Thrust bearing arrangement for marine outboard drives

A marine outboard drive and more particularly to two embodiments of improved transmission and propeller shaft thrust taking arrangements for the lower unit. In each embodiment, the forward and reverse driving thrusts are transmitted independently to the lower unit housing. In one embodiment, a single thrust flange transmits the thrust from the propeller shaft to both of the thrust bearings and in the other embodiment, the thrust is transmitted to the thrust bearings on opposite sides of the forward, reverse transmission for axially separating the driving thrusts from each other.

BACKGROUND OF THE INVENTION 
This invention relates to a thrust bearing arrangement for the propeller 
shaft of marine outboard drives and more particularly to an improved 
thrust bearing arrangement. 
In marine outboard drives, be they either the lower unit of an outboard 
motor or the lower unit of the outboard portion of an inboard/outboard 
drive, it is the normal practice to embody a selectively operable forward, 
neutral and reverse transmission. As a result, the propeller shaft must be 
capable of transmitting both forward and reverse driving thrusts to the 
lower unit. Due to the relatively compact nature of marine outboard 
drives, this has presented certain problems in providing adequate thrust 
bearing arrangements and yet thrust bearing arrangements that will provide 
long life and good serviceability. 
In one type of thrust bearing arrangement for such marine outboard drives, 
it has been the practice to employ a single thrust flange on the propeller 
shaft and a pair of oppositely disposed thrust bearings that cooperate 
with this flange so as to take both forward and reverse driving thrusts. 
With the prior art constructions of the type described, the thrust 
bearings have been held between a pair of bearing housings which are, in 
turn, held in engagement with the thrust bearing and flange by supporting 
bolts or bolt and nut assemblies. Although this arrangement provides a 
relatively compact configuration, the reverse loadings on the propeller 
shaft tend to cause the bolt and nut assemblies to work loose and the 
thrust bearings will become loose and worn. 
It is, therefore, a principal object of this invention to provide an 
improved thrust bearing arrangement for a marine outboard drive. 
It is a further object of this invention to provide an improved thrust 
bearing arrangement for marine outboard drives wherein the thrusts are 
transmitted by the forward and reverse thrust bearings directly to the 
lower unit housing and independently of each other. The term 
"independently of each other" is used herein to mean that the thrust from 
the individual thrust bearings is transmitted to the lower unit housing 
without the thrusts from both bearings having to pass through a common 
element. 
Although there are some advantages in connection with the use of only a 
single thrust flange on the propeller shaft, such a configuration locates 
both the forward and reverse driving thrusts in the same area of the lower 
unit housing. Certain advantages may be obtained if the respective driving 
thrusts are confined to spaced apart areas of the lower unit housing. 
It is, therefore, a still further object of this invention to provide a 
thrust bearing arrangement for a marine outboard drive wherein forward and 
reverse thrusts are transmitted to the lower unit housing at axially 
spaced apart locations. 
In normal outboard motors or outboard drives, the forwardly disposed gear 
of the forward, neutral, reverse transmission is the forward driving gear 
and the forward driving thrusts may be transmitted directly from it to the 
lower unit housing. However, where there are twin outboard drives, it is 
the practice to employ drive shafts that drive in the same directions. As 
a result, the added outboard drive is operated so that its rearwardly 
disposed gear is the forward drive gear and a different thrust taking 
arrangement must be provided. One way in which this may be done is by 
providing a splined connection between the transmission output shaft and 
the propeller shaft so that the thrusts may be taken directly by the 
propeller shaft rather than by the gears of the transmission. This also 
has the advantage of reducing the thrusts which are exerted from this gear 
to the driving bevel gear of the transmission when the rear gear is the 
forward drive gear. This problem does not exist when the front gear is the 
forward drive gear. 
It is, therefore, yet another object of this invention to provide an 
improved thrust taking arrangement for the added outboard drive of a twin 
outboard arrangement. 
SUMMARY OF THE INVENTION 
A first feature of this invention is adapted to be embodied in a thrust 
bearing arrangement for the propeller shaft of a marine outboard drive 
that comprises a lower unit housing, a drive shaft supported for rotation 
with the lower unit housing, a propeller shaft and transmission means for 
selectively driving the propeller shaft in forward and reverse directions 
from the drive shaft. In accordance with this feature of the invention, a 
first thrust bearing is provided for taking driving thrusts in one 
direction from the propeller shaft and a second thrust bearing is provided 
for taking the driving thrusts in the opposite direction from the 
propeller shaft. Means are provided for transmitting the driving thrusts 
from the first and second thrust bearings to the lower unit housing 
independently of each other. 
