Switchable finger lever

1. A switchable finger lever ( 1 ) for a valve train of an internal combustion engine, said finger lever ( 1 ) comprising an inner lever ( 2 ) comprising an underside ( 3 ) on one end ( 4 ), a support ( 5 ) for a gas exchange valve and on another end ( 6 ), a contact surface ( 7 ) for a head of a support element, said inner lever ( 2 ) comprising on the one end ( 4 ), outer arms ( 8 ) which are pivotable relative to the inner lever ( 2 ), which outer arms ( 8 ) extend in direction of the another end ( 6 ) while flanking outer walls ( 9 ) of the inner lever ( 2 ) and comprise on upper sides ( 10 ), contacting surfaces ( 11 ) for high lift cams, a coupling device ( 12 ) comprising a coupling slide ( 13 ) for simultaneously connecting the outer arms ( 8 ) to the inner lever ( 2 ) being seated in a section of the another end ( 6 ) in the inner lever ( 2 ), wherein the coupling slide ( 13 ) is seated in an oblong hole ( 14 ) extending transversely through the inner lever ( 2 ) as also in longitudinal direction of the finger lever ( 2 ), the coupling slide ( 13 ) comprises two end portions ( 15 ) which protrude beyond the outer walls ( 9 ), and for effecting coupling [high valve lift], the coupling slide ( 13 ) can be displaced with the two end portions ( 15 ) towards the one end ( 4 ) partially in or under entraining surfaces ( 16 ) of the outer arms ( 8 ) ending therein, whereas for effecting uncoupling, the coupling slide ( 13 ) can be displaced out of the entraining surfaces ( 16 ) towards the another end ( 6 ), and wherein at least one restoring spring ( 17 ) extends in a region of the another end ( 6 ) between the inner lever ( 2 ) and the outer arms ( 8 ).

2. The switchable finger lever of claim 1 , wherein the inner lever ( 2 ) comprises in a region above the contact surface ( 7 ), a longitudinal bore ( 18 ) comprising an entraining piston ( 19 ), which entraining piston ( 19 ), defines with one front end ( 20 ), a pressure chamber ( 21 ) for hydraulic medium that can be supplied out of the contact surface ( 7 ) for displacing the entraining piston ( 19 ) in one longitudinal direction [coupling or uncoupling direction] while at least one compression spring ( 23 ) acts against another front end ( 22 ) of the entraining piston ( 19 ), and a further end of the compression spring ( 23 ) acts against a support ( 24 ) on a corresponding end region ( 25 ) of the longitudinal bore ( 18 ), and wherein the entraining piston ( 19 ) comprises on an outer periphery ( 27 ), one of a crosswise extending incision ( 26 ) or a crosswise extending bore in which incision ( 26 )/bore the coupling slide ( 13 ) is seated.

3. The switchable finger lever of claim 2 , wherein the longitudinal bore ( 18 ) starts from a front end surface ( 28 ) of the inner lever ( 2 ) on the another end ( 6 ) and is closed in this region by a closing element such as a plug ( 29 ), the pressure chamber ( 21 ) for the hydraulic medium being formed between this plug ( 29 ) and the facing one front end ( 20 ) of the entraining piston ( 19 ), wherein the at least one compression spring ( 23 ) acts on one side against the another, inner front end ( 22 ) or against a bottom ( 29 a ) of a pocket recess ( 30 ) of the inner front end ( 22 ) of the entraining piston ( 19 ) and, on another side, against a bottom ( 31 ) of the longitudinal bore ( 18 ) or against a corresponding inner stop of the longitudinal bore ( 18 ), said bottom ( 31 )/said inner stop comprising a ventilating aperture ( 32 ) opening directly into the outside.

4. The switchable finger lever of claim 2 , wherein the incision ( 26 ) on the entraining piston ( 19 ) for the coupling slide ( 13 ) is arranged on an upper side ( 33 ) of the entraining piston ( 19 ) and the oblong hole ( 14 ) is arranged on an upper side ( 34 ) of the longitudinal bore ( 18 ) to intersect the longitudinal bore ( 18 ), and wherein, when the entraining piston ( 19 ) has reached its retracted coupling position, the one, outer front end ( 20 ) of the entraining piston ( 19 ) does not intersect an outer end ( 35 ) of the oblong hole ( 14 ).

5. The switchable finger lever of claim 2 , wherein the contact surface ( 7 ) for the support element is configured as a semi-spherical cavity on the underside ( 3 ) of the inner lever ( 2 ), from which contact surface ( 7 ) either a) a branch bore leads directly into the pressure chamber ( 21 ) behind the one, outer front end ( 20 ) of the entraining piston ( 19 ), or b) the entraining piston ( 19 ) or the longitudinal bore ( 18 ) or both comprise a longitudinal channel ( 36 ) which at least indirectly intersects the contact surface ( 7 ) and opens into the pressure chamber ( 21 ).

