U.S. patent number RE34,833 [Application Number 08/119,264] was granted by the patent office on 1995-01-17 for vehicle transmission assembly.
This patent grant is currently assigned to Kanzaki Kokyukoki Mfg. Co., Ltd.. Invention is credited to Toshiyuki Hasegawa, Ryota Ohashi, Shigenori Sakigawa.
United States Patent |
RE34,833 |
Hasegawa , et al. |
January 17, 1995 |
**Please see images for:
( Certificate of Correction ) ** |
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.
Inventors: |
Hasegawa; Toshiyuki (Ashiya,
JP), Sakigawa; Shigenori (Itami, JP),
Ohashi; Ryota (Sakai, JP) |
Assignee: |
Kanzaki Kokyukoki Mfg. Co.,
Ltd. (Amagasaki, JP)
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Family
ID: |
17893946 |
Appl.
No.: |
08/119,264 |
Filed: |
September 9, 1993 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
607864 |
Nov 1, 1990 |
05046994 |
Sep 10, 1991 |
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Foreign Application Priority Data
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Nov 20, 1989 [JP] |
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1-301197 |
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Current U.S.
Class: |
475/83; 180/53.1;
475/200; 74/15.2 |
Current CPC
Class: |
B60K
17/105 (20130101); B60K 17/28 (20130101); B60K
2025/026 (20130101) |
Current International
Class: |
B60K
17/28 (20060101); B60K 17/10 (20060101); B60K
17/00 (20060101); B60K 25/00 (20060101); F16H
037/08 () |
Field of
Search: |
;74/15.2,15.6
;475/83,200 ;180/53.1,53.4,53.7,53.8 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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62-210132 |
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Sep 1987 |
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JP |
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1-17883 |
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Apr 1989 |
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JP |
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1-175526 |
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Jul 1989 |
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JP |
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Primary Examiner: Wright; Dirk
Claims
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.
Description
FIELD OF THE INVENTION
This invention relates to a transmission assembly for use in
transmitting vehicle-driving power and auxiliary implement-driving
power in a relatively small-sized vehicle, such as a mower tractor
having a mid-mount mower.
BACKGROUND OF THE INVENTION
In a relatively small-sized vehicle which requires a small-sized
transmission assembly for propelling the vehicle, a transmission
assembly is often employed in which a hydrostatic transmission
which may be designed in a compact fashion, and a mechanical
transmission mechanism, which is designed in a compact fashion, are
connected in series. And, in a case where the mechanical
transmission mechanism is disposed within a transmission casing
which supports left and right rear wheel axles for driving the
vehicle through left and right rear wheels, the hydrostatic
transmission is often mounted on an outer surface of the
transmission casing. Pump shaft of the hydraulic pump of such
hydrostatic transmission is often used as a power source for a
rear-PTO (power take-off) shaft which extends rearwardly from the
transmission casing for driving an auxiliary implement, such as a
grass collector, to be drawn by the vehicle. The pump shaft is
often used further as a power source for a mid-PTO shaft which
extends forwardly from the transmission casing for driving an
auxiliary implement of mid-mount type, such as a mid-mount mower,
to be mounted at an underside of the vehicle and between front and
rear wheels.
Typical examples of the vehicle transmission assembly of this type
are disclosed in JP, B2 No.1-17883; JP, A No.62210132; and JP, A
No.1-175526.
In the transmission assembly disclosed in JP, B2 NO.1-17883,a
hydrostatic transmission comprising a hydraulic pump and hydraulic
motor which are disposed respectively at higher and lower levels is
mounted on a front surface of a transmission casing. Within the
transmission casing, there are disposed not only a mechanical
transmission mechanism for transmitting vehicle-driving power but
another mechanical transmission mechanism for transmitting
auxiliary implement-driving power to a rear-PTO shaft, extending
rearwardly from the transmission casing, and to a mid-PTO shaft
which extends forwardly from the transmission casing at a level
below the hydrostatic transmission. In correspondence to the pump
and motor arrangement in the hydrostatic transmission that the
hydraulic motor having a motor shaft from which vehicle-driving
power is transmitted into the transmission casing is located below
the hydraulic pump having a pump shaft from which auxiliary
implement-driving power is transmitted into the transmission
casing, the mechanical transmission mechanism for transmitting
vehicle-driving power is disposed at a lower half within the
transmission casing while the mechanical transmission mechanism for
transmitting auxiliary implement-driving power is disposed at an
upper half within the casing. The transmission mechanism for
transmitting auxiliary implement-driving power includes a
fluid-operated frictional PTO-clutch which is operable to connect
selectively between a drive shaft, which is disposed at a high
level within the transmission casing and is coupled to the pump
shaft, and a clutch shaft which is disposed below the drive shaft
and on which the PTO-clutch is mounted.
