Slide fork assembly and method

Abstract

The invention provides a sliding fork assembly and a method. The slide yoke assembly includes a cylindrical portion extending along an axis and having a first end. An inner surface of the cylindrical portion defines a cavity along the axis. The inner surface defines a plurality of axially extending inner teeth. The first end defines a counterbore surrounding the cavity. The counterbore is defined by a first wall extending at a transverse angle relative to the axis. A second wall extends substantially axially from the first wall. A disk plug is located in the counterbore and spans the cavity in axial alignment with a second wall of the counterbore for engaging the second wall and providing a primary seal of the cavity. A lip seal ring is located in the counterbore against the first wall and axially between the first wall and the disk plug for providing a supplemental seal of the cavity.

Description

Field of the Invention

[0001] The present invention generally relates to a slip yoke assembly, such as a slip yoke assembly for a vehicle drive shaft, and a method of manufacturing a slip yoke assembly. Background Art

[0002] This section of the written disclosure provides background information related to slip yoke assemblies and related methods and is not necessarily prior art to the inventive concepts disclosed and claimed in the present application.

[0003] The drive shaft assemblies of rear wheel drive (RWD) and four wheel drive (4WD) vehicles typically include an internal spline slip yoke assembly for connection to a transmission or transfer case output. The internal spline teeth on the cylindrical portion of the slip yoke are manufactured by pulling one or more spline broach bars through a passage through the cylindrical portion. This results in the formation of an open cavity that must then be closed to contain transmission or transfer case fluid that is pumped into the spline cavity to lubricate the splines and allow axial movement or telescoping through the splines during vehicle operation. The conventional method of closing and sealing the cavity relies on placing a spherical expansion steel disk plug into a counterbore and securing it in place by roll forming a lip. Sealing of the counterbore is accomplished without the use of any type of sealant or elastomer and is achieved solely by the interference pressure generated by the expansion of the disk plug and the roll formed retaining lip. Due to variations in the manufacturing process, this conventional method provides inadequate sealing in some cases, which can result in fluid leakage around the slip yoke disk plug.

[0004] Accordingly, there is still a need for improvements to slip yoke assemblies and related methods. Summary of the Invention

[0005] This section provides a general overview of the inventive concepts related to the present invention but is not intended to be construed as a complete and comprehensive listing of all aspects, objects, features, and advantages thereof.

[0006] In accordance with one aspect of the present invention, a slip yoke assembly includes a cylindrical portion that extends along an axis and has a first end. An inner surface of the cylindrical portion defines a cavity along the axis. The inner surface defines a plurality of axially extending inner teeth. The first end defines a counterbore surrounding the cavity. The counterbore is defined by a first wall that extends at a transverse angle relative to the axis. A second wall extends substantially axially from the first wall. A disk plug is located in the counterbore and spans the cavity axially aligned with the second wall of the counterbore for engaging the second wall and providing a primary seal for the cavity. A lip seal ring is located in the counterbore against the first wall and axially between the first wall and the disk plug for providing a secondary seal for the cavity.

[0007] According to another aspect of the present invention, a method of manufacturing a sliding fork assembly includes providing a cylindrical portion that extends along an axis and has a first end. An inner surface of the cylindrical portion defines a cavity along the axis. The inner surface defines a plurality of axially extending internal teeth. The first end defines a counterbore surrounding the cavity. The counterbore has a first wall extending in a direction transverse to the axis and a second wall extending substantially axially from the first wall. The method further includes positioning a lip seal and a disk plug in the counterbore, wherein the disk plug spans the cavity and is positioned on the lip seal. The disk plug also has a convex top surface that extends upward. The method further includes pressing down on the top surface of the disk plug such that the disk plug axially presses the lip seal against the first wall of the counterbore and such that the disk plug radially presses against the second wall of the counterbore, thereby causing the lip seal and the disk plug to seal the cavity.

[0008] The combination of the disk plug and the lip seal provides a redundant and robust sealing mechanism for the cavity. In addition, both the disk plug and the lip seal are located in a simple and easily machined counterbore. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The drawings described herein are only for illustration of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present invention.

[0010] Figure 1 is a side cross-sectional view of a sliding fork assembly according to one aspect of the present invention.

[0011] Figure 2 is a side cross-sectional view of an end of the cylindrical portion of the sliding fork assembly, showing the arrangement of the disk plug and the lip seal before compressing the disk plug.

[0012] Figure 3 is a side cross-sectional view of an end of the cylindrical portion of the sliding fork assembly, showing the arrangement of the disk plug and the lip seal during compressing the disk plug.

[0013] Figure 4 is a side cross-sectional view of an end of the cylindrical portion of the sliding fork assembly, showing the arrangement of the disk plug and the lip seal after compressing the disk plug.

