WO2010089068A1 - Valve train of an internal combustion engine - Google Patents

Abstract

The invention relates to a valve train of an internal combustion engine, having a camshaft (1) comprising a mandrel (2) and a cam piece (3) disposed rotationally fixedly and axially displaceably thereon and comprising adjacent cams (4, 5) having different cam heights and an axial slotted link (7) formed as a groove and having outer groove walls (10, 11, 12, 13) for prescribing two intersecting slotted link paths (8, 9), and having an actuating pin (14) for displacing the cam piece in the direction of both slotted link paths, wherein the cam piece has a guide device comprising two guide vanes (19, 20) rotating in opposite directions for forming inner groove walls (21, 22, 23, 24) axially displaceable relative to the outer groove walls, and switching between the slotted link paths in the manner of a railway switch in the intersection area (15) of the slotted link paths, so that only one slotted link path is unblocked for the actuating pin. The guide device thereby comprises a linkage synchronizing the rotary motion of the guide vanes.

Description

 Valve gear of an internal combustion engine

description

The invention relates to a valve train of an internal combustion engine, comprising a carrier shaft and a rotatably and axially displaceably arranged cam piece comprising a cam carrier with at least one cam group directly adjacent cams with different cam lobes and a groove formed as a groove with outer groove walls to specify two Having intersecting slide tracks, and with an engageable in the Axialkulisse actuating pin for moving the cam piece in the direction of both slide tracks, wherein the cam piece is provided with a control pin controlled by the guide, the two oppositely rotating guide vanes to form relative to the outer groove walls axially movable inner groove walls Has axial slide and switches in the manner of a switch in the crossing region of the slide tracks between them, so that released for the actuating pin one of the slide tracks u nd the other slide is locked. Background of the invention

A variable valve train with displaceable cam pieces is known in the prior art in principle and in view of the present invention from DE 101 48 177 A1. There two cam pieces are disclosed with alternatively designed Axialkulissen, wherein the first Axialkulisse has a central guide web to form inner groove walls for the actuating pin and the second Axialkulisse consists only of outer groove walls.

The latter embodiment has the advantage that the production cost for the axial slide is significantly smaller due to the omission of the guide bar. A significant risk in terms of the reliability of the valve train in this embodiment, however, is that the displacement of the cam piece only complete, i. is completed without a fault when the mass inertia of the cam piece is sufficient to move the cam piece during and after passing through the crossing region of the slide tracks, even without forced action of the actuating pin in a sense in the free flight to its other end position. A prerequisite for the sufficient inertia of the cam piece is of course a minimum speed of the camshaft, which is dependent on the friction between the cam piece and the carrier shaft. As will become clear later in the description of an embodiment of the invention, a displacement of the rotating below this minimum speed cam piece can cause the cam piece "stops midway" and a gas exchange valve acting cam follower of several cams of the cam group and uncontrolled Moreover, in this case, there is no longer any possibility of subsequently displacing the cam piece into one of the end positions by means of the actuating pin, because then the axial association between the actuating pin and the outer groove walls is no longer ensured.

Although this functional risk is in the former embodiment of the Axialkulisse with central guide bar, the inner groove walls at low speeds of the Nockenstϋcks act as the actuating pin further accelerating positive guidance, significantly lower. Nevertheless, there is also the risk here that the actuating pin does not engage in the predetermined slide track after passing through the crossing area, but also collides with the end face of the guide bar under high mechanical load.

In both embodiments of the Axialkulisse therefore remains a more or less high risk of faulty circuits, which in particular a safe switching of the cam piece from one to the other end position even at lowest speeds, for example, during the starting process of the internal combustion engine.