In the transmission assembly disclosed in this JP, B2 NO.1-17883,
the mechanical transmission mechanism for transmitting
vehicle-driving power within the transmission casing includes
transmission shafts, which extend axially of the transmission
casing, and a differential gearing which is disposed behind the
transmission shafts and has, as its output shafts, left and right
rear wheel axles. Consequently, the transmission casing is still
pretty large in axial length. Further, the rear wheel axles are
located at a rearmost portion of the transmission assembly having
the hydrostatic transmission and transmission casing so that
turnability with a small radius of turn is not assured particularly
when the transmission assembly is located in a vehicle as rearwards
as possible so as to secure a large axial space for a mid-mount
mower or the like between front and rear wheels. With respect to a
small-sized vehicle, turnability with a small radius of turn is
very important.
The transmission assembly disclosed in JP, A No.62-210132 is
intended to eliminate the problems set forth above and comprises a
hydrostatic transmission which is located at a rearmost portion in
the transmission assembly. The hydrostatic transmission comprises a
hydraulic pump and hydraulic motor which are disposed respectively
at higher and lower levels. To a lower half of front surface of the
hydrostatic transmission, a transmission casing is attached at an
upper half of the casing into which a motor shaft of the
hydrostatic transmission extends. Within the transmission casing, a
mechanical transmission mechanism for transmitting vehicle-driving
power is disposed which includes plural transmission shafts all
extending laterally of the transmission casing and which is
connected drivenly to the motor shaft through a bevel gearing. Pump
shaft of the hydraulic pump has an input end extending forwardly at
a level above the transmission casing. This pump shaft also extends
rearwardly so as to be used as a rear-PTO shaft.
In the transmission assembly according to this JP, A No.62-210132,
axial length of the transmission casing is largely reduced owing to
the lateral arrangement of all of the transmission shafts. Further,
left and right rear wheel axles supported by the transmission
casing which is arranged in front of the hydrostatic transmission
are located at a foremost portion of the transmission assembly so
that, even when the transmission assembly is located in a
small-sized vehicle as rearwards as possible, turnability of the
vehicle with a small radius of turn is well secured.
On the other hand, the level of the pump shaft which is used as a
rear-PTO shaft is too high so that a transmission shaft for
connecting the pump shaft to an input shaft of a grass collector or
the like takes a large inclination resulting in generation of a
large noise at universal joints at the ends of the transmission
shaft. Another problem consists in how a PTO-clutch is provided.
Further, the transmission assembly disclosed in this JP, A
No.62-210132 does not permit to use the pump shaft as a power
source for driving an auxiliary implement of mid-mount type such as
a mid-mount mower. Indeed, in the mower tractor disclosed in this
literature, it is fashioned that power for driving a mid-mount
mower is taken off directly from an engine.
Finally, the transmission assembly disclosed in JP, A No.1-175526
is fashioned, similarly to the one disclosed in JP, B2 No.1-17883,
such that a hydrostatic transmission comprising a hydraulic pump of
a higher level and a hydraulic motor of a lower level is mounted on
a front surface of a transmission casing within which a mechanical
transmission mechanism for transmitting vehicle-driving power,
having forwards and rearwards extending transmission shafts, is
disposed at a lower half of the casing. In the transmission
assembly disclosed in this JP, A No.1-175526, however, a drive
shaft which is disposed at a high level within the transmission
casing and is coupled to a pump shaft of the hydraulic pump extends
rearwardly from the transmission casing. On a rear end portion of
this drive shaft, a hollow clutch shaft extending through a rear
end cover of the transmission casing is rotatably mounted which is
connected selectively to the drive shaft by an electromagnetic
PTO-clutch disposed on the rear of the transmission casing. The
clutch shaft is connected drivingly to a rear-PTO shaft, extending
rearwardly from the transmission casing, and to a mid-PTO shaft,
extending forwardly from the transmission casing at a level below
the hydrostatic transmission, through gear trains which are
disposed at a rear end portion within the transmission casing.
As compared to a PTO-clutch disposed within a transmission casing,
a PTO-clutch disposed at a location outside of a transmission
casing such as the one set forth above will heighten the freedom of
design of a transmission assembly and, also, will make the assembly
procedure and maintenance of it easier. However, it requires to
take measures for safety and against water and dust. A
fluid-operated frictional clutch which may be engaged in a smooth
manner with ease cannot be employed as a PTO-clutch to be disposed
at an outside of a transmission casing, because a fluid-operated
frictional clutch has a structure such that oil for lubricating
frictional elements of the clutch may overflow out of its clutch
housing.
OBJECT
Accordingly, a primary object of the present invention is to
provide a novel transmission assembly, for use in relatively
small-sized vehicles, which is reduced in size in a fashion such
that it assures turnability of a vehicle with a small radius of
turn, which permits to provide a rear-PTO shaft, to be driven by a
pump shaft of hydrostatic transmission through a PTO-clutch
disposed within a transmission casing, at an appropriate level, and
which permits to provide a mid-PTO shaft so as to be driven also by
the pump shaft and so as not to sacrifice a compactness of the
transmission assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the invention will become readily
apparent as the specification is considered in conjunction with the
accompanying drawings in which:
FIG. 1 is a sectional side view, partially cut away and partially
developed, of a first embodiment of the transmission assembly
according to the present invention;
FIG. 2 is a sectional view taken generally along line II--II of
FIG. 1;
FIG. 3 is a sectional view, partially developed, of a part of the
transmission assembly shown in FIG. 1;
FIG. 4 is a sectional view, partially omitted, taken generally
along line IV-IV of FIG. 1;
FIG. 5 is a schematic side view, partially cut away, of a mower
tractor in which the first embodiment is employed;
FIG. 6 is a sectional side view similar to FIG. 1, but showing a
second embodiment of the transmission assembly according to the
present invention; and
FIG. 7 is a sectional side view showing a modification of a part of
the second embodiment shown in FIG. 6.
