Patent ID: 12188537

DETAILED DESCRIPTION OF EMBODIMENTS

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

FIG.1depicts an automotive engine mount10as a first practical embodiment of a fluid-filled vibration damping device constructed according to the present disclosure. The engine mount10has a structure in which a first mounting member12and a second mounting member14are elastically connected by a main rubber elastic body16. In the following description, as a general rule, the vertical direction refers to the vertical direction inFIG.1which coincides with the mount axial direction.

The first mounting member12integrally includes a bracket attachment part18having a rectangular tube shape and extending in the axis-perpendicular direction, and a tubular fastening part20extending downward from the periphery of a circular hole penetrating the lower wall of the bracket attachment part18. The first mounting member12can be obtained by, for example, press working of a metal plate material.

The second mounting member14has a stepped, approximately round tubular shape, with its upper part constituting a large-diameter tube part22and its lower part constituting a small-diameter tube part24having a smaller diameter than that of the large-diameter tube part22. The second mounting member14is arranged below the first mounting member12on approximately the same center axis, and the main rubber elastic body16is arranged between the first mounting member12and the second mounting member14.

The main rubber elastic body16has an approximately frustoconical shape, with its upper part on the small-diameter side being bonded by vulcanization to the fastening part20of the first mounting member12, while the outer circumferential surface of its lower part on the large-diameter side being bonded by vulcanization to the large-diameter tube part22of the second mounting member14. The main rubber elastic body16includes a recess26which opens onto the lower surface and decreases in diameter upward. The recess26is located below the fastening part20of the first mounting member12, and is located on the radial inside of the small-diameter tube part24of the second mounting member14.

A stopper rubber28integrally formed with the main rubber elastic body16is fastened to the outer circumferential surface of the bracket attachment part18of the first mounting member12, while a fitting rubber30integrally formed with the main rubber elastic body16is fastened to the inner circumferential surface of the bracket attachment part18. The inner circumferential surface of the small-diameter tube part24of the second mounting member14is integrally formed with the main rubber elastic body16, and is covered with a seal rubber layer32extending downward from the periphery of the recess26.

A flexible film34is attached to the small-diameter tube part24of the second mounting member14. The flexible film34is a thin rubber film having flexibility and has a slack in the vertical direction. An annular fixing member36is fastened to the outer peripheral end of the flexible film34, and the fixing member36is fixed to the lower end part of the small-diameter tube part24of the second mounting member14. By the fixing member36being fixed to the second mounting member14, the flexible film34is arranged so as to close the lower opening of the second mounting member14. The method of fixing the fixing member36to the second mounting member14is not particularly limited, but for example, with the fixing member36inserted inside the second mounting member14, the second mounting member14is subjected to a diameter reduction process, whereby the fixing member36is fixed to the second mounting member14. Since the seal rubber layer32is interposed between the small-diameter tube part24of the second mounting member14and the fixing member36, a fluid-tight sealing is provided between the second mounting member14and the fixing member36.

By the flexible film34being attached to the second mounting member14fastened to the main rubber elastic body16, a fluid chamber38is defined between the opposed main rubber elastic body16and flexible film34so as to be fluid-tight with respect to the outside. The fluid chamber38is filled with a non-compressible fluid. The non-compressible fluid is not limited to a particular fluid or liquid. For example, water, ethylene glycol, alkylene glycol, polyalkylene glycol, silicone oil, a mixture liquid of them or the like can be adopted.

A partition40is arranged in the fluid chamber38. As shown inFIGS.2and3, the partition40has an approximately circular disk shape, and includes a first partition plate42and a second partition plate44.

The first partition plate42has a circular disk shape overall, and is a rigid member made of metal, synthetic resin, or the like. At the outer peripheral end of the first partition plate42, a peripheral groove46is formed so as to open onto the outer circumferential surface and extend in the circumferential direction. In the central portion of the first partition plate42, a circular central recess48is formed so as to open onto the upper surface on the radial inside of the peripheral groove46. On the bottom wall of the central recess48, there is formed a first central through hole50having a circular cross section and penetrating the center in the vertical direction. Besides, a plurality of first outer peripheral through holes52penetrate the bottom wall of the central recess48in the vertical direction on the radial outside of the first central through hole50. In the central portion of the first partition plate42, a circular housing recess54is formed so as to open onto the lower surface. The housing recess54is larger in diameter and shallower than the central recess48, and the outer peripheral end of the housing recess54is located on the radial outside of the central recess48. The upper wall inner surface of the housing recess54comprises a first wall inner surface55. Regarding the first wall inner surface55, the radially middle portion constitutes a first narrowing part56projecting downward. The first central through hole50and the first outer peripheral through holes52are formed by penetrating the common portion of the bottom wall of the central recess48and the housing recess54so as to connect the central recess48and the housing recess54.

