Patent Application
20130252749
The present invention relates generally to propshafts, propshaft assemblies, and methods for fabricating propshafts, and more particularly to fiber reinforced composite propshafts for transferring torque in a motor vehicle, propshaft assemblies that include such propshafts, and methods for fabricating such propshafts.
Motorized vehicles traditionally include a propeller shaft, i.e., propshaft, for transmitting an output torque from a transmission or transfer case through a differential to the wheels of the vehicle. For example, a transmission receives a drive torque from an internal combustion engine and employs gear ratios to modify the input torque to obtain various desired output torques. The output torque is then transmitted, e.g., directly from the transmission or indirectly from a transfer case, through a propshaft assembly to a front or rear differential unit, which evenly distributes the torque between a pair of axle shafts. The axle shafts, in turn, cause movement of the vehicle through the vehicle wheels.
During operation, propshaft assemblies are subjected to significant torsion and shear stresses and must be strong enough to bear these stresses. These assemblies, however, need to avoid too much weight that would otherwise substantially increase their inertia. Fiber reinforced composite propshafts offer significant weight savings over propshafts made from more traditional materials, such as metals, without decreasing the mechanical properties of the propshafts. The reduction in mass has a direct impact on the force required to accelerate and decelerate the vehicle. Due to the relatively low density and high mechanical properties of fiber reinforced composite propshafts, the moment of inertia (e.g. measure of the rotational inertia of the part) is significantly less than steel propshafts, thereby improving the overall vehicle performance.
Propshaft assemblies often include a shaft body having universal joints coupled at both ends for transmitting rotational energy and torque along the shaft body, and an intermediate slip yoke assembly for allowing for some axial movement along the shaft body to facilitate assembly, manage build variation, and the like. Current slip yoke assemblies for fiber reinforced composite propshafts are relatively large and heavy so that they can handle the significant loads carried by propshafts. As such, fiber reinforced composite propshaft assemblies often require significant package space, which is often very limited, to accommodate a slip yoke assembly. Additionally, the significant weight of these slip yoke assemblies can diminish some or many of the benefits of using a fiber reinforced composite propshaft.
Accordingly, it is desirable to provide fiber reinforced composite propshafts for transferring torque in a motor vehicle that allow for some axial movement while reducing package space requirements and/or weight, propshaft assemblies that include such propshafts, and methods for fabricating such propshafts. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.
Propshafts and propshaft assemblies for transferring torque in motor vehicles, and methods for fabricating such propshafts are provided herein. In accordance with an exemplary embodiment, a propshaft for transferring torque in a motor vehicle comprises a fiber reinforced composite tube having a channel and a splined female insert. The fiber reinforced composite tube comprises a composite wall that is disposed around the channel. The splined female insert comprises a buried wall portion that is disposed in the channel operatively coupled to the composite wall. The buried wall portion has an inner surface and a plurality of internal splines formed along the inner surface.
In accordance with another exemplary embodiment, a propshaft assembly for transferring torque in a motor vehicle comprises a first propshaft member and a second propshaft member. The first propshaft member comprises a fiber reinforced composite tube and a splined female insert. The fiber reinforced composite tube has a channel and comprises a composite wall that is disposed around the channel. The splined female insert comprises a buried wall portion that is disposed in the channel operatively coupled to the composite wall. The buried wall portion has an inner surface and a plurality of internal splines formed along the inner surface. The second propshaft member comprises a male yoke. The male yoke has external splines that are engaged with the internal splines of the buried wall portion to allow telescopic movement between the male yoke and the splined female insert.
In accordance with another exemplary embodiment, a method for fabricating a propshaft for transferring torque in a motor vehicle is provided. The method comprises the steps of providing a fiber reinforced composite tube. The fiber reinforced composite tube comprises a composite wall that is disposed around a channel. A splined female insert is positioned into the fiber reinforced composite tube such that a buried wall portion of the splined female insert is positioned in the channel operatively coupled to the composite wall. The buried wall portion has a plurality of internal splines formed along an inner surface of the buried wall portion.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:
The following Detailed Description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.
