Dynamic analysis of mechanical transmissions - Example: dynamics of self-propelled chassis
Example: simulation of dynamics of the self-propelled chassis hydro mechanical transmission
Fig. 9. The scheme of hydro mechanical transmission of self-propelled chassis
Let's consider as an example dynamics of hydro mechanical transmission (Fig. 9а) at following movement modes of the machine:
1) racing on the 1-st transfer by means of inclusion of a friction clutch 7 – 22 at resistance to moving of the machine W= – 30 kN (Fig. 9b);
2) transition from the 1-st transfer to the 2-nd at switching-off of a friction clutch 7 – 22 and inclusion of a friction clutch 21 – 23 with simultaneous reduction of external resistance up to W= – 10 kN (Fig. 9b);
3) switching-off the 2-nd transfer, movement forcefully during 0.8 s and braking up to a full stop of the machine at W= – 10 kN (Fig. 9b).
Base parameters of the system:
machine mass – 10 t;
engine – diesel А-01МД;
hydraulic torque converter with active diameter of work wheels 0.34 m;
transfer numbers of a gear box: the 1-st transfer – 4.98, the 2-nd transfer – 2.75;
differential: symmetric with transfer number of a gear0.376;
wheel: radius of trunks in a free condition0.74 m;
transfer numbers of a gear of selection of power: 1.183 (node 2) and 0.847 (node 3);
transfer numbers of onboard gears: 5.07.
On Fig. 9b graphs of external influences and control signals are shown: pressures of frictional clutches control, the brake moments in nodes 14 and 15; resistance to moving of machine W as function of moving х.
As a result of calculation the transient processes in hydro mechanical transmission have been received.
Fig. 10. Dynamics of hydro mechanical transmission (results of simulation)
On Fig. 10 graphs of variables in the certain nodes of the scheme are shown: the moments and angular speeds, and also district efforts on wheels and speed of the machine. Numbers of nodes serve for indexation of variables, for example: – the torque moment in node 1, – angular speed in node 7, etc. The observable interval of time – 11 s. On graphs of angular speeds of disks of friction clutchesmodes of blocking – intervals AB both CD accordingly, and modes of slipping of frictional clutches are precisely traced. Dependences of the moments transferred by friction clutches, illustrate process of movement on the 1-st transfer, switching transfers from the 1-st to the 2-nd (point E), movement on the 2-nd transfer , switching off the 2-nd transfer and braking. At the moments of inclusion of the 1-st transfer (t = 0) and switching from the 1-st transfer to the 2-nd transfer jumps and fluctuations of district efforts on wheels are observed due to elastic properties (mainly trunks and partially elastic shaft of transmission) which to a lesser degree affect fluctuations of angular speeds and speed of progressive movement of the machine v.