A fluid-filled tubular vibration-damping device including: an inner shaft member; an intermediate tube member spaced radially outward therefrom; a main rubber elastic body connecting the two members; an outer tube member fastened externally onto the intermediate tube member; a pair of fluid chambers formed between the inner shaft member and the outer tube member so as to be on opposite sides of the inner shaft member; and an orifice passage interconnecting the fluid chambers. In at least one of the fluid chambers, at least one of side walls positioned on axially opposite sides includes a thick central connector positioned in a circumferentially central portion of the side wall and extending in an axis-perpendicular direction, and thin flexible walls that are thinner than the central connector while being positioned and spreading on circumferentially opposite sides of the side wall.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fluid-filled tubular vibration-damping device in which an inner shaft member and an outer tube member are connected by the main rubber elastic body, and fluid chambers are formed on opposite sides of the inner shaft member. The device exhibits a vibration damping effect with respect to vibration input in the axis-perpendicular direction based on the flow action of the fluid through an orifice passage connecting the fluid chambers.

2. Description of the Related Art

Conventionally, as a vibration damping device which is interposed between two members constituting a vibration transmission system to connect both members in a vibration damping manner, there is known a device in which a non-compressible fluid such as water or an alkylene glycol is sealed inside. As a specific example, as disclosed in U.S. Pat. No. 7,866,639, the sealed fluid is configured to flow by a pressure gradient generated at the time of vibration input. The device utilizes vibration damping effects based on flow action such as resonance action of the fluid.

In particular, the fluid-filled tubular vibration-damping device disclosed in U.S. Pat. No. 7,866,639 has a structure in which an inner shaft member and an outer tube member, which are spaced apart from each other by a prescribed distance in the radial direction, are connected by a main rubber elastic body, and a pair of fluid chambers provided on opposite sides of the inner shaft member are held in communication with each other by an orifice passage. Such a tubular vibration-damping device is used for an automotive member mount for a suspension, an upper support, an engine mount, a body mount, and the like.

Meanwhile, with the vibration damping device, there are cases where various types of input vibrations are input, and it may be difficult to reliably achieve the vibration damping ability required with respect to those vibrations. For example, with a tubular vibration-damping device used for automotive body mounts or the like, in the axis-perpendicular direction which is the vehicle front-back direction, high spring rigidity for support and attenuating capability are required with respect to low-frequency vibrations such as shakes exerted when the automobile drives over a bump or the like. Meanwhile, vibration isolating capability owing to low dynamic spring characteristics may be required with respect to high-frequency vibrations such as road noise exerted during driving.

However, with the fluid-filled tubular vibration-damping device of the conventional structure, when attempting to achieve high spring rigidity for support and attenuating capability with respect to low-frequency vibrations by increasing dynamic spring characteristics in the axis-perpendicular direction which is the vehicle front-back direction, there is a problem that expansion spring rigidity due to the main rubber elastic body constituting the wall part of the fluid chamber may become large, thereby making it difficult to satisfy the vibration damping ability with respect to high-frequency vibrations. Furthermore, fluid flow resistance of the orifice passage tuned to low-frequency vibration becomes extremely large in a high-frequency range due to antiresonance action, and moreover, the expansion spring rigidity of the wall part of the fluid chamber is large. Thus, there is a problem that it may be more difficult to obtain the vibration damping effect with respect to the high-frequency vibrations.

SUMMARY OF THE INVENTION

It is therefore one object of this invention to provide a fluid-filled tubular vibration-damping device of novel structure which is able to achieve excellent vibration damping ability with respect to vibrations in both low-frequency range and high-frequency range in a compatible manner.

A first preferred embodiment of the present invention provides a fluid-filled tubular vibration-damping device comprising: an inner shaft member; an intermediate tube member spaced radially outward from the inner shaft member; a main rubber elastic body connecting the inner shaft member and the intermediate tube member; an outer tube member fastened externally onto the intermediate tube member; a pair of fluid chambers formed between the inner shaft member and the outer tube member, the fluid chambers being formed on opposite sides of the inner shaft member; and an orifice passage through which the fluid chambers are held in communication, wherein in at least one of the fluid chambers, at least one of side walls positioned on axially opposite sides includes a thick central connector positioned in a circumferentially central portion of the side wall and extending in an axis-perpendicular direction, and thin flexible walls that are thinner than the central connector while being positioned and spreading on circumferentially opposite sides of the side wall.