[0014] Figure 5 is a side cross-sectional view of the disk plug and the lip seal.

[0015] Figure 6 is a cross-sectional perspective view of the disk plug and the lip seal.

[0016] Figure 7It is an enlarged cross-sectional view of one side of the disk plug and the lip seal ring.

[0017] Figure 8 It is a flowchart showing a method of manufacturing a sliding fork assembly according to one aspect of the present invention. Detailed Description

[0018] Referring to the accompanying drawings, in which like numerals represent corresponding components in multiple views, a sliding fork assembly 10 is generally shown. The sliding fork assembly 10 of the present invention can be used in various vehicles, such as the drive trains of automobiles, off-road vehicles, and recreational vehicles.

[0019] As Figure 1 shown, the sliding fork assembly 10 includes a cylindrical portion 12 that extends along an axis A between a first end 14 and a second end 16. The cylindrical portion 12 has an inner surface 18 that defines a cavity 20 that extends axially between the first end 14 and the second end 16. The inner surface 18 defines a plurality of internal teeth 22 that extend axially and are positioned in a circumferentially spaced relationship with each other. The internal teeth 22 are configured to interleave with external teeth of another shaft (not shown) received in the cavity 20 so as to provide relative axial movement between the cylindrical portion 12 and the shaft while transmitting rotational movement between the cylindrical portion 12 and the shaft. For example, the other shaft can be an output shaft of a transfer case that houses transmission fluid.

[0020] A pair of lugs 24 extend from the first end 14 of the cylindrical portion 12 and are located on opposite circumferential sides of the cylindrical portion 12. Each of the lugs 24 is arcuate, and the lugs 24 are generally U-shaped. Each of the lugs 24 defines a hole 26 that extends through the lug 24 perpendicular to the axis A for connection to a cross shaft of a universal joint. The holes 26 of the two lugs 24 are aligned with each other.

[0021] As Figures 2 to 4 shown, the first end 24 of the cylindrical portion 12 defines a counterbore 28 that extends axially into the cylindrical portion 12 and surrounds the cavity 20 of the cylindrical portion 12 between the lugs 24. The counterbore 28 has a first wall 30 and a second wall 32. The cross-section of the first wall 30 extends at a slightly obtuse angle relative to the axis A, and the second wall 32 extends substantially axially from the first wall 30. The slightly obtuse angle of the first wall 30 relative to the axis A ensures that after the disk plug 34 is flattened and expanded, the contact between the first wall 30 and the disk plug 34 mainly occurs at the outer edge of the disk plug 34, where an edge seal can be formed by a high contact pressure. However, a variation angle between 90° and 100° can be used. Thus, the first wall 30 and the second wall 32 together define a simple and easy-to-machine counterbore 28.

[0022] As discussed in further detail, the sliding yoke assembly 10 of the present invention includes a lip seal ring 38 of elastomeric material and a disk plug 34 of steel material, which are together received in a counterbore 28 and pressed against the walls 30, 32 of the counterbore 28 to form a redundant seal for the cavity 20 of the cylindrical portion 12.

[0023] More specifically, the lip seal ring 38 is connected to the bottom surface 52 of the disk plug 34 and is axially positioned in the counterbore 28 between the first wall 30 of the counterbore 28 and the disk plug 34. According to a preferred embodiment, the lip seal ring 38 is made of an injection molded and bonded elastomeric material, but it can also be made of other suitable materials and by other methods without departing from the scope of the present invention. As Figures 5 to 7 best shown, the lip seal ring 38 has a first portion 40, the cross-section of the first portion 40 being generally triangular. The first portion 40 has a bottom 42 that extends perpendicular to the axis A against the first wall 30 of the counterbore 28 and has a top 44 that extends in a bent-up manner relative to the bottom 42 in an uncompressed state to match the contour of the bottom surface 52 of the disk plug 34, as Figure 2 and Figures 5 to 7 shown. The first portion 40 has a side wall 46 on the radially inner side (towards the axis A) of the annular lip seal ring 38. The lip seal ring 38 also has a second portion 48 that extends from the top 44 of the first portion 40 towards the axis in a similarly bent-up manner relative to the bottom 42 of the first portion 40 in an uncompressed state, such that a step is defined between the side wall 46 and the bottom surface 50 of the second portion 48. As Figures 2 to 4 best shown, the second portion 48 radially covers the cavity 20 of the cylindrical portion 12, while the first portion 40 is radially offset from the cavity 20. The lip seal ring 38 is fully axially positioned below the disk plug 34. The overall shape of the lip seal ring 38 having the first portion 40 and the second portion 48 provides the advantage of keeping the lip seal ring 38 centered on the counterbore 28 rather than on the spline region of the cavity 20.

