Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR MANUFACTURING A FACE GEAR
BACKGROUND OF THE INVENTION
[0001] The present invention is directed generally to a method and apparatus
for the development of face gears and, more specifically, to a method and
apparatus for the development of face gears suitable for high power
transmission.
[0002] The development of face gears for high power transmission is a
relatively recent phenomenon. Historically, the transmission of power through
a
face gear set has been limited to relatively low levels because of two
factors: 1)
the tooth profile of the mating gears has been generated by shaper cutting;
and 2)
although an acceptable tooth profile could be generated, the tooth produced by
the
shaping operation did not have a hardened surface. The tooth profile produced
by
the shaping operation required that the resulting face gear set be kept in
almost
perfect alignment. In the past, any operation performed on the face gear set
to
harden the surface of the shaped teeth tended to distort the shape of the face
gear
set during the hardening operation.
[0003] A previous method of manufacture of face gears was developed by
Fellows Corporation. The method uses a gear shaper apparatus, and the finished
product is useful for low power applications.
[0004] The Fellows Corporation method employs a metal cutting process for
shaping the gear teeth of the face gear. This process can only be applied to
materials with suitable hardness and metal cutting characteristics. If the
material is
too hard, the shaper tool will not cut effectively. This shaping process can
only be
used effectively for finish cutting face gear teeth from metals suitable for
low
power applications. This process does not give the accuracy and surface finish
required for higher power applications.
CA 02581724 2010-01-27
[0005] The applicants have previously developed a novel method and
apparatus for manufacturing face gear sets suitable for high power
transmission
applications, which method and method and apparatus are described in U.S.
Patent
Number 6,390,894 which may be referred to for further details.
BRIEF SUMMARY OF THE INVENTION
[0006] The present invention is directed to a precision grinding apparatus for
grinding face gears having a gear table portion controllably driven for
rotation
about a central axis B and also being movable in a vertical plane along an
axis W in a
controlled manner. The apparatus further includes a case hardened face gear
mounted on the gear table portion. A grinding wheel mounted on the apparatus
has
controlled driven rotation about a central axis C, and is provided with a
grinding
surface of predetermined shape. The grinding wheel is movable in a controlled
manner toward and away from the gear along a feed axis V, the grinding wheel
being movable in a controlled manner in a tangential direction with respect to
the
gear and orthogonal to the feed axis V along a tangential feed axis TF wherein
the
motion of the grinding wheel in the C, V and TF axes, and movement of the gear
in-
B and W axes, is controlled by a central control means.
[0007] In an alternate embodiment of the present invention, the apparatus
further includes a feed mechanism for generating teeth on a face gear, said
feed
mechanism adapted to move said face gear in a composite vertical and
horizontal
direction such that said face gear traverses the entire width of the tooth
face of said
face gear.
[0008] In yet another embodiment, the present invention provides a grinding
apparatus for a tapered pinion gear having a base with a grinding portion
mounted
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thereon for generating teeth in a gear by abrasion, a gear driving portion
mounted
on said base in juxtaposition to and cooperating with the grinding portion,
and a
case hardened tapered pinion gear having preformed teeth of a predetermined
size
and configuration mounted on the gear driving portion. In this embodiment, the
gear driving portion has the capability of rotating the pinion gear in a
manner
controlled by a first CNC control portion in a central axis designated B 1,
and also
has the capability of moving said pinion gear up and down in a vertical axis
designated W in a manner controlled by a second CNC control portion. The
grinding portion includes a grinding wheel having a grinding surface thereon
in
which a worm of predetermined configuration is generated, and is rotatably
driven
and controlled by a third CNC control portion to control the rotation of the
grinding wheel in its central axis designated C. The grinding wheel also
includes a
fourth CNC control portion to control the motion of the grinding wheel toward
and
away from said pinion gear along a V axis, and a fifth CNC control portion to
control the motion of the grinding wheel in a tangential direction with
respect to
the pinion gear and orthogonal to said V axis along a TF axis. The CNC control
portions cooperate together to mesh said worm with said teeth of said pinion
gear
to form teeth in said gear in a continuous grinding operation.