Another feature of the invention is adapted to be embodied also in a thrust 
bearing arrangement for the propeller shaft of a marine outboard drive of 
the type as described in the preceding paragraph having the lower unit 
housing, the drive shaft, the propeller shaft and the selective forward 
and reverse transmission. In accordance with this embodiment of the 
invention, a first thrust bearing is provided between the propeller shaft 
and the lower unit housing for the taking the driving thrust in one 
direction and on one side of the forward, reverse transmission. A second 
thrust bearing is provided for transmitting the driving thrusts from the 
propeller shaft to the lower unit housing in the opposite direction and on 
the opposite axial side of the forward, reverse transmission.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1, an outboard motor constructed in accordance with 
an embodiment of the invention is identified generally by the reference 
numeral 11 and is shown primarily in phantom. Although the invention is 
described in conjunction with an outboard motor, the invention relates to 
the final drive unit and specifically the lower unit and, accordingly, the 
invention may be practiced equally as well with the outboard drive unit of 
an inboard/outboard arrangement. The outboard motor 11 is particularly 
adapted for use as one of the two units of a twin outboard drive. The 
motor 11 is particularly adapted for use as the additional motor wherein 
the input or drive shaft rotates in the same direction as a conventional 
motor but wherein the propeller shaft rotates in an opposite direction and 
has a propeller that is of an opposite hand so as to balance the driving 
thrust. 
The outboard motor 11 includes a power head 12 including an internal 
combustion engine and a surrounding protective cowling. The engine of the 
power head 12 drives a vertically disposed drive shaft (to be described) 
that extends through a drive shaft housing 13 and terminates within a 
lower unit 14. Contained within the lower unit 14 is a transmission 
mechanism which will now be described by particular reference to FIGS. 2 
through 4. 
The engine driven drive shaft previously referred to is identified by the 
reference numeral 15 and has a driving bevel gear 16 affixed to its lower 
end for simultaneous rotation with the drive shaft 15. A pair of driven 
bevel gears 17 and 18 are in mesh with diametrically opposite sides of the 
driving bevel gear 16 so that the driven gears 17 and 18 will rotate in 
opposite directions upon rotation of the driving gear 16. 
The driven bevel gear 17 has its hub portion rotatably journaled by means 
of a tapered roller thrust bearing 19 which is, in turn, carried in a 
bearing carrier 21. The bearing carrier 21 is held in position within an 
internal cavity of the lower unit housing 14 by means including a 
retaining nut 22. The opposite end of the thrust bearing 19 and 
specifically its outer race is engaged with a thrust stop 23 that is 
affixed between the bearing carrier 21 and the housing of the lower unit 
14. 
The driven bevel gear 18 has its hub portion journaled in the housing of 
the lower unit 14 by means of a roller bearing assembly 24. The driven 
gears 17 and 18, in turn, rotatably journal an intermediate shaft 25 by 
means of axially spaced needle bearings 26 and 27, respectively. The 
intermediate shaft 25 has a splined rear end 28 which is received within 
an internally splined opening 29 formed in an enlarged portion of a 
propeller shaft 31. The propeller shaft 31 is journaled within the bearing 
carrier 21 by means of a pair of axially spaced needle bearings 32 and 33. 
Because of the use of the two axially spaced bearing assemblies 32 and 33, 
the propeller shaft 31 will be rigidly held and not in a cantilevered 
manner as with certain prior art constructions. In addition, the needle 
bearing 32 engages the larger diameter portion of the propeller shaft 31 
that is formed with the internal splines 29 so as to provide a good load 
bearing capability. 