With the fluid-filled tubular vibration-damping device structured following the present preferred embodiment, in the direction in which the fluid chambers are opposed to each other and in which vibrations targeted for damping are to be input, the thick central connector is provided so as to extend astride the inner shaft member and the outer tube member. Therefore, in such direction of vibration input, the central connector is able to effectively exhibit spring rigidity in the direction of compression/tension, thereby obtaining high spring rigidity. Moreover, between the fluid chambers opposed to each other in the direction of vibration input, fluid flow through the orifice passage will take place based on relative pressure fluctuations, and high attenuating effect based on the resonance action of the fluid can also be exhibited. This makes it possible to realize excellent vibration damping performance as a whole.

Meanwhile, since the thin flexible walls are provided on the side wall of the fluid chamber, with respect to pressure fluctuations at the time of input of high-frequency vibration having small amplitude, the flexible walls will exhibit low expansion spring rigidity. Therefore, the pressure in the fluid chamber will be allowed to escape, thereby making it possible to avoid high spring behavior due to fluid pressure, as well as to eliminate high dynamic spring behavior due to antiresonance of the orifice passage.

As a result, with respect to low-frequency, large-amplitude vibrations, excellent vibration damping performance is exhibited by the high spring rigidity owing to the central connector and the high attenuating effect owing to the fluid flow action. Meanwhile, with respect to high-frequency, small-amplitude vibrations, high dynamic spring behavior based on the pressure fluctuations in the fluid chamber will be avoided, thereby exhibiting excellent vibration damping performance owing to the low dynamic spring characteristics.

A second preferred embodiment of the present invention provides the fluid-filled tubular vibration-damping device according to the first preferred embodiment, wherein the flexible walls have a cross-sectional shape curving and extending in the axis-perpendicular direction between the inner shaft member and the outer tube member.

With the fluid-filled tubular vibration-damping device according to the present preferred embodiment, flexibility and hence expansion elasticity of the flexible walls can be set low owing to the shape effect without excessively thinning the wall thickness of the flexible walls. Therefore, it is possible to advantageously obtain improvement effect of the vibration-damping performance with respect to high-frequency vibrations owing to the flexible wall, while improving durability.

A third preferred embodiment of the present invention provides the fluid-filled tubular vibration-damping device according to the first or second preferred embodiment, wherein the at least one of the side walls of the at least one of the fluid chambers includes recesses positioned on the circumferentially opposite sides thereof and opening to an axial outer face thereof, and the flexible walls are provided by the side wall being thin-walled by the recesses, and an axial inner face of the side wall spreads in a circumferential direction with an inner face shape that is constant over the central connector and the flexible walls.

With the fluid-filled tubular vibration-damping device according to the present preferred embodiment, simplification of the parting structure of the mold is facilitated in comparison with the case where the flexible walls are provided by recesses opening to the inner face of the fluid chamber. Besides, it is also possible to allow the axial inner face of the side wall of the fluid chamber to have a smooth surface shape without steps in the circumferential direction. This may improve flow efficiency and hence the vibration damping performance by reducing flow resistance of the sealed fluid.

A fourth preferred embodiment of the present invention provides the fluid-filled tubular vibration-damping device according to any one of the first through third preferred embodiments, wherein in both of the fluid chambers formed on the opposite sides of the inner shaft member, each of the side walls positioned on the axially opposite sides includes the central connector and the flexible walls.

With the fluid-filled tubular vibration-damping device according to the present preferred embodiment, the central connector and the flexible walls are provided on both side walls positioned on the axially opposite sides of both fluid chambers. This makes it possible to more efficiently realize the excellent vibration damping effect based on high attenuation characteristics with respect to the low-frequency vibrations and the excellent vibration damping effect based on low dynamic spring characteristics with respect to the high-frequency vibrations as described above in a compatible manner.