[0009] Any of the described embodiments of the present invention may
further include a high-pressure temperature-controlled coolant system to
prevent
burning of the gear teeth during grinding.
BRIEF DESCRIPTION OF THE DRAWINGS
[00010] FIG. 1 is an elevational view of a prior art spur gear cutting
machine.
[00011] FIG. 2 is a partial view of a prior art blank grinding wheel (before
the
wheel is shaped).
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[00012] FIG. 3 is a partial view of a spur gear grinding wheel of the prior
art
showing the dressing tool used to provide a cutting profile.
[00013] FIG. 4 is a perspective view of a face gear and a mating pinion gear.
[00014] FIG. 5 is a sectional view of a mating pinion and face gear.
[00015] FIG. 6 is a sectional view of a prior art face gear shaping apparatus.
[00016] FIG. 7 is an elevational view of a grinding apparatus of the present
invention adapted for grinding teeth on regular, concave, and convex face
gears.
[00017] FIG. 8 illustrates exemplary regular, concave, and convex face gears.
[00018] FIG. 9 is a perspective view of a complete grinding machine for
grinding teeth on a convex face gear and constructed in accordance with the
teachings of the present invention.
[00019] FIG. 10 is a plan view of the grinding wheel of the present invention
showing associated dresser apparatus motion.
[00020] FIG. 11 is a plan view of a grinding machine constructed in
accordance with the teachings of the present invention.
[00021] FIG. 12 is a spatial representation of the three major components of a
face gear machine constructed in accordance with the teachings of the present
invention, to more clearly illustrate the various component axes.
[00022] FIG. 13 is a spatial representation of the three major components of a
face gear machine constructed in accordance with the teachings of the present
invention and adapted for producing teeth on a pinion gear.
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[00023] FIG. 14 is a perspective view of a face gear grinding apparatus
adapted for producing teeth on a pinion gear.
[00024] FIG. 15 is an elevational view of a grinding wheel showing a typical
face gear configuration used in this invention.
[00025] FIG. 16 is an end view of the machine of FIG. 9.
[00026] FIG. 17 is an elevational view of the machine of FIG. 9.
DETAILED DESCRIPTION OF THE INVENTION
[00027] Turning now to the drawings, wherein like numerals represent like
parts, the numeral 10 represents generally a prior art spur gear grinding
apparatus.
A machine 12 (partially shown) is provided with a moveable carrier 14 that is
capable of executing rectilinear motion, as indicated by a double arrow 16.
Carrier
14 is provided with a gear driving head 18, which is connected to lead shaft
20.
The end of shaft 20 remote from driving head 18 is centered in tailstock 22 in
order
to stabilize shaft 20. A spur gear 24 is mounted on shaft 20 so as to be
controllably
rotated by driving head 18.
[00028] A spur gear grinding wheel 26 is shown engaging the peripheral
surface of spur gear 24. Grinding wheel 26 takes the same form as grinding
wheel
36, shown in FIG. 3, and must be capable of movement toward and away from
gear 24 as indicated by double arrow 28. The rotation of the grinding wheel is
coordinated with the rotation of the spur gear.
[00029] To produce a ground spur gear, the grinding wheel 26 is advanced
toward gear 24 while gear 24 is synchronously rotated to be in step with the
"worm" profile at grinding wheel 26, until grinding wheel 26 has advanced to
the
desired depth into a selected area of the spur gear. The spur gear is now
gradually
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moved in an axial direction to permit grinding wheel 26 to complete the
grinding
along the tooth length of the gear. This process is repeated for increased
material
removal until tooth size and profile are achieved.
[00030] FIG. 2 shows a grinding wheel 30 of the prior art before being dressed
to have a grinding profile.
