Patent Description:
Various assemblies that dampen vibrations and relative movement between components are known in the art. Many of these arrangements use an elastomer or natural rubber material disposed between first and housing portions that are secured to first and second vehicle components. It is desirable to limit vibration from the first component to the second component, for example, between a first component such as an automotive frame and a second component such as an engine. For example, an engine mount assembly includes a first housing portion mounted to the frame and a second housing portion secured to the engine and a material such as an elastomer or rubber interposed between the first and second housing portions that dampens the vibrations. The document <CIT> discloses an anti-vibration assembly including a rigid bracket fixed to a vehicle power train. Disclosure <CIT> refers to an elastomeric bearing comprising an integrally formed housing and a hydraulic unit which is arranged and fixed in the housing. Publication <CIT> relates to a bearing comprising a spring body, which forms a first attachment point of the bearing, and a base body having a first base part and a second base part. Patent document <CIT> relates to a mount assembly or damper, and particularly a mount assembly that damps vibrations imposed on the assembly in a load bearing environment.

One known assembly for dampening vibrations is shown and described in commonly assigned <CIT>. This patent is directed to a hydraulic mount assembly including a first fluid chamber and a second fluid chamber that communicate with one another through an inertia track. The inertia track is interposed between the first and second fluid chambers, and is used as a fluid actuating plunger to move relative to at least one of the first and second chambers in response to vibration to pump fluid from the first chamber to the second chamber, and vice versa, through the inertia track. An opening extends through the first and second fluid chambers and the inertia track and receives a shaft therein. The inertia track is secured to the shaft so that axial movement of the shaft results in axial movement of the inertia track.

While known hydraulic mount assemblies, including the embodiments shown in <CIT> have proven to be acceptable for their intended purpose, a need for continuous improvement in the relevant art remains.

According to the invention, the present teachings provide a hydraulic damper for a mount assembly. The hydraulic damper includes a housing and a subassembly. The housing defines a cavity and is integrally formed to include a plurality of retention features. The subassembly is at least partially disposed in the cavity and is secured relative to the housing by the plurality of retention features. At least one of the plurality of retention features and the subassembly is elastically deformable in a radial direction from an initial diameter to an elastically deformed diameter such that the subassembly is sized to axially pass by the plurality of retention features in the initial diameter for insertion of the subassembly into the housing and the plurality of retention members radially extend over the subassembly in the elastically deformed diameter to secure the subassembly relative to the housing.

According to another particular aspect, the present teachings provide a hydraulic damper for a mount assembly including a housing and a subassembly. The housing defines a cavity and is integrally formed to include a plurality of radial projections. The radial projections each including a radially innermost portion on an imaginary circle having an imaginary circle diameter. The subassembly includes a washer, an inertia track circumferentially surrounding the washer and a compliance member circumferentially surrounding the inertia track. The compliance member is elastically deformable in a radial direction such that the subassembly has an initial diameter when free of outside forces and an elastically deformed diameter when subject to a radially directed force. The initial diameter is greater than the imaginary circle diameter and the elastically deformed diameter is less than the imaginary circle diameter such that the subassembly is able to axially pass the plurality of radial projections with the elastically deformed diameter and the radial projections extend over the subassembly in when the subassembly has the initial diameter.

According to another particular aspect, the present teachings provide a hydraulic damper for a mount assembly including a housing and a subassembly. The housing defines a cavity and is integrally formed to include a plurality of axially extending projections. The axially extending projections each including a radially innermost portion. The axially extending projections are elastically deformable such that the radially innermost portions are on a first imaginary circle having an initial diameter when the axially extending projections are free from outside forces and the radially innermost portions are on a second imaginary circular having an elastically deformed diameter when the axially extending projections are subject to a radial force. The subassembly is at least partially disposed in the housing and includes a shaft, a compliance member circumferentially surround the shaft, and an end cap carried at a radially outer portion of the compliance member. The subassembly includes an outer diameter that is greater than the initial diameter and less than the elastically deformed diameter such that the subassembly is able to axially pass by the plurality of retention features in the elastically deformed diameter for insertion of the subassembly into the housing and the plurality of retention members radially extend over the subassembly in the initial deformed diameter to secure the subassembly relative to the housing.

According to yet another particular aspect, the present teachings provide a method of assembling a hydraulic damper. The method includes elastically deforming one of the plurality of retention features and the subassembly with a radially directed force from an initial diameter to an elastically deformed diameter. The method additionally includes inserting the subassembly into the housing axially past the plurality of retention features. The method further includes removing the radially directed force to positioning the plurality retention features axially over the subassembly.

Still other features and benefits will be found in the following detailed description.

