Abstract: By means of the coordinate transformation, the equivalent displacement formula of the gear installation errors along the mesh lines for the encased differential herringbone train is deduced. Based on the theory of the concentrated parameter, a dynamics model of this train which adopts the intermediate floating component is set up. Through calculation of the load sharing coefficients of the internal and external mesh in the 2-stage, the curves of the relationships between the gear installation errors and the load sharing coefficients of the internal and external mesh are obtained and the impact of installation errors on the load sharing characteristic is analyzed. The research results show that under the action of the gear installation errors the load sharing coefficients in the differential stage are bigger than that in the encased stage. In the differential stage, the load sharing coefficient of the internal (external) mesh increases with the installation error of the internal (sun) gear, the installation error of the internal (sun) gear has very small impact on the load sharing coefficient of the external (internal) mesh. In the encased stage, the load sharing coefficients are bigger with the installation error of the internal gear, the installation error of the sun gear has minor effect on that. The installation error of the planet (star) gear has lesser influence on the load sharing coefficients in the differential (encased) stage. The load sharing coefficients in the differential stage are not sensitive to the position angles of the installation errors of the center gear, but the position angles of installation errors of the center gear in the encased stage have bigger influence on the load sharing coefficients.

Key words: Dynamics, Encased differential planet train, Herringbone, Installation error, Load sharing