Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR
CORRECTING DIAMETRICAL TAPER
ON A WORKPIECE
Technical Field
This invention relates generally to a diamet-
rical taper correction system, and specifically to a
machine and machine arm assembly utilizing in-process
gauging to correct diametrical taper on a workpiece
journal surface.
to Background Art
This invention relates to a method and appara-
tus for correcting diametrical taper formed on workpiece
journal surfaces, which were previously ground in a
large scale manufacturing grinding machine. Taper, as
known in the art, is a condition in which the diameter
of a bearing surface is not constant along the axial
length of the surface. This condition occurs when
grinding machines used to grind the workpieces are
improperly maintained or when the various abrading means
used to remove material from the workpiece are
inadequately dressed during operation.
The prior art contains various examples of
grinding processes and machines that utilize an in-
process gauging system for altering or inducing modifi-
cations in a grinding process to correct taper. As it
is known in the art, in-process gauging is a method of
controlling a grinding or finishing operation in a
machine wherein engagement of the grinding or abrading
means with the workpiece is controlled in real-time by
a measurement signal generated from a gauge that is
likewise in contact with the workpiece surface. The
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grinding process can then be varied and different
results achieved by modifying various controls within
the grinding process in relation to the gauging signals.
Prior to this invention, in-process gauging
was used to correct taper existing on a plurality of
diameters on a workpiece by altering the grinding angle
of the grinding wheel in relation to the workpiece
during the grinding process. An example of this method
is disclosed in U.S. Reissue Patent No. 28,082 to Price,
reissued July 23, 1974. The Price patent discloses a
multiple or wide wheel grinding machine with a means
provided to vary the relative grinding angle between the
surfaces of a workpiece to be ground and the grinding
wheel.
In the grinding machine of the Price patent,
a pair of electrical size gauges are disposed alongside
the workpiece on separate axially spaced bearing
surfaces. These size gauges generate electrical signals
as the workpiece is being rotated about its longitudinal
axis during the grinding cycle. The two signals are
compared directly and a third signal is generated when
the difference between the signals exceeds a predeter-
mined value. The third signal actuates a means for
deflecting the grinding wheel and varying the angle of
the grinding contact point in response to the third
signal, correcting the taper previously existing on the
part while it is in the overall grinding process.
U.S. Patent No. 3,271,910 to Aisch discloses
a method for correcting the size and angular relation
between a workpiece to be ground and the grinding wheel.
Again, two size gauges are axially spaced from each
other on two different bearing surfaces of a workpiece
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such as a automotive crankshaft. The two gauge signals _
measure the diameters at the extreme ends of the work-
piece. When differences are noted in the measured
diameters and an independent master diameter, a servo
motor is engaged to displace the tail stock, thereby
changing the angle that the grinding wheel contacts the
workpiece surfaces being ground. This displacement
continues until deviations from the master diameter are
compensated for (i.e. until there is no longer differ-
ences between the diameters measured and the master
diameter).
As energy efficiency and fuel consumption
considerations become more and more important to automo-
tive manufacturers, bearing journal surfaces on internal
combustion engine components and related machine compo-
nents will continue to be machined to closer and closer
tolerances. Increased bearing loads, higher operating
speeds and greater durability requirements in today's
internal combustion engine manufacturers also further
the need for precision finishing of journal bearing
surfaces. Included with the requirement for more
precision finishing is the need to reduce diametrical
taper existing on bearing surfaces. As disclosed in the
prior art patents above, taper correction was generally
utilized as part of the ongoing grinding process and not
as an independent operation used to generate higher
quality parts.
Prior art methods utilized a modification in
angular relation between the longitudinal axis of the
workpiece being ground and the longitudinal axis of the
grinding tool or wheel. Taper conditions were measured
by taking individual diameter readings from two differ-
ent bearing surfaces spaced axially apart. As disclosed
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in the prior art patents, the gauge points were general- _
ly spaced apart as far as possible by placing one gauge
point on the bearing surface closest to one end of the
workpiece and one gauge point on the bearing surface
closest to the opposite end of the workpiece.
