EP1907673A1

EP1907673A1 - Valve drive for an internal combustion engine

Info

Publication number: EP1907673A1
Application number: EP06762261A
Authority: EP
Inventors: Stephan Möck; Arndt Ihlemann
Original assignee: Schaeffler KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2005-07-15
Filing date: 2006-06-29
Publication date: 2008-04-09
Also published as: US20090071427A1; US7963261B2; DE102005033018A1; CN101223339A; WO2007009565A1

Abstract

The invention relates to a valve drive for an internal combustion engine comprising a variable hub profile for a valve (13). According to the invention, a lever (11) is supported on a variable support point by means of a switchable support element (16) which provides possibilities for influencing the hub profile. Alternatively and cumulatively, the cam (17, 23) is axially displaced such that various cam paths (25, 26) are active on the lever (11). The possibilities for a variation of the hub profile can be broadened due to the inventive embodiment or the same variation possibilities are formed by a support element (16) having a reduced longitudinal extension and smaller idle stroke.

Description

Name of the invention

Valve train for an internal combustion engine

description

Field of the invention

The invention relates to a valve train for an internal combustion engine, in which an axially displaceable cam with two cam tracks acts on a lever which actuates a valve of the internal combustion engine.

Background of the invention

From DE 196 11 641 C1 discloses a camshaft is arranged on the axially displaceable in three locking positions a cam with three axially adjacent cam tracks with different Hubprofilen. In the three locking positions, a drag lever cooperates in each case with a cam track for actuating a gas exchange valve. A change of a cam track and thus a change from a detent position to another detent position via radially actuated pins which can occur in the circumferential direction of the cam grooves, wherein the grooves have an axial component for bringing about the axial movement of the cam.

Object of the invention

The present invention has for its object to propose a valve train with improved possibilities for influencing the Hubprofils under consideration of the space requirements.

Summary of the invention

According to the invention, this object is achieved by the features of the independent patent tentanspruchs 1 solved. Further embodiments of the invention will become apparent according to the features of the dependent claims 2 to 6.

According to the invention, the stroke movement of a valve of an internal combustion engine, ie its phase position and / or the stroke as a function of the angle of rotation, is determined by a lever, in particular a (roller) drag lever or else a rocker arm. The invention is based on the finding that the position of a connection point for the valve on the lever is dependent on the position of two characteristic points of the lever, namely on the one hand the contact point of the lever on a cam track and on the other hand on a support point, which forms a bearing point. depends. According to the invention, not only one of the aforementioned characteristic points is acted upon, but on both characteristic points, namely the support point of the lever on the one hand and the effective cam track on the other hand, resulting in improved possibilities for changing the Hubprofils:

According to a first possibility, the support or bearing point is arranged approximately stationary, while a pivoting of the lever takes place as a result of the cam. Since the cam is axially displaceable, so that in a first axial position, a first cam is effective and in a second axial position, a second cam is effective, two different Hubprofile are already possible for this first possibility, with regard to the Hubverlaufes and / or of the phase angle can differ from each other.

According to a second possibility, a superposition of two movements, namely on the one hand as a result of the adjusting movement, which is achieved by the cam, and on the other hand, due to a movement of the support point, can be achieved. By suitably influencing the support point, the stroke caused by the cam can be increased or decreased. Here, the same movement of the support point (or a different movement of the support point) in conjunction with both the first cam as can also be used with the second cam track.

For a movement of the support point a movement between different, discrete and effective for several revolutions of the camshaft positions is possible. Alternatively or additionally, a position of the support point which is variable with one revolution of the camshaft and which can result from active actuating means or from passive elements is possible.

According to a preferred embodiment of the invention, the support point is formed with a support element, which is switchable with a first switching position in which the support point is fixed, and with a second switching position in which the support point is movable during rotation of the camshaft. In the first switching position, the movement of the lever and thus the lifting profile of the valve are primarily dictated by the first cam track substantially in the first axial position of the cam, while in the second axial position the second cam track determines the lifting profile. By contrast, in the second switching position, the lifting profile results from a superposition of the movements of the support point and the respectively effective cam track.

