Note: Descriptions are shown in the official language in which they were submitted.
Title of the Invention
TRACTION SURFACE COOLING SYSTEM
FOR TORQUE TRANSMISSION
Background of the Invention
This invention relates to traction drive torque
transmissions and more particularly, it concerns improvements
in traction surface cooling apparatus for such transmissions.
In traction drive transmissions, torque is trans-
mitted by rolling friction hetween one or more pairs of
traction surfaces on components arranged to be retained
against one another in a manner to develop normal forces
adequate to prevent slippage between the surfaces. Such
transmissions are particularly useful in the transmission of
power at continuously or infinitely variable speed ratios
because of the facility offered by the smooth rolling sur-
faces of each traction surface pair for an infinitely vari-
able radius ratio. Examples of such infinitely variable
transmissions are disclosed in U.S. Patents No. Re 29,328,
reissued August 2, 1977, No. 4,112,779 and 4,112,780, both
issued September 12, 1978, and No. 4,152,946 issued May 8,
1979, all of which are owned by the assignee of the present
invention.
Though seemingly inconsistent with transmission of
torque by friction, the rolling or traction surfaces of the
transmission exemplified by the disclosures of the afore-
mentioned patents are lubricated and coGled by circulating a
liquid lubricant through the transmission housing. Torque
transfer is, in actuality, by viscous shear of a very thin
film of lubricant between the traction surfaces which are of
smooth tool steel. The lubricants used are synthetic oils
developed specifically for traction drives
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and increase in viscosity under the pressures existing
between the traction surfaces to a point of becoming almost
glassy in character. Accordingly, high coefficients of
traction are possible without abnormal deterioration of the
contacting surfaces.
As indicated, the liquid lubricant functions also
as a heat storage medium by which the heat developed at the
traction surfaces is transferred to the exterior of the
transmission housing by recirculation and cooling of the
lubricant. Partially because of the relative motion between
the traction surfaces and the recirculated lubricant, and
also in part because of the viscosities reached by the
lubricant, a boundary layer of lubricant tends to build on
the surfaces to a point where the torque transmitting
efficiencies of the lubricant is reduced and more critically,
the transfer of heat to the recirculated lubricant is impeded.
These problems created by the boundary layer of lubricant
are, moreover, dichotomous in the sense that the reduction
of torque transmit~ing efficiency can be avoided by circulating
less lubricant over the surfaces whereas the removal of heat
developed by the stresses imposed on the traction surfaces
requires large quantities of the lubricant to be circulated
over the same surfaces. Hence, the solution of these problems
in the past have involved a trade-off or compromise between
rated power transmission capacity and useful life of a
particular transmission unit.
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Summary of the Invention
In accordance with the present invention, the
removal of thermal energy or heat from the rolling friction
surfaces of traction drive transmissions by recirculation of
a liquid lubricant is enhanced without reduction in viscous
film torque transmitting efficiency by mechanically wiping
or scraping the traction surfaces to eliminate the boundary
layer of lubricant on the surfaces. This operation is
achieved in a traction drive torque transmission having at
least two traction surfaces in rolling frictional engagement
with each other under normal force loading, a rotatable body
movable relative to both such surfaces and a lubricant .
circulating system by which a liquid lubricant is delivered
to and collected from the traction surfaces by the improve-
ment comprising traction surface engaging means for removing
lubricant from each of the traction surfaces during opera- :
tion of the transmission, and means to support said traction
surface engaging means from the rotatable body so that said
engaging means will be in continuous contact and movable
relative to the traction surfaces, said traction surface
engaging means being operative to remove lubricant from the
traction surfaces.
~; Accordingly, a principal object of the present
invention is the provision of an improved cooling apparatus
for traction drive torque transmissions. Otner objects and
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further scope of applicability of the present invention will
become apparent from the detailed description to follow
taken in conjunction with the accompanying drawings.
Brief Description of the Drawings
Fig. 1 is a longitudinal cross-section illustration
of a transmission incorporating the invention;
Fig. 2 is an enlarged fragmentary cross-section on
line 2-2 of Fig. l;
Fig. 3 is an enlarged fragmentary cross-section on
line 3-3 of Fig. l;
Fig. 4 is a plan view of a transmission component
incorporating an alternative embodiment of the invention;
Fig. 5 is a cross-section on line 5-5 of Fig. 4;
Fig. 6 is a fragmentary cross-section on line 6-6
of Fig. 5;
Fig. 7 is a plan view like Fig. 4 but illustrating
another alternative embodiment; and
Fig. 8 is a fragmentary cross-section on line 8-8
of Fig. 7.
