WO2009082399A1

WO2009082399A1 - Isolating propshaft bracket

Info

Publication number: WO2009082399A1
Application number: PCT/US2007/088604
Authority: WO
Inventors: Craig A. Campbell; Arthur Ball; Brian M. Valovick
Original assignee: Gkn Driveline North America, Inc.
Priority date: 2007-12-21
Filing date: 2007-12-21
Publication date: 2009-07-02

Abstract

An isolator for a center bearing assembly of a motor vehicle propshaft assembly is provided that includes a metal material and at least one bearing attachment point. The bearing attachment point connects the damping material to the center bearing assembly.

Description

ISOLATING PROPSHAFT BRACKET Technical Field

The present disclosure relates to an isolator for a center bearing assembly, and in particular to an isolator that includes a metal material and at least one bearing attachment point for connecting the metal material to the center bearing assembly.

Background

A motor vehicle generally utilizes a propshaft to connect the transmission or power takeoff unit to the driving axle. Propshafls may become rotationally unstable if operated at the rotational speed where the propshaft residual balance forces coincide with the propshaft natural bending resonance. This rotational speed is known as the critical speed. One factor influencing the natural bending resonance is the length of the propshaft. As the length of the propshaft increases, and bending frequency decreases, and so does the critical speed. One known method used to increase the bending frequency is to split the shaft into multiple sections. Each shorter piece will have a higher bending resonance.

Another reason for using a multiple-section propshaft is due to packaging constraints. The layout of the underbody of a motor vehicle may not allow for a completely linear propshaft. This may occur when the pathway of a one-piece propshaft would normally connect the power take-off unit and the rear differential together is obstructed by other underbody components, such as the fuel tank or the exhaust system. A multiple-section propshaft may be installed to a motor vehicle in a variety of non-linear configurations. A universal joint, such as a Cardan universal joint, may be used to connect the multiple propshafts together.

A center bearing may be utilized in conjunction with multiple-section propshafts to reduce translation of vibration from the propshafts to the vehicle chassis during driving conditions. Additionally, the center bearing may also reduce shudder by limiting the transfer of vibration to the vehicle chassis.

The center bearing may also reduce axle gear whine from either the front axle or the rear axle. Although axle gear whine relates to gear mesh force, it is understood that control of the propshaft dynamics to minimize the sensitivity to gear mesh variation may also be important. The center bearing includes an isolator and bearing that may be constructed from a polymer, membrane, or other similar material that isolates vibration. The polymer acts as an isolating material that isolates vibrations from the propshaft. However, existing polymers only isolate vibrations at a limited range of temperatures where the polymer is flexible. At lower temperatures ranging from about -4O⁰C to about -20° C, the polymer will usually exhibit decreased damping properties, because the polymer is not as flexible in cold temperatures, especially below the glass transition temperature.

Further, the polymer's damping properties may also degrade if the polymer is subjected to extreme heat. At elevated temperatures at about 15O⁰C, the polymer may experience a heat set. The heat set usually causes the polymer to lose at least part of the elasticity properties. The elevated temperatures originate from the exhaust system of the vehicle. Additionally, the elevated temperatures are also generated when the frequency of the polymer is low. The low frequency causes a large amount of displacement within the polymer. The large displacement generates heat, which also contributes to the heat set of the polymer as well.

Thus, there exists a need for a center bearing assembly that includes nearly uniform vibration absorbing properties at a range of temperatures from about -4O⁰C to about 15O⁰C.

Brief Description of the Drawings

Features and advantages of the isolator will become apparent to those skilled in the art from the following detailed description of embodiments thereof, when read in light of the accompanying drawings, in which:

FIG. 1 is a top view of an exemplary driveline system;

FIG. 2 is a partial sectional top view of the propshaft illustrated in FIG. 1;

FIG. 3 is a partial sectional view of the propshaft of FIG. 2;

FIG. 3 A is an enlarged view of Region 3A in FIG. 3;

FIG. 3B is an enlarged view of Region 3A in FIG. 3 in a compressed configuration;

FIG. 4 is a partial cross sectional view of a braided metal cable of FIG. 3; FIG. 5 is a partial sectional plan view of an alternative illustration of FIG. 3;

FIG. 5A is an enlarged view of Region 5A of FIG. 5;

FIG. 5B is an enlarged view of Region 5 A in FIG. 5 in a compressed configuration;

FIG. 6 is a partial sectional view of an alternative illustration of FIG. 3;

FIG. 6 A is an enlarged view of Region 5 A in FIG. 6;

FIG. 7 is a partial sectional view of an alternative illustration of FIG. 3;

FIG. 8 is a partial sectional view of an alternative illustration of FIG. 3; and

FIG. 8 A is a partial sectional view of Section A-A of FIG. 8.

