Patent Description:
The present invention is related, generally, to a pivot joint for pivotably attaching a pivot support with a steering knuckle in a vehicle steering and suspension system.

Pivot joints are commonly found in vehicle suspension assemblies for operably attaching a knuckle with a pair of control arms in order to allow the knuckle and control arms to rotate and articulate relative to one another during operation of the vehicle. Such pivot joints could take a range of different configurations including configurations with and without ball studs. There is a continuing need for improved pivot joints which can be installed in a vehicle more easily, can be manufactured more cost effectively, and which offer improved durability.

<CIT> for example relates to a ball joint that comprises a ball stud and a socket having a chamber. A bearing is located in the chamber and the ball stud has a ball end portion received in the bearing and rotatable in the bearing to provide for relative movement between a first and second suspension member. The ball stud and the bearing are movable together in the chamber relative to the socket.

<CIT> discloses a ball joint assembly including a housing with an inner wall that surrounds an axially extending open bore. A ball portion of a ball stud is received in the open bore of the housing, and a shank portion of the ball stud projects out of the open bore. A pair of bearings are disposed in the inner bore of the housing and are interposed between the ball portion and the inner wall. Each bearing has a curved bearing surface which slidably contacts the ball portion. Each bearing has an outer surface that slidably contacts the inner wall. A pair of biasing elements bias the bearings in opposite directions against the ball portion of the ball stud.

<CIT> discloses a ball joint comprising a socket, a bearing, and a stud. The bearing includes first and second relatively movable bearing elements. The first bearing element is movable with the first end portion of the stud in the socket and has a pivot center. The second bearing element is disposed between the first bearing element and the socket, and supports the first bearing element and the stud for pivotal movement relative to the socket about the pivot center. A biasing spring acting between the socket and the second bearing element resists movement of the first and second bearing elements relative to the socket.

<CIT> discloses according to the preamble of claim <NUM>.

In accordance with the present invention, a pivot joint as set forth in claim <NUM> is provided. Further embodiments are inter alia disclosed in the dependent claims. The pivot joint assembly includes a housing, wherein the housing has an opening which extends along an axis. The pivot joint assembly also includes a bearing which is received in the opening of the housing and which has a cylindrical outer surface that is in slidable contact with another surface so that the bearing can slide in an axial direction relative to the housing. The bearing has a curved inner bearing surface. The pivot joint assembly also includes an inner ring with a curved outer surface that is in slidable contact with the curved inner bearing surface of the bearing so that the inner ring can rotate and articulate relative to the housing.

According to another aspect of the present invention, an outer ring is received in the opening of the housing and has a cylindrical inner surface and wherein the surface that is in slidable contact with the cylindrical outer surface of the bearing is the cylindrical inner surface of the outer ring.

According to yet another aspect of the present invention, the bearing is made as a monolithic piece of a material which consists of <NUM>-<NUM> wt% Polytetrafluoroethylene (PTFE), <NUM>-<NUM> wt% carbon fibers, and the remainder is of polyoxymethylene (POM).

According to the claimed invention, the housing has a bottom wall.

According to the claimed invention, the bottom wall has a raised portion which has an annular shape and which surrounds a recessed portion that is recessed relative to the raised portion.

According to the claimed invention, the bearing can slide in the axial direction until a portion of the bearing is axially located between the raised portion and the recessed portion and can slide such that the bearing is entirely located on an opposite side of the raided portion from the recessed portion.

According to still a further aspect of the present invention, the housing is made as a monolithic piece of metal.

According to another aspect of the present invention, the housing presents at least three bolt openings which are separate from the opening that extends along the axis.

According to yet another aspect of the present invention, the bearing includes a plurality of slits which are circumferentially spaced from one another by fingers and wherein the fingers are flexible in a radial direction for receiving and capturing the inner ring.

Another aspect of the present invention is related to a vehicle suspension system. The vehicle suspension system includes a knuckle, a control arm, and a joint assembly. The joint assembly operably connects the knuckle with the control arm while providing the knuckle with three rotational degrees of freedom and one translational degree of freedom for moving relative to the control arm. The joint assembly includes a housing which is fixedly attached with the control arm. The housing has an opening which extends along an axis. A bearing is received in the opening of the housing. The bearing has a cylindrical outer surface that is in slidable contact with another surface so that the bearing can slide in an axial direction relative to the housing. The bearing has a curved inner bearing surface. The joint assembly further includes an inner ring that has a curved outer bearing surface that is in slidable contact with the curved inner bearing surface of the bearing so that the inner ring can rotate and articulate relative to the housing. The inner ring is fixedly attached with the knuckle.

