WO2015185046A1

WO2015185046A1 - Variable valve train for a cylinder unit of a reciprocating internal combustion engine

Info

Publication number: WO2015185046A1
Application number: PCT/DE2015/200236
Authority: WO
Inventors: Joachim Seitz
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2014-06-05
Filing date: 2015-03-31
Publication date: 2015-12-10
Also published as: DE102014210734A1

Abstract

The invention relates to a variable valve train for a cylinder unit of a reciprocating internal combustion engine, comprising a lever-like cam follower (1) which is mounted on a lever shaft (12) such that same can swivel, and which can move in the axis direction of the lever shaft (12). The cam follower (1) can be brought into at least indirect contact with different cam profiles at least of two cams (9 and 10) of a cam group (3), and the cam follower cooperates with an end of a valve shaft (6) of a gas exchange valve (5). In order to create an assembly of a cam follower, that can move in the axis direction of a lever shaft, and the adjustment thereof, which is suitable for a mass-produced reciprocating internal combustion engine, the cam follower (1) is fixed on the lever shaft (12) in the axial direction, wherein the lever shaft (12) can be moved in the longitudinal direction by a linear actuator (30).

Description

Variable valve train for a cylinder unit of a reciprocating internal combustion engine

description

Field of the invention

The invention relates to a variable valve train for a cylinder unit Hubkol- benbrennkraftmaschine with a lever-like cam follower which is pivotally mounted on a lever axis and displaceable in the axial direction of the lever axis, the cam follower on the one hand at least indirectly with different cam profiles at least two cams of a cam group in contact can be brought and cooperates with the other with one end of a valve stem of a gas exchange valve.

State of the art

In standard trained valve trains of internal combustion engines, a camshaft is constantly driven by the crankshaft and the arranged on this cam actuate so via cam follower gas exchange valves with an opening and closing time and valve lift, which by the fixed phase angle of the camshaft and the arrangement and shape of the Cam are specified. In modern types of internal combustion engines, the opening and closing time of the gas exchange valves can be continuously varied by a camshaft adjuster, this camshaft adjuster is usually designed as a hydraulic phaser with arranged in pressure chambers swinging wings. For the creation of a variable valve train with which the charge cycle of the internal combustion engine, based on their respective operating state, can be optimized, the valve lift and the valve opening duration are adjusted in a corresponding manner in addition to the change of the phasing of the camshaft. This optimization of the charge change with respect to the respective operating state leads to the reduction of the fuel consumption and to the improvement of the exhaust gas values. For the change of the valve lift and the valve duration by means of a switchable valve train, switchable cam followers or shift cam systems are used. In known valve trains with switchable cam followers, contact surfaces or rollers of the cam follower are continuously connected to different cams. Via coupling means, which are provided within the cam follower, the actuation of the corresponding gas exchange valve can be switched from one cam contour to the other. In sliding cam systems, the valve actuation is switched over by the cam follower, which is designed essentially as standard, being selectively brought into engagement with cams of different contour, the cams being arranged on a cam unit which is displaceable relative to a base camshaft.

A variable valve train for a reciprocating internal combustion engine of the type described in the preamble of claim 1 is known from DE 10 201 1 101 871 A1. The cam follower is designed as a rocker arm and pivotally mounted on a lever axis. A camshaft has a cam group with two cams whose respective Hubkurvenverlaenen and maximum cam lift differ from each other. The cam follower can be axially displaced in the base circle phase corresponding to both cams, so that it is switched over from one cam to the other.

According to a first exemplary embodiment of DE 10 201 1 101 871 A1, the camshaft, the lever axis and an adjusting shaft provided with a multi-toothed guide run parallel to one another, wherein a sleeve provided with a guide track is arranged rotationally fixed and axially displaceable on the adjusting shaft. In the guideway, on the one hand, a stationary pin and, on the other hand, a lever pin emanating from the cam follower engage. Therefore, due to a rotation of the adjusting of the cam follower in the axial direction of the lever axis is moved on this. In a second embodiment is dispensed with the lever axis and the cam follower is pivotally guided on a bearing sleeve, wherein both the bearing sleeve and a sleeve lying next to this rotatably and axially displaceably guided on the multi-toothed guide of the adjusting. From a hub of the cam follower In this case, a driver provided with a pin extends into a guideway provided on an outer lateral surface of the sleeve.

Disclosure of the invention

It is an object of the present invention, an arrangement of a displaceable in the axial direction of a lever axis cam follower and its adjustment form such that the corresponding valve train for a mass-produced reciprocating internal combustion engine is suitable.

This object is achieved by the independent claim 1. Advantageous embodiments are given in the dependent claims, which in themselves or in various combinations with each other can constitute an aspect of the invention.

