Fluid-filled cushioning device having sealing arrangement for easy assembling

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a cushioning device disposed between two members, for damping or isolating vibrations applied thereto primarily in its axial direction, and more particularly to a technique for increased ease of assembling of a fluid-filled cushioning device for damping or isolating input vibrations, based on flows of a non-compressible fluid within the device.

2. Discussion of the Prior Art

Various types of fluid-filled cushioning devices have been recently proposed as a vibration damping/isolating mount or support disposed between two members of a vibration system. A cushioning device of these types is filled with a suitable non-compressible fluid, for damping and/or isolating input vibrations, in dependence on flows of the fluid through an orifice or restricted fluid passage formed in the device, or by utilizing an effect of inertia of the fluid mass.

An example of such a fluid-filled cushioning device is a strut bar cushion used in a vehicle suspension system, which is connected between a shaft member such as a strut bar, and a suitable support member such as a body of the vehicle, in order to damp or isolate mainly a vibrational load applied in its axial direction.

A commonly known fluid-filled cushioning device includes (a) an inner sleeve through which a suitable shaft member is inserted for attachment to the device, (b) a cylindrical elastic body mounted on an axially intermediate portion of the inner sleeve and provided at its outer circumferential portion with orifice-defining means which has an orifice formed therethrough, (c) a pair of annular elastic members each having an integrally formed inner retainer member and an integrally formed outer sleeve which are spaced apart from each other in an axial direction of the elastic members, the elastic members being mounted on the inner sleeve such that the inner retainer member is press-fitted in a corresponding one of opposite axial end portions of the inner sleeve while the orifice-defining means of the cylindrical elastic body is sandwiched by and between corresponding axial end faces of the outer sleeves of the annular elastic members, in the axial direction of the elastic members, and such that the inner sleeve, the cylindrical elastic body and the pair of annular elastic members cooperate with each other to define two fluid chambers which are filled with a suitable non-compressible fluid and which are separated from each other by the elastic body and communicate with each other through the orifice, and (d) a cylindrical bracket which is mounted on outer circumferential surfaces of the outer sleeves of the annular elastic members, and which is attached to a suitable support member.

In the thus constructed fluid-filled cushioning device, the mounting of the annular elastic members on the inner sleeve, and the mounting of the cylindrical bracket on the outer sleeves of the annular elastic members, are both conducted within a mass of the non-compressible fluid, so that the fluid chambers are filled with the fluid. The two outer sleeves of the annular elastic members are forced against each other in the opposite axial directions by the cylindrical bracket, so that fluid tightness of the fluid chambers is maintained.

In the known fluid-filled cushioning device constructed as described above, however, the mere mounting of the pair of annular elastic members on the inner sleeve does not establish fluid tightness of the fluid chambers which are defined in the intermediate assembly of the inner sleeve and the elastic members. Accordingly, the cylindrical bracket must be mounted on the outer sleeves of the annular elastic members, also within the fluid mass, following the mounting of the elastic members on the inner sleeve. This mounting of the cylindrical bracket is difficult, since the bracket should be subjected to an operation to urge the outer sleeves against each other within the fluid mass. Therefore, the assembling efficiency is comparatively low. Further, there may be left the fluid within spaces other than the fluid chambers, for instance, within a clearance between the outer surfaces of the outer sleeves and the inner surface of the cylindrical bracket. The fluid in such spaces may leak during installation or use of the cushioning device on the vehicle body, causing undesirable contamination of the device itself and the environment of the device.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a fluid-filled cushioning device which is easy to assemble, and which assures fluid tightness of its fluid chambers.

Another object of the invention is to provide such a fluid-filled cushioning device which permits mounting of its cylindrical bracket on its annular elastic members, in the atmosphere.

The above objects may be achieved according to the principle of the present invention, which provides a fluid-filled cushioning device connected to two support members for damping vibrations applied therebetween, comprising an inner sleeve through which one of the two support members is inserted for attachment thereto, a cylindrical elastic body, a pair of annular elastic members and a cylindrical bracket. The cylindrical elastic body is mounted on an axially intermediate portion of the inner sleeve. The elastic body is provided at its outer circumferential portion with orifice-defining mean which has an orifice formed therethrough.

