WO2008131992A1

WO2008131992A1 - Three-dimensional valve gear with modified three-dimensional cam geometry

Info

Publication number: WO2008131992A1
Application number: PCT/EP2008/053279
Authority: WO
Inventors: Jens Schäfer; Siegfried Tisch; Sebastian Zwahr
Original assignee: Schaeffler Kg
Priority date: 2007-04-28
Filing date: 2008-03-19
Publication date: 2008-11-06
Also published as: DE102007020129A1; DE202007013509U1

Abstract

The invention relates to a three-dimensional valve gear (1) for an internal combustion engine with at least one cam shaft (3), which is constructed with one or more three-dimensional cams (2) and which is movable axially in a cam shaft axis (4), wherein a cam follower (5) is provided, which interacts with the three-dimensional cam (2), in order to transfer the lifting information of the three-dimensional cam contour to at least one valve (6). The three-dimensional cam contour is constructed in such a manner that, in at least one axial position of the cam shaft (3), the lifting of the valve (6) is omitted, in order to create a switching off of the valve (6).

Description

Name of the invention

Room cam valve drive with modified room cam geometry

description

Field of the invention

The present invention relates to a space cam valve drive for an internal combustion engine having at least one camshaft configured with one or more space cams which is axially movable in a camshaft axis. In this case, the space cam valve drive comprises a cam follower which cooperates with the space cam to transmit the stroke information of the space cam contour on at least one valve.

Room cam valve drives, in which the valve lift information is stored on the room cams, are generally known. The three-dimensional space cam in combination with the cam follower contains at least the valve lift information in a further embodiment as well as the phase angle information. The contact between the space cam and the cam follower can be done via tap rollers, with a sliding contact is possible. The contact is usually formed as line contact between the elements, wherein the camshaft can be adjusted axially and the tapping element picks up different strokes by the changing cam contour.

In such room cam valve drives, the problem often arises, if possible to allow all degrees of freedom within the room cam valve drive. Although the valve lift between a maximum stroke and a Minimum stroke can be varied, however, it is often advantageous to provide a shutdown of individual valves. Known systems for switching off individual valves, which also perform no stroke in the operation of the internal combustion engine and prevent the charge cycle in the associated cylinder, are very complicated, consist of a variety of items and are often based on the principle of decoupling the camshaft or the camshaft section to their deactivation. A cam follower can control one, two or more valves.

It is therefore an object of the present invention to provide a room cam valve drive, which in addition to the function of different valve timing and different adjustable valve strokes additionally has the function of a valve shutdown.

This object is achieved on the basis of a space cam valve drive according to the preamble of claim 1 in conjunction with its characterizing features. Advantageous developments of the invention are specified in the dependent claims.

The invention includes the technical teaching that the Raumnockenkontur is formed such that the stroke of the valve is omitted in at least one axial position of the camshaft to provide a shutdown of the valve.

Thus, the advantage is achieved that a shutdown of individual valves or valve pairs in a specific axial position of the camshaft is possible without additional facilities. If the camshaft is moved to the axial position in which the space cam contour has the geometric design to prevent a valve lift, the valve or the valves, which are articulated by a corresponding space cam, shut down. An advantageous embodiment of a space cam valve drive according to the invention comprises a space cam contour, which has a first helix angle, which merges into an enlarged second helix angle. The helix angle describes the angle of the contact surface on the space cam contour relative to the camshaft axis, within which the space cam is axially movable. For the usual change between a maximum stroke and a minimum stroke, the tapping element is in contact with the portion on the space cam contour which has the first helix angle, and to shut off the valvetrain the tapping member of the cam follower is in contact with the space cam contour which having the larger second skew angle. The second helix angle is formed so large that the stroke of the valve is zero and the valve is turned off, since the contour in the space cam, the tap element is no longer sufficient or not deflected. Thus, the minimum effective radius of the space cam contour does not end in an area which causes only a minimum valve lift, but this ends only in a range of a second helix angle, which is formed so that the valve lift is zero.

Advantageously, the camshaft comprises a plurality of space cams associated with valves of different cylinders of the internal combustion engine. The camshaft further comprises at least one space cam, which has only the first helix angle, wherein at least one further space cam is provided on the same camshaft having the first and the second helix angle and allows a shutdown of the valves associated with this space cam. The camshaft is designed with several room cams, which each carry cylinder-specific valve lift information. The result is a camshaft with space cam, which has different Raumnockenkonturen or differing Raumno- ckenwellen, and wherein the space cam of the respective tap kinematics can be adjusted. This option is particularly advantageous for engines with several cylinder banks, so that a cylinder bank can be completely or partially shut off, for example, while the other cylinder bank provides the operation of all cylinders. The individual connection or disconnection of cylinder banks or individual cylinders is therefore only by axial adjustment of the camshaft. Furthermore, there are noise advantages of the internal combustion engines through the lower valve lifts, with a smaller valve lift leads to a lower noise, since fewer items are moved, and the moving parts are subjected to lower dynamics.