To remedy this problem, it is proposed in the unpublished DE 10 2008 024 911 A1, to provide the cam piece with a flexible guide for the actuating pin. The illustrated in Figure 1 of this document operating principle of the guide already reveals two oppositely rotating guide vanes to form the axially movable relative to the outer groove walls inner groove walls of the Axialkulisse. As in the case of a switch, depending on the position of the guide vanes, one guide track is released for the actuation pin and the other slide track is blocked for the actuation pin. Due to the blocking and release action of the flexible guide, the advantageous properties of axial scenes can be combined with intersecting slide tracks on the one hand and with separate slide tracks on the other. The main advantage of intersecting slide track is that only a single actuating pin is required for both displacement directions of the cam piece, while separate slide tracks over their entire Axialhub constitute a forced guidance for the actuating pin and consequently the risk of operational malfunction of a in and after the Exclude intersection of the slide tracks uncontrolled further displacing cam piece.

However, the above is not to be understood that always only a single cooperating with the axial slide actuating pin and corresponding Two cams per cam group are provided. Because regardless of the guide rather there is the possibility to provide two or more in the same Axialkulisse alternately engaging actuating pins and a number of cams per cam group, which is larger by one than the number of actuation pins. However, such an embodiment of the valve train is the subject of the likewise not previously published DE 10 2007 051 739 A1 and not explained in detail here.

Object of the invention

The present invention has for its object to provide a valve train of the type mentioned, in which the proposed in the above-cited DE 10 2008 024 911 A1 operating principle of the guide is structurally advantageous designed or in which the guide a constructive development to that in the mentioned embodiment described with verschränkendem circlip.

Summary of the invention

The solution of this problem arises from the characterizing features of claim 1, while advantageous developments and refinements of the invention are the dependent claims can be removed. Accordingly, the guide vanes should be provided with journals which are rotatably received in both sides of the crossing region of the slide tracks on the groove bottom of the axial slide bearing points, and the guide should have a guide vanes coupling steering linkage, which is hinged to the bearing pin and synchronized the opposing rotational movement of the guide vanes , The guide device thus comprises different functional elements, namely the guide vanes on the one hand and the steering linkage synchronizing their movement on the other hand, so that with respect to the known safety ring a largely independent, ie low-compromise and targeted optimization of the functional properties of these elements is possible. In an advantageous embodiment of the invention, it is provided that the guide vanes have a variable in the circumferential direction of the Axialkulisse profile such that the outer groove walls and the inner groove walls in the crossing region of the slide tracks are substantially equidistant from each other and axialspielarm to the actuating pin. The uniform spacing of the groove walls causes a low-jerk transition between the outer and inner groove walls merging into each other in the crossing region, while at the same time minimizing the dynamic excitation of acoustically and mechanically undesired axial vibrations of the cam piece relative to the actuating pin due to the small axial play of the actuating pin within the respective guide track.

In a structurally particularly preferred embodiment of the invention, the cam piece is to be provided with a radially extending below the Axialkulisse recess extending with an annular or kreisringstückförmigen cross section in the axial direction of the cam piece, and in which the steering linkage is completely absorbed. As is also clear from a later explained embodiment of the invention, this results in a space-saving and mechanically protected arrangement of the guide vanes coupling Lenkge- stänges in the radial space between the carrier shaft and the Axialkulisse.

Compared with known designs with separately manufactured and joined by means of interference fit Axialkulisse the Axialkulisse and the cam carrier can be made in one piece with each other and the annular recess and preferably by means of longitudinal grooving profile turning.

Conveniently, the steering linkage is axially fixed by means of a securing ring, which is inserted on the front side of the cam piece in the annular recess. The circlip may be made of flat material and may be pressed flat (i.e., not upright) in the recess.

In addition, the steering linkage should have two arcuate links that rotate axially next to one another, in opposite directions, and turn in a radially outward direction. are stored supported in the recess and whose end portions are articulated eccentrically to the extending into the recess bearing journal of the guide vanes.