The second partition plate44is a rigid member like the first partition plate42, and has an approximately circular disk shape thinner than the first partition plate42. A second central through hole58having a circular cross section penetrates the central portion of the second partition plate44in the vertical direction. A plurality of second outer peripheral through holes60penetrate the second partition plate44in the vertical direction on the radial outside of the second central through hole58so as to be arranged side by side in the circumferential direction. A second narrowing part62projecting upward is provided circumferentially between the second outer peripheral through holes60in the second partition plate44. A groove-shaped seal contact part64is provided on the radial outside of the second narrowing part62of the second partition plate44so as to open onto the upper surface and extend in the circumferential direction. The upper surface of the second partition plate44, which is constituted by the seal contact part64and the radially inner portion with respect to the seal contact part64, comprises a second wall inner surface65vertically opposed to the first wall inner surface55in the partition40.

The first partition plate42and the second partition plate44are overlapped with each other in the vertical direction. By the second partition plate44being overlapped with the lower surface of the first partition plate42, the opening of the housing recess54of the first partition plate42is covered by the second partition plate44, so as to form a housing space66between the first partition plate42and the second partition plate44. The upper wall inner surface of the housing space66on the side of a pressure receiving chamber84, which will be described later, is constituted by the first wall inner surface55of the first partition plate42, while the lower wall inner surface of the housing space66on the side of an equilibrium chamber86, which will be described later, is constituted by the second wall inner surface65of the second partition plate44. In the partition40, the first central through hole50and the first outer peripheral through holes52penetrate the upper wall of the housing space66and communicate with the housing space66, while the second central through hole58and the second outer peripheral through holes60penetrate the lower wall of the housing space66and communicate with the housing space66. The first central through hole50and the second central through hole58are arranged at positions corresponding to each other in the vertical direction, while the first outer peripheral through holes52and the second outer peripheral through holes60are arranged at positions corresponding to each other in the vertical direction.

A movable film68is arranged in the housing space66of the partition40. As shown inFIGS.4and5, the movable film68has a circular disk shape overall. The movable film68is formed of a rubber elastic body, and is allowed to undergo elastic flexural deformation in the thickness direction. Depending on the required vibration damping performance, the deformation rigidity of elastic protrusions70described later, or the like, a rigid plate made of, for example, metal, resin or the like may be partially or entirely embedded in the movable film68, thereby adjusting partial or entire deformation characteristics.

Elastic protrusions70protruding upward are integrally formed at the outer peripheral end of the movable film68. The elastic protrusions70protrude from the outer peripheral end of the movable film68upward, namely, toward the side of the pressure receiving chamber84, which will be described later. The elastic protrusions70are provided in plurality so as to be arranged apart from one another in the circumferential direction. The elastic protrusion70has an approximately circular cross section. The elastic protrusion70has a tapered shape that gradually contracts (becomes smaller in diameter) toward the protruding distal end. The protruding distal end face of the elastic protrusion70may be a flat surface, a sharp-shaped convex surface, or the like. However, in the present practical embodiment, the protruding distal end face of the elastic protrusion70comprises a spherical cap-shaped curved surface that is convex toward the protruding distal end. The number and arrangement of the elastic protrusions70are not particularly limited, but in the present practical embodiment, sixteen elastic protrusions70are arranged side by side at approximately equal intervals in the circumferential direction.

A sealing part72is provided at the outer peripheral end of the movable film68. The sealing part72constitutes a lower end portion of the outer peripheral end of the movable film68. In the present practical embodiment, the sealing part72includes an outside lip74and an inside lip76serving as a seal lip. As shown in an enlarged manner inFIG.6, the outside lip74protrudes from the outer peripheral edge portion of the movable film68downward, namely, toward the side of the equilibrium chamber86, which will be described later, and has an annular shape that continuously extends in the circumferential direction. The inside lip76protrudes downward on the radial inside of the outside lip74, and has an annular shape extending in the circumferential direction in parallel with the outside lip74.