The relative positioning of these gauges is
useful in determining whether there is a difference in
diameter between the two surfaces being gauged but fails
to measure any of the bearing surface configurations
spaced axially between the two gauged surfaces on the
workpiece. As is known in the art, there are numerous
variables in the grinding process such as grinding means
dress intervals, grinding means dress quality and the
overall general maintenance of the grinding machine.
Thus, utilizing in-process gauging to determine the
diameters of the bearing surfaces at two axially spaced
positions does not give an accurate indication of the
diametrical taper conditions that may exist on bearing
surfaces spaced between the two engaging positions.
In process gauging in combination with micro-
finishing operations is disclosed in U.S. Patent No.
5,095,663 to Judge et al. The Judge et al patent dis-
closes a microfinishing device using in process gauging
to measure the diameter of an internal bearing system
during the microfinishing process. The microfinishing
process is terminated once a predetermined diameter is
achieved on the part. The Judge et al patent discloses
the use of size control shoes which monitor the diameter
of the journal surface using stationary probes in con-
junction with air gauges.
The Judge et al patent further discloses the
use of an abrasive backed tape to remove material upon
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the journal surface upon rotation of the workpiece. A
microfinishing shoe is used for pressing the abrasive coated
film against a portion of a circumference of a journal
surface. The microfinishing shoe disclosed is configured as
a one-piece, solid, construction capable of applying only
grinding forces transferred from the scissor type action of
the grinding arm the shoe is affixed to.
It is an object of the present invention to provide a
taper correcting microfinishing arm assembly for reducing
taper on selected journal bearing surfaces of a workpiece.
Another object of the present invention is to provide a
taper correcting microfinishing arm that reduces taper on
selected journal bearing surfaces of a workpiece by
utilizing in-process gauging at selected bearing surfaces to
be finished along the axial length of a workpiece.
It is another object of the present invention to
provide a means for reducing taper automatically without
losing contact between the grinding means on the surface of
a workpiece and the bearing journal surface.
It is a still further object of the present invention
to provide a means for comparing the diameters found on the
bearing surface of the workpiece and controlling a means for
applying a variable pressure to the bearing surface to
reduce the defined diametrical taper.
Accordingly, the present invention relates to a
microfinishing arm assembly for reducing taper on selected
bearing journal surfaces of a workpiece which is rotated
about a longitudinal axis, past predetermined locations
CA 02182953 2000-OS-29
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comprising: a primary finishing arm; taper correction means
for applying a plurality of adjacent, independently variable
grinding pressures to the journal surfaces at the predeter-
mined locations, the taper correction means mounted on the
primary finishing arm; primary abrasive means for finishing
the journal surfaces, the abrasive means mounted on the
primary finishing arm and adapted for use in cooperation
with the taper correction means; measuring means for gauging
the bearing journal surfaces at a plurality of spaced points
thereon during rotation of the workpiece to generate a
plurality of gauging signals; processor means in electrical
contact with the measuring means for receiving the gauging
signals, calculating the diameters of the journal surfaces
at the spaced points, and generating a plurality of output
signals corresponding to the diameters of the journal sur-
faces at the spaced points; and comparator means in electri-
cal contact with the processor means for comparing the
output signals to determine the taper on the selected
journal surfaces, and,controlling the extent to which the
taper correction means applies variable grinding pressure to
the selected surfaces to correct the taper.