Thereafter, the cam follower according to the invention should be fixed in the axial direction on the lever axis, wherein the lever axis via a linear actuator in the longitudinal direction is displaceable. The lever-like cam follower is consequently pivotable and mounted on the lever axis, which executes the positioning movements for switching the cam follower from one cam contour to the next. These adjusting movements are transmitted by a linear actuator directly to the lever axis, so that a delay-free switching of the valve train in the base circle phase of the at least two cams can take place. Both the overall arrangement of this inventively designed valve train as well as the switching device of the cam follower are inexpensive to produce cost and therefore suitable for mass production. The linear actuator according to the invention can be actuated electrically, hydraulically or pneumatically. Alternatively to the direct control of the lever axis via the linear actuator, an indirect control can also be provided. It is also conceivable to carry out the linear adjusting movement on the lever axis by means of an adjusting device provided with a ramp contour.

In contrast, in the case of the valve drive described in DE 10 201 1 101 871 A1 as a second exemplary embodiment, a changeover takes place in that the adjusting shaft is rotated in one of its two directions of rotation. The in the guideway of Sleeve engaging stationary pin then generates a longitudinal movement of the sleeve, which is transmitted via a further connected to the driver pin ultimately on the cam follower. The latter pin also engages in the guideway. Due to the number of transmission elements and the unavoidable between these game a delay-free switching during operation of the reciprocating internal combustion engine with appropriate speed of the camshaft can not be performed with certainty. In addition, the structural complexity of the entire valve train is relatively high because of the required components. In a further embodiment of the invention, the lever axis and the linear actuator to be arranged in a lever bridge, wherein the lever bridge is fixed to a cylinder head of the reciprocating internal combustion engine and wherein a first and a second leg of the lever bridge extend on both sides of the cam follower. The two legs of the lever bridge have mutually aligned guide holes, in which the lever axis is slidably guided. The linear actuator preferably engages in a stepped portion of one of the guide bores and may be single or double acting. In the case of a single-acting design of the linear actuator can be provided at the end facing away from the linear actuator end of the lever axis, a compression spring which acts as a return spring and shifts the lever axis in a further position when canceling the Veriebiebekraft of the linear actuator.

It is further provided that the cam follower is pivotally mounted on the lever axis via a receiving bore and guided in the longitudinal direction via stop means. The stop means act as the cam follower leading shelves and thus guide the cam follower on the lever axis. Preferably, the stop means are fixed in circumferential grooves of the lever axis and limit cooperating with stop surfaces of a lever bridge, the adjusting movement of the lever axis. In this case, the stop means can be designed to be elastic in order to reduce the impact energy at each of the end stops formed on the legs of the lever bridge.

In addition, the lever axis should be latchable via latching means in at least two positions. In these latched positions of the lever axis of the cam follower takes a position, in which its contact surfaces optimally to the corresponding Cam and are positioned to the valve stem end. Instead of a contact surface may be provided on the cam-side lever end also mounted on a roller bearing roller. In this case, the latching means can be designed as at least one ball catch arranged in the lever bridge and at least two latching grooves provided on the lever axis. For this purpose, for example, a transverse to the lever axis blind bore is provided in one of the legs of the lever bridge, in which a compression spring and a detent ball are arranged. The locking grooves have a cross section which is adapted to the outer contour of the detent ball. In this case, the locking grooves may be provided with ramp-shaped edges, so that the force to be applied by the linear actuator can be reduced. In addition, of course, it is also possible to provide ratchet body whose geometric shape deviates from that of a ball.

The cam follower is preferably designed as a rocker arm or rocker arm. When a rocker arm is a two-armed lever, wherein the one end of the lever abuts the valve stem end of the gas exchange valve, while in the region of the other end of the lever one of the preferably two cams engages. In its central region of the rocker arm according to the invention is mounted on the longitudinally displaceable lever axis. A rocker arm is a one-armed lever, one end of which is mounted on the longitudinally displaceable lever axis. Spaced to this storage and to a cooperating with the valve stem end of the gas exchange valve end of the lever lever is actuated by the lying above this valve train elements camshaft. For both types of cam followers, the direct actuation according to the invention by means of the linear actuator and the lever axis is particularly suitable.

Finally, in the invention, a plate-shaped adapter is to be placed on the valve stem end of the gas exchange valve, via which the cam follower actuates the gas exchange valve. By means of this plate-shaped adapter, which has a blind bore which is adapted to the radial dimension of the valve stem end, an areal contact of the cam follower is achieved in every position of the cam follower. In addition, in the preferably two positions of the cam follower, the valve actuating forces can be optimally introduced into the gas exchange valve. The invention is not limited to the specified combination of the features of the independent claims and the dependent claims. In addition, there are further possibilities for combining individual features, in particular if they result from the claims, the following description of the exemplary embodiments or directly from the figures. In addition, reference to the figures by the use of reference numerals is not intended to limit the scope of the claims to the illustrated embodiment examples.

