Title of Invention	A METHOD FOR FORMING AN INTERNAL GEAR MEMBER AND A BROACHING TOOL
Abstract	The apparatus of the present invention provides a broaching machine configured to produce an internal gear member. The broaching machine includes a broaching tool defining a central axis. The broaching tool includes a first set of broaching teeth configured to cut both a first flank portion and a second flank portion of a plurality of gear teeth. The broaching tool also includes a second set of broaching teeth configured to cut only the second flank portion of the plurality of gear teeth. The plurality of gear teeth are formed such that the first and second flank portions of each gear tooth are tapered between a first end portion and a second end portion. The broaching machine also includes a motor configured to rotate the broaching tool about the central axis at a selectable rate and in a selectable direction. A corresponding method for producing an internal gear member is also provided.

Title of Invention

A METHOD FOR FORMING AN INTERNAL GEAR MEMBER AND A BROACHING TOOL

Abstract

The apparatus of the present invention provides a broaching machine configured to produce an internal gear member. The broaching machine includes a broaching tool defining a central axis. The broaching tool includes a first set of broaching teeth configured to cut both a first flank portion and a second flank portion of a plurality of gear teeth. The broaching tool also includes a second set of broaching teeth configured to cut only the second flank portion of the plurality of gear teeth. The plurality of gear teeth are formed such that the first and second flank portions of each gear tooth are tapered between a first end portion and a second end portion. The broaching machine also includes a motor configured to rotate the broaching tool about the central axis at a selectable rate and in a selectable direction. A corresponding method for producing an internal gear member is also provided.

Full Text	BROACHING APPARATUS AND METHOD FOR PRODUCING A GEAR MEMBER WITH TAPERED GEAR TEE 11I TECHNICAL FIELD [0001] The present invention pertains generally to a broaching apparatus and method for producing a gear member with tapered gear teeth. BACKGROUND OF THE INVENTION [0002] When a planetary gearset is under load, even under light load in the context of generally experienced gear noise situations, the planet carrier may deflect and the planet pinion bearings, which are not perfectly rigid, may become slightly displaced. As a result, the gears of a planetary gearset may not remain perfectly parallel under load. In other words, gears that perfectly mesh in theory may. under actual working conditions, contact each other at a point that is not centered in the middle of the tooth flank. [0003] It is well known to subject gear members to a heat treatment process in order to improve material characteristics such as strength or rigidity. Under certain circumstances, the heat treatment process can vary or alter tooth flank geometry which can also cause misalignment between the teeth of engaged gear members. This misalignment, either from planet carrier deflection or from the heat treatment process, can shift the load distribution on a gear tooth thereby increasing gear noise and reducing durability. SUMMARY OF THE INVENTION [0004] The present invention provides a broaching machine configured to produce an internal gear member. The broaching machine includes a broaching tool defining a central axis. The broaching tool includes a first set of broaching teeth configured to cut both a iirst flank portion and a second flank portion of a plurality of gear teeth; and a second set of broaching teeth configured to cut only the second flank portion of the plurality of gear teeth. The plurality of gear teeth arc formed such that the first and second flank portions of each gear tooth are tapered between a first end portion and a second end portion. The broaching machine also includes a motor configured to rotate the broaching tool about the central axis at a selectable rate and in a selectable direction. [0005] The present invention also provides a method for forming an internal gear member having a plurality of gear teeth. The method includes providing a broaching tool having a first set of broaching teeth and a second set of broaching teeth, and providing a gear blank defining an internal aperture. The broaching tool is passed through the internal aperture of the gear blank to form the gear teeth. The broaching tool is rotated at a first predefined rate as it passes through the internal aperture of the gear blank such that the first set of broaching teeth cut both a first flank portion and a second flank portion of each tooth. The broaching tool is then rotated at a second predefined rate as it passes through the internal aperture of the gear blank such that the second set of broaching teeth cut only the second flank portion of each tooth. [0006] The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0007] FIGURE 1 is a schematic illustration of a broaching machine in accordance with the present invention; [0008] FIGURE 2 is a perspective illustration of an internal gear member produced in accordance with a method of the present invention; [0009] FIGURE 3a is a schematic sectional illustration of the gear member of FIGURE 2 engaged by broaching