A fifth preferred embodiment of the present invention provides the fluid-filled tubular vibration-damping device according to any one of the first through fourth preferred embodiments, wherein the intermediate tube member includes a pair of windows opening at portions that are opposed to each other in the axis-perpendicular direction in an axially middle portion of the intermediate tube member, the main rubber elastic body includes a pair of pockets opening to an outer circumferential surface of the intermediate tube member through the respective windows thereof, and the windows of the intermediate tube member are covered by the outer tube member so that the fluid chambers are provided by the pockets.

With the fluid-filled tubular vibration-damping device according to the present preferred embodiment, it is possible to provide the pair of fluid chambers with excellent fluidtightness to the external space and with a simple structure. Thus, the fluid-filled tubular vibration-damping device structured following the present invention can be more easily put into practical use.

With the fluid-filled tubular vibration-damping device constructed according to the present invention, with respect to low-frequency, large-amplitude vibrations, excellent vibration damping performance will be exhibited by the high spring rigidity owing to the central connector and the high attenuating effect owing to the fluid flow action. Besides, with respect to high-frequency, small-amplitude vibrations, high dynamic spring behavior based on the pressure fluctuations in the fluid chamber will be avoided, thereby exhibiting excellent vibration damping performance owing to the low dynamic spring characteristics. This makes it possible to achieve excellent vibration damping ability with respect to low-frequency vibrations and high-frequency vibrations in a compatible manner.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, practical embodiments of the present invention will be described in reference to the drawings.

FIGS. 1 to 5show an automotive suspension member mount10as a first practical embodiment of a fluid-filled tubular vibration-damping device of construction according to the present invention. The suspension member mount10according to the present practical embodiment includes an inner shaft member12of metal and an intermediate tube member14, which are radially spaced apart from each other by a prescribed distance. The inner shaft member12and the intermediate tube member14are elastically connected by a main rubber elastic body16. Besides, an outer tube member18of metal is externally placed about the intermediate tube member14and fastened fitting thereto.

With such member mount10, the inner shaft member12is attached to a vehicle body side in a state in which the vertical direction inFIG. 1roughly coincides with the vehicle vertical direction, and the vertical direction and the lateral direction inFIGS. 2 and 3respectively coincide with the front-back direction and the lateral direction of the vehicle. Meanwhile, the outer tube member18is attached to a suspension member. By so doing, the member mount10is configured to be interposed at the mounting portion of the suspension member to the vehicle body. In the following description, as a general rule, the vertical direction refers to the vertical direction inFIG. 1.

Described more specifically, the inner shaft member12has a round tubular shape extending straightly in the vertical direction. In the present practical embodiment, the upper end of the inner shaft member12is slightly enlarged in diameter, and a mounting flange19is secured by being press-fitted therein. Further, around the inner shaft member12, the intermediate tube member14of metal is disposed radially outward at a prescribed distance in a coaxial manner.

The intermediate tube member14has a large-diameter, roughly thin-walled tubular shape overall, and its axially middle portion is reduced in diameter so as to have a groove shape that is continuous in the circumferential direction. Accordingly, the intermediate tube member14has a tubular wall including a small-diameter part20and large-diameter parts22,22provided on axially opposite sides of the small-diameter part20. Besides, the intermediate tube member14includes in its roughly axially middle portion a pair of windows26,26formed at portions that are opposed to each other in the axis-perpendicular direction, which is the vehicle front-back direction. The windows26,26each extend for a length less than half the circumference.

The main rubber elastic body16having a roughly thick-walled, round tubular shape overall is interposed between the radially opposed faces of the inner shaft member12and the intermediate tube member14, and the inner shaft member12and the intermediate tube member14are elastically connected by the main rubber elastic body16. As shown inFIG. 6, the main rubber elastic body16is formed as an integrally vulcanization molded component28in which the inner shaft member12and the intermediate tube member14are bonded by vulcanization respectively on the inner circumferential surface and the outer circumferential surface of the main rubber elastic body16.