Short description of the drawing

For further explanation of the invention reference is made to the drawing, is shown in simplified form two embodiments. Show it:

Figure 1 is a plan view of a schematic representation of an inventive

Arrangement of a valve train for a cylinder unit of a reciprocating internal combustion engine with a section through a lever bridge, in which a trained as a rocker cam follower is in a position for a large valve lift, a position of the rocker arm of Figure 1, in which this performs a small valve lift , Figure 3 is a plan view of a schematic representation of an inventive

Arrangement of a valve drive for a cylinder unit of a reciprocating internal combustion engine with a section through a lever bridge, in which a cam follower designed as a rocker arm is in a position for a large valve lift,

Figure 4 shows a position of the rocker arm according to the figure 3, in which this performs a small valve lift and Figure 5 is an illustration of a gas exchange valve in a side view, wherein the gas exchange valve receives at a valve stem end a plate-shaped adapter shown in section. Detailed description of the drawing

In FIGS. 1 and 2, 1 designates a cam follower designed as a rocker arm 2, which cooperates with a cam group 3 of a camshaft 4 and a gas exchange valve 5 which is arranged in a cylinder head of a reciprocating internal combustion engine (not shown). The gas exchange valve 5 has a valve stem 6, with the end of a plate-shaped adapter 7, which will be discussed in connection with Figure 5, is connected. The rocker arm 2 receives at its end facing the cam group 3 a roller 8 which is mounted on the rocker arm 2 via a rolling bearing, not shown. About this role 8, the rocker arm 2 can optionally be drivingly connected to a first cam 9 for a large valve lift of the gas exchange valve 5 or with a second cam 10 for a small valve lift of the gas exchange valve 5.

As an alternative to the illustrated design of the rocker arm 2, it is possible to make the end cooperating with the valve stem 6 wider in order to ensure a secure contact at the end of the valve stem 6 over the entire adjustment range. The lever end could be designed in a similar manner as that on a lever end provided on a rocker arm shown in FIGS. 3 to 4. In the figure 1, the rocker arm 2 is actuated by the first cam 9 with a large stroke, so that the gas exchange valve 5 performs a maximum valve lift. According to the figure 2, the rocker arm 2 assumes a position in which it is actuated by the second cam 10 with a smaller stroke.

As further seen in Figures 1 and 2, the rocker arm 2 is provided in the region of its center with a receiving bore 1 1, in which a solid shaft designed as a lever shaft 12 is arranged, so that the rocker arm 2 in operation of the reciprocating internal combustion engine to this lever axis 12th performs a generated by one of the two cams 9 or 10 pivotal movement. The lever axis 12 may be formed to reduce the weight as a hollow shaft. The tilting lever 2 in the longitudinal direction of the lever axis 12 to this fixed by elastic stop means 13, which are designed as spring rings 14 and 15.

The lever axis 12 is arranged longitudinally displaceable in a lever bridge 18 having two legs 16 and 17, wherein the legs 16 and 17 have guide bores 19 and 20 for receiving the lever axis 12. In addition, the rocker arm 2 facing surfaces of the legs 16 and 17 serve as a stop means 21 and 22, which cooperate with the arranged on the lever axis 12 elastic stop means 13. These stop means 13, 21 and 22 jointly limit the longitudinal movement of the lever axis 12 and come into contact with each other when the rocker arm 2 reaches a position in which the roller 8 passes substantially centrally to the respective cam 9 or 10. In this case, the impact energy is reduced when hitting the elastic stop means on the surfaces of the legs 16 or 17. Furthermore, the lever axis 12 in a region in which it is guided in the guide bore 19 of the leg 16, provided with two spaced detent grooves 23 and 24. These locking grooves 23 and 24 together with a ball catch 25 latching means 26 for fixing the lever axis 12 in their respective end positions in which the axially fixed to the lever axis 12 rocker arm 2 is positioned exactly to one of the cams 9 or 10. The ball catch 25 is formed in that in the leg 16 a transverse to the lever axis 12 extending blind bore 27 is provided with a therein arranged via a compression spring 25 biases Rastkugel29. On the leg 16 of the lever bridge 18, a linear actuator 30 is also attached, from which a connected to the lever axis 12 plunger 31 goes out. This plunger 31 can be actuated either electrically, hydraulically or pneumatically. Preferably, the linear actuator 30 should be double-acting. But it is also possible to use a single-acting version, in which case at the other end of the lever axis 12, a return spring could be provided.

It is thus apparent from FIGS. 1 and 2 that the rocker arm 2 is displaced by the linear actuator 30, via the lever axle 12 which simultaneously supports it, from a position in which it is actuated, for example, by the first cam 9, into a position, in which an actuation of the gas exchange valve 5 via the second cam 10 takes place. The legs 16 and 17 of the lever bridge 18 are spaced apart from each other for this purpose so that the rocker arm 2 can perform this sliding movement. In the corresponding positions, the lever axis 12 is locked relative to the leg 16.