In the drawings, like numerals designate like parts throughout the
several views thereof.
SUMMARY OF THE INVENTION
The present invention relates to a transmission assembly which
comprises, as depicted respectively in FIGS. 1 and 2 and in FIG. 6,
a hydostatic transmission 14 which includes a hydraulic pump 16
having a pump shaft 18 and a hydraulic motor 17 having a motor
shaft 19. The transmission assembly further comprises a mechanical
transmission mechanism 21 which is disposed within a transmission
casing 15 for transmitting vehicle-driving power to left and right
rear wheel axles 20 supported by the transmission casing. The motor
shaft 19 is connected drivingly to the rear wheel axles 20 through
the transmission mechanism 21, whereas the pump shaft 18 is
connected drivingly to at least one of a rear-PTO shaft 23 and
mid-PTO shaft 24 for taking-off auxiliary implement-driving
power.
As shown respectively in FIG. 1 and in FIG. 6, the transmission
assembly is fashioned according to the present invention to include
a plate member 30 which is fixedly secured to a front of the
transmission casing 15. The hydraulic pump 16 is mounted on a rear
surface of the plate member 30 and is disposed at an upper portion
within the transmission casing 15 in a condition such that an input
end 18a of the pump shaft 18 extends forwardly of the plate member
30, whereas the hydraulic motor 17 is mounted on a front surface of
the plate member 30 at a level lower than that of the hydraulic
pump in a condition such that the motor shaft 19 extends rearwardly
from the motor.
As shown respectively in FIGS. 1 to 3 and in FIG. 6, the mechanical
transmission mechanism 21 is disposed within the transmission
casing 15 at a level lower than that of the hydraulic pump 16 and
is fashioned to include plural transmission shafts 31, 32 and 33
all of which extend leftwards and rightwards of the transmission
casing. This transmission mechanism 21 is connected drivenly to the
motor shaft 19 through a bevel gearing 34.
As shown respectively in FIGS. 1 and 4 and in FIG. 6, a drive shaft
41 is disposed within the transmission casing 15 rearwardly of the
hydraulic pump 16 and co-axially with the pump shaft 18. The pump
shaft extends rearwardly from the pump 16 and is coupled to the
drive shaft 41. The drive shaft is connected drivingly to one of
the PTO shafts 23 (FIGS. 1 and 4) or 24 (FIG. 6; FIG. 7) through a
PTO-clutch 42, which is mounted on the drive shaft 41, and through
a gear train 43 (FIGS. 1 and 4); 143 (FIG. 6); or 243 (FIG. 7)
which is disposed at a rear end portion within the transmission
casing 15.
The transmission assembly according to the present invention having
the structure set forth above will reduce the axial length of the
transmission casing 15, because all of the plural transmission
shafts 31, 32 and 33 of the mechanical transmission mechanism 21
within the transmission casing extend laterally of the casing 15 so
that the transmission mechanism 21 may largely be reduced in size
in the axial direction of the transmission casing, as compared to a
transmission mechanism which includes transmission shafts extending
forwards and rearwards, and because the gear train 43, 143 or 243
in the power take-off line is disposed between the drive shaft 41
and PTO shaft 23 or 24, both of which extend axially of the
transmission casing 15, so that this gear train may be disposed
within a narrow space as viewed in the axial direction of the
transmission casing. The hydraulic pump 16 of the hydrostatic
transmission and the PTO-clutch 42 each having a relatively large
axial length may be disposed within an axial span occupied by the
transmission mechanism 21 and gear train 43, 143 or 243 of the
underside owing to the structure that the drive shaft 41 mounting
the PTO-clutch 42 is coupled directly to the pump shaft 18. The
arrangement of these hydraulic pump 16 and PTO-clutch 42 leaves no
substantial dead space in the upper portion within the transmission
casing 15. Turnability of a vehicle with a small readius of turn is
assured, because the lateral arrangement of plural shafts 31, 32
and 33 of the mechanical transmission mechanism 21 will reduce the
axial interval between the power input point by means of motor
shaft 19 and the position of rear wheel axles 20 so that the rear
wheel axles are located as forwardly as possible within the axial
length of the transmission casing 15.
