Device for altering the control timing of gas exchange...

Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing

Reexamination Certificate

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Details

C123S090170, C123S090270, C123S090310, C251S012000, C464S160000

Reexamination Certificate

active

06619248

ABSTRACT:

BACKGROUND
The invention relates to a device for altering the control times of gas exchange valves of an internal combustion engine, especially an apparatus for hydraulic rotational angle adjustment of a camshaft relative to a crankshaft, in which the device is arranged on the drive side end of a camshaft mounted in the cylinder head of the internal combustion engine and is basically constructed as hydraulic actuator controllable as a finction of various operating parameters of the internal combustion engine. The device includes a drive unit drivingly connected with a crankshaft and bounded axially by two lateral covers as well as of an output unit connected in a rotationally fast manner to a camshaft and inserted into the drive unit. The drive unit of the device is connected to provide power transmission to the output unit of the device through at least two pressure chambers formed inside the device, which are alternatively or simultaneously acted upon by a hydraulic pressure medium, The action of pressure in the pressure chambers takes place under constant compensation for external pressure medium leakages and brings about a relative twisting or a hydraulic clamping of the output unit in relation to the drive unit. For adapting the adjustment speed of the device in both adjustment directions as well as for attaining a preferred position of the output unit toward the drive unit for the start of the internal combustion engine, the device has a spring apparatus constructed as a coil spring arranged outside the device in front of a lateral cover of the drive unit which is fastened with one end on the drive unit and with the other end on the output unit, and it is especially advantageously realizable on an apparatus for hydraulic rotational angle adjustment of a camshaft relative to a crankshaft.
From DE 100 01 200 A1, a representative device for altering the control times of the gas exchange valves of an internal combustion engine is known which is arranged on the drive-side end of a camshaft mounted in the cylinder head of an internal combustion engine and is constructed, depending upon various operating parameters of the internal combustion engine, of controllable hydraulic actuators. This device basically includes a drive unit drivingly connection with the crankshaft and axially bounded by two walls, as well as an output unit connected in a rotationally fixed manner with the camshaft and inserted into the drive unit, which stand in power transmitting connection through at least two pressure chambers pressure chambers constructed within the device which are alternatively or simultaneously subject to action by a hydraulic pressure medium. The drive unit is formed in connection with this device by a hollow cylinder drive gear constructed with exterior teeth in which, due to radial partitions, several hydraulic operating spaces arise. Correspondingly, with this device, an impeller is provided as output unit which is constructed with several vanes extending radially away from its wheel hub which subdivide the operating spaces in the drive unit into at all times two of the hydraulic pressure chambers mentioned. When these pressure chambers are acted upon by pressure, there consequently arises (with constant compensation for external pressure medium leakage) a relative rotation or a hydraulic clamping of the output unit of the device, and therewith of the camshaft in relation to the crankshaft of the internal combustion engine. In addition, this device has, for adapting their adjustment speeds in both adjustment directions as well as for reaching a preferred position of the output unit in relation to the drive unit for starting the engine, a spring apparatus which is constructed as a coil spring arranged outside the device adjacent to a side cover of the drive unit and fastened with one end on the drive unit and with the other end on the output unit.
With this known device, it has nonetheless turned out in practice that the coil spring used is excited to sympathetic vibrations on the basis of its free arrangement outside the device by the vibrations emitted by the internal combustion engine. If the coil spring then oscillates in its resonant frequencies, in an unfavorable case oscillation amplitudes of such magnitude occur that the excess tension elevations lead to breakage of the coil spring. With an altered winding of the coil spring, the resonance frequency can indeed be diminished by restricting the path of the spring turn available for oscillation. But such measures have not proved sufficient for designing the coils springs secure against breakage.
SUMMARY
For this reason, the object is to provide a device for altering the control times of gas exchange valves of an internal combustion engine, especially an apparatus for hydraulic rotational angle adjustment of a camshaft in relation to a crankshaft, where without impairing the function of the device as well as without alterations of the structural space of the device, using simple means, an oscillation of the coil spring excited by vibrations of the internal combustion engine in its resonant frequencies, and an oscillation breakage of the coil spring therewith, is avoided.
This object is accomplished with a device according to the invention in such a way that the coil spring arranged outside the device is arranged using an additional housing in a closed annular space formed together with the adjacent side cover of the drive unit through encapsulation, which in interaction with the centrifugal forces arising in the operation of the internal combustion engine, is completely fillable with the external pressure medium leakage from the device, and out of which the hydraulic pressure medium is once again dissipatable as leakage, whereby when the annular space is completely filled, the hydraulic pressure medium functions at the same time as a damping agent against the resonant frequencies of the spring turns of the coil spring resulting from vibrations of the internal combustion engine.
In a preferred aspect of the device constructed in accordance with the invention, the additional housing is made of a cup-like housing cover into the base of which a coaxial circular opening is provided, which forms the outer bounding walls of the annular space, as well as well as of a casing-like housing hub which is insertable into the circular opening in the housing cover and which forms the internal boundary wall of the annular space. The two part construction of the additional housing has proven to be particularly advantageous with respect to the economical manufacture of the housing parts as stamped-drawn parts as well as with respect to fastening the ends of the coil spring on the one hand on the drive unit and on the other on the output unit. Nevertheless, a more than two part construction of the housing is also possible, along with its manufacture in non-cutting formed or a machined part.
An further advantageous configuration of the cup-like housing cover of the device constructed in accordance with the invention includes a circumferential wall which has an inner diameter corresponding approximately to the outer diameter of the adjacent side cover of the drive unit as well as a lengthened edge part with which the housing cover is affixable on the side cover of the drive unit. The circumferential wall is here preferably bent at right angles to the base of the housing cover and, due to the lengthened edge part, has a height which goes slightly beyond the width of the coil spring arranged in the annular space.
For affixing the housing cover on the lateral cover of the drive unit, the housing cover has in further configuration of the invention a circular step in its circumferential wall which lies face-side on the lateral cover of the drive unit and consequently on the one hand forms an axial stop for the housing cover to avoid an axial clamping of the coil spring arranged on the housing, and on the other hand centers the housing cover toward the lateral cover of the drive unit. Through several detents distributed uniformly in the circumference i

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