1. Field of the Invention
The present invention relates to a fluid-filled vibration damping device used for automobile engine mounts and the like.
2. Description of the Related Art
From the past, vibration damping devices have been known which are interposed between members constituting a vibration transmission system, and for which those members have a mutual vibration damping connection and vibration damping support, and as one type of vibration damping device, fluid-filled vibration damping devices are also known that exhibit a vibration damping effect based on the fluid flow action of the fluid sealed inside. This fluid-filled vibration damping device has a first mounting member and a second mounting member elastically connected by a main rubber elastic body, and on both sides of a partition member supported by the second mounting member are formed a pressure-receiving chamber and an equilibrium chamber, sealed in which is a non-compressible fluid. Furthermore, the pressure-receiving chamber and the equilibrium chamber are in communication with each other through an orifice passage, and the target vibration damping effect is exhibited based on the fluid flow action of the fluid that flows through the orifice passage. For example, that is what is shown in Japanese Unexamined Patent Publication No. JP-A-2009-243510.
However, with the fluid-filled vibration damping device, while the orifice passage effectively exhibits a vibration damping effect based on the fluid flow action of fluid on vibrations of a frequency at which the orifice passage is tuned, it is difficult to obtain an effective vibration damping effect on vibrations of a frequency outside the tuning frequency. In particular, when a vibration of a higher frequency than the tuning frequency is input, the orifice passage is substantially blocked by the anti-resonance, so there is the problem that the vibration damping performance by high action spring reaction decreases.
In light of that, with the structure noted in JP-A-2009-243510, a liquid pressure transmission mechanism is provided that is equipped with a fluid flow path that allows transmission of liquid pressure between the pressure-receiving chamber and the equilibrium chamber when vibration of a higher frequency than the tuning frequency of the orifice passage is input. In specific terms, this liquid pressure transmission mechanism has a structure by which a movable member (movable plate) is arranged held in a housing space formed on a partition member, and each of the liquid pressure of the pressure-receiving chamber and the liquid pressure of the equilibrium chamber is applied to both surfaces of the movable member through a communicating hole (fluid flow path) formed by piercing through a wall part of a housing space. Then, when inputting a high frequency, low amplitude vibration, the movable member has minute displacement or minute deformation, allowing transmission of liquid pressure between the pressure-receiving chamber and the equilibrium chamber, and when vibration of the orifice passage tuning frequency range is input, the movable member closes the communicating hole, preventing transmission of liquid pressure between the chambers. By so doing, it is possible to selectively and effectively obtain either the vibration damping effect exhibited by the flow action of the fluid that passed through the orifice passage, or the vibration damping effect exhibited by the liquid pressure absorption effect of the liquid pressure transmission mechanism.
However, with the fluid-filled vibration damping device equipped with this kind of liquid pressure transmission mechanism, when the movable member contacts the inner surface of the housing space, it is easy to have the problem of having a striking noise occur based on the impact force. Specifically, the impact energy when the movable member contacts the inner surface of the housing space is applied to a vehicle body via the partition member and the second mounting member that supports it, so there was the risk of noise occurring inside the passenger area.