Owing to the arrangement with respect to the hydrostatic
transmission 14 that only the hydraulic motor 17 of a lower
position is mounted on the front of the transmission casing 15 and
the hydraulic pump 16 is located within the transmission casing,
position of a joint between the pump shaft 18 and a transmission
shaft for transmitting power of an engine to the pump shaft is
replaced considerably rearwardly, as compared to an arrangement
that the hydraulic pump is mounted also on the front of the
transmission casing 15, so that an operator on a seat, which is
usually disposed above the transmission casing, is well released
from apprehension with respect to his feet. As already described,
the hydraulic pump 16 disposed within the transmission casing
leaves no substantial dead space within the casing 15. In addition,
the hydraulic motor 17 disposed on the front of the transmission
casing contributes to a reduction of the axial length of the casing
15 and to a frontward location of the rear wheel axles 20. The
plate member 30 supporting the hydraulic pump 16 and motor 17 of
the hydrostatic transmission 14 may be used for including in it
fluid passages and valves required for the hydrostatic
transmission.
The PTO-clutch 42 disposed within the transmission casing 15 may be
fashioned without any problem to a fluid-operated frictional clutch
which may be engaged in a smooth manner with ease. The rear-PTO
shaft 23 which is driven by the drive shaft 41 of a high level
through the PTO-clutch 42 and through the gear train 43 may be
disposed at an optional level by choosing or adjusting the
arrangement of the gear train 43 so that this rear-PTO shaft 23 may
be disposed at an appropriate level for transmitting power to an
auxiliary implement, such as a grass collector, to be drawn by the
vehicle.
A mid-PTO shaft which is used for driving a mid-mount implement is
to be disposed at a low level, because a mid-mount implement is
mounted at an underside of a vehicle. Consequently, the gear train
43 which is disposed at a rear end portion within the transmission
casing 15 for transmitting power to the rear-PTO shaft 23 may be
used for a mid-PTO shaft 24, extending forwardly from the
transmission casing at a low level, in a fashion such that the
mid-PTO shaft is connected drivenly to the gear train 43 at a rear
and low portion within the transmission casing 15. Although the
transmission mechanism for propelling the vehicle is disposed at a
fronter side within the transmission casing, passing of only the
mid-PTO shaft is afforded. It is thus seen that a mid-PTO shaft
driven by the pump shaft 18 of the hydrostatic transmission may be
provided without sacrificing a compactness of the transmission
assembly by utilizing the gear train 43 for the rear-PTO shaft.
In an embodiment of the present invention, the mechanical
transmission mechanism 21 within the transmission casing 15 is
fashioned so as to permit a two-stage change of the rotational
speed of the rear wheel axles 20 without unduly lowering the level
of the axles. As shown in FIGS. 1 to 3, the transmission mechanism
21 is fashioned to include, as its transmission shafts set forth
before, an input shaft 31 which is disposed at a level
substantially equal to that of the motor shaft 19 and is connected
to the motor shaft through the bevel gearing 34, an intermediate
shaft 32 which is disposed rearwardly of the input shaft 31 at a
level higher than that of the input shaft, and an output shaft 33
which is disposed co-axially with the input shaft 31 and is
connected drivingly to the left and right rear wheel axles 20. A
speed-reducing gear train 35 is provided which is operable to
transmit rotation of the input shaft 31 to the output shaft 33
through the intermediate shaft 32 with a reduced speed of rotation.
A shiftable clutch member 36 is mounted on the output shaft 33 and
is fashioned to have a first position, where the clutch member
connects the input shaft 31 directly to the output shaft 33, and a
second position where the clutch member 36 connects the input shaft
31 to the output shaft 33 through the speed-reducing gearing
35.
According to this structure, the intermediate shaft 32 for the
speed-reducing gear train 35 for transmitting rotation from the
input shaft 31 to the output shaft 33 with a reduced speed of
rotation is located rearwardly and upwardly of the input and output
shafts 31 and 33 so as to enlarge the interval between the shafts
31, 33 and 32 and so as to thereby permit to provide a large
speed-reducing ratio to the gear train 35. Nevertheless, the
interval between the output shaft 33 and rear wheel axles 20 is
kept equal to the interval between the input shaft 31 and wheel
axles 20 owing to the co-axial arrangement of the input and output
shafts 31 and 33 so that the level of the rear wheel axles 20 is
not unduly lowered.
In connection with the co-axial arrangement of the shafts 31 and 33
set forth above, it is preferred that the input shaft 31 is formed
into a hollow shaft and is rotatably mounted on the output shaft
33. In this case, a simple support structure for the input shaft 31
is provided. Further, when the mechanical transmission mechanism is
varied in design so that the mechanism does not perform a
speed-change transmission, it may be attained simply by removing
the input and intermediate shafts 31 and 32 and by connecting the
output shaft 33 to the motor shaft 19 by means of a bevel
gearing.
In a case where a differential gearing 37 is disposed, as shown in
FIG. 2, within the transmission casing 15 and between the left and
right rear wheel axles 20, it is preferred for heightening torque
of the rear wheel axles 20 to fixedly mount on the output shaft 33
a small spur gear 38 which meshes with a larger input spur gear 39
of the differential gearing 37.
