Ball joint with injection molded bearing

Abstract

A ball joint includes a stud extending from a ball. A housing has a bore that receives the ball. The housing has an interior surface facing the ball that includes a groove. A plastic bearing is arranged between the ball and the housing. The plastic bearing has first and second sides opposite one another. The first side has a spherical surface engaging the ball. The second side has a protrusion opposite the spherical surface that is received in and fills the groove and a recess in the spherical surface opposite the protrusion.

Claims

1. A ball joint comprising: a stud extending from a ball; a housing having a bore that receives the ball, the housing having an interior surface at the bore facing the ball that includes an elongate cavity facing the ball; the housing including a cover enclosing an end of the bore opposite the stud; and a plastic bearing arranged between the ball and the housing, the plastic bearing having first and second sides opposite one another to provide a thickness, the first side having a spherical surface engaging the ball, and the second side having a protrusion that is received in and fills the elongate cavity in the housing, a recess in the spherical surface directly opposite the protrusion relative to the thickness, and a plastic cap provided over the cover and connected to the bearing to provide a monolithic plastic structure.

2. The ball joint of claim 1, comprising grease provided between the first side and the ball.

3. The ball joint of claim 2, wherein the bearing has a perimeter lip arranged about a circumference of the ball at the housing, and the perimeter lip is in an interference fit between the housing and the ball to seal the grease within the housing.

4. The ball joint of claim 2, wherein a hole extends through the stud and the ball, and the grease is provided in the hole.

5. The ball joint of claim 4, wherein a single opening is provided in the ball and is aligned with the hole.

6. The ball joint of claim 5, wherein the bearing includes a depression in the bearing surface beneath the hole.

7. The ball joint of claim 1, wherein a perimeter of the cover is welded to the housing with a weld.

8. The ball joint of claim 1, wherein the cover includes an opening, and multiple elongate cavities are circumferentially spaced about the cover and radiate outwardly from the opening.

9. The ball joint of claim 1, wherein the housing includes a hole on a side opposite the stud, the hole in fluid communication with the recess formed on a side of the bearing facing the ball and aligned with the cavity, wherein the hole is filled with grease.

10. The ball joint of claim 9, comprising a plug secured to the housing over the hole to retain the grease.

11. The ball joint of claim 1, wherein the housing includes an annular wall canted inward toward the ball that retains the ball within the bore.

12. A ball joint comprising: a stud extending from a ball; a housing having a bore that receives the ball, the housing having an interior surface facing the ball that includes an elongate cavity; the housing including a cover enclosing an end of the bore opposite the stud; a plastic bearing arranged between the ball and the housing, the plastic bearing having first and second sides opposite one another, the first side having a spherical surface engaging the ball, and the second side having a protrusion opposite the spherical surface that is received in and fills the cavity, a recess in the spherical surface opposite the protrusion, and a plastic cap provided over the cover and connected to the bearing to provide a monolithic plastic structure; and grease provided between the first side and the ball, wherein the grease is a first grease, and comprising a boot arranged onto the housing over the stud and filled with a second grease that is different than the first grease, the plastic bearing separating the first and second greases.

13. A ball joint comprising: a stud extending from a ball; a housing having a bore that receives the ball, the housing having an interior surface facing the ball that includes an elongate cavity; the housing including a cover enclosing an end of the bore opposite the stud; and a plastic bearing arranged between the ball and the housing, the plastic bearing having first and second sides opposite one another, the first side having a spherical surface engaging the ball, and the second side having a protrusion opposite the spherical surface that is received in and fills the cavity, a recess in the spherical surface opposite the protrusion, and a plastic cap provided over the cover and connected to the bearing to provide a monolithic plastic structure, wherein the housing includes an annular projection, and the cap is arranged over the annular projection.

14. The ball joint of claim 13, wherein the annular projection is deflected onto the cover to retain the cover over the bore.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

(2) FIG. 1 is a cross-sectional view through a ball joint arranged in a suspension element to provide a suspension member.

(3) FIG. 2 is an exploded view of the ball joint shown in FIG. 1.

(4) FIG. 3A illustrates a ball joint inserted into a bore of a housing.

(5) FIG. 3B illustrates a cover welded to the housing over the ball.

(6) FIG. 4 schematically depicts an injection molding process that forms the bearing and a cap arranged over the cover.

(7) FIG. 5 is a partial cross-sectional view through a portion of the ball joint.

(8) FIG. 6 illustrates grease injected into the ball joint.

(9) FIG. 7A illustrates a bearing surface and a recess provided therein to accommodate the grease.

(10) FIG. 7B is an enlarged view of the portion of the ball joint shown in FIG. 7A.

(11) FIGS. 8A and 8B are partial cross-sectional views of a portion of the bearing arranged between the ball and the housing as molded.

(12) FIGS. 8C and 8D illustrate the deflection of the bearing in an exaggerated fashion subsequent to grease being injected into the ball joint.

(13) FIG. 9 is a cross-sectional view through the ball joint illustrating the first and second greases.

(14) FIGS. 10A and 10B are cross-sectional views respectively of one-piece housing and two-piece housing alternative ball joint embodiments.