teeth shown in Figure 1 during a fust stage of broaching formation; and [0010] FIGURE 3b is a schematic sectional illustration of the gear member of FIGURE 2 engaged by broaching teeth shown in Figure 1 during a second stage of broaching formation. DESCRIPTION OF THE PREFERRED EMBODIMENTS [0011] Referring to the drawings, wherein like reference numbers refer to like components, Figure 1 shows a broaching machine 6 in accordance with the present invention. The broaching machine 6 includes a motor 8 configured to selectively rotate a broaching tool 10 about an axis 18 as will be described in detail hereinafter. The broaching tool 10 includes a shank 12, a plurality of broach teeth 14, and an end portion 16. The plurality of broach teeth 14 are not explicitly shown in Figure 1, but are schematically represented by the series of annular ribs or flanges shown. It should be appreciated by one skilled in the art that the annular ribs each include a sequence of notches (not shown) to form the individual broach teeth 14. The plurality of broach teeth 14 include a first section of teeth 20 and a second section of teeth 22. [0012] Referring to Figure 2, a gear member 26 produced in accordance with the method of the present invention is shown. The gear member 26 is preferably machined from an annular gear blank (not shown) defining a centrally located aperture 28. As will be described in detail hereinafter, the broaching tool 10 is pulled through the aperture 28 to form a plurality of internal gear teeth 30. The gear teeth 30 each define a first end portion 32, a second end portion 34, a first flank 36 and a second flank 38. The gear teeth 30 are tapered, which means that the first and second flanks 36, 38 arc not parallel. According to the preferred embodiment, the first end portion 32 is generally parallel to the second end portion 34, and the second end portion 34 is wider than the first end portion 32. The tapered configuration of the first and second flanks 36, 38 in combination with the parallel first and second end portions 32, 34 arc generally configured to define a trapezoidal cross section for the teeth 30 as shown in Figure 2. [0013] The gear member 26 is preferably supported as the broaching tool 10 is pulled through the aperture 28 to cut the gear teeth 30. According to the preferred embodiment, the gear member 26 is preferably rigidly supported and the broaching tool 10 is selectively rotated about its axis 18 as it is pulled through the aperture 28. According to an alternate embodiment, the gear member 26 may rotate while the broaching tool 10 is pulled through the aperture 2K in a non-rotating manner. According to another alternate embodiment, both the gear member 26 and the broaching tool 10 can both be rotated as the broaching tool 10 is pulled through the aperture 28. [0014] Figures 3a-3b illustrate a sequence of steps or stages during which the gear member 26 is formed. More precisely, Figure 3a shows a first stage wherein a gear member 26a is formed by the broaching teeth 20, and Figure 3b shows a second stage wherein a gear member 26b is formed by the broaching teeth 22. Like reference numbers are used in Figures 3a-3b to refer to like components from Figures 1 and 2. For example, the suffix "a" added to a reference numeral identifies a similar component during a first stage of formation. Similarly, the suffix "b" added to a reference numeral identifies a similar component during second stage of formation. [0015] Referring to Figure 3a, a sectional view of the gear member 26a during a first stage of formation is shown. As shown, the broach teeth 20 engage both the first and second flanks 36a, 38a to produce a plurality of generally parallel gear teeth 30a. During this stage, the broaching tool 10 (shown in Figure 1) is rotated about its central axis 18 (shown in Figure 1) in a counter-clockwise direction such that the gear teeth 30a formed during this stage define a parallelogram but arc not rectangular. In other words, the flanks 36a, 38a are not perpendicular to the end portions 32a, 34a. The angle formed between the flanks 36a, 38a and the end portions 32a, 34a is selectable by controlling the rate at which the broaching tool 10 is rotated. For purposes of the present invention, the gear teeth 30a are "parallel" when the first and second Hanks 36a, 38a ol each gear tooth 30a are generally parallel with each other. Additionally, the first and second end portions 32a, 34a are preferably generally parallel with each other and substantially the same length. [0016] Referring to Figure 3b, a sectional view of the gear member 26b during a second stage of formation is shown. During this stage, the broaching tool 10 (shown in Figure 1) is rotated about its central axis 18 (shown in Figure 1) in a clockwise direction such that the broaching teeth 22 are brought into engagement with the first (lank 36b of each tooth 30b. As shown, the first Hank 36b of each tooth 30b becomes "tapered" or non-parallel relative to the second flank 38b as the first Hank 36b is cut by the broaching teeth 22. The rate at which the broaching tool 10 is rotated is selectable to control the degree of taper of the first flank 36b. The first and second end portions 32b. 34b are preferably generally parallel, and one of the end portions (e.g.. the first end portion 32b) is narrower than the other of the end