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FIELD OF THE INVENTION
The present invention relates to an axle driving apparatus with a
hydro-static-transmission used as a driving apparatus for a light tractor.
BACKGROUND OF THE INVENTION
Conventionally, an axle driving apparatus, which vertically divides a
casing thereof and journals axles at the divided surfaces and drives the
axles by a hydro-static-transmission attached to the casing, is well known
as disclosed in, for example, the Japanese Utility Model Publication
Gazette No. Sho 62-44198 and the Japanese Patent Laid-Open Gazette Sho
62-101945, filed by the same applicant.
In this conventional apparatus, however, the hydro-static-transmission,
separate from the axle driving apparatus, is fixed to the outside thereof
in a manner of being exposed, whereby the apparatus is large-sized as a
whole and larger in gross weight. Also, it is required, for driving the
horizontally disposed axles by a motor shaft of a hydraulic motor
vertically disposed at the exterior, to interpose bevel gears in a drive
system for both the motor shaft and axles.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an axle driving apparatus
which contains the hydraulic motor and a hydraulic pump of the
hydro-static-transmission in a transmission casing of the axle driving
apparatus, and a center section for connecting the hydraulic motor and
hydraulic pump is disposed in the transmission casing, the center section
being fixed to the butt joint surface of upper and lower sections of the
transmission casing.
The center section is formed in a L-like shape when viewed in section and
an oil passage from the hydraulic pump to the hydraulic motor is bent at a
right angle to thereby extend the motor shaft in parallel to the driven
axle. Hence, instead of conventional bevel gears used to turn the rotation
direction, the oil passage in the center section is used to turn the power
transmitting direction.
In a case where the center section is fixed to the butt joint surfaces of
the half casings, when the half casings are fixedly jointed directly with
aluminum die casting by use of four bolts, the center section may be
distorted, thereby using three tightening bolts.
The above and further objects and novel features of the invention will more
fully appear from the following detailed description when the same is read
in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a light tractor attached with an axle driving
apparatus of the invention,
FIG. 2 is a sectional front view of the axle driving apparatus,
FIG. 3 is a sectional view taken on the line I--I in FIG. 2, in which an
upper half casing is removed,
FIG. 4 is a sectional view taken on the line V--V in FIG. 3,
FIG. 5 is a sectional view taken on the line VI--VI in FIG. 3,
FIG. 6 is a sectional view taken on the line II--II in FIG. 3,
FIG. 7 is a sectional front view of a modified embodiment of the axle
driving apparatus of the invention, in which the arrangement of the check
valves is changed,
FIG. 8 is a plan view of the same,
FIG. 9 is a sectional view taken on the line III--III in FIG. 7,
FIG. 10 is a sectional view taken on the line IV--IV in FIG. 7,
FIG. 11 is a perspective exploded view of the axle driving apparatus of the
invention,
FIG. 12 is a sectional front view of another modified embodiment of the
invention, in which a center section is fixed to the inner surface of the
bottom wall of a lower half casing,
FIG. 13 is a plan view of the FIG. 12 embodiment,
FIG. 14 is a sectional front view of a further modified embodiment of the
invention, in which a center section has three bolt-bores into which three
fixing bolts are inserted so that the center section is fixed therethrough
to the upper half casing,
FIG. 15 is a plan view of the FIG. 14 embodiment, and
FIG. 16 is a sectional plan view of the center section of FIG. 14.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, a light tractor loading thereon an engine E of a
vertical crank shaft is shown.
A pulley is fixed to the vertical crank shaft of the engine so that a
driving power is transmitted from the pulley through a belt to a pulley
fixed to a pump shaft 4 of a hydraulic pump P projecting upwardly from an
axle driving apparatus of the invention.
The tractor is provided at the front or under the body with a mower R or R'
to thereby mow a lawn.
The present invention relates to an axle driving apparatus and is
specifically described herein as driving axles 13 of the tractor.
Next, the axle driving apparatus will be detailed of its construction in
accordance with FIGS. 1 through 6.
A transmission casing of the axle driving apparatus is formed by upper and
lower half casings 1 and 2, respectively, both of the casings being
jointed to form one closed-type transmission casing.
