Center bearing assembly including a support member containing a rheological fluid

A center bearing assembly rotatably supports an intermediate portion of a vehicle driveshaft assembly during use. The center bearing assembly includes a rigid bracket that is secured to a support surface of the vehicle, a support member that is supported within the rigid bracket, and an annular bearing that is supported within the support member for rotatably supporting the intermediate portion of the vehicle driveshaft assembly. The support member is formed from a resilient material and has a cavity formed therein. A sponge is disposed within the cavity formed in the support member. The sponge may be formed from any material that is capable of absorbing or otherwise retaining a quantity of a rheological fluid therein. A control circuit is provided for selectively generating and applying an energy field to the Theological fluid contained within the sponge and thereby varying the resistance to flow or shear thereof. As a result, the vibration dampening characteristics of the support member can be varied.

BACKGROUND OF THE INVENTION

This invention relates in general to bearings for supporting shafts for rotation. In particular, this invention relates to an improved structure for a center bearing assembly for rotatably supporting an intermediate portion of a vehicle driveshaft assembly.

In most land vehicles in use today, a drive train system is provided for transmitting rotational power from an output shaft of an engine/transmission assembly to an input shaft of an axle assembly so as to rotatably drive one or more wheels of the vehicle. To accomplish this, a typical vehicular drive train system includes a driveshaft assembly having first and second end fittings (such as tube yokes) that are secured to the opposed ends thereof. The first end fitting forms a portion of a first universal joint, which provides a rotatable driving connection from the output shaft of the engine/transmission assembly to the first end of the driveshaft assembly while accommodating a limited amount of angular misalignment between the rotational axes thereof. Similarly, the second end fitting forms a portion of a second universal joint, which provides a rotatable driving connection from the second end of the driveshaft assembly to the input shaft of the axle assembly while accommodating a limited amount of angular misalignment between the rotational axes thereof.

In some vehicles, the distance separating the engine/transmission assembly and the axle assembly is relatively short. For these vehicles, the driveshaft assembly can be formed from a single, relatively long driveshaft tube having the first and second end fittings secured to the ends thereof. In other vehicles, however, the distance separating the engine/transmission assembly and the axle assembly is relatively long, making the use of a single driveshaft tube impractical. For these vehicles, the driveshaft assembly can be formed from a plurality (typically two) of separate, relatively short driveshaft sections. In a compound driveshaft assembly such as this, a first end of the first driveshaft section is connected to the output shaft of the engine/transmission assembly by a first universal joint, a second end of the first driveshaft section is connected to a first end of the second driveshaft section by a second universal joint, and a second end of the second driveshaft section is connected to the input shaft of the axle assembly by a third universal joint.

A compound driveshaft assembly that is composed of two or more separate driveshaft sections usually requires the use of a structure for supporting the intermediate portions thereof for rotation during use. A typical intermediate support structure for a driveshaft assembly (which is typically referred to as a center bearing assembly) includes an annular bearing having an inner race that engages one of the driveshaft sections and an outer race that supports the inner race for rotation relative thereto. The outer race of the annular bearing is supported within a generally annular support member that is usually formed from a relatively resilient material, such as rubber. The resilient support member is, in turn, supported within a rigid bracket that is secured to a support surface provided on the vehicle. Thus, the center bearing assembly functions to support the intermediate portion of the driveshaft assembly for rotation during use. Many center bearing assembly structures of this general type are known in the art.

As is well known, the engine/transmission assembly of a typical vehicular drive train system generates a variety of torsional and other relatively high frequency vibrations in the driveshaft assembly as it is rotated during use. Such driveshaft assembly vibrations often result in the generation of noise that can undesirably be transmitted into the vehicle. The resilient support member is provided in the center bearing assembly to absorb at least some of such vibrations so as to reduce the amount of noise that is transmitted from the driveshaft assembly to the vehicle frame. To accomplish this, the resilient support member is usually formed from an elastomeric material, such as rubber, having a resonant frequency that is approximately the same as the frequency of the vibrations that are generated in the driveshaft assembly. When the resonant frequency of the resilient support member is approximately the same as the frequency of the noise and other vibrations in the driveshaft assembly, then such noise and other vibrations will be substantially absorbed by the resilient support member and will not transmitted to the vehicle frame during use.

