Roller bearing unit for planetary gear

A roller bearing unit for a planetary gear is made such that the rollers between the thrust washers are restrained from interference with the thrust washers upon an inclining of the planetary gear either by making the distance between the axially inner faces of washers sufficiently large, or by preventing axial movement of the guide ring between the rollers, so that the axially outer ends are prevented from rubbing hard against the axially inner faces of the washers during running.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a roller bearing unit for planetary gear 
used in an automatic transmission unit for vehicle to rotatably support 
the planetary gear on a support shaft in the transmission unit. 
2. Description of the Prior Art 
A typical planetary gear unit of a vehicle automatic transmission is 
arranged as shown in FIG. 7. In this arrangement, the planetary gear unit 
is rotatably provided with respect to a support shaft 1. The planetary 
gear unit comprises a sun gear 2, a planetary gear 6 which is rotatably 
supported on the support shaft 1 and a support member 3 which is mounted 
so as to be freely rotatable about an axis of rotation of the sun gear 2 
of the planetary gear unit. The support shaft 1 is fixedly attached at its 
one end (the left end in FIG. 7) to the support member 3, and formed with 
a cylindrically convex inner race 4 on a central outer peripheral surface 
thereof. 
The planetary gear unit further has a retaining collar 5 which is securely 
attached to the outer peripheral surface at the other end of the support 
shaft 1 (right end in the figure). 
The planetary gear 6 is provided with gear teeth 7 on an outer peripheral 
surface thereof, and a cylindrically concave outer raceway 8 formed on an 
inner peripheral surface thereof. The planetary gear 6 is maintained on 
the support shaft 1 so as to be freely rotatable about the central outer 
peripheral surface of the support shaft 1 between the retaining collar 5 
and the support member 3. 
A double row of first and second free floating rollers 9 are provided 
without retainer between the inner raceway 4 and the outer raceway 8. A 
guide ring 10 for guiding the axially inner ends of the rollers 9 (the 
ends of the rollers 9 of the respective rows facing each other) is 
provided between the rows of rollers 9. The outer peripheral face of the 
guide ring 10 is provided adjacent to the outer raceway 8, so that the 
guide ring 10 rotates with the planetary gear 6. 
At least one thrust washer 11 (two washers in the drawings) is provided at 
the axially inner end faces of the retaining collar 5 and the support 
member 3 (the faces facing each other), respectively, so that the axially 
outer ends of the plurality of rollers 9 are faced to the thrust washers 
11. 
With the above construction, the planetary gear 0 is supported so as to 
rotate freely with respect to the support shaft 1, and meshes with the sun 
gear 2 and with a ring gear 12 which is maintained concentric with the 
axis of the sun gear 2. The gears 2, 6 and 12 are selectively rotated or 
immobilized with respect to each other, a speed change, or reverse 
rotation of the output with respect to the input may be achieved in the 
planetary gear unit. 
With the above mentioned planetary gear unit, the distance L between the 
support member 3 and the retaining collar 5, or between the pairs of 
thrust washers 11 when the thrust washers 11 are provided,--this is the 
case for all examples of the present specification, is made a little 
larger than the sum of the length l(el).sub.1 of the first rollers 9 in 
one (first row) of the rows of rollers, plus the length l(el).sub.2 of the 
second rollers 9 in the other row (second row) of rollers (in general 
l(el).sub.1 =l(el).sub.2), plus the axial length a of the guide ring 10. 
That is, L&gt;l(el).sub.1 +l(el).sub.2 +a. Consequently, under normal 
conditions, the axially outer ends of the respective rollers 9 do not rub 
hard against the thrust washers 11. However, if the guide ring 10, which 
rotates in accordance with operation of the planetary gear unit, becomes 
inclined, there is the possibility of the axially outer ends of the 
rollers 9 rubbing hard against the thrust washers 11. 
More specifically, as shown in FIG. 8, during rotation of the planetary 
gear unit for transmission, the planetary gear 6 may become inclined as a 
result of axial components of force T1, T2 produced as a result of meshing 
between the planetary gear 6 and the sun gear 2 and ring gear 12. 
Consequently the end portions 9a (adjacent the thrust washers 11) of the 
first and second rollers 9 are driven by the outer raceway 8. As a result, 
the axes of the rollers 9 are skewed relative to the axis of the support 
shaft 1 giving rise to a force in an axial direction of the respective 
rollers 9. As shown by the arrow A in FIG. 8, this force at one point on 
the inner peripheral surface of the outer raceway 8 pushes on the first 
rollers 9 of one (first row) of the rows of rollers in an axially inward 
direction A, while at an opposite point on the inner peripheral surface of 
the outer raceway 8 (180 degrees around the periphery) the similar force 
pushes on the second rollers 9 of the other row (second row) of rollers in 
an axially inward direction indicated by the arrow B of the same figure. 
