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The paper will present the design of shift fork for automotive manual gearbox dedicated for the manufacturing with powder metal technology. Based on limitations and requirements of new production technology of shifting sleeve, the new design of shifting sleeve and shifting fork are created. The prototypes of shift fork and sleeve were built, but for cost reasons, were manufactured from steel. The functionality of several forks with different tolerances was tested. Prototypes were put through functional and durability tests on testing bench in real automotive gearbox. The tests were accomplished on the inertia test stand. Drawings and CAD models of tested prototypes, custom tools and designed shift forks are described in detail in this article.

This work looks into the development of power-split planetary gear set for hybrid vehicle. The aim is to research possible solution of hybrid powertrain integrating DHT (Dedicated Hybrid Transmission), which will comply with demands of compact cars, where simplicity and low price is a primary focus. On the other hand, this solution must offer full-hybrid capability. The search of new solution is focused on the usage of one electric motor in combination with internal combustion engine, the planetary gear set (PGS) and stepped transmission. For low forward speeds and reverse the electric drive can be used. The low forward speed can be ensured also by combination of electric motor and ICE, the medium speed range will be covered by powersplit or combination/addition of power of ICE and electric motor, for highway usage the direct drive from ICE via stepped transmission is envisaged. Most of the functional modes allow also the electric energy recuperation.

The paper is dedicated to design of a new dog-clutch gearshift mechanism for passenger car gearboxes with external synchronization. There are two main targets of presented work: 1 Replace the standard synchronizer with cheap and compact shift device, which will keep the internal architecture of classical manual transmission. 2 Keep all the other important functions of synchronizer: a minimal circular backlash to avoid clash during change of sense of the torque flow, b prevent unwanted disengagement, c guarantee the shift anytime, d determine neutral position (preferably). Czech Technical University in Prague is for several years active in the field of design and testing of shift mechanisms, as well as in design of new shift clutches. The currently presented clutch is 3rd generation of inventions of dog clutch systems. All clutches were fabricated as prototype and tested. All designs will be briefly described in the paper.

In the laboratories of CTU in Prague, an inertia test stand was recently built for endurance tests of the internal shift mechanisms of passenger cars. With regard to the instrumentation of the stand, it can be used also for determination of lost power of the not-loaded transmission. In this paper we present the values for the no-load losses measured during different conditions (temperature, shifted speed, speed of rotation) on the automotive mechanical gearbox for the transversal disposition of the drivetrain. For the further usage of the measured values is important to determine the proportion of the different sources of losses. We are mainly interested to identify the proportion of the churning losses and losses in the sealing, since these two losses remain the same, whatever the load of the gearbox will be. The losses of bearings on input and secondary shaft were calculated with the tool available from SKF. The load of the bearings was calculated from the measured drag torque.

The target of the work is to find out the algorithm of definition of the ratios of mechanical part of complex powersplit CVT/IVT system with regard to the highest achievable efficiency. The presented synthesis is focused on powersplit systems, which will consist of a CVT part, differential and eventually by-pass gear. The algorithm will be programmed and become an integral part of the program Sungear developed on Czech Technical University in Prague for analyses and synthesis of planetary stepped transmissions and CVT/IVT powersplit systems. The article will mainly present the algorithm of definition of efficient powersplit system. For the search of the efficient powersplit system we assume that the following parameters are given: a Spread and efficiency of used CVT system. b Total spread of the whole powersplit CVT/IVT mechanism. c Optional: Ratios of the used CVT system. d Optional: Ratios of the whole powersplit CVT/IVT system.

The article is divided into two parts. The first part is dedicated to the analysis of mechanical systems by means of the matrix method. The power of the matrix method lies in its easy implementation in computer calculations. In this article we will present the program “SunGear.” This program is devoted to calculation of such Power-split systems and complete analysis of mechanical stepped planetary gearboxes. The second part of the article will describe the analysis of Power-split systems. In our study we focus on Power-split systems with mechanical CVT. The analysis will be presented by means of two examples: a) IVT (no shift elements) with the spread from reverse (ratio equals −2) up to the overdrive with a ratio of 0,6. The power is split between CVT (spread 0,25 up to 4) and mechanical gear set. The differential (planetary or bevel gear device with 2 degrees of freedom) is placed on the input or on the output of the mechanism.

The paper presents computer-aided calculation of planetary gear systems in automotive transmissions. We distinguish between two approaches to make the calculations: the direct problem and the inverse problem. The direct problem starts with a given nested gear set, calculated by means of the matrix method. This method, previously used only for nested gear trains consisting of simple planetary gear sets, is extended for computation of the Ravigneaux gear-sets as well. The matrix method-based program is presented. The inverse problem starts with the known kinematic parameters of a gear set. Two known methods used for defining of structure of nested planetary gear-box are briefly described: the iterative approach and the analytic parametric approach.