However, it has been found that the resonant frequency of the resilient support member may not always be approximately the same as the frequency of the noise and other vibrations in the driveshaft assembly. For example, it has been found that changes in the ambient temperature of the resilient support member can cause the resonant frequency thereof to vary. However, the torsional and other relatively high frequency vibrations that are generated by the engine and the transmission in the driveshaft assembly as it is rotated during use remain relatively constant. If the resonant frequency of the resilient support member is not approximately the same as the frequency of the noise and other vibrations in the driveshaft assembly, then the ability of the resilient support member to absorb such noise and other vibrations will be adversely affected. Thus, it would be desirable to provide a resilient support member for a center bearing assembly having a resonant frequency that can be adjusted in accordance with changes in the operating conditions of the vehicle such that the resonant frequency of the resilient support member is always approximately the same as the frequency of the noise and other vibrations in the driveshaft assembly. Therefore, noise and other vibrations will be substantially absorbed by the resilient support member and will not transmitted to the vehicle frame during use.

SUMMARY OF THE INVENTION

This invention relates to an improved structure for a center bearing assembly for rotatably supporting an intermediate portion of a vehicle driveshaft assembly during use. The center bearing assembly includes a rigid bracket that is secured to a support surface of the vehicle, a support member that is supported within the rigid bracket, and an annular bearing that is supported within the support member for rotatably supporting the intermediate portion of the vehicle driveshaft assembly. The support member is formed from a resilient material and has a cavity formed therein. A sponge is disposed within the cavity formed in the support member. The sponge may be formed from any material that is capable of absorbing or otherwise retaining a quantity of a Theological fluid therein. A control circuit is provided for selectively generating and applying an energy field to the rheological fluid contained within the sponge and thereby varying the resistance to flow or shear thereof. As a result, the vibration dampening characteristics of the support member can be varied.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, there is illustrated inFIG. 1a drive train system, indicated generally at10, for a vehicle that is adapted to transmit rotational power from an engine/transmission assembly11to a plurality of driven wheels (not shown). The illustrated drive train system10is intended merely to illustrate one environment in which this invention may be used. Thus, the scope of this invention is not intended to be limited for use with the specific structure for the vehicle drive train system10illustrated inFIG. 1or, for that matter, to vehicle drive train systems in general. On the contrary, as will become apparent below, this invention may be used to support any desired component for rotation.

The engine/transmission assembly11is conventional in the art and includes an externally splined output shaft (not shown) that is connected to a first slip yoke, indicated generally at12. The first slip yoke12is conventional in the art and includes an end portion13having a smooth cylindrical outer surface and an internally splined inner surface. The internally splined inner surface of the end portion13of the first slip yoke12engages the externally splined output shaft of the engine/transmission assembly11in a known manner. As a result, the first slip yoke12is rotatably driven by the output shaft of the engine/transmission assembly11, but is free to move axially relative thereto to a limited extent.

An annular seal11amay be provided within or adjacent to the end of the engine/transmission assembly11. The end portion13of the first slip yoke12extends through the annular seal11a. In a known manner, the seal11aengages and seals against the smooth outer cylindrical surface of the end portion13of the first slip yoke12to prevent dirt, water, and other contaminants from entering into the engine/transmission assembly11. The seal11ais conventional in the art and can be formed having any desired structure. To insure a reliable seal, however, it is usually important for the outer cylindrical surface of the end portion13of the first slip yoke12to be generally smooth and free from relatively large surface irregularities, such as nicks and dents. If desired, the seal11amay be retained in an annular ridge (not shown) formed in the engine/transmission assembly11.

