Vehicle transmission assembly

Abstract

In a vehicle transmission assembly which includes a hydrostatic transmission (14) and mechanical transmission mechanism (21) for driving rear wheel axles (20) of the vehicle at a variable speed, a hydraulic pump (16) and hydraulic motor (17) of the hydrostatic transmission are mounted on a plate member (30), secured to a front of a transmission casing (15), at an upper and lower locations such that only the motor is disposed within the transmission casing at a location above the mechanical transmission mechanism. The mechanical transmission mechanism includes plural transmission shafts (31, 32, 33) all extending laterally of the transmission casing and is connected drivenly to the motor. Pump shaft (18) of the hydraulic pump is adapted to drive at least one of a rear-PTO shaft (23) and mid-PTO shaft (24) through a drive shaft (41) disposed co-axially with the pump shaft, a fluid-operated PTO-clutch (42) mounted on the drive shaft, and a gear train (43; 143; 243) disposed at a rear end portion within the transmission casing. A compactness of the transmission assembly and turnability of the vehicle with a small radius of turn are assured.

We claim: 
     
       1. A vehicle transmission assembly comprising a hydrostatic transmission, which includes a hydraulic pump having a pump shaft and a hydraulic motor having a motor shaft, and a mechanical transmission mechanism disposed within a transmission casing for transmitting vehicle-driving power to left and right rear wheel axles which are supported by said transmission casing, said motor shaft being connected drivingly to said rear wheel axles through said mechanical transmission mechanism, at least one of a rear-PTO shaft and mid-PTO shaft for taking-off auxiliary implement-driving power being supported by said transmission casing and connected drivenly to said pump shaft, characterized in: that a plate member (30) is fixedly secured to a front of said transmission casing (15), said hydraulic pump (16) being mounted on a rear surface of said plate member and disposed at an upper portion within said transmission casing such that an input end (18a) of said pump shaft (18) extends forwardly of said plate member, and said hydraulic motor (17) being mounted on a front surface of said plate member at a level lower than said level of said hydraulic pump such that said motor shaft (19) extends rearwardly from said motor;   that said mechanical transmission mechanism (21) is disposed at a level lower than said level of said hydraulic pump (16) and is fashioned to include plural transmission shafts (31, 32, 33) all of which extend leftwards and rightwards of said transmission casing (15), said mechanical transmission mechanism being connected to said motor shaft (19) through a bevel gearing (34); and   that a drive shaft (41) is disposed within said transmission casing (15) rearwardly of said hydraulic pump (16) and co-axially with said pump shaft (18), said pump shaft extending rearwardly from said hydraulic pump and being coupled to said drive shaft, and said drive shaft being connected drivingly to said one PTO shaft (23; 24) through a PTO-clutch (42) mounted on said drive shaft and through a gear train (43; 143; 243) which is disposed at a rear end portion within said transmission casing.   
     
     
       2. A vehicle transmission assembly as set forth in claim 1, wherein said mechanical transmission mechanism (21) includes, as said transmission shafts, an input shaft (31) which is disposed at a level substantially equal to said level of said motor shaft (19) and is connected to said motor shaft through said bevel gearing (34), an intermediate shaft (32) which is disposed rearwardly of said input shaft at a level higher than said level of said input shaft, and an output shaft (33) which is disposed co-axially with said input shaft and is connected drivingly to said left and right rear wheel axles (20), and wherein a speed-reducing gear train (35) is provided which is operable to transmit rotation of said input shaft to said output shaft through said intermediate shaft with a reduced speed of rotation, a shiftable clutch member (36) being mounted on said output shaft and having a first position, where said clutch member connects said input shaft directly to said output shaft, and a second position where said clutch member connects said input shaft to said output shaft through said speed-reducing gear train. 
     
     
       3. A vehicle transmission assembly as set forth in claim 2, wherein said input shaft (31) is formed into a hollow shaft and is rotatably mounted on said output shaft (33). 
     
     
       4. A vehicle transmission assembly as set forth in claim 2, wherein a differential gearing (37) is disposed within said transmission casing (15) and between said left and right rear wheel axles (20), said output shaft (33) fixedly carrying a spur gear (38) which meshes with a larger input spur gear (39) of said differential gearing. 
     
