Switchable finger lever

This application claims the benefit of German Patent Application No. 10 2009 035 531.6, filed Jul. 31, 2009, which is incorporated by reference herein as if fully set forth.

The invention concerns a switchable finger lever for a valve train of an internal combustion engine, with the finger lever comprising an inner lever and further comprising, on one end, outer arms which are pivotable relative to the inner lever and extend, while flanking outer walls of the inner lever, in the direction of the other end, with the outer arms comprising on upper sides, running surfaces for high-lift cams, a support for at least one gas exchange valve extending on an underside of a crossbar of the inner lever in a vicinity of the one end, a contact surface for a head of a support element being provided on the another end, with the finger lever further comprising a coupling slide for an optional connection of the outer arms to the inner lever, and at least one resetting spring being clamped between the inner lever and the outer arms.

Finger levers known from the prior art (such as DE 102 20 904 B4) have a solid configuration and their realization is only possible through complex and expensive fabrication methods. It is further conspicuous that economic fabrication methods cannot be used and, at least partially, it is not possible to have recourse to standard parts for the lever.

The object of the invention is therefore to provide a switchable finger lever of the above-noted type in which the aforesaid drawbacks are eliminated. In particular, it is intended to provide a switchable finger lever which is easy to manufacture at lower costs and in which, it is possible, at least partially, to have recourse to standard elements.

The invention achieves the above object in that the inner lever is made of thin-walled sheet steel and has a U-shaped cross-section, and the outer walls are configured as separate pieces from each other and made, optionally, likewise out of thin-walled sheet steel. The inner lever comprises, in a region of the one end, integrally connected lateral guide tabs for the gas exchange valve, a separate insert comprising the contact surface is installed in a region of the other end between side walls of the inner lever. The coupling slide is seated in this insert, and the resetting spring likewise extends in the region of the other end between the inner lever and the outer arms.

The aforesaid drawbacks are effectively eliminated through the above measures. Preferably, but not exclusively, both parts of the finger lever (inner lever, outer arms) are made out of thin-walled sheet steel by a punching and bending method. However, it is also envisioned to make only the inner lever out of sheet steel and the outer arms which are discrete parts and not connected through a crossbar, for instance, by casting.

In a particularly preferred development of the invention, it is proposed to have recourse to a standard finger lever of a non-switchable type (see for example, DE 198 11 658 B4). In this case, only minor modifications, such as provision of a recess in the crossbar for accommodating the separate insert with the coupling slide provided by the invention are needed.

The novel finger lever can be configured as a so-called lift alteration switch [full lift-partial lift] or as a lift deactivator [full lift-zero lift].

Because the outer arms are made as separate components from each other, their manufacture is as simple as imaginable. Where appropriate, they can be configured identically. Moreover, it is obvious that their discrete and thin-walled configuration results in a saving of mass.

It is further provided to connect the separate insert arranged on the other end of the finger lever through positive engagement to side walls of the inner lever. For this purpose, two crosswise extending axles are seated in the side walls of the inner lever and inserted through corresponding cross-bores of the insert. Alternatively, it is also conceivable to connect the separate insert to the inner lever solely by force-locking or by a combination of force-locking and positive engagement. If need be, the insert can also be connected by welding or the like.

The present finger lever possesses a low mass moment of inertia because, among other things, important parts of the finger lever, such as the resetting spring and the coupling mechanism in the region of its mounting support are positioned on a head of a support element.

In addition, it is advantageous if the end pieces of the lever-distal axle for fixing the insert project beyond the outer walls of the inner lever. In this way, a coil assembly of the resetting spring, configured preferably but not exclusively in the form of a torsion leg spring, can be mounted on each of the projecting end pieces.

Simple stops for the resetting spring (lost motion spring) are created by the fact that a first leg bears against an underside of the respective outer arm and a second leg abuts against the outer longitudinal end of the insert, that is to say, behind the insert.

In place of two separate torsion leg springs, it is also possible to use an assembled unit comprising two coil assemblies whose second legs can be connected to each other behind the outer longitudinal end of the insert.

As provided by the invention, the inner lever has a simple U-shaped cross-section that is generated preferably by a punching and bending method. An inverted U-profile or an H-profile is also conceivable.

Further, the guide tabs for the lateral guidance of the gas exchange valve advantageously project integrally from the inner liver. They can be configured, for instance, as prolongations of its inner walls on one end and be bent over onto an underside of the finger lever. However, it is also conceivable to make the guide tabs by a stamping method.

