Spring devices – Resilient shock or vibration absorber – Including energy absorbing means or feature
Reexamination Certificate
1998-11-12
2001-03-13
Graham, Matthew C. (Department: 3613)
Spring devices
Resilient shock or vibration absorber
Including energy absorbing means or feature
Reexamination Certificate
active
06199840
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hydraulic vibration-isolator which is applicable, for instance, to hydraulic suspension-bushings used as a vibration-insulating member for suspension mechanisms installed onto vehicles.
2. Description of the Related Art
In a suspension mechanism installed onto a vehicle, there has been provided a hydraulic vibration-isolator for decreasing vibrations resulting from a road surface or a vehicle tire. The hydraulic vibration-isolator is installed, for instance, at an L letter-shaped lower arm of a FR suspension mechanism in such a manner that an axial direction of the hydraulic vibration-isolator corresponds to a length direction of the vehicle. In this case, as for the hydraulic vibration-isolator, a main axis fitting thereof is fixed to the lower arm, an outer cylinder-shaped fitting is fixed to a supporting member of the vehicle body, partition walls thereof are disposed in a vertical direction of the vehicle, and a pair of divided fluid chambers thereof is disposed in a width direction of the vehicle. When vibrations are inputted between the main axis fitting and the outer cylinder-shaped fitting, the vibrations can effectively be damped on the basis of an elastic function of a rubber elastic member and on the basis of a fluid-column-resonating action caused by a fluid which flows in the fluid chamber owing to the elastic function of the rubber elastic member.
In such a way, the hydraulic vibration-isolator, utilizing fluid-column-resonating action caused by the fluid flowing in the fluid chamber, is constituted to decrease load noises, vertical vibrations transmitted from the road surface and the vehicle tire.
Recently, decrease of load noises is further requested. So, as ways for achieving this request, it is thought that a rubber material having a low spring property and a static spring constant in a vertical direction is desired.
Such materials, however, decrease a frequency region of fluid-column-resonating action utilizing the inner stopper to lower regions. When a frequency region of the fluid-column-resonating action decreases to a practical frequency region, i.e. a frequency region of less than 500 Hz, it is possible to use a fluid-column-resonating action for isolating vibrations. However, the fluid-column-resonating action surely exerts anti-resonance which effects a bad influence in decreasing the load noises.
SUMMARY OF THE INVENTION
The present invention has been developed in view of the aforementioned situations associated with the conventional hydraulic vibration-isolator.
It is therefore an object of the present invention to provide an hydraulic vibration-isolator which can effectively decrease load noises.
The present inventor has known the phenomenon that an influence of anti-resonance is hardly generated in the hydraulic vibration-isolator when a frequency region of fluid-column-resonating action is increased to a higher frequency region which does not impede a practical function in the hydraulic vibration-isolator. In other words, the present inventor has known that it is desirable to increase a frequency region of the fluid-column-resonating action to a higher frequency region to flow the fluid easily in the fluid chamber of the hydraulic vibration-isolator.
FIGS. 5 and 6
show a conventional hydraulic vibration-isolator including: a main axis fitting
100
; an outer cylinder-shaped fitting
200
; a rubber elastic member
300
having a pair of ring-shaped side walls
301
, a pair of partition walls
302
, and orifice passages
303
; stopper fittings
400
; and fluid chambers
500
. As shown in
FIG. 6
, the stopper fitting
400
projects into the fluid chamber
500
, facing each of axial end surfaces
400
x
of the stopper fittings
400
to a gap
500
x
of the fluid chamber
500
, and impedes fluid flow through the fluid chamber
500
. So, it is possible to achieve the aforementioned object of the present invention to restrict the stopper fitting
400
at both of the axial end surfaces
400
x
thereof. Namely, a spacer is formed from the rubber elastic member at the axial end surface of the stopper fitting, which is used in increasing a frequency region of the fluid-column-resonating action to a higher frequency region in the hydraulic vibration-isolator.
According to the present invention, a hydraulic vibration-isolator comprises:
a main axis fitting having an outer circumferential surface, axially opposite ends, and an axially middle portion;
an outer cylinder-shaped fitting disposed at the outside of the main axis fitting away from it;
a rubber elastic member having a pair of ring-shaped side walls connecting the main axis fitting integrally with the outer cylinder-shaped fitting at the axially opposite ends of the main axis fitting, a pair of partition walls extending axially, and an orifice passage disposed in at least one of the partition walls, the ring-shaped side walls constituting an inner room at the axially middle portion of the main axis fitting by encircling it with the ring-shaped side walls, the partition walls dividing the inner room into two fluid chambers in a circumferential direction;
a stopper fitting disposed at the outer circumferential surface of the main axis fitting, projecting towards the fluid chamber, and having axial end surfaces;
a fluid contained in the fluid chambers; and
the improvement comprising:
the rubber elastic member having a whole spacer filling a gap between each of the axial end surface of the stopper fitting and each of the ring-shaped side walls facing each other; and
each of the axial end surfaces of the stopper fitting being unsurrounded by the fluid chamber.
According to the present invention, the hydraulic vibration-isolator can increase a frequency region of fluid-column-resonating action to a higher frequency region which hardly impede a practical function in the hydraulic vibration-isolator. As a result, as for vibration-isolating ability, the hydraulic vibration-isolator hardly has a bad influence caused by anti-resonance generated near a frequency region of the fluid-column-resonating action.
According to a preferable mode of the present invention, a hydraulic vibration-isolator is characterized in that it comprises a main axis fitting, an outer cylinder-shaped fitting, a rubber elastic member having a pair of partition walls and an orifice passage, a stopper fitting, and a fluid contained in fluid chambers; wherein the rubber elastic member has a spacer filling entirely a gap between an axial end surface of the stopper fitting and a ring-shaped side wall facing each other, and the axial end surface of the stopper fitting is free from the fluid chamber not to face the fluid chamber.
According to the preferable mode of the present invention, the main axis fitting is provided with a pair of stopper fittings disposed symmetrically with respect to its axis and projecting outwardly in a radius direction. The stopper fitting restricts a relative displacement between the main axis fitting and the outer cylinder-shaped fitting, and it can be formed of metal like the main axis fitting. The fluid, such as alkylane-glycol or silicone oil, having an incompressible property, is contained in the inner room, i.e. the fluid chamber, formed in the rubber elastic member.
The partition wall may be formed at a circumferential phase shifted an angle of approximately 90 degree away from the stopper fitting. The partition walls of the rubber elastic member preferably has a thin portion extending axially. The spacer formed with the rubber elastic member is to suppress a fluid-resistance which is received by the axial surface of the stopper fitting. Namely, in the conventional case where the stopper fitting projects into the fluid chamber to face its axial end surface to the fluid chamber, the stopper fitting raises fluid-resistance when the contained fluid flows in the fluid chamber.
In a preferable mode, the hydraulic vibration-isolator has a formula of K1:K2=1: (0.5-2.0). K1 exhibits a static spring constant in a direction j
Graham Matthew C.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tokai Rubber Industries Ltd.
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