Note: Descriptions are shown in the official language in which they were submitted.
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BACT~GP~OUND OF T~R I~IVE~`~TION
This invention relates to a tor~ue transfer gear assembly
for supply of drive power to either 2 or ~ wheels of a vehicle and
more particularly to a gear transfer unit having an input shaft
and two output shafts with different angular output orientations
to permit optimization of orienta-tion of the unit and a-t the same
time facilitating ready aligned connection to the front and rear
drive shafts of the vehicle.
Torque txansfer mechanisms for supply of drive power to
four wheels of a vehicle are usually connected to the vehicle
transmission which in turn is connected to be driven by the vehicle
engine. The torque transfer unit is thus an e~tension of the engine
and transmission drive train and its location, usually under the
driver's compar~l~ent, is limited in range by the important consid-
erations of effectiveness and efficiencv of operation of the powersupply train and need for accommadation to the presence of other
adjacent automotive components such as exhaust system components.
~hen the engine is located over the front wheels of the vehicle,
as is generallv the case, the engine and its connected transmission
and torque transfer units are angled downwardly in alignment with
-'he rear drive shaft leading to the rear wheel differential.
Customarily the front and rear outpu-t shafts of the transfer uni-t
such as a conventional five gear transfer unit, however, are
parallel with the input shaft, and the front wheel output shaft is
therefore usually no-t oriented optimally for ready connection with
the front wheel drive shaft. ~n other words, the transfer unit in
connection with the engine and transmission can be aligned in
straight line relation with the rear wheel drive shaft, but this
does not place the front output shaft of the transfer unit in
proper orientation Eor straight line connection with the Eront
drive shaft to the fron-t differential. This inabili-ty to establish
straight align~ent with the front drive shaft can be compensated
for to a degree by special joints and, in some cases to a degree by
compound doule angular joints, but such joints are usually less
`',l~,
than desirable because of their comple~ity in mechanics and
dvnamics of operation, need for care and costliness.
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SU~MARY OF THE INVENTION
It is therefore an object of the present invention to
provide a torque transfer gear assembly unit for four wheel drive
operation of an automotive vehicle which can be designed with output
shafts having orientations which allow angular lateral orientation
of the unit itself as well as ready aligned connection to the front
and rear wheel drive shafts without need for other than simple
ordinary connecting joints.
This and other objects of the invention are accomplished by
the present invention by providing in a tor~ue transfer unit having
constant mesh gearing, cross axised helical gearing to allow at least
one of the output shafts to be set at a proper angle for optimization
of drive shaft joint connections. The constant mesh gearing in which
the invention is herein exempliEied comprises an input gear set
1~ associated supplied with power by an input shaft and an output gear
set associated supplying power to both a rear wheel outpu-t shaft and
a front wheel output shaft. In the preferred embodiment of the
invention an intermediate shaft acts in a sense as a power path
shifting shaft permitting selective connection to both the rear and
front wheel output shafts. The front output shaft is driven by a
front output cross axised helical gear mated with a gear on the
intermediate shaft and driven as one of the ou-tput set of gears. The
angular cut of teeth of the helical gear permits a corresponding
angular orientation of the front output shaft relative to the input
shaft to allow establishment of a lower angle connection with the
front drive shaft than is possible with an output shaft parallel to
the input shaft. Ordinary connecting joint members such as a
conventional cardan joint at each end of the drive shaft can be
utilized to complete the power connection between the transfer unit
and front wheel differential. As another embodiment of the invention,
both the front output and the intermediate shafts can be provided
a cross axised orientation to each other as well as having a cross
axised relation between the intermediate shaft and the input shaft,
thereby, distributing and increasing the possible fron-t output shaft
angle relative to the input shaft. A greater design flexibility
is thus provided in placement and connection of the unit to the rear
and front drive shafts of the torque transfer unit.
