Damping system for gear transmissions

Abstract

Damping system for gear transmissions for reducing noise generation, wherein: - at least one gear (1) of the transmission consists of at least two areas that vibrate relative to each other, - a damping element is provided on at least one of the gear areas, which consists of a damping layer in contact with one of the gear areas and a cover plate (7), - the damping layer is formed from elastomeric material (8; 11; 13), - the elastomeric material (8; 11; 13) is vulcanized or bonded to the cover plate (7), - which is connected with the elastomeric material (8; 11;13) connected cover plate (7) directly abuts the respective gear section and is fastened to the respective gear section by a screw or rivet, - the cover plate (7) has the form of a metal band (9) whose wide side is axially oriented and extends circumferentially around the entire circumference of the respective gear section, or - the cover plate (7) has the form of a metal band (10) whose wide side is radially oriented and extends annularly around the entire circumference of the respective gear section (4), or - the cover plate (7) has in cross-section the form of an angle (12), one leg of which points axially and the other leg radially, and the angled cover plate (7) extends around the entire circumference of at least one gear section (4, 5).

Description

The invention relates to a damping system for gear transmission for reducing the generation of noise, wherein at least one gear wheel of the transmission consists of at least two regions which oscillate relative to one another.Gear noise, especially in reduction gears followed by electric motors, is caused by periodic excitation mechanisms and also generated by the drive wheel itself. Such excitation mechanisms lead directly and / or directly to sounds in the form of airborne sound. Direct sound emitting mechanisms are the excitation mechanisms that are transmitted from the excited reduction gear to the gear housing. These transmission noises can be suppressed, for example, only to a limited extent by a correspondingly designed transmission housing. More important are the indirect vibration transmissions which are introduced by a time-varying operating force into the transmission structure, where they are radiated in the form of airborne sound and perceived as transmission coils. The causes for this are shape errors of the gear geometries, axial distance errors and / or gear surface errors, which can lead to a modulation of the operating force and to deformations and displacements of the gear itself. In practice, this sum of errors is very difficult to control and with very high technical complexity.In a known damping system of the type mentioned at the beginning (DE 31 41 101 A1), a gearwheel has disks fastened to the end faces of its gearwheel body. Viscoelastic damping members are provided between the disks and the gearwheel body, which damping members are firmly connected in a positive-locking manner both to the gearwheel body and to the disks. The disks are fastened to the gear body with a viscoelastic adhesive, which in the present case represents the damping element. According to this prior art, the gear body, the elastic damping members in the form of the viscoelastic adhesive and the disks thus form a positively connected unit. With such a system, it is not possible to damp the entire frequency band which arises in particular when the drives of electric vehicles develop noise. Moreover, this known damping system acts only for damping radial oscillations.Another known damping system of the type mentioned at the beginning (DE 37 11 359 A1) operates according to the same principle, wherein, however, not only radial vibrations but also axial vibrations as well as a combination of axial vibrations and radial vibrations can be damped. However, this known system also does not dampen the complete frequency band of the noises, which are caused in particular by the electric motors of electrically operated motor vehicles.Finally, it is known from U.S. Pat. No. 4,825,712 that a cover plate is connected to the respective gearwheel region via a screw connection. This known damping system is designed in sandwich construction, wherein a plate of viscoelastic material is enclosed between the respective cover plate and the gearwheel body, which plate is connected to the gearwheel on one side and to the respective cover plate on the other side via separate adhesive layers. Such a damping system has the same disadvantages as in the damping systems described above.It is already known from DE 100 58 482 A1 to minimize this noise generation by means of angular momentum damping in that one of the gears of the transmission is composed of at least two axially aligned wheel parts which are connected to one another in a torque-proof manner by elastic means, but having internal damping. The means for the elastic connection of the parts are formed by bolts distributed uniformly over the circumference with an elastomer, wherein a rigid part of the bolts is firmly connected to a first wheel part, while the elastomer concentrically surrounding the rigid part of the bolt engages positively in bores of the second wheel part.Furthermore, EP 2 228 564 A1 discloses modified gear systems for noise control, which consist of a main gear transmitting the torque and an auxiliary gear offset with respect to the main gear in the basic position, wherein the auxiliary gear is elastically supported with respect to the main gear in the circumferential direction via spring elements made of polymer materials. During operation, the spring elements are subject to thrust when the auxiliary gearwheel is rotated relative to the main gearwheel. As a result, due to the properties of the polymer material, a certain amount of damping occurs, which leads to a reduction in the noise.The invention is based on the object of reducing the noise generation of gear drives even further and in particular of attenuating the entire frequency spectrum which arises in particular in reduction gearings of electric drives in motor vehicles.According to the invention, this object is achieved by a novel combination of features according to claim 1, wherein a damping means is provided on at least one of the gearwheel regions, said damping means consisting of a damping layer which bears against one of the gearwheel regions and a cover plate, the damping layer being formed from elastomeric material, the elastomeric material being vulcanized or adhesively bonded onto the cover plate, the cover plate connected to the elastomeric material bears directly against the respective gearwheel region and is fastened to the respective gearwheel region by means of a screw connection or riveting, the cover plate having the shape of a metal strip, the broad side of which is aligned axially and extends in the circumferential direction around the entire circumference of the respective gearwheel region, or the cover plate having the shape of a metal strip, the broad side of which is aligned in a radial arrangement and extends annularly around the entire circumference of the respective gearwheel region, or the cover plate has in cross section the shape of an angle, of which one limb points in the axial direction and the other limb points in the radial direction, and the angled cover plate extends around the entire circumference of at least one gearwheel region.The damping system according to the invention can act both in the circumferential direction and in the axial