Powertrain mounting system

A powertrain mounting system includes a pair of engine and transmission mount assemblies. The engine mount assemblies include an isolator assembly having an elastomeric bushing with an encapsulated mounting member, an integral snubber, and a bracket assembly having a one piece can arranged to house the bushing and having an interlock arranged to engage the bushing. The bushing is press-fit into the can and arranged to isolate the mounting member from the can thereby dampening powertrain vibration and controlling powertrain movement, and the snubber is arranged to limit movement of the bushing relative to the can. The transmission mount assembly includes a support member, a pair of isolators positioned relative to each other, and a pair of mounting brackets positioned on the isolators; wherein the isolators are arranged to maintain the mounting brackets in spaced relation to the support member thereby dampening powertrain vibration and controlling powertrain movement.

FIELD OF INVENTION

The present invention relates generally to a powertrain mounting system and, more particularly, to an engine and transmission mounting system for a vehicle.

BACKGROUND OF INVENTION

Various vehicle engine and transmission mounting arrangements have been employed throughout the years that are intended to hold such powertrain components in place in the vehicle while also providing vibration isolation between the components and the vehicle body. Often such arrangements utilize multi-piece brackets and multi-piece, symmetrical pre-loaded engine bushings (PLEB) to mount and isolate the engine from the vehicle body. These multi-piece brackets typically require several welding operations to form the finished bracket, resulting in added manufacturing expense and a potential for the welded areas to break down over time. In addition, transmission mounting arrangements often utilize one mount typically located under a central portion of the transmission. While this transmission mounting arrangement has been used over the years, one potential drawback of this arrangement is less control over cross-car transmission vibration. As a result, there is a need for a powertrain mounting arrangement with reduced manufacturing complexity and improved noise, vibration and harshness (NVH) performance.

SUMMARY OF INVENTION

Accordingly, an improved powertrain mounting system for an engine and transmission is provided. In accordance with one aspect of the present invention, the mounting system includes a pair of engine mount assemblies and a transmission mount assembly. Each engine mount assembly includes an engine mount isolator assembly and an engine mount bracket assembly. The engine mount isolator assembly includes an elastomeric bushing with an encapsulated mounting member and an integral snubber. The engine mount bracket assembly includes a one piece can arranged to house the isolator assembly, and a flange for attaching the engine mount bracket assembly to a vehicle frame component, the one piece can also includes an interlock arranged to engage the elastomeric bushing. The engine mount isolator assembly is press-fit into the can and the interlock is arranged to retain the engine mount isolator assembly relative to the can, wherein the integral snubber is arranged to limit movement of the mounting member and bushing to a predetermined amount relative to the can, and wherein the bushing is arranged to isolate the mounting member from the can thereby dampening powertrain vibration and controlling powertrain movement relative to the vehicle frame component.

The transmission mount assembly includes a support member arranged to be attached to a vehicle frame component, a pair of elastomeric transmission isolators positioned relative to each other on the support member, and a pair of transmission mounting brackets arranged to be positioned on the isolators and attached to a transmission component; wherein the transmission isolators are arranged to maintain the transmission mounting brackets in spaced relation to the support member thereby dampening powertrain vibration and controlling powertrain movement relative to the vehicle.

In accordance with another aspect of the present invention, a powertrain mounting system is provided having a pair of elastomeric transmission isolators positioned relative to each other and a support member including an isolator support portion positioned on each end of a central connecting portion and angled relative to the central connecting portion at an angle of between 20 and 27 degrees, wherein the elastomeric transmission isolators are positioned relative to each other on the isolator support portions of the support member.

In accordance with yet another aspect of the present invention, a powertrain mounting system is provided having a pair of elastomeric transmission isolators positioned relative to each other and a support member including an isolator support portion positioned on each end of a central connecting portion and angled relative to the central connecting portion at an angle of between 20 and 27 degrees, wherein the elastomeric transmission isolators are positioned relative to each other and spaced apart a distance between 220 mm and 240 mm on the isolator support portions of the support member.

In accordance with yet another aspect of the present invention, a powertrain mounting system is provided having pair of transmission isolators including a first isolator having a first isolator surface opposed to a transmission and a first isolator axis projecting normal to the first isolator surface and intersecting a torque reaction axis of the transmission; and a second isolator having a second isolator surface opposed to the transmission and a second isolator axis projecting normal to the second isolator surface and intersecting the torque reaction axis of the transmission; wherein the first and second isolator axes intersect the torque reaction axis at substantially a ninety degree angle to each other.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS(S)

In the following description, several well-known features of a vehicle frame structure and more specifically an engine cradle and a transmission mounting cross-member are not shown or described so as not to obscure the present invention. With general reference to the various views and embodiments illustrated inFIGS. 1-6, the present invention provides a powertrain mounting system for an engine and transmission of a vehicle. With more particular reference toFIGS. 1 and 2, a powertrain mounting system10for an engine20and transmission30is provided. Powertrain mounting system10includes a pair of engine mount assemblies40(each identified with reference numeral40) arranged to mount engine20to a vehicle frame structural component, such as engine cradle assembly60, and a transmission mount assembly50arranged to likewise mount transmission30to a vehicle frame structural component, such as transmission mounting cross-member70.

Referring now toFIGS. 1-4, engine mount assemblies40each include a bracket assembly100having a flange portion110for mounting bracket assembly100to engine20and a can member120for housing an isolator assembly130. The can member120is constructed of a one-piece stamping for improved durability, as opposed to a two piece stamping assembly that is welded together and is then welded to flange portion110. Can member120further includes an interlock140arranged to provide retention of isolator assembly130to can member120. Interlock140includes a protrusion150positioned in a central portion of a width of the can member120and extending around a perimeter thereof as best shown inFIG. 3. Interlock140is arranged to engage isolator assembly130upon insertion into can member120.