These and other features and advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:.

Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a vehicle suspension system <NUM> is generally shown in <FIG>. The exemplary suspension system <NUM> includes a pair of vertically spaced apart control arms <NUM> and a single-piece pivot support <NUM> which extends between and is operatively attached with the control arms <NUM>. A knuckle <NUM> is operably attached with the pivot support <NUM> via a pair of joints <NUM>, <NUM>, namely an upper joint <NUM> and a lower joint <NUM>. As shown in <FIG>, as the control arms <NUM> pivot in sync with one another up and down, the pivot support <NUM> and the knuckle <NUM> translate with generally fixed orientations so that a wheel which is operably connected with the knuckle <NUM> does not pivot.

The upper joint <NUM> has the form of a ball joint which has a ball joint housing that is received in an opening in the pivot support <NUM>. The upper joint <NUM> also has a ball stud which extends downwardly for attachment with the knuckle <NUM>. The lower joint <NUM> is a pivot joint which has an opening that receives a downwardly extending post <NUM> (shown in <FIG>) in the knuckle <NUM>. The ball stud of the upper joint <NUM> and a central location of the opening of the lower joint <NUM> are aligned with one another about a common central axis A. As shown in <FIG>, the axial alignment of the upper and lower joints <NUM>, <NUM> allows the knuckle <NUM> and a wheel (not shown) attached thereto to pivot about the central axis A in response to steering input from a tie rod <NUM> that is attached with the knuckle <NUM>.

Referring now to <FIG>, the lower joint <NUM> has a housing <NUM> with a cup-shaped opening which is defined by a bottom wall <NUM> and a side wall <NUM>. The opening extends along the central axis A from the bottom wall <NUM> at a closed first end to an open second end. The bottom wall <NUM> has an annular raised portion <NUM> which surrounds a recessed central portion <NUM>. The central axis A extends through the recessed central portion <NUM>. The annular raised portion <NUM> is planar and extends to a bottom end of the side wall <NUM>.

The housing <NUM> is preferably made of a single, monolithic piece of metal, such as steel or an alloy steel, and is preferably shaped through forging or casting and then machining to establish the final form of the cup-shaped opening. In the exemplary embodiment, the housing <NUM> has three bolt openings which receive bolts to fixedly attach the housing <NUM> with the pivot support <NUM>. However, it should be appreciated that the housing <NUM> could take other shapes and configurations and may be fixedly attached with the pivot support <NUM> through any suitable fastening means.

An outer ring <NUM> is fixedly received in the cup-shaped opening of the housing <NUM> and abuts the raised portion <NUM> of the bottom wall <NUM> of the housing <NUM>. In the Exemplary embodiment, the outer ring <NUM> is press fit into the opening of the housing <NUM> such that, once installed, the outer ring <NUM> remains in a fixed location within the opening of the housing <NUM>. A cap <NUM> is also fixed with the housing <NUM> and the outer ring <NUM> to fixedly attach these components together. When in an assembled position, the outer ring <NUM> projects out of the cup-shaped opening of the housing <NUM> in an axial direction. The outer ring <NUM> has an inner surface which has a major portion <NUM> with a generally constant diameter. The major portion <NUM> extends axially from adjacent the bottom wall <NUM> of the housing <NUM> to a tapered portion <NUM> which tapers radially outwardly and which is located, axially, outside of the cup-shaped opening of the housing <NUM>. The outer ring <NUM> may be made of metal or plastic and may be shaped through any suitable operation.

The lower joint <NUM> further includes an inner ring <NUM> that has a through opening which is shaped to receive the post <NUM> of the knuckle <NUM> and includes a plastic bearing <NUM> which is disposed between the outer and inner rings <NUM>, <NUM>. In the exemplary embodiment, the inner ring <NUM> is press-fit onto the post <NUM> such that, once attached, these components move with one another. The inner ring <NUM> is preferably made of metal, such as steel, and has a semi-spherically curved outer face.

