Note: Descriptions are shown in the official language in which they were submitted.
1(~7504Z
This invention relates to variable speed mechanical
torque transmissions and more particularly, it concerns improve-
ments in transmissions by which a variable speed ratio is achieved
by varying the radii of one set of rolling surfaces relative to
another set of rolling surfaces in frictional engagement with
the one set and in which one set of rolling surfaces is moved
orbitally relative to the other.
Canadian Patent Application No. 258,210, filed July 20,
1976 and commonly owned with the present invention, discloses
several embodiments of a variable speed transmission having a first
element defining a pair of rolling surfaces of revolution about a
first axis, a second element having a pair of rolling surfaces
about a second axis intersecting the first at a point of axes
intersection, a frame in which the first and second elements are
supported to fix the angular orientation of the two axes, and a
mechanical system for urging the respective rolling surfaces into
frictional engagement with each other at two points of contact
on opposite sides of the point of axes intersection. The rolling
surfaaes on one of the members are cone-like in shape whereas the
rolling surfaces on the other element are ring-like and movable
axially in opposite directions with respect to the point of axes
intersection. The relative ratio of rolling surface radii at the
points of contact may be made to vary to provide an infinitely
variable speed ratio.
In one embodiment, the first element is provided with
the cone-like rolling surfaces and is rotatable about the first
axis at a velocity ~. The second element carries the ring-like
rolling surfaces and is journalled in a crank-like support such
that the second axis may travel in a biconical path about the
first axis at a velocity ~. The second element may or may not
undergo rotation about the second axis at a velocity ~. Also,
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the disclosure incorporates a mechanical linking system by
which any two of the components rotating at velocities a,
and ~ may be interconnected or in which all three of such
velocity components may be connected by means of an epicycloidal
train. -
In the operation of one embodiment, the first element
on which the cone-like rolling surfaces are provided is
connected directly with an output shaft and thus rotatable -
at a velocity ~. The second element is driven in nutational
movement in which the second axis travels in a biconical
path about the first axis at a velocity a. The second element
is prevented from rotating on the second axis t~ = 0) by a -
mechanical linkage in the form of conical gears having an
apex coincident with the point of axes intersection, one of
which gears is fixed to the frame while the other is carried
by the second element. Thus, the output shaft velocity w
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will be related to input velocity a as a result of the ratio
of radii at the two points of rolling friction contact
between the rolling surfaces on the first and second elements. -- -
Although the aforementioned embodiment disclosed
in Canadian Application Serial No. 258,210 provides a highly
,~ effective variable speed transmission, the rolling surfaces
of the first element are defined by two truncated cones with --
opposing bases, and having an apical half-angle equal to or
slightly less than the angle of inclination of the second
axis with respect to the first axis. The rolling surfaces
of the second element are formed by two annular rings.
Because of their respective geometrical forms, at least one ---
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of the two couples of rolling surfaces of the transmissions
described must be moved with respect to each other over a
relatively long distance by means of a maneuvering component
in order to produce a pronounced variation of transmission
ratio. This diminishes rapidity of maneuver and increases
consumption of power. Additionally, there is room for
improvement in the mechanical linkage by which the second
element is linked with the frame. The conical gear linkage
is relatively noisy and represents a source of friction losses
which diminish the efficiency of the overall transmission.
Also because the gears are located midway along the length
of the second element, they increase the overall transverse
size of the transmission in some measure.