In addition to the aforementioned degrees of freedom and positioning options, according to a further embodiment of the invention, the support element having a valve clearance compensation element, which does not serve to change the Hubprofiles, but the compensation of an undesirable game.

A further embodiment of the invention is of particular importance in connection with a deactivation of the valve, in particular in conjunction with a cylinder deactivation. In this case, the valve should remain in its closed position. According to the invention, in order to bring about such a stationary valve, in spite of a rotating cam, first the cam track is selected which has the smallest stroke. In addition, the support element is spent in the second switching position, in which the support point is movable during rotation of the camshaft. Accordingly, according to this embodiment, the support point corresponding to the rotation of the cam track and its stroke suitable for, so that the lever pivots in this case to the attachment point of the valve. This so-called "idle stroke" of the support element is dimensioned in such a way that, during one revolution around the associated cam track, the support point is moved by approximately the idle stroke in one direction and then back again, while the valve remains at least largely stationary.

In order for such an idle stroke of a support element to be connected to an axially displaceable cam with cam tracks of different strokes, the idle stroke of the support element can be reduced compared to comparable idle support elements in conjunction with axially non-displaceable cams with only one cam track. This results in a reduced longitudinal extent of the support element, which can be of decisive advantage in the case of cramped installation conditions in the region of a cylinder head.

Furthermore, according to the invention, the cam track with a smaller stroke on the one hand with the support element in the first switching position, ie at approximately fixed support point, operated, which may be suitable for example for operation of the engine with reduced power, reduced torque and / or reduced speed. With the same cam, but with the support member in the second switching position can continue to be effected in a simple way a cylinder deactivation.

For a further embodiment of the valve drive according to the invention, a control device (or control device) is provided which acts on suitable actuators, which on the one hand can influence and predetermine the axial position of the cam and on the other hand can transfer the support element into the respective shift positions. The control device and the actuators can in this case be of any desired design, for example electrically, electromagnetically, hydraulically and / or controlled by suitable CPUs. The actuation of the actuators is such that in a first phase of operation, the support element is set, while in the cam a first Cam track, preferably with a large lift profile, is effective. In a second phase of operation, the support element is also fixed, while in the cam, the other cam track, for example, the cam track with a smaller stroke, is effective. For a change of the stroke with effective second cam track, in particular for a zero stroke can be spent in a second phase, the support element in the second switching position, so that in addition to the movement of the contact point between the lever and cam and the support point of the lever is variable to the support element.

A particularly compact device for controlling a plurality of valves can be provided by the fact that two cams with two cam tracks are displaced together, for example by the two cams are rigidly interconnected. By such a common displacement of the cams, on the one hand, the cam tracks acting on the associated valves can be correlated with each other in a particularly reliable manner. Furthermore, the effort for the actuators to influence the axial position of the cams can be reduced because not necessarily a separate actuator is required for each cam.

For prior art roller cam followers which cooperate with non-axially displaceable cams with only one cam track, cylinder deactivation or a desired reduced stroke can only be achieved if the support point is displaceable in the range between 6 and 12 mm. Due to the inventive superposition of the movement of the support element on the one hand and the different cam tracks on the other hand, a support element can be used, which is displaceable only less than 5 mm, preferably 2 to 4 mm and in particular 2.5 to 3.5 mm.

Brief description of the drawings

Further features of the invention will become apparent from the following description and the accompanying drawings, in which embodiments of the invention are shown schematically. Show it:

FIG. 1 shows a roller cam follower which actuates a valve in one end region, is centrally connected to a cam track via a roller and is mounted in another end region via a support element;

FIG. 2 shows a three-dimensional view of a camshaft with axially displaceable cams and roller cam followers supported by supporting elements.