portions (e.g., the second end portion 34b). [0017] In addition to producing a gear member having square gear teeth as shown in Figure 2, the method of the present invention may also be implemented to produce a helical gear member (not shown) such as those used in a planetary gearsct. To produce a helical gear member, a helical broaching tool (not shown) is generally rotated in only one direction, however the rate of rotation is varied. [0018] Advantageously, the tapered geometry of gear members produced in accordance with the present invention can be adapted to accommodate for carrier deflection of a planetary gcarset (not shown) which is under load. Therefore, the alignment of the gear members within a planetary gearsct may be improved by incorporating tapered gear teeth such that gear noise is reduced and durability is increased. Similarly, it has been observed that the tapered gear tooth geometry can be adapted to accommodate for tooth flank deformation caused by a heat treatment process. In other words, the gear teeth can be tapered by an amount necessary to compensate for heat treatment induced tooth flank deformation and thereby improve looth alignment of engaged gear members. [0019] While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims. CLAIMS 1. A method for forming an internal gear member having a plurality of gear teeth comprising: providing a broaching tool having a first set ol" broaching teeth and a second set of broaching teeth; providing a gear blank defining an internal aperture; passing the broaching tool through the internal aperture of the gear blank; rotating the broaching tool at a first predefined rate as the broaching tool passes through the internal aperture of the gear blank such that the first set of broaching teeth cut both a first flank portion and a second flank portion of the plurality of gear teeth; and rotating the broaching tool at a second predefined rate as the broaching tool passes through the internal aperture of the gear blank such that the second set of broaching teeth cut only the second flank portion of the plurality of gear teeth; wherein the broaching tool is rotated sufficiently such that the first and second flank portions of each gear tooth are tapered between a first end portion and a second end portion so that one of said end portions is narrower than the other of said end portions. 2. The method of claim 1, further comprising rotating the broaching tool in one direction as the first set of broaching teeth cut both the first Hank portion and the second flank portion of the plurality of gear teeth, and rotating the broaching tool in an opposite direction as the second set of broaching teeth cut only the second flank portion of the plurality of gear teeth. 3. A broaching tool configured to form an internal gear member comprising: a first set of broaching teeth configured to cut both a first (lank portion and a second flank portion of a plurality of gear teeth; and a second set of broaching teeth configured to cut only the second flank portion of the plurality of gear teeth; wherein the broaching tool forms the plurality of gear teeth such that the first and second flank portions of each gear tooth arc tapered between a first end portion and a second end portion so that one of said end portions is narrower than the other of said end portions. 4. The broaching tool of claim 3, further comprising a shank. 5. The broaching tool of claim 3, further comprising an end portion. 6. A broaching machine configured to produce an internal gear member comprising: a broaching tool defining a central axis including: a first set of broaching teeth configured to cut both a first Hank portion and a second flank portion of a plurality of gear teeth; and a second set of broaching teeth configured to cut only the second flank portion of the plurality of gear teeth; wherein the broaching tool forms the plurality of gear teeth such that the first and second flank portions of each gear tooth are tapered between a first end portion and a second end portion so that one of said end portions is narrower than the other of said end portions; and a motor configured to rotate the broaching tool about the central axis at a selectable rate and in a selectable direction to form said tapered flank portions. 7. The broaching machine of claim 6. wherein the broaching tool includes a shank. 8. The broaching machine of claim 7, wherein the broaching tool includes an end portion.596-KOL-2007 The apparatus of the present invention provides a broaching machine configured to produce an internal gear member. The broaching machine includes a broaching tool defining a central axis. The broaching tool includes a first set of broaching teeth configured to cut both a first flank portion and a second flank portion of a plurality of gear teeth. The broaching tool also includes a second set of broaching teeth configured to cut only the second flank portion of the plurality of gear teeth. The plurality of gear teeth are formed such that the first and second flank portions of each gear tooth are tapered between a first end portion and a second end portion. The broaching machine also includes a motor configured to rotate the broaching tool about the central axis at a selectable rate and in a selectable direction. A corresponding method for producing an internal gear member is also provided.