In the radially inner portion of the movable film68, a plurality of cushion projections78are provided on both the upper and lower surfaces. The cushion projection78has an approximately semispherical shape. The projecting height dimension and width dimension of the cushion projection78are smaller than those of the elastic protrusion70. As shown inFIGS.4to6, the cushion projections78of the present practical embodiment are minute projections, and a plurality of the cushion projections78are arranged side by side in an approximately cross shape.

As shown inFIG.1, the movable film68is arranged in the housing space66of the partition40. In the movable film68, the outer peripheral end provided with the elastic protrusions70and the sealing part72is located on the radial outside of the first outer peripheral through holes52and the second outer peripheral through holes60, and is arranged between the opposed first partition plate42and second partition plate44. The elastic protrusions70are pressed against the first wall inner surface55of the first partition plate42, while the sealing part72is pressed against the second wall inner surface65(the seal contact part64) of the second partition plate44, so that the outer peripheral end of the movable film68is clasped vertically between the first partition plate42and the second partition plate44. Besides, the vertical dimension of the radially inner portion of the housing space66is larger than the vertical dimension of the radially inner portion of the movable film68, and the radially inner portion of the movable film68is allowed to undergo displacement in the vertical direction accompanied by elastic deformation.

The outer diameter dimension of the movable film68is smaller than the inner diameter dimension of the housing space66. In the state where the movable film68is arranged in the housing space66, the outer circumferential surface of the movable film68and the peripheral wall inner surface of the housing space66are apart from and opposed to each other in the radial direction. With this configuration, an annular gap80extending in the circumferential direction is provided radially between the outer circumferential surface of the movable film68and the peripheral wall inner surface of the housing space66. In the present practical embodiment, the gap80is provided over the entire circumference in the circumferential direction. However, as long as generation of cavitation is sufficiently prevented by a relief passage including the gap when the internal pressure of the pressure receiving chamber84drops, as will be described later, the radial gap between the outer circumferential surface of the movable film and the peripheral wall inner surface of the housing space may be partial in the circumferential direction.

In the state where the elastic protrusions70are pressed against the upper wall inner surface of the housing space66, an empty space is maintained circumferentially between the elastic protrusions70,70arranged adjacent to each other in the circumferential direction. The empty space between the elastic protrusions70,70forms a communication passage82that extends between the movable film68and the partition40so as to communicate with the gap80. In the present practical embodiment, a plurality of the communication passages82extend in a spoke-wise fashion, but the communication passages do not necessarily extend in the radial direction of the movable film68, and the number of the communication passages82is not limited as long as they are provided in plurality. The outer peripheral end of the movable film68is in contact with the wall inner surface of the housing space66on the side of the pressure receiving chamber84(described later) (namely, the first wall inner surface55) at portions where the elastic protrusions70are formed, while being separated from the first wall inner surface55at a position circumferentially away from the elastic protrusions70. Therefore, a contact part that is in contact with the pressure receiving chamber84-side wall inner surface55of the housing space66is formed by the elastic protrusions70, and is partially provided in the circumferential direction. That is, in the present practical embodiment, the communication passages82communicating with the gap80are provided at the positions circumferentially away from the elastic protrusions70, which serve as a contact part, in the outer peripheral end of the movable film68.

The sealing part72is pressed against the seal contact part64of the second partition plate44over the entire circumference, so that the sealing part72constitutes a sealing structure for preventing the gap80from communicating with the second central through hole58and the second outer peripheral through hole60. In the present practical embodiment, the sealing part72includes the outside lip74and the inside lip76, and both the outside lip74and the inside lip76are pressed against the second partition plate44to provide a double sealing structure. However, it would also be possible to adopt a sealing structure with a single seal lip, a multiple sealing structure with three or more seal lips, and the like. Moreover, the seal lip is dispensable.

As described above, the outer peripheral end of the movable film68including the elastic protrusions70and the sealing part72is vertically clasped and supported by the partition40. The radially inner portion of the movable film68is allowed to undergo tiny displacement in the vertical direction accompanied by flexural deformation in the housing space66.

