Abstract
In automated mechanical transmissions, engaging sleeve with clutch gear causes the switches of mechanical coupling modes of engaging-related parts, and impacts may happen to make the part speeds have discrete transitions during the engaging. The two characters make the engaging process exhibit both continuity and discreteness. The aim of the paper is to develop a high-fidelity model to capture the trajectories of the parts in the transmission. We treat the engaging as a two-phase process—sleeve first interacting with synchro ring and then with clutch gear. The part movements under a certain constraint are governed by multibody dynamics, and the speed jumps caused by impacts are described using the Poisson coefficient of restitution. To couple the continuous evolutions and discrete transitions of the states, a hybrid automaton model is developed. This model allows for the characteristic analysis of the engaging process with multiple interaction cases between the engaging-related parts, and it is validated by bench tests. The effects of two key factors—the relative tooth position of sleeve and clutch gear and the shifting force—on engaging duration and impact are studied through numerical simulations.
Highlights
Engaging sleeve with clutch gear is the key process of shifting gears in automated mechanical transmissions (AMT)
Our results show that when the relative tooth position of sleeve and clutch gear is different, the sleeve and the clutch gear have five possible interaction ways, which result in different engaging duration and impact impulse
We develop an impact model to capture the discrete transitions of the axial and rotational speeds of the sleeve, the synchro ring, and the clutch gear when an impact happens on their tooth chamfers
Summary
Engaging sleeve with clutch gear is the key process of shifting gears in automated mechanical transmissions (AMT). It occupies more than 70 % power off time of a gear shift in an AMT, and undesirable impacts may happen during an engaging [2, 13]. If the sleeve arrives at the desired clutch gear at an improper rotational tooth position, it would lead to an impact, which makes the engaging delayed and jerky [1, 3, 6, 11]. In order to shorten the power off time and reduce the impact caused by shifting gears, careful modeling and analysis for the engaging process is needed
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