Differential device and drive power transmission unit using the same
The number of the teeth of a second sun gear is slightly different from that of a first sun gear. A first planetary gears mesh with both the first sun gear and the second sun gear. A first carrier supports the first planetary. The number of the teeth of a third sun gear is same as that of the first sun gear. The second planetary gears mesh with both the second sun gear and the third sun gear. The second carrier supports the second planetary gears with preventing the same from revolving. The second power source generates a torque for rotating the first carrier.
1. A differential device comprising;
an input shaft receiving a torque from a first power source;
a differential mechanism having
an input element receiving the torque from the first power source through the input shaft,
a first output element,
a second output elements, and
gear elements for distributing the torque transmitted from the input element to the two output elements with allowing the differential rotation therebetween;
a first sun gear connected to the input element to integrally rotate with the input element and disposed around the first output element to be coaxial with the first output element;
a second sun gear disposed around the first output element to be coaxial with the first output element, wherein the number of the teeth of the second sun gear is slightly different from that of the first sun gear;
first planetary gears meshing with both the first sun gear and the second sun gear;
a first carrier supporting the first planetary gears around the first and second sun gears with allowing the planetary gears to rotate around its center axis and to revolve to go around the first and second sun gears;
a third sun gear connected to the first output element to integrally rotate with the first output element around the same axis as the first output element, wherein the number of the teeth of the third sun gear is same as that of the first sun gear;
second planetary gears meshing with both the second sun gear and the third sun gear;
a second carrier supporting the second planetary gears around the second and the third sun gears with allowing the planetary gears to rotate around its center axis and with preventing the planetary gears from revolving to go around the second and third sun gears; and
a second power source generating a torque for rotating the first carrier around its center axis.
2. A differential device according to claim 1 , wherein difference between the numbers of the teeth of the first and second sun gear is set within the range from one to three.
3. A differential device according to claim 1 , further including a casing containing the first output element, the first sun gear, the first planetary gear, the first carrier, the second sun gear, third sun gear and the second planetary gear, wherein the second carrier is fixed to the casing.
4. A drive power transmission unit comprising;
a differential device according to claim 1 wherein the differential device produces and limits a differential rotation between right and left wheels of a set of front wheels or a set of rear wheels;
a drive power transmission device distributing the torque from the first power source to the set of the front wheels and the set of rear wheels;
a first housing containing the differential device; and
a second housing containing the drive power transmission device.
5. A drive power transmission unit according to claim 4 wherein, the first housing is provided with a small diameter portion at a portion in which the input shaft is accommodated, the outer diameter of the small diameter portion is smaller than that of a portion accommodating the differential mechanism, and the second power source is arranged on the upper side of the small diameter portion in the direction of the gravity.