Friction induced vibrations in shift gearboxes

Abstract

In shift gearboxes, audible vibrations can arise during the process of clutch engagement. Measurements show an unstable axial motion of the gear unit input shaft. In order to explain this effect, an approach which establishes the interaction of the slipping clutch and the gearing is proposed. The suggested model consists of a pressure plate, a clutch disc, a gear unit input shaft and a tooth contact. The gear unit input shaft is rigidly connected to the gearing and the clutch disc and has translational and rotational degrees of freedom. The tooth contact imposes a kinematic constraint on the system. This is why the sliding friction torque is transformed into forces in axial and radial direction of the shaft. Depending on the gearing parameters and the slip, the contact normal force between clutch disc and pressure plate is amplified (motor accelerating) or reduced (motor slowing down) by the toothing. For both shifting situations, a region of flutter instability in the parameter space can be found. The dynamic behavior of the system with parameters in the latter region is analyzed. It is shown that there exists a stable piecewise-continuous limit cycle: During one period, the contact between the clutch disc and the pressure plate opens shortly. A variation of parameters is performed to show the dependence of the limit cycle on the geometry and on the operation conditions.

On the influence of the lamella's elasticity on self‐excited vibrations in gearboxes

“…Thus, for this body, the kinetic energy T G , the stored energy in the bearing U B and the dissipation δW B Diss contribute to H. Gear flanks on B (1) and B (2) have no penetration. This condition results in a nonholonomic constraint 0 = n (1) c · v rel as a simple but adequate gear model [4], where the Lagrange multiplier is the contact normal force. Friction effects in the gears and the influence of the flank stiffness are neglected.…”

“…In vehicle drivetrains, there are several friction sources with the clutch disc the most important representative. The eek instability at frequencies in the range of 200Hz and 1000Hz (mode-coupling flutter), which arises between clutch discs, has extensively been studied [2][3][4]. In particular in [4], an eek instability was found in a rigid body model of the clutch disc, shafts and gears, where the effect arises because of the interaction of friction between the discs and coupling of DoFs in the gears.…”