Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
1999-10-08
2001-01-09
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090370
Reexamination Certificate
active
06170447
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns an internal sealing of a camshaft-adjusting device in an internal combustion engine, particularly a vane-type adjusting device comprising a drive pinion configured as an outer rotor which is connected to a crankshaft of an internal combustion engine by a toothed belt or a timing chain or by gears, said drive pinion comprising a hollow space defined by a circumferential wall and two side walls, a toothing being provided on the outer surface of the circumferential wall and at least one working chamber having limiting walls directed toward the central longitudinal axis of the drive pinion being made in the inner surface of the circumferential wall, a winged wheel which has at least one radial wing and is configured as an inner rotor rotationally fixed to the camshaft being inserted into the hollow space of the drive pinion, wings of the winged wheel dividing each working chamber into two pressure chambers which, when pressurized successively or simultaneously by a pressure oil, effect a rotation and/or an infinitely variable hydraulic clamping of the camshaft relative to the crankshaft.
BACKGROUND OF THE INVENTION
In vane-type adjusting devices of the aforesaid type commonly known in the art, the sealing of the pressure chambers in the hollow space of the drive pinion against pressure oil leakage is generally effected on the one hand by two narrow radial gaps arranged between the wings of the winged wheel and the circumferential wall and between the hub of the winged wheel and the circumferential wall of the drive pinion, and on the other hand by two narrow axial gaps between the side walls of the wings of the winged wheel and the side walls of the drive pinion. From the manufacturing point of view, it is, however, not possible, or possible only at very high expense, to make two narrow or sealing gaps in radial direction in such vane-type adjusting devices because this results in an overdetermination between the winged wheel and the drive pinion so that one of the radial gaps inevitably does not seal as intended. In spite of complicated manufacturing and a perfect fit of the individual parts of such adjusting devices, increasing leakage of the pressure oil through the radial and axial gaps in excess of the restricted leakage required, per se, occurs with increasing temperature of the pressure oil during engine operation. This leads to a reduction of the oil supply pressure and thus to retarded adjustment and a too weak hydraulic clamping of the winged wheel and thus of the camshaft. This has a strong detrimental effect at high oil temperatures because the viscosity and the oil supply pressure are then particularly low so that a frequent re-adjustment of the adjusting positions given by the characteristic diagram of engine timing is required and/or higher oil flow rates have to be provided for.
From another actuating device for a camshaft disclosed in DE-OS 39 22 962, it is further known to make axial and radial grooves in the wings of the winged wheel and arrange spring-mounted seals in these grooves to sealingly cooperate with the circumferential wall and the side walls of the hollow space of the drive pinion.
The manufacturing of vane-type adjusting devices with such sealing measures has proved to be very complicated and expensive, and, due to the transition junctions between the individual axial and radial seals, these sealing measures cannot assure a satisfactory reduction of leakage values.
OBJECT OF THE INVENTION
It is therefore the object of the invention to conceive an internal sealing for a camshaft adjusting device of an internal combustion engine, particularly a vane-type adjusting device, with which undesired pressure oil leakage between the pressure chambers in the hollow space of the drive pinion can be reduced to a minimum by simple and cost-effective means.
SUMMARY OF THE INVENTION
This object is achieved according to the invention in a vane-type adjusting device by the fact that each wing of the winged wheel is configured as a separate wing segment which is displaceable within a guide in the winged wheel and exhibits a distance both radially from the circumferential wall of the drive pinion in the respective working chamber and axially from the side walls of the drive pinion, which distance is sealed leak-tight radially by the radial centrifugal force which results from the rotation of the vane-type adjusting device during engine operation and acts on the wing segment, and axially by least one prestressed axial sealing element.
The vane-type adjusting device configured according to the invention thus contrasts positively with the state of the art in that the fabrication of the winged wheel is substantially simplified and, at the same time, the leakage values in the hollow space of the drive pinion are minimized to the greatest possible extent. It is true that the winged wheel configured according to the invention comprises more individual elements than hitherto usual but these elements do not have to be made to the close tolerances required in prior art vane-type adjusting devices which have a disadvantageous effect on the time and costs involved in the manufacturing of the vane-type adjusting device. Additionally, due to the inventive separation of the wings of the winged wheel from the hub of the winged wheel, an overdetermination between the hub, the winged wheel and the drive pinion is no longer possible so that an exact radial sealing gap can be obtained between the hub of the winged wheel and the circumferential wall of the drive pinion.
In an advantageous embodiment of the invention, the guide for each wing segment is made in the hub of the winged wheel preferably as a radial groove which extends parallel to the central longitudinal axis, has axial side walls parallel to each other and surrounds the inserted, preferably cuboid wing segment approximately up to half of its height. The optimum solution with regard to achieving the desired angle of adjustment between the crankshaft and the camshaft as well as the required adjusting speed and hydraulic clamping force is to provide three such radial grooves uniformly spaced on the hub of the winged wheel and arrange three identical wing segments in these radial grooves. The scope of protection of the invention, however, also extends to configurations in which the winged wheel has less than three or even more than three wing segments, and/or configurations in which the wing segments are surrounded by the radial grooves to a higher or even a lower level than half their height. Similarly, the preferred cuboid configuration of the wing segments is only one of several possible shapes because with such wing segments, it is possible to achieve a relatively long radial sealing gap and thus a high degree of leak-tightness between the pressure chambers in each working chamber.
According to a further feature of the invention, the sealing surface of each wing segment cooperating with the circumferential wall of the drive pinion in each working chamber therefore preferably has in radial direction, the same radius and in axial direction, the same surface contour as the circumferential wall in each working chamber. In contrast, the bottom surface of each wing segment situated opposite this sealing surface, which may also have a smaller radius, preferably has a straight configuration, so that the wing segment, at the same time, possesses good sliding properties within the working chamber during the adjusting operation, and a canting or tilting of the wing segments within the guides is substantially excluded. Pressure medium leakage through the gaps formed on a side wall of the guide and/or under the bottom surface of the wing segments due to the radial movability of the wing segments is likewise substantially excluded because the pressure of the pressure medium prevailing in a pressure chamber at any time is likewise present in these gaps. As is the case with steel sealing rings, this pressure effects, on the one hand, that the wing segments are sealingly pressed against the side w
Auchter Jochen
Kohrs Mike
Schafer Jens
Biermzan, Muserlian and Lucas
Ina Schaeffler oHG
Lo Weilun
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