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~RIEF DESC~IPTION OF THR DRAWINGS
-
Figure 1 is a schematic side elevational view of a vehicle
illustrating the conventional alignment and connection of a
transfer unit in the power train for supply o:E power to both -the
rear and front wheels;
Figure 2 is an enlarged schematic view of a portion of a
vehicle drive train illustrating the transfer unit of the present
invention with straight line joint connections between the rear
and front output shafts with the rear and front drive shafts,
resnectively;
Figure 3 is a hori~ontal cross sectional view of the gear
assembl~ of the tor~ue transfer unit of Figure 2 illustrating how
the invention can be incorporated in a constant mesh five gear
torque transfer arrangement to efCect a straight line alignmen-t of
the unit with drive shalts for 2 and 4 wheel drive modes of the
vehicle;
Figure 4 is an end elevational view of an end of the gear
case for the transfer uni-t of Figure 3 illustrating the general
angular orientation of the unit relative to ground level of the
vehicle;
Figure 5 is a schematic illustration of the five gear
assembly of Figure 3 and;
Figure 6 is a sche~atic illustration of the five gear
assemhly of another embodiment of the invention in which the total
angle of the front output shaft relative to the input shaft is
provided by angular orientation of both the intermediate and front
output shafts rela-tive to the input shaf-t.
BEST MODE OF CARRYING OUT THE INVENTION
Referring to the drawings in greater detail, Figure 1
illustrates a four wheeled vehicle 10 having a conventional
straight alignment of drive components from the engine 11 to the
rear wheel diffe~ential through the transmission 12 and the
transfer unit 14 which are connected hy way of a connecting joint
15 to a rear drive shaft 16 joined to the differential 18 hy a
connection joint 17 to drive the rear wheels 19. Since the rear
wheels are at a lower level than the engine level, this alignment
is generally downward toward the rear of the vehicle. The rear
output shaft of the transfer unit 14 is thus also inclined
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generally downwardly. This causes the front output shaft extending
forward from the conventional geared transfer uni-t and which is
usually para]lel -to the rear OUtpllt shaft to have a generally upward
inclination. In view of this upward inclina-tion of the front output
shaft, an angular joint 25 must be provided for connection with the
drive shaft 26 extending downwardly therefrom to the front differ-
ential 28 which has a joint connection 27 at its other end to drive
the front wheels 29.
Beside the front output shaft of the transfer unit 14 being
misaligned and requiring an angular connection 25 to the front drive
shaft 26, another aspect of this alignment arrangement is that the
transex unit 14 is recruired to be oriented with a la-terally downwarcl
angle from the level of the input and rear output shaft to the lower
level of the front output shaft as illustrated in Figure 4 to permit
adjacent accommodation oE other components on the underside of the
vehicle such as exhaust system components.
Figure 2 is a schematic illustration of the -transmission
unit 12 having a straight line relation with a torque transfer unit
24 of the present invention wherein the power output of the unit 24
to the front wheel differential 28 can be supplied in straight
alignment with an angularlv oriented fron-t drive shaft 32, thus
eliminating need for the otherwise more complex angular connection
required in the angular connecting arrangement illustred in Figure 1.
Figure 3 is a cross sectional view of the torque transfer
unit 24 showing interior de-tails of the gear assembly of this pre-
ferred form of the invention illustrated schematically in Figure 2.
An input drive shaft 20 supplies torque power to the associated gear
assembly for driving the rear and front wheel output shafts, 30 and
32, respectively. The input drive shaft 20 is axially aligned with
the rear output shaft 30, each shaft being rotatable independent
of the other, but inter-associated by providing the input shaft 20
with a reduced diameter end portion extending coa~ially into a
hollowed end portion oE the rear output shaft 30. A small gap be-
tween the mated coaxial ends of the shaEts provide a space for a
needle bearing 37 to provide mutual support for the two shafts 20
and 30.