For an easy assembly and maintenance of the PTO-clutch 42 to be
disposed within the transmission casing 15 and also for an easy
assembly of the gear train 43 in the power take-off line into the
transmission casing, the transmission casing 15 is preferably
fashioned, as shown in FIGS. 1 and 4, to include an open rear end,
to be closed by a cover member 44, and an internal partition wall
15a which is disposed forwardly of the PTO-clutch 42 and rearwardly
of the mechanical transmission mechanism 21. The drive shaft 41 and
rear-PTO shaft 23 are preferably supported by the cover member 44
and by the partition wall 15a, respectively, and the gear train 43
is preferably disposed between the partition wall 15a and cover
member 44.
According to this structure, the PTO-clutch 42 may be assembled
onto the drive shaft 41 through the rear end opening of the
transmission casing 15 before the cover member 44 has been
attached. The rear-PTO shaft 23 and gear train 43 may previously be
supported by the cover member 44 and then may be assembled into the
space between the partition wall 15a and cover member 44 by
attaching the cover member to the rear of the transmission casing.
Maintenance with respect to the PTO-clutch 42 may be carried out
with ease by removing the cover member 44.
The partition wall 15a set forth above may also be used, when the
PTO-clutch 42 is fashioned to a fluid-operated frictional clutch,
for providing a rotary joint for connecting a clutch-operating
fluid passage in the rotatable drive shaft 41 to a stationary or
fixed fluid passage. As shown in FIG. 1, the gear train 43 includes
an input gear 45 which is rotatably mounted on the drive shaft 41.
According to a preferred embodiment of the present invention, the
PTO-clutch is fashioned to a fluid-operated frictional clutch which
is operable to couple the input gear 45 selectively to the drive
shaft 41. This drive shaft includes a fluid passage 46 for
operating the clutch 42. A rotary joint for communicating this
fluid passage 46 with stationary fluid passage is provided by an
annular groove 47, which is formed in an outer circumference of the
drive shaft 41, and by a cylindrical portion 48 which is formed in
the partition wall 15a so as to sealingly cover the annular goove
47.
In a transmission assembly in which a mid-PTO shaft is provided in
addition to the rear-PTO shaft, it is preferred, as shown in FIGS.
1 and 4, to mount a final gear 49 of the gear train 43 rotatably on
the rear-PTO shaft 23. A rear-PTO clutch 50 is mounted on the
rear-PTO shaft 23 for coupling the final gear 49 selectively to the
shaft 23. A mid-PTO shaft 24 is disposed at a low level within the
transmission casing 15 such that it includes a rear end portion
located below the rear-PTO shaft 23 and extends forwardly from the
transmission casing at a level below the plate member 30. A gear 51
which is connected drivenly to the final gear 49 on the rear-PTO
shaft is rotatably mounted on the mid-PTO shaft 24 and is adapted
to be coupled selectively to the mid-PTO shaft by a mid-PTO clutch
52 which is mounted on the shaft 24.
The rear-PTO clutch 50 and mid-PTO clutch 52 set forth above will
enable to drive the rear-PTO shaft 23 and mid-PTO shaft 24
independently of each other. The PTO-clutch 42 is once disengaged
before operating each of the rear-PTO clutch 50 and mid-PTO clutch
52 for smoothening the operation and for preventing clutch elements
of the clutches 50 and 52 from being damaged.
In a vehicle which is used only for working purposes by means of
mid-mount auxiliary implements, only a mid-PTO shaft is provided
and a rear-PTO shaft is not required. In such vehicle, it is
preferred, as shown in FIG. 6, that a mid-PTO shaft 24 is provided
which extends forwardly from a rear and lower portion within the
transmission casing 15 and projects forwardly from the transmission
casing at a level below the plate member 30. The gear train 143
preferably includes an input gear 145, rotatably mounted on the
drive shaft 41, and a final gear 151 which is fixedly mounted on
the mid-PTO shaft 24. The PTO-clutch 42 is fashioned to a
fluid-operated frictional clutch which is operable to couple the
input gear 145 selectively to the drive shaft 41.
According to this structure, the fluid-operated frictional clutch
42 which may be engaged in a smooth manner using a valve is
exclusively and conveniently used for the mid-PTO shaft 24.
DESCRIPTION OF PREFERRED EMBODIMENTS
The first embodiment shown in FIGS. 1 to 4 is employed in a mower
tractor shown in FIG. 5 which is equipped with a mid-mount mower M
at an underside of the vehicle and between pairs of front wheels 11
and rear wheels 12.
As shown in FIG. 5, an engine 13 is mounted on a front portion of
the vehicle. Power is supplied from this engine 13 to the pump
shaft 18 of the hydrostatic transmission 14, referred to before,
through a transmission shaft 22 which extends axially of the
vehicle. The mid-PTO shaft 24 is used for transmitting
mower-driving power to a gear box Ma of the mower M through a
transmission shaft 25.
A seat 26 is disposed above the transmission casing 15 and a
steering wheel 27 for operating the front wheels 11 to turn is
located before the seat 21. A pair of single-acting hydraulic
cylinders 28 are disposed between the transmission casing 15 and
seat 26 for lifting and lowering a grass collector or the like
which is to be driven by the rear-PTO shaft 23. A hydraulic pump 29
for supplying fluid under pressure to the cylinders 28 is mounted
on a rear of the transmission casing 15.