According to a further development of the invention, the coupling piston in the insert is not loaded directly by hydraulic medium or by a compression spring. The coupling piston is seated, namely, in a recess of a longitudinally extending entraining piston arranged in the insert. It is exactly this entraining piston that is loaded hydraulically in one direction of displacement and in the other direction of displacement, through the force of at least one spring element. Its loading through other a servo such as an electromagnetic actuator or a loading in both directions by a hydraulic medium is also conceivable.

As a mechanical spring for displacing the coupling slide in one direction (here, uncoupling direction), one embodiment of the invention provides a sheet metal clip. This can be made and mounted in a simple manner. Each side strip of the sheet metal clip acts in push-out direction on a respective protruding end of the coupling slide.

Another aspect of the invention is to provide at least one splash oil channel extending through the insert to its upper side. This splash oil channel can lead to the cam running surfaces. It would also be conceivable to route the hydraulic medium directly towards the cam contact region.

If the finger lever is configured as a lift alteration switch, another development of the invention provides arranging a rotatable roller between the side walls of the inner lever. However, it is also conceivable and intended to use a sliding contact in this region. It is further possible to provide the outer arms with a roller contact or a disk contact.

The running surfaces of the outer arms are configured as slightly arched sliding surfaces which may also be provided with deposited anti-wear coatings.

Last but not least, the invention provides a simple method of connecting the outer arms to the inner lever. To this end, an axle projects through the side walls of the inner lever on the one end, and the outer arms, which are freely movable relative to each other, are mounted on the outwards protruding ends of the axle. An anti-loss device for the outer arms may be provided, for instance, by snap rings seated on the axle or by other similar measures.

The appended drawings show:

FIG. 1 , a side view of a finger lever of the invention,

FIG. 2 , a longitudinal section through the finger lever of FIG. 1 ,

FIG. 3 , a side view of the inner lever,

FIG. 4 , a top view of the inner lever of FIG. 3 ,

FIG. 5 , a side view of the insert,

FIG. 6 , a longitudinal section through the insert of FIG. 5 ,

FIG. 7 , a side view of the spring means for resetting the coupling slide,

FIG. 8 , a top view of the spring means of FIG. 7 , and

FIG. 9 , a three dimensional view of the finger lever.

The figures show a switchable finger lever 1 for a valve train of an internal combustion engine. The finger lever 1 has a U-shaped inner lever 2 made of thin-walled sheet steel. The inner lever 2 comprises two substantially upright side walls 14 with outer walls 6 (see also FIG. 4 ). On an underside 8 , the inner lever 2 comprises, in the region of one end 3 , a support 10 for a gas exchange valve. Guidance of the gas exchange valve is effected through two guide tabs 11 that project integrally from front end 36 of the inner lever 2 on the one end 3 and are bent through 180° to extend onto the underside 8 .

In the region of the other end 5 , the inner lever 2 is widened into a fork-shape and comprises a recess 32 . As best shown in FIG. 2 , a rolling bearing-mounted roller 55 is installed between the side walls 14 of the inner lever 2 as a contact partner for a low-lift cam.

In the region of the one end 3 , an axle 56 extends through the side walls 14 of the inner lever 2 , one of the outer arms 4 being pivotally mounted on each of the ends of the axle 56 protruding beyond the outer walls 6 . The outer arms 4 are likewise made of sheet steel. Each outer arm 4 comprises an upper side 7 comprising a corresponding running surface 7 a for a high-lift cam. If appropriate, the finger lever 1 may also comprise only one outer arm 4 .

The outer arms 4 are substantially smooth-faced and extend snugly on the outer walls 6 of the inner lever 2 . However, the outer arms 4 do not extend over the entire length of the inner lever 2 . Each outer arm 4 comprises on an underside in the region of the other end 5 , an entraining surface 45 for a coupling slide 15 described later.

In the aforesaid recess 22 of the inner lever 2 on the other end 5 is seated a separate insert 12 which projects with an extension 35 into the recess 32 , so that an underside 34 of the insert 12 protrudes beyond transverse edges 33 a , 33 b of the recess 32 . The insert 12 is connected to the inner lever 2 by positive engagement. The insert 12 comprises two cross-bores 19 , 20 . An axle 22 whose ends are seated in bores of the side walls 14 of the inner lever 2 extends through the cross-bore 20 . For lodging a further axle 21 (in the cross-bore 19 ), the inner lever 2 comprises in the region of front ends 24 of its side walls 14 on the another end 5 , a jaw-like open configuration, so that end pieces 26 of the axle 21 are received between jaw surfaces 25 .