For example, it is advantageous that the camshaft associated with a first cylinder bank comprises a plurality of space cams which are formed at least partially with the first helix angle and the second helix angle and the camshaft associated with a second cylinder bank comprises a plurality of space cams which are formed only with the first helix angle are. Using the example of a four-cylinder cylinder, the present invention provides the advantage that the camshaft is associated with a cylinder bank having four cylinders assigned in series, the camshaft having four space cams associated with the respective cylinders. The space cams associated with the two middle cylinders are formed with the first and the second helix angle, wherein the space cams associated with the two outer cylinders are formed only with the first helix angle. The particular effect of this arrangement of the present invention manifests itself in internal combustion engines with four cylinders in a special way, since in a low load range, two cylinders can be switched off, so that the advantage of reducing the moving masses, the emitted noise and the fuel consumption and exhaust emissions in the Part load operation can be achieved.

Possible embodiments of the cam follower include rocker arms, rocker arms or similarly configured lever systems, which differ in particular by the kinematics that are achieved by different bearing points. The tilt or drag levers include one or several tap rollers, which are in contact with the room cam. The tapping rollers are received in a rocker assembly within the frame-like tilting or pivoting lever, so that they can follow the changing contour of the space cam. Thus, depending on the axial position of the camshaft, a first tapping roller contacts the portion of the first helix angle, with a second tappet roller contacting the region of the second helix angle. The effective stroke, which is achieved in this operating situation, can be so small that the stroke of the at least one valve is omitted.

By a corresponding development of the second helix angle, this can also be designed so that the effective radius of the cam corresponds to the base circle of the room cam. If the tapping element is in contact with this area of the room cam, then there is no change in radius with respect to the base circle of the space cam, so that this area can be described as a pure cylindrical shape. The tapping element rolls only over the outer circumference of the cylindrical portion, so that a stroke can be omitted even during rotation of the camshaft. The transition between the helix angles is designed with radii so that overall a spherical contour of the space cam results with a "zero-stroke range." Modern production possibilities, which include forming and machining operations, allow the design of any geometry of the space cam Therefore, with the radius of the base circle of the space cam is no production-technical obstacle, so that only the kinematics of the space cam must be adjusted with respect to their rolling motion on the spherical contour.

Further measures improving the invention will be described in more detail below, together with the description of a preferred embodiment of the invention, with reference to the figures. It shows:

Figure 1 is a schematic view of a Raumno- ckenventiltriebes invention for an internal combustion engine with four cylinders;

Figure 2a is a schematic side view of a Raumnockenkontur having only the first helix angle (corresponds to the prior art);

Figure 2b is a schematic side view of a space cam contour with a first and a second helix angle, wherein the second helix angle is greater than the first helix angle.

3a shows a set of curves of valve lifts over the cam angle, which can be generated with a cam according to FIG. 2a; and

FIG. 3b shows a family of curves of valve lifts over the cam angle, which can be achieved with a space cam according to FIG. 2b.

FIG. 1 shows schematically a space cam valve drive 1 according to the invention. This is designed for a four-cylinder, so that four space cam 2 are arranged on the camshaft 3. The camshaft 3 is rotatably and axially movably mounted in the camshaft axis 4 and performs a rotational movement during operation of the space cam valve drive 1. Due to their rotational position, the two outer space cams can be recognized from their rear side so that the formation of the cam contour is not apparent. The two middle space cams 2, however, are shown in a side view, in which the geometric configuration of the cam contour with the first helix angle α1 and the second helix angle α2 are shown. The representation of the helix angles α1 and σ2 is only schematically shown again. given that the area of the cam contour with the first helical angle α1 has the larger stroke, so that this area is in contact with the tap rollers 7, when the internal combustion engine is operated in an operating range with a higher load. As a result of an axial displacement of the camshaft 3, the tapping rollers 7 grip the contour region of the space cams 2, which is arranged adjacent to the first helix angle .alpha.1 in the second helix angle .alpha.2, causing the valves 6 to be shuttered off.

The lifting movement in the Abgriffsrollen 7, which is generated by the rotating space cam 2 is transmitted to a cam follower 5, which may be formed as a rocker arm or pivot lever. The lifting movement is converted into a pivoting or tilting movement, and generates the strokes in the valves 6. According to the schematic representation, each cam follower 5 is assigned two valves 6, which execute a parallel stroke with one another. If the camshaft 3 is displaced axially to the right in relation to the image plane, the tapping rollers 7 come into contact with the area of the space cam 2, which has the second helix angle α2. In this case, the stroke that is introduced into the Abgriffsrollen 7, so small that it runs to zero. Thus, the valves 6 are put out of operation, wherein the helix angles α1 and α2 can be designed individually for each space cam differently. For a cylinder-individual control of the internal combustion engine is possible to operate them as a function of their operating point with all cylinders in the low load range or only with individual cylinders.