Another aspect of the present invention relates to a
method of reducing taper on selected bearing journal sur-
faces of a workpiece which is rotated about a longitudinal
axis past predetermined locations, comprising the steps of:
providing a finishing arm having abrasive means mounted
thereon for finishing selected journal bearing surfaces;
providing a measuring means mounted on the finishing arm;
measuring the selected journal bearing surfaces at a
plurality of spaced points thereon during rotation of the
workpiece; generating a plurality of gauging signals in
accordance with the journal bearing surface measurements;
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analyzing the gauging signals and calculating the diameters
of the selected journal surfaces at the spaced points;
generating a plurality of output signals corresponding to
the diameters of the selected journal surfaces at the spaced
points; providing comparator means for comparing the output
signals to determine the taper on the selected journal
surfaces and generating corresponding control signals;
providing taper correction means in electrical contact with
the comparator means for receiving the control signals, the
taper correction means mountable on the primary finishing
arm; and applying variable grinding pressure to the selected
journal surfaces in accordance with the control signal to
correct the taper.
The above objects and other objects, features, and
advantages of the present invention are readily apparent
from the following detailed description of the best mode for
carrying out the invention when taken in connection with the
accompanying drawings, wherein:
FIGURE 1 is a side view of the taper correcting
microfinishing arm assembly of the present invention showing
a journal diameter in cross-section;
FIGURE 2 is a partial front view of the present
invention showing the variable grinding apparatus and a
workpiece with an exaggerated taper and including the
location of gauging points;
FIGURE 3 is a schematic view of the general control
system for the present invention; and
FIGURE 4 is a side view of a plurality of
microfinishing arm assemblies according to the present
invention shown in use with a crankshaft.
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Best Mode For Carryinqv Out The Invention
Referring now to Figure 1, a microfinishing
arm assembly in accordance with a first embodiment of
the present invention is shown and generally designated
S by reference numeral 10. Microfinishing arm assembly 10
is shown in use adjacent a crankshaft 12 having a
bearing journal surface 14 which requires taper correc-
tion. Taper correction fixture 16 is attached to micro-
finishing arm assembly 10 and is disposed directly
adjacent bearing journal surface 14.
Figure 2 shows an enlarged view of a bearing
journal surface 14 in contact with taper correction
fixture 16 and a greatly exaggerated depiction of dia-
metrical taper existing on the bearing journal surface.
Actual diametrical taper from the high side tci the low
side existing on various workpieces range anywhere from
1 (one) to 2 ttwo) thousandths of an inch. As discussed
previously, this diametrical taper is generally induced
in the prior grinding processes due to numerous vari-
ables including improperly dressed grinding materials,
improperly maintained grinding machines, and material
variations in different grinding processes.
Details of the mechanical components of the
microfinishing arm assembly of the present invention are
best described with reference to Figures 1 and 3.
Microfinishing back-up shoes 18 and 20 are disposed
immediately adjacent each other and mounted upon first
finishing arm 22. It should be understood that back-up
shoe 20 is identical to back-up shoe 18 and both operate
in an identical manner with identical mechanical compo-
nents. Backup shoe 20 is not shown in Figure 1. Backup
shoe 18 is affixed to first finishing arm 22 by mounting
CA 02182953 2000-OS-29
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members 38 and 40. Mounting members 38 and 40 have
threaded portions 42 and 44 which fit into tapped mount-
ing holes 46 and 48 within backup shoe 18.
Mounting members 38 and 40 are also positioned
within finishing arm mounting holes 50 and 52. Posi-
tioning dowels 34 and 36 are permanently affixed to
backup shoe 18 and are positioned in slip fit engagement
to corresponding dowel pin holes within first finishing
arm 22 as shown in Figure 1. In this arrangement,
backup shoe 18 is affixed to first finishing arm 22 and
is capable of vertical movement subject to pre-
established limits corresponding to mounting members 38
and 4 0 .
First finishing arm 22 has an elongated bore
26 and a corresponding reciprocating piston 28. Elong-
ated bore 26 can be configured in various shapes and
sizes depending upon the fluid compressor means util-
ized. Reciprocating piston 28 is positioned inside
elongated bore 26 and backup shoe engaging portion 56 is
in direct contact with first backup shoe 18. O-rings 30
and 32 are disposed as shown in Figure 1 for bore
sealing purposes. Fluid inlet 24 is in direct fluid
communication with cylinder bore 26. Figure 1 shows
abrasive inserts 58 used as an abrasive means for
removing material from the bearing journal surface 14.