The partition40housing the movable film68is arranged in the fluid chamber38as shown inFIG.1. The partition40arranged in the fluid chamber38extends in the axis-perpendicular direction, and the outer circumferential surface thereof is overlapped with and supported by the inner circumferential surface of the small-diameter tube part24of the second mounting member14. Since the outer circumferential surface of the partition40is overlapped with the second mounting member14via the seal rubber layer32, a fluid-tight sealing is provided between the overlapped surfaces of the partition40and the second mounting member14. The method of fixing the second mounting member14and the partition40is not particularly limited. However, for example, with the partition40inserted inside the second mounting member14, the second mounting member14is subjected to a diameter reduction process, and the inner circumferential surface of the second mounting member14and the outer circumferential surface of the partition40are pressed against each other via the seal rubber layer32to be fixed. By the diameter reduction process of the second mounting member14, it is possible to perform pre-compression of the main rubber elastic body16, attachment of the flexible film34to the second mounting member14, and attachment of the partition40to the second mounting member14at once.

The fluid chamber38is bifurcated into upper and lower parts by the partition40, and the pressure receiving chamber84and the equilibrium chamber86are defined. That is, the upper side with respect to the partition40in the fluid chamber38comprises the pressure receiving chamber84whose wall is partially defined by the main rubber elastic body16. The lower side with respect to the partition40in the fluid chamber38comprises the equilibrium chamber86whose wall is partially defined by the flexible film34. Both the pressure receiving chamber84and the equilibrium chamber86are filled with a non-compressible fluid, and internal pressure fluctuations are induced in the pressure receiving chamber84at the time of vibration input, while the equilibrium chamber86is allowed to change in volume. The non-compressible fluid is sealed in the pressure receiving chamber84and the equilibrium chamber86by, for example, performing the attachment work of the flexible film34and the partition40to the second mounting member14in the non-compressible fluid.

By the partition40being attached to the second mounting member14, the opening of the peripheral groove46is fluid-tightly closed by the second mounting member14covered with the seal rubber layer32, so as to form the flow path extending in the circumferential direction. One end of the said flow path communicates with the pressure receiving chamber84through a first communication aperture88formed in the first partition plate42, while the other end thereof communicates with the equilibrium chamber86through a second communication aperture90formed in the second partition plate44. This configuration forms an orifice passage92through which the pressure receiving chamber84and the equilibrium chamber86are held in communication with each other by utilizing the peripheral groove46. In the orifice passage92, the resonance frequency of the flowing fluid is tuned to the frequency of vibration to be damped by adjusting the ratio of the passage length to the passage cross sectional area while considering the spring of the wall of the pressure receiving chamber84and the like. In the present practical embodiment, the tuning frequency of the orifice passage92is set to a low frequency of around 10 Hz, which corresponds to engine shake.

The housing space66of the partition40communicates with the pressure receiving chamber84through the first central through hole50and the first outer peripheral through holes52, while communicating with the equilibrium chamber86through the second central through hole58and the second outer peripheral through holes60. Regarding the movable film68arranged in the housing space66, the liquid pressure of the pressure receiving chamber84is exerted on the upper surface thereof, while the liquid pressure of the equilibrium chamber86is exerted on the lower surface thereof. Therefore, when a relative internal pressure differential occurs between the pressure receiving chamber84and the equilibrium chamber86, a vertical force acts on the movable film68, and the movable film68is deformed or displaced. The resonance frequency of the flexural deformation of the movable film68is set to the frequency of vibration to be damped which is higher than the tuning frequency of the orifice passage92, and the movable film68is configured to actively deform in the resonant state by the input of the said vibration to be damped.

The gap80provided on the outer periphery of the movable film68communicates with the pressure receiving chamber84through the communication passage82, the first central through hole50, and the first outer peripheral through holes52.

Due to the sealing structure provided by the contact between the sealing part72of the movable film68and the second wall inner surface65of the housing space66, the gap80does not communicate with the equilibrium chamber86, and the pressure receiving chamber84and the equilibrium chamber86are blocked by the movable film68without communicating with each other through the housing space66. The sealing structure provided by the contact between the sealing part72and the second wall inner surface65is not necessarily limited to the one that completely blocks the flow of the fluid. It is acceptable as long as the sealing structure blocks such a fluid flow as to cause deterioration in the vibration damping performance at the time of normal vibration input.

