Patent Application
20170361865
This invention relates in general to vehicle power steering assemblies and in particular to a multiple piece pinion housing for use in such a vehicle power steering assembly.
Automotive vehicles typically include a power steering assembly to assist in turning steerable wheels of the vehicle. The power steering assembly will typically include a rack and pinion assembly to convert rotational movement of a steering wheel of the vehicle into linear movement to effect turning of the steerable wheels. The rack and pinion assembly includes a pinion that is held within a pinion housing. Typically, the pinion housing comprises a pinion tower, a tube portion housing the rack, and a belt housing, all of which are formed monolithically as a unitary casting for efficiency during fabrication and subsequent assembly.
Multiple piece pinion housings for hydraulic power steering systems have been fabricated as a hollow tube connecting a cast pinion tower and a cast belt housing. However, the cast belt housing is heavy and significantly increases vehicle weight. To reduce vehicle weight, the pinion housing may be cast from aluminum. However, casting of the pinion housing requires an extended period of time for the molten aluminum to enter and flow throughout a mold for the large and complex casting. The molten aluminum cools during the extended period of time. As molten aluminum cools, air cavities or voids form. The air cavities increase porosity for the cast pinion housing. Thus it would be desirable to have a lighter weight pinion housing with reduced porosity.
This invention relates to a multiple piece pinion housing for a vehicle power steering assembly.
According to one embodiment, a method of fabricating a pinion housing for a vehicle power steering assembly may comprise, individually and/or in combination, one or more of the following features: forming a first housing from a first material, forming a second housing from a second material, and forming a third housing from a third material. The third housing is a stamping. The second material has a lesser unit weight than the first material and the third material has a greater unit weight than the second material. The first, second, and third housings are each formed separately. The formed first, second, and third housings are joined together to form the pinion housing.
According to another embodiment, a pinion housing for a vehicle power steering assembly may comprise, individually and/or in combination, one or more of the following features: A first housing formed from a first material, a second housing formed from a second material, and a third housing stamped from a third material. The second material has a lesser unit weight than the first material and the third material has a greater unit weight than the second material. The first, second, and third housings are each formed separately and joined together to form the pinion housing.
According to another embodiment, a pinion housing for a vehicle power steering assembly may comprise, individually and/or in combination, one or more of the following features: a plurality of housings formed separately and joined together to form the pinion housing. The plurality of housings includes at least a stamped housing and a cast housing. The cast housing has a lesser material unit weight than the stamped housing.
An advantage of an embodiment is a lighter weight pinion housing with reduced porosity. Other advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.
Referring now to
The power steering assembly 100 is partially housed in a housing, indicated generally at 102. The housing 102 includes a portion that is a first embodiment of a pinion housing, indicated generally at 104, produced in accordance with the present invention. The pinion housing 104 is comprised of a first housing or sub-housing 104A, a second housing or sub-housing 104B, and a third housing or sub-housing 104C, all of which will be discussed further. The housing 102 has further portions that will be discussed.
The power steering assembly 100 is associated with first and second front steerable wheels 106A and 106B, respectively, of a vehicle and includes a rotatable input shaft 108. A vehicle steering wheel 110 is operatively coupled to the input shaft 108 for rotation therewith about a steering axis X1. A torque sensor 112 encircles the input shaft 108 and is located within a pinion tower cover 114 connected to the second housing 104B. For example, the pinion tower cover 114 may be bolted to the second housing 104B. The torque sensor 112 generates signals in response to rotation of the input shaft 108. The signals are transmitted over a data network 116 to an electronic control unit (ECU) 118. The signals indicate a direction and magnitude of steering torque applied to the steering wheel 110.
A torsion bar 120 connects the input shaft 108 to a pinion 122 disposed in the second housing 104B such that the second housing 104B houses or encloses the pinion 122. The torsion bar 120 twists in response to the steering torque applied to the steering wheel 110. When the torsion bar 120 twists, relative rotation occurs between the input shaft 108 and the pinion 122.
The second housing 104B is attached to the first housing 104A in a manner which will be discussed. A linearly moveable steering member 124 extends axially through, and is disposed in, the first housing 104A such that the first housing 104A houses or encloses the steering member 124. The steering member 124 is linearly, or axially, moveable along a rack axis X2. A rack portion 126 of the steering member 124 is provided with a series of rack teeth which meshingly engage gear teeth provided on the pinion 122. The steering member 124 further includes a screw portion 128 having an external screw thread convolution. The steering member 124 is connected to the first steerable wheel 106A by a first tie rod 130A and the second steerable wheel 106B by a second tie rod 130B. The first and second tie rods 130A and 130B, respectively, are located at distal ends of the steering member 124. Linear movement of the steering member 124 along the rack axis X2 results in steering movement of the first and second steerable wheels 106A and 106B, respectively, in a known manner.
