Note: Descriptions are shown in the official language in which they were submitted.
JEL-037
TITLE
PROCESS FOR PRODUCING SINTERED ARTICLE
FIELD
100011 The present disclosure relates to sintered articles, and
particularly to a planetary
carrier assembly comprising two components that are connected to each other by
sinter-
brazing and a design that considerably increases the strength of the assembly
compared to
the prior art for making the sintered article.
BACKGROUND
100021 Powder metallurgy (PM) is an important process used in the
manufacture
of automotive, marine and aviation components. For example, conventional press
and
sinter process has been widely used for manufacturing components such as
planetary gear
carriers. A typical planetary carrier usually includes a plate, a spider and a
number of legs
connecting the plate to the spider. For some planetary carries, the legs are
connected to
plate by sinter-brazing. Sharp corners are formed at positions where the legs
and the plate
are joined. One problem with such manufacturing process is that higher stress
concentration exists at the sharp corners.
BRIEF DESCRIPTION OF THE DRAWINGS
100031 Fig. 1 is an isometric view of a planetary gear carrier compact
including a first
compact and a second compact.
100041 Fig. 2 is an isometric view of the first compact of Fig. 1.
100051 Fig. 3 is an isometric view of the second compact of Fig. 1.
100061 Fig. 4 is a flow chart of a process for making a sintered article
according to one
embodiment.
100071 Fig. 5 is a flow chart of a process for making a sintered article
according one
embodiment.
100081 Fig. 6 illustrates the isometric view of prior art for the first
compact.
100091 Fig. 7 illustrates the isometric view of prior art for the second
compact.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
100101 Embodiments of the present disclosure will be described in detail
in conjunction
with the drawings. It should be noted that the figures are illustrative rather
than limiting.
The figures are not drawn to scale, do not illustrate every aspect of the
described
embodiments, and do not limit the scope of the present disclosure.
[0011] A sintered article according to an embodiment of the present
disclosure includes
a first component, a second component and one or more connecting members
connecting
the first component to the second component. The following descriptions
provide an
example of the sinter article taken in the form of a planetary gear carrier.
It should be noted
that the sintered article is not limited to the planetary gear carrier
described below.
[0012] Referring to FIGS. 1-3, the planetary gear carrier includes a
first component and
a second component that are respectively made by sintering a first compact 10
and a
second compact 20. The first compact 10 and the second compact 20 are each
formed by
applying pressure to powders of a selected composition.
[0013] The first compact 10 includes a first plate 11 that can be
circular, triangular,
square or any other shape depending on application and a number of first
protruding posts
12. The protruding posts 12 protrude from one side of the plate 11, and are
distributed
around a hole defined in the center of the plate 11. Each protruding post 12
has a cross
section that is typically of similar isosceles trapezoids, but can also be
cylindrical or any
other shape depending on requirements. Here, the cross section is taken
parallel to the side
where the protruding posts 12 protrude. Each protruding post 12 has a height
substantially
sufficient to incorporate corner radii, and also when stacked with second
protruding posts
of the second compact 20 total height is suitable for the required distance
between the first
plate 11 and the second plate of the second compact 20. The protruding posts
12 are sized
in such a way that they can provide a stable support for second protruding
posts of the
second compact 20 to stack thereon. The second plate and the second protruding
posts will
be described in detail in the following descriptions.
100141 The second compact 20 includes a second plate 21 that can be
circular,
triangular, square or any other shape depending on application and a number of
second
protruding posts 22. The second protruding posts 22 protrude from one side of
the second
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plate 21, and are evenly distributed around a hole defined in the center of
the second plate
21. Each second protruding post 22 has a cross section substantially the same
as the cross
section of a corresponding first protruding post 12. Here, the cross section
of the second
protruding post is taken parallel to the side where the protruding posts 22
protrude.
100151 In the embodiment, the first protruding posts 12 are
substantially perpendicular
to the plate 11, and the second protruding posts 22 are substantially
perpendicular to the
second circular plate 21. Corner radii 13 are formed between the first
protruding posts 12
and the first plate 11, and corner radii 23 are also formed between the second
protruding
posts 22 and the second plate 21.
100161 In the embodiment, the first compact 10 and the second compact 20
are
configured in such a way that a gap 3 is formed between the first protruding
posts 12 and
the second protruding posts 22 so as to place brazing material therein when
the first
compact 10 is placed on the second compact 20.