DETAILED DESCRIPTION

Exemplary illustrations are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual illustration, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints that will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

FIG. 1 illustrates a driveline 20 of a vehicle (not shown). A propeller shaft 40 includes a front prop shaft 52, a rear prop shaft 54, a joint assembly 50, a center bearing assembly 56 and two high speed constant velocity joints 60. A portion of the center bearing assembly 56 is attached to the underbody of the vehicle (not shown). The constant velocity joints 60 are located on the ends of the propeller shaft 40. The constant velocity joints 60 allow for transmission of constant velocities at angles which are found in everyday driving of the vehicle. The driveline 20 represents an all wheel drive vehicle, however it should be noted that the center bearing assembly 56 may also be used in rear wheel drive vehicles, front wheel drive vehicles, all wheel drive vehicles and four wheel drive vehicles.

As seen in FIG. 2, the center bearing assembly 56 receives a shaft 70 that may be connected to the rear prop shaft 54. The center bearing assembly 56 includes a bearing 72 and an isolator 74. The bearing 72 may be selectively received by the isolator 74, and both the bearing 72 and the isolator 74 cooperate to absorb vibrations from the propeller shaft 40 as well as isolate the vehicle body from vibrations of the propeller shaft 40. The isolator 74 may be bonded to an outer race 82 of the bearing 72.

The isolator 74 includes a metal damping material 76, a bracket 78 for connection to the vehicle and at least one bearing attachment point 80 for connecting the metal damping material 76 to the center bearing assembly 56. In particular, the metal damping material 76 is connected to the outer race 82, and the bearing attachment point 80 may be a mechanical connection, such as, but not limited to, a mechanical crimp, folded flange, weld, solder and braze.

The area around center bearing assembly 56 may reach elevated temperatures as high as 15O⁰C due to the exhaust system (not shown) of the vehicle. Unlike the polymer materials currently used for a typical isolator, such as Nitrile Butadiene Rubber (NBR), Hydrogenaled Nitrile Butadiene Rubber (HNBR) and Polychloroprene (CR), the metal damping material 76 does not exhibit reduced damping properties in extreme temperature conditions. The material properties of the metal damping material 76 are discussed in greater detail below.

The metal damping material 76 includes at least one bracket attachment point 92 for connecting the metal damping material 76 to the bracket 78. In one illustration, as seen in FIG. 3, the metal damping material 76 is a plurality of elongated damping members. More specifically, the metal damping material 76 is a plurality of braided metal cables 84, 86, 88 and 90. Thus, the isolator 74 may include a plurality of bearing attachment points 80 and a plurality of bracket attachment points 92 for connecting the metal damping material 76 to the bearing 72. More specifically, each of the braided metal cables 84, 86, 88 and 90 include a first end 94 for connecting the braided metal cable to the bearing 72, and a second end 96 for connecting the braided metal cable to the bracket 78. Although FIG. 3 illustrates the isolator 74 including four braided metal cables 84, 86, 88 and 90 any number of braided metal cables may be used to connect the bearing 72 to the bracket 78. Moreover, it is understood that while FIGs. 2-3 illustrate the metal damping material 76 as the braided metal cables 84, 86, 88 and 90, any suitable metal damping material, such as a knitted wire mesh, which is discussed in greater detail below, may be used as well.

FIG. 3A illustrates the braided metal cable 88 elongated. That is, as the shaft 70 rotates towards a direction B, as seen in FIG. 3, a force F is exerted in the direction B and the braided metal cable 88 will decompress. Alternatively, when the shaft 70 rotates towards a direction A, the force F is exerted in the direction A and the braided metal cable 88 will be compressed, as seen in FIG. 3B. More specifically., the braided metal cable 88 is woven from a plurality of metal wires 87 that allow for the braided metal cable 88 compress and elongate, depending on the direction of the force F.

When a deflection due to vibration moves the bearing 72 slightly towards the direction B the braided metal cable 88 is decompressed or elongated. As the bearing 72 moves in the direction B the force F will also urge the braided metal cable 84, located in the opposite direction, to compress. This is because the outer race 82 is adhered to the braided metal cable 84 at the bearing attachment point 80. Additionally, as the shaft 70 is urged towards the direction C, the braided metal cable 86 will compress, and the braided metal cable 90 will be elongated.

