Patent ID: 7867132

Claim:
A gear transmission for driving an axle of a vehicle comprising: an input shaft; an output shaft for driving the axle; a high speed clutch; a high speed gear train interposed through the high speed clutch between the input shaft and the output shaft; a low speed clutch; a low speed gear train interposed through the low speed clutch between the input shaft and the output shaft; and a traveling load detection means which detects a traveling load that is a load applied on the output shaft during traveling of the vehicle, the traveling load detection means including an upstream detection member provided relatively rotatably on the output shaft so as to be drivingly connected to the input shaft through either the high speed gear train or the low speed gear train and either the correspondingly engaged high speed clutch or low speed clutch, a downstream detection member provided relatively unrotatably on the output shaft, wherein one of the upstream and downstream detection members is an axially slidable detection member which is axially slidable along the output shaft, and a biasing member biasing the upstream detection member and the downstream detection member toward each other, wherein one of the upstream and downstream detection members has a first engagement part and a second engagement part, wherein, when the axially slidable detection member slides in the biasing direction of the biasing member, the first engagement part is engaged with the other of the upstream and downstream detection members, wherein, when the axially slidable detection member slides opposite to the biasing direction of the biasing member, the second engagement part is engaged with the other of the upstream and downstream detection members, wherein the first engagement part and the second engagement part generate respective forces for sliding the axially slidable detection member opposite to the biasing direction of the biasing member, wherein the forces are changed according to variation of the traveling load, wherein, when the traveling load is increased and becomes larger than a first switching point, the axially slidable detection member slides away from the other upstream or downstream detection member opposite to the biasing direction of the biasing member, so that the high speed clutch is disengaged and the low speed clutch is engaged, and wherein, when the traveling load is reduced and becomes smaller than a second switching point which is smaller than the first switching point, the axially slidable detection member slides toward the other upstream or downstream detection member in the biasing direction of the biasing member, so that the high speed clutch is engaged and the low speed clutch is disengaged.