Each annular elastic member has an integrally formed inner retainer member and an integrally formed outer sleeve which are spaced apart from each other in an axial direction of the elastic members. These annular elastic members are mounted on the inner sleeve such that the inner retainer member is press-fitted in a corresponding one of axial end portions of the inner sleeve while the orifice-defining means of the cylindrical elastic body is sandwiched by and between corresponding axial end faces of the outer sleeves of the pair of annular elastic members, in the axial direction.

The cylindrical bracket is mounted on outer circumferential surfaces of the outer sleeves of the annular elastic members, and is fixed to the other of the two support members. The bracket is adapted to force the outer sleeves of the elastic members against each other via the orifice-defining means in the axial direction. The inner sleeve, the cylindrical elastic body and the annular elastic members cooperate with each other to define two fluid chambers which are separated from each other by the elastic body and which communicate with each other through the orifice. The fluid chambers are filled with a non-compressible fluid.

An axial dimension of the each annular elastic member before mounted on the inner sleeve is determined to permit each annular elastic member to be axially compressed upon mounting of the pair of annular elastic members on the inner sleeve, so that the outer sleeves are urged against the orifice-defining means with a sufficient force to maintain fluid tightness between the pair of annular elastic members and the orifice-defining means, whereby the mounting of the cylindrical bracket on the outer sleeves of the elastic members may be effected in a condition that the two fluid chambers are filled with the non-compressible fluid.

In the fluid-filled cushioning device of the present invention constructed as described above, fluid tightness of the two fluid chambers is maintained owing to the elastic force produced by the pair of annular elastic members mounted on the inner sleeve. Therefore, the mounting of the cylindrical bracket on the outer sleeves of the annular elastic members can be accomplished in the atmosphere, after the annular elastic members are mounted on the inner sleeve, within a mass of the non-compressible fluid so as to fill the fluid chambers, and the thus prepared intermediate product is removed from the fluid mass. In other words, the fluid tightness of the intermediate product is tentatively established by the annular elastic members which are mounted on the inner sleeve so as to seal the fluid chambers, and the fluid tightness of the end product is permanently maintained by the cylindrical bracket which holds the outer sleeves of the annular elastic members in pressed abutting contact with each other via the orifice-defining means of the cylindrical elastic body.

As described above, the constructional arrangement of the instant fluid-filled cushioning device not only permits easy mounting of the bracket on the intermediate product, but also assures freedom from leakage of the fluid from the finally assembled device, which causes contamination of the assembling environment and the end product.

In one form of the fluid-filled cushioning device of the invention, the above-indicated one of the two support members which is inserted through the inner sleeve consists of a strut bar of a suspension system of a motor vehicle, while the other of the two support members which is attached to the cylindrical bracket consists of a body of the vehicle.

In another form of the present invention, the inner sleeve and the cylindrical elastic body having the orifice-defining means constitute a first intermediate component prepared in the process of manufacture of the device, while the pair of annular elastic members are prepared as second intermediate components which are mounted on the inner sleeve of the first intermediate component, within a mass of the non-compressible fluid. The cylindrical bracket is mounted on the outer sleeves of the second intermediate components after an assembly of the first and second intermediate components is removed from the mass of the non-compressible fluid.

In a further form of the present invention, each annular elastic member includes an annular rubber wall which connects the inner retainer member and the outer sleeve so that the outer sleeves of the pair of annular elastic members are urged against the orifice-defining means by axial elastic deformation of the annular rubber walls of the elastic members.

In a still further form of the invention, the orifice-defining means comprises a first orifice-defining metal member secured to the outer circumferential portion of the cylindrical elastic body, and a second orifice-defining metal member which is aligned with the first orifice-defining metal member such that the first and second orifice-defining metal members cooperate with each other to define the orifice.

In one arrangement of the above form of the invention, the first orifice-defining metal member has a U-shaped portion defining an annular groove, and the second orifice-defining metal member has an annular portion which closes the annular groove so as to define an annular passage between the U-shaped portion and the annular portion. The U-shaped portion has a through hole communicating with the annular passage and one of the two fluid chambers, while the annular portion has a cutout which communicates with the annular passage and the other of the two fluid chambers. The annular passage, the through hole and the cutout cooperate with each other to define the orifice.