Consequently, due to the inward pushing forces on the double row of rollers 
9 at opposite positions 180 degrees around the periphery, like couple of 
forces, the guide ring 10 disposed between the rows of rollers 9 becomes 
inclined, so that the apparent axial length of the guide ring 10 is 
increased to b (b&gt;a). 
As a result, the outer ends of the respective rollers 9 rub hard against 
the thrust washers 11 so that as well as producing an increase in drive 
(transmission) losses, there is the possibility of failure due to 
excessive friction and seizure under harsh conditions such as with 
insufficient lubrication. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a roller bearing unit 
for planetary gear unit which addresses the above unsatisfactory 
situation, specifically in which the axially outer ends of the rollers are 
prevented from rubbing hard against the axially inner faces of the support 
member and the retaining collar or washers for them.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
According to a first aspect of the present invention, there is provided a 
roller bearing unit for planetary gear similar to the conventional roller 
bearing unit for planetary gear in that it comprises a support member, a 
support shaft having first and second ends and a central portion, the 
first end fixedly attached to the support member, the central portion 
formed with a cylindrically convex inner raceway on its outer peripheral 
surface, a retaining collar fixed to the second end, a planetary gear 
having outer and inner pripheral surfaces, the outer peripheral surface 
formed with a gear and the inner peripheral surface formed with a 
cylindrically concave outer raceway, so as to rotate freely on the outer 
peripheral surface of the support shaft between the retaining collar and 
the support member, a double row of free floating rollers provided without 
retainer between the inner raceway and outer raceway, and a guide ring 
provided at a intermediate portion between the two rows of rollers for 
guiding the axially inner ends of the plurality of rollers. In addition, 
with the roller bearing unit for planetary gear of the first aspect of the 
present invention, the guide ring is fixed to either of the outer 
peripheral surface of the support shaft or the inner peripheral surface of 
the planetary gear so as not to move axially relative. 
In this construction the guide ring is not displaced even under a force 
tending to change the axial position of the rollers during running, so 
that the apparent axial length of the guide ring does not increase. 
Consequently, the respective rollers are not forced outward by the guide 
ring. Hence the axially outer ends of the respective rollers are not 
pressed hard against the axially inner face of the support member or the 
axially inner face of the retaining collar, thereby overcoming the problem 
of severe rubbing between the outer ends of the respective rollers and the 
inner faces of the support member and the retaining collar. 
FIG. 1 shows an embodiment according to the present invention. A planetary 
gear 6 has a gear 7 formed on an outer peripheral surface thereof and an 
outer raceway 8 formed on an inner peripheral surface thereof with a 
retainer groove 13 formed at an axially central position on the outer 
raceway 8. A stop ring 14 is retained in the retainer groove 13 with an 
outer peripheral half portion fittingly engaged therein. Furthermore, a 
floating ring 15 is provided on either side of the radially inner half 
portion of the stop ring 14 protruding from the outer raceway 8, thereby 
making up a guide ring. 
The planetary gear 6 having the stop ring 14 and floating rings 15 provided 
at an intermediate portion of the inner peripheral surface of the outer 
raceway 8, as with the conventional construction shown in FIG. 7, is 
rotatably supported on a support shaft 1 by means of rollers 9. 
Furthermore, in this arrangement, the axially inner ends of the respective 
rollers 9 face the floating rings 15, respectively. 
With the roller bearing unit for planetary gear of the present invention 
having the above construction, the guide ring comprised of the stop ring 
14 and the floating rings 15 is not displaced even when a load is applied 
in an axial direction upon the rollers 9 during rotation. Consequently, 
the apparent axial length of the guide ring does not increase. 
As a result, the respective rollers 9 are not pressed axially outwards by 
the guide ring, and hence the outer end portions of the respective rollers 
9 are not pressed hard against the inner face of the support member 3 or 
the inner face of the retaining collar 5. Hence severe rubbing between the 
axially outer ends of the respective rollers 9 and the axially inner faces 
of the support member 3 and the retaining collar 5 does not occur. 
FIG. 2 shows a second embodiment according to the present invention. With 
this embodiment, a radially inner peripheral half of the stop ring 14 is 
fitted into a groove of open channel shape in cross section formed in an 
outer peripheral surface of a single floating ring 15a, so that the 
axially inner ends of the rollers 9 of the double rows (not shown in FIG. 
2) face toward the axially opposite sides of the floating ring 15a. Other 
details of the construction and operation are substantially the same as 
for the above mentioned first embodiment. 
FIG. 3 shows a third embodiment according to the present invention. With 
this embodiment, a cylindrical shaped spacer 16 is press fitted into the 
outer raceway 8 at an intermediate portion thereof, thereby making up a 
guide ring for guiding the double rows of rollers 9. Other details of 
construction and operation are substantially the same as for the above 
described first and second embodiments. 