A propeller 34 is affixed to the exposed rear end of the propeller shaft 31 
by means of a torsionally resilient coupling 35. The normal direction of 
rotation of the propeller shaft 31 for forward motion is the opposite as 
that of a conventional outboard motor because of the fact that the motor 
11 is designed as the added non-conventional unit of a twin outboard 
drive. For that reason, the propeller 34 has an opposite hand to that of 
the conventional propellers. In order to drive the propeller shaft 31 in 
such a counter direction, the gear 17 functions as the forward drive gear 
while in a conventional outboard drive, the drive gear 18 comprises the 
forward drive gear. Since the gear 17 is the forward drive gear, some 
arrangement should be provided so as to insure that the driving thrusts do 
not increase the pressure between the gears 17 and 16 and cause undue 
wear. The splined connection 28 serves to assist in insuring that the 
forward driving thrusts will not be exerted upon the gear 17 in this 
embodiment. 
The propeller shaft 31 is provided with an annular thrust collar 36 which 
is integrally formed with the enlarged diameter portion and generally 
centrally of the internal splines 29. The thrust collar 36 has a forwardly 
facing thrust surface 37 that is engaged with the inner race of the thrust 
bearing 19 so that forward driving thrusts are transmitted from the 
propeller shaft 31 through the face 37 to the inner race of the bearing 19 
and from the bearing 19 through the thrust sleeve 23 to the housing of the 
lower unit 14. In a similar manner, the thrust flange 36 is formed with a 
rearwardly facing surface 38 that is engaged with a needle type thrust 
bearing 39 which, in turn, is engaged with the bearing housing 21 so as to 
transfer reverse driving thrusts to the housing of the lower unit 14 
through the thrust bearing 39 and bearing housing 21. Thus, the forward 
and reverse thrusts are taken by two different bearings and these bearings 
may each be sized to accommodate the respective loads. The thrusts are 
also independently transmitted to the housing of the lower unit 14. It 
should be noted that the forward driving thrusts are greater and, hence, 
the thrust bearing 19 is larger than the thrust bearing 39. In addition 
and as has been noted, the bearing 19 serves to rotatably journal the 
driven gear 17 and the intermediate shaft 25. 
The method for drivingly coupling either of the gears 17 or 18 selectively 
for rotation with the intermediate shaft 25, propeller shaft 31 and 
propeller 34 includes a dog clutching sleeve 41 that has a splined 
connection to the central portion of the intermediate shaft 25. By virtue 
of this splined connection, the dog clutching sleeve 41 may move axially 
relative to the intermediate shaft 25 but is rotatably affixed to it. The 
sleeve 41 has oppositely facing dog clutching teeth 42 and 43 that are 
adapted to engage and mesh with corresponding clutching teeth 44 and 45 on 
the driven gears 17 and 18, respectively. 
The mechanism for shifting the clutching sleeve 41 from the neutral 
position shown in FIGS. 2 and 4 to the engaged position with either the 
gears 17 or 18 includes a pin 46 that extends diametrically through the 
shaft 25 and into the sleeve 41. The pin 46 is held axially in position by 
means of a torsional spring 47 that is received within a circumferential 
groove 48 in the sleeve 41. The pin 46 extends through axially extending 
diametrically opposed slots formed in the intermediate shaft 25 so as to 
permit its axial movement relative to the intermediate shaft 25 while 
being held against rotation relative to the shaft 25. 
The pin 46 is staked to one end of a shifting sleeve 49 that is slidably 
supported within a bore of the intermediate shaft 25. A detent mechanism, 
indicated generally by the reference numeral 51 and having a construction 
as described in copending application Ser. No. 503,570, filed June 13, 
1983, entitled "Detent Mechanism For Clutches", and assigned to the same 
assignee of this application, is provided for holding the dog clutching 
sleeve 41 and shifting sleeve 49 in the neutral position and for assisting 
in the movement of the dog clutching sleeve 41 into engagement as 
described in that copending application which is incorporated herein by 
reference. 
A tongue and groove connection 52 connects the forward end of the shifting 
sleeve 49 to a shifting cam assembly 53. The cam assembly 53 is supported 
for reciprocation within a bore 54 of the housing of the lower unit 14. 
The tongue and groove connection 52 permits rotation of the shifting 
sleeve 49 relative to the shifting cam 53 while coupling these two 
elements together for simultaneous axial movement. 
A shift rod 55 extends vertically through the drive shaft housing and has a 
crank shaped portion 56 at its lower end. The crank shaped portion 56 is 
received in a slot 57 in the cam 53 so that rotation of the shifting rod 
55 will cause reciprocation of the shifting cam 53 and, accordingly, of 
the shifting sleeve 49 and dog clutching sleeve 41 to engage either the 
gear 17 or the gear 18 for rotation with the intermediate shaft 25 and the 
propeller shaft 31. 