In a yet further form of the present invention, the cylindrical elastic body includes a partition rubber member which has a thin-walled rubber layer covering an outer circumferential surface of the inner sleeve, and further has a partition wall portion which extends radially outwardly from an axially intermediate portion of the rubber layer. The rubber layer has a sealing portion which covers an outer edge part of at least one of opposite axial end faces of the inner sleeve. The retainer member is fitted in the corresponding one of the axial end portions of the inner sleeve such that the retainer member is held in pressed abutting contact with the sealing protion of the rubber layer.

In one arrangement of the above form of the invention, the outer edge part of the above-indicated at least one end face of the inner sleeve provides a relief portion which is covered by the sealing portion of the rubber layer. The retainer member has a cylindrical wall portion fitted in the corresponding one of the opposite axial end portions of the inner sleeve, and an abutting surface which is held in contact with the end face of the inner sleeve and the sealing portion of the rubber layer such that a clearance defined by the abutting surface of the retainer member and the relief portion of the inner sleeve is filled by the sealing portion. In this case, the relief portion may consist of a rounded outer edge of the end face, a chamferred outer edge of the end face, or the outer edge part whose edge is removed so as to form a rectangular cutout.

According to the above arrangement, the abutting surface of the retainer member and the end face of the inner sleeve are held in direct abutting contact with each other, while at the same time the clearance defined by the abutting surface and the end face is filled by the elastically compressed and deformed sealing portion of the rubber layer. Hence, the retainer member is securely fastened to the inner sleeve, while the fluid tightness between these two members is maintained by the sealing portion of the rubber layer. Further, the direct contact of the abutting surface of the retainer member with the end face of the inner sleeve prevents reduction of the sealing performance of the sealing portion and rattling or looseness of the retainer member with respect to the inner sleeve, which would occur due to fatigue of the sealing portion if the abutting surface of the retainer member and the end face of the inner sleeve is held apart from each other by the sealing portion. Thus, the present arrangement assures improved sealing capability and durability between the inner sleeve and the retainer member.

In another arrangement of the above form of the invention, the thin-walled rubber layer has at least one annular lip formed axially inwardly of the sealing portion.

According the present invention, there is also provided a sealing structure between a first member having a first abutting surface, and a second member which has a second abutting surface on an end face thereof and a surface adjacent to the end face and covered by a rubber layer, the first and second members being assembled with respect to each other such that the first and second abutting surfaces are held in abutting contact with each other, the sealing structure comprising a relief portion provided on an edge which is defined by the end face of the second member and the surface of the second member covered by the rubber layer, such that a clearance is formed between the first abutting surface of the first member and the relief portion of the second member while the first and second abutting surfaces are held in abutting contact with each other. The rubber layer has an elastic sealing portion which integrally extends therefrom so as to cover the relief portion. The sealing portion protrudes in a direction perpendicular to the second abutting surface when the first and second abutting surfaces are spaced apart from each other. The sealing portion is elastically deformed upon abutment of the first and second abutting surfaces on each other, whereby the clearance is filled by the sealing portion so as to maintain fluid tightness between the first and second members.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and optional objects, features and advantages of the present invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in conjunction with the accompanying drawings, in which:

FIG. 1 is an elevational view in axial cross section (taken along line I--I of FIG. 2) of one embodiment of the invention in the form of a strut bar cushion;

FIG. 2 is a cross sectional view taken along line II--II of FIG. 1;

FIG. 3 is an elevational view in axial cross section of a first intermediate component of the strut bar cushion, which includes an inner metal sleeve, and a cylindrical elastic body which is formed by vulcanization on the inner metal sleeve, together with a first orifice-defining metal member;

FIG. 4 is a bottom plan view of the intermediate product of FIG. 3;

FIG. 5 is a plan view of a second orifice-defining metal member;

FIG. 6 is an elevational view in cross section of one of a pair of second intermediate components in the form of annular elastic members each formed by vulcanization with a retainer member and an outer metal sleeve;

FIG. 7 is an elevational view in axial cross section of an intermediate product prepared in the process of manufacture of the strut bar cushion, which product consists of the first and second intermediate components which are assembled with respect to each other;

FIG. 8 is a cross sectional view of a cylindrical bracket which is another component of the strut bar cushion;

FIG. 9 is an elevational view in axial cross section of the strut bar cushion attached to a strut bar of a motor vehicle;

