Claims
- 1. A switchable cam follower (1) for a valve train of an internal combustion engine, which valve train is actuated by tappet push rods, said cam follower having the following features:the cam follower (1) is installed in driving relationship between a camshaft and an end of the tappet push rod, said cam follower (1) comprising an outer and an inner section (4,5) as well as coupling means (22), the outer section (4) is inserted with its outer peripheral surface (6) into a reception in an engine block of the internal combustion engine, the inner section (5) being mounted in a recess (13) of the outer section (4) while being movable relative to the outer section (4), one of said sections (4 or 5) has a support (3) for the end of the tappet push rod and the other of said sections (5 or 4) has an axially opposite contacting surface (2) for a cam of the camshaft, the recess (13) for the inner section (5) in the outer section (4) comprises an end (15) remote from the contacting surface (2), the inner section (5) is mounted in the recess (13) on an axle (14) which is guided in the outer section (4), and the inner section (5) is pivotable relative to the outer section (4) on the axle (14), said sections (4,5) can be coupled to each other by the coupling means (22) so that on coupling, a high lift of a valve train gas exchange valve which is loadable by the tappet push rod can be effected and, on uncoupling of the sections (4,5) by the coupling means (22), a low lift or a zero lift of the gas exchange valve is obtainable, characterized in thata locking means (27) is associated to the coupling means (22), and the locking means (2) is configured so as to permit a displacement of the coupling means (22) during a contact of a first portion of a base circle of the cam with the cam contacting surface and to block a displacement of the coupling means (22) during a contact of a last portion or an end of a base circle of the cam and during contact of an adjoining first portion of a valve lifting flank of the cam with the cam contacting surface.
- 2. A cam follower according to claim 1,characterized in thatthe coupling means (22) is made as a slide, a reception (24, 25) being arranged in each of the inner section (5) and the outer section (4), which receptions (24, 25) are aligned to each other for coupling of the sections (4,5), the receptions (24, 25) extend diametrically or secant-like through the cam follower (1), the coupling means (22) is arranged in one of the receptions (24 to 25) while being displaceable in at least one of its directions of displacement by a servo medium including a hydraulic medium and in the respective other direction of displacement by a mechanical means (23) including at least one compression spring, or likewise by a servo medium, the cam possesses a signal track for the locking means (27), the locking means (27) is made as a slide which, at one end (32), scans the signal tract while being associated at the other end (31) to the respective coupling means (22), the coupling means (22) comprises wedge-shaped catch recesses (29,30) which are spaced from each other at a distance corresponding to the dimension of a desired maximum displacement of the coupling means (22) from the coupled into the uncoupled state, and into which catch recesses (29,30) the other end (31) of the locking means (27) is forcibly displaceable by the signal track of the cam for blocking a displacement of the coupling means (22).
- 3. A cam follower according to claim 2, characterized in thatthe locking means (27) is guided on a longitudinal guide through or along one of the sections (4 or 5) and is made as a pin which engages into the catch recesses (29, 30) of the coupling means (22) on a side thereof opposite the cam.
- 4. A cam follower according to claim 2,characterized in thatthe outer section (4) possesses the support (3) for the end of the tappet push rod, and the inner section (5) comprises the contacting surface (2) for the cam, the inner section (5) is loaded against its direction of pivot by a spring means, and the outer section (4) can be guided secure against rotation in the reception in the engine block so that the receptions (24,25) for the coupling means (22) and the axle (14) extend parallel to the axis of the camshaft.
- 5. A cam follower according to claim 4, characterized in thatthe spring means for the inner section (5) is configured as a torsion spring which is constituted by the axle (14).
- 6. A cam follower according to claim 5,charactrized in thatthe axle (14) is fixed at one end by a first rotation preventin device (16) including a flattened region or a polygon in a complementary reception (17) of the outer section (4), while being fixed in the inner section (5) at an axially largest distance from the first rotation preventing device (16), by a section rotation preventing device (18) including a flattened region or a plygon in a complementary reception (19) of the inner section (5).
- 7. A cam follower according to claim 2 or 3, characterized in thatthe locking means (27) has an elastic configuration in the axial direction of the cam follower (1).
PRIOR APPLICATION
This application is based upon provisional patent application Ser. No. 60/112,415 filed Dec. 15, 1998.
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Kind |
5203289 |
Hara et al. |
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5558052 |
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Provisional Applications (1)
|
Number |
Date |
Country |
|
60/112415 |
Dec 1998 |
US |