Bearing for a ball nut assembly of a vehicle power steering assembly

A vehicle power steering assembly includes a housing, a ball nut configured to be operatively disposed in the housing and including an extension portion provided with a convex bearing surface, an insert supported on the housing and provided with a concave bearing surface. The concave bearing surface is complementary to the convex bearing surface. The convex and concave bearing surfaces are a plain bearing configured to provide sliding movement relative to each other. The sliding movement provides relative rotation between the convex and concave bearing surfaces in a first direction on the ball nut axis and a second direction on a rotation axis that is transverse to the ball nut axis.

BACKGROUND OF INVENTION

This invention relates in general to vehicle power steering assemblies and in particular to an improved bearing structure for a ball nut assembly of such a vehicle power steering assembly.

An automotive vehicle commonly includes a power steering assembly to assist in turning steerable wheels of the vehicle. The vehicle power steering assembly may include a rack and pinion assembly to convert rotational movement of a steering wheel into linear movement of a steering member. Specifically, a pinion gear is rotated by the steering wheel and the steering member has a rack portion. The steerable wheels are connected by tie rods to opposite ends of the steering member. The linear movement of the steering member then turns the steerable wheels. A ball nut assembly may be mounted on the steering member and operably connected to a power source. Specifically, the power source drives an axially restrained ball nut that is disposed around the steering member. The power source and ball nut assembly together assist in the linear movement of the steering member in response to rotation of the steering wheel.

The vehicle power steering assembly includes a housing for its components. The housing may comprise individual housings that are joined together. For example, the individual housings may be a pinion gear housing and an outboard housing that are joined together. However, tolerances allowed for casting and machining of the individual housings may result in their misalignment when joined together. The misalignment may result in the ball nut assembly binding, which increases internal friction for the vehicle power steering assembly. Thus, it would be desirable to reduce binding in the ball nut assembly due to misalignment of the individual housings.

Furthermore, a rolling or four point bearing having rolling elements—e.g., ball bearings—is typically used to support the ball nut assembly on the housing. However, the rolling bearing has many components such as inner and outer chases, in addition to the rolling elements, that must be provided and assembled. This complexity increases a cost of the rolling bearing that in turn increases a cost of the ball nut assembly. Thus, it would also be desirable to have a simpler support for the ball nut assembly on the housing to reduce the cost of the ball nut assembly.

SUMMARY OF INVENTION

This invention relates to an improved bearing structure for a ball nut assembly of a vehicle power steering assembly.

According to one embodiment, a vehicle power steering assembly may comprise, individually and/or in combination, one or more of the following features: a housing, a ball nut configured to be operatively disposed in the housing, the ball nut including an extension portion provided with a convex outer bearing surface, an insert supported on the housing, the insert provided with a concave inner bearing surface. The concave inner bearing surface is complementary to the convex outer bearing surface. The convex outer bearing surface and concave inner bearing surface are configured to provide relative sliding movement between the convex outer bearing surface and the concave inner bearing surface.

According to this embodiment, the concave inner bearing surface may be in contact with the convex outer bearing surface and the concave inner bearing surface and the convex outer bearing surface may slide on each other.

According to this embodiment, the concave inner bearing surface and the convex outer bearing surface may be a plain bearing.

According to this embodiment, the extension portion may be formed integrally with the ball nut.

According to this embodiment, the extension portion may extend radially outward from an end of the ball nut.

According to this embodiment, the convex outer bearing surface supported on the concave inner bearing surface may axially restrain the ball nut along an axis of the ball nut.

According to this embodiment, the insert may be formed of a polymer material.

According to this embodiment, the vehicle power steering assembly may further include a retention member configured to retain the insert in the housing.