Between the butt joint surfaces of the upper and lower half casings 1 and 2
are held bearings an parallel thereto, for the axles 13 and a counter
shaft 24; and a bearing 34 for one end of a motor shaft 5 (FIG. 3).
At the lower surface of the upper half casing 1 is formed a mounting
surface so that a center section 3 fixedly supporting the hydraulic pump P
and a hydraulic motor M is mountable to the mounting surface through bolts
39 inserted into bolt holes 3g from below.
In the state where the center section 3, fixing thereto the hydraulic motor
M and hydraulic pump P, is mounted to the lower surface of the upper half
casing 1, the lower half casing 2 is jointed from below with the lower
surface of the upper half casing 1 in a manner of closing the lower half
casing 2 and bolts are used to connect both the upper and lower half
casings 1 and 2.
The upper and lower half casings 1 and 2 are formed by aluminum die
casting, whereby parts subjected to mechanical processing are reduced to
lower the manufacturing cost.
The HST type transmission stored within the axle driving apparatus
comprises the hydraulic pump P, center section 3 and hydraulic motor M, so
that a pump mounting surface 3d formed on the center section 3 is parallel
to the axles 13 and a motor mounting surface 3e formed on the center
section 3 is perpendicular to the axles 13.
Pairs of crescent-shaped oil passages 3a' and 3b' and 3a" and 3b" are
formed at the pump mounting surface 3d and motor mounting surface 3e, the
pair of crescent-shaped oil passages 3a" and 3b" at the motor mounting
surface 3e and pair of crescent-shaped oil passages 3a' and 3b' at the
pump mounting surface 3d being connected to two oil passages 3a and 3b to
constitute a closed circuit or fluid path.
A cylinder block 10 for the hydraulic pump P is rotatably mounted on the
pump mounting surface 3d and pistons 12 are inserted vertically slidably
into a plurality of piston holes at the cylinder block 10 respectively.
When the pump shaft 4, supported by a bearing 31 at the upper half casing 1
and a spherical bush 32 at the pump mounting surface 3d, is rotated, the
cylinder block 10 and pistons 12 rotate.
A thrust bearing 15 abutting against the upper end of each piston is
changed at an angle by a swash plate 9, so that the discharge rate and
discharge direction of the hydraulic pump P are changed to supply the
discharged pressure oil from the oil passages 3a' and 3b' at the center
section 3 to the hydraulic motor M through the oil passages 3a and 3b.
As shown in FIG. 4, the swash plate 9 is changeable of its angle through a
positioning plate 6a in association with rotation of a speed change lever
shaft 6, a detent unit 20 for holding the neutral position of the speed
change lever shaft 6 being constituted in the upper half casing 1.
The detent unit 20 is fitted into a recess 6b at the positioning plate 6a,
thereby enabling the neutral position to be ensured.
As shown in FIGS. 2 and 3, a short-circuit valve 25 of slidable selector
valve for short-circuiting between the two oil passages 3a and 3b at the
discharge side and the return side is disposed, so that when the valve 25
is changed over to haul the body of tractor, generation of the state where
the hydraulic motor M side is driven to send the pressure oil toward the
hydraulic pump side can be avoided.
Reference numeral 7 designates a control for operating the short-circuit
valve 25.
The short-circuit valve 25 and control 7 are slidably operated to push, to
be disengageable, or pull, without engagement, in order to be controllable
in the abutting condition. Such construction enables simple assembly of
the apparatus.
Between the oil passages 3a and 3b at the center section 3 are interposed
check valves 26 and 27 to form an oil feed route 30, and between the check
valves 26 and 27 is bored an operating oil suction port 3c extending
downwardly.
In the lower end of operating oil suction port 3c is fitted an oil filter 8
formed of a spongy fine-porous material, the oil filter 8 contacting with
the lower half casing 2 so as to be held thereto.
Thus, the oil filter 8, operating oil suction port 3c and check valves 26
and 27 are provided to communicate with the oil passages 3a and 3b through
the check valves 26 and 27, whereby in a case where the hydraulic motor M
and hydraulic pump P operate and the operating oil leaks from the interior
of the closed circuit so as to decrease, the oil passage 3a or 3b
generates therein negative pressure so that lubricating oil in the casing
is taken in as the operating oil.
In addition, reference character 0 designates an oil or fluid level of
lubricating oil or fluid filled into the transmission casing (FIG. 2).