     
       5. A vehicle transmission assembly as set forth in claim 1, wherein said transmission casing (15) has an open rear end closed by a cover member (44) and includes an internal partition wall (15a) which is disposed forwardly of said PTO-clutch (42) and rearwardly of said mechanical transmission mechanism (21), said drive shaft (41) and a rear-PTO shaft (23) being supported by said cover member and by said partition wall, respectively, and said gear train (43) for connecting between said drive shaft and said rear-PTO shaft being disposed between said partition wall and said cover member. 
     
     
       6. A vehicle transmission assembly as set forth in claim 5, wherein said gear train (43) includes an input gear (45) which is rotatably mounted on said drive shaft (41), said PTO-clutch being fashioned to a fluid-operated frictional clutch (42) for selectively coupling said input gear to said drive shaft and said drive shaft including a fluid passage (46) for operating said fluid-operated frictional clutch, a rotary joint for communicating said fluid passage with a stationary fluid passage being provided by an annular groove (47) formed in an outer circumference of said drive shaft and by a cylindrical portion (48) formed in said partition wall (15a) so as to sealingly cover said annular groove. 
     
     
       7. A vehicle transmission assembly as set forth in claim 1, which includes both of said rear-PTO shaft (23) and mid-PTO shaft (24), said rear-PTO shaft extending rearwardly from said transmission casing (15), whereas said mid-PTO shaft having a rear end portion disposed below said rear-PTO shaft and extending forwardly from said transmission casing at a level below said plate member (30), and wherein said gear train (43) includes a final gear (49) which is rotatably mounted on said rear-PTO shaft and is adapted to be coupled selectively to said rear-PTO shaft by a rear-PTO clutch (50) mounted on said rear-PTO shaft, whereas a gear (51) drivenly connected to said final gear is rotatably mounted on said mid-PTO shaft and is adapted to be coupled selectively to said mid-PTO shaft by a mid-PTO clutch (52) mounted on said mid-PTO shaft. 
     
     
       8. A vehicle transmission assembly as set forth in claim 1, wherein a mid-PTO shaft (24) is provided which extends forwardly from a rear and lower portion within said transmission casing (15) and projects forwardly from said transmission casing at a level below said plate member (30), and wherein said gear train (143) includes an input gear (145) rotatably mounted on said drive shaft (41) and a final gear (151) fixedly mounted on said mid-PTO shaft, said PTO-clutch being fashioned to a fluid-operated frictional clutch (42) which is operable to couple said input gear selectively to said drive shaft. .Iadd. 
     
     
       9.  In a vehicle transmission assembly comprising: a power input shaft (18) to be connected drivenly to a prime mover (13); a hydrostatic transmission (14) having a hydraulic pump (16) driven by said power input shaft and a hydraulic motor (17) connected in closed fluid circuit to said hydraulic pump so as to be driven by said pump, said hydrostatic transmission including an output shaft (19); a transmission casing (15) supporting left and right wheel axles (20); a mechanical transmission mechanism (21) disposed within said transmission casing for transmitting vehicle-driving power from said output shaft to said left and right wheel axles; and a PTO-shaft (23) supported by said transmission casing so as to extend outwardly of said casing for taking-off auxiliary implement-driving power, said PTO-shaft being drivenly connected to said power input shaft through a PTO-clutch (42), the improvement characterized in: that said hydrostatic transmission (14) includes a plate-shaped support member (30) which includes therein fluid passages and is attached to a front of said transmission casing (15);   that said transmission casing (15) includes a shaft-supporting internal partition wall (15a), a front end opening covered by said plate-shaped support member (30), and a rear end opening closed by a cover member (44; 244) attached to a rear of said transmission casing;   that said hydraulic pump (16) is mounted on a rear surface of said plate-shaped support member (30), said pump and said mechanical transmission mechanism (21) being disposed within said transmission casing (15) at a location before said internal partition wall (15a); and   that said PTO-shaft (23) is disposed behind said internal partition wall (15a) and is connected to said PTO-clutch (42) through a gear train (43; 243), said PTO-clutch and said gear train being disposed between said internal partition wall and said cover member (44; 244). .Iaddend. .Iadd.   
     