According to another embodiment, a vehicle power steering assembly may comprise, individually and/or in combination, one or more of the following features: a housing, a ball nut configured to be operatively disposed in the housing, the ball nut including an extension portion provided with a convex bearing surface, an insert supported on the housing, the insert provided with a concave bearing surface, and a ball nut axis of the ball nut on which the ball nut is configured to rotate to effect linear motion of a steering member. The concave bearing surface is complementary to the convex bearing surface. The convex and concave bearing surfaces are configured to provide sliding movement relative to each other to provide relative rotation between the convex and concave bearing surfaces in a first direction on the ball nut axis and a second direction on a rotation axis that is transverse to the ball nut axis.

According to this embodiment, the rotation axis may be perpendicular to the ball nut axis.

According to this embodiment, the concave bearing surface may be in contact with the convex bearing surface and the concave bearing surface and the convex bearing surface slide on each other.

According to this embodiment, the concave bearing surface and the convex bearing surface may be a plain bearing.

According to this embodiment, the extension portion may be formed integrally with the ball nut.

According to this embodiment, the extension portion may extend radially outward from an end of the ball nut.

According to this embodiment, the concave bearing surface supported on the convex bearing surface may axially restrain the ball nut along the ball nut axis.

According to this embodiment, the insert may be formed of a polymer material.

According to this embodiment, the vehicle power steering assembly may further include a retention member configured to retain the insert in the housing.

According to yet another embodiment, a vehicle power steering assembly may comprise, individually and/or in combination, one or more of the following features: a housing, a recess in the housing, a ball nut configured to be operatively disposed in the housing and including an extension portion provided with a convex bearing surface, an insert supported in the recess and provided with a concave bearing surface, and a retention member configured to retain the insert in the recess. The ball nut has a ball nut axis on which the ball nut is configured to rotate to effect linear motion of a steering member. The extension portion is formed integrally with the ball nut and extends radially outward from an end of the ball nut. The concave bearing surface is complementary to the convex bearing surface and the convex and concave bearing surfaces are a plain bearing. The plain bearing provides relative rotation between the convex and concave bearing surfaces in a first direction on the ball nut axis and a second direction on a rotation axis that is transverse to the ball nut axis.

According to this embodiment, the concave bearing surface may be in sliding contact with the convex bearing surface.

According to this embodiment, the convex bearing surface being supported on the concave bearing surface may axially restrain the ball nut along the ball nut axis.

One or more potential and/or realized advantages of an embodiment of the bearing structure for a ball nut assembly of a vehicle power steering assembly include reductions of binding and cost for the ball nut assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now toFIGS. 1 and 2, there is schematically illustrated a power steering assembly, indicated generally at100, for a vehicle. The vehicle power steering assembly100has a ball nut assembly, indicated generally at102, produced in accordance with the present invention.

The general structure and operation of the vehicle power steering assembly100is conventional in the art. For example, the vehicle power steering assembly100may be as disclosed by U.S. Pat. No. 8,307,940 to Bugosh et al. or U.S. Pat. No. 7,055,646 to Bugosh, the disclosures of both of which are hereby incorporated by reference in entirety herein. Thus, only those portions of the vehicle power steering assembly100which are necessary for a full understanding of this invention will be explained and illustrated in detail. Although this invention will be described and illustrated in connection with the particular vehicle power steering assembly100disclosed herein, it will be appreciated that this invention may also be used in connection with other types of vehicle power steering assemblies, including other electric, hydraulic, or otherwise powered vehicle power steering assemblies known to those skilled in the art.

As will be discussed, components of the vehicle power steering assembly100, including the ball nut assembly102, are housed within, and supported by, a housing, indicated generally at104. As illustrated, the housing104comprises first and second individual housings104A and104B, respectively, that have been joined together to form the housing104at a housing interface106(indicated by a dashed line). The first and second individual housings104A and104B, respectively, are joined together at the housing interface106by a known means. As non-limiting examples, the first and second individual housings104A and104B, respectively, may be joined together by a press fit, welding, bolts, or screws. Alternatively, the housing104may comprise more than the two individual housings illustrated. Alternatively, the ball nut assembly102may be utilized with the housing104when the housing104is a single, unitary housing not comprised of individual housings.