Detailed Description of the Preferred Embodiments
In Fig. 1 of the drawings, an exemplary embodiment
of an infinitely variable traction drive transmission incor-
porating the present invention is shown in longitudinal cross-
section and designated generally by the reference numeral
-- 4
.
10. Although the structure and operation of the transmission
is fully described in the aforementioned U.S. Patents, a
summary description of the transmission 10 will facilitate a
complete understanding of the present invention.
The plane of the cross-section in Fig. 1 includes
a first or primary transmission axis 12 and a second or
nutational axis 14 inclined with respect to the axis 12 and
intersecting same at a point S of axes intersection. The
orientation of the first axis 12 is established by a fixed
frame 14 in the form of a cylindrical housing 16 closed at
opposite ends by ]ournalled end sections 18 and 20. Com-
ponents located within the housing 16 include a crank-like
alpha body 26 supported by bearings 28 and 30 in the frame
; end sections 18 and 20 for rotation about the primary or
first axis 12. An input shaft 32 is connected directly to
the alpha body 26 and is thus concentric with the axis 12.
A nutatable beta body, generally designated by the reference
numeral 34, is supported by bearings 36 and 38 in the alpha
body 26 for rotation about the second axis 14. In the dis-
closed embodiment, the beta body 34 includes a central
supporting shaft 42 on which a pair of oppositely convergent
conical members 44 and 46 are supported for some measure of
both axial and rotational movement relative to the shaft 42.
A ball/ramp unit 48 is slidably keyed or splined on the
shaft 42 between the cone members 44 and 46. For a complete
understanding
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of the present invention, it is necessary only to appreciate
that the unit 48 functions to bias the cone members in opposite
directions away from the point S in response to a torque
differential between the shaft 42 and the cone members 44
and 46 and to couple the cone members rotatably with the
shaft. It will be noted also that the conical surfaces of
the members 44 and 46, also referred to herein as beta
traction surfaces, are concentric with the second axis 14
and are of a variable radius ~b with respect to that axis.
The axial bias of the cone members 44 and 46 by
the ball/ramp unit 48 along the shaft 42, coupled with the
angular relationship of the axis 14 as well as the configura-
tion of the conical members, causes the conical beta surfaces
on the members 44 and 46 to be urged into engagement with a
pair of axially adjustable omega rings 50 and 52 defining
interior omega rolling or traction surfaces 54 and 56 which
are of revolution about the primary axis 12 and of a constant
radius Rw. The rings 50 and 52 are secured against rotation
in the frame section 16 and are fixed at the inner ends of
annular piston members 58 and 60 operably positioned respec-
tively in annular chambers 62 and 64. The chambers 62 and
64 are ported to hydraulic fluid conduits (not shown) in
such a manner that pressurized control fluid in the chambers
62 and 64 will cause the pistons and thus the rings 50 and
52 to move along the axis 12 toward or away from the point
S of axes intersection.
In the operation of the transmission 10 to transmit
torque originating at the input shaft 32, the alpha body 26
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is rotated directly with the input shaft 32 causing the
second axis 14 and thus the beta body 34 to nutate about the
first axis 12 with the beta traction surfaces on the exterior
of the cone members 44 and 46 in contact on opposite sides
of the primary axis 12 with the omega traction surfaces 54
and 56 on the rings 50 and 52. The shaft 42, rotatable with
the cone members 44 and 46 on the second axis 14 is coupled
or linked to an output shaft 66 by an epicyclic gear set 68.
Thus it will be seen that torque at the output shaft 66 will
be the result of input torque driving the alpha body 26 in
rotation about the first axis to cause planetary movement in
the gear set 68 together with torque transmitted by friction
between the omega surfaces 54 and 56 and the beta surfaces
on the cone members 44 and 46 to cause rotation of the beta
body 34 and the shaft 42 about the second axis 14. Further,
the ball/ramp system 48 urges the cone members 44 into
engagement with the omega rings 50 and 52 to develop a normal
force proportional to torque transmitted by the shaft 42.
