Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2000-10-25
2002-07-16
Walberg, Teresa (Department: 3742)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090170, C123S090310, C123S090120
Reexamination Certificate
active
06418893
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device for varying valve timing of gas exchange valve of an internal combustion engine, and in particular to a hydraulic camshaft adjusting device of a rotary piston type, wherein:
the device is disposed on a drive-proximate end of a camshaft mounted in the cylinder head of the internal combustion engine and generally comprises a drive pinion configured as an outer rotor and a winged wheel configured as an inner rotor;
the drive pinion is in driving relation with a crankshaft of the internal combustion engine through a circumferential gearing, and the winged wheel is fixedly mounted on the camshaft;
the drive pinion comprises a hollow cylindrical circumferential wall, a camshaft-distal side wall and a camshaft-proximate side wall, said circumferential and side walls being connected to one another and together defining a hollow space;
at least one hydraulic working chamber is formed in the hollow space of the drive pinion by at least two limiting walls that start from an inner side of the circumferential wall and extend in radial direction toward a central longitudinal axis of the device;
a hub of the winged wheel comprises at least one wing on a periphery thereof which wing extends in radial direction into the working chamber of the drive pinion and divides the working chamber into two hydraulic pressure chambers;
a rotation or a fixing of the winged wheel relative to the drive pinion, and thus also of the camshaft relative to the crankshaft, is effected respectively by a selective or a simultaneous pressurization of the pressure chambers with a hydraulic pressure medium.
BACKGROUND OF THE INVENTION
A device of the pre-cited type is disclosed in the German document DE-OS 198 29 049. This device is arranged on the drive-proximate end of a camshaft mounted in the cylinder head of the internal combustion engine and generally comprises a drive pinion configured as an outer rotor and a winged wheel configured as an inner rotor. The drive pinion of the device is in driving relation with a crankshaft of the internal combustion engine through a circumferential gearing, and the winged wheel is fixedly mounted on the camshaft of the internal combustion engine. The drive pinion further comprises a hollow cylindrical circumferential wall, a camshaft-distal and a camshaft-proximate side wall, which walls are connected to one another and to a gearing, made in the described embodiment as a separate annular toothed belt pulley, by a number of screw connections and together define a hollow space. Six hydraulic working chambers are formed in the hollow space of the drive pinion by six limiting walls that start from an inner side of the circumferential wall and extend in radial direction toward the central longitudinal axis of the device. Each working chamber is divided into two hydraulic pressure chambers by a wing of the winged wheel arranged on the periphery of the hub of the winged wheel and extending in radial direction into each working chamber. These pressure chambers can be selectively or simultaneously pressurized by a hydraulic pressure medium so that a rotation or a hydraulic fixing of the winged wheel relative to the drive pinion, and thus also a rotation or a fixing of the camshaft relative to the crankshaft is effected.
From the device of a similar structure for effecting a rotation of a camshaft relative to a crankshaft of an internal combustion engine disclosed in U.S. Pat. No. 4,858,572, it is also known to configure the circumferential wall and the camshaft-proximate wall of the drive pinion together with a circumferential gearing for a toothed belt as a one-piece shaped component on which a camshaft-distal side cover is screwed to thus form a hollow space. In this hollow space, too, six hydraulic working chambers are formed by limiting walls extending from the inner side of the circumferential wall. However, in this device, the first three working chambers can be pressurized by a hydraulic pressure medium only in one direction of rotation, and the second three working chambers, only in the other direction of rotation for realizing a rotation or a fixing of the winged wheel relative to the drive pinion.
A drawback of these prior art devices, however, is that, particularly due to the solid configuration of the circumferential wall and side walls of the drive pinion as separate steel parts or even as integrally shaped parts out of sintered metal, they have a relatively high weight and require a large axial design space in or on the cylinder head of the internal combustion engine and, at the same time, they increase the manufacturing and mounting costs of such devices. Connecting the individual elements of the drive pinion to one another by screws has the further drawback that the bores required for the screws can lead to the formation of additional leak points, particularly in the side walls, and may have to be additionally sealed. A drive pinion made out of shaped sintered metal parts on the other hand, has the inherent drawback that rounded corners are formed at the inner transition from the circumferential wall to the side wall which make the fabrication of suitable wings more difficult or cause higher inner, pressure medium leakage in the device. Practice has further shown that in belt-driven devices whose camshaft-proximate side wall comprises an aperture for the camshaft having a shaft-seal receiving edge portion that is angularly disposed relative to the cylinder head, sintered metal is unsuitable as a running surface for the shaft seal that seals the device relative to the cylinder head.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to provide a device for varying the valve timing of gas exchange valves of an internal combustion engine, and in particular a hydraulic camshaft adjusting device of a rotary piston type, which has a low weight and small overall dimensions, while being economic to manufacture and mount.
Another object of the invention is to provide the above device with a simple structure which reduces internal and external pressure medium leakage to a minimum.
These and other objects and advantages of the invention will become obvious from the following detailed description.
SUMMARY OF THE INVENTION
The invention achieves the above objects in a device of the initially described type by the fact that the camshaft-proximate side wall of the drive pinion is configured as a weight- and design space-saving component which is shaped out of a circular blank and at least partially surrounds the circumferential wall of the drive pinion while comprising an edge region that is bent at least almost at a right angle. The camshaft-distal side wall, the circumferential wall and the gearing of the drive pinion are fixed by common fastening means to one another, while the camshaft-proximate side wall is secured on the drive pinion by a separate connection that increases the axial stiffness of the side wall.
The common fixing of the camshaft-distal side wall, the circumferential wall and the gearing of the drive pinion is advantageously realized according to the invention in that the circumferential wall of the drive pinion comprises on an outer side thereof a preferably circumferentially continuous enlarged diameter connecting flange on whose rear side the camshaft-distal side wall and on whose front side the gearing of the drive pinion are secured by common screws. The camshaft-distal side wall has the same diameter as the connecting flange of the circumferential wall of the drive pinion and is in flat contact with this and with the camshaft-distal axial surfaces of the limiting walls of the drive pinion. To further reduce the weight of the device, the circumferential connecting flange may be replaced with a plurality of equally spaced local flanges on the outer side of the circumferential wall of the drive pinion, and/or the camshaft-distal side wall may be made with a diameter corresponding to the smaller diameter of the rest of the circumferential wall and with a corresponding number of flange
Auchter Jochen
Strauss Andreas
Bierman, Muserlian and Lucas
Dahbour Fadi H.
INA Walzlager Schaeffler oHG
Walberg Teresa
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