5 months ago

MDA Technologies 3/2014

MDA Technologies 3/2014

Machine Elements

Machine Elements Efficient Bearing Solutions for Agricultural Machine Gearboxes Carsten Landeck OEMs and the supply industry face great challenges in developing new products due to the broad range of applications of modern mobile work machines in construction and agriculture. Read how modern bearing solutions help to solve these tasks. Author: Carsten Landeck, Application and Agricultural Engineering, Schaeffler Technologies GmbH & Co. KG, Herzogenaurach, Germany 24 MDA Technologies 3/2014

Machine Elements Along with being required to adhere to numerous legal regulations with regard to environmental protection and pollutant emissions (Tier IV), mobile work machines need to efficiently and reliably master the day-to-day workload under the most adverse ambient conditions. In agriculture, especially, the range of demands in the countless operating cycles is very broad. Due to the vast number of implements and auxiliary units involved, tractors have a demand profile that is far beyond the conventional range of applications. Cultivation, transport operation, and their use in communities requires them to be a universal work unit – both a powerful drawing vehicle in slow field operation as well as a fast transport vehicle for logistic tasks. However, it is not the product that is technically the best and the most universal that proves to be most useful for the customer, but rather a solution that offers the best compromise when it comes to machine pricing, efficiency, and fulfilling the technical application demands. Along with the cost of procurement, it is primarily operating efficiency that plays a central role in the process of choosing a new tractor, since diesel fuel and catalytic additives for exhaust gas treatment constitute a major portion of the operating costs. Operating the engine with an efficient engine map, a friction-optimized drive train configuration, and systematic engine gearbox management are a few of the many criteria that directly affect consumption patterns. Since pollutant emissions directly depend on fuel consumption, increasing efficiency results in a reduction in the emission quantity at the same time. Another important aspect is the reliability and longevity of the entire vehicle. During this development process, special attention needs to be given to the drive train components – particularly the bearings. Schaeffler not only offers high-tech products for this, but comprehensive engineering solutions for all engine and gearbox installation locations as well. Designing cutting-edge and efficient rolling bearings 01 When designing critical bearing locations Schaeffler can draw conclusions during the design phase Rolling bearings make power transmission and low-friction relative movement possible between machine components that are stationary in relation to each other. The incentive and challenge for Schaeffler as a supplier and development partner for cutting-edge machine components is to continuously optimize friction conditions for the rolling contact while maintaining at least stable levels for load-carrying capacity and operating life. In this process of development, the bearing design, the individual production steps, and the specific application are all analyzed and optimized. It is primarily the quality of the surfaces, the inner design, the lubrication conditions, and the bearing load that affect friction in the bearing. With the aid of state-of-the-art simulation and calculation programs developed by Schaeffler (such as Bearinx and CABA3D), conclusions can already be made during the design phase as to how the bearings will behave later under the specific operating conditions of the application. This, in collaboration with the customer, shortens the time needed for development and thus directly reduces development costs. This approach makes particular sense when designing critical bearing positions in gearboxes – e.g. pinion shaft bearings. The pinion shaft distributes the torque at the gearbox output to the rear axle differ- ential and the drive shaft of the front axle. The shaft rotates very slowly when starting up and during field operation, yet transmits high torque levels depending on the power required by the implement. The opposite may be true during transport operation, however, with very low torque levels and speeds of over 5,000 rpm. The pinion shaft needs to be guided rigidly and with zero clearance in order to keep any shifting of the meshing point between the pinion and the differential’s crown wheel to a minimum. A reduction in friction is one final, though still important, requirement for bearing support, to keep both power loss and heat input into the gearbox as low as possible. High-capacity and low-friction Thanks to their innovative inner design, FAG tapered roller bearings in X-life quality are an efficient bearing type for providing pinion shaft bearing support in tractor gearboxes and are especially suitable for extreme load demands. Specially machined raceway and roller surfaces as well as optimized contact geometry between the rolling element end face and the inner ring rib reduce power loss by up to 50 %. At low speeds during start-up or field operation, the improved surfaces enable an MDA Technologies 3/2014 25


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