Isolator assembly130includes an elastomeric bushing160with a molded-in, encapsulated mounting member170as best shown inFIG. 4. Bushing160is designed and tuned for specific engine and vehicle applications, with a predetermined parallelogram shape, such as a rectangular shape shown inFIG. 4, for error-proofing during assembly operations. Mounting member170is preferably constructed from a metallic material, such as steel or aluminum, and includes a bore180for receiving a fastener and integral projections190extending parallel to the longer side of the rectangular shape of busing160. Protrusions190aid in retention of mounting member170in bushing160as well as provide tuning by varying a length of the projections for specific engine/vehicle requirements.

Bushing160is sized in connection with can member120such that it will be press-fit into can member120resulting in a predetermined pre-load from the press-fit assembly and also has greater than 4:1 compression to shear rate ratio. More specifically, the compression to shear rate ratio is determined form a combination of a length to height ratio of the bushing prior to being press-fit, the resulting pre-load from pressing the bushing into the can and, the shape of the mounting member170(and specifically the protrusions).

Bushing160is centrally positioned in can member120and has a width less than a width200of can member120as best shown inFIG. 3. In addition, isolator assembly130further includes integral snubbers210that extend or protrude outward from bushing160toward an external edge220of can member120as best shown inFIGS. 3 and 4. Integral snubbers can vary in length, but generally do not extend beyond edge220of can member120. Integral snubbers210are arranged to limit movement of bushing160beyond edge220by coming into contact with an engine mounting component (not shown) positioned contiguous to edge220of can member120when engine mount assembly40is utilized to secure engine20to engine cradle60. In the exemplary embodiment, there are two snubbers210per each side of busing160. However, it should be appreciated that the size and number of snubbers can be varied depending on specific engine/vehicle mounting and tuning (NVH) requirements. By integrating snubbers210into busing160, the need for separate, additional bushing components designed to limit over-travel is eliminated thus reducing cost and complexity.

Turning toFIGS. 1,2,5and6transmission mount assembly50of powertrain mounting system10includes a lower support member300and an upper support member310. Lower support member300is arranged to be secured to transmission cross member70with fasteners320and support a pair of isolators330positioned relative to each other and transmission30as best shown inFIG. 5. Upper support member310is positioned on a top surface340of isolators330and is arranged to provide cross-car support for mounting assembly50as well as structural support for transmission mounting brackets350. Mounting brackets350as well as upper support member310and isolators330are respectively secured to lower support member300with a fastener360as best shown inFIG. 2.

With particular reference toFIG. 5, isolator support areas370of lower support member300are spaced apart from each other in a cross-car direction and angled inwardly towards transmission30. Upper support member310is likewise configured such that it nests on top surfaces of340of isolators330as shown inFIG. 5. By using a pair of transmission mounts spaced and angled as described above, transmission torque reaction as well as vibration and cross-car movement are better controlled versus one mount positioned under a central area of transmission30.

It should be understood that the distance that isolators330are spaced apart from each other and a thickness of isolators330will depend on transmission and vehicle tuning and packaging requirements. Notwithstanding, it has been found that optimum NVH performance and control of transmission movement can be obtained through use of specific angular and spacing relationships of isolators330relative to each other and transmission30. More specifically, as shown inFIG. 5, isolator support areas370are angled at an angle410of between 20 and 27 degrees relative to a central connecting portion375as well as positioned centrally under a torque reaction axis390of transmission30. In addition, isolators330are positioned relative to each other with a spacing420of between 220 mm and 240 mm. Finally, it should be noted that the transmission mounting system can be offset cross-car relative to the torque reaction axis390of the transmission and still be effective in controlling and dampening vibration created by the transmission during engine idle and while moving forward and reverse at vehicle speed.

In accordance with another aspect of the transmission mounting system, and referring toFIG. 6, each of the isolators330are spaced apart and angled towards transmission30such that an axis380projecting perpendicular to top surface340intersects the torque reaction axis390of transmission30as shown inFIG. 5. In addition, it has been found that improved performance can be achieved by having each axis380intersect torque reaction axis390at substantially a ninety degree angle400to each other.

In operation, powertrain mounting system10provides a focused, tunable four isolator pad mounting system for a vehicle. The mounting system provides superior NVH performance through use of the four pad isolator system where the isolators are positioned in spaced relation to each other and relative to the engine and transmission. The engine mounts utilize a one piece housing providing improved durability as well as maintenance of the predetermined pre-load through elimination of the possibility of the housing separating over time thereby lessening the press-fit and thus the pre-load. The geometry of the can housing can also be designed to be common to all engine mounts, further reducing cost and complexity. In addition, the transmission mount arrangement provides superior NVH performance and movement control through use of two isolators positioned in spaced relation to each other and with specific angular relationships as compared to an arrangement utilizing one mount positioned under a central portion of the transmission.

The foregoing description constitutes the embodiments devised by the inventors for practicing the invention. It is apparent, however, that the invention is susceptible to modification, variation, and change that will become obvious to those skilled in the art. Inasmuch as the foregoing description is intended to enable one skilled in the pertinent art to practice the invention, it should not be construed to be limited thereby but should be construed to include such aforementioned obvious variations and be limited only by the proper scope or fair meaning of the accompanying claims.