The vehicle power steering assembly100is associated with first and second steerable wheels108A and108B, respectively, of a vehicle and includes a rotatable input shaft110. A vehicle steering wheel or input112is operatively coupled to the input shaft110for rotation therewith about a steering axis114. A torque sensor116is located within the housing104. The torque sensor116generates signals in response to rotation of the input shaft110. The signals are transmitted over a data network118to an electronic control unit (ECU)120. The signals indicate a direction and magnitude of steering torque applied to the steering wheel112.

A torsion bar122connects the input shaft110to a pinion gear124, which is located inside the housing104. The torsion bar122twists in response to the steering torque applied to the steering wheel112. When the torsion bar122twists, relative rotation occurs between the input shaft110and the pinion gear124.

Alternatively, as a non-limiting example, the input shaft110, steering wheel112, torque sensor116, torsion bar122, and/or pinion gear124, along with other associated components or hardware thereof, may be omitted when the vehicle power steering assembly100is used with an autonomous or otherwise self driving vehicle. In such a case, steering may be effected only by the ball nut assembly102.

A linearly moveable steering member126is at least partially in, and extends linearly or axially through, the housing104. The steering member126extends linearly between the first and second steerable wheels108A and108B, respectively. A rack portion128of the steering member126is provided with a series of rack teeth which meshingly engage with pinion teeth provided on the pinion gear124to operatively connect the pinion gear124and the rack portion128. The steering member126further includes a first or inner screw portion130having an external screw thread convolution.

The steering member126is connected to the first steerable wheel108A by a first tie rod132A and the second steerable wheel108B by a second tie rod132B. The first and second tie rods132A and132B, respectively, are located at distal ends of the steering member126. The steering member126and the first and second tie rods132A and132B, respectively, are moveable relative to the housing104. The linear movement of the steering member126along a housing design axis134results in steering movement of the first and second steerable wheels108A and108B, respectively, in a known manner. The housing design axis134is an axis the housing104is designed to align with. However, allowable tolerances allow an as-built axis (not shown) along which the assembled housing104actually aligns with to deviate from the housing design axis134.

The ball nut assembly102is housed in the housing104and includes a bearing structure, indicated generally at136. The ball nut assembly102is supported on the housing104by the bearing structure136. The bearing structure136will be discussed in detail with reference toFIGS. 3-6B. As will also be discussed in detail, the bearing structure136is of a plain bearing type.

The vehicle power steering assembly100further includes a power source138drivably connected to the ball nut assembly102. The power source138is illustrated as an electric motor, but may be other than an electric motor. As a non-limiting example, the power source138may be a hydraulic system. The ECU120controls the power source138in accordance with the signals received from the torque sensor116. Control signals for the power source138are transmitted from the ECU120to the power source138via the data network118.

The illustrated power source138and the ball nut assembly102are operatively connected by a pulley assembly140. The pulley assembly140includes a belt transmitting rotational power between an output of the power source138and a ball nut142of the ball nut assembly102. The pulley assembly140includes a pulley (not shown) that is rotated by the belt. The pulley is rotationally fixed to the ball nut142. Alternatively, the power source138may be operatively connected to the ball nut assembly102by a force transmission means other than the pulley assembly140.

The ball nut142is operatively connected with the inner screw portion130of the steering member126in a known manner. As illustrated, the ball nut142has a second or outer screw portion144. The outer screw portion has an internal screw thread convolution. Force transmitting members (not shown) are held in a track, defined by the inner screw portion130and the outer screw portion144, to operatively connect the ball nut142with the steering member126. As a non-limiting example, the force transmitting members may be ball bearings. Alternatively, the ball nut142may be operatively connected with the steering member126other than as illustrated.

