The idea of a dog clutch without circular backlash is based on a unique and patented mechanical blocking mechanism which secures the clutch in desired positions - engaged or neutral. Using this blocking mechanism, we can shape the dogs in the way not common for dog clutches - narrower tip than root. This design minimizes the amount of circular backlash typical for dog clutches and thereby improves ride quality. It also enables disengagement under load which can fasten the gearshift of the dog clutch already being a quick gearshift device. Using external synchronization is necessary. Prototype of the dog clutch with blocking mechanism was successfully tested and proven functional. Improved design regarding to test results will be presented.

Manufacturing of prototypes and their testing is very money- and time-consuming. The same can be said about optimizing the design through comparison of multiple variants. Using multi-body simulation software seems very convenient in this situation. The very basic model of a dog clutch consisting of two dog rings engaging into each other has been already made. Further optimization can be divided into two tasks.
Firstly, the dog clutch with blocking mechanism was initially designed to cooperate with the gear selector system based on manual (MT) or automated manual (AMT) gearboxes. This means that the driver or gearshift actuator acts on the gearshift mechanism until it senses that the gear is fully engaged and cannot move any further. Only then the gearshift force is removed. This ensures that the dog clutch is pushed to its furthest position possible and the blocking mechanism is securely engaged. The first task is to adapt the dog clutch on the gear selector mechanism with kinematic endpoints - typically sequential shifting. In this case the endpoint of the dog clutch depends on the dimensional precision of affected components. In order to provide secure blocking under every circumstance, modification requiring additional flexible part might be necessary. This should make the dog clutch with blocking mechanism suitable for wider variety of applications.

Secondary, quality of the engagement process is affected by large number of parameters. Good gearshift is usually wanted to be quick and silent. This can be controlled using mainly these parameters - mismatch speed, gearshift force, number of dogs, angles of their sides and faces, height of the dogs. Multi-body model created for previous task will be used for design optimizations to fulfill the quality criteria.

Keywords: Dog Clutch; Circular Backlash; Multi-Body Simulation; Engagement Process; Gearshift Quality

Ing. Michal Jasný, Czech Technical University in Prague, CZECH REPUBLIC; Dr.-Ing. Michal Hajžman, University of West Bohemia, CZECH REPUBLIC; Dr.-Ing. Radek Bulín, University of West Bohemia, CZECH REPUBLIC