As shown in FIG. 1, the hydraulic pump 16 and hydraulic motor 17 of
the hydrostatic transmission 14 each having its own casing are
mounted on the plate member 30, having a relatively large
thickness, in the arrangement having been detailed before. A charge
pump 54 for supplementing fluid to a closed circuit (not shown)
between the hydraulic pump 16 and motor 17 is fashioned to a
trochoid pump, which is constructed by employing as its pump shaft
the pump shaft 18 of the hydraulic pump 16, and is mounted on the
front surface of the plate member 30. An extension shaft 56 is
coupled to the motor shaft 19 at a location within the plate member
30 using a coupling sleeve 55 and has at its rear end an integral
bevel gear 34A which constitutes a gear of the drive side of the
bevel gearing 34. As is usual, the hydraulic pump 16 is fashioned
to a variable displacement pump including a swash plate 16a shown
in FIG. 2 the inclination of which may be varied through a control
arm 58 attached to a control shaft 57 which extends through a side
wall of the transmission casing 15. The hydrostatic transmission 14
will vary the vehicle speed in response to the change of
inclination angle of the swash plate 16a in a non-stepwise manner
with a selective reversing of the vehicle.
As shown in FIGS. 2 and 3, the input shaft 31 of the mechanical
transmission mechanism 21 is made of a hollow shaft having a small
length and is rotatably mounted on the output shaft 33 which is
supported by the side walls of the transmission casing 15. The
intermediate shaft 32 which is disposed, as shown in FIG. 1,
rearwardly and upwardly of the input and output shafts 31 and 33 is
supported by the side walls of the transmission casing, as shown in
FIG. 3. A bevel gear 34B which constitutes a gear of the driven
side of the bevel gearing 34 is fixedly mounted on the input shaft
31 and meshes with the bevel gear 34A, as shown in FIG. 1. As shown
in FIGS. 1 to 3, the speed-reducing gear train 35 referred to
before comprises a first reduction train of meshing gears 60 and
61, which are fixedly mounted respectively on the input shaft 31
and intermediate shaft 32, and a second reduction train of meshing
gears 62 and 63. One of the gears 62 of the second reduction train
is fixedly mounted on the intermediate shaft 32, whereas the other
gear 63 is formed integral with the clutch member 36. The clutch
member 36 is slidably but non-rotatably mounted on a splined sleeve
64 which is in turn fixedly mounted on the output shaft 33. This
clutch member 36 may be shifted to a position shown in FIG. 3,
where gear 63 is engaged with the gear 62 so as to place the
speed-reducing gear train 35 into its operative condition, and to
another position where the clutch member is engaged with both of
splines formed in the outer circumferences of the input and output
shafts 31 and 33 so as to connect the output shaft directly to the
input shaft.
For operating the clutch member 36 to displace between the two
positions set forth above, a shifter fork 65 shown in FIGS. 1 and 3
is fixedly mounted on a fork shaft 66 which is slidably supported
by the side walls of the transmission casing 15. As shown in FIG.
3, a rotatable control shaft 67 which extends through a top wall of
the transmission casing 15 carries at its inner end an eccentric
shifter pin 68, engaging the shifter fork 65, and at its outer end
a shifter arm 69. The arrangement of this shifting mechanism is
such that, when the shifter arm 69 is operated so as to rotate
about the axis of the control shaft 67, the shifter fork 65 is
slidingly displaced together with the fork shaft 66 in a lateral
direction of the transmission casing so as to displace the clutch
member 36. A latching means 70 is associated to the fork shaft 66,
as shown in FIG. 3.
As shown in FIGS. 2 and 3, a frictional brake 71 for braking the
output shaft is disposed at one end portion of this shaft 33. This
brake is operated through a cam mechanism including balls 71a.
As shown in FIG. 2, the differential gearing 37 referred to before
is disposed in a lower portion within the transmission casing 15 at
a location nearer to one of the side walls of the transmission
casing. The input spur gear 39 is attached to a differential casing
37a using bolts 72 and is engaged with the smaller spur gear 38
which is formed integral with the output shaft 33. The left and
right wheel axles 20 extending leftwards and rightwards from the
differential casing 37a are supported respectively by left and
right axle cases 73, attached to the sides of transmission casing,
and have at their outer ends rear wheel-attaching flanges 20a, as
shown in FIG. 2 with respect to the rear wheel axle 20 of one side.
As also shown in FIG. 2, a differential-locking clutch member 74 is
mounted on the rear wheel axle 20 of one side and has a locking pin
74a which, when projected into the differential casing 37a, locks a
differential gear to the casing 37a. This clutch member 74 is
operated to slide by a fork 76 shown in FIG. 1 which is slidably
mounted on a guide shaft 75 extending laterally of the transmission
casing 15.