Full Text

BROACHING APPARATUS AND METHOD FOR PRODUCING
A GEAR MEMBER WITH TAPERED GEAR TEE 11I
TECHNICAL FIELD
[0001] The present invention pertains generally to a broaching apparatus and
method for producing a gear member with tapered gear teeth.
BACKGROUND OF THE INVENTION
[0002] When a planetary gearset is under load, even under light load in the
context of generally experienced gear noise situations, the planet carrier may deflect and
the planet pinion bearings, which are not perfectly rigid, may become slightly displaced.
As a result, the gears of a planetary gearset may not remain perfectly parallel under load.
In other words, gears that perfectly mesh in theory may. under actual working conditions,
contact each other at a point that is not centered in the middle of the tooth flank.
[0003] It is well known to subject gear members to a heat treatment process in
order to improve material characteristics such as strength or rigidity. Under certain
circumstances, the heat treatment process can vary or alter tooth flank geometry which
can also cause misalignment between the teeth of engaged gear members. This
misalignment, either from planet carrier deflection or from the heat treatment process,
can shift the load distribution on a gear tooth thereby increasing gear noise and reducing
durability.
SUMMARY OF THE INVENTION
[0004] The present invention provides a broaching machine configured to
produce an internal gear member. The broaching machine includes a broaching tool
defining a central axis. The broaching tool includes a first set of broaching teeth
configured to cut both a iirst flank portion and a second flank portion of a plurality of
gear teeth; and a second set of broaching teeth configured to cut only the second flank
portion of the plurality of gear teeth. The plurality of gear teeth arc formed such that the
first and second flank portions of each gear tooth are tapered between a first end
portion and a second end portion. The broaching machine also includes a motor
configured to rotate the broaching tool about the central axis at a selectable rate and in a
selectable direction.
[0005] The present invention also provides a method for forming an internal gear
member having a plurality of gear teeth. The method includes providing a broaching tool
having a first set of broaching teeth and a second set of broaching teeth, and providing a
gear blank defining an internal aperture. The broaching tool is passed through the
internal aperture of the gear blank to form the gear teeth. The broaching tool is rotated at
a first predefined rate as it passes through the internal aperture of the gear blank such that
the first set of broaching teeth cut both a first flank portion and a second flank portion of
each tooth. The broaching tool is then rotated at a second predefined rate as it passes
through the internal aperture of the gear blank such that the second set of broaching teeth
cut only the second flank portion of each tooth.
[0006] The above features and advantages and other features and advantages of
the present invention are readily apparent from the following detailed description of the
best modes for carrying out the invention when taken in connection with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIGURE 1 is a schematic illustration of a broaching machine in
accordance with the present invention;
[0008] FIGURE 2 is a perspective illustration of an internal gear member
produced in accordance with a method of the present invention;
[0009] FIGURE 3a is a schematic sectional illustration of the gear member of
FIGURE 2 engaged by broaching teeth shown in Figure 1 during a fust stage of
broaching formation; and
[0010] FIGURE 3b is a schematic sectional illustration of the gear member of
FIGURE 2 engaged by broaching teeth shown in Figure 1 during a second stage of
broaching formation.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011] Referring to the drawings, wherein like reference numbers refer to like
components, Figure 1 shows a broaching machine 6 in accordance with the present
invention. The broaching machine 6 includes a motor 8 configured to selectively rotate a
broaching tool 10 about an axis 18 as will be described in detail hereinafter. The
broaching tool 10 includes a shank 12, a plurality of broach teeth 14, and an end portion
16. The plurality of broach teeth 14 are not explicitly shown in Figure 1, but are
schematically represented by the series of annular ribs or flanges shown. It should be
appreciated by one skilled in the art that the annular ribs each include a sequence of
notches (not shown) to form the individual broach teeth 14. The plurality of broach teeth
14 include a first section of teeth 20 and a second section of teeth 22.