6. The switchable finger lever of claim 2 , wherein the coupling slide ( 13 ) in the incision ( 26 ) of the entraining piston ( 19 ) is guided solely by side walls ( 37 ) of the incision ( 26 ).

7. The switchable finger lever of claim 2 , wherein an axial fixing of the coupling slide ( 13 ) is realized through two retaining elements ( 39 ) such as frictionally locking snap rings or shaft snap rings [in annular groove] which extend on an outer periphery ( 38 ) of the coupling slide ( 13 ) and directly adjoin the outer walls ( 9 ) of the inner lever ( 2 ).

8. The switchable finger lever of claim 2 , wherein, starting from the another end ( 6 ) of the inner lever ( 2 ) comprising the longitudinal bore ( 18 ), the inner lever ( 2 ) branches in direction of the one end ( 4 ), at least in a central region, into two spaced apart arms ( 40 ) between which a rolling bearing-mounted or slide bearing-mounted roller ( 41 )/disk is received as a running surface for a low lift cam [valve lift alteration] or for a zero lift cam [valve deactivation].

9. A method of assembling the coupling device ( 12 ) and adjusting a coupling lash in a finger lever ( 1 ) of claim 2 , comprising following steps:

a) Insertion of the at least one compression spring ( 23 ) into the longitudinal bore ( 18 );

b) Installation of the entraining piston ( 19 ) in the longitudinal bore ( 18 );

c) Insertion of a constant diameter calibrating coupling slide into the incision ( 26 )/the bore of the entraining piston ( 19 ) and displacement of the entraining piston ( 19 ) into coupling position;

d) Loading, in a cam-opposed direction, the outer arms ( 8 ) which bear against an inner or an outer stop acting in cam direction, till the outer arms ( 8 ) come to be seated with entraining surfaces of the center arms ( 8 ) ( 16 ) configured as flats or cylindrically shaped portions, on end portions of the calibrating coupling slide, and measurement of this idle displacement;

e) Removal of the calibrating coupling slide, calculation of a required thickness of a coupling slide and appropriate pairing and installation of a variable thickness off-the-shelf coupling slide ( 13 ), so that a defined minimum coupling lash is obtained;

f) Axial securing of the coupling slide ( 13 ) and closing of the longitudinal bore ( 18 ).

10. The switchable finger lever of claim 1 , wherein the contacting surfaces ( 11 ) of the outer arms ( 8 ) are cylindrically arched sliding surfaces and project after the manner of wings away from the outer arms ( 8 ).

11. The switchable finger lever of claim 1 , wherein an axle stub ( 42 ) projects integrally from each of the outer walls ( 9 ) of the inner lever ( 2 ) on the one end ( 4 ), or end portions of a continuous axle project outwards, on which axle stubs ( 42 ) or end portions, the outer arms ( 8 ) are seated for rotation.

12. The switchable finger lever of claim 11 , wherein the outer arms ( 8 ) seated on the axle stubs ( 42 )/end portions comprise an axial anti-loss device ( 43 ) in form of a securing element such as either a snap ring/a snap washer with friction locking or a shaft snap ring/a shaft snap washer or a bent shaft snap ring/a bent shaft snap washer.

13. The switchable finger lever of claim 1 , wherein the entraining surfaces ( 16 ) on undersides of the outer arms ( 8 ) extend directly in the region of front ends ( 44 ) of the outer arms ( 8 ) on the side of the another end ( 6 ) and are configured either as flats or as cylindrically shaped portions.

14. The switchable finger lever of claim 1 , wherein two restoring springs ( 17 ) configured as torsion leg springs are arranged on the another end ( 6 ), each coil assembly ( 45 ) of each torsion leg spring is seated on an axle stub ( 46 ) which protrudes in a section of the another end ( 6 ) from the outer wall ( 9 ) of the inner lever ( 2 ), and wherein a first and a second leg ( 47 , 48 ) extends away from each coil assembly ( 45 ), said first leg ( 47 ) being biased against a stop ( 49 ) of the inner lever ( 2 ) and said second leg ( 48 ) being biased against a support ( 50 ) of an underside of a respective one of the outer arms ( 8 ).

15. The switchable finger lever of claim 14 , wherein flanks of the second legs ( 48 ) in mesh [contact region ( 51 )] with the support ( 50 ) of the respective outer arm ( 8 ) correspond at least partially to an involute toothing of gearwheel teeth in mesh with each other.

16. The switchable finger lever of claim 1 , wherein the outer arms ( 8 ) are made as separate pieces from each other.