[00031] FIG. 3 shows a grinding wheel 36 that contains a worm profile 38
(used for grinding spur gear teeth as previously described), which profile is
formed
by dressing tool 40, which carries a specially shaped dressing disc 42 to
provide
the worm profile. The dressing tool 40 is moved across the surface of the
grinding
wheel 36 as grinding wheel 36 rotates. Disc 42 is advanced into the surface of
wheel 36 until the desired tooth form is achieved. The shape of profile 38 on
the
surface of wheel 36 is formed by the shape of the profile of grinding disc 42
(i.e.
the axis of rotation of disc 42 is usually parallel to the axis of rotation of
wheel 36).
[00032] FIG. 4 shows an illustration of a regular face gear 50 and a meshing
piston 52. The teeth 54 on face gear 50 extend in a radial direction; the
teeth 56 on
pinion 52 are parallel to the axis of rotation of pinion 52.
[00033] FIG. 5 shows the face gear 50 and pinion in section. The teeth 54 and
56 are shown in a meshed condition.
[00034] FIG. 6 is an illustration of a prior art method of shaping the teeth
on
face gear 50 by shaper cutter 60. The shaper cutter 60 is reciprocated in an
axial
direction (as shown by arrows 62) while it and the face gear 50 and the shaper
cutter 60 are constantly moving in a simulated meshing engagement, until the
desired tooth form has been generated.
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[00035] FIG. 7 depicts a face gear work head 68 and face gear grinding head
100 constructed in accordance with the teachings of the present invention. The
embodiment shown in FIG. 7 is used for grinding the teeth of either regular,
convex, or concave shaped face gears. In the illustration, a convex face gear
70 is
shown mounted on a controllable rotating table 72 so as to rotate about axis
74.
Rotating table 72 is directly mounted on CNC drive motor 80. Motor 80 serves
to
drive rotating table 72 and is mounted directly on base 76. Face gear work
head 68
is able to swivel about swivel axis 78. The degree of swivel of face gear work
head 68 is closely controlled by swivel selector 108, shown in FIG. 9. The
entire
rotating face gear head 68 is preferably capable of executing controlled
motion in a
vertical direction during a tooth grinding operation, as shown by arrow 90.
CNC
control permits controlled motion in the vertical axis. In the illustration
shown, the
gear axis of rotation is maintained in a horizontal orientation during
grinding.
[00036] Grinding head 100 has a grinding wheel 102 rotatably mounted
thereon. Grinding head 100 is precisely located with respect to face gear work
head 68 and grinding wheel 102. The whole grinding head 100 must be capable of
executing controlled motion in a horizontal direction during a tooth grinding
operation as shown by arrow 210. CNC control permits controlled motion in the
horizontal axis.
[00037] Grinding wheel 102 is provided with a special worm profile 268 (see,
for example, FIGS. 10 and 15), and the grinding operation is carried out by
advancing grinding wheel 102 toward face gear 70 so that grinding wheel
profile
268 and the face gear mesh precisely (i.e. the worm of grinding wheel 102 has
a
profile that meshes with the teeth of face gear 70). The feed mechanism for
generating the teeth on face gear 70 slowly moves face gear 70 in a composite
vertical and horizontal direction until the grinding wheel has traversed the
entire
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width of tooth face 71 of face gear 70. Grinding wheel 102 is gradually
advanced
into the surface of tooth face 71 of face gear 70 with each succeeding pass,
until
the desired tooth profile 268 is produced.
[00038] FIG. 8 shows examples of configurations of face gears that the present
invention is capable of grinding. Regular face gear 50, convex face gear 70,
and
concave face gear 106 can all be ground using the teachings of the present
invention. The criteria used for determining the face gear description include
the
angle measurement between the gear tooth face 71 and the gear axis of rotation
82.
The present invention can also be adapted to grind a pinion gear, detailed
below,
not shown in this figure.