With regard to the smallest possible radial space requirement of the steering linkage, the handlebars should be made of flat material and stored flat in the recess. In this case, the bearing journals of the guide vanes may each be provided with an orthogonal to the axis of rotation extending longitudinal groove, in which the end portions of the trained as thrust links handlebars are added without traction. The term "traction free" is to be understood that the articulation of the links on the bearing pin no tensile forces, but only compressive forces can be transmitted, so that to be inserted during assembly of the cam piece, the flat end portions of the links only in the longitudinal grooves of the journals Alternatively, there is also the possibility of suspending the links on the trunnions with a connection transmitting both compressive and tensile forces, in which case a single link, articulated eccentrically to the trunnion, is sufficient as a linkage to guide the guide vanes in the opposite direction To move the rotary motion.

According to the invention, a guide pin controlled by the actuation pin, that is to passively switch over, is provided with a run-on guide wing and an outgoing guide wing. With the incoming guide wing is the one designated, which comes with respect to the cam rotation direction first with the actuating pin into engagement, while the expiring guide wing cooperates with the actuating pin after the crossing area and is responsible for the meshing of the actuating pin in the predetermined slide track. The opposing rotation of the guide vanes is initiated by the incoming guide vanes, in that it is displaced axially by the actuating pin and its rotational movement is transmitted synchronously synchronously via the steering linkage to the outgoing guide vanes. By switching in conjunction with the actuating pin selbststeuernd between the slide tracks guide can be a structurally complex, costly and / or error-prone foreign or active control of the expiring Leitblügels be replaced. In the event that an independent of the actuating pin external control of the guide is provided for switching the slide tracks, can also be dispensed with the auflaufenden guide vanes.

Brief description of the drawings

Further features of the invention will become apparent from the following description and from the drawings, in which an embodiment of the invention is shown. Unless otherwise stated, the same or functionally identical components or features are provided with the same reference numbers. Show it:

FIGS. 1A-1D show the displacement process of a cam piece according to the invention in interaction with an actuating pin in a sequence which is approximately 90.degree.

FIGS. 2A-2C show a basic kinematic representation of a guide device controlled by the actuating pin;

Figures 3, 4, the cam piece of Figure 1 in perspective assembled or exploded representation;

Figure 5 is a schematic representation of a known cam piece whose Axialkulisse has only outer groove walls and

FIG. 6 shows the cam piece according to FIG. 5 with possible faulty circuits.

Detailed description of the drawings

The invention will be explained for better understanding starting from the figures 5 and 6, in which a section of a known variable valve train of a Internal combustion engine according to the initially cited DE 101 48 177 A1 is shown. The valve drive has a camshaft 1 which comprises a carrier shaft 2 and a cam piece 3 'arranged thereon in a rotationally fixed and axially displaceable manner. For this purpose, the carrier shaft 2 has an outer longitudinal toothing, while the cam piece 3 'is provided with a corresponding inner longitudinal toothing. The teeth are known per se and not shown here. The cam piece 3 'has a cam group of immediately adjacent cams 4 and 5 with the same base circle radius and different cam lobes, from a here symbolized by a cam roller 6 cam follower, such as a drag lever, on a not shown gas exchange valve depending on the axial position of the cam piece 3'. be transferred selectively. Among the different cam elevations are either different amounts of the respective Nockenhubs and / or different valve timing of the cams 4, 5 to understand.

For axial displacement of the cam piece 3 'in the indicated direction of the arrow for the purpose of switching the currently active in Figure 5 cam 4 on the cam 5 and back, the cam piece 3' with an axial slide T in the form of a groove with two intersecting slide tracks 8, 9 is provided. These are given here only by outer groove walls 10 to 13, which cooperate with an actuating pin 14 so that the rotating in the direction of the radial arrow cam piece 3 'according to the slide track 8 is shifted to the left and according to the slide track 9 to the right. The slide track 8 is symbolized by a center point track shown in the axial direction of the camshaft 1 stationary in the internal combustion engine arranged actuating pin 14 relative to the groove bottom 18 of the axial slide 7 '. The midpoint track 9 is mirror-symmetrical to the midpoint track 8.