The first slip yoke12further includes a yoke portion14that forms one part of a first universal joint assembly, indicated generally at15. The first universal joint assembly15is also conventional in the art and includes a tube yoke16that is connected to the yoke portion14of the first slip yoke12by a cross in a known manner. The tube yoke16is secured, such as by welding, to a first end of a first driveshaft section17for rotation therewith. The first universal joint assembly15thus provides a rotational driving connection between the output shaft of the engine/transmission assembly11and the first driveshaft section17, while permitting a limited amount of axial misalignment therebetween.

The first driveshaft section17extends through and is supported for rotation by a center bearing assembly, indicated generally at20. The structure of the center bearing assembly20will be explained in detail below. The center bearing assembly20is secured to a support surface22, such as a portion of a frame, chassis, or body of the vehicle. The first driveshaft section17has a second end23that, in the illustrated embodiment, is reduced in diameter relative to the first end of the first driveshaft section17, although such is not necessary. The reduced diameter end23can be formed as a separate structure that is welded onto the larger diameter first end of the first drive shaft section17. In any event, a portion of the outer surface of the reduced diameter second end23of the first driveshaft section17is formed having a plurality of external splines (not shown).

A second slip yoke, indicated generally at25, is connected, such as by welding, to the reduced diameter second end23of the first driveshaft section17for rotation therewith. The second slip yoke25is conventional in the art and includes an end portion26having an internally splined inner surface (not shown). The internally splined inner surface of the end portion26of the second slip yoke25engages the externally splined portion of the second end23of the first driveshaft section17in a known manner. As a result, the second slip yoke25is rotatably driven by the first driveshaft section17, but is free to move axially relative thereto to a limited extent.

An annular seal, indicated generally at28, may be mounted on the end portion26of the second slip yoke25. The reduced diameter second end23of the first driveshaft section17extends through the annular seal28. In a known manner, the annular seal28engages and seals against the smooth outer cylindrical surface of the reduced diameter second end23of the first driveshaft section17to prevent dirt, water, and other contaminants from entering into the region of the cooperating splines. The seal28is conventional in the art and can be formed having any desired structure.

The second slip yoke25further includes a yoke portion27that forms one part of a second universal joint assembly, indicated generally at30. The second universal joint assembly30is also conventional in the art and includes a tube yoke31that is connected to the yoke portion27of the second slip yoke25by a cross in a known manner. The tube yoke31is secured, such as by welding, to a first end of a second driveshaft section32for rotation therewith. The second universal joint assembly30thus provides a rotational driving connection between the second end23of the first driveshaft section17and the first end of the second driveshaft section32, while permitting a limited amount of axial misalignment therebetween.

The second end of the second driveshaft section32is secured, such as by welding to a tube yoke33that forms one part of a third universal joint assembly, indicated generally at34. The third universal joint assembly34is also conventional in the art and includes a third slip yoke, indicated generally at35. The third slip yoke35is conventional in the art and includes a yoke portion36that is connected to the tube yoke33by a cross in a known manner. The third slip yoke35further includes an end portion37having a smooth cylindrical outer surface and an internally splined inner surface (not shown). The internally splined inner surface of the end portion37of the third slip yoke12engages an externally splined input shaft (not shown) of a conventional axle assembly38that is connected to the plurality of driven wheels of the vehicle in a known manner. As a result, the input shaft of the axle assembly38is rotatably driven by the second driveshaft section32, but is free to move axially relative thereto to a limited extent.

An annular seal (not shown) may be provided within or adjacent to the end of the axle assembly38. The annular seal may be similar in structure and operation to the annular seal11adescribed above. The end portion37of the third slip yoke35extends through the annular seal. In a known manner, the annular seal engages and seals against the smooth outer cylindrical surface of the end portion37of the third slip yoke35to prevent dirt, water, and other contaminants from entering into the axle assembly38. The seal is conventional in the art and can be formed having any desired structure. To insure a reliable seal, however, it is usually important for the outer cylindrical surface of the end portion37of the third slip yoke35to be generally smooth and free from relatively large surface irregularities, such as nicks and dents. If desired, the seal may be retained in an annular ridge (not shown) formed in the axle assembly38.