Detailed description of the invention

1 shows a valve drive 10, in which a lever 11 is in an end region 12 in operative connection with a valve 13, so that the valve 13 performs an opening and closing movement in accordance with the movement and pivoting of the lever 11. In the end region 14 opposite the end region 12, the lever 11 is supported in a support point 15 with respect to a support element 16. Between the end portions 12, 14 acts on the lever 11, a cam 17, here with the interposition of a roller 18. The position of the end portion 12 and thus the position of the valve 13 may be via a change in the distance of a contact point 19 of a cam track 20 from the longitudinal axis 21st an associated camshaft 22 and / or a movement of the support point 15 as a result of a change of the support element 16 are changed.

FIG. 2 shows a camshaft 22, by way of which six valves 13 are actuated, of which in particular two valves each are assigned to a combustion chamber as intake or exhaust valves. Each valve is associated with a respective lever 11 and a support element 16 corresponding to FIG. In each case two cams 17, 23 are rigidly connected to one another via a connecting region 24 and are displaceable axially relative to the camshaft 22 in the direction of the longitudinal axis 21 -21, but are connected in a form-fitting manner with the latter in the circumferential direction. Each cam 17, 23 has a first cam track 25 and a second cam track 26, which adjoin one another directly in the axial direction, ie in the direction of the longitudinal axis 21 - 21 and have different stroke profiles, in particular different Hubverläufe, different maximum strokes and different phase angles.

For the axial displacement of the axially displaceable structural unit formed with the cams 17, 23 and the connecting region 24, two actuators 27, 28 act on the structural units in the end regions. The actuators 27, 28 have pins 29, 30 which can be moved in and out transversely to the longitudinal axis 21 and which, in the extended state, can enter scenes or grooves 31, 32 arranged in the end regions of the abovementioned structural unit, the grooves 31, 32 not being complete are oriented in the circumferential direction, but are slightly inclined in the axial direction, whereby an axial stroke is effected.

For providing an axial displaceability of the cam, any configuration may be employed which involves the use of different cam tracks by the same lever as a result of axial displacement of the cam, cam track or camshaft itself.

By way of example only, reference is made to the following design options for the axial displaceability of the cam:

It is possible embodiment according to the aforementioned DE 196 11 641 with a locking device for fixing the axial position, three adjacent cam tracks and two opposing grooves to allow the Axialhubes with four radially actuated pins. It is also possible according to DE 199 45 340 A1 that a cam track with a zero stroke cam is used. Furthermore, according to this document, the actuator for actuating the guide pin can be integrated with the guide pin in the cam follower.

According to DE 101 48 177 A1 intersecting sliding grooves can be used for different axial stroke directions, in which only a single pin is introduced for a stroke in both axial directions.

According to DE 101 48 179 A1, a bearing of the camshaft, with respect to which the assembly is displaceable, take place via the lateral surface of the assembly, in which case the bearing is designed as an axially displaceable, pure radial bearing. Preferably, a lateral surface between two cams of the assembly is utilized, wherein a suitable displacement in the region of this lateral surface is provided.

In addition, according to DE 101 48 243 A1, in the region of the abovementioned bearing, a detenting of the structural unit in the area of the bearing also takes place, wherein the bearing supports the structural unit with respect to the cylinder head.

According to DE 103 30 871 A1, the combined use of an axial adjustment of a cam with a camshaft adjuster by means of which the phase of the camshaft can be changed, in particular in the form of a single or double internal eccentric gear, as a wobble, tungsten, Planetary, harmonic drive, bevel gear or worm gear.

With regard to influencing the position of the support point 15, any actuators or support elements 16 can be used. This can be the Support member 16 in addition to a shift of the support point 15 take on more functions, for example, contain a valve clearance compensation element.

Only by way of example reference is made to the following embodiments of a support element 16, which can be used in the course of the invention:

According to DE 40 00 531 A1, a hydraulically acted upon, spring-loaded piston according to the hydraulic state to ensure different positions and / or movements of the support point 15.

According to DE 199 30 573 A1, an adjustable to three different Hubverläufe support 16 can be used. Preferably, in this case, the lever is formed in two parts and has two fingers. The fingers are applied to different portions of the support element, wherein the respective effective portion is switchable via a shift rod. According to DE 199 30 574 A1, the fingers can interact with different cams, namely a large-stroke cam and a small-stroke cam, or cooperate with different cam tracks with the present invention, so that different cam tracks can be used even without axial displacement by the same lever in accordance with the switching rod. wherein different transmission mechanisms to the valve are selectable by the different fingers.

