Sheet steel rocker arm

A rocker arm (1) made of thin-walled sheet steel which rocker arm is intended for a suspended arrangement together with other like rocker arms under a girder-like carrier (2) of a valve train of an internal combustion engine, the rocker arm having an inverted U-shaped profile, a support (7) for a gas exchange valve is formed on one end (6) of an underside (5) of a crossbar (4) of the rocker arm, an upper side (9) of the crossbar (4) is stamped in the region of the support (7) by a stamping and extrusion molding method toward the underside (5), so that an M-like cross-section with a longitudinal channel (10) formed on the upper side (9) is obtained and at its other end (11), the rocker arm (1) has a fork-shaped, open configuration and merges into a region (12) which is angularly bent towards the underside (5) and on which a roller (13) forming a cam contacting surface is arranged, said rocker arm (1) of this type possesses, among other things, an excellent stiffness, is simple to manufacture and has a small design height requirement.

This application is a 371 of PCT/EP2006/070092 filed Dec. 21, 2006.

FIELD OF THE INVENTION

The invention concerns a rocker arm made of thin-walled sheet steel for pivotable, suspended arrangement under a girder-like carrier of a valve train of an internal combustion engine, said rocker arm having an inverted U-shaped cross-section, a support for a gas exchange valve being arranged on one end of an underside of a crossbar of the rocker arm, and a roller forming a cam contacting surface being arranged on another end. The invention further concerns a girder-like carrier on which a row of rocker arms of the pre-cited type are suspended.

BACKGROUND OF THE INVENTION

A rocker arm of the pre-cited type is disclosed in EP 1 119 689 B1, see, for example,FIGS. 2-6. This rocker arm is likewise mounted for pivoting by suspension under a girder-like carrier of a valve train of an internal combustion engine. A drawback of this prior art, considered to be generic, is that the rocker arm possesses inadequate stiffness, particularly in the region of the valve stem support but also over its entire length. Its manufacture and assembly also prove to be relatively complex because, for example, a separate, crosswise extending support member for the valve stem is provided on the one end. For fixing the support member, the side walls have to be provided with separate recesses. Besides this, it is noted that the crossbar of this rocker arm, as viewed in longitudinal direction, extends behind the region of the roller forming the cam contacting surface. Due to its substantially “straight” shape, where necessary, the rocker arm must be made with relatively large dimensions.

OBJECT OF THE INVENTION

The object of the invention is therefore to provide a rocker arm and a girder-like carrier with at least one rocker arm suspended thereon, in which the aforesaid drawbacks are eliminated.

SUMMARY OF THE INVENTION

The invention achieves this object with the novel features of claim1. In particular, the rocker arm, or the at least one rocker arm fixed on the carrier, has an M-like cross-section on the one end, which cross-section is preferably (not compulsorily) generated through a stamping and extrusion molding method. At the same time, at the other end on which the roller is arranged, the rocker arm has a fork-shaped open configuration and is angularly bent toward the underside.

With these measures, the aforesaid drawbacks are eliminated. The rocker arm is simple to manufacture and its stiffness is improved in comparison with the cited prior art. It is precisely through the stamping and extrusion molding method used for creating the M-shaped support that the rocker arm has excellent stiffness properties in this region and, where appropriate, it can be made with thinner walls.

In addition, material is also saved through the fork-shaped open angular bend on the other end on which the roller is arranged. The angular bend creates an additional increase of stiffness. The rocker arm also possesses an improved mass moment of inertia compared to the rocker arm discussed above because less mass is accumulated away from the fulcrum.

Further advantageous measures form the subject matter of dependent claims that, each one alone or in combination with further claims, can also contain patentable features.

According to claim2, the angular bend on the other end is advantageously so large that an axial line of the roller is situated below an imaginary prolongation of undersides of the side walls.

According to a further advantageous development of the invention, the crossbar has a substantially smooth-faced, closed configuration and therefore ends in front of the angularly bent portion. The crossbar can comprise at least one recess for fixing a spring clip therein. However, it is also conceivable to provide a plurality of longitudinally spaced apart recesses in the crossbar or in the side walls that lead to a reduction of mass. If need be, a person skilled in the art will assure an adequate stiffness of the rocker arm by providing suitable beadings/stiffening ribs etc.

The longitudinal channel created by the stamping and extrusion molding process in the upper side of the crossbar must be made narrower than a distance between inner surfaces of the side walls situated under the longitudinal channel. Advantageously, this longitudinal channel has straight side walls and a flat bottom surface. Thus, through this measure, a particularly stiff valve stem support is created in a simple manner. The stamping and extrusion molding step can be integrated into the actual punching and bending operation while making the rocker arm which can be executed, for example, in a plurality of drawing steps on an automatic punching and bending machine.

According to a further proposal of the invention, for achieving a simple mounting of the rocker arm on the girder-like carrier, a semi-spherical cavity is arranged in an upper side of the crossbar. This also makes it possible to fix, preferably, a clip in this region with which the respective rocker arm can be fixed by suspension for pivoting on a head piece projecting out of the carrier. This creates a simple possibility of pre-assembling the carrier with the head pieces and the (preferably) like rocker arms fixed thereon. The entire device can thus be kept in stock in a completely pre-assembled state for subsequent installation by the engine manufacturer.