The embodiment shown in Figures 3 and 4 differs from that of Figures 1 and 2 only in that instead of the rocker arm

Rocking lever 32 is used. The components that are substantially identical to those of Figures 1 and 2 are therefore provided with the same reference numerals. The oscillating lever 32 is provided at its one end with a lever receiving bore 33, by means of which the rocker arm 32 is pivotally mounted on the lever axis 12. The oscillating lever 32 actuates the gas exchange valve 5 via its other widened lever end 34, whereby a valve-shaped adapter 7 is again arranged on its valve stem 6. Furthermore, in contrast to Figures 1 and 2 according to Figures 3 and 4, the camshaft 4 is arranged above the rocker arm due to the function of a rocker arm drive. In the figure 3, the rocker arm 32 is in a position in which the first cam 9 generates a large valve lift on the gas exchange valve 5. From this position, the rocker arm 32 can be moved to the position shown in FIG. 4 by means of the linear actuator 30 and the lever axis 12. In this, a smaller Ventilbub the gas exchange valve 5 is achieved by the second cam 10 of the cam group 3.

In the figure 5 the provided with the plate-shaped adapter 7 gas exchange valve 5 is shown. Thereafter, the adapter 7 has a hollow cylindrical projection 35, which is adapted to the radial dimension of the valve stem 6, at least from its end. With this approach 35, the adapter 7 is fixed on the end of the valve stem 6. LIST OF REFERENCES

1 cam follower

2 rocker arms

3 cam group

4 camshaft

5 gas exchange valve

6 valve stem from 5

7 plate-shaped adapter

8 roll

9 first cam

10 second cam

1 1 locating hole of 2

12 lever axis

13 elastic slings

14 spring ring

15 spring washer

16 thighs

17 thighs

18 lever bridge

19 pilot hole

20 pilot hole

21 slings

22 slings

23 locking groove

24 locking groove

25 ball catch

26 locking means

27 blind hole

28 compression spring

29 detent ball

30 linear actuator

31 pestles

32 rocker arm Receiving bore widened lever end hollow cylindrical approach

Claims

claims

1 . Variable valve drive for a cylinder unit of a reciprocating internal combustion engine with a lever-shaped cam follower (1) pivotally mounted on one

Lever axle (12) is mounted and in the axial direction of the lever axis (12) displaceable, wherein the cam follower (1) on the one hand at least indirectly with different cam profiles at least two cams (9 and 10) of a cam group (3) is brought into contact and the other with an end of a valve stem (6) of a gas exchange valve (5) cooperates, characterized in that the cam follower (1) in the axial direction on the lever axis (12) is fixed and that the lever axis (12) via a linear actuator (30) in Is longitudinally displaceable.

2. Variable valve train according to claim 1, characterized in that the lever axis (12) and the linear actuator (30) in a lever bridge (18) are arranged, that the lever bridge (18) is attached to a cylinder head of Hubkolbenbrennkraft- machine and that a first and a second leg (16 and 17) of the lever bridge (18) extend on both sides of the cam follower (1).

3. Variable valve train according to claim 1, characterized in that the cam follower (1) via a receiving bore (1 1) pivotally mounted on the lever axis (12) and guided in the longitudinal direction via stop means (13).

4. Variable valve train according to claim 3, characterized in that the stop means (13) in the circumferential grooves of the lever axis (12) are fixed and, with stop surfaces (21 and 22) of a lever bridge (18) cooperating, limit the adjusting movement of the lever axis (12) ,

5. Variable valve train according to claim 4, characterized in that the stop means (13) are designed to be elastic.

6. Variable valve train according to claim 1, characterized in that the lever axis (12) via latching means (26) can be latched in at least two positions.

7. Variable valve train according to claim 6, characterized in that the lever axis (12) and the linear actuator (30) are arranged in a lever bridge (18) that the lever bridge (18) is attached to a cylinder head of Hubkolbenbrennkraft- machine and that the Locking means (26) as at least one in the lever bridge (18) arranged ball catch (25) and at least two provided on the lever axis (12) locking grooves (23 and 24) are formed.

8. Variable valve train according to claim 1, characterized in that the cam follower (1) as a rocker arm (2) or rocker arm (32) is formed.

9. Variable valve train according to claim 1, characterized in that the linear actuator (30) is electrically, hydraulically or pneumatically actuated.

10. Variable valve train according to claim 1, characterized in that on one end of the valve stem (6) of the gas exchange valve (5) a plate-shaped adapter (7) can be placed over which the cam follower (1) actuates the gas exchange valve (5).