[00039] FIG. 9 depicts a full grinding machine 200 constructed in accordance
with the teachings of the present invention. A base 202 is provided to permit
face
gear work head 68 to be mounted thereon in a predetermined fashion. This
apparatus drives rotating table 72 on which face gear 70 is mounted in a
controlled
manner about its axis (designated axis `B"). Rotating table 72 is directly
mounted
on CNC drive motor 80. Motor 80 serves to drive rotating table 72 and is
directly
mounted on base 76. Base 76 is mounted on work table 214, which allows face
gear work head 68 to also swivel about its mounting on worktable 214. This
permits the face gear to have a manually adjustable angular swivel setting
designated as the "WTS" axis. Worktable 214 is constrained to permit it to
move
in a vertical plane along rails 216 by drive motor 222. This vertical axis is
designated as the "W" axis.
[00040] Grinding head 100, on which grinding wheel 102 is mounted, is
mounted on base 202 in such a manner that grinding wheel 102 may be moved
toward and away from face gear work head 68, and grinding wheel 102 may move
tangentially to work head 68 as well. Grinding head 100 is permitted to move
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along rails 259 to produce the motion of the carriage 254 toward and away from
face gear work head 68. This is a feed axis, which is designated as the "V"
axis.
Carriage 254 is also mounted on rail 252 to produce the motion of grinding
wheel
102 in a tangential direction with respect to face gear 70. This axis is
designated as
the "TF" axis. Grinding table 258 is capable of pivoting carriage 254 about
pivot
260. This is the grinding wheel pivot axis and is designated as the "WT" axis.
Grinding wheel 102 rotates about an axis designated as axis "C" and is driven
by
motor 262, which is integrally mounted on carriage 254. Grinding wheel 102 has
a
predetermined profile inscribed on its surface as shown in FIG. 10. Other
views of
the grinding machine of FIG. 9 are provided in FIGS. 16 and 17.
[000411 During the initial set up of machine 200, axes "TF" and "WT" are set
and locked with respect to the tooth configuration already existing on face
gear 70.
(Face gear 70 has already undergone tooth shaping and surface hardening
operations before being mounted in machine 200). During the initial approach
of
grinding wheel 102 to face gear 70, motor 262 is rotating grinding wheel 102
about
axis "C" and motor 80 is rotating face gear 70 about axis B. The rotation of
axis
"C" & "B" are in a prescribed synchronized manner. Carriage 254 is fed along
the
"V" axis to carry grinding wheel 102 toward face gear 70 until the desired
grinding
position is reached. During grinding, face gear table 214 undergoes controlled
movement along the feed axis "W" and grinding head 100 undergoes controlled
movement along the feed axis "V" until the grinding wheel has moved
sufficiently
so that the entire tooth face 71 of face gear 70 has been traversed by
grinding
wheel 102. Grinding wheel 102 is then moved slightly toward table 214 and the
grinding operation is repeated until the desired depth of the tooth form and
shape is
generated.
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[00042] A rotary diamond dressing tool assembly 264 is also mounted on
grinding table 258, along rail 256. Assembly 264 includes a rotary device 266,
which rotates a diamond impregnated disc 280 (see FIG. 10). Disc 280 is used
to
generate (by abrasion) a prescribed form in grinding wheel 102. Device 266 is
adjustable in height and angle on and about post 270, on which device 266 is
mounted. The entire dresser assembly 264 is mounted on table 258 so as to be
capable of controlled motion in three axes. A first axis of motion allows the
dresser
assembly mounted on feed table 274 to move backwards and forwards along rails
272 away from and towards grinding wheel 102. This axis is designated as the
"Y"
axis.
[00043] Movement of dressing tool assembly 264 along rails 256 in a
translatory fashion (parallel to the axis of grinding wheel 102) is designated
as the
"X" axis. Movement of dresser wheel 280 about post 270 in an angular fashion
will
define the angular axis "A". The grinding wheel profile demands that the move-
ment of feed table assembly 274 for dresser assembly 264 be synchronized with
the rotation of grinding wheel 102 such that disc 280 of dresser assembly 264
properly meshes the profile of grinding wheel 102.