In Figures 2a and 2b space cam 2 are shown, wherein the space cam in Figure 2a only the first helix angle α1 and the space cam according to the representation in Figure 2b includes the first helix angle α1 and the second helix angle α2. Thus, the space cam in Figure 2a can be considered as a conventional space cam (prior art), whereas the space cam in Figure 2b has the inventive design. The camshaft axis 4 is schematically represented by a chelten line, around which the space cam 2 rotates. Depending on the axial position along the camshaft axis 4, the tapping rollers (see FIG. 1) can pick off the region of the second helix angle α2, so that the space cam valve drive is deactivated in the axial position of the space cam 2. Valve strokes of 30, 60 and 100% are indicated, with the valve lift of 100% corresponding to the maximum stroke. Due to the second angle of inclination α2, no lift is produced in the cam follower in the low load range, so that the valves and thus the charge changes of the associated cylinders are switched off when the internal combustion engine is idling.

FIG. 3 a shows the family of curves of a plurality of valve strokes which are plotted against the angle of rotation of the camshaft. At idle, for example, the valve lift is 3% of the maximum stroke, with a curve plotted for 30%, 60% and 100%. The 3% valve lift corresponds to the idling of the cylinder, which does not correspond to the actual shutdown of the cylinder, but only corresponds to a low load range.

FIG. 3b shows a family of curves of four valve strokes, whereby the valve stroke is no longer visible according to idling. This runs along the abscissa, since the valve is switched off by the inventive design of the space cam according to the figure 2.

The family of curves shown in FIG. 3 a can be produced by a space cam according to FIG. 2 a, wherein the group of curves according to FIG. 3 b can be generated by a space cam 2 according to the invention, which is shown in FIG. 2 b.

The invention is not limited in its execution to the above-mentioned preferred embodiment. Rather, a number of variants is conceivable, which makes use of the illustrated solution even with fundamentally different types of use. LIST OF REFERENCE NUMBERS

1 room cam valve

2 room cams

3 camshaft

4 camshaft axis

5 cam followers

6 valve

7 pick roller

α1 first helix angle α2 second helix angle

Claims

claims

1. Raumnockenventiltrieb (1) for an internal combustion engine with at least one with one or more space cam (2) running camshaft (3) which is axially movable in a camshaft axis (4), wherein a cam follower (5) is provided, with the space cam

(2) cooperates to transmit the stroke information of the space cam contour on at least one valve (6), characterized in that the space cam contour is formed such that the stroke of the valve (6) in at least one axial position of the camshaft (3) remains to create a shutdown of the valve (6).

2. space cam valve drive (1) according to claim 1, characterized in that the space cam contour has a first helix angle (α1), which merges into an enlarged second helix angle (α2).

3. space cam valve drive (1) according to claim 1 or 2, characterized in that the camshaft (3) comprises a plurality of space cam (2), the valves (6) of different cylinders of the internal combustion engine are assigned.

4. space cam valve drive (1) according to one of claims 1 to 3, characterized in that the camshaft (3) comprises at least one space cam (2) which has only the first helix angle (α1) and at least one further space cam (2) comprising the first and second helix angles (α2).

5. space cam valve drive (1) according to one of the preceding claims, characterized in that the space cam valve drive (1) has two camshafts (3) which are arranged on mutually separate cylinder banks of the internal combustion engine.

6. Raumnockenventiltrieb (1) according to claim 5, characterized in that the first cylinder bank associated camshaft (3) comprises a plurality of space cam (2) which are at least partially formed with the first helix angle (α1) and the second helix angle (α2) and associated with a second cylinder bank

Camshaft (3) comprises a plurality of space cam (2), which are formed only with the first helix angle (α1).

7. space cam valve drive (1) according to one of the preceding claims, characterized in that the camshaft (3) is associated with a cylinder bank with four cylinders arranged in series, wherein the camshaft (3) has four associated with the respective cylinders space cam (2).

8. space cam valve drive (1) claim 7, characterized in that the two middle cylinders associated space cam (2) with the first helix angle (α1) and the second helix angle (α2) are formed and the two outer cylinders associated space cam only with the first helix angle (od) are formed.

9. space cam valve drive (1) according to one of the preceding claims, characterized in that the cam follower (5) is a rocker arm, a rocker arm or a bucket tappet.

10. space cam valve drive (1) according to one of the preceding claims, characterized in that the cam follower (5) is designed as a rocker arm or as a drag lever, which has at least two Abgriffsrollen (7).

11. space cam valve drive (1) according to claim 10, characterized in that in dependence on the axial position of the camshaft (3) a first Abgriffsrolle (7) with the region of the first helix angle (α1) in contact and a second Abgriffsrolle (7 ) is in contact with the area of the second helix angle (α2).

Space cam valve drive (1) according to claim or 11, characterized in that in the axial position in which a first Abgriffsrolle (7) with the region of the first helix angle (α1) in contact and a two Abgriffsrolle (7) with the area the second helix angle (α2) is in contact, a shutdown of the at least one associated valve takes place.