Fluid-filled active vibration damping device

Details Fluid-filled active vibration damping device Fluid-filled active vibration damping device

2002-09-04

2004-10-26

Siconolfi, Robert A. (Department: 3683)

Spring devices

Resilient shock or vibration absorber

Including energy absorbing means or feature

C267S064140, C267S064280, C267S140200

Reexamination Certificate

active

06808168

ABSTRACT:

INCORPORATED BY REFERENCE
The disclosure of Japanese Patent Application No. 2001-268355 filed on Sep. 5, 2001 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a fluid-filled active vibration damping device, which has a primary fluid chamber filled with a non-compressible fluid, and which is capable of actively offsetting or reducing vibrations applied to the primary fluid chamber by controlling a fluid pressure in the primary fluid chamber. More particularly, the present invention is concerned with such a fluid-filled active vibration damping device that is suitably applicable to an active elastic mount and an active dynamic damper or oscillator for use in automotive vehicles.
2. Description of the Related Art
Vibration damping devices have been used for damping or isolating vibrations (including noises induced by the vibrations) of a subject member such as a body of an automotive vehicle or other members suffering from these vibrations or noises. Known examples of such vibration damping devices include a vibration damping coupling or mount, e.g., an engine mount, which is interposed between the subject member and a vibration source, e.g., a power unit, so as to connect these two members in a vibration damping fashion for eliminating or reducing a vibration transmitted from the vibration source to the subject member; and a vibration damper that is fixed to the subject member for absorbing or reducing the vibration of the subject member.
A fluid-filled active vibration damping device has been proposed as one type of such vibration damping devices, as disclosed in JP-A-11-82611, JP-A-11-201220, JP-A-2000-356240. The known fluid-filled active vibration damping devices include: an elastic body elastically deformed due to vibrational loads applied thereto; a primary fluid chamber partially defined by the elastic body and an elastically displaceably movable member, while being filled with a non-compressible fluid; and a working air chamber formed on one side of the movable member that is remote from the other side on which the primary fluid chamber is formed. The pressure of the fluid in the primary fluid chamber varies due to the elastic deformation of the elastic body upon application of the vibrational loads to the elastic body, and is also actively controllable by applying a suitable air pressure variation to the working air chamber from the external area, which is transmitted to the primary fluid chamber via the movable member. Such a known fluid-filled active vibration damping device is capable of actively controlling a fluid pressure variation induced in the primary fluid chamber by applying an air pressure variation corresponding to a vibration to be damped, thereby exhibiting an active vibration damping effect or an offsetting effect with respect to vibrations excited in the subject member to which the fluid-filled active vibration damping device is installed.
Generally, the known fluid-filled active vibration damping device utilizes as a vacuum source a negative pressure available from an air intake port of an internal combustion engine, as discussed in the above-indicated documents, and the negative pressure of the vacuum source and the atmospheric pressure is alternately applied to the working air chamber for thereby inducing the air pressure variation in the working air chamber.
For ensuring the known fluid-filled active vibration damping device to exhibit an excellent damping effect with respect to vibrations to be damped, it is required to generate the air pressure variation whose magnitude corresponds to the magnitude of the vibrations to be damped. To meet this requirement, it has been studied to regulate the magnitude of the negative pressure transmitted from the negative pressure source to the working air chamber in an attempt to suitably regulate a range of air pressure variation extending between the atmospheric pressure and a given negative pressure, based on the actual magnitude of the vibrations excited in the subject member, which may be detected by means of an accelerator sensor or the like, or alternatively may be estimated according to a predetermined data map or the like. Namely, it has been considered to regulate the magnitude of the negative pressure applied to the working air chamber so as to generate the air pressure variation induced in the working air chamber, whose magnitude corresponds to that of vibrations excited in the subject member.
However, further extensive studies conducted by the present inventors reveals that when the level of the negative pressure is made higher (i.e., an absolute value of the negative pressure is increased), and the resultant air pressure variation induced in the working air chamber ranges from the atmospheric pressure to a relatively high level of the negative pressure, undesirable air pressure variation as a subordinate frequency component, which does not correspond to the vibrations to be damped, is prone to occur in the working air chamber, and undesirably is transmitted to the primary fluid chamber. This results in deterioration of the vibration damping characteristics of the fluid-filled active vibration damping device.
In addition, when the level of the negative pressure generated in the negative pressure source is made higher and the resultant air pressure variation induced in the working air chamber ranges over a wide negative pressure region, an amount of elastic deformation of the movable member is excessively increased, possibly deteriorating durability of the movable member.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a fluid-filled active vibration damping device, which is novel in construction, and which is capable of inducing an air pressure variation having a large magnitude in an working air chamber, while preventing undesirable occurrence of an air pressure variation at a subordinate frequency range in the working air chamber.
The above and/or other objects of this invention may be attained according to at least one of the following modes of the invention. Each of these modes of the invention is numbered like the appended claims and depending from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the principle of the invention is not limited to these modes of the invention and combinations of the technical features, but may otherwise be recognized based on the teachings of the present invention disclosed in the entire specification and drawings or that may be recognized by those skilled in the art in the light of the present disclosure in its entirety.
(1) A fluid-filled active vibration damping device including: an elastic body elastically deformed due to vibrational loads applied thereto, a primary fluid chamber partially defined by the elastic body and filled with a non-compressible fluid; a movable member being elastically displaceable and partially defining the primary fluid chamber on one of opposite sides thereof; a working air chamber disposed an other of opposite sides of the movable member, which is remote from the primary fluid chamber; and a vacuum pump including an air intake port and an exhaust port that are connected to the working air chamber via a valve mechanism, wherein a fluid pressure variation in the primary fluid chamber is induced by an elastic deformation of the elastic body while being actively controlled by transmitting an air pressure variation applied to the working air chamber from an external area to the primary fluid chamber via the movable member, and wherein the valve mechanism is operable to perform a switching operation thereof for selectively applying a negative pressure generated in the air intake port and a positive pressure generated in the exhaust port to the working air chamber in order to generate the air pressure variation in the working air chamber.
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