FIG. 10 is a perspective view of a relevant part of the vehicle, indicating the manner in which the strut bar cushion is installed on the vehicle;

FIG. 11 is a fragmentary elevational view in cross section of a sealing arrangement between the inner metal sleeve and the retainer member of another embodiment of the invention;

FIG. 12 is a fragmentary cross sectional view showing the inner metal sleeve and the retainer member which are assembled with respect to each other;

FIGS. 13 and 14 are views corresponding to that of FIG. 11, showing modified sealing arrangements used in further embodiments of the invention;

FIG. 15 is a fragmentary cross sectional view of the inner metal sleeve with a modified sealing rubber layer used in a still further embodiment of the invention; and

FIGS. 16 and 17 are views corresponding to those of FIGS. 11 and 12, showing a known sealing arrangement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIGS. 1 and 10, the strut bar cushion is indicated generally at 16. As shown in FIG. 10, the strut bar cushion 16 is used in a suspension system of a motor vehicle such that the cushion 16 is disposed between a strut bar 12 which is connected at its one end to a suspension arm 10 of the vehicle, and a body 14 of the vehicle. The strut bar cushion 16 functions primarily for damping and isolating vibrations which are applied thereto in its axial direction.

The construction of the instant strut bar cushion 16 will be described in detail, by reference to FIGS. 1 through 9.

In the axial and transverse cross sectional views of FIGS. 1 and 2, reference numeral 18 designates a cylindrical inner metal sleeve. As also shown in FIGS. 3 and 4, a cylindrical elastic body in the form of a partition rubber member 20 is formed by vulcanization on the outer circumferential surface of the inner metal sleeve 18.

Described more specifically, the partition rubber member 20 consists of a thin-walled cylindrical portion 22 secured to the entire outer circumferential surface of the inner metal sleeve 18, and a partition wall portion 24 which is formed integrally with the thin-walled portion 22 such that the partition wall portion 24 extends radially outwardly from an axially intermediate part of the thin-walled portion 22. Thus, the partition wall portion 24 has a considerably larger outside diameter than the thin-walled portion 22. As shown most clearly in FIG. 3, the outer edges of the opposite end faces of the inner metal sleeve 18 are covered by the opposite ends of the thin-walled cylindrical portion 22 of the partition rubber member 20. That is, a sealing portion 26 extends from each axial end of the thin-walled portion 22, for the purpose which will be described. Several modifications of the sealing portion 26 will be described with respect to the other embodiments of the invention.

While the partition rubber member 20 is formed by vulcanization of an unvulcanized rubber material, a first orifice-defining metal member 28 having a generally substantially annular shape is secured to a radially outer part of the partition wall portion 24. This first orifice-defining metal member 28 consists of a groove portion 30 defining a U-shaped groove which extends along its entire circumference, and a flange portion 32 which extends radially outwardly from an outer wall of the groove portion 30. The metal member 28 is positioned with respect to the partition rubber member 20 such that the U-shaped groove is open in the axial direction of the strut bar cushion 16. The metal member 28 is secured to the partition wall portion 24 such that an inner wall of the groove portion 30 is embedded in the radially outer part of the partition wall portion 24.

Referring next to FIG. 5, there is illustrated a second orifice-defining metal member 34 which also has a generally annular shape. This second orifice-defining metal member 34 is aligned with the first orifice-defining metal member 28, such that the second metal member 34 closes an opening of the circumferential groove defined by the first metal member 28. The inner wall of the groove portion 30 of the first orifice-defining metal member 28 has a larger axial dimension than the outer wall, and the inner circumference of the second orifice-defining metal member 34 is held in abutting contact with the outer circumferential surface of the inner wall of the groove portion 30, via a thin rubber layer 24a of the partition rubber member 20, as indicated in FIG. 1, whereby fluid tightness between the mutually abutting surfaces of the two orifice-defining metal members 28, 34 is maintained.