[0024] The disk plug 34 is made of a hard material such as steel. The disk plug 34 is located in the counterbore 28 and spans the cavity 20. Figure 2 and Figures 5 to 7 shows the disk plug 34 in an initial, pre-flattened state, while Figures 3 to 4 shows the disk plug 34 after the flattening operation. Before flattening, the disk plug 34 is generally in the shape of a disk with a convex center on its top surface 35, and after flattening, the top surface 35 is generally planar, although there may be some variation in flatness, as Figure 1 、 Figure 3 and Figure 4 shown. As Figure 3As shown, a downward force is applied at the center of the top surface 35 by a cylindrical flattening tool 36 or other suitable flattening mechanism to flatten the disk plug 34. The flattening force causes the first portion 40 of the lip seal 38 to be pressed against the first wall 30 of the counterbore 28 to seal the lip seal 38 to the first wall 30, and causes the outer diameter of the disk plug 34 to move radially outward, thereby pressing against the second wall 32 of the counterbore 28 to seal the disk plug to the cylindrical portion 12. As Figures 3 to 4 shown, once compressed, the lip seal 38 extends substantially in a horizontal shape perpendicular to the axis A.

[0025] The lip seal 38 is molded to be substantially flush with the bottom 52 of the disk plug 34 and is adhesively bonded to the bottom 52. According to a preferred embodiment, the lip seal 38 is adhesively bonded to the bottom 52 of the disk plug 34 in the injection molding process used to manufacture the lip seal 38. Bonding the lip seal 38 to the bottom 52 in this manner prior to assembling the slip yoke assembly 10 is beneficial for protecting the lip seal 38. More specifically, since the lip seal is located below the disk plug 34 even before the disk plug 34 is compressed downward, the chance of damaging the lip seal 38 is reduced. This is contrary to conventional slip yoke assemblies, which typically include protruding lip seals or separate O-rings, each of which is prone to damage prior to assembly. In addition, the presence of the second portion 48 of the lip seal 38 provides an enlarged bonding surface for the disk plug 34 to improve robustness. Further, the approximately 45-degree angle at the top of the first portion 40 and the second portion 48 of the lip seal 38 allows the lip seal 38 to fit snugly against the bottom 52 of the disk plug 34.

[0026] Reference Figure 8, a method of manufacturing a sliding fork assembly 10 is also provided. The method includes step 102: providing a cylindrical portion 12 having a counterbore 28 as described above. The method further includes step 104: securing a lip seal ring 38 to the bottom surface 52 of the disk plug 34. The method also includes step 106: positioning the lip seal ring 38 and the disk plug 34 in the counterbore 28. At this time, the disk plug 34 has a convex top surface 35 and spans the cavity 20. In addition, the lip seal ring 38 is axially located between the disk plug 34 and the first wall 30 of the counterbore 28. Initially, the disk plug 34 is loosely fitted (clearance fit), and at this time the lip seal ring 38 is not compressed. The method proceeds to step 108: pressing the disk plug 34 downward against the lip seal ring 38 such that the disk plug 34 deforms radially outwardly and engages the second wall 32 of the counterbore 28 to seal the disk plug 34 against the second wall 32. At this time, the lip seal ring 38 is also axially pressed against the first wall 30 of the counterbore 28 to provide a supplementary seal. The method further includes step 110: deforming the top of the second wall 32 of the counterbore 28 onto the top of the disk plug 34 to further secure the disk plug 34 in place, thereby permanently securing the disk plug 34 and further enhancing the seal. According to a preferred embodiment, this step is performed using a rotational molding machine.

[0027] In view of the above, the sliding fork assembly 10 uses two different sealing mechanisms - the disk plug 34 and the lip seal ring 38 - to achieve redundancy and robustness. Specifically, it uses a metal-to-metal seal where the disk plug 34 expands onto the second wall 32 of the counterbore 28, and a roll-formed portion of the second wall 32 covers the disk plug 34, while additional robustness is provided by compressing the lip seal ring 38. Additionally, the sliding fork assembly 10 uses a simple and easily machined counterbore 28 geometry. It does not require a new machined counterbore or other features to provide controlled compression of the lip seal ring 38, which is common in traditional sliding fork assemblies. Instead, the process of flattening the disk plug 34 provides controlled compression of the lip seal ring 38.

[0028] Furthermore, the sliding fork assembly 10 is fully compatible with traditional sliding fork assembly processes because the shape of the disk plug 34 does not require changing the part feeding system, and traditional plug flattening and roll-forming processes can be utilized.