The pump mounting surface 3d at the center section 3 is somewhat larger in
its flat surface to also serve as the surface through which the center
section 3 is mounted to the lower surface of the upper half casing 1.
A cylinder block 11 is rotatably mounted onto the motor mounting surface 3e
at the center section 3, and pistons 14 are slidably fitted into a
plurality of piston holes at the cylinder block 11 and always abut at the
heads against a thrust bearing 16. In such construction, the pistons 14
push the thrust bearing 16 through the pressure oil from the oil passages
3a and 3b and slide down at the heads along the slanted surface of the
thrust bearing so as to generate a torque, thereby rotating the cylinder
block 11 and motor shaft 5.
The thrust bearing 16 is supported by an annular support 35 in relation of
being slanted at a predetermined angle, the annular support 35 being
fixedly sandwiched between the upper and lower half casings 1 and 2.
The motor shaft 5 is provided at one axial end journalled to the center
section 3 with a spherical bush 33 and at the other end with a spherical
bush 34, which are sandwiched between the upper and lower half casings 1
and 2.
A gear 17 is mounted on the motor shaft 5 and engages with a gear 21 on the
counter shaft 24, the gears 17 and 21 constituting the first deceleration
means (FIG. 3).
A small diameter gear 22 on the counter shaft 24 engages with a ring gear
23 at a differential gear unit D, which gives differential rotations to
drive the axles 13.
The small diameter gear 22 and ring gear 23 constitute the second
deceleration means.
A brake drum 18 is fixed to the foremost end of the motor shaft 5 and brake
shoes are expanded radially outwardly by a brake lever 19 to contact with
the brake drum 18, thereby exerting the braking action.
In FIG. 6, part of motor mounting surface 3e, against which the motor
casing 11 for the hydraulic motor M abuts, is shown.
Referring to FIGS. 7, 8, 9 and 10, a modified embodiment of the axle
driving apparatus of the invention will be described.
In the embodiment shown in FIGS. 2 and 3, the oil passages 3a and 3b and
supply oil passage 30 are provided at the same plane, but in this case,
the motor mounting surface 3e must separate with respect to the pump
mounting surface 3d, whereby the center section 3 cannot be compact to
that extent and also the casing becomes larger.
Therefore, in the embodiment shown in FIGS. 7 through 10, in order to
eliminate the above defects, the supply oil passage 30 is disposed to
overlap with the oil passages 3a and 3b in a range of thickness of the
lower portion of the center section 3 and below the oil passages 3a and
3b.
The supply oil passage 30 is bored to communicate at the upper half thereof
with the lower half in a manner of overlapping therewith. Hence, the oil
passage connecting both the oil passages 30 and 3a, 3b is not required,
thereby enabling the center section 3 to be made as small as possible in
thickness.
At the center of the supply oil passage 30 is open an operating oil suction
port 3c toward an oil filter 8 positioned below, and check valves 26 and
27 for opening or closing the communicating portion between the oil
passages 3a and 3b are interposed in the supply oil passage 30 in relation
of putting the operating oil suction port 3c between the check valves 26
and 27. Supply oil from the operating oil suction port 3c flows to the oil
passages 3a and 3b through the portion at the supply oil passage 30 where
the supply oil passes the check valves 26 and 27.
Thus, within the center section 3, the oil passages 3a and 3b, supply oil
passage 30 and oil filter 8 overlap with each other, whereby the motor
mounting surface 3e can approach the pump mounting surface 3d so as to
enable the center section 3 to be compact.
Next, explanation will be given on the embodiment in FIGS. 12 and 13.
In this embodiment, a center section 3 abuts from above against the inner
surface of the bottom wall of the lower half casing 2 and is fixed
thereto.
Bolts 39 for fixing the center section 3 also are inserted from above into
the bolt bores and screw with the lower half casing 2 respectively.
The center section 3 in this embodiment, as shown in FIG. 12, is about or
substantially L-like-shaped when viewed in section from the rear surface.
The pump mounting surface 3d is formed on the longer part of the L-shape,
while the motor mounting surface 3e is formed on the shorter part of the
L-shape, perpendicular to the pump mounting surface.
Other constructions of this embodiment are about the same as the aforesaid
embodiment.
Next, explanation will be given on the embodiment in FIGS. 14, 15 and 16.