Assembly is performed as follows: the respective rocker arm with the pre-assembled spring clip, whose recess is situated on top of the semi-spherical cavity, is pressed over the head piece projecting out of the carrier so that the recess of the spring clip engages into an undercut in the head piece.

According to a further advantageous feature of the invention, the roller must project beyond the other end of the rocker arm and beyond the upper and the underside of the side walls. This results in an additional saving of material.

It is also possible to make the rocker arm narrower in the region of its ends than in its central region near the cavity. Thus, the design space requirement of the rocker arm in sideward direction is also relatively small. It will also be clear to the person skilled in the art that the narrower end regions of the rocker arm lead to a saving of mass, so that the mass moment of inertia can be reduced.

The roller on the one end can be mounted through a rolling bearing (preferably, a needle roller bearing) but equally well also through a sliding bearing on a pin whose ends are fixed in the side walls in the angularly bent region. If more appropriate, it is also conceivable and intended to provide a sliding contact for the cam in the angularly bent region.

The subject matter of the invention likewise includes a girder-like carrier on which the aforesaid rocker arms are fixed by suspension through their spring clips. The respective head piece for each rocker arm may either be a component of a pressure piston of a hydraulic lash adjuster or a component of a mechanical lash adjuster.

DETAILED DESCRIPTION OF THE DRAWING

The drawing discloses a rocker arm1made of thin-walled sheet steel. The rocker arm1is intended for a suspended arrangement on a girder-like carrier2of a valve train of an internal combustion engine (see alsoFIGS. 5 and 6). The rocker arm1generally comprises two longitudinally extending side walls3that are connected on their upper side9through a crossbar4. The rocker arm1thus generally forms an inverted U-shaped profile in cross-section.

In the region of one end6, the rocker arm1comprises on an underside5of its crossbar4, a support7for a gas exchange valve. In this region, the rocker arm1possesses an M-like cross-sectional profile (seeFIG. 4). This profile is preferably created by a stamping and extrusion molding method in which, inter alia, a stamping die of the entire tool engages the upper side9of the crossbar4on the one end6, so that this upper side9is progressively stamped toward the underside5and a longitudinal channel10starting directly from the one end6is thus formed in the upper side9. Said profile of the support7can be generated during the non-chipping production of the rocker arm1in large series (automatic cutting and bending machine). The region of the support7possesses excellent stiffness properties.

As further disclosed (see, for exampleFIG. 3), the largest width of the rocker arm1is in the central region of the rocker arm1. The crossbar4comprises on its upper side9, a semi-spherical cavity17through which the rocker arm1, as disclosed inFIGS. 5 and 6, can be arranged indirectly for pivoting on a carrier2(s. below).

On another end11, the rocker arm1comprises a region12that is bent angularly downward. In the present example of embodiment, this region12has a fork-shaped, open configuration, so that the crossbar4ends approximately in front of the angularly bent region12. Fixed in this region12, in the side walls3, is a pin24on which a roller13for a low-friction cam contact is arranged through a rolling bearing23a. Due to said angularly bent region, the stiffness of the rocker arm1is additionally enhanced.

As can be seen in the detail illustrated inFIG. 4, the longitudinal channel10formed during the stamping and extrusion molding step in the upper side9of the crossbar4has vertical side walls15and a flat bottom surface16. The region thus stamped through can have the same thickness as the rest of the crossbar, but may also be thicker or thinner.

One side of a spring clip19is fixed in the recess20in the crossbar4shown inFIG. 1(see also,FIGS. 5 and 6). Another side of the spring clip19is “hooked” over a front end21of the crossbar4in front of the angularly bent region12.

The spring clip19comprises a recess22above the cavity17. For a pivotal fixing of the rocker arm1on the corresponding head piece18of the carrier2, the rocker arm1must be placed with the spring clip19over the head piece18in such a way that the recess22of the spring clip19snaps into an undercut23of the respective head piece18. This leads to the creation of a simple, articulated and inseparable pre-assembly of the rocker arm1on the carrier2situated above the rocker arm1. However, other types of articulated and inseparable connections of the rocker arm1to the carrier2are also conceivable.

According toFIG. 5, the head piece18is a component of a pressure piston25of a hydraulic lash adjuster26. A row of pressure pistons25extend downward from the carrier2, so that respective rocker arms1can be pivotally mounted through clips on each pressure piston25. A supply of hydraulic medium to the hydraulic lash adjusters26can be realized through a longitudinal channel27intersecting these.

According toFIG. 6, the lash adjuster is a mechanical lash adjuster28. The respective head piece18has a bolt-like configuration and is a component of the mechanical lash adjuster28that needs no further description in the present context. This solution differs from that ofFIG. 5by the fact that two rows, preferably, of like rocker arms1oriented away from each other are arranged on one carrier2.