According to DE 198 19 068 A1, a support element can be switched via an electromagnetic actuator via a rotation so that either the support element is fixed or can perform a relative movement, so that no effective support by the support element is present.

According to DE 198 38 909 A1, a switchable support element can ensure a zero stroke in a switching position, wherein to avoid Faulty switching means are used which cause a lock in response to a pivot angle of the shift lever.

From DE 199 30 572 A1 discloses a switchable support member is known in which a longitudinally displaceable and rotatable shift rod is used, which cooperates with a sleeve having a coupling and a decoupling, which cause a circuit of the support element. Accordingly, a circuit can take place only when the cooperating with the cam cam in the region of the base circle of the cam or the cam track.

Likewise, a switchable support element according to DE 100 55 014 A1 can be used, in which an outer and an inner anti-rotation device are designed as one component.

A switchable support element with reduced overall height and simple supply of a hydraulic medium to a clearance compensation element results from DE 101 22 373 A1.

- An improved hydraulic loading of a switchable support element results, for example, from DE 103 30510 A1.

The use of materials such as glass or carbon fiber reinforced plastic, in particular for a pressure piston, is known from DE 103 32 362 A1.

Another known switchable support element results from DE 102 47 949 A1.

According to the invention, a combination of the previously listed embodiments for enabling an axial displaceability of a No ckens for activating two cam tracks with the different embodiments for Abstϋtzelemente done.

LIST OF REFERENCE NUMBERS

10 valve train

11 lever

12 end area

13 valve

14 end area

15 support point

16 Abstϋtzelement

17 cams

18 roll

19 contact point

20 cam track

21 longitudinal axis

22 camshaft

23 cams

24 connection area

25 first cam track

26 second cam track

27 actuator

28 actuator

29 pen

30 pen

31 groove

32 groove

Claims

claims

1. Valve drive for an internal combustion engine with a valve (13) opening and closing lever (11) of a cam (17, 23) of a camshaft (22) relative to a support point (15) is pivotable, wherein a) the cam ( 17, 23) is displaceable in a first axial position and a second axial position, - has a first, in the first axial position effective cam track (25) and a second, in the second axial position effective cam track (26) and b) the Support point (15) for changing the lifting movement of the valve (13) is variable.

2. Valve drive according to claim 1, characterized in that the support point (15) with a support element (16) is formed, which is switchable with a first switching position, in which the support point (15) is fixed, and a second switching position, in the the support point (15) is movable during a rotation of the camshaft.

3. Valve drive according to claim 2, characterized in that the support element (16) has a valve clearance compensation element.

4. Valve drive according to claim 2 or 3, characterized in that the second cam track (26) has a smaller stroke than the first cam track (25) and a possible idle stroke of the support element (16) in the second switching position is dimensioned such that during a Circumferentially around the entire second cam track (26) of the support point (15) is moved by about the idle stroke in one direction and then back, while the valve (13) at least largely stationary remains.

5. Valve drive according to one of claims 2 to 4, characterized in that a control device is provided, which is connected to actuators (27, 28), a displacement of the cam (17, 23) in the first and second axial position and a Conversion of the support element (16) effect in the first and the second switching position, wherein the control device is designed such that in a first phase of operation, the support element (16) in the first switching position and the cam (17, 23) in the first axial

Position is arranged in a second phase of operation, the support element (16) in the first switching position and the cam (17, 23) is arranged in the second axial position and - in a third phase of operation, the support element (16) in the second switching position and the cam (17, 23) is arranged in the second axial position.

6. Valve drive according to one of the preceding claims, character- ized in that two cams (17, 23) with two cam tracks (25, 26) are displaceable together.

7. Valve drive according to one of the preceding claims, characterized in that the support point (15) is displaceable in the second switching position less than five millimeters.