Abrasive inserts 58 are affixed within backup shoe 18
such that compressive contact of the abrasive inserts 58
with rotating bearing surface 14 removes material from
bearing surface 14. Finishing arm 22, backup shoes 18
and 20, reciprocating piston 28, fluid inlet 24 and the
other mechanical components used to move backup shoes 18
and 20 vertically comprise taper correction fixture 16.
A second finishing arm 21 is shown in phantom in Figure
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1 located below and opposite first finishing arm 22.
Second finishing arm 21 includes an abrasive means (i.e.
abrasive insert or abrasive coated tape) for finishing
bearing surface 14 as discussed previously with respect
to the abrasive means of finishing arm 22. The second
finishing arm 21 is not necessary for the preferred
embodiment of the present invention but may be utilized
to aid in removing material from bearing surface 14.
Electromechanical gauges 60 and 62 are
partially shown and disposed diametrically opposite each
other on bearing journal surface 14. A second set of
electromechanical gauges are not shown but are spaced
axially apart from the first set of electromechanical
gauges. All four electromechanical gauges lie in a
plane parallel to the central axis of rotation of said
workpiece.
Figure 3 is a schematic representation of the
principle features and method of using the present
invention. Bearing journal surface 14 is rotated about
a longitudinal axis "C" while a first set of gauge
points 64 and 66 are disposed diametrically opposite
each other adjacent the bearing journal surface 14. A
second set of gauge points 68 and 70 are disposed dia-
metrically opposite each other along bearing journal
surface 14 and are also spaced apart and adjacent the
first set of gauge points.
It is understood that these gauge points
represent either electromechanical gauges, optical
gauges, or air jet gauges. The type of gauge chosen
will depend upon the number of workpieces the manu-
facturer intends to pass through the machine and the
maintenance schedule the manufacturer intends to apply
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to the machine . It is known in the art that air j et
gauges possess characteristics more conducive to heavy
finishing or grinding operations because they require
fewer cleaning intervals than other gauges. This
characteristic is inherent in air gauges because of the
constant flux of clean air which the gauge utilizes in
operation. It is understood that electromechanical
gauges and optical gauges can also be utilized in this
invention depending upon the various uses the assembly
is subject to. _
Any gauge chosen must be capable of detecting
changes in size of at least .00005 inches. Gauges.
located at gauge points 64, 66, 68 and 70 comprise a
measuring means for gauging the bearing journal surface
at spaced points upon the surface. These gauges gener-
ate a plurality of gauging signals which are transferred
to a processor for calculating the diameters according
to the gauging signals. This processor or means for
calculating diameter is designated as reference numeral
72 in Figure 3. Commercial processors are available to
process the gauging signals to generate signals repre-
senting a diameter of the bearing journal surface at two
planes on the bearing journal surface shown in Figure 3
as diameters D, and D2. The processor then transfers
these signals representing diameters to a comparator 74.
The output diameter signals are compared and used to
establish whether a diametrical taper exists between the
two diameter locations.
Comparator 74 is programmed with instructions
for determining if a taper exists on the journal surface
as shown in Figure 3. Output signals received from the
processor represent diameters D1 and D2. If the differ-
ence between D1 and DZ reaches a predetermined value Vo,
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a correctable taper is determined to be present on the
part and the comparator sends a signal to the taper
correction fixture for reducing taper. Predetermined
constant Va is determined by the user' and is programmable
into the comparator. This predetermined constant can be
as low as .0002 of an inch.
Processing apparatus for comparing the
diameters is commercially available and known in the
prior art as a programmable controller system capable of
producing a series of control signals. The comparator
sends control signals to a taper correction means that
applies a variable pressure to a fluid compressor 54.
