A hydraulic excavator cab is mounted on a viscous mount. When the weight of the cab is heavy, the neutral position is depressed. Besides, at a large load, the cab receives compressive repulsion power of oil thereby restricting its damping ability. In addition, it is difficult to obtain an arbitrary damping performance separately.
To overcome these problems, which combines the shear force due to viscous fluid with elastic force due to air-spring a mount, was invented. The neutral position of composite mount is adjustable by air-spring according to the weight. And viscous oil is not sealed up. So, viscous oil can flow at a large load. Therefore, it may not experience the repulsion force of oil in spite of a large load. Moreover, the generated elastic force is adjustable according to change of pressure in the air spring, and the generated damping force is adjustable according to change of viscous fluid's viscosity or volume.
In this research, excitation tests under several conditions were performed to investigate the dynamic characteristics of the composite mount and its dependence on several conditions (displacement, frequency, pressure and viscosity). Next, the formulation of the dynamic characteristic was derived by the design parameter. The accuracy of the formulation was confirmed by comparing the formulation with the excitation test results. This paper might be useful to fundamental research of mounts.