Internal-combustion engines – Particular piston and enclosing cylinder construction – Cylinder head
Reexamination Certificate
2002-06-18
2004-06-29
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Particular piston and enclosing cylinder construction
Cylinder head
C123S090270
Reexamination Certificate
active
06755172
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thrust stopper for a camshaft in a cylinder head arrangement for an internal combustion engine. In particular, the present invention is directed to a thrust stopper that is fixed within the cylinder head arrangement to secure a camshaft within the cylinder head housing against axial movement and lateral movement. The thrust stopper in accordance with the present invention ensures that the valve operating assembly is positioned correctly within the cylinder head arrangement.
2. Description of Related Art
JP 09-144 512 A describes a cylinder head with a camshaft and a rocker arm shaft to actuate inlet and exhaust valves, in which the camshaft is secured in the axial direction by two thrust stoppers. Each thrust stopper functions as an axial stop for the camshaft in one direction. The thrust stoppers, which are in the form of sheet metal parts, are secured to the cylinder head arrangement using bolts. This thrust stopper requires multiple installation steps and the use of fasteners, which increases costs and assembly time.
A similar method for securing the camshaft has been used by the assignee of the present invention in scooter motors for a number of years. In this instance, the thrust stopper is also of sheet metal and is secured using bolts to one end face of the cylinder head. In contrast to JP 09-144 512 A, however, the sheet metal part engages in a slot-like recess in the camshaft, and this ensures axial retention in both directions. Thus, only one thrust stopper is required. The slot-like recess or groove is positioned between a camshaft drive assembly and the cam lobes and thus reduces the cross section of the camshaft, which could weaken the camshaft.
Austrian Reference No. AT 3.202 U1 describes a cylinder head with a camshaft and a rocker arm shaft. A positioning device is provided to ensure that the rocker arm shaft is positioned correctly. The positioning device includes a plug that is fixed in a receiving opening in the rocker arm shaft. The plug has a projection formed as a ridge that fits in a groove in the end of the rocker arm shaft. This ensures the rapid and correct positioning of the rocker arm shaft, although the rocker arm shaft can be installed in two positions that are rotated through 180 degrees relative to each other. This positioning device, however, is inadequate for rocker arm shafts that can be used only in one single position.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a thrust stopper for securing a camshaft in a proper orientation within a cylinder head arrangement within an internal combustion engine.
It is another object of the present invention to provide a thrust stopper that prevents axial movement of the camshaft within the cylinder head arrangement.
It is another object of the present invention to provide a thrust stopper for securing the camshaft within the cylinder head arrangement using limited parts and reduced assembly time.
It is another object of the present invention to provide a thrust stopper for securing a valve operating assembly in a proper orientation within the cylinder head arrangement.
It is another object of the present invention to provide a thrust stopper for securing both a camshaft and valve operating assembly in proper orientations within the cylinder head arrangement.
It is another object of the present invention to provide a thrust stopper that may be installed within a cylinder head housing without the use of fasteners.
It is another object of the present invention to provide a thrust stopper that is installed within a cylinder head housing and does not clatter within the housing.
It is another object of the present invention to provide a thrust stopper for securing both a camshaft and a pair of valve operating assemblies in proper orientations within the cylinder head arrangement.
It is yet another object of the present invention to provide a common thrust stopper design that is capable of being used in various engines and engine configurations.
SUMMARY OF THE INVENTION
In response to the foregoing challenges, applicants have developed a thrust stopper for use in a cylinder head arrangement of an internal combustion engine to retain a camshaft in a desired orientation while preventing axial movement of the same. The thrust stopper is configured essentially as a lock that is inserted into a receiving opening or recess in the cylinder head housing. It is contemplated that the thrust stopper can be used for different types of engines. Once the camshaft has been slid into a receiving bore in the cylinder head housing, the camshaft can be secured axially by inserting the thrust stopper into the receiving opening in the cylinder head housing. In order to simplify removal of the thrust stopper from the receiving opening, the receiving opening may incorporate a dismantling recess.
In accordance with the present invention, the thrust stopper includes a first orienting assembly for orienting the camshaft in a predetermined camshaft orientation within the cylinder head housing. The first orienting assembly includes a retaining section formed in the thrust stopper. The retaining section is sized to be received within a groove formed in an outer surface of the camshaft. The groove in the camshaft is located adjacent an end of the camshaft that is opposite to the camshaft drive assembly. The retaining section may have a reduced cross section or thickness with respect to the remainder of the thrust stopper. The retaining section is preferably assymetrically disposed with respect to a vertical mid-plane extending through the thrust stopper.
In accordance with the present invention, the thrust stopper includes a recess located adjacent the retaining section. The recess has a shape that corresponds to the cross section of the outer diameter of the camshaft. The location of the retaining section and the recess on the lower end of the thrust stopper permits the thrust stopper to be inserted into the cylinder head housing in only one orientation. This arrangement ensures that the thrust stopper and in particular the second orienting assembly, described below, is properly oriented. It is preferable that the retaining section is located on one side of the vertical mid-plane and the recess is located on an opposite side of the vertical mid-plane.
As discussed above, the retaining section fits in an annular groove in the camshaft to form an interlocking connection. The side surfaces of the retaining section of the first orienting assembly also serve as an axial bearing for the camshaft. The thrust stopper, and in particular, the retaining section of the first orienting assembly has a plate-like shape. Consequently, the receiving opening is preferably formed as a slot. The plate-like shape permits the retaining section of the thrust stopper to rest against the side surfaces of the annular groove over a relatively large area, which reduces wear. In order to absorb the considerable mechanical stresses in the area of the first orienting assembly, it is preferred that the thrust stopper be formed of a sintered metal.
To save space, the thrust stopper may be arranged in the cylinder head housing at an end of the camshaft that is remote from the camshaft drive system. The thrust stopper can be held captive by a rocker arm shaft and/or by a valve cover on the cylinder head housing. This prevents movement of the thrust stopper in the receiving opening. In some instances, the rocker arm shaft is positioned within the cylinder head housing such that rocker arm shaft secures the thrust stopper within the receiving opening in the cylinder head housing whereby a portion of the rocker arm shaft extends over the thrust stopper. No additional fasteners are needed to fix the thrust stopper in place within the cylinder head housing.
In accordance with the present invention, the thrust stopper may further include a breather channel formed therein. The breather channel forms a passageway from the recess in the thrust stopper adjacent th
Heer Siegfried
Neubock Johann
BRP-Legal Services
BRP-Rotax GmbH & Co. KG
McMahon Marguerite
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