[0012] Referring to Figure 2, a gear member 26 produced in accordance with the
method of the present invention is shown. The gear member 26 is preferably machined
from an annular gear blank (not shown) defining a centrally located aperture 28. As will
be described in detail hereinafter, the broaching tool 10 is pulled through the aperture 28
to form a plurality of internal gear teeth 30. The gear teeth 30 each define a first end
portion 32, a second end portion 34, a first flank 36 and a second flank 38. The gear teeth
30 are tapered, which means that the first and second flanks 36, 38 arc not parallel.
According to the preferred embodiment, the first end portion 32 is generally parallel to
the second end portion 34, and the second end portion 34 is wider than the first end
portion 32. The tapered configuration of the first and second flanks 36, 38 in
combination with the parallel first and second end portions 32, 34 arc generally
configured to define a trapezoidal cross section for the teeth 30 as shown in Figure 2.
[0013] The gear member 26 is preferably supported as the broaching tool 10 is
pulled through the aperture 28 to cut the gear teeth 30. According to the preferred
embodiment, the gear member 26 is preferably rigidly supported and the broaching tool
10 is selectively rotated about its axis 18 as it is pulled through the aperture 28.
According to an alternate embodiment, the gear member 26 may rotate while the
broaching tool 10 is pulled through the aperture 2K in a non-rotating manner. According
to another alternate embodiment, both the gear member 26 and the broaching tool 10 can
both be rotated as the broaching tool 10 is pulled through the aperture 28.
[0014] Figures 3a-3b illustrate a sequence of steps or stages during which the gear
member 26 is formed. More precisely, Figure 3a shows a first stage wherein a gear
member 26a is formed by the broaching teeth 20, and Figure 3b shows a second stage
wherein a gear member 26b is formed by the broaching teeth 22. Like reference numbers
are used in Figures 3a-3b to refer to like components from Figures 1 and 2. For example,
the suffix "a" added to a reference numeral identifies a similar component during a first
stage of formation. Similarly, the suffix "b" added to a reference numeral identifies a
similar component during second stage of formation.
[0015] Referring to Figure 3a, a sectional view of the gear member 26a during a
first stage of formation is shown. As shown, the broach teeth 20 engage both the first and
second flanks 36a, 38a to produce a plurality of generally parallel gear teeth 30a. During
this stage, the broaching tool 10 (shown in Figure 1) is rotated about its central axis 18
(shown in Figure 1) in a counter-clockwise direction such that the gear teeth 30a formed
during this stage define a parallelogram but arc not rectangular. In other words, the
flanks 36a, 38a are not perpendicular to the end portions 32a, 34a. The angle formed
between the flanks 36a, 38a and the end portions 32a, 34a is selectable by controlling the
rate at which the broaching tool 10 is rotated. For purposes of the present invention, the
gear teeth 30a are "parallel" when the first and second Hanks 36a, 38a ol each gear tooth
30a are generally parallel with each other. Additionally, the first and second end
portions 32a, 34a are preferably generally parallel with each other and substantially the
same length.
[0016] Referring to Figure 3b, a sectional view of the gear member 26b during a
second stage of formation is shown. During this stage, the broaching tool 10 (shown in
Figure 1) is rotated about its central axis 18 (shown in Figure 1) in a clockwise direction
such that the broaching teeth 22 are brought into engagement with the first (lank 36b of
each tooth 30b. As shown, the first Hank 36b of each tooth 30b becomes "tapered" or
non-parallel relative to the second flank 38b as the first Hank 36b is cut by the broaching
teeth 22. The rate at which the broaching tool 10 is rotated is selectable to control the
degree of taper of the first flank 36b. The first and second end portions 32b. 34b are
preferably generally parallel, and one of the end portions (e.g.. the first end portion 32b)
is narrower than the other of the end portions (e.g., the second end portion 34b).
[0017] In addition to producing a gear member having square gear teeth as shown
in Figure 2, the method of the present invention may also be implemented to produce a
helical gear member (not shown) such as those used in a planetary gearsct. To produce a
helical gear member, a helical broaching tool (not shown) is generally rotated in only one
direction, however the rate of rotation is varied.