[00044] The grinding operation of the partially completed and surface
hardened face gear 70 is as follows:
[00045] Rotating table 72 is manually set to a predetermined tilt (WTT) and
swivel (WTS) settings and these positions are locked. The partially finished
gear is
mounted on rotating table 72 so as to have a predetermined angular position on
axis "B". Grinding wheel carriage 254 is then set at the appropriate angle on
the
pivot axis WT and locked. Carriage 254 is moved along rail 252 until grinding
wheel 102 is set at a predetermined position on the "TF" axis with respect to
face
gear 70.
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[00046] The rotating grinding wheel 102 is now moved along the "V" "feed"
axis to move toward the partially finished rotating face gear 70 in a
horizontal
direction. Next, rotating face gear 70 is moved along the "W" "feed" axis
towards
the engagement point with the rotating grinding wheel in a vertical direction.
These
linear axes can be moved independently or simultaneously under CNC control to
achieve the initial face gear grinding position.
[00047] To perform the grinding of face gear 70, and to permit the grinding
wheel 102 to traverse the entire width of tooth face 71 of gear 70, work table
214 is
now moved vertically along rails 216. Carriage 254 is moved horizontally along
rails 259 under CNC control in a composite manner. The combined CNC motion
of the "V" & "W" feed axis enables the face gear manufacturing apparatus to
grind
various face gear configurations (concave to convex), as will be apparent to
those
of skill in the art upon reading this disclosure. This process is repeated in
a series
of grinding passes until the desired size and tooth configuration is generated
in face
gear 70.
[00048] Periodically, during the grinding operation, the profile of the
grinding
wheel 102 must be restored. When this is necessary, grinding wheel 102 is
retracted from face gear 70 and dresser assembly 264 is brought into position
on
rails 272 and 256 to engage grinding wheel 102 and to restore the profile on
wheel
102 to its original profile. Grinding disc 280 is engaged with grinding wheel
102
in accordance with CNC control to move in a controlled manner to restore the
profile 268 to wheel 102 to its required dimensional shape.
[00049] FIG. 14 shows the apparatus of FIG. 9 modified to permit the finish
grinding of a pinion gear 300. Pinion 300, in this instance, is a tapered spur
gear
pinion. Grinding wheel 302 now carries a significantly different profile from
the
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profile inscribed in the surface of grinding wheel 102 for face gear grinding.
The
profile inscribed on the surface of wheel 302 is similar to that shown in FIG.
3.
[00050] The face gear work head 68 of FIG. 9 has been replaced with work
table 304, which supports and rotates pinion 300 during grinding.
[00051] Tapered pinion 300 rotates about an axis designated as "B 1" in an
angular motion synchronized with grinding wheel 302. The worktable assembly
304 is capable of vertical translatory motion along rails 216, designated the
"W"
axis as previously described with respect to FIG. 9. The motion of grinding
wheel
302 along the "V" axis is CNC controlled, as is the movement of pinion 300
along
the "W' axis. It will be obvious to those skilled in the art that the motion
of
grinding wheel 302 in the "V" axis must be carefully coordinated with the
motion
of table 304 along rails 216 in order to produce tapered spur gear pinion 300.
[00052] The dresser apparatus for grinding wheel 302 is required as
previously, but is omitted from FIG. 14 for reasons of clarity.
[00053] It is further contemplated that any of the face gear grinding devices
of
the present invention may include a high-pressure temperature-controlled
coolant
system to prevent burning of the gear teeth being ground.