The backup shoes 18 and 20 are aligned above and adja-
cent the bearing journal surface 14. The control of the
reciprocating piston thus controls the finishing pres-
sure applied to the backup shoes. The pressure applied
to the backup shoes is in turn transferred to the abra-
sive means located between the backup shoes and the
bearing journal surface.
The backup shoes 18 and 20 are identical and
have surface configurations corresponding to the shape
of the bearing journal surface. The fluid compressor
reacts correspondingly to .signals sent by the comparator
and can apply pressures as small as 10 (ten) pounds to
the backup shoes.
Fluid compressor 54, not shown in Fig. 1,
induces fluid either air or liquid, into elongated bore
26 through fluid inlet 24. Thus, the variable pressure
that can be induced by the fluid compressor reciprocates
piston 28 vertically inside cylinder 26. Piston 28 has
an engaging portion 56 which is located directly above
backup shoe 18 as shown in Figure 1.
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As pressure is applied from the fluid compres-
sor through the bore and to backup shoe 18, backup shoe
18 comes in contact with an abrading means for removing
material on the bearing journal surface. This abrading
means can be an abrasive coated tape 61 as shown in
Figure 3 or a hard abrasive insert 58 as shown in Figure
1. Referring to Figure 3, the conventional abrasive
coated tape is disposed between shoes 18 and 20 and
bearing surface 14. As those skilled in the art will
recognize, any conventional abrasive coated tape feed
device may be affixed to fixture 16 to feed abrasive
tape between the shoes 18 and 20 and the bearing surface
14. Hard abrasive inserts can be found in various
compositions such as diamond honing stones, garnet
honing stones or other like rnaterials. Different compo-
sitions remove material at different rates and produce
different surface finishes.
In operation, the exaggerated taper shown in
Fig. 2 is reduced by the following procedure. The
control signals received from comparator 74 are sent to
fluid compressor 54 which activates and brings either
backup shoe 18 or 20 or both down into compressive
contact with journal bearing surface 14 depending upon
the amount and direction of taper existing on the work-
piece. Figure 2 shows an exaggerated taper existing on
the bearing journal surface with the high side of the
taper below backup shoe 18 and the low side below backup
shoe 20. If a taper exists on the journal bearing
surface as shown in Fig. 2, backup shoe 18 and 20 are
brought down simultaneously at pressures corresponding
to signals received from the comparator. These signals
will force backup shoes 18 and 20 down into compressive
contact with an abrading means for removing material on
the bearing journal surface. This variable pressure
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will continue until the amount of material removed from
the surface brings the differences between diameters D1
and Dz below predetermined constant Vo.
Figure 4 shows seven taper correction micro-
s finishing arm assemblies used in conjunction with a
means for rotating a workpiece about a longitudinal
axis. The means for rotating, head stock 76 and tail
stock 78 is shown in Figure 4. The microfinishing
machine of the present invention can be configured to
~ accommodate as many microfinishing arm assemblies as
needed for each individual journal bearing surface
included on a workpiece.
Figure 4 shows a crankshaft having seven
journal surfaces and seven corresponding taper cor-
rection arm assemblies. Four taper correction micro-
finishing arm assemblies 82, 84, 86, 88 are disposed
adjacent four main bearing journal surfaces 90, 92, 94,
96. Three taper correction microfinishing arm assem-
blies 98, 100, 102 are disposed adjacent three pin
bearing journal surfaces 104, 106, 108. A machine base
is used to mount head stock 76, tail stock 78 and micro-
finishing arm assemblies according to the present inven-
tion. The workpiece, in this example a crankshaft, can
be rotated by various methods such as power roller or
between centers as shown in Figure 4.
While the above description constitutes the
preferred embodiments of the present invention, it will
be appreciated that the invention is susceptible of
modification, variation and change without departing
3 0 f rom the proper scope and f air meaning of the accompany-
ing claims.