In the illustration as shown, each of the braided metal cables 84, 86, 88 and 90 are constructed of the metal wires 87 that are woven together in a braided configuration. The braided configuration of the metal wires 87 allow for the braided metal cables 84, 86, 88 and 90 to compress and decompress. The metal wires 87 are constructed from heat-resistant metals such as, but not limited to, stainless steel or copper. Because the metal wire 87 is constructed from metal, both the damping properties and the isolation properties of the material will remain generally uniform over high and low temperatures ranging from about 15O⁰C to about -4O⁰C.

In one illustration, as best seen in FIG. 4, the braided metal cable 86 is hollow inside. That is, the braided configuration of the metal wires 87 are woven as a sleeve, thus leaving an empty space 98 within the interior of the braided metal cable 86. Although FIG. 4 is an illustration of a partial cross section of the braided metal cable 86, it is understood that all or any of the braided metal cables 84, 86, 88 and 90 may also be woven as a sleeve.

FIG. 5 is an alternative illustration of an isolator 174 including a center bearing assembly 156 that includes a center bearing 172 and a grommet 196 for receiving the center bearing 172. The grommet 196 includes two attachment points 180 for connecting the grommet 196 to a metal damping material 176. In the illustration as shown in FIG. 5, the attachment point 180 is a distal end 206 of an arm 190 that extends radially outwardly from the grommet 196. Although FIG. 5 illustrates the grommet 196 including two arms 190, it is understood the grommet 196 may include a plurality of arms 190, or only one arm 190 as well.

The metal damping material 176 may also include attachment points 192 for operatively connecting the isolator 174 to the vehicle, Each of the attachment points 192 are an aperture that selectively receives a bolt 194 or other fastening device, such as a rod or a tube. The bolts 194 each include a first end 197 and a second end 198, where the first end 197 is received by the attachment point 192 and the second end 198 is connected to the vehicle underbody.

As best seen in FIG. 5 A, the metal damping material 176 is a knitted wire mesh 200, such as, but not limited to, Metex Φ knitted wire mesh. The knitted wire mesh 200 will absorb deflection when compressed. FIG. 5 A is an enlarged view of an area 220 of the metal damping material 176. The knitted wire mesh 200 is typically constructed from an endless wire 202 that is formed into a series of loops 204, similar to the knitted structure of a stocking or a sweater. The wire 202 is constructed from any metal that is heat resistant, such as, but not limited to, stainless steel or copper.

When a force F' is applied to the metal damping material 176, the knitted wire mesh 200 is compressed. This is, each of the loops 204 collapse into one another when the knitted wire mesh 200 is compressed, as seen in FIG. 5B. However, the knitted wire mesh 200 is still able to resume to the original shape as seen in FIG. 5 A once the force F^! is removed, so as long as the wire 202 is not deformed past the yield point of the metal of the wire 202. The knitted wire mesh 200 has distinct advantages over polymers when used as a damping material. By way of example, because the knitted wire mesh 200 is metal, both the damping and isolation properties of the material will remain generally uniform over high and low temperatures ranging from about 15O⁰C to about -4O⁰C.

As seen in FIG. 5, force F' is applied in a direction A' as a shaft 170 rotates towards the direction A'. As the center bearing 172 moves slightly towards the direction A' the knitted wire mesh 200 is compressed at the area 220, as seen in FIG. 5B. Alternatively, as the center bearing 172 moves in a direction B' the force F' will then urge the knitted wire mesh 200 located at the area 220 back to the uncompressed configuration as seen in FIG. 5A. Moreover, an area 222 of the metal damping material 176, that is located opposite the area 220 between the distal end 206 of the arm 190, will then compress in the direction B' as seen in FIG. 5B.

In the illustrations as shown in FIGs. 5-7, the metal damping material 176 is a knitted wire mesh 200. As illustrated in FIG. 5, the knitted wire mesh 200 is sandwiched between two washers 203. Alternatively, as seen in FIGs. 6-7, the knitted wire mesh 200 is in the form of an elongated member.

In one illustration as seen in FIG. 6, an attachment point 280 for connecting a grommet 296 to a metal damping material 276 is an aperture 298. The aperture 298 receives at least a portion of the metal damping material 276. More specifically, the aperture 298 allows for the metal damping material 276, which is in the form of an elongated member 310, to pass therethrough. In addition to the apertures 298, the grommet 296 may also include at least one retaining flange 302 as well. The retaining flange 302 receives the elongated member 310 of the metal damping material 276.