The bearing <NUM> is disposed in the opening of the housing between the outer and inner rings <NUM>, <NUM> for allowing these components to freely rotate relative to one another during operation of the vehicle suspension system <NUM>. Specifically, the bearing <NUM> is made of a low-friction material and has a semi-spherically curved inner face <NUM> that is in slidable contact with the curved outer face of the inner ring <NUM> to allow the inner ring <NUM> and the knuckle <NUM> to freely rotate about the central axis A (as shown in <FIG>) and to freely articulate, or pivot, relative to the outer ring <NUM>. For example, <FIG> shows the inner ring <NUM> as being articulated relative to the bearing <NUM> and to the housing <NUM>. In other words, the slidable relationship between the inner ring <NUM> and the bearing <NUM> gives the knuckle <NUM> three rotational degrees of freedom by allowing it to rotate and articulate relative to the housing <NUM> and to the control arm <NUM> (shown in <FIG>) affixed thereto and vice versa. As discussed in further detail below, the bearing <NUM> is preferably made of a low friction plastic material and is preferably shaped through an injection molding operation.

The bearing <NUM> has an axial length which is less than an axial lengths of the outer and inner rings <NUM>, <NUM>. In operation, an outer surface of the plastic bearing <NUM> can slide axially along the inner surface of the outer ring <NUM>. As shown in <FIG>, the slidable relationship between bearing <NUM> and the outer ring <NUM> in combination with the configuration of the recessed portion <NUM> of the bottom wall <NUM> allows the inner ring <NUM> and the plastic bearing <NUM> to slide axially downwardly until both the inner ring <NUM> and the plastic bearing <NUM> are partially below the outer ring <NUM>. In other words, the slidable relationship between the plastic bearing <NUM> and the outer ring <NUM> provides the knuckle <NUM> with one translational degree of freedom by allowing it to translate relative to the control arm <NUM> (shown in <FIG>) and vice versa.

As shown in <FIG>, the bearing <NUM> has a plurality of circumferentially spaced apart and axially extending slots <NUM> formed therein. The slots <NUM> extend to one axial end of the bearing <NUM> and separate a plurality of fingers which can flex radially outwardly in an elastic manner when inserting the inner ring <NUM> into a cavity defined by the inner face <NUM> of the bearing <NUM>. Once a maximum outer diameter of the inner ring <NUM> clears the distal ends of the fingers, the fingers snap radially inwardly to capture the inner ring <NUM> within the bearing <NUM> while still allowing these components to rotate and articulate relative to one another.

The bearing <NUM> is preferably made of a material which consists of: <NUM>-<NUM> wt% Polytetrafluoroethylene (PTFE), <NUM>-<NUM> wt% carbon fibers, and the remainder is of polyoxymethylene (POM). This material has been found to provide the bearing <NUM> with low friction; sufficient strength to transfer forces between the outer and inner rings <NUM>, <NUM> without damage; and sufficient elasticity to deflect when receiving the inner ring <NUM> therein during assembly of the lower joint <NUM>.

The lower joint <NUM> further includes a dust boot <NUM> which is sealed against the inner ring <NUM> and is sealable against the knuckle <NUM> for maintaining a lubricant within and keeping contaminants out of the lower joint <NUM>. The dust boot <NUM> may be fixedly attached with the inner ring <NUM> through any suitable means including, e.g., an adhesive.

Claim 1:
A pivot joint (<NUM>), comprising:
a housing (<NUM>) with an opening which extends along an axis (A), wherein said housing (<NUM>) has a bottom wall (<NUM>), wherein said bottom wall (<NUM>) has a raised portion (<NUM>) which has an annular shape and which surrounds a recessed portion (<NUM>) that is recessed relative to said raised portion (<NUM>);
a bearing (<NUM>) received in said opening of said housing (<NUM>) and having a cylindrical outer surface that is in slidable contact with another surface so that said bearing (<NUM>) can slide in an axial direction relative to said housing (<NUM>);
said bearing (<NUM>) having a semi-spherically curved inner bearing surface (<NUM>); and
an inner ring (<NUM>) having a semi-spherically curved outer bearing surface that is in slidable contact with said semi-spherically curved inner bearing surface (<NUM>) of said bearing (<NUM>) so that said inner ring (<NUM>) can rotate and articulate relative to said housing (<NUM>);
wherein said bearing (<NUM>) can slide such that said bearing (<NUM>) is entirely located on an opposite side of said raised portion (<NUM>) from said recessed portion,
characterized in that
said bearing (<NUM>) is configured to slide in said axial direction until a portion of said bearing (<NUM>) is axially located between said raised portion (<NUM>) and said recessed portion (<NUM>).