In accordance with the present invention, a trans-
mission is provided which is similar in operation to the
mentioned embodiment of Canadian Patent Application Serial
No. 258,210 and as such, includes a frame, a first element on
a first axis fixed in the frame and having rolling surfaces
of revolution about said first axis, one such rolling surface
on each side of a first plane perpendicular to said first
axis at a point of axes intersection, a second element on a
second axis intersecting the first axis at the point of axes
intersection and having concentric journal and rolling surfaces
of revolution about the second axis, the rolling surfaces
of the second element being disposed one on each side of a
second plane passing through the point of axes intersection
~ and perpendicular to the second axis, support means rotatable
; on the first axis and journalled with the journal surfaces
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of the second element for movement of the second element in
- a biconical path circumferentially of the first axis, the
apex of such biconical path being coincident with said point
of axes intersection, the respective rolling surfaces on the
first and second elements being in rolling frictional engage-
ment at two points of contact in a third plane containing
the first and second axes and located one on each side of
the first plane, the rolling surfaces of at least one of the
first and second elements being defined by generatrices
10 inclined oppositely with respect to the axis of revolution
thereof and symmetrically with respect to the point of axes
- intersection, thereby to provide in the respective rolling
surfaces of said first and second elements a variable ratio
. of rolling surface radii at points of contact for variation
in the spacing of the points of contact from the point of
axes intersection, and means for forcing said respective
.~ rolling surfaces on said first and second elements into
rolling friction engagement with each other at the two
points of contact. In the present invention, however, the
20 rolling surfaces on one of the first and second elements
is characterized as being defined by a curved generatrix
to be convex in longitudinal section and the rolling surfaces
of the other of the elements is characterized as being also
defined by a curved generatrix bent to be concave in longitu-
; dinal section.
Described in detail below, as non-limiting examples,
are a particular method of construction in accordance with
.
. the invention, referring to the appended drawings.
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Figure 1 shows a longitudinal section of a trans-
mission designed in the above-mentioned manner made by a
plane passing through the first and second axes.
Figures 2, 3 and 4 shown respectively, in perspec-
tive and on a larger scale, three of the components of the
transmission of Figure 1 which have ~een shown in a cutaway
perspective view in Figures 2 and 4 in order to make the
drawing clearer.
The transmission shown includes a fixed frame
having two ends of flanks Al and A2 at each end which are
joined by a crank case A3 of a generally cylindrical form.
On this frame A, a first element 2 and a second element 3 ~- -
are mounted so as to be rotatable by means of bearings.
The first element 2 is rotatable around a first
axis 7 which is the longitudinal axis of the transmission and
which is fixed with respect to the frame A. The first element
2 includes two semi-sections 4 and 5 containing two rolling
surfaces 8 and 9 approximately of the shape of truncated cones
and which will be more specifically described below. These
two semi-sections 4 and 5 are mounted on a shaft 11 (output
shaft) that is coaxial with the first axis 7 and are movable
axially with respect to each other in the longitudinal direction
of the first axis 7. Keys 22a and 22b fasten the semi-sections
4 and S to the shaft 11 so that they may rotate together.
Two annular chambers 14a and 14b are constructed between
the interior wall of the two semi-sections 4 and 5 and the exterior
surface of shaft 11. These annular chambers communicate with the
outside by means of conduits 17a, 17b and 15 which are constructed
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for this purpose in the body of shaft 11. A cylindrical groove
18, which surrounds shaft 11, permits introducing a fluid into
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chambers 14a and 14b when shaft 11 rotates on itc own axis 7.
Sealing joints 21a, 21b, 21c, 21d, 21e and 21f assure tightness
of the system of annular chambers and of the fluid supply conduits
for these annular chambers. The effect of introducing a fluid
into the annular chambers 14a and 14b is to simultaneously dis-
place the two semi-sections 4 and 5 and the rolling surfaces 8
and 9 axially, thus separating them. The hydraulic apparatus
consists of the maneuvering component intended to modify the
relative positions of contact points Pl and P2 and consequently,
the txansmission ratio.
The rolling surfaces 8 and 9 rotate around the first
axis 7. They are symmetrically arranged on opposite sides of a
plane that is perpendicular to the first axis 7 at a point S of -
this axis. The two major bases of the semi-sections 4 and 5
face each other.
The shaft 11 is supported by frame A, at each of its
extremities, by a system of bearings including a first series
of roller bearings la and lb which are coaxial with the first --
axis 7.