and / or radial direction and alternatively also simultaneously in all said directions.For the damping layer, an elastomeric material is suitably selected which is provided with both resilient and damping properties.The damping system according to the invention is suitable in particular for use in reduction gears of motor vehicles with an electric drive, wherein the reduction gears can be designed as a single-stage or multi-stage spur gear or also as a planetary gear.The invention is illustrated by way of example in the drawing and described in detail below with reference to the drawing. The following are shown: FIG. 1 : shows a schematic illustration of a first exemplary embodiment of a gearwheel with damping system mounted on a shaft, FIG. 2 shows a second exemplary embodiment of a gearwheel with a damping system mounted on a shaft, FIG. 3 : a third exemplary embodiment of a gearwheel with damping system mounted on a shaft, FIG. 4 : a first application example for a toothed wheel with the damping system according to the invention, FIG. 5 : a second application example for a toothed wheel with the damping system according to the invention, and FIG. 6 : a third application example for a toothed wheel with the damping system according to the invention.The gearwheel 1 shown in FIGS. 1, 2 to 3 is seated fixedly on a shaft 2 and is divided into three gearwheel regions 3, 4 and 5 merely for the purpose of illustration. Although the gear wheel 1 is made in one piece, the regions 3, 4 and 5 are only shown as separate blocks in order to show which oscillations the gear wheel 1 performs in the individual regions during operation. The illustration is of course greatly exaggerated and is normally only in the micro- or nanometer range.In the exemplary embodiments shown in FIGS. 1, 2 to 3, a damping system 6 for the gearwheel 1 consists of a cover plate 7 designed as a cover plate which is coated on at least one side with an elastomeric material. Depending on the application, the coated cover plate 7 is fastened to at least one of the gear wheel regions, preferably to the middle and outer regions 4 and 5. The covering sheet 7 consisting of metal is coated by vulcanizing or bonding the elastomeric material onto the covering sheet 7. In the assembled state, the elastomeric material then bears directly against the gearwheel regions to be damped.In the exemplary embodiment shown in FIG. 1, in which damping is intended to take place primarily in the circumferential direction, the cover plate 7 has the form of a metal strip 9, the broad side of which is aligned axially. The cover plate 7 extends around the inner circumference of the outer gear wheel region 5.The outer circumference of the cover plate 7 is coated with the elastomeric material 8, which in the assembled state abuts the outer gear wheel region 5 and is fastened to the latter, for example by screws or rivets, which are not shown in the drawing.In the exemplary embodiment shown in FIG. 2, the cover plate 7 is designed as a metal strip 10 which is aligned in a radial arrangement and extends annularly around the central gearwheel region 4. In this exemplary embodiment, too, the metal strip 10 is coated on at least one side with an elastomeric material 11. In the assembled state, the side of the metal strip 10 coated with the elastomeric material 11 abuts the central gearwheel region 4. In this exemplary embodiment, the damping system acts primarily in the axial and / or radial direction.In the exemplary embodiment of the damping system illustrated in FIG. 3, the cover plate 7 has the shape of an angle 12 which is coated with elastomer material 13 on the side adjoining the gearwheel 1. The angle 12 abuts with its legs, which are coated on the outside with the elastomeric material 13, against the middle gear region 4 and the outer gear region 5. In this embodiment, the damping takes place both in the circumferential direction and in the radial and axial direction. In this exemplary embodiment, too, the coated angle 12 is fastened to the corresponding gearwheel regions 4 and 5 by means of screws and / or rivets.FIG. 4 shows an example of application of a gear wheel provided with the damping system according to the invention, specifically in a reduction gear 14 of a motor vehicle having an electric drive 15.The damping system 6 according to the invention is in this case formed on the gearwheel 18 provided with the internal toothing 17, wherein the cover plate 19 coated with the elastomeric material can be attached both to the two end faces of the gearwheel 18 and to the outer side of the toothed ring provided with the internal toothing 17.The gearwheel 18 provided with the damping system 6 is mounted on a common shaft with a further gearwheel 20 which meshes with the differential gearwheel 21.FIG. 5 again illustrates the damping system 6 according to the invention in the case of a reduction gear 22 which is connected downstream of an electric motor 23.In this exemplary embodiment, the reduction gear 22 is designed to be switchable in two stages, wherein in each case two gearwheels 24 and 25 with different diameters are rotatably arranged on the output shaft of the electric motor 23. Both gears 24 and 25 designed as idler gears mesh with gears 26 and 27 which are fixedly arranged on an intermediate shaft 28. The two gearwheels 26 and 27 seated on the intermediate shaft 28 are equipped with the damping system 6 according to the invention. One of the two gears 24 and 25 is shifted by means of a synchronization device 29 so that one of the two gears 26 and 27 seated on the intermediate shaft 28 is driven.On the intermediate shaft 28 there is also mounted a further gearwheel 30, which meshes as an output gearwheel with the differential gearwheel 31. From there, the torque is transmitted to the drive wheels of the motor vehicle.FIG. 6 shows an example of application of the damping system 6 according to the invention in a reduction gear designed as a planetary gear transmission 32, which is connected downstream of an electric motor 33.In this application example, a sun gear 35 is arranged on the input shaft 34 of the planetary gear transmission 32, which sun gear meshes with planetary gears 36. In this application example, the planetary gears 36 are equipped with the damping system 6 shown in FIGS. 1, 2 to 3.The planet gears 36 are fixedly arranged on a hollow shaft 38 together with a respective gearwheel 37. The gears 37 mesh with a ring gear 40 rigidly arranged in a transmission housing 39; axles 42 which are mounted on a common cross bar 41 extend through the hollow shaft 38 and drive the differential transmission 43, from where the torque is transmitted to the drive wheels of a motor vehicle.List of reference characters1 Gearwheel 2 Shaft 3 Gearwheel region (inner) 4 Gearwheel region (middle) 5 Gearwheel region (outer) 6 Damping system 7 Cover plate 8 Elastomeric material 9 Metal strip (axial alignment) 10 Metal strip (radial alignment) 11 Elastomeric material 12 Angle 13 Elastomeric material 14 Reduction gearing 15 Electric drive 16 Pinion 17 Internal gearing 18 Gearwheel 19 Cover plate 20 Gearwheel 21 Differential gearwheel 22 Reduction gearing 23 Electric motor 24 Gearwheel 25 Gearwheel 26 Gearwheel 27 Gearwheel 28 Intermediate shaft 29 Synchronizing device 30 Gearwheel 31 Differential gearwheel 32 Planetary gearing 33 Electric motor 34 Input shaft 35 Sun gearwheel 36 Planetary gearing 37 Gearwheel 38 Hollow shaft 39 Gearing housing 40 Ring gear 41 Cross bracket 42 Axles 43 Differential gearing