The engine mount10of the above construction is mounted to a vehicle by, for example, the first mounting member12being mounted on a power unit via an inner bracket (not shown) fitted into the bracket attachment part18, and the second mounting member14being mounted on a vehicle body via an outer bracket (not shown) externally fitted around the second mounting member14.

With the engine mount10mounted on the vehicle, when a low-frequency, large-amplitude vibration corresponding to engine shake or the like is input in the vertical direction across the first mounting member12and the second mounting member14, the pressure receiving chamber84, whose wall is partially defined by the main rubber elastic body16, experiences an internal pressure change. Then, based on the relative pressure differential arising between the pressure receiving chamber84and the equilibrium chamber86, fluid flow is actively generated in the resonant state between the pressure receiving chamber84and the equilibrium chamber86through the orifice passage92, thereby attaining vibration damping effect (vibration attenuating action) based on the flow action of the fluid.

At the time of input of the low-frequency, large-amplitude vibration, the deformation of the movable film68cannot follow the amplitude of the input vibration. Thus, the movable film68is substantially restrained, so that the action of absorbing liquid pressure of the pressure receiving chamber84due to the deformation of the movable film68is not sufficiently exhibited. Therefore, an internal pressure differential arising between the pressure receiving chamber84and the equilibrium chamber86is largely obtained, and the fluid flow through the orifice passage92is efficiently generated, thereby advantageously attaining the vibration damping effect due to the orifice passage92. When the greatly deformed movable film68strikes the wall inner surfaces55,65of the housing space66and is restrained, the minute cushion projections78projecting from both the front and back faces of the movable film68preferentially come into contact with the wall inner surfaces55,65of the housing space66. This reduces striking noise during the contact.

When a mid- to high-frequency, small-amplitude vibration corresponding to idling vibration or the like higher than the tuning frequency of the orifice passage92is input, the orifice passage92is substantially blocked by antiresonance. The movable film68actively undergoes flexural deformation in the resonant state in response to the input vibration, and absorbs the internal pressure fluctuations of the pressure receiving chamber84caused by the vibration input. This avoids marked high dynamic spring behavior due to the substantial sealing of the pressure receiving chamber84, thereby exhibiting vibration damping effect (vibration isolation effect) due to low dynamic spring behavior.

When the vehicle rides over a bump or the like during driving such that a vibration with markedly large amplitude is input and the internal pressure of the pressure receiving chamber84drops significantly, based on a relative internal pressure differential arising between the pressure receiving chamber84and the equilibrium chamber86, a force toward the upper side, which is the pressure receiving chamber84side, acts on the movable film68. As shown inFIG.7, the elastic protrusions70of the movable film68are compressed and contracted in the vertical direction by the action of this force, and the lower surface of the outer peripheral end of the movable film68is displaced upward. Accordingly, the sealing part72provided at the outer peripheral end of the movable film68is separated upward from the seal contact part64constituting the second wall inner surface65of the housing space66, for example, over approximately the entire circumference in the circumferential direction. In the present practical embodiment in particular, at the outer peripheral end of the movable film68, the elastic protrusions70efficiently undergo compressive deformation in the vertical direction, while the deformation of the portion other than the portion forming the elastic protrusions70is relatively suppressed. As a result, the sealing part72at the outer peripheral end of the movable film68is displaced upward over approximately the entire circumference in the circumferential direction including the portion forming the elastic protrusions70, and is separated from the seal contact part64. By so doing, the gap80provided on the outer peripheral side of the movable film68communicates with the equilibrium chamber86through the second outer peripheral through holes60, such that a relief passage94through which the pressure receiving chamber84and the equilibrium chamber86are held in communication is formed including the gap80and the communication passage82. Then, the sealed fluid flows from the equilibrium chamber86into the pressure receiving chamber84through the relief passage94, so that the drop in the internal pressure of the pressure receiving chamber84is promptly reduced or eliminated, thereby preventing generation of cavitation due to the drop in the internal pressure of the pressure receiving chamber84. As a result, the occurrence of noise and vibration caused by the cavitation is prevented, thereby improving quietness and ride comfort of the vehicle.