FIG. 4 shows a fourth embodiment according to the present invention. With 
this embodiment, the guide ring comprises a cylindrical shaped spacer 16 
press fitted into the outer raceway 8 at an intermediate portion thereof 
as well as a floating ring 15 provided on each side of the spacer 16 to 
guide the double row of rollers 9. Other details of the construction and 
operation are substantially the same as for the above described first to 
third embodiments. 
FIG. 5 shows a fifth embodiment according to the present invention. With 
this embodiment, the guide ring comprises a radially inwardly directed 
flange member 17 formed integral with the outer raceway 8 at an 
intermediate portion thereof. The double row of rollers 9 (not shown in 
FIG. 5) are guided by the flange member during operation. Other details of 
the construction and operation are substantially the same as for the above 
described first to fourth embodiments. 
According to another aspect of the present invention, there is provided a 
roller bearing unit for planetary gear, wherein the dimensions of the 
components are made so that a relationship L&gt; l(el).sub.l +l(el).sub.2 +b 
is established, wherein L is the distance between the support member and 
the retaining collar, l(el).sub.l is the axial length of the rollers in 
one of the rows of rollers, l(el).sub.2 is the axial length of the rollers 
in the other row of rollers, and b is the apparent axial length of the 
guide ring when the center axis of the guide ring is inclined at a maximum 
amount to the center axis of the support shaft. 
With this construction of the roller bearing unit for planetary gear, the 
axially outer ends of the rollers do not rub hard against the axially 
inner face of the support member or of the retaining collar even when a 
force is applied to the rollers to displace them in an axial direction 
during running. The distance L between the support member and the 
retaining collar is greater than the total of the length l(el).sub.1 of 
the rollers in one row of rollers, plus the length l(el).sub.2 of the 
rollers in the other row of rollers, plus the apparent axial length b of 
the guide ring, even when the axis of rotation of the guide ring is 
inclined at a maximum incline to the axis of the support shaft. 
Consequently, even when the respective rollers are forced outward by the 
guide ring, the outer axially ends of the respective rollers do not press 
hard against the axially inner face of the support member or the inner 
face of the retaining collar. Hence the severe rubbing between the axially 
outer ends of the respective rollers and the axially inner faces of the 
support plate and retaining collar is overcome. 
FIG. 6 shows a sixth embodiment according to the present invention. With 
this embodiment, the structural components of the assembled body are 
similar to those described in FIGS. 7 and 8 for the conventional 
construction. In particular, with this embodiment, the dimensions of the 
components are made so that the distance L between axially inner most face 
of the first thrust washers 11 provided on the inner face of the support 
member 3 and the axially innermost face of the second thrust washers 11 
provided on the inner face of the retaining collar 5 is greater than the 
sum of the length l(el).sub.1 of the first rollers 9 of one (first row) of 
the rows of rollers plus the length l(el).sub.2 of the second rollers 9 of 
the other row (second row) of rollers plus the apparent axial length b of 
the guide ring 10 when the axis of rotation of the guide ring 10 is 
inclined at a maximum inclination with respect to the axis of the support 
shaft 1 (ie. L&gt;l(el).sub.1 +l(el).sub.2 +b). 
With this embodiment, even when the axis of the guide ring 10 is inclined 
at a maximum amount with respect to the axis of the support shaft 1, the 
distance L between the axially innermost face of the first thrust washer 
11 on the inner face of the support member 3 and the axially innermost 
face of the second thrust washer 11 on the inner face of the retaining 
collar 5 is greater than the total of the length l(el).sub.1 of the first 
rollers 9 of one (first row) of the row of rollers plus the length 
l(el).sub.2 of the second rollers 9 of the other row (second row) of 
rollers plus the apparent axial length b of the guide ring 10. 
As a result, even when the respective rollers 9 are forced outward by the 
guide ring 10, the axially outer ends of the respective rollers 9 are not 
pressed hard against the axially inner face of the first thrust washers 11 
provided on the axially inner face of the support member 3, or the axially 
inner face of the second thrust washers 11 provided on the axially inner 
face of the retaining collar 5, so that severe rubbing between the axially 
outer ends of the respective rollers 9 and the axially inner faces of the 
respective thrust washers 11 does not occur. 
With the roller bearing unit for planetary gear of the present invention, 
due to the above construction, the severe rubbing between the axially 
outer ends of the rollers and the mating portions adjacent the axially 
outer ends of the rollers is alleviated. Hence the transmission losses and 
failure due to abnormal wear and seizure of the components can be 
significantly reduced. 
Aspects of the present invention have been described by way of example only 
and it should be appreciated that modifications and additions may be made 
thereto without departing from the scope thereof as defined in the 
appended claims.