Claims

Damping system for gear transmission for reducing the generation of noise, wherein - at least one gear wheel (1) of the gear mechanism consists of at least two regions which oscillate relative to one another, - a damping means is provided on at least one of the gear wheel regions, said damping means consisting of a damping layer which bears against one of the gear wheel regions and a cover plate (7), - the damping layer is formed from elastomeric material (8; 11; 13), - the elastomeric material (8; 11; 13) is vulcanized or adhesively bonded onto the cover plate (7), - said damping means being vulcanized or adhesively bonded to the elastomeric material (8; 11; Cover plate (7) which is connected to the cover plate bears directly against the respective gearwheel region and is fastened to the respective gearwheel region by screwing or riveting, - the cover plate (7) has the form of a metal strip (9), the broad side of which is aligned axially and extends in the circumferential direction around the entire circumference of the respective gearwheel region, or - the cover plate (7) has the form of a metal strip (10), the broad side of which is aligned in a radial arrangement and extends annularly around the entire circumference of the respective gearwheel region (4), or - the cover plate (7) has, in cross section, the form of an angle (12), of which one limb points in the axial direction and the other limb points in the radial direction, and the angular cover plate (7) extends around the entire circumference of at least one gearwheel region (4, 5).Damping system according to claim 1, characterised in that the elastomeric material (8; 11; 13) has both resilient and damping properties.Damping system according to claim 1 or 2, for use in a reduction gear (14; 22; 32) of an electric drive motor vehicle (15; 23; 33).A damping system according to any one of claims 1 to 3 for use on a driven gear in a reduction gear of an electric drive motor vehicle (15; 23; 33).

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