The ball nut142effects the linear movement of the steering member126upon rotation of the steering wheel112. As discussed, the power source138is operated in response to rotation of the steering wheel112and the ball nut assembly102is driven by the power source138via the pulley assembly140. When the ball nut142is driven, the ball nut142rotates and, because the ball nut142is axially fixed in position on the housing design axis134, the steering member126moves linearly along the housing design axis134. The linear movement of the steering member126effects steering movement of the first and second steerable wheels108A and108B, respectively, of the vehicle. The power source138thus provides steering assistance in response to the applied steering torque.

In the event of an inability of the power source138to effect the linear movement of the steering member126, a mechanical connection between the pinion teeth on the pinion gear124and the rack teeth on the rack portion128of the steering member126permits manual steering of the vehicle. The pinion gear124and the rack portion128cooperate to convert rotation of the steering wheel112around the steering axis114into linear movement of the steering member126along the housing design axis134.

Referring now toFIGS. 3-6B, the bearing structure136is illustrated in detail. The bearing structure136includes an “outer” insert146and an “inner” annular extension portion148of the ball nut142. The insert146has a center opening152(best shown inFIGS. 5A and 5B) in which the ball nut extension portion148is positioned. The bearing structure136further includes a retention member150that retains the insert146in the housing104.

The ball nut142extends cylindrically along a longitudinal ball nut axis154. The extension portion148is fixed in position on the ball nut142along the ball nut axis154. The steering member126also extends along the ball nut axis154. As discussed, the ball nut142rotates on the steering member126to produce linear movement of the steering member126along the ball nut axis154and the housing design axis134.

InFIGS. 3 and 4, the ball nut axis154is illustrated as co-linear with the housing design axis134. The ball nut axis154being co-linear with the housing design axis134is an ideal or design position of the ball nut axis154relative to the housing design axis134. As will be discussed, the ball nut axis154and housing design axis134are commonly other than co-linear because of allowable tolerances in production and assembly of the housing104.

The insert146defines an inner bearing surface156and an outer bearing surface158. The center opening152is defined by the insert inner bearing surface156. As illustrated, the insert inner bearing surface156has a concave shape along the housing design axis134. Preferably, the concave insert inner surface156has a constant radius. As a non-limiting example, the concave insert inner surface156may have a radius of 10.65 millimeters. The insert outer bearing surface158has a linear shape that is parallel to the housing design axis134. Alternatively, the insert outer bearing surface158may have other than a linear shape along the housing design axis134. The insert outer bearing surface158supports the ball nut142on the housing104.

The insert146has an annular shape that extends around the housing design axis134and the ball nut142. The insert146is defined by revolving the insert concave inner and linear outer surfaces156and158, respectively, around the housing design axis134while both the concave insert inner surface156and linear insert outer bearing surface158are coplanar with the housing design axis134.

Preferably, the insert146further has first and second insert portions160and162, respectively, that extend annularly around the housing design axis134. Preferably, the first and second insert portions160and162, respectively, are parallel to the housing design axis134and/or the insert outer bearing surface158. The concave insert inner surface156is interspaced between the first and second insert portions160and162, respectively. Alternatively, one or both of the first and second insert portions160and162, respectively, may be omitted.

Preferably, the insert146is produced from a polymer material. As a non-limiting example, the polymer material may be rubber. Producing the insert146from a polymer material reduces friction with the extension portion148as well as reduces overall noise, vibration, and harshness of the bearing structure136, ball nut assembly102, and vehicle power steering assembly100. Alternatively, the insert146may be produced from other materials such as a metallic material such as steel or aluminum or a polyethylene material. As a further non-limiting example, the insert146may be produced from a nylon material. Alternatively, the insert146may be produced from a combination of materials such as rubber or a metal material coated with polyethylene material. As illustrated, the insert146is a solid member although such is not necessary.

Furthermore, the insert146is illustrated as a continuous annular shape. Alternatively, the insert146may be other than a continuous annular shape. As a non-limiting example, the insert146may comprise two or more annular segments or sub-members (not shown). Gaps may or may not be provided between the two or more annular segments or sub-members.

