Wraparound drive of internal combustion engines for auxiliary assemblies which are coupled with a force-transmitting connection

Field of the Invention

The invention relates to a wraparound drive of internal combustion en¬ gines for auxiliary assemblies which drive or are driven with a force- transmitting connection and have periodically reoccurring torque fluctua- tions, in particular for piston compressors.

Background of the Invention

Control drives of internal combustion engines having a crankshaft driving wheel, at least one camshaft driven wheel and a chain or a toothed belt or else other assembly drives which are present on internal combustion en¬ gines are subjected to vibrational changes on account of torque fluctua¬ tions or angular velocity changes, which vibrational changes can lead to audible noises in resonant ranges. Associated with this are increased fric- tional forces which can impair the service life of the wraparound drive and its efficiency.

In order to counter these difficulties, it has already been proposed to con¬ figure at least one of the wheels in such a way that it imparts a npnuni- formity to the drive during rotation, this being achieved in DE 195 20 508 A1 by virtue of the fact that either a driving wheel or a driven wheel is con¬ figured to be out of center and/or is mounted eccentrically. Here, this only functions by virtue of the fact that, in control drives of this type, there is exact coordination of the different driving and driven wheels via the toothed belt or the chain, with the result that the compensation can be ef¬ fected by the arrangement of an out of center wheel at any desired loca¬ tion. The out of center compensation wheel can be set and operated with¬ out problems in phase with the torque fluctuations of a completely different driving or driven wheel.

Summary of the Invention

This possibility is absent, however, in the case of wraparound drives for driving or driven auxiliary assemblies which are driven only with a force- transmitting connection, that is to say via Poly V pulleys in a manner af¬ fected by air, a V-ribbed belt being used which does not have teeth which extend transversely with respect to the running direction, but rather pro¬ filed ribs which extend in the running direction.

In order to also attain torque compensation for transmission systems of this type with a force-transmitting connection, that is to say which are sub¬ ject to slip, without synchronization, there is provision according to the invention for the driving or driven wheel of the auxiliary assembly, that is to say, for example, of an air conditioning compressor or of a power steering pump, to be configured out of center in such a way that the nonuniformity which is imparted to the drive as a result compensates at least partially for the torque fluctuations, which can be brought about in the simplest case by the fact that the out of center wheel has elevations which are distributed equidistantly, the number of elevations corresponding to the frequency of the torque fluctuations.

Depending on the type of torque fluctuations which are caused by the nonuniformities on account of the curved movement of the auxiliary as- semblies, there can be provision here, in a refinement of the invention, for the elevations of the out of center wheel to be offset, so as to lead or trail, with regard to the torque fluctuations of the auxiliary assembly, in order for it to be possible in this way to achieve optimum drive smoothing. Brief Description of the Drawings

Further advantages, features and details of the invention emerge from the following description of an exemplary embodiment and using the drawing, in which:

fig. 1 shows a section through an air conditioning compressor having torque compensation,

fig. 2 shows a diagram of the force at the driving wheel plotted against the rotational angle, and

fig. 3 shows a view of the out of center driving wheel, shown in an exaggerated manner for illustrative reasons.

Detailed Description of the Drawings

Fig. 1 shows an air conditioning compressor, in the case of which the movement of the pistons 1 causes periodically reoccurring torque fluctua- tions in accordance with the number of pistons, which torque fluctuations can also not be suppressed by the various axial bearings 2 and 3 and the radial bearings 4, 5 and 6. The driven wheel 7 which is configured as a Poly V pulley shows the force profile, which is indicated diagrammatically in fig. 2 against the rotational angle, with periodic fluctuations in accor- dance with the five pistons which are provided here. In order to compen¬ sate for these torque fluctuations, the driven wheel 7 is configured to be out of center, as is shown in an exaggerated manner in a side view in fig. 3. There are five equidistantly distributed elevations 8 with depressions 9 lying between them, compared with a base circle 10. Here, the wheel 7 is arranged on the shaft 11 of the air conditioning compressor in such a way that there is a defined angular offset between the maxima of the force fluc¬ tuations in fig. 2 and the position of the peaks of the raised portions 8, in order for it to be possible to achieve optimum drive smoothing by means of such a leading or trailing arrangement. The configuration of the driving wheel 7 of the air conditioning compressor as an out of center compensa¬ tion wheel makes synchronization possible with respect to the periodically reoccurring torque fluctuations caused by the piston movements of the air conditioning compressor, although drive is effected in a manner which is subject to slip and is unsynchronized with respect to the internal combus¬ tion engine. List of reference numerals

Piston Axial bearing Axial bearing Radial bearing Radial bearing Radial bearing Wheel Elevations Depressions Base circle Shaft