To lubricate and to cool the operating components
of the transmission 10, a liquid lubricant is circulated
from an external storage source such as a sump 70 to the
interior of the housing 16 and returned to the sump by a
gravity flow line 72. The lubricant is fed to the transmission
by a pump 74 through a conduit 76 to a sealed gland or
manifold 78 in the end frame 18 adjacent the bearing 28.
The shaft 32 is internally bored to provide a lubricant
passageway 80 which communicates with branch passages 84 in
the alpha body 26. These latter passages communicate directly
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with discharge ports ~6 in the body 26 as ma~ be understood
by reference to Figs. 1 and 3.
In the embodiment of Figs. 1-3, the alpha body 26
carries two sets of elongated blade-like scrapers 90 and 92,
respectively. As shown in Fig. 1, the blades 90 are positioned
to engage the omega traction surfaces 54 diametrically
opposite from the point at which these surfaces are engaged
by the beta traction surfaces on the conical members 44 and
46. These blades are elongated so that they will engage the
surfaces 54 and 56 throughout axial movement of the rings
50 and 52 in the operation of the transmission 10 to vary
the speed ratio thereof. As shown in Fig. 2, the blades 90
project from the surface of the alpha body 26 in a manner
effective to scrape the traction surfaces 54 as a result of
the direction of rotation of the alpha body 26. Though
illustrated in Fig. 2 to have a tapered or knife-like edge,
the blades may be of a variety of specific configurations
appropriately secured to the body 26 such as by clamping
wedges 94. Also, the material from which the blades are
formed may include synthetic resinous materials or may be
metallic.
Because of the relative rotation of the respective
transmission bodies 26 and 34, the blades 92, which are
identical in construction to the blades 90, project inwardly
from the alpha body 26 in a manner to effectively remove
lubricant from the surfaces of the members 44 and 46 as a
result of relative rotation between the bodies 26 and 34.
The blades 92 also extend in length through at least the
axial distance of contact between the omega and beta surfaces.
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Although the precise location of the blades 92 on
the alpha body 26 is not critical, it will be noted that the
oil discharge ports 86 from which oil is directed against
the surfaces of the beta cone members 44 and 46 are positioned
behind the blades 92 in terms of alpha-beta body rotation. As
a result, residual lubricant on the surfaces of the cones,
including lubricant resulting from a boundary layer phenomenon
will be removed from these surfaces in advance of the applica-
tion of newly recirculated lubricant from the ports 86. In
this way the heat transfer from the surfaces 54 and 56 to the
lubricant will be enhanced.
In the operation of the transmission 10, relatively
cool lubricant will be pumped from the sump 70 through the
passageways 80 and 84 in the alpha body 26 and be discharged
through the ports 86 directly against the beta traction surfaces
on the exterior of the cone members 44 and 46. Though not
shown in the drawings, it is contemplated that the lubricant
may be cooled by an appropriate heat exchanger associated
with the sump 70 or with the passages 72 or 76 on the exterior
of the transmission 10. Because of the location of the ports
86 relative to the blades 92, the fresh, cooled lubricant
will engage the beta surfaces immediately after they have
been wiped clean of any residual lubricant, thereby to
enhance the passage of heat from the cone members 44 and 46
to the freshly supplied lubricant. The major portion of the
lubricant will pass outwardly by centrifugal force to the
omega rings 50 and 52 and other components inside the
housing 16 from which it will pass back to the sump through
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the line 72. Although no direct porting is provided by
which fresh lubricant is passed directly to the omega
traction surfaces 54 and 56, the location of these rings
about the exterior of the alpha body 26 and the beta body 34
enables a supply of lubricant to pass to these surfaces
adequate to maintain lubrication of these surfaces as needed
for the prevention of wear or deterioration of the surfaces
54 and 56. Cooling of the surfaces 54 and 56 will occur as
a result of heat transfer from the surfaces 54 and 56 to the
conical surfaces on the members 44 and 46 as well as by heat
transfer to the lubricant recirculated to the sump 70. In
this latter respect, although the temperature of the lubricant
on reaching the rings 50 and 52 may be higher than it is at
the surfaces on the cones 44 and 46, the removal of residual
lubricant from the surfaces 54 and 56 by the blades 90
coupled with the relatively large ratio of total ring
surface area to the area of working or traction surfaces 54
and 56 will prevent any excessive heat build up in the rings
50 and 52.
