Patent ID: 7730807

Claim:
A transmission for a tractor comprising: a forward/reverse transmission unit for selectively changing a rotational direction of power of a first shaft connected with an engine and transmitting the power to a second shaft connected with an axle shaft; a main transmission unit installed between the second shaft and the axle shaft and having a plurality of gears to speed-change the power transmitted from the second shaft in four-speed; and a sub-transmission unit installed between the main transmission unit and the axle shaft and having a plurality of gears to speed-change again the power transmitted from the main transmission unit in four-speed, wherein the main transmission unit includes: a third shaft connected with the second shaft; a fourth shaft selectively connected with the third shaft; a fifth shaft arranged parallel to the third and fourth shafts; a sixth gear installed on the third shaft; a seventh gear, an eighth gear and a ninth gear installed in parallel on the fourth shaft; a tenth gear installed on the fifth shaft and engaged with the sixth gear; an eleventh gear installed on the fifth shaft and engaged with the seventh gear; a twelfth gear installed on the fifth shaft and engaged with the eighth gear; a thirteenth gear installed on the fifth shaft and engaged with the ninth gear; a first coupling gear installed on one side of the sixth gear; a second coupling gear installed on one side of the seventh gear opposite to the first coupling gear; a first hub linearly movably installed on the fourth shaft to be selectively connected with the first or second coupling gear; a third coupling gear installed on one side of the eighth gear; a fourth coupling gear installed on one side of the ninth gear opposite to the third coupling gear; and a second hub linearly movably installed on the fourth shaft to be selectively connected with the third or fourth coupling gear.