The power steering assembly 100 further includes a power source 132 drivably connected to a ball nut assembly 134 housed between the third housing 104C and a ball nut portion 136 of the housing 102. The power source 132 is illustrated as an electric motor, but may be other than an electric motor. For example, the power source 132 may be a hydraulic system. The ECU 118 controls the power source 132 in accordance with the signals received from the torque sensor 112. Control signals are transmitted from the ECU 118 to the power source 132 via the data network 116.
The ball nut assembly 134 is operatively connected with the screw portion 128 of the steering member 124. The power source 132 and ball nut assembly 134 are operatively connected by a pulley assembly 138 that includes a belt between an output of the power source 132 and the ball nut assembly 134. The pulley assembly 138 is disposed in the third housing 104C such that the pulley assembly is at least partially enclosed or housed by the third housing 104C.
Rotation of the pulley assembly 138 causes the ball nut assembly 134 to be rotated and thereby produce linear movement of the steering member 124. The power source 132 rotates the pulley assembly 138 which in turn transmits the drive force of the power source 132 to a ball nut of the ball nut assembly 134. Because the ball nut is fixed in position on the rack axis X2, the steering member 124 is driven to move linearly in response to rotation of the ball nut to, as discussed, effect steering movement of the first and second steerable wheels 106A and 106B, respectively, of the vehicle. The power source 132 thus provides steering assist in response to the applied steering torque.
In the event of the inability of the power source 132 to effect linear movement of the steering member 124, the mechanical connection between the gear teeth on the pinion 122 and the rack teeth on the rack portion 126 permits manual steering of the vehicle.
Referring now to
The first housing 104A is formed from a first material, the second housing 104B is formed from a second material, and the third housing 104C is formed from a third material. The first and third materials have a greater unit weight than the second material. For example, the first material may be a first grade of steel, the second material may be aluminum, and the third material may be a second grade of steel. Alternatively, the first and third materials may be the same grade of steel. Alternatively, the first material may be aluminum, plastic, or a polymer. Alternatively, the third material may be a high strength plastic
As illustrated, the first housing 104A is a drawn tube, the second housing 104B is a casting, and the third housing 104C is a stamping. Alternatively, the first housing 104A, the second housing 104B, or the third housing 104C may be formed using different methods—i.e., different than drawing for the first housing 104A, casting for the second housing 104B, or stamping for the third housing 104C—known to those skilled in the art. Each of the first, second, and third housings 104A, 104B, and 104C, respectively, is formed separately.
The pinion housing 104 is formed when the first, second, and third housings 104A, 104B, and 104C, respectively, are joined together. The second housing 104B is joined to the first housing 104A. For example, the first housing 104A may be press fit into the second housing 104B. The first housing 104A is also joined to the third housing 104C. For example, the first housing 104A may be press fit and welded to the third housing 104C.
Referring now to
As illustrated and discussed, the pinion housing 104 is comprised of three pieces: the first, second, and third housings 104A, 104B, and 104C, respectively. Alternatively, the pinion housing 104 may be comprised of more or fewer than three pieces.
Referring now to
The pinion housing 204 has a first housing or sub-housing, indicated generally at 204A, that is comprised of a first tube 250 and a second tube 252. The first and second tubes 250 and 252, respectively, are formed separately and joined together to form the first housing 204A. For example, the first and second tubes 250 and 252, respectively, may be welded, bolted, or riveted together to form the first housing 204A.
As illustrated, the first and second tubes 250 and 252, respectively, are separately drawn tubes. Alternatively, the first and second tubes 250 and 252, respectively, may be tubes formed other than by drawing. The first tube 250 is formed from a fourth material and the second tube 252 is formed from a fifth material that may be the same as the fourth material. The fourth and fifth materials each have greater unit weights than a second material from which a second housing or sub-housing 204B is formed. For example, the fourth and fifth materials may be steel of either the same of different grades. Alternatively, the fourth and fifth materials may each be aluminum, plastic, or a polymer.
Referring now to
Referring now to
The pinion housing 304 has a second housing or sub-housing, indicated generally at 304B, that is comprised of a bottom portion 354 and a top portion 356. For example, the bottom portion 354 may be a pinion tower bottom and the top portion 356 may be a pinion bowl. The bottom portion 354 is formed separately from the top portion 356. For example, the bottom portion 354 may be cast separately from casting of the top portion 356. The bottom portion 354 is formed from a sixth material and the top portion 356 is formed from a seventh material. The sixth and seventh materials may be the same or different. For example, each of the sixth or seventh materials may be steel, aluminum, plastic, or a polymer. The bottom portion 354 and top portion 356 are joined together to form the second housing 304B. For example, the bottom portion 354 and top portion 356 may be joined by a threaded connection, rivets, bolts, thermal fusion, or chemically.
As illustrated, the pinion housing 304 has a first tube 350, a second tube 352, the bottom portion 354, and the top portion 356, wherein the first and second tubes 350 and 352, respectively, comprise a first housing or sub-housing 304A. However, the first housing 304A may alternatively be formed as a single component—i.e., similar to the first housing 104A.
Referring now to
In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been described and illustrated in its preferred embodiments. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.