In this embodiment, three bolt bores 3g for three bolts 39 for fixing the
center section 3 to the lower surface of the upper half casing 1 are
provided at a casing mounting surface on the center section 3, the three
bolts 39 fixing the center section 3 at the casing mounting surface to the
upper half casing 1.
The center section 3 and upper half casing 1 constitute material with
aluminum die casting, the mounting surfaces of both the members being not
applied with machining.
Rather than using four bolts 39 to fix the center section 3 in which, an
error in material may distort the section and prevent a tight fit.
In the present invention, three bolts 39 are inserted into three bolt bores
3g to fix the center section 3, thereby keeping all the bolts in good
tight conditions.
In the embodiment in FIGS. 14, 15 and 16, the pump mounting surface 3d is
not adjacent to the motor mounting surface 3e at the center section 3, but
rather is substantially level with the casing mounting surface near the
axle 13.
Oil passages 3a and 3b are bored from a pair of crescent-shaped oil
passages provided at the motor mounting surface 3e and extend in parallel
to the axles 13, oil passages 3m and 3n being bored from a pair of
crescent-shaped oil passages and extending perpendicularly to the axles
13, so that both oil passages 3m and 3a and 3n and 3b communicating with
each other in the center section 3.
The open ends of oil passages 3m and 3n are plugged and the plugs are
locked by projections formed at the bottom of the lower half casing 2
respectively.
Check valves 36 and 37 are provided at open ends of oil passages 3a and 3b,
valve levers 36b and 37b of which are connected to a leaf spring 38.
The valve levers 36b and 37b are open only in the direction of flowing oil
from the operating oil suction ports 3p and 3q into the oil passages 3a
and 3b, so that the check valves 36 and 37 flowing into the oil passages
3a and 3b the supply operating oil after passing the plate-like oil filter
8 discharges to the exterior the pressure oil in the oil passages 3a and
3b by pushing the valve levers 36b and 37b through the leaf spring 38
pushed by a control 7, thereby serving as the short circuit valves to
cause the free condition of hydraulic motor M.
As seen from the above discussion, the center section 3, carrying the
hydraulic pump P horizontally and the hydraulic motor M vertically, is
provided and contained within the transmission casing while carrying both
the pump P and motor M, whereby the operating oil, even when leaked from
the hydraulic pump P or hydraulic motor M, does not flow out to the
exterior. Also, since the oil passages are formed at the center section 3,
no piping is required in or out of the transmission casing.
The center section 3 is fixed to the upper half casing 1 or the lower half
casing 2, thereby being simple to support. Also, the pump shaft 4 and
motor shaft 5 are simple to support.
The pump mounting surface 3d and motor mounting surface 3e are disposed in
an L-like-shape and the center section 3 is about L-like-shaped when
viewed in section, so that the pump shaft 4 of input shaft is vertical and
the motor shaft 5 of output shaft is horizontal, thereby making the axle
driving apparatus compact without interposing the bevel gears, and the
power transmitting direction can be changed at an angle of 90.degree.,
thereby having advantages for the tractor loading a vertical shaft-output
shaft type engine.
The center section 3 is fixed to the lower side of the butt joint surface
of the upper half casing 1 so that the pump mounting surface 3d is level
with the mounting surface of the center section 3 to the upper half
casing, whereby the surfaces of the upper half casing 1, lower half casing
2 and center section 3 can be restricted to a minimum.
Three bores 3g for the three fixing bolts 39 through which the center
section 3 is fixed to the lower surface of the upper half casing 1 are
formed, so that when the mounting surfaces of center section 3 and of
upper half casing 1 are fixed as they are not flattened but cast, there is
no fear that a poor tightening condition is created on the center section
3.
The spherical bush 32 at the pump shaft 4 and spherical bush at the bearing
for the motor shaft 5 are used, so that even when the center section 3 is
mounted slantwise due to an assembly error or a machining error, a shift
of the pump shaft 4 or the motor shaft 5 is absorbable.
Also, the spherical bush is smaller in the size than the usual bearing,
whereby the bearing is disposable without interfering with the oil
passages bored at the center section.
Although several embodiments have been described, they are merely exemplary
of the invention and not to be construted as limiting, the invention being
defined solely by the appended claims.
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