Note: Descriptions are shown in the official language in which they were submitted.
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TORQUE TRANSMITTING ASSEMBLY
AND METHOD OF PRODUCING
BACKGROUND
A pinion carrier is a support structure that locates pinion (or planet) gears
in
a planetary gear set and transmits torque to other components within a vehicle
transmission. A drive shell or planet carrier is a tubular metal component
that
carries torque from the pinion carrier to another component axially displaced
from the pinion carrier in the transmission. The drive shell also revolves
around
the central axis of the pinion carrier and supports the pinion gears.
Some known methods for producing a pinion carrier include progressively
stamping a cup and an end plate and welding the two pieces together; producing
powdered metal components which are brazed or bolted together; or cold
forming a cup which is welded to a stamped plate.
Current methods for producing a drive shell include deep drawing sheet
metal to a tubular shape and forming splines on an inner wall thereof, and
cutting a thin walled tube to length and forming splines on an inner surface
thereof.
Known methods of producing a combined carrier and drive shell include
progressively stamping cups from metal stock having different diameters which
are then welded together facing each other. The inner cup is used as the
pinion
carrier, and the outer cup is used as the drive shell.
In respect of the practices listed above, several problems are experienced in
forming the pinion carrier portion of the assembly. Due to the brittle nature
of
powdered metal parts, the cross-section of the portion of the pinion carrier
that
separates the retaining faces must be structurally large. During
the
manufacturing process, a grain density variation is created at the bases of
the
portion of the pinion carrier that separate retaining faces where it meets
much
thinner retaining faces. This density variation, along with the concurrent
thickness change in the same area, results in a stress riser that frequently
causes
fracture and failure of the component. To counteract this, the legs and
retaining
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faces must be made thicker than would be needed when produced from wrought
material in order for the part to survive its application. This results in
increased
weight and space consumption, both of which are expensive and undesirable in
an automatic transmission environment.
For stamped parts, the production method provides more flexibility than
powdered metal and generally reduces space consumption by comparison.
However, there is no ability to significantly change the material thickness
for
any component of the assembly. Therefore, the entire part will be the same
thickness as that portion of the assembly needing the most strength. The
result is
excess mass and space consumption, although it represents a large improvement
in these aspects as compared to parts produced from powdered metal. The
biggest weakness of stamped parts is the lack of stiffness. Under heavy
loading,
the stamped parts frequently deflect to the point that the gears may become
misaligned causing undesirable noise and wear.
For cold formed parts, improved stiffness is experienced over stampings,
and the process can create various material thicknesses in different locations
on
the components. Therefore, it can minimize overall mass while concentrating
material in critical areas. Furthermore, tooling is comparable to that for
powdered metal and far less expensive and complex than that required for
stamping. The level of detail achievable in cold forming is good enough that
many applications require no machining other than creating the pinion shaft
holes after forming. However, cold forming is somewhat limited in its ability
to
create long extrusions cost-effectively.
It would be desirable to produce a torque transmitting assembly wherein
production efficiency is maximized and weight and production costs are
minimized.
SUMMARY OF THE INVENTION
According to the invention there is provided a torque transmitting
assembly including a generally cup shaped outer shell having a closed end and
an open end. The closed end has at least one raised portion formed therein.
The
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outer shell includes an outwardly extending lip surrounding the open end of
the
outer shell. The open end of the outer shell is adapted to be operatively
engaged
with a first rotating member. A generally disk shaped inner member has a
central aperture and a central axis. The inner member includes at least one
tab
extending axially outwardly therefrom and engages the raised portion of the
outer shell to facilitate a transfer of rotation between the outer shell and
the inner
member. The central aperture is adapted to be operatively engaged with a
second rotating member. The inner member is received inside said outer shell.
According to the invention there is also provided a torque transmitting
assembly including a drive shell having a closed end and an open end. The
closed end has a plurality of raised portions formed therein. The drive shell
includes an outwardly extending lip surrounding the open end of the drive
shell.
The open end of the drive shell is adapted to be operatively engaged with a
first
rotating member. A pinion carrier has a central aperture and a central axis.
The
pinion carrier includes a plurality of tabs extending axially outwardly
therefrom
and engages the raised portions of the drive shell to facilitate a transfer of
rotation between the drive shell and the pinion carrier. The central aperture
is
adapted to be operatively engaged with a second rotating member.
According to the invention there is also provided a method of producing a
pinion carrier and drive shell assembly. The method includes the steps of
providing a drive shell having a closed end and an open end, the closed end
has a
plurality of raised portions formed therein, the drive shell includes an
outwardly
extending lip surrounding the open end of the drive shell, the open end of the
drive shell is adapted to be operatively engaged with a first rotating member,
providing a pinion carrier having a central aperture and a central axis, the
pinion
carrier includes a plurality of tabs extending axially outwardly therefrom,
the
central aperture is adapted to be operatively engaged with a second rotating
member, inserting the pinion carrier into the drive shell and attaching the
tabs of
the pinion carrier to the raised portions of the drive shell to facilitate a
transfer of
rotation between the drive shell and the pinion carrier.
