Search

Geared reducers are mechanisms designed to reduce the number of revolutions using geared elements and nowadays they present one of the most commonly used types of mechanical transmissions in mechanical engineering. Due to the different shapes of geared elements, there are different types of geared transmissions: helical, bevel, worm, special and combined transmissions. This paper analyses only helical geared transmissions, since there is a great extent of whole this matter. Helical transmissions are analysed only with external helical gearing, since internal geared pairs represent a special and very large group of gears. Within the external helical geared transmissions, only torque transmissions are analysed, while the transmissions of motion are not analysed and they represent another large group of transmissions. Only universal gear reducers with axial, or almost-axial, parallel shafts are considered (two-stage and three-stage transmissions). Although, single-stage gear reducer produced with parallel shafts are not considered by the paper in order to reduce the area of researching. Gear reducers are most commonly delivered to customer with electric motor, known as motor geared reducer, and they are studied here extensively. Gear reducer can be also delivered without motor, only with input shaft. The basic aim of this paper is to present all characteristics and specificities of motor geared reducer in one place.

The basic parameters of the universal gear drives, except the axis height, are not defined by the standard, so the manufacturers of universal gear reducers can define them in their way. Most of the manufacturers followed the parameter values of universal gear reducers of leading world producers in order to ensure their interchangeability and the better positioning of their gear units at the market. This paper deals with the analysis of the influence of the gear pair teeth number on the size of the module, as well as on the load carrying capacity of single-stage universal gear units. For defined gear ratio values, different combinations of teeth number of pinion and driven gear were selected. Further, it was made calculation of the basic geometric dimensions of the gear pair, as well as the load capacity.

Universal helical gear motors are among mechanisms that operate with a very high efficiency (about 0.98 per gear pair) [1, 2] and thus their thermal power capacity has not received enough attention, even in the cases when they overheat (usually at higher ambient temperature and high power motors). Therefore, it is necessary to define the thermal capacity in the catalogues of the speed reducer with a solid input shaft, as it is done by worm and helical-worm gear units which operate with much lower efficiency. Some manufacturers [3] pay necessary attention to this factor and thus enable the proper selection of gear reducers; this means they have prepared certain procedures to be undertaken if such occasion occurs, in order to overcome possible problems that may arise due to overheating the gear reducer. With this approach in the universal gear unit selection, some positive benefits can be surely achieved in the market of gear reducers, and that should not be ignored.