Referring now toFIGS. 2 and 3, the structure of the center bearing assembly20is illustrated in detail. As shown therein, the center bearing assembly20includes a rigid bracket or frame41that is secured to the support surface22of the vehicle. Typically, the bracket41has a generally U-shaped body portion having respective flange portions (not shown) extending outwardly from the ends thereof. Threaded fasteners (not shown) can extend through respective apertures formed through the flange portions to secure the bracket41to the support surface22of the vehicle. If desired, the body portion of the bracket41can be formed having a generally U-shaped cross sectional shape, as shown inFIG. 2, to increase the strength and rigidity thereof.

The center bearing assembly20also includes a support member42that is supported within the rigid bracket41. The support member42is generally annular in shape and is preferably formed from a resilient material, such as a conventional elastomeric material (rubber, for example) of the type that is typically used in conventional center bearing assemblies. The support member42has a cavity42aformed therein that, in the illustrated embodiment, is a generally annular recess that extends circumferentially about the inner portion of the support member42. However, the cavity42amay be formed having any desired shape and may, if desired, be formed completely enclosed within the support member42. If desired, the support member42can have a rigid support ring43secured thereto. In the illustrated embodiment, the support ring43is formed from an annular band of a metallic material and is molded to an inner portion of the support member42. However, the support ring43can be formed having any desired shape and can be formed from any desired material.

The center bearing assembly20further includes a sponge44that is disposed within the cavity42aformed in the support member42. In the illustrated embodiment, the sponge44has a generally circular cross sectional shape and extends circumferentially throughout the entire extent of the annular cavity42a. However, it will be appreciated that the sponge44can be formed having any desired shape and need not extend completely throughout the annular cavity42a. Furthermore, it will be appreciated that a plurality of individual sponges44may be disposed within the cavity42ainstead of a single continuous sponge44, as shown inFIG. 3. The sponge44may be formed from any material that is capable of absorbing or otherwise retaining a quantity of a fluid therein, for a purpose that will be explained in greater detail below. For example, the sponge44may be formed from a conventional open cell foam material, such as polyethylene. However, the sponge44may be formed from any other desired material.

If desired, a retaining and positioning member45can be provided within the cavity42aof the support member42. In the illustrated embodiment, the retaining and positioning member45is disposed radially inwardly of the sponge44and extends circumferentially throughout the entire extent of the annular cavity42a. However, it will be appreciated that the retaining and positioning member45need not extend completely throughout the annular cavity42a. Furthermore, it will be appreciated that a plurality of individual retaining and positioning members45may be disposed within the cavity42ainstead of a single continuous retaining and positioning member45. The retaining and positioning member45is preferably formed from a resilient material, such as the same elastomeric material that is used to form the support member42. However, the retaining and positioning member45may be formed from any other desired material. The retaining and positioning member45can be provided to positively position the sponge44within the cavity42aand to prevent the entry of dirt, water, and other contaminants into such cavity42a. If desired, the retaining and positioning member45can be bonded or otherwise secured to the support ring43.

Lastly, the center bearing assembly20includes an annular bearing, indicated generally at46, for rotatably supporting the first driveshaft section17thereon. The annular bearing46includes an outer race46athat is supported on the support ring43, an inner race46bthat engages the first driveshaft section17, and a plurality of balls46cdisposed between the outer race46aand the inner race46bso that the inner race46bis supported for rotation relative to the outer race46a. Thus, the first driveshaft section17is supported for rotation by the center bearing assembly20.