A support 13 is rotatable around the first axis 7 by
means of bearings 25a and 25b inserted between frame A and a
` support 13. The abovementioned bearing lb is itself mounted
inside of support 13, approximately within the transversal plane
of bearing 25b at one extremity of the transmission so that the
first element 2 may turn with respect to support 13 which may
itself turn with respect to frame A.
Support 13, which is essentially symmetrical, is in-
; clined with respect to the longitudinal axis 7 of the transmission.
It is intended to support the second element 3 by means of roller
bearings 26a and 26b.
- The second element 3 is a solid of revolution, cylind-
rical in form, and it is rotatable with respect to support 13
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around a second axis 12 passing through point S of the first axis
7 and inclined at a constant angle a with respect to the latter.
The second element 3 carries two rolling surfaces 19
and 20 concentric with a second axis 12 and which are arranged
in s~mmetrical fashion to the second axis at point S. These
rolling surfaces are formed on two annular rings 27 and 28 which
are movable axially with respect to each other in the longitud-
inal direction of the second axis 12, inside the body of the
second element 3, and which are coupled for rotation with the
second element 3.
A mechanical system drives the two rolling surfaces
19 and 20 of the second element 3 axially in such a manner as
to apply them with force at two constant points Pl and P2,
against the rolling surfaces 8 and 9 of the first element 2.
Several methods of designing this mechanical system are des-
cribed in the aforementioned Canadian Application Serial No.
258,210 and these methods are applicable in the case of the
present improvements. By way of illustration, another method is
indicated in Figures 1 to 3 which are herewith appended. Accord-
ing to this method, each ring 27 and 28 (Figures 1 and 3) poss-
esses exterior helicoidal ramps, opposite in direction, which
make contact with interior helicoidal ramps 121a and 121b borne
by rings 122 and 123 which are housed within the second element
3 and are fastened to it. It is clear that the reaction between
the helicoidal ramps 120a and 120b, on the one hand, and 121a
and 121b, on the other hand, has a tendency to separate the semi-
sections 4 and 5 from each other and to apply the bearing tracks
8 and 9 against bearing tracks 19 and 20 with a normal force
sufficient to transmit the input torque without slipping.
Apparatus which shall be described below prevents the
second element 3 from turning around the first axis 7 with respect
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to frame A. Finally, an input shaft 33 is mounted so as to
rotate in support 13. This shaft 33 is coaxial with axis 7.
The transmission which has been described up to this
point with reference to Figure 1 is practically identical to
the one for which several designs have been described in the
aforementioned co-pending patent application. It would be use-
ful to review its method of operation here.
The rolling surfaces 8 and 9 of the first element 2
are in rolling frictional contact at Pl and P2 against surfaces
19 and 20 of the second element 3. The specific contact pressure
is created by ramps 120a and 120b, 121a and 121b. Due to the
action of an input torque couple applied to shaft 33, surfaces
19 and 20 are caused to rotate, on the one hand, at velocity
~* around their own axis ~the second axis 12) and, on the other
hand, in a conical motion of the apex S, around the first axis
7, at velocity a.
The aforementioned rotational velocities ~*, a and
the rotational velocity ~ of the first element 2 around axis
7 are related to each other by a kinematic equation depending on
the geometry of the rolling surfaces. In the present case where
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the velocities ~ and ~ are maintained at a constant ratio (equal -
to 1), there is therefore only one output velocity at which the
transmission output shaft 11 will be driven for a given relative
position of points Pl and P2. -
It should be pointed out that the rolling surfaces 8
- and 9 of the first element 2 and the surfaces 19 and 20 of the
second element 3 automatically center themselves symmetrically
with respect to point S. In fact, decentering of one of these
surfaces of the first element would have the effect of correla-
tively decentering the corresponding surface of the second
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element. Consequently, the pressure at contact points Pl and
P2 would be different since one of the surfa¢es would receive
less thrust from the helicoidal ramps 120a and 120b than the
other one. This would result in a difference of fluid pressure
contained in annular chambers 14a and 14b, which is impossible
since these chambers are connected. Therefore, dissymmetry
between the surface, it does occur, disappears automatically.
