Patent Application
20140179449
Described herein is a constant velocity joint and an improved boot therefore.
Constant velocity joints (CV joints) are common components in vehicles. CV joints are often employed where transmission of a constant velocity rotary motion is desired or required. CV joints are typically greased or otherwise lubricated for the life of the component. The joints are preferably sealed to retain the grease or lubricant inside the joint while keeping contaminants and foreign matter, such as water and dirt, out of the joint. Moreover, a sealing boot, which may be made of rubber, thermoplastic, silicone material, or the like, usually encloses portions of the CV joints. The boot provides a flexible barrier to retain the grease in the joint so as to reduce friction and extend the life of the joint.
Boots come in a variety of types such as internal rolling diaphragm (IRD) and external rolling diaphragm (ERD). Traditional boots may be connected to the shaft of a CV joint via crimping. Centrifugal forces and friction created by the internal components of the CV joint result in expansion or ballooning of the flexible boot. These forces are also created as a result of pressure created from heat and high speed operation. The constant expansion and contraction of the flexible member results in fatigue, wear, and eventual failure of the boot. Further, during manufacturing, the boot may be crimped or clamped to the shaft, creating an additional step and the need for additional parts in the manufacturing process. Accordingly, there is a need for a durable seal between the boot and the shaft, as well as an efficient method of securing the boot to the shaft.
Referring to the drawings, a constant velocity joint (CV Joint) is shown. It should be noted that all types of CV joints, such as plunging tripods, fixed ball joints, etc., may be used with the present disclosure. Advantages realized by the disclosure may be applied to substantially all types of constant velocity joints, and, therefore, the disclosure should not be limited to the illustrated embodiments. Further, references in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.”
Disclosed herein is a CV joint having a boot and a shaft connected via a groove defined by the shaft and a lip of the neck of the boot. An attachment mechanism may be disposed with the neck to maintain the neck in the groove of the shaft. The attachment mechanism may be at least partially overmolded into at least a portion of the neck before the boot is placed and attached to the shaft. Thus, the attachment mechanism may be integral with the boot neck and the need to attach the boot to the shaft via a separate and additional mechanical clamp or other traditional crimping method is eliminated. In removing the traditional clamping and/or crimping step, the manufacturing process is more seamless and less cumbersome. By eliminating this step, the need for clamping parts, as well as clamping and crimping machinery is eliminated. Moreover, the problem of improper placement of the boot clamp when clamping and losing the boot clamp, which often occur during the manufacturing, are also eliminated.
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The joint assembly 16 may include a cage 46, a first rotational member or outer race 32, a second rotational member or inner race 44, and a plurality of balls 48. The cage 46 retains the balls 48 between the first rotational member 32 and the second rotational member 44 in a generally equally spaced circumferential orientation. The shaft 18 is splined to second rotational member 44 to allow axial movement therebetween.
Collectively, at least the shaft 18, the boot cover assembly 20, the first rotational member 32, and the grease cover 22, form a joint chamber 49. The joint chamber 49 contains grease or other lubricants (not shown) for lubrication between the cage 46, the first rotational member 32, the second rotational member 44, and the balls 48. During operation of the CV joint 10, lubricant contained within joint chamber 49 will generally be drawn outwards toward the first rotational member by centrifugal forces generated by the spinning of the CV joint 10. The boot cover assembly 20 may help prevent grease and other lubricant from leaving the chamber 49.
The boot 42 of the boot assembly 20 may include a boot neck 50 (see, e.g.
The groove 54 may be configured to receive the lip 52 of the boot neck 50 and provide for axial placement of the boot 42 relative to the shaft 18 or inner race 44. For example, the boot 42 may be slid over the shaft 18 or inner race 44 and locked to the shaft 18 when the lip 52 is received by the groove 54. The proximal lip end 56 may help facilitate the sliding of the lip 52 into the groove 54. Moreover, the distal lip end 58 may abut the distal groove wall 62, preventing the boot neck 50 from sliding past the groove 54. Thus, the distal groove wall 62 may help maintain the lip 52 within the groove 54 by acting as a stop against the distal lip end 58. The proximal groove wall 60 may abut the proximal lip end 56 to further secure the lip 52 within the groove 54 at the proximal end. Thus, the lip 52 may fit securely within the groove 54 via a frictional engagement.
In one exemplary configuration, the walls 60, 62 of the groove 54 may become integral with the lip ends 56, 58. As the lip 52 is located within the groove 54, the lip ends 56, 58 may be forced between the groove walls 60, 62. The lip ends 56, 58 may conform, at least partially, to the shape of the groove walls 60, 62. For example, the groove walls 60, 62 may form approximately ninety degree angles while the lip ends 56, 58 may form an inclined slope. The sloped lip ends 56, 58 may conform and mold with the groove walls 60, 62, thus creating another frictional and integral fit between the lip 52 and the groove 54. Additionally or alternatively, the groove walls 60, 62 may also conform to the sloped lip ends 56, 58.
The boot neck 50 may further be secured in the groove 54 via an attachment mechanism 68. The attachment mechanism 68 may be overmolded into the boot neck 50 and be configured to exert a compressive force at the boot neck 50 into the shaft groove 54. Thus, once the boot neck 50 has been slid onto the shaft 18 or inner race 44 and held in place by the interconnection of lip 52 and groove 54, the attachment mechanism 68 may further secure the boot 42 to the shaft 18 or inner race 44. The attachment mechanism 68 may be any one of a garter spring, band, banded clamp, eared circlip, plastic clip, etc. Various exemplary arrangements of the attachment mechanism 68 are described below.
The attachment mechanism 68 may be disposed within the boot neck 50, wherein during manufacturing of the boot neck 50 thereof, the attachment mechanism 68 may be overmolded about the attachment mechanism 68. When the boot neck 50 is slid over the shaft, the attachment mechanism 68 is configured to be sufficiently elastic such that the attachment mechanism 68 may expand just enough to allow the boot 42 to move along the shaft. Once the boot neck 50 reaches the groove 54 of the shaft, the lip 52 of the boot neck 50 may be received by the groove 54 and the attachment mechanism 68 may be configured to automatically retract and exert a radially inward force on the groove 54. In one example, the width of the attachment mechanism 68 may not exceed that of the neck 50. The width of the attachment mechanism 68 may also not exceed the width of the groove 54. This may ensure that the force exerted by the attachment mechanism 68 may be exerted within the lip/groove fit, thereby ensuring that the boot 42 is maintained about the shaft at the groove 54.
As discussed below, some of the figures show an exemplary attachment mechanism 68 being overmolded entirely within the boot 42, while others show an attachment mechanism 68 being at least partially overmolded within the boot, leaving portions of the attachment mechanism 68 exposed.
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Thus, a CV joint having a boot and a shaft connected at a groove of the shaft via an attachment mechanism integrated into the neck of the boot is disclosed herein. By integrating the attachment mechanism into the boot before assembling the boot to the shaft, the need to attach the boot to the shaft after placement thereof via a mechanical clamp or other traditional crimping methods is eliminated.
Accordingly, it is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments and applications other than the examples provided would be apparent to those of skill in the art upon reading the above description. The scope of the invention should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the arts discussed herein, and that the disclosed systems and methods will be incorporated into such future embodiments. In sum, it should be understood that the invention is capable of modification and variation that is limited only by the following claims.
All terms used in the claims are intended to be given their broadest reasonable construction and their ordinary meanings as understood by those skilled in the art unless an explicit indication to the contrary is made herein. In particular, use of the singular articles such as “a,” “the,” “said,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary.
