Powershift Differential Transmission with Three Flows of Power

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Nowadays simple shaft- and planetary transmissions are the most used types of transmissions because of its concept simplicity. In these transmissions it is necessary to engage and disengage one or more control components in order to gear the chosen speed gear, whereby a single gear pair is often used in one speed gear only. On the other hand the differential transmissions enable to achieve the power split to more flows by its construction, so they offer higher number of speed gears at lower count of gears and control components. The base of the transmission is a planetary set, which works as a gear at several speed gears, at other speed gears as a differential. This principle is a base of the described powershift differential transmission with three flows of power.

The basic of described powershift transmission is a differential with four shafts - combined planetary mechanism, which consists of two simple planetary gears (Fig. 1). This differential has three input shafts and one output shaft. In case of inserting several countershaft gears before the differential it is possible to create the configuration, in which the power can be split into three flows and subsequently merged in this four-shaft-differential. So originates the configuration of three flows of power.

Behind the four-shaft-differential is situated the additional group. This consists of shaft clutch with powershift functioned with the help of clutches S4 and S5, which enables two speed gears. The additional group multiplies the number of speed gears, so the result is fourteen speed gears.

The individual clutches and brakes are engaged and disengaged in order to shift the speed gears exactly according to Fig. 2. All the transmission ratios are resumed in Fig. 2 and Fig. 3. The gear signed as 0 is intended for starting-up of loaded vehicle at hard conditions on soft surface. Other twelve speed gears can be used at standard operating conditions.

Differential transmissions offer wide possibilities by request of higher number of speed gears. For example the combination of two planetary sets provides 36 possible structures and every structure enables different speed gear redistribution. The chosen conception has appeared as suitable for exploitation in freight-vehicle-drives because of its number of available speed gears and its differentiation.

Described transmission enables the powershift, which meets actual requirements insisted on vehicle transmissions. To achieve thirteen speed gears eight control components are needed. The advantage of this type of the transmission is the fact that it does not request the same number of gear meshes in comparison with countershaft transmission in order to achieve the same number of speed gears. The result is that the transmission efficiency of differential transmission is higher too.

Theoretically computed kinematic and moment characteristics are in accordance with the values achieved by simulations - it also applies to the theoretical efficiency of individual speed gears. There is no power circulation in transmission, at several speed gears power split appears only.


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  • Name:
    Jaroslav Pito?ák
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  • Jaroslav's favorite design and analysis tools:
    powertrain, transmissions, drivelines
  • Jaroslav is inspired by:
    other transmissions
  • Software used for this entry:
    Matlab, SimDriveline
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