Two sets of constant mesh gears make up the torque transfer
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gear assembly, namely an input gear set and an output gear set. The
input gear set includes an input gear 40 in constant mesh with a
larger diameter low speed gear 45. The input gear 40 is fixed on
input shaft 20 and can be formed integrally with the input shaft
as shown, to provide a solid constantly aligned combination. The
low speed gear 45 is mounted for rotation on roller bearings on an
intermediate shaft 47.
The output gear set includes a rear drive gear 50 in constant
mesh relation with a smaller intermediate gear 55 which in turn is
in constant mesh with the .Eront output gear 57 generally of the same
size as the rear drive gear 50 and angularly oriented with its
output shaft extending in a generally downward direction, as :Eurther
explained hereinafter. The rear drive gear 50 is supported in
rotational relation on the rear output shaft 30 while the
intermediate gear 55 is rotatably mounted on roller bearings on the
intermediate shaft 47 and the front drive gear 57 is fixed in splined
relation on the ball bearing supported front output shaft 32.
The drive power paths through the gear assembly are
selectively changed by lateral shifting of internally splined collars
60 and 52 on and between splines 48 and 68 at the confronting
exterior ends of the input and rear output shafts 20 and 30,
respectively, splines 51 on the exterior of a hub of the rear drive
gear 50 and splines 46 and 56 on confronting hubs of the low speed
gear 45 and the intermediate gear 55 respectively, both on the
intermediate shaft 47.
A single manually controlled laterally moveable fork (not
shown) engages and moves both the high and low speed collars 60 and
52, respectively, into selected positions for desired operating modes
of the transfer unit 24. Two wheel high, four wheel high, neutral
and four wheel low speed modes can thus be selec-ted by progressive
step by step repositioning of the collars 60 and 52 to the right
Erom their pOSitiOII in Figure 3. The collars as shown in Figure 3
are in the two wheel high speed mode in that the internal splines
of collar 60 engage splines 48 of the input gear in bridging relation
with splines 68 of the rear output shaft 30 while the low speed
collar 52 is in inactive position on the splines 42 of the hub of
the low speed gear 45. The input shaft 20 and rear output shaft
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30 are thus connected together in straight line relation for direct
drive of the rear wheels.
Upon shift of the collars 60 and 52 step to -the right in
unison, the splines 51 on the hub of the rear drive gear 50 are
additionally engaged, thus causing the three output gears 50, 55 and
57 to be driven by the input shaft 20 through the rear output shaft
30 and causing the angularly oriented front output shaft 32 to be
driven in addition to the rear output shaft 30. Since the rear
output gear 50 and the front output gear 57 have the same effective
size, both the rear and front output shafts are driven at the same
rotational speeds in the four wheel high speed driving mode.
Upon movement of the collars 60 and 52 another step to the
right in Figure 3, the collar 60 is disengaged Erom the splines
48 of input gear 40 and collar 52 still remains in an inactive
position on splines 46 of the low speed gear 45. The assembly thus
is placed in a neutral mode in which neither the rear or front drive
shafts, 30 and 32 respectively, are driven.
Upon moving -the collars 60 and 52 still another step to the
right in Figure 3, the splines 56 of the intermediate gear 55 are
brought into bridging relation with the splines 46 of the low speed
input gear 45. Since the slow speed gear 45 has a larger diameter
than the input gear 40 with which it is in constan-t mesh, its
rotational speed is less than that of the input gear and
correspondingly, the rotational speed of the intermediate gear 55
~5 of the output set of gears is driven at a slower rotational speed
than that of the input shaft 20. In this mode the intermediate gear
55 drives both the rear output gear 50 and the output shaft 30 as
well as the angularly mated front output gear 57 and the
corresponding angularly oriented front output shaft 32. The output
shafts 30 and 32 are driven at rotational speeds less than the speed
of the input shaf-t 20, both because of the lower speed of the gear
55 and the fact that the output gears 50 and 57 are larger in
diameter than the intermediate gear 55.