A link 58 is affixed to the upper end of the shifting rod 55 and is, in 
turn, connected to a second link 59 which carries a cam groove 61 at its 
outer end. An actuator element 62 is received in the cam groove 61 and is 
connected to a pair of flexible transmitters 63 and 64. The flexible 
transmitters 63 and 64 are connected at their forward end to a shift lever 
65 of a shift control mechanism 66 that is positioned within the 
associated watercraft in proximity to the operator. The shift lever 65 is 
shiftable from the neutral position as shown in FIG. 1 in a forward 
direction to the forward transmission ratios selecting position. During 
such forward movement, the shifting rod 55 rotates in a counterclockwise 
direction so as to urge the shifting cam 53 and shifting sleeve 49 
rearwardly so that the dog clutch teeth 42 engage the dog clutching teeth 
44 and forward drive is selected. Movement of the shift lever 65 in the 
rearward direction accomplishes forward movement of the shifting cam 53 
and the dog clutching teeth 43 will engage the dog clutching teeth 45 and 
select reverse gear of the transmission. As has been noted, the forward 
driving thrust from the propeller 34 is transferred through the propeller 
shaft 31 and thrust collar 37 to the thrust bearing 19. However, the 
intermeshing bevel gears 16 and 17 exert a force in the opposite direction 
upon the thrust bearing 19. Therefore, the actual axial thrust carried by 
the bearing 19 is reduced by the fact that the two thrusts acting in 
opposite directions are transferred directly to it. 
In the embodiment of FIGS. 1 through 4, the forward and reverse driving 
thrusts were transmitted from the propeller shaft to the lower unit 
housing from a single thrust flange that was formed integrally on the 
propeller shaft. Although this may have some advantages, there may be 
certain advantages in connection with transmitting the thrusts in the 
forward and reverse directions from the propeller shaft to the lower unit 
housing at axially spaced positions. By separating the thrust taking 
locations, it is possible to avoid the splined connection as utilized in 
the previously described embodiment. Such an embodiment is shown in FIG. 
5. In connection with the embodiment of FIG. 5, only the lower unit 
assembly has been illustrated and is identified generally by the reference 
numeral 91. The mechanism for shifting the transmission and its 
association with the remaining components may be considered to be the same 
as the embodiment of FIGS. 1 through 4 and, for that reason, these 
components have not been illustrated. 
In this embodiment, a lower unit housing 92 rotatably journals the lower 
end of the engine driven drive shaft 93. The drive shaft 93, in turn, has 
affixed to its lower end a driving bevel gear 94. The driving bevel gear 
94 is engaged with a pair of diametrically opposed oppositely rotating 
bevel gears 95 and 96. Like the embodiment of FIGS. 1 through 4, the 
outboard motor illustrated is designed to be utilized as the additional 
non-conventional motor of a twin outboard drive and hence the propeller 
shaft normally rotates in an opposite direction to a conventional outboard 
motor during forward drive and the propeller has an opposite hand. 
The driven bevel gear 95 has its hub portion rotatably journaled within a 
combined roller and thrust bearing 97 of the tapered roller type. The 
thrust bearing 97 is, in turn, supported within a bearing housing 98 that 
is contained within the lower unit housing 92 and which is axially held in 
place by means of a retainer nut 99 which encircles the opening at the 
rear end of the lower unit 91. The outer race of the thrust bearing 97 is 
engaged with a thrust collar 101 that is contained within the lower unit 
housing and is axially held in place by the bearing housing 98. 
The driven bevel gear 96 has its hub portion rotatably journaled within the 
lower unit housing 92 by means of a needle bearing assembly 102. In 
addition, a needle type thrust bearing 103 is interposed between the 
forward face of the driven bevel gear 96 and the lower unit housing 92 for 
taking the driving thrusts on the driven bevel gear 96. 
A propeller shaft indicated by the reference numeral 104 is journaled 
within the lower unit housing by means of a first needle bearing assembly 
105 that is positioned between the interior of the driven bevel gear 96 
and the forward end of the propeller shaft 105, a second needle bearing 
assembly 106 that is positioned between the hub of the driven bevel gear 
95 and the intermediate portion of the propeller shaft 104 and a third 
needle bearing assembly 107 that is disposed between the bearing carrier 
98 and the rearward end of the propeller shaft 104. 