The displacement of the cam piece 3 'is initiated by radially coupling the actuating pin 14 into the axial slide T. The rotating and simultaneously axially displaceable on the support shaft 2 cam piece 3 'is initially supported by the accelerating groove wall 10 and - due to its axial inertia - from the crossing region 15 of the slide tracks 8, 9 with the ver. hesitant groove wall 12 on the actuating pin 14 from. The displacement of the cam piece 3 'back to the right takes place by means of the accelerating groove wall 11 and the delaying groove wall 13 symmetrically thereto. Since the axial mass inertia of the cam piece 3 'depends on its speed, it is easy to understand that too low a speed and / or excessive friction in the toothing of cam piece 3' and carrier shaft 2 in the crossing region 15 of the slide tracks 8, 9 required Investment change of the actuating pin 14 between the accelerating groove wall 10 and 11 and the retarding groove wall 12 and 13 can prevent.

Examples of an unsuccessful displacement operation of the cam piece 3 'are shown in FIG. These are the center point tracks 16 and 17 of the actuating pin 14 drawn in the direction of the cam after the crossing region 15 of the guide tracks 8, 9 on the left and in the center of the axial slide T. The center point track 16 results from the cam piece 3 'being engaged by an Known and not shown here locking device between the support shaft 2 and the cam piece 3 'is withdrawn into its right end position. The midpoint track 17 represents a far more critical misoperation of the cam piece 3 'in view of a renewed switchover attempt, since it remains "halfway" between its end positions Fall of a renewed retraction into the axial slide T can no longer engage with the groove walls 10 to 13.

As can be seen in Figures 1A to 1 D in plan view of an inventive cam piece 3, the above-described problem is eliminated by a controlled by the actuating pin 14 guide. This has two guide vanes 19, 20, which lie against the groove bottom 18 of the axial slotted guide 7 and rotate in opposite directions, whose axial end faces 10 to 13 form axially movable inner groove walls 21 to 24 relative to the outer groove walls. The guide is equipped with a later-explained steering linkage for coupling the guide vanes 19, 20, so that they fold in the intersection region 15 of the link tracks 8, 9 in opposite directions synchronously back and forth. This is where their lie Ends respectively axially opposite to the outer groove walls 10 or 11 or 12 or 13 at. Consequently, the guide in the crossing region 15 of the slide tracks 8, 9 is a forced operation in the manner of a switch for the actuating pin 14 by the currently to be traveled through slide track 8 or 9 released and the other slide track 9 or 8 is locked.

The starting point of the sequence illustrated in FIGS. 1A to 1D and extending over approximately 90 ° cam angle from left to right of the cam piece 3 rotating in the direction of the arrow is its left-hand end position (FIG. 1A). At this time, the last passed through slide track 9 is still released when moving the cam piece 3 from right to left, i. in the crossing region 15 of the slide tracks 8, 9 are the inner groove wall 21 of the leading guide wing 19 on the outer groove wall 10 and the inner groove wall 23 of the expiring guide vanes 20 on the outer groove wall 12 at. During subsequent cam angle of the guide vanes 19 is displaced axially by the displacement effect of the actuating pin 14 and rotated so that finally its inner groove wall 22 abuts the outer groove wall 11. According to FIG. 1D, the actuating pin 14 is at this point shortly before the point of intersection of the guide tracks 8, 9. As mentioned, the guide vanes 19, 20 are coupled with each other in rotation in opposite directions, so that now the inner groove wall 24 of the running guide vane 20 abuts the outer groove wall 13 come to rest and the actuating pin 14 during the subsequent rotational movement of the cam piece 3 in the released slide track 8 einspurt and the cam piece 3 completely shifts in its right end position.

The return displacement of the cam piece 3 from the right to the left end position is carried out in an analogous manner to the sequence shown.

FIGS. 2A to 2C show a kinematic schematic representation of the guide device with the guide vanes 19, 20 and the steering linkage for the synchronously opposite rotational coupling of the guide vanes 19, 20. The steering linkage consists of two linkages 25 and 26 which are designed as push elements are and their end portions zugkraftfrei on planar actuating surfaces 27, 28 ange- are deflected, which are eccentric at bearing pin 29 of the reciprocating guide vanes 19, 20.

