1. A power transmission device for a tractor, wherein a first speed change mechanism (8) of a travel system that converts power of a propeller shaft (6), and a second speed change mechanism (9, 10) that converts power from the first speed change mechanism (8), are provided in a mission case (M), a PTO drive shaft (16) is coaxially and directly connected to a rear portion of the propeller shaft (6), and a PTO power transmission shaft (17) is provided at the back of the PTO drive shaft (16) and is linked via a PTO clutch (18) to the PTO drive shaft (16), a rear-axle supporting holder (28) that supports a rear portion of the second speed change mechanism (9, 10) and through which the PTO drive shaft (16) penetrates and is provided is removably mounted in the mission case (M), and pump drive power extracting means (60) that transmits power of the PTO drive shaft (16) to a hydraulic pump (61) mounted to an outer surface of the mission case (M) is provided between the rear-axle supporting holder (28) and the PTO clutch (18), and the pump drive power extracting means (60) has a power transmission bevel gear (62) mounted to the PTO drive shaft (16), and an extraction bevel pinion (63) that is engaged with the power transmission bevel gear (62) and is removably linked to a pump shaft (61a) of the hydraulic pump (61), characterized in that a gear holding portion (28e) that supports the power transmission bevel gear (62), and a pinion holding portion (28f) that protrudes backward and supports the extraction bevel pinion (63), are provided on a back surface of the rear-axle supporting holder (28), the pinion holding portion (28f) being formed integrally with the rear-axle supporting holder (28).

2. The power transmission device according to claim 1, wherein a first and a second supporting wall (Ma, Mb) are provided in a front mission case (MF) provided between a flywheel housing (F) and a rear mission case (MR) to form a first chamber (20) that is in communication with an interior of the flywheel housing (F), a second or middle chamber (21), and a third or rear chamber (22), and a rear-axle supporting holder (28) that forms a back wall of the third chamber (22) is removably mounted in the front mission case (MF), a forward/reverse drive switch mechanism (8) that converts power of the propeller shaft (6) into forward or reverse drive power is provided as the first speed change mechanism (8) in the second chamber (21) between the propeller shaft (6) and a reverse-drive power transmission shaft (29), and a main speed change mechanism (9) that switches between multiple speeds, and a sub-speed change mechanism (10) that switches between a high and a low speed and transmits rear-wheel drive power from a countershaft (38) to an output shaft (47), are provided as the second speed change mechanism (9, 10) in the third chamber (22) between an input shaft (37) to which the forward or reverse drive power is transmitted from the forward/reverse drive switch mechanism (8), and the countershaft (38).

3. The power transmission device according to claim 2, wherein bearing portions of the input shaft (37), the countershaft (38), and the output shaft (47) are triangularly arranged and formed on a front surface of the rear-axle supporting holder (28), and the gear holding portion (28e) is formed on a back surface of the bearing portion of the countershaft (38).

4. The power transmission device according to claim 2 or 3, wherein a rear end of the pinion holding portion (28f) of the rear-axle supporting holder (28) and a rear end of a mounting portion of the hydraulic pump (61) are located further forward than a rear mission case joining surface (70) at a rear end of the front mission case (MF). , Description:Please see the attached document

Claims:WE CLAIM :

1. A power transmission device for a tractor, wherein
a first speed change mechanism (8) of a travel system that converts power of a propeller shaft (6), and a second speed change mechanism (9, 10) that converts power from the first speed change mechanism (8), are provided in a mission case (M), a PTO drive shaft (16) is coaxially and directly connected to a rear portion of the propeller shaft (6), and a PTO power transmission shaft (17) is provided at the back of the PTO drive shaft (16) and is linked via a PTO clutch (18) to the PTO drive shaft (16),
a rear-axle supporting holder (28) that supports a rear portion of the second speed change mechanism (9, 10) and through which the PTO drive shaft (16) penetrates and is provided is removably mounted in the mission case (M), and pump drive power extracting means (60) that transmits power of the PTO drive shaft (16) to a hydraulic pump (61) mounted to an outer surface of the mission case (M) is provided between the rear-axle supporting holder (28) and the PTO clutch (18), and
the pump drive power extracting means (60) has a power transmission bevel gear (62) mounted to the PTO drive shaft (16), and an extraction bevel pinion (63) that is engaged with the power transmission bevel gear (62) and is removably linked to a pump shaft (61a) of the hydraulic pump (61),
characterized in that
a gear holding portion (28e) that supports the power transmission bevel gear (62), and a pinion holding portion (28f) that protrudes backward and supports the extraction bevel pinion (63), are provided on a back surface of the rear-axle supporting holder (28), the pinion holding portion (28f) being formed integrally with the rear-axle supporting holder (28).

2. The power transmission device according to claim 1, wherein
a first and a second supporting wall (Ma, Mb) are provided in a front mission case (MF) provided between a flywheel housing (F) and a rear mission case (MR) to form a first chamber (20) that is in communication with an interior of the flywheel housing (F), a second or middle chamber (21), and a third or rear chamber (22), and a rear-axle supporting holder (28) that forms a back wall of the third chamber (22) is removably mounted in the front mission case (MF),
a forward/reverse drive switch mechanism (8) that converts power of the propeller shaft (6) into forward or reverse drive power is provided as the first speed change mechanism (8) in the second chamber (21) between the propeller shaft (6) and a reverse-drive power transmission shaft (29), and a main speed change mechanism (9) that switches between multiple speeds, and a sub-speed change mechanism (10) that switches between a high and a low speed and transmits rear-wheel drive power from a countershaft (38) to an output shaft (47), are provided as the second speed change mechanism (9, 10) in the third chamber (22) between an input shaft (37) to which the forward or reverse drive power is transmitted from the forward/reverse drive switch mechanism (8), and the countershaft (38).

3. The power transmission device according to claim 2, wherein
bearing portions of the input shaft (37), the countershaft (38), and the output shaft (47) are triangularly arranged and formed on a front surface of the rear-axle supporting holder (28), and the gear holding portion (28e) is formed on a back surface of the bearing portion of the countershaft (38).

4. The power transmission device according to claim 2 or 3, wherein
a rear end of the pinion holding portion (28f) of the rear-axle supporting holder (28) and a rear end of a mounting portion of the hydraulic pump (61) are located further forward than a rear mission case joining surface (70) at a rear end of the front mission case (MF).

, Description:Please see the attached document