Dual clutch transmission-equipped power unit

1. A dual clutch transmission-equipped power unit comprising:

a prime mover comprising a drive shaft; and

a dual clutch transmission that changes the speed of rotation produced by rotational power output by the drive shaft,

the dual clutch transmission comprising:

a first input shaft configured to be connected to the drive shaft;

a second input shaft configured to be connected to the drive shaft;

a first clutch configured to disable power transmission from the drive shaft to the first input shaft;

a second clutch configured to disable power transmission from the drive shaft to the second input shaft;

a countershaft;

a plurality of first speed change gear pairs configured to transmit power from the first input shaft to the countershaft; and

a plurality of second speed change gear pairs configured to transmit power from the second input shaft to the countershaft, wherein

the first input shaft overlaps the drive shaft when viewed in a first direction perpendicular to the drive shaft,

the second input shaft overlaps the drive shaft when viewed in a second direction perpendicular to the drive shaft,

the countershaft overlaps the drive shaft when viewed in a third direction perpendicular to the drive shaft, and

the dual clutch transmission-equipped power unit further comprises:

a drive gear mounted on an end portion of the drive shaft;

a first primary gear mounted on an end portion of the first input shaft and being in mesh with the drive gear; and

a second primary gear mounted on an end portion of the second input shaft and being in mesh with the drive gear.

2. The dual clutch transmission-equipped power unit according to claim 1 , further comprising:

a case enclosing the drive shaft, the first input shaft, and the second input shaft, wherein

the end portion of the drive shaft, the end portion of the first input shaft, and the end portion of the second input shaft project outward from the case in the same direction,

the first primary gear has a larger outer diameter than gears of the first speed change gear pairs,

the second primary gear has a larger outer diameter than gears of the second speed change gear pairs,

the drive gear, the first primary gear, and the second primary gear are located outside the case and on the same side with respect to the case, and

the first and second speed change gear pairs are located inside the case.

3. The dual clutch transmission-equipped power unit according to claim 2 , wherein

the first clutch is adjacent to the first primary gear,

the second clutch is adjacent to the second primary gear, and

the first and second clutches are located outside the case.

4. The dual clutch transmission-equipped power unit according to claim 2 , wherein

the first clutch overlaps the drive shaft when viewed in the first direction, and

the first clutch is located inside the case.

5. The dual clutch transmission-equipped power unit according to claim 4 , wherein

the second clutch overlaps the drive shaft when viewed in the second direction, and

the second clutch is located inside the case.

6. The dual clutch transmission-equipped power unit according to claim 1 , wherein

the prime mover is an engine comprising a crankshaft and a cylinder,

the drive shaft is the crankshaft,

the crankshaft extends in a fourth direction,

the cylinder projects in a fifth direction perpendicular to the fourth direction,

the first input shaft is located on one side with respect to the crankshaft in the fifth direction and adjacent to the cylinder, and

the second input shaft is located on the other side with respect to the crankshaft in the fifth direction.

7. The dual clutch transmission-equipped power unit according to claim 1 , wherein

the cylinder comprises an intake port and an exhaust port, and

the exhaust port is located closer to the dual clutch transmission than the intake port.

8. The dual clutch transmission-equipped power unit according to claim 1 , wherein

the countershaft is located on one side with respect to the drive shaft in a direction perpendicular to the drive shaft, and

the first and second input shafts are located on the one side with respect to the drive shaft.

9. The dual clutch transmission-equipped power unit according to claim 1 , wherein

the drive gear, the first primary gear, and the second primary gear are located in an imaginary plane, and

the first speed change gear pairs and the second speed change gear pairs are located on one side with respect to the drive gear, the first primary gear, and the second primary gear in a direction perpendicular to the imaginary plane.

10. The dual clutch transmission-equipped power unit according to claim 1 , wherein

the dual clutch transmission includes a clutch damper,

the prime mover is an engine,

the drive shaft is a crankshaft of the engine, and

the clutch damper interfaces with the crankshaft and is mounted around an axis of the crankshaft.

11. The dual clutch transmission-equipped power unit according to claim 1 , wherein the first clutch and the second clutch are arranged in an up-down direction.

12. The dual clutch transmission-equipped power unit according to claim 1 , wherein the first clutch is located on one side with respect to a straight line drawn between the drive shaft and the countershaft, the second clutch is located on another side with respect to the straight line.

13. The dual clutch transmission-equipped power unit according to claim 1 , further comprising an output shaft through which a drive power output by the dual clutch transmission is transmitted to a rear axle of a vehicle.

14. The dual clutch transmission-equipped power unit according to claim 1 , wherein the dual clutch transmission further comprises:

a final gear that receives a drive power from the countershaft and is located below the countershaft; and

a case that encloses the first input shaft, the second input shaft, the countershaft, and the final gear, wherein the case includes a case main body and an oil pan located beneath the case main body.