Patent Application
20130220254
The invention concerns a rocker arm for actuating a gas exchange valve of an internal combustion engine.
In internal combustion engines, rocker arms are located in a valve train as transmission elements between cams and the gas exchange valves to be actuated. Rocker arms consist of a lever body that is supported at one of its ends on a support element and with its other end engages, through a contact surface, the gas exchange valve to be opened. In a section of the lever body near the center, a cam pickup surface is provided on which a cam of a camshaft runs during operation of an internal combustion engine, causing a pivoting motion of the rocker arm. The cam pickup surface can be implemented as a sliding surface or as a cam roller.
A rocker arm for actuating a gas exchange valve of an internal combustion engine is known from DE 10 2008 029,333 A1. At one end, the rocker arm has an oval opening that encompasses a valve stem end of the gas exchange valve. In addition, the rocker arm provides a cam roller in a section near the center.
WO2011/157499 A1 discloses a rocker arm that has a cam roller supported on an axle pin by means of a needle roller and cage assembly. A contact surface for a valve stem end of the gas exchange valve is provided at one end of the rocker arm. Side bars are provided in the region of the contact surface to guide the rocker arm on the valve stem end.
The object of the present invention is to provide a rocker arm that can be manufactured economically and that ensures adequate stiffness.
According to the invention this object is attained by a rocker arm for actuating at least one gas exchange valve of an internal combustion engine having an elongated lever body with a floor and with side walls angled away therefrom, wherein a first end section of the lever body has a cup for a support element formed in the floor, and in that a section near the center is provided with a cam engagement surface and in that a second end section of the lever body has a contact surface for a valve stem end of the gas exchange valve, wherein a crossbar extends between the section near the center and the second end section and wherein the crossbar has a stamping that is provided on the side facing away from the section near the center.
In the rocker arm according to the invention, the crossbar is provided with a stamping. The stamping can be an embossing, for example. The stamping in the crossbar makes it possible to avoid contact between the valve stem end and the lever body during pivoting motions of the rocker arm. The necessary stiffening of the rocker arm is ensured by the crossbar, which in turn results in increased strength of the rocker arm.
In a preferred embodiment of the invention, the shape of the stamping is matched to the valve stem end. This means that the shape of the stamping is designed to be complementary to the shape of the valve stem end. Preferably the stamping is implemented as a cylindrical molding.
Preferably the second end section of the lever body has a W-shaped profile when viewed in cross-section. As a result of the W-shaped profile, the side bars known from the prior art that would be necessary for valve guidance are eliminated. This has the advantage that the weight of material used can be reduced, and thus the production costs can be decreased. The W-shaped profile preferably is open in the direction facing away from the gas exchange valve. However, a reversed arrangement of the W-shaped profile is also possible.
In another embodiment of the invention, a distance between a longitudinal center of the cup and a center of rotation of the cam pickup surface is half as large as or less than half a distance between the longitudinal center of the cup and a center of a contact region of the gas exchange valve at the contact surface. Accordingly, the cam pickup surface can be positioned close to the contact region of the gas exchange valve. This has the advantage that the overall length of the rocker arm can be shortened to achieve a compact component.
In one embodiment, the cam pickup surface is implemented by a cam roller, and the section near the center has a recess in the floor that serves to accommodate the cam roller. The recess in the floor creates the necessary free space for the cam roller so that rotary motion of the cam roller is possible.
Preferably, the lever body is either produced by stamping and forming techniques from a sheet metal material, or by extrusion molding. However, other materials and manufacturing methods are also possible.
An exemplary embodiment of the invention is explained below using three figures.
They show:
Formed in the part of the floor 3 running along the first end section 6 is a cup 9, which rises between the side walls 4, 5. The cup 9 provides support on a support element that is not shown.
In the region of the section 7 near the center, each of the side walls 4,5 has a bore 10 serving to support a cam roller that is not shown. The cam roller that is not shown defines a cam pickup surface. A recess 11 designed with a rectangular outer contour is provided in the part of the floor 3 running along the section 7 near the center.
A contact surface 12 for a valve stem end, not shown, of a gas exchange valve is provided on the part of the floor 3 running along the second end section 8 of the lever body 2. A crossbar 13 that is provided between the side walls 4,5 extends between the second end section 8 and the section 7 near the center. The crossbar 13 has a stamping 14, which is implemented as a cylindrical molding, on the side facing away from the section 7 near the center. The stamping 14 makes it possible for adequate clearance of the contact surface relative to the gas exchange valve, not shown, to be present during pivoting motions of the rocker arm 1.
A distance L1 is defined between the longitudinal center 15 of the cup 9 and the center of rotation 17 of the cam pickup surface. A distance L2 is defined between the longitudinal center 15 of the cup 9 and a center of the contact region 18 of the gas exchange valve. The distance L1 here is half as large as or less than half the distance L2. This distance ratio makes possible a short, compact lever body 2.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102012203107.3 | Feb 2012 | DE | national |