Moreover, the main rubber elastic body16includes a pair of pockets30,30having a depressed form, which are positioned on opposite sides of the inner shaft member12in the vehicle front-back direction and each extend for a length less than half the circumference. The pockets30,30open to the outer circumferential surface of the intermediate tube member14through the respective windows26,26of the intermediate tube member14.

Furthermore, each pocket30is configured such that the bottom wall of is constituted by the outer circumferential surface of the inner shaft member12covered by a thin rubber layer, while the peripheral walls are constituted by the main rubber elastic body16. Among the peripheral walls, the circumferentially opposite side walls of the pocket30are constituted by thick partition wall rubbers32,32which partition the pockets30,30. The axial thickness of the partition wall rubber32is close to the entire length of the intermediate tube member14.

Meanwhile, axially opposite side walls34,34of the pocket30, which partition the axially opposite sides of the pocket30with respect to the external space, are provided so as to extend in the circumferential direction between the radially opposed faces of the inner shaft member12and the outer tube member18(the intermediate tube member14). Besides, on an axial outer face35of each side wall34, there are formed a pair of recesses36,36which are positioned on the circumferentially opposite sides thereof and open to axially outward.

The circumferentially opposite side portions of the side wall34are thin-walled by the recesses36,36. Thus, the circumferentially central portion of the side wall34is not thin-walled by the recess36, and constitutes a thick central connector38extending in the radial direction between opposed faces of the inner shaft member12and the outer tube member18(the intermediate tube member14). On the other hand, the circumferentially opposite side portions of the side wall34are made thinner in the axial direction than the central connector38by being thin-walled from the axially outer side by the recess36, and constitute flexible walls40,40being allowed to undergo elastic deformation in the axial direction, which is inside and outside of the pocket30, more easily than the central connector38is.

In the pair of pockets30,30, the central connectors38,38of the side walls34,34respectively positioned on the axially opposite sides extend in series in the axis-perpendicular direction with the inner shaft member12interposed therebetween. Besides, the flexible walls40are provided at positions circumferentially deviated from the axis-perpendicular direction in which the central connectors38,38extend.

Particularly in the present practical embodiment, with respect to the shape of an axial inner face41of the side wall34of each pocket30, a sloping part is provided at the middle portion in the depth direction. Thus, the axial inside dimension of the pocket30is varied in the depth direction, namely, its opening side is made larger in axial inside dimension than its bottom side. Besides, by the sloping part being provided at the middle portion in the depth direction, the inner face shape of the side wall34is curved in a tan (tangent) curve shape in the depth direction, which is the radial direction. The inner face shape of the side wall34having such a curved surface shape spreads roughly constantly in the circumferential direction over the central connector38and the flexible walls40,40provided on the opposite sides thereof.

Moreover, the bottom face shape of the recess36formed in the side wall34is curved in the radial direction so as to have a roughly similar shape corresponding to the inner face shape of the side wall34. Accordingly, the side wall34(the flexible wall40) provided between the bottom parts of the pocket30and the recesses36,36spreads while curving in the radial direction and in the circumferential direction with a roughly constant thickness dimension.

Furthermore, on the outer peripheral surface of the integrally vulcanization molded component28, a pair of orifice members42,42are attached. Each of these orifice members42,42has an arcuate plate shape which is of length less than half the circumference, and is disposed astride the openings of the pair of windows26,26in the circumferential direction. The circumferentially opposite end portions of the orifice member42are overlapped on and supported by the opening edge parts on the circumferentially opposite sides of each window26.

Additionally, the orifice members42,42are provided with grooves44,44opening onto the outer circumferential surface thereof and extending in the circumferential direction. The first circumferential ends of the grooves44provided in the respective orifice members42communicate with each other. The second circumferential ends of the grooves44,44provided in the respective orifice members42,42communicate with the respective pockets30,30via through holes46,46provided penetrating the bottom walls of the grooves44,44.

Then, the outer tube member18is externally placed onto the integrally vulcanization molded component28to which such orifice members42,42are attached, and is secured fitting thereto by being subjected to a diameter reduction process as needed. A thin seal rubber layer48is formed over the roughly entire surface of the inner circumferential surface of the outer tube member18, and the fitting surfaces to the intermediate tube member14and the orifice members42,42are fluid-tightly sealed.