[0018] Advantageously, the tapered geometry of gear members produced in
accordance with the present invention can be adapted to accommodate for carrier
deflection of a planetary gcarset (not shown) which is under load. Therefore, the
alignment of the gear members within a planetary gearsct may be improved by
incorporating tapered gear teeth such that gear noise is reduced and durability is
increased. Similarly, it has been observed that the tapered gear tooth geometry can be
adapted to accommodate for tooth flank deformation caused by a heat treatment process.
In other words, the gear teeth can be tapered by an amount necessary to compensate for
heat treatment induced tooth flank deformation and thereby improve looth alignment of
engaged gear members.
[0019] While the best modes for carrying out the invention have been described
in detail, those familiar with the art to which this invention relates will recognize various
alternative designs and embodiments for practicing the invention within the scope of the
appended claims.
CLAIMS
1. A method for forming an internal gear member having a plurality of gear
teeth comprising:
providing a broaching tool having a first set ol" broaching teeth and a
second set of broaching teeth;
providing a gear blank defining an internal aperture;
passing the broaching tool through the internal aperture of the gear blank;
rotating the broaching tool at a first predefined rate as the broaching tool
passes through the internal aperture of the gear blank such that the first set of broaching
teeth cut both a first flank portion and a second flank portion of the plurality of gear
teeth; and
rotating the broaching tool at a second predefined rate as the broaching
tool passes through the internal aperture of the gear blank such that the second set of
broaching teeth cut only the second flank portion of the plurality of gear teeth;
wherein the broaching tool is rotated sufficiently such that the first and
second flank portions of each gear tooth are tapered between a first end portion and a
second end portion so that one of said end portions is narrower than the other of said end
portions.
2. The method of claim 1, further comprising rotating the broaching tool in
one direction as the first set of broaching teeth cut both the first Hank portion and the
second flank portion of the plurality of gear teeth, and rotating the broaching tool in an
opposite direction as the second set of broaching teeth cut only the second flank portion
of the plurality of gear teeth.
3. A broaching tool configured to form an internal gear member comprising:
a first set of broaching teeth configured to cut both a first (lank portion and
a second flank portion of a plurality of gear teeth; and
a second set of broaching teeth configured to cut only the second flank
portion of the plurality of gear teeth;
wherein the broaching tool forms the plurality of gear teeth such that the
first and second flank portions of each gear tooth arc tapered between a first end portion
and a second end portion so that one of said end portions is narrower than the other of
said end portions.
4. The broaching tool of claim 3, further comprising a shank.
5. The broaching tool of claim 3, further comprising an end portion.
6. A broaching machine configured to produce an internal gear member
comprising:
a broaching tool defining a central axis including:
a first set of broaching teeth configured to cut both a first Hank
portion and a second flank portion of a plurality of gear teeth; and
a second set of broaching teeth configured to cut only the second
flank portion of the plurality of gear teeth;
wherein the broaching tool forms the plurality of gear teeth such
that the first and second flank portions of each gear tooth are tapered between a first end
portion and a second end portion so that one of said end portions is narrower than the
other of said end portions; and
a motor configured to rotate the broaching tool about the central axis at a
selectable rate and in a selectable direction to form said tapered flank portions.
7. The broaching machine of claim 6. wherein the broaching tool includes a
shank.
8. The broaching machine of claim 7, wherein the broaching tool includes an
end portion.596-KOL-2007

The apparatus of the present invention provides a broaching machine
configured to produce an internal gear member. The broaching machine includes a
broaching tool defining a central axis. The broaching tool includes a first set of
broaching teeth configured to cut both a first flank portion and a second flank portion of
a plurality of gear teeth. The broaching tool also includes a second set of broaching
teeth configured to cut only the second flank portion of the plurality of gear teeth. The
plurality of gear teeth are formed such that the first and second flank portions of each
gear tooth are tapered between a first end portion and a second end portion. The
broaching machine also includes a motor configured to rotate the broaching tool about
the central axis at a selectable rate and in a selectable direction. A corresponding
method for producing an internal gear member is also provided.

A METHOD FOR FORMING AN INTERNAL GEAR MEMBER AND A BROACHING TOOL

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