Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
1999-07-06
2001-02-13
Walberg, Teresa (Department: 3742)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090370
Reexamination Certificate
active
06186103
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a device for varying valve timing of gas exchange valves of an internal combustion engine, particularly a vane-type camshaft adjusting device comprising:
a drive pinion configured as an outer rotor and connected in driving relationship to a crankshaft of the internal combustion engine by a traction means, said drive pinion having a hollow space defined by a circumferential wall and two side walls,
a winged wheel configured as an inner rotor and connected rotationally fast to a camshaft of the internal combustion engine, which winged wheel is inserted into the hollow space of the drive pinion and has a wheel hub on whose periphery are radially arranged at least two wings,
at least two working chambers defined within the hollow space of the drive pinion by limiting walls extending from an inner surface of the circumferential wall towards a central longitudinal axis of the drive pinion, radial end faces of the limiting walls being in sealing contact with the wheel hub of the winged wheel by sealing strips arranged in axial retaining grooves, each working chamber being divided into two hydraulic pressure chambers by one of the wings of the winged wheel, radial end faces of the wings being in sealing contact in each working chamber with the inner surface of circumferential wall by sealing strips likewise arranged in axial retaining grooves, and
a turning and/or fixing of the winged wheel relative to the drive pinion, and thus a relative rotation and/or a continuous hydraulic clamping of the camshaft relative to the crankshaft is obtained by an optional successive or simultaneous pressurizing of the pressure chambers by a hydraulic pressure medium.
BACKGROUND OF THE INVENTION
A generic camshaft adjusting device of the pre-cited type is known from EP 0 799 976 A1 and comprises a drive pinion configured as an outer rotor which is connected in driving relationship to a crankshaft of an internal combustion engine by a traction means, and a winged wheel configured as an inner rotor and connected rotationally fast to a camshaft of the internal combustion engine. The drive pinion comprises a hollow space defined by a circumferential wall and two side walls, into which hollow space is inserted the winged wheel which comprises four radially arranged wings on the periphery of its wheel hub. Four hydraulic working chambers are defined within the hollow space of the drive pinion by four uniformly spaced limiting walls which extend from the inner surface of the circumferential wall toward the central longitudinal axis of the drive pinion. Each of the working chambers is divided into two hydraulic pressure chambers by one of the wings of the winged wheel. The radial end faces of the limiting walls of the drive pinion are in sealed contact with the wheel hub of the winged wheel by sealing strips arranged in axial retaining grooves, while, at the same time, the radial end faces of the wings of the winged wheel are in sealed contact with the inner surface of the circumferential wall of the drive pinion by sealing strips likewise arranged in axial retaining grooves. Thus, by an optional successive or simultaneous pressurizing of the pressure chambers by a hydraulic pressure medium, the winged wheel can be turned and/or fixed relative to the drive pinion to obtain a relative rotation and/or a continuous hydraulic clamping of the camshaft relative to the crankshaft.
A drawback of this prior art device is that, besides the radial sealing of the individual pressure chambers from one another by the sealing strips on the radial end faces of the wings and the limiting walls, no measures are provided for an axial sealing of the pressure chambers of the device from one another. Thus, particularly when manufacturing tolerances in the axial dimension of the drive pinion and the winged wheel add up and produce a relatively large axial play between the winged wheel and the drive pinion, it is possible that internal pressure medium leaks or hydraulic short circuits between the pressure chambers, which always have a detrimental effect on the functioning of the adjusting device, take place through the gaps formed between the wings of the winged wheel and the side walls of the drive pinion. These malfunctions manifest themselves generally in the form of reduced adjusting speeds of the device which are the cause of a delayed response of the device to changing conditions of operation of the internal combustion engine, or in the form of an insufficient hydraulic clamping of the winged wheel in the drive pinion, so that the desired angular position of the camshaft relative to the crankshaft cannot be exactly maintained.
Further, DE-OS 39 22 962 discloses the use of axial sealing strips arranged in radial retaining grooves on the end surfaces of the wings in addition to the radial seals on the end faces of the wings in a camshaft adjusting device likewise comprising a drive pinion with four working chambers and a winged wheel with four wings.
However, such a sealing of the individual pressure chambers of the device has the drawback that it requires a large number of separate sealing strips and thus considerably more assembly work is involved in the manufacturing of the device. Moreover, due to the joint gaps naturally formed between the individual sealing strips, high pressure medium leakage can still occur so that the aforesaid resulting malfunctions of the device are not completely eliminated by such a sealing arrangement.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to create a device for varying the timing of gas exchange valves of an internal combustion engine, particularly a vane-type camshaft adjusting device whose hydraulic pressure chambers are additionally sealed from one another in axial direction without the need of a plurality of separate sealing strips and irrespective of manufacturing tolerances of the axial dimension of the drive pinion and the winged wheel.
It is a further object of the invention to reduce internal pressure medium leakage in the device 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 these objects in a device of the pre-cited type by the fact that the sealing strips on the radial end faces of the limiting walls of the drive pinion and/or the sealing strips on the radial end faces of the wings of the winged wheels are joined to each other by radial and coaxial struts along axial end surfaces of the drive pinion and/or along axial end surfaces of the winged wheel to form a one- or a multi-piece sealing cage which enables a sealing of the hydraulic pressure chambers in the hollow space of the drive pinion from one another both radially on the circumferential wall of the drive pinion and/or on the wheel hub of the winged wheel, as also axially on the side walls of the drive pinion, the sealing cage further enabling a compensation of axial manufacturing tolerances between the drive pinion and the winged wheel of the device.
In a first preferred embodiment of the seal of the invention, the pressure chambers in the hollow space of the drive pinion are sealed radially on the circumferential wall of the drive pinion by the sealing strips on the radial end faces of the wings of the winged wheel, and for sealing the pressure chambers radially on the wheel hub of the winged wheel and axially on the side walls of the drive pinion, only the sealing strips on the radial end faces of the limiting walls of the drive pinion are joined to one another to form a one- or a multi-piece sealing cage. Each limiting wall of the drive pinion preferably comprises two sealing strips arranged next to each other in retaining grooves provided on the radial end faces of the limiting walls. Each sealing strip of a limiting wall is joined to a sealing strip of the adjacent limiting wall to form a sealing cage element which seals the pressure chambers of one of the working chambers of the drive pinion axially and radially and c
Schafer Jens
Schindler Manfred
Bierman, Muserlian and Lucas
Ina Walzlager Schaeffler OHG
Patel Vinod D.
Walberg Teresa
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