204 BEARING CONCEPTS 12 20512 BEARING CONCEPTSSchaeffler Symposium 2018 The hybridization of transmissions at the P2 posi tion is of particular interest 6 In P2 hybrid modules the electric motor is arranged between the transmission and the internal combustion engine Two clutches and their clever activation makes it possible to drive with just the internal combustion engine with electricity only or with a combination of both drives 7 In addition coas ting and recuperation can be implemented That is why Schaeffler has developed hybrid modules for the P2 position The optimized bearing sup ports for electrified transmissions are used in these hybrid modules as well as in Schaeffler s electric axles 8 Integrated bearing systems Besides optimized rolling bearings more and more smaller assemblies have lately found their way into transmission applications The com bined use of components allows the development of integrated bearing solutions that offer advan tages with regard to operating efficiency as well as mounting and installation space hybrid systems or electric axles That is why Schaeffler has developed bearings for electric drives that are combined in a modular range with preferred types and adapted specifically to these new requirements for electrified transmissions Figure 12 The preferred types result in short sam ple delivery times as well as competitive pricing High manufacturing accuracies in combination with specially developed greases seals and ca ges permit the achievement of limits for n x dm speed times the pitch circle diameter of more than 1 3 million mm min This has already been proven by testing Typical speed parameters for electric motors in an electrified powertrain today are between 0 5 and 1 0 million mm min How ever experts are already working on increasing drive speeds in order to obtain compact drives with high power density In electric axles not only the rotor shaft of the en gine rotates at high speed but also the transmis sion input shaft that is connected to the engine via a spline With an open design the newly deve loped bearings are thus suitable for the oil lubri cated bearing supports of this transmission shaft sage of electric current in generators and traction motors of rail vehicles but they may shift the problem of electric current to other parts of the powertrain That is why Schaeffler has developed bearings with integrated grounding to prevent the buildup of electric potentials between the inner and outer ring Initial tests have already proved the effectiveness of grounding Due to the largely radial loads as well as based on cost deep groove ball bearings 5 are used as bearing supports for electric motors The bearing supports of electric motors must ensure the relia ble guidance of the rotor to the stator compen sate misalignments and allow safe operation with low noise levels The bearings are adjusted elas tically and axially in order to compensate the in creased radial internal clearance that is neces sary due to the great difference in temperatures of the inner and outer ring The bearing rings are di mensionally stabilized to prevent ring growth due to high operating temperatures Sealed high speed bearings that are greased for life are required in almost all electric motors in Low self heatin g High speed performanc e Low seal friction Low running noise High running precision Grease for high spee d and high temperatur e 13 Integration of bearing systems using a bearing cartridge for a hypoid drive as an example One example of this type of integration is the bearing cartridge for the hypoid drive in which the pinion flange bearing and the pinion head bearing are combined as a compact unit Figure 13 This solution results in high rigidity for small bearing dimensions 12 Bearing concept requirements for electric drives 14 Locating non locating bearing supports as a compact unit with a shaft and gear teeth for a hydraulic auxiliary drive in commercial vehicles

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