The extension portion148of the ball nut142defines an outer bearing surface164. The extension outer surface164has a convex shape that is complementary to a shape of the concave inner surface156of the insert146. As illustrated, the extension outer surface164has a convex shape extending along the housing design axis134. The extension portion148extends from an external surface166of the ball nut142such that the extension portion148is defined between the convex extension outer surface164and the external surface166(shown by dashed lines at the extension portion148). The convex extension outer surface164extends from the external surface166of the ball nut142in a radially outward direction from the housing design axis134and the ball nut axis154. Preferably, the convex extension outer surface164extends from an end of the ball nut142.

The extension portion148has an annular shape that extends around the housing design axis134and the ball nut142. The extension portion148is defined by revolving the convex extension outer surface164around the housing design axis134while the convex extension outer surface164is coplanar with the housing design axis134.

The extension portion148is rigidly secured to, or otherwise fixed in position on, the ball nut142. Preferably, the extension portion148is produced monolithically or integrally with the ball nut142when the ball nut142is formed. As a non-limiting example, the extension portion148may be produced when the ball nut142is cold formed from a metallic material such as steel. As such, the extension portion148is produced from the same material as the ball nut142. Alternatively, the extension portion148may be a separate member that is fastened, attached, or otherwise secured to the ball nut142. As a non-limiting example, the extension portion148may be produced from a polymer material, such as rubber, and secured to the external surface166of the ball nut142. As further non-limiting examples, the extension portion148may be produced form a metallic material or a polyethylene material and secured to the external surface166.

As discussed, the bearing structure136further includes the retention member150to retain the insert146in the housing104. Preferably, the retention member150is an annular ring having first threads167. As a non-limiting example, the retention member150may be a spanner nut. Alternatively, the retention member150may be other than a threaded ring. As a non-limiting example, the retention member may be a spring loaded snap ring.

The bearing structure136is preferably assembled by first positioning the concave insert inner surface156on the convex extension outer surface164. Specifically, the extension portion148is inserted in the center opening152such that the insert146is supported on the extension portion148. As a non-limiting example, when the insert146is produced from an elastic material such as rubber, the insert146may be stretched to allow the extension portion148to enter the center opening152and then released to be supported on the extension portion148. Alternatively, as previously discussed, the insert146may be produced as two or more annular segments or sub-members that are arranged or otherwise assembled around the extension portion148to form the insert146. Alternatively, the concave insert inner surface156may be positioned on the convex extension outer surface164other than as described.

Next, after the concave insert inner surface156is positioned on the convex extension outer surface164, the insert146is positioned in a recess168on an inner surface170of the housing104. As illustrated, the recess168is an annular step in the housing104but may be otherwise shaped. As a non-limiting example, the recess168may be a machined counter bore. Alternatively, the insert146may be positioned in the housing104in other than the recess168and/or the recess168may be other than a machined counter bore.

Lastly, after the insert146is positioned in the recess168, the retention member150is installed in the housing104to retain the insert146in the recess168. Preferably, when installed in the housing104, the retention member150abuts or otherwise axially supports or contacts the insert146to retain the insert146in the recess168.

When the retention member150is provided with the first threads167, the retention member150is preferably screwed onto second threads171provided on the housing inner surface170. The retention member150with the first threads167is preferably screwed onto the second threads171tight against the insert146. Alternatively, when the retention member150is provided other than with the first threads, such as when the retention member150is the spring loaded snap ring, the retention member150is installed in the housing104by suitable means.

Alternatively, the bearing structure136may be installed in the housing104other than as described herein. As a non-limiting example, threads may be provided on the insert outer bearing surface158such that the insert146is retained in the recess168by screwing the insert146into the housing104. In such a case, the retention member150may be omitted.

When the bearing structure136is assembled, the convex extension outer surface164and the concave insert inner surface156are in contact such that the convex extension outer surface164bears, rests, or is otherwise supported on, the concave insert inner surface156. This is because of the complementary shapes between the convex extension outer surface164and the concave insert inner surface156. The convex extension outer surface164is free to oscillate, rotate, slide, or otherwise move on the concave insert inner surface156.

