TECHNICAL FIELD
The present disclosure generally relates to constant velocity joints and, more particularly, to high-speed constant velocity joint and external rolling diaphragm boot cover assemblies.
BACKGROUND
Constant velocity joints and similar rotating couplings operate to transmit torque between two rotational members. The constant velocity joint typically includes an inner joint member for engagement with one rotational member, an outer joint member for engagement with the other rotational member, and a boot cover assembly or a grease cover to enclose and protect the rotating assembly positioned within the outer member during operation. Since the boot cover assembly is partially flexible, the boot cover assembly is able to seal around one of the rotating members while permitting articulation and relative axial movement between the two rotating members. The boot cover assembly provides a barrier to retain the grease in the internal cavity of the joint so as to reduce friction and extend the life of the joint. The boot cover assembly helps to seal out dirt, water and other contaminants to protect the functionality of the joint.
Constant velocity joints require constant lubrication (grease) to remain in operation in the environment in which they are utilized. Typically, such joints use a sealed system to contain the grease, the main component of which is the boot cover assembly that includes a boot and associated mounting can. Boots come in a variety of types. Some examples include convoluted, internal rolling diaphragm (IRD) and external rolling diaphragm (ERD). Particularly relating to IRD and ERD boots, the current industry standard is to have the diaphragm boot crimped onto the mounting can, and then to have the mounting can fit onto the joint. The mounting can and boot may be vulcanized together or crimped together at the top only, which allows grease that is under pressure from centrifugal forces during the joint rotation to be pushed between the sides of the boot and the mounting can (blow-out).
However, an important characteristic of the constant velocity joint is the ability of the joint to allow relative axial movement between two shafts while maintaining a seal to the outside environment. Typically, constant velocity joints include a seal groove that extends circumferentially about the outer surface of the outer member. This groove is generally machined or cut into the outer joint member, causing additional labor, cost and time. The groove provides a channel for receiving and positioning an o-ring type seal at a connection point between the boot assembly, boot-can and the outer member of the constant velocity joint. The seal is used to help prevent the blow-out phenomenon associated with the build-up of pressure.
Additionally, the centrifugal forces and friction associated with the internal components of the constant velocity joint assembly result in expansion or ballooning of the flexible boot cover as a result of the pressure created from heat and high speed operation. The deformation of the flexible boot cover may be affected by lubricant load, a pumping action of the lubricant due to constant velocity joint articulation, temperature, speed, release of gas volatiles from the grease, and the shape of the flexible boot. The constant expansion and contraction of the flexible member results in fatigue, wear and eventual failure of the flexible boot and ultimately the constant velocity joint. Typically, a vent is provided to relieve any pressure and minimize or eliminate the expansion of the flexible boot. However, this vent also allows dirt, water and other debris to enter the constant velocity joint. Specifically, venting the constant velocity joint can lead to lubricant leakage or loss, as well as the infiltration of contaminants into the joint, reducing its overall life.
What is needed, therefore, is a constant velocity joint and boot cover assembly that eliminates the need for a separate seal disposed about the outer surface of the outer member. Additionally, there is a need for a constant velocity joint and boot cover assembly that is configured to eliminate the need for a flexible boot vent.
SUMMARY
The present application discloses a constant velocity joint boot assembly. The constant velocity joint boot assembly may include a boot-can having an axially extending main cylindrical body, a radially extending transition portion, an axially extending and generally cylindrical mounting portion. The radially extending transition portion may intersect the axially extending main cylindrical body and the generally cylindrical mounting portion. A flexible boot member may be attached to an inner surface of at least two of the cylindrical body, the transition portion and the mounting portion at a coupling region for use with an associated constant velocity joint (CVJ). The present application may be applicable to a wide variety of CVJ's, including, but not limited to, plunging, tripod, fixed and high speed. The boot may be affixed to at least two internal surfaces of the boot-can by any known process such as, but not limited to, overmoulding, adhering and bonding. Specifically, the flexible boot may be affixed to a first joint connection end, such that the boot creates a seal between an end surface of the CVJ and the first end of the boot-can. By positioning the flexible boot between the boot-can and the CVJ, the need for an exteriorly positioned seal is eliminated.
BRIEF DESCRIPTION OF DRAWINGS
Referring now to the drawings, preferred illustrative embodiments are shown in detail. Although the drawings represent some embodiments, the drawings are not necessarily to scale and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present disclosure. Further, the embodiments set forth herein are not intended to be exhaustive or otherwise limit or restrict the claims to the precise forms and configurations shown in the drawings and disclosed in the following detailed description:
FIG. 1 illustrates a side cross-sectional view of an exemplary constant velocity joint assembly and attached flexible boot assembly;
FIG. 2A illustrates a side cross-sectional view of an exemplary flexible boot assembly;
FIG. 2B illustrates an enlarged view of encircled area 2B of the exemplary flexible boot and boot-can coupling region;
FIG. 3 illustrates an isometric view of an exemplary flexible boot assembly with the flexible boot in an “as molded” position;
FIG. 4 illustrates an isometric view of an exemplary flexible boot assembly with the flexible boot and further including the diaphragm in position;
FIG. 5 illustrates an isometric cross-sectional view of an exemplary flexible boot assembly with the flexible boot diaphragm in position; and
FIG. 6 illustrates an isometric partial cross-sectional view of an exemplary constant velocity joint assembly and attached flexible boot assembly.