[0017] In one embodiment, each first protruding post 12 includes a
positioning
protrusion 121 and each second protruding post 22 defines a positioning recess
221 that
allows a corresponding positioning protrusion 121 to fit therein so as to
position the first
compact 10. Specifically, the positioning protrusion 121 is formed on the end
surface of
the first protruding post 12, and the positioning recess 221 is defined in the
end surface of
the second protruding post 22. The gap 3 is formed between the top end
surfaces of the
first protruding posts 12 and the second end surfaces of the second protruding
posts 22
when the first positioning protrusions 121 fit in the corresponding
positioning recesses
221. After the first compact 10 is placed on the second compact 20 with the
brazing
material also placed between the first protruding posts 12 and the second
protruding posts
22, the first compact 10 and the second compact 20 with the brazing material
are
assembled as shown in Fig 1. Then assemblies are brought into a sintering
furnace, so that
both compacts 10 and 20 are sintered at a predetermined temperature, at the
same time that
the brazing material is fused so as to join the first protruding posts 12 and
the second
protruding posts 22.
10018] In the embodiment, the brazed joints for joining the first
compact 10 and the
second compact 20 are located between the ends of the first protruding posts
12 and the
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second protruding posts 22. Compared with conventional brazed joints that are
formed
between the plate and the legs, no sharp corners are formed between the
protruding posts
12/22 and the circular plates 11/21. In addition, the first protruding posts
12 and the second
protruding posts 22 have substantially the same sized cross section. No sharp
corners are
formed at the positions where the first protruding posts 12 and the second
protruding posts
22 are joined.
100191 Compared to conventional planetary gear carriers, and the prior
art described
and that uses components 1 and 2 as shown in Figures 6 and 7, the planetary
gear carrier
produced by using the processes of the above embodiments eliminates the sharp
corners
between the plate and the legs, and is thus capable of withstanding higher
torque. Further,
sensitivity to brazing flaws or imperfections is reduced by moving the joint
away from the
highest stress location.
[0020] Referring to FIG. 4, in one embodiment, a process for making the
sintered
article includes the following steps: Step S401: blending powders of a
selected
composition; Step S402: pressing the blended powders to form the first compact
10 having
a first protruding post 12 and a second compact 20 having a second post 22;
and Step
S403: sintering the first compact 10 and the second compact 20 and joining the
first
protruding post 12 and the second protruding post 22 by sinter-brazing to form
the
sintered powder metal article.
100211 Referring to FIG. 5, in an alternative embodiment, a process for
making the
sintered article includes the following steps: Step S501: blending powders of
a selected
composition; Step S502: compacting the blended powders to form the first
compact 10
having a first protruding post 12 and a second compact 20 having a second post
22; Step
S503: positioning the first compact 10 with respect to the second compact 20,
with a
brazing material placed between the first protruding post 12 and the second
protruding post
22; and Step S504: heating to sinter the first compact 10 and the second
compact 20 and
fuse the brazing material so as to join the first protruding post 12 and the
second
protruding post 22 to form the sintered powder metal article.
[0022] In the embodiment, the manufacturing method described herein can
be applied
to a broad range of alloy compositions as required. Typical powders that can
be used with
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the process described herein to produce the sintered powder metal articles
include a
number of compositions with the remainder being iron and unavoidable
impurities.
100231 The formulated ferrous blend of powder, either admixed alloying
powders, pre-
alloyed iron, or partially pre-alloyed iron, together with carbon (which is
usually added as
graphite), ferro alloys if required, and lubricant, will be compacted in the
usual manner as
described by pressing in rigid tools.
100241 The compacted article is then sintered either at conventional
temperatures for
prealloyed and partially prealloyed iron which are, for example, in the range
of 1100 C to
1350 C. Sintering the base iron powder with ferro alloys is conducted at high
temperature
sintering generally greater than 1250 C. During the sintering, the brazing
material will be
fused and join the first protruding posts 12 and the second protruding posts
22.
100251 According to the embodiments of the present disclosure, corner
radii is
incorporated by designing the first compact 10 with a short post protruding
from the plate,
which facilitates the reduction of stress concentration where highest
resultant force is. In
addition, it is conducive to reducing deflection by designing the first
compact 10 with a
short post because the first component made by sintering the first compact has
a thicker
cross section.
100261 According to the embodiments of the present disclosure, the
processes enable
incorporation of radii at both ends of the legs, i.e., the part made by
sintering the first and
the second protruding posts, where highest stresses are seen, thereby
improving the
strength of the sintered article.
100271 According to the embodiments of the present disclosure, brazed
joint can
withstand higher forces due to reduction of deflection of the first component.
Samples
tested showed 70% improvement as measured in terms of separation force.
100281 The design claim and the art, as shown, is to change the
construction of prior art
from what is described and shown in Fig. 6 & 7, to Fig. 2 & 3 thus
incorporating corner
radii for the protrusions of both component 1 and 2. These corners, when the
sinter brazed
assembly is subjected to operating torque, suffer from the high stresses.
Prior art, once
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assembled results in radius on component 10 and a sharp corner where it joins
component
20 whereas claim of this new design is that by incorporating radii on both
components
assembly is capable of carrying higher torque since stress is reduced.
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