     
       10.  A vehicle transmission assembly as set forth in claim 9, wherein a differential gearing (37) for providing a rotational differential to said left and right wheel axles (20) is disposed within said transmission casing (15) at a location before said internal partition wall (15a), said mechanical transmission mechanism (21) including a transmission shaft (33) which extends leftwards and rightwards of said transmission casing and has thereon a co-rotatable spur gear (38)said spur gear meshing with a larger input spur gear (39) of said differential gearing. .Iaddend. .Iadd.11. A vehicle transmission assembly as set forth in claim 9, wherein a second PTO-shaft (24) is supported by said transmission casing (15) and has one end extending outwardly of said casing at an opposite side of said PTO-shaft (23), a gear (51; 251) for driving said second PTO-shaft being mounted on the other end of second PTO-shaft and being meshed with a gear (49; 282) of said gear train (43; 243). .Iaddend. .Iadd.12. A vehicle transmission assembly as set forth in claim 9, wherein said PTO-clutch is fashioned to a fluid-operated frictional clutch (42) mounted on a drive shaft (41) which is drivenly connected to said power input shaft (18) and includes therein a fluid passage (46) for operating said fluid-operated frictional clutch, a rotary joint for communicating said fluid passage with a stationary fluid passage (93) being provided by an annular groove (47) formed in an outer circumference of said drive and by a cylindrical portion (48) formed in said internal partition wall (15a) so as to sealingly cover said annular groove. .Iaddend. .Iadd.13. A vehicle transmission assembly as set forth in claim 9, wherein said PTO-clutch is fashioned to a fluid-operated frictional clutch (42) mounted on a drive shaft (41) which is drivenly connected to said power input shaft (18) and includes therein a fluid passage (46) for operating said fluid-operated frictional clutch, a rotary joint for communicating said fluid passage with a stationary fluid passage (193) being provided by a fluid chamber (147) which is defined by a cylindrical portion (148) formed in said cover member (244) and by a rear end face of said drive shaft. .Iaddend. .Iadd.14. In a vehicle transmission assembly comprising: a power input shaft (18) to be connected drivenly to a prime mover (13); a hydrostatic transmission (14) having a hydraulic pump (16) driven by said power input shaft and a hydraulic motor (17) connected in closed fluid circuit to said hydraulic pump so as to be driven by said pump, said hydrostatic transmission including an output shaft (19); a transmission casing (15) supporting left and right wheel axles (20); a mechanical transmission mechanism (21) disposed within said transmission casing for transmitting vehicle-driving power from said output shaft to said left and right wheel axles; and a PTO-shaft (23) supported by said transmission casing so as to extend outwardly of said casing for taking-off auxiliary implement-driving power, said PTO-shaft being drivenly connected to said power input shaft, the improvement characterized in: that said hydrostatic transmission (14) includes a plate-shaped support member (30) which includes therein fluid passages and is attached to a front of said transmission casing (15);   that said transmission casing (15) includes a shaft-supporting internal partition wall (15a) and a front end opening, said front end opening being covered by said plate-shaped support member (30); and   that said hydraulic pump (16) is housed within its own casing and is mounted on a rear surface of said plate-shaped support member (30) together with said own casing such that said hydraulic pump is disposed within said transmission casing (15) and between said support member and said internal partition wall (15a). .Iaddend. .Iadd.15. A vehicle transmission assembly as set forth in claim 14, wherein said hydraulic pump (16) has a pump shaft (18) which is supported at its one end by said plate-shaped support member (30) and at the other end by said own casing. .Iaddend. .Iadd.16. A vehicle transmission assembly as set forth in claim 14, wherein said hydraulic pump (16) is mounted on said rear surface of said plate-shaped support member (30) at an upper half of said support member. .Iaddend. .Iadd.17. In a vehicle transmission assembly comprising: a power input shaft (18) to be connected drivenly to a prime mover (13); a hydrostatic transmission (14) having a hydraulic pump (16) driven by said power input shaft and a hydraulic motor (17) connected in closed fluid circuit to said hydraulic pump so as to be driven by said pump, said hydrostatic transmission including an output shaft (19); a transmission casing (15) supporting left and right wheel axles (20); a mechanical transmission mechanism (21) disposed within said transmission casing for transmitting vehicle-driving power from said output shaft to said left and right wheel axles; and a PTO-shaft (23) supported by said transmission casing so as to extend outwardly of said casing for taking-off auxiliary implement-driving power, said PTO-shaft being drivenly connected to said power input shaft, the improvement characterized in:   that said hydrostatic transmission (14) includes a plate-shaped support member (30) which includes therein fluid passages and is attached to a front of said transmission casing (15);   that said transmission casing (15) includes a shaft-supporting internal partition wall (15a) and a front end opening, said front end opening being covered by said plate-shaped support member (30);   that said hydraulic pump (16) is mounted on a rear surface of said plate-shaped support member (30) such that said hydraulic pump is disposed within said transmission casing (15) and between said support member and said internal partition wall (15a); and   that said hydraulic pump (16) further includes a tiltable swash plate (16a) which is operatively connected at an inside of said transmission casing (15) to a control shaft (57), said control shaft extending through a side wall of said transmission casing and having at its outer end a control arm (58) attached thereto. .Iaddend. .Iadd.18. In a vehicle transmission assembly comprising: a power input shaft (18) to be connected drivenly to a prime mover ( 13); a hydrostatic transmission (14) having a hydraulic pump (16) driven by said power input shaft and a hydraulic motor (17) connected in closed fluid circuit to said hydraulic pump so as to be driven by said pump, said hydrostatic transmission including an output shaft (19); a transmission casing (15) supporting left and right wheel axles (20); a mechanical transmission mechanism (21) disposed within said transmission casing for transmitting vehicle-driving power from said output shaft to said left and right wheel axles; and a PTO-shaft (23) supported by said transmission casing so as to extend outwardly of said casing for taking-off auxiliary implement-driving power, said PTO-shaft being drivenly connected to said power input shaft through a PTO-clutch (42), the improvement characterized in:   that said hydrostatic transmission (14) includes a plate-shaped support member (30) which includes therein fluid passages and is attached to a front of said transmission casing (15);   that said transmission casing (15) includes a shaft-supporting internal partition wall (15a), a front end opening covered by said plate-shaped support member (30), and a rear end opening closed by a cover member (44) attached to a rear of said transmission casing;   that said hydraulic pump (16) is mounted on a rear surface of said plate-shaped support member (30), said pump and said mechanical transmission mechanism (21) being disposed within said transmission casing (15) at a location before said internal partition wall (15a);   that said PTO-shatt (23) is disposed behind said internal partition wall (15a) and and is connected to said PTO-clutch (42) through a gear train (43), said PTO-clutch and said gear train being disposed between said internal partition wall and said cover member (44); and   that another hydraulic pump (29) is mounted on a rear of said cover member (44) and has a pump shaft (29a) which extends into said transmission casing (15) through an opening formed in said cover member, said pump shaft being connected drivenly to said power input shaft (18). .Iaddend.   
     