A contact surface 13 for mounting the finger lever 1 on a head of a support element, not shown, is formed in the aforesaid extension 35 of the insert 12 . This contact surface 13 is represented in the present case as a semi-spherical cavity.

As can best be seen in FIG. 2 , the insert 12 comprises a longitudinal bore 37 with an entraining piston 38 displaceable therein. The latter defines with its outer front end 39 on the side of the other end 5 , a pressure chamber 40 for hydraulic medium. The pressure chamber 40 is closed axially outwards through a separate closing element 47 (plug) and is supplied with hydraulic medium through the aforesaid contact surface 13 .

A splash oil channel 48 leads from the pressure chamber 40 to an upper side 49 of the insert 12 . Thus, a supply of hydraulic medium to the contacting cams and running surfaces 7 a , 55 (running surface, roller) on the finger lever 1 can be realized through the splash oil channel 48 .

The entraining piston 38 comprises a cut-out 41 starting from its upper side and extending in transverse direction. The above-mentioned coupling slide 15 is seated in this cut-out 41 and its ends extend through oblong holes 43 in the insert 12 .

As best disclosed in FIG. 1 in combination with FIGS. 7 and 8 , a spring 46 projects outwards from an upper side 49 of the insert 12 . This spring 46 is made up substantially of three sheet metal strips which are joined at one end to a perpendicularly projecting connecting metal sheet 52 . A center strip 50 is bent with one of its ends 53 over the insert 12 and thus fixed thereon. Laterally of the center strip 50 are disposed side strips 51 with bent-over ends 54 . As shown in FIG. 9 , these ends 54 act on the end pieces 42 of the coupling slide 15 in direction of the another end 5 .

If a high valve lift is desired (coupled state), the aforesaid pressure chamber 40 is pressurized through hydraulic medium pressure in the cam base circle phase. This causes the entraining piston 38 with the inserted coupling slide 15 to be displaced in direction of the one end 3 , so that the end pieces 42 of the coupling slide 15 are displaced into a position under the entraining surfaces 45 of the outer arms 4 . Thus, the finger lever 1 follows the lift of the high-lift cam now loading the running surfaces 7 a of the outer arms 4 .

If uncoupling is desired (low lift), the high pressure in the pressure chamber 40 is switched off, at the latest, with the cam base circle phase. Now, the spring 46 comes into play which, through the ends 53 of its side strips 51 disengages the coupling slide 15 from the entraining surfaces 45 of the outer arms 4 . Thus, during the next cam lift, the outer arms 4 pivot without load and the finger lever 1 follows the low lift of the cam then loading the inner lever 2 .

A resetting of the outer arms 4 is accomplished through a resetting spring 16 configured, in the present case, as a torsion leg spring assembly. One coil assembly 27 of the resetting spring 16 is seated on each protruding end piece 26 of the axle 21 . A first leg 28 engages an underside 29 of the respective outer arm 4 . A second leg 30 extends to behind the other end 5 of the inner lever 2 and is connected there to the further second leg 30 of the other coil assembly 27 .

1 Finger lever

2 Inner lever

3 One end

4 Outer arm

5 Other end

6 Outer wall of inner lever

7 Upper side of outer arm

7 a Running surface

8 Underside

9 Crossbar

10 Support

11 Guide tab

12 Insert

13 Contact surface

14 Side wall

15 Coupling slide

16 Resetting spring

17 Outer longitudinal end of insert

18 Inner longitudinal end of insert

19 Cross-bore of insert

20 Cross-bore of insert

21 Axle

22 Axle

23 Bore of side wall

24 Front end of side wall

25 Jaw surface

26 End piece of lever-distal axle

27 Coil assembly

28 First leg

29 Underside of outer arm

30 Second leg

31 Widened portion

32 Recess of crossbar

33 Transverse edge (a, b)

34 Underside of insert

35 Extension of insert

36 Front end of one end

37 Longitudinal bore of insert

38 Entraining piston

39 Outer front end of entraining piston

40 Pressure chamber

41 Cut-out

42 End piece of coupling slide

43 Oblong hole

44 Outer wall of insert

45 Entraining surface

46 Spring

47 Closing element

48 Splash oil channel

49 Upper side of insert

50 Center strip

51 Side strip

52 Connecting metal sheet

53 End

54 End

55 Roller

56 Axle