120°, in which the change between the two guide tracks has to take place as well, thus remains between the on-track region and the off-track region and opposite to the crossing region. The changing between the guide tracks thus has to take place essentially within one-fourth of a rotation of the slotted guide, for the purpose of which a reliable ejection of the switching pin from the preceding guide track is absolutely required. By means of the radial projection, which is provided according to the invention, it is thereby even possible in particular to design the guide track-free angular range located between on-track and off-track region to be smaller, because a changing can take place more quickly.
In the case of a further advantageous embodiment of the solution according to the invention, the radial projection extends over an angular range β of 5°<β<20°, in particular by an angle β of approx. 10°. However, the projection, which is comparatively small in the circumferential direction, is already sufficient to reliably move the switching pin out of the guide track, whereby the material application required for this purpose is marginal, so that virtually no imbalances and virtually no additional costs are created.
In the case of an advantageous further development of the solution according to the invention, a maximum depth tmax of a guide track is between 10 and 15% of a maximum outer diameter D of the slotted guide. A reliable and correct guidance of the respective switching pin in the guide track can be attained thereby.
The present invention is further based on the general idea of specifying a valve train for an internal combustion engine, which has an above-described slotted guide on a camshaft. The camshaft itself has at least one cam follower, which cooperates with the camshaft and which can be axially adjusted, for example a tilt lever, wherein a switching pin is arranged perpendicular to a cam follower longitudinal axis in the respective cam follower. Via this switching pin, the cam follower cooperates with the guide tracks of the slotted guide in such a way that the cam follower in the first guide track cooperates with a first cam and in the second guide track cooperates with a second cam or taps the latter, respectively. In particular inlet and outlet times of individual valves or also a cylinder turn-off can be realized comparatively easily through this. With the use of the slotted guide according to the invention in the valve train according to the invention, a quick and functionally reliable extending of the switching pin out of the respective guide track can also be attained.
Advantageously, the slotted guide is connected in a rotationally fixed manner to the camshaft via a thermal joint seat. Thermal joint seats of this type are already well-known for the rotationally fixed fixation of components on camshafts and can thus be realized reliably. With a thermal joint seat of this type, a simultaneous joining of the slotted guide with the cams can additionally take place, whereby the production process can be streamlined and the assembly costs can be reduced.
Further important features and advantages of the invention follow from the subclaims, from the drawings, and from the corresponding figure description on the basis of the drawings.
It goes without saying that the above-mentioned features and the features, which will be described below, cannot only be used in the respective specified combination, but also in other combinations or alone, without leaving the scope of the present invention.
Preferred exemplary embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, whereby identical reference numerals refer to identical or similar or functionally identical components.
In each case schematically,
According to
When now looking at the slotted guide 8 according to the invention in more detail, it can be seen that the two guide tracks 9, 10 for guiding the switching pin 6 cross one another in a crossing point 13, wherein each guide track 9, 10 is limited by lateral edges 14. Each guide track 9, 10 furthermore has an on-track region 15 (see
Different embodiments are to be differentiated thereby, for example one, in the case of which the radial projection 19 connects directly to the off-track region 17 of at least one guide track 9, 10, so that the projection 19 represents an extension of the off-track region 17, whereby an ejection of the switching pin 6, which is guided in the guide track 9, 10, is possible even in the case of an immersion depth, which is small or not available, in the corresponding guide track 9, 10.
It can be provided thereby that a width a width and an axial position of the at least one radial projection 19 corresponds to a width and to an axial position of at least one guide track 9, 10, so that the switching pin 6, which is guided in the guide track 9, 10, can come into contact with the projection on the front side. The radial projection 19 is thus arranged so as to be essentially aligned with the respective guide track 9, 10 in the circumferential direction.
In the alternative, it can also be provided that a width of the radial projection 19 downstream from the off-track region 17 is larger than the width of the corresponding guide track 9, 10. In this region, the radial depth t of the guide track is already negative. In this region, the radial projection 19 even extends in alignment with the edges 14. The radial projection 19 can thereby extend over the entire width of the slotted guide 8 and can be interrupted by maximally one guide track 9, 10, so that the number of the resulting undercuts is minimized.
In the alternative, a radial projection 19 (see
When looking at
A maximum depth tmax (measured in the radial direction) of a guide track 9, 10 is thereby between 10 and 15% of a maximum outer diameter D of the slotted guide 8, whereby a material reduction and thus a reduction of the weight can be attained on the one hand, and a reliable guidance of the switching pin 6 in the respective guide track 9, 10 can be effected on the other hand.
As illustrated according to
As a whole, a reliable ejection of the switching pin 6 from the guide track 9, 10 can be made possible by means of the slotted guide 8 according to the invention, even in response to an upwards movement of the tilt lever or of the cam follower 4, respectively, whereby in particular an ejection of the switching pin 6 in the case of a brake cam profile, in the case of which the cam follower 4, together with switching pin 6, is already in an upwards movement, immediately downstream from the profile switchover, are ensured. This is not possible without problems with current slotted guides, which are known from the prior art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102019203429.2 | Mar 2019 | DE | national |