The grommet 296 as illustrated in FIG. 6 includes the retaining flange 302 on opposing sides of the grommet 296, and two apertures 298 on opposing sides of the grommet 296 as well. The elongated member 310 is looped around each of the retaining flanges 302. This configuration is advantageous, because looping the elongated member 310 will minimize any movement of the elongated member 310 inside of the flange 302. Minimizing movement of the elongated member 310 will also reduce unwanted fraying of the metal damping material 276. This is because rubbing or contacting the grommet 296 against the elongated member 310 will cause wear and tear of the metal damping material 276. It is understood that any arrangement of apertures 298 located on the grommet 296 and retaining flanges 302 may be used to secure the grommet 296 in place along the elongated members 310. Moreover, the apertures 298 may be included on the grommet 296 without the additional retaining flanges 302 as well.

FIG. 6 illustrates a knitted wire mesh 300 of the elongated member 310 in tension. That is, as best seen in FIG. 6A, the elongated member 310 is held taut because the knitted wire mesh 300 is in tension. Therefore, the elongated member 310 is taut, and will not allow for displacement of the grommet 296. More specifically, as a shaft 370 rotates towards the direction B" a force F" is exerted in the direction B". However, because the elongated member 310 is held taut, movement of the grommet 296 is limited and the elongated member 310 will urge the grommet 296 towards an opposite direction A". Additionally, as the grommet 296 is urged towards the direction C", the knitted wire mesh 300 located along an area Region C" will compress. Alternatively, when the shaft 370 is urged in the direction D", the knitted wire mesh 300 located along an area Region D" will compress instead.

The metal damping material 276 is crimped on an end 304 of the elongated member 310. The crimp assists in retaining the elongated members 310 in place. The crimp 306 also includes a second attachment point 292 for operatively connecting the isolator 274 to the vehicle. As discussed above, the second attachment point 292 is an aperture that selectively receives a bolt 294 or other fastening device. It should be noted that while FIG. 6 illustrates the elongated member 310 constructed from the knitted wire mesh 300, the braided metal cable, or any other metal damping material that absorbs deflection may be used as well.

Yet another illustration, as seen in FIG. 7, includes at least two flanges 402 that are attachment points 380 for connecting a grommet 396 to a metal damping material 376. The retaining flanges 402 receive an elongated member 410 that is constructed from a knitted wire mesh 400, and suspend the grommet 396. The two retaining flanges 402 each hold one of the elongated members 410 taut. Each of the elongated members 410 are crimped on an end 404.

As discussed above, because the knitted wire mesh 400 is held taut the elongated member 410 is in tension. Thus, the elongated member 410 resists movement in the direction A'" when the force F'" is applied in the direction A'". Moreover, as the force F'" is applied in the direction B'", the knitted wire mesh 400 is allowed to compress, thereby absorbing the force F'". When the force F'" is applied in the C" direction the knitted wire mesh 400 located in an area Region C" will compress, allowing for a shaft 470 to remain centered along the center axis A-A. Alternatively, when the shaft 470 is urged in the direction D'", the knitted wire mesh 400 located along an area Region D'" will compress instead. It should be noted that while FIG. 7 illustrates the elongated member 410 constructed from the knitted wire mesh 400, the braided metal cable, or any other metal damping material that absorbs deflection may be used as well.

In yet another illustration as seen in FIG. 8, a grommet 496 includes a flange 502 and apertures 498 for an elongated member 510 Io pass therethrough. The flange 502 receives the elongated member 510 that is constructed from a knitted wire mesh 500, and suspends the grommet 496. The two apertures 498 each hold one of the elongated members 510 taut as well. Each of the elongated members 510 are crimped on an end 504.

As best seen in FIG. 8A, the aperture 498 includes a collar 512 that compresses the elongated member 510, thereby holding the elongated member 510 in place. In the illustration as shown, the collar 512 is crimped such that the elongated member 510 is secured by the grommel 496. Including the collar 512 is advantageous because the elongated member 510 is firmly held in place inside of each of the two apertures 498, thereby reducing any unwanted movement. Thus, including at least one aperture 498 with the collar 512 with the grommet 496 will firmly secure the elongated member 510. Securing the elongated member 510 to the collar 512 will also reduce any unwanted fraying or wear of the elongated member 510. This is because the elongated member 510 is constructed from a metal damping material 576, which is subject to wear when rubbed or moved against a portion of the grommet 496. Moreover, the elongated member 510 is also looped around each of the apertures 498, thus further reducing the possibility of fraying of the metal damping material 576, as discussed above.