Besides, an inner flange50is formed at one axial end of the outer tube member18, and is engaged with one axial end of the intermediate tube member14. Moreover, an outer flange52is formed at the other axial end of the outer tube member18, while a constricted part54is formed at the radially inner edge part on the proximal side of the outer flange52so as to be engaged with the other axial end of the intermediate tube member14. On the inner flange50and the outer flange52of the outer tube member18, cushioning rubbers56,56each projecting axially outward are integrally formed with the seal rubber layer48.

By the outer tube member18being fastened externally onto the integrally vulcanization molded component28, the openings of the windows26,26are covered by the outer tube member18, and the openings of the pair of pockets30,30are fluid-tightly covered. Accordingly, a pair of fluid chambers58,58, which are opposed to each other with the inner shaft member12interposed therebetween in the vehicle front-back direction, are formed by the main rubber elastic body16constituting their peripheral walls. That is, the axially opposite wall parts in the fluid chambers58,58are constituted by the side walls34,34,34,34. Besides, the grooves44,44of the orifice members42,42are also fluid-tightly covered by the outer tube member18, thereby providing an orifice passage60meandering in the circumferential direction along the inner circumferential surface of the outer tube member18and extending for a length equal to once around the circumference or more. The fluid chambers58,58are held in communication with each other through the orifice passage60.

Furthermore, a fluid-filled zone including the fluid chambers58,58and the orifice passage60, which is fluid-tightly blocked with respect to the external space, is filled with a predetermined non-compressible fluid or liquid. As the non-compressible fluid to be filled, water, alkylene glycols, polyalkylene glycols, silicone oil or the like may be employed, and in particular, in order to effectively obtain the vibration damping effect based on the resonance action of the fluid, a low-viscosity fluid having viscosity of 0.1 Pa·s or lower is preferably employed.

Filling of the non-compressible fluid into the sealed zone can be advantageously accomplished by, for example, attaching the orifice members42,42to the integrally vulcanization molded component28of the main rubber elastic body16, and then carrying out external attachment of the outer tube member18within a non-compressible fluid, or the like.

Then, the member mount10structured as described above is mounted onto the vehicle in a state in which the vertical direction inFIG. 1roughly coincides with the vehicle vertical direction, and the vertical direction and the lateral direction inFIGS. 2 and 3respectively coincide with the front-back direction and the lateral direction of the vehicle.

In this installed state, in the vehicle lateral direction in which a rolling load at the time of turning is exerted, a large spring rigidity is exhibited by the pair of partition wall rubbers32,32positioned between the inner shaft member12and the outer tube member18(the intermediate tube member14). This makes it possible to realize good steering stability.

Besides, in the vehicle front-back direction in which low-frequency, large-amplitude vibrations are exerted when driving over a bump, etc., the pair of fluid chambers58,58are opposed to each other with the inner shaft member12interposed therebetween. Based on the relative pressure fluctuations induced between the fluid chambers58,58, fluid flow through the orifice passage60will be produced, and excellent vibration damping performance can be obtained by the high attenuating effect utilizing the resonance action of the fluid.

Particularly in the vehicle front-back direction, the pair of central connectors38,38are disposed at the axially opposite sides so as to connect the inner shaft member12and the outer tube member18(the intermediate tube member14) in series. Therefore, the attenuating action by the spring rigidity in the axis-perpendicular direction can also be exhibited. Further, the expansion spring rigidity of the fluid chamber58is also sufficiently obtained by the central connector38. Thus, escape of the pressure fluctuations induced in the fluid chamber58at the time of vibration input will be suppressed, thereby efficiently obtaining a sufficient amount of fluid flow through the orifice passage60. Accordingly, an intended vibration damping effect based on the fluid flow action will be exhibited more stably.

On the other hand, at the time of input of high-frequency, small-amplitude vibration such as driving rumble, the fluid flow resistance through the orifice passage60is greatly increased by the antiresonance action of the fluid flow. However, since the expansion spring rigidity of the flexible wall40provided to the side wall34of each fluid chamber58is low, the pressure fluctuations in the fluid chamber58can be allowed to escape and reduced by the elastic deformation of the flexible wall40. As a result, a significant increase in dynamic spring constant will be avoided, thereby achieving good vibration damping performance owing to the low dynamic spring characteristics.