With general reference to the drawings, a hydraulic damper for a mount assembly constructed in accordance with the present teachings is illustrated and generally identified at reference character <NUM>. In the general manner shown and described in common assigned <CIT>, the hydraulic damper <NUM> is intended to be used with a load bearing body mount (not particularly shown herein) to limit vibration between first and second components of a vehicle, for example. It will be understood that the hydraulic damper <NUM> may be used for various other applications within the scope of the present teachings. It will be further understood that the particular load bearing body mount used with the hydraulic damper is beyond the scope of the present teachings.

The hydraulic damper <NUM>, which may also be referred to as a lower mount assembly, is shown to generally include a housing <NUM>. The hydraulic damper <NUM> is shown to further generally include a first subassembly <NUM>, a second subassembly <NUM>, and a third subassembly <NUM>. As will be discussed further below, the housing <NUM> may be constructed to include retention features that cooperate with at least one of the subassemblies <NUM>, <NUM> and <NUM> to receive and retain at least one of the subassemblies <NUM>, <NUM> and <NUM> in a snap-fit.

The hydraulic damper <NUM> may be "double pumping" design in which hydraulic fluid is forced back and forth by a pumping action between a first or upper fluid chamber <NUM> and a second or lower chamber <NUM> (see <FIG>, for example). The general construction and operation of a double pumping hydraulic damper is known in the art and need not be described in detail herein. Various aspects of the present teachings, however, contribute to a unique arrangement that reduces weight, improves packaging, and improves assembly, among other advantages.

The first subassembly or lower assembly <NUM> may include a lower shaft portion 22A of a center shaft <NUM> of the hydraulic damper <NUM>, a ferrule <NUM> and a first or lower compliance member <NUM>. The first compliance member <NUM> may be formed of an elastomeric material or natural rubber. The first compliance member <NUM> circumferentially surrounds the lower shaft portion 22A and may be overmolded on the lower shaft portion 22A. The ferrule <NUM> and the lower shaft portion 22A may be constructed of metal. The ferrule <NUM> may be welded or otherwise suitable attached to the lower shaft portion 22A. Alternatively, the ferrule <NUM> may be formed with the lower shaft portion 22A.

With particular reference to <FIG>, the second subassembly <NUM> is shown removed from the hydraulic damper <NUM>. The second subassembly or center subassembly <NUM> may include a washer <NUM> and an inertia track <NUM>. The inertia track <NUM> circumferentially surrounds the washer <NUM> and may be overmolded to the washer <NUM>. The second subassembly <NUM> may additionally include a second or center compliance member <NUM>. The second compliance member <NUM> may be formed of rubber. Again, suitable materials include elastomeric materials or natural rubber. The second compliance member <NUM> may be connected to the inertia track <NUM> through a generally cylindrical rigid element or radially inner sidewall <NUM>. The second subassembly <NUM> may further include a radially outer, rigid sidewall <NUM> that may be mold bonded to the second compliance member <NUM>.

The third subassembly or upper subassembly <NUM> may include an end cap <NUM>, a third or upper compliance member <NUM> and an upper shaft portion 22B of the center shaft <NUM>. The third compliance member <NUM> may circumferentially surrounds the upper shaft portion 22B and may be overmolded on the upper shaft portion 22B. The third compliance member <NUM> may be formed of rubber. Again, suitable materials include elastomeric materials or natural rubber. The end cap <NUM> may be carried on an outer peripheral portion of the third compliance member <NUM>.

In the illustrated embodiment, the upper fluid chamber <NUM> is bounded on an upper end by the third compliance member <NUM> and bounded on a lower end by the second compliance member <NUM>. Similarly, the lower fluid chamber <NUM> is bounded on an upper end by the second compliance member <NUM> and bounded on a lower end by the first compliance member <NUM>. The first and second fluid chambers <NUM> and <NUM> are separated by the inertia track <NUM>. In the embodiment illustrated, the inertia track <NUM> is an elongated, serpentine interconnecting passage for damping vibrations between the upper and lower ends of the hydraulic damper <NUM>. This damping is accomplished in a conventional manner insofar as the present teachings are concerned.

The housing <NUM> may constructed of a plastic material. While other materials may be used for the housing <NUM>, one suitable material is Nylon <NUM>. As shown in the illustrated embodiment, the housing <NUM> may be integrally formed. The housing <NUM> may include a generally cylindrical portion 12A defining a central axis A and a pair of mounting tabs 12B. As shown in <FIG> and <FIG>, the mounting tabs 12B may define holes <NUM> for receiving fasteners <NUM>. The fasteners <NUM> may be mounting bolts for engaging an upper mount (not shown) of the assembly and securing the assembly to a vehicle, for example.

