Note: Descriptions are shown in the official language in which they were submitted.
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BEARING ARRANGEMENT FOR MARINE PROPULSION
DEVICE REVERSING TRANSMISSION
Backqround of the Invention
The invention relates to reversing
transmissions for marine propulsion devices, and, more
particularly, to bearing arrangements for such
reversing transmissions.
A typical marine propulsion device reversing
transmission includes forward and rearward bevel gears
which are in meshing engagement with a third bevel gear
driven by the engine, which are coaxial with the
propeller shaft, and which are selectively and
alternatively drivingly connectable to the propeller
shaft. The hub of each of the forward and rearward
bevel gears is rotatably supported by a bearing, such
as a roller bearing, located between the hub and the
gearcase. See, for example, U.S. Hagen Patent No.
3,919,964, which issued November 18, 1975.
The longevity of a reversing transmission
depends primarily upon how well the gears are aligned
and how well the gears are "squared up" relative to the
gearcase. Hub bearings are traditionally designed to
best support or square the gears under all possible
loads. Sometimes, under certain load conditions, the
gears are not properly squared. This can cause
premature failure of the reversing transmission.
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Attention is also directed to the following
U.S. Patents:
Armantrout 3,182,629 May 11, 1965
Shi~anckas 3,216,392 No~. 9, 1985
Alexander, Jr. 3,399,647 Sept. 3, 1968
Strang 3,556,040 Jan. 19, 1971
Blount 3,584,593 June 15, 1971
Langley 3,589,204 June 29, 1971
Shimanckas 3,818,855 June 25, 1974
Nossiter 3,826,219 July 30, 1974
McCormick 4,530,667 July 30, 1985
Taguchi 4,637,802 Jan. 20, 1987
Harada 4,689,027 Aug. 25, 1987
SummarY of the Invention
The invention provides a marine propulsion
device comprising a gearcase, a propeller shaft
supported by the gearcase for rotation about an axis
and adapted to support a propeller, a forwardly located
gear including a hub which is of constant diameter and
which is coaxial with the propeller shaft, first and
second axially adjacent elongated roller bearings
located between the hub and the gearcase and supporting
the hub for rotation about the axis, each of which
first and second bearings has opposite ends in bearing
engagement between said gearcase and said hub, and
means for drivingly connecting the bevel gear to the
propeller shaft.
In one embodiment, the first bearing has a
first length in the direction of the axis, and the
second bearing has a second length in the direction of
the axis, the second length being greater than the
first length.
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In one embodiment, the hub has an end
supporting a plurality of gear teeth, and the second
bearing is located adjacent the end.
In one embodiment, the bearings provide only
radial support for the hub.
In one embodiment, the bearings are
anti-friction bearings.
In one embodiment, the first and second
bearings have substantially equal lengths in the
direction of the axis.
In one embodiment, the second bearing is
larger than the first bearing.
In one embodiment, the hub has an end
supporting a plurality of gear teeth, and the second
bearing is located adjacent the end.
The invention also provides a marine
propulsion device comprising a gearcase, a propeller
shaft supported by the gearcase for rotation about an
axis and adapted to support a propeller, a forwardly
located bevel gear including a first hub which is of
constant diameter and which is coaxial with the
propeller shaftl first and second axially ad~acent
bearings located between the first hub and the gearcase
and supporting the forward bevel gear for rotation
about the axis, each of which first and second bearings
has opposite ends in bearing engagement between the
gearcase and the hub, a rearwardly located bevel gear
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including a second hub which is of constant diameter
and which is coaxial with the propeller shaft, bearing
means located between the second hub and the gearcase
and supporting the rearward bevel gear for rotation
about the axis, and means for selectively and
alternatively drivingly connecting the forward and
rearward bevel gears to the propeller shaft.
The invention also provides a marine
propulsion device comprising an engine, a gearcase, a
propeller shaft supported by the gearcase for rotation
about an axis and adapted to support a propeller, a
forwardly located bevel gear including a first hub
which is of constant diameter and which is coaxial with
the propeller shaft, first and second axially adjacent
bearings located between the first hub and the gearcase
and supporting the forward bevel gear for rotation
about the axis, the first bearing having a first length
in the direction of the axis, and the second bearing
having a second length in the direction of the axis,
the second length being greater than the first length,
each of the first and second bearings having opposite
ends in bearing engagement between the g0arcase and the
hub, a rearwardly located bevel gear including a second
hub coaxial with the propeller shaft, bearing means
located between the second hub and the gearcase and
supporting the rearward bevel gear for rotation about
the axis, a third bevel gear
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drivingly engaging both of the forward and rearward
bevel gears, a drive shaft drivingly connecting the
engine to the third bevel gear, and means for
selectively and alternatively drivingly connecting the
forward and rearward bevel gears to the propeller
shaft.
