Patent ID: 8147371

Claim:
A differential gear comprising, a differential case configured to receive a driving force, a helical pinion gear arranged on an axis parallel to a rotation axis of the differential case and rotatably held in a hole formed inside the differential case, a pair of helical output gears meshing with the helical pinion gear, partly axially facing each other and outputting driving forces, and helix angles of the helical pinion gear and helical output gears being set so that, if the differential case turns in a first direction, the helical output gears receive thrusting forces axially acting away from each other, and if the differential case turns in a second direction, the helical output gears receive thrusting forces axially acting toward each other, the differential gear further comprising: inward support faces formed on the differential case so as to be axially inwardly oriented and configured to axially support the helical output gears under the thrusting forces; annular inward and outward counter faces formed on radial inner circumferential sides of ends of each helical output gear, the inward counter faces of the helical output gears facing each other, the outward counter faces of the helical output gears facing the inward support faces of the differential case; and a thrust bearing having a plurality of rollers and and a pair of annular plates interposed in at least one of a first gap defined axially between each inward support face and each outward counter face and a second gap defined axially between the inward counter faces, the annular plates in the first gap being in contact with the inward support face and outward counter face thereof and the annular plates in the second gap being in contact with the inward counter faces thereof; the helical output gears being pushed axially toward the first gap in reaction to the thrusting forces resulting from the turning of the case in the first direction so as to slide each outward counter face on each inward support face or to slide the inward counter faces on each other so as to produce differential limiting force, the helical output gears being pushed axially toward the second gap in reaction to the thrusting forces resulting from the turning of the case in the second direction so as to force the inward counter faces on each other or each outer counter face on each inward support face through the thrust bearing so as to reduce sliding resistance therebetween; the rollers of the thrust bearing being arranged radially with respect to the inward and outward counter faces; and one of the annular plates comprises a radial inner end radially and directly supported by one of the helical output gears.