FIG. 2A corresponds to FIG. 1A: at this time, the guide vanes 19, 20 are still in the position in which the last run through link track 9 has been released. The displaced according to Figure 2B from the actuating pin 14 and thereby rotating incoming guide vanes 19 actuated via the actuating surface 27 which is a handlebar 25, which in turn offset via the actuating surface 28, the running guide vanes 20 in rotation. The movement of the other link 26 follows the movement of the actuating surfaces 27, 28 in the opposite direction, as illustrated by the arrows. Figure 2C corresponds to Figure 1C: the rotational movement of the guide vanes 19, 20 is almost complete, so that now the slide track 9 locked for the actuating pin 14 and the slide track 8 is almost released.

The illustrated with reference to Figures 1A to 1 D cam piece 3 is shown in perspective in Figures 3 and 4, as an assembly or as an explosion. The cam piece 3 consists essentially of a cam carrier 30 with two on both sides of a sliding bearing 31 extending cam groups of different cams 4 and 5, the axial slide 7 and the previously explained in principle guide. The cam carrier 30 and the Axialkulisse 7 are made of a single blank in one piece with each other. Radially below the Axialkulisse 7 runs a cutting produced by means of longitudinal grooving profile turning recess 32 which extends with an annular cross section in the axial direction of the cam piece 3 and serves to receive the steering linkage. The here also designed as thrust links arm 25, 26 are made of sheet metal and bent concentrically to the recess 32 arcuately. They are axially juxtaposed, rotatable in opposite directions and supported at a low radial clearance in radially outward direction flat in the recess 32.

Since the links 25, 26 extend only over an arc of about 180 °, the recess 32 in an embodiment, not shown, also a NEN corresponding circular ring-shaped cross-section, so that the cam piece below the recess remains massive.

The groove bottom 18 of the axial slide 7 is provided on both sides of the crossing region 15 of the link tracks 8, 9 with bearings 33 for the cylindrical bearing pin 29 of the guide vanes 19, 20. In the bearing journals 29 a respective orthogonal to the axis of rotation extending longitudinal groove 34 for forming the actuating surfaces 27, 28 incorporated according to the figures 2A to 2C. In the longitudinal grooves 34, the front side provided with contact slopes 35 end portions of the links 25, 26 are inserted zugkraftfrei. The depth of the bearing points 33 produced as concentric blind bores is dimensioned such that the longitudinal grooves 34 of the bearing pins 29 extending into the recess 32 are largely aligned with the cross section of the recess 32.

For axial positioning and fixation of the links 25, 26 in the recess 32 is a front side on the cam piece 3 inserted into the recess 32 circlip 36. This is here also made of sheet metal thin-walled bush formed and is pressed into the recess 32 after mounting the guide ,

As is clear in a combination of FIGS. 3 and 4 with FIGS. 1A to 1 D, the guide vanes 19, 20 have a profile which varies in the circumferential direction of the axial slide 7 and is crescent-shaped in this case. This is designed so that in the crossing region 15 of the slide tracks 8, 9 at released link track 8, the outer groove wall 10 and the inner groove wall 21 and the outer groove wall 12 and the inner groove wall 23 substantially equidistant to each other and with little axial play to the actuating pin 14. In the case of a released slide track 9, this applies correspondingly to the outer groove walls 11 and 13 and the inner groove walls 22 and 24. In the present embodiment, a few tenths of a millimeter are to be understood by a small axial clearance around which the slide tracks 8, 9 thus formed are wider than the latter Diameter of the actuating pin 14 is. The guide vanes 19, 20 are further profiled such that the aligned in an outer groove walls 10 to 13 and inner groove walls 21 to 24 - In Figure 1 D, this is the groove walls 10 and 23 or 21 and 12 - as far as possible steplessly connect to each other, so that the actuating pin 14, the crossing region 15 of the slide tracks 8, 9 happens as smoothly as possible.

