The objectives of the research project were to investigate the limits concerning possible reduction of lubricant quantity in gears without detrimental influence on the load carrying capacity. The investigations covered the influence of the oil level in dip lubricated systems as well as the oil flow rate in spray lubricated systems namely oil-air supply systems on power loss, heat generation and load carrying capacity. The load carrying capacity in terms of characteristic gear failure modes was determined and was compared to the results using conventional lubricant volumes with dip lubrication. Therefore in back-to-back gear tests the parameters speed, load and oil quantity were varied for examination of the four main gear flank damages: scuffing, wear, pitting and micropitting. The investigations showed the application potential of oil/air lubrication also for heavy duty transmissions nevertheless there exists a natural limitation for lowering the oil quantity in transmissions without detrimental influence on the load carrying capacity.

Power loss in a transmission is strongly related to the properties of the gear lubricant. Viscosity of the lubricant determines the no-load splash and churning losses. The losses in the EHD regime depend on the base oil type. In the boundary and mixed lubrication regime losses are mainly related to the chemical composition of the additive system. A test method was developed to evaluate the frictional properties of candidate transmission lubricants in relation to a mineral reference oil ISO VG 100 with a typical sulphur-phosphorus additive package. The test results can be expressed in simple correlation factors for no-load, EHD and boundary lubrication conditions, in comparative steady-state temperature development for given mean values of operating conditions, and in a ranking scale of different candidates. For a more detailed analysis of the expected power loss in a transmission in practice the results of the efficiency test can be introduced into an equation for the mean coefficient of gear friction for the respective oil. Thus the test results can be applied to any gear in practice at any operating conditions for any gear geometry. Examples of the influence of viscosity, base oil and additive type on the frictional behavior of gear lubricants and their effect on power loss reduction and energy savings in a gearbox are discussed.

Vibration and noise generation of gear stages is mainly caused by the excitation of the gear mesh. This excitation is significantly influenced by geometry of the tooth. Here, both the macro-geometry (main geometry) and the micro-geometry (flank corrections) of the teeth are important. Corrections of the tooth flanks usually have to meet the requirements of low excitation and high load capacity. Furthermore it is oftenly necessary, especially for transmissions with variable speed, to account for the dynamic effects (e.g. resonance behavior) of noise excitation. The computer program DZP (Dynamic Tooth Force Program) provides extensive calculation methods for analyzing mesh excitation and transmission dynamics. The frame program DZPopt provides extensive possibilities to determine an optimum excitation flank correction based on the calculation capabilities of DZP.

This paper presents results of a research project which is carried out at the Technical University Munich, Germany. In this project the “CVT-Hybrid-Driveline” is designed, manufactured and investigated in close cooperation with OEM (GM Powertrain Europe) and suppliers (EPCOS AG, ZF Friedrichshafen AG and ZF SACHS AG). The focus is put on reduction of fuel consumption at low additional cost for hybrid components. The “CVT-Hybrid-Driveline” is a hybrid car driveline using Diesel-engine, electric motor with double layer capacitors and a CVT-type transmission. The driveline is assembled into an OPEL VECTRA vehicle for investigations on practical use of this hybrid system. In addition the driveline is installed at test rig for detailed investigations on consumption, energy flow and control system behavior. The concept is presented and explained in this document. Based on simulation of the hybrid system the drivability is shown for various situations of driving; fuel consumption of the CVT-Hybrid is evaluated and discussed both for standard cycle and for specific driving course.

Nowadays the task to diminish energy consumption and air pollution caused in large shares by road traffic occupies a key issue. One possible approach is the Autark Hybrid, a well balanced configuration of an usual internal ic-engine, an electric motor with dedicated battery system in combination with a CVT of wide ratio range. Main target of the drive train is to reduce fuel consumption. After designing this powertrain at Technische Universita¨t Mu¨nchen a prototype vehicle has been assembled in order to verify the concept under real circumstances. Starting from its standard configuration a compact class vehicle has been modified. The test vehicle already started operation on a roller test bench as well as on separate testing roads and in public road traffic. Function and handling characteristics are demonstrated.