The convex extension outer surface164bearing on the concave insert inner surface156forms a plain bearing. As used herein, “plain bearing” is meant to mean a bearing comprising only a bearing surface without any rolling elements—e.g., ball bearings. Instead of rolling elements, the concave insert inner surface156and the convex extension outer surface164slide on each other. There are no rolling force transmitting elements, ball bearings or otherwise, in the bearing structure136. The plain bearing may also be known as a sliding bearing or slide bearing to those skilled in the art.

Preferably, and as illustrated, the contact between the convex extension outer surface164and the concave insert inner surface156is direct contact between the convex extension outer surface164and the concave insert inner surface156. Alternatively, a damping material(s) may be provided between the convex extension outer surface164and the concave insert inner surface156as part of the plain bearing. As a non-limiting example, the damping material may be formed from a polymer or nylon material. When the damping material is provided, one of the convex extension outer surface164or the concave insert inner surface156slides on the damping material.

The convex extension outer surface164oscillates or rotates on the concave insert inner surface156along a first rotation arc172to provide relative rotation between the insert146and the extension portion148. The convex extension outer surface164oscillating or rotating on the concave insert inner surface156also provides relative rotation between the ball nut assembly102and the housing104. This is because, as discussed, the extension portion148is rigidly secured to the ball nut142of the ball nut assembly102. Alternatively, the insert inner surface156and the extension outer surface164may be shapes other than those illustrated—i.e., other than concave and convex shapes, respectively—that allow the extension outer surface164to oscillate or rotate on the insert inner surface156.

The first rotation arc172is in a plane. The housing design axis134and the ball nut axis154also both lie in the plane. The convex extension outer surface164rotating on the concave insert inner surface156results in the ball nut assembly102rotating on a rotation axis174(also shown inFIG. 2) while the housing104remains in position—i.e., the housing104is rotationally fixed on the rotation axis174. The housing design axis134, ball nut axis154, and rotation axis174all intercept at a single point.

Preferably, the rotation axis174is perpendicular to the ball nut axis154. The rotation axis174is not limited to a single or specific perpendicular orientation to the housing design axis134. InFIG. 5A, the rotation axis174may be oriented anywhere between 0 and 360 degrees about the housing design axis134. A specific orientation of the rotation axis174to the housing design axis134is preferably a result of allowable tolerances in production and assembly of the housing104—i.e., the specific orientation of the rotation axis174to the housing design axis134results from the deviation of the as-built axis of the housing104from the housing design axis134. Thus, the bearing structure136supports the ball nut assembly102on the housing while allowing the ball nut assembly102to rotate about multiple axes. Alternatively, the rotation axis174may be otherwise transverse to the ball nut axis154.

Rotation of the ball nut assembly102on the rotation axis174results in different portions of the convex extension outer surface164oscillating or rotating in different directions along the first rotation arc172. For example, a first portion of the convex extension outer surface164illustrated as above the ball nut axis154inFIG. 4may oscillate or rotate in a first direction along the first rotation arc172and a second portion of the convex extension outer surface164illustrated as below the ball nut axis154inFIG. 4may oscillate or rotate in a second direction along the first rotation arc172that is opposite the first direction.

As such, a position of the ball nut assembly102may “float,” pitch, move, oscillate, or otherwise be adjusted relative to the housing104. Such float may, as a non-limiting example, be used to properly align the components—e.g., the steering member126—of the vehicle power steering assembly100in the housing104during assembly of the vehicle power steering assembly100. Alignment of the steering member126in the housing104may result in the ball nut assembly102oscillating, rotating, or pitching on the rotation axis174and the convex extension outer surface164oscillating or otherwise rotating on the concave insert inner surface156. The ball nut assembly102oscillates, rotates, or floats such that the components of the vehicle power steering assembly100may align with the as-built axis of the housing104during assembly of the vehicle power steering assembly100.