A principal feature of the invention is the
provision of a reversing transmission wherein the hub
of the forward bevel gear is supported by a pair of
axially adjacent roller bearings. This arrangement has
at least two advantages. First, the two bearings
square the gear better than the single bearing of known
prior arrangements, because the gear is supported at
two "points" rather than one and is therefore less able
to cock relative to the propeller shaft. Second, the
two bearings permit the bearing load capacity to be
increased without the problem of roller skewing that
might occur with a single bearing of similar load
capacity and axial length.
Another principal feature of the invention
is the provision of an arrangement as described above
wherein the bearings have unequal lengths. This
permits the use of an infinite number of combinations
of bearing sizes for any required overall length. (If
the bearings have equal lengths, only one bearing size
can be used for any required overall length.) This
also permits the use of a longer bearing closest to the
gear teeth, where the greater load is supported.
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Another principal feature of the
invention is the provision of an arrangement as
described above wherein the bearing closest to the
gear teeth has a greater radial thickness. This
arrangement also provides greater support for the
gear where it is most needed, i.e., near the gear
teeth.
Another principal feature of the
invention is the provision of an arrangement as
described above wherein the bearings are
substantially identical, i.e., have equal lengths and
eQual radial thicknesses. This provides at least two
advantages. First, a person assembling the reversing
transmission cannot arrange the bearings improperly
by putting the smaller bearing closest to the gear
teeth. Second, the manufacturer of the reversing
transmission can stock a single bearing size, rather
than two bearing sizes.
Other features and advantages of the
invention will become apparent to those skilled in
the art upon review of the following detailed
description, claims and drawings.
Description of the Drawings
Figure 1 is a side elevational view of
a marine propulsion device embodying the invention
and including a gearcase.
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Figure 2 is an enlarged, partial,
sectional view of the gearcase.
Figure 3 is a partial view which is
similar to Fig. 2 and which illustrates an
alternative embodiment of the invention.
Before one embodiment of the invention
is explained in detail, it is to be understood that
the invention is not limited in its application to
the details of construction and the arrangements of
components set forth in the following description or
illustrated in the drawings. The invention is
capable of other embodiments and of being practiced
or being carried out in various ways. Also, it is to
be understood that the phraseology and terminology
used herein is for the purpose of description and
should not be re~arded as limiting.
Description of the Preferred Embodiment
A marine propulsion device 10 embodying
the invention is illustrated in the drawings. While
the illustrated marine propulsion device 10 is an- ~~ 20 outboard motor, it should be understood that the
invention is also applicable to other types of marine
propulsion devices, such as stern drive units.
The marine propulsion device 10
comprises a mounting assembly 12. While various
suitable mounting assemblies can be employed, in the
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preferred embodiment, the mounting assembly 12
includes a transom bracket 14 fixedly mounted on the
transom 16 of a boat 18. The mounting assembly 12
also includes a swivel bracket 20 mounted on the
transom bracket 14 for pivotal movement relative
thereto about a generally horizontal tilt axis 22.
The marine propulsion device 10 also
comprises a propulsion unit 24 mounted on the swivel
bracket 20 for pivotal movement relative thereto
about a generally vertical steering axis 26. The
propulsion unit 24 includes a lower unit 28
comprising a gearcase 30, a propeller shaft 32
supported by the gearcase 30 for rotation about an
axis 34, and a propeller 36 mounted on the propeller
shaft 32 for rotation therewith. The propulsion unit
24 also includes an engine 38 mounted on the lower
unit 28, and a drive shaft 40 including an upper end
driven by the engine 38 and a lower end having
thereon a bevel gear 42.
The propulsion unit 24 also includes a
reversing transmission 44 for connecting the bevel
gear 42 to the propeller shaft 32. The reverslng
transmission 44 includes forward and rearward bevel
gears 46 and 48, respectively, mounted in spaced
relation axially of the propeller shaft 32 and for
rotation coaxially with and independently of the
propeller shaft 32. The bevel gears 46 and 48
include respective sleeve-like hubs 50 and 52
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surrounding the propeller shaft 32. Each of the hubs
50 and 52 includes a first or inner end supporting a
plurality of teeth which are in meshing engagement
with the bevel gear 42, and each of the hubs 50 and
52 also includes a second or outer end opposite the
first end.
The reversing transmission 44 also
includes radial bearing means 54 located between the
hub 52 and the gearcase 30 and supporting the hub 52
for rotation about the axis 34. The reversing
transmission 44 also includes a thrust bearing 56
located between the rearward bevel gear 48 and the
gearcase 30.