As mentioned above, the sponge44may be formed from any material that is capable of absorbing or otherwise retaining a quantity of a fluid therein. In the preferred embodiment, the sponge44contains a quantity of a Theological fluid. As used herein, the term “Theological fluid” refers to a fluid that exhibits a change in its ability to flow or shear in the presence or upon the application of an appropriate energy field. In the preferred embodiment, the rheological fluid is a magneto-rheological (MR) fluid that is responsive to the presence of a magnetic field for changing its ability to flow or shear. MR fluids are formed of magnetizable particles, such as carbonyl iron, in a fluid carrier, such as a silicone oil. When exposed to a magnetic field, the particles align and reduce the ability of the fluid to flow. The shear resistance of the MR fluid is a function of the magnitude of the applied magnetic field. MR fluids are preferred for use in this invention because they are capable of generating relatively high fluid shear stresses and can be controlled using power supplies that are normally available in vehicles. TRW MR fluid, which is commercially available from TRW, Inc., is an example of one known Theological fluid that has been found suitable for use in this invention. However, other rheological fluids can also be used in accordance with this invention. For example, electro-rheological (ER) fluids that are responsive to the presence of electrical energy (such as voltage or current) may also be used.

A control circuit, indicated generally at50inFIG. 4, is provided for selectively generating and applying an energy field to the Theological fluid contained within the sponge44. The specific nature of the control circuit50will depend upon the particular type of rheological fluid that is selected for use. In the preferred embodiment, where the theological fluid is an MR fluid, the control circuit includes one or more electromagnetic coils51that are provided within the center bearing assembly20adjacent to the sponge44. The electromagnetic coil51is conventional in the art and is composed of a winding of an electrical conductor having leads51aand51bthat extend therefrom through to a source of electrical power, such as an electrical current generator52. In a manner that is known in the art, when a closed electrical circuit is established through the leads51aand51bbetween the electromagnetic coil51and the source of current controller52, electrical current flows through the coil51. As a result, a magnetic field is generated by the electromagnetic coil51.

The electromagnetic coil51may be arranged in any manner such that when it is energized, a magnetic field is applied to the MR fluid contained in the sponge44. The electromagnetic coil51is preferably arranged so that the applied magnetic field is generally uniform throughout the sponge44. In the illustrated embodiment, the coil51is disposed between the bracket41and the support member42. However, the coil42may be located at any desired position relative to the bracket41and the support member43.

By varying the magnitude of the electrical current that is supplied to the electromagnetic coil51, the strength of the magnetic field that is applied to the MR fluid in the sponge44can be varied. As a result, the resistance to flow or shear of the MR fluid, which affects the vibration dampening characteristics of the support member42, can be varied. To accomplish this, the control circuit50also includes a controller53that controls the operation of the current controller52. The controller53is conventional in the art and may be embodied as any microprocessor or other programmable controller that is responsive to a signal from one or more sensors54for controlling the operation of the current generator52. The sensor54is also conventional in the art and is adapted to generate an electrical signal that is representative of an operating condition of the vehicle. For example, some of the vehicle operating conditions that can be monitored by the sensor54can include ambient temperature, vehicle speed, vehicle acceleration, rotational speed of the first driveshaft section17, angular displacement of the first driveshaft section17, radial acceleration of the center bearing assembly20, axial acceleration of the center bearing assembly20, radial displacement of the center bearing assembly20, and axial displacement of the center bearing assembly20. However, any operating condition or group of conditions of the vehicle may be sensed and used to control the vibration dampening characteristics of the support member30.

The controller53is programmed to periodically or continuously read the electrical signals from the sensor54and to generate an electrical control signal in response to a pre-programmed algorithm. The algorithm that is used by the controller53can be easily derived using known vibration data or by testing on the vehicle. For example, by measuring the amount of vibration that is generated for given value of the sensed operating condition, a look-up table can be created that correlates the value of the sensed operating condition with a value for the control signal that will minimize the generation of such vibration. The same procedure can be followed when two or more operating conditions are sensed. The current generator52is also conventional in the art and is responsive to the output signal from the controller53for generating a corresponding electrical current to the coil51, which generates the magnetic field in response thereto. Thus, it can be seen that the magnitude of the output signal generated by the controller53determines the magnitude of the electromagnetic field generated by the electromagnetic coil51and, thus, varies the flow or shear characteristics of the MR fluid contained in the sponge44. The vibration dampening characteristics of the support member42can, therefore, be continuously varied according to the control algorithm and the information provided by the sensor54.

In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been described in its preferred embodiment. However, it should be noted that this invention may be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.