As discussed in each of FIGs. 6-7, because the knitted wire mesh 500 is held taut the elongated member 510 is in tension. Therefore, the elongated member 510 is taut, and will not allow for displacement of the grommet 496. More specifically, as a shaft 570 rotates towards the direction B"" a force F"" is exerted in the direction B"". However, because the elongated member 510 is held taut, movement of the grommet 496 is limited and the elongated member 510 will urge the grommet 496 towards an opposite direction A" " . When the force F"" is applied in the C"" direction lhe knitted wire mesh 500 located in an area Region C"" will compress, allowing for the shaft 570 to remain centered along the center axis A-A. Alternatively, when the shaft 570 is urged in the direction D"", the knitted wire mesh 500 located along an area Region D"" will compress instead.

The present disclosure has been particularly shown and described with reference to the foregoing embodiments, which are merely illustrative of the best modes for carrying out the disclosure. It should be understood by those skilled in the art that various alternatives to the embodiments of the disclosure described herein may be employed in practicing the disclosure without departing from the spirit and scope of the disclosure as defined in the following claims. It is intended that the following claims define the scope of the disclosure and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. This description of the disclosure should be understood to include all novel and non- obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. Moreover, the foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application.

Claims

ClaimsWhat is claimed is:

1. An isolator for a center bearing assembly of a motor vehicle propshaft assembly, comprising:

a metal material; and

at least one bearing attachment point for connecting said metal material to the center bearing assembly.

2. The isolator as recited in claim 1, wherein said metal material is constructed from one of a knitted wire mesh and a braided metal cable.

3. The isolator as recited in claim 1, wherein said isolator further comprises a bracket for connection to a motor vehicle,

4. The isolator as recited in claim 3, wherein said metal material includes at least one bracket attachment point for connecting said metal material to said bracket.

5. The isolator as recited in claim 3, wherein said metal material comprises a plurality of bearing attachment points and a plurality of bracket attachment points.

6. The isolator as recited in claim 3, wherein said metal material comprises a plurality of elongated damping members, each of said damping members including a first end for connecting said damping members to the center bearing assembly, and a second end for connecting said metal damping member to said bracket.

7. The isolator as recited in claim 1 , wherein said bearing attachment point is one of a mechanical crimp, folded flange, weld, solder and braze.

8. The isolator as recited in claim 1, including a bearing assembly comprising a center bearing and a grommet for receiving said center bearing.

9. The isolator as recited in claim 8, wherein said grommet includes at least one attachment point for connecting said grommet to said metal material.

10. The isolator as recited in claim 9, wherein said attachment point is a distal end of at least one arm extending radially outwardly therefrom.

11. The isolator as recited in claim 9, wherein said attachment point is an aperture, said aperture receiving at least a portion of said metal material therethrough.

12. The isolator as recited in claim 1, wherein said metal material includes a first compressed configuration and a second uncompressed configuration.

13. The isolator as recited in claim 1, wherein said metal material is constructed from one of stainless steel and copper.

14. An isolator for a center bearing assembly of a motor vehicle propshaft assembly, comprising:

a metal material;

at least one bracket for connection to a motor vehicle;

at least one bearing attachment point for connecting said metal material to the center bearing assembly; and

at least one bracket attachment point for connecting said metal material to said bracket.

15. The isolator as recited in claim 14, wherein said metal material is constructed from one of a knitted wire mesh and a braided metal cable.

16. The isolator as recited in claim 14, wherein said metal material comprises a plurality of bearing attachment points and a plurality of bracket attachment points for connecting said metal material to the center bearing assembly.

17. The isolator as recited in claim 14, wherein said metal material comprises a plurality of elongated damping members, each of said damping members including a first end for connecting said damping members to a bearing assembly, and a second end for connecting said damping members to said bracket.

18. An isolator for a center bearing of a motor vehicle a propshaft assembly, comprising:

a metal material;

a grommet for receiving a center bearing; and

at least one bearing attachment point for connecting said metal material to said grommet.

19. The isolator as recited in claim 18, wherein said bearing attachment point is at least one arm extending radially outwardly from said grommet.

20. The isolator as recited in claim 18, wherein said bearing attachment point is an aperture, and said aperture receives at least a portion of said metal material therethrough.