The cylindrical portion 12A of the housing <NUM> may have a stepped configuration. As perhaps most clearly shown in the cross-sectional view of <FIG>, the cylindrical portion 12A includes a sidewall <NUM> with a lowermost portion 44A defining a smallest diameter. Additional portions of the sidewall <NUM> are identified in the drawings at reference characters 44B, 44C, 44D and 44E. The diameters defined by the sidewall portions 44A-44E are shown to sequentially increase from the lowermost portion 44A in an upward direction. In the embodiment illustrated, the sidewall portions 44A-44E are shown to be oriented generally parallel to the central axis A. In other embodiments, the sidewall portions 44A-44E may be angled relative to the central axis A.

According to one particular aspect of the present teachings, final assembly of the hydraulic damper <NUM> may be accomplished quickly and easily with three general steps. The first, second and third subassemblies <NUM>, <NUM> and <NUM> may be preassembly in such a manner that first, second and third subassemblies <NUM>, <NUM> and <NUM> may be individually secured to the housing <NUM> as separate units (i.e., subassemblies).

With particular reference to <FIG> and <FIG>, the hydraulic damper <NUM> of the present teachings is illustrated following a first general step in which the first subassembly <NUM> is attached to the housing <NUM>. The first compliance member <NUM> defines a groove <NUM> in a radially outer surface thereof that receives the lowermost sidewall portion 44A of the housing <NUM>. The lower portion 22A of the center shaft <NUM> is aligned with the longitudinal axis A. A radially inner portion <NUM> of the first compliance member <NUM> may extend substantially along the entire length of the lower portion 22A of the center shaft <NUM>. At an upper end, the radially inner portion <NUM> of the first compliance member may taper.

With particular reference to <FIG>, the hydraulic damper <NUM> of the present teachings is illustrated following a second general step in which the second subassembly <NUM> is attached to the housing <NUM>. The sidewall <NUM> is adjacent to and radially surrounded by sidewall portion 44C of the housing <NUM>. A lower end 35A of the sidewall <NUM> is axially adjacent to a step defined between the sidewall portion 44C and the sidewall portion 44B. The washer <NUM> axially abuts an upper end of the lower portion 22A of the center shaft <NUM>. Downward positioning of the second subassembly <NUM> within the housing <NUM> may be limited by <NUM>) the engagement between the sidewall <NUM> and the step defined between the sidewall portion 44C and the sidewall portion 44B; and/or <NUM>) axial engagement between the washer <NUM> and the center shaft <NUM>.

The housing <NUM> includes a first plurality of retention features <NUM> for receiving the second subassembly <NUM> in a snap-fit and securing the second subassembly <NUM> within the housing <NUM>. In the embodiment illustrated, the first plurality of retention features includes a plurality of radial projections <NUM>. The radial projections <NUM> extend radially inward from the sidewall <NUM>. In the embodiment illustrated, the radial projections <NUM> extends radially inward from the sidewall portion 44C and may be integrally formed with the sidewall <NUM>. In one particular embodiment, the housing <NUM> may be formed to include eight radial projections <NUM> equally spaced circumferentially about an inner side of the sidewall <NUM>. It will be understood, however, that a greater or lesser number of radial projections <NUM> may be incorporated within the scope of the present teachings. As shown, each radial projection <NUM> may include a tapered lead-in surface 52A and an undercut 52B.

The second subassembly <NUM> is introduced into the housing <NUM> through an open upper end of the housing 12A. As the second subassembly <NUM> is downwardly displaced, at least one of <NUM>) the radial projections <NUM>; and <NUM>) the second subassembly <NUM> is elastically deformed in a radial direction in response to a radial force.

In the embodiment illustrated, the housing <NUM> and the radial projections <NUM> are substantially rigid such that there is little or no associated elastic deformation. As shown in the schematic views of <FIG>, innermost portions of the radial projections <NUM> lie substantially on an imaginary circle C<NUM> (see the schematic <FIG>). Further in the embodiment illustrated, the second compliance member <NUM> of the second subassembly <NUM> is elastically deformable in the radial direction. Explaining further, the second compliance member <NUM> may be radially compressed such that the second subassembly <NUM> has a first outer diameter D<NUM> when it is not subject to any outside forces and a second outer diameter D, when acted upon by a radial force. The radial force may be a radial component of the force imparted by the lead-in surfaces 52A of the radial projections <NUM>. In this manner, the second subassembly <NUM> may be downwardly displaced within the housing <NUM> to a position below the undercuts 52B of the radial projections <NUM>.

After the second subassembly <NUM> axially passes the undercuts 52B, the inherent properties of the second compliance member <NUM> cause the second compliance member <NUM> to radially expand and thereby cause the second subassembly <NUM> to return to the first outer diameter D<NUM>. The first outer diameter D<NUM> is greater than the imaginary circle C<NUM> on which innermost portions of the radial projections <NUM> are lying. The second outer diameter D<NUM> of the second subassembly <NUM> is less than the imaginary circle C<NUM>. As shown in <FIG>, the undercuts 52B of the projections radially extend over the upper end 35B of the sidewall <NUM> to thereby retain the second subassembly <NUM> within the housing <NUM>.