[00054] The axes defined herein are as follows:
AXIS DEFINITION CONTROL
C Grinding Wheel 102 (302 Rotation CNC
V Grinding Wheel 102 (203) in Feed CNC
WT Grinding Wheel 102 (302) Tilt Manual
TF Grinding Wheel 102 (302) Tangential CNC or
Feed Manual
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B Rotating Table 72 Rotation (Face Gears) CNC
B 1 Driving head 318 Rotation (Tapered Spur CNC
Gear Pinion)
W Work Table 214 Axial Feed CNC
WTS Work Head 212 (69, 304) Swivel Manual
A Dresser Tool 264 Rotary Feed CNC
X Dresser Tool 264 Cross Feed CNC
Y Dresser Tool 264 In Feed CNC
DH Dresser Tool 264 Height Manual
DT Dresser Tool 264 Tilt Manual
[00055] BASIC OPERATION OF THE FACE GEAR GRINDING
MACHINE
[00056] FIG. 11 provides a plan view of a face gear grinding machine
constructed in accordance with the teachings of the present invention. Machine
200 utilizes a CNC system that enables the axes under its control to be moved
in a
predetermined manner via a set of instructions in a program. Numerous programs
will be created to control the dressing cycle and gear grinding cycle of
machine
200 for different configurations of gears. The CNC control enables the axes of
motion to be continually synchronized even when switching between the dressing
and grinding cycles.
[00057] MANUAL SETTINGS
[00058] The work table 212 swivel "WTS" is commonly set in the vertical
position and locked for the gears described herein. This feature is
incorporated for
helical gear form requirements. Grinding wheel 102 tilt "WT" is set for lead
angle
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compensation. Grinding wheel tangential feed "TF" positions the wheel with
respect to the central axis of the gear in a horizontal plane. This feature,
when CNC
controlled, is incorporated for helical gear form requirements. Dresser rotary
device 266 tilt is set for angular clearance "DT" and diamond disc 280
grinding
wheel 102 centerline height "DH".
[00059] GRINDING WHEEL DRESSINGS CNC CONTROLLED
[00060] CNC programs stored in the memory of the CNC control are selected
to control this process. These programs command the motion of dresser axes X,
Y,
A, and grinding wheel 102 axis C in a prescribed manner to generate the
required
form on the grinding wheel. These programs control the speed and direction of
rotation of grinding wheel 102 with respect to the speed and direction of
motion of
dresser assembly 264, axis X, Y and A.
[00061] Via the CNC and the selected program, the speed of rotation of
grinding wheel 102 (axis C) relative to the speed of rotation of gear 70 (axis
B)
being ground is controlled. This relationship is controlled via an electronic
gearbox, which is a feature of the CNC. It is an important feature as the
grinding
process simulates the meshing of a worm gear which is the grinding wheel 102
with a face gear such as 70, which is the gear being finish ground. Also via
the
program and CNC, the following functions are also controlled:
[00062] Depth of Cut (axis V) - infeed of grinding wheel 102 to workpiece
(face gear 70);
[00063] Vertical feed of workpiece across grinding wheel 102 (axis W);
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[00064] Tangential Feed (TF) - positioning of grinding wheel 102 to
workp ece (face gear 70);
[00065] Dresser diamond disc 280 speed;
[00066] Control of dresser motion X,Y and A axis for initial and periodic re-
dressing of the grinding wheel 102;
[00067] Dimensional offsets and adjustments; and
[00068] Coolant on/off, and machine lubrication.
[00069] Examples of the composition of the basic material for gear 70 that
may be used successfully to practice the present invention is:
(a) SAE 9310 having components
Iron - 94.765%
Nickel - 3.25%
Chromium - 1.20%
Manganese - 0.55%
Molybdenum - 0.11 %
Carbon-0.10%
Silicon - 0.045% max.; or
TM
(b) PYROWEAR ALLOY 53 having the following components:
Iron - 90.2%
Molybdenum - 3.25%
Copper - 2.00%
Nickel - 2.00%
Chromium -1.00%
Silicon - 1.00%
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Carbon - 0.1 %
Vanadium - 0.1 %
[000701 The foregoing description of the embodiments of the invention has
been presented for purposes of illustration and description, and is not
intended to
be exhaustive or to limit the invention to the precise form disclosed. The
description was selected to best explain the principles of the invention and
practical application of these principles in order to enable others skilled in
the art
to best utilize the invention in various embodiments and with-such
modifications as
are suited to the particular use contemplated. It is intended that the scope
of the
invention not be limited by the specification, but be defined by the claims as
set
forth below.
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