Various embodiments contemplated herein relate to fiber reinforced composite propshafts for transferring torque in a motor vehicle, propshaft assemblies that include such propshafts, and methods for fabricating such propshafts. Unlike the prior art, the exemplary embodiments taught herein provide a propshaft that comprises a fiber reinforced composite tube that includes a composite wall disposed around a channel. A splined female insert is arranged in the channel of the fiber reinforced composite tube. A wall portion of the splined female insert that is buried or positioned in the channel is operatively coupled to the fiber reinforced composite tube along the composite wall so that the splined female insert rotates together with the fiber reinforced composite tube to transfer torque in the motor vehicle.
In an exemplary embodiment, a plurality of internal splines is formed along an inner surface of the buried wall portion of the splined female insert. A male yoke that has external splines is operatively coupled with the splined female insert along the buried wall portion that is positioned in the channel to form an axial slip connection. In particular, the external splines of the male yoke are rotationally engaged with the internal splines of the splined female insert for transmitting rotational energy and torque while allowing for some telescopic movement, e.g., axial movement, between the male yoke and the splined female insert.
By positioning at least a portion of the axial slip connection formed by the male yoke and the splined female insert in the channel of the fiber reinforced composite tube, the package space requirements and weight for the propshaft can be reduced. In particular, the male yoke and the splined female insert are at least partially packaged in the internal channel space of the fiber reinforced composite tube and therefore, less package space is required outside of the fiber reinforced composite tube for packaging the axial slip connection. Additionally, the size and/or thickness of the splined female insert can be significantly reduced because the buried wall portion of the splined female insert is surrounded and structurally supported by the composite wall of the fiber reinforced composite tube. In particular, the composite wall is made from a relatively high strength fiber reinforced composite material, such as, for example, a resin matrix reinforced with carbon fibers and/or the like. The high strength fiber reinforced composite material, which is operatively coupled to the splined female insert, reinforces the splined female insert so that the splined female insert can be made with less structure, e.g., relatively thin and/or with less material, while still being strong enough to bear the significant loads carried by the propshaft. As such, the splined female insert can be made relatively light so that the axial slip connection including the splined female insert in combination with the male yoke weighs less than conventional slip yoke assemblies for propshafts.
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The fiber reinforced composite tube 16 has a first axial end portion 34 that has a plurality of groove 36 formed along an internal surface 32 of the composite wall 28. In an exemplary embodiment, the grooves 36 extend longitudinally along the internal surface 32 a distance (indicated by double headed arrow “d1”) from an outer-most end 38 of at least about 50 mm, for example of from about 50 to about 100 mm. In one exemplary embodiment, the fiber reinforced composite tube 16 has an internal diameter (indicated by double headed arrow “d2”) of from about 20 to about 25 mm, and a wall stock thickness (indicated by single headed arrows “t”) of from about 3 to about 5 mm.
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As illustrated, the wall 40 of the splined female insert 18 has a plurality of internal splines 54 extending longitudinally along the inner surface 52 of the buried wall portion 44 and optionally the exposed wall portion 46. In an exemplary embodiment, the internal splines 54 formed along the exposed wall portion 46 extend into the buried wall portion 44, and thus, extend longitudinally into the channel of the fiber reinforced composite tube 16 a distance (indicated by double headed arrow “d3” in
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Accordingly, fiber reinforced composite propshafts for transferring torque in a motor vehicle, propshaft assemblies that include such propshafts, and methods for fabricating such propshafts. Unlike the prior art, the exemplary embodiments taught herein provide a propshaft that comprises a fiber reinforced composite tube that includes a composite wall disposed around a channel. A splined female insert is arranged in the channel of the fiber reinforced composite tube. A wall portion of the splined female insert that is buried or positioned in the channel is operatively coupled to the fiber reinforced composite tube along the composite wall. A plurality of internal splines is formed along an inner surface of the buried wall portion of the splined female insert. A male yoke that has external splines is operatively coupled with the splined female insert along the buried wall portion in the channel to form an axial slip connection. By positioning at least a portion of the axial slip connection in the channel of the fiber reinforced composite tube, the package space requirements and weight for the propshaft can be reduced.
While at least one exemplary embodiment has been presented in the foregoing detailed description of the disclosure, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the disclosure. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the disclosure as set forth in the appended claims.