In Figs. 4-6 of the drawings, an alternative embodi-
` ment of the invention is shown in which parts identical with
those of Figs. 1-3 are designated by the same reference numeral
whereas parts having the same function but modified in structure
are designated by the same reference numerals primed. Thus,
in Figs. 4 and 5 the alpha body 26 is shown by itself and in
somewhat more detail than in Fig. 1. It will be seen more
clearly in these figures, for example, that the body 26 is
an integral or unitary member having a pair of symmetrical
-- 10 --
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frusto-conical cavities 96 and 98 extending between a central
cylindrical portion 100 to counterbores 102 in which the
bearings 36 and 38 (see Fig. 1) are seated. The cavities 96
and 98 complement the exterior shape of the cone members 44
and 46 in a manner such that the cavity delimiting surfaces
are normally spaced out of contact with the cone members.
The cavities 96 are also sectors in the sense that they open
at diametrically opposite windows 104 and 106 through which
the cone members 44 and 46 contact the traction surfaces 54
10and 56 on the omega rings 50 and 52. The arrangement of
lubricant passages 84 and ports 86 is the same in Figs. 4-6
as that of Fig. 1.
~, In the embodiment of Figs. 4-6, a single wiper
blade assembly 90' is again positioned on the e~terior of
the alpha body 26 to wipingly engage the traction surfaces
54 and 56. In this instance, the blades 90' are defined by
spaced edges of flexible material retained by a central bar
94' in essentially the same manner as the blades 90 of the
embodiment of Figs. 1-3. In place of the single blades 92,
however, a plurality of blade-like portions 92' are employed
in this embodiment. As shown most clearly in Figs. 5 and 6,
the multiple blades 92' extend longitudinally to be effective
over the full length of each of the cone members 44 and 46
and are provided as integral formations on a sheet-like
molding 108 of a shape to conform with the frusto-conical
configuration of the cavities 96 and 980 The sheet-like
molding 108 may be secured by an appropriate adhesive or
bonded within the cavities in the position illustrated.
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To insure a complete distribution of lubricant
between the blade portions 92' and thus against the exterior
of the cone members 44 and 46, the blades 92' are interrupted
along their respective lengths to establish lubricant passing
openings or gaps 110. The openings 110 are preferably
staggered or offset from each other axially in order that
the wiping function of the blade portions 92' will be
effective throughout the working length of the cone members
44 and 46.
In light of the provision of multiple blade portions
92' in the embodiment of Figs. 4-6, a more complete removal
of residual lubricant remaining on the cone members 44 and
46 will be effected. On the other hand, a complete distribu-
tion of fresh and cool lubricant over a substantial portion
of the cone surfaces will enhance the removal of heat from
and thus cool the working traction surfaces on the conical
members 44 and 46.
In Figs. 7 and 8, a still further embodiment of
the invention is illustrated. In this embodiment, the
function of the blades 92 and 92' of the previous embodiments
is served by a plurality of discrete wiping plugs 111 arranged
within the frusto-conical cavities of the alpha body 26 to
be in a staggered pattern again effective over the entire
length of the conical surfaces on the members 44 and 46. As
shown most clearly in Fig. 8, the wiping elements 110 are in
the nature of plugs of felt-like material individually
receivable in relativeIy shallow holes 112 bored into the
surfaces of the cavities 96 and 98. The pattern of the
- 12 -
14
plugs will in itself assure uniform distribution of fresh or
cool lubricant fully over the surfaces of the cone members
44 and 46.
Thus it will be seen that as a result of the
present invention, a highly effective apparatus is provided
for cooling the frictionally engaged rolling surfaces of
traction drive transmissions and by which the above-mentioned
objectives are completely fulfilled. Also it will be appreciated
that modifications may be made in the embodiments disclosed
without departure from the inventive concepts manifested by
such embodiments. It is expressly intended, therefore, that
the foregoing description is illustrative of a preferred
embodiment, not limiting, and that the true spirit and scope
of the present invention be determined by reference to the
appended claims.