Referring now more specifically to the invention as embodied
in the relation of the front output shaft 32, supported in the front
and the rear bearings 33 and 34, respectively, the front output gear
57 is a frustum shaped conical gear to permit the downward angular
orientation of the front output shaft 32. In addition, the teeth of
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the gear 57 are provided a cross cut or helical orientation which
permits the non-intersectin~ cross axised orientation of the shaft
32 extending outside the plane Oc the shafts 20, 30 and 47 to
produce the desired straight line connection of the output shaft 32
with the front drive shaft 26 extending to the front differerltial
28 of the vehicle 10. In other words, because of the required
angular disposition of the torque unit 24 in the vehicle relative
to the ground level, the rear output shaft 30 and front output shaft
32 are laterallv separated and at dlfferent levels from ground level.
Ordinary bevel gears thus are not ade~uate to provide the front
output shaft 32 with the compound angled orientation desired for
alignment. It has been found that the combination of both a frustum
shape for the gear and helical teeth will provide the required cross
axised orientation of shaft 32 for the desired straight line
]5 connection with the drive shaft 26.
The helical cut teeth of the gear 57 ~ay be provided an
angle to per~it its mating with axis-parallel teeth of spur gear
forms of the rear output and intermediate gears 50 and 55,
respectively. To provide a smoother and quieter operation of the
2n gears, however, the rear output and inter~ediate ~ears can also be
provided with matching helical or cross cut teeth having sliahtly
different angled helical teeth Crom the front output gear 57 to
accomplish the angular orientation of the gears and front output shaft
32 on which it is mounted. Such cross cut or helical gear teeth
provide the additional beneficial results in the form of less
vibrational and quieter operation in comparison to spur gears for the
rear output and intermediate gears 50 and 55, respectively.
Figure 5 illustrates schematically the aear assembl~v of
Fi~ure 3 and represents in plan view both the lateral and vertical
3n displacement of the output end of the front output shaft 32 compared
to the parallel relation of the parallel input, rear output and
intermediate shafts 20, 30 and 47, respectivel~.
Figure 6 illustrates schematically another embodiment of the
gear assembly of this invention wherein both the intermediate and
front output shafts 47 and 3~, respectively, have cross axised
orientations in lines non-intersecting relative to each other as
well as to the associated input and rear output shafts 20 and 30,
respectively. A constant mesh input set of gears in this assembly
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include an input gear 140 and a low speed gear 145. A constant mesh
output set of gears include a rear output gear 150, an intermediate
gear 155 on the intermediate shaft 47 and a front output gear 157
on the front output shaft 32. The total angular difference is
orientation or displacement of the output end of the front output
shaft 32 both downward and laterally from parallelism with the input
shaft 20 in this embodiment is distributed or shared by the
cumulative angular displacement of the intermediate shaft 47 relative
to the input shaft 20. This sharing of the total angle of the
output shaft 32 by an angular intermediate shaft 47 reduces the angle
from shaft to shaft to provide the desired front output shaft angle
and simpifies tooling for manufacture of the angular toothed gears.
The low speed gear ~45 and output gears 155 and 157 are conical
gears of frustum shape and in veiw of the compound non-intersecting
cross axised angular orientation of the intermediate shaft 47 and
front output shaft 32 relative to each other and relative to the
input shaft 20, they are produced with angular helical cut gear
teeth matching the needs for the shaft orientations desired.
The range of selection of angular displacement of the front
output shaft relative to the axis of the rear output shaft in the
preferred embodiment represented in Figures 2 to 5 is from 3 degrees
to 25 degrees. When the angular displacement from the rear output
shaft is to be about 15 degrees and over, however, the embodiment
of Figure 6 is preferred in which case a maximum of 30 degree
displacement of the front output shaft relative to the rear output
shaft is possible with a 15 degree angle of the intermediate shaft
axis relative to the rear output shaft.
In view of the foregoing it will be understood that
variations of the invention can be provided within the broad scope
of principles embodied therein. Thus while particular preferred
embodiments have been shown and described, it is intended by the
appended claims to cover all such modifications which fall within
the true spirit and scope of the invention.