(15) FIGS. 11 and 12 illustrate partial cross-sectional views of the one-piece housing prior and subsequent to swaging.

(16) FIGS. 13A and 13B depict grooves in the one-piece and two-piece housings.

(17) FIG. 13C illustrates grooves in the two-piece housing misaligned.

(18) FIGS. 14A and 14B are respectively cross-sectional exploded views of portions of the one-piece housing and two-piece housing ball joints.

(19) FIG. 15 schematically depicts the injection molding process wherein a plastic is injected from a side of the housing adjacent the ball.

(20) FIGS. 16A and 16B are respectively cross-sectional views through the one-piece housing and two-piece housing ball joints with grease in the bearing and without the boots installed.

(21) FIG. 17 illustrates a plug installed over the hole used to supply the bearing with grease.

(22) FIG. 18 illustrates a bearing without a lip.

(23) The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

DETAILED DESCRIPTION

(24) Referring to FIGS. 1 and 2, a ball joint 14 is provided in a suspension element 12 to provide a suspension member 10, such as a control arm or tie rod end. A ball joint 14 includes a housing 16, which may be constructed from steel. A ball 18 has a stud 20 extending therefrom, which typically includes a threaded end for securing the ball joint 14 to another suspension component, such as a steering knuckle. In the example, a single, linear hole 28 extends through the ball 18 and stud 20 and is blocked by a plug 68. The exterior surface of the ball 18 is spherical in shape to permit the ball 18 to pivot and articulate in a bore 52 of the housing 16.

(25) In a two-piece housing configuration, a cover 24 forms another portion of the housing structure and is secured to one end of the bore 52, such as by welding, to enclose and capture the ball 18 within the housing 16. A bearing 22, constructed from a material such as acetyl, is injection-molded into the space between the ball 18 and the housing 16. A boot 26 with a seal rim 30 is provided over the stud 20 and is secured to the housing 16 opposite the cover 24 to seal the ball 18 from the elements and prevent corrosion.

(26) Referring to FIGS. 3A-5, the ball joint 14 is manufactured by arranging the ball 18 in the bore 52. The bore 52 is provided by a tapered wall 54, which captures the ball 18 at an end of the housing 16 opposite the cover 24. The cover 24 includes a domed portion 32 having a perimeter flange 34 providing a ridge 36. The ridge 36 abuts a ledge 48 at a perimeter of the bore 52. An edge 46 of the flange 34 is welded to the housing 16, for example, by laser welding, to provide a weld 50 securing the cover 24 to the housing 16.

(27) One side of the domed portion 32 provides a spherical surface 38 having circumferentially spaced apart grooves 42 adjoining and radiating outwardly from an opening 44 in the cover 24. The grooves 42 may be formed by coining, for example.

(28) A plastic injection molding process is shown in FIG. 4. Molding equipment 56 is used to inject a molten plastic, such as acetyl, into the space between the housing 16, the cover 24 and the ball 18 to provide the bearing 22.

(29) Multiple mold portions engage various components of the ball joint 14 to maintain a space provided by first and second cavities 70, 72 on opposite sides of the cover 24 and that are in fluid communication with one another. In one example, a first mold portion 58 abuts the housing 16 to create a second cavity 72 between the first mold portion 58 and a bottom portion of the housing 16 and the cover 24. A second mold portion 60, such as a pin, is inserted into the hole 28 to plug and block any molten plastic from entering the hole 28. A third mold portion 62 includes first and second chamfers 64, 66 that respectively abut the housing 16 and the ball 18 to prevent molten plastic from escaping the first cavity 70 during molding.

(30) A plastic injector 63 injects molten plastic through an outlet in the first mold portion 58 into the second cavity 72, through the opening 44 in the cover 24 and into the first cavity 70.

(31) The opening 44 is aligned with the hole 28. During injection, plastic flows through the opening 44 forming protrusions 77 that fill the grooves 42 in the cover 24 on a side facing the ball 18. A spherical surface is formed on a first side 82 of the bearing 22 that engages the corresponding spherical surface of the ball 18. A depression 69 is provided in the bearing surface at the first side 82 of the bearing 22 and is formed by an end of the second mold portion 60, such that the depression 69 is beneath the hole 28 and aligned with the opening 44.

(32) An end of the housing 16 includes an annular projection 73 circumscribing the bore 52. A cap 74 is over-molded over the cover 24, the weld 50 and a portion of the annular projection 73 (with extension 71) to provide a water-tight seal and prevent corrosive elements from entering the ball joint 14. A monolithic plastic structure is thus formed including the bearing 22 joined to the cap 74 by a connector 75.

(33) As the plastic cools, it shrinks slightly, approximately 2%. The wall thickness of the bearing 22 varies due to the presence of the grooves 42 in the cover. Thus, a first thickness 76 of the bearing 22 in the area of the grooves 42 is larger than that of a second thickness 78 provided by the adjacent bearing structure, as shown in FIG. 7A. As a result of the plastic shrinking, a recess 80 will form next to the ball 18 in the spherical bearing surface on the first side 82 at a location opposite each groove 42, as best shown in FIG. 7B.

