Abstract
Because of the density mismatch between the decoupler and surrounding fluid, the decoupler of all hydraulic engine mounts (HEM) might float, sink, or stick to the cage bounds, assuming static conditions. The problem appears in the transient response of a bottomed-up floating decoupler hydraulic engine mount. To overcome the bottomed-up problem, a suspended decoupler design for improved decoupler control is introduced. The new design does not noticeably affect the mechanism's steady-state behavior, but improves start-up and transient response. Additionally, the decoupler mechanism is incorporated into a smaller, lighter, yet more tunable and hence more effective hydraulic mount design. The steady-state response of a dimensionless model of the mount is examined utilizing the averaging perturbation method applied to a set of second-order nonlinear ordinary differential equations. It is shown that the frequency responses of the floating and suspended decoupled designs are similar and functional. To have a more realistic modeling, utilizing nonlinear finite elements in conjunction with a lumped parameter modeling approach, we evaluate the nonlinear resorting characteristics of the components and implement them in the equations of motion.
Highlights
Introduction and Statement of ProblemModern vehicles illustrate a trend toward lighter, higher performance, aluminum-based engines thereby increasing the potential for vibration
Utilizing FEM we show how to determine the elastic behavior of the decoupler, upper bellow, and lower collector compliances
This study has introduced a decoupler design motivated by the desire to improve upon the current floating-decoupler design
Summary
Modern vehicles illustrate a trend toward lighter, higher performance, aluminum-based engines thereby increasing the potential for vibration. Because the decoupler provides a low restriction to fluid flow, it becomes the preferred flow path, and acts on reducing the damping coefficient of the engine mount This system works quite well and is in place on the large majority of automotive applications to date. In the current floating-decoupler design the decoupler might sit against one of the cage bounds while not excited, depending upon mounting configurations and density mismatch with the surrounding fluid, causing the system to initially utilize only the inertia track. With either condition it becomes apparent, after some consideration, that because it is the decoupler that allows the mount to act as either a low damping or a high damping mechanism by means of its position, the position of the decoupler during the aforementioned excitations is quite important
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