The relief passage94is provided so as to wrap around the outer peripheral end of the movable film68. Thus, in comparison with the case where the relief passage is provided in the central portion of the movable film as in the conventional structure, the length dimension in the circumferential direction is largely obtained, and the passage cross sectional area is largely obtained. With this configuration, the flow rate of the relief passage94is increased, so that the sealed fluid quickly flows from the equilibrium chamber86into the pressure receiving chamber84, thereby rapidly reducing the negative pressure in the pressure receiving chamber84. Besides, in the relief passage94, the passage length is shorter than that of the orifice passage92, and the ratio of the passage cross sectional area to the passage length is larger than that of the orifice passage92. In the relief passage94, flow resistance is smaller than that of the orifice passage92, and the flow rate is largely obtained.

Since the elastic protrusion70has a tapered shape, the spring increases non-linearly as the amount of compressive deformation increases, so that further compressive deformation is less likely to occur. Therefore, when the internal pressure of the pressure receiving chamber84drops significantly, blocking of the communication passage82due to excessive collapse of the elastic protrusions70is avoided while allowing the relief passage94to open quickly due to the compressive deformation of the elastic protrusions70, thereby maintaining the communicating state of the relief passage94.

When a vibration with markedly large amplitude is input and the internal pressure of the pressure receiving chamber84rises significantly, the sealing part72is further compressed and the outer peripheral end of the movable film68may be displaced downward. In this case, even if the distal end face of the elastic protrusion70is separated from the first wall inner surface55of the housing space66, since the protruding distal end face of the elastic protrusion70has a tapered spherical cap shape, the striking noise when coming into contact with the first wall inner surface55again will be reduced.

FIG.8depicts an automotive engine mount100as a second practical embodiment of a fluid-filled vibration damping device constructed according to the present disclosure. In the following description, components and parts that are substantially identical with those in the first practical embodiment will be assigned like symbols and not described in any detail.

The engine mount100has a structure in which a movable film102is arranged in the housing space66of a partition104. The movable film102does not include the elastic protrusion70shown in the first practical embodiment at the outer peripheral end, and the upper surface of the outer peripheral end comprises a flat surface.

A first partition plate106constituting the partition104includes a plurality of concave grooves108opening onto the pressure receiving chamber84-side wall inner surface (the first wall inner surface55) of the housing space66. The concave groove108extends in the radial direction in the outer peripheral portion of the housing space66, and the radially inner end is opened to the first outer peripheral through hole52. In other words, it can also be understood that the pressure receiving chamber84-side wall inner surface (the first wall inner surface55) of the housing space66includes a plurality of convex ridges extending in the radial direction and projecting downward, and the concave grooves108opening downward are relatively formed circumferentially between the said convex ridges. That is, the convex ridges are integrally formed with the first partition plate106, and are rigid convex ridges. Here, the convex ridges may be elastic convex ridges. For example, it would also be acceptable that the elastic convex ridges formed separately from the first partition plate106are fastened later, so as to form the plurality of concave grooves108.

The portion of the first wall inner surface55of the housing space66that is circumferentially away from the concave grooves108is in contact with the upper surface of the outer peripheral end of the movable film102. With this configuration, the outer peripheral end of the movable film102is vertically clasped by the partition104at the portion circumferentially away from the concave grooves108. Therefore, at the outer peripheral end of the movable film102, the portion that is circumferentially away from the concave grooves108and is in contact with the first partition plate106constitutes the contact part of the present practical embodiment.

By the movable film102being arranged in the housing space66, the lower openings of the concave grooves108are covered with the movable film102, and a communication passage110extending in the radial direction is formed by the concave grooves108. In the communication passage110, the radially inner end communicates with the pressure receiving chamber84through the first outer peripheral through hole52, while the outer peripheral end communicates with the gap80provided on the outer peripheral side of the movable film102.