Referring to the power take-off transmission mechanism, the drive
shaft 41 set forth before is coupled to the pump shaft 18, as shown
in FIG. 1, at a location before the cylindrical portion 48 of the
partition wall 15a using a coupling sleeve 48. A clutch housing 78
is fixedly mounted on the drive shaft 41 at a location behind the
partition wall 15a. The PTO-clutch 42 is fashioned to a
fluid-operated frictional clutch comprising opposite sets of
frictional elements which are slidably but non-rotatably supported
by the clutch housing 78 and by the input gear 45 of the gear train
43. As is usual, the fluid-operated PTO-clutch 42 further comprises
a piston 80 which is disposed within the clutch housing 78 and is
biased to move away from the frictional elements by a return spring
79. The clutch 42 is engaged by fluid under pressure, supplied
through the fluid passage 46 in the drive shaft 41, which causes
the piston 80 to move toward the frictional elements against the
biasing force of return spring 79.
As shown in FIGS. 1 and 4, an intermediate shaft 81 having a small
length is disposed at a level between the drive shaft 41 and
rear-PTO shaft 23 and is rotatably supported by the partition wall
15a and by the cover member 44. The gear train 43 includes two
gears 82 and 83, fixedly mounted on the intermediate shaft 81, one
of which meshes with gear 45 on the drive shaft 41 and the other of
which meshes with gear 49 rotatably mounted on the rear-PTO shaft
23.
The rear-PTO shaft 23 shown in formed to a hollow shaft which
includes in its rear end portion internal splines 23a for
connecting a joint (not shown). The inner end of this hollow shaft
is closed using an internal cover 84. The rear-PTO clutch 50
comprises a clutch member 50a which is slidably but non-rotatably
mounted on the rear-PTO shaft 23 and is operable to couple the gear
49 selectively to the shaft 23. Gear 51 is rotatably mounted on the
mid-PTO shaft 24 and meshes directly with the gear 49. The mid-PTO
clutch 52 comprises a clutch member 52a which is slidably but
non-rotatably mounted on the mid-PTO shaft 24 and is operable to
couple the gear 51 selectively to the shaft 24. As shown in FIG. 2,
the mid-PTO shaft 24 is disposed in a lower portion within the
transmission casing 15 at a side opposite to the differential
gearing 37. The inner bottom wall of the transmission casing 15
includes at a location below the rear wheel axle 20 of one side an
elongated groove 85 within which a lower half of the mid-PTO shaft
24 is located.
The clutch members 50a and 52a of the rear-PTO clutch 50 and
mid-PTO clutch 52 are operated to slide respectively by shifter
forks 87 and 88, shown in FIG. 4, mounted slidably on guide shafts
85 and 86 which extend axially of the transmission casing,
respectively. Rotatable control shafts 89 and 90 extend
respectively through a side wall of the transmission casing 15 and
carry at their inner ends respectively arms 89a and 90a which have
shift pins engaging the respective shifter forks 87 and 88. The
control shafts 89 and 90 carry at their outer ends clutch arms 89a
and 90b, respectively.
In FIG. 2, numeral 91 designates an oil filter which is disposed at
a deepest portion within the transmission casing 15. This oil
filter 91 includes outlets (not shown) for filtered oil at both of
its front and rear ends. The front outlet is communicated through a
fluid passage (not shown) in the front wall of the transmission
casing to a fluid passage (a part of which is shown in FIG. 1) in
the plate member 30 and then to the charge pump 54. The charge pump
54 shown is used not only for supplementing fluid into the closed
circuit or fluid path between the hydraulic pump 16 and motor 17
but for supplying clutch-operating fluid to the PTO-clutch 42. As
shown in FIG. 2, one of the side walls of the transmission casing
15 includes a fluid passage 92 which is communicated to an outlet
port of the charge pump 54 through a fluid passage (a part of which
is shown in FIG. 1) in the plate member 30. The fluid passage 92 is
connected to the rotary joint, referred to before, within the
cylindrical portion 48 through a fluid passage 93 which is formed
in an internal wall between the side wall and partition wall 15a of
the transmission casing. The rear outlet of the oil filter 91 is
connected to the pump 29 for the hydraulic cylinders 28 through a
pipe 94 shown in FIGS. 4 and 5. As shown in FIG. 1, the pump 29 has
a pump shaft 29a, coupled to the drive shaft 41 using a coupling
sleeve 95, and is driven by the drive shaft.
The mower tractor shown in FIG. 5 is used for various working
purposes with travelling the vehicle by driving left and right rear
wheels 12. In such use, the vehicle is travelled at a speed
controlled by the hydrostatic transmission 14, which varies the
speed indefinitely with a selective reverse of travelling
direction, and by the mechanical transmission mechanism 21 which
varies the speed in two stages. The brake 71 shown in FIGS. 2 and 3
is used for braking the vehicle during its travel and when the
vehicle is to be parked, whereas the differential-locking clutch
mechanism having the clutch member 74 shown in FIG. 2 is used for
disabling the differential gearing when the vehicle meets with the
earch of a bad condition or the like.