The present improvements concern the mechanical link-
age introduced in the case of the special design employed
between frame A and the second element 3 in order to prevent
the latter from turning around the first axis 7 with respect
to frame A. ~Consequently, ~* = ~ = 0).
In accordance with these improvements, this linking
system is arranged to drive the second element 3 by one of the
longitudinal extremities, that is, the left extremity in accord-
ance with Figure 1. Although this system could be designed to
use an Oldham or similar joint, it is preferable to design it
using a transverse component connecting frame A to the second
element 3 and offering, on the one hand, sufficient flexibi-
lity in the transverse direction to permit conical movement of
the second element 3 around point S and, on the other hand,
offering practically zero flexibility in the circumferential
direct~on.
In accordance with the preferred design method which
is depicted in Figures 1 and 4, the abovementioned transverse
component is an annular diaphragm 124 with concentric corruga-
tions whose exterior edge is attached to frame A by means o~ a
first rigid ring 125 and whose interior edge is attached to the
second element 3 on one of the extreme transversal faces of
the latter by means of a second rigid ring 126. Ring 125 may
be axially blocked by flank Al against the exterior cage of
bearing 25a by interposing an annular brace 127 and prevented
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from rotating by means of keys 128 inserted in exterior slots
129 ~Figure 4) of ring 125. As for ring 126, it can be attached
to the second element 3 by means of screw 130 which also serves
to attach annular ring 122. The operation of diaphragm 124 (or
equivalent component) does not need any supplementary explana-
tion. It is obvious that, with respect to the conical gears of
the aforementioned patent application, it facilitates the con-
struction of the transmission by freeing the central portion
of the latter and by permitting the entire essentially cylindri-
cal portion of support 13 to be constructed in one place.
In accordance with another aspect, the present improve-
ments concern the shape of the rolling surfaces 8 and 9 of the
first element 2 and rolling surfaces,l9 and 20 of the second
element 3 and aim to provide surfaces of a nature such that a
relatively small axial displacement performed by the hydraulic
type maneuvering component will result in a relativel~ large
axial displacement of contact points Pl and P2.
For this purpose, the two couples of these rolling
surfaces have curved generatrices whose radii of curvature are
comparable and are long with respect to the average distance
of each surface from its axis of revolution 7 or 12. The ratio
between these radii of curvature and this average distance is
preferably between 10 and 100.
According to the method of construction shown in
Figure 1, the generatrices of the two rolling surfaces 8 and 9
of one of the couples, that is, those of the first element 2,
are concave in form whereas the generatrices of the two sur-
faces 19 and 20 are convex in form~ In Figure 1, rl indicates
the radius of curvature of one of the two generatrices of
the surface 8 which are located within the plane of the fig-
ure and r2 indicates the radius of curvature of one of the two
generatrices of the surfa~e 19 which also is located within
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this plane, these two generatricec being tangent at point Pl.
Radius rl is slightly larger than radius r2 but is of the same
order of magnitude.
It is easy to calculate (generally with the help of
a computer) the radius of curvature rl and r2 as a function of
the angle of inclination a so as to obtain the desired result.
The latter is a compromise between acceptable efficiency (related
to the area of contact points or zones) and a large displace-
ment of points Pl and P2 for a relatively small displacement
of semi-sections 4 and 5 and, consequently, of rings 27 and 28.
Because of this, a variation of transmission ratio is obtained
which is not only economical but practically without inertia.
Having explained the invention and its importance as
justified by detailed examples, the applicant reserves exclu-
sive rights to it for the duration of the patent without
any limitations other than the terms of the following claims.
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