The first orifice-defining metal member 28 has a recess 42 in the inner wall of the groove portion 30, as shown in FIG. 4, while the second orifice-defining metal member 34 has a protrusion 44 on the inner circumferential surface, as shown in FIG. 5. These recess and protrusion 42, 44 engage each other, whereby the relative circumferential position of the two metal members 28, 34 is determined. Further, the first metal member 28 has a through hole 38 in the bottom wall of the groove portion 30, as shown in FIGS. 1-4, while the second metal member 34 has a cutout 40 formed on the inner circumference, as shown in FIGS. 2 and 5. With the two metal members 28, 34 positioned relative to each other as described above, the circumferential passage defined by the two metal members 28, 34 communicates with fluid chambers 48 (which will be described) through the through hole 38 and the cutout 40. Thus, an orifice in the form of a restricted passage 36 is formed through the cylindrical elastic body in the form of the partition rubber member 20. It will be understood from the above description that the first and second orifice-defining metal members 28, 34 constitute means for defining the orifice 36.

FIG. 3 shows a first intermediate component prepared in the process of manufacture of the strut bar cushion 16. The first intermediate component is prepared by suitably positioning the inner metal sleeve 18 and first and second orifice-defining metal members 28, 34, such that the thin-walled cylindrical portion 22 of the partition rubber member 20 is secured to the outer circumferential surface of the inner metal sleeve 18, and the first orifice-defining metal member 28 is secured to the radially outer part of the partition wall portion 24 of the partition rubber member 20 while the second orifice-defining metal member 34 is aligned with the first orifice-defining metal member 28 as described above. With the three metal members 18, 28, 34 thus positioned in a mold, a suitably prepared unvulcanized rubber material is poured into the mold, and the rubber material is vulcanized in a known manner, whereby the first intermediate component of FIG. 3 is obtained.

FIG. 6 shows one of a pair of annular elastic members 46, 46 which are second intermediate components also prepared in the process of manufacture of the cushion 16. These annular elastic members 46, 46 are mounted on the opposite axial end portions of the first intermediate component of FIG. 3, so that the two annular fluid chambers 48, 48 are defined by the first and second intermediate components, that is, by the inner metal sleeve 18, partition rubber member 20 (cylindrical elastic body) and the two annular elastic members 46, 46. The fluid chambers 48, which are separated by the partition rubber member 20, are held in fluid communication with each other through the orifice 36 defined by the first and second orifice-defining metal members 28, 34 secured to the partition rubber member 20.

Described more specifically by reference to FIG. 6, each annular elastic member or second intermediate component 46 consists of: a metallic retainer member 51 secured to the appropriate end of the inner metal sleeve 18; an outer metal sleeve 54 which is disposed radially outwardly of the retainer member in coaxial relation with the inner metal sleeve 18; and an annular rubber wall 56 which is disposed between the retainer member 51 and the outer metal sleeve 54 and is secured thereto by vulcanization. The retainer member 51 has an inner wall 52 and an outer wall 53 which define an annular groove. This annular groove is U-shaped in cross section and is open in the axial direction of the inner metal sleeve 18. The inner wall 52 is press-fitted in the appropriate end of the inner metal sleeve 18 as shown in FIG. 1. The retainer member 51 and the outer metal sleeve 54 are spaced apart from each other by a suitable distance in the axial direction. The annular rubber wall 56 is secured at its inner circumference to the outer wall 53 of the retainer member 51, and at its outer circumference to the inner circumferential surface of the outer metal sleeve 54.

The pair of thus constructed second intermediate components or annular elastic members 46, 46 are mounted on the first intermediate component of FIG. 3 consisting of the inner metal sleeve 18 and the partition rubber member 20, such that the inner wall 52 is press-fitted in the appropriate axial end portion of the inner metal sleeve 18, while the outer circumferential portions of the aligned and superposed first and second orifice-defining metal members 28, 34 are sandwiched by and between the opposite end faces of the two outer metal sleeves 54, 54. Thus, there is prepared an intermediate product as shown in FIG. 7, which has the two annular fluid chambers 48, 48 which are disposed on both sides of the partition wall portion 24 of the partition rubber member 20 and which communicate with each other through the orifice 36.

The end face of the outer circumferential portion of the annular rubber wall 56 of each annular elastic member 46 is held in abutting contact with the corresponding first or second orifice-defining metal member 28, 34, adjacent to the outer circumferential edge portion sandwiched by the two outer metal sleeves 54, 54, as indicated in FIGS. 1 and 7. Thus, fluid tightness between the orifice-defining metal members 28, 34 and the outer metal sleeves 54, 54 is maintained. Further, fluid tightness between the retainer members 51 of the annular elastic members 46 and the corresponding opposite end faces of the inner metal sleeve 18 is