With particular reference to <FIG> and <FIG> and the cross-sectional view of <FIG>, the hydraulic damper <NUM> of the present teachings is illustrated following a third general step in which the third subassembly <NUM> is attached to the housing <NUM>. The housing <NUM> is illustrated to include a second plurality of retention features <NUM> for receiving the third subassembly <NUM> in a snap-fit and securing the third subassembly <NUM> within the housing <NUM>. In the embodiment illustrated, the second plurality of retention features includes a plurality of projections or fingers <NUM>. The fingers <NUM> axially extend upward from the upper end of sidewall <NUM> and may be integrally formed with the sidewall <NUM>. In one particular embodiment, the housing <NUM> may be formed to include ten axially extending fingers <NUM> spaced circumferentially about the open upper end of the housing <NUM>. It will be understood, however, that a greater or lesser number of axially extending fingers <NUM> may be incorporated within the scope of the present teachings. As shown, each axially extending finger <NUM> includes a radially extending portion having a tapered lead-in surface 54A and an undercut 54B (see <FIG>, for example).

An axially extending guide member <NUM> is disposed between adjacent pairs of axially extending fingers <NUM>. As compared to the axially extending fingers, the guide members <NUM> are formed without lead-in surfaces 54A and undercuts 54B. The guide members <NUM> may assist with alignment of the third subassembly <NUM> during assembly.

The third subassembly <NUM> is introduced into the housing <NUM> through the open upper end of the housing 12A. As the third subassembly <NUM> is downwardly displaced at least one of <NUM>) the plurality of axially extending fingers <NUM>; and <NUM>) the third subassembly <NUM> is elastically deformed in a radial direction. In the embodiment illustrated, the housing <NUM> and the plurality of axially extending fingers <NUM> are elastically deformed in a radial direction. In other embodiments, however, the third subassembly <NUM> may alternatively elastically deform or may additionally elastically deform.

As schematically illustrated in <FIG>, the lower ends of the lead-in surfaces 54B of the axial extending fingers <NUM> lie substantially on a second imaginary circle C<NUM> when not subject to any outside force and are radially displaceable to a third imaginary circle C<NUM> having a larger diameter when subject to a radially directed force. The radially directed force may be a radial component of the force imported by the third subassembly <NUM> on the plurality of axially extending fingers <NUM>. In this manner, the third subassembly <NUM> may be downwardly displaced to a position below the undercuts 54B of the axially extending fingers <NUM>.

After the third subassembly <NUM> axially passes the undercuts 54B, the inherent properties of the axial extending fingers <NUM> cause the axial extending fingers <NUM> to radially return from the third imaginary circle C<NUM> to the second imaginary circle C<NUM>. An outer diameter D<NUM> of the third subassembly <NUM> is less than a diameter of the third imaginary circle C<NUM> but greater than a diameter of the second imaginary circle C<NUM>. After the third subassembly <NUM> passes the undercuts 54B, the undercuts 54B of the axial extending fingers <NUM> radially extend over the upper end of the third subassembly <NUM> to retain the third subassembly <NUM>.

Claim 1:
A hydraulic damper (<NUM>) for a mount assembly, the hydraulic damper (<NUM>) comprising:
a housing (<NUM>) defining a cavity, the housing (<NUM>) integrally formed to include a plurality of retention features (<NUM>) and a generally cylindrical portion (12A) including a sidewall (<NUM>) having a stepped configuration; and
a subassembly (<NUM>) at least partially disposed in the cavity and secured relative to the housing (<NUM>) by the plurality of retention features (<NUM>), the subassembly (<NUM>) including a washer (<NUM>), an inertia track (<NUM>) circumferentially surrounding the washer (<NUM>), a compliance member (<NUM>) circumferentially surrounding the inertia track (<NUM>), the compliance member (<NUM>) being elastically deformable in the radial direction, and a rigid outer sidewall (<NUM>) having an upper end (35B) and a lower end (35A), the rigid outer sidewall (<NUM>) bonded to the compliance member (<NUM>);
wherein at least one of the plurality of retention features (<NUM>) and the subassembly (<NUM>) is elastically deformable in a radial direction from an initial diameter to an elastically deformed diameter such that the subassembly (<NUM>) is sized to axially pass by the plurality of retention features (<NUM>) for insertion of the subassembly (<NUM>) into the housing (<NUM>), wherein the lower end (35A) of the rigid outer sidewall (<NUM>) of the subassembly (<NUM>) is adjacent to a step of the sidewall (<NUM>) and the plurality of retention features (<NUM>) radially extend over the upper end (35B) of the rigid outer sidewall (<NUM>) of the subassembly (<NUM>) to secure the subassembly (<NUM>) relative to the housing (<NUM>).