In the engine mount100constructed according to the present practical embodiment, similar to the first practical embodiment, when the internal pressure of the pressure receiving chamber84significantly drops due to the vibration input, the pressure receiving chamber84and the equilibrium chamber86are held in communication by the relief passage (not shown) including the gap80and the communication passage110. Specifically, when the internal pressure of the pressure receiving chamber84significantly drops, a force toward the pressure receiving chamber84acts on the movable film102due to the relative pressure differential arising between the pressure receiving chamber84and the equilibrium chamber86, and the contact part of the outer peripheral end of the movable film102is compressed in the vertical direction. By so doing, the outer peripheral end of the movable film102is displaced toward the pressure receiving chamber84, and the sealing part72of the movable film102is separated from the seal contact part64constituting the equilibrium chamber86-side wall inner surface (the second wall inner surface65) of the housing space66. As a result, the gap80communicating with the pressure receiving chamber84through the communication passage110communicates with the equilibrium chamber86through between the sealing part72and the seal contact part64and through the second outer peripheral through holes60, so as to form the relief passage, through which the pressure receiving chamber84and the equilibrium chamber86are held in communication, including the gap80and the communication passage110. Then, the sealed fluid flows from the equilibrium chamber86into the pressure receiving chamber84through the relief passage, thereby suppressing the drop in the internal pressure of the pressure receiving chamber84and preventing the generation of cavitation.

In the first practical embodiment, the communication passage82and the contact part are formed by providing the elastic protrusions70to the movable film68so as to form irregularities on the outer peripheral portion of the movable film68at the portion to be overlapped with the first wall inner surface55. However, as in the present practical embodiment, it is also possible to form the communication passage110and the contact part by providing irregularities on the partition104at the portion clasping the movable film102.

FIG.9depicts a partition120of an engine mount as a third practical embodiment of a fluid-filled vibration damping device constructed according to the present disclosure. In the fluid-filled vibration damping device of the present practical embodiment, the same structure as that of the first practical embodiment can be adopted other than the structure of the partition120, and thus the illustration is omitted. The shapes or the like of the partition120and a movable film122housed inside the partition120are also the same as those of the partition40and the movable film68in the first practical embodiment. However, regarding the movable film122in the present practical embodiment, for example, the deformation rigidity at each portion or the like is made different from that of the movable film68in the first practical embodiment. With this configuration, in the present practical embodiment, a relief passage124is configured to be manifested in a mode different from that of the first practical embodiment.

Specifically, for example, in the first practical embodiment, by changing and adjusting the material, size, and compression rate in the mounted state etc. of the movable film68, the elastic protrusions70, and the like, the elastic protrusions70easily undergo compressive deformation and the outer peripheral end of the movable film68is raised from the seal contact part64throughout its entirety to manifest the relief passage94. However, in the present practical embodiment, elastic deformation characteristics of the movable film122including elastic protrusions126are made different from those in the first practical embodiment.

In the present practical embodiment, elastic deformation, which is to be manifested when the opposite surfaces of the movable film122are subjected to a relative pressure differential, is likely to be manifested as elastic deformation of the surface of the movable film122in the direction of flexure, and is less likely to be manifested as compressive deformation of the elastic protrusions126in the direction of protrusion. Therefore, for example, when the internal pressure of the pressure receiving chamber84drops, due to the action of the relative internal pressure differential arising between the pressure receiving chamber84and the equilibrium chamber86, a force toward the upper side acts on the movable film122. Then, as shown inFIG.9, the portions of the outer peripheral end of the movable film122where the elastic protrusions126are not provided (namely, the middle portions between the circumferentially adjacent elastic protrusions126,126to which a deformation restraining force exerted by the elastic protrusions126is less likely to be applied) undergo elastically flexural deformation so as to be raised upward. The movable film122in such a deformed state is shown inFIG.10. InFIG.10, illustration of the cushion projections78is omitted.

That is, as shown inFIG.9, at the portions where the elastic protrusions126are formed in the outer peripheral end of the movable film122, the elastic protrusions126serving as a contact part are in contact with the pressure receiving chamber84-side wall inner surface (the first wall inner surface55) of the housing space66, while the sealing part72is in contact with the equilibrium chamber86-side wall inner surface (the second wall inner surface65) of the housing space66(see the right side ofFIG.9). On the other hand, as shown inFIG.10, circumferentially between the elastic protrusions126,126at the outer peripheral end of the movable film122, the sealing part72is deformed so as to be separated upward from the equilibrium chamber86-side wall inner surface (the second wall inner surface65) in the housing space66. In this way, by deformed portions128, which are deformed upward, being provided circumferentially between the elastic protrusions126,126at the outer peripheral end of the movable film122, the sealing part72is provided with raised portions130raised from the second wall inner surface65at the circumferential positions corresponding to the deformed portions128. At the positions where the raised portions130are formed, the contact of the sealing part72with the seal contact part64is released, so that the gap80and the equilibrium chamber86are held in communication with each other through a space created by the raised portions130.