List of reference numbers

1 camshaft

2 carrier wave

3 cam piece

4 cams

5 cams

6 cam roller

7 Axial scenery

8 slide track

9 slide track

10 outer groove wall

11 outer groove wall

12 outer groove wall

13 outer groove wall

14 actuating pin

15 crossing area of the slide tracks

16 midpoint track of the actuating pin

17 Center point track of the actuating pin

18 groove bottom of the axial slide

19 leading wing

20 running guide wing

21 inner groove wall

22 inner groove wall

23 inner groove wall

24 inner groove wall

25 handlebars

26 handlebars

27 actuating surface

28 actuating surface

29 journals cam support

slide bearing

recess

Bearing for bearing journal

longitudinal groove

contact slope

circlip

Claims

claims 1. Valve drive of an internal combustion engine, comprising a carrier shaft (2) and a rotationally fixed and axially displaceable cam piece (3) comprising a cam carrier (30) with at least one cam group directly adjacent cams (4, 5) Having different cam lobes and a groove formed as axial slide (7) with outer groove walls (10, 11, 12, 13) for specifying two intersecting slide tracks (8, 9), and with a in the axial slide (7) can be coupled actuating pin (14 ) for moving the cam piece (3) in the direction of both slide tracks (8, 9), wherein the cam piece (3) is provided with a control device controlled by the actuating pin (14), the two oppositely rotating guide vanes (19, 20) for forming relative to the outer groove walls (10, 11, 12, 13) axially movable inner groove walls (21, 22, 23, 24) of the Axialkulisse (7) and in the manner of a switch in the crossing region (15) of the coolies senbahnen (8, 9) switches between them, so that for the actuating pin (14) one of the slide tracks (8, 9) released and the other slide track (9, 8) is locked, characterized in that the guide vanes (19, 20) bearing journals (29) are provided, which are rotatably received in bearing points (33) running on both sides of the crossing region (15) of the guide tracks (8, 9) on the groove base (18) of the axial slide (7), and in that the guide device comprises a guide wing (33). 19, 20) coupling steering linkage, which is hinged to the bearing pin (29) and the opposite direction of rotation of the guide vanes (19, 20) synchronized. 2. Valve drive according to claim 1, characterized in that the guide vanes (19, 20) in the circumferential direction of the Axialkulisse (7) variable profile such that the outer groove walls (10, 11, 12, 13) and the inner groove walls (21 , 22, 23, 24) in the crossing region (15) of the ball railways (8, 9) are substantially equidistant from each other and axially play with the actuating pin (14). 3. Valve drive according to claim 1, characterized in that the cam piece (3) with a radially below the Axialkulisse (7) extending recess (32) is provided, which with an annular or kreisring ringstückförmigen cross-section in the axial direction of the cam piece (3 ) and in which the steering linkage is completely received. 4. Valve gear according to claim 3, characterized in that the Axialku- lisse (7) and the cam carrier (30) integral with each other and the annular recess (32) are made by machining. 5. Valve drive according to claim 4, characterized in that the recess (32) is made by means of longitudinal grooving profile turning. 6. Valve drive according to claim 3, characterized in that the steering linkage by means of a securing ring (36) are axially fixed, the front side of the cam piece (3) in the annular recess (32) is inserted. 7. Valve gear according to claim 6, characterized in that the securing ring (36) made of flat material and is pressed flat in the recess (32). 8. Valve drive according to claim 3, characterized in that the steering linkage has two arcuate links (25, 26), the axially side by side, in opposite directions rotatable and in radially outward direction ab- are stored in the recess (32) and whose end portions are articulated eccentrically to the in the recess (32) extending bearing pin (29) of the guide vanes (19, 20). 9. Valve drive according to claim 8, characterized in that the links (25, 26) made of flat material and are stored flat in the recess (32). 10. Valve gear according to claim 9, characterized in that the bearing pin (29) of the guide vanes (19, 20) each with an orthogonal to the Rotary axis extending longitudinal groove (34) are provided, in which the end portions of the push members designed as handlebars (25, 26) are added without traction.