DETAILED DESCRIPTION
FIG. 1 illustrates an exemplary CVJ assembly 110 incorporating an exemplary arrangement of a boot assembly 112. More specifically, CVJ assembly 110 may include flexible boot assembly 112 and CVJ 114. The CVJ 114 may include an outer joint member 116, an inner joint member 118, a joint cage 120 and a plurality of torque transmitting balls 122. The outer joint member 116 may include a first end 124 and a second end 126. The first end 124 maybe configured to mate with the flexible boot assembly 112, and the second end 126 maybe engaged with a second rotational member (not shown). A first rotational member or drive shaft 128 may extend through the flexible boot assembly 112 and may be engaged with or affixed to the inner joint member 118.
With continued reference to FIG. 1, an exemplary arrangement of the flexible boot assembly 112 includes a generally cylindrical boot-can 130 configured to receive a flexible boot 132. As discussed above, flexible boots may come in a variety of types. Merely by way of example, internal rolling diaphragm (IRD) and external rolling diaphragm (ERD) boots are discussed in greater detail below. The flexible boot 132 includes a first end 144 and a second end 146. The first end 144 may be configured to bond to the generally cylindrical boot-can 130. The exemplary flexible boot 132 may be constructed of a flexible material, such as, but not limited to, rubber based products, plastics, silicones, elastomers, silicone, thermoplastic elastomer (TPE), and any other flexible composite materials. It is understood, however, that other suitable materials may be used depending on the application, such as, but not limited to, materials having a hardness value in the range of about 55-75 Shore A or about 35-55 Shore D. In another embodiment, the material may have a hardness of about 40-44 Shore D. Materials that are specifically compatible with a typical flexible boot cover assembly 112 environment are relatively rigid thermoplastic polyesters due to the desirable bonding formed in coupling region 140 during a molding process, which may be used to secure the boot 132 to the boot-can 130, as will be explained below.
The generally cylindrical boot-can 130 may include an axially extending main cylindrical body 134, a radially extending transition portion 136, and an axially extending and generally cylindrical mounting portion 138. The boot-can 130 is formed of a first substantially rigid material, such as, but not limited to, aluminum, steel, carbon fiber and composite.
In one exemplary arrangement, the flexible boot 132 may be molded directly to the boot-can 130 to create a physical and/or a chemical bond at a coupling region 140. The coupling region 140 may extend from a portion of the axially extending main cylindrical body 134, across the radially extending transition portion 136 and terminating at a portion of the axially extending and generally cylindrical mounting portion 138. The coupling region 140 allows the bond between the flexible boot 132 and the boot-can 130 to occur on at least two surfaces. However, the exemplary arrangement, as shown in the drawings, details that the two surfaces are perpendicular.
As illustrated, the generally cylindrical mounting portion 138 may be configured to engage with and mate to an outer surface of the second end 126 of the outer joint member 116. Additionally, the second end 126 may also include an engagement groove 150 that extends circumferentially about the outer surface of the outer joint member 116. The engagement groove 150 may provide a tactile indicator or positive stop for engaging a lip 142 on the generally cylindrical mounting portion 138.
Turning to FIGS. 2A and 2B, a view showing an exemplary flexible boot assembly 112 with an optional angle is depicted. In these figures, the flexible boot 132 is illustrated in a post assembled “as-molded” state, where the boot-can 130 is placed in a mold (not shown), and the boot is molded in a cone shape, which generally mimics the characteristics of an IRD shape. During assembly the boot may be inverted to create the ERD shape, which creates a diaphragm 154 (shown in FIG. 1), as discussed above. The axially extending main cylindrical body 134 intersects the radially extending transition portion 136 and in one exemplary arrangement, forms a first generally 90° angle at the coupling region 140. Additionally, the transition portion 136 intersects the generally cylindrical mounting portion 138 to create a second generally 90° angle, which as illustrated, the first and second generally 90° angle intersections may resemble a stepped feature. It should be known that additional intersecting angles may be sufficient provided the surfaces 134, 138 intersect the transition portion 136. Additionally, other boot-can 132 configurations may also be used including boot-cans that have non-linear walls with bends or other shaped features configured in/on the boot-can 130 based on the clearance needs and application needs, as related to the various constant velocity joints employed. These features may include projections 160 at an outer edge or curves formed on the boot-can 130 for clearance related to the internal constant velocity joint 114 components 118, 120 and 122.