Moreover, the central connector38and the flexible walls40,40are provided to each of the side walls34,34,34,34on the axially opposite sides of the pair of fluid chambers58,58. This makes it possible to even more stably attain vibration damping effect with respect to both the low-frequency, large-amplitude vibration and the high-frequency, small-amplitude vibration.

Furthermore, in the present practical embodiment, the axial inner and outer faces of the flexible wall40have the shapes corresponding to each other. Accordingly, the flexible wall40has a roughly constant thickness dimension in the axis-perpendicular direction, and can be elastically deformed while reducing the risk of unintended deformation and the like. In particular, since the flexible wall40has a curved shape, elastic deformation is further facilitated. Therefore, it is not necessary to make the flexible wall excessively thin in order to easily cause elastic deformation, thereby improving durability as well.

Besides, the thin-walled flexible wall40is formed by providing the recess36on the axially outer side of the side wall34. Thus, in comparison with the case where the recess is formed on the axially inner side, removability of the mold may be improved. In addition, by providing the recess36on the axially outer side of the side wall34, it is also possible to form each of the axial inner faces41of the both side walls34,34of the fluid chamber58so as to spread in the circumferential direction with a roughly constant curved surface shape. Therefore, the fluid in the fluid chambers58,58can smoothly flow, thereby improving the flow efficiency.

Additionally, in the present practical embodiment, the intermediate tube member14is provided with the windows26,26, and the pockets30,30open to the outer peripheral side through the windows26,26. With the simple structure in which the openings of the pockets30,30are covered by the outer tube member18, the pair of fluid chambers58,58can be formed. In particular, the orifice members42,42having the grooves44,44on its outer peripheral side are fitted in the pockets30,30, and by the openings of the grooves44,44being covered by the outer tube member18, the orifice passage60is constituted. Therefore, the shape of the orifice passage60will be stably maintained even with respect to the input from the outside.

While the present invention has been described hereinabove in terms of a certain practical embodiment, this is merely exemplary, and the invention shall not be construed as limited in any way to the specific disclosures in the practical embodiment.

For example, the number, size, and the like of the central connector and the flexible wall provided to the side wall can be appropriately set according to the required vibration damping characteristics. Specifically, it would also be acceptable to provide the central connector and the flexible walls only to one axial side wall of the pocket. Besides, when one side wall is provided with the central connector and the flexible walls on opposite sides of the central connector, with respect to the other walls, the flexible wall may be formed on only one circumferential side of the central connector or the like, for example.

In the present invention, the technical effect as described above can be obtained by providing the thick central connector having a thickness dimension varied in the axial direction and the thin flexible walls to the side wall of the fluid chamber. In this respect, the specific wall thickness, shape and the like of the central connector and the flexible wall can be appropriately set according to the required vibration damping characteristics. It would be acceptable as long as the flexible wall is thinner than the central connector, and by setting the thickness dimension of the flexible wall so as to facilitate swelling deformation accompanying input of the vibration to be damped, desired working effects of the present invention described in the preceding practical embodiment can be exhibited.

In the preceding practical embodiment, the flexible walls40,40are provided continuously on the circumferentially opposite sides of the central connector38. However, it would also be possible for example to provide a transitional region or the like circumferentially between the central connector and the flexible wall with a prescribed circumferential dimension, the transitional region having a thickness dimension of an intermediate value between those of the central connector and the flexible wall, and smoothly connecting their inner and outer faces.

Moreover, the specific shape and structure of the orifice passage are set according to the required vibration damping characteristics, and are not limited in any way. Further, the orifice member is not essential in the present invention. For example, it would also be acceptable to provide a groove on the outer peripheral surface of the partition wall rubber through which the pair of pockets communicate with each other, and to form the orifice passage by covering the groove by the outer tube member.

It is also to be understood that the present invention may be embodied with various changes, modifications and improvements which may occur to those skilled in the art, without departing from the spirit and scope of the invention.