Preferably at the same time, as the convex extension outer surface164oscillates or rotates on the concave insert inner surface156, the ball nut142also rotates on the steering member126to effect the linear movement of the steering member126. The ball nut142rotates on the steering member126while supported by the bearing structure136—i.e., by the convex extension outer surface164being supported on the concave insert inner surface156. When rotating on the steering member126, the ball nut142rotates on the ball nut axis154. The ball nut142rotates on the steering member126along a second rotation arc176that is substantially perpendicular to the ball nut axis154.

The convex extension outer surface164being positioned within the concave shape of the concave insert inner surface156also axially restrains the ball nut142in position on the housing design axis134to effect the linear movement of the steering member126when the ball nut142is rotated. When the first and second insert portions160and162, respectively, are provided, the convex extension outer surface164is preferably positioned in the concave shape of the concave insert inner surface156between the first and second insert portions160and162, respectively.

Preferably, portions of the concave insert inner surface156closest to the ball nut axis154when the ball nut assembly102is assembled have a radial minimal distance178from the ball nut axis154. Preferably, the portions of the concave insert inner surface156with the radial minimal distance178adjoin or abut the first and second insert portions160and162, respectively. The radial minimal distance178is preferably perpendicular to the ball nut axis154.

Also preferably, a portion of the convex extension outer surface164furthest from the ball nut axis154when the ball nut assembly102is assembled has a radial maximal distance180from the ball nut axis154. The radial maximal distance180is preferably also perpendicular to the ball nut axis154.

An absolute value of the radial maximal distance180is preferably greater than an absolute value of the radial minimal distance178. As illustrated, the first and second insert portions160and162, respectively, have the same radial minimal distance178. Alternatively, the first and second insert portions160and162, respectively, may have different values that are each, as absolute values, preferably less than the radial maximal distance180. As such, the ball nut142may be axially restrained on the housing design axis134.

Referring now toFIGS. 7 and 8, there is illustrated non-limiting example positions of the ball nut assembly102when the convex extension outer surface164of the ball nut142has oscillated or rotated on the concave insert inner surface156.FIGS. 7 and 8are schematic and oscillation or rotation of the steering member126and the ball nut assembly102is exaggerated for clarity.

Specifically, FIG,7illustrates the position of the ball nut assembly102when the convex extension outer surface164has oscillated or rotated on the concave insert inner surface156in a first direction182. InFIG. 5, the steering member126and the ball nut assembly102have rotated together. As a result, the housing design axis134and the ball nut axis154are no longer co-linear. Instead, there is a first deflection or pitch184between the housing design axis134and the ball nut axis154such that the components of the vehicle power steering assembly100may align with the as-built axis of the housing104during assembly of the vehicle power steering assembly100. As a non-limiting example, the first deflection184may have an absolute value of 0.5 degrees.

Similarly,FIG. 8illustrates the position of the ball nut assembly102when the convex extension outer surface164has oscillated or rotated on the concave insert inner surface156in a second direction186, wherein the second direction186is opposite the first direction182. Again, inFIG. 6, the steering member126and the ball nut assembly102have rotated together. As a result, the housing design axis134and the ball nut axis154are again no longer co-linear. Instead, there is a second deflection or pitch188between the housing design axis134and the ball nut axis154such that the components of the vehicle power steering assembly100may align with the as-built axis of the housing104during assembly of the vehicle power steering assembly100. As a non-limiting example, the second deflection188may have an absolute value of 0.5 degrees, wherein the first and second deflections184and188, respectively, have opposite magnitudes.

FIGS. 7 and 8show examples of the ball nut axis154rotated relative to the housing design axis134in a vertical plane extending between top and bottom of the vehicle having the vehicle power steering assembly100. Alternatively, the ball nut axis154may rotate relative to the housing design axis134in a plane with any direction or orientation. As a non-limiting example, the ball nut axis154may rotate relative to the housing design axis134in a horizontal plane extending between front and back of the vehicle.