Various objects and advantages of this invention will become apparent to
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those skilled in the art from the following detailed description of the
invention,
when read in light of the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is an exploded perspective view of a pinion carrier and drive shell
assembly in accordance with the present invention.
Fig. 2 is a perspective view of the pinion carrier and drive shell assembly of
Fig. 1 shown assembled.
Fig. 3 is a section view of the pinion carrier and drive shell assembly of
Fig.
2 taken along line 3-3.
Fig. 4a is a perspective view of the pinion carrier of Fig. 1 illustrating
projections extending from tabs.
Fig. 4b is an enlarged fragmentary view of the projections of Fig. 4a.
DESCRIPTION OF INVENTION
The present invention will now be described with occasional reference to the
specific embodiments of the invention. This invention may, however, be
embodied in different forms and should not be construed as limited to the
embodiments set forth herein. Rather, these embodiments are provided so that
this disclosure will be thorough and complete, and will fully convey the scope
of
the invention to those skilled in the art.
Unless otherwise defined, all technical and scientific terms used herein have
the same meaning as commonly understood by one of ordinary skill in the art to
which this invention belongs. The terminology used in the description of the
invention herein is for describing particular embodiments only and is not
intended to be limiting of the invention. As used in the description of the
invention and the appended claims, the singular forms "a," "an," and "the" are
intended to include the plural forms as well, unless the context clearly
indicates
otherwise.
Unless otherwise indicated, all numbers expressing quantities of dimensions
such as length, width, height, and so forth as used in the specification and
claims
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are to be understood as being modified in all instances by the term
"about." Accordingly, unless otherwise indicated, the numerical properties set
forth in the specification and claims are approximations that may vary
depending
on the desired properties sought to be obtained in embodiments of the present
5 invention.
Notwithstanding that the numerical ranges and parameters setting
forth the broad scope of the invention are approximations, the numerical
values
set forth in the specific examples are reported as precisely as possible. Any
numerical values, however, inherently contain certain errors necessarily
resulting
from error found in their respective measurements.
The description and figures disclose a torque transmitting assembly,
combining a drive shell and a pinion carrier. Generally, the pinion carrier is
configured to seat against raised portions of the drive shell. The term "drive
shell", as used herein, is defined to mean any cup-shaped structure used to
transmit torque to other components. The term "pinion carrier", as used
herein,
is defined to mean any structure configured to locate pinion gears in a
planetary
gear set and transmit torque to other components.
Referring now to the drawings, and particularly Fig. 1, there is shown
generally at 10 an exploded perspective view of a pinion carrier and drive
shell assembly or torque transmitting assembly (hereafter "assembly")
incorporating the features of the invention. The assembly 10 includes a
drive shell 12 and a pinion carrier 14.
The drive shell 12 is a generally cup shaped or bowl shaped outer shell
having an open end 16, a closed end 18, and an outer wall 20. The closed end
18
of the drive shell 12 includes a central aperture 22 formed therein. An
annular
array of raised portions 24 is formed in the closed end 18 and surrounds the
aperture 22. In the illustrated embodiment, each of the raised portions 24 has
a
generally arcuate contour that radially aligns with the annular shape of the
outer
wall 20. Alternatively, each of the raised portions 24 can have other desired
contours. The raised portions 24 have an upper surface 25 as shown in Fig. 3.
In the illustrated embodiment, the upper surfaces 25 are substantially flat.
However, in other embodiments, the upper surfaces 25 can have other desired
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shapes, such as for example, crowned shapes. The raised portions 24 can be
formed using conventional methods for semi-piercing the closed end 18 of the
drive shell 12, such as the non-limiting examples of cold forming or stamping.
Referring again to Fig. 1, holes 26 are substantially interposed between
adjacent raised portions 24 to form an annular array of the holes 26 around
the
aperture 22 of the closed end 18. A plurality of access holes 28 is formed in
the
outer wall 20 of the drive shell 12. In the embodiment shown, the access holes
28 are formed adjacent the holes 26 to provide access thereto and facilitate
fabrication of the assembly 10.
An outwardly extending lip 30 surrounds the open end 16 of the drive shell
12. A plurality of splines or teeth 32 is formed on an inner surface of the
lip 30.
The pinion carrier 14 is a generally disk shaped inner member with a central
rotational axis A, a first side 34, and a second side 36. A plurality of tabs
38
extends axially outwardly from the second side 36 adjacent an outer edge 40 of
the pinion carrier 14. Referring now to Fig. 4a, each end of the tabs 38 has a
plurality of projections 39 extending axially therefrom. The projections 39
will
be discussed in more detail below.