     
        .Iadd.19.  In a vehicle transmission assembly comprising: a power input shaft (18) to be connected drivenly to a prime mover (13); a hydrostatic transmission (14) having a hydraulic pump (16) driven by said power input shaft and a hydraulic motor (17) connected in closed fluid circuit to said hydraulic pump so as to be driven by said pump, said hydrostatic transmission including an output shaft (19); a transmission casing (15) supporting left and right wheel axles (20); a mechanical transmission mechanism (21) disposed within said transmission casing for transmitting vehicle-driving power from said output shaft to said left and right wheel axles; and a PTO-shaft (23) supported by said transmission casing so as to extend outwardly of said casing for taking-off auxiliary implement-driving power, said PTO-shaft being drivenly connected to said power input shaft, the improvement characterized in: that said hydrostatic transmission (14) includes a plate-shaped support member (30) which includes therein fluid passages and is attached to a front of said transmission casing (15);   that said transmission casing (15) includes a shaft-supporting internal partition wall (15a) and a front end opening, said front end opening being covered by said plate-shaped support member (30);   that said hydraulic pump (16) is mounted on a rear surface of said plate-shaped support member (30) such that said hydraulic pump is disposed within said transmission casing (15) and between said support member and said internal partition wall (15a); and   that a charge pump (54) for supplementing fluid to said closed fluid circuit between said hydraulic pump (16) and said hydraulic motor (17) is mounted on a front of said plate-shaped support member (30) and is drivenly connected to said power input shaft (18). .Iaddend.