The reversing transmission 44 also
includes first and second or forward and rearward
a~ially adjacent, radial, anti-friction bearings 58
and 60, respectively, located between the hub 50 and
the gearcase 30 and supporting the hub 50 for
rotation about the axis 34. While the illustrated
bearings 58 and 60 are roller bearings, it should be
understood that other types of anti-friction
bearings, such as ball bearings or tapered roller
bearings, can be employed. The forward bearing 58 is
located adjacent the forward or outer end of the hub
S0, and the rearward bearing 60 is located adjacent
the inner or rearward end of the hub S0. In the
preferred embodiment, the bearings 58 and 60 do not
have the same length. Furthermore, in the preferred
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embodiment, the forward bearing 58 has a first length
in the direction of the axis 34, and the rearward
bearing 60 has a second length in the direction of
the axis, the second length being greater than the
first length. It is desirable to have the rearward
bearinq 60 be the longer bearing because, since the
teeth of the forward bevel gear 46 are supported by
the rearward end of the hub 50, the rearward bearing
60 must support a greater load than the forward
bearing 58.
In the preferred embodiment, the roller
bearings 58 and 60 provide only radial support for
the hub 50, and the reversing transmission 44 also
includes a thrust bearing 62 located between the
gearcase 30 and the forward bevel gear 46 and
providing axial support for the forward bevel gear 46.
The reversing transmission 44 also
includes a roller bearing 63 located between the
forward bevel gear 46 and the propeller shaft 32.
The bearing 63 supports the propeller shaft 32 for
rotation about the axis 44 under certain drive
conditions (explained below). In alternative
embodiments (not shown), the roller bearing 63 can be
replaced by a bushing. ~ecause the propeller shaft
32 is supported by bearings (not shown) located
rearwardly of the rearward bevel gear 48, the
reversing transmission 44 does not include a bearing
or bushing between the rearward gear 48 and the
propeller shaft 32.
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The reversing transmission 44 also
includes a clutch dog 64 which is carried on the
propeller shaft 32 intermediate the bevel gears 46
and 48 for common rotation with the propeller shaft
32, and for movement axially of the propeller shaft
32 between a central or neutral position (shown in
Figure 2) wherein the clutch dog 6~ is out of
engagement with the bevel gears 46 and 48, a forward
drive position (not shown) wherein the clutch dog 64
is in driven rotary engagement with drive lugs on the
forward bevel gear 46, and a rearward drive position
(not shown) wherein the clutch dog 64 is in driven
rotary engagement with drive lugs on the rearward
bevel gear 48.
The reversing transmission also
includes a shift actuator 66 which is housed in an
axial bore 67 in the propeller shaft 32, which is
moveable axially of the propeller shaft 32 and which
is connected to the clutch dog 64 for moving the
clutch dog 64 between the forward drive, neutral, and
rearward drive positions. In the illustrated
construction, the actuator 66 is connected to the
clutch dog 64 by a transverse pin 68 which extends
through diametrically opposed, elongated slots 70 in
the propeller shaft 32. The reversing transmission
44 also includes a conventional shift linkage 72
connected to the forward end of the shift actuator 66
for moving the shift actuator 66 axially of the
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propeller shaft 32. For an example of a suitable
shift linkage, see U.S. Patent No. 3,919,964.
When the clutch dog 64 is in the
neutral position, the propeller shaft 32 is out of
engagement with both bevel gears 46 and 48, and the
propeller shaft 32 is rotatably supported by the
roller bearing 63 and by the bearings (not shown)
behind the rearward bevel gear 48. When the clutch
dog 64 is in the forward drive position, the
propeller shaft 32 is in driven engagement with the
forward bevel gear 46, and the propeller shaft 32 is
rotatably supported by the bearings 58 and 60 (which
support the forward bevel gear 46) and by the
bearings (not shown) behind the rearward bevel gear
48. When the clutch dog 64 is in the rearward drive
position, the propeller shaft 32 is in driven
engagement with the rearward bevel gear 48, and the
propeller shaft 32 is rotatably supported by the
bearing 63 and by the bearings (not shown) behind the
rearward bevel gear 48.
An alternative embodiment of the
invention is illustrated in Figure 3. Except as
described below, the alternative embodiment is
identical to the preferred embodiment, and common
elements have been given the same reference numerals.
In the alternative embodiment, the
bearings 58 and 60 have equal lengths, and the
rearward bearing 60 is larger than the forward
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bearing 58, i.e., has a greater radial thickness than
the forward bearing 58. While a greater radial
thickness can be achieved either with a smaller inner
diameter or a larger outer diameter, or both, in the
illustrated construction, the rearward bearing 60 has
a larger outer diameter than the forward bearing 58.
The larger size of tne rearward bearing 60 permits it
to support a greater load.
In a second alternative embodiment (not
shown), the bearings S8 and 60 are substantially
identical, i.e., have equal lengths and equal radial
thickness.
In initial testing, the use of two
radial bearings to support the bevel gear hub 50 was
found to significantly improve clutch dog and forward
bevel gear drive lug life, to significantly reduce
the propeller thrust required to square up the
forward bevel gear 46, and to significantly improve
alignment of the forward bevel gear 46.
Various features of the invention are
set forth in the following claims.
