VALVETRAIN SWITCHABLE LEVER ARM FOR INTERNAL COMBUSTION ENGINE USING COLLAPSING PIVOT ELEMENT AT CENTER PIVOT

Abstract

Proposed is a switchable valvetrain (1) for an internal combustion engine, having a row of rocker arms (2) which extend in the longitudinal direction of a cylinder head, which rocker arms (2) run via a recess (7) on an upper side (6) on a head (8) of a bearing journal (9), which bearing journal (9) is axially moveably arranged in a bore (10) of a carrier (11) which runs above, with piston-like coupling means (12) being provided for selectively coupling the bearing journal (9) to the carrier (11).

Description

DESCRIPTION OF THE DRAWING

Illustrated is a switchable valvetrain 1 for an internal combustion engine. Said switchable valvetrain 1 is composed of an “overhead” carrier 11 for a row of rocker arms 2 which extend in the longitudinal direction of a cylinder head. The rocker arm 2 illustrated here has, on its underside 3 at one end, a run-on face 4 (rolling-bearing-mounted roller) for a cam 30, and at the other end a valve rest 5 for at least one gas exchange valve 29.

Between the ends, on an upper side 6, the respective rocker arm 2 has a spherical-cap-shaped recess 7. A head 8 of a bearing journal 9 runs in said recess 7. The head 8 is a constituent part of a pressure piston 26 of a hydraulic play compensating device 25. The bearing journal 9, which therefore has the play compensating device 25, runs with its outer casing 14 in a downwardly open bore 10 of the carrier 11/insert part 11a. Said bearing journal 9 is held in a telescopically moveable mariner relative to said bore 10. As can also be seen, the bore 10 of the carrier 11/insert part 11a has an annular groove 13a. At least the upper annular face 15 of said annular groove 13a runs perpendicularly with respect to the axial line of the bearing journal 9.

Running orthogonally with respect to the longitudinal direction of the carrier 11 (a cross section is shown) in the bearing journal 9 is a recess 16, which is formed as a through bore 23, with two pistons situated diametrically opposite as coupling means 12. Said pistons 12 are shown in their state in which they are engaged into the annular groove 13a (coupled state). Said pistons 12 have, proceeding from their radially outer face end 17, one flattening 18 each on their upper side, which flattening 18, in the coupled case, lies under the upper annular face 15 of the annular groove 13a. The coupling state disclosed can for example be produced by the force of a spring means 19, such as at least one coil pressure spring, which acts between the inner face ends 20 of the pistons 12 (cam base circle phase). A return displacement into the decoupled position is carried out by means of a hydraulic medium which is supplied to an outer face end 17 of the respective piston 12 from the carrier 11/insert part 11a. The outer face ends 17 of the pistons 12 can additionally be designed so as to follow the curvature of the annular groove 13a.

In addition, it is disclosed in the drawing that a lost motion spring 13 is integrated within the bore 10 of the carrier 11/insert part 11a. Said lost motion spring 13 is seated at one end against a face end 27, which faces away from the rocker arm 2 of the bearing journal 9, and acts at the other end against a base 28 of the bore 10. A cover-like element 24 is applied here as a base 28.

In order to avoid edge wear, it is proposed to bevel an edge region 21 of the upper annular face 15 of the annular groove 13a, and likewise an edge region 22 of the flattening 18 of the respective radially outer face end 17 of the piston 12.

It is also provided to retain the respective rocker arm 2 pivotably on the head 8 of the bearing journal 9 by means of a connecting means 23a such as a thin-walled holding clamp which is formed in the region of the recess 7 of said rocker arm 2. The entire modular unit (carrier 11 with insert parts 11a, bearing journal 9, rocker arms 2 suspended on the latter . . . ) can be stored, delivered to the engine manufacturer and installed there, in a pre-assembled state. The assembly expenditure at the engine manufacturer is therefore drastically reduced.

