Pomiar sztywności kątowej zawieszenia samochodu

Pojazdy z wysoko położonym środkiem masy mają tendencję do wywracania się, szczególnie podczas wykonywania gwałtownych manewrów skrętu. Na parametry określające stateczność boczną pojazdu ma wpływ wiele czynników między innymi: położenie środka masy, sztywność zawieszenia, moment bezwładności oraz parametry ruchu pojazdu. Prowadzone w Katedrze Silników Spalinowych i Pojazdów badania pozwalają na określenie wpływu czynników konstrukcyjnych na stateczność samochodów ciężarowych. Podobne zagadnienia dotyczą samochodów osobowych, z tą różnicą, że tu niebezpieczeństwo przewrócenia pojazdu jest mniejsze. Przedstawiona praca stanowi opis przeprowadzonych badań pojazdu oraz sposobu wyznaczania sztywności kątowej zawieszeń. Sztywność ta pozwala na określenie granicznych warunków, przy których dojdzie do przewrócenia pojazdu.

Vehicles with high location of the centre of mass tend to roll over, particularly while executing the sudden turn manoeuvres. Many factors influence the parameters determining the vehicle side stability, such as: the location of the centre of the mass, the suspension stiffness, the moment of inertia of a car body and the vehicle motion parameters. Investigations conducted in the Department of Combustion Engines and Vehicles makes it possible to determine the influence of construction factors on the truck stability. Similar problems refer to automobiles, however, the probability of overturn is smaller in that case. The paper presents the performed investigations of the vehicle and the procedure for determining the torsional stiffness of suspensions. The automobile suspensions cause that during the vehicle movement in the after-effect of the forces operation, the body leans and the centre of the mass moves. The change of the centre of the mass position causes lowering the critical parameters for which there occurs the vehicle rollover. The angle of the body tilting is dependent on the suspension stiffness. The proportionality coefficient between the angle of the car body inclination and the reactionary moment of the resilience of suspen-sions is called the torsional stiffness of suspensions. Its reverse is the vehicle rollover threshold. The value of the torsional stiffness of suspensions k? will be uniform in the case of the drive steady conditions. During executions of sudden manoeuvres damping forces in suspensions will cause the change of their characteristics. This will enlarge the effective stiffness. Additional springy units cooperate at large angles of the car body inclination and change the suspension characteristic. On the basis of the measurements taken and analyses performed one can state that: - it is possible to define the vehicle suspension torsional stiffness on a basis of road tests, - the measurement accuracy is determined by many factors such as: the investigated track surface irregularity, deviation from the given drive velocity, deviation from the given steering wheel angle, change of the schedule of the weight on wheels, change of the friction coefficient between wheels and road, etc.- the determined stiffness values oscillate around the average value which was assumed to be the suspension torsional stiffness value of the tested vehicle.The torsional stiffness obtained from the suspension investigations can be used for calculations of the critical velocity of possible vehicle rollover.