With continued reference to FIG. 2A, the flexible boot 132, as discussed above, in one exemplary arrangement is illustrated as being overmoulded to the boot-can 130 at the coupling region 140, such that a portion of the flexible boot 132 and a portion of the boot-can 130 are bonded together at a predetermined dimensional area using known methods. Specifically, the predetermined dimensional area includes the flexible boot 132, which may be, in on exemplary arrangement, approximately 1.5 mm to 3 mm thick in the area directly adjacent the axially extending portion of the coupling region 140, and the flexible boot 132 may be approximately 0.25 mm to 1 mm thick at the coupling region adjacent the transition portion 136. The area bonded to the axially extending main cylindrical body 134 may extend approximately 7.5 mm to 10.5 mm from an internal face 148 of the transition portion 136 along the interior surface of the coupling region 140. Thus, it should be known that the coupling region 140 bonds a total length of approximately 8.5 mm to 14.5 mm, covering at least two external surfaces of the flexible boot 132 and the internal surfaces of the boot-can 130, as discussed above.
Turning specifically to FIG. 2B, a continued area of adhesion is illustrated in detail. The area depicts an angled projection 156 positioned adjacent an intersection of the transition portion 136 and the generally cylindrical mounting portion 138. Specifically, in one exemplary arrangement, the area has an approximate 45° angle, which may provide an additional thickness of flexible boot 132 materials at the interior corner of the 90° angle. This additional thickness of material may be flexible enough to provide additional sealing capabilities. Specifically, the flexible boot 132 may compress and assume a connection area (not illustrated) between the CVJ face 162 and the boot-can coupling region 140 when the flexible boot assembly 112 is mated with the CVJ assembly 114 to create the CVJ assembly 110. The created seal between the two assemblies 112, 114 eliminates the need for an auxiliary seal (not shown) positioned on the outer surface of the outer joint member 116 as is commonly found in previous CVJ assemblies (not shown).
Referring to FIGS. 3 and 4, the flexible boot assembly 112 may be inverted to convert the “as-molded” outwardly extending IRD conical shaped boot (See FIG. 3) to an ERD shape where the flexible boot 132 arcs inwardly upon itself (See FIG. 4) to create the diaphragm 154. Specifically, turning to FIG. 5 an exemplary section view of the flexible boot assembly 112 is illustrated with the first end 144 molded to the boot-can 130 at the coupling region 140 and the second end 146 is now adjacent the coupling region 140. The ERD shape creates the external diaphragm 154, which appears as a balloon effect that may expand and contract without permanent deformation that may damage the flexible boot 132.
Turning to FIG. 6, an isometric partial cross-sectional view of the exemplary CVJ assembly 110 is illustrated. Specifically, when the boot-can 130 is engaged with the CVJ 114, a portion of the flexible boot 132 that is bonded to the coupling region 140 may be in a compressed between the boot-can 130 and the CVJ face 162 of the outer joint part 116. Compression of the portion of the flexible boot 132 provides a seal between the CVJ 114 and the boot-can 130. The angled area 156, if incorporated, may provide additional material to compress to seal the compression area (not shown) that may be present due to a chamfer or other machined feature on the end of the CVJ 114. Additionally, as illustrated in FIG. 4, the second end 146 of the flexible boot 132 extends circumferentially around the rotating member 128. A band 158 or other type of tightening element may be used to secure the flexible boot 132 to the shaft/rotating member 128 that is engaged with the inner joint member 118 of the CVJ 114.
The exemplary embodiments of FIGS. 1-6 depict an exemplary CVJ assembly 110 that provides an operator with the ability to reduce manufacturing time and provides a more resilient CVJ with an increased life. As illustrated in the exemplary embodiments, an operator (not shown) may assemble the flexible boot assembly 112 and the CVJ assembly 114 without the use of an auxiliary seal extending about the outside edge of the outer joint 116. Additionally, by providing a flexible boot assembly 112 that is adhered to the boot-can 130, as described above, the assembly is able to use a flexible boot that has a unitary body without the need for any auxiliary vent apertures. Thus, as discussed above, exemplary embodiments have been illustrated that depict a CVJ assembly 110 that includes a flexible boot that compresses between the coupling region 140 and the CVJ face 162. This compressed area creates a sealed feature between the two 140, 162 and eliminates the exterior seal while providing a solid attachment surface. Specifically, when the second end 146 of the flexible boot 132 is secured to the shaft 128 by the band 158 the flexible boot 132 is able to expand and contract without the use of a vent. Therefore, the elimination of the vent apertures provides a more resilient CVJ assembly by eliminating any debris or contaminates that may flow into the previously provided vent on previous designed boot assemblies (not shown).
The present invention has been particularly shown and described with reference to the foregoing embodiment, which are merely illustrative of the best modes for carrying out the invention. It should be understood by those skilled in the art that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention without departing from the spirit and scope of the invention as defined in the following claims. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. This description of the invention should be understood to include all novel and nonobvious 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.
Patent Application
20140221109