(34) As shown in FIGS. 6-7B and 9, grease 84 is injected through the hole 28 into the depression 69 left by the second mold portion 60, permitting the grease 84 to travel into the recesses 80 that adjoin the depression 69. A plug 68 is inserted into the hole 28 to retain the grease 84 and prevent entry of debris.

(35) As shown in FIGS. 8A-8B, a slight perimeter lip 88 is provided at the end 86 of the bearing 22. As grease 84 fills the depressions, the bearing 22 deforms, pulling the lip 88 a distance 90 into the space between the ball 18 and the housing 16 (exaggerated in FIGS. 8C-8D) creating an interference fit and an enhanced seal between the ball 18 and the housing 16. A second grease 94, which is different than the first grease 84, is provided between the boot 26 and the ball 18. The lip 88 separates the first and second greases 84, 94, as shown schematically in FIG. 9.

(36) Variations of the ball joint 14 described above may also be used. Like numerals (e.g., 14, 114, 214 for “ball joints”) are used to describe similar elements between the various embodiments. A one-piece housing ball joint 114 is shown in FIG. 10A, and another two-piece housing ball joint 214 is shown in FIG. 10B. The one-piece housing ball joint 114 uses thicker walls, which may be more suitable in particular for higher axial loads. Grease is injected through the housing 116, 216 rather than the stud 120, 220 in both example ball joints 114, 214.

(37) Referring to FIGS. 10A, 11 and 12, the ball joint 114 has a housing 116 that includes an annular wall 116a on a side by the stud 120 and opposite a base 116b of the housing 116. After the ball 118 has been placed into the bore 152 and prior to injecting the bearing 122, the annular wall 116a is deformed inward toward the ball 118, e.g., swaged, to enclose the ball 118 within the bore, as shown in FIG. 12. However, the annular wall 116a remains spaced from the ball 118 to provide the first cavity 170 that receives the bearing 122 during molding.

(38) As described in connection with the ball joint 14 shown in FIG. 7B, the plastic bearing 22 shrinks as it cools, which forms the recesses 80 next to the ball 18 in the spherical bearing surface on the first side 82 at a location opposite each groove 42. It may be desirable to provide the grease farther up toward the stud for improved lubrication. To this end, as shown in FIGS. 13A-14B, the housings 116, 216 each have grooves 142, 242 that extend to an end 117, 217 of the housing 116, 216 to provide corresponding recesses 180, 280. However, it should be understood that the grooves 142, 242 need not extend all the way through to the terminal end of the housings 116, 216 as shown in the example embodiments. For the two-piece housing 216, a portion of the groove 242 is provided in the cover 224, which is preferably circumferentially aligned with the grooves in the other housing portion. Even if the grooves 242 are not circumferentially aligned with the grooves in the other housing portion (FIG. 13C), grease will still flow into the recess 283 (FIG. 14B) formed from the bearing 222 shrinking at a junction 281 between the cover 224 and the other housing portion.

(39) As shown in FIG. 13B, the annular projection 273 may be folded over, or swaged, onto the cover 224 as an alternative to welding thereby reducing the likelihood of corrosion.

(40) The bearing 122, 222 of each of the ball joints 114, 214 is injected through the base of the housing 116, 216 opposite the stud 120, 220. The plastic injection molding process for the ball joint 214 is shown in FIG. 15. First and third mold portions 258, 262 are arranged about the ball joint 214 in a manner similar to that described in connection with FIG. 4. A second mold portion 259 includes an end 261 that is inserted into the opening 244 in the cover 224 and into abutment with the ball 218. A fluid passage 261a that is connected to a plastic injector 263 is in communication with radially extending first and second passageways 261b, 261c.

(41) A first cavity 270 is provided between the ball 218 and the cover 224, and a second cavity 272 is provided between the cover 224 and the first mold portion. The first and second passageways 261b and 261c are aligned respectively with the first and second cavities 270, 272, which correspondingly provide the bearing 222 and the cap 274. The lip 88 described in FIGS. 8A-8D may be omitted, as shown in FIG. 18.

(42) The ball joints 114, 214 are shown in FIGS. 16A and 16B subsequent to molding the bearings 122, 222. The second mold portion 259 is withdrawn from the ball joint 214 subsequent to molding, leaving a hole 269 that adjoins the recesses 280 (FIG. 14B). Grease 284 is injected through the hole 269 and into the recesses 280 where it lubricates the ball 218. The injected grease 284 causes the bearing 222 to balloon slightly and achieve the desired lubrication of and load characteristic on the ball 218. The hole 169 (FIG. 16A), 269 (FIG. 16B) acts as a reservoir for the grease 184, 284. Referring to FIG. 17, a plug 268 is installed onto the cap 274 to cover the hole 269 and retain the grease 284 within the ball joint 114. The plug 268 may be snapped and/or ultrasonically welded onto the cap 274.

(43) It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention.

(44) Although the different examples have specific components shown in the illustrations, embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples.

(45) Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.