Differential limiter

1. A differential limiter, comprising:

1) a differential mechanism, including:

i) an input member for receiving a driving torque,

ii) a first output member,

iii) a second output member, and

iv) a differential gear for connecting the input member, the first output member and the second output member in such a manner that the input member, the first output member and the second output member differentially rotate;

2) a shaft member connected to the first output member and serving as an output member of a driving force;

3) a first cam mechanism including:

i) a first cam face formed on the first output member, and

ii) a second cam face formed on the shaft member,

the first cam face and the second cam face being so connected with each other as to oppose each other in an axial direction, to thereby cause respectively a first axial thrust force and a second axial thrust force according to the driving torque; and

4) a frictional clutch disposed between the first output member and the second output member, and transmitting a differential limit torque, wherein

the first axial thrust force caused to the first output member presses the frictional clutch from a first axial end, and

the second axial thrust force caused to the shaft member presses the frictional clutch from a second axial end opposite to the first axial end.

2. The differential limiter as claimed in claim 1 , wherein

i) the input member is a planetary carrier,

ii) the first output member is a sun gear,

iii) the second output member is an internal gear, and

iv) the differential gear is a pinion configured to serve as a planetary gear supported to the planetary carrier, and wherein

the sun gear is configured to press, by means of the first axial thrust force, the frictional clutch from the first axial end via the planetary carrier, and

the shaft member is configured to press, by means of the second axial thrust force, the frictional clutch from the second axial end via a press member unitedly movable in the axial direction.

3. The differential limiter as claimed in claim 1 , further comprising:

an actuator capable of externally controlling a clutching force of the frictional clutch, and

a second cam mechanism for amplifying an operational force of the actuator, to thereby apply the clutching force to the frictional clutch.

4. The differential limiter as claimed in claim 3 , wherein

in combination with the second axial thrust force, a thrust force which is the clutching force of the second cam mechanism presses the frictional clutch via the press member.

5. The differential limiter as claimed in claim 2 , wherein

the first axial thrust force and the second axial thrust force vary according to a transmission torque passing through the first cam mechanism, and

a differential limiting function caused to the frictional clutch by a clutching force of the first cam mechanism is, thereby, torque sensitive.

6. The differential limiter as claimed in claim 5 , wherein

the first axial thrust force and second axial thrust force of the torque sensitive differential limiting function are offset in a closed loop including the sun gear, an annular washer, a planetary carrier, the frictional clutch, the press member, a snap ring and the shaft member.

7. The differential limiter as claimed in claim 3 , wherein

the actuator includes an electromagnet, and

the second cam mechanism is a ball cam.