Rack gear and method of making the same
AssigneeTRW Inc.
InventorHarry E. Clary
Life of this patent
Estimating the term…
Abstract
An improved vehicle steering apparatus includes a lightweight hollow rack gear. The rack gear has a plurality of hollow teeth which engage a pinion gear in the steering assembly. In order to provide a variable ratio steering apparatus, the pitch of the teeth of the rack gear varies along the length of the gear. The rack gear is made by utilizing a pair of dies to form hollow gear teeth in a side wall of the tubular member. In forming the rack gear, one die is inserted into the tubular member while the other die is placed outside the tubular member with its teeth aligned with recesses between the teeth of the die inside the tubular member. The two dies are then pressed together. To form rack gear teeth with different pitches, the dies are provided with teeth of different pitches.
Claims21
An apparatus for turning steerable vehicle wheels, said apparatus comprising a pinion adapted to be connected with and rotated in response to rotation of a manually actuatable member, and a hollow rack gear disposed in meshing engagement with said pinion and adapted to be connected with the steerable vehicle wheels, said rack gear including a hollow tubular member having a longitudinally extending side wall in which a plurality of hollow teeth are formed, said side wall being continuous and free of joints in a plane extending transversely to the central axis of the tubular member throughout the length of a portion of the tubular member in which the hollow gear teeth are formed.
A method of making a rack gear having hollow teeth, said method comprising the steps of providing a tubular member having an open end and a longitudinally extending side wall with inner and outer surfaces which are continuous in a plane extending transversely to the longitudinal axis of the tubular member, providing a first longitudinally extending die having projections and recesses therebetween with configurations corresponding to the configuration of the inner surfaces of the hollow teeth of the rack gear, moving at least a portion of the first die into the tubular member through the open end of the tubular member to position at least a portion of the projections on the first die adjacent to the longitudinally extending inner surface of the tubular member, providing a second die having projections and recesses therebetween with configurations corresponding to the configuration of the outer surfaces of the hollow teeth of the rack gear, positioning the second die adjacent to the longitudinally extending outer surface of the tubular member with the projections on the second die aligned with the recesses on the first die, simultaneously forming a plurality of hollow gear teeth in the side wall of the tubular member by effecting relative movement between the first and second dies and pressing the side wall of the tubular member into the recesses between the projections on the first die with the projections on the second die and pressing the side wall of the tubular member into the recesses between the projections on the second die with the projections on the first die to form the hollow gear teeth, and removing the first die from the tubular member.
A method of making a rack gear for use in a variable ratio steering system, said method comprising the steps of providing a longitudinally extending wall with first and second side surfaces, providing a first longitudinally extending die having a first series of teeth with at least two different pitches, positioning the first series of die teeth adjacent to the first side surface of the wall, providing a second longitudinally extending die having a second series of teeth with at least two different pitches, positioning the second series of die teeth adjacent to the second side surface of the side wall, forming in the wall a series of hollow gear teeth having at least two different pitches, by pressing the wall of the longitudinally extending member into recesses between the teeth on the first die with the crests of the teeth on the second die.
A method of making a rack gear for use in a variable ratio steering system, said method comprising the steps of providing a longitudinally extending metal member having a longitudinally extending side wall with first and second side surfaces, providing a first longitudinally extending die having a series of teeth disposed in a first linear array which includes a first plurality of teeth having a first pitch and a second plurality of teeth having a second pitch which is greater than the first pitch, positioning the linear array of teeth on the first die adjacent to the first side surface of the side wall, providing a second longitudinally extending die having a series of teeth disposed in a second linear array which includes a third plurality of teeth having a pitch which is the same as the pitch of the first plurality of teeth on the first die and a fourth plurality of teeth having a pitch which is the same as the pitch of the second plurality of teeth on the first die, positioning the second linear array of teeth on the second die adjacent to the second side surface of the side wall, said step of positioning the second linear array of teeth including positioning the crests of the third plurality of teeth in alignment with recesses between the teeth of the first plurality of teeth and positioning the crests of the fourth plurality of teeth in alignment with recesses between the teeth of the second plurality of teeth, forming a linear array of hollow gear teeth having a plurality of pitches in the side wall of the longitudinally extending member, said step of forming a linear array of hollow gear teeth including the step of forming a first plurality of hollow gear teeth having a pitch equal to the first pitch by pressing the side wall of the longitudinally extending member into the recesses between the first plurality of teeth on the first die with the crests of the third plurality of teeth on the second die and pressing the side wall of the longitudinally extending member into the recesses between the third plurality of teeth on the second die with the crests of the first plurality of teeth on the first die, said step of forming a linear array of hollow gear teeth further includes the step of forming a second plurality of hollow gear teeth having a pitch equal to the second pitch by pressing the side wall of the longitudinally extending member into the recesses between the second plurality of teeth on the first die with the crests of the fourth plurality of teeth on the second die and pressing the side wall of the longitudinally extending member into the recesses between the fourth plurality of teeth on the second die with the crests of the second plurality of teeth on the first die.
A method of making a rack gear having hollow teeth, said method comprising the steps of providing a tubular member having a longitudinally extending central axis, providing a first die having a first series of teeth, positioning at least a portion of the first series of teeth on the first die in the tubular member, providing a second die having a second series of teeth, positioning the second die adjacent to the tubular member with the crests of the second series of teeth aligned with the roots of the first series of teeth, forming hollow gear teeth by pressing the wall of the tubular member toward the roots of the first series of teeth with the crests of the second series of teeth and by pressing the wall of the tubular member toward the roots of the second series of teeth with the crest of the first series of teeth, and removing the first die from the tubular member after forming the hollow gear teeth, said step of removing the first die including moving the first die transversely to the central axis of the tubular member through a distance sufficient to move the crests of the first series of teeth inwardly of the roots of the hollow gear teeth and then removing the first die along the central axis of the tubular member.
Dependencies are inferred from the claim text.