Referring again to Fig. 1, a central collar 42 extends axially outwardly from
the first side 34 of the pinion carrier 14 and has a central aperture 44
formed
therein. An annular array of teeth 46 is formed on an inner surface of the
central
collar 42 and is adapted to receive an end of a shaft (not shown) therein, the
shaft having teeth formed on an outer surface thereof. An annular array of
holes
48 is formed in the pinion carrier 14 and is positioned to be aligned with the
holes 26 formed in the closed end 16 of the drive shell 12.
Referring again to the embodiment shown in Fig. 4a, the projections 39 have
a generally arcuate contour that corresponds to the arcuate contour of the
raised
portions 24 of the drive shell 12. In other embodiments, the projections 39
can
have other desired contours corresponding to the contour of the raised
portions
24. In the embodiment shown in Fig. 4a, the projections 39 extend
substantially
the length of the tabs 38. Alternatively, the projections 39 can extend less
than
the length of the tabs 38. In still other embodiments, the projections 39 can
be
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formed from discontinuous sections.
Referring now to Fig. 4b, each of the tabs 38 has a quantity of two
projections 39 that combine to form a saw tooth cross-sectional pattern. As
will
be explained in more detail below, the saw tooth pattern is used to increase
the
strength of a weldment attaching the pinion carrier 14 to the drive shell 12.
It
should be appreciated that in other embodiments, more or less than two
projections 39 can be used and the projections can form other desired cross-
sectional patterns sufficient to increase the strength of the weldment.
Assembly of the assembly 10 is accomplished by providing the drive shell
12 and the pinion carrier 14 as shown and described. The tabs 38 of the pinion
carrier 14 are aligned with the raised portions 24 of the drive shell 12. Once
aligned, the projections 39 are brought into contact with the upper surfaces
25 of
the raised portions 24. Bolts or rods (not shown) can be inserted through the
holes 26 and the holes 48 to assist in alignment of the tabs 38 and the raised
portions 24. The rods or bolts can be removed or left in as desired after
assembly of the assembly 10 is complete. Once the projections 39 contact the
upper surface 25 of the raised portions 24, the tabs 38 are welded to the
raised
portions 24 of the drive shell 12 to militate against separation of the drive
shell
12 and the pinion carrier 14 when in use. Desirable results have been obtained
using capacitance discharge welding to join the tabs 38 with the drive shell
12,
however, it is understood that other welding and joining methods can be used.
As discussed above, the saw tooth cross-sectional pattern formed by the
projections 39 is configured to increase the strength of the weldment by
increasing the area of the tab 38 being welded to the raised portion 24. Other
cross-sectional patterns that increase the weldment area can be used without
departing from the scope and spirit of the invention.
While the embodiment of the pinion carrier shown in Figs. 1-3 and 4a show
the tabs 38 as having a plurality of projections 39, it should be appreciated
that
in other embodiments the tabs can be formed without projections, i.e. the tabs
can have surfaces devoid of projections without departing from the scope and
spirit of the invention.
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Once assembled, the shaft having teeth formed on the outer surface thereon
is inserted through the aperture 22 of the closed end 18 of the drive shell 12
and
into the aperture 44 of the collar 42 to mate with the teeth 46 formed
therein. A
rotating member (not shown) is received adjacent the lip 30 to engage the
splines
32 thereof Thus, rotation of the shaft can be transferred to the rotating
member,
or from the rotating member to the shaft through the assembly 10. The assembly
is especially useful in a vehicle transmission, but it is understood that the
assembly 10 can be used in other applications as well.
The drive shell 12 and the pinion carrier 14 can be formed by any
10 conventional production method such as stamping, cutting, drawing, cold
forming, and flow forming, for example. Desirable results have been achieved
by forming the drive shell 12 using a flow formed or cold formed method and
forming the pinion carrier 14, often referred to as a "cup" or "pedestal", by
cold
forging or stamping. The use of flow forming, which is similar to cold
forming,
can concentrate the material where it is needed for strength. In addition,
extremely long tubular sections can be produced, and are therefore well suited
to
creating the drive shell 12 of the assembly 10.
Several benefits are achieved by forming and assembling the drive shell 12
and the pinion carrier 14 using the methods described. First, an assembled
joint
is eliminated between the pinion carrier 14 and the drive shell 12 which
typically
includes a retaining ring and two mating splines. Second, cold work hardening
of the drive shell 12 increases the strength thereof and thus, the mass of the
drive
shell 12 can be reduced compared to a stamped drive shell 12 at the same
torque
rating. Third, better alignment of critical portions of the pinion carrier and
drive
shell assembly 10 is experienced with minimized backlash between unnecessary
spline joints while maximizing balance. Fourth, material thickness can be
varied
throughout the assembly 10 with thicker material where needed for locating the
pinion shafts and resisting twisting of the planetary carrier portion and
thinner
material where permissible such as on the drive shell 12, for example. Fifth,
the
cost of the pinion carrier can be substantially reduced since the length of
the tabs
38 can be shortened. Sixth, since the closed end 18 of the drive shell 12 is
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devoid of apertures other than the central aperture 22 and the holes 26, the
closed end 18 is structurally more solid, thereby providing more strength to
the
assembly 10.