[0029] Obviously, in view of the above teachings, many modifications and variations of the present invention are possible and it can be practiced in a manner different from that specifically described within the scope of the appended claims. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but where applicable, they can be interchanged and used in selected embodiments even if not specifically shown or described.

Claims

1. A sliding fork assembly, characterized in that: The sliding fork assembly comprises: a cylindrical portion extending along an axis and having a first end and an inner surface defining a cavity along the axis; The inner surface defines a plurality of axially extending internal teeth; the first end defining a counterbore surrounding the cavity, the counterbore being defined by a first wall extending at a transverse angle relative to the axis and a second wall extending substantially axially from the first wall; a disk plug located in the counterbore and spanning the cavity, axially aligned with the second wall of the counterbore for engaging the second wall and providing a primary seal of the cavity; A lip seal ring is located in the counterbore and axially between the first wall and the disk plug, and is used to provide supplementary sealing for the cavity.

2. The sliding fork assembly according to claim 1, characterized in that: The disk plug is compressed and sealingly engages the second wall of the counterbore.

3. The sliding fork assembly according to claim 1, characterized in that: The first wall of the counterbore extends at an obtuse angle of up to 100 degrees relative to the axis.

4. The sliding fork assembly according to claim 1, characterized in that: The disk plug has a convex top surface and a concave bottom surface extending upward, and wherein the lip seal ring has a first portion, the first portion having a bottom extending substantially perpendicularly to the axis to the first wall of the counterbore, and a top extending at a certain angle relative to the bottom, so that the first portion has a substantially triangular shape, and wherein the first portion has a side wall on the radial inner side of the lip seal ring.

5. The sliding fork assembly according to claim 4, characterized in that: The top of the lip seal ring extends in contacting relationship with the bottom surface of the disk plug.

6. The sliding fork assembly according to claim 5, characterized in that: The lip seal ring further includes a second portion, which protrudes from the top of the first portion toward the axis and forms a contact relationship with the bottom surface of the disk plug, thereby defining a step between the side wall and the bottom surface of the second portion.

7. The sliding fork assembly according to claim 6, characterized in that: The second portion radially covers the cavity of the cylindrical portion.

8. The sliding fork assembly according to claim 6, characterized in that: The first portion of the lip seal ring engages a first wall of the counterbore, and the second portion of the lip seal ring covers a cavity of the cylindrical portion.

9. The sliding fork assembly according to claim 1, characterized in that: The lip seal ring is completely axially located below the disk plug.

10. The sliding fork assembly according to claim 1, characterized in that: The lip seal ring is bonded to the bottom of the disk plug.

11. The sliding fork assembly according to claim 10, characterized in that: Substantially the entire top surface of the lip seal ring is bonded to the bottom of the disk plug.

12. A method for manufacturing a sliding fork assembly, characterized in that: The method comprises the following steps: providing a cylindrical portion extending along an axis and having a first end and an inner surface defining a cavity along the axis, wherein the inner surface defines a plurality of axially extending internal teeth, and wherein the first end defines a counterbore surrounding the cavity, wherein the counterbore has a first wall extending in a direction transverse to the axis and a second wall extending substantially axially from the first wall; Positioning a lip seal ring and a disk plug in the counterbore, wherein the disk plug is positioned on the lip seal ring and spans the cavity, wherein the disk plug has an upwardly extending convex top surface and a concave bottom surface; The top surface of the disk plug is pressed downward so that the disk plug axially presses the lip seal ring against the first wall of the counterbore and radially presses the disk plug against the second wall of the counterbore, thereby allowing the lip seal ring and the disk plug to seal the cavity.

13. The method according to claim 12, characterized in that: The method also includes deforming a top portion of a second wall of the counterbore over a top portion of the disk plug to further secure the disk plug in place.

14. The method according to claim 12, characterized in that: The method also includes bonding the lip seal ring to a bottom of the disk plug prior to positioning the lip seal ring and the disk plug in the counterbore.

15. The method according to claim 14, characterized in that: Substantially the entire top surface of the lip seal ring is bonded to the bottom of the disk plug.

16. The method of claim 12, wherein: The lip seal ring has a first portion, the first portion has a bottom portion extending in a direction transverse to the axis and a top portion extending and contacting the bottom surface of the disk plug, wherein the first portion has a side wall located radially inside the lip seal ring, and wherein the lip seal ring also includes a second portion, the second portion protruding from the top of the first portion toward the axis and forming a contact relationship with the bottom surface of the disk plug, thereby defining a step between the side wall and the bottom surface of the second portion.

17. The method of claim 16, wherein: After pressing the top surface of the disk plug, the first portion of the lip seal ring engages with the first wall of the counterbore, and the second portion of the lip seal ring covers the cavity of the cylindrical portion.

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