Rearwardly of the bearing 107, the propeller shaft 104 extends through an 
opening in the lower unit housing and is rotatably coupled to a propeller 
108 by means of a torsionally resilient coupling 109. 
Forward driving thrusts are transmitted from the propeller shaft 104 to the 
lower unit housing 92 forwardly of the driven bevel gears 95 and 96 by 
means of a thrust collar 111 that is engaged with a forward shoulder of 
the propeller shaft 104 and which forms a portion of a thrust bearing 
arrangement 112. The thrust bearing arrangement 112 also includes a 
forward race 113 that is in thrust transmitting engagement direction with 
the lower unit housing 92 so as to transmit the forward driving thrust 
directly to the housing 92 forwardly of the forward, neutral, reverse 
transmission. 
Rearward driving thrusts are transmitted to the lower unit housing 92 
rearwardly of this transmission by means including a thrust flange 114 
that is formed integrally with the propeller shaft 104. The flange 114 
engages a needle type thrust bearing 115 which, in turn, transfers its 
thrust to the bearing housing 98 and from the bearing housing to the lower 
unit housing 92 through the retaining nut 99. Hence, it should be readily 
apparent that the forward and reverse driving thrusts are transmitted 
directly and independently to the lower unit housing 92 on axially spaced 
opposite sides of the forward, neutral, reverse transmission. 
The means for drivingly coupling the driven bevel gears 95 and 96 to the 
propeller shaft 104 for completing this forward, neutral, reverse 
transmission includes a clutching sleeve 116 that has a splined connection 
to the propeller shaft 104 between the bearings 105 and 106 for rotation 
with the propeller shaft 104 but axially movable along this shaft. The 
clutching sleeve 116 has oppositely facing dog clutching surfaces 117 and 
118 that are adapted to selectively engage dog clutching teeth 119 and 121 
formed on the driven bevel gears 95 and 96, respectively. 
The clutching sleeve 116 is adapted to be moved axially along the shaft 104 
by means including a pin 122 that extends diametrically through axially 
extending slots formed in the propeller shaft 104 and which is staked 
within the clutching sleeve 116. The pin 122 is held in position by means 
of a torsional spring 123 that is received within a groove 124 formed in 
the dog clutching sleeve 116. 
The pin 122 is, in turn, axially affixed to a shifting sleeve 125 that is 
slidably supported within a bore of the propeller shaft 104. The clutching 
sleeve 125 has a tongue and groove connection 126 to a shifting cam 127. 
The shifting cam 127 is, in turn, slidably supported within a bore 128 of 
the lower unit housing. 
A shifting rod 129 has a crank shaped portion 131 that is received within a 
slot 132 of the shifting cam 127 for axially moving the cam 127 and 
shifting sleeve 125 upon rotation of the shifting rod 129. As has been 
previously noted, the upper end of the shifting rod 129 is appropriately 
connected to a shaft control mechanism, for example, of the type shown in 
FIGS. 1 through 4. 
A detent mechanism, indicated generally by the reference numeral 133, is 
provided for holding the dog clutching sleeve 116 in its neutral position 
and for exerting a force tending to accelerate the movement of the 
clutching sleeve 116 into its forward or neutral positions. The detent 
mechanism 113 has a construction of the type as described in the 
aforenoted copending application Ser. No. 503,570, which has been 
incorporated herein by reference. 
The shifting of this embodiment is believed to be readily clear since the 
transmission is, for the most part, generally similar to the transmission 
of the embodiment of FIGS. 1 through 4 and only the thrust taking and 
bearing arrangement for the propeller shaft is different from the 
previously described embodiment. 
It should be readily apparent from the foregoing description that a 
relatively compact and yet robust arrangements are provided for taking the 
forward and reverse driving thrusts of a marine outboard drive 
transmission and also for insuring that these thrusts are independently 
transmitted to the propeller shaft housing. In one embodiment, the place 
of transmission of these thrusts is widely separated from the other in an 
axial direction. 
It is to be understood that the foregoing is only a description of 
preferred embodiments of the invention and various changes and 
modifications may be made without departing from the spirit and scope of 
the invention, as defined by the appended claims.