List of Reference Symbols

• 1) Valvetrain
• 2) Rocker arm
• 3) Underside
• 4) Run-on face
• 5) Valve rest
• 6) Upper side
• 7) Recess
• 8) Head
• 9) Bearing journal
• 10) Bore
• 11) Carrier
• 11 a) Insert part
• 12) Coupling means, piston
• 13) Lost motion spring
• 13 a) Annular groove
• 14) Outer casing
• 15) Upper annular face
• 16) Recess
• 17) Outer face end
• 18) Flattening
• 19) Spring means
• 20) Inner face end
• 21) Edge region, annular groove
• 22) Edge region, flattening
• 23) Through bore
• 23 a) Connecting means
• 24) Plug/element
• 25) Play compensating device
• 26) Pressure piston
• 27) Face end
• 28) Base
• 29) Gas exchange valve
• 30) Cam

Claims

1. Switchable valvetrain for an internal combustion engine, comprising a row of rocker arms which extend in the longitudinal direction of a cylinder head, which rocker arms on the one hand intrinsically have, on an underside at one end, an at least indirect run-on face for at least one cam, and at the other end, a valve rest; and that run on the other hand via a recess on their upper side on a head of a bearing journal, with at least a subset of the bearing journals being axially moveably arranged in a corresponding bore of an above-situated carrier or of an insert part which is connected to the carrier, with each modular unit being assigned coupling means for selectively coupling the moveable bearing journal at least indirectly to the carrier, so that in the deployed state of the moveable bearing journal, a large valve lift is generated when coupled and a relatively small or zero valve lift is generated when decoupled, and with the respectively moveable bearing journal being acted on out of its bore by means of a lost motion spring, wherein an annular groove is arranged in the bore of the carrier or insert part, the at least axially upper annular face of which annular groove runs orthogonally with respect to the axial line of the bore of the carrier or insert part, with the bearing journal having at least one radially-running or secant-shaped recess which intersects its outer casing and in which, in the decoupled case, is seated at least one piston as a coupling means, which coupling means, proceeding from its radially outer face end, is of stepped design with a flattening situated above, and which coupling means, for the coupled case, can be displaced with its flattening in sections under the upper annular face of the annular groove of the bore of the carrier or insert part.

2. Valvetrain according to claim 1, wherein two pistons situated diametrically opposite are provided in the recess, which is formed as a through bore, of the bearing journal.

3. Valvetrain according to claim 1 wherein a displacement of the respective piston for the coupled case is effected radially outward by a mechanical spring means running in the recess such as at least one coil pressure spring which interacts with a radially inner face end of the respective piston, with a return displacement of the respective piston for the decoupled case taking place radially inward by means of hydraulic medium which can be supplied out of the carrier/the insert part in front of the radially outer face end of said piston.

4. Valvetrain according to claim 1, wherein the outer face end, which faces toward the annular groove, of the piston has a curvature which correlates at least approximately with a radius of the annular groove.

5. Valvetrain according to claim 1, wherein edge regions which are in engagement with one another, of the annular groove and of the flattening of the piston, are beveled in the transition region to the outer face end.

6. Valvetrain according to claim 1, wherein the carrier is embodied as a continuous rail for at least one row or at least a partial section of one row of the rocker arms which extend in the longitudinal direction of the cylinder head.

7. Valvetrain according to claim 1, wherein the carrier is produced from a lightweight material such as aluminum.

8. Method for assembling the valvetrain according to claim 1, wherein valvetrain is provided fully pre-assembled with rocker arms retained thereon in a suspended manner by connecting means such as clamps, and is subsequently mounted as a modular unit on the cylinder head of the internal combustion engine.

9. Valvetrain according to claim 1, wherein the bearing journal is provided with a hydraulic play compensating device whose pressure piston is a constituent part of the bearing journal and has the head.

10. Valvetrain according to claim 1, wherein the respective rocker arm is retained on the head of the bearing journal by a connecting means such as a thin-walled clamp or a joint.

11. Valvetrain according to claim 1, wherein the lost motion spring runs in the bore of the carrier or insert part, is embodied as at least one coil or spiral pressure spring, and acts at one end against a face end, which faces away from the rocker arm of the bearing journal, and at the other end against a base, which is closed off either in a unipartite fashion or by means of a separate plug/a separate pot-like element, of the bore of the carrier/insert part.