When a mowing operation is carried out using the mower M shown in
FIG. 5, the mid-PTO clutch 52 shown in FIG. 1 is engaged, and when
the mowed grass is to be collected at the same time by a grass
collector which is drawn by the vehicle and is driven by the
rear-PTO shaft 23, the rear-PTO clutch 50 is also engaged. Besides,
the rear-PTO shaft 23 is used for taking-off a required power when
a stationary working by means of a sprayer or the like is carried
out or when the vehicle is used for a working purpose by means of
an auxiliary implement to be drawn by the vehicle such as a
fertilizing implement, seeding implement, tiller or the like. As
already described, the PTO-rotary clutch 42 is once disengaged
prior to an operation of the rear-PTO clutch 50 or mid-PTO clutch
52.
Referring now to FIG. 6, there is shown a second embodiment of the
present invention in which only a mid-PTO shaft 24 is provided.
In this second embodiment, a gear train 143 which is disposed at a
rear end portion within the transmission casing 15 and between the
partition wall 15a and a rear end cover member 144 comprises an
input gear 145, which is rotatably mounted on the drive shaft 41
and may be coupled selectively to this shaft by a fluid-operated
frictional PTO-clutch 42, an intermediate gear 182 which is
supported at its integral fronter and rearer shaft portions by the
partition wall 15a and by the cover member 144 and meshes with the
input gear 145, and a final gear 151 which is fixedly mounted on
the mid-PTO shaft 24 and meshes with the intermediate gear 182. As
shown, the input gear 145 is fashioned to have a thickness larger
than the intermediate gear 182 by a reason which will be detailed
later.
In the second embodiment shown in FIG. 6, a cylindrical portion
corresponding to the cylindrical portion 48 shown in FIGS. 1 and 2
is not formed in the partition wall 15a. In place of it, the cover
member 144 is provided with an integral cylindrical portion 148 in
which a rear end portion of the drive shaft 41 is received. Within
this cylindrical portion 148, a fluid chamber 147 is formed for
connecting the fluid passage 46 in the rotatable drive shaft 41 to
a stationary fluid passage 193. Fluid passages 192A and 192B which
correspond to the fluid passage 92 shown in FIG. 2 are formed
respectively in a side wall of the transmission casing 15 and in
the cover member 144 and are communicated to the fluid passage 193
set forth above. Also, motor shaft 19 of the hydrostatic
transmission 14 employed in the second embodiment has a length
larger than that of the motor shaft 19 shown in FIG. 1 and extends
into the transmission casing. A bevel gear 34A of the drive side of
the bevel gearing 34 is fixedly mounted on a rear end portion of
the motor shaft 19.
The other parts of the second embodiment are fashioned similarly to
the corresponding parts of the first embodiment and are designated
by like numerals.
In the second embodiment, the fluid-operated PTO-clutch is used
exclusively for the mid-PTO shaft 24.
FIG. 7 shows a modification in which a rear-PTO shaft 23 is
additionally provided to the structure shown in FIG. 6.
In this modification, a rear end cover member 244 for the
transmission casing 15 is employed which includes an integral
cylindrical portion 148 corresponding to the cylindrical portion
148 of the cover member 144 shown in FIG. 6 but which has at its
portion below the cylindrical portion 148 an axial depth larger
than that of the cover member 144 shown in FIG. 6. A gear train 243
which corresponds to the gear train 143 shown in FIG. 6 comprises
an input gear 145 rotatably mounted on the drive shaft 41, an
intermediate gear 282 rotatably mounted on the rear-PTO shaft 23,
and a final gear 251 rotatably mounted on the mid-PTO shaft 24. On
the mid-PTO shaft, a splined sleeve 201 is fixedly mounted on which
a clutch member 252a is in turn slidably but non-rotatably mounted
so as to provide a mid-PTO clutch 252 for coupling the gear 251
selectively to the mid-PTO shaft 24.
Between the drive shaft 41 and rear-PTO shaft 23, another gear
train 202 is disposed which comprises the input gear 145 set forth
above, a gear 249 rotatably mounted on the rear-PTO shaft 23, and
an intermediate gear (not shown) which meshes with both of the
gears 145 and 249. For the purpose of providing this another gear
train 202 by employing the input gear 145 as it is, the thickness
of the corresponding gear 145 is made larger than required in the
device shown in FIG. 6. Further, diameter D of the fronter shaft
portion of the intermediate gear 182 shown in FIG. 6 is made equal
to the outer diameter D of an inner end portion of the rear-PTO
shaft 23 shown in FIG. 7 so that a shaft-supporting portion formed
in the partition wall 15a may be commonly used for the intermediate
gear 182 shown in FIG. 6 and for the rear-PTO shaft 23 shown in
FIG. 7. A rear-PTO clutch 250 having a slidable clutch member 250a
is mounted on the rear-PTO shaft 23 for coupling the gear 249
selectively to this shaft 23.
The rear-PTO clutch 250 and mid-PTO clutch 252 shown in FIG. 7 are
used respectively in the same manner as described before with
respect to the corresponding clutches 50 and 52 employed in the
first embodiment.
* * * * *