As described above, in the present practical embodiment, the space through which the gap80and the equilibrium chamber86are held in communication is provided at the same circumferential position as the circumferential position circumferentially between the elastic protrusions126,126, and the said space is provided intermittently over the entire circumference in the circumferential direction. With this configuration, the pressure receiving chamber84and the equilibrium chamber86are held in communication through the relief passage124including the gap80and the communication passage82, thereby preventing generation of cavitation.

The engine mount of the present practical embodiment including the partition120having the above-mentioned structure can also exhibit the same effect as that of the first practical embodiment. In particular, unlike the first practical embodiment, even in the case where the deformation rigidity of the elastic protrusion126is relatively larger than that of the movable film122, the portions circumferentially between the elastic protrusions126,126at the outer peripheral end of the movable film122(the deformed portions128) are deformed to provide the raised portions130in the sealing part72, thereby bringing the relief passage124into the communicating state.

While the present disclosure has been described in detail hereinabove in terms of the practical embodiments, the disclosure is not limited by the specific description thereof. For example, the elastic protrusions70may have a certain length in the circumferential direction, and may have a shape that continuously extends in the circumferential direction with a predetermined length. Moreover, the elastic protrusions may also be formed by, for example, an annular ridge being provided with a plurality of partial grooves in the circumferential direction. The portions circumferentially between the said grooves serve as the elastic protrusions.

The through hole connecting the pressure receiving chamber84and the housing space66does not have to include the first central through hole50and the first outer peripheral through holes52, but may include, for example, only the first outer peripheral through holes52. The through hole connecting the equilibrium chamber86and the housing space66does not have to include the second central through hole58and the second outer peripheral through holes60, but may include, for example, only the second outer peripheral through holes60.

The specific sealing structure provided by the sealing part being pressed against the seal contact part is not particularly limited as long as the structure provides a fluid-tight sealing between the sealing part and the seal contact part. Specifically, for example, it would also be acceptable that the contact surface of the sealing part being in contact with the seal contact part is a flat surface, and a seal projection projecting from the seal contact part continuously in the circumferential direction is pressed against the flat surface of the sealing part, so as to provide a sealing between the sealing part and the seal contact part. Besides, as long as the fluidtightness can be reliably obtained, the contact surfaces of both the sealing part and the seal contact part may be flat surfaces.

Furthermore, the portion to be deformed, the specific deformation mode of the movable film, and the like are not limited. For example, it would also be possible that the central portion of the movable film is deformed, and the deformation is transmitted to the outer peripheral end so that the sealing part at the outer peripheral end of the movable film is separated from the seal contact part of the second partition plate, whereby the pressure receiving chamber and the equilibrium chamber are held in communication by the relief passage. In the fluid-filled vibration damping device according to the present disclosure, the deformation rigidity and the like of the movable film and the elastic protrusion are not limited including the size, shape, and the like. Also, no limitation is imposed as to the deformation mode of the movable film and the elastic protrusion when the internal pressure of the pressure receiving chamber drops. Therefore, it is possible to freely design the shape of the movable film depending on the desired vibration damping characteristics and the like, and the present disclosure is able to provide a fluid-filled vibration damping device having a high degree of freedom in design.

In the third practical embodiment, when the internal pressure of the pressure receiving chamber84drops and a force toward the upper side acts on the movable film68, not only the deformed portions128but also the elastic protrusions126may be sufficiently compressed in the vertical direction by being pressed against the first partition plate42. That is, for the space between the sealing part72and the seal contact part64, it would also be acceptable to adopt a mode in which the space has the annular portion over the entire circumference in the circumferential direction, while the vertical dimension of the space is increased at the position where the raised portions130are formed (approximately the center between the circumferentially adjacent elastic protrusions126,126). Namely, the said space may adopt such a mode as to combine